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Synthesis, characterization and magnetic properties of Co@Au core-shell nanoparticles encapsulated by nitrogen-doped multiwall carbon nanotubes
Get PDF"Co/Au bilayer thin films were deposited on Si/SiOx substrates using the magnetron sputtering method and used as a catalytic support to grow forests of aligned nitrogen-doped multiwalled carbon nanotubes (N-MWCNT) via chemical vapor deposition (CVD) at 850 °C, using benzylamine (C6H5CH2NH2) as a carbon and nitrogen source. Interestingly, the resulting N-MWCNT contains Co@Au core-shell nanoparticles located at their tips. We found that the metal particle cores consist of cobalt coated by an Au shell of few nanometers. Magnetic measurements revealed a ferromagnetic behavior of the system composed of Co@Au nanoparticles encapsulated inside N-MWCNT. The results are compared with pristine N-MWNT containing only Co nanoparticles encapsulated in their cores.
Pine-tree-like morphologies of nitrogen-doped carbon nanotubes: Electron field emission enhancement
No full text"Nitrogen-doped multiwalled carbon nanotube (CNT) bundles exhibiting pine-tree-like morphologies were synthesized on silicon-silicon oxide (Si/SiO2) substrates using a pressure-controlled chemical vapor deposition process. Electron field emission (FE) measurements showed a notable emission improvement at low turn-on voltages for the CNT pine-like morphologies (e.g., 0.59 V/-m) in comparison with standard aligned N-doped CNTs (>1.5 V/-m). We envisage that these pine-tree-like structures could be potentially useful in the fabrication of efficient FE and photonic devices.
Bases moleculares de la incompatibilidad replicativa de dos cepas de Rhynchosia mosaic Sinaloa virus
Get PDFTesis (Maestría en Ciencias en Biología Molecular)"Los begomovirus tienen un genoma compuesto por una o dos moléculas circulares de DNA de cadena sencilla (ssDNA) de ~2.6 kb, que se replican por el mecanismo de círculo rodante (RCR) en el núcleo de la célula vegetal. La proteína iniciadora de la replicación (Rep) codificada por estos virus pertenece a la superfamilia de endonucleasas HUH, las cuales tienen un papel importante en la RCR de plásmidos, bacteriófagos, y virus circulares de ssDNA de organismos eucariotas, en la transferencia de plásmidos durante la conjugación bacteriana, y en distintos tipos de transposición. En el 2006 se aisló de una planta de Rhynchosia mínima colectada en Guasave, Sinaloa, una nueva especie de begomovirus que se denominó Rhynchosia mosaic Sinaloa virus (RhMSinV). En el presente trabajo aislamos tres begomovirus diferentes de una planta de R. minima colectada en Manzanillo, Colima, y su secuenciación reveló que uno de esos virus es una nueva cepa de RhMSinV (<92% de identidad). Este nuevo virus RhMSinV-CO exhibe en el origen de replicación cuatro presuntos sitios de unión de Rep (iterones) cuya secuencia (TGGAGTC). es diferente a la de los elementos homólogos del aislado original de Guasave (TGGAGGA), y a una variante de este último aislado también en este estudio, que denominamos RhMSinV-GUco. El alineamiento de las proteínas Rep codificadas por las dos cepas reveló una diferencia en el residuo amninoácido 71 (N-D), que fue identificado en trabajos previos de nuestro laboratorio como un potencial determinante de especificidad (SPD) de la proteína Rep. El modelado de la estructura tridimensional del dominio endonucleolítico de las proteínas Rep de RhMSinV-CO y -GU reveló que sus presuntos SPDs (los residuos 9, 11, 71 y 73) exponen sus grupos laterales hacia la superficie de una mini-hoja beta (β1-β5) que se considera crítica para el reconocimiento y unión de Rep a su DNA cognado. Experimentos de replicación transitoria en protoplastos, y de inoculación por biobalística de plantas de Nicotiana benthamiana, demostraron que RhMSinV-GU y RhMSinV-CO son incompatibles en replicación, como se predijo a partir de las diferencias en sus potenciales determinantes de especificidad (iterones y Rep-SPDs). En contraste, el DNA-A de la cepa RhMSinV-CO y el DNA-B de un begomovirus filogenéticamente distante, Pepper golden mosaic virus (PepGMV) que presenta iterones y Rep-SPDs similares, formaron pseudo-recombinantes viables que indujeron síntomas severos en las plantas bombardeadas.""The begomoviruses have genomes composed by one or two circular molecules of single stranded DNA (ssDNA), ~2,6 kb in length, which are replicated by a rollingcircle (RC) mechanism in the nucleus of the plant cell. The replication initiation protein (Rep) encoded by the begomoviruses belongs to the HUH endonuclease superfamily, and is essential for the replication process. Those proteins play a key role in the RCR of plasmids and bacteriophages, in plasmid transfer, in the replication of several eukaryotic viruses, and in various types of transposition. In 2006 we isolated from a leguminous weed (Rhynchosia minima) collected in Guasave, Sinaloa, a new begomoviral species named Rhynchosia mosaic Sinaloa virus (RhMSinV). In this work three different begomoviruses were isolated from a single R. minima plant collected in Colima, and their sequencing revealed that two of those viruses are novel strains of RhMSinV (<92% identity). One of these exhibited four Rep-binding sites (iterons) similar to those of the original isolate (i.e., TGGAGGA), whereas the second strain displayed iterons with a TGGAGTC core sequence. Sequence alignments of the two Rep proteins showed a difference in the aa residue at position 71 (N/D), which is one of the five aa residues which were predicted to function as major determinants of geminivirus Rep DNA-binding specificity (SPDs). Modeling of the 3-D structure of the Rep endonuclease domain revealed that the putative SPDs (i.e. 9, 11, 71 y 73) point their side chains toward the exposed surface of the small beta-sheet (s1-s5) element, that is apparently critical for high-affinity DNA-binding of Rep proteins. Experiments of transient replication in protoplasts and plant inoculation by biobalistics revealed that RhMSinV-GU and RhMSinV-CO are incompatible in replication. In contrast, biolistic coinoculation of N. benthamiana plants with RhMSinV-CO DNA-A and the genomic component B of Pepper golden mosaic virus (PepGMV), a distant relative harboring similar replication specificity determinants, induced severe symptoms 15 dpi, thus demonstrating the formation of infectious pseudo-recombinants. Taken together, our data provide strong support to the hypothesis that specific amino acid residues sited at beta-strands 1 and 5 of the RhMSinV Rep protein are actually virus-specific replication determinants.
Análisis proteínico del grano de amaranto (Amaranthus hypochondriacus y A. cruentus) y obtención del mapa proteómico de Amaranthus cruentus
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"El amaranto es un grano que ha resurgido en este nuevo milenio con relevancia internacional debido a sus propiedades nutracéuticas y nutricionales. Una característica muy importante que posee el grano del amaranto es su capacidad de tolerar condiciones ambientales adversas a lo largo de su desarrollo desde su estado embrionario, pasando por la germinación y el desarrollo. Los mecanismos por los cuales esta planta resiste dichas condiciones se fundamentan en la función e interacción de las proteínas que permiten el equilibrio metabólico de las células. Se tienen escasos reportes de la presencia de proteínas que permiten la tolerancia al estrés en el grano de amaranto, específicamente en A. cruentus. Una de las modificación postraduccionales involucradas en el procesamiento y transferencia de información celular es la fosforilación de las proteínas, es por eso que se rastreó la presencia de esta modificación en las proteínas de reserva del grano de A. hypochondriacus y A. cruentus; donde reportamos una presencia significativa de proteínas fosforiladas en grano maduro de ambas especies de amaranto. Se encontraron diferencias en los patrones electroforéticos de las proteínas totales de 5 cultivos de las especies de A. hypochondriacus y A. cruentus, tambien se reportó la presencia de la proteína tipo lunasin en ambas especies. En el presente trabajo se realizó por primera vez una aproximación al proteoma del grano de A. cruentus y se describió la presencia de proteínas involucradas en los mecanismos de dormancia.""Amaranth is a grain that has gained international importance due to their nutraceutical and nutritional properties. A very important feature of amaranth is its ability to tolerate adverse weather conditions throughout its development from its embryonic state, through its germination and development. The mechanisms by which this plant resists such conditions are dictated by the function and interaction of proteins that allow the metabolic balance of cells. From our knowledge, no reports, regarding Amaranthus cruentus, exist about the presence of proteins that allow stress tolerance of amaranth grain. Differences in the total protein profile of three cultivars of A. hypochondriacus and two of A. cruentus were determined. as one of the posttranslational modifications involved in the processing and transfer of cellular information is phosphorylation of proteins, we report the presence of this modification in storage proteins of A. hypochondriacus and A. cruentus, where a significant presence of tyrosine-phosphorylated proteins were found. Also the presence of lunasin-like protein in both species was reported. This is the first suty dealing with the Amaranthus cruentus grain proteome which describes the presence of proteins involved in the mechanisms of dormancy.
The VISHMOD methodology with hydrochemical modeling in intermountain (karstic) aquifers: case of the Sierra Madre Oriental, Mexico
Get PDF"Hydrogeochemistry can be studied qualitatively using graphics such as scatter plots and Piper, Durov, and Schoeller diagrams, among others, and quantitatively by applying mass balance mixing models. The VISHMOD methodology (Virtual Samples in Hydrochemical Modeling) combines these two forms of hydrogeochemical characterizations. It is performed by applying hydrogeochemical modeling to virtual samples. This method makes standardization and control possible in order to demonstrate the extent to which a model is able to reproduce field measurements. Therefore, hydrogeochemical models of hydrogeological systems must be calibrated. This methodology was applied to carbonate and homogeneous media in the Sierra Madre Oriental in Mexico. Using the VISHMOD methodology in this region resulted in the classification of the water type as calcium bicarbonate (Ca-HCO3), representing a ternary mixture in which 45.5% was associated with local flow, 38.5% to intermediate flow and 16.5% to water-rock interaction. The main mineral phases were saturated calcite and sub-saturated dolomite, both from limestone contained in the Tamaulipas Formation.
El receptor P2X4 del cobayo presenta un cambio puntual que altera su fenotipo
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Los receptores canal P2X activados por ATP son permeables a cationes y median potenciales post sinápticos excitatórios rápidos. Se encuentra ampliamente distribuidos en distintos tejidos del cuerpo humano y se conservan en una gran variedad de mamíferos (cobayo, ratón, rata, perro chimpancé, etc.), aves y peces. Por su parte el receptor P2X4 el cual tiene una amplia distribución en diferentes tejidos, ha sido involucrado en una gran variedad de procesos fisiológicos. Previamente se ha mostrado un efecto potenciador predominante a bajas concentraciones de suramina en las corrientes evocadas por ATP en las neuronas mientéricas del cobayo. Ya que un efecto similar ha sido reportado únicamente en receptores P2X4 recombinantes de rata y ratón nuestra hipótesis es que ésta subunidad se encuentra presente en la mayoría de las neuronas mientéricas del cobayo. Este es el primer estudio que muestra la secuencia de la subunidad P2X4 del cobayo, la cual se encuentra en la mayor parte de las neuronas mientéricas. El efecto potenciador de la suramina sobre la corriente inducida por ATP (IATP) en estas neuronas junto con la co-inmunoprecipitación de esta subunidad con otros miembros de la familia de canales P2X apoya la participación de esta subunidad en la formación de canales funcionales. Contrario a lo que se observó en otras especies, la ivermectina y el etanol no tuvieron efecto sobre la IATP, lo cual asociamos a un cambio en el aminoácido T57 por K el cual se ubica en el binding pocket de la ivermectina y del etanol.""The ATP activated P2X channel receptors are cation permeable and mediate fast excitatory post-synaptic potentials. They are widely distributed in human tissues and are conserved among mammals (guinea pig, mice, rat, dog, chimpanzee, etc.), birds and fish. The P2X4 receptor, on its own, has been involved in a variety of physiological processes. Previously, a potentiating effect has been shown in the ATP evoked currents in guinea pig myenteric neurons by low suramin concentration. Since a similar effect has been reported in recombinant P2X4 receptors in rat and mice, we propose a hypothesis where this subunit is present in most guinea pig myenteric neurons. This is the first study reporting the sequence of the P2X4 guinea pig sequence, which is present in most of the myenteric neurons analyzed. Taken together, the potentiating effect of suramin on the ATP evoked current in these neurons and the co-immunoprecipitation of the P2X4 subunit with other members of the P2X channel family, support the participation of this subunit in the formation of functional channels. Contrary to what is observed in other species, ivermectin and ethanol did not have an effect on the ATP evoked current in myenteric neurons. We associate this effect to particular changes in the amino acid sequence of guinea pig P2X, namely V49L and T57K, which are located in the binding pocked of ivermectin and ethanol.
Epidemiología molecular de la tuberculosis en San Luis Potosí
Get PDF"CONTEXTO: El estado de San Luis Potosí sufre las vulnerabilidades socioeconómicas y factores de riesgo determinantes de la TB y aunque México es un país prioritario para elcontrol de la TB, los estudios de epidemiología molecular son escasos en general y nulos en el estado. MÉTODOS: Recolectamos y analizamos los datos sociodemográficos y clínicos completos de 248 pacientes de TB pulmonar (TBP) entre los 432 casos confirmados por cultivo en el periodo 2006-2010 de la población sujeta a vigilancia epidemiológica de esta enfermedad. Por otro lado, determinamos los espoligotipos, especies, linajes y familias del Complejo Mycobacterium tuberculosis (CMTB) de 332 aislados de TBP diagnosticados entre 2006 y 2011. Estimamos los índices de diversidad genética de Nei y de Simpson y el índice de transmisión-mutación (TMI). Los aislados del CMTB involucrados en cadenas de transmisión reciente fueron identificados por sus patrones de 15 loci MIRU-VNTR entre clústeres de aislados con espoligotipos idénticos y vínculos geográficos. Los índices discriminatorios de los genotipos VNTR fueron calculados con la fórmula de Hunter-Gaston y las cepas emergentes del CMTB identificadas con el método de Storey aplicado a los espoligotipos. RESULTADOS. La tasa de incidencia de TBP varió entre 2.4 y 33.4 (casos por 100,000 habitantes) en las seis jurisdicciones sanitarias del estado, que fueron agrupadas en regiones de baja (jurisdicciones I, II y III), intermedia (IV y V) y alta incidencia (VI) con tasas de 6.2, 17.3 y 33.4 respectivamente. La mediana de edad de los pacientes fue 50 años y los casos predominaron en hombres y amas de casa. Entre los aislados del CMTB 324 tuvieron espoligotipos de M. tuberculosis (97.6%) y ocho de M. bovis (2.4%). Doscientos veinticuatro aislados se agruparon en espoligoclústeres, siendo los principales de los genotipos SIT53 (n = 96) y SIT42 (n = 20). Predominó el Linaje 4 (Euro-Americano) con 304 aislados, seguido del Linaje 1 (Indo-Oceánico) con 14 aislados y el Linaje 2 (Asiático Oriental) con seis aislados. Los valores de los índices fueron: H = 0.91 (Nei), S = 0.09 (Simpson), TMI = 0.11. Entre los 32 espoligoclústeres identificados estuvieron geográficamente relacionados siete, formados por 31 aislados (9.3% del total) en clústeres de 2 a 14 aislados.""BACKGROUND: The state of San Luis Potosí is adversely affected by socio-economic vulnerabilities and risk factors determinant of tuberculosis (TB) and, although Mexico is a high-priority country for the TB control, molecular epidemiology studies are scarce at large in the country and inexistent in the state. METHODS: We collected and analyzed complete sociodemographic and clinical data from 248 patients of pulmonary TB (PTB) confirmed by culture in the population under epidemiologic surveillance from 2006 to 2010. On the other hand, we determined the spoligotypes, species, lineages and families of 332 Mycobacterium tuberculosis Complex (MTC) isolates from the PTB cases diagnosed from 2006 to 2011. We estimated Nei’s and Simpson’s diversity indexes and the transmissionmutation index (TMI). MTC isolates involved in recent transmission chains were identified through their 15 MIRU-VNTR loci patterns from spoligoclusters with identical patterns and geographic links. The discriminatory genotype indexes for each MIRU-VNTR locus were calculated with the Hunter-Gaston formula, and emergent MTC strains identified with the Storey method applied to spoligotypes. RESULTS. The PTB incidence rates varied from 2.4 to 33.4 (cases by 100.000 inhabitants) in the six state sanitary jurisdictions, which were grouped in regions of low (jurisdictions I, II and III), intermediate (IV and V) and high incidence (VI) with respective rates of 6.2, 17.3 and 33.4. The median age of patients was 50 years and TBP cases predominated in men and housewives. Amongst the MTC isolates, 324 (97.6%) had M. tuberculosis spoligotypes and eight (2.4%) had M. bovis spoligotypes. Two hundred twenty-four isolates were grouped in spoligoclusters, mainly of SIT53 (n = 96) and SIT42 (n = 20) genotypes. The Lineage 4 (Euro-American) predominated with 304 isolates, followed by Lineage 1 (Indo-Oceanic) with 14 isolates, and Lineage 2 (East-Asian) with six isolates. Values of the indexes were: H = 0.91 (Nei), S= 0.09 (Simpson), TMI = 0.11. Among the 32 spoligoclusters —constituted by 31 isolates (9.3%) in clusters of 2 to 14— only seven were geographically linked. In these clusters we resolved twenty-five MIRU-VNTR types, and identified six pairs of isolates involved in recent transmission chains (3.7% of the total); three pairs from cases with proven contacts and three without proven contacts corresponding to the Beijing family. The Gunter-Gaston discriminatory index for the 15 MIRU-VNTR loci was 0.997.
Análisis proteómico de los cloroplastos de Amaranthus cruentus var. Amaranteca
Get PDF"Las mayoría de las plantas C4 desarrollan la anatomía de Kranz, en la cual, el sistema vascular (SV) está rodeado por tejido fotosintético denominado células de la vaina del haz e inmediatas a estas se encuentran las células del mesófilo, esto implica la presencia de 2 tipos de cloroplastos, los del mesófilo (CM) involucrados en la fijación del CO2 y los de la vaina del haz (CVH) encargados de metabolizar el CO2. Mientras que en las plantas C3-C4, que también desarrollan la anatomía de Kranz, las enzimas de ambos procesos se localizan en los dos tipos de cloroplastos. El género Amaranthus spp. es considerado una planta C4 del subtipo NAD-enzima málica (NAD-ME), sin embargo, la morfología de los cloroplastos de Amaranthus cruentus var. Amaranteca observada por microscopio de transmisión electrónica (TEM) es similar, ambos cloroplastos pose grana y cúmulos de almidón. Además por inmunohistoquímica se detectó la subunidad grande de RuBisCO (RbcL) en los 2 tipos de cloroplastos, sugiriendo que el ciclo de Calvin está activo en ambos. Por otra parte, el análisis de los complejos tilacoidales de los cloroplastos en dos dimensiones usando geles nativos (BN) en la primera dimensión seguidos de la separación desnaturalizante en segunda dimensión en SDS-PAGE (2-DE BN/SDS-PAGE) mostró que las proteínas involucradas en la actividad del PSII fueron más abundantes en CM y que un tratamiento salino provoca variación en la acumulación de las subunidades de los complejos PSI y PSII, ATP sintetasa, CYTb6f, enzimas glicolíticas y otras enzimas involucradas en la síntesis de jasmonatos. Esto sugiere que a pesar de su morfología similar la composición de los complejos tilacoidales de los CVH y CM es diferente y que reaccionan a la presencia de sal en el suelo, incrementando la fotosíntesis y sintetizando moléculas involucradas en la respuesta de la planta a este tipo de estrés.""Most of the C4 plants develop the Kranz anatomy, where the vascular system (VS) is surrounded by photosynthetic tissue named bundle sheath cells and immediate to them are located the mesophyll cells . This implies the presence of two types of chloroplasts, the mesophyll chloroplasts (MC) involved in the CO2 fixation and bundle sheath chloroplasts (BSC) responsible for metabolizing CO2. The C3-C4 intermediary plants also develop the Kranz anatomy but the enzymes of fixation and metabolizing the CO2 are expressed in the both chloroplasts. The Amaranthus spp. Genus is considered as C4 plant subtype NAD-malic enzyme (NAD-ME), however, the chloroplast morphology of Amaranthus cruentus var. Amaranteca observed by transmition electron microscopy (TEM) is quite similar, they have grana and starch cumulus. By immunohistochemical analysis it was possible to detect the RuBisCO´s large subunit (RbcL) in both chloroplasts type. However, the analyses of thylakoid protein complexes in two dimensions using blue native gels as first dimension followed by denaturing electrophoresis in SDS-PAGE in the second dimension (2-DE BN/SDS-PAGE), showed that proteins involved in the PSII activity were more represented in MC. When plants were subjected to salt stress, there was a variation of PSI and PSII core proteins, ATP synthetize complex, proteins involved in the jasmonates synthesis and glycolytic pathway. This suggests that despite the similar morphology of chloroplasts the composition of BSC and MC is different and that they responded to salt in the soil by increasing the photosynthesis and synthesis of molecules involved in the responses of plant to this kind of stress.
Magnetostructural transition and magnetocaloric effect in MnNiGe1.05 melt-spun ribbons
Get PDF"Alloy ribbons of nominal composition MnNiGe1.05 were produced using the melt-spinning technique. As-quenched (aq) polycrystalline ribbons are single-phase showing the hexagonal Ni2In-type crystal structure. After thermal annealing at 1148 K, the formation of the orthorhombic TiNiSi-type crystal structure by martensitic transformation is favored. However, XRD patterns for different temperatures indicate that the phase transition from hexagonal to orthorhombic structure is incomplete. The starting and finishing temperatures for the direct and reverse martensitic transformation for aq (annealed) samples determined by DSC were MS = 264 (268) K Mf = 235 (255) K, AS = 259 (266) K, and Af = 289 (276) K. Across this structural phase transition the annealed sample undergoes a drop in magnetization giving rise to a narrow temperature dependence of the magnetic entropy change with a peak value on heating (cooling) of 5.8 (4.8) Jkg−1K−1 for a field change of 5 T.
Stability of gain scheduling control for aircraft with highly nonlinear behavior
Get PDF"The main goal of this work is to study the stability properties of an aircraft with nonlinear behavior, controlled using a gain scheduled approach. An output feedback is proposed which is able to guarantee asymptotical stability of the task-coordinates origin and safety of the operation in the entire flight envelope. The results are derived using theory of hybrid and singular perturbed systems. It is demonstrated that both body velocity and orientation asymptotic tracking can be obtained in spite of nonlinearities and uncertainty. The results are illustrated using numerical simulations in F16 jet.