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Stabilization of bed Inclination angle in rotary drums by using computer vision
Get PDF"Computer vision systems have had great importance in research of different industrial processes. Videos and photographs have been used to characterize the bed behavior in a rotary drum; in this way, the bed motion, repose angles, trajectories, and particle velocity can be determined This work shows the development of a computer vision system that measures the bed inclination angle in industrial rotary drums. The purpose of the vision system is to capture the images when the angular velocity on the drum changes. Eventually, with the data measured during the two experiments in industrial rotary drums, we have identified two input-output models representing the slumping motion. Based on the control objective, we considered two approaches: regulation and tracking PI and PII2 controllers have been designed to show that a bed inclination angle can be stabilized for rolling motion considering plants that represent slumping motion and the inclination angle as the measured variable.
Growth of Ni nanoclusters on irradiated graphene: A molecular dynamics study
No full text"We studied the soft landing of Ni atoms on a previously damaged graphene sheet by means of molecular dynamics simulations. We found a monotonic decrease of the cluster frequency as a function of its size, but few big clusters comprise an appreciable fraction of the total number of Ni atoms. The aggregation of Ni atoms is also modeled by means of a simple phenomenological model. The results are in clear contrast with the case of hard or energetic landing of metal atoms, where there is a tendency to form mono-disperse metal clusters. This behavior is attributed to the high diffusion of unattached Ni atoms, together with vacancies acting as capture centers. The findings of this work show that a simple study of the energetics of the system is not enough in the soft landing regime, where it is unavoidable to also consider the growth process of metal clusters.
A class of Chua-like systems with only two saddle-foci of different type
Get PDF"Since the reported Chua’s system, several generalizations of this system have been presented, these approaches include new equilibria in order to obtain three or more scrolls in the attractor. One of these generalizations requires at least the same number of saddle-foci with local two-dimensional unstable manifolds as the desired number of scrolls. In this work, we present the generation of a double-scroll chaotic attractor called Chua-like system. Once that an equilibrium point has been removed from the Chua’s system and there are only two saddle-foci of different class, i.e. the dimension of one of the local unstable manifolds is one while the other is of dimension two. The new class is constructed based on the existence of a heteroclinic loop by linear affine systems with two saddle-focus equilibrium points of different type. Furthermore, the chaotic behavior of the proposed system is tested by the maximum Lyapunov exponent and the 0 — 1 chaos test.
Phase transition systematics in BiVO4 by means of high-pressure-high-temperature Raman experiments
Get PDF"We report here high-pressure-high-temperature Raman experiments performed on BiVO4. We characterized the fergusonite and scheelite phases (powder and single crystal samples) and the zircon polymorph (nanopowder). The experimental results are supported by ab initio calculations, which, in addition, provide the vibrational patterns. The temperature and pressure behavior of the fergusonite lattice modes reflects the distortions associated with the ferroelastic instability. The linear coefficients of the zircon phase are in sharp contrast to the behavior observed in the fergusonite phase. The boundary of the fergusonite-to-scheelite second-order phase transition is given by TF-Sch (K) = -166(8)P(GPa) + 528(5). The zircon-to-scheelite, irreversible, first-order phase transition takes place at T-Z-(Sch )(K) = -107(8)P(GPa) + 690(10). We found evidence of additional structural changes around 15.7 GPa, which in the downstroke were found to be not reversible. We analyzed the anharmonic contribution to the wave-number shift in fergusonite using an order parameter. The introduction of a critical temperature depending both on temperature and pressure allows for a description of the results of all the experiments in a unified way.
Methanogenic and Sulfate-Reducing Activities in a Hypersaline Microbial Mat and Associated Microbial Diversity
Get PDF"Methanogenesis and sulfate reduction are important microbial processes in hypersaline environments. However, key aspects determining substrate competition between these microbial processes have not been well documented. We evaluated competitive and non-competitive substrates for stimulation of both processes through microcosm experiments of hypersaline microbial mat samples from Guerrero Negro, Baja California Sur, Mexico, and we assessed the effect of these substrates on the microbial community composition. Methylotrophic methanogenesis evidenced by sequences belonging to methanogens of the family Methanosarcinaceae was found as the dominant methanogenic pathway in the studied hypersaline microbial mat. Nevertheless, our results showed that incubations supplemented with acetate and lactate, performed in absence of sulfate, also produced methane after 40 days of incubation, apparently driven by hydrogenotrophic methanogens affiliated to the family Methanomicrobiaceae. Sulfate reduction was mainly stimulated by addition of acetate and lactate; however, after 40 days of incubation, an increase of the H2S concentrations in microcosms amended with trimethylamine and methanol was also observed, suggesting that these substrates are putatively used for sulfate reduction. Moreover, 16S rRNA gene sequencing analysis showed remarkable differences in the microbial community composition among experimental treatments. In the analyzed sample amended with acetate, sulfate-reducing bacteria (SRB) belonging to the family Desulfobacteraceae were dominant, while members of Desulfohalobiaceae, Desulfomicrobiaceae, and Desulfovibrionaceae were found in the incubation with lactate. Additionally, we detected an unexpected high abundance of unclassified Hydrogenedentes (near 25%) in almost all the experimental treatments. This study contributes to better understand methanogenic and sulfate-reducing activities, which play an important role in the functioning of hypersaline environments.
Sincronización y control de redes dinámicas con topología conmutada
Get PDF"Las redes dinámicas conmutadas son modelos matemáticos de sistemas dinámicos complejos que se presentan en todas las áreas del conocimiento, las cuales capturan propiedades de interés, como la estructura, evolución de los estados y cambios en la forma de conexión. En este trabajo abordamos el problema de sincronización y el de control por pinning en una red dinámica conmutada. Analizamos condiciones bajo las cuales una red dinámica compleja logra sincronización idéntica, y diseñamos un controlador para llevar los estados de la red a un punto de equilibrio. Para determinar la estabilidad de la solución de sincronización y del punto de equilibrio al que se regula la red, consideramos una perspectiva de sistemas conmutados y los resultados se establecen usando el Teorema de la función común de Lyapunov. El modelo considerado es una red de nodos idénticos con dinámica no lineal y estructura de conexión que conmuta de acuerdo a una función del tiempo constante por partes y continua por la derecha. Todas las estructuras consideradas son difusivas, simétricas e irreducibles. Suponemos que todas las matrices Laplacianas cumplen alguna de las condiciones de diagonalización o triangularización simultánea para usar un cambio de variables que permite desacoplar la dinámica del error simplificando el problema. Si no se satisfacen estas suposiciones mostramos condiciones adicionales para garantizar la sincronización idéntica de la red. Consideramos el mismo modelo de red para aplicar control por pinning, que es diseñar controles por retroalimentación para un número muy reducido de nodos a fin de llevar las soluciones de todos los nodos de la red a un punto fijo de modo que sea asintóticamente estable. Se presentan ejemplos y simulaciones numéricas de sincronización y control para ilustrar los resultados.""Switched complex dynamical networks are mathematical models of dynamical complex systems that appear in all areas of knowledge, which capture properties of interest, such as structure, evolution of states and changes in the form of connection. In this paper we address the problem of synchronization and control by pinning in the switched dynamic network. We analyze conditions under which a complex dynamical network achieves identical synchronization, and we design a controller to bring the states of the network to a equilibrium point. To determine the stability of the synchronization solution and the equilibrium point to which the network is regulated, we use consider a perspective of switched systems and the results are established using the Lyapunov common function theorem. The model considered is a network of identical nodes with non-linear dynamics and connection structure that switches according to a constant in parts time function and continue on the right. All structures considered are diffusive, symmetric and irreducible. We suppose that all the Laplacian matrices satisfy either the conditions of simultaneous diagonalization or triangulation to use a change of variables that allows us to uncouple the error dynamics, simplifying the problem. If these assumptions are not met, additional conditions to ensure identical network synchronization are presented. We consider the same network model to apply pinnign control, which is to design feedback controls for a very small number of nodes in order to bring the solutions of all the nodes of the network to a fixed point so that it is asymptotically stable. Examples and numerical simulations of synchronization and control are presented to illustrate the results.
Design of plasmonic gold nanoantennas and their evaluation for photothermal therapy
Get PDF"Anisotropic gold nanoparticles (AuNPs) are known as promising tools for localized photo-thermal therapy (PTT) of malignant cells. These anisotropic AuNPs present tunable surface plasmon resonances (SPR) with ideal NIR optical response to be applied as theranostic agents (nanoantennas systems). To this purpose, nanoparticles with branches are suitable because of the electromagnetic field concentrated at their vertices. In this work, we standardized a protocol to synthesize multibranched gold nanoparticles (MB-AuNPs) by the seed-growth method, and found size-seed dependence tunability on the hierarchy of branching. The optical response of MB-AuNPs was evaluated by UV-Vis spectroscopy, and their morphology by electronic microscopy (SEM and HRTEM). Once evaluated the optical response and monodispersity of AuNPs, we tested the MB-AuNPs immersed in skin-equivalent phantoms by dynamic infrared thermography (DIRT).1 The particle density of the synthesized colloids, has being determined by inducted coupled plasma spectrometry (ICP). Once a nano-synthesized system is being intended for biological purposes, it is necessary to carefully design the surface layer. In principle, the molecules at the surface of nanoparticles (NPs) will provide the signals to its long-term circulation, their biocompatibility and the selectivity to target cellular sites. Therefore, in this work and for intended medical applications of MB-AuNPs, a conjugated complex was prepared with bovine serum albumin (MB-AuNPs@BSA). The optical signals of the conjugate formation were evaluated by UV-Vis and fluorescence spectroscopy. The interaction of the protein with the surface of the MB-AuNPs was analyzed by Raman spectroscopy, to ensure the structure and function preservation of the protein. The full formation of a protein corona was determined by protein quantification in a microplates reader and later observed by HRTEM. The efficiency and stability of the conjugated was analyzed by Z-potential and through the interaction of the conjugated complex with cibacron blue. Toxicological test of bare MB-AuNPs and MB-AuNPs@BSA were performed in different cell lines. The models in-vitro were chosen according to main systems of indirect interaction of intravenously administered NPs. Cell viability and proliferation, mitochondrial activity and membrane integrity were analyzed.""Las nanopartículas de oro (AuNPs) anisotrópicas han destacado como materiales con propiedades prometedoras para ser aplicados en la terapia fototérmica localizada (PTT) de células malignas. Las AuNPs anisotrópicas tienen la facilidad de modular la respuesta de la resonancia del plasmón superficial (SPR), siendo esto una respuesta óptica clave para su aplicación como agentes teranósticos
(nanoantenas). Para este propósito, las nanopartículas con ramificaciones son un modelo ideal, debido a la concentración de campo electromagnético en sus vértices. En este trabajo, estandarizamos el protocolo de síntesis de nanopartículas de oro multirramificadas (MB-AuNPs) mediante el método de dos pasos (semilla – crecimiento). La respuesta óptica de las MB-AuNPs fue evaluada por espectroscopia UV-Vis y su morfología por microscopía electrónica de barrido y transmisión (SEM y TEM) Una vez evaluado su respuesta óptica y la monodispersidad del coloide, las MB-AuNPs fueron evaluadas por termografía dinámica (DIRT) en un matriz modelo de las propiedades de la piel.1 La densidad
de partículas presentes en el coloide sintetizado, fue determinado mediante espectroscopia de plasma inducido (ICP). Cuando se pretende aplicar un sistema nanoestructurado en áreas biológicas, es necesario el diseño cuidadoso de la cobertura, ya que las moléculas en su superficie van a proporcionar las señales que determinen su tiempo de circulación por la sangre, su biocompatibilidad y la selectividad al sitio objetivo para administrar la terapia. Debido a esto, y con la intención de diseñar MB-AuNPs para aplicaciones médicas, se diseñó un conjugado con albúmina sérica bovina (MB-AuNPs@BSA). La evaluación mas básica de la formación del conjugado se realizó por espectroscopias UV-Vis y de fluorescencia. La interacción de la proteína con la superficie de la MB-AuNPs fue analizada por
espectroscopia Raman, y así se determinó la permanencia de su estructura básica y por lo tanto de su función. La formación de una corona proteica fue determinada mediante la cuantificación de proteína por UV-Vis y micrografías HRTEM del conjugado. La eficiencia y estabilidad del conjugado fue analizada por medición del potencial Z y a través de la interacción del complejo con cibacron blue. Finalmente, se llevaron a cabo análisis toxicológicos de las MB-AuNPs y del conjugado en diferentes líneas celulares. Los modelos in-vitro elegidos forman parte de los principales sistemas con los pueden interactuar las nanopartículas de forma inintencionada después de ser administradas vía intravenosa. Se evaluó la
viabilidad celular y la proliferación por conteo con hematímetro, así como la actividad mitocondrial y la integridad de la membrana plasmática por métodos colorimétricos."While performing the work the author received a scholarship from the National Council for Science and Technology (Registry No. 250290) and support from the research project with number 106437, also from the Institute for Scientific & Technological Research at San Luis Potosí
Light induces oxidative damage and protein stability in the fungal photoreceptor Vivid
Get PDF"Flavin-binding photoreceptor proteins sense blue-light (BL) in diverse organisms and have become core elements in recent optogenetic applications. The light-oxygen-voltage (LOV) protein Vivid (VVD) from the filamentous fungus Neurospora crassa is a classic BL photoreceptor, characterized by effecting a photocycle based on light-driven formation and subsequent spontaneous decay of a flavin-cysteinyl adduct. Here we report that VVD presents alternative outcomes to light exposure that result in protein self-oxidation and, unexpectedly, rise of stability through kinetic control. Using optical absorbance and mass spectrometry we show that purified VVD develops amorphous aggregates with the presence of oxidized residues located at the cofactor binding pocket. Light exposure increases oxidative levels in VVD and specific probe analysis identifies singlet oxygen production by the flavin. These results indicate that VVD acts alternatively as a photosensitizer, inducing self-oxidative damage and subsequent aggregation. Surprisingly, BL illumination has an additional, opposite effect in VVD. We show that light-induced adduct formation establishes a stable state, delaying protein aggregation until photoadduct decay occurs. In accordance, repeated BL illumination suppresses VVD aggregation altogether. Furthermore, photoadduct formation confers VVD stability against chemical denaturation. Analysis of the aggregation kinetics and testing of stabilizers against aggregation reveal that aggregation in VVD proceeds through light-dependent kinetic control and dimer formation. These results uncover the aggregation pathway of a photosensor, where light induces a remarkable interplay between protein damage and stability.
Producción de biohidrógeno en un reactor de tanque agitado continuo: Evaluación de los hidrolizados de bagazo de agave obtenidos con enzimas comerciales
Get PDF"La producción de hidrógeno por métodos biológicos a partir de fuentes renovables, como la fermentación oscura de biomasa, resulta una alternativa prometedora para reducir la dependencia a los combustibles fósiles ya que el biohidrógeno es un combustible libre de carbono que sólo genera agua cuando se quema. El bagazo de Agave tequilana Weber es uno de los principales residuos lignocelulósicos generados por la industria del tequila en México. Este bagazo tiene un gran potencial para la producción de H2 debido a su alto contenido de azúcares, que pueden liberarse a través de una hidrólisis enzimática. Actualmente, se ha demostrado que mezclas enzimáticas (celulasas y hemicelulasas) mejoran significativamente la liberación de los azúcares, sin embargo, son costosas. En este trabajo se evaluó el potencial de producción de hidrógeno en un reactor CSTR a partir de hidrolizados obtenidos con una mezcla enzimática importada (Celluclast 1.5L/Viscozyme) y una enzima comercial nacional (Stonezyme). El desempeño del CSTR alimentado con el hidrolizado obtenido con la mezcla enzimática fue excelente, alcanzando una velocidad volumétrica de producción de hidrógeno (VVPH) máxima de 12.9 L H2/L-d que se logró a una carga orgánica volumétrica (COV) de 90 g DQO/L-d. Cuando se operó un segundo reactor CSTR con el hidrolizado obtenido a partir de una enzima comercial nacional se obtuvo una VVPH máxima de 2.2 L H2/L-d a una COV de 100 g DQO/L-d. La remoción de azúcares durante este ensayo fue de 83%, menor al obtenido con la mezcla enzimática que fue de 93%. En ambos ensayos se observó una relación directa entre la COV y la VVPH. Los distintos desempeños fueron atribuidos a que la producción de hidrógeno fue influenciada significativamente por la composición de los azúcares de los hidrolizados. El presente trabajo muestra que la alta VVPH obtenida con la mezcla enzimática da como resultado un menor costo en la producción por litro de H2, en comparación con la enzima comercial nacional.""Hydrogen production by biological methods from renewable sources, such as dark
fermentation of biomass, is a promising alternative to reduce dependence on fossil
fuels since biohydrogen it a carbon-free fuel that only generates water when it is
burned. The Agave tequilana Weber bagasse is one of the main lignocellulosic
residues generated by the tequila industry in Mexico. This bagasse has a great
potential to produce H2 due to its high content of sugars, which can be released
through an enzymatic hydrolysis. Currently, it has been shown that mixtures of
cellulases and hemicellulases significantly improves the release of sugars, however,
are very expensive. In this work the potential of hydrogen production in a CSTR
reactor was evaluated from hydrolysates obtained with an imported enzymatic
mixture and a national commercial enzyme. The performance of the CSTR fed with
the hydrolysate obtained with the enzymatic mixture was excellent; reaching a
maximum volumetric hydrogen production rate (VHPR) of 12.9 L H2/L-d achieved at
an organic loading rate (OLR) of 90 g COD/L-d. In the second test when operating
the CSTR with the hydrolysate obtained whit a single commercial enzyme
preparation, a maximum VHPR of 2.2 L H2/L-d was obtained at an OLR of 100 g
COD/L-d. The removal of sugars during this trial was 83%, lower than that obtained
with the enzymatic mixture that was 93%. In both trials, a direct relationship was
observed between OLR and VHPR. The different performances were attributed to
the fact that the production of hydrogen was significantly influenced by the
composition of the sugars of the hydrolysates. The present work shows that the high
VHPR obtained with the enzymatic mixture results in a lower cost in the production
per liter of H2, compared with the national commercial enzyme.
Efectos desmagnetizantes en materiales magnéticos no continuos
Get PDF"En este trabajo se propone un modelo de campo medio para describir los efectos
desmagnetizantes en sistemas magnéticos que contienen inclusiones no-magnéticas, como pueden ser poros, huecos, fases no magnéticas, entre otros. El modelo propuesto se basa en parámetros geométricos del sistema, en particular la geometría del volumen de material magnético, un factor geométrico promedio de las inclusiones no magnéticas y la fracción de volumen que ocupan las inclusiones no magnéticas en la matriz magnética. El modelo permite obtener expresiones simples para parámetros magnéticos de interés como son la susceptibilidad magnética y anisotropía magnética, las cuales incorporan explícitamente los efectos de las inclusiones no magnéticas. El modelo ha sido probado experimentalmente a partir de los ciclos de histéresis de tres tipos diferentes de materiales: empaquetados
cilíndricos de micropartículas magnéticas esféricas, una película porosa de níquel (esponja de níquel) y películas formadas por redes de nanoalambres magnéticos entrecruzados. A partir del modelo, las mediciones magnéticas han sido interpretadas a partir de factores geométricos y dimensiones características de cada sistema y las observaciones coinciden bien con lo predicho por el modelo. En particular, para los empaquetados cilíndricos de partículas magnéticas esféricas, el sistema muestra una anisotropía magnética siendo el eje del cilindro la dirección de fácil magnetización y donde la magnitud de esta anisotropía aumenta al incrementar la altura del empaquetado cilíndrico. Estos resultados están en muy buen acuerdo con lo predicho por el modelo.""In this work a medium field model is proposed to describe the demagnetizing effects in magnetic systems that contain non-magnetic inclusions, such as pores, voids, non-magnetic phases, among others. The proposed model is based on geometrical parameters of the system, in particular the geometry of the volume of magnetic material, an average geometric factor of the non-magnetic inclusions and the fraction of volume occupied by the non-magnetic inclusions in the magnetic matrix. The model allows to obtain simple expressions for magnetic parameters of interest such as magnetic susceptibility and magnetic anisotropy, which explicitly incorporate the effects of non-magnetic inclusions. The model has been tested experimentally from the hysteresis cycles of three different types of materials: cylindrical packed of spherical magnetic microparticles, a porous nickel film (nickel sponge) and films formed by networks of crosslinked magnetic nanowires. From the model, the magnetic measurements have been interpreted from geometrical factors and characteristic dimensions of each system and the observations coincide well with what was predicted by the model. In particular, for the cylindrical packaging of spherical magnetic particles, the system shows a magnetic anisotropy, the axis of the cylinder being the direction of easy magnetization and where the magnitude of this anisotropy increases as the height of the cylindrical packaging increases. These results are in very good agreement with what was predicted by the model.