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Large and reversible elastocaloric effect near room temperature in a Ga-doped Ni–Mn–In metamagnetic shape-memory alloy
No full text"We report a giant elastocaloric effect near room temperature in a polycrystalline Ga-doped Ni-Mn-In ferromagnetic shape-memory alloy. The elastocaloric effect has been quantified by measuring both isothermal stress-induced entropy changes and adiabatic stress-induced temperature changes. A reproducible maximum entropy change,Delta S-rev similar or equal to 25 J . K-1 . kg(-1), upon cycling across the martensitic transition was obtained by application of a compressive stress of 100MPa. The corresponding maximum amount of cooling, Delta T-adi similar or equal to -4.9K, was measured when this stress was rapidly removed. These values are comparable with those reported for giant magnetocaloric materials, which are induced by application and release of a high magnetic field. Therefore, the studied material is a good candidate to be used in solid-state refrigeration devices based on the elastocaloric effect.
In vivo evidence for homo- and heterodimeric interactions of Arabidopsis thaliana dehydrins AtCOR47, AtERD10, and AtRAB18
Get PDF"Dehydrins (DHNs) are intrinsically disordered proteins that play central roles in plant abiotic stress responses; however, how they work remains unclear. Herein, we report the in planta subcellular localization of Arabidopsis thaliana DHNs AtCOR47, AtERD10, and AtRAB18 through GFP translational fusions. To explore the dimerization ability of the Arabidopsis acidic DHNs AtCOR47 and AtERD10, we conducted an in planta DHN binding assay using the Bimolecular Fluorescence Complementation (BiFC) technique. Our analyses revealed homodimeric interactions for AtCOR47 and AtERD10; interestingly, heterodimeric associations also occurred with these DHNs, and these interactions were observed in the cytosol of tobacco cells. Furthermore, we evaluated whether Arabidopsis basic DHNs, such as AtRAB18, could also interact with itself and/or with AtCOR47 and AtERD10 in the BiFC system. Our data revealed homodimeric RAB18 complexes in the nucleus and cytosol, while heterodimeric associations between AtRAB18 and acidic DHNs occurred only in the cytosol. Finally, we demonstrated the presence of heterodimeric complexes among Arabidopsis AtCOR47, AtERD10, and AtRAB18 DHNs with their acidic ortholog the OpsDHN1 from Opuntia streptacantha; these heterodimeric interactions showed different subcellular distributions. Our results guide DHN research toward a new scenario where DHN/DHN oligomerization could be explored as a part of their molecular mechanism.
Effect of inoculum pretreatment on hydrogen production in high cellular density reactors and evaluation of interactions between their microbial functional groups
Get PDFTesis (Doctorado en Ciencias Ambientales)"Se considera que el hidrógeno tendrá una gran relevancia como combustible en el futuro próximo, llegando incluso a hablarse de una economía basada en el hidrógeno, ya que además de ser usado de manera directa es posible usarlo como acarreador intermediario de energía. Sin embargo, aunque la tecnología para su aprovechamiento tiene ya varias décadas de desarrollo, su producción aún depende en gran medida de los combustibles fósiles a los que tendría que suplantar. Uno de los métodos más prometedores es la fermentación oscura, por medio de la cual se aprovechan las características fisiológicas de bacterias creciendo en condiciones anaerobias. Hay una gran variedad de parámetros que influyen en la producción de biohidrógeno por fermentación oscura, como el tiempo de residencia hidráulica, la velocidad de carga orgánica, pH, tipo de sustrato y características del inóculo. La mayoría de estos parámetros han sido ya estudiados y descritos en la literatura. Sin embargo, poco se ha logrado esclarecer acerca de la interdependencia y demás interacciones entre los distintos componentes de la comunidad microbiana anaerobia que permitn altas producciones de hidrógeno. Estas comunidades existen naturalmente en
los lodos anaerobios de las plantas de tratamiento y se intercalan con las productoras de metano. Por esto, las fuentes más comunes de obtención de inóculo para producción de metano son las naturales y/o de plantas de tratamiento, a las que es necesario dar un tratamiento previo para inhibir toda actividad metanogénica. En esta tesis se evaluaron dos diferentes pretratamientos como estrategias de enriquecimiento para obtener comunidades hidrogenogénicas, el choque térmico y el lavado celular. Los reactores de biomasa inmovilizada tienen la capacidad de alcanzar mayores concentraciones de biomasa
microbiana, permitiendo mayor eficiencia en la producción de biohidrógeno. Usando reactores granulares de lecho expandido (EGSB), los máximos rendimientos molares (0.92 mol H2/mol de hexosa) y de velocidad volumétrica de producción de hidrógeno (4.23 L H2/L-d), con una carga orgánica de 36 g de glucosa/L-d a un tiempo de retención de 10 h con lodo tratado por lavado celular. En reactores anaerobios de lecho fluidificado (AFB), el lodo tratado por lavado celular produjo valores máximos de volumen de producción y
rendimiento molar de 7 L H2/L-d y 3.5 mol H2/mol hexosa, respectivamente a una carga de 60 g de glucosa y 6 h de tiempo de retención. En ambos casos el lavado celular produjo mejores rendimientos y desempeño en general del reactor que lo obtenido usando inóculo tratado térmicamente, a pesar de ser este último el más ampliamente reportado. Ambos reactores mostraron alta abundancia de miembros de los taxa Clostridia, Enterobacteriaceae y bacterias ácido lácticas. En reactores EGSB, miembros de la familia
Enterobacteriaceae en conjunto tuvieron una abundancia relativa mayor, pero los aumentos en la producción de hidrógeno estaban relacionados con el aumento en la presencia de miembros del género Clostridium. En el caso de reactores AFB, Clostridium fue el principal componente de la comunidad. Las bacterias ácido lácticas, principalmente de los géneros Lactobacillus, Sporolactobacillus y Lactococcus estuvieron presentes durante la operación de ambos tipos de reactores, estando relacionados en ambos casos con disminuciones en la producción de hidrógeno. En general, los reactores AFB mostraron
mayor abundancia de Clostridia en comparación con EGSB, indicando una selección positiva por parte del carbón activado granular usado como soporte inerte y el régimen hidrodinámico obtenido por la configuración del reactor. El papel de los diferentes grupos funcionales ecológicos en la producción de hidrógeno también fue estudiado, observando que aunque Clostridium es el principal productor de hidrógeno, otros géneros como Megasphaera pueden también participar activamente aún cuando el sustrato principal se ha consumido, aumentando la producción y mejorando el desempeño. Aunque la
configuración del reactor tiene un efecto directo e inmediato en el rendimiento del hidrógeno, es la estructura y composición de la microbiota que constituye la biomasa que determina el potencial para la producción de hidrógeno en condiciones adecuadas.""It is considered that hydrogen will have great relevance as a fuel in the near future, even going so far as to speak of a hydrogen-based economy, since besides of being used directly it is possible to use it as an energy intermediary carrier. However, although the technology for its use has already several decades of development, its production still depends to a great extent on the fossil fuels. One of the most promising methods is the dark fermentation, by means of which the physiological characteristics of bacteria growing in anaerobic conditions are exploited. There are a variety of parameters that influence biohydrogen production by dark fermentation, such as hydraulic residence time, organic loading rate, pH, type of substrate and characteristics of the inoculum. Most of these parameters have already been studied and described in the literature. However, little has been achieved to clarify the interdependence and other interactions between the different components of the anaerobic microbial community that allows high rates in hydrogen production. These communities exist naturally, and are intercalated with methane producers. For this reason, the most common source of inoculum for the production of methane are natural ones and / or treatment plants, which need to be pre-treated to inhibit all methanogenic activity. In this thesis two different pretreatments were evaluated as enrichment strategies to obtain hydrogenogenic communities, thermal shock and cell washout. The immobilized biomass reactors have the capacity to reach higher concentrations of microbial biomass, allowing greater efficiency in the production of biohydrogen. Using expanded granular sludge bed (EGSB) reactors, maximum molar yield (0.92 mol H2 / mol hexose) and volumetric hydrogen production rate (4.23 L H2/L-d) with an organic loading rates of 36 g glucose/L-d at HRT of 10 h with cell wash-out pretreated sludge. In anaerobic fluidized bed (AFB) reactors, sludge that was pretreated with cell wash-out produced maximum volumetric and molar yield values of 7 L H2/L-d and 3.5 mol H2/mol hexose, respectively, at 60 g glucose/L-d and HRT of 6 h. In both cases cell wash-out produced better yields and overall performance of reactor than that obtained using thermally treated inoculum, despite being the latter the most widely reported in the literature. Both reactors showed abundance mainly in members of Clostridia, Enterobacteriaceae and lactic acid bacteria taxa.
Photosynthetically active radiation and carbon gain drives the southern orientation of Myrtillocactus geometrizans fruits
Get PDF"The equatorial orientation of reproductive structures is known in some columnar cacti from extratropical deserts. It has been hypothesised that photosynthetically active radiation (PAR) interception is the main reason for this orientation, because of its key effect on nocturnal CO2 uptake. However, there are no studies addressing both the effect of PAR and its consequence, carbon gain, on fruit orientation. Accordingly, we tested whether PAR and carbon gain could explain the southern fruit orientation of Myrtillocactus geometrizans, an inter-tropical columnar cactus. We studied three populations of M.geometrizans in Mexico. For each population, azimuth of fruits, total daily PAR, nocturnal acid accumulation (NAA) and fruit production were measured. The relationships between rib orientation and number of fruits, as well as total daily PAR, were evaluated using periodic regressions. The effect of total daily PAR and NAA on number of fruits was assessed using generalised linear models. During spring, mean fruit orientation had a south azimuth for three populations. Likewise, rib orientation had a significant effect on fruit production, with the south-facing ribs having the maximum number of fruits. Total daily PAR was highest in the south-facing ribs, at least for those in the northern and central populations. Furthermore, during spring, there was a significant positive effect of total daily PAR and NAA on fruit production. Our results provide strong evidence that the higher carbon gain in equatorial ribs, through a highest interception of PAR, would be the responsible factor for equatorial orientation of fruits in an inter-tropical columnar cactus.
Magnetic matrices used in high gradient magnetic separation (HGMS): a review
Get PDF"HGMS is effective in separating or filtering fine and weakly magnetic particles and widely applied in mineral processing, water treatment, cell and protein purification. The magnetic matrix is a crucial device used in magnetic separator to generate high magnetic field gradient and provide surface sites for capturing magnetic particles. The material, geometry, size and arrangement of the matrix elements can significantly affect the gradient and distribution of the magnetic field, and the separating or filtrating performance. In this paper, the researches and developments of magnetic matrices used in HGMS are reviewed.
Transformation behavior and inverse caloric effects in magnetic shape memory Ni44-xCuxCo6Mn39Sn11 ribbons
Get PDF"An influence of the Cu doping on structural, magnetic and thermoelastic properties of the Heusler Ni44-xCuxCo6Mn39Sn11 (x = 1–4 at%) ribbons has been investigated. It is found that the addition of Cu stabilizes austenite phase. Martensite transformation (MT) temperatures generally decrease when Cu concentration increases, which is attributed to the atom size effect. The inverse magnetocaloric and elastocaloric effects in the vicinity of MT under moderate magnetic fields and stresses have been evaluated. Small Cu addition enhances both effects as compared to quaternary Ni–Co–Mn–Sn alloy. The magnetic entropy change under low magnetic field of 15 kOe increases from 2.9 J kg−1K−1 for Cu0 to 6.3 J kg−1K−1 for Cu2.
Precambrian plate tectonic setting of Africa from multidimensional discrimination diagrams
Get PDF"New multi-dimensional discrimination diagrams have been used to identify plate tectonic setting of Precambrian terrains. For this work, nine sets of new discriminant-function based multi-dimensional discrimination diagrams were applied for thirteen case studies of Precambrian basic, intermediate and acid magmas from Africa to highlight the application of these diagrams and probability calculations. The applications of these diagrams indicated the following results: For northern Africa: to Wadi Ghadir ophiolite, Egypt indicated an arc setting for Neoproterozoic (746 ± 19 Ma). For South Africa: Zandspruit greenstone and Bulai pluton showed a collision and a transitional continental arc to collision setting at about Mesoarchaean and Neoarchaean (3114 ± 2.3 Ma and 2610-2577 Ma); Mesoproterozoic (1109 ± 0.6 Ma and 1100 Ma) ages for Espungabera and Umkondo sills were consistent with an island arc setting. For eastern Africa, Iramba–Sekenke greenstone belt and Suguti area, Tanzania showed an arc setting for Neoarchaean (2742 ± 27 Ma and 2755 ± 1 Ma). Chila, Bulbul-Kenticha domain, and Werri area indicated a continental arc setting at about Neoproterozoic (800-789 Ma); For western Africa, Sangmelima region and Ebolowa area, southern Cameroon indicated a collision and continental arc setting, respectively for Neoarchaean (?2800–2900 Ma and 2687-2666 Ma); Finally, Paleoproterozoic (2232-2169 Ma) for Birimian supergroup, southern Ghana a continental arc setting; and Paleoproterozoic (2123-2108 Ma) for Katiola-Marabadiassa, Côte d'Ivoire a transitional continental arc to collision setting. Although there were some inconsistencies in the inferences, most cases showed consistent results of tectonic settings. These inconsistencies may be related to mixed ages, magma mixing, crustal contamination, degree of mantle melting, and mantle versus crustal origin.
Synthesis of mesoporous materials of SiO2 and its applications in azoxybenzene synthesis and Tetraselmis suecica inactivation
No full textTesis de maestría Nanociencias y Materiales"Recientemente, los materiales mesoporosos a base de dióxido de silicio han adquirido atención relevante debido a sus excelentes propiedades como área superficial alta y tamaño de poro controlable que los hacen útiles tanto en aplicaciones biológicas y químicas.
En este trabajo fue realizada la inactivación de la microalga T. suecica causante de la marea verde por medio de FWGS y perlitas recubiertas con Ag-SiO2 y Ag-Al2O3 obtenidas por el método de sonoquímica usando como agente estabilizante PVA, obteniendo el mejor resultado con el uso de FWGS recubiertas con Ag-Al2O3 dejando sólo el 6% de microalga viva después de 24 h. Así mismo, fue evaluada la liberación controlada de carvacrol, una molécula orgánica con propiedades antimicrobianas, sin embargo, el uso de ésta ocasiono un decremento del 50% en la población de las microalgas después de 8 h.
Considerando los resultados obtenidos las Ag-Al2O3/FWGS podrían ser una opción para resolver la problemática de la marea verde.
Por otro lado, fue realizada la síntesis de azoxibenceno por medio de la oxidación de anilina usando H2O2 como agente oxidante en presencia de catalizadores a base de SiO2 modificados con TiO2, WO3 y AgNPs. Los mejores resultados fueron obtenidos con Ag-SiO2 imp. siendo 70% de conversión de anilina, 70% de selectividad a azoxibenceno con 50% de rendimiento.""Recently, mesoporous materials based on siliceous dioxide have acquired a lot of attention due to their excellent features such as high surface area and controllable pore size that make them useful both in biological and chemical applications.
In this thesis, we achieved the inactivation of the T. suecica microalgae, which is responsible for the green tide, by means of FWGS and perlites coated with Ag-SiO2 and Ag-Al2O3 obtained by sonochemical method using PVA as stabilizing agent. The best result was obtained with FWGS coated with Ag-Al2O3 leaving only 6% of microalgae alive after 24 h. In addition, the controlled release of carvacrol, an organic molecule with antimicrobial properties, has been evaluated. However, its use caused a 50% decrease in the microalgae population after 8 h.
According to our results, Ag-Al2O3/FWGS could be employed to solve the problem of the green tide.
On the other hand, the azoxybenzene synthesis by the aniline oxidation using H2O2 as oxidizing agent was performed in the presence of SiO2 catalysts modificated with TiO2, WO3 and AgNPs. The best results were obtained with Ag-SiO2 imp. being 70% aniline conversion, 70% selectivity to azoxybenzene and 50% yield.
Activation of neuronal ensembles via controlled synchronization
Get PDF"In this contribution we present the activation of neuronal ensembles of Hindmarsh-Rose neurons by controlled synchronization. The main problem consists in to impose a particular spiking-bursting behavior in all the neurons of the network. We consider a network where the neurons are in its resting state, it is desired that the neurons change their resting state to a particular behavior of activation, dictated by a neuron called the reference neuron. The goal is reached by controlling some neurons in the network controlling only the membrane potential (electrical synapse). The key feature of the present contribution is that by controlling a small number of neurons in the network a desired behavior is induced in all the neurons in the network despite its network topology. The important parameters are the control gain and the coupling strength, thus the activation of the network lays down on a compromise between the control gain and the coupling strength.
Histone deacetylase HDA-2 regulates Trichoderma atroviride growth, conidiation, blue light perception, and oxidative stress responses
No full text"Fungal blue-light photoreceptors have been proposed as integrators of light and oxidative stress. However, additional elements participating in the integrative pathway remain to be identified. In Trichoderma atroviride, the blue-light regulator (BLR) proteins BLR-1 and -2 are known to regulate gene transcription, mycelial growth, and asexual development upon illumination, and recent global transcriptional analysis revealed that the histone deacetylase-encoding gene hda-2 is induced by light. Here, by assessing responses to stimuli in wild-type and ?hda-2 backgrounds, we evaluate the role of HDA-2 in the regulation of genes responsive to light and oxidative stress. ?hda-2 strains present reduced growth, misregulation of the con-1 gene, and absence of conidia in response to light and mechanical injury. We found that the expression of hda-2 is BLR-1 dependent and HDA-2 in turn is essential for the transcription of early and late light-responsive genes that include blr-1, indicating a regulatory feedback loop. When subjected to reactive oxygen species (ROS), ?hda-2 mutants display high sensitivity whereas ?blr strains exhibit the opposite phenotype. Consistently, in the presence of ROS, ROS-related genes show high transcription levels in wild-type and ?blr strains but misregulation in ?hda-2 mutants. Finally, chromatin immunoprecipitations of histone H3 acetylated at Lys9/Lys14 on cat-3 and gst-1 promoters display low accumulation of H3K9K14ac in ?blr and ?hda-2 strains, suggesting indirect regulation of ROS-related genes by HDA-2. Our results point to a mutual dependence between HDA-2 and BLR proteins and reveal the role of these proteins in an intricate gene regulation landscape in response to blue light and ROS.