Formación de enlaces dobles carbon-carbon promovidos con R3P y metales electropositivos

Tesis (Maestría en Ciencias con Especialidad en Química Orgánica) UANL

Effects of atmospheric carbon dioxide fertilization on biomass and secondary metabolites of some plant species with pharmacological interes under greenhouse conditions

RESUMEN El aumento del CO2 atmosférico debido al cambio global y/o a las prácticas hortícolas promueve efectos directos sobre crecimiento vegetal y el desarrollo. Estas respuestas pueden ocurrir en ecosistemas naturales, pero también se pueden utilizar para aumentar la producción de algunas plantas y de algunos compuestos secundarios. El actual trabajo intenta estudiar los efectos del enriquecimiento atmosférico del CO2 bajo condiciones de invernadero en el crecimiento y la concentración y la composición de metabolitos secundarios de Taxus bacatta, Hypericum perforatum y Echinacea purpurea en condiciones ambientales mediterráneas. La fertilización del CO2 muestra perspectivas interesantes para la mejorara y aplicabilidad de técnicas hortícolas para aumentar productividad de plantas medicinales, a pesar de diferencias claras entre la especie. En general esta técnica promueve aumentos importantes y significativos en producción primaria y, en algunos casos, también en compuestos secundarios. Esto tiene una gran importancia hortícola porque la productividad a nivel de cosecha total aumenta, directamente porque se aumenta la concentración e indirectamente porque se aumenta la biomasa. SUMMARY The increase of atmospheric CO2 due to global change and/or horticultural practices promotes direct effects on plant growth and development. These responses may occur in natural ecosystems, but also can be used to increase the production of some plants and some secondary compounds. Present work tries to study the effects of atmospheric CO2 enrichment under greenhouse conditions on growth and in the concentration and composition of secondary metabolites of Taxus bacatta, Hypericum perforatum and Echinacea purpurea under Mediterranean environmental conditions. CO2 fertilization shows interesting perspectives to increase and improve horticultural techniques in order to increase plant medicinal productivity, in spite of clear differences among the species. In general this technique promotes important and significant increases in primary productivity and, in some cases, also in secondary compounds. This has a great horticultural relevance because the total productivity of this kind of products increase at crop level, directly because concentration is increased and /or indirectly because biomass is increased. RESUM L'augment del CO2 atmosfèric a causa del canvi global i/o a les pràctiques hortícoles promou efectes directes sobre creixement vegetal i el desenvolupament. Aquestes respostes poden ocórrer en ecosistemes naturals, però també es poden utilitzar per a augmentar la producció d'algunes plantes i d'alguns compostos secundaris. L'actual treball intenta estudiar els efectes de l'enriquiment atmosfèric del CO2 sota condicions d'hivernacle en el creixement i la concentració i la composició de metabòlits secundaris de Taxus bacatta, Hypericum perforatum i Echinacea purpurea en condicions ambientals mediterrànies. La fertilització del CO2 mostra perspectives interessants per a la millora i aplicabilitat de tècniques hortícoles per a augmentar productivitat de plantes medicinals, a pesar de diferències clares entre l'espècie. En general aquesta tècnica promou augments importants i significatius en producció primària i, en alguns casos, també en compostos secundaris. Això té una gran importància hortícola perquè la productivitat a nivell de collita total augmenta, directament perquè s'augmenta la concentració i indirectament perquè s'augmenta la biomassa.

Procesos secuenciales de adsorción/oxidación con H2O2 para la eliminación de compuestos orgánicos volátiles

Volatile Organic Compounds (VOCs) are one of the main groups of odour causing compounds in Waste Water Treatment Plants (WWTP). Adsorption technology is already established, in recent years the interest for the optimization of the costs associated with this technique has grown significantly. In particular, there are different options, from the use of low cost adsorbents, to reducing costs associated with carbon regeneration process. In this thesis, the adsorption of the three VOCs on sewage sludge based adsorbents was studied. It was proved that adsorbents obtained by chemical activation of sewage sludge with alkaline hydroxides are comparable to commercial activated carbons (ACs). Likewise, the adsorption of multicomponent gaseous streams was also studied. Related to the ACs regeneration, it was proposed a regeneration treatment of VOC saturated ACs with H2O2 based on advanced oxidation processes (AOP). The influence of the surface chemistry of ACs in this regeneration process was also studied.

Análisis de elementos de madera reforzados con materiales compuestos

Gran parte del patrimonio construido cuenta con edificios cuya estructura está compuesta por elementos de madera. El volumen económico que supone el mantenimiento y renovación de dicho patrimonio es considerable, por ello, es de especial interés el estudio de las diferentes técnicas de refuerzo aplicables a este tipo de estructuras. Las estructuras de madera han sido tradicionalmente reforzadas con piezas del mismo material, aumentando la sección de los elementos dañados, o con acero. La aparición de los materiales compuestos de polímeros reforzados con fibras, y su progresiva aplicación en obras de construcción, hizo que a principios de la década de los noventa se comenzara a aplicar este material en refuerzos de estructuras de madera (Puente de Sins, 1992). La madera es un material natural con una excelente relación entre sus características mecánicas y su peso. Con el uso de materiales compuestos como refuerzo ésta característica se mantiene. En cuanto a su modelo constitutivo, se admite un comportamiento elástico lineal a tracción paralela a la fibra hasta la rotura, mientras que a compresión, se considera un comportamiento lineal elástico inicial, seguido de un tramo plástico. En vigas de madera aserrada sometidas a flexión predomina el modo de fallo por tracción localizándose la fractura frecuentemente en el canto inferior. Los FRP tienen un comportamiento elástico lineal a tracción hasta la rotura y cuentan con excelentes propiedades mecánicas en relación a su peso y volumen. Si se refuerza la viga por el canto inferior se aumentará su capacidad de absorber tracciones y por tanto, es previsible que se produzca un incremento en la capacidad de carga, así como un aumento de ductilidad. En este trabajo se analizan los beneficios que aportan distintos sistemas de refuerzos de materiales compuestos. El objetivo es contribuir al conocimiento de esta técnica para la recuperación o aumento de las propiedades resistentes de elementos de madera sometidos a flexión. Se ha llevado a cabo un estudio basado en datos obtenidos experimentalmente mediante el ensayo a flexión de vigas de madera de pino silvestre reforzadas con materiales compuestos. Las fibras que componen los tejidos utilizados para la ejecución de los refuerzos son de basalto y de carbono. En el caso de los compuestos de fibra de basalto se aplican en distintos gramajes, y los de carbono en tejido unidireccional y bidireccional. Se analiza el comportamiento de las vigas según las variables de refuerzo aplicadas y se comparan con los resultados de vigas ensayadas sin reforzar. Además se comprueba el ajuste del modelo de cálculo no lineal aplicado para predecir la carga de rotura de cada viga reforzada. Con este trabajo queda demostrado el buen funcionamiento del FRP de fibra de basalto aplicado en el refuerzo de vigas de madera y de los tejidos de carbono bidireccionales con respecto a los unidireccionales. ABSTRACT Many of the buildings of the built heritage include a structure composed by timber elements. The economic volume involved in the maintenance and renewal of this built heritage is considerable, therefore, the study of the different reinforcement techniques applicable to this type of structure is of special interest. The wooden structures have traditionally been reinforced either with steel or with pieces of the same material, increasing the section of the damaged parts. The emergence of polymer composites reinforced with fibers, and their progressive use in construction, started to be applied as reinforcement in timber structures at the beginning of the nineties decade in the 20th century (Sins Bridge, 1992). Wood is a natural material with an excellent ratio between its mechanic characteristics and its weight. This feature is maintained with the use of composites as reinforcement. In terms of its constitutive model, linear elastic behavior parallel to the fiber up to fracture is admitted when subjected to tensile stress, while under compression, an initial linear elastic behavior, followed by a section plasticizing, is considered. In sawn timber beams subjected to bending, the predominant failure is mainly due to tensile stress; and frequently the fracture is located at the beam lower face. The FRP have a linear elastic behavior until fracture occurs, and have excellent mechanical properties in relation to their weight and volume. If the beam is reinforced by its lower face, its capacity to absorb tensile stresses will increase, and therefore, an increase in its carrying capacity is likely to be produced, as well as an increase in ductility. This work analyzes the benefits different reinforcement systems of composite materials provide, with the aim of contributing to the knowledge of this technique for recovering or increasing the strength properties of timber elements subjected to bending loads. It is a study based on data obtained experimentally using bending tests of pine timber beams reinforced with composite materials. Fibers used for the execution of the reinforcement are basalt and carbon. Basalt fiber composites are applied in different grammages, whereas with carbon composites, unidirectional and bidirectional fabrics are used. The behavior of the beams was analyzed regarding the reinforcement variables applied, and the results are compared with those of the tested beams without reinforcement. Furthermore it has been proved adjunting the nonlinear calculation model applied to predict the failure load of each reinforced beam. This work proves the good behavior of fiber reinforce plastic (FRP) with basalt fiber when applied to timber beams, and that of bidirectional carbon fabrics as opposed to the unidirectional ones.

Bending reinforcement of timber beams with composite carbon fiber and basalt fiber materials

En el presente trabajo se lleva a cabo un estudio basado en datos obtenidos experimentalmente mediante el ensayo a flexión de vigas de madera de pino silvestre reforzadas con materiales compuestos. Las fibras que componen los tejidos utilizados para la ejecución de los refuerzos son de basalto y de carbono. En el caso de los compuestos de fibra de basalto se aplican en distintos gramajes, y los de carbono en tejido unidireccional y bidireccional. El material compuesto se realizó in situ, simultáneamente a la ejecución del refuerzo. Se aplicaron en una y en dos capas, según el caso, y la forma de colocación fue en ?U?, adhiriéndose al canto inferior y a las caras laterales de la viga mediante resina o mortero epoxi. Se analiza el comportamiento de las vigas según las variables de refuerzo aplicadas y se comparan con los resultados de vigas ensayadas sin reforzar. Con este trabajo queda demostrado el buen funcionamiento del FRP de fibra de basalto aplicado en el refuerzo de vigas de madera y de los tejidos de carbono bidireccionales con respecto a los unidireccionales.

Comportamiento de pilares de hormigón armado confinados con materiales compuestos sometidos a compresión centrada

En la actualidad muchas estructuras de hormigón armado necesitan ser reforzadas debido a diversas razones: errores en el proyecto o construcción, deterioro debido a efectos ambientales, cambios de uso o mayores requerimientos en los códigos. Los materiales compuestos, también conocidos como polímeros reforzados con fibras (FRP), están constituidos por fibras continuas de gran resistencia y rigidez embebidas en un material polimérico. Los FRP se utilizan cada vez más en aplicaciones estructurales debido a sus excelentes propiedades (elevadas resistencia y rigidez específicas y resistencia a la corrosión). Una de las aplicaciones más atractivas es el refuerzo de pilares mediante confinamiento para incrementar su resistencia y ductilidad. El confinamiento puede conseguirse pegando capas de FRP envolviendo el pilar en la dirección de los cercos (con las fibras orientadas en dirección perpendicular al eje del elemento). Se han realizado numerosos estudios experimentales en probetas cilíndricas pequeñas confinadas con encamisados de FRP y sometidas a compresión axial, y se han propuesto varios modelos sobre el hormigón confinado con FRP. Es sabido que el confinamiento de pilares de sección no circular es menos eficiente. En una sección circular, el FRP ejerce una presión de confinamiento uniforme sobre todo el perímetro, mientras que en una sección rectangular la acción de confinamiento se concentra en las esquinas. Esta tesis presenta los resultados de una investigación experimental sobre el comportamiento de probetas de hormigón de sección cuadrada confinadas con FRP y sometidas a compresión centrada. Se realizaron un total de 42 ensayos investigándose el comportamiento en las direcciones axial y transversal. Las variables del estudio incluyen: la resistencia del hormigón, el tipo de fibras (vidrio o carbono), la cuantía de refuerzo y el radio de curvatura de las esquinas. Los resultados de los ensayos realizados muestran que el confinamiento con FRP puede mejorar considerablemente la resistencia y ductilidad de pilares de hormigón armado de sección cuadrada con las esquinas redondeadas. La mejora conseguida es mayor en los hormigones de baja resistencia que en los de resistencia media. La deformación de rotura de la camisa de FRP es menor que la que se obtiene en ensayos de tracción normalizados del laminado, y la eficiencia del confinamiento depende en gran medida del radio de redondeo de las esquinas. Los resultados se han comparado con los obtenidos según los modelos teóricos más aceptados. Hay dos parámetros críticos en el ajuste de los modelos: el factor de eficiencia de la deformación y el efecto de confinamiento en secciones no circulares. Nowadays, many existing RC structures are in need of repair and strengthening for several reasons: design or construction errors, deterioration caused by environmental effects, change in use of the structures or revisions of code requirements. Composite materials, also known as fibre reinforced polymers (FRP), are composed of high strength and stiffness continuous fibres embedded in a polymer material. FRP materials are being increasingly used in many structural applications due to their excellent properties (high strength- and stiffness-toweight ratio, good corrosion behaviour). One of the most attractive applications of FRP is the confinement of concrete columns to enhance both strength and ductility. Concrete confinement can be achieved by bonding layers of hoop FRP around the column (fibres oriented perpendicular to the longitudinal axis). Many experimental studies have been conducted on small-scale plain concrete specimens of circular cross-sections confined with FRP and subjected to pure axial compressive loading, and several design models have been proposed to describe the behaviour of FRP-confined concrete. It is widely accepted that the confinement of non-circular columns is less efficient than the confinement of circular columns. In a circular cross section, the jacket exerts a uniform confining pressure over the entire perimeter. In the case of a rectangular cross section, the confining action is mostly concentrated at the corners. This thesis presents the results of a comprehensive experimental investigation on the behaviour of axially loaded square concrete specimens confined with FRP. A total of 42 compression tests were conducted, and the behaviour of the specimens in the axial and transverse directions were investigated. The parameters considered in this study are: concrete strength, type of fibres (glass or carbon), amount of FRP reinforcement and corner radius of the cross section. The tests results indicate that FRP confinement can enhance considerably the compressive strength and ductility of RC square columns with rounded corners. The enhancement is more pronounced for low- than for normal-strength concrete. The rupture strain of the FRP jacket is lower than the ultimate strain obtained by standard tensile testing of the FRP material, and the confinement efficiency significantly depends on the corner radius. The confined concrete behaviour was predicted according to the more accepted theoretical models and compared with experimental results. There are two key parameters which critically influence the fitting of the models: the strain efficiency factor and the effect of confinement in non-circular sections.

Graphene And Carbon Nanotube Nanocomposite For Gene Transfection.

Graphene and carbon nanotube nanocomposite (GCN) was synthesised and applied in gene transfection of pIRES plasmid conjugated with green fluorescent protein (GFP) in NIH-3T3 and NG97 cell lines. The tips of the multi-walled carbon nanotubes (MWCNTs) were exfoliated by oxygen plasma etching, which is also known to attach oxygen content groups on the MWCNT surfaces, changing their hydrophobicity. The nanocomposite was characterised by high resolution scanning electron microscopy; energy-dispersive X-ray, Fourier transform infrared and Raman spectroscopies, as well as zeta potential and particle size analyses using dynamic light scattering. BET adsorption isotherms showed the GCN to have an effective surface area of 38.5m(2)/g. The GCN and pIRES plasmid conjugated with the GFP gene, forming π-stacking when dispersed in water by magnetic stirring, resulting in a helical wrap. The measured zeta potential confirmed that the plasmid was connected to the nanocomposite. The NIH-3T3 and NG97 cell lines could phagocytize this wrap. The gene transfection was characterised by fluorescent protein produced in the cells and pictured by fluorescent microscopy. Before application, we studied GCN cell viability in NIH-3T3 and NG97 line cells using both MTT and Neutral Red uptake assays. Our results suggest that GCN has moderate stability behaviour as colloid solution and has great potential as a gene carrier agent in non-viral based therapy, with low cytotoxicity and good transfection efficiency.

Carbon Nanoparticles For Gene Transfection In Eukaryotic Cell Lines.

For the first time, oxygen terminated cellulose carbon nanoparticles (CCN) was synthesised and applied in gene transfection of pIRES plasmid. The CCN was prepared from catalytic of polyaniline by chemical vapour deposition techniques. This plasmid contains one gene that encodes the green fluorescent protein (GFP) in eukaryotic cells, making them fluorescent. This new nanomaterial and pIRES plasmid formed π-stacking when dispersed in water by magnetic stirring. The frequencies shift in zeta potential confirmed the plasmid strongly connects to the nanomaterial. In vitro tests found that this conjugation was phagocytised by NG97, NIH-3T3 and A549 cell lines making them fluorescent, which was visualised by fluorescent microscopy. Before the transfection test, we studied CCN in cell viability. Both MTT and Neutral Red uptake tests were carried out using NG97, NIH-3T3 and A549 cell lines. Further, we use metabolomics to verify if small amounts of nanomaterial would be enough to cause some cellular damage in NG97 cells. We showed two mechanisms of action by CCN-DNA complex, producing an exogenous protein by the transfected cell and metabolomic changes that contributed by better understanding of glioblastoma, being the major finding of this work. Our results suggested that this nanomaterial has great potential as a gene carrier agent in non-viral based therapy, with low cytotoxicity, good transfection efficiency, and low cell damage in small amounts of nanomaterials in metabolomic tests.

A Highly Improved Method For Sensitive Determination Of Amitriptyline In Pharmaceutical Formulations Using An Unmodified Carbon Nanotube Electrode In The Presence Of Sulfuric Acid.

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

One-dimensional Silicon And Germanium Nanostructures With No Carbon Analogues.

In this work we report new silicon and germanium tubular nanostructures with no corresponding stable carbon analogues. The electronic and mechanical properties of these new tubes were investigated through ab initio methods. Our results show that these structures have lower energy than their corresponding nanoribbon structures and are stable up to high temperatures (500 and 1000 K, for silicon and germanium tubes, respectively). Both tubes are semiconducting with small indirect band gaps, which can be significantly altered by both compressive and tensile strains. Large bandgap variations of almost 50% were observed for strain rates as small as 3%, suggesting their possible applications in sensor devices. They also present high Young's modulus values (0.25 and 0.15 TPa, respectively). TEM images were simulated to help in the identification of these new structures.

Evaluation Of The Cytotoxicity And Phototoxicity Of Caryocar Brasiliense Supercritical Carbon Dioxide Extract.

Caryocar brasiliense Camb (Pequi) is a typical Brazilian Cerrado fruit tree. Its fruit is used as a vitamin source for culinary purposes and as a source of oil for the manufacture of cosmetics. C. brasiliense supercritical CO2 extracts exhibit antimicrobial activity against the bacteria Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus and also possess antioxidant activity. This study was designed to evaluate the in vitro cytotoxicity and phototoxicity of the supercritical CO2 extract obtained from the leaves of this species. In vitro cytotoxicity and phototoxicity of C. brasiliense supercritical CO2 extracts were assessed using a tetrazolium-based colorimetric assay (XTT) and Neutral Red methods. We found that the C. brasiliense (Pequi) extract obtained by supercritical CO2 extraction did not present cytotoxic and phototoxic hazards. This finding suggests that the extract may be useful for the development of cosmetic and/or pharmaceutical products.

Brazilian Natural Fiber (jute) As Raw Material For Activated Carbon Production.

Jute fiber is the second most common natural cellulose fiber worldwide, especially in recent years, due to its excellent physical, chemical and structural properties. The objective of this paper was to investigate: the thermal degradation of in natura jute fiber, and the production and characterization of the generated activated carbon. The production consisted of carbonization of the jute fiber and activation with steam. During the activation step the amorphous carbon produced in the initial carbonization step reacted with oxidizing gas, forming new pores and opening closed pores, which enhanced the adsorptive capacity of the activated carbon. N2 gas adsorption at 77K was used in order to evaluate the effect of the carbonization and activation steps. The results of the adsorption indicate the possibility of producing a porous material with a combination of microporous and mesoporous structure, depending on the parameters used in the processes, with resulting specific surface area around 470 m2.g-1. The thermal analysis indicates that above 600°C there is no significant mass loss.

Supercritical Carbon Dioxide Extraction Of Capsaicinoids From Malagueta Pepper (capsicum Frutescens L.) Assisted By Ultrasound.

Extracts from malagueta pepper (Capsicum frutescens L.) were obtained using supercritical fluid extraction (SFE) assisted by ultrasound, with carbon dioxide as solvent at 15MPa and 40°C. The SFE global yield increased up to 77% when ultrasound waves were applied, and the best condition of ultrasound-assisted extraction was ultrasound power of 360W applied during 60min. Four capsaicinoids were identified in the extracts and quantified by high performance liquid chromatography. The use of ultrasonic waves did not influence significantly the capsaicinoid profiles and the phenolic content of the extracts. However, ultrasound has enhanced the SFE rate. A model based on the broken and intact cell concept was adequate to represent the extraction kinetics and estimate the mass transfer coefficients, which were increased with ultrasound. Images obtained by field emission scanning electron microscopy showed that the action of ultrasonic waves did not cause cracks on the cell wall surface. On the other hand, ultrasound promoted disturbances in the vegetable matrix, leading to the release of extractable material on the solid surface. The effects of ultrasound were more significant on SFE from larger solid particles.

Analysis Of Cellular Adhesion On Superhydrophobic And Superhydrophilic Vertically Aligned Carbon Nanotube Scaffolds.

We analyzed GFP cells after 24h cultivated on superhydrophilic vertically aligned carbon nanotube scaffolds. We produced two different densities of VACNT scaffolds on Ti using Ni or Fe catalysts. A simple and fast oxygen plasma treatment promoted the superhydrophilicity of them. We used five different substrates, such as: as-grown VACNT produced using Ni as catalyst (Ni), as-grown VACNT produced using Fe as catalyst (Fe), VACNT-O produced using Ni as catalyst (NiO), VACNT-O produced using Fe as catalyst (FeO) and Ti (control). The 4',6-diamidino-2-phenylindole reagent nuclei stained the adherent cells cultivated on five different analyzed scaffolds. We used fluorescence microscopy for image collect, ImageJ® to count adhered cell and GraphPad Prism 5® for statistical analysis. We demonstrated in crescent order: Fe, Ni, NiO, FeO and Ti scaffolds that had an improved cellular adhesion. Oxygen treatment associated to high VACNT density (group FeO) presented significantly superior cell adhesion up to 24h. However, they do not show significant differences compared with Ti substrates (control). We demonstrated that all the analyzed substrates were nontoxic. Also, we proposed that the density and hydrophilicity influenced the cell adhesion behavior.

Long-term Decline Of The Amazon Carbon Sink.

Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink probably located in the tropics, particularly in the Amazon. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models.