916 resultados para Especies xerófitas
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CASTELLANO. La introducción de especies exóticas invasoras es una de las causas más importantes de pérdida de biodiversidad. Baccharis halimifolia es una de las 20 especies exóticas invasoras mas perjudiciales en España e invade gran parte de la marisma de Urdaibai. En dicha marisma se aplicaron tratamientos de control mediante la corta y aplicación de herbicida (glifosato) tras los cuales se observó un variable porcentaje de rebrote en función de la salinidad edáfica. Se realizó un experimento en el que las plantas recolectadas en las parcelas tratadas fueron sometidas en el invernadero a un tratamiento de salinidad y a otro de glifosato con el fin de estudiar la interacción entre ambos tratamientos en individuos originados por germinación y por rebrote y las posibles diferencias entre sexos. Se estudiaron los parámetros de biomasa y acumulación de iones sodio. No se han observado diferencias significativas entre los sexos para ninguno de los parámetros. Sin embargo, los rebrotes acumulan más Na+ que los individuos procedentes de germinación y su biomasa disminuye significativamente tras la aplicación de glifosato, únicamente en medio no salino. Nuestros resultados sugieren que los rebrotes de B. halimifolia reaccionan en mayor medida a la salinidad y al glifosato, lo que proporciona información de interés para la gestión.
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Cap. 1. Patrimonialización cultural y natural: un proceso, múltiples aproximaciones. Cap. 2. Comment un musée de ville peut-il être au service des citoyens? Un parcours et quelques pistes d’action. Jean-François Leclerc. Cap. 3. Los museos comunitarios de Kuna Yala y la memoria histórica. Anelio Merry López Cap. 4. Turismo y museos en la ciudad de Valencia. Javier Martí. Cap. 5. La Red de Museos Etnográficos de Asturias: proyecto y realidad. Juaco López Álvarez. Cap. 6. Culturas campesinas y conservación del patrimonio natur-rural. Jaime Izquierdo. Cap. 7. Faire et savoir faire un « territoire patrimonial » : Parc naturel régional du Haut-Jura (France). Olivier Givre. Cap. 8. Espacios naturales y especies salvajes. La construcción de la naturaleza como patrimonio en el Pallars Sobirà, Pirineo catalán. Oriol Beltran e Ismael Vaccaro. Cap. 9. L’histoire au cœur de la cité : l’exemple du laboratoire d’histoire et de patrimoine de Montréal. Joanne Burgess.
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which carne into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean. Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, and Venezuela in 1992. Ecuador withdrew from the IATTC in 1968, Mexico in 1978, Costa Rica in 1979, and Canada in 1984. Costa Rica readhered to the convention in 1989. The Commission held its 51st meeting in Port Vila, Vanuatu, on June 8-10, 1993. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto a la afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacífico oriental. Bajo esta estipulación, la República de Panamá se afilió en 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, y Venezuela en 1992. Ecuador se retiró de la CIAT en 1968, México en 1978, Costa Rica en 1979, y Canadá en 1984. Costa Rica se adhirió de nuevo al Convenio en 1989. La Comisión celebró su 51ª reunión en Port Vila (Vanuatu) del 8 al 10 de junio de 1993. (PDF contains 316 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean. Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, and Venezuela in 1992. Ecuador withdrew from the IATTC in 1968, Mexico in 1978, and Canada in 1984. The Commission held its 53rd meeting in Cumaná, Venezuela, on June 7-8, 1994. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad ydirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto a la afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacífico oriental. Bajo esta estipulación, la República de Panamá seafilióen 1953, Ecuadoren 1961, México en 1964, Canadáen 1968,Japónen 1970, FranciayNicaragua en 1973, Vanuatu en 1990, y Venezuela en 1992. Ecuador se retiró de la CIAT en 1968, México en 1978, y Canadá en 1984. La Comisión celebró su 53a reunión en Cumaná (Venezuela) el 7 y 8 de junio de 1994. (PDF contains 296 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean. Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, and Venezuela in 1992. Ecuador withdrew from the IATTC in 1968, Mexico in 1978, and Canada in 1984. The IATTC held its 55th meeting in La Jolla, California, USA, on June 13-15, 1995. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad ydirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto a la afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacífico oriental. Bajo esta estipulación, la República de Panamá seafilióen 1953, Ecuadoren 1961, México en 1964, Canadáen 1968,Japónen 1970, FranciayNicaragua en 1973, Vanuatu en 1990, y Venezuela en 1992. Ecuador se retiró de la CIAT en 1968, México en 1978, y Canadá en 1984. La CIAT celebró su 55a reunión en La Jolla, California (EE.DU.) del 13 al15 de junio de 1995. (PDF contains 336 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean. Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, and Venezuela in 1992. Ecuador withdrew from the IATTC in 1968, Mexico in 1978, and Canada in 1984. The IATTC held its 57th meeting in La Jolla, California, USA, on October 21-23, 1996. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto a la afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacífico oriental. Bajo esta estipulación, la República de Panamá seafilióen 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, y Venezuela en 1992. Ecuador se retiró de la CIAT en 1968, México en 1978, y Canadá en 1984. La CIAT celebró su 57a reunión en La Jolla, California (EE.DU.) del 21 a123 de octubre de 1996. (PDF contains 360 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean (EPO). Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, Venezuela in 1992, and EI Salvador in 1997. Mexico withdrew from the IATTC in 1978 and Canada in 1984. The 58th meeting of the IATTC was held in San Jose, Costa Rica, on June 3-4, 1997. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto ala afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacifico oriental (OPO). Bajo esta estipulación, la República de Panamá seafilió en 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, Venezuela en 1992, y El Salvador en 1997. México se retiro de la CIAT en 1978, y Canadá en 1984. La CIAT celebró su 58' reunión en San Jose de Costa Rica el 3 y 4 de junio de 1997. (PDF contains 310 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean (EPO). Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, Venezuela in 1992, and El Salvador in 1997. Canada withdrew from the IATTC in 1984. The 60th meeting of the IATTC was held in La Jolla, California, USA, on February 7, 1998. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto ala afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacifico oriental (OPO). Bajo esta estipulación, la República de Panamá seafilió en 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, Venezuela en 1992, y El Salvador en 1997. México se retiro de la CIAT en 1978, y Canadá en 1984. La 60a reunión de la CIAT tuvo lugar el 7 de febrero de 1998. (PDF contains 358 pages.)
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ENGLISH: The Inter-American Tropical Tuna Commission (IATTC) operates under the authority and direction of a convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other governments whose nationals fish for tropical tunas and tuna-like species in the eastern Pacific Ocean (EPO). Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, Venezuela in 1992, and El Salvador in 1997. Canada withdrew from the IATTC in 1984. The 63rd meeting of the IATTC was held in Guayaquil, Ecuador, on June 8-10,1999. SPANISH: La Comisión Interamericana del Atún Tropical (CIAT) funciona bajo la autoridad y dirección de un convenio suscrito originalmente por Costa Rica y los Estados Unidos de América. El convenio, vigente desde 1950, está abierto ala afiliación de cualquier país cuyos ciudadanos pesquen atunes tropicales y especies afines en el Océano Pacifico oriental (OPO). Bajo esta estipulación, la República de Panamá seafilió en 1953, Ecuador en 1961, México en 1964, Canadá en 1968, Japón en 1970, Francia y Nicaragua en 1973, Vanuatu en 1990, Venezuela en 1992, y El Salvador en 1997. México se retiro de la CIAT en 1978, y Canadá en 1984. La 63a reunión de la CIAT tuvo lugar del 8 al 10 de junio de 1999 en Guayaquil (Ecuador). (PDF contains 184 pages.)
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This thesis deals with the oligochaete taxa (Annelida, Clitellata) from several karst units in the Cantabrian region, northern Iberian Peninsula. Groundwater oligochaetes are still poorly known fauna and the area seems to be a promising hotspot for groundwater taxa. Metodology is based on both morphological and molecular analyses. More than 7,000 specimens were collected from five karst units and >60 taxa were identified. Stygobiont oligochaete fauna in the northern Iberian Peninsula is diverse and mostly endemic (range areas <300 km). Three new stygogiont oligochaete species are described: Gianius navarroi Rodriguez & Achurra, 2010, Isochaetides gianii Rodriguez & Achurra, 2010 and Troglodrilus jugeti Achurra et al., 2012; and another four new taxa will be described in the near future. Taxonomic remarks on Lophochaeta ignota Stolc, 1886 and Troglodrilus galarzai (Giani & Rodriguez, 1988) are provided. The controversial separation of L. ignota and Heterochaeta costata Claparède, 1863 from Tubifex Lamarck, 1816 is corroborated by mitochondrial molecular data. Following the DNA barcoding method, individuals of the stygoxene species Stylodrilus heringianus Claparède, 1862 from different geographic areas are shown to represent a single metapopulation. The first phylogenetic analysis of the subfamily Tubificinae based on molecular data is attemped, which although incompletely resolved, evidences for the first time a close relationship between a stygobiont oligochaete (Troglodrilus Juget et al. 2006) and an estuarine especies (Heterochaeta costata Claparéde, 1863). A marine ancestor is hypothesised for Troglodrilus. Finally, Ereñozar karst unit (Biscay) is suggested to be a hotspot for groundwater oligochaetes (11 stygobiont taxa, of which 4 are endemic to the karst unit) and several biodiversity indices (Species richness, Rarity, Vulnerability and Complementarity) are shown to be useful tools for conservation management of groundwater habitats in that karst area.
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Dentro de las medidas protectoras sobre la Reserva de la Biosfera de Urdaibai se encuentra el EDAR (Estación Depuradora de Aguas Residuales) de Lamiaran (Bermeo), que entrará en funcionamiento próximamente (otoño 2014). Para evaluar su impacto sobre el medio costero, el presente estudio realiza una primera valoración del estado ecológico de la costa abierta de la reserva mediante diversos parámetros del fitobentos intermareal. Se estableció una red de muestreo compuesta por dos localidades impactadas y cuatro control. En cada localidad se eligieron aleatoriamente dos estaciones y se muestrearon dos niveles en la zona intermareal inferior. Las localidades impactadas por aguas residuales reflejaban valores bajos de riqueza específica, cobertura, diversidad y cobertura de perennes junto a una mayor abundancia de especies estacionales de morfología simple. Sin embargo los análisis estadísticos no detectaron diferencias significativas entre ambos grupos de localidades (impactadas vs control) detectando únicamente diferencias significativas a nivel de estación, debido en gran medida al efecto de la dispersión de las unidades muestrales para los parámetros estudiados.
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208 p.
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[EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named “Formación de Personal Investigador” at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut für Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks renewable and non-renewable, gases and liquids through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using γ-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30–60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1–3 µm) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625°C and 725°C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on α-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using α-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.
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ENGLISH: In April 1981 the IATTC convened a working group of scientists in Managua, Nicaragua to discuss the tuna-dolphin association and to suggest priorities for future research which would enable the effects of any interaction to be detected or quantified. The yellowfin tuna, Thunnus albacares, fishery in the eastern tropical Pacific is unique in that a significant proportion of the catch is of fish found in association with one or more species of dolphins. This association has never been fully understood but for many years tuna fishermen have used the more visible and more easily herded dolphin schools to help them locate and capture the tuna. In recent years, the concept of managing renewable resources in relation to their environments has been more fully developed. Any renewable resource is closely linked to other components in its general system and it is becoming increasingly more apparent that the harvesting of one resource affects another. This is the case with yellowfin tuna and dolphins in the eastern tropical Pacific, although the dolphins are killed incidental to the fishery and are not harvested. There would seem to be obvious advantages in managing the tuna-dolphin complex as a whole. To do this it is necessary to understand the effect that tuna and dolphins have on each other and the causal mechanisms of the interactions. SPANISH: En abril de 1981, la CIAT convoco un grupo de trabajo de investigadores en Managua (Nicaragua), para deliberar sobre la asociación atún-delfín e indicar prioridades referentes a una investigación futura que pueda facilitar la cuantificación o el reconocimiento de los efectos de cualquier interacción. La pesca del atún aleta amarilla Thunnus albacares en el Pacifico oriental tropical, es única, ya que una proporción importante de su captura es de peces encontrados en asociación con una o mas especies de delfines. No se ha logrado comprender cabalmente esta asociación, pero por varios anos los pescadores atuneros han utilizado los cardúmenes de delfines que son mas visibles y que pueden agruparse mas fácilmente para poder localizar y capturar los atunes. En los últimos anos, el concepto de administrar los recursos renovables con relación a su ambiente, ha tenido mas auge. Cualquier recurso renovable se vincula estrechamente a otros componentes en el sistema general y actualmente es mas evidente que la explotación de un recurso afecta otro. Este es el caso del atún aleta amarilla y de los delfines en el Pacifico oriental tropical aunque los delfines mueren incidentalmente con relación a la pesca y no son explotados. Parece que se obtendr1an ventajas evidentes si se administrara como un todo el conjunto atún-delfín. Para realizar esto es necesario comprender los efectos que tienen los atunes y delfines los unos sabre los otros y los mecanismos causantes de la interacción.
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English: For nearly a century, fisheries scientists have studied marine fish stocks in an effort to understand how the abundances of fish populations are determined. During the early lives of marine fishes, survival is variable, and the numbers of individuals surviving to transitional stages or recruitment are difficult to predict. The egg, larval, and juvenile stages of marine fishes are characterized by high rates of mortality and growth. Most marine fishes, particularly pelagic species, are highly fecund, produce small eggs and larvae, and feed and grow in complex aquatic ecosystems. The identification of environmental or biological factors that are most important in controlling survival during the early life stages of marine fishes is a potentially powerful tool in stock assessment. Because vital rates (mortality and growth) during the early life stages of marine fishes are high and variable, small changes in those rates can have profound effects on the properties of survivors and recruitment potential (Houde 1989). Understanding and predicting the factors that most strongly influence pre-recruit survival are key goals of fisheries research programs. Spanish: Desde hace casi un siglo, los científicos pesqueros han estudiado las poblaciones de peces marinos en un intento por entender cómo se determina la abundancia de las mismas. Durante la vida temprana de los peces marinos, la supervivencia es variable, y el número de individuos que sobrevive hasta las etapas transicionales o el reclutamiento es difícil de predecir. Las etapas de huevo, larval, y juvenil de los peces marinos son caracterizadas por tasas altas de mortalidad y crecimiento. La mayoría de los peces marinos, particularmente las especies pelágicas, son muy fecundos, producen huevos y larvas pequeños, y se alimentan y crecen en ecosistemas acuáticos complejos. La identificación los factores ambientales o biológicos más importantes en el control de la supervivencia durante las etapas tempranas de vida de los peces marinos es una herramienta potencialmente potente en la evaluación de las poblaciones. Ya que las tasas vitales (mortalidad y crecimiento) durante las etapas tempranas de vida de los peces marinos son altas y variables, cambios pequeños en esas tasas pueden ejercer efectos importantes sobre las propiedades de los supervivientes y el potencial de reclutamiento (Houde 1989). Comprender y predecir los factores que más afectan la supervivencia antes del reclutamiento son objetivos clave de los programas de investigación pesquera.