Con el objetivo de evaluar el efecto de la fertilización orgánica (FO: 2000 kg compostaje ha-1) e... more Con el objetivo de evaluar el efecto de la fertilización orgánica (FO: 2000 kg compostaje ha-1) e inorgánica (FI: 200 kg N + 85 kg P ha-1) sobre variables agroproductivas y composición química del pasto estrella, se condujo un ensayo durante el periodo seco en parcelas experimentales ubicadas en un bosque seco tropical, sobre un suelo franco de mediana fertilidad y bajo diseño de bloques al azar con tres repeticiones. Se evaluaron las variables altura de plantas (AP), producción de biomasa verde (BV) y seca (BS), materia seca acumulada (MSA), rendimientos de materia seca en hojas (RMSH) y rendimientos de materia seca en tallos (RMST), así como relación hoja-tallo (RHT), tasa de crecimiento diario (TCD), proteína cruda (PC), cenizas totales (CT), macro y microelementos presentes, a los 21, 35, 49 y 63 días post-fertilización (dpf). Los datos resultantes fueron sometidos a un análisis de varianza y separación de medias mediante la prueba LSD Fisher. La FI mostró un efecto signifi cativamente mayor en promedio para AP (49,8 cm), BV y BS (10952,5 y 3017,5 Kg.ha•corte, respectivamente), excepto para RHT donde no se encontraron diferencias entre los tratamientos. La MSA fue mayor en los pastos bajo FO (30,7%), mientras que los RMSH y RMST (2513 y 1068 Kg•ha-1 , respectivamente) fueron superiores en la FI a los 63 dpf, al igual que la TCD (33,8 g MS•m 2 •día-1). La composición química del pasto no se vio afectada por las fuentes de fertilización empleadas, a excepción del hierro y zinc que disminuyeron signifi cativamente su contenido en las plantas que fueron fertilizadas.
We study a situation in which an auctioneer wishes to sell an object to one of N risk-neutral bid... more We study a situation in which an auctioneer wishes to sell an object to one of N risk-neutral bidders with heterogeneous preferences. The auctioneer does not know bidders ' preferences but has private information about the characteristics of the object, and must decide how much infor-mation to reveal prior to the auction. We show that the auctioneer has incentives to release less information than would be e±cient and that the amount of information released increases with the level of competition (as measured by the number of bidders). Furthermore, in a perfectly competitive market the auctioneer would provide the e±cient level of information.
This study provides new insights into how the soil microbiome of urban greenspaces differs from s... more This study provides new insights into how the soil microbiome of urban greenspaces differs from surrounding natural ecosystems.
Sorensen et al. Roots Mediate Snowpack Decline Effects negatively correlated with ectomycorrhizal... more Sorensen et al. Roots Mediate Snowpack Decline Effects negatively correlated with ectomycorrhizal and saprotrophic fungi, respectively, and these relationships were mediated by root exclusion. The results from this study suggest that a declining winter snowpack and its effect on plant roots each have direct effects on the diversity and abundance of soil bacteria and fungal communities that interact to determine rates of soil N cycling in northern hardwood forests.
Latin American Journal of Solids and Structures, 2018
Fatigue assessments by the more robust strain-based approach demand the determination of the loca... more Fatigue assessments by the more robust strain-based approach demand the determination of the local strain history from nominal stresses. For notched members, a cyclic constitutive relation, the stress concentration factor SCF and a strain concentration rule are used with this aim in some approximate solutions. The plastic part of the cyclic constitutive relations for many materials is well adjusted by a Ramberg-Osgood RO type equation. The parameters in the RO equation are the cyclic strength coefficient and exponent H' and n' respectively. These parameters can be experimentally determined or estimated from the condition of strain compatibility between the RO and the Coffin-Manson-Basquin CMB equations. The present paper discusses the influence that the use of both types of parameters, independent or experimentally determined and compatible or estimated , has on the numerical stress-life curves of the AISI 4340 Aircraft Quality steel. By numerical stress-life curves we mean the stress amplitudes and the fatigue-life that result from the numerical solution of both, the strain-life CMB and the stress-strain RO relations, for the same strain amplitude. This would be equivalent to using a linear strain concentration rule notched members with two RO equations, one with independent parameters and the other with compatible parameters, for stress and life calculations. The effects of the stress state are also accounted for in the present investigation since both, stress-life and stressstrain equations are modified in accordance with the total deformation theory of plasticity and through the introduction of a plane stress biaxial ratio. The principal finding of the present paper is that, for the studied material, the numerical stress-life curves that result from the use of compatible and independent parameters are indistinguishable for the same stress state. Consequently, there are no important implications on life time calculations when the cyclic stress-strain curve is estimated in such a way that compatibility conditions for the AISI 4340 aircraft quality steel are ensured.
All organisms have to cope with spatial and temporal heterogeneity of the environment. At short t... more All organisms have to cope with spatial and temporal heterogeneity of the environment. At short temporal and small spatial scales, organisms may respond by behavioural or physiological mechanisms. To test for physiological adjustments to variation in host quality among tree individuals within a host species, we performed a transfer experiment in a climate chamber using larvae of the polyphagous gypsy moth (Lymantria dispar). We reared larvae for two weeks on leaves of one of three Quercus robur individuals. We found differences in the growth rate of larvae across the host individuals, which indicate that the oak individuals differed in their quality. Furthermore, families of larvae varied in their growth rate and there was variation among the families of gypsy moth larvae in response to leaves from the different oak individuals. After two weeks we offered larvae either leaves of the same or a different individual of the three oaks. We found no effect of transferring larvae to a different tree individual. The results thus do not support the idea of physiological adjustment of a generalist insect herbivore to variation in leaf quality among host individuals.
Snow cover is projected to decline during the next century in many ecosystems that currently expe... more Snow cover is projected to decline during the next century in many ecosystems that currently experience a seasonal snowpack. Because snow insulates soils from frigid winter air temperatures, soils are expected to become colder and experience more winter soil freeze-thaw cycles as snow cover continues to decline. Tree roots are adversely affected by snowpack reduction, but whether loss of snow will affect root-microbe interactions remains largely unknown. The objective of this study was to distinguish and attribute direct (e.g., winter snow- and/or soil frost-mediated) vs. indirect (e.g., root-mediated) effects of winter climate change on microbial biomass, the potential activity of microbial exoenzymes, and net N mineralization and nitrification rates. Soil cores were incubated in situ in nylon mesh that either allowed roots to grow into the soil core (2 mm pore size) or excluded root ingrowth (50 μm pore size) for up to 29 months along a natural winter climate gradient at Hubbard B...
Estonia loses 0.2% to 0.3% of its working age population through emigration each year Emigration ... more Estonia loses 0.2% to 0.3% of its working age population through emigration each year Emigration is driven by a large differential with respect to wages abroad, especially for less-skilled labour Raising the basic tax-exemption and the minimum wage are two options to mitigate disincentives to work at home Caution is warranted with respect to raising the minimum wage given the slowdown of exports
Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a comp... more Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a complex mix of biological and climatic drivers. In excess, N is linked to a variety of soil, water, and air pollution issues. Here, we use results from an elevation gradient study and historical data from the longterm Hubbard Brook Ecosystem Study (New Hampshire, USA) to examine relationships between changes in climate, especially during winter, and N supply to northern hardwood forest ecosystems. Low elevation plots with less snow, more soil freezing, and more freeze/thaw cycles supported lower rates of N mineralization than high elevation plots, despite having higher soil temperatures and no consistent differences in soil moisture during the growing season. These results are consistent with historical analyses showing decreases in rates of soil N mineralization and inorganic N concentrations since 1973 that are correlated with long-term increases in mean annual temperature, decreases in annual snow accumulation, and a increases in the number of winter thawing degree days. This evidence suggests that changing climate may be driving decreases in the availability of a key nutrient in northern hardwood forests, which could decrease ecosystem production but have positive effects on environmental consequences of excess N.
V\UNICODE{0xed}ctor R\UNICODE{0xed}os-Rull, Henri Sneessens, and Claude Wampach, for comments and... more V\UNICODE{0xed}ctor R\UNICODE{0xed}os-Rull, Henri Sneessens, and Claude Wampach, for comments and suggestions. This paper was partly written at the IRES and the CEPREMAP. Jorge Dur\UNICODE{0xe1}n acknowledges financial support from PAI P4/01 project from the Belgian government at IRES and from a European Marie Curie fellowship (Grant HPMF-CT-1999-00410) at CEPREMAP. Alexandra Rillaers acknowledges financial support from FDS and from PAI P4/01 project from the Belgian government at IRES.
La micafungina en el tratamiento de la candidiasis invasiva en pacientes sometidos a trasplante d... more La micafungina en el tratamiento de la candidiasis invasiva en pacientes sometidos a trasplante de órgano sólido Jesús Fortún-Abete 65-68 Utilidad clínica de la micafungina en el tratamiento de las candidiasis invasoras en el paciente crítico
Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American... more Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas. Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses. rs1800497 (ANKK1) shows association with waist circumference (p = 0.00...
Se estudió el efecto de la adición de 1%, 2% y 3% de urea y dos fermentaciones (FAe= aeróbica y F... more Se estudió el efecto de la adición de 1%, 2% y 3% de urea y dos fermentaciones (FAe= aeróbica y FAn= anaeróbica), sobre parámetros fermentativos y microbiológicos en microsilos con caña de azúcar, confeccionados en bolsas de polietileno negro de capacidad 3 Kg. Los tratamientos evaluados fueron: caña sola (testigo) y caña adicionada con 3 niveles de urea en función del peso fresco, sometidos a 2 fermentaciones durante 30 d. Se evaluaron las variables Materia Seca (MS), nitrógeno amoniacal (N-NH 3), pH y recuento de fl ora fúngica, estos dos últimos a las 0, 24 y 48 h de exposición aeróbica post-fermentación. Se utilizó un diseño factorial 4 x 2 (4 tratamientos x 2 fermentaciones) con 3 repeticiones. Los datos obtenidos fueron procesados a través del programa estadístico InfoStat. Se observó mayor porcentaje de MS con la adición de urea al 1% bajo ambas fermentaciones (FAn= 23,02% y FAe= 26,45%), disminuyendo a medida que se incrementó el nivel de urea en los microsilos. En cuanto al porcentaje de N-NH 3 se evidenció un ascenso a medida que se aumentó los niveles de urea, obteniéndose los mayores valores para FAn (2,13%) y FAe (1,45%) al adicionar urea al 3%. Fueron encontrados valores de pH aceptables para la FAn (3,43; 4,38 y 4,54), después de ser sometida la masa ensilada a condiciones aeróbicas durante 0, 24 y 48 h respectivamente, mientras que para FAe (3,26; 3,93 y 5,90) llegó a niveles cercanos a la neutralidad transcurridas 48 h. En cuanto al desarrollo fúngico, se corroboró el efecto fungistático de la urea a partir del 1% de concentración, aún cuando el silo estuvo expuesto al aire por 48 h, siendo Aspergillus sp. la especie más resistente a los tratamientos. En conclusión, la adición de urea al 1% en silajes de caña de azúcar contribuye a mantener la estabilidad del silo una vez expuesto a condiciones aeróbicas pos-fermentación.
We explore an economy with two regions and independent local administrations. Local governments c... more We explore an economy with two regions and independent local administrations. Local governments collect taxes to finance public education, but once educated agents can choose to migrate to the other region. The Nash equilibrium of the long-run game between the two governments is compared to a golden rule-type social optimum. Preliminary results show that the Nash equilibrium will result in
* The authors acknowledge Jeremy Greenwood and Javier Ruiz-Castillo for their valuable comments a... more * The authors acknowledge Jeremy Greenwood and Javier Ruiz-Castillo for their valuable comments and suggestions on some critical issues. This project was initiated while Jorge Durán was an assistant professor at the Univesitat d'Alacant; financial support from IVIE, Generalitat Valenciana, and from the Spanish Ministry of Sciences and Technology under project BEC2001-0535 are gratefully acknowledged. Omar Licandro aknowledges finacial support from the European Commision under contract HPRN-CT-2002-00237, and from the Spanish Ministry of Sciences and Technology under contracts SEJ2004-0459/ECON and ECO2010-17943.
Incoming solar radiation is the main determinant of terrestrial ecosystem processes, such as prim... more Incoming solar radiation is the main determinant of terrestrial ecosystem processes, such as primary production, litter decomposition, or soil mineralization rates. Light in terrestrial ecosystems is spatially and temporally heterogeneous due to the interaction among sunlight angle, cloud cover and tree-canopy structure. To integrate this variability and to know light distribution over time and space, a high number of measurements are needed, but tools to do this are usually expensive and limited. An easy-to-use and inexpensive method that can be used to measure light over time and space is needed. We used two photodegrading fluorescent organic dyes, rhodamine WT (RWT) and fluorescein, for the quantification of light. We measured dye photodegradation as the decrease in fluorescence across an irradiance gradient from full sunlight to deep shade. Then, we correlated it to accumulated light measured with PAR quantum sensors and obtained a model for this behavior. Rhodamine WT and fluorescein photodegradation followed an exponential decay curve with respect to accumulated light. Rhodamine WT degraded slower than fluorescein and remained unaltered after exposure to temperature changes. Under controlled conditions, fluorescence of both dyes decreased when temperatures increased, but returned to its initial values after cooling to the pre-heating temperature, indicating no degradation. RWT and fluorescein can be used to measure light under a varying range of light conditions in terrestrial ecosystems. This method is particularly useful to integrate solar radiation over time and to measure light simultaneously at different locations, and might be a better alternative to the expensive and time consuming traditional light measurement methods. The accuracy, low price and ease of this method make it a powerful tool for intensive sampling of large areas and for developing high resolution maps of light in an ecosystem.
Con el objetivo de evaluar el efecto de la fertilización orgánica (FO: 2000 kg compostaje ha-1) e... more Con el objetivo de evaluar el efecto de la fertilización orgánica (FO: 2000 kg compostaje ha-1) e inorgánica (FI: 200 kg N + 85 kg P ha-1) sobre variables agroproductivas y composición química del pasto estrella, se condujo un ensayo durante el periodo seco en parcelas experimentales ubicadas en un bosque seco tropical, sobre un suelo franco de mediana fertilidad y bajo diseño de bloques al azar con tres repeticiones. Se evaluaron las variables altura de plantas (AP), producción de biomasa verde (BV) y seca (BS), materia seca acumulada (MSA), rendimientos de materia seca en hojas (RMSH) y rendimientos de materia seca en tallos (RMST), así como relación hoja-tallo (RHT), tasa de crecimiento diario (TCD), proteína cruda (PC), cenizas totales (CT), macro y microelementos presentes, a los 21, 35, 49 y 63 días post-fertilización (dpf). Los datos resultantes fueron sometidos a un análisis de varianza y separación de medias mediante la prueba LSD Fisher. La FI mostró un efecto signifi cativamente mayor en promedio para AP (49,8 cm), BV y BS (10952,5 y 3017,5 Kg.ha•corte, respectivamente), excepto para RHT donde no se encontraron diferencias entre los tratamientos. La MSA fue mayor en los pastos bajo FO (30,7%), mientras que los RMSH y RMST (2513 y 1068 Kg•ha-1 , respectivamente) fueron superiores en la FI a los 63 dpf, al igual que la TCD (33,8 g MS•m 2 •día-1). La composición química del pasto no se vio afectada por las fuentes de fertilización empleadas, a excepción del hierro y zinc que disminuyeron signifi cativamente su contenido en las plantas que fueron fertilizadas.
We study a situation in which an auctioneer wishes to sell an object to one of N risk-neutral bid... more We study a situation in which an auctioneer wishes to sell an object to one of N risk-neutral bidders with heterogeneous preferences. The auctioneer does not know bidders ' preferences but has private information about the characteristics of the object, and must decide how much infor-mation to reveal prior to the auction. We show that the auctioneer has incentives to release less information than would be e±cient and that the amount of information released increases with the level of competition (as measured by the number of bidders). Furthermore, in a perfectly competitive market the auctioneer would provide the e±cient level of information.
This study provides new insights into how the soil microbiome of urban greenspaces differs from s... more This study provides new insights into how the soil microbiome of urban greenspaces differs from surrounding natural ecosystems.
Sorensen et al. Roots Mediate Snowpack Decline Effects negatively correlated with ectomycorrhizal... more Sorensen et al. Roots Mediate Snowpack Decline Effects negatively correlated with ectomycorrhizal and saprotrophic fungi, respectively, and these relationships were mediated by root exclusion. The results from this study suggest that a declining winter snowpack and its effect on plant roots each have direct effects on the diversity and abundance of soil bacteria and fungal communities that interact to determine rates of soil N cycling in northern hardwood forests.
Latin American Journal of Solids and Structures, 2018
Fatigue assessments by the more robust strain-based approach demand the determination of the loca... more Fatigue assessments by the more robust strain-based approach demand the determination of the local strain history from nominal stresses. For notched members, a cyclic constitutive relation, the stress concentration factor SCF and a strain concentration rule are used with this aim in some approximate solutions. The plastic part of the cyclic constitutive relations for many materials is well adjusted by a Ramberg-Osgood RO type equation. The parameters in the RO equation are the cyclic strength coefficient and exponent H' and n' respectively. These parameters can be experimentally determined or estimated from the condition of strain compatibility between the RO and the Coffin-Manson-Basquin CMB equations. The present paper discusses the influence that the use of both types of parameters, independent or experimentally determined and compatible or estimated , has on the numerical stress-life curves of the AISI 4340 Aircraft Quality steel. By numerical stress-life curves we mean the stress amplitudes and the fatigue-life that result from the numerical solution of both, the strain-life CMB and the stress-strain RO relations, for the same strain amplitude. This would be equivalent to using a linear strain concentration rule notched members with two RO equations, one with independent parameters and the other with compatible parameters, for stress and life calculations. The effects of the stress state are also accounted for in the present investigation since both, stress-life and stressstrain equations are modified in accordance with the total deformation theory of plasticity and through the introduction of a plane stress biaxial ratio. The principal finding of the present paper is that, for the studied material, the numerical stress-life curves that result from the use of compatible and independent parameters are indistinguishable for the same stress state. Consequently, there are no important implications on life time calculations when the cyclic stress-strain curve is estimated in such a way that compatibility conditions for the AISI 4340 aircraft quality steel are ensured.
All organisms have to cope with spatial and temporal heterogeneity of the environment. At short t... more All organisms have to cope with spatial and temporal heterogeneity of the environment. At short temporal and small spatial scales, organisms may respond by behavioural or physiological mechanisms. To test for physiological adjustments to variation in host quality among tree individuals within a host species, we performed a transfer experiment in a climate chamber using larvae of the polyphagous gypsy moth (Lymantria dispar). We reared larvae for two weeks on leaves of one of three Quercus robur individuals. We found differences in the growth rate of larvae across the host individuals, which indicate that the oak individuals differed in their quality. Furthermore, families of larvae varied in their growth rate and there was variation among the families of gypsy moth larvae in response to leaves from the different oak individuals. After two weeks we offered larvae either leaves of the same or a different individual of the three oaks. We found no effect of transferring larvae to a different tree individual. The results thus do not support the idea of physiological adjustment of a generalist insect herbivore to variation in leaf quality among host individuals.
Snow cover is projected to decline during the next century in many ecosystems that currently expe... more Snow cover is projected to decline during the next century in many ecosystems that currently experience a seasonal snowpack. Because snow insulates soils from frigid winter air temperatures, soils are expected to become colder and experience more winter soil freeze-thaw cycles as snow cover continues to decline. Tree roots are adversely affected by snowpack reduction, but whether loss of snow will affect root-microbe interactions remains largely unknown. The objective of this study was to distinguish and attribute direct (e.g., winter snow- and/or soil frost-mediated) vs. indirect (e.g., root-mediated) effects of winter climate change on microbial biomass, the potential activity of microbial exoenzymes, and net N mineralization and nitrification rates. Soil cores were incubated in situ in nylon mesh that either allowed roots to grow into the soil core (2 mm pore size) or excluded root ingrowth (50 μm pore size) for up to 29 months along a natural winter climate gradient at Hubbard B...
Estonia loses 0.2% to 0.3% of its working age population through emigration each year Emigration ... more Estonia loses 0.2% to 0.3% of its working age population through emigration each year Emigration is driven by a large differential with respect to wages abroad, especially for less-skilled labour Raising the basic tax-exemption and the minimum wage are two options to mitigate disincentives to work at home Caution is warranted with respect to raising the minimum wage given the slowdown of exports
Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a comp... more Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a complex mix of biological and climatic drivers. In excess, N is linked to a variety of soil, water, and air pollution issues. Here, we use results from an elevation gradient study and historical data from the longterm Hubbard Brook Ecosystem Study (New Hampshire, USA) to examine relationships between changes in climate, especially during winter, and N supply to northern hardwood forest ecosystems. Low elevation plots with less snow, more soil freezing, and more freeze/thaw cycles supported lower rates of N mineralization than high elevation plots, despite having higher soil temperatures and no consistent differences in soil moisture during the growing season. These results are consistent with historical analyses showing decreases in rates of soil N mineralization and inorganic N concentrations since 1973 that are correlated with long-term increases in mean annual temperature, decreases in annual snow accumulation, and a increases in the number of winter thawing degree days. This evidence suggests that changing climate may be driving decreases in the availability of a key nutrient in northern hardwood forests, which could decrease ecosystem production but have positive effects on environmental consequences of excess N.
V\UNICODE{0xed}ctor R\UNICODE{0xed}os-Rull, Henri Sneessens, and Claude Wampach, for comments and... more V\UNICODE{0xed}ctor R\UNICODE{0xed}os-Rull, Henri Sneessens, and Claude Wampach, for comments and suggestions. This paper was partly written at the IRES and the CEPREMAP. Jorge Dur\UNICODE{0xe1}n acknowledges financial support from PAI P4/01 project from the Belgian government at IRES and from a European Marie Curie fellowship (Grant HPMF-CT-1999-00410) at CEPREMAP. Alexandra Rillaers acknowledges financial support from FDS and from PAI P4/01 project from the Belgian government at IRES.
La micafungina en el tratamiento de la candidiasis invasiva en pacientes sometidos a trasplante d... more La micafungina en el tratamiento de la candidiasis invasiva en pacientes sometidos a trasplante de órgano sólido Jesús Fortún-Abete 65-68 Utilidad clínica de la micafungina en el tratamiento de las candidiasis invasoras en el paciente crítico
Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American... more Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas. Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses. rs1800497 (ANKK1) shows association with waist circumference (p = 0.00...
Se estudió el efecto de la adición de 1%, 2% y 3% de urea y dos fermentaciones (FAe= aeróbica y F... more Se estudió el efecto de la adición de 1%, 2% y 3% de urea y dos fermentaciones (FAe= aeróbica y FAn= anaeróbica), sobre parámetros fermentativos y microbiológicos en microsilos con caña de azúcar, confeccionados en bolsas de polietileno negro de capacidad 3 Kg. Los tratamientos evaluados fueron: caña sola (testigo) y caña adicionada con 3 niveles de urea en función del peso fresco, sometidos a 2 fermentaciones durante 30 d. Se evaluaron las variables Materia Seca (MS), nitrógeno amoniacal (N-NH 3), pH y recuento de fl ora fúngica, estos dos últimos a las 0, 24 y 48 h de exposición aeróbica post-fermentación. Se utilizó un diseño factorial 4 x 2 (4 tratamientos x 2 fermentaciones) con 3 repeticiones. Los datos obtenidos fueron procesados a través del programa estadístico InfoStat. Se observó mayor porcentaje de MS con la adición de urea al 1% bajo ambas fermentaciones (FAn= 23,02% y FAe= 26,45%), disminuyendo a medida que se incrementó el nivel de urea en los microsilos. En cuanto al porcentaje de N-NH 3 se evidenció un ascenso a medida que se aumentó los niveles de urea, obteniéndose los mayores valores para FAn (2,13%) y FAe (1,45%) al adicionar urea al 3%. Fueron encontrados valores de pH aceptables para la FAn (3,43; 4,38 y 4,54), después de ser sometida la masa ensilada a condiciones aeróbicas durante 0, 24 y 48 h respectivamente, mientras que para FAe (3,26; 3,93 y 5,90) llegó a niveles cercanos a la neutralidad transcurridas 48 h. En cuanto al desarrollo fúngico, se corroboró el efecto fungistático de la urea a partir del 1% de concentración, aún cuando el silo estuvo expuesto al aire por 48 h, siendo Aspergillus sp. la especie más resistente a los tratamientos. En conclusión, la adición de urea al 1% en silajes de caña de azúcar contribuye a mantener la estabilidad del silo una vez expuesto a condiciones aeróbicas pos-fermentación.
We explore an economy with two regions and independent local administrations. Local governments c... more We explore an economy with two regions and independent local administrations. Local governments collect taxes to finance public education, but once educated agents can choose to migrate to the other region. The Nash equilibrium of the long-run game between the two governments is compared to a golden rule-type social optimum. Preliminary results show that the Nash equilibrium will result in
* The authors acknowledge Jeremy Greenwood and Javier Ruiz-Castillo for their valuable comments a... more * The authors acknowledge Jeremy Greenwood and Javier Ruiz-Castillo for their valuable comments and suggestions on some critical issues. This project was initiated while Jorge Durán was an assistant professor at the Univesitat d'Alacant; financial support from IVIE, Generalitat Valenciana, and from the Spanish Ministry of Sciences and Technology under project BEC2001-0535 are gratefully acknowledged. Omar Licandro aknowledges finacial support from the European Commision under contract HPRN-CT-2002-00237, and from the Spanish Ministry of Sciences and Technology under contracts SEJ2004-0459/ECON and ECO2010-17943.
Incoming solar radiation is the main determinant of terrestrial ecosystem processes, such as prim... more Incoming solar radiation is the main determinant of terrestrial ecosystem processes, such as primary production, litter decomposition, or soil mineralization rates. Light in terrestrial ecosystems is spatially and temporally heterogeneous due to the interaction among sunlight angle, cloud cover and tree-canopy structure. To integrate this variability and to know light distribution over time and space, a high number of measurements are needed, but tools to do this are usually expensive and limited. An easy-to-use and inexpensive method that can be used to measure light over time and space is needed. We used two photodegrading fluorescent organic dyes, rhodamine WT (RWT) and fluorescein, for the quantification of light. We measured dye photodegradation as the decrease in fluorescence across an irradiance gradient from full sunlight to deep shade. Then, we correlated it to accumulated light measured with PAR quantum sensors and obtained a model for this behavior. Rhodamine WT and fluorescein photodegradation followed an exponential decay curve with respect to accumulated light. Rhodamine WT degraded slower than fluorescein and remained unaltered after exposure to temperature changes. Under controlled conditions, fluorescence of both dyes decreased when temperatures increased, but returned to its initial values after cooling to the pre-heating temperature, indicating no degradation. RWT and fluorescein can be used to measure light under a varying range of light conditions in terrestrial ecosystems. This method is particularly useful to integrate solar radiation over time and to measure light simultaneously at different locations, and might be a better alternative to the expensive and time consuming traditional light measurement methods. The accuracy, low price and ease of this method make it a powerful tool for intensive sampling of large areas and for developing high resolution maps of light in an ecosystem.
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Papers by Jorge Duran