2,939 research outputs found
Factores determinantes de la relación entre el crecimiento económico, la equidad y la competitividad
En este artÃculo se describen y analizan distintos enfoques que explican la relación entre las variables agregadas: el crecimiento económico, la productividad y la competitividad de la economÃa. Se señalan y agrupan las controversias sobre la causalidad desigualdad – crecimiento, y además de mostrar un modelo propuesto por Ros (2004) apoyado en el enfoque de la contabilidad del crecimiento (Residuo de Solow), se analizan otros resultados de evidencias econométricas, para finalmente enumerar las deficiencias de la investigación teórica y de los estudios estadÃsticos y econométricos de tales interrelaciones y sus determinantes. Igualmente, el escrito es prolijo en la descripción y análisis de los distintos enfoques y modelos sobre la competitividad de las naciones, desagregando el conjunto de variables que son consideradas por las instituciones de mayor reconocimiento en el tratamiento del tema -CEPAL, FORO ECONOMICO MUNDIAL- para evaluar la evolución de la competitividad estructural, sistémica y global de las economÃas. Luego de trasegar por una gama de posturas que le son inherentes al tema, se concluye la falta de contundencia de los enfoques teóricos y las pocas evidencias empÃricas sobre las relaciones entre el crecimiento económico, la desigualdad, la pobreza y la competitividad
Geotourism and local development based on geological and mining sites utilization, zaruma-portovelo, Ecuador
This study offers a detailed assessment of the geosites and mining sites present in the Zaruma-Portovelo mining district (Ecuador) through their qualitative and quantitative assessment. It shows up the potentiality of this area taking advantage of its geological-mining heritage. The methodological process includes: (i) compilation and inventory of all the sites within the study area with particular geological or mining interest; (ii) preparation of reports and thematic cartography, (iii) assessment and classification of the elements of geological-mining interest; (iv) SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis and TOWS (Threats, Opportunities, Weaknesses, Strengths) matrix preparation seeking strategies to guarantee the viability of geotourism. A total of 16 sites of geological interest and 11 of mining interest were identified. The 77% of these sites was proved to be of high and very high interest in scientific terms. Likewise, their susceptibility to degradation assessed from their vulnerability and fragility was found to be high or very high in the 30% of the cases. As for the protection priority, all the studied sites obtained a medium-high result. Finally, the study based on the SWOT-TOWS revealed the possibility of applying action strategies in order to facilitate the compatibility of geotourism with the current productive activities, despite the difficult situation in the study area created by mining activities
On the origin of the neutral hydrogen supershells: the ionized progenitors and the limitations of the multiple supernovae hypothesis
Here we address the question whether the ionized shells associated with giant
HII regions can be progenitors of the larger HI shell-like objects found in the
Milky Way and other spiral and dwarf irregular galaxies. We use for our
analysis a sample of 12 HII shells presented recently by Rela\~no et al. (2005,
2007). We calculate the evolutionary tracks that these shells would have if
their expansion is driven by multiple supernovae explosions from the parental
stellar clusters. We find, contrary to Rela\~no et al. (2007), that the
evolutionary tracks of their sample HII shells are inconsistent with the
observed parameters of the largest and most massive neutral hydrogen
supershells. We conclude that HII shells found inside giant HII regions may
represent the progenitors of small or intermediate HI shells, however they
cannot evolve into the largest HI objects unless, aside from the multiple
supernovae explosions, an additional energy source contributes to their
expansion.Comment: Accepted for publication in ApJ, tentatively scheduled for the ApJ
July 1, 2008, v681n1 issue. 19 pages, 4 figure
Recommended from our members
Ethnic Differences in Physiological Responses to Fear Conditioned Stimuli
The idea that emotional expression varies with ethnicity is based largely on questionnaires and behavioral observations rather than physiological measures. We therefore compared the skin conductance responses (SCR) of Hispanic (Puerto Rican) and White non-Hispanic subjects in a fear conditioning and fear extinction task. Subjects were recruited from two sites: San Juan, Puerto Rico (PR), and Boston, Massachusetts (MA), using identical methods. A total of 78 healthy subjects (39 from PR, 39 from MA) were divided by sex and matched for age and educational level. Females from the two sites did not differ in their SCRs during any experimental phase of fear conditioning (habituation, conditioning, or extinction). In contrast, PR males responded significantly to the conditioned stimulus than MA males or PR females. Subtracting ethnic differences observed during the habituation phase (prior to conditioning) eliminated differences from subsequent phases, suggesting that PR males are elevated in their response to novelty rather than fear learning. Our findings suggest that, in addition to sex differences, there are ethnic differences in physiological responses to novel stimuli at least in males, which could be relevant for the assessment and treatment of anxiety disorders
Ethnic Differences in Physiological Responses to Fear Conditioned Stimuli
The idea that emotional expression varies with ethnicity is based largely on questionnaires and behavioral observations rather than physiological measures. We therefore compared the skin conductance responses (SCR) of Hispanic (Puerto Rican) and White non-Hispanic subjects in a fear conditioning and fear extinction task. Subjects were recruited from two sites: San Juan, Puerto Rico (PR), and Boston, Massachusetts (MA), using identical methods. A total of 78 healthy subjects (39 from PR, 39 from MA) were divided by sex and matched for age and educational level. Females from the two sites did not differ in their SCRs during any experimental phase of fear conditioning (habituation, conditioning, or extinction). In contrast, PR males responded significantly to the conditioned stimulus than MA males or PR females. Subtracting ethnic differences observed during the habituation phase (prior to conditioning) eliminated differences from subsequent phases, suggesting that PR males are elevated in their response to novelty rather than fear learning. Our findings suggest that, in addition to sex differences, there are ethnic differences in physiological responses to novel stimuli at least in males, which could be relevant for the assessment and treatment of anxiety disorders
First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae)
Background and Aims Bromeliaceae is a species-rich neotropical plant family that uses a variety of pollinators, principally vertebrates. Tillandsia is the most diverse genus, and includes more than one-third of all bromeliad species. Within this genus, the majority of species rely on diurnal pollination by hummingbirds; however, the flowers of some Tillandsia species show some characteristics typical for pollination by nocturnal animals, particularly bats and moths. In this study an examination is made of the floral and reproductive biology of the epiphytic bromeliad Tillandsia macropetala in a fragment of humid montane forest in central Veracruz, Mexico. Methods The reproductive system of the species, duration of anthesis, production of nectar and floral scent, as well as diurnal and nocturnal floral visitors and their effectiveness in pollination were determined. Key Results Tillandsia macropetala is a self-compatible species that achieves a higher fruit production through outcrossing. Nectar production is restricted to the night, and only nocturnal visits result in the development of fruits. The most frequent visitor (75 % of visits) and the only pollinator of this bromeliad (in 96 % of visits) was the nectarivorous bat Anoura geoffroyi (Phyllostomidae: Glossophaginae). Conclusions This is the first report of chiropterophily within the genus Tillandsia. The results on the pollination biology of this bromeliad suggest an ongoing evolutionary switch from pollination by birds or moths to bat
Factores Determinantes de la Relación entre el Crecimiento Económico, la Equidad y la Competitividad
En este articulo se describen y analizan distintos enfoques que explican la relación entre las variables agregadas: el crecimiento economico, la productividad y la competitividad de la economia. Se senalan y agrupan las controversias sobre la causalidad desigualdad – crecimiento, y ademas de mostrar un modelo propuesto por Ros (2004) apoyado en el enfoque de la contabilidad del crecimiento (Residuo de Solow), se analizan otros resultados de evidencias econometricas, para finalmente enumerar las deficiencias de la investigacion teorica y de los estudios estadÃsticos y econometricos de tales interrelaciones y sus determinantes. Igualmente, el escrito es prolijo en la descripcion y analisis de los distintos enfoques y modelos sobre la competitividad de las naciones, desagregando el conjunto de variables que son consideradas por las instituciones de mayor reconocimiento en el tratamiento del tema -CEPAL, FORO ECONOMICO MUNDIAL- para evaluar la evolucion de la competitividad estructural, sistemica y global de las economias. Luego de trasegar por una gama de posturas que le son inherentes al tema, se concluye la falta de contundencia de los enfoques teoricos y las pocas evidencias empiricas sobre las relaciones entre el crecimiento economico, la desigualdad, la pobreza y la competitivida
Factores Determinantes de la Relación entre el Crecimiento Económico, la Equidad y la Competitividad
Novel spiro-core dopant-free hole transporting material for planar inverted Perovskite solar cells
Hole-transporting materials (HTMs) have demonstrated their crucial role in promoting charge extraction, interface recombination, and device stability in perovskite solar cells (PSCs). Herein, we present the synthesis of a novel dopant-free spiro-type fluorine core-based HTM with four ethoxytriisopropylsilane groups (Syl-SC) for inverted planar perovskite solar cells (iPSCs). The thickness of the Syl-SC influences the performance of iPSCs. The best-performing iPSC is achieved with a 0.8 mg/mL Syl-SC solution (ca. 15 nm thick) and exhibits a power conversion efficiency (PCE) of 15.77%, with Jsc = 20.00 mA/cm2, Voc = 1.006 V, and FF = 80.10%. As compared to devices based on PEDOT:PSS, the iPSCs based on Syl-SC exhibit a higher Voc, leading to a higher PCE. Additionally, it has been found that Syl-SC can more effectively suppress charge interfacial recombination in comparison to PEDOT:PSS, which results in an improvement in fill factor. Therefore, Syl-SC, a facilely processed and efficient hole-transporting material, presents a promising cost-effective alternative for inverted perovskite solar cells
Picolinic and Isonicotinic Acids: A Fourier Transform Microwave Spectroscopy Study
Producción CientÃficaThe rotational spectra of laser ablated picolinic and isonicotinic acids have been studied using broadband chirped pulse (CP-FTMW) and narrowband molecular beam (MB-FTMW) Fourier transform microwave spectroscopies. Two conformers of picolinic acid, s-cis-I and s-cis-II, and one conformer of isonicotinic acid have been identified through the analysis of their rotational spectra. The values of the inertial defect and the quadrupole coupling constants obtained for the most stable s-cis-I conformer of picolinic acid, evidence the formation of an O–H···N hydrogen bond between the acid group and the endocyclic N atom. The stabilization provided by this hydrogen bond compensates the destabilization energy due to the adoption of a −COOH trans configuration in this conformer. Its rs structure has been derived from the rotational spectra of several 13C, 15N, and 18O species observed in their natural abundances. Mesomeric effects have been revealed by comparing the experimental values of the 14N nuclear quadrupole coupling constants in the isomeric series of picolinic, isonicotinic, and nicotinic acids.Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA175U13
- …