Metabolismos Rurales : indicadores económico ecológicos y su aplicación a sistemas cafeteros

Una dimensión clave en la nueva teoría del metabolismo social es aquella que se centra en el estudio de la apropiación de la naturaleza, y que puede definirse como metabolismo rural o agrario. Como una nueva contribución al análisis teórico y práctico de los metabolismos rurales, el presente ensayo propone un marco conceptual para la construcción de indicadores económico ecológicos. Los indicadores son elaborados mediante cálculos monetarios, emergéticos y de trabajo y se aplican al análisis del comportamiento ecológico y económico de las unidades de apropiación. La sustentabilidad se define desde la escuela de la economía ecológica como el estudio de apropiaciones de la sociedad al medio natural, identificando todo tipo de relaciones. (Martinez Alier 1999). Toledo (2003) define cinco pilares de una sociedad sustentable que están en permanente articulación unos con otros. Estos son: diversidad, autosuficiencia, integralidad, equidad, y democracia. El presente artículo construye índices económico ecológicos que permiten establecer una medida comparativa de la apropiación de los cafeteros al medio natural y los respectivos intercambios conla sociedad para finalmente aportar a la medición de la sustentabilidad. Esta investigación se llevó a cabo en familias productoras de café bajo el sistema de policultivos en varias regiones del centro occidente colombiano.A key dimension in the new theory of social metabolism is one that focuses on the study of the appropriation of nature, and which can be defined as rural or agrarian metabolisms. As a new contribution to the theoretical and practical analysis of rural metabolisms, this paper proposes a conceptual framework for building ecological economic indexes. Indices are produced using energy and monetary calculations and applied to the analysis of the environmental and economic performance of the units of appropriation. Sustainability is defined following the school of ecological economics as the study of appropriation of society to the natural environment, identifying all types of potential relationships. (Martinez Alier 1999). Toledo (2003) defines five keystones of a sustainable society that are in permanent relationships with each other. They are: diversity, self-sufficiency, completeness, fairness, and democracy. This paper builds economical and ecological indexes using these factors, becoming a comparative measure of the appropriation of coffee to the natural environment and the respective exchanges with society. This research was conducted in coffee producing families under polyculture systems in various regions of west central Colombia

Hypoxic Cell Waves around Necrotic Cores in Glioblastoma: A Biomathematical Model and its Therapeutic Implications

Glioblastoma is a rapidly evolving high-grade astrocytoma that is distinguished pathologically from lower grade gliomas by the presence of necrosis and microvascular hiperplasia. Necrotic areas are typically surrounded by hypercellular regions known as "pseudopalisades" originated by local tumor vessel occlusions that induce collective cellular migration events. This leads to the formation of waves of tumor cells actively migrating away from central hypoxia. We present a mathematical model that incorporates the interplay among two tumor cell phenotypes, a necrotic core and the oxygen distribution. Our simulations reveal the formation of a traveling wave of tumor cells that reproduces the observed histologic patterns of pseudopalisades. Additional simulations of the model equations show that preventing the collapse of tumor microvessels leads to slower glioma invasion, a fact that might be exploited for therapeutic purposes.Comment: 29 pages, 9 figure

Efficiency and sustainability of public service obligations on scheduled air services between Almeria and Seville

The objective of this paper is to examine how the imposition of Public Service Obligations (PSO) on certain routes may affect the transportation sector, with a focus on aviation in the European Single Market. Thus, this research investigates how this form of public intervention can be useful to access adequeate transport system in remote and peripherical regions. Subsequently, this paper intends to display that the imposition of PSO on aviation routes should be considered as a unique mean of market intervention on behalf of territorial cohesion. To accomplish this, an analysis of the economic impact in terms of efficiency and sustainability in the case of the scheduled air route between Almeria and Seville in addition to other transportation alternatives such the bus or train was conducted. Additionally, this research attempts to shift the research focus away from PSO routes in order to determine the convenience of administrative concession as a way to foster the creation of specific routes, which furthermore cannot be covered by the entrepreneurship of private initiative in a free market regime. Consequently, this approach recognises that this form of public intervention is a way of correcting particular market failures, such as the lack of the adequate transportatio

Glutaraldehido

Se estudia el comportamiento del aldehido glutárico, a dos niveles de concentración, como recurtiente de cueros para capellada, solo y en mezcla con extracto de quebracho sulfitado. Se pone de manifiesto que es posible regular la rigidez, la distensión de la flor y la resistencia al desgarramiento modificando las concentraciones relativas de ambos recurtientes.This article refers to the use of glutaraldehyde as retanning agent of side leather, alone and mixed with sulfited quebracho extract. It is possible to regulate the leather softness the grain distention, and the tear strenght, making variations at the relative concentrations of both retanning agents

Size distribution and frustrated antiferromagnetic coupling effects on the magnetic behavior of ultrafine akaganéite (β-FeOOH) nanoparticles

The magnetic properties of low dimensional materials of several iron oxyhydroxide phases, such as akaganéite (β-FeOOH) or lepidocrocite (γ-FeO(OH)), remain poorly explored, probably due to their specific preparation as single crystalline phase requires special conditions owing to their structural instability. In the present work, ultrafine akaganéite nanoparticles were prepared by the hydrolysis of FeCl3 solutions at room temperature induced by the presence of NaOH. The resulting product was characterized by several analytical techniques. Structural investigations using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) revealed that the sample was mainly constituted by rather-equiaxial akaganéite nanocrystals with mean diameter of 3.3 ± 0.5 nm. In addition, a small amount of rodlike akaganéite particles with 23 ± 5 nm in length and 5 ± 1 nm in width was also detected. The study of the respective dependences of the dc magnetization and the ac susceptibility on temperature and exciting magnetic field revealed complex magnetic relaxation processes, high coercivity values at low temperature, and exchange bias effect. These results have been tentatively explained considering size distribution effects and the presence of superparamagnetic and spin glass-like contributions arising from the frustration of the antiferromagnetic order owing to surface effects and an insufficient filling of the akaganéite channels with Cl- anions.Financial support from the Mexican Council of Science and Technology (CONACYT) and Universidad Autonoma de Nuevo León under research projects CB12-179486 and PAICYT-CE793-11, respectively, is acknowledged. Spanish funding under the MINECO research project MAT2010-20798-C05-04 and FEDER is also acknowledged.Peer Reviewe

Are Altmetrics-traditional systems correlations affected by the journals' social media marketing plan? The journal Comunicar

En este estudio se analizan las correlaciones entre los datos aportados por los sistemas de citas tradicionales y las altmétricas de los artículos publicados durante cinco años en la revista Comunicar, que destaca sobre las demás de su área por su avanzado plan de marketing en medios sociales. Además, se presentan los indicadores que ofrecen datos altmétricos y se lleva a cabo una revisión bibliográfica sobre las publicaciones que han tratado el tema de las correlaciones, destacando relaciones débiles entre métricas tradicionales y altmétricas. Del estudio de correlaciones sobre los datos de la revista, se confirman las débiles relaciones entre los tipos de métricas y se concluye que son significativas para evaluar el nivel de atención que reciben las publicaciones en distintos ámbitos. Como recomendación a los investigadores y editores se destaca la importancia de utilizar los medios sociales, en especial Mendeley y Twitter, para dar visibilidad y difundir la producción científica.This study analyses the correlations between data provided by the traditional citation systems on one hand and altmetrics on the other hand, related to the articles published in the journal Comunicar during five years. This journal stands out among the others in its field due to its advanced social media marketing plan. First, a presentation of the most representative aspects of altmetrics is given, according to published studies. Next, a bibliographic review is carried out on the publications dealing with the subject of the correlations and that emphasize the low correlation between citations and altmetrics. With the aim of helping researchers to understand what they involved and how they are used for their own benefit, this review is followed by a cross-metric validation study of the articles that concludes that altmetrics do not measure the authors' scientific impact, but they are significant in assessing the level of attention received by their publications in different fields and indicate the interest and the importance of using social media, especially Mendeley and Twitter, to give visibility and disseminate their scientific outputs

Grandes accionistas y costes de agencia de la deuda. El caso español

This paper analyses the influence of large controlling shareholders on the terms of bank loans for a sample of 984 loans to 261 non-financial Spanish public and private firms over the period 2001-2017. The results show that the presence of large controlling shareholders increases the interest rate spread of bank loans only in public firms, whereas the influence is insignificant for private firms. Similarly, a less evenly balanced distribution of ownership among large shareholders is associated with higher loan spreads for public firms. Our results reveal that large controlling shareholders expropriate wealth from other investors in public firms, in line with the existence of lower benefits for borrowers due to having large controlling shareholders when they have other internal and external mechanisms of control.El objetivo del presente trabajo consiste en analizar la influencia que los grandes accionistas tienen sobre las condiciones de los préstamos bancarios para una muestra compuesta por 984 préstamos realizados a 261 empresas cotizadas y no cotizadas españolas no financieras durante el periodo 2001-2017. Los resultados muestran que la presencia de grandes accionistas incrementa el tipo de interés pagado por los préstamos en el caso de las empresas cotizadas, mientras el efecto no es significativo para las empresas no cotizadas. De forma similar, una distribución de la propiedad menos equilibrada entre los grandes accionistas está asociada con un mayor tipo de interés pagado por las empresas cotizadas. Los resultados ponen de manifiesto que los grandes accionistas expropian riqueza de otros inversores en las empresas cotizadas, en línea con la existencia de menores beneficios para los prestatarios de la existencia de grandes accionistas cuando disponen de otros mecanismos, tanto internos como externos, de control

Ni-Co Alloy and Multisegmented Ni/Co Nanowire Arrays Modulated in Composition: Structural Characterization and Magnetic Properties

Design of novel multisegmented magnetic nanowires can pave the way for the next generation of data storage media and logical devices, magnonic crystals, or in magneto-plasmonics, among other energy conversion, recovery, and storage technological applications. In this work, we present a detailed study on the synthesis, morphology, structural, and magnetic properties of Ni, Co, and Ni-Co alloy and multisegmented Ni/Co nanowire