2,646 research outputs found
Determining the Magnetization of the Quiet Sun Photosphere from the Hanle Effect and Surface Dynamo Simulations
The bulk of the quiet solar photosphere is thought to be significantly
magnetized, due to the ubiquitous presence of a tangled magnetic field at
subresolution scales with an average strength ~ 100 G. This conclusion was
reached through detailed three-dimensional (3D) radiative transfer modeling of
the Hanle effect in the Sr I 4607 line, using the microturbulent field
approximation and assuming that the shape of the probability density function
of the magnetic field strength is exponential. Here we relax both
approximations by modeling the observed scattering polarization in terms of the
Hanle effect produced by the magnetic field of a 3D photospheric model
resulting from a (state-of-the-art) magneto-convection simulation with surface
dynamo action. We show that the scattering polarization amplitudes observed in
the Sr I 4607 line can be explained only after enhancing the magnetic strength
of the photospheric model by a sizable scaling factor, F=10, which implies
= 130 G in the upper photosphere. We argue also that in order to explain both
the Hanle depolarization of the Sr I 4607 line and the Zeeman signals observed
in Fe I lines we need to introduce a height-dependent scaling factor, such that
the ensuing = 160 G in the low photosphere and = 130 G in the upper
photosphere.Comment: To appear in ApJ Letter
A financial analysis of born-global firms: evidence from Spain
From the beginning of the 1970s to the present day, significant changes have taken place in the competitive and organizational
behavior of small and medium-sized companies (SMEs). Recently, some of these factors have applied more
intensively, and this has given rise to growth in the number of new companies that undertake overseas operations almost
immediately (known as born globals).
The phenomenon of early internationalization is relatively recent, so there are still many aspects that need to be studied.
The objective of this study is to contribute to the scarce empirical literature existing in Spain on this topic, by providing
evidence on the possible differences in character of the born-global firms compared with the rest of exporting
companies. To this end, the focus of the study is on the analysis of variables such as the size and sector of activity of
these companies, and their principal economic and financial magnitudes.
A sample of 1,324 Spanish SMEs that were exporting in 2007 was surveyed; of this total approximately 12% identified
themselves as having adopted early internationalization.
The results obtained indicate that the born-global firms are, on average, smaller; they are classified mostly to the services
sector; and they are much more leveraged than the rest of Spanish SMEs that export
Magnetic flux in the inter-network quiet Sun from comparison with numerical simulations
Khomenko et al. estimate the mean magnetic field strength of the quiet Sun to
be 20 G. The figure is smaller than several existing estimates, and it comes
from the comparison between observed Zeeman polarization signals and synthetic
signals from numerical simulations of magneto-convection. The numerical
simulations require an artificially large magnetic diffusivity, which smears
out magnetic structures smaller than the grid scale. Assuming a turbulent
cascade for the unresolved artificially smeared magnetic fields, we find that
their unsigned magnetic flux is at least as important as that explicitly shown
in the simulation. The unresolved fields do not produce Zeeman polarization but
contribute to the unsigned flux.Since they are not considered by Khomenko et
al., their mean magnetic field strength has to be regarded as a lower limit.
This kind of bias is not specific of a particular numerical simulation or a
spectral line. It is to be expected when observed quiet Sun Zeeman signals are
compared with synthetic signals from simulations.Comment: Accepted A&A. 4 pages, 0 figure
Promotion of healthy habits from the childhood education stage: comparative research between a british school and another spanish school of the andalusian community
Las costumbres y hábitos saludables son considerados aspectos esenciales que hacen alcanzar una óptima calidad de vida. Gracias a ellos, vamos adquiriendo un bienestar no solo físico sino también psicológico. La acción de educar en Hábitos saludables es considerada primordial desde la etapa de infantil. Es el método más efectivo para el aumento y/o mejora de la salud de la vida del sujeto a largo plazo, eludiendo posibles enfermedades como por ejemplo la obesidad. Nuestra prioridad como futuras docentes es la de promover en nuestro alumnado estas rutinas, sin embargo, hay que tener en cuenta que la familia al constituir el escenario principal del niño/a, debe servir como modelo, introduciendo así esta serie de valores en la vida diaria del individuo. En primer lugar se realiza un estudio de corte transversal, a una muestra de 9 profesores/as y a 9 familias en España e Inglaterra, midiendo variables relacionadas con la alimentación y la actividad física de niños/as de 3-6 años. Los resultados darán lugar a las conclusiones, las cuales se basarán en reforzar y promover hábitos saludablesThe traditions and healthy habits are considered essential aspects that achieve an optimal quality of life. Thanks to them, we are acquiring a well-being not only physical but also psychological. The action of educating in healthy habits is considered essential from the childhood stage. It is the most effective method for increasing and / or improving the health of the subject's life in the long term, avoiding possible diseases such as obesity. Our priority as future teachers is to promote these routines in our students; however, it is important to keep it in mind that the family, as the main scenario of the child, must serve as a model, thus introducing this series of values in daily life of the individual. Firstly, a cross-sectional study was carried out, with a sample of 9 teachers and 9 families in Spain and England, measuring variables related to food and physical activity of children from 3 to 6 years of age. The results will lead to conclusions, which will be based on reinforcing and promoting healthy habits.Universidad de Sevilla. Grado en Educación Infanti
Valorización de la Sociedad Minera Cerro Verde (al primer trimestre del 2016)
El presente estudio pretende realizar la valorización de la Sociedad Minera Cerro Verde (SMCV), empresa dedicada a la extracción, producción y comercialización de minerales: cobre, molibdeno y plata. Forma parte del grupo Freeport-McMoRan (Freeport) con sede principal en Arizona, Estados Unidos. Para realizar la valorización se emplearon dos metodologías: Flujo de Caja Descontado (FCD) y Múltiplos. La metodología del Modelo de Dividendos Descontados (MDD) no fue empleada debido a que SMCV mantiene como política no repartir dividendos. SMCV es el tercer productor de cobre del Perú con el 15,05% de la producción nacional en 2015, luego de la Compañía Minera Antamina (24,22%) y Southern Perú Copper (18,92%). Produce principalmente cobre (concentrado y en cátodos), alcanzando ventas por US 4.600 millones. Luego de ello, la capacidad instalada de la planta concentradora se elevó de 120.000 a 360.000 TM/día. Esta inversión reduciría además los costos de producción debido a mejoras en la eficiencia del proceso productivo. Para realizar la valorización, se tomaron en cuenta los estados financieros al primer trimestre de 2016, la información histórica de los periodos previos y las memorias anuales. Una fuente importante de información fueron los documentos emitidos por Freeport, tanto a la Security Exchange Comission (SEC), como por los informes dirigidos a los inversionistas publicados en su página web, donde se brinda información sobre las perspectivas empresariales de la empresa y los detalles de las inversiones recientes. Para la información financiera de SMCV y de las empresas comparables se hizo uso de las herramientas financieras de la plataforma Bloomberg y de la información disponible en la Superintendencia de Mercados y Valores (SMV). Los principales factores tomados en cuenta para realizar la valorización por FCD fueron la estructura de costos luego de culminada la ampliación de la planta, el precio del cobre, el CAPEX proyectado, las obligaciones financieras futuras y la perspectiva de la economía mundial en el mediano y largo plazo
Use of a new enrichment nanosorbent for speciation of mercury by FI-CV-ICP-MS
Mercury is one of the most toxic environmental pollutants and its effects on human and ecosystem health are well known. All mercury species are toxic, with organic mercury compounds generally being more toxic than inorganic species. Chromatography techniques (GC, HPLC) coupled to element specific detectors, are able to separate mercury species in order to elucidate mercury transformation and transport processes where the determination of all mercury species is desirable. However, in practice, especially in sampling campaigns for sea water analysis where a large number of samples are collected over a longer period of time, a combination of methods is usually applied to accurately determine the most toxic mercury species. These include non-chromatographic methods based on the different chemical and/or physical behavior of the mercury species. These non-chromatographic methods can be less time consuming, more cost effective and available, and present competitive limits of detection. Especially when mercury could vapor (CV) generation technique is employed, which reduces salt effect on the analytical signal and improve the sensibility. Among non-chromatographic methods, solid phase extraction and microextraction (SPE and SPME) which is becoming increasingly popular for sample preparation in organic analysis, found its way to speciation analysis of organometals. SPE/SPME is the most popular sample preconcentration method for its simplicity, high enrichment factor, low or no consumption of organic solvents and feasibly to be automated. On the other hand, the exploration of new materials, especially nanometer sized materials, as the support phase is another active research area in SPE/SPME for mercury determination. The use of nanoparticles leads to higher extraction capacity/efficiency and rapid dynamics of extraction originated from the higher surface area to volume ratio and short diffusion route.
In this work, a new enrichment nanosorbent functionalized with 1,5 bis (2-pyridyl) methylene thiocarbohidrazide was synthesized and characterized. From the study of its adsorption capacity toward metal ions, Hg2+ was observed to be one of the most retained 173.1 µmol g-1 at pH 5. Thus, a flow injection solid phase extraction and cold vapor generation method for its determination and speciation based on the use of this new chelating nanosorbent was optimized. The method developed has showed to be useful for the automatic pre-concentration and sequential speciation of mercury and methylmercury in environmental and biological samples. The system was based on chelating retention of the analytes onto a mini-column filled with the new nanosorbent and their sequential elution by using two different eluents, 0.2 % HCl for CH3Hg+ and 0.1 % thiourea in 0.5 % HCl for Hg2+. The determination was performed using inductively coupled plasma mass spectrometry. Under the optimum conditions and 120 s preconcentration time, the enrichment factors were 4.7 and 11.0; the detection limits (3σ) were 0.002 and 0.004 µg L-1; the determination limits (10σ) were 0.011 and 0.024 µg L-1; and the precisions (calculated for 10 replicate determinations at a 2 µg L-1 standard of both species) were 2.8 and 2.6 % (RSD); for CH3Hg+ and Hg2+, respectively. Linear calibration graphs were obtained for both species from the determination limits to at least 70 µg L-1. For the quality control of the analytical performance and the validation of the newly developed method, the analysis of two certified samples, LGC 6016 estuarine water and SRM 2976 mussel tissue were addressed. The results showed good agreement with the certified values. The method was successfully applied to the speciation of mercury in sea-water samples collected in the Málaga Bay.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Diseño arquitectónico y estructural de una vivienda de interés social rural en guadua (angustifolia Kunth)
Trabajo de InvestigaciónLa guadua, en la actualidad, se constituye como un material de construcción alternativo y sostenible, gracias a sus propiedades físico mecánicas, que le brindan una resistencia comparada con el acero, por tanto, su uso como material estructural para viviendas se hace cada vez más fuerte. Por lo anterior en el presente artículo se muestran los resultados de la investigación desarrollada, la cual tuvo como objetivo elaborar el diseño arquitectónico y estructural de una vivienda de interés social rural en guadua Angustifolia Kunth que cumpla con los requerimientos de sismo resistencia exigidos por normatividad colombiana, como alternativa de vivienda para poblaciones ruralesINTRODUCCIÓN 1. GENERALIDADES 2. REQUERIMIENTOS DEL DISEÑO ARQUITECTÓNICO Y ESTRUCTURAL DE 3. CARACTERIZACIÓN DE LAS PROPIEDADES FÍSICO MECÁNICAS DE LA 4. DISEÑO ARQUITECTÓNICO Y ESTRUCTURAL DE UNA VIVIENDA DE INTERÉS 5. CONCLUSIONES 6. RECOMENDACIONES BIBLIOGRAFÍA ANEXOSPregradoIngeniero Civi
Fermentación de Autumn Bliss para la elaboración de Vino de Frambuesa.
El presente trabajo fue desarrollado en el laboratorio de biotecnologíade la facultad de Química de la UAEM Así como en el Departamento de Biotecnologíade la UAM Unidad Iztapalapa, teniendo como objetivo general la elaboración de un vino de frambuesa variedad Autumn bliss; ̩éste como ruta alterna para la comercialización y productividad de la frambuesa
Modelos de elección discreta : revisión y aplicación mediante cuadratura Gaussiana
This work titled MODELOS DE ELECCION DISCRETA Revision y aplicacion mediante cuadratura gaussiana gathers the characteristic foundations of this models which are useful in Microeconometrics -- Characteristics of Binary Choice and Multinomial Choice Models are described -- Lastly, a practical application about labor dynamic of married women, both, in United States and Colombia using Gaussian Quadrature is presented -- Estimated models are highly significant in their parameters and the procedure of Gaussian Quadrature is stable and reliabl
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