Estudio cinético de la termólisis del oxoacetato de etilo

La termólisis del oxoacetato de etilo se llevó a cabo utilizando un sistema de reacción estático en el rango de 389,9-430,3° C y 29,0- 157,0 mmHg, en presenciade un inhibidor de radicales libres. El análisis cromatográfico de los productos reveló presencia de un aldehído y un éster, evidenciando la existencia de dos reacciones paralelas: decarboxilación y decarbonilación. Ambas reacciones resultaron ser unimoleculares, homogéneas y siguen una ley de velocidad deprimer orden, siendo las correspondientes expresiones de la ecuación de Arrhenius: decarboxilación: logk1 = (13,43±0,25) – (213,1± 3,3) kJ mol–1 (2,303RT)–1, decarbonilación: log k2 = (14,06±0,54) – (232,9±7,0) kJ mol–1 (2,303RT) –1 y reacción global: log kT =(13,72±0,25) – (216,1± 3,3) kJ mol–1 (2,303RT) –1. Los mecanismos son descritos en términos de estado detransición cíclico concertado.

Effective anisotropies and energy barriers of magnetic nanoparticles with Néel surface anisotropy

Magnetic nanoparticles with Néel surface anisotropy, different internal structures, surface arrangements, and elongation are modeled as many-spin systems. The results suggest that the energy of many-spin nanoparticles cut from cubic lattices can be represented by an effective one-spin potential containing uniaxial and cubic anisotropies. It is shown that the values and signs of the corresponding constants depend strongly on the particle's surface arrangement, internal structure, and shape. Particles cut from a simple cubic lattice have the opposite sign of the effective cubic term, as compared to particles cut from the face-centered cubic lattice. Furthermore, other remarkable phenomena are observed in nanoparticles with relatively strong surface effects. (i) In elongated particles surface effects can change the sign of the uniaxial anisotropy. (ii) In symmetric particles (spherical and truncated octahedral) with cubic core anisotropy surface effects can change the sing of the latter. We also show that the competition between the core and surface anisotropies leads to a new energy that contributes to both the second- and fourth-order effective anisotropies. We evaluate energy barriers ΔE as functions of the strength of the surface anisotropy and the particle size. The results are analyzed with the help of the effective one-spin potential, which allows us to assess the consistency of the widely used formula ΔE/V= K∞ +6 Ks /D, where K∞ is the core anisotropy constant, Ks is a phenomenological constant related to surface anisotropy, and D is the particle's diameter. We show that the energy barriers are consistent with this formula only for elongated particles for which the surface contribution to the effective uniaxial anisotropy scales with the surface and is linear in the constant of the Néel surface anisotropy. © 2007 The American Physical Society

Caracterización de la demanda de transporte

Incluye Bibliografí

Control of the structural intervention in the area of the Roman Theatre of Cadiz

El Teatro Romano de Cádiz (España) es parte de la herencia romana que ha permanecido oculta durante siglos bajo el casco histórico de la ciudad. Se trata del teatro romano más antiguo y de mayores dimensiones localizado en España. En el año 2010, se inició una intervención con el fin de descubrirlo. La intervención consiste en la construcción de una serie de bóvedas de hormigón bajo los edificios construidos sobre el teatro aplicando la técnica de la inyección armada. El control de esta intervención se está realizando por medio de dos técnicas: control topográfico y Análisis Modal Operacional. La metodología seguida para el control de la intervención en el área del teatro romano y los resultados obtenidos de la misma son los principales objetivos del presente artículo.The Roman Theatre of Cadiz (Spain) is a piece of heritage that has been buried for centuries under the historical town. It is the oldest and biggest Roman theatre in Spain. In 2010, an intervention began in order to dig it up but respecting the monumental landmarks over it. The intervention consisted on the construction of some vaults under the blocks by grout injection. The control of this intervention is being done by two different techniques: topographic control points and Operational Modal Analysis. The methodology that has been followed to control the intervention on this area and the obtained results are the main goals of this paper

Comunicaciones móviles en entornos complejos: Planificación de redes LTE.

En este proyecto se estudiarán las interferencias en el canal adyacente de los sistemas celulares, ubicados en las bandas de 900 y 1800 MHz. Para esto, se analizarán medidas de interferencia entre LTE y otros sistemas de comunicación celular. En el primer capítulo, se dará una breve descripción de los principales parámetros empleados en los distintos estándares de comunicaciones móviles, que operan en las bandas de frecuencia de interés. En el segundo, se van a explicar los distintos tipos de interferencias existentes entre sistemas celulares. También se verán las diferentes técnicas para reducir dichas interferencias, como por ejemplo, la de control de potencia y la de coordinación de interferencia entre celdas. Además, se explicarán los parámetros para determinar la interferencia en el canal adyacente, como son el ACLR, ACS y ACIR. Para finalizar se resumirán las principales características de los sistemas LTE y WiMAX. En el tercer capítulo, se estudiarán las interferencias que genera principalmente LTE a los otros sistemas celulares, mediante los parámetros que miden la interferencia en el canal adyacente explicados en el capítulo dos. Además, se determinará la separación en frecuencia que debe existir entre los canales para que los sistemas puedan coexistir. El capítulo cuatro se basa en la simulación de tres escenarios de interferencia entre dichos sistemas. Para esto, se utilizará el software de simulación de propagación radio, denominado Radio Plan. Con estas simulaciones se cuantificarán las pérdidas de rendimiento que sufren los sistemas interferidos. Por último, en el capítulo cinco se resumirán las conclusiones a las que se llegaron después de simular los diferentes escenarios de interferencia. SUMMARY In this project an adjacent channel interference study for cellular systems, allocated within 900 MHz and 1800 MHz bands will be performed. For this aim a set of measurements will be analyzed. In the first chapter, a brief explanation of the main parameters used in different mobile communications standards that operate in the frequency bands of interest, will be given. In the second chapter, different types of interference between cellular systems will be explained, as well as different techniques to reduce such interference. For example, power control and interference coordination between cells, will be shown. Furthermore, the parameters to determine the adjacent-channel interference, such as the ACLR, ACS and ACIR will be overviewed. Finally, the main features of LTE and WiMAX systems will be summarized. In the third chapter, the interference generated by the other mainly LTE cellular systems via parameters that measure the adjacent channel interference explained in chapter two will be studied. Also, the frequency separation that must exist between the channels so that the systems can coexist will be determined. The fourth chapter is based on the simulation of three scenarios of interference between these systems. For this purpose, a radio propagation simulation software package Radio Plan will be used. These simulations will quantify performance losses suffered by systems that interfered. Finally, in chapter five the conclusions about the results of simulations of interference in different scenarios will be presented

Addressing conflict between fishermen and the Titicaca Grebe ( Rollandia microptera ) through diet analysis

Human–wildlife conflict is often a driver of species declines, and understanding the material basis of this conflict is the first step in addressing it. The Titicaca Grebe Rollandia microptera is an endangered endemic species found solely in the Lake Titicaca watershed of Peru and Bolivia, and has experienced population declines due to fisheries bycatch. Human fishers often have negative opinions of the Titicaca Grebe, because they consider it as a competitor for declining fish stocks. We tested that assumption by an analysis of the bird's diet and found that the Titicaca Grebe does not compete with fishers for more lucrative fish species such as trout Oncorhynchus sp. and Pejerrey Odontesthes bonariensis, but does compete for the less desirable (to human fishers) native Orestias sp

Gene duplication, population genomics, and species-level differentiation within a tropical mountain shrub.

Gene duplication leads to paralogy, which complicates the de novo assembly of genotyping-by-sequencing (GBS) data. The issue of paralogous genes is exacerbated in plants, because they are particularly prone to gene duplication events. Paralogs are normally filtered from GBS data before undertaking population genomics or phylogenetic analyses. However, gene duplication plays an important role in the functional diversification of genes and it can also lead to the formation of postzygotic barriers. Using populations and closely related species of a tropical mountain shrub, we examine 1) the genomic differentiation produced by putative orthologs, and 2) the distribution of recent gene duplication among lineages and geography. We find high differentiation among populations from isolated mountain peaks and species-level differentiation within what is morphologically described as a single species. The inferred distribution of paralogs among populations is congruent with taxonomy and shows that GBS could be used to examine recent gene duplication as a source of genomic differentiation of nonmodel species

Reseña de "Hacia una arquitectura del placer" de Henri Lefebvre

Obra ressenyada: Henri LEFEBVRE, Hacía una arquitectura del placer. Madrid: Centro de Investigaciones Sociológicas, 2018

JPCam: A 1.2Gpixel camera for the J-PAS survey

JPCam is a 14-CCD mosaic camera, using the new e2v 9k-by-9k 10microm-pixel 16-channel detectors, to be deployed on a dedicated 2.55m wide-field telescope at the OAJ (Observatorio Astrofisico de Javalambre) in Aragon, Spain. The camera is designed to perform a Baryon Acoustic Oscillations (BAO) survey of the northern sky. The J-PAS survey strategy will use 54 relatively narrow-band (~13.8nm) filters equi-spaced between 370 and 920nm plus 3 broad-band filters to achieve unprecedented photometric red-shift accuracies for faint galaxies over ~8000 square degrees of sky. The cryostat, detector mosaic and read electronics is being supplied by e2v under contract to J-PAS while the mechanical structure, housing the shutter and filter assembly, is being designed and constructed by a Brazilian consortium led by INPE (Instituto Nacional de Pesquisas Espaciais). Four sets of 14 filters are placed in the ambient environment, just above the dewar window but directly in line with the detectors, leading to a mosaic having ~10mm gaps between each CCD. The massive 500mm aperture shutter is expected to be supplied by the Argelander-Institut fur Astronomie, Bonn. We will present an overview of JPCam, from the filter configuration through to the CCD mosaic camera. A brief outline of the main J-PAS science projects will be included.Comment: 11 pages and 9 figure

Dating young open clusters using delta Scuti stars. Results for Trumpler 10 and Praesepe

Aims. The main goal of this work is to date young open clusters using $\delta$ Sct stars. Seismic indices such as the large separation and the frequency at maximum power can help to constrain the models to better characterise the stars. We propose a reliable method to identify some radial modes, which gives us greater confidence in the constrained models. Methods. We extract the frequency content of a sample of $\delta$ Sct stars belonging to the same open cluster. We estimate the low-order large separation by means of different techniques and the frequency at maximum power for each member of the sample. We use a grid of models built with the typical parameters of $\delta$ Sct stars, including mass, metallicity and rotation as independent variables, and determine the oscillation modes. We select the observed frequencies whose ratios match those of the models. Once we find a range of radial modes matching the observed frequencies, mainly the fundamental mode, we add it to the other seismic parameters to derive the stellar age. Assuming star groups have similar chemistry and age, we estimate their mean age by computing a weighted probability density function fit to the age distribution of the seismically constrained models. Results. We estimate the age of Trumpler 10 to be $30_{-20}{+30}$ Myr, and that of Praesepe to be $580 \pm 230$ Myr. In this latter case, we find two apparent populations of $\delta$ Sct stars in the same cluster, one at $510 \pm 140$ Myr and another at $890 \pm 140$ Myr. This may be due to two different formation events, different rotational velocities of the members in our sample of stars (as rapid rotation may modify the observed large separation), or to membership of unresolved binary systems.Comment: 20 pages, 25 figure, uses the open-source code MultiModes (see https://github.com/davidpamos/MultiModes). It will be published in A&