Cosmological implications of Bumblebee vector models

The Bumblebee Model of spontaneous Lorentz symmetry breaking is explored in a cosmological context, considering a single non-zero time component for the vector field. The relevant dynamic equations for the evolution of the Universe are derived and its properties and physical significance studied. We conclude that a late-time de Sitter expansion of the Universe can be replicated, and attempt to constrain the parameter of the potential driving the spontaneous symmetry breaking.Comment: 11 pages, 10 figures, 1 table. Accepted for publication in PR

Monitoring Corrosion Products on Metal Artefacts by Linear Sweep Voltammetry (LSV)

Metallic surfaces are highly sensitive to their surroundings, and prone to react with airborne pollutants to form complex layers. Electrochemical techniques have the possibility of simultaneously identifying different electroactive compounds [1]. The high sensitivity of Linear Sweep Voltammetry (LSV) allows the detection of extremely thin surface films before they became visible. LSV leads to reduction peaks, which can identify the compounds within the “tarnishing” layer and also its relative abundance [1, 2]. The potentialities of this and others electrochemical techniques has been well demonstrated in several recent works and they seem to be promising and non-invasive tools, even for in situ investigations on the metallic artifacts from cultural heritage. This communication presents data showing the application of the technique to silver and sterling silver coupons exposed, during periods of 1 and 12 months, in the Treasure Room in the Museum (inside showcases) and near the Holy Altar of the Chapel, of Porto Cathedral (Portugal). The influence of various conditions: the atmosphere (Museum and Chapel), exposure time (1 and 12 months) and season (spring, summer, autumn and winter) have been analysed. The LSV spectra of blank polished samples as well as samples covered with thin films of silver sulphide and of silver chloride, formed under controlled conditions, respectively: (i) H2S, 1000 ppm, RH= 53% ± 2, T= 21 ºC ± 1, over periods of 24, 48 and 72 h) and (ii) 3.5% of NaCl, RH=41% periods of 5 h, have been used as references. Concerning the nature of the products developed on the surface during the exposure, data has revealed that the tarnishing layers have a complex nature and are not composed only by silver sulphide. It happens even that silver sulphide is a relative minor component in the tarnish layer. Peaks corresponding to silver chloride and silver oxides were well visible. Small peaks assigned to silver sulphide were identified on the samples exposed in the Chapel. For the 12 months exposures both peaks have increased in size with the peak assigned to chloride being much higher in the case of the Chapel. The seasonal influence, even for the 1 month exposures, was particularly notable on those samples with exposures started in winter with well visible effects on the chloride peak on the tarnish layer of the samples exposed in the Chapel. Obviously, that to obtain analytical information electrochemical techniques can be complemented with spectroscopic techniques, namely, X- ray photon spectroscopy (XPS), laser induced breakdown spectroscopy (LIBS), x-rays fluorescence spectroscopy, among others. [1] A. Doménech-Carbó, M.T. Doménech-Carbó, V. Costa (2009), Electrochemical Methods in Archaeometry, Conservation and Restoration, Berlin: F. Scholz. [2] V. Costa, M. Dubus (2007), Impact of the environmental conditions on the conservation of metal artifacts: an evaluation using electrochemical techniques, in National Museum of Denmark, Museum Microclimates, Copenhagen: T. Padfield and K. Borchersen, 63-65

Characterization of archaeological bronze corrosion products crossing EIS with voltammetry of immobilized particles

Electrochemical impedance measurements were applied to microparticulate deposits of copper corrosion products attached to graphite electrodes in contact with different aqueous electrolytes (0.25 M HAc/NaAc (pH 4.75), 0.10 M HCl and 0.10 M HClO4) and the application of an interval of potentials between +0.25V to -0.75V. The conditions of operation were selected from a compromise between repeatability and sensitivity, being 0.10 M HClO4 and bias potential of 0.25 V adopted. The electrochemical impedance data were modeled on the basis of available equivalent circuits for corroded metal surfaces and the correlation between several pairs of circuit elements provided the characterization of different corrosion compounds regardless the amount of microparticulate solid on the electrode. Electrochemical grouping of samples from the archaeological Roman site of Gadara (Jordan, 4th century AD) suggests different provenances/manufacturing techniques, consistent with voltammetry of immobilized particles (VIMP) measurements. Thus, illustrating the capabilities of the intersection of such techniques in the archaeometric domain

Contabilidad Ad Hoc para la gestión municipal de una crisis epidémica: la fiebre amarilla en Cádiz en 1800

Este trabajo pretende contribuir a un mayor conocimiento acerca de cómo se generaron y se utilizaron en el pasado prácticas ad hoc de registro y de rendición de cuentas en el contexto del gobierno local para hacer frente a una situación de crisis. Para ello, se considera un problema de salud pública en un contexto concreto, la epidemia de fiebre amarilla en Cádiz en 1800. La particularidad del contexto estudiado, donde existía un gran bagaje contable, contribuye a que se establezcan como objetivos específicos del trabajo los siguientes: (1) explicar la génesis de los sistemas de rendición de cuentas y la propia contabilidad utilizados en la gestión municipal de una epidemia y (2) explorar la versatilidad y plasticidad que la perspectiva contable aportó a los registros generados en este contexto. Para ello, se consideran fuentes primarias y también publicaciones de la época. Las evidencias obtenidas muestran la emergencia en el ámbito local de un sistema de rendición de cuentas y de registro contable que recibe influencias del acervo contable y médico de la ciudad. Asimismo, sugieren que este acervo contable permite un uso e interpretación interesados, tanto por parte del gobierno local como por la Iglesia, los comerciantes y la profesión médica. El valor que la sociedad local confiere a los libros contables colabora en este sentido.This paper aims to extend the knowledge about how ad hoc accounting and accountability practices arose and were used in the past to face a situation of crisis in the context of local government. With this purpose, it addresses a health public problem in a specific context, the yellow fever epidemic in Cadiz in 1800. The specific characteristics of the setting, where acquaintance with accounting was usual, allow setting the following specific objectives: (1) to explain the genesis of the accountability systems and the accounting itself used for local government management of the epidemic and (2) to explore the versatility and plasticity that accounting background provides to the records produced in this context. To accomplish them, primary sources as well as publications of the time have been considered. The evidence obtained shows that both an accountability system and a basic bookkeeping system influenced by the local accounting and medical background arose in the local context. Moreover, the findings suggest that the generalized accounting background promoted the self-serving use and interpretation of the records by local government, local Church, trade association and medical profession. The value that local society attributed to accounting books was important in this sense

Productive Development Policies in Latin America and the Caribbean: The Case of Mexico

While Mexico has potential to grow rapidly, its economic growth has remained low for the past three decades. There is no consensus on the country’s development path or on how to achieve specific goals. Since the policy debate remains ideological and lacks pragmatism, productive development policies (PDPs) are often uncoordinated, redundant or even incongruent with each other. It is therefore important to understand the process whereby PDPs are designed and the institutional setting in which they are are implemented. This paper consequently examines whether PDPs respond to market failures and/or government failures. When PDPs are not designed to address specific market failures they can produce unwanted results or prove completely ineffective. When PDPs do address government failures, it is important to determine the reasons why the failure cannot be corrected in the first place and whether PDPs will be effective at addressing the problem in a second-best manner.Industrial Policy, Institutions, Policymaking, Mexico

La organización escolar y la movilización de los profesores y estudiantes en el uso de un nuevo Plan de Estudios de la Educación Secundaria General en Timor Oriental

Given that reforms involving how to deal with the past are extremely difficult, especially when the past involves memories of victimization, death, and destruction so widespread that a high percentage of the population is affected, the main purpose of this article is to describe how the general secondary education (GSE) curriculum in East Timor – an ancient Portuguese colony – is organized in terms of principles and objectives, themes, and methodological guidelines that give priority to assisting students to minimize or manage problems associated with conflict. Subsequently, the current state of GSE is characterized, in terms of school organization and logistics, and mobilization of teachers and students in using the new curriculum. The empirical results show that curricular materials incorporate aspects that can contribute to understanding and minimizing or managing problems created by the conflict, as well as contributing to avoid new conflicts. Nevertheless, although textbooks incorporate these aspects and teachers and students express interest in use them, problems remain regarding their appropriate usage due to numerous factors such as: logistics; school organization and poor teacher skills, despite training given and continued focused investment.Las reformas que implican lidiar con el pasado son extremadamente difíciles, especialmente cuando implican recuerdos de víctimas, muerte y destrucción tan generalizados que un alto porcentaje de la población se ve afectada. En ese sentido, el propósito principal de este a rtículo es describir cómo el Plan General de Estudios de Educación Secundaria (GSE) en Timor Oriental – una antigua colonia portuguesa – se organiza en términos de principios, objetivos, temas y orientaciones metodológicas que dan prioridad a la formación de los estudiantes para minimizar o controlar los problemas asociados con el conflicto. Por tanto, el estado actual de GSE se caracteriza por el uso del nuevo plan de estudios, en términos de organización escolar, logística, y de movilización de profesores y estudiantes. Los resultados empíricos muestran que los materiales curriculares incorporan aspectos que pueden contribuir a comprender y minimizar o controlar los problemas creados por el conflicto, así como para contribuir a evitar nuevos conflictos. Sin embargo, aunque los libros de texto incorporan estos aspectos y los profesores y los estudiantes expresan interés en el uso de ellos, hay problemas relativos a su utilización adecuada debido a numerosos factores, tales como: logística; la organización escolar y la mala preparación que todavía tienen los profesores, a pesar de la formación que se les ha brindado

Black hole accretion versus star formation rate: theory confronts observations

We use a suite of hydrodynamical simulations of galaxy mergers to compare star formation rate (SFR) and black hole accretion rate (BHAR) for galaxies before the interaction ('stochastic' phase), during the `merger' proper, lasting ~0.2-0.3 Gyr, and in the `remnant' phase. We calculate the bi-variate distribution of SFR and BHAR and define the regions in the SFR-BHAR plane that the three phases occupy. No strong correlation between BHAR and galaxy-wide SFR is found. A possible exception are galaxies with the highest SFR and the highest BHAR. We also bin the data in the same way used in several observational studies, by either measuring the mean SFR for AGN in different luminosity bins, or the mean BHAR for galaxies in bins of SFR. We find that the apparent contradiction or SFR versus BHAR for observed samples of AGN and star forming galaxies is actually caused by binning effects. The two types of samples use different projections of the full bi-variate distribution, and the full information would lead to unambiguous interpretation. We also find that a galaxy can be classified as AGN-dominated up to 1.5 Gyr after the merger-driven starburst took place. Our study is consistent with the suggestion that most low-luminosity AGN hosts do not show morphological disturbances.Comment: MNRAS Letters, in pres

Growing black holes and galaxies: black hole accretion versus star formation rate

We present a new suite of hydrodynamical simulations and use it to study, in detail, black hole and galaxy properties. The high time, spatial and mass resolution, and realistic orbits and mass ratios, down to 1:6 and 1:10, enable us to meaningfully compare star formation rate (SFR) and BH accretion rate (BHAR) timescales, temporal behaviour and relative magnitude. We find that (i) BHAR and galaxy-wide SFR are typically temporally uncorrelated, and have different variability timescales, except during the merger proper, lasting ~0.2-0.3 Gyr. BHAR and nuclear (<100 pc) SFR are better correlated, and their variability are similar. Averaging over time, the merger phase leads typically to an increase by a factor of a few in the BHAR/SFR ratio. (ii) BHAR and nuclear SFR are intrinsically proportional, but the correlation lessens if the long-term SFR is measured. (iii) Galaxies in the remnant phase are the ones most likely to be selected as systems dominated by an active galactic nucleus (AGN), because of the long time spent in this phase. (iv) The timescale over which a given diagnostic probes the SFR has a profound impact on the recovered correlations with BHAR, and on the interpretation of observational data.Comment: Accepted for publication in MNRA

A chemical model for the interstellar medium in galaxies

We present and test chemical models for three-dimensional hydrodynamical simulations of galaxies. We explore the effect of changing key parameters such as metallicity, radiation and non-equilibrium versus equilibrium metal cooling approximations on the transition between the gas phases in the interstellar medium. The microphysics is modelled by employing the public chemistry package KROME and the chemical networks have been tested to work in a wide range of densities and temperatures. We describe a simple H/He network following the formation of H$_2$, and a more sophisticated network which includes metals. Photochemistry, thermal processes, and different prescriptions for the H$_2$ catalysis on dust are presented and tested within a one-zone framework. The resulting network is made publicly available on the KROME webpage. We find that employing an accurate treatment of the dust-related processes induces a faster HI--H$_2$ transition. In addition, we show when the equilibrium assumption for metal cooling holds, and how a non-equilibrium approach affects the thermal evolution of the gas and the HII--HI transition. These models can be employed in any hydrodynamical code via an interface to KROME and can be applied to different problems including isolated galaxies, cosmological simulations of galaxy formation and evolution, supernova explosions in molecular clouds, and the modelling of star-forming regions. The metal network can be used for a comparison with observational data of CII 158 $\mu$m emission both for high-redshift as well as for local galaxies.Comment: A&A accepte