An MS-CASPT2 Study of the Photodecomposition of 4- Methoxyphenyl Azide. Role of Internal Conversion and Intersystem Crossing

Aryl azides photochemistry is strongly dependent on the substituent relative position, as has been studied by time resolved resonant Raman (TR3) spectroscopy for 4-methoxyphenyl azide and its isomer 3-methoxyphenyl azide. When irradiated at 266 nm, the former results in 4,4’-dimethoxyazobenzene whereas the latter forms 1,2-didehydroazepine. It is proposed that the key step of the reactions is the formation of a nitrene derivative. Recently, it has been proposed by us that nitrenes might have a relevant role in the Surface-Enhanced Raman Scattering (SERS) of p-aminothiophenol, however, the molecular mechanism is not well known in neither of these cases. Therefore, we studied the photodecomposition of 4-methoxyphenyl azide using multiconfigurational self-consistent field methods (MC-SCF) with the CAS-SCF and MS-CASPT2 approximations and calculated the resonant Raman spectra of the relevant species using a multi-state version of Albrecht’s vibronic theory. The results propose that the reaction follows a two steps sequence after irradiation at 266 nm: an intersystem crossing 21A’/23A’’ which decays through a 21A’/21A’’ conical intersection producing molecular nitrogen and triplet 4-methoxyphenyl nitrene in its ground state.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Frequency shift on the potential-dependent surface-enhanced Raman scattering of pyridine: simplified models for metal and solvent effects

The electronic structure of adsorbates is altered when it interacts with a surface, modifying the properties of both entities and giving rise to interesting phenomena related to heterogeneous catalysis or molecular electronics. If such surface is a metallic substrate, the electrode potential can be used to tune this interaction. Potential-dependent Surface-Enhanced Raman Scattering (SERS) is a particularly useful technique to study the induced effects on the molecule when the metal-adsorbate surface complex is formed, as the observed frequency shifts of the vibrational modes can provide information about it. However, from the computational point of view, these systems are difficult to model, because the macroscopic metal cannot be modelled easily using quantum mechanics. As an approach, we propose a simple model using silver atomic wires with different size and charge bonded to the molecule (AgnPyq, n = 2,3,5,7 and q = 0 and ±1 for n even and odd, respectively) which has been developed by the group and provides a good description of the effect of the electrode potential on the chemical enhancement mechanism of SERS.1-3 Electronic calculations were performed using Density Functional Theory (DFT). In order to study the frequency shifts, solvent effects have been taken into account by using the Polarizable Continuum Model (PCM). We have used three different functionals (B3LYP, PW91 and M06HF) and two basis sets (LANL2DZ for all atoms and LANL2DZ for Ag and 6-31G(d) for C,N,H) and, in all cases, a good agreement is achieved in terms of amplitude and trend of the frequency shift for most of the vibrational modes, especially when solvent interactions are included. The method was extended to other metals and solvents giving results in agreement with the available experimental data.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Computational modelling of iron-ore mineralisation with stratigraphic permeability anisotropy

This study develops a computational framework to model fluid transport in sedimentary basins, targeting iron ore deposit formation. It offers a simplified flow model, accounting for geological features and permeability anisotropy as driving factors. A new finite element method lessens computational effort, facilitating robust predictions and cost-effective exploration. This methodology, applicable to other mineral commodities, enhances understanding of genetic models, supporting the search for new mineral deposits amid the global energy transition

Charge Transfer mechanism in the Surface Enhanced Raman Scattering of 2,2'-bipyridine recorded on a silver electrode

Nowadays, Surface Enhanced Raman Spectroscopy (SERS) has become a powerful technique to investigate the electronic structure of surface-molecule hybrid systems due to the huge enhancement of the Raman signal. It is established that the origin of this enhancement has two main contributions; the electromagnetic (EM), related to surface plasmons, and the chemical mechanism, due to resonant charge transfer (CT) processes between the adsorbate and the metal. With the aim to investigate the SERS-CT of bipyridine and to identify charge transfer process, the spectra were recorded on silver electrode by using three different wavelengths (473, 532 and 785 nm) in a range from 0.0 up to -1.4 V electrode potential. The electrode potential was modelled in the calculations with atomic silver wires of different size and charge attached to the BPy molecule (AgnBPyq, with q = 0 for n = 2 and q = ±1 for n = 3, 5, 7) and were computed with Density Functional Theory (DFT). Although BPy shows a trans conformation in solution, a cis conformation was chosen for its chelating properties. The results indicate that the intensification of the ~1550 cm-1 band at negative potentials is due the Franck-Condon factors related to the resonant CT process from the metal to the BPy molecule.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Localizacion de los centros de distribucion de la empresa Coca-Cola Embonor S.A. (Planta Talca) mediante la aplicacion de un modelo matematico

146 p.La presente memoria tiene un enfoque en el modelamiento matemático y su aplicación en el sistema logístico de transporte de la empresa Coca-Cola Embonor S.A. (Planta Talca),teniendo como objetivo principal el determinar el número mínimo y localización de los Centros de Distribución necesarios, capaces de satisfacer la demanda de los clientes ubicados entre las ciudades de Teno y Parral. Los pasos a seguir para la realización de esta son: conocer la problemática de la empresa, para lo cual es necesario realizar un reconocimiento del proceso de distribución de productos de la empresa. Posteriormente se hizo necesario introducirse en el tema de logística de transporte, para luego buscar las alternativas de solución a través de herramientas matemáticas, buscando los modelos y/o metodologías aplicables según la naturaleza del problema a abordar, lo que corresponderá a los aspectos teóricos de la memoria. Dichos modelos y/o metodologías deberán arrojar los respectivos resultados que finalmente serán interpretados, entregando una conclusión que permita solucionar la totalidad o gran parte de la problemática de la empresa o también entregar las recomendaciones necesarias para dicho objetivo. La alternativa informática que se manejo para la resolución de los modelos matemáticos fue el software Ilog OPL, cuya ventaja es que posee compatibilidad con las hojas de cálculo de Microsoft Excel, lo que permite observar de inmediato los cambios en las soluciones al realizar variaciones en los parámetros del modelo. El resultado obtenido al correr el modelo es básicamente la asignación Cliente-Centro de distribución, que permita realizar el proceso de distribución que produzca los menores costos para la empresa. El principal resultado obtenido es la eliminación del Centro de Distribución de Hualañé, cuyos clientes fueron reasignados a los Centros de Distribución Constitución, Curicó y Planta Talca Como resultado se obtuvo una disminución de un 2,2% en los costos de distribución, lo cual representa un ahorro importante a considerar por la empresa, por lo cuál se recomienda la implementación de las mejoras propuestas

Modeling the effect of the electrode potential in SERS by electronic structure calculations.

Surface Enhanced Raman Spectroscopy (SERS), due to the ability of greatly intensify the weak Raman signal of molecules adsorbed to metal surfaces, has proven to be a very useful tool to investigate changes in the electronic structure of metal-molecule surface complex. A deep knowledge of the electronic structure of these metal-molecule hybrid systems is key in electrochemistry, catalysis, plasmonics, molecular electronics, and in the development of selective and ultra-sensitive analytical sensors. The origin of this huge enhancement in SERS is due to two contributions: the electromagnetic (EM), related to surface plasmons, and the chemical mechanism, due to resonant charge transfer (CT) process between the adsorbate and the metal (CTSERS). Unfortunately, the SERS implies very complex phenomena where the molecule and the metal nanoparticle are involved. This fact makes challenging to build realistic theoretical models that take into account both the metal and the molecule at quantum level. We propose a methodology, based on DFT and ab initio electronic calculations, to simulate the effect of the electrode potential on the absorption, on the charge transfer states energies, and on the electronic excitations in metal-molecule hybrid systems from a microscopic point of view. This methodology consists on the prediction of Raman intensities from ab initio calculations of the geometries or the energy gradients at the excited states Franck-Condon point, bringing the possibility to predict the intensities in CTSERS as well as in resonance Raman without the need to know the excited state geometries, not always feasible to compute. The microscopic model adopted to mimic the effect of the interphase electric potential consist in a molecule adsorbed to a linear silver cluster [Agn-Adsorbate]q, were n is the number of silver atoms, and the total charge of the system (q) is zero for n=2 and q=±1 for n=1, 3 and 7.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Biofilms in Focus : A Threat to Foods

The world of food microbiology, and by extension that of food safety, has evolved significantly at the turn of the century. In fact, from carrying out controls on the presence or absence of pathogens in finished products, we have gone on to try to detect, not only where the pathogens are found, to apply the appropriate corrective measures to the problem, but also to look beyond. At this point, the number of publications related to biofilms, considered as forms of resistance of microorganisms in food facilities, has increased significantly. Thus, according to PubMed, since 2010, 1494 articles have been published on biofilms and food safety. Therefore, the study of biofilms is being considered as an important element to improve food safety conditions nowadays

A comparative analysis between two statistical deviation–based consensus measures in group decision making problems

The mean absolute deviation and the standard deviation, two statistical measures commonly used in quantifying variability, may become an interesting tool when defining consensus measures. Two consensus indexes which obtain the level of consensus in some problems of Group Decision Making are introduced in this paper by expanding the aforementioned statistical concepts. A comparative analysis reveals that the levels of consensus derived from these indexes are close to those obtained employing distance functions when a fuzzy preference relations frame is considered, so they turn out to be a useful tool in this context. In addition, these indexes are different from each other and with the distance functions considered. Thus, they are applicable tools in the calculation of consensus in our context and are different from those commonly used

Valparaíso como Patrimonio de la Humanidad, entre expulsión y participación

The declaration of Valparaíso City as a World Heritage Site carries not only an honor for its geographical and urban qualities, it is also a conceptual value translated into a series of policies that influence the organization of life ways of those who make up this territory. Through this exercise, the city breaks with its social activity, to be determined by external devices, such as public policies emanating from a central power or as pressures from an economy that transforms and shapes the space according to the orders of the market, in view of turning it into a commercial product. This article presents the clash that occurs with heritage practices that seek to reduce forms of life to an abstract conceptual apparatus and restrict the activity of the city in favor of an alien and imposed identity. The applied methodology was hermeneutic-criticism, but also observation of cases and textual sources. The proposal of citizen participation is made explicit, which can be configured as an exercise that breaks the regulatory structures that govern the city.La declaración de la ciudad de Valparaíso como Patrimonio de la Humanidad conlleva no sólo un honor por sus cualidades geográficas y urbanas, a su vez, es un valor conceptual que se traduce en una serie de políticas que influyen en la organización de las formas de vida de quienes conforman dicho territorio. A través de este ejercicio, la ciudad rompe con su actividad social, para ser determinada por dispositivos externos, tales como políticas públicas emanadas de un poder central o como presiones de una economía que transforma y moldea el espacio según las órdenes del mercado, en vistas a convertirla en un producto comercial. Este artículo presenta el choque que se produce con las prácticas patrimoniales, que procuran reducir las formas de vida a un aparato conceptual abstracto y coartan la actividad de la ciudad en favor de una identidad ajena e impuesta. La metodología aplicada fue la hermenéutico-crítica, pero también la de observación de casos, y fuentes textuales. Se explicita la propuesta de la participación ciudadana, que puede configurarse como un ejercicio que rompa las estructuras normativas que rigen la ciudad