Influence of Embankments with Parapets on the Cross-Wind Turbulence Intensity at the Contact Wire of Railway Overheads

Winds as an environmental factor can cause significant difficulties for the railway system operation. The railway overhead has been particularly vulnerable to cross-winds related problems, such as development of undamped oscillations due to galloping phenomenon. The installation of windbreaks to decrease the aerodynamic loads on the train can affect the loads on railway overheads triggering cable galloping. One essential parameter to indicate the influence of the parapet wake on the catenary contact wire is the turbulence intensity. In this paper the results of an experimental analysis of the turbulence intensity due to the presence of parapets carried out in a wind tunnel are reported. Embankments equipped with different parapets have been tested and turbulence intensity has been measured at both contact wire locations, windward and leeward. The relative influence of the parapets is measured through a reduced turbulence intensity, defined as the ratio between the turbulence intensity measured with parapet and the turbulence intensity in the case without any parapet on the embankment. In general the reduced turbulence intensity increases as the height of the parapet increases

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

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

Genes and proteins associated with chemotherapeutic resistance in breast cancer

Breast cancer is the main type of cancer that affects women in the world. Treatment with chemotherapeutic agents for this type of cancer depends to a large extent on the phenotypic characteristics that appear in the tumor, such as some receptors. The treatment of breast cancer is complex since not all patients respond adequately to it and this is partly due to mechanisms of resistance to treatment. The resistance either acquired or intrinsic to chemotherapeutics against breast cancer is related to multiple genes and proteins that are actively involved in the development of resistance mechanisms, which may be inhibiting the binding of the drug to the target receptor, inhibiting the gene expression of the receptors, activating signaling pathways, inducing the action of transporters that expel the drug from the cell, etc. As a result of this review, the mechanisms of chemotherapeutic resistance in breast cancer derived from genes and proteins related to say disease are described, including genes related to different types of breast cancer, as well as with different therapeutic strategies. These genes and their products of expression include a wide range of interactions and activations of signalling pathways that trigger a poor response to treatment, which translates into a worse prognosis, higher risk of prevalence and death, favouring breast cancer to be the main cause of cancer death in women. Objective: Conduct an updated review of genes and proteins, that have been associated with conferring resistance to the different chemotherapeutic agents used for the treatment of breast cancer, including the mechanism of resistance and the type of cancer in which it is generated. Method: The search for indexed articles in the PubMed (https://www.ncbi.nlm.nih.gov/pubmed/) and ScienceDirect (http://www.sciencedirect.com) databases was performed, using the words “Breast cancer resistance” as a search criterion, articles published in the period 2015-2017 were selected

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

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

A simplified approach to determine aerodynamic damping of railway overheads

The railway overhead (or catenary) is the system of cables responsible for providing electric current to the train. This system has been reported as wind-sensitive (Scanlon et al., 2000), and particularly to the occurrence of galloping phenomena. Galloping phenomena of the railway overhead consists of undamped cable oscillations triggered by aerodynamic forces acting on the contact wire. As is well known, aerodynamic loads on the contact wire depends on the incident flow mean velocity and the angle of attack. The presence of embankments or hills modifies both vertical velocities profiles and angles of attack of the flow (Paiva et al., 2009). The presence of these cross-wind related oscillations can interfere with the safe operation of the railway service (Johnson, 1996). Therefore a correct modelling of the phenomena is required to avoid these unwanted oscillations

Percepción De La Calidad De Servicio Y Su Relación Con El Nivel De Ventas De Garantía Extendida De La Tienda Saga Falabella Sucursal Chiclayo 2017

La presente investigación tuvo como objetivo determinar la relación entre la percepción de calidad de servicio y el nivel de ventas de garantía extendida en la tienda Saga Falabella sucursal Chiclayo. La investigación fue cuantitativa siguiendo un diseño: transversal, no experimental y correlacional. La población estuvo constituida por clientes que acuden a la tienda Saga Falabella durante los meses de enero – junio, de estos, se obtuvo una muestra, conformada por 345 clientes. Se empleó como instrumento un cuestionario estructurado bajo la escala de Likert, el que estuvo constituido por 22 ítems para calidad de servicio y 10 ítems para nivel de ventas, además fue validado mediante el coeficiente Alfa de Cronbach. Luego, los datos fueron procesados, analizados y estudiados mediante el programa estadístico SPSS 24. En la discusión de resultados, se obtuvo un coeficiente de correlación de Pearson de 0,851 y es significativa dado que el p<0,05 entre las dos variables de estudio, porque cuando el coeficiente de correlación se encuentra entre 0,72 a 0,90 existe una correlación positiva considerable por aproximarse a uno. Por tanto, se concluyó que, si existe relación significativa entre la percepción de calidad de servicio y el nivel de ventas de garantía extendida de la tienda Saga Falabella sucursal Chiclayo. El capítulo I contiene: Introducción, realidad problemática, trabajos previos, teorías relacionadas al tema, formulación del problema, justificación del estudio, hipótesis y objetivos. El capítulo II abarca el diseño de investigación, las variables de Operacionalización, la población y muestra, técnicas e instrumento de recolección de datos, método de análisis de datos y los aspectos éticos. El capítulo III resultados en el IV la discusión de resultados, en el V las conclusiones, en el VI las recomendaciones, en el VII bibliografía consultada y anexos. Esperando el reconocimiento de los aportes hechos en este trabajo de investigación, asumiré con humildad su veredicto a la ejecución del mismo, así como todas las observaciones y correcciones que consideren necesarias

Análisis multifractal del oleaje usando la metodología de Análisis Multifractal sin Tendencia (MF-DFA)

En este trabajo se aplica el análisis multifractal sin tendencia (MF-DFA) a la altura significativa espectral de ola de 52 mediciones de boyas distribuidas en el Mediterráneo occidental, entre el período de 2000-2005, en forma de cuadrícula con un distanciamiento de las mismas en torno a un grado de longitud. Se utilizó la descomposición STL para separar la serie temporal en una serie estacional y una serie de ruido. De esta manera, se pudo tratar la serie del ruido por separado, la cual está determinada posiblemente por los cambios climáticos que se produzcan a nivel global. Por tanto, se estudiaron, específicamente, las series temporales residuales del oleaje de cada boya a partir de un MF-DFA. Obteniendo los resultados típicos de una estructura multifractal, permitiendo su estudio a partir de los parámetros multifractales (exponente generalizado de Hurst, el parámetro de anchura, el parámetro de masa y el parámetro de asimetría). Esto permite generar un mapeo de los parámetros, facilitando su comparación y relacionándolo con los posibles sucesos que ocasionen la serie de ruido. Además, proporciona una gran cantidad de información, como podría ser su dimensión fractal o multifractalidad. A parte, los parámetros de forma individual proporcionan información adicional, por ejemplo, de la persistencia de la altura significativa de ola, la estructura fractal de la serie temporal, el comportamiento de las fluctuaciones y el dominio de los exponentes fractales. Los resultados del estudio concluyen que las zonas de mayor asimetría están relacionadas con la inestabilidad del viento y la altura de ola. Observándose una persistencia con tendencia ascendente de la altura de ola en fetchs influenciados por vientos fuertes del Norte. Estos efectos destacarán en la costa este española y, en menor medida, la costa francesa, la costa sur de España, Marruecos, Argelia y Túnez. En definitiva, el MF-DFA permite estudiar el comportamiento de la altura significativa de ola y predecir su evolución

Búsqueda de resistencia genética en la colección central colombiana - CCC a la polilla guatemalteca de la papa y evaluación de un material transgénico :informe técnico final

Los problemas que enfrenta el Agricultor de la papa en Colombia, son tanto de orden técnico como socioeconómico. Dentro de los primeros, los insectos plagas Tecia solanivora conocido como la polilla Guatemalteca y el gusano blanco, Premnotrypes vorax, junto con la enfermedad causada por el hongo Phytophthora /nfestans, conocida como gota o Tizón tardio, constituyen los mayores limitantes fitosanitarios en el cultivo. Para su control normalmente se utilizan los plaguicidas químicos, clasificados en las categorías toxicológicas más altas, lo cual implica grandes riesgos para la salud humana y el medio ambiente. Las plagas mencionadas pueden ocasionar daños en campo y almacén que superan en algunos casos el 50%. Para la polilla Guatemalteca se han estimado daños en promedio anual del 15 % equivalentes en perdidas económicas a unos $ 99.000.000.000 (Cevipapa, 2003)Papa-Solanum tuberosu