Pronóstico de incumplimientos de pago mediante máquinas de vectores de soporte: una aproximación inicial a la gestión del riesgo de crédito

Este documento describe la metodología desarrollada por Vapnik (1995), denominada máquinas de vectores de soporte (SVM, por sus siglas en inglés) y realiza dos aplicaciones al caso de clasificación de agentes para el otorgamiento de créditos a partir de sus características. El primer caso de estudio clasifica individuos de un banco alemán. En el segundo caso se pronostica el incumplimiento del pago de créditos comerciales otorgados a empresas colombianas utilizando las características iniciales del crédito. SVM se compara con dos metodologías utilizadas en el análisis de este tipo de problemas, regresión logística y análisis lineal discriminante. Los resultados arrojan un mejor desempeño en la predicción por parte de SVM respecto a las otras dos metodologías.Clasificación, máquinas de aprendizaje, riesgo de crédito, support vector machines. Classification JEL:C44, C50, C60, G32.

Actualización de la descomposición del BEI cuando se dispone de nueva información

Este documento utiliza la metodología de Melo et al. (2003) para la actualización de la descomposición del Break Even Inflation (BEI) presentado en Melo y Granados (2010) cuando se dispone de nuevas observaciones. El procedimiento de actualización utiliza una transformación del modelo de estado espacio del BEI en el que se supone que los parámetros del modelo siguen una caminata aleatoria.Break even inflation, filtro de Kalman, modelos de estado espacio. Classification JEL: C13, C50, E31.

The international transmission of risk : causal relations among developed and emerging countries' term premia

We study the effect of shocks to the United States government bonds term premium on Latin American government bonds term premia. For doing so, we compute dynamic multipliers. Our main findings indicate that Latin American countries' term premia respond p

Using a new high-throughput video-tracking platform to assess behavioural changes in Daphnia magna exposed to neuro-active drugs

© 2019. ElsevierOne of the major challenges that faces today regulatory risk assessment is to speed up the way of assessing threshold sublethal detrimental effects of existing and new chemical products. Recently advances in imaging allows to monitor in real time the behaviour of individuals under a given stress. Light is a common stress for many different organisms. Fish larvae and many invertebrate species respond to light altering their behaviour. The water flea Daphnia magna as many other zooplanktonic species has a marked diel vertical phototactic swimming behaviour against light due to fish predation. The aim of this study was to develop a high throughput image analysis to study changes in the vertical swimming behaviour to light of D. magna first reproductive adult females exposed to 0.1 and 1 µg/L of four psychiatric drugs: diazepam, fluoxetine, propranolol and carbamazepine during their entire life. Experiments were conducted using a new custom designed vertical oriented four 50 mL chamber device controlled by the Noldus software (Netherlands). Changes in speed, preferred area (bottom vs upper areas) and animal aggregation were analysed using groups of animals under consecutive periods of dark and apical light stimulus of different intensities. Obtained results indicated that light intensity increased the speed but low light intensities allowed to better discriminate individual responses to the studied drugs. The four tested drugs decreased the response of exposed organisms to light: individuals move less, were closer to the bottom and at low light intensities were closer each other. At high light intensities, however, exposed individuals were less aggregated. Propranolol, carbamazepine and fluoxetine were the compounds effecting most the behaviour. Our results indicated that psychiatric drugs at environmental relevant concentrations alter the vertical phototactic behaviour of D. magna individuals and that it is possible to develop appropriate high-throughput image analysis devices to measure those responses.Peer ReviewedPostprint (author's final draft

Electromagnetic Study of Behaviour of Plasmonic Units

SUMMARY: For any memory or computing device, fast switching speed and low switching energy are most attractive attributes, and approaches by which speed and energy efficiency can be improved are always desirable. Plasmonics offers a way to achieve those attributes of fast switching and low energy consumption: plasmonic resonant structures are inherently capable of harnessing and focusing optical energy on sub-wavelength scales, far beyond the capabilities of conventional optical and photonic elements. Plasmonics can provide us with access to both of these scenarios. Indeed, plasmonics offers additional light manipulation tools, otherwise inaccessible with conventional photonics. The collective oscillation of conduction electrons in a suitably shaped metallic nanoparticle (the so-called localized surface plasmon, LSP) can couple with impinging radiation, which in turn squeezes light into much reduced volumes, and greatly magnifies the local electric field, usually leading to a much reduced (non-diffraction limited) device footprint. This deliverable presents an analysis of the electromagnetic interaction of plasmonic units with phase-change materials (PCMs) as selected in the project PHEMTRONICS. As plasmonic units, we start by considering the common plasmonic metals of gold and silver, analyzing their possibilities and limits. Based on those, we consider the use of metallic nanoantennas made of Ga nanoparticle dimers. Ga has been selected due to its good plasmonic performance, physical and chemical properties and to its polymorphism. We have analyzed the coupling of plasmonic nanoantennas with the PCMs under consideration at the moment in the project, namely, GaS and Sb2S3 in their amorphous and crystalline phases. These two PCMs have been combined with Ga NPs and some gold configurations to make the nanoantenna reconfigurabilty wider and improve its tunability and performance. Further, plasmon coupling to PCM waveguides made of Sb2S3, has been analyzed through metallic grating couplers. Two basic configurations have been selected which could be the base to design a plasmonic enhanced PCM photodetector in collaboration with the PHEMTRONICS partners. Finally, conclusions have been drawn together with the identification of the practical solutions to couple plasmonics with novel PCMs

Dynamic reflective color pixels based on molybdenum oxide

Active materials which show phase transitions, usually known as Phase Change Materials (PCM), have paved the way to a new generation of reconfigurable plasmonic platforms. Tunable color devices have experienced a great development in the recent years. In particular, reflective color filters can take advantage from sunlight to select and reflect a specific resonant wavelength in the visible spectrum range. Reflective displays are usually structural color filters based on asymmetric Fabry-Perot cavities (AFPCs). For a fixed geometry, most of AFPCs filters generate static color, limiting their potential as tunable color devices. Dynamic color is achieved by introducing an active layer whose optical properties can be modulated by an external stimuli. In this paper, we propose AFPCs based on molybdenum oxide (MoOx, 2<x<3) to achieve switchable on/off color reflective pixels. On and off states of the pixels are controlled through the stoichiometry of the MoOx layer.This work has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement (No 899598 – PHEMTRONICS)

A New Algorithm for Multivariate Genome Wide Association Studies Based on Differential Evolution and Extreme Learning Machines

Genome-wide association studies (GWAS) are observational studies of a large set of genetic variants, whose aim is to find those that are linked to a certain trait or illness. Due to the multivariate nature of these kinds of studies, machine learning methodologies have been already applied in them, showing good performance. This work presents a new methodology for GWAS that makes use of extreme learning machines and differential evolution. The proposed methodology was tested with the help of the genetic information (370,750 single-nucleotide polymorphisms) of 2049 individuals, 1076 of whom suffer from colorectal cancer. The possible relationship of 10 different pathways with this illness was tested. The results achieved showed that the proposed methodology is suitable for detecting relevant pathways for the trait under analysis with a lower computational cost than other machine learning methodologies previously proposed

A label-free optical system with a nanohole array biosensor for discriminating live single cancer cells from normal cells

Developing a simple, fast, and label-free method for discrimination between live cancer cells and normal cells in biological samples still remains a challenge. Here, a system is described that fulfills these features to analyze individual living cells. The system consists of a gold nanohole array biosensor plus a microscope optical design to isolate the spectral response of a single cell. It is demonstrated that differences in the spectral behavior between tumor (colorectal cancer cell lines and primary cells from colorectal cancer tissue) and non-tumor cells (peripheral blood mononuclear cells, skin fibroblasts and colon epithelial cells) are influenced by the actin cortex, which lies within the short penetration depth of the surface plasmon electromagnetic field. The efficacy of this system was assessed by the analysis of about one thousand single cells showing the highest discrimination capacity between normal colon epithelial cells and colorectal cancer cells from surgical specimens, with values of sensitivity and specificity ranging 80-100% and 87-100%, respectively. It is also demonstrated that cell discrimination capacity of the system is highly reduced by disrupting the formation of actin cortex. This plasmonic system may find wide applications in biomedicine and to study key cellular processes that involve the actin cortex, including proliferation, differentiation, and migration.This work was supported by the Instituto de Salud Carlos III through grant DTS18/00141, co-funded by European Regional Development Fund/ European Social Fund “A way to make Europe/Investing in your future” and Instituto de Investigación Valdecilla (IDIVAL) (APG/03)

Differential effects of Anti-TNFα and Anti-α4β7 drugs on circulating dendritic cells migratory capacity in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an idiopathic and chronic disorder that includes ulcerative colitis (UC) and Crohn’s disease (CD). Both diseases show an uncontrolled intestinal immune response that generates tissue inflammation. Dendritic cells (DCs) are antigen-presenting cells that play a key role in tolerance maintenance in the gastrointestinal mucosa. Although it has been reported that DC recruitment by the intestinal mucosa is more prominent in IBD patients, the specific mechanisms governing this migration are currently unknown. In this study, the expression of several homing markers and the migratory profile of circulating DC subsets towards intestinal chemo-attractants were evaluated and the effect of biological drugs with different mechanisms of action, such as anti-TNFα or anti-integrin α4β7 (vedolizumab), on this mechanism in healthy controls (HCs) and IBD patients was also assessed. Our results revealed that type 2 conventional DCs (cDC2) express differential homing marker profiles in UC and CD patients compared to HCs. Indeed, integrin β7 was differentially modulated by vedolizumab in CD and UC. Additionally, although CCL2 displayed a chemo-attractant effect over cDC2, while biological therapies did not modulate the expression of the homing markers, we paradoxically found that anti-TNF-treated cDC2 increased their migratory capacity towards CCL2 in HCs and IBD. Our results therefore suggest a key role for cDC2 migration towards the intestinal mucosa in IBD, something that could be explored in order to develop novel diagnostic biomarkers or to unravel new immunomodulatory targets in IBD.This study has been funded through the Instituto de Salud Carlos III (Sara Borrell fellowships, CD17/00014; CD21/00014), Asociación Española de Gastroenterología (Beca del Grupo Joven), Programa Estratégico Instituto de Biología y Genética Molecular (IBGM Junta de Castilla y León. Ref. CCVC8485), Plan Nacional (PID2019-104218RB-I00) from the Spanish Government, Janssen and MSD

The UV plasmonic behavior of distorted rhodium nanocubes

For applications of surface-enhanced spectroscopy and photocatalysis, the ultraviolet (UV) plasmonic behavior and charge distribution within rhodium nanocubes is explored by a detailed numerical analysis. The strongest plasmonic hot-spots and charge concentrations are located at the corners and edges of the nanocubes, exactly where they are the most spectroscopically and catalytically active. Because intense catalytic activity at corners and edges will reshape these nanoparticles, distortions of the cubical shape, including surface concavity, surface convexity, and rounded corners and edges, are also explored to quantify how significantly these distortions deteriorate their plasmonic and photocatalytic properties. The fact that the highest fields and highest carrier concentrations occur in the corners and edges of Rh nanocubes (NCs) confirms their tremendous potential for plasmon-enhanced spectroscopy and catalysis. It is shown that this opportunity is fortuitously enhanced by the fact that even higher field and charge concentrations reside at the interface between the metal nanoparticle and a dielectric or semiconductor support, precisely where the most chemically active sites are located.This research has been supported by MICINN (Spanish Ministry of Science and Innovation, project FIS2013-45854-P). Research was sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-17-2-0023. Y.G. wants to thank the University of Cantabria for her FPU (formación del profesorado universitario) gran