Three essays on the use of neural networks for financial prediction

The number of studies trying to explain the causes and consequences of the economic and financial crises usually rises considerably after a banking crisis occurs. The dramatic effects of the most recent financial crisis on the real economy around the world call for a better comprehension of previous crises as a way to anticipate future crisis episodes. It is precisely this objective, preventing future crises, the main motivation of this PhD dissertation. We identify two important mechanisms that have failed during the latest years and that are closely related to the onset of the financial crisis: The assessment of the solvency of banks along with the systemic risk over the time, and the detection of the macroeconomic imbalances in some countries, especially in Europe, which made the financial crisis evolve through a sovereign crisis. Our dissertation is made up of three different essays, trying to go a step ahead in the knowledge of these mechanisms.Departamento de Economía Financiera y ContabilidadDoctorado en Economía de la Empres

Effects of contract and trust on franchisor performance

The franchisor-franchisee relationship is governed by contracts and trust. This paper analyzes how formal (contracts) and relational (trust) governance mechanisms affected franchisor performance in a service sector franchise for the period 2008¬2015. Using the SOM method in the empirical analysis, the results revealed that trust-based governance was more prominent than contractbased governance in the multi-unit franchise network and the cross-franchising network, negatively affecting franchisor performance in the multi-unit franchise network and positively affecting franchisor performance in the cross-franchising network. In contrast, contracts were more prominent than trust in single-unit franchising, negatively affecting franchisor performance. The primary practical implication is that the franchisor should prevent franchisees in the MUF network from opening new outlets in the same city and competing for the existing outlet’s customers

Unsupervised Neural Networks for Identification of Aging Conditions in Li-Ion Batteries

This paper explores a new methodology based on data-driven approaches to identify and track degradation processes in Li-ion batteries. Our goal is to study if it is possible to differentiate the state of degradation of cells that present similar aging in terms of overall parameters (similar remaining capacity, state of health or internal resistance), but that have had different applications or conditions of use (different discharge currents, depth of discharges, temperatures, etc.). For this purpose, this study proposed to analyze voltage waveforms of cells obtained in cycling tests by using an unsupervised neural network, the Self-Organizing Map (SOM). In this work, a laboratory dataset of real Li-ion cells was used, and the SOM algorithm processed battery cell features, thus carrying out smart sensing of the battery. It was shown that our methodology differentiates the previous conditions of use (history) of a cell, complementing conventional metrics such as the state of health, which could be useful for the growing second-life market because it allows for determining more precisely the state of disease of a battery and assesses its suitability for a specific application

Lithium-Ion Battery Parameter Identification via Extremum Seeking Considering Aging and Degradation

Battery parameters such as State of Charge (SoC) and State of Health (SoH) are key to modern applications; thus, there is interest in developing robust algorithms for estimating them. Most of the techniques explored to this end rely on a battery model. As batteries age, their behavior starts differing from the models, so it is vital to update such models in order to be able to track battery behavior after some time in application. This paper presents a method for performing online battery parameter tracking by using the Extremum Seeking (ES) algorithm. This algorithm fits voltage waveforms by tuning the internal parameters of an estimation model and comparing the voltage output with the real battery. The goal is to estimate the electrical parameters of the battery model and to be able to obtain them even as batteries age, when the model behaves different than the cell. To this end, a simple battery model capable of capturing degradation and different tests have been proposed to replicate real application scenarios, and the performance of the ES algorithm in such scenarios has been measured. The results are positive, obtaining converging estimations both with new and aged batteries, with accurate outputs for the intended purpose

Mapas Auto-Organizados (SOM) para la detección de envejecimiento en baterías

Este artículo presenta la problemática asociada a la predicción de degradación de baterías mediante métricas clásicas, proponiéndose una metodología con redes neuronales SOM para clasificar las celdas según condiciones de uso distintas asociadas a diferentes valores de profundidad de descarga, temperatura ambiente y corriente de descarga

Evaluation of the neuroprotective efficacy of the gramine derivative ITH12657 against NMDA-induced excitotoxicity in the rat retina

PurposeThe aim of this study was to investigate, the neuroprotective effects of a new Gramine derivative named: ITH12657, in a model of retinal excitotoxicity induced by intravitreal injection of NMDA.MethodsAdult Sprague Dawley rats received an intravitreal injection of 100 mM NMDA in their left eye and were treated daily with subcutaneous injections of ITH12657 or vehicle. The best dose–response, therapeutic window study, and optimal treatment duration of ITH12657 were studied. Based on the best survival of Brn3a + RGCs obtained from the above-mentioned studies, the protective effects of ITH12657 were studied in vivo (retinal thickness and full-field Electroretinography), and ex vivo by quantifying the surviving population of Brn3a + RGCs, αRGCs and their subtypes α-ONsRGCs, α-ONtRGCs, and α-OFFRGCs.ResultsAdministration of 10 mg/kg ITH12657, starting 12 h before NMDA injection and dispensed for 3 days, resulted in the best significant protection of Brn3a + RGCs against NMDA-induced excitotoxicity. In vivo, ITH12657-treated rats showed significant preservation of retinal thickness and functional protection against NMDA-induced retinal excitotoxicity. Ex vivo results showed that ITH12657 afforded a significant protection against NMDA-induced excitotoxicity for the populations of Brn3a + RGC, αRGC, and αONs-RGC, but not for the population of αOFF-RGC, while the population of α-ONtRGC was fully resistant to NMDA-induced excitotoxicity.ConclusionSubcutaneous administration of ITH12657 at 10 mg/kg, initiated 12 h before NMDA-induced retinal injury and continued for 3 days, resulted in the best protection of Brn3a + RGCs, αRGC, and αONs-RGC against excitotoxicity-induced RGC death. The population of αOFF-RGCs was extremely sensitive while α-ONtRGCs were fully resistant to NMDA-induced excitotoxicity

Management of acute diverticulitis with pericolic free gas (ADIFAS). an international multicenter observational study

Background: There are no specific recommendations regarding the optimal management of this group of patients. The World Society of Emergency Surgery suggested a nonoperative strategy with antibiotic therapy, but this was a weak recommendation. This study aims to identify the optimal management of patients with acute diverticulitis (AD) presenting with pericolic free air with or without pericolic fluid. Methods: A multicenter, prospective, international study of patients diagnosed with AD and pericolic-free air with or without pericolic free fluid at a computed tomography (CT) scan between May 2020 and June 2021 was included. Patients were excluded if they had intra-abdominal distant free air, an abscess, generalized peritonitis, or less than a 1-year follow-up. The primary outcome was the rate of failure of nonoperative management within the index admission. Secondary outcomes included the rate of failure of nonoperative management within the first year and risk factors for failure. Results: A total of 810 patients were recruited across 69 European and South American centers; 744 patients (92%) were treated nonoperatively, and 66 (8%) underwent immediate surgery. Baseline characteristics were similar between groups. Hinchey II-IV on diagnostic imaging was the only independent risk factor for surgical intervention during index admission (odds ratios: 12.5, 95% CI: 2.4-64, P =0.003). Among patients treated nonoperatively, at index admission, 697 (94%) patients were discharged without any complications, 35 (4.7%) required emergency surgery, and 12 (1.6%) percutaneous drainage. Free pericolic fluid on CT scan was associated with a higher risk of failure of nonoperative management (odds ratios: 4.9, 95% CI: 1.2-19.9, P =0.023), with 88% of success compared to 96% without free fluid ( P <0.001). The rate of treatment failure with nonoperative management during the first year of follow-up was 16.5%. Conclusion: Patients with AD presenting with pericolic free gas can be successfully managed nonoperatively in the vast majority of cases. Patients with both free pericolic gas and free pericolic fluid on a CT scan are at a higher risk of failing nonoperative management and require closer observation

Analysis of sustainable consumer behavior as a business opportunity

The purpose of this paper is to analyze how consumers incorporate sustainability issues into their buying behavior. This paper applies the Self-Organizing Map method to a sample of 223 consumers who answered a questionnaire based on their current behavior rather than the way they thought they ought to behave. The results of this study indicate that consumers incorporate the dimensions of sustainability, acting in a more socially responsible manner, when they have a perception of the effectiveness of their buying behavior. The identified segments can help firms develop sustainability strategies to align their sustainable strategic goals with the needs and behavior of consumers, thereby targeting potential socially responsible customers more effectively. The main conclusion is that the manufacturers should increase transparency regarding the product manufacturing and distribution processes and include the product traceability information on the label or through some other medium

Vertical Transmission of Bacterial Eye Infections, Angola, 2011–2012

To determine transmission rates for neonatal conjunctivitis causative microorganisms in Angola, we analyzed 312 endocervical and 255 conjunctival samples from mothers and newborns, respectively, during 2011–2012. Transmission rates were 50% for Chlamydia trachomatis and Neisseria gonorrhoeae and 10.5% for Mycoplasma genitalium. Possible pathogenic effects of M. genitalium in children’s eyes are unknown