Analysis of Gender Differences in Facial Expression Recognition Based on Deep Learning Using Explainable Artificial Intelligence

Potential uses of automated Facial Expression Recognition (FER) cover a wide range of applications such as customer behavior analysis, healthcare applications or providing personalized services. Data for machine learning play a fundamental role, therefore, understanding the relevancy of the data in the outcomes is of utmost importance. In this work we present a study on how gender influences the learning of a FER system. We analyze with Explainable Artificial intelligence (XAI) techniques how gender contributes to the learning and assess which facial expressions are more similar regarding face regions that impact on the classification. Results show that there exist common regions in some expressions both for females and males with different intensities (e.g. happiness); however, there are other expressions like disgust, where important face regions differ. The insights of this work will help improving FER systems and understand the source of any inequality

Novel hybrid organic/inorganic poly(thiourethane) covalent adaptable networks

Organic-inorganic hybrid materials combine the advantages of both phases: hardness and strength of inorganic phase and elasticity and toughness of the organic matrix. In the present study, we have prepared nanocomposites with a poly(thiourethane) polymeric matrix and silsesquioxane-type structures, with thiols as reactive groups (POSS-A or POSS-B, synthesized in different pressure conditions), looking for a covalent interaction between both phases, and good dispersion. Due to the click behavior of the reaction between the isocyanate and the thiol groups, highly homogeneous materials are obtained. Both monomers, catalyst (dibutyltin dilaurate, DBTDL), and the POSS precursor (3-mercaptopropyl trimethoxysilane, MPTMS), are commercially available, which present the advantage of being industrially scalable. The incorporation of POSS leads to an increase in glassy and rubbery storage moduli and the temperature of the maximum of tan delta curve. The vitrimeric behavior of the poly(thiourethanes) improved with the POSS incorporation, getting lower relaxation times. With a higher proportion of closed cages, POSS-B leads to the most significant improvements. All the materials prepared showed high transparency and the fracture of POSS modified materials indicates an improved toughness.This work is part of the R & D projects PID2020-115102RB-C21 and PID2020-115102RB-C22 funded by MCINAEI/10.13039/501100011033. We acknowledge these grants and the Generalitat de Catalunya (2017-SGR-77 and BASE3D) . The authors declare the following financial interests/personal re-lationships which may be considered as potential competing interests: Angels Serra reports financial support was provided by Spain Ministry of Science and Innovation

Preparation and Characterization of a Series of Self-Healable Bio-Based Poly(thiourethane) Vitrimer-like Materials

A series of poly(thiourethanes) (PTUs) from biobased monomers have been synthesized. Limonene and squalene were transformed into polyfunctional thiols by thiol-ene reaction with thioacetic acid and further saponification. They were then reacted in different proportions with hexamethylene diisocyanate (HDI) in the presence of a catalyst to prepare bio-based poly(thiourethane) vitrimer-like materials. The different functionalities of squalene and limonene thiols (six and two, respectively) allow for changing the characteristics of the final material by only varying their relative proportions in the reactive mixture. The proportions of thiol and isocyanate groups were stoichiometric in all the formulations tested. An acidic and a basic catalyst were tested in the preparation of the networked polymers. As the acidic catalyst, we selected dibutyltin dilaurate (DBTDL), and as the basic catalyst, a tetraphenylborate salt of 1,8-diazabicyclo(5.4.0)undec-7-ene (BGDBU), which has the advantage of only releasing the base at high temperatures. The materials obtained were characterized by thermogravimetry and thermomechanical analysis. The vitrimeric-like behavior was evaluated, and we could see that higher proportions of the limonene derivative in the formulations led to faster stress relaxation of the material. The use of the base catalyst led to a much shorter relaxation time. The materials obtained demonstrated good self-healing efficiencyPeer ReviewedPostprint (published version

New bio-based materials obtained by thiol-ene/thiol-epoxy dual curing click procedures from eugenol derivates

Novel bio-based and dual-curable thermosets were prepared from eugenol derivatives. The curing sequence combined two click reactions, a photoinduced radical thiol-ene reaction followed by a thermally activated thiol-epoxy reaction. Eugenol was transformed into a triallyl (3A-EU) and a diallyl glycidyl derivative (2AG-EU) with high yields, and they were used as starting monomers in order to study the thiol-ene reaction and the dual-curing process, respectively. Three different thiol crosslinkers were tested, one commercially available tetrathiol derived from pentaerythritol (PETMP) and two other that were also synthesized: a trithiol derived from eugenol (3SH-EU) and a hexathiol derived from squalene (6SH-SQ). FTIR and DSC were used to monitor both curing stages and analyze the obtained materials. The results evidenced the occurrence of side reactions that led to incomplete thiol-ene reaction. The dual-curable materials showed higher Tgs than the materials obtained by a simple thiol-ene process and presented higher mechanical and thermomechanical performance.Postprint (author's final draft

The use of lanthanide triflates in the preparation of poly(thiourethane) covalent adaptable networks

Covalent adaptable networks (CANs) are new polymeric materials with the mechanical properties of thermosets and the possibility of being recycled like thermoplastics. Poly(thiourethane) networks have demonstrated vitrimeric-like behavior at high temperatures due to the trans-thiocarbamoylation process, which Lewis acids and bases can accelerate. In this study, we report the use of lanthanide triflates (La, Sm, Dy, Er, and Yb) as Lewis acid catalysts, a greener alternative to other metallic catalysts as dibutyltin dilaurate (DBTDL) widely used in poly (urethane) and poly(thiourethane) networks. Moreover, they are not as reactive as DBTDL, and the curing mixture can be manipulated for a longer time at room temperature. As monomers, trimethylolpropane tris(3- mercapto propionate) (S3), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) have been used. We have demonstrated that the materials prepared with lanthanum triflate present the lowest relaxation times than those prepared with other lanthanide triflates or DBTDL. Calorimetry (DSC) and infrared spectroscopy (FTIR) were applied to study the curing process. The materials obtained were fully characterized by thermog- ravimetric analysis (TGA) and thermomechanical tests (DMA).This work is part of the R&D projects PID2020-115102RB-C21 and PID2020-115102RB-C22 funded by MCNI/AEI/10.13039/ 501100011033. We acknowledge these grants and to the Generalitat de Catalunya (2021-SGR-00154 and BASE3D). F.G. thanks to MCNI/AEI for the grant PRE2018-084192.Postprint (published version

Vitrimeric Epoxy-Amine Polyimine Networks Based on a Renewable Vanillin Derivative

A series of bio-based polyimine vitrimers was obtained and characterized. A diimine-diglycidyl monomer (DIDG) was synthesized by condensing vanillin with 4,4'-oxydianiline (ODA) and further glycidylation with epichlorohydrin. This compound was cross-linked with three different Jeffamines (Jeff230, JeffD400, and JeffT403) with a different number of poly(propylene glycol) units in their structure and different functionalities. Trimethylolpropane triglycidyl ether (TMPTE) was added to the formulation to improve the thermal, mechanical, and thermomechanical properties. All of the materials prepared showed Tg’s above 66 °C, good vitrimeric behavior being the maximum relaxation rate reached by the material prepared from JeffD400, which also allows the most extensive degradation when treated with an acidic aqueous solution. These polyimine vitrimers can entirely relax the stress in less than 10.5 min at 150 °C without any added catalyst. All of the materials prepared could be satisfactorily recycled up to 200 °C also presenting an excellent self-welding ability.Peer ReviewedPostprint (published version

Sequential curing of off-stoichiometric thiol-epoxy thermosets with a custom-tailored structure

A new dual-curing system based on sequential thiol-epoxy click polycondensation and epoxy anionic homopolymerization was studied. Formulations of diglycidyl ether of bisphenol A and trimethylolpropane tris(3-mercaptopropionate) with 1-methylimidazole as a base catalyst and excess of epoxy groups were prepared and characterized. The curing process is sequential: fast thiol-epoxy polycondensation takes place first, followed by slower homopolymerization of excess epoxy groups. This makes it possible to define curing sequences with easy time-temperature control for both curing stages. The network buildup process during the first curing stage can be easily modelled assuming ideal polycondensation, which allows tailoring the structure and properties of the intermediate materials. The homopolymerization of the excess epoxy groups in the second curing stage results in a higher glass transition temperature (T-g) in comparison with the stoichiometric thiol-epoxy material, thus extending the application of thiol-epoxy thermosets to wider temperature ranges.Postprint (published version

Investigaciones en ciencias humanas y sociales : del ABC disciplinar a la reflexión metodológica

Diversidad de objetos, variedad de enfoques, prácticas disciplinares y multidisciplinares, y ejemplos de ejecución de proyectos de investigación y desarrollo son los rasgos distintivos de los siete capítulos que integran esta obra. En ellos se recoge el material desplegado en los Seminarios-Talleres de Metodología de la Investigación en Humanidades que se realizaron en el marco de las V Jornadas de Investigación de la Facultad de Filosofía y Letras de la Universidad Nacional de Cuyo en setiembre de 2004: estudios sobre procesos sociales, cuestiones educativas, geográficas, históricas, lingüísticas y literarias. Algunos capítulos han mantenido el estilo y formato característicos del contexto de los seminarios-talleres, a veces con ligeras modificaciones; otros han sido enteramente reescritos para la convocatoria de esta publicación. Este libro refleja entonces abordajes disciplinares y pluridisciplinares diversos a problemáticas igualmente variadas. Por tratarse de propuestas orientadas a y/o basadas en seminarios-talleres, está claro que los autores involucrados no pueden abarcar todos los aspectos de los objetos de estudio respectivos. Sin embargo, la idea es al menos brindar algún punto de vista sobre el estadio de desarrollo de algunas de las investigaciones actualmente en ejecución en nuestra Facultad

EGFR Inhibition in Glioma Cells Modulates Rho Signaling to Inhibit Cell Motility and Invasion and Cooperates with Temozolomide to Reduce Cell Growth

Enforced EGFR activation upon gene amplification and/or mutation is a common hallmark of malignant glioma. Small molecule EGFR tyrosine kinase inhibitors, such as erlotinib (Tarceva), have shown some activity in a subset of glioma patients in recent trials, although the reported data on the cellular basis of glioma cell responsiveness to these compounds have been contradictory. Here we have used a panel of human glioma cell lines, including cells with amplified or mutant EGFR, to further characterize the cellular effects of EGFR inhibition with erlotinib. Dose-response and cellular growth assays indicate that erlotinib reduces cell proliferation in all tested cell lines without inducing cytotoxic effects. Flow cytometric analyses confirm that EGFR inhibition does not induce apoptosis in glioma cells, leading to cell cycle arrest in G1. Interestingly, erlotinib also prevents spontaneous multicellular tumour spheroid growth in U87MG cells and cooperates with sub-optimal doses of temozolomide (TMZ) to reduce multicellular tumour spheroid growth. This cooperation appears to be schedule-dependent, since pre-treatment with erlotinib protects against TMZ-induced cytotoxicity whereas concomitant treatment results in a cooperative effect. Cell cycle arrest in erlotinib-treated cells is associated with an inhibition of ERK and Akt signaling, resulting in cyclin D1 downregulation, an increase in p27kip1 levels and pRB hypophosphorylation. Interestingly, EGFR inhibition also perturbs Rho GTPase signaling and cellular morphology, leading to Rho/ROCK-dependent formation of actin stress fibres and the inhibition of glioma cell motility and invasion

Facial detection and expression recognition applied to social robots

[eng] Facial expression is a non-verbal language that plays an important role in the communication, behaviour and interaction among humans. Recently, there has been a growing interest in the recognition of facial expressions in the field of Human-Robot Interaction (HRI). This interaction between robots and persons finds applications in different areas such as video surveillance, health care, road safety, etc. This research work has progressed in three lines designed to improve this interaction: face detection, facial expression recognition, and their integration into a human-robot interaction system implemented in a social robot. Face detection is the first step in a system in order to interact with a person. Many algorithms have been proposed for face detection. In this thesis a new method inspired on the classical Viola-Jones algorithm but using an a contrario statistical model in the detection step is presented. This method improves the accuracy of the original method, at a much lower computational cost. Facial expression classification is performed with a convolutional neuronal network, after a pre-processing of the input face images and using different datasets for training and testing. The developed network has achieved a success rate close to that of humans. In addition, the human capacity to recognize expressions has been evaluated and the results have been compared with the ones obtained with the neural network. Finally, an application with a social robot has been designed for the evaluation and validation of the proposed system in a real environment. The robot interacts with the user through a dynamic game where the player performs a series of facial expressions and the robot acts in response to the emotion expressed by the player.[spa] El reconocimiento de expresiones faciales es un lenguaje no verbal que determina un papel importante en la comunicación, comportamiento e interacción del ser humano. Recientemente ha surgido un gran interés en realizar reconocimiento de expresiones faciales en el ámbito de la Interacción Hombre-Robot (IHR). Dicha interacción entre robot y persona está orientada a diferentes ámbitos como vídeo-vigilancia, cuidados sanitarios, seguridad vial, detección de engaños, etc. En este trabajo de investigación se ha avanzado en tres líneas encaminadas a mejorar dicha interacción: detección de caras, reconocimiento de la expresión facial, y un sistema de interacción hombre-robot implementado en el robot social. La detección de caras es el primer eslabón de un sistema capaz de interactuar con una persona. Referente a este tópico existen numerosos algoritmos capaces de detectar el rostro. En esta tesis se presenta un nuevo método basado en el trabajo propuesto por Viola-Jones pero utilizando un modelo a contrario, el cual mejora la precisión de una cascada clásica, a un coste computacional mucho menor. La clasificación de la expresión facial se lleva a cabo con una red neuronal convolucional, aplicando un pre-procesamiento y haciendo uso de diferentes bases de datos. Con ello se ha conseguido una tasa de acierto cercana a la del ser humano. Además, se ha evaluado la capacidad humana para reconocer las expresiones y se han contrastado los resultados con la red neuronal. Por último, se ha diseñado una aplicación con el robot social para la evaluación y validación del sistema propuesto en un entorno real. El robot interactúa con el usuario a través de una dinámica de juego donde el jugador debe ir realizando expresiones faciales y el robot actúa en consecuencia a la emoción que ha expresado el jugador.[cat] El reconeixement d'expressions facials és un llenguatge no verbal que té un paper important en la comunicació, comportament i interacció de l'ésser humà. Recentment ha sorgit un gran interès a realitzar reconeixement d'expressions facials a l'àmbit de la Interacció Home-Robot (IHR). Aquesta interacció entre el robot i la persona està orientada a diferents àmbits com la vídeo-vigilància, cures sanitàries, seguretat viària, detecció d'enganys, etc. En aquest treball de recerca s'ha avançat en tres línies destinades a millorar la interacció: la detecció de cares, el reconeixement de l'expressió facial, i un sistema d'interacció home-robot implementat en el robot social. La detecció de cares és el primer pas d'un sistema capaç d'interactuar amb una persona. Referent a aquest tema, hi ha nombrosos algoritmes capaços de detectar la cara. En aquesta tesi es presenta un nou mètode basat en el treball proposat per Viola-Jones però utilitzant un model "a contrario", el qual millora la precisió d’una cascada clàssica, a un cost computacional molt menor. La classificació d'expressió facial es duu a terme amb una xarxa neuronal convolucional, aplicant un pre-processament i fent ús de diferents bases de dades. D’aquesta manera s'ha aconseguit una taxa d'encert propera a la de l'ésser humà. A més, s'ha avaluat la capacitat humana en reconèixer expressions facials i s'han contrastat aquests resultats amb la xarxa neuronal. Finalment, s'ha dissenyat una aplicació amb el robot social per a l'avaluació i validació del sistema proposat en un entorn real. El robot interactua amb l'usuari a través d'una dinàmica de joc, on el jugador ha d'anar realitzant expressions facials i el robot actua en conseqüència a l'emoció que s’ha expressat