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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Factors affecting the amplitude of the feedback-related negativity during the balloon analogue risk task

McCoy, Anthony William January 1900 (has links)
Master of Science / Department of Psychological Sciences / Michael Young / When making decisions, the probability and magnitude of errors can play a major role in changing preferences. Electroencephalography (EEG) research examining the error-related negativity (ERN) and the associated feedback-related negativity (FRN) has indicated that the amplitude of each component may predict subsequent behavioral change. The current study used a version of the Balloon Analogue Risk Task (BART) that involves outcomes that are dynamically changing over time. As the balloon grows, more points are available but the probability of the balloon popping (netting zero points) is higher; the participant decides when to stop the balloon’s expansion to maximize points. The BART was adapted to facilitate the study of the FRN in dynamic environments. The purpose of Experiment 1 was to determine the effect of error magnitude on FRN amplitude during popped (incorrect) trials, whereas Experiment 2 was aimed at determining the effect of error magnitude on FRN amplitude during cashed-in (correct) trials. It was hypothesized that larger errors (i.e., the balloon popping after waiting a long time to cash-in) would result in a larger FRN than smaller errors. In Experiment 1, error magnitude did not contribute to the amplitude of the FRN. In Experiment 2, the masked points possible condition was a replication of Experiment 1. In the unmasked points possible condition, the number of points that could have been earned for each balloon was presented before participants found out how many points were earned. It was expected that there would be a larger FRN magnitude after cashed-in trials in the unmasked points possible condition compared to the masked points possible condition based on the magnitude of the error. In Experiment 2, the amplitude of the FRN was affected by the magnitude of the error on cashed-in trials in the unmasked condition, but not the masked condition. These results are seemingly at odds, and cannot be assimilated into any currently extant model of the FRN. An explanation relying on the motivational importance of errors is discussed.
52

Present with an Uncertain Future: Dispositional Mindfulness, Covariation Bias, and Event-Related Potential Responses to Emotional Stimuli in Uncertain Contexts

Goodman, Robert J. 01 January 2014 (has links)
Uncertainty represents a robust threat that can amplify aversive experiences and exaggerate negative expectations about uncertain future outcomes. Mindfulness – an open and receptive attention to present moment experiences -- has been shown to facilitate adaptive regulation when faced with a variety of distinct emotional threats. Reduced experiential avoidance and equanimity in the face of unpleasant emotional experiences have been theorized as central to these emotional regulatory benefits. The present study explored whether dispositional mindfulness would promote adaptive responses to uncertainty during the anticipation of, and after exposure to emotional stimuli, as indicated by self-reports and neural (event-related potential) markers of anticipation and appraisal. Participants were exposed to stimulus cues that informed them about the valence of a subsequent emotional picture as neutral, aversive, or uncertain. Consistent with past research, uncertainty during the anticipation of an emotional stimulus amplified unpleasant stimulus appraisals, and participants demonstrated biased expectations to associate uncertainty with aversiveness. Dispositional mindfulness was associated with lower expectations for unpleasant stimuli, and was found to amplify the effect of uncertainty on a cortical marker of stimulus appraisal called the late positive potential (LPP). Traits that contrasted with mindfulness predicted opposite patterns of association with these measures. However, these findings were directly the opposite of findings from past research. A theoretically defensible explanation is discussed for these findings and suggestions were made for future research on the role of mindfulness on ERP variability. The results from the present study contribute to a growing body of evidence that suggests that uncertainty during the anticipation of potentially negative future outcomes can exert a potent downstream influence on emotional anticipation and appraisal processes. Further research is needed to clarify the role of dispositional mindfulness during emotional stimulus anticipation and appraisal following uncertainty.
53

Does mindfulness reduce negativity bias? A potential mechanism for reduced emotional distress

Kiken, Laura 22 May 2009 (has links)
The present research examined if mindfulness reduced negativity bias on measures of attitude formation and cognitive style, as a potential explanation for the beneficial effects of mindfulness on emotional disturbance. Two studies were conducted. Study One was correlational and found that trait mindfulness inversely correlated with measures of negative cognitive style, and that the latter partially mediated an inverse association between mindfulness and predisposition to depression and anxiety. Further, correlations between mindfulness and both positive attitude formation and optimism hinted at a potential positivity bias. Study Two extended these findings using a randomized experimental design comparing a mindfulness induction to an unfocused attention control condition. The mindfulness condition demonstrated a positivity bias in attitude formation and increased optimism compared to the control condition, but did not demonstrate bias in attitude generalization. Potential explanations and implications for emotional disturbance are discussed.
54

Entre-nós: uma análise da conjugalidade homoafetiva feminina sob a ótica das alianças inconscientes / Between us: an analysis of the female homosexual conjugality from the perspective of unconscious alliances

Lopreato, Marina Roquette 31 May 2019 (has links)
O aparecimento das novas configurações familiares LGBT tem gerado discussões candentes no cenário mundial. Nos últimos anos, o Brasil teve conquistas jurídicas e sociais importantes. Porém, mesmo diante desses avanços, o país ocupa a posição de primeiro lugar no ranking mundial de assassinatos por homolesbotransfobia. Os relacionamentos homoafetivos, cada vez mais expressivos e visíveis, trazem a necessidade de compreender como esses casais investem subjetivamente na relação e os dilemas que vivenciam. Esta pesquisa teve por objetivo investigar a conjugalidade homoafetiva feminina e conhecer os impactos do campo de representação social predominantemente atravessado por preceitos heteronormativos nos intercâmbios inconscientes que estruturam o vínculo intersubjetivo desses casais. Foram realizadas entrevistas abertas com casais homoafetivos femininos, no qual a pesquisadora pediu para as entrevistadas compartilharem de forma livre como foi a construção do relacionamento e que pontos da relação elas julgavam importantes de serem compartilhados. O exame do material teve o apoio teórico da psicanálise, baseado nos postulados de René Kaës,que compreende o sujeito do inconsciente enquanto sujeito do grupo. Os conceitos de intersubjetividade, alianças inconscientes e negatividade serviram de embasamento conceitual-teórico e nortearam as discussões. Nos relatos das protagonistas, foram identificadas diversas formas de violência na qual foram vítimas, impingidas através de atos sutis ou de estigmatização dessubjetivante, sugerindo uma recusa da existência legítima e da visibilidade da homoconjugalidade pelos laços sociais e vínculos familiares. Negativamente marcadas, elas narraram episódios de homofobia e um imaginário de associação da mulher homoafetiva com a marginalidade. Esse cenário social de hostilidade desafia os avalistas metassociais e psíquicos do vínculo intersubjetivo e impacta nas alianças de base, fundamentais para a função narrativa e legitimadora da relação / The onset of the new LGBT Family configurations has been generating burning discussions in the world scenario. Brazil has had important legal and social achievements in the last years. However, even considering such advances, the country ranks first in murders due to homophobie. The homosexual relationships, each time more significant and visible, bring a need to understand how these couples subjectively invest in the relationship and, therefore, the dilemma that they experience. In the present research, I propose the research of the female homosexual conjugality and the knowledge of the impacts of the field of social representation, which are predominantly crossed by heteronormative precepts in the unconscious exchanges that structure the intersubjective bond of these couples. Open interviews with female homosexual couples were made, in which the interviewed were asked to freely share the construction of their relationship as well as the aspects of the relationship they found important to be shared. Theoretical support of psychoanalysis was sought in the analysis of the material, especially in the postulates of René Kaës, who understands the subject of the unconscious as the subject of the group.The concepts of intersubjectivity, unconscious alliances and negativity were taken as conceptual and theoretical background and they guided discussions. Various forms of violence were identified in the report of the victims themselves, in which they were foisted either through subtile acts or through desubjectivating stigmatization, suggesting a refusal of both the legitimate existence and the visibility of the homoconjugality through social ties and family bonds. These subjects are strikingly marked and they narrate episodes of homophobia and an imagery of association of homosexual woman and marginality. This social scenario of hostility challenges the metasocial and psychic guarantors of the intersubjective bond and it presents a negativity in the alliances of base that are essential for the role of the narrative and legitimising of the relationship
55

Excommunicatio. Ensaio para uma teoria negativa da comunicação / Excommunicatio: an essay for a negative theory of communication

Nascimento, Maurício Augusto Pimentel Liesen 19 March 2014 (has links)
Este trabalho de doutorado esboça uma teoria negativa da comunicação a partir da reelaboração negativa dos seus três conceitos fundamentais: a comunicação, o medium e a comunidade. Grosso modo, a comunicação é figurada como uma experiência radical de alteridade; o medium como a descrição dos modos de percepção desta experiência e a comunidade como a incorporação das possibilidades de sua ocorrência. A comunicação manifesta uma experiência que transforma o \'eu\' em \'mim\', pois o sujeito não é necessariamente causa ou efeito desta experiência, mas é exposto à ela, como uma ferida aberta. O medium é o modo de percepção que opera esta experiência: ele não é uma ponte entre o abismo que separa o mim do outro, pois ele acentua esse abismo, na medida em que ele se imaterializa no momento da experiência, como uma materialidade que se descorporifica. E quando essa experiência efetua-se, é porque se toma parte em algo comum, em uma comunidade: mesmo que precária ou evanescente, ela incorpora a possibilidade da ocorrência deste fenômeno. Na teoria negativa da comunicação, o medium torna-se transparente, a comunidade torna-se expositória e a comunicação torna-se transcendente. Ponderar sobre a negatividade da comunicação é ir ao encontro de uma ex-comunicação: uma despalavra que busca ex-pôr aquilo que nos fenômenos comunicacionais escapa à discursividade, seja a medialidade do meio, a inefabilidade da relação ou a comunidade daqueles que não constituem qualquer comunidade. O prefixo ex assinala não apenas uma simples negação, mas um deslocamento fundamental: ele é o inegável que se pré-supõe, que constitui a comunicação, mas que resiste à qualquer conceituação. Ao mesmo tempo em que possibilita, o prefixo ex assegura a impossibilidade da sua re-presentação: um comunicar que não se estrutura em signos, mas se mostra - uma comunicação negativa, existencial, intransitiva, inexprimível, mística. / Ex-communication is an «un-word» that emphasizes what eludes in the communicational phenomenon: be it the mediality of the medium, the incomprehensibility of a relation or the community of those who have no community. The «ex» means not only a negation, but also a fundamental drift: it is the irrevocable and the irreconcilable that the communication presupposes and constitutes, although it defies conceptualization. The «ex» guarantees the impossibility of re-presentation. A communication that is not structured by signs, but rather shows itself: it is an existential, intransitive or mystical communication. This PhD thesis aims to establish the general outline for a negative theory of communication. By using the negative and posthermeneutic media philosophy developed by the philosopher Dieter Mersch, this dissertation intends a negative reelaboration of the three main concepts of a communicational theory: media, community and communication. In general, communication is taken as a radical alterity experience, medium as the modes of perception of this experience, and community as the possibility and condition of the communicacional event. In other words: in the negative theory of communication, the medium is transparent, the community is what ex-poses, and communication is transcendent.
56

Der Begriff der Reflexion bei Hegel

Cho, Chong-Hwa 15 January 2007 (has links)
Die Hegelsche Wissenschaft der Logik gilt zurecht als das grundlegende, wenn auch komplexeste und dunkelste Werk Hegels. In ihr entfaltet Hegel den begrifflich-methodischen Hintergrund seines Systems mit dem Anspruch, eine spekulative Metaphysik zu etablieren. Dafür spielt eine wichtige Rolle der Reflexionsbegriff, der explizit in der Wesenslogik zur Darstellung kommt und als die Natur der Reflexion, als die immanente Reflexion von Reflexion in Anderes und Reflexion in sich, charakterisiert wird. Die Reflexion als objektive Reflexion bezieht sich einerseits auf die selbstbezügliche Negativität, die in ihrem vollständigen Sinne die einheitliche Struktur der negativen Selbstbeziehung ausmacht, und andererseits auf den Widerspruch, der die selbstbezügliche Negativität zur Natur hat und selber als der sich aufhebender Widerspruch die Reflexionseinheit als Grund bildet; diese Reflexionseinheit hat jene einheitliche Struktur der negativen Selbstbeziehung in sich. Solche Reflexion bringt das Sein zur Darstellung als das, was es in Wahrheit ist, nämlich als Selbstsein im Anderssein, das für Hegel der Begriff bzw. das Subjekt ist. Wenn das Sein sich als das Selbstsein im Anderssein erweist, kann die Selbstbewegung des Begriffs selbst ermöglicht werden, die Hegel in seiner Wissenschaft der Logik in Anspruch nimmt. Ohne das Verständnis dafür, wie die Begriffe der Negativität, des Widerspruchs und der Reflexion bei Hegels System sich zueinander verhalten, könnte man nicht genau die Wissenschaft der Logik verstehen. / Hegel’s Science of Logic is considered to be a fundamental, but at the same time the most complex and difficult, work of Hegel. He has developed in this work the conceptual and methodic background of his system, claiming that he tries to establish a speculativ metaphysics. The concept of reflexion plays an important role in this project. The concept of reflexion is explained in the Logic of Essence and the nature of reflexion is charaterized as the immanent reflexion of the reflexion in the other and in itself. The reflexion as the objektive reflexion is related, on the one hand, with the self-related negation, which makes up the unified structure of the negative self-relation, on the ohter hand, with the contradiction, whose nature lies in the self-related negativity. The contradiction builds up the unity of reflexion as the ground(Grund), because it must sublime (aufheben) itself. The unity of reflexion has the unified structure of the negative self-relation in itself. Such reflexion describes the being as what it truly is, namely as the self-being in the other-being. This means for Hegel the concept or the subject. If the being proves itself as the self-being in the other-being, the self-movement of concept itself becomes possible through it. The self-movement of concept was an aim of Hegel in his Science of Logik. Without unstanding the reciprocal relations between the concept of negation, contradiction and reflexion in the system of Hegel, we cound never exactly understand the Science of Logic.
57

O cinturão verde de São Paulo: a relação cidade-campo como expressão crítica do capital a partir da década de 1970 / São Paulos Green Belt: the relationship between city and countryside as a critical expression of the capital since the 1970s

El-Khatib, Walid Mahmoud Abd Ellatif Mahmoud 30 November 2018 (has links)
O cinturão verde de São Paulo aparece à consciência fetichista como expressão fenomênica do processo de acumulação e de desenvolvimento civilizatório do capital. No entanto, esse mesmo processo, sob a perspectiva da teoria crítica do valor pode ser pensado como explicitação do negativo como determinação da reprodução social. Nesse sentido, a partir da literatura geográfica e de trabalhos de campo pode-se compreender o processo de formação do cinturão verde, não mais como algo dado e naturalizado, mas como expressão social na relação sujeito-objeto, na qual o negativo põe a identidade aos termos. Desloca-se a análise da cisão entre rural e urbano, entre cidade e campo para o campo da crítica, na qual a cisão predicada como negativa impõe à análise a explicitação da negatividade constituinte de seus momentos lógicos e categoriais. Da produção crítica de valor, engendrada pelo desenvolvimento social das forças produtivas e pela divisão social do trabalho, tem-se a produção imanente do negativo como elemento determinante à reprodução social, que por sua vez se fenomeniza conformando na cisão cidade campo, o cinturão verde. É nesse cinturão que a agricultura e o imobiliário confrontam-se, mediados pelo capital financeiro, explicitando, sob o véu material da urbanização, o contrário da acumulação, explicitando que o desenvolvimento do cinturão verde não se põe como acumulação de capital e urbanização, mas como crise e negatividade imanentes ao capital. / Sao Paulo\'s green belt appears to the fetishized consciousness as a phenomenal expression of the accumulation and the civilizational development of the capital. However, this same process, from the perspective of value criticism can be thought as an explicitness of the negative as a determination of social reproduction. In this sense, as from geographic literature and as from fieldwork the formation process of the green belt may be no longer understood as something given and naturalized, but as a social expression of the specific relationship between subject and object, in which is the negative that sets the identity of the terms. Therefore, it moves the scission between rural and urban, between city and countryside to other qualitatively different level, in which the scission predicated as negative requires an analysis of the explicitness from the constituent negativity of its logical and categorical moments. The critical production of value, engendered by the social development of the forces of production and by the social division of labor, engenders the immanent production of the negative as a determining element to the social reproduction, which in turn makes a phenomenon pursuant to the scission city-countryside and therefore the green belt. In the green belt agriculture and the real estate market confront one another mediated by financial capital, explaining in the apparent urbanization the otherwise of accumulation, explaining that the development of the green belt it is not set as an urbanization/accumulation, but as immanent negativity and crises of the capital.
58

A dependência química em mulheres: figurações de um sintoma partilhado / The chemical dependency in women: figurations of a shared symptom

Gomes, Katia Varela 03 September 2010 (has links)
Os problemas decorrentes do uso, abuso e dependência de drogas tornaram-se uma preocupação mundial, mobilizando recursos e ações interventivas na atenção aos usuários e dependentes. Entre os grupos, encontramos as mulheres, com características próprias, exigindo pesquisas e programas de tratamento específicos. Esta pesquisa procura privilegiar as especificidades do feminino e a dependência de drogas, através dos referenciais teóricos da psicanálise sobre a sexualidade feminina e a feminilidade. Utilizam-se, também, as concepções sobre o sujeito do grupo, que implicam uma subjetividade constituída nos e pelos conjuntos intersubjetivos, conforme desenvolve René Kaës. Considera-se que, de acordo com os postulados desse autor, a negatividade está na base de todo laço social, configurando as alianças inconscientes e as formações intermediárias no vínculo entre os sujeitos. Nesse sentido, propõe-se uma linha de investigação psicanalítica sobre a dependência química como um sintoma partilhado, objetivando: a) investigar os processos psíquicos relacionados à produção de sintomas em mulheres dependentes químicas, através dos discursos produzidos em uma situação de grupo; b) investigar as formações intermediárias e as modalidades de negatividade na manutenção do sintoma e do laço social. Como procedimento, foi utilizado um grupo psicoterapêutico em um Centro de Atenção Psicossocial Álcool e outras drogas (CAPS ad) e na análise foram consideradas: a interdiscursividade e a linearidade dos enunciados; a transferência e a contratransferência; e a realidade psíquica do/no grupo. Através da análise do discurso em situação de grupo, foram elaboradas três categorias representantes da produção intersubjetiva: as formações intermediárias (porta-voz, porta-sintoma, porta-ideal), as modalidades de negatividade (a negatividade de obrigação e a negatividade radical) e o complexo fraterno. Conclui-se que a dependência química em mulheres é uma formação intermediária, representando aspectos denegados dos conjuntos intersubjetivos a que pertencem (família e instituição de tratamento). Através do pacto denegativo, a vulnerabilidade e o desamparo são expulsos da dinâmica intersubjetiva e intrapsíquica marcas da feminilidade na constituição subjetiva. A aliança inconsciente fundamenta-se, portanto, na denegação dos elementos relacionados à dimensão do sensível, do corpo, da sexualidade, do desejo e da incompletude humana. A dependência química feminina configura-se como portavoz do que é intolerável na feminilidade. / The problems arisen from drug use, abuse and dependence became a global issue, mobilizing resources and interventional actions concerning recreational users and addicts. Among different groups of users there are women, with their own characteristics that demand specific research and treatment programs. This research aims at focusing the specificity of the feminine and drug dependence through theoretical psychoanalytical references about feminine sexuality and femininity. We will also use the concept of subject of a group that implies constituted subjectivity within and by inter-subjective groups, according to René Kaës. He states that negativity is in the base of every social tie, configuring unconscious alliances and intermediary formations regarding connections among subjects. In this sense, we propose a psychoanalytical investigative method about chemical dependency as a shared symptom aiming at: a) investigating the chemical processes related to symptoms production in chemical dependent women through speeches produced in a group situation; b) investigating the intermediary formations and the modalities of negativity in symptoms and social ties maintenance. We worked with a psychotherapy group in an Alcohol and other drugs Psychosocial Attention Center (CAPS ad). In our analysis we considered: the interdiscursivity and the linearity of the utterances; the transference and the countertransference; the psychic reality of/in the group. Through discourse analysis, we elaborated three representative categories of the inter-subjective production: the intermediary formations (spokesperson, symptomatic-person, ideal-person), the modalities of negativity (the negativity of obligation and the radical negativity) and the sibling complex. We can conclude that chemical dependency in women is an intermediary formation, representing denied aspects of the inter-subjective groups which they belong to (family and treatment institution). Through the pact of denial, the vulnerability and the defenseless are driven out of the inter-subjective and intra-psychic dynamic which are aspects of the femininity in the subjective constitution. The unconscious alliance is founded, thus, on the denial of the elements related to the dimension of the sensibility, of the body, of the sexuality, of the desire and of the human incompleteness. The feminine chemical dependency takes form as the spokesperson of what is unbearable in femininity.
59

Error-related negativity (ERN) as a transdiagnostic endophenotype for irritability traits in a comunity sample : a rdoc perspective

Souza, Ana Maria Frota Lisboa Pereira de January 2017 (has links)
Mental disorders present difficulties in the research of their mechanisms, considering the high levels of comorbidity and the lack of specific neuroscience data to evaluate them. Estipulating deficit circuits in the disorders and the best treatment is a complex task, given the limited comprehension of the factors that correlate to the disorders. The utilization of biomarkers has proved an efficient and reliable alternative to provide precise diagnosis. Among the biomarkers, the Error-Related Negativity component, an event-related cortical potential, has presented high indexes of stability and validity in correlating to anxiety, obsessive, and mood-related mental disorders. The present dissertation evaluated irritability traits in a community sample, using a Flanker task, that has consistently elicited Error-Related Negativity according to the literature. Our results corroborate literature and found a frontocentral negativity, that peaked around 100ms after the commission of an error in the Flanker Task. However, our manipulation of negative feedback did not support literature, and ERN amplitudes were less enhanced post negative feedback. The relationship between irritability and ERN remains unclear. Future studies should, therefore, address these questionings.
60

Décompositions parcimonieuses pour l'analyse avancée de données en spectrométrie pour la Santé / Sparse decompositions for advanced data analysis of hyperspectral data in biological applications

Rapin, Jérémy 19 December 2014 (has links)
La séparation de sources en aveugle (SSA) vise à rechercher des signaux sources inconnus et mélangés de manière inconnue au sein de plusieurs observations. Cette approche très générique et non-supervisée ne fournit cependant pas nécessairement des résultats exploitables. Il est alors nécessaire d’ajouter des contraintes, notamment physiques, afin de privilégier la recherche de sources ayant une structure particulière. La factorisation en matrices positives (non-negative matrix factorization, NMF) qui fait plus précisément l’objet de cette thèse recherche ainsi des sources positives observées au travers de mélanges linéaires positifs.L’ajout de davantage d’information reste cependant souvent nécessaire afin de pouvoir séparer les sources. Nous nous intéressons ainsi au concept de parcimonie qui permet d’améliorer le contraste entre celles-ci tout en produisant des approches très robustes, en particulier au bruit. Nous montrons qu’afin d’obtenir des solutions stables, les contraintes de positivité et la régularisation parcimonieuse doivent être appliqués de manière adéquate. Aussi, l’utilisation de la parcimonie dans un espace transformé potentiellement redondant, permettant de capturer la structure de la plu- part des signaux naturels, se révèle difficile à appliquer au côté de la contrainte de positivité dans l’espace direct. Nous proposons ainsi un nouvel algorithme de NMF parcimonieuse, appelé nGMCA (non-negative Generalized Morphological Component Analysis), qui surmonte ces difficultés via l’utilisation de techniques de calcul proximal. Des expérimentations sur des données simulées montrent que cet algorithme est robuste à une contamination par du bruit additif Gaussien, à l’aide d’une gestion automatique du paramètre de parcimonie. Des comparaisons avec des algorithmes de l’état-de-l’art en NMF sur des données réalistes montrent l’efficacité ainsi que la robustesse de l’approche proposée.Finalement, nous appliquerons nGMCA sur des données de chromatographie en phase liquide - spectrométrie de masse (liquid chromatography - mass spectrometry, LC-MS). L’observation de ces données montre qu’elles sont contaminées par du bruit multiplicatif, lequel détériore grandement les résultats des algorithmes de NMF. Une extension de nGMCA conçue pour prendre en compte ce type de bruit à l’aide d’un a priori non-stationnaire permet alors d’obtenir d’excellents résultats sur des données réelles annotées. / Blind source separation aims at extracting unknown source signals from observations where these sources are mixed together by an unknown process. However, this very generic and non-supervised approach does not always provide exploitable results. Therefore, it is often necessary to add more constraints, generally arising from physical considerations, in order to favor the recovery of sources with a particular sought-after structure. Non-negative matrix factorization (NMF), which is the main focus of this thesis, aims at searching for non-negative sources which are observed through non-negative linear mixtures.In some cases, further information still remains necessary in order to correctly separate the sources. Here, we focus on the sparsity concept, which helps improving the contrast between the sources, while providing very robust approaches, even when the data are contaminated by noise. We show that in order to obtain stable solutions, the non-negativity and sparse constraints must be applied adequately. In addition, using sparsity in a potentially redundant transformed domain could allow to capture the structure of most of natural image, but this kind of regularization proves difficult to apply together with the non-negativity constraint in the direct domain. We therefore propose a sparse NMF algorithm, named nGMCA (non-negative Generalized Morphological Component Analysis), which overcomes these difficulties by making use of proximal calculus techniques. Experiments on simulated data show that this algorithm is robust to additive Gaussian noise contamination, with an automatic control of the sparsity parameter. This novel algorithm also proves to be more efficient and robust than other state-of-the-art NMF algorithms on realistic data.Finally, we apply nGMCA on liquid chromatography - mass spectrometry data. Observation of these data show that they are contaminated by multiplicative noise, which greatly deteriorates the results of the NMF algorithms. An extension of nGMCA was designed to take into account this type of noise, thanks to the use of a non-stationary prior. This extension is then able to obtain excellent results on annotated real data.

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