L'imagerie intravasculaire ultrasonore (IVUS) est une technologie médicale par cathéter qui produit des images de coupe des vaisseaux sanguins. Elle permet de quantifier et d'étudier la morphologie de plaques d'athérosclérose en plus de visualiser la structure des vaisseaux sanguins (lumière, intima, plaque, média et adventice) en trois dimensions. Depuis quelques années, cette méthode d'imagerie est devenue un outil de choix en recherche aussi bien qu'en clinique pour l'étude de la maladie athérosclérotique. L'imagerie IVUS est par contre affectée par des artéfacts associés aux caractéristiques des capteurs ultrasonores, par la présence de cônes d'ombre causés par les calcifications ou des artères collatérales, par des plaques dont le rendu est hétérogène ou par le chatoiement ultrasonore (speckle) sanguin. L'analyse automatisée de séquences IVUS de grande taille représente donc un défi important. Une méthode de segmentation en trois dimensions (3D) basée sur l'algorithme du fast-marching à interfaces multiples est présentée. La segmentation utilise des attributs des régions et contours des images IVUS. En effet, une nouvelle fonction de vitesse de propagation des interfaces combinant les fonctions de densité de probabilité des tons de gris des composants de la paroi vasculaire et le gradient des intensités est proposée. La segmentation est grandement automatisée puisque la lumière du vaisseau est détectée de façon entièrement automatique. Dans une procédure d'initialisation originale, un minimum d'interactions est nécessaire lorsque les contours initiaux de la paroi externe du vaisseau calculés automatiquement sont proposés à l'utilisateur pour acceptation ou correction sur un nombre limité d'images de coupe longitudinale. La segmentation a été validée à l'aide de séquences IVUS in vivo provenant d'artères fémorales provenant de différents sous-groupes d'acquisitions, c'est-à-dire pré-angioplastie par ballon, post-intervention et à un examen de contrôle 1 an suivant l'intervention. Les résultats ont été comparés avec des contours étalons tracés manuellement par différents experts en analyse d'images IVUS. Les contours de la lumière et de la paroi externe du vaisseau détectés selon la méthode du fast-marching sont en accord avec les tracés manuels des experts puisque les mesures d'aire sont similaires et les différences point-à-point entre les contours sont faibles. De plus, la segmentation par fast-marching 3D s'est effectuée en un temps grandement réduit comparativement à l'analyse manuelle. Il s'agit de la première étude rapportée dans la littérature qui évalue la performance de la segmentation sur différents types d'acquisition IVUS. En conclusion, la segmentation par fast-marching combinant les informations des distributions de tons de gris et du gradient des intensités des images est précise et efficace pour l'analyse de séquences IVUS de grandes tailles. Un outil de segmentation robuste pourrait devenir largement répandu pour la tâche ardue et fastidieuse qu'est l'analyse de ce type d'images. / Intravascular ultrasound (IVUS) is a catheter based medical imaging technique that produces cross-sectional images of blood vessels. These images provide quantitative assessment of the vascular wall, information about the nature of atherosclerotic lesions as well as the plaque shape and size. Over the past few years, this medical imaging modality has become a useful tool in research and clinical applications, particularly in atherosclerotic disease studies. However, IVUS imaging is subject to catheter ring-down artifacts, missing vessel parts due to calcification shadowing or side-branches, heterogeneously looking plaques and ultrasonic speckle from blood. The automated analysis of large IVUS data sets thus represents an important challenge. A three-dimensional segmentation algorithm based on the multiple interface fast-marching method is presented. The segmentation is based on region and contour features of the IVUS images: a new speed fonction for the interface propagation that combines the probability density functions (PDFs) of the vessel wall components and the intensity gradients is proposed. The segmentation is highly automated with the detection of the lumen boundary that is fully automatic. Minimal interactions are necessary with a novel initialization procedure since initial contours of the external vessel wall border are also computed automatically on a limited number of longitudinal images and then proposed to the user for acceptance or correction. The segmentation method was validated with in-vivo IVUS data sets acquired from femoral arteries. This database contained 3 subgroups: pullbacks acquired before balloon angioplasty, after the intervention and at a 1 year follow-up examination. Results were compared with validation contours that were manually traced by different experts in IVUS image analysis. The lumen and external wall boundaries detected with the fast-marching method are in agreement with the experts' manually traced contours with similarly found area measurements and small point-to-point contour differences. In addition, the 3D fast-marching segmentation method dramatically reduced the analysis time compared to manual tracing. Such a valdiation study, with comparison between pre- and post-intervention data, has never been reported in the IVUS segmentation literature. In conclusion, the fast-marching method combining the information on the gray level distributions and intensity gradients of the images is precise and efficient to analyze large IVUS sequences. It is hoped that the fast-marching method will become a widely used tool for the fastidious and difficult task of IVUS image processing.

L'imagerie intravasculaire ultrasonore (IVUS) est une technologie médicale par cathéter qui produit des images de coupe des vaisseaux sanguins. Elle permet de quantifier et d'étudier la morphologie de plaques d'athérosclérose en plus de visualiser la structure des vaisseaux sanguins (lumière, intima, plaque, média et adventice) en trois dimensions. Depuis quelques années, cette méthode d'imagerie est devenue un outil de choix en recherche aussi bien qu'en clinique pour l'étude de la maladie athérosclérotique. L'imagerie IVUS est par contre affectée par des artéfacts associés aux caractéristiques des capteurs ultrasonores, par la présence de cônes d'ombre causés par les calcifications ou des artères collatérales, par des plaques dont le rendu est hétérogène ou par le chatoiement ultrasonore (speckle) sanguin. L'analyse automatisée de séquences IVUS de grande taille représente donc un défi important. Une méthode de segmentation en trois dimensions (3D) basée sur l'algorithme du fast-marching à interfaces multiples est présentée. La segmentation utilise des attributs des régions et contours des images IVUS. En effet, une nouvelle fonction de vitesse de propagation des interfaces combinant les fonctions de densité de probabilité des tons de gris des composants de la paroi vasculaire et le gradient des intensités est proposée. La segmentation est grandement automatisée puisque la lumière du vaisseau est détectée de façon entièrement automatique. Dans une procédure d'initialisation originale, un minimum d'interactions est nécessaire lorsque les contours initiaux de la paroi externe du vaisseau calculés automatiquement sont proposés à l'utilisateur pour acceptation ou correction sur un nombre limité d'images de coupe longitudinale. La segmentation a été validée à l'aide de séquences IVUS in vivo provenant d'artères fémorales provenant de différents sous-groupes d'acquisitions, c'est-à-dire pré-angioplastie par ballon, post-intervention et à un examen de contrôle 1 an suivant l'intervention. Les résultats ont été comparés avec des contours étalons tracés manuellement par différents experts en analyse d'images IVUS. Les contours de la lumière et de la paroi externe du vaisseau détectés selon la méthode du fast-marching sont en accord avec les tracés manuels des experts puisque les mesures d'aire sont similaires et les différences point-à-point entre les contours sont faibles. De plus, la segmentation par fast-marching 3D s'est effectuée en un temps grandement réduit comparativement à l'analyse manuelle. Il s'agit de la première étude rapportée dans la littérature qui évalue la performance de la segmentation sur différents types d'acquisition IVUS. En conclusion, la segmentation par fast-marching combinant les informations des distributions de tons de gris et du gradient des intensités des images est précise et efficace pour l'analyse de séquences IVUS de grandes tailles. Un outil de segmentation robuste pourrait devenir largement répandu pour la tâche ardue et fastidieuse qu'est l'analyse de ce type d'images. / Intravascular ultrasound (IVUS) is a catheter based medical imaging technique that produces cross-sectional images of blood vessels. These images provide quantitative assessment of the vascular wall, information about the nature of atherosclerotic lesions as well as the plaque shape and size. Over the past few years, this medical imaging modality has become a useful tool in research and clinical applications, particularly in atherosclerotic disease studies. However, IVUS imaging is subject to catheter ring-down artifacts, missing vessel parts due to calcification shadowing or side-branches, heterogeneously looking plaques and ultrasonic speckle from blood. The automated analysis of large IVUS data sets thus represents an important challenge. A three-dimensional segmentation algorithm based on the multiple interface fast-marching method is presented. The segmentation is based on region and contour features of the IVUS images: a new speed fonction for the interface propagation that combines the probability density functions (PDFs) of the vessel wall components and the intensity gradients is proposed. The segmentation is highly automated with the detection of the lumen boundary that is fully automatic. Minimal interactions are necessary with a novel initialization procedure since initial contours of the external vessel wall border are also computed automatically on a limited number of longitudinal images and then proposed to the user for acceptance or correction. The segmentation method was validated with in-vivo IVUS data sets acquired from femoral arteries. This database contained 3 subgroups: pullbacks acquired before balloon angioplasty, after the intervention and at a 1 year follow-up examination. Results were compared with validation contours that were manually traced by different experts in IVUS image analysis. The lumen and external wall boundaries detected with the fast-marching method are in agreement with the experts' manually traced contours with similarly found area measurements and small point-to-point contour differences. In addition, the 3D fast-marching segmentation method dramatically reduced the analysis time compared to manual tracing. Such a valdiation study, with comparison between pre- and post-intervention data, has never been reported in the IVUS segmentation literature. In conclusion, the fast-marching method combining the information on the gray level distributions and intensity gradients of the images is precise and efficient to analyze large IVUS sequences. It is hoped that the fast-marching method will become a widely used tool for the fastidious and difficult task of IVUS image processing.

Cette thèse se situe à l’interface de deux des sujets de recherche du LEPSi8S, la perception et la réalité virtuelle, appliqués aux transports routiers. L’objectif de la thèse est d’améliorer l’état de l’art concernant le rendu des images de synthèse pour les simulateurs de conduite. L’axe privilégié est le réalisme perceptif des images. L’approche retenue propose un mode de rendu High Dynamic Range, qui permet de générer une image en luminance. La technique proposée permet de réutiliser des environnements virtuels classiques, avec un minimum d’informations supplémentaires concernant les sources lumineuses. Les textures et matériaux existants sont utilisés pour un rendu aussi proche physiquement de la réalité que possible. Ensuite, l’image est traitée avec un opérateur de reproduction de tons, qui compresse la dynamique pour tenir compte des limites liées au dispositif d’affichage, tout en respectant autant que possible un réalisme perceptif du rendu. L’opérateur a été choisi de façon à ce qu’il soit adapté à la simulation de conduite, notamment pour les cas extrêmes (nuit, éblouissement, soleil rasant). Une simulation de l’éblouissement a également été implémentée. L’ensemble du rendu est temps réel, et a été intégré dans la boucle visuelle les simulateurs de conduite du LEPSiS. Enfin, des comparaisons réel-virtuel ont permis de montrer la qualité du rendu HDR obtenu. Des expérimentations avec sujets, sur des photographies (avec une référence réelle) et sur des vidéos, ont de plus montré les meilleures performances d’un opérateur doté d’un modèle visuel humain pour la simulation de conduite, notamment par sa capacité à s’adapter temporellement aux variations de luminance. / The LEPSiS is leading applied research on the transportation field. This PhD addresses perception and virtual reality, two research topics at the LEPSiS. The objective of my PhD was to improve the state of the art of the computer graphic image rendering for driving simulator applications. The main issue was the perceptual realism of the images, notably in high dynamic range conditions (night, glare). The proposed approach puts forward a High Dynamic Range mode, allowing us to render images in luminance.We use classic virtual environments, with small additional information about the light sources. The textures and materials are used for a rendering as close as possible to physical reality. Then, the image is processed by a tone mapping operator, which compresses the luminance dynamic, taking into account the limited range of the display device and the perceptual realism of the rendering. The chosen tone mapping is adapted to driving simulations, and especially to extreme situations (night, skimming sun). A glare simulation was also added. The entire rendering is real time, and is now included in the driving simulators of the LEPSiS. Lastly, real-virtual comparisons assessed the quality of the obtained HDR rendering. Moreover, two psycho-visual experiments with subjects, on photographs (with a real reference) and on video (without reference), showed the relevance of a tone mapping with a human visual model, including temporal adaptation to changing luminance, for driving simulations.

A presente dissertação pretende mostrar marcas de uma possível criação de um \"espaço ficcional\" no contato do aluno de espanhol como língua estrangeira (LE) e a língua que estuda. Para chegar a estas marcas postulamos uma metáfora que pode comparar o \"espaço ficcional\" com as representações sobre a língua espanhola no Brasil. Como amostra de pesquisa coletamos redações de alunos de espanhol como LE de níveis intermediário e avançado. Foram obtidas cinco amostras com diferentes gêneros e temáticas. Analisando as redações encontramos regularidades que nos levam a perceber a criação de um \"espaço ficcional\", cuja descrição crítica pode ser outro modo de ver o que acontece com a subjetividade na aprendizagem de uma LE. No caminho que nos leva em direção ao espaço ficcional, encontramos uma série de tons e vozes. E também enunciados sobre um encantamento com a língua espanhola que parece promover a possibilidade de entrar em espaços novos e transformar estes espaços alheios em próprios por uma apropriação ou absorção do estranho. / The present dissertation intends to show marks of a possible creation of a \'fictional space\' in the contact of a student of Spanish as a foreign language and with the language he studies. In order to get these marks a metaphor that can compare the \'fictional space\' to the representations on the Spanish language in Brazil was postulated. As research sample, compositions of intermediate and advanced-level students of Spanish were collected. Five samples with different genres and themes were made. Analyzing the compositions we have found regularities that lead us to notice the creation of a \'fictional space\', whose critical description can be another way of seeing what happens with the subjectivity in the learning of one foreign language. On the road that takes us towards the fictional space, we have found a series of tones and voices. It is also enunciated an enchantment with the Spanish language that seems to promote the possibility to enter in new spaces and to transform these strange spaces in their own for a stranger\'s appropriation or absorption.

L'objectif de cette étude est d'apporter une contribution aux recherches portant sur les effets prosodiques du contact de langues à travers l'étude du système prosodique du français centrafricain, une variété de français ayant émergé suite au contact avec une langue africaine à densité tonale maximale, le sango. La République centrafricaine est un pays extrêmement multilingue. Entre 60 et 100 langues y sont parlées, outre les deux langues officielles que constituent le sango - lingua franca, et le français - langue principale de l'enseignement et de l'administration publique. Dans la capitale, Bangui, le sango est la langue parlée d'ordinaire dans la vie quotidienne, tandis que le français s'utilise essentiellement dans des contextes professionnels. Cette étude se base sur des enregistrements de parole spontanée de 12 locuteurs francophones de Bangui. Des analyses acoustiques montrent que l'intonation du français centrafricain partage des caractéristiques communes avec le sango. La majorité de mots ont des patrons tonals qui restent inchangés quel que soit leur place dans l'énoncé, et chaque syllabe porte un ton. Le système se distingue ainsi considérablement du système intonatif du français européen où la courbe mélodique est contrainte au niveau post-lexical et dépend entre autres de facteurs rythmiques, syntaxiques et pragmatiques. La conclusion principale de cette étude est que le français centrafricain se classifie d'un point de vue typologique comme une langue à tons lexicaux. Il ressort que le système prosodique du français centrafricain est plus proche de celui du sango et que de celui du français européen. Les faits mis au jour dans cette thèse montrent que la prosodie peut changer de façon fondamentale dans une situation de contact de langue.

Orientador: Prof. Dr. André Guilherme Ribeiro Balan / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência da Computação, 2017. / Uma cena real possui uma grande variação de contraste que, quando vista pelo olho humano, resulta em detalhes que sensores de câmeras digitais comuns não conseguem capturar. Isso ocorre devido às limitações dos dispositivos para obter e exibir diferentes valores de cor. Imagens HDR (High Dynamic Range), por sua vez, são representações que conseguem reproduzir essa amplitude de valores. Para gerar e exibir imagens HDR, diante das limitações dos dispositivos, é necessário trabalhar em um domínio de menor alcance, com imagens LDR (Low Dynamic Range). Os algoritmos que mapeiam os valores entre os domínios são chamadas de operadores de tone-mapping. Apenas a aplicação de tone-mapping não gera resultados de alta qualidade, sendo necessárias técnicas de redução de ruídos e decomposição de imagem para tal. Essas técnicas implicam um alto custo computacional e demandam muito tempo quando executados na CPU. Por outro lado, o processamento na GPU oferece um paralelismo natural, por viabilizar operações a serem aplicadas a todos os pixels, simultaneamente. Uma das maneiras de programar essas operações na GPU é através do uso de shaders gráficos, alterando a forma que os pixels da imagem são reproduzidos. Com o constante crescimento da utilização de dispositivos móveis, um tema recorrente é o desempenho e a viabilidade de aplicações de alta performance em tais dispositivos, que atualmente, na maioria dos casos, possuem em sua arquitetura uma GPU programável. Nesse trabalho, desenvolvemos shaders gráficos OpenGL para processar operações de tonemapping, bem como a decomposição multiescala de imagens utilizando filtros não lineares importantes e modernos, a fim de preservar a maioria dos detalhes das imagens. Isso gera resultados mais nítidos quando comparados com técnicas que aplicam os operadores de tone-mapping diretamente nas imagens. Por outro lado, o processamento em GPU representa uma enorme melhoria de velocidade em relação ao processamento da CPU. A aplicação que desenvolvemos é multiplataforma para que ele possa ser executado em desktops e dispositivos móveis. Utilizamos a aplicação para avaliar o desempenho de diferentes operadores de tone-mapping e diferentes filtros de imagem não lineares para executar a decomposição de imagens em vários níveis. / A typical scene may have a highly nonuniform illumination that common digital camera sensors are currently not able to deal with, as well as typical screen monitors. A High Dynamic Range image (HDR) is an image model capable to store much larger illumination range than regular models, what is more similar to our human system view. To generate and display HDR images, given the limitations of the devices (cameras and screen monitors), it is necessary to work in a domain with smaller range, called LDR images (Low Dynamic Range). The algorithms that map HDR images to LDR images are called tone-mapping operators. These algorithms, when operating on very high resolution HDR images, demand very high computational effort that CPU are also not currently capable to deal with. On the other hand, GPU offers a natural parallelism by enabling operations to be applied on thousands of pixels simultaneously. One way to program these operations on the GPU is through the use of graphics shaders, directly changing a graphical pipeline that reproduce pixels of the image, such as OpenGL pipeline. Nowadays, mobile devices are also highly available devices that can have powerful GPUs. Hence, an important research subject is to access the viability of using such devices on HDR image processing and tone-mapping. In this work, we develop OpenGL graphic shaders to process tone-mapping operation as well as image multiscale decomposition using important and modern nonlinear image filters, in order to preserve the most of the images details. This generates sharper results when compared to techniques that directly apply tone-mapping operators on the images. On the other hand, GPU processing represents a huge speed improvement over CPU processing. The application we develop is multiplatform so it can run on desktops and mobile devices. We used it to evaluate the performance of different tone-mapping operators and different nonlinear image filters to perform image multiscale decomposition.

A presente dissertação pretende mostrar marcas de uma possível criação de um \"espaço ficcional\" no contato do aluno de espanhol como língua estrangeira (LE) e a língua que estuda. Para chegar a estas marcas postulamos uma metáfora que pode comparar o \"espaço ficcional\" com as representações sobre a língua espanhola no Brasil. Como amostra de pesquisa coletamos redações de alunos de espanhol como LE de níveis intermediário e avançado. Foram obtidas cinco amostras com diferentes gêneros e temáticas. Analisando as redações encontramos regularidades que nos levam a perceber a criação de um \"espaço ficcional\", cuja descrição crítica pode ser outro modo de ver o que acontece com a subjetividade na aprendizagem de uma LE. No caminho que nos leva em direção ao espaço ficcional, encontramos uma série de tons e vozes. E também enunciados sobre um encantamento com a língua espanhola que parece promover a possibilidade de entrar em espaços novos e transformar estes espaços alheios em próprios por uma apropriação ou absorção do estranho. / The present dissertation intends to show marks of a possible creation of a \'fictional space\' in the contact of a student of Spanish as a foreign language and with the language he studies. In order to get these marks a metaphor that can compare the \'fictional space\' to the representations on the Spanish language in Brazil was postulated. As research sample, compositions of intermediate and advanced-level students of Spanish were collected. Five samples with different genres and themes were made. Analyzing the compositions we have found regularities that lead us to notice the creation of a \'fictional space\', whose critical description can be another way of seeing what happens with the subjectivity in the learning of one foreign language. On the road that takes us towards the fictional space, we have found a series of tones and voices. It is also enunciated an enchantment with the Spanish language that seems to promote the possibility to enter in new spaces and to transform these strange spaces in their own for a stranger\'s appropriation or absorption.

Belgian composer Joseph Jongen (1873-1953) was an eclectic composer who successfully maintained his own unique musical vocabulary—particularly in his piano compositions. Jongen composed very little between 1940-1941—the period in which he and his family fled to the countryside of Mazères, France, living as refugees for several months before returning to Sart-lez-Spa, Belgium, due to the outbreak of WWII. Reflective of this time in his life, Vingt-quatre petits préludes dans tous les tons pour piano, op. 116 is composed in a particularly intimate and despairing way. Through a complete Schenkerian analysis and outline of the musical framework of op. 116—Jongen's last collection of piano pieces—this dissertation sheds light on the technique, imagination, and uniqueness of Jongen's WWII-period piano compositions. More specifically, this research outlines the deep-level tonal and formal structures, investigates the cryptic semantic meaning and intimate personal expression, and defines the aesthetic achievements of Jongen's Twenty-four Little Preludes in All Keys for Piano, op. 116.

Análise dos dez Estudos para violão de Radamés Gnattali com ênfase no aspecto harmônico, utilizando as ferramentas analíticas desenvolvidas no século XX para tratar de procedimentos harmônicos não-tradicionais. Tem como objetivo compreender as estruturas sonoras, salientando questões como movimento harmônico, prolongamento harmônico e melódico, sonoridades octatônicas e de tons inteiros e forma. / Analysis of the ten Studies for guitar by Radamés Gnattali, emphasizing the harmonic aspect, using the analytical tools developed in the 20th century to treat non-traditional harmonic procedures. The objective is to understand the sound structures, highlighting issues such as harmonic movement, harmonic and melodic prolongation, octatonic and whole tone sonorities, and form.

L’objectif de cette étude est d’apporter une contribution aux recherches portant sur les effets prosodiques du contact de langues à travers l’étude du système prosodique du français centrafricain, une variété de français ayant émergé suite au contact avec une langue africaine à densité tonale maximale, le sango. La République centrafricaine est un pays extrêmement multilingue. Entre 60 et 100 langues y sont parlées, outre les deux langues officielles que constituent le sango – lingua franca, et le français – langue principale de l’enseignement et de l’administration publique. Dans la capitale, Bangui, le sango est la langue parlée d’ordinaire dans la vie quotidienne, tandis que le français s’utilise essentiellement dans des contextes professionnels. Cette étude se base sur des enregistrements de parole spontanée de 12 locuteurs francophones de Bangui. Des analyses acoustiques montrent que l’intonation du français centrafricain partage des caractéristiques communes avec le sango. La majorité de mots ont des patrons tonals qui restent inchangés quel que soit leur place dans l’énoncé, et chaque syllabe porte un ton. Le système se distingue ainsi considérablement du système intonatif du français européen où la courbe mélodique est contrainte au niveau post-lexical et dépend entre autres de facteurs rythmiques, syntaxiques et pragmatiques. La conclusion principale de cette étude est que le français centrafricain se classifie d’un point de vue typologique comme une langue à tons lexicaux. Il ressort que le système prosodique du français centrafricain est plus proche de celui du sango et que de celui du français européen. Les faits mis au jour dans cette thèse montrent que la prosodie peut changer de façon fondamentale dans une situation de contact de langue. / This study is concerned with prosody and language contact. The fact that language contact induces change is well documented, but few studies focus on the prosodic effects of contact-induced change. The aim of this study is to provide a case study of the prosodic system of the contact variety Central African French, which has emerged from the contact between French and the African tone language, Sango.The Central African Republic is a multilingual country with between 60 to 100 different regional languages spoken within its borders in addition to two official languages, the lingua franca Sango and French. French has been the main language of education and of public administration since colonial times. In the capital Bangui, Sango is the most used language in everyday communication whereas French is spoken in professional contexts. This study is based on recordings of spontaneous speech of 12 French-speaking informants from Bangui. Acoustic analyses of the recordings show that the prosody of Central African French shares with Sango some fundamental characteristics: most words have fixed tonal patterns independently of their position in the sentence and every syllable carries a static tone. This system greatly differs from the system of European varieties of French, where the sentence melody is determined at the post-lexical level and depends on factors such as rhythm, syntax and pragmatics. The main conclusion of this study is that Central African French may be classified as a tone language and thus is endowed with a prosodic system that is closer to Sango than to European French. This finding suggests that intonation might change radically in contact situations ; the change is not only superficial but concerns the underlying system.