1,108 research outputs found
SHELL (BIVALVIA, PTERIOMORPHIA)
No full textBiominerals are organo-minerals structures produced by living systems. Since the Cambrian, they contribute to the adaptation of living organisms to different environments by fulfilling a variety of functions that go along with adapted morphologies. One of the aims of biomineralization is to understand how organisms "sculpt" these complex morphologies at nano and molecular scales: we know that occluded organic matrix (OM) proteins influence the lattice parameters of biominerals [1] and that many of them strongly interact with the mineral phase in in vitro assays, but their exact roles are still to be known. The aim of my PhD is to understand the complex relationships between the organic and mineral phases. In the present study, I discuss the case of the Mediterranean fan mussel Pinna nobilis.
Like most molluscs, Pinna nobilis, the fan mussel, envelops its soft body with a highly ordered shell composed of two mineralized layers: the internal one is nacreous made of aragonite, while the outer one is made of long calcitic prisms that grow perpendicularly to the surface of the shell. This latter shell layer comprises an assemblage of insoluble periprismatic matrix (proteins + saccharides) and very acidic "intracrystalline" proteins and sugars, together with pigments. This shell layer was submitted to:
Morphological and spectral characterization: To unveil the complex and hierarchical structures of biomineral models, we have acquired high-resolution 2D and 3D images by using different microscopic and spectro-microscopic techniques at Synchrotron SOLEIL. Under UV light, we have recently evidenced a striking luminescent pattern - never observed before - in relation to pigments.
Biochemical analysis of organic matrix: we have analyzed the intra and inter-prismatic OM by gel electrophoresis, ELISA test and western blot. Moreover, a transcriptome constructed from the mantle tissues has helped us to identify by proteomics a large set of proteins associated to the formation of prisms.
The significance of our results is discussed here. Our data tend to show that the formation of "simple prisms" is an extremely regulated process, which requires several molecular actors
Analysis of Mathieu Equation Stable Solutions in the First Zone of Stability
No full textAbstractThe paper presents the results of a homogeneous Mathieu equation studies. Mathieu equation solutions are oscillations, modulated in amplitude and frequency. In the computational experiments we found dependences of the given oscillations on the ratio of the coefficients. These dependences are shown in graphs that can be used for an approximate estimation of the Mathieu equation solutions without integration
Pensar las escalas para pensar las luchas: Autor: Mathieu UHEL
No full textA través de un título sugerente, “pensar las escalas para pensar las luchas”, Mathieu Uhel entreteje la construcción teórico-crítica del concepto escala, generada por la geografía radical anglosajona de finales del siglo XX, con la necesidad/utilidad práctica de la escala para concienciar las luchas sociales. El artículo cumple un doble propósito: por un lado, delinear los elementos de lectura sobre el concepto escala; y, con ello, promover la atención de esta problemática en las luchas contemporáneas. En un primer apartado, Uhel ubica las discusiones académicas en torno a la escala, como herramienta metodológica útil para comprender la complejidad de las sociedades capitalistas; en el segundo apartado, el autor avanza la exposición en torno al contexto de la dimensión escalar del imperialismo capitalista; finalmente, el autor se centra en el rol de la actividad política a escala nacional en la tensa relación entre las imposiciones del capital y la lucha social.Por meio de um título sugestivo, “pensando escalas para pensar lutas”, Mathieu Uhel entrelaça a construção teórico-crítica do conceito de escala, gerado pela geografia radical anglo-saxônica do final do século XX, com a necessidade / utilidade prática escala para aumentar a consciência das lutas sociais. O artigo tem um duplo propósito: por um lado, delinear os elementos de leitura sobre o conceito de escala; e, com isso, promover atenção a esse problema nas lutas contemporâneas. Na primeira seção, Uhel localiza as discussões acadêmicas em torno da escala, como uma ferramenta metodológica útil para compreender a complexidade das sociedades capitalistas; na segunda seção, o autor avança a exposição em torno do contexto da dimensão escalar do imperialismo capitalista; por fim, o autor enfoca o papel da atividade política em escala nacional na tensa relação entre as imposições do capital e a luta social.Mathieu Uhel\u27s suggestive title, “Thinking about scales to think about struggles”, he interweaves the theoretical-critical construction of concept scale, generated by radical Anglo-Saxon geography in the late 20th century, with it´s practical utility to social struggles. The article serves two purposes: on the one hand, Uhel locates academic discussion around scale; and, with this, he promotes attention to this problem in contemporary struggles. In the first section, Uhel locates academic discussions around scale, as a useful methodological tool to understand the complexity of capitalist societies; in the second section, the author advances the argument around the context of the scalar dimension of capitalist imperialism; finally, the author focuses on the role of political activity on a national scale in the tense relationship between the impositions of capital and the social movement
Les noirs de Pierre Soulages
No full textArticle co-rédigé par Pauline Hélou-de La Grandière, conservateur-restaurateur de peinture et doctorante (Héritages/INP/EUR Humanités, Création et Patrimoine) Pauline Hélou-de La Grandière, Mathieu Thoury et Lionel Simonot "Les noirs de Pierre Soulages", Technè, n° 55, "Matières noires, sens et substances, 1", 2023, p. 36-49 Commander le numéro Texte intégral disponible en novembre 2024 Introduction de l'article Bien que de nombreux travaux et ouvrages aient été consacrés à l’œ..
Microspectroscopic Investigation of Metal Soaps in Oil Paintings--a Case Study on late 19th Century Cobalt Green ((CoxZn1-xO) Paint
No full textMicrospectroscopic Investigation of Metal Soaps in Oil Paintings--a Case Study on late 19th Century Cobalt Green ((CoxZn1-xO) Pain
Mathieu Ichou, Les Enfants d’immigrés à l’école
No full textIt is common to hear in the fields of educational and immigration sociology that on average, the children of immigrants do not perform as well in school as children of native-born parents. Mathieu Ichou offers an innovative sociological analysis on a topic that is heavily exploited by political and media discourse, and subject to much scientific controversy. The author takes distance from the homogenized vision of a “second generation” of students who have totally failed academically, and rep..
Identification non-destructive des vernis des oeuvres d'art par fluorescence UV
No full textFor centuries, varnishes applied on works of art have been prepared with natural resins. These natural products degrade in the course of time and consequently modify the visual aspect of the work of arts. Thus, restorers must reduce the layer of varnish using solvents chosen according to the nature of varnish and not deteriorating the pictorial layer. The identification of varnishes is thus essential for the choice of the apt solvent. Until now, that identification was obtained by chemical analyses using samples. With UV fluorescence, we developed a technique allowing nondestructive identification of varnishes which can be carried out in-situ and giving results in real time. This method is based on the comparison of the spectrum of fluorescence of an unknown varnish with those of a database of recent, artificially and naturally aged varnishes of reference. Examples of identification of varnishes on several works of art are presented in this work. In parallel, the first step toward the separation and the identification of principal the fluorophores contained within the resins were carried out by liquid chromatography coupled with the electrospray mass spectrometry.Depuis des siècles, les vernis apposés sur des œuvres anciennes sont constitués de résines naturelles. Ceux-ci se dégradent au cours du temps et modifient l'aspect visuel de l'œuvre. Les restaurateurs doivent donc alléger la couche de vernis à l'aide de solvants choisis selon la nature du vernis et n'altérant pas la couche picturale. L'identification des vernis est donc essentielle pour le choix solvant. Elle était, jusqu'ici obtenue par des analyses chimiques faites à partir de prélèvements. A l'aide de la fluorescence UV, nous avons développé une technique d'identification non-destructive des vernis, réalisable in-situ et donnant des résultats en temps réel. Cette méthode s'appuie sur la comparaison du spectre de fluorescence d'un vernis inconnu avec ceux d'une base de données de vernis de référence récents, vieillis artificiellement ou naturellement. Des exemples de reconnaissance des vernis sur plusieurs œuvres d'art du patrimoine sont présentés. Parallèlement, la séparation et l'identification des principaux fluorophores contenus au sein des résines ont été réalisées par chromatographie liquide couplée à la spectrométrie de masse utilisant l'ionisation par électrospray
L'impatto dell'attività tintoria sull'ambiente. Firenze alla fine del Medioevo
No full textThe author aims to examine and categorize the range of dyeings materials used in the Florentine wool and silk textile industries in the late Middle Ages, focusing mainly on those produced within the regional space in order to evaluate the impact of the Florentine dyeing activity on the natural environment and the productive landscape of the Tuscan countryside. In particular, the author establishes a line of demarcation between cultivated and uncultivated resources in order to verify which constitutes an indication of the level of industrial development of medieval textile production. This further focuses on how the transition from the exploitation of wild resources to the exploitation of cultivated resources could reflect a greater degree of economic integration between the countryside and the city and contribute to the formation of a regional economic space
Mathieu de Fossey: su visión del mundo indígena mexicano
No full textThroughout these pages the author shows how Mathieu de Fossey perceived that it was not easy to make indigenous communities fit within the mould of the nation-state which, being based on the liberal and egualitarian ideology, was against the recognition of special regimes, such as those that created a peculiar status for the native population of the American territory during the period of Spanish colonial domination
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