Le travail des sans-emploi : analyse sociologique de l'assignation à un programme d'emploi temporaire

RESUMECette recherche empirique porte sur les emplois temporaires subventionnés (ETS) instaurés dans le cadre du chômage et de l'aide sociale en Suisse depuis une dizaine d'années. La mise en place de politiques d'activation dans le cadre de la protection sociale met l'accent sur les liens explicites, souvent réglementaires, qu'entretiennent actuellement la protection sociale, les politiques de l'emploi et le marché du travail dans les pays industrialisés. Ces transformations ont largement contribué au développement d'activités exercées en marge du marché de l'emploi. Dans le cadre du chômage, comme dans celui de l'aide sociale, une mise au travail peut être exigée en contrepartie du versement des indemnités ; en Suisse, on nomme ce procédé l'assignation au travail. L'assignation est le processus par lequel un-e conseiller?ère en placement peut contraindre, sous peine de sanction (suppression des indemnités pour un temps déterminé) une personne au chômage (inscrit-e auprès d'un office régional de placement) à souscrire à une mesure du marché du travail (MMT), particulièrement les ETS.Cette recherche propose une analyse de l'assignation à un programme d'emploi temporaire sous l'éclairage de la sociologie du travail. Elle adopte une perspective compréhensive attentive aux tensions que vivent les individus pris dans une situation de travail hybride et inédite qui les place aux frontières des différentes catégories administratives de chômage, d'inactivité et de population occupée. Partant d'une étude empirique auprès de personnes assignées, cette recherche mène une analyse qualitative des conditions et de l'organisation du travail en ETS, des modalités contractuelles et statutaires des personnes assignées à une activité de travail contrainte et matériellement non reconnue, puisque non salariée. Elle s'attache également à cerner le vécu de l'assignation au travail, ainsi que le sens que les personnes lui attribuent dans leur trajectoire biographique et professionnelle.SUMMARYThis research investigates a specific and new form of labor, namely «temporary subsidized jobs» {emplois temporaires subventionnés, ETS) that have been developed since the late 1990s in Switzerland in the context of unemployment and social assistance benefits. Although ETS are specific to Switzerland, they echo similar «workfare» measures imposed on unemployed and welfare recipients introduced in recent years in almost all industrialized countries. Indeed, the evolution of public policies and the generalization of «active labour-market policies» {politiques d'activation) have become central to social protection in the majority of Western countries and have emerged in parallel to the expansion of work activities situated at the margins of traditional wage- labor.My analysis of the ETS phenomenon is informed by labor sociology and discusses the pertinence of a classical approach in grasping this hybrid and new work situation, which sets individual persons at the border between various administrative categories such as «unemployed», «inactive» and «at work». I investigate in particular the issue of contractual and statutory modalities imposed on persons who have been assigned to a form of activity that is both constraining as well as materially non-recognized (as it remains outside of traditional wage-labor forms). In order to understand ETS conditions and labor organization, my fieldwork consist of interviews of persons who have been assigned to it and observations. I investigate their personal experience, as well as the meaning that these individuals attribute to the ETS experience in the context of their biographical and professional trajectory.

Doctoral education's reform in Switzerland and Norway : a public management analyis

This doctoral thesis examines a recent phenomenon in European higher education, namely the reform of doctoral education. On the basis of a number of case studies, consisting of Swiss and Norwegian doctoral schools, and their institutional, national and international context, it demonstrates to what extent changes appear in doctoral education and its governance. Findings indicate new practices regarding doctoral students' recruitment, curricular component, supervision, scientific exchange, follow-up and their career. Doctoral education's character is not anymore exclusively determined by individual supervisors, but increasingly by interdisciplinary and interinstitutional colleges of academics. Finally, general governance patterns are identified: according to the type of scientific discipline and higher education institution, the institution's size and national political system, the field of higher education is more or less dominated by New Public Management or Network Governance characteristics.

Utilization of Boron (10B) derived from fertilizer by sugar cane

The response to B in agricultural systems of sugar cane is still an unexplored issue; B application has however recently been widely publicized and used with a certain degree of frequency. The use of 10B-labeled fertilizers may further contribute to clarify this practice. With the objective of evaluating sugar cane use of B (10B) derived from fertilizer (boric acid), an experiment was conducted under field conditions in the 2005/2006 growing season. The experiment consisted of the installation of microplots (2 x 1.5 m) where 4 kg ha-1 B (boric acid with 85.95 % in 10B atoms) dissolved in water was applied 90 days after planting (May 2005). The solution was applied to the soil on both sides of the plant row at a distance of 20 cm. After harvest (June 2006) the B content and 10B abundance in % atoms in all parts of the sugar cane plants (stalks, dry leaves, tips and roots) were determined. Results showed that the total B accumulated was 471 g ha-1 in the entire plant (35 % in the stalks, 22 % in the dry leaves, 9 % in the tips and 34 % in the roots). The sugar cane plants used on average 14 % of the total accumulated B in the above-ground part (44 g ha-1) and 11 % in the roots (19 g ha-1), totaling 13 % in the entire plant (63 g ha-1). The recovery of 10B-fertilizer by sugar cane plants was low, around 2 % of the total applied amount.

Integration of teacher education into the Swiss higher education system

The integration of specific institutions for teacher education into the higher education system represents a milestone in the Swiss educational policy and has broad implications. This thesis explores organizational and institutional change resulting from this policy reform, and attempts to assess structural change in terms of differentiation and convergence within the system of higher education. Key issues that are dealt with are, on the one hand, the adoption of a research function by the newly conceptualized institutions of teacher education, and on the other, the positioning of the new institutions within the higher education system. Drawing on actor-centred approaches to differentiation, this dissertation discusses system-level specificities of tertiarized teacher education and asks how this affects institutional configurations and actor constellations. On the basis of qualitative and quantitative empirical data, a comparative analysis has been carried out including case studies of four universities of teacher education as well as multivariate regression analysis of micro-level data on students' educational choices. The study finds that the process of system integration and adaption to the research function by the various institutions have unfolded differently depending on the institutional setting and the specific actor constellations. The new institutions have clearly made a strong push to position themselves as a new institutional type and to find their identity beyond the traditional binary divide which assigns the universities of teacher education to the college sector. Potential conflicts have been identified in divergent cognitive normative orientations and perceptions of researchers, teacher educators, policy-makers, teachers, and students as to the mission and role of the new type of higher education institution. - L'intégration dans le système d'enseignement supérieur d'institutions qui ont pour tâche spécifique de former des enseignants peut être considérée comme un événement majeur dans la politique éducative suisse, qui se trouve avoir des conséquences importantes à plusieurs niveaux. Cette thèse explore les changements organisationnels et institutionnels résultant de cette réforme politique, et elle se propose d'évaluer en termes de différentiation et de convergence les changements structurels intervenus dans le système d'éducation tertiaire. Les principaux aspects traités sont d'une part la nouvelle mission de recherche attribuée à ces institutions de formation pédagogique, et de l'autre la place par rapport aux autres institutions du système d'éducation tertiaire. Recourant à une approche centrée sur les acteurs pour étudier les processus de différen-tiation, la thèse met en lumière et en discussion les spécificités inhérentes au système tertiaire au sein duquel se joue la formation des enseignants nouvellement conçue et soulève la question des effets de cette nouvelle façon de former les enseignants sur les configurations institutionnelles et les constellations d'acteurs. Une analyse comparative a été réalisée sur la base de données qualitatives et quantitatives issues de quatre études de cas de hautes écoles pédagogiques et d'analyses de régression multiple de données de niveau micro concernant les choix de carrière des étudiants. Les résultats montrent à quel point le processus d'intégration dans le système et la nouvelle mission de recherche peuvent apparaître de manière différente selon le cadre institutionnel d'une école et la constellation spécifique des acteurs influents. A pu clairement être observée une forte aspiration des hautes écoles pédagogiques à se créer une identité au-delà de la structure binaire du système qui assigne la formation des enseignants au secteur des hautes écoles spéciali-sées. Des divergences apparaissent dans les conceptions et perceptions cognitives et normatives des cher-cheurs, formateurs, politiciens, enseignants et étudiants quant à la mission et au rôle de ce nouveau type de haute école. - Die Integration spezieller Institutionen für die Lehrerbildung ins Hochschulsystem stellt einen bedeutsamen Schritt mit weitreichenden Folgen in der Entwicklung des schweizerischen Bildungswesens dar. Diese Dissertation untersucht die mit der Neuerung verbundenen Veränderungen auf organisatorischer und institutioneller Ebene und versucht, die strukturelle Entwicklung unter den Gesichtspunkten von Differenzierung und Konvergenz innerhalb des tertiären Bildungssystems einzuordnen. Zentrale Themen sind dabei zum einen die Einführung von Forschung und Entwicklung als zusätzlichem Leistungsauftrag in der Lehrerbildung und zum andern die Positionierung der pädagogischen Hochschulen innerhalb des Hochschulsystems. Anhand akteurzentrierter Ansätze zur Differenzierung werden die Besonderheiten einer tertiarisierten Lehrerbildung hinsichtlich der Systemebenen diskutiert und Antworten auf die Frage gesucht, wie die Reform die institutionellen Konfigurationen und die Akteurkonstellationen beeinflusst. Auf der Grundlage qualitativer und quantitativer Daten wurde eine vergleichende Analyse durchgeführt, welche Fallstudien zu vier pädagogischen Hochschulen umfasst sowie Regressionsanalysen von Mikrodaten zur Studienwahl von Maturanden. Die Ergebnisse machen deutlich, dass sich der Prozess der Systemintegration und die Einführung von Forschung in die Lehrerbildung in Abhängigkeit von institutionellen Ordnungen und der jeweiligen Akteurkonstellation unterschiedlich gestalten. Es lässt sich bei den neu gegründeten pädagogischen Hochschulen ein starkes Bestreben feststellen, sich als neuen Hochschultypus zu positionieren und sich eine Identität zu schaffen jenseits der herkömmlichen binären Struktur, welche die pädagogischen Hochschulen dem Fachhochschul-Sektor zuordnet. Potentielle Konflikte zeichnen sich ab in den divergierenden kognitiven und normativen Orientierungen und Wahrnehmungen von Forschern, Ausbildern, Bildungspolitikern, Lehrern und Studierenden hinsichtlich des Auftrags und der Rolle dieses neuen Typs Hochschule.

Fat oxidation kinetics : effect of exercise

ABSTRACT Fat oxidation kinetics: effect of exercise. During graded exercise, absolute whole body fat oxidation rates increase from low to moderate intensities, and then markedly decline at high intensities, implying an exercise intensity (Fatmax) at which the fat oxidation rate is maximal (MFO). The main aim of the present work was to examine the effect of exercise on whole body fat oxidation kinetics. For this purpose, a sinusoidal mathematical model (SIN) has been developped in the first study to provide an accurate description of the shape of fat oxidation kinetics during graded exercise, represented as a function of exercise intensity, and to determine Fatmax and MFO. The SIN model incorporates three independent variables (i.e., dilatation, symmetry, and translation) that correspond to main expected modulations of the basic fat oxidation curve because of factors such as mode of exercise or training status. The results of study 1 showed that the SIN model was a valuable tool to determine Fatmax and MFO, and to precisely characterize and quantify the different shape of fat oxidation kinetics through its three variables. The effectiveness of the SIN model to detect differences in fat oxidation kinetics induced by a specific factor was then confirmed in the second study, which quantitatively described and compared fat oxidation kinetics in two different popular modes of exercise: running and cycling. It was found that the mean fat oxidation kinetics during running was characterized by a greater dilatation and a rightward asymmetry compared with the symmetric parabolic curve in cycling. In the two subsequent studies, the effect of a prior endurance exercise of different intensities and durations on whole body fat oxidation kinetics was examined. Study 3 determined the impact of a 1-h continuous exercise bout at an exercise intensity corresponding to Fatmax on fat oxidation kinetics during a subsequent graded test, while study 4 investigated the effect of an exercise leading to a more pronounced muscle glycogen depletion. The results of these two latter studies showed that fat oxidation rates, MFO, and Fatmax were enhanced following endurance exercise, but were increased to a greater extent with a more severe mucle glycogen depletion, inducing therefore modifications in the postexercise fat oxidation kinetics (i.e., greater dilatation and rightward asymmetry). In perspective, further studies have been suggested 1) to assess physiological meaning of the three independent variables of the SIN model; and 2) to compare the effect of two different training programs on fat oxidation kinetics in obese subjects.

Sewage sludge as nitrogen and phosphorus source for cane-plant and first ratoon crops

The use of sewage sludge in Brazilian agriculture was regulated by the resolution no. 375 Conama, in 2006. However, there is a lack of research to adequate the mineral N and P fertilizer doses to be applied in agricultural fields treated with this residue. In a field experiment, the effects of application rates of sewage sludge and mineral N and P fertilizers on the productivity and technical characteristics of the cane-plant and first ratoon (residual effect) crops were evaluated. Four doses of sewage sludge (0, 3.6, 7.2 and 10.8 t ha-1, dry base), of N (0, 30, 60 and 90 kg ha-1) and of P2O5 (0, 60, 120 and 180 kg ha-1) were combined in a factorial and laid out on randomized block design, a with two replications. To evaluate the residual effect of the sludge, 120 kg ha-1 N and 140 kg ha-1 of K2O were applied in all plots. Sludge application at cane planting, with or without N and/or P fertilizer increased the stalk yield from 84 up to 118 t ha-1, with no alteration in the sugarcane quality, compared with the application of NPK fertilizer alone, resulting in a stalk yield of 91 t ha-1. The study of the response surface for stalk yield on lowfertility soil was the basis for a recommendation of mineral N and P fertilizer doses for sugarcane implantation as related to sewage sludge application rates. It was also concluded that a sludge application of 10.8 t ha-1, which is the sludge dose established based on the N criterion according to the resolution Conama nº 375, could a) reduce the use of mineral N by 100 % and of P2O5 by 30 %, with increments of 22 % in stalk yield, as a direct effect of sludge application to cane plant crop, and b) increase the stalk yield in the second harvest (first ratoon) by up to 12 % and sugar yield by up to 11 %, by the residual effect of sludge application to sugar cane.

Efeito residual da adubação na cana-planta e da adubação nitrogenada e potássica na cana-soca colhidas com e sem a queima da palhada

A aplicação de vinhaça na cana-de-açúcar, complementada com adubação nitrogenada e manutenção da palhada na superfície do solo, melhoram as propriedades físicas, químicas e biológicas do solo, podendo resultar em aumento da produtividade da cultura. O objetivo deste estudo foi avaliar o efeito residual de adubação na cana-planta e a adubação da cana-soca, com e sem aplicação de vinhaça, sob diferentes sistemas de colheita no município de Conceição da Barra - ES. O experimento foi conduzido no período de 2005 a 2007, num Argissolo Amarelo em Tabuleiros Costeiros. Utilizou-se o delineamento de blocos ao acaso com quatro repetições, no esquema fatorial 2 x 7, com parcelas subdivididas, sendo dois tratamentos cana crua e cana queimada e sete subtratamentos com diferentes doses de N associadas a doses de K2O na forma de cloreto de K e vinhaça. Os tratamentos foram: testemunha (T1); vinhaça (T2); vinhaça + 80 kg de N incorporado (T3); vinhaça + 80 kg de N em cobertura (T4); vinhaça + 40 kg de N em cobertura (T5); K2O + 80 kg de N incorporado (T6); e K2O + 80 kg de N em cobertura (T7). Não houve efeito residual de adubação na produtividade de colmos na cana-planta. A cana crua apresentou produtividade superior à da cana queimada na cana-soca. Nesta, a fertilização com vinhaça complementada com N incorporado ou em cobertura e a adubação com 120 kg de K2O na forma de KCl + 80 kg de N incorporados ao solo proporcionaram produtividade superior à dos demais tratamentos. Não foi verificada diferença na produtividade de colmos entre as doses de 40 e 80 kg ha-1 de N, aplicadas em cobertura na cana-soca. A extração e retorno de nutrientes ocorreu de forma similar entre cana-planta e cana-soca.

Manejo da adubação potássica na cultura da cana-de-açúcar

O Brasil é o maior produtor mundial de cana-de-açúcar e, devido à crescente demanda por fontes renováveis de energia, a área cultivada encontra-se em expansão. Regularmente, a cultura é plantada em solos com baixos teores de nutrientes, o que pode limitar sua produtividade. A adubação potássica da cana-de-açúcar é feita basicamente no sulco de plantio, o que pode comprometer a eficiência de utilização desse nutriente devido a possíveis perdas por lixiviação ou salinidade às raízes das plantas. O objetivo deste estudo foi avaliar produtividade de colmos e atributos tecnológicos da cana-de-açúcar em função de doses e modos de aplicação de K. O experimento foi conduzido em um Latossolo Vermelho distrófico durante o ciclo de cana-planta, com o cultivar SP90 3414, em esquema fatorial 2 x 4, sendo dois modos de aplicação (100 % no plantio e 50 % no plantio + 50 % em cobertura) e quatro doses de K (0, 100, 150 e 200 kg ha-1 de K2O), com quatro repetições. Aos nove meses após o plantio, foram avaliados a altura das plantas e o perfilhamento e, na colheita, a produtividade de colmos e os atributos tecnológicos da cana-de-açúcar. As doses de K aumentaram o crescimento em altura e o perfilhamento da cana-de-açúcar, para os dois modos de aplicação; a produtividade de colmos e de açúcar aumentou com as doses de K até um ponto de máximo de, aproximadamente, 160 kg ha-1 de K2O; e a produtividade máxima estimada de cerca de 160 t ha-1 foi obtida com 130 e 150 kg ha-1 de K2O, para a aplicação parcelada e única do fertilizante, respectivamente.

Ammonium chloride as nitrogen source in sugarcane harvested without burning

The great difficulty of incorporation of N fertilizers into the "green sugarcane" system causes concern and since urea is the most commonly used source, there is the risk of loosing NH3 through volatilization. For this reason, a field experiment was undertaken (in a Hapludox Typic) with the objective of evaluating the agronomic efficiency of ammonium chloride on stubble of the second ratoon (SP89 1115), as well as its residual effect on the subsequent cycle (third ratoon). The experimental design was randomized blocks with four replications. Treatments consisted of three N rates (60, 120 and 180 kg ha-1 N) in the form of NH4Cl, in addition to a control treatment without the addition of N fertilizer. The ratoon cane of the second cutting was harvested in November 2006 and the treatments were applied in December 2006. The second ratoon was harvested mechanically in November 2007 and in December 2007, 450 kg ha-1 of the NPK mixture 20-05-19 was applied, providing 90, 22 and 86 kg ha-1 N, P2O5 and K2O, respectively, for the purpose of evaluating the effect of residual-N from the treatments implanted in December 2006. An increase in the rates of N-NH4Cl had a positive effect on the leaf concentrations of P, Mg and S. Stalk yield (MSS - Mg ha-1 of sugarcane stalks) and sugar (MSH - Mg ha-1 of sucrose) in the November 2006 harvest responded linearly to the increase of N doses in the form of NH4Cl. In relation to the effect of residual-N in the 2007/2008 harvest, it was observed, in general, that the concentrations of macronutrients in the sugarcane leaf +1 were within the range considered adequate in the state of São Paulo, Brazil. The residual-N of the NH4Cl doses resulted in a significant reduction in stalk (MSS) and sugar (MSH) production. It may be concluded that the NH4Cl source at a dose of 120 kg ha-1 N in ratoon fertilization of the second cutting was agronomically efficient, presenting, however, less efficiency of residual-N in the subsequent cycle.

Extração e exportação de nutrientes por variedades de cana-de-açúcar cultivadas sob irrigação plena

A pesquisa tecnológica para suporte do setor sucroalcooleiro nacional mostra que são esporádicos os trabalhos desenvolvidos com cana-de-açúcar irrigada envolvendo a exigência nutricional. Nesse contexto, objetivou-se quantificar, durante o ciclo de cana-planta de 11 variedades de cana-de-açúcar (SP79-1011, RB813804, RB863129, RB872552, RB943365, RB72454, RB763710, SP78-4764, SP81-3250, RB867515 e RB92579) cultivadas sob irrigação plena, a capacidade de extração e exportação de N, P, K, Ca e Mg, bem como a exigência nutricional para produção de uma tonelada de colmo por hectare (TCH). A pesquisa foi realizada em campo, no município de Carpina, PE, durante a safra agrícola 2006/2007. O delineamento experimental empregado foi de blocos casualizados, com 11 tratamentos e quatro repetições. A extração e exportação de nutrientes, assim como a exigência nutricional, foram avaliadas aos 360 dias após o plantio (DAP) na parte aérea das plantas. A extração de nutrientes na parte aérea da cana-planta apresentou, em média, valores de 179, 25, 325, 226 e 87 kg ha-1 de N, P, K, Ca e Mg, respectivamente, o que proporcionou a seguinte ordem decrescente de extração: K > Ca > N > Mg > P. A exportação média de N, P, K, Ca e Mg pelo colmo das variedades irrigadas foi de 92; 15; 188; 187; e 66 kg ha-1; correspondendo, respectivamente, a 51, 60, 58, 83 e 76 % de todo o nutriente extraído na parte aérea da cana-planta, com destaque para as variedades RB92579 e SP81-3250 para o N, RB813804, RB863129, RB872552, RB763710, RB92579, SP78-4764, SP81-3250 e SP79-1011 para o P, SP79-1011, SP81-3250, RB813804, RB872552 e RB763710 para o K, RB92579 e RB863129 para o Ca e RB92579 para o Mg. Para produção de uma TCH, foram exigidos pelas variedades durante o ciclo de cana-planta valores médios de 0,91; 0,13; 1,71; 1,18; e 0,44 kg de N, P, K, Ca e Mg, respectivamente.

Physical properties of a rhodic haplustox under two sugarcane harvesting systems

This study had the purpose of evaluating the effects of two management types of sugarcane: harvesting of burnt cane (BCH) and mechanized harvesting of unburnt green cane (MCH), on some soil physical properties of a dystrophic Rhodic Haplustox. The data were then compared with results for the same soil type under native forest. A completely randomized design was used, with three treatments and 20 replications. The following characteristics were determined: organic matter, aggregate stability, soil bulk density, and porosity at depths of 0-0.20 m and soil penetration resistance. After 15 years of cultivation, there were some alterations in the soil under cane burnt before harvesting, evidenced by a drop in the weighted average diameter of stable aggregates in water and increased soil bulk density. Significant changes were also detected in total porosity and pore distribution under both harvesting systems. Critical values for penetration resistance were observed in the area under mechanized sugar cane harvesting, with a value of 4.5 MPa in the 40-55 cm layer. This value is considered high and could indicate compaction and restriction of root growth. Soil properties under the green cane (unburned) management system were closest to those of the soil under native forest.

Voir le monde à travers les lunettes du métacontraste : un modèle mathématique inspiré de la psychologie sociale

Résumé La théorie de l'autocatégorisation est une théorie de psychologie sociale qui porte sur la relation entre l'individu et le groupe. Elle explique le comportement de groupe par la conception de soi et des autres en tant que membres de catégories sociales, et par l'attribution aux individus des caractéristiques prototypiques de ces catégories. Il s'agit donc d'une théorie de l'individu qui est censée expliquer des phénomènes collectifs. Les situations dans lesquelles un grand nombre d'individus interagissent de manière non triviale génèrent typiquement des comportements collectifs complexes qui sont difficiles à prévoir sur la base des comportements individuels. La simulation informatique de tels systèmes est un moyen fiable d'explorer de manière systématique la dynamique du comportement collectif en fonction des spécifications individuelles. Dans cette thèse, nous présentons un modèle formel d'une partie de la théorie de l'autocatégorisation appelée principe du métacontraste. À partir de la distribution d'un ensemble d'individus sur une ou plusieurs dimensions comparatives, le modèle génère les catégories et les prototypes associés. Nous montrons que le modèle se comporte de manière cohérente par rapport à la théorie et est capable de répliquer des données expérimentales concernant divers phénomènes de groupe, dont par exemple la polarisation. De plus, il permet de décrire systématiquement les prédictions de la théorie dont il dérive, notamment dans des situations nouvelles. Au niveau collectif, plusieurs dynamiques peuvent être observées, dont la convergence vers le consensus, vers une fragmentation ou vers l'émergence d'attitudes extrêmes. Nous étudions également l'effet du réseau social sur la dynamique et montrons qu'à l'exception de la vitesse de convergence, qui augmente lorsque les distances moyennes du réseau diminuent, les types de convergences dépendent peu du réseau choisi. Nous constatons d'autre part que les individus qui se situent à la frontière des groupes (dans le réseau social ou spatialement) ont une influence déterminante sur l'issue de la dynamique. Le modèle peut par ailleurs être utilisé comme un algorithme de classification automatique. Il identifie des prototypes autour desquels sont construits des groupes. Les prototypes sont positionnés de sorte à accentuer les caractéristiques typiques des groupes, et ne sont pas forcément centraux. Enfin, si l'on considère l'ensemble des pixels d'une image comme des individus dans un espace de couleur tridimensionnel, le modèle fournit un filtre qui permet d'atténuer du bruit, d'aider à la détection d'objets et de simuler des biais de perception comme l'induction chromatique. Abstract Self-categorization theory is a social psychology theory dealing with the relation between the individual and the group. It explains group behaviour through self- and others' conception as members of social categories, and through the attribution of the proto-typical categories' characteristics to the individuals. Hence, it is a theory of the individual that intends to explain collective phenomena. Situations involving a large number of non-trivially interacting individuals typically generate complex collective behaviours, which are difficult to anticipate on the basis of individual behaviour. Computer simulation of such systems is a reliable way of systematically exploring the dynamics of the collective behaviour depending on individual specifications. In this thesis, we present a formal model of a part of self-categorization theory named metacontrast principle. Given the distribution of a set of individuals on one or several comparison dimensions, the model generates categories and their associated prototypes. We show that the model behaves coherently with respect to the theory and is able to replicate experimental data concerning various group phenomena, for example polarization. Moreover, it allows to systematically describe the predictions of the theory from which it is derived, specially in unencountered situations. At the collective level, several dynamics can be observed, among which convergence towards consensus, towards frag-mentation or towards the emergence of extreme attitudes. We also study the effect of the social network on the dynamics and show that, except for the convergence speed which raises as the mean distances on the network decrease, the observed convergence types do not depend much on the chosen network. We further note that individuals located at the border of the groups (whether in the social network or spatially) have a decisive influence on the dynamics' issue. In addition, the model can be used as an automatic classification algorithm. It identifies prototypes around which groups are built. Prototypes are positioned such as to accentuate groups' typical characteristics and are not necessarily central. Finally, if we consider the set of pixels of an image as individuals in a three-dimensional color space, the model provides a filter that allows to lessen noise, to help detecting objects and to simulate perception biases such as chromatic induction.

Qualidade física de três solos sob colheita mecanizada de cana-de-açúcar

A colheita mecanizada da cultura da cana-de-açúcar (Saccharum officinarum) pode aumentar os riscos de degradação e perda da qualidade física dos solos. O objetivo deste estudo foi determinar o intervalo hídrico ótimo (IHO) e o índice S como indicadores da qualidade física de solos cultivados com cana-de-açúcar sob colheita mecanizada. Foram estudados três solos: um Latossolo Vermelho (LV) textura argilosa, um Latossolo Vermelho (LV) textura média e um Argissolo Vermelho-Amarelo (PVA) textura arenosa, utilizando-se amostras das camadas de 0-0,20 m e 0,20-0,40 m de profundidade. O IHO foi maior no LV argiloso > PVA arenoso > LV textura média. No LV textura média, a densidade do solo crítica (Dsc) foi de 1,76 e 1,77 Mg m-3, respectivamente, nas camadas de 0-0,20 e 0,20-0,40 m, enquanto no PVA arenoso e no LV argiloso não se constatou Dsc, tendo em vista a amplitude de valores de densidade obtidos nas amostragens. O índice S apresentou valor maior que 0,050 no LV argiloso, de 0,024 no LV textura média e maior que 0,033 no PVA arenoso, indicando qualidade física muito boa, muito pobre e pobre, respectivamente. Em função dos valores de IHO e de S foi possível constatar que o LV textura média se apresenta mais sensível aos efeitos do manejo da cultura sob colheita mecanizada, com maiores restrições físicas para o crescimento e desenvolvimento de raízes da cultura da cana-de-açúcar.

Produtividade e desenvolvimento da cana-planta e soca em função de doses e fontes de manganês

A cana-de-açúcar possui grande importância econômico-social e política para o Brasil. Este trabalho teve como objetivo avaliar o efeito de doses e fontes de manganês nessa cultura. O experimento foi realizado no sítio Fujimoto, área administrada pela Destilaria Vale do Paraná S/A Álcool e Açúcar, no município de Suzanápolis, SP. O delineamento experimental utilizado foi o de blocos ao acaso no esquema fatorial 5 x 3, sendo cinco doses de Mn (0; 2,5; 5,0; 7,5; e 10,0 kg ha-1) e três fontes (quelato, FTE e sulfato de manganês), aplicadas no sulco de plantio, em quatro repetições. As parcelas foram constituídas por quatro linhas de 5 m de comprimento e espaçadas 1,5 m. A variedade de cana-de-açúcar utilizada foi a RB 86-7515, realizando-se dois cortes. As fontes de Mn proporcionaram semelhantes produtividades de colmos, tanto da cana-planta quanto da primeira cana-soca. O quelato de Mn proporcionou maior número de colmo por metro de sulco na cana-soca. As doses de Mn não influenciaram a produtividade de colmos da cana-planta e da cana- soca, porém aumentaram o número de internódios e o diâmetro de colmo na cana-planta até as doses de 6,9 e 6,6 kg ha-1 de Mn, respectivamente.

A Picture of Performance Goals in the Social Plenum: The Interpersonal Antecedents and Consequences of Performance Goals

Bien que les activités où la compétence est un enjeu (p. ex. : problème académique) prennent souvent place dans des contextes interpersonnels (p. ex. : classe), hiérarchiques (p. ex. : enseignant-e/élèves), et spécifiques en termes de normes et de valeurs (p. ex. : culture), l'étude des buts de performance-le désir de se montrer compétent-e relativement à autrui-a le plus souvent été conduite au seul niveau intrapersonnel. S'appuyant sur le modèle transactionnel du stress et du coping, le modèle circumplexe des comportements interpersonnels, ainsi que sur la théorie de l'élaboration du conflit, la première partie de cette thèse révèle les conséquences interpersonnelles des buts de performance sur la régulation d'un comportement spécifique, à savoir le conflit sociocognitif (c.-à-d., une situation de confrontation avec un intéractant en désaccord) : les buts de performance-approche-le désir d'être meilleur-e qu'autrui-prédisent une régulation du conflit fortement agentique (dominante), soit la validation de son point de vue au détriment de celui de l'intéractant (que nous désignons régulation compétitive) ; alors que les buts de performance-évitement-le désir de ne pas être moins bon-ne qu'autrui-prédisent une régulation du conflit faiblement agentique (soumise), soit l'invalidation de son point de vue au bénéfice de celui de l'intéractant (que nous désignons régulation protective). De plus, les effets susmentionnés augmentent à mesure que l'intéractant est présenté comme supérieurement (vs. similairement) compétent. S'appuyant sur la littérature sur les structures de buts de groupe, et celle sur la socialisation des valeurs, la seconde partie de cette thèse révèle les antécédents interpersonnels des buts de performance, et plus spécifiquement le rôle du superviseur dans la socialisation des buts de performance : les buts de performance-approche d'un superviseur sont positivement associés avec l'émergence au cours du temps des buts de performance-approche de ses subordonnés (particulièrement lorsqu'ils se perçoivent comme compétents) et celle de leurs buts de performance-évitement (particulièrement lorsqu'ils se perçoivent comme incompétents). En outre, ce phénomène consistant en un processus de socialisation, les effets susmentionnés augmentent lorsque l'identification à l'endogroupe des subordonnées augmente, et lorsque l'adhésion aux valeurs culturelles occidentales dominantes (c.-à-d., rehaussement de soi) du superviseur augmente. Dans leur ensemble, ces résultats soulignent la nécessité d'étudier les buts dans leur plenum social, autrement dit, en adoptant une perspective interpersonnelle (c.-à-d., étudier les effets des buts entre les individus), positionnelle (c.-à-d., entre des individus de différentes positions sociales), et idéologique (c.- à-d., entre des individus se conformant à des normes spécifiques et adhérant à des valeurs spécifiques). -- Although competence-relevant activities (e.g., solving an academic problem) are often embedded in interpersonal (e.g., classroom), hierarchical (e.g., teacher/pupils), and norm-/value-specific (e.g., culture) settings, the study of performance goals-the desire to demonstrate competence relative to others-has mostly been conducted at the intrapersonal level alone. Drawing on the transactional model of stress and coping, the circumplex model of interpersonal behaviors, as well as on the conflict elaboration theory, the first part of this thesis reveals the interpersonal consequences of performance goals on the regulation of a specific behavior, namely socio-cognitive conflict (i.e., a situation of confrontation with a disagreeing interactant): Performance-approach goals-the desire to outperform others- predicted a highly agentic (dominant) conflict regulation, that is, the validation of one's point of view at the expense of that of the interactant (which we labeled competitive regulation); whereas performance-avoidance goals-the desire not to be outperformed by others- predicted a poorly agentic (submissive) conflict regulation, that is, the invalidation of one's point of view to the benefit of that of the interactant (which we labeled protective regulation). Furthermore, both the aforementioned effects were found to increase when the interactant was presented as being superiorly (vs. equally) in competence. Drawing on the literature on group goal structure, as well as on research on socialization of supervisors-based values, the second part of this thesis reveals the interpersonal antecedents of performance-based goals endorsement, focusing-more specifically-on the role of group-supervisors in performance goals socialization: Supervisor's performance-approach goals were positively associated with the emergence over time of subordinates' performance-approach (especially when perceiving themselves as competent) and -avoidance goals (especially when perceiving themselves as incompetent). Furthermore, providing evidence that this phenomenon essentially reflects a socialization process, both the aforementioned effects were found to increase as subordinates' in-group identification increased, and as supervisors' adherence to dominant Western values (i.e., self-enhancement values) increased. Taken together, these results advocate the need to study performance goals in their social plenum, that is, adopting an interpersonal (i.e., studying the effects of goals between individuals), positional (i.e., between individuals from different social positions), and ideological (i.e., between individuals following specific norms and endorsing specific values) perspective.