La question de l’évolution du parc nucléaire français peut être considérée via l’étude de scénarios électronucléaires. Ces études présentent un rôle important, compte-tenu des enjeux, de l’ampleur des investissements, des durées et de la complexité des systèmes concernés, et fournissent des éléments d’aide au processus décisionnel. Elles sont menées à l’aide du code COSI (développé au CEA/DEN), qui permet de calculer les inventaires et les flux de matières transitant dans le cycle (réacteurs nucléaires et installations associées), via notamment le couplage avec le code d’évolution CESAR. Les études actuelles menées avec COSI nécessitent de définir les paramètres d’entrée des scénarios simulés, de sorte à satisfaire différents critères comme minimiser la consommation d’uranium naturel, la production de déchets, etc. Ces paramètres portent notamment sur les quantités et l’ordonnancement des combustibles usés au retraitement ou encore le nombre, la filière et les dates de mises en service des réacteurs à déployer. Le présent travail vise à développer, valider et appliquer une méthodologie d’optimisation couplée à COSI pour la recherche de scénarios électronucléaires optimaux pour un problème multicritère. Cette méthodologie repose en premier lieu sur la réduction de la durée d’évaluation d’un scénario afin de permettre l’utilisation de méthodes d’optimisation en un temps raisonnable. Dans ce cadre, des métamodèles d’irradiation par réseaux de neurones sont établis à l’aide de la plateforme URANIE (développée au CEA/DEN) et sont implémentés dans COSI. L’objet du travail est ensuite d’utiliser, adapter et comparer différentes méthodes d’optimisation, telles que l’algorithme génétique et l’essaim particulaire disponibles dans la plateforme URANIE, afin de définir une méthodologie adéquate pour ce sujet d’étude spécifique. La mise en place de cette méthodologie suit une approche incrémentale qui fait intervenir des ajouts successifs de critères, contraintes et variables de décision dans la définition du problème d’optimisation. Les variables ajoutées au problème, qui décrivent la cinétique de déploiement des réacteurs et la stratégie de retraitement des combustibles usés, sont choisies en fonction de leur sensibilité sur les critères définis. Cette approche permet de faciliter l’interprétation des scénarios optimaux, la détection d’éventuelles difficultés liées au processus d’optimisation, et finalement d’émettre des recommandations d’utilisation de la méthodologie mise en place en fonction de la nature du problème. Les études d'optimisation s’appuient sur un scénario de déploiement de réacteurs à neutrons rapides avec recyclage du plutonium, inspiré des études menées dans le cadre de la loi de 2006 sur la gestion des matières et déchets radioactifs. Une illustration des possibilités de la méthodologie est réalisée sur ce scénario, et permet notamment de démontrer le caractère optimal du scénario issu des études menées selon cette loi vis-à-vis de la limitation de l’entreposage de matières fissiles. Ce résultat souligne l’importance de la mise en œuvre d’une gestion dynamique du plutonium via le recours au combustible MOX pour le déploiement progressif des RNR. / The issue of the evolution French nuclear fleet can be considered through the study of nuclear transition scenarios. These studies are of paramount importance as their results can greatly affect the decision making process, given that they take into account industrial concerns, investments, time, and nuclear system complexity. Such studies can be performed with the COSI code (developed at the CEA/DEN), which enables the calculation of matter inventories and fluxes across the fuel cycle (nuclear reactors and associated facilities), especially when coupled with the CESAR depletion code. The studies today performed with COSI require the definition of the various scenarios’ input parameters, in order to fulfil different objectives such as minimising natural uranium consumption, waste production and so on. These parameters concern the quantities and the scheduling of spent fuel destined for reprocessing, and the number, the type and the commissioning dates of deployed reactors.This work aims to develop, validate and apply an optimisation methodology coupled with COSI, in order to determine optimal nuclear transition scenarios for a multi-objective platform. Firstly, this methodology is based on the acceleration of scenario evaluation, enabling the use of optimisation methods in a reasonable time-frame. With this goal in mind, artificial neural network irradiation surrogate models are created with the URANIE platform (developed at the CEA/DEN) and are implemented within COSI. The next step in this work is to use, adapt and compare different optimisation methods, such as URANIE’s genetic algorithm and particle swarm methods, in order to define a methodology suited to this type of study. This methodology development is based on an incremental approach which progressively adds objectives, constraints and decision variables to the optimisation problem definition. The variables added, which are related to reactor deployment and spent fuel reprocessing strategies, are chosen according to their sensitivity to the defined objectives. This approach makes optimal scenarios interpretation easier, makes it possible to identify potential difficulties with the optimisation process, and then to provide recommendations on the use of the deployed methodology according to the problem type. The optimisation studies consider a fast reactor deployment scenario with plutonium recycling, which is inspired by studies carried out in the scope of the 2006 Act for Waste Management. An illustration of the possibilities of this methodology is provided with this scenario, demonstrating the optimality of the scenario inspired by the studies that were carried out for the 2006 Act, regarding stored fissile materials limitation. This result highlights the importance of dynamic plutonium management through MOX fuel usage during fast reactor deployment.

Chez les mammifères, l'attachement pour la mère, est caractérisé par un effet sécurisant de la présence de cette figure qui permet au jeune d'explorer son environnement. Plusieurs études ont suggéré qu’un attachement pouvait se développer pour des substituts maternels tels qu’un congénère ou un objet. Cette thèse sur l'agneau montre, au travers de l'évaluation des caractéristiques de l'attachement, l'absence d'un tel lien en absence de figure maternelle pour un congénère de même âge ou un objet. L'altération de l'attachement chez ces individus est associée à une modification de l'axe corticotrope (HPA) et du système ocytocinergique : les agneaux élevés en absence de figure maternelle montrent un stress accru à 24 heures de vie, traduit au niveau central par une réduction du nombre de neurones contenant de la corticolibérine et une augmentation de ceux contenant l'ocytocine à 21 jours. Cette étude suggère un rôle apaisant de la figure maternelle pouvant faciliter la mise en place de l'attachement et influençant le développement de l'axe HPA. Ce travail suggère par ailleurs l'implication de l'ocytocine dans l'adaptation du jeune à un contexte social stressant. / In mammals, attachment to the mother is characterized by a secure effect of the presence of such figure which allows the young to explore its environment. Several studies have suggested that attachment bond could develop for mother surrogates such as peers or objects. This thesis shows through the evaluation of attachment key features in lambs, the absence of attachment in motherless lambs for a same-aged peer or an object. The alteration of attachment in these individuals is associated with a modification of the hypothalamic-pituitaryadrenal (HPA) axis and the oxytocinergic system: peer- and object-reared lambs show physiological sign of stress 24h after birth, reflected at the central level by a decrease of the number of neurons containing corticoliberin and increase of those containing oxytocin at 21 days of age. This study suggests a soothing effect of the mother figure that could facilitate the establishment of attachment and influence the development of the HPA axis. This work also suggests the involvement of oxytocin in the young to cope with stressful early social context.

Dans les essais cliniques randomisés (ECR) en cancérologie, un critère de substitution est une mesure biologique utilisée à la place d’un critère cliniquement pertinent pour le patient, par exemple la survie globale (SG), qui doit permettre de prédire l’effet attendu du traitement. Des critères alternatifs à la SG, par exemple la survie sans progression, sont de plus en plus fréquemment utilisés en tant que critère de jugement principal dans les ECR. En pratique cependant, les capacités de substitution à la SG de ces critères ne sont pas systématiquement évaluées. Nous avons dressé un état des lieux des critères de substitution validés en cancérologie à partir d’une revue systématique de la littérature. Par la suite, nous avons évalué par une approche méta-analytique des critères de substitution dans le contexte des sarcomes des tissus mous en situation avancée et du cancer du sein en situation adjuvante. Les résultats n’ont pas permis de définitivement valider de critères de substitution à la SG dans ces indications. La SG doit donc rester le critère de jugement principal des ECR, même si certains critères alternatifs restent informatifs dans des évaluations plus précoces (phase II, analyse de futilité), sous réserve que les données de survie continuent à être recueillies. Ce travail fournit des informations clés pour le développement des ECR en cancérologie afin notamment de sélectionner au mieux les critères de jugement de l’efficacité thérapeutique. / In cancer randomized controlled trials (RCT), a surrogate endpoint is intended to substitute a clinically relevant endpoint, e.g. overall survival (OS), and it is supposed to predict treatment effect. Alternative endpoints, for example progression-free survival, are increasingly being used in place of OS as primary efficacy endpoints in RCTs. In practice however, the surrogate properties of these endpoints are not systematically assessed. We performed a systematic literature review to identify surrogate endpoints validated in oncology. We next conducted MAs to evaluate surrogate endpoints in two cancer settings: advanced soft-tissue sarcoma and adjuvant breast cancer. Results could not definitely validate surrogate endpoints in these indications. OS must remain the primary efficacy endpoint in these settings, even though alternative endpoints may provide valuable input in earlier phase studies (phase II trials, futility analyses). This work provides key information for the design of cancer RCTs, in particular for the choice of primary endpoints to assess treatment efficacy.

É indiscutível os inúmeros benefícios decorrentes do avanço da ciência, principalmente no campo da reprodução artificial, entretanto cada vez mais se mostra necessário impor limites, tanto na área médica quanto na jurídica, devendo-se regulamentar, legal e especificamente a matéria, com o fim de se coibir abusos e proteger direitos. Ademais, o avanço rápido da ciência tem preocupado sobremaneira a sociedade relativamente às conseqüências decorrentes do uso indevido por parte de pesquisadores, médicos e clínicas reprodutivas, das inovações e possibilidades nesta área. Nada justifica que a busca científica desenfreada, por exemplo, de seres humanos geneticamente melhorados, ultrapasse limites éticos, morais e sociais, discriminando-se àqueles que não se enquadram nos padrões sociais previamente estereotipados. Na presente pesquisa, a responsabilidade civil e penal é tratada como forma inibidora de tais atos, mas não se mostra como única solução possível. Sendo assim, questões como o direito dos embriões, o direito a vida, a dignidade humana, a sucessão hereditária, a filiação, entre outros, são objeto primordial da presente obra, de forma que lhe sejam assegurados ampla tutela jurídica nesse sentido. Também questões relativas à gestação de substituição e a autorização daqueles que pretendem implantar um embrião, sejam pais genéticos ou não, na utilização das técnicas de reprodução artificial, aqui se encontram abordadas. Busca-se também proteger o direito de igualdade entre filhos, proibindo-se consequentemente a discriminação entre eles em razão de sua origem. São também esclarecidas as técnicas de reprodução artificial, bem como as teorias relativas ao início da vida para caracterizar-se a personalidade jurídica. Por fim, há ainda, nesta obra, preocupação em esclarecer conceitos, diferenciando-se terminologias e estabelecendo-se definições necessárias tanto na área jurídica quanto médica. / It is undiscuss the numerous benefits resulting from Science advance, especially concerning artificial reproduction, however it is necessary put on limits in medical and legal concernes, having to regulatory, legal rules in order to cohabit abuses and protect rights. Moreover, fast science advance has been worring the society about consequences becomes from the improper use from reserarchers, medical and reproductive clinics concerning innovations and possibilities in this area. Nothing can justifies the fast serch, for example, for humans genetically improveds, it exceeds ethical, moral and social limits, broking down who is not in conform to social standar previously sterotyped. In this research, the civil and penal liability is treated as inhibitory form of such acts, but not appears as the only possible solution. In order, issues concerning embryos rights, such as life rights, human dignity, hereditary succession, among others, are primary subject of this book, performing ensured broad legal protection accordingly. Also issues related to surrogate mother and the authorization of those intending to deploy an embryo, be or not the genetic fathers, in the use of artificial reproduction technical, here related in this work. Also seeks proteting to the rights of equality between sons, in order to forbid discrimination among them because of their origins. The work also clarified the techniques of artificial reproductions, as well as theories concerning the beginning of life to be characterized legal personality. Finally, in this current work, there is worry to clarify the concepts, differing terminologies and definitions needed both in legal and medical fields.

Made available in DSpace on 2014-06-11T19:27:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-03-23Bitstream added on 2014-06-13T19:15:35Z : No. of bitstreams: 1 silva_fm_me_sjrp.pdf: 817059 bytes, checksum: eb6c0e0e69f3687d3831dbbbc3cf6e09 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho consiste numa extensão do estudo de um problema de dimensionamento de lotes com custo de transporte feito por Norden e Velde [53], onde a produção dos itens é transportada, em paletes, para um armazém. O transporte é feito por uma empresa terceirizada sob um contrato com os seguintes custos pré-estabelecidos: um custo fixo de contrato, um custo para o transporte de um determinado volume de paletes e um custo adicional para paletes extras. O problema foi estendido, no presente trabalho, considerando restrições de capacidade e a possibilidade de atrasos no atendimento a demanda. Nosso objetivo é propor um modelo matemático para o problema estendido e desenvolver dois métodos heurísticos de resolução. Tais métodos são baseados em dois tipos de relaxação: relaxação Lagrangiana e relaxação Lagrangiana/Surrogate. Os resultados obtidos pelas heurísticas são comparados com os resultados obtidos pelo pacote de otimização CPLEX 10.0. Além disso, é feita uma comparação entre os métodos heurísticos. / This work consist of an extension of a study of the capacitated lot-sizing problems with transportation cost by Norden and Velde [53], where the production of itens is transported into pallets to an warehouse. The transportation is executed by another company, under a contract with the following transportation cost established: a fixed contract cost, a transportation cost for determined quantity of pallets and an additional cost for extra pallets. The problem was extended, in this work, considering capacity constraint and backlogging. Our objective is to propose a mathematical model for the extended problem and to develop two heuristics methods of resolution. The methods are based on two types of relaxation: Lagrangian relaxation and Lagrangian/Surrogate relaxation. The results obtained by heuristics are compared with the results obtained by CPLEX 10.0. Furthermore, a comparison between the heuristics is made.

The primary focus of these theses is issue of unwanted children and possible solution which is allowed by Czech law. Definition of the term unwanted child is not simple. The child can become unwanted even before his birth (for example in case of unwanted pregnancy) or during his childhood which is more common. For purpose of these theses child is considered a person who is under the age of eighteen. This is also supported by The European Constitution of the right of the child. Among the solutions of the issue of unwanted children I included the possibility of legal abandonment of the newborn after birth and issue of babyboxes. Both of the institutions focus on the newborn and their mothers. If the mother decides to postponement of the newborn after birth and the same time she wants to conceal her identity she can choose concealed birth or discrete birth. In the chapter describing the babyboxes I focused on legal issue of this institution and basic questions related to the problems of the babybox. This institute has many opponents and patrons from the professionals or general public. The following four chapters describe surrogate children care which is providing a solution for the unwanted child not only after birth but also during childhood. Legislation of institutional care when child is placed in...

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-10-04T19:09:24Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese mariana viana para BC revisado profa Rita.pdf: 5880006 bytes, checksum: 58b21f8952495e3aba8663b4efa5c48c (MD5) / Made available in DSpace on 2016-10-04T19:09:24Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) tese mariana viana para BC revisado profa Rita.pdf: 5880006 bytes, checksum: 58b21f8952495e3aba8663b4efa5c48c (MD5) Previous issue date: 2016-02-12 / Capes / O câncer de mama desenvolve-se de maneira silenciosa, podendo levar a óbito se não for tratado em sua fase inicial. Por este motivo, é necessário desenvolver técnicas para sua detecção precoce. A carcinogênese altera a temperatura dos tecidos na região afetada e o uso da simulação computacional calcula como ocorre tal fenômeno. A imagem por infravermelho é capaz de indicar a distribuição superficial de temperatura e a comparação destes valores com os cálculos obtidos na simulação computacional é uma ferramenta promissora para a detecção precoce do câncer de mama. O objetivo desta tese é construir a geometria substituta tridimensional (3D) da mama feminina a partir de imagens por infravermelho da paciente. Isso possibilita o cálculo da distribuição de temperatura através de software de dinâmica dos fluidos computacional (CFD – Computational Fluid Dynamics). O corregistro de uma prótese mamária externa aos contornos da paciente modelou a superfície da geometria tridimensional da mama. No interior dessa geometria existem os lóbulos mamários, os ductos lactíferos, o tecido adiposo da mama e a lesão conforme indicado no exame de ultrassonografia da paciente. Um software de CFD realizou o preparo da geometria e subsequente cálculo da distribuição de temperatura na mama. Um estudo de caso verificou o impacto da inserção das estruturas citadas na geometria substituta. O erro entre as temperaturas máximas indicadas pela imagem por infravermelho das pacientes na região da pele sobre a anomalia e a temperatura máxima alcançada no cálculo de temperatura sobre a região correspondente na geometria substituta foi de 0,20%. A geometria 3D aqui apresentada adequa-se aos contornos de cada paciente e é mais próxima da mama real do que a geometria substituta 3D obtida pelo escaneamento de próteses mamárias externas e outras apresentadas na literatura técnica. Além disso, a geometria desenvolvida permitiu o cálculo de temperatura nos casos em que não era possível com a geometria anteriormente utilizada. / Breast cancer develops silently and can lead to death if not treated in its early stages. For this reason, it is necessary to develop techniques for its early detection. The carcinogenesis changes the temperature of the tissue in the affected area, the use of computer simulation to evaluate how such a phenomenon occurs. The infrared image can indicate the surface temperature distribution, and the comparison of these figures with the calculations obtained in a computer simulation is a promising tool for early detection of breast cancer. The purpose of this thesis is to build three-dimensional (3D) surrogate geometry of the female breast from infrared images of the patient. It allows the calculation of the distribution of temperature through Computational Fluid Dynamics (CFD) software. The breast prosthesis co-registration to the contours of the patient modeled the external surface of the 3D geometry of the breast. Within this geometry, there are mammary lobules, lactiferous ducts and adipose tissue of the breast and the lesion as indicated in the ultrasound examination of the patient. CFD software performed the preparation of the geometry and subsequent calculation of the breast temperature distribution. A case study verified the impact of the insertion of such structures in the surrogate geometry. The error between the maximum temperature indicated by the infrared image of the patient in the area of the skin over the abnormality and the maximum temperature achieved in the temperature calculation in the corresponding region in the surrogate geometry were 0.20%. The 3D geometry presented here fits the contours of each patient, and it is closer to the real breast than the surrogate 3D geometries acquired by the scanning of external breast prostheses and others ones presented in the technical literature. Furthermore, the modeled geometry allowed the temperature calculation in cases where it was not possible with the geometry that was previously used.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-01-09T11:49:25Z No. of bitstreams: 1 taleslimafonseca.pdf: 6292275 bytes, checksum: 0e7e3e7f61b734dce43a0db483431c0f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-01-23T11:18:02Z (GMT) No. of bitstreams: 1 taleslimafonseca.pdf: 6292275 bytes, checksum: 0e7e3e7f61b734dce43a0db483431c0f (MD5) / Made available in DSpace on 2018-01-23T11:18:02Z (GMT). No. of bitstreams: 1 taleslimafonseca.pdf: 6292275 bytes, checksum: 0e7e3e7f61b734dce43a0db483431c0f (MD5) Previous issue date: 2017-08-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Problemas de otimização são comuns em diversas áreas. Nas engenharias, em muitas situações, os problemas de otimização eram modelados desconsiderando certas características do fenômeno estudado com a finalidade de simplificar as simulações durante o processo de busca. Contudo, com o passar do tempo, a evolução das máquinas possibilitou a modelagem de problemas de otimização com mais informações, aproximando os modelos da forma mais fidedigna possível. No entanto, uma parcela significativa desses problemas demanda um alto custo computacional para realizar as avaliações das soluções candidatas, tornando muitos deles de difícil análise e simulação. Dessa forma, o objetivo deste trabalho é a utilização de métodos de aprendizado de máquina acoplado a um algoritmo de otimização com intuito de direcionar o processo de busca de um algoritmo genético, inserindo possíveis soluções na população do algoritmo genético a cada geração com o intuito de reduzir o alto custo computacional de se encontrar as soluções ótimas. Além disso, é realizado um estudo comparativo para verificar quais métodos de aprendizado de máquina obtêm bons resultados na técnica proposta. Os experimentos são realizados em problemas de otimização com um alto custo computacional comumente encontrados na literatura. / Optimization problems are common in many areas. In engineering, in many situations optimization problems were modeled disregarding certain characteristics of the studied phenomenon in order to simplify the simulations during the search process. However, over time, the evolution of the machines allowed the modeling of optimization problems with more information, approaching the models in the most reliable way possible. In this way, a significant portion of these problems requires a high computational cost to perform the evaluations of candidate solutions, making many of them difficult to analyze and simulate. Thus, the objective of this work is the use of machine learning methods coupled with an optimization algorithm with the purpose of directing the search process of a genetic algorithm, inserting new good quality solution into the population at each generation with the intention of reducing the high computational cost of finding the optimal solutions. In addition, a comparative study is carried out to verify which machine learning methods obtain good results in the proposed technique. The experiments are performed on optimization problems with a high computational cost commonly found in the literature.

Parmi les techniques de mesure nucléaire non destructives utilisées par les instrumentistes du noyau atomique, la spectrométrie gamma est aujourd’hui une méthode d’identification et de quantification de radionucléides largement employée dans le cadre de la gestion d’objets nucléaires complexes tels que des déchets radioactifs, des fûts de déchets ou des boîtes à gants. Les caractéristiques physico-nucléaires non-reproductibles et variées de ces objets, telles que leurs compositions, la répartition des matériaux, leurs densités et formes géométriques, ou le nombre et la forme de leurs termes sources émetteurs, induisent une inaptitude des méthodes d’étalonnage traditionnel à permettre l’obtention de l’activité d’un matériau nucléaire donné. Cette thèse propose une méthode de quantification de radionucléides multi-émetteurs, limitant, voire supprimant, l’utilisation d’informations dites a priori issues de l’avis d’expert ou du retour d’expériences. Cette méthode utilise entre autres la métamodélisation pour construire une efficacité de détection gamma équivalente de la scène de mesure, le formalisme de résolution de problème inverse par Chaines de Markov Monte-Carlo (MCMC), le tout placé dans un cadre de travail probabiliste bayésien afin d’estimer les densités de probabilités des variables d’intérêt telle qu’une masse de radionucléide. Un protocole de validation expérimentale permet de vérifier la robustesse de la méthode à estimer une masse de 239Pu au sein d’objets similaires à ceux traités en routine par le laboratoire. Les perspectives de la méthode concernent la réduction des temps de calcul, des coûts financiers et humains par limitation de l’approche type expert, et la réduction des incertitudes associées. / Gamma spectrometry is a commonly passive nondestructive assay used to identify and quantify radionuclides present in more or less complex objects such as waste packages, waste drums or glove boxes. Basic methods using empirical calibration with a standard in order to quantify the activity of nuclear materials by determining the absolute calibration efficiency are useless on non-reproducible, complex and single nuclear objects such as waste packages. Package specifications as composition or geometry change from one package to another and involve a high variability of objects. Current quantification process uses numerical modeling of the measured scene with few available data such as geometry or composition. These data are density, material, screen, geometrical shape, matrix composition and source distribution. Some of them are strongly dependent on package data knowledge. The method developed in this thesis suggests combining a global stochastic approach which uses, among others, surrogate models available to simulate the gamma attenuation behaviour, a Bayesian approach which considers conditional probability density functions of problem inputs, and Markov Chains Monte Carlo algorithms (MCMC) which solve inverse problems, with gamma ray emission radionuclide spectrum and outside dimensions of interest objects. The methodology is testing to standard in terms of actinide masses, locations and distributions. Activity uncertainties are taken into account by this adjustment methodology. An experimental protocol is built to validate the quantification method in terms of robustness with the quantification of 239Pu. The perspectives of the method are to save time by improving the nuclear measurement process, to cut back on costs by avoiding as far as possible expert approaches, and to reduce the actinide mass uncertainties by increasing the precision of quantification process.

The thesis explores the impact of the new Children’s Act 38 of 2005 on the acquisition of parental responsibilities and rights within a newly proposed framework designed for the purpose of reflecting the various ways in which parental responsibilities and rights can be acquired. The research has shown that the Children’s Act has fundamentally transformed the way in which parental responsibilities and rights are acquired. The transformation has created a scheme for the acquisition of parental responsibilities and rights that is for the most part constitutionally compliant and progressive insofar as it gives recognition to the different family forms found in South Africa. To this end the Children’s Act has considerably expanded the ways in which parental responsibilities and rights can be acquired. Whereas previously exclusively the preserve of heterosexual married parents in a nuclear family, parental responsibilities and rights can now automatically be acquired by a committed biological father and a married lesbian couple conceiving by artificial means. Apart from authorising courts to assign parental responsibilities and rights, the Children’s Act allows any holder of parental responsibilities and rights to confer responsibilities and rights on another by prior approved agreement. The Act also includes specific provisions to regulate the acquisition of parental responsibilities and rights by commissioning parents in the case of a surrogate motherhood agreement. The structure developed for the research topic reflects the transformation of the law in this regard by making the application of the best interests-standard, rather than the marital status of the child’s parents, the distinguishing feature of the subdivision between automatic and assigned acquisition. In this way the structure is an embodiment of the paramountcy of the best interests principle in section 28(2) of the Constitution. Insofar as the law still requires a distinction to be made between biological mothers and fathers, on the one hand, and naturally and artificially conceived children, on the other, the structure also highlights the remaining shortcomings of the law in this regard. The structure is, furthermore, necessarily complicated by the need to distinguish between the acquisition of care, on the one hand, and guardianship, on the other. As far as fathers are still not treated the same as mothers in the automatic allocation of parental responsibilities and rights, the Act is deemed not to have been progressive enough. Conferring full parental responsibilities and rights on both parents based on their biological link to the child would not only be in line with worldwide trends, but would also meet the constitutional demands of substantive sex and gender equality. It will further place the focus on the best interests of the child, which emphasises the importance of both parents for the child. While the research shows that tensions between the biological and social constructs of parenthood may possibly hamper the legal recognition of de facto care-givers or other persons with whom the child has developed a psychological bond, the greatest weakness of the Act would seem to lie in the failure to implement an integrated family court structure. Please cite as follows: Louw, AS 2009, Acquisition of parental responsibilities and rights, PhD thesis, University of Pretoria, Pretoria, viewedyymmdd < http://upetd.up.ac.za/thesis/available/etd-09102009-170707/ > Copyright / Thesis (LLD)--University of Pretoria, 2009. / Private Law / unrestricted