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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Text- und texturale Momente in Motetten des Codex Bamberg

Grüß, Hans 08 January 2020 (has links)
No description available.
22

The Impact of AI-generated Code on Web Development: A Comparative Study of ChatGPT and GitHub Copilot

Fajkovic, Edvin, Rundberg, Erik January 2023 (has links)
Background. Machine learning and artificial intelligence are advancing faster than ever, code generation is becoming a hot topic and is starting to gain traction in the industry. This creates the question, is it possible to create a complete website from scratch using only code generated by AI? Objectives. To determine whether it is possible to create complete websites from start to finish with the code-generating tools. The tools in question are OpenAI’s ChatGPT and GitHub’s Copilot. Methods. A design-based research was conducted where two tools were evaluated for the task of recreating a wireframe as closely as possible in terms of efficiency, accuracy, maintainability, and ease of use. The code was then analyzedboth manually with a code review and using the tools SonarQube, ESLint, and Pylint. Results. The experiment resulted in that both tools delivered code that was similar in quality, both tools managed to create the websites according to wireframe with minor styling differences. We found that it is easier to create a website from scratch using OpenAI's ChatGPT than it is with GitHub's Copilot even though it uses OpenAI's Codex model which focuses on code generation. Conclusion. Code-generating AI is not advanced enough to create systems from scratch in a time-efficient way without introducing bugs and security risks.
23

Virtual reunification of papyrus fragments

Vannini, Lucia 20 April 2016 (has links) (PDF)
Many Greek and Latin papyri, originally belonging to only one book (be it in roll or codex form), are currently scattered among different libraries. While it is not possible to physically rejoin these fragments as they cannot be moved from their institutions, they may be virtually reunited thanks to the techniques of digitisation, image processing and electronic publishing. This paper focuses on some issues – emerged from the work of my MA dissertation – that virtual reunification of Greek and Latin papyri presents. Firstly, I propose a workflow for the creation of a digital edition of virtually rejoined fragments, by applying the model of virtual reunification recently suggested by R. Punzalan in Understanding Virtual Reunification (2014), the first systematic study on this topic. Also, as a principal reference point among the existing projects, I follow the Sinaiticus Project website, which, similarly, deals with an ancient Greek manuscript now dispersed in different institutions; however, while the Sinaiticus Project is exclusively dedicated to that artefact, the edition here proposed includes the possibility to be widened, in order to allow researchers to possibly include more reunified papyri in the future. Secondly, I propose some recommendations that can be followed by the owning institutions in order to digitise their fragments according to a common strategy. Finally, I focus on how a virtual reunification of papyrus fragments can be technically achieved – in other words, how the transcription code can present unified information about the papyrus as a whole and mark the parts of text belonging to each fragment. This project will hopefully help researchers study papyri divided among different libraries in a more systematic way, thanks to the availability of an electronic edition including the whole text and images of the virtually reunited fragments, and thanks to a consolidation of metadata.
24

Après Teotihuacan et Monte Alban : les marqueurs archéologiques et ethnohistoriques de la crise ou de la transition dans la Mixteca (800-1200 apr. J.-C.) ? / After Teotihuacan and Monte Alban : archeological and ethnohistorical markers for aither a crisis or a transition in the Mixteca (A. D. 800-1200) ?

Saumur, Jennifer 25 November 2017 (has links)
Lors de la période classique, entre 200 et 800 ap. J.-C., les centres urbains complexes se développèrent en sur l’ensemble de la Mixteca, en lien étroit avec les cités de Teotihuacan sur les hauts plateaux centraux et de Monte Alban dans les vallées centrales d'Oaxaca. La période plus tardive du Postclassique récent, à partir de 1200 apr. J.-C. et jusqu’à la conquête espagnole, est à nouveau documentée, par les codex peints et les vestiges archéologiques : la Mixteca était densément peuplée et très dynamique, et ses populations liées par une idéologie commune. Le Postclassique ancien, entre 800 et 1200 apr. J.-C., est mal connu. Aucun marqueur archéologique n'a été relevé et daté pour cette période, les Mixtecas Aira et Baja en particulier semblèrent désertées. Cependant, les codex peints plus tardifs témoignent de dynamiques importantes lors de cette période intermédiaire, période la plus ancienne peinte dans les codex. La présente recherche consiste en une synthèse éclairée des données publiées et d'archives, des collections de musées et de réserves archéologiques dans le but de mettre en évidence, dans un premier temps, les marqueurs archéologiques du Postclassique ancien dans la Mixteca, Alta en particulier, et de les dater fermement. Dans un second temps il s'agit de confronter ces données à celles issues des codes mixtèques concernant le Postclassique ancien, témoignant de corrélations évidentes. Ces données collectées, datées et organisées permettent de dresser un premier bilan concernant le Postclassique ancien, de la réorganisation politique, religieuse et spatiale des sociétés après les effondrements politiques classiques. / During the classical period, between A.D. 200-800, complex urban centers grew ail over the Mixteca, in close contact with the cities of Teotihuacan in the central highlands and of Monte Alban, in the central valley of Oaxaca. The later Late Postclassic, from A.D. 1200 to the Spanish Conquest, is documented by painted codex and archaeological remains : the Mixteca was densely populated and very dynamic, populations were united by a shared ideology. Early Postclassic, between A.D. 800 and 1200, is poorly known. No archaeological marker has been identified and precisely dated for this rime, Mixtecas Alta and Baja seemed uninhabited. However, late painted codex demonstrate important dynamics during this intermediary period, the older one painted in codex. This research includes an enlightened overview of published and unpublished data, of museum artefacts and of storage archaeological collections in order to, first, highlight and put a date on archaeological markers for the Early Postclassic in the Mixteca, especially the Mixteca Alta. Then, this research compares these archaeological data to the ethnohistorical ones from the mixtecan codex concerning the Early Postclassic period, showing obvious correlations. These collected, dated and organized data draw up a first report on the Early Postclassic, about political, religious and spatial reorganization of societies after the classical political collapses.
25

Etude des matières picturales du Codex Borbonicus – Apport des spectroscopies non-invasives à la codicologie / A study of the Codex Borbonicus coloring materials - Non-invasive spectroscopies applied to codicology

Pottier, Fabien 19 January 2017 (has links)
Le contenu et l’état de conservation exceptionnel du Codex Borbonicus en font un témoin précieux de la culture du bassin de Mexico-Tenochtitlan à l’époque de l’arrivée des conquistadors. Pour certains historiens il s’agit d’un document assurément précolombien, tandis que pour d’autres, une partie de son contenu graphique dénote une influence culturelle Européenne. Afin d’explorer les savoir-faire mis en œuvre lors de sa production et d’apporter de nouvelles données à ce débat, la nature et le mode de préparation des constituants du manuscrit sont étudiés, dans les limites offertes par les instrumentations transportables et non-invasives (spectroscopies de fluorescence de rayons X, de réflexion, d’émission et Raman). Une première interprétation des données analytiques enregistrées sur le manuscrit se base sur les connaissances issues des sources historiques et du corpus de manuscrits mésoaméricains déjà étudiés. Une analyse plus fine des données est apportée par des calculs de combinaisons spectrales et par l’étude expérimentale de certains colorants, qui permettent une compréhension plus avancée des techniques de production picturale employées. Afin de généraliser les conclusions tirées des mesures localisées, la distribution des constituants sur la totalité du document est également abordée. L’imagerie hyperspectrale, par l’application d’outils statistiques et le développement de cartographies de motifs spectraux spécifiques, apporte ainsi une nouvelle perspective aux résultats des analyses. L’utilisation exclusive de colorants organiques d’origine animale (Dactylopius coccus) ou végétale (Indigofera suffruticosa, Comellina coelestis, Justicia spicigera) dans le Codex Borbonicus, seuls ou en mélanges, correspond aux traditions précolombiennes. L’hypothèse d’une influence européenne ne peut donc s’appuyer sur la nature des constituants du document. Les données présentées viennent par ailleurs enrichir les connaissances sur les techniques de production de manuscrits Mésoaméricains. / The Codex Borbonicus is a great source of knowledge regarding different aspects of the culture of the basin of Mexico-Tenochtitlan at the time of the Spanish conquest. For some historians, the manuscript is definitely Precolumbian while for others, parts of its graphical contents reveal a European cultural influence. In order to investigate the technological knowledge that was involved for its creation, and to bring fresh data to the debate, the manuscript material constituents are studied with transportable, non-invasive analytical techniques (X-Ray fluorescence, reflexion, emission and Raman spectroscopies). A first interpretation of the analytical data recorded on the document is based on the historical records and the corpus of Mesoamerican manuscripts that have already been studied. A finer analysis of the data is done through the calculation of spectral combinations as well as the experimental studies of certain coloring materials, that allow a better understanding of the paint preparation techniques. In order to generalize the conclusion based on localized analyses, the spatial distribution of the constituent on the whole document is also explored. Hyperspectral imaging, with the aid of statistical tools and the mapping of specific spectral features, brings new insights to the first results. The exclusive use of organic colorants extracted from animal (Dactylopius coccus) or vegetable sources (Indigofera suffruticosa, Comellina coelestis, Justicia spicigera) in the Codex Borbonicus, alone or in mixtures, fits what is known of Precolumbian traditions. Therefore, the hypothesis of a European influence can’t be supported by the nature of the manuscript constituents. Moreover, these new data enrich the current knowledge on Mesoamerican manuscript production techniques.
26

論我國針對含萊克多巴胺畜產品之進口管制與WTO規範下SPS協定之合致性 / The Legal Analysis of Taiwan's Meat Regulation regarding Ractopamine under SPS Agreement of WTO

田起安 Unknown Date (has links)
自2005年以降,我國針對是否開放含萊克多巴胺畜產品進口之問題即屬多事之秋,其主因係在食品添加物專家委員會(Joint FAO/WHO Expert Committee on Food Additives,簡稱JECFA)所擬每日容許攝食量下,國際上之相關科學研究無法確切證明萊克多巴胺是否完全安全,抑或其可能對於人體造成之危害及程度,因此多數肉品出口國仍常於家畜飼養過程中添加萊克多巴胺於飼料中,藉以增加畜產品之瘦肉比例並提升經濟效率;另一方面,由於不肖業者違法使用乙型受體素(如克崙特羅、沙丁胺醇)導致人體中毒的案件時有所聞,影響民眾對於畜產品的消費意願及產業發展,是故雖然萊克多巴胺之毒性相較於其他乙型受體素為低,惟受他種毒素高出數倍的乙型受體素之累,在我國自2006年起亦屬禁用之列。在國際食品標準委員會(Codex Alimentarius Commission,簡稱Codex委員會)於去(2012)年以普通多數決之方式制定萊克多巴胺的國際標準後,我國遂修訂食品衛生管理法第11條(2013年新法第15條)、第17-1條 (新法第25條)及動物用藥殘留標準第3條,並公告農防字第1011473960號之行政命令,採行「安全容許、牛豬分離、強制標示、排除內臟」之檢疫政策,在牛肉(含脂肪)的部分採行與國際標準相同之檢疫標準;惟在豬肉及內臟的部分,則為兼顧「國人特殊膳食習慣」及「相關產業發展」,仍維持既有「零檢出」的檢疫政策,全面禁止含萊克多巴胺的畜產品進口。針對此我國特殊之管制作法,本文將以國際經貿法的觀點,依據WTO協定中與檢疫措施最密切相關的SPS協定規範、過往案例之判決及相關文獻,分析我國進口檢疫規定之適法性,藉以思考目前畜產品進口的議題,並判斷該措施將來是否存在遭非難之可能,希冀能對於我國日後檢疫政策走向提供一實質性之參考及展望。 / Since 2005, the issue of liberalizing the import of meat containing Ractopamine had sparked great controversy in Taiwan, resulting from the lack of clear and definite scientific evidences worldwide to prove the harmlessness toward human body under JECFA’s maximal residue level and acceptable daily intake. Owing to the abusing of other much more poisonous Beta-adrenergic agonist (e.g., Clenbuterol, Salbutamol) by some of illegal stockbreeders causing the vibration of meat market and industry, Taiwan’s government had decided to ban the residual of Beta-adrenergic agonist including Ractopamine contained in both domestic and import meat products since 2006. After Codex Alimentarius Commission finally voted through the international standard of Ractopamine in 2012, Taiwan’s Legislative Yuan amended former regulations, approving the import of beef which conformed to Codex’s international standard, while still remained the prohibition of pork containing Ractopamine. This essay staying with the view of international trade law, in particular the Agreement on the Application of Sanitary and Phytosanitary Measures under World Trade Organization, tries to analyze the consistency of Taiwan’s meat regulations with the SPS agreement in order to prospect Taiwan’s trade policy and meat regulations regarding Ractopamine in the future.
27

國際貿易下食品衛生安全措施之同等效力機制研究 / A study on equivalence mechanism of food sanitary measures under international trade

施虹妤 Unknown Date (has links)
在食品貿易全球化的趨勢下,食源性疾病將隨著跨國貿易而擴散,如何在促進貿易的同時亦確保人類食用之安全,即為當今重要之議題。WTO作為涵蓋最多貿易經濟體,並係目前處理國際貿易規則的唯一全球貿易國際組織,對於食品安全與貿易議題,在SPS協定第4條訂有「同等效力」規範作為權衡兩種利益之對策。在國際食品貿易領域下,同等效力係指若進口國對於出口國所採「相異」於進口國本身之SPS措施,如出口國之SPS措施達到與進口國國內「相同」的保護水準,即可認定出口國之措施具備同等效力而承認之,而非要求出口國採用與進口國完全一致之SPS措施。 國際間依據該規範,尤以美國及歐盟為例,實施「輸入前系統性查核機制」,即在食品輸入前先行對出口國之食品安全體系及政府監督措施進行審查,經評估後判定其保護水準與進口國具備同等效力後,該出口國始得出口食品,大幅提升食品安全之保護水準。我國亦順應該趨勢,於民國103年2月11日由衛生福利部公布施行〈輸入食品系統性查核實施辦法〉,將食品安全管制時點從邊境提前至境外。 為瞭解我國規範是否完善,本文將利用比較法的方式,先了解各該國際規範以及美國與歐盟兩大食品貿易國之規範內容,並檢視我國系統性查核機制並提出可能之建議。本文以為,我國已具備同等效力之基本運作架構,惟細部的運作規則、如何判斷同等效力、如何確保後續同等效力之維持,並無明確之規定。故本文建議應先健全我國系統性查核機制之運作及法律機制,以備將來擴大適用。 / With the trend of international trade in food products, foodborne illnesses spread through cross-border trade. Therefore, how to ensure food safety of human consumption while facilitating trade is the most critical issue nowadays. As the only international organization dealing with the global rules of trade between nations, the WTO SPS agreement article 4 provides the “equivalence” mechanism as a way to balance the rights between trade and food safety. In the field of international food trade, the equivalence means that SPS measures does not require duplication or sameness of measures between exporting and importing Members, but the acceptance of alternative measures that meet importing Member's appropriate level of sanitary or phytosanitary protection. Based on the provisions governing equivalence mechanism, each state would implement ante systematic audit, via reviewing food safety system and monitoring measures adopted by competent authorities of exporting party before the importation of food products. As long as the importing state makes a positive determination recognizing of the appropriate level of protection has been achieved, the food products from exporting party are eligible to export to the market of importing state. Such mechanism facilitates cross-border trade in food products and secures the interests of food safety. With this trend, our government enacted the Regulations for Systematic Inspection of Imported Food in recent years. This thesis tries to review the soundness of current Regulation through comparative analysis with international rules and regulations of the US as well as EU. The conclusion is that our system lacks of the specific rules for operation, determination of equivalence and the assurance of the equivalent persistency. Consequently, our government should set up these core elements before transforming current rules to a more comprehensive mechanism in the future.
28

S'affronter pour réguler : le conflit transatlantique sur le boeuf aux hormones dans l'organisation internationale du commerce agroalimentaire. / Ruling by conflicts : Transatlantic “beef-hormones” war and the international organization of food trade

Dangy, Louise 12 March 2018 (has links)
L’objectif de la thèse est de comprendre dans quelle mesure le conflit entre l’Amérique du Nord et l’Europe sur l’utilisation d’hormones de croissance en élevage a participé à l’histoire institutionnelle de la régulation du commerce mondial de denrées alimentaires. Entre 1980 et la période contemporaine (2016), plusieurs épisodes critiques ont mis en évidence la perspective atypique de l’Union européenne à l’égard de l’emploi de ces médicaments vétérinaires ainsi que la contestation suscitée par cette réglementation spécifique dans le cadre de la mondialisation commerciale. Ce conflit se joue sur plusieurs scènes : au sein de la Communauté européenne qui, pendant la décennie 1980, peine à trouver un accord interinstitutionnel quant à une législation commune sur les hormones de croissance ; dans le cadre du General agreement on tariffs and trade (GATT) puis del’Organisation mondiale du commerce (OMC) ; et enfin au sein du Codex Alimentarius, l’organisation internationale chargée d’élaborer des normes alimentaires. Dans chacune de ces instances, la gestion du conflit coïncide avec une phase importante du point de vue institutionnel : création d’organes spécifiques, nouveaux principes et procédures de travail. Dès lors, notre travail visait à détailler l’impact éventuel du conflit sur les hormones de croissance sur chacune de ces institutions ainsi quesur la façon dont, globalement, elles participent à la régulation du commerce international dans le domaine agroalimentaire.Notre travail s’est appuyé sur une enquête socio-historique utilisant un matériau riche et varié permettant de couvrir l’ensemble des institutions identifiées sur la période 1980-2016 : un corpus documentaire a été constitué grâce aux archives des différentes institutions, une trentaine d’entretiens semi-directifs ont été menés. Enfin, plusieurs centaines d’heures d’observationethnographique ont pu être réalisées, la plupart grâce à notre statut de fonctionnaire française du ministère de l’agriculture. Il met en évidence l’évolutivité des fonctions remplies par le conflit sur les hormones de croissance : celui-ci a en premier lieu permis de fédérer l’ensemble des acteurs concernés de la nécessité de renforcer les institutions supranationales, que ce soit à l’échelon européen ou international. Il a ensuite participé à l’élaboration concrète des institutions en permettant d’en tester les instruments au fur et à mesure de leur création, et ainsi, de permettre de réaliser les ajustements jugés nécessaires. De ce point de vue, la gestion du conflit sur les hormones révèle la perception des relations internationales des différents acteurs et sa variabilité temporelle. Enfin, constituant un paramètre pérenne que les acteurs intègrent à leur stratégie de négociationinternationale, le conflit sur les hormones est devenu un point d’ancrage autour duquel s’est structurée une communauté. Il doit ainsi être considéré pour son potentiel socialisateur.Notre enquête apporte également des informations concernant les attentes d’un certain nombre d’acteurs privés en termes de régulation internationale. Le cas des hormones mobilise l’attention des grandes firmes pharmaceutiques qui poussent à l’établissement de normes internationales contraignantes pour le commerce de produits agricoles et concentrent plus particulièrement leur action sur les instances productrices de normes (comme le Codex Alimentarius). Ce comportement semble indiquer que ces acteurs utilisent les instruments de régulation mondiale pour la diffusion de principes d’action publique. / The goal of this work is to understand how deep the commercial war between North America and Europe regarding the use of growth hormones in food-producing animals impacted institutional history of global food trade regulation. Between 1980 and the contemporary period (2016), several crises revealed the atypical nature of the European Union ban. As a result, the European Union views legitimacy was contested in the globalization context. The conflict takes places in several arenas. First of all, it constitutes an issue for Europe, which strived to find an interinstitutional agreement on how to legislate on growth hormones at the European level during the 80ies. Then, it has been one of the most talked about disagreements of the General agreement on tariffs and trade (GATT) and the World trade organization (WTO) negotiations from 1987 onwards. Finally, it involves the CodexAlimentarius Commission, the international organization in charge of setting food standards. In each of these institutions, the beef-hormones conflict management goes with important institutional changes: new specific units, working principles and procedures were created. Thus, my work aimed to precisely describe what consequences the beef-hormones conflict might have had on any of these institutions. As a result, I show how this specific case contributed to the instauration of internationalfood trade regulation.My work relies on a socio-historical inquiry based on diverse and rich empirical data, in order to cover the three aforesaid institutions between 1980 and 2016. I constituted a documentary corpus from institutional archives, and I performed about thirty sociological interviews. I spent several hundreds of hours realizing ethnographing observation, most of which being facilitated by my belonging to the ministry of agriculture’s services. Analysis of this data emphasizes the transforming role of the beef-hormones conflict at an international scale. The conflict first convinced all the stakeholders that it was crucial to strengthen supranational institutions (be it at the European or at the global level). It also allowed to test newly created instruments in their practical functioning. From this prospective, the beef-hormones conflict management reveals the different actors’ internationalrelations perceptions and their evolution during the studied period. Finally, as the beef-hormones conflict has constituted a pattern to the establishment of negotiation strategies, it became a cultural reference structuring an international community. It is therefore a socializing factor.My inquiry also enables a better understanding of private actors’ expectations about international regulation. Veterinary drug industries are actively involved in the institutional discussions surrounding the beef-hormones case, requesting for binding international food trade standards. They are more particularly interested in the activity of standard-setting bodies like Codex. This attitude indicates that those actors use global regulation instruments to advocate for their preferred collective action principles
29

Novas metodologias de ressonância magnética nuclear para o estudo da dinâmica lenta em materiais orgânicos no estado sólido: aplicações em polímeros e proteínas / New nuclear magnetic resonance methods for studying slow dynamics in organic solids: applications to polymers and proteins

Azevêdo, Eduardo Ribeiro de 30 November 2001 (has links)
RMN de Exchange em estado sólido é uma importante técnica utilizada na caracterização de processos dinâmicos em ciência dos materiais. Entretanto, a utilização desta técnica no estudo de materiais complexos tem sido limitada. Neste trabalho, serão propostas novas metodologias de RMN de Exchange em estado sólido, que permitem analisar eficientemente movimentos moleculares na escala de tempo de milisegundos. A técnica denominada Pure Exchange Solid-State NMR (PUREX), provê a supressão dos segmentos rígidos dos espectros de exchange, tomando possível observar os segmentos com mobilidade na escala de ms seletivamente. A técnica Centerband-Only Detection of Exchange (CODEX), permite a observação e caracterização de reorientações moleculares lentas com a maior sensibilidade e resolução disponíveis em RMN de estado sólido, através de espectros obtidos sob rotação da amostra em tomo do ângulo mágico (MAS). Utilizando essas técnicas as funções e tempos de correlação e a geometria de movimentos moleculares lentos podem ser determinadas diretamente, sem a necessidade da utilização de modelos que relacionem as grandezas medidas e as características do movimento molecular. A utilização dos métodos apresentados, permite a identificação e caracterização da dinâmica lenta em materiais complexos, tais como polímeros amorfos, semicristalinos e proteínas. Com objetivo inicial de demonstrar as técnicas, elas foram aplicadas para confirmar detalhes da dinâmica molecular em amostras modelo. Através destas técnicas foi possível confirmar a escala de tempo e os ângulos de reorientação envolvidos na dinâmica molecular de cristais orgânicos, Dimetil Sulfona (DMS), e também para revisitar processos de relaxação local em alguns polímeros, polimetacritato de metila (PMMA) e isotatico polipropileno (iPP). As metodologias foram também aplicadas no estudo da transição vítrea em polímeros semicristalinos, isotatico poli(1-buteno) (iPB 1) e sindiotático polipropileno, os quais não tinham sido ainda estudados por técnicas de RMN de Exchange, já que neste caso a maioria dos segmentos moleculares (porção cristalina do polímero) é rígida durante a transição vítrea. Utilizando os métodos CODEX e PUREX os movimentos lentos que ocorrem na região amorfa destes polímeros em temperaturas próximas as suas temperaturas de transição vítrea foram caracterizados. Um estudo dos movimentos lentos que ocorrem em tomo das temperaturas de transição vítrea nas cadeias poliméricas de dois tipos de nanocompostos híbridos siloxano/(polietileno glicol) (ormolitas) também é apresentado. Heterogeneidades nos movimentos das cadeias poliméricas associados com a interação PEG/siloxano foram diretamente observadas através de experimentos PUREX 1D de Exchange 2D. Evidenciais da presença de movimentos de grande e pequena amplitude foram observados para os dois tipos de híbridos. Os resultados revelam que a restrição do movimento das cadeias poliméricas pelas estruturas de siloxano depende tanto do comprimento da cadeia como da natureza das interações entre as fases orgânica e inorgânica do nanocomposto. Finalmente os resultados referentes a caracterização da dinâmica molecular rápida e lenta e sua relação com as propriedades estruturais de um hidrogel protéico são apresentados. Utilizando uma versão modificada da técnica CODEX, juntamente com experimentos de polarização direta, polarização cruzada e RMN de correlação 2D, foi possível não somente confirmar a estrutura e o modelo de formação propostos para o gel, mas também determinar a geometria e a escala de tempo dos movimentos lentos que ocorrem na região de hélice do hidrogel protéico em grandes detalhes. A demonstração teórica e experimental das técnicas e suas aplicações no estudo dessas importantes classes de materiais serão apresentadas. / Solid-State Exchange NMR is an important method to characterize details of dynamic process in materials science. However, the application of these techniques to study complex materials has been limited. In this work new solid-state Exchange NMR techniques, which allows efficient analysis of molecular motions in the millisecond time scale, are presented. The Pure Exchange Solid-State NMR (PUREX) method provides the suppression of the rigid segments in standard exchange spectrum, making possible to observe the slow moving moieties selectively. The Centerband-Only Detection of Exchange (CODEX) technique allows observing and characterizing slow segmental reorientations with the highest available NMR sensitivity and site resolution, in a magic angle spinning (MAS) NMR spectrum. Correlation functions, correlation times and information about the motional amplitude and geometry can be direct1y obtained using the techniques, without any model assumption. These methods allowed identifying and characterizing slow dynamics in complex materials such as, semicrystalline and amorphous polymers and proteins. To demonstrated the proposed techniques they have been applied to confirm some kwon aspect of the slow dynamics of model samples. Using the methods it was possible o confirm the time scale and the reorientation angles involved in the molecular dynamics of organic crystals, Dimethyl Sulfone (DMS), and also to revisit some relaxation process in standard polymers, such as the beta relaxation of poly(methyl metacrylate) (PMMA) and the alfa relaxation in isotactic polypropylene (iPP). The time scale and the geometry of the molecular motions responsible by these relaxation process obtained using the PUREX and CODEX techniques are in excellent agreement with the data taken from the literature, confirming the reliability of the proposed methods. Moreover, the techniques were also applied to study the slow molecular motions involved in the glass transition of semicrystalline polymers, such as isotactic poly (l-butene) form I (iPB1) and syndiotactic Polypropylene (sPP). The glass transition of these polymers had not been studied using Exchange NMR methods because most of the molecular segments (crystalline portion of the polymers) are rigid during the glass transition. Using the PUREX and CODEX methods the slow molecular reorientations within the amorphous region of the polymers were characterized for temperatures near its glass transition. A study of the slow motions occurring around the glass transition temperature in the polymer chains of two types of siloxane/(polyethylene glycol) nanocomposites (ormolites) is also presented. Motional heterogeneities associated with PEG/ siloxane interactions were directly observed in the 13C 1D PUREX and 2D exchange data. Evidences of both small and large angle amplitude motions were direct1y observed for both types of hybrids. The results revealed that the hindrance to the slow molecular motions of the polymer chains due to the siloxane structures depends on the chain length and the nature of the interaction between the organic and inorganic phases. Finally the results concerning the characterization of the fast and slow dynamics and its relationship with the structural properties of a protein hidrogel are presented. Using a modified version of the CODEX technique, together with standard direct polarization, cross polarization and 2D NMR correlation experiments, it was possible not only to confirm the proposed structure and the gel formation model, but also to characterize the geometry and the time scale of the slow motions in the helical domains of the protein hidrogel in great detail. The theoretical and experimental demonstration of all proposed methods and also its applications in these important classes of material will be present.
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Weltuntergang 2012?

Bürger, Thomas 23 March 2012 (has links) (PDF)
Seit Produzent und Regisseur Roland Emmerich (Independece Day, Stargate) mit seinem Kinoerfolg „2012“ unsere Welt mit allen Mitteln digitaler Illusion zusammenkrachen ließ, wollen Journalisten aus aller Welt von der SLUB nur noch das eine wissen: Was prophezeit der Maya-Kalender zum 21. Dezember 2012, was steht tatsächlich im Codex Dresdensis über einen Weltuntergang? Die Antwort schrieb Spiegel TV gleich selbst ins Gästebuch: Wenn die Welt auch untergeht – wir senden weiter. An einen Weltuntergang glaubt (fast) niemand, aber viele reden drüber: bei Google findet man in 0,08 Sekunden 2,8 Millionen Weltuntergangs-Treffer. An erster Stelle steht die Uhr, die Tage, Stunden und Sekunden rückwärts zählt…

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