9 research outputs found

    Appearance Changes due to Light Exposure

    Get PDF
    The fading of materials due to light exposure over time is a major contributor to the overall aged appearance of man-made objects. Although much attention has been devoted to the modeling of aging and weathering phenomena over the last decade, comparatively little attention has been paid to fading effects. In this dissertation, we present a theoretical framework for the physically-based simulation of time-dependent spectral changes induced by absorbed radiation. This framework relies on the general volumetric radiative transfer theory, and it employs a physicochemical approach to account for variations in the absorptive properties of colourants. Employing this framework, a layered fading model that can be readily integrated into existing rendering systems is developed using the Kubelka-Munk theory. We evaluate its correctness through comparisons of measured and simulated fading results. Challenges in the acquisition of reliable measurements are discussed. The performance characteristics of the proposed model are analysed, and techniques for improving the runtime cost are outlined. Finally, we demonstrate the effectiveness of this model through renderings depicting typical fading scenarios

    The histology of ossification in the caudal fin of Larval Zebrafish, Danio rerio

    Get PDF
    1 online resource (59 unnumbered pages) : illustrations (some colour), charts (some colour), graphs (some colour)Includes abstract and appendices.Includes bibliographical references (unnumbered pages 45-50).Endochondral ossification is a bone developing process in which a cartilaginous template gets replaced by bone. Zebrafish, Danio rerio, are teleost fish that undergo this process throughout their skeletons. This thesis is focussed on their tail bones, specifically within the hypurals and parhypural of the caudal fin. The morphological changes in the cells of the hypurals and parhypural during ossification have not been recorded so the aim of this study is to investigate these changes taking a histological approach. To determine the morphological cellular changes Hall Brunt’s Quadruple staining was used to stain the bone and cartilage within zebrafish sized 4 to 9 mm standard length. Changes within the chondrocytes were measured and descriptions of the amount of ossification were made. It was found that all five hypurals and the parhypural begin ossifying around 5.0 mm SL, while the chondrocytes underwent hypertrophy by 7.0 mm SL there was a lower percentage of hypertrophied chondrocytes in 8.0 – 9.0 mm SL specimens for hypurals 2 and 3. Hypural 2 and 3 were the elements primarily focused on, that had an increase in total hypural length (µm). These results suggest that the hypurals share features of both endochondral and perichondral ossification. Further studies are needed to further understand ossification within the zebrafish caudal fin

    The Effect of Sprinkler Spray on Combustion Products Leaving a Compartment

    Get PDF
    Performance based design (PBD) is becoming increasingly popular for designing structures that would not be possible using prescriptive- based codes. To effectively use PBD, engineers need to have access to engineering tools that can predict how a structure would be affected in fire scenarios. Building on previous work, 27 full scale fire tests were performed in attempt to determine a method to account for the effect of a single sprinkler on fire induced doorway flows. A new engineering tool was developed based on integrating the superposition of mass flux profiles in the doorway for both fire-only and sprinkler-only conditions. The results of this study are a first step to being able to predict the effect of a sprinkler on fire induced doorway flows from a compartment

    The symbolic and functional exploitation of ochre during the South African Middle Stone Age

    Get PDF
    Ochre is a ubiquitous artefact in Middle Stone Age (MSA) contexts throughout Africa and the Near East. Archaeological evidence for the abrasive processing of ochre to extract pigment powder becomes increasingly prevalent after 100 ka. The habitual exploitation of ochre is interpreted as evidence for symbolism, a proxy for the origin of language and as a key element of ‘symbolic’ and ‘modern’ human behaviour. Evolutionary explanations agree that ochre and the products of its processing played a significant role in the adaptive strategies of early modern humans, but they differ in the functions assigned to it. I therefore ask the following question: What role did symbolic and functional applications of ochre play in the enhancement of prehistoric technology, and how may these have functioned to promote and maintain social relations within MSA Homo sapiens societies? With the aim of answering this question, I follow a chaîne opératoire approach to elucidate the exploitation of ochre during the MSA. First, I present the results of an experimental study devised to infer the methods employed to process ochre. It is demonstrated that functional data derived from actualistic experiments can enhance our understanding prehistoric behaviour. Second, I describe one of the oldest instances of a deliberate engraving on ochre at 100 ka to 85 ka. I consider the possibility that specific types of raw material were selected for engraving purposes and expand on whether all engraved depictions inevitably functioned in ‘symbolic’ contexts. The third objective entails the evaluation of an often cited functional hypothesis for ochre, namely the use of red ochre as a ‘hide-tanning’ ingredient. I also introduce and discuss three further functional hypotheses, namely those concerning the use of ochre as a form of mineral supplementation and detoxification agent, as a sunprotection element and as an insect repellent. Ethnoarchaeological research has proven to be informative in terms of revealing a range of functional uses for red ochre. I therefore consider how data derived from the Ovashimba of northern Namibia can enhance current understandings of ochre use in the MSA. I propose that in order to assess any hypothesis concerning the exploitation of ochre in the MSA methodically and in a scientific manner, it is necessary to engage with the theories and analytical methods of cognitive and technical sciences not normally viewed as applicable to archaeological enquiry

    NASA thesaurus. Volume 2: Access vocabulary

    Get PDF
    The access vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries and pseudo-multiword terms that are permutations of words that contain words within words. The access vocabulary contains almost 42,000 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing

    NASA thesaurus. Volume 1: Hierarchical Listing

    Get PDF
    There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions

    MtEFD, un facteur de transcription impliqué dans les interactions symbiotique et pathogène ainsi que dans le développement racinaire chez Medicago truncatula

    Get PDF
    La rhizosphère est peuplée de nombreux microorganismes pouvant être bénéfiques ou au contraire néfastes pour les plantes. La légumineuse modèle M. truncatula permet d'étudier les associations symbiotiques avec la bactérie fixatrice d'azote Sinorhizobium meliloti, mais aussi les interactions avec la bactérie pathogène racinaire Ralstonia solanacearum. Les interactions symbiotiques fixatrices d'azote nécessitent la formation d'un nouvel organe racinaire, appelé nodosité, au sein duquel les bactéries différenciées fixent l'azote atmosphérique au bénéfice de la plante hôte. L'organogenèse nodulaire s'accompagne d'une phase de différenciation des cellules végétales, dont le contrôle est mal connu, au cours de laquelle le facteur de transcription MtEFD (M. truncatula ethylene response factor required for nodule differentiation) joue un rôle important. Durant ma thèse, nous avons montré que MtEFD pourrait contrôler la différenciation nodulaire via la régulation de gènes hautement spécifiques des nodosités, et qu'une mutation dans MtEFD impacte sur un processus clé de la différenciation, l'endoréduplication, plus précisément le nombre d'endocycles (cycle cellulaire sans mitose) des cellules végétales et bactériennes. De plus, nous avons observé une similitude dans le profil d'expression de MtEFD au cours du développement nodulaire et racinaire et montré que MtEFD a un effet à la fois sur la formation des racines latérales et la synthèse d'ADN dans les extrémités racinaires. Enfin, nous avons démontré que MtEFD joue également un rôle positif dans le développement de la maladie causée par R. solanacearum. Dans la recherche de mécanismes communs à ces différents processus, nous avons porté une attention particulière aux cytokinines (CK), phytohormones dont MtEFD contrôle un régulateur négatif, le gène MtRR4 (M. truncatula response regulator 4).The rhizosphere is composed of microorganisms which are beneficial or pathogenic for the plants. The model legume M. truncatula is used to study the symbiotic interaction with the nitrogen-fixing bacteria Sinorhizobium meliloti, but also the pathogenic interaction with the telluric bacteria Ralstonia solanacearum. The nitrogen-fixing symbiotic associations involve the formation of a new root organ, called nodule, in which differentiated bacteria are able to fix atmospheric nitrogen to benefit the host plant. The nodule organogenesis is associated with a stage of plant cell differentiation, whose control is poorly understood, and during which the transcription factor MtEFD (M. truncatula ethylene response factor required for nodule differentiation) plays an important role. During my thesis, we showed that MtEFD could control the nodule differentiation via the regulation of highly nodule specific genes, and a mutation in MtEFD impacts a key process of the differentiation, the endoreduplication, more precisely the number of endocycles (cell cycle without mitosis) of plant cells and bacteria. Moreover, we observed a similarity in the MtEFD expression pattern during nodule and root development, and we showed that MtEFD has an impact in both the lateral root formation and the DNA synthesis in the root tips. Finally, we also proved that MtEFD was positively involved in the disease development induced by R. solanacearum. In the search of common mechanism in these different processes, we paid particular attention to cytokinins (CK), as MtEFD controls a CK negative regulator, the MtRR4 (M. truncatula response regulator 4) gene
    corecore