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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.
1

Nutrient cycling and oxygen availability in ancient oceans : extinction events and evolutionary opportunities

Mettam, Colin January 2018 (has links)
No description available.
2

A study of early and intermediate type stars at the Galactic Poles

McFadzean, A. D. January 1985 (has links)
A catalogue of faint blue stars at the North Galactic Pole, compiled from the literature, is presented. Spectral classifications for catalogue stars within 3° of the pole have been obtained from U.K.S.T. objective prism and St. Andrews grism plates. Photometric data on the uvbyβ system is presented for 572 U-F8 stars at the South Galactic Pole, with radial velocities being given for 161 of these stars. From this South Galactic Pole data the interstellar reddening towards the Pole is shown to be negligible, in agreement with the findings of other authors. A number of photometrically odd stars are isolated, including several intermediate Population II, Population II and Am stars. From available data at both Poles the relative proportions of various population groups as a function of height are discussed. There is an apparent excess of PI A over iPII stars out to Ikpc., relative to the numbers expected on the basis of the 'thick disk' of iPII stars reported by Gilmore and Reid (1983). The w-velocity distributions of Pop.I A and F stars within 200pc. of both Poles are shown to be well fitted by gaussians and these gaussians are shown to be the same for both Poles. The Pop.I A stars are shown to have a mean w-velocity of 0,6 kms⁻¹ (rms 11.1 kms.⁻¹) and the corresponding F stars to have a mean w-velocity of -2.9 kms⁻¹ (rms 10.9 kms⁻¹), implying negligible net streaming through the galactic plane.
3

The first and second neural projections of the insect eye

Meinertzhagen, Ian A. January 1971 (has links)
1. The patterns of projection of some of the perpendicular neurones between the retina and medulla of the optic lobes of various insects have been studied. Axon paths have been studied from consecutive semi-thin plastic sections cut transversely and stained with toluidine blue. The termination positions and the paths of axons are both highly ordered and predictable. 2. In all insects with fused-rhabdomere eyes the axons of one ommatidium project to one cartridge of the lamina and the array of cartridges duplicates the array of ommatidia. In insects with open-rhabdomere eyes visual information is distributed amongst a number of lamina cartridges so that each cartridge receives information originating from one visual axis. 3. In both open- and fused-rhabdomere types the cartridge, array of the lamina is exactly duplicated in the medulla but by the intervention of the chiasma is reversed about a dorso-ventral plane. The axons of one lamina cartridge contribute to one medulla cartridge. Thus, in all insects studied, the visual field is projected exactly from retina to medulla. 4. Most of the retinula axons from one ommatidium terminate in the lamina but usually one pair passes directly to the medulla. These are from the central retinula cells (open-rhabdomere eyes) or from the small retinula cells (apposition type fused-rhabdomere eyes). Retinal responses are known mainly only for the short retinula axons so that visual information delivered to the medulla cartridge is still largely unresolved. 5. The lamina neuropile probably contains the elements responsible for the lateral correlation between parallel receptor inputs which is necessary for movement perception, but units with long lasting responses which could act as the delay circuit of movement perception are unknown. 6. The occurrence of errors in termination of the first projection of the optic lobe of the fly, which are reported for the first time in this work, provide no direct clues to the developmental processes by which such a morphologically complex system arises. Nevertheless errors may arise within a sequence of growth processes which are fundamentally quite simple and not obvious from knowledge of the generalized perfect pattern of connections.
4

Factors influencing the white-tailed deer harvest in Virginia, 1947-1967 \

Mechler, John Louis January 1970 (has links)
Virginia's deer kill data, 1947 to 1967, were analyzed. Multiple linear regression analysis was used as the deer kill, in general, is still increasing in the counties of Virginia. The data concerning proximity, access, human population, farm size, farmland uses, and the types and acreages of forest stands were studied in 10 western Virginia counties. Correlation analysis was used for this data. The significant variables were identified but were not included in the multiple linear regression analysis because yearly estimates were not available. Estimates of deer density made by personnel of the Virginia Commission of Game and Inland Fisheries are very reliable and are significantly correlated with deer kill. Variables concerning weather during the hunting season, hunting season regulations and characteristic components of the deer kill in previous hunting seasons were utilized in multiple linear regression analyses of the data from the counties of Virginia. Predictions of deer kill for groups of counties (i.e. management units) are more reliable than predictions for individual counties. It was found that predictions of hunting pressure are not as reliable as predictions of deer kill. Tile shifting of hunters in response to reports of favorable hunting is likely responsible. Analysis of the indices of hunting pressure also revealed that hunting pressure changes with different season types in western Virginia. / Master of Science
5

Perturbation of cell renewal in the haemopoetic tissues of drug-treated and leukaemic mice

Meldrum, Rosalind A. January 1983 (has links)
The murine lympho-myeloid complex is depleted by a large dose of nitrogen mustard and the pattern of recovery of the haemopoietic tissues and cells followed to establish the relationships ox the precursor and mature cells. Culture of bone marrow in agar and stathmokinetic techniques are used to examine the controlled proliferation for the granulocyte elements in the bone marrow recovering from nitrogen mustard and the influence of the spleen is also considered. The control of the proliferation of the granulocyte cells is lost in myeloid leukaemia. Stathmokinetic methods and spleen colon assays are used to asses cell proliferation in irradiation-induced myeloid leukaemias in mice and the relevance of these parameters so measured to those demonstrated by normal bone marrow is discussed.
6

Systém pro monitorování a nastavení signálového procesoru v digitálním reproduktorovém systému / System for monitoring and setup of signal processor in digital loudspeaker system

Laník, Jakub January 2013 (has links)
This project solves teoretical design of digital reproductor system and controlling GUI software. This digital system is composed of one master unit, which digitalize different audio sources and stream them by ethernet to slave units. The controlling software is be able to set and monitor the audio system.
7

Function of M4 protein in vitro and in vivo

Wang, Xuan January 2013 (has links)
Herpesviruses are ubiquitous in both humans and animals and can cause life-threatening disease. The discovery of murine gammaherpesvirus 68 (MHV-68), which has many similarities in genome and pathogenesis as the human pathogens Epstein-Barr virus and Kaposi’s sarcoma-associated herpesvirus, provides a model for further investigation of the pathogenesis of gammaherpesviruses. The M4 gene was found to be at the left end region of MHV-68 genome. The presence of the M4 protein is required during the early establishment of MHV-68 latency. However, the function of M4 protein remains unclear. The aim of this project was to investigate the function of the M4 protein in vitro and during infection. By using an ELISA, the recombinant M4 protein was shown to bind several Cxc-chemokines and stop the interaction between Cxcl4 and GAGs. The role of M4 protein during MHV-68 lytic infection and in the early establishment of latency was studied by comparing the pathogenesis of virus which does not express M4 (M4stop) and wild type virus (WT). Compared to WT infection, this study found that M4stop was decreased in the lungs at day 8 post infection (p.i.). At the same time point, the viral loads were higher in M4stop infected spleens, which was accompanied by increased expression of the CD4+ T cell activation marker PD-1 and the macrophage activation marker CD69. However, at day 14 p.i., the M4stop infected spleens had lower viral loads, and the expression of CD69 was decreased on CD4+, CD8+ T cells, B cells and macrophages. Furthermore, gene expression PCR arrays were used to investigate how cellular activation and inflammation were transcriptionally regulated. It has been found that the transcription of several genes, which are involved in germinal centre development, was lower in the spleens of WT infected mice at day 12 and 14 p.i. compared to day 10 p.i. of WT infection, as well as day 12 and 14 p.i. of M4stop infection. In addition, the percentage of germinal centre B cells was found to be higher in spleens infected with M4stop at day 10 p.i.. However, there was no difference in percentages of TFH and plasma cells in the spleens. Finally, in order to understand the role of IFN-γ in control of infection in M4stop infected mice, IFN-γR-/- mice were infected with M4stop and WT. Although there were differences in pathogenesis between WT and M4Stop virus infected IFN-γR-/- mice, there was no clear evidence that M4 function is involved in inhibiting IFN-γ pathways. In this study, we found M4 can disturb the interaction of chemokine and GAGs and might delay virus trafficking to the spleen, which could lead to a reduction of cellular activation. M4 may also impair the development of germinal centres at the beginning of latent infection in the spleens.
8

A philosophy of home : a study on an alternative experience of domesticity

Noutsou, Styliani January 2018 (has links)
The major objective of this thesis is to provide an alternative to the predominant model of the Western urban home, arguing that it is more detrimental than beneficial to its inhabitants. In order to achieve this, it first explores the development of home through a genealogical analysis. It then considers the concepts with which it is traditionally connected, such as those of identity, safety, privacy and satisfaction, supporting that the idealised home hides numerous issues of concern (e.g. class and sex inequalities, physical and psychological violence). In order to form a more comprehensive picture, the thesis draws on different philosophical approaches discussing the idea of home, while it explores a variety of contemporary habitation and home-making practices (e.g. smart and second homes, new technologies inside the house, home and consumerism). The normative and overly-idealised domestic model, promoted in Western urban societies, is presented as detrimental both on a personal and on a social level. Therefore, alternatives are explored in Adorno's 'Hotel Room', Jameson's 'Dirty Realism' and Deleuze and Guattari's 'Nomadology'. The lack of viability characterising the abovementioned proposals leads to the examination of the Deleuzoguattarian concept of the Body without Organs; the home as a BwO provides the contemporary agents with the tools to reconstruct an autonomous space where they can recreate their personal discourse and influence the social ground accordingly. Through the analysis of home this thesis explores how and why it has been appropriated by systemic forces and highlights a very serious issue: the fact that our personal space is no longer personal. Simultaneously, a common concern of feminist and post-structuralist background is addressed regarding the process of selfredefinition and the ways to approach it. The response entails a reconstructed autonomous home with a respective influence on the public sphere.
9

The transmission and evolution of human culture

Mesoudi, Alex January 2005 (has links)
'Culture' is defined as information, such as knowledge, beliefs, skills, attitudes or values, that is passed from individual to individual via social (or cultural) transmission and expressed in behaviour or artifacts. 'Cultural evolution' holds that this cultural inheritance system is governed by the same Darwinian processes as gene-based biological evolution. In Part A of this thesis it is argued that as compelling a case can now be made for a Darwinian theory of cultural evolution as Darwin himself presented in The Origin Of Species for biological evolution, If culture does indeed evolve, then it follows that the structure of a science of cultural evolution should broadly resemble that of the science of biological evolution. Hence Part A concludes by outlining a unified science of cultural evolution based on the sub-disciplines of evolutionary biology. Parts B and C comprise original empirical and theoretical work constituting two branches of this science of cultural evolution. Part B describes a series of experiments testing for a number of hypothesised biases in cultural transmission. Evidence was found for a 'social bias' that acts to promote information concerning third-party social relationships over equivalent non-social information, and a 'hierarchical bias' that acts to transform knowledge of everyday events from low-level actions into higher-level goals. Three other hypothesised biases concerning status, anthropomorphism and neoteny were not supported, although each gave rise to potential, future work using this methodology. Part C presents a theoretical investigation into the coevolution of the genetic bases of human mating behaviour and culturally inherited folk beliefs regarding paternity. Gene-culture coevolution and agent-based models suggested that beliefs in 'partible paternity' (that more than one man can father a child) create a new more polygamous form of society compared with beliefs in singular paternity (that only one man can father a child).
10

Plasticidade de receptores colinérgicos muscarínicos M4 hipocampais decorrentes de uma consolidação da memória como possível marcador sináptico do engrama : ensaios farmacológico-comportamentais

Diehl, Felipe January 2010 (has links)
O sistema colinérgico muscarínico desempenha uma função central na memória, mas o papel de cada subtipo de receptor é pouco compreendido separadamente. As toxinas muscarínica (MTs) extraídas da peçonha das serpentes Dendroaspis sp são ferramentas farmacológicas seletivas aos diferentes subtipos de receptores muscarínicos. O subsistema M4 muscarínico modula os processos de consolidação e evocação. Recentemente, tem se dado atenção aos processos subseqüentes à evocação e vários trabalhos demonstraram que a reconsolidação e a extinção da memória compreendem etapas importantes na formação do processo. O objetivo desse trabalho é investigar o envolvimento do subsistema M4 colinérgico muscarínico hipocampal na consolidação, evocação, reconsolidação e extinção da memória, além de investigar os receptores M4 da amígdala basolateral na consolidação e reconsolidação. Em trabalhos anteriores, foi demonstrado que os receptores M4 mudavam seu papel modulatório entre a consolidação e evocação, portanto, neste trabalho investigamos, também, em que momento do processo de consolidação ocorre essa mudança e se essa alteração é dependente de transcrição gênica. A toxina MT3, antagonista seletiva ao receptor M4, e a escopolamina, antagonista inespecífico, foram as ferramentas farmacológicas utilizadas e seus efeitos foram estudados na tarefa de condicionamento aversivo contextual (CAC) e esquiva inibitória (EI). Quando infundidos no hipocampo antes do treino CAC, ambos os fármacos foram amnésicos sobre a consolidação, entretanto, somente MT3 foi efetiva quando infundida antes do teste, sendo o efeito oposto, facilitatório. Além disso, somente a MT3 intra-hipocampal foi facilitatória sobre a reconsolidação e bloqueou a extinção da tarefa de CAC. Infundidas na amígdala basolateral os antagonistas foram amnésicos sobre a consolidação e a reconsolidação de CAC. Os experimentos com a esquiva inibitória demonstraram que a MT3 intra-hipocampal é amnésica somente quando infundida imediatamente após o treino. Porém, modifica seu efeito quando administrada 90 e 180 minutos após o treino, passando a ser facilitatória. A administração de um inibidor de transcrição gênica (DRB) imediatamente após o treino de EI reverte o efeito facilitatório da MT3 pré-teste. Os resultados sugerem uma modulação positiva do sistema colinérgico muscarínico hipocampal durante a consolidação e a extinção da memória de CAC, porém, uma ação contrária é observada durante a evocação e reconsolidação. Os resultados em conjunto sugerem que os receptores M4 hipocampais sofram alterações plásticas durante o processo de consolidação passando a controlar negativamente a atividade excitatória dos neurônios glutamatérgicos, fenômeno que parece não ocorrer na amígdala basolateral. / The cholinergic muscarinic system plays a central role in learning and memory, yet little is known about the specific roles of each receptor subtype. Muscarinic toxins (MTs) from Dendroaspis snakes venom are selective for muscarinic receptor subtypes. The hippocampus M4 subsystem, for instance, was shown to take part in the modulation of memory consolidation and retrieval. The memory phenomenon, by its turn, is being recently unveiled as a much more complex set of processes than previously thought, encompassing post-retrieval situations such as reconsolidation and extinction, each with its particular mechanisms. The scope of this study is to explore the involvement of the hippocampal cholinergic M4 muscarinic subsystem on the consolidation, retrieval, reconsolidation and extinction of memories, moreover to investigate the role of M4 subsystem of basoalteral amygdala on the consolidation and reconsolidation. Last works shown a different modulatory role of hippocampal M4 receptors about consolidation and retrieval processes, therefore This work aims to investigate the muscarinic cholinergic modulation at hippocampal circuits by M4 receptors, along different periods of memory consolidation for an inhibitory avoidance task, and verify if the change effect of pre-test MT3 are dependent of mRNA synthesis. MT3, a very selective M4 antagonist, and the less selective antagonist scopolamine were infused bilaterally into the rat CA1 area, and their effects studied in a contextual fear conditioning task (CFC) and inhibitory avoidance task (IA). When infused immediately after training, both treatments caused disruption of the memory consolidation, however, only MT3 was effective when infused before the test session, and the effect, was the opposite, i.e., memory facilitation. Moreover, only MT3 enhanced the reconsolidation of CFC following its infusion into the hippocampus or blocked its extinction. Infused into the basolateral amygdala, muscarínic antagonists shown an amnestic effect about the consolidation and reconsolidation of CFC memory. In the IA experiments, MT3 infused immediately after training was amnestic upon the consolidation process, while an “opposite effect” –memory facilitation– was observed in the 90-180min time window. The DRB was amnestic too upon the consolidation, showing that the transcriptional process is essential to the memory. Moreover, the DRB reverted the facilitatory effect of pre-test MT3. These results suggest an endogenous positive modulation of the cholinergic muscarinic system present during the consolidation or the extinction of an aversive memory, but an opposite action during memory retrieval or memory reconsolidation. Moreover, these results suggest that M4 receptors are likely expressed at different hippocampal localizations where they underlie different processes and plasticity events, may be over expressed upon glutamatergic excitatory cells.

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