The launch of the Large Area Telescope (LAT), on board the Fermi spacecraft, has led to an astounding increase in the number of known y-ray pulsars. This wealth of new data has generated renewed interest in the field of pulsar astrophysics, with many of the established geometric models for y-ray emission coming under fresh scrutiny. In this work the outer gap (OG) and two-pole caustic (TPC) geometric -ray models are employed alongside a simple empirical radio model to obtain best-fit light curves by eye for six single-peak Fermi LAT pulsars first reported by Weltevrede et al. (2010). These best-fit solutions aim to reproduce both the shapes of the radio and y-ray light curves, and the radio-to- phase lag. A parameter study of the geometric models is also conducted, and the increased qualitative understanding of these models thus gained is then employed to obtain the best fits possible. The combination of radio and -ray models is found to be remarkably powerful in constraining the values of the geometric parameters of the individual pulsars: the inclination and observer angles. Generally the constraints implied by the radio model act perpendicularly to those implied by the y-ray models, thus yielding smaller solution contours. The constraints on the geometric parameters obtained for the six Fermi LAT pulsars in question agree quite well with those obtained by Weltevrede et al. (2010). This agreement is remarkable considering that the approach employed in this study is independent from the one employed by Weltevrede et al. (2010). The errors obtained in this study on the values of the inclination angle for each pulsar are generally smaller than those obtained by Weltevrede et al. (2010). As a secondary result, the value of the flux correction factor, which is a measure of how well the observed y-ray energy flux of the pulsar correlates with the overall y-ray energy flux, is constrained for each pulsar. / MSc (Space Physics), North-West University, Potchefstroom Campus, 2014

The launch of the Large Area Telescope (LAT), on board the Fermi spacecraft, has led to an astounding increase in the number of known y-ray pulsars. This wealth of new data has generated renewed interest in the field of pulsar astrophysics, with many of the established geometric models for y-ray emission coming under fresh scrutiny. In this work the outer gap (OG) and two-pole caustic (TPC) geometric -ray models are employed alongside a simple empirical radio model to obtain best-fit light curves by eye for six single-peak Fermi LAT pulsars first reported by Weltevrede et al. (2010). These best-fit solutions aim to reproduce both the shapes of the radio and y-ray light curves, and the radio-to- phase lag. A parameter study of the geometric models is also conducted, and the increased qualitative understanding of these models thus gained is then employed to obtain the best fits possible. The combination of radio and -ray models is found to be remarkably powerful in constraining the values of the geometric parameters of the individual pulsars: the inclination and observer angles. Generally the constraints implied by the radio model act perpendicularly to those implied by the y-ray models, thus yielding smaller solution contours. The constraints on the geometric parameters obtained for the six Fermi LAT pulsars in question agree quite well with those obtained by Weltevrede et al. (2010). This agreement is remarkable considering that the approach employed in this study is independent from the one employed by Weltevrede et al. (2010). The errors obtained in this study on the values of the inclination angle for each pulsar are generally smaller than those obtained by Weltevrede et al. (2010). As a secondary result, the value of the flux correction factor, which is a measure of how well the observed y-ray energy flux of the pulsar correlates with the overall y-ray energy flux, is constrained for each pulsar. / MSc (Space Physics), North-West University, Potchefstroom Campus, 2014

Phosphorus is an essential element for plant growth and development. Due to its low availability, solubility and mobility, phosphate is often the limiting macronutrient for crops and other plants. Plants have evolved several responses to phosphate deficiency. However, very little is known about the molecular basis of these responses. Here, I study the expression of PAP12, its role in the phosphate starvation response and the interaction of its promoter with nuclear factors. Analysis of a PAP12 T-DNA insertion line (pap12-1) revealed PAP12 is responsible for the majority of the acid phosphatase activity detected by the standard in-gel assay. RNA gel blots showed that PAP12 was induced only by Pi deficiency, and not by general nutrient stress. PAP12 expression, at the RNA and protein level, reflected endogenous phosphate levels in two mutants with altered phosphate accumulation. In the pho1 mutant, PAP12 expression and activity were up-regulated with respect to wild-type plants, and in the pho2 mutant, PAP12 expression and activity were reduced. Analysis of the PAP12 promoter using promoter-GUS fusions revealed expression in leaves, roots, flowers, hydathodes, root tips, and pollen grains. This broad pattern of expression suggests that PAP12 functions throughout the plant in response to low phosphate concentrations. The results showed PAP12 does not play a major role in phosphate remobilization, acquisition or in helping plants cope with low phosphate environments. Instead, the major phenotype associated with PAP12 deficiency was a significant delay in flowering in the low-phosphate pho1 background and a slight acceleration of flowering in the high-phosphate pho2 background over-expressing PAP12. These results suggest that PAP12 may have a role in linking phosphate status with the transition to flowering. Finally, I used promoter deletion and DNA-protein interaction assay to understand PAP12 expression upon phosphate starvation. A 35-bp region of the PAP12 promoter was identified as an important phosphate regulatory cis-element required for induction during phosphate starvation. We isolated a 23.5 kDa nuclear factor, which binds to this 35-bp region of the PAP12 promoter in a phosphate-dependent manner. The work presented here will add to our knowledge about the molecular processes that regulate phosphate nutrition.

Phosphorus is an essential element for plant growth and development. Due to its low availability, solubility and mobility, phosphate is often the limiting macronutrient for crops and other plants. Plants have evolved several responses to phosphate deficiency. However, very little is known about the molecular basis of these responses. Here, I study the expression of PAP12, its role in the phosphate starvation response and the interaction of its promoter with nuclear factors. Analysis of a PAP12 T-DNA insertion line (pap12-1) revealed PAP12 is responsible for the majority of the acid phosphatase activity detected by the standard in-gel assay. RNA gel blots showed that PAP12 was induced only by Pi deficiency, and not by general nutrient stress. PAP12 expression, at the RNA and protein level, reflected endogenous phosphate levels in two mutants with altered phosphate accumulation. In the pho1 mutant, PAP12 expression and activity were up-regulated with respect to wild-type plants, and in the pho2 mutant, PAP12 expression and activity were reduced. Analysis of the PAP12 promoter using promoter-GUS fusions revealed expression in leaves, roots, flowers, hydathodes, root tips, and pollen grains. This broad pattern of expression suggests that PAP12 functions throughout the plant in response to low phosphate concentrations. The results showed PAP12 does not play a major role in phosphate remobilization, acquisition or in helping plants cope with low phosphate environments. Instead, the major phenotype associated with PAP12 deficiency was a significant delay in flowering in the low-phosphate pho1 background and a slight acceleration of flowering in the high-phosphate pho2 background over-expressing PAP12. These results suggest that PAP12 may have a role in linking phosphate status with the transition to flowering. Finally, I used promoter deletion and DNA-protein interaction assay to understand PAP12 expression upon phosphate starvation. A 35-bp region of the PAP12 promoter was identified as an important phosphate regulatory cis-element required for induction during phosphate starvation. We isolated a 23.5 kDa nuclear factor, which binds to this 35-bp region of the PAP12 promoter in a phosphate-dependent manner. The work presented here will add to our knowledge about the molecular processes that regulate phosphate nutrition.

Low drop out (LDO) voltage regulators are widely used for post regulating the switching ripples generated by the switched mode power supplies (SMPS). Due to demand for portable applications, industry is pushing for complete system on chip power management solutions. Hence, the switching frequencies of the SMPS are increasing to allow higher level of integration. Therefore, the subsequent post-regulator LDO must have good power supply rejection (PSR) up to switching frequencies of SMPS. Unfortunately, the conventional LDOs have poor PSR at high frequencies. The objective of this research is to develop novel LDO regulators that can achieve good high frequency PSR performance. In this thesis, two PSR improvement methods are presented. The first method proposes a novel power supply noise-cancelling scheme to improve the PSR of an external-capacitor LDO. The proposed power supply noise-cancelling scheme is designed using adaptive power consumption, thereby not degrading the power efficiency of the LDO. The second method proposes a feed forward ripple cancellation technique to improve the PSR of capacitor-less LDO; also a dynamically powered transient improvement scheme has been proposed. The feed forward ripple cancellation is designed by reusing the load transient improvement block, thus achieving the improvement in PSR with no additional power consumption. Both the projects have been designed in TSMC 0.18 μm technology. The first method achieves a PSR of 66 dB up to 1 MHz where as the second method achieves a 55 dB PSR up to 1 MHz.

Genomes usually work together to promote the fitness of the organism, but sometimes parts of the genome cause intragenomic conflict, and act selfishly in order to promote their transmission. An example of this conflict is a selfish B chromosome known as paternal sex ratio (PSR) in the jewel wasp Nasonia vitripennis. Transmitted solely to new progeny with the sperms hereditary material, PSR completely destroys the paternal genome during the first mitotic division of the newly fertilized embryo. This effect enhances transmission of the PSR chromosome because of the unique haplodiploid reproductive mode of Nasonia and other members of the hymenopteran insect group. Through transcriptomic analyses, our group recently discovered that the PSR chromosome expresses eleven transcripts in the wasp testis. A plausible hypothesis is that one or more of these transcripts play some role in paternal genome elimination. In this study I have begun to test this hypothesis by screening through a set of previously produced truncated versions of the PSR chromosome. Specifically, I used PCR in order to screen these truncated chromosomes for the presence of each of these PSR-specific transcripts. I could then correlate the level of genome elimination induced by each truncated PSR chromosome with the presence or absence of the expressed transcripts. My work has established that (i) three of the eleven transcripts are likely not involved in genome elimination; (ii) no single transcript alone causes genome elimination; (iii) the remaining eight of eleven transcripts are viable candidates for causing genome elimination; and (iv) it is likely that a sub-group of these transcripts may operate together to induce this effect. I discuss several models in which PSR-expressed RNA molecules could operate to cause genome elimination.

Social media enable celebrity to interact with their followers and enable followers to build the relationship through the interaction. Former research has found that openness and perceived interactivity are antecedents for parasocial interaction. In order to investigate the way to increase user’s engagement in celebrity’s social media page, this research examines the relationship between celebrity’s posts employ openness and perceived interactivity, other user’s posts employ openness and perceived interactivity, parasocial interaction, parasocial relationship, and social media engagement. Survey data were collected from 595 followers of one Chinese celebrity through an online survey. The results indicate that neither celebrity’s nor other user’s posts employ openness and perceived interactivity direct lead to user’s social media engagement. However, PSI and PSR, which increased by celebrity’s and other user’s posts employ openness and perceived interactivity, have a positive relationship with user’s social media engagement. It provides support for the mediating role of PSI and PSR to social media engagement.

Diese Arbeit berichtet über die Suche nach gepulster und ungepulster hochenergetischer (VHE) Gammastrahlung mit dem High Energy Stereoscopic System (H.E.S.S.) im Energiebereich von 100 GeV bis 100 TeV von drei Pulsaren. Gepulste VHE Gammastrahlung wurde bisher nur fuer den jungen Krebspulsar gefunden. Eine besondere Gruppe von Pulsarwindnebeln (PWN) sind die zusammengesetzten Supernovaüberreste (SNR), bei denen sich ein PWN im Zentrum einer expandierenden SNR Schale befindet. Die Resultate der Suche nach gepulster und ungepulster VHE Gammastrahlung von zwei Millisekundenpulsaren, PSR J0437-4715 und PSR J1824-2452, werden im ersten Teil dieser Arbeit vorgestellt. Teile der Beobachtungen wurden in einer speziellen Triggerkonfiguration (dem Topologischen Trigger mit konvergenter Ausrichtung) durchgeführt, um die Energieschwelle des Instruments zu senken. Kein Hinweis auf gepulste oder ungepulste Emission wurde gefunden und obere Grenzen auf den gepulsten und ungepulsten Fluss wurden bestimmt. Die oberen Grenzen auf den gepulsten Fluss werden mit bestehenden Modellvorhersagen verglichen und erlauben für PSR J1824-2452 den Bereich möglicher Geometrien in einigen Modellen einzuschränken. Die Resultate der Suche nach gepulster und ungepulster VHE Gammastrahlung aus der Richtung des zusammengesetzten SNR Kes 75 werden im zweiten Teil dieser Arbeit präsentiert. Der PWN im Zentrum von Kes 75 wird von einem sehr jungen und energiereichen Pulsar, PSR J1846-0258, angetrieben, der ein aussergewöhnlich starkes Magnetfeld besitzt. Während kein Hinweis auf gepulste Strahlung gefunden wurde, konnte ungepulste Emission von VHE Gammastrahlung von einer Punktquelle mit einer statistischen Signifikanz von 10 sigma nachgewiesen werden. Die VHE Gammastrahlung ist räumlich koinzident mit dem PWN und mit der SNR Schale. Beide werden als mögliche Quelle für die beobachtete Emission diskutiert. Der Pulsar von Kes 75 wäre der jüngste bisher bekannte Pulsar, der einen Pulsarwindnebel antreibt. / This work reports on the search for pulsed and steady very-high energy (VHE) gamma-ray emission in the energy range extending from 100 GeV up to 100 TeV from the direction of three pulsars with the High Energy Stereoscopic System (H.E.S.S.). Pulsed gamma-ray radiation from pulsars with energies beyond 100 GeV was found thus far only for the young and energetic Crab pulsar. A special class of pulsar wind nebulae (PWNe) is associated with composite supernova remnants (SNRs) where the PWN is centered in an expanding SNR shell. In the first part of this thesis, the results on the search for pulsed and steady VHE gamma-ray emission from the two millisecond pulsars, PSR J0437-4715 and PSR J1824-2452, are presented. Parts of the observations were conducted in a special trigger setup (the topological trigger with convergent pointing) to reduce the energy threshold of the instrument. No signal of pulsed or steady emission is found and upper limits on the pulsed and steady gamma-ray flux are derived. The upper limits on the pulsed gamma-ray flux are compared to existing model predictions and, in the case of PSR J1824-2452, allow the range of possible viewing geometries in some models to be constrained. In the second part of this work, results on the search for pulsed and steady VHE gamma-ray emission from the direction of the composite SNR Kes 75 are presented. The PWN in the center of Kes 75 is powered by a very young and powerful pulsar, PSR J1846-0258, that has an exceptionally high magnetic field. While no hint for pulsed emission is found, steady VHE gamma-ray emission is detected with a statistical significance of 10 sigma from a point-like source. The VHE gamma-ray emission is spatially coincident with the PWN and the SNR shell. Both are discussed as a possible origin for the observed emission. The pulsar of Kes 75 would be the youngest pulsar known to date to power a VHE PWN.

Made available in DSpace on 2016-06-02T18:57:49Z (GMT). No. of bitstreams: 1 5771.pdf: 1594808 bytes, checksum: 1c1dd50839606ad9f36aa7a82494e49f (MD5) Previous issue date: 2013-10-25 / Financiadora de Estudos e Projetos / Contemporary society faces problems arising from impacts to the environment, causing damage to the countryside, agricultural production and family farming. This study aimed to know the relationship of man field with his work environment, evaluating management practices used by him to guarantee a living for his family and their financial stability. It were interviewed school-age young adults and milk producers of thirteen family farms located around the Mantiqueira Ecological Corridor under influence of Ibitipoca State Park. . The physical and socioeconomic characteristics of the study area was based on relief, vegetation, climate, use and land cover, the local economy, the relationship between the community and the Ibitipoca State Park, and communities profile. It was used a qualitative-quantitative methodology named Discourse of Collective Subject (DCS),, with tabulation and organization of interviews by means of the Qualiquantisoft® Software. Based on the PSR (Pressure-State- Response) model, indicators were proposed that generated pressure indexes on the producer s decision making (IP), for the application state of management practices (IE) and for the response of the environment to the producer s management (IR). The property sustainability index (ISP) was calculated from the arithmetic mean between IP, IE and IR, and indicated the evolutionary trend for these properties.The results indicate that the study area has a history of environmental, social and economic pressure. Despite the intense scrutiny and understanding of the need environmental conservation, a variety of environmentally inadequate management practices are used in order to supply family demands and maintainining the family income. Farmers and school-age young adults consider the environment an obstacle to production and stay in the field. We conclude that, despite the historical tradition of agriculture in the studied area, the way in which dairy cattle activity has been developed can compromise environmental integrity and therefore the life quality and the local population income. / A sociedade atual enfrenta problemas decorrentes de impactos ao ambiente, que causam prejuízos ao espaço rural, à produção agrícola e à agricultura familiar. Este trabalho teve por objetivo conhecer a relação do homem do campo com seu ambiente de trabalho, avaliando as práticas de manejo utilizadas por ele para garantir o sustento de sua família e a sua estabilidade financeira. Foram entrevistados jovens em idade escolar e produtores de leite de treze propriedades rurais familiares localizadas no entorno do Corredor Ecológico da Mantiqueira, sob influência do Parque Estadual de Ibitipoca. A caracterização física e socioeconômica da área de estudo foi feita com base no relevo, na vegetação, no clima, no uso e cobertura do solo, na economia local, na relação da comunidade com o Parque Estadual de Ibitipoca e no perfil das comunidades. Foi utilizada a metodologia quali-quantitativa do Discurso do Sujeito Coletivo (DSC), com tabulação e organização dos depoimentos por meio do software Qualiquantisoft®. Com base no modelo PSR (Pressão-Estado-Resposta), foram propostos indicadores que geraram índices de pressão sobre a tomada de decisão do produtor (IP), para o estado da aplicação das práticas de manejo (IE) e para a resposta do ambiente ao manejo do produtor (IR). O índice de sustentabilidade da propriedade (ISP) foi calculado a partir da média aritmética entre IP, IE e IR e apontou a tendência evolutiva das propriedades avaliadas. Os resultados mostraram que a área estudada possui um histórico de pressão ambiental, social e econômica. Apesar da fiscalização intensa e do entendimento da necessidade de conservação do ambiente, uma diversidade de práticas de manejo ambientalmente inadequadas são utilizadas a fim de suprir as demandas familiares e manter a renda da família. Os produtores rurais e os jovens em idade escolar consideram o ambiente um entrave à produção e à permanência no campo. Conclui-se que, apesar da tradição histórica da agropecuária na área estudada, o modo como a atividade bovino leiteira vem sendo desenvolvida pode vir a comprometer a integridade do ambiente e consequentemente a qualidade de vida e a renda da população local.

This thesis reports on the recent results of a continuing, high-precision pulsar timing project, currently focused on the nearby, binary millisecond pulsar, PSR J0437_4715. Pulse arrival time analysis has yielded a remarkable series of constraints on the physical parameters of this system and evidence for the distortion of space-time as predicted by the General Theory of Relativity. Owing to the proximity of the PSR J0437_4715 system, relative changes in the positions of the Earth and pulsar result in both annual and secular evolution of the line of sight to the pulsar. Although the changes are miniscule, the effects on the projected orbital parameters are detectable in our data at a high level of significance, necessitating the implementation of an improved timing model. In addition to producing estimates of astrometric parameters with unparalleled precision, the study has also yielded the first three-dimensional orbital geometry of a binary pulsar. This achievement includes the first classical determination of the orbital inclination, thereby providing the unique opportunity to verify the shape of the Shapiro delay and independently confirm a general relativistic prediction. With a current post-fit arrival time residual RMS of 130 ns over four years, the unrivaled quality of the timing data presented herein may eventually contribute to the most stringent limit on the energy density of the proposed stochastic gravitational wave background. Continuing the quest for even greater timing precision, a detailed study of the polarimetry of PSR J0437_4715 was undertaken. This effort culminated in the development of a new, phase-coherent technique for calibrating the instrumental response of the observing system. Observations were conducted at the Parkes 64-m radio telescope in New South Wales, Australia, using baseband recorder technologies developed at York University, Toronto, and at the California Institute of Technology. Data were processed off-line at Swinburne University using a beowulf-style cluster of high-performance workstations and custom software developed by the candidate as part of this thesis.