Millisecond pulsars (MSP) are old neutron stars that have been spun up to high spin frequencies(as fast as 716 Hz) through the accretion of matter from a companion star. The extreme stellar densities in the core of globular clusters creates numerous accreting neutron star systems through exchange interactions; this leads to the formation of MSPs in larger numbers than in the galactic disk. Over the course of this project, we have collected over 17 TB of data on the 3 globular clusters M28, NGC6440 and NGC6441 plus 2 observations on NGC6522 and NGC6624 as part of the recently begun S-band survey using the Green Bank telescope. I have analyzed and conducted acceleration searches on 70% of the data and discovered 7 of the 23 new millisecond pulsars reported in this work. One year of timing observations of the pulsars in M28 and NGC6440 has led to the phase connected solution for 12 of the 15 new pulsars in those two clusters, 7 of which are in binaries. We have measured the rate of advance of periastron for two highly eccentric binaries and assuming this is purely due to general relativity, this leads to total system masses of (1.616 - 0.014)M and (2.2 - 0.8)M for M28C and NGC6440B respectively. The small mass function combined with this information imply that the most likely neutron star mass of NGC6440B is either very large or else there could be significant contribution to the advance of periastron from a nonzero quadrupole moment due to tidal interaction with the companion. Measurements of the period derivatives for many of the pulsars show that they are dominated by the dynamical effect of the gravitational field of the clusters. Finally, we have discovered the potential presence of a Mars-mass planet orbiting the pulsar NGC6440C with a period of 21 days. A dedicated timing campaign will be necessary to confirm the presence of such an object.

A thorough understanding of nucleosynthesis and element formation in stars of all evolutionary phases is of vital importance in stellar astrophysics. It provides information about internal structure, conditions and nuclear processes occurring in the stellar interior. The heavy elements formed in a star throughout its life are returned to the interstellar medium through mass loss processes. New populations of stars are then formed from this previously enriched material. This continues the cycle of element recycling in the Universe and has great consequence for galactic chemical evolution. As both modelling and observing techniques advance, more surveys are required to ensure there is agreement between the two. It is hoped that when a thorough understanding of the internal processes in giant stars is reached, the evolutionary models will reproduce the observed elemental yields. This work provides an internally self-consistent analysis of the element abundances produced via nucleosynthesis and s-process element formation occurring in giant stars in different stellar environments. High resolution spectroscopic observations have been taken of Asymptotic Giant Branch (AGB) and Red Giant Branch (RGB) stars in three different stellar environments. Spectrum synthesis has been used to determine s-process element abundances for RGB stars in the Hyades open cluster, RGB and AGB stars in the globular cluster, 47 Tucanae, and AGB stars in the galactic field. It was found that the two Hyades giant studied showed solar, or near-solar, abundances of s-process elements. Enhancements in the light s-process elements, Y and Zr, of +0.02 to +0.11 were observed, while enhancements in the heavy s-process elements, La, Pr and Nd, ranged from +0.06 to +0.16. These results are consistent with previous findings of enhancements in Y of ~+0.12, and of ~+0.15 for the heavy s-process elements. The results from 47 Tucanae suggest a genuine star-to-star scatter in the s-process element abundances in the giant stars of this globular cluster. This is unexpected due to the fact that stars in a globular cluster are thought to have the same formation and chemical history. However, spreads in s-process element abundances of as much as +-0.7 dex are observed between this study and three other studies of similar stars in the same cluster. A range of field stars along the AGB phase, ranging from M to MS to S to SC, have been analysed for s-process enrichment. The observed element abundances are compared with those predicted by recent modelling of the AGB phase of evolution. Enhancements in s-process element abundances range from [s/Fe]~0.00 for M stars, to ~+0.50 for MS stars, through to ~+0.95 for S stars. The comparison of these enhancements with those predicted by modelling provides an indication of the success of these models and will enable theoreticians to further refine their understanding of the internal nucleosynthetic processes present in giant stars.

Thesis (Ph.D.). / Written for the Dept. of Food Science and Agricultural Chemistry. Title from title page of PDF (viewed 2009/06/05). Includes bibliographical references.

This dissertation presents a detailed study of many aspects of the Horizontal Branch (HB) phase of stellar evolution. A classical technique of stellar structure analysis is summarized, and applied to Zero-Age Horizontal Branch (ZAHB) models. The chief conclusions from this work are firstly, that the total mass of the envelope sensitively affects the luminosity of the hydrogen-burning shell and the equilibrium of the helium-rich core. Secondly, the rapid progression of models across the Hertzsprung-Russell diagram with decreasing mass is the result of important changes in the hydrostatic structure of the stars. Thirdly, the luminosity-metallicity relationship of the Zero Age models results from the change in the core equilibrium luminosity with the CNO abundance of the shell region, together with the decrease in stellar mass at fixed effective temperature. The change in the mass-temperature relation with CNO is found to be the most important determining factor in the Horizontal Branch stellar distribution, and therefore is the most appropriate ‘first parameter’ for HB morphology. The evolution of the stars is then considered, and the analysis of the interior structures provides a reclassification of HB track morphology into three categories, depending on whether the model contains an outer convection zone or a radiative outer envelope, and on the luminosity of the hydrogen-burning shell. Lastly, the question of the formation of red-giant stars is considered; the general conclusions of this part of the study support the arguments presented by Yahil and van den Horn (1985). Next, the evolution of the convective core of HB stars is reviewed, together with a detailed account of the numerical techniques developed for modelling semi-convection. The problems associated with the late phase of HB evolution are also discussed. A brief review of the physical inputs and numerical methods used in the interior is presented, focussing on the calculation and implementation of the Equation of State. The calculations performed for this study are then presented in detail. The effects of oxygen enhancement on zero-age sequences are illustrated for a range in metallicity, and theoretical relations between luminosity and metallicity for the ZAHBs are demonstrated. The evolutionary tracks computed are illustrated and summarized in extensive tabulations in the Appendices. The final chapter reproduces previously published studies of globular clusters. The first of these investigates the globular cluster NGC104 (47 Tucanae). By fitting the theoretical models to recent CCD photometry of the cluster, it was found that its initial helium content must have been close to 24% by mass. In addition, the best fits show that models for [Fe/H] = -0.65 provide an excellent match to the horizontal branch, if (m - M )v ≈ 13.44, and thereby yield consistency over the entire color-magnitude diagram of the cluster. The second study presents an investigation of the horizontal branch of M15. Detailed matches of our theoretical sequences to the cluster observations indicate that high envelope helium abundances are incompatible with the observed morphology. It is found that there is a clear preference for values of 0.21 ≾ Y ≾ 0.25, independent of the value of [O/Fe]. The precision of the method is reduced by uncertainties in the observations and in the available synthetic temperature-bolometric-correction relations. The oxygen enhanced zero-age HB models are found to have a period-colour relationship which is almost identical to that of their scaled-solar counterparts, but they reduce significantly the predicted double-mode variable masses. Importantly, it is found that, for reasonable assumptions about the reddening to M15, there is no discrepancy between the predicted and observed periods for the RR Lyrae variables. However, the period shift between M3 and M15 can be explained by canonical models only if the helium abundance in both clusters is low (Yhb ~ 0.21), and the bulk of the RR Lyrae star population in M15 is at late stages of evolution. These conclusions are reconsidered in the light of the new calculations presented here. / Graduate

Submitted by Emanoel Martins Filho (emanoelfilho@ufba.br) on 2016-07-11T12:56:30Z No. of bitstreams: 1 Alfeu Dissertacao.pdf: 478381 bytes, checksum: 83c0e1548ee1f84af5bfb31a0849646a (MD5) / Approved for entry into archive by Patricia Barroso (pbarroso@ufba.br) on 2016-07-13T01:16:39Z (GMT) No. of bitstreams: 1 Alfeu Dissertacao.pdf: 478381 bytes, checksum: 83c0e1548ee1f84af5bfb31a0849646a (MD5) / Made available in DSpace on 2016-07-13T01:16:39Z (GMT). No. of bitstreams: 1 Alfeu Dissertacao.pdf: 478381 bytes, checksum: 83c0e1548ee1f84af5bfb31a0849646a (MD5) / Programa de Demanda Social (CAPES) / Foram realizados dois estudos: No primeiro foi avaliado o método FAMACHA© em caprinos e ovinos, mantidos nas mesmas condições, no sertão do Estado da Bahia, Brasil. Foram selecionados 60 caprinos mestiços Anglo Nubiano e 60 ovinos mestiços (Santa Inês x Dorper), entre quatro e oito meses de idade, criados em sistema extensivo e mantidos nas mesmas pastagens. A cada semana durante três meses, Julho a Outubro, foi determinado o grau FAMACHA© e o escore corporal (EEC) e coletadas amostras de fezes e de sangue. A comparação de médias da contagem de ovos nas fezes (OPG) foi de 1991(116,3) nos caprinos e 596,2(104,4) em ovinos; do volume globular (VG) foi de 25,4% (0,38) nos caprinos e 31,5%(0,37) em ovinos; grau FAMACHA© 2,8(0,06) nos caprinos e 1,9(0,34) em ovinos; fibrinogênio plasmático nos caprinos 338,6 mg/dl(10,17) em ovinos 269,9 mg/dl8,62) e de larvas do gênero Haemonchus caprinos 41,1%(3,37) em ovinos 26,4%(4,3), estatisticamente diferente (P<0,05), entretanto o mesmo não foi observado com o valor da proteína plasmática e do percentual de larvas dos gêneros Trichostrongylus e Oesophagostomum. Na análise de todas as avaliações foi demonstrado que o grau 3 foi mais predominante nos caprinos e o grau 2 para os ovinos, com as percentual válido de 47,93 e 57,14, respectivamente. Na comparação entre a presença de anemia e o grau FAMACHA©, a especificidade foi alta e a sensibilidade baixa para ambas as espécies. O valor preditivo positivo foi baixo, porém o negativo foi alto, o que pode assegurar que animais com um resultado negativo no método FAMACHA© realmente não tenham anemia. No segundo experimento, realizado na mesma propriedade, utilizando a mesma base de dados foi feita a análise de agrupamento, utilizando grau FAMACHA©, OPG, e o VG sendo selecionadas 10 cabras com potencial para resistência (PR) e 10 com potencial para suscetibilidade (PS) aos nematóides, acompanhados quinzenalmente por mais 2 meses. Doze destes animais, seis do grupo PR e seis do grupo PS, foram abatidos para contagem e identificação dos xi helmintos gastrintestinais. Os caprinos pertencentes ao grupo PS apresentaram os maiores valores do grau FAMACHA©, do OPG, do percentual de L3 de Haemonchus,, Trichostrongylus e Oesophagostomum e da concentração de fibrinogênio, e os menores valores de VG e escore corporal, diferindo estatisticamente (P<0,05), enquanto a proteína total não diferiu estatisticamente. Na análise de todas as avaliações foi demonstrado que os graus 3 e 4 foi mais predominante nos animais PS, com as percentuais válidos de 45,5 e 30,5 respectivamente, e os graus 2 e 3 nos PR, com os respectivos percentuais válidos de 34,4% e 51,9. Observou-se também que 58,4% dos animais PS e 90,6% dos PR estão entre o grau FAMACHA© 1 e 3. O aumento do nível de infecção parasitária refletiu estatisticamente na diminuição dos valores médios do volume globular dos PS. O total de estádios jovens e adultos de nematóides obtidos dos caprinos PS foi 2660,41 contra 1669,34 dos PR. Apesar de não ser encontrado diferença estatística significativa entre as espécies de nematóides, o grau de infecção foi moderado para o H. contortus nos animais do grupo PS e leve nos PR, enquanto a infecção por T. colubriformes foi considerada pesada e moderada nos grupos PS e PR respectivamente, e para ambos os grupos a infecção por O. columbianum foi alta. A associação dessas técnicas é um modelo importante na abordagem das nematodeoses em caprinos em condições do semi-árido onde possibilitou monitorar a haemoncose em pequenos ruminantes criados no sertão baiano, auxiliando no controle das parasitoses. / Two studies were carried out: On the first study FAMACHA© system was evaluated in sheep and goats, kept under the same conditions, in Bahia state, Brazil. Sixty Anglo Nubiano mixed goats and sixty Santa Inês x Dorper cross breed sheep, four to eight months old age, raised at extensive farming system under the same pasture area were selected. FAMACHA© score, body condition, blood and faecal samples were collected every week during three months, from July to October. Mean faecal worm egg counts (FEC) comparisons were 1991(116.3) for goats and 596.2(104.4) for sheep; packed cell volume (PCV) were 25.4% (0.38) for goats and 31,5%(0.37) for sheep; FAMACHA© score 2.8(0.06) for goats and 1.9(0.34) for sheep; plasma fibrinogen in goats 338.6 mg/dl(10.17) and in sheep 269.9 mg/dl(8.62) and Haemonchus larvae in goat 41.1%(3.37) and in sheep 26.4%(4.3), were statistically different (P<0.05), that was not observed with plasmatic protein and Trichostrongylus and Oesophagostomum larvae percentages. FAMACHA© score 3 for goats and score 2 for sheep were the most predominant observation in overall analysis of all evaluations, with valid percentages of 47.93 and 57.14, respectively. Comparing presence of anemia and FAMACHA© score, specificity was high and sensibility was low, for both species. Positive predictive value was low, but negative value was high, assuring that animals with FAMACHA© negative results were not anemic. The second experiment, conducted at the same property, used the same database for groupment analysis, using FAMACHA© score, EPG and PCV. Ten goats with potential to resistance (PR) and 10 goats with potential to suscetibility (PS) to nematode infection were evaluated at 15 days intervals during 2 months. Twelve animals, six of the PR group and six of the PS group were killed for gastro-intestinal helminth counts and identification. Goats from PS group presented the highest FAMACHA© scores, EPG counts, Haemonchus, Trichostrongylus and Oesophagostomum L3 larvae percentages and plasma fibrinogen concentration, and the lowest PCV values and body condition scores, differing statistically (p<0.05), whereas total serum protein showed no statistical difference. Analysis of all evaluations showed xiii that scores 3 and 4 were the most predominant in animals PS with valid percentages of 45.4 and 30.5, respectively, and scores 2 and 3 in PR, with respective valid percentages of 34.4 and 51.9. Is was also observed that 58.4% of the PS animals and 90.6% of PR are between FAMACHA© score 1 and 3. Increase of the parasitic infection level was statistically related to mean PCV value reduction in PS. Total number of immature and adult nematodes were 2660.41 in PS goats against 1669.34 in PR. Although there was no statistically significant difference among nematode species, H. contortus infection degree was moderate in PS animals and slight in PR, whereas T. colubriformes infection was considered intense and moderate in groups PS and PR, respectively, and O. columbianum infection was intense in both groups. Association of these techniques is an important model to access nematodiosis in goats under semi-arid conditions. It was possible to evaluate haemonchosis in small ruminants raised in Bahia, and aid parasite control.

abstract: Using high-resolution three-dimensional adaptive mesh refinement simulations I study the interaction between primordial minihalo, a clump of baryonic and dark matter with a virial temperature below the atomic cooling limit, and a galaxy outflow. In Chapter 2 I concentrate on the formation of molecular coolants and their effect on the evolution of the minihalo gas. Molecular coolants are important since they allow gas to cool below 10000 K. Therefore, I implement a primordial chemistry and cooling network that tracks the evolution and cooling from these species. I show that the shock from the galaxy outflow produces an abundance of coolants in the primordial gas which allows the gas to cool to below 10000 K. I also show that this interaction produces compact stellar clusters that are ejected from their parent dark matter halos. In Chapter 3 I look at the turbulent mixing of metals that occur between the minihalo and outflow. To do this, I develop a sub-grid model for turbulence that reproduces three primary fluid instabilities. I find that the metals from the outflow are well mixed throughout the minihalo gas. In addition, the metal abundance found roughly corresponds to the observed abundances in halo globular clusters. In Chapter 4, I conduct a suite of simulations that follow this interaction over a wide range of parameters. In almost all cases, the shocked minihalos form molecules and cool rapidly to become compact, chemically homogenous stellar clusters. Furthermore, I show that the unique properties of these clusters make them a prime observational target for study with the next generation of telescopes. Given the unique properties of these clusters there are reasons to suspect that their low-redshift counterparts are halo globular clusters. I outline this comparison in Chapter 5 and give my conclusions in Chapter 6. Finally, I summarize my current work in Chapter 7 and future extensions in Chapter 8. By the end, I hope to convince you that the interaction between a galaxy outflow and a primordial minihalo provides a formation pathway for present day halo globular clusters. / Dissertation/Thesis / Ph.D. Astrophysics 2012

Globular cluster studies suggest that a signature in the spectra of RGB stars in a globular cluster are anti-correlations in Mg-Al and Na-O. In this work, a small sample of 12 RGB stars of the globular cluster M30 is investigated using VLT-UVES high-resolution spectrograph. I use photometric stellar parameters to derive the abundances of Fe, Na, Al and Mg in SIU – a visual spectral analysis tool using 1-dimensional hydrostatic plane parallel MAFAGS atmospheres assuming mixing length convection and treating line formation in LTE. We found signatures of Mg-Al anti-correlation in M30 with the majority of the stars belonging to the intermediate polluted group. Oxygen couldn’t be measured but an indirect clue to the Na-O anti-correlation is found due to the direct correlation of Al-Na. These results are consistent with recent studies of other globular clusters.

Millisecond pulsars (MSP) are old neutron stars that have been spun up to high spin frequencies(as fast as 716 Hz) through the accretion of matter from a companion star. The extreme stellar densities in the core of globular clusters creates numerous accreting neutron star systems through exchange interactions; this leads to the formation of MSPs in larger numbers than in the galactic disk. Over the course of this project, we have collected over 17 TB of data on the 3 globular clusters M28, NGC6440 and NGC6441 plus 2 observations on NGC6522 and NGC6624 as part of the recently begun S-band survey using the Green Bank telescope. I have analyzed and conducted acceleration searches on 70% of the data and discovered 7 of the 23 new millisecond pulsars reported in this work. One year of timing observations of the pulsars in M28 and NGC6440 has led to the phase connected solution for 12 of the 15 new pulsars in those two clusters, 7 of which are in binaries. We have measured the rate of advance of periastron for two highly eccentric binaries and assuming this is purely due to general relativity, this leads to total system masses of (1.616 - 0.014)M and (2.2 - 0.8)M for M28C and NGC6440B respectively. The small mass function combined with this information imply that the most likely neutron star mass of NGC6440B is either very large or else there could be significant contribution to the advance of periastron from a nonzero quadrupole moment due to tidal interaction with the companion. Measurements of the period derivatives for many of the pulsars show that they are dominated by the dynamical effect of the gravitational field of the clusters. Finally, we have discovered the potential presence of a Mars-mass planet orbiting the pulsar NGC6440C with a period of 21 days. A dedicated timing campaign will be necessary to confirm the presence of such an object. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Linker histones (H1) are a family of lysine-rich proteins that bind to or near the point at which DNA enters and exits the nucleosomal core. A number of studies have shown that H1 expression levels are altered in cancer and that variant-specific changes can be observed in different tumor cells. Although several crystal structures are published for core-histone/DNA complex (nucleosome), the location of linker histone and its interactions are poorly understood. This study attempts to answer several questions regarding the interactions of histone H1 with double stranded partner DNA. Preliminary NMR assignments of this protein have been determined. We also investigated the structural changes in histone H1.0 globular domain induced by DNA binding. During the course of this project it was observed that subtle changes in pH could affect NMR spectral quality. We investigated the pH dependence of the protein stability by performing Circular Dichroism (CD) experiments.

<p> Globular clusters (GCs) can be divided into two subpopulations when plotted on a colour-magnitude diagram: one red and metal-rich (MR), and the other blue and metal-poor (MP). For each subpopulation, any correlation between colour and luminosity can then be converted into mass-metallicity relations (MMRs).</p> <p> Tracing the MMRs for fifteen GC systems (GCSs) - all around Brightest Cluster Galaxies - we see a nonzero trend for the MP subpopulation but not the MR. This trend is characterised by p in the relation Z=M^p. We find p ~ 0.35 for the MP GCs, and a relation for the MR GCs that is consistent with zero. When we look at how this trend varies with the host galaxy luminosity, we extend previous studies (e.g., Mieske et al, 2006b) into the bright end of the host galaxy sample.</p> <p> In addition to previously presented (B-I) photometry for eight GCSs obtained with ACS/WFC on the HST, we present seven more GCSs. Four of these are newly analysed from HST data, one is previously presented (g-i) photometry obtained with GMOS on Gemini South, and two are the author's newly reduced and analysed (g-i) photometry also obtained with GMOS on Gemini South.</p> <p> Interpretation of these results is important for further understanding the formation and evolution of galaxies within the hierarchical-merging picture, and what process enables the production of two subpopulations.</p> / Thesis / Master of Science (MSc)