The colour-magnitude relation of Globular Clusters in Centaurus and Hydra - Constraints on star cluster self-enrichment with a link to massive Milky Way GCs

We investigate the colour-magnitude relation of metal-poor globular clusters, the 'blue tilt', in the Hydra and Centaurus galaxy clusters and constrain the primordial conditions for star cluster self-enrichment. We analyse U,I photometry for about 2500 globular clusters in the central regions of Hydra and Centaurus, based on FORS1@VLT data. We convert the measured colour-magnitude relations into mass-metallicity space and obtain a scaling of Z \propto M^{0.27 \pm 0.05} for Centaurus GCs and Z \propto M^{0.40 \pm 0.06} for Hydra GCs, consistent with results in other environments. We find that the GC mass-metallicity relation already sets in at present-day masses of a few 10^5 solar masses and is well established in the luminosity range of massive MW clusters like omega Centauri. We compare the mass-metallicity relation with predictions from the star cluster self-enrichment model by Bailin & Harris (2009). For this we include effects of dynamical and stellar evolution and a physically well motivated primordial mass-radius scaling. The self-enrichment model reproduces the observed relations well for average primordial half-light radii r_h ~ 1-1.5 pc, star formation efficiencies f_* ~ 0.3-0.4, and pre-enrichment levels of [Fe/H] ~ -1.7 dex. Within the self-enrichment scenario, the observed blue tilt implies a correlation between GC mass and width of the stellar metallicity distribution. We find that this implied correlation matches the trend of width with GC mass measured in Galactic GCs, including extreme cases like omega Cen and M54. We conclude that 1. A primordial star cluster mass-radius relation provides a significant improvement to the self-enrichment model fits. 2. Broadenend metallicity distributions as found in some massive MW globular clusters may have arisen naturally from self-enrichment processes, without the need of a dwarf galaxy progenitor.Comment: 15 pages, 13 figures. Language edited version of paper accepted for publication in Astronomy & Astrophysics. Colour-composite in Figure 1 reduced in resolutio

Long-Term Spiritual Growth and its Influence on Professional Endeavor

This paper presents a qualitative study of how long-term practitioners of Integral Yoga working in four fields of professional endeavour—business management, education, health care, and the arts—have applied Integral Yoga in their work and how they perceived its influences. The paper gives a brief overview of the nature of Integral Yoga, especially its aspect of karmayoga, and an explanation of the study’s method which involved semi-structured interviews with 12 residents or regular visitors to the Sri Aurobindo Ashram or Auroville. Ten common themes were identified which emerged in at least three of the interviews and in at least two fields of work. The report of the findings focuses on the participants’ lived experiences of Integral Yoga and its perceived effects in their various fields of work

Morphogenetic Principles of Brain Organisation in Health and Disease

Non-invasive neuroimaging methods, such as MRI, provide a window into the structure of the mammalian brain. However, despite the ubiquity of these methods, the biological interpretation of the information obtained using these tools remains elusive. In order to accurately link this macroscale data to microscale measurements, it is critical that the construct validity is high. This thesis provides novel analyses, pipelines and methods to: i) generate and validate maps of brain organisation obtained via MRI, and ii) demonstrate the utility of these methods in capturing elements of cognition and psychopathology. First, in Chapter 1, I review some of the neuroscientific context for the new methods presented, from cytoarchitecture to gene expression to connectomes. Chapters 2-4 introduce a new method, “Morphometric Similarity Mapping”, which captures the brain organisation of an individual by mapping the relationships of multiple features of the cerebral cortex. Chapter 2 focuses on the development of the analysis pipeline and the graph theoretical features of the resulting morphometric similarity networks (MSNs), with an emphasis on reproducibility. Chapter 3 highlights the generalisability of MSNs to the macaque monkey, linking MSNs to ex vivo tract tracing experiments and presenting new tools for processing non-human imaging data; as well as evidence that MSN topography is organised by cytoarchitectonic features. Chapter 4 is focused on determining the transcriptomic correlates of MSNs using publicly available gene expression maps, and on applying MSNs to examine the relationship between brain organisation and intelligence. Chapter 5 is dedicated to rigorous evaluation of the applicability of MSNs to measure specific disease-relevant phenotypes in 8 rare genetic disorder cohorts. This includes the validation of novel methods for utilising data from both single-cell sequencing technologies and differential gene expression experiments (in multiple tissue types) in analysing neuroimaging and bulk transcriptomic brain maps. Chapter 6 provides a brief summary and presents some ongoing and future projects expanding on this original work. It also importantly discusses a general framework of comparing brain maps, including MSNs and gene expression, as well as other canonical maps of brain structure and function. Altogether, this thesis presents and evaluates novel methods and applications for integrating multimodal neuroimaging data with genetic data derived from multiple tissue types and through various acquisition strategies. It also includes tools for performing these analyses in non-human primates, and pipelines for statistically comparing brain maps. These results not only provide insight into the manifestation of brain-related changes due to various components of human variation, but also provides a framework for evaluating this variation at multiple biological scales purely from non-invasive neuroimaging data