Intergranular diffusion rates from the analysis of garnet surfaces: implications for metamorphic equilibration

Novel approaches to garnet analysis have been used to assess rates of intergranular diffusion between different matrix phases and garnet porphyroblasts in a regionally metamorphosed staurolite-mica-schist from the Barrovian-type area in Scotland. X-ray maps and chemical traverses of planar porphyroblast surfaces reveal chemical heterogeneity of the garnet grain boundary linked to the nature of the adjacent matrix phase. The garnet preserves evidence of low temperature retrograde exchange with matrix minerals and diffusion profiles documenting cation movement along the garnet boundaries. Garnet–quartz and garnet–plagioclase boundaries preserve evidence of sluggish Mg, Mn and Fe diffusion at comparable rates to volume diffusion in garnet, whereas diffusion along garnet–biotite interfaces is much more effective. Evidence of particularly slow Al transport, probably coupled to Fe3+ exchange, is locally preserved on garnet surfaces adjacent to Fe-oxide phases. The Ca distribution on the garnet surface shows the most complex behaviour, with long-wavelength heterogeneities apparently unrelated to the matrix grain boundaries. This implies that the Ca content of garnet is controlled by local availability and is thought likely to reflect disequilibrium established during garnet growth. Geochemical anomalies on the garnet surfaces are also linked to the location of triple junctions between the porphyroblasts and the matrix phases, and imply enhanced transport along these channels. The slow rates of intergranular diffusion and the characteristics of different boundary types may explain many features associated with the prograde growth of garnet porphyroblasts. Thus, minerals such as quartz, Fe-oxides and plagioclase whose boundaries with garnet are characterized by slow intergranular diffusion rates appear to be preferentially trapped as inclusions within porphyroblasts. As such grain boundary diffusion rates may be a significant kinetic impediment to metamorphic equilibrium and garnet may struggle to maintain chemical and textural equilibrium during growth in pelites

Constraining Scatter in the Stellar Mass--Halo Mass Relation for Haloes Less Massive than the Milky Way

Most galaxies are hosted by massive, invisible dark matter haloes, yet little is known about the scatter in the stellar mass--halo mass relation for galaxies with host halo masses $M_{h}\le 10^{11}M_{\odot}$. Using mock catalogues based on dark matter simulations, we find that two observable signatures are sensitive to scatter in the stellar mass--halo mass relation even at these mass scales; i.e., conditional stellar mass functions and velocity distribution functions for neighbouring galaxies. We compute these observables for 179,373 galaxies in the Sloan Digital Sky Survey (SDSS) with stellar masses $M_{\ast} > 10^9 M_{\odot}$ and redshifts 0.01 $< z <$ 0.307. We then compare to mock observations generated from the $\textit{Bolshoi-Planck}$ dark matter simulation for stellar mass--halo mass scatters ranging from 0 to 0.6 dex. The observed results are consistent with simulated results for most values of scatter ($<$0.6 dex), and SDSS statistics are insufficient to provide firm constraints. However, this method could provide much tighter constraints on stellar mass--halo mass scatter in the future if applied to larger data sets, especially the anticipated Dark Energy Spectroscopic Instrument Bright Galaxy Survey. Constraining the value of scatter could have important implications for galaxy formation and evolution.Comment: 11 pages, 1 table, 9 main body figures, 9 appendix figure

Size Matters: The Impact of Capital Market Liberalization on Individual Firms

We attempt to answer the following questions: What are the revaluation effects and the impact on performance, volatility, and return correlation from stock market liberalization in emerging markets? These questions have been studied extensively at the market-level but not at the firm level. Our results show significantly different impact of stock market liberalization across firms. Large firms tend to exhibit large revaluation effects, insignificant change in performance, large declines in volatility, and insignificant change in correlation from liberalization. Small firms show small revaluation effects, improved performance, smaller decline in volatility and decreases in correlation after liberalization. These results hold after controlling for movements in world stock returns, concurrent economic reforms and macroeconomic fundamentals. They are also robust to the length of the liberalization window. Our results have important implications for international investors seeking to manage their global exposure as well as for policy makers considering capital market liberalization. Nous étudions les questions suivantes: Quels sont les effets de réévaluation et l'impact sur les performances, la volatilité et les corrélations de la libéralisation du marché boursier dans les marchés naissants? Ces questions ont été étudiées intensivement au niveau des marchés mais pas au niveau des entreprises. Nos résultats montrent que l'impact de la libéralisation des marchés est significativement différent selon la taille des entreprises. Les grandes entreprises présentent en général des effets de réévaluation importants, des changements insignifiants au niveau des performances, des chutes importantes de volatilité et des changements insignifiants des corrélations en raison de la libéralisation. Les petites entreprises présentent quant à elles de faibles effets de réévaluation, une amélioration des performances, un déclin plus faible de la volatilité et une diminution des corrélations à la suite de la libéralisation. Ces résultats demeurent valables lorsqu'on contrôle pour les mouvements des rendements boursiers mondiaux, les réformes économiques concourantes et les principes fondamentaux de macro-économie. Ils sont également robustes à la longueur de la fenêtre de libéralisation. Nos résultats ont des implications importantes pour les investisseurs internationaux qui cherchent à gérer leur exposition globale ainsi que pour les responsables qui envisagent la libéralisation de marchés financiers.Emerging Markets, Volatility, Correlation, Performance, Revaluation Effects, Marchés naissants, volatilité, corrélation, performance, effets de réévaluation

Some Guidance on Conducting and Reporting Qualitative Studies

This paper sets out to address the problem of the imbalance between the number of quantitative and qualitative articles published in highly ranked research journals, by providing guidelines for the design, implementation and reporting of qualitative research. Clarification is provided of key terms (such as quantitative and qualitative) and the interrelationships between them. The relative risks and benefits of using guidelines for qualitative research are considered, and the importance of using any such guidelines flexibly is highlighted. The proposed guidelines are based on a synthesis of existing guidelines and syntheses of guidelines from a range of fields