Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Disruption of stem cell niche-confined R-spondin 3 expression leads to impaired hematopoiesis

Self-renewal and differentiation of stem and progenitor cells are tightly regulated to ensure tissue homeostasis. This regulation is enabled both remotely by systemic circulating cues, such as cytokines and hormones, and locally by various niche-confined factors. R-spondin 3 (RSPO3) is one of the most potent enhancers of Wnt signaling and its expression is usually restricted to the stem cell niche where it provides localized enhancement of Wnt signaling to regulate stem cell expansion and differentiation. Disruption of this niche-confined expression can disturb proper tissue organization and lead to cancers. Here, we investigate the consequences of disrupting the niche restricted expression of RSPO3 in various tissues including the hematopoietic system. We show that normal Rspo3 expression is confined to the perivascular niche in the bone marrow. Induction of increased systemic levels of circulating RSPO3 outside of the niche results in prominent loss of early-B cell progenitors and anemia but surprisingly has no effect on hematopoietic stem cells (HSCs). Using molecular, pharmacological and genetic approaches, we demonstrate that these RSPO3-induced hematopoietic phenotypes are Wnt and RSPO3 dependent and mediated through non-canonical Wnt signaling. Our study highlights a distinct role for a Wnt/RSPO3 signaling axis in the regulation of hematopoiesis, as well as possible challenges related to therapeutic usage of R-spondins for regenerative medicine

Quests for therapy in northern Uganda: healing at Laropi revisited

This article presents a case of diachronic ethnography. It examines quests for therapy among the Madi people of northern Uganda. It is based on ethnographic fieldwork carried out in and around the small trading centre of Laropi; originally in the late 1980s and again in 2008. By revisiting the same field site at different points in time, and by drawing on related ethnographic material collected in the 1950s and 70s, we are able to examine how such quests have altered and to discuss factors influencing these changes. We also comment on shifts in conceptual approaches of medical anthropology that have influenced perceptions and analysis. Laropi lies close to the border with Sudan and its inhabitants have experienced much upheaval and political isolation. We examine how this has influenced understandings and responses to ill-health and misfortune. Particularly important in recent years has been the increasing availability and accessibility of biomedicine, which the population have embraced and indigenized as a mark of progress and political recognition. On the face of it, this has rendered recourse to more "traditional" forms of healing obsolete. However, as we describe, the situation is more ambiguous. Notions of witchcraft, spirit possession and ancestor veneration are more pervasive than they might seem