Inclusion of the Cape genus Anisothrix in the Namibian-centred genus Pentatrichia (Asteraceae, Gnaphalieae) based on a molecular phylogenetic analysis

AbstractA phylogenetic analysis of the small genus Pentatrichia, containing three species endemic to South Africa and Namibia, was undertaken using nuclear (ITS and 3′ ETS) and chloroplast (trnT–trnL) DNA sequence data. Generic circumscription was examined via the inclusion of appropriate outgroup taxa (Anisothrix and Athrixia). A fully-resolved phylogenetic hypothesis found all Pentatrichia species and subspecies to be reciprocally monophyletic based on three sampled specimens of each taxon. A well-supported sister relationship between the radiate P. rehmii subsp. avasmontana and non-radiate P. rehmii subsp. rehmii confirmed the results of a previous morphometric study. Pentatrichia was found to be non-monophyletic with the exclusion of Anisothrix kuntzei and A. integra, which were placed as a subclade within Pentatrichia, and sister to the type species P. petrosa. Morphological synapomorphies supporting the inclusion of Anisothrix with Pentatrichia are discussed, as well as the evolution of capitulum structure in the group. Anisothrix is synonymised with Pentatrichia and two new combinations were made. The expanded morphological concept of the genus Pentatrichia is presented with a key to all five species

Role of Sterile Neutrino Warm Dark Matter in Rhenium and Tritium Beta Decays

Sterile neutrinos with mass in the range of one to a few keV are important as extensions of the Standard Model of particle physics and are serious dark matter (DM) candidates. This DM mass scale (warm DM) is in agreement with both cosmological and galactic observations. We study the role of a keV sterile neutrino through its mixing with a light active neutrino in Rhenium 187 and Tritium beta decays. We pinpoint the energy spectrum of the beta particle, 0 < T_e < (Q_{beta} - m_s), as the region where a sterile neutrino could be detected and where its mass m_s could be measured. This energy region is at least 1 keV away rom the region suitable to measure the mass of the light active neutrino, located near the endpoint Q_{beta} . The emission of a keV sterile neutrino in a beta decay could show up as a small kink in the spectrum of the emitted beta particle. With this in view, we perform a careful calculation of the Rhenium and Tritium beta spectra and estimate the size of this perturbation by means of the dimensionless ratio R of the sterile neutrino to the active neutrino contributions. We comment on the possibility of searching for sterile neutrino signatures in two experiments which are currently running at present, MARE and KATRIN, focused on the Rhenium 187 and Tritium beta decays respectively.Comment: 16 pages, 10 figures. Version to appear in Nucl. Phys. B. Results and conclusions unchange

Genome-wide meta-analysis identifies new loci and functional pathways influencing Alzheimer’s disease risk

Alzheimer’s disease (AD) is highly heritable and recent studies have identified over 20 disease-associated genomic loci. Yet these only explain a small proportion of the genetic variance, indicating that undiscovered loci remain. Here, we performed a large genome-wide association study of clinically diagnosed AD and AD-by-proxy (71,880 cases, 383,378 controls). AD-by-proxy, based on parental diagnoses, showed strong genetic correlation with AD (rg = 0.81). Meta-analysis identified 29 risk loci, implicating 215 potential causative genes. Associated genes are strongly expressed in immune-related tissues and cell types (spleen, liver, and microglia). Gene-set analyses indicate biological mechanisms involved in lipid-related processes and degradation of amyloid precursor proteins. We show strong genetic correlations with multiple health-related outcomes, and Mendelian randomization results suggest a protective effect of cognitive ability on AD risk. These results are a step forward in identifying the genetic factors that contribute to AD risk and add novel insights into the neurobiology of AD