Dark Matter with Dirac and Majorana Gaugino Masses

We consider the minimal supersymmetric extension of the Standard Model allowing both Dirac and Majorana gauginos. The Dirac masses are obtained by pairing up extra chiral multiplets: a singlet S for U(1)_Y, a triplet T for SU(2) and an octet O for SU(3) with the respective gauginos. The electroweak symmetry breaking sector is modified by the couplings of the new fields S and T to the Higgs doublets. We discuss two limits: i) both the adjoint scalars are decoupled with the main effect being the modification of the Higgs quartic coupling; ii) the singlet remaining light, and due to its direct coupling to sfermions, providing a new contribution to the soft masses and inducing new decay/production channels. We discuss the LSP in this scenario; after mentioning the possibility that it may be a Dirac gravitino, we focus on the case where it is identified with the lightest neutralino, and exhibit particular values of the parameter space where the relic density is in agreement with WMAP data. This is illustrated for different scenarios where the LSP is either a bino (in which case it can be a Dirac fermion) or bino-higgsino/wino mixtures. We also point out in each case the peculiarity of the model with respect to dark matter detection experiments.Comment: 43 pages, 5 figures; one reference added. Corresponds to published version in JCA

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Relationships between taxonomic resolution and spatial scales of multivariate variation

The definitive version is available at www.blackwell-synergy.com1. We investigated the effects of changes in taxonomic resolution on analyses of patterns of multivariate variation at different spatial scales for the highly diverse fauna inhabiting holdfasts of the kelp Ecklonia radiata. 2. Multivariate analyses were performed using several transformations to examine differences in spatial patterns of variation from metres up to hundreds of kilometres for composition vs. relative abundance in assemblages. 3. The greatest variability in assemblages occurred at the smallest spatial scale, from plant to plant, pointing to the existence of important small-scale processes. The proportional amount of variation at the smallest spatial scale decreased with decreasing taxonomic resolution (i.e. from species through to phyla). For composition, the next-greatest source of variation was at the largest spatial scale (hundreds of kilometres), while for relative abundance, the next-greatest source of variation was at the level of sites (hundreds of metres to kilometres). 4. For abundance data, location-level variation became less important and site-level variation became more important with decreasing taxonomic resolution, while for compositional data, the opposite pattern occurred. This suggests that variation in the presence of species or taxa at a particular location along the coast is driven by large-scale processes, while variation in relative abundances within locations is driven by medium-scale processes. 5. The lack of significant variation in the proportional abundances of phyla at large spatial scales suggests that some consistency of pattern may emerge at larger scales (spatial and/or taxonomic), even in the presence of high small-scale variability. These findings strengthen the idea that substantial local variation need not preclude the existence of broad-scale organization in ecological patterns and biodiversity. © 2005 British Ecological Society.Marti J. Anderson, Sean D. Connell, Bronwyn M. Gillanders, Carol E. Diebel, Wilma M. Blom, Justine E. Saunders, Todd J. Lander