Λ\LambdaCDM or self-interacting neutrinos? - how CMB data can tell the two models apart

Of the many proposed extensions to the $\Lambda$CDM paradigm, a model in which neutrinos self-interact until close to the epoch of matter-radiation equality has been shown to provide a good fit to current cosmic microwave background (CMB) data, while at the same time alleviating tensions with late-time measurements of the expansion rate and matter fluctuation amplitude. Interestingly, CMB fits to this model either pick out a specific large value of the neutrino interaction strength, or are consistent with the extremely weak neutrino interaction found in $\Lambda$CDM, resulting in a bimodal posterior distribution for the neutrino self-interaction cross section. In this paper, we explore why current cosmological data select this particular large neutrino self-interaction strength, and by consequence, disfavor intermediate values of the self-interaction cross section. We show how it is the $\ell \gtrsim 1000$ CMB temperature anisotropies, most recently measured by the Planck satellite, that produce this bimodality. We also establish that smaller scale temperature data, and improved polarization data measuring the temperature-polarization cross-correlation, will best constrain the neutrino self-interaction strength. We forecast that the upcoming Simons Observatory should be capable of distinguishing between the models.Comment: 7 pages, 7 figures, comments welcome, references added, version submitted to PR

Évaluation des habiletés de vie autonome chez les personnes psychotiques

Ce texte détaille les caractéristiques métrologiques de l'Échelle des habiletés de Vie Autonome (EHVA) mesurant les habiletés requises chez des personnes psychotiques, pour fonctionner de façon autonome au sein de la communauté. Ce questionnaire, qui comprend 65 items répartis en dix échelles d'habiletés, a été administré à 276 personnes psychotiques. Les résultats indiquent que, dans l'ensemble, la fidélité de cet instrument est bonne, mesurée par l'accord interjuges et les coefficients alpha. Trois des 10 échelles, soit les échelles Déplacement, Recherche d'emploi et Maintien de l'emploi, n'ont pu être conservées dans la version finale. Les quatre aspects de la validité examinés dans cette étude se révèlent très satisfaisants; il s'agit du degré de convergence entre l'évaluation faite par les participants eux-mêmes et par un membre du personnel soignant, des analyses discriminantes, des corrélations convergentes-divergentes avec d'autres instruments de mesure du fonctionnement psychosocial et de l'analyse factorielle exploratoire. Après ces analyses, la version finale de l'EHVA comprend 48 items répartis sous sept échelles. La discussion fait ressortir les qualités psychométriques d'un tel instrument en langue française et suggère des pistes de recherche pour poursuivre le développement de l'EHVA.This article studies in detail the metrological characteristics of the "Autonomous Life Skills Test" ("Echelle des Habiletés de Vie Autonome" or "EHVA") which measures the skills required of psychotic patients to function on their own in the community. The questionnaire, distributed to 276 psychotic patients, made use of 10 parameters of skills broken down into 65 items. Results show that, overall, this instrument is quite reliable, as measured by the inter-rater reliability and alpha coefficients. Three of the ten parameters, namely Mobility, Employment Search and Employment Holding, were not retained in the final version. The four validity aspects were found to be very satisfactory, namely the degree of convergence between the participant's self-evaluation and the evaluation provided by healthcare personnel, (discriminating analysis), convergent-divergent correlations with other instruments measuring psychosocial functioning and the exploratory factorial analysis. Following these analysis, the final version of the "EHVA" includes 48 items covering seven parameters. A discussion of results underscores the psychometric qualities of such a French-language instrument and suggests avenues to pursue the development of the "EHVA"

Nivat's conjecture holds for sums of two periodic configurations

Nivat's conjecture is a long-standing open combinatorial problem. It concerns two-dimensional configurations, that is, maps $\mathbb Z^2 \rightarrow \mathcal A$ where $\mathcal A$ is a finite set of symbols. Such configurations are often understood as colorings of a two-dimensional square grid. Let $P_c(m,n)$ denote the number of distinct $m \times n$ block patterns occurring in a configuration $c$. Configurations satisfying $P_c(m,n) \leq mn$ for some $m,n \in \mathbb N$ are said to have low rectangular complexity. Nivat conjectured that such configurations are necessarily periodic. Recently, Kari and the author showed that low complexity configurations can be decomposed into a sum of periodic configurations. In this paper we show that if there are at most two components, Nivat's conjecture holds. As a corollary we obtain an alternative proof of a result of Cyr and Kra: If there exist $m,n \in \mathbb N$ such that $P_c(m,n) \leq mn/2$, then $c$ is periodic. The technique used in this paper combines the algebraic approach of Kari and the author with balanced sets of Cyr and Kra.Comment: Accepted for SOFSEM 2018. This version includes an appendix with proofs. 12 pages + references + appendi

Hsp70 in mitochondrial biogenesis

The family of hsp70 (70 kilodalton heat shock protein) molecular chaperones plays an essential and diverse role in cellular physiology, Hsp70 proteins appear to elicit their effects by interacting with polypeptides that present domains which exhibit non-native conformations at distinct stages during their life in the cell. In this paper we review work pertaining to the functions of hsp70 proteins in chaperoning mitochondrial protein biogenesis. Hsp70 proteins function in protein synthesis, protein translocation across mitochondrial membranes, protein folding and finally the delivery of misfolded proteins to proteolytic enzymes in the mitochondrial matrix

Turbulent nitrate fluxes in the Lower St. Lawrence Estuary, Canada

Turbulent vertical nitrate fluxes were calculated using new turbulent microstructure observations in the Lower St. Lawrence Estuary (LSLE), Canada. Two stations were compared: the head of the Laurentian Channel (HLC), where intense mixing occurs on the shallow sill that marks the upstream limit of the LSLE, and another station located about 100 km downstream (St. 23), more representative of the LSLE mean mixing conditions. Mean turbulent diffusivities and nitrate fluxes at the base of the surface layer for both stations were, respectively (with 95% confidence intervals): inline image and inline image. Observations suggest that the interplay between large isopleth heaving near the sill and strong turbulence is the key mechanism to sustain such high turbulent nitrate fluxes at the HLC (two to three orders of magnitude higher than those at Station 23). Calculations also suggest that nitrate fluxes at the HLC alone can sustain primary production rates of inline image over the whole LSLE, approximately enough to account for a large part of the phytoplankton bloom and for most of the postbloom production. Surfacing nitrates are also believed to be consumed within the LSLE, not leaving much to be exported to the rest of the Gulf of St. Lawrence

A comparison of spectral element and finite difference methods using statically refined nonconforming grids for the MHD island coalescence instability problem

A recently developed spectral-element adaptive refinement incompressible magnetohydrodynamic (MHD) code [Rosenberg, Fournier, Fischer, Pouquet, J. Comp. Phys. 215, 59-80 (2006)] is applied to simulate the problem of MHD island coalescence instability (MICI) in two dimensions. MICI is a fundamental MHD process that can produce sharp current layers and subsequent reconnection and heating in a high-Lundquist number plasma such as the solar corona [Ng and Bhattacharjee, Phys. Plasmas, 5, 4028 (1998)]. Due to the formation of thin current layers, it is highly desirable to use adaptively or statically refined grids to resolve them, and to maintain accuracy at the same time. The output of the spectral-element static adaptive refinement simulations are compared with simulations using a finite difference method on the same refinement grids, and both methods are compared to pseudo-spectral simulations with uniform grids as baselines. It is shown that with the statically refined grids roughly scaling linearly with effective resolution, spectral element runs can maintain accuracy significantly higher than that of the finite difference runs, in some cases achieving close to full spectral accuracy.Comment: 19 pages, 17 figures, submitted to Astrophys. J. Supp

Difference schemes with point symmetries and their numerical tests

Symmetry preserving difference schemes approximating second and third order ordinary differential equations are presented. They have the same three or four-dimensional symmetry groups as the original differential equations. The new difference schemes are tested as numerical methods. The obtained numerical solutions are shown to be much more accurate than those obtained by standard methods without an increase in cost. For an example involving a solution with a singularity in the integration region the symmetry preserving scheme, contrary to standard ones, provides solutions valid beyond the singular point.Comment: 26 pages 7 figure