Resonant thickening of self-gravitating discs: imposed or self-induced orbital diffusion in the tightly wound limit

The secular thickening of a self-gravitating stellar galactic disc is investigated using the dressed collisionless Fokker-Planck equation and the inhomogeneous multicomponent Balescu-Lenard equation. The thick WKB limits for the diffusion fluxes are found using the epicyclic approximation, while assuming that only radially tightly wound transient spirals are sustained by the disc. This yields simple quadratures for the drift and diffusion coefficients, providing a clear understanding of the positions of maximum vertical orbital diffusion within the disc, induced by fluctuations either external or due to the finite number of particles. These thick limits also offer a consistent derivation of a thick disc Toomre parameter, which is shown to be exponentially boosted by the ratio of the vertical to radial scale heights. Dressed potential fluctuations within the disc statistically induce a vertical bending of a subset of resonant orbits, triggering the corresponding increase in vertical velocity dispersion. When applied to a tepid stable tapered disc perturbed by shot noise, these two frameworks reproduce qualitatively the formation of ridges of resonant orbits towards larger vertical actions, as found in direct numerical simulations, but overestimates the time-scale involved in their appearance. Swing amplification is likely needed to resolve this discrepancy, as demonstrated in the case of razor-thin discs. Other sources of thickening are also investigated, such as fading sequences of slowing bars, or the joint evolution of a population of giant molecular clouds within the disc.Comment: 31 pages, 19 figure

Specific Aspects of Internal Corrosion of Nuclear Clad Made of Zircaloy

In PWR, the Zircaloy based clad is the first safety barrier of the fuel rod, it must prevent the dispersion of the radioactive elements, which are formed by fission inside the UO2 pellets filling the clad. We focus here on internal corrosion that occurs when the clad is in tight contact with the UO2 pellet. In this situation, with temperature of 400^{\circ}C on the internal surface of the clad, a layer of oxidised Zircaloy is formed with a thickness ranging from 5 to 15 $\mu$m. In this paper, we will underline the specific behaviour of this internal corrosion layer compared to wet corrosion of Zircaloy. Simulations will underline the differences of stress field and their influences on corresponding dissolved oxygen profiles. The reasons for these differences will be discussed as function of the mechanical state at inner surface of the clad which is highly compressed. Differences between mechanical conditions generated by an inner or outer corrosion of the clad are studied and their influences on the diffusion phenomena are highlighted

Conflict resolution for pipelined layered LDPC decoders

International audienceMany of the current LDPC implementations of DVB-S2, T2 or WiMAX standard use the so-called layered architecture combined with pipeline. However, the pipeline process may introduce memory access conflicts. The resolution of these conflicts requires careful scheduling combined with dedicated hardware and/or idle cycle insertion. In this paper, based on the DVB-T2 example, we explain explicitly how the scheduling can solve most of the pipeline conflicts. The two contributions of the paper are 1) how to split the matrix to relax the pipeline conflicts at a cost of a reduced maximum available parallelism 2) how to project the problem of the research of an efficient scheduling to the well-known "Travelling Salesman Problem" and use a genetic algorithm to solve it

Conflict Resolution by Matrix Reordering for DVB-T2 LDPC Decoders

International audienceLayered decoding is known to provide efficient and high-throughput implementation of LDPC decoders. However, the implementation of the layered architecture is not always straightforward because of the memory access conflicts in the a-posteriori information memory. In this paper, we focus our attention on a particular type of conflict introduced by the existence of multiple diagonal matrices in the DVB-T2 parity check matrix structure. We illustrate how the reordering of the matrix reduces the number of conflicts, at the cost of limiting the level of parallelism. We then propose a parity extending process to solve the remaining conflicts. Fixed point simulation results show coherent performance without modifying the layered architecture

Exploring Parents' Everyday Experiences With Digital Media: Barriers and Opportunities for Digital Inclusion

This article presents qualitative research findings on parents' digital media practices. Through 32 in-depth interviews with parents of 0-6-year-olds in French-speaking Belgium, the study addresses digital inclusion by exploring the diverse ways parents experience and benefit (or not) from digital media. Our research uncovers the dual nature of digital media use in parenting, presenting both advantageous and problematic outcomes across four dialectical dimensions. Our work sheds light on how digital media can (a) offer informational support or constitute an informational challenge, (b) provide emotional assistance or cause emotional struggles, (c) grant access to social support or contribute to social pressures, and (d) serve as a tool for the daily organisation or complicate daily life. Our article also investigates the factors associated with either positive or negative outcomes. We show the role of personal, situational, social, and normative factors. To conclude, we identify strategies for childcare and parenting support professionals to promote digital inclusion among parents by addressing barriers to positive experiences and outcomes related to the use of digital media. By integrating the outcomes of parents' experiences with digital media into discussions of digital inclusion, this article contributes to a comprehensive approach to promoting digital equity beyond questions of access and skills. It calls for user-centric strategies that consider the diverse experiences and concrete outcomes associated with digital media use and emphasises the importance of supporting parents and families regarding these tools

A Prospective Cohort Study on the Intergenerational Transmission of Childhood Adversity and Subsequent Risk of Psychotic Experiences in Adolescence

BACKGROUND AND HYPOTHESIS: Previous studies have shown a robust relationship between childhood adversity and subsequent psychotic symptoms. However, the role of familial risk factors underlying this relationship remains largely unclear. Here, we tested whether offspring childhood adversity and postnatal maternal psychopathology mediated the relationship between maternal childhood adversity and offspring psychotic experiences. STUDY DESIGN: N = 3068 mother-offspring dyads were included. Maternal history of childhood adversity was retrospectively assessed using the Childhood Trauma Questionnaire during pregnancy. Maternal psychopathology was assessed during and after pregnancy. Twenty-four offspring childhood adversities were assessed by maternal interview when the child was 10 years old. Offspring psychotic experiences were examined using self-report at 14 years. Structural equation mediation models were conducted to explore whether maternal postnatal psychopathology and offspring childhood adversities sequentially mediated the relationship between maternal childhood adversity and offspring psychotic experiences. Analyses were adjusted for sociodemographic confounders. STUDY RESULTS: Maternal history of childhood adversity was associated with offspring childhood adversities (β = 0.12, 95% CI: 0.09 to 0.16). Offspring childhood adversity mediated the association of maternal childhood adversity with offspring hallucinations (βindirect effect = 0.008, 95% CI: 0.002 to 0.014, proportion mediated = 16.3%) and delusions (βindirect effect = 0.006, 95% CI: 0.000 to 0.012, proportion mediated = 13.1%). CONCLUSIONS: Intergenerational transmission of childhood adversity can be considered of relevance in the etiology of psychosis vulnerability and can potentially serve as a modifiable risk factor

Nt-acetylation-independent turnover of SQUALENE EPOXIDASE 1 by Arabidopsis DOA10-like E3 ligases

The acetylation-dependent (Ac/)N-degron pathway degrades proteins through recognition of their acetylated N-termini (Nt) by E3 ligases called Ac/N-recognins. To date, specific Ac/N-recognins have not been defined in plants. Here we used molecular, genetic, and multiomics approaches to characterize potential roles for Arabidopsis (Arabidopsis thaliana) DEGRADATION OF ALPHA2 10 (DOA10)-like E3 ligases in the Nt-acetylation-(NTA)-dependent turnover of proteins at global- and protein-specific scales. Arabidopsis has two endoplasmic reticulum (ER)-localized DOA10-like proteins. AtDOA10A, but not the Brassicaceae-specific AtDOA10B, can compensate for loss of yeast (Saccharomyces cerevisiae) ScDOA10 function. Transcriptome and Nt-acetylome profiling of an Atdoa10a/b RNAi mutant revealed no obvious differences in the global NTA profile compared to wild type, suggesting that AtDOA10s do not regulate the bulk turnover of NTA substrates. Using protein steady-state and cycloheximide-chase degradation assays in yeast and Arabidopsis, we showed that turnover of ER-localized SQUALENE EPOXIDASE 1 (AtSQE1), a critical sterol biosynthesis enzyme, is mediated by AtDOA10s. Degradation of AtSQE1 in planta did not depend on NTA, but Nt-acetyltransferases indirectly impacted its turnover in yeast, indicating kingdom-specific differences in NTA and cellular proteostasis. Our work suggests that, in contrast to yeast and mammals, targeting of Nt-acetylated proteins is not a major function of DOA10-like E3 ligases in Arabidopsis and provides further insight into plant ERAD and the conservation of regulatory mechanisms controlling sterol biosynthesis in eukaryotes

Early risk factors of overweight developmental trajectories during middle childhood

Background Research is needed to identify early life risk factors associated with different developmental paths leading to overweight by adolescence. Objectives To model heterogeneity in overweight development during middle childhood and identify factors associated with differing overweight trajectories. Methods Data was drawn from the Quebec Longitudinal Study of Child Development (QLSCD; 1998- 2010). Trained research assistants measured height and weight according to a standardized protocol and conducted yearly home interviews with the child’s caregiver (mother in 98% of cases). Information on several putative early life risk factors for the development of overweight were obtained, including factors related to the child’s perinatal, early behavioral family and social environment. Group-based trajectories of the probability of overweight (6- 12 years) were identified with a semiparametric method (n=1678). Logistic regression analyses were used to identify early risk factors (5 months- 5 years) associated with each trajectory. Results Three trajectories of overweight were identified: “early-onset overweight” (11.0 %), “lateonset overweight” (16.6%) and “never overweight” (72.5%). Multinomial analyses indicated that children in the early and late-onset group, compared to the never overweight group, had 3 common types of risk factors: parental overweight, preschool overweight history, and large size for gestational age. Maternal overprotection (OR= 1.12, CI: 1.01-1.25), short nighttime sleep duration (OR=1.66, CI: 1.07-2.57), and immigrant status (OR=2.01, CI: 1.05-3.84) were factors specific to the early-onset group. Finally, family food insufficiency (OR=1.81, CI: 1.00-3.28) was weakly associated with membership in the late-onset trajectory group. Conclusions The development of overweight in childhood follows two different trajectories, which have common and distinct risk factors that could be the target of early preventive interventions