On the charge of nanograins in cold environments and Enceladus dust

In very-low energy plasmas, the size of nanograins is comparable to the distance (the so-called Landau length) at which the interaction energy of two electrons equals their thermal energy. In that case, the grain's polarization induced by approaching charged particles increases their fluxes and reduces the charging time scales. Furthermore, for grains of radius smaller than the Landau length, the electric charge no longer decreases linearly with size, but has a most probable equilibrium value close to one electron charge. We give analytical results that can be used for nanograins in cold dense planetary environments of the outer solar system. Application to the nanodust observed in the plume of Saturn's moon Enceladus shows that most grains of radius about 1 nm should carry one electron, whereas an appreciable fraction of them are positively charged by ion impacts. The corresponding electrostatic stresses should destroy smaller grains, which anyway may not exist as crystals since their number of molecules is close to the minimum required for crystallization.Comment: Revised version of paper submitted to Icaru

Cortisol awakening response in infants during the first six postnatal months and its relation to birth outcome

Context: The rise of cortisol concentrations after awakening is well documented in adults and children and commonly used as easily accessible marker of hypothalamic-pituitary-adrenal (HPA) reactivity. Objective: The purpose of this study was to demonstrate the existence of a salivary cortisol awakening response (CAR) in infants, and to estimate its association with birth outcome. Setting: The study was conducted in the general community. Participants: Healthy infants up to six months age (N=64). Main outcome measures: Mothers were instructed to collect their infant’s saliva immediately and 30 min after awakening on two days within 45 days, irrespective of awakening time. Information on birth outcome was collected from medical records and questionnaires. Results: Linear mixed models analysis revealed a significant rise of infant salivary cortisol concentrations within 30 minutes after awakening (b=0.128, SE=0.024, t61=5.31, p<0.001), which was quite stable across the two sampling days (r=0.40, p=0.002). The infant CAR was predicted by length of gestation (t61=2.43, p=0.018). Conclusions: The current data demonstrate the existence of a CAR in infants as early as during the first six postnatal months; its relationship with length of gestation supports its usefulness for questions related to developmental neuroscience. Therefore, the infant CAR emerges as non-invasive biomarker of HPA axis dynamics at this early stage of life, with relevance for future research and potential clinical applications

Andrew Sobanet. Generation Stalin: French Writers, the Fatherland, and the Cult of Personality. Indiana UP, 2018.

Review of Andrew Sobanet. Generation Stalin: French Writers, the Fatherland, and the Cult of Personality. Indiana UP, 2018. xi + 296 pp

Foreign Language Enrollment Attrition: Exploring the Key Factors of Motivation, Academic Success, Instruction, and Anxiety at the Elementary Level

The Olathe District Schools has been experiencing a trend of enrollment decline in middle School Spanish since 2007 despite the implementation of a video-based elementary Spanish program. The purpose of this study was to investigate the influential factors of motivation (integrative/instrumental), instruction, academic success, and anxiety, which are found in the literature related to foreign language enrollment attrition, to determine whether any of these four variables could predict whether students continued or discontinued enrollment in Spanish upon entering their middle school years in the Olathe School District. Gardner's mini-AMTB with slight modifications was administered to 560 5th grade students. A binary logistic regression was then run. Results revealed that students with higher levels of integrative motivation were more likely to continue in their Spanish studies upon entering middle school. In addition, the results of this study support the findings of several foreign language program enrollment attrition studies done at the secondary level. Recommendations for the Superintendent, International Language Assistants (ILA's), and the District Foreign Language Coordinator were made based on the findings of this study

Dust in the Interplanetary Medium

The mass density of dust particles that form from asteroids and comets in the interplanetary medium of the solar system is, near 1 AU, comparable to the mass density of the solar wind. It is mainly contained in particles of micrometer size and larger. Dust and larger objects are destroyed by collisions and sublimation and hence feed heavy ions into the solar wind and the solar corona. Small dust particles are present in large number and as a result of their large charge to mass ratio deflected by electromagnetic forces in the solar wind. For nano dust particles of sizes 1 - 10 nm, recent calculations show trapping near the Sun and outside from about 0.15 AU ejection with velocities close to solar wind velocity. The fluxes of ejected nano dust are detected near 1AU with the plasma wave instrument onboard the STEREO spacecraft. Though such electric signals have been observed during dust impacts before, the interpretation depends on several different parameters and data analysis is still in progress.Comment: 12 pages, 8 figures, accepted for publication in Plasma Physics and Controlled Fusion, special issue 37th EPS Conference on Plasma Physic

Les hommes qui enseignent à l’école primaire :: une espèce en voie d’extinction ?

Dans le contexte actuel de l’école primaire, l’absence d’enseignants masculins est indéniable. Mais comment comprendre ce phénomène ? Ce que nous avons voulu identifier en premier lieu dans ce travail de recherche sont les causes de l’absence des hommes dans la formation pédagogique ainsi que dans l’enseignement primaire. Ensuite, nous avons voulu brosser le tableau général de l’homme dans l’enseignement primaire. Quel regard porte-t-il sur sa profession et comment pense-t-il être perçu ? Quelles sont ses motivations ? Comment définit-il son statut ? Y a-t-il une place pour le carriérisme dans sa profession d’enseignant ? Et quel rôle tient le salaire dans tout cela ? Telles sont les thématiques abordées dans ce travail de recherche

The effects of stereotype disconfirming information and self-disclosure on stereotype endorsement, prejudice, and social tolerance of schizophrenia and major depressive disorder.

The current study examined how Disclosure, Stereotype Disconfirming Information, and Stereotype Disconfirming Information and Disclosure Combined) influences an individual\u27s stigma (stereotype endorsement, emotional reactions, and discrimination) against individuals with Schizophrenia and Depression. The results of this experiment suggest that both Stereotype Disconfirming Information and Disclosure are successful in reducing stereotypes, emotional reactions, and social distance in the context of an interpersonal encounter. Self-disclosure, however, is stronger in increasing Pity and decreasing the desire for Social Distance than Stereotype Disconfirming Information. The combination of Stereotype Disconfirming Information and Disclosure provided the strongest stigma reduction, suggesting that Disclosure can benefit from the addition of Stereotype Disconfirming Information. However, our study also suggests that these strategies may have different effects depending on the disorder in question. The implication of these results and directions for future studies will be discussed

On the plasma quasi-thermal noise in the outer heliosphere

The recent paper by Li et al. on electron quasi-thermal noise in the outer heliosphere is flawed. It assumes the plasma drift speed to be much smaller than the electron thermal speed, even though both quantities are of the same order of magnitude in the outer heliosphere inward of the termination shock, because of the low plasma temperature. In this case, the Langmuir wave dispersion equation and the quasi-thermal noise in the antenna frame are completely changed. Furthermore, these calculations neglect the shot noise, which should produce a large contribution below the plasma frequency with the Voyager antennas in the outer heliosphere.Comment: Accepted as Research Note of the AAS (18/03/2024

Maximum relative speeds of living organisms: why do bacteria perform as fast as ostriches?

International audienceSelf-locomotion is central to animal behaviour and survival. It is generally analysed by focusing on preferred speeds and gaits under particular biological and physical constraints. In the present paper we focus instead on the maximum speed and we study its order-of-magnitude scaling with body size, from bacteria to the largest terrestrial and aquatic organisms. Using data for about 460 species of various taxonomic groups, we find a maximum relative speed of the order of magnitude of ten body lengths per second over a 10 20-fold mass range of running and swimming animals. This result implies a locomotor time scale of the order of one tenth of second, virtually independent on body size, anatomy and locomotion style, whose ubiquity requires an explanation building on basic properties of motile organisms. From first-principle estimates, we relate this generic time scale to other basic biological properties, using in particular the recent generalisation of the muscle specific tension to molecular motors. Finally, we go a step further by relating this time scale to still more basic quantities, as environmental conditions at Earth in addition to fundamental physical and chemical constants