The 2D dynamics of radiative zones of low-mass stars

In the context of secular evolution, we describe the dynamics of the radiative core of low-mass stars to understand the internal transport of angular momentum in such stars which results in a solid rotation in the Sun from 0.7R_sun to 0.2R_sun and a weak radial core-envelope differential rotation in solar-type stars. This study requires at least a 2D description to capture the latitudinal variations of the differential rotation. We build 2D numerical models of a radiative core on the top of which we impose a latitudinal shear so as to reproduce a cylindrical differential rotation in a convective envelope. We perform a systematic study over the Rossby number measuring the latitudinal differential rotation at the radiative-convective interface. The imposed shear generates a geostrophic flow implying a cylindrical differential rotation. When compared to the baroclinic flow that arises from the stable stratification, we find that the geostrophic flow is dominant when the Rossby number is high enough with a cylindrical rotation profile. For low Rossby numbers, the baroclinic solution dominates with a quasi-shellular rotation profile. Using scaling laws from 3D simulations, we show that slow rotators are expected to have a cylindrical rotation profile. Fast rotators may have a shellular profile at the beginning of the main-sequence in stellar radiative zones. This study enables us to predict different types of differential rotation and emphasizes the need of a new generation of 2D rotating stellar models developed in synergy with 3D numerical simulations. The shear induced by a surface convective zone has a strong impact on the dynamics of the underlying radiative zone in low-mass stars. But, it cannot produce a flat internal rotation profile in a solar configuration calling for additional processes for the transport of angular momentum in both radial and latitudinal directions.Comment: 12 pages, 7 figures, accepted for publication in A&

2D dynamics of the radiative core of low mass stars

Understanding the internal rotation of low mass stars all along their evolution is of primary interest when studying their rotational dynamics, internal mixing and magnetic field generation. In this context, helio- and asteroseismology probe angular velocity gradients deep within solar type stars at different evolutionary stages. Still the rotation close to the center of such stars on the main sequence is hardly detectable and the dynamical interaction of the radiative core with the surface convective envelope is not well understood. For instance, the influence of the differential rotation profile sustained by convection and applied as a boundary condition to the radiation zone is very important in the formation of tachoclines. In this work, we study a 2D hydrodynamical model of a radiative core when an imposed, solar or anti-solar, differential rotation is applied at the upper boundary. This model uses the Boussinesq approximation and we find that the shear induces a cylindrical differential rotation associated with a unique cell of meridional circulation in each hemisphere (counterclockwise when the shear is solar-like and clockwise when it is anti-solar). The results are discussed in the framework of seismic observables (internal rotation rate, core-to-surface rotation ratio) while perspectives to improve our modeling by including magnetic field or transport by internal gravity waves will be discussed.Comment: 5 pages, 4 figures. To appear in the proceedings of "Seismology of the Sun and the Distant Stars 2016, Joint TASC2 & KASC9 Workshop - SPACEINN & HELAS8 Conference" (ed. M\'ario J. P. F. G. Monteiro, Margarida S. Cunha, Jo\~ao Miguel T. Ferreira ), Azores, Portugal, 11-15 July 201

Historia de las creencias y ceremonias religiosas de todos los pueblos

Es reimp. de la ed. de París

AFFECTIVE COMMITMENT, MENTORING, AND ANTICIPATED TURNOVER AMONG MILLENNIALS

ABSTRACT Millennials comprise the largest group of individuals in the workforce, yet organizations struggle to keep millennials engaged in the workplace. Millennials move from job to job, with an average stay at one employer between 12 and 18 months (Hechl, 2017). Researchers have reported that millennials cause the majority of turnover in the workplace. Globally, human resources practitioners experience difficulties retaining millennials (Sahraee et al., 2021). Previous studies have researched millennials, affective commitment, mentoring, and turnover. However, no known research has used all four factors to solve a global problem. In their discussion of the highly competitive labor market, Ramírez García et al. (2019) determined that employers must compete for talented millennials to maintain appeal within the workforce. Further, turnover remains costly for organizations (Ramírez García et al., 2019). This study examined the relationship between affective commitment, mentoring, and anticipated turnover among millennials in the public sector. The researcher attempted to answer the research question and objectives by conducting a non-experimental, quantitative correlation study using surveys through an online platform called Amazon Mechanical Turk. The study resulted in four findings. This study confirms that as affective commitment increases, anticipated turnover decreases. The results indicated a positive correlation between affective commitment and mentoring in assessing the relationship between affective commitment and mentoring. The results revealed that mentoring impacts millennials’ decision to stay with their organization. The findings indicated a negative correlation between mentoring and anticipated turnover. However, a mediation analysis could not be performed to answer research objective five. The findings from this study could contribute as a foundation for assessing millennials in the private and non-profit sectors. Also, organizations should implement some form of mentoring in the workplace to increase affective commitment in retaining millennials. Keywords: human resources, mentoring, millennials, retention, turnover, workforc

The impact of whole-plant instruction preservice elementary teachers\u27 understanding of plant science principles

The purpose of this research was to determine how an inquiry-based, whole-plant instructional strategy would affect preservice elementary teachers’ understanding of plant science principles. This study probed: what preservice teachers know about plant biology concepts before and after instruction, their views of the interrelatedness of plant parts and the environment, how growing a plant affects preservice teachers’ understanding, and which types of activity-rich plant themes studies, if any, affect preservice elementary teachers’ understandings. The participants in the study were enrolled in two elementary science methods class sections at a state university. Each group was administered a preinstructional test at the beginning of the study. The treatment group participated in inquiry-based activities related to the Principles of Plant Biology (American Society of Plant Biologists, 2001), while the comparison group studied those same concepts through traditional instructional methods. A focus group was formed from the treatment group to participate in co-concept mapping sessions. The participants’ understandings were assessed through artifacts from activities, a comparison of pre- and postinstructional tests, and the concept maps generated by the focus group. Results of the research indicated that the whole-plant, inquiry-based instructional strategy can be applied to teach preservice elementary teachers plant biology while modeling the human constructivist approach. The results further indicated that this approach enhanced their understanding of plant science content knowledge, as well as pedagogical knowledge. The results also showed that a whole-plant approach to teaching plant science concepts is an instructional strategy that is feasible for the elementary school. The theoretical framework for this study was Human Constructivist learning theory (Mintzes & Wandersee, 1998). The content knowledge and instructional strategy was informed by the Principles of Plant Biology (American Society of Plant Biologists, 2001) and Botany for the Next Millennium (Botanical Society of America, 1995). As a result of this study, a better understanding of the factors that influence preservice elementary teachers’ knowledge of plant science principles may benefit elementary science educator in preparing teachers that are “highly qualified.

A new case of duplication of the metasoma and telson in the scorpion \u3cem\u3eEuscorpius flavicaudis\u3c/em\u3e (DeGeer, 1778) (Euscorpiidae)

The specimen presented in this note is a juvenile female of Euscorpius flavicaudis (DeGeer, 1778), with a total length of 13 mm, including the telson. It was collected by the junior author, while searching for scor-pions in the Alps, during the early summer of 2010, at Laragne-Montéglin, Hautes-Alpes in France

Experiencing Financial Aid at a Historically White Institution: A Critical Race Analysis

While scholars have looked at the intersection of financial aid and various identities, little work has examined how, if at all, race and racism are imbued into financial aid in higher education using qualitative inquiry. This paper begins that work by using a Critical Race Theory lens to analyze how, in the seemingly colorblind structure and process of financial aid, race matters. Using interview data collected from 35 Black juniors and seniors at a selective, historically White institution (HWI), the authors examine how race has informed students’ perceptions of themselves, their families, and their futures through their experiences with financial aid. The authors found that financial aid took the form of 1) a racial stereotype and microaggression, 2) added labor in searching for scholarships, and 3) a factor in reinforcing the racial wealth divide. More than a resource to facilitate college access and persistence, these scholars argue that financial aid is racialized, uniquely shaping the campus experience of Black collegians

Dynamique des étoiles de masse intermédiaire en rotation rapide et contraction gravitationnelle

Rotation greatly impacts stellar structure and evolution. Particularly, it is known to be responsible of macroscopic mixings of chemical elements and transport of angular momentum within the radia­tive zones of stars. In the first part of this thesis, we show how the actual state of stellar modeling calls for a bi-dimensional approach going beyond usual assumptions of slow rotation and spherical differential rotation. We develop, in the second part of this thesis, a simplified model (Boussinesq approximation) of rapidly rotating stars in two dimensions, where the establishing differential rotation and associated meridional circulation are solved self-consistently. We describe the relevant parameters of the flow induced by a gravitational contraction in a stably stratified environment. In the third part, we demonstrate that this spin-up flow outweighs the baroclinic flow on a Kelvin-Helmholtz timescale. The differential rotation adopts an universal cylindrical profile and the meridional circulation is typical of the spin-up flow. A Stewartson layer appears too upon the tangent cylinder to the core and could explain an efficient coupling between the rotation of the core and the one of the envelope for stars at the end of the Main Sequence. In the last part of this thesis, we study Achernar, a rapidly rotating Be star, with the full-compressible ESTER code. Models we obtain tend to show that the star is undergoing a post Main Sequence gravitational contraction. To account this, the ESTER code has been modified to follow the chemical evolution of stars on a nuclear timescale.La rotation a un impact majeur sur la structure et l'évolution des étoiles. En particulier, elle est connue pour être responsable de processus de mélanges macroscopiques des éléments chimiques et de transport de moment cinétique au sein des zones radiatives des étoiles. Dans la première partie de cette thèse, nous montrons comment l'état actuel de la modélisation stellaire justifie une nouvelle approche bi-dimensionnelle qui ne repose pas sur les hypothèses usuelles de rotation faible ou de rotation différentielle sphérique. Nous développons, dans la deuxième partie, un modèle simplifié (approximation de Boussinesq) d'étoiles en rotation rapide, en deux dimensions, où la rotation différentielle qui s'instaure et la circulation méridienne associée sont calculées de manière cohérente. Nous y identifions les paramètres pertinents à la description de l'écoulement induit par une contraction gravitationnelle dans un environnement stratifié de manière stable. Dans la troisième partie, nous démontrons que cet écoulement de spin-up l'emporte sur l'écoulement barocline à l'issue d'un temps de Kelvin-Helmholtz. La rotation différentielle adopte un profil universel cylindrique et la circulation méridienne est celle d'un écoulement de spin-up. Une couche de Stewartson s'établit aussi sur le cylindre tangent au noyau du modèle et pourrait être la source d'un couplage efficace de la rotation du noyau et de celle de l'enveloppe d'une étoile en fin de Séquence Principale. Dans la dernière partie de cette thèse, nous étudions Achernar, étoile en rotation rapide de type Be à l'aide du code compressible ESTER. Les modèles obtenus tendent à montrer que l'étoile est en contraction gravitationnelle post-Séquence Principale. Pour en rendre compte, le code ESTER a été modifié afin de suivre l'évolution chimique de l'étoile sur une échelle de temps nucléaire

Genetic variation in height and diameter of tamarack (Larix Laricina) and their correlation with syllepsis

The broad sense heritability of total height, annual height increment, diameter, volume index and syllepsis of II provenances of tamarack in northwestern Ontario were examined. Genetic and Pearson Product Moment correlations among these characters were also examined. Broad sense heritability ranged from O.I3 at age three to 0.36 at age 11 for total height among provenances. Broad sense heritability within individual provenances generally increased from age three to age II but showed no geographic trend. Genetic age-age correlation between total height at ages three and 1I was 0.61. Number of sylleptic long shoots at age three and four correlated better with height at age II than height at the early ages. Good correlation between height and diameter suggests that both height and diameter could be improved by selecting for total height