Theoretical study of the regio- and stereoselectivity of the 1,3-DC reaction of 2,3,4,5-tetrahydropyridine-l-oxide with methyl crotonate

A theoretical study of the regio- and stereoselectivities of the 1,3-dipolar cycloaddition reaction between methyl crotonate and 2,3,4,5-tetrahydropyridine-l-oxide has been carried out using density functional theory (DFT) calculations at B3LYP/6-31G(d) level of theory. Analysis of the global reactivity and local electrophilicity indices has been used to explaining the regioselectivity of the titled reaction. Overall, our results show that the studied 1, 3-dipolar cycloaddition reactions favor the formation of the meta-endo cycloadduct in both cases. The bond order and charge transfer at the transition states and activation energies indicate that these reactions proceed via an asynchronous concerted mechanism. Thermodynamic and kinetic quantities for the possible stereoisomeric and regioisomeric pathways have been calculated at gas and solvent phase. Solvent effects do not modify the gas-phase selectivities but slightly increases the reactivity of the reagents. A good concordance is found between the obtained results and the experimental outcomes

ZnTe/CdSe type-II core/shell spherical quantum dot under an external electric field

International audienceWe have investigated in the framework of the envelope function approximation and taking into account the dependence of the electron effective mass on radius the energy of an electron inside a ZnTe/CdSe core/shell spherical quantum dot. In order to make the problem more realistic, we describe the conduction band-edge alignment between core and shell materials by a finite height barrier. By applying the Ritz variational principle the effect of the electric field on the electronic states was also examined. Our numerical results show the opportunity to control the energy states position of the charge carriers inside our core/shell nanostructures by controlling the size (core radius, shell thickness) of the nanostructure and the strength of the external electric field

The influence of layer defect in the Ferroelectric films

Using the modified transverse Ising model, and the effective field theory based on the probability distribution technique, the phase transition temperature, the polarization and susceptibility for ferroelectric thin films with structural defects are studied. It is shown that the defect layers in ferroelectric thin films can induce strong increase or decrease of the critical temperature of ferroelectric phase transition due to different exchange interactions in the defect layers. The obtained results are in qualitative agreement with experimental data for thin ferroelectric film with different thickness.Using the modified transverse Ising model, and the effective field theory based on the probability distribution technique, the phase transition temperature, the polarization and susceptibility for ferroelectric thin films with structural defects are studied. It is shown that the defect layers in ferroelectric thin films can induce strong increase or decrease of the critical temperature of ferroelectric phase transition due to different exchange interactions in the defect layers. The obtained results are in qualitative agreement with experimental data for thin ferroelectric film with different thickness

Stability of an Exciton bound to an Ionized Donor in Quantum Dots

Total energy, binding energy, recombination rate (of the electron hole pair) for an exciton (X) bound in a parabolic two dimensional quantum dot by a donor impurity located on the z axis at a distance d from the dot plane, are calculated by using the Hartree formalism with a recently developed numerical method (PMM) for the solution of the Schroedinger equation. As our analysis indicates there is a critical dot radius such that for radius less than the critical radius the complex is unstable and with an increase of the impurity distance this critical radius increases. Furthermore, there is a critical value of the mass ratio such that for mass ratio less than the critical value the complex is stable. The appearance of this stability condition depends both on the impurity distance and the dot radius, in a way that with an increase of the impurity distance we have an increase in the maximum dot radius where this stability condition appears. For dot radii greater than this maximum dot radius (for fixed impurity distance) the complex is always stable.Comment: 17 pages, 7 figures Applying a new numerical method which is based on the adiabatic stability of quantum mechanics, we study the stability of an exciton (X) bound in a parabolic two dimensional quantum dot by a donor impurity located on the z axis at a distance d from the dot plan

Influence of long-range dipolar interactions on the phase stability and hysteresis shapes of ferroelectric and antiferroelectric multilayers

Phase transition and field driven hysteresis evolution of a two-dimensional Ising grid consisting of ferroelectric-antiferroelectric multilayers that take into account the long range dipolar interactions were simulated by a Monte-Carlo method. Simulations were carried out for a 1+1 bilayer and a 5+5 superlattice. Phase stabilities of components comprising the structures with an electrostatic-like coupling term were also studied. An electrostatic-like coupling, in the absence of an applied field, can drive the ferroelectric layers towards 180º domains with very flat domain interfaces mainly due to the competition between this term and the dipole-dipole interaction. The antiferroelectric layers do not undergo an antiferroelectric-to-ferroelectric transition under the influence of an electrostatic-like coupling between layers as the ferroelectric layer splits into periodic domains at the expense of the domain wall energy. The long-range interactions become significant near the interfaces. For high periodicity structures with several interfaces, the interlayer long-range interactions substantially impact the configuration of the ferroelectric layers while the antiferroelectric layers remain quite stable unless these layers are near the Neel temperature. In systems investigated with several interfaces, the hysteresis loops do not exhibit a clear presence of antiferroelectricity that could be expected in the presence of anti-parallel dipoles, i. e., the switching takes place abruptly. Some recent experimental observations in ferroelectric-antiferroelectric multilayers are discussed where we conclude that the different electrical properties of bilayers and superlattices are not only due to strain effects alone but also long-range interactions. The latter manifests itself particularly in superlattices where layers are periodically exposed to each other at the interfaces

Tuberculose de l’omoplate chez l’enfant: à propos d’une localisation exceptionnelle

La tuberculose osseuse est une maladie infectieuse qui constitue un véritable problème de santé publique dans les pays en voie de développement où elle sévit de manière endémique. L'atteinte ostéo-articulaire représente 1 à 5% des cas de tuberculose toutes localisations confondues, l'atteinte de l'épaule reste très rare et représente 1 à 2% des localisations ostéo-articulaires. Nous présentons ici un nouveau cas exceptionnel d'une infection tuberculeuse de l'omoplate, atteignant le corps de l'omoplate. La tuberculose est encore un diagnostic différentiel important des maladies rares ou chroniques des os, notamment tumorales. Le diagnostic a été redressé par l'étude anatomopathologique.Mots clés: Omoplate, tuberculose, enfantEnglish Title: Scapular involvement: uncommon presentation of childhood tuberculosisEnglish AbstractTuberculosis of bone is an infectious disease which represents a major public health problem in developing countries where it is endemic. Osteoarticular involvement accounts for 1-5% of all cases of tuberculosis, shoulder involvement is very rare and accounts for 1-2% of all cases of osteoarticular tuberculosis. We here report an uncommon case of TB infection involving the scapula, reaching the scapular body. Tuberculosis is still an important differential diagnosis of rare or chronic bone diseases, including tumors. In our study anatomopathological examination led to the diagnosis.Keywords: Scapula, tuberculosis, chil

Mixed neuroendocrine-non-neuroendocrine neoplasms of the right colon: a case report

Mixed neuroendocrine-non neuroendocrine neoplasm (MiNENs) is a rare gastrointestinal neoplasm that has been redefined by the World Health Organization (WHO) in 2017 as the association of two types of components, neuroendocrine and non-neuroendocrine, each of them present in at least 30% of the tumour mass. Small case reports and case series have demonstrated the occurrence of this neoplasm in the colon. We here report the case of a 47-year-old man undergoing colonscopy for anemia. This showed impassable polypoidal tumor budding in the right colic flexure. Computerized tomography (CT) scan and magnetic resonance imaging (MRI) showed the presence of liver metastases. As the tumor was hemorrhagic, right hemicolectomy with lymph node dissection was performed. The histological examination showed MiNEN of the ascending colon. The patient received adjuvant chemotherapy

Психометрическое исследование: валидация инструмента оценки качества школьного образования

Introduction. School evaluation is a complex process, and it is now a central priority for education systems with varied practices and multiple actors. It affects many aspects: teachers, institutions, training, management, educational policies, and design. Thus, it is necessary to think first about the regulation of the indicators that will serve as a system of valuation/sanction of the quality measured. Aim. The present research aims to construct a grid for evaluating pedagogical and administrative quality of secondary school. Furthermore, producing a quality evaluation system based on indicators to allow quality to be witnessed remains a challenge. We have optimized and validated a coherent evaluation system of indicators (School Quality Assessment System SEQES). It is based on rigorous scientific research, evaluating school quality and testing with 196 stakeholders (school administrators, teachers, educational inspectors, and planning). Research methodology and methods. The design and validation of this evaluation grid were carried out based on Churchill’s (1979) theory of measurement with a methodological process of numerous steps of analysis and emergent categorisation of items, scaling, refinement, and field testing. Results and scientific novelty. The exploratory factor analysis (EFA) was administered to 196 stakeholders and initially yielded 153 items from 289. They articulated qualitative steps (interviews with members of audit cells, techniques: Focus Group, TGN, TRIAGE) and quantitative (Exploratory Factor Analysis). The results made it possible to identify a scale of seven dimensions and fields of 37 items, considering theoretical, empirical, and methodological considerations. Practical significance. This measurement instrument is a toolbox that can be developed for decision-makers to establish a reference system for systematic external quality evaluation at the national level and a toolkit for inspectors and headteachers.Введение. Оценка школьного образования является сложным процессом, и в настоящее время это один из центральных приоритетов в системах образования с различными видами практики и многочисленными субъектами. Она затрагивает многие аспекты: учителей, учреждения, обучение, управление, политику в области образования и дизайн. Таким образом, необходимо сначала подумать о регулировании показателей, которые будут служить системой оценки/санкционирования измеряемого таким образом качества. Цель. Основная цель – построить шкалу для оценки педагогического и административного качества средних школ. Построение такой системы на основе показателей, которые позволили бы засвидетельствовать качество, остается сложной задачей. В этом контексте авторы оптимизировали и утвердили последовательную систему оценки показателей (Система оценки качества школы – SEQES), основанную на строгих научных исследованиях, оценивающих качество школы, и провели эксперимент с 196 участниками и исходными лицами (администраторы школ, учителя, педагогические инспекторы, представители руководства и отделов планирования). Методология и методы исследования. Разработка и утверждение данной оценочной шкалы осуществлялись на основе теории измерения Черчилля (1979) и методологического процесса, состоящего из многочисленных этапов анализа и эмерджентной категоризации пунктов, шкалирования, уточнения и полевого тестирования. Результаты и научная новизна. В исследовательском факторном анализе принялиучастие 196 заинтересованных лиц, и первоначально он дал результаты по 153 пунктам из 289. Сформулированы качественные этапы (интервью с членами аудиторских ячеек, методики: фокус-группа, TGN, TRIAGE) и количественные (исследовательский факторный анализ). Результаты позволили определить шкалу из 7 измерений и полей из 37 пунктов с учетом теоретических, эмпирических и методологических принципов. Практическая значимость. Эта оценочная шкала является инструментарием, который может использоваться для создания эталонной системы для систематической внешней оценки качества на национальном уровне, лицами, принимающими решения, а также инспекционными органами и руководителями учебных заведений

Action d'un champ magnétique et d'un champ électrique sur un exciton lié à une impureté de type donneur ionisé dans un puits quantique de semi-conducteur

Not availableLe travail présenté dans ce mémoire de thèse est consacré à l'étude des propriétés électroniques d'un exciton lié à une impureté ionisée de type donneur (D+, X), dans les puits quantiques de type GaAs/Ga1-xAlxAs et CdTe/Cd1-xZnxTe, en présence des champs magnétique et électrique. Cette étude s'inscrit dans un contexte de recherche en plein développement, en raison des applications potentielles des nanostructures dans le domaine de l'optoélectronique. dans le cadre de l'approximation de la masse effective et dans un modèle à deux bandes paraboliques simples et non dégénérées, nous avons comparé l'énergie de corrélation du complexe (D+, X), du donneur neutre (D0) et de l'exciton libre (X) dans un puits quantique. Nous avons déduit que le complexe est toujours stable dans le domaine de variation de la largeur L du puits étudié. Nous avons discuté également l'effet de la position du donneur dans un puits quantique sur la stabilité du complexe pour une largeur du puits donnée. Enfin nous avons examiné l'influence d'un champ magnétique et d'un champ électrique sur l'énergie de l'état fondamental et sur la stabilité du complexe dans un puits quantique. Dans le cas d'un puits quantique de type GaAs/Ga1-xAlxAs, l'application d'un champ magnétique conduit à une augmentation de l'énergie du complexe. La stabilité du complexe doit être étudiée soit par rapport au donneur, soit par rapport à l'exciton suivant une valeur critique du champ qui diminue quand la largeur du puits augmente. Dans les puits quantiques de type GaAs/Ga1-xAlxAs et CdTe/Cd1-xZnxTe le complexe est stable par rapport aux produits de dissociation les plus probables, dans tout le domaine de la largeur du puits et de l'intensité de champ magnétique étudié. En présence d'un champ électrique, l'énergie de corrélation du complexe dépend de l'intensité du champ applique : dans le cas d'un puits quantique de type GaAs/Ga1-xAlxAs, cette dépendance, faible pour un puits étroit, devient significative pour un puits large. Le complexe est stable dans le domaine de la largeur du puits et d'intensité du champ électrique étudiés