Magnetic nanoparticles of complex architecture core-shell : exchange bias coupling and dipolar interaction

Le travail de thèse est consacré à l'étude numérique de nanoparticules (NPs) magnétiques core@shell Fe3O4@CoO présentant des propriétés d'échange bias (EB) en utilisant la méthode Monte Carlo (MC). En particulier, nous nous sommes concentrés sur l'étude de l'effet des réponses collectives (interactions inter-particules telles que les interactions dipolaires (ID)) sur les propriétés magnétiques de ces structures. Des résultats expérimentaux préliminaires, montrant l'existence d'une relation entre le décalage du cycle d'hystérésis et l'interaction entre NPs, ont motivé le travail numérique mené dans le cadre de cette thèse.La première partie de ce mémoire est une étude méthodologique visant à trouver les conditions optimales pour simuler les cycles d'hystérésis d'une façon correcte par MC.Les résultats révèlent une dépendance linéaire entre le champ coercitif Hc et la constante d'anisotropie effective pour des conditions non biaisées (algorithme libre, algorithme du cône, algorithme mixte). La deuxième partie est consacrée à l'étude, à l'échelle atomique, des nanostructures présentant l'EB dont nous avons reproduit les deux caractéristiques (un décalage du cycle d'hystérésis, une augmentation importante de Hc).Nous avons également proposé une méthode permettant l'évaluation de la valeur de l'anisotropie effective.En passant à l'échelle d'une assemblée de NPs, plusieurs modèles furent étudiés. Nous arrivons à interpréter les résultats expérimentaux selon le degré d'agrégation des NPs. Nous montrons que l'agrégation (interactions d'échanges entre les NPs) a un effet direct sur le champ d'échange bias, mais le rôle d'ID sur le champ d'échange mérite des études complémentaires.This thesis is dedicated to the numerical study by means of Monte Carlo (MC) simulations of core@shell Fe3O4@CoO magnetic nanoparticles (NPs) presenting exchange bias properties (EB). In particular, we focused our study on the effect of collective responses (inter-particle interactions as dipolar interactions (DI)) on the magnetic properties of these structures. Our numerical work is motivated by some preliminary experimental results showing the existence of a relationship between the hysteresis loop shift (exchange bias field) and the interaction between NPs. The first part of this thesis is a methodological study to figure out the optimal conditions to simulate hysteresis loops correctly by MC. The results reveal that the coercive field Hc is linearly related to the effective anisotropy constant for non-biased conditions (free algorithm, cone algorithm, mixed algorithm). The second part is dedicated to the study of exchange-biased nanostructures at the atomic scale. We have been able to reproduce both characteristics of EB (hysteresis loop shift, significant increase in Hc). A method allowing the evaluation of the effective anisotropy has been proposed. Considering an assembly of nanoparticles, several models are studied. The experimental results are interpreted according to the degree of aggregation of NPs. It was shown that the aggregation (exchange interactions between NPs) has a direct effect on the exchange bias field, but the role of the ID on the exchange field requires complimentary calculations to be clarified

Assessment of Chemical and Microbiological Drinking Water of Beirut and Mount Lebanon

Lebanon is known for its abundant water resources, but it faces significant challenges with water supply shortages, particularly in delivering water to residential areas and public facilities. This problem is compounded by a high rate of pollution, both in pipelines and bottled water. To address the issue of water-related diseases, this research was conducted to assess the water quality of 79 drinking water samples from Beirut and Mount Lebanon using the Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES) with Ultra Sonic Nebulizer (USN) method. The study found that most element concentrations in the water samples are within the acceptable range set by the World Health Organization (WHO). However, four elements were highlighted as areas of concern: sodium, arsenic, mercury, and calcium, as their concentrations were outside the accepted WHO range. Specifically, 23% of sites showed high mercury concentrations from various potential sources, 76% of sites had elevated arsenic levels, and 91% of sites had low calcium concentrations, indicating weak mineralization in the drinking water. Additionally, 20% of sites had high sodium concentrations, and 9% had high calcium concentrations due to the presence of carbonate rock reservoirs, particularly limestone, which increases water hardness. The microbiological analysis of water samples showed that 60.76% of the samples contained bacteria. Among the samples, 46% were contaminated by total coliform, and 33% showed contamination by fecal coliform. Additionally, 30% of the samples contained Pseudomonas aeruginosa, and 39% were contaminated with E. coli. These findings indicate that a significant percentage of the tested water samples have microbial contamination, posing potential health risks to consumers. Proper water treatment and monitoring measures are essential to ensure the safety and quality of drinking water and to reduce the incidence of waterborne diseases. Keywords: Lebanon, Drinking water, Pollution, heavy metals, treatment. DOI: 10.7176/JEES/13-6-01 Publication date:August 31st 202

Chemical Inhomogeneity in Iron Oxide@CoO Core–Shell Nanoparticles: A Local Probe Study Using Zero-Field and In-Field 57 Fe Mössbauer Spectrometry

International audienc

An Update on the Tissue Renin Angiotensin System and Its Role in Physiology and Pathology

In its classical view, the renin angiotensin system (RAS) was defined as an endocrine system involved in blood pressure regulation and body electrolyte balance. However, the emerging concept of tissue RAS, along with the discovery of new RAS components, increased the physiological and clinical relevance of the system. Indeed, RAS has been shown to be expressed in various tissues where alterations in its expression were shown to be involved in multiple diseases including atherosclerosis, cardiac hypertrophy, type 2 diabetes (T2D) and renal fibrosis. In this chapter, we describe the new components of RAS, their tissue-specific expression, and their alterations under pathological conditions, which will help achieve more tissue- and condition-specific treatments