Thermodynamic Modeling of Aluminum-Magnesium-Rare Eearth Systems

Le magnésium et ses alliages sont les matériaux métalliques structuraux les plus légers et, de ce fait, jouent un rôle croissant dans les domaines de l’automobile, de l’aérospatial et de l’électronique. Bien que le magnésium puisse être recyclé aisément et ait une conductivité thermique élevée et de bonnes propriétés de protection électromagnétique, il présente des inconvénients : une force insuffisante, une faible résistance à la corrosion et au fluage,… L’utilisation d’alliages de magnésium est l’une des méthodes fréquemment utilisées pour améliorer les propriétés du magnésium. L’ajout de terres rares (RE : « Rare Earth ») à des alliages de magnésium peut améliorer leur force et leur résistance au fluage à température élevée en formant des précipités stables à base de Mg (REyMgx), Al (REyAlx) ou Zn (REyZnx). Parallèlement au développement d’alliages de Mg, les alliages Al–RE (aluminium-terre rare) sont d’intérêt en science des matériaux dans le cadre du développement d’alliages légers. Les terres rares sont des éléments d’alliage d’importance croissante pour les alliages d’aluminium à cause de leur capacité à améliorer les propriétés à haute température et les caractéristiques de moulage. De plus, les alliages Al–RE rapidement solidifiés offrent aussi la possibilité d’obtenir un meilleur comportement en corrosion. Les méthodes calculatoires sont des outils importants et puissants pour la sélection et l’élaboration de nouveaux alliages de magnésium. Elles aident à comprendre le comportement des matériaux et réduisent significativement la quantité de travail expérimental requise. De plus, les terres rares pures sont très coûteuses. Jusqu’à présent, il n’existait aucun diagramme de phases pour les systèmes Mg-Al-Mischmetal optimisé à l’aide du modèle quasichimique (prenant en compte l’ordre à courte distance) pour la phase liquide, à l’exception de quelques optimisations récentes (Al–Ce, Al–Y, Al–Sc) effectuées par le Dr. Youn-Bae Kang au CRCT de l’Ecole Polytechnique de Montréal. De plus, certains systèmes (Al–Mg–Pr, Al–Mg–Nd, Al–Mg–Tb, Al–La–Nd, Al–Pr–Nd, Al–La–Pr, Al–Ce–La et Al–Ce–Pr) n’avaient pas encore été optimisés thermodynamiquement. L’objectif principal de cette thèse est de développer une banque de données thermodynamiques pour le système Al–Mg–La–Ce–Pr–Nd–Sm–Gd–Tb–Dy–Ho–Er. Ainsi, des modèles thermodynamiques pour le liquide, les solutions solides et les composés stœchiométriques ont été proposés; les diagrammes de phases et les propriétés thermodynamiques des systèmes binaires Al–RE, Mg–RE et RE'–RE", ainsi que des systèmes ternaires Mg–Al–RE et Al–RE'–RE" ont été optimisés à l’aide des données expérimentales et / ou théoriques. Le second objectif consiste à faire des expériences clés dans la région riche en magnésium afin de vérifier les équilibres des phases, car cela est très important pour la conception de nouveau alliage à base de magnésium. L’étude expérimentale a été effectuée pour les systèmes ternaires Al–Mg–La, Al–Mg–Ce, Al–Mg–Pr et Al–Mg–Nd afin d'obtenir les phases en équilibres ainsi que les informations concernant les solubilités des solutions solides. Le troisième objectif de la recherche consiste à développer des méthodes originales pour estimer les données thermodynamiques absentes de la littérature scientifique pour les phases contenant des terres rares. Nous avons tout d’abord optimisé les systèmes binaires Al–RE (RE= La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) à partir d’une revue de la littérature pour les solides (composés intermétalliques, structures cristallographiques, températures de fusion, chaleurs de formation, températures de transformation,…), pour les propriétés du liquide (enthalpie de mélange intégrale, enthalpie de mélange partielle, activités des composants, capacités calorifiques, solubilités à l’état solide,…) et pour les données expérimentales de diagrammes de phases. Une approche systématique a été adoptée au cours des optimisations thermodynamiques. Puisque les terres rares sont chimiquement proches, une comparaison avec les terres rares voisines et une analyse systématique de la température de fusion des composés a facilité l’optimisation du système Al–Tb pour lequel peu de données expérimentales étaient disponibles. Deuxièmement, pour les systèmes Mg–RE pour lesquels les données expérimentales étaient rares ou contradictoires, des calculs de premier principe ont été utilisés pour évaluer l’enthalpie de formation de certains composés ainsi que l’enthalpie de mélange pour les phases FCC et HCP à l’aide de la technique “supercell”. En parallèle, des estimations ont été faites à l’aide du modèle semi-empirique de Miedema puis ont été comparées aux calculs de premier principe. Il a été suggéré que le modèle semi-empirique de Miedema peut fournir un bon estimé initial pour l’enthalpie de formation des composés et l’enthalpie de mélange de solutions sans un coût élevé en calculs. Ainsi, le modèle de Miedema a été utilisé pour estimer l’enthalpie de formation des composés ternaires et des phases métastables dans les systèmes ternaires Mg–Al–RE. Troisièmement, en ce qui concerne les systèmes ternaires Mg–Al–RE, leurs propriétés thermodynamiques et leurs équilibres de phase ont été moins étudiées comparativement aux autres systèmes métalliques. Les évaluations et optimisations thermodynamiques des systèmes Al–Mg–RE (RE= La, Ce, Pr, Nd, et Sm) ont été effectuées systématiquement sur la base de l’information disponible dans la littérature et de nos résultats expérimentaux. Dans ce travail, des expériences-clés ont été réalisées pour les systèmes Mg–Al–La, Mg–Al–Ce, Mg–Al–Pr, et Mg–Al–Nd pour vérifier les équilibres de phases dans le coin riche en Mg et les solubilités à l’état solide. Les estimations à l’aide du modèle de Miedema de l’enthalpie de formation pour les composés ternaires ont été utilisées pour les optimisations thermodynamiques de tous les systèmes Mg–Al–terre rare. Dans les systèmes Mg–Al–Gd (Dy, Ho), des compromis ont été faits entre les données expérimentales (température du liquidus) et les optimisations en considérant la fiabilité limitée des expériences à haute température (1200 K et plus). Nous n’avons pas jugé nécessaire l’utilisation de nombreux paramètres ternaires en excès pour le liquide pour bien reproduire les données expérimentales. Le système Mg–Al–Tb a été estimé en supposant des similarités avec les systèmes Mg–Al–Gd (Dy), et les résultats correspondants ont été présentés pour la première fois dans la présente étude. Une technique d’interpolation de type Kohler a été utilisée, considérant le fait que les enthalpies de mélange des liquides Al–Mg, Al–RE et Mg–RE sont très différentes les unes des autres. Quatrièmement, pour les systèmes Al–RE'–RE", les systèmes binaires RE'–RE" (La–Ce, La–Pr, La–Nd, Ce–Pr, Ce–Nd, Pr–Nd) ont été optimisés à partir de l’information expérimentale disponible. A l’exception des systèmes La–Nd et Ce–Pr, aucun paramètre en excès n’a été utilisé pour le liquide. Des données expérimentales ne sont disponibles que pour le système Al–Ce–Nd. Les autres systèmes Al–RE'–RE” ont été optimisés en supposant des propriétés thermodynamiques similaires à celles du système Al–Ce–Nd. Finalement, des applications de la banque de données thermodynamiques ont été montrées. La banque de données thermodynamiques pour les systèmes Mg–Al–RE fournira une ligne directrice claire pour la sélection et l’élaboration d’alliages de Mg et de Al; ce qui permettra d’éviter des expériences à long-terme improductives portant sur des alliages ayant moins de potentiel pour des applications pratiques. ---------- As the current lightest structural metallic material, magnesium and its alloys play an increasingly important role in automotive, aerospace and electronic consumer products. Although magnesium has excellent recyclability, high thermal conductivity, good electromagnetic shielding characteristics and so on, it suffers from its shortcomings: insufficient strength, poor corrosion and low creep resistance, etc. Alloying magnesium is one of the frequently used methods to improve its properties. Adding Rare Earth (RE) metals to magnesium alloys can improve their strength and creep resistance at elevated temperatures by forming stable precipitates with Mg, for example, (REyMgx), Al (REyAlx) or Zn (REyZnx). Parallel to Mg alloys development, Al–RE (aluminum – rare earths) alloys have been of interest to materials scientists who want to develop light weight alloys. Rare earths have an increasing importance as alloying elements in aluminum alloys because of their ability to enhance the high temperature properties and casting characteristics. Moreover, rapidly solidified Al–RE alloys also offer the possibility of obtaining better corrosion behavior. Computational methods are important and powerful tools in the selection and design of new magnesium alloys. These methods help our understanding of materials behavior, while they significantly reduce extensive and time-consuming experimental work. Furthermore, pure rare earth metals are expensive. Up to the present, few phase diagrams for Mg–Al–Mischmetal systems have been optimized using the quasichemical model (which takes into account short-range ordering) for the liquid phase except some recent optimizations (Al–Ce, Al–Y, and Al–Sc) by Dr. Youn-Bae Kang of CRCT at École Polytechnique de Montréal. Furthermore, some systems (Al–Mg–Pr, Al–Mg–Nd, Al–Mg–Tb, Al–La–Nd, Al–Pr–Nd, Al–La–Pr, Al–Ce–La, and Al–Ce–Pr) have not yet been thermodynamically optimized. The main objective of this thesis is to build a thermodynamic database for Al–Mg–La–Ce–Pr–Nd–Sm–Gd–Tb–Dy–Ho–Er systems. To this end, thermodynamic models of liquid and solid solutions and stoichiometric compounds have been proposed; phase diagrams and thermodynamic properties of binary Al–RE, Mg–RE, RE'–RE" systems, ternary Mg–Al–RE and Al– RE'– RE" systems have been optimized based on experimental and/or theoretical data. The secondary objective of this research is to do key experiments in the magnesium-rich corners of ternary systems to check phase equilibrium, since this is very important for Mg alloy design. Key experimental investigations have been performed for the Al–Mg–La, Al–Mg–Ce, Al–Mg–Pr and Al–Mg–Nd ternary systems in order to obtain phase equilibria and solid solubilities information. The third objective in this work is to find or develop proper methods for estimating the missing thermodynamic data for the binary and ternary phases which include rare earth elements. First, Al–RE (RE= La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) binary systems were optimized, based on literature review for the solids (intermetallic compounds, their crystal structures, melting points, enthalpy of formation, transformation temperature, etc), liquid properties (integral enthalpy of mixing, partial enthalpy of mixing, activities of the components, heat capacities, solid solubility and so on) and experimental phase diagram data. A systematic approach has been used in the course of thermodynamic optimizations. Since rare earths are chemically similar, comparision with neighboring rare earth elements and systematic analysis of melting point of compounds helped in the optimization of the Al–Tb system, in which few experimental data are available. Second, for the Mg–RE systems in which the experimental data were scarce or contradictory, First-Principles were employed to calculate the enthalpy of formation of certain compounds and enthalpy of mixing for the FCC and HCP phases using the supercell technique. Meantime, estimations from the semi-empirical Miedema model were made and compared to First-Principles calculations. It was suggested that the semi-empirical Miedema model can provide a good initial guess for the enthalpy of formation of compounds and the enthalpy of mixing for solutions for thermodynamic optimizations, without high computing cost. Therefore, the Miedema model was used to estimate the enthalpy of formation of the ternary compounds and metastable phases in Mg–Al–RE ternary systems. Third, as for Mg–Al–RE ternary systems, less research has been done on the thermodynamic properties and phase equilibria of these systems compared to other metallic systems. Thermodynamic evaluations and optimizations of the Al–Mg–RE (RE= La, Ce, Pr, Nd, Sm) systems have been systematically carried out on the basis of literature information and our experimental results. In this work, key experiments were performed for the Mg–Al–La, Mg–Al–Ce, Mg–Al–Pr, and Mg–Al–Nd systems to check phase equilibria in the Mg-rich corners and solid solubilities. The estimations of enthalpy of formation for the ternary compounds from Miedema model were used for thermodynamic optimizations of all the Mg–Al–rare earth systems. In the Mg–Al–Gd (Dy, Ho) systems, careful weighting was made between the experimental data (liquidus temperature) and optimization results, considering the restricted accuracy of experimental results at high temperatures (1200 K and more). It was judged unnecessary to use many excess ternary parameters for the liquid to fit satisfactorily the experimental data. The Mg–Al–Tb system was estimated by assuming similarities to the Mg–Al–Gd (Dy) systems and is presented for the first time in the present study. The Kohler-type interpolation method was used, seeing that the enthalpies of mixing of the liquid in the Al–Mg, Al–RE, and Mg–RE systems differ significantly. Fourth, RE'–RE" (La–Ce, La–Pr, La–Nd, Ce–Pr, Ce–Nd, Pr–Nd) binary systems were optimized based on the available experimental information. Except for the La–Nd and Ce–Pr systems, no excess parameters were used for the liquid. For the Al–RE'–RE" systems, experimental data are available only for the Al–Ce–Nd system. Other Al– RE'–RE” systems were optimized assuming thermodynamic properties similar to those of the Al–Ce–Nd system. Finally, some applications of this thermodynamic database were shown. The thermodynamic database of the Mg–Al–RE systems will provide clear guidelines for Mg and Al alloy selection and design, thereby avoiding unproductive long-term experiments with alloys which have less potential for practical applications

The Influence of Reward on Recognition Memory and Source Memory

Reward motivation is an important factor that influences human learning and memory. In this behavioural study, we explored the influence of reward anticipation on recognition memory and source memory in a dual rewarded memory task. The experiment consisted of a study phase followed by separate recognition memory and source memory test phases. During the study phase, participants saw words following high or low or reward cues. The reward cues indicated the monetary rewards participants would get by the correct memory judgments in the following recognition memory and source memory tests. The words were presented in one of four locations of a computer screen. Participants were instructed to remember the words and memorize the locations of the words. In the recognition memory test, studied (old) words mixed with some new words were presented to the participants one at a time. Participants made an old/new recognition memory judgment to these words. In the subsequent source memory test, all old words were shown again in the middle of a screen. Participants made source memory judgments to indicate the location of the words which were shown during the study phase. Participants were rewarded for the correct judgments in the recognition memory and source memory tests. The results showed that the recognition memory and source memory performances in the high-reward and low-reward conditions were not significantly different. Our findings indicate that rewards cannot enhance item recognition memory and source memory in a dual rewarded memory task. In our study, we both rewarded item recognition memory and source memory with the same amount of monetary rewards. In a dual rewarded memory task, due to the people’ s processing resources are limited, rewards might lead to resource competition and influence resource allocation. Because rewards given to the correct item recognition memory and source memory were the same, the resource allocated to memorize the item and location might be nearly equal. This discouraged participants from allocating more resources to one type of memory to enhance either item or source memory performance. Thus, in our dual rewarded memory task, rewards may have failed to improve memory performance due to nearly equal resource distribution between item and source memory. Our data also suggest that the dopaminergic reward mechanism cannot explain memory performance in our dual rewarded memory task. However, the executive control mechanism might act on our dual rewarded memory task to influence resource allocation. In future work, we want to further test our hypotheses on reward-guided resource allocation and memory, and explore other factors that might influence the effects of reward on human memory

The Influence of Reward on Recognition Memory and Source Memory

Reward motivation is an important factor that influences human learning and memory. In this behavioural study, we explored the influence of reward anticipation on recognition memory and source memory in a dual rewarded memory task. The experiment consisted of a study phase followed by separate recognition memory and source memory test phases. During the study phase, participants saw words following high or low or reward cues. The reward cues indicated the monetary rewards participants would get by the correct memory judgments in the following recognition memory and source memory tests. The words were presented in one of four locations of a computer screen. Participants were instructed to remember the words and memorize the locations of the words. In the recognition memory test, studied (old) words mixed with some new words were presented to the participants one at a time. Participants made an old/new recognition memory judgment to these words. In the subsequent source memory test, all old words were shown again in the middle of a screen. Participants made source memory judgments to indicate the location of the words which were shown during the study phase. Participants were rewarded for the correct judgments in the recognition memory and source memory tests. The results showed that the recognition memory and source memory performances in the high-reward and low-reward conditions were not significantly different. Our findings indicate that rewards cannot enhance item recognition memory and source memory in a dual rewarded memory task. In our study, we both rewarded item recognition memory and source memory with the same amount of monetary rewards. In a dual rewarded memory task, due to the people’ s processing resources are limited, rewards might lead to resource competition and influence resource allocation. Because rewards given to the correct item recognition memory and source memory were the same, the resource allocated to memorize the item and location might be nearly equal. This discouraged participants from allocating more resources to one type of memory to enhance either item or source memory performance. Thus, in our dual rewarded memory task, rewards may have failed to improve memory performance due to nearly equal resource distribution between item and source memory. Our data also suggest that the dopaminergic reward mechanism cannot explain memory performance in our dual rewarded memory task. However, the executive control mechanism might act on our dual rewarded memory task to influence resource allocation. In future work, we want to further test our hypotheses on reward-guided resource allocation and memory, and explore other factors that might influence the effects of reward on human memory

A Questionnaire Study on Attitudes toward Birth and Child-rearing of University Students in Japan, China,and South Korea

This study examines the attitudes of young Japanese, Chinese, and South Koreans toward birth and child-rearing. The survey targeted four-year university students (n＝1,668) who responded to an anonymous survey using self-report questionnaires between December 2012 and April 2013. The collection rates were 72.5%, 94.7%, and 96.5% for the Japanese, Chinese, and South Korean students, respectively. Correlations among the respondentsʼ attributes, medical and scientific literacy levels, and views of preferred qualities of children were analyzed using chi-square test, supplemented by residual analysis (significance level set at p＜0.05). Participants were asked whether they were willing to use the following methods for obtaining preferred qualities in their children:(1) choosing a spouse (43.2%, 72.6%, and 85.1% of the Japanese, Chinese, and South Koreans, respectively, agreed);(2) using a sperm bank (cryobank) (5.8%, 60.1%, and 81.7% of the Japanese, Chines, and South Koreans, respectively, agreed);and (3) using an egg cell bank (ova bank or cryobank) (5.3%, 47.2%, and 70.3% of the Japanese, Chinese, and South Koreans, respectively, agreed). The proportion of affirmative responses (indicating “eugenic inclination”) to these statements was significantly higher among the Chinese and South Korean participants than their Japanese counterparts (p＜0.001). Significant differences were also found in the attitudes of the 3 groups toward methods for obtaining the preferred qualities for their children:prenatal diagnosis, pre-implantation diagnosis, the environment during pregnancy, and child-rearing

Critical Evaluation and Thermodynamic Optimization of the Cu-Zn, Cu-Se and Zn-Se Binary Systems

ABSTRACT: In our study, a complete review of the literature, critical evaluation and thermodynamic assessment of the Cu-Zn, Cu-Se and Zn-Se binary systems were carried out. The modified quasi-chemical model (MQM) was applied to describe the Gibbs energy of the liquid phase. The Gibbs energies of all intermetallic compounds and terminal solid solutions were described using the compound energy formalism (CEF) model. The re-optimization of the Cu-Zn binary system was carried out by considering the ordered bcc_B2 crystal structure of the β’ phase. Moreover, the β and δ phases in the Cu-Zn binary system with the same bcc_A2 crystal structure were modeled as one single phase in the present work. A self-consistent thermodynamic database was constructed for the Cu-Zn, Cu-Se and Zn-Se binary systems, work that formed part of a comprehensive thermodynamic database development project researching zinc-based biodegradable materials

Advanced lung cancer inflammation index is associated with long-term cardiovascular death in hypertensive patients: national health and nutrition examination study, 1999–2018

Background: Hypertension is one of the main causes of cardiovascular death. Inflammation was considered influential factors of cardiovascular (CVD) death in patients with hypertension. Advanced lung cancer inflammation index (ALI) is an index to assess inflammation, few studies have investigated the relationship between advanced lung cancer inflammation index and cardiovascular death in hypertensive patients.Objective: The aim of this study was to investigate the association between advanced lung cancer inflammation index and long-term cardiovascular death in hypertensive patients.Method: Data from the National Health and Nutrition Examination Survey (NHANES) 1999–2018 with mortality follow-up through 31 December 2019 were analyzed. Advanced lung cancer inflammation index was calculated as BMI (kg/㎡) × serum albumin level (g/dL)/neutrophil to lymphocyte ratio (NLR). A total of 20,517 participants were evaluated. Patients were divided into three groups based on tertiles of advanced lung cancer inflammation index as follows: T1 (n = 6,839), T2 (n = 6,839), and T3 (n = 6,839) groups. The relationship between advanced lung cancer inflammation index and long-term cardiovascular death was assessed by survival curves and Cox regression analysis based on the NHANES recommended weights.Results: The median advanced lung cancer inflammation index value in this study was 61.9 [44.4, 84.6]. After full adjustment, the T2 group (hazard ratio [HR]: 0.59, 95% confidence interval [CI]: 0.50–0.69; p < 0.001) and T3 group (HR: 0.48, 95% CI: 0.39–0.58; p < 0.001) were found to have a significantly lower risk of cardiovascular death compared to the T1 group.Conclusion: High levels of advanced lung cancer inflammation index were associated with reduced risk of cardiovascular death in hypertensive patients

Reemerging superconductivity at 48 K across quantum criticality in iron chalcogenides

Pressure plays an essential role in the induction1 and control2,3 of superconductivity in iron-based superconductors. Substitution of a smaller rare-earth ion for the bigger one to simulate the pressure effects has surprisingly raised the superconducting transition temperature Tc to the record high 55 K in these materials4,5. However, Tc always goes down after passing through a maximum at some pressure and the superconductivity eventually tends to disappear at sufficiently high pressures1-3. Here we show that the superconductivity can reemerge with a much higher Tc after its destruction upon compression from the ambient-condition value of around 31 K in newly discovered iron chalcogenide superconductors. We find that in the second superconducting phase the maximum Tc is as high as 48.7 K for K0.8Fe1.70Se2 and 48 K for (Tl0.6Rb0.4)Fe1.67Se2, setting the new Tc record in chalcogenide superconductors. The presence of the second superconducting phase is proposed to be related to pressure-induced quantum criticality. Our findings point to the potential route to the further achievement of high-Tc superconductivity in iron-based and other superconductors.Comment: 20 pages and 7 figure

Novel Strategies for Drug Discovery Based on Intrinsically Disordered Proteins (IDPs)

Intrinsically disordered proteins (IDPs) are proteins that usually do not adopt well-defined native structures when isolated in solution under physiological conditions. Numerous IDPs have close relationships with human diseases such as tumor, Parkinson disease, Alzheimer disease, diabetes, and so on. These disease-associated IDPs commonly play principal roles in the disease-associated protein-protein interaction networks. Most of them in the disease datasets have more interactants and hence the size of the disease-associated IDPs interaction network is simultaneously increased. For example, the tumor suppressor protein p53 is an intrinsically disordered protein and also a hub protein in the p53 interaction network; α-synuclein, an intrinsically disordered protein involved in Parkinson diseases, is also a hub of the protein network. The disease-associated IDPs may provide potential targets for drugs modulating protein-protein interaction networks. Therefore, novel strategies for drug discovery based on IDPs are in the ascendant. It is dependent on the features of IDPs to develop the novel strategies. It is found out that IDPs have unique structural features such as high flexibility and random coil-like conformations which enable them to participate in both the “one to many” and “many to one” interaction. Accordingly, in order to promote novel strategies for drug discovery, it is essential that more and more features of IDPs are revealed by experimental and computing methods