Kinetics of heat flux avalanches at the first order transition in La(Fe-Mn-Si)13_{13}-H1.65_{1.65} compounds

We study heat flux avalanches occurring at the first order transition in La(Fe-Mn-Si)$_{13}$-H$_{1.65}$ magnetocaloric material. As the transition is associated to the phase boundaries motion that gives rise to the latent heat, we develop a non equilibrium thermodynamic model. By comparing the model with experimental calorimetry data available for Mn=0.18, we find the values of the intrinsic kinetic parameter $R_L$, expressing the damping for the moving boundary interface, at different magnetic fields. We conclude that by increasing field, thus approaching the critical point, the avalanches increase in number and their kinetics is slowed down.Comment: PDFLaTeX, 5 pages, 2 figures, 1 table, accepted for publication in Journal of Physics: Conference Series as Conference Proceeding of JEMS 2016 (8th Joint European Magnetic Symposia

Physical behaviour and properties at the first order phase transition of magnetocaloric materials

This Ph.D. project was mainly devoted to the study of the connection between magnetocaloric properties and first order phase transitions in ferromagnetic materials based on the La(Fe,Si)13 compound. The magneto caloric effect (MCE) and its application in magnetic cooling cycles rely on the reversible magnetization and demagnetization of a magnetic material by an external magnetic field, resulting in a temperature change that is maximal at temperatures close to a magnetic phase transition. The possibility to improve the performance of the active refrigerator materials, depends on many factors: the need of a Curie temperature close to ambient temperature, a low magnetic and thermal hysteresis and a high magnetic entropy variation for magnetic fields below two Tesla. The latter requisite can be found in first order magnetic phase transitions that, unfortunately, are accompanied by intrinsic thermo-magnetic hysteresis. This drawback for magneto cooling cycles, motivates the present study on the phase transitions dynamics. On the other hand, the investigation of magneto-thermal phenomena in magnetic materials is of great importance also for solving fundamental problems of magnetism and solid state physics, for example, it is recognized that the properties of interest of such functional materials are intimately linked to the detailed micro structure, however, the nature of this link itself is not understood very often. In this Ph.D. project, thermo-magnetic phase transitions in La(Fe,Si)13 compounds were investigated through the comparison of various experimental techniques within a collaboration between the applied superconductivity group of Politecnico of Torino and the electromagnetism division of INRiM (National Institute of Metrological Research). To achieve a proper physical understanding of the connection between thermo-magnetic hysteresis at the microscopic level and the microstructure, a magneto optical method was applied to samples of La-F-Si-13 with cobalt substitutions, so to allow the dynamical visualisation of the phase boundaries motion in a first order phase transition. These type of experiments have been compared with low rate calorimetry data and, from the experimental work, it has been found that the presence of avalanches is a characteristic feature of these alloys and it is related to their thermal hysteresis. The difference between first and second order phase transition dynamics were highlighted thanks to the employment of different techniques, which also favoured the separation of the general aspects of hysteresis, common to all irreversible processes, from features more strictly dependent on specific microstructural properties. For the aim of this Ph.D., other techniques were also used to observe temperature induced magnetic phase transitions in functional magnetic materials. Among them an in-temperature ferromagnetic resonance method was implemented for the study of the magnetization dynamics in canted spin structures. The present research activity has been partially related to the European Project DRREAM [1] (a collaborative research project funded by the EC under the Seventh Framework Program 2013-2015), whose goal is to reduce the use of rare earth elements in the life cycle of technologies that use magnetic phase change materials, in particular magnetic refrigerators

Scale-Up of Magnetocaloric NiCoMnIn Heuslers by Powder Metallurgy for Room Temperature Magnetic Refrigeration

We present a new approach for a large-scale production of the rare-earth free NiCoMnIn Heusler alloy for room temperature magnetic refrigeration applications. This class of compounds has recently attracted attention, thanks to the large reversible isothermal entropy change (ΔSiso) and adiabatic temperature change (ΔTad) associated to a first-order magnetostructural phase transition. A large-scale production method, however, has not yet been proposed. For giant magnetocaloric materials and especially for Heusler compounds, the synthesis has a predominant role in tailoring the physical–chemical properties, due to the high sensitivity of the first-order transition characteristics on chemical composition and microstructure. Up to 250 g of the nominal composition Ni45.7Co4.2Mn36.6In13.3 alloy was prepared in a unique sample starting from industrial-grade powdered elements. The phase transition temperatures and magnetocaloric properties were investigated by magnetic and direct adiabatic temperature measurements and were found to be homogeneous in the whole sample. The mechanical stability of the produced alloy and its workability were investigated. A low-temperature thermal treatment was identified and showed promising results by reducing hysteresis and transition width

APOLLO 11 Project, Consortium in Advanced Lung Cancer Patients Treated With Innovative Therapies: Integration of Real-World Data and Translational Research

Introduction: Despite several therapeutic efforts, lung cancer remains a highly lethal disease. Novel therapeutic approaches encompass immune-checkpoint inhibitors, targeted therapeutics and antibody-drug conjugates, with different results. Several studies have been aimed at identifying biomarkers able to predict benefit from these therapies and create a prediction model of response, despite this there is a lack of information to help clinicians in the choice of therapy for lung cancer patients with advanced disease. This is primarily due to the complexity of lung cancer biology, where a single or few biomarkers are not sufficient to provide enough predictive capability to explain biologic differences; other reasons include the paucity of data collected by single studies performed in heterogeneous unmatched cohorts and the methodology of analysis. In fact, classical statistical methods are unable to analyze and integrate the magnitude of information from multiple biological and clinical sources (eg, genomics, transcriptomics, and radiomics). Methods and objectives: APOLLO11 is an Italian multicentre, observational study involving patients with a diagnosis of advanced lung cancer (NSCLC and SCLC) treated with innovative therapies. Retrospective and prospective collection of multiomic data, such as tissue- (eg, for genomic, transcriptomic analysis) and blood-based biologic material (eg, ctDNA, PBMC), in addition to clinical and radiological data (eg, for radiomic analysis) will be collected. The overall aim of the project is to build a consortium integrating different datasets and a virtual biobank from participating Italian lung cancer centers. To face with the large amount of data provided, AI and ML techniques will be applied will be applied to manage this large dataset in an effort to build an R-Model, integrating retrospective and prospective population-based data. The ultimate goal is to create a tool able to help physicians and patients to make treatment decisions. Conclusion: APOLLO11 aims to propose a breakthrough approach in lung cancer research, replacing the old, monocentric viewpoint towards a multicomprehensive, multiomic, multicenter model. Multicenter cancer datasets incorporating common virtual biobank and new methodologic approaches including artificial intelligence, machine learning up to deep learning is the road to the future in oncology launched by this project

Modeling specific heat and entropy change in La(Fe–Mn–Si)13–H compounds

In this paper we model the magnetocaloric effect of LaFexMnySiz–H1.65 compound (x+y+z=13), a system showing a transition temperature finely tunable around room temperature by Mn substitution. The thermodynamic model takes into account the coupling between magnetism and specific volume as introduced by Bean and Rodbell. We find a good qualitative agreement between experimental and modeled entropy change −Δs(H,T). The main result is that the magnetoelastic coupling drives the phase transition of the system, changing it from second to first order by varying a model parameter η . It is also responsible for a decrease of −Δs at the transition, due to a small lattice contribution to the entropy counteracting the effect of the magnetic one. The role of Mn is reflected exclusively in a decrease of the strength of the exchange interaction, while the value of the coefficient β, responsible for the coupling between volume and exchange energy, is independent on the Mn content and it appears to be an intrinsic property of the La(Fe–Si)13 structure