Static magneto optical birefringence of New Electric Double Layered Magnetic Fluids

Magnetic birefringence measurements are performed under a static eld on Electric Double Layered Magnetic Fluids based on copper and zinc ferrite nanostructures. The optical birefringence is related to a single-particle e ect and well described by a Langevin model which includes a lognormal distribution of particles. By the eld-induced birefringence level, these new magnetic fluids are comparable to usual ones, a result which could o er a new way for biological applications

Efeitos de tamanho finito e interface em nanopartículas e nanocolóides magnéticos

Tese (doutorado)—Universidade de Brasília, Instituto de Física, 2008.Investigamos neste trabalho nanopartículas magnéticas à base de ferrita de cobre, com diâmetros entre 3,5 nm e 10,7 nm. Esses nanomateriais são obtidos por coprecipitação hidrotérmica e permitem a obtenção de nanocolóides magnéticos em meio aquoso ácido graças a uma estratégia do tipo núcleo-superficie, que previne a dissolução das partículas. Conseqüentemente essas são formadas por um núcleo de ferrita de cobre estequiométrica recoberto por uma camada superficial de maguemita. Medidas de magnetização em função da temperatura permitam distinguir o núcleo monodomínio magneticamente ordenado da camada superficial que apresenta em baixa temperatura uma estrutura do tipo vidro de spin. Ainda a temperatura de congelamento é maior em presença de interações dipolares magnéticas (pó). Medidas de espectroscopia Mössbauer, em presença e em ausência de campo aplicado, confirmam a existência da estrutura magnética do tipo núcleo-superfície, com um núcleo apresentando inversão catiônica, e conduzem à determinação da energia de anisotropia. Ainda a investigação da dinâmica de rotação browniana a partir da utilização de um arranjo de birrefringência magneto-ótica em campo cruzado também permite sondar a anisotropia magnética das nanopartículas. Em ambas as determinações, os resultados indicam uma forte contribuição de superfície para as nanopartículas de menores diâmetros. _____________________________________________________________________________________ ABSTRACTIn this work, we investigated magnetic nanoparticles based on copper ferrite, with mean sizes ranging between 3,5 nm e 10,7 nm. Such nanomaterials are chemically synthesized by hydrothermal coprecipitation and allow elaborating magnetic nanocolloids in aqueous and acidic medium thanks to a core-shell strategy that prevent the nanoparticles from dissolution. Consequently, they consist in a core made of stoichiometric copper ferrite surrounded by a maghemite shell. Magnetization measurements as a function of the temperature allow to separate the magnetically ordered core monodomain from the surface shell which presents at low temperature a spin-glass like disordered structure. Moreover, the freezing temperature is larger in the presence of magnetic dipolar interactions between particles (powder). Mössbauer spectroscopy measurements, in the presence and absence of an applied magnetic field confirm the existence of the magnetic core-shell model, with cation inversion in the ordered magnetic core, and lead to the determination of the anisotropy energy. Furthermore, the investigation of the Brownian rotation dynamics using an experimental setup of magneto-optical birefringence in crossed fields also permits to determine the magnetic anisotropy energy of the particles. For both determinations, the results suggest an intense surface contribution for smaller nanoparticles

The OCARIoT Experience

Brazilian Ministry of Science, Technology and Innovation through Rede Nacional de Ensino e Pesquisa (RNP), under Grant 003008. Publisher Copyright: © 2023 IEEE.Objective: Long term behavioural disturbances and interventions in healthy habits (mainly eating and physical activity) are the primary cause of childhood obesity. Current approaches for obesity prevention based on health information extraction lack the integration of multi-modal datasets and the provision of a dedicated Decision Support System (DSS) for health behaviour assessment and coaching of children. Methods: Continuous co-creation process has been applied in the frame of the Design Thinking Methodology, involving children, educators and healthcare professional in the whole process. Such considerations were used to derive the user needs and the technical requirements needed for the conception of the Internet of Things (IoT) platform based on microservices. Results: To promote the adoption of healthy habits and the prevention of the obesity onset for children (9-12 years old), the proposed solution empowers children -including families and educators- in taking control of their health by collecting and following-up real-time information about nutrition, physical activity data coming from IoT devices, and interconnecting healthcare professionals to provide a personalised coaching solution. The validation has two phases involving +400 children (control/intervention group), on four schools in three countries: Spain, Greece and Brazil. The prevalence of obesity decreased in 75.5% from baseline levels in the intervention group. The proposed solution created a positive impression and satisfaction from the technology acceptance perspective. Conclusions: Main findings confirm that this ecosystem can assess behaviours of children, motivating and guiding them towards achieving personal goals. Clinical and Translational Impact Statement - This study presents Early Research on the adoption of a smart childhood obesity caring solution adopting a multidisciplinary approach; it involves researchers from biomedical engineering, medicine, computer science, ethics and education. The solution has the potential to decrease the obesity rates in children aiming to impact to get a better global health.publishersversionpublishe