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1.
Phys Chem Chem Phys ; 25(28): 19214-19229, 2023 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-37431713

RESUMO

Transition-metal (TM) substituted SrTiO3 has attracted much attention because its magnetism and/or ferroelectricity can be tuned via cation substitution, point defects, strain and/or oxygen deficiency. For example, Goto et al. [Phys. Rev. Applied, 7, 024006 (2017)] reported the magnetization of SrTi1-xFexO3-δ (STF) grown under different oxygen pressures and on various substrates. Here, we use hybrid density functional theory to calculate the effects of different oxygen vacancy (VO) states in STF on the magnetization for a variety of Fe cation arrangements. The magnetic states of the cations associated with the VO ground-states for x = {0.125, 0.25} are used within a Monte Carlo model for collinear magnetism to simulate the spontaneous magnetization. Our model captures several experimental features of STF, i.e., an increase in magnetization for small δ up to a maximum of ∼0.35µB per formula unit at an intermediate number of vacancies, with a slower decrease in magnetization with an increasing number of vacancies. Our approach gives insight into the relation between vacancy concentration and the oxygen pressure required to maximize the magnetization.

2.
Rev. lasallista investig ; 18(1): 114-133, ene.-jun. 2021. tab, graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1365833

RESUMO

Resumen Introducción: el estudio de las campañas de retiro de productos defectuosos del mercado {recalls} es un tema vigente y complejo en el contexto de la gestión de la calidad en cadenas de suministro para garantizar la seguridad y la protección de los consumidores. Objetivo: identificar los principales enfoques académicos y legales utilizados a nivel nacional e internacional para el diseño y ejecución de estrategias de retiro de productos. Materiales y métodos: se aplicó un enfoque exploratorio de la investigación, a través de una revisión de literatura y análisis bibliométrico con Vosviewer, considerando los artículos publicados en el periodo entre 1999 y 2019, en las bases de datos Taylor and Francis, EBSCO, Science Direct, Scopus, Springer Link, IEEE, Google académico y Proquest. Resultados: se evidenció un crecimiento en el número de recalls en los últimos 20 años, especialmente en la industria de juguetes (161 %), sector automotriz (140%), productos de belleza (70 %) y suministros eléctricos (64 %). Las principales metodologías para el estudio de los recalls son de naturaleza cualitativa. Conclusiones: son requeridos nuevos aportes académicos orientados al desarrollo de modelos y metodologías que permitan involucrar a todos los miembros de la cadena de suministro en el diseño y ejecución de estrategias coordinadas para disminuir los riesgos de ocurrencia de productos defectuosos o inseguros en el mercado.


Abstract Introduction: the recall study is a current and complex issue of supply chain quality management to ensure the safety and protection of consumers. Objective: identify the main national and international academic and legal approaches used to design and perform product recall strategies. Materials and Methods: an exploratory research approach was applied, through a literature review and bibliometric analysis with the Vosviewer software, by considering the articles published between 1999 and 2019 in the databases Taylor and Francis, EBSCO, Science Direct, Scopus databases, Springer Link, IEEE, Google Scholar, and Proquest. Results: there was an increase in the number of recalls in the last 20 years, especially in the toy industry (161 %), the automotive sector (140 %), beauty products (70 %) and electrical supplies (64 %). The main methodologies for studying product recalls are qualitative ones. Conclusions: new academic contributions are required for developing models and methodologies that allow all the supply chain members to be involved in designing and performing coordinated strategies to reduce the risks of defective or unsafe products in the market.


Resumo Introdução: o estudo de recolha de produtos defeitos é uma questão actual e complexa de gestão da qualidade da cadeia de abastecimento para garantir a segurança e a protecção dos consumidores. Objetivo: identificar as principais abordagens acadêmicas e jurídicas nacionais e internacionais utilizadas para conceber e executar estratégias de recolha de produtos. Materiais e métodos: foi aplicada uma abordagem de pesquisa exploratória, por meio de uma revisão da literatura e análise bibliométrica com Vosviewer, considerando os artigos publicados no período entre 1999 e 2019, nas bases de dados de Taylor e Francis, EBSCO, Science Direct, Scopus, Springer Link, IEEE, Google Scholar e Proquest. Resultados: houve um aumento no número de recalls nos últimos 20 anos, principalmente na indústria de brinquedos (161 %), no setor automotivo (140 %), produtos de beleza (70 %) e suprimentos elétricos (64 %). As principais metodologias para o estudo de recalls são de natureza qualitativa. Conclusões: são necessárias novas contribuições académicas para o desenvolvimento de modelos e metodologias que permitam a todos os membros da cadeia de fornecimento estarem envolvidos na concepção e execução de estratégias coordenadas para reduzir os riscos de produtos defeituosos ou inseguros no mercado.

3.
Entropy (Basel) ; 20(8)2018 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-33265646

RESUMO

In this work, we report the magnetocaloric effect (MCE) in two systems of non-interactive particles: the first corresponds to the Landau problem case and the second the case of an electron in a quantum dot subjected to a parabolic confinement potential. In the first scenario, we realize that the effect is totally different from what happens when the degeneracy of a single electron confined in a magnetic field is not taken into account. In particular, when the degeneracy of the system is negligible, the magnetocaloric effect cools the system, while in the other case, when the degeneracy is strong, the system heats up. For the second case, we study the competition between the characteristic frequency of the potential trap and the cyclotron frequency to find the optimal region that maximizes the ΔT of the magnetocaloric effect, and due to the strong degeneracy of this problem, the results are in coherence with those obtained for the Landau problem. Finally, we consider the case of a transition from a normal MCE to an inverse one and back to normal as a function of temperature. This is due to the competition between the diamagnetic and paramagnetic response when the electron spin in the formulation is included.

4.
Pest Manag Sci ; 65(8): 892-9, 2009 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-19418481

RESUMO

BACKGROUND: Mycosphaerella fijiensis Morelet causes black sigatoka, the most important disease in bananas and plantains. Disease control is mainly through the application of systemic fungicides, including sterol demethylation inhibitors (DMIs). Their intensive use has favoured the appearance of resistant strains. However, no studies have been published on the possible resistance mechanisms. RESULTS: In this work, the CYP51 gene was isolated and sequenced in 11 M. fijiensis strains that had shown different degrees of in vitro sensitivity to propiconazole, one of the most widely used DMI fungicides. Six mutations that could be related to the loss in sensitivity to this fungicide were found: Y136F, A313G, Y461D, Y463D, Y463H and Y463N. The mutations were analysed using a homology model of the protein that was constructed from the crystallographic structure of Mycobacterium tuberculosis (Zoff.) Lehmann & Neumann. Additionally, gene expression was determined in 13 M. fijiensis strains through quantitative analysis of products obtained by RT-PCR. CONCLUSION: Several changes in the sequence of the gene encoding sterol 14alpha-demethylase were found that have been described in other fungi as being correlated with resistance to azole fungicides. No correlation was found between gene expression and propiconazole resistance.


Assuntos
Ascomicetos/genética , Sistema Enzimático do Citocromo P-450/genética , Farmacorresistência Fúngica/genética , Proteínas Fúngicas/genética , Genes Fúngicos , Triazóis/farmacologia , Sequência de Aminoácidos , Ascomicetos/fisiologia , Domínio Catalítico , Sistema Enzimático do Citocromo P-450/química , Proteínas Fúngicas/química , Regulação Fúngica da Expressão Gênica , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Homologia de Sequência , Esterol 14-Desmetilase
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