176 research outputs found

    ESTIMATION AND ASYMPTOTIC THEORY FOR A NEW CLASS OF MIXTURE MODELS

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    In this paper a new model of mixture of distributions is proposed, where the mixing structure is determined by a smooth transition tree architecture. Models based on mixture of distributions are useful in order to approximate unknown conditional distributions of multivariate data. The tree structure yields a model that is simpler, and in some cases more interpretable, than previous proposals in the literature. Based on the Expectation-Maximization (EM) algorithm a quasi-maximum likelihood estimator is derived and its asymptotic properties are derived under mild regularity conditions. In addition, a specific-to-general model building strategy is proposed in order to avoid possible identification problems. Both the estimation procedure and the model building strategy are evaluated in a Monte Carlo experiment, which give strong support for the theory developed in small samples. The approximation capabilities of the model is also analyzed in a simulation experiment. Finally, two applications with real datasets are considered. KEYWORDS: Mixture models, smooth transition, EM algorithm, asymptotic properties, time series, conditional distribution.

    The role of the dental surgeon in the early diagnosis of oral cancer: a concise systematic review

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    Introduction: Oral cancers (OC) represent more than 90% of cases. It is estimated that more than 400,000 new cases of oral cancer are diagnosed each year worldwide. OC is preventable as most of the different identified risk factors, such as tobacco use, alcohol consumption, and betel nut chewing, are behaviors that increase the likelihood of the disease. Surgical biopsy remains the gold standard, but adjunctive tools have been developed to aid diagnoses, such as vital toluidine blue staining and autofluorescence imaging. Objective: To emphasize and present the importance of the dental surgeon in the early diagnosis and prevention of oral cancer. Methods: The survey was conducted from July 2021 to August 2021 and developed based on Scopus, PubMed, Science Direct, Scielo, and Google Scholar, following the rules of Systematic Review-PRISMA. Study quality was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results: Early detection and treatment of OC were found to be important predictors for improving survival and reducing mortality. A thorough clinical inspection of the oral cavity can detect up to 99% of oral cancers. Other diagnostic types have been developed to help overcome the limits of standard oral clinical examination, highlighting toluidine blue staining, light-based detection techniques, and salivary biomarkers. Self-examination is an effective strategy to reduce the levels of mortality and morbidity caused by this pathology. A gain of 8.09% more in sensitivity and 11.36% more in specificity was observed with the fluorescence test. Conclusion: The findings clearly showed that early diagnosis of oral cancer is essential to increase the chances of cure and survival of patients, avoiding invasive surgical intervention. Currently, there are several diagnostic tools for screening and visual devices for the early detection of oral lesions through auxiliary methods, logically maintaining biopsy as the gold standard

    Understanding the Shape-Memory Alloys Used in Orthodontics

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    Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA

    Perspectives of psychodynamics of work use in Brazil : theory, method, and practice

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    Este artigo tem a intenção de refletir sobre o uso da psicodinâmica do trabalho no Brasil como teoria e método, e como tal, o papel que vem desempenhando para a compreensão das relações entre a saúde mental e o trabalho. Trata-se de uma abordagem preliminar e exploratória, que teve como base 79 artigos, dissertações, teses e outras publicações que apontam o modo como a psicodinâmica do trabalho vem sendo referenciada. Observa-se que, na grande maioria das vezes, a psicodinâmica é usada apenas como referencial teórico, sem terem sido seguidos os passos propostos no método para a investigação. Considera-se que, apesar de suas categorias teóricas serem amplamente utilizadas por pesquisadores brasileiros, ainda há um grande desconhecimento da potencialidade que oferece esse instrumento, enquanto método e possível prática, para o avanço do conhecimento neste campo de pesquisa e sua aplicação.This article has the intention of contemplating about the use of the methodology of psychodynamics of work in Brazil as theory, method and practice, while a score for the understanding of the relationships between the mental health. It is treated of an exploratory approach that had as base 79 articles, dissertations, thesis, etc. where the methodology of psychodynamics of Work was used as a reference. It was observed that that methodology was used, in the great majority of the times, just as a theoretical reference, without it being following the steps proposed in the method for the investigation. It is considered that, in spite of their categories they be used thoroughly by Brazilian researchers, there is still a great ignorance of the potentiality that offers that instrument

    Force Relaxation Characteristics of Medium Force Orthodontic Latex Elastics: A Pilot Study

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    To evaluate force extension relaxation of different brands and diameters of latex elastics subjected to static tensile testing under an apparatus designed to simulate oral environments, sample sizes of 5 elastics from American Orthodontics (AO), Tp, and Morelli Orthodontics (Mo) of equivalent medium force, (3/16, 1/4, and 5/16 inch size) were tested. The forces were read after 1-, 3-, 6-, 12- and 24-hour periods in Emic testing machine with 30 mm/min cross-head speed and load cell of 20 N. Two-way ANOVA and Bonferroni tests were used to identify statistical significance. There were statistically differences among different manufacturers at all observation intervals (P < 0.0001). The relationships among loads at 24-hour time period were as follows: Morelli>AO>Tp for 3/16, 1/4, and 5/16 elastics. The force decay pattern showed a notable drop-off of forces until 3 hours, a slight increase in some groups from 3–6 hours and a more homogeneous force pattern over 6–24 hours

    A diabetes não dói, não se sente, mas está cá dentro! Metáforas de adultos idosos diabéticos tipo 2 portugueses

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    In Portugal more than a quarter of the population aged between 60 and 79 years old has type 2 diabetes mellitus. Therapeutic recommendations request patients’ self-management, since changes in lifestyles are involved. However, just around 20% of the patients are outstanding self-managers. Self-management is associated to beliefs, and metaphors are mechanisms that reflect the beliefs used by individuals to understand and take action. This study aims to analyse metaphors of type 2 older (≥ 65 years) diabetics, about “what is diabetes” (identity; causes; timeline and consequences), which is relevant for clinical practice. This qualitative and exploratory study uses the cognitive metaphor theory to uncover participants’ metaphors through semi-structured interviews. It comprises 17 participants that reported 84 metaphors. The interviews were submitted to content analysis. Main findings show that: identity is described by “illness that does not hurt, it is not felt, but it is here”; causes involve “I don’t know” and “I inherited it”; timeline and consequences portrayed as “slowly it destroys us”. These metaphors suggest that the old-aged type 2 diabetics experience the illness as something “mysterious”, which will most probably difficult their self-management.Em Portugal mais de um quarto da população entre os 60 e os 79 anos tem diabetes mellitus tipo 2. As recomendações terapêuticas exigem autogestão pelos pacientes, pois envolvem mudanças de estilo de vida. Contudo, apenas cerca de 20% dos pacientes são ótimos autogestores. A autogestão está associada a crenças, sendo as metáforas mecanismos que refletem as crenças usadas pelos indivíduos para compreender e agir. O objetivo deste estudo é analisar as metáforas de adultos idosos (≥ 65 anos) diabéticos tipo 2, sobre “o que é a diabetes” (identidade; causa; evolução e consequências), relevante pelas implicações para a prática clínica, pois revela metáforas que poderão influenciar a autogestão. Este estudo qualitativo e exploratório recorre à teoria cognitiva da metáfora, explorando metáforas dos participantes através de entrevistas semiestruturadas. Compreende 17 participantes que relataram 84 metáforas. As entrevistas foram submetidas a análise de conteúdo. Os principais resultados indicam: identidade descrita por “doença que não dói, não se sente, mas está cá dentro”; causas envolvem “não sei como se apanha” e “herdei esta doença”; evolução e consequências associam-se a “lentamente vai dando cabo da pessoa”. Estas metáforas sugerem que os adultos idosos diabéticos tipo 2 vivem a doença como algo “misterioso”, o que poderá dificultar o seu envolvimento na autogestão

    A Blind Spot?

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    Middle-aged and older men who have sex with men (MSM) are one of the most underestimated populations with regard to HIV/AIDS infection, despite the worldwide trend of increasing prevalence in recent years. This population also has low rates of testing, although rare studies are done exclusively with middle-aged and older MSM assessing the factors associated with this prevalence. Thus, based on data from an exclusive online survey with middle-aged and older MSM who use geolocation-based dating applications, the purpose of the study was to analyze factors associated with not taking the HIV test among middle-aged (50 years old) and older MSM in Brazil. Using a modification of time-location sampling adapted to virtual reality, 412 volunteers were approached in Grindr®, Hornet®, SCRUFF®, and Daddyhunt®. The multivariate logistic regression model was adopted to produce adjusted odds ratios (ORa), considering a significance level at.05. There were factors associated with not taking the test: being in a relationship (ORa: 0.24; 95% CI [0.10, 0.53]); knowing partner through the applications (ORa: 1.84; 95% CI [1.07, 3.15]); not knowing the serological status (ORa: 5.07; 95% CI [1.88, 13.67]); ejaculating outside of anal cavity (ORa: 1.79; 95% CI [1.04, 3.05]); practicing sex without penetration (ORa: 2.30; 95% CI [1.17, 4.50]); not taking the test as a form of prevention (ORa: 2.83; 95% CI [1.05, 7.68]); and rarely using Viagra in sexual intercourse (ORa: 1.91; 95% CI [1.20, 3.65]). There is a blind spot in the prevalence of HIV testing in older MSM because this population is not being covered by services, which compromises the overall response to HIV, the goals set for universal health coverage.publishersversionpublishe

    Matemáticas, Software y YouTube: Posibilidades para profesores y alumnos en el aula

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    Os alunos tem familiaridade e contam com fácil acesso a smartphones, tablets, computadores e aplicativos e gostam de utilizá-los. Assim, o objetivo desse artigo é apresentar uma proposta de aula que utiliza tecnologias digitais e seus recursos para o processo de ensino-aprendizagem na disciplina de matemática. Trata-se de um artigo de revisão bibliográfica. Desta forma, a partir da revisão: identificamos os desafios e potencialidades das Tecnologias Digitais de Informação e Comunicação – TDIC aplicadas a Educação; apontamos as principais dificuldades no ensino-aprendizagem do conteúdo “gráfico de função do segundo grau” e sugerimos um plano de aula para o ensino deste conteúdo nas aulas de matemática utilizando dois recursos: o software GeoGebra e vídeos no YouTube. A literatura e as potencialidades e características dos recursos sugeridos demonstram como a proposta pode contribuir para melhor compreensão do conteúdo, por exemplo, na visualização pelo aluno do gráfico de função. Deste modo, consideramos que a proposta apresentada favorece o processo de ensino-aprendizagem.Students are familiar and have easy access to smartphones, tablets, computers and applications and enjoy using them. Thus, the purpose of this article is to present a lesson proposal that uses digital technologies and its resources for the teaching-learning process in the mathematics discipline. This is a bibliographical review article. Thus, from the review: we identify the challenges and potentialities of Digital Information and Communication Technologies - TDIC applied to Education; we pointed out the main difficulties in teaching-learning "second degree function graph" content and suggested a lesson plan for teaching this content in math classes using two resources: GeoGebra software and videos on YouTube. The literature and the potentialities and characteristics of the suggested resources demonstrate how the proposal can contribute to a better understanding of the content, for example, in the student's visualization of the function graph. Thus, we consider that the proposal presented favors the teaching-learning process.Los alumnos tienen familiaridad y cuentan con fácil acceso a smartphones, tabletas, computadoras y aplicaciones y les gusta usarlos. Así, el objetivo de este artículo es presentar una propuesta de clase que utiliza tecnologías digitales y sus recursos para el proceso de enseñanza-aprendizaje en la disciplina de matemáticas. Se trata de un artículo de revisión bibliográfica. De esta forma, a partir de la revisión: identificamos los desafíos y potencialidades de las Tecnologías Digitales de Información y Comunicación - TDIC aplicadas a la Educación; apuntamos a las principales dificultades en la enseñanza-aprendizaje del contenido “gráfico de función del segundo grado” y sugerimos un plan de clase para la enseñanza de este contenido en las clases de matemáticas utilizando dos recursos: el software GeoGebra y vídeos en YouTube. La literatura y las potencialidades y características de los recursos sugeridos demuestran cómo la propuesta puede contribuir a una mejor comprensión del contenido, por ejemplo, en la visualización por el alumno del gráfico de función. De este modo, consideramos que la propuesta presentada favorece el proceso de enseñanza-aprendizaje
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