RESUMO Objetivo: O objetivo deste artigo foi modelar a série de minuto das taxas de câmbio do par EUR/USD por meio dos métodos singular spectrum analysis (SSA) e ARIMA-GARCH, e avaliar qual gera previsões melhores para um horizonte de cinco minutos. Originalidade/valor: Apesar de o SSA se mostrar uma técnica bem-sucedida em outros ramos da ciência, suas aplicações em finanças ainda são recentes. Além disso, a modelagem da taxa de câmbio é um problema complexo que envolve conceitos e propriedades estatísticas. No entanto, apesar da complexidade, a análise de tal série é de suma importância para diversos agentes que atuam direta ou indiretamente na economia e no mercado financeiro. Design/metodologia/abordagem: Estimaram-se modelos de séries temporais com as técnicas ARIMA-GARCH e SSA, sendo consideradas três amostras do fechamento da cotação ask do câmbio: tendências de alta, de baixa e sem tendência dominante. Resultados: As previsões realizadas pelo SSA foram as que mais se aproximaram das observações originais para os três casos. Para as medidas de qualidade, o SSA obteve melhores resultados para as amostras com tendências de alta e de baixa, enquanto, para a amostra sem tendência dominante, os resultados apontaram que a técnica ARIMA-GARCH atingiu resultados mais satisfatórios. Portanto, concluiu-se que as previsões do SSA, no que diz respeito às taxas de câmbio no período em questão, são mais adequadas que aquelas obtidas pelo modelo ARIMA-GARCH, independentemente do movimento do mercado.

ABSTRACT Purpose: The objective of this article is to model a minute series of exchange rates for the EUR/USD pair using the singular spectrum analysis (SSA) and ARIMA-GARCH methods and evaluate which one offers better forecasts for a five-minute horizon. Originality/value: Despite being a successful technique in other branches of science, the application of SSA in finance is quite new. Furthermore, exchange rate modeling is a complex problem, comprising statistical concepts and properties. However, despite the complexity, the analysis of this series is extremely important for several agents playing, directly or indirectly, a role in the economy and the financial market. Design/methodology/approach: Time series models were estimated using the ARIMA-GARCH and SSA techniques, taking into account three samples of the ask exchange rate (closing): uptrend, downtrend, and no well-defined trend. Findings: The forecasts carried out by the SSA were the ones closest to the original observations for the three cases. Regarding the quality measurements, SSA obtained the best results for both uptrend and downtrend samples; for the sample with no well-defined trend, the findings indicated that the ARIMA-GARCH technique attained better results. However, it was concluded that the SSA forecasts, regarding exchange rates during the studied period, are more appropriate than the ones obtained by the ARIMA-GARCH model, regardless of the market movement.

OBJECTIVES: To identify the most cited articles in general surgery published by Brazilian authors. INTRODUCTION: There are several ways for the international community to recognize the quality of a scientific article. Although controversial, the most widely used and reliable methodology to identify the importance of an article is citation analysis. METHODS: A search using the Institute for Scientific Information citation database (Science Citation Index Expanded) was performed to identify highly cited Brazilian papers published in twenty-six highly cited general surgery journals, selected based on their elevated impact factors, from 1970 to 2009. Further analysis was done on the 65 most-cited papers. RESULTS: We identified 1,713 Brazilian articles, from which nine papers emerged as classics (more than 100 citations received). For the Brazilian contributions, a total increase of about 21-fold was evident between 1970 and 2009. Although several topics were covered, articles covering trauma, oncology and organ transplantation were the most cited. The majority of classic studies were done with international cooperation. CONCLUSIONS: This study identified the most influential Brazilian articles published in internationally renowned general surgery journals.

Realizamos um estudo transversal prospectivo cujo objetivo foi avaliar a acurácia do auto-exame de mamas (AEM) na detecção de nódulos mamários palpáveis e a relação com sua freqüência. Foram entrevistadas 2672 mulheres que realizaram mamografia na Região do Vale dos Sinos/RS no período de janeiro de 94 a julho de 97, questionando-se quanto à freqüência da realização de AEM. As mulheres foram divididas em dois grupos: grupo I (mensalmente), grupo II (quase nunca). As mulheres que relataram realizar o AEM ocasionalmente foram excluídas da análise principal. Foi perguntado à paciente se ela ou seu médico haviam palpado alguma lesão mamária. Comparou-se os achados de palpação da paciente com os do médico (relatados pela paciente). A sensibilidade do AEM foi maior no grupo I comparado ao II (57,4% versus 33,3%; P <0,05). Concluímos que existe uma associação entre a realização mensal de AEM e uma maior sensibilidade na detecção de nódulos mamários palpáveis.

We conducted a prospective cross-sectional study to evaluate the accuracy of the breast self-examination (BSE) in the detection of palpable breast lumps and the relation to its frequency of performance. Two thousand six hundred and seventy two women who have had a mammogram in a private clinic in Vale dos Sinos-RS between January 1994 and July 1997 were asked about BSE performance frequency. They were divided in two groups: group I (monthly), group II (almost never). The women who referred performing BSE on a occasional basis were excluded from the main analysis. The woman was asked wheter she or her physician had palpated something in her breasts. The patient's BSE findings were compared with those of her physician (based on the patients' report). The sensitivity of the BSE was higher in group I compared to group II (57.4% versus 33.3%; rho<0.05). We concluded that there is an association between frequency of performance and sensitivity of BSE to detect breast lumps.