Least-action principle and path-integral for classical mechanics

In this paper we show how the equations of motion of a superfield, which makes its appearance in a path-integral approach to classical mechanics, can be derived without the need of the least-action principleComment: to appear IN PHYS.REV.D (Brief Report

Costs and Benefits of Privatization: Evidence from Brazil

Although the Brazilian privatization program has been a sweeping endeavor involving more than 100 firms and billions of dollars, most of the studies have been published only in Brazil, and in Portuguese. This paper is the most comprehensive study to date in terms of the companies covered, and includes the most recent data. It looks at the results of privatization in Brazil for a broad range of economic variables to answer the question: Has the widespread popular discontent with the program been justified? The paper also examines the effects of privatization on aspects that affect the development of financial markets, including minority shareholder rights. It concludes with recommendations for democratizing capital ownership through public offers in which workers would be entitled to participate using public sector liabilities such as FGTS deposits.

Evolution of statistical analysis in empirical software engineering research: Current state and steps forward

Software engineering research is evolving and papers are increasingly based on empirical data from a multitude of sources, using statistical tests to determine if and to what degree empirical evidence supports their hypotheses. To investigate the practices and trends of statistical analysis in empirical software engineering (ESE), this paper presents a review of a large pool of papers from top-ranked software engineering journals. First, we manually reviewed 161 papers and in the second phase of our method, we conducted a more extensive semi-automatic classification of papers spanning the years 2001--2015 and 5,196 papers. Results from both review steps was used to: i) identify and analyze the predominant practices in ESE (e.g., using t-test or ANOVA), as well as relevant trends in usage of specific statistical methods (e.g., nonparametric tests and effect size measures) and, ii) develop a conceptual model for a statistical analysis workflow with suggestions on how to apply different statistical methods as well as guidelines to avoid pitfalls. Lastly, we confirm existing claims that current ESE practices lack a standard to report practical significance of results. We illustrate how practical significance can be discussed in terms of both the statistical analysis and in the practitioner's context.Comment: journal submission, 34 pages, 8 figure

On Birnbaum-Saunders Inference

The Birnbaum-Saunders distribution, also known as the fatigue-life distribution, is frequently used in reliability studies. We obtain adjustments to the Birnbaum--Saunders profile likelihood function. The modified versions of the likelihood function were obtained for both the shape and scale parameters, i.e., we take the shape parameter to be of interest and the scale parameter to be of nuisance, and then consider the situation in which the interest lies in performing inference on the scale parameter with the shape parameter entering the modeling in nuisance fashion. Modified profile maximum likelihood estimators are obtained by maximizing the corresponding adjusted likelihood functions. We present numerical evidence on the finite sample behavior of the different estimators and associated likelihood ratio tests. The results favor the adjusted estimators and tests we propose. A novel aspect of the profile likelihood adjustments obtained in this paper is that they yield improved point estimators and tests. The two profile likelihood adjustments work well when inference is made on the shape parameter, and one of them displays superior behavior when it comes to performing hypothesis testing inference on the scale parameter. Two empirical applications are briefly presented.Comment: Paper accepted for publication in Computational Statistics and Data Analysi

Controle pós-colheita da antracnose do maracujazeiro-amarelo com aplicação de óleo de copaíba.

O objetivo deste trabalho foi avaliar a aplicação de óleo essencial de copaíba no controle da antracnose, nos frutos do maracujazeiro-amarelo, e comparar sua ação fungicida/fungistática in vitro com o óleo resina de copaíba. No experimento in vivo, os frutos foram inoculados com uma suspensão de esporos da ordem de 106 conídios mL-1 e 1% de Tween 80, acondicionados em bandejas de polipropileno e colocados em câmara incubadora com temperatura de 25°C e 90% de umidade relativa do ar. Passadas 24 horas da inoculação, pulverizou-se óleo essencial nas seguintes concentrações: T1= 0 mL L-1; T2= 0,25 mL L-1; T3= 0,5 mL L-1; T4= 0,75 mL L-1; T5= 1,0 mL L-1, sendo avaliados a perda de massa do fruto, a severidade da antracnose e o número de lesões, ambas aos seis dias. Para o experimento in vitro, utilizou-se do meio de cultura batata-dextrose-ágar (BDA) que, após ser esterilizado em autoclave (120 ºC), recebeu óleo essencial e óleo resina de copaíba (0; 0,5; 1,0; 1,5 e 2,0 mL L-1). Após o resfriamento do meio de cultura, foi repicado para o centro da placa um disco de micélio de 12,5 mm de diâmetro de Colletotrichum gloeosporioides; e as placas, incubadas a 25°C e 90% de umidade. A aferição do crescimento micelial foi verificada com o auxílio de paquímetro analógico, após sete dias de crescimento micelial. O óleo essencial de copaíba, nas concentrações de 0,25 mL L-1 a 1.0 mL L-1, não foi eficaz no controle pós-colheita do fungo da antracnose in vivo e na perda de massa dos frutos de maracujá. O óleo resina de copaíba inibiu o crescimento de C. gloeosporioides in vitro de forma mais eficiente que o óleo essencial de copaíba

Integrated didactics: an example of a curriculum model enhancing knowledge crossing

In this paper, we introduce an innovative course in the Portuguese Context, the Master's Course in “Integrated Didactics in Mother Tongue, Maths, Natural and Social Sciences”, taking place at the Lisbon School of Education and discussing in particular the results of the evaluation made by the students who attended the Curricular Unit - Integrated Didactics (CU-ID). This course was designed for in-service teachers of the first six years of schooling and intends to improve connections between different curriculum areas. In this paper, we start to present a few general ideas about curriculum development; to discuss the concept of integration; to present the principles and objectives of the course created as well as its structure; to describe the methodology used in the evaluation process of the above mentioned CU-ID. The results allow us to state that the students recognized, as positive features of the CU-ID, the presence in all sessions of two teachers simultaneously from different scientific areas, as well as invitations issued to specialists on the subject of integration and to other teachers that already promote forms of integration in schools. As negative features, students noted a lack of integrated purpose, applying simultaneously the four scientific areas of the course, and also indicated the need to be familiar with more models of integrated education. Consequently, the suggestions for improvement derived from these negative features. The students also considered that their evaluation process was correct, due to the fact that it was focused on the design of an integrated project for one of the school years already mentioned