Reações ácido-base: conceito, representação e generalização a partir das energias envolvidas nas transformações

Undergraduate students on the first year of Chemistry Courses are unfamiliar with the representation of acid-base reactions using the ionic equation H+ + OH- → H2O. A chemistry class was proposed about acid-base reactions using theory and experimental evaluation of neutralization heat to discuss the energy involved when water is formed from H+ and OH- ions. The experiment is suggested using different strong acids and strong base pairs. The presentation of the theme within a chemistry class for high school teachers increased the number of individuals that saw the acid-base reaction from this perspective.

RESONANCE PRODUCTION IN PERIPHERAL HEAVY-ION COLLISIONS

Heavy-ion collisions at ultrarelativistic energies may be used as a powerful source of photons and pomerons. We compute the rates for pseudoscalar meson production through two-photon and two-pomeron scattering, at energies that will be available at RHIC and LHC. Light mesons will mostly be produced by pomeron fusion at large rates, the two processes are comparable for charmed mesons, while electromagnetic production will be dominant for bottom mesons. We discuss the possibility of observing the reaction gammagamma(PP) --> R --> gammagamma, and comment on the particular case where R could be a scalar resonance at 650 MeV.

Legitimacy and context: Implications for public sector reform in developing countries

This article examines the interplay between legitimacy and context as key determinants of public sector reform outcomes. Despite the importance of variables Such as legitimacy of public institutions, levels of civic morality and socio-economic realities, reform strategies often fail to take such contextual factors into account. The article examines, first, relevant literature both conceptual and empirical, including data from the World Values Survey project. It is argued that developing countries have distinctive characteristics which require particular reform strategies. The data analysed shows that in Latin American countries, there is no clear Correlation between confidence in public institutions and civic morality. Other empirical studies show that unemployment has a negative impact on the level of civic morality, while inequality engenders corruption. This suggests that poorer and socio-economically stratified countries face greater reform challenges owing to the lack of legitimacy of public institutions. The article concludes that reforms should focus on areas of governance that impact on poverty. This will in turn help produce more stable outcomes. Copyright (C) 2008 John Wiley & Sons, Ltd.

Estudios sobre la juventud marginal latinoamericana

Incluye Bibliografía

Towards development in landlocked economies

Includes bibliography

Unusual presentation of oral squamous cell carcinoma in a young woman

Oral squamous cell carcinoma (OSCC) is the most common oral malignant neoplasm, mainly affecting individuals over 50 years old with a history of tobacco and alcohol use. The occurrence of this oral cancer in individuals under 40 years old is unusual and, when it does occur, shows a weaker relation to those risk factors and a more aggressive clinical course. Due to the paucity of reports in this population, it is difficult to prove its increasing trend. A case of oral squamous cell carcinoma in a 39-year-old woman with no history of tobacco or alcohol use is reported. Clinical and histopathological findings, aetiology, and treatment are discussed. The increasing trend of oral squamous cell carcinoma in young women without known risk factors highlights the need for clinicians to be prepared to diagnose this lesion quickly and precisely, providing a better prognosis, chance of survival, and quality of life for the patient.

Reproduction, food dynamics and exploitation level of Oreochromis niloticus (Perciformes: Cichlidae) from artisanal fisheries in Barra Bonita Reservoir, Brazil

Nile tilapia (Oreochromis niloticus), which is exotic to South America, is the most common species caught in artisanal fisheries at the Barra Bonita Reservoir, Southeastern Brazil. This species is of great socioeconomic importance for the region and keeps active a population of about 500 fishers. In the present study we assess reproduction, food dynamics and level of exploitation of O. niloticus, caught by artisanal fisheries in the Barra Bonita Reservoir. Specimens were collected monthly, from July 2004-June 2005, and a total of 1 715 specimens were analyzed. Each specimen was examined to obtain biological and biometric data: standard length (cm), total weight (g), reproductive data (sex and stage of maturation), and stomach contents (empty, partly full, and full). We also estimated the sex ratio (by macroscopic observation of gonads), reproductive period (by ovarian development and seasonal average of gonadosomatic index in females), and feeding habits (by stomach contents). The possible relationship between abiotic factors and the reproductive period was statistically verified using Spearman's Rank Correlation. The FiSAT (ELEFAN I) package was used to assess growth parameters, mortality rates and to infer exploitation rate from standard length frequencies. The O. niloticus population had a sex ratio of 1.3:1 (M:F). Results indicated that ripe females were captured throughout the year, with a higher frequency during the winter-2004 (with a frequency of 59%, at a mean temperature of 20.5°C), and in spring-2004 (with a frequency of 60.5% at a mean temperature of 21.18°C). The GSI mean values obtained by season were: winter-2004: 1.71; spring-2004: 1.72; summer-2005: 0.80, and autumn-2005: 1.19. The Spearman correlation indicated positive values with respect to pH, dissolved oxygen, electric conductivity, transparency and chlorophyll a, and negative values with respect to temperature, accumulated rainfall and altimetric benchmark. The main food items were phytoplankton and periphytic algae, observed in 99.6% of the analyzed stomachs. The estimated growth and mortality parameters were: L∞=33.60cm, k=0.63/year, longevity= 4.76years, Z=2.81/ year, M=1.20/year and F=1.61/year. The weight-length relationship was Ln Wt=-2.8532+2.8835 Ln Lp. The estimated yield per recruit values were as follows: E=0.570, Emax=0.776, E0.1=0.604 and E0.5=0.349. These results indicate that a well established population of O. niloticus is present at Barra Bonita Reservoir; with an active reproduction throughout the year, more intense during winter and spring, and that O. niloticus is a phytoplanktophagus species. There were no indications that this species is being overfished, we therefore recommend that, due to its exotic condition, no restrictions need to be taken on its fishing activities.

True branched nostocalean cyanobacteria from tropical aerophytic habitats and molecular assessment of two species from field samples

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Proyecto de programa de trabajo del sistema de la CEPAL, 2002-2003

El Proyecto de programa de trabajo del sistema de la CEPAL, 2002-2003, fue presentado Vigesimoctavo período de sesiones México, D.F., 3 al 7 de abril de 2000. La versión electrónica de los subprogramas tiene solamente carácter informativo.

Draft programme of work of the ECLAC system, 2002-2003

The proposed programme of work for the ECLAC system for 2002-2003 was submitted to the member States of the Commission at its Twenty-eighth session. Mexico City, 3-7 April 2000. The electronic version is for information purposes only.

La formación para el trabajo en la Argentina: situación actual y perspectivas para el futuro

Incluye Bibliografía

Ambiente computacional interativo para auxílio do processo de ensino aprendizagem de matemática básica

A aprendizagem é um processo continuo permeado por construções e reconstruções do conhecimento, com a inserção do computador no processo de ensino aprendizagem, juntamente com a análise das abordagens da Psicologia Educacional e Educação Matemática, foi possível, neste trabalho, a elaboração de um prototipo computacional voltado para o auxilio a aprendizagem da matemática. Este prototipo e um ambiente computacional interativo para auxiliar o aprendizado das quatro operações básicas (adição, subtração,multiplicação e divisão). Assunto este de grande repercussão no ambiente escolar, pois se não aprendido adequadamente, apresenta sérios problemas na evolução do aprendizado matemático do estudante. O trabalho envolve quatro etapas: Aspectos teóricos sobre o processo de ensino aprendizagem, dando-se maior ênfase a abordagem construtivista; Processo de ensino aprendizagem de Matemática, suas dificuldades e perspectivas de mudanças mediante ao aprendizado auxiliado por meios computacionais; concepção e modelagem do prototipo seguido dos Resultados obtidos durante aplicações do mesmo, resultados esses favoráveis a proposta inicial do trabalho.

A multidomain approach to asteroid families' identification

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Rede de tags para recuperação da informação no contexto da Representação Iterativa

Information retrieval is a recurrent subject in search of information science. This kind of study aim to improve results in both searches on the Web and in various other digital information environment. In this context, the Iterative Representation model suggested for digital repositories, appears as a differential that changes the paradigm of self-archiving of digital objects, creating a concept of relationship between terms that link the user thought the material deposited in the digital environment. The links effect by the Iterative Representation aided Assisted Folksonomy generate a shaped structure that connects networks, vertically and horizontally, the objects deposited, relying on some kind of structure for representing knowledge of specialty areas and therefore, creating an information network based on knowledge of users. The network of information created, called the network of tags is dynamic and effective a different model of information retrieval and study of digital information repositories.Keywords Digital Repositories; Iterative Representation; Folksonomy; Folksonomy Assisted; Semantic Web; Network Tags.