The role of chain scission and chain branching in high density polyethylene during thermo-mechanical degradation

The mechanical and thermo-oxidative degradation of high density polyethylene (HDPE) was measured in a twin-screw extruder using various processing conditions. Two types of HDPE, Phillips and Ziegler-Natta, having different levels of terminal vinyl unsaturation were analysed. Mild screw profiles, having mainly conveying elements, have short mean residence times then profiles with kneading discs and left hand elements. Carbonyl and traps-vinylene group concentrations increased, whereas vinyl group concentration decreased with number of extrusions. Higher temperature profiles intensified these effects. The thermo-mechanical degradation mechanism begins with chain scission in the longer chains due to their higher probability of entanglements. These macroradicals then react with the vinyl terminal unsaturations of other chains producing chain branching. Shorter chains are more mobile, not suffering scission but instead are used for grafting the macroradicals, increasing the molecular weight. Increase in the levels of extrusion temperature, shear and vinyl end groups content facilitates the thermo-mechanical degradation reducing the amount of both, longer chains via chain scission and shorter chains via chain branching, narrowing the polydispersity. Phillips HDPE produces a higher level of chain branching than does the Ziegler-Natta type. (C) 2004 Elsevier Ltd. All rights reserved.

Utilização do coque verde de petróleo da Petrobras em substituição parcial ao carvão mineral das misturas injetadas em altos fornos

The Petrobras produced green petroleum coke (GPC) is a carbon rich fuel, virtually ash-free, with low sulfur content, and is a fuel suitable to replace metallurgical coke in blast furnaces. The GPC was tested in a pulverized coal injection simulator built in the Volta Redonda research center. It presented a low burning efficiency due to low volatile material content and high substitution rate by the carbon content. The tests were carried out in blast furnaces with ≤ 50% Petrobras GPC in the coal blends. The injected coal/CVP mixtures produced no negative side effects in the blast furnace grinding systems, pneumatic conveying, or operating process. The mixture burning process inside the blast furnace showed a decrease in fuel consumption, with a significant reduction in metallurgical coke consumption. The industrial-scale tests of the GPC mixtures did not reach the 70% maximum for lack of the GPC feedstock, which is necessary to continue with standard coal mixtures.

Qualidade da água utilizada para consumo em escolas no município de São Carlos-SP

Pós-graduação em Alimentos e Nutrição - FCFAR

Sexualidade, gênero e pedagogias culturais: representações e problematizações em contexto escolar

Pós-graduação em Educação para a Ciência - FC

Análise e demonstração do comportamento do escoamento bifásico gás-sólido

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bias na Representação de Assunto: Uma Discussão de Oposições Binárias nos Functional Requirements for Subject Authority Data (FRSAD)

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

Procedimentos para descrição de figuras em texto impresso visando à acessibilidade para pessoas cegas: um estudo a partir de um livro de educação física adaptada

This study was aimed to analyze a procedure that makes the description of pictures in printed text from a book that promotes accessibility for blind people. In addition, the study was aimed to analyze the reformulations suggested by the judges and the index of agreement between researcher and judges. The descriptions were submitted to judges to evaluate the content of the material. The results were obtained through the analysis of two assessments: 1) agreement rate ‒ between the researcher and judges A and B, and between judge A and judge B and 2) analysis of the suggested reformulation. In quantitative terms, the results indicated that the material described achieved a high reliability. In qualitative terms, the reliability achieved represents the quality of the material offered, with well structured descriptions where writing meaning is equivalent to image information, fulfilling the purpose to present in printed text the elements represented in the pictures, effectively conveying their meaning.

Os animais não humanos no material didático do programa São Paulo Faz Escola

The relationship between humans and non-human animals dates back to the Prehistoric Era, when groups of humans migrated from the nomadic and extractive stage to sedentariness, starting to develop agriculture and animal husbandry. Ancient Greek philosophy, notably the Aristotelian school of philosophy, posited that nature has not done anything for nothing, and all things have a purpose: plants were created for the sake of animals, and these for the good of men, while the Bible preaches the view that the world was created for the good of men and other species were subordinated to their wants and needs. During the Renaissance, centuries XIV to XVI, anthropocentrism was established as the main philosophical concept. However, in relation to the treatment of animals, Renaissance did not differ substantially from medieval scholasticism, considering animals like machines, devoid of pain and immortal soul. In this context, scientific knowledge about plants, non-human animals and nature in general, is built on anthropocentric values, thus influencing the construction of school education in the disciplines of Science and Biology. Nowadays, at São Paulo state schools, specifically in the Ensino Fundamental II (6th to 9th grade), the program of the discipline Ciências da Natureza e suas Tecnologias is set by the Currículo Oficial do Estado de São Paulo, via the São Paulo Faz Escola Program, implemented by the Secretaria Estadual de Educação in 2010. This documentary research used the methodology of Content Analysis and aimed to analyze the presentation of non-human animals in Caderno do Professor and Caderno do Aluno, from 6th to 9th grades of the discipline Ciências da Natureza e suas Tecnologias. The analysis of the courseware revealed that its contents were influenced by the anthropocentric view, in both implicitly and explicitly ways, conveying anthropomorphic, utilitarian, stereotyped and derogatory statements towards...