Learning from multimedia and hypermedia

Computer-based multimedia and hypermedia resources (e.g., the world wide web) have become one of the primary sources of academic information for a majority of pupils and students. In line with this expansion in the field of education, the scientific study of learning from multimedia and hypermedia has become a very active field of research. In this chapter we provide a short overview with regard to research on learning with multimedia and hypermedia. In two review sections, we describe the educational benefits of multiple representations and of learner control, as these are the two defining characteristics of hypermedia. In a third review section we describe recent scientific trends in the field of multimedia/hypermedia learning. In all three review sections we will point to relevant European work on multimedia/hypermedia carried out within the last 5 years, and often carried out within the Kaleidoscope Network of Excellence. According to the interdisciplinary nature of the field this work might come not only from psychology, but also from technology or pedagogy. Comparing the different research activities on multimedia and hypermedia that have dominated the international scientific discourse in the last decade reveals some important differences. Most important, a gap seems to exist between researchers mainly interested in a “serious” educational use of multimedia/ hypermedia and researchers mainly interested in “serious” experimental research on learning with multimedia/hypermedia. Recent discussions about the pros and cons of “design-based research” or “use-inspired basic research” can be seen as a direct consequence of an increasing awareness of the tensions within these two different cultures of research on education

Psychology and aggression

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68264/2/10.1177_002200275900300301.pd

Oxidative stress response in sugarcane

Oxidative stress response in plants is still poorly understood in comparison with the correspondent phenomenon in bacteria, yeast and mammals. For instance, nitric oxide is assumed to play various roles in plants although no nitric oxide synthase gene has yet been isolated. This research reports the results of a search of the sugarcane expressed sequence tag (SUCEST) database for homologous sequences involved in the oxidative stress response. I have not found any gene similar to nitric oxide synthase in the SUCEST database although an alternative pathway for nitric oxide synthesis was proposed. I have also found several genes involved in antioxidant defense, e.g. metal chelators, low molecular weight compounds, antioxidant enzymes and repair systems. Ascorbate (vitamin C) is a key antioxidant in plants because it reaches high concentrations in cells and is a substrate for ascorbate peroxidase, an enzyme that I found in different isoforms in the SUCEST database. I also found many enzymes involved in the biosynthesis of low molecular weight antioxidants, which may be potential targets for genetic manipulation. The engineering of plants for increased vitamin C and E production may lead to improvements in the nutritional value and stress tolerance of sugarcane. The components of the antioxidant defense system interact and their synthesis is probably closely regulated. Transcription factors involved in regulation of the oxidative stress response in bacteria, yeast and mammals differ considerably among themselves and when I used them to search the SUCEST database only genes with weak similarities were found, suggesting that these transcription regulators are not very conserved. The involvement of reactive oxygen species and antioxidants in plant defense against pathogens is also discussed.<br>A resposta ao estresse oxidativo não é bem conhecida em plantas como em bactérias, leveduras e humanos. Por exemplo, assume-se que óxido nítrico tem várias funções em plantas apesar do gene que codificaria para óxido nítrico sintetase nunca ter sido isolado. Este trabalho descreve os resultados de uma busca no banco de dados de seqüências expressas de cana de açúcar (SUCEST) de genes envolvidos na resposta ao estresse oxidativo. Eu não encontrei genes similares a óxido nítrico no banco de dados do SUCEST, mas uma via alternativa para a produção deste radical livre pode ser proposta. Eu também encontrei vários genes envolvidos na defesa antioxidante, como quelantes de metais, antioxidantes de baixo peso molecular, enzimas antioxidantes e sistemas de reparo. Ascorbato (vitamina C) é um importante antioxidante em plantas porque é encontrado em altas concentrações em células vegetais e porque é substrato de ascorbato peroxidase, uma enzima que eu encontrei em diferentes isoformas no banco de dados do SUCEST. Eu também encontrei várias enzimas envolvidas na biossíntese de antioxidantes de baixo peso molecular que podem ser alvos para manipulação genética. A obtenção de plantas modificadas geneticamente que sintetizariam vitaminas C e E em altos níveis poderiam melhorar o valor nutricional e a tolerância a estresses de cana de açúcar. Os diversos componentes do sistema de defesa antioxidante interagem entre si e as suas sínteses devem ser muito bem reguladas. Fatores de transcrição envolvidos na regulação da resposta ao estresse oxidativo de bactérias, leveduras e de humanos diferem consideravelmente entre si e quando foram utilizados para buscas no banco de dados do SUCEST, somente genes com similaridades fracas foram encontrados, sugerindo que estas proteínas não são muito conservadas. O envolvimento de espécies reativas de oxigênio e nitrogênio na defesa de plantas contra patógenos também é discutido neste trabalho