Teste Repositóri
2014-01-01
Resultados de pesquisa
Foram encontrados 14.700 registos.
Severe and generalized mutilation of the crown in urban trees is always technical, economic and aesthetically wrong. The new growth after pruning develops from adventitious buds which were formed at the cuts. Their sprouting is more dense and bushy than before, originating a need for expensive new pruning in the next few years, consuming reserves which become not available for growth and exposing the trees to pathogens. These negative factors must be added to several other agressions that can potentially damage urban trees, frequently leading to their antecipated death. Tree care and maintenance in urban areas must be planned and supervised by technitians with a degree in forestry or other adequate skill. The workers involved in those operations should have good professional qualification, which is difficult to harmonize with the low s...
Mestrado em Engenharia do Ambiente - Tecnologias Ambientais - Instituto Superior de Agronomia
Dissertação de Mestrado Integrado em Medicina Veterinária
The outbreak of highly pathogenic avian
influenza of the H5N1 virus subtype in Western
European countries induced the fear that it could
reach Portugal through wild bird migration. Ducks,
geese and swans are some of the bird groups with
higher prevalence of influenza virus that might be
vectors of virus dissemination, considering the
existing studies on low pathogenic subtypes that are
common in nature (Olsen et al. 2006), and also
occur in Portugal (D. Rodrigues et al., unpublished
data). Although swans do not occur frequently in
Portugal and geese are mostly restricted to Tagus
River Estuary Nature Reserve (e.g. Farinha & Costa
1999), ducks are common in Portugal and mostly
concentrated on wetlands near the coast (Costa &
Guedes 1997), and wintering Aythya duck species
are much less numerous than wintering Anas
speci...
Mestrado em Engenharia Agronómica - Instituto Superior de Agronomia
Economic theory has hitherto discussed five ways in which an economy can emerge from a depression. This paper presents a brief review of the performance of these five ways out of depression during the 19th and 20th centuries, and prognosticates their future in the 21st century. Innovations appear as the most effective way to overcome depressions. This leads to an analysis of Schumpeter's typology of innovations and to a discussion of the claim of endogenous growth theory that innovations are no longer the result of the activity of entrepreneurs, but have become a built-in feature of market capitalist economies. The paper concludes with a consideration of the sustainability of the flow of innovations in the future, in view of the phenomena of population stabilisation and the reduction in available natural resources, which will very prob...
