Browsing by Issue Date, starting with "2000-03"
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- Kinetics of photodegradation of the fungicide fenarimol in natural waters and in various salt solutions: salinity effects and mechanistic considerationsPublication . Mateus, Maria da Conceição; Silva, Abílio M. da; Burrows, Hugh D.The rate of photodegradation of the Fungicide fenarimol (alpha-(2-chlorophenyl)-alpha-(4-chlorophenyl)-5-pyrimidine-methanol) by solar radiation has been studied in natural waters with different salinities. Photodegradation rates and quantum yields are found to decrease with increasing salinity. To explain this behaviour, experiments were pei formed with different salt solutions (NaCl, NaBr, BaCl2 and ZnCl2) using both solar irradiation and a photoreactor (lambda(excit) 313 nm). As with natural waters, marked effects of added salt were observed on the photolysis rater which decreased significantly from 0.67 h(-1) in the absence of salt to 0.11 h(-1) in the presence of BaCl2. In photoreactor studies, the observed order of quenching was BaCl2 > ZnCl2 and NaBr > NaCl. In contrast, neither the triplet state quencher sorbic acid nor oxygen had any effect on the photolysis, supporting the idea that photodegradation goes by the lowest excited singlet state of fenarimol. To understand the origin of the effect of added salts, fluorescence quenching studies have been performed with various halide and nonhalide salts and the respective quenching constants determined. With NaCl and NaBr, the ratio of fluorescence quenching constants is identical to the ratio of reciprocal quantum yields for photodegradation of fenarimol, indicating a common mechanism. The correlation of fluorescence quenching rates with halide ion oxidation potentials strongly suggests that this involves an electron transfer mechanism. It is suggested that the effect may be used to stabilise the fungicide towards photodegradation. (C) 2000 Elsevier Science Ltd. All rights reserved.
- O alargamento da União Europeia aos países da Europa Central e Oriental e consequências para PortugalPublication . Faria, Renato Orlando Machado de; Jesus, Avelino deEste trabalho de investigação denominado “Alargamento da União Europeia aos Países da Europa Central e Oriental (Peco) e consequências para Portugal” tem por objectivo analisar a evolução de todo este processo de alargamento da U.E. aos Peco e apurar quais poderão ser as vantagens/ desvantagens desta adesão para a União Europeia como um todo, mas particularmente para Portugal. Os Países da Europa Central e Oriental aquando da separação do antigo bloco de Leste ficaram com as suas economias envolvidas numa grande instabilidade económica, política e social, e viram na Europa Ocidental a oportunidade de reconstrução e recuperação destas mesmas economias. Por sua vez, a U.E., com a libertação dos Peco da economia centralizada e do “ jugo” soviético, viu a oportunidade de reunificar novamente a Europa reconhecendo a vocação dos países da Europa Central e Oriental de se virem a tornar membros efectivos, desde que partilhem os Valores e normas fundamentais da U.E. . Ao longo da dissertação irão ser analisados quais os condicionalismos que a comunidade coloca à entrada destes países na União Europeia, quais as dificuldades que se irão colocar neste processo de negociações e quais aqueles países que melhor estão preparados para ultrapassar estas mesmas dificuldades e assim aderirem mais rapidamente à União Europeia.
- Cloning and expression of an elongation factor-1α in sea bream ( Sparus aurata ) larvae and adult tissuePublication . Nowell, M. A.; Power, Deborah; Guerreiro, P. M.; Llewellyn, Lynda; Ramsurn, Vimi P.; Wigham, Trevor; Sweeney, Glen E.A clone encoding the polypeptide elongation factor EF-1a was isolated from a complementary DNA library prepared from sea bream (Spartus aurata) larvae 1 to 10 days after hatching. The deduced amino acid sequence is between 82% and 95% similar to EF-1a in other animal species. EF-1a messenger RNA is present at low abundance in sea bream embryos prior to gastrulation, but at around 15 hours postfertilization, there is a 10-fold increase in transcript levels. This increase presumably reflects midblastula transition in this species. In adult sea bream, EF-1a appeared to have a relatively uniform distribution across all the tissues analyzed.