The afterglow, redshift and extreme energetics of the γ-ray burst of 23 January 1999

Long-lived emission, known as afterglow, has now been detected from about a dozen γ-ray bursts. Distance determinations place the bursts at cosmological distances, with redshifts, z, ranging from ~1 to 3. The energy required to produce these bright γ-ray flashes is enormous: up to ~1053 erg, or 10 per cent of the rest-mass energy of a neutron star, if the emission is isotropic. Here we present optical and near-infrared observations of the afterglow of GRB990123, and we determine a redshift of z ≥ 1.6. This is to date the brightest γ-ray burst with a well-localized position and if the γ-rays were emitted isotropically, the energy release exceeds the rest- mass energy of a neutron star, so challenging current theoretical models of the sources. We argue, however, that our data may provide evidence of beamed (rather than isotropic) radiation, thereby reducing the total energy released to a level where stellar-death models are still tenable

Reconsidering patient participation in guideline development

Health care has become increasingly patient-centred and medical guidelines are considered to be one of the instruments that contribute towards making it so. We reviewed the literature to identify studies on this subject. Both normative and empirical studies were analysed. Many studies recommend active patient participation in the process of guideline development as the instrument to make guidelines more patient-centred. This is done on the assumption that active patient participation will enhance the quality of the guidelines. We found no empirical evidence, however, to support this assumption. Moreover, the studies show that patients experience several difficulties in the participation process, which cannot solely be traced back to flawed practices. Given this poor track record we conclude that the plea to actively involve patients in the guideline development process should be reconsidered

Biogeochemical mechanisms controlling trophic state and micropollutant concentrations in a tropical artificial lake

Universidade de Brasília. Instituto de Geociências. Brasília, DF, Brazil.Universidade de Brasília. Instituto de Geociências. Brasília, DF, Brazil.Universidade Federal de Tocantins. Departamento de Química Ambiental. Tocantins, TO, Brazil.Universidade de Brasília. Instituto de Geociências. Brasília, DF, Brazil.Companhia de Saneamento do Distrito Federal. Brasília, Df, Brazil.Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil.Universidade de Brasília. Instituto de Geociências. Brasília, DF, Brazil.Lake Paranoá is a human-made water reservoir created in 1959 together with the new capital of Brazil (Brasilia). With the demands of urban development, population growth, and land use changes, the lake presented severe deterioration of water quality due to the disposal of wastewater with a high concentration of nutrients. To better elucidate the natural and anthropogenic sources controlling the water quality from Lake Paranoá, this study aimed to (1) investigate the main geochemical processes controlling water quality of the lake and its tributaries; (2) evaluate Lake Paranoá’s trophic state; and (3) determine the occurrence and fate of organic micropollutants in Lake Paranoá waters and WWTPs effluents. The waters from Lake Paranoá tributaries are naturally acidic due to the nature of the extremely weathered ferralsols and the crustal material composition. The main processes linked with anthropogenic activities that affect the water quality from the tributaries are the input of untreated domestic wastewater and the dissolution of carbonate minerals arising from construction material residues. Generally, the waters of Lake Paranoá presented low nutrient and chlorophyll-a concentrations, indicating a low trophic state (oligo-mesotrophic). A significant increase in the trophic state (super-eutrophic) was observed at specific regions of the lake that have high nutrient input from tributaries, caused by the continuous disposal of untreated domestic sewage. In Lake Paranoá waters, the organic micropollutants that were identified and quantified (caffeine, bezafibrate, bisphenol A, diethyl phthalate, and nonylphenol) presented concentrations consistent with previous studies and within the threshold of toxicity, except bisphenol A