RESUMO

Water scarcity is a global issue that is threatening social and economic development. One approach to alleviating scarcity is the incorporation of new water sources into supply systems, including desalinated seawater for industrial and municipal use. In Chile, large volumes of water are used in water-scarce regions where mining takes place, alongside agriculture and small communities. This situation has driven a debate around policies to increase the use of seawater to satisfy the water demand of the mining industry. The economic, social and environmental implications of such a policy, however, are poorly understood and the current regulatory framework to address concerns and uncertainties is inadequate. This paper presents a technical, legal, economic and environmental appraisal of such a policy and considers options to improve outcomes. The appraisal suggests that clear regulations derived from economic, social and environmental analysis must be generated to provide legal certainty and reduce risks. Alternative or complementary water supply options should be allowed where mining operations can demonstrate negligible hydrological and social impacts or use innovative solutions such as stakeholder water rights swaps and water efficiency technologies. We provide insight that will help to drive a better policymaking process aimed at tackling water scarcity in Chile and in similar areas of the world.

Assuntos

RESUMO

AIM: To investigate the plasma amino acid response and tolerance to normal or high protein meals in patients with cirrhosis. METHODS: The plasma amino acid response to a 20 g mixed protein meal was compared in 8 biopsy-proven compensated cirrhotic patients and 6 healthy subjects. In addition the response to a high protein meal (1 g/kg body weight) was studied in 6 decompensated biopsy-proven cirrhotics in order to evaluate their protein tolerance and the likelihood of developing hepatic encephalopathy (HE) following a porto-caval shunt procedure. To test for covert HE, the "number connection test" (NCT) was done on all patients, and an electroencephalogram was recorded in patients considered to be at Child-Pugh C stage. RESULTS: The changes in plasma amino acids after a 20 g protein meal were similar in healthy subjects and in cirrhotics except for a significantly greater increase (P < 0.05) in isoleucine, leucine and tyrosine concentrations in the cirrhotics. The baseline branched chain amino acids/aromatic amino acids (BCAA/AAA) ratio was higher in the healthy persons and remained stable-but it decreased significantly after the meal in the cirrhotic group. After the high protein meal there was a marked increase in the levels of most amino acids, but only small changes occurred in the levels of taurine, citrulline, cysteine and histidine.The BCAA/AAA ratio was significantly higher 180 and 240 min after the meal. Slightly elevated basal plasma ammonia levels showed no particular pattern. Overt HE was not observed in any patients. CONCLUSION: Patients with stable liver disease tolerate natural mixed meals with a standard protein content. The response to a high protein meal in decompensated cirrhotics suggests accumulation of some amino acids but it did not precipitate HE. These results support current nutritional guidelines that recommend a protein intake of 1.2-1.5 g/kg body weight/day for patients with cirrhosis.

RESUMO

Urban drainage system models can be useful to assess and manage system performance and to plan its development. However, due to data and computational costs, sophisticated, high-resolution contemporary models of the sewer system may not be applicable. This constraint is particularly marked in developing country mega-cities where catchments can be large, data tend to be scarce, and there are many unknowns, for example regarding sources, losses and wrong connections. This paper presents work undertaken over the last 7 years to develop a suitable monitoring and modelling framework to support operation and development of the wastewater system of Bogotá (Colombia). Components of the framework covered here are: (a) the flow and water quality database, (b) a wastewater pollution load generator, and (c) a semi-distributed sewer network model, which aims at a complexity that matches the information available from the previous two components. Results from a catchment within Bogotá, area 150 km(2) and with 2.5 million inhabitants, show that the model outputs capture the scale and dynamics of the observed concentrations and loads at various points on the sewer system. However uncertainty is high because much of variability of observed dry weather flow profiles is apparently random. Against this variability, the effects of in-sewer processes were not identifiable except where backwaters caused particularly high retention times. Hence the work has resulted in an operational model with a scientifically justified, yet useful, level of complexity for Bogotá. More generally, the work demonstrates the value of monitoring and modelling programmes, including having modellers actively involved in monitoring specification and operations; and the insights into suitable level of model complexity that may be gained by uncertainty and sensitivity analysis.

Assuntos

RESUMO

Due to increasing customer and political pressures, and more stringent environmental regulations, sediment and other blockage issues are now a high priority when assessing sewer system operational performance. Blockages caused by sediment deposits reduce sewer system reliability and demand remedial action at considerable operational cost. Consequently, procedures are required for identifying which parts of the sewer system are in most need of proactive removal of sediments. This paper presents an exceptionally long (7.5 years) and spatially detailed (9658 grid squares--0.03 km² each--covering a population of nearly 7.5 million) data set obtained from a customer complaints database in Bogotá (Colombia). The sediment-related blockage data are modelled using homogeneous and non-homogeneous Poisson process models. In most of the analysed areas the inter-arrival time between blockages can be represented by the homogeneous process, but there are a considerable number of areas (up to 34%) for which there is strong evidence of non-stationarity. In most of these cases, the mean blockage rate increases over time, signifying a continual deterioration of the system despite repairs, this being particularly marked for pipe and gully pot related blockages. The physical properties of the system (mean pipe slope, diameter and pipe length) have a clear but weak influence on observed blockage rates. The Bogotá case study illustrates the potential value of customer complaints databases and formal analysis frameworks for proactive sewerage maintenance scheduling in large cities.

Assuntos

Assuntos

Assuntos

RESUMO

Varias substancias presumiblemente tóxicas tales como el amonio se han implicado en la patogenia de la encefalopatía hepática porto-sistémica (EPS). Recientemente se ha propuesto la hipótesis del ácido gama-aminobutríco (GABA) donde el aumento del tono gabaérgico y la presencia de uno o más ligandos para el receptor GABA/benzodiacepínicos juegan un papel central. Con el objeto de investigar la asociación entre las elevaciones plasmáticas de amonio y GABA y el grado de encefalopatía hepática, estudiamos tres grupos de pacientes con enfermedad hepática que cursaban con episodio de EPS aguda espontánea o precipitada por hemorragia gastrointestinal o sepsis, en quienes se determinaron los niveles de amonio y GABA en plasma antes y después de tratamiento convencional con lactulosa. La EPS se valoró mediante el índice de EPs incluyendo pruebas del estado mental y electroencefalograma (EEG) entre otras. Los niveles de GABA en plasmas se encontraron significativamente elevados en pacientes con EPS pura (458+-108 pmol/mL) comparados con sujetos sanos (110+-23 pmol/mL)(p<0.01) aunque no se encontró correlación entre las concentraciones de GABA y el grado de encefalopátía. Sin embargo, los cambios en los niveles de amonio correlacionaron con los cambios en el índice de EPS (r=0.56;p<0.02) y con las alteraciones en el EEG (r=0.65;

Assuntos

RESUMO

Con el objeto de investigar las diferencias en el perfil de aminoácidos en plasma y reevaluar el uso de la razón AACR/AAA (aminoácidos de cadena ramificada/aminoácidos aromáticos) (valina+isoleucina+leucina/fenilalanina+tirosina) para la valoración del grado de deterioro hepático, se estudió la concentración de aminoácidos plasmáticos en tres grupos de pacientes cirróticos: cirróticos compensados (estables), cirróticos descompensados y cirróticos con encefalopatía portosistémica (EPS) agudo, comparados con un grupo de sujetos normales (control). Los cirróticos estables mostraron concentraciones de aminoácidos similares al grupo control; la razón AACR/AAA en los cirróticos estables (2.9 +- 0.2) fue significativamente menor que en el grupo control (3.9+-0.3) (p<0.05). Los cirróticos descompensados mostraron diferencias en los aminoácidos plasmáticos y la razón AACR/AAA (1.7+-0.3) fue significativamente menor comparados con los cirróticos estables y con el grupo control, respectivamente (p<0.005 y p<0.01). Los pacientes con EPS aguda mostraron una elevación externa en la mayoría de los aminoácidos comparados con los otros grupos y la razón AARC/AAA (0.8+-0.07)fue la menor de los cuatro grupos (p<0.001 comparado con el grupo control). Se concluye que es posible detectar diferencias en las concentraciones de aminoácidos plasmáticos en diferentes grupos de cirróticios con diferentes grados de daño hepático y que la razón AACR/AAA es un índice útil en la valoración del grado de deterioro en la función hepática. Se propone el uso de este índice en el seguimiento de pacientes cirróticos seleccionados, tales como aquellos pacientes candidatos a cirugía mayor y trasplante hepático en quienes se podría utilizar este índice para precisar el momento más apropiado para el trasplante.

Assuntos