Modelling distributed lag effects in mortality and air pollution studies: the case of Santiago

Most of the epidemiological literature on air pollution and mortality deals only with single or dual pollutant models whose results are hard to interpret and of questionable value from the policy perspective. In addition, much of the existing literature deals only with the very short-term effects of air pollution whereas policy makers need to know when, whether and to what extent pollution-induced increases in mortality counts are reversed. This involves modelling the infinite distributed lag effects of air pollution. Borrowing from econometrics this paper presents a method by which the infinite distributed lag effects can be estimated parsimoniously but plausibly estimated. The paper presents a time series study into the relationship between ambient levels of air pollution and daily mortality counts for Santiago employing this technique which confirms that the infinite lag effects are highly significant. It is also shown that day to day variations in NO2 concentrations and in the concentrations of both fine and coarse particulates are associated with short-term variations in death rates. These findings are made in the context of a model that simultaneously includes six different pollutants. Evidence is found pointing to the operation of a very short term harvesting effect

Electrodialytic separation of Cu(II) and As(V) in acidic electrolytes

[ES]Se investigó el uso de la electrodiálisis para separar cobre y arsénico desde soluciones ácidas a temperatura ambiente. Se estudió el efecto de la densidad de corriente y grado de acidez del electrolito en la separación a través de experimentos en celda batch de 5 compartimientos durante 3 h. Los parámetros cinéticos indican que la velocidad de transporte de Cu(II) fue de 0,75 mol/h/m2 y de As(V) fue de 0,002 mol/h/m2 a una densidad de corriente de 225 A/m2. Se logró obtener una eficiente separación de Cu(II) y As(V), con la generación de una solución concentrada de cobre sin presencia de arsénico, lo cual fue independiente del grado de acidez de la operación y de la densidad de corriente. El efecto de la distribución de las especies iónicas de As(V) con el pH también se discute.[EN]The separation of copper and arsenic from acidic electrolytes by electrodialysis was investigated at room temperature. The effect of current density and pH was studied in a batch cell during 3 hours. The kinetic parameters showed that Cu(II) transport rate was 0.75 mol/m2/h and the As(V) transport rate was 0.002 mol/m2/h. An efficient separation between Cu(II) and As(V) was achieved; generating a concentrated solution of copper with no arsenic, which was obtained independently of the electrolyte acidity and current density used. The effect of the arsenic speciation with pH is discussed as well.Peer reviewe

Local entrainment velocity in a premixed turbulent annular jet flame

The local entrainment velocity of the enstrophy interfaces of a methane-air turbulent premixed turbulent annular jet flame stabilized on a bluff-body burner has been investigated using a high-fidelity flame-resolved three-dimensional simulation. The enstrophy (inner and outer) and the scalar interfaces have been defined and characterized by their propagation speeds, VE and Sd , relative to the fluid flow. Mean values ( and ) conditioned on the reaction progress variable c have been obtained. A thin layer (near the enstrophy interfaces) has been used to compute mean values (, , and its different contributions) conditional upon enstrophy E. At the inner interface, results indicate that . Sd |. E> > 0 (entrainment of fresh reactants into the flame front and hot products), while < 0 and < 0 (entrainment of hot products into the reacting jet across the inner enstrophy interface). The outer enstrophy interface displays > 0 (ambient gases are predominantly entrained into the jet of reactants), which implies a lean mixture in its neighborhood. These preliminary results aim at understanding the physical mechanisms of flame anchoring, in terms of entrainments of either hot products or fresh reactants into the diffusive-reactive region. Local geometries of the inner and outer interfaces have also been examined, through the computation of joint probability density functions of the mean curvature km and Gauss curvature kg of the iso-enstrophy surfaces, and through |. km, kg at the inner and outer interfaces. This information has subsequently been used to discuss the physics of how the turbulent entrainment process affects premixed flames

Anaerobic Methane Oxidation in a Landfill-Leachate Plume

The alluvial aquifer adjacent to Norman Landfill, OK, provides an excellent natural laboratory for the study of anaerobic processes impacting landfill-leachate contaminated aquifers. We collected groundwaters from a transect of seven multilevel wells ranging in depth from 1.3 to 11 m that were oriented parallel to the flow path. The center of the leachate plume was characterized by (1) high alkalinity and elevated concentrations of total dissolved organic carbon, reduced iron, and methane, and (2) negligible oxygen, nitrate, and sulfate concentrations. Methane concentrations and stable carbon isotope (δ13C) values suggest anaerobic methane oxidation was occurring within the plume and at its margins. Methane δ13C values increased from about -54‰ near the source to >-10‰ downgradient and at the plume margins. The isotopic fractionation associated with this methane oxidation was -13.6±1.0‰. Methane 13C enrichment indicated that 80-90% of the original landfill methane was oxidized over the 210-m transect. Firstorder rate constants ranged from 0.06 to 0.23 per year, and oxidation rates ranged from 18 to 230µM/y. Overall, hydrochemical data suggest that a sulfate reducermethanogen consortium may mediate this methane oxidation. These results demonstrate that natural attenuation through anaerobic methane oxidation can be an important sink for landfill methane in aquifer systems

The stimulus-response crisis

Yarkoni correctly recognizes that one reason for psychology\u27s generalizability crisis is the failure to account for variance within experiments. We argue that this problem, and the generalizability crisis broadly, is a necessary consequence of the stimulus-response paradigm widely used in psychology research. We point to another methodology, perturbation experiments, as a remedy that is not vulnerable to the same problems