Oxygen equilibrium curve of normal human blood and its evaluation by Adair's equation

Oxygen equilibrium curves of fresh, normal human blood have been measured by new methods which allow the control of pH, pCO2, and 2,3-diphosphoglycerate and which yield higher accuracy at the extremes of saturation than was possible previously. The curve determined by these techniques lies slightly to the right of the standard curve of Roughton et al. (Roughton, F.J.W., Deland, E.C., Kernohan, J.C., and Severinghaus, J.W. (1972) in Oxygen Affinity of Hemoglobin and Red Cell Acid Base Status (Astrup, P., and R\uf8rth, M., eds) pp. 73-83, Academic Press, New York). The greatest difference is at low oxygen saturation, probably owing to the fact that the latter data were obtained under conditions which would lead to depletion of cellular 2,3-diphosphoglycerate. The range of p50 (oxygen pressure at half-saturation) values for four normal subjects was 28.3 mm Hg to 29.0 mm Hg. Adair's stepwise oxygenation scheme has been used to analyze the curves with the result that a1 = 0.1514 X 10(-1) (+/- 10%) mm-1; a2 = 0.9723 X 10(-3) (+/- 8%) mm-2; a3 = 0.1703 X 10(-3) (+/- 50%) mm-3; a4 = 0.1671 X 10(-5) (+/- 2%) mm-4 for the best of four data sets. Because these constants are very sensitive to changes in the shape of the oxygenation curve, this analysis is much more useful than p50 measurements in the investigation of the various allosteric effectors of the function of hemoglobin within the red cell

Avoided emissions of a fuel-efficient biomass cookstove dwarf embodied emissions

Three billion people cook their food on biomass-fueled fires. This practice contributes to the anthropogenic radiative forcing. Fuel-efficient biomass cookstoves have the potential to reduce CO2-equivalent emissions from cooking, however, cookstoves made from modern materials and distributed through energy-intensive supply chains have higher embodied CO2-equivalent than traditional cookstoves. No studies exist examining whether lifetime emissions savings from fuel-efficient biomass cookstoves offset embodied emissions, and if so, by what margin. This paper is a complete life cycle inventory of “The Berkeley–Darfur Stove,” disseminated in Sudan by the non-profit Potential Energy. We estimate the embodied CO2-equivalent in the cookstove associated with materials, manufacturing, transportation, and end-of-life is 17 kg of CO2-equivalent. Assuming a mix of 55% non-renewable biomass and 45% renewable biomass, five years of service, and a conservative 35% reduction in fuel use relative to a three-stone fire, the cookstove will offset 7.5 tonnes of CO2-equivalent. A one-to-one replacement of a three-stone fire with the cookstove will save roughly 440 times more CO2-equivalent than it “costs” to create and distribute. Over its five-year life, we estimate the total use-phase emissions of the cookstove to be 13.5 tonnes CO2-equivalent, and the use-phase accounts for 99.9% of cookstove life cycle emissions. The dominance of use-phase emissions illuminate two important insights: (1) without a rigorous program to monitor use-phase emissions, an accurate estimate of life cycle emissions from biomass cookstoves is not possible, and (2) improving a cookstove's avoided emissions relies almost exclusively on reducing use-phase emissions even if use-phase reductions come at the cost of substantially increased non-use-phase emissions

Re-Entrant Excitation Initiated in Models of Inhomogeneous Atrial Tissue

We demonstrate that a shift of the vulnerable window caused by tissue inhomogeneity can play a role in the generation of reentrant excitation. The Earm-Hilgemann-Noble equations were incorporated into 1- and 2-dimensional inhomogeneous partial differential equation models of atrial tissue. Inhomogeneity was produced by a reduction of g Na over part of the medium and the vulnerable window for initiating re-entrant activity in homogeneous models determined from numerical integrations. Reduction of g Na 40% produced little effect on the width of the vulnerable window, but the onset of the vulnerable window was delayed. The delay of the vulnerable window allows re-entry to be initiated at junction between media with normal and reduced excitability, even though there is no appreciable change in action potential duration. 1 Introduction Many cardiac arrhythmias, including atrial tachycardia [Allessie, et al. 1977], atrial flutter [Allessie et al., 1984] and atrial fibrillation [Allessie et a..