The relationship between temperature, oxygen condition and embryo encapsulation in the marine gastropod Chorus giganteus

Intracapsular oxygen availability is one of the main factors affecting embryo development of marine gastropod species with encapsulation. This is because the low solubility and diffusion rate of O2 in water, plus the low oxygen diffusion rate that the capsule wall presents, reduces oxygen inside capsules. In addition, temperature affects embryo development inside capsules through its effect on embryo metabolic rate and oxygen availability. In spite of both factors being highly correlated and that a synergic effect on embryo development may be expected, there are few studies evaluating temperature and intracapsular oxygen availability simultaneously. In this work we evaluated the role of the capsule wall of the marine gastropod Chorus giganteus as a barrier for oxygen diffusion and its interaction with temperature affecting intracapsular oxygen availability and embryonic development. For that, we cultivated capsules in seawater at three different temperatures, 9, 12 and 15°C, for a time to complete embryo development. Oxygen level was measured inside capsules with and without embryos, and outside capsules at all temperatures. The number of capsules successfully hatched at the end of the experiment, and early and late embryo mortality were recorded. Finally, we measured embryo metabolic rate at the three different temperatures assayed. We found that embryo mortality and abnormal morphological development were more frequent at higher temperatures. Intracapsular oxygen availability decreases at higher temperatures in capsules with and without embryos. These results may be explained by an increase in the total intracapsular embryo metabolic rate (per capsule) with temperature and an inadequate oxygen diffusion rate from seawater through the capsule wall and intracapsular fluid to the embryonic cells. Our findings suggest that encapsulation is constrained at high temperatures in C. giganetus affecting significantly its reproductive success. This may have important consequences in a scenario of global warming.

Reduction of NOx and CO to Below 2ppm in a Diffusion Flame

The so-called “sudden death reaction” theory, for a diffusion flame, assumes that the fuel and oxidizer diffuse toward a stoichiometric concentration surface, and then suddenly disappear, due to their combustion which produces water and carbon dioxide. The presence of NOx and CO in the combustion products cannot be explained by the “sudden death” theory. NOx, due to its high activation energy may not be formed prior to the formation of H2O and CO2. NOx is created when both oxygen and nitrogen are present in a high temperature volume; after all the combustible species are consumed. Appearance of CO indicates a lack of oxygen or a low gaseous temperature. Traditionally, when steam is injected into the combustion air, its high heat capacity reduces the flame temperature, which then reduces NOx formation, and this is usually accompanied by high CO formation. This phenomenon is caused by the dilution of oxygen as a quenching effect. This paper describes a novel approach that reverses the traditional wisdom of using steam to control NOx and CO formation, by accelerating the combustion process. This new approach begins with (1) shrinking the flame envelope, (2) enhancing the oxygen diffusion rate, and (3) suppressing the nitrogen concentration diffusion rate. Test results showed that (1) a high temperature volume could form NOx after the combustion of fuel is reduced to a minimum, and (2) that a very high fuel jet momentum increases the oxygen diffusion rate, thus reducing the flame envelope. Also due to the inward movement of the flame envelope, the residential time for NOx formation is also reduced and with the presence of a diluent, the nitrogen penetration rate into the flame is controlled. When all three phenomena are working together, total NOx was reduced downward to below 2 ppm without losing flame stability. Since this process generates enhanced oxygen diffusion, CO has always been seen to be below 2ppm, which indicates extremely high combustion efficiency. The above theory was first simulated by numerical methods using a 3-step reaction for nitrogen and oxygen, and was further expanded to a 28-step chemical kinetic model. The simulation used gas turbine compressor discharge temperatures to produce real adiabatic flame temperatures. Atmospheric tests of real full-scale gas turbine combustors were used with appropriate air temperatures, to simulate adiabatic flame temperatures. Below 2ppm NOx and CO were consistently obtained, independent of turbine types. Actual turbine tests on GE 6B and W501D5A turbines consistently indicated pressure dependent exponents of 0.1.