Carbon burning nitrogen cycle

The sun with a central temperature of 15.7 million degrees, (Tg0 = 15.7) burns by p-p chains. Slightly more massive star (with central temperature Tq > 20) burns H by the CNO cycle also. Davis et al.s solar neutrino experiment [23], which in 1968 had only an upper limit of the neutrino flux, itself put a limit of less than 9% of the sun s energy is produced by the carbon-nitrogen cycle (the more recent upper limit [36] is 7.3%, from an analysis of several solar neutrino experiments, including the Kamland measurements). Note however that for the standard solar model, the actual contribution of CNO cycle to solar luminosity is 1.5% [15]). In CNO cycle, nuclei such as C, N, O serve as catalysts do in a chemical reaction. The pp-chain and the CNO cycle reaction sequences are illustrated in Figs. 4 and 10. 

Most plastics bum cleanly, producing emissions of carbon dioxide, nitrogen oxides, and water vapor, but some produce unwanted by-products such as polyvinyl chloride (PVC). However, PVC and such other by-products can be safely burned at high temperatures of 980 to 1,650°C (1,800-3,000°F), using controlled oxygen input, sufficient cycle (residence) time, typically i to 2 minutes, and appropriate auxiliary equipment like scrubbers and solid salts. However, most U.S. incinerators operate below 87°C (1,600°F) and use only limited auxiliary equipment. For example, incinerated PVC generates undesirable chlorine (and bleached paper generates much more chlorine). Exhaust scrubber systems must be used to remove this chlorine. 

Hydrogen burning occurs in two key reaction sequences, the PP (or proton-proton) chains and the CNO (Carbon-Nitrogen-Oxygen) bi-cycle. Both sequences were first understood by Hans Bethe and his collaborators in the 1930s, for which work Bethe won the Nobel Prize in 1967 (5). 

In CNO burning, the synthesis of He is catalyzed by pre-existing isotopes of carbon, nitrogen, and oxygen, which were present in the star s starting composition. The CNO bi-cycle consists of two cycles operating simultaneously. In the CN cycle, the reaction sequence is the following ... 

The carbon, nitrogen, and oxygen (CNO)-cycle of hydrogen burning... 

As well as the sulfur cyde, there are other cycles in nature water, nitrogen, phosphorus and carbon. Man has influenced them all, but the sulfur cycle is the most disturbed among aU these cydic processes. Fossil fuels are burned in order to warm up houses and to provide cars, power stations and industries with energy. Then the sulfur that was built into coal, oil and natural gas, millions of years ago, is set free. It is transported as sulfur dioxide to the atmosphere, the SO content of which has increased considerably compared to the equilibrium content of the natural cyde. The acid gas is transported by the winds over the continents, and, long distances from a specific source, people experience a rain of sulfuric acid . This acid rain not only attacks the needles and leaves of trees but also damages the roots of plants. In acidified lakes the ability of fish to reproduce is disturbed. If acidification is not neutralized by liming, metal ions may be leached from rocks and damage animal life. 

---