Protons fusion

First proposal of stellar nucleosynthesis by proton fusion to helium and heavier nuclides... 

Proton-proton fusion chain reactions (Bethe and Critchfield 1938) the first long-lived intermediate of nuclear fusion in low-mass stars, He, adds to one He to yield (radioactive) Be which eventually produces two He by capture of another proton and radioactive decay of B (pp-111 chain) or vice versa along the Be decay product Li -l- p (pp-11). 

Temperatures required for fusion reactions exist in stars where fusion reactions are the principle components of energy release. In the Sun, approximately 90 percent of solar energy is a result of proton-proton interactions in several steps to form helium of mass number 4. These steps all involve binuclear collisions since multinuclei collisions are very improbable events. Initially, two protons interact to form a deuterium nucleus (deuterium is an isotope of hydrogen with one proton and one neutron the nucleus is a deuteron) that collides with another proton to form a He (tritium) nucleus. This nucleus collides with a neutron or another He nucleus (with the emission of two protons) to form He. The net reaction can be represented as four protons fusing to form a He nucleus releasing 26.7 MeV. When a sufficient number of the He and He nuclei are formed in the star, they begin fusion reactions to form heavier nuclei such as Li and Be. The number of proton-proton fusion reactions in the Sun amounts to... 

The ordinary isotope of hydrogen, H, is known as Protium, the other two isotopes are Deuterium (a proton and a neutron) and Tritium (a protron and two neutrons). Hydrogen is the only element whose isotopes have been given different names. Deuterium and Tritium are both used as fuel in nuclear fusion reactors. One atom of Deuterium is found in about 6000 ordinary hydrogen atoms. 

Nuclear Fusion Reactions. Tritium reacts with deuterium or protons (at sufftciendy high temperatures) to undergo nuclear fusion ... 

In addition to binding to sialic acid residues of the carbohydrate side chains of cellular proteins that the virus exploits as receptors, hemagglutinin has a second function in the infection of host cells. Viruses, bound to the plasma membrane via their membrane receptors, are taken into the cells by endocytosis. Proton pumps in the membrane of endocytic vesicles that now contain the bound viruses cause an accumulation of protons and a consequent lowering of the pH inside the vesicles. The acidic pH (below pH 6) allows hemagglutinin to fulfill its second role, namely, to act as a membrane fusogen by inducing the fusion of the viral envelope membrane with the membrane of the endosome. This expels the viral RNA into the cytoplasm, where it can begin to replicate. 

In fact, the sun is not a first-generation main-sequence star since spectroscopic evidence shows the presence of many heavier elements thought to be formed in other types of stars and subsequently distributed throughout the galaxy for eventual accretion into later generations of main-sequence stars. In the presence of heavier elements, particularly carbon and nitrogen, a catalytic sequence of nuclear reactions aids the fusion of protons to helium (H. A. Bethe... 

The most plausible fusion reaction for producing energy commercially involves two isotopes of hydrogen, deuterium (D) and tritium (T), or H and H. Deuterium contains one proton and one neutron for an atomic number of two. Tritium contains one proton and two neutrons for an atomic number of three. The reaction is... 

Consider the fusion of boron-10 with an alpha partide. The products of the fusion are carbon-13 and a proton. 

Currently, five different molecular classes of mdr efflux pumps are known [5], While pumps of the the ATP-binding cassette (ABC) transporter superfamily are driven by ATP hydrolysis, the other four superfamilies called resistance-nodulation-division (RND), major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), and small multidrag resistance transporter (SMR) are driven by the proton-motive force across the cytoplasmic membrane. Usually a single pump protein is located within the cytoplasmic membrane. However, the RND-type pumps which are restricted to Gram-negative bacteria consist of two additional components, a periplasmic membrane fusion protein (MFP) which connects the efflux pump to an outer... 

These are produced by bombarding Th or U with 100-MeV protons, or lighter targets with 100-MeV heavier ions produced in cyclotrons or linear accelerators. Thus the complete fusion of targets such as Pb, Au or T1 with the projeetiles B, C, O, N or Ne produces Fr isotopes below mass number 223. 

One of these, C, catalyzes the fusion of H to form He. As shown schematically in Figure 22-18. protons... 

In a second-generation star, fusion of protons to produce helium occurs in a catalytic cycle by the sequential addition of protons to... 

C22-0043. Is the repulsive barrier for fusion of two protons larger, smaller, or about the same as that for the fusion of two deuterium nuclei Which of the resulting helium nuclei is less stable Explain. 

Fig. 1. Luminosity evolution of tracks of 0.5 M0 starting at different central temperature, labelled in the figure. At the bottom we sketch the energy liberated per gram due to the deuterium fusion with protons. The tracks of logT > 6.0 start in the middle of D-burning.

At 2000 K there is sufficient energy to make the H2 molecules dissociate, breaking the chemical bond the core density is of order 1026 m-3 and the total diameter of the star is of order 200 AU or about the size of the entire solar system. The temperature rise increases the molecular dissociation, promoting electrons within the hydrogen atoms until ionisation occurs. Finally, at 106 K the bare protons are colliding with sufficient energy to induce nuclear fusion processes and the protostar develops a solar wind. The solar wind constitutes outbursts of material that shake off the dust jacket and the star begins to shine. 

Nuclear fusion processes derive energy from the formation of low-mass nuclei, which have a different binding energy. Fusion of two nuclear particles produces a new nucleus that is lighter in mass than the masses of the two fusing particles. This mass defect is then interchangeable in energy via Einstein s equation E = me2. Specifically, the formation of an He nucleus from two protons and two neutrons would be expected to have mass ... 

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