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Hace 6 días · At mid-B, the intensity of the latter relative to that of Si II λλ4128-30 is the defining characteristic, while for late B, it is the intensity of Mg II λ4481 relative to that of He I λ4471. These stars tend to be found in their originating OB associations, which are associated with giant molecular clouds.
22 de jun. de 2024 · With increasing temperature, non-vaporized carbon prefers to be adsorbed, in line with increased vaporization at similar conditions. With helium, there is a slight increase in adsorbed carbon and...
Hace 3 días · The fusion of nuclei in a star, starting from its initial hydrogen and helium abundance, provides that energy and synthesizes new nuclei. Different reaction chains are involved, depending on the mass of the star (and therefore the pressure and temperature in its core).
26 de jun. de 2024 · In the late 1930s Hans Bethe first recognized that the fusion of hydrogen nuclei to form deuterium is exoergic (i.e., there is a net release of energy) and, together with subsequent nuclear reactions, leads to the synthesis of helium.
17 de jun. de 2024 · When about 10 percent of the star’s mass has been converted to helium, the structure of the star changes drastically. All of the hydrogen in the core has been burned out, and this central region is composed almost entirely of inert helium, with trace admixtures of heavier elements.
26 de jun. de 2024 · This study identified a ca. 454–451 Ma monzogranite pluton characterized by abundant inherited zircons at the northern margin of the South Altyn Tagh HP–UHP metamorphic terrane (Figure 1c).Based on a detailed field and whole-rock geochemistry investigation, we utilized inherited and synmagmatic zircon U–Pb dating, as well as Hf–O isotope analyses to decrypt the source rocks and ...
22 de jun. de 2024 · The insertion of helium into CaNbF 6 reduces the magnitude of its negative thermal expansion, increases the bulk modulus, and modifies its phase behavior. On compressing pristine CaNbF 6, at 50 and 100 K, a cubic (Fm3̅m) to rhombohedral (R3̅) phase transition was observed at <0.20 GPa.
