نتایج جستجو برای: helium purification
تعداد نتایج: 71071 فیلتر نتایج به سال:
We investigate the consequences of an increase in the envelope helium abundance of pre-helium flash red giants in globular clusters, an occurrence suggested by chemical peculiarities in many red giant atmospheres. Comparing predictions with the CM diagrams of a few crucial globular clusters, one finds no evidence for a substantial increase in the surface helium content of horizontal branch memb...
The performance of plasma facing components (PFC) is of great important for the realization of prototype nuclear fusion. Tungsten has been considered as the leading high-Z PFC material for these reactors and tokamaks due to its superior thermophysical properties, high melting point, low sputtering yield, and low tritium inventory. However, its surface deteriorates significantly under helium ion...
The presence of helium in carbon systems, such as diamonds and fullerenes is of interest for planetary sciences, geophysics, astrophysics, and evolution biology. Such systems typically involve a large number of atoms and require a fast method for assessing the interaction potential and forces. We developed a tight-binding approach, based on density functional calculations, which includes a many...
We present optical spectra of the Type Ic supernova 1994I in M51 and preliminary non-LTE analysis of the spectra. Our models are not inconsistent with the explosions of C+O cores of massive stars. While we find no direct evidence for helium in the optical spectra, our models cannot rule out small amounts of helium. More than 0.1 M⊙ of helium seems unlikely.
Systematic studies of the phase and density dependence of the delayed annihilation time spectra of antiprotons (DATS) in gaseous, liquid and solid helium have been performed using the Low Energy Antiproton Ring (LEAR) at CERN. The results show a small but signiicant dependence of DATS on the phase and density of the helium medium. The average lifetime of antiprotons (T av) in gas at 10-30 K was...
BACKGROUND Prolonged weaning from mechanical ventilation has a major impact on ICU bed occupancy and patient outcome, and has significant cost implications.There is evidence in patients around the period of extubation that helium-oxygen leads to a reduction in the work of breathing. Therefore breathing helium-oxygen during weaning may be a useful adjunct to facilitate weaning. We hypothesised t...
Warm Neptuneand sub-Neptune-sized exoplanets in orbits smaller than Mercury’s are thought to have experienced extensive atmospheric evolution. Here we propose that a potential outcome of this atmospheric evolution is the formation of helium-dominated atmospheres. The hydrodynamic escape rates of Neptuneand sub-Neptune-sized exoplanets are comparable to the diffusion-limited escape rate of hydro...
Identifying the progenitors of Type Ib and Type Ic supernovae requires knowing, among other things, whether SNe Ib eject hydrogen, and whether SNe Ic eject helium, and perhaps even hydrogen. Recently it has become clear that some SNe Ib do eject hydrogen, and it may be that all SNe Ib do. Two arguments that have been made in the past that SNe Ic eject helium are difficult to confirm, but I disc...
The knowledge of the metallization of warm dense helium has important implications for understanding the thermal histories, stellar structure and magnetic field environment of giant planets. However, it is also a pendent scientific topic. For a revisiting into the properties of warm dense helium, we performed extensive quantum Langevin molecular dynamic simulations and electronic structure calc...
Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux ...
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