نتایج جستجو برای: helium
تعداد نتایج: 14695 فیلتر نتایج به سال:
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 ...
Comparison of end expiratory lung volume (EELV) measured by the helium dilution technique and the nitrogen washout/ washin method. (a) The EELV measured by the helium dilution as a function of the EELV measured by nitrogen washout/washin method (EELV helium dilution = -111.85 + 0.89 × EELV GE, r2 = 0.82, p < 0.00001). (b) The BlandAltman plot of the EELV measured with the nitrogen washout/washi...
The ground and excited state properties of small helium clusters, HeN , containing nanoscale (∼3–10 Å) planar aromatic molecules have been studied with quantum Monte Carlo methods. Ground state structures and energies are obtained from importance-sampled, rigid-body diffusion Monte Carlo. Excited state energies due to helium vibrational motion are evaluated using the projection operator, imagin...
Three different sets of experiments conducted in the Navy Laboratory (NAWCWD) at China Lake, California (1990-1994) clearly established that helium-4 is the main fusion product in the Pd/D2O+LiOD electrolysis system. A correlation between excess enthalpy and excess helium-4 was measured in 18 out of 21 experiments. The observation of no excess enthalpy was correlated with no excess helium in 12...
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any hel...
The empirical model explaining microsolvation of molecules in superfluid helium droplets proposes a non-superfluid helium solvation layer enclosing the dopant molecule. This model warrants an empirical explanation of any helium induced substructure resolved for electronic transitions of molecules in helium droplets. Despite a wealth of such experimental data, quantitative modeling of spectra is...
In solar euv spectra the He i and He ii resonance lines show unusual behaviour and have anomalously high intensities compared with other transition region lines. The formation of the helium resonance lines is investigated through extensive non-LTE radiative transfer calculations. The model atmospheres of Vernazza, Avrett & Loeser (1981) are found to provide reasonable matches to the helium reso...
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