نتایج جستجو برای: helium
تعداد نتایج: 14695 فیلتر نتایج به سال:
Positron scattering from helium has been historically limited to experiments with energy resolution of 0.5 eV or worse. A new apparatus has been developed that allows the investigation of scattering processes with an energy resolution as good as 30 meV, allowing new experimental insight into positron helium interactions. High resolution measurements of low energy scattering from helium will be ...
© 2009 American Institute of Physics, S-0031-9228-0910-020-0 Early research with liquid helium showed that it had remarkable new properties, especially below the so-called lambda transition near 2.2 K, where there is a sharp, narrow peak in the specific heat (see figure 1a). The liquid below the transition was named helium II to distinguish it from the liquid above the transition, called helium...
2S 0918–549 is a low-mass X-ray binary (LMXB) with a low optical to X-ray flux ratio. Probably it is an ultracompact binary with an orbital period shorter than 60 min. Such binaries cannot harbor hydrogen rich donor stars. As with other (sometimes confirmed) ultracompact LMXBs, 2S 0918–549 is observed to have a high neon-to-oxygen abundance ratio (Juett et al. 2001) which has been used to argue...
This article gives a survey of the different methods which can be used to polarize the nuclear spin of helium-3. These techniques are particularly discussed in relation to the production of polarized helium-3 targets for nuclear physics experiments, such as electron or proton scattering and neutron spin filters. Some emphasis is given to the development of new powerful solid state lasers now us...
This article provides a review of recent work in the field of helium nanodroplet spectroscopy with emphasis on the dynamical aspects of the interactions between molecules in helium as well as their interaction with this unique quantum solvent. Emphasis is placed on experimental methods and studies introducing recent new approaches, in particular including time-resolved techniques. Corresponding...
magine blowing a cold breeze of helium on a bleeding wound and watching the blood coagulate as the wound starts to heal at a faster rate than it normally would. It sounds far-fetched, but teams of scientists with expertise in plasma science, microbiology, biochemistry, and medicine are working on making something like that actually happen. They do not use helium exactly, but rather helium (or o...
In the preceding paper (Paper I) we discussed the thermodynamic and microscopic transport properties of hydrogen-helium fluid mixtures. These results are used in the present paper for a semiquantitative analysis of the thermal and compositional history of an evolving hydrogenhelium planet such as Jupiter or Saturn. First, the evolution of a homogeneous planet with no first-order phase transitio...
Abstract. We present the results of a spectral analysis of a large sample of subdwarf B stars selected from followup observations of candidates from the Hamburg Quasar Survey. Fundamental parameters (effective temperature, gravity, and helium abundance) were determined by matching synthetic line profiles calculated from model atmospheres to all hydrogen and helium absorption lines present in th...
We report the discovery of the ultracompact hot subdwarf (sdOB) binary OW J074106.0-294811.0 with an orbital period of Porb=44.66279±1.16×10 min, making it the most compact hot subdwarf binary known. Spectroscopic observations using the VLT, Gemini and Keck telescopes revealed a He-sdOB primary with an intermediate helium abundance, Teff =39400±500 K and logg =5.74± 0.09. High signal-to-noise r...
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