Results 111 to 120 of about 2,627,055 (211)
Ionization-bounded and Density-bounded Planetary Nebulae [PDF]
arXiv, 2009 Planetary nebulae (and in general any photoionized region) can be classified as ionization-bounded or density-bounded. It is important to determine in which case is the planetary nebula studied to be able to estimate from nebular observations, for example, the total rate of ionizing photons produced by the central star.
arxiv
Earth and Space Science, Volume 12, Issue 4, April 2025.Abstract We propose a new method for automatically identifying radiation belt electron enhancement events using Ca, a ground‐based 1D surrogate index for the global dynamics of the electron radiation belts. Our method improves event identification by accurately determining start and end dates, considering intensification and return‐to‐equilibrium ...
Guillerme Bernoux +3 more
wiley +1 more source
NASA Science4Girls and Their Families: Connecting Local Libraries with NASA Scientists and Education Programs to Engage Girls in STEM [PDF]
NASA Science4Girls and Their Families (NS4G) partners NASA Science Mission Directorate (SMD) education programs with public libraries to provide hands-on science, technology, engineering, and math (STEM) activities and career information for girls and ...
Bleacher, L. V. +4 more
core +1 more source
Geochemistry, Geophysics, Geosystems, Volume 26, Issue 4, April 2025.Abstract The identification and evaluation of abiotic methane remain an active research area due to uncertainties in traditional indicators that may lead to “false‐positive” detections. As an emerging isotopic tool, methane clumped isotope can provide novel information about the generation and post‐generation processes of methane gases.
Jiacheng Li +5 more
wiley +1 more source
Abundance determinations in HII regions and planetary nebulae [PDF]
In: Cosmochemistry. The melting pot of the elements, edited by C.
Esteban, R. J. Garc\'ia L\'opez, A. Herrero, F. S\'anchez. Cambridge
contemporary astrophysics. Cambridge, UK: Cambridge University Press, 2004,
p. 115 - 170, 2002 The methods of abundance determinations in HII regions and planetary nebulae are described, with emphasis on the underlying assumptions and inherent problems. Recent results on abundances in Galactic HII regions and in Galactic and extragalactic Planetary Nebulae are reviewed.
arxiv
Geochemistry, Geophysics, Geosystems, Volume 26, Issue 4, April 2025.Abstract Sediment transported to fjords is redistributed by turbidity currents and sometimes fails on steep sidewall slopes, forming marine geohazards that are known to impact infrastructure. Since marine geohazards are poorly understood in Arctic Fjords due to lack of data and monitoring, a comprehensive study of Southwind Fjord, Baffin Island, was ...
Alexandre Normandeau +6 more
wiley +1 more source
Calculation of Synthetic Ionizing Spectra for Planetary Nebulae [PDF]
arXiv, 2002 We present a new grid (solar and halo abundance ratios) of state-of-the-art fully line-blanketed NLTE model atmospheres which covers the parameter range of central stars of planetary nebulae. The grid is available at the WWW.
arxiv
Linking Cenozoic Magmatism in the North‐Central Tibetan Plateau With Plateau Growth
Geochemistry, Geophysics, Geosystems, Volume 26, Issue 4, April 2025.Abstract Accurate reconstruction of paleo‐crustal and lithospheric thicknesses is crucial for understanding the deep geodynamic processes driving the uplift and growth of the Tibetan Plateau (TP) and their association with Cenozoic magmatism. We reconstruct the Cenozoic crustal thickness evolution of the north‐central TP using a machine learning model ...
Peng Guo, Ting Yang, Wei‐Qiang Ji
wiley +1 more source
Geochemistry, Geophysics, Geosystems, Volume 26, Issue 4, April 2025.Abstract High silica granites may host major rare metal deposits. The petrogenesis of these granites, some of which have very low Zr/Hf, Nb/Ta, and Eu/Eu* ratios, has been highly debated. The existing views mainly favor either extreme magmatic fractionation or fluid‐magma interaction.
Hui Huang +5 more
wiley +1 more source
Investigating the Lid Effect on the Generation of Ocean Island Basalts: 2. Geodynamical Simulations
Geochemistry, Geophysics, Geosystems, Volume 26, Issue 4, April 2025.Abstract The concept that oceanic lithosphere mechanically limits upwelling and decompression melting of mantle plumes is known as the lid effect and is backed up by observations of ocean island basalt (OIB) geochemistry. Nevertheless, in a recent companion study on OIB geochemistry, several additional factors were identified that further influence OIB
Shihao Jiang +5 more
wiley +1 more source