New issue 598: Particle fields should be created inside closures https://bitbucket.org/yt_analysis/yt/issue/598/particle-fields-should-be-cre... Matthew Turk: Each particle field should be created inside a closure; none should exist in the primary namespace. This means that while accessing something like "ParticleMassMsun" will still be possible, it will map internally to always having "all","ParticleMassMsun". In doing so we'll ensure that at all times in the generation of the fields themselves, the particle types being requested are explicit; this will reduce or eliminate the guesswork necessary and simplify detection methods. Responsible: MatthewTurk