. "2009-07-06 15:41:29.0" . "SDN:P07::CF12N215" . . "1" . "1" . . . "2009-07-06 15:41:29.0" . "Mass concentration means mass per unit volume and is used in the construction mass_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. Alkenes are unsaturated hydrocarbons as they contain chemical double bonds between adjacent carbon atoms. Alkenes contain only hydrogen and carbon combined in the general proportions C(n)H(2n); \"alkenes\" is the term used in standard names to describe the group of chemical species having this common structure that are represented within a given model. The list of individual species that are included in a quantity having a group chemical standard name can vary between models. Where possible, the data variable should be accompanied by a complete description of the species represented, for example, by using a comment attribute. Standard names exist for some individual alkene species, e.g., ethene and propene."@en . "mass_concentration_of_alkenes_in_air"@en . . "SDN:P07::CF12N215" . . . . "false" . "SDN:P07::CF12N215" . "" . "accepted"@en .