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  2. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    For example, the conversion factor between a mass fraction of 1 ppb and a mole fraction of 1 ppb is about 4.7 for the greenhouse gas CFC-11 in air (Molar mass of CFC-11 / Mean molar mass of air = 137.368 / 28.97 = 4.74). For volume fraction, the suffix "V" or "v" is sometimes appended to the parts-per notation (e.g. ppmV, ppbv, pptv).

  3. PPT - Wikipedia

    en.wikipedia.org/wiki/PPT

    .ppt, the file format used by Microsoft PowerPoint presentation software; Parts-per notation for parts-per-trillion (more common) or parts-per-thousand (less common) PerlPowerTools, a revitalized of the classic Unix command set in pure Perl; Positive partial transpose, a criterion used in quantum mechanics

  4. Alternative approaches to redefining the kilogram - Wikipedia

    en.wikipedia.org/wiki/Alternative_approaches_to...

    That relative standard uncertainty has been 50 parts per billion (ppb) since 2006. By fixing the Avogadro constant, the practical effect of this proposal would be that the uncertainty in the mass of a 12 C atom—and the magnitude of the kilogram—could be no better than the current 50 ppb uncertainty in the Planck constant. Under this ...

  5. National Ambient Air Quality Standards - Wikipedia

    en.wikipedia.org/wiki/National_Ambient_Air...

    The EPA first set primary and secondary standards in 1971. Dual primary standards were set at 140 ppb averaged over a 24-hour period, and at 30 ppb averaged annually. The secondary standard was set at 500 ppb averaged over a 3-hour period, not to be exceeded more than once a year.

  6. List of PDF software - Wikipedia

    en.wikipedia.org/wiki/List_of_PDF_software

    Default PDF and file viewer for GNOME; replaces GPdf. Supports addition and removal (since v3.14), of basic text note annotations. CUPS: Apache License 2.0: No No No Yes Printing system can render any document to a PDF file, thus any Linux program with print capability can produce PDF files Pdftk: GPLv2: No Yes Yes

  7. PDF - Wikipedia

    en.wikipedia.org/wiki/PDF

    Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems.

  8. Perfluorooctanoic acid - Wikipedia

    en.wikipedia.org/wiki/Perfluorooctanoic_acid

    The levels of PFOS and PFOA concentrations under which adverse health effects are not anticipated to occur over a lifetime of exposure are 0.07 ppb (70 ppt). [107] In March 2021 EPA announced that it would develop a National Primary Drinking Water Regulation for these contaminants.

  9. Useful conversions and formulas for air dispersion modeling

    en.wikipedia.org/wiki/Useful_conversions_and...

    Although ppmv and grains per dscf have been used in the above examples, concentrations such as ppbv (i.e., parts per billion by volume), volume percent, grams per dscm and many others may also be used. 1 percent by volume = 10,000 ppmv (i.e., parts per million by volume).