Word of the day: centroid

The word of the day is centroid:
< centre n. and adj. (or its source) + -oid suffix.

1. = centrode n.  [In this sense introduced by Prof. A. B. W. Kennedy, 1876, on the analogy of cycloid and other names of curves, but subsequently abandoned for centrode.]

2. Centre of mass, or of gravity.

"The main features of this algorithm are isotope cluster identification, automated charge determination, generation of a theoretical isotopic abundance distribution, matching the theoretical and experimental isotopic abundance distributions, identification of other overlapping isotopic peak clusters, determination of improved accuracy of averaged centroid mass values, matching of assigned mass values to proteolytic or MS/MS fragment ions, and baseline plus S/N calculations using data between the isotopic peaks."

 - Bogdanov and Smith, "Proteomics by FTICR mass spectrometry: top down and bottom up", Mass Spectrometry Reviews 24:168 (2005)

I think what they mean here is the averaged mass of all the isotopes, as opposed to the monoisotopic mass.

Word of the day: abscissa

The word of the day is abscissa:

< post-classical Latin abscissa portion of the axis of symmetry of a conic section lying between its vertex and a given chord (1673 (in Leibniz) or earlier), (in Cartesian coordinates) distance of a point from the y-axis, measured parallel to the x-axis (1692 (in Leibniz) or earlier), use as noun (short for abscissa linea a cut-off line) of feminine past participle of classical Latin abscindereabscind v. With sense 1 compare slightly earlier absciss n. Compare also earlier ordinate n.
In plural form abscissae after the Latin plural form.

Math.

 1. The portion of a conic section lying between its points of intersection with two parallel chords; (also) the portion of the axis of symmetry of a conic section lying between its vertex and a given chord. Cf. ordinate n. 1. Obs.    

2. In Cartesian coordinates: the distance of a point from the y-axis, measured parallel to the x-axis; the x-coordinate of a point. Formerly also: a straight line drawn from a given point parallel to the x-axis and meeting the y-axis. Cf. ordinate n. 2. (OED)

"FTICR mass spectra (the abscissa represents a convolution of the deuterium incorporation after 1 hr and the initial natural-abundance isotopic distribution of the fully protonated ion) following gas-phase H/D exchange for 1 hr at 2 x 10^-7 Torr D2O for the 11 - 13+ charge states of bovine ubiquitin."

 - Bogdanov and Smith, "Proteomics by FTICR mass spectrometry: top down and bottom up", Mass Spectrometry Reviews 24:168 (2005)


As far as I can tell, this word has been replaced by "x-axis" and "x-coordinate" (depending on its use).  I guess Dr. Bogdanov didn't get the memo.