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In APS journals, equations may appear within a sentence (run-in) or displayed. Displayed equations are set off from the main text, with space above and below the equation, and the equation is centered in this space. Any multi-level ("stacked") equation should be displayed. All displayed equations are marked up and set manually, requiring particular attention to detail on the part of copy editors. Follow CBE, 6th ed., p. 206-216, for copyediting style.
Authors are often very particular about how they style the terms in their equations, and no major restyling should take place without either verifying with the author that proposed changes are okay or looking at past papers published in APS journals by the same author to see how similar equations were handled in the past.
Authors often spend a lot of time making sure their equations are correct and appear the way they want, and they usually do not realize that all display equations are rekeyed. It is, therefore, advisable to include a query in an equation-laden manuscript, briefly explaining the process and assuring the author that all necessary changes will be made.
The order of fences in equations is the same as in regular text. From innermost to outermost: parentheses ( ), square brackets [ ], curly braces { }. Repeat this sequence in complex expressions, if needed.
APS style follows the accepted order of operations: parentheses, exponents, multiplication/division, subtraction/addition.
Math variables are italic. Boldface italics are used for vectors and tensors. Boldface is used for matrices.
X and Y for axis plots (regression equations) are considered variables, and therefore are always italicized. They may be capitalized or lowercase; follow manuscript.
y = 3.57 + 0.17x
Y = 3.57 + 0.17X
If used as variables, abbreviations are italic.
Trig terms are usually roman.
If a lowercase 'd' is not defined as a variable, look for keywords and phrases that indicate that 'd' is an abbreviation for differential (e.g., differentiation, difference, change, etc.), which is roman, not italic. It is possible to have 'd' defined as a variable in the same article where 'd' stands for differential.
One common use of the differential is the term dV/dt, which is commonly defined as the rate of change of the command voltage ramp. Do not query author to define if dV/dt is used as a term. Do not mark spacing around differentials and fences.
Exponent is abbreviated as italic e. The use of fences (braces, brackets, or parens) with 'exp' or e follows these rules:
exp(-t/n21)
e(-t/ni1) or e-t/ni1
Fraction style in displayed equations is empiece: ½, ¼. However, in text and in super- or subscripts, use shill and numerals on line.
1/4
X1/2
Label the first use of a summation (Σ), product (Π), or integral (∫) in text and in display.
The copy editor must mark ellipses for style. Ellipses in a mathematical expression are baseline if there is punctuation on both sides. No marking is necessary.
X1, X2, . . . , Xn
Ellipses in a mathematical expression must be marked for centering if there is no punctuation or punctuation only on one side.
X1 + X2 ... Xn
X1 + X2 + ... + Xn
X1 + X2, ... + Xn
Insert 1-em space between groups.
A + B = C (r = 0.37)
T - t = 4 (t < 5)
A - B = C (if B ≤ 2)
Mark hyphens with a caret or the printer will set minuses.
Delete text punctuation before, within, and after displayed equations, even when a new sentence begins the line of text after a displayed equation.
Displayed equations may be sequentially numbered, unnumbered, or mixed. Follow the manuscript or query author if the numbering is inconsistent. In text, refer to numbered displayed equations as Eq. 1, but spell out Equation 1 at the beginning of a sentence.
Equation numbers are italic, enclosed in roman parentheses, flush right: (1). The copy editor should mark them for style. Numbers for equations in an appendix have a capital italic letter corresponding to the appendix they are located in (A, B, C, etc.) and italic equation number, bumped: (A1). Note: An author may number equations in the paper and appendix as a single sequence, in which case equations in the appendix should not carry the letter corresponding to the appendix.
The text following a displayed equation is flush left when it contains description of the preceding equation. A paragraph indent is needed when the author is explicitly beginning a new paragraph.
An explanation of the variables frequently follows a displayed equation. Do not delete it, even if previously defined in a glossary.
where A is ...., B is..., and C is... .
Some authors provide a list of abbreviations titled "Abbreviations," "Nomenclature," "Glossary," etc. For lists describing symbols and variables used in the equations, call it a "Glossary" and format accordingly. Place the glossary in a logical spot preceding the occurrence of the first equation. If the list submitted by the author contains only abbreviations used in text (rather than in the equations), delete the list.
Simple equations should be run in with text if possible, unless they are numbered. A combination of displayed and run-in equations in the same paper is permitted. Do not make changes that require renumbering of equations without contacting the author.
Long equations running across both columns must be separated by 21-pica rules placed above and below the equation in the column opposite the one in which the equation occurs.
In the manuscript, mark each display equation with the code ZZZ. It will instruct the compositor/printer to insert the equation into the text in the place specified by the copy editor. The equation itself must be edited and marked up by hand.
Remember to use the «f» code if you are starting the text flush left after a displayed equation.
Equations in text may be written using the complex coding rules, if necessary. If an equation in text requires special typesetting beyond the scope of complex coding, mark it with ZZZ as a displayed equation.
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last edited 06/26/03