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lasing is achieved, both are smaller than photo-break
dissociation rate.
Wrong The laser pulse was reasonably stationary, although, at 1.6
msec, motion of the arc is evident.
Correct The laser pulse was reasonably stationary, although at 1.6
msec,motion of the arc is evident.
" A comma both precedes and follows nonrestrictive introductory elements:
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Chapter 3. Punctuation
Correct Note that, even though they are unbounded, the delta
functions are plotted as arrows with their heights
representing the coefficient magnitudes.
Coordinate adjectives
"Adjectives are coordinate if (1) they can be linked by and and (2) they independently modify the substantive"
(Linton 1962).
" Separate by commas only those consecutive adjectives that are coordinate. Deciding whether adjectives are
coordinate can be tricky; two tests might help. First try inserting and between the adjectives:
The delta function has a long controversial history. (long and controversial?)
A comma is appropriate between long and controversial.
Consider a linear shift-invariant system. (linear and shift-invariant?)
If still in doubt, try reversing the adjectives (if they independently modify the noun, order makes no difference):
Consider a shift-invariant linear system.
The adjectives shift-invariant and linear are probably coordinate, but the final decision requires someone who
understands the technical meaning of the adjectives. (Good luck with trying to explain this grammatical dilemma!)
When in doubt, do not insert the comma between adjectives. The current tendency is to omit the comma between
two coordinate adjectives anyway (Ebbitt and Ebbitt 1982). The comma adds emphasis though to the adjectives as
separate modifiers.
Elliptical constructions
When clauses in a sentence contain repeated elements (for example, the verb), the omission of these elements is
indicated by a comma:
Wind speed is obtained from antenna brightness temperature; rain rate, from the brightness
temperature difference at two frequencies; and wind vector, from radar cross section.
The comma may be omitted if the clauses are short:
Wind speed is obtained from antenna brightness temperature, and wind vector from radar cross
section.
Note: See section 3.15.4 for the use of the semicolon in elliptical constructions.
Direct quotations and questions
Direct quotations and questions are separated from the rest of the sentence with either commas or colons. A colon
is used to introduce a long or formal quotation.
" Separate a direct quotation or question from the rest of the sentence with a comma:
In reference 6, he states, "Thermal neutron fluxes up to 1020 might be required."
The obvious question is, how good is this estimate?
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Chapter 3. Punctuation
Note: The first word of the question may or may not be capitalized.
" Neither a comma nor a colon sets off an indirect quotation or one that is part of the grammatical structure of the
sentence:
In reference 6, he stated that thermal neutron fluxes up to 1020 may be required.
In case of fire, the command for stopping the test is "Recover, fire."
3.5.2. Commas That Enclose
A comma that encloses requires a partner, which may be another comma or a colon, semicolon, period, question
mark, or exclamation mark.
Nonrestrictive modifiers
A nonrestrictive modifier does not affect the meaning of the basic sentence; it could be removed from the sentence
without altering meaning.
" Nonrestrictive modifiers must be enclosed by commas (at least). The important point to remember is that an
enclosing comma requires a partner, which can be another comma or another mark of punctuation.
The nonrestrictive prepositional and verbal phrases are enclosed with commas in the following examples:
The record need not be continuous but may, in fact, be digital data.
Theoreticians prefer to work in terms of radian frequency, defined for both positive and negative
frequencies.
The power spectral density is integrated over some finite bandwidth, such as a one-third octave.
The second integral, being the integral of an odd function over even limits,is zero.
" Be sure to distinguish between restrictive and nonrestrictive internal phrases that introduce clauses (see section
introductory):
Restrictive A random process is stationary if for all n, its nth density
function is independent of time.
Nonrestrictive The coefficient could be placed elsewhere because, though
preferred, the placement shown is arbitrary.
" Nonrestrictive relative clauses are enclosed with commas:
Restrictive The most common panel methods are the codes which Hess
and Smith (ref. 26) designed for nonlifting bodies.
Nonrestrictive The most common panel methods are the codes of Hess and
Smith (ref. 26), which were developed for nonlifting
bodies.
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Chapter 3. Punctuation
" Nonrestrictive adverbial clauses are enclosed with commas:
Restrictive The last chapter introduces specialized areas where research
is in progress.
Nonrestrictive The power spectral density of the signal is shown in figure
9, where arrows represent delta functions.
Restrictive Two random processes are uncorrelated if their cross
correlation satisfies equation (6).
Nonrestrictive Independent random processes are uncorrelated, since their
cross correlation always satisfies equation (6).
" Whether restrictive or nonrestrictive, an introductory adverbial clause is separated by a comma from the clause it
modifies (see section introductory).
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