Cell counting estimates the number of biological cells in a preparation. A count per calibrated volume gives number density; multiplying by the whole preparation's volume estimates its total count. A trypan blue exclusion test adds an operational distinction between dye-excluding and dye-stained biological cells.

For positive recoverable counts $N_0,N_1$ bracketing one growth interval, define its net cell line population doublings byThe formula counts how many factors of two produce the observed net factor. For exactly two divisions per original biological cell, with all daughters recovered, $N_1=2^2{N}_0$, giving $d=2$. Death or loss of biological cells makes this a net estimate of division.^[ref]

Under constant-rate exponential growth, $N(t)=N_0{e}^{rt}$, a growth interval of duration $\Delta t$ givesFor the constructed fourfold increase over $48\mathrm{h}$, $d=2$ and the model doubling time is $24\mathrm{h}$. The proof follows by taking the natural logarithm and solving $e^{r{t}_2}=2$. This is a fitted property of that interval and model: it is not a universal HeLa doubling time, nor the interval between two divisions of each individual biological cell. Across successive growth intervals, add their $d$ values; keep transfer losses separate as in cell culture passage accounting.

A subculture transfers part of a cell culture into fresh cell culture medium; each transfer adds one passage.^[ref]

An immortalised cell line can apparently sustain unlimited cell line population doublings under suitable conditions. Immortality describes lineage reproduction, not individual biological cell survival.^[ref]

An autoclave uses heated, pressurized water vapor to sterilize suitable materials, including equipment for cell culture.

A cell culture medium supplies a cell culture's nutrients and chemical environment.^[ref]

A primary cell culture precedes the first successful subculture.^[ref]

An oligosaccharide is a short chain of linked monosaccharides. Attached oligosaccharides can undergo Golgi cargo processing.

Online text: openstax.org/books/calculus-volume-3/pages/6-4-greens-theorem

This section belongs to the textbook whose senior contributing authors are Gilbert Strang and Edwin “Jed” Herman; no separate section byline is verified.

Cited passages: §6.4, Theorem 6.12 and equation (6.13): circulation form and hypotheses; the following proof: rectangle edge calculation and the fundamental theorem of calculus.

Section of Calculus Volume 2 by Gilbert Strang and others; no separate chapter author or section revision date is established.

Online text: openstax.org/books/calculus-volume-2/pages/5-2-infinite-series

Cited passages: §5.2, Telescoping Series, definition, finite partial-sum identities and finite-limit convergence criterion.

A buffer solution used as a running medium in DNA gel electrophoresis; it maintains pH while allowing electric current through the apparatus.