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A family of light-sensing proteins with interconvertible red-absorbing and far-red-absorbing forms. Phytochrome links light perception to plant development, including the lettuce red and far-red germination experiment.^[ref]

The width of a frequency range assigned to a signal. Exact spectral support and widths defined by a retained-power fraction or amplitude threshold must be distinguished.

Recovering two orthogonal components of a signal by averaging its products with sine and cosine reference signals at the chosen frequency.

Signal distortion is an unwanted change in a signal's shape or information-bearing relationships. A nonlinear response $y=ax+b{x}^2$ driven by a sinusoid produces DC and a second harmonic, introducing frequencies absent from the input. A linear system can also distort a waveform when its gain or phase response varies across the signal bandwidth, changing the relation between existing components. Distortion differs from additive noise, although both can degrade a measurement. The relevant comparison is to the intended signal transformation; an intentional filter is not faulty merely because it changes the waveform.

An analog multiplier produces an output proportional to the product of two input signals, often $v_o=v_x{v}_y/V_s$ for a specified scale voltage $V_s$. Multiplying two sinusoids generates sum and difference frequencies by the product-to-sum identity. This supports modulation, synchronous detection and frequency mixing. Real devices have limits on input range, bandwidth, offset and feedthrough, so an unwanted output can remain when one nominal input is zero. A four-quadrant multiplier accepts either sign on both inputs; more restricted devices implement fewer sign combinations.

A protein obtained from cattle serum and widely used as a reference sample in biochemistry. It serves as a protein standard for assays such as the bicinchoninic acid assay, and as a model protein in dialysis experiments.

Cohesin is a multisubunit chromosome-associated protein complex involved in sister-chromatid cohesion and chromosome organization. Cleavage of a cohesin component helps permit sister separation at anaphase. Cohesin also contributes to chromosomal loop organization: acute removal can eliminate loop domains without implying that every aspect of gene expression changes immediately. Its segregation and interphase-organization roles are related but experimentally separable. ^[ref][ref]

A program written in the input notation of a compiler or interpreter, before the particular translation being discussed.

Polystyrene is a polymer with repeating units $-\mathrm{C}{\mathrm{H}}_2-\mathrm{CH}({\mathrm{C}}_6{\mathrm{H}}_5)-$, placing a phenyl side group on alternate backbone carbons. Addition polymerization retains the monomer's phenyl group while converting its carbon-carbon double bond into backbone bonds.

Polystyrene standards are used for organic-solvent size-exclusion chromatography. Their hydrodynamic size supplies a conditional SEC molar mass calibration; a different polymer of equal molar mass need not have the same coil size or elution volume.^[ref]

Teflon is a trade name strongly associated with polytetrafluoroethylene, whose repeat unit is $-\mathrm{C}{\mathrm{F}}_2-\mathrm{C}{\mathrm{F}}_2-$. The fluorinated chain gives the polymer a low-energy surface and high chemical resistance in many conditions.

Its familiar low-friction and nonwetting behavior belongs to a material surface, not to a free fluorine atom. Product formulations and other fluoropolymers sold under the same brand context should be specified separately when material identity matters.

The sympathetic nervous system is an autonomic division with pathways connecting central activity to peripheral organs. Preganglionic and postganglionic stages have different locations and transmitter relationships. Its effects depend on target tissue and receptor, rather than one uniform increase in every organ’s activity.

An adrenal gland is an endocrine organ near a kidney, containing distinct cortical and medullary regions. These regions have different developmental origins and secretory products. The adrenal medulla is closely connected to sympathetic neural signaling, rather than being equivalent to the whole gland.

Online text: s3.us-east-2.amazonaws.com/asc-mag-media/ArborLabs/PDF_Files/ASLab_43.pdf

Two-page teaching worksheet and teacher notes issued by Arbor Scientific. No personal byline or publication date is stated; the Amazon S3 host is distinct from the issuer. The student readings are blank.

Cited passages: PDF p. 1, Teacher’s Notes, Required Equipment, Concept Overview and Lab Tips; PDF p. 2, Materials and Procedure 1–11.

By Thomas J. Fellers and Michael W. Davidson.

Online text: www.microscopyu.com/microscopy-basics/linear-measurements-micrometry

MicroscopyU educational article published by Nikon Instruments Inc.. The Contributing Authors byline names both authors; no article publication date is established.

Cited passages: Stage Micrometers; Eyepiece Reticle Calibration, Figure 4 and procedure; Conclusions, line-edge errors and digital calibration at identical pixel resolution.

Online text: www.microscopyu.com/microscopy-basics/infinity-optical-systems

MicroscopyU educational article issued by Nikon Instruments Inc.. The displayed Contributing Authors heading is empty; no personal author or publication date is established. Footer copyright is distinct from article publication.

Cited passages: finite-system introduction; Figure 2(a–b); parallel bundles, tube lens and magnification discussion before Figure 3.

Institutional laboratory guide issued by Physics Undergraduate Labs, University of Colorado Boulder, in the PHYS 4430 course route. No individual instructor authorship is assigned.

Online text: physicslabs.colorado.edu/courses/phys-4430/lab-guides/michelson-interferometer/week-1/

Page revision: 15 August 2026, explicitly labeled Last Updated; this is an online revision date.

Cited passages: §4.1 and Figure 1: source, splitter, mirrors and detector; §§5.1–5.3: hardware, manual micrometer, near/far alignment, fringe patterns and live voltage or oscilloscope readout; §§6.1–6.4: angular mismatch, splitter ratio, polarization controls and noise estimates. The guide gives a protocol, rather than a published measured dataset.

By Charles H. Holbrow, Enrique Galvez, Beth Parks; the paper prints C. H. Holbrow, E. Galvez and M. E. Parks.

Published in American Journal of Physics 70(3), pp. 260–265, March 2002. DOI: 10.1119/1.1432972. Colgate University hosts this copy.

Online text: www.colgate.edu/media/5506/download

Cited passages: §IV and §IV.A, printed p. 262, Figure 4 and equations (1)–(5): field transformations and unitary beam-splitter model; §IV.D, printed p. 264, Figure 5: polarization routing into separate detected paths. The source uses its own port and phase conventions.

By Randall M. Schoonover, Mei-Sywe Hwang, James Taylor, Cheryl Smith.

NISTIR 5375, issued by National Institute of Standards and Technology in February 1994, reprinting ISA paper 93-091, printed pp. 299–320. The reprinted paper bears an ISA 1993 copyright; this is distinct from the NIST report publication.^[ref]

Online text: nvlpubs.nist.gov/nistpubs/Legacy/IR/nistir5375.pdf

Cited passages: printed pp. 313–316, Pycnometer Calibration, Figure 5 and Pycnometer Application: calibration and correction for bath-versus-weighing temperature; printed p. 315: tin-oxide charge precaution, no detected charge, and pycnometer data not yet analyzed.

Online text: www.thorlabs.com/catalogpages/Obsolete/2021/HFB001.pdf

Institutional issuer: Thorlabs. The catalogue PDF contains the teaching insight “Is the max acceptance angle constant across the core of a multimode fiber?”; no personal author is identified.

The inspected indexed teaching section labels 2 January 2019 as its last-edit date. No catalogue publication date is established.

Cited passages: Search-index extracted PDF p. 4/9, Is the max acceptance angle constant across the core of a multimode fiber?; Figs. 3–5 and Step-Index Multimode Fiber / Graded-Index Multimode Fibers paragraphs; Date of Last Edit: Jan. 2, 2019.

Online text: www.thorlabs.us/newgrouppage9.cfm?objectgroup_id=1362&pn=P1-630A-FC-10

Institutional issuer: Thorlabs. This teaching insight appears in the Insights into Optical Fiber section of a product page; no personal author is identified.

The inspected indexed section labels 20 January 2020 as its last-edit date. That date belongs to the insight, not to the product's introduction.

Cited passages: Search-index full extracted section When does NA provide a good estimate of the fiber's acceptance angle?; Geometry Defines the Relationship; Single Mode Fibers are Different; Date of Last Edit: Jan. 20, 2020.