All articles starting with S

Spectral superchannel transmission

Spectral superchannel transmission is an optical fiber communication technique combining several closely spaced modulated subcarriers into a single high-capacity channel, each at an electrically affordable baud rate.

Spectral theorem

The spectral theorem, or eigen decomposition theorem, states that self-adjoint operators decompose into real eigenvalues and an orthonormal basis of eigenvectors, underlying PCA and quantum mechanics.

Spectral triple

A spectral triple is data (A, H, D) encoding a geometric space, the basic object of Alain Connes' noncommutative geometry, where it generalizes Riemannian manifolds with the Dirac operator.

Spectral unmixing

Spectral unmixing, or unmixing, is a remote sensing technique that decomposes a pixel's spectrum into constituent material spectra, called endmembers, weighted by their fractional abundances, yielding sub-pixel information for mineral mapping and land-cover studies.

Spectrally selective coating

A spectrally selective coating is a microscopically thin multilayer low-E coating on window glass or film that admits visible daylight while reflecting solar ultraviolet and near-infrared heat.

SPECTRE

SPECTRE (SPecial Executive for Counter-intelligence, Terrorism, Revenge, and Extortion) is Ian Fleming's fictional global crime organization led by Ernst Stavro Blofeld, introduced in Thunderball (1961), central to the Bond films, and returned to EON's series after the 2013 McClory rights settlement.

Spectre (2015 film)

Spectre (2015) is the 24th James Bond film and Daniel Craig's fourth as 007, directed by Sam Mendes, released 6 November 2015, 148 minutes, 63% on Rotten Tomatoes.

Spectre (DC Comics character)

The Spectre is DC Comics' spirit of divine vengeance, created by Jerry Siegel and Bernard Baily, debuting in More Fun Comics #52 (February 1940) as murdered detective Jim Corrigan, later hosted by Hal Jordan and Crispus Allen.

Spectre (security vulnerability)

Spectre is a hardware security vulnerability, disclosed in 2018, that abuses speculative execution to leak data through cache side channels on Intel, AMD, and ARM processors.

Spectre (song)

Spectre is a 2015 song by Radiohead, written for the James Bond film Spectre but rejected as too dark; released free on 25 December 2015, it differs from Sam Smith's chosen theme and Laibach's 2014 album of the same name.

Oct 21, 2026

Spectrin-associated autosomal recessive cerebellar ataxia

Spectrin-associated autosomal recessive cerebellar ataxia, also known as SCAR14, is a rare genetic disease caused by SPTBN2 mutations, marked by developmental delay, intellectual disability, and cerebellar atrophy.

Spectro-Polarimetric High-Contrast Exoplanet Research

SPHERE (VLT-SPHERE) is an extreme adaptive optics instrument on the European Southern Observatory's Very Large Telescope in Chile, built to directly image exoplanets since 2014.

Spectrochemical series

The spectrochemical series is an empirical ranking of ligands by the ligand field splitting they cause in transition-metal complexes, from iodide (weak field) to cyanide and carbon monoxide (strong field).

Spectrogram

Spectrogram (sonograph, voiceprint): a time-frequency image of a signal computed as the squared magnitude of the short-time Fourier transform. Developed at Bell Labs during WWII, commercialized as the Kay Sona-Graph in 1951, now the standard deep-learning audio feature.

Spectrometer

A spectrometer is an instrument that separates electromagnetic radiation, such as light, into its constituent wavelengths and measures the intensity at each one, usually with a diffraction grating.

Spectromicroscopy

Spectromicroscopy combines an imaging microscope with a spectrometer, recording a spectrum at every pixel so that chemical composition and electronic structure can be mapped at microscopic resolution.

Spectrophotometric titration

Spectrophotometric titration, also called photometric titration, is an analytical method that determines concentration, stoichiometry, or equilibrium constants by measuring how absorbance changes as titrant is added, allowing automated endpoint detection in colored solutions.

Spectrophotometry

Spectrophotometry is the measurement of the absorption or transmission of light by a substance as a function of wavelength, used to identify chemical species and measure concentrations.

Spectropolarimetry

Spectropolarimetry is an optical technique recording the complete polarization state of light, the four Stokes parameters, versus wavelength, used to measure magnetic fields in the Sun and stars.

Spectroradiometer

A spectroradiometer is an instrument that measures optical radiation intensity as a function of wavelength, using input optics, a prism or grating, and a calibrated detector.

Spectroscopic binary

A spectroscopic binary is a pair of stars orbiting too closely to resolve in a telescope, identified by periodic Doppler shifts in its combined spectrum, first recognized in 1889.

Spectroscopic ellipsometry

Spectroscopic ellipsometry is a nondestructive optical technique that determines film thickness and optical constants from wavelength-dependent polarization changes in obliquely reflected light, widely used in semiconductor manufacturing.

Spectroscopic redshift

A spectroscopic redshift is the displacement of a star's, galaxy's, or quasar's spectral lines from their rest wavelengths, expressed as z and about ten times more precise than photometric redshifts.

Spectroscopy

Spectroscopy is the study of physical systems by the electromagnetic radiation they absorb or emit, used to identify composition, measure motion, and analyze starlight from ground and space telescopes.

Spectrum

A spectrum is a record of how radiation's energy or intensity is distributed over wavelength or frequency, as when a prism spreads white light into a rainbow.

Spectrum (arena)

Spectrum Center, formerly Charlotte Bobcats Arena and Time Warner Cable Arena, is the 19,077-seat NBA arena in Uptown Charlotte, home of the Charlotte Hornets since 2005, renovated for $245 million and reopened October 2025.

Spectrum (functional analysis)

The spectrum, also called the operator spectrum, is the set of scalars λ for which T − λI has no bounded inverse, generalizing a matrix's eigenvalues.

Spectrum analyzer

A spectrum analyzer, also called a spectral analyzer, is a test instrument that displays signal power versus frequency, used in RF work such as wireless communications, radar, and EMC measurement.

Spectrum auction

A spectrum auction is a competitive bidding process by which a government regulator awards licenses to use radio spectrum, first held by the US FCC in 1994.