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Spectral line shape

The spectral line shape, also called the line profile, describes how a spectral line's intensity is distributed around its center, broadened mainly by Doppler and pressure effects.

Spectral mammography is an X-ray breast imaging technique that measures energy-dependent attenuation to characterize breast tissue, including contrast-enhanced spectral mammography, which uses iodinated contrast to show enhancing lesions.

Spectral method

A spectral method is a numerical technique for solving partial differential equations using global basis functions like Fourier modes, achieving exponential convergence for smooth solutions.

Spectral mixture analysis

Spectral mixture analysis (SMA) is a remote sensing technique that decomposes each pixel's spectrum into fractional abundances of endmember materials such as vegetation, soil, and impervious surface.

Spectral norm

The spectral norm of a matrix, also called the matrix 2-norm, is the operator norm induced by the Euclidean vector norm, equal to the matrix's largest singular value.

Spectral proper orthogonal decomposition

Spectral proper orthogonal decomposition (SPOD) is a modal decomposition method that extracts energy-ranked coherent structures from statistically stationary flow data, yielding orthogonal modes at each frequency.

Spectral radius

The spectral radius of a graph is the largest absolute value among the eigenvalues of its adjacency matrix, central to spectral graph theory and epidemic modeling.

Spectral sequence

A spectral sequence is a sequence of differential modules used to compute homology and cohomology groups page by page, introduced by Jean Leray in 1946.

Spectral subtraction

Spectral subtraction is a single-channel speech enhancement method introduced by Steven Boll in 1979 that estimates background noise during pauses in speech and subtracts it from the noisy signal.

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.