All articles starting with D
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Doppelgänger
Doppelgänger (German, "double-goer"; Doppeltgänger, coined by Jean Paul in Siebenkäs 1796–1797) is a ghostly double of a living person, an omen of death in folklore, with parallels such as the Egyptian ka, Yoruba ikẹjì, Norse vardøger, and Celtic fetch.
Doppelganger (disinformation campaign)
Doppelganger (Doppelgänger), also known as RRN, is a Russia-based disinformation campaign active since May 2022 that clones Western media and government websites via typosquatted domains, attributed to Struktura and the Social Design Agency, sanctioned by the EU and US, and disrupted by the DOJ in 2024.
Doppler (lunar crater)
Doppler is a 101.79-km-wide impact crater on the far side of the Moon at 12.58°S, 159.84°W, near the Korolev basin and Galois crater; IAU-named in 1970 for physicist Johann Christian Doppler.
Doppler broadening
Doppler broadening is the widening of a spectral line caused by thermal motion of the emitting or absorbing atoms, one of the two principal line-broadening causes.
Doppler Color Echocardiography
Doppler color echocardiography (color flow echocardiography, MeSH D018618) superimposes color-coded blood flow on gray-scale heart ultrasound in real time; pulsed-Doppler based, red/blue directional display, limited by Nyquist aliasing and angle dependence.
Doppler cooling
Doppler cooling is a laser technique that slows atoms by tuning light slightly below an atomic resonance, proposed in 1975 by Hänsch and Schawlow and underlying the magneto-optical trap.
Doppler echocardiography
Doppler echocardiography measures cardiac blood-flow velocities via the Doppler effect to estimate valve gradients and pulmonary pressures noninvasively; modes include continuous-wave, pulsed-wave, color-flow, and tissue Doppler, validated against right heart catheterization.
Doppler effect
The Doppler effect, or Doppler shift, is the change in a wave's observed frequency when source and observer move toward or away from each other.
Doppler effect for waves in a medium
The classical Doppler effect is the change in observed frequency of a wave when source, observer, or medium moves, first studied by Christian Doppler in 1842.
Doppler flowmetry
Doppler flowmetry is a noninvasive diagnostic method that measures blood flow velocity by detecting the Doppler frequency shift of ultrasound reflected from moving red blood cells.
Doppler imaging (astronomy)
Doppler imaging is an astronomical technique that reconstructs maps of brightness, temperature, or chemical abundance on a rotating star from time-resolved spectral line profile variations.
Doppler lidar
Doppler lidar is a remote-sensing instrument that measures wind velocity from the Doppler shift of laser light backscattered by aerosols, used for weather, wind energy, and airport wind-shear detection.
Doppler on Wheels
Doppler on Wheels (DOW) is a network of truck-mounted Doppler weather radars designed by Joshua Wurman and first deployed in 1995 to drive to and scan tornadoes and hurricanes.
Doppler optical coherence tomography
Doppler optical coherence tomography, also called optical Doppler tomography, is an imaging method combining OCT with Doppler shift measurement to quantify blood flow velocity in living tissue.
Doppler orbitography
Doppler orbitography is a satellite tracking technique that uses the Doppler shift of radio signals between satellite and ground stations to find orbits or ground positions with centimeter accuracy.
Doppler peak
The Doppler peak, also called the acoustic or Sakharov peak, is a prominent peak in the cosmic microwave background's power spectrum, produced by acoustic oscillations of the early photon-baryon plasma.
Doppler Pulsed Echocardiography
Pulsed Doppler echocardiography (pulsed-wave, PW Doppler) measures blood flow or tissue velocity at a selected sample volume using pulsed ultrasound; limited by the Nyquist limit and aliasing above roughly 1.5 to 2 m/s.
Doppler Pulsed Ultrasonography
Doppler pulsed ultrasonography, or pulsed-wave Doppler, is an ultrasound technique that measures blood-flow velocity at a specific depth, unlike continuous-wave Doppler, and is used in vascular and cardiac diagnosis.
Doppler radar
Doppler radar is a radar system that measures a target's radial velocity, the component of motion toward or away from the antenna, using the Doppler effect.
Doppler reflectometry
Doppler reflectometry, also called Doppler backscattering (DBS), is a microwave diagnostic used in magnetic-confinement fusion experiments to measure turbulence velocity, the perpendicular electric field, and plasma flow.
Doppler spectroscopy
Doppler spectroscopy, also called the radial-velocity method, measures wavelength shifts of a moving object's light to find its velocity, and detected the first exoplanet around a Sun-like star in 1995.
Doppler tomography
Doppler tomography is an indirect-imaging technique in astronomy that reconstructs a two-dimensional map of line emission in velocity space from spectra of a binary star taken over its orbit.
Doppler ultrasonography
Doppler ultrasonography is an ultrasound technique that measures the frequency shift of sound waves reflected from moving blood cells, assessing blood flow noninvasively in arteries, veins, the heart, and pregnancy.
Doppler ultrasound
Doppler ultrasound is a medical imaging technique that measures the speed, direction, and amount of blood flow by bouncing sound waves off moving red blood cells.
Doppler velocity log
The Doppler velocity log (DVL), also called a Doppler sonar velocity log, is an underwater acoustic sensor that measures a vessel's velocity relative to the seafloor.
Dopyeonguisasa
Dopyeonguisasa (도평의사사, 都評議使司), also called Dodang, was the supreme deliberative and administrative council of the Goryeo dynasty, renamed from the Dobyeongmasa in 1279 and reorganized as Joseon's Uijeongbu after 1392.
Doquz Khatun
Doquz Khatun (دوقوز خاتون), a Nestorian Christian Kerait princess, was the chief wife of Hülegü, founder of the Mongol Ilkhanate, and an influential figure at the early Ilkhanid court until her death in 1265.
Dor (डोर) (film)
Dor (डोर) is a 2006 Hindi drama directed by Nagesh Kukunoor, an adaptation of the Malayalam film Perumazhakkalam, starring Ayesha Takia, Gul Panag, and Shreyas Talpade; a wife seeks a widow's pardon to save her husband from execution in Saudi Arabia.
Dor Ben‐Amotz
Dor Ben-Amotz (born 1954) is an Israeli-born physical chemist who spent his career at Purdue University and is known for hydration-shell spectroscopy, a Raman-based method for studying water around dissolved molecules.
Dor Knafo (דור כנפו)
Dor Knafo (דור כנפו) is an Israeli venture capital investor and General Partner at Cyberstarts, known for co-founding Axis Security, a SASE company acquired by HPE in 2023.