42,772 articles
Optomechanical quantum sensing
Optomechanical quantum sensing measures quantities like force, acceleration, and magnetic fields by reading out a mechanical oscillator through an optical or microwave cavity, using techniques such as squeezed light to beat the standard quantum limit.
Optoplasmonic single-molecule sensing
Optoplasmonic single-molecule sensing is a label-free optical detection technique in which a whispering-gallery-mode microresonator combined with a plasmonic nanoparticle registers single molecules, even single ions, as resonance shifts.
Opus (audio format)
Opus is a royalty-free, lossy audio codec standardized by the IETF as RFC 6716 in 2012, combining Skype's SILK and Xiph.Org's CELT for speech and music.
OR gate
The OR gate, or OR circuit, is a digital logic circuit whose output is HIGH when at least one input is HIGH, implementing inclusive logical disjunction.
Ora Mendelsohn Rosen
Ora Mendelsohn Rosen (1935–1990) was an American biochemist who showed the insulin receptor is an insulin-activated tyrosine kinase, helped clone its gene in 1985, and led research at Einstein and Sloan Kettering.
Oracle machine
An oracle machine, also called an oracle Turing machine, is a Turing machine that queries a fixed set as an oracle, introduced by Alan Turing in 1939.
Orange
Orange is the color between yellow and red on the visible spectrum, produced by light with wavelengths of roughly 590 to 620 nanometers. The name comes from the fruit.
Orange (colour)
Orange is the color between red and yellow in the visible spectrum, with wavelengths of roughly 590 to 625 nanometers, and takes its name from the fruit.
Orange G
Orange G, also known as C.I. Acid Orange 10, is an anionic monoazo dye used industrially on textiles, paper, wood, and leather, and as a stain in cytology and histology.
ORAS5
ORAS5, or Ocean Reanalysis System 5, is ECMWF's fifth-generation global ocean and sea-ice reanalysis, operational since 2016, providing ocean and sea-ice initial conditions for all its coupled forecasting systems.
OrbiSIMS
OrbiSIMS, also called 3D OrbiSIMS, is a secondary ion mass spectrometry instrument combining time-of-flight and Orbitrap analyzers, introduced by the UK National Physical Laboratory in 2016.
Orbit
An orbit, also called orbital motion, is the gravitationally curved path one object takes around another or their common center of mass, in continuous freefall.
Orbit determination
Orbit determination is the estimation of a satellite's or celestial body's orbital elements from observed positions, pioneered by Gauss in 1801 to recover Ceres and now central to space situational awareness.
Orbit of the Moon
The orbit of the Moon is its slightly elliptical path around Earth, with a mean distance of 384,400 km, a 27.32-day sidereal period, and its plane tilted 5.1 degrees to the ecliptic.
Orbital angular momentum of light
Orbital angular momentum of light, or photon orbital angular momentum, is the component of a beam's angular momentum from its helical wavefront, each photon carrying ℓℏ, identified in 1992 and used in communications and optical trapping.
Orbital Chern insulator
An orbital Chern insulator is a magnetic insulating state in graphene moiré superlattices where orbital motion, not spin, produces a quantized anomalous Hall effect at zero magnetic field.
Orbital current
An orbital current is a flow of electrons carrying orbital angular momentum in a solid, generated electrically by the orbital Hall effect without needing spin-orbit coupling.
Orbital decay
Orbital decay, or a decaying orbit, is the progressive loss of orbital energy that shrinks a satellite's orbit, driven mainly by atmospheric drag in low Earth orbit.
Orbital ferromagnetism
Orbital ferromagnetism is ferromagnetic order arising from spontaneous polarization of electron orbital magnetization rather than spin, clearest in graphene heterostructures showing a quantized anomalous Hall effect.
Orbital ferromagnetism in magic-angle graphene
Orbital ferromagnetism in magic-angle graphene is a form of magnetism in twisted bilayer graphene twisted about 1.1°, arising from circulating electron currents rather than spin polarization.
Orbital ferromagnetism in moiré graphene
Orbital ferromagnetism in moiré graphene is a magnetic state of twisted graphene multilayers in which the ordered moment arises from electron orbital motion rather than spin, enabling electric control.
Orbital Feshbach resonance
The orbital Feshbach resonance is a magnetically tunable scattering resonance in ultracold alkaline-earth atoms, where orbital degrees of freedom replace electron spin, proposed and observed in 2015.
Orbital Hall effect
The orbital Hall effect is the electric-field generation of a transverse flow of orbital angular momentum, independent of spin-orbit coupling, first directly observed in 2023, and central to orbitronics.
Orbital hybridisation
Orbital hybridisation, or hybridization theory, is the mixing of an atom's s and p orbitals into equivalent hybrids, such as the sp3 orbitals of methane.
Orbital magnetism
Orbital magnetism is magnetism arising from the orbital motion of electrons rather than their spin, and it dominates in moiré graphene systems with flat bands.
Orbital magnetization
Orbital magnetization is the contribution to a material's magnetization from the orbital motion of electrons rather than spin, dominant in twisted graphene moiré materials where it exceeds any possible spin magnetization.
Orbital ordering
Orbital ordering is the patterned, preferential occupation of specific d orbitals across the sites of transition-metal compounds, lifting an orbital degeneracy and shaping magnetic and electronic properties.
Orbital overlap
Orbital overlap is the sharing of the same region of space by atomic orbitals on two atoms, allowing them to combine into molecular orbitals and form a covalent bond.
Orbital period
The orbital period, or revolution period, is the time a body takes to complete one orbit around another, from Mercury's 88 days to satellites circling Earth in about 90 minutes.
Orbital resonance
An orbital resonance is a gravitational configuration where orbital periods of two or more bodies sit near a ratio of small integers, as with Pluto and Neptune.