All articles starting with O
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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 floor reconstruction
Orbital floor reconstruction is a surgical procedure that repairs defects in the bony floor of the eye socket, repositioning herniated contents and placing an implant or graft.
Orbital fracture
Orbital fracture, including blowout fracture of the orbital floor or medial wall: break in the eye socket bones from blunt trauma, causing diplopia, enophthalmos, and V2 numbness; diagnosed by thin-cut CT, managed observationally or surgically.
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 Implants
Orbital implants are devices placed in the socket after eye removal (enucleation, evisceration) to restore volume; porous types include hydroxyapatite, Medpor polyethylene, and aluminum oxide, versus nonporous PMMA and silicone.
Orbital inclination
Orbital inclination is the angle between an orbit's plane and a reference plane, one of six Keplerian elements: 0° rides the equator, 90° passes over the poles.
Orbital inclination change
An orbital inclination change, also called a plane change, is a maneuver that rotates a spacecraft's orbital plane and is among the most expensive in orbital mechanics.
Orbital infection
Orbital infection, chiefly orbital cellulitis, is infection of tissues behind the orbital septum, usually spreading from ethmoid sinusitis. Incidence 1.6/100,000 children; staged by Chandler classification; treated with IV antibiotics and sometimes drainage.
Orbital inflammation
Orbital inflammation (nonspecific orbital inflammation, idiopathic orbital inflammation, orbital pseudotumor) is benign noninfectious inflammation of orbital tissues, diagnosed by exclusion, third commonest after thyroid eye disease and lymphoma, treated first with corticosteroids.
Orbital leiomyoma
Orbital leiomyoma (ORPHA:52994) is a rare benign smooth muscle tumor of the eye socket, arising from orbital vessel walls or Müller's muscle, slow-growing, encapsulated, causing painless proptosis, treated by complete excision with excellent prognosis.
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 Maneuvering System
The Orbital Maneuvering System (OMS) was the Space Shuttle orbiter's primary in-space propulsion system, two AJ10 rocket engines that performed orbital insertion, orbit changes, rendezvous, and the de-orbit burn.
Orbital Marine Power
Orbital Marine Power is a Scottish engineering company, headquartered in Orkney, that develops floating tidal stream turbines; its O2 turbine has generated grid power at EMEC since 2021.
Orbital mechanics
Orbital mechanics, also known as astrodynamics or orbital dynamics, is the branch of mechanics that studies the motion of spacecraft and planets under gravity to plan space missions.
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 rendezvous
Orbital rendezvous is the set of maneuvers by which a chaser spacecraft matches a target's position and velocity in orbit, a required step for docking and space station missions.
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.
Orbital Sciences Corporation
Orbital Sciences Corporation was an American aerospace company founded in 1982 and based in Dulles, Virginia, that built the Pegasus rocket, the Antares rocket, and the Cygnus cargo spacecraft before merging into Orbital ATK in 2015.
Orbital spaceflight
Orbital spaceflight, or orbital flight, is flight in which a spacecraft travels fast enough to fall freely around a celestial body instead of back to its surface.
Orbital speed
Orbital speed, or orbit velocity, is the speed at which a body travels along its orbit, increasing the closer it is to the central body.
Orbital station-keeping
Orbital station-keeping is the propulsive maneuvers that keep a spacecraft within its designated orbital position or window despite perturbations such as drag, gravity irregularities, and solar radiation pressure.
Orbital subperiosteal abscess
Orbital subperiosteal abscess (SPA), Chandler stage III orbital infection: pus between the orbital wall and periorbita, usually medial, complicating ethmoid or frontal sinusitis; managed medically in selected young patients, drained otherwise.
Orbital torque
Orbital torque is a torque on a ferromagnet's magnetization produced when orbital angular momentum generated in an adjacent light metal is converted to spin by spin-orbit coupling.