All articles starting with O

Occipital neuralgia

Occipital neuralgia, also called Arnold's neuralgia or C2 neuralgia, is paroxysmal stabbing pain in the greater, lesser, or third occipital nerve distributions, first described in 1821, incidence 3.2 per 100,000, confirmed by diagnostic nerve block.

Occipital Structure Sensor

The Occipital Structure Sensor is a structured-light depth sensor made by Occipital of Boulder, Colorado, launched on Kickstarter in 2013 as the first mobile 3D sensor.

Occipitalisation of atlas

Occipitalisation of the atlas, also called atlanto-occipital assimilation, is a congenital fusion of C1 with the occipital bone; pooled prevalence 0.64%, often asymptomatic, associated with basilar invagination and vertebral artery anomalies.

Occitan language

Occitan (lenga d'oc, langue d'oc) is a Romance language of southern France, the Val d'Aran, and Piedmont, related to Catalan. Medieval troubadour language; three dialect groups; obsolescent in France with active revival institutions.

Oct 22, 2026

Occitan literature

Occitan literature is the body of writing in Occitan, the Romance language of southern France, from the 10th century to today. Its medieval troubadour lyric is treated as a founding moment of European vernacular literature.

Occitania

Occitania (Occitània) is the cultural-historical region of southern France, with edges in Spain and Italy, where Occitan and its six dialects, from Gascon to Provençal, are traditionally spoken; medieval troubadour land, now an endangered-language revival region.

Occitania (administrative region)

Occitania (Occitanie), French administrative region created 1 January 2016 from Languedoc-Roussillon and Midi-Pyrénées, capital Toulouse; 13 departments, 72,724 km², about 6.2 million people, France's fastest-growing metropolitan region after Corsica.

Occluded front

An occluded front, or front occlusion, forms when a faster-moving cold front overtakes a warm front in an extratropical cyclone, signaling the low has reached its mature, decaying stage.

Occludin

Occludin (OCLN, UniProt Q16625) is a ~65 kDa four-transmembrane protein at tight junctions, first identified in 1993 from chicken liver; it binds ZO-1, regulates barrier permeability, and links to Pseudo-TORCH syndrome.

Occludin homology domain

Occludin homology domain (OCEL, Pfam PF07303), a ~107-amino-acid coiled-coil domain at the C-terminus of occludin and ELL transcription factors; binds ZO-1, targets occludin to tight junctions, and regulates paracellular barrier function.

Occlusal adjustment

Occlusal adjustment, also known as occlusal equilibration or coronoplasty, is a dental procedure that reshapes biting surfaces so the teeth contact each other harmoniously; it is irreversible.

Occlusal Splints

Occlusal splints, also called bite guards or nightguards, are removable rigid or flexible dental appliances covering the teeth, used to manage temporomandibular disorders, clenching, bruxism, and jaw pain.

Occlusive Dressings

Occlusive dressings are wound coverings (films, foams, hydrocolloids, hydrogels, alginates) that seal wounds to maintain moisture, speeding reepithelialization and lowering infection rates versus gauze, though surgical-trial and cost benefits vary by wound type.

Occult

The occult, from Latin occultus meaning hidden, describes beliefs in forces impenetrable to the senses, spanning Renaissance occult sciences and the nineteenth-century revival of occultism.

Occult macular dystrophy

Occult macular dystrophy (OMD, Miyake disease, 三宅病) is a rare autosomal dominant retinal disease causing progressive central vision loss with a normal-appearing fundus, normal full-field ERG, attenuated focal macular ERG, and RP1L1 mutations.

Occultation

An occultation is the passage of one celestial body in front of a more distant one, hiding it from view, used to probe planetary atmospheres and discover rings.

Occultation observer networks

Occultation observer networks are organized groups of telescopes, often run by volunteers, spread along a predicted occultation path to measure asteroid and Kuiper Belt object shadows.

Occultation observing techniques

Occultation observing techniques are the methods used to record a star's light being blocked by the Moon or an asteroid, using high-resolution detectors and accurate GPS timing.

Occultation prediction

Occultation prediction is the computation of when and where a star's light will be blocked by the Moon, an asteroid, or another Solar System body.

Occultations by planets and satellites

An occultation by a planet or satellite occurs when the body passes in front of a star, briefly blocking its light; the dimming reveals atmospheres and rings.

Occultations in the history of astronomy

Occultations in the history of astronomy traces discoveries made when one celestial body hides another: six of eight known dense ring systems, Pluto's 1985 atmosphere discovery, and ancient Chinese records.

Occultations of stars by asteroids

Occultations of stars by asteroids occur when an asteroid briefly blocks a star's light. Observers along the shadow path measure asteroid sizes and shapes with kilometric precision.

Occultism in Nazism

Occultism in Nazism, also called Nazi occultism, is the real but limited role of esoteric ideas in Nazi ideology, and the false myth of occult Nazi masters.

Occupancy estimation

Occupancy estimation is a statistical method in ecology that estimates the probability a species occupies a site from detection/nondetection surveys, accounting for imperfect detection; it was introduced in 2002.

Occupancy grid mapping

Occupancy grid mapping is a robot perception method that divides space into cells, each holding a probability of being occupied, free, or unknown, formalized by Alberto Elfes in 1989.

Occupancy model

An occupancy model is a hierarchical statistical model used in ecology to estimate the probability that a species occupies a site, while separately estimating detection probability.

Occupancy modeling

Occupancy modeling is a statistical method in ecology that estimates the probability a species occupies a site from detection-nondetection survey data, while correcting for imperfect detection.

Occupancy sensing (building automation)

Occupancy sensing in building automation is the detection of the presence, number, or location of people in a building, used to automatically control lighting, heating, ventilation, and air conditioning.

Occupancy sensor

An occupancy sensor detects people in a space and automatically controls lighting or HVAC, most often via passive infrared or ultrasonic technology, saving 10% to 90% of lighting energy.