All articles starting with R
22,461 articles
Rectal biopsy
A rectal biopsy is a diagnostic procedure removing a small sample of rectal mucosa for histological examination, chiefly to diagnose or exclude Hirschsprung disease, first reported in 1955.
Rectal cellulitis
Rectal cellulitis (ICD-11 DB36.12) is bacterial soft-tissue infection around the rectum, also called perianal or perirectal cellulitis; classically group A streptococcal, it also denotes spreading infection complicating anorectal abscess.
Rectal discharge
Rectal discharge (anal discharge) is any non-fecal substance, usually mucus, pus, or blood, passing from the rectum. Main causes are proctitis from STIs or IBD, hemorrhoids, radiation, and diversion; CDC regimen is ceftriaxone plus doxycycline.
Rectal douching
Rectal douching: rinsing the rectum with water or saline before or after receptive anal intercourse, common among MSM (up to 88% ever); associated with increased odds of HIV and other STIs via mucosal injury and gut dysbiosis.
Rectal examination
Rectal examination (digital rectal exam, DRE): gloved-finger palpation of the rectum, anal tone, and prostate. Historic prostate cancer screening test, now largely replaced by PSA and MRI for screening but retained for staging and neurologic assessment.
Rectal foreign body
Rectal foreign body (RFB, retained anorectal foreign body): an object stuck in the rectum, usually self-inserted, requiring medical removal. Managed stepwise: transanal extraction, TAMIS or endoscopy, then milking or enterotomy; laparotomy in 8–10% of cases.
Rectal microbicide
Rectal microbicide: topical HIV pre-exposure prophylaxis applied in the rectum before receptive anal intercourse, also called rectal PrEP. Tenofovir gels and douches are in phase 1-2 trials; none is approved.
Rectal prolapse
Rectal prolapse: the rectum descends through the anus (complete or partial), mainly affecting older women, with constipation and incontinence; treated surgically by abdominal or perineal approaches, with 6-27% reported recurrence.
Rectal resection
Rectal resection, including the low anterior resection, is surgery that removes all or part of the rectum, most often to treat rectal cancer using total mesorectal excision.
Rectal tenesmus
Rectal tenesmus (anal or anorectal tenesmus) is the persistent urge to pass stool despite an empty bowel, mainly from inflammatory bowel disease, proctitis, radiation, or rectal cancer, treated by addressing the underlying cause.
Rectangle
A rectangle is a quadrilateral with four right angles, a special parallelogram with equal, parallel opposite sides and equal diagonals; its area is length times width.
Rectangular function
The rectangular function, also called the rect or gate function, equals 1 on an interval centered at zero and 0 elsewhere; its Fourier transform is the sinc function.
Rectangular hyperbola
A rectangular hyperbola, also called an equilateral or right hyperbola, is a hyperbola whose two asymptotes are perpendicular, equivalent to equal semi-axes (a = b) and giving it the fixed eccentricity √2.
Rectangular Micro QR Code
The Rectangular Micro QR Code, or rMQR code, is a rectangular two-dimensional barcode symbology developed by Denso Wave, the creator of the QR Code, and standardized in ISO/IEC 23941:2022.
Rectangular potential barrier
The rectangular potential barrier, also called the finite potential barrier, is a standard quantum mechanics model used to describe tunneling through a region of constant potential.
Rectangular rapid-flashing beacon
A rectangular rapid-flashing beacon, or RRFB, is a pedestrian-actuated US traffic device whose two yellow LED beacons flash rapidly at crosswalks, with motorist yielding rates as high as 98 percent.
Rectangular waveguide
A rectangular waveguide is a hollow metallic tube of rectangular cross-section that guides microwaves; its dominant TE10 mode propagates only above a cutoff frequency set by the broad wall.
Rectenna
A rectenna is a device combining an antenna and a rectifier to convert electromagnetic radiation into direct current, first demonstrated by William C. Brown in 1964.
Rectification (chemistry)
Rectification is a distillation method in which a liquid mixture is repeatedly vaporized and condensed inside a column, used for high-purity separations such as crude-oil refining and alcohol purification.
Rectification of names (正名)
Rectification of names (正名, zhengming) is a Confucian doctrine from Analects 13.3 holding that correct naming underpins speech, ritual, and government; systematized by Xunzi and reinterpreted by Hu Shi and modern scholars.
Rectification process
The Rectification process (Proceso de Rectificación) was a Cuban economic and political campaign launched by Fidel Castro in 1986 that reversed market mechanisms and recentralized the economy.
Rectified flow
Rectified flow is a generative training method, introduced by Liu et al. in 2022, that learns an ODE moving noise to data along nearly straight paths for few-step generation.
Rectified spirit
Rectified spirit, also called neutral spirit or ethyl alcohol of agricultural origin, is highly purified ethanol from repeated distillation (rectification), typically 95 to 96 percent ABV, tasteless, and used as the base for vodka, gin, and liqueurs.
Rectifier
A rectifier, also called an AC to DC converter, is an electrical circuit that converts alternating current into one-direction direct current, and is built into most power supplies.
Rectifier (neural networks)
The rectifier, best known as the rectified linear unit or ReLU, is an activation function that outputs positive inputs unchanged and zero otherwise, and became the default nonlinearity of deep learning.
Rectifier transformer
A rectifier transformer is a specialized power transformer that supplies AC from the grid to a rectifier converting it to DC, serving electrolysis, plating, and DC drives.
Rectify
Rectify is an American television drama series created by Ray McKinnon that aired on SundanceTV from 2013 to 2016, following Daniel Holden, released after nineteen years on death row.
Rectilinear enclosures
Rectilinear enclosures: archaeological sites, mainly late prehistoric to Roman Britain, defined by straight-sided ditches or banks with well-defined corners; detected as cropmarks, used as settlements, farmsteads, and field systems.
Rectilinear locomotion
Rectilinear locomotion is one of the four traditional modes of snake locomotion, in which a snake moves straight ahead by alternately shortening and lengthening its belly skin.
Rectocele
Rectocele (posterior vaginal wall prolapse): herniation of the rectum through the rectovaginal septum into the vagina. Causes include vaginal childbirth and chronic straining; treated first with fiber, fluids, pelvic floor therapy, and pessaries, then surgery.