All articles starting with R

Radiant (meteor shower)

The radiant of a meteor shower is the point in the sky the meteors appear to come from, a perspective effect on nearly parallel paths.

Radiant barrier

A radiant barrier is a reflective building material, typically aluminum foil, that blocks radiant heat transfer; most are installed in attics, cutting cooling costs by 8 to 12 percent.

Radiant cooling

Radiant cooling is a method of space cooling in which a chilled ceiling or floor, fed by circulating water, removes heat from a room mainly by thermal radiation.

Radiant energy, also known as electromagnetic energy, is energy emitted, transferred, or received as electromagnetic waves, measured in joules and underlying solar irradiance, laser output, and Earth's radiation budget.

Radiant Historia

Radiant Historia is an Atlus/Headlock time-travel JRPG for Nintendo DS (2010), remade as Perfect Chronology for 3DS (2017). Protagonist Stocke uses the White Chronicle across parallel timelines; grid-based combat; Metacritic 85; composer Yoko Shimomura.

Radiant Nuclear

Radiant Nuclear, formerly Radiant Industries, is a nuclear startup in El Segundo, California, founded by former SpaceX engineer Doug Bernauer to develop Kaleidos, a transportable microreactor that fits in a single shipping container.

Radiation

Radiation is energy emitted from a source that travels through material or space. It takes electromagnetic forms, such as light and X-rays, and particulate forms.

Radiation and Nuclear Safety Authority

The Radiation and Nuclear Safety Authority (Säteilyturvakeskus, STUK) is Finland's national regulatory authority for nuclear safety, radiation protection, safeguards, and emergency preparedness, reporting annually to the Ministry of Economic Affairs and Employment.

Sep 29, 2026

Radiation boost

A radiation boost is an extra dose of radiotherapy delivered to the tumor bed after or during primary radiotherapy, most commonly after breast-conserving surgery for early breast cancer.

Radiation burn

Radiation burn, or radiodermatitis, is tissue damage from ionizing or UV radiation that resembles sunburn but follows a delayed, cyclic schedule distinct from thermal burns.

Radiation damage

Radiation damage: injury to living tissue from ionizing radiation, via direct DNA bond breakage and indirect water-derived ions. Covers deterministic thresholds (ARS about 1 Sv), LNT stochastic cancer risk, DDREF, and radiotherapy injury such as radiation necrosis.

Oct 20, 2026

Radiation Dose Fractionation

Radiation dose fractionation, also called hypofractionation when larger, fewer fractions are used, divides a total radiotherapy dose into sessions; randomized trials in breast, prostate, and rectal cancer show similar survival to conventional 2 Gy daily schedules with fewer visits.

Radiation Dose Hypofractionation

Radiation dose hypofractionation delivers radiotherapy in fewer, larger fractions than the conventional 1.8-2.0 Gy: moderate (2.4-3.4 Gy) and ultrahypofractionation (≥5 Gy), established mainly in prostate cancer.

Radiation duodenitis

Radiation duodenitis, radiation-induced duodenal inflammation, is a complication of abdominal radiotherapy, especially pancreatic SBRT; fixed retroperitoneal position raises dose, causing ulcers, bleeding, stenosis, guided by dose-volume constraints.

Radiation Effects

Radiation effects are biological changes from radiation exposure, classified as deterministic tissue reactions with dose thresholds and stochastic effects such as cancer; includes LNT model, Gy/Sv quantities, and history from Röntgen and the Curies onward.

Radiation effects on optical fibers

Radiation effects on optical fibers are the changes caused in a fiber by ionizing radiation, chiefly radiation-induced attenuation from color centers that absorb light in the glass.

Radiation Effects Research Foundation

The Radiation Effects Research Foundation (RERF) is a Japanese-American research institute studying the long-term health effects of radiation exposure in Hiroshima and Nagasaki atomic bomb survivors and their children.

Radiation Equipment and Supplies

Radiation Equipment and Supplies (MeSH D055618, E07.710): instruments, apparatus, components, and expendables for radiation applications, from linacs and cobalt-60 units to brachytherapy afterloaders, dosimeters, and treatment planning systems, with their QA, safety, and regulation.

Radiation exposure

Radiation exposure, also called radioactive exposure, is subjection to ionizing radiation from external sources such as X-ray machines or internal radioactive material, with health effects depending on dose.

Radiation gastritis

Radiation gastritis is inflammation of the stomach lining caused by ionizing radiation, usually during radiotherapy for stomach, esophageal, or pancreatic tumors, ranging from mild nausea to severe ulcers and bleeding.

Radiation hardening

Radiation hardening, also called nuclear hardness, is the practice of making electronic devices and systems tolerate ionizing radiation in space, by hardening the semiconductor process, circuit design, or shielding.

Radiation hydrodynamics

Radiation hydrodynamics (RHD) treats radiation energy and momentum explicitly alongside the fluid, requiring simultaneous solution of fluid and radiation transport equations, and underlies models of stars, supernovae, and inertial confinement fusion.

Radiation Laboratory

The Radiation Laboratory, known as the Rad Lab, was a microwave radar research laboratory at MIT, established in 1940 to develop radar for the Allies.

Radiation myelitis

Radiation myelitis, or radiation-induced myelopathy, is spinal cord injury from radiotherapy, spanning transient Lhermitte's-sign myelopathy and chronic progressive myelitis; risk is dose- and fractionation-dependent, rising sharply above 50 Gy.

Radiation oesophagitis

Radiation oesophagitis (radiation-induced esophagitis, RE, ICD-11 DA24.22) is radiation-caused inflammation of the esophageal mucosa after thoracic radiotherapy, causing dysphagia and odynophagia 2-3 weeks in, usually self-limited.

Radiation Oncologists

Radiation oncologists, also called radiotherapists or therapeutic radiologists, are physicians trained to treat cancer with radiation. They lead a team of physicists and dosimetrists, practice fractionation developed in the 1920s, and number over 5,300 in the US.