All articles starting with R
22,461 articles
Reach for the Sky
Reach for the Sky is a 1956 British biographical war film directed by Lewis Gilbert, starring Kenneth More as legless RAF ace Douglas Bader; based on Paul Brickhill's 1954 biography, it topped the 1956 British box office and won the BAFTA for Best British Film.
Reachability analysis
Reachability analysis is a formal verification method that computes the set of states a dynamical system can enter, certifying safety by checking that reachable states avoid unsafe regions.
Reachability map
A reachability map is a discretized voxel grid of a robot's workspace recording which end-effector positions and orientations are reachable, used for base placement, grasp planning, and workspace analysis.
Reachable set analysis
Reachable set analysis computes which states a dynamical system can enter from given initial states under all inputs, including which robot footsteps prevent a fall.
Reacher (TV series)
Reacher is a Prime Video action crime series developed by Nick Santora, adapting Lee Child's Jack Reacher novels one per season with Alan Ritchson starring; renewed through season 6 with the Neagley spinoff.
Reacher season 1
Reacher season 1 is the eight-episode 2022 Prime Video debut of the series Reacher, adapting Lee Child's first Jack Reacher novel, Killing Floor; Alan Ritchson stars as Reacher, arrested for murder in Margrave, Georgia, with Nick Santora showrunning and a 92% Rotten Tomatoes score.
Reacher season 2
Reacher season 2 is the Prime Video crime drama's 2023 sophomore season, adapting Lee Child's 11th Jack Reacher novel Bad Luck and Trouble, reuniting Reacher with his 110th MP unit; it scored 98% on Rotten Tomatoes and was Prime Video's most viewed 2023 release.
Reacher season 3
Reacher season 3, Prime Video action season adapting Lee Child's Persuader, premiered February 20, 2025 with eight episodes; new villains Quinn (Brian Tee) and 7'2" Paulie (Olivier Richters); received as a return to form.
Reacher season 4
Reacher season 4, the 2026 Prime Video season adapting Lee Child's Gone Tomorrow (book 13), sets Jack Reacher (Alan Ritchson) in Philadelphia after a subway encounter; eight episodes, 66 million viewers in 28 days, Tamara Green replaces the novel's Theresa Lee.
Reachy
Reachy is a family of open-source humanoid robots from Pollen Robotics, a Bordeaux company founded in 2016 that Hugging Face acquired in 2025, including Reachy 2 and Reachy Mini.
REACS study
REACS (NCT02415452), a Chinese retrospective cohort study by Capital Medical University, tested whether retinal artery lesion staging predicts MACCE and mortality in 660 acute coronary syndrome patients after drug-eluting stent implantation; Stage ≥2 lesions independently predicted adverse events.
ReAct
ReAct is a 2022 prompting and agent-execution method in which a language model interleaves reasoning traces with actions such as tool calls, each action feeding the next thought.
React (media franchise)
React is the Fine Brothers' YouTube reaction-video franchise (Kids React, Teens React, Elders React), begun 2010, spun onto its own channel in 2014; its 2016 React World trademark attempt collapsed after mass backlash.
React Native
React Native is an open-source framework created by Meta, first released in 2015, for building mobile apps with JavaScript and React that render real native views on iOS and Android.
ReAct prompting
ReAct prompting is a technique for large language models that interleaves reasoning traces with actions, introduced in a 2022 paper by Shunyu Yao and colleagues and presented at ICLR 2023.
React Router
React Router is a routing library for React that maps URLs to components and handles data loading, first released in 2014 by Ryan Florence and Michael Jackson.
Reactance (psychology)
Reactance (psychology), from Jack Brehm's 1966 reactance theory: an aversive motivational state, mixing anger and counterarguing, triggered by threats to behavioral freedom, producing resistance, boomerang effects, and reduced persuasion in health campaigns.
Reaction bonding
Reaction bonding is a ceramic fabrication method that converts a shaped metal powder compact, usually silicon, into ceramic by reaction with nitrogen or another infiltrant.
Reaction control system
A reaction control system (RCS) is a set of small rocket thrusters on a spacecraft or aircraft, used for attitude control, small maneuvers, and station keeping, unlike main propulsion.
Reaction coordinate
A reaction coordinate is a geometric parameter, typically a bond length or bond angle, whose value measures the progress of an elementary reaction; it forms the x-axis of energy profiles.
Reaction intermediate
A reaction intermediate is a molecular entity formed from reactants that reacts further to give products, existing at an energy minimum between the transition states of a stepwise reaction's elementary steps.
Reaction mass spectrometry
Reaction mass spectrometry is a family of mass spectrometry methods using gas-phase ion–molecule reactions, including CI-MS, FA, SIFT-MS, and PTR-MS, for trace gas analysis and reaction kinetics.
Reaction mechanism
A reaction mechanism, also called a chemical mechanism, is the stepwise sequence of elementary reactions, intermediates, and electron movements by which an overall chemical reaction occurs.
Reaction Mechanism Generator
Reaction Mechanism Generator (RMG) is a free, open-source software suite developed at MIT and Northeastern University that automatically builds detailed chemical kinetic models from elementary reaction steps.
Reaction patterns in inflammatory skin disease
Reaction patterns in inflammatory skin disease are the recurring microscopic tissue responses, six canonical patterns such as spongiotic and lichenoid, into which more than 100 named dermatoses are classified.
Reaction quotient
The reaction quotient, denoted Q, is calculated from the concentrations or partial pressures of products and reactants at any moment, in the same form as the equilibrium constant.
Reaction rate
The reaction rate is the speed at which a chemical reaction converts reactants into products, the central quantity of chemical kinetics; catalysts raise it by lowering activation energy.
Reaction rate constant
The reaction rate constant, also called the rate coefficient, is the proportionality factor k in a rate law linking reaction rate to reactant concentrations; it depends on temperature.
Reaction time task
A reaction time task measures how quickly a person responds to a stimulus, in simple, choice, and go/no-go forms, serving as an index of processing speed.
Reaction wheel
A reaction wheel, also called a momentum wheel, is a flywheel spun by an electric motor to control a spacecraft's orientation; three or four wheels give precise three-axis pointing.