All articles starting with N
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Negative linear compressibility in metal–organic frameworks
Negative linear compressibility in metal–organic frameworks is the expansion of a MOF crystal along one or more axes under hydrostatic pressure, typically produced by a hinging wine-rack geometry.
Negative Man
Negative Man is DC Comics superhero Larry Trainor, a radioactive test pilot who releases a negatively charged energy being, debuting in My Greatest Adventure #80 (June 1963) as a founding Doom Patrol member.
Negative mass
Negative mass is hypothetical matter whose mass is negative, distinguished into inertial, passive gravitational, and active gravitational cases; negative rest mass has never been observed.
Negative number
A negative number, also called a directed number, is a real number less than zero; Brahmagupta gave early rules in 628, though Western acceptance came only in the 19th century.
Negative parallelism
Negative parallelism, also called contrastive phrasing or the 'not X, but Y' construction, is a rhetorical figure stating what something is not before what it is; an old form of antithesis now best known as a persistent AI-writing tell.
Negative pricing
Negative pricing in electricity markets is a wholesale price below zero, meaning sellers pay buyers to take power, which arises when inflexible generators keep producing during low demand.
Negative prompt
A negative prompt is text given to an image-generation model describing what the output should not contain, arising in the Stable Diffusion community in 2022.
Negative refraction
Negative refraction is the bending of a wave at an interface to the opposite side of the normal, predicted by Veselago in the 1960s and first observed in metamaterials in 2001.
Negative refraction of surface acoustic waves
Negative refraction of surface acoustic waves is the bending of a surface-guided elastic wave to the same side of the normal as the incident wave, demonstrated in phononic crystals.
Negative results (research)
A negative result, also called a null result, is a scientific study outcome that fails to confirm the hypothesis tested. It is published far less often than positive findings, causing publication bias.
Negative room pressure
Negative room pressure is a technique keeping a room below the pressure of adjacent spaces, so air flows inward and airborne contaminants cannot escape, used in hospital isolation rooms and laboratories.
Negative sampling (machine learning)
Negative sampling is a machine learning training technique that replaces expensive softmax normalization with binary classification, distinguishing a positive example from a few random negatives.
Negative screening
Negative screening is the practice of ruling securities out of a portfolio because their issuers fail defined environmental, social, or ethical criteria, such as tobacco or weapons.
Negative selection (cell separation)
Negative selection, also called negative cell selection, is a cell separation method in which unwanted cells are antibody-tagged and removed, leaving desired cells unbound and unmanipulated.
Negative skin friction
Negative skin friction (NSF) is the downward shear force settling soil exerts on a pile shaft, typically from consolidating soft clay, fill, or groundwater lowering.
Negative space
Negative space, or white space, is the unoccupied area around and between the figure in a composition, equivalent to Gestalt ground. Known from Chinese ink painting to Swiss Style typography; carries shape and suppresses competing forms perceptually.
Negative Spaces
Negative Spaces is Poppy's sixth studio album, released November 15, 2024 on Sumerian Records, co-produced by ex-Bring Me The Horizon's Jordan Fish; a 15-track metalcore-pop record scoring 86 on Metacritic.
Negative staining
Negative staining is an electron microscopy sample preparation method in which a specimen appears light against a dark heavy-metal stain, used to screen samples before cryo-EM.
Negative stiffness
Negative stiffness is a mechanical property in which an element deforms to assist the applied force, making such elements unstable unless embedded in positive stiffness material; metamaterials exploiting it use snap-through curved beams.
Negative stiffness metamaterial
A negative stiffness metamaterial is an architected material containing unstable elements, typically post-buckled beams or columns, whose force decreases as displacement increases, so they assist deformation and boost damping beyond ordinary composite bounds.
Negative temperature
Negative absolute temperature is a thermodynamic temperature below zero on the Kelvin scale, possible when a system's energy states have an upper limit; such systems are hotter than any positive temperature.
Negative temperature feedback
Negative temperature feedback in a nuclear reactor is the inherent effect by which rising temperature lowers reactivity, so fission and heat output fall without any operator action.
Negative thermal expansion
Negative thermal expansion is the property of a material whose volume contracts rather than expands when heated. Discovered in solids by Scheel in 1907, it is used to counteract expansion in precision devices.
Negative thermal expansion metamaterials
Negative thermal expansion metamaterials are mechanical metamaterials that contract, or expand slowly, when heated, through geometry rather than material properties, first demonstrated by Lakes and colleagues in 1996.
Negative triangularity
Negative triangularity is a reversed-D plasma shaping regime for tokamak fusion devices, first explored on the TCV tokamak in Switzerland in the 1990s, offering high confinement without damaging ELMs.
Negative utilitarianism
Negative utilitarianism is a utilitarian variant holding that right action minimizes total suffering rather than maximizing pleasure minus pain; labeled by R.N. Smart (Mind, 1958), rooted in Karl Popper, and best known for the world destruction objection.
Negative-calorie food
Negative-calorie food: claimed foods like celery, lettuce, and grapefruit that supposedly burn more calories in digestion than they provide. No evidence supports the claim; digestion costs 5–30% of food energy, and low energy density is the real benefit.
Negative-index metamaterial
A negative-index metamaterial, also called a left-handed or double-negative material, is an engineered composite with a negative refractive index, first demonstrated at microwave frequencies in 2001 after Veselago's 1967 prediction.
Negative-Pressure Ventilators
Negative-pressure ventilators (iron lungs, cuirass ventilators, Exovent) assist breathing by lowering pressure around the chest; mainstay of polio care until 1950s, now used for neuromuscular disorders and kyphoscoliosis.
Negative-pressure wound therapy
Negative-pressure wound therapy (NPWT), also called vacuum-assisted closure, is a wound treatment using a sealed dressing connected to a vacuum pump. Pioneered by Argenta and Morykwas in the 1990s; best evidence supports incisional use to reduce surgical site infections.