42,772 articles
November 2014 Bering Sea cyclone
The November 2014 Bering Sea cyclone was an extratropical storm from the remnants of Typhoon Nuri that deepened to 924 millibars, among the strongest North Pacific cyclones recorded.
Novikov conjecture
The Novikov conjecture is a conjecture in geometric topology, formulated by Sergei Novikov around 1970, stating that the higher signatures of closed oriented manifolds are invariant under oriented homotopy equivalence.
Novikov self-consistency principle
The Novikov self-consistency principle, also called the self-consistency principle, states that time travel via closed timelike curves allows only self-consistent events, giving paradoxical ones probability zero.
Novobiocin
Novobiocin is an aminocoumarin antibiotic produced by Streptomyces niveus that inhibits the ATPase activity of DNA gyrase, used mainly against penicillin-resistant Staphylococcus aureus and later withdrawn.
Nowcasting
Nowcasting is the production of detailed weather forecasts from the present to 6 hours ahead, defined by the WMO and built mainly from weather radar observations.
NOx
NOx, or oxides of nitrogen, is the sum of nitric oxide and nitrogen dioxide emitted mainly by fuel combustion, regulated as a Clean Air Act criteria pollutant.
Nozaki–Hiyama–Kishi reaction
The Nozaki–Hiyama–Kishi reaction is a chromium(II)/nickel(II)-mediated coupling of aldehydes or ketones with vinyl or allyl halides forming allylic alcohols, valued for its chemoselectivity, discovered in 1977 and formalized in 1986.
NP (complexity)
NP, or nondeterministic polynomial time, is the complexity class of decision problems whose proposed solutions can be verified in polynomial time; whether NP is larger than P is a famous unsolved problem.
NPK fertilizer
NPK fertilizer is a fertilizer containing nitrogen, phosphorus, and potassium, sold as compounds or blends; its three-number label code gives each nutrient's percentage by weight.
NREL Materials Database
The NREL Materials Database (NLRMatDB) is an open computational database from the National Renewable Energy Laboratory holding DFT and GW calculated properties of inorganic materials for renewable energy applications.
NRQCD
NRQCD, or nonrelativistic QCD, is an effective field theory describing heavy quark-antiquark bound states such as charmonium and bottomonium, introduced by Caswell and Lepage in 1986.
NRSurrogate waveform models
NRSurrogate waveform models are fast, data-driven models of gravitational waves from binary black hole mergers, built by interpolating directly on numerical relativity simulations rather than analytic approximations.
NRTL
NRTL (non-random two-liquid) is a semi-empirical local-composition activity-coefficient model for liquid mixtures, published by Renon and Prausnitz in 1968 and widely used for phase-equilibrium calculations.
NSF Convergence Accelerator
The NSF Convergence Accelerator is a National Science Foundation program launched in 2019 that funds multidisciplinary teams to turn use-inspired research on national-scale challenges into sustainable solutions, expanding to ten regional accelerators since 2024.
Nth root
An nth root of a number a is a number b satisfying b^n = a; over the reals, odd roots of negatives are real while even roots are not.
NTP pool
The NTP Pool, at pool.ntp.org, is a volunteer-run cluster of thousands of donated Network Time Protocol servers, assigned to clients via DNS and serving as the default time service for most major Linux distributions.
Nu Eridani
Nu Eridani (ν Eri, HD 29248) is a bright B-type giant star in Eridanus, about 675 light-years from Earth, that pulsates in many modes simultaneously.
Nu Scorpii
Nu Scorpii, also known as Jabbah, is a multiple star system in Scorpius, probably composed of seven stars, making it one of two known septuple star systems, about 470 light-years away.
NU-1000
NU-1000 is a zirconium-based metal–organic framework reported in 2013 at Northwestern University, with large 30 Å mesopores, chemically addressable Zr₆ nodes, and wide use in catalysis.
NU-1500-Cr
NU-1500-Cr is a chromium(III) metal–organic framework with 1.4 nm hexagonal pores that absorbs over 1 g of water per gram, made for atmospheric water harvesting.
Nuclear binding energy
Nuclear binding energy is the energy required to separate an atomic nucleus into free protons and neutrons, appearing physically as a loss of mass, the mass defect.
Nuclear chain reaction
A nuclear chain reaction, or neutron chain reaction, is a self-sustaining sequence of fissions in which released neutrons cause further fissions, the principle behind nuclear reactors and weapons.
Nuclear charge radius
The nuclear charge radius, the root-mean-square measure of the electric charge distribution in an atomic nucleus, reveals shell structure, deformation, and halo configurations along isotope chains.
Nuclear chemistry
Nuclear chemistry is the branch of chemistry that studies nuclei and nuclear reactions using chemical methods, closely allied with radiochemistry and applied to radiopharmaceuticals, isotope production, and radioactive dating.
Nuclear clock
A nuclear clock, also called a nuclear optical clock, is a frequency standard that keeps time using a transition between energy states of an atomic nucleus, demonstrated with thorium-229.
Nuclear cross section
A nuclear cross section is a measure of the probability that a nuclear reaction occurs when a particle strikes an atomic nucleus, expressed as an effective area.
Nuclear data
Nuclear data is the body of numerical information describing nuclear reactions and structure, principally cross sections, decay data, and fission yields, compiled for reactor design, shielding, and fusion research.
Nuclear deformation
Nuclear deformation is the deviation of an atomic nucleus from a spherical shape, a central subject of nuclear structure physics measured by deformation parameters such as beta and gamma.
Nuclear density
Nuclear density is the number of protons and neutrons per unit volume inside an atomic nucleus, about 0.16 nucleons per cubic femtometer in heavy nuclei.
Nuclear density functional theory
Nuclear density functional theory is a computational framework describing nuclei through an energy functional of the nucleon density, the most complete global model of nuclear ground states.