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High-altitude balloon
A high-altitude balloon, also called a stratospheric balloon or stratostat, is an unpowered lighter-than-air craft carrying instruments into the stratosphere, typically reaching 20 to 40 kilometers.
High-angle annular dark-field scanning transmission electron microscopy
High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is an imaging mode where heavier atomic columns scatter more electrons and appear brighter, giving Z-contrast images.
High-density carbon capsule implosions
High-density carbon capsule implosions are inertial confinement fusion experiments whose fuel capsules use a nanocrystalline diamond ablator, the standard design behind NIF's December 2022 ignition and 2025 record yield.
High-density polyethylene
High-density polyethylene (HDPE) is a linear, largely unbranched form of polyethylene with 60 to 80 percent crystallinity, making it stiffer and stronger than low-density polyethylene and widely used for bottles, tanks, and pipe.
High-dimensional neural network potentials
A high-dimensional neural network potential (HDNNP) is a machine-learning interatomic potential introduced by Behler and Parrinello in 2007, summing per-atom network energies for near-DFT accuracy at large scale.
High-dimensional quantum key distribution
High-dimensional quantum key distribution (HD-QKD) is a form of quantum key distribution that encodes information in qudits with more than two dimensions, raising key rates and noise tolerance.
High-energy astrophysical neutrinos
High-energy astrophysical neutrinos are neutrinos produced when cosmic rays collide with gas or photons in distant sources, with IceCube discovering the diffuse TeV–PeV flux in 2013.
High-energy-density physics
High-energy-density physics (HEDP) is the study of matter and radiation at extremely high temperatures and pressures, conditions found in stars and recreated in laboratories for fusion and astrophysics research.
High-energy-resolution fluorescence detection
High-energy-resolution fluorescence detection (HERFD) is a detection mode for X-ray absorption spectroscopy in which emitted fluorescence is analyzed with a crystal spectrometer, reducing core-hole lifetime broadening.
High-entropy alloy electrocatalysis
High-entropy alloy electrocatalysis is the use of alloys containing five or more principal elements in near-equal proportions as catalysts for reactions like hydrogen evolution and CO₂ reduction.
High-entropy alloy nanoparticles
High-entropy alloy nanoparticles (HEA NPs) are nanoscale particles mixing four or more elements in near-equal proportions into a single-phase solid solution, studied mainly as catalysts.
High-entropy alloy thin films
High-entropy alloy thin films are micron-scale or thinner coatings made from multicomponent alloys of five or more principal elements, bringing high hardness, wear resistance, and corrosion resistance to surfaces.
High-entropy halide perovskites
High-entropy halide perovskites are halide perovskites with several cations occupying the same crystallographic site at high concentrations, so configurational entropy stabilizes the phase, improving solar cell stability.
High-entropy oxide electrodes
High-entropy oxide electrodes are battery and electrocatalyst electrodes made from oxides with five or more randomly mixed metal cations in a single phase, stabilized by configurational entropy since 2015.
High-entropy oxides
High-entropy oxides are multicomponent oxide ceramics, typically with five or more cations in near-equiatomic ratios, known for intrinsically low thermal conductivity and use in thermal barrier coatings.
High-entropy shape-memory alloys
High-entropy shape-memory alloys (HESMAs) are shape-memory alloys following the high-entropy alloy principle, mixing five or more principal elements for higher strength, wider transformation temperature range, and better thermal cycling stability than conventional alloys.
High-harmonic fast-wave heating
High-harmonic fast-wave (HHFW) heating is a radio-frequency technique for heating fusion plasmas and driving current by launching the fast magnetosonic wave at high harmonics of the ion cyclotron frequency so electrons absorb it.
High-harmonic generation
High-harmonic generation (HHG) is an extreme nonlinear optical process in which intense femtosecond laser pulses drive atoms or solids to emit coherent extreme-ultraviolet light and attosecond pulses.
High-harmonic spectroscopy
High-harmonic spectroscopy (HHS) is an all-optical technique that uses an intense laser to drive an electron from its atom or molecule and back, probing the medium with attosecond resolution.
High-level trigger
The high-level trigger (HLT) is the software-based second stage of event selection at particle collider experiments, used at the LHC by ATLAS, CMS, and LHCb.
High-Luminosity Large Hadron Collider
The High-Luminosity Large Hadron Collider (HL-LHC, also HiLumi LHC) is a CERN upgrade replacing parts of the 27-kilometer LHC with new superconducting magnets to multiply its data tenfold, operating from mid-2030.
High-nutrient, low-chlorophyll region
A high-nutrient, low-chlorophyll (HNLC) region is an open-ocean area where surface waters hold plentiful nitrate and phosphate year-round, yet phytoplankton stays scarce, chiefly because iron is depleted.
High-performance anion-exchange chromatography
High-performance anion-exchange chromatography (HPAEC) is a liquid chromatography technique that separates carbohydrates and other anions in strongly alkaline eluents, introduced by Rocklin and Pohl in 1983 and usually paired with pulsed amperometric detection.
High-performance liquid chromatography
High-performance liquid chromatography, also written high-pressure liquid chromatography, is an analytical technique that pumps a dissolved sample through a packed column to separate its components. It dominates pharmaceutical analysis.
High-performance liquid chromatography–electrospray ionization tandem mass spectrometry
High-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI-MS/MS) is an analytical method that separates compounds by liquid chromatography, ionizes them by electrospray, and quantifies them by two mass-analysis stages, dominant in clinical diagnostics.
High-performance thin-layer chromatography
High-performance thin-layer chromatography (HPTLC) is a planar chromatography technique that separates compounds on plates with fine particles, giving better resolution than conventional TLC at low cost.
High-pressure area
A high-pressure area, also known as an anticyclone or high, is a region where surface pressure exceeds that of surrounding air, bringing sinking air, light winds, and dry, settled weather.
High-pressure chemistry
High-pressure chemistry is an interdisciplinary science using high-pressure experiments and theories to study interactions, reactions, and transformations among atoms or molecules, chiefly with diamond anvil cells.
High-pressure differential scanning calorimetry
High-pressure differential scanning calorimetry (HP DSC) measures sample heat flow under elevated gas pressure, revealing how pressure shifts phase transitions and reaction rates in polymer, petrochemical, and food labs.
High-pressure electride
A high-pressure electride is a material that under extreme compression traps valence electrons in lattice voids, where they act as anions; compressed sodium becomes a transparent insulator above 200 GPa.