42,772 articles
PH
PH, also called the pH scale or potential of hydrogen, is a logarithmic measure of the acidity of an aqueous solution, where each unit is a tenfold change.
pH imaging
pH imaging is an analytical technique that produces a pixel-wise map of pH across a sample, most often with pH-sensitive fluorescent probes in living cells.
PH indicator
pH indicator (acid-base indicator): weak acid or base whose acid and conjugate-base forms differ in color, shifting with pH; transition range about pKa ± 1; used in titrations and universal indicator; concept tied to Sørensen's 1909 pH scale.
PH meter
A pH meter is an electronic instrument that measures the acidity or alkalinity of a solution using a glass electrode paired with a reference electrode, converting the voltage to pH.
Phagraphene
Phagraphene is a theoretically predicted two-dimensional carbon allotrope proposed in 2015, built from fused pentagonal, hexagonal, and heptagonal rings with distorted Dirac cones like graphene.
Phane nomenclature
Phane nomenclature is an IUPAC method, introduced in 1998, for naming organic structures of rings or ring systems linked directly or through chains, such as cyclophanes.
Phanerozoic (Φανεροζωικός)
The Phanerozoic (Greek for "visible life") is the most recent eon of geologic time, running from 538.8 million years ago to the present and divided into the Paleozoic, Mesozoic, and Cenozoic eras.
Phantom power
Phantom power, also called phantom powering, supplies DC voltage, usually 48 volts, to condenser microphones over the same balanced cable that carries their audio signal.
Phantom time conspiracy theory
The phantom time conspiracy theory, or Phantom Time Hypothesis, is a pseudohistorical claim by German author Heribert Illig, first published in 1991, that the years AD 614 to 911 never existed.
Pharmacophore model
A pharmacophore model is a computational representation of the spatial arrangement of steric and electronic features a molecule needs to interact with a biological target, used in drug discovery.
Pharmacotherapy
Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy, a monthly peer-reviewed journal founded by Russell R. Miller in 1981 and official journal of the American College of Clinical Pharmacy, publishing human pharmacology and drug therapy research.
Pharmacovigilance
Pharmacovigilance, also known as drug safety, is the science of detecting, assessing, understanding, and preventing adverse effects and other drug-related problems, as defined by the World Health Organization.
Phase (matter)
In chemistry and thermodynamics, a phase of matter is a region of a material system uniform in composition and physical state, such as solid, liquid, or gas.
Phase (waves)
Phase, also called wave phase, is the position of a point in time on a waveform cycle, expressed as an angle where one full cycle equals 360°.
Phase closure
Phase closure is an astronomical interferometry technique that sums visibility phases around a closed loop of baselines, typically a triangle of three telescopes, canceling antenna-based phase errors.
Phase coherence and dephasing in mesoscopic conductors
Phase coherence and dephasing in mesoscopic conductors describe how far electrons keep a predictable quantum phase, a distance up to tens of micrometers limited by collisions.
Phase curve
A phase curve is a graph of how the brightness of an orbiting or rotating body, or a dynamical system's state, changes with its phase in a cycle.
Phase cycling (spectroscopy)
Phase cycling is a coherence-selection technique in pulsed magnetic resonance and optical spectroscopy, varying pulse phases across scans so desired pathways add while others cancel.
Phase diagram
A phase diagram, or P–T diagram, is a graph showing which phase of a substance is stable at each pressure and temperature, with triple and critical points.
Phase Doppler anemometry
Phase Doppler anemometry (PDPA), also called phase Doppler particle analysis, is a laser technique that measures the size and velocity of spherical particles, such as spray droplets.
Phase equilibrium
Phase equilibrium is the condition in which two or more phases of a system, such as a vapor and its liquid, coexist with no net change.
Phase field crystal model
The phase field crystal model is a continuum simulation method resolving atomic-scale crystal structure and defects over diffusive timescales, proposed by Elder and colleagues in 2002.
Phase field simulation
Phase field simulation is a computational modeling method that represents evolving microstructures, such as solidifying dendrites and coarsening grains, using continuous order parameter fields with diffuse interfaces instead of explicitly tracked boundaries.
Phase H
Phase H is a dense hydrous magnesium silicate, MgSiO4H2, stable at lower-mantle pressures and regarded as the deepest mineral able to carry subducted water into the deep mantle.
Phase matching
Phase matching is the condition in nonlinear optics where the wave vectors of interacting light waves are balanced, allowing frequency conversion in crystals to add coherently and efficiently.
Phase noise
Phase noise is the random fluctuation of an oscillator's phase, reported as a spectrum in dBc/Hz; it degrades clock signals and is the frequency-domain counterpart of timing jitter.
Phase of the wave function and gauge transformations
The phase of the wave function is the angle of its complex value; global phase is unobservable, while local phase changes tie quantum mechanics to electromagnetism.
Phase problem
The phase problem is the loss of phase information in diffraction experiments, where detectors record intensities but not phases, leaving crystal structures unsolvable without recovery methods.
Phase reduction
Phase reduction is a mathematical technique that replaces a high-dimensional model of a weakly perturbed limit-cycle oscillator with a single phase variable, making synchronization of neural, chemical, and circadian oscillators tractable.
Phase retrieval
Phase retrieval, also called phase recovery, reconstructs a signal from the magnitude of its Fourier transform when detectors record only intensity, as in diffraction imaging, astronomy, and radar.