All articles starting with P
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Photios I
Photios I (Φώτιος), twice Ecumenical Patriarch of Constantinople from 858 to 867 and again from 878 to 886, was the leading scholar of his age and a saint of the Orthodox Church.
Photios II
Photios II (Φώτιος Β´), in secular life Dimitrios Maniatis, was Ecumenical Patriarch of Constantinople from 7 October 1929 until his death on 29 December 1935.
Photo 51
Photo 51 is the clearest X-ray diffraction photograph of B-form DNA, taken in May 1952 under Rosalind Franklin at King's College London, informing the 1953 double-helix model.
Photo booth
A photo booth is a self-service machine with a camera that produces a strip of portraits within minutes, first commercialized as Anatol Josepho's Photomaton in 1925.
Photo Booth
Photo Booth is the built-in camera application on Apple's Mac computers, capturing single photos, four-photo 4-up sequences, and video with effects applied live before capture.
Photo print sizes
Photo print sizes, also known as standard photographic print sizes, are standardized dimensions into which photos are printed, chiefly 4×6, 5×7, and 8×10 inches, with larger enlargements above them.
Photo shoot
Photo shoot (photoshoot): a session in which a photographer takes pictures of a person, product, or scene for publication or commercial use. Covers studio history from 1840, editorial versus commercial shoots, model releases, and AI-era changes.
Photo-allergic contact dermatitis
Photo-allergic contact dermatitis (PACD, photoallergic eczema) is a type IV hypersensitivity skin reaction to a light-activated contact allergen, mainly sunscreens and topical NSAIDs, diagnosed by photopatch testing and distinguished from phototoxic dermatitis by delayed onset and sensitization.
Photo-elicitation
Photo-elicitation is a qualitative interview technique in which photographs are shown to participants to evoke memories, emotions, and narratives that purely verbal interviews may miss.
Photo-essay
A photo-essay, also called a photo story, is a series of photographs, often with text, that tells a story, a form that emerged in German illustrated journals in the late 1920s.
Photo-Fenton oxidation
Photo-Fenton oxidation is an advanced oxidation process for water treatment that combines iron, hydrogen peroxide, and UV or sunlight to generate hydroxyl radicals degrading organic pollutants.
Photo-Fenton reaction
The photo-Fenton reaction is a light-assisted advanced oxidation process in which irradiating an iron–hydrogen peroxide mixture generates hydroxyl radicals that degrade organic pollutants and inactivate microorganisms in water.
Photo-induced hidden phase in 1T-TaS2
The photo-induced hidden phase in 1T-TaS2 is a long-lived metallic state of tantalum disulfide reached by striking its insulating ground state with a single femtosecond laser pulse.
Photo-induced superconductivity in K3C60
Photo-induced superconductivity in K3C60 is a claimed state where mid-infrared pulses make the fulleride superconductor behave superconductingly at up to room temperature, well above its 20 K transition temperature.
Photo-Secession
The Photo-Secession was a New York society of photographers founded by Alfred Stieglitz in 1902 to establish photography as a fine art, dissolving in 1917.
Photoacid generator
A photoacid generator (PAG) is a compound that releases a strong acid when exposed to radiation, the light-sensitive acid source in chemically amplified photoresists used to pattern silicon wafers.
Photoacoustic detection
Photoacoustic detection is a spectroscopy method in which modulated light absorbed by a sample is converted into sound, enabling trace-gas measurements at parts-per-billion to parts-per-trillion levels.
Photoacoustic effect
The photoacoustic effect is the generation of sound or ultrasound waves when a material absorbs light energy, discovered by Alexander Graham Bell in 1880 and used in biomedical imaging.
Photoacoustic imaging
Photoacoustic imaging (PAI) is a hybrid biomedical imaging method that uses pulsed light to generate ultrasound in tissue, combining optical-absorption contrast with ultrasound-like resolution beyond the optical diffusion limit.
Photoacoustic microscopy
Photoacoustic microscopy (PAM) is a label-free biomedical imaging technique that maps optical absorption in tissue using pulsed laser light and ultrasound, including OR-PAM and AR-PAM forms.
Photoacoustic nanoprobes
Photoacoustic nanoprobes are nanoparticles, typically tens to hundreds of nanometers, that serve as contrast agents in photoacoustic imaging, adding molecular specificity and functional readouts beyond endogenous absorbers like hemoglobin.
Photoacoustic spectroscopy
Photoacoustic spectroscopy (PAS) determines the absorption spectrum of gases, liquids, or solids by detecting sound from absorbed modulated light, enabling trace-gas sensing and analysis of opaque samples.
Photoacoustic Techniques
Photoacoustic techniques (optoacoustic techniques) are diagnostic and investigative methods using sound waves generated by absorption of electromagnetic radiation, chiefly laser-based biomedical imaging combining optical contrast with ultrasound resolution, from Bell's 1880 effect to PACT and PAM systems.
Photoacoustic tomography
Photoacoustic tomography, also called photoacoustic computed tomography, is a biomedical imaging method combining ultrasound resolution with optical contrast from hemoglobin, reaching centimeter depths for breast cancer imaging.
Photoactivated localization microscopy
Photoactivated localization microscopy (PALM) is a single-molecule fluorescence microscopy method introduced in 2006 that images cellular structures at about 20–30 nm resolution, ten times finer than conventional light microscopy.
Photoaffinity labeling
Photoaffinity labeling (PAL) is a chemical biology technique in which a probe with a photoreactive group binds its target, and light triggers a covalent bond, enabling target identification and binding-site mapping.
Photoaging of the skin
Photoaging of the skin: UV radiation-driven premature skin aging, mainly UVA (95% of terrestrial UV) and UVB, causing wrinkles, lentigines, solar elastosis, immunosuppression; treated with sunscreens and topical retinoids.
Photoanode
A photoanode is the illuminated electrode of a photoelectrochemical cell where oxidation reactions occur, typically an n-type semiconductor such as TiO2, hematite, or BiVO4, often used for solar water splitting.
Photoassociation
Photoassociation is a process in which two colliding laser-cooled atoms below 1 millikelvin absorb a photon and form an electronically excited molecule, probing molecular states near the dissociation limit.
Photobacterium
Photobacterium, a Vibrionaceae genus of Gram-negative marine rods named by Beijerinck in 1889; luminous species such as P. leiognathi and P. phosphoreum form fish light-organ symbioses and spoil seafood.