All articles starting with P
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Perfluorobutanesulfonic acid
Perfluorobutanesulfonic acid (PFBS), also called nonafluorobutanesulfonic acid, is a four-carbon short-chain PFAS that replaced PFOS after 2000 and is highly mobile in water with low bioaccumulation.
Perfluorocarbon nanoemulsions
Perfluorocarbon nanoemulsions (PFC nanoemulsions) are submicrometer emulsions of inert liquid perfluorocarbon droplets in water, first studied as artificial blood and later used for 19F MRI tracers and targeted drug delivery.
Perfluorodecanoic acid
Perfluorodecanoic acid (PFDA), also called nonadecafluorodecanoic acid, is a synthetic long-chain perfluoroalkyl carboxylic acid used in stain-proof coatings and identified by ECHA as toxic for reproduction, persistent, and bioaccumulative.
Perfluoroelastomer
A perfluoroelastomer (FFKM) is a fully fluorinated synthetic rubber, designated FFKM under ASTM D1418, that combines the chemical resistance of PTFE with elastomeric recovery, making it the sealing material where conventional rubbers fail.
Perfluorohexane
Perfluorohexane (C₆F₁₄) is a colorless, volatile perfluorocarbon liquid, boiling at 56 °C and dissolving large amounts of gas, used in ultrasound contrast nanodroplets, ¹⁹F MRI, and electronics cleaning.
Perfluorohexanesulfonic acid
Perfluorohexanesulfonic acid (PFHxS) is a synthetic six-carbon PFAS formerly used as a surfactant, now regulated globally as a persistent organic pollutant with a human half-life exceeding 7 years.
Perfluorohexanoic acid
Perfluorohexanoic acid (PFHxA) is a persistent, colorless liquid PFAS compound used as a short-chain substitute for PFOA, also forming as a degradation product of long-chain PFAS, and restricted in the EU in 2024.
Perfluorohexyloctane
Perfluorohexyloctane (F6H8) is a chemically inert semifluorinated alkane used in prescription eye drops for dry eye disease, marketed as MIEBO in the United States since 2023.
Perfluorononanoic acid
Perfluorononanoic acid (PFNA) is a man-made perfluoroalkyl carboxylic acid used since 1975, mainly as its ammonium salt for fluoropolymer dispersions, and it persists in the environment.
Perfluorooctane
Perfluorooctane is a chemically inert, dense fluorocarbon liquid with the formula C8F18, made by electrochemical fluorination and used in vitreoretinal surgery and Fluorinert FC-77 coolant.
Perfluorooctanesulfonic acid
Perfluorooctanesulfonic acid, known as PFOS, is a synthetic fluorinated surfactant once used in stain repellents and firefighting foams, now regulated worldwide as a persistent organic pollutant.
Perfluorooctanoic acid
Perfluorooctanoic acid (PFOA) is a synthetic PFAS "forever chemical" made since 1947, classified carcinogenic to humans in 2023 and limited in US drinking water to 4 parts per trillion in 2024.
Perfluoropolyether
Perfluoropolyether (PFPE) is a synthetic fluorinated polymer whose oils and greases are chemically inert, non-toxic, and nonflammable, used as lubricants in spacecraft, hard disk drives, and vacuum pumps since the 1960s.
Perfluoropolyether grease
Perfluoropolyether (PFPE) grease is a synthetic lubricating grease made from fully fluorinated PFPE oil thickened with PTFE, used in vacuum, oxygen, and chemically aggressive service.
Perfluoropolyether lubricant
A perfluoropolyether (PFPE) lubricant is a stable synthetic oil applied as a film under 2 nm on hard disk drive disks, where it has reduced friction and wear for over 30 years.
Perfluoropropane
Perfluoropropane, also called octafluoropropane (C₃F₈), is a colorless, odorless, nonflammable gas used as an intraocular gas in retinal detachment surgery and in ultrasound contrast agents.
Perfluorosulfonic acid membrane
A perfluorosulfonic acid membrane is a fully fluorinated proton-conducting polymer, best known as Nafion, developed by DuPont in the 1960s and standard in PEM fuel cells and electrolyzers.
Perforated eardrum
Perforated eardrum (tympanic membrane perforation): a hole or tear in the eardrum from infection, injury, loud noise, or pressure change; usually heals within weeks to two months, with myringoplasty for persistent holes.
Perforated ulcer
Perforated ulcer (perforated peptic ulcer): a full-thickness hole in a stomach or duodenal ulcer causing peritonitis. Treated by omental (Graham) patch repair, increasingly laparoscopic; mortality 9-40%.
Perforating dermatoses
Perforating dermatoses (acquired perforating dermatosis, reactive perforating collagenosis, Kyrle disease, perforating folliculitis, elastosis perforans serpiginosa) are skin disorders marked by transepidermal elimination of collagen or elastin, mainly in diabetes and chronic kidney disease.
Perforation of duodenum
Perforation of duodenum: transmural duodenal wall injury, also called duodenal perforation. Main causes are peptic ulcer (H. pylori, NSAIDs), ERCP and other iatrogenic injury, and trauma; mortality 8-25%, higher with peritonitis.
Perforation of large intestine
Perforation of large intestine is a complete breach of the colonic wall that leaks bowel contents into the abdomen, causing peritonitis; common causes include cancer, diverticulitis, and colonoscopy injury.
Perforation of oesophagus
Perforation of oesophagus (esophageal perforation, Boerhaave syndrome when spontaneous), ICD-11 DA20.3: a hole in the oesophageal wall leaking contents into mediastinum; mostly iatrogenic, mortality about 10-15%.
Perforation of small intestine
Perforation of small intestine (ICD-11 ME24.30), also called non-traumatic small bowel perforation: full-thickness breach of the jejunal or ileal wall leaking contents into the abdomen, causing peritonitis; causes include iatrogenic injury, ischemia, malignancy, Crohn disease, and trauma.
Perforator flap
A perforator flap is a reconstructive technique in which skin and fat are transferred on small vessels piercing the muscle, sparing the muscle, most often for breast reconstruction.
Performance
Performance is the degree to which an organization, program, or system achieves its stated goals, measured by frameworks such as the Balanced Scorecard, introduced by Kaplan and Norton in 1992.
Performance (film)
Performance (1970) is a British crime drama co-directed by Donald Cammell and Nicolas Roeg, starring James Fox and Mick Jagger. Shot in 1968, shelved by Warner Bros for two years, initially reviled, now a cult classic restored in 4K.
Performance and community use of small-town opera houses
Small-town American opera houses were civic auditoriums, usually under 500 seats, hosting touring shows, lyceum concerts, dances, and movies rather than opera, declining after 1917 as films and automobiles took over.
Performance API
The Performance API is a group of web standards for measuring web application performance, providing browser metrics for navigation, resource loading, and rendering, plus developer-defined measurements.
Performance appraisal
Performance appraisal, also known as a performance review or evaluation, is the formal process of judging an employee's job performance against set standards, usually producing a written rating of record.