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Fipronil
Fipronil, a phenylpyrazole insecticide launched in 1993, blocks insect GABA- and glutamate-gated chloride channels; used in termite control, baits, and pet spot-on products, restricted in the EU for bee risk.
Fir
Fir (Abies, silver firs) is a genus of about 58–60 evergreen conifer species of the Northern Hemisphere, with flat needles and erect cones that disintegrate on the tree; includes threatened species like Abies nebrodensis and excludes Douglas fir.
Firdausi Qadri
Firdausi Qadri, born 1951, is a Bangladeshi immunologist at icddr,b in Dhaka whose trials showed a single oral dose of cholera vaccine protects older children and adults.
Fire ant
Fire ant: stinging Solenopsis ants, chiefly the invasive red imported fire ant (Solenopsis invicta) and black imported fire ant (S. richteri), native to South America, introduced via Mobile, Alabama, infesting over 367 million U.S. acres.
Fire belly newt
Fire belly newt: Oriental fire-bellied newt, Hypselotriton orientalis (formerly Cynops orientalis, 东方蝾螈), a small Chinese salamandrid with orange underside, tetrodotoxin skin defense, common in pet trade.
Fire blight
Fire blight, caused by Erwinia amylovora, is the first-detected bacterial plant disease, devastating apple and pear worldwide except China and Australia; managed by sanitation, forecasting models, streptomycin, biologicals, and resistant rootstocks.
Fire salamander
Fire salamander (Salamandra salamandra), a large toxic European salamander with yellow-on-black aposematic coloration, viviparous stream-breeding reproduction, 12-17 subspecies, IUCN Vulnerable since 2022, threatened by the Bsal fungus.
Firebird (жар-птиця) (Slavic folklore)
Firebird (жар-птиця, zhar-ptitsa) is the glowing golden bird of Russian and Slavic folklore, a rare treasure in Afanasyev's tales and the subject of Stravinsky's 1910 Ballets Russes ballet.
Firefly
Fireflies (Lampyridae), also called lightning bugs, are bioluminescent beetles, not flies or true bugs, with about 2,200-2,500 species that glow via luciferin and luciferase, flash species-specific courtship signals, and face habitat loss, pesticides, and light pollution.
Firefly squid
Firefly squid (Watasenia scintillans, hotaru-ika), a small bioluminescent enope squid of the Sea of Japan with about 800 ventral photophores, ATP-dependent blue bioluminescence, and spring spawning runs in Toyama Bay, Japan.
Firibastat
Firibastat (RB150, QGC001) is an oral brain aminopeptidase A inhibitor prodrug of EC33 developed by Quantum Genomics for hypertension; phase 3 FRESH missed its endpoint and development stopped in 2022.
Firmonertinib
Firmonertinib (formerly furmonertinib, alflutinib, AST2818; brand Ivesa) is an oral third-generation EGFR TKI approved in China since 2021 for EGFR-mutated NSCLC, with strong CNS activity, and in global development by ArriVent for uncommon EGFR mutations.
First Affiliated Hospital of Zhengzhou University
First Affiliated Hospital of Zhengzhou University (郑州大学第一附属医院), founded 1928 in Kaifeng, a Grade III Class A teaching hospital in Zhengzhou, Henan, with four campuses, remote-medicine network, and major clinical trial and research output.
First aid
First aid is the immediate initial care given at the scene of an injury or sudden illness, with three goals: preserve life, prevent deterioration, and promote recovery.
First aid kit
First aid kit: a packaged collection of supplies for emergency initial treatment. Regulated via OSHA 1910.151 and ANSI Z308.1 Class A/B kits in the US, BS 8599 in the UK, CSA Z1220 in Canada.
First branchial cleft anomaly
A first branchial cleft anomaly is a rare congenital malformation in which incomplete closure of the first branchial cleft leaves a cyst, sinus, or fistula near the ear.
First degree haemorrhoids
First degree haemorrhoids (grade I, ICD-11 DB60.0) are internal haemorrhoids that bulge into the anal canal and bleed but do not prolapse; treated first with fiber, fluids, and bowel-habit counseling, then office banding if refractory.
First Fruits
First fruits (Hebrew reshit, bikkurim; Greek aparchai): earliest harvest portions offered to a deity. Israelite barley sheaf waved Nisan 16, wheat loaves at Pentecost; rabbinic one-sixtieth rule; Temple ritual ended 70 CE.
First pass effect
The first pass effect, or first-pass metabolism, is the metabolism of an oral drug in the liver and intestinal wall before it reaches systemic circulation, reducing bioavailability.
First pharyngeal arch
First pharyngeal arch (mandibular arch): the first embryonic pharyngeal arch, appearing in week 4, dividing into maxillary and mandibular processes; forms the jaw, malleus, incus, mastication muscles, supplied by CN V.
First responder
First responder: person protecting life, property, and the environment in the earliest stages of an incident; chiefly police, firefighters, and EMS personnel. Modern US role shaped by the 1966 NAS report, Highway Safety Act, and EMT certification; high occupational stress-injury risk.
First universal common ancestor
First universal common ancestor (FUCA): hypothetical first ancestor of all modern and extinct life, predating LUCA (~4.2 Ga, ~2,600 proteins). Distinguished from LUCA, the oldest reconstructable ancestor; no direct genetic evidence exists for FUCA.
First-degree atrioventricular block
First-degree atrioventricular block (first-degree AV delay): PR interval over 200 ms with 1:1 conduction, usually asymptomatic; Framingham data link it to atrial fibrillation, pacemaker implantation, and mortality.
First-Pass Ventriculography
First-pass ventriculography (FPRNV, first-pass radionuclide angiography): nuclear medicine technique imaging a radionuclide bolus during one transit through the heart; preferred for right ventricular ejection fraction and intracardiac shunts, distinct from equilibrium MUGA.
Fish
Fish: aquatic gill-breathing vertebrates with fins, spanning jawless, cartilaginous, and bony groups (not a true clade); over 32,000 species, ~500-million-year fossil record, and record 235 million tonnes of fisheries and aquaculture production in 2024.
Fish anatomy
Fish anatomy: body structure of bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish. Covers skeleton, tessellated cartilage, fins, myotomes, swim bladder, otoliths, lateral line, gills, and circulation.
Fish as food
Fish as food: fish and other aquatic animals eaten by humans, from capture fisheries and aquaculture. 89-90 percent of production is consumed as food; per capita intake rose from 9.0 kg (1961) to 20.5 kg (2019); farmed output surpassed wild catch in 2022.
Fish ball
Fish ball (魚蛋): a minced-fish or surimi ball with starch, salt, and seasonings, a southern Chinese and Southeast Asian staple; Hong Kong curry fish balls, Teochew white balls, Fuzhou pork-filled balls, 50% fish-content rules, and high sodium.
Fish farming
Fish farming, also known as fish culture or farmed fisheries, is the rearing of fish in ponds, cages, and tanks for food, the finfish branch of aquaculture.
Fish fin
Fish fin: median fins (dorsal, anal, caudal) and paired fins (pectoral, pelvic) used for thrust, steering, and stability; BCF versus MPF swimming; regenerating teleost caudal fin; origin of paired fins and fin-to-limb transition.