F18
F18 or F-18 may refer to:Transportation
F/A-18 Hornet
The F/A-18 Hornet is a twin-engine, carrier-capable, multirole fighter and attack aircraft developed in the 1970s by McDonnell Douglas for the United States Navy and Marine Corps.[2] It was designed to fulfill both fighter and attack roles, providing air superiority, close air support, and precision strikes from aircraft carriers or land bases, with capabilities for all-weather and night operations.[3] The aircraft features a conventional tail design, digital fly-by-wire controls, and composite materials in its structure for enhanced durability and reduced weight.[4] Key specifications include a length of 56 feet (17.07 meters), a wingspan of 40 feet 5 inches (12.3 meters), a maximum speed of Mach 1.7+ at high altitude, and a ferry range of 1,546 nautical miles with external fuel tanks.[5][4] It is powered by two General Electric F404-GE-402 turbofan engines, each producing 17,700 pounds of static thrust with afterburner, enabling a service ceiling above 50,000 feet and a maximum takeoff weight of approximately 51,900 pounds.[5] The armament suite supports multirole missions, featuring a 20mm M61A1 Vulcan cannon, up to 13,700 pounds of ordnance on nine external hardpoints, including air-to-air missiles such as the AIM-9 Sidewinder and AIM-120 AMRAAM, air-to-ground munitions like the AGM-65 Maverick, and various precision-guided bombs.[3] Development of the F/A-18 began under the U.S. Navy's VFAX (Variable Fighter/Attack eXperimental) program in the early 1970s, aimed at replacing the A-7 Corsair II and F-4 Phantom II with a single airframe capable of both roles.[2] McDonnell Douglas was selected as the prime contractor in May 1976, building on the design of the Northrop YF-17 lightweight fighter prototype.[3] The first prototype flew on November 18, 1978, and the aircraft achieved initial operational capability with the Navy in 1983, entering full production shortly thereafter.[5] Upgrades over time included improved avionics, radar systems like the APG-65/73, and night-attack capabilities introduced in the late 1980s.[2] The primary variants are the F/A-18A (single-seat fighter/attack version), F/A-18B (two-seat trainer), F/A-18C (single-seat improved model with enhanced avionics and weapons integration), and F/A-18D (two-seat improved version for forward air control and reconnaissance).[3] These models form the core of the "Legacy Hornet" family, with over 1,480 aircraft produced between 1982 and 2000 by McDonnell Douglas and later Boeing following their 1997 merger.[2] Operators of the F/A-18 Hornet include the United States Navy and Marine Corps as primary users, alongside international forces such as the Royal Australian Air Force, Royal Canadian Air Force (as the CF-18), Finnish Air Force, Kuwait Air Force, Royal Malaysian Air Force, Spanish Navy, and Swiss Air Force.[3] These nations acquired the aircraft for carrier-based operations, homeland defense, and expeditionary missions, with export versions featuring customized avionics and radar.[2] In combat history, the F/A-18 saw extensive use during the 1991 Gulf War, where U.S. Navy and Marine Corps squadrons flew over 9,000 sorties, including 4,551 strike missions, with minimal losses to enemy action.[2] It also participated in Operation Deliberate Force over Bosnia in 1995, enforcing no-fly zones during Operation Southern Watch in Iraq throughout the 1990s, and various operations in the early 2000s, demonstrating its versatility in suppressing enemy air defenses and supporting ground forces.[3] The U.S. Navy retired the F/A-18A-D in 2019, while the Marine Corps plans to phase out its remaining aircraft by the mid-2030s, replacing them with the F-35C Lightning II for carrier operations to meet evolving threats with stealth and sensor fusion capabilities.[5][6] The F/A-18 Hornet served as the basis for its successor, the larger F/A-18E/F Super Hornet.[2]Formula 18
The Formula 18 (F18) is a one-design class of high-speed beach catamarans designed for international sailing competitions, governed by World Sailing through the International Formula 18 Class Association, with an emphasis on simplicity, low cost, and high performance to enable fair, handicap-free racing across diverse boat designs from multiple manufacturers.[7][8] Developed to accommodate mixed, female, and male crews of varying weights (typically 115–150+ kg total), the class promotes accessibility for amateur sailors while delivering exciting, stable platforms capable of speeds comparable to other high-performance small boats.[9] The class originated in 1993 under the French Sailing Federation's Catamaran Section, created by Pierre-Charles Barraud and Olivier Bovyn using SCHRS rating formulas to establish performance parameters for 18-foot catamarans.[9] It received ISAF (now World Sailing) recognition in 1996, leading to the formation of the International Formula 18 Catamaran Class Association with Olivier Bovyn as its first president.[9] The inaugural Formula 18 World Championship was held in 1998, and since then, over 1,000 boats have been built, with at least 12 affordable designs available to support broad participation.[9] Key specifications include a length of 18 ft (5.49 m), beam of 8.5 ft (2.6 m), total sail area of 284 sq ft (26.4 m²), and a crew of two, with no spinnaker required but optional for enhanced downwind performance.[10] The class operates under a box rule that imposes strict limits on dimensions, weight (minimum 396 lbs or 180 kg), mast height, and equipment to ensure equitable racing while permitting innovation within those boundaries, such as robust construction for longevity and interchangeable parts.[10] Popular models include the Cirrus 1800 for its stability, the Hurricane 18 for agility, and the Nacra F18 for lightweight competitiveness.[10][11] The Formula 18 World Championships are held annually, rotating among host nations and attracting over 130 boats from more than 20 countries in recent events, such as the 2024 regatta in Spain with 131 entries representing 23 nations.[12] These championships integrate with other catamaran classes like the A-Class and Formula 16, often sharing venues for multi-fleet regattas, though the F18 distinguishes itself with its two-person crew format compared to the single-handed Formula 16.[13] The class enjoys strong popularity in Europe, Australia, New Zealand, and the Americas, where it supports club-level racing, continental events like the F18 Americas Championship, and international regattas, prioritizing affordability and ease of use to draw amateur competitors into high-level competition.[9][14]Medicine and science
Fluorine-18
Fluorine-18 is a radioactive isotope of fluorine with an atomic mass of 18, characterized by its instability and use in nuclear medicine. It decays primarily through positron emission (β⁺ decay), with 97% of decays producing a positron that annihilates with an electron to emit two 511 keV gamma rays, ultimately forming stable oxygen-18; the remaining 3% occurs via electron capture. The isotope has a half-life of 109.8 minutes, which allows for practical imaging windows in clinical settings while limiting long-term radiation persistence.[15][16][17] Production of fluorine-18 typically occurs in medical cyclotrons via the bombardment of oxygen-18-enriched water targets with protons, yielding high specific activity fluoride ions through the nuclear reaction^{18}\mathrm{O}(p,n)^{18}\mathrm{F}.
This method, operational since the mid-20th century, generates activities sufficient for routine radiopharmaceutical synthesis, often exceeding several curies per batch in modern facilities. The process requires enriched targets to minimize impurities and is followed by purification steps to isolate [¹⁸F]fluoride for labeling.[18][19] Discovered and first reported in 1937 by Arthur H. Snell through deuteron irradiation of neon-20, fluorine-18 saw limited early applications until the 1970s, when advancements in positron emission tomography (PET) enabled its integration into metabolic imaging protocols. Its adoption accelerated with the synthesis of key tracers like [¹⁸F]fluorodeoxyglucose (FDG) in the late 1970s, establishing it as the premier positron-emitting radionuclide for clinical and research use due to its chemical versatility and favorable decay properties.[20][21] In medicine, fluorine-18 serves as the cornerstone radionuclide for PET imaging, particularly in [¹⁸F]FDG, which visualizes glucose metabolism to detect malignancies in oncology, assess brain function in neurology, and evaluate myocardial viability in cardiology. Specialized tracers include florbetapir F-18, approved for estimating β-amyloid plaque density in patients with cognitive impairment to aid Alzheimer's disease diagnosis, and fluoroestradiol F-18, which binds estrogen receptors to identify ER-positive lesions in recurrent or metastatic breast cancer. Beyond oncology and neurology, sodium fluoride F-18 enables high-sensitivity skeletal imaging by accumulating at sites of osteoblastic activity, outperforming traditional bone scans in detecting metastases and fractures. Recent advancements include the 2023 FDA approval of [¹⁸F]flurpiridaz for cardiac perfusion imaging and [¹⁸F]FDS for renal function assessment (as of 2025).[22][23][24][25][26] These applications leverage PET's ability to provide quantitative metabolic insights, guiding diagnosis, staging, and therapy response assessment.[27] The short half-life of fluorine-18 inherently reduces patient and staff radiation exposure compared to longer-lived isotopes, with effective doses from typical [¹⁸F]FDG scans around 7-14 mSv, akin to CT scans. However, its production demands on-site cyclotrons or nearby facilities to ensure fresh supply, as transport viability is limited to hours; safety protocols emphasize ALARA principles, including shielding, contamination monitoring, and time restrictions during handling.[28][29]
F18 (ICD-10)
Block F18 in the International Classification of Diseases, 10th Revision (ICD-10), falls under Chapter V (Mental and behavioural disorders) and specifically addresses "Mental and behavioural disorders due to use of volatile solvents."[30] This category encompasses a range of psychiatric and behavioral conditions arising from the intentional inhalation of volatile solvents, which are psychoactive substances that produce rapid euphoric effects by depressing the central nervous system.[31] Volatile solvents typically include organic compounds found in everyday products such as glue, paint thinners, gasoline, correction fluids, cleaning agents, and aerosol sprays, which are inhaled to achieve intoxication. These disorders share clinical features with those induced by other substances, such as alcohol, but are distinguished by the rapid onset and short duration of effects due to the direct absorption of vapors into the bloodstream via the lungs.[31] The F18 block is structured with subcodes that specify the type of disorder based on clinical presentation and severity:| Subcode | Description |
|---|---|
| F18.0 | Acute intoxication[32] |
| F18.1 | Harmful use[33] |
| F18.2 | Dependence syndrome[34] |
| F18.3 | Withdrawal state[35] |
| F18.4 | Withdrawal state with delirium[36] |
| F18.5 | Psychotic disorder[37] |
| F18.6 | Amnesic syndrome[38] |
| F18.7 | Residual and late-onset psychotic disorder[39] |
| F18.8 | Other mental and behavioural disorders[40] |
| F18.9 | Unspecified mental and behavioural disorder[41] |