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"Actinomyces naeslundii is a Gram-positive, rod-shaped bacterium found in the mouth of humans. The species has been implicated in periodontal disease, as well as various tooth cavities. In other cases, A. naeslundii is associated with good oral health. It is one of the first bacteria to occupy the oral cavity and colonize the tooth's surface. It has also been isolated from women with bacterial vaginosis. Description A. naeslundii appears Gram- positive and pleomorphic by microscopy. It does not form spores, and is considered anaerobic or microaerophilic. In 2009, the species A. naeslundi was split. Bacteria formerly known as "Actinomyces naeslundi genospecies 2" were reclassified under the new species name Actinomyces oris. Those formerly known as "Actinomyces naeslundi genospecies WVA 963" were reclassified as Actinomyces johnsonii. Role in disease Many species of the genus Actinomyces, including A. naeslundii, cause a chronic disease called actinomycosis, which is characterized by swelling and formation of an abscess which may exude pus. This can be accompanied by tissue fibrosis. Infections of the mouth, face, and neck are the most commonly recognized infections; however, the thoracic region, abdomen, pelvis, and the central nervous system can also be involved. References External links * Actinomyces naeslundii MG1 Genome Page * Type strain of Actinomyces naeslundii at BacDive - the Bacterial Diversity Metadatabase Category:Actinomycineae Category:Bacterial vaginosis Category:Bacteria described in 1951 "
"Carbon-12 (12C) is the more abundant of the two stable isotopes of carbon (carbon-13 being the other), amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 is of particular importance in its use as the standard from which atomic masses of all nuclides are measured, thus, its atomic mass is exactly 12 daltons by definition. Carbon-12 is composed of 6 protons, 6 neutrons, and 6 electrons. History Before 1959, both the IUPAP and IUPAC used oxygen to define the mole; the chemists defining the mole as the number of atoms of oxygen which had mass 16 g, the physicists using a similar definition but with the oxygen-16 isotope only. The two organizations agreed in 1959/60 to define the mole as follows. > '' The mole is the amount of substance of a system which contains as many > elementary entities as there are atoms in 12 gram of carbon 12; its symbol > is "mol". This was adopted by the CIPM (International Committee for Weights and Measures) in 1967, and in 1971, it was adopted by the 14th CGPM (General Conference on Weights and Measures). In 1961, the isotope carbon-12 was selected to replace oxygen as the standard relative to which the atomic weights of all the other elements are measured. In 1980, the CIPM clarified the above definition, defining that the carbon-12 atoms are unbound and in their ground state. In 2018, IUPAC specified the mole as exactly 6.022 140 76 × 1023 "elementary entities". The number of moles in 12 grams of carbon-12 became a matter of experimental determination. Hoyle state The Hoyle state is an excited, spinless, resonant state of carbon-12. It is produced via the triple-alpha process, and was predicted to exist by Fred Hoyle in 1954. The existence of the 7.7 MeV resonance Hoyle state is essential for the nucleosynthesis of carbon in helium-burning red giant stars, and predicts an amount of carbon production in a stellar environment which matches observations. The existence of the Hoyle state has been confirmed experimentally, but its precise properties are still being investigated. The Hoyle state is populated when a helium-4 nucleus fuses with a beryllium-8 nucleus in a high-temperature (108 K) environment with densely concentrated (105 g/cm3) helium. This process must occur within 10−16 seconds as a consequence of the short half-life of 8Be. The Hoyle state also is a short- lived resonance with a half-life of seconds; it primarily decays back into its three constituent alpha particles, though 0.0413(11)% of decays occur by internal conversion into the ground state of 12C. In 2011, an ab initio calculation of the low-lying states of carbon-12 found (in addition to the ground and excited spin-2 state) a resonance with all of the properties of the Hoyle state. Isotopic purification The isotopes of carbon can be separated in the form of carbon dioxide gas by cascaded chemical exchange reactions with amine carbamate. See also * Avogadro constant * Carbon-11 * Carbon-13 * Carbon-14 * Isotopes of carbon * Isotopically pure diamond * Mole (unit) References Category:Isotopes of carbon "
"The Royal Marines Division was formed in August 1940 as the British Royal Marines expanded to meet operational demands during the Second World War. The RM Division's primary role was to serve as an amphibious warfare formation. It was to be organised on the same lines as an Army division with 3 infantry brigades, an artillery brigade, an engineer battalion, a machine gun battalion, and a 'mobile' battalion equipped with motorcycles.The Royal Marines 1939-93 Nick van der Bijl (Osprey)Tell It to the Marines Mike Bennighof (Avalanche Press) Operational history Men of the Royal Marines Division training in deep snow at Hawick, Scotland during March 1942 101 Brigade, supported by 2 battalions from 102 Brigade, went into action at Dakar, Senegal in July 1940 at part of Operation Menace, the unsuccessful attempt by the British and Free French to seize control of the Vichy French port in West Africa. 103 Brigade never reached full strength as its recruits were constantly drafted to provide personnel for the Royal Marines naval base defence forces. The division headquarters participated in the Allied planning for Operation Ironclad (the capture of Madagascar), but the RM division itself was not assigned to the operation as its infantry brigades were understrength and its divisional artillery had not formed. In 1943, the decision was taken to disband the division and reassign its personnel. Several of the infantry battalions were converted to Royal Marine Commandos and other divisional personnel were assigned as landing craft crews. The division headquarters under Major General Robert Sturges formed the new Headquarters Special Service Group (Commando).The Royal Marines 1939-93 Nick van der Bijl (Osprey)British Commandos 1940-46 Tim Moreman (Osprey)Tell It to the Marines Mike Bennighof (Avalanche Press) Organization * 101 Brigade - infantry * 102 Brigade - infantry * 103 Brigade - infantry * 104 (Training) Brigade - established in 1942 * 15 Machine Gun Battalion - artillery * 18 (Mobile) Battalion - engineering See also * List of British divisions in World War II References Category:Royal Marine formations and units Category:British World War II divisions Category:Military units and formations established in 1940 Category:Military units and formations disestablished in 1943 "