(n.) A non-metallic, gaseous element, strongly acid or negative, or associated with chlorine, bromine, and iodine, in the halogen group of which it is the first member. It always occurs combined, is very active chemically, and possesses such an avidity for most elements, and silicon especially, that it can neither be prepared nor kept in glass vessels. If set free it immediately attacks the containing material, so that it was not isolated until 1886. It is a pungent, corrosive, colorless gas. Symbol F. Atomic weight 19.
Example Sentences:
(1) Fluorination with [18F]acetylhypofluorite yields 6-[18F]fluoro-L-dopa with 95% radiochemical purity; fluorination of the same substrate with [18F]F2 yields a mixture of all three structural isomers in a ratio of 70:16:14 for 6-, 5-, and 2-fluoro compounds.
(2) Recent studies with fluorine-18 (F-18) fluorodeoxyglucose suggest inhomogeneity of myocardial glucose metabolism in the normal human heart, which may relate to substrate availability.
(3) In vitro sensitizing activities were correlated to the promotion efficiency of radiolytic hydroxylation of thymine to thymine glycol and to the one-electron reduction potential of a variety of fluorinated and non-fluorinated nitroazole derivatives.
(4) The new fluorinated adenine analog, fludarabine, has been tested for efficacy in many tumor types over the past ten years.
(5) The campaign’s focus was the damage to the ozone layer caused by fluorinated gases, such as HFCs.
(6) After administration of niflumic acid, flufenamic and antrafenine, the urinary elimination of ionized fluorine increase in all the subjects.
(7) The introduction of fluorines at C-24 and extension of the sterol side chain at C-26 and C-27 by methylene groups results in vitamin D analogues that have biological activity in vivo similar to those of the respective nonfluorinated natural sterols.
(8) Early prenatal suppression of the fetal adrenal cortex with fluorinated corticosteroids can prevent virilization of female fetuses with 21-hydroxylase deficiency.
(9) The fluorine modification of nitroazole sensitizers could enhance both the absolute activity and the tumor affinity.
(10) Haemophilus influenzae strains with varied ampicillin resistance and beta-lactamase production patterns were tested against three investigational fluorinated quinolones (CI-960, fleroxacin, temafloxacin) using Haemophilus Test Medium (HTM) and National Committee for Clinical Laboratory Standards (NCCLS) methods.
(11) It has been found that workers in factories who have not been considered as subjected to fluorine hazard and therefore have not been controlled had significantly elevated urinary fluoride levels.
(12) (19)F-Nuclear magnetic resonance studies of specifically fluorinated hemoglobin derivatives have been used to determine the apparent pK(a) of the histidine beta146 imidazole in deoxyhemoglobin.
(13) To measure [Ca2+]i, fluorine NMR spectra were acquired in a separate group of hearts loaded with the Ca2+ indicator 5F-BAPTA [5,5'-difluoro derivative of 1,2-bis-(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid].
(14) This is due to the influence of the fluorine substituent(s) on the basicity of the amine function proximal to the fluoromethylene group, this effect being amplified by geminal disubstitution.
(15) In intact cells of all 5-FC-susceptible strains the metabolism of 5-FU progressed to the formation of other fluorinated derivatives which were visualized as a single, broad resonance band at a lower field with respect to 5-FC and 5-FU.
(16) A major advance in antimicrobial chemotherapy was the synthesis of newer quinolones containing at least 1 fluorine atom and a piperazinyl group.
(17) We studied the relationship between antitumor efficacy of UFT, which is a most widely used drug among fluorinated pyrimidines recently, and its effect on the content and the inhibition rate of thymidylate synthase (TS) in 15 human tumor xenografts derived from stomach, colon, breast and pancreatic cancer patients.
(18) Fluorine-19 nuclear magnetic resonance images of rabbit hearts have been obtained with the administration of a fluorinated contrast compound.
(19) 31P NMR measurements of the magnesium-dependent shift between alpha- and beta-phosphates of ATP demonstrate that there is no measurable lowering of Mgi during loading with fluorinated o-aminophenol-N,N,O-triacetate.
(20) Thus, for fluoroanilines with a fluorine substituent at the para position bioactivation to the reactive benzoquinoneimine can be a direct result of the cytochrome P-450 dependent conversion.
Fluorite
Definition:
(n.) Calcium fluoride, a mineral of many different colors, white, yellow, purple, green, red, etc., often very beautiful, crystallizing commonly in cubes with perfect octahedral cleavage; also massive. It is used as a flux. Some varieties are used for ornamental vessels. Also called fluor spar, or simply fluor.
Example Sentences:
(1) Animal experiments showed that calcium fluorite can induce only a foreign body reaction in the lungs; the fibrous nodular lesions induced by the fluorite mine dust are due mainly to its silica component.
(2) On the basis of the investigations a complex filter made of silver plated minerals--dolomite and fluorite--has been developed.
(3) NMR analysis showed FAP or FHAP as a reaction product of fluoride uptake under all conditions, regardless of whether CaF2 was formed, unambiguously demonstrating fluorite as an additive rather than substitute form of F reactivity.
(4) The occurrence of fluorite in mysid statoliths confirms the earlier interpretations based on insufficient documentation.
(5) It was also demonstrated that having engulfed calcium fluorite, silica, or fluorite mine mixed dust, PAMs release an elastase-active substance.
(6) Use of acetyl hypo[18F]fluorite gives [18F]-4 in 60 min in 20-42% radiochemical yield.
(7) The environmental survey included measurements of the dust respirable fraction and fluorite concentration in the air.
(8) The authors suggest that the emphysematous lesion seen in autopsy material of pneumoconiosis of fluorite mine workers may be caused by calcium fluorite and silica.
(9) A compact autosynthesizer was developed and used successfully for the production of 2-deoxy-2-[18F]fluoro-D-glucose [18FDG] from gaseous acetyl hypo[18F]fluorite.
(10) X-ray diffraction patterns show that the statoliths of marine mysid crustaceans are composed of fluorite, and that this mineral is also a principal phase of the gizzard plates of some tectibranch gastropods.
(11) At pH's less than 5.0 to 6.0 the solubility product of fluorite, and not that of fluorapatite, is the governing principle under the experimental conditions used.
(12) It was demonstrated that either silica or the mixed dust of a fluorite mine can stimulate pulmonary alveolar macrophages (PAMs) to release fibrogenetic factors in vitro, but calcium fluorite cannot.
(13) Furthermore, fluorite (CaF2) makes the slag more fluid.
(14) The authors investigated the influence of working conditions--with particular reference to dust and fluorite pollution--on the epidemiology of chronic bronchitis in 197 subjects working in a fertilizer producing plant in Krakow (Poland).
(15) The pathogenicity of mixed dust from a fluorite mine was studied by animal experiments and in vitro tests.
(16) The unit has been similarly configured and programmed to synthesize 2-deoxy-2-[18F]fluoro-D-mannose (48% EOB), 3-(2'-[18F]fluoroethyl)spiperone (29% EOB), and [18F]fluoroacetate (66% EOB) from aqueous [18F]-fluoride ion, and 2-[18F]FDG from gaseous acetyl hypo[18F]fluorite (20% EOB).
(17) All sample fumes from low hydrogen welding in several atmospheric conditions contained fluorite (CaF2).