(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.
Hydrofluoric
Definition:
(a.) Pertaining to, or containing, hydrogen and fluorine; fluohydric; as, hydrofluoric acid.
Example Sentences:
(1) A technique is described which the glass coverslip of a culture, flat embedded in epoxy resins can be removed easily using hydrofluoric acid.
(2) Especially in the case of Scotchprime treatment, hydrofluoric acid etching was remarkably effective on the increase in the bond strengths.
(3) We have reported the case of a man who was totally immersed in a 10% hydrofluoric acid solution.
(4) We present two fatal cases resulting from extensive exposure to hydrofluoric acid which produced acute systemic metabolic acidosis with profound hypocalcemia and hypomagnesemia.
(5) Dynamic studies showed that the combined action of phosphine and hydrofluoric acid damages the Krebs cycle reactions, dehydrogenization of isocitrate and synthesis of citrate in homogenized rat liver.
(6) With the exception of the excessive exposure to acidulated fluoride, ammonium bifluoride, or hydrofluoric acid, there is little risk of surface degradation of virtually all current dental ceramics.
(7) This system purportedly eliminates hydrofluoric acid-etching and silane pretreatment.
(8) Hydrolysis, treatment with aqueous hydrofluoric acid, and 1H and 13C nuclear magnetic resonance studies showed that the glycoprotein glycan is a high-molecular-weight polymer (approximate Mr, 15,000) of tetrasaccharide repeating units with the component sugars N-acetylgalactosamine (GalNAc), N-acetylmannosamine (ManNAc), and N-acetylbacillosamine (BacNAc; 2-N-acetyl-4-amino-2,4,6-trideoxy glucose) linked by monophosphate diesters.
(9) Hydrofluoric acid is used in a variety of industries and poses a considerable medical hazard.
(10) From SEM observation, hydrofluoric acid etching gave greater roughness to the porcelain surface, which resulted in greater mechanical interlocking of the resin.
(11) Hydrofluoric acid can thus be used to specifically cleave Rha-containing polysaccharides.
(12) If an ophthalmologist is the first to treat a patient with chemical exposure, the history of hydrofluoric acid exposure must be obtained, and the burn team and other medical specialists must be quickly consulted to avoid potentially fatal complications.
(13) Introduction of a halogen atom at C-2 of steroid 3-ketofluorohydrins, obtained from the corresponding 5alpha,6alpha-epoxides by trans-diaxial opening with hydrofluoric acid, prevents the 6beta-fluorine atom from undergoing rearrangement to the more stable 6alpha configuration when the 5-tert-hydroxyl is split off to yield to yield a conjugated double bond.
(14) The experimental variables included three porcelain surface preparations, as polished, etched with phosphoric acid, or etched with hydrofluoric acid and three kinds of commercially available silane coupling agents.
(15) Following hydrofluoric acid (HF) treatment, tau PHF proteins are heat- and acid-stable, soluble in 2-(N-morpholino)ethanesulfonic acid buffers and display the same molecular weight, pI, and immunochemical properties as normal tau s. Alkaline phosphatase treatment of dissociated PHF results in similar, although less extensive, electrophoretic changes and a reduction in PHF-1 immunoreactivity.
(16) In a previous report, observations were made on the apporopriate concentrations of hydrofluoric acid and durations of application in treating porcelain surfaces to improve the bonding strength at the porcelain-resin interface.
(17) The fluoride ion levels (geometric mean) in the urine and in the serum of the non-hydrofluoric-acid workers were determined to be 0.59 ppm and 12 ppb, respectively.
(18) Acidified sample (1l) with a known amount of 95Zr was evaporated to dryness, treated with hydrofluoric and nitric acids, and then with nitric and perchloric acids, and evaporated nearly to dryness.
(19) We have deglycosylated the enzyme gamma-glutamyl transpeptidase by treatment of the protein with anhydrous hydrofluoric acid at 0 degree C. After deglycosylation, the heavy and light subunits showed a molecular weight of 43 and 23 Kd respectively.
(20) A patient with hydrofluoric acid burns involving only 8% of his body surface area died from intractable cardiac arrhythmia secondary to the depletion of ionized calcium by fluoride ion.