Search results for "fluoride"
showing 10 items of 314 documents
Resolving the forbidden band of SF6
2013
Sulfur hexafluoride is an important molecule for modeling thermophysical and polarizability properties. It is also a potent greenhouse gas of anthropogenic origin, whose concentration in the atmosphere, although very low is increasing rapidly; its global warming power is mostly conferred by its strong infrared absorption in the ν3 S-F stretching region near 948 cm(-1). This heavy species, however, features many hot bands at room temperature (at which only 31% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6 = 1 vibrational state. Unfortunately, the ν6 band itself (near 347 cm(-1)), in the first approximation, is both infrared- and Raman…
Supramolecular chirality and symmetry breaking of fluoride complexes of achiral foldamers
2017
Aromatic oligoamide foldamers containing a central pyridine-2,6-dicarbonyl motif are partially preorganized to favor the binding of fluoride anions. In the solid state, the foldamer-fluoride complexes form achiral, polar and chiral crystal structures depending on the chemical structure of the foldamer. One of the six foldamers studied here, a C2v symmetrical foldamer (1), formed repeatedly chiral crystal structures when crystallized with tetra-butylammonium fluoride, showing supramolecular bulk chirality and symmetry breaking in crystallization.
Deformation of sulfur hexafluoride and floppiness of trifluoromethyl sulfur pentafluoride
2006
International audience; With recent advances in space exploration and atmospheric chemistry there is an increased need for more spectroscopic tools to allow the of study complex species. One such tool is the theory of frame transformation of coupled rotor systems. In this article, the theory of frame transformation along with the concept of rotational energy surface is used to study the symmetry that occurs in trifluoromethyl sulfur pentafluoride due to the internal rotation of the CF3 radical and, more generally, to the extent of floppiness of SF5CF3. Other lower symmetries when a CF4 molecule is stuck on the various symmetry axes of an SF6 molecule are also discussed.
Characteristics of haloethylene-induced acetonemia in rats.
1980
A series of halogenated ethylenes (vinyl chloride, vinylidene fluoride,cis- andtrans-1,2-dichloroethylene, perchloroethylene) induces increased acetone exhalation in rats. Exposures of differently pre-treated rats to vinylidene fluoride suggest that a metabolite of the haloethylene must be envolved in eliciting this formation of acetone. This conclusion is based on (a) dependence of acetone exhalation on the concentration of vinylidene fluoride, (b) effect of inducing agents, (c) effect of pyrazol, a metabolic inhibitor, (d) effect of cysteine, (e) effect of hypoxia and (f) the time course of acetone exhalation.
Qualitative and quantitative evaluation of solitary thyroid nodules with contrast-enhanced ultrasound: initial results
2005
To assess the feasibility of contrast-enhanced ultrasound (CEUS) of the thyroid gland and to evaluate the potential of this method for characterising solitary thyroid nodules.18 patients affected by solitary thyroid nodules (size range: 0.6 to 3.6 cm; mean: 1.8 cm) confirmed by surgery (nine papillary carcinomas, four follicular carcinomas, three hyperplasias, one follicular adenoma and one Plummer’s adenoma) underwent pulse inversion US at low M.I. (0.06 to 0.08) after i.v. injection of a 2.4-mL bolus of SonoVue. Baseline echogenicity and the dynamic enhancement pattern of each nodule, in comparison with adjacent thyroid parenchyma, were assessed. Signal intensity values on grey-scale imag…
Complexes of organometallic compounds
1966
Abstract The compounds (C2H5)2PbCl2, (C2H5)3PbCl and PbCl2 were studied by paper electrophoresis in aqueous LiCl solutions of various molarities. Determination was made of the formation of chloride complexes in which the electric charge was a function of ligand concentration in the solution. From the results of these experiments, and from a comparative examination of anion exchange data obtained in previous researches, useful information is obtained for determining the ligand concentrations relative to the preponderance of cationic, neutral and anionic complexes in the aqueous solutions. From this information it is possible to assume (C2H5)2PbCl42− and (C2H5)3PbCl32− as the fully coordinate…
Gingival bleeding reduction using a carbamide peroxide based tooth paste with lactoperoxidase
2011
Introduction: The combination of carbamide peroxide, thiocyanate or enzymes such as amynoglucosidase or gluco-oxidase is able to reduce gingival inflammation. Objective: To evaluate antiseptic efficacy, in relation to reduced gingival bleeding, of a new dentifrice containing carbamide peroxide and lactorperoxidase. Materials and method: A sample of 32 patients, with periodontal pockets of more than 3mm in the vestibular area and 4 mm at interproximal sites, was divided into two groups of 16 and 17 patients respectively. Group A used a dentifrice containing 3% carbamide peroxide and 5% lactoperoxidase plus 0.022% sodium fluoride for three weeks followed by a control dentifrice with only 0.02…
Evaluation of the Clinical Efficacy of Potassium nitrate Desensitizing Mouthwash and a Toothpaste in the Treatment of Dentinal Hypersensitivity
2012
Potassium Nitrate has been used as a desensitizing agent to treat dentinal hypersensitivity. The effectiveness of a potassium nitrate is evaluated both in the form of a toothpaste and a mouthwash in a clinical study. Thirty patients were assessed using evaporative stimuli and thermal stimuli and response was evaluated using Visual Analogue Scale at baseline, at 2 weeks and 4 weeks. The patients were divided into. group I: fifteen patients who used toothpaste containing 5% potassium nitrate, sodium fluoride, xylitol and triclosan, group II: Fifteen patients who used mouthwash containing 3% potassium nitrate, sodium fluoride, xylitol and triclosan . The results of both the assessment methods …
Exciton emission and defect formation in yttrium trifluoride
2005
Two intrinsic emission bands at 220 and 280 nm have been detected in nominally pure YF3 powders at 10 K. Excitation spectra for both emissions have a sharp peak at 12 eV near the edge of interband transition. Observed emissions are assigned to the radiative decay of self-trapped excitons in YF3. The strong thermal quenching of intrinsic luminescence was observed at temperature above 120 K. It was supposed that non-radiative decay of self-trapped exciton at high temperatures lead to defect formation in YF3. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL)-linker in the synthesis of glycopeptide partial structures of complex cell surface glycoproteins.
2003
The (2-phenyl-2-trimethylsilyl)ethyl-(PTMSEL) linker represents a novel fluoride-sensitive anchor for the solid-phase synthesis of protected peptides and glycopeptides. Its cleavage is achieved under almost neutral conditions using tetrabutylammonium fluoride trihydrate in dichloromethane thus allowing the construction of complex molecules sensitive to basic and acidic media commonly required for the cleavage of standard linker systems. The advantages of the PTMSEL linker are demonstrated in the synthesis of glycopeptides from the liver intestine (LI)-cadherin and the mucin MUC1, bearing carbohydrate moieties such as N-linked chitobiose or O-linked sialyl-T(N)-residues. The synthesis of the…