نتایج جستجو برای: fluorine
تعداد نتایج: 7204 فیلتر نتایج به سال:
The viscosities of eight melt compositions in the System albite-H20-F20_1 have been determined at high pressure and temperature. Measurements were performed using the falling sphere method at 1000-1600°C and 2.5 to 22.5 kbar. Fluorine and water strongly decrease the viscosity of albite melt at all pressures and temperatures investigated. The viscosity of a fluorine-bearing albitic melt decrease...
In polar aprotic organic solvents, fluorine might be an element of choice for life that uses selected fluorinated building blocks as monomers of choice for self-assembling of its catalytic polymers. Organofluorine compounds are extremely rare in the chemistry of life as we know it. Biomolecules, when fluorinated such as peptides or proteins, exhibit a "fluorous effect", i.e., they are fluorophi...
Our selection of new super greenhouse gases to fill a putative "window" in a future Martian atmosphere relies on quantum-mechanical calculations. Our study indicates that if Mars could somehow acquire an Earth-like atmospheric composition and surface pressure, then an Earth-like temperature could be sustained by a mixture of five to seven fluorine compounds. Martian mining requirements for repl...
A Cameca IMS 300 ion analyzer has been used to measure fluorine concentrations in tooth material. Samples of human and shark teeth were studied. Negative oxygen primary ions produce secondary mass spectra in which positive as well as negative fluorine ion peaks are well re presented. With constant measuring conditions, the reproducibility of the F/Ca ion ratios is satis factory. Fluorine conc...
The purpose of the present study was to examine the effectiveness of fluorine and silver ions implanted and deposited into acrylic resin (poly(methyl methacrylate)) using a hybrid process of plasma-based ion implantation and deposition. The surface characteristics were evaluated by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy. In addition, an a...
The effect of fluorine addition on morphological, structural and electrical properties of superconducting samples of composition Y3Ba5Cu8Oy-xFx (x = 0.0, 0.2, 0.4 & 0.6) were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transition temperature (Tc) measurements. The samples were synthesized by solid state reaction method. The XRD of the samples revealed a struc...
We report the first detection of interstellar hydrogen fluoride. Using the Long Wavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO), we have detected the 121.6973 μm J = 2 − 1 line of HF in absorption toward the far-infrared continuum source Sagittarius B2. The detection is statistically significant at the 13σ level. On the basis of our model for the excitation of HF in Sgr B2...
The electron-impact mass spectra of the tris(pentafluorophenyl)boroxine (1) and triphenylboroxine (2) were analyzed to probe the McLafferty type of rearrangements involving 1,3-fluorine or 1,3-hydrogen migrations to boron from the adjacent aromatic rings. 1,3-Sigmatropic fluorine migration leading to the McLafferty rearrangement of 1 results in the formation of the tetrafluorobenzyne radical ca...
Effect of water on the fluorine and chlorine partitioning behavior between olivine and silicate melt
Halogens show a range from moderate (F) to highly (Cl, Br, I) volatile and incompatible behavior, which makes them excellent tracers for volatile transport processes in the Earth's mantle. Experimentally determined fluorine and chlorine partitioning data between mantle minerals and silicate melt enable us to estimate Mid Ocean Ridge Basalt (MORB) and Ocean Island Basalt (OIB) source region conc...
NMR is a powerful method for identification and quantification of drug components and contaminations. These problems present themselves as mixtures, and here, one of the most powerful tools is DOSY. DOSY works best when there is no spectral overlap between components, so drugs containing fluorine substituents are well-suited for DOSY analysis as (19)F spectra are typically very sparse. Here, we...
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