نتایج جستجو برای: fluorine

تعداد نتایج: 7204  

2010
B. O. Mysen

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...

2014
Nediljko Budisa Vladimir Kubyshkin Dirk Schulze-Makuch

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...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2001
M F Gerstell J S Francisco Y L Yung C Boxe E T Aaltonee

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...

Journal: :Zeitschrift fur Naturforschung. Section C, Biosciences 1974
L G Petersson G Frostell A Lodding

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...

Journal: :Acta biomaterialia 2012
Yukari Shinonaga Kenji Arita

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...

2013
K. Srinivasan George Thomas

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...

1997
David A. Neufeld Jonas Zmuidzinas Peter Schilke Thomas G. Phillips

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...

2013
Nanditha G. Nair Jose L. Mendoza-Cortes Ravinder Abrol William A. Goddard Prakash Reddy

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...

2017
Bastian Joachim André Stechern Thomas Ludwig Jürgen Konzett Alison Pawley Lorraine Ruzié-Hamilton Patricia L Clay Ray Burgess Christopher J Ballentine

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...

Journal: :Magnetic resonance in chemistry : MRC 2014
Guilherme Dal Poggetto Denize C Favaro Mathias Nilsson Gareth A Morris Cláudio F Tormena

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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