WorldWideScience

Sample records for earth fluoride complexes

  1. Synthesis of complex fluorides for optical applications

    Science.gov (United States)

    Stepleton, Seth Eugene

    size were produced, and many spectroscopically active rare earth elements were doped into both hosts. A novel synthetic pathway to the hexagonal beta-RbGd3F 10, was discovered which led to the novel compound, beta-RbHo 3F10. The hydrothermal synthesis of hexafluoroelpasolites and lanthanide sesquioxides is also investigated. The hydrothermal synthesis described in this work has furthered the study of complex fluorides for optical applications. Novel synthetic pathways were discovered to known optical materials. Novel materials were also discovered. 1Takashima, M. In Advanced Inorganic Fluorides: Synthesis, Characterization and Applications, Nakajima, T.; Zemva, B.; Tressaud, A.; Elsevier: Amsterdam, The Netherlands, 2000, 176. 2Fouassier, C. In Advanced Inorganic Fluorides: Synthesis, Characterization and Applications, Nakajima, T.; Zemva, B.; Tressaud, A.; Elsevier: Amsterdam, The Netherlands, 2000, 316. 3Capper, P. In Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials, John Wiley and Sons: Great Britain, 2005. 4Solans, X.; Gonzalez-Silgo, C.; Calvet, T.; Ruiz-Perez, C.; Martinez-Sarrion, M. L.; Mestres, L. Phys. Rev. B 1998, 57(9), 5122-5125. 5Azorin-Nieto, J.; Khaidukov, N.M.; Sanchez-Rodriguez, A.; Azorin-Vega, J.C. Nuclear Instruments and Methods in Physics Research, 2007, B263, 36-40. 6Wang, D.; Min, Y.; Xia, S.; Makhov, V.N.; Khaidukov, N.M.; J.C. Krupa, J.C. Journal of Alloys and Compounds, 2003, 361, 294-298.

  2. Hydrothermal synthesis of mixed rare earth-alkali metal or ammonium fluorides

    Institute of Scientific and Technical Information of China (English)

    由芳田; 黄世华; 时秋峰

    2010-01-01

    The recent results on hydrothermal synthesis of mixed rare earth-alkali or ammonium fluorides were presented. The initial ratios of the starting materials, pH value and reaction temperature were the critical factors for obtaining the single-phase product. Four main types of complex rare earth fluorides, AREF4, A2REF5, ARE2F7 and ARE3F10 (A=Na+, K+, Rb+, NH4+), appeared in the primary hydrothermal reactions. The correlation between cation sizes and the formation of mixed rare earth fluorides under mild hydro...

  3. Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles

    OpenAIRE

    Timothy A. DeVol; Basak Yazgan-Kukouz; Baris Kokuoz; DiMaio, Jeffrey R.; Kevin B. Sprinkle; Tiffany L. James; Courtney J. Kucera; JACOBSOHN, Luiz G.; John Ballato

    2010-01-01

    This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminesc...

  4. Preparation of mixed rare earths modified chitosan for fluoride adsorption

    Institute of Scientific and Technical Information of China (English)

    梁鹏; 张艺; 汪东风; 徐莹; 罗斓

    2013-01-01

    This paper described the fluoride removal from water using a new adsorbent namely mixed rare earths modified chitosan (CR). Mixed rare earths mainly contained La followed by Ce which was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). La(III)-modified chitosan (CL) was also prepared as control. For the batch technique, the effects of various parameters such as contact time, pH, adsorbent dose, initial fluoride concentration and co-ions on fluoride adsorption were studied. Fourier trans-form infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to characterize adsorbents. It was observed that the fluo-ride adsorption capacity of CR (3.72 mgF-/g) was higher than CL (3.16 mgF-/g) at 2 h. The presence of co-ions such as bicarbonate and carbonate greatly affected the fluoride adsorption from water. Characterization experiments indicated the successful chelation between mixed rare earths and chitosan. The possible fluoride adsorption mechanism of CR was explained by a chemical reaction.

  5. Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles

    Directory of Open Access Journals (Sweden)

    Timothy A. DeVol

    2010-03-01

    Full Text Available This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF3:RE and PbF2, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF3/LaF3, and CaF2/CaF2 core/(multi-shell nanoparticles, and the CaF2-LaF3 system.

  6. Fluoride complexation of element 104, rutherfordium.

    Science.gov (United States)

    Haba, Hiromitsu; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Nishinaka, Ichiro; Hirata, Masaru; Yaita, Tsuyoshi; Ichikawa, Shin-Ichi; Nagame, Yuichiro; Yasuda, Ken-Ichiro; Miyamoto, Yutaka; Kaneko, Tetsuya; Goto, Shin-Ichi; Ono, Sawako; Hirai, Toshiyuki; Kudo, Hisaaki; Shigekawa, Mitsuru; Shinohara, Atsushi; Oura, Yasuji; Nakahara, Hiromichi; Sueki, Keisuke; Kikunaga, Hidetoshi; Kinoshita, Norikazu; Tsuruga, Naoya; Yokoyama, Akihiko; Sakama, Minoru; Enomoto, Shuich; Schädel, Matthias; Brüchle, Willy; Kratz, Jens V

    2004-04-28

    Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the 18O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effects on the fluoride complexation of Rf.

  7. Determination of the stability constant of Np(V) fluoride complex using a fluoride ion selective electrode

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, R.M.; Rizvi, G.H.; Chaudhuri, N.K.; Patil, S.K. (Bhabha Atomic Research Centre, Bombay (India). Radiochemistry Div.)

    1985-04-01

    Fluoride complexing of Np(V) was studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 0.01M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported.

  8. Trace Level Rare Earth Elements Separation From Gram Scale Uranium by Calcium Fluoride Coprecipitation

    Institute of Scientific and Technical Information of China (English)

    WANG; Xiu-feng

    2013-01-01

    In the fission yield measurement of rare earth elements of uranium induced by neutron,and the analysis of rare earth elements in spent fuel,the separation of trace rare earth elements from a large number of uranium has very important significance.We separated trace level rare earth elements from gram scale uranium by calcium fluoride coprecipitation in this paper.

  9. Studies on fluoride complexing of hexavalent actinides using a fluoride ion selective electrode

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, R.M.; Chaudhuri, N.K.; Rizvi, G.H.; Patil, S.K.

    1985-08-01

    Complex formation between actinide(VI) and fluoride ions in aqueous solutions was investigated using a fluoride ion selective electrode (F-ISE). As fairly high acidity used to suppress hydrolysis of the actinide(VI) ions, significant liquid junction potentials (Esub(j)) existed in the system. An iterative procedure was developed for computing free hydrogen ion concentration (Hsup(+)) as it could not be measured directly, using data obtained with F-ISE. Esub(j) values were estimated from known (Hsup(+)) and the stability constants of fluoride complexes of actinide(VI) ions were calculated following King and Gallagher's method using a computer program. The stability constants were found to follow the order U(VI) > Np(VI) > Pu(VI). (author). 18 refs.; 3 figs.; 9 tables.

  10. Fluoride

    Science.gov (United States)

    Fluoride is used to prevent tooth decay. It is taken up by teeth and helps to strengthen ... and block the cavity-forming action of bacteria. Fluoride usually is prescribed for children and adults whose ...

  11. Polarographic determination of fluoride using the adsorption wave of the Ce(III)-alizarin complexone-fluoride complex.

    Science.gov (United States)

    Guanghan, L; Xiaoming, L; Zhike, H; Shuanglong, H

    1991-09-01

    A very sensitive electrochemical method for trace measurement of fluoride in water is discussed. The complex of cerium(III) with alizarin complexone (ALC) and fluoride ion is adsorbed at the dropping mercury electrode. In cathodic sweeps, the peak height is directly proportional to the concentration of fluoride over the range 8 x 10(-8)-5 x 10(-6)M (1.5 x 10(-9)-9.5 x 10(-8) g/ml), and the detection limit is 5 x 10(-8)M (9.5 x 10(-10) g/ml). The proposed method was applied to the determination of fluoride in water.

  12. Dynamics of dipolar defects in rare earth-doped alkaline-earth fluoride crystals

    Science.gov (United States)

    Charnock, Forrest Taylor

    Alkaline-earth fluoride crystals such as SrF2 provide an excellent sample material for investigating the physics of point defects in crystal lattices. High quality crystals are easily grown, and they readily accept many dopant ions into the lattice, particularly rare earth ions. Rare earth dopant ions (typically trivalent) occupy substitutional sites in the lattice by replacing a Sr2+ ion. Due to the extra charge of the rare earth ion, charge compensation is often provided by an extra fluoride ion (F--) located in a nearby interstitial position. If located in the nearest-neighbor (nn) interstitial position, it forms a defect with C4n symmetry; if located in the next-nearest-neighbor (nnn) intersitial position, it forms a defect with C3n symmetry. Given sufficient thermal energy, this interstitial F ion can move to adjacent interstitial sites and hence reorient the defect. The rate w at which the ion moves from one interstitial site to another is well described by a simple Arrhenius expression: w=n0e-E/kT , where n0 is the attack frequency of the F-- and E is the activation energy. This motion can profoundly affect both the electronic polarizability of the material and the polarization of light emitted or absorbed by the rare earth ion. This thesis describes the normal mode motion of interstitial ions which may occupy either nn or nnn interstitial sites. Using electron paramagnetic resonance (EPR), I observed the relative populations of nn and nnn defects in SrF2 doped with Gd3+ as a function of temperature. These measurements show that dipolar reorientation of the nnn F occurs through the nn interstitial position. Not all interstitial F-- motion is thermally driven. Fluorescence depolarization measurements of SrF2:Pr3+ indicate that optically stimulating a Pr3+ may induce interstitial motion of a nn F--. Such motion was confirmed by showing that nn defects in SrF2:Pr3+ may be polarized at very low temperatures when the sample is illuminated with resonant light. I

  13. Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

    Science.gov (United States)

    West, William C.; Whitacre, Jay F.; Leifer, Nicole; Greenbaum, Steve; Smart, Marshall; Bugga, Ratnakumar; Blanco, Mario; Narayanan, S. R.

    2007-01-01

    We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

  14. Spectroscopy and dynamics of rare earth doped fluorides

    NARCIS (Netherlands)

    Ebens, Willem Omco

    1995-01-01

    The defect structure of RE doped Fluorides has been studied along with the conductivity properties, using a variety of techniques, both experimental and theoretical. Two systems have been studied in detail, which represent two kinds of defect states for RE doped SrFr. The system SrFr:CeF, has been t

  15. A new approach to prepare nanoscopic rare earth metal fluorides: the fluorolytic sol-gel synthesis of ytterbium fluoride.

    Science.gov (United States)

    Schmidt, L; Dimitrov, A; Kemnitz, E

    2014-06-25

    A new approach for the preparation of approx. 5 nm sized ytterbium fluoride nanoparticles based on the fluorolytic sol-gel route is reported. DLS, TEM, IR and XRD were used to characterize the particles as well as the aging behavior of the sols. Furthermore, a new Yb(III) complex was isolated from the precursor solution and characterized by X-ray single crystal structure determination.

  16. FORMATION (DECOMPOSITION) ENTHALPY CALCULATIONS FOR CRYSTAL LATTICES OF ALKALINE-EARTH FLUORIDES

    OpenAIRE

    Gruba, O.; Germanyuk, N.; Ryabukhin, A.

    2015-01-01

    A series of calculations of structural and thermochemical properties has been carried out for the alkaline-earth fluorides. The calculations have been carried out using the modified model of effective ionic radii and the model of enthalpy calculation for the crystal lattice. The results of the calculations are in accordance with the known experimental data within confidence intervals.

  17. Nanocrystalline rare earth fluorides doped with Pr3+ions

    Institute of Scientific and Technical Information of China (English)

    Marcin Runowski; Stefan Lis

    2016-01-01

    Praseodymium(III) doped CeF3, CeF3:Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, sur-factant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subjected to a hydrothermal treatment, which led to the formation of crystalline nanoluminophores, composed of spherical (≈30 nm) and elongated (≈40–200 nm) nanos-tructures. Due to the presence of Pr3+ions, the synthesized nanomaterials showed yellow luminescence under a blue light irradiation. The nanoluminophore based on the YF3 host revealed the most promising spectroscopic properties, i.e., bright and intensive emission, hence it was investigated in detail. The photophysical properties of the nanomaterials obtained were studied by powder X-ray diffrac-tion (XRD), transmission electron microscopy (TEM) and spectrofluorometry, i.e., measurements of excitation/emission spectra and luminescence decay curves.

  18. Creation of trapped electrons and holes in alkaline-earth fluoride crystals doped by rare-earth ions

    Science.gov (United States)

    Radzhabov, E.

    2002-06-01

    Defects in Ce 3+- and Eu 2+-doped alkaline-earth fluorides, created by vacuum ultraviolet (VUV) photons with energy lower than that of the band gap, were investigated by various methods: thermostimulated luminescence, photostimulated luminescence and optical absorption. The CaF 2:Eu 2+ thermoluminescence curves in the range of 60-330 K due to various types of trapped holes were the same after VUV illumination as after X-ray irradiation. Thermoluminescence curves of Ce 3+-doped alkaline-earth fluorides created by VUV illumination or X-ray irradiation were generally similar. However, Vk thermoluminescence peaks were absent in VUV-illuminated CaF 2:Ce 3+ and SrF 2:Ce 3+ crystals. Creation of Ce 2+ characteristic bands was observed in photostimulated luminescence spectra as well as in optical absorption spectra of vacuum ultraviolet-illuminated or X-ray-irradiated Ce 3+-doped crystals. The proposed mechanism of creation of trapped hole and trapped electron defects by vacuum ultraviolet illumination involves charge transfer-type transitions, in which the electron transfers from valence band to an impurity level, lying in the band gap. Comparison of all involved energies of transitions in the crystals investigated shows that the sum of all transition energies is less than that of the band gap by 1-3 eV. This energy difference can be considered as the energy of lattice relaxation around created Ce 2+ or Eu + ions.

  19. INTERACTION OF FLUORIDE COMPLEXES DERIVED FROM GLASS-IONOMER CEMENTS WITH HYDROXYAPATITE

    Directory of Open Access Journals (Sweden)

    Lewis S. M.

    2013-09-01

    Full Text Available A study has been undertaken of the interaction of complexed fluoride extracted from glass-ionomer dental cements with synthetic hydroxyapatite powder. Extracts were prepared from two commercial glass-ionomers (Fuji IX and ChemFlex under both neutral and acidic conditions. They were analysed by ICP-OES and by fluoride-ion selective electrode with and without added TISAB to decomplex the fluoride. The pH of the acid extracts was 4, conditions under which fluoride complexes with protons as HF or HF2-, it also complexes with aluminium, which was found to be present in higher amounts in the acid extracts. Fluoride was found to be almost completely complexed in acid extracts, but not in neutral extracts, which contained free fluoride ions. Exposure of these extracts to synthetic hydroxyapatite powder showed that fluoride was taken up rapidly (within 5 minutes, whether or not it was complexed. SEM (EDAX study of recovered hydroxyapatite showed only minute traces of aluminium taken up under all conditions. This showed that aluminium interacts hardly at all with hydroxyapatite, and hence is probably not involved in the remineralisation process.

  20. Alkali metal cation complexation and solvent interactions by robust chromium(III) fluoride complexes

    DEFF Research Database (Denmark)

    Birk, T.; Magnussen, M.J.; Piligkos, Stergios

    2010-01-01

    Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF2(py)(4)](+), mer-[CrF3(terpy)], and fac-[CrF3(Me(3)tacn)]. Crystalline products isolated from solution exhibit...... mu(2)-bridging by the fluoride ligands in a linear fashion between Na+-ions and chromium centres in catena-[Na(H2O)(4)(mu-F)-trans-{CrF(py)(4))](HCO3)(2) and in the dimers [Li(H2O)(n)(mu-F)-trans-{CrF(py)(4))}](2+) (n = 3, 4). The uncharged chromium complexes fac-[CrF3(Me(3)tacn)] and mer-[CrF3(terpy......)] have been synthesized from mer-[CrF3(py)(3)] and shown to precipitate sodium salts from solution, of which 3[CrF3(Me(3-)tacn)]center dot 2Na(Bph(4)).solv and 6[CrF3(terpy)]center dot 4Na(Bph(4)).solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring...

  1. Metal Fluoride Complexes of Na,K-ATPase

    Science.gov (United States)

    Cornelius, Flemming; Mahmmoud, Yasser A.; Toyoshima, Chikashi

    2011-01-01

    The Na,K-ATPase belongs to the P-type ATPase family of primary active cation pumps. Metal fluorides like magnesium-, beryllium-, and aluminum fluoride act as phosphate analogues and inhibit P-type ATPases by interacting with the phosphorylation site, stabilizing conformations that are analogous to specific phosphoenzyme intermediates. Cardiotonic steroids like ouabain used in the treatment of congestive heart failure and arrhythmias specifically inhibit the Na,K-ATPase, and the detailed structure of the highly conserved binding site has recently been described by the crystal structure of the shark Na,K-ATPase in a state analogous to E2·2K+·Pi with ouabain bound with apparently low affinity (1). In the present work inhibition, and subsequent reactivation by high Na+, after treatment of shark Na,K-ATPase with various metal fluorides are characterized. Half-maximal inhibition of Na,K-ATPase activity by metal fluorides is in the micromolar range. The binding of cardiotonic steroids to the metal fluoride-stabilized enzyme forms was investigated using the fluorescent ouabain derivative 9-anthroyl ouabain and compared with binding to phosphorylated enzyme. The fastest binding was to the Be-fluoride stabilized enzyme suggesting a preformed ouabain binding cavity, in accord with results for Ca-ATPase where Be-fluoride stabilizes the E2-P ground state with an open luminal ion access pathway, which in Na,K-ATPase could be a passage for ouabain. The Be-fluoride stabilized enzyme conformation closely resembles the E2-P ground state according to proteinase K cleavage. Ouabain, but not its aglycone ouabagenin, prevented reactivation of this metal fluoride form by high Na+ demonstrating the pivotal role of the sugar moiety in closing the extracellular cation pathway. PMID:21708939

  2. Fluoride, bifluoride and trifluoromethyl complexes of iridium(I) and rhodium(I).

    Science.gov (United States)

    Truscott, Byron J; Nahra, Fady; Slawin, Alexandra M Z; Cordes, David B; Nolan, Steven P

    2015-01-01

    Herein we report robust methods for the preparation and full characterisation of a range of Ir(I) and Rh(I) fluoride and bifluoride complexes using N-heterocyclic carbenes (NHCs) as ancillary ligands. The processes that link the fluoride and the bifluoride species are investigated and reports of the first Ir-bifluoride and Ir(I)-NHC and Rh(I)-NHC trifluoromethyl complexes are revealed.

  3. Ab Initio Calculation of 19F NMR Chemical Shielding for Alkaline-earth-metal Fluorides

    Institute of Scientific and Technical Information of China (English)

    CAI,Shu-Hui(蔡淑惠); CHEN,Zhong,(陈忠); LU,Xin(吕鑫); CHEN,Zhi-Wei(陈志伟); WAN,Hui-Lin(万惠霖)

    2001-01-01

    Gauge-independent atomic orbital (GIAO) method atHartree-Fock (HF) and density functional theory (DFr) lev-els,respectively,was employed to calculate 19F NMR chemi-cal shieldings of solid state alkaline-earth-metal fluorides MF2 (M = Mg,Ca,Sr,Ba).The results show that,although thecalculated19F chemical shieldings tend to be larger than the experinental values,they have a fairly good linear relation-ship with the observed ones.The calculated results based on different combinations of basis sets show that the B3LYP (ahybrid of DFT with HF) predictions are greatly superior tothe I-IF predictions.When a basis set of metal atom with ef- fecfive core potential (ECP) has well representation of valencewavefunction,especially wavefuncfion of d component,andproper definition of core electron nmnher,it can be applied toobtain 19F chemical shielding which is dose to that of all-elec-tron calculation.Tne variation of 19F chemical shielding of al-kaline-earth-metal fluorides correlates well with the latticefactor A/R2.``

  4. Endothelialization of novel magnesium-rare earth alloys with fluoride and collagen coating.

    Science.gov (United States)

    Zhao, Nan; Workman, Benjamin; Zhu, Donghui

    2014-03-25

    Magnesium (Mg) alloys are promising scaffolds for the next generation of cardiovascular stents because of their better biocompatibility and biodegradation compared to traditional metals. However, insufficient mechanical strength and high degradation rate are still the two main limitations for Mg materials. Hydrofluoric acid (HF) treatment and collagen coating were used in this research to improve the endothelialization of two rare earth-based Mg alloys. Results demonstrated that a nanoporous film structure of fluoride with thickness of ~20 µm was formed on the Mg material surface, which improved the corrosion resistance. Primary human coronary artery endothelial cells (HCAECs) had much better attachment, spreading, growth and proliferation (the process of endothelialization) on HF-treated Mg materials compared to bare- or collagen-coated ones.

  5. Endothelialization of Novel Magnesium-Rare Earth Alloys with Fluoride and Collagen Coating

    Directory of Open Access Journals (Sweden)

    Nan Zhao

    2014-03-01

    Full Text Available Magnesium (Mg alloys are promising scaffolds for the next generation of cardiovascular stents because of their better biocompatibility and biodegradation compared to traditional metals. However, insufficient mechanical strength and high degradation rate are still the two main limitations for Mg materials. Hydrofluoric acid (HF treatment and collagen coating were used in this research to improve the endothelialization of two rare earth-based Mg alloys. Results demonstrated that a nanoporous film structure of fluoride with thickness of ~20 µm was formed on the Mg material surface, which improved the corrosion resistance. Primary human coronary artery endothelial cells (HCAECs had much better attachment, spreading, growth and proliferation (the process of endothelialization on HF-treated Mg materials compared to bare- or collagen-coated ones.

  6. Exploration on Crystallization Habit of Rare Earth Fluoride Crystal BaY2F8

    Institute of Scientific and Technical Information of China (English)

    Lin Junyi; Ruan Yongfeng; Wang Jun; Liu Jian; Huan Boxian

    2004-01-01

    Single rare earth fluoride crystal of BaY2F8 was grown by Czochralski method. The crystallization habit of BaY2F8 and the crystal growth technique, including temperature gradient, rotation and pulling rates, were investigated.The effects of growth parameters on the crystal quality were studied. Crystal growth procedure was optimized as the temperature gradient of 15 ~ 25 ℃ ·cm -1 , the rotation rate of 15 ~ 20 r ·min -1 and the pulling rate of 1.0 mm · h-1.The X-ray diffraction and the transparent spectrum of BaY2F8 crystal were measured and reported.

  7. Ontology of Earth's nonlinear dynamic complex systems

    Science.gov (United States)

    Babaie, Hassan; Davarpanah, Armita

    2017-04-01

    As a complex system, Earth and its major integrated and dynamically interacting subsystems (e.g., hydrosphere, atmosphere) display nonlinear behavior in response to internal and external influences. The Earth Nonlinear Dynamic Complex Systems (ENDCS) ontology formally represents the semantics of the knowledge about the nonlinear system element (agent) behavior, function, and structure, inter-agent and agent-environment feedback loops, and the emergent collective properties of the whole complex system as the result of interaction of the agents with other agents and their environment. It also models nonlinear concepts such as aperiodic, random chaotic behavior, sensitivity to initial conditions, bifurcation of dynamic processes, levels of organization, self-organization, aggregated and isolated functionality, and emergence of collective complex behavior at the system level. By incorporating several existing ontologies, the ENDCS ontology represents the dynamic system variables and the rules of transformation of their state, emergent state, and other features of complex systems such as the trajectories in state (phase) space (attractor and strange attractor), basins of attractions, basin divide (separatrix), fractal dimension, and system's interface to its environment. The ontology also defines different object properties that change the system behavior, function, and structure and trigger instability. ENDCS will help to integrate the data and knowledge related to the five complex subsystems of Earth by annotating common data types, unifying the semantics of shared terminology, and facilitating interoperability among different fields of Earth science.

  8. Efficient SN2 fluorination of primary and secondary alkyl bromides by copper(I) fluoride complexes

    KAUST Repository

    Liu, Yanpin

    2013-11-11

    Copper(I) fluoride complexes ligated by phenanthroline derivatives have been synthesized and structurally characterized by X-ray crystallography. These complexes adopt as either ionic or neutral forms in the solid state, depending on the steric bulkiness of the substituent groups on the phenanthroline ligands. These complexes react with primary and secondary alkyl bromides to produce the corresponding alkyl fluorides in modest to good yields. This new method is compatible with a variety of important functional groups such as ether, thioether, amide, nitrile, methoxyl, hydroxyl, ketone, ester, and heterocycle moieties. © 2013 American Chemical Society.

  9. Chitosan-praseodymium complex for adsorption of fluoride ions from water

    Institute of Scientific and Technical Information of China (English)

    Eny Kusrini; Nofrijon Sofyan; Nyoman Suwartha; Gefin Yesya; Cindy Rianti Priadi

    2015-01-01

    Engineering of chitosan by praseodymium has been investigated to improve the adsorption properties as well as physical characteristics of chitosan. Modification of chitosan changes the original properties of chitosan so that it can be more suitable for ad-sorption of fluoride ions. In this study, chitosan-praseodymium (Chi-Pr) was synthesized by impregnation method. The Chi-Pr com-plex was characterized by scanning electron microscopic-energy dispersive X-ray spectroscopy (SEM-EDX), Fourier transform in-frared (FTIR) and employed as an adsorbent for removal of fluorides ions from water in the batch system. The variables such as con-tact time, concentration of Pr, adsorbent dose, initial concentration of fluoride ions, and competitor anions were studied. The adsorp-tion efficiency of fluoride ions (η) with increasing Pr loading into chitosan (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.% and 25 wt.%) were 35.5%, 56.1%, 72.0%, 68.5% and 62.5%, respectively. The Chi-Pr (15 wt.%) complex had the highest fluoride removal efficiency (72.0%). The experimental data fitted well to the Langmuir isotherm with maximum adsorption capacity (qmax) of 15.87 mg/g and an equilibrium constant (kL) of 0.15 mg. Kinetic study revealed that the adsorption of fluoride ions from water followed pseudo-second-order model with a maximum adsorption capacity (q2) of 8.20 mg/g and a rate constant (k2) of 0.01 g/mg·min. Ad-sorption efficiency of fluoride ions in the simulated drinking water was diminished with the changes in pH levels. The presence of Pr3+in chitosan increased chitosan's performance as an adsorbent for adsorption of fluoride ions.

  10. Ensuring complete absence of Ce(IV) and measurement of the stability constant of the fluoride complex of Ce(III)

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, R.M.; Chaudhuri, N.K.; Ramakumar, K.L. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, 400 085 Mumbai (India)

    2001-01-05

    Literature survey revealed a wide variation in the measured stability constant values of the aqueous fluoride complexes of trivalent cerium. This could be due to inadequate care for full conversion and maintenance of the oxidation state of cerium to trivalent state. In the present work quinhydrone has been used to ensure complete absence of Ce(IV) and the stability constant of CeF{sup 2+} in 1 M NaClO{sub 4} has been measured potentiometrically using a fluoride ion selective electrode. Log {beta}{sub 1} obtained in this work was 2.936{+-}0.024 and fitted well with the general trend of stability constants of the lanthanide (rare earths) fluorides in aqueous solution.

  11. Ensuring complete absence of Ce(IV) and measurement of the stability constant of the fluoride complex of Ce(III).

    Science.gov (United States)

    Sawant, R M; Chaudhuri, N K; Ramakumar, K L

    2001-01-05

    Literature survey revealed a wide variation in the measured stability constant values of the aqueous fluoride complexes of trivalent cerium. This could be due to inadequate care for full conversion and maintenance of the oxidation state of cerium to trivalent state. In the present work quinhydrone has been used to ensure complete absence of Ce(IV) and the stability constant of CeF(2+) in 1 M NaClO(4) has been measured potentiometrically using a fluoride ion selective electrode. Log beta(1) obtained in this work was 2.936+/-0.024 and fitted well with the general trend of stability constants of the lanthanide (rare earths) fluorides in aqueous solution.

  12. Formation of a porphyrin pi-cation radical in the fluoride complex of horseradish peroxidase.

    Science.gov (United States)

    Farhangrazi, Z S; Sinclair, R; Powers, L; Yamazaki, I

    1995-11-21

    Horseradish peroxidase (HRP) was oxidized by IrCl6(2-) to a mixture of compounds I and II, the rate of oxidation and the ratio of the mixture being greatly affected by pH (Hayashi & Yamazaki, 1979). Oxidation of HRP by IrCl6(2-) in the presence of fluoride was significantly accelerated. This resulted in the formation of a new compound which is a ferric fluoride complex containing a porphyrin pi-cation radical. The spectrum of the new compound showed a decreased absorption band in the Soret region and a broad band at 570 nm; which was converted to that of the original ferric fluoride complex by addition of ascorbate or hydroquinone. Addition of cyanide slowed down the oxidation of HRP by IrCl6(2-), and the oxidation product was the same as that obtained in the absence of cyanide. Compound I was formed when H2O2 was added to HRP in the presence of fluoride or cyanide. The one-electron reduction potential (Eo') of the oxidized HRP-fluoride complex was measured at several pH values, the Eo' value at pH 7 being 861 +/- 4 mV. The ratio of delta Eo' to delta pH was 49 mV/pH unit.

  13. Perfluoroalkyl Cobalt(III) Fluoride and Bis(perfluoroalkyl) Complexes: Catalytic Fluorination and Selective Difluorocarbene Formation.

    Science.gov (United States)

    Leclerc, Matthew C; Bayne, Julia M; Lee, Graham M; Gorelsky, Serge I; Vasiliu, Monica; Korobkov, Ilia; Harrison, Daniel J; Dixon, David A; Baker, R Tom

    2015-12-30

    Four perfluoroalkyl cobalt(III) fluoride complexes have been synthesized and characterized by elemental analysis, multinuclear NMR spectroscopy, X-ray crystallography, and powder X-ray diffraction. The remarkable cobalt fluoride (19)F NMR chemical shifts (-716 to -759 ppm) were studied computationally, and the contributing paramagnetic and diamagnetic factors were extracted. Additionally, the complexes were shown to be active in the catalytic fluorination of p-toluoyl chloride. Furthermore, two examples of cobalt(III) bis(perfluoroalkyl)complexes were synthesized and their reactivity studied. Interestingly, abstraction of a fluoride ion from these complexes led to selective formation of cobalt difluorocarbene complexes derived from the trifluoromethyl ligand. These electrophilic difluorocarbenes were shown to undergo insertion into the remaining perfluoroalkyl fragment, demonstrating the elongation of a perfluoroalkyl chain arising from a difluorocarbene insertion on a cobalt metal center. The reactions of both the fluoride and bis(perfluoroalkyl) complexes provide insight into the potential catalytic applications of these model systems to form small fluorinated molecules as well as fluoropolymers.

  14. Synthesis of the Complex Fluoride LiBaF3 through a Solvothermal Process

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The complex fluoride LiBaF3 is solvothermally synthesized at 180℃ and characterized by means of X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. In the solvothermal process, the solvents, mole ratios of initial mixtures and reaction temperature play important roles in the growth of the single crystal.

  15. Fluoride, bifluoride and trifluoromethyl complexes of iridium(I) and rhodium(I)

    OpenAIRE

    Truscott, Byron; Nahra, Fady; Slawin, Alexandra Martha Zoya; Cordes, David Bradford; Nolan, Steven Patrick

    2015-01-01

    The ERC (Advanced Researcher Award FUNCAT to SPN), the EPSRC and Sasol (Stipend to BJT) are gratefully acknowledged for support. Herein we report robust methods for the preparation and full characterisation of a range of Ir(I) and Rh(I) fluoride and bifluoride complexes using N-heterocyclic carbenes (NHCs) as ancillary ligands. The processes that link the fluoride and the bifluoride species are investigated and reports of the first Ir–bifluoride and Ir(I)–NHC and Rh(I)–NHC trifluoromethyl ...

  16. Copper-Mediated Fluorination of Arylboronate Esters. Identification of a Copper(III) Fluoride Complex

    Science.gov (United States)

    Fier, Patrick S.; Luo, Jingwei; Hartwig, John F.

    2013-01-01

    A method for the direct conversion of arylboronate esters to aryl fluorides under mild conditions with readily available reagents is reported. Tandem reactions have also been developed for the fluorination of arenes and aryl bromides through aryl-boronate ester intermediates. Mechanistic studies suggest that this fluorination reaction occurs through facile oxidation of Cu(I) to Cu(III) followed by rate-limiting transmetallation of a bound arylboronate to Cu(III). Fast C-F reductive elimination is proposed to occur from an aryl-copper(III)-fluoride complex. Cu(III) intermediates have been generated independently and identified by NMR spectroscopy and ESI-MS. PMID:23384209

  17. Ionic conductivity of binary fluorides of potassium and rare earth elements

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, N. I., E-mail: nsorokin1@yandex.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2016-01-15

    The ionic conductivity s of KYF{sub 4} and K{sub 2}RF{sub 5} single crystals (R = Gd, Ho, Er) and KNdF{sub 4} and K{sub 2}RF{sub 5} ceramic samples (R = Dy, Er) has been studied in the temperature range of 340–500°C. A comparative analysis of the σ values for these objects has been performed. Binary fluorides of potassium and rare earth elements were synthesized by the hydrothermal method (temperature 480°C, pressure 100–150 MPa) in the R{sub 2}O{sub 3}–KF–H{sub 2}O systems. The σ values of tetraf luorides are 3 × 10{sup –5} S/cm (KYF{sub 4} single crystal) and 3 × 10{sup –6} S/cm (KNdF{sub 4} ceramics) at 435°C. A K{sub 2}ErF{sub 5} single crystal with σ = 1.2 × 10{sup –4} S/cm at 435°C has the maximum value of ionic conductivity among pentafluorides. The anisotropy of ionic transport was found in K{sub 2}HoF{sub 5} single crystals, σ{sub ∥c}/σ{sub ⊥c} = 2.5, where σ{sub ∥c} and σ{sub ⊥c} are, respectively, the conductivities along the crystallographic c axis and in the perpendicular direction.

  18. Determination of Boron Trifluoride in Boron Trifluoride Complex by Fluoride Ion Selective Electrode

    Institute of Scientific and Technical Information of China (English)

    郎五可; 张卫江; 唐银; 徐姣; 张雷

    2016-01-01

    A method was proposed to determine boron trifluoride in boron trifluoride complex using fluoride ion selective electrode(ISE). Hydroxide was chosen to mask aluminum for the determination of 0.01—0.1 mol/L of fluoride. The simulation indicated that the permissible aluminum masked at a certain pH value was limited and hardly related to F-concentration and boric acid. It is better to control pH value below 11.5 and the aluminum con-centration within 0.025 mol/L to minimize the interference of hydroxide to the fluoride ISE. The decomposition conditions of boron trifluoride by aluminum chloride were investigated. It is found that the F-detection ratio will approach 1.0 if the Al/F molar ratio is 0.3—0.7 and aluminum concentration is no more than 0.02 mol/L when heated at 80℃ for 10 min. In one word, hydroxide is quite fit to mask aluminum for samples which contain high content of fluoride and aluminum and the BF3 content can be successfully determined by this method.

  19. Electrochemistry of the Oxofluoro Complexes of Boron in Fluoride Melts

    DEFF Research Database (Denmark)

    Polyakova, L.P.; Bukatova, G.A.; Polyakov, E.G.

    1997-01-01

    Electrochemical behavior of oxofluoro complexes of boron, synthesized both in situ in FLINAK melt and added into the melt as Na3B3O3F6 compound, was by linear voltammetry within the range of 570-750 oC. It was shown that in lower part of this range the electrochemical reduction of BOF2- complexes...

  20. Electrochemistry of the Oxofluoro Complexes of Boron in Fluoride Melts

    DEFF Research Database (Denmark)

    Polyakova, L.P.; Bukatova, G.A.; Polyakov, E.G.

    1997-01-01

    Electrochemical behavior of oxofluoro complexes of boron, synthesized both in situ in FLINAK melt and added into the melt as Na3B3O3F6 compound, was by linear voltammetry within the range of 570-750 oC. It was shown that in lower part of this range the electrochemical reduction of BOF2- complexes...

  1. Hydrothermal and Solvothermal Synthesis of the Complex Fluoride α′-SrAIF5

    Institute of Scientific and Technical Information of China (English)

    贾志宏; 华瑞年; 石春山

    2003-01-01

    The complex fluoride α′-SrAlF5 has been synthesized through hydrothermal and solvothermal methods under mild conditions.The effects of the molar ratio of starting materials,temperature,reaction time and solvents on the synthesis of α′-SrAlF5 were discussed.The final products were characterized by XRD and SEM.The rod-like shape of α′-SrAlF5 is shown in SEM images.

  2. Effect of fluoridated casein phospopeptide-amorphous-calcium phosphate complex, chlorhexidine fluoride mouthwash on shear bond strength of orthodontic brackets: A comparative in vitro study

    Directory of Open Access Journals (Sweden)

    C A Abdul Shahariyar

    2016-01-01

    Full Text Available Objective: The aim of the current study was to determine the effects of casein phosphopeptide amorphous calcium-phosphate (CPP-ACP complex, chlorhexidine fluoride mouthwash on shear bond strengths (SBSs of orthodontic brackets. Materials and Methods: About sixty extracted healthy human premolar teeth with intact buccal enamel were divided into two equal groups to which brackets were bonded using self-etching primers (SEPs and conventional means respectively. These were further equally divided into three subgroups - (1 control (2 CPP-ACP (3 chlorhexidine fluoride mouthwash. The SBSs were then measured using a universal testing machine. Results: SBS of the conventional group was significantly higher than the self-etching group. The intragroup differences were statistically insignificant. Conclusion: CPP-ACP, chlorhexidine fluoride mouthwash did not adversely affect SBS of orthodontic brackets irrespective of the method of conditioning. Brackets bonded with conventional technique showed greater bond strengths as compared to those bonded with SEP.

  3. Oxidizing behavior of some platinum metal fluorides. [Xe complexes with Pt, Pd fluorides; Chlorine-2 oxidation by transition metal hexafluorides

    Energy Technology Data Exchange (ETDEWEB)

    Graham, L.

    1978-10-01

    The previously known compounds Xe/sub 2/F/sub 3//sup +/PtF/sub 6//sup -/, XeF/sup +/PtF/sub 6//sup -/ and XeF/sub 2/.2PtF/sub 4/(XePt/sub 2/F/sub 10/) were prepared by the interaction of XeF/sub 2/ with PtF/sub 4/. The new compounds XeF/sub 2/.PdF/sub 4/ and XeF/sub 2/.2PdF/sub 4/(XePd/sub 2/F/sub 10/) were produced by interaction of XeF/sub 2/ with either PdF/sub 4/ or Pd/sub 2/F/sub 6/. A weight loss-versus-time curve indicated the presence of 4:1, 3:1 and 2:1 XeF/sub 2//PdF/sub 4/ complexes. The thermal decomposition of XeFPtF/sub 6/ or XePd/sub 2/F/sub 10/ yields highly pure XeF/sub 4/. Thus the interaction of XeF/sub 2/ with platinum fluorides (PtF/sub 4/ or PtF/sub 5/) or palladium fluorides (Pd/sub 2/F/sub 6/ or PdF/sub 4/) provides for the conversion of XeF/sub 2/ to XeF/sub 4/. The compound XePd/sub 2/F/sub 10/ is a close structural relative of XePt/sub 2/F/sub 10/, and spectroscopic evidence suggests that both are salts of XeF/sup +/ and a polymeric (M/sub 2/F/sub 9/)/sub x//sup x-/ ion. A Xe:PtF/sub 6/ material of approximately 1:1 stoichiometry has been prepared and compared with XePdF/sub 6/(XeF/sub 2/.PdF/sub 4/). The interaction of chlorine with the third-series transition metal hexafluorides has been investigated. Gravimetric and tensimetric evidence indicate that the initial product of the Cl/sub 2/ plus IrF/sub 6/ reaction is a solid of composition Cl/sub 2/IrF/sub 6/. Vibrational spectroscopic and other evidence indicates that this solid yields a sequence of products, of which Cl/sub 3//sup +/IrF/sub 6//sup -/, Cl/sub 3//sup +/Ir/sub 2/F/sub 11//sup -/ and Ir/sub 4/F/sub 20/ have been identified, the last being the ultimate solid product of the room temperature decomposition of the adduct. A new chlorine fluoride generated in the room temperature decomposition of Cl/sub 2/IrF/sub 6/ has been tentatively formulated as Cl/sub 3/F from infrared evidence.

  4. Speciation analysis of aluminium and aluminium fluoride complexes by HPIC-UVVIS.

    Science.gov (United States)

    Frankowski, Marcin; Zioła-Frankowska, Anetta

    2010-10-15

    The study presents a new analytical method for speciation analysis in fractionation of aluminium fluoride complexes and free Al(3+) in soil samples. Aluminium speciation was studied in model solutions and soil extract samples by means of high performance ion chromatography (HPIC) with UV-VIS detection using post-column reaction with tiron for the separation and detection of aluminium fluoride complex and Al(3+) forms during one analysis. The paper presents particular stages of the chromatographic process optimization involving selecting the appropriate eluent strength, type of elution or concentration and quantity of derivatization reagent. HPIC was performed on a bifunctional analytical column Dionex IonPac CS5A. The use of gradient elution and the eluents A: 1M NH(4)Cl and B: water acidified to pH of eluent phase, enabled full separation of fluoride aluminium forms as AlF(2)(+), AlF(3)(0), AlF(4)(-) (first signal), AlF(2+) (second signal) and form Al(3+) in a single analytical procedure. The proposed new method HPIC-UVVIS was applied successfully in the quantitative and qualitative analysis of soil samples. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Presence and Origin of Fluoride in the Complex Terminal Water of Ouargla Basin (Northern Sahara of Algeria)

    OpenAIRE

    Imed E. Nezli; Samia Achour; Mohamed Djidel; Saïd Attalah

    2009-01-01

    Problem statement: The underground waters in the oriental regions of the Algerian Sahara, present real chemical quality problems. Their content in fluorides always exceeds the limit of the recommended levels. That is 0.8 mg L-1, according to the maximum temperature in the region. Combined to a high salinity, it affects the health of the population living around the region. The present work, deals with the presence of fluoride and the geochemical origin in the Complex Terminal aquifer of Ouarg...

  6. Crystal Structures of Fluoride and Chloride Complexes of Tris[(2-benzimidazolyl)methyl]amine

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The crystal structures of fluoride and chloride complexes of tris[(2-benzimida-zolyl)methyl]amine 1 were characterized by X-ray crystallography.1 adopts C3 symmetrical geometry and cone-like conformation so as to allow its three NHs to associate with the anions through hydrogen bonds.Despite the different sizes of the anions, the two crystals are unexpectedly isostructural.The binding ability of the anions of 1 in solution was also studied by using of UV-vis spectroscopy.

  7. Enhanced solar photons harvesting of a-SiC:H solar cells with ZBLA fluoride glasses containing rare earth ions

    Energy Technology Data Exchange (ETDEWEB)

    Song, Pei, E-mail: psong@sues.edu.cn; Zhang, Chaomin; Zhu, Pengfei

    2016-09-05

    As encapsulation glasses for a-SiC:H cells, Yb{sup 3+}/Ce{sup 3+}-Er{sup 3+} tri-doped ZBLA fluoride glasses were prepared using the high temperature melt-quenching method and the optical characteristic of the glass were measured. Depending on the nature of rare earth doped ZBLA fluoride glasses, both near infrared (low-energy) and ultraviolet (high-energy) solar photons can be transformed into visible photons. By downshifting the ultraviolet (280–350 nm) light combined with upconverting the near infrared (900–1100 nm) light, the glass can emit strong visible (500–700 nm) light, which matches well with the spectral responsivity of a-SiC:H cells. The conversion of non-absorption photons energies by upconversion and downshifting leads to promote the improvement of a-SiC:H cells performances, and measurement shows relatively increase of 7.6%–0.8% in cell efficiencies. - Highlights: • Yb{sup 3+}-Ce{sup 3+}-Er{sup 3+} tri-doped ZBLA fluoride glasses have been prepared. • An efficient energy transfer can occur from Yb{sup 3+} and Ce{sup 3+} ions to Er{sup 3+} ions. • Both ultraviolet and near-infrared photons can be converted into visible photons. • A-SiC:H cell efficiency is effectively raised by encapsulated with RE-ZBLA glass. • The emission of glasses matched well with the spectral response of a-SiC:H cell.

  8. Study on Copolymerization of Rare Earth-Carboxylic Acid Complex

    Institute of Scientific and Technical Information of China (English)

    Qiu Guanmin(邱关明); Zhang Ming(张明); Yan Chang hao(严长浩); Zhou Lanxiang(周兰香); Dai Shaojun(戴少俊); Okamo to Hiroshi

    2003-01-01

    Complex of rare earth with carboxylic acid was prepared by precipita tion and direct method. It was copolymerized with such monomers as acrylic acid and other ones to synthesize ionomer of rare earth and organic polymer with different rare earth contents. Its glass-transition temperature and heat stability were analyzed by TG and DTA. Infra-red detector was used to show its structure. The effect of rare earth complex prepared by different methods on copolymerization and properties of copolymers was also discussed.

  9. Presence and Origin of Fluoride in the Complex Terminal Water of Ouargla Basin (Northern Sahara of Algeria

    Directory of Open Access Journals (Sweden)

    Imed E. Nezli

    2009-01-01

    Full Text Available Problem statement: The underground waters in the oriental regions of the Algerian Sahara, present real chemical quality problems. Their content in fluorides always exceeds the limit of the recommended levels. That is 0.8 mg L-1, according to the maximum temperature in the region. Combined to a high salinity, it affects the health of the population living around the region. The present work, deals with the presence of fluoride and the geochemical origin in the Complex Terminal aquifer of Ouargla, rarely examined in the Algerian Sahara. Approach: Is based on the following aspects: Sampling and physico-chemicals analysis of water, statistical treatment of the physico-chemical water parameters and simulation to natural and isotherm 25°C evaporation of water parameters. Results: The results show the presence of fluoride in the studied water. The rates vary between 1 and 2 mg L-1. The calculation of water saturation index in relation with the preponderant minerals, using the thermodynamic model ‹‹phreeqci›› reveals a sensitivity of carbonate minerals towards precipitation and dissolution of evaporitic minerals and clayey fluorides as well. Conclusions/Recommendations: The increasing alkalinity of water in contact with the aquifer during long periods of stay decreases the chemical activity of calcium and helps with alteration of clayey minerals and fluoride as a necessary condition for a possible fluorite mineralization. Knowing the origin of that fluoridation leads to possible solutions, through the optimization of a water treatment meets the standards.

  10. Mn 3+ stabilization in complex phosphate-fluoride fluxes and its incorporation into langbeinite framework

    Science.gov (United States)

    Ogorodnyk, Ivan V.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Shishkin, Oleg V.; Vorona, Igor P.

    2007-10-01

    Two new mixed valence manganese-containing orthophosphates with a langbeinite structure have been obtained from the complex fluoride-phosphate melts using the high-temperature flux technique. MIVF 4 and K 2MIVF 6 ( MIV—Zr, Hf) were used as fluoride and polyvalent metal precursors. Obtained langbeinites were investigated using a single-crystal X-ray diffraction, FTIR-, UV-VIS- and electron paramagnetic resonance (EPR)-spectroscopy. Both compounds crystallize in a cubic system (sp. gr. P2 13) with cell parameters a=10.2106(12) and 10.1896(9) Å for K 1.96Mn 0.57Zr 1.43(PO 4) 3 and K 1.93Mn 0.53Hf 1.47(PO 4) 3, respectively. The rigid langbeinite-like framework is built up from the isolated [MO 6] octahedra and [PO 4] tetrahedra interlinked via oxygen vertices. Potassium cations occupy positions in the large closed cavities of the framework. Statistical distribution of manganese and tetravalent metal over two crystallographic positions in octahedral oxygen environment can be observed. The presence of the mixed valence manganese in the reported phosphates was confirmed using UV-VIS and EPR-spectroscopy.

  11. Luminescence spectroscopy from the vacuum ultra-violet to the visible for Er 3+ and Tm 3+ in complex fluoride crystals

    Science.gov (United States)

    Khaidukov, N. M.; Lam, S. K.; Lo, D.; Makhov, V. N.; Suetin, N. V.

    2002-05-01

    Spectra and decay kinetics of luminescence from several complex fluorides of alkali elements and yttrium or gadolinium doped with Er 3+ or Tm 3+ have been studied in the vacuum ultra-violet (VUV), ultra-violet (UV) and visible spectral ranges under excitation by the 157 nm radiation from a pulsed molecular F 2-laser. It has been found that yttrium crystals have intense VUV luminescence due to interconfiguration 5d-4f transitions in the rare earth ions. On the other hand, the 5d-4f luminescence from Er 3+ or Tm 3+ in gadolinium crystals is completely absent and the nonradiative decay as a result of cross-relaxation is the dominant decay channel from the 5d level of the doping rare earth ion in these crystals. This process leads to complete conversion of absorbed VUV radiation into the lower energy part of the spectrum. These gadolinium fluorides appear to be promising materials for VUV-excited phosphors with high-quantum efficiency.

  12. Fluoride binding in water with the use of micellar nanodevices based on salophen complexes.

    Science.gov (United States)

    Keymeulen, Flore; De Bernardin, Paolo; Giannicchi, Ilaria; Galantini, Luciano; Bartik, Kristin; Dalla Cort, Antonella

    2015-02-28

    The use of micelles to transpose lipophilic receptors, such as uranyl-salophen complexes, into an aqueous environment is a valuable and versatile tool. Receptor 1 incorporated into CTABr micelles forms a supramolecular system that exhibits excellent binding properties towards fluoride in water, despite the competition of the aqueous medium. To fully evaluate the potential of micellar nanodevices, we extended our previous study to other types of surfactants and to a uranyl-salophen receptor with a more extended aromatic surface. Paramagnetic relaxation enhancement experiments were used to obtain information on the location of the two receptors within the micelles and complementary information was obtained from dynamic light scattering experiments. With these data it is possible to account for the key factors necessary to obtain an efficient supramolecular device for anion binding in water.

  13. Pollution level and inhalation exposure of ambient aerosol fluoride as affected by polymetallic rare earth mining and smelting in Baotou, north China

    Science.gov (United States)

    Zhong, Buqing; Wang, Lingqing; Liang, Tao; Xing, Baoshan

    2017-10-01

    Airborne fluoride associated with total suspended particles (TSP) and respirable particulate (PM10) in the rare earth mining and smelting areas were analyzed during August 2012 and March 2013. In March, average concentrations of fluoride bound to TSP in the mining and smelting areas were 0.598 ± 0.626 μg/m3 and 3.615 ± 4.267 μg/m3, respectively, whereas that in August were 0.699 ± 0.801 μg/m3 and 1.917 ± 2.233 μg/m3, respectively. TSP samples were classified into four categories by different sampling periods and locations using Kohonen's self-organizing map, which demonstrates that high airborne fluoride concentrations in March in the smelting area were probably attributed to industrial emissions from smelting activities and wind-blown dust from tailings pond, influenced by meteorologic parameters such as temperature, relative humidity, precipitation and wind speed. The mean daily amount of fluoride inhaled in the mining and smelting areas were estimated to be in the range of 2.77-57.61 μg/day and 3.39-64.32 μg/day, respectively. These results indicate the high potential exposure level of fluoride inhaled for local residents in the polymetallic mining and smelting areas.

  14. Thermoluminescence of double fluorides doped with rare earths; Termoluminiscencia de fluoruros dobles dopados con tierras raras

    Energy Technology Data Exchange (ETDEWEB)

    Azorin N, J.; Sanchez R, A. [UAM-I, 09340 Mexico D.F. (Mexico); Khaidukov, N.M. [Kurnakov Institute of General and Inorganic Chemistry, 119991 Moscow (Russian Federation)

    2004-07-01

    In this work the thermoluminescent characteristics of double fluorides K{sub 2}YF{sub 5}, K{sub 2}GdF{sub 5} and K{sub 2}LuF{sub 5} doped are presented with Tb{sup 3+}, studied in the interval of temperature from 30 to 400 C. The materials that presented better answer to the irradiation with particles beta and with ultraviolet light they were the K{sub 2}YF{sub 5}: Tb (1% at. Tb{sup 3+}) and the K{sub 2}LuF{sub 5}: Tb (1% at. Tb{sup 3+}); while the K{sub 2}YF{sub 5}: Tb to high concentrations (10% and 20% at. Tb{sup 3+}) and the K{sub 2}LuF{sub 5}: Tb (1% at. Tb{sup 3+}) and the K{sub 2}LuF{sub 5}: Tb (1% at. Tb{sup 3+}) they presented an acceptable answer in front of the gamma radiation. The intensity of the Tl answer induced in these materials is a decisive factor to continue studying its dosimetric characteristics, what allows to consider them as the base for the development of potential materials to use them in the dosimetry of beta particles, of the UV light of the gamma radiation using the thermoluminescence method. (Author)

  15. Laser refrigeration of rare-earth doped sodium-yttrium-fluoride nanowires

    Science.gov (United States)

    Zhou, Xuezhe; Roder, Paden B.; Smith, Bennett E.; Pauzauskie, Peter J.

    2017-02-01

    Hexagonal sodium yttrium fluoride (β-NaYF4) crystals are currently being studied for a wide range of applications including color displays, solar cells, photocatalysis, and bio-imagβing. β-NaYF4 has also been predicted to be a promising host material for laser refrigeration of solids. However, due to challenges with growing Czochralski β- NaYF4 single-crystals, laser refrigeration of bulk β-NaYF4 has not yet been achieved6. Recently hydrothermal processing has been reported to produce Yb-doped β-NaYF4 nanowires (NWs) that undergo laser refrigeration during single-beam optical trapping experiments in heavy water. The local refrigeration of the individual nanowire is quantified through the analysis of its Brownian motion through the analysis of forward scattered light that is focused onto a quadrant photodiode. The individual β-NaYF4 nanowires show maximum local cooling of 9°C below ambient conditions. Here we present the emission lifetime for the 4S3/2 - 4I15/2 transition for Er(III) ions in Yb/Er-codoped -NaYF4 NW ensembles was measured to be (220 +/- 6) μs using a an electron multiplying charge coupled device (EMCCD) as a detector with high spatial resolution. This lifetime is consistent with values reported in the literature.

  16. Rare earth Ibuprofen complexes: Highlighting a pharmaceutical

    Science.gov (United States)

    Kaup, Gina; Meiners, Denise; Kynast, Ulrich H.

    2017-01-01

    Complexes of Gd3+, Eu3+ and Tb3+ with the widely applied, nonsteroidal, anti-inflammatory drug Ibuprofen ("ibu") have been prepared and characterized with respect to their photo-physical properties. The native complexes proved to be non-luminescent, but acquired very high quantum efficiencies of up to 75% with Eu3+ on co-coordination with bidentate ligands (1,10-phenanthroline, 2,2‧-bipyridine), accompanied by luminescent life times approaching 2 ms. However, due to energy back transfer to the ligand's triplet and the lack of suitable Tb3+ receptor states, the long life times could not grant the expected high efficiencies for Tb(ibu)3phen, the highest value amounting to 27% only despite an accompanying decay of 1.927 ms.

  17. Preparation and up-conversion luminescence of 8 nm rare-earth doped fluoride nanoparticles.

    Science.gov (United States)

    Tikhomirov, V K; Mortier, M; Gredin, P; Patriarche, G; Görller-Walrand, C; Moshchalkov, V V

    2008-09-15

    Free-standing, 8 nm diameter, rare-earth doped nanoparticles Re(10)Pb(25)F(65) have been prepared, where Re stands for either single rare-earth ion, such as Er(3+), Yb(3+), Eu(3+), Dy(3+), Ho(3+), Tm(3+) or combinations of those ions. The nanoparticles have been extracted by chemical etching from the oxyfluoride nano-glass-ceramics template and analyzed by transmission electron microscope with energy dispersion spectroscopy. The nanoparticles show durable up-conversion photoluminescence, which is neither concentration nor impurity quenched after 6 months ageing in ambient atmosphere. High doping levels in these nanoparticles ensure high, up to 15%, quantum yield of up-conversion luminescence.

  18. Removal of fluoride ion from aqueous solution by a cerium-poly(hydroxamic acid) resin complex.

    Science.gov (United States)

    Haron, M J; Yunus, W M

    2001-05-01

    A cerium-loaded poly(hydroxamic acid) chelating ion exchanger was used for fluoride ion removal from aqueous solution. The resin was effective in decreasing the fluoride concentration from 5 mM down to 0.001 mM in acidic pH between 3 and 6. The sorption followed a Langmuir model with a maximum capacity of 0.5 mmol/g. The removal is accomplished by an anion exchange mechanism. The rate constant for the sorption was found to be 9.6 x 10(-2) min-1. A column test shows that the fluoride ion was retained on the column until breakthrough point and the fluoride sorbed in the column can be eluted with 0.1 M NaOH. The column can be reused after being condition with hydrochloric acid at pH 4. The resin was tested and found to be effective for removal of fluoride from actual industrial wastewater.

  19. Magnetic properties of the new rare earth carbide fluoride layered compound: Ho 2CF 2

    Science.gov (United States)

    Kremer, R. K.; Cockcroft, J. K.; Mattausch, Hj.; Raju, N. P.; Simon, A.

    1992-02-01

    We present magnetic susceptibility, specific heat and neutron diffraction data of the new layered rare earth carbide flouride Ho 2CF 2. The susceptibility displays a rounded maximum centered around 4.6 K and a Curie-Weiss law at higher temperatures with a paramagnetic Curie temperature of -4.9(2) K. The specific heat shows a sharp anomaly at 3.61(5) K indicating the onset of long range ordering but also a considerable high temperature tail pointing to low dimensional magnetic behaviour. Low temperature neutron powder diffraction reveals additional magnetic Bragg peaks with significant critical scattering remaining well above the long range ordering temperature.

  20. Mechanochemical synthesis, structure, and properties of solid solutions of alkaline earth metal fluorides: Ma1-xMbxF2 (M: Ca, Sr, Ba)

    Science.gov (United States)

    Heise, M.; Scholz, G.; Düvel, A.; Heitjans, P.; Kemnitz, E.

    2016-10-01

    The capability of mechanochemical synthesis for the formation of solid solutions of alkaline earth metal fluorides Ma1-xMbxF2 (M: Ca, Sr, Ba) was tested by fluorination of metal acetates and metal hydroxides with ammonium fluoride directly at milling. Evidence was found for a mutual substitution of cations on their lattice positions in Ca1-xSrxF2 and Ba1-xSrxF2 samples. For the Ba/Ca-system this synthesis route is only partially successful. X-ray diffraction and 19F MAS NMR spectroscopy were used to characterize all samples concerning their crystal structure and local fluorine coordination. Calculations of 19F chemical shifts with the superposition model along with probability calculations for the intensity of the individual 19F lines, performed in dependence on the molar composition of the samples, perfectly agree with the experimental findings. The fluoride ion conductivity of as-prepared samples, determined by temperature dependent DC conductivity measurements, is significantly higher than those of crystalline binary fluorides. Moreover, a higher F- ion conductivity is observed for samples with higher mixing grade in the Ca/Sr-and the Ba/Sr-systems.

  1. Structure of Rare-earth/Alkali Halide Complexes

    Science.gov (United States)

    Akdeniz, Z.; Önem, Z. Çiçek; Tosia, M. P.

    2001-11-01

    Vapour complex formation of rare-earth halides with alkali halides strongly increases the volatility of these compounds. We evaluate the structure taken by such complexes having the chemical formulas MRX4, M2RX5 and M3RX6, where X = F or Cl and typically M = Li or Na and R = La. The roles played by the two types of metal atom is investigated in MRX4 complexes by also taking M = K, Rb or Cs and R = Gd or Lu. The main predictions that emerge from our calculations are as follows: (i) in MRX4 a fourfold coordination of the rare-earth atom is accompanied by twofold or threefold coordination of the alkali atom, the energy difference in favour of the twofold-coordination state being about 0.3 eV in the case of the LiF complexing agent but even changing sign as the ionic radius of either the alkali or the halogen is increased; (ii) in M2RX5 a fivefold coordination of the rare-earth atom is energetically more stable than a fourfold one, by again not more than about 0.3 eV; (iii) in M3RX6 the fivefold and sixfold coordinations of the rare-earth atom are energetically competitive; and (iv) in both M2RX5 and M3RX6 each coordination state can be realized in various forms that differ in detail but are close in energy. Bond fluctuations and disorder around the rare-earth atom can be expected to be a general feature at elevated temperatures, both in the vapour and in liquid rare-earth/alkali halide mixtures.

  2. Development of novel rare earth doped fluoride and oxide scintillators for two-dimensional imaging

    Institute of Scientific and Technical Information of China (English)

    A. Yoshikawa; T. Iguchi; G. Boulon; M. Nikd; T. Yanagida; Y. Yokota; K. Kamada; N. Kawaguchi; K. Fukuda; A. Yamazaki; K. Watanabe; A. Uritani

    2011-01-01

    Two topics were focused.The first one was about the gamma-ray scintillator,pr3+:Lu3Al5O12 (LuAG).The second one was about neutron scintillator,Ce3+:6LiCaAlF6 and Eu2+:6LiCaAlF6 (6LiCAF).Those scintillators have been developed very recently for modem imaging applications in the medical and homeland security fields.In both cases,the rare earth ions are playing the crucial role as emission centers.Pr3+ in LuAG provided fast 5d→4f transition providing noticeably shorter decay time than that of Ce3+.Among several candidate hosts,LuAG showed the best performance.Bulk crystal growth,basic scintillation properties,two-dimensional gamma-ray imaging and positron emission mammography (PEM) application were demonstrated.Due to the international situation,the homeland security was compromized by illicit traffic of explosives,drugs,nuclear materials,etc.and the ways to its improvement became an important R&D topic.For this purpose the Ce and Eu doped LiCAF appeared competitive candidates.Especially,when substitution of 3He neutron detectors was considered,the discrimination ability of gamma-ray from alpha-ray was important.Bulk crystal growth,basic scintillation properties and two-dimensional neutron imaging were demonstrated.

  3. Structure and distortion of lead fluoride nanocrystals in rare earth doped oxyfluoride glass ceramics.

    Science.gov (United States)

    Ge, Jin; Zhao, Lijuan; Guo, Hui; Lan, Zijian; Chang, Lifen; Li, Yiming; Yu, Hua

    2013-10-28

    A series of rare earth (RE) doped oxyfluoride glasses with the composition of (45-x) SiO2-5Al2O3-40PbF2-10CdF2-xRe2O3 (x = 1, 5, 10, 15) (mol%) were prepared by a traditional melt-quenching method. Glass ceramics (GCs) were obtained after thermal treatment and characterized by X-ray diffraction (XRD) to investigate the nanocrystal structure and distortion. Both the dopant type and the doping level play an important role in the distortion of the PbF2-RE lattice. It is found that a cubic Pb3REF9 phase forms in low doping GCs, a tetragonal PbREF5 phase forms in middle doping GCs and cubic PbRE3F11 forms in high doping GCs. Accordingly, the site symmetry of RE(3+) dopants in β-PbF2 nanocrystal undergoes a transition of Oh···D4h···Oh with the increase of doping level. The change in the ligands coordinating the RE(3+) ions was further illustrated by the optical changes in Yb-doped GCs. This paper provides insights on the nanocrystal structure of RE at the atomic level and tries to make a complete description of the nanocrystal structure and distortion in these glass-ceramic materials, which will benefit the optimization of optical properties.

  4. In-volume waveguides by fs-laser direct writing in rare-earth-doped fluoride glass and phosphate glass

    Science.gov (United States)

    Esser, D.; Wortmann, D.; Gottmann, J.

    2009-02-01

    Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er- and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (τ=500fs, λ=1045nm, f=0.1-5MHz) from an Ybfiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50μm in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.

  5. 稀土氟化物在硝酸中溶解性质的研究%Solubility of rare earth fluorides in nitric acid

    Institute of Scientific and Technical Information of China (English)

    仇婷婷; 彭佳; 何淑华; 郑小北; 刘玉侠; 周伟; 张岚

    2015-01-01

    Background: A varity of rare-earth fluorides can be produced with thorium uranium fuel circulating post-processing. These fluorides need to be dissolubled in solvent for seperation and contents measurement.Purpose: This paper aims to develop a fast and efficient pretreatment method to dissolve slightly soluble rare earth fluorides in nitric acid.Methods: Rare earth fluorides related to the thorium molten salt reactor (TMSR) fuel circulating post-processing including NdF3, EuF3, GdF3 and CeF3 were studied by using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). After 2-h microwave digestion at temperature of 190 ºC, the maximum solubility of these fluorides in 10 mL nitric acid (16 mol·L−1) is determined by ICP-AES.Results: The saturated concentration varies from 2.5 g·L−1 to 3.9g·L−1, which are two or three orders of magnitude higher than their solubility reported in previous literature. The standard deviation (n=3) of measurement by ICP-AES is under 4.2% and the linear correlation coefficient (r) is in the range of 0.999 47−0.999 96.Conclusion:An efficient chemical procedure for dissolving some rare earth fluorides has been developed. It provides a reference for pretreatment of insoluble rare earth fluorides in the solid molten salt samples of thorium uranium fuel circulating post-processing.%采用微波消解-电感耦合等离子体原子发射光谱(Inductively Coupled Plasma Atomic Emission Spectroscopy, ICP-AES),系统研究了钍铀燃料循环后处理中4种典型稀土氟化物(NdF3、EuF3、GdF3、CeF3)在硝酸中的溶解性质。结果表明,在10 mL、浓度为16 mol·L−1的硝酸中,微波消解2 h,190ºC下,4种稀土氟化物的最大溶解量可达2.5−3.9 g·L−1,均比文献报道的数值高2−3个数量级;采用ICP-AES测试溶解液,线性范围0.99947−0.99996,标准偏差SD≤4.2%(n=3),该溶解方法旨在为核燃料后处理流程中含有难溶稀土氟

  6. Synthesis and Characterization of Rare Earth Complexes of Ferrocenylcarbonylhydrazine

    Institute of Scientific and Technical Information of China (English)

    边占喜; 董彬; 李保国

    2002-01-01

    Rare earth complexes of ferrocenylcarbonylhydrazine Ln(FH)x(ClO4)3*nH2O (where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, x=3; Ln = Er, Tm, Yb, Lu, x=4; n=2~6, FH=ferrocenylcarbonylhydrazin) were synthesized and characterized by elemental analyses, MS, IR and 1H NMR spectra. The ligand FH is bidentate, coordinating through the carbonyl oxygen and the amino nitrogen atom. The redox properties of the ligand and its complexes were investigated using cyclic voltammetric method. The solid state fluorescence spectra of Sm, Tb and Dy complexes were also studied.

  7. Thermoluminescence spectra from sulphates, fluorides and garnets doped with rare earth ions

    CERN Document Server

    Al Maghrabi, M M

    2001-01-01

    difficult due to experimental limitations. Hence their role in luminescence generation is normally ignored. here (0.01%) there is evidence of cluster formation. Samples with high RE content show low values of the frequency factor consistent with the energy transfer model in that the emission from RE-RE cluster dominates over the emission from direct charge recombination within the defect complex. The effect of concentration and the TL mechanism operating below room temperature are also discussed. Luminescence signals from the near surface of YAG:Nd (via CL) were contrasted with those from the bulk material via RL. Results indicate that the outer few micron layers differ significantly in luminescence response from the bulk crystal. The differences were ascribed to result from solvents that enter the YAG lattice during the growth stage or subsequently from cleaning treatments via the dislocations caused by cutting and polishing. Additionally, the growth stage may include gases from the residual air in the growt...

  8. High-pressure synthesis and characterization of the rare-earth fluoride borate LaB{sub 2}O{sub 4}F

    Energy Technology Data Exchange (ETDEWEB)

    Hinteregger, Ernst; Kocsis, Krisztina; Hofer, Thomas S.; Heymann, Gunter; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Perfler, Lukas [Innsbruck Univ. (Austria). Inst. fuer Mineralogie und Petrographie

    2013-09-15

    The rare-earth fluoride borate LaB{sub 2}O{sub 4}F was synthesized under high-pressure/high-temperature conditions of 1.1 GPa and 1300 C in a Walker-type multianvil apparatus from lanthanum oxide, lanthanum fluoride, and boron oxide. The single-crystal structure determination revealed that LaB{sub 2}O{sub 4}F is isotypic to CeB{sub 2}O{sub 4}F. The compound crystallizes in the orthorhombic space group Pbca (no. 61) with eight formula units and the lattice parameters a = 8.2493(9), b = 12.6464(6), c = 7.3301(5) A, V = 764.7(2) A{sup 3}, R{sub 1} = 0.0354, and wR{sub 2} = 0.0474 (all data). The structure exhibits a 9+1 coordinated lanthanum cation, one threefold coordinated fluoride ion and a chain of corner-sharing [BO{sub 3}]{sup 3-} groups. In addition to the IR- and Raman-spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands. (orig.)

  9. Synthesis, bonding, and reactivity of a cerium(IV) fluoride complex.

    Science.gov (United States)

    Williams, Ursula J; Robinson, Jerome R; Lewis, Andrew J; Carroll, Patrick J; Walsh, Patrick J; Schelter, Eric J

    2014-01-06

    Oxidation of Ce[N(SiMe3)2]3 in the presence of PF6(-) or BF4(-) afforded isolation of CeF[N(SiMe3)2]3. Structural and electrochemical characterization shows that this compound is in its tetravalent oxidation state and contains a terminal fluoride ligand. Spectroscopy and density functional theory have been used to characterize the Ce-F bond as ionic, which is reinforced by an initial reactivity study that demonstrates the nucleophilicity of the fluoride ligand.

  10. High-pressure syntheses and characterization of the rare-earth fluoride borates RE{sub 2}(BO{sub 3})F{sub 3} (RE = Tb, Dy, Ho)

    Energy Technology Data Exchange (ETDEWEB)

    Hinteregger, Ernst; Pitscheider, Almut; Wurst, Klaus; Heymann, Gunter; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Enders, Michael [Innsbruck Univ. (Austria). Inst. fuer Pharmazie

    2013-11-15

    The new rare-earth fluoride borates RE{sub 2}(BO{sub 3})F{sub 3} (RE = Tb, Dy, Ho) were synthesized under high-pressure/high-temperature conditions of 1.5 GPa/1200 C for Tb{sub 2}(BO{sub 3})F{sub 3} and 3.0 GPa/900 C for Dy{sub 2}(BO{sub 3})F{sub 3} and Ho{sub 2}(BO{sub 3})F{sub 3} in a Walker-type multianvil apparatus from the corresponding rare-earth sesquioxides, rare-earth fluorides, and boron oxide. The single-crystal structure determinations revealed that the new compounds are isotypic to the known rare-earth fluoride borate Gd{sub 2}(BO{sub 3})F{sub 3}. The new rare-earth fluoride borates crystallize in the monoclinic space group P2{sub 1}/c (Z = 8) with the lattice parameters a = 16.296(3), b = 6.197(2), c = 8.338(2) A, {beta} = 93.58(3) for Tb{sub 2}(BO{sub 3})F{sub 3}, a = 16.225(3), b = 6.160(2), c = 8.307(2) A, {beta} = 93.64(3) for Dy{sub 2}(BO{sub 3})F{sub 3}, and a = 16.189(3), b = 6.124(2), c = 8.282(2) A, {beta} = 93.69(3) for Ho{sub 2}(BO{sub 3})F{sub 3}. The four crystallographically different rare-earth cations (CN = 9) are surrounded by oxygen and fluoride anions. All boron atoms form isolated trigonal-planar [BO{sub 3}]{sup 3-} groups. The six crystallographically different fluoride anions are in a nearly planar coordination by three rare-earth cations. (orig.)

  11. Supramolecular structures constructed from three novel rare earth metal complexes

    Indian Academy of Sciences (India)

    Huaze Dong; Xiaojun Feng; Xia Liu; BiN Zheng; Jianhong Bi; Yan Xue; Shaohua Gou; Yanping Wang

    2015-05-01

    Three rare earth metal supramolecular complexes, {[Tb(2)4](ClO4)3·2H2O(1), [Eu(2)2(H2O)5] (ClO4)3(2) and [Gd(NO3)3(2)2]·2CH3CH2OH(3) ( 2 = 3-Dimethylamino-1-pyridin-2-yl-propenone), have been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. The crystal structure analysis reveals that the coordination numbers of three complexes (1–3) are 8, 9 and 10, respectively. Three complexes assembled into 3D frameworks based on C-H⋯O, O-H⋯O hydrogen bond linkages.

  12. Synthesis and luminescence of some rare earth metal complexes

    Science.gov (United States)

    Bochkarev, Mikhail N.; Pushkarev, Anatoly P.

    2016-12-01

    In the present paper the synthesis, photoand electroluminescent properties of new rare earth metal complexes prepared and studied at the Razuvaev Institute of Organometallic Chemistry during the last decade are reviewed. The obtained compounds give luminescence in UV, visible and NIR regions. The substituted phenolates, naphtholates, mercaptobenzothiazolate, 8-oxyquinolinolate, polyfluorinated alcoholates and chalcogenophosphinates were used as ligands. The synthesis and structure of unusual three-nuclear sulfidenitride clusters of Nd and Dy are described. The new excitation mechanism of ytterbium phenolates and naphtholates, which includes the stage of reversible reduction of Yb to divalent state and oxidation of the ligands in the excitation process, is discussed.

  13. Synthesis and luminescent properties of novel pyrazolone rare earth complexes

    Institute of Scientific and Technical Information of China (English)

    BAO Jiqing; TANG Chunhua; TANG Ruiren

    2011-01-01

    A novel pyrazolone pyridine-containing ligand,2,6-bis(l-phenyl-4-ethoxycarbonyl-5-pyrazolone-3-yl)pyridine(H2L)was designed and synthesized from Pyridine-2,6-dicarboxylic acid(1),and its Eu(Ⅲ)and Tb(Ⅲ)complexes were prepared.The 1igand and complexes were characterized in detailbased on FT-IR spectra,1H NMR,elemental ahalysis and thermal analysis,and the formula of Ln2L3·4H2O(Ln=Eu or Tb)of rare earth complexes was confirmed.The UV-vis absorption spectm and photoluminescence properties of the complexes were investigated,which showed that the Eu(Ⅲ)and Tb(Ⅲ)ions could be sensitized efficiently by the ligand(H2L)and emit the photoluminescence with high intensity, narrow half-peak width,and monochromic light.The results indicated that the complexes showed potential as excellent luminescent materials.

  14. Fluoride and Oral Health.

    Science.gov (United States)

    O'Mullane, D M; Baez, R J; Jones, S; Lennon, M A; Petersen, P E; Rugg-Gunn, A J; Whelton, H; Whitford, G M

    2016-06-01

    The discovery during the first half of the 20th century of the link between natural fluoride, adjusted fluoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fluoride in improving oral health. Epidemiological studies of fluoridation programmes have confirmed their safety and their effectiveness in controlling dental caries. Major advances in our knowledge of how fluoride impacts the caries process have led to the development, assessment of effectiveness and promotion of other fluoride vehicles including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fluorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision of the original 1994 document, again using the expertise of researchers from the extensive fields of knowledge required to successfully implement complex interventions such as the use of fluorides to improve dental and oral health. Financial support for research into the development of these new fluoride strategies has come from many sources including government health departments as well as international and national grant agencies. In addition, the unique role which industry has played in the development, formulation, assessment of effectiveness and promotion of the various fluoride vehicles and strategies is noteworthy. This updated version of 'Fluoride and Oral Health' has adopted an evidence-based approach to its commentary on the different fluoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published in peer reviewed literature.

  15. Coordination field analysis of rare earth complexes with triangular symmetry

    Institute of Scientific and Technical Information of China (English)

    范英芳; 潘大丰; 杨频

    1997-01-01

    The calculation of the complex matrixes in odd triangular symmetry was accomplished.The configurations of the coordination unit with various triangular symmetries and different ligand numbers were discussed.On the basis of the double-sphere coordination point-charge (DSCPCF) model,the detailed forms of the DSCPCF parameters Bmk and the expressions of the perturbation matrix elements in triangular field (D3,D3h,D3d) were derived.Thereby,the calculation scheme of coordination field perturbation energy of the rare earth complexes with triangular symmetry was constructed After the calculation scheme was programmed,the Stark energies of the crystalline TbAl3(BO3)4 were calculated The results were considerably close to the experimental values

  16. Dissolution of fluoride complexes following microwave-assisted hydrofluoric acid digestion of marine sediments.

    Science.gov (United States)

    Muratli, Jesse M; McManus, James; Mix, Alan; Chase, Zanna

    2012-01-30

    Microwave-assisted, hydrofluoric acid digestion is an increasingly common tool for the preparation of marine sediment samples for analysis by a variety of spectrometric techniques. Here we report that analysis of terrigenous-dominated sediment samples occasionally results in anomalously low values for several elements, including Al, Ba, Ca, Mg, and Sr. Measured concentrations of these elements increased with time between sample preparation and sample analysis, reaching stable values after 8-29 days. This lag is explained by the formation and subsequent dissolution of poorly soluble fluoride phases during digestion. Other elements, such as Fe, Mn, and Ti, showed little or no lag and were quickly measurable at a stable value. Full re-dissolution of the least soluble fluorides, which incorporate Al and Mg, requires up to four weeks at room temperature, and this duration can vary among sedimentary matrices. This waiting time can be reduced to 6 days (or shorter) if the samples are heated to ≈ 60°C for 24h.

  17. Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe.

    Science.gov (United States)

    Wang, Yue; Song, Renfeng; Feng, Huan; Guo, Ke; Meng, Qingtao; Chi, Haijun; Zhang, Run; Zhang, Zhiqiang

    2016-12-16

    A new Gadolinium(III)-coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F(-)) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid (CA) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd-CA, the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity (r₁). The fluorescent detection limit for fluoride ions was determined to be 8 μM based on a 3σ/slope. The desirable features of the proposed DO3A-Gd-CA, such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd-CA could be potentially used in biomedical diagnosis fields.

  18. Modelling of Rare Earth Elements Complexation With Humic Acid

    Science.gov (United States)

    Pourret, O.; Davranche, M.; Gruau, G.; Dia, A.

    2006-12-01

    The binding of rare earth elements (REE) to humic acid (HA) was studied by combining Ultrafiltration and ICP- MS techniques. REE-HA complexation experiments were performed at various pH conditions (ranging from 2 to 10.5) using a standard batch equilibration method. Results show that the amount of REE bound to HA strongly increase with increasing pH. Moreover, a Middle REE (MREE) downward concavity is evidenced by REE distribution patterns at acidic pH. Modelling of the experimental data using Humic Ion Binding Model VI provided a set of log KMA values (i.e. the REE-HA complexation constants specific to Model VI) for the entire REE series. The log KMA pattern obtained displays a MREE downward concavity. Log KMA values range from 2.42 to 2.79. These binding constants are in good agreement with the few existing datasets quantifying the binding of REE with humic substances except a recently published study which evidence a lanthanide contraction effect (i.e. continuous increase of the constant from La to Lu). The MREE downward concavity displayed by REE-HA complexation pattern determined in this study compares well with results from REE-fulvic acid (FA) and REE-acetic acid complexation studies. This similarity in the REE complexation pattern shapes suggests that carboxylic groups are the main binding sites of REE in HA. This conclusion is further supported by a detailed review of published studies for natural, organic-rich, river- and ground-waters which show no evidence of a lanthanide contraction effect in REE pattern shape. Finally, application of Model VI using the new, experimentally determined log KMA values to World Average River Water confirms earlier suggestions that REE occur predominantly as organic complexes (> 60 %) in the pH range between 5-5.5 and 7-8.5 (i.e. in circumneutral pH waters). The only significant difference as compared to earlier model predictions made using estimated log KMA values is that the experimentally determined log KMA values

  19. Stabilisation of tetravalent cerium in perchloric acid medium and measurement of the stability constants of its fluoride complexes using ion selective potentiometry.

    Science.gov (United States)

    Sawant, R M; Rastogi, R K; Mahajan, M A; Chaudhuri, N K

    1996-01-01

    The stability constants of the fluoride complexes of cerium(IV) in 1 M (HClO(4), NaClO(4)) medium have been measured potentiometrically using a fluoride ion-selective electrode. Quantitative oxidation of cerium to its tetravalent state and its stabilisation in the perchlorate medium were accomplished by oxidation with AgO followed by quick addition of a known amount of fluoride ion. This procedure ensures stability of the oxidation state and prevents hydrolysis and polymerisation of Ce(IV). Logarithms of the average values of beta(1), beta(2), beta(3) and beta(4) were estimated to be 7.57+/-0.04, 14.50+/-0.03, 20.13+/-0.37 and 24.14+/-0.10 respectively.

  20. The DNA-binding and bioactivity of rare earth metal complexes.

    Science.gov (United States)

    Yang, Li; Wang, Bochu; Tan, Jun; Zhu, Liancai

    2013-08-01

    Recently more and more attention is paid to the rare earth metal complexes, because the properties of the rare earth metals are similar to those of the transition metals such as the similar atomic and the ionic radius. A large number of rare metal complexes were synthesized, and their bioactivities were also studied. This review highlights recent researches on the interaction of some rare earth metal complexes with DNA, analyzes how the configuration of the complexes influences the binding affinity, and focuses on the pharmacological activities of the complexes, such as anticancer, antibacterial, antioxidant, anti-inflammatory and anti-virus.

  1. Synthesis and Characterization of Rare Earth Solid Complexes with Sodium 5-Aminosalicylate

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiuying; Li Shujing; Lei Xuefeng; Ma Junxian

    2005-01-01

    Ten new rare earth solid complexes were synthesized by the reaction of sodium 5-aminosalicyliate with rare earth chloride. The structure character, physical and chemical properties of these complexes were studied by IR, UV, 1H NMR spectra, TG-DTA, fluorescence, elemental analyses, molar conductance and magnetic susceptibility. The ten rare earth complexes exist in dimeric form probably and the coordination number is seven. The antibacterial activity of the ligand and six complexes was also tested against Staphylococcus aureus, Escherichia coli and Bacillus subtilis, and the effect of Yb complex at 20 mg·ml-1 against Staphylococcus aureus is most significant.

  2. CATALYTIC ACTIVITIES OF RARE-EARTH CALIXARENE COMPLEXES IN POLYMER SYNTHESES

    Institute of Scientific and Technical Information of China (English)

    Zhi-quan Shen

    2005-01-01

    The studies of our group on the catalytic activities of rare earth calixarene complexes in polymer syntheses are reviewed. Rare earth calixarene complexes are effect catalysts for the polymerizations of butadiene, isoprene, ethylene,styrene, propylene oxide, styrene oxide, trimethylene carbonate and 2,2-dimethyl-trimethylene carbonate.

  3. Dentifrice Fluoride

    Science.gov (United States)

    Rakita, Philip E.

    2004-05-01

    The effectiveness of the fluoride ion in lowering the incidence of dental caries is a major factor in the field of dental health. Observations and research studies in the first half of the 20th century have lead to the widespread adoption of fluoridated water and the use of inorganic fluoride compounds in oral care products, such as toothpaste and dental rinses. This article provides a brief review of the types of compounds used and the chemistry involved.

  4. Complex polyfluoride additives in Fmoc-amino acid fluoride coupling processes. Enhanced reactivity and avoidance of stereomutation.

    Science.gov (United States)

    Carpino, Louis A; Ionescu, Dumitru; El-Faham, Ayman; Beyermann, Michael; Henklein, Peter; Hanay, Christiane; Wenschuh, Holger; Bienert, Michael

    2003-04-01

    [reaction: see text] Isolated Fmoc amino acid fluorides have previously been shown to be among the most efficient reagents for peptide bond formation. Now, it has been found that anionic, polyhydrogen fluoride additives are capable of diverting many of the classical peptide coupling processes to acid fluoride couplings. Examples include the use of N-HBTU or N-HATU and the carbodiimide technique. As HF-containing species, these additives provide a more suitable medium for the coupling of systems that are sensitive to loss of configuration at the reactive carboxyl function.

  5. Alkaline-alkaline earth fluoride carbonate crystals ABCO3F (A = K, Rb, Cs; B = Ca, Sr, Ba) as nonlinear optical materials.

    Science.gov (United States)

    Zou, Guohong; Ye, Ning; Huang, Ling; Lin, Xinsong

    2011-12-14

    A new series of alkaline-alkaline earth fluoride carbonates (KSrCO(3)F, RbSrCO(3)F, KCaCO(3)F, RbCaCO(3)F, CsCaCO(3)F, and Cs(3)Ba(4)(CO(3))(3)F(5)) were synthesized by spontaneous crystallization with molten fluxes. Their crystal structures, except for Cs(3)Ba(4)(CO(3))(3)F(5), exhibit the stacking of [AF](∞) (A = K, Rb, Cs) and [B(CO(3))](∞) (B = Ca, Sr) layers, and the coplanar alignment of [CO(3)] triangles. The results from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges were all below 200 nm, except for Cs(3)Ba(4)(CO(3))(3)F(5), which is about 210 nm. Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that these carbonates are all phase-matchable materials in both visible and the UV region, and their measured SHG coefficients were about 3.33, 3.33, 3.61, 1.11, 1.11, and 1.20 times as large as that of d(36) (KDP), respectively. © 2011 American Chemical Society

  6. Analysis of Equilibrium and Kinetics of Chromium-Fluoride Complexation from Spectroscopic Data via Chemometrics Methods

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The complexation of Cr3+ with F- undergoes a multistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L(metal to ligand) and 50 ℃, the result of Principal Component Analysis(PCA) shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis(TTFA). Meanwhile, a reactive intermediate was observed before the formation of MLx during the specific kinetic study at 15 ℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.

  7. Studies on solid phase synthesis,characterization and fluorescent property of the new rare earth complexes

    OpenAIRE

    Shi, Jianwei; Xiaoxu TENG; Wang, Linling; Long, Rong

    2015-01-01

    Rare earth-β-diketone ligand complex luminescent material has stable chemical properties and excellent luminous property. Using europium oxide and (γ-NTA) as raw materials, novel rare earth-β-dione complexes are synthesized by solid state coordination chemistry. The synthesis temperature and milling time are discussed for optimization. Experimental results show that the suitable reaction situation is at 50 ℃ and 20 h for solid-phase synthesis. The compositions and structures of the complexes...

  8. Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

    Directory of Open Access Journals (Sweden)

    Magnus Liljenberg

    2013-04-01

    Full Text Available A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the “σ-complex approach”, has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k from the literature with a theoretical quantity, which we call the sigma stability (SS. The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3 and anionic (MeO− nucleophiles are quite satisfactory (r = 0.93 to r = 0.99, and SS is thus useful for quantifying both global (substrate and local (positional reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

  9. Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides.

    Science.gov (United States)

    Liljenberg, Magnus; Brinck, Tore; Rein, Tobias; Svensson, Mats

    2013-01-01

    A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the "σ-complex approach", has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k) from the literature with a theoretical quantity, which we call the sigma stability (SS). The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3) and anionic (MeO(-)) nucleophiles are quite satisfactory (r = 0.93 to r = 0.99), and SS is thus useful for quantifying both global (substrate) and local (positional) reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

  10. Bridging complexes of rare earth and cobalt cluster as catalyst precursors for Fischer-Tropsch synthesis

    Institute of Scientific and Technical Information of China (English)

    ZENG Shanghong; DU Dongping; BAI Fenghua; SU Haiquan

    2011-01-01

    Three new bridging complexes of rare earth and cobalt cluster were synthesized and characterized via ICP, IR and TG techniques.The structure of the complexes was speculated as: two rare earth atoms were bridged with four CF3COO-, and rare earth atoms were coordinated with cobalt carbonyl clusters to form a steady structure. Application of the complexes as the catalyst precursors was explored for Fischer-Tropsch synthesis. The study showed that the bridging complexes of rare earth and cobalt cluster had large molecular size and were difficult to enter pore path of γ-Al2O3, so they were dispersed on the surface of γ-A12O3 support. In addition, the performance of Co(Ce)/γ-Al2O3 was the best among the catalysts with complex as precursor and maintained 77.7% CO conversion at 220 ℃ for 80 operation hours.

  11. Complex Electronic Structure of Rare Earth Activators in Scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Yu, S. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhou, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-27

    To aid and further the understanding of the microscopic mechanisms behind the scintillator nonproportionality that leads to degradation of the attainable energy resolution, we have developed theoretical and experimental algorithms and procedures to determine the position of the 4f energy levels of rare earth dopants relative to the host band edge states.

  12. Preparation and Property of Acrylic Acid Rare Earth Complex and Its Hydrosilylation

    Institute of Scientific and Technical Information of China (English)

    Zhang Ming; Chen Haiyan; Chen Xiaosong; Dai Shaojun; Inoue Shinich; Okamoto Hiroshi

    2004-01-01

    Acrylic acid rare earth complex was prepared. Its chemical composition was determined by chemical and elemental analysis, and its structure as well as properties was characterized using IR, Fluorescence and UV spectrum, and its solubility was also investigated. Meanwhile a kind of elastic functional polymer with rare earth units in the side chains was produced. It is confirmed by IR spectrum that the Si-H bonds really react with acrylic acid rare earth.

  13. Efficient manganese luminescence induced by Ce3+-Mn2+ energy transfer in rare earth fluoride and phosphate nanocrystals

    Directory of Open Access Journals (Sweden)

    Ding Yun

    2011-01-01

    Full Text Available Abstract Manganese materials with attractive optical properties have been proposed for applications in such areas as photonics, light-emitting diodes, and bioimaging. In this paper, we have demonstrated multicolor Mn2+ luminescence in the visible region by controlling Ce3+-Mn2+ energy transfer in rare earth nanocrystals [NCs]. CeF3 and CePO4 NCs doped with Mn2+ have been prepared and can be well dispersed in aqueous solutions. Under ultraviolet light excitation, both the CeF3:Mn and CePO4:Mn NCs exhibit Mn2+ luminescence, yet their output colors are green and orange, respectively. By optimizing Mn2+ doping concentrations, Mn2+ luminescence quantum efficiency and Ce3+-Mn2+ energy transfer efficiency can respectively reach 14% and 60% in the CeF3:Mn NCs.

  14. Substituent effects of N4 Schiff base ligands on the formation of fluoride-bridged dicobalt(ii) complexes via B-F abstraction: structures and magnetism.

    Science.gov (United States)

    Cho, Yae In; Ward, Meredith L; Rose, Michael J

    2016-09-14

    We report the synthesis of two fluoride bridged cobalt(ii) dimers - [Co(μ-F)(pnN4-PhCl)2(OH2)(MeCN)](BF4)3 (1) and [Co(μ-F)2(pnN4-PhCl)2](BF4)2 (2) - and related complexes derived from propyl-bridged N4 Schiff base plus pyridine ligands. Notably, the bridging fluoride ion(s) emanate from B-F abstraction processes on the BF4 anions in the starting salt, [Co(H2O)6](BF4)2. Two types of bridging motifs are generated - mono-bridged (μ-F) or di-bridged (μ-F)2- synthetically differentiated by the absence or presence of pyridine, respectively, during metalation. The synergistic roles of pyridine and the (ClPh)N4 ligand in promoting B-F abstraction were clarified by the isolation and crystallization of the simple tetrakis-pyridine monomeric complex [Co(py)4(MeCN)2](BF4)2 (4) [no B-F abstraction]; subsequent addition of the (ClPh)N4 ligand to 4 resulted in formation of the dimeric, di-bridged complex 2. Omission of pyridine during metalation resulted in formation of the mono-bridged dimer 1. The bulky chlorophenyl substituents were obligate for B-F abstraction, as metalation of the unsubstituted N4 ligand resulted in the non-fluoride-bridged dimer, [Co(pnN4)3](BF4)4 (3). In magnetic studies, complexes 1 (μeff = 6.24μB, 298 K) and 2 (μeff = 7.70μB, 298 K) both exhibit antiferromagnetic (AFM) coupling, but to different extents. Temperature-dependent magnetic susceptibility measurements (SQUID, 2 → 300 K) reveal that the linearity of the mono-fluoride bridge in 1 [∠Co-F-Co = 159.47(11)°] results in very strong AFM coupling (J = -14.9 cm(-1)). In contrast, the more acute Co2F2 diamond core [∠Co-F-Co = 98.8(2)°, 99.1(2)°] results in a smaller extent of AFM coupling (J = -2.97 cm(-1)). Overall, the results indicate the 'non-innocence' of the BF4 counterion in cobalt(ii) chemistry, and dimers 1 and 2 affirm the effect of the geometry of the bridging fluoride ion(s) in determining the extent of AFM coupling.

  15. Complexity and Self-Organized Criticality of Solid Earth System(Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The author puts forward the proposition of "Complexity and Self-Organized Criticality of Solid Earth System" in the light of: (1) the science of complexity studies the mechanisms of emergence of complexity and is the science of the 21st century, (2) the study of complexity of the earth system would be one of the growing points occupying a strategic position in the development of geosciences in the 21st century. By the proposition we try to cogitate from a new viewpoint the ancient yet ever-new solid earth system. The author abstracts the fundamental problem of the solid earth system from the essence of the generalized geological systems and processes which reads: "the complexity and self-organized criticality of the global nature, structure and dynamical behavior of the whole solid earth system emerging from the multiple coupling and superposition of non-linear interactions among the multicomponents of the earths material and the multiple generalized geological (geological, geophysical, and geochemical) processes". Starting from this cognizance the author proposes eight major themes and the methodology of researches on the complexity and self-organized criticality of the solid earth system.

  16. Complexity and Self-Organized Criticality of Solid Earth System(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The author puts forward the proposition of "Complexity and Self-Organized Criticality of Solid Earth System" in the light of: (1) the science of complexity studies the mechanisms of emergence of complexity and is the science of the 21st century, (2) the study of complexity of the earth system would be one of the growing points occupying a strategic position in the development of geosciences in the 21st century. By the proposition we try to cogitate from a new viewpoint the ancient yet ever-new solid earth system. The author abstracts the fundamental problem of the solid earth system from the essence of the generalized geological systems and processes which reads: "the complexity and self-organized criticality of the global nature, structure and dynamical behavior of the whole solid earth system emerging from the multiple coupling and superposition of non-linear interactions among the multicomponents of the earths material and the multiple generalized geological (geological, geophysical, and geochemical) processes". Starting from this cognizance, the author proposes eight major themes and the methodology of researches on the complexity and self-organized criticality of the solid earth system.

  17. Effects of chronic fluoride exposure on object recognition memory and mRNA expression of SNARE complex in hippocampus of male mice.

    Science.gov (United States)

    Han, Haijun; Du, Wenjuan; Zhou, Bingrui; Zhang, Wen; Xu, Guoli; Niu, Ruiyan; Sun, Zilong

    2014-04-01

    This study aimed to investigate the effects of long-term fluoride exposure on object recognition memory and mRNA expression of soluble N-ethylmaleimidesensitive fusion protein attachment protein receptors (SNARE) complex (synaptosome-associated protein of 25 kDa (SNAP-25), vesicle-associated membrane protein 2 (VAMP-2), and syntaxin 1A) in the hippocampus of male mice. Sixty sexually matured male Kunming mice were randomly divided into four groups: control group (given distilled water), low F group (25 mg/L NaF, corresponding to 11 mg/L F(-)), medium F group (50 mg/L NaF, corresponding to 22 mg/L F(-)), and high F group (100 mg/L NaF, corresponding to 45 mg/L F(-)). After 180 days, the spontaneous locomotor behavior and object recognition memory were detected by open field test and novel object recognition (NOR) test. Results showed that compared with the control group, frequency in each zone, total distance, and line crosses were significantly increased in low F and medium F groups, suggesting fluoride enhanced excitement of mice, while there were no marked changes in high F group. Twenty-four hours after training, a deficit of long-term memory (LTM) occurred only in high F group (P recognition memory, and upregulate VAMP-2 mRNA expression, which are involved in the adverse effects of fluoride on the object recognition memory of nervous system.

  18. Environmental fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Marier, J.R.; Rose, D.

    1971-01-01

    Modern-day man is probably exposed to more environmental fluoride than was heretofore suspected, and consideration must be given to the total ingestion from various sources as well as the types of fluoride present in air, foods, beverages, and other commodities. An effort should also be made to study the symptomology of chronic fluorine intoxication, especially the early non-skeletal manifestations of arthritic-like symptoms that may be complicated by metabolic and/or nutritional inadequacies. Finally, it must be emphasized again that dental fluorosis (i.e. mottling) will only be seen in subjects who have been exposed to fluoride during the time when the enamel of the permanent teeth is being formed, and its absence cannot be assumed to indicate freedom from other fluoride-induced effects including effects of organofluorides and their metabolites. 168 references.

  19. Removal of fluoride from fluoride-bering cerium sulfate solution by hydrous zirconium oxide

    Directory of Open Access Journals (Sweden)

    J. G. He

    2014-04-01

    Full Text Available In this paper the removal of fluoride from fluoride-bearing cerium sulfate solution by amorphous hydrous zirconium oxide was studied. The FTIR, SEM, EDS and UV-vis spectra show that fluoride is successfully adsorbed on hydrous zirconium oxide, and cerium exists as Ce4+ in solution. The study indicates that it is feasible to separate fluorine and cerium from fluorine-bearing rare earth sulfate solution using hydrous zirconium oxide, and eliminate the influence of fluoride on the extraction separation of rare earths.

  20. Rare earth why complex life is uncommon in the Universe

    CERN Document Server

    Ward, Peter D

    2000-01-01

    n November 12, 2002, Dr. John Chambers of the NASA Ames - search Center gave a seminar to the Astrobiology Group at the OUniversity of Washington. The audience of about 100 listened with rapt attention as Chambers described results from a computer study of how planetary systems form. The goal of his research was to answer a dec- tively simple question: How often would newly forming planetary systems produce Earth-like planets, given a star the size of our own sun? By “Ear- like” Chambers meant a rocky planet with water on its surface, orbiting within a star’s “habitable zone. ” This not-too-hot and not-too-cold inner - gion, relatively close to the star, supports the presence of liquid water on a planet surface for hundreds of million of years—the time-span probably n- essary for the evolution of life. To answer the question of just how many Earth-like planets might be spawned in such a planetary system, Chambers had spent thousands of hours running highly sophisticated modeling p- grams through a...

  1. New Rare Earth(Ⅲ) Complexes with H2tmtaa

    Institute of Scientific and Technical Information of China (English)

    WANG Zeng-Lin; ZHANG Mei-Li; LIU Zong-Huai; YANG Zu-Pei

    2006-01-01

    A series of Ln(tmtaa)(Htmtaa)·CH2Cl2 (Ln = Sm, Tb, Er and Yb) complexes were prepared and characterized by infrared spectra, mass spectra and molecular electronic spectroscopy as well as DSC measurement. A sandwich structure containing all the eight nitrogen atoms of tmtaa and Htmtaa was proposed for these complexes. X-ray photoelectron spectra (XPS) of these complexes revealed that four nitrogen atoms of both tmtaa and Htmtaa were chemically equivalent to each other, respectively. The acidic hydrogen of Htmtaa did not bind specifically to any nitrogen atom of Htmtaa, but was shared by all the four nitrogen atoms. The magnetic properties of these complexes were found to be in good agreement with their theoretical values.

  2. Other Fluoride Products

    Science.gov (United States)

    ... What's this? Submit What's this? Submit Button Other Fluoride Products Recommend on Facebook Tweet Share Compartir On ... August 17, 2001;50(RR-14):1–42. Fluoride Products Fluoride Toothpaste Form Concentrations of fluoride in ...

  3. Bottled Water and Fluoride

    Science.gov (United States)

    ... bottled water and fluoride. Does bottled water contain fluoride? Bottled water products may contain fluoride, depending on ... How can I find out the level of fluoride in bottled water? The FDA does not require ...

  4. Other Fluoride Products

    Science.gov (United States)

    ... Water Fluoridation Journal Articles for Community Water Fluoridation Other Fluoride Products Recommend on Facebook Tweet Share Compartir ... Use the information listed below to compare the other fluoride products that may lower the risk for ...

  5. Synthesis, Characterization of α-Oxopentanedioic Acid-Isonicotinoyl Hydrazone Rare Earth-Complexes and Relaxivity of Gd-complex

    Institute of Scientific and Technical Information of China (English)

    杨正银; 杨汝栋

    2004-01-01

    α-Oxopentanedioic acid isonicotinoyl hydrazone (H2L) and its five rare earth complexes were synthesized with a view to further investigating MRI activities of the polycarboxylic Schiff base complexes. The complexes were characterized on the basis of elemental analyses, IR, UV, 1H NMR spectra and thermal analyses. The general formula of the complexes is [Ln(HL)(H2O)2]Cl2·H2O (where Ln(Ⅲ)=La, Pr, Nd, Eu and Gd). In addition, the relaxivity (R1) of the Gd-complex was determined by INVREC Au program.

  6. The utility of Earth system Models of Intermediate Complexity

    NARCIS (Netherlands)

    Weber, S.L.

    2010-01-01

    Intermediate-complexity models are models which describe the dynamics of the atmosphere and/or ocean in less detail than conventional General Circulation Models (GCMs). At the same time, they go beyond the approach taken by atmospheric Energy Balance Models (EBMs) or ocean box models by

  7. Synthesis, Characterization and Vulcanizing Properties of Rare Earth Complexes with 2-Mercaptobenthiazole

    Institute of Scientific and Technical Information of China (English)

    张启交; 韦凤仙; 章伟光; 黄庙由; 罗远芳

    2002-01-01

    Eight complexes of rare earth with 2-mercaptobenthiazole, RELCl2*RE(OH)3*xH2O (L=2-mercaptobenthiazole, RE= La~Gd, Y, except for Pm,x=0, 2~4), were synthesized in unhydrous ethanol and characterized by elemental analyses, IR spectra and thermal analyses. The results show that the ligand is coordinated to the RE ion through both the exocyclic sulfur and the thiazole nitrogen. The vulcanizing properties of the La complex as accelerator were studied in the traditional tire rubber, which indicate that the cross-linked rubber accelerated by the rare earth complex has good physical and dynamic mechanical properties by comparison.

  8. Metathesis synthesis and characterization of complex metal fluoride, KMF3 (M = Mg, Zn, Mn, Ni, Cu and Co) using mechanochemical activation

    Indian Academy of Sciences (India)

    V Manivannan; P Parhi; Jonathan W Kramer

    2008-12-01

    Metathesis synthesis of complex metal fluorides using mechanochemical activation has been reported. The high lattice energy of the byproduct KCl helps the reaction towards product formation in under 20 min. The proposed process, in contrast to the available methods of synthesis, is very rapid, economical and results in products with controlled morphology. The structural, optical and chemical properties of synthesized powders are determined by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, magnetization measurements and diffused reflectance spectra in the UV–VIS range.

  9. Preparation and Properties of Eu3+ Rare Earth Complex and Fluorescent Fiber

    Institute of Scientific and Technical Information of China (English)

    HE Yu-xian; XI Peng; HUANG Xiang-an

    2006-01-01

    A novel Eu3+ rare earth complex, composed of 4 -hydroxybenzolate acid and 1, 10 - phenanthroline ligands was synthesized. The apparent morphology, composition,thermal stability and fluorescent property of the rare earth complex were measured by TEM, Element analysis, IR, TG and Fluorescence spectrometer. The results indicated that this rare earth complex has sphere-like morphology and its diameter was about 100 nm. The complex has good thermal stability due to the strong coordination between the Eu3+ions and the ligands. Based on the composition analysis, the complex structure formula was: Eu(HOC6 H4 COO)3(phen)complex emission peaks were corresponding to the transition of 5D0→7 FJ(J=0,1,2,4), and the highest intensity fluorescence peak was at 617 nm. The luminescent fiber was prepared by blending melt-spinning with rare earth complex and polypropylene resin. It also has a good luminescent quality,which the strongest emission peak was at 619 nm. It could be considered suitable for industrial application.

  10. The measuring complex for detection of radioactive waste in near-earth space

    Science.gov (United States)

    Ulin, S. E.; Vlasik, K. F.; Grachev, V. M.; Dmitrenko, V. V.; Novikov, A. S.; Uteshev, Z. M.; Shustov, A. E.; Chernishova, I. V.; Bakhtigaraev, N. S.; Rykhlova, L. V.; Kazantsev, S. G.

    2017-01-01

    Description of a measuring complex intended for detection and identification of radioactive waste in the near-earth space is presented. The complex consists of several xenon gamma-ray spectrometers, developed on the base of the thin-walled impulse ionization chamber with sensitive volume of four litres. Their main physics - technical characteristics are considered. An estimation probability for detection of various elements comprising radioactive waste by means of the measuring complex on board the spacecraft “Meteor” is given.

  11. An Encapsulation of the Rare Earth Complex in Modified Mesoporous Molecular Sieve MCM-41

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The encapsulation of a rare earth (RE) complex Eu(DBM)3phen in modified Si-MCM-41 with 3-aminopropyltriethoxysilane is reported for the first time.The luminescence intensity of the RE complex in the modified Si-MCM-41 is about 9 times as strong as in unmodified Si-MCM-41 and the luminescence of the RE complex in the modified Si-MCM-41 has good color purity.

  12. Using Google Earth Surface Metrics to Predict Plant Species Richness in a Complex Landscape

    Directory of Open Access Journals (Sweden)

    Sebastián Block

    2016-10-01

    Full Text Available Google Earth provides a freely available, global mosaic of high-resolution imagery from different sensors that has become popular in environmental and ecological studies. However, such imagery lacks the near-infrared band often used in studying vegetation, thus its potential for estimating vegetation properties remains unclear. In this study, we assess the potential of Google Earth imagery to describe and predict vegetation attributes. Further, we compare it to the potential of SPOT imagery, which has additional spectral information. We measured basal area, vegetation height, crown cover, density of individuals, and species richness in 60 plots in the oak forests of a complex volcanic landscape in central Mexico. We modelled each vegetation attribute as a function of surface metrics derived from Google Earth and SPOT images, and selected the best-supported linear models from each source. Total species richness was the best-described and predicted variable: the best Google Earth-based model explained nearly as much variation in species richness as its SPOT counterpart (R2 = 0.44 and 0.51, respectively. However, Google Earth metrics emerged as poor predictors of all remaining vegetation attributes, whilst SPOT metrics showed potential for predicting vegetation height. We conclude that Google Earth imagery can be used to estimate species richness in complex landscapes. As it is freely available, Google Earth can broaden the use of remote sensing by researchers and managers in low-income tropical countries where most biodiversity hotspots are found.

  13. Understanding Student Cognition about Complex Earth System Processes Related to Climate Change

    Science.gov (United States)

    McNeal, K. S.; Libarkin, J.; Ledley, T. S.; Dutta, S.; Templeton, M. C.; Geroux, J.; Blakeney, G. A.

    2011-12-01

    The Earth's climate system includes complex behavior and interconnections with other Earth spheres that present challenges to student learning. To better understand these unique challenges, we have conducted experiments with high-school and introductory level college students to determine how information pertaining to the connections between the Earth's atmospheric system and the other Earth spheres (e.g., hydrosphere and cryosphere) are processed. Specifically, we include psychomotor tests (e.g., eye-tracking) and open-ended questionnaires in this research study, where participants were provided scientific images of the Earth (e.g., global precipitation and ocean and atmospheric currents), eye-tracked, and asked to provide causal or relational explanations about the viewed images. In addition, the students engaged in on-line modules (http://serc.carleton.edu/eslabs/climate/index.html) focused on Earth system science as training activities to address potential cognitive barriers. The developed modules included interactive media, hands-on lessons, links to outside resources, and formative assessment questions to promote a supportive and data-rich learning environment. Student eye movements were tracked during engagement with the materials to determine the role of perception and attention on understanding. Students also completed a conceptual questionnaire pre-post to determine if these on-line curriculum materials assisted in their development of connections between Earth's atmospheric system and the other Earth systems. The pre-post results of students' thinking about climate change concepts, as well as eye-tracking results, will be presented.

  14. Rare-earth dialkyl and dihydride complexes bearing monoanionic ancillary ligands

    Institute of Scientific and Technical Information of China (English)

    CHENG JianHua; HOU ZhaoMin

    2011-01-01

    Rare-earth elements,including scandium,yttrium,and the lanthanides (La-Lu),possess unique chemical and physical properties,and constitute one of the last frontiers in the periodic table.Rare-earth elements are vital for many high-tech industry products such as smartphones and electric cars.However,the fundamental chemistry of the rareearth elements has been explored to a far less extent.The first organo rare-earth complexes Cp3Ln (1,Figure 1),which bear three cyclopentadienyl (Cp) ligands,were reported in the early 1950s [1],but these complexes did not receive much attention because of the lack of significant reactivity.In the early 1980s,the alkyl and hydride complexes supported by two cyclopentadienyl ligands (such as 2in Figure 1) were reported [2].

  15. Studies on solid phase synthesis,characterization and fluorescent property of the new rare earth complexes

    Directory of Open Access Journals (Sweden)

    Jianwei SHI

    2015-04-01

    Full Text Available Rare earth-β-diketone ligand complex luminescent material has stable chemical properties and excellent luminous property. Using europium oxide and (γ-NTA as raw materials, novel rare earth-β-dione complexes are synthesized by solid state coordination chemistry. The synthesis temperature and milling time are discussed for optimization. Experimental results show that the suitable reaction situation is at 50 ℃ and 20 h for solid-phase synthesis. The compositions and structures of the complexes are characterized by means of elemental analysis, UV-Vis and FTIR methods, and the phase stability of the complex is determined by using TG-DTA technique. It is proved that preparation of waterless binary rare earth complexes by the solid phase reaction method results in a higher product yield. The fluorescence spectra show that between Eu (Ⅲ and γ-NTA, there exists efficient energy transfer, and the rare earth complexes synthesis is an excellent red bright light-emitting material with excellent UV excited luminescence properties.

  16. Fluoride release from newly marketed fluoride varnishes.

    Science.gov (United States)

    Jablonowski, Beth L; Bartoloni, Joseph A; Hensley, Donna M; Vandewalle, Kraig S

    2012-03-01

    New fluoride varnishes have been marketed that reportedly release more fluoride (Enamel Pro) or release fluoride more slowly (Vanish XT). The purpose of this study was to compare the amount and rate of fluoride release of new fluoride varnishes with other traditional fluoride varnishes. Extracted molars were cut into block sections. The enamel surfaces of the sections were painted with Enamel Pro, Duraphat, Vanish, or Vanish XT fluoride varnishes. One group was not treated and served as a negative control. The tooth sections were immersed in artificial saliva. The concentration of fluoride in parts per million was measured after the first 30 minutes, daily for the first week, and weekly until the level was below the limit of detection. Fluoride release was plotted over time. Cumulative fluoride release and rate of release (slope) were analyzed using one-way ANOVA/Tukey (α = .05). Enamel Pro had the greatest cumulative fluoride release. There was no significant difference between Duraphat and Vanish. Vanish XT had the lowest cumulative fluoride release. The rate of fluoride release from 1 week to limit of detection was Enamel Pro > Vanish > Duraphat > Vanish XT. The two newly marketed fluoride varnishes (Enamel Pro and Vanish XT) had significantly different fluoride release from the two conventional fluoride varnishes (Duraphat and Vanish).

  17. Fluoridation Basics

    Science.gov (United States)

    ... level in water is not enough to prevent tooth decay; however, some groundwater and natural springs can have ... the tooth’s surface, or enamel. Water fluoridation prevents tooth decay by providing frequent and consistent contact with low ...

  18. Complex rare-earth aluminum hydrides: mechanochemical preparation, crystal structure and potential for hydrogen storage.

    Science.gov (United States)

    Weidenthaler, Claudia; Pommerin, André; Felderhoff, Michael; Sun, Wenhao; Wolverton, Christopher; Bogdanović, Borislav; Schüth, Ferdi

    2009-11-25

    A novel type of complex rare-earth aluminum hydride was prepared by mechanochemical preparation. The crystal structure of the REAlH(6) (with RE = La, Ce, Pr, Nd) compounds was calculated by DFT methods and confirmed by preliminary structure refinements. The trigonal crystal structure consists of isolated [AlH(6)](3-) octahedra bridged via [12] coordinated RE cations. The investigation of the rare-earth aluminum hydrides during thermolysis shows a decrease of thermal stability with increasing atomic number of the RE element. Rare-earth hydrides (REH(x)) are formed as primary dehydrogenation products; the final products are RE-aluminum alloys. The calculated decomposition enthalpies of the rare-earth aluminum hydrides are at the lower end for reversible hydrogenation under moderate conditions. Even though these materials may require somewhat higher pressures and/or lower temperatures for rehydrogenation, they are interesting examples of low-temperature metal hydrides for which reversibility might be reached.

  19. Investigation of Polyacrylate Anion-Exchangers for Separation of Rare Earth Element Complexes with EDTA

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The rare earth complexes with EDTA, Ln(edta), show an unusual sequence of affinity for the anion-exchangers. The sorption and chromatographic separation of Y3+ for Nd3+ complexes with EDTA was studied by using the strongly basic gel and macroporous polyacrylate anion-exchangers, Amberlite IRA 458 and Amberlite 958, and the weakly basic gel polyacrylate anion-exchanger, Amberlite IRA-68. The investigations on sorption and separation of rare earth complexes with EDTA on the polyacrylate anion-exchangers applied mainly in the environment protection so far indicate that they can be applied in anionexchange separation of lanthanide complexes with aminopolycarboxylic acids. It was shown that the weakly basic polyacrylate gel anion-exchanger Amberlite IRA-68 is the most effective in purification of Y3+ from Nd3+ in comparison with the strongly basic anion-exchangers of this type.

  20. Synthesis, Characterization and Bioactivity of Complexes of Rare Earth with Bis-Schiff Base from Furoylpyrazolone

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Eleven new complexes of rare earths with bis-Schiff base derived from N,N'-bis[(1-phenyl-3-methyl-5-oxo-4-pyrazolinyl)α-furylmethylidyne] ethylenediimine ((HPMαFP)2en) were synthesized. On the basis of elemental analysis and molar conductance, a general formula of the complexes, [RE(HPMαFP)2 en(NO3)2]NO3 (RE=La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb,Y), was given. The complexes were characterized by IR, UV-visible, 1H NMR, 13C NMR and fluorescence. The results show that the bis-Schiff base is a quadridentate ligand and the rare earth ions exhibit coordination of eight in the complexes. The antibacterial experiments indicate that they have high antibacterial activities against S. aureus, B. subtillis, E. coli, E.carotovora, C. flaccumfaciens.

  1. Fabrication and Luminescence of Rare Earth Complex/SiO2 Hybrid Nanospheres

    Institute of Scientific and Technical Information of China (English)

    赵丹; 秦伟平; 吴长锋; 张继森; 秦冠仕; 林海燕

    2004-01-01

    The organic rare earth complex was embedded in silica spheres to form inorganic-organic hybrid. Photoactive rare earth complexes with various organic ligands exhibit intense narrow emission band, and the silica is an excellent matrix for inorganic-organic structure. The transmission electron microscope image presents the hybrid nanospheres. The diameter of the hybrid is about 100 nm. The europium complex that incorporated into silica sphere is also proved by the IR spectra, the excitation and emission spectra. The lifetimes of the Eu3+ ions in the hybrid nanospheres and in the pure europium complex were also detected. This hybrid with inhomogeneous compositions exhibits specifically tailored chemical and optical properties, such as perfect thermal and mechanical stability, colorimetric purity and so on. It can be used as luminescent and optical material in EL and PL fields.

  2. Preparation and Characterization of Layered Compound Zirconium Bis(monohydrogenphosphate) Intercalated with Rare Earth Complex

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Layered compound zirconium bis(monohydrogenphosphate)(α -ZrP) intercalated with rare earth complex Eu(DBM)3phen was prepared. The pre-intercalation of p-methoxyaniline into α -ZrP makes the interlayer separation large enough to exchange PMA with europium complex, thus, the luminescent assembly was prepared. This was confirmed by X-ray diffraction, UV-visible spectra and elemental analysis. The fluorescence spectra and lifetime of the assembly were also presented.

  3. Neutral binuclear rare-earth metal complexes with four μ₂-bridging hydrides.

    Science.gov (United States)

    Rong, Weifeng; He, Dongliang; Wang, Meiyan; Mou, Zehuai; Cheng, Jianhua; Yao, Changguang; Li, Shihui; Trifonov, Alexander A; Lyubov, Dmitrii M; Cui, Dongmei

    2015-03-25

    The first neutral rare-earth metal dinuclear dihydrido complexes [(NPNPN)LnH2]2 (2-Ln; Ln = Y, Lu; NPNPN: N[Ph2PNC6H3((i)Pr)2]2) bearing μ2-bridging hydride ligands have been synthesized. In the presence of THF, 2-Y undergoes intramolecular activation of the sp(2) C-H bond to form dinuclear aryl-hydride complex 3-Y containing three μ2-bridging hydride ligands.

  4. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  5. Conformation Switching in Gas-Phase Complexes of Histidine with Alkaline Earth Ions

    NARCIS (Netherlands)

    Dunbar, R. C.; Hopkinson, A. C.; Oomens, J.; Siu, C. K.; Siu, K. W. M.; Steill, J. D.; Verkerk, U. H.; Zhao, J. F.

    2009-01-01

    Infrared multiple photon dissociation spectroscopy of gas-phase doubly charged alkaline earth complexes of histidine reveals a transition from dominance of the zwitterion (salt bridge, SB) conformation with Ba2+ to substantial presence of the canonical (charge-solvated, CS) conformation with Ca2+. T

  6. Application of NASA management approach to solve complex problems on earth

    Science.gov (United States)

    Potate, J. S.

    1972-01-01

    The application of NASA management approach to solving complex problems on earth is discussed. The management of the Apollo program is presented as an example of effective management techniques. Four key elements of effective management are analyzed. Photographs of the Cape Kennedy launch sites and supporting equipment are included to support the discussions.

  7. Triangular exchange interaction patterns in K3Fe6F19: an iron potassium fluoride with a complex tungsten bronze related structure.

    Science.gov (United States)

    Mezzadri, Francesco; Calestani, Gianluca; Righi, Lara; Pernechele, Chiara; Solzi, Massimo; Ritter, Clemens

    2013-11-04

    The synthesis and structural and magnetic characterizations of K3Fe6F19, a new iron potassium fluoride with a complex tungsten bronze related structure, are presented. This phase was found during the investigation of relatively low-temperature (600 °C) synthesis conditions of classical tetragonal tungsten bronze (TTB) fluorides and can be considered an intermediate that forms at this temperature owing to faster crystallization kinetics. The K3Fe6F19 compound has an orthorhombic structure (space group Cmcm (63), a = 7.6975(3) Å, b = 18.2843(7) Å, c = 22.0603(9) Å) related to the TTB one, where the perovskite cage is substituted by a large S-shaped channel simultaneously occupied by two potassium atoms. The magnetic structure, characterized by magnetization measurements on an oriented single crystal and powder neutron diffraction, is dominated by the presence of interconnected double stripes of antiferromagnetic triangular exchange interaction patterns alternately rotated in clock- and anticlockwise fashion. The magnetic order takes place in a wide temperature range, by increasing progressively the interaction dimensionality.

  8. VUV spectroscopy of complex fluoride systems Na0.4(Y1-xREx)0.6F2.2 (RE3+ = Nd3+, Tm3+)

    Science.gov (United States)

    Makhov, V. N.; Uvarova, T. V.; Kirm, M.; Vielhauer, S.

    2016-05-01

    Emission and excitation spectra as well as luminescence decay kinetics of complex non-stoichiometric fluoride crystals Na0.4(Y1-xNdx)0.6F2.2 (x = 0.005, 0.05, 0.2, 1) and Na0.4(Y1-xTmx)0.6F2.2 (x = 0.0005, 0.01, 0.05, 0.1) have been studied in the VUV spectral range at liquid-helium (T ∼ 10 K) temperatures. It has been shown that these crystals show intense broad-band VUV luminescence due to the interconfiguration 5d-4f transitions in Nd3+ and Tm3+ ions. Remarkable concentration quenching is observed for Nd3+ 5d-4f luminescence whereas fast (spin-allowed) 5d-4f luminescence of Tm3+ shows no concentration quenching for the studied doping level up to 10%. The spin-allowed 5d-4f luminescence of Tm3+ in these crystals was found to be rather weak compared to spin-forbidden 5d-4f luminescence because of efficient nonradiative relaxation from higher-energy 5d states of Tm3+ to the lowest-energy 5d level responsible for spin-forbidden 5d-4f luminescence. The studied fluoride systems can be considered as promising active media for the development of VUV solid state lasers with optical pumping.

  9. [Enamel fluoride uptake following fluoride application and fluoride precipitation].

    Science.gov (United States)

    Buchalla, Wolfgang; Lennon, Aine M; Trage, Katrin; Becker, Klaus; Attin, Thomas

    2007-01-01

    This study is on fluoride uptake into enamel following fluoride precipitation with calcium hydroxide. Five specimens each from 12 bovine incisors were polished, covered with a salivary pellicle, and distributed into five groups (n=12). A fluoride solution (43,500 ppm F from magnesiumfluorosilicate, copper-(II)-fluorosilicate and sodium-fluoride, pH 2; Tiefenfluorid Touchierlösung, Humanchemie) and Ca(OH)2-solution (Tiefenfluorid Nachtouchierlösung) were applied subsequently in group TN. "Touchierlosung" only was used in group T, sodium-fluoride (43,500 ppm F, pH 2) in group NaF, and aminefluoride (Elmex fluid, 10,000 ppm F, pH 4) in group EF. No fluoride was used in group NK (negative control). Following rinsing and 24 h storage in artificial saliva surface KOH-soluble fluoride content (KOHF), and structurally bound fluoride content (SBF) from three layers (0-33, 33-66 and 66-99 pm) was determined by fluoride electrode procedures. KOHF (median in microg/cm2) of NK was below the lower limit of quantification of the fluoride electrode. The other group values were significantly higher (Mann-Whitney test, p precipitation reaction with Ca(OH)2 following fluoridation did not increase enamel fluoride uptake.

  10. Historical and idealized climate model experiments: an intercomparison of Earth system models of intermediate complexity

    DEFF Research Database (Denmark)

    Eby, M.; Weaver, A. J.; Alexander, K.;

    2013-01-01

    and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO2, additional greenhouse gases, land use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20......Both historical and idealized climate model experiments are performed with a variety of Earth system models of intermediate complexity (EMICs) as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE...

  11. Synthesis, characterization and DNA binding of the complexes of rare earth with phenanthroline and demethylcantharate

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fan; ZHU Wenzhong; LIN Qiuyue; GUO Weidong; ZHANG Lingling; LI Shikun

    2011-01-01

    Three novel rare earth complexes, [Ln2(DCA)2(phen)2](NO3)2·6H2O (Ln(Ⅲ)=Sm(Ⅲ)(1), Er(Ⅲ)(2), Yb(Ⅲ)(3); DCA2-=demethylcantharate, 7-oxabicyclo[2.2.1] heptane-2,3-dicarboxylate, C8H8O52-; phen=1,10-phenanthroline, C12H8N2) were synthesized. The structures were characterized by elemental analysis, molar conductance, IR and TGA. The results suggested that the structural features of the complexes were: in each DCA2-, one carboxylate group, as bidentate bridging group, connected two rare earth ions; the other carboxylate group, as bidentate chelate group took part in the coordination with rare earth ion. And cyclic ether oxygen of DCA2- and nitrogen atoms of phen took part in the coordination. The probable coordination number was seven. The interaction of the complexes with DNA was studied by UV-spectra, fluorescence spectra and viscosity measurements. Following increasing the concentration of DNA, the UV absorption bands nearby 265 mn of the three complexes appeared hypochromism and red-shift phenomena. And the values of binding constants Kb were 1.89× 105 L/mol (1), 3.54× 104 L/mol (2) and 3.83× 104 L/mol (3). The complexes could quench the fluorescence of EB-DNA system, and the values of equilibrium constants Ksq were 1.72(1), 0.56(2) and 1.09(3). The relative viscosity of DNA steadily decreased with increasing theconcentration of complexes. So, we could infer that the complexes may partially insert into DNA. The study of agarose gel electrophoresis showed that the complexes could cleave plasmid DNA, and the process of the reaction was through unclassical redox mechanism.

  12. Phase Behavior and Crystal Structure of Perovskite-Type Rare Earth Complex Oxides

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33Mn0.33Ti0.67O3 (A=Ca or Sr and Ln=rare earth) were found to have orthorhombic symmetry with the space group Pnma, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Ca0.67Ln0.33Mn0.33Ti0.67O3 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.

  13. Complex demodulation in VLBI estimation of high frequency Earth rotation components

    Science.gov (United States)

    Böhm, S.; Brzeziński, A.; Schuh, H.

    2012-12-01

    The spectrum of high frequency Earth rotation variations contains strong harmonic signal components mainly excited by ocean tides along with much weaker non-harmonic fluctuations driven by irregular processes like the diurnal thermal tides in the atmosphere and oceans. In order to properly investigate non-harmonic phenomena a representation in time domain is inevitable. We present a method, operating in time domain, which is easily applicable within Earth rotation estimation from Very Long Baseline Interferometry (VLBI). It enables the determination of diurnal and subdiurnal variations, and is still effective with merely diurnal parameter sampling. The features of complex demodulation are used in an extended parameterization of polar motion and universal time which was implemented into a dedicated version of the Vienna VLBI Software VieVS. The functionality of the approach was evaluated by comparing amplitudes and phases of harmonic variations at tidal periods (diurnal/semidiurnal), derived from demodulated Earth rotation parameters (ERP), estimated from hourly resolved VLBI ERP time series and taken from a recently published VLBI ERP model to the terms of the conventional model for ocean tidal effects in Earth rotation recommended by the International Earth Rotation and Reference System Service (IERS). The three sets of tidal terms derived from VLBI observations extensively agree among each other within the three-sigma level of the demodulation approach, which is below 6 μas for polar motion and universal time. They also coincide in terms of differences to the IERS model, where significant deviations primarily for several major tidal terms are apparent. An additional spectral analysis of the as well estimated demodulated ERP series of the ter- and quarterdiurnal frequency bands did not reveal any significant signal structure. The complex demodulation applied in VLBI parameter estimation could be demonstrated a suitable procedure for the reliable reproduction of

  14. CORRELATION AMONG FLUORIDE AND METALS IN IRRIGATION ...

    African Journals Online (AJOL)

    Preferred Customer

    For comparative analysis of fluoride and metals in soil and water, water samples were ..... one is from rapidly soluble fluoride complex like cryolite (Na3AlF6) found in water ..... Atlabachew, M.; Chandravanshi, B.S.; Zewge, F.; Redi, M. Toxicol.

  15. Synthesis and spectroscopic characterization of fluorescent solid rare earth complexes with hydroxamic acids

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The complexes RE2(DHYA)3 .nH2O in the title bar were synthesized through some reactions oftrivalent rareearth ions. In the process of synthesis, dihydroxamic acids were taken as ligands while the alcohol was taken as a solvent.The ligands included adipylhydroxamic acid (ADHA), p-phthalichydroxamic acid (PPHA), oxalohydroxamic acid (OXHA), butadihydroxamic acid (BDHA), o-phthalichydroxamic acid (OPHA), benzoylhydroxamic acid (BHA), etc.Measured at 25 ℃, the molar conductances in various modes are 13.00-21.05 S. cm2. mol-1, which shows that rare-earth complexes are nonelectrolytes and the hydroxamino groups of the complexes have taken part in bonding. Infrared spectra, ultraviolet spectra, nuclear magnetic resonance (1HNMR) spectra, and fluorescence spectra were used to investigate the complexes. Experiments have proved that the complexes of Eu3+ and Tb3+ with aromatic hydroxamic acids have good fluorescent characteristics.

  16. Statistical Mechanics and Information-Theoretic Perspectives on Complexity in the Earth System

    Directory of Open Access Journals (Sweden)

    Konstantinos Eftaxias

    2013-11-01

    Full Text Available This review provides a summary of methods originated in (non-equilibrium statistical mechanics and information theory, which have recently found successful applications to quantitatively studying complexity in various components of the complex system Earth. Specifically, we discuss two classes of methods: (i entropies of different kinds (e.g., on the one hand classical Shannon and R´enyi entropies, as well as non-extensive Tsallis entropy based on symbolic dynamics techniques and, on the other hand, approximate entropy, sample entropy and fuzzy entropy; and (ii measures of statistical interdependence and causality (e.g., mutual information and generalizations thereof, transfer entropy, momentary information transfer. We review a number of applications and case studies utilizing the above-mentioned methodological approaches for studying contemporary problems in some exemplary fields of the Earth sciences, highlighting the potentials of different techniques.

  17. Helical ternary complexes of alkaline earth picrates with open-chain crown ether

    Institute of Scientific and Technical Information of China (English)

    刘伟生; 温永红; 刘雪原; 谭民裕

    2003-01-01

    Four solid complexes of alkaline earth picrates with N,N,N′,N′-tetraphenyl-3,6,9-tri- oxaundecanediamide (TTD), M (Pic)2TTD (1, M = Mg; 2, M = Ca; 3, M = Sr; 4, M = Ba), have been prepared and characterized by elemental analysis, conductivity measurement, IR spectra, 1H NMR spectra and TG-DTA techniques. Crystal structure of complex 3 shows that the Sr(Ⅱ) ion is 9-coordinated by five oxygen atoms from TTD and four oxygen atoms from two bidentate picrates, and the coordination polyhedron is distorted tricapped trigonal prism. TTD as a pentadentate ligand forms a right-handed helical coordination structure. The chelating helical chain has a relative fixed radius and then shows a high coordination selectivity to metal ion. The high selectivity of TTD to alkaline earth ions is explained elementarily from the special coordination structures.

  18. Synthesis and characterization of rare earth complexes with Phthalaldehyde-lysine Schiff base

    Institute of Scientific and Technical Information of China (English)

    Hu Meixian; Li Ning; Yao Kemin

    2006-01-01

    Ten new rare earth complexes with Schiff base (HL) derived from phthalaldehyde with two -CHO groups and lysine,which has unsymmetrical α-and ε-NH2 groups,were synthesized and characterized by elemental analysis,TG-DTA analysis,UV-Vis,IR,and 1H NMR spectra.They spectively.Furthermore,their coordination mechanism,spectral properties and probable molecular structures were also discussed.

  19. Determination of fluoride content in drinking water and tea infusions using fluoride ion selective electrode

    Directory of Open Access Journals (Sweden)

    Rajković Miloš B.

    2007-01-01

    Full Text Available Potentiometric analysis of fluoride content (as F- ion in solutions by using fluoride ion-selective electrode is simple, reliable and cheap. Very small concentrations of fluoride-ions (to 10-6 mol/dm3 can be determined by fluoride selective electrode, with regulation of ion strength of a solution and control of concentration of hydroxide ions and interfering ions of metals. The influence of pH and complexing ions of metals can be successfully regulated by the TISAB solution and by preserving pH value in the range from 5.00 to 7.00. The content of fluorides in the samples can be determined by the method of direct potentiometer, and in the case of very low concentration by standard addition method. In this paper it was analyzed the determination of fluoride ions concentration in bottled mineral waters and water from Belgrade plumbing in two Belgrade districts (Palilula and Novi Beograd and in tea, by using the fluoride selective electrode. It was determined that the content of fluoride ions in bottled mineral water significantly differs from values given on declaration, and that content of fluoride ions varies over a period of time. The content of fluoride ions in water from plumbing in two Belgrade districts at the time of analysis was significantly increased and exceeded values given in Regulation for drinking water quality. The received results from the analysis of fluorides in teas show that fluorides exist in teas in different concentrations. There are also differences between the same kinds of tea, which is noted with mint (Mentha piperitae folium, as a consequence of differences between soils where it was planted. As taking of fluorides, according to World Health Organisation recommendation (WHO, is limited in the range from 2 to 4 mg per day, it is necessary to give the content of fluorides on all products that are used in human consumption.

  20. Synthesis, Catalysis of Rare Earth Complexes with Aliphatic Noncyclic Polyether-Amino Acid Schiff Base

    Institute of Scientific and Technical Information of China (English)

    Li Ning; Yao Kemin; Shen Lianfang

    2005-01-01

    Eleven new rare earth complexes with aliphatic Schiff base, condensed from diglycol aldehyde and bis-arginine, were synthesized and characterized. They are confirmed as Ln(H2DAAR)(NO3)3·7H2O (Ln=La, Pr, Nd, Gd), Ln3(H2DAAR)2(NO3)9·5H2O (Ln=Dy, Y) and Ln2(H2DAAR)(NO3)6·3H2O (Ln=La, Nd, Sm, Gd), Ln3(DAAR)(NO3)7·4H2O (Ln=Dy, Yb, Y) respectively under different molar ratios of metal to ligand (DAAR=diglycol aldehyde bis-arginine). The present paper deals with a synthetic method and catalytic properties of obtained complexes. The result shows that proper pH value is important for synthesis of the complexes and compositions of the lighter and the heavier rare earth complexes are different under the same reaction condition. Some new complexes obtained have proved their catalytic activity and 80% conversion with the viscosity-average molecular weight 230,000 for the polymerization of methyl methacrylate (MMA) without addition of any cocatalyst.

  1. Investigation of properties of rare earth complexes with dibromo--methyl-methylsulfonazo by spectral correction technique

    Indian Academy of Sciences (India)

    Hong-Wen Gao; Fa-Shui Hong; Qing-Song Ye

    2000-12-01

    The reactions were sensitive between seven rare earth (RE) metals Nd(III), La(III), Ce(III), Pr(III), Sm(III), Eu(III) and Gd(III) and dibromo--methylmethylsulfonazo (DBMMSA) in acidic solution. The spectral correction method has been applied in the determination of properties of RE complexes instead of ordinary spectrophotometry. Composition ratios, real molar absorptivities ( ) and stepwise stability constants () of each of the RE complexes were determined easily because the method eliminated the absorption influence of excess of ligand on complex. Results showed that the cumulative values of the complexes were between 3 91 × 1014 and 2 34 × 1028 and the real (not apparent) absorptivity between 8 85 × 104 and 2 12 × 105 l mol-1cm-1 at 640 nm.

  2. Synthesis, characterization, and anticancer properties of rare earth complexes with Schiff base and o-phenanthroline

    Institute of Scientific and Technical Information of China (English)

    XU Dongfang; MA Shuzhi; DU Guangying; HE Qizhuang; SUN Dazhi

    2008-01-01

    Five novel ternary complexes of the rare earth ions with o-phenanthroline(Phen) and Schiff base salicylaldehyde L-phenyla-lanine(KHL) were synthesized in ethanol. Their compositions were characterized by elemental analysis, molar conductance, 1H NMR, FT-IR,and Raman spectra. The formulas of the complexes were verified to be RE(L)(Phen)Cl(H2O) (RE=La3+, Ce3+, Nd3+, Er3+, and Gd3+; L=Schiff base salicylaldehyde L-phenylalanine; phen=o-phenanthroline). Methyl thiazolyl tetrazolium (MTT) colorimetry and flow cytometry were used to test the anticancer effect of the complexes with K562 tumor cell. The research showed that the complexes could inhibit K562 tumor cell's growth, generation, and induce apoptosis. The inhibition ratio was accelerated by increasing the dosage, and it had significant positive correlation with the medication dosage.

  3. [Synthesis and fluorescence property of novel rare earth europium, terbium complexes with beta-diketone].

    Science.gov (United States)

    Ren, Xiao-Ming; Wei, Chang-Ping; Cheng, Guo; Lü, Jing-Wen

    2011-11-01

    A novel beta-diketone 1-(4-aminophenyl)-4,4,4-trifluorobutane-1, 3-dione(p-NBFA) was synthesized by Classical claisen condensation reaction. With p-NBFA as the first ligand and 1,10-phenanthroline(phen) as the secondary ligand, two new rare earth Eu(III), Tb(III) ternary complexes were prepared. Elemental analysis demonstrated that the compositions of the complexes were Eu(p-NBFA)3 phen and Tb(p-NBFA)3 phen. IR spectra indicated that rare earth ions were coordinated with oxygen atoms of the first ligand and two nitrogen atoms of the secondary ligand. UV spectra showed that the main absorption was from the first ligand in the complexes, the secondary ligand was acted as the synergistic coordination. Fluorescence spectra demonstrated that the emission intensity of Eu(p-NBFA)3 phen was obviously stronger than that of Tb(p-NBFA)3 phen. Further investigation showed that the emission intensity was influenced by the matching situation of energy level between the triplet state of ligand and the emission energy of rare earth ion. In Tb(p-NBFA)3phen, due to that the triplet state energy level of p-NBFA was too near to the energy level of 5D4, then the energy transfered back to the ligand, most of the excitation energy was consumed, so the terbium complex showed lower luminescence intensity and competitive luminescence of p-NBFA also appeared. In Eu(p-NB-FA)3phen, the energy level difference was well matched and the emission of europium complex was characteristic and high.

  4. Occupational fluoride exposure. [Review

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, H.C. (Univ. of California, San Francisco); Smith, F.A.

    1977-01-01

    Effects of airborne fluoride on industrial health are discussed with regard to acute and chronic effects. Injuries to lungs and skin from acute exposures are described. Chronic effects are discussed with regard to industrial sources of fluoride and air concentrations vs. urinary concentrations of fluoride. An extensive literature review is presented in the form of a table showing responses in man exposed to industrial airborne fluorides. Osteosclerosis is discussed with regard to the fluoride air standard, bone fluoride, and air fluoride concentrations. Occupational exposures to fluoride are also discussed with regard to arthritis, shortness of breath, asthma, upper respiratory infections, chronic respiratory disease, effects on kidneys, effects on pregnancy, and indices of fluoride intoxication. A table is presented showing references to studies on responses in neighborhood residents exposed to fluoride emissions. (HLW)

  5. The complex dynamics of the seasonal component of Earth's surface temperature

    Directory of Open Access Journals (Sweden)

    A. Vecchio

    2010-06-01

    Full Text Available The dynamics of the climate system has been investigated by analyzing the complex seasonal oscillation of monthly averaged temperatures recorded at 1167 stations covering the whole USA. We found the presence of an orbit-climate relationship on time scales remarkably shorter than the Milankovitch period related to the nutational forcing. The relationship manifests itself through occasional destabilization of the phase of the seasonal component due to the local changing of balance between direct insolation and the net energy received by the Earth. Quite surprisingly, we found that the local intermittent dynamics is modulated by a periodic component of about 18.6 yr due to the nutation of Earth, which represents the main modulation of the Earth's precession. The global effect in the last century results in a cumulative phase-shift of about 1.74 days towards earlier seasons, in agreement with the phase shift expected from Earth's precession. The climate dynamics of the seasonal cycle can be described through a nonlinear circle-map, indicating that the destabilization process can be associated to intermittent transitions from quasi-periodicity to chaos.

  6. Making a report of a short trip in an ophiolitic complex with Google Earth

    Science.gov (United States)

    Aubret, Marianne

    2017-04-01

    Plate tectonics is taught in French secondary school (lower and upper-sixth). According to the curriculum, the comprehension of plate-tectonic processes and concepts should be based on field data. For example, the Alpine's ocean history is studied to understand how mountain ranges are formed. In this context, Corsica is a great open-air laboratory, but unfortunately, the traffic conditions are very difficult in the island and despite the short distances, it's almost impossible for teachers to take their students to the remarkable geologic spots. The «défilé de l'Inzecca» is one of them: there you can see a part of the alpine's ophiolitic complex. The aim of this activity is to elaborate a « KMZ folder » in Google Earth as a report of a short trip thanks to the students' data field; it is also the occasion to enrich the Google Earth KMZ folder already available for our teaching.

  7. Effects of alkaline earth metal ion complexation on amino acid zwitterion stability: Results from infrared action spectroscopy

    NARCIS (Netherlands)

    Bush, M. F.; Oomens, J.; Saykally, R. J.; Williams, E. R.

    2008-01-01

    The structures of isolated alkaline earth metal cationized amino acids are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and theory. These results indicate that arginine, glutamine, proline, serine, and valine all adopt zwitterionic structures when complexed with diva

  8. Synthesis, Characterization and Fluorescence of Rare earth Nitrate Complexes with Triaza-crown Ether Derivative

    Institute of Scientific and Technical Information of China (English)

    胡晓黎; 崔书亚; 闫兰; 杨汝栋

    2003-01-01

    Four new complexes of rare earths with a triaza-crown ether (L) derived from N3O2-macro cycle 1,12,15-triaza-3, 4: 9,10-dibenzo-5, 8-dioxacycloheptadecane were synthesized and characterized by elemental analysis, IR, molar conductance, TG-DTA analysis and fluorescence spectra. The composition of the complexes determined as [RE(NO3)3L*3H2O]*H2O (RE=Sm, Eu, Tb and Dy). It is found that Sm3+, Eu3+, Tb3+ and Dy3+ complexes all show strong fluorescence emission in the solid state. Among these complexes, Tb3+ complex has the strongest luminescence intensity. It shows that the ligand L triplet state energy matches 5D4 energy level of Tb3+. In the Eu3+ complex, η(5D0→7F2/5D0→7F1) is 2.6, which indicates that Eu3+ locates at the asymmetric coordination field.

  9. Private Well Water and Fluoride

    Science.gov (United States)

    ... well. What do I need to know about fluoride and groundwater from a well? Fluoride is present ... well has less than the recommended level of fluoride for preventing tooth decay? The recommended fluoride level ...

  10. Fluoride and Water (For Parents)

    Science.gov (United States)

    ... Teaching Kids to Be Smart About Social Media Fluoride and Water KidsHealth > For Parents > Fluoride and Water ... in healthy tooth development and cavity prevention. About Fluoride Fluoride, which exists naturally in water sources, is ...

  11. Zirconium dioxide nanofilled poly(vinylidene fluoride-hexafluoropropylene) complexed with lithium trifluoromethanesulfonate as composite polymer electrolyte for electrochromic devices

    Energy Technology Data Exchange (ETDEWEB)

    Puguan, John Marc C.; Chinnappan, Amutha [Department of Energy and Biotechnology, Energy and Environment Fusion Technology Center, Myongji University, Yongin, Gyeonggi-do 449-728 (Korea, Republic of); Kostjuk, Sergei V. [Research Institute for Physical Chemical Problems, Belarusian State University, Minsk 220030 (Belarus); Kim, Hern, E-mail: hernkim@mju.ac.kr [Department of Energy and Biotechnology, Energy and Environment Fusion Technology Center, Myongji University, Yongin, Gyeonggi-do 449-728 (Korea, Republic of)

    2015-09-15

    Highlights: • Successful synthesis of electrolyte by blending PVdF-HFP, ZrO{sub 2} and LiCF{sub 3}SO{sub 3}. • ZrO{sub 2} increased electrolyte conductivity by two orders of magnitude. • ZrO{sub 2} doubled bulk mechanical strength of electrolyte in terms of Young’s modulus. • Electrolytes gave a optimum optical transmittance of 52.6%. - Abstract: Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) polymer electrolyte containing zirconium dioxide nanocrystals (ZrO{sub 2}-NC) and lithium trifluoromethanesulfonate (LiCF{sub 3}SO{sub 3}) has been synthesized using the conventional solution casting method. The addition of ZrO2-NC into the polymeric substrate gave remarkable properties in terms of the electrolyte’s ionic conductivity as well as its bulk mechanical strength. The enhanced amorphicity of the polymeric substrate due to ZrO{sub 2} and the nanofiller’s high dielectric constant make an excellent combination to increase the ionic conductivity (above 10{sup −4} S cm{sup −1}). Increasing the nanofiller content raises the ionic conductivity of the electrolyte by two orders of magnitude of which the optimum is 2.65 × 10{sup −4} S cm{sup −1} at 13.04 wt% ZrO{sub 2}-NC loading. Also, the Young’s modulus, an indicator of electrolyte’s mechanical stability, dramatically increased to 207 MPa upon loading 13.04 wt% ZrO{sub 2}-NC. Using UV–vis spectroscopy, the electrolytes with 13.04% ZrO{sub 2}-NC scanned from 200–800 nm wavelengths exhibited a maximum optical transmittance of 52.6% at 10 μm film thickness. The enhanced conductivity, high mechanical strength and reasonable optical transmittance shown by our composite polymer electrolyte make an excellent electrolyte for future energy saving smart windows such as electrochromic devices.

  12. Emission of Rare Earth Complex Tb0.5Eu0.5(asprin)3phen

    Institute of Scientific and Technical Information of China (English)

    沈鸿; 徐征; 陶栋梁; 徐怡庄; 章婷; 杨军

    2003-01-01

    The coprecipitate Tb0.5Eu0.5(asprin)3phen was synthesized. By doping the rare earth complex into polymer PVK, the EL device was fabricated with the structure of ITO/PVK∶RE/PBD/Al. Compared with the device using PVK/Eu(asprin)3phen blend as the light emitting layer, the emission of Eu3+ in the PVK/Tb0.5Eu0.5(asprin)3 phen blend is greatly enhanced along with the quenching of the emission of PVK.

  13. Water Fluoridation: A Critical Review of the Physiological Effects of Ingested Fluoride as a Public Health Intervention

    Science.gov (United States)

    2014-01-01

    Fluorine is the world's 13th most abundant element and constitutes 0.08% of the Earth crust. It has the highest electronegativity of all elements. Fluoride is widely distributed in the environment, occurring in the air, soils, rocks, and water. Although fluoride is used industrially in a fluorine compound, the manufacture of ceramics, pesticides, aerosol propellants, refrigerants, glassware, and Teflon cookware, it is a generally unwanted byproduct of aluminium, fertilizer, and iron ore manufacture. The medicinal use of fluorides for the prevention of dental caries began in January 1945 when community water supplies in Grand Rapids, United States, were fluoridated to a level of 1 ppm as a dental caries prevention measure. However, water fluoridation remains a controversial public health measure. This paper reviews the human health effects of fluoride. The authors conclude that available evidence suggests that fluoride has a potential to cause major adverse human health problems, while having only a modest dental caries prevention effect. As part of efforts to reduce hazardous fluoride ingestion, the practice of artificial water fluoridation should be reconsidered globally, while industrial safety measures need to be tightened in order to reduce unethical discharge of fluoride compounds into the environment. Public health approaches for global dental caries reduction that do not involve systemic ingestion of fluoride are urgently needed. PMID:24719570

  14. Water Fluoridation: A Critical Review of the Physiological Effects of Ingested Fluoride as a Public Health Intervention

    Directory of Open Access Journals (Sweden)

    Stephen Peckham

    2014-01-01

    Full Text Available Fluorine is the world’s 13th most abundant element and constitutes 0.08% of the Earth crust. It has the highest electronegativity of all elements. Fluoride is widely distributed in the environment, occurring in the air, soils, rocks, and water. Although fluoride is used industrially in a fluorine compound, the manufacture of ceramics, pesticides, aerosol propellants, refrigerants, glassware, and Teflon cookware, it is a generally unwanted byproduct of aluminium, fertilizer, and iron ore manufacture. The medicinal use of fluorides for the prevention of dental caries began in January 1945 when community water supplies in Grand Rapids, United States, were fluoridated to a level of 1 ppm as a dental caries prevention measure. However, water fluoridation remains a controversial public health measure. This paper reviews the human health effects of fluoride. The authors conclude that available evidence suggests that fluoride has a potential to cause major adverse human health problems, while having only a modest dental caries prevention effect. As part of efforts to reduce hazardous fluoride ingestion, the practice of artificial water fluoridation should be reconsidered globally, while industrial safety measures need to be tightened in order to reduce unethical discharge of fluoride compounds into the environment. Public health approaches for global dental caries reduction that do not involve systemic ingestion of fluoride are urgently needed.

  15. Rare Earth Metal Complexes of Bidentate Nitroxide Ligands: Synthesis and Electrochemistry.

    Science.gov (United States)

    Kim, Jee Eon; Bogart, Justin A; Carroll, Patrick J; Schelter, Eric J

    2016-01-19

    We report rare earth metal complexes with tri- and bidentate ligands including strongly electron-donating nitroxide groups. The tridentate ligand 1,3,5-tris(2'-tert-butylhydroxylaminoaryl)benzene (H3arene-triNOx) was complexed to cerium(IV) in a 2:1 ligand-to-metal stoichiometry as Ce(Harene-triNOx)2 (1). Cyclic voltammetry of this compound showed stabilization of the tetravalent cerium cation with a Ce(IV/III) couple at E1/2 = -1.82 V versus Fc/Fc(+). On the basis of the uninvolvement of the third nitroxide group in the coordination chemistry with the cerium(IV) cation, the ligand system was redesigned toward a simpler bidentate mode, and a series of rare earth metal-arene-diNOx complexes were prepared with La(III), Ce(IV), Pr(III), Tb(III), and Y(III), [RE(arene-diNOx)2](-) ([2-RE](-), RE = La, Pr, Y, Tb) and Ce(IV)(arene-diNOx)2, where H2arene-diNOx = 1,3-bis(2'-tert-butylhydroxylaminoaryl)benzene. The core structures were isostructural throughout the series, with three nitroxide groups in η(2) binding modes and one κ(1) nitroxide group coordinated to the metal center in the solid state. In all cases except Ce(IV)(arene-diNOx)2, electrochemical analysis described two subsequent, ligand-based, quasi-reversible redox waves, indicating that a stable [N-O•] group was generated on the electrochemical time scale. Chemical oxidation of the terbium complex was performed, and isolation of the resulting complex, Tb(arene-diNOx)2·CH2Cl2 (3·CH2Cl2), confirmed the assignment of the cyclic voltammograms. Magnetic data showed no evidence of mixing between the Tb(III) states and the states of the open-shell ligand.

  16. Fluoride varnish or fluoride mouth rinse?

    DEFF Research Database (Denmark)

    Keller, M K; Klausen, B J; Twetman, S

    2016-01-01

    OBJECTIVE: In many Danish communities, school-based fluoride programs are offered to children with high caries risk in adjunct to tooth brushing. The purpose of this field trial was to compare the caries-preventive effectiveness of two different fluoride programs in 6-12 year olds. BASIC RESEARCH...... different schools were enrolled after informed consent and their class unit was randomly allocated to one of two fluoride programs. INTERVENTIONS: One group received a semi-annual fluoride varnish applications (FV) and the other group continued with an existing program with fluoride mouth rinses once per...... in caries development over two years among children participating in a school-based fluoride varnish or mouth rinse program....

  17. Unravelling the Complexities of the Earth's Radiation Belts: Findings from the Van Allen Probes mission

    Science.gov (United States)

    Mauk, Barry; Fox, Nicola; Kessel, Ramona; Sibeck, David; Kanekal, Shri

    2014-05-01

    Within the first year of Van Allen Probe operations, team members made a series of highly publicized decisive discoveries concerning the structure and evolution of the Earth's radiation belts, the processes that energize particles there, and the locations where they operate. Nevertheless, much more extensive and less publicized findings from the Van Allen Probes suggest that Earth's radiation belts regions remain a highly complex and puzzling place. Although the relation between magnetic storm and radiation belt enhancements and loss has been emphasized, dynamics during non-storm periods has occasionally been shown to be dramatic. While emphasis has been placed on new findings regarding local non-adiabatic energization mechanisms, adiabatic mechanisms have also been shown to be important. Furthermore, the interplay between, and relative importance of, these and other energization processes remain uncertain. The role of seed populations has been highlighted, with some studies pointing to localized mechanisms and others pointing to the role of substorms in transporting and injecting such populations. Here we review some of the less publicized findings and future objectives of the Van Allen Probes mission to get a broader and in-depth view of present understanding of Earth's inner magnetosphere.

  18. Synthesis, characterization and luminescence properties of rare earth complexes with a new biphenylamide

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yan-Ling, E-mail: guoyl2004@163.com [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Dou, Wei; Wang, Yu-Jiao; Zhou, Xiao-Yan; Liu, Wei-Sheng [College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)

    2013-03-15

    A new amide-based ligand derived from biphenyl, N,N-dibenzyl-2-{l_brace}2 Prime -[(dibenzylcarbamoyl)-methoxy]-biphenyl-2-yloxy{r_brace} -acetamide (L), and its complexes of rare earth picrates were synthesized. The complexes were characterized by elemental analysis, IR, {sup 1}H NMR, UV-Vis spectra and conductivity measurements. Under the excitation, the europium(III) complex exhibited characteristic emissions of europium. The luminescence properties of the europium(III) complex in solid state and in CHCl{sub 3}, acetone, acetonitrile and DMF were investigated. The lifetime of the {sup 5}D{sub 0} level of the Eu{sup 3+} ion in the complex is 0.68 ms. The quantum yield {Phi} of the europium picrate complex was found to be 2.54 Multiplication-Sign 10{sup -3} with quinine sulfate as reference. The lowest triplet state energy level of the ligand indicates that the triplet state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion. - Highlights: Black-Right-Pointing-Pointer Synthesis of a new amide type podand and its lanthanide picrate complexes. Black-Right-Pointing-Pointer Characterization was done by elemental analysis, conductivity, IR, {sup 1}H NMR and UV-Vis. Black-Right-Pointing-Pointer Luminescence properties of Eu{sup 3+} complex were analyzed. Black-Right-Pointing-Pointer Triplet state energy level of ligand matches better to the resonance level of Eu{sup 3+} than Tb{sup 3+} ion.

  19. Formation and dynamics of "waterproof" photoluminescent complexes of rare earth ions in crowded environment.

    Science.gov (United States)

    Ignatova, Tetyana; Blades, Michael; Duque, Juan G; Doorn, Stephen K; Biaggio, Ivan; Rotkin, Slava V

    2014-12-28

    Understanding behavior of rare-earth ions (REI) in crowded environments is crucial for several nano- and bio-technological applications. Evolution of REI photoluminescence (PL) in small compartments inside a silica hydrogel, mimic to a soft matter bio-environment, has been studied and explained within a solvation model. The model uncovered the origin of high PL efficiency to be the formation of REI complexes, surrounded by bile salt (DOC) molecules. Comparative study of these REI-DOC complexes in bulk water solution and those enclosed inside the hydrogel revealed a strong correlation between an up to 5×-longer lifetime of REIs and appearance of the DOC ordered phase, further confirmed by dynamics of REI solvation shells, REI diffusion experiments and morphological characterization of microstructure of the hydrogel.

  20. Synthesis of glycine-containing complexes in impacts of comets on early Earth

    Science.gov (United States)

    Goldman, Nir; Reed, Evan J.; Fried, Laurence E.; William Kuo, I.-F.; Maiti, Amitesh

    2010-11-01

    Delivery of prebiotic compounds to early Earth from an impacting comet is thought to be an unlikely mechanism for the origins of life because of unfavourable chemical conditions on the planet and the high heat from impact. In contrast, we find that impact-induced shock compression of cometary ices followed by expansion to ambient conditions can produce complexes that resemble the amino acid glycine. Our ab initio molecular dynamics simulations show that shock waves drive the synthesis of transient C-N bonded oligomers at extreme pressures and temperatures. On post impact quenching to lower pressures, the oligomers break apart to form a metastable glycine-containing complex. We show that impact from cometary ice could possibly yield amino acids by a synthetic route independent of the pre-existing atmospheric conditions and materials on the planet.

  1. Preparation, Characterization and Luminescent Properties of MCM-41 Type Materials Impregnated with Rare Earth Complex

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hybrid materials incorporating Eu-(TTA)3.2H2O(hereafter designated as Eu-TTA, with TTA:thenoyltrifluoroacetone)in unmodified or modified MCM-41 by 3-aminopropyl-triethoxysilane (APTES)were prepared by impregnation method.The obtained materials were characterized using X-ray diffraction(XRD),IR and diffuse reflectance spectroscopy and luminescence spectra.All the hybrid samples exhibited the characteristic emission bands of Eu3+ under UV light excitation at room temperature, and the excitation spectra showed significant blue-shifts compared to the pure rare-earth complex. Although the red emission intensity in the modified hybrid was almost the half of the red emission intensity in the pure Eu-TTA complex at room temperature,the hybrid showed a much higher thermal stability due to the shielding character of the MCM-41host.

  2. On the existence of near-Earth-object meteoroid complexes producing meteorites

    Science.gov (United States)

    Trigo-Rodriguez, J.; Madiedo, J.; Williams, I.

    2014-07-01

    It is generally thought that meteorites are formed as a result of collisions within the main belt of asteroids [1]. They are delivered onto Earth-crossing orbits because of the effects of orbital resonances, primarily with Jupiter. About 15 meteorites are known where their passage through the atmosphere was observed and recorded, allowing the parameters of the pre-encounter orbit to be derived [2]. The cosmic-ray-exposure ages (CREAs) are suggesting that most meteorites have been exposed to cosmic rays for tens of millions of years (Myrs) [3], re-enforcing the belief that the process of modifying the orbit from being near-circular in the main belt to highly elliptical as an Earth-crossing orbit was a gradual process like the effects of resonance. However, there is growing evidence that some meteorite could originate directly from the near-Earth-object (NEO) population. A good example of this is the recent discovery of rare primitive groups in the Antarctic, an example being Elephant Moraine (EET) 96026: a C4/5 carbonaceous chondrite with a measured cosmic ray exposure age of only 0.28 Ma [4]. Here, we focus on recent dynamic links that have been established between meteorite-dropping bolides and NEOs that support the idea of short-life meteoroid streams that can generate meteoroids on Earth. The fact that such streams can exist allows rocky material from potentially-hazardous asteroids (PHA) to be sampled and investigated in the laboratory. The existence of meteoroid streams capable of producing meteorites has been proposed following the determination of accurate meteoroid orbits of fireballs obtained by the Canadian Meteorite Observation and Recovery Project (MORP) [5]. Some asteroids in the Earth's vicinity are undergoing both dynamical and collisional evolution on very short timescales [6]. Many of these objects are crumbly bodies that originated from the collisions between main-belt asteroids during their life-time. An obvious method of forming these complexes

  3. Rare earth ions enhanced near infrared fluorescence of Ag2S quantum dots for the detection of fluoride ions in living cells.

    Science.gov (United States)

    Ding, Caiping; Cao, Xuanyu; Zhang, Cuiling; He, Tangrong; Hua, Nan; Xian, Yuezhong

    2017-09-28

    In this work, a novel phenomenon was discovered that the fluorescence intensity of silver sulfide quantum dots (Ag2S QDs) could be enhanced in the presence of rare earth ions through aggregation-induced emission (AIE). Based on the strong coordination between rare earth ions and F(-), a facile and label-free strategy was developed for the detection of F(-) in living cells. Ag2S QDs were synthesized using 3-mercaptopropionic acid as sulfur source and stabilizer in aqueous solution. The near infrared (NIR) emitting QDs exhibited excellent photostalilty, high quantum yield and low toxic. Interestingly, the fluorescence intensity of QDs was obviously enhanced upon the addition of various rare earth ions, especially in the presence of Gd(3+). The AIE mechanism was proved via the TEM, zeta potential and dynamic light scattering analysis. Moreover, the coordination between rare earth ions and F(-) could lead to the quenching of fluorescence QDs due to the weakening the AIE. Based on these findings, we developed a highly sensitive and selective method for detection of F(-). The label-free NIR fluorescence probe was successfully used for F(-) bioimaging in live cells.

  4. Fluoride in diet

    Science.gov (United States)

    Diet - fluoride ... bones and teeth. Too much fluoride in the diet is very rare. Rarely, infants who get too ... of essential vitamins is to eat a balanced diet that contains a variety of foods from the ...

  5. Competition between humic acid and carbonates for rare earth elements complexation.

    Science.gov (United States)

    Pourret, Olivier; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

    2007-01-01

    The competitive binding of rare earth elements (REE) to humic acid (HA) and carbonates was studied experimentally at various pH and alkalinity values by combining ultrafiltration and inductively coupled plasma mass spectrometry techniques. The results show that the REE species occur as binary humate or carbonate complexes but not as ternary REE-carbonate-humate as previously proposed. The results also reveal the strong pH and alkalinity dependence of the competition as well as the existence of a systematic fractionation across the REE series. Specifically, carbonate complexation is at a maximum at pH 10 and increase with increasing alkalinity and with the atomic number of the REE (LuCO(3)>LaCO(3)). Modeling of the data using Model VI and recently published stability constants for complexation of REE by humic acid well reproduced the experimental data, confirming the ability of Model VI to accurately determine REE speciation in natural waters. This modeling also confirms the reliability of recently published stability constants. This work shed more light not only on the competition between carbonates and HA for REE complexation but also on the reliability of WHAM 6 and Model VI for calculating the speciation of REE with organic matter in alkaline organic-rich water.

  6. Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd, E-mail: gerd.meyer@uni-koeln.de

    2014-11-15

    Comproportionation reactions of rare-earth metal trihalides (RX{sub 3}) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ((T{sub 3}R{sub 11})X{sub 15}-type, P6{sub 3}/m), tetramers ((T{sub 4}R{sub 16})X{sub 28}(R{sub 4}) (P-43m), (T{sub 4}R{sub 16})X{sub 20} (P4{sub 2}/nnm), (T{sub 4}R{sub 16})X{sub 24}(RX{sub 3}){sub 4} (I4{sub 1}/a) and (T{sub 4}R{sub 16})X{sub 23} (C2/m) types of structure) and pentamers ((Ru{sub 5}La{sub 14}){sub 2}Br{sub 39}, Cc) of (TR{sub r}){sub n} (n=2–5) clusters. These oligomers are further enveloped by inner (X{sup i}) as well as outer (X{sup a}) halido ligands, which possess diverse functionalities and interconnect like oligomers through i–i, i–a and/or a–i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of (TR{sub 6}) octahedra via common edges are more frequent than trimers and pentamers, in which the (TR{sub r}) clusters share common faces. - Graphical abstract: Rare earth-metal cluster complexes with endohedral transition metal atoms (TR{sub 6}) may connect via common edges or faces to form dimers, trimers, tetramers and pentamers of which the tetramers are the most prolific. Packing effects and electron counts play an important role. - Highlights: • Rare-earth metal cluster complexes encapsulate transition metal atoms. • Oligomers are built via connection of octahedral clusters via common edges or faces. • Dimers through pentamers with closed structures are known. • Tetramers including a tetrahedron of endohedral atoms are the most prolific.

  7. Degradation of Extraction from Seaweed and Its Complex with Rare Earths for Organophosphorous Pesticides

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with RE on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The results showed that the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent.The residues of the pesticides treated by the extract decreased by 96.88%, 52.30%, 49.52%, and 22.88%, respectively, for chlorpyrifos, dichlorvos, omethoate, and dimethoate, and those by the complex decreased by 95.99%, 54.23%, 48.79%, and 25.66%, respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach sprayed with the complex were decreased by 90.64% and 76.56%, respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d. The fresh weight of brassica chinensis and cabbage increased by 28.62% and 18.72%, and their dry weight increased by 44.49% and 14.74%, respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia chinese were decreased by 36.36% and 50.00%, respectively, and their rate of decrease in cabbage was 40.00% and 75.00%, respectively, on 5th day after spraying with the complex, when compared with those in the vegetable from control. These results suggest that this complex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables.

  8. Energies of 4f^N and 4f^N-15d States Relative to Host Bands in Rare-earth-doped Fluorides

    Science.gov (United States)

    Thiel, C. W.; Joubert, M.-F.; Tkachuk, A.

    2005-03-01

    Energies of 4f^N states relative to crystal band states were measured for rare-earth ions in the optical host materials LiYF4, Na0.4Y0.6F2.2, and LaF3 using x-ray photoemission spectroscopy. Spectra were modeled to determine the valence band maximum and 4f^ electron binding energies in each material. These results were combined with 4f^N to 4f^N-15d transition energies to determine 5d binding energies for the lowest levels of excited 4f^N-15d configurations. While 4f^N ground-state energies vary within several eV of the valence band maximum for different rare-earth ions in each host, the lowest 4f^N-15d states have similar energies and are several eV below the bottom of the conduction band. A simple model accurately described 4f^N and 4f^N-15d binding energies across the entire series of rare-earth ions. These results improve the understanding of optical materials for lasers, phosphors, and spectral hole burning applications for optical signal processing and data storage.

  9. Synthesis and structural diversity of trivalent rare-earth metal diisopropylamide complexes.

    Science.gov (United States)

    Spallek, Tatiana; Heß, Oliver; Meermann-Zimmermann, Melanie; Meermann, Christian; Klimpel, Michael G; Estler, Frank; Schneider, David; Scherer, Wolfgang; Tafipolsky, Maxim; Törnroos, Karl W; Maichle-Mössmer, Cäcilia; Sirsch, Peter; Anwander, Reiner

    2016-09-21

    A series of rare-earth metal diisopropylamide complexes has been obtained via salt metathesis employing LnCl3(THF)x and lithium (LDA) or sodium diisopropylamide (NDA) in n-hexane. Reactions with AM : Ln ratios ≥3 gave ate complexes (AM)Ln(NiPr2)4(THF)n (n = 1, 2; Ln = Sc, Y, La, Lu; AM = Li, Na) in good yields. For smaller rare-earth metal centres such as scandium and lutetium, a Li : Ln ratio = 2.5 accomplished ate-free tris(amido) complexes Ln(NiPr2)3(THF). The chloro-bridged dimeric derivatives [Ln(NiPr2)2(μ-Cl)(THF)]2 (Ln = Sc, Y, La, Lu) could be obtained in high yields for Li : Ln = 1.6-2. The product resulting from the Li : La = 1 : 1.6 reaction revealed a crystal structure containing two different molecules in the crystal lattice, [La(NiPr2)2(THF)(μ-Cl)]2·La(NiPr2)3(THF)2. Recrystallization of the chloro-bridged dimers led to the formation of the monomeric species Ln(NiPr2)2Cl(THF)2 (Ln = Sc, Lu) and La(NiPr2)3(THF)2. The reaction of YCl3 and LDA with Li : Y = 2 in the absence of THF gave a bimetallic ate complex LiY(NiPr2)4 with a chain-like structure. For scandium, the equimolar reactions with LDA or NDA yielded crystals of tetrametallic mono(amido) species, {[Sc(NiPr2)Cl2(THF)]2(LiCl)}2 and [Sc(NiPr2)Cl2(THF)]4, respectively. Depending on the Ln(iii) size, AM, and presence of a donor solvent, ate complexes (AM)Ln(NiPr2)4(THF)n show distinct dynamic behaviour as revealed by variable temperature NMR spectroscopy. The presence of weak LnCH(iPr) β-agostic interactions, as indicated by Ln-N-C angles <105°, is corroborated by DFT calculations and NBO analysis.

  10. Fluoride glass fiber optics

    CERN Document Server

    Aggarwal, Ishwar D

    1991-01-01

    Fluoride Glass Fiber Optics reviews the fundamental aspects of fluoride glasses. This book is divided into nine chapters. Chapter 1 discusses the wide range of fluoride glasses with an emphasis on fluorozirconate-based compositions. The structure of simple fluoride systems, such as BaF2 binary glass is elaborated in Chapter 2. The third chapter covers the intrinsic transparency of fluoride glasses from the UV to the IR, with particular emphasis on the multiphonon edge and electronic edge. The next three chapters are devoted to ultra-low loss optical fibers, reviewing methods for purifying and

  11. XUV complex refractive indices of aerosols in the atmospheres of Titan and the primitive Earth

    Science.gov (United States)

    Gavilan, Lisseth; Neumann, Maciej; Bulkin, Pavel; Popescu, Horia; Steffan, Martin; Esser, Norbert; Carrasco, Nathalie

    2016-10-01

    The complex refractive indices of tholins, simulating aerosols in the atmosphere of Titan and the primitive earth, have been measured over a wide spectral range, including the soft X-ray, vacuum-ultraviolet (VUV), and UV-Visible. The soft X-ray and VUV spectral ranges are in particular relevant to radiative transfer models of solar irradiation of primitive atmospheres (Lammer et al. 2008) and may elucidate the (anti-)greenhouse potential of photochemical aerosols.Thin films were grown using the PAMPRE capacitively coupled plasma setup (Szopa et al. 2006; Carrasco et al. 2009). Gas mixtures consisting of CH4/N2 with 5:95 ratios were used to simulate Titan's atmospheric composition. For the primitive Earth, gas mixtures of N2/CO2/H2 and N2/CO2/CH4 were used as described in Fleury et al. (2014).State-of-the-art laboratory techniques were used to determine the refractive indices of such tholin films. These include VUV ellipsometry (performed in collaboration with the Metrology Light Source in Berlin) and synchrotron X-ray spectroscopy (performed at the SEXTANTS beamline of the SOLEIL synchrotron). While VUV spectroscopy reveals new electronic transitions due to plasmon resonances in tholins, X-ray spectra reveal the C and O absorption edges of these solids. The refractive indices are compared to results from Khare et al. (1984). Implications on the optical properties of these aerosol analogs on the radiative modeling of primitive atmospheres will be discussed.

  12. Earth-Facing Antenna Characterization in a Complex Ground Plane/Multipath Rich Environment

    Science.gov (United States)

    Welch, Bryan W.; Piasecki, Marie T.

    2015-01-01

    The Space Communications and Navigation (SCAN) Testbed was a Software Defined Radio (SDR)-based payload launched to the International Space Station (ISS) in July of 2012. The purpose of the SCAN Testbed payload was to investigate the applicability of SDRs to NASA space missions in an operational space environment, which means that a proper model for system performance in said operational space environment is a necessary condition. The SCAN Testbed has line-of-sight connections to various ground stations with its S-Band Earth-facing Near-Earth Network Low Gain Antenna (NEN-LGA). Any previous efforts to characterize the NEN-LGA proved difficult, therefore, the NASA Glenn Research Center built its own S-Band ground station, which became operational in 2015, and has been successfully used to characterize the NEN-LGAs in-situ pattern measurements. This methodology allows for a more realistic characterization of the antenna performance, where the pattern oscillation induced by the complex ISS ground plane, as well as shadowing effects due to ISS structural blockage are included into the final performance model. This paper describes the challenges of characterizing an antenna pattern in this environment. It will also discuss the data processing, present the final antenna pattern measurements and derived model, as well as discuss various lessons learned.

  13. Earth-Facing Antenna Characterization in Complex Ground Plane/Multipath Rich Environment

    Science.gov (United States)

    Welch, Bryan W.; Piasecki, Marie T.

    2015-01-01

    The Space Communications and Navigation (SCAN) Testbed was a Software Defined Radio (SDR)-based payload launched to the International Space Station (ISS) in July of 2012. The purpose of the SCAN Testbed payload was to investigate the applicability of SDRs to NASA space missions in an operational environment, which means that a proper model for system performance in said operational space environment is a necessary condition. The SCAN Testbed has line-of-sight connections to various ground stations with its S-Band Earth-facing Near-Earth-Network Low Gain Antenna (NEN-LGA). Any previous efforts to characterize the NEN-LGA proved difficult, therefore, the NASA Glenn Research Center built its own S-Band ground station, which became operational in 2015, and has been used successfully to characterize the NEN-LGA's in-situ pattern measurements. This methodology allows for a more realistic characterization of the antenna performance, where the pattern oscillation induced by the complex ISS ground plane, as well as shadowing effects due to ISS structural blockage are included into the final performance model. This paper describes the challenges of characterizing an antenna pattern in this environment. It will also discuss the data processing, present the final antenna pattern measurements and derived model, as well as discuss various lessons learned

  14. Nanoclays: Two-dimensional shuttles for rare earth complexes in aqueous solution

    Science.gov (United States)

    Lezhnina, M. M.; Bentlage, M.; Kynast, U. H.

    2011-08-01

    Nanoclays are shown to be attractive substrates in at least two major respects. Firstly, Hectorite analogous commercial clays ("Laponite") can facilitate the usage of luminescent rare earth ions in aqueous solution, as their adherence to the clay surface strongly reduces water coordination and thus enables dramatically improved emission intensities. This also holds true for complexes of Tb 3+, which coordinate water in their native crystalline state, as demonstrated for tris(bipyiridine) complexes. For these, the laponite interaction affords a 16-fold gain in emission intensity in aqueous solution over the dissolved complex. Secondly, the two-dimensional, disk-like morphology of the clays enables a sufficient proximity of Ce 3+ and Tb 3+ to allow an energy transfer even at comparably low solution concentrations. In partially laminated, solid powders the efficiencies of the corresponding interlayer species decrease due to intimate interactions with the surrounding silicate and interlayer water, which can, however be counteracted by keeping the disks apart with long-chain, alkylammonium cations as spacers between the disks.

  15. Bis(imidazolin-2-iminato) rare earth metal complexes: synthesis, structural characterization, and catalytic application.

    Science.gov (United States)

    Trambitas, Alexandra G; Melcher, Daniel; Hartenstein, Larissa; Roesky, Peter W; Daniliuc, Constantin; Jones, Peter G; Tamm, Matthias

    2012-06-18

    Reaction of anhydrous rare earth metal halides MCl(3) with 2 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH) and 2 equiv of trimethylsilylmethyl lithium (Me(3)SiCH(2)Li) in THF furnished the complexes [(Im(Dipp)N)(2)MCl(THF)(n)] (M = Sc, Y, Lu). The molecular structures of all three compounds were established by single-crystal X-ray diffraction analyses. The coordination spheres around the pentacoordinate metal atoms are best described as trigonal bipyramids. Reaction of YbI(2) with 2 equiv of LiCH(2)SiMe(3) and 2 equiv of the imino ligand Im(Dipp)NH in tetrahydrofuran did not result in a divalent complex, but instead the Yb(III) complex [(Im(Dipp)N)(2)YbI(THF)(2)] was obtained and structurally characterized. Treatment of [(Im(Dipp)N)(2)MCl(THF)(n)] with 1 equiv of LiCH(2)SiMe(3) resulted in the formation of [(Im(Dipp)N)(2)M(CH(2)SiMe(3))(THF)(n)]. The coordination arrangement of these compounds in the solid state at the metal atoms is similar to that found for the starting materials, although the introduction of the neosilyl ligand induces a significantly greater distortion from the ideal trigonal-bipyramidal geometry. [(Im(Dipp)N)(2)Y(CH(2)SiMe(3))(THF)(2)] was used as precatalyst in the intramolecular hydroamination/cyclization reaction of various terminal aminoalkenes and of one aminoalkyne. The complex showed high catalytic activity and selectivity. A comparison with the previously reported dialkyl yttrium complex [(Im(Dipp)N)Y(CH(2)SiMe(3))(2)(THF)(3)] showed no clear tendency in terms of activity.

  16. Coordination field calculation for rare earth complexes in dihedral symmetry field

    Institute of Scientific and Technical Information of China (English)

    范英芳; 杨频; 潘大丰; 王越奎

    1995-01-01

    The coordination field perturbation matrix element expressions about D2-field of the terms 2S+1Lf (J=0 - 8 and 7=1/2 - 15/2) with fN (N=1 -13) configuration have been derived The concrete forms of the DSCPCF parameters Akm in the dihedral field (D2, C2v) for various ligand numbers (5 -12) and their reducing behavior in the higher symmetry fields (D4, C4v, D2d, D4d, D2k, D4h and Oh) are discussed with the double sphere coordination point charge field (DSCPCF) model and the irreducible operator tensor method. Besides, the corresponding computational schemes have been developed and the computer program DSF.D has been compiled, which is applicable for the spectral analysis of the rare earth ion complexes with arbitrary ligand numbers in the dihedral, tetragonal and cubical symmetry fields.

  17. Interfacial assembly of sandwich mixed (Phthalocyaninato)(Porphyrinato) rare earth triple-decker complexes

    Energy Technology Data Exchange (ETDEWEB)

    Liu Qingyun [College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510 (China); Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Department of Chemistry, Shandong University, Jinan 250100 (China); Li Yong; Liu Hongguo [Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Department of Chemistry, Shandong University, Jinan 250100 (China); Jiang Jianzhuang [Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Department of Chemistry, Shandong University, Jinan 250100 (China); Department of Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Bian Yongzhong, E-mail: yzbian@sas.ustb.edu.cn [Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Department of Chemistry, Shandong University, Jinan 250100 (China); Department of Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2011-07-20

    Interfacial assembly of sandwich mixed (phthalocyaninato)(porphyrinato) rare earth triple-decker complexes [(Pc)Eu(Pc)Eu(TPyP)] (1) and [(TPyP)Sm(Pc)Sm(TPyP)] (2) (Pc = phthalocyaninate, TPyP = meso-tetrakis(4-pyridyl)porphyrinate) has been comparatively studied at the air/pure water and the air/CdCl{sub 2} aqueous solution subphase interfaces. Surface pressure-area isotherms revealed the remarkable increase of limiting mean molecular area of the triple-deckers with the presence of Cd{sup 2+}, suggesting the occurrence of in situ interfacial coordination. The formation of coordination bonds between the pyridyl groups of TPyP macrocycles in the triple-deckers and Cd{sup 2+} ions from the subphase was further supported by FT-IR spectroscopic data. Electronic absorption measurements showed the formation of J-aggregates of the triple-decker molecules in the interfacial assembled films.

  18. A major light rare-earth element (LREE) resource in the Khanneshin carbonatite complex, southern Afghanistan

    Science.gov (United States)

    Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Horton, Forrest; Buttleman, Kim; Scott, Emily R.

    2012-01-01

    The rapid rise in world demand for the rare-earth elements (REEs) has expanded the search for new REE resources. We document two types of light rare-earth element (LREE)-enriched rocks in the Khanneshin carbonatite complex of southern Afghanistan: type 1 concordant seams of khanneshite-(Ce), synchysite-(Ce), and parisite-(Ce) within banded barite-strontianite alvikite, and type 2 igneous dikes of coarse-grained carbonatite, enriched in fluorine or phosphorus, containing idiomorphic crystals of khanneshite-(Ce) or carbocernaite. Type 1 mineralized barite-strontianite alvikite averages 22.25 wt % BaO, 4.27 wt % SrO, and 3.25 wt % ∑ LREE2O3 (sum of La, Ce, Pr, and Nd oxides). Type 2 igneous dikes average 14.51 wt % BaO, 5.96 wt % SrO, and 3.77 wt % ∑ LREE2O3. A magmatic origin is clearly indicated for the type 2 LREE-enriched dikes, and type 1 LREE mineralization probably formed in the presence of LREE-rich hydrothermal fluid. Both types of LREE mineralization may be penecontemporaneous, having formed in a carbonate-rich magma in the marginal zone of the central vent, highly charged with volatile constituents (i.e., CO2, F, P2O5), and strongly enriched in Ba, Sr, and the LREE. Based on several assumptions, and employing simple geometry for the zone of LREE enrichment, we estimate that at least 1.29 Mt (million metric tonnes) of LREE2O3 is present in this part of the Khanneshin carbonatite complex.

  19. Mapping of second-nearest-neighbor fluoride ions of orthorhombic Gd 3+-Ag + complexes in CaF 2

    Science.gov (United States)

    Nakata, R.; Den Hartog, H. W.

    The ENDOR technique is applied to determine the positions of 24 second-nearest-neighbor F - ions around an orthorhombic Gd 3+-Ag + complex in CaF 2 crystals. Experimental ENDOR data of the second-nearest-neighbor F - ions are analyzed by using the usual spin Hamiltonian and a least-squares fitting method. The best fits of the experimental results give superhyperfine (shf) constants and the F - directions ( K, L, M) with respect to the Gd 3+ ion, from which the distance between the second-nearest-neighbor F - ion and the Gd 3+ ion is determined by assuming that the hyperfine interaction is due to the classical dipole-dipole interaction. The displacements of the F - ions are estimated and compared with the theoretical values calculated by Bijvank and den Hartog on the basis of a polarizable point charge model.

  20. Solid electrolytes for fluoride ion batteries: ionic conductivity in polycrystalline tysonite-type fluorides.

    Science.gov (United States)

    Rongeat, Carine; Reddy, M Anji; Witter, Raiker; Fichtner, Maximilian

    2014-02-12

    Batteries based on a fluoride shuttle (fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of fluoride families can be considered for electrolyte applications: alkaline-earth fluorides having a fluorite-type structure and rare-earth fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La(1-y)Ba(y)F(3-y) (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction mechanism in tysonite-type fluorides with a blocking effect of the grain boundaries. Heat treatment of the electrolyte material was performed and leads to an improvement of the ionic conductivity. This confirms the detrimental effect of grain boundaries and opens new route for the development of solid electrolytes for FIB with high ionic conductivities.

  1. Removal of fluoride from fluoride contaminated industrial waste water by electrolysis.

    Science.gov (United States)

    Joshi, Vijaya A; Nanoti, Madan V

    2003-01-01

    Wastewater containing fluoride are generally treated with lime or calcium salt supplemented with aluminium salts. Wastewater generated from different industries does not always behave in the same way due to the presence of interfering contaminants. A number of techniques have been developed and studied for the removal of excessive fluoride. Most of these are based on use of aluminium salt. In alum coagulation the sorption properties of product of hydrolysis of aluminium salts and capacity of fluoride for complex formation plays a very important role. These hydrolysis products of aluminium can be produced by passing direct current through aluminium electrode. The text presented in the paper deals with the various aspect of removal of fluoride by electrolysis using aluminium electrode from fluoride chemical based industrial wastewater.

  2. Are Modern Concepts of Complex Systems Science Useful for Earth Sciences? (Lewis Fry Richardson Medal Lecture)

    Science.gov (United States)

    Kurths, Jürgen

    2013-04-01

    The application of methods of complex systems science has a rich tradition in Earth sciences and has enabled substantially new insights into various complex processes there. However, some approaches and findings have been controversially discussed over the last decades. One reason is that they are often basing on strong restrictions and their violation may lead to pitfalls and misinterpretations. Here, we discuss three general concepts of complex systems science: synchronization, recurrence and complex networks and explain that they are indeed useful for better understanding phenomena as recent and past monsoon or El Nino, to detect paleoclimate-variability transitions which are related to human evolution and to identify teleconnections. References Marwan, N., Romano, M., Thiel, M., Kurths, J., Physics Reports 438, 237-329 (2007). Arenas, A., Diaz-Guilera, A., Kurths, J., Moreno, Y., Zhou, C., Physics Reports 469, 93-153 (2008). Marwan, N., Donges, J.F., Zou, Y., Donner, R. and Kurths, J., Phys. Lett. A 373, 4246 (2009). Donges, J.F., Zou, Y., Marwan, N. and Kurths, J. Europhys. Lett. 87, 48007 (2009). Donner, R., Zou, Y., Donges, J.F., Marwan, N. and Kurths, J., Phys. Rev. E 81, 015101(R) (2010). Mokhov, I. I., D. A. Smirnov, P. I. Nakonechny, S. S. Kozlenko, E. P. Seleznev, and J. Kurths, Geophys. Res. Lett. 38, L00F04 (2011). Donges, J., H. Schultz, N. Marwan, Y. Zou, J. Kurths, Eur. J. Phys. B 84, 635-651 (2011). Donges, J., R. Donner, M. Trauth, N. Marwan, H.J. Schellnhuber, and J. Kurths, PNAS 108, 20422-20427 (2011). Malik, N., B. Bookhagen, N. Marwan, and J. Kurths, Climate Dynamics 39, 971 (2012). Runge, J. , J. Heitzig, V. Petoukhov, J. Kurths, Phys. Rev. Lett. 108, 258701 (2012). Menck, P., J. Heitzig, N. Marwan, J. Kurths, Nature Physics (2013).

  3. Fluorescent naphthalene-based benzene tripod for selective recognition of fluoride in physiological condition

    Indian Academy of Sciences (India)

    Barun kumar Datta; Chirantan Kar; Gopal Das

    2015-02-01

    Aluminium complex of a naphthalene-based benzene tripod ligand system has been reported for the selective recognition of fluoride in aqueous medium in physiological condition. The ligand can selectively recognize Al3+ through enhancement in the fluorescence intensity and this in situ formed aluminium complex recognizes fluoride through quenching of fluorescence. The receptor system detects fluoride in nanomolar range. The sensing property was extended for practical utility to sense fluoride in tap water, pond water and river water.

  4. Automated bare earth extraction technique for complex topography in light detection and ranging surveys

    Science.gov (United States)

    Stevenson, Terry H.; Magruder, Lori A.; Neuenschwander, Amy L.; Bradford, Brian

    2013-01-01

    Bare earth extraction is an important component to light detection and ranging (LiDAR) data analysis in terms of terrain classification. The challenge in providing accurate digital surface models is augmented when there is diverse topography within the data set or complex combinations of vegetation and built structures. Few existing algorithms can handle substantial terrain diversity without significant editing or user interaction. This effort presents a newly developed methodology that provides a flexible, adaptable tool capable of integrating multiple LiDAR data attributes for an accurate terrain assessment. The terrain extraction and segmentation (TEXAS) approach uses a third-order spatial derivative for each point in the digital surface model to determine the curvature of the terrain rather than rely solely on the slope. The utilization of the curvature has shown to successfully preserve ground points in areas of steep terrain as they typically exhibit low curvature. Within the framework of TEXAS, the contiguous sets of points with low curvatures are grouped into regions using an edge-based segmentation method. The process does not require any user inputs and is completely data driven. This technique was tested on a variety of existing LiDAR surveys, each with varying levels of topographic complexity.

  5. A LADAR bare earth extraction technique for diverse topography and complex scenes

    Science.gov (United States)

    Neuenschwander, Amy L.; Stevenson, Terry H.; Magruder, Lori A.

    2012-06-01

    Bare earth extraction is an important component to LADAR data analysis in terms of terrain classification. The challenge in providing accurate digital models is augmented when there is diverse topography within the data set or complex combinations of vegetation and built structures. A successful approach provides a flexible methodology (adaptable for topography and/or environment) that is capable of integrating multiple ladar point cloud data attributes. A newly developed approach (TE-SiP) uses a 2nd and 3rd order spatial derivative for each point in the DEM to determine sets of contiguous regions of similar elevation. Specifically, the derivative of the central point represents the curvature of the terrain at that position. Contiguous sets of high (positive or negative) values define sharp edges such as building edges or cliffs. This method is independent of the slope, such that very steep, but continuous topography still have relatively low curvature values and are preserved in the terrain classification. Next, a recursive segmentation method identifies unique features of homogeneity on the surface separated by areas of high curvature. An iterative selection process is used to eliminate regions containing buildings or vegetation from the terrain surface. This technique was tested on a variety of existing LADAR surveys, each with varying levels of topographic complexity. The results shown here include developed and forested regions in the Dominican Republic.

  6. Advanced analysis of complex seismic waveforms to characterize the subsurface Earth structure

    Science.gov (United States)

    Jia, Tianxia

    2011-12-01

    This thesis includes three major parts, (1) Body wave analysis of mantle structure under the Calabria slab, (2) Spatial Average Coherency (SPAC) analysis of microtremor to characterize the subsurface structure in urban areas, and (3) Surface wave dispersion inversion for shear wave velocity structure. Although these three projects apply different techniques and investigate different parts of the Earth, their aims are the same, which is to better understand and characterize the subsurface Earth structure by analyzing complex seismic waveforms that are recorded on the Earth surface. My first project is body wave analysis of mantle structure under the Calabria slab. Its aim is to better understand the subduction structure of the Calabria slab by analyzing seismograms generated by natural earthquakes. The rollback and subduction of the Calabrian Arc beneath the southern Tyrrhenian Sea is a case study of slab morphology and slab-mantle interactions at short spatial scale. I analyzed the seismograms traversing the Calabrian slab and upper mantle wedge under the southern Tyrrhenian Sea through body wave dispersion, scattering and attenuation, which are recorded during the PASSCAL CAT/SCAN experiment. Compressional body waves exhibit dispersion correlating with slab paths, which is high-frequency components arrivals being delayed relative to low-frequency components. Body wave scattering and attenuation are also spatially correlated with slab paths. I used this correlation to estimate the positions of slab boundaries, and further suggested that the observed spatial variation in near-slab attenuation could be ascribed to mantle flow patterns around the slab. My second project is Spatial Average Coherency (SPAC) analysis of microtremors for subsurface structure characterization. Shear-wave velocity (Vs) information in soil and rock has been recognized as a critical parameter for site-specific ground motion prediction study, which is highly necessary for urban areas located

  7. Fluoride toothpastes and fluoride mouthrinses for home use

    OpenAIRE

    Andrew Rugg-Gunn; Jolan Bánóczy

    2013-01-01

    Objective. To provide a brief commentary review of fluoride-containing toothpastes and mouthrinses with emphasis on their use at home. Toothpastes and mouthrinses are just two of many ways of providing fluoride for the prevention of dental caries. The first investigations into incorporating fluoride into toothpastes and mouthrinses were reported in the middle 1940s. Unlike water fluoridation (which is ‘automatic fluoridation’), fluoride-containing toothpastes and fluoride-containing mouthrins...

  8. Exraction and separation of CERIUM(IV)/FLUORINE in fluoride-bearing cerium sulfate solution with fluoride coordination agent

    OpenAIRE

    Li, Y; J. G. He; X. X. Xue; Ru, H. Q.; X. W. Huang; Yang, H.

    2014-01-01

    In this paper the extraction and separation of cerium/fluorine in fluoride-bearing cerium sulfate solution with fluoride coordination agent has been studied. The UV-vis spectra suggest that Zr6+ and Al3+ can scrub the F- from [CeF2] 2+ complex. The separation and conductivity studies show that aluminum salt is the most suitable fluoride coordination agent, and an ion-exchange reaction is involved between Ce4+/ [CeF2] 2+ and hydrogen ion.

  9. Synthesis and relaxivity of polycarboxylic hydrazone rare earth complexes--Relaxivity of a -oxo-pentanedioic acid benzoyl hydrazone Gd-complexes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Synthesis of ligand, a -oxo-pentanedioic acid benzoyl hydrazone (H2LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and 1H NMR spectra. Besides, relaxivity (R1) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R1=8.05 mmol.L-1.s-1. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD50) is equal to (468.2±30) mg/kg.

  10. Study on Adsorption Behavior of Rare Earth Complexes on Nanometer-Size Titanium Dioxide with ICP-AES

    Institute of Scientific and Technical Information of China (English)

    梁沛; 江祖成; 胡斌; 秦永超

    2003-01-01

    A new method of using nanometer TiO2 as solid-phase extractant coupled with ICP-AES was proposed for speciation of rare earth elements. The adsorption behavior of rare earth complexes on nanometer TiO2 was investigated. Effect of pH value, contact time, elution solution and interfering ions on the recovery of the rare earth complexes were studied. A quantitative recovery (>90%) was found in the pH range of 4~9.0 for Eu-citric, 4.5~9.0 for Eu-oxine and Eu-HIBA, and 6.5~9.0 for Eu3+. Eu-EDTA can not be adsorbed in the pH range studied. There is large difference in the adsorption behavior on nanometer TiO2 between rare earth element and its complexes. The possibility of application of nanometer TiO2 on the speciation of rare earth element was explored.

  11. Microcalorimetric study on host-guest complexation of naphtho-15-crown-5 with four ions of alkaline earth metal

    Institute of Scientific and Technical Information of China (English)

    SONG Ming-zhi; ZHU Lan-ying; GAO Xi-ke; DOU Jian-min; SUN De-zhi

    2005-01-01

    Thermodynamic parameters of complexation of naphto- 15-crown-5 with four alkaline earth ions in aqueous media was determined using titration microcalorimetry at 298.15 K. The stability of the complexes, thermal effect and entropy effect of the complexation is discussed on the basis of the guest ions structure and the solvent effect. The stability constants tendency to vary with ion radius was interpreted. Complex of naphtha-15-crown-5 with calcium ion is very stable due to the synergism of static electric interaction and size selectivity between the host and the guest.

  12. Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides

    Directory of Open Access Journals (Sweden)

    Hiroki Iwanaga

    2010-07-01

    Full Text Available The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs and security media. The thermodynamic properties of Eu(III complexes are correlated with the solubility. Correlations between coordination structures and emission intensity were explained by NMR analysis. The luminous flux of red LED devices with Eu(III complexes is very high (20 mA, 870 m lumen. A new white LED has its largest spectra intensity in the red region and a human look much more vividly under this light.

  13. Fluoride removal by adsorption on thermally treated lateritic soils

    Directory of Open Access Journals (Sweden)

    Kefyalew Gomoro

    2012-12-01

    Full Text Available The ability of lateritic soils to remove fluoride from water has been studied. Important issues considered in the study include the relation between the mineral composition of soils and their ability to remove fluoride, the effect of thermal treatment of the soil on fluoride removal; the predominant fluoride containing species remain in the treated water and the possible mechanism of fluoride removal by lateritic soils. The fluoride removal capacity of thermally treated lateritic soils used in this study is in the range of 22 to 47 mmol/kg. The maximum capacity of 47 mmol/kg was obtained for RGS fired at 500 oC. The results obtained indicate that there is strong correlation between fluoride removal capacity and gibbsite content of the soil. From this it can be concluded that gibbsite is the active component in lateritic soils that strongly influence the fluoride removal capability. Speciation analysis reveals that at low initial fluoride concentrations the dissolution of gibbsite is facilitated by the adsorption of fluoride onto gibbsite. This may result in the formation of aluminum fluoro complexes in water.DOI: http://dx.doi.org/10.4314/bcse.v26i3.5

  14. Using modular 3D digital earth applications based on point clouds for the study of complex sites

    NARCIS (Netherlands)

    Martinez-Rubi, O.; Kleijn, M. de; Verhoeven, S.; Drost, N.; Attema, J.; Meersbergen, M. van; Nieuwpoort, R. van; Hond, R. de; Dias, E.; Svetachov, P.

    2016-01-01

    This article discusses the use of 3D technologies in digital earth applications (DEAs) to study complex sites. These are large areas containing objects with heterogeneous shapes and semantic information. The study proposes that DEAs should be modular, have multi-tier architectures, and be developed

  15. STUDY ON POLYMER-RARE EARTH METAL ION COMPLEXES I. FLUORESCENT PROPERTIES OF POLY(ACRYLIC ACID-CO-4-VINYLPYRIDINE)-RARE EARTH METAL COMPLEXES

    Institute of Scientific and Technical Information of China (English)

    LU Hong; FANG Shibi; JIANG Yingyan

    1987-01-01

    A kind of copolymer of acrylic acid and vinylpyridine was synthesized and the fluorescent properties of the complexes of the copolymer with Eu3+ or Tb3+ were studied. It was found that the fluorescence intensity of the complexes of the copolymer with Eu3+ was 20 times as high as that of the complexes of polyacrylic acid with Eu3+ and twice as high as that of the complexes of polyvinylpyridine with Eu3+. The effects of the composition of the copolymer and the content of Eu3+ or Tb3+ in the complexes were studied.The fluorescence lifetime of the complexes was measured and it was found that two or more kinds of energy transfer mechanism existed.

  16. Fluoride contamination in rain water of Sigrauli region

    Energy Technology Data Exchange (ETDEWEB)

    Chaurasia, S.; Mishra, S.K. [Mahatma Gandhi Chitrakoot Gramodaya, Chitrakoot (India)

    2007-07-01

    In this paper fluoride was monitored in rain water during rainy season at seven locations of Sigrauli region in 2004. The sampling location covered the impact of industrial complex of the area, and its impact on surface water sources monitored for the fluoride, pH, and electrical conductivity. The higher concentration of fluoride in rain water was observed 2.03 mg/L at Dudhar and in ponds water highest value was 3.14 mg/L. This suggested that serious fluoride pollution is occurring in Singrauli region posing a threat to the health and livelihood of the people of the region. Fluoride transported by the air route from coal burning emissions of large thermal power plants concentrate in small geographical area, and industries. Fluoride pollution in Singrauli area deserve intensive scientific studies and urgent attention. 2 figs., 2 tabs.

  17. Surface structure of the Ag-In-(rare earth) complex intermetallics

    Science.gov (United States)

    Hars, S. S.; Sharma, H. R.; Smerdon, J. A.; Yadav, T. P.; Al-Mahboob, A.; Ledieu, J.; Fournée, V.; Tamura, R.; McGrath, R.

    2016-05-01

    We present a study of the surface structure of the Ag-In-RE (RE: rare-earth elements Gd, Tb, and Yb) complex intermetallics using scanning tunneling microscopy and low-energy electron diffraction. The surface of the Ag-In-Yb approximant prepared by sputter-annealing methods under ultrahigh-vacuum conditions produces a flat (100) surface with no facets. However, the Ag-In-Gd and Ag-In-Tb 1/1 approximants, which have a surface miscut of about 12∘ relative to the (100) plane, develop surface facets along various crystallographic directions. The structure of each facet can be explained as a truncation of the rhombic triacontahedral clusters, i.e., the main building blocks of these systems. Despite their differences in atomic structure, symmetry, and density, the facets show common features. The facet planes are In rich. The analysis of the nearest-neighbor atom distances suggests that In atoms form bonds with the RE atoms, which we suggest is a key factor that stabilizes even low-density facet planes.

  18. Orbital modulation of millennial-scale climate variability in an earth system model of intermediate complexity

    Directory of Open Access Journals (Sweden)

    T. Friedrich

    2009-07-01

    Full Text Available The effect of orbital variations on simulated millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC is studied using the earth system model of intermediate complexity LOVECLIM. It is found that for present-day topographic boundary conditions low obliquity values (~22.1° favor the triggering of internally generated millennial-scale variability in the North Atlantic region. Reducing the obliquity leads to changes of the pause-pulse ratio of the corresponding AMOC oscillations. Stochastic excitations of the density-driven overturning circulation in the Nordic Seas can create regional sea-ice anomalies and a subsequent reorganization of the atmospheric circulation. The resulting remote atmospheric anomalies over the Hudson Bay can release freshwater pulses into the Labrador Sea leading to a subsequent reduction of convective activity. The millennial-scale AMOC oscillations disappear if LGM bathymetry (with closed Hudson Bay is prescribed. Furthermore, our study documents the marine and terrestrial carbon cycle response to millennial-scale AMOC variability. Our model results support the notion that stadial regimes in the North Atlantic are accompanied by relatively high levels of oxygen in thermocline and intermediate waters off California – in agreement with paleo-proxy data.

  19. Study on fluorescence properties of rare earth complexes influenced bysteric effect

    Institute of Scientific and Technical Information of China (English)

    YUAN Wei; XU Yizhuang; CUI Yumin; SHI Ruijuan; TAO Dongliang; WANG Yongzhong; ZHANG Wenbao; CHEN Jitang; SUN Lin; LIU Shaoxuan

    2011-01-01

    The rare earth complexes Th(o-BrBA)3,Tb(m-BrBA)3 and Tb(p-BrBA)3 were synthesized using o-,m-,p-bromo benzoic acids (2-bromo benzoic acid,3-bromo benzoic acid and 4-bromo benzoic acid) as ligand,respectively.The UV spectra showed that the absorption ability of Th(m-BrBA)3 was the strongest.However,the fluorescent intensity of Th(o-BrBA)3 was the weakest.The effect of the molecular structure,the energy level of Tb3+ and energy transfer efficiency from ligands to Tb3+ were discussed to explain the experimental results.The results indicated that,due to the large atomic radius of bromine,the steric effect caused by the different substitution bromine on the benzene ring might strongly affect the bond length formed by the coordination atoms and Tb3+.The longer the bond length was,the lower the efficiency of energy transfer was,and the weaker the fluorescent intensity was.

  20. Mechanisms and time scales of glacial inception simulated with an Earth system model of intermediate complexity

    Directory of Open Access Journals (Sweden)

    R. Calov

    2009-02-01

    Full Text Available We investigate glacial inception and glacial thresholds in the climate-cryosphere system utilising the Earth system model of intermediate complexity CLIMBER-2, which includes modules for atmosphere, terrestrial vegetation, ocean and interactive ice sheets. The latter are described by the three-dimensional polythermal ice-sheet model SICOPOLIS. A bifurcation which represents glacial inception is analysed with two different model setups: one setup with dynamical ice-sheet model and another setup without it. The respective glacial thresholds differ in terms of maximum boreal summer insolation at 65° N (hereafter referred as Milankovich forcing (MF. The glacial threshold of the configuration without ice-sheet dynamics corresponds to a much lower value of the MF compared to the full model. If MF attains values only slightly below the aforementioned threshold there is fast transient response. Depending on the value of MF relative to the glacial threshold, the transient response time of inland-ice volume in the model configuration with ice-sheet dynamics ranges from 10 000 to 100 000 years. We investigate implications of these time scales for past glacial inceptions and for the overdue Holocene glaciation hypothesis by Ruddiman (W. F. Ruddiman, Climatic Change 2003, Vol. 61, 261–293. We also have shown that the asynchronous coupling between climate and inland-ice components allows one sufficient realistic simulation of glacial inception and, at the same time, a considerable reduction of computational costs.

  1. Photovoltaic and Electroluminescence Bifunctional Devices with Starburst Amine and Rare-Earth-Complexes

    Institute of Scientific and Technical Information of China (English)

    WEN Fu-Shan; LI Wen-Lian; WEI Han-Zhi; LIU Yun-Qi; KIM Jin-Hyeok

    2007-01-01

    We fabricate the organic photovoltaic (P V) devices, in which 4,4',4"-tris-(2-methylphenylphenylamino)triphenylamine (m-MTDATA) and rare earth (RE) (dibenzoylmethanato)3(bathohenanthroline) (RE(DBM)3bath) (RE = Nd or Pr) are used as electron donor and acceptor, and investigate their PV properties. The PV diode fabricated in the ptimum processing conditions shows the open-circuit voltage of 1.91 V, short-circuit current of 0.1mA/cm2, fill factor of 0.38, and the overall power conversion efficiency of 1.9% when it is irradiated under UV light (4mW/cm2). The photocurrent density exhibits an increase of 20% at least when a very thin LiF layer is inserted between the RE-complexes and the Al cathode. A strong electroluminescence from the interface is also observed and the maximum luminance of a yellow emission resulted from the exciplex is 580 cd/m2 at 17V bias.

  2. Thermochemical analysis on rare earth complex of gadolinium with salicylic acid and 8-hydroxyquinoline

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Sheng-Xiong, E-mail: 54xsx@163.com [Hunan Provincial Key Laboratory of Rare-Precious Metals Compounds and Applications, Department of Chemistry and Life Science, Xiangnan University, Chenzhou 423000, Hunan Province (China); Li, Ai-Tao; Jiang, Jian-Hong; Huang, Shuang; Xu, Xiao-Yan; Li, Qiang-Guo [Hunan Provincial Key Laboratory of Rare-Precious Metals Compounds and Applications, Department of Chemistry and Life Science, Xiangnan University, Chenzhou 423000, Hunan Province (China)

    2012-11-20

    Highlights: Black-Right-Pointing-Pointer A new novel rare earth complex Gd(C{sub 7}H{sub 5}O{sub 3}){sub 2}{center_dot}(C{sub 9}H{sub 6}NO) was synthesized and characterized. Black-Right-Pointing-Pointer The dissolution enthalpies of the relevant substances were determined. Black-Right-Pointing-Pointer The enthalpy change of the reaction was determined to be (211.54 {+-} 0.69) kJ mol{sup -1}. Black-Right-Pointing-Pointer The standard molar enthalpy of formation of complex was -(1890.7 {+-} 3.1) kJ mol{sup -1}. - Abstract: The rare earth complex, Gd(C{sub 7}H{sub 5}O{sub 3}){sub 2}{center_dot}(C{sub 9}H{sub 6}NO), was synthesized by the reaction of Gadolinium nitrate hexahydrate with salicylic acid (C{sub 7}H{sub 6}O{sub 3}) and 8-hydroxyquinoline (C{sub 9}H{sub 7}NO). And it was characterized by elemental analysis, UV spectra, IR spectra, molar conductance and thermogravimetric analysis. In a optimalizing calorimetric solvent, the dissolution enthalpies were determined by an advanced solution-reaction isoperibol microcalorimeter, respectively: {Delta}{sub s}H{sub m}{sup {Theta}} [2 C{sub 7}H{sub 6}O{sub 3}(s) + C{sub 9}H{sub 7}NO(s), 298.15 K] = 41.95 {+-} 0.44 kJ mol{sup -1}, {Delta}{sub s}H{sub m}{sup {Theta}} [Gd(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O(s), 298.15 K] = -29.11 {+-} 0.39 kJ mol{sup -1}, {Delta}{sub s}H{sub m}{sup {Theta}} [Gd(C{sub 7}H{sub 5}O{sub 3}){sub 2}{center_dot}(C{sub 9}H{sub 6}NO)(s), 298.15 K] = -46.99 {+-} 0.39 kJ mol{sup -1} and {Delta}{sub s}H{sub m}{sup {Theta}} [Solution D(aq), 298.15 K] = -90.33 {+-} 0.37 kJ mol{sup -1}. The enthalpy change of the synthesized reaction was estimated to be {Delta}{sub r}H{sub m}{sup {Theta}}=211.54{+-}0.69 kJ mol{sup -1}. From data in the literature, through Hess' law, the standard molar enthalpy of formation of Gd(C{sub 7}H{sub 5}O{sub 3}){sub 2}{center_dot}(C{sub 9}H{sub 7}NO)(s) was calculated to be {Delta}{sub f}H{sub m}{sup {Theta}} [Gd(C{sub 7}H{sub 5}O{sub 3}){sub 2}{center_dot}(C{sub 9}H

  3. Historical and idealized climate model experiments: an intercomparison of Earth system models of intermediate complexity

    Directory of Open Access Journals (Sweden)

    M. Eby

    2013-05-01

    Full Text Available Both historical and idealized climate model experiments are performed with a variety of Earth system models of intermediate complexity (EMICs as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO2, additional greenhouse gases, land use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20th century trends in surface air temperature and carbon uptake are reasonably well simulated when compared to observed trends. Land carbon fluxes show much more variation between models than ocean carbon fluxes, and recent land fluxes appear to be slightly underestimated. It is possible that recent modelled climate trends or climate–carbon feedbacks are overestimated resulting in too much land carbon loss or that carbon uptake due to CO2 and/or nitrogen fertilization is underestimated. Several one thousand year long, idealized, 2 × and 4 × CO2 experiments are used to quantify standard model characteristics, including transient and equilibrium climate sensitivities, and climate–carbon feedbacks. The values from EMICs generally fall within the range given by general circulation models. Seven additional historical simulations, each including a single specified forcing, are used to assess the contributions of different climate forcings to the overall climate and carbon cycle response. The response of surface air temperature is the linear sum of the individual forcings, while the carbon cycle response shows a non-linear interaction between land-use change and CO2 forcings for some models. Finally, the preindustrial portions of the last millennium simulations are used to assess historical model carbon-climate feedbacks. Given the specified forcing, there

  4. Complex inner core of the Earth: The last frontier of global seismology

    Science.gov (United States)

    Tkalčić, Hrvoje

    2015-03-01

    The days when the Earth's inner core (IC) was viewed as a homogeneous solid sphere surrounded by the liquid outer core (OC) are now behind us. Due to a limited number of data sampling the IC and a lack of experimentally controlled conditions in the deep Earth studies, it has been difficult to scrutinize competitive hypotheses in this active area of research. However, a number of new concepts linking IC structure and dynamics has been proposed lately to explain different types of seismological observations. A common denominator of recent observational work on the IC is increased complexity seen in IC physical properties such as its isotropic and anisotropic structure, attenuation, inner core boundary (ICB) topography, and its rotational dynamics. For example, small-scale features have been observed to exist as a widespread phenomenon in the uppermost inner core, probably superimposed on much longer-scale features. The characterization of small-scale features sheds light on the nature of the solidification process and helps in understanding seismologically observed hemispherical dichotomy of the IC. The existence of variations in the rate and level of solidification is a plausible physical outcome in an environment where vigorous compositional convection in the OC and variations in heat exchange across the ICB may control the process of crystal growth. However, further progress is hindered by the fact that the current traveltime data of PKIKP waves traversing the IC do not allow discriminating between variations in isotropic P wave velocity and velocity anisotropy. Future studies of attenuation in the IC might provide crucial information about IC structure, although another trade-off exists—that of the relative contribution of scattering versus viscoelastic attenuation and the connection with the material properties. Future installations of dense arrays, cross paths of waves that sample the IC, and corresponding array studies will be a powerful tool to image and

  5. Fluoride Rinses, Gels and Foams

    DEFF Research Database (Denmark)

    Twetman, Svante; Keller, Mette K

    2016-01-01

    AIM: The aim of this conference paper was to systematically review the quality of evidence and summarize the findings of clinical trials published after 2002 using fluoride mouth rinses, fluoride gels or foams for the prevention of dental caries. METHODS: Relevant papers were selected after...... (6 on fluoride mouth rinse, 10 on fluoride gel and 3 on fluoride foam); 6 had a low risk of bias while 2 had a moderate risk. All fluoride measures appeared to be beneficial in preventing crown caries and reversing root caries, but the quality of evidence was graded as low for fluoride mouth rinse......, moderate for fluoride gel and very low for acidulated fluoride foam. No conclusions could be drawn on the cost-effectiveness. CONCLUSIONS: This review, covering the recent decade, has further substantiated the evidence for a caries-preventive effect of fluoride mouth rinse, fluoride gel and foam...

  6. Fluorides and non-fluoride remineralization systems.

    Science.gov (United States)

    Amaechi, Bennett T; van Loveren, Cor

    2013-01-01

    Caries develops when the equilibrium between de- and remineralization is unbalanced favoring demineralization. De- and remineralization occur depending on the degree of saturation of the interstitial fluids with respect to the tooth mineral. This equilibrium is positively influenced when fluoride, calcium and phosphate ions are added favoring remineralization. In addition, when fluoride is present, it will be incorporated into the newly formed mineral which is then less soluble. Toothpastes may contain fluoride and calcium ions separately or together in various compounds (remineralization systems) and may therefore reduce demineralization and promote remineralization. Formulating all these compounds in one paste may be challenging due to possible premature calcium-fluoride interactions and the low solubility of CaF2. There is a large amount of clinical evidence supporting the potent caries preventive effect of fluoride toothpastes indisputably. The amount of clinical evidence of the effectiveness of the other remineralization systems is far less convincing. Evidence is lacking for head to head comparisons of the various remineralization systems. Copyright © 2013 S. Karger AG, Basel.

  7. Main group chemistry of 9-hydroxophenalenone: Syntheses and structural characterization of the alkaline earth and zinc complexes

    Indian Academy of Sciences (India)

    Arup Mukherjee; Prinson P Samuel; Carola Schulzke; Swadhin K Mandal

    2014-09-01

    Herein, we report the synthesis and characterization of 9-hydroxophenalenone based alkaline earth and zinc complexes.The reaction of 9-hydroxophenalenone (HO,O-PLY (1)) with one equivalent of KN(SiMe3)2 and MI2 in THF yields heteroleptic complexes [(O,O-PLY)M(THF)]I [M= Mg (2), Ca (3), Sr (4), Ba (5); n = 1-4], while use of two equivalents of KN(SiMe3)2 in THF (with respect to PLY) produces homoleptic complex (O,O-PLY)2Mg(THF)2 (6). Moreover, reaction between two equivalents of 1 with one equivalent of ZnMe2 in THF produces complex (O,O-PLY)2Zn(THF)2 (7). All these complexes were characterized by NMR spectroscopy and elemental analyses. The solid state structures of complexes 2, 6 and 7 were established by single crystal X-ray diffraction analysis.

  8. PRODUCTION OF THORIUM FLUORIDE

    Science.gov (United States)

    Zachariasen, W.H.

    1959-08-11

    A process is presented for producing anhydrous thorium fluoride comprising the step of contacting a saturated aqueous solution of thorium nitrate with an aqueous solution of hydrofluoric acid having a concentration of about 45 to 50% by weight at a temperature above 70 deg C whereby anhydrous thorium fluoride precipitates.

  9. Responding to complex societal challenges: A decade of Earth System Science Partnership (ESSP) interdisciplinary research

    NARCIS (Netherlands)

    Ignaciuk, A.; Rice, M.; Bogardi, J.; Canadell, J.G.; Dhakal, S.; Ingram, J.; Leemans, R.; Rosenberg, M.

    2012-01-01

    The Earth system is an integrated, self-regulating system under increasing pressure from anthropogenic transformation. The Earth System Science Partnership (ESSP), which was established by the international global environmental change research programs (i.e., DIVERSITAS, IGBP, IHDP and WCRP) facilit

  10. Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

    Science.gov (United States)

    Deng, Y.; Nordstrom, D.K.; Blaine, McCleskey R.

    2011-01-01

    Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1–10), temperature, and high concentrations of fluoride (up to 50 mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50 °C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006–2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from 99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H+ and Al3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3–30% for more than 90% of samples at or above 10−6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F−, and major complexes (HF(aq)0">HF(aq)0, AlF2+, AlF2+">AlF2+and AlF30">AlF30) account for more than 95% of total fluoride. Occasionally, some complex species like AlF4-">AlF4-, FeF2+, FeF2+">FeF2+, MgF+ and BF2(OH)2-">BF2(OH)2- may comprise 1–10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al.

  11. A modular ex situ conversion process for thick MOD-fluoride RBCO precursors.

    Energy Technology Data Exchange (ETDEWEB)

    Feenstra, R.; List, F. A.; Li, X. P.; Rupich, M. W.; Miller, D. J.; Maroni, V. A.; Zhang, Y.; Thompson, J. R.; Christen, D. K.; Materials Science Division; ORNL; American Superconductor Corp.

    2009-06-01

    Following a review of heating induced chemical and structural changes in RBa{sub 2}Cu{sub 3}O{sub 7} (RBCO) fluoride precursors (R = rare earth of Y) deposited by metalorganic deposition (MOD) and physical vapor deposition (PVD), a modular process comprising successive, functionally distinct, brief annealing steps (modules) is introduced. By decoupling events that otherwise occur simultaneously, the modular process provides a framework for addressing the complex kinetics associated with the temperature ramp of the ex situ conversion anneal. Modules for modifying the F concentration, porosity and microstructure, and RBCO nucleation are described.

  12. Mechanisms and time scales of glacial inception simulated with an Earth system model of intermediate complexity

    Directory of Open Access Journals (Sweden)

    R. Calov

    2009-06-01

    Full Text Available We investigate glacial inception and glacial thresholds in the climate-cryosphere system utilising the Earth system model of intermediate complexity CLIMBER-2, which includes modules for atmosphere, terrestrial vegetation, ocean and interactive ice sheets. The latter are described by the three-dimensional polythermal ice-sheet model SICOPOLIS. A bifurcation which represents glacial inception is analysed with two different model setups: one setup with dynamical ice-sheet model and another setup without it. The respective glacial thresholds differ in terms of maximum boreal summer insolation at 65° N (hereafter referred as Milankovitch forcing (MF. The glacial threshold of the configuration without ice-sheet dynamics corresponds to a much lower value of MF compared to the full model. If MF attains values only slightly below the aforementioned threshold there is fast transient response. Depending on the value of MF relative to the glacial threshold, the transient response time of inland-ice volume in the model configuration with ice-sheet dynamics ranges from 10 000 to 100 000 years. Due to these long response times, a glacial threshold obtained in an equilibrium simulation is not directly applicable to the transient response of the climate-cryosphere system to time-dependent orbital forcing. It is demonstrated that in transient simulations just crossing of the glacial threshold does not imply large-scale glaciation of the Northern Hemisphere. We found that in transient simulations MF has to drop well below the glacial threshold determined in an equilibrium simulation to initiate glacial inception. Finally, we show that the asynchronous coupling between climate and inland-ice components allows one sufficient realistic simulation of glacial inception and, at the same time, a considerable reduction of computational costs.

  13. Room temperature polymerization of alkyl isocyanates catalyzed by rare earth Schiff base complexes

    Institute of Scientific and Technical Information of China (English)

    YANG XiongFa; NI XuFeng; SHEN ZhiQuan

    2009-01-01

    The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum (Ln(H_2salen)_2Cl_3·2C_2H_7OH/Al(i-Bu)_3) at room temperature was investigated.The influences of ligand structure,catalyst composition,polymerization temperature,polymerization time,the concentration of catalyst and monomer,and the polymerization solvent on the polymerization of isocyanates were studied.It was found that under the polymerization conditions,examined La(H_2salen_A)_2Cl_3·2C_(2-)H_7OH/Al(i-Bu)_3 (H_2salen_A=N,N'-disalicylideneethylene diamine) is a fairly high efficient catalyst for the polymerization of n-hexyl isocyanate (n-HexNCO) to prepare high molecular weight poly(n-hexyl isocyanate) (PHNCO) with narrower molecular weight distribution at room temperature.PHNCO could be prepared with yield of 74.0%,number-average molecular weight (M_n) of 40.20×10~4 and MWD of 1.79 under the following optimum conditions:[Al]/[La]=30 (molar ratio),[n-HexNCO]/[La]=100 (molar ratio),[n-HexNCO]=3.43 mol/L polymerization at 20℃ for 12 h in toluene.In the same polymerization conditions,poly (n-octyl isocyanate) (PONCO) with yield of 67.3%,and poly(n-butyl isocyanate) (PBNCO) with yield of 45.5%,could be prepared respectively.The kinetics of the polymerization of n-HexNCO was also investigated and found to be first-order with respect to both monomer and catalyst concentrations.

  14. Fluoride varnishes and enamel caries

    NARCIS (Netherlands)

    Bruyn, Hugo de

    1987-01-01

    Topical fluoride applications have the aim of increasing the fluoride uptake in enamel and consequently reducing caries. In the early ‘60s fluoride varnishes were introduced because they had a long contact period with the enamel which resulted in a higher fluoride uptake than from other topical appl

  15. Fluoride varnishes and enamel caries

    NARCIS (Netherlands)

    Bruyn, Hugo de

    1987-01-01

    Topical fluoride applications have the aim of increasing the fluoride uptake in enamel and consequently reducing caries. In the early ‘60s fluoride varnishes were introduced because they had a long contact period with the enamel which resulted in a higher fluoride uptake than from other topical

  16. Organic complexation of rare earth elements in natural waters: Evaluating model calculations from ultrafiltration data

    Science.gov (United States)

    Pourret, Olivier; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

    2007-06-01

    The Stockholm Humic Model (SHM) and Humic Ion-Binding Models V and VI were compared for their ability to predict the role of dissolved organic matter (DOM) in the speciation of rare earth elements (REE) in natural waters. Unlike Models V and VI, SHM is part of a speciation code that also allows us to consider dissolution/precipitation, sorption/desorption and oxidation/reduction reactions. In this context, it is particularly interesting to test the performance of SHM. The REE specific equilibrium constants required by the speciation models were estimated using linear free-energy relationships (LFER) between the first hydrolysis constants and the stability constants for REE complexation with lactic and acetic acid. Three datasets were used for the purpose of comparison: (i) World Average River Water (Dissolved Organic Carbon (DOC) = 5 mg L -1), previously investigated using Model V, was reinvestigated using SHM and Model VI; (ii) two natural organic-rich waters (DOC = 18-24 mg L -1), whose REE speciation has already been determined with both Model V and ultrafiltration studies, were also reinvestigated using SHM and Model VI; finally, (iii) new ultrafiltration experiments were carried out on samples of circumneutral-pH (pH 6.2-7.1), organic-rich (DOC = 7-20 mg L -1) groundwaters from the Kervidy-Naizin and Petit-Hermitage catchments, western France. The results were then compared with speciation predictions provided by Model VI and SHM, successively. When applied to World Average River Water, both Model VI and SHM yield comparable results, confirming the earlier finding that a large fraction of the dissolved REE in rivers occurs as organic complexes This implies that the two models are equally valid for calculating REE speciation in low-DOC waters at circumneutral-pH. The two models also successfully reproduced ultrafiltration results obtained for DOC-rich acidic groundwaters and river waters. By contrast, the two models yielded different results when compared to

  17. Synthesis, structure and spectroscopic properties of rare earth complexes with a new aryl amide 2,2'-bipydine derivative

    Science.gov (United States)

    Song, Xue-Qin; Zheng, Jiang-Rong; Liu, Wei-Sheng; Ju, Zheng-Hua

    2008-01-01

    Solid complexes of rare earth nitrates and picrates with a new aryl amide ligand 3.3'-bis(benzylamido)-2,2'-bipyridine ( L) were synthesized and characterized by elemental analysis, IR and molar conductivity measurements. The molecular structures of the complex [TbL 2(NO 3) 3H 2O]·2H 2O have been determined by single-crystal X-ray diffraction. The fluorescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated in detail. Under the excitation, these complexes exhibited characteristic emissions of europium and terbium ions. It is worth noting that the nature of the anion has a great effect upon the composition of the complexes as well as emission properties of them.

  18. Magnetic properties of lithium rare-earth fluorides: Ferromagnetism in LiErF4 and LiHoF4 and crystal-field parameters at the rare-earth and Li sites

    DEFF Research Database (Denmark)

    Hansen, P. E.; Johansson, Torben; Nevald, Rolf

    1975-01-01

    was observed, but extrapolation indicates that below 0.5 K it will be ferromagnetic with the magnetic moments in the crytalline ab plane. From the susceptibilities the crystal-field parameters Bnm with (n, m)=(2, 0), (4, 0), (4, 4), (6, 0), (6, 4) have been extracted giving for Er3+ in LiErF4: 430., -985......-order crystal-field parameters at the Li site: q=0.0363, 0.0354, and 0.0343 Å-3 for the Er, Ho, and Tb compound, respectively. The crystal-field parameters are compared to values calculated from point charges, showing agreement at the Li sites but not at the rare earth sites.......Single crystals of LiErF4 and LiHoF4 have been grown and their magnetic properties measured from 1.3 K to 300 K. LiHoF4 turned out to be a nearly ideal Ising ferromagnet with TC=1.30±0.05 K and a saturation magnetization along the crystalline c axis of (6.98±0.02)μB. In LiErF4 no ordering...

  19. Rare Earth or Cosmic Zoo: Testing the Frequency of Complex Life in the Universe

    Science.gov (United States)

    Bains, W.; Schulze-Makuch, D.

    2017-02-01

    We propose how to test between two major hypotheses about the frequency of life in the universe (Rare Earth and Cosmic Zoo) using future remote sensing capabilities targeted at exoplanets and site visits of planetary bodies in our solar system.

  20. Salt fluoridation and oral health

    OpenAIRE

    Thomas M. Marthaler

    2013-01-01

    The aim of this paper is to make known the potential of fluoridated salt in community oral health programs, particularly in South Eastern Europe. Since 1922, the addition of iodine to salt has been successful in Switzerland. Goiter is virtually extinct. By 1945, the cariesprotective effect of fluorides was well established. Based on the success of water fluoridation, a gynecologist started adding of fluoride to salt. The sale of fluoridated salt began in 1956 in the Swiss Canton of Zurich,...

  1. The cariostatic mechanisms of fluoride

    OpenAIRE

    Kata Rošin-Grget; Kristina Peroš; Ivana Šutej; Krešimir Bašić

    2013-01-01

    This article discusses the possible cariostatic mechanisms of the action of fluoride. In the past, fluoride inhibition of caries was ascribed to reduced solubility of enamel due to incorporation of fluoride (F–) into the enamel minerals. The present evidence from clinical and laboratory studies suggests that the caries-preventive mode of action of fluoride is mainly topical. There is convincing evidence that fluoride has a major effect on demineralisation and remineralisation of dental hard t...

  2. Western Mineral and Environmental Resources Science Center--providing comprehensive earth science for complex societal issues

    Science.gov (United States)

    Frank, David G.; Wallace, Alan R.; Schneider, Jill L.

    2010-01-01

    supports approximately 40 USGS research specialists who utilize cooperative agreements with universities, industry, and other governmental agencies to support their collaborative research and information exchange. Scientists of the WMERSC study how and where non-fuel mineral resources form and are concentrated in the earth's crust, where mineral resources might be found in the future, and how mineral materials interact with the environment to affect human and ecosystem health. Natural systems (ecosystems) are complex - our understanding of how ecosystems operate requires collecting and synthesizing large amounts of geologic, geochemical, biologic, hydrologic, and meteorological information. Scientists in the Center strive to understand the interplay of various processes and how they affect the structure, composition, and health of ecosystems. Such understanding, which is then summarized in publicly available reports, is used to address and solve a wide variety of issues that are important to society and the economy. WMERSC scientists have extensive national and international experience in these scientific specialties and capabilities - they have collaborated with many Federal, State, and local agencies; with various private sector organizations; as well as with foreign countries and organizations. Nearly every scientific and societal challenge requires a different combination of scientific skills and capabilities. With their breadth of scientific specialties and capabilities, the scientists of the WMERSC can provide scientifically sound approaches to a wide range of societal challenges and issues. The following sections describe examples of important issues that have been addressed by scientists in the Center, the methods employed, and the relevant conclusions. New directions are inevitable as societal needs change over time. Scientists of the WMERSC have a diverse set of skills and capabilities and are proficient in the collection and integration of

  3. Urinary fluoride excretion after application of fluoride varnish and use of fluoride toothpaste in young children

    DEFF Research Database (Denmark)

    Lockner, Frida; Twetman, Svante; Stecksén-Blicks, Christina

    2017-01-01

    the levels with and without parallel use of fluoride toothpaste. DESIGN: Fifteen healthy children were enrolled to a randomized crossover trial that was performed in two parts: Part I with twice-daily tooth brushing with fluoride toothpaste and Part II with twice-daily brushing with a non-fluoride toothpaste......: There was a statistically significant increase in the 6-h fluoride excretion after application of both experimental varnishes, with and without parallel use of fluoride toothpaste (P toothpaste was used, the mean fluoride excretion was 0.20 mg/6 h after application of Duraphat and 0.29 mg/6 h...... after application of Profluorid Varnish (P = 0.18). CONCLUSIONS: Topical applications of 0.1 mL of fluoride varnish significantly increased the 6-h fluoride excretion. As some individuals displayed excretion levels exceeding the optimal fluoride exposure, a restricted use of fluoride toothpaste...

  4. Cationic methyl complexes of the rare-earth metals: an experimental and computational study on synthesis, structure, and reactivity.

    Science.gov (United States)

    Kramer, Mathias U; Robert, Dominique; Arndt, Stefan; Zeimentz, Peter M; Spaniol, Thomas P; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Okuda, Jun

    2008-10-20

    Synthesis, structure, and reactivity of two families of rare-earth metal complexes containing discrete methyl cations [LnMe(2-x)(thf)n]((1+x)+) (x = 0, 1; thf = tetrahydrofuran) have been studied. As a synthetic equivalent for the elusive trimethyl complex [LnMe3], lithium methylates of the approximate composition [Li3LnMe6(thf)n] were prepared by treating rare-earth metal trichlorides [LnCl3(thf)n] with 6 equiv of methyllithium in diethyl ether. Heteronuclear complexes of the formula [Li3Ln2Me9L(n)] (Ln = Sc, Y, Tb; L = Et2O, thf) were isolated by crystallization from diethyl ether. Single crystal X-ray diffraction studies revealed a heterometallic aggregate of composition [Li3Ln2Me9(thf)n(Et2O)m] with a [LiLn2Me9](2-) core (Ln = Sc, Y, Tb). When tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = Y, Lu) was reacted with less than 1 equiv of [NR3H][BPh4], the dimethyl cations [LnMe2(thf)n][BPh4] were obtained. The coordination number as well as cis/trans isomer preference was studied by crystallographic and computational methods. Dicationic methyl complexes of the rare-earth metals of the formula [LnMe(thf)n][BAr4]2 (Ln = Sc, Y, La-Nd, Sm, Gd-Lu; Ar = Ph, C6H4F-4) were synthesized, by protonolysis of either the ate complex [Li3LnMe6(thf)n] (Ln = Sc, Y, Gd-Lu) or the tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = La-Nd, Sm, Dy, Gd) with ammonium borates [NR3H][BAr4] in thf. The number of coordinated thf ligands varied from n = 5 (Ln = Sc, Tm) to n = 6 (Ln = La, Y, Sm, Dy, Ho). The configuration of representative examples was determined by X-ray diffraction studies and confirmed by density-functional theory calculations. The highly polarized bonding between the methyl group and the rare-earth metal center results in the reactivity pattern dominated by the carbanionic character and the pronounced Lewis acidity: The dicationic methyl complex [YMe(thf)6](2+) inserted benzophenone as an electrophile to give the alkoxy complex [Y(OCMePh2)(thf)5](2+). Nucleophilic addition of

  5. Investigation of Surfactant-Stain-Metal Interaction: Naphthochrome Green/Cetyltrimethylammonium Bromide/Rare Earths Ternary Complexation

    Institute of Scientific and Technical Information of China (English)

    郑立新; 沈荣; 郜洪文

    2003-01-01

    The ternary interaction of naphthochrome green (NCG) with cetyltrimethylammonium bromide (CTAB) and rare earths (Res: Yb, Dy, Er and Eu) has been investigated with the microsurface adsorption-spectral correction technique (MSASC). The aggregation of NCG on CTAB obeys the Langmuir isothermal adsorption. The enrichment of NCG on CTAB and the presence of NaCl sensitize the complexation between Res and NCG. Both the binary aggregate and the ternary complex were characterized in the presence and absence of NaCl at pH 8.30 at 20 and 40℃.

  6. PARAMAGNETIC PROPERTIES OF THE ALKALINE EARTH FLUORIDES.

    Science.gov (United States)

    decreases with increasing temperature; and the temperature dependance is stronger for SrF2. The results have been interpreted using the Simanek-Orbach theory of a phonon-induced hyperfine field. (Author)

  7. Description of the Earth system model of intermediate complexity LOVECLIM version 1.2

    Directory of Open Access Journals (Sweden)

    H. Goosse

    2010-11-01

    Full Text Available The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation, the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The ocean component is CLIO3, which consists of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is of 3° by 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the ocean carbon cycle is represented by LOCH, a comprehensive model that takes into account both the solubility and biological pumps. The ice sheet component AGISM is made up of a three-dimensional thermomechanical model of the ice sheet flow, a visco-elastic bedrock model and a model of the mass balance at the ice-atmosphere and ice-ocean interfaces. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, and an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is

  8. Preparation of polymer-rare earth complex using salicylic acid-containing polystyrene and its fluorescence emission property

    Energy Technology Data Exchange (ETDEWEB)

    Gao Baojiao, E-mail: gaobaojiao@126.com [Department of Chemical Engineering, North University of China, Taiyuan 030051 (China); Zhang Wei; Zhang Zhengguo; Lei Qingjuan [Department of Chemical Engineering, North University of China, Taiyuan 030051 (China)

    2012-08-15

    Salicylic acid (SA) was first bonded onto the side chains of polystyrene (PS), obtaining functional macromolecule SAPS. Using the salicylic acid-containing polystyrene as a macromolecular ligand, a polymer-rare earth complex, SAPS-Eu(III), was prepared. The structure of SAPS-Eu(III) was characterized, and the fluorescence properties of SAPS-Eu(III) were mainly investigated. The experimental results show that the complex SAPS-Eu(III) has fine chemical stability because of the bidentate chelating effect of salicylic acid ligand. More important, the ligand SA on the side chains of PS can strongly sensitize the fluorescence emission of the center ion, Eu{sup 3+} ion, and it enables the complex SAPS-Eu(III) to produce the apparent 'Antenna Effect'. In the diluted solution of the functional macromolecule SAPS, the formed complex SAPS-Eu(III) belongs to an intramolecular complex, or an intrachain complex. For the binary intramolecular complex SAPS-Eu(III), the apparent saturated coordination number of SA of SAPS towards Eu{sup 3+} ion is equal to 10, and here the binary intrachain complex SAPS-Eu(III) has the strongest fluorescence emission. On this basis, small-molecule 1,10-phenanthroline (Phen) acting as a co-ligand is added and the ternary complex SAPS-Eu(III)-Phen will be formed. As long as a small amount of Phen is added (in the molar ratio 1:1 (n(Phen):n(Eu))), the coordination of the two kinds of ligands, SA of SAPS and Phen, to Eu{sup 3+} ion will reach complete saturation, and here the fluorescence emission of the ternary complex will be further enhanced via the complementary coordination effect in comparison with that of the binary complex SAPS-Eu(III). - Highlights: Black-Right-Pointing-Pointer We prepared the functional polystyrene, SAPS, on whose side chain salicylic acid ligand was bonded. Black-Right-Pointing-Pointer The polymer-rare earth complex, SAPS-Eu(III), was prepared and a stronger 'antenna effect' was produced. Black

  9. Crystal structures of the complexes of rare earth picrates with N, N, N’, N’-tetraphenyl-3, 6-dioxaoctanediamide

    Institute of Scientific and Technical Information of China (English)

    刘伟生; 柳士霞; 谭民裕; 郁开北; 谭干祖

    1997-01-01

    The complexes of rare earth picrate with N,N,N’,N’-tetraphenyl-3,6-dioxaoctanediamide(TDD),Eu(picc(TDD)] 2CH3CN and [ Y(pic)3(TDD)],have been synthesized.The crystal structures reveal that TDD at is as n tetradentate ligand,forming a ring-like coordination structure with its oxygen atoms together with one oxygen atom of the bidentate pterate In the Eu(Ⅲ) complex,the europium ion with a larger ionic radius lies out of the ring,while in the Y(Ⅲ) complex,the yttrium ion with a smaller ionic radius enters the cavity of the ligand.The structures of the complexes are greatly affected by the ionic radii due to participation of the picrates in coordination.

  10. Fluoride inhibition of Klebsiella aerogenes urease: mechanistic implications of a pseudo-uncompetitive, slow-binding inhibitor.

    Science.gov (United States)

    Todd, M J; Hausinger, R P

    2000-05-09

    Klebsiella aerogenes urease uses a dinuclear nickel active site to catalyze the hydrolysis of urea. Here, we describe the steady-state and pre-steady-state kinetics of urease inhibition by fluoride. Urease is slowly inhibited by fluoride in both the presence and absence of substrate. Steady-state rate studies yield parallel double-reciprocal plots; however, we show that fluoride interaction with urease is not compatible with classical uncompetitive inhibition. Rather, we propose that fluoride binds to an enzyme state (E) that is in equilibrium with resting enzyme (E) and produced during catalysis. Fluoride binding rates are directly proportional to inhibitor concentration. Substrate reduces both the rate of fluoride binding to urease and the rate of fluoride dissociation from the complex, consistent with urea binding to E and E.F in addition to E. Fluoride inhibition is pH-dependent due to a protonation event linked to fluoride dissociation. Fluoride binding is pH-independent, suggesting that fluoride anion, not HF, is the actual inhibitor. We assess the kinetic results in terms of the known protein crystal structure and evaluate possible molecular interpretations for the structure of the E state, the site of fluoride binding, and the factors associated with fluoride release. Finally, we note that the apparent uncompetitive inhibition by fluoride as reported for several other metalloenzymes may need to be reinterpreted in terms of fluoride interaction with the corresponding E states.

  11. ADSORPTIVE REMOVAL OF FLUORIDE FROM WATER USING ...

    African Journals Online (AJOL)

    Preferred Customer

    fluoride solutions for adsorption and analysis were prepared by diluting an ..... The rate constant k2, can be determined by plotting t/qt vs. t based on ... aqueous solution is complex process and the intraparticle diffusion was not the only rate-.

  12. Fluoridation: strategies for success.

    Science.gov (United States)

    Isman, R

    1981-07-01

    Of 19 referenda on community water fluoridation held in the first six months of 1980, 17 were defeated. Among the postulated reasons are a growing distrust of government and the health establishment. The public remains largely ignorant of the purpose and benefits of fluoridation. The emotionalism surrounding the issue has made it difficult to generate public support outside of the health professions. Opponents have also learned to fight fluoridation with increasingly sophisticated techniques. Some of the strategies used in recent successful campaigns in Oakland, California, and Portland, Oregon are described; recommendations that can be applied to communities considering fluoridation include careful wording of ballot measures so they are unequivocally clear and simple; timing ballot measures with elections likely to draw the largest voter turnout; broadening the base of political and financial support; using a figurehead if possible; and making maximum use of the media.

  13. Energetic Ionic Liquids Based on Anionic Rare Earth Nitrate Complexes (Preprint)

    Science.gov (United States)

    2008-07-10

    hydrolytically unstable [ bmim ]Ln(SCN)7. [5b] However, the former exist as hydrates and are not stable in the absence of water of hydration and are not typical...ionic liquids. The instability of [ bmim ]Ln(SCN)7 to moisture and air also limits their applications. Since our new rare-earth ionic liquids do not...component in energetic ionic liquids.[7] Rare earth metals coordinate with O-donor ligands more strongly than N-donor ligands,[8] e. g., in [ bmim ]Ln

  14. Synthesis of monomeric and polymeric alkali and alkaline earth metal complexes using a phosphinoselenoic amide ligand in metal coordination sphere

    Indian Academy of Sciences (India)

    Jayeeta Bhattacharjee; Ravi K Kottalanka; Harinath Adimulam; Tarun K Panda

    2014-09-01

    We report the monomeric complexes of magnesium and calcium of composition [M(THF){2-Ph2P(Se)N(CMe3)}2] [M= Mg (3), n = 1 andM = Ca (4), n = 2)] and polymeric complexes of potassium and barium of composition [K(THF)2{Ph2P(Se)N(CMe3)}] (2) and [K(THF)Ba{Ph2P(Se)N(CMe3)}3](5) respectively. The potassium complex 2 was readily prepared by the reaction of potassium bis(trimethylsilyl)amide with phosphinoselenoic amide ligand (1) at ambient temperature. The calcium complex 4 was prepared by two synthetic routes: in the first method, commonly known as salt metathesis reaction, the potassium complex 2 was made to react with alkaline earth metal diiodide at room temperature to afford the corresponding calcium complex. The metal bis(trimethylsilyl)amides were made to react with protic ligand 1 in the second method to eliminate the volatile bis(trimethyl)silyl amine. The magnesium complex 3 and barium complex 5 were prepared only through the first method. Solid-state structures of all the new complexes were established by single crystal X-ray diffraction analysis. The smaller ionic radii of Mg2+ (0.72Å) and Ca2+ (0.99Å) ions form the monomeric complex, whereas the larger ions K+ (1.38Å) and Ba2+ (1.35Å) were found to form onedimensional polymeric complexes with monoanionic ligand 1. Compound 2 serves an example of magnesium complex with a Mg-Se direct bond.

  15. Recovery of protactinium from molten fluoride nuclear fuel compositions

    Science.gov (United States)

    Baes, C.F. Jr.; Bamberger, C.; Ross, R.G.

    1973-12-25

    A method is provided for separating protactinium from a molten fluonlde salt composition consisting essentially of at least one alkali and alkaline earth metal fluoride and at least one soluble fluoride of uranium or thorium which comprises oxidizing the protactinium in said composition to the + 5 oxidation state and contacting said composition with an oxide selected from the group consisting of an alkali metal oxide, an alkaline earth oxide, thorium oxide, and uranium oxide, and thereafter isolating the resultant insoluble protactinium oxide product from said composition. (Official Gazette)

  16. Photofunctional hybrids of rare earth complexes covalently bonded to ZnO core-shell nanoparticle substrate through polymer linkage.

    Science.gov (United States)

    Shao, Yan-Fei; Yan, Bing

    2012-06-28

    A novel series of multi-component hybrids are assembled based on rare earth coordinated to rare earth ion (Eu(3+), Tb(3+), Sm(3+), Dy(3+)) complex systems and ZnO nanocomposites through three different ester units (ethyl methacrylate (EMA), 2-hydroxyethyl methacrylate (HEMA) and 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFMA)) as functional polymer linkages. Methacrylic-group-modified ZnO nanoparticles (designated ZnO-MAA) are synthesized based on the reaction between zinc methacrylate and LiOH with the molar ratio 1 : 3.5 via sol-gel process. The final hybrid materials are prepared by introducing rare earth complexes into ZnO-MAA matrix via addition polymerization reaction in the presence of benzoyl peroxide (BPO) as the initiator. The detailed characterization and luminescence of these hybrid materials are discussed. It is found that ZnO-MAA-HEMA/EMA/HFBMA-RE-phen hybrid systems have effective intramolecular energy transfer process and exhibit longer lifetime and higher quantum efficiency.

  17. ExploreNEOs: Average albedo by taxonomic complex in the near-Earth asteroid population

    NARCIS (Netherlands)

    Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; Bhattacharya, B.; Bottke, W. F.; Chesley, S.; Delbo, M.; Fazio, G.; Harris, A. W.; Mainzer, A.; Mommert, M.; Morbidelli, A.; Penprase, B.; Smith, H. A.; Spahr, T. B.; Stansberry, J. A.

    2011-01-01

    Understanding the albedo distribution of the Near- Earth Object (NEO) population allows for a better understanding of the relationship between absolute magnitude and size, which impacts calculations of size frequency distribution and impact hazards. Examining NEO albedos also sheds light on the diff

  18. ExploreNEOs: Average albedo by taxonomic complex in the near-Earth asteroid population

    NARCIS (Netherlands)

    Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; Bhattacharya, B.; Bottke, W. F.; Chesley, S.; Delbo, M.; Fazio, G.; Harris, A. W.; Mainzer, A.; Mommert, M.; Morbidelli, A.; Penprase, B.; Smith, H. A.; Spahr, T. B.; Stansberry, J. A.

    2011-01-01

    Understanding the albedo distribution of the Near- Earth Object (NEO) population allows for a better understanding of the relationship between absolute magnitude and size, which impacts calculations of size frequency distribution and impact hazards. Examining NEO albedos also sheds light on the

  19. Replicating the Ice-Volume Signal of the Early Pleistocene with a Complex Earth System Model

    Science.gov (United States)

    Tabor, C. R.; Poulsen, C. J.; Pollard, D.

    2013-12-01

    Milankovitch theory proposes high-latitude summer insolation intensity paces the ice ages by controlling perennial snow cover amounts (Milankovitch, 1941). According to theory, the ~21 kyr cycle of precession should dominate the ice-volume records since it has the greatest influence on high-latitude summer insolation. Modeling experiments frequently support Milankovitch theory by attributing the majority of Northern Hemisphere high-latitude summer snowmelt to changes in the cycle of precession (e.g. Jackson and Broccoli, 2003). However, ice-volume proxy records, especially those of the Early Pleistocene (2.6-0.8 Ma), display variability with a period of ~41 kyr (Raymo and Lisiecki, 2005), indicative of insolation forcing from obliquity, which has a much smaller influence on summer insolation intensity than precession. Several hypotheses attempt to explain the discrepancies between Milkankovitch theory and the proxy records by invoking phenomena such as insolation gradients (Raymo and Nisancioglu, 2003), hemispheric offset (Raymo et al., 2006; Lee and Poulsen, 2009), and integrated summer energy (Huybers, 2006); however, all of these hypotheses contain caveats (Ruddiman, 2006) and have yet to be supported by modeling studies that use a complex GCM. To explore potential solutions to this '41 kyr problem,' we use an Earth system model composed of the GENESIS GCM and Land Surface model, the BIOME4 vegetation model, and the Pennsylvania State ice-sheet model. Using an asynchronous coupling technique, we run four idealized transient combinations of obliquity and precession, representing the orbital extremes of the Pleistocene (Berger and Loutre, 1991). Each experiment is run through several complete orbital cycles with a dynamic ice domain spanning North America and Greenland, and fixed preindustrial greenhouse-gas concentrations. For all orbital configurations, model results produce greater ice-volume spectral power at the frequency of obliquity despite significantly

  20. Water Fluoridation Statistics - Percent of PWS population receiving fluoridated water

    Data.gov (United States)

    U.S. Department of Health & Human Services — 2000-2014. Water Fluoridation Statistics is a biennial report of the percentage and number of people receiving fluoridated water from 2000 through 2014, originally...

  1. Water Fluoridation Statistics - Percent of PWS population receiving fluoridated water

    Data.gov (United States)

    U.S. Department of Health & Human Services — 2000-2014 Water Fluoridation Statistics is a biennial report of the percentage and number of people receiving fluoridated water from 2000 through 2014, originally...

  2. Water Fluoridation Statistics - Percent of PWS population receiving fluoridated water

    Data.gov (United States)

    U.S. Department of Health & Human Services — 2000-2014. Water Fluoridation Statistics is a biennial report of the percentage and number of people receiving fluoridated water from 2000 through 2014, originally...

  3. Permeability and fluoride release of lining materials containing amine fluorides.

    Science.gov (United States)

    Nordbö, H; Eriksen, H M

    1976-11-01

    The addition of amine fluorides to a copal recin (Copalite) and a chlorine caoutchouc varnish (Pergut S-40) has been studied. The permeability of Copalite films was only slightly increased whereas the excellent film-forming qualities of Pergut S-40 were destroyed by the addition of fluorides. A high fluoride release was found initially from test films of the materials but within 2-3 weeks a decrease to very low fluoride levels was observed.

  4. Multiple magnetic relaxation processes, magnetocaloric effect and fluorescence properties of rhombus-shaped tetranuclear rare earth complexes.

    Science.gov (United States)

    Gao, Hong-Ling; Jiang, Li; Liu, Shuang; Shen, Hai-Yun; Wang, Wen-Min; Cui, Jian-Zhong

    2016-01-07

    Seven new tetranuclear rare earth (RE) complexes [RE4(acac)4L6(μ3-OH)2] (HL = 5-(4-fluorobenzylidene)-8-hydroxylquinoline; acac = acetylacetonate; RE = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Tm (6) and Lu (7)) have been synthesized and completely characterized. Complex exhibits multiple zero-field slow magnetic relaxation processes typical of Single Molecule Magnets (SMMs). Two distinct slow magnetic relaxation processes, with effective energy barriers of Ueff = 48 K for the slow relaxation (SR) process and Ueff = 121 K for the fast relaxation (FR) process, are mainly attributed to the presence of two crystallographically independent Dy(III) sites. The magnetocaloric effect (MCE) was detected as -ΔSm(T) = 20.8 J kg(-1) K(-1) for complex . The fluorescence properties of complexes 1, 2, 4, 5 and 7 were also investigated. Complexes 2, 4 and 5 show the characteristic peaks for their corresponding RE(III) center, while complexes 1 and 7 show similar emission peaks to the Schiff base ligand when they are excited at the appropriate wavelength.

  5. Evaluation of Grounding Impedance of a Complex Lightning Protective System Using Earth Ground Clamp Measurements and ATP Modeling

    Science.gov (United States)

    Mata, Carlos T.; Rakov, V. A.; Mata, Angel G.

    2010-01-01

    A new Lightning Protection System (LPS) was designed and built at Launch Complex 39B (LC39B), at the Kennedy Space Center (KSC), Florida, which consists of a catenary wire system (at a height of about 181 meters above ground level) supported by three insulators installed atop three towers in a triangular configuration. A total of nine downconductors (each about 250 meters long, on average) are connected to the catenary wire system. Each of the nine downconductors is connected to a 7.62-meter radius circular counterpoise conductor with six equally spaced 6-meter long vertical grounding rods. Grounding requirements at LC39B call for all underground and above ground metallic piping, enclosures, raceways, and cable trays, within 7.62 meters of the counterpoise, to be bounded to the counterpoise, which results in a complex interconnected grounding system, given the many metallic piping, raceways, and cable trays that run in multiple direction around LC39B. The complexity of this grounding system makes the fall of potential method, which uses multiple metallic rods or stakes, unsuitable for measuring the grounding impedances of the downconductors. To calculate the downconductors grounding impedance, an Earth Ground Clamp (a stakeless grounding resistance measuring device) and a LPS Alternative Transient Program (ATP) model are used. The Earth Ground Clamp is used to measure the loop impedance plus the grounding impedance of each downconductor and the ATP model is used to calculate the loop impedance of each downconductor circuit. The grounding impedance of the downconductors is then calculated by subtracting the ATP calculated loop impedances from the Earth Ground Clamp measurements.

  6. A Study of Heteropoly Complexes of Rare Earths as Catalyst Promoter in the Synthesis of Ethyl Acetate

    Institute of Scientific and Technical Information of China (English)

    Shui Yang HE; Ke PENG; Di ZHANG; Wang Ting WU; Gang Lin XUE; Qi Zhen SHI

    2004-01-01

    The capability of the synthesized heteropoly complexes of rare earths {K10 [(O39W11Si) Ln(Gly)3Ln(SiW11O39)]·9H2O (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy)} as the catalyst promoter in the synthesis of the ethyl acetate was studied. The results showed that the quantity of H2SO4 used for synthesizing the ethyl acetate can be reduced by 75% and the yield reached 98% at the optional condition.

  7. Urinary fluoride excretion after application of fluoride varnish and use of fluoride toothpaste in young children.

    Science.gov (United States)

    Lockner, Frida; Twetman, Svante; Stecksén-Blicks, Christina

    2017-01-20

    The efficacy and safety of combined use of topical fluoride products are essential issues that must be monitored. To assess urinary excretion of fluoride after application of two different dental varnishes containing 2.26% fluoride in 3- to 4-year-old children and to compare the levels with and without parallel use of fluoride toothpaste. Fifteen healthy children were enrolled to a randomized crossover trial that was performed in two parts: Part I with twice-daily tooth brushing with fluoride toothpaste and Part II with twice-daily brushing with a non-fluoride toothpaste. After a 1-week run-in period, 0.1 mL of the two fluoride varnishes (Duraphat and Profluorid Varnish) was topically applied in a randomized order. Baseline and experimental urine was collected during 6-h periods. The fluoride content was determined with an ion-sensitive electrode. There was a statistically significant increase in the 6-h fluoride excretion after application of both experimental varnishes, with and without parallel use of fluoride toothpaste (P fluoridated toothpaste was used, the mean fluoride excretion was 0.20 mg/6 h after application of Duraphat and 0.29 mg/6 h after application of Profluorid Varnish (P = 0.18). Topical applications of 0.1 mL of fluoride varnish significantly increased the 6-h fluoride excretion. As some individuals displayed excretion levels exceeding the optimal fluoride exposure, a restricted use of fluoride toothpaste in connection with the varnish applications would decrease fluoride exposure. © 2017 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Fluoride removal using lanthanum incorporated chitosan beads.

    Science.gov (United States)

    Bansiwal, Amit; Thakre, Dilip; Labhshetwar, Nitin; Meshram, Siddharth; Rayalu, Sadhana

    2009-11-01

    Highly selective material based on naturally occurring biomaterial namely chitosan has been designed for the defluoridation of water. Lanthanum incorporated chitosan beads (LCB) were prepared using precipitation method. The synthesis was optimized by varying different synthesis parameters namely lanthanum loading, complexation and precipitation time, strength of ammonia solution used for precipitation, drying time, etc. Lanthanum incorporated chitosan beads were characterized using SEM, FTIR, XRD and EDX. Surface area of LCB was observed to be 2.76 m(2)g(-1). The equilibrium adsorption data fitted well to Langmuir adsorption isotherm and showing maximum fluoride adsorption capacity of 4.7 mg g(-1) with negligible lanthanum release. Kinetic study reveals that adsorption of fluoride is fast and follows pseudo-first-order kinetics. The effect of pH was also studied and the best efficiency was observed at pH 5. Presence of sulphate, nitrate and chloride marginally affected the removal efficiency, however drastic reduction in fluoride uptake was observed in the presence of carbonate and bicarbonate. Negative value of change in free energy (DeltaG degrees) and positive value of change in entropy (DeltaS degrees) suggest the adsorption of fluoride by LCB is feasible and spontaneous process. Positive value of change in enthalpy (DeltaH degrees) suggests the process of fluoride adsorption is endothermic in nature. Regeneration study reveals that 1M ammonium chloride solution appears to be the promising regeneration media showing 81.22% regeneration. The adsorption capacity of LCB was similar in fluoride-contaminated ground water collected from Dhar district of Madhya Pradesh, India, as compared to simulated water.

  9. Fluoride retention by kaolin clay

    DEFF Research Database (Denmark)

    Kau, P. M. H.; Smith, D. W.; Binning, Philip John

    1997-01-01

    To evaluate the potential effectiveness of kaolin clay liners in storage of fluoride contaminated waste, an experimental study of the sorption and desorption behaviour of fluoride in kaolin clay was conducted. The degree of fluoride sorption by kaolin was found to depend on solution p...

  10. Fluoride Rinses, Gels and Foams

    DEFF Research Database (Denmark)

    Twetman, Svante; Keller, Mette K

    2016-01-01

    AIM: The aim of this conference paper was to systematically review the quality of evidence and summarize the findings of clinical trials published after 2002 using fluoride mouth rinses, fluoride gels or foams for the prevention of dental caries. METHODS: Relevant papers were selected after an el...... brushing with fluoride toothpaste....

  11. Fluoride resistance in Streptococcus mutans

    NARCIS (Netherlands)

    Liao, Ying

    2017-01-01

    Fluoride has been used as the most effective anti-caries agent for over five decades. It functions not only on the dental hard tissues, but also as an antimicrobial agent. It is known that oral bacteria are able to develop resistance to fluoride, which may affect the effectiveness of fluoride in

  12. Recent progress report on DNA B-Z transition modulated by rare earth-amino acid complex and Alzheimer's disease amyloid beta

    Institute of Scientific and Technical Information of China (English)

    GENG

    2010-01-01

    Rare earth dements have unique physical, magnetic, luminescent and catalytic properties. They have been successfully used as medicine and probes in luminescent resonance energy transfer (LRET) for bioassays, as well as reagents for diagnosis in magnetic resonance imaging (MRI). In this progress report, we will focus on recent progress on how rare earth amino complexes bind to DNA and change DNA structure, especially on DNA B-Z transition induced by rare earth amino acid complex and its potential impact on Alzheimer's disease (AD).

  13. Heavy Metal Fluoride Glasses.

    Science.gov (United States)

    1987-04-01

    i 2N E ihhhhh1112h MEmhhhhEEEohhhhE I.’....momo 111111111’-20 LA ’Ll2. AFWL-TR-86-37 AFWL-TR- 86-37 oT C ,l C ’-’ N HEAVY METAL FLUORIDE GLASSES 0nI...Secwrit CkasmfcationJ HEAVY METAL FLUORIDE GLASSES 12. PERSONAL AUTHOR(S) Reisfield, Renata; and Eyal, Mrek 13. TYPE OF REPORT 113b. TIME COVERED 114...glasses containing about 50 mole% of ZrF4 [which can be replaced by HfF 4 or TIF 4 (Refs. 1-3) or heavy metal fluorides based on PbF2 and on 3d-group

  14. Effect of Complex Agents on Structure and Activity of Fe-Substituted Rare Earth Hexaaluminate Catalysts for Methane Combustion

    Institute of Scientific and Technical Information of China (English)

    Wu Peng; Hu Ruisheng; Long Zerong; Meng He

    2004-01-01

    A series of catalysts were prepared by using complex sol-gel methods.Experimental results confirm the effect of different agents on structure and activity of Fe-substituted rare earth hexaaluminate catalyst (LaFeAl11 O19 ) for methane combustion.The catalyst is yielded by complex sol-gel, respectively using three different complex agents (maltose, glucose and citric acid).XRD demonstrated that haxaaluminate is the major phase of catalyst prepared by maltose,while LaAlO3 is the major one of the catalyst by glucose and citric acid.At the same time, there is a little LaFeO3 and surface areas as well as 29.5 nm particle diameter when the complex agent is maltose.However, T10 ( temperature for 10% conversion of methane) and T100 ( temperature for 100% conversion of methane) for catalyst by glucose is 543 and 758 ℃, which is the best among the three complex agents for methane combustion.

  15. Fluorescence and Judd-Ofelt analysis of rare earth complexes with maleic anhydride and acrylic acid

    Institute of Scientific and Technical Information of China (English)

    WEN Shipeng; ZHANG Xiaoping; HU Shui; ZHANG Liqun; LIU Li

    2008-01-01

    Two kinds of Eu-complexes, Eu(TTA)2(Phen)(AA) and Eu(TTA)2(Phen)(MA) (HTFA=2-Thenoyltrifluoroacetone, Phen=1,10-phenanthroline, AA=acrylic acid, MA=Maleic anhydride), which combined the excellent fluorescence properties of Eu(TTA)2(Phen)(H2O) and the reactivity of acrylic acid and maleic anhydride with radicals, were synthesized. The two complexes were characterized by elemental analysis, infrared (IR) spectra, and X-ray photoelectron spectroscopy (XPS). Based on the data shown from the fluorescent spectra of the Eu-MA and Eu-AA complexes, the Ωλ (λ=2 and 4) experimental intensity parameters were calculated. The results demonstrated that the Ω2 intensity parameters for the two complexes were smaller than those for the Eu(TTA)2(Phen)(H2O) complex, indicating that a less symmetri-cal chemical environment existed in the complexes. It implied that the radiative efficiency of the 5D0 of these two complexes could be en-hanced by ligand of MA and AA, respectively. The luminescent lifetime of the Eu-AA (τ=7.26×10-4 s) or Eu-MA complex (τ=-8.12×10-4 s) was higher than that of the Eu(TTA)2(Phen)(H2O) complex, which was attributed to the substitution of the water molecule (H2O) in Eu(TTA)2(Phen)(H2O) by the MA or AA ligand.

  16. High-temperature corrosion of metals in the salt and metallic melts containing rare earths

    Science.gov (United States)

    Karpov, V. V.; Abramov, A. V.; Zhilyakov, A. Yu.; Belikov, S. V.; Volkovich, V. A.; Polovov, I. B.; Rebrin, O. I.

    2016-09-01

    A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl- KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of "low stability" materials.

  17. Relationships of human plasma fluoride and bone fluoride to age

    Energy Technology Data Exchange (ETDEWEB)

    Parkins, F.M.; Tinanoff, N.; Moutinho, M.; Anstey, M.B.; Waziri, M.H.

    1976-04-01

    There is evidence that fluoride levels in plasma correlate with the fluoride content in bones. The authors determined whether or not fluoride in plasma and bones might correlate with age. In 41 in-patients at the University Hospital, Iowa City, 36 of whom had been residing in fluoridated communities plasma fluoride was determined in the fasting stage by the fluoride ion selective electrode. The teeth of these children were compared with those of a neighboring city where the natural fluoride content in drinking water was 0.1 ppm. For the second sampling 42 months following the beginning of the program only 10 and 11 year old children - who had been 6 and 7 years old at the beginning of the experiment - were selected. Twenty-five boys and girls in each group were compared with a similar group of children as controls. After 28 months (approximately 33 rinsing with sodium fluoride solution) the DMF index in the fluoride-treated children was 18.4% less than in the controls. In the second group among 10 and 11 year old children after 42 months with 55 rinsings the difference was 35.0%. The author acknowledged that factors other than applications of sodium fluoride may have contributed to the prevention of caries in the fluoride-treated groups.

  18. Fluoride release from fluoride varnishes under acidic conditions.

    Science.gov (United States)

    Lippert, F

    2014-01-01

    The aim was to investigate the in vitro fluoride release from fluoride varnishes under acidic conditions. Poly(methyl methacrylate) blocks (Perspex, n=3 per group) were painted with 80 ± 5 mg fluoride varnish (n=10) and placed into artificial saliva for 30 min. Then, blocks were placed into either 1% citric acid (pH 2.27) or 0.3% citric acid (pH 3.75) solutions (n=3 per solution and varnish) for 30 min with the solutions being replaced every 5 min. Saliva and acid solutions were analyzed for fluoride content. Data were analyzed using three-way ANOVA (varnish, solution, time). The three-way interaction was significant (p>0.0001). Fluoride release and release patterns varied considerably between varnishes. Fluoride release in saliva varied by a factor of more than 10 between varnishes. Some varnishes (CavityShield, Nupro, ProFluorid, Vanish) showed higher fluoride release in saliva than during the first 5 min of acid exposure, whereas other varnishes (Acclean, Enamel-Pro, MI Varnish, Vella) showed the opposite behavior. There was little difference between acidic solutions. Fluoride release from fluoride varnishes varies considerably and also depends on the dissolution medium. Bearing in mind the limitations of laboratory research, the consumption of acidic drinks after fluoride varnish application should be avoided to optimize the benefit/risk ratio.

  19. Temperature-induced collapse of alkaline Earth cation-polyacrylate anion complexes.

    Science.gov (United States)

    Lages, Sebastian; Schweins, Ralf; Huber, Klaus

    2007-09-06

    Polyacrylate anions are used to inhibit CaCO3 precipitation and may be a promising additive to control formation of inorganic nanoparticles. The origin of this applicability lies in specific interactions between the alkaline earth cations and the carboxylate functions along the polyacrylate chains. In the absence of CO32- anions, these interactions eventually cause precipitation of polyelectrolytes. Extended investigation of dilute sodium polyacrylate solutions approaching this precipitation threshold revealed a dramatic shrinking of the PA coil dimensions once the threshold is reached (Eur. Phys. J. E 2001, 5, 117). Recent isothermal calorimetric titration experiments by Antonietti et al. (Macromolecules 2004, 37, 3444) indicated that the driving force of this precipitation is entropic in nature. In the present work, we investigated the impact of temperature on the structural changes of dissolved polyacrylate chains decorated with alkaline earth cations. To this end, large polyacrylate chains were brought close to the precipitation threshold by the addition of distinct amounts of Ca2+ or Sr2+ cations. The resulting structural intermediates were then subjected to temperature variations in the range of 15 degrees C polyacrylate coils were recorded by means of light and neutron scattering. As a major result, we could unambiguously demonstrate that the coils can reversibly be collapsed and extended by increasing and decreasing the temperature, respectively.

  20. Quantitative Determination of Lattice Fluoride Effects on the Solubility and Crystallinity of Carbonated Apatites with Incorporated Fluoride

    Science.gov (United States)

    Yan, Guang; Moribe, Kunikazu; Otsuka, Makoto; Papangkorn, Kongnara; Higuchi, William I.

    2013-01-01

    The purpose of this study was to evaluate quantitatively the effects of fluoride on the solubility and crystallinity of carbonated apatites (CAPs) after its incorporation into the crystal lattice using the metastable equilibrium solubility (MES) distribution method. Fluoride incorporated CAPs (F-CAPs) of two different carbonate levels (3% and 5%) and fluoride contents from 0 to 20,000 μg/g were synthesized. X-ray diffraction experiments and Rietveld analysis were conducted to obtain crystallite microstrain and unit cell parameters. Acetate buffer MES solution media were prepared at two solution fluoride concentrations (0.2 mg/L and 2.0 mg/L) and at two pHs (5.0 and 5.7). The unit cell a-axis values of the F-CAPs were found to decrease as the fluoride content increased; consistent with the fluoride being incorporated into the crystal lattice. The fluoride concentrations in the MES solution media were high enough to provide a “swamping” effect such that the fluoride released from the F-CAPs during dissolution was minimal in changing the solution fluoride concentration. Employing the MES distribution superposition method, it was shown that the surface complex possessing the fluorapatite (FAP) stoichiometry (Ca10(PO4)6F2) accounted for the MES distribution behavior of all experiments. In addition, the mean pIFAP [the value of −log(aca 10PO46aF2) calculated from ionic activity product based on FAP stoichiometry of the MES dissolution media in which 50% of the F-CAP had dissolved] correlated well with the crystallite microstrain parameters of the F-CAPs. The incorporated fluoride in the F-CAPs showed only modest effects on F-CAP crystallinity and solubility. PMID:23235353

  1. Exraction and separation of CERIUM(IV/FLUORINE in fluoride-bearing cerium sulfate solution with fluoride coordination agent

    Directory of Open Access Journals (Sweden)

    Y. Li

    2014-07-01

    Full Text Available In this paper the extraction and separation of cerium/fluorine in fluoride-bearing cerium sulfate solution with fluoride coordination agent has been studied. The UV-vis spectra suggest that Zr6+ and Al3+ can scrub the F- from [CeF2] 2+ complex. The separation and conductivity studies show that aluminum salt is the most suitable fluoride coordination agent, and an ion-exchange reaction is involved between Ce4+/ [CeF2] 2+ and hydrogen ion.

  2. Small molecule fluoride toxicity agonists.

    Science.gov (United States)

    Nelson, James W; Plummer, Mark S; Blount, Kenneth F; Ames, Tyler D; Breaker, Ronald R

    2015-04-23

    Fluoride is a ubiquitous anion that inhibits a wide variety of metabolic processes. Here, we report the identification of a series of compounds that enhance fluoride toxicity in Escherichia coli and Streptococcus mutans. These molecules were isolated by using a high-throughput screen (HTS) for compounds that increase intracellular fluoride levels as determined via a fluoride riboswitch reporter fusion construct. A series of derivatives were synthesized to examine structure-activity relationships, leading to the identification of compounds with improved activity. Thus, we demonstrate that small molecule fluoride toxicity agonists can be identified by HTS from existing chemical libraries by exploiting a natural fluoride riboswitch. In addition, our findings suggest that some molecules might be further optimized to function as binary antibacterial agents when combined with fluoride. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Fluoride Rinses, Gels and Foams

    DEFF Research Database (Denmark)

    Twetman, Svante; Keller, Mette K

    2016-01-01

    AIM: The aim of this conference paper was to systematically review the quality of evidence and summarize the findings of clinical trials published after 2002 using fluoride mouth rinses, fluoride gels or foams for the prevention of dental caries. METHODS: Relevant papers were selected after...... an electronic search for literature published in English between 2003 and 2014. The included papers were assessed for their risk of bias and the results were narratively synthesized due to study heterogeneity. The quality of evidence was expressed according to GRADE. RESULTS: A total of 19 papers were included...... (6 on fluoride mouth rinse, 10 on fluoride gel and 3 on fluoride foam); 6 had a low risk of bias while 2 had a moderate risk. All fluoride measures appeared to be beneficial in preventing crown caries and reversing root caries, but the quality of evidence was graded as low for fluoride mouth rinse...

  4. Small Molecule Fluoride Toxicity Agonists

    Science.gov (United States)

    Nelson1, James W.; Plummer, Mark S.; Blount, Kenneth F.; Ames, Tyler D.; Breaker, Ronald R.

    2015-01-01

    SUMMARY Fluoride is a ubiquitous anion that inhibits a wide variety of metabolic processes. Here we report the identification of a series of compounds that enhance fluoride toxicity in Escherichia coli and Streptococcus mutans. These molecules were isolated by using a high-throughput screen (HTS) for compounds that increase intracellular fluoride levels as determined via a fluoride riboswitch-reporter fusion construct. A series of derivatives were synthesized to examine structure-activity relationships, leading to the identification of compounds with improved activity. Thus, we demonstrate that small molecule fluoride toxicity agonists can be identified by HTS from existing chemical libraries by exploiting a natural fluoride riboswitch. In addition, our findings suggest that some molecules might be further optimized to function as binary antibacterial agents when combined with fluoride. PMID:25910244

  5. Growth and characterization of fluoride monocrystalline fibres of the type LiY{sub 1-x} RE{sub x}F{sub 4} (RE=rare-earths); Crescimento e caracterizacao de fibras monocristalinas de fluoretos do tipo LiY{sub 1-x} TR{sub x}F{sub 4} (TR=terras raras)

    Energy Technology Data Exchange (ETDEWEB)

    Espirito Santo, Ana Maria do

    2005-07-01

    In this work we present the growth and characterization of LiF pure and rare-earth doped (Er and Nd) yttrium-lithium tetra-fluoride (LiYF{sub 4} or YLF) by the micropulling- down technique (muPD). The use of this technique is original for the present purpose. A mu-PD prototype in the resistive mode was firstly built to understand the most important operational parameters. A commercial equipment was later installed and specifically modified to grow fluoride fibres. Regular and transparent single-crystalline fibres of LiF (diameter of 0.6 mm and length up to 150 mm) were obtained. LiF crystalline fibres as a potential laser media presented the same spectroscopic properties of bulk crystals. The influence of capillary and crucible shapes, growth atmosphere and start composition stoichiometry on the growth process of YLF fibers were also investigated. In general, the fluorides are very sensitive to moisture contamination. The growth atmosphere plays an important role on the stoichiometry deviation. Since this fluoride melts incongruently, any compositional changes influences the solidification behavior of the material. Additionally, a limited pulling rate is required to the YLF phase formation and to the compositional homogeneity along the fiber. Homogeneous and regular section YLF fibres, with diameters between 0.5 to 0.8 mm and up to 60 mm in length, were obtained in a suitable and reproducible growth process. Er-doped (with nominal concentration of 10 and 40 mol%) and Nd-doped (with nominal concentration of 1.7 mol%) fibres were also successfully grown. Er-doped fibres were crack-free and the dopant concentration was practically uniform along the YLF phase. However, Nd-doped fibres presented a short initial transient in its concentration. The Nd distribution coefficient was evaluated as 0.58 for the YLF fibre. This value is greater than those estimated for YLF bulk crystals grown by normal freezing processes. The optical properties of the YLF:Nd fibres were similar

  6. Synthesis, characterization, and biological properties of nano-rare earth complexes with L-glutamic acid and imidazole

    Institute of Scientific and Technical Information of China (English)

    ZHOU Meifeng; HE Qizhuang

    2008-01-01

    Four nano-rare earth ternary complexes of L-glutamic acid and imidazole RE(Glu)3ImCl3·3H2O (RE=Ce3+, Pr3+, Sm3+, Dy3+, Glu= L-glutamic acid , and Im=imidazole) were synthesized. Their composition was characterized with elemental analysis, IR, and molar conductance. The TEM image indicated that the complexes were regular shaped and the length was about 30~60 nm. The antibacterial activity test showed that all these complexes exhibited better antibacterial ability against Escherichia coli, Staphylociccus aureus, and Candida albican (MIC were about 180, 100, and 310 μg/ml, respectively) and could be considered as broad-spectral antimicrobial. Their antitumor activity in vitro against leukemia K562 cells was measured using the MTT method. The results indicate that the four complexes possess strong inhibition effect on leukemia K562 cells. An approximately linear relationship is discovered between the relative inhibition rate and concentration, with the correlation coefficients R>0.7 and P<0.05, which is considered statistically significant.

  7. Modeling rare earth complexes: Sparkle/AM1 parameters for thulium (III)

    Science.gov (United States)

    Freire, Ricardo O.; Rocha, Gerd B.; Simas, Alfredo M.

    2005-08-01

    The Sparkle/AM1 model, recently defined for Eu(III), Gd(III) and Tb(III) [R.O. Freire, G.B. Rocha, A.M., Simas, Inorg. Chem. 44 (2005) 3299], is extended to Tm(III). A set of 15 structures of high crystallographic quality from the Cambridge Crystallographic Database, with ligands chosen to be representative of all complexes with nitrogen or oxygen directly bonded to the Tm(III) ion, was used as a training set. For the 15 complexes, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the Tm(III) ion and the oxygen or nitrogen ligand atoms of the first sphere of coordination, is 0.07 Å, a level of accuracy useful for luminescent complex design.

  8. Fluoride and Oral Health

    DEFF Research Database (Denmark)

    O'Mullane, D M; Baez, R J; Jones, S

    2016-01-01

    and strategies is noteworthy. This updated version of ‘Fluoride and Oral Health’ has adopted an evidence-based approach to its commentary on the different fl uoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published...

  9. How Does Fluoride Work?

    Science.gov (United States)

    ... A Movies & More Quizzes Kids' Dictionary of Medical Words En Español What Other Kids Are Reading 7 Videos: Kids Talk About ... There's fluoride in your toothpaste and even in your water. But how does it work to keep teeth ...

  10. Salt fluoridation and oral health

    Directory of Open Access Journals (Sweden)

    Thomas M. Marthaler

    2013-11-01

    Full Text Available The aim of this paper is to make known the potential of fluoridated salt in community oral health programs, particularly in South Eastern Europe. Since 1922, the addition of iodine to salt has been successful in Switzerland. Goiter is virtually extinct. By 1945, the cariesprotective effect of fluorides was well established. Based on the success of water fluoridation, a gynecologist started adding of fluoride to salt. The sale of fluoridated salt began in 1956 in the Swiss Canton of Zurich, and several other cantons followed suit. Studies initiated in the early seventies showed that fluoride, when added to salt, inhibits dental caries. The addition of fluoride to salt for human consumption was officially authorized in 1980-82. In Switzerland 85% of domestic salt consumed is fluoridated and 67% in Germany. Salt fluoridation schemes are reaching more than one hundred million in Mexico, Colombia, Peru and Cuba. The cost of salt fluoridation is very low, within 0.02 and 0.05 € per year and capita. Children and adults of the low socio-economic strata tend to have substantially more untreated caries than higher strata. Salt fluoridation is by far the cheapest method for improving oral health. Conclusions. Salt fluoridation has cariostatic potential like water fluoridation (caries reductions up to 50%. In Europe, meaningful percentages of users have been attained only in Germany (67% and Switzerland (85%. In Latin America, there are more than 100 million users, and several countries have arrived at coverage of 90 to 99%. Salt fluoridation is by far the cheapest method of caries prevention, and billions of people throughout the world could benefit from this method.

  11. Synthesis, Characterization and Activity of Rare Earth Complexes with Schiff Base From 2,6-Diformylpyridine N-Oxide and 4-Amino-antipyrine

    Institute of Scientific and Technical Information of China (English)

    于青; 唐瑜; 谭民裕

    2002-01-01

    Six new rare earth complexes with Schiff base from 2,6-diformylpyridine N-oxide and 4-amino-antipyrine were synthesized. These complexes with general formula REL(NO3)3 (RE=La, Pr, Eu, Tb, Er, Y) were characterized by elemental analysis, IR, UV, molar conductance measurements and antimicrobial activity.

  12. Structural diversity in binuclear complexes of alkaline earth metal ions with 4,6-diacetylresorcinol

    Science.gov (United States)

    Shebl, Magdy; Khalil, Saied M. E.; Taha, A.; Mahdi, M. A. N.

    2012-11-01

    A new series of binuclear and mixed-ligand complexes with the general formula: [M 2(LO)yClz]; where M = Mg(II), Ca(II), Sr(II) and Ba(II); H2L = 4,6-diacetylresorcinol, the secondary ligand L' = acetylacetone (acac), 8-hydroxyquinoline (8-HQ) or 2,2'-bipyridyl (Bipy), n = 0-2, m = 1, 2, x = 0, 1, 2, 4, y = 0, 2, 4, 5 and z = 0-2; have been synthesized. They have been characterized by the analytical and spectral methods (IR, 1H NMR and mass) as well as TGA and molar conductivity measurements. The spectroscopic and conductance data suggested that the H2L ligand behaves as a neutral, monobasic or dibasic tetradentate ligand, depending on the basicity of the secondary ligand, through the two phenolic and two carbonyl groups. Binuclear octahedral geometry has been assigned to all of the prepared complexes in various molar ratios 2:2; 2:2:2; 1:2:1 and 1:2:4 (L:M:L'). Molecular orbital calculations were performed for the ligands and their complexes using Hyperchem 7.52 program on the bases of PM3 level and the results were correlated with the experimental data. The ligand and some of its alkaline metal(II) complexes showed antibacterial activity towards some of Gram-positive and Gram-negative bacteria, yeast (Candida albicans) and fungus (Aspergillus fumigatus).

  13. Thermochemical Study of Mixed Ligand Complexes of Rare Earths with Glycine and L-alanine

    Institute of Scientific and Technical Information of China (English)

    QU Jing-nian; LIU Yi; YU Hua-guang; LEI Ke-lin; YAN Cheng-nong; QU Song-sheng

    2004-01-01

    In order to obtain the standard molar enthalpies of formation of Rare-Earth amino acid coordination compounds, precise isothermal solution-reaction calorimetric method was used. The value of ΔrHΘm of two coordination reactions was determined at T = 298.2 K. From the experimental results and other auxiliary values, the standard molar enthalpies of formation of Ln(Gly)5/2(Ala)3/2 (ClO4)3·H2O(s) [Ln = La, Yb] at T = 298.2 K were obtained. The values of them is to be ΔrHΘm [La(Gly)5/2(Ala)3/2(ClO4)3·H2O(s)] =-3545.45 kJ/ mol and ΔrHΘm [Yb(Gly)5/2(Ala)3/2(ClO4)3·H2O(s)]= -3793.81 kJ/mol, respectively.

  14. Investigation on the Coordinate Structures of the Rare Earth Metal Complexes with Edta and Cydta Ligands

    Institute of Scientific and Technical Information of China (English)

    WangJun; ZhangXiang-dong; ZhangYang; LiuZhen-rong

    2003-01-01

    The crystal and molecular structures of cydta(trans-1, 2-cyclohexanediaminetetraacetic acid) have been determined by single-crystal X-ray structure analyses. The reasons that REⅢ-edta and REⅢ-cydta complexes select different coordinate structures were discussed and illustrated through the comparison of the molecular and crystal structures between edta and cydta, (NH4)[Ⅲ(edta) (H2O)3]·5H2O and (NH4)[YⅢ(cydta)(H2O)2]·5H2O as well as (NH4)[GdⅢ(edta)(H2O)3]·5H2O and (NH4)[GdⅢ(cydta)(H2O)2]·5H2O complexes.

  15. Investigation on the Coordinate Structures of the Rare Earth Metal Complexes with Edta and Cydta Ligands

    Institute of Scientific and Technical Information of China (English)

    Wang Jun; Zhang Xiang-dong; Zhang Yang; Liu Zhen-rong

    2003-01-01

    The crystal and molecular structures of cydta (trans-1, 2-cyclohexanediaminetetraacetic acid) have been determined by single-crystal X-ray structure analyses. The reasons that REⅢ-edta and REⅢ-cydta complexes select different coordinate structures were discussed and illustrated through the comparison of the molecular and crystal structures between edta and cydta, (NH4)[YⅢ(edta)(H2O)3]*5H2O and (NH4)[YⅢ(cydta)(H2O)2]*5H2O as well as (NH4)[GdⅢ(edta)(H2O)3]*5H2O and (NH4)[GdⅢ(cydta)(H2O)2]*5H2O complexes.

  16. Modeling rare earth complexes: Sparkle/PM3 parameters for thulium(III)

    Science.gov (United States)

    Freire, Ricardo O.; Rocha, Gerd B.; Simas, Alfredo M.

    2006-07-01

    The Sparkle model, recently defined for Tm(III) within AM1 [R.O. Freire, G.B. Rocha, A.M. Simas, Chem. Phys. Lett. 411 (2005) 61], is now extended to PM3. For the same 15 complexes previously used, the Sparkle/PM3 unsigned mean error, for all interatomic distances between the Tm(III) ion and the directly coordinating oxygen or nitrogen atoms, is 0.08 Å, a level of accuracy equivalent to the Sparkle/AM1 figure of 0.07 Å, as well as to results from present day ab initio effective core potential calculations. The results thus indicate that both Sparkle/AM1 and Sparkle/PM3 models may prove useful for luminescent Tm(III) complex design.

  17. Health Effects Associated with Water Fluoridation.

    Science.gov (United States)

    Richmond, Virginia L.

    1979-01-01

    Discussion is presented concerning fluoridation of water supplies. Correlation between fluoride in drinking water and improved dental health is reviewed. Relationship is expressed between fluoridation and reduced tooth decay. Use of fluoride in treating skeletal disorders is discussed. Author advocates fluoridating water supplies. (SA)

  18. Enthalpies of Solution of Complexes of Rare Earth Nitrate with L-α-Histidine in Water

    Institute of Scientific and Technical Information of China (English)

    刘洋; 房艳; 高胜利; 陈三平; 史启祯

    2002-01-01

    The enthalpies of solution in water of complexes of RE(NO3)3 (RE=La~Nd, Sm~Lu, Y) with L-α-Histidine (His) were measured at 298.15 K. The standard enthalpies of formation of RE(His)3+(aq) were calculated. The "tetrad effect" regularity was observed from the curve, which is the enthalpies of solution plotted against the atomic numbers of the elements in lanthanide series.

  19. Drilling through the largest magma chamber on Earth: Bushveld Igneous Complex Drilling Project (BICDP)

    Science.gov (United States)

    Trumbull, R. B.; Ashwal, L. D.; Webb, S. J.; Veksler, I. V.

    2015-05-01

    A scientific drilling project in the Bushveld Igneous Complex in South Africa has been proposed to contribute to the following scientific topics of the International Continental Drilling Program (ICDP): large igneous provinces and mantle plumes, natural resources, volcanic systems and thermal regimes, and deep life. An interdisciplinary team of researchers from eight countries met in Johannesburg to exchange ideas about the scientific objectives and a drilling strategy to achieve them. The workshop identified drilling targets in each of the three main lobes of the Bushveld Complex, which will integrate existing drill cores with new boreholes to establish permanently curated and accessible reference profiles of the Bushveld Complex. Coordinated studies of this material will address fundamental questions related to the origin and evolution of parental Bushveld magma(s), the magma chamber processes that caused layering and ore formation, and the role of crust vs. mantle in the genesis of Bushveld granites and felsic volcanic units. Other objectives are to study geophysical and geodynamic aspects of the Bushveld intrusion, including crustal stresses and thermal gradient, and to determine the nature of deep groundwater systems and the biology of subsurface microbial communities.

  20. An evaluation of parametric sensitivities of different climatic variables simulated by the Earth System Model of Intermediate Complexity LOVECLIM

    Science.gov (United States)

    Shi, Yuhan; Duan, Qingyun

    2017-04-01

    Earth System Models (ESMs) are an important tool for understanding past climate evolution and for predicting future climate change. However, the ESM model outputs contain significant uncertainties. A major source of uncertainties is from the specification of model parameters. Specification of ESM model parameters is complicated as most ESMs contain a large number of model parameters. Further, ESMs simulate many different climatic variables and are computationally expensive to run. In this study, we intend to use a design of experiment approach to evaluate the parametric sensitivities of different climatic variables simulated by LOVECLIM, an Earth System Model of Intermediate Complexity (EMIC). Three sensitivity analysis methods are used to explore the sensitivities of different outputs of LOVECLIM, such as global mean temperature, global land/ocean precipitation and evaporation to different model parameters. A newly developed software package, Uncertainty Quantification Python Laboratory (UQ-PyL), is employed to execute the sensitivity analysis. A total of 23 adjustable parameters of the model were considered. This presentation will present the preliminary results of parameter sensitivity analysis, which, in turn, should form the basis for further optimization of the model parameters to better simulate the climate system.

  1. Syntheses and crystal structures of rare earth (Nd, Gd) 1-D chain complexes with N-p-tolylsulfonyl-β-alanine

    Institute of Scientific and Technical Information of China (English)

    MA Lufang; LI Xiaodong; WANG Liya; LIANG Fupei; ZHANG Manbo; YU Kaibei

    2005-01-01

    Two rare earth complexes of Ts-β-AlaH with the formula of [Ln2(H2O)4(Ts-β-AlaH)6]n·4nH2O (where Ln =Nd(1), Gd(2); Ts-β-AlaH = N-p-tolylsulfonyl-β-Alanine) have been synthesized and characterized by elemental analysis, IR,and X-ray diffraction. The results show that the two complexes are isostructural. They crystallize in a monoclinic system with P21/n space group. Crystal data for 1: a = 0.95149(19) nm, b = 1.9012(4) nm, c = 2.2863(5) nm, β= 100.37(3)°, Z = 4,Dc = 1.509 mg/cm3, F(000) = 1880, R1 = 0.0560, wR2 = 0.1564 [Ⅰ> 2σ(Ⅰ)]; for 2: a = 0.9495(2) nm, b = 1.9037(4) nm, c =2.2987(5) nm, β= 99.87(3)°, Z = 4, Dc= 1.541 mg/cm3, F(000) = 1916, R1 = 0.0515, wR2= 0.1566 [Ⅰ>2σ (Ⅰ)]. The two complexes are one-dimensional chains and the coordination number of the Nd3+ or Gd 3+ ion is nine.

  2. Monitoring of fluoride in water samples using a smartphone

    Energy Technology Data Exchange (ETDEWEB)

    Levin, Saurabh [Akvo Foundation (Netherlands); Krishnan, Sunderrajan [INREM Foundation (India); Rajkumar, Samuel; Halery, Nischal; Balkunde, Pradeep [Akvo Foundation (Netherlands)

    2016-05-01

    In several parts of India, groundwater is the only reliable, year round source for drinking water. Prevention of fluorosis, a chronic disease resulting from excess intake of fluoride, requires the screening of all groundwater sources for fluoride in endemic areas. In this paper, the authors present a field deployable colorimetric analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the colored solution as well as an easy-fit, and compact sample chamber (Akvo Caddisfly). Phones marketed by different smartphone makers were used. Commercially available zirconium xylenol orange reagent was used for determining fluoride concentration. A software program was developed to use with the phone for recording and analyzing the RGB color of the picture. Linear range for fluoride estimation was 0–2 mg l{sup −1}. Around 200 samples, which consisted of laboratory prepared as well as field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Ion Selective Electrode (ISE) method and Akvo Caddisfly (Phones A, B and C), with correlation coefficient ranging between 0.9952 and 1.000. In addition, there was no significant difference in the mean fluoride content values between ISE and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for groundwater fluoride analysis in the field. - Highlights: • Fluoride is an inorganic pollutant in ground water, affecting human health. • A colorimetric method for measurement of fluoride in drinking water with smartphone • Measurement is by mixing water with zirconyl xylenol orange complex reagent. • Results are comparable with laboratory-based ion selective fluoride electrode method.

  3. Industrial fluoride pollution: chronic fluoride poisoning in Cornwall Island cattle

    Energy Technology Data Exchange (ETDEWEB)

    Krook, L.; Maylin, G.A.

    1979-04-01

    An aluminum plant on the south bank of the St. Lawrence River, southwest of Cornwall Island, Ontario, Canada, has emitted 0.816 metric tons of fluoride daily since 1973. Considerably higher amounts were emitted from 1959 to 1973. The plant was designated as the major source of fluoride emissions impacting on Cornwall Island. Cattle located on this island showed signs of chronic fluoride poisoning. This poisoning was manifested clinically by stunted growth and dental fluorosis to a degree of severe interference with drinking and mastication. This Cornwall Island herds study indicates that the established tolerance level of fluoride for performance of dairy and beef cattle is not valid since the tolerance level was set based on experiments with healthy calves which were exposed to dietary fluoride from 3 to 4 months of age and not on cattle which were chronically exposed to fluoride from conception to death. 56 references.

  4. Enhanced Brightness of Eu3+ Complex in Organic Electroluminescent Devices by Using Another Rare-Earth Ion

    Institute of Scientific and Technical Information of China (English)

    白峰; 邓振波; 高新; 李勇; 徐怡庄; 吴瑾光

    2002-01-01

    Rare-earth ions Tb3+ and La3+ were used as a bridge to improve the energy transfer from the polymer to an Eu complex. The material Tb(La)0.5Eu0.5 (BSA)3phen was synthesized and used as the emission layer in the device:ITO/PVK:Tb(La)0.5Eu0.5 (BSA)3phen/Alq/Al. The two device were compared in detail and it was found that the device using La0.5Eu0.5 (BSA)3phen as the emission material had better monochromatic characteristics with the maximal brightness of 102cd/m2 and the colour coordinates x = 0.55 and y = 0.36.

  5. Rare earth elements and titanium in plants, soils and groundwaters in the alkaline-ultramafic complex of Salitre, MG Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ceccantini, G. [Instituto de Biociencias, Sao Paulo, (Brazil). Dept. de Botanica; Figueiredo, A.M.G. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil). Div. de Radioquimica; Sondag, F.; Soubies, F. [ORSTOM, 93 - Bondy (France); Soubies, F. [Universite Paul Sabatier, 31 - Toulouse (France)

    1997-12-31

    The contents of rare earth elements (REE) and titanium in various plant species, in groundwaters and in soils from the alkaline-ultramafic complex of Salitre, have been determined. Due to the the particular mineralogy of the bedrock, REE and Ti exhibit high concentrations in the soils. Despite this, plants generally present REE concentrations within the ranges usually found in plants, and the transfer factor from soil to plant is at least ten times below the range reported in the literature, confirming that the concentrations of REE in the plants are widely independent of the soil content. All species present normalized patterns similar to those of the soils, characterized by an enrichment in light REE. Several plants show Ti concentrations about three times higher than the reference values. It is suggested that in the studied ecosystem, the plant metabolism affect the REE distribution in the groundwaters, leading to an enrichment of the superficial waters in heavy REE

  6. Imidazolin-2-iminato complexes of rare earth metals with very short metal-nitrogen bonds: experimental and theoretical studies.

    Science.gov (United States)

    Panda, Tarun K; Trambitas, Alexandra G; Bannenberg, Thomas; Hrib, Cristian G; Randoll, Sören; Jones, Peter G; Tamm, Matthias

    2009-06-15

    The reactions of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH, 1-H) with trimethylsilylmethyl lithium (LiCH(2)SiMe(3)) and anhydrous rare earth metal trichlorides MCl(3) afforded the imidazolin-2-iminato complexes [(1)MCl(2)(THF)(3)] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and [(1)GdCl(2)(THF)(2)] x [LiCl(THF)(2)] (2d). Treatment of complexes 2 with dipotassium cyclooctatetradienide, K(2)(C(8)H(8)) resulted in the formation of two- or three-legged piano-stool complexes of the type [(eta(8)-C(8)H(8))M(1)(THF)(n)] (3a, M = Sc, n = 1; 3b, M = Y, n = 2; 3c, M = Lu, n = 2; 3d, M = Gd, n = 2). X-ray diffraction analyses of all eight complexes 2 and 3 revealed the presence of very short metal-nitrogen bonds, which are among the shortest ever observed for these elements. [(eta(8)-C(8)H(8))Sc(1)(THF)] (3a) reacted with 2,6-dimethylphenyl isothiocyanate (Xy-NCS) to form the [2 + 2]-cycloaddition product 4, which contains a thioureato-N,N' moiety. The related COT-titanium complex [(eta(8)-C(8)H(8))TiCl(1)] (6) could be obtained from [(1)TiCl(3)] (5) by reaction with K(2)(C(8)H(8)) and was structurally characterized. As a theoretical analysis of the nature of the metal-nitrogen bond, density functional theory (DFT) calculations have been carried out for complexes 3a and 6 and also for the model complexes [(eta(8)-C(8)H(8))Sc(NIm(Me))] (7), [(eta(8)-C(8)H(8))Ti(NIm(Me))](+) (8), and [(eta(8)-C(8)H(8))Ti(NXy)] (9), revealing a marked similarity of the bonding in imidazolin-2-iminato and conventional imido metal complexes.

  7. Synthesis, Characterization and Luminescent Properties of Complexes of Rare Earth Nitrates with 2,2′:4′,4″:2″,2-Quaterpyridine

    Institute of Scientific and Technical Information of China (English)

    唐瑜; 张正华; 谭民裕; 王锐

    2002-01-01

    The rare earth nitrate complexes with 2,2′:4′,4″:2″,2-quaterpyridine (L) were prepared in ethylacetate. These new complexes with the general formula [RE(NO3)3L]*H2O (RE = La, Pr, Eu, Tb, Er, Y) were characterized by elemental analysis, IR spectra, thermal analysis and molar conductance measurements. The luminescence properties of these complexes were also studied.

  8. A user-friendly earth system model of low complexity: the ESCIMO system dynamics model of global warming towards 2100

    Science.gov (United States)

    Randers, Jorgen; Golüke, Ulrich; Wenstøp, Fred; Wenstøp, Søren

    2016-11-01

    We have made a simple system dynamics model, ESCIMO (Earth System Climate Interpretable Model), which runs on a desktop computer in seconds and is able to reproduce the main output from more complex climate models. ESCIMO represents the main causal mechanisms at work in the Earth system and is able to reproduce the broad outline of climate history from 1850 to 2015. We have run many simulations with ESCIMO to 2100 and beyond. In this paper we present the effects of introducing in 2015 six possible global policy interventions that cost around USD 1000 billion per year - around 1 % of world GDP. We tentatively conclude (a) that these policy interventions can at most reduce the global mean surface temperature - GMST - by up to 0.5 °C in 2050 and up to 1.0 °C in 2100 relative to no intervention. The exception is injection of aerosols into the stratosphere, which can reduce the GMST by more than 1.0 °C in a decade but creates other serious problems. We also conclude (b) that relatively cheap human intervention can keep global warming in this century below +2 °C relative to preindustrial times. Finally, we conclude (c) that run-away warming is unlikely to occur in this century but is likely to occur in the longer run. The ensuing warming is slow, however. In ESCIMO, it takes several hundred years to lift the GMST to +3 °C above preindustrial times through gradual self-reinforcing melting of the permafrost. We call for research to test whether more complex climate models support our tentative conclusions from ESCIMO.

  9. Geochemical Characteristics of Rare Earth Elements of Guidong Granitic Complex and Relationship with Uranium Mineralization

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhanshi; Hua Renmin; Liu Xiaodong; Deng Ping; Wu Lieqin

    2007-01-01

    Guidong granitic complex is constituted by Luxi intrusion, Xiazhuang intrusion, Maofeng intrusion, Sundong intrusion, Aizi intrusion and Siqian intrusion, which emplaced in Indosinian and early Yanshanian Periods. These intrusions varied from each other not only in major element content, aluminium saturation index, but also in values of ΣREE, δEu, and LREE/HREE, (La/Yb)N, (La/Sm)N and (Gd/Yb)N. The Maofeng intrusion, which has the closest relationship with uranium mineralization, belongs to strong peraluminous granites. Having undergone much intense fluid-rock interaction, it is characterized by typical M-type tetrad effects and lowest values of ΣREE, δEu, LREE/HREE, (La/Yb)N, (La/Sm)N and (Gd/Yb)N ratios than other studied intrusions.

  10. Pharmacological Study on Antitumor Activity of 5-Fluorouracil-1-Acetic Acid and Its Rare Earth Complexes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The antitumor activity of 5-fluorouracil-1-acetic acid(HFAA) and its lanthanide complexes(La(FAA)3, Eu(FAA)3) were studied. The results show that HFAA, La(FAA)3 and Eu(FAA)3 with the concentrations of 1.0×10-5~1.0×10-2 μg·ml-1 inhibit the colony formation of leukemia cells(L1210) and the growth of transplanted tumor sarcoma 180(S180), hepatic carcinoma(HEPA) and ehrlich ascites tumor(EC) as well. The maximum inhibitory rate of Eu(FAA)3 for S180 is 38.4%, that HFAA and La(FAA)3 for EC are 22.4% and 43.4%, respectively. The life prolongation rate of Eu(FAA)3 for HEPA bearing mice is as long as 284%.

  11. Measured rates of fluoride/metal association correlate with rates of superoxide/metal reactions for Fe(III)EDTA(H2O)- and related complexes.

    Science.gov (United States)

    Summers, Jack S; Baker, Joseph B; Meyerstein, Dan; Mizrahi, Amir; Zilbermann, Israel; Cohen, Haim; Wilson, Christopher M; Jones, Jamie R

    2008-02-06

    The effects of 10 paramagnetic metal complexes (Fe(III)EDTA(H2O)-, Fe(III)EDTA(OH)2-, Fe(III)PDTA-, Fe(III)DTPA2-, Fe(III)2O(TTHA)2-, Fe(III)(CN)6(3-), Mn(II)EDTA(H2O)2-, Mn(II)PDTA2-, Mn(II)beta-EDDADP2-, and Mn(II)PO4(-)) on F- ion 19F NMR transverse relaxation rates (R2 = 1/T2) were studied in aqueous solutions as a function of temperature. Consistent with efficient relaxation requiring formation of a metal/F- bond, only the substitution inert complexes Fe(III)(CN)6(3-) and Fe(III)EDTA(OH)2- had no measured effect on T2 relaxation of the F- 19F resonance. For the remaining eight complexes, kinetic parameters (apparent second-order rate constants and activation enthalpies) for metal/F- association were determined from the dependence of the observed relaxation enhancements on complex concentration and temperature. Apparent metal/F- association rate constants for these complexes (k(app,F-)) spanned 5 orders of magnitude. In addition, we measured the rates at which O2*- reacts with Fe(III)PDTA-, Mn(II)EDTA(H2O)2-, Mn(II)PDTA2-, and Mn(II)beta-EDDADP2- by pulse radiolysis. Although no intermediate is observed during the reduction of Fe(III)PDTA- by O2*-, each of the Mn(II) complexes reacts with formation of a transient intermediate presumed to form via ligand exchange. These reactivity patterns are consistent with literature precedents for similar complexes. With these data, both k(app,O2-) and k(app,F-) are available for each of the eight reactive complexes. A plot of log(k(app,O2-)) versus log(k(app,F-)) for these eight showed a linear correlation with a slope approximately 1. This correlation suggests that rapid metal/O2*- reactions of these complexes occur via an inner-sphere mechanism whereas formation of an intermediate coordination complex limits the overall rate. This hypothesis is also supported by the very low rates at which the substitution inert complexes (Fe(III)(CN)6(3-) and Fe(III)EDTA(OH)2-) are reduced by O2*-. These results suggest that F- 19F NMR

  12. Fluoride Content in Alcoholic Drinks

    OpenAIRE

    Goschorska, Marta; Gutowska, Izabela; Baranowska-Bosiacka, Irena; Ra?, Monika Ewa; Chlubek, Dariusz

    2015-01-01

    The aim of the study was to determine the role of alcoholic drinks as a potential source of dietary fluoride by means of measuring fluoride levels in selected alcoholic drinks available on the Polish market that are also diverse in terms of the percentage content of ethanol. The study was conducted on 48 types of drinks with low, medium, and high alcohol content available on the Polish market and offered by various manufacturers, both Polish and foreign. Fluoride concentrations in individual ...

  13. Optical detection of sodium salts of fluoride, acetate and phosphate by a diacylhydrazine ligand by the formation of a colour alkali metal complex

    Indian Academy of Sciences (India)

    Purnandhu Bose; Ranjan Dutta; I Ravikumar; Pradyut Ghosh

    2011-11-01

    A solution of N, N'-diacylhydrazine ligand in organic solvent is potential for colourimetric detection of F−/AcO−/PO$^{3−}_{4}$ via -NH deprotonation, tautomerization and its stabilization as a colour alkali metal complex.

  14. Thermodynamic stability of complexes of BF{sub 3}, PF{sub 5} and AsF{sub 5} with chlorine fluorides, oxyfluorides, and related compounds

    Energy Technology Data Exchange (ETDEWEB)

    Trowbridge, L.D.

    1996-07-01

    The recent discovery of solid, water sensitive, arsenic-containing deposits in auxiliary process piping in the PGDP led to a search for explanations that could account for such accumulated material. A plausible explanation for the deposits is the formation of complexes of AsF{sub 5} with one or more gases that may have been present as a result of cascade equipment cleanup activities. A literature search was performed. The target of the search was literature that would provide information on the dissociation pressure of complexes of AsF{sub 5} or its hydrolysis products with any gases that may be (at least intermittently) present in the cascade location where the deposits were found. While the precise information sought (namely reliable, accurate dissociation pressures of such complexes at cascade temperatures) was not found in the detail desired. other information on these or similar complexes was obtained which permits prediction of the conditions under which the complexes might form, dissociate, or migrate, and how they might behave in the presence of atmospheric moisture. Information was gathered on potential AsF{sub 5} complexes with ClF, ClF{sub 3}, ClF{sub 5}, ClF{sub 3}O, ClO{sub 2}F, and ClO{sub 3}F. Information was also collected on many other related complexes as it was encountered, particularly for series of complexes which could assist in predicting chemical trends. Thermodynamic analysis and property estimation methods have been used to generate provisional estimates of the dissociation pressures of the two complexes ClF{sub 3}*AsF{sub 5} and ClO{sub 2}F*AsF{sub 5}. In addition, several hydrolysis species have been identified, and stability properties of the most relevant such complex (H{sub 3}O*AsF{sub 6}) have similarly been estimated. While the predicted dissociation pressures are somewhat uncertain. they do lead to a tentative picture of the formation and behavior of such complexes in a cascade cleanup environment.

  15. Fluoride removal by Al, Ti, and Fe hydroxides and coexisting ion effect.

    Science.gov (United States)

    Zhang, Jianfeng; Brutus, Timothy E; Cheng, Jiemin; Meng, Xiaoguang

    2017-07-01

    Batch experiments were conducted to evaluate fluoride removal by Al, Fe, and Ti-based coagulants and adsorbents, as well as the effects of coexisting ions and formation of aluminum-fluoride complexes on fluoride removal by co-precipitation with alum (Al2(SO4)3·18H2O). Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8. Nano-crystalline TiO2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3-5. Coexisting anions in water decreased the removal of fluoride in the order: phosphate (2.5mg/L)>arsenate (0.1mg/L)>bicarbonate (200mg/L)>sulfate (100mg/L)=nitrate (100mg/L)>silicate (10mg/L) at a pH of 6.0. The effect of silicate became more significant at pH>7.0. Calcium and magnesium improved the removal of fluoride. Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al(OH)3 precipitates from 8.9 to 8.4, indicating the chemical adsorption of fluoride at the surface. The presence of fluoride in solution significantly increased the soluble aluminum concentration at pHfluoride during co-precipitation with aluminum sulfate. Copyright © 2017. Published by Elsevier B.V.

  16. The Ghost in the Machine: Fracking in the Earth's Complex Brittle Crust

    Science.gov (United States)

    Malin, P. E.

    2015-12-01

    This paper discusses in the impact of complex rock properties on practical applications like fracking and its associated seismic emissions. A variety of borehole measurements show that the complex physical properties of the upper crust cannot be characterized by averages on any scale. Instead they appear to follow 3 empirical rule: a power law distribution in physical scales, a lognormal distribution in populations, and a direct relation between changes in porosity and log(permeability). These rules can be directly related to the presence of fluid rich and seismically active fractures - from mineral grains to fault segments. (These are the "ghosts" referred to in the title.) In other physical systems, such behaviors arise on the boundaries of phase changes, and are studied as "critical state physics". In analogy to the 4 phases of water, crustal rocks progress upward from a un-fractured, ductile lower crust to nearly cohesionless surface alluvium. The crust in between is in an unstable transition. It is in this layer methods such as hydrofracking operate - be they in Oil and Gas, geothermal, or mining. As a result, nothing is predictable in these systems. Crustal models have conventionally been constructed assuming that in situ permeability and related properties are normally distributed. This approach is consistent with the use of short scale-length cores and logs to estimate properties. However, reservoir-scale flow data show that they are better fit to lognormal distributions. Such "long tail" distributions are observed for well productivity, ore vein grades, and induced seismic signals. Outcrop and well-log data show that many rock properties also show a power-law-type variation in scale lengths. In terms of Fourier power spectra, if peaks per km is k, then their power is proportional to 1/k. The source of this variation is related to pore-space connectivity, beginning with grain-fractures. We then show that a passive seismic method, Tomographic Fracture

  17. Fluoride ion release and solubility of fluoride enriched interim cements.

    Science.gov (United States)

    Lewinstein, Israel; Block, Jonathan; Melamed, Guy; Dolev, Eran; Matalon, Shlomo; Ormianer, Zeev

    2014-08-01

    Interim and definitive restorations cemented with interim cements for a prolonged interval are susceptible to bacterial infiltration and caries formation. The purpose of this in vitro study was to evaluate the long-term fluoride release and solubility of aged ZnO-based interim cements enriched separately with 0.4% NaF and SnF2. Four different brands of cements (Tempbond, Tempbond NE, Procem, and Freegenol) were tested for fluoride release and solubility. For every test, 6 disk specimens of each cement with NaF and SnF2, and 6 with no fluoride enrichment (control) were fabricated, for a total of 72 specimens. The disks were incubated in deionized water. Fluoride ion release was recorded at 1, 7, 14, 21, 63, 91, and 182 days. Solubility was calculated as weight percent after 90 days of incubation. The data were analyzed by analysis of variance with repeated measures and the Tukey honestly significant difference post hoc test (Pfluorides released fluoride ions for at least 182 days. Cements mixed with NaF released more fluoride ions than those mixed with SnF2 (P.97), indicating a diffusion-controlled fluoride release. Cement and fluoride types were the main affecting factors in fluoride ion release. The addition of fluorides slightly increased the solubility of the cements. Given their long-term sustained and diffusive controlled release, these fluorides, particularly NaF when mixed with ZnO-based interim cements, may be useful for caries prevention under provisionally cemented restorations. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  18. Novel synergism by complex ligands in solvent extraction of rare earth metals(III) with {beta}-diketones

    Energy Technology Data Exchange (ETDEWEB)

    Imura, H. [Department of Environmental Sciences, Faculty of Science, Ibaraki University, Mito 310-8512 (Japan)]. E-mail: imura@mx.ibaraki.ac.jp; Ebisawa, M. [Department of Environmental Sciences, Faculty of Science, Ibaraki University, Mito 310-8512 (Japan); Kato, M. [Department of Environmental Sciences, Faculty of Science, Ibaraki University, Mito 310-8512 (Japan); Ohashi, K. [Department of Environmental Sciences, Faculty of Science, Ibaraki University, Mito 310-8512 (Japan)

    2006-02-09

    The extraction of rare earth metals(III) (RE) with hexafluoroacetylacetone (Hhfa) and 2-thenoyltrifluoroacetone (Htta) was studied in the presence of some cobalt(III) chelates such as tris(acetylacetonato)cobalt(III), tris(4-isopropyltropolonato)cobalt(III), tris(8-quinolinolato)cobalt(III), tris(8-quinolinethiolato)cobalt(III), and tris(diethyldithiocarbamato)cobalt(III) in benzene or toluene. The synergistic enhancement of the extraction of RE, especially of lanthanum(III) was found in all the systems. Therefore, those cobalt(III) chelates act as synergists or complex ligands. The equilibrium analysis and IR spectroscopic study were performed to evaluate the present synergistic mechanism. It was found that the RE-{beta}-diketone chelates form 1:1 adducts, i.e., binuclear complexes, with the cobalt(III) chelates in the organic phase. The formation constants ({beta} {sub s,1}) were determined and compared with those reported previously. The spectroscopic studies demonstrated that adducts have two different structures with inner- and outer-sphere coordination. In the former the cobalt(III) chelate directly coordinated to the RE ion and displaced the coordinated water molecules. In the latter the hydrogen-bonding was formed between the coordinating oxygen or sulfur atoms of cobalt(III) chelate and hydrogen atoms of the coordinated water molecules in the RE-{beta}-diketone chelate. The types of the adducts are mainly due to the steric factors of the RE-{beta}-diketone chelates and the cobalt(III) chelates.

  19. Preparation of rare-earth metal complex oxide catalysts for catalytic wet air oxidation

    Institute of Scientific and Technical Information of China (English)

    LI Ning; LI Guangming; YAO Zhenya; ZHAO Jianfu

    2007-01-01

    Catalytic wet air oxidation(CWAO)is one of the most promising technologies for pollution abatement.Developing catalysts with high activity and stability is crucial for the application of the CWAO process.The Mn/Ce complex oxide catalyrsts for CWAO of high concentration phenol containing wastewater were prepared by coprecipitation.The catalyst preparation conditions were optimized by using an orthogonal layout method and single-factor experimental analysis.The Mn/Ce serial catalysts were characterized by Brunauer-Emmett-Teller(BET)analysis and the metal cation leaching was measured by inductively coupled plasma torch-atomic emission spectrometry(ICP-AES).The results show that the catalysts have high catalytic activities even at a low temperature(80℃)and low oxygen partial pressure(0.5 MPa)in a batch reactor.The metallic ion leaching is comparatively low(Mn<6.577 mg/L and Ce<0.6910 mg/L,respectively)in the CWAO process.The phenol,CODCD and TOC removal efficiencies in the solution exceed 98.5% using the optimal catalyst(named CSP).The new catalyst would have a promising application in CWAO treatment of high concentration organic wastewater.

  20. A calcite permeable reactive barrier for the remediation of Fluoride from spent potliner (SPL) contaminated groundwater

    DEFF Research Database (Denmark)

    Turner, B.D.; Binning, Philip John; Sloan, S.W.

    2008-01-01

    The use of calcite (CaCO3) as a substrate for a permeable reactive barrier (PRB) for removing fluoride from contaminated groundwater is proposed and is illustrated by application to groundwater contaminated by spent potliner leachate (SPL), a waste derived from the aluminium smelting process....... The paper focuses on two issues in the implementation of calcite permeable reactive barriers for remediating fluoride contaminated water: the impact of the groundwater chemical matrix and CO2 addition on fluoride removal. Column tests comparing pure NaF solutions, synthetic SPL solutions, and actual SPL...... leachate indicate that the complex chemical matrix of the SPL leachate can impact fluoride removal significantly. For SPL contaminant mixtures, fluoride removal is initially less than expected from idealized, pure, solutions. However, with time, the effect of other contaminants on fluoride removal...

  1. EarthServer: Use of Rasdaman as a data store for use in visualisation of complex EO data

    Science.gov (United States)

    Clements, Oliver; Walker, Peter; Grant, Mike

    2013-04-01

    plotted with the same system. For more complex multi-spectral data, WCPS allows the user to explore novel combinations of bands in standard band-ratio algorithms through a web browser with dynamic updating of the resultant image. To visualise very large datasets Rasdaman has the capability to dynamically scale a dataset or query result so that it can be appraised quickly for use in later unscaled queries. All of these techniques are accessible through a web based GIS interface increasing the number of potential users of the system. Lastly we will show the advances in dynamic web based 3D visualisations being explored within the EarthServer project. By utilising the emerging declarative 3D web standard X3DOM as a tool to visualise the results of WCPS queries we introduce several possible benefits, including quick appraisal of data for outliers or anomalous data points and visualisation of the uncertainty of data alongside the actual data values.

  2. Acceptability of Salt Fluoridation in a Rural Latino Community in the United States: An Ethnographic Study.

    Directory of Open Access Journals (Sweden)

    Judith C Barker

    acceptable, the feasibility of producing and distributing fluoridated salt in the United States is, however, complex and challenging.

  3. Prevalence of fluorosis and identification of fluoride endemic areas in Manur block of Tirunelveli District, Tamil Nadu, South India

    Science.gov (United States)

    Gopalakrishnan, Subarayan Bothi; Viswanathan, Gopalan; Siva Ilango, S.

    2012-12-01

    Prevalence of fluorosis is mainly due to the consumption of more fluoride through drinking water. It is necessary to identify the fluoride endemic areas to adopt remedial measures for the people under the risk of fluorosis. The objectives of this study were to identify the exact location of fluoride endemic areas in Manur block of Tirunelveli District and to estimate fluoride exposure level through drinking water for different age groups. Identification of fluoride endemic areas was performed through Isopleth and Google earth mapping techniques. Fluoride level in drinking water samples was estimated by fluoride ion selective electrode method. A systematic clinical survey conducted in 19 villages of Manur block revealed the rate of prevalence of fluorosis. From this study, it has been found that Alavanthankulam, Melapilliyarkulam, Keezhapilliyarkulam, Nadupilliyarkulam, Keezhathenkalam and Papankulam are the fluoride endemic villages, where the fluoride level in drinking water is above 1 mg/l. Consumption of maximum fluoride exposure levels of 0.30 mg/kg/day for infants, 0.27 mg/kg/day for children and 0.15 mg/kg/day for adults were found among the respective age group people residing in high fluoride endemic area. As compared with adequate intake level of fluoride of 0.01 mg/kg/day for infants and 0.05 mg/kg/day for other age groups, the health risk due to excess fluoride intake to the people of Alavanthankulam and nearby areas has become evident. Hence the people of these areas are advised to consume drinking water with optimal fluoride to avoid further fluorosis risks.

  4. FORMATION OF PHOSPHATE-CONTAINING CALCIUM-FLUORIDE AT THE EXPENSE OF ENAMEL, HYDROXYAPATITE AND FLUORAPATITE

    NARCIS (Netherlands)

    CHRISTOFFERSEN, J; CHRISTOFFERSEN, MR; ARENDS, J; LEONARDSEN, ES

    1995-01-01

    During the caries process complex reactions involving calcium, phosphate, hydrogen and fluoride ions as main species take place. In this study the precipitation and dissolution reactions occurring in suspensions of enamel, hydroxyapatite (HAP) and fluorapatite (FAP) on addition of fluoride were inve

  5. FORMATION OF PHOSPHATE-CONTAINING CALCIUM-FLUORIDE AT THE EXPENSE OF ENAMEL, HYDROXYAPATITE AND FLUORAPATITE

    NARCIS (Netherlands)

    CHRISTOFFERSEN, J; CHRISTOFFERSEN, MR; ARENDS, J; LEONARDSEN, ES

    1995-01-01

    During the caries process complex reactions involving calcium, phosphate, hydrogen and fluoride ions as main species take place. In this study the precipitation and dissolution reactions occurring in suspensions of enamel, hydroxyapatite (HAP) and fluorapatite (FAP) on addition of fluoride were

  6. Synthesis, Characterization and Antibacterial Properties of Rare Earth (Ce3+, Pr3+, Nd3+, Sm3+, Er3+)Complexes with L-Aspartic Acid and o-Phenanthroline

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Five novel ternary complexes of rare earth ions with L-Aspartic acid (Asp) and o-phenanthroline (Phen) were synthesized in ethanol aqueous solution. Their compositions were characterized by elemental analysis, molar conductance, FT-IR, Raman, UV-VIS and TG-DTA. The compositions of the complexes were confirmed to be: RE(Asp)3PhenCl3·3H2O (RE: Ce3+, Pr3+, Nd3+, Sm3+, Er3+). The antibacterial activity test shows that all these complexes exhibit excellent antibacterial ability against Escherichia coli, Staphylococcus aureus and Candida albicans. The antimicrobial spectrum of the complexes are broad.

  7. Synthesis and characterization of N-aryloxo-functiona-lized B-ketoiminate rare-earth complexes and their catalytic activity for the polymerization of ε-caprolactone

    Institute of Scientific and Technical Information of China (English)

    HAN XiangZong; WU LiangLiang; YAO YingMing; ZHANG Yong; SHEN Qi

    2009-01-01

    The synthesis and characterization of dimeric rare-earth amides stabilized by a dianionic N-aryloxo functionalized β-ketoiminate Iigand are described. Reactions of 4-(2-hydroxy-5-methyl-phenyl) im-ino-2-pentanone (LH_2) with Ln[N(SiMe_3)_2]_3(μ-Cl)Li(THF)_3 in a 1:1 molar ratio in THF gave the dimeric rare-earth amido complexes [LLn{N(SiMe_3)_2}(THF)]_2 [Ln= Nd (1), Sm (2), Yb (3), Y (4)]. These complexes were well characterized, and the definitive molecular structures of complexes 3 and 4 were determined. It was found that complexes 1-4 can initiate the ring-opening polymerization of ε-caprolactone, and the ionic radii of the central metals have significant effect on the catalytic activity.

  8. Can't we just keep it simple? Using thermodynamic limits to formulate simple models and to get robust predictions of the complex Earth system

    Science.gov (United States)

    Kleidon, Axel

    2016-04-01

    The Earth is, undoubtedly, a vastly complex system that is shaped by a range of processes, from solar radiation to planetary motion, geochemical cycling, biotic and human activity, all interacting across a range of time scales to shape the emergent state of the system. The common approach to deal with modelling parts of or the whole Earth system is to build increasingly more comprehensive models, with higher resolutions, a greater range of processes, and a greater number of interactions being represented. Yet, this also yields increasingly incomprehensible models in which the underlying assumptions in the model parameterizations are obscured. I present an alternative approach to model the complex Earth system that focuses on fundamental physical constraints and that allows for insights from simple, back-of-the-envelope calculations. This approach is based on describing the Earth as a thermodynamic system with dynamics that are driven by energy conversions, and in which its complexity is dealt with by the assumption that the dynamics operate at their thermodynamic limit. It requires us to think of Earth system processes in terms of the energy that they convert, the origin of this energy, the interactions that result from the energy conversion, and how these factors shape the resulting thermodynamic limit. The behavior of the complex Earth system then becomes predictable by relatively simple means, not because we deal with a simple system, but because it is so complex that it is ultimately constrained by fundamental thermodynamic limits that can be derived by comparably simple means. I illustrate this approach with three examples, dealing with the hydrologic sensitivity to global warming, the surface energy balance partitioning on land at the diurnal scale, and the limits to wind power as renewable energy. Each example shows that the approach matches observations or complex climate models very well, highlighting that this approach provides a simple alternative to

  9. Fluoride Content in Alcoholic Drinks.

    Science.gov (United States)

    Goschorska, Marta; Gutowska, Izabela; Baranowska-Bosiacka, Irena; Rać, Monika Ewa; Chlubek, Dariusz

    2016-06-01

    The aim of the study was to determine the role of alcoholic drinks as a potential source of dietary fluoride by means of measuring fluoride levels in selected alcoholic drinks available on the Polish market that are also diverse in terms of the percentage content of ethanol. The study was conducted on 48 types of drinks with low, medium, and high alcohol content available on the Polish market and offered by various manufacturers, both Polish and foreign. Fluoride concentrations in individual samples were measured by potentiometric method with a fluoride ion-selective electrode. The highest fluoride levels were determined in the lowest percentage drinks (less than 10 % v/v ethanol), with the lowest fluoride levels observed in the highest percentage drinks (above 40 % v/v ethanol). In terms of types of alcoholic drinks, the highest fluoride levels were determined in beers and wines, while the lowest levels were observed in vodkas. These data confirm the fact that alcoholic beverages need to be considered as a significant source of fluoride delivered into the body.

  10. Comparison of the Biological Impacts of the Fluoride Compounds by Graphical Risk Visualization Map Technique.

    Science.gov (United States)

    Usuda, Kan; Kono, Rei; Ueno, Takaaki; Ito, Yuichi; Dote, Tomotaro; Yokoyama, Hirotaka; Kono, Koichi; Tamaki, Junko

    2015-09-01

    Various fluoride compounds are widely used in industry. The present risk assessment study was conducted using a series of inorganic binary fluorides of the type XFn, where X(n) = Na(+), K(+), Li(+), Mg(2+), Ca(2+), Sr(2+), Ba(2+), Al(3+), Nd(3+), La(3+), Ce(3+), Sm(3+), Gd(3+), Y(3+), Yb(2+), and Zn(2+). The aqueous solutions of these salts were orally administrated to 16 experimental groups (one for each of the salts tested). The levels of fluoride, N-acetyl-β-D-glucosaminidase in cumulative 24-h urine samples and creatinine clearance were measured to assess possible acute renal damages. The levels of fluoride, alanine aminotransferase, and aspartate aminotransferase were also determined in serum samples to assess possible acute hepatic damages. The results reveal that sodium fluoride (NaF), potassium fluoride (KF), and zinc fluoride tetrahydrate (ZnF2 (.)4H2O) can carry the fluoride ion into the bloodstream and that it is excreted via urine more readily than the other compounds tested. These fluorides were assigned the highest risk impact factor. Most of the rare earth fluorides are insoluble in water while those groups 2 and 13 of the periodic table are slightly soluble, so that they do not have a significant negative risk. These findings suggest that the biological impact of fluoride depends on the accompanying counter ion and its solubility. The risk map obtained in the present study shows that the graphical visualization map technique employed is a valuable new tool to assess the toxicological risk of chemical compounds.

  11. Characterizing cosmochemical materials with genetic affinities to the Earth: Genetic and chronological diversity within the IAB iron meteorite complex

    Science.gov (United States)

    Worsham, Emily A.; Bermingham, Katherine R.; Walker, Richard J.

    2017-06-01

    The IAB iron meteorite complex consists of a main group (MG) and five chemical subgroups (sLL, sLM, sLH, sHL, and sHH). Here, mass-independent Mo and radiogenic 182W isotope compositions are reported for IAB complex meteorites to evaluate the genetics and chronology, respectively, of the MG and subgroups. Osmium isotopes are used to correct for cosmic ray exposure effects on isotopes of Mo and W. The MG and three subgroups (i.e., sLL, sLM, and sLH), characterized by low Au abundances, have the same Mo isotopic compositions within analytical uncertainty, consistent with a common genetic origin. These meteorites, together with winonaites, are the only cosmochemical materials yet identified with Mo isotopic compositions that are identical to Earth. The Mo isotopic compositions of two subgroups characterized by higher Au abundances (sHL and sHH) are identical to one another within uncertainty, but differ from the low Au subgroups, indicating derivation from genetically distinct materials. The MG has a 182W, post calcium-aluminum inclusion (CAI) formation model age of 3.4 ± 0.7 Ma. One of the low Au subgroups (sLM) is ∼1.7 Ma younger, whereas the high Au subgroups are ∼1.5-3 Ma older. The new Mo-W data, coupled with chemical data, indicate that the MG and the low Au subgroups formed in different impact-generated melts, some of which evidently formed on a chemically disparate, but genetically identical parent body. The high Au subgroups likely formed via core-formation processes on separate, internally-heated parent bodies from other IAB subgroups. The IAB complex meteorites fall on a linear trend defined by 94Mo/96Mo vs. 95Mo/96Mo, along with most other iron meteorite groups. Variation along this line was caused by mixing between at least two nebular components. One component was likely a pure s-process enriched nucleosynthetic carrier, and the other a homogenized nebular component. Sombrerete, currently classified as an sHL iron, has a Mo isotopic composition that

  12. Impact and remedial strategy of Fluoride in Ground Water – A Review

    Directory of Open Access Journals (Sweden)

    Bhagwan yadav

    2014-02-01

    Full Text Available According to WHO report 20% of the fluoride-affected villages in the whole world are in India, viz 33,231 villages are affected by fluoride in the country. Drinking water with excessive concentration of fluoride causes fluorosis which progresses gradually and becomes a crippling malady in the long run. It affects people of all age group, rich, rural, and urban population. It has attained a very alarming dimension. Rajasthan suffers both the problems of quantity and quality of water. In most part of the state groundwater is either saline or having high nitrates and fluoride content. Obviously, groundwater is the major source of drinking water and over 94% of the drinking water demand is met by groundwater. Fluoride concentrations beyond the standards cause dental and skeletal fluorosis. Fluoride toxicity can also cause non-skeletal diseases like aches and pain in the joints, non-ulcer dyspepsia, Polyurea and polydipsia, muscle weakness, fatigue, anemia with very low hemoglobin levels, etc besides other reasons. Many researchers have used various types of inexpensive and effective adsorption medium like clays, solid industrial wastes such as red mud, spent bleaching earths, spent catalysts and fly ash, activated alumina, carbonaceous materials, bone charcoal, natural and synthetic zeolites, etc. for the treatment of fluoride contamination. This paper presents a review, which focuses on the sources of fluoride in ground water, its impacts on health and different control measures.

  13. Topical fluoride for caries prevention

    Science.gov (United States)

    Weyant, Robert J.; Tracy, Sharon L.; Anselmo, Theresa (Tracy); Beltrán-Aguilar, Eugenio D.; Donly, Kevin J.; Frese, William A.; Hujoel, Philippe P.; Iafolla, Timothy; Kohn, William; Kumar, Jayanth; Levy, Steven M.; Tinanoff, Norman; Wright, J. Timothy; Zero, Domenick; Aravamudhan, Krishna; Frantsve-Hawley, Julie; Meyer, Daniel M.

    2015-01-01

    Background A panel of experts convened by the American Dental Association (ADA) Council on Scientific Affairs presents evidence-based clinical recommendations regarding professionally applied and prescription-strength, home-use topical fluoride agents for caries prevention. These recommendations are an update of the 2006 ADA recommendations regarding professionally applied topical fluoride and were developed by using a new process that includes conducting a systematic review of primary studies. Types of Studies Reviewed The authors conducted a search of MEDLINE and the Cochrane Library for clinical trials of professionally applied and prescription-strength topical fluoride agents—including mouthrinses, varnishes, gels, foams and pastes—with caries increment outcomes published in English through October 2012. Results The panel included 71 trials from 82 articles in its review and assessed the efficacy of various topical fluoride caries-preventive agents. The panel makes recommendations for further research. Practical Implications The panel recommends the following for people at risk of developing dental caries: 2.26 percent fluoride varnish or 1.23 percent fluoride (acidulated phosphate fluoride) gel, or a prescription-strength, home-use 0.5 percent fluoride gel or paste or 0.09 percent fluoride mouthrinse for patients 6 years or older. Only 2.26 percent fluoride varnish is recommended for children younger than 6 years. The strengths of the recommendations for the recommended products varied from “in favor” to “expert opinion for.” As part of the evidence-based approach to care, these clinical recommendations should be integrated with the practitioner's professional judgment and the patient's needs and preferences. PMID:24177407

  14. A preorganized metalloreceptor for alkaline earth ions showing calcium versus magnesium selectivity in water: biological activity of selected metal complexes.

    Science.gov (United States)

    Amatori, Stefano; Ambrosi, Gianluca; Fanelli, Mirco; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Macedi, Eleonora; Micheloni, Mauro; Paoli, Paola; Rossi, Patrizia

    2014-08-25

    The N,N'-bis[(3-hydroxy-4-pyron-2-yl)methyl]-N,N'-dimethylethylendiamine (Malten = L) forms the highly stable [CuH(-2)L] species in water, in which the converging maltol oxygen atoms form an electron-rich area able to host hard metal ions. When considering the alkaline earth series (AE), the [Cu(H(-2)L)] species binds all metal ions, with the exception of Mg(2+), exhibiting the relevant property to discriminate Ca(2+) versus Mg(2+) at physiological pH 7.4; the binding of the AE metal is visible to the naked eye. The stability constant values of the trinuclear [AE{Cu(H(-2)L)}2](2+) species formed reach the maximum for Ca(2+) (log K=7.7). Ca(2+) also forms a tetranuclear [Ca{Cu(H(-2)L)}]2(4+) species at a high Ca(2+) concentration. Tri- and tetranuclear calcium complexes show blue- and pink-colored crystals, respectively. [Cu(H(-2)L)] is the most active species in inducing DNA alterations. The DNA damages are compatible with its hydrolytic cleavages.

  15. Accomplishing simple, solubility-based separations of rare earth elements with complexes bearing size-sensitive molecular apertures.

    Science.gov (United States)

    Bogart, Justin A; Cole, Bren E; Boreen, Michael A; Lippincott, Connor A; Manor, Brian C; Carroll, Patrick J; Schelter, Eric J

    2016-12-27

    Rare earth (RE) metals are critical components of electronic materials and permanent magnets. Recycling of consumer materials is a promising new source of rare REs. To incentivize recycling, there is a clear need for the development of simple methods for targeted separations of mixtures of RE metal salts. Metal complexes of a tripodal hydroxylaminato ligand, TriNOx(3-), featured a size-sensitive aperture formed of its three η(2)-(N,O) ligand arms. Exposure of cations in the aperture induced a self-associative equilibrium comprising RE(TriNOx)THF and [RE(TriNOx)]2 species. Differences in the equilibrium constants Kdimer for early and late metals enabled simple separations through leaching. Separations were performed on RE1/RE2 mixtures, where RE1 = La-Sm and RE2 = Gd-Lu, with emphasis on Eu/Y separations for potential applications in the recycling of phosphor waste from compact fluorescent light bulbs. Using the leaching method, separations factors approaching 2,000 were obtained for early-late RE combinations. Following solvent optimization, >95% pure samples of Eu were obtained with a 67% recovery for the technologically relevant Eu/Y separation.

  16. Enhanced optical limiting effects in a double-decker bis(phthalocyaninato) rare earth complex using radially polarized beams

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jia-Lu; Gu, Bing, E-mail: gubing@seu.edu.cn; Liu, Dahui; Cui, Yiping, E-mail: cyp@seu.edu.cn [Advanced Photonics Center, Southeast University, Nanjing 210096 (China); Sheng, Ning [Advanced Photonics Center, Southeast University, Nanjing 210096 (China); Key Laboratory of Inorganic Chemistry in Universities of Shandong, Department of Chemistry and Chemical Engineering, Jining University, Qufu 273155 (China)

    2014-10-27

    Optical limiting (OL) effects can be enhanced by exploiting various limiting mechanisms and by designing nonlinear optical materials. In this work, we present the large enhancement of OL effects by manipulating the polarization distribution of the light field. Theoretically, we develop the Z-scan and nonlinear transmission theories on a two-photon absorber under the excitation of cylindrical vector beams. It is shown that both the sensitivity of Z-scan technique and the OL effect using radially polarized beams have the large enhancement compared with that using linearly polarized beams (LPBs). Experimentally, we investigate the nonlinear absorption properties of a double-decker Pr[Pc(OC{sub 8}H{sub 17}){sub 8}]{sub 2} rare earth complex by performing Z-scan measurements with femtosecond-pulsed radially polarized beams at 800 nm wavelength. The observed two-photon absorption process, which originates from strong intramolecular π–π interaction, is exploited for OL application. The results demonstrate the large enhancement of OL effects using radially polarized beams instead of LPBs.

  17. The mechanism behind internally generated centennial-to-millennial scale climate variability in an earth system model of intermediate complexity

    Directory of Open Access Journals (Sweden)

    T. Friedrich

    2010-08-01

    Full Text Available The mechanism triggering centennial-to-millennial-scale variability of the Atlantic Meridional Overturning Circulation (AMOC in the earth system model of intermediate complexity LOVECLIM is investigated. It is found that for several climate boundary conditions such as low obliquity values (~22.1° or LGM-albedo, internally generated centennial-to-millennial-scale variability occurs in the North Atlantic region. Stochastic excitations of the density-driven overturning circulation in the Nordic Seas can create regional sea-ice anomalies and a subsequent reorganization of the atmospheric circulation. The resulting remote atmospheric anomalies over the Hudson Bay can release freshwater pulses into the Labrador Sea and significantly increase snow fall in this region leading to a subsequent reduction of convective activity. The millennial-scale AMOC oscillations disappear if LGM bathymetry (with closed Hudson Bay is prescribed or if freshwater pulses are suppressed artificially. Furthermore, our study documents the process of the AMOC recovery as well as the global marine and terrestrial carbon cycle response to centennial-to-millennial-scale AMOC variability.

  18. Urinary Fluoride Concentration in Children with Disabilities Following Long-Term Fluoride Tablet Ingestion

    Science.gov (United States)

    Liu, Hsiu-Yueh; Chen, Jung-Ren; Hung, Hsin-Chia; Hsiao, Szu-Yu; Huang, Shun-Te; Chen, Hong-Sen

    2011-01-01

    Urine is the most commonly utilized biomarker for fluoride excretion in public health and epidemiological studies. Approximately 30-50% of fluoride is excreted from urine in children. Urinary fluoride excretion reflects the total fluoride intake from multiple sources. After administering fluoride tablets to children with disabilities, urinary…

  19. 49 CFR 173.163 - Hydrogen fluoride.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen fluoride. 173.163 Section 173.163... Hydrogen fluoride. (a) Hydrogen fluoride (hydrofluoric acid, anhydrous) must be packaged as follows: (1) In... filling ratio of 0.84. (b) A cylinder removed from hydrogen fluoride service must be condemned in...

  20. Growth of fluoride treated Kalanchoe pinnata plants

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, H.N.; Applegate, H.G.

    1962-01-01

    Kalanchoe pinnata plants can absorb fluoride through roots. The absorption is related to the amount of fluoride applied to the soil. There appeared to be a relationship between the amount of fluoride adsorbed and the subsequent growth of the plants. Plants which adsorbed the largest amounts of fluoride had the greatest increase in growth.

  1. Acceptability of Salt Fluoridation in a Rural Latino Community in the United States: An Ethnographic Study

    Science.gov (United States)

    Barker, Judith C.; Hoeft, Kristin S.

    2016-01-01

    , the feasibility of producing and distributing fluoridated salt in the United States is, however, complex and challenging. PMID:27391112

  2. Fluoride: A naturally-occurring health hazard in drinking-water resources of Northern Thailand.

    Science.gov (United States)

    Chuah, C Joon; Lye, Han Rui; Ziegler, Alan D; Wood, Spencer H; Kongpun, Chatpat; Rajchagool, Sunsanee

    2016-03-01

    In Northern Thailand, incidences of fluorosis resulting from the consumption of high-fluoride drinking-water have been documented. In this study, we mapped the high-fluoride endemic areas and described the relevant transport processes of fluoride in enriched waters in the provinces of Chiang Mai and Lamphun. Over one thousand surface and sub-surface water samples including a total of 995 collected from shallow (depth: ≤ 30 m) and deep (> 30 m) wells were analysed from two unconnected high-fluoride endemic areas. At the Chiang Mai site, 31% of the shallow wells contained hazardous levels (≥ 1.5 mg/L) of fluoride, compared with the 18% observed in the deep wells. However, at the Lamphun site, more deep wells (35%) contained water with at least 1.5mg/L fluoride compared with the shallow wells (7%). At the Chiang Mai site, the high-fluoride waters originate from a nearby geothermal field. Fluoride-rich geothermal waters are distributed across the area following natural hydrological pathways of surface and sub-surface water flow. At the Lamphun site, a well-defined, curvilinear high-fluoride anomalous zone, resembling that of the nearby conspicuous Mae Tha Fault, was identified. This similarity provides evidence of the existence of an unmapped, blind fault as well as its likely association to a geogenic source (biotite-granite) of fluoride related to the faulted zone. Excessive abstraction of ground water resources may also have affected the distribution and concentration of fluoride at both sites. The distribution of these high-fluoride waters is influenced by a myriad of complex natural and anthropogenic processes which thus created a challenge for the management of water resources for safe consumption in affected areas. The notion of clean and safe drinking water can be found in deeper aquifers is not necessarily true. Groundwater at any depth should always be tested before the construction of wells.

  3. Fluoride-induced chronic renal failure.

    Science.gov (United States)

    Lantz, O; Jouvin, M H; De Vernejoul, M C; Druet, P

    1987-08-01

    Renal fluoride toxicity in human beings is difficult to assess in the literature. Although experimental studies and research on methoxyflurane toxicity have shown frank renal damage, observations of renal insufficiency related to chronic fluoride exposure are scarce. We report a case of fluoride intoxication related to potomania of Vichy water, a highly mineralized water containing 8.5 mg/L of fluoride. Features of fluoride osteosclerosis were prominent and end-stage renal failure was present. The young age of the patient, the long duration of high fluoride intake, and the absence of other cause of renal insufficiency suggest a causal relationship between fluoride intoxication and renal failure.

  4. Effect of Al2O3 on the Structure and Photoluminescence Properties of Sol-gel Glass Doped with Rare Earth Organic Complex

    Institute of Scientific and Technical Information of China (English)

    肖静; 付桂军; 刘韩星; 欧阳世Xi

    2005-01-01

    Both silica glass materials singly doped with rare earth organic complex and co-doped with Al3+ were prepared by in situ sol-gel method respectively. XRD and SEM measurements were performed to verify the non-crystalline structure of the glass. The excitation spectra, emission spectra and IR spectra were measured to analyze the influence of the glass contents on the structure of the glass and the energy level of the doped Eu(IH) ions. The effect of Al3+ on the photoluminescence properties of rare earth organic complex in silica glass was investigated. The IR spectra indicated that the in situ synthesized europium complex molecule was confined to the micropores of the host and the vibration of the ligands was frozen. When Al2O3 was doped into the silica host gel, the rare earth ions in the silica network were wrapped up and dispersed by Al2O3, so the distribution of Eu(Ⅲ) complex in the host was morehomogeneous, and the luminescence intensity of 5D0-7F2 transition emission of the Eu3+ ions was improved. The results showed that an appropriate amount of Al3+ added to the gel glass improved the emission intensity of the complex in the silica glass, and when the content of Al2O3 reached 4 mol%, the maximum emission intensity could be obtained compared with that of other samples containing different Al2O3 contents.

  5. Stability of Rare Earth Ion-N,N′-bis(2′-Pyridine)methyl-1,10-Phenanthroline-2,9-Dimethanmine Binary Complexes

    Institute of Scientific and Technical Information of China (English)

    刘天府; 王中明; 林华宽; 朱守荣; 徐猛; 陈云悌

    2003-01-01

    The stability constants of binary complexes Ln-L (Ln=La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, L=N, N′-bis(2′-pyridine)methyl-1,10-phenanthroline-2,9- dimethanamine) were determined by pH potentiometric titration method at 25±0.1 ℃ in 0.1 mol*L-1 NaClO4. The probable structures of the corresponding complexes were proposed. The influence of the metal ions to the stability of binary complexes and the stability difference between the complexes of rare earth ion and the corresponding complexes of Co2+, Ni2+, Cu2+ ions were discussed. The stability constants of the corresponding binary complex of radioactive Pm3+ ion were estimated by linear regression.

  6. Enhanced luminescence of rare-earth complexes Tb 1- xEu x( m-NBA) 3Phen in ZnS

    Science.gov (United States)

    Lv, Yuguang; Zhang, Jingchang; Cao, Weiliang; Song, Lin; Xu, Zheng

    2008-07-01

    Rare-earth ternary complexes Tb 1- xEu x( m-NBA) 3Phen ( X = 1, 0.25, 0.5, 0.75, 1.0) were synthesized and characterized by IR, DTA-TG, UV, fluorescent spectra and elemental analysis. It was found that luminescence of Eu 3+ complex was enhanced by doped with Tb 3+. It is proved by TG curve that the complexes are stable, ranging from ambient temperature to 360 °C in air. The organic-inorganic combined structural device was fabricated, and the electroluminescence intensity of the combined structural device was improved compared with the device of the purely organic components.

  7. Enhanced luminescence of rare-earth complexes Tb(1-x)Eu(x)(m-NBA)3Phen in ZnS.

    Science.gov (United States)

    Lv, Yuguang; Zhang, Jingchang; Cao, Weiliang; Song, Lin; Xu, Zheng

    2008-07-01

    Rare-earth ternary complexes Tb(1-x)Eu(x)(m-NBA)(3)Phen (X=1, 0.25, 0.5, 0.75, 1.0) were synthesized and characterized by IR, DTA-TG, UV, fluorescent spectra and elemental analysis. It was found that luminescence of Eu(3+) complex was enhanced by doped with Tb(3+). It is proved by TG curve that the complexes are stable, ranging from ambient temperature to 360 degrees C in air. The organic-inorganic combined structural device was fabricated, and the electroluminescence intensity of the combined structural device was improved compared with the device of the purely organic components.

  8. Extraction of rare earth elements from their oxides using organophosphorus reagent complexes with HNO_3 and H_2O in supercritical CO_2

    Institute of Scientific and Technical Information of China (English)

    段五华; 曹丕佳; 朱永(贝睿)

    2010-01-01

    Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...

  9. Matrix supported tailored polymer for solid phase extraction of fluoride from variety of aqueous streams

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Neha; Kumar, Sanjukta A.; Wagh, D.N. [Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Das, Sadananda; Pandey, Ashok K. [Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kumar, Sangita D., E-mail: sangdk@barc.gov.in [Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Reddy, A.V.R. [Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2012-01-30

    Highlights: Black-Right-Pointing-Pointer Th complexed with poly (bis[2-(methacryloyloxy)-ethyl]phosphate) as tailored polymer membranes. Black-Right-Pointing-Pointer Membranes offered high capacity and selectivity for fluoride in aqueous media. Black-Right-Pointing-Pointer Quantitative uptake (80 {+-} 5%) of fluoride. Black-Right-Pointing-Pointer Fast sorption kinetics. Black-Right-Pointing-Pointer Reusability of polymer membranes. - Abstract: Fluoride related health hazards (fluorosis) are a major environmental problem in many regions of the world. It affects teeth; skeleton and its accumulation over a long period can lead to changes in the DNA structure. It is thus absolutely essential to bring down the fluoride levels to acceptable limits. Here, we present a new inorganic-organic hybrid polymer sorbent having tailored fixed-sites for fluoride sorption. The matrix supported poly (bis[2-(methacryloyloxy)-ethyl]phosphate) was prepared by photo-initiator induced graft-polymerization in fibrous and microporous (sheet) host poly(propylene) substrates. These substrates were conditioned for selective fluoride sorption by forming thorium complex with phosphate groups on bis[2-methacryloyloxy)-ethyl] phosphate (MEP). These tailored sorbents were studied for their selectivity towards fluoride in aqueous media having different chemical conditions. The fibrous sorbent was found to take up fluoride with a faster rate (15 min for Almost-Equal-To 76% sorption) than the sheet sorbent. But, the fluoride loading capacity of sheet sorbent (4320 mg kg{sup -1}), was higher than fibrous and any other sorbent reported in the literature so far. The sorbent developed in the present work was found to be reusable after desorption of fluoride using NaOH solution. It was tested for solid phase extraction of fluoride from natural water samples.

  10. Funing Rare Earths Industrial Co. Ltd

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The company covers separation with whole lines of light, medium and heavy rare earths, with annual separation volume of rare earth oxides of 4,500 tons. It also produces rare earth oxides, fluorides and salts. Products with high-purity and super-high-purity are produced according to customer's request. Under the technological guidance of domestic experts and application of modern high-pressure

  11. Portland Water Fluoridation: A Newspaper Analysis.

    Science.gov (United States)

    Bianchi, Allison; Bergren, Martha Dewey; Lewis, Patricia Ryan

    2017-03-01

    Portland, Oregon is the largest city in the United States without community water fluoridation (CWF). A newspaper analysis was conducted of the failed 2013 CWF campaign to evaluate anti-fluoridation and pro-fluoridation messaging provided by newspapers during the campaign. News content was categorized by type and slant (pro-fluoridation, anti-fluoridation, or neutral) and 34 variables were tabulated (23 anti-fluoridation, 11 pro-fluoridation). Results showed overall messaging was slightly pro-fluoridation, as compared to anti-fluoridation or neutral content (35%, 32%, and 33% respectively). Editorial content was 85% pro-fluoridation and 15% anti-fluoridation. The most frequent anti-fluoridation variables were alternatives to water fluoridation, mass/forced medication and concerns about the political process. Conversely, tooth decay and social justice were the most commonly cited pro-fluoridation variables. Newspapers can be influential in shaping public policy opinions in the fight for community water fluoridation. © 2016 Wiley Periodicals, Inc.

  12. Complex Demodulation in Monitoring Earth Rotation by VLBI: Testing the Algorithm by Analysis of Long Periodic EOP Components

    Science.gov (United States)

    Wielgosz, A.; Brzeziński, A.; Böhm, S.

    2016-12-01

    The complex demodulation (CD) algorithm is an efficient tool for extracting the diurnal and subdiurnal components of Earth rotation from the routine VLBI observations (Brzeziński, 2012). This algorithm was implemented by Böhm et al (2012b) into a dedicated version of the VLBI analysis software VieVs. The authors processed around 3700 geodetic 24-hour observing sessions in 1984.0-2010.5 and estimated simultaneously the time series of the long period components as well as diurnal, semidiurnal, terdiurnal and quarterdiurnal components of polar motion (PM) and universal time UT1. This paper describes the tests of the CD algorithm by checking consistency of the low frequency components of PM and UT1 estimated by VieVS CD and those from the IERS and IVS combined solutions. Moreover, the retrograde diurnal component of PM demodulated from VLBI observations has been compared to the celestial pole offsets series included in the IERS and IVS solutions. We found for all three components a good agreement of the results based on the CD approach and those based on the standard parameterization recommended by the IERS Conventions (IERS, 2010) and applied by the IERS and IVS. We conclude that an application of the CD parameterization in VLBI data analysis does not change those components of EOP which are included in the standard adjustment, while enabling simultaneous estimation of the high frequency components from the routine VLBI observations. Moreover, we deem that the CD algorithm can also be implemented in analysis of other space geodetic observations, like GNSS or SLR, enabling retrieval of subdiurnal signals in EOP from the past data.

  13. Long-term ice sheet-climate interactions under anthropogenic greenhouse forcing simulated with a complex Earth System Model

    Energy Technology Data Exchange (ETDEWEB)

    Vizcaino, Miren [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); University of California, Department of Geography, Berkeley, CA (United States); Mikolajewicz, Uwe; Maier-Reimer, Ernst [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Groeger, Matthias [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); IFM-GEOMAR, Kiel (Germany); Schurgers, Guy [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Lund University, Department of Physical Geography and Ecosystems Analysis, Lund (Sweden); Winguth, Arne M.E. [Center for Climatic Research, Department of Atmospheric and Oceanic Sciences, Madison (United States)

    2008-11-15

    Several multi-century and multi-millennia simulations have been performed with a complex Earth System Model (ESM) for different anthropogenic climate change scenarios in order to study the long-term evolution of sea level and the impact of ice sheet changes on the climate system. The core of the ESM is a coupled coarse-resolution Atmosphere-Ocean General Circulation Model (AOGCM). Ocean biogeochemistry, land vegetation and ice sheets are included as components of the ESM. The Greenland Ice Sheet (GrIS) decays in all simulations, while the Antarctic ice sheet contributes negatively to sea level rise, due to enhanced storage of water caused by larger snowfall rates. Freshwater flux increases from Greenland are one order of magnitude smaller than total freshwater flux increases into the North Atlantic basin (the sum of the contribution from changes in precipitation, evaporation, run-off and Greenland meltwater) and do not play an important role in changes in the strength of the North Atlantic Meridional Overturning Circulation (NAMOC). The regional climate change associated with weakening/collapse of the NAMOC drastically reduces the decay rate of the GrIS. The dynamical changes due to GrIS topography modification driven by mass balance changes act first as a negative feedback for the decay of the ice sheet, but accelerate the decay at a later stage. The increase of surface temperature due to reduced topographic heights causes a strong acceleration of the decay of the ice sheet in the long term. Other feedbacks between ice sheet and atmosphere are not important for the mass balance of the GrIS until it is reduced to 3/4 of the original size. From then, the reduction in the albedo of Greenland strongly accelerates the decay of the ice sheet. (orig.)

  14. Removal of fluoride ions from aqueous solution at low pH using schwertmannite.

    Science.gov (United States)

    Eskandarpour, Akbar; Onyango, Maurice S; Ochieng, Aoyi; Asai, Shigeo

    2008-04-01

    Wastewater containing fluoride requires polishing after precipitation/coagulation treatment in order to meet stringent environmental legislation. Accordingly, adsorption characteristics of fluoride onto schwertmannite adsorbent were studied in a batch system with respect to changes in initial concentration of fluoride, equilibrium pH of sample solution, adsorbent dosage and co-existing ions. Equilibrium adsorption data were obtained at 295.6, 303 and 313 K, and are interpreted in terms of two-site Langmuir, Freundlich, Langmuir-Freundlich, Redlich-Peterson, Tóth and Dubinin-Radushkevitch isotherm models. The experimental and equilibrium modeling results revealed that the capacity of schwertmannite for fluoride is high but insensitive to changes in solution temperature. An increase in equilibrium pH of sample solution reduced significantly the fluoride removal efficiency. In binary component systems, inner-sphere complex forming species had negative effects on fluoride adsorption while outer-sphere complex forming species improved slightly the fluoride removal efficiency. The schwertmannite adsorbent was regenerable and had the ability to lower the fluoride concentration to acceptable levels.

  15. Fluorination utilizing thermodynamically unstable fluorides and fluoride salts thereof

    Energy Technology Data Exchange (ETDEWEB)

    Bartlett, Neil (Orinda, CA); Whalen, J. Marc (Corning, NY); Chacon, Lisa (Corning, NY)

    2000-12-12

    A method for fluorinating a carbon compound or cationic carbon compound utilizes a fluorination agent selected from thermodynamically unstable nickel fluorides and salts thereof in liquid anhydrous hydrogen fluoride. The desired carbon compound or cationic organic compound to undergo fluorination is selected and reacted with the fluorination agent by contacting the selected organic or cationic organic compound and the chosen fluorination agent in a reaction vessel for a desired reaction time period at room temperature or less.

  16. Estimated Fluoride Doses from Toothpastes Should be Based on Total Soluble Fluoride

    OpenAIRE

    Cury,Jaime A.; Saul M Paiva; Tenuta,Livia M.A; Oliveira,Maria José L.; Martins, Carolina C.

    2013-01-01

    The fluoride dose ingested by young children may be overestimated if based on levels of total fluoride (TF) rather than levels of bioavailable fluoride (total soluble fluoride-TSF) in toothpaste. The aim of the present study was to compare doses of fluoride intake based on TF and TSF. Fluoride intake in 158 Brazilian children aged three and four years was determined after tooth brushing with their usual toothpaste (either family toothpaste (n = 80) or children's toothpaste (n = 78)). The esti...

  17. 二价碱土金属氟化物对Er3+/Tm3+/Yb3+共掺氟氧锗酸盐玻璃热稳定性和光谱特性影响的研究%Effect of Bivalent Alkaline Earth Fluorides Introduction on Thermal Stability and Spectroscopic Properties of Er3+/Tm3+/Yb3+ Co-Doped Oxyfluorogermanate Glasses

    Institute of Scientific and Technical Information of China (English)

    胡曰博; 张新娜; 周大利; 焦清; 王荣飞; 黄劲峰; 龙晓波; 邱建备

    2012-01-01

    制备了分别含有MgF2,CaF2,SrF2或BaF2的Er3+/Tm3+/Yb3+共掺氟氧锗酸盐玻璃试样和包含BaF2纳米晶的玻璃陶瓷试样,所制备试样均具有良好的透光性.对试样的热稳定性和上转换发光特性进行了研究.通过分析试样的吸收光谱发现,随着所含二价阳离子原子量的增大,试样的紫外吸收截止波长明显向短波方向移动.结果显示:通过改变所含二价碱土金属离子的种类能够对激发光的颜色进行调节,特别值得关注的是Mg2+的影响;结果证实:通过对包含二价碱土金属的玻璃进行微晶化处理或者增加二价碱土金属的含量均能提高上转换发光的强度.%Transparent Er3+ /Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides.

  18. Structural criteria for the rational design of selective ligands. Extension of the MM3 force field to aliphatic ether complexes of the alkali and alkaline earth cations

    Energy Technology Data Exchange (ETDEWEB)

    Hay, B.P.; Rustad, J.R. (Pacific Northwest Lab., Richland, WA (United States))

    1994-07-13

    Structural requirements for strain-free metal ion complexation by an aliphatic ether group are investigated through the use of both ab initio molecular orbital and molecular mechanics calculations. Hartree-Fock calculations on simple models, M-O(Me)[sub 2] and M-O(Me)(Et), reveal a preference for trigonal planar geometry when aliphatic ether oxygens are coordinated to alkali and alkaline earth cations. This preference is found to be strongest in small, high-valent cations and weakest in large, low-valent cations. Results from the Hartree-Fock calculations are used to extend the MM3 force field for calculation on aliphatic ether complexes with the alkali (Li to Cs) and alkaline earth (Mg to Ba) cations. The resulting molecular model (i) reproduces the experimental crystal structures of 51 different complexes of multidentate ethers with alkali and alkaline earth cations, (ii) explains experimental trends in the structure of five-membered chelate rings of aliphatic ethers, (iii) reveals a fundamental difference between the metal ion size selectivity of five-membered chelate rings of ethers versus that of amines, and (iv) rationalizes trends in the stability of four potassium complexes with the diasteriomers of dicyclohexyl-18-crown-6. 40 refs., 9 figs., 5 tabs.

  19. Synthesis and luminescence properties of rare earth ternary complexes consisting of Tb(Ⅲ),β-diketones and 1,10-phenanthroline (phen)

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to study the luminescent properties of ternary rare earth complexes with fl-diketone ligand,three new β-diketone ligands,1-phenyl-3-(p-phenylethynylphenyl)-1,3-propanedione(HPPP), 1-(2-thienyl)-3-(p-phenylethynylphenyl)-l,3-propanedione (HTPP) and 1-(2-furyl)-3-(p-phenylethynylphenyl)-1,3-propanedione (HFPP),were synthesized by Sonogashira coupling reaction and Claisen condensation.Three new ternary rare earth complexes,TbL3phen (L = PPP,TPP,or FPP),were synthesized by the reaction of rare earth chloride TbCl3,1,10-phenanthroline (phen) with HPPP,HTPP,or HFPP respectively,in alcohol solution.The compositions were characterized by means of elernental analysis,chemical analysis,and IR spectra.Luminescent properties of the three new complexes have been studied.The results show that the ternary Tb(Ⅲ) complexes only emit the weak fluorescence of the Tb(Ⅲ) ion,which reveals the triplet state energy of the ligands does not match well with the excited state vibrating energy of Tb3+ ion.

  20. Systematic Structural Elucidation for the Protonated Form of Rare Earth Bis(porphyrinato) Double-Decker Complexes: Direct Structural Evidence of the Location of the Attached Proton.

    Science.gov (United States)

    Yamashita, Ken-Ichi; Sakata, Naoya; Ogawa, Takuji

    2016-09-01

    Direct structural evidence of the presence and location of the attached proton in the protonated form of rare earth bis(porphyrinato) double-decker complexes is obtained from an X-ray diffraction study of single crystals for a series of protonated forms of bis(tetraphenylporphyrinato) complexes [M(III)(tpp)(tppH)] (M = Tb, Y, Sm, Nd, and La). When CHCl3 is used as a solvent for crystallization of the complexes, their nondisordered molecular structures are obtained and the attached proton is identified on one of the eight nitrogen atoms. Use of other solvents affords another type of crystal, in which the position of the proton is disordered and thus the molecular structure is averaged. La complex also affords the disordered average structure even when CHCl3 is used for crystallization. A variable-temperature diffraction study for the Tb complex reveals that the dynamics of the proton in the nondisordered crystal is restricted.

  1. Spectrophotometric determination of fluoride in drinking water using ...

    African Journals Online (AJOL)

    2011-03-14

    Mar 14, 2011 ... for 1.5 mg∙ℓ-1 fluoride for the method using chrome azurol B were ... in drinking water can give rise to a number of adverse effects ... reagents, due to their spectrophotometric properties described .... Possible structure for aluminium chrome azurol B 1:2 complex ..... zirconium-eriochrome cyanine R. Anal.

  2. Optical properties of Langmuir-Blodgett film of hemicyanine containing the rare earth complex anion Dy(BPMPHD) (-2)

    Science.gov (United States)

    Wang, Kezhi; Huang, Chunhui; Xu, Guangxian; Zhao, Xinsheng; Xia, Xiaohua; Wu, Nianzu; Xu, Lingge; Li, Tiankai

    1994-12-01

    (E)-N-hexadecyl-4-(2-(4-dimethylaminophnyl) ethenyl) pyridinium bis(1,6-bis (1'-phenyl-3'-methyl-5'-pyrazolone-4') hexanedio-nato-(1,5)) dysprosium(III) was synthesized. The monolayers formed on a pure water subphase (pH 5.6,C) were transferred onto hydrophilic quartz, calcium fluoride, and glass substrates successively with a transfer ratio of around unity. From second-harmonic generation (SHG) experiments, the second-order molecular hyperpolarizability beta was evaluated to be about 4.8 x 10(exp -48) C cu m/sq V. The results of UV-visible, IR and X-ray photoelectron spectroscopy of the Langmuir-Blodgett films are also reported.

  3. Sun-to-Earth Characteristics of Two Coronal Mass Ejections Interacting near 1 AU: Formation of a Complex Ejecta and Generation of a Two-Step Geomagnetic Storm

    CERN Document Server

    Liu, Ying D; Wang, Rui; Luhmann, Janet G; Richardson, John D; Lugaz, Noé

    2014-01-01

    On 2012 September 30 - October 1 the Earth underwent a two-step geomagnetic storm. We examine the Sun-to-Earth characteristics of the coronal mass ejections (CMEs) responsible for the geomagnetic storm with combined heliospheric imaging and in situ observations. The first CME, which occurred on 2012 September 25, is a slow event and shows an acceleration followed by a nearly invariant speed in the whole Sun-Earth space. The second event, launched from the Sun on 2012 September 27, exhibits a quick acceleration, then a rapid deceleration and finally a nearly constant speed, a typical Sun-to-Earth propagation profile for fast CMEs \\citep{liu13}. These two CMEs interacted near 1 AU as predicted by the heliospheric imaging observations and formed a complex ejecta observed at Wind, with a shock inside that enhanced the pre-existing southward magnetic field. Reconstruction of the complex ejecta with the in situ data indicates an overall left-handed flux rope-like configuration, with an embedded concave-outward shoc...

  4. SUN-TO-EARTH CHARACTERISTICS OF TWO CORONAL MASS EJECTIONS INTERACTING NEAR 1 AU: FORMATION OF A COMPLEX EJECTA AND GENERATION OF A TWO-STEP GEOMAGNETIC STORM

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying D.; Yang, Zhongwei; Wang, Rui [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China); Luhmann, Janet G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Richardson, John D. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Lugaz, Noé, E-mail: liuxying@spaceweather.ac.cn [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States)

    2014-10-01

    On 2012 September 30-October 1 the Earth underwent a two-step geomagnetic storm. We examine the Sun-to-Earth characteristics of the coronal mass ejections (CMEs) responsible for the geomagnetic storm with combined heliospheric imaging and in situ observations. The first CME, which occurred on 2012 September 25, is a slow event and shows an acceleration followed by a nearly invariant speed in the whole Sun-Earth space. The second event, launched from the Sun on 2012 September 27, exhibits a quick acceleration, then a rapid deceleration, and finally a nearly constant speed, a typical Sun-to-Earth propagation profile for fast CMEs. These two CMEs interacted near 1 AU as predicted by the heliospheric imaging observations and formed a complex ejecta observed at Wind, with a shock inside that enhanced the pre-existing southward magnetic field. Reconstruction of the complex ejecta with the in situ data indicates an overall left-handed flux-rope-like configuration with an embedded concave-outward shock front, a maximum magnetic field strength deviating from the flux rope axis, and convex-outward field lines ahead of the shock. While the reconstruction results are consistent with the picture of CME-CME interactions, a magnetic cloud-like structure without clear signs of CME interactions is anticipated when the merging process is finished.

  5. Ferroelectric fluoride compositions and methods of making and using same

    Science.gov (United States)

    Halasyamani, P Shiv; Chang, Hong-Young

    2015-04-07

    A method for synthesis of a ferroelectric material characterized by the general formula A.sub.xB.sub.yF.sub.z where A is an alkaline earth metal, B is transition metal or a main group metal, x and y each range from about 1 to about 5, and z ranges from about 1 to about 20 comprising contacting an alkaline earth metal fluoride, a difluorometal compound and a fluoroorganic acid in a medium to form a reaction mixture; and subjecting the reaction mixture to conditions suitable for hydrothermal crystal growth.

  6. Rare earth complexes with a novel ligand N-(naphthalen-2-yl)- N-phenyl-2-(quinolin-8-yloxy)acetamide: Preparation and spectroscopic studies

    Science.gov (United States)

    Wu, Wei-Na; Tang, Ning; Yan, Lan

    2008-12-01

    Six complexes of rare earth nitrates (Ln = La, Sm, Eu, Gd, Tb, Dy) with a new amide type ligand, N-(naphthalen-2-yl)- N-phenyl-2-(quinolin-8-yloxy)acetamide (L) have been prepared and characterized by elemental analysis, conductivity measurements, IR and and 1H NMR spectra. Under excitation, Eu(III) and Sm(III) complexes exhibited strong red emissions. And the luminescence intensity of Sm(III) complex is higher than that of Eu(III) complex. Thus the Eu(III) and Sm(III) complexes are the potential light conversion agent. However, the Tb(III) and Dy(III) complexes cannot exhibit characteristic emissions of terbium and dysprosium ions, respectively. The results of phosphorescence spectrum show that the triplet-state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion. In addition, the luminescence of the Eu(III) complex is also relatively strong in highly diluted tetrahydrofuran solution (2 × 10 -4 mol/L) compared with the powder. This is not only due to the solvate effects but also to the changes of the structure of the Eu(III) complex after being dissolved into the solvents. Furthermore, owing to the co-luminescence effect, the proper La(III) or Gd(III) doped Eu(III) complexes show stronger luminescence than the pure Eu(III) complex.

  7. Light rare earth element systematics as a tool for investigating the petrogenesis of phoscorite-carbonatite associations, as exemplified by the Phalaborwa Complex, South Africa

    Science.gov (United States)

    Milani, Lorenzo; Bolhar, Robert; Frei, Dirk; Harlov, Daniel E.; Samuel, Vinod O.

    2017-01-01

    In-situ trace element analyses of fluorapatite, calcite, dolomite, olivine, and phlogopite have been undertaken on representative phoscorite and carbonatite rocks of the Palaeoproterozoic Phalaborwa Complex. Textural and compositional characterization reveals uniformity of fluorapatite and calcite among most of the intrusions, and seems to favor a common genetic origin for the phoscorite-carbonatite association. Representing major repositories for rare earth elements (REE), fluorapatite and calcite exhibit tightly correlated light REE (LREE) abundances, suggesting that partitioning of LREE into these rock forming minerals was principally controlled by simple igneous differentiation. However, light rare earth element distribution in apatite and calcite cannot be adequately explained by equilibrium and fractional crystallization and instead favors a complex crystallization history involving mixing of compositionally distinct magma batches, in agreement with previously reported mineral isotope variability that requires open-system behaviour.

  8. An in vitro assessment of fluoride uptake by tooth enamel from four different fluoride dentifrices.

    Science.gov (United States)

    Patil, V H; Anegundi, R T

    2014-10-01

    The aim of this study was to evaluate fluoride uptake by tooth enamel with four different fluoride dentifrices. Sixty human premolars extracted for orthodontic purpose were selected for the study. The teeth were covered with nail varnish leaving a window of 4 × 4 mm on the enamel surface of the buccal and lingual sides. The teeth were demineralised and were divided into four groups with 15 teeth in each group. The buccal window served as experimental and the lingual as control. The teeth were immersed in toothpaste slurry containing: sodium fluoride (Group A); sodium monofluorophosphate (Group B); stannous fluoride (Group C) and amine fluoride (Group D). The fluoride content in the etched superficial enamel layer in the windows was analysed using a fluoride ion-specific electrode. Within the parameters of this study, the uptake of fluoride was statistically significant in Group D (p fluoride by tooth enamel in an increasing order was Group A fluoride had the highest fluoride uptake.

  9. FLUORIDE TOXICITY – A HARSH REALITY

    Directory of Open Access Journals (Sweden)

    Bandlapalli Pavani

    2011-04-01

    Full Text Available There are many incidents of fluoride toxicity whether it is acute or chronic. Fluoride toxicity is an environmental hazard which arises from the upper layers of geological crust and is dissolved in water. Prolonged drinking of such water causes chronic fluoride toxicity. Use of fluoride containing compounds for various purposes such as dental products, metal, glass, refrigerator and chemical industries act as a source of fluoride poisoning and increase the risk of toxicity. This review reflects the deleterious effects of fluorides on various organs in the physiological system.

  10. Fluoride bioavailability in saliva and plaque

    Science.gov (United States)

    2012-01-01

    Background Different fluoride formulations may have different effects on caries prevention. It was the aim of this clinical study to assess the fluoride content, provided by NaF compared to amine fluoride, in saliva and plaque. Methods Eight trained volunteers brushed their teeth in the morning for 3 minutes with either NaF or amine fluoride, and saliva and 3-day-plaque-regrowth was collected at 5 time intervals during 6 hours after tooth brushing. The amount of collected saliva and plaque was measured, and the fluoride content was analysed using a fluoride sensitive electrode. All subjects repeated all study cycles 5 times, and 3 cycles per subject underwent statistical analysis using the Wilcoxon-Mann-Whitney test. Results Immediately after brushing the fluoride concentration in saliva increased rapidly and dropped to the baseline level after 360 minutes. No difference was found between NaF and amine fluoride. All plaque fluoride levels were elevated after 30 minutes until 120 minutes after tooth brushing, and decreasing after 360 minutes to baseline. According to the highly individual profile of fluoride in saliva and plaque, both levels of bioavailability correlated for the first 30 minutes, and the fluoride content of saliva and plaque was back to baseline after 6 hours. Conclusions Fluoride levels in saliva and plaque are interindividually highly variable. However, no significant difference in bioavailability between NaF and amine fluoride, in saliva, or in plaque was found. PMID:22230722

  11. Studies of fluoride varnishes in Finland.

    Science.gov (United States)

    Seppä, L

    1991-01-01

    Despite the artificial fluoridation of drinking water in Kuopio, part of the children have high caries incidence. We therefore started our studies on fluoride varnishes in 1977 in an attempt to find a feasible means of applying fluoride topically in children at high risk of caries. In our first trial, the sodium fluoride varnish Duraphat was found to be effective in preventing caries, but the effectiveness of the silane fluoride varnish Fluor Protector could not be unequivocally established, despite the fact that Fluor Protector deposited markedly more fluoride in enamel than Duraphat. In a second study in children in a low-fluoride area, use of Duraphat was found to be more effective than fortnightly fluoride rinses or Fluor Protector. Increasing the frequency of application from two to four times a year did not increase the effectiveness of Duraphat even in highly caries-prone children in a 2-year trial. On the basis of peak values of fluoride in parotid saliva after application, use of either fluoride varnishes was considered safe. Although the fluoride content of the enamel remained elevated for at least two years after discontinuation of treatment with both varnishes, the caries preventive effect did not continue after the applications were stopped. This shows that increasing the fluoride content of enamel is not the main mechanism by which fluoride varnishes prevent caries, and that the applications need to be continued as long as caries is a problem.

  12. Chronic Fluoride Toxicity: Dental Fluorosis

    Science.gov (United States)

    DenBesten, Pamela; Li, Wu

    2012-01-01

    Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2–3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface; with more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix/mineral interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the doserelated decrease in cycles of ameloblast modulation from ruffleended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As

  13. Chronic fluoride toxicity: dental fluorosis.

    Science.gov (United States)

    Denbesten, Pamela; Li, Wu

    2011-01-01

    Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2-3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface. With more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the dose-related decrease in cycles of ameloblast modulation from ruffle-ended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As further

  14. Dynamics of Fluoride Bioavailability in the Biofilms of Different Oral Surfaces after Amine Fluoride and Sodium Fluoride Application

    OpenAIRE

    Ella A. Naumova; Christoph Dickten; Rico Jung; Florian Krauss; Henrik Rübesamen; Katharina Schmütsch; Tudor Sandulescu; Stefan Zimmer; Wolfgang H. Arnold

    2016-01-01

    It was the aim of this study to investigate differences in fluoride bioavailability in different oral areas after the application of amine fluoride (AmF) and sodium fluoride (NaF). The null hypothesis suggested no differences in the fluoride bioavailability. The tongue coating was removed and biofilm samples from the palate, oral floor and cheeks were collected. All subjects brushed their teeth with toothpaste containing AmF or NaF. Specimens were collected before, as well as immediately afte...

  15. Fluoride level in saliva after bonding orthodontic brackets with a fluoride containing adhesive

    NARCIS (Netherlands)

    Ogaard, B; Arends, J; Helseth, H; Dijkman, G; vanderKuijl, M

    1997-01-01

    The fluoride level in saliva is considered an important parameter in caries prevention. Elevation of the salivary fluoride level by a fluoride-releasing orthodontic bonding adhesive would most likely be beneficial in the prevention of enamel caries. In this study, the fluoride level in saliva was me

  16. Fluoride level in saliva after bonding orthodontic brackets with a fluoride containing adhesive

    NARCIS (Netherlands)

    Ogaard, B; Arends, J; Helseth, H; Dijkman, G; vanderKuijl, M

    The fluoride level in saliva is considered an important parameter in caries prevention. Elevation of the salivary fluoride level by a fluoride-releasing orthodontic bonding adhesive would most likely be beneficial in the prevention of enamel caries. In this study, the fluoride level in saliva was

  17. The Sun, Its Extended Corona, the Interplanetary Space, the Earth's Magnetosphere, Ionosphere, Middle and Low Atmosphere, are All Parts of a Complex System - the Heliosphere

    Science.gov (United States)

    Gopalswamy, Natchimuthuk

    2011-01-01

    Various manifestations of solar activity cause disturbances known as space weather effects in the interplanetary space, near-Earth environment, and all the Earth's "spheres. Longterm variations in the frequency, intensity and relative importance of the manifestations of solar activity are due to the slow changes in the output of the solar dynamo, and they define space climate. Space climate governs long-term variations in geomagnetic activity and is the primary natural driver of terrestrial climate. To understand how the variable solar activity affects the Earth's environment, geomagnetic activity and climate on both short and long time scales, we need to understand the origins of solar activity itself and its different manifestations, as well as the sequence of coupling processes linking various parts of the system. This session provides a forum to discuss the chain of processes and relations from the Sun to the Earth's surface: the origin and long-term and short-term evolution of solar activity, initiation and temporal variations in solar flares, CMEs, coronal holes, the solar wind and its interaction with the terrestrial magnetosphere, the ionosphere and its connection to the neutral dominated regions below and the plasma dominated regions above, the stratosphere, its variations due to the changing solar activity and its interactions with the underlying troposphere, and the mechanisms of solar influences on the lower atmosphere on different time-scales. Particularly welcome are papers highlighting the coupling processes between the different domains in this complex system.

  18. Water Fluoridation Reporting System (Public Water Systems)

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Water Fluoridation Reporting System (WFRS) has been developed to provide tools to assist states in managing fluoridation programs. WFRS is designed to track all...

  19. Syntheses, Characterization and Antitumour Activities of Rare Earth Metal Complexes with 2-(((4,6-dimethyl)-2-Pyrimidinyl)thio)-Acetic Acid

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Eight rare earth metal (Ⅲ) complexes with 2-(((4,6-dimethyl)-2-pyrimidinyl)thio)-acetic acid, LnL3*nH2O [HL=2-(((4,6-dimethyl)-2-pyrimidinyl)thio)-acetic acid; Ln=La, Ce, Pr, Nd, Sm Eu, Gd, Tb; n=4 or 5], were prepared and characterized by elemental analysis, complexometric titration, thermal analysis, conductivity, IR and 1H-NMR. The results reveal that carboxyl group of the ligand coordinates with rare earth ions in bidentate mode after deprotonated. The water molecules exist as crystal water in the complexes. The anti-tumour activities of HL and some complexes were tested by both the MTT and SRB methods. The results show that the suppression ratios of some complexes against the tested tumour cells (HL-60 human leukemia cell lines, BGC-823 human gastric carcinoma cell lines, hela human cervix adenocarcinoma cell lines and Bel-7402 human hepatic carcinoma cell lines) are superior to HL.

  20. Developments in the use of rare earth metal complexes as efficient catalysts for ring-opening polymerization of cyclic esters used in biomedical applications

    Science.gov (United States)

    Cota, Iuliana

    2017-04-01

    Biodegradable polymers represent a class of particularly useful materials for many biomedical and pharmaceutical applications. Among these types of polyesters, poly(ɛ-caprolactone) and polylactides are considered very promising for controlled drug delivery devices. These polymers are mainly produced by ring-opening polymerization of their respective cyclic esters, since this method allows a strict control of the molecular parameters (molecular weight and distribution) of the obtained polymers. The most widely used catalysts for ring-opening polymerization of cyclic esters are tin- and aluminium-based organometallic complexes; however since the contamination of the aliphatic polyesters by potentially toxic metallic residues is particularly of concern for biomedical applications, the possibility of replacing organometallic initiators by novel less toxic or more efficient organometallic complexes has been intensively studied. Thus, in the recent years, the use of highly reactive rare earth initiators/catalysts leading to lower polymer contamination has been developed. The use of rare earth complexes is considered a valuable strategy to decrease the polyester contamination by metallic residues and represents an attractive alternative to traditional organometallic complexes.

  1. Identifying the presence of a disulfide linkage in peptides by the selective elimination of hydrogen disulfide from collisionally activated alkali and alkaline earth metal complexes.

    Science.gov (United States)

    Kim, Hugh I; Beauchamp, J L

    2008-01-30

    We report a new method for identifying disulfide linkages in peptides using mass spectrometry. This is accomplished by collisional activation of singly charged cationic alkali and alkaline earth metal complexes, which results in the highly selective elimination of hydrogen disulfide (H2S2). Complexes of peptides possessing disulfide bonds with sodium and alkaline earth metal are generated using electrospray ionization (ESI). Isolation followed by collision induced dissociation (CID) of singly charged peptide complexes results in selective elimination of H2S2 to leave newly formed dehydroalanine residues in the peptide. Further activation of the product yields sequence information in the region previously short circuited by the disulfide bond. For example, singly charged magnesium and calcium ion bound complexes of [Lys8]-vasopressin exhibit selective elimination of H2S2 via low-energy CID. Further isolation of the product followed by CID yields major b- and z-type fragments revealing the peptide sequence in the region between the newly formed dehydroalanine residues. Numerous model peptides provide mechanistic details for the selective elimination of H2S2. The process is initiated starting with a metal stabilized enolate anion at Cys, followed by cleavage of the S-C bond. An examination of the peptic digest of insulin provides an example of the application of the selective elimination of H2S2 for the identification of peptides with disulfide linkages. The energetics and mechanisms of H2S2 elimination from model compounds are investigated using density functional theory (DFT) calculations.

  2. Fluoridering af drikkevandet i Danmark?

    DEFF Research Database (Denmark)

    Arvin, Erik; Spliid, Henrik; Bruvo, M.;

    2010-01-01

    Første gang sammenhængen mellem caries (huller i tænderne) og fluoridindholdet i drikkevand blev diskuteret i vandværkskredse i Danmark var ved årsmødet i 1958. Her blev det oplyst, at fluorid i drikkevand beskytter mod caries, men man konstaterede også, at der nok ikke var stemning for fluorid......-tilsætning til drikkevandet (fluoridering). Siden da er emnet ikke taget op. Formålet med dette indlæg er at besvare spørgsmålene: 1. Er der behov for fluoridering af drikkevandet i Danmark? 2. Er der alternativer? Hvordan påvirker blødgøring af vand og andre vandbehandlingsmetoder dental caries hos børn og unge......? Som baggrund herfor vil vi redegøre for resultaterne af et netop afsluttet studium af sammenhængen mellem caries og drikkevandets sammensætning, specielt m.h.t. luoridindholdet og vandets calciumindhold (hårdhed). Undersøgelsen bekræfter, at fluorid i drikkevand i væsentlig grad beskytter mod caries...

  3. Preparation, thermodynamic property and antimicrobial activity of some rare-earth (III) complexes with 3-bromo-5-iodobenzoic acid and 1,10-phenanthroline

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jing-Yu [Testing and Analysis Center, Hebei Normal University, Shijiazhuang 050024 (China); College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang 050024 (China); Ren, Ning [Department of Chemistry, Handan College, Handan 056005 (China); Zhang, Jian-Jun, E-mail: jjzhang6@126.com [Testing and Analysis Center, Hebei Normal University, Shijiazhuang 050024 (China); College of Chemistry and Material Science, Hebei Normal University, Shijiazhuang 050024 (China); Zhang, Cun-Ying [No.1 High School of Shijiazhuang, Shijiazhuang 050011 (China)

    2013-10-20

    Graphical abstract: Four new rare-earth complexes of general formula [Ln(3-Br-5-IBA){sub 3}phen]{sub 2} [Ln = Er (1), Tb (2), Dy (3) and Ho (4); 3-Br-5-IBA = 3-bromo-5-iodobenzoate; phen = 1,10-phenanthroline] were synthesized and characterized by elemental analysis, IR, UV and TG/DSC-FTIR technology. Heat capacities of the four complexes were measured by differential scanning calorimetry (DSC). The antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans were tested using disc diffusion method. - Highlights: • Four new complexes [Ln(3-Br-5-IBA){sub 3}phen]{sub 2} were synthesized and characterized. • The non-isothermal kinetics of the first stage for the complexes was studied. • The heat capacities of the complexes were measured by differential scanning calorimeter. • The antimicrobial activities for these complexes were tested. • The fluorescence properties of the complexes 2 and 3 were studied. - Abstract: Four new rare-earth complexes of general formula [Ln(3-Br-5-IBA){sub 3}phen]{sub 2} (Ln(III) = Er (1), Tb (2), Dy (3) and Ho (4); 3-Br-5-IBA = 3-bromo-5-iodobenzoate; phen = 1,10-phenanthroline) were synthesized by solution-precipitation method, and investigated using elemental analysis, infrared spectra, ultraviolet spectra and TG/DSC-FTIR technology. The non-isothermal kinetics of the first stage for the complexes was studied by using non-linear integral isoconversional method and double equal-double steps method. The heat capacities of the complexes were measured between 263.15 and 485.55 K by means of differential scanning calorimeter, and the values of the experimental heat capacities were fitted to a polynomial equation with the least-squares method. And the thermodynamic functions [H{sub T} − H{sub 298.15}], [S{sub T} − S{sub 298.15}] and [G{sub T} − G{sub 298.15}] were also derived based on the fitted polynomials and thermodynamic relationships with temperature interval of 10 K. Moreover, the

  4. Acute toxicity of uranium hexafluoride, uranyl fluoride and hydrogen fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Just, R.A.

    1988-01-01

    Uranium hexafluoride (UF/sub 6/) released into the atmosphere will react rapidly with moisture in the air to form the hydrolysis products uranyl fluoride (UO/sub 2/F/sub 2/) and hydrogen fluoride (HF). Uranium compounds such as UF/sub 6/ and UO/sub 2/F/sub 2/ exhibit both chemical toxicity and radiological effects, while HF exhibits only chemical toxicity. This paper describes the development of a methodology for assessing the human health consequences of a known acute exposure to a mixture of UF/sub 6/, UO/sub 2/F/sub 2/, and HF. 4 refs., 2 figs., 5 tabs.

  5. Optically active mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes: synthesis, spectroscopy, and solvent-dependent molecular conformations.

    Science.gov (United States)

    Zhang, Xiaomei; Muranaka, Atsuya; Lv, Wei; Zhang, Yuexing; Bian, Yongzhong; Jiang, Jianzhuang; Kobayashi, Nagao

    2008-01-01

    Reaction between the optically active metal-free phthalocyanine with a pi system with noncentrosymmetrical C(2) [corrected] symmetry ((S)- and (R)-H(2){Pc(OBNP)(2)}; OBNP=binaphthylphthalocyanine) and half-sandwich complexes [M(III)(acac)(TClPP)] (M=Y, Eu; TClPP=meso-tetrakis(4-chlorophenyl)porphyrinate; acac=acetylacetonate), which were generated in situ from [M(acac)(3)].n H(2)O and H(2)(TClPP) in n-octanol at reflux, provided the first optically active protonated mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes [M(III)H{Pc(OBNP)(2)}(TClPP)] (M=Y, Eu) in good yield. In addition to electronic absorption spectroscopy and magnetic circular dichroism results, circular dichroism shows different spectroscopic features of these mixed-ring rare-earth double-decker compounds in different solvents, such as DMF and CHCl(3), which was well-reproduced on the basis of time-dependent density functional theory calculation results for the yttrium species (S)-[Y(III){Pc(OBNP)(2)}(Por)](-) (Por=porphyrinate, which is obtained by removing the four chlorophenyl groups from the TClPP ligand) in terms of the change in the rotation angle between the two macrocyclic ligands in the double-decker molecules. These results revealed the solvent-dependent nature of the molecular conformation of mixed-ring rare-earth double-decker complexes, which suggests a new way of tuning the optical and the electrochemical properties of sandwich-type bis(tetrapyrrole)-metal double-decker complexes in solution by changing the solvent.

  6. Distribution of Rare Earth Metals in Technogenic Wastes of Energy Enterprises (Results of the Laboratory Studies

    Directory of Open Access Journals (Sweden)

    Alexandr Ivanovich Khanchuk

    2016-12-01

    Full Text Available The results of the research interaction between ash and slag samples from Vladivostok TPP’s landfills saturated with underburning and ammonium hydrodifluoride were given. It was found out that the reactions of the main components of a concentrate with NH4HF2 are flowing with creation of complex ammonium fluoro-metalate. It is shown that the distribution of REM (rare earth metals between foam and heavier products is going during the flotation process of carbon-containing ash and slag samples without significant concentrating. It is shown that the water leaching of fluoridated product lets transfer silicone, aluminum and iron salts into solution and concentrate rare earth elements in insoluble residue in the form of complex salts of NaLnF4 general formula. We propose a schematic diagram of hydrodifluoride recycling of carbon-containing sample, which provides concentrating of REM with incomplete separation of macro-components.

  7. The Effect of Fluoride in Osteoporosis.

    Science.gov (United States)

    Hedlund, L. R.; Gallagher, J. C.

    1987-01-01

    This article discusses the effect of fluoride on bone tissue and the possible role of fluoride in the treatment of osteoporosis. At present, fluoride treatment should be restricted to clinical trials until its risks and benefits have been further evaluated. (Author/MT)

  8. Fluoride in African groundwater: Occurrence and mitigation

    NARCIS (Netherlands)

    Vasak, S.; Griffioen, J.; Feenstra, L.

    2010-01-01

    Fluoride in groundwater has both natural and anthropogenic sources. Fluoride bearing minerals, volcanic gases and various industrial and agricultural activities can contribute to high concentrations. High intake of fluoride from drinking water is the main cause of fluorosis and may lead to many othe

  9. Fluoride: its role in dentistry

    Directory of Open Access Journals (Sweden)

    Livia Maria Andaló Tenuta

    2010-01-01

    Full Text Available In spite of decades of research on fluoride and the recognition of its role as the cornerstone of dental caries reduction in the last fifty years, questions still arise on its use at community, self-applied and professional application levels. Which method of fluoride delivery should be used? How and when should it be used? How can its benefits be maximized and still reduce the risks associated with its use? These are only some of the challenging questions facing us daily. The aim of this paper is to present scientific background to understand the importance of each method of fluoride use considering the current caries epidemiological scenario, and to discuss how individual or combined methods can be used based on the best evidence available.

  10. Molten fluorides for nuclear applications

    Directory of Open Access Journals (Sweden)

    Sylvie. Delpech

    2010-12-01

    Full Text Available The importance of pyrochemistry is being increasingly acknowledged and becomes unavoidable in the nuclear field. Molten salts may be used for fuel processing and spent fuel recycling, for heat transfer, as a homogeneous fuel and as a breeder material in fusion systems. Fluorides that are stable at high temperature and under high neutron flux are especially promising. Analysis of several field cases reveals that corrosion in molten fluorides is essentially due to the oxidation of metals by uranium fluoride and/or oxidizing impurities. The thermodynamics of this process are discussed with an emphasis on understanding the mass transfer in the systems, selecting appropriate metallic materials and designing effective purification methods.

  11. Microcratering in Polyvinylidene Fluoride

    Science.gov (United States)

    Shu, Anthony John

    Dust is defined as macroparticles as small as a few molecules up to several micrometers in diameter. In the context of space exploration, it was originally seen only as a technical obstacle to applications; dust can damage instrument surfaces, coat mating surfaces preventing proper seals, and impair or obstruct measurements. Because of the ubiquity of dust in the solar system and its role in the origin of planets and other bodies, the study of dust and related phenomena has evolved to a scientific subdiscipline which can provide us insight into the origins and evolution of our solar system. In order to facilitate this, a hypervelocity dust accelerator has been built at the University of Colorado at Boulder and is being used to probe impact phenomena, dust mitigation techniques, dust detection techniques, and more. One such dust detector is a Polyvinylidene Fluoride (PVDF) dust detector. The PVDF dust detector is very lightweight and consumes little power. Due to these properties, PVDF detectors can potentially be used on any spacecraft to gain information on the local dust environment. It is not fully understood how this PVDF dust detector signal is generated, so at present can only be used as a dust counter. In this thesis I discuss the importance of the study of dust phenomena, describe the accelerator experiment, and describe a study conducted to determine the underlying physical principles of PVDF dust detectors. This included measuring crater size scaling laws, measuring the detailed shape of craters, and applying this data to simulations of the signals being generated by PVDF detectors.

  12. High-fluoride groundwater.

    Science.gov (United States)

    Rao, N Subba

    2011-05-01

    Fluoride (F(-)) is essential for normal bone growth, but its higher concentration in the drinking water poses great health problems and fluorosis is common in many parts of India. The present paper deals with the aim of establishment of facts of the chemical characteristics responsible for the higher concentration of F(-) in the groundwater, after understanding the chemical behavior of F(-) in relation to pH, total alkalinity (TA), total hardness (TH), carbonate hardness (CH), non-carbonate hardness (NCH), and excess alkalinity (EA) in the groundwater observed from the known areas of endemic fluorosis zones of Andhra Pradesh that have abundant sources of F(-)-bearing minerals of the Precambrians. The chemical data of the groundwater shows that the pH increases with increase F(-); the concentration of TH is more than the concentration of TA at low F(-) groundwater, the resulting water is represented by NCH; the TH has less concentration compared to TA at high F(-) groundwater, causing the water that is characterized by EA; and the water of both low and high concentrations of F(-) has CH. As a result, the F(-) has a positive relation with pH and TA, and a negative relation with TH. The operating mechanism derived from these observations is that the F(-) is released from the source into the groundwater by geochemical reactions and that the groundwater in its flowpath is subjected to evapotranspiration due to the influence of dry climate, which accelerates a precipitation of CaCO(3) and a reduction of TH, and thereby a dissolution of F(-). Furthermore, the EA in the water activates the alkalinity in the areas of alkaline soils, leading to enrichment of F(-). Therefore, the alkaline condition, with high pH and EA, and low TH, is a more conducive environment for the higher concentration of F(-) in the groundwater.

  13. Synthesis, Characterization and Luminescent Properties of Complexes of Rare Earth Nitrates with Tris {2-[N-(pyridine-methanoyl)amino]ethyl} amine

    Institute of Scientific and Technical Information of China (English)

    台夕市; 唐瑜; 刘伟生; 谭民裕

    2003-01-01

    A tripodal ligand, tris{2-[N-(pyridine-methanoyl)amino]ethyl}amine(L), and its complexes with rare earth nitrates were synthesized. These new complexes with the general formula of Ln(NO3)3*L*6H2O(where Ln=La, Nd, Eu, Tb, Y) were characterized by elemental analysis, IR spectra, thermal analysis, 1 H NMR spectra, molar conductivity and luminescent spectra. All the complexes are stable in air and their conductances in acetonitrile solution lie in the range of 142~150 S*cm2*mol-1, indicating 1∶1 type electrolytes. The IR and 1H NMR spectra of the ligand and its complexes show that all the C=O groups take part in coordination to the metal ions. The thermal behaviour of Eu complex shows that the weight losses at 75~120 ℃ and 120~210 ℃ correspond to the loss of four lattice water molecules and that of two coordinated water molecules, respectively. The luminescent spectra of the complexes of Eu(Ⅲ) and Tb(Ⅲ) were investigated in methanol.

  14. Synthesis,characterization and properties of some rare earth complexes with pyrazolone and 2,6-pyridinecarboxylic acid

    Directory of Open Access Journals (Sweden)

    CHEN Jing

    2014-06-01

    Full Text Available A new solid ternary complex of copper with 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 and 2,6-pyridinecarboxylic acid Na[Cu(PMBP (PDA]has been synthesized and characterized by elemental analysis,FT-IR,UV-Vis,XRD,TG-DTA,and XPS.The antibacterial test indicated that the complex exhibited moderate antibacterial ability against Escherichia coli and Staphylococcus aureus.The interactions of the complex with calf thymus DNA (CT DNAwas investigated by employing florescence spectroscopic studies and ultraviolet spectrum spectrom etries.The results indicated that the complex can intercalate between DNA base pairs.

  15. Novel Approach to Characterization of Rare Earth Complexation with 1, 5-Bis(2-Hydroxy-5-Chlorphenyl)-3-Cyanoformazan in Presence of Cetyltrimethylammonium Bromide

    Institute of Scientific and Technical Information of China (English)

    郑立新; 胡张军; 郜洪文

    2002-01-01

    The ternary interaction of 1, 5-bis(2-hydroxy-5-chlorphenyl)-3-cyanoformazan (HCPCF) with cetyltrimethylammonium bromide (CTAB) and rare earths (RE: Yb, Dy, Er and Eu) was investigated at pH 9.84 by the microsurface adsorption - spectral correction technique (MSASC). The aggregation of HCPCF on CTAB obeys the Langmuir isothermal adsorption and the interaction of RE with the HCPCF-CTAB aggregate was first found to accord with the monolayer binding. The effects of temperature and ionic strength of solution on the aggregations were made. The binary aggregate and the ternary complex were characterized.

  16. Lithological Influences on Occurrence of High-Fluoride Waters in The Central Kenya Rift

    Science.gov (United States)

    Olaka, L. A.; Musolff, A.; Mulch, A.; Olago, D.; Odada, E. O.

    2013-12-01

    Within the East African rift, groundwater recharge results from the complex interplay of geology, land cover, geomorphology, climate and on going volcano-tectonic processes across a broad range of spatial and temporal scales. The interrelationships between these factors create complex patterns of water availability, reliability and quality. The hydrochemical evolution of the waters is further complex due to the different climatic regimes and geothermal processes going on in this area. High fluoridic waters within the rift have been reported by few studies, while dental fluorosis is high among the inhabitants of the rift. The natural sources of fluoride in waters can be from weathering of fluorine bearing minerals in rocks, volcanic or fumarolic activities. Fluoride concentration in water depends on a number of factors including pH, temperature, time of water-rock formation contact and geochemical processes. Knowledge of the sources and dispersion of fluoride in both surface and groundwaters within the central Kenya rift and seasonal variations between wet and dry seasons is still poor. The Central Kenya rift is marked by active tectonics, volcanic activity and fumarolic activity, the rocks are majorly volcanics: rhyolites, tuffs, basalts, phonolites, ashes and agglomerates some are highly fractured. Major NW-SE faults bound the rift escarpment while the rift floor is marked by N-S striking faults We combine petrographic, hydrochemistry and structural information to determine the sources and enrichment pathways of high fluoridic waters within the Naivasha catchment. A total of 120 water samples for both the dry season (January-February2012) and after wet season (June-July 2013) from springs, rivers, lakes, hand dug wells, fumaroles and boreholes within the Naivasha catchment are collected and analysed for fluoride, physicochemical parameters and stable isotopes (δ2 H, δ18 O) in order to determine the origin and evolution of the waters. Additionally, 30 soil and

  17. The role of fluoride in erosion therapy.

    Science.gov (United States)

    Huysmans, Marie-Charlotte; Young, Alix; Ganss, Carolina

    2014-01-01

    The role of fluoride in erosion therapy has long been questioned. However, recent research has yielded positive results. In this chapter, an overview of the literature is provided regarding the application of fluorides in the prevention and treatment of erosion and erosive wear. The results are presented and discussed for different fluoride sources such as monovalent and polyvalent fluorides, and for different vehicles such as toothpastes, solutions and rinses, as well as varnishes and gels. It is concluded that fluoride applications are very likely to be of use in the preventive treatment of erosive wear. Most promising are high-concentration, acidic formulations and the polyvalent fluoride sources, with the best evidence available for stannous fluoride. However, the evidence base for clinical effectiveness is still small. © 2014 S. Karger AG, Basel.

  18. Comparison of salivary fluoride levels following use of dentifrices containing different concentrations of fluoride

    Directory of Open Access Journals (Sweden)

    Nagpal D

    2007-03-01

    Full Text Available Many industrialized countries have reported a decline in caries prevalence over the past few decades. These reductions have been related to the regular use of fluoride dentifrices. Fluoride dentifrices are the most cost-effective and efficient means of caries prevention. However, there have been concerns regarding the risk of fluorosis in children due to the ingestion of dentifrices. This has led to the use of dentifrices with low concentration of fluoride. Salivary fluoride levels after tooth-brushing have been shown to be related to the anticaries efficacy of fluoride dentifrices. The present study was designed to evaluate the effect of the concentration of fluoride in the dentifrice, on the salivary fluoride level in children. Twenty children in the age group of five to six years were randomly selected and divided into two groups using, either 500ppm or 1000ppm fluoride dentifrice (sodium monofluorophosphate. Salivary fluoride levels at 0, 15, 30, 45, 60, minutes after brushing were estimated. The data collected was statistically evaluated using the unpaired t-test. The results showed that salivary fluoride levels following use of 500ppm fluoride dentifrice were significantly lower than 1000ppm fluoride dentifrice. The low salivary fluoride levels may thereby reduce the anticaries efficacy. Hence, the pros and cons of recommending a low fluoride concentration dentifrice must be judiciously considered.

  19. Fluoride remediation using floating macrophytes

    Directory of Open Access Journals (Sweden)

    Naba Kumar Mondal

    2014-04-01

    Full Text Available Six aquatic macrophytes, such as Pistia stratiotes, Ceratophyllum demersum, Nymphoides indica, Lemna major, Azolla pinnata,and Eichhornia crassipes were considered for remove fluoride from aqueous solution. Five different concentrations (10, 30, 50, and 100 ppm of fluoride solution were taken in 1 L plastic container. Fixed weight (20 g of macrophytes along with 500 ml fluoride solution was taken in each plastic container for 72 hours observation. Results demonstrated all the macrophytes show highest fluoride removal during 24 h to 48 h, but after 72 h their efficiency reduced drastically. The species N. indica showed better removal efficiency than other experimental macrophytes. In general, pigment measurement data indicated higher concentration at 72 h. However, Pistia sp. showed higher concentration of pigmentation at intermediate time interval (48 h. Higher level of dry weight to fresh weight ratio was recorded for L. major and A. pinnata at all concentrations, excepting at 10 ppm. In addition, all macrophytes showed lower RGR at higher concentration. Isotherm study indicated that macrophyte C. demersum is a good fitted with Freundlich and Langmuir isotherm whereas L. major with Langmuir isotherm during 24 hours.

  20. Special Report: Fluoridation of Water.

    Science.gov (United States)

    Hileman, Bette

    1988-01-01

    Reviews the controversy regarding water fluoridation in the United States during the last 50 years. Discusses the current status; benefits; and health risks including skeletal fluorosis, kidney disease, hypersensitivity, mutagenic effects, birth defects, and cancer. Presents statistics and anecdotal accounts. (CW)

  1. Special Report: Fluoridation of Water.

    Science.gov (United States)

    Hileman, Bette

    1988-01-01

    Reviews the controversy regarding water fluoridation in the United States during the last 50 years. Discusses the current status; benefits; and health risks including skeletal fluorosis, kidney disease, hypersensitivity, mutagenic effects, birth defects, and cancer. Presents statistics and anecdotal accounts. (CW)

  2. Alimentary fluoride intake in preschool children

    Science.gov (United States)

    2011-01-01

    Background The knowledge of background alimentary fluoride intake in preschool children is of utmost importance for introducing optimal and safe caries preventive measures for both individuals and communities. The aim of this study was to assess the daily fluoride intake analyzing duplicate samples of food and beverages. An attempt was made to calculate the daily intake of fluoride from food and swallowed toothpaste. Methods Daily alimentary fluoride intake was measured in a group of 36 children with an average age of 4.75 years and an average weight of 20.69 kg at baseline, by means of a double plate method. This was repeated after six months. Parents recorded their child's diet over 24 hours and collected duplicated portions of food and beverages received by children during this period. Pooled samples of food and beverages were weighed and solid food samples were homogenized. Fluoride was quantitatively extracted from solid food samples by a microdiffusion method using hexadecyldisiloxane and perchloric acid. The content of fluoride extracted from solid food samples, as well as fluoride in beverages, was measured potentiometrically by means of a fluoride ion selective electrode. Results Average daily fluoride intake at baseline was 0.389 (SD 0.054) mg per day. Six months later it was 0.378 (SD 0.084) mg per day which represents 0.020 (SD 0.010) and 0.018 (SD 0.008) mg of fluoride respectively calculated per kg bw/day. When adding the values of unwanted fluoride intake from the toothpaste shown in the literature (0.17-1.21 mg per day) the estimate of the total daily intake of fluoride amounted to 0.554-1.594 mg/day and recalculated to the child's body weight to 0.027-0.077 mg/kg bw/day. Conclusions In the children studied, observed daily fluoride intake reached the threshold for safe fluoride intake. When adding the potential fluoride intake from swallowed toothpaste, alimentary intake reached the optimum range for daily fluoride intake. These results showed that

  3. Fissure seal or fluoride varnish?

    Science.gov (United States)

    Deery, Christopher

    2016-09-01

    Data sourcesCochrane Oral Health Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, the US National Institutes of Health Trials Register and the World Health Organization (WHO) Clinical Trials Registry PlatformStudy selectionRandomised controlled trials (RCTs) with at least 12 months follow-up, in which fissure sealants, or fissure sealants together with fluoride varnishes, were compared with fluoride varnishes alone for preventing caries in occlusal surfaces of permanent teeth of children and adolescents.Data extraction and synthesisTwo reviewers independently screened search results, extracted data and assessed risk of bias of included studies. Studies were grouped and analysed on the basis of sealant material type (resin-based sealant and glass ionomer-based sealant, glass ionomer and resin-modified glass ionomer) and different follow-up periods. Odds ratio were calculated for caries or no caries on occlusal surfaces of permanent molar teeth. Mean differences were calculated for continuous outcomes and data. Evidence quality was assessed using GRADE (Grades of Recommendation, Assessment, Development and Evaluation) methods.ResultsEight RCTs involving a total of 1747 children aged five to ten years of age were included. Three trials compared resin-based fissure sealant versus fluoride varnish. Results from two studies (358 children) after two years were combined. Sealants prevented more caries, pooled odds ratio (OR) = 0.69 (95%CI; 0.50 to 0.94). One trial with follow-up at four and nine years found that the caries-preventive benefit for sealants was maintained, with 26% of sealed teeth and 55.8% of varnished teeth having developed caries at nine years. Evidence for glass-ionomer sealants was of low quality. One split-mouth trial analysing 92 children at two-year follow-up found a significant difference in favour of resin-based fissure sealant together with fluoride varnish compared with fluoride varnish only (OR

  4. Synthesis, characterization, antibacterial and antifungal studies of some transition and rare earth metal complexes of N-benzylidene-2-hydroxybenzohydrazide

    Directory of Open Access Journals (Sweden)

    T.K. Chondhekar

    2011-12-01

    Full Text Available The solid complexes of Cu(II, Co(II, Mn(II, La(III and Ce(III were prepared from bidentate Schiff base, N-benzylidene-2-hydroxybenzohydrazide. The Schiff base ligand was synthesized from 2-hyhdroxybenzohydrazide and benzaldehyde. These metal complexes were characterized by molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, FTIR, 1H-NMR, UV-Vis and mass spectroscopy. The analytical data of these metal complexes showed metal:ligand ratio of 1:2. The physico-chemical study supports the presence of square planar geometry around Cu(II and octahedral geometry around Mn(II, Co(II, La(III and Ce(III ions. The IR spectral data reveal that the ligand behaves as bidentate with ON donor atom sequence towards central metal ion. The molar conductance values of metal complexes suggest their non-electrolyte nature. The X-ray diffraction data suggest monoclinic crystal system for these complexes. Thermal behavior (TG/DTA and kinetic parameters calculated by Coats-Redfern method are suggestive of more ordered activated state in complex formation. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus niger and Trichoderma.

  5. Urinary fluoride excretion in preschool children after intake of fluoridated milk and use of fluoride-containing toothpaste

    DEFF Research Database (Denmark)

    Norman, M; Twetman, S; Hultgren Talvilahti, A

    2017-01-01

    Objective: To assess the urinary fluoride excretion in preschool children after drinking fluoridated milk with 0.185 mg F and 0.375 mg F and to study the impact of use of fluoride toothpaste. Basic research design: Double-blind cross-over study. Participants: Nine healthy children, 2.5-4.5 years...... of age. Intervention: In a randomized order, participants drank 1.5 dl milk once daily for 7 days with no fluoride added (control), 0.185 mg fluoride added and 0.375 mg fluoride added. The experiment was performed twice with (Part I) and without (Part II) parental tooth brushing with 1,000 ppm fluoride...... toothpaste. The fluoride content in the piped drinking water was 0.5 mg F/L. Main outcome measure: Urinary fluoride excretion. Results: The 24-hour urinary fl uoride excretion/kg body weight varied from 0.014 mg F for the placebo intervention and non-fluoride toothpaste to 0.027 mg F for the 0.375 mg...

  6. The coordination complex structures and hydrogen bonding in the three-dimensional alkaline earth metal salts (Mg, Ca, Sr and Ba) of (4-aminophenyl)arsonic acid.

    Science.gov (United States)

    Smith, Graham; Wermuth, Urs D

    2017-01-01

    (4-Aminophenyl)arsonic acid (p-arsanilic acid) is used as an antihelminth in veterinary applications and was earlier used in the monosodium salt dihydrate form as the antisyphilitic drug atoxyl. Examples of complexes with this acid are rare. The structures of the alkaline earth metal (Mg, Ca, Sr and Ba) complexes with (4-aminophenyl)arsonic acid (p-arsanilic acid) have been determined, viz. hexaaquamagnesium bis[hydrogen (4-aminophenyl)arsonate] tetrahydrate, [Mg(H2O)6](C6H7AsNO3)·4H2O, (I), catena-poly[[[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O']-[diaquacalcium]-bis[μ2-hydrogen (4-aminophenyl)arsonato-κ(2)O:O

  7. The Laboratory Complex for the Calibration of Photometers Using the Optical Method for Determination of the Water Vapor Content in the Earth Atmosphere

    CERN Document Server

    Galkin, V D; Nikanorova, I N; Leiterer, U; Niebert, T; Alekseeva, G A; Novikov, V V; Ilyin, G N; Pakhomov, V P

    2010-01-01

    We describe the laboratory complex for the calibration of photometers that are used in weather service to measure the water vapor content in the Earth atmosphere. The complex was built up in Pulkovo Observatory and developed within the framework of collaboration between Pulkovo Observatory and Lindenberg Meteorological Observatory (Meteorologisches Observatorium Lindenberg - Richard-A{\\ss}mann-Observatorium, Lindenberg, Germany). It is used to obtain calibration dependences for individual devices, and also to develop and compare various methods of construction of calibration dependences. These techniques are based on direct calibration of the photometers, on the use of spectral laboratory transmission functions for water vapor, on calculation methods using spectroscopical databases for individual lines. We hope that when the parameters of the equipment are taken into account in detail and new results for the absorptive power of water vapor are used, the accuracy of determination of the water vapor content in ...

  8. Global affordability of fluoride toothpaste

    Directory of Open Access Journals (Sweden)

    Holmgren Christopher J

    2008-06-01

    Full Text Available Abstract Objective Dental caries remains the most common disease worldwide and the use of fluoride toothpaste is a most effective preventive public health measure to prevent it. Changes in diets following globalization contribute to the development of dental caries in emerging economies. The aim of this paper is to compare the cost and relative affordability of fluoride toothpaste in high-, middle- and low-income countries. The hypothesis is that fluoride toothpaste is not equally affordable in high-, middle- and low-income countries. Methods Data on consumer prices of fluoride toothpastes were obtained from a self-completion questionnaire from 48 countries. The cost of fluoride toothpaste in high-, middle- and low-income countries was compared and related to annual household expenditure as well as to days of work needed to purchase the average annual usage of toothpaste per head. Results The general trend seems to be that the proportion of household expenditure required to purchase the annual dosage of toothpaste increases as the country's per capita household expenditure decreases. While in the UK for the poorest 30% of the population only 0.037 days of household expenditure is needed to purchase the annual average dosage (182.5 g of the lowest cost toothpaste, 10.75 days are needed in Kenya. The proportion of annual household expenditure ranged from 0.02% in the UK to 4% in Zambia to buy the annual average amount of lowest cost toothpaste per head. Conclusion Significant inequalities in the affordability of this essential preventive care product indicate the necessity for action to make it more affordable. Various measures to improve affordability based on experiences from essential pharmaceuticals are proposed.

  9. On the Eu2+ luminescence in some perovskite fluorides

    Science.gov (United States)

    Belsare, P. D.; Joshi, C. P.; Moharil, S. V.; Omanwar, S. K.

    2015-08-01

    In the recent years due to their various optical and technological applications fluoride materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. The perovskite type fluorides of formula ABF3 where A= Alkali earth metal (Li,Na,K,Rb,Cs) and B= Alkaline earth metal (Mg,Ca,Ba,Sr) are of special interest to the research workers because of their wide range of applications that includes these materials as thermoluminescence detector, laser material, scintillator, X-ray imaging and storage phosphor, quantum cutter for VUV applications etc. Due to the high symmetry and technological efficiency of the growth process these crystals are good model objects for fundamental studies and in some cases they are of great practical value. This paper reports photoluminescence properties of UV emitting KMgF3, NaMgF3 and LiBaF3 phosphors prepared by reactive atomospheric process. X-ray diffraction and photoluminescence characteristics of these phosphors are also mentioned.

  10. Extraction Behaviors of Heavy Rare Earths with Organophosphoric Extractants: The Contribution of Extractant Dimer Dissociation, Acid Ionization, and Complexation. A Quantum Chemistry Study.

    Science.gov (United States)

    Jing, Yu; Chen, Ji; Chen, Li; Su, Wenrou; Liu, Yu; Li, Deqian

    2017-03-30

    Heavy rare earths (HREs), namely Ho(3+), Er(3+), Tm(3+), Yb(3+) and Lu(3+), are rarer and more exceptional than light rare earths, due to the stronger extraction capacity for 100 000 extractions. Therefore, their incomplete stripping and high acidity of stripping become problems for HRE separation by organophosphoric extractants. However, the theories of extractant structure-performance relationship and molecular design method of novel HRE extractants are still not perfect. Beyond the coordination chemistry of the HRE-extracted complex, the extractant dimer dissociation, acid ionization, and complexation behaviors can be crucial to HRE extraction and reactivity of ionic species for understanding and further improving the extraction performance. To address the above issues, three primary fundamental processes, including extractant dimer dissociation, acid ionization, and HRE complexation, were identified and investigated systematically. The intrinsic extraction performances of HRE cations with four acidic organophosphoric extractants (P507, P204, P227 and Cyanex 272) were studied by using relativistic energy-consistent 4f core pseudopotentials, combined with density functional theory and a solvation model. Four acidic organophosphoric extractants have been qualified quantitatively from microscopic structures to chemical properties. It has been found that the Gibbs free energy changes of the overall extraction process (sequence: P204 > P227 > P507 > Cyanex 272) and their differences as a function of HREs (sequence: Ho/Er > Er/Tm > Tm/Yb > Yb/Lu) are in good agreement with the experimental maximum extraction capacities and separation factors. These results could provide an important approach to evaluate HRE extractants by the comprehensive consideration of dimer dissociation, acid ionization, and complexation processes. This paper also demonstrates the importance of the P-O bond, the P-C bond, isomer substituent, and solvation effects on the structure

  11. Alkaline earth organometallic compounds in homogeneous catalysis : Synthesis, characterization and catalytic activity of calcium and magnesium complexes

    NARCIS (Netherlands)

    Penafiel, Johanne

    2016-01-01

    Homogeneous catalysis has been developed mainly through the use of transition metal complexes. However, transition-metal catalysts, often highly toxic, are becoming increasingly rare and consequently more expensive. Therefore, the search for sustainable alternatives is nowadays of great importance.

  12. Investigation on the Use of the Weakly Basic Polyacrylate Anion-Exchanger Amberlite IRA-68 for Sorption and Separation of Iminodiacetate Complexes of Rare Earth Elements

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on the determined affinity series of rare earth element complexes with IMDA for the anion-exchangers, purification of macroquantities of Nd3+ from Y3+, Sm3+ from Ho3+, La3+ from Nd3+ and La3+ from Pr3+ on the weakly basic gel anion-exchanger Amberlite IRA-68 was studied. Using the presented method on 1 L of Amberlite IRA-68 in the acetate form, it is possible to obtain about 240 g Nd2O3 purified from Y2O3. Great difference in affinity of La3+ and Nd3+ as well as Pr3+ complexes for this anion-exchanger in the acetate form indicates the possibility of applying this process for purification of lanthanum on the increased scale. On 1 L of Amberilte IRA-68 in the acetate form it is possible to obtain about 1125 g La2O3 purified from Nd2O3. On the basis of these results it can be assumed that unique properties of polyacrylate anion-exchangers enable their application for separation of rare earth elements.

  13. Rare earth(III) complexes for the development of new magnetic and luminescent probes; Complexes de lanthanides(III) pour le developpement de nouvelles sondes magnetiques et luminescentes

    Energy Technology Data Exchange (ETDEWEB)

    Nonat, A

    2007-10-15

    The simultaneous optimisation of the molecular parameters determining the relaxivity (number of coordinated water molecules, water-exchange, rotation dynamics of the whole complex, electronic relaxation, Gd(III)-proton distance) is essential to prepare efficient contrast agents. The aim of this work is on the one hand to design and study complexes with a high number of bound water molecules and to understand the influence of the coordination sphere on the stability and on the electronic relaxation and on the other hand, to use the ligand as a chromophore for the development of luminescent probes for biomedical imaging. We present the structure, the stability and the relaxivity of Gd(III) complexes of two series of tripodal ligands containing picolinate units based either on the 1,4,7-tri-aza-cyclononane ring or on a tertiary amine. These complexes show high relaxivity in water and in serum and can establish a non covalent interaction with serum albumin. The interpretation of the water proton relaxivity with the help of new relaxometric methods based on an auxiliary probe solute has allowed us to show that both the presence of the picolinate groups and the 1,4,7-tri-aza-cyclononane framework can lead to Gd(III) complexes with favourable electronic relaxation properties. This ligands have also been used for Eu(III) and Tb(III) complexation leading to strong luminescence in visible light. Other complexes derived from 8-hydroxyquinoline unit which display a very high luminescence in infrared are also studied. (author)

  14. Synthesis, structure, infrared and fluorescence spectra of new rare earth complexes with 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone

    Science.gov (United States)

    Wang, Bao-Dui; Yang, Zheng-Yin; Zhang, Ding-Wa; Wang, Yan

    2006-01-01

    A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand and its four complexes, [LnL2(NO3)2]NO3 [Ln = Eu(1), Sm(2), Tb(3), Dy(4)], were synthesized. The complexes were characterized by the elemental analyses, molar conductivity and IR spectra. The crystal and molecular structure of Sm(III) complex was determined by single-crystal X-ray diffraction: crystallized in the triclinic system, space group P-1, Z = 1, a = 11.037(4) Å, b = 14.770(5) Å, c = 15.032(7) Å, α = 60.583(4), β = 75.528(7), γ = 88.999(4), R1 = 0.0349. The fluorescence properties of complexes in the solid state and in the organic solvent were studied in detail, respectively. Under the excitation of ultraviolet light, strong red fluorescence of solid europium complex was observed. But the green fluorescence of solid terbium complex was not observed. These observations show that the ligand favor energy transfers to the emitting energy level of Eu3+. Some factors that influence the fluorescent intensity were also discussed.

  15. Rare-earth metal methylidene complexes with Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 core structure.

    Science.gov (United States)

    Schädle, Dorothea; Meermann-Zimmermann, Melanie; Maichle-Mössmer, Cäcilia; Schädle, Christoph; Törnroos, Karl W; Anwander, Reiner

    2015-11-07

    Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an "intermediate" species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C-H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, (1)H and (13)C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)].

  16. Dipotassium hydrogencarbonate fluoride monohydrate

    Directory of Open Access Journals (Sweden)

    Volker Kahlenberg

    2013-04-01

    Full Text Available Single crystals of the title compound, K2(HCO3F·H2O, were obtained as a secondary product after performing flux synthesis experiments aimed at the preparation of potassium rare earth silicates. The basic building unit of the structure is an [(HCO3(H2OF]2− zigzag chain running parallel to [001]. Both types of anions as well as the water molecules reside on mirror planes perpendicular to [010] at y = 0.25 and y = 0.75, respectively. Linkage between the different constituents of the chains is provided by O—H...O and O—H...F hydrogen bonding. The K+ cations are located between the chains and are coordinated by two F and five O atoms in form of a distorted monocapped trigonal prism.

  17. Focus on fluorides: update on the use of fluoride for the prevention of dental caries.

    Science.gov (United States)

    Carey, Clifton M

    2014-06-01

    Improving the efficacy of fluoride therapies reduces dental caries and lowers fluoride exposure. Fluoride is delivered to the teeth systemically or topically to aid in the prevention of dental caries. Systemic fluoride from ingested sources is in blood serum and can be deposited only in teeth that are forming in children. Topical fluoride is from sources such as community water, processed foods, beverages, toothpastes, mouthrinses, gels, foams, and varnishes. The United States Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA) have proposed changes in their long standing recommendations for the amount of fluoride in community drinking water in response to concerns about an increasing incidence of dental fluorosis in children. Current research is focused on the development of strategies to improve fluoride efficacy. The purpose of this update is to inform the reader about new research and policies related to the use of fluoride for the prevention of dental caries. Reviews of the current research and recent evidence based systematic reviews on the topics of fluoride are presented. Topics discussed include: updates on community water fluoridation research and policies; available fluoride in dentifrices; fluoride varnish compositions, use, and recommendations; and other fluoride containing dental products. This update provides insights into current research and discusses proposed policy changes for the use of fluoride for the prevention of dental caries. The dental profession is adjusting their recommendations for fluoride use based on current observations of the halo effect and subsequent outcomes. The research community is focused on improving the efficacy of fluoride therapies thus reducing dental caries and lowering the amount of fluoride required for efficacy. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Fluoride Varnishes--Is There a Correlation Between Fluoride Release and Deposition on Enamel?

    Science.gov (United States)

    Bolis, Carlo; Härtli, Gian Peider; Lendenmann, Urs

    2015-01-01

    Fluoride uptake of enamel after application of fluoride varnishes was compared with fluoride release into artificial saliva. The hypothesis was that fluoride uptake is higher for products exhibiting faster fluoride release. Fluoride varnishes, i.e. Fluor Protector S, Duraphat, MI Varnish, Clinpro White Varnish, Profluorid Varnish and Enamel Pro Varnish were applied on bovine enamel specimens. Subsequently, specimens were incubated in artificial saliva. After removal of the varnishes, surface bound fluoride was extracted with potassium hydroxide and measured with an ion-selective electrode. Structurally bound fluoride was etched from the same specimens with perchloric acid. Fluoride release of varnish films into artificial saliva was measured for comparison. After 4 h in artificial saliva, the highest total enamel fluoride uptake of 47.9 μg F·cm-² was found with Fluor Protector S, followed by Enamel Pro Varnish with 22.1 μg F·cm-². The other products ranged between 12-16 μg F·cm-². This was several times higher than the negative control. Fluoride uptake did not correlate with release into artificial saliva. During the first 4 h, Duraphat released the lowest and MI Varnish the highest amount of fluoride with 7.7 and 249 μg F·cm-², respectively. The fluoride uptake of these two products was not statistically different. Enamel fluoride uptake cannot be predicted from the fluoride release rate of a product. Hence, based on the results of this study, fluoride release into artificial saliva is no measure for the efficacy of a fluoride varnish.

  19. Focus on Fluorides: Update on the Use of Fluoride for the Prevention of Dental Caries

    Science.gov (United States)

    Carey, Clifton M.

    2014-01-01

    Declarative Title: Improving the efficacy of fluoride therapies reduces dental caries and lowers fluoride exposure. Background Fluoride is delivered to the teeth systemically or topically to aid in the prevention of dental caries. Systemic fluoride from ingested sources is in blood serum and can be deposited only in teeth that are forming in children. Topical fluoride is from sources such as community water, processed foods, beverages, toothpastes, mouthrinses, gels, foams, and varnishes. The United States Centers for Disease Control and Prevention (CDC) and the American Dental Association (ADA) have proposed changes in their long standing recommendations for the amount of fluoride in community drinking water in response to concerns about an increasing incidence of dental fluorosis in children. Current research is focused on the development of strategies to improve fluoride efficacy. The purpose of this update is to inform the reader about new research and policies related to the use of fluoride for the prevention of dental caries. Methods Reviews of the current research and recent evidence based systematic reviews on the topics of fluoride are presented. Topics discussed include: updates on community water fluoridation research and policies; available fluoride in dentifrices; fluoride varnish compositions, use, and recommendations; and other fluoride containing dental products. This update provides insights into current research and discusses proposed policy changes for the use of fluoride for the prevention of dental caries. Conclusions The dental profession is adjusting their recommendations for fluoride use based on current observations of the halo effect and subsequent outcomes. The research community is focused on improving the efficacy of fluoride therapies thus reducing dental caries and lowering the amount of fluoride required for efficacy. PMID:24929594

  20. Fluoride retention in saliva and in dental biofilm after different home-use fluoride treatments

    Directory of Open Access Journals (Sweden)

    Daniela Correia Cavalcante SOUZA

    2014-08-01

    Full Text Available This single-blind, randomized, crossover study aimed at assessing the long-term fluoride concentrations in saliva and in dental biofilm after different home-use fluoride treatments. The study volunteers (n = 38 were residents of an area with fluoridated drinking water. They were administered four treatments, each of which lasted for one week: twice-daily placebo dentifrice, twice-daily fluoride dentifrice, twice-daily fluoride dentifrice and once-daily fluoride mouthrinse, and thrice-daily fluoride dentifrice. At the end of each treatment period, samples of unstimulated saliva and dental biofilm were collected 8 h after the last oral hygiene procedure. Fluoride concentrations in saliva and dental biofilm were analyzed using a specific electrode. The fluoride concentrations in saliva and dental biofilm 8 h after the last use of fluoride products did not differ among treatments. The results of this study suggest that treatments with home-use fluoride products have no long-term effect on fluoride concentrations in saliva and in dental biofilm of residents of an area with a fluoridated water supply.

  1. Eukaryotic resistance to fluoride toxicity mediated by a widespread family of fluoride export proteins

    Science.gov (United States)

    Li, Sanshu; Smith, Kathryn D.; Davis, Jared H.; Gordon, Patricia B.; Breaker, Ronald R.; Strobel, Scott A.

    2013-01-01

    Fluorine is an abundant element and is toxic to organisms from bacteria to humans, but the mechanisms by which eukaryotes resist fluoride toxicity are unknown. The Escherichia coli gene crcB was recently shown to be regulated by a fluoride-responsive riboswitch, implicating it in fluoride response. There are >8,000 crcB homologs across all domains of life, indicating that it has an important role in biology. Here we demonstrate that eukaryotic homologs [renamed FEX (fluoride exporter)] function in fluoride export. FEX KOs in three eukaryotic model organisms, Neurospora crassa, Saccharomyces cerevisiae, and Candida albicans, are highly sensitized to fluoride (>200-fold) but not to other halides. Some of these KO strains are unable to grow in fluoride concentrations found in tap water. Using the radioactive isotope of fluoride, 18F, we developed an assay to measure the intracellular fluoride concentration and show that the FEX deletion strains accumulate fluoride in excess of the external concentration, providing direct evidence of FEX function in fluoride efflux. In addition, they are more sensitive to lower pH in the presence of fluoride. These results demonstrate that eukaryotic FEX genes encode a previously unrecognized class of fluoride exporter necessary for survival in standard environmental conditions. PMID:24173035

  2. Fluoride retention in saliva and in dental biofilm after different home-use fluoride treatments.

    Science.gov (United States)

    Souza, Daniela Correia Cavalcante; Maltz, Marisa; Hashizume, Lina Naomi

    2014-01-01

    This single-blind, randomized, crossover study aimed at assessing the long-term fluoride concentrations in saliva and in dental biofilm after different home-use fluoride treatments. The study volunteers (n = 38) were residents of an area with fluoridated drinking water. They were administered four treatments, each of which lasted for one week: twice-daily placebo dentifrice, twice-daily fluoride dentifrice, twice-daily fluoride dentifrice and once-daily fluoride mouthrinse, and thrice-daily fluoride dentifrice. At the end of each treatment period, samples of unstimulated saliva and dental biofilm were collected 8 h after the last oral hygiene procedure. Fluoride concentrations in saliva and dental biofilm were analyzed using a specific electrode. The fluoride concentrations in saliva and dental biofilm 8 h after the last use of fluoride products did not differ among treatments. The results of this study suggest that treatments with home-use fluoride products have no long-term effect on fluoride concentrations in saliva and in dental biofilm of residents of an area with a fluoridated water supply.

  3. Synthesis, structural, thermal and optical studies of rare earth coordinated complex: Tb(Sal){sub 3}Phen

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Gagandeep; Dwivedi, Y. [Laser and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Rai, S.B., E-mail: sbrai49@yahoo.co.in [Laser and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005 (India)

    2011-11-01

    Highlights: {yields} RE coordinated complex of Tb(Sal){sub 3}Phen in crystalline phases were synthesized. {yields} Enhancement in luminescence of Tb{sup 3+} was observed in complex on 355 nm excitation. {yields} Fluorescence enhancement is due to the efficient energy transfer from Sal to Tb{sup 3+}. {yields} An observed increase in lifetime of Tb{sup 3+} is due to encapsulation in Sal/Phen network. {yields} The present system is a deserving candidate for LSC when coupled with solar cells. - Abstract: Complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized coordinated with terbium ion (Tb{sup 3+}) in crystalline phases. The structural characterizations of the lanthanide complex were made using FT-IR, NMR ({sup 1}H and {sup 13}C) and XRD techniques. These measurements confirm the formation of Tb(Sal){sub 3}Phen complex structure. The thermal aspects of the complex were examined using DTA and TGA techniques. An enhancement in luminescence intensity of Tb{sup 3+} ion bands were observed in Tb(Sal){sub 3}Phen complex as compared to TbCl{sub 3} crystals on 355 nm laser excitation. Enhancement is reported due to the efficient energy transfer process from Sal to Tb{sup 3+} ions. This is also confirmed by the time resolved photoluminescence spectroscopy with increase in lifetime of Tb{sup 3+} ions due to encapsulation in Sal/Phen network. Our system in itself can be a deserving candidate for luminescent solar collector material when coupled with solar cells.

  4. The Public Health Reach of High Fluoride Vehicles: Examples of Innovative Approaches.

    Science.gov (United States)

    Tellez, Marisol; Wolff, Mark S

    2016-01-01

    Fluorides and sealants have been shown to reduce caries in populations, making fluoride interventions a large part of the dental public health effort. Although public health programs have traditionally focused on fluoride vehicles delivering less than 1,000 ppm of fluoride, more recent efforts have shifted toward the use of high fluoride vehicles such as varnishes and prescription toothpastes. In the USA, states are developing innovative strategies to increase access to dental services by using primary care medical providers to deliver early preventive services as part of well-child care visits. Currently, Medicaid programs in 43 states reimburse medical providers for preventive services including varnish application. Still, there is uncertainty about the cost-effectiveness of such interventions. In many resource-strained environments, with shortages of dental health care providers, lack of fluoridated water and lower dental awareness, it is necessary to develop sustainable programs utilizing already established programs, like primary school education, where caries prevention may be set as a priority. Dental caries among the elderly is an ongoing complex problem. The 5,000-ppm F toothpaste may be a reasonable approach for developing public health programs where root caries control is the main concern. Fluoride varnish and high concentration fluoride toothpaste are attractive because they can easily be incorporated into well-child visits and community-based geriatric programs. Additional research on the effectiveness and costs associated with population-based programs of this nature for high risk groups is needed, especially in areas where a community-based fluoride delivery program is not available.

  5. Synthesis, spectroscopy, thermal studies and supramolecular structures of two new alkali-earth 4-nitrobenzoate complexes containing coordinated imidazole

    Indian Academy of Sciences (India)

    Bikshandarkoil R Srinivasan; Jyoti V Sawant; Pallepogu Raghavaiah

    2007-01-01

    The reaction of hydrated magnesium or calcium 4-nitrobenzoate (4-nba) generated in situ, with imidazole (Im) results in the formation of the complexes [Mg(H2O)2(Im)2(4-nba)2] 1 and [Ca(H2O)3(Im)(4-nba)2]$\\cdot$Im 2, which exhibit the same metal:4-nba:Im ratio but different degrees of hydration. Complex 1 crystallizes in the triclinic $_{\\bar{i}}$ space group and the Mg atom is located on an inversion centre, while 2 crystallizes in the monoclinic 21/ space group and all atoms are located in general positions. In 1 the Im ligands, which are trans to each other, are coordinated to Mg, while 2 contains coordinated as well as free Im. The monodentate 4-nba ligands are disposed trans to each other in 1, while they adopt a cis orientation in 2 resulting in different supramolecular structures. Complex 1 exhibits two types of H-bonding interactions namely O-HO and N-HO, while in 2 three varieties of H-bond, viz. O-HO, N-HO and O-HN are observed. The Im ligand functions as a bifurcated H-bond donor in 1 while the O atom of the nitro group functions as a H-bond acceptor. In contrast, the nitro group in 2 is not involved in any H-bonding interactions. The free Im in 2 functions as a bifurcated acceptor and forms an extended chain linking adjacent complex molecules. The chains thus formed are further cross-linked with the aid of H-donor bonds from both the free as well as the coordinated Im. Both 1 and 2 exhibit - stacking interactions. Complex 1 is thermally more stable as compared to 2, and both complexes can be dehydrated to the corresponding anhydrous complexes by heating at 140 and 100°C respectively. At elevated temperatures, both the complexes can be pyrolysed to the corresponding oxide. The anhydrous complexes can be rehydrated to obtain the starting hydrated materials.

  6. 76 FR 37129 - Determination That SODIUM FLUORIDE F 18 (Sodium Fluoride F-18) Injection, 10 to 200 Millicuries...

    Science.gov (United States)

    2011-06-24

    ... HUMAN SERVICES Food and Drug Administration Determination That SODIUM FLUORIDE F 18 (Sodium Fluoride F... Drug Administration (FDA) has determined that SODIUM FLUORIDE F 18 (sodium fluoride F-18) injection, 10... FLUORIDE F 18 injection, 10 to 200 mCi/mL, if all other legal and regulatory requirements are met. FOR...

  7. Influence of Fluoride Addition on the Composition of Solutions in Equilibrium with Acid Soils

    Institute of Scientific and Technical Information of China (English)

    A. ROMAR; C. GAGO; M. L. FERN(A)NDEZ-MARCOS; E. (A)LVAREZ

    2009-01-01

    Atmospheric emissions of fluoride from an aluminium smelter-alumina refinery located on the northern coast of Galicia, NW Spain, increase the content of fluorine in soils and vegetation in the vicinity of the complex. The effects of the addition of fluoride solutions on the chemical properties of soil samples from the area surrounding the complex were investigated in laboratory experiments. Addition of fluoride to soils resulted in increases in pH and concentrations of Fe, A1, and organic matter in the equilibrium solutions and decreases in concentrations of Ca, Mg, and K. No consistent effects were observed on the Cu, Mg, or Zn concentrations. Most of the Al in solution was bound to organic matter. Within the fraction "labile aluminium", the concentration of Al-OH complexes decreased and the Al-F complexes increased, especially AlF3 and AlF4, which are less toxic than Al3+ and Al-OH species.

  8. Chromogenic and fluorogenic Schiff base chemosensor for nano scale level fluoride detection with logical interpretation

    Science.gov (United States)

    Ghosh, Pritam; Banerjee, Priyabrata

    2016-10-01

    Schiff base Organic Frameworks (SOFs) based chemosensor have been synthesized and utilized for recognization of biologically relevant fluoride anion. The chemosensor is selective for fluoride (F-) and exhibits reversible UV-Vis response with alternate addition of aluminum (Al3+). Interestingly a fluorescence 'turn on' response has been noticed with concomitant addition of fluoride. TICT, PTTS and restricted Cdbnd N isomerization has been taken into account in order to explain the florescence 'turn on' phenomenon. Significantly, the limit of fluoride detection is nano molar level (∼10 nM). The reversible UV-Vis phenomena have been used for designing AND-NAND-NOT-NOR-OR-XOR-XNOR based complex logic circuit to prepare potential feedstock as 'Lab-on a-Molecule'.

  9. Salivary fluoride levels after use of high-fluoride dentifrice.

    Science.gov (United States)

    Vale, Glauber Campos; Cruz, Priscila Figueiredo; Bohn, Ana Clarissa Cavalcante Elvas; de Moura, Marcoeli Silva

    2015-01-01

    The aim of the study was to evaluate salivary fluoride (F) availability after toothbrushing with a high-F dentifrice. Twelve adult volunteers took part in this crossover and blind study. F concentration in saliva was determined after brushing with a high-F dentifrice (5000 µg F/g) or with a conventional F concentration dentifrice (1100 µg F/g) followed by a 15 mL distilled water rinse. Samples of nonstimulated saliva were collected on the following times: before (baseline), and immediately after spit (time = 0) and after 1, 2, 3, 4, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min. F analysis was performed with a fluoride-sensitive electrode and the area under curve of F salivary concentration × time (µg F/mL × min(-1)) was calculated. At baseline, no significant difference was found among dentifrices (P > 0.05). After brushing, both dentifrices caused an elevated fluoride level in saliva; however salivary F concentration was significantly higher at all times, when high-F dentifrice was used (P dentifrices (P dentifrice enhanced the bioavailability of salivary F, being an option for caries management in patients with high caries risk.

  10. Renal fluoride excretion in children following topical application of fluoride varnish.

    Science.gov (United States)

    García-Hoyos, F; Barbería, E; García-Camba, P; Varela, M

    2012-12-01

    To demonstrate that the application of dental fluoride varnishes in children increases urinary fluoride excretion. From a randomly assembled group of 42 children aged between 5 and 8 years, residing in a community with non-fluoridated water, spot urinary samples were taken before the topical application of dental fluoride varnish and 2 hours afterwards. In an age-matched control group of 16 children from the same community, who received no treatment, samples were taken the same way. The urinary excretion of fluoride was analysed by determining fluoride ion (F-) level and fluoride/creatinine (F/Cr) ratio in the urine. In the study group, the average pre- and post-treatment F/Cr ratios were 0.42 and 1.38 mg/g, respectively (p fluoride varnish leads to a significant increase in urine F-, which is attributable to the application of the product.

  11. Fluoride intake from fluids and urinary fluoride excretion by young children in Kuwait: a non-fluoridated community.

    Science.gov (United States)

    Akpata, Enosakhare S; Behbehani, Jawad; Akbar, Jaber; Thalib, Lukman; Mojiminiyi, Olusegun

    2014-06-01

    To determine the pattern of fluid consumption, fluoride intake from the fluids and urinary fluoride excretion by children aged 1-9 years in Kuwait, a nonfluoridated community. Using the cluster sampling technique, children aged 1-9 years were chosen from 2000 randomly selected households in Kuwait. Questionnaires were then administered to their mothers to determine the children's daily fluid intake. Fluoride concentrations in tap water as well as all brands of bottled water and beverages consumed by the children were measured, using the fluoride ion-specific electrode. Fluoride excretion was determined in 400 randomly selected children, based on fluoride/creatinine ratio. The mean daily fluid consumption by the children was high, being 1115-1545 ml. About 40% of the fluid intake was plain (tap and bottled) water and approximately 10% of the children drank bottled water exclusively. Fluoride concentration in tap water was low (0.04±SD 0.02 ppm), but was higher in bottled water (0.28±SD 0.40 ppm). Mean daily fluoride ingestion from fluids was 0.013-0.018 mg/kg body weight (bw). Even after allowing for fluoride ingestion from other sources, mean daily fluoride ingestion was still below 0.1 mg/kg bw set by the United States of America Institute of Medicine as the lowest-observed-adverse-effect level for moderate enamel fluorosis in children aged up to 8 years. Furthermore, the mean daily urinary fluoride excretion of 128-220 μg was below the provisional standard of 360-480 μg for optimal fluoride usage by children aged 3-5 years. Fluoride ingestion from fluids and urinary fluoride excretion by the children were below the recommendations for optimal fluoride usage. Thus, there is room for an upward adjustment of fluoride level in public drinking water supplies in Kuwait, as a caries preventive measure. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Determination of Fluoride in Various Samples and Some Infusions Using a Fluoride Selective Electrode

    OpenAIRE

    TOKALIOĞLU, Şerife; Kartal, Şenol; ŞAHİN, Uğur

    2004-01-01

    The determination of fluoride in some environmental samples was performed using a fluoride ion-selective electrode. Fluoride concentrations were determined in drinking waters (from different provinces, districts and villages in Turkey), fruit juices, bottled water samples, toothpastes and tooth powders, liquors of Turkish coffee, coffee, linden, rose hip, and various brand tea infusions, and dust samples collected from the Erciyes University campus car park. The average fluoride conc...

  13. On the formation and structure of rare-earth element complexes in aqueous solutions under hydrothermal conditions with new data on gadolinium aqua and chloro complexes

    Science.gov (United States)

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2007-01-01

    Synchrotron X-ray spectroscopy experiments were made on the Gd(III) aqua and chloro complexes in low pH aqueous solutions at temperatures ranging from 25 to 500????C and at pressures up to 480??MPa using a hydrothermal diamond anvil cell. Analysis of fluorescence Gd L3-edge X-ray absorption fine structure (XAFS) spectra measured from a 0.006m Gd/0.16m HNO3 aqueous solution at temperatures up to 500????C and at pressures up to 260??MPa shows that the Gd-O distance of the Gd3+ aqua ion decreases steadily at a rate of ??? 0.007??A??/100????C whereas the number of coordinated H2O molecules decreases from 9.0 ?? 0.5 to 7.0 ?? 0.4. The loss of water molecules in the Gd3+ aqua ion inner hydration shell over this temperature range (a 22% reduction) is smaller than exhibited by the Yb3+ aqua ion (42% reduction) indicating that the former is significantly more stable than the later. We conjecture that the anomalous enrichment of Gd reported from measurement of REE concentrations in ocean waters may be attributed to the enhanced stability of the Gd3+ aqua ion relative to other REEs. Gd L3-edge XAFS measurements of 0.006m and 0.1m GdCl3 aqueous solutions at temperatures up to 500????C and pressures up to 480??MPa reveal that the onset of significant Gd3+-Cl- association occurs around 300????C. Partially-hydrated stepwise inner-sphere complexes most likely of the type Gd(H2O)??-nCln+3-n occur in the chloride solutions at higher temperatures, where ?? ??? 8 at 300????C decreasing slightly to an intermediate value between 7 and 8 upon approaching 500????C. This is the first direct evidence for the occurrence of partially-hydrated REE Gd (this study) and Yb [Mayanovic, R.A., Jayanetti, S., Anderson, A.J., Bassett, W.A., Chou, I-M., 2002a. The structure of Yb3+ aquo ion and chloro complexes in aqueous solutions at up to 500 ??C and 270 MPa. J. Phys. Chem. A 106, 6591-6599.] chloro complexes in hydrothermal solutions. The number of chlorides (n) of the partially-hydrated Gd

  14. Estuarine response of fluoride - Investigations in Azhikode Estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Joseph, T.; Sankaranarayanan, V.N.

    Concentrations of fluoride in Azhikode estuarine region (Kerala, India) were measured as a function of chlorinity during the different seasons. The type of behaviour indicated that fluoride was regulated by sea water incursion alone. Fluoride...

  15. Magnesium Fluoride Reduction Vessel Liners

    Science.gov (United States)

    1986-03-26

    Carolina Metals, the fluoride is reduced to power by means of a Mikro #2 hemmer mill (Figure 5). The material is then separated into the different...The jolter table previously referred to in the liner pro - ceasing operation, is the knockout station. As shown in Figure 36, the vessel is inverted...was much more extensive than normally performed to establish the quality of thý metal pro - duced using the MgF2 liners. There are no indications of

  16. Fluoride Importance in Controlling Caries and Fluorosis

    OpenAIRE

    Gaurav Solanki

    2012-01-01

    The use of fluorides for oral health has always involved a balance between the protective benefit against dental caries and the risk of developing fluorosis. The link between fluoride and dental health was established to determining the causes of dental fluorosis or enamel mottling. Fluorosis in Indian children was highly prevalent in the early 1990s. Policy were introduced to control fluoride exposure and to reduce the prevalence of fluorosis. The study aimed of describing the prevalence, se...

  17. Fluoride Importance in Controlling Caries and Fluorosis

    OpenAIRE

    Gaurav Solanki

    2012-01-01

    The use of fluorides for oral health has always involved a balance between the protective benefit against dental caries and the risk of developing fluorosis. The link between fluoride and dental health was established to determining the causes of dental fluorosis or enamel mottling. Fluorosis in Indian children was highly prevalent in the early 1990s. Policy were introduced to control fluoride exposure and to reduce the prevalence of fluorosis. The study aimed of describing the prevalence, se...

  18. Crossing the Olentangy River: The Figure of the Earth and the Military-Industrial-Academic-Complex, 1947-1972

    Science.gov (United States)

    Cloud, John

    This paper explores the history of a unique assemblage of researchers in the geodetic and allied sciences organised at Ohio State University (OSU) in 1947 at the beginning of the Cold War. From about 1950 to 1970, the OSU geodetic sciences group was the most significant group of geodetic researchers in the world. Funded almost entirely by military and intelligence agencies, they pioneered the technologies, organised the research initiatives, ordered the data sets, and trained the generation of geodesists who eventually created the Cold War Figure of the Earth to both prosecute and prevent global nuclear war. They devised elaborate mechanisms to pursue in secrecy and isolation research that had hitherto been performed collaboratively and globally. They invented methods to maintain professional associations and protocols, both to distribute-and disguise-the fruits of their geodetic research. In accomplishing this, their work also undermined the basic hypothesis of isostasy that had been foundational to geodesy for the previous century. Fundamental progress in the geosciences and military and intelligence directives were inextricably linked during the Cold War, although the extent of their convergence has been masked by the security protocols organised to disguise it. With the declassification of key programmes underway, it is now both possible and necessary to substantially revise the history of Cold War-era geosciences and their associated technologies.

  19. Effect of titanium tetrafluoride, amine fluoride and fluoride varnish on enamel erosion in vitro

    NARCIS (Netherlands)

    Vieira, A; Ruben, JL; Huysmans, MCDNJM

    2005-01-01

    This study aimed at evaluating the effect of 1 and 4% titanium tetrafluoride (TiF4) gels, amine fluoride (AmF) 1 and 0.25% and a fluoride varnish (FP) on the prevention of dental erosion. Two experimental groups served as controls, one with no pretreatment and another one pre-treated with a fluoride

  20. Role of Mononuclear Rare Earth Metal Complexes in Promoting the Hydrolysis of 2-Hydroxypropyl p-Nitrophenyl Phosphate

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; LIN Hai; LIN Hua-Kuan

    2007-01-01

    Two long-chain multidentate ligands: 2,9-di-(n-2',5',8'-triazanonyl)-1,10-phenanthroline (L1) and 2,9-di-(n-4',7',10'-triazaundecyl)-1,10-phenanthroline (L2) were synthesized. The hydrolytic kinetics of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) catalyzed by the complexes of L1 or L2 with La(Ⅲ) or Gd(Ⅲ) have been studied lytic effect of GdL1 was the best among the four complexes for hydrolysis of HPNP. Its kLnLH-1, kLnL and pKa are structure of the ligands and the properties of the metal ions, and deduced the catalysis mechanism.

  1. Synthesis, spectral, optical and anti-inflammatory activity of complexes derived from 2-aminobenzohydrazide with some rare earths

    Institute of Scientific and Technical Information of China (English)

    Nasser Mohammed Hosny; El Sayed A El Morsy; Yousery E Sherif

    2015-01-01

    Three new metal complexes derived from Er(III), Dy(III) and Zr(IV) with 2-aminobenzohydrazide (ABH) were synthe-sized and characterized by elemental analyses, IR,1H-NMR, ES-MS and transmission electron microscopy (TEM). The morphology and the particle size were determined by TEM. The results showed that the ligand acted as neutral bi-dentate coordinating to the metal ions through the carbonyl oxygen and amidic amino nitrogen. The aromatic amine group remained inert towards coordination. The optical band gap was measured and found to be 3.3, 3.5 and 4.3 eV for Er(III), Dy(III) and Zr(IV), respectively. The optical band gap values indicated a semi-conducting nature of the investigated complexes. Theanti-inflammatory and analgesic activities of the tested compounds were determined and compared with standard meloxicam.

  2. Effect of low-concentration daily topical fluoride application on fluoride release of giomer and compomer: An in vitro study

    Directory of Open Access Journals (Sweden)

    K S Dhull

    2011-01-01

    Full Text Available Aims and Objective: To determine the effect of low-concentration daily topical fluoride application on fluoride release of Giomer and Compomer and to compare the amount of fluoride release from Giomer to that of Compomer. Materials and Methods: Forty-eight specimens of each Giomer and Compomer were divided into four treatment groups, namely, control group, fluoridated dentifrice (500 ppm once-daily group, fluoridated dentifrice (500 ppm twice-daily group and fluoridated dentifrice (500 ppm once-daily + fluoridated mouthwash (225 ppm group. Each specimen was suspended in demineralising solution for 6 h and remineralising solution for 18 h. Fluoride release was measured in both the demineralising solution and the remineralising solution daily for 21 days. Total daily fluoride release for each specimen was calculated by adding the amount released in the demineralising solution to that released in the remineralising solution. Results and Conclusion: The fluoride release (ppm was found to be higher in Giomer when compared with Compomer. The fluoride released from Giomer and Compomer was significantly higher in the acidic demineralising solution than in the neutral remineralising solution. It was found that increasing fluoride exposure significantly increased fluoride release from Giomer and Compomer. It was found that the fluoride release from the subgroups of Giomer and Compomer was in the following order: fluoridated dentifrice twice-daily > fluoridated dentifrice once-daily + fluoridated mouthwash > fluoridated dentifrice once-daily > control group. It was found that Giomer showed a greater fluoride uptake Compomer.

  3. Preparation, crystal structure and optical spectroscopy of the rare earth complexes (RE 3+=Sm, Eu, Gd and Tb) with 2-thiopheneacetate anion

    Science.gov (United States)

    Teotonio, Ercules E. S.; Brito, Hermi F.; Felinto, Maria Cláudia F. C.; Thompson, Larry C.; Young, Victor G.; Malta, Oscar L.

    2005-09-01

    Rare earth complexes with the formulae Sm(TPAC) 3·3H 2O, Eu 2(TPAC) 6·5.25H 2O and RE(TPAC) 3·3.5H 2O (where RE=Gd and Tb), and TPAC=2-thiopheneacetate) have been synthesized and characterized by complexometric titration, elemental analyses, infrared spectroscopy, and X-ray crystallography. Infrared data suggested the presence of both bridging and chelating TPAC anions. The crystal structure of the [Eu 2(TPAC) 6·(H 2O) 3]·2.25H 2O complex in the solid state, determined by X-ray diffraction, revealed that it crystallizes in the orthorhombic crystal system (space group Aba2), with two crystallographically independent Eu 3+ centers (Eu1 and Eu2). These europium centers are held together by one bidentate bridging and two tridentate bridging carboxylate groups. The existence of two Eu 3+ centers was also supported by the emission spectrum. The luminescence properties of the RE-TPAC complexes were investigated by measuring the excitation and emission spectra, and the intramolecular ligand-to-rare earth energy transfer mechanisms were discussed. The emission spectra of the Eu 3+ and Tb 3+ ions displayed only narrow bands arising from 5D 0→ 7F 0 and 5D 0→ 7F 0-4 transitions, respectively, indicating an efficient luminescence sensitization of these ions by the TPAC 'antenna'. On the other hand, the emission spectrum of the Sm 3+-complex displayed a broad band from the phosphorescence of the TPAC ligand which overlapped the 4f 5-intraconfigurational transitions. The theoretical intensity parameters Ωλ ( λ=2 and 4), maximum splitting of the 7F 1 state (Δ E) and the ratio between the 5D 0→ 7F 0 and 5D 0→ 7F 2 transition intensities ( R02) were calculated based on the X-ray crystalline structure for the Eu 3+-complex, and a comparison with experimental data were made. The emission quantum efficiency ( η) of the D5 emitting level of the Eu 3+ ion was also determined.

  4. Gramicidin D enhances the antibacterial activity of fluoride

    OpenAIRE

    Nelson, James W.; ZHOU, ZHIYUAN; Breaker, Ronald R.

    2014-01-01

    Fluoride is a toxic anion found in many natural environments. One of the major bacterial defenses against fluoride is the cell envelope, which limits passage of the membrane-impermeant fluoride anion. Accordingly, compounds that enhance the permeability of bacterial membranes to fluoride should also enhance fluoride toxicity. In this study, we demonstrate that the pore-forming antibiotic gramicidin D increases fluoride uptake in B. subtilis and that the antibacterial activity of this compound...

  5. Analysis of 1-Minute Potentially Available Fluoride from Dentifrice

    OpenAIRE

    Carey, Clifton M.; Erin C. Holahan; Schmuck, Burton D

    2014-01-01

    Previous reports found that some fluoride-containing dentifrices do not release effective concentrations of fluoride during brushing. Failure to release fluoride can be due to dentifrice matrix components that interfere with the solubilization of the fluoride salts during brushing. A new generation of dentifrices has the capability to precipitate beneficial fluoride salts during tooth brushing. Therefore, a method that assesses the potentially available fluoride during the 1-minute brushing i...

  6. Fluoride assay methodology for carbonated beverages.

    Science.gov (United States)

    Heilman, Judith R; Levy, Steven M; Wefel, James S; Patterson, Kristine Y; Cutrufelli, Rena; Pehrsson, Pamela R; Holden, Joanne M

    2006-01-01

    The purpose of this paper was to review different methodological techniques used for the assessment of fluoride in carbonated beverages, and compare results using a fluoride ion electrode direct read method with and without a prior decarbonation treatment. The carbonated beverages in this study were either purchased locally at grocery stores in Iowa City, Iowa, or purchased as part of a national representative sampling approach included in the National Fluoride Database and Intake Assessment Study (NFDIAS). The samples were compared with and without a decarbonating process. Soda pop and beer samples were analyzed by removing a 1-ml sample and adding a 1-ml buffer solution. The fluoride concentration of the sample and buffer combination was then determined using a fluoride ion specific electrode. There was no significant difference in the fluoride concentration of the samples with or without prior decarbonation. The mean absolute difference between the soda pop group with and without decarbonation was 0.01 ppm F, while results from the beer samples showed variation of 0.00 to 0.02 parts per million fluoride (ppm F). These differences were not statistically significant for the soda pop or beer groups (P=.50 and P=.74, respectively). Whether or not decarbonation was conducted prior to analysis, the fluoride assay results were the same. Therefore, decarbonation of soda pop and beer was deemed unnecessary prior to fluoride analysis.

  7. High fluoride exposure in hemodialysis patients.

    Science.gov (United States)

    Bello, V A; Gitelman, H J

    1990-04-01

    The observation of higher plasma flouride levels in our hemodialysis (HD) patients than our continuous ambulatory peritoneal dialysis (CAPD) patients (4.0 +/- 0.5 mumol/L [n = 17] v 2.5 +/- 0.3 mumol/L [n = 17], P less than 0.005) prompted an evaluation of fluoride metabolism during HD. We found that serum fluoride was completely ultrafiltrable across cuprophane membranes (99% +/- 4%) and that HD produced acute changes in plasma fluoride levels that correlated well with the fluoride gradient between plasma and dialysis fluid at the start of dialysis. Our HD fluids contained significantly higher fluoride concentrations than were present in commercially prepared peritoneal dialysis fluid. Our fluids are prepared from fluoridated tap water that is purified by reverse osmosis (RO). We conclude that the different concentrations of fluoride in our dialysis fluids account for the differences in the plasma flouride concentrations between our dialysis groups. Since many HD units rely on RO systems to purify fluoridated tap water, it is likely that many HD patients are being exposed inadvertently to increased concentrations of fluoride.

  8. Application of fluoride iontophoresis to improve remineralization.

    Science.gov (United States)

    Kim, H E; Kwon, H K; Kim, B I

    2009-10-01

    Iontophoresis is generally used to maximize the therapeutic action of drugs in medicine. This technique can be used to improve the remineralization effect of topical fluoride applications in dentistry. The aim of this study was to compare the remineralization effect of fluoride iontophoresis (FI) with the conventional fluoride application (CFA) method in vitro. Sixty bovine enamel specimens were divided into three groups: no fluoride treatment, CFA and FI. Fluoride was applied to the demineralized specimens for 4 min in each experimental group. The types of fluoride system used for application were 1.23% acidulated phosphate fluoride gel (12 300 p.p.m. F, pH 3.5) and 2% sodium fluoride solution (9050 p.p.m. F, pH 7) in the experimental groups. All the specimens were then placed in a remineralizing solution for 24 h. This cycle was repeated five times. An iontophoresis device (0.4 mA, 12 V) was used in the FI groups. The efficacy of this technique was evaluated by measuring changes in the surface microhardness and lesion depth of the specimens using confocal laser scanning microscope (CLSM). Data were analysed using anova and Tukey's post hoc test (P fluoride application methods (P > 0.05). When the lesion depth was measured using CLSM imaging, there was also no significant difference between the FI and CFA groups (P > 0.05). In conclusion, FI was not significantly superior to CFA in terms of the remineralization effect.

  9. Theoretical and NMR experimental insights on urea, thiourea and diindolyurea as fluoride carriers

    Science.gov (United States)

    Mendonça, João Guilherme P.; Silla, Josué M.; Andrade, Laize A. F.; Fernandes, Sergio A.; Cormanich, Rodrigo A.; Freitas, Matheus P.

    2016-06-01

    Urea and thiourea derivatives are widely known as anion transporters. The pristine urea and thiourea compounds were theoretically and spectroscopically evaluated as fluoride ligands, since transportation of F- is involved in many biochemical processes and this anion is suitable to be analyzed through NMR. Conformational changes induced by anions can be useful to probe ligand-anion complexation, but urea and thiourea do not undergo conformational isomerization. Thus, diindolylurea (DIU) was computationally investigated to search for its conformational preferences upon complexation with fluoride. Overall, the NMR proton signal for urea and thiourea moved downfield and broadened upon addition of one equivalent of fluoride anion in DMSO solution, indicating complexation. The 19F signal for the thiourea-F- mixture also shifted relative to the anion source. However, a J(N)H,F coupling constant was not observed, probably because of entropy and bulk solvation effects. In addition, the conformational preference of DIU changed drastically after simulated complexation with fluoride, in agreement with previous studies with other anions. This confirms the potential of urea derivatives as fluoride carriers.

  10. Earth Observation-Based Dwelling Detection Approaches in a Highly Complex Refugee Camp Environment — A Comparative Study

    Directory of Open Access Journals (Sweden)

    Kristin Spröhnle

    2014-09-01

    Full Text Available For effective management of refugee camps or camps for internally displaced persons (IDPs relief organizations need up-to-date information on the camp situation. In cases where detailed field assessments are not available, Earth observation (EO data can provide important information to get a better overview about the general situation on the ground. In this study, different approaches for dwelling detection were tested using the example of a highly complex camp site in Somalia. On the basis of GeoEye-1 imagery, semi-automatic object-based and manual image analysis approaches were applied, compared and evaluated regarding their analysis results (absolute numbers, population estimation, spatial pattern, statistical correlations and production time. Although even the results of the visual image interpretation vary considerably between the interpreters, there is a similar pattern resulting from all methods, which shows same tendencies for dense and sparse populated areas. The statistical analyses revealed that all approaches have problems in the more complex areas, whereas there is a higher variance in manual interpretations with increasing complexity. The application of advanced rule sets in an object-based environment allowed a more consistent feature extraction in the area under investigation that can be obtained at a fraction of the time compared to visual image interpretation if large areas have to be observed.

  11. Effects of different kinds of fluorides on enolase and ATPase activity of a fluoride-sensitive and fluoride-resistant Streptococcus mutans strain

    NARCIS (Netherlands)

    van Loveren, C.; Hoogenkamp, M.A.; Deng, D.M.; ten Cate, J.M.

    2008-01-01

    Enolase and ATPase are sensitive to fluoride. It is unclear whether this sensitivity differs for F-sensitive and F-resistant cells or for different types of fluoride. Permeabilized cells of the fluoride-sensitive strain Streptococcus mutans C180-2 and its fluoride-resistant mutant strain C180-2 FR w

  12. Effects of different kinds of fluorides on enolase and ATPase activity of a fluoride-sensitive and fluoride-resistant Streptococcus mutans strain

    NARCIS (Netherlands)

    van Loveren, C.; Hoogenkamp, M.A.; Deng, D.M.; ten Cate, J.M.

    2008-01-01

    Enolase and ATPase are sensitive to fluoride. It is unclear whether this sensitivity differs for F-sensitive and F-resistant cells or for different types of fluoride. Permeabilized cells of the fluoride-sensitive strain Streptococcus mutans C180-2 and its fluoride-resistant mutant strain C180-2 FR

  13. Urinary fluoride output in children following the use of a dual-fluoride varnish formulation

    Directory of Open Access Journals (Sweden)

    Kelly Polido Kaneshiro Olympio

    2009-06-01

    Full Text Available OBJECTIVE: This study evaluated the bioavailability of fluoride after topical application of a dual-fluoride varnish commercially available in Brazil, when compared to DuraphatTM. MATERIAL AND METHODS: The urinary fluoride output was evaluated in seven 5-year-old children after application of the fluoride varnishes, in two different phases. In the first phase (I, children received topical application of the fluoride varnish Duofluorid XII (2.92% fluorine, calcium fluoride + 2.71% fluorine, sodium fluoride, FGM TM. After 1-month interval (phase II, the same amount (0.2 mL of the fluoride varnish Duraphat (2.26% fluorine, sodium fluoride, ColgateTM was applied. Before each application all the volunteers brushed their teeth with placebo dentifrice for 7 days. Urinary collections were carried out 24 h prior up to 48 h after the applications. Fluoride intake from the diet was also estimated. Fluoride concentration in diet samples and urine was analyzed with the fluoride ion-specific electrode and a miniature calomel reference electrode coupled to a potentiometer. Data were tested by ANOVA and Tukey's post hoc test (p<0.05. RESULTS: There were significant differences in the urinary fluoride output between phases I and II. The use of Duofluorid XII did not significantly increase the urinary fluoride output, when compared to baseline levels. The application of Duraphat caused a transitory increase in the urinary fluoride output, returning to baseline levels 48 h after its use. CONCLUSIONS: The tested varnish formulation, which has been shown to be effective in in vitro studies, also can be considered safe.

  14. Water Pollution Transport Complex Framework Based on the Digital Earth%数字地球下的复杂水污染运移仿真框架

    Institute of Scientific and Technical Information of China (English)

    李建勋; 高阳; 李维乾; 严栋飞

    2014-01-01

    针对水污染运移模拟仿真表现能力不足的问题,运用复杂性理论和数字地球技术,实施水污染事件数据资源的汇集,开展干流河道的多尺度拆分,建立水质复杂 Agent 及其特征属性、行为模式,并引入高性能计算机技术提高运移演算效率,基于数字地球形成一个融合水质模型且具有丰富展现力的水污染运移仿真框架。实验表明:该框架增强了污染物运移过程的空间表征能力,为污染物运移仿真模拟和情景分析提供了一体化平台。%According to the problem of insufficient performance ability for water pollution transport simulation, by adopting to the digital earth technology and complexity theory, the data resources of water pollution event was integrated. The trunk stream of watercourse was decomposed into multi-scale resolution. A water quality complex agent was established with characteristics and behavior patterns. And the efficiency of the migration of calculus was improved by introducing of high-performance computer technology. Then a water pollution transport simulation framework was constructed based-on the digital earth technology which merging together the water quality model and having high expressive force. Results show that this framework has enhanced the ability of spatial representation of pollutant transport process, and provided an integrated platform for pollutant transport simulation and scenario analysis.

  15. Lu Hf systematics of the ultra-high temperature Napier Metamorphic Complex in Antarctica: Evidence for the early Archean differentiation of Earth's mantle

    Science.gov (United States)

    Choi, Sung Hi; Mukasa, Samuel B.; Andronikov, Alexandre V.; Osanai, Yasuhito; Harley, Simon L.; Kelly, Nigel M.

    2006-06-01

    The Napier Complex of the East Antarctic Craton comprises some of the oldest rocks on Earth (˜ 3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing a fully equilibrated assemblage from this UHT granulite belt have yielded a Lu-Hf isochron age of 2403 ± 43 Ma, the first ever determined on a UHT mineral assemblage. Preservation of the UHT mineral assemblage in the rock analyzed, without any significant retrogression, suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ˜ 800 °C. This mineral-whole rock isochron yields an initial 176Hf/ 177Hf ratio corresponding to an ɛHf value of - 14 ± 1, acquired during UHT metamorphism. Such a low value demonstrates that overall UHT granulites evolved in a low Lu/Hf environment, probably formed when the rocks were first extracted from a highly depleted mantle. Zircon ɛHf values we have measured "see through" the UHT metamorphism and show that the source materials for the magmas that formed the Napier Complex were extremely depleted (> + 5.6 ɛHf at 3.85 Ga) relative to the chondritic uniform reservoir (CHUR). These results also suggest significant depletion of the early Archean mantle, in agreement with the early differentiation of the Earth that the latest core formation models require.

  16. A novel approach to the dynamical complexity of the Earth's magnetosphere at geomagnetic storm time-scales based on recurrences

    Science.gov (United States)

    Donner, Reik; Balasis, Georgios; Stolbova, Veronika; Wiedermann, Marc; Georgiou, Marina; Kurths, Jürgen

    2016-04-01

    Magnetic storms are the most prominent global manifestations of out-of-equilibrium magnetospheric dynamics. Investigating the dynamical complexity exhibited by geomagnetic observables can provide valuable insights into relevant physical processes as well as temporal scales associated with this phenomenon. In this work, we introduce several innovative data analysis techniques enabling a quantitative analysis of the Dst index non-stationary behavior. Using recurrence quantification analysis (RQA) and recurrence network analysis (RNA), we obtain a variety of complexity measures serving as markers of quiet- and storm-time magnetospheric dynamics. We additionally apply these techniques to the main driver of Dst index variations, the V BSouth coupling function and interplanetary medium parameters Bz and Pdyn in order to discriminate internal processes from the magnetosphere's response directly induced by the external forcing by the solar wind. The derived recurrence-based measures allow us to improve the accuracy with which magnetospheric storms can be classified based on ground-based observations. The new methodology presented here could be of significant interest for the space weather research community working on time series analysis for magnetic storm forecasts.

  17. Analytical study, by modelling methods, of the alkali and alkaline earth cations influence on the stability and the reactivity of aluminium (III) oxides or halides complexes; Etude analytique, par des techniques de modelisation, de l`influence de cations alcalins ou alcalino-terreux sur la stabilite et la reactivite de complexes de l`aluminium(III) avec des ions halogenures ou oxydes

    Energy Technology Data Exchange (ETDEWEB)

    Bouyer, F.

    1995-10-05

    The electric power consumption in aluminium production and electrorefining processes is high. A study of the electrochemical processes can be very useful for a better understanding of phenomena in electrolytic baths and then for reducing the production costs. A structural and vibrational analysis of species which exist in ionic solutions has been carried out with software based on the functional density theory. Concerning the electrolyte used for the aluminium refining, the anions study has shown that the aluminium chloro-fluoride complexes are preferentially tetrahedral. Moreover, the aluminium oxyfluoride complexes structures (which come from the alumina dissolution in cryolitic media) have been analyzed in the same way and the preferential coordination numbers for aluminium and oxygen have been shown clearly. The anionic model (which is limited to the nearest aluminium neighbours) does not allow to account for the thermodynamics of the cryolitic media. A more elaborated model has then been found to obtain the cryolite structure. The reactions enthalpies have been estimated and have lead to the calculus of species concentration gradients in liquid phase. The counterions effects as for instance sodium and calcium have been investigated. A model for the gaseous phase allowing to know the preferential species has been given. At last, a statistic thermochemistry program has been conceived and developed. It gives the thermodynamical functions at all temperature for the different complexes and allows to reckon the reactions coefficients in gaseous phase as well as the partial pressures profiles with those of calcium and sodium fluorides. (O.M.) 204 refs.

  18. Fluorescent Sensing of Fluoride in Cellular System

    Science.gov (United States)

    Jiao, Yang; Zhu, Baocun; Chen, Jihua; Duan, Xiaohong

    2015-01-01

    Fluoride ions have the important roles in a lot of physiological activities related with biological and medical system, such as water fluoridation, caries treatment, and bone disease treatment. Great efforts have been made to develop new methods and strategies for F- detection in the past decades. Traditional methods for the detection of F- including ion chromatography, ion-selective electrodes, and spectroscopic techniques have the limitations in the biomedicine research. The fluorescent probes for F- are very promising that overcome some drawbacks of traditional fluoride detection methods. These probes exhibit high selectivity, high sensitivity as well as quick response to the detection of fluoride anions. The review commences with a brief description of photophysical mechanisms for fluorescent probes for fluoride, including photo induced electron transfer (PET), intramolecular charge transfer (ICT), fluorescence resonance energy transfer (FRET), and excited-state intramolecular proton transfer (ESIPT). Followed by a discussion about common dyes for fluorescent fluoride probes, such as anthracene, naphalimide, pyrene, BODIPY, fluorescein, rhodamine, resorufin, coumarin, cyanine, and near-infrared (NIR) dyes. We divide the fluorescent probes for fluoride in cellular application systems into nine groups, for example, type of hydrogen bonds, type of cleavage of Si-O bonds, type of Si-O bond cleavage and cylization reactions, etc. We also review the recent reported carriers in the delivery of fluorescent fluoride probes. Seventy-four typical fluorescent fluoride probes are listed and compared in detail, including quantum yield, reaction medium, excitation and emission wavelengths, linear detection range, selectivity for F-, mechanism, and analytical applications. Finally, we discuss the future challenges of the application of fluorescent fluoride probes in cellular system and in vivo. We wish that more and more excellent fluorescent fluoride probes will be developed

  19. Fluoride and Oral Health

    DEFF Research Database (Denmark)

    O'Mullane, D M; Baez, R J; Jones, S

    2016-01-01

    of the original 1994 document, again using the expertise of researchers from the extensive fi elds of knowledge required to successfully implement complex interventions such as the use of fl uorides to improve dental and oral health. Financial support for research into the development of these new fl uoride......The discovery during the fi rst half of the 20th century of the link between natural fl uoride, adjusted fl uoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fl uoride in improving oral health...... including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fl uorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision...

  20. Fluoride-bridged {GdIII3MIII2} (M=Cr, Fe, Ga) molecular magnetic refrigerants

    DEFF Research Database (Denmark)

    Pedersen, Kasper Steen; Lorusso, Giulia; Morales, Juan José

    2014-01-01

    -lying excited states for successful design of molecular refrigerants. Molecular coolers: Even labile fluoride complexes (see picture; Gd purple, Cr/Fe/Ga orange, F green, O red) are useful precursors for polynuclear, fluoride-bridged 3d-4f systems. Molecular geometry enforces weak exchange interactions, which...

  1. Comparative Evaluation of Longevity of Fluoride Release From three Different Fluoride Varnishes – An Invitro Study

    Science.gov (United States)

    Roshan, NM; Poornima, P; Nagaveni, NB; Neena, IE; Bharath, KP

    2016-01-01

    Introduction Fluoride varnishes play a pivotal role in inhibition of dental caries by increasing remineralization. Aim To determine the longevity of fluoride release from 3 different fluoride varnishes over a period of time through salivary fluoride estimation. Materials and Methods Twenty four extracted human deciduous anterior teeth were divided into four groups, i.e., ClinproTM XT, Flouritop SR, Flourprotector and Control group. Fluoride varnishes were applied on 3mm x 3mm window on labial surface of the teeth and then the teeth were immersed and stored in artificial saliva. The concentration of fluoride in ppm was measured after 1 week, 1 month, 3 months and 6 months. Fluoride release at each time interval for different groups was statistically analyzed using ANOVA and Post Hoc Tukey’s test. Results Although all the fluoride varnishes released fluoride, with greatest release observed during 1st week by Fluoritop SR (66.92±16.30ppm), ClinproTM XT Varnish released consistently and substantially more fluoride than Fluoritop SR and Fluorprotector during 6 months analysis (pVarnish released consistently and substantially more fluoride than other tested products. PMID:27656559

  2. Fluoride intake and its safety among heavy tea drinkers in a British fluoridated city.

    Science.gov (United States)

    Jenkins, G N

    1991-01-01

    Tea-drinking in very young children has been studied in a British city. The results suggested that the fluoride in tea would, in some cases, be sufficient to influence caries. Clinical findings to some extent supported this. The main purpose of the investigation reported here was to determine maximum possible fluoride intake in adults who were heavy tea drinkers in a fluoridated city and relate it to toxic thresholds. Heavy tea drinkers were traced through Health Visitors and voluntary organizations and the volumes and fluoride concentrations of their drinks were measured. Even the highest intake found (9 mg) is below the probable intake in Bartlett, Texas (8 ppm of fluoride), in relation to which no undesirable symptoms have been reported (Leone et al. 1954). This confirms the safety of fluoridation. The effects on fluoride concentration of evaporating soft and hard fluoride-containing waters to small bulk were compared. The results showed ceilings of 3 ppm of fluoride in hard water and about 14 ppm in soft water, much higher than the levels expected on the basis of the usually stated solubility of CaF2 (16 or 8 ppm of fluoride). However, under normal household conditions, it is most unlikely that dangerous levels of fluoride would be ingested from boiled water.

  3. TEMPERATURE TRENDS OF THE PERMITTIVITY IN COMPLEX OXIDES OF RARE-EARTH ELEMENTS WITH PEROVSKITE-TYPE STRUCTURE

    Directory of Open Access Journals (Sweden)

    A.G.Belous

    2003-01-01

    Full Text Available Ceramic materials based on complex oxides with both the perovskite structure (Ln2/3Nb2O6 and the structure of tetragonal tungsten bronze (Ba6-xLn8+2x/3Ti18O54 have been investigated over a wide frequency and temperature ranges. The results obtained for certain structures denote the presence of the temperature anomalies of dielectric parameters (ε, tanδ. These anomalies occur over the wide frequency range including submilimeter (SMM wavelength range, and are related neither with the processing peculiarities nor with the presence of the phase transitions. Temperature behavior of the permittivity has been considered in terms of the polarization mechanism based on the elastic-strain lattice oscillations. It has been assumed that the observed anomalies could be ascribed to a superposition of harmonic and anharmonic contribution to lattice oscillations that determines τε sign and magnitude.

  4. Modification of carbon derived from Sargassum sp. by lanthanum for enhanced adsorption of fluoride.

    Science.gov (United States)

    Yu, Yang; Wang, Chenghong; Guo, Xue; Paul Chen, J

    2015-03-01

    Excessive fluoride in water causes serious environmental issues and adverse impacts on human health. In this study, an innovative lanthanum-modified carbon (LMC) adsorbent rooted in Sargassum sp. was developed for fluoride removal. Excellent removal efficiency was observed over a wide pH range of 3-9. Almost 90% of fluoride adsorption occurred within the first 1h; the equilibrium was established within 4h. The maximum adsorption capacity of LMC could reach 94.34 mg/g at neutral pH, much higher than many commercial adsorbents. Although the presence of such competitive anions as SiO3(2-), SO4(2-), HCO3(-), PO4(3-) and AsO3(-) had certain interference on fluoride uptake, it was noticed that there was no significant impact in the presence of humic acid. Furthermore, according to the instrumental analysis, the fluoride removal was majorly controlled by outer-sphere complex adsorption, while electrostatic attraction and ion exchange mechanisms could also be observed in the fluoride adsorption process. The findings from this study suggest that our adsorbent may have a great potential in industrial applications. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Fluoride removal by calcite: evidence for fluorite precipitation and surface adsorption.

    Science.gov (United States)

    Turner, Brett D; Binning, Philip; Stipp, S L S

    2005-12-15

    Fluoride contamination of groundwater, both anthropogenic and natural, is a major problem worldwide. In this study, fluoride removal by crushed limestone (99% pure calcite) was investigated by batch studies and surface-sensitive techniques from solutions with fluoride concentrations from 150 micromol/L (3 mg/L) to 110 mM (approximately 2100 mg/L). Surface-sensitive techniques, including atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) as well as zeta potential measurements, confirm that, in addition to precipitation reactions, adsorption of fluoride also occurs. Results indicate that fluoride adsorption occurs immediately over the entire calcite surface with fluorite precipitating at step edges and kinks, where dissolved Ca2+ concentration is highest. The PHREEQ geochemical model was applied to the observed data and indicates that existing models, especially at low fluoride concentrations and high pH (>7.5) are not equipped to describe this complex system, largely because the PHREEQ model includes only precipitation reactions, whereas a combination of adsorption and precipitation parameters are required.

  6. Review on fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention.

    Science.gov (United States)

    ten Cate, J M

    1997-10-01

    Low concentrations of fluoride have a beneficial effect on enamel and dentin de- and remineralization. After fluoride treatments, such as topical applications, rinses or dentifrices, salivary fluoride concentrations decrease exponentially in a biphasic manner to very low concentrations within a few hours. For treatments to be effective over periods longer than the brushing and the following salivary clearance, fluoride needs to be deposited and slowly released. Calcium fluoride (or like) deposits act in such a way, owing to a surface covering of phosphate and/or proteins, which makes the CaF2 less soluble under in vivo conditions than in a pure form in inorganic solutions. Moreover, due to the phosphate groups on the surface of the calcium fluoride globules, fluoride is assumed to be released with decreasing pH when the phosphate groups are protonated in the dental plaque.

  7. Ion release from, and fluoride recharge of a composite with a fluoride-containing bioactive glass

    Science.gov (United States)

    Davis, Harry B.; Gwinner, Fernanda; Mitchell, John C.; Ferracane, Jack L.

    2014-01-01

    Objectives Materials that are capable of releasing ions such as calcium and fluoride, that are necessary for remineralization of dentin and enamel, have been the topic of intensive research for many years. The source of calcium has most often been some form of calcium phosphate, and that for fluoride has been one of several metal fluoride or hexafluorophosphate salts. Fluoride-containing bioactive glass (BAG) prepared by the sol-gel method acts as a single source of both calcium and fluoride ions in aqueous solutions. The objective of this investigation was to determine if BAG, when added to a composite formulation, can be used as a single source for calcium and fluoride ion release over an extended time period, and to determine if the BAG-containing composite can be recharged upon exposure to a solution of 5,000 ppm fluoride. Methods BAG 61 (61% Si; 31% Ca; 4% P; 3% F; 1% B) and BAG 81 (81% Si; 11% Ca; 4% P; 3% F; 1% B) were synthesized by the sol gel method. The composite used was composed of 50/50 Bis-GMA/TEGDMA, 0.8% EDMAB, 0.4% CQ, and 0.05% BHT, combined with a mixture of BAG (15%) and strontium glass (85%) to a total filler load of 72% by weight. Disks were prepared, allowed to age for 24 h, abraded, then placed into DI water. Calcium and fluoride release was measured by atomic absorption spectroscopy and fluoride ion selective electrode methods, respectively, after 2, 22, and 222 h. The composite samples were then soaked for 5 min in an aqueous 5,000 ppm fluoride solution, after which calcium and fluoride release was again measured at 2, 22, and 222 h time points. Results Prior to fluoride recharge, release of fluoride ions was similar for the BAG 61 and BAG 81 composites after 2 h, and also similar after 22 h. At the four subsequent time points, one prior to, and three following fluoride recharge, the BAG 81 composite released significantly more fluoride ions (pfluoride, although the BAG 81 composite was recharged more than the BAG 61 composite. The BAG 61

  8. FLUORIDE LEVELS IN COMMERCIALLY AVAILABLE RICE IN ...

    African Journals Online (AJOL)

    Preferred Customer

    2013-05-05

    May 5, 2013 ... There are several studies reporting the dietary intake of fluoride from water, ..... fluoride in rice samples showed the trend BR > ERR > NERICA > JR > RR > EWR. .... in cooked rice in Iran ranged from 0.2-1.6 mg F/kg [2].

  9. HOUSEHOLD PURIFICATION OF FLUORIDE CONTAMINATED MAGADI (TRONA)

    DEFF Research Database (Denmark)

    1997-01-01

    Purification of fluoride contaminated magadi is studied using bone char sorption and calcium precipitation. The bone char treatment is found to be workable both in columns and in batches where the magadi is dissolved in water prior to treatment. The concentrations in the solutions were 89 g magadi...... treatment method. A procedure for purification of fluoride contaminated magadi at household level is described....

  10. Inhibition of erosive wear by fluoride varnish

    NARCIS (Netherlands)

    Vieira, A.; Jager, D. H. J.; Ruben, J. L.; Huysmans, M. C. D. N. J. M.

    2007-01-01

    It has been suggested that fluoride products with a protective mechanical component are advantageous in the prevention of erosive wear. The aim of this study was to evaluate in situ the effect of fluoride varnish (FV) in the prevention of wear due to erosion and combined erosion and toothbrush abras

  11. Potentiometric Determination of Fluoride Concentration in Beers.

    Science.gov (United States)

    Jaudenes, Juan Ramón; Hardisson, Arturo; Paz, Soraya; Rubio, Carmen; Gutiérrez, Angel José; Burgos, Antonio; Revert, Consuelo

    2017-04-26

    Beer is a widely consumed drink throughout the world, and because its manufacture involves the use of water, beer can be, in some cases, a source of fluorides. For this reason, the objective of this study was to determine the concentration of fluorides in 50 samples of beers from different sources sold in two different types of container (aluminum can and glass bottle). The possible significant differences between the different types of packaging and the intake of fluoride from the consumption of these beers were evaluated. The concentration of fluoride in beers has been determined using the potentiometric method of fluoride determination by standard addition. The concentration of fluoride ranged between 0.06 and 1.77 mg/L. In general, the concentration was below 1 mg/L, except for three beer samples from Ireland and the USA, whose concentration was over 1.5 mg/L. No significant differences were found between the types of packaging. The contribution of fluoride to the diet from beer consumption is not high (fluoride in the water supply.

  12. Inhibition of erosive wear by fluoride varnish

    NARCIS (Netherlands)

    Vieira, A.; Jager, D. H. J.; Ruben, J. L.; Huysmans, M. C. D. N. J. M.

    2007-01-01

    It has been suggested that fluoride products with a protective mechanical component are advantageous in the prevention of erosive wear. The aim of this study was to evaluate in situ the effect of fluoride varnish (FV) in the prevention of wear due to erosion and combined erosion and toothbrush

  13. Thermal stability of the anionic sigma complexes of 2,4,6-trinitroanisole with the methylates of the alkaline-earth metals

    Energy Technology Data Exchange (ETDEWEB)

    Glaz, A.I.; Soldatova, T.A.; Golopolosova, T.V.; Gitis, S.S.

    1987-09-10

    The study of the stability of the 1,1-dimethoxy-2,4,6-trinitrocyclohexadienates of the alkali metals when they are heated in air showed that their temperature of decomposition and the heat effect of the process are dependent on the nature of the cation. Our study centered on the thermal decomposition of the products resulting from the addition of the methylates of calcium, strontium, and barium to 2,4,6-trinitroanisole. For a quantitative assessment of the process we used the combined methods of differential-thermal analysis and differential thermogravimetry. The anionic sigma-complexes of 2,4,6-trinitroanisole with the methylates of the alkaline-earth metals decompose on heating into the corresponding picrates; at the same time, when one passes from the calcium slat to the strontium and barium salts the decomposition temperature and the heat effect of the process show a drop which is linked to the structure both of the complexes and of the picrates forming therefrom.

  14. Synthesis, Crystal Structure and Characterization of a One-dimensional Supramolecular Rare Earth Complex of N-(6-(4-Methylpyridinyl))ketoacetamide

    Institute of Scientific and Technical Information of China (English)

    XU Li; TANG Kuan-Zhen; MA Yu-Fei; TANG Yu; TAN Min-Yu

    2007-01-01

    A one-dimensional (1D) supramolecular rare earth complex [Nd(NO3)2L2-(C3H6O)][NdL(NO3)4]} (L=N-(6-(4-methylpyridinyl))ketoacetamide) has been prepared and characterized by elemental analysis, IR and electronic spectroscopy, and single-crystal X-ray diffraction. The crystal crystallizes in the triclinic system, space group P-1 with a=0.9146(6), b=1.2581(8), c=2.2316(14) nm, α=99.352(10),β=97.209(9), γ=103.935(9)°, V=2.422(3) nm3, Dc=1.776 g/cm3, C33H42N12Nd2O25, Mr=1295.27, Z=2, F(000)=1288, μ=2.217 mm-1, R=0.0508and wR=0.1046 for 5173 observed reflections (I > 2σ(I)). In the structure of the title complex,one-dimensional supramolecular double-chains are formed by intermolecular hydrogen bonding interactions.

  15. Complexity

    CERN Document Server

    Gershenson, Carlos

    2011-01-01

    The term complexity derives etymologically from the Latin plexus, which means interwoven. Intuitively, this implies that something complex is composed by elements that are difficult to separate. This difficulty arises from the relevant interactions that take place between components. This lack of separability is at odds with the classical scientific method - which has been used since the times of Galileo, Newton, Descartes, and Laplace - and has also influenced philosophy and engineering. In recent decades, the scientific study of complexity and complex systems has proposed a paradigm shift in science and philosophy, proposing novel methods that take into account relevant interactions.

  16. Discovery of Interstellar Hydrogen Fluoride

    Science.gov (United States)

    Neufeld, David A.; Zmuidzinas, Jonas; Schilke, Peter; Phillips, Thomas G.

    1997-01-01

    We report the first detection of interstellar hydrogen fluoride. Using the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO), we have detected the 121.6973 micron J = 2-1 line of HF in absorption toward the far-infrared continuum source Sagittarius B2. The detection is statistically significant at the 13 sigma level. On the basis of our model for the excitation of HF in Sgr B2, the observed line equivalent width of 1.0 nm implies a hydrogen fluoride abundance of approximately 3 x 10(exp -10) relative to H2. If the elemental abundance of fluorine in Sgr B2 is the same as that in the solar system, then HF accounts for approximately 2% of the total number of fluorine nuclei. We expect hydrogen fluoride to be the dominant reservoir of gas-phase fluorine in Sgr B2, because it is formed rapidly in exothermic reactions of atomic fluorine with either water or molecular hydrogen; thus, the measured HF abundance suggests a substantial depletion of fluorine onto dust grains. Similar conclusions regarding depletion have previously been reached for the case of chlorine in dense interstellar clouds. We also find evidence at a lower level of statistical significance (approximately 5 sigma) for an emission feature at the expected position of the 4(sub 32)-4(sub 23) 121.7219 micron line of water. The emission-line equivalent width of 0.5 nm for the water feature is consistent with the water abundance of 5 x 10(exp -6) relative to H2 that has been inferred previously from observations of the hot core of Sgr B2.

  17. Fluoride Importance in Controlling Caries and Fluorosis

    Directory of Open Access Journals (Sweden)

    Gaurav Solanki

    2012-04-01

    Full Text Available The use of fluorides for oral health has always involved a balance between the protective benefit against dental caries and the risk of developing fluorosis. The link between fluoride and dental health was established to determining the causes of dental fluorosis or enamel mottling. Fluorosis in Indian children was highly prevalent in the early 1990s. Policy were introduced to control fluoride exposure and to reduce the prevalence of fluorosis. The study aimed of describing the prevalence, severity and risk factors for fluorosis, and to describe the trend of fluorosis among Indian children. The study also aimed of exploring the effect of the change in fluoride exposure on dental fluorosis and caries. Establishing an appropriate use of fluoride toothpaste could be successful in reducing fluorosis without a significant increase in caries experience.

  18. Diethylenetriaminium hexafluoridotitanate(IV fluoride

    Directory of Open Access Journals (Sweden)

    J. Lhoste

    2008-11-01

    Full Text Available The title compound, (C6H21N4[TiF6]F, was synthesized by the reaction of TiO2, tris(2-aminoethylamine, HF and ethanol at 463 K in a microwave oven. The crystal structure consists of two crystallographically independent [TiF6]2− anions, two fluoride anions and two triply-protonated tris(2-aminoethylamine cations. The Ti atoms are coordinated by six F atoms within slightly distorted octahedra. The anions and cations are connected by intermolecular N—H...F hydrogen bonds.

  19. Density functional theory study of the magnetic properties of rare earth complexes:the magnetic coupling mechanism in Y~Ⅲ and Gd~Ⅲ complexes with nitronyl nitroxide

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The magnetic coupling interactions of the nitronyl nitroxide radicals bound to diamagnetic(YⅢ) and paramagnetic(GdⅢ) rare earth ions in two model magnetic systems based on novel rare earth organic radical complexes Ln(hfac)3(NITPhOCH3)2(Ln=YⅢ 1,GdⅢ 2;hafc = hexafluoroacetylacetonate;NIT-PhOCH3 = 4’-methoxyo-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been investigated by density functional theory(DFT).The magnetic coupling mechanisms were also explored from the viewpoint of molecular orbital and spin density populations.DFT calculations show that the empty 4d-orbitals of YⅢ and 5d-orbitals of GdⅢ play an important role in the antiferromagnetic coupling between the two nitronyl nitroxide radical ligands,and that the ferromagnetic coupling between the GdⅢ ion and the radical magnetic centers can be attributed to the nearly complete localization of the isotropic 4f-shell and singly occupied magnetic orbital(π) of the nitronyl nitroxide.

  20. Density functional theory study of the magnetic properties of rare earth complexes:the magnetic coupling mechanism in Y~Ⅲ and Gd~Ⅲ complexes with nitronyl nitroxide

    Institute of Scientific and Technical Information of China (English)

    REN Jie; WANG BingWu; CHEN ZhiDa

    2009-01-01

    The magnetic coupling interactions of the nitronyl nitroxide radicals bound to diamagnetic (Y~Ⅲ) and paramagnetic (Gd~Ⅲ) rare earth ions in two model magnetic systems based on novel rare earth organic radical complexes Ln(hfac)_3(NITPhOCH_3)_2 (Ln=Y~Ⅲ 1,Gd~Ⅲ 2;hafc=hexafluoroacetylacetonate;NITPhOCH_3=4'-methoxyo-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been investigated by density functional theory (DFT).The magnetic coupling mechanisms were also explored from the viewpoint of molecular orbital and spin density populations.DFT calculations show that the empty 4d-orbitals of Y~Ⅲ and 5d-orbitals of Gd~Ⅲ play an important role in the antiferromagnetic coupling between the two nitronyl nitroxide radical ligands,and that the ferromagnetic coupling between the Gd~Ⅲ ion and the radical magnetic centers can be attributed to the nearly complete localization of the isotropic 4f-shell and singly occupied magnetic orbital (Π*) of the nitronyl nitroxide.

  1. Earth modeling and estimation of the local seismic ground motion due to site geology in complex volcanoclastic areas

    Directory of Open Access Journals (Sweden)

    V. Di Fiore

    2002-06-01

    Full Text Available Volcanic areas often show complex behaviour as far as seismic waves propagation and seismic motion at surface are concerned. In fact, the finite lateral extent of surface layers such as lava flows, blocks, differential welding and/or zeolitization within pyroclastic deposits, introduces in the propagation of seismic waves effects such as the generation of surface waves at the edge, resonance in lateral direction, diffractions and scattering of energy, which tend to modify the amplitude as well as the duration of the ground motion. The irregular topographic surface, typical of volcanic areas, also strongly influences the seismic site response. Despite this heterogeneity, it is unfortunately a common geophysical and engineering practice to evaluate even in volcanic environments the subsurface velocity field with monodimensional investigation method (i.e. geognostic soundings, refraction survey, down-hole, etc. prior to the seismic site response computation which in a such cases is obviously also made with 1D algorithms. This approach often leads to highly inaccurate results. In this paper we use a different approach, i.e. a fully 2D P-wave Çturning rayÈ tomographic survey followed by 2D seismic site response modeling. We report here the results of this approach in three sites located at short distance from Mt. Vesuvius and Campi Flegrei and characterized by overburdens constituted by volcanoclastic deposits with large lateral and vertical variations of their elastic properties. Comparison between 1D and 2D Dynamic Amplification Factor shows in all reported cases entirely different results, both in terms of peak period and spectral contents, as expected from the clear bidimensionality of the geological section. Therefore, these studies suggest evaluating carefully the subsoil geological structures in areas characterized by possible large lateral and vertical variations of the elastic properties in order to reach correct seismic site response

  2. Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Ka King [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe2)3 and KC(SiHMe2})3TMEDA are synthesized by deprotonation of the hydrocarbon HC(SiHMe2)3 with potassium benzyl. KC(SiHMe2)3TMEDA crystallizes as a dimer with two types of three-center-two-electron KH- Si interactions. Homoleptic Ln(III) tris(silylalkyl) complexes containing β-SiH groups M{C(SiHMe2)3}3 (Ln = Y, Lu, La) are synthesized from salt elimination of the corresponding lanthanide halide and 3 equiv. of KC(SiHMe2)3. The related reactions with Sc yield bis(silylalkyl) ate-complexes containing either LiCl or KCl. The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. The compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) and La{C(SiHMe2)3}3 react with 1 equiv of B(C6F5)3 to give 1,3- disilacyclobutane {Me2Si-C(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L, and La{C(SiHMe2)3}2HB(C6F5)3, respectively. The corresponding reactions of Ln{C(SiHMe2)3}3 (Ln = Y, Lu) give the β-SiH abstraction product [{(Me2HSi)3C}2LnC(SiHMe2)2SiMe2][HB(C6F5)3] (Ln = Y, Lu), but the silene remains associated with the Y or Lu center. The abstraction reactions of M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2or TMEDA) and Ln{C(SiHMe2)3}3 (Ln = Y, Lu, La) and 2 equiv of B(C6

  3. Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Ka King [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe2)3 and KC(SiHMe2})3TMEDA are synthesized by deprotonation of the hydrocarbon HC(SiHMe2)3 with potassium benzyl. KC(SiHMe2)3TMEDA crystallizes as a dimer with two types of three-center-two-electron KH- Si interactions. Homoleptic Ln(III) tris(silylalkyl) complexes containing β-SiH groups M{C(SiHMe2)3}3 (Ln = Y, Lu, La) are synthesized from salt elimination of the corresponding lanthanide halide and 3 equiv. of KC(SiHMe2)3. The related reactions with Sc yield bis(silylalkyl) ate-complexes containing either LiCl or KCl. The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. The compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) and La{C(SiHMe2)3}3 react with 1 equiv of B(C6F5)3 to give 1,3- disilacyclobutane {Me2Si-C(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L, and La{C(SiHMe2)3}2HB(C6F5)3, respectively. The corresponding reactions of Ln{C(SiHMe2)3}3 (Ln = Y, Lu) give the β-SiH abstraction product [{(Me2HSi)3C}2LnC(SiHMe2)2SiMe2][HB(C6F5)3] (Ln = Y, Lu), but the silene remains associated with the Y or Lu center. The abstraction reactions of M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2or TMEDA) and Ln{C(SiHMe2)3}3 (Ln = Y, Lu, La) and 2 equiv of B(C6

  4. High performance fluoride optical coatings for DUV optics

    Science.gov (United States)

    Zhang, Lichao; Cai, Xikun

    2014-08-01

    In deep ultraviolet region that typical applications are used on the ArF wavelength, coated optics should meet stringent requirements of optical systems. To meet these requirements, systematical researches are carried out on fabrication and characterization methods of fluoride coatings. First, by optimizing of deposition processes, dense coatings with the refractive index of ~1.7 for LaF3 and ~1.4 for MgF2, together with extinction coefficients of ~2×10-4 on 193nm were realized. The transmission of AR coating for 193nm achieved by using optimized deposition techniques is 99.8%. Second, a method of designing shadowing masks was developed to solve the problem of correcting coating thickness distributions for complex DUV systems. By using the method, the thickness distribution error specification of 3% PV has been achieved on substrates with ~300mm diameters and large curvatures. Finally, the laser calorimetry method is used to evaluate the laser radiation stability of fluoride coatings. It is turned out that the damage coefficients of fluoride coatings, which are defined as the values of unrecoverable increase of the absorption during the laser irradiation process, are much lower than that of fused silica substrates. The above progresses could further support the realization of high performance DUV optical systems.

  5. Metal Fluoride Inhibition of a P-type H+ Pump

    Science.gov (United States)

    Pedersen, Jesper Torbøl; Falhof, Janus; Ekberg, Kira; Buch-Pedersen, Morten Jeppe; Palmgren, Michael

    2015-01-01

    The plasma membrane H+-ATPase is a P-type ATPase responsible for establishing electrochemical gradients across the plasma membrane in fungi and plants. This essential proton pump exists in two activity states: an autoinhibited basal state with a low turnover rate and a low H+/ATP coupling ratio and an activated state in which ATP hydrolysis is tightly coupled to proton transport. Here we characterize metal fluorides as inhibitors of the fungal enzyme in both states. In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H+-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state. Thus, the stability of the ATPase inhibitor complex decreased significantly when the pump transitioned from the activated to the basal state, particularly when using beryllium fluoride, which mimics the bound phosphate in the E2P conformational state. Taken together, our results indicate that the phosphate bond of the phosphoenzyme intermediate of H+-ATPases is labile in the basal state, which may provide an explanation for the low H+/ATP coupling ratio of these pumps in the basal state. PMID:26134563

  6. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Poly(vinyl fluoride) resins. 175.270 Section 175... Substances for Use as Components of Coatings § 175.270 Poly(vinyl fluoride) resins. Poly(vinyl fluoride... the purpose of this section, poly(vinyl fluoride) resins consist of basic resins produced by the...

  7. Fluoride Programs in the School Setting: Preventive Dental Health.

    Science.gov (United States)

    Rebich, Theodore, Jr.; And Others

    1982-01-01

    Two types of school-based programs that increase students' use of fluoride for preventive dental health are described. In fluoride mouthrinse programs, teachers give their students a fluoride solution once a week in a paper cup. In areas where the level of fluoride in the water supply is insufficient, the flouride tablet program is used. (JN)

  8. Spectroscopic and Crystal Field Consequences of Fluoride Binding by [Yb⋅DTMA]3+ in Aqueous Solution

    Science.gov (United States)

    Blackburn, Octavia A; Chilton, Nicholas F; Keller, Katharina; Tait, Claudia E; Myers, William K; McInnes, Eric J L; Kenwright, Alan M; Beer, Paul D; Timmel, Christiane R; Faulkner, Stephen

    2015-01-01

    Yb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F]2+ and [Yb⋅DTMA⋅OH2]3+ are in slow exchange on the relevant NMR timescale (<2000 s−1), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding. This changes the magnetic anisotropy of the YbIII ground state from easy-axis to easy-plane type, and this change is easily detected in the observed magnetic anisotropy despite thermal population of more than just the ground state. The spectroscopic consequences of such drastic changes to the ligand field represent important new opportunities in developing fluoride-responsive complexes and contrast agents. PMID:26223970

  9. Fluoride in saliva and dental biofilm after 1500 and 5000 ppm fluoride exposure.

    Science.gov (United States)

    Staun Larsen, Line; Baelum, Vibeke; Tenuta, Livia Maria Andaló; Richards, Alan; Nyvad, Bente

    2017-09-01

    The aim of this randomized, double-blind, crossover study was to measure fluoride in saliva and 7-day-old biofilm fluid and biofilm solids after rinsing three times per day for 3 weeks with 0, 1500, or 5000 ppm fluoride (NaF). Following the 3-week wash-in/wash-out period, including 1 week of biofilm accumulation, saliva and biofilm samples were collected from 12 participants immediately before (background fluoride), and 10, 30, and 60 min after a single rinse. Biofilm samples were separated into fluid and solids, and samples were analyzed using a fluoride electrode (microanalysis). The background fluoride concentration was statistically significantly higher in the 5000 compared to the 1500 ppm F rinse group in all three compartments (22.3 and 8.1 μM in saliva, 126.8 and 58.5 μM in biofilm fluid, and 10,940 and 4837 μmol/kg in biofilm solids). The 1-h fluoride accumulation for the 5000 ppm F rinse was higher than for the 1500 ppm F rinse in all three compartments, although not statistically significant for saliva and biofilm solids. Regular exposure to 5000 ppm fluoride elevates background fluoride concentrations in saliva, biofilm fluid, and biofilm solids compared to 1500 ppm fluoride. Increasing the fluoride concentration almost 3.5 times (from 1500 to 5000 ppm) only elevates the background fluoride concentrations in saliva, biofilm fluid, and biofilm solids twofold. Even though fluoride toothpaste may be diluted by saliva, the results of the present study indicate that use of 5000 ppm fluoride toothpaste might lead to improved caries control.

  10. Effects of Substrate Complexing Light Rare Earth on Growth, Cd Absorption and Organ Distribution of Sweet Pepper (Capsicum annuum var. annuum)%Effects of Substrate Complexing Light Rare Earth on Growth, Cd Absorption and Organ Distribution of Sweet Pepper (Capsicum annuum var. annuum)

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    [Objective] The aim was to research effects of substrate complexing light rare earth on growth, Cd absorption and organ distribution of sweet pepper to pro- vide references for development of rhizosphere regulation products in farmland seri- ously polluted. [Method] In the test, effects of substrate cakes (at the same size) and light rare earth (in different doses) on growth, Cd absorption and distribution of green peppers under stress from Cd were explored with a pot experiment. [Result] When 40 mg/kg of rare earth was added into a substrate cake, plant height of pep- per seedlings and the dry weight increased by 21.52% and 11.11%, compared with control group; when Cd was at 5.19 mg/kg (a highly graded pollution), the shoot biomass, olant biomass and dry weight of fruits all enhanced significantly, but root system changed little in the groups where substrate cakes were saved, compared with the group where the substrate cake was washed away. No matter RE was added into substrate cakes or not, root system was significantly inhibited by Cd stress (5.19 mg/kg), but RE at proper dose improved growth of green pepper and had little effect on fruit yielding. In addition, RE had little inhibition on Cd content in roots. RE at 10 mg/kg promoted Cd contents in stems and leaves, but reduced the content in fruits substantially. The regressive equation of Cd content and rare dose in leaves was as follows: y=4E-05x%0.009 6x+0.655 6, FF=0.542 6; the regression equations of Cd content in root, stem and fruit did not make sense. [Conclusion] The experiment lays foundation for further research on heavy metals rhizosphere complexing controlling.

  11. Complex

    African Journals Online (AJOL)

    CLEMENT O BEWAJI

    Schiff bases and their complex compounds have been studied for their .... establishing coordination of the N–(2 – hydroxybenzyl) - L - α - valine Schiff base ..... (1967); “Spectrophotometric Identification of Organic Compounds”, Willey, New.

  12. Physiologic Conditions Affect Toxicity of Ingested Industrial Fluoride

    Directory of Open Access Journals (Sweden)

    Richard Sauerheber

    2013-01-01

    Full Text Available The effects of calcium ion and broad pH ranges on free fluoride ion aqueous concentrations were measured directly and computed theoretically. Solubility calculations indicate that blood fluoride concentrations that occur in lethal poisonings would decrease calcium below prevailing levels. Acute lethal poisoning and also many of the chronic effects of fluoride involve alterations in the chemical activity of calcium by the fluoride ion. Natural calcium fluoride with low solubility and toxicity from ingestion is distinct from fully soluble toxic industrial fluorides. The toxicity of fluoride is determined by environmental conditions and the positive cations present. At a pH typical of gastric juice, fluoride is largely protonated as hydrofluoric acid HF. Industrial fluoride ingested from treated water enters saliva at levels too low to affect dental caries. Blood levels during lifelong consumption can harm heart, bone, brain, and even developing teeth enamel. The widespread policy known as water fluoridation is discussed in light of these findings.

  13. Physiologic Conditions Affect Toxicity of Ingested Industrial Fluoride

    Science.gov (United States)

    Sauerheber, Richard

    2013-01-01

    The effects of calcium ion and broad pH ranges on free fluoride ion aqueous concentrations were measured directly and computed theoretically. Solubility calculations indicate that blood fluoride concentrations that occur in lethal poisonings would decrease calcium below prevailing levels. Acute lethal poisoning and also many of the chronic effects of fluoride involve alterations in the chemical activity of calcium by the fluoride ion. Natural calcium fluoride with low solubility and toxicity from ingestion is distinct from fully soluble toxic industrial fluorides. The toxicity of fluoride is determined by environmental conditions and the positive cations present. At a pH typical of gastric juice, fluoride is largely protonated as hydrofluoric acid HF. Industrial fluoride ingested from treated water enters saliva at levels too low to affect dental caries. Blood levels during lifelong consumption can harm heart, bone, brain, and even developing teeth enamel. The widespread policy known as water fluoridation is discussed in light of these findings. PMID:23840230

  14. Expanding earth

    Energy Technology Data Exchange (ETDEWEB)

    Carey, S.W.

    1976-01-01

    Arguments in favor of an expanding earth are presented. The author believes that the theory of plate tectonics is a classic error in the history of geology. The case for the expanding earth is organized in the following way: introductory review - face of the earth, development of expanding earth concept, necessity for expansion, the subduction myth, and definitions; some principles - scale of tectonic phenomena, non-uniformitarianism, tectonic profile, paleomagnetism, asymmetry of the earth, rotation of the earth, and modes of crustal extension; regional studies - western North America, Central America, South-East Asia, and the rift oceans; tests and cause of expansion. 824 references, 197 figures, 11 tables. (RWR)

  15. Fluoride Adsorption by Pumice from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Amir Hossein Mahvi

    2012-01-01

    Full Text Available Drinking water provides many vital elements for the human body, but the presence of some dissolved elements more than permissible concentration can endanger human health. Among the dissolved elements in drinking water, fluoride is noticeable, because both the very low or very high concentrations have adverse health impacts such as dental caries. Therefore, fluoride concentration should be kept in acceptable levels. In this study Pumice was used for fluoride removal. It was found that Fluoride sorption kinetic was fitted by pseudo-second-order model. The maximum sorption capacity of Pumice was found to be 13.51 mg/g at laboratory temperature (24°C. Maximum sorption study occurred at pH= 3. Results of Isotherm showed the fluoride sorption has been well fitted with Freundlich isotherm model. This study has demonstrated that Pumice can be used as effective adsorbents for fluoride removal from aqueous solutions. The adsorbent prepared in this study was cheap and efficient in removal of fluoride than other adsorbents.

  16. Current status of fluoride volatility method development

    Energy Technology Data Exchange (ETDEWEB)

    Uhlir, J.; Marecek, M.; Skarohlid, J. [UJV - Nuclear Research Institute, Research Centre Rez, CZ-250 68 Husinec - Rez 130 (Czech Republic)

    2013-07-01

    The Fluoride Volatility Method is based on a separation process, which comes out from the specific property of uranium, neptunium and plutonium to form volatile hexafluorides whereas most of fission products (mainly lanthanides) and higher transplutonium elements (americium, curium) present in irradiated fuel form nonvolatile tri-fluorides. Fluoride Volatility Method itself is based on direct fluorination of the spent fuel, but before the fluorination step, the removal of cladding material and subsequent transformation of the fuel into a powdered form with a suitable grain size have to be done. The fluorination is made with fluorine gas in a flame fluorination reactor, where the volatile fluorides (mostly UF{sub 6}) are separated from the non-volatile ones (trivalent minor actinides and majority of fission products). The subsequent operations necessary for partitioning of volatile fluorides are the condensation and evaporation of volatile fluorides, the thermal decomposition of PuF{sub 6} and the finally distillation and sorption used for the purification of uranium product. The Fluoride Volatility Method is considered to be a promising advanced pyrochemical reprocessing technology, which can mainly be used for the reprocessing of oxide spent fuels coming from future GEN IV fast reactors.

  17. Topical fluoride as a cause of dental fluorosis in children

    OpenAIRE

    Wong, MCM; Lo, ECM; Glenny, AM; Tsang, BWK; Worthington, HV; Marinho, VCC

    2009-01-01

    BACKGROUND: For many years, topical use of fluorides has gained greater popularity than systemic use of fluorides. A possible adverse effect associated with the use of topical fluoride is the development of dental fluorosis due to the ingestion of excessive fluoride by young children with developing teeth. OBJECTIVES: To describe the relationship between the use of topical fluorides in young children and the risk of developing dental fluorosis. SEARCH STRATEGY: Electronic search of the Cochra...

  18. A study of fluoride groundwater occurrence in Nathenje, Lilongwe, Malawi

    Science.gov (United States)

    Msonda, K. W. M.; Masamba, W. R. L.; Fabiano, E.

    A study was carried out to determine fluoride concentration in groundwaters of Nathenje area situated in Lilongwe District in the central region of Malawi. Water samples were collected from 176 boreholes and shallow wells during different months in 2001 and 2002. Samples were then analysed for fluoride by using a fluoride electrode and an ion selective meter. The results showed that fluoride concentrations for the rainy season varied from dental fluorosis in areas where the fluoride concentration was high.

  19. A fluoride release-adsorption-release system applied to fluoride-releasing restorative materials.

    Science.gov (United States)

    Suljak, J P; Hatibovic-Kofman, S

    1996-09-01

    This investigation compared the initial fluoride release and release following refluoridation of three resin-modified glass-ionomer cements (Photac-Fil Applicap, Vitremer, and Fuji II LC) and a new polyacid-modified resin composite material (Dyract). After daily flouride release was measured for 8 days, specimens were refluoridated in 1,000-ppm solutions of fluoride ion for 10 minutes and fluoride release was measured for 5 days. Two further 5-day refluoridation-release periods were carried out. All materials released fluoride initially. Photac released the most; Dyract released the least. Initial release was greatest over the first few days. All materials released significantly more fluoride for 24 to 48 hours after refluoridation. Less fluoride was released with each successive refluoridation for the three glass-ionomer cements. The release from the Dyract compomer remained at a comparatively constant and significantly lower level following each refluoridation.

  20. The use of Multiple Representations to Enhance Student Mental Model Development of a Complex Earth System in an Introductory Geoscience Course

    Science.gov (United States)

    Sell, K. S.; Heather, M. R.; Herbert, B. E.

    2004-12-01

    Exposing earth system science (ESS) concepts into introductory geoscience courses may present new and unique cognitive learning issues for students including understanding the role of positive and negative feedbacks in system responses to perturbations, spatial heterogeneity, and temporal dynamics, especially when systems exhibit complex behavior. Implicit learning goals of typical introductory undergraduate geoscience courses are more focused on building skill-sets and didactic knowledge in learners than developing a deeper understanding of the dynamics and processes of complex earth systems through authentic inquiry. Didactic teaching coupled with summative assessment of factual knowledge tends to limit student¡¦s understanding of the nature of science, their belief in the relevancy of science to their lives, and encourages memorization and regurgitation; this is especially true among the non-science majors who compose the majority of students in introductory courses within the large university setting. Students organize scientific knowledge and reason about earth systems by manipulating internally constructed mental models. This pilot study focuses on characterizing the impact of inquiry-based learning with multiple representations to foster critical thinking and mental model development about authentic environmental issues of coastal systems in an introductory geoscience course. The research was conducted in nine introductory physical geology laboratory sections (N ˜ 150) at Texas A&M University as part of research connected with the Information Technology in Science (ITS) Center. Participants were randomly placed into experimental and control groups. Experimental groups were exposed to multiple representations including both web-based learning materials (i.e. technology-supported visualizations and analysis of multiple datasets) and physical models, whereas control groups were provided with the traditional ¡workbook style¡" laboratory assignments

  1. Grid-Free 2D Plasma Simulations of the Complex Interaction Between the Solar Wind and Small, Near-Earth Asteroids

    Science.gov (United States)

    Zimmerman, M. I.; Farrell, W. M.; Poppe, A. R.

    2014-01-01

    We present results from a new grid-free 2D plasma simulation code applied to a small, unmagnetized body immersed in the streaming solar wind plasma. The body was purposely modeled as an irregular shape in order to examine photoemission and solar wind plasma flow in high detail on the dayside, night-side, terminator and surface-depressed 'pocket' regions. Our objective is to examine the overall morphology of the various plasma interaction regions that form around a small body like a small near-Earth asteroid (NEA). We find that the object obstructs the solar wind flow and creates a trailing wake region downstream, which involves the interplay between surface charging and ambipolar plasma expansion. Photoemission is modeled as a steady outflow of electrons from illuminated portions of the surface, and under direct illumination the surface forms a non-monotonic or ''double-sheath'' electric potential upstream of the body, which is important for understanding trajectories and equilibria of lofted dust grains in the presence of a complex asteroid geometry. The largest electric fields are found at the terminators, where ambipolar plasma expansion in the body-sized night-side wake merges seamlessly with the thin photoelectric sheath on the dayside. The pocket regions are found to be especially complex, with nearby sunlit regions of positive potential electrically connected to unlit negative potentials and forming adjacent natural electric dipoles. For objects near the surface, we find electrical dissipation times (through collection of local environmental solar wind currents) that vary over at least 5 orders of magnitude: from 39 Micro(s) inside the near-surface photoelectron cloud under direct sunlight to less than 1 s inside the particle-depleted night-side wake and shadowed pocket regions

  2. New reversed phase-high performance liquid chromatographic method for selective separation of yttrium from all rare earth elements employing nitrilotriacetate complexes in anion exchange mode.

    Science.gov (United States)

    Dybczyński, Rajmund S; Kulisa, Krzysztof; Pyszynska, Marta; Bojanowska-Czajka, Anna

    2015-03-20

    Separation of Y from other rare earth elements (REE) is difficult because of similarity of its ionic radius to ionic radii of Tb, Dy and Ho. In the new RP-HPLC system with C18 column, tetra-n-butyl ammonium hydroxide (TBAOH) as an ion interaction reagent (IIR), nitrilotriacetic acid (NTA) as a complexing agent at pH=2.8-3.5, and post column derivatization with Arsenazo III, yttrium is eluted in the region of light REE, between Nd and Sm and is base line separated from Nd and Sm and even from promethium. Simple model employing literature data on complex formation of REE with NTA and based on anion exchange mechanism was developed to foresee the order of elution of individual REE. The model correctly predicted that lanthanides up to Tb will be eluted in the order of increasing Atomic Number (At.No.) but all heavier REE will show smaller retention factors than Tb. Concurrent UV/VIS detection at 658nm and the use of radioactive tracers together with γ-ray spectrometric measurements made possible to establish an unique elution order of elution of REE: La, Ce, Pr, Nd, Pm, Y, Sm, Er, Ho, Tm, Yb, Eu, Lu, Dy+Gd, Tb, Sc. The real place of Y however, in this elution series differs from that predicted by the model (Y between Sm and Eu). The method described in this work enables selective separation of Y from La, Ce, Pr, Nd, Pm, Sm and all heavier REE treated as a group.

  3. [Remineralization of artificial root caries by fluoride dentifrice of different fluoride concentration in vitro].

    Science.gov (United States)

    Liu, Hong-Chun; Yu, Shao-Jie; Hu, De-Yu

    2010-12-01

    Although the effectiveness of fluoride dentifrice in remineralizing enamel caries has been established, the optimum fluoride concentration for remineralization root caries has not been defined. The aim of this study was to assess and compare the effect of 1.1g/L, 1.45g/L and 5g/L fluoride dentifrices in remineralization of artificial root caries. Sound human tooth fragments obtained from the cervical portion of root were stored in a demineralization solution for 96h at 37 degrees centigrade to induce artificial root caries lesions. The fragments were then randomly divided into four treatment groups including 1.1g/L, 1.45g/L, 5g/L fluoride dentifrice group and non-fluoride dentifrice control group. The demineralized samples were pH-cycled through treatment solutions, acidic buffer and neutral buffer for 8 days at 6 cycles per day. The samples were evaluated using electrical caries monitor(ECM), polarized light microscopy (PLM) and confocal laser scanning microscopy (CLSM). The data was analyzed using ANOVA with SPSS13.0 software package. Variations of LgECM, total fluorescence and average fluorescence from CLSM after remineralization in fluoride dentifrice groups were significantly higher than those in the control group(Pdentifrice group were significantly higher than those in the 1.1g/L and 1.45g/L fluoride dentifrice groups(Pdentifrice groups. A wider mineral band was seen in the 5g/L fluoride dentifrice group than in the 1.1g/L and 1.45g/L fluoride dentifrice groups. Fluoride dentifrice is effective in remineralizing artificial root caries and 5g/L fluoride dentifrice has better effect than 1.1g/L and 1.45g/L fluoride dentifrices.

  4. Spatial Dynamics of the Communities and the Role of Major Countries in the International Rare Earths Trade: A Complex Network Analysis.

    Science.gov (United States)

    Wang, Xibo; Ge, Jianping; Wei, Wendong; Li, Hanshi; Wu, Chen; Zhu, Ge

    2016-01-01

    Rare earths (RE) are critical materials in many high-technology products. Due to the uneven distribution and important functions for industrial development, most countries import RE from a handful of suppliers that are rich in RE, such as China. However, because of the rapid growth of RE exploitation and pollution of the mining and production process, some of the main suppliers have gradually tended to reduce the RE production and exports. Especially in the last decade, international RE trade has been changing in the trade community and trade volume. Based on complex network theory, we built an unweighted and weighted network to explore the evolution of the communities and identify the role of the major countries in the RE trade. The results show that an international RE trade network was dispersed and unstable because of the existence of five to nine trade communities in the unweighted network and four to eight trade communities in the weighted network in the past 13 years. Moreover, trade groups formed due to the great influence of geopolitical relations. China was often associated with the South America and African countries in the same trade group. In addition, Japan, China, the United States, and Germany had the largest impacts on international RE trade from 2002 to 2014. Last, some policy suggestions were highlighted according to the results.

  5. Spatial Dynamics of the Communities and the Role of Major Countries in the International Rare Earths Trade: A Complex Network Analysis.

    Directory of Open Access Journals (Sweden)

    Xibo Wang

    Full Text Available Rare earths (RE are critical materials in many high-technology products. Due to the uneven distribution and important functions for industrial development, most countries import RE from a handful of suppliers that are rich in RE, such as China. However, because of the rapid growth of RE exploitation and pollution of the mining and production process, some of the main suppliers have gradually tended to reduce the RE production and exports. Especially in the last decade, international RE trade has been changing in the trade community and trade volume. Based on complex network theory, we built an unweighted and weighted network to explore the evolution of the communities and identify the role of the major countries in the RE trade. The results show that an international RE trade network was dispersed and unstable because of the existence of five to nine trade communities in the unweighted network and four to eight trade communities in the weighted network in the past 13 years. Moreover, trade groups formed due to the great influence of geopolitical relations. China was often associated with the South America and African countries in the same trade group. In addition, Japan, China, the United States, and Germany had the largest impacts on international RE trade from 2002 to 2014. Last, some policy suggestions were highlighted according to the results.

  6. Fluoride content in plaque solids and fluid after ingestion of fluoridated milk.

    Science.gov (United States)

    Martínez-Mier, Esperanza A; Soto-Rojas, Armando E; Buckley, Christine; Weitz, Andrea; Villa, Alberto; Zero, Domenick T

    2013-09-01

    This study explored differences in dental biofilm solids and fluid fluoride after ingestion of NaF or Na2FPO3 in milk or non-fluoridated milk. Eighteen volunteers ingested 1 mg fluoride in 200 mL of milk or 200 mL of non-fluoridated milk. Biofilm samples were collected at baseline, 30, 60, and 240 min and biofilm solids and fluid were micro-analyzed for fluoride. Analysis of variance was performed and the total delivery, retention, and clearance of fluoride to biofilm solids and fluid were estimated as the area under the curve between 0 and 240 min. No statistically significant differences were found for baseline values. Biofilm fluid fluoride values ranged from 0.11 ± 0.05 to 0.21 ± 0.08 µg F/mL while biofilm solid values ranged from 0.62 ± 0.39 to 1.75 ± 1.16 µg F/g. Biofilm fluid values were significantly lower at 60 min for Na2FPO3 in milk. Clearance profiles for biofilm fluid diverged after the initial 60 min. Na2FPO3 had a smaller area under the curve from 60 to 240 min than NaF. Results of this study indicate that the release and clearance of fluoride in biofilm vary among fluoridation compounds and that the concentrations in biofilm solids and fluid also vary and are not correlated to each other in many cases.

  7. Dental fluorosis and skeletal fluoride content as biomarkers of excess fluoride exposure in marsupials.

    Science.gov (United States)

    Death, Clare; Coulson, Graeme; Kierdorf, Uwe; Kierdorf, Horst; Morris, William K; Hufschmid, Jasmin

    2015-11-15

    Particulate and gaseous fluoride emissions contaminate vegetation near fluoride-emitting industries, potentially impacting herbivorous wildlife in neighboring areas. Dental fluorosis has been associated with consumption of fluoride-contaminated foliage by juvenile livestock and wildlife in Europe and North America. For the first time, we explored the epidemiology and comparative pathology of dental fluorosis in Australian marsupials residing near an aluminium smelter. Six species (Macropus giganteus, Macropus rufogriseus, Wallabia bicolor, Phascolarctos cinereus, Trichosurus vulpecula, Pseudocheirus peregrinus) demonstrated significantly higher bone fluoride levels in the high (n=161 individuals), compared to the low (n=67 individuals), fluoride areas (pdental lesions considered characteristic of dental fluorosis in eutherian mammals. Within the high-fluoride area, 67% of individuals across the six species showed dental enamel lesions, compared to 3% in the low-fluoride areas. Molars that erupted before weaning were significantly less likely to display pathological lesions than those developing later, and molars in the posterior portion of the dental arcade were more severely fluorotic than anterior molars in all six species. The severity of dental lesions was positively associated with increasing bone fluoride levels in all species, revealing a potential biomarker of excess fluoride exposure. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. High density fluoride glass calorimeter

    Science.gov (United States)

    Xie, Q.; Scheltzbaum, J.; Akgun, U.

    2014-04-01

    The unprecedented radiation levels in current Large Hadron Collider runs, and plans to even increase the luminosity creates a need for new detector technologies to be investigated. Quartz plates to replace the plastic scintillators in current LHC calorimeters have been proposed in recent reports. Quartz based Cherenkov calorimeters can solve the radiation damage problem, however light production and transfer have proven to be challenging. This report summarizes the results from a computational study on the performance of a high-density glass calorimeter. High-density, scintillating, fluoride glass, CHG3, was used as the active material. This glass has been developed specifically for hadron collider experiments, and is known for fast response time, in addition to high light yield. Here, the details of a Geant4 model for a sampling calorimeter prototype with 20 layers, and its hadronic as well as electromagnetic performances are reported.

  9. Morphology of Polyvinylidene Fluoride Based Gel Polymer Electrolytes

    Institute of Scientific and Technical Information of China (English)

    田立颖; 黄小彬; 唐小真

    2004-01-01

    Two series of polyvinylidene fluoride (PVDF) based gel polymer electrolytes, with different LiClO4 or propylene carbonate (PC) content, were prepared and analyzed by infrared spectrometer, differential scanning calorimetry, scanning electron microscope and complex impedance spectrometer. The results show that there are great interactions between PVDF, PC and lithium cations. Both LiClO4 and PC content lead to evident change of the morphology of the gel polymer electrolytes. The content of LiClO4 and PC also influences the ionic conductivity of the samples,and an ionic conductivity of above 10-3S·cm-1 can be reached at room temperature.

  10. Spectroscopic Investigation of Ce(3+) Doped Fluoride Crystals

    Science.gov (United States)

    Reinhart, Donald H.; Armagan, Guzin; Marsh, Waverly; Barnes, James; Chai, B. H. T.

    1995-01-01

    Doping of the trivalent rare-earth cerium ion into fluoride crystals is of interest in producing turnable ultra-violet solid state lasers. These lasers are desirable for many applications in medicine, industry, and scientific research, including remote sensing. High absorption and stimulated emission cross sections of the dipole allowed 4f-5d transitions show promise in cerium as a laser ion in crystals. Several research groups have already reported the observation of stimulated emission of cerium in LiYF4, LiSrAlF6, and LiCaAlF6. However, the color center formation in the crystals due to the excited state absorption of ultra-violet pump light adds difficulty to achieving laser action. We have investigated the spectroscopic properties of cerium such as absorption and emission spectra, and lifetimes in four different fluoride crystals, including LiCaAlF6, LiSrAlF6, KyF4 and LiYF4. We have derived the polarized absorption and stimulated emission cross sections from transmission and fluorescence emission measurements for each of the host crystals. we have measured the lifetime of the lowest 5d level; moreover, investigated the temperature dependence of this lifetime and color center formation. Our results on absorption and stimulated emission cross sections for LiCaAlF6 and LiSrAlF6 are similar to the results already published.

  11. Interaction between a transition-metal fluoride and a transition-metal hydride: water-mediated hydrofluoric acid evolution following fluoride solvation.

    Science.gov (United States)

    Chierotti, Michele R; Rossin, Andrea; Gobetto, Roberto; Peruzzini, Maurizio

    2013-11-04

    The reaction between the nickel(II) PCP pincer fluoride complex ((tBu)PCP)Ni(F) [(tBu)PCP = 2,6-C6H3(CH2P(t)Bu2)2] and the tungsten(II) carbonyl hydride CpW(H)(CO)3 (Cp = η(5)-C5H5(-)) leads to hydrofluoric acid evolution and formation of the bimetallic isocarbonylic species [CpW(CO)2(μ-κ,C:κ,O-CO)···Ni((tBu)PCP)]. The process has been monitored through multinuclear ((19)F, (31)P{(1)H}, (1)H) variable-temperature NMR spectroscopy, collecting (19)F T1 data values for a fluoride ligand bound to a transition metal. The extremely short relaxation time (minimum value of 13 ms at 193 K) is ascribed to the large chemical shift anisotropy of the Ni-F bond (688 ppm). The in-depth NMR analysis has revealed that the fluoride-hydride interaction is not direct but water-mediated, at odds with what was previously observed for the "hydride-hydride" case ((tBu)PCP)Ni(H)/CpW(H)(CO)3. Kinetic measurements have unveiled that the first step of the overall mechanism is thought to be solvation of the fluoride ligand (as a result of Ni-F···H2O hydrogen bonding), while further reaction of the solvated fluoride with CpW(H)(CO)3 is extremely slow and competes with the side reaction of fluoride replacement by a water molecule on the nickel center to form the [((tBu)PCP)Ni(H2O)](+) aquo species. Finally, density functional theory analysis of the solvation process through a discrete + continuum model has been accomplished, at the M06//6-31+G(d,p) level of theory, to support the mechanistic hypothesis.

  12. FLUORIDE REMOVAL BY ADSORPTION ON THERMALLY ...

    African Journals Online (AJOL)

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    is strong correlation between fluoride removal capacity and gibbsite content of the soil. From this .... obtained from market were tested in the same experiments. The soil ... prepared from this stock solution by dilution with distilled water. In order ...

  13. Synthesis and Anion Recognition of Novel Molecular Tweezer Receptors Based on Carbonyl Thiosemicarbazide for Fluoride Ions

    Institute of Scientific and Technical Information of China (English)

    WEI,Wei; ZHANG,You-Ming; WEI,Tai-Bao

    2008-01-01

    Three title compounds have been designed and synthesized in high yields as novel anion receptors, which show a higher selectivity for F- than other halide ions. The binding properties for fluoride ions of the receptors have been examined by UV-Vis and 1H NMR spectroscopy, indicating that a 1 : 1 stoichiometry complex is formed between the receptors and fluoride ions through hydrogen bonding interactions in DMSO solution. In addition, because these receptors have more binding points, they have better binding properties for anions than the molecular tweezer receptors based on thiourea we reported last time.

  14. New Neutral Receptors for Fluoride Based on Calix[4]arene Bearing Thiourea and Amide

    Institute of Scientific and Technical Information of China (English)

    刘顺英; 徐括喜; 何永炳; 秦海娟; 孟令芝

    2005-01-01

    Two-armed neutral anion receptors (4,5), calix[4]arenes beating thiourea and amide binding sites, were prepared and examined their anion-binding ability by the UV-vis spectra. The results of non-linear curve fitting and Job plot indicate that 4 or 5 forms 1:1 stoichiometry complex with fluoride by hydrogen bonding interactions. Receptors 4 and 5 have an excellent selectivity for fluoride but have no binding ability with acetate, dihydrogen phosphate and the halogen anions (Cl-,Br-,I-).

  15. Materials processing apparatus development for fluoride glass

    Science.gov (United States)

    Smith, Guy A.; Kosten, Sue; Workman, Gary L.

    1994-01-01

    Fluoride glasses have great potential for optical fiber communications due to the high transmittance when no microcrystallites occur during drawing operations. This work has developed apparatus to test the occurrence of microcrystallites during recrystallization in reduced gravity on the KC-135. The apparatus allows fluoride glass fiber, such as ZBLAN, to be melted and recrystallized during both the low and high g portions the parabolic flight.

  16. Topical laser application enhances enamel fluoride uptake and tribological properties.

    Science.gov (United States)

    Jeng, Y-R; Lin, T-T; Huang, J-S; Peng, S-R; Shieh, D-B

    2013-07-01

    Topical fluoride treatment prevents dental caries. However, the resulting calcium-fluoride-like deposits are soft and have poor wear resistance; therefore, frequent treatment is required. Lasers quickly heat surfaces and can be made portable and suitable for oral remedies. We examined the morphology, nanohardness, elastic modulus, nanowear, and fluoride uptake of fluoride-treated enamel followed by CO2 laser irradiation for 5 and 10 sec, respectively. We found that laser treatments significantly increased the mechanical properties of the calcium-fluoride-like deposits. The wear resistance of the calcium-fluoride-like deposits improved about 34% after laser irradiation for 5 sec and about 40% following irradiation for 10 sec. We also found that laser treatments increased fluoride uptake by at least 23%. Overall, laser treatment significantly improved fluoride incorporation into dental tissue and the wear resistance of the protective calcium-fluoride layer.

  17. Analysis of fluoride concentration in solutions prepared at dispensing pharmacies

    Directory of Open Access Journals (Sweden)

    Eduardo Pizzatto

    2011-07-01

    Full Text Available Introduction: Fluoride plays an important role in oral health promotion and is considered important in dental caries prevention both in children and adults. Fluoride is widely used at high-risk conditions of caries, when the use of fluoride-containing mouthwashes is recommended, considering that fluoride itself reduces the risk of dental caries. Objective: To evaluate the fluoride concentration in solutions prepared at different dispensing pharmacies in the city of Curitiba – PR, Brazil. Material and methods: The analysis of fluoride concentration was preformed through Ion Chromatography method (DIONEX. Results: The results obtained through this analysis showed that all solutions presented fluoride concentration above that required in the dentist’s prescription, varying between 5.48% and 24.02% more fluoride, at absolute concentration. Conclusion: This finding highlights the increasing risk of fluoride acute intoxication in cases of accidental ingestion of the solution.

  18. Fluoride release and uptake capacities of fluoride-releasing restorative materials.

    Science.gov (United States)

    Attar, Nuray; Turgut, Melek D

    2003-01-01

    Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount fluoride release of these materials is still uncertain. This study investigated the fluoride release and uptake characteristics of four flowable resin composites (Heliomolar Flow, Tetric Flow, Wave, Perma Flo), one flowable compomer (Dyract flow), one conventional glass ionomer cement mixed with two different powder/liquid ratios (ChemFlex Syringeable and ChemFlex Condensable), one packable resin composite (SureFil), one ion-releasing composite (Ariston pHc) and one resin-modified glass ionomer cement (Vitremer). Seven discs (6-mm diameter and 1.5-mm height) were prepared for each material. Each disc was immersed in 3.5 ml of deionized water within a plastic vial and stored at 37 degrees C. The deionized water was changed every 24 hours and the release of fluoride was measured for 30 days. At the end of this period, the samples were recharged with 2 ml of 1.23% acidulated phosphate fluoride (APF) gel for four minutes. Then, all samples were reassessed for an additional 10 days. The fluoride release of all samples was measured with a specific fluoride electrode and an ionanalyzer. Statistical analyses were conducted using two-way repeated measure ANOVA and Duncan's multiple range tests. For all tested materials, the greatest fluoride release was observed after the first day of the study (p0.05). Ariston pHc released the highest amount of fluoride, followed by ChemFlex Syringeable, Vitremer and ChemFlex Condensable. There were statistically significant differences among these materials (p<0.05). Fluoride release of all materials were significantly increased after the first day following refluoridation and Ariston pHc released the greatest among all materials (p<0.01). At the end of two days of refluoridation, the fluoride release rate for each material dropped quickly and stabilized within three days.

  19. The effective use of fluorides in public health.

    Science.gov (United States)

    Jones, Sheila; Burt, Brian A.; Petersen, Poul Erik; Lennon, Michael A.

    2005-01-01

    Dental caries remain a public health problem for many developing countries and for underprivileged populations in developed countries. This paper outlines the historical development of public health approaches to the use of fluoride and comments on their effectiveness. Early research and development was concerned with waterborne fluorides, both naturally occurring and added, and their effects on the prevalence and incidence of dental caries and dental fluorosis. In the latter half of the 20th century, the focus of research was on fluoride toothpastes and mouth rinses. More recently, systematic reviews summarizing these extensive databases have indicated that water fluoridation and fluoride toothpastes both substantially reduce the prevalence and incidence of dental caries. We present four case studies that illustrate the use of fluoride in modern public health practice, focusing on: recent water fluoridation schemes in California, USA; salt fluoridation in Jamaica; milk fluoridation in Chile; and the development of "affordable" fluoride toothpastes in Indonesia. Common themes are the concern to reduce demands for compliance with fluoride regimes that rely upon action by individuals and their families, and the issue of cost. We recommend that a community should use no more than one systemic fluoride (i.e. water or salt or milk fluoridation) combined with the use of fluoride toothpastes, and that the prevalence of dental fluorosis should be monitored in order to detect increases in or higher-than-acceptable levels. PMID:16211158

  20. Well Waters Fluoride in Enugu, Nigeria

    Directory of Open Access Journals (Sweden)

    ISI Ogbu

    2012-03-01

    Full Text Available Abnormal fluoride levels in drinking water have been associated with adverse health effects. To determine the fluoride content of well waters in Enugu, southeastern Nigeria, water samples from 50 artisan wells chosen by multistage sampling procedure from the 5 zones of Enugu municipality were analyzed in duplicates for their fluoride content. The zonal mean values were 0.60, 0.70, 0.62, 0.62, and 0.63 mg/L for Abakpa Nike, Achara Layout, Obiagu/ Ogui, Trans Ekulu and Uwani, respectively (p<0.05. The mean value for the whole city was 0.63 mg/L. Although, the mean level of fluoride recorded in this study is currently within safe limits (1.5 mg/L, WHO 2011, it is important to monitor continuously the fluoride content of well waters in the municipality in view of the increasing industrial activities going on in the city and heavy reliance on well water for domestic purposes and the widespread use of consumer products containing fluoride.