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Sample records for alkaline earth ion

  1. Controlled charge exchange between alkaline earth metals and their ions

    NASA Astrophysics Data System (ADS)

    Gacesa, Marko; Côté, Robin

    2015-05-01

    We theoretically investigate the prospects of realizing controlled charge exchange via magnetic Feshbach resonances in cold and ultracold collisions of atoms and ions. In particular, we focus on near-resonant charge exchange in heteroisotopic combinations of alkaline earth metals, such as 9Be++10 Be<-->9 Be+10Be+ , which exhibit favorable electronic and hyperfine structure. The quantum scattering calculations are performed for a range of initial states and experimentally attainable magnetic fields in standard coupled-channel Feshbach projection formalism, where higher-order corrections such as the mass-polarization term are explicitely included. In addition, we predict a number of magnetic Feshbach resonances for different heteronuclear isotopic combinations of the listed and related alkaline earth elements. Our results imply that near-resonant charge-exchange could be used to realize atom-ion quantum gates, as well as controlled charge transfer in optically trapped cold quantum gases. This work is partially supported by ARO.

  2. Structure and ionic diffusion of alkaline-earth ions in mixed cation glasses

    SciTech Connect

    Konstantinou, Konstantinos; Sushko, Petr; Duffy, Dorothy M.

    2015-08-15

    A series of mixed cation silicate glasses of the composition A2O – 2MO – 4SiO2, with A=Li,Na,K and M=Ca,Sr,Ba has been investigated by means of molecular dynamics simulations in order to understand the effect of the nature of the cations on the mobility of the alkaline-earth ions within the glass network. The size of the alkaline-earth cation was found to affect the inter-atomic distances, the coordination number distributions and the bond angle distributions , whereas the medium-range order was almost unaffected by the type of the cation. All the alkaline-earth cations contribute to lower vibrational frequencies but it is observed that that there is a shift to smaller frequencies and the vibrational density of states distribution gets narrower as the size of the alkaline-earth increases. The results from our modeling for the ionic diffusion of the alkaline-earth cations are in a qualitative agreement with the experimental observations in that there is a distinct correlation between the activation energy for diffusion of alkaline earth-ions and the cation radii ratio. An asymmetrical linear behavior in the diffusion activation energy with increasing size difference is observed. The results can be described on the basis of a theoretical model that relates the diffusion activation energy to the electrostatic interactions of the cations with the oxygens and the elastic deformation of the silicate network.

  3. Ab initio calculations on the positive ions of the alkaline-earth oxides, fluorides, and hydroxides

    NASA Technical Reports Server (NTRS)

    Partridge, H.; Langhoff, S. R.; Bauschlicher, C. W., Jr.

    1986-01-01

    Theoretical dissociation energies are presented for the alkaline-earth fluoride, hydroxide, and oxide positive ions that are considered to be accurate to 0.1-0.2 eV. The r(e) for the positive ions are found to be consistently shorter than the corresponding neutrals by 0.07 + or -0.02 A. The bonding in the ground states is demonstrated to be of predominantly M + 2 X - character. The a 3 Pi and A 1 Pi are found to lie considerably above the X 1 Sigma + ground states of the alkaline-earth fluoride and hydroxide positive ions. The overall agreement of the theoretical ionization potentials with the available experimental appearance potentials is satisfactory; these values should represent the most accurate and consistent set available.

  4. Energetics of alkali and alkaline earth ion-exchanged zeolite A

    DOE PAGES

    Sun, Hui; Wu, Di; Liu, Kefeng; Guo, Xiaofeng; Navrotsky, Alexandra

    2016-06-30

    Alkali and alkaline earth ion-exchanged zeolite A samples were synthesized in aqueous exchange media. They were thoroughly studied by powder X-ray diffraction (XRD), electron microprobe (EMPA), thermogravimetric analysis and differential scanning calorimetry (TG-DSC), and high temperature oxide melt solution calorimetry. The hydration energetics and enthalpies of formation of these zeolite A materials from constituent oxides were determined. Specifically, the hydration level of zeolite A has a linear dependence on the average ionic potential (Z/r) of the cation, from 0.894 (Rb-A) to 1.317 per TO2 (Mg-A). The formation enthalpies from oxides (25 °C) range from –93.71 ± 1.77 (K-A) to –48.02more » ± 1.85 kJ/mol per TO2 (Li-A) for hydrated alkali ion-exchanged zeolite A, and from –47.99 ± 1.20 (Ba-A) to –26.41 ± 1.71 kJ/mol per TO2 (Mg-A) for hydrated alkaline earth ion-exchanged zeolite A. As a result, the formation enthalpy from oxides generally becomes less exothermic as Z/r increases, but a distinct difference in slope is observed between the alkali and the alkaline earth series.« less

  5. Isotope fractionation in surface ionization ion source of alkaline-earth iodides

    SciTech Connect

    Suzuki, T.; Kanzaki, C.; Nomura, M.; Fujii, Y.

    2012-02-15

    The relationship between the isotope fractionation of alkaline-earth elements in the surface ionization ion source and the evaporation filament current, i.e., filament temperature, was studied. It was confirmed that the isotope fractionation depends on the evaporation filament temperature; the isotope fractionation in the case of higher temperature of filament becomes larger. The ionization and evaporation process in the surface ionization ion source was discussed, and it was concluded that the isotope fractionation is suppressed by setting at the lower temperature of evaporation filament because the dissociations are inhibited on the evaporation filament.

  6. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals

    PubMed Central

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-01-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: [3]Li+, [3]Na+, [4]K+, [4]Rb+, [6]Cs+, [3]Be2+, [4]Mg2+, [6]Ca2+, [6]Sr2+ and [6]Ba2+, but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of [6]Na+, the ratio U eq(Na)/U eq(bonded anions) is partially correlated with 〈[6]Na+—O2−〉 (R 2 = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li+ in [4]- and [6]-coordination, Na+ in [4]- and [6

  7. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals.

    PubMed

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-08-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with 〈([6])Na(+)-O(2-)〉 (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in

  8. Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals.

    PubMed

    Gagné, Olivier Charles; Hawthorne, Frank Christopher

    2016-08-01

    Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38 594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24 487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with 〈([6])Na(+)-O(2-)〉 (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Three interesting coordination compounds based on metalloligand and alkaline-earth ions: Syntheses, structures, thermal behaviors and magnetic property

    NASA Astrophysics Data System (ADS)

    Zhou, Qiang; Qian, Jun; Zhang, Chi

    2016-09-01

    Based on metalloligand LCu ([Cu(2,4-pydca)2]2-, 2,4-pydca2- = pyridine-2,4-dicarboxylate) and alkaline-earth ions (Ca2+, Sr2+, and Ba2+), three interesting coordination compounds, [Ca(H2O)7][LCu·H2O]·H2O (1), {Sr[LCu·H2O]·4H2O}n (2), and {Ba[LCu·H2O]·8H2O}n (3), have been synthesized and well-characterized by elemental analysis, infrared spectroscopy, thermogravimetric and single-crystal X-ray diffraction analysis. X-ray crystallographic studies reveal that 1 features a discrete 0D coordination compound, while 2 and 3 exhibit the 2D network and 1D chain structures, respectively. Compound 2 is constructed from {LCu}2 dimers connected with {Sr2} units, which is fabricated by two Sr2+ ions bridged via two μ2-O bridges, while compound 3 is formed by 1D {Ba}n chain linked with metalloligands LCu and exhibits an interesting sandwich like chain structure. It is noted that the coordination numbers of alkaline-earth ions are in positive correlation with their radiuses. Moreover, the magnetic property of compound 2 has been studied.

  11. EPR and optical absorption studies of Cu{sup 2+} ions in alkaline earth alumino borate glasses

    SciTech Connect

    Ramesh Kumar, V.; Rao, J.L. . E-mail: jlrao46@yahoo.co.in; Gopal, N.O.

    2005-08-11

    Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu{sup 2+} ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ({chi}) was calculated at different temperatures (T) and from the 1/{chi}-T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g} transition of the Cu{sup 2+} ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane {sigma} bonding between Cu{sup 2+} ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap (E {sub opt}) and the Urbach energy ({delta}E) are evaluated. The variation in E {sub opt} and {delta}E is explained based on the number of defect centers in the glass.

  12. Physical and optical absorption studies of Fe3+ - ions doped lithium borate glasses containing certain alkaline earths

    NASA Astrophysics Data System (ADS)

    Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.

    2016-05-01

    Iron ion doped lithium borate glasses with the composition 15RO-25Li2O-59B2O3-1Fe2O3 (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to 6A1g(S) → 4Eg (G) of Fe3+ ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties is discussed.

  13. Synthesis of a new family of ionophores based on aluminum-dipyrrin complexes (ALDIPYs) and their strong recognition of alkaline earth ions.

    PubMed

    Saikawa, Makoto; Daicho, Manami; Nakamura, Takashi; Uchida, Junji; Yamamura, Masaki; Nabeshima, Tatsuya

    2016-03-14

    Mononuclear and dinuclear aluminum-dipyrrin complexes (ALDIPYs) were synthesized as a new family of ionophores. They exhibited colorimetric and fluorometric responses to alkaline earth ions in an aqueous mixed solvent. The strong recognition was achieved via multipoint interactions with the oxygen atoms appropriately incorporated into the ligand framework. PMID:26935409

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

    PubMed

    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. Mass Spectrometric Observation of Doubly Charged Alkaline-Earth Argon Ions.

    PubMed

    Hattendorf, Bodo; Gusmini, Bianca; Dorta, Ladina; Houk, Robert S; Günther, Detlef

    2016-09-01

    Doubly charged diatomic ions MAr(2+) where M=Mg, Ca, Sr or Ba have been observed by mass spectrometry with an inductively coupled plasma ion source. Abundance ratios are quite high, 0.1 % for MgAr(2+) , 0.4 % for CaAr(2+) , 0.2 % for SrAr(2+) and 0.1 % for BaAr(2+) relative to the corresponding doubly charged atomic ions M(2+) . It is assumed that these molecular ions are formed through reactions of the doubly charged metal ions with neutral argon atoms within the ion source. Bond dissociation energies (D0 ) were calculated and agree well with previously published values. The abundance ratios MAr(+) /M(+) and MAr(2+) /M(2+) generally follow the predicted bond dissociation energies with the exception of MgAr(2+) . Mg(2+) should form the strongest bond with Ar [D0 (MgAr(2+) )=124 to 130 kJ mol(-1) ] but its relative abundance is similar to that of the weakest bound BaAr(2+) (D0 =34 to 42 kJ mol(-1) ). The relative abundances of the various MAr(2+) ions are higher than those expected from an argon plasma at T=6000 K, indicating that collisions during ion extraction reduce the abundance of the MAr(2+) ions relative to the composition in the source. The corresponding singly charged MAr(+) ions are also observed but occur at about three orders of magnitude lower intensity than MAr(2+) . PMID:27252087

  16. Hyperpolarizabilities of alkaline-earth metal ions Be+, Mg+, and Ca+

    NASA Astrophysics Data System (ADS)

    Yin, Dong; Zhang, Yong-Hui; Li, Cheng-Bin; Gao, Ke-Lin; Shi, Ting-Yun

    2016-09-01

    The knowledge of the hyperpolarizabilities of atoms and ions is helpful for the analysis of the high order effects of the frequency shifts in precision spectroscopy experiments. Liu et al. [Phys. Rev. Lett. 114, 223001 (2015)] proposed to establish all-optical trapped ion clocks using laser at the magic wavelength for clock transition. To evaluate the high-order frequency shifts in this new scheme of optical clocks, hyperpolarizabilities are needed, but absent. Using the finite field method based on the B-spline basis set and model potentials, we calculated the electric-field-dependent energy shifts of the ground and low-lying excited states in Be+, Mg+, and Ca+ in the field strength range of 0.0-6×10-5 a.u.. The scalar and tensor polarizabilities ( α 0, α 2) and hyperpolarizabilities ( γ 0, γ 2, γ 4) were deduced. The results of the hyperpolarizabilities for Be+ showed good agreement with the values in literature, implying that the present method can be applied for the effective estimation of the atomic hyperpolarizabilities, which are rarely reported but needed in experiments. The feasibility of optical trapping of Ca+ is discussed, and the contributions of hyperpolarizabilities to the transition frequency shift for Ca+ in the optical dipole trap are estimated using quasi-electrostatic approximation.

  17. Properties of alkali-metal atoms and alkaline-earth-metal ions for an accurate estimate of their long-range interactions

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Nandy, D. K.; Arora, Bindiya; Sahoo, B. K.

    2015-01-01

    Accurate knowledge of interaction potentials among the alkali-metal atoms and alkaline-earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali-metal atoms with the Ca+, Ba+, Sr+, and Ra+ alkaline-earth ions systematically, which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation R . Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above-mentioned systems, which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random-phase approximation. We also compare our estimated polarizabilities with the other available theoretical and experimental results to verify accuracies in our calculations. In addition, we also evaluate the lifetimes of the first two low-lying states of the ions using the above matrix elements. Graphical representations of the dispersion coefficients versus R are given among all the alkaline ions with Rb.

  18. A new N-hydroxyethyliminodiacetic acid modified core-shell silica phase for chelation ion chromatography of alkaline earth, transition and rare earth elements.

    PubMed

    McGillicuddy, Nicola; Nesterenko, Ekaterina P; Nesterenko, Pavel N; Stack, Elaine M; Omamogho, Jesse O; Glennon, Jeremy D; Paull, Brett

    2013-12-20

    Bare core-shell silica (1.7μm) has been modified with iminodiacetic acid functional groups via standard silane chemistry, forming a new N-hydroxyethyliminodiacetic acid (HEIDA) functionalised core-shell stationary phase. The column was applied in high-performance chelation ion chromatography and evaluated for the retention of alkaline earth, transition and heavy metal cations. The influence of nitric acid eluent concentration, addition of complexing agent dipicolinic acid, eluent pH and column temperature on the column performance was investigated. The efficiencies obtained for transition and heavy metal cations (and resultant separations) were comparable or better than those previously obtained for alternative fully porous silica based chelation stationary phases, and a similarly modified monolithic silica column, ranging from ∼15 to 56μm HETP. Increasing the ionic strength of the eluent with the addition of KNO3 (0.75M) and increasing the column temperature (70°C) facilitated the isocratic separation of a mixture of 14 lanthanides and yttrium in under 12min, with HETP averaging 18μm (7μm for Ce(III)).

  19. Photoelastic response of alkaline earth aluminosilicate glasses.

    PubMed

    Smedskjaer, Morten M; Saxton, Scott A; Ellison, Adam J; Mauro, John C

    2012-02-01

    Understanding the structural origins of the photoelastic response in oxide glasses is important for discovering new families of zero-stress optic glasses and for developing a predictive physical model. In this Letter, we have investigated the composition dependence of the stress optic coefficient C of 32 sodium aluminosilicate glasses with different types of alkaline earth oxides (MgO, CaO, SrO, and BaO). We find that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkaline earth-oxygen bond metallicity. High bond metallicity is required to allow bonds to be distorted along both the bonding direction and perpendicular to it. These findings are valuable for understanding the photoelastic response of oxide glasses.

  20. Alkaline earth filled nickel skutterudite antimonide thermoelectrics

    DOEpatents

    Singh, David Joseph

    2013-07-16

    A thermoelectric material including a body centered cubic filled skutterudite having the formula A.sub.xFe.sub.yNi.sub.zSb.sub.12, where A is an alkaline earth element, x is no more than approximately 1.0, and the sum of y and z is approximately equal to 4.0. The alkaline earth element includes guest atoms selected from the group consisting of Be, Mb, Ca, Sr, Ba, Ra and combinations thereof. The filled skutterudite is shown to have properties suitable for a wide variety of thermoelectric applications.

  1. Dynamical simulations of superionicity in alkaline-earth halides

    NASA Astrophysics Data System (ADS)

    Zhou, L. X.; Hardy, J. R.; Cao, H. Z.

    1996-04-01

    Superionicity in alkaline-earth halides CaF 2, SrF 2 and BaF 2 has been studied by molecular dynamical simulations using Gordon-Kim potentials. These dynamical simulations employ a novel technique to monitor the motion of ions which clearly demonstrates the nature of the superionic phases in these crystals. While in the superionic phase, the Ca 2+, Ba 2+, and Sr 2+ ions maintain ideal lattice positions, the F - ions flow between them in a correlated linear manner closely related to that proposed previously by Boyer.

  2. Alkaline and alkaline earth metal phosphate halides and phosphors

    SciTech Connect

    Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

    2012-11-13

    Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

  3. The alkaline earth intercalates of molybdenum disulfide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

    1975-01-01

    Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

  4. Alkaline earth cation extraction from acid solution

    DOEpatents

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  5. {sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    SciTech Connect

    Arevalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernandez-Maldonado, Arturo J.

    2012-07-15

    The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

  6. Forward and reverse ion-exchange kinetics for some alkali and alkaline earth metal ions on amorphous zirconium(IV) aluminophosphate

    SciTech Connect

    Varshney, K.G.; Pandith, A.H.

    1999-10-26

    The Nernst-Planck equations are applied to study the ion-exchange kinetics on the surface of zirconium(IV) aluminophosphate for Li{sup +}/H{sup +}, Na{sup +}/H{sup +}, K{sup +}/H{sup +}, Mg{sup 2+}/H{sup +}, Ca{sup 2+}/H{sup +}, and Sr{sup 2+}/H{sup +} exchanges in the forward and reverse directions under the conditions favoring particle diffusion. On the basis of these studies, various physical parameters such as the self-diffusion coefficient (D{sub 0}), the energy of activation (E{sub a}), and the entropy of activation ({Delta}S*) have been determined and a correlation has been made of these parameters with the ion-exchange characteristics of the material. The study gives an insight into the ion-exchange processes going on in the exchanger phase and its potential use in metal ion separations.

  7. Recent advances in Rydberg physics using alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Dunning, F. B.; Killian, T. C.; Yoshida, S.; Burgdörfer, J.

    2016-06-01

    In this brief review, the opportunities that the alkaline-earth elements offer for studying new aspects of Rydberg physics are discussed. For example, the bosonic alkaline-earth isotopes have zero nuclear spin which eliminates many of the complexities present in alkali Rydberg atoms, permitting simpler and more direct comparison between theory and experiment. The presence of two valence electrons allows the production of singlet and triplet Rydberg states that can exhibit a variety of attractive or repulsive interactions. The availability of weak intercombination lines is advantageous for laser cooling and for applications such as Rydberg dressing. Excitation of one electron to a Rydberg state leaves behind an optically active core ion allowing, for high-L states, the optical imaging of Rydberg atoms and their (spatial) manipulation using light scattering. The second valence electron offers the possibility of engineering long-lived doubly excited states such as planetary atoms. Recent advances in both theory and experiment are highlighted together with a number of possible directions for the future.

  8. Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

    2016-09-01

    Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

  9. Method of increasing the sulfation capacity of alkaline earth sorbents

    DOEpatents

    Shearer, J.A.; Turner, C.B.; Johnson, I.

    1980-03-13

    A system and method for increasing the sulfation capacity of alkaline earth carbonates to scrub sulfur dioxide produced during the fluidized bed combustion of coal in which partially sulfated alkaline earth carbonates are hydrated in a fluidized bed to crack the sulfate coating and convert the alkaline earth oxide to the hydroxide. Subsequent dehydration of the sulfate-hydroxide to a sulfate-oxide particle produces particles having larger pore size, increased porosity, decreased grain size and additional sulfation capacity. A continuous process is disclosed.

  10. Method of increasing the sulfation capacity of alkaline earth sorbents

    DOEpatents

    Shearer, John A.; Turner, Clarence B.; Johnson, Irving

    1982-01-01

    A system and method for increasing the sulfation capacity of alkaline earth carbonates to scrub sulfur dioxide produced during the fluidized bed combustion of coal in which partially sulfated alkaline earth carbonates are hydrated in a fluidized bed to crack the sulfate coating and convert the alkaline earth oxide to the hydroxide. Subsequent dehydration of the sulfate-hydroxide to a sulfate-oxide particle produces particles having larger pore size, increased porosity, decreased grain size and additional sulfation capacity. A continuous process is disclosed.

  11. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    PubMed

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology. PMID:26891039

  12. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    SciTech Connect

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-15

    The effect of partial substitution of alkaline earth (AE) ions, Sr{sup 2+} and Ca{sup 2+}, for the rare earth (RE) ions, La{sup 3+}, Ce{sup 3+}, Pr{sup 3+}, and Sm{sup 3+}, on the physical properties of REVO{sub 4} compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO{sub 4}-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H{sub 2} fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode. - Graphical abstract: Coulometric titration isotherms for ({open_square}) LaVO{sub 4}, ( White-Circle ) PrVO{sub 4}, ( Lozenge ) CeVO{sub 4}, ( Black-Up-Pointing-Triangle ) Ce{sub 0.7}Sr{sub 0.3}VO{sub 3.85}, and ( Black-Square ) Ce{sub 0.7}Ca{sub 0.3}VO{sub 3.85}, at 973 K. Highlights: Black-Right-Pointing-Pointer Infiltration procedures were used to prepare SOFC anodes from various vanadates. Black-Right-Pointing-Pointer Doping of Alkaline Earth to Rare Earth Vanadates showed to improve conductivity and chemical stability. Black-Right-Pointing-Pointer Alkaline Earth Doped Rare Earth Vanadates-YSZ composites showed conductivities as high as 5 S cm{sup -1} at 973 K. Black-Right-Pointing-Pointer As with other ceramic anodes, the addition of a catalyst was required to achieve low anode impedance.

  13. Thermoelectric Properties of Barium Plumbate Doped by Alkaline Earth Oxides

    NASA Astrophysics Data System (ADS)

    Eufrasio, Andreza; Bhatta, Rudra; Pegg, Ian; Dutta, Biprodas

    Ceramic oxides are now being considered as a new class of thermoelectric materials because of their high stability at elevated temperatures. Such materials are especially suitable for use as prospective thermoelectric power generators because high temperatures are encountered in such operations. The present investigation uses barium plumbate (BaPbO3) as the starting material, the thermoelectric properties of which have been altered by judicious cation substitutions. BaPbO3 is known to exhibit metallic properties which may turn semiconducting as a result of compositional changes without precipitating a separate phase and/or altering the basic perovskite crystal structure. Perovskite structures are noted for their large interstitial spaces which can accommodate a large variety of ``impurity'' ions. As BaPbO3 has high electrical conductivity, σ = 2.43x105Ω-1 m-1 at room temperature, its thermopower, S, is relatively low, 23 μV/K, as expected. With a thermal conductivity, k, of 4.83Wm-1K-1, the figure of merit (ZT =S2 σ Tk-1) of BaPbO3 is only 0.01 at T = 300K. The objective of this investigation is to study the variation of thermoelectric properties of BaPbO3 as Ba and Pb ions are systematically substituted by alkaline earth ions.

  14. Coordination Chemistry of Alkali and Alkaline-Earth Cations with Macrocyclic Ligands.

    ERIC Educational Resources Information Center

    Dietrich, Bernard

    1985-01-01

    Discusses: (l) alkali and alkaline-earth cations in biology (considering naturally occurring lonophores, their X-ray structures, and physiochemical studies); (2) synthetic complexing agents for groups IA and IIA; and (3) ion transport across membranes (examining neutral macrobicyclic ligands as metal cation carriers, transport by anionic carriers,…

  15. Phosphate glass electrode with good selectivity for alkaline-earth cations

    USGS Publications Warehouse

    Truesdell, A.H.; Pommer, A.M.

    1963-01-01

    A phosphate glass has been found to have a significant electrode specificity toward alkaline-earth ions. The order of selectivity is 2H + > Ba++ > Sr++ > Ca++ > 2K+ > 2Na+ > Mg++. Exchange properties are discussed in relation to possible structure. Its use to determine activity of Ca++ in natural systems containing Mg++ is suggested.

  16. A set of alkali and alkaline-earth coordination polymers based on the ligand 2-(1H-benzotriazol-1-yl) acetic acid: Effects the radius of metal ions on structures and properties

    SciTech Connect

    Wang, Jin-Hua; Tang, Gui-Mei; Qin, Ting-Xiao; Yan, Shi-Chen; Wang, Yong-Tao; Cui, Yue-Zhi; Weng Ng, Seik

    2014-11-15

    Four new metal coordination complexes, namely, [Na(BTA)]{sub n} (1), [K{sub 2}(BTA){sub 2}(μ{sub 2}-H{sub 2}O)]{sub n} (2), and [M(BTA){sub 2}(H{sub 2}O){sub 2}]{sub n} (M=Ca(II) and Sr(II) for 3 and 4, respectively) [BTA=2-(1H-benzotriazol-1-yl) acetic anion], have been obtained under hydrothermal condition, by reacting the different alkali and alkaline-earth metal hydroxides with HBTA. Complexes 1–4 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes display low-dimensional features displaying various two-dimensional (2D) and one-dimensional (1D) coordination motifs. Complex 1 displays a 2D layer with the thickness of 1.5 nm and possesses a topologic structure of a 11 nodal net with Schläfli symbol of (3{sup 18}). Complex 2 also shows a thick 2D sheet and its topologic structure is a 9 nodes with Schläfli symbol of (3{sup 11}×4{sup 2}). Complexes 3 and 4 possess a 1D linear chain and further stack via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 1–4, which display violet photoluminescence. Additionally, ferroelectric, dielectric and nonlinear optic (NLO) second-harmonic generation (SHG) properties of 2 are discussed in detail. - Graphical abstract: A set of alkali and alkaline-earth metal coordination polymers were hydrothermally synthesized by 2-(1H-benzotriazol-1-yl)acetic acid, displaying interesting topologic motifs from two-dimension to one-dimension and specific physical properties. - Highlights: • Alkali and alkaline-earth metal coordination polymers have been obtained. • The ligand 2-(1H-benzotriazol-1-yl)acetic acid has been adopted. • The two-dimensional and one

  17. The pressure induced B1-B2 phase transition of alkaline halides and alkaline earth chalcogenides. A first principles investigation

    SciTech Connect

    Potzel, Oliver; Taubmann, Gerhard

    2011-05-15

    In this work, we considered the pressure induced B1-B2 phase transition of AB compounds. The DFT calculations were carried out for 11 alkaline halides, 11 alkaline earth chalcogenides and the lanthanide pnictide CeP. For both the B1 and the B2 structures of each compound, the energy was calculated as a function of the cell volume. The transition pressure, the bulk moduli and their pressure derivatives were obtained from the corresponding equations of state. The transition path of the Buerger mechanism was described using roots of the transition matrix. We correlated the computed enthalpies of activation to some structure defining properties of the compounds. A fair correlation to Pearsons hardness of the ions was observed. -- Graphical abstract: Pressure induced transition from the B1 structure (left) via the transition state (middle) to the B2 structure (right). Display Omitted highlights: > Pressure induced phase transitions in AB compounds were considered. > Alkaline halides and alkaline earth chalcogenides were treated. > DFT calculations with periodic boundary conditions were applied. > The transition path was described by roots of the transition matrix. > The enthalpy of activation was calculated for numerous compounds.

  18. Instability of some divalent rare earth ions and photochromic effect

    NASA Astrophysics Data System (ADS)

    Egranov, A. V.; Sizova, T. Yu.; Shendrik, R. Yu.; Smirnova, N. A.

    2016-03-01

    It was shown that the divalent rare earth ions (La, Ce, Gd, Tb, Lu, and Y) in cubic sites in alkaline earth fluorides are unstable with respect to electron autodetachment since its d1(eg) ground state is located in the conduction band which is consistent with the general tendency of these ions in various compounds. The localization of doubly degenerate d1(eg) level in the conduction band creates a configuration instability around the divalent rare earth ion that leading to the formation of anion vacancy in the nearest neighborhood, as was reported in the previous paper [A. Egranov, T. Sizova, Configurational instability at the excited impurity ions in alkaline earth fluorites, J. Phys. Chem. Solids 74 (2013) 530-534]. Thus, the formation of the stable divalent ions as La, Ce, Gd, Tb, Lu, and Y (PC+ centers) in CaF2 and SrF2 crystals during x-ray irradiation occurs via the formation of charged anion vacancies near divalent ions (Re2+va), which lower the ground state of the divalent ion relative to the conductivity band. Photochromic effect occurs under thermally or optically stimulated electron transition from the divalent rare earth ion to the neighboring anion vacancy and reverse under ultraviolet light irradiation. It is shown that the optical absorption of the PC+ centers due to d → d and d → f transitions of the divalent rare-earth ion.

  19. Supramolecular recognition control of polyethylene glycol modified N-doped graphene quantum dots: tunable selectivity for alkali and alkaline-earth metal ions.

    PubMed

    Yang, Siwei; Sun, Jing; Zhu, Chong; He, Peng; Peng, Zheng; Ding, Guqiao

    2016-02-01

    The graphene quantum dot based fluorescent probe community needs unambiguous evidence about the control on the ion selectivity. In this paper, polyethylene glycol modified N-doped graphene quantum dots (PN-GQDs) were synthesized by alkylation reaction between graphene quantum dots and organic halides. We demonstrate the tunable selectivity and sensitivity by controlling the supramolecular recognition through the length and the end group size of the polyether chain on PN-GQDs. The relationship formulae between the selectivity/detection limit and polyether chains are experimentally deduced. The polyether chain length determines the interaction between the PN-GQDs and ions with different ratios of charge to radius, which in turn leads to a good selectivity control. Meanwhile the detection limit shows an exponential growth with the size of end groups of the polyether chain. The PN-GQDs can be used as ultrasensitive and selective fluorescent probes for Li(+), Na(+), K(+), Mg(2+), Ca(2+) and Sr(2+), respectively. PMID:26730814

  20. Interaction of adenylic acid with alkaline earth metal ions in the crystalline solid and aqueous solution. Evidence for the sugar C'2-endo/anti, C'3-endo/anti and C'4-exon/anti conformational changes.

    PubMed

    Tajmir-Riahi, H A

    1990-09-10

    The reaction of adenosine 5'-monophosphoric acid (H2-AMP) with the alkaline earth metal ions has been investigated in aqueous solution at neutral pH. The solid salts of Mg-AMP.5H2O, Ca-AMP.6H2O, Sr-AMP.7H2O and Ba-AMP.7H2O were isolated and characterized by Fourier transform infrared, 1H-NMR spectroscopy and X-ray powder diffraction measurements. Spectroscopic and other evidence showed that the Sr-AMP.7H2O and Ba-AMP.7H2O are isomorphous, whereas the Mg-AMP.5H2O and Ca-AMP.6H2O are not similar. The Mg2+ binding is through the N-7 (inner-sphere) and the phosphate group (outer-sphere via H2O), while the Ca2+ binds to the phosphate group (inner-sphere) and to the base N-7 site (outer-sphere through H2O). The Sr2+ and Ba2+ bind to H2O molecules, H-bonding to the N-7, N-1 and the phosphate group (outer-sphere). In aqueous solution, an equilibrium between the inner- and outer-sphere metal ion bindings can be established. The sugar moiety exhibited C'2-endo/anti conformation, in the free H2-AMP acid and the magnesium salt, C'3-endo/anti in the calcium salt and unusual C'4-exo/anti, in the strontium and barium salts.

  1. Kinetic approach to evaluate the energy and entropy of activation for the exchange of alkaline earth metal ions on tin(IV) tungstate cation exchanger

    SciTech Connect

    Varshney, K.G.; Khan, A.A.; Varshney, K.; Agrawal, S.

    1984-01-01

    A new approach based on the Nernst-Planck equations has been applied to study the reaction kinetics on the surface of tin(IV) tungstate for the Mg(II)-H(I), Ca(II)-H(I), Sr(II)-H(I) and Ba(II)-H(I) exchanges under the conditions favouring a particle diffusion phenomenon. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated which give some informations regarding the mechanism of ion-exchange on the surface of inorganic materials. 25 references, 3 figures, 3 tables.

  2. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  3. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  4. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  5. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  6. 40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Hydrated alkaline earth metal salts of... Specific Chemical Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. (a... hydrated alkaline earth metal salts of metalloid oxyanions (PMN P-94-1557) is subject to reporting...

  7. Theoretical study of the alkali and alkaline-earth monosulfides

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

    1988-01-01

    Ab initio calculations have been used to obtain accurate spectroscopic constants for the X2Pi and A2Sigma(+) states of the alkali sulfides and the X1Sigma(+), a3Pi, and A1Pi states of the alkaline-earth sulfides. In contrast to the alkali oxides, the alkali sulfides are found to have X2Pi ground states, due to the larger electrostatic interaction. Dissociation energies of 3.27 eV for BeS, 2.32 eV for MgS, 3.29 eV for CaS, and 3.41 eV for SrS have been obtained for the X1Sigma(+) states of the alkaline-earth sulfides, in good agreement with experimental results. Core correlation is shown to increase the Te values for the a3Pi and A1Pi states of MgS, CaS, and SrS.

  8. Thermal design of high temperature alkaline-earth vapor cells

    NASA Astrophysics Data System (ADS)

    Armstrong, Jordan L.; Lemke, Nathan D.; Martin, Kyle W.; Erickson, Christopher J.

    2016-03-01

    Europium doped calcium fluoride is a machinable and alkaline-earth resistant crystal that is suitable for constructing a calcium or strontium vapor cell. However, its heat capacity, emissivity, and high coefficient of thermal expansion make it challenging to achieve optically dense calcium vapors for laser spectroscopy on narrow linewidth transitions. We discuss a low size, weight and power heating package that is under development at the Air Force Research Laboratory.

  9. Steady-state superradiance with alkaline-earth-metal atoms

    SciTech Connect

    Meiser, D.; Holland, M. J.

    2010-03-15

    Alkaline-earth-metal-like atoms with ultranarrow transitions open the door to a new regime of cavity quantum electrodynamics. That regime is characterized by a critical photon number that is many orders of magnitude smaller than what can be achieved in conventional systems. We show that it is possible to achieve superradiance in steady state with such systems. We discuss the basic underlying mechanisms as well as the key experimental requirements.

  10. Ab Initio Thermochemistry and Elastic Properties of Alkaline Earth Hydrides

    NASA Astrophysics Data System (ADS)

    Hector, Louis, Jr.; Herbst, Jan; Wolf, Walter; Saxe, Paul

    2006-03-01

    In addition to comprising a scientifically interesting class of materials, the binary alkaline earth hydrides are important components of hydrogen sorption/desorption reactions. Of critical importance for predicting the thermodynamic stability of hydrides is the enthalpy of hydride formation, δH, which links the temperature and pressure of hydrogen sorption via the van't Hoff relation. We compare LDA and GGA predictions of the heats of formation and elastic properties of alkaline earth metals and their binary hydrides BeH2, MgH2, CaH2, SrH2, and BaH2 using a plane wave density functional method. Phonon calculations using the direct method enabled prediction of the zero point energies of each material and the 0K and 298K heats of formation. We also computed the 0K and 298K cohesive energies for the alkaline earth metals. Born effective charge tensors were computed via the Berry phase method and enabled prediction of the phonon dispersion curves with LO/TO zone center splittings. It was found that the LO/TO splittings have no effect on the computed zero point energies and heats of formation. The elastic constants were computed with a least squares fitting method using a set of sequentially-applied strains to improve the accuracy of each calculation. Comparison of results from the least squares methodology with prior results using the Hartree-Fock method suggest that the former is substantially more accurate for predicting hydride elastic properties.

  11. A Database of Alkaline-Earth-Coordinated Peptide Cross Sections: Insight into General Aspects of Structure

    NASA Astrophysics Data System (ADS)

    Dilger, Jonathan M.; Valentine, Stephen J.; Glover, Matthew S.; Clemmer, David E.

    2013-05-01

    A database of 1470 collision cross sections (666 doubly- and 804 triply-charged) of alkaline-earth-coordinated tryptic peptide ions [where the cation (M2+) correspond to Mg2+, Ca2+, or Ba2+] is presented. The utility of such an extensive set of measurements is illustrated by extraction of general properties of M2+-coordinated peptide structures. Specifically, we derive sets of intrinsic size parameters (ISPs) for individual amino acid residues for M2+-coordinated peptides. Comparison of these parameters with existing ISPs for protonated peptides suggests that M2+ binding occurs primarily through interactions with specific polar aliphatic residues (Asp, Ser, and Thr) and the peptide backbone. A comparison of binding interactions for these alkaline-earth metals with interactions reported previously for alkali metals is provided. Finally, we describe a new analysis in which ISPs are used as probes for assessing peptide structure based on amino acid composition.

  12. Quantum computing with alkaline-Earth-metal atoms.

    PubMed

    Daley, Andrew J; Boyd, Martin M; Ye, Jun; Zoller, Peter

    2008-10-24

    We present a complete scheme for quantum information processing using the unique features of alkaline-earth-metal atoms. We show how two completely independent lattices can be formed for the 1S0 and 3P0 states, with one used as a storage lattice for qubits encoded on the nuclear spin, and the other as a transport lattice to move qubits and perform gate operations. We discuss how the 3P2 level can be used for addressing of individual qubits, and how collisional losses from metastable states can be used to perform gates via a lossy blockade mechanism.

  13. Proposal for Laser Cooling of Alkaline Earth Monoalkoxide Free Radicals

    NASA Astrophysics Data System (ADS)

    Baum, Louis; Kozyryev, Ivan; Matsuda, Kyle; Doyle, John M.

    2016-05-01

    Cold samples of polyatomic molecules will open new avenues in physics, chemistry, and quantum science. Non-diagonal Franck-Condon factors, technically challenging wavelengths, and the lack of strong electronic transitions inhibit direct laser cooling of nonlinear molecules. We identify a scheme for optical cycling in certain molecules with six or more atoms. Replacing hydrogen in alcohols with an alkaline earth metal (M) leads to alkaline earth monoalkoxide free radicals (MOR), which have favorable properties for laser cooling. M-O bond is very ionic, so the metal orbitals are slightly affected by the nature of R on the ligand. Diagonal Franck-Condon factors, laser accessible transitions, and a small hyperfine structure make MOR molecules suitable for laser cooling. We explore a scheme for optical cycling on the A - X transition of SrOCH3 . Molecules lost to dark vibrational states will be repumped on the B - X transition. Extension to larger species is possible through expansion of the R group since transitions involve the promotion of the metal-centered nonbonding valence electron. We will detail our estimations of the Franck-Condon factors, simulations of the cooling process and describe progress towards the Doppler cooling of MOR polyatomics.

  14. Alkaline earths as main group reagents in molecular catalysis.

    PubMed

    Hill, Michael S; Liptrot, David J; Weetman, Catherine

    2016-02-21

    The past decade has witnessed some remarkable advances in our appreciation of the structural and reaction chemistry of the heavier alkaline earth (Ae = Mg, Ca, Sr, Ba) elements. Derived from complexes of these metals in their immutable +2 oxidation state, a broad and widely applicable catalytic chemistry has also emerged, driven by considerations of cost and inherent low toxicity. The considerable adjustments incurred to ionic radius and resultant cation charge density also provide reactivity with significant mechanistic and kinetic variability as group 2 is descended. In an attempt to place these advances in the broader context of contemporary main group element chemistry, this review focusses on the developing state of the art in both multiple bond heterofunctionalisation and cross coupling catalysis. We review specific advances in alkene and alkyne hydroamination and hydrophosphination catalysis and related extensions of this reactivity that allow the synthesis of a wide variety of acyclic and heterocyclic small molecules. The use of heavier alkaline earth hydride derivatives as pre-catalysts and intermediates in multiple bond hydrogenation, hydrosilylation and hydroboration is also described along with the emergence of these and related reagents in a variety of dehydrocoupling processes that allow that facile catalytic construction of Si-C, Si-N and B-N bonds. PMID:26797470

  15. Alkaline earth metal doped tin oxide as a novel oxygen storage material

    SciTech Connect

    Dong, Qiang; Yin, Shu; Yoshida, Mizuki; Wu, Xiaoyong; Liu, Bin; Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro; Sato, Tsugio

    2015-09-15

    Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.

  16. Spectroscopic studies of copper doped alkaline earth lead zinc phosphate glasses

    NASA Astrophysics Data System (ADS)

    Sastry, S. Sreehari; Rao, B. Rupa Venkateswara

    2014-02-01

    In this paper spectroscopic investigation of Cu2+ doped alkaline earth lead zinc phosphate glasses was done through the spectroscopic techniques like X-ray diffraction, Ultra Violet (UV) absorption Spectroscopy, Electron Paramagnetic Resonance (EPR - X band), Fourier Transform Infra Red (FTIR) and Raman Spectroscopy. Alkaline earth lead zinc phosphate glasses containing 0.1% copper oxide (CuO) were prepared by the melt quenching technique. Spectroscopic studies indicated that there is a greater possibility for the copper ions to exist in Cu2+ state in these glasses. The optical absorption spectra indicated that the absorption peak of Cu2+ is a function of composition. The maxima absorption peak was reported at 862 nm for strontium lead zinc phosphate glass. Bonding parameters were calculated for the optical and EPR data. All these spectral results indicated clearly that there are certain structural changes in the present glass system with different alkaline earth contents. The IR and Raman spectra noticed the breaking of the P-O-P bonds and creating more number of new P-O-Cu bonds.

  17. Theoretical dissociation energies for the alkali and alkaline-earth monofluorides and monochlorides

    NASA Technical Reports Server (NTRS)

    Langhoff, S. R.; Bauschlicher, C. W., Jr.; Partridge, H.

    1986-01-01

    Spectroscopic parameters are accurately determined for the alkali and alkaline-earth monofluorides and monochlorides by means of ab initio self-consistent field and correlated wave function calculations. Numerical Hartree-Fock calculations are performed on selected systems to ensure that the extended Slater basis sets employed are near the Hartree-Fock limit. Since the bonding is predominantly electrostatic in origin, a strong correlation exists between the dissociation energy (to ions) and the spectroscopic parameter r(e). By dissociating to the ionic limits, most of the differential correlation effects can be embedded in the accurate experimental electron affinities and ionization potentials.

  18. Alkaline Earth Core Level Photoemission Spectroscopy of High-Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Vasquez, R.

    1993-01-01

    This paper examines photoemission measurements of the alkaline Earth core levels of high-temperature superconductors and related materials, models that seek to explain the large negative shifts observed relative to the corresponding alkaline Earth metals, and the effect of lattice site disorder on the core level spectra and the presence or absence of intrinsic surface peaks.

  19. Evolution of plasmonic and hybrid photoionization properties of alkaline earth metallofullerenes with the increasing fullerene size

    NASA Astrophysics Data System (ADS)

    Patel, Aakash; Chakraborty, Himadri

    2013-05-01

    A theoretical study of the photoionization of endohedral fullerenes with a selection of fullerene molecules of increasing size and with confined alkaline earth atoms like Be and Mg is carried out. The fullerene ion cores, comprised of C4+ ions, are smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the electrons of the encaged atom are treated in the Kohn-Sham local density approximation (LDA). Only the spherical geometry is considered. The photoionization spectra are calculated by the time-dependent LDA that includes essential electron correlations. A systematic evolution of the mixing of valence atomic levels with states of fullerene single-electron bands is found along the sequence. This hybridization as a function of the fullerene size is seen to primarily define the properties of the subshell-differential ionization spectra both in the low energy plasmonic as well as the high energy oscillatory regions. Supported by NSF and DOE.

  20. Mixed alkaline earth effect in the compressibility of aluminosilicate glasses.

    PubMed

    Smedskjaer, Morten M; Rzoska, Sylwester J; Bockowski, Michal; Mauro, John C

    2014-02-01

    The mixed modifier effect (MME) in oxide glasses manifests itself as a non-additive variation in certain properties when one modifier oxide species is substituted by another one at constant total modifier content. However, the structural and topological origins of the MME are still under debate. This study provides new insights into the MME by investigating the effect of isostatic compression on density and hardness of mixed MgO/CaO sodium aluminosilicate glasses. This is done using a specially designed setup allowing isostatic compression of bulk glass samples up to 1 GPa at elevated temperature. A mixed alkaline earth effect is found in the compressibility and relative change of hardness, viz., a local maximum of density as a function of Mg/Ca ratio appears following compression, whereas a local minimum of hardness in the uncompressed glasses nearly disappears after compression. Moreover, the densification of these glasses is found to occur at temperatures much below the glass transition temperature, indicating that a non-viscous mechanism is at play. This is further supported by the fact that density relaxes in a stretched exponential manner upon subsequent annealing at ambient pressure with an exponent of ∼0.62. This is close to the Phillips value of 3/5 for relaxation in three dimensions when both short- and long-range interactions are activated.

  1. Improvement of thermoelectric properties of alkaline-earth hexaborides

    SciTech Connect

    Takeda, Masatoshi . E-mail: takeda@mech.nagaokaut.ac.jp; Terui, Manabu; Takahashi, Norihito; Ueda, Noriyoshi

    2006-09-15

    Thermoelectric (TE) and transport properties of alkaline-earth hexaborides were examined to investigate the possibility of improvement in their TE performance. As carrier concentration increased, electrical conductivity increased and the absolute value of the Seebeck coefficient decreased monotonically, while carrier mobility was almost unchanged. These results suggest that the electrical properties of the hexaboride depend largely on carrier concentration. Thermal conductivity of the hexaboride was higher than 10 W/m K even at 1073 K, which is relatively high among TE materials. Alloys of CaB{sub 6} and SrB{sub 6} were prepared in order to reduce lattice thermal conductivity. Whereas the Seebeck coefficient and electrical conductivity of the alloys were intermediate between those of CaB{sub 6} and SrB{sub 6} single phases, the thermal conductivities of the alloys were lower than those of both single phases. The highest TE performance was obtained in the vicinity of Ca{sub 0.5}Sr{sub 0.5}B{sub 6}, indicating that alloying is effective in improving the performance. - Graphical abstract: Thermoelectric figure-of-merit, ZT, for (Ca,Sr)B{sub 6} alloys. The highest ZT value of 0.35 at 1073 K was obtained due to effective reduction of thermal conductivity by alloying.

  2. Porphyrin-Alkaline Earth MOFs with the Highest Adsorption Capacity for Methylene Blue.

    PubMed

    Hou, Yuxia; Sun, Junshan; Zhang, Daopeng; Qi, Dongdong; Jiang, Jianzhuang

    2016-04-25

    A series of four porphyrin-alkaline earth metal- organic frameworks [Mg(HDCPP)2 (DMF)2 ]n ⋅(H2 O)7 n (1), [Ca(HDCPP)2 (H2 O)2 ]n (DMF)1.5 n (2), [Sr(DCPP)(H2 O)(DMA)]n (3), and [Ba(DCPP)(H2 O)(DMA)]n (4) was isolated for the first time from solvothermal reaction between metal-free 5,15-di(4- carboxyphenyl)porphyrin (H2 DCPP) and alkaline earth ions. Single-crystal X-ray diffraction analysis reveals the 2D and 3D supramolecular network with periodic nanosized porosity for 1/2 and 3/4, respectively. The whole series of MOFs, in particular, compounds 1 and 2 with intrinsic low molecular formula weight, exhibit superior adsorption performance for methylene blue (MB) with excellent capture capacity as represented by the thus far highest adsorption amount of 952 mg g(-1) for 2 and good selectivity, opening a new way for the potential application of the main group metal-based MOFs. PMID:27002679

  3. The Characterization of Eu2+-Doped Mixed Alkaline-Earth Iodide Scintillator Crystals

    SciTech Connect

    Neal, John S; Boatner, Lynn A; Ramey, Joanne Oxendine; Wisniewski, D.; Kolopus, James A; Cherepy, Nerine; Payne, Stephen A.

    2011-01-01

    The high-performance inorganic scintillator, SrI2:Eu2+, when activated with divalent europium in the concentration range of 3 to 6%, has shown great promise for use in applications that require high-energy-resolution gamma-ray detection. We have recently grown and tested crystals in which other alkaline-earth ions have been partially substituted for Sr ions. Specifically, europium-doped single crystals have been grown in which up to 30 at % of the strontium ions have been substituted for either by barium, magnesium, or calcium ions. In the case of the strontium iodide scintillator host, a material that is characterized by an orthorhombic crystal structure, there are three other column IIA elements that are obvious choices for investigations whose purpose is to realize potential improvements in the performance of SrI2:Eu2+-based scintillators via the replacement of strontium ions with either Mg2+, Ca2+, or Ba2+. Light yields of up to 81,400 photons/MeV with an associated energy resolution of 3.7% (fwhm for 662 keV gamma-rays) have been observed in the case of a partial substitution of Ba2+ for Sr2+. The measured decay times ranged from 1.1 to 2.0 s, while the peak emission wavelengths ranged from 432 to 438 nm.

  4. Alkaline earth-based coordination polymers derived from a cyclotriphosphazene-functionalized hexacarboxylate

    NASA Astrophysics Data System (ADS)

    Ling, Yajing; Bai, Dongjie; Feng, Yunlong; He, Yabing

    2016-10-01

    Combination of hexakis(4-carboxylatephenoxy)cyclotriphosphazene with alkaline earth ions of increasing ionic radii (Mg2+, Ca2+ and Ba2+) under different solvothermal conditions yielded three new coordination polymers, and their crystal structures were determined by single-crystal X-ray diffraction analysis. The magnesium compound displays a three dimensional (3D) network structure constructed from the deprotonated ligand and the secondary building block Mg(COO)4, which can be rationalized as a (4,6)-connected topological net with the Schläfli symbol of (44·62)3(49·66)2. The calcium compound consists of 1D infinite "Ca-O" inorganic chains connected by the deprotonated ligands to from a 3D framework. The barium compound exhibits a 3D framework in which 1D "Ba-O" inorganic chains are connected together by the deprotonated organic linkers. Due to the semi-rigid nature, the ligand adopts distinctly different conformations in the three compounds. The metal ions' influence exerted on the final structure of the resulting coordination polymers is also discussed. When the radii of alkaline earth ions increases descending down the group from Mg(II) to Ba(II), the coordination number becomes larger and more versatile: from 6 in the magnesium compound, to 6,7 and 10 in the calcium compound, and to 8 and 9 in the barium compound, thus substantially influencing the resulting final framework structures. Also, the photophysical properties were investigated systematically, revealing that the three compounds are photoluminscent in the solid state at room temperature. This work demonstrates that although the multiplicity of conformation in the hexacarboxylate ligand based on the inorganic scaffold cyclotriphosphazene makes it difficult to predict how this ligand will form extended network, but provides unique opportunities for the formation of diverse inorganic-organic hybrids exhibiting rich structural topologies.

  5. Coordination of alkaline earth metal ions in the inverted cucurbit[7]uril supramolecular assemblies formed in the presence of [ZnCl4]2- and [CdCl4]2-.

    PubMed

    Li, Qing; Zhang, Yun-Qian; Zhu, Qian-Jiang; Xue, Sai-Feng; Tao, Zhu; Xiao, Xin

    2015-05-01

    A convenient method to isolate inverted cucurbit[7]uril (iQ[7]) from a mixture of water-soluble Q[n]s was established by eluting the soluble mixture of Q[n]s on a Dowex (H(+) form) column so that iQ[7] could be selected as a ligand for coordination and supramolecular assembly with alkaline earth cations (AE(2+)) in aqueous HCl solutions in the presence of [ZnCl(4)](2-) and [CdCl(4)](2-) anions as structure-directing agents. Single-crystal X-ray diffraction analysis revealed that both iQ[7]-AE(2+) -[ZnCl(4)](2-) -HCl and iQ[7]-AE(2+) -[CdCl(4)](2-) -HCl interaction systems yielded supramolecular assemblies, in which the [ZnCl(4)](2-) and [CdCl(4)](2-) anions presented a honeycomb effect, and this resulted in the formation of linear iQ[7]/AE(2+) coordination polymers through outer-surface interactions of Q[n]s.

  6. Modulation of cardiac ryanodine receptor channels by alkaline earth cations.

    PubMed

    Diaz-Sylvester, Paula L; Porta, Maura; Copello, Julio A

    2011-01-01

    Cardiac ryanodine receptor (RyR2) function is modulated by Ca(2+) and Mg(2+). To better characterize Ca(2+) and Mg(2+) binding sites involved in RyR2 regulation, the effects of cytosolic and luminal earth alkaline divalent cations (M(2+): Mg(2+), Ca(2+), Sr(2+), Ba(2+)) were studied on RyR2 from pig ventricle reconstituted in bilayers. RyR2 were activated by M(2+) binding to high affinity activating sites at the cytosolic channel surface, specific for Ca(2+) or Sr(2+). This activation was interfered by Mg(2+) and Ba(2+) acting at low affinity M(2+)-unspecific binding sites. When testing the effects of luminal M(2+) as current carriers, all M(2+) increased maximal RyR2 open probability (compared to Cs(+)), suggesting the existence of low affinity activating M(2+)-unspecific sites at the luminal surface. Responses to M(2+) vary from channel to channel (heterogeneity). However, with luminal Ba(2+)or Mg(2+), RyR2 were less sensitive to cytosolic Ca(2+) and caffeine-mediated activation, openings were shorter and voltage-dependence was more marked (compared to RyR2 with luminal Ca(2+)or Sr(2+)). Kinetics of RyR2 with mixtures of luminal Ba(2+)/Ca(2+) and additive action of luminal plus cytosolic Ba(2+) or Mg(2+) suggest luminal M(2+) differentially act on luminal sites rather than accessing cytosolic sites through the pore. This suggests the presence of additional luminal activating Ca(2+)/Sr(2+)-specific sites, which stabilize high P(o) mode (less voltage-dependent) and increase RyR2 sensitivity to cytosolic Ca(2+) activation. In summary, RyR2 luminal and cytosolic surfaces have at least two sets of M(2+) binding sites (specific for Ca(2+) and unspecific for Ca(2+)/Mg(2+)) that dynamically modulate channel activity and gating status, depending on SR voltage. PMID:22039534

  7. Release characteristics of alkali and alkaline earth metallic species during biomass pyrolysis and steam gasification process.

    PubMed

    Long, Jiang; Song, Hu; Jun, Xiang; Sheng, Su; Lun-Shi, Sun; Kai, Xu; Yao, Yao

    2012-07-01

    Investigating the release characteristics of alkali and alkaline earth metallic species (AAEMs) is of potential interest because of AAEM's possible useful service as catalysts in biomass thermal conversion. In this study, three kinds of typical Chinese biomass were selected to pyrolyse and their chars were subsequently steam gasified in a designed quartz fixed-bed reactor to investigate the release characteristics of alkali and alkaline earth metallic species (AAEMs). The results indicate that 53-76% of alkali metal and 27-40% of alkaline earth metal release in pyrolysis process, as well as 12-34% of alkali metal and 12-16% of alkaline earth metal evaporate in char gasification process, and temperature is not the only factor to impact AAEMs emission. The releasing characteristics of AAEMs during pyrolysis and char gasification process of three kinds of biomass were discussed in this paper. PMID:22525260

  8. Alkaline earth metal cation exchange: effect of mobile counterion and dissolved organic matter.

    PubMed

    Indarawis, Katrina; Boyer, Treavor H

    2012-04-17

    The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening.

  9. Relationship between microstructure and efficiency of lithium silicate scintillating glasses: The effect of alkaline earths

    SciTech Connect

    Bliss, M.; Craig, R.A.; Sunberg, D.S.; Weber, M.J.

    1996-12-31

    Lithium silicate glasses containing Ce{sup 3+} are known to be scintillators. Glasses in this family in which the Li is enriched ({sup 6}Li) are used as neutron detectors. The addition of Mg to this glass is known to increase the scintillation efficiency. We have found that substituting other alkaline earths results in a monotonic decrease of the scintillation efficiency with increasing atomic number. The total variation in scintillation efficiency from Mg to Ba is nearly a factor of 3. Prior experiments with this glass family show small differences in Raman and fluorescence spectra; evidence from thermoluminescence experiments indicates that the scintillation efficiency is most strongly correlated with structural effects in the neighborhood of the Ce{sup 3+} activator ion. The results of low-temperature studies of fluorescence and thermoluminescence of these glasses will be reported.

  10. Theoretical study of the diatomic alkali and alkaline-earth oxides

    NASA Technical Reports Server (NTRS)

    Langhoff, S. R.; Bauschlicher, C. W., Jr.; Partridge, H.

    1986-01-01

    Theoretical dissociation energies for the ground states of the alkali and alkaline earth oxides are presented that are believed to be accurate to 0.1 eV. The 2 Pi - 2 Sigma + separations for the alkali oxides are found to be more sensitive to basis set than to electron correlation. Predicted 2 Pi ground states for LiO and NaO and 2 Sigma + ground states for RbO and CsO are found to be in agreement with previous theoretical and experimental work. For KO, a 2 Sigma + state is found at both the numerical Hartree-Fock (NHF) level and at the singles plus doubles configuration interaction level using a Slater basis set that is within 0.02 eV of the NHF limit. It is found that an accurate balanced treatment of the two states requires correlating the electrons on both the metal and oxide ion.

  11. Process for preparing higher oxides of the alkali and alkaline earth metals

    NASA Technical Reports Server (NTRS)

    Sadhukhan, P.; Bell, A. (Inventor)

    1978-01-01

    High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr.

  12. The MCVD synthesis and characterization of water tolerant fiber optic waveguides based on alkaline earth-doped silicas

    NASA Astrophysics Data System (ADS)

    Farley, Kevin F.

    Optical fibers that transmit throughout the entire telecommunications spectrum (1.2--1.7 mum) are presently manufactured by the removal of hydrogen or OH from the host preform glass. Hydrogen-oxygen torches are utilized in the conventional preform manufacturing process, but result in the formation of hydroxyls in germanium-doped silica fiber. The hydroxyl species generate unacceptably high losses for long haul telecommunications systems. This thesis has explored an alternative strategy for reducing OH-related absorption in silica-based glasses. Alkaline earth modifiers have been introduced via the modified chemical vapor deposition (MCVD) process to successfully damp out and dramatically reduce the extrinsic attenuation associated with both water and hydrogen. Specifically, alkaline earth ions were introduced into alumino-silicate glasses to form MgO-Al2O3-SiO2, CaO-Al 2O3-SiO2, and SrO-Al2O3-SiO 2 compositions. The utilization of halide precursors based on the vapor delivery of rare earths was incorporated into the existing MCVD set-up to fabricate these optical preforms. Both the bulk preforms and fibers drawn from them were characterized to determine relevant optical properties, including the attenuation, index profiles and extinction coefficients arising from OH in each host. The data indicate that modification of the silica glass structure through the additions of modifying ions can significantly reduce OH related absorption. For example, the doping of alkaline earth ions decreased the extinction coefficient measured at the 1.39 mum) OH overtone, to values < 0.2 L/(mol*cm). Prompt gamma activation analysis (PGAA) measurements conducted at the National Institute of Standards and Technology (NIST) found OH concentrations in the glasses in the range from 10 to 27.5 ppm. The alkaline earth-doped fibers exhibited lower OH absorption at 1.39 mum) than germanium and aluminum-doped reference fibers. Fibers doped with either magnesium, calcium or strontium displayed up

  13. Occlusion and ion exchange in the molten (lithium chloride + potassium chloride + alkaline earth chloride) salt + zeolite 4A system with alkaline earth chlorides of calcium and strontium, and in the molten (lithium chloride + potassium chloride + actinide chloride) salt + zeolite 4A system with the actinide chloride of uranium.

    SciTech Connect

    Lexa, D.; Chemical Engineering

    2003-04-01

    The interaction between molten salts of the type LiCl-KCl-MeCl n (Me=Ca, Sr, U; x{sub MeCLn} $$ = to 0.45; and x {sub KCl}/x LiCl=0.69) and zeolite 4A have been studied at 823 K. The main interactions between these salts and zeolite are molten salt occlusion to form salt-loaded zeolite and ion exchange between the molten salt and salt-loaded zeolite. An irreversible chemical reaction has been observed in the LiCl-KCl-UCl{sup 3+}zeolite system. The extent of occlusion is a function of the concentration of MeCl n in the zeolite and is equal to 10{+-}1 Cl- per zeolite unit cell, (AlSiO{sub 4}){sub 12}, at infinite MeCl n dilution. The ion-exchange mole-fraction equilibrium constants (separation factors) with respect to Li are decreasing functions of the concentration of SrCl{sub 2} and UCl{sub 3}, but an increasing function of the concentration of CaCl{sub 2} in the zeolite. At infinite MeCl n dilution, they are equal to 0.9, 11.9, and 13 for CaCl{sub 2}, SrCl{sub 2}, and UCl{sub 3}, respectively. The standard ion-exchange chemical potentials are equal to -50.0, -84, and -101.1 kJ x mol-1 for Ca{sup 2+}, Sr{sup 2+}, and U{sup 3+}, respectively.

  14. The effects of alkaline and alkaline earth metal salts on the performance of a polymer actuator based on single-wal led carbon nanotube-ionic liquid gel

    NASA Astrophysics Data System (ADS)

    Terasawa, Naohiro; Takeuchi, Ichiroh; Mukai, Ken; Asaka, Kinji

    We investigated an effect for alkaline metal salts or an alkaline earth metal salt on electrochemical and electromechanical properties of an actuator using a single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode, and much better performance of the actuator containing the metal salt/IL. The actuator containing the alkaline metal salt /IL or alkaline earth metal salt/IL performed much better than that containing only the IL. It is considered that the higher ionic conductivity of the gel electrolyte layer containing the alkaline metal salt /IL or alkaline earth metal salt/IL produces the quick response actuator, and that the large capacitance gives the large generated strain.

  15. Structural investigation of Eu{sup 2+} emissions from alkaline earth zirconium phosphate

    SciTech Connect

    Hirayama, Masaaki; Sonoyama, Noriyuki; Yamada, Atsuo; Kanno, Ryoji

    2009-04-15

    Eu{sup 2+} doped A{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3} (A=Ca, Sr, Ba) phosphors with the NASICON structure were synthesized by a co-precipitation method. Their photoluminescent and structural properties were investigated by photoluminescent spectroscopy and powder X-ray Rietveld analysis, which determined two sites for Eu{sup 2+} ions in the host structure, 3a and 3b. The Eu-O bond lengths were increased by changing alkaline earth ions from Ca to Ba, causing Eu{sup 2+} emission bands to shift from blue-green to blue. A correlation was observed between the peak wavelength positions and the Eu-O bond length. The photoluminescent properties are discussed in terms of crystal field strength and nephelauxetic effect, and a schematic diagram of Eu{sup 2+} emissions is proposed for the Eu{sup 2+} doped NASICON phosphor. - Graphical abstract: Eu{sup 2+} doped NASICON structured A{sub 0.5}Zr{sub 2}(PO{sub 4}){sub 3} (A=Ca, Sr, Ba) showed the blue and blue-green colored emissions attributed to 4f{sup 6}5d{sup 1}-4f{sup 7} transitions. The photoluminescent properties are discussed in terms of crystal field strength and nephelauxetic effect using powder X-ray Rietveld analysis.

  16. Chemical trend of pressure-induced metallization in alkaline earth hydrides

    SciTech Connect

    Zhang, Sijia; Chen, Xiao-Jia; Zhang, Rui-Qin; Lin, Hai-Qing

    2010-09-02

    The pressure-induced metallization of alkaline earth hydrides was systematically investigated using ab initio methods. While BeH{sub 2} and MgH{sub 2} present different semimetallic phases, CaH{sub 2}, SrH{sub 2}, and BaH{sub 2} share the same metallic phase (P6/mmm). The metallization pressure shows an attractive decrease with each increment of metal radius, and this trend is well correlated with both the electronegativity of alkaline earth metals and the band gap of alkaline earth hydrides at ambient pressure. Our results are consistent with current experimental data, and the obtained trend has significant implications for designing and engineering metallic hydrides for energy applications.

  17. Preparation of decarboxylic-functionalized weak cation exchanger and application for simultaneous separation of alkali, alkaline earth and transition metals.

    PubMed

    Peng, Yahui; Gan, Yihui; He, Chengxia; Yang, Bingcheng; Guo, Zhimou; Liang, Xinmiao

    2016-06-01

    A novel weak cation exchanger (WCX) with dicarboxyl groups functionalized has been developed by clicking mercaptosuccinic acid onto silica gel. The simple synthesis starts with modification of silica gel with triethoxyvinylsilane, followed by efficient coupling vinyl-bonded silica with mercaptosuccinic acid via a "thiol-ene" click reaction. The obtained WCX demonstrated good separation and high selectivity towards common metals. Simultaneous separation of 10 alkali, alkaline earth and transition metals was achieved within 12min. Ion exchange and complex mechanism dominates the separation process. Its utility was demonstrated for determination of metals in tap water. PMID:27130093

  18. Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Rey, Ana Maria

    2010-03-01

    Recently, substantial experimental efforts have been directed at cooling, trapping, and manipulating alkaline-earth metal atoms, and many of the capabilities previously demonstrated with alkali atoms are starting to be reproduced with alkaline-earth atoms. In this talk I will describe our proposal to exploit the decoupling between the nuclear spins and the electronic degrees of freedom present in the 1S0 and 3P0 states of alkaline-earth atoms to implement atomic analogs of Hamiltonians which rely on the interplay between charge, spin and orbital degrees of freedom. As an example, I will discuss the implementation of the Kondo lattice model used in condensed matter to describe heavy fermion materials. The decoupling between nuclear and spin degrees of freedom also leads to an enlargement of the spin rotation symmetry from SU(2) to SU(N), with N as large as 10. I will show that this enlarged symmetry can have striking physical consequences, such as the disappearance of magnetic ordering and the formation of spin liquid phases. [4pt] [1] Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms, A. V. Gorshkov et.al. arXiv:0905.2610 (to appear in Nature Physics). [0pt] [2] Mott Insulators of Ultracold Fermionic Alkaline Earth Atoms: Underconstrained Magnetism and Chiral Spin Liquid, M. Hermele, V. Gurarie, A, M. Rey , Phys. Rev. Lett. 103, 135301 (2009). [0pt] [3] Probing the Kondo Lattice Model with Alkaline Earth Atoms, M. Foss-Feig, M. Hermele, A.M. Rey, arXiv:0912.4762

  19. Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-pi-arene interactions.

    PubMed

    Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Ruhlandt-Senge, Karin; St Prix, Courtney; Zuniga, Maria F

    2009-01-01

    Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

  20. Inhibitory effect of metal ions on alkaline mesentericopeptidase.

    PubMed

    Raykova, D; Dorovska-Taran, V; Blagoev, B

    1981-01-01

    The effect of AG+, Cu2+, Cd2+, Co2+ and Ni2+ on the activity of alkaline mesentericopeptidase (EC 3.4.21.-) has been studied. Ag+, Cu2+ and Cd2+ were found to be reversible non-competitive inhibitors of the enzyme. The pH-dependence of Ki for Ag+-inhibition is sigmoidal with a pKa near 6. The Kilim values, calculated for the pH-independent region of the metal-enzyme inhibition, are close to the corresponding dissociation constants of metal-imidazole complexes, thus implying that the inhibitory effect of metal ions on enzyme activity is due to complex formation with the imidazole group of the active site histidine. The method of the two-component inhibition showed that Cu2+ and Ag+ bind to the same ligand of the enzyme molecule. The addition of Cu2+ decreases the rate of deacylation of the hydrolysis of p-nitrophenyl valerate, catalyzed by alkaline mesentericopeptidase in contrast to alpha-chymotrypsin where the acylation step is affected.

  1. Mott insulators of ultracold fermionic alkaline Earth atoms: underconstrained magnetism and chiral spin liquid.

    PubMed

    Hermele, Michael; Gurarie, Victor; Rey, Ana Maria

    2009-09-25

    We study Mott insulators of fermionic alkaline earth atoms, described by Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to SU(2) magnetism, more than two spins are required to form a singlet. On the square lattice, the classical ground state is highly degenerate and magnetic order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground state with topological order and Abelian fractional statistics. We discuss its experimental detection. Chiral spin liquids with non-Abelian anyons may also be realizable with alkaline earth atoms.

  2. Tris(pyrazolyl)methanides of the alkaline earth metals: influence of the substitution pattern on stability and degradation.

    PubMed

    Müller, Christoph; Koch, Alexander; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias

    2015-01-20

    Trispyrazolylmethanides commonly act as strong tridentate bases toward metal ions. This expected coordination behavior has been observed for tris(3,4,5-trimethylpyrazolyl)methane (1a), which yields the alkaline-earth-metal bis[tris(3,4,5-trimethylpyrazolyl)methanides] of magnesium (1b), calcium (1c), strontium (1d), and barium (1e) via deprotonation of 1a with dibutylmagnesium and [Ae{N(SiMe3)2}2] (Ae = Mg, Ca, Sr, and Ba, respectively). Barium complex 1e degrades during recrystallization that was attempted from aromatic hydrocarbons and ethers. In these scorpionate complexes, the metal ions are embedded in distorted octahedral coordination spheres. Contrarily, tris(3-thienylpyrazolyl)methane (2a) exhibits a strikingly different reactivity. Dibutylmagnesium is unable to deprotonate 2a, whereas [Ae{N(SiMe3)2}2] (Ae = Ca, Sr, and Ba) smoothly metalates 2a. However, the primary alkaline-earth-metal bis[tris(3-thienylpyrazolyl)methanides] of Ca (2c), Sr (2d), and Ba (2e) represent intermediates and degrade under the formation of the alkaline-earth-metal bis(3-thienylpyrazolates) of calcium (3c), strontium (3d), and barium (3e) and the elimination of tetrakis(3-thienylpyrazolyl)ethene (4). To isolate crystalline compounds, 3-thienylpyrazole has been metalated, and the corresponding derivatives [(HPz(Tp))4Mg(Pz(Tp))2] (3b), dinuclear [(tmeda)Ca(Pz(Tp))2]2 (3c), mononuclear [(pmdeta)Sr(Pz(Tp))2] (3d), and [(hmteta)Ba(Pz(Tp))2] (3e) have been structurally characterized. Regardless of the applied stoichiometry, magnesiation of thienylpyrazole 3a with dibutylmagnesium yields [(HPz(Tp))4Mg(Pz(Tp))2] (3b), which is stabilized in the solid state by intramolecular N-H···N···H-N hydrogen bridges. The degradation of [Ae{C(Pz(R))3}2] (R = Ph and Tp) has been studied by quantum chemical methods, the results of which propose an intermediate complex of the nature [{(Pz(R))2C}2Ca{Pz(R)}2]; thereafter, the singlet carbenes ([:C(Pz(R))2]) dimerize in the vicinity of the alkaline

  3. Depolarizing collisions with hydrogen: Neutral and singly ionized alkaline earths

    SciTech Connect

    Manso Sainz, Rafael; Ramos, Andrés Asensio; Bueno, Javier Trujillo; Aguado, Alfredo

    2014-06-20

    Depolarizing collisions are elastic or quasielastic collisions that equalize the populations and destroy the coherence between the magnetic sublevels of atomic levels. In astrophysical plasmas, the main depolarizing collider is neutral hydrogen. We consider depolarizing rates on the lowest levels of neutral and singly ionized alkali earths Mg I, Sr I, Ba I, Mg II, Ca II, and Ba II, due to collisions with H°. We compute ab initio potential curves of the atom-H° system and solve the quantum mechanical dynamics. From the scattering amplitudes, we calculate the depolarizing rates for Maxwellian distributions of colliders at temperatures T ≤ 10,000 K. A comparative analysis of our results and previous calculations in the literature is completed. We discuss the effect of these rates on the formation of scattering polarization patterns of resonant lines of alkali earths in the solar atmosphere, and their effect on Hanle effect diagnostics of solar magnetic fields.

  4. The alkali and alkaline earth metal doped ZnO nanotubes: DFT studies

    NASA Astrophysics Data System (ADS)

    Peyghan, Ali Ahmadi; Noei, Maziar

    2014-01-01

    Doping of several alkali and alkaline earth metals into sidewall of an armchair ZnO nanotube has been investigated by employing the density functional theory in terms of energetic, geometric, and electronic properties. It has been found that doping processes of the alkali and alkaline metals are endothermic and exothermic, respectively. Based on the results, contrary to the alkaline metal doping, the electronic properties of the tube are much more sensitive to alkali metal doping so that it is transformed from intrinsic semiconductor with HOMO-LUMO energy gap of 3.77 eV to an extrinsic semiconductor with the energy gap of ~1.11-1.95 eV. The doping of alkali and alkaline metals increases and decreases the work function of the tube, respectively, which may influence the electron emission from the tube surface.

  5. Ion exchange pretreatment of alkaline radwaste for cesium removal

    SciTech Connect

    Bibler, J.P.

    1994-08-01

    A cation exchange resin has been tested for its ability to remove the Cs ion from simulants of highly alkaline liquid nuclear wastes found at the Savannah River Site, Oak Ridge, and Hanford. The resin is a condensation polymer of the K salt of resorcinol and formaldehyde. It removes milli- and micromolar amounts of Cs{sup +} from solutions that contain as high as 11 molar Na{sup +}. Small column tests indicate that approximately 200 column volumes of SRS simulant and 205 column volumes of OR Tank 25 supernatant simulant can be processed before the resin requires regeneration. For these two wastes, a carousel arrangement of two columns in series and a third in reserve can be used effectively in a process. Hanford 101-AW simulant generates a less sharp breakthrough profile with this resin, though an operation using a maximum of three columns in series with another column off-line for regeneration would be effective if the resin beds are allowed to reach about 90% breakthrough before taking them out of service. Parameters that effect the performance of the resin with a particular feed solution are the concentrations of the two primary ions of interest, Cs{sup +} and Na{sup +}, as well as the concentrations of K{sup +} and OH{sup {minus}}. A further ramification of the hydroxide ion concentration is its role in assisting oxidation of the resin, thereby destroying its usefulness in cesium removal. Although the performance of the resin is unaffected at doses of 1 E+8 rad ionizing radiation, it shows noticeable degradation after storage for 100 hours in alkaline solutions, generating quinone and ketone groups, as determined from C-13 NMR and by an increase in total organic C content of the contacting solution. Gases detected from the radiolysis of the resin/simulant mixture are CO{sub 2} from the resin, N{sub 2}O from nitrate in the simulant, and H{sub 2} possibly from resin and simulant. Oxygen depletion in the mixture results from radiolysis and chemical degradation.

  6. Valence photoionization of small alkaline earth atoms endohedrally confined in C60

    NASA Astrophysics Data System (ADS)

    Javani, M. H.; McCreary, M. R.; Patel, A. B.; Madjet, M. E.; Chakraborty, H. S.; Manson, S. T.

    2012-07-01

    A theoretical study of photoionization from the outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 is reported. The fullerene ion core, comprised of sixty C4+, is smudged into a continuous jellium charge distribution, while the delocalized cloud of carbon valence electrons plus the encaged atom are treated in the time-dependent local density approximation (TDLDA). Systematic evolution of the mixing of outer atomic level with states of the C60 valence band is found along the sequence. This is found to influence the plasmonic enhancement of atomic photoionization at low energies and the geometry-revealing confinement oscillations at high energies in significantly different ways: (a) the extent of enhancement is mainly determined by the strength of atomic ionization, giving the strongest enhancement for Be even though Ca suffers the largest mixing. But (b) strongest collateral oscillations are uncovered for Ca, since, relative to Be and Mg, the mixing causes the highest photoelectron production at confining boundaries of Ca. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework.

  7. Cation effects in the oxidative coupling of methane on silica-supported binary alkali and alkaline earths

    SciTech Connect

    Voyatzis, R.; Moffat, J.B. )

    1993-07-01

    The oxidative coupling of methane has been investigated with a series of silica-supported binary oxide catalysts containing alkali or alkaline earths or combinations of the former and latter. The conversion of methane and the stability of the silica-supported binary alkali metal oxides were found to increase with decreasing cation mobility, while the selectivities and conversions observed with the binary alkaline earths increase with cation size. The selectivities and conversions of binary alkali/alkaline earths appear to depend upon the size of the alkali and alkaline earth cations, respectively. With small quantities of TCM (CCl[sub 4]) added continuously to the feedstream, catalysts containing small alkali and large alkaline earth cations produced the largest selectivities and conversions. 23 refs., 14 figs., 2 tabs.

  8. Carbonatite and alkaline intrusion-related rare earth element deposits–A deposit model

    USGS Publications Warehouse

    Verplanck, Philip L.; Van Gosen, Bradley S.

    2011-01-01

    The rare earth elements are not as rare in nature as their name implies, but economic deposits with these elements are not common and few deposits have been large producers. In the past 25 years, demand for rare earth elements has increased dramatically because of their wide and diverse use in high-technology applications. Yet, presently the global production and supply of rare earth elements come from only a few sources. China produces more than 95 percent of the world's supply of rare earth elements. Because of China's decision to restrict exports of these elements, the price of rare earth elements has increased and industrial countries are concerned about supply shortages. As a result, understanding the distribution and origin of rare earth elements deposits, and identifying and quantifying our nation's rare earth elements resources have become priorities. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The general mineral deposit model summarized here is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. Carbonatite and alkaline intrusion-related REE deposits are discussed together because of their spatial association, common enrichment in incompatible elements, and similarities in genesis. A wide variety of commodities have been exploited from carbonatites and alkaline igneous rocks, such as rare earth elements, niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other enrichments include manganese, strontium, tantalum, thorium, vanadium, and uranium.

  9. Ab initio study of the alkali and alkaline-earth monohydroxides

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Langhoff, S. R.; Partridge, H.

    1986-01-01

    A systematic study of the structures and dissociation energies of all the alkali and alkaline-earth monohydroxides is conducted. A theoretical model for determining accurate dissociation energies of ionic molecules is discussed. The obtained theoretical structures and dissociation energies of the alkali and alkaline-earth monohydroxides, respectively, are compared with experimental data. It is found that the theoretical studies of the bending potentials of BeOH, MgOH, and CaOH reveal the different admixture of covalent character in these systems. The BeOH molecule with the largest degree of covalent character is found to be bent (theta equals 147 deg). The MgOH is also linear. The theoretical dissociation energies for the alkali and akaline-earth hydroxides are thought to be accurate to 0.1 eV.

  10. Dissolution of alkaline earth sulfates in the presence of montmorillonite

    USGS Publications Warehouse

    Eberl, D.D.; Landa, E.R.

    1985-01-01

    In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

  11. Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

    DOEpatents

    Tierney, J.W.; Wender, I.; Palekar, V.M.

    1995-01-31

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  12. Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1995-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  13. Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.

    PubMed

    Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

    2014-05-01

    Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors.

  14. Effects of inherent alkali and alkaline earth metallic species on biomass pyrolysis at different temperatures.

    PubMed

    Hu, Song; Jiang, Long; Wang, Yi; Su, Sheng; Sun, Lushi; Xu, Boyang; He, Limo; Xiang, Jun

    2015-09-01

    This work aimed to investigate effects of inherent alkali and alkaline earth metallic species (AAEMs) on biomass pyrolysis at different temperatures. The yield of CO, H2 and C2H4 was increased and that of CO2 was suppressed with increasing temperature. Increasing temperature could also promote depolymerization and aromatization reactions of active tars, forming heavier polycyclic aromatic hydrocarbons, leading to decrease of tar yields and species diversity. Diverse performance of inherent AAEMs at different temperatures significantly affected the distribution of pyrolysis products. The presence of inherent AAEMs promoted water-gas shift reaction, and enhanced the yield of H2 and CO2. Additionally, inherent AAEMs not only promoted breakage and decarboxylation/decarbonylation reaction of thermally labile hetero atoms of the tar but also enhanced thermal decomposing of heavier aromatics. Inherent AAEMs could also significantly enhance the decomposition of levoglucosan, and alkaline earth metals showed greater effect than alkali metals.

  15. Effects of inherent alkali and alkaline earth metallic species on biomass pyrolysis at different temperatures.

    PubMed

    Hu, Song; Jiang, Long; Wang, Yi; Su, Sheng; Sun, Lushi; Xu, Boyang; He, Limo; Xiang, Jun

    2015-09-01

    This work aimed to investigate effects of inherent alkali and alkaline earth metallic species (AAEMs) on biomass pyrolysis at different temperatures. The yield of CO, H2 and C2H4 was increased and that of CO2 was suppressed with increasing temperature. Increasing temperature could also promote depolymerization and aromatization reactions of active tars, forming heavier polycyclic aromatic hydrocarbons, leading to decrease of tar yields and species diversity. Diverse performance of inherent AAEMs at different temperatures significantly affected the distribution of pyrolysis products. The presence of inherent AAEMs promoted water-gas shift reaction, and enhanced the yield of H2 and CO2. Additionally, inherent AAEMs not only promoted breakage and decarboxylation/decarbonylation reaction of thermally labile hetero atoms of the tar but also enhanced thermal decomposing of heavier aromatics. Inherent AAEMs could also significantly enhance the decomposition of levoglucosan, and alkaline earth metals showed greater effect than alkali metals. PMID:26005925

  16. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 2. Ca

    SciTech Connect

    De Visscher, Alex; Vanderdeelen, Jan

    2012-06-15

    The alkaline earth carbonates are an important class of minerals. This article is part of a volume in the IUPAC-NIST Solubility Data Series that compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1 outlined the procedure adopted in this volume, and presented the beryllium and magnesium carbonates. Part 2, the current paper, compiles and critically evaluates the solubility data of calcium carbonate. The chemical forms included are the anhydrous CaCO{sub 3} types calcite, aragonite, and vaterite, the monohydrate monohydrocalcite (CaCO{sub 3}{center_dot} H{sub 2}O), the hexahydrate ikaite (CaCO{sub 3}{center_dot}6H{sub 2}O), and an amorphous form. The data were analyzed with two model variants, and thermodynamic data of each form consistent with each of the models and with the CODATA key values for thermodynamics are presented.

  17. Improved alkaline earth-oxyhalide electrochemical cell for low-temperature use

    SciTech Connect

    Binder, M.; Walker, C.W.

    1988-05-20

    This invention relates in general to an alkaline earth-oxyhalide electrochemical cell and in particular, to an improved alkaline earth oxyhalide electrochemical cell for low temperature use. A typical cell includes a calcium anode, 1M Ca(AlCl/sub 4/)/sub 2/ thionyl chloride/75% Shawinigan - 25% acetone washed Black Pearls 2000 carbon black cathode. The improvement to this cell involves the addition of 10 vol. % bromine to the electrolyte. During discharge at about -30 C, cathode potential is raised by about 0.5 volt providing a cell voltage well above the 2.0 volt minimum which is a standard military specification. Without bromine, cell capacity is about one minute. With the addition of bromine, load voltage is initially 2.5 volts, then slowly decreases to 2.0 volts over about twelve minutes.

  18. Properties of the triplet metastable states of the alkaline-earth-metal atoms

    SciTech Connect

    Mitroy, J.; Bromley, M.W.J.

    2004-11-01

    The static and dynamic properties of the alkaline-earth-metal atoms in their metastable state are computed in a configuration interaction approach with a semiempirical model potential for the core. Among the properties determined are the scalar and tensor polarizabilities, the quadrupole moment, some of the oscillator strengths, and the dispersion coefficients of the van der Waals interaction. A simple method for including the effect of the core on the dispersion parameters is described.

  19. Surface energetics of alkaline-earth metal oxides: Trends in stability and adsorption of small molecules

    NASA Astrophysics Data System (ADS)

    Bajdich, Michal; Nørskov, Jens K.; Vojvodic, Aleksandra

    2015-04-01

    We present a systematic theoretical investigation of the surface properties, stability, and reactivity of rocksalt type alkaline-earth metal oxides including MgO, CaO, SrO, and BaO. The accuracy of commonly used exchange-correlation density functionals (LDA, PBE, RPBE, PBEsol, BEEF-vdW, and hybrid HSE) and random-phase approximation (RPA) is evaluated and compared to existing experimental values. Calculated surface energies of the four most stable surface facets under vacuum conditions, the (100) surface, the metal and oxygen terminated octopolar (111), and the (110) surfaces, exhibit a monotonic increase in stability from MgO to BaO. On the MgO(100) surface, adsorption of CO, NO, and CH4 is characterized by physisorption while H2O chemisorbs, which is in agreement with experimental findings. We further use the on-top metal adsorption of CO and NO molecules to map out the surface energetics of each alkaline-earth metal oxide surface. The considered functionals all qualitatively predict similar adsorption energy trends. The ordering between the adsorption energies on different surface facets can be attributed to differences in the local geometrical surface structure and the electronic structure of the metal constituent of the alkaline-earth metal oxide. The striking observation that CO adsorption strength is weaker than NO adsorption on the (100) terraces as the period of the alkaline-earth metal in the oxide increases is analyzed in detail in terms of charge redistribution within the σ and π channels of adsorbates. Finally, we also present oxygen adsorption and oxygen vacancy formation energies in these oxide systems.

  20. Advances in the growth of alkaline-earth halide single crystals for scintillator detectors

    SciTech Connect

    Boatner, Lynn A; Ramey, Joanne Oxendine; Kolopus, James A; Neal, John S; Cherepy, Nerine; Payne, Stephen A.; Beck, P; Burger, Arnold; Rowe, E; Bhattacharya, P.

    2014-01-01

    Alkaline-earth scintillators such as strontium iodide and other alkaline-earth halides activated with divalent europium represent some of the most efficient and highest energy resolution scintillators for use as gamma-ray detectors in a wide range of applications. These applications include the areas of nuclear nonproliferation, homeland security, the detection of undeclared nuclear material, nuclear physics and materials science, medical diagnostics, space physics, high energy physics, and radiation monitoring systems for first responders, police, and fire/rescue personnel. Recent advances in the growth of large single crystals of these scintillator materials hold the promise of higher crystal yields and significantly lower detector production costs. In the present work, we describe new processing protocols that, when combined with our molten salt filtration methods, have led to advances in achieving a significant reduction of cracking effects during the growth of single crystals of SrI2:Eu2+. In particular, we have found that extended pumping on the molten crystal-growth charge under vacuum for time periods extending up to 48 hours is generally beneficial in compensating for variations in the alkaline-earth halide purity and stoichiometry of the materials as initially supplied by commercial sources. These melt-pumping and processing techniques are now being applied to the purification of CaI2:Eu2+ and some mixed-anion europium-doped alkaline-earth halides prior to single-crystal growth by means of the vertical Bridgman technique. The results of initial studies of the effects of aliovalent doping of SrI2:Eu2+ on the scintillation characteristics of this material are also described.

  1. Advances in the growth of alkaline-Earth halide single crystals for scintillator detectors

    NASA Astrophysics Data System (ADS)

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, J. S.; Cherepy, N. J.; Beck, P. R.; Payne, S. A.; Burger, A.; Rowe, E.; Bhattacharya, P.

    2014-09-01

    Alkaline-earth scintillators such as strontium iodide and other alkaline-earth halides activated with divalent europium represent some of the most efficient and highest energy resolution scintillators for use as gamma-ray detectors in a wide range of applications. These applications include the areas of nuclear nonproliferation, homeland security, the detection of undeclared nuclear material, nuclear physics and materials science, medical diagnostics, space physics, high energy physics, and radiation monitoring systems for first responders, police, and fire/rescue personnel. Recent advances in the growth of large single crystals of these scintillator materials hold the promise of higher crystal yields and significantly lower detector production costs. In the present work, we describe new processing protocols that, when combined with our molten salt filtration methods, have led to advances in achieving a significant reduction of cracking effects during the growth of single crystals of SrI2:Eu2+. In particular, we have found that extended pumping on the molten crystalgrowth charge under vacuum for time periods extending up to 48 hours is generally beneficial in compensating for variations in the alkaline-earth halide purity and stoichiometry of the materials as initially supplied by commercial sources. These melt-pumping and processing techniques are now being applied to the purification of CaI2:Eu2+ and some mixed-anion europium-doped alkaline-earth halides prior to single-crystal growth by means of the vertical Bridgman technique. The results of initial studies of the effects of aliovalent doping of SrI2:Eu2+ on the scintillation characteristics of this material are also described.

  2. Probing the Kondo lattice model with alkaline-earth-metal atoms

    SciTech Connect

    Foss-Feig, Michael; Hermele, Michael; Rey, Ana Maria

    2010-05-15

    We study transport properties of alkaline-earth-metal atoms governed by the Kondo lattice Hamiltonian plus a harmonic confining potential, and suggest simple dynamical probes of several different regimes of the phase diagram that can be implemented with current experimental techniques. In particular, we show how Kondo physics at strong coupling, at low density, and in the heavy fermion phase is manifest in the dipole oscillations of the conduction band upon displacement of the trap center.

  3. Accumulation of alkaline earth metals by the green macroalga Bryopsis maxima.

    PubMed

    Takahashi, Shigekazu; Aizawa, Kyoko; Nakamura, Saki; Nakayama, Katsumi; Fujisaki, Shingo; Watanabe, Soichiro; Satoh, Hiroyuki

    2015-04-01

    Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of (131)I, (134)Cs, (137)Cs, and (140)Ba as fission products of (235)U. Interestingly, B. maxima contained naturally occurring radionuclides derived from (226)Ra and (228)Ra. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive (85)Sr incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the (85)Sr was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that (85)Sr radioactivity was permeable through a dialysis membrane, the (85)Sr was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70% of the Sr did not precipitate as SrSO4, indicating that a proportion of the Sr may bind with small molecules in B. maxima. PMID:25744028

  4. Accumulation of alkaline earth metals by the green macroalga Bryopsis maxima.

    PubMed

    Takahashi, Shigekazu; Aizawa, Kyoko; Nakamura, Saki; Nakayama, Katsumi; Fujisaki, Shingo; Watanabe, Soichiro; Satoh, Hiroyuki

    2015-04-01

    Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of (131)I, (134)Cs, (137)Cs, and (140)Ba as fission products of (235)U. Interestingly, B. maxima contained naturally occurring radionuclides derived from (226)Ra and (228)Ra. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive (85)Sr incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the (85)Sr was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that (85)Sr radioactivity was permeable through a dialysis membrane, the (85)Sr was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70% of the Sr did not precipitate as SrSO4, indicating that a proportion of the Sr may bind with small molecules in B. maxima.

  5. Optical Properties of Alkaline Earth Ions Doped Bismuth Borate Glasses

    SciTech Connect

    Kundu, Virender; Dhiman, R. L.; Maan, A. S.; Goyal, D. R.

    2011-07-15

    The optical properties of glasses with composition xLi{sub 2}O(30-x)Bi{sub 2}O{sub 3}-70B{sub 2}O{sub 3}; x = 0, 5, 10, 15 and 20 mol %, prepared by normal melt quench technique were investigated by means of UV-VIS measurement. It was observed that the optical band gap of the present glass system decreases with increasing Li{sub 2}O content up to 15 mol%, and with further increase in lithium oxide content i.e. x>15 mol% the optical band gap increases. It was also observed that the present glass system behaves as an indirect band gap semiconductor.

  6. Theoretical investigation of the structures, stabilities, and NLO responses of calcium-doped pyridazine: alkaline-earth-based alkaline salt electrides.

    PubMed

    Wang, Yin-Feng; Huang, Jiangen; Jia, Li; Zhou, Guangpei

    2014-02-01

    Currently, whether alkaline-earth-doped compounds with electride characteristics are novel candidates for high-performance nonlinear optical (NLO) materials is unknown. In this paper, using quantum chemical computations, we show that: when doping calcium atoms into a family of alkaline-substituted pyridazines, alkaline-earth-based alkaline salt electrides M-H₃C₄N₂⋯Ca (M=H, Li, and K) with distended excess electron clouds are formed. Interestingly, from the triplet to the singlet state, the chemical valence of calcium atom changes from +1 to 0, and the dipole moment direction (μ₀) of the molecule reverses for each M-H₃C₄N₂⋯Ca. Changing pyridazine from without (H₄C₄N₂⋯Ca) to with one alkaline substituent (M-H₃C₄N₂⋯Ca, M=Li and K), the ground state changes from the triplet to the singlet state. The alkaline earth metal doping effect (electride effect) and alkaline salt effect on the static first hyperpolarizabilities (β₀) demonstrates that (1) the β₀ value is increased approximately 1371-fold from 2 (pyridazine, H₄C₄N₂) to 2745au (Ca-doped pyridazine, H₄C₄N₂⋯Ca), (2) the β₀ value is increased approximately 1146-fold from 2 in pyridazine (H₄C₄N₂) to 2294au in an Li-substituted pyridazine (Li-H₃C₄N₂), and (3) the β₀ value is increased 324-(M=Li) and 106-(M=K) fold from 826 (MLi) and 2294au (MK) to 268,679 (M=Li) and 245,878au (M=K), respectively, from the alkalized pyridazine (M-H₃C₄N₂) to the Ca-doped pyridazine (M-H₃C₄N₂⋯Ca). These results may provide a new means for designing high-performance NLO materials.

  7. N-type carbon nanotube by alkaline-earth metal Sr doping

    NASA Astrophysics Data System (ADS)

    Kim, Byung Hoon; Park, Tae Hoi; Baek, Seung Jae; Lee, Dong Su; Park, Seung Joo; Kim, Jun Sung; Park, Yung Woo

    2008-05-01

    Alkaline-earth metal, Sr, was doped on multiwalled carbon nanotubes (MWNTs) by vapor phase reaction method. The tunneling electron microscopy, energy dispersive x ray, and Raman spectroscopy were studied for verifying the Sr doping on MWNT. The temperature-dependent resistivity [ρ(T)] and thermoelectric power [S(T)] were also performed for both pristine MWNT and Sr-doped MWNT (Sr-MWNT). ρ(T ) of Sr-MWNT did not significantly change compared to pristine MWNT. However, S(T ) of Sr-MWNT considerably changes, i.e., it shows n-type behavior in contrast to pristine MWNT.

  8. The potential of trees to record aluminum mobilization and changes in alkaline earth availability

    SciTech Connect

    Bondietti, E.A.; Baes, C.F. III; McLaughlin, S.B.

    1988-01-01

    The mobilization of exchangeable soil cations by atmospheric depositions of mineral acid anions and the distribution of polyvalent cations in the xylem are described to provide the basis for interpreting both radial concentration and concentration ratio patterns of polyvalent cations in annual growth rings of trees. There is strong circumstantial evidence that increases in Al:Ca ratios in annual rings are related to aluminum mobilization, and that changes in the availability of alkaline earth elements and radial growth rated may also be related to cation mobilization. Suggestions for further research are presented.

  9. Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same

    DOEpatents

    Abraham, Marvin M.; Chen, Yok; Kernohan, Robert H.

    1981-01-01

    This invention relates to novel and comparatively inexpensive semiconductor devices utilizing semiconducting alkaline-earth-oxide crystals doped with alkali metal. The semiconducting crystals are produced by a simple and relatively inexpensive process. As a specific example, a high-purity lithium-doped MgO crystal is grown by conventional techniques. The crystal then is heated in an oxygen-containing atmosphere to form many [Li].degree. defects therein, and the resulting defect-rich hot crystal is promptly quenched to render the defects stable at room temperature and temperatures well above the same. Quenching can be effected conveniently by contacting the hot crystal with room-temperature air.

  10. Liquefaction process for solid carbonaceous materials containing alkaline earth metal humates

    DOEpatents

    Epperly, William R.; Deane, Barry C.; Brunson, Roy J.

    1982-01-01

    An improved liquefaction process wherein wall scale and particulate agglomeration during the liquefaction of solid carbonaceous materials containing alkaline earth metal humates is reduced and/or eliminated by subjecting the solid carbonaceous materials to controlled cyclic cavitation during liquefaction. It is important that the solid carbonaceous material be slurried in a suitable solvent or diluent during liquefaction. The cyclic cavitation may be imparted via pressure cycling, cyclic agitation and the like. When pressure cycling or the like is employed an amplitude equivalent to at least 25 psia is required to effectively remove scale from the liquefaction vessel walls.

  11. Biogenesis and Early Life on Earth and Europa: Favored by an Alkaline Ocean?

    NASA Astrophysics Data System (ADS)

    Kempe, Stephan; Kazmierczak, Jozef

    2002-03-01

    Recent discoveries about Europa - the probable existence of a sizeable ocean below its ice crust; the detection of hydrated sodium carbonates, among other salts; and the calculation of a net loss of sodium from the subsurface - suggest the existence of an alkaline ocean. Alkaline oceans (nicknamed "soda oceans" in analogy to terrestrial soda lakes) have been hypothesized also for early Earth and Mars on the basis of mass balance considerations involving total amounts of acids available for weathering and the composition of the early crust. Such an environment could be favorable to biogenesis since it may have provided for very low Ca2+ concentrations mandatory for the biochemical function of proteins. A rapid loss of CO2 from Europa's atmosphere may have led to freezing oceans. Alkaline brine bubbles embedded in ice in freezing and impact-thawing oceans could have provided a suitable environment for protocell formation and the large number of trials needed for biogenesis. Understanding these processes could be central to assessing the probability of life on Europa.

  12. Health Effects of Alkaline Diet and Water, Reduction of Digestive-tract Bacterial Load, and Earthing.

    PubMed

    Mousa, Haider Abdul-Lateef

    2016-04-01

    In the article, the author discusses the issue of chronic, low-grade acidosis that is thought to be brought about primarily by 2 factors: (1) advancing age, with a consequent decline in renal function; and (2) diet. An acid-forming diet can induce low-grade metabolic acidosis, which causes very small decreases in blood pH and plasma bicarbonate (HCO3-) that remain within the range considered to be normal. However, if the duration of the acidosis is prolonged or chronically present, even a low degree of acidosis can become significant. This article reviews supporting evidence in the literature that has shown that consumption of abundant alkaline-forming foods can result in improvement in bone mineral density (BMD) and muscle mass, protection from chronic illnesses, reduced tumor-cell invasion and metastasis, and effective excretion of toxins from the body. In addition, a large number of studies showing the benefits of alkaline water (mineral water) have revealed that people consuming water with a high level of total dissolved solids (TDS) (ie, with a high mineral content) have shown a lower incidence of coronary heart disease (CHD), cardiovascular disease (CVD), and cancer and lower total mortality rates. Consumption of alkaline water also may prevent osteoporosis and protect pancreatic beta cells with its antioxidant effects. In addition, this article discusses the literature that shows that reducing digestive-tract bacterial load can play an important role in increasing blood alkalinity toward the normal upper limit. That change occurs through good oral hygiene, flossing of teeth, perfect chewing of food, and bowel evacuation as soon as possible. Finally, the author reviews the literature that shows that earthing (ie, the direct contact of the human body with the earth) can supply a current of plentiful electrons. Earthing has been shown to reduce acute and chronic inflammation, blood glucose in patients with diabetes, red blood cell (RBC) aggregation, and blood

  13. Health Effects of Alkaline Diet and Water, Reduction of Digestive-tract Bacterial Load, and Earthing.

    PubMed

    Mousa, Haider Abdul-Lateef

    2016-04-01

    In the article, the author discusses the issue of chronic, low-grade acidosis that is thought to be brought about primarily by 2 factors: (1) advancing age, with a consequent decline in renal function; and (2) diet. An acid-forming diet can induce low-grade metabolic acidosis, which causes very small decreases in blood pH and plasma bicarbonate (HCO3-) that remain within the range considered to be normal. However, if the duration of the acidosis is prolonged or chronically present, even a low degree of acidosis can become significant. This article reviews supporting evidence in the literature that has shown that consumption of abundant alkaline-forming foods can result in improvement in bone mineral density (BMD) and muscle mass, protection from chronic illnesses, reduced tumor-cell invasion and metastasis, and effective excretion of toxins from the body. In addition, a large number of studies showing the benefits of alkaline water (mineral water) have revealed that people consuming water with a high level of total dissolved solids (TDS) (ie, with a high mineral content) have shown a lower incidence of coronary heart disease (CHD), cardiovascular disease (CVD), and cancer and lower total mortality rates. Consumption of alkaline water also may prevent osteoporosis and protect pancreatic beta cells with its antioxidant effects. In addition, this article discusses the literature that shows that reducing digestive-tract bacterial load can play an important role in increasing blood alkalinity toward the normal upper limit. That change occurs through good oral hygiene, flossing of teeth, perfect chewing of food, and bowel evacuation as soon as possible. Finally, the author reviews the literature that shows that earthing (ie, the direct contact of the human body with the earth) can supply a current of plentiful electrons. Earthing has been shown to reduce acute and chronic inflammation, blood glucose in patients with diabetes, red blood cell (RBC) aggregation, and blood

  14. Long-range interacting many-body systems with alkaline-earth-metal atoms.

    PubMed

    Olmos, B; Yu, D; Singh, Y; Schreck, F; Bongs, K; Lesanovsky, I

    2013-04-01

    Alkaline-earth-metal atoms can exhibit long-range dipolar interactions, which are generated via the coherent exchange of photons on the (3)P(0) - (3)D(1) transition of the triplet manifold. In the case of bosonic strontium, which we discuss here, this transition has a wavelength of 2.6 μm and a dipole moment of 4.03 D, and there exists a magic wavelength permitting the creation of optical lattices that are identical for the states (3)P(0) and (3)D(1). This interaction enables the realization and study of mixtures of hard-core lattice bosons featuring long-range hopping, with tunable disorder and anisotropy. We derive the many-body master equation, investigate the dynamics of excitation transport, and analyze spectroscopic signatures stemming from coherent long-range interactions and collective dissipation. Our results show that lattice gases of alkaline-earth-metal atoms permit the creation of long-lived collective atomic states and constitute a simple and versatile platform for the exploration of many-body systems with long-range interactions. As such, they represent an alternative to current related efforts employing Rydberg gases, atoms with large magnetic moment, or polar molecules.

  15. The influence of alkali and alkaline earths on the working range for bioactive glasses.

    PubMed

    Brink, M

    1997-07-01

    Viscosity-temperature dependence has been investigated for glasses in a system where bioactive compositions are found. A glass is called bioactive when living bone can bond to it. In this work, high-temperature microscopy was used to determine viscosity-temperature behaviour for 40 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2. The silica content in the glasses was 39-70 wt% % All glasses containing < 54 mol % SiO2 devitrified during the viscosity measurements. Generally, glasses that devitrified contained more alkali but less alkaline earths than glasses with a large working range. A working range is the temperature interval at which forming of a glass can take place. This temperature interval can, for bioactive glasses, be enlarged by decreasing the amount of alkali, especially Na2O, in the glass and by increasing the amount of alkaline earths, especially MgO. Optionally, B2O3 and P2O5 can be added to the glass. An enlarged working range is a prerequisite for an expanded medical use of bioactive glasses as e.g., sintered and blown products, and fibers. PMID:9212395

  16. A 3-photon process for producing degenerate gases of metastable alkaline-earth atoms

    NASA Astrophysics Data System (ADS)

    Barker, Daniel S.; Pisenti, Neal C.; Reschovsky, Benjamin J.; Campbell, Gretchen K.

    2016-05-01

    We present a method for creating quantum degenerate gases of metastable alkaline-earth atoms. A degenerate gas in any of the 3 P metastable states has not previously been obtained due to large inelastic collision rates, which are unfavorable for evaporative cooling. Samples prepared in the 1S0 ground state can be rapidly transferred to either the 3P2 or 3P0 state via a coherent 3-photon process. Numerical integration of the density matrix evolution for the fine structure of bosonic alkaline-earth atoms shows that transfer efficiencies of ~= 90 % can be achieved with experimentally feasible laser parameters in both Sr and Yb. Importantly, the 3-photon process does not impart momentum to the degenerate gas during excitation, which allows studies of these metastable samples outside the Lamb-Dicke regime. We discuss several experimental challenges to the successful realization of our scheme, including the minimization of differential AC Stark shifts between the four states connected by the 3-photon transition.

  17. Three-photon process for producing a degenerate gas of metastable alkaline-earth-metal atoms

    NASA Astrophysics Data System (ADS)

    Barker, D. S.; Pisenti, N. C.; Reschovsky, B. J.; Campbell, G. K.

    2016-05-01

    We present a method for creating a quantum degenerate gas of metastable alkaline-earth-metal atoms. This has yet to be achieved due to inelastic collisions that limit evaporative cooling in the metastable states. Quantum degenerate samples prepared in the 1S0 ground state can be rapidly transferred to either the 3P2 or 3P0 state via a coherent three-photon process. Numerical integration of the density-matrix evolution for the fine structure of bosonic alkaline-earth-metal atoms shows that transfer efficiencies of ≃90 % can be achieved with experimentally feasible laser parameters in both Sr and Yb. Importantly, the three-photon process can be set up such that it imparts no net momentum to the degenerate gas during the excitation, which will allow for studies of metastable samples outside the Lamb-Dicke regime. We discuss several experimental challenges to successfully realizing our scheme, including the minimization of differential ac Stark shifts between the four states connected by the three-photon transition.

  18. Matrix diffusion of some alkali- and alkaline earth-metals in granitic rock

    SciTech Connect

    Johansson, H.; Byegaard, J.; Skarnemark, G.; Skaalberg, M.

    1997-12-31

    Static through-diffusion experiments were performed to study the diffusion of alkali- and alkaline earth-metals in fine-grained granite and medium-grained Aespoe-diorite. Tritiated water was used as an inert reference tracer. Radionuclides of the alkali- and alkaline earth-metals (mono- and divalent elements which are not influenced by hydrolysis in the pH-range studied) were used as tracers, i.e., {sup 22}Na{sup +}, {sup 45}Ca{sup 2+} and {sup 85}Sr{sup 2+}. The effective diffusivity and the rock capacity factor were calculated by fitting the breakthrough curve to the one-dimensional solution of the diffusion equation. Sorption coefficients, K{sub d}, that were derived from the rock capacity factor (diffusion experiments) were compared with K{sub d} determined in batch experiments using crushed material of different size fractions. The results show that the tracers were retarded in the same order as was expected from the measured batch K{sub d}. Furthermore, the largest size fraction was the most representative when comparing batch K{sub d} with K{sub d} evaluated from the diffusion experiments. The observed effective diffusivities tended to decrease with increasing cell lengths, indicating that the transport porosity decreases with increasing sample lengths used in the diffusion experiments.

  19. Topological nodal-line semimetals in alkaline-earth stannides, germanides, and silicides

    NASA Astrophysics Data System (ADS)

    Huang, Huaqing; Liu, Jianpeng; Vanderbilt, David; Duan, Wenhui

    2016-05-01

    Based on first-principles calculations and an effective Hamiltonian analysis, we systematically investigate the electronic and topological properties of alkaline-earth compounds A X2 (A =Ca , Sr, Ba; X =Si , Ge, Sn). Taking BaSn2 as an example, we find that when spin-orbit coupling is ignored, these materials are three-dimensional topological nodal-line semimetals characterized by a snakelike nodal loop in three-dimensional momentum space. Drumheadlike surface states emerge either inside or outside the loop circle on the (001) surface depending on surface termination, while complicated double-drumhead-like surface states appear on the (010) surface. When spin-orbit coupling is included, the nodal line is gapped and the system becomes a topological insulator with Z2 topological invariants (1;001). Since spin-orbit coupling effects are weak in light elements, the nodal-line semimetal phase is expected to be achievable in some alkaline-earth germanides and silicides.

  20. Theoretical study of the alkaline-earth metal superoxides BeO2 through SrO2

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Sodupe, Mariona; Langhoff, Stephen R.

    1992-01-01

    Three competing bonding mechanisms have been identified for the alkaline-earth metal superoxides: these result in a change in the optimal structure and ground state as the alkaline-earth metal becomes heavier. For example, BeO2 has a linear 3Sigma(-)g ground-state structure, whereas both CaO2 and SrO2 have C(2v)1A1 structures. For MgO2, the theoretical calculations are less definitive, as the 3A2 C(2v) structure is computed to lie only about 3 kcal/mol above the 3Sigma(-)g linear structure. The bond dissociation energies for the alkaline-earth metal superoxides have been computed using extensive Gaussian basis sets and treating electron correlation at the modified coupled-pair functional or coupled-cluster singles and doubles level with a perturbational estimate of the triple excitations.

  1. Effect of various alkaline metal ions on electrochemical behavior of lead electrode in sulfuric acid solution

    NASA Astrophysics Data System (ADS)

    Hirai, Nobumitsu; Yamamoto, Yui

    2015-10-01

    The effect of various alkaline metal ions on electrochemical behavior of lead electrode in sulfuric acid solution has been investigated. It was found that "the specific anodic oxidation peak" appears at the cathodic scan in cyclic voltammogram of lead electrode in sulfuric acid solution containing Li2SO4, K2SO4, Na2SO4, Rb2SO4, or Cs2SO4. The height of the specific anodic oxidation peak varies with the alkaline sulfate in the solution; K2SO4 >> Na2SO4 > Cs2SO4 > Rb2SO4 > Li2SO4. It should be note that alkaline ions exist in lead sulfate formed on lead electrode in sulfuric acid solution containing potassium sulfate when the electrode was immersed in the solution at the rest potential for more than 1 h.

  2. MODELING AN ION EXCHANGE PROCESS FOR CESIUM REMOVAL FROM ALKALINE RADIOACTIVE WASTE SOLUTIONS

    SciTech Connect

    Smith, F; Luther Hamm, L; Sebastian Aleman, S; Johnston Michael, J

    2008-08-26

    The performance of spherical Resorcinol-Formaldehyde ion-exchange resin for the removal of cesium from alkaline radioactive waste solutions has been investigated through computer modeling. Cesium adsorption isotherms were obtained by fitting experimental data using a thermodynamic framework. Results show that ion-exchange is an efficient method for cesium removal from highly alkaline radioactive waste solutions. On average, two 1300 liter columns operating in series are able to treat 690,000 liters of waste with an initial cesium concentration of 0.09 mM in 11 days achieving a decontamination factor of over 50,000. The study also tested the sensitivity of ion-exchange column performance to variations in flow rate, temperature and column dimensions. Modeling results can be used to optimize design of the ion exchange system.

  3. Metal based synthetic routes to heavy alkaline earth aryloxo complexes involving ligands of moderate steric bulk.

    PubMed

    Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Guino-o, Marites; Ruhlandt-Senge, Karin

    2009-07-01

    Treatment of an alkaline earth metal (Ca, Sr, Ba) with 2,4,6-trimethylphenol (HOmes) at elevated temperatures in the presence of mercury under solvent-free conditions, followed by extraction of the reaction mixture with 1,2-dimethoxyethane (dme), afforded dinuclear alkaline earth aryloxo complexes [Ae2(Omes)4(dme)4] (Ae = Ca 1, Sr 3, Ba 6). Extraction of the Ca metal and HOmes reaction mixture with thf afforded [Ca3(Omes)6(thf)] 2. In contrast, redox transmetallation ligand exchange reactions between an alkaline earth metal, diphenylmercury and HOmes in dme yielded solely 1 for Ca metal, a mixture of 3 and the methoxide bridged cage [Sr5(Omes)5(OMe)5(dme)4] x 2dme 4 for Sr metal, and solely [Ba5(Omes)5(OMe)5(dme)4] x dme 7 for Ba metal. The methoxide ligands originate from the C-O activation of the dme solvent. Treatment of liquid ammonia activated Sr or Ba metal with HOmes in thf afforded the linear species [Ae3(Omes)6(thf)6] (Ae = Sr 5, Ba 8), and 8 was also obtained from barium metal and HOmes in refluxing thf. The structures of 1 and 3, determined by X-ray crystallography, consist of two six coordinate Ae metal atoms, to each of which is bound a terminal aryloxide ligand, two bridging aryloxide ligands, and chelating and unidentate dme ligands. The structures of 4 and 7 contain five Ae metal atoms arranged on the vertices of a distorted square based pyramid. The Ae atoms are linked by four mu3-OMe ligands and a mu4-OMe ligand. Four bridging aryloxide ligands and four chelating dme ligands complete the coordination spheres of the four seven coordinate Ae atoms at the base of the pyramid, and a terminal aryloxide ligand is bound to the five coordinate apical Ae atom. The structures of 5 and 8 consist of a trinuclear linear array of Ae metal atoms, and contain solely bridging aryloxide ligands. Three thf ligands are bound to each terminal Ae atom, giving all Ae atoms a coordination number of six. PMID:19662279

  4. Lifshitz and other transitions in alkaline-earth 122 pnictides under pressure

    NASA Astrophysics Data System (ADS)

    Quader, Khandker; Widom, Michael

    2014-10-01

    We carry out T =0 first-principles total energy calculations in the entire set of alkaline 122-pnictides (A Fe2As2 ; A = alkaline-earth element Ca, Sr, Ba, Ra) as a function of hydrostatic pressure. We find multiple distinct transitions to occur, namely an enthalpic transition in which the zero-pressure striped antiferromagnetic orthorhombic (OR-AFM) phase becomes thermodynamically less stable than a competing tetragonal (T) phase, a magnetic transition in which the OR-AFM phase loses its magnetism and orthorhombicity, and a lattice parameter anomaly in which the tetragonal c-axis collapses and a collapsed tetragonal (cT) phase becomes stable. Our results for energy band dispersions and spectra, lattice parameters, enthalpies, magnetism, and elastic constants over a wide range of hydrostatic pressure provide a coherent understanding of these experimentally observed transitions. In particular, the T-cT transition and anomalies in lattice parameters and elastic properties, observed at finite temperatures, are interpreted as arising from proximity to T =0 Lifshitz transitions, wherein pressure causes nontrivial changes in the Fermi surface topology in these materials.

  5. Impacts of artificial ocean alkalinization on the carbon cycle and climate in Earth system simulations

    NASA Astrophysics Data System (ADS)

    González, Miriam Ferrer; Ilyina, Tatiana

    2016-06-01

    Using the state-of-the-art emissions-driven Max Planck Institute Earth system model, we explore the impacts of artificial ocean alkalinization (AOA) with a scenario based on the Representative Concentration Pathway (RCP) framework. Addition of 114 Pmol of alkalinity to the surface ocean stabilizes atmospheric CO2 concentration to RCP4.5 levels under RCP8.5 emissions. This scenario removes 940 GtC from the atmosphere and mitigates 1.5 K of global warming within this century. The climate adjusts to the lower CO2 concentration preventing the loss of sea ice and high sea level rise. Seawater pH and the carbonate saturation state (Ω) rise substantially above levels of the current decade. Pronounced differences in regional sensitivities to AOA are projected, with the Arctic Ocean and tropical oceans emerging as hot spots for biogeochemical changes induced by AOA. Thus, the CO2 mitigation potential of AOA comes at a price of an unprecedented ocean biogeochemistry perturbation with unknown ecological consequences.

  6. Realizing SU(N) magnets in thermal alkaline-earth gases

    NASA Astrophysics Data System (ADS)

    Beverland, Michael; Gorshkov, Alexey; Rey, Ana Maria; Alagic, Gorjan

    2014-03-01

    We show that thermal fermionic alkaline-earth atoms in flat-bottom traps allow one to implement a spin model displaying two symmetries: the symmetry that swaps atoms occupying different vibrational levels of the trap and the SU(N) symmetry associated with N nuclear spin states. The high symmetry allows us to analytically calculate the full spectrum, the eigenstates, and the dynamics. Armed with such a solid understanding, we show how this system can be used to generate entangled states usable for Heisenberg limited metrology (e.g. clocks), to make measurements useful for quantum information processing, and to understand spin diffusion in SU(N) systems. The best news is that this highly symmetric spin model should be readily realizable even when the vibrational levels are occupied according to a high-temperature thermal or a non-thermal distribution.

  7. Magnetic crystals and helical liquids in alkaline-earth fermionic gases

    PubMed Central

    Barbarino, Simone; Taddia, Luca; Rossini, Davide; Mazza, Leonardo; Fazio, Rosario

    2015-01-01

    The joint action of a magnetic field and of interactions is crucial for the appearance of exotic quantum phenomena, such as the quantum Hall effect. Owing to their rich nuclear structure, equivalent to an additional synthetic dimension, one-dimensional alkaline-earth(-like) fermionic gases with synthetic gauge potential and atomic contact repulsion may display similar related properties. Here we show the existence and the features of a hierarchy of fractional insulating and conducting states by means of analytical and numerical methods. We demonstrate that the gapped states are characterized by density and magnetic order emerging solely for gases with effective nuclear spin larger than 1/2, whereas the gapless phases can support helical modes. We finally argue that these states are related to an unconventional fractional quantum Hall effect in the thin-torus limit and that their properties can be studied in state-of-the-art laboratories. PMID:26350624

  8. Properties of metastable alkaline-earth-metal atoms calculated using an accurate effective core potential

    SciTech Connect

    Santra, Robin; Christ, Kevin V.; Greene, Chris H.

    2004-04-01

    The first three electronically excited states in the alkaline-earth-metal atoms magnesium, calcium, and strontium comprise the (nsnp){sup 3}P{sub J}{sup o}(J=0,1,2) fine-structure manifold. All three states are metastable and are of interest for optical atomic clocks as well as for cold-collision physics. An efficient technique--based on a physically motivated potential that models the presence of the ionic core--is employed to solve the Schroedinger equation for the two-electron valence shell. In this way, radiative lifetimes, laser-induced clock shifts, and long-range interaction parameters are calculated for metastable Mg, Ca, and Sr.

  9. High-temperature properties of fermionic alkaline-earth-metal atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Hazzard, Kaden R. A.; Gurarie, Victor; Hermele, Michael; Rey, Ana Maria

    2012-04-01

    We calculate experimentally relevant properties of trapped fermionic alkaline-earth-metal atoms in an optical lattice, modeled by the SU(N) Hubbard model. We employ a high-temperature expansion that is accurate when the temperature is larger than the tunneling rate, similar to current regimes in ultracold atom experiments. In addition to exploring the Mott insulator-metal crossover, we calculate final temperatures achieved by the standard experimental protocol of adiabatically ramping from a noninteracting gas, as a function of initial gas temperature. Of particular experimental interest, we find that increasing N for fixed particle numbers and initial temperatures gives substantially colder Mott insulators after the adiabatic ramping, up to more than a factor of 5 for relevant parameters. This cooling happens for all N, fixing the initial entropy, or for all N≲20 (the exact value depends on dimensionality), at fixed, experimentally relevant initial temperatures.

  10. Magnesiacyclopentadienes as alkaline-earth metallacyclopentadienes: facile synthesis, structural characterization, and synthetic application.

    PubMed

    Wei, Junnian; Liu, Liang; Zhan, Ming; Xu, Ling; Zhang, Wen-Xiong; Xi, Zhenfeng

    2014-05-26

    Metallacyclopentadienes have attracted much attention as building blocks for synthetic chemistry as well as key intermediates in many metal-mediated or metal-catalyzed reactions. However, metallacyclopentadienes of the alkaline-earth metals have not been reported, to say nothing of their structures, reaction chemistry, and synthetic applications. In this work, the first series of magnesiacyclopentadienes, spiro-dilithio magnesiacyclopentadienes, and dimagnesiabutadiene were synthesized from 1,4-dilithio 1,3-butadienes. Single-crystal X-ray structural analysis of these magnesiacycles revealed unique structural characteristics and bonding modes. Their reaction chemistry and synthetic application were preliminarily studied and efficient access to amino cyclopentadienes was established through their reaction with thioformamides. Experimental and DFT calculations demonstrated that these magnesiacyclopentadienes could be regarded as bis(Grignard) reagents wherein the two Mg-C(sp(2)) bonds have a synergetic effect when reacting with substrates. PMID:24711256

  11. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1995-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  12. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite

    DOEpatents

    Tierney, J.W.; Wender, I.; Palekar, V.M.

    1995-01-24

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  13. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems. PMID:25317749

  14. Excitonic effects in the optical properties of alkaline earth chalcogenides from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Nejatipour, Hajar; Dadsetani, Mehrdad

    2015-08-01

    This paper studies excitonic effects in the optical properties of alkaline earth chalcogenides (AECs) by solving the equation of motion of the two-particle Green function, the Bethe-Salpeter equation (BSE). On the basis of quasi-particle states obtained by the GW approximation, (BSE + GW), the solution of BSE improves agreement with experiments. In these compounds, the main excitonic structures were reproduced appropriately. In the optical absorption spectra of AECs, the main excitonic structures originate in the direct transitions at X and Γ symmetry points, as confirmed by the experiments. In addition to real and imaginary parts of the dielectric functions, excitonic effects were studied in the electron energy loss functions of AECs. Moreover, the G0W0 approximation was used in order to determine the energy band gaps of AECs. This showed that except for MgO and BaO, the other AECs under study have indirect band gaps from Γ to X.

  15. Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.

    PubMed

    Yin, Jun; Hu, Ying; Yoon, Juyoung

    2015-07-21

    All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems.

  16. Laser-Induced Kondo Effect in Ultracold Alkaline-Earth Fermions.

    PubMed

    Nakagawa, Masaya; Kawakami, Norio

    2015-10-16

    We demonstrate that laser excitations can coherently induce a novel Kondo effect in ultracold atoms in optical lattices. Using a model of alkaline-earth fermions with two orbitals, it is shown that the optically coupled two internal states are dynamically entangled to form the Kondo-singlet state, overcoming the heating effect due to the irradiation. Furthermore, a lack of SU(N) symmetry in the optical coupling provides a peculiar feature in the Kondo effect, which results in spin-selective renormalization of effective masses. We also discuss the effects of interorbital exchange interactions, and reveal that they induce novel crossover or reentrant behavior of the Kondo effect owing to control of the coupling anisotropy. The laser-induced Kondo effect is highly controllable by tuning the laser strength and the frequency, and thus offers a versatile platform to study the Kondo physics using ultracold atoms.

  17. Quantum Degenerate Mixtures of Alkali and Alkaline-Earth-Like Atoms

    SciTech Connect

    Hara, Hideaki; Takasu, Yosuke; Yamaoka, Yoshifumi; Doyle, John M.; Takahashi, Yoshiro

    2011-05-20

    We realize simultaneous quantum degeneracy in mixtures consisting of the alkali and alkaline-earth-like atoms Li and Yb. This is accomplished within an optical trap by sympathetic cooling of the fermionic isotope {sup 6}Li with evaporatively cooled bosonic {sup 174}Yb and, separately, fermionic {sup 173}Yb. Using cross-thermalization studies, we also measure the elastic s-wave scattering lengths of both Li-Yb combinations, |a{sub {sup 6}Li-{sup 174}Yb}|=1.0{+-}0.2 nm and |a{sub {sup 6}Li-{sup 173}Yb}|=0.9{+-}0.2 nm. The equality of these lengths is found to be consistent with mass-scaling analysis. The quantum degenerate mixtures of Li and Yb, as realized here, can be the basis for creation of ultracold molecules with electron spin degrees of freedom, studies of novel Efimov trimers, and impurity probes of superfluid systems.

  18. Theoretical study of the dipole moments of selected alkaline-earth halides

    NASA Technical Reports Server (NTRS)

    Langhoff, S. R.; Bauschlicher, C. W., Jr.; Partridge, H.; Ahlrichs, R.

    1986-01-01

    Ab initio calculations at the self-consistent-field (SCF), singles-plus-doubles configuration-interaction (SDCI), and coupled-pair functional (CPF) level, are reported for the dipole moments and dipole derivatives of the X2Sigma(+) ground states of BeF, BeCl, MgF, MgCl, CaF, CaCl, and SrF. For comparison, analogous calculations are performed for the X1Sigma(+) state of KCl. The CPF results are found to be in remarkably better agreement with experiment than are the SCF and SDCI results. Apparently higher excitations are required to properly describe the radial extent along the bond axis of the remaining valence electron on the alkaline-earth metal.

  19. Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor.

    PubMed

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    Recent improvements to SrAl2O4:Eu2+, Dy3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl2O4:Eu2+, Dy3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl2O4:Eu2+, Dy3+ crystals. We found that a Dy3+/Eu2+ ratio of ~2.4 and ~0.935 mol Eu2+ (per mol of SrAl2O4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li+ (per mol of SrAl2O4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg2+ and 0.005 mol Li+ (per 1 mol SrAl2O4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:26731086

  20. Adsorption of alkali, alkaline-earth, and 3d transition metal atoms on silicene

    NASA Astrophysics Data System (ADS)

    Sahin, H.; Peeters, F. M.

    2013-02-01

    The adsorption characteristics of alkali, alkaline-earth, and transition metal adatoms on silicene, a graphene-like monolayer structure of silicon are analyzed by means of first-principles calculations. In contrast to graphene, interaction between the metal atoms and the silicene surface is quite strong due to its highly reactive buckled hexagonal structure. In addition to structural properties, we also calculate the electronic band dispersion, net magnetic moment, charge transfer, work function, and dipole moment of the metal adsorbed silicene sheets. Alkali metals, Li, Na, and K, adsorb to hollow sites without any lattice distortion. As a consequence of the significant charge transfer from alkalis to silicene, metalization of silicene takes place. Trends directly related to atomic size, adsorption height, work function, and dipole moment of the silicene/alkali adatom system are also revealed. We found that the adsorption of alkaline-earth metals on silicene is entirely different from their adsorption on graphene. The adsorption of Be, Mg, and Ca turns silicene into a narrow gap semiconductor. Adsorption characteristics of eight transition metals Ti, V, Cr, Mn, Fe, Co, Mo, and W are also investigated. As a result of their partially occupied d orbital, transition metals show diverse structural, electronic, and magnetic properties. Upon the adsorption of transition metals, depending on the adatom type and atomic radius, the system can exhibit metal, half-metal, and semiconducting behavior. For all metal adsorbates, the direction of the charge transfer is from adsorbate to silicene, because of its high surface reactivity. Our results indicate that the reactive crystal structure of silicene provides a rich playground for functionalization at nanoscale.

  1. Effect of Composition and Impurities on the Phosphorescence of Green-Emitting Alkaline Earth Aluminate Phosphor

    PubMed Central

    Kim, Doory; Kim, Han-Eol; Kim, Chang-Hong

    2016-01-01

    Recent improvements to SrAl2O4:Eu2+, Dy3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl2O4:Eu2+, Dy3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl2O4:Eu2+, Dy3+ crystals. We found that a Dy3+/Eu2+ ratio of ~2.4 and ~0.935 mol Eu2+ (per mol of SrAl2O4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li+ (per mol of SrAl2O4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg2+ and 0.005 mol Li+ (per 1 mol SrAl2O4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. PMID:26731086

  2. Electrogeneration of hydroperoxide ion using an alkaline fuel cell

    SciTech Connect

    Alcaide, F.; Brillas, E.; Cabot, P.L.; Casado, J.

    1998-10-01

    Hydrogen peroxide is a pollution-control chemical commonly used as a bleaching agent, as a disinfectant, and as a nonselective oxidant for water purification and in different industrial processes. This paper describes a novel electrochemical method for the generation of HO{sub 2}{sup {minus}} using an alkaline fuel cell (AFC). The system is formed by an undivided cell containing a H{sub 2}-diffusion anode, an O{sub 2}-diffusion cathode, and a KOH solution as electrolyte. It can work in batch or in continuous mode, cogenerating electricity and HO{sub 2}{sup {minus}}, which is formed from the two-electron reduction of O{sub 2} at the cathode. The evolution of cell voltage, current density, HO{sub 2}{sup {minus}} production, and current efficiency with time have been determined when the electrolyte remains quiescent, recirculates through the cell, or is continuously injected to it. This last device yields the best operative parameters, allowing current densities of 130 mA/cm{sup 2} and current efficiencies close to 100% using 1 mol/dm{sup 3} KOH at 20 C. The effect of HO{sub 2}{sup {minus}} upon the anodic and cathodic reactions has been studied by linear sweep voltammetry. Adsorption of this species on the cathode can explain the loss of performance of the AFC with working time using a quiescent electrolyte or under recirculation conditions. The O{sub 2}-diffusion cathode and the AFC showed good reversibility when the cell contained a fresh KOH solution with HO{sub 2}{sup {minus}}.

  3. SEPARATION OF PLUTONYL IONS

    DOEpatents

    Connick, R.E.; McVey, Wm.H.

    1958-07-15

    A process is described for separating plutonyl ions from the acetate ions with which they are associated in certaln carrier precipitation methods of concentrating plutonium. The method consists in adding alkaline earth metal ions and subsequently alkalizing the solution, causing formation of an alkaltne earth plutonate precipitate. Barium hydroxide is used in a preferred embodiment since it provides alkaline earth metal ion and alkalizes the solution in one step forming insoluble barium platonate.

  4. Influence of alkaline earth metals on molecular structure of 3-nitrobenzoic acid in comparison with alkali metals effect

    NASA Astrophysics Data System (ADS)

    Samsonowicz, M.; Regulska, E.; Lewandowski, W.

    2011-11-01

    The influence of beryllium, magnesium, calcium, strontium and barium cations on the electronic system of 3-nitrobenzoic acid was studied in comparison with studied earlier alkali metal ions [1]. The vibrational FT-IR (in KBr and ATR techniques) and 1H and 13C NMR spectra were recorded for 3-nitrobenzoic acid and its salts. Characteristic shifts in IR and NMR spectra along 3-nitrobenzoates of divalent metal series Mg → Ba were compared with series of univalent metal Li → Cs salts. Good correlations between the wavenumbers of the vibrational bands in the IR spectra for 3-nitrobenzoates and ionic potential, electronegativity, inverse of atomic mass, atomic radius and ionization energy of metals were found for alkaline earth metals as well as for alkali metals. The density functional (DFT) hybrid method B3LYP with two basis sets: 6-311++G** and LANL2DZ were used to calculate optimized geometrical structures of studied compounds. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in NMR spectra were obtained. Geometric aromaticity indices, atomic charges, dipole moments and energies were also calculated. The calculated parameters were compared to experimental characteristic of studied compounds.

  5. Synergetic effect of alkaline earth metal oxides and iron oxides on the degradation of hexachlorobenzene and its degradation pathway.

    PubMed

    Su, Guijin; Liu, Yexuan; Huang, Linyan; Shi, Yali; Zhang, Aiqian; Zhang, Lixia; Liu, Wenbin; Gao, Lirong; Zheng, Minghui

    2013-01-01

    The degradation of hexachlorobenzene (HCB) was carried out over physical mixtures of a series of alkaline earth metal oxides (MO: M=Mg, Ca, Sr, Ba) and iron oxides with different crystal types (Fe(x)O(y):Fe(2)O(3) or Fe(3)O(4)) at 300°C. These physical mixtures all showed a synergetic effect toward the degradation of HCB. A range of degradation products were identified by various methods, including tri- to penta-chlorobenzenes by gas chromatography/mass spectrometry (GC-MS), tri- to penta-chlorophenols, tetrachlorocatechol (TCC) and tetrachlorohydroquinone (TCHQ) by GC-MS after derivatization, and formic and acetic acids by ion chromatography. Two degradation pathways, hydrodechlorination and oxidative degradation, appear to occur competitively. However, more sequential chlorinated benzene and phenol congeners were formed over mixed MO/Fe(3)O(4) than over mixed MO/Fe(2)O(3) under the same conditions. The oxidative reaction dominated over mixed MO/Fe(2)O(3) and was promoted as the major reaction by the synergetic effect, while both the oxidative and hydrodechlorination reactions were important over mixed MO/Fe(3)O(4), and both pathways are remarkably promoted by the synergetic effect. The enhanced hydrodechlorination may be attributed to free electrons generated by the transformation of Fe(3)O(4) into Fe(2)O(3), and hydrogen provided by water adsorbed on the MO.

  6. Activation of X-H and X-D bonds (X = O, N, C) by alkaline-earth metal monoxide cations: experiment and theory.

    PubMed

    Bozović, Andrea; Bohme, Diethard K

    2009-07-28

    Experimental investigations are reported for reactions of MO (+) (M = Ca, Sr, and Ba) with elemental hydrides water, ammonia and methane proceeding in the gas phase at 295 +/- 3 K in helium buffer gas at a pressure of 0.35 +/- 0.01 Torr. Measurements were taken with an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer and a novel electrospray ion source/ion selection quadrupole/selected-ion flow tube/triple quadrupole (ESI/qQ/SIFT/QqQ) mass spectrometer. All three alkaline-earth metal oxide ions exclusively abstract a H-atom from the three hydrides with rate coefficients > 1 x 10(-11) cm(3) molecule(-1) s(-1). Formation of metal hydroxide ion was followed by sequential addition of water or ammonia, but not methane. Density functional calculations have provided potential energy surfaces for the X-H bond activations leading to H-atom abstraction as well as those for O-atom transfer and H(2)O elimination (with ammonia and methane). A comparison of experimental and theoretical isotope effects points toward a mechanism involving the direct atom transfer from XH and XD to O in MO (+)via a three-centered transition structure. PMID:19588017

  7. Observations of molecular ions in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Craven, P. D.; Chappell, C. R.; Kakani, L.; Olsen, R. C.

    1985-01-01

    The retarding ion mass spectrometer on Dynamics Explorer 1 operating over the polar cap during a large magnetic storm has measured fluxes of up to 10 to the 6th ions/sq cm s of the molecular ions N2(+), NO(+), and O2(+). These ions were measured beginning low in the satellite orbit (1.1 earth radii) and extending to about 3 earth radii geocentric altitude. Near perigee, the ions have a rammed distribution indicating a cold Maxwellian plasma (1000-2000 K). The molecular ions gradually shift to a field-aligned distribution at the higher alitudes. An upward flow of 5-10 km/s is found in these field-aligned measurements. The density of the molecular ions is on the order of 2/cu cm at all altitudes, and the energy of the ions generally increases as the satellite moves sunward across the southern polar cap. Kinetic energies of at least 20 eV were found at 2.5 earth-radii geocentric distance.

  8. Structural, elastic, electronic and optical properties of layered alkaline-earth halofluoride scintillators

    NASA Astrophysics Data System (ADS)

    Kanchana, V.; Yedukondalu, N.; Vaitheeswaran, G.

    2013-09-01

    A systematic investigation of structural properties at ambient as well as at high pressure has been carried out for layered scintillators CaClF, CaBrF, SrClF, SrBrF and SrIF based on density functional theory. Semi-empirical dispersion correction scheme has been used to account for the van der Waals interactions and the obtained results are in good agreement with experimental data. The pressure-dependent structural and elastic properties reveal that the c-axis is more compressible than the a-axis (C ? ? ) in all these materials due to weakly bonded layers stacked along the c-axis. In addition, the electronic structure and optical properties of these materials are calculated using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential. Among the five investigated compounds which are structurally anisotropic, a weak optical anisotropy is found in CaClF and SrClF and strong optical anisotropy in CaBrF, SrBrF and SrIF. The present study suggests that unlike alkaline-earth dihalides which are fast scintillators, these materials can act as storage phosphors and the possible reason is speculated from the band structure calculations.

  9. Mixed alkali effect on the spectroscopic properties of alkali-alkaline earth oxide borate glasses

    NASA Astrophysics Data System (ADS)

    Srinivas, G.; Ramesh, B.; Shareefuddin, Md.; Chary, M. N.; Sayanna, R.

    2016-05-01

    The mixed alkali and alkaline earth oxide borate glass with the composition xK2O - (25-x) Li2O-12.5BaO-12.5MgO-50B2O3 (x = 0, 5, 10, 15, 20 and 25mol %) and doped with 1mol% CuO were prepared by the melt quenching technique. From the optical absorption spectra the optical band gap, electronic polarizability(α02-), interaction parameter (A), theoretical and experimental optical basicity (Λ) values were evaluated. From the Electron Paramagnetic Resonance (EPR) spectral data the number of spins (N) and susceptibility (χ) were evaluated. The values of (α02-), and (Λ) increases with increasing of K2O content and electronic polarizability and interaction parameter show opposite behaviuor which may be due to the creation of non-bridging oxygens and expansion of borate network. The reciprocal of susceptibility (1/χ) and spin concentration (N) as a function of K2O content, varied nonlinearly which may be due to creation of non-bridging oxygens in the present glass system. This may be attributed to mixed alkali effect (MAE).

  10. Collective non-equilibrium spin exchange in cold alkaline-earth atomic clocks

    NASA Astrophysics Data System (ADS)

    Acevedo, Oscar Leonardo; Rey, Ana Maria

    2016-05-01

    Alkaline-earth atomic (AEA) clocks have recently been shown to be reliable simulators of two-orbital SU(N) quantum magnetism. In this work, we study the non-equilibrium spin exchange dynamics during the clock interrogation of AEAs confined in a deep one-dimensional optical lattice and prepared in two nuclear levels. The two clock states act as an orbital degree of freedom. Every site in the lattice can be thought as populated by a frozen set of vibrational modes collectively interacting via predominantly p-wave collisions. Due to the exchange coupling, orbital state transfer between atoms with different nuclear states is expected to happen. At the mean field level, we observe that in addition to the expected suppression of population transfer in the presence of a large magnetic field, that makes the single particle levels off-resonance, there is also an interaction induced suppression for initial orbital population imbalance. This suppression resembles the macroscopic self-trapping mechanism seen in bosonic systems. However, by performing exact numerical solutions and also by using the so-called Truncated Wigner Approximation, we show that quantum correlations can significantly modify the mean field suppression. Our predictions should be testable in optical clock experiments. Project supported by NSF-PHY-1521080, JILA-NSF-PFC-1125844, ARO, AFOSR, and MURI-AFOSR.

  11. CP(N - 1) quantum field theories with alkaline-earth atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Laflamme, C.; Evans, W.; Dalmonte, M.; Gerber, U.; Mejía-Díaz, H.; Bietenholz, W.; Wiese, U.-J.; Zoller, P.

    2016-07-01

    We propose a cold atom implementation to attain the continuum limit of (1 + 1) -d CP(N - 1) quantum field theories. These theories share important features with (3 + 1) -d QCD, such as asymptotic freedom and θ-vacua. Moreover, their continuum limit can be accessed via the mechanism of dimensional reduction. In our scheme, the CP(N - 1) degrees of freedom emerge at low energies from a ladder system of SU(N) quantum spins, where the N spin states are embodied by the nuclear Zeeman states of alkaline-earth atoms, trapped in an optical lattice. Based on Monte Carlo results, we establish that the continuum limit can be demonstrated by an atomic quantum simulation by employing the feature of asymptotic freedom. We discuss a protocol for the adiabatic preparation of the ground state of the system, the real-time evolution of a false θ-vacuum state after a quench, and we propose experiments to unravel the phase diagram at non-zero density.

  12. Promotion by tetrachloromethane of the oxidative coupling of methane on silica-supported alkaline earth oxides

    SciTech Connect

    Ahmed, S.; Moffat, J.B. )

    1990-02-01

    The introduction of a small quantity of tetrachloromethane (TEM) into the feed stream has been shown to remarkably enhance the oxidative coupling of methane over alkaline earth oxides supported on silica. That this enhancement, in terms of both selectivity and yield to C{sub 2} hydrocarbons, occurs over a wide range of catalyst loading, feed composition, reaction temperature, and contact time has been illustrated using BaO/SiO{sub 2} as the catalyst. It has been demonstrated that over this catalyst, the coupling and nonselective oxidation processes occur predominantly independently of each other. The high ratio of C{sub 2}H{sub 4}/C{sub 2}H{sub 6} observed in the products is accounted for by the rapid homogeneous oxidative dehydrogenation of C{sub 2}H{sub 6}, a process which is evidently further enhanced by the presence of TCM. It is suggested that TCM promotes the coupling reaction by facilitating the hydrogen abstraction step from methane. Continuous cofeeding of the additive is required to maintain high selectivity and yield of C{sub 2} hydrocarbons in the products.

  13. Superconducting critical fields of alkali and alkaline-earth intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Somoano, R. B.

    1976-01-01

    Results are reported for measurements of the critical-field anisotropy and temperature dependence of group-VIB semiconductor MoS2 intercalated with the alkali and alkaline-earth metals Na, K, Rb, Cs, and Sr. The temperature dependences are compared with present theories on the relation between critical field and transition temperature in the clean and dirty limits over the reduced-temperature range from 1 to 0.1. The critical-field anisotropy data are compared with predictions based on coupled-layers and thin-film ('independent-layers') models. It is found that the critical-field boundaries are steep in all cases, that the fields are greater than theoretical predictions at low temperatures, and that an unusual positive curvature in the temperature dependence appears which may be related to the high anisotropy of the layer structure. The results show that materials with the largest ionic intercalate atom diameters and hexagonal structures (K, Rb, and Cs compounds) have the highest critical temperatures, critical fields, and critical-boundary slopes; the critical fields of these materials are observed to exceed the paramagnetic limiting fields.

  14. Optical properties of alkaline-earth metal oxides from first principles

    NASA Astrophysics Data System (ADS)

    Dadsetani, M.; Beiranvand, R.

    2009-12-01

    This study reports the results of an ab initio electronic and optical calculation of alkaline-earth metal oxides (MgO, CaO, SrO and BaO) in the NaCl crystal structure using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory. The exchange-correlation potential is treated by the generalized gradient approximation within the Perdew et al scheme. Moreover, the Engel-Vosko GGA formalism is applied so as to optimize the corresponding potential for band structure calculations. The real and imaginary parts of the dielectric function ɛ( ω), the optical absorption coefficient I( ω), the reflectivity R( ω) and the energy loss function are calculated by random phase approximation (RPA). The calculated results show a qualitative agreement with the available experimental results in the sense that we can recognize some peaks qualitatively, those due to single particle transitions. Furthermore the interband transitions responsible for the structures in the spectra are specified. It is shown that the oxygen 2 p states and metal d states play the major role in optical transitions as initial and final states respectively. The effect of the spin-orbit coupling on the optical properties is also investigated and found to be quite small, especially in the low energy region. The dielectric constants are calculated and compared with the available theoretical and experimental results.

  15. Process for depositing epitaxial alkaline earth oxide onto a substrate and structures prepared with the process

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    1996-01-01

    A process and structure involving a silicon substrate utilize molecular beam epitaxy (MBE) and/or electron beam evaporation methods and an ultra-high vacuum facility to grow a layup of epitaxial alkaline earth oxide films upon the substrate surface. By selecting metal constituents for the oxides and in the appropriate proportions so that the lattice parameter of each oxide grown closely approximates that of the substrate or base layer upon which oxide is grown, lattice strain at the film/film or film/substrate interface of adjacent films is appreciably reduced or relieved. Moreover, by selecting constituents for the oxides so that the lattice parameters of the materials of adjacent oxide films either increase or decrease in size from one parameter to another parameter, a graded layup of films can be grown (with reduced strain levels therebetween) so that the outer film has a lattice parameter which closely approximates that of, and thus accomodates the epitaxial growth of, a pervoskite chosen to be grown upon the outer film.

  16. Theoretical Investigation of the M+-RG2 (m = Alkaline Earth Metal; RG = Rare Gas) Complexes

    NASA Astrophysics Data System (ADS)

    Gardner, Adrian M.; Plowright, Richard J.; Graneek, Jack; Wright, Timothy G.; Breckenridge, W. H.

    2012-06-01

    Metal cation rare gas complexes provide an expectedly simple system with which to investigate intermolecular interactions. Despite this, we have previously found the M+-RG (M = alkaline earth metal) complexes to very complicated systems, with the complexes of the heavier rare gases displaying surprisingly large degrees of chemical character. Here we extend these studies by examining the nature of these interactions with increasing degrees of solvation through investigating the M+-RG_2 complexes using high level {ab initio} techniques. Intriguing trends in the geometries and dissociation energies of these complexes have been observed and are rationalized. A. M. Gardner, C. D. Withers, J. B. Graneek, T. G. Wright, L. A. Viehland and W. H. Breckenridge, J. Phys. Chem. A, 2000, 114, 7631. A. M. Gardner, C. D. Withers, T. G. Wright, K. I. Kaplan, C. Y. N. Chapman, L. A. Viehland, E. P. F. Lee and W. H. Breckenridge, J. Chem. Phys., 2010, 132, 054302. M. F. McGuirk, L. A. Viehland, E. P. F. Lee, W. H. Breckenridge, C. D. Withers, A. M. Gardner, R. J. Plowright and T. G. Wright, J. Chem. Phys., 2009, 130, 194305.

  17. Alkaline earth silicate wools - A new generation of high temperature insulation.

    PubMed

    Brown, Robert C; Harrison, Paul T C

    2012-11-01

    Intensive study of the natural asbestiform minerals that cause human diseases, and the consequent understanding of their hazardous characteristics, has enabled the development of manufactured fibres whose physical and/or chemical properties, in particular as they relate to biopersistence, have been adjusted to minimize possible harm to health. A strong driver for the developmentof new high temperature insulation materials wasthe perception of the toxicity of refractory ceramic fibres (RCF)and their classification in the EU as a category 2 carcinogen under Directive 67/548/EEC. Such classification carries with it the requirement for substitution by less hazardous materials. This paper focuses on the development of alkaline earth silicate (AES) wools as a new class of high temperature insulation with the capability of such substitution in a number of applications. These wools have only a low potential to cause harm because they do not persist in lung tissue once deposited, and have produced minimal effects in experimental test systems. AES wools are increasingly being used in a wide range of high temperature applications.

  18. Earth's polar cap ionization patches lead to ion upflow

    NASA Astrophysics Data System (ADS)

    Zhang, Q. H.; Zong, Q.; Lockwood, M. M.; Liang, J.; Zhang, B.; Moen, J. I.; Zhang, S.; Zhang, Y.; Ruohoniemi, J. M.; Thomas, E. G.; Liu, R.; Dunlop, M. W.; Yang, H. G.; Hu, H.; Liu, Y.; Lester, M.

    2014-12-01

    The Earth constantly losses matter through ions escaping from the polar ionosphere. This makes the ionosphere as an important source of plasma for the magnetosphere and could modulate atmospheric isotope abundances on geological timescales, depending on what fraction of the upflowing ions subsequently return to the ionosphere and what fraction are ejected into interplanetary space. It has been proposed that the magnetosphere is dynamically modulated by the presence of the ionospheric ions, particularly heavy ions O+, during magnetic substorms and storms. The origin and formation mechanism of ionospheric ion upflow is, however, poorly understood, particularly under disturbed space weather conditions. We report simultaneous direct observations of ion upflow and a patch of ionization at the center of the polar cap region during a geomagnetic storm. Our observations indicate enhanced fluxes of upwelling O+ ions originate from the patch and were accelerated by the enhanced ambipolar electric field. This enhancement is caused by soft electron precipitations. Polar cap patches therefore provide an important source of upwelling ions for accelerations mechanisms at greater altitudes which can eject the ions. These observations give new insight into the processes of ionosphere-magnetosphere coupling and the potential loss of terrestrial water dissociation products into space which, although extremely slow in the case of Earth, may be significant for other planets and moons.

  19. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals.

    PubMed

    Liu, Yuanyue; Merinov, Boris V; Goddard, William A

    2016-04-01

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

  20. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals.

    PubMed

    Liu, Yuanyue; Merinov, Boris V; Goddard, William A

    2016-04-01

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems. PMID:27001855

  1. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals

    NASA Astrophysics Data System (ADS)

    Liu, Yuanyue; Merinov, Boris V.; Goddard, William A., III

    2016-04-01

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion-substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.

  2. Effect of common ions on nitrate removal by zero-valent iron from alkaline soil.

    PubMed

    Tang, Cilai; Zhang, Zengqiang; Sun, Xining

    2012-09-15

    Zero-valent iron (Fe(0))-based permeable reactive barrier (PRB) technology has been proved to be effective for soil and groundwater nitrate remediation under acidic or near neutral conditions. But few studies have been reported about it and the effects of coexistent ions under alkaline conditions. In this study, nitrate reduction by Fe(0) was evaluated via batch tests in the presence of alkaline soil and common cation (Fe(2+), Fe(3+) and Cu(2+)) and anion (citrate, oxalate, acetate, SO(4)(2-), PO(4)(3-), Cl(-) and HCO(3)(-)). The results showed that cation significantly enhanced nitrate reduction with an order of Fe(3+)>Fe(2+)>Cu(2+) due to providing Fe(2+) directly or indirectly. Most anions enhanced nitrate reduction, but PO(4)(3-) behaved inhibition. The promotion decreased in the order of citrate>acetate>SO(4)(2-)>Cl(-)≈HCO(3)(-)≈oxalate≫PO(4)(3-). Ammonium was the major final product from nitrate reduction by Fe(0), while a little nitrite accumulated in the beginning of reaction. The nitrogen recovery in liquid and gas phase was only 56-78% after reaction due to ammonium adsorption onto soil. The solution pH and electric conductivity (EC) varied depending on the specific ion added. The results implied that PRB based Fe(0) is a potential approach for in situ remediation of soil and groundwater nitrate contamination in the alkaline conditions.

  3. Formation of iron oxides in a highly alkaline medium in the presence of palladium ions

    NASA Astrophysics Data System (ADS)

    Krehula, Stjepko; Musić, Svetozar

    2009-04-01

    The effect of the presence of palladium ions in a highly alkaline precipitation system on the formation of iron oxides was investigated using X-ray powder diffraction (XRPD), Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Acicular α-FeOOH particles precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. The initial addition of palladium ions to that precipitation system had a significant effect on the formation of iron oxide phases and their properties. In the presence of palladium ions, the initially formed α-FeOOH has been transformed to α-Fe 2O 3 crystals in the form of hexagonal bipyramids via a dissolution-reprecipitation mechanism with a simultaneous formation of metallic palladium nanoparticles. These palladium nanoparticles acted as a catalyst for the reductive dissolution of α-Fe 2O 3 particles and the formation of Fe 3O 4 crystals in the form of octahedrons. Increase in the initial concentration of palladium ions in the precipitation system accelerated the transformation process α-FeOOH → α-Fe 2O 3 → Fe 3O 4 and influenced changes in the shape of α-Fe 2O 3 and Fe 3O 4 particles.

  4. The contents of alkali and alkaline earth metals in soils of the southern Cis-Ural region

    NASA Astrophysics Data System (ADS)

    Asylbaev, I. G.; Khabirov, I. K.

    2016-01-01

    The contents and distribution patterns of alkali and alkaline earth metals in soils and rocks of the southern Cis-Ural region were studied. A database on the contents of these metals was developed, the soils were classified with respect to their provision with these metals, and corresponding schematic maps showing their distribution in soils of the region were compiled. It was found that the contents of these metals decrease from east to west (from the Yuryuzan-Aisk Piedmont Plain to the Ufa Plateau and to the Belebeevsk Upland), and their distribution patterns change. Among alkali metals, the highest accumulation in the soils is typical of potassium, sodium, and cesium; among alkaline earth metals, of strontium and barium.

  5. Optimizing the performance of bandpass photon detectors for inverse photoemission: Transmission of alkaline earth fluoride window crystals

    SciTech Connect

    Thiede, Christian Schmidt, Anke B.; Donath, Markus

    2015-08-15

    Bandpass photon detectors are widely used in inverse photoemission in the isochromat mode at energies in the vacuum-ultraviolet spectral range. The energy bandpass of gas-filled counters is usually formed by the ionization threshold of the counting gas as high-pass filter and the transmission cutoff of an alkaline earth fluoride window as low-pass filter. The transmission characteristics of the window have, therefore, a crucial impact on the detector performance. We present transmission measurements in the vacuum-ultraviolet spectral range for alkaline earth fluoride window crystals in the vicinity of the transmission cutoff as a function of crystal purity, surface finish, surface contamination, temperature, and thickness. Our findings reveal that the transmission characteristics of the window crystal and, thus, the detector performance depend critically on these window parameters.

  6. Evaluation of the Influence of Beam Ions Exhausted from Ion Thrusters on Earth's Environment and Communication

    NASA Astrophysics Data System (ADS)

    Yamagiwa, Yoshiki; Kumatani, Yasuhiro; Miyamoto, Shigehiro; Otsu, Hirotaka

    The influence of exhausted beam ions from ion thrusters on Earth's environment and communication was analyzed by the detailed modeling of the exhausted ions' and electrons' motion and the energy exchange process between the exhausted ions and the circumferential particles. The analytical results showed that the density distribution of plasma components near the earth will change locally by the energy input of exhausted ions trapped by the geomagnetic field if the large scale operation of ion thrusters is performed, but its influence on earth's environment will be small compared with that by the natural phenomena such a magnetic storm. However, the influence on GPS communication will be large and the electrical charge of spacecraft will be progressed.

  7. The etching process of boron nitride by alkali and alkaline earth fluorides under high pressure and high temperature

    SciTech Connect

    Guo, W.; Ma, H.A.; Jia, X.

    2014-03-01

    Graphical abstract: - Highlights: • Appropriate etch processes of hBN and cBN under HPHT are proposed. • The degree of the crystallization of hBN was decreased. • A special cBN growth mechanism with a triangular unit is proposed. • Plate-shape cBN crystals with large ratio of length to thickness were obtained. • A strategy provides useful guidance for controlling the cBN morphology. - Abstract: Some new etching processes of hexagonal boron nitride (hBN) and cubic boron nitride (cBN) under high pressure and high temperature in the presence of alkali and alkaline earth fluorides have been discussed. It is found that hBN is etched distinctly by alkali and alkaline earth fluorides and the morphology of hBN is significantly changed from plate-shape to spherical-shape. Based on the “graphitization index” values of hBN, the degree of the crystallization of hBN under high pressure and high temperature decreases in the sequence of LiF > CaF{sub 2} > MgF{sub 2}. This facilitates the formation of high-quality cBN single crystals. Different etch steps, pits, and islands are observed on cBN surface, showing the strong etching by alkali and alkaline earth fluorides and the tendency of layer-by-layer growth. A special layer growth mechanism of cBN with a triangular unit has been found. Furthermore, the morphologies of cBN crystals are apparently affected by a preferential surface etching of LiF, CaF{sub 2} and MgF{sub 2}. Respectively, the plate-shape and tetrahedral cBN crystals can be obtained in the presence of different alkali and alkaline earth fluorides.

  8. Charge Compensation in RE3+ (RE = Eu, Gd) and M+ (M = Li, Na, K) Co-Doped Alkaline Earth Nanofluorides Obtained by Microwave Reaction with Reactive Ionic Liquids Leading to Improved Optical Properties

    SciTech Connect

    Lorbeer, C; Behrends, F; Cybinska, J; Eckert, H; Mudring, Anja -V

    2014-01-01

    Alkaline earth fluorides are extraordinarily promising host matrices for phosphor materials with regard to rare earth doping. In particular, quantum cutting materials, which might considerably enhance the efficiency of mercury-free fluorescent lamps or SC solar cells, are often based on rare earth containing crystalline fluorides such as NaGdF4, GdF3 or LaF3. Substituting most of the precious rare earth ions and simultaneously retaining the efficiency of the phosphor is a major goal. Alkaline earth fluoride nanoparticles doped with trivalent lanthanide ions (which are required for the quantum cutting phenomenon) were prepared via a microwave assisted method in ionic liquids. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect was thoroughly studied by powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR spectroscopy. Monovalent alkali ions were codoped with the trivalent lanthanide ions to relieve stress and achieve a better crystallinity and higher quantum cutting abilities of the prepared material. 19F-magic angle spinning (MAS)-NMR-spectra, assisted by 19F{23Na} rotational echo double resonance (REDOR) studies, reveal distinct local fluoride environments, the populations of which are discussed in relation to spatial distribution and clustering models. In the co-doped samples, fluoride species having both Na+ and La3+ ions within their coordination sphere can be identified and quantified. This interplay of mono- and trivalent ions in the CaF2 lattice appears to be an efficient charge compensation mechanism that allows for improved performance characteristics of such co-doped phosphor materials.

  9. The significance of secondary interactions during alkaline earth-promoted dehydrogenation of dialkylamine-boranes.

    PubMed

    Bellham, Peter; Anker, Mathew D; Hill, Michael S; Kociok-Köhn, Gabriele; Mahon, Mary F

    2016-09-21

    a modified mechanism for group 2-mediated dimethylamine borane dehydrocoupling that is dependent on the intermediacy of key derivatives of the [NMe2·BH3](-) and [NMe2BH2NMe2BH3](-) anions but does not require the formation of high energy alkaline earth hydride intermediates. Although these results are specifically focussed on the applications of alkaline earth species, this mechanistic insight may also be relevant to other redox-inactive main group element-based systems and to our understanding of hydrogen evolution from saline derivatives of ammonia borane. PMID:27529536

  10. Novel alkaline earth copper germanates with ferro and antiferromagnetic S=1/2 chains

    SciTech Connect

    Brandao, Paula; Reis, Mario S; Gai, Zheng; Moreira Dos Santos, Antonio F

    2013-01-01

    Two new alkaline earth copper(II) germanates were hydrothermally synthesized: CaCuGeO4 center dot H2O (1) and BaCu2Ge3O9 center dot H2O (2), and their structures determined by single crystal X-ray diffraction. Compound (1) crystallizes in space group P2(1)/c with a=5.1320(2) angstrom, b=16.1637(5) angstrom, c=5.4818(2) angstrom, beta=102.609(2)degrees, V=443.76(3) angstrom(3) and Z=4. This copper germanate contains layers of composition [CuGeO4](infinity)(2-) comprising CuO4 square planes and GeO4 tetrahedra with calcium and water molecules in the inter-layer space. Compound (2) crystallizes in the Cmcm space group with a=5.5593(3) angstrom, b=10.8606(9) angstrom, c=13.5409(8) angstrom, V=817.56(9) angstrom(3) and Z=4. This structure contains GeO6 and CuO6 octahedra as well as GeO4 tetrahedra, forming a three-dimensional network of interconnecting six-membered ring channels. The magnetic susceptibility for both samples can be interpreted as S=1/2 chains, in agreement with the copper topology observed in the crystal structure. The susceptibility of (1) exhibits a Bonner-Fisher type behavior, resulting from antiferromagnetic intra-chain interactions without three-dimensional ordering down to 5 K-the lowest measured temperature. This observation, together with the absence of super-exchange paths between the copper chains, make this system particularly promising for the study of low dimensional magnetism. The magnetic properties of (2) show a very weak ferromagnetic near-neighbor interaction along the chain. In this compound a peak the chi T plot seems to indicate the onset of interchain antiferromagentic correlations. However, no ordering temperature is detected in the susceptibility data.

  11. Density Measurement of Molten Alkaline-Earth Fluorides Using Archimedean Dual-Sinker Method

    NASA Astrophysics Data System (ADS)

    Takeda, Osamu; Yanagase, Kei-ichi; Anbo, Yusuke; Aono, Masahiro; Hoshino, Yosuke; Sato, Yuzuru

    2015-11-01

    The densities of molten alkaline-earth fluorides ({MgF}2, {CaF}2, {SrF}2, and {BaF}2) were measured over the temperature range from 1526 K to 1873 K at ambient pressure using an Archimedean dual-sinker densitometer designed and set up by the authors. The volume difference between two sinkers was precisely determined by considering the wetting conditions between tungsten sinkers and water; appropriate experimental techniques were developed. The wetting condition became unstable when the sinkers were being moved for immersion in water, because the sinkers were moved in a direction that increased the contact angle. The wetting condition became stable when the sinkers were pulled up from the water, because the sinkers were moved in a direction that decreased the contact angle. The force exerted by the surface tension was efficiently canceled, and the volume difference became constant when the sinkers were pulled up. In this study, the total uncertainty was about 0.3 % at a maximum. The densities measured at high temperatures showed good linearity, with small scatter, over a wide temperature range. The densities and molar volumes increased in the following order: {MgF}2, {CaF}2, {SrF}2, and {BaF}2. The thermal-expansion coefficients showed anomalous behavior. The large thermal-expansion coefficient of {MgF}2 is attributed to a decrease in the cohesive force as a result of a partial loss of the coulombic force, because of the high charge density.

  12. Syntheses, structural analyses and luminescent property of four alkaline-earth coordination polymers

    SciTech Connect

    Zhang, Sheng; Qu, Xiao-Ni; Xie, Gang; Wei, Qing; Chen, San-Ping

    2014-02-15

    Four alkaline-earth coordination polymers, [Ba(Pzdc)(H{sub 2}O)]{sub n} (1), [Ba(Pzdc)]{sub n} (2), [AgSr(Pzdc)(NO{sub 3})(H{sub 2}O)]{sub n} (3), [Ag{sub 2}Ca(Pzdc){sub 2}(H{sub 2}O)]{sub n} (4) (H{sub 2}Pzdc=2, 3-pyrazinedicarboxylic acid) have been synthesized and characterized by single-crystal X-ray diffraction. Compounds 1 and 2 afford 2D layer networks generated by one-dimensional chains containing the [Ba{sub 2}O{sub 11}N] units. Compound 3 is of 2D mixed-metal coordination network formed by one-dimensional chain units, while 4 is of a 3D heterometallic framework. Interestingly, 1 and 2 can undergo reversible SCSC structural transformation upon dehydration/rehydration of coordinated water molecules. In addition, the π–π stacking interactions dominate fluorescent properties of compounds 1 and 2. - Graphical abstract: Four new coordination polymers [Ba(Pzdc)(H{sub 2}O)]{sub n} (1), [Ba(Pzdc)]{sub n} (2), [AgSr(Pzdc)(NO{sub 3})(H{sub 2}O)]{sub n} (3), [Ag{sub 2}Ca(Pzdc){sub 2}(H{sub 2}O)]{sub n} (4) (H{sub 2}Pzdc=2, 3-pyrazinedicarboxylic acid) have been synthesized. Compounds 1–3 display 2D topology structures and compound 4 exhibits a 3D topology structure. Fortunately, 1 and 2 undergo reversible dehydration/rehydration of coordinated water molecules. Display Omitted - Highlights: • All structures are generated by 1D chains. • 1 and 2 show reversible dehydration/rehydration of coordinated water molecules. • The π–π stacking interactions dominate fluorescent properties of compounds 1 and 2.

  13. Ocean-Based Alkalinity Enhancement: Mitigation Potential, Side Effects and the Fate of Added Alkalinity Assessed in an Earth System Model

    NASA Astrophysics Data System (ADS)

    Gonzalez, M. F.; Ilyina, T.

    2014-12-01

    Artificial ocean alkalinization (AOA) has been proposed as a mean to mitigate climate change and ocean acidification. Whilst the mitigation potential of this geo-engineering technology may sound promising, it poses environmental risks. Within the Priority Program "Climate Engineering" of the German Science Foundation (DFG), we investigate the mitigation potential of AOA to reduce atmospheric CO2 and counteract the consequences of ocean acidification. We are particularly interested in the residence time of the added alkalinity at the ocean surface because it must stay in the upper ocean in order to increase the oceanic CO2 uptake. The mitigation potential, risks and the unintended consequences of this geo-engineering method are also exhaustively studied. These questions are tackled through the analysis of different alkalinity enhancement scenarios in the state-of-the-art Earth system model of the Max Planck Institute for Meteorology (MPI-ESM) in a configuration based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Model scenarios are designed so that AOA is performed to keep the atmospheric CO2 concentrations similar to values of the stabilization scenario RCP4.5, while fossil fuel CO2 emissions follow the pathway of the high-CO2 scenario RCP8.5. Alkalinity is added globally into the upper 12 meters of the ocean in different seasons and years. We found that on the time scale of relevance (i.e. from years to decades), season and location are key aspects to take into account in the implementation of AOA. This is because of inhomogeneous vertical mixing of added alkalinity due to the mixed layer depth which is established by the season. We also show that the rate of addition greatly determines impact and outcome of this geo-engineering method. Changes driven by the implementation of this method in the ocean biogeochemistry are also discussed. For instance, the associated changes in the carbon cycle, marine oxygen levels, saturation state of

  14. Selective trans-membrane transport of alkali and alkaline earth cations through graphene oxide membranes based on cation-π interactions.

    PubMed

    Sun, Pengzhan; Zheng, Feng; Zhu, Miao; Song, Zhigong; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Little, Reginald B; Xu, Zhiping; Zhu, Hongwei

    2014-01-28

    Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K(+), Mg(2+), Ca(2+), and Ba(2+)). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp(2) clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations.

  15. Assessment of commercially available ion exchange materials for cesium removal from highly alkaline wastes

    SciTech Connect

    Brooks, K.P.; Kim, A.Y.; Kurath, D.E.

    1996-04-01

    Approximately 61 million gallons of nuclear waste generated in plutonium production, radionuclide removal campaigns, and research and development activities is stored on the Department of Energy`s Hanford Site, near Richland, Washington. Although the pretreatment process and disposal requirements are still being defined, most pretreatment scenarios include removal of cesium from the aqueous streams. In many cases, after cesium is removed, the dissolved salt cakes and supernates can be disposed of as LLW. Ion exchange has been a leading candidate for this separation. Ion exchange systems have the advantage of simplicity of equipment and operation and provide many theoretical stages in a small space. The organic ion exchange material Duolite{trademark} CS-100 has been selected as the baseline exchanger for conceptual design of the Initial Pretreatment Module (IPM). Use of CS-100 was chosen because it is considered a conservative, technologically feasible approach. During FY 96, final resin down-selection will occur for IPM Title 1 design. Alternate ion exchange materials for cesium exchange will be considered at that time. The purpose of this report is to conduct a search for commercially available ion exchange materials which could potentially replace CS-100. This report will provide where possible a comparison of these resin in their ability to remove low concentrations of cesium from highly alkaline solutions. Materials which show promise can be studied further, while less encouraging resins can be eliminated from consideration.

  16. Triazenide complexes of the heavier alkaline earths: synthesis, characterization, and suitability for hydroamination catalysis.

    PubMed

    Barrett, Anthony G M; Crimmin, Mark R; Hill, Michael S; Hitchcock, Peter B; Kociok-Köhn, Gabriele; Procopiou, Panayiotis A

    2008-08-18

    A series of triazenide complexes of the heavier alkaline earths, Ca, Sr and Ba, have been synthesized by either protonolysis or salt metathesis routes. Although complexes of the form [{Ar 2N 3}M{N(SiMe 3) 2}(THF) n ] (M = Ca, n = 2; M = Sr, n = 3; Ar = 2,6-diisopropylphenyl) and [{Ar 2N 3}Ca(I)(THF) 2] 2 could be isolated and characterized by X-ray crystallography, solution studies revealed the propensity of these species to undergo Schlenk-like redistribution with the formation of [{Ar 2N 3} 2M(THF) n ] (M = Ca, n = 1; M = Sr, n = 2). The latter compounds have been synthesized independently. In the case of the large barium dication, attempts to synthesize the heaviest analogue of the series, [{Ar 2N 3} 2Ba(THF) n ], failed and led instead to the isolation of the potassium barate complex [K{Ar 2N 3}Ba{N(SiMe 3) 2} 2(THF) 4]. Single crystal X-ray diffraction studies demonstrated that, although in all the aforementioned cases the triazenide ligand binds to the electrophilic group 2 metal centers via symmetrical kappa (2)- N, N-chelates, in the latter compound an unprecedented bridging mode is observed in which the triazenide ligand coordinates through both terminal and internal nitrogen centers. A series of density-functional theory computational experiments have been undertaken to assist in our understanding of this phenomenon. In further experiments, the calcium and strontium amide derivatives [{Ar 2N 3}M{N(SiMe 3) 2}(THF) n ] (M = Ca, n = 2; M = Sr, n = 3) proved to be catalytically active for the intramolecular hydroamination of 1-amino-2,2-diphenylpent-4-ene to form 2-methyl-4,4-diphenylpyrrolidine, with the calcium species demonstrating a higher turnover number than the strontium analogue ( 2a, TOF = 500 h (-1); 2b, TOF = 75 h (-1)). In these instances, because of ambiguities in the structural charcterization of the precatalyst in solution, such quantification holds little value and detailed catalytic studies have not been conducted. PMID:18620384

  17. Eocene seasonality and seawater alkaline earth reconstruction using shallow-dwelling large benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Evans, David; Müller, Wolfgang; Oron, Shai; Renema, Willem

    2013-11-01

    Intra-test variability in Mg/Ca and other (trace) elements within large benthic foraminifera (LBF) of the family Nummulitidae have been investigated using laser-ablation inductively-coupled plasma mass spectrometry (LA-ICPMS). These foraminifera have a longevity and size facilitating seasonal proxy retrieval and a depth distribution similar to 'surface-dwelling' planktic foraminifera. Coupled with their abundance in climatically important periods such as the Paleogene, this means that this family of foraminifera are an important but under-utilised source of palaeoclimatic information. We have calibrated the relationship between Mg/Ca and temperature in modern Operculina ammonoides and observe a ˜2% increase in Mg/Ca °C-1. O. ammonoides is the nearest living relative of the abundant Eocene genus Nummulites, enabling us to reconstruct mid-Eocene tropical sea surface temperature seasonality by applying our calibration to fossil Nummulites djokdjokartae from Java. Our results indicate a 5-6 °C annual temperature range, implying greater than modern seasonality in the mid-Eocene (Bartonian). This is consistent with seasonal surface ocean cooling facilitated by enhanced Eocene tropical cyclone-induced upper ocean mixing, as suggested by recent modelling results. Analyses of fossil N. djokdjokartae and Operculina sp. from the same stratigraphic interval demonstrate that environmental controls on proxy distribution coefficients are the same for these two genera, within error. Using previously published test-seawater alkaline earth metal distribution coefficients derived from an LBF of the same family (Raitzsch et al., 2010) and inorganic calcite, with appropriate correction systematics for secular Mg/Casw variation (Evans and Müller, 2012), we use our fossil data to produce a more accurate foraminifera-based Mg/Casw reconstruction and an estimate of seawater Sr/Ca. We demonstrate that mid-Eocene Mg/Casw was ≲2 molmol, which is in contrast to the model most

  18. Alkaline-Earth-Catalysed Cross-Dehydrocoupling of Amines and Hydrosilanes: Reactivity Trends, Scope and Mechanism.

    PubMed

    Bellini, Clément; Dorcet, Vincent; Carpentier, Jean-François; Tobisch, Sven; Sarazin, Yann

    2016-03-18

    Alkaline-earth (Ae=Ca, Sr, Ba) complexes are shown to catalyse the chemoselective cross-dehydrocoupling (CDC) of amines and hydrosilanes. Key trends were delineated in the benchmark couplings of Ph3 SiH with pyrrolidine or tBuNH2 . Ae{E(SiMe3)2}2 ⋅(THF)x (E=N, CH; x=2-3) are more efficient than {N^N}Ae{E(SiMe3)2}⋅(THF)n (E=N, CH; n=1-2) complexes (where {N^N}(-) ={ArN(o-C6H4)C(H)=NAr}(-) with Ar=2,6-iPr2 -C6H3) bearing an iminoanilide ligand, and alkyl precatalysts are better than amido analogues. Turnover frequencies (TOFs) increase in the order Ca30 products) includes diamines and di(hydrosilane)s. Kinetic analysis of the Ba-promoted CDC of pyrrolidine and Ph3SiH shows that 1) the kinetic law is rate=k[Ba](1) [amine](0) [hydrosilane](1), 2) electron-withdrawing p-substituents on the arylhydrosilane improve the reaction rate and 3) a maximal kinetic isotopic effect (kSiH/kSiD =4.7) is seen for Ph3SiX (X=H, D). DFT calculations identified the prevailing mechanism; instead of an inaccessible σ-bond-breaking metathesis pathway, the CDC appears to follow a stepwise reaction path with N-Si bond-forming nucleophilic attack of the catalytically competent Ba pyrrolide onto the incoming silane, followed by rate limiting hydrogen-atom transfer to barium. The participation of a Ba silyl species is prevented energetically. The reactivity trend Ca

  19. Monte Carlo simulations of electron thermalization in alkali iodide and alkaline-earth fluoride scintillators

    SciTech Connect

    Wang Zhiguo; Gao Fei; Kerisit, Sebastien; Xie Yulong; Campbell, Luke W.

    2012-07-01

    A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF{sub 2} and BaF{sub 2}. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF{sub 2}, BaF{sub 2}, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident {gamma}-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs{sup +} relative to Na{sup +}, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI.

  20. Monte Carlo simulations of electron thermalization in alkali iodide and alkaline-earth fluoride scintillators

    SciTech Connect

    Wang, Zhiguo; Xie, YuLong; Campbell, Luke W.; Gao, Fei; Kerisit, Sebastien N.

    2012-07-01

    A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF2 and BaF2. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 {per_thousand}nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF2, BaF2, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident {gamma}-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs+ relative to Na+, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI.

  1. Alkaline-Earth-Catalysed Cross-Dehydrocoupling of Amines and Hydrosilanes: Reactivity Trends, Scope and Mechanism.

    PubMed

    Bellini, Clément; Dorcet, Vincent; Carpentier, Jean-François; Tobisch, Sven; Sarazin, Yann

    2016-03-18

    Alkaline-earth (Ae=Ca, Sr, Ba) complexes are shown to catalyse the chemoselective cross-dehydrocoupling (CDC) of amines and hydrosilanes. Key trends were delineated in the benchmark couplings of Ph3 SiH with pyrrolidine or tBuNH2 . Ae{E(SiMe3)2}2 ⋅(THF)x (E=N, CH; x=2-3) are more efficient than {N^N}Ae{E(SiMe3)2}⋅(THF)n (E=N, CH; n=1-2) complexes (where {N^N}(-) ={ArN(o-C6H4)C(H)=NAr}(-) with Ar=2,6-iPr2 -C6H3) bearing an iminoanilide ligand, and alkyl precatalysts are better than amido analogues. Turnover frequencies (TOFs) increase in the order Ca30 products) includes diamines and di(hydrosilane)s. Kinetic analysis of the Ba-promoted CDC of pyrrolidine and Ph3SiH shows that 1) the kinetic law is rate=k[Ba](1) [amine](0) [hydrosilane](1), 2) electron-withdrawing p-substituents on the arylhydrosilane improve the reaction rate and 3) a maximal kinetic isotopic effect (kSiH/kSiD =4.7) is seen for Ph3SiX (X=H, D). DFT calculations identified the prevailing mechanism; instead of an inaccessible σ-bond-breaking metathesis pathway, the CDC appears to follow a stepwise reaction path with N-Si bond-forming nucleophilic attack of the catalytically competent Ba pyrrolide onto the incoming silane, followed by rate limiting hydrogen-atom transfer to barium. The participation of a Ba silyl species is prevented energetically. The reactivity trend Ca

  2. Influence of doping with alkaline earth metals on the optical properties of thermochromic VO2

    NASA Astrophysics Data System (ADS)

    Dietrich, Marc K.; Kramm, Benedikt G.; Becker, Martin; Meyer, Bruno K.; Polity, Angelika; Klar, Peter J.

    2015-05-01

    Thin films of doped VO2 were deposited, analyzed, and optimized with regard to their solar energy transmittance (Tsol) and visible/luminous light transmittance (Tlum) which are important parameters in the context of smart window applications in buildings. The doping with alkaline earth metals (AEM) like Mg, Ca, Sr, or Ba increased both Tsol and Tlum due to a bandgap widening and an associated absorption edge blue-shift. Thereby, the brown-yellowish color impression of pure VO2 thin films, which is one major hindrance limiting the usage of VO2 as thermochromic window coating, was overcome. Transparent thin films with excellent switching behavior were prepared by sputtering. Highly doped V1-xMexO2 (Me = Ca, Sr, Ba) kept its excellent thermochromic switching behavior up to x(Me) = Me/(Me + V) = 10 at. % doping level, while the optical bandgap energy was increased from 1.64 eV for undoped VO2 to 2.38 eV for x(Mg) = 7.7 at. %, 1.85 eV for x(Ca) = 7.4 at. %, 1.84 eV for x(Sr) = 6.4 at. % and 1.70 eV for x(Ba) = 6.8 at. %, as well as the absorption edge is blue shifted by increasing AEM contents. Also, the critical temperature ϑc, at which the semiconductor-to-metal transition (SMT) occurs, was decreased by AEM doping, which amounted to about -0.5 K/at. % for all AEM on average. The critical temperature was determined by transmittance-temperature hysteresis measurements. Furthermore, Tsol and Tlum were calculated and were found to be significantly enhanced by AEM doping. Tlum increased from 32.0% in undoped VO2 to 43.4% in VO2 doped with 6.4 at. % Sr. Similar improvements were found for other AEM. The modulation of the solar energy transmittance ΔTsol, which is the difference of the Tsol values in the low and high temperature phase, was almost constant or even slightly increased when the doping level was increased up to about 10 at. % Ca, Sr, or Ba.

  3. Ion and electron pulses observed in the earth's magnetospheric environment

    NASA Technical Reports Server (NTRS)

    Lin, Y. C.; Fan, C. Y.; Gloeckler, G.; Hovestadt, D.

    1980-01-01

    Pulses of about 100 keV ions and electrons of time duration of several minutes are frequently detected in the earth's magnetotail and in the upstream region from the earth's bow shock. The distribution of the locations of the IMP 7 satellite where the particles were observed over the period from Sept. 29, 1972 to Oct. 6, 1973 is presented. The physical implications of these findings as related to (1) the source locations and (2) the dynamic nature of the acceleration and propagation of these particles are discussed.

  4. Quantifying phytate in dairy digesta and feces: alkaline extraction and high-performance ion chromatography.

    PubMed

    Ray, P P; Shang, C; Maguire, R O; Knowlton, K F

    2012-06-01

    Development of an analytical method with appropriate combination of extraction and quantification approaches for undigested phytate in ruminant feces and digesta will advance knowledge of phytate degradation in ruminants and help to reduce phosphorus excretion. Established quantification methods give satisfactory results for feedstuffs and nonruminant manure but recovery of phytate is incomplete for ruminant feces and digesta because of their complex sample matrix and low ratio of phytate to inorganic P. The objective was to develop a robust, accurate, sensitive, and inexpensive method to extract and quantify phytate in feeds, ruminant feces, and digesta. Diets varying in phytate content were fed to dairy heifers, dry cows, and lactating cows to generate digesta and fecal samples of varying composition to challenge extraction and quantification methods. Samples were extracted with 0.5 M HCl or 0.25 M NaOH + 0.05 M EDTA. Acid extracts were mixed with 20% NaCl, alkaline extracts were acidified to final pH < 2, and then both extracts were clarified with C₁₈ cartridges and 0.2-μm filters. High-performance ion chromatography (HPIC) was used to quantify phytate. In feed samples, the measured phytate was comparable in alkaline and acid extracts (2,965 vs. 3,085 μg/g of DM). In digesta and fecal samples, alkaline extraction yielded greater estimates of phytate content than did acid extraction (40.7 vs. 33.6 and 202.9 vs. 144.4 μg/g of DM for digesta and fecal samples, respectively). Analysis of alkaline extracts by HPIC is usually not possible because of sample matrix interferences; acidification and C(18)-cartridge elution of alkaline extracts prevented this interference. Pure phytate added to dry samples before extraction was almost completely recovered (88 to 105%), indicating high extraction efficiency, no adverse effect of extract clean-up procedures, and accurate quantification of phytate. The proposed method is rapid, inexpensive, robust, and combines the

  5. Unified mechanism of alkali and alkaline earth catalyzed gasification reactions of carbon by CO2 and H2O

    USGS Publications Warehouse

    Chen, S.G.; Yang, R.T.

    1997-01-01

    From molecular orbital calculations, a unified mechanism is proposed for the gasification reactions of graphite by CO2 and H2O, both uncatalyzed and catalyzed by alkali and alkaline earth catalysts. In this mechanism, there are two types of oxygen intermediates that are bonded to the active edge carbon atoms: an in-plane semiquinone type, Cf(O), and an off-plane oxygen bonded to two saturated carbon atoms that are adjacent to the semiquinone species, C(O)Cf(O). The rate-limiting step is the decomposition of these intermediates by breaking the C-C bonds that are connected to Cf(O). A new rate equation is derived for the uncatalyzed reactions, and that for the catalyzed reactions is readily available from the proposed mechanism. The proposed mechanism can account for several unresolved experimental observations: TPD and TK (transient kinetics) desorption results of the catalyzed systems, the similar activation energies for the uncatalyzed and catalyzed reactions, and the relative activities of the alkali and alkaline earth elements. The net charge of the edge carbon active site is substantially changed by gaining electron density from the alkali or alkaline earth element (by forming C-O-M, where M stands for metal). The relative catalytic activities of these elements can be correlated with their abilities of donating electrons and changing the net charge of the edge carbon atom. As shown previously (Chen, S. G.; Yang, R. T. J. Catal. 1993, 141, 102), only clusters of the alkali compounds are active. This derives from the ability of the clusters to dissociate CO2 and H2O to form O atoms and the mobility of the dissociated O atoms facilitated by the clusters.

  6. Minor Ion Manifestations In The Earth's Magnetotail: Analysis of Waves Observed During Cassini's Earth Flyby

    NASA Astrophysics Data System (ADS)

    Bogdanov, A. T.; Glassmeier, K.-H.; Musmann, G.; Dougherty, M.; Kellock, S.; Tsurutani, B.

    The waves observed by the magnetic field experiment on Cassini in theEarth magneto- tail during its swingby manoeuvre are analysed. We show that they belong roughly to two classes. The first one is comprised of transverse waves in the ion cyclotron range which can be uniquely identified as bi-ion cyclotron waves on the He++ resonance branch. In the Earth's magnetotail at distances between 30 and 65 Re such waves are observed for the first time. A statistical study of their polarisation, frequency distri- bution and propagation direction properties produces a picture which is in very good agreement with theoretical predictions for low frequency waves in a bi-ion plasma with energetic proton component of anisotropic velocity distribution. We interpret the piling up of the waves about half the proton cyclotron frequency in terms of bi-ion cyclotron wave excitation at the gyrofrequency of a heavy ion constituent and as a proof for the presence in this region of a low concentration of double charged He-ions of solar wind origin. The second type of waves are highly compressional and we at- tempt to explain them as a manifestation of mirror mode structures. We discuss this hypothesis and analyse the possible origin scenarios and the relation of these waves to deep magnetotail mirror mode observations reported previously.

  7. Enhancement of oxygen surface exchange kinetics of SrTiO(3) by alkaline earth metal oxides.

    PubMed

    Argirusis, Christos; Wagner, Stefan; Menesklou, Wolfgang; Warnke, Carsten; Damjanovic, Tanja; Borchardt, Günter; Ivers-Tiffée, Ellen

    2005-10-21

    The oxygen incorporation reaction in undoped SrTiO(3) was investigated by electrical measurements (pressure modulation technique) in the temperature range from 650-920 degrees C and by means of tracer exchange experiments in the temperature range from 458-600 degrees C. The surface of the undoped SrTiO(3) single crystals was modified by alkaline earth metal compounds leading to a tremendous enhancement of the effective surface exchange rate for oxygen incorporation as compared to the uncoated surface.

  8. Preheated ignition and work function studies on alkaline earth metal oxides coated tungsten electrodes of fluorescent lamps

    NASA Astrophysics Data System (ADS)

    Langer, Reinhard; Dar, Farrukh; Hilscher, Achim; Horn, Siegfried; Tidecks, Reinhard

    2015-03-01

    This paper describes measurements on the alkaline earth (Ba, Sr, Ca) oxide layers utilized as emitting material in fluorescent lamp electrodes. In a first approach we compared the emission capabilities of the different materials (BaO, SrO and CaO coatings on tungsten filaments) by their ability to facilitate the start of a lamp. In a second investigation the work function was measured quantitatively by means of a Kelvin probe. Basically, the results of both measurements coincide. The impact of sample geometry on measurement results of a Kelvin probe applied for work function measurements of lamp electrodes are discussed in detail.

  9. Ion probe measurement of rare earth elements in biogenic phosphates

    SciTech Connect

    Grandjean, P.; Albarede, F. )

    1989-12-01

    The rare earth element (REE) distributions in individuals fish teeth and conodonts have been measured by ion probe. Concentrations and La/Yb ratios show little variations, except in the enamel, which suggests that REE uptake from the sedimented biogenic debris takes place at the water-sediment interface as an essentially quantitative process without fractionation. Late diagenetic disturbances remained of marginal importance. Hence, REE in phosphatic debris might reflect the input from the overlying water column.

  10. Ion probe measurement of rare earth elements in biogenic phosphates

    NASA Astrophysics Data System (ADS)

    Grandjean, Patricia; Albarède, Francis

    1989-12-01

    The rare earth element (REE) distributions in individual fish teeth and conodonts have been measured by ion probe. Concentrations and La/Yb ratios show little variations, except in the enamel, which suggests that REE uptake from the sedimented biogenic debris takes place at the water-sediment interface as an essentially quantitative process without fractionation. Late diagenetic disturbances remained of marginal importance. Hence, REE in phosphatic debris might reflect the input from the overlying water column.

  11. Novel alkaline earth copper germanates with ferro and antiferromagnetic S=1/2 chains

    SciTech Connect

    Brandao, Paula; Reis, Mario S.; Santos, Antonio M. dos

    2013-02-15

    Two new alkaline earth copper(II) germanates were hydrothermally synthesized: CaCuGeO{sub 4}{center_dot}H{sub 2}O (1) and BaCu{sub 2}Ge{sub 3}O{sub 9}{center_dot}H{sub 2}O (2), and their structures determined by single crystal X-ray diffraction. Compound (1) crystallizes in space group P2{sub 1}/c with a=5.1320(2) Angstrom-Sign , b=16.1637(5) Angstrom-Sign , c=5.4818(2) Angstrom-Sign , {beta}=102.609(2) Degree-Sign , V=443.76(3) Angstrom-Sign {sup 3} and Z=4. This copper germanate contains layers of composition [CuGeO{sub 4}]{sub {infinity}}{sup 2-} comprising CuO{sub 4} square planes and GeO{sub 4} tetrahedra with calcium and water molecules in the inter-layer space. Compound (2) crystallizes in the Cmcm space group with a=5.5593(3) Angstrom-Sign , b=10.8606(9) Angstrom-Sign , c=13.5409(8) Angstrom-Sign , V=817.56(9) Angstrom-Sign {sup 3} and Z=4. This structure contains GeO{sub 6} and CuO{sub 6} octahedra as well as GeO{sub 4} tetrahedra, forming a three-dimensional network of interconnecting six-membered ring channels. The magnetic susceptibility for both samples can be interpreted as S=1/2 chains, in agreement with the copper topology observed in the crystal structure. The susceptibility of (1) exhibits a Bonner-Fisher type behavior, resulting from antiferromagnetic intra-chain interactions without three-dimensional ordering down to 5 K-the lowest measured temperature. This observation, together with the absence of super-exchange paths between the copper chains, make this system particularly promising for the study of low dimensional magnetism. The magnetic properties of (2) show a very weak ferromagnetic near-neighbor interaction along the chain. In this compound a peak the {chi}T plot seems to indicate the onset of interchain antiferromagentic correlations. However, no ordering temperature is detected in the susceptibility data. - Graphical abstract: Copper chains present in CaCuGeO{sub 4}{center_dot}H{sub 2}O and BaCu{sub 2}Ge{sub 3}O{sub 9}{center

  12. Alkaline deoxygenated graphene oxide as adsorbent for cadmium ions removal from aqueous solutions.

    PubMed

    Liu, Jun; Du, Hongyan; Yuan, Shaowei; He, Wanxia; Yan, Pengju; Liu, Zhanhong

    2015-01-01

    Alkaline deoxygenated graphene oxide (aGO) was prepared through alkaline hydrothermal treatment and used as adsorbent to remove Cd(II) ions from aqueous solutions for the first time. The characterization results of transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectra indicate that aGO was successfully synthesized. The batch adsorption experiments showed that the adsorption kinetics could be described by the pseudo-second-order kinetic model, and the isotherms equilibrium data were well fitted with the Langmuir model. The maximum adsorption capacity of Cd(II) on aGO was 156 mg/g at pH 5 and T=293 K. The adsorption thermodynamic parameters indicated that the adsorption process was a spontaneous and endothermic reaction. The mainly adsorption mechanism speculated from FT-IR results may be attributed to the electrostatic attraction between Cd2+ and negatively charged groups (-CO-) of aGO and cation-π interaction between Cd2+ and the graphene planes. The findings of this study demonstrate the potential utility of the nanomaterial aGO as an effective adsorbent for Cd(II) removal from aqueous solutions. PMID:26038925

  13. Ion acoustic solitons in Earth's upward current region

    SciTech Connect

    Main, D. S.; Scholz, C.; Newman, D. L.; Ergun, R. E.

    2012-07-15

    The formation and evolution of ion acoustic solitons in Earth's auroral upward current region are studied using one- and two-dimensional (2D) electrostatic particle-in-cell simulations. The one-dimensional simulations are confined to processes that occur in the auroral cavity and include four plasma populations: hot electrons, H{sup +} and O{sup +} anti-earthward ion beams, and a hot H{sup +} background population. Ion acoustic solitons are found to form for auroral-cavity ion beams consistent with acceleration through double-layer (DL) potentials measured by FAST. A simplified one-dimensional model simulation is then presented in order to isolate the mechanisms that lead to the formation of the ion acoustic soliton. Results of a two-dimensional simulation, which include both the ionosphere and the auroral cavity, separated by a low-altitude DL, are then presented in order to confirm that the soliton forms in a more realistic 2D geometry. The 2D simulation is initialized with a U-shaped potential structure that mimics the inferred shape of the low altitude transition region based on observations. In this simulation, a soliton localized perpendicular to the geomagnetic field is observed to form and reside next to the DL. Finally, the 2D simulation results are compared with FAST data and it is found that certain aspects of the data can be explained by assuming the presence of an ion acoustic soliton.

  14. Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

    SciTech Connect

    Levitskaia, Tatiana G.; Lumetta, Gregg J.; Moyer, Bruce A.; Bonnesen, Peter V.

    2006-06-01

    The purpose of this research involving collaboration between Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) is to explore new approaches to the separation of sodium hydroxide, sodium nitrate, and other sodium salts from high-level alkaline tank waste. The principal potential benefit is a major reduction in disposed waste volume, obviating the building of expensive new waste tanks and reducing the costs of low-activity waste immobilization. Principles of ion recognition are being researched toward discovery of liquid extraction systems that selectively separate sodium hydroxide and sodium nitrate from other waste components. The successful concept of pseudohydroxide extraction using fluorinated alcohols and phenols is being developed at ORNL and PNNL toward a greater understanding of the controlling equilibria, role of solvation, and of synergistic effects involving crown ethers. Studies at PNNL are directed toward new solvent formulation for the practical sodium pseudohydroxide extraction systems.

  15. Rare earth element complexation by carbonate and oxalate ions

    NASA Astrophysics Data System (ADS)

    Cantrell, Kirk J.; Byrne, Robert H.

    1987-03-01

    Rare earth carbonate and oxalate complexation constants have been determined through ex-amination of distribution equilibria between tributyl phosphate and an aqueous perchlorate phase. Carbonate complexation constants appropriate to the REE in seawater (25°C, 35%., 1 atm) can be described in terms of atomic number, Z. nlog swβ1 = 4.853 + 0.1135( Z - 57) - 0.003643( Z - 57) 2log swβ2 = 80.197 + 0.1730( Z - 57) - 0.002714( Z -57) 2 where swβ 1 = [MCO +3] /[M 3+][CO 2-3] T, swβ 2 = [M(CO 3) -3] /[M 3+][CO 2-3] 2' T [ M3+] is an uncomplexed rare earth concentration in seawater, [ MCO+3] and [ M( CO-3) 2] are carbonate complex concentrations, and [CO 2-3] T is the total (free plus ion paired) carbonate ion concentration in seawater (molal scale). Our analyses indicate that in seawater with a total carbonate ion concentration of 1.39 × 10 -4 moles/Kg H 2O, carbonate complexes for the lightest rare earth, La, constitute 86% of the total metal, 7% is free La 3+ and the remaining 7% exists as hydroxide, sulfate, chloride and fluoride complexes. For Lu, the heaviest rare earth, carbonate complexes are 98% of the total metal, 0.3% is uncomplexed and 1.5% is complexed with hydroxide, sulfate, chloride and fluoride. Oxalate and carbonate constants are linearly correlated. This correlation appears to be quite useful for estimating trivalent metal-arbonate stability constants from their respective oxalate stability constants.

  16. Valence photoionization of small alkaline earth atoms endohedrally confined in C60: From the many-electron collectivity to single-electron interferences

    NASA Astrophysics Data System (ADS)

    Javani, Mohammad; McCreary, Meghan; Patel, Aakash; Madjet, Mohamed; Chakraborty, Himadri; Manson, Steve

    2012-06-01

    Results of a theoretical study of the photoionization from outermost orbitals of Be, Mg and Ca atoms endohedrally confined in C60 are presented. The fullerene ion-core of sixty C^4+ ions is smudged into a continuous jellium distribution while the delocalized cloud of carbon valence electrons, plus the encaged atom, are treated in the time-dependent local density approximation (TDLDA) [1]. Systematic evolution of the mixing of outer atomic level with the C60 band is detected along the sequence. This is found to influence the plasmon-driven enhancement at low energies and the geometry-revealing confinement oscillations from multi-path interferences at high energies in significantly different ways. The study paints the first comparative picture of the atomic valence photospectra for alkaline earth metallofullerenes in a dynamical many-electron framework [2].[4pt] [1] M.E. Madjet et al., Phys. Rev. A 81, 013202 (2010)[0pt] [2] M.H. Javani et al., to be published.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Oxidation behavior of Cr(III) during thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides.

    PubMed

    Mao, Linqiang; Gao, Bingying; Deng, Ning; Liu, Lu; Cui, Hao

    2016-02-01

    The oxidation behavior of Cr(III) during the thermal treatment of chromium hydroxide in the presence of alkali and alkaline earth metal chlorides (NaCl, KCl, MgCl2, and CaCl2) was investigated. The amounts of Cr(III) oxidized at various temperatures and heating times were determined, and the Cr-containing species in the residues were characterized. During the transformation of chromium hydroxide to Cr2O3 at 300 °C approximately 5% of the Cr(III) was oxidized to form intermediate compounds containing Cr(VI) (i.e., CrO3), but these intermediates were reduced to Cr2O3 when the temperature was above 400 °C. Alkali and alkaline earth metals significantly promoted the oxidation of Cr(III) during the thermal drying process. Two pathways were involved in the influences the alkali and alkaline earth metals had on the formation of Cr(VI). In pathway I, the alkali and alkaline earth metals were found to act as electron transfer agents and to interfere with the dehydration process, causing more intermediate Cr(VI)-containing compounds (which were identified as being CrO3 and Cr5O12) to be formed. The reduction of intermediate compounds to Cr2O3 was also found to be hindered in pathway I. In pathway II, the alkali and alkaline earth metals were found to contribute to the oxidation of Cr(III) to form chromates. The results showed that the presence of alkali and alkaline earth metals significantly increases the degree to which Cr(III) is oxidized during the thermal drying of chromium-containing sludge.

  19. Faraday Rotation of Rare Earth Ions in Orthoferrites

    NASA Astrophysics Data System (ADS)

    Gomi, Manabu; Abe, Masanori; Nomura, Soichiro

    1980-09-01

    The Faraday rotation spectra corresponding to the 4I15/2→4F9/2(Er3+) and 3H6→3F2(Tm3+) transitions in ErFeO3 and TmFeO3 were found to be in dissipative and dispersive shapes, respectively, in both the \\varGamma2(Fx) and \\varGamma4(Fz) spin configurations. The Faraday rotation due to the electronic transition of the rare earth ions (R3+) was analysed in terms of the molecular field perturbation acting on the R3+ ions. In the case of the R3+ ions with odd number of electrons such as Er3+(4f11), the crystal field state of the J-multiplet is split into degenerate Kramers doublets which makes the spectrum of the Faraday rotation dissipative when \\varGamma(linewidth)≲\\varDelta(Kramers splitting)≪kT; while in the case of the R3+ ions with even number of electrons such as Tm3+(4f12), the crystal field state is split into nondegenerate singlets, which makes the spectrum of the Faraday rotation dispersive.

  20. Extraction of cesium from an alkaline leaching solution of spent catalysts using an ion-exchange column

    SciTech Connect

    Dumont, N.; Favre-Reguillon, A.; Dunjic, B.; Lemaire, M.

    1996-04-01

    The selective extraction of cesium from an alkaline leaching solution of spent catalysts using phenolic resins was studied. The resins were synthesized by alkaline polycondensation of formaldehyde by phenol, resorcinol, catechol, and phloroglucinol. Their ionoselectivities for five alkali metals were evaluated with a solid-liquid extraction, and their ion-exchange capacities were compared. The resin with the best selectivity for cesium was tested with a real solution at different pH values. An on-column extraction is proposed to obtain cesium with high purity.

  1. Dispersion coefficients for H and He interactions with alkali-metal and alkaline-earth-metal atoms

    SciTech Connect

    Mitroy, J.; Bromley, M.W.J.

    2003-12-01

    The van der Waals coefficients C{sub 6}, C{sub 8}, and C{sub 10} for H and He interactions with the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are determined from oscillator strength sum rules. The oscillator strengths were computed using a combination of ab initio and semiempirical methods. The dispersion parameters generally agree with close to exact variational calculations for Li-H and Li-He at the 0.1% level of accuracy. For larger systems, there is agreement with relativistic many-body perturbation theory estimates of C{sub 6} at the 1% level. These validations for selected systems attest to the reliability of the present dispersion parameters. About half the present parameters lie within the recommended bounds of the Standard and Certain compilation [J. Chem. Phys. 83, 3002 (1985)].

  2. Adsorption of alkali and alkaline-earth metal atoms on the reconstructed graphene-like BN single sheet

    NASA Astrophysics Data System (ADS)

    Hao, Jun-Hua; Wang, Zheng-Jia; Wang, Yu-Fang; Yin, Yu-Hua; Jiang, Run; Jin, Qing-Hua

    2015-12-01

    A graphene-like BN single sheet with absorbed alkali and alkaline-earth metal atoms have been investigated by using a first-principles method within the framework of density functional theory (DFT). The electronic structure of BN sheet with adsorbed metal atoms is mainly determined by the metal electronic state which is near to the Fermi level owing to the wide band gap of pure BN sheet. So, we calculated the adsorption energy, charge transfer and work function after the metal adsorbed on BN sheet. We found that the interaction between the metal atoms and BN surface was very strong, and the stable adsorption site for all the adsorbed atoms concluded was high-coordination surface site (H-center) rather than the surface dangling bond sites from the perspective of simple bond-counting arguments. Our results indicate that the interaction of BN sheet with metal atoms could help in the development of metallic nanoscale devices.

  3. Two-band superfluidity and intrinsic Josephson effect in alkaline-earth-metal Fermi gases across an orbital Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Iskin, M.

    2016-07-01

    We first show that the many-body Hamiltonian governing the physical properties of an alkaline-earth 173Yb Fermi gas across the recently realized orbital Feshbach resonance is exactly analogous to that of two-band s -wave superconductors with contact interactions; i.e., even though the free-particle bands have a tunable energy offset in between and are coupled by a Josephson-type attractive interband pair scattering, the intraband interactions have exactly the same strength. We then introduce two intraband order parameters within the BCS mean-field approximation and investigate the competition between their in-phase and out-of-phase (i.e., the so-called π -phase) solutions in the entire BCS-BEC evolution at zero temperature.

  4. Cyclotron dynamics of a Kondo singlet in a spin-orbit-coupled alkaline-earth-metal atomic gas

    NASA Astrophysics Data System (ADS)

    Jiang, Bo-Nan; Lv, Hao; Wang, Wen-Li; Du, Juan; Qian, Jun; Wang, Yu-Zhu

    2014-11-01

    We propose a scheme to investigate the interplay between the Kondo-exchange interaction and the quantum spin Hall effect with ultracold fermionic alkaline-earth-metal atoms trapped in two-dimensional optical lattices using ultracold collision and laser-assisted tunneling. In the strong Kondo-coupling regime, although the loop trajectory of the mobile atom disappears, collective dynamics of an atom pair in two clock states can exhibit an unexpected spin-dependent cyclotron orbit in a plaquette, realizing the quantum spin Hall effect of the Kondo singlet. We demonstrate that the collective cyclotron dynamics of the spin-zero Kondo singlet is governed by an effective Harper-Hofstadter model in addition to second-order diagonal tunneling.

  5. High-T sub c thin films on low microwave loss alkaline-rare-earth-aluminate crystals

    SciTech Connect

    Sobolewski, R.; Gierlowski, P.; Kula, W.; Zarembinski, S.; Lewandowski, S.J.; Berkowski, M.; Pajaczkowska, A. ); Gorshunov, B.P.; Lyudmirsky, D.B.; Sirotinsky, O.I. )

    1991-03-01

    This paper reports on the alkaline-rare-earth aluminates (K{sub 2}NiF{sub 4}-type perovskites) which are an excellent choice as the substrate material for the growth of high-T{sub c} thin films suitable for microwave and far-infrared applications. The CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals have been grown by Czochralski pulling and fabricated into the form of (001) oriented wafers. The Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films deposited on these substrates by a single-target magnetron sputtering exhibited very good superconducting and structural properties.

  6. Methanol synthesis using a catalyst combination of alkali or alkaline earth salts and reduced copper chromite for methanol synthesis

    DOEpatents

    Tierney, John W.; Wender, Irving; Palekar, Vishwesh M.

    1993-01-01

    The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a catalyst combination comprising reduced copper chromite and basic alkali salts or alkaline earth salts. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

  7. Frontier Orbital Engineering of Metal-Organic Frameworks with Extended Inorganic Connectivity: Porous Alkaline-Earth Oxides.

    PubMed

    Hendon, Christopher H; Walsh, Aron; Dincă, Mircea

    2016-08-01

    The development of conductive metal-organic frameworks is challenging owing to poor electronic communication between metal clusters and the organic ligands that bridge them. One route to overcoming this bottleneck is to extend the inorganic dimensionality, while using the organic components to provide chemical functionality. Using density functional theory methods, we demonstrate how the properties of the alkaline-earth oxides SrO and BaO are transformed upon formation of porous solids with organic oxygen sources (acetate and trifluoroacetate). The electron affinity is significantly enhanced in the hybrid materials, while the ionization potential can be tuned over a large range with the polarity of the organic moiety. Furthermore, because of their high-vacuum fraction, these materials have dielectric properties suitable for low-κ applications.

  8. Magnetism of perovskite cobaltites with Kramers rare-earth ions

    SciTech Connect

    Jirák, Z. Hejtmánek, J.; Knížek, K.; Novák, P.; Šantavá, E.; Fujishiro, H.

    2014-05-07

    The band-gap insulators RECoO{sub 3} (RE = Nd{sup 3+}, Sm{sup 3+}, and Dy{sup 3+}) with Co{sup 3+} ions stabilized in the non-magnetic low-spin state have been investigated by specific heat measurements. The experiments evidence an antiferromagnetic ordering of the rare earths with Néel temperature of T{sub N} = 1.25, 1.50, and 3.60 K for NdCoO{sub 3}, SmCoO{sub 3}, and DyCoO{sub 3}, respectively. With increasing external field, the lambda peak in specific heat, indicative of the transition, shifts to lower temperatures and vanishes for field of about 3 T. Starting from this point, a broader Schottky peak is formed, centered in 1 K range, and its position is moved to higher temperatures proportionally to applied field. The origin of the peak is in Zeeman splitting of the ground Kramers doublet, and the gradual shift with field defines effective g-factors for the rare-earth pseudospins in studied compounds. The results obtained are confronted with the calculations of crystal field splitting of the rare-earth multiplets.

  9. Sign Changes in the Electric Dipole Moment of Excited States in Rubidium-Alkaline Earth Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Pototschnig, Johann V.; Lackner, Florian; Hauser, Andreas W.; Ernst, Wolfgang E.

    2015-06-01

    In a recent series of combined experimental and theoretical studies we investigated the ground state and several excited states of the Rb-alkaline earth molecules RbSr and RbCa. The group of alkali-alkaline earth (AK-AKE) molecules has drawn attention for applications in ultracold molecular physics and the measurement of fundamental constants due to their large permanent electric and magnetic dipole moments in the ground state. These properties should allow for an easy manipulation of the molecules and simulations of spin models in optical lattices. In our studies we found that the permanent electric dipole moment points in different directions for certain electronically excited states, and changes the sign in some cases as a function of bond length. We summarize our results, give possible causes for the measured trends in terms of molecular orbital theory and extrapolate the tendencies to other combinations of AK and AKE - elements. F. Lackner, G. Krois, T. Buchsteiner, J. V. Pototschnig, and W. E. Ernst, Phys. Rev. Lett., 2014, 113, 153001; G. Krois, F. Lackner, J. V. Pototschnig, T. Buchsteiner, and W. E. Ernst, Phys. Chem. Chem. Phys., 2014, 16, 22373; J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Chem. Phys., 2014, 141, 234309 J. V. Pototschnig, G. Krois, F. Lackner, and W. E. Ernst, J. Mol. Spectrosc., in Press (2015), doi:10.1016/j.jms.2015.01.006 M. Kajita, G. Gopakumar, M. Abe, and M. Hada, J. Mol. Spectrosc., 2014, 300, 99-107 A. Micheli, G. K. Brennen, and P. Zoller, Nature Physics, 2006, 2, 341-347

  10. Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

    DOE PAGES

    Du, Mao -Hua; Singh, David J.; Zhang, Lijun; Li, Yuwei; Xu, Qiaoling; Ma, Yanming; Zheng, Weitao

    2016-04-19

    Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn2O3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn2O3 and BaSn2O3, which can bemore » stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn2O3) to 3.15 (SrSn2O3) eV, and hole effective masses ranging from 0.87 (BaSn2O3) to above 6.0 (SrSn2O3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

  11. Origins of energetic ions in the Earth's magnetosheath

    NASA Technical Reports Server (NTRS)

    Fuselter, S. A.; Shelley, E. G.; Klumpar, D. M.

    1992-01-01

    The analysis and interpretation of the combined scientific data from the Hot Plasma Composition Experiment (HPCE) and the Charge Energy Mass (CHEM) spectrometer on the Active Mesospheric Particle Tracer Experiment (AMPTE) Charge Composition Explorer (CCE) spacecraft are discussed. These combined data sets have and will be used to survey the energetic ion environment in the Earth's magnetosheath to determine the origins and relative strengths of the energetic ion populations found there. A computer code was developed to analyze and interpret the data sets. The focus of the first year was on the determination of the contribution of leaked magnetospheric protons to the total energetic proton population. Emphasis was placed on intervals when the AMPTE spacecraft was in the plasma depletion layer because it was argued that in this region, only the leaked population contributes to the energetic ion population. Manipulation of the CHEM data and comparison of the CHEM and HPCE data over their common energy range near the magnetopause also contributed directly to a second study of that region.

  12. The dissolution of carbon dioxide and the diffusion of carbonate ions in alkaline fuel cells

    NASA Astrophysics Data System (ADS)

    Deruiter, B.

    If alkaline fuel cells are used, it is more economical to get the necessary oxygen from the air, instead of using pure oxygen. A problem that arises, when air is used, is the dissolution of carbon dioxide into the electrolyte solution (in the form of carbonate). After a certain period the carbonate concentration can be so high that potassium carbonate crystals are formed. This research consists of two parts. A mathematical model was made to describe the diffusion of carbon dioxide and carbonate ions in the air electrode. Second, long run tests were carried out (38 days) with two fuel cells. One cell was connected to a current source which aplied a current density of 50 mA/sq cm. The other cell was not connected to a current source. During the tests, the increase of carbonate concentration was measured. The carbonate concentration was measured by titration with HCl. The precision titration equipment made it possible to analyze very small samples (30 microns). The loss of elecrolyte was therefore negligible. The data are presented in Gran plots. The mathematical model resulted in a set of three partial differential equations which have to be solved numerically. The long run tests showed that the increase of carbonate concentration was the same in both fuel cells. The test also showed that the carbonate concentration increases linearly with respect to time.

  13. Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

    SciTech Connect

    Levitskaia, Tatiana G.; Lumetta, Gregg J.; Moyer, Bruce A.; Bonnesen, Peter V.

    2005-06-01

    The purpose of this research involving collaboration between Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) is to explore new approaches to the separation of sodium hydroxide, sodium nitrate, and other sodium salts from high-level alkaline tank waste. The principal potential benefit is a major reduction in disposed waste volume, obviating the building of expensive new waste tanks and reducing the costs of low-activity waste immobilization. Principles of ion recognition are being researched toward discovery of liquid-liquid extraction systems that selectively separate sodium hydroxide and sodium nitrate from other waste components. The successful concept of pseudohydroxide extraction using fluorinated alcohols and phenols is being developed at ORNL and PNNL toward a greater understanding of the controlling equilibria, role of solvation, and of synergistic effects involving crown ethers. Synthesis efforts are being directed toward enhanced sodium binding by crown ethers, both neutral and proton-ionizable. Studies with real tank waste at PNNL will provide feedback toward solvent compositions that have promising properties.

  14. Ion Recognition Approach to Volume Reduction of Alkaline Tank Waste by Separation of Sodium Salts

    SciTech Connect

    Moyer, Bruce A.; Bonnesen, Peter V.; Custelcean, Radu; Delmau, Laetitia H.; Engle, Nancy L.; Kang, Hyun-Ah; Keever, Tamara J.; Marchand, Alan P.; Gadthula, Srinivas; Gore, Vinayak K.; Huang, Zilin; Sivappa, Rasapalli; Tirunahari, Pavan K.; Levitskaia, Tatiana G.; Lumetta, Gregg J.

    2005-09-26

    The purpose of this research involving collaboration between Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) is to explore new approaches to the separation of sodium hydroxide, sodium nitrate, and other sodium salts from high-level alkaline tank waste. The principal potential benefit is a major reduction in disposed waste volume, obviating the building of expensive new waste tanks and reducing the costs of vitrification. Principles of ion recognition are being researched toward discovery of liquid-liquid extraction systems that selectively separate sodium hydroxide and sodium nitrate from other waste components. The successful concept of pseudo hydroxide extraction using fluorinated alcohols and phenols is being developed at ORNL and PNNL toward a greater understanding of the controlling equilibria, role of solvation, and of synergistic effects involving crown ethers. Synthesis efforts are being directed toward enhanced sodium binding by crown ethers, both neutral and proton-ionizable. Studies with real tank waste at PNNL will provide feedback toward solvent compositions that have promising properties.

  15. The effects of alkaline earth metal ions and halogen ions on the chromium oxide activities in alkaline earth metal oxide-halide-Cr2O3 system fluxes

    NASA Astrophysics Data System (ADS)

    Li, Lian-Fu; Jiang, Mao-Fa; Wang, Wen-Zhong; Chen, Zhao-Ping

    2000-06-01

    The solid electrolyte cell — Mo|Cr + Cr2O3‖ZrO2(MgO)‖{Cu-Cr}alloy + (Cr2O3)fluxes|Mo+ is used at 1673 K to determine Cr2O3 activities in MO-MX 2-Cr2O3 (M = Ca2+, Ba2-, X = F- or Cl-) ternary fluxes, which are in equilibrium with the copper-chromium binary alloy. The ternary isothermal phase diagrams of CaO-CaF2-Cr2O3 and BaO-BaCl2-Cr2O3 system fluxes are inferred on the basis of the experimental results and binary phase diagrams. The results indicate that Cr2O3 activities in all fluxes always decrease with the increase of the X MO /X MX2 ratio. Partial replacement of BaO in BaO-BaF2-Cr2O3 fluxes by CaO is acceptable for economy and efficiency considerations. At the same time, partial substitution of BaO for CaO in CaO-CaF2-Cr2O3 fluxes is advantageous for phosphorus removal and chromium retention as a result of the increased Cr2O3 activities, increased basicities, and widening of the liquid zones. Compared to those in BaO-BaF2-Cr2O3 fluxes, Cr2O3 activities in CaO-CaF2-Cr2O3 fluxes approximately follow the same curve as the former, although the position and the width of the liquid zones are considerably different, and activities in BaO-BaCl2-Cr2O3 fluxes are higher at the lower Cr2O3 content, or vice versa. The activity coefficients of Cr2O3 in the fluxes decrease with the increase of the X MO /X MX 2 ratios.

  16. The Transport of Solar Ions Through the Earth's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1999-01-01

    This report covers the initial phase of an investigation that was originally selected by NASA Headquarters for funding by a grant but was later transferred to NASA GSFC for continued funding under a new and separate contract. The principal objective of the investigation, led by Dr. O.W. Lennartsson, is to extract information about the solar origin plasma in Earth's magnetosphere, specifically about the entry and transport of this plasma, using energetic (10 eV/e to 18 keV/e) ion composition data from the Lockheed Plasma Composition Experiment on the NASA/ESA International Sun-Earth Explorer One (ISEE 1) satellite. These data were acquired many years ago, from November 1977 through March of 1982, but, because of subsequent failures of similar experiments on several other spacecraft, they are still the only substantial ion composition data available from Earth's magnetotail, beyond 10 R(sub E), in the critically important sub-kev to keV energy range. All of the Lockheed data now exist in a compacted scientific format, suitable for large-scale statistical investigations, which has been archived both at Lockheed Martin in Palo Alto and at the National Space Science Data Center (NSSDC) in Greenbelt. The completion of the archiving, by processing the remaining half of the data, was made possible by separate funding through a temporary NASA program for data restoration and was given priority over the data analysis by a no-cost extension of the subject grant. By chance, the period of performance coincided with an international study of source and loss processes of magnetospheric plasma, sponsored by the International Space Science Institute (ISSI) in Bern, Switzerland, for which Dr. Lennartsson was invited to serve as one of 12 co-chairs. This study meshed well with the continued analysis of the NASA/Lockheed ISEE ion composition data and provided a natural forum for a broader discussion of the results from this unique experiment. What follows is arranged, for the most

  17. Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

    NASA Astrophysics Data System (ADS)

    Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

    2016-08-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

  18. Direct interactions between Z-DNA and alkaline earth cations, discovered in the presence of high concentrations of MgCl2 and CaCl2.

    PubMed

    Chatake, Toshiyuki; Sunami, Tomoko

    2013-07-01

    In this study, crystals of Z-DNA hexamer d(CGCGCG) complexed with MgCl2 and CaCl2 were obtained in the presence of high concentrations of alkaline earth salts (500mM) using a temperature control technique, and their crystal structures were determined at 1.3Å resolution. Mg(2+) and Ca(2+) cations in these structures tend to interact directly with phosphate groups of Z-DNA duplexes; however, they tend to form water-mediated interactions with Z-DNA in the presence of lower concentrations of alkaline earth salts. In these crystals, a DNA duplex was laid along its c-axis and interacted with its 6 neighboring DNA duplexes through coordination bonds of PO…(Mg(2+) or Ca(2+))…OP. A symmetrical hexagonal Z-DNA duplex assembly model may explain DNA condensation caused by alkaline earth salts. These structures offer insights into the functions of alkaline earth cations essential to the structures and assembly of Z-DNA duplexes.

  19. Control of physicochemical properties and catalytic activity of tris(2,2'-bipyridine)iron(II) encapsulated within the zeolite Y cavity by alkaline earth metal cations.

    PubMed

    Martis, Martin; Mori, Kohsuke; Yamashita, Hiromi

    2014-01-21

    A series of materials containing the tris(2,2'-bipyridine)iron(ii) (Fe(bpy)3(2+)) complex inside zeolite Y cavities with alkaline earth metals (Mg(2+), Ca(2+), Sr(2+), Ba(2+)) as charge compensating cations have been synthesized via a "ship in the bottle" method. The influence of the alkaline earth metal cations on the physicochemical properties and catalytic activity was investigated. The successful formation of the Fe(bpy)3(2+) complex was verified by XRD, diffuse-reflectance UV-vis spectroscopy, and Fe K-edge XAFS measurements. The BET surface area and the Fe content decreased in the presence of the larger alkaline earth metal, but the intensity of the MLCT adsorption band of Fe(bpy)3(2+) increased with the heavier cation. The electron density of the Fe atoms decreased, and the average interatomic bond distance Fe-N/O and the coordination number increased with the heavier alkaline earth metal cation. The encapsulation of Fe(bpy)3(2+) resulted in the creation of a photocatalytic system able to oxidize styrene to benzaldehyde and styrene oxide under visible light irradiation (λ > 430 nm) in the presence of molecular oxygen.

  20. X-ray-absorption spectroscopic investigation of alkali and alkaline earth catalysts in coal gasification. Final report, January 1987-September 1989

    SciTech Connect

    Huggins, F.E.; Shah, N.; Huffman, G.P.

    1990-04-01

    The structures of alkali and alkaline-earth metal catalyst species in lignite and polymer chars and during pyrolysis pretreatment and char gasification have been investigated using ambient and newly-developed, in situ XAFS spectroscopic techniques. The XAFS data, which were obtained at the Stanford Synchrotron Radiation Laboratory, were supplemented by char characterization and reactivity measurements made at the Pennsylvania State University. The findings of the investigation are as follows: (i) the catalytic species, as introduced to the char or lignite, is an atomically-dispersed, metal-ion-oxygen-anion complex, and remains a metal-oxygen complex throughout pyrolysis and gasification; (ii) the catalyst species transforms to a bulk oxide species during pyrolysis pretreatment; (iii) during gasification, the catalyst species rapidly transforms to bulk alkali carbonate in the case of the alkali-metal species and slowly to calcium oxide in the case of the calcium species; (iv) higher catalyst loadings results in an increased number of catalytic sites, rather than any structural variation of the catalyst site due to concentration effects; and (v) reaction of alkali with aluminosilicates (from clays) or silica is the major catalyst poisoning reaction, unless the coal is demineralized in which case the alkali may react with residual halide from HCl or HF used to clean the coal. Such poisoning reactions were not demonstrated for calcium-oxygen species.

  1. Optical probes for the detection of protons, and alkali and alkaline earth metal cations.

    PubMed

    Hamilton, Graham R C; Sahoo, Suban K; Kamila, Sukanta; Singh, Narinder; Kaur, Navneet; Hyland, Barry W; Callan, John F

    2015-07-01

    Luminescent sensors and switches continue to play a key role in shaping our understanding of key biochemical processes, assist in the diagnosis of disease and contribute to the design of new drugs and therapies. Similarly, their contribution to the environment cannot be understated as they offer a portable means to undertake field testing for hazardous chemicals and pollutants such as heavy metals. From a physiological perspective, the Group I and II metal ions are among the most important in the periodic table with blood plasma levels of H(+), Na(+) and Ca(2+) being indicators of several possible disease states. In this review, we examine the progress that has been made in the development of luminescent probes for Group I and Group II ions as well as protons. The potential applications of these probes and the mechanism involved in controlling their luminescent response upon analyte binding will also be discussed. PMID:25742963

  2. Optical probes for the detection of protons, and alkali and alkaline earth metal cations.

    PubMed

    Hamilton, Graham R C; Sahoo, Suban K; Kamila, Sukanta; Singh, Narinder; Kaur, Navneet; Hyland, Barry W; Callan, John F

    2015-07-01

    Luminescent sensors and switches continue to play a key role in shaping our understanding of key biochemical processes, assist in the diagnosis of disease and contribute to the design of new drugs and therapies. Similarly, their contribution to the environment cannot be understated as they offer a portable means to undertake field testing for hazardous chemicals and pollutants such as heavy metals. From a physiological perspective, the Group I and II metal ions are among the most important in the periodic table with blood plasma levels of H(+), Na(+) and Ca(2+) being indicators of several possible disease states. In this review, we examine the progress that has been made in the development of luminescent probes for Group I and Group II ions as well as protons. The potential applications of these probes and the mechanism involved in controlling their luminescent response upon analyte binding will also be discussed.

  3. Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics.

    PubMed

    Taran, Olga; Medrano, Felipe; Yatsimirsky, Anatoly K

    2008-12-14

    Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M2(OH)3+, M(OH)+, M(OH)2 and M2(OH)5- species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate-concentration profiles. Observed first-order rate constants in the presence of 1-2 mM Mg(II) or Ca(II) in neutral and weakly basic solutions were 10(8)-10(11) times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced <100-fold accelerations. Possible structures of DMSO solvated catalyst-substrate complexes were modeled by DFT calculations with Mg(II). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst.

  4. Alkaline-Earth-Metal-Induced Liberation of Rare Allotropes of Elemental Silicon and Germanium from N-Heterocyclic Metallylenes.

    PubMed

    Blom, Burgert; Said, Amro; Szilvási, Tibor; Menezes, Prashanth W; Tan, Gengwen; Baumgartner, Judith; Driess, Matthias

    2015-09-01

    The synthesis and striking reactivity of the unprecedented N-heterocyclic silylene and germylene ("metallylene") alkaline-earth metal (Ae) complexes of the type [(η(5)-C5Me5)2Ae←:E(N(t)BuCH)2] (3, 4, and 7-9; Ae = Ca, E = Ge 3; Ae = Sr, E = Ge 4; Ae = Sr, E = Si 7; Ae = Ba, E = Si 8; Ae = Ba, E = Ge 9) are reported. All complexes have been characterized by spectroscopic means, and their bonding situations investigated by density functional theory (DFT) methods. Single-crystal X-ray diffraction analyses of examples revealed relatively long Si-Ae and Ge-Ae distances, respectively, indicative of weak E:→Ae (E = Si, Ge) dative bonds, further supported by the calculated Wiberg bond indices , which are rather low in all cases (∼0.5). Unexpectedly, the complexes undergo facile transformation to 1,4-diazabuta-1,3-diene Ae metal complexes of the type [(η(5)-C5Me5)2Ae(κ(2)-{N(t)Bu═CHCH═N(t)Bu})] (Ae = Sr 10, Ae = Ba 11) or in the case of calcium to the dinuclear complex [(η(5)-C5Me5)2Ca←:N((t)Bu)═CHCH═((t)Bu)N:→Ca(η(5)-C5Me5)2] (12) under concomitant liberation of elemental silicon and germanium. The formation of elemental silicon and germanium is proven by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. Notably, the decomposition of the Si(II)→Ba complex 8 produces allo-silicon, a rare allotropic form of elemental silicon. Similarly, the analogous Ge(II)→Ba complex 9, upon decomposition, forms tetragonal germanium, a dense and rare allotrope of elemental germanium. The energetics of this unprecedented alkaline-earth-metal-induced liberation of elemental silicon and germanium was additionally studied by DFT methods, revealing that the transformations are pronouncedly exergonic and considerably larger for the N-heterocyclic germylene complexes than those of the corresponding silicon analogues.

  5. Alkaline-Earth-Metal-Induced Liberation of Rare Allotropes of Elemental Silicon and Germanium from N-Heterocyclic Metallylenes.

    PubMed

    Blom, Burgert; Said, Amro; Szilvási, Tibor; Menezes, Prashanth W; Tan, Gengwen; Baumgartner, Judith; Driess, Matthias

    2015-09-01

    The synthesis and striking reactivity of the unprecedented N-heterocyclic silylene and germylene ("metallylene") alkaline-earth metal (Ae) complexes of the type [(η(5)-C5Me5)2Ae←:E(N(t)BuCH)2] (3, 4, and 7-9; Ae = Ca, E = Ge 3; Ae = Sr, E = Ge 4; Ae = Sr, E = Si 7; Ae = Ba, E = Si 8; Ae = Ba, E = Ge 9) are reported. All complexes have been characterized by spectroscopic means, and their bonding situations investigated by density functional theory (DFT) methods. Single-crystal X-ray diffraction analyses of examples revealed relatively long Si-Ae and Ge-Ae distances, respectively, indicative of weak E:→Ae (E = Si, Ge) dative bonds, further supported by the calculated Wiberg bond indices , which are rather low in all cases (∼0.5). Unexpectedly, the complexes undergo facile transformation to 1,4-diazabuta-1,3-diene Ae metal complexes of the type [(η(5)-C5Me5)2Ae(κ(2)-{N(t)Bu═CHCH═N(t)Bu})] (Ae = Sr 10, Ae = Ba 11) or in the case of calcium to the dinuclear complex [(η(5)-C5Me5)2Ca←:N((t)Bu)═CHCH═((t)Bu)N:→Ca(η(5)-C5Me5)2] (12) under concomitant liberation of elemental silicon and germanium. The formation of elemental silicon and germanium is proven by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray spectroscopy. Notably, the decomposition of the Si(II)→Ba complex 8 produces allo-silicon, a rare allotropic form of elemental silicon. Similarly, the analogous Ge(II)→Ba complex 9, upon decomposition, forms tetragonal germanium, a dense and rare allotrope of elemental germanium. The energetics of this unprecedented alkaline-earth-metal-induced liberation of elemental silicon and germanium was additionally studied by DFT methods, revealing that the transformations are pronouncedly exergonic and considerably larger for the N-heterocyclic germylene complexes than those of the corresponding silicon analogues. PMID:26305163

  6. Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations.

    PubMed

    Redondo, Pilar; Largo, Antonio; Rayón, Víctor Manuel; Molpeceres, Germán; Sordo, José Ángel; Barrientos, Carmen

    2014-08-14

    The reactions, in the gas phase, between alkali-earth monocations (Mg(+), Ca(+), Sr(+), Ba(+)) and CH3X (X = Cl, Br) have been theoretically studied. The stationary points on the potential energy surfaces were characterized at the Density Functional Theory level on the framework of the mPW1K functional with the QZVPP Ahlrichs's basis sets. A complementary kinetics study has also been performed using conventional/variational microcanonical transition state theory. In the reactions of Mg(+) with either chloro- or bromomethane the transition structure lies in energy clearly above the reactants rendering thermal activation of CH3Cl or CH3Br extremely improbable. The remaining reactions are exothermic and barrierless processes; thus carbon-halogen bonds in chloro- or bromomethane can be activated by calcium, strontium or barium monocations to obtain the metal halogen cation and the methyl radical. The Mulliken population analysis for the stationary points of the potential energy surfaces supports a "harpoon"-like mechanism for the halogen-atom abstraction processes. An analysis of the bonding situation for the stationary points on the potential energy surface has also been performed in the framework of the quantum theory of atoms in molecules. PMID:24967575

  7. Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations.

    PubMed

    Redondo, Pilar; Largo, Antonio; Rayón, Víctor Manuel; Molpeceres, Germán; Sordo, José Ángel; Barrientos, Carmen

    2014-08-14

    The reactions, in the gas phase, between alkali-earth monocations (Mg(+), Ca(+), Sr(+), Ba(+)) and CH3X (X = Cl, Br) have been theoretically studied. The stationary points on the potential energy surfaces were characterized at the Density Functional Theory level on the framework of the mPW1K functional with the QZVPP Ahlrichs's basis sets. A complementary kinetics study has also been performed using conventional/variational microcanonical transition state theory. In the reactions of Mg(+) with either chloro- or bromomethane the transition structure lies in energy clearly above the reactants rendering thermal activation of CH3Cl or CH3Br extremely improbable. The remaining reactions are exothermic and barrierless processes; thus carbon-halogen bonds in chloro- or bromomethane can be activated by calcium, strontium or barium monocations to obtain the metal halogen cation and the methyl radical. The Mulliken population analysis for the stationary points of the potential energy surfaces supports a "harpoon"-like mechanism for the halogen-atom abstraction processes. An analysis of the bonding situation for the stationary points on the potential energy surface has also been performed in the framework of the quantum theory of atoms in molecules.

  8. Ion acceleration to supra-thermal energies in the near-Earth magnetotail

    NASA Astrophysics Data System (ADS)

    Elena, Kronberg

    2016-07-01

    We here present an analysis of ion composition measurements by the RAPID instruments onboard Cluster. We discuss the evidence for an acceleration of ions to energies above 100 keV in the near-Earth current sheet, in the vicinity of a possible near-Earth neutral line, and we investigate the physical details of such an acceleration. We present observations of tailward bulk flows in the near-Earth tail associated with plasmoid-like magnetic structures. These flows are superimposed by low-frequency magnetic and electric field fluctuations. Observations and modelling show that resonant interactions between ions and low-frequency electromagnetic fluctuations facilitate the ion energization inside plasmoids.

  9. Spectroscopic and electron microscopic investigation of iron oxides formed in a highly alkaline medium in the presence of rhodium ions

    NASA Astrophysics Data System (ADS)

    Krehula, Stjepko; Musić, Svetozar

    2010-07-01

    The effect of the presence of rhodium ions on the formation of iron oxides in a highly alkaline precipitation system was investigated using X-ray powder diffraction (XRD), 57Fe Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Acicular α-FeOOH particles precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. Characterization of α-FeOOH samples formed in the presence of rhodium ions showed a somewhat smaller mean crystallite size, increased unit-cell dimensions, a reduced average hyperfine magnetic field and a slight shift in the position of IR absorption bands in comparison with the reference α-FeOOH sample. By additional heating of the precipitation system, α-FeOOH precipitated in the presence of rhodium ions transformed to α-Fe 2O 3 crystals in the form of hexagonal bipyramids via a dissolution-recrystallization process. Metallic rhodium nanoparticles were formed simultaneously by the reduction of Rh 3+ ions in the presence of the products of TMAH thermal decomposition (trimethylamine and methanol). These rhodium nanoparticles acted as a catalyst for the reductive dissolution of α-Fe 2O 3 particles and the formation of Fe 3O 4 crystals in the form of octahedrons.

  10. X-ray Diffraction Studies of the Structure and Thermochemistry of Alkaline-Earth Oxide-Coated Thermionic Cathodes

    NASA Technical Reports Server (NTRS)

    Karikari, E. K.; Bassey, E.; Wintucky, Edwin G.

    1998-01-01

    NASA LeRC has a broad, active cathode technology development program in which both experimental and theoretical studies are being employed to further development of thermionic cathodes for use as electron sources in vacuum devices for communications and other space applications. One important type of thermionic cathode under development is the alkaline-earth oxide-coated (BaO, SrO, CaO) cathode. Significant improvements in the emission characteristics of this cathode have been obtained through modification of the chemical composition and morphology of the oxide coating, with the best result thus far coming from the addition of In2O3 and Sc2O3. Whereas the In2O3 produces a finer, more uniform particle structure, the exact chemical state and role of the Sc2O3 in the emission enhancement is unknown. The purpose of this cooperative agreement is to combine the studies of the surface chemistry and electron emission at NASA LeRC of chemically modified oxide coatings with a study of the thermochemistry and crystal structure using X-ray diffraction equipment and expertise at Clark Atlanta University (CAU). The study at CAU is intended to provide the description and understanding of the structure and thermochemistry needed for further improvement and optimization of the modified coatings. A description of the experimental procedure, preliminary X-ray diffraction test results, together with the design of an ultrahigh vacuum chamber necessary for high temperature thermochemistry studies will be presented.

  11. Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides.

    PubMed

    Hereijgers, Bart P C; Weckhuysen, Bert M

    2009-01-01

    A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on lanthanum oxide supported on high-surface-area alumina.

  12. Effect of alkaline earth metals on the liquid-phase hydrogenation of hydroquinone over Ru-based catalysts

    NASA Astrophysics Data System (ADS)

    Li, Hongwei; Ji, Dong; Li, Yu; Liang, Yalan; Li, Gui Xian

    2015-12-01

    A series of Ru-based catalysts modified by alkaline earth metals were prepared by the impregnation-precipitation method and characterized using transmission electron microscopy, X-ray diffraction, ICP optical emission spectroscopy, Infrared Spectroscopy of adsorbed pyridine analysis and surface area analysis. The performance of the catalysts was measured via liquid-phase hydroquinone hydrogenation reaction. Results show that the Ru-Sr/NaY catalyst has the best activity and selectivity among those Ru-based catalysts. The conversion of hydroquinone and the selectivity to 1,4-cyclohexanediol reached up to 99.6% and 89.6% at optimum reaction condition (700 r/min, 423 K and 5 MPa pressure of H2 in 3 h). This may be attributed to the fact that the right amount of Strontium is beneficial to the good dispersion of the ruthenium nanoclusters on the surface of NaY and modify the acidic properties of the catalyst. Moreover, IR of adsorbed pyridine analysis suggested the proper ratio of L/B acid of the catalysts played an important role in the performance of the hydroquinone hydrogenation reaction.

  13. Thermoelectric properties of pnictogen-substituted skutterudites with alkaline-earth fillers using first-principles calculations

    NASA Astrophysics Data System (ADS)

    Bang, Semi; Wee, Daehyun; Li, An; Fornari, Marco; Kozinsky, Boris

    2016-05-01

    First-principles calculations have been performed to investigate electronic band structures, vibrational characters, and related transport properties of pnictogen-substituted skutterudites filled with alkaline-earth elements ( MxCo4A6B6 , where M = Ca, Sr, or Ba, A = Ge or Sn, B = Se or Te, and x = 0.5 or 1). Electronic transport properties related to thermoelectricity, including the Seebeck coefficient and the electrical conductivity, are computed by using the Boltzmann transport formalism within the constant-relaxation-time approximation. The results are compared against the corresponding properties of the unfilled pnictogen-substituted ternary skutterudites ( CoA1.5B1.5 ) to identify the effects of filling to estimate the potential for thermoelectric applications. The changes in the ionic character of the interatomic bonding between the Group 14 (A) and Group 16 (B) elements, which was suspected to be a major scattering source in unfilled pnictogen-substituted ternary skutterudites, are probed by analyzing the projected density of states, the charge densities, and the Born effective charges, in an attempt to identify a potential path for improvement of the thermoelectric performance. Our computational results suggest that the analyzed performance of the filled pnictogen-substituted skutterudites should exhibit no significant improvement over that of the corresponding unfilled pnictogen-substituted ternary skutterudites, unless significant reduction in thermal conductivity is achieved by the rattling motion of the filler atoms.

  14. CO2 gasification reactivity of biomass char: catalytic influence of alkali, alkaline earth and transition metal salts.

    PubMed

    Lahijani, Pooya; Zainal, Zainal Alimuddin; Mohamed, Abdul Rahman; Mohammadi, Maedeh

    2013-09-01

    This study investigates the influence of alkali (Na, K), alkaline earth (Ca, Mg) and transition (Fe) metal nitrates on CO2 gasification reactivity of pistachio nut shell (PNS) char. The preliminary gasification experiments were performed in thermogravimetric analyzer (TGA) and the results showed considerable improvement in carbon conversion; Na-char>Ca-char>Fe-char>K-char>Mg-char>raw char. Based on TGA studies, NaNO3 (with loadings of 3-7 wt%) was selected as the superior catalyst for further gasification studies in bench-scale reactor; the highest reactivity was devoted to 5 wt% Na loaded char. The data acquired for gasification rate of catalyzed char were fitted with several kinetic models, among which, random pore model was adopted as the best model. Based on obtained gasification rate constant and using the Arrhenius plot, activation energy of 5 wt% Na loaded char was calculated as 151.46 kJ/mol which was 53 kJ/mol lower than that of un-catalyzed char. PMID:23880130

  15. Electronic structures and second hyperpolarizabilities of alkaline earth metal complexes end-capped with NA2 (A = H, Li, Na).

    PubMed

    Banerjee, Paramita; Nandi, Prasanta K

    2016-05-14

    The ground state structures and NLO properties of a number of alkaline earth metal complexes end-capped with NA2 groups (A = H, Li, Na) are calculated by employing the CAM-B3LYP, wB97XD and B2PLYP functionals along with MP2 and CCSD(T) for 6-311++G(d,p), 6-311++G(3df,3pd), aug-cc-pVTZ, aug-pc-2 and Hypol basis sets. The complexes are found to be significantly stable. The magnitude of second hyperpolarizability enhances appreciably with increase in the number of magnesium and calcium atoms in the chain, which has been indicated by the power law dependence γ = a + bn(c) with c values ranging from 2.4-4.3 for Mg and 2.4-3.7 for Ca complexes, respectively. The largest second-hyperpolarizability (10(9) au) is obtained for the complex Ca7(NNa2)2 at the CAM-B3LYP level. The two state model has been used to explain the variation of hyperpolarizabilities. PMID:27088138

  16. Dissolution of glass wool, rock wool and alkaline earth silicate wool: morphological and chemical changes in fibers.

    PubMed

    Campopiano, Antonella; Cannizzaro, Annapaola; Angelosanto, Federica; Astolfi, Maria Luisa; Ramires, Deborah; Olori, Angelo; Canepari, Silvia; Iavicoli, Sergio

    2014-10-01

    The behavior of alkaline earth silicate (AES) wool and of other biosoluble wools in saline solution simulating physiological fluids was compared with that of a traditional wool belonging to synthetic vitreous fibers. Morphological and size changes of fibers were studied by scanning electron microscopy (SEM). The elements extracted from fibers were analyzed by inductively coupled plasma atomic emission spectrometry. SEM analysis showed a larger reduction of length-weighted geometric mean fiber diameter at 4.5 pH than at 7.4 pH. At the 7.4 pH, AES wool showed a higher dissolution rate and a dissolution time less than a few days. Their dissolution was highly non-congruent with rapid leaching of calcium. Unlike rock wool, glass wool dissolved more rapidly at physiological pH than at acid pH. Dissolution of AES and biosoluble rock wool is accompanied by a noticeable change in morphology while by no change for glass wool. Biosoluble rock wool developed a leached surface with porous honeycomb structure. SEM analysis showed the dissolution for glass wool is mainly due to breakage transverse of fiber at pH 7.4. AES dissolution constant (Kdis) was the highest at pH 7.4, while at pH 4.5 only biosoluble rockwool 1 showed a higher Kdis.

  17. A Density Functional Theory Study of Codoping Characteristics of Sulfur with Alkaline Earth in Delafossite CuAlO2

    NASA Astrophysics Data System (ADS)

    Liu, Qi-Jun; Qin, Han; Liu, Zheng-Tang

    2016-04-01

    The structural, electronic properties and formation energies of sulfur and alkaline earth codoped delafossite CuAlO2 have been investigated using the first-principles density functional theory calculations. Our results reveal that the volume of codoping systems increases with the increasing atomic radius of metal atoms. The formation energies under different growth conditions have been calculated, showing that the codoping systems are formed easily under O-rich growth conditions. Electronic band structures and density of states have been obtained. The decreased bandgaps, enhanced covalence and appearance of electron acceptors after codoping are all good for p-type conductivity. Supported by the National Natural Science Foundation of China under Grant Nos. 11347199, 51402244, and 11547311, the Specialized Research Fund for Doctoral Program of Higher Education of China under Grant No. 20130184120028, the Fundamental Research Fund for the Central Universities, China under Grant Nos. 2682014CX084, 2682014ZT30, and 2682014ZT31, and the fund of the State Key Laboratory of Solidification Processing in NWPU under Grant No. SKLSP201511

  18. CO2 gasification reactivity of biomass char: catalytic influence of alkali, alkaline earth and transition metal salts.

    PubMed

    Lahijani, Pooya; Zainal, Zainal Alimuddin; Mohamed, Abdul Rahman; Mohammadi, Maedeh

    2013-09-01

    This study investigates the influence of alkali (Na, K), alkaline earth (Ca, Mg) and transition (Fe) metal nitrates on CO2 gasification reactivity of pistachio nut shell (PNS) char. The preliminary gasification experiments were performed in thermogravimetric analyzer (TGA) and the results showed considerable improvement in carbon conversion; Na-char>Ca-char>Fe-char>K-char>Mg-char>raw char. Based on TGA studies, NaNO3 (with loadings of 3-7 wt%) was selected as the superior catalyst for further gasification studies in bench-scale reactor; the highest reactivity was devoted to 5 wt% Na loaded char. The data acquired for gasification rate of catalyzed char were fitted with several kinetic models, among which, random pore model was adopted as the best model. Based on obtained gasification rate constant and using the Arrhenius plot, activation energy of 5 wt% Na loaded char was calculated as 151.46 kJ/mol which was 53 kJ/mol lower than that of un-catalyzed char.

  19. Proposal for laser cooling of rare-earth ions

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; Hong, Ye; Wyart, Jean-François; Lepers, Maxence

    2016-05-01

    The efficiency of laser cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect, rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser cooling of singly ionized erbium Er+ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er+, using a combination of ab initio and least-squares-fitting techniques. We identify five weak closed transitions suitable for laser cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes.We expect our detailed study on Er+ to give good insight into the laser cooling of neighboring ions such as Dy+. Supported by ``Agence Nationale de la Recherche'' (ANR), under the project COPOMOL (Contract No. ANR-13-IS04-0004-01).

  20. [Development of metal ions analysis by ion chromatography].

    PubMed

    Yu, Hong; Wang, Yuxin

    2007-05-01

    Analysis of metal ions by ion chromatography, including cation-exchange ion chromatography, anion-exchange ion chromatography and chelation ion chromatography, is reviewed. The cation-exchange ion chromatography is a main method for the determination of metal ions. Stationary phases in cation-exchange ion chromatography are strong acid cation exchanger (sulfonic) and weak acid cation exchanger (carboxylic). Alkali metal ions, alkaline earth metal ions, transition metal ions, rare earth metal ions, ammonium ions and amines can be analyzed by cation-exchange ion chromatography with a suitable detector. The anion-exchange ion chromatography is suitable for the separation and analysis of alkaline earth metal ions, transition metal ions and rare earth metal ions. The selectivity for analysis of metal ions with anion-exchange ion chromatography is good. Simultaneous determination of metal ions and inorganic anions can be achieved using anion-exchange ion chromatography. Chelation ion chromatography is suitable for the determination of trace metal ions in complex matrices. A total of 125 references are cited.

  1. Evaluation of AA5052 alloy anode in alkaline electrolyte with organic rare-earth complex additives for aluminium-air batteries

    NASA Astrophysics Data System (ADS)

    Wang, Dapeng; Li, Heshun; Liu, Jie; Zhang, Daquan; Gao, Lixin; Tong, Lin

    2015-10-01

    Behaviours of the AA5052 aluminium alloy anode of the alkaline aluminium-air battery are studied by the hydrogen evolution test, the electrochemical measurements and the surface analysis method. The combination of amino-acid and rare earth as electrolyte additives effectively retards the self-corrosion of AA5052 aluminium alloy in 4 M NaOH solution. It shows that the combination of L-cysteine and cerium nitrate has a synergistic effect owing to the formation of a complex film on AA5052 alloy surface. The organic rare-earth complex can decrease the anodic polarisation, suppress the hydrogen evolution and increase the anodic utilization rate.

  2. NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on γ-Al2O3

    SciTech Connect

    Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

    2008-07-15

    NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on γ-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the γ-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/γ-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

  3. Separation of alkali, alkaline earth and rare earth cations by liquid membranes containing macrocyclic carriers. Third progress report, September 1, 1980-April 1, 1981

    SciTech Connect

    Christensen, J.J.

    1981-04-15

    The overall objective of this project is to study the use of liquid membrane systems employing macrocyclic ligand carriers in making separations among metal cations. During the third year of the project, work continued in the development of a mathematical model to describe cation transport. The model was originally developed to describe the relationship between cation transport rate (J/sub M/) and the cation-macrocycle stability constant (K). The model was tested by determining the rates of transport of alkali and alkaline earth cations through chloroform membranes containing carrier ligands where the stability constants for their reaction with cations in methanol were known. From the results, it is clear that the model correctly describes the dependence of J/sub M/ on log K. The model also correctly describes the effect of cation concentration and carrier concentration on cation transport rates, as detailed in the previous progress report. During the third year of the project, the transport model was expanded so as to apply to competitive transport of cations from mixtures of two cations in the source aqueous phase. Data were collected under these conditions and the ability of the model to predict the flux of each cation was tested. Representative data of this type are presented along with corresponding data which were obtained when each cation was transported by the same carrier from a source phase containing only that cation. Comparison of transport rates determined under the two experimental conditions indicates that the relationship between the two sets of data is complex. To date, a few of these data involving transport from binary cation mixtures have been tested against the transport model. It was found that the model correctly predicts the cation fluxes from cation mixtures. These preliminary results indicate that the transport model can successfully predict separation factors when cation mixtures are used.

  4. Ab Initio Quantum Mechanical Study of the Structure and Stability of the Alkaline Earth Metal Oxides and Peroxides

    NASA Astrophysics Data System (ADS)

    Königstein, Markus; Catlow, C. Richard A.

    1998-10-01

    We report a detailed computationally study of the stability of the alkaline earth metal peroxidesMO2(M=Ba, Sr, Ca, Mg, Be) with respect to decomposition into the corresponding oxidesMOand molecular oxygen using Hartree-Fock and density functional theory (DFT) techniques. A comparison between calculated and experimental binding energies indicates that the DFT method is most suitable for a correct description of the peroxide bond. The DFT reaction energies for the peroxide decompositionMO2→MO+{1}/{2}O2show that only BaO2and SrO2are thermodynamically stable compounds, while CaO2(in the calcium carbide structure), MgO2, and BeO2(in the pyrite structure) are energetically unstable with reaction energies of -24.7, -26.8, and -128.7kJ/mol, respectively, and are therefore unlikely to exist as pure compounds. The published calcium carbide structure for CaO2is probably incorrect, at least for pure calcium peroxide, since apart from the thermodynamical instability the compound is more stable in the pyrite structure by 25.5 kJ/mol. Our analysis suggests that the water and/or hydrogen peroxide content of experimentally prepared MgO2samples is necessary for the stabilization of the structure, while BeO2is clearly unstable under ambient conditions. We studied also the effect of the zero point energies and the entropies on the decomposition free energies and, for this purpose, performed atomistic lattice simulations based on interatomic potentials, which we derived from ourab initiodata; the results indicate a negligible effect of the zero point energies, while the entropy terms favor the decomposition reaction by ca. 20 kJ/mol at 298.15 K.

  5. Cation radii induced structural variation in fluorescent alkaline earth networks constructed from tautomers of a nucleobase analogue.

    PubMed

    Deng, Zhao-Peng; Kang, Wei; Zhu, Zhi-Biao; Huo, Li-Hua; Zhao, Hui; Gao, Shan

    2012-07-21

    Nucleobase tautomers and their metal complexes have attracted considerable attention due to their fascinating architectures along with wide applications. In this paper, 4,6-dihydroxypyrimidine (H(2)DHP), an analogue of uracil and thymine, was employed to react with the vital elements of alkaline earth metals in an aqueous solution and lead to the formation of four novel complexes, [Mg(HDHP)(2) (H(2)O)(4)] (1), [Ca(HDHP)(2)(H(2)O)(3)](n)·nH(2)O (2), [Sr(HDHP)(2)(H(2)O)(3)](n)·nH(2)O (3), and [Ba(HDHP)(2)(H(2)O)(2)](n)·nH(2)O (4), which have been characterized by elemental analysis, IR, TG, UV-Vis, PL, powder and single-crystal X-ray diffraction and progressively evolve from zero-dimensional (0D) mononuclear, one-dimensional (1D) zig-zag double chain, two-dimensional (2D) double layer, to a three-dimensional (3D) porous network along with the increase of cation radii. This tendency in dimensionality follows salient crystal engineering principles and can be explained by considering factors such as hard-soft acid-base principles and cation radii. The deprotonated H(2)DHP ligand exhibits four new coordination modes, namely, O-monodentate (complex 1), N,O-chelating (complexes 2 and 3), O,O-bridging (complexes 2 and 3), and κ(1)O:κ(2)O-bridging mode (complex 4). Interestingly, the structural investigation indicates that the HDHP(-) monoanion shows three unusual types of tautomers, which are essential for the diagnosis of disease and investigation of medicine. Furthermore, the four complexes exhibit strong blue emission compared to free H(2)DHP ligand at room temperature and may be potential candidates for blue fluorescent biological materials used in organisms.

  6. Ab initio study of permanent electric dipole moment and radiative lifetimes of alkaline-earth-metal--Li molecules

    SciTech Connect

    Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

    2011-12-15

    We calculate permanent electric dipole moments (PDMs), as well as spontaneous and black body lifetimes, of alkaline-earth-metal-Li (AEM-Li) ultracold polar molecules to study anisotropic long-range dipole-dipole interactions in a single quantum state. We obtain potential energy curves for the {sup 2} {Sigma} ground state of MgLi, CaLi, SrLi, and BaLi molecules at the coupled cluster singles and doubles with partial triples [CCSD(T)] level of electron correlation. Calculated spectroscopic constants for the isotopes: {sup 24}Mg{sup 7}Li, {sup 40}Ca{sup 7}Li, {sup 88}Sr{sup 7}Li, and {sup 138}Ba{sup 7}Li, show good agreement with available theoretical and experimental results. We obtain PDM curves using finite field perturbation theory at the CCSD(T) level. We find that AEM-Li molecules have moderate values of PDM at the equilibrium bond distance (MgLi: 0.90 D, CaLi: 1.15 D, SrLi: 0.33 D, and BaLi: -0.42 D) and hence might be suitable candidates for the proposed study in a single quantum state. Radiative lifetime calculations of the {nu} = 0 state ({sup 24}Mg{sup 6}Li: 22 s, {sup 40}Ca{sup 6}Li: 39 s, {sup 88}Sr{sup 6}Li: 380 s, and {sup 138}Ba{sup 6}Li: 988 s) are found to be longer than the typical time scale associated with ultracold experiments with these molecules. The uncertainty in the lifetime calculations are estimated to be less than 10%.

  7. Counter-ion specificity explored in abnormal expansion of supra-molecular aggregates in aqueous solution of alkaline metal salts.

    PubMed

    Huang, Ningdong; Tao, Jiaojiao; Wei, Shenghui; Chen, Mingming; Wei, Chengsha; Li, Liangbin

    2015-09-21

    Ionic effects in aqueous solution of macro-ions showing specificity and unconventional characters, respectively, receive a lot of interests recently; however, the complexity of specific ion effects in unconventional phenomena remains ambiguous. In this study, the effects of univalent ions on aggregation of supra-molecular nano-fibrils with charged carboxylate groups on the surface as a prototype of macro-ions are investigated by Small Angle X-ray Scattering (SAXS) in aqueous solutions of alkaline metal chlorides. It is found that the columnar bundles of charged fibrils are expanded in certain salt concentration range contradicting the conventional screening effects of salts. The degree of expansion is dominated by cations as Na(+) induces drastic effects in comparison to rather gentle changes from K(+) and Cs(+). The specific cations effects observed by SAXS correlate with the pH behavior of the solutions, an indicator of surface charge, or number of carboxylate groups along the supra-molecular fibrils. It is postulated that while Na(+) with stronger affinity to carboxylates apparently reduces the surface charge, K(+) and Cs(+) only weakly interact with carboxylates and induce minor changes, accounting for the cation-sensitive aggregation behavior of fibrils observed by SAXS. By probing the bundling aggregation of charged supra-molecular nano-fibrils in salty water, we provide direct evidence of specific counter-ion effects in unusual expansion caused by univalent salts. PMID:26395732

  8. The influence of platinum(IV) ions on the formation of iron oxides in a highly alkaline medium

    NASA Astrophysics Data System (ADS)

    Krehula, Stjepko; Musić, Svetozar

    2011-05-01

    The effect of the presence of platinum(IV) ions, in the form of Pt(OH)62- at a high pH, on the formation of iron oxides in a highly alkaline precipitation system was investigated using X-ray powder diffraction (XRD), 57Fe Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Monodispersed lath-like α-FeOOH (goethite) particles precipitated by hydrothermal treatment in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. In the presence of 1 or 5 mol% of platinum ions in the precipitation system the lath-like α-FeOOH particles were formed as a single phase after a short hydrothermal treatment (2 h). No significant change in the size and shape of these particles in comparison to the reference sample was observed. After 6 h of autoclaving the formation of platinum nanoparticles at the surface of α-FeOOH particles via reduction by TMAH and/or its decomposition products became visible. These nanoparticles acted as a catalyst for the reduction of Fe(III) ions into Fe(II) and gradual transformation of α-FeOOH into a mixed Fe(II)-Fe(III) oxide (Fe 3O 4, magnetite) by the dissolution-recrystallization mechanism. The presence of a higher concentration of platinum ions accelerates the process of α-FeOOH → Fe 3O 4 transformation with the appearance of α-Fe 2O 3 (hematite) particles as an intermediate product.

  9. Selectivity of ion exchangers in extracting cesium and rubidium from alkaline solutions

    NASA Astrophysics Data System (ADS)

    Shelkovnikova, L. A.; Kargov, S. I.; Gavlina, O. T.; Ivanov, V. A.; Al'tshuler, G. N.

    2013-01-01

    We compare the ion exchange selectivity of phenol-type sorbents based on phenol formaldehyde resins, products of condensation of diatomic phenols with formaldehyde, and crosslinked polymer based on C-phenyl[4]resorcinarene resin, for cesium and rubidium ions. It is shown that phenol formaldehyde sorbents are the ones most selective. The interaction of alkali metal cations with the anion of calix[4]arene is investigated via quantum-chemical modeling. It is shown that the selectivity toward cesium and rubidium ions in ion exchangers of the phenolic type is not due to specific interactions of ions with phenolic groups.

  10. Ionizable calixarene-crown ethers with high selectivity for radium over light alkaline earth metal ions

    SciTech Connect

    Chen, X.; Ji, M.; Fisher, D.R.; Wai, C.M.

    1999-11-15

    {alpha} particle emitters are of increasing interest as the radionuclide attached to monoclonal antibodies of other targeting mechanisms for applications in cell-directed therapy of cancer. {alpha} particles are more effective than {beta}{sup {minus}} particles for cell-killing and promise a more effective treatment of cancer than other forms of radiation. This is because {alpha} particles have high initial energy (4--8 MeV), short path lengths (40--80 {micro}m, or several cell diameters), and consequently greater energy dissipation per unit length. Cell-directed immunotherapy can help improve irradiation of tumor cells while sparing normal tissues. The success of this approach will require effective chemistry for attaching the radionuclide to the antibody. Therefore, a concerted effort has been directed toward the design of chelating agents capable of holding the desired {alpha}-emitting radionuclide, both selectively and with high stability, to the antibody.

  11. Spectroscopic study of Mg(II) ion influence on the autoxidation of gallic acid in weakly alkaline aqueous solutions

    NASA Astrophysics Data System (ADS)

    Nikolić, G. M.; Veselinović, A. M.; Nikolić, R. S.; Mitić, S. S.

    2011-12-01

    Gallic acid autoxidation in weakly alkaline aqueous solutions was studied by UV-Vis spectrophotometry and ESR spectroscopy under various conditions. Lowering the pH value from 10 to 8.5 probably changes the mechanism of the autoxidation reaction as evidenced by the different time variations of UV-Vis spectra of solutions. The presence of Mg(II) ions greatly influences the autoxidation reaction at pH 8.5. Although the UV-Vis spectral changes with time follow the similar pattern during the gallic acid autoxidation at pH 10 and at pH 8.5 in the presence of Mg(II) ions, some small differences indicate that Mg(II) ions not only affect the electron density of absorbing species but also influence the overall mechanism of the autoxidation reaction. ESR spectra of free radials formed during the initial stage of gallic acid autoxidation at pH 8.5 in the presence of Mg(II) ions were recorded. Computer simulation of ESR spectra allows partial characterization of these free radicals.

  12. The influence of alkaline earth metal equilibria on the rheological, melting and textural properties of Cheddar cheese.

    PubMed

    Cooke, Darren R; McSweeney, Paul L H

    2013-11-01

    The total calcium content of cheese, along with changes in the equilibrium between soluble and casein (CN)-bound calcium during ripening can have a major impact on its rheological, functional and textural properties; however, little is known about the effect of other alkaline earth metals. NaCl was partially substituted with MgCl2 or SrCl2 (8·7 and 11·4 g/kg curd, respectively) at the salting stage of cheesemaking to study their effects on cheese. Three cheeses were produced: Mg supplemented (+Mg), Sr supplemented (+Sr) and a control Cheddar cheese. Ca, Mg and Sr contents of cheese and expressible serum obtained therefrom were determined by atomic absorption spectroscopy. Addition of Mg2+ or Sr2+ had no effect on % moisture, protein, fat and extent of proteolysis. A proportion of the added Mg2+ and Sr2+ became CN-bound. The level of CN-bound Mg was higher in the +Mg cheese than the control throughout ripening. The level of CN-bound Ca and Mg decreased during ripening in all cheeses, as did % CN-bound Sr in the +Sr cheese. The presence of Sr2+ increased % CN-bound Ca and Mg at a number of ripening times. Adding Mg2+ had no effect on % CN-bound Ca. The +Sr cheese exhibited a higher G' at 70 °C and a lower LTmax than the control and +Mg cheeses throughout ripening. The +Sr cheese had significantly lower meltability compared with the control and +Mg cheeses after 2 months of ripening. Hardness values of the +Sr cheese were higher at week 2 than the +Mg and control cheeses. Addition of Mg2+ did not influence the physical properties of cheese. Supplementing cheese with Sr appeared to have effects analogous to those previously reported for increasing Ca content. Sr2+ may form and/or modify nanocluster crosslinks causing an increase in the strength of the para-casein matrix. PMID:24124804

  13. The influence of alkaline earth metal equilibria on the rheological, melting and textural properties of Cheddar cheese.

    PubMed

    Cooke, Darren R; McSweeney, Paul L H

    2013-11-01

    The total calcium content of cheese, along with changes in the equilibrium between soluble and casein (CN)-bound calcium during ripening can have a major impact on its rheological, functional and textural properties; however, little is known about the effect of other alkaline earth metals. NaCl was partially substituted with MgCl2 or SrCl2 (8·7 and 11·4 g/kg curd, respectively) at the salting stage of cheesemaking to study their effects on cheese. Three cheeses were produced: Mg supplemented (+Mg), Sr supplemented (+Sr) and a control Cheddar cheese. Ca, Mg and Sr contents of cheese and expressible serum obtained therefrom were determined by atomic absorption spectroscopy. Addition of Mg2+ or Sr2+ had no effect on % moisture, protein, fat and extent of proteolysis. A proportion of the added Mg2+ and Sr2+ became CN-bound. The level of CN-bound Mg was higher in the +Mg cheese than the control throughout ripening. The level of CN-bound Ca and Mg decreased during ripening in all cheeses, as did % CN-bound Sr in the +Sr cheese. The presence of Sr2+ increased % CN-bound Ca and Mg at a number of ripening times. Adding Mg2+ had no effect on % CN-bound Ca. The +Sr cheese exhibited a higher G' at 70 °C and a lower LTmax than the control and +Mg cheeses throughout ripening. The +Sr cheese had significantly lower meltability compared with the control and +Mg cheeses after 2 months of ripening. Hardness values of the +Sr cheese were higher at week 2 than the +Mg and control cheeses. Addition of Mg2+ did not influence the physical properties of cheese. Supplementing cheese with Sr appeared to have effects analogous to those previously reported for increasing Ca content. Sr2+ may form and/or modify nanocluster crosslinks causing an increase in the strength of the para-casein matrix.

  14. Temperature dependent mobility measurements of alkali earth ions in superfluid helium

    NASA Astrophysics Data System (ADS)

    Putlitz, Gisbert Zu; Baumann, I.; Foerste, M.; Jungmann, K.; Riediger, O.; Tabbert, B.; Wiebe, J.; Zühlke, C.

    1998-05-01

    Mobility measurements of impurity ions in superfluid helium are reported. Alkali earth ions were produced with a laser sputtering technique and were drawn inside the liquid by an electric field. The experiments were carried out in the temperature region from 1.27 up to 1.66 K. The temperature dependence of the mobility of Be^+-ions (measured here for the first time) differs from that of the other alkali earth ions Mg^+, Ca^+, Sr^+ and Ba^+, but behaves similar to that of He^+ (M. Foerste, H. Günther, O. Riediger, J. Wiebe, G. zu Putlitz, Z. Phys. B) 104, 317 (1997). Theories of Atkins (A. Atkins, Phys. Rev.) 116, 1339 (1959) and Cole (M.W. Cole, R.A. Bachmann Phys. Rev. B) 15, 1388 (1977) predict a different defect structure for He^+ and the alkali earth ions: the helium ion is assumed to form a snowball like structure whereas for the alkali earth ions a bubble structure is assumed. If the temperature dependence is a characteristic feature for the different structures, then it seems likely that the Be^+ ion builds a snowball like structure.

  15. METHOD OF SEPARATING RARE EARTHS BY ION EXCHANGE

    DOEpatents

    Spedding, F.H.; Powell, J.E.

    1960-10-18

    A process is given for separating yttrium and rare earth values having atomic numbers of from 57 through 60 and 68 through 71 from an aqueous solution whose pH value can range from 1 to 9. All rare earths and yttrium are first adsorbed on a cation exchange resin, and they are then eluted with a solution of N-hydroxyethylethylenediaminetriacetic acid (HEDTA) in the order of decreasing atomic number, yttrium behaving like element 61; the effluents are collected in fractions. The HEDTA is recovered by elution with ammonia solution and the resin is regenerated with sulfuric acid. Rare earths are precipitated from the various effluents with oxalic acid, and each supernatant is passed over cation exchange resin for adsorption of HEDTA and nonprecipitated rare earths: the oxalic acid is not retained by the resin.

  16. Highly Charged Ions in Rare Earth Permanent Magnet Penning Traps

    NASA Astrophysics Data System (ADS)

    Guise, Nicholas D.; Brewer, Samuel M.; Tan, Joseph N.

    A newly constructed apparatus at the United States National Institute of Standards and Technology (NIST) is designed for the isolation, manipulation, and study of highly charged ions. Highly charged ions are produced in the NIST electron-beam ion trap (EBIT), extracted through a beamline that selects a single mass/charge species, then captured in a compact Penning trap. The magnetic field of the trap is generated by cylindrical NdFeB permanent magnets integrated into its electrodes. In a room-temperature prototype trap with a single NdFeB magnet, species including Ne10+ and N7+ were confined with storage times of order 1 second, showing the potential of this setup for manipulation and spectroscopy of highly charged ions in a controlled environment. Ion capture has since been demonstrated with similar storage times in a more-elaborate Penning trap that integrates two coaxial NdFeB magnets for improved B-field homogeneity. Ongoing experiments utilize a second-generation apparatus that incorporates this two-magnet Penning trap along with a fast time-of-flight MCP detector capable of resolving the charge-state evolution of trapped ions. Holes in the two-magnet Penning trap ring electrode allow for optical and atomic beam access. Possible applications include spectroscopic studies of one-electron ions in Rydberg states, as well as highly charged ions of interest in atomic physics, metrology, astrophysics, and plasma diagnostics.

  17. Nondestructive photon detection using a single rare-earth ion coupled to a photonic cavity

    NASA Astrophysics Data System (ADS)

    O'Brien, Chris; Zhong, Tian; Faraon, Andrei; Simon, Christoph

    2016-10-01

    We study the possibility of using single rare-earth ions coupled to a photonic cavity with high cooperativity for performing nondestructive measurements of photons, which would be useful for global quantum networks and photonic quantum computing. We calculate the achievable fidelity as a function of the parameters of the rare-earth ion and photonic cavity, which include the ion's optical and spin dephasing rates, the cavity linewidth, the single-photon coupling to the cavity, and the detection efficiency. We suggest a promising experimental realization using current state-of-the-art technology in Nd:YVO4.

  18. High-pressure densified solid solutions of alkaline earth hexaborides (Ca/Sr, Ca/Ba, Sr/Ba) and their high-temperature thermoelectric properties

    SciTech Connect

    Gürsoy, M.; Takeda, M.; Albert, B.

    2015-01-15

    Solid solutions of alkaline earth hexaborides were synthesized and densified by spark plasma sintering at 100 MPa. The high-temperature thermoelectric properties (Seebeck coefficients, electrical and thermal diffusivities, heat capacities) were measured between room temperature and 1073 K. CaB{sub 6}, SrB{sub 6}, BaB{sub 6} and the ternary hexaborides Ca{sub x}Sr{sub 1−x}B{sub 6}, Ca{sub x}Ba{sub 1−x}B{sub 6}, Sr{sub x}Ba{sub 1−x}B{sub 6} (x = 0.25, 0.5, 0.75) are n-type conducting compounds over the whole compositional and thermal ranges. The values of the figure of merit ZT for CaB{sub 6} (ca. 0.3 at 1073 K) were found to be significantly increased compared to earlier investigations which is attributed to the densification process. - Highlights: • Solid solutions of alkaline earth hexaborides were synthesized. • High-temperature thermoelectric properties of mixed calcium borides are excellent. • Spark plasma source densification results in high ZT values. • Borides are rare-earth free and refractory materials.

  19. A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1994-01-01

    Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

  20. Eu(2+)-Activated Alkaline-Earth Halophosphates, M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect.

    PubMed

    Kim, Donghyeon; Kim, Sung-Chul; Bae, Jong-Seong; Kim, Sungyun; Kim, Seung-Joo; Park, Jung-Chul

    2016-09-01

    Eu(2+)-activated M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M5(PO4)3Cl:Eu(2+) (M = Ca, Sr, Ba) compounds were blue-shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr5(PO4)3X:Eu(2+) (X = F, Cl, Br) compounds were red-shifted along the series of halides, F → Cl → Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu(2+)) in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d → 4f transition energies of Eu(2+) using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu(2+) ions preferably enter the fully oxygen-coordinated sites in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field. PMID:27494550

  1. Developments in MEMS scale printable alkaline and Li-ion technology

    NASA Astrophysics Data System (ADS)

    Littau, K. A.; Cobb, C. L.; Spengler, N.; Solberg, S.; Weisberg, M.; Chang, N.; Rodkin, A.

    2011-06-01

    Two technologies for MEMS (Microelectromechanical Systems) scale cell formation are discussed. First, the fabrication of planar alkaline cell batteries compatible with MEMS scale power storage applications is shown. Both mm scale and sub-mm scale individual cells and batteries have been constructed. The chosen coplanar electrode geometry allows for easy fabrication of series connected cells enabling higher voltage while simplifying the cell sealing and electrode formation. The Zn/Ag alkaline system is used due to the large operating voltage, inherent charge capacity, long shelf life, and ease of fabrication. Several cells have been constructed using both plated and spun-on silver. The plated cells are shown to be limited in performance due to inadequate surface area and porosity; however, the cells made from spun-on colloidal silver show reasonable charge capacity and power performance with current densities of up to 200 uA/mm2 and charge capacities of up to 18 mA-s/mm2. Second, a new printing method for interdigitated 3-D cells is introduced. A microfluidic printhead capable of dispensing multiple materials at high resolution and aspect ratio is described and used to form fine interdigitated cell features which show >10 times improvement in energy density. Representative structures enabled by this method are modeled, and the energy and power density improvements are reported.

  2. Removal of toxic and alkali/alkaline earth metals during co-thermal treatment of two types of MSWI fly ashes in China.

    PubMed

    Yu, Jie; Qiao, Yu; Jin, Limei; Ma, Chuan; Paterson, Nigel; Sun, Lushi

    2015-12-01

    This study aims to vaporize heavy metals and alkali/alkaline earth metals from two different types of fly ashes by thermal treatment method. Fly ash from a fluidized bed incinerator (HK fly ash) was mixed with one from a grate incinerator (HS fly ash) in various proportions and thermally treated under different temperatures. The melting of HS fly ash was avoided when treated with HK fly ash. Alkali/alkaline earth metals in HS fly ash served as Cl-donors to promote the vaporization of heavy metals during thermal treatment. With temperature increasing from 800 to 900°C, significant amounts of Cl, Na and K were vaporized. Up to 1000°C in air, less than 3% of Cl and Na and less than 5% of K were retained in ash. Under all conditions, Cd can be vaporized effectively. The vaporization of Pb was mildly improved when treated with HS fly ash, while the effect became less pronounced above 900°C. Alkali/alkaline earth metals can promote Cu vaporization by forming copper chlorides. Comparatively, Zn vaporization was low and only slightly improved by HS fly ash. The low vaporization of Zn could be caused by the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4. Under all conditions, less than 20% of Cr was vaporized. In a reductive atmosphere, the vaporization of Cd and Pb were as high as that in oxidative atmosphere. However, the vaporization of Zn was accelerated and that of Cu was hindered because the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4 and copper chloride was depressed in reductive atmosphere. PMID:26303652

  3. Solubility of ion and trace metals from stabilized sewage sludge by fly ash and alkaline mine tailing.

    PubMed

    Zhang, Hongling; Sun, Lina; Sun, Tieheng

    2008-01-01

    Stabilized sewage sludge (SS) by fly ash (FA) and alkaline mine tailing as artificial soil, to be applied on the ecological rehabilitation at mining junkyards, offers a potentially viable utilization of the industrial by-product, as well as solves the shortage of soil resource in the mine area. An incubation experiment with different ratios of SS and FA was conducted to evaluate the solubility of ions and trace elements from stabilized sewage sludge. Results showed that fly ash offset a decrease in pH value of sewage sludge. The pH of (C) treatment (FA:SS = 1:1) was stable and tended to neutrality. The SO4(2-) and Cl- concentrations of the solution in the mixture were significantly decreased in the stabilized sewage sludge by alkaline fly ash and mine tailing, compared to the single SS treatment. Stabilized sewage sludge by FA weakened the nitrification of total nitrogen from SS when the proportion of FA in the mixture was more than 50%. The Cr, Ni, and Cu concentrations in the solution were gradually decreased and achieved a stable level after 22 days, for all treatments over the duration of the incubation. Moreover stabilized sewage sludge by fly ash and/or mine tailing notably decreased the trace metal solubility. The final Cr, Cu, and Ni concentrations in the solution for all mixtures of treatments were lower than 2.5, 15, and 50 microg/L, respectively. PMID:18763566

  4. Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach

    USGS Publications Warehouse

    Bullen, T.D.; Bailey, S.W.

    2005-01-01

    Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87Sr/86Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87Sr/86Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87Sr/86Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible

  5. Electronic structure, optical properties and bonding in alkaline earth halo-fluoride scintillators: BaClF, BaBrF and BaIF

    SciTech Connect

    Yedukondalu, N.; Babu, K. Ramesh; Bheemalingam, Ch.; Singh, David J; Vaitheeswaran, G.; Kanchana, V.

    2011-01-01

    We report first-principles studies of the structural, electronic, and optical properties of the alkaline-earth halofluorides, BaXF (X = Cl, Br, and I), including pressure dependence of structural properties. The band structures show clear separation of the halogen p derived valence bands into higher binding energy F and lower binding energy X derived manifolds reflecting the very high electronegativity of F relative to the other halogens. Implications of this for bonding and other properties are discussed. We find an anisotropic behavior of the structural parameters especially of BaIF under pressure. The optical properties on the other hand are almost isotropic, in spite of the anisotropic crystal structures.

  6. Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N-(2-Pyridylethyl)-N'-(2,6-diisopropylphenyl)pivalamidine.

    PubMed

    Kalden, Diana; Oberheide, Ansgar; Loh, Claas; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias

    2016-07-25

    N-(2,6-Diisopropylphenyl)-N'-(2-pyridylethyl)pivalamidine (Dipp-N=C(tBu)-N(H)-C2 H4 -Py) (1), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp-N=C(tBu)-N-C2 H4 -Py}] (6), [Mg{Dipp-N=C(tBu)-N-C2 H4 -Py}2 ] (3), and heteroleptic [{(Me3 Si)2 N}Ae{Dipp-N=C(tBu)-N-C2 H4 -Py}], with Ae being Ca (2 a) and Sr (2 b). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β-metalation and an immediate deamidation reaction yielding [(thf)2 Na{Dipp-N=C(tBu)-N(H)}] (4 a) or [(thf)2 K{Dipp-N=C(tBu)-N(H)}] (4 b), respectively, as well as 2-vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI2 in tetrahydrofuran yields N-(2,6-diisopropylphenyl)pivalamidine (Dipp-N=C(tBu)-NH2 ) (5), or [(thf)4 Ca{Dipp-N=C(tBu)-N(H)}2 ] (7), respectively. The reaction of AN(SiMe3 )2 (A=Na, K) with less bulky formamidine Dipp-N=C(H)-N(H)-C2 H4 -Py (8) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp-N=C(H)-N-C2 H4 -Py}]2 (9 a) or [(thf)K{Dipp-N=C(H)-N-C2 H4 -Py}]2 (9 b), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β-metalation/deamidation of N-(2-pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single-crystal X-ray structure analysis and are maintained in solution. PMID:27355970

  7. Comparison of oxygen ion outflow on Earth and Mars during space weather events

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Fraenz, M.; Dubinin, E.; Barabash, S.; Dandouras, I. S.; Lundin, R. N.

    2012-12-01

    Solar wind controls non-thermal escape of planetary atmospheric volatiles, regardless of the strength of planetary magnetic fields. For both Earth with a strong dipole and Mars with weak remnant fields, the oxygen ion (O+) outflow has been separately found to be enhanced during corotating interaction region (CIR) passage. To discern the role of terrestrial dipole in protecting planetary volatiles, here for the first time, we compared the enhancements of O+ outflow on Earth and Mars to a CIR which passed by in January, 2008 when Sun, Earth and Mars were approximately aligned. The CIR propagation was recorded by STEREO, ACE, Cluster and Mars Express (MEX). During the CIR passage, Cluster observed enhanced flux of upwelling oxygen ions above the Earth's polar region, while MEX detected increased escape flux of oxygen ions in the Martian magnetosphere. We found that, under a solar wind dynamic pressure increase by 2-3 nPa, the rate of increase in Martian O+ outflow flux was one order higher than those on Earth, thus the dipole effectively prevents coupling of solar wind kinetic energy to planetary ions. Surprisingly, as response to the same part of the CIR body, the rate of increase in Martian O+ outflow flux was on the same order as for Earth. We suggest that, besides existence of a dipole field, the distance to the Sun is also crucially important for planetary volatile loss in our inner solar system.

  8. Magnetic exchange interaction between rare-earth and Mn ions in multiferroic hexagonal manganites

    SciTech Connect

    Talbayev, Diyar; Trugman, Stuart A; Taylor, Antoinette J; Averitt, Richard D; Namjung, Hur; Andrew, Laforge D; Dimitri, Basov N

    2008-01-01

    The authors report a study of magnetic dynamics in multiferroic hexagonal manganite HoMnO{sub 3} by far-infrared spectroscopy. Low-temperature magnetic excitation spectrum of HoMnO{sub 3} consists of magnetic-dipole transitions of Ho ions within the crystal-field split J = 8 manifold and of the triangular antiferromagnetic resonance of Mn ions. They determine the effective spin Hamiltonian for the Ho ion ground state. The magnetic-field splitting of the Mn antiferromagnetic resonance allows us to measure the magnetic exchange coupling between the rare-earth and Mn ions.

  9. Solar forcing, and ionospheric ion outflow from Venus, Earth and Mars - A comparison

    NASA Astrophysics Data System (ADS)

    Lundin, R. N.

    2012-12-01

    Solar forcing by e.g. EUV radiation and the solar wind leads to outflow and escape of ionospheric ions from Earth, Venus and Mars. In-situ measurements in the Earth's space environment have demonstrated that the ion escape rate correlates with the magnitude of solar forcing, i.e. high solar EUV and solar wind forcing leads to enhanced escape rates. The Terrestrial outflow is dominated by H+ and O+ suggesting that the ultimate origin of outflowing ions is water. Recent measurements from the two arid planets Mars and Venus, their atmospheres dominated by CO2, display characteristics similar to that of the Earth - an outflow dominated by hydrogen (H+) and oxygen (O+, O2+) ions. Despite major differences in atmospheric composition, the composition of the ion outflow from Earth and Venus is very similar, i.e. H+ and O+ dominates and the outflow has a stoichiometric H/O ratio of close to 2. The latter implies escape of water. The ion outflow from Mars is dominated by O+, O2+, and H+. Here the stoichiometric ratio between hydrogen and oxygen ion is ≈1, implying that if the ion outflow originates from water, about half of the hydrogen mass disappears by other means. The primary origin of the ion outflow from Earth, Venus and Mars is a complex issue. Nevertheless, a predominant hydrogen and oxygen loss implies that water can easily escape planets orbiting close to the Sun, while Carbon-based molecules (e.g. CO2) resides more easily. Observations shows that the outflow of e.g. CO+ and CO2+ from Mars and Venus is minute compared to the outflow of hydrogen and oxygen ions. Magnetic shielding is an issue affecting the net ion outflow and escape from a planet, because acceleration processes are also the characteristics of magnetized plasmas. Recent findings suggests that, despite magnetic field pile-up at Mars and Venus, the stand-off distance is insufficient to prohibit a direct interaction between the solar wind and the magnetized ionospheric plasma in the induced

  10. Electrochemical Behavior of Nano-grained Pure Copper in Dilute Alkaline Solution with Chloride Ion Trace

    NASA Astrophysics Data System (ADS)

    Fattah-Alhosseini, Arash; Imantalab, Omid; Attarzadeh, Farid Reza

    2016-10-01

    Effect of nano-grained structure on the interface behavior of pure copper in 0.01M KOH solution with chloride ion trace is investigated by various electrochemical techniques. Nano-grained structure was achieved by accumulative roll bonding (ARB) technique. Before any electrochemical measurements, microstructure was evaluated by means of optical microscopy and transmission electron microscopy (TEM). TEM observations showed that nano-grains (with an average size of below 100 nm) appeared after eight passes of ARB. Polarization curves revealed that increasing chloride ion concentration leads to a decrease in the corrosion and pitting potentials of both annealed and nano-grained pure copper samples. Electrochemical impedance spectroscopy revealed that chloride ion trace lowers passive film resistance and charge-transfer resistance in both annealed and nano-grained samples. Mott-Schottky analysis showed that the surface films formed on annealed and nano-grained samples in KOH solution with and without NaCl addition are of p-type semiconducting behavior. Moreover, this analysis showed that the acceptor density increases by increasing chloride ion concentration.

  11. Electrochemical Behavior of Nano-grained Pure Copper in Dilute Alkaline Solution with Chloride Ion Trace

    NASA Astrophysics Data System (ADS)

    Fattah-Alhosseini, Arash; Imantalab, Omid; Attarzadeh, Farid Reza

    2016-08-01

    Effect of nano-grained structure on the interface behavior of pure copper in 0.01M KOH solution with chloride ion trace is investigated by various electrochemical techniques. Nano-grained structure was achieved by accumulative roll bonding (ARB) technique. Before any electrochemical measurements, microstructure was evaluated by means of optical microscopy and transmission electron microscopy (TEM). TEM observations showed that nano-grains (with an average size of below 100 nm) appeared after eight passes of ARB. Polarization curves revealed that increasing chloride ion concentration leads to a decrease in the corrosion and pitting potentials of both annealed and nano-grained pure copper samples. Electrochemical impedance spectroscopy revealed that chloride ion trace lowers passive film resistance and charge-transfer resistance in both annealed and nano-grained samples. Mott-Schottky analysis showed that the surface films formed on annealed and nano-grained samples in KOH solution with and without NaCl addition are of p-type semiconducting behavior. Moreover, this analysis showed that the acceptor density increases by increasing chloride ion concentration.

  12. Enhanced Electroresponse of Alkaline Earth Metal-Doped Silica/Titania Spheres by Synergetic Effect of Dispersion Stability and Dielectric Property.

    PubMed

    Yoon, Chang-Min; Lee, Seungae; Cheong, Oug Jae; Jang, Jyongsik

    2015-09-01

    A series of alkaline earth metal-doped hollow SiO2/TiO2 spheres (EM-HST) are prepared as electrorheological (ER) materials via sonication-mediated etching method with various alkaline earth metal hydroxides as the etchant. The EM-HST spheres are assessed to determine how their hollow interior and metal-doping affects the ER activity. Both the dispersion stability and the dielectric properties of these materials are greatly enhanced by the proposed one-step etching method, which results in significant enhancement of ER activity. These improvements are attributed to increased particle mobility and interfacial polarization originating from the hollow nature of the EM-HST spheres and the effects of EM metal-doping. In particular, Ca-HST-based ER fluid exhibits ER performance which is 7.1-fold and 3.1-fold higher than those of nonhollow core/shell silica/titania (CS/ST) and undoped hollow silica/titania (HST)-based ER fluids, respectively. This study develops a versatile and simple approach to enhancing ER activity through synergetic effects arising from the combination of dispersion stability and the unique dielectric properties of hollow EM-HST spheres. In addition, the multigram scale production described in this experiment can be an excellent advantage for practical and commercial ER application.

  13. Origin of low sodium capacity in graphite and generally weak substrate binding of Na and Mg among alkali and alkaline earth metals

    PubMed Central

    Liu, Yuanyue; Merinov, Boris V.; Goddard, William A.

    2016-01-01

    It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion–substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems. PMID:27001855

  14. Rare earth ion doped non linear laser crystals

    NASA Astrophysics Data System (ADS)

    Jaque, D.; Romero, J. J.; Ramirez, M. O.; Garcia, J. A. S.; de Las Heras, C.; Bausa, L. E.; Sole, J. G.

    2003-01-01

    We show how non linear crystals activated with Yb3+ or Nd3+ ions can be used to develop diode pumped solid state lasers emitting in the visible region of the electromagnetic spectrum. For this purpose we have selected relevant examples of systems investigated in our laboratory.

  15. Novel luminescent hybrids by incorporating rare earth β-diketonates into polymers through ion pairing with an imidazolium counter ion.

    PubMed

    Li, Qiu-Ping; Yan, Bing

    2013-09-01

    A series of luminescent polymers are synthesized by incorporating rare earth complex units into polymer matrices. Firstly, we functionalize the selected polymer matrices with the imidazolium moieties, and then introduce the rare earth tetrakis(β-diketonate) complexes into polymer matrices through a mild anion exchange method. The resulting materials are characterized by FTIR, XRD, EDAX, SEM, thermogravimetric analysis, luminescence excitation spectra and emission spectra, luminescence lifetime measurements and diffuse reflectance UV-Vis spectra. The photoluminescence measurements indicate that all these rare earth complex functionalized polymers exhibit a characteristic luminescence emission originating from the corresponding rare earth ions. Among the hybrids, the europium tetrakis(TTA) complex functionalized polymers show remarkable luminescence quantum yields and relatively long (5)D0 lifetimes at room temperature.

  16. Transport toward earth of ions sputtered from the moon's surface by the solar wind

    NASA Astrophysics Data System (ADS)

    Cladis, J. B.; Francis, W. E.; Vondrak, R. R.

    1994-01-01

    The transport of typical ions from the surface of the Moon to the vicinity of Earth was calculated using a test particle approach. It was assumed that the ions were sputtered from the surface by the solar wind, with fluxes in the range determined experimentally by Elphic et al. (1991), and were accelerated initially to 10 eV by the potential of the Moon on its sunlit side. Si(+) and Ca(+) ions were selected for this transport analysis because their masses are within two prominent ion mass groups that have high sputtering yields. In the solar wind the ion trajectories were traced in the following superimposed fields: (1) a steady magnetic field B0 at an angle of 45 deg to the solar wind velocity VSW, (2) the motional electric field Ezero = -V(sub SW x B0, and (3) turbulent magnetic and electric fields generated by hydromagnetic waves with a k-space power spectrum of absolute value of k-5/3 propagating along both directions of the magnetic field B0. Interactions with Earth's bow shock and magnetosphere were included. Case histories of the ions were recorded in the XGSM, YGSM plane and in various planes perpendicular to the E0 x B0 drift direction of the ions between the Moon and Earth. The number density, energy and angular distributions, and directional and omnidirectional fluxes of the ions were constructed from the case histories. It was found that the diffusion of the ions increases rapidly as the amplitude of the turbulence delta Brms increases beyond the value 0.04 B0. Recent measurements of lunar ions upstream of the bow shock by Hilchenbach et al. (1992) generally confirm the predicted behavior of the ions.

  17. Effect of metal cation replacement on the electronic structure of metalorganic halide perovskites: Replacement of lead with alkaline-earth metals

    NASA Astrophysics Data System (ADS)

    Pazoki, Meysam; Jacobsson, T. Jesper; Hagfeldt, Anders; Boschloo, Gerrit; Edvinsson, Tomas

    2016-04-01

    Organic and inorganic lead halogen perovskites, and in particular, C H3N H3Pb I3 , have during the last years emerged as a class of highly efficient solar cell materials. Herein we introduce metalorganic halogen perovskite materials for energy-relevant applications based on alkaline-earth metals. Based on the classical notion of Goldschmidt's rules and quantum mechanical considerations, the three alkaline-earth metals, Ca, Sr, and Ba, are shown to be able to exchange lead in the perovskite structure. The three alkaline-earth perovskites, C H3N H3Ca I3,C H3N H3Sr I3 , and C H3N H3Ba I3 , as well as the reference compound, C H3N H3Pb I3 , are in this paper investigated with density functional theory (DFT) calculations, which predict these compounds to exist as stable perovskite materials, and their electronic properties are explored. A detailed analysis of the projected molecular orbital density of states and electronic band structure from DFT calculations were used for interpretation of the band-gap variations in these materials and for estimation of the effective masses of the electrons and holes. Neglecting spin-orbit effects, the band gap of MACa I3,MASr I3 , and MABa I3 were estimated to be 2.95, 3.6, and 3.3 eV, respectively, showing the relative change expected for metal cation exchange. The shifts in the conduction band (CB) edges for the alkaline-earth perovskites were quantified using scalar relativistic DFT calculations and tight-binding analysis, and were compared to the situation in the more extensively studied lead halide perovskite, C H3N H3Pb I3 , where the change in the work function of the metal is the single most important factor in tuning the CB edge and band gap. The results show that alkaline-earth-based organometallic perovskites will not work as an efficient light absorber in photovoltaic applications but instead could be applicable as charge-selective contact materials. The rather high CB edge and the wide band gap together with the large

  18. Oxides doped with rare-earth ions as a recording medium with multiple rewriting

    NASA Astrophysics Data System (ADS)

    Zimenko, Vladislav I.; Petrov, Viacheslav V.; Kravets, Vasyliy G.; Motuz, Vasily V.; Prygun, Alexander V.; Yanchuk, N. E.

    1997-02-01

    The optical memory on materials having the properties of electron trapping is a new direction at development of information storage and rewrite. Currently are pursued investigations directed on creation of a new type recording medium with the opportunity of information rewrite by optical methods as well as a medium for heteroassociative memory in optical neural systems. Primarily as such medium are used alkaline-earth metal sulphides activated by two rare-earth elements. When creating the memory on materials with electron trapping on the basis of alkaline-earth sulphides there arises a number of difficulties: (1) these materials are chemically unstable, especially they are subject to the action of water vapors; (2) films prepared by electron-beam evaporation technique have a polycrystalline structure with grain sizes in the order of 20 nm what has an essential influence on the signal-to-noise ratio at information reading. The main objective which is pursued by us consists in investigating the optical properties of new synthesized materials having the electron trapping properties which are characterized by chemical stability and are easy manufacture at preparation of amorphous structures. We have also recommended to use CaO (MgO) doped with Eu, Sm. It has known, that the optical stimulated luminescence (OSL) obtains in CaO. But OSL appears in the special prepared structures with defects. For this aim there are some methods: thermochemical reduction or radiation processing by electron beam. Besides that the OSL obtains only by nitrogen temperature (77 K).

  19. Relationship between Salivary Alkaline Phosphatase Enzyme Activity and The Concentrations of Salivary Calcium and Phosphate Ions

    PubMed Central

    Jazaeri, Mina; Malekzadeh, Hosein; Abdolsamadi, Hamidreza; Rezaei-Soufi, Loghman; Samami, Mohammad

    2015-01-01

    Although salivary alkaline phosphatase (ALP) can balance deand remineralization processes of enamel, there is no evidence regarding its effects on the concentrations of calcium and phosphate in saliva. The present study aims to determine the relationship between salivary ALP activity and the concentrations of calcium and phosphate in saliva. In this cross-sectional study, we evaluated salivary markers in 120 males, ages 19 to 44 years. All participants provided 5 mL of unstimulated whole saliva and the level of enzyme activity as well as calcium and phosphate concentrations were measured using a colorimetric method. Data were gathered and analyzed by statistical package for social sciences (SPSS) 13.00 using Pearson correlation test. A p value of <0.05 was considered statistically significant. The mean age of participants in the present study was 32.95 ± 8.09 years. The mean pH of saliva was 6.65 ± 0.62. Salivary parameters included average ALP activity (5.04 ± 1.866 U/dL), calcium (4.77 ± 0.877 mg/dL) and phosphate (10.38 ± 2.301 mg/dL). Pearson correlation test showed no significant relationship between ALP activity and calcium and phosphate concentrations in saliva (p>0.05). According to the results of the present study, there was no significant relation between salivary ALP activity and calcium and phosphate concentrations in saliva. However, further research is highly recommended. PMID:25870846

  20. Trivalent rare-earth ions as photon down-shifter for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Steudel, Franziska; Loos, Sebastian; Ahrens, Bernd; Schweizer, Stefan

    2014-05-01

    Rare-earth doped borate glasses are investigated for their potential as photon down-shifting cover glass for CdTe solar cells. Note, that CdTe solar cells have a poor response in the ultraviolet and blue spectral range due to absorption in the CdS buffer layer having a band gap of 2.4 eV. The following trivalent rare-earth ions are analyzed in detail: Sm3+, Eu3+, and Tb3+. These ions provide strong absorption bands in the ultraviolet / blue spectral range and an intense emission in the red (Sm3+ and Eu3+) or green (Tb3+) spectral range. The gain in short-circuit current density of a CdTe solar cell is calculated for different rare-earth ion concentrations. The calculations are based on the rare-earth's absorption coefficients as well as their photoluminescence (PL) quantum efficiency. For Sm3+, the PL quantum efficiency depends significantly on the doping concentration. Finally, the potential of double-doped borate glasses, i.e. glasses doped with two different rare-earth ions, is investigated.

  1. Ion distributions in the Earth's foreshock upstream from the bow shock

    NASA Technical Reports Server (NTRS)

    Fuselier, S. A.

    1995-01-01

    A variety of suprathermal and energetic ion distributions are found upstream from shocks. Some distributions, such as field-aligned beams, are generated directly at the shock either through reflection processes or through leakage from the hotter downstream region. Other distributions, such as intermediate distributions, evolve from these parent distributions through wave-particle interactions. This paper reviews our current understanding of the creation and evolution of suprathermal distributions at shocks. Examples of suprathermal ion distributions are taken from observations at the Earth's bow shock. Particular emphasis is placed on the creation of field-aligned beams and specularly reflected ion distributions and on the evolution of these distributions in the Earth's ion foreshock. However, the results from this heavily studied region are applicable to interplanetary shocks, bow shocks at other planets, and comets.

  2. Enzymatically mediated bioprecipitation of heavy metals from industrial wastes and single ion solutions by mammalian alkaline phosphatase.

    PubMed

    Chaudhuri, Gouri; Shah, Gaurav A; Dey, Pritam; S, Ganesh; Venu-Babu, P; Thilagaraj, W Richard

    2013-01-01

    The study was aimed at investigating the potential use of calf intestinal alkaline phosphatase (CIAP) enzyme in the removal of heavy metals (Cd(2+), Ni(2+), Co(2+) and Cr(3+/6+)) from single ion solutions as well as tannery and electroplating effluents. CIAP mediated bioremediation (white biotechnology) is a novel technique that is eco-friendly and cost effective unlike the conventional chemical technologies. Typical reactions containing the enzyme (CIAP) and p-nitrophenyl phosphate (pNPP) as substrate in Tris-HCl buffer (pH 8 and 11) and either single ion metal solutions (250 ppm and 1000 ppm) or effluents from tannery or electroplating industry were incubated at 37°C for 30 min, 60 min and 120 min. The inorganic phosphate (P(i)) generated due to catalytic breakdown of pNPP complexes free metal ions as metal-phosphate and the amount of metal precipitated was derived by estimating the reduction in the free metal ion present in the supernatant of reactions employing atomic absorption spectrophotometer (AAS). Better precipitation of metal was obtained at pH 11 than at pH 8 and between the two concentrations of different metals tested, an initial metal concentration of 250 ppm in the reaction gave more precipitation than with 1000 ppm. Experimental data showed that at pH 11, the percentage of removal of metal ions (for an initial concentration of 250 ppm) was in the following order: Cd(2+) (80.99%) > Ni(2+) (64.78%) > Cr(3+) > (46.15%) > Co(2+) (36.47%) > Cr(6+) (32.33%). The overall removal of Cr(3+) and Cr(6+) from tannery effluent was 32.77% and 37.39% respectively in 120 min at pH 11. Likewise, the overall removal of Cd(2+), Co(2+) and Ni(2+) from electroplating effluent was 50.42%, 13.93% and 38.64% respectively in 120 min at pH 11. The study demonstrates that bioprecipitation by CIAP may be a viable and environmental friendly method for clean-up of heavy metals from tannery and electroplating effluents. PMID:23030390

  3. Enzymatically mediated bioprecipitation of heavy metals from industrial wastes and single ion solutions by mammalian alkaline phosphatase.

    PubMed

    Chaudhuri, Gouri; Shah, Gaurav A; Dey, Pritam; S, Ganesh; Venu-Babu, P; Thilagaraj, W Richard

    2013-01-01

    The study was aimed at investigating the potential use of calf intestinal alkaline phosphatase (CIAP) enzyme in the removal of heavy metals (Cd(2+), Ni(2+), Co(2+) and Cr(3+/6+)) from single ion solutions as well as tannery and electroplating effluents. CIAP mediated bioremediation (white biotechnology) is a novel technique that is eco-friendly and cost effective unlike the conventional chemical technologies. Typical reactions containing the enzyme (CIAP) and p-nitrophenyl phosphate (pNPP) as substrate in Tris-HCl buffer (pH 8 and 11) and either single ion metal solutions (250 ppm and 1000 ppm) or effluents from tannery or electroplating industry were incubated at 37°C for 30 min, 60 min and 120 min. The inorganic phosphate (P(i)) generated due to catalytic breakdown of pNPP complexes free metal ions as metal-phosphate and the amount of metal precipitated was derived by estimating the reduction in the free metal ion present in the supernatant of reactions employing atomic absorption spectrophotometer (AAS). Better precipitation of metal was obtained at pH 11 than at pH 8 and between the two concentrations of different metals tested, an initial metal concentration of 250 ppm in the reaction gave more precipitation than with 1000 ppm. Experimental data showed that at pH 11, the percentage of removal of metal ions (for an initial concentration of 250 ppm) was in the following order: Cd(2+) (80.99%) > Ni(2+) (64.78%) > Cr(3+) > (46.15%) > Co(2+) (36.47%) > Cr(6+) (32.33%). The overall removal of Cr(3+) and Cr(6+) from tannery effluent was 32.77% and 37.39% respectively in 120 min at pH 11. Likewise, the overall removal of Cd(2+), Co(2+) and Ni(2+) from electroplating effluent was 50.42%, 13.93% and 38.64% respectively in 120 min at pH 11. The study demonstrates that bioprecipitation by CIAP may be a viable and environmental friendly method for clean-up of heavy metals from tannery and electroplating effluents.

  4. Long-lived artificial ion clouds in the earth's ionosphere

    SciTech Connect

    Milinevsky, G.P. ); Kashirin, A.I. ); Romanovsky, Yu.A. ); Stenbaek-Nielson, H.C. ); Kelley, M.C. )

    1993-06-07

    The authors report on two observations made over the Caribbean during the summer of 1991 of barium ion cloud releases, ten hours after the clouds were released. One release was made in the morning twilight, and one in the evening twilight, and each was observed again in the following twilight period by a low light level TV imager and a TV spectrograph onboard a Russian research vessel. These observations were very surprising at the time, but the authors present arguments as to why in retrospect they may not be so unusual in practise. Such cloud releases may provide very sensitive tests of ionspheric convection models.

  5. Ion transport and loss in the Earth`s quiet ring current: 2. Diffusion and magnetosphere-ionosphere coupling

    SciTech Connect

    Sheldon, R.B.

    1994-04-01

    The author has studied the transport and loss of H{sup +}, He{sup +}, and He{sup ++} ions in the Earth`s quite time ring current (1-300 keV/e, 3-7 R{sub E}, Kp<2+, {vert_bar}Dst{vert_bar}<11, 70{degrees}-110{degrees} pitchangles, all LT) comparing the standard radial diffusion model developed for the higher-energy radiation belt particles with measurements of the lower energy ring current ions in a previous paper. Large deviations of that model, which fit only 50% of the data to within a factor of 10, suggested that another transport mechanism is operating in the ring current. Here the author derives a modified diffusion coefficient corrected for electric field effects on ring current energy ions that fit nearly 80% of the data to within a factor of 2. Thus he infers that electric field fluctuations from the low-latitude to midlatitude ionosphere (ionosphere dynamo) dominate the ring current transport, rather than high-latitude or solar wind fluctuations. Much of the remaining deviation may arise from convective electric field transport of the E<30 keV particles. Since convection effects cannot be correctly treated with this azimuthally symmetric model, the author defers treatment of the lowest-energy ions to another paper. The author gives {Chi}{sup 2} contours for the best fit, showing the dependence of the fit upon the internal/external spectral power of the predicted electric and magnetic field fluctuations. 64 refs., 7 figs., 1 tab.

  6. Selective ion exchange recovery of rare earth elements from uranium mining solutions

    NASA Astrophysics Data System (ADS)

    Rychkov, Vladimir N.; Kirillov, Evgeny V.; Kirillov, Sergey V.; Bunkov, Grigory M.; Mashkovtsev, Maxim A.; Botalov, Maxim S.; Semenishchev, Vladimir S.; Volkovich, Vladimir A.

    2016-09-01

    A comparative study of rare earth, ferric and aluminum ions ion exchange behavior on gel sulfonated p;olystyrene cation exchange resins depending on the degree of the matrix cross-linking and pH of the solution is presented. Selective ion exchange of REEs is possible at the pH range of 1.5-2.0 using strongly acidic cation exchange resins containing more than 8 % of DVB. The preliminary results of testing the efficiency of REEs recovery from the industrial uranium underground leaching solutions are also presented.

  7. Performance and Comparison of Lithium-Ion Batteries Under Low-Earth-Orbit Mission Profiles

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Smart, Marshall C.; Bugga, Ratnakumar V.; Manzo, Michelle A.; Miller, Thomas B.; Gitzendanner, Rob

    2007-01-01

    The performance of two 28 V, 25 Ah lithium-ion batteries is being evaluated under low-Earth-orbit mission profiles for satellite and orbiter applications. The batteries are undergoing life testing and have achieved over 12,000 cycles to 40 percent depth-of-discharge.

  8. Investigations of hyperfine and isotope structures in optical spectra of crystals with rare-earth ions

    NASA Astrophysics Data System (ADS)

    Popova, M. N.

    2015-10-01

    This is a review of works on hyperfine and isotope structures in the spectra of rare-earth ions in crystals that have been performed at the Laboratory of Fourier Spectroscopy of the Institute for Spectroscopy, Russian Academy of Sciences. The applicability of these studies to the development of optical quantum memory is discussed.

  9. Prevention of cathode damage from positive ion bombardment

    NASA Technical Reports Server (NTRS)

    Bennett, W. H.

    1972-01-01

    Mixed alkaline earth oxide compounds deposited into hole at cathode surface center prevent ion back bombardment damage to cathode by reducing oxide layer and by creating metallic diffusion along sides of hole for enhanced electron emission.

  10. Observation of Photon Echoes From Evanescently Coupled Rare-Earth Ions in a Planar Waveguide.

    PubMed

    Marzban, Sara; Bartholomew, John G; Madden, Stephen; Vu, Khu; Sellars, Matthew J

    2015-07-01

    We report the measurement of the inhomogeneous linewidth, homogeneous linewidth, and spin-state lifetime of Pr3+ ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3+∶Y2SiO5 crystal allows the 3H4↔1D2 transition of Pr3+ ions to be probed by the optical evanescent field that extends into the substrate. The 2-GHz inhomogeneous linewidth, the optical coherence time of 70±5  μs, and the spin-state lifetime of 9.8±0.3  s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated, and high performance rare-earth-ion quantum systems based on a waveguide platform. PMID:26182097

  11. Cloning, expression, purification and activation by Na ion of halophilic alkaline phosphatase from moderate halophile Halomonas sp. 593.

    PubMed

    Ishibashi, Matsujiro; Oda, Kazuki; Arakawa, Tsutomu; Tokunaga, Masao

    2011-03-01

    We have succeeded in the cloning of alkaline phosphatase gene, haalp, from moderate halophile Halomonas sp. 593. A deduced amino acid sequence showed a high ratio of acidic to basic amino acids, characteristic of halophilic proteins. The gene product was efficiently expressed in Escherichia coli BL21 Star (DE3) pLysS, but in an inactive form. The purified recombinant HaALP was separated into four fractions by gel filtration. When they were dialyzed against 50 mM Tris-HCl (pH 8.0)/2 mM MgCl₂ buffer containing 3 M NaCl, one of these four fractions was activated to almost full activity. This fraction contained a folding intermediate that was converted to the native structure by the salt. Among the additional salts tested, i.e., KCl, KBr, LiCl, MgCl₂, (NH₄)₂SO₄, and Na₂SO₄, only Na₂SO₄ was effective, suggesting the importance of Na ion.

  12. Kinetic isotope effects for alkaline phosphatase reactions: implications for the role of active-site metal ions in catalysis.

    PubMed

    Zalatan, Jesse G; Catrina, Irina; Mitchell, Rebecca; Grzyska, Piotr K; O'brien, Patrick J; Herschlag, Daniel; Hengge, Alvan C

    2007-08-01

    Enzyme-catalyzed phosphoryl transfer reactions have frequently been suggested to proceed through transition states that are altered from their solution counterparts, with the alterations presumably arising from interactions with active-site functional groups. In particular, the phosphate monoester hydrolysis reaction catalyzed by Escherichia coli alkaline phosphatase (AP) has been the subject of intensive scrutiny. Recent linear free energy relationship (LFER) studies suggest that AP catalyzes phosphate monoester hydrolysis through a loose transition state, similar to that in solution. To gain further insight into the nature of the transition state and active-site interactions, we have determined kinetic isotope effects (KIEs) for AP-catalyzed hydrolysis reactions with several phosphate monoester substrates. The LFER and KIE data together provide a consistent picture for the nature of the transition state for AP-catalyzed phosphate monoester hydrolysis and support previous models suggesting that the enzymatic transition state is similar to that in solution. Moreover, the KIE data provides unique information regarding specific interactions between the transition state and the active-site Zn2+ ions. These results provide strong support for a model in which electrostatic interactions between the bimetallo Zn2+ site and a nonbridging phosphate ester oxygen atom make a significant contribution to the large rate enhancement observed for AP-catalyzed phosphate monoester hydrolysis.

  13. Coupling of a locally implanted rare-earth ion ensemble to a superconducting micro-resonator

    SciTech Connect

    Wisby, I. Tzalenchuk, A. Ya.; Graaf, S. E. de; Adamyan, A.; Kubatkin, S. E.; Gwilliam, R.; Meeson, P. J.; Lindström, T.

    2014-09-08

    We demonstrate the coupling of rare-earth ions locally implanted in a substrate (Gd{sup 3+} in Al{sub 2}O{sub 3}) to a superconducting NbN lumped-element micro-resonator. The hybrid device is fabricated by a controlled ion implantation of rare-earth ions in well-defined micron-sized areas, aligned to lithographically defined micro-resonators. The technique does not degrade the internal quality factor of the resonators which remain above 10{sup 5}. Using microwave absorption spectroscopy, we observe electron-spin resonances in good agreement with numerical modelling and extract corresponding coupling rates of the order of 1 MHz and spin linewidths of 50–65 MHz.

  14. Determination of rare earth elements, uranium and thorium in geological samples by ICP-MS, using an automatic fusion machine as an alkaline digestion tool.

    NASA Astrophysics Data System (ADS)

    Granda, Luis; Rivera, Maria; Velasquez, Colon; Barona, Diego; Carpintero, Natalia

    2014-05-01

    At the present time, rare earth elements deposits have became in strategic resources for extraction of raw materials in order to manufacture high tech devices (computers, LCD, cell phones, batteries for hybrid vehicles, fiber optics and wind turbines) (1).The appropriate analytical determination of the REE ( rare earth elements) in sediment and rock samples , is important to find potential deposits and to recognize geological environments for identifying possible alterations and mineral occurrences. The alkaline fusion, which aim is to move the entire sample from solid to liquid state by forming water soluble complexes of boron and lithium, as a previous procedure for the determination of these elements, usually takes a lot of time due to the complexity of the analysis phase and by the addition of other reagents (Tm and HF ) (2) to compensate the lack of strict temperature control. The objective of this work is to develop an efficient alternative to alkaline digestion using an electrical fusion machine, which allows to create temperature programs with advanced process control and supports up to 5 samples simultaneously, which generates a reproducibility of the method and results during the melting step. Additionally, this new method permits the processing of a larger number of samples in a shorter time. The samples analyzed in this method were weighed into porcelain crucibles and subjected to calcination for 4 hours at 950 ° C in order to determine the Lost on Ignition (LOI ) , that serves to adjust the analytical results and to preserve the shelf life of the platinum ware. Subsequently, a fraction of the calcined sample was weighed into platinum crucibles and mixed with ultra-pure lithium metaborate ( flux ) 1:4 . The crucible was then placed in the fusion machine, which was programmed to take the sample from room temperature to 950 ° C in five minutes, make a small ramp to 970 ° C maintain that temperature for five minutes and download the melt in a 10 % v / v

  15. Adsorption of alkali, alkaline-earth, simple and 3d transition metal, and nonmetal atoms on monolayer MoS{sub 2}

    SciTech Connect

    Li, X. D.; Fang, Y. M.; Wu, S. Q. E-mail: wsq@xmu.edu.cn; Zhu, Z. Z. E-mail: wsq@xmu.edu.cn

    2015-05-15

    Single adsorption of different atoms on pristine two-dimensional monolayer MoS{sub 2} have been systematically investigated by using density functional calculations with van der Waals correction. The adatoms cover alkali metals, alkaline earth metals, main group metal, 3d-transition metals, coinage metal and nonmetal atoms. Depending on the adatom type, metallic, semimetallic or semiconducting behavior can be found in direct bandgap monolayer MoS{sub 2}. Additionally, local or long-range magnetic moments of two-dimensional MoS{sub 2} sheet can also attained through the adsorption. The detailed atomic-scale knowledge of single adsorption on MoS{sub 2} monolayer is important not only for the sake of a theoretical understanding, but also device level deposition technological application.

  16. Imidazolium-based Block Copolymers as Solid-State Separators for Alkaline Fuel Cells and Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Nykaza, Jacob Richard

    In this study, polymerized ionic liquid (PIL) diblock copolymers were explored as solid-state polymer separators as an anion exchange membrane (AEM) for alkaline fuel cells AFCs and as a solid polymer electrolyte (SPE) for lithium-ion batteries. Polymerized ionic liquid (PIL) block copolymers are a distinct set of block copolymers that combine the properties of both ionic liquids (e.g., high conductivity, high electrochemical stability) and block copolymers (e.g., self-assembly into various nanostructures), which provides the opportunity to design highly conductive robust solid-state electrolytes that can be tuned for various applications including AFCs and lithium-ion batteries via simple anion exchange. A series of bromide conducting PIL diblock copolymers with an undecyl alkyl side chain between the polymer backbone and the imidazolium moiety were first synthesized at various compositions comprising of a PIL component and a non-ionic component. Synthesis was achieved by post-functionalization from its non-ionic precursor PIL diblock copolymer, which was synthesized via the reverse addition fragmentation chain transfer (RAFT) technique. This PIL diblock copolymer with long alkyl side chains resulted in flexible, transparent films with high mechanical strength and high bromide ion conductivity. The conductivity of the PIL diblock copolymer was three times higher than its analogous PIL homopolymer and an order of magnitude higher than a similar PIL diblock copolymer with shorter alkyl side chain length, which was due to the microphase separated morphology, more specifically, water/ion clusters within the PIL microdomains in the hydrated state. Due to the high conductivity and mechanical robustness of this novel PIL block copolymer, its application as both the ionomer and AEM in an AFC was investigated via anion exchange to hydroxide (OH-), where a maximum power density of 29.3 mW cm-1 (60 °C with H2/O2 at 25 psig (172 kPa) backpressure) was achieved. Rotating disk

  17. Syntheses and characterization of energetic compounds constructed from alkaline earth metal cations (Sr and Ba) and 1,2-bis(tetrazol-5-yl)ethane

    SciTech Connect

    Xia Zhengqiang; Chen Sanping; Wei Qing; Qiao Chengfang

    2011-07-15

    Two new energetic compounds, [M(BTE)(H{sub 2}O){sub 5}]{sub n} (M=Sr(1), Ba(2)) [H{sub 2}BTE=1,2-bis(tetrazol-5-yl)ethane], have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that they are isomorphous and exhibit 2D (4,4) net framework, generated by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs linked up by two independent binding modes of H{sub 2}BTE, and the resulting 2D structure is interconnected by hydrogen-bond and strong face to face {pi}-{pi} stacking interactions between two tetrazole rings to lead to a 3D supramolecular architecture. DSC measurements show that they have significant catalytic effects on thermal decomposition of ammonium perchlorate. Moreover, the photoluminescence properties, thermogravimetric analyses, and flame colors of the as-prepared compounds are also investigated in this paper. - Graphical abstract: Two novel 2D isomorphous alkaline earth metal complexes were assembled by 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two independent binding modes of H{sub 2}BTE ligands, and the catalytic performances toward thermal decomposition of ammonium perchlorate and photoluminescent properties of them were investigated. Highlights: > Two novel alkaline earth energetic coordination polymers have been prepared.{yields} Both structures are layered based on 4-connected Sr{sub 2}(H{sub 2}O){sub 10}/Ba{sub 2}(H{sub 2}O){sub 10} SBUs and two distinct H{sub 2}BTE coordination modes.{yields} The dehydrated products of the compounds possess good thermostability and significant catalytic effects on thermal decomposition of AP.

  18. Chromatography of alkaline earths and transition metals on tin(iv) arsenosilicate and arsenophosphate thin layers in buffered EDTA solutions

    SciTech Connect

    Varshney, K.G.; Anwar, S.; Khan, A.A.

    1985-01-01

    The complex forming ability of ethylene diamine tetraacetic acid at various pH values and the ion exchange behavior of tin(IV) arsenosilicate and arsenophosphate cation exchangers have been combined in a chromatographic study of some metal ions. As a result some interesting observations have been made, which have led to certain analytically difficult separations such as Ca/sup 2 +/ -Sr/sup 2 +/, Ca/sup 2 +/ -Ba/sup 2 +/ and Hg/sup 2 +/ from Cu/sup 2 +/, Ni/sup 2 +/, Zn/sup 2 +/, Co/sup 2 +/ and Mn/sup 2 +/.

  19. A new method for the determination of the nitrogen content of nitrocellulose based on the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis.

    PubMed

    Alinat, Elodie; Delaunay, Nathalie; Archer, Xavier; Mallet, Jean-Maurice; Gareil, Pierre

    2015-04-01

    A new method was proposed to determine the nitrogen content of nitrocelluloses (NCs). It is based on the finding of a linear relationship between the nitrogen content and the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis. Capillary electrophoresis was used to monitor the concentration of nitrite and nitrate ions. The influences of hydrolysis time and molar mass of NC on the molar ratio of nitrite-to-nitrate ions were investigated, and new insights into the understanding of the alkaline denitration mechanism of NCs, underlying this analytical strategy is provided. The method was then tested successfully with various explosive and non-explosive NC-containing samples such as various daily products and smokeless gunpowders. Inherently to its principle exploiting a concentration ratio, this method shows very good repeatability in the determination of nitrogen content in real samples with relative standard deviation (n = 3) inferior to 1.5%, and also provides very significant advantages with respect to sample extraction, analysis time (1h for alkaline hydrolysis, 3 min for electrophoretic separation), which was about 5 times shorter than for the classical Devarda's method, currently used in industry, and safety conditions (no need for preliminary drying NC samples, mild hydrolysis conditions with 1M sodium hydroxide for 1h at 60 °C). PMID:25562808

  20. A new method for the determination of the nitrogen content of nitrocellulose based on the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis.

    PubMed

    Alinat, Elodie; Delaunay, Nathalie; Archer, Xavier; Mallet, Jean-Maurice; Gareil, Pierre

    2015-04-01

    A new method was proposed to determine the nitrogen content of nitrocelluloses (NCs). It is based on the finding of a linear relationship between the nitrogen content and the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis. Capillary electrophoresis was used to monitor the concentration of nitrite and nitrate ions. The influences of hydrolysis time and molar mass of NC on the molar ratio of nitrite-to-nitrate ions were investigated, and new insights into the understanding of the alkaline denitration mechanism of NCs, underlying this analytical strategy is provided. The method was then tested successfully with various explosive and non-explosive NC-containing samples such as various daily products and smokeless gunpowders. Inherently to its principle exploiting a concentration ratio, this method shows very good repeatability in the determination of nitrogen content in real samples with relative standard deviation (n = 3) inferior to 1.5%, and also provides very significant advantages with respect to sample extraction, analysis time (1h for alkaline hydrolysis, 3 min for electrophoretic separation), which was about 5 times shorter than for the classical Devarda's method, currently used in industry, and safety conditions (no need for preliminary drying NC samples, mild hydrolysis conditions with 1M sodium hydroxide for 1h at 60 °C).

  1. Ion velocity distributions in the vicinity of the current sheet in Earth's distant magnetotail

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Kivelson, M. G.; Yamamoto, T.; Fairfield, D. H.

    1994-01-01

    Observations of the three-dimensional velocity distributions of positive ions and electrons have been recently gained for the first time in Earth's distant magnetotail with the Galileo and Geotail spacecraft. For this brief discussion of these exciting results the focus is on the overall character of the ion velocity distributions during substorm activity. The ion velocity distributions within and near the magnetotail current sheet are not accurately described as convecting, isotropic Maxwellians. The observed velocity distributions are characterized by at least two robust types. The first type is similar to the 'lima bean'-shaped velocity distributions that are expected from the nonadiabatic acceleration of ions which execute Speiser-type trajectories in the current sheet. The second distribution is associated with the presence of cold ion beams that presumably also arise from the acceleration of plasma mantle ions in the electric and weak magnetic fields in the current sheet. The ion velocity distributions in a magnetic field structure that is similar to that for plasmoids are also examined. Again the velocity distributions are not Maxwellian but are indicative of nonadiabatic acceleration. An example of the pressure tensor within the plasmoid-like event is also presented because it is anticipated that the off-diagonal elements are important in a description of magnetotail dynamics. Thus our concept of magnetotail dynamics must advance from the present assumption of co-moving electron and ion Maxwellian distributions into reformulations in terms of global kinematical models and nonadiabatic particle motion.

  2. Estimation of Heavy Ion Densities From Linearly Polarized EMIC Waves At Earth

    SciTech Connect

    Kim, Eun-Hwa; Johnson, Jay R.; Lee, Dong-Hun

    2014-02-24

    Linearly polarized EMIC waves are expected to concentrate at the location where their wave frequency satisfies the ion-ion hybrid (IIH) resonance condition as the result of a mode conversion process. In this letter, we evaluate absorption coefficients at the IIH resonance in the Earth geosynchronous orbit for variable concentrations of helium and azimuthal and field-aligned wave numbers in dipole magnetic field. Although wave absorption occurs for a wide range of heavy ion concentration, it only occurs for a limited range of azimuthal and field-aligned wave numbers such that the IIH resonance frequency is close to, but not exactly the same as the crossover frequency. Our results suggest that, at L = 6.6, linearly polarized EMIC waves can be generated via mode conversion from the compressional waves near the crossover frequency. Consequently, the heavy ion concentration ratio can be estimated from observations of externally generated EMIC waves that have polarization.

  3. Nonthermal ions and associated magnetic field behavior at a quasi-parallel earth's bow shock

    NASA Technical Reports Server (NTRS)

    Wilkinson, W. P.; Pardaens, A. K.; Schwartz, S. J.; Burgess, D.; Luehr, H.; Kessel, R. L.; Dunlop, M.; Farrugia, C. J.

    1993-01-01

    Attention is given to ion and magnetic field measurements at the earth's bow shock from the AMPTE-UKS and -IRM spacecraft, which were examined in high time resolution during a 45-min interval when the field remained closely aligned with the model bow shock normal. Dense ion beams were detected almost exclusively in the midst of short-duration periods of turbulent magnetic field wave activity. Many examples of propagation at large elevation angles relative to the ecliptic plane, which is inconsistent with reflection in the standard model shock configuration, were discovered. The associated waves are elliptically polarized and are preferentially left-handed in the observer's frame of reference, but are less confined to the maximum variance plane than other previously studied foreshock waves. The association of the wave activity with the ion beams suggests that the former may be triggered by an ion-driven instability, and possible candidates are discussed.

  4. Comparisons between adsorption and diffusion of alkali, alkaline earth metal atoms on silicene and those on silicane: Insight from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Bo, Xu; Huan-Sheng, Lu; Bo, Liu; Gang, Liu; Mu-Sheng, Wu; Chuying, Ouyang

    2016-06-01

    The adsorption and diffusion behaviors of alkali and alkaline-earth metal atoms on silicane and silicene are both investigated by using a first-principles method within the frame of density functional theory. Silicane is staler against the metal adatoms than silicene. Hydrogenation makes the adsorption energies of various metal atoms considered in our calculations on silicane significantly lower than those on silicene. Similar diffusion energy barriers of alkali metal atoms on silicane and silicene could be observed. However, the diffusion energy barriers of alkali-earth metal atoms on silicane are essentially lower than those on silicene due to the small structural distortion and weak interaction between metal atoms and silicane substrate. Combining the adsorption energy with the diffusion energy barriers, it is found that the clustering would occur when depositing metal atoms on perfect hydrogenated silicene with relative high coverage. In order to avoid forming a metal cluster, we need to remove the hydrogen atoms from the silicane substrate to achieve the defective silicane. Our results are helpful for understanding the interaction between metal atoms and silicene-based two-dimensional materials. Project supported by the Natural Science Foundation of Jiangxi Province, China (Grant Nos. 20152ACB21014, 20151BAB202006, and 20142BAB212002) and the Fund from the Jiangxi Provincial Educational Committee, China (Grant No. GJJ14254). Bo Xu is also supported by the Oversea Returned Project from the Ministry of Education, China.

  5. Simultaneous determination of total nitrogen and total phosphorus in environmental waters using alkaline persulfate digestion and ion chromatography.

    PubMed

    De Borba, Brian M; Jack, Richard F; Rohrer, Jeffrey S; Wirt, Joan; Wang, Dongmei

    2014-11-21

    An ion chromatography (IC) method was developed for the simultaneous determination of total nitrogen and total phosphorus after alkaline persulfate digestion. This study takes advantage of advances in construction of high-resolution, high-capacity anion-exchange columns that can better tolerate the matrices typically encountered when a determination of total nitrogen and total phosphorous is required. Here, we used an electrolytically generated hydroxide eluent combined with a high-capacity, hydroxide-selective, anion-exchange column for the determination of total nitrogen (as nitrate-N) and total phosphorus (as phosphate-P) in environmental samples by IC. This method yielded LODs for nitrate-N and phosphate-P of 1.0 and 1.3 μg/L, respectively. The LOQs determined for these analytes were 3.4 and 4.2 μg/L, respectively. Due to the dilution factor required and the blank nitrate-N concentration after the persulfate digestion, the quantification limits increased for nitrate-N and phosphate-P to 171 and 63 μg/L, respectively. The suitability of the method was evaluated by determining the nitrogen and phosphorus concentrations from known concentrations of organic-containing nitrogen and phosphorus compounds. In addition, environmental samples consisting of six different wastewaters and 48 reservoir samples were evaluated for total nitrogen and phosphorus. The recoveries of nitrogen and phosphorus from the organic-containing compounds ranged from 93.1 to 100.1% and 85.2 to 97.1%, respectively. In addition, good correlation between results obtained by the colorimetric method and IC was also observed. The linearity, accuracy, and evaluation of potential interferences for determining TN and TP will be discussed.

  6. Simultaneous determination of total nitrogen and total phosphorus in environmental waters using alkaline persulfate digestion and ion chromatography.

    PubMed

    De Borba, Brian M; Jack, Richard F; Rohrer, Jeffrey S; Wirt, Joan; Wang, Dongmei

    2014-11-21

    An ion chromatography (IC) method was developed for the simultaneous determination of total nitrogen and total phosphorus after alkaline persulfate digestion. This study takes advantage of advances in construction of high-resolution, high-capacity anion-exchange columns that can better tolerate the matrices typically encountered when a determination of total nitrogen and total phosphorous is required. Here, we used an electrolytically generated hydroxide eluent combined with a high-capacity, hydroxide-selective, anion-exchange column for the determination of total nitrogen (as nitrate-N) and total phosphorus (as phosphate-P) in environmental samples by IC. This method yielded LODs for nitrate-N and phosphate-P of 1.0 and 1.3 μg/L, respectively. The LOQs determined for these analytes were 3.4 and 4.2 μg/L, respectively. Due to the dilution factor required and the blank nitrate-N concentration after the persulfate digestion, the quantification limits increased for nitrate-N and phosphate-P to 171 and 63 μg/L, respectively. The suitability of the method was evaluated by determining the nitrogen and phosphorus concentrations from known concentrations of organic-containing nitrogen and phosphorus compounds. In addition, environmental samples consisting of six different wastewaters and 48 reservoir samples were evaluated for total nitrogen and phosphorus. The recoveries of nitrogen and phosphorus from the organic-containing compounds ranged from 93.1 to 100.1% and 85.2 to 97.1%, respectively. In addition, good correlation between results obtained by the colorimetric method and IC was also observed. The linearity, accuracy, and evaluation of potential interferences for determining TN and TP will be discussed. PMID:25441080

  7. Field-aligned ion beams upstream of the earth's bow shock Evidence for a magnetosheath source

    NASA Technical Reports Server (NTRS)

    Thomsen, M. F.; Gosling, J. T.; Bame, S. J.; Feldman, W. C.; Paschmann, G.; Sckopke, N.

    1983-01-01

    High time resolution ISEE-1 and -2 observations of upstream field-aligned ion beams at several crossings of the earth's bow shock indicate that some beams are due to high energy magnetosheath particles leaking through the shock into the upstream region. The distribution immediately downstream of these oblique shocks consists of a 'core' of directly transmitted, slightly heated ions, plus a crescent-shaped, high-velocity distribution, centered roughly on the magnetic field in the direction toward the upstream region, with a fairly well defined low velocity cutoff.

  8. A simple model for /f-->d transitions of rare-earth ions in crystals

    NASA Astrophysics Data System (ADS)

    Duan, C. K.; Reid, M. F.

    2003-02-01

    Theoretical simulation and interpretation of f→ d transitions of rare earth ions in crystals are more difficult than for f→ f transitions, because f→ d transitions involve many more energy levels and are further complicated by strong vibronic transitions, so the experimental spectra contain many fewer resolvable peaks. In order to better understand the structure of the spectra, a simple model is developed to take into account the main interactions in the fN-1 d configuration. This model leads to quantum numbers characterizing the states and the associated transition selection rules. Relative transition intensities can be quantitatively estimated. The model is applied to Eu 2+ and Sm 3+ ions in crystals.

  9. Earth

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1984-01-01

    The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

  10. Neutral atomic oxygen beam produced by ion charge exchange for Low Earth Orbital (LEO) simulation

    NASA Technical Reports Server (NTRS)

    Banks, Bruce; Rutledge, Sharon; Brdar, Marko; Olen, Carl; Stidham, Curt

    1987-01-01

    A low energy neutral atomic oxygen beam system was designed and is currently being assembled at the Lewis Research Center. The system utilizes a 15 cm diameter Kaufman ion source to produce positive oxygen ions which are charge exchange neutralized to produce low energy (variable from 5 to 150 eV) oxygen atoms at a flux simulating real time low Earth orbital conditions. An electromagnet is used to direct only the singly charged oxygen ions from the ion source into the charge exchange cell. A retarding potential grid is used to slow down the oxygen ions to desired energies prior to their charge exchange. Cryogenically cooled diatomic oxygen gas in the charge exchange cell is then used to transfer charge to the oxygen ions to produce a neutral atomic oxygen beam. Remaining non-charge exchanged oxygen ions are then swept from the beam by electromagnetic or electrostatic deflection depending upon the desired experiment configuration. The resulting neutral oxygen beam of 5 to 10 cm in diameter impinges upon target materials within a sample holder fixture that can also provide for simultaneous heating and UV exposure during the atomic oxygen bombardment.

  11. Source and Acceleration of Energetic He(+) Ions at the Earth's Bow Shock

    NASA Astrophysics Data System (ADS)

    Wang, Kemei

    1998-12-01

    This thesis have presented the first detailed study of the sources and the acceleration of energetic He+ ions in front of the Earth's bow shock, using data from AMPTE/IRM and AMPTE/CCE. the bow shock was an almost perfect perpendicular shock, we compared the results of a simulation to the observed event. The model provides a good quantitative description of the phase space distribution of the gyrating ions. A large portion (approximately 63%) of the incident pickup ions are reflected and gain energy in the interaction. It is also consistent with their spatial distribution in front of the shock. It is shown that a significant fraction of the upstream ions undergo more than one reflection at the bow shock, and gain substantial energy in this interaction. distributions of H+,/ He2+,/ He+ and O+ ions upstream of the shock, as well as a comparison of the observed spectra upstream of the shock and m the magnetosphere with results from the calculations, we concluded that He+ is locally accelerated. The subsequent modeling of the injection and diffusive acceleration at the shock presented evidence that pickup ions can be injected and accelerated more efficiently than solar wind plasma. pickup ions and anomalous cosmic rays.

  12. Ion engine propelled Earth-Mars cycler with nuclear thermal propelled transfer vehicle, volume 2

    NASA Technical Reports Server (NTRS)

    Meyer, Rudolf X.; Baker, Myles; Melko, Joseph

    1994-01-01

    The goal of this project was to perform a preliminary design of a long term, reusable transportation system between earth and Mars which would be capable of providing both artificial gravity and shelter from solar flare radiation. The heart of this system was assumed to be a Cycler spacecraft propelled by an ion propulsion system. The crew transfer vehicle was designed to be propelled by a nuclear-thermal propulsion system. Several Mars transportation system architectures and their associated space vehicles were designed.

  13. Multicomponent analysis of mixed rare-earth metal ion solutions by the electronic tongue sensor system

    SciTech Connect

    Legin, A.; Kirsanov, D.; Rudnitskaya, A.; Rovny, S.; Logunov, M.

    2007-07-01

    Novel electrochemical sensors based on well-known extracting agents are developed. Sensors have shown high sensitivity towards a variety of rear earth metal ions in acidic media at pH=2. Multi-sensor system (electronic tongue) comprising newly developed sensors was successfully applied for the analysis of binary and ternary mixtures of Ce{sup 3+}, Nd{sup 3+}, Sm{sup 3+} and Gd{sup 3+} cations in different combinations. (authors)

  14. Late Precambrian alkaline plutons in southwest India: Geochronologic and rare-earth element constraints on Pan-African magmatism

    NASA Astrophysics Data System (ADS)

    Santosh, M.; Iyer, S. S.; Vasconcellos, M. B. A.; Enzweiler, J.

    1989-12-01

    The Precambrian granulite facies terrain of southwestern India is intruded by a suite of alkali granite and syenite plutons. RbSr whole-rock isotope data for the Angadimogar syenite (AM) and the Peralimala alkali granite (PM), belonging to this suite, define isochron ages of 638 ± 28 and 750 ± 40 Ma, respectively, with initial {87Sr}/{86Sr} ratios of 0.7032 ± 0.0008 and 0.7031 ± 0.0008, respectively. These age data, together with data from previous studies, demonstrate long-lived magmatic activity in the time span from the late Proterozoic to the early Palaeozoic, broadly contemporaneous with Pan-African events in other fragments of the Gondwana supercontinent. REE patterns are reported for four plutons of this Pan-African alkali granite-syenite suite: Chengannoor (CR), Vellingiri (VL) and the two dated intrusions (AM and PM). CR and AM are characterised by high total REE, strongly LREE-enriched patterns with no Eu anomaly, associated with low Sr, Rb, U and Th. K 2O, {K2O }/{Na2O }, {K2O }/{MgO} and the agpaitic index are lower for these plutons as compared to the other two. The PM and VL intrusions have lower total REE and less strongly fractionated REE patterns, associated with high K 2O, {K2O }/{Na2O } and {K2O }/{MgO} ratios, high Sr and Rb levels, but low U and Th. The geochemical patterns in these rocks compare them well with A-type granites and their tectonic relations assign affinities to magmatism of within-plate type. The alkaline magmatism manifests an extensional phase associated with the pre-rift tectonics of the Indian continent within the Gondwana assemblage. A petrogenetic model is development for these plutons, involving decompression-induced melting of deep crustal source materials characterised by low initial {87Sr}/{86Sr} and high {K}/{Rb} ratios.

  15. Solid Phase Luminescence of Several Rare Earth Ions on Ion-Exchange Films

    NASA Technical Reports Server (NTRS)

    Tanner, Stephen P.; Street, Kenneth W., Jr.

    1999-01-01

    The development and characterization of a novel ion-exchange film for solid-phase fluorometry and phosphorimetry is reported. This new cation-exchange material is suitable for spectroscopic applications in the ultraviolet and visible regions. It is advantageous because it, as a single entity, is easily recovered from solution and mounted in the spectrofluorometers. After preconcentration on the film, the luminescence intensity of lanthanide ions is several orders of magnitude greater than that of the corresponding solution, depending on the volume of solution and the amount of film. This procedure allows emission spectral measurements and determination of lanthanide ions at solution concentrations of < 5 (micro)g/L. The film may be stored for subsequent reuse or as a permanent record of the analysis. The major drawback to the use of the film is slow uptake of analyte due to diffusion limitations.

  16. Optical detection of a single rare-earth ion in a crystal

    PubMed Central

    Kolesov, R.; Xia, K.; Reuter, R.; Stöhr, R.; Zappe, A.; Meijer, J.; Hemmer, P.R.; Wrachtrup, J.

    2012-01-01

    Rare-earth-doped laser materials show strong prospects for quantum information storage and processing, as well as for biological imaging, due to their high-Q 4f↔4f optical transitions. However, the inability to optically detect single rare-earth dopants has prevented these materials from reaching their full potential. Here we detect a single photostable Pr3+ ion in yttrium aluminium garnet nanocrystals with high contrast photon antibunching by using optical upconversion of the excited state population of the 4f↔4f optical transition into ultraviolet fluorescence. We also demonstrate on-demand creation of Pr3+ ions in a bulk yttrium aluminium garnet crystal by patterned ion implantation. Finally, we show generation of local nanophotonic structures and cell death due to photochemical effects caused by upconverted ultraviolet fluorescence of praseodymium-doped yttrium aluminium garnet in the surrounding environment. Our study demonstrates versatile use of rare-earth atomic-size ultraviolet emitters for nanoengineering and biotechnological applications. PMID:22929786

  17. Femtosecond Laser-Induced Upconversion Luminescence in Rare-Earth Ions by Nonresonant Multiphoton Absorption.

    PubMed

    Yao, Yunhua; Xu, Cheng; Zheng, Ye; Yang, Chengshuai; Liu, Pei; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

    2016-07-21

    The upconversion luminescence of rare-earth ions has attracted considerable interest because of its important applications in photoelectric conversion, color display, laser device, multiplexed biolabeling, and security printing. Previous studies mainly explored the upconversion luminescence generation through excited state absorption, energy transfer upconversion, and photon avalanche under the continuous wave laser excitation. Here, we focus on the upconversion luminescence generation through a nonresonant multiphoton absorption by using the intense femtosecond pulsed laser excitation and study the upconversion luminescence intensity control by varying the femtosecond laser phase and polarization. We show that the upconversion luminescence of rare-earth ions under the intense femtosecond laser field excitation is easy to be obtained due to the nonresonant multiphoton absorption through the nonlinear interaction between light and matter, which is not available by the continuous wave laser excitation in previous works. We also show that the upconversion luminescence intensity can be effectively controlled by varying the femtosecond pulsed laser phase and polarization, which can open a new technological opportunity to generate and control the upconversion luminescence of rare-earth ions and also can be further extended to the relevant application areas. PMID:27367751

  18. Ion Composition and Energization in the Earth's Inner Magnetosphere and the Effects on Ring Current Buildup

    NASA Astrophysics Data System (ADS)

    Keika, K.; Kistler, L. M.; Brandt, P. C.

    2014-12-01

    In-situ observations and modeling work have confirmed that singly-charged oxygen ions, O+, which are of Earth's ionospheric origin, are heated/accelerated up to >100 keV in the magnetosphere. The energetic O+ population makes a significant contribution to the plasma pressure in the Earth's inner magnetosphere during magnetic storms, although under quiet conditions H+ dominates the plasma pressure. The pressure enhancements, which we term energization, are caused by adiabatic heating through earthward transport of source population in the plasma sheet, local acceleration in the inner magnetosphere and near-Earth plasma sheet, and enhanced ion supply from the topside ionosphere. The key issues regarding stronger O+ energization than H+ are non-adiabatic local acceleration, responsible for increase in O+ temperature, and more significant O+ supply than H+, responsible for increase in O+ density. Although several acceleration mechanisms and O+ supply processes have been proposed, it remains an open question what mechanism(s)/process(es) play the dominant role in stronger O+ energization. In this paper we summarize important spacecraft observations including those from Van Allen Probes, introduces the proposed mechanisms/processes that generate O+-rich energetic plasma population, and outlines possible scenarios of O+ pressure abundance in the Earth's inner magnetosphere.

  19. The photochemistry of a bis-crown ether based on benzobis(thiazole) and its alkaline earth metal cation complexes.

    PubMed

    Fedorov, Yu; Fedorova, O; Schepel, N; Alfimov, M; Turek, A M; Saltiel, J

    2006-01-01

    Irradiation of acetonitrile solutions of the bis-crown ether E,E-2,7-bis[2-(6,7,9,10,12,13,15,16-octahydro-5,8,11,14,17-pentaoxabenzocyclopentadecen-2-yl)vinyl]-benzo[1,2-d;3,4-d']bisthiazole (hereafter, 1) gives efficient E --> Z photoisomerization (initial phi(trans --> cis) = 0.48), leading to lambda(exc)-dependent quasi-photostationary states composed primarily of E,Z and E,E isomer mixtures. Further irradiation gives [2 + 2]-cycloadducts of 1. In the presence of Ba2+ ions, essentially quantitative formation of 2:2 complexes, 1(2) x (Ba2+)2 controls the photochemical outcome. E --> Z photoisomerization of the ligand is entirely suppressed and efficient intramolecular [2 + 2]-photocycloaddition in the complexes leads to cyclobutane dimers of 1 (phiCB = 0.26). The reactivity of 1 in the presence of Mg2+ ions for which 1:2 complex formation dominates gives both cis-trans photoisomerization and enhanced photocycloaddition.

  20. Effects of solvent and alkaline earth metals on the heat-induced precipitation process of sodium caseinate.

    PubMed

    Lopez, Francesco; Cuomo, Francesca; Nostro, Pierandrea Lo; Ceglie, Andrea

    2013-01-01

    The precipitation temperatures of sodium caseinate in H(2)O and D(2)O in the presence of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were investigated through fluorescence, turbidity and conductivity experiments. As for the ability of the divalent cations (1-17.5mM) to induce the precipitation process in H(2)O, the sequence Ba(2+) ≥ Ca(2+)>Mg(2+)>Sr(2+) was found. Remarkably, while at low salt concentrations (<10mM) precipitation temperatures (T(Ps)) were found to change significantly depending on the specific cation, at higher concentrations (>10mM) the differences among the different cations were greatly reduced. By fitting these results with a modified Jones-Dole equation, we confirmed that the less hydrated ions possess a greater capacity to induce precipitation. In D(2)O, the order of ion ability to induce caseinate precipitation was Ba(2+)>Ca(2+)>Sr(2+)>Mg(2+). The different hydrophobicity between D(2)O and H(2)O was shown to affect significantly the T(Ps) of caseinate in the presence of calcium, strontium and barium.

  1. Evidence for solar wind origin of energetic heavy ions in the earth's radiation belt

    NASA Technical Reports Server (NTRS)

    Hovestadt, D.; Klecker, B.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.; Fan, C. Y.; Fisk, L. A.; Ogallagher, J. J.

    1978-01-01

    Analysis of data from our energetic ion composition experiment on ISEE-1 has revealed the presence of substantial fluxes of carbon, oxygen, and heavier ions above 400 keV/nucleon at L values between approximately 2.5 and 4 earth radii. The measured C/O ratio varies systematically from 1.3 at 450 keV/nucleon to 4.1 at 1.3 MeV/nucleon, and no iron is observed above 200 keV/nucleon. These results provide strong evidence for a solar wind origin for energetic ions in the outer radiation belt. The absence of iron and the increase of the carbon-to-oxygen ratio with energy suggest that the condition for the validity of the first adiabatic invariant may have a strong influence on the trapping of these particles.

  2. Ion conics and counterstreaming electrons generated by lower hybrid waves in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Chang, Tom; Crew, Geoffrey B.; Retterrer, John M.; Jasperse, John R.

    1989-01-01

    The exotic phenomenon of energetic ion-conic and counterstreaming electron formation by lower hybrid waves along discrete auroral field lines in the earth magnetosphere is considered. Mean-particle calculations, plasma simulations, and analytical treatments of the acceleration processes are described. It is shown that, in the primary auroral electron-beam region, lower hybrid waves could be an efficient mechanism for the transverse heating of H (+) and O(+) ions of ionospheric origin, as well as for the field-aligned heating of the ambient electrons leading to coincident counterstreaming electron distributions. For O(+) ions to be energized by such a wave-particle interaction process, however, some sort of preheating mechanism is required.

  3. Quasi-linear analysis of ion Weibel instability in the earth's neutral sheet

    NASA Technical Reports Server (NTRS)

    Lui, Anthony T. Y.; Yoon, Peter H.; Chang, Chia-Lie

    1993-01-01

    A quasi-linear analysis of the ion Weibel instability (IWI) for waves with parallel propagation is carried out for parameters appropriate to the earth's neutral sheet during the substorm interval. For ion drift speed reaching sizable fraction of the ion thermal speed, unstable waves grow to a nonlinear regime in a time interval greater than an ion gyroperiod. The saturation level is attained with current density reduced to about 15-28 percent of its preactivity level. The unstable wave amplitude normalized to the initial ambient field is found to be in the range of 0.2-0.8. This is accompanied by ion heating along the magnetic field with the parallel temperature being enhanced by 25-90 percent. Thus, the IWI can provide nonadiabatic heating of ions in current disruptions during substorms. The associated anomalous resistivity is estimated to be about 1 x 10 exp -7 to 1 x 10 exp -6 s, which is about 11 to 12 orders of magnitude above the classical resistivity.

  4. Investigation of the Transport of Solar Ions Through the Earth's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.; Evans, David (Technical Monitor)

    2000-01-01

    The objective of this study has been to infer, by statistical means, the most probable mode of entry of solar wind plasma into Earth's magnetotail, using a particular set of archived data from the Lockheed Plasma Composition Experiment on the International Sun-Earth Explorer One (ISEE-1) satellite, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) in the 1970's and 80's. Despite their considerable age, the Lockheed ISEE-1 data are still, at the time of this report, the only substantial ion composition data in the sub-keV to keV energy range available from the magnetotail beyond 9 R(sub E), because of various technical problems with ion mass spectrometers on later missions, and are therefore a unique source of information about the mixing of solar and terrestrial origin plasmas in the tail, within the ISEE-1 apogee of almost 23 R(sub E). The entire set of archived data used in this study, covering the 4.5 years of operation of the instrument and comprising not only tail measurements but also data from the inner magnetosphere as well as data from outside the magnetopause, is now available to the public via the WorldWideWeb at the address: http://cis.spasci.com/ISEE_ions The fundamental assumption of this and other studies of magnetosphere ion composition is that He++ and O+ ions are virtually certain "tags" of solar and terrestrial origins, respectively. This is an assumption with strong theoretical basis and it is corroborated by observational evidence, including the often substantial differences between the velocity distribution functions of those two species. The H+ ions can have a dual origin, in principle, but the close resemblance in the ISEE-1 data between the dynamics of H+ and He++ ions indicates a predominantly solar origin of the H+ ions in the tail, at least. By the same token, the usually minor He+ ions are probably almost entirely of terrestrial origin, because of their similarity to the O

  5. Photoluminescence properties of the rare-earth ions in the TiO{sub 2} host nanofibers prepared via electrospinning

    SciTech Connect

    Wang Haiying; Wang Yu; Yang Yang; Li Xiang; Wang Ce

    2009-02-04

    Luminescent rare-earth (RE) ions doped TiO{sub 2} nanofibers have been prepared by electrospinning of a mixture solution of rare-earth acetylacetone (RE(C{sub 5}H{sub 7}O{sub 2}){sub 3})/titanium tetraisopropoxide (Ti (OiPr){sub 4})/poly(vinyl pyrrolidone) (PVP) (RE = Eu, Er, Ce, Pr), followed by calcination at high temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses demonstrated the morphology and the structure of the rare-earth doped TiO{sub 2} nanofibers. Exciting the nanofibers results in an energy transfer from surface states of TiO{sub 2} to that of the rare-earth ions and the photoluminescence is observed from the crystal field states of the rare-earth ions.

  6. Emerging cool white light emission from Dy(3+) doped single phase alkaline earth niobate phosphors for indoor lighting applications.

    PubMed

    Vishwakarma, Amit K; Jha, Kaushal; Jayasimhadri, M; Sivaiah, B; Gahtori, Bhasker; Haranath, D

    2015-10-21

    Single-phase cool white-light emitting BaNb2O6:Dy(3+) phosphors have been synthesized via a conventional solid-state reaction method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) observations and spectrofluorophotometric measurements. XRD and Rietveld structural refinement studies confirm that all the samples exhibit pure orthorhombic structure [space group -C2221(20)]. SEM observations reveal the dense particle packaging with irregular morphology in a micron range. The as-prepared phosphors exhibit blue (482 nm) and yellow (574 nm) emissions under 349, 364, 386 and 399 nm excitations corresponding to (4)F9/2→(6)HJ (J = 15/2, 13/2) transitions of Dy(3+) ions. The energy transfer mechanism between Dy(3+) ions has been studied in detail and the luminescence decay lifetime for the (4)F9/2 level was found to be around 146.07 μs for the optimized phosphor composition. The calculated Commission Internationale de L'Eclairage (CIE) chromaticity coordinates for the optimized phosphor are (x = 0.322, y = 0.339), which are close to the National Television Standard Committee (NTSC) (x = 0.310, y = 0.316) coordinates. The values of CIE chromaticity coordinates and correlated color temperature (CCT) of 5907 K endorse cool white-light emission from the phosphor. The study reveals that BaNb2O6:Dy(3+) phosphor could be a potential candidate for near ultra-violet (NUV) excited white-LED applications. PMID:26374377

  7. Ion transport and loss in the Earth`s quiet ring current 1. Data and standard model

    SciTech Connect

    Sheldon, R.B.; Hamilton, D.C.

    1993-08-01

    The authors have studied the transport and loss of ions in the Earth`s quiet time ring current, comparing the standard radial diffusion model developed for the higher-energy radiation belt particles with measurements of the lower-energy ring current ions. They compiled a data set with full local time coverage from the quietest days seen by the AMPTE/CCE/CHEM instrument in near-equatorial orbit at L=2-9 R{sub E}. This data set provides, for the first time, ionic composition information in an energy range that includes the bulk of the ring current energy density, 1-300 keV/e. Protons were found to dominate the quiet time energy density at all altitudes, peaking near L{approximately}4 at 60 keV cm{sup {minus}3}, with much smaller contributions from O{sup +} (1-10%), He{sup +} (1-5%), and He{sup ++} (<1%). The authors improved on previously used model loss processes by incorporating the latest atomic physics cross sections from the literature, updating the last survey done 15 years ago. They also included the effects of finite electron temperature on Coulomb drag. A {chi}{sup 2} minimization procedure was used to fit the amplitudes of the standard electric radial diffusion coefficient, giving D{sub LL}{sup E} = 5.8 x 10{sup {minus}11} R{sub E}{sup 2}/s. Yet the model was unable to fit the data (to within a factor of 10) over 50% of the energy and radial ranges of the data set, particularly at L<4 or E<30 keV. Assuming that the loss terms in the model are correct, the data can be inverted to extract a radial diffusion coefficient that had nearly constant amplitude from 2-7 R{sub E}. This suggests that another transport mechanism is operating in the ring current region, which is strongest at smaller radial distances. The authors speculate that fluctuating ionospheric electric fields may be the source of this additional diffusion. 164 refs., 14 figs., 3 tabs.

  8. Probing the role of encapsulated alkaline earth metal atoms in endohedral metallofullerenes M@C76 (M = Ca, Sr, and Ba) by first-principles calculations.

    PubMed

    Yang, Tao; Zhao, Xiang; Xu, Qian; Zheng, Hong; Wang, Wei-Wei; Li, Sheng-Tao

    2012-05-01

    By means of density functional theory and statistical mechanics, we investigate the geometric and electronic structures, thermodynamic stability and infrared (IR) vibrational frequencies of alkaline earth metal endohedral fullerenes, M@C(76) (M = Ca, Sr, and Ba). The results reveal that M@C(1)(17,459)-C(76) possesses the lowest energy followed by M@C(2v)(19,138)-C(76) with a very small energy difference. Both the structures have a pair of adjacent pentagons and are related by a single Stone-Wales transformation. Equilibrium statistical thermodynamic analyses based on Gibbs energy treatments suggest that M@C(1)(17,459)-C(76) has a prominent thermodynamic stability at higher temperatures, in contrast with M@C(2v)(19,138)-C(76) whose thermodynamic stability is affected by the encapsulated metal atom. The encapsulated metallic atoms as well as cage structures significantly influence the electronic properties of endohedral fullerenes such as electron affinities and ionization potentials. On the other hand, the singlet-triplet splitting energy ΔE(S-T) depends on the cage structures. In addition, IR spectra and chemical shifts of these compounds have been computed to assist further experimental characterization.

  9. Volatilisation of alkali and alkaline earth metallic species during the pyrolysis of biomass: differences between sugar cane bagasse and cane trash.

    PubMed

    Keown, Daniel M; Favas, George; Hayashi, Jun-ichiro; Li, Chun-Zhu

    2005-09-01

    Sugar cane bagasse and cane trash were pyrolysed in a novel quartz fluidised-bed/fixed-bed reactor. Quantification of the Na, K, Mg and Ca in chars revealed that pyrolysis temperature, heating rate, valence and biomass type were important factors influencing the volatilisation of these alkali and alkaline earth metallic (AAEM) species. Pyrolysis at a slow heating rate (approximately 10 K min(-1)) led to minimal (often <20%) volatilisation of AAEM species from these biomass samples. Fast heating rates (>1000 K s(-1)), encouraging volatile-char interactions with the current reactor configuration, resulted in the volatilisation of around 80% of Na, K, Mg and Ca from bagasse during pyrolysis at 900 degrees C. Similar behaviour was observed for monovalent Na and K with cane trash, but the volatilisation of Mg and Ca from cane trash was always restricted. The difference in Cl content between bagasse and cane trash was not sufficient to fully explain the difference in the volatilisation of Mg and Ca.

  10. [High current microsecond pulsed hollow cathode lamp excited ionic fluorescence spectrometry of alkaline earth elements in inductively coupled plasma with a Fassel-torch].

    PubMed

    Zhang, Shao-Yu; Gong, Zhen-Bin; Huang, Ben-Li

    2006-02-01

    High current microsecond pulsed hollow cathode lamp (HCMP-HCL) excited ionic fluorescence spectrometry (IFS) of alkaline earth elements in inductively coupled plasma (ICP) with a Fassel-torch has been investigated. In wide condition ranges only IFS was observed, whilst atomic fluorescence spectrometry (AFS) was not detectable. More intense ionic fluorescence signal was observed at lower observation heights and at lower incident RF powers. Without introduction of any reduction organic gases into the ICP, the limit of detection (LOD, 3sigma) of Ba was improved by 50-fold over that of a conventional pulsed (CP) HCL with the Baird sleeve-extended torch. For Ca and Sr, the LODs by HCMP-HCL-ICP-IFS and CP-HCL-ICP-AFS show no significant difference. Relative standard deviations were 0.6%-1.4% (0.1-0.2 microg x mL(-1), n = 10) for 5 ionic fluorescence lines. Preliminary studies showed that the intensity of ionic fluorescence could be depressed in the presence of K, Al and P.

  11. CO2 capture properties of alkaline earth metal oxides and hydroxides: A combined density functional theory and lattice phonon dynamics study

    NASA Astrophysics Data System (ADS)

    Duan, Yuhua; Sorescu, Dan C.

    2010-08-01

    By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO2 absorption/desorption reactions with alkaline earth metal oxides MO and hydroxides M(OH)2 (where M=Be,Mg,Ca,Sr,Ba) are analyzed. The heats of reaction and the chemical potential changes of these solids upon CO2 capture reactions have been calculated and used to evaluate the energy costs. Relative to CaO, a widely used system in practical applications, MgO and Mg(OH)2 systems were found to be better candidates for CO2 sorbent applications due to their lower operating temperatures (600-700 K). In the presence of H2O, MgCO3 can be regenerated into Mg(OH)2 at low temperatures or into MgO at high temperatures. This transition temperature depends not only on the CO2 pressure but also on the H2O pressure. Based on our calculated results and by comparing with available experimental data, we propose a general computational search methodology which can be used as a general scheme for screening a large number of solids for use as CO2 sorbents.

  12. Dipole polarizability of alkali-metal (Na, K, Rb)–alkaline-earth-metal (Ca, Sr) polar molecules: Prospects for alignment

    SciTech Connect

    Gopakumar, Geetha Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

    2014-06-14

    Electronic open-shell ground-state properties of selected alkali-metal–alkaline-earth-metal polar molecules are investigated. We determine potential energy curves of the {sup 2}Σ{sup +} ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes ({sup 23}Na, {sup 39}K, {sup 85}Rb)–({sup 40}Ca, {sup 88}Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields.

  13. The long-range non-additive three-body dispersion interactions for the rare gases, alkali, and alkaline-earth atoms.

    PubMed

    Tang, Li-Yan; Yan, Zong-Chao; Shi, Ting-Yun; Babb, James F; Mitroy, J

    2012-03-14

    The long-range non-additive three-body dispersion interaction coefficients Z(111), Z(112), Z(113), and Z(122) are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb), and the alkaline-earth atoms (up to Sr). The term Z(111) arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms Z(112), Z(113), and Z(122) arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as dipole-dipole-quadrupole, dipole-dipole-octupole, and dipole-quadrupole-quadrupole coefficients. Results for the four Z coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, and Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supplementary data.

  14. Thermal stability of the anionic sigma complexes of 2,4,6-trinitroanisole with the methylates of the alkaline-earth metals

    SciTech Connect

    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.

  15. GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK

    SciTech Connect

    Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Dandouras, Iannis E-mail: Kis.Arpad@csfk.mta.hu

    2013-07-01

    It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.

  16. Numerical simulations of the optical gain of crystalline fiber doped by rare earth and transition ion

    NASA Astrophysics Data System (ADS)

    Daoui, A. K.; Boubir, B.; Adouane, A.; Demagh, N.; Ghoumazi, M.

    2015-02-01

    A fiber laser is a laser whose gain medium is a doped fiber, although lasers whose cavity is made wholly of fibers have also been called fiber lasers. The gain media in a fiber laser is usually fiber doped with rare-earth ions, such as erbium (Er), neodymium (Nd), ytterbium (Yb), thulium (Tm), or praseodymium (Pr), which is doped into the core of the optical fiber, similar to those used to transmit telecommunications signals. Fiber lasers find many applications in materials processing, including cutting, welding, drilling, and marking metal. To maximize their market penetration, it is necessary to increase their output power. In this work, we present a detailed study based on the numerical simulation using MATLAB, of one of the principal characteristics of a fiber laser doped with rare earth ions and transition ion. The gain depends on several parameters such as the length of the doped fiber, the density, the pump power, noise, etc.). The used program resolves the state equations in this context together with those governing the light propagation phenomena. The developed code can also be used to study the dynamic operating modes of a doped fiber laser.

  17. Assessment of DNA damage of Lewis lung carcinoma cells irradiated by carbon ions and X-rays using alkaline comet assay

    NASA Astrophysics Data System (ADS)

    Li, Ping; Zhou, Li-Bin; Jin, Xiao-Dong; He, Jing; Dai, Zhong-Ying; Zhou, Guang-Ming; Gao, Qing-Xiang; Li, Sha; Li, Qiang

    2008-01-01

    DNA damage and cell reproductive death determined by alkaline comet and clonogenic survival assays were examined in Lewis lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. Based on the survival data, Lewis lung carcinoma cells were verified to be more radiosensitive to the carbon ion beam than to the X-ray irradiation. The relative biological effectiveness (RBE) value, which was up to 1.77 at 10% survival level, showed that the DNA damage induced by the high-LET carbon ion beam was more remarkable than that induced by the low-LET X-ray irradiation. The dose response curves of “Tail DNA (%)” (TD) and “Olive tail moment” (OTM) for the carbon ion irradiation showed saturation beyond about 8 Gy. This behavior was not found in the X-ray curves. Additionally, the carbon ion beam produced a lower survival fraction at 2 Gy (SF2) value and a higher initial Olive tail moment 2 Gy (OTM2) than those for the X-ray irradiation. These results suggest that carbon ion beams having high-LET values produced more severe cell reproductive death and DNA damage in Lewis lung carcinoma cells in comparison with X-rays and comet assay might be an effective predictive test even combining with clonogenic assay to assess cellular radiosensitivity.

  18. Comparative study of ion cyclotron waves at Mars, Venus and Earth

    NASA Astrophysics Data System (ADS)

    Wei, H. Y.; Russell, C. T.; Zhang, T. L.; Blanco-Cano, X.

    2011-08-01

    Ion cyclotron waves are generated in the solar wind when it picks up freshly ionized planetary exospheric ions. These waves grow from the free energy of the highly anisotropic distribution of fresh pickup ions, and are observed in the spacecraft frame with left-handed polarization and a wave frequency near the ion's gyrofrequency. At Mars and Venus and in the Earth's polar cusp, the solar wind directly interacts with the planetary exospheres. Ion cyclotron waves with many similar properties are observed in these diverse plasma environments. The ion cyclotron waves at Mars indicate its hydrogen exosphere to be extensive and asymmetric in the direction of the interplanetary electric field. The production of fast neutrals plays an important role in forming an extended exosphere in the shape and size observed. At Venus, the region of exospheric proton cyclotron wave production may be restricted to the magnetosheath. The waves observed in the solar wind at Venus appear to be largely produced by the solar-wind-Venus interaction, with some waves at higher frequencies formed near the Sun and carried outward by the solar wind to Venus. These waves have some similarity to the expected properties of exospherically produced proton pickup waves but are characterized by magnetic connection to the bow shock or by a lack of correlation with local solar wind properties respectively. Any confusion of solar derived waves with exospherically derived ion pickup waves is not an issue at Mars because the solar-produced waves are generally at much higher frequencies than the local pickup waves and the solar waves should be mostly absorbed when convected to Mars distance as the proton cyclotron frequency in the plasma frame approaches the frequency of the solar-produced waves. In the Earth's polar cusp, the wave properties of ion cyclotron waves are quite variable. Spatial gradients in the magnetic field may cause this variation as the background field changes between the regions in which

  19. Lithium-Ion Batteries Being Evaluated for Low-Earth-Orbit Applications

    NASA Technical Reports Server (NTRS)

    McKissock, Barbara I.

    2005-01-01

    The performance characteristics and long-term cycle life of aerospace lithium-ion (Li-ion) batteries in low-Earth-orbit applications are being investigated. A statistically designed test using Li-ion cells from various manufacturers began in September 2004 to study the effects of temperature, end-of-charge voltage, and depth-of-discharge operating conditions on the cycle life and performance of these cells. Performance degradation with cycling is being evaluated, and performance characteristics and failure modes are being modeled statistically. As technology improvements are incorporated into aerospace Li-ion cells, these new designs can be added to the test to evaluate the effect of the design changes on performance and life. Cells from Lithion and Saft have achieved over 2000 cycles under 10 different test condition combinations and are being evaluated. Cells from Mine Safety Appliances (MSA) and modules made up of commercial-off-the-shelf 18650 Li-ion cells connected in series/parallel combinations are scheduled to be added in the summer of 2005. The test conditions include temperatures of 10, 20, and 30 C, end-of-charge voltages of 3.85, 3.95, and 4.05 V, and depth-of-discharges from 20 to 40 percent. The low-Earth-orbit regime consists of a 55 min charge, at a constant-current rate that is 110 percent of the current required to fully recharge the cells in 55 min until the charge voltage limit is reached, and then at a constant voltage for the remaining charge time. Cells are discharged for 35 min at the current required for their particular depth-of-discharge condition. Cells are being evaluated in four-cell series strings with charge voltage limits being applied to individual cells by the use of charge-control units designed and produced at the NASA Glenn Research Center. These charge-control units clamp the individual cell voltages as each cell reaches its end-of-charge voltage limit, and they bypass the excess current from that cell, while allowing the full

  20. The Role of the Ion Microprobe in Solid-Earth Geochemistry

    NASA Astrophysics Data System (ADS)

    Hauri, E. H.

    2002-12-01

    Despite the early success of the electron microprobe in taking petrology to the micron scale, and the widespread use of mass spectrometers in geochemistry and geochronology, it was not until the mid-1970s that the ion microprobe came into its own as an in situ analytical tool in the Earth sciences. Despite this inauspicious beginning, secondary ion mass spectrometry (SIMS) was widely advertised as a technology that would eventually eclipse thermal ion mass spectrometry (TIMS) in isotope geology. However this was not to happen. While various technical issues in SIMS such as interferences and matrix effects became increasingly clear, an appreciation grew for the complimentary abilities of SIMS and TIMS that, even with the advent of ICP-MS, continues to this day. Today the ion microprobe is capable of abundance measurements in the parts-per-billion range across nearly the entire periodic table, and SIMS stable isotope data quality is now routinely crossing the 1 per mil threshold, all at the micron scale. Much of this success is due to the existence of multi-user community facilities for SIMS research, and the substantial efforts of interested scientists to understand the fundamentals of sputtered ion formation and their application to geochemistry. Recent discoveries of evidence for the existence of ancient crust and oceans, the emergence of life on Earth, the large-scale cycling of surficial materials into the deep Earth, and illumination of fundamental high-pressure phenomena have all been made possible by SIMS, and these (and many more) discoveries owe a debt to the vision of creating and supporting multi-user community facilities for SIMS. The ion microprobe remains an expensive instrument to purchase and maintain, yet it is also exceedingly diverse in application. Major improvements in SIMS, indeed in all mass spectrometry, are visible on the near horizon. Yet the geochemical community cannot depend on commercial manufacturers alone to design and build the next

  1. Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance

    NASA Astrophysics Data System (ADS)

    André, Mats

    2015-12-01

    This is a review of the mass balance of planet Earth, intended also for scientists not usually working with space physics or geophysics. The discussion includes both outflow of ions and neutrals from the ionosphere and upper atmosphere, and the inflow of meteoroids and larger objects. The focus is on ions with energies less than tens of eV originating from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We have invented a technique to observe low-energy ions based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the ion density and the outward flux in large volumes in the magnetosphere. The global outflow is of the order of 1026 ions s-1. This is a significant fraction of the total number outflow of particles from Earth, and changes plasma processes in near-Earth space. We compare order of magnitude estimates of the mass outflow and inflow for planet Earth and find that they are similar, at around 1 kg s-1 (30 000 ton yr-1). We briefly discuss atmospheric and ionospheric outflow from other planets and the connection to evolution of extraterrestrial life.

  2. A possible new host mineral of large-ion elements in the Earth's deep interior

    NASA Astrophysics Data System (ADS)

    Kawai, K.; Tsuchiya, T.

    2015-12-01

    The radiogenic heat production as well as the secular cooling is essential in order to better understand the thermal history and dynamics in the Earth. Potassium is thought to be one of the important radioactive elements in the Earth's interior. Although these elements are concentrated in the continental and oceanic crusts due to chemical differentiations through partial melting at plate boundaries due to their large ion-radii, they have been considered to return into the deep mantle accompanied with subducting slab through time . However, since there are few studies on host minerals of potassium in the high P,T condition, it has yet to be clear how much and where host rocks of such radioactive elements exist in the Earth. Hence, it is important to understand the fate of the potassium-bearing phase subducted into the deep Earth's interior. Here we have studied the high-pressure stability and elasticity of KMg2Al5SiO12 hexagonal aluminous phase (K-Hex with three different size of cation cites, by means of the density functional computation method. Results indicate that the K-Hex phase remains mechanically stable up to 150 GPa and also energetically more stable than an isochemical form with the calcium-ferrite (K-CF) and calcium-titanate (K-CT) type structure with two different size of cation cites. In addition, when the spinel composition coexists with the K-hollandite (K-Hol) phase, which is ), which is considered to be able to host potassium the K-Hex phase becomes more stable than the K-Hol phase at pressures above ~27 GPa. These demonstrate that the Hex phase is substantially stable in the lower mantle, suggesting that it could be a potential host of potassium and other incompatible large-ion elements.

  3. A Study on Removal of Rare Earth Elements from U.S. Coal Byproducts by Ion Exchange

    NASA Astrophysics Data System (ADS)

    Rozelle, Peter L.; Khadilkar, Aditi B.; Pulati, Nuerxida; Soundarrajan, Nari; Klima, Mark S.; Mosser, Morgan M.; Miller, Charles E.; Pisupati, Sarma V.

    2016-03-01

    Rare earth elements are known to occur in low concentrations in U.S. coals and coal byproducts. These low concentrations may make rare earth element recovery from these materials unattractive, using only physical separation techniques. However, given the significant production of rare earths through ion exchange extraction in China, two U.S. coal byproducts were examined for ion extraction, using ammonium sulfate, an ionic liquid, and a deep eutectic solvent as lixiviants. Extraction of rare earth elements in each case produced high recoveries of rare earth elements to the solution. This suggests that in at least the cases of the materials examined, U.S. coal byproducts may be technically suitable as REE ores. More work is required to establish economic suitability.

  4. Ion-neutral coupling in Earth's thermosphere, estimated from concurrent radar and optical observations above Alaska

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Kosch, M. J.; Nicolls, M. J.; Conde, M.

    2013-12-01

    During March-April 2011 a campaign of coordinated observations was undertaken between the Poker Flat Advanced Modular Incoherent Scatter Radar and the Poker Flat Scanning Doppler Imager. These instruments provide horizontally resolved maps of plasma and neutral parameters in Earth's thermosphere. We report on data collected during the campaign, and use these data to investigate two key aspects of ion-neutral coupling, namely Joule heating and the ion-neutral collision frequency. Volumetric Joule heating rates were often well correlated with measured ion temperature enhancements. The contribution of the neutral wind dynamo to the observed heating rates was positive when the absolute horizontal magnetic field perturbation (|ΔH|) was less than approximately 40 nT, and negative above that level. The total momentum-transfer ion-neutral collision frequency was estimated to be 1.02-0.152+0.179 s-1 at an altitude of 260 km, which, for a neutral composition of 75% atomic oxygen, yielded an estimate of the O+-O collision frequency of 0.766-0.114+0.134 s-1.

  5. Statistical analysis of diffuse ion events upstream of the Earth's bow shock

    NASA Technical Reports Server (NTRS)

    Trattner, K. J.; Mobius, E.; Scholer, M.; Klecker, B.; Hilchenbach, M.; Luehr, H.

    1994-01-01

    A statistical study of diffuse energetic ion events and their related waves upstream of the Earth's bow shock was performed using data from the Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM) satellite over two 5-month periods in 1984 and 1985. The data set was used to test the assumption in the self-consistent model of the upstream wave and particle populations by Lee (1982) that the particle acceleration through hydromagnetic waves and the wave generation are directly coupled. The comparison between the observed wave power and the wave power predicted on the observed energetic particle energy density and solar wind parameters results in a high correlation coefficient of about 0.89. The intensity of diffuse ions falls off approximately exponentially with the distance upstream from the bow shock parallel to the magnetic field with e-folding distances which vary from approximately 3.3 R(sub E) to approximately 11.7 R(sub E) over the energy range from 10 keV/e to 67.3 keV/e for both protons and alpha particles. After normalizing the upstream particle densities to zero bow shock distance by using these exponential variations, a good correlation (0.7) of the density of the diffuse ions with the solar wind density was found. This supports the suggestion that the solar wind is the source of the diffuse ions. Furthermore, the spectral slope of the diffuse ions correlates well with the solar wind velocity component in the direction of the interplanetary magnetic field (0.68 and 0.66 for protons and alpha particles) which concurs with the notion that the solar wind plays an important role in the acceleration of the upstream particles.

  6. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices--CCSD(T) calculations and atomic site occupancies.

    PubMed

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm(-1)). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications. PMID:26827218

  7. Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices--CCSD(T) calculations and atomic site occupancies.

    PubMed

    Davis, Barry M; McCaffrey, John G

    2016-01-28

    Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y(1)P ← a(1)S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅ RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm(-1)). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr2 while this transition is quenched in Ba2. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba2 indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.

  8. Interaction of Rydberg atoms in circular states with the alkaline-earth Ca(4s{sup 2}) and Sr(5s{sup 2}) atoms

    SciTech Connect

    Mironchuk, E. S.; Narits, A. A.; Lebedev, V. S.

    2015-11-15

    The resonant mechanism of interaction of alkaline-earth atoms having a low electron affinity to Rydberg atoms in circular (l = vertical bar m vertical bar = n–1) and near-circular states has been studied. To describe the dynamics of resonant processes accompanied by nonadiabatic transitions between ionic and Rydberg covalent terms of a quasimolecule, an approach based on the integration of coupled equations for the probability amplitudes has been developed taking into account the possibility of the decay of an anion in the Coulomb field of the positive ionic core of a highly excited atom. The approach involves the specific features of the problem associated with the structure of the wavefunction of a Rydberg electron in states with high orbital angular momenta l ∼ n–1. This approach provides a much more accurate description of the dynamics of electronic transitions at collisions between atoms than that within the modified semiclassical Landau–Zener model. In addition, this approach makes it possible to effectively take into account many channels of the problem. The cross sections for resonant quenching of Rydberg states of the Li(nlm) atom with given principal n, orbital l = n–1, and magnetic m quantum numbers at thermal collisions with the Ca(4s{sup 2}) and Sr(5s{sup 2}) atoms have been calculated. The dependences of the results on n, m, and angle α between the relative velocity of the atoms and the normal to the plane of the orbit of the Rydberg electron have been obtained. The influence of orientational effects on the efficiency of the collisional destruction of circular and near-circular states has been studied. The results indicate a higher stability of such states to their perturbations by neutral particles as compared to usually studied nl states with low values of l (l ≪ n)

  9. Promoting alkali and alkaline-earth metals on MgO for enhancing CO2 capture by first-principles calculations.

    PubMed

    Kim, Kiwoong; Han, Jeong Woo; Lee, Kwang Soon; Lee, Won Bo

    2014-12-01

    Developing next-generation solid sorbents to improve the economy of pre- and post-combustion carbon capture processes has been challenging for many researchers. Magnesium oxide (MgO) is a promising sorbent because of its moderate sorption-desorption temperature and low heat of sorption. However, its low sorption capacity and thermal instability need to be improved. Various metal-promoted MgO sorbents have been experimentally developed to enhance the CO2 sorption capacities. Nevertheless, rigorous computational studies to screen an optimal metal promoter have been limited to date. We conducted first-principles calculations to select metal promoters of MgO sorbents. Five alkali (Li-, Na-, K-, Rb-, and Cs-) and 4 alkaline earth metals (Be-, Ca-, Sr-, and Ba-) were chosen as a set of promoters. Compared with the CO2 adsorption energy on pure MgO, the adsorption energy on the metal-promoted MgO sorbents is higher, except for the Na-promoter, which indicates that metal promotion on MgO is an efficient approach to enhance the sorption capacities. Based on the stabilized binding of promoters on the MgO surface and the regenerability of sorbents, Li, Ca, and Sr were identified as adequate promoters among the 9 metals on the basis of PW91/GGA augmented with DFT+D2. The adsorption energies of CO2 on metal-promoted MgO sorbents for Li, Ca, and Sr atoms are -1.13, -1.68, and -1.48 eV, respectively. PMID:25319405

  10. Multi-phase glass-ceramics as a waste form for combined fission products: alkalis, alkaline earths, lanthanides, and transition metals

    SciTech Connect

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna

    2012-04-01

    In this study, multi-phase silicate-based glass-ceramics were investigated as an alternate waste form for immobilizing non-fissionable products from used nuclear fuel. Currently, borosilicate glass is the waste form selected for immobilization of this waste stream, however, the low thermal stability and solubility of MoO{sub 3} in borosilicate glass translates into a maximum waste loading in the range of 15-20 mass%. Glass-ceramics provide the opportunity to target durable crystalline phases, e.g., powellite, oxyapatite, celsian, and pollucite, that will incorporate MoO{sub 3} as well as other waste components such as lanthanides, alkalis, and alkaline earths at levels 2X the solubility limits of a single-phase glass. In addition a glass-ceramic could provide higher thermal stability, depending upon the properties of the crystalline and amorphous phases. Glass-ceramics were successfully synthesized at waste loadings of 42, 45, and 50 mass% with the following glass additives: B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, CaO and SiO{sub 2} by slow cooling form from a glass melt. Glass-ceramics were characterized in terms of phase assemblage, morphology, and thermal stability. The targeted phases: powellite and oxyapatite were observed in all of the compositions along with a lanthanide borosilicate, and cerianite. Results of this initial investigation of glass-ceramics show promise as a potential waste form to replace single-phase borosilicate glass.

  11. Simultaneous determination of inorganic and organic anions, alkali, alkaline earth and transition metal cations by capillary electrophoresis with contactless conductometric detection.

    PubMed

    Kubán, Pavel; Kubán, Petr; Kubán, Vlastimil

    2002-11-01

    Simultaneous separation of up to 22 inorganic and organic anions, alkali, alkaline earth and transition metal cations was achieved in less than 3 min in the capillary electrophoresis system with contactless conductometric detector. The sample was injected from both capillary ends (dual opposite end injection) and anionic and cationic species were detected in the center of the separation capillary. The parameters of the separation electrolyte, such as pH, concentration of the electrolyte, concentration of complexing agents and concentration of 18-crown-6 were studied. Best results were achieved with electrolytes consisting of 8 mM L-histidine, 2.8 mM 2-hydroxyisobutyric acid, 0.32 mM 18-crown-6 at pH 4.25 or 9 mM L-histidine, 4.6 mM lactic acid, 0.38 mM 18-crown-6 at pH 4.25. Other electrolytes containing complexing agents such as malic or tartaric acid at various concentrations could also be used. The detection limits achieved for most cations and anions were 7.5 - 62 micro gL(-1) except for Ba2+ (90 micro gL(-1)), Cd 2+, Cr 3+ and F- (125 micro gL(-1)), and fumarate (250 micro gL(-1)). The repeatability of migration times and peak areas was better than 0.4% and 5.9%, respectively. The developed method was applied for analysis of real samples, such as tap, rain, drainage and surface water samples, plant exudates, plant extracts and ore leachates.

  12. Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-02-07

    We examine theoretically the three channels that are associated with the detachment of a single water molecule from the aqueous clusters of the alkaline earth dications, [M(H2O)n]2+, M = Mg, Ca, Sr, Ba, n ≤ 6. These are the unimolecular water loss (M2+(H2O)n-1 + H2O) and the two hydrolysis channels resulting to the loss of hydronium ([MOH(H2O)n-2]+ + H3O+) and Zundel ([MOH(H2O)n-3]+ + H3O+(H2O)) cations. The Potential Energy Curves (PECs) corresponding to those three channels were constructed at the Møller-Plesset second order perturbation (MP2) level of theory with basis sets of double- and triple-ζ quality. We furthermore investigated the water and hydronium loss channels from the mono-hydroxide water clusters with up to four water molecules, [MOH(H2O)n]+, 1 ≤ n ≤ 4. Our results indicate the preference of the hydronium loss and possibly the Zundel cation loss channels for the smallest size clusters, whereas the unimolecular water loss channel is preferred for the larger ones as well as the mono-hydroxide clusters. Although the charge separation (hydronium and Zundel cation loss) channels produce more stable products when compared to the ones for the unimolecular water loss, they also require the surmounting of high energy barriers, a fact that makes the experimental observation of fragments related to these hydrolysis channels difficult.

  13. Interaction of Rydberg atoms in circular states with the alkaline-earth Ca(4 s 2) and Sr(5 s 2) atoms

    NASA Astrophysics Data System (ADS)

    Mironchuk, E. S.; Narits, A. A.; Lebedev, V. S.

    2015-11-01

    The resonant mechanism of interaction of alkaline-earth atoms having a low electron affinity to Rydberg atoms in circular ( l = | m| = n-1) and near-circular states has been studied. To describe the dynamics of resonant processes accompanied by nonadiabatic transitions between ionic and Rydberg covalent terms of a quasimolecule, an approach based on the integration of coupled equations for the probability amplitudes has been developed taking into account the possibility of the decay of an anion in the Coulomb field of the positive ionic core of a highly excited atom. The approach involves the specific features of the problem associated with the structure of the wavefunction of a Rydberg electron in states with high orbital angular momenta l ~ n-1. This approach provides a much more accurate description of the dynamics of electronic transitions at collisions between atoms than that within the modified semiclassical Landau-Zener model. In addition, this approach makes it possible to effectively take into account many channels of the problem. The cross sections for resonant quenching of Rydberg states of the Li( nlm) atom with given principal n, orbital l = n-1, and magnetic m quantum numbers at thermal collisions with the Ca(4 s 2) and Sr(5 s 2) atoms have been calculated. The dependences of the results on n, m, and angle α between the relative velocity of the atoms and the normal to the plane of the orbit of the Rydberg electron have been obtained. The influence of orientational effects on the efficiency of the collisional destruction of circular and near-circular states has been studied. The results indicate a higher stability of such states to their perturbations by neutral particles as compared to usually studied nl states with low values of l ( l ≪ n).

  14. Characterization of Surface and Bulk Nitrates of γ-Al2O3-Supported Alkaline Earth Oxides using Density Functional Theory

    SciTech Connect

    Mei, Donghai; Ge, Qingfeng; Kwak, Ja Hun; Kim, Do Heui; Verrier, Christelle M.; Szanyi, Janos; Peden, Charles HF

    2009-05-14

    “Surface" and "bulk" nitrates formed on a series of alkaline earth oxides (AEOs), AE(NO3)2, were investigated using first-principles density functional theory calculations. The formation of these surface and bulk nitrates was modeled by the adsorption of NO2+NO3 pairs on gamma-Al2O3-supported monomeric AEOs (MgO, CaO, SrO, and BaO) and on the extended AEO(001) surfaces, respectively. The calculated vibrational frequencies of the surface and bulk nitrates based on our proposed models are in good agreement with experimental measurements of AEO/gamma-Al2O3 materials after prolonged NO2 exposure. This indicates that experimentally observed "surface" nitrates are most likely formed with isolated two dimensional (including monomeric) AEO clusters on the gamma-Al2O3 substrate, while the "bulk" nitrates are formed on exposed (including (001)) surfaces (and likely in the bulk as well) of large three dimensional AEO particles supported on the gamma-Al2O3 substrate. Also in line with the experiments, our calculations show that the low and high frequency components of the vibrations for both surface and bulk nitrates are systematically red shifted with the increasing basicity and cationic size of the AEOs. The adsorption strengths of NO2+NO3 pairs are nearly the same for the series of alumina-supported monomeric AEOs, while the adsorption strengths of NO2+NO3 pairs on the AEO surfaces increase in the order of MgO < CaO < SrO ~ BaO. Compared to the NO2+NO3 pair that only interacts with monomeric AEOs, the stability of NO2+NO3 pairs that interact with both the monomeric AEO and the gamma-Al2O3 substrate is enhanced by about 0.5 eV. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  15. Ion Acceleration at Earth, Saturn and Jupiter and its Global Impact on Magnetospheric Structure

    NASA Astrophysics Data System (ADS)

    Brandt, Pontus

    2016-07-01

    The ion plasma pressures at Earth, Saturn and Jupiter are significant players in the electrodynamic force-balance that governs the structure and dynamics of these magnetospheres. There are many similarities between the physical mechanisms that are thought to heat the ion plasma to temperatures that even exceed those of the solar corona. In this presentation we compare the ion acceleration mechanisms at the three planetary magnetospheres and discuss their global impacts on magnetopsheric structure. At Earth, bursty-bulk flows, or "bubbles", have been shown to accelerate protons and O+ to high energies by the earthward moving magnetic dipolarization fronts. O+ ions display a more non-adiabatic energization in response to these fronts than protons do as they are energized and transported in to the ring-current region where they reach energies of several 100's keV. We present both in-situ measurements from the NASA Van Allen Probes Mission and global Energetic Neutral (ENA) images from the High-Energy Neutral Atom (HENA) Camera on board the IMAGE Mission, that illustrate these processes. The global impact on the magnetospheric structure is explored by comparing the empirical magnetic field model TS07d for given driving conditions with global plasma pressure distributions derived from the HENA images. At Saturn, quasi-periodic energization events, or large-scale injections, occur beyond about 9 RS around the post-midnight sector, clearly shown by the Ion and Neutral Atom Camera (INCA) on board the Cassini mission. In contrast to Earth, the corotational drift dominates even the energetic ion distributions. The large-scale injections display similar dipolarization front features can be found and there are indications that like at Earth the O+ responds more non-adiabatically than protons do. However, at Saturn there are also differences in that there appears to be energization events deep in the inner magnetosphere (6-9 RS) preferentially occurring in the pre

  16. Particle acceleration during interactions between transient ion foreshock phenomena and Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Turner, Drew; Angelopoulos, Vassilis; Wilson, Lynn; Hietala, Heli; Omidi, Nick; Masters, Adam

    2014-05-01

    Foreshocks are regions upstream of supercritical astrophysical shock waves that are in communication with the shock via suprathermal charged particles that have been energized and reflected by the shock and are counter-streaming into the incident plasma. These regions form upstream of the quasi-parallel region of the shock, in which the angle between the magnetic field in the incident plasma and the shock normal direction is less than ~40 deg. The relative drift between the reflected suprathermal particles and the incident bulk flow is a source of free energy, which is capable of producing a variety of kinetic plasma instabilities and enhanced wave activity. Simulations and observations of Earth's and other planetary foreshocks have shown that large-scale transient phenomena can also develop due to nonlinear processes and interactions between foreshock particles and discontinuities in the incident solar wind. Several of these transient ion foreshock phenomena (TIFP), such as short large-amplitude magnetic structures (SLAMS), hot flow anomalies (HFAs), and foreshock bubbles (FBs), can result in the development of nonlinear wave activity and additional shocks upstream of the main bow shock. We present in situ observations, made by NASA's THEMIS mission, of ion and electron distributions from within and without SLAMS, HFAs, and FBs, examining the particle heating and acceleration taking place within those TIFP. The observations are compared to theoretical expectations for shock-drift acceleration, Fermi acceleration, and energy diffusion via wave-particle interactions. Our preliminary results show that SLAMS, HFAs, and FBs can be ideal particle accelerators. Finally, we develop an understanding for the upper energy limits for ion and electron acceleration in each of these TIFP at Earth's bow shock and use this to investigate how TIFP may accelerate particles at other astrophysical shocks, such as planetary and astrospherical bow shocks, shocks in stellar winds, and

  17. Toward a System-Based Approach to Electromagnetic Ion Cyclotron Waves in Earth's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Gamayunov, K. V.; Engebretson, M. J.; Rassoul, H.

    2015-12-01

    We consider a nonlinear wave energy cascade from the low frequency range into the higher frequency domain of electromagnetic ion cyclotron (EMIC) wave generation as a possible source of seed fluctuations for EMIC wave growth due to the ion cyclotron instability in Earth's magnetosphere. The theoretical analysis shows that energy cascade from the Pc 4-5 frequency range (2-22 mHz) into the range of Pc 1-2 pulsations (0.1-5 Hz) is able to supply the level of seed fluctuations that guarantees growth of EMIC waves up to an observable level during one pass through the near equatorial region where the ion cyclotron instability takes place. We also analyze magnetic field data from the Polar and Van Allen Probes spacecraft to test this nonlinear mechanism. We restrict our analysis to magnetic spectra only. We do not analyze the third-order moment for total energy of the magnetic and velocity fluctuations, but judge whether a nonlinear energy cascade is present or whether it is not by only analyzing the appearance of power-law distributions in the low frequency part of the magnetic field spectra. While the power-law spectrum alone does not guarantee that a nonlinear cascade is present, the power-law distribution is a strong indication of the possible development of a nonlinear cascade. Our data analysis shows that a nonlinear energy cascade is indeed observed in both the outer and inner magnetosphere, and EMIC waves are growing from this nonthermal background. All the analyzed data are in good agreement with the theoretical model presented in this study. Overall, the results of this study support a nonlinear energy cascade in Earth's magnetosphere as a mechanism which is responsible for supplying seed fluctuating energy in the higher frequency domain where EMIC waves grow due to the ion cyclotron instability. Keywords: nonlinear energy cascade, ultra low frequency waves, electromagnetic ion cyclotron waves, seed fluctuationsAcknowledgments: This paper is based upon work

  18. Application of Laser Induced Breakdown Spectroscopy to Monitor Rare Earth Ions in Glass Matrix

    NASA Astrophysics Data System (ADS)

    Sharma, Prakash; Carter, Michael; Kumar, Akshaya

    2013-05-01

    The Laser Induced breakdown spectroscopy (LIBS) is a real time online technique that can be used to monitor the concentration of rare earth ions in amorphous glass matrix. This study has significant application in the glass industry where the composition of the glass can be monitored in real time using LIBS technology for quality control. The Eu3 + ions doped silicate glasses were developed via sol gel method. The glasses of varying molar percentages of Eu3 + (0.02, 0.05 and 0.08 mole percent), were prepared to study the effect of variation in concentration of Eu3 + ions on the LIBS signal and to calculate its limit of detection (LOD). The spectral assignment of the observed LIBS spectrum has been made. In order to find the maximum signal to noise ratio, we also recorded the intensity of LIBS signal for various integration start delay (ISD) time at a constant power of (pulsed Nd: YAG) laser. The ocean optics LIBS 2500plus spectrometer along with a Q switched Nd:YAG laser (Quantel, Big Sky) were used to record the LIBS spectrum.

  19. An Update on the Lithium-Ion Cell Low-Earth-Orbit Verification Test Program

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Manzo, Michelle A.; Miller, Thomas B.; McKissock, Barbara I.; Bennett, William

    2007-01-01

    A Lithium-Ion Cell Low-Earth-Orbit Verification Test Program is being conducted by NASA Glenn Research Center to assess the performance of lithium-ion (Li-ion) cells over a wide range of low-Earth-orbit (LEO) conditions. The data generated will be used to build an empirical model for Li-ion batteries. The goal of the modeling will be to develop a tool to predict the performance and cycle life of Li-ion batteries operating at a specified set of mission conditions. Using this tool, mission planners will be able to design operation points of the battery system while factoring in mission requirements and the expected life and performance of the batteries. Test conditions for the program were selected via a statistical design of experiments to span a range of feasible operational conditions for LEO aerospace applications. The variables under evaluation are temperature, depth-of-discharge (DOD), and end-of-charge voltage (EOCV). The baseline matrix was formed by generating combinations from a set of three values for each variable. Temperature values are 10 C, 20 C and 30 C. Depth-of-discharge values are 20%, 30% and 40%. EOCV values are 3.85 V, 3.95 V, and 4.05 V. Test conditions for individual cells may vary slightly from the baseline test matrix depending upon the cell manufacturer s recommended operating conditions. Cells from each vendor are being evaluated at each of ten sets of test conditions. Cells from four cell manufacturers are undergoing life cycle tests. Life cycling on the first sets of cells began in September 2004. These cells consist of Saft 40 ampere-hour (Ah) cells and Lith ion 30 Ah cells. These cells have achieved over 10,000 cycles each, equivalent to about 20 months in LEO. In the past year, the test program has expanded to include the evaluation of Mine Safety Appliances (MSA) 50 Ah cells and ABSL battery modules. The MSA cells will begin life cycling in October 2006. The ABSL battery modules consist of commercial Sony hard carbon 18650 lithium-ion

  20. Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

    NASA Astrophysics Data System (ADS)

    Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

    2012-03-01

    For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120-9336 μg g-1) as well as for Sr (9-2150 μg g-1). Concentration variations in enamel are partly induced during post-mortem alteration and during amelogenesis, but the major contribution originates from the variable water chemistry in the habitats of the Hippopotamids which is dominated by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.5. These elements are well correlated with MgO and Na2O in single specimens, thus suggesting that their distribution is determined by a common, single process. Presuming that the shape of the tooth is established at the end of the secretion process and apatite composition is in equilibrium with the enamel fluid, the maturation process can be modeled by closed system Rayleigh crystallization. Enamel from many Hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores, but the compositions extend well into the levels of plants and carnivores. Within enamel from single specimens these element ratios covary and provide a specific fingerprint of the Hippopotamid habitat. All specimens together, however, define subparallel trends with different Ba

  1. Honeycomb-shaped coordination polymers based on the self-assembly of long flexible ligands and alkaline-earth ions

    NASA Astrophysics Data System (ADS)

    Lian, Chen; Liu, Liu; Guo, Xu; Long, Yinshuang; Jia, Shanshan; Li, Huanhuan; Yang, Lirong

    2016-01-01

    Two novel coordination polymers, namely, [Ca(NCP)2]∞ (I) and [Sr(NCP)2]∞ (II) were synthesized under hydrothermal conditions based on 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline (HNCP) and characterized by elemental analysis, infrared spectrometry, X-ray powder diffraction and single crystal X-ray diffraction. Findings indicate that I and II are isomorphous and isostructural, containing the unit of M(NCP-)4 (M=Ca(II) and Sr(II)), based on which to assemble into three-dimensional (3D) porous 4-fold interpenetration honeycomb-shaped neutral coordination polymers (CPs). Between the adjacent lamellar structures in I and II, there exist π-π interactions between the pyridine rings belonging to phenanthroline of NCP- which stabilize the frameworks. Both I and II display stronger fluorescence emissions as well as high thermal stability.

  2. Ion Temperatures in Earth's Inner Magnetosphere: Ring Current Dynamics, Transient Effects, and Data-Model Comparisons

    NASA Astrophysics Data System (ADS)

    Elfritz, Justin G.

    Earth's magnetosphere is an inherently complex, strongly nonlinear system with intrinsic coupling between internal and external drivers. In general, magnetospheric systems can be understood as a balance between multiple regions which all exhibit unique plasma properties. The feedback processes between each region depend on geomagnetic activity levels and the preceding states of the solar wind and the respective magnetospheric regions. Of particular interest is understanding how ion temperatures evolve during geomagnetically active periods, and also understanding the space weather impacts of hot ion populations injected during such periods. Dynamic, spatiotemporally resolved ion temperature boundary conditions have been implemented into the Comprehensive Ring Current Model (CRCM); the temperatures are based on 2-D equatorial maps derived from remotely imaged energetic neutral atom (ENA) measurements. The high-speed-stream-driven event on 22 July 2009 and the coronal mass ejection-driven event on 30-31 October 2013 are simulated and compared against identical simulations using a statistically derived boundary condition model. This new method for establishing boundary conditions allows users to include event-specific observations associated with a dynamic plasma sheet. It is found that spatial and energy distributions in the storm-time ring current exhibit sensitive dependence on boundary conditions during these events. The coupling of boundary conditions to the time history of the convection electric field strength is found to play an important role in throttling the influence of the boundary plasma on the inner magnetosphere. Storm-time dusk-dawn asymmetries consistent with observational data are reproduced well when CRCM is provided with the event-specific boundary condition model. The dependence of average, global magnetospheric ion temperatures derived from ENA maps is also investigated as a function of various combinations of solar wind parameters, IMF

  3. Spectroscopic analyses of trivalent rare-earth ions doped in different host materials

    NASA Astrophysics Data System (ADS)

    Chandrasekharan, Sreerenjini

    2011-12-01

    Trivalent rare-earth (RE3+) ions of 4f n electronic configurations are found to possess potential applications in the field of optoelectronic and biophotonic technologies owing to their unique optical properties. They have been used as optical activators in a large number of solid-state laser host materials due to their rich energy level structure. This work focuses on the spectroscopic study of two RE 3+ ions, namely, trivalent erbium and neodymium (Er3+ and Nd3+, respectively), embedded in some important single crystal and nanocrystalline host materials including yttrium orthoaluminate (YAlO3), erbium oxide (Er2O3), yttrium oxide (Y2O3) and a combined host system of Y2O 3 and a vinyl polymer named Polymethyl Methacrylate (PMMA). Each one of these host materials are known to be unique for their characteristic properties such as chemical durability, thermal stability, optical clarity, wide band gaps, biocompatibility, and success as phosphors in various optoelectronic devices. The complete material characterization has been performed through morphology analyses using advanced microscopy techniques and spectroscopic analyses of the characteristic absorption and emission spectra by applying phenomenological crystal-field splitting and Judd-Ofelt techniques. The important spectroscopic parameters such as line strengths, radiative decay rates, and branching ratios have been obtained for the intermanifold transitions from the upper multiplets to the corresponding lower-lying multiplet manifolds 2S+1LJ of RE3+ ions doped in various host systems. Using the radiative decay rates, radiative life times are obtained and the experimental analyses of the fluorescent spectra yield the measured lifetimes of emitting metastable states. Finally, the results are compared with the previously published set of values for the same ions doped in similar type of host systems. Detailed analyses of the spectroscopic properties show that the studied systems RE3+ doped single crystals and

  4. Modification of phonon processes in nanostructured rare-earth-ion-doped crystals

    NASA Astrophysics Data System (ADS)

    Lutz, Thomas; Veissier, Lucile; Thiel, Charles W.; Cone, Rufus L.; Barclay, Paul E.; Tittel, Wolfgang

    2016-07-01

    Nano-structuring impurity-doped crystals affects the phonon density of states and thereby modifies the atomic dynamics induced by interaction with phonons. We propose the use of nano-structured materials in the form of powders or phononic bandgap crystals to enable or improve persistent spectral hole burning and coherence for inhomogeneously broadened absorption lines in rare-earth-ion-doped crystals. This is crucial for applications such as ultra-precise radio-frequency spectrum analyzers and optical quantum memories. As an example, we discuss how phonon engineering can enable spectral hole burning in erbium-doped materials operating in the convenient telecommunication band and present simulations for density of states of nano-sized powders and phononic crystals for the case of Y2SiO5 , a widely used material in current quantum memory research.

  5. Improving the intensity and efficiency of compressed echo in rare-earth-ion-doped crystal

    NASA Astrophysics Data System (ADS)

    Xiu-Rong, Ma; Yu-Qing, Liang; Song, Wang; Shuang-Gen, Zhang; Yun-Long, Shan

    2016-07-01

    We investigate the intensity and efficiency of a compressed echo, which is important in arbitrary waveform generation (AWG). A new model of compressed echo is proposed based on the optical Bloch equations, which exposes much more detailed parameters than the conventional model, such as the time delay of the chirp lasers, the nature of the rare-earth-ion-doped crystal, etc. According to the novel model of compressed echo, we find that reducing the time delay of the chirp lasers and scanning the lasers around the center frequency of the inhomogeneously broadened spectrum, while utilizing a crystal with larger coherence time and excitation lifetime can improve the compressed echo’s intensity and efficiency. The theoretical analysis is validated by numerical simulations. Project supported by Special Funds for Scientific and Technological Innovation Projects in Tianjin, China (Grant No. 10FDZDGX00400) and the Tianjin Research Program of Application Foundation and Advanced Technology, China (Grant No. 15JCQNJC01100).

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

    PubMed

    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. PMID:25379879

  7. Improving the intensity and efficiency of compressed echo in rare-earth-ion-doped crystal

    NASA Astrophysics Data System (ADS)

    Xiu-Rong, Ma; Yu-Qing, Liang; Song, Wang; Shuang-Gen, Zhang; Yun-Long, Shan

    2016-07-01

    We investigate the intensity and efficiency of a compressed echo, which is important in arbitrary waveform generation (AWG). A new model of compressed echo is proposed based on the optical Bloch equations, which exposes much more detailed parameters than the conventional model, such as the time delay of the chirp lasers, the nature of the rare-earth-ion-doped crystal, etc. According to the novel model of compressed echo, we find that reducing the time delay of the chirp lasers and scanning the lasers around the center frequency of the inhomogeneously broadened spectrum, while utilizing a crystal with larger coherence time and excitation lifetime can improve the compressed echo’s intensity and efficiency. The theoretical analysis is validated by numerical simulations. Project supported by Special Funds for Scientific and Technological Innovation Projects in Tianjin, China (Grant No. 10FDZDGX00400) and the Tianjin Research Program of Application Foundation and Advanced Technology, China (Grant No. 15JCQNJC01100).

  8. Effect of rare earth ions on the properties of glycine phosphite single crystals

    NASA Astrophysics Data System (ADS)

    Senthilkumar, K.; Moorthy Babu, S.; Kumar, Binay; Bhagavannarayana, G.

    2013-01-01

    Optically transparent glycine phosphite (GPI) single crystals doped with rare earth metal ions (Ce, Nd and La) were grown from aqueous solution by employing the solvent evaporation and slow cooling methods. Co-ordination of dopants with GPI was confirmed by X-ray fluorescence spectroscopic analysis. Single crystal X-ray diffraction analysis was carried out to determine the lattice parameters and to analyze the structural morphology of GPI with dopants, which indicates that cell parameters of doped crystals were significantly varied with pure GPI. Crystalline perfection of doped GPI crystals was determined by high resolution X-ray diffraction analysis by means of full width at half maximum values. Influence of the dopants on the optical properties of the material was determined. Paraelectric to ferroelectric transition temperature (Tc) of doped GPI crystals were identified using differential scanning calorimetric measurements. Piezoelectric charge coefficient d33 was measured for pure and doped GPI crystals. Hysteresis (P-E) loop was traced for ferroelectric b-axis and (100) plane of pure and doped GPI crystals with different biasing field and ferroelectric parameters were calculated. Mechanical stability of crystals was determined by Vickers microhardness measurements; elastic stiffness constant 'C11' and yield strength 'σy' were calculated from hardness values. Mechanical and ferroelectric properties of doped crystals were improved with doping of rare earth metals.

  9. Hybrid quantum nanophotonic devices for coupling to rare-earth ions

    NASA Astrophysics Data System (ADS)

    Miyazono, Evan; Hartz, Alex; Zhong, Tian; Faraon, Andrei

    2015-03-01

    With an assortment of narrow line-width transitions spanning the visible and IR spectrum and long spin coherence times, rare-earth doped crystals are the leading material system for solid-state quantum memories. Integrating these materials in an on-chip optical platform would create opportunities for highly integrated light-matter interfaces for quantum communication and quantum computing. Nano-photonic resonators with high quality factors and small mode volumes are required for efficient on-chip coupling to the small dipole moment of rare-earth ion transitions. However, direct fabrication of optical cavities in these crystals with current nanofabrication techniques is difficult and unparallelized, as either exotic etch chemistries or physical milling processes are required. We fabricated hybrid devices by mechanically transferring a nanoscale membrane of gallium arsenide (GaAs) onto a neodymium-doped yttrium silicon oxide (Y2SiO5) crystal and then using electron beam lithography and standard III-V dry etching to pattern nanobeam photonic crystal cavities and ring resonator cavities, a technique that is easily adapted to other frequency ranges for arbitrary dopants in any rare earth host system. Single crystalline GaAs was chosen for its low loss and high refractive index at the transition wavelength. We demonstrated the potential to evanescently couple between the cavity field and the 883 nm 4I9/2- 4F3/2 transition of nearby neodymium impurities in the host crystal by examining transmission spectra through a waveguide coupled to the resonator with a custom-built confocal microscope. The prospects and requirements for using this system for scalable quantum networks are discussed.

  10. Visible WGM emissions from rare earth ion doped ZnO microspheres

    NASA Astrophysics Data System (ADS)

    K, Fabitha; Rao, M. S. Ramachandra

    ZnO is known to be an ideal candidate for short wavelength range opto-electronic device applications due to its wide and direct bandgap (3.37 eV) and high excitonic binding energy (60 meV). Apart from the UV emission at ~380 nm (free exciton emission) ZnO also possesses a broad emission band centered at ~530 nm which is expected to be originated from the oxygen vacancy (Vo) defects. In rare earth (RE) ion doped ZnO, emissions originate from the 4f levels of RE ions will be obtained in addition to the characteristic emissions of ZnO. Small micro/nanostructures made of ZnO with high crystalline quality show unique characteristics in light emission, especially in lasing applications. A micro/ nanostructured ZnO crystal generally has a wurtzite structure with a natural hexagonal cross section, which serves as a WGM lasing micro cavity owing to its high reflective index (~2). However, there exists a potential optical loss at corners of hexagons; therefore, an isotropic structure like spheres may be a better candidate to achieve efficient light confinement. In our work, highly smooth micro spheres with different diameters were grown. Raman spectroscopy measurements confirm the hexagonal wurtzite structure of ZnO, SEM and AFM studies shows the smooth surfaced spheres. WGM lasing characteristics of ZnO spheres have been investigated using optical pumping with 488 nm laser in a micro-PL system. Details of the results will be presented.

  11. Upconversion effective enhancement by producing various coordination surroundings of rare-Earth ions.

    PubMed

    Huang, Qingming; Yu, Han; Ma, En; Zhang, Xinqi; Cao, Wenbing; Yang, Chengang; Yu, Jianchang

    2015-03-16

    In this manuscript, we present a simple route to enhance upconversion (UC) emission by producing two different coordination sites of trivalent cations in a matrix material and adjusting crystal field asymmetry by Hf(4+) co-doping. A cubic phase, Y3.2Al0.32Yb0.4Er0.08F12, with these structural characteristics was synthesized successfully by introducing a small ion (Al(3+)) into YF3. X-ray diffraction (XRD), nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), X-ray spectroscopy (XPS), and fluorescence spectrophotometry (FS) were employed for its crystalline structure and luminescent property analysis. As a result, the coordination environments of the rare-earth ions were varied more obviously than a hexagonal NaYF4 matrix with the same Hf(4+) co-doping concentration, with vertical comparison, UC luminescent intensities of cubic Y3.2Al0.32Yb0.4Er0.08F12 were largely enhanced (∼32-80 times greater than that of different band emissions), while the maximum enhancement of hexagonal NaYF4 was by a factor of ∼12. According to our experimental results, the mechanism has been demonstrated involving the crystalline structure, crystal field asymmetry, luminescence lifetime, hypersensitive transition, and so on. The study may be helpful for the design and fabrication of high-performance UC materials.

  12. Unambiguously identifying spin states of transition-metal ions in the Earth (Invited)

    NASA Astrophysics Data System (ADS)

    Hsu, H.

    2010-12-01

    The spin state of a transition-metal ion in crystalline solids, defined by the number of unpaired electrons in the ion’s incomplete 3d shell, may vary with many factors, such as temperature, pressure, strain, and the local atomic configuration, to name a few. Such a phenomenon, known as spin-state crossover, plays a crucial role in spintronic materials. Recently, the pressure-induced spin-state crossover in iron-bearing minerals has been recognized to affect the minerals’ structural and elastic properties. However, the detailed mechanism of such crossover in iron-bearing magnesium silicate perovskite, the most abundant mineral in the Earth, remains unclear. A significant part of this confusion arises from the difficulty in reliably extracting the spin state from experiments. For the same reason, the thermally-induced spin-state crossover in lanthanum cobaltite (LaCoO3) has been controversial for more than four decades. In this talk, I will discuss how first-principle calculations can help clarifying these long-standing controversies. In addition to the total energy, equation of state, and elastic properties of each spin state, first-principle calculations also predict the electric field gradient (EFG) at the nucleus of each transition-metal ion. Our calculations showed that the nuclear EFG, a quantity that can be measured via Mössbauer or nuclear magnetic resonance (NMR) spectroscopy, depends primarily on the spin state, irrespective of the concentration or configuration of transition-metal ions. Such robustness makes EFG a unique fingerprint to identify the spin state. The combination of first-principle calculations and Mössbauer/NMR spectroscopy can therefore be a reliable and efficient approach in tackling spin-state crossover problems in the Earth. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The

  13. Removal of titanium dioxide nanoparticles by coagulation: effects of coagulants, typical ions, alkalinity and natural organic matters.

    PubMed

    Wang, H T; Ye, Y Y; Qi, J; Li, F T; Tang, Y L

    2013-01-01

    To investigate the possibility of removing titanium dioxide nanoparticles (TiO2 NPs) from water by coagulation, as well as to find the optimal coagulant and experimental conditions for TiO2 NP removal, four types of coagulant were adopted: polyferric sulfate (PFS), ferric chloride (FeCl3), polyaluminum chloride (PACl), and alum (Al2(SO4)3). It was found that the removal of TiO2 NPs by coagulation was affected by ionic strength, alkalinity, as well as types and dosages of coagulants. PFS and FeCl3 achieved much higher removal efficiency of TiO2 NPs than PACl and Al2(SO4)3 did. For 30 mg/L TiO2 NPs, a dosage of 0.3 mM PFS (as Fe) achieved 84% removal after coagulation followed by 30 min settlement. Optimal ionic strength (0.1 M NaCl or 0.03 M CaCl2) is of vital importance for the performance of PFS. Na2SO4 is unfavorable for the performance of PFS. Optimal alkalinity (0.01-0.03 M NaHCO3) is necessary for FeCl3 to remove TiO2 NPs. Natural organic matter, as represented by humic acid (HA) up to 11 mg/L, reduces the removal of TiO2 NPs by coagulation. These findings indicate that coagulation is a good option for the removal of TiO2 NPs from water, and more attention should be paid to the effects of water quality when using coagulation to remove TiO2 NPs from aqueous matrices. This provides a possible solution to alleviate the potential hazard caused by TiO2 NPs.

  14. Possibility of formation of rare-earth negative ions by attachment of [ital f] electrons to the atomic ground state

    SciTech Connect

    Datta, D.; Beck, D.R. )

    1993-06-01

    Some recent experiments indicate that certain rare-earth negative ions exist. Some local-density calculations indicate that attachment of [ital f] electrons is most favorable for Tm and Md. Here we investigate by means of relativistic configuration-interaction methods whether Tm[sup [minus

  15. Dawn-dusk asymmetry in ion pitch-angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, C.; Zaharia, S. G.; Lyons, L. R.; Angelopoulos, V.

    2012-12-01

    We found a strong dawn-dusk asymmetry in ion pitch-angle anisotropy from spatial distributions statistically determined using THEMIS observations. The asymmetry varies significantly with ion energies and is a result of different processes. The anisotropy of ions below several hundreds eV in the tail plasma sheet (beyond X = 10 Re) and the near-Earth magnetosphere (inside r = 10 Re) is dominantly negative (relatively higher particle fluxes near 0 and 180 degree pitch-angle) and is more strongly negative in the post-midnight sector than the pre-midnight sector. The negative anisotropy is likely caused by field-aligned ionosphere outflow and the post-midnight enhancement is correlated with stronger electron precipitation energy fluxes that create stronger outflow. For ions between 1 to 10 keV in the near-Earth magnetosphere, anisotropy is found to be strongly positive (relatively higher fluxes near 90 degree pitch-angle) in the morning sector while near isotropic in the evening sector. Comparing the fluxes within the region of the positive anisotropy with other MLTs suggests that the positive anisotropy is caused by field-aligned ions not being able to drift as earthward as 90 degree ions. For ions of 10 keV and above, magnetic drift shell splitting results in strongly positive anisotropy on the dayside, while additional magnetopause shadowing causes strongly negative anisotropy in the post-midnight sector.

  16. Off-centering of rare-earth ion in (Ba,R)(Ti,Mg)O3 (R = Gd, Dy)

    NASA Astrophysics Data System (ADS)

    Takeda, Shoichi; Yasuda, Satoshi; Moriyoshi, Chikako; Kuroiwa, Yoshihiro; Honda, Atsushi; Inoue, Noriyuki; Higai, Shin'ichi; Ando, Akira

    2016-10-01

    To investigate the off-centering behavior of rare-earth ions that were partially substituted for A site ions in ABO3-type crystals, accurate crystal structure analyses of (Ba,R)(Ti,Mg)O3 (R = Gd, Dy) were performed by high-energy synchrotron radiation X-ray powder diffraction analysis and the maximum entropy method (MEM)/Rietveld method. The R ions were observed at the six equivalent off-center sites in the <100> directions from the corner of a unit cell in the cubic phase. In the tetragonal phase, the R ions occupied one off-center site along the [001] direction. The R off-centering can be attributed to the covalent nature of the bond between the R and O ions in (Ba,R)(Ti,Mg)O3 crystals.

  17. Enhanced diffusive ion scattering in front of the Earth's quasi-parallel bow shock: a case study

    NASA Astrophysics Data System (ADS)

    Kis, Arpad; Scholer, Manfred; Klecker, Berndt; Lucek, Elisabeth; Dandouras, Iannis; Lemperger, István; Wesztergom, Viktor; Novák, Attila; Szalai, Sándor

    2014-05-01

    In our study we report on observations of energetic ions upstream of the Earth's quasi-parallel bow shock by Cluster at times of large inter-spacecraft separation distance. For the analysis we use the ion data provided by the CIS-HIA in the 10-32 keV energy range and the magnetic data recorded by the FGM instrument. We determine the spatial gradient of partial energetic ion densities at various distances from the bow shock. The gradient in all energy channels decreases exponentially with distance and the e-folding distance of the gradients depends approximately linearly on energy but there is a significant difference in their values obtained at the observed three upstream ion events. We demonstrate for the first time that under specific interplanetary conditions the mechanism of the diffuse ion scattering can change significantly and results in an anomalous diffusive process charactized by an unusually small e-folding distance.

  18. Corrosion of Sn-Co alloy in alkaline media and the effect of Cl - and Br - ions

    NASA Astrophysics Data System (ADS)

    Refaey, S. A. M.

    1999-05-01

    Sn-Co electrodeposits alloy of approximate composition 80% Sn-20% Co (wt%) can be obtained from a gluconate bath as single phase CoSn 2, which is similar in appearance to decorative chromium. The potentiodynamic and cyclic voltammogram techniques were used to study the corrosion behaviour of CoSn 2 in sodium borate solutions (Na 2B 4O 7) at pH=9.6. The effect of different factors such as concentration of borate ions, pH, potential scan rate, successive cyclic voltammetry, and progressive addition of halide ions (Cl - and Br -) on the electrochemical behaviour of CoSn 2 alloys are discussed. The observed corrosion resistance of electrodeposited CoSn 2 alloy is due to the formation of a thin passive film, which is examined by X-ray spectroscopy and believed to be mainly tin and cobalt oxides. The voltammograms involve four anodic peaks, the first and second of which correspond to the formation of SnO and SnO 2 and the third and fourth related to the formation of cobalt oxides. SEM examination confirms that pitting corrosion takes place in presence of borax and is increased by adding halide ions.

  19. Impurity trapped exciton states related to rare earth ions in crystals under high hydrostatic pressure

    SciTech Connect

    Grinberg, M. Mahlik, S.

    2013-01-15

    Emission related to rare earth ions in solids takes place usually due to 4f{sup n} {yields} 4f{sup n} and 4f{sup n-1}5d{sup 1} {yields} 4f{sup n} internal transitions. In the case of band to band excitation the effective energy transfer from the host to optically active impurity is required. Among other processes one of the possibilities is capturing of the electron at excited state and hole at the ground state of impurity. Localization of electron or hole at the dopand site creates a long range Coulomb potential that attracts the second carrier which then occupies the localized Rydberg-like states. Such a system can be considered as impurity trapped exciton. Usually impurity trapped exciton is a short living phenomenon which decays non-radiatively leaving the impurity ion in the excited state. However, in several compounds doped with Eu{sup 2+} the impurity trapped exciton states become stable and contribute to the radiative processes though anomalous luminescence that appears apart of the 4f{sup 7} {yields} 4f{sup 7} and 4f{sup 7}5d{sup 1} {yields} 5f{sup 7} emission. In this contribution pressure effect on energies of the 4f{sup n-1}5d{sup 1}{yields}5f{sup n} transitions in Ln doped oxides and fluorides as well as influence of pressure on the energy of impurity trapped exciton states is discussed. The latest results on high pressure investigations of luminescence related to Pr{sup 3+}, and Eu{sup 2+} in different lattices are reviewed.

  20. On the origin of the energetic ion events measured upstream the Earth's bow shock by STEREO, Cluster and Geotail

    NASA Astrophysics Data System (ADS)

    Kronberg, Elena; Bucik, Radoslav; Haaland, Stein E.; Klecker, Berndt; Keika, Kunihiro; Desai, Mihir; Daly, Patrick; Yamauchi, M.; Gomez-Herrero, Raul; Lui, Anthony

    The observations of upstream events up to distance of 3800 RE from Earth's bow shock were reported during the declining phase of the solar cycle in 2007. These upstream events mainly occurred after corotating interaction region (CIR) passed the Earth's magnetosphere. We study the relation between the upstream events observed from about 70 to 1750 RE away from the Earth and observations in the vicinity of the terrestrial bow shock (up to 30 RE). For this purpose, simultaneous measurements of energetic ions from STEREO-A, STEREO-B (far upstream region), and from Cluster and Geotail (near the bow shock) are used. In almost all cases the energetic ions far upstream are associated with the upstream events near the bow shock. The latter often coincide with sunward directed electron bursts, increased AE index (¿200 nT), intermittent sunward ion flows and the presence of the O+ ions, all of which imply a magnetospheric origin. We investigate possible mechanisms of CIR -magnetosphere interactions triggering acceleration and / or release of energetic particles.

  1. Synthesis and structure of some nano-sized rare-earth metal ions doped potassium hexacyanoferrates

    NASA Astrophysics Data System (ADS)

    Narayan, Himanshu; Alemu, Hailemichael; Nketsa, Pusetso F.; Manatha, Toka J.; Madhavi Thakurdesai, And

    2015-05-01

    Rare-earth ions doped potassium hexacyanoferrates (KR-HCF); with the general formula KRFe(CN)6 · 3H2 O [with, R≡Y, Gd and Yb] nanoparticles were synthesized through precipitation. Characterization was done through particle-size analyzer, scanning electron microscopy (SEM), Fourier Transform infra-red (FTIR) and Raman spectroscopy, and powder X-ray diffraction (XRD). The XRD data was analyzed on FullProf Software Suite program and the unit-cell structure and lattice parameters of KR-HCF samples were determined from scratch and refined further. All the three KR-HCF nanoparticles seem to crystallize in the orthorhombic primitive PMMM space-group. Reasonably good agreement was found with the previously reported lattice constants of KGd-HCF and KYb-HCF orthorhombic single-crystals, except that they assume different space-groups. The observed dissimilarity of space-groups may be attributed to the different time scales involved in the synthesis process. Moreover, the crystal structure of KYFe(CN)6 · 3H2 O nanoparticles is being reported for the very first time.

  2. First-principles study of fission product (Xe, Cs, Sr) incorporation and segregation in alkaline earth metal oxides, HfO2, and MgO-HfO2 interface

    SciTech Connect

    Liu, Xiang-yang; Uberuaga, Blas P; Sickafus, Kurt E

    2008-01-01

    In order to close the nuclear fuel cycle, advanced concepts for separating out fission products are necessary. One approach is to use a dispersion fuel form in which a fissile core is surrounded by an inert matrix that captures and immobilizes the fission products from the core. If this inert matrix can be easily separated from the fuel, via e.g. solution chemistry, the fission products can be separated from the fissile material. We examine a surrogate dispersion fuel composition, in which hafnia (HfO{sub 2}) is a surrogate for the fissile core and alkaline earth metal oxides are used as the inert matrix. The questions of fission product incorporation in these oxides and possible segregation behavior at interfaces are considered. Density functional theory based calculations for fission product elements (Xe, Sr, and Cs) in these oxides are carried out. We find smaller incorporation energy in hafnia than in MgO for Cs and Sr, and Xe if variation of charge state is allowed. We also find that this trend is reversed or reduced for alkaline earth metal oxides with large cation sizes. Model interfacial calculations show a strong tendency of segregation from bulk MgO to MgO-HfO{sub 2} interfaces.

  3. Alkaline quinone flow battery.

    PubMed

    Lin, Kaixiang; Chen, Qing; Gerhardt, Michael R; Tong, Liuchuan; Kim, Sang Bok; Eisenach, Louise; Valle, Alvaro W; Hardee, David; Gordon, Roy G; Aziz, Michael J; Marshak, Michael P

    2015-09-25

    Storage of photovoltaic and wind electricity in batteries could solve the mismatch problem between the intermittent supply of these renewable resources and variable demand. Flow batteries permit more economical long-duration discharge than solid-electrode batteries by using liquid electrolytes stored outside of the battery. We report an alkaline flow battery based on redox-active organic molecules that are composed entirely of Earth-abundant elements and are nontoxic, nonflammable, and safe for use in residential and commercial environments. The battery operates efficiently with high power density near room temperature. These results demonstrate the stability and performance of redox-active organic molecules in alkaline flow batteries, potentially enabling cost-effective stationary storage of renewable energy. PMID:26404834

  4. Alkaline quinone flow battery.

    PubMed

    Lin, Kaixiang; Chen, Qing; Gerhardt, Michael R; Tong, Liuchuan; Kim, Sang Bok; Eisenach, Louise; Valle, Alvaro W; Hardee, David; Gordon, Roy G; Aziz, Michael J; Marshak, Michael P

    2015-09-25

    Storage of photovoltaic and wind electricity in batteries could solve the mismatch problem between the intermittent supply of these renewable resources and variable demand. Flow batteries permit more economical long-duration discharge than solid-electrode batteries by using liquid electrolytes stored outside of the battery. We report an alkaline flow battery based on redox-active organic molecules that are composed entirely of Earth-abundant elements and are nontoxic, nonflammable, and safe for use in residential and commercial environments. The battery operates efficiently with high power density near room temperature. These results demonstrate the stability and performance of redox-active organic molecules in alkaline flow batteries, potentially enabling cost-effective stationary storage of renewable energy.

  5. Ion exchange polymers and method for making

    NASA Technical Reports Server (NTRS)

    Philipp, Warren H. (Inventor); Street, Kenneth W., Jr. (Inventor)

    1994-01-01

    An ion exchange polymer comprised of an alkali metal or alkaline earth metal salt of a poly(carboxylic acid) in a poly(vinyl acetal) matrix is described. The polymer is made by treating a mixture made of poly(vinyl alcohol) and poly(acrylic acid) with a suitable aldehyde and an acid catalyst to cause acetalization with some cross-linking. The material is then subjected to an alkaline aqueous solution of an alkali metal salt or an alkali earth metal salt. All of the film forming and cross-linking steps can be carried out simultaneously, if desired.

  6. A study on lithium/air secondary batteries-Stability of the NASICON-type lithium ion conducting solid electrolyte in alkaline aqueous solutions

    NASA Astrophysics Data System (ADS)

    Shimonishi, Yuta; Zhang, Tao; Imanishi, Nobuyuki; Im, Dongmin; Lee, Dong Joon; Hirano, Atsushi; Takeda, Yasuo; Yamamoto, Osamu; Sammes, Nigel

    The stability of the high lithium ion conducting glass ceramics, Li 1+ x+ yTi 2- xAl xSi yP 3- yO 12 (LTAP) in alkaline aqueous solutions with and without LiCl has been examined. A significant conductivity decrease of the LTAP plate immersed in 0.057 M LiOH aqueous solution at 50 °C for 3 weeks was observed. However, no conductivity change of the LTAP plate immersed in LiCl saturated LiOH aqueous solutions at 50 °C for 3 weeks was observed. The pH value of the LiCl-LiOH-H 2O solution with saturated LiCl was in a range of 7-9. The molarity of LiOH and LiCl in the LiOH and LiCl saturated aqueous solution were estimated to be 5.12 and 11.57 M, respectively, by analysis of Li + and OH -. The high concentration of LiOH and the low pH value of 8.14 in this solution suggested that the dissociation of LiOH into Li + and OH - is too low in the solution with a high concentration of Li +. These results suggest that the water stable LTAP could be used as a protect layer of the lithium metal anode in the lithium/air cell with LiCl saturated aqueous solution as the electrolyte, because the content of OH - ions in the LiCl saturated aqueous solution does not increase via the cell reaction of Li + 1/2O 2 + H 2O → 2LiOH, and LTAP is stable under a deep discharge state.

  7. Carbon quantum dots directly generated from electrochemical oxidation of graphite electrodes in alkaline alcohols and the applications for specific ferric ion detection and cell imaging.

    PubMed

    Liu, Mengli; Xu, Yuanhong; Niu, Fushuang; Gooding, J Justin; Liu, Jingquan

    2016-04-25

    Carbon quantum dots (CQDs) are attracting tremendous interest owing to their low toxicity, water dispersibility, biocompatibility, optical properties and wide applicability. Herein, CQDs with an average diameter of (4.0 ± 0.2) nm and high crystallinity were produced simply from the electrochemical oxidation of a graphite electrode in alkaline alcohols. The as-formed CQDs dispersion was colourless but the dispersion gradually changed to bright yellow when stored in ambient conditions. Based on UV-Vis absorption, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM), this colour change appeared to be due to oxygenation of surface species over time. Furthermore, the CQDs were used in specific and sensitive detection of ferric ion (Fe(3+)) with broad linear ranges of 10-200 μM with a low limit of detection of 1.8 μM (S/N = 3). The application of the CQDs for Fe(3+) detection in tap water was demonstrated and the possible mechanism was also discussed. Finally, based on their good characteristics of low cytotoxicity and excellent biocompatibility, the CQDs were successfully applied to cell imaging. PMID:26878217

  8. Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

    SciTech Connect

    Chen Daqin; Wang Yuansheng Yu Yunlong; Huang Ping; Weng Fangyi

    2008-10-15

    Transparent SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} bulk nano-composites triply doped with Ho{sup 3+}, Tm{sup 3+} and Yb{sup 3+} were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the {beta}-YF{sub 3} crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%. - Graphical abstract: Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb{sup 3+} to Ho{sup 3+} or Tm{sup 3+}. Various colors of luminescence, including bright perfect white light with CIE-X=0.351 and CIE-Y=0.306, can be easily tuned by adjusting the concentrations of the rare earth ions in the transparent oxyfluoride glass ceramics.

  9. Stark level analysis of the spectral line shape of electronic transitions in rare earth ions embedded in host crystals

    NASA Astrophysics Data System (ADS)

    Steinkemper, H.; Fischer, S.; Hermle, M.; Goldschmidt, J. C.

    2013-05-01

    Rare earth ions embedded in host crystals are of great interest for many applications. Due to the crystal field of the host material, the energy levels of the rare earth ions split into several Stark levels. The resulting broadening of the spectral line shapes of transitions between those levels determines the upconversion phenomena, especially under broad-spectrum illumination, which are relevant for photovoltaics for instance. In this paper, we present a method to determine the spectral line shape of energy level transitions of rare earth ions from the absorption spectrum of the investigated material. A parameter model is used to describe the structure of the individual energy levels based on a representation of the Stark splitting. The parameters of the model are then determined with an evolutionary optimization algorithm. The described method is applied to the model system of β-NaEr0.2Y0.8F4. The results indicate that for illumination with a wavelength around 1523 nm, simple upconversion processes such as two-step absorption or direct energy transfer are less efficient than commonly assumed. Hence a sequence of efficient processes is suggested as an explanation for the high upconversion quantum yield of β-NaEr0.2Y0.8F4, which has not yet been reported in the literature.

  10. Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides

    PubMed Central

    Wang, Lili; Li, Bin; Zhao, Xiaohong; Chen, Chunxia; Cao, Jingjing

    2012-01-01

    Background The study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported. Methodology/Principal Findings The stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail. Conclusions/Significance S-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites. PMID:22693627

  11. Isolation and characterization of a metal ion-dependent alkaline protease from a halotolerant Bacillus aquimaris VITP4.

    PubMed

    Shivanand, Pooja; Jayaraman, Gurunathan

    2011-04-01

    A halotolerant bacterium Bacillus acquimaris VITP4 was used for the production of extracellular protease. Fractional precipitation using ammonium chloride was used to obtain the enzyme. The protease exhibited optimum activity at pH 8.0 and 40 degrees C and retained 50% of its optimal proteolytic activity even in the presence of 4 M NaCl, suggesting that it is halotolerant. The molecular mass of protease, as revealed by SDS-PAGE was found to be 34 kDa and the homogeneity of the enzyme was confirmed by gelatin zymography and reverse-phase HPLC. Upon purification, the specific activity of th enzyme increased from 533 U/mg to 1719 U/mg. Protease inhibitors like phenyl methane sulphonyl fluoride and 2-mercaptoethanol did not affect the activity of the enzyme, but EDTA inhibited the activity, indicating the requirement of metal ions for activity. Cu2, Ni2+ and Mn2+ enhanced the enzyme activity, but Zn2+, Hg2+ and Fe2+ decreased the activity, while Mg2+, Ca2+ and K+ had no effect on the enzyme activity. The protease was quite stable in the presence of cationic (CTAB), anionic (SDS) and neutral detergents (Triton X-100 and Tween-20) and exhibited antimicrobial activity against selected bacterial and fungal strains. The stability characteristics and broad spectrum antimicrobial activity indicated the potential use of this protease in industrial applications.

  12. Theory for charge states of energetic oxygen ions in the earth's radiation belts

    NASA Technical Reports Server (NTRS)

    Spjeldvik, W. N.; Fritz, T. A.

    1978-01-01

    Fluxes of geomagnetically trapped energetic oxygen ions have been studied in detail. Ion distributions in radial locations below the geostationary orbit, energy spectra between 1 keV and 100 MeV, and the distribution over charge states have been computed for equatorially mirroring ions. Both ionospheric and solar wind oxygen ion sources have been considered, and it is found that the charge state distributions in the interior of the radiation belts are largely independent of the charge state characteristics of the sources. In the MeV range, oxygen ions prove to be a more sensitive probe for radiation belt dynamics than helium ions and protons.

  13. Petrogenesis of coeval silica-saturated and silica-undersaturated alkaline rocks: Mineralogical and geochemical evidence from the Saima alkaline complex, NE China

    NASA Astrophysics Data System (ADS)

    Zhu, Yu-Sheng; Yang, Jin-Hui; Sun, Jin-Feng; Zhang, Ji-Heng; Wu, Fu-Yuan

    2016-03-01

    A combined study of zircon U-Pb ages, mineral chemistry, whole-rock elements and Sr-Nd-Hf isotopes was carried out for the Saima alkaline complex in the northeastern China, in order to investigate the source and petrogenesis of coeval silica-saturated and silica-undersaturated alkaline rocks. The Saima alkaline complex consists of nepheline syenites, quartz-bearing syenites and alkaline volcanic rocks (i.e., phonolite and trachyte), with minor mafic dikes and carbonatitic veins. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS) zircon U-Pb dating gives consistent ages of 230-224 Ma for these rocks, suggesting that they are coeval. All alkaline rocks in the Saima complex are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs) with significant negative Nb, Ta and Ti anomalies. Geochemical data and Sr-Nd-Hf isotopic compositions indicate that the various alkaline rocks were all derived from partial melting of an ancient, re-enriched lithospheric mantle in the garnet stability field, but experienced variable siliceous- or carbonate-rich crustal contamination. Based on petrographic evidence, mineral compositions, and whole-rock geochemical data, two distinct magmatic evolutionary trends are proposed to explain the coeval emplacement of the various rock types within the Saima alkaline complex. The silica-undersaturated rocks (nepheline syenites and phonolites) result from alkali feldspar + apatite + titanite crystal fractionation of an alkaline mafic parental melt combined with assimilation of marine carbonate host rocks. In contrast, the generation of silica-saturated rocks (quartz-bearing syenites and trachytes) may be attributed to subsequent and continued clinopyroxene + apatite + biotite crystal fractionation coupled with assimilation of siliceous sediments.

  14. A few remarks on the simulation and use of crystal field energy level schemes of the rare earth ions

    NASA Astrophysics Data System (ADS)

    Hölsä, Jorma; Lastusaari, Mika; Maryško, Miroslav; Tukia, Mika

    2005-02-01

    The usefulness of the simulation of the energy level schemes of the trivalent rare earth ( R3+) ions in the prediction of the properties of the rare earth compounds is demonstrated for a few selected cases emphasizing the connection between different spectroscopic and magnetic properties of the R 3+ ions. The importance of the calculated energy level schemes in the UV-VUV range in interpreting complicated spectra and designing new phosphors by energy transfer and quantum cutting is described. In the absence of direct measurements, the calculated energy level values can be very useful. The possibilities to interpret the magnetic properties of the R3+ (and R2+) ions are described by using the wave functions of the energy levels obtained from the energy level simulations. As a fine example, it is shown how the amount of an Eu 2+ impurity can be obtained from the calculation of the paramagnetic susceptibility as a function of temperature. The problems involved in the simulation of the 7FJ crystal field energy level scheme of the Eu 3+ ion are highlighted by using a comparison between the extensive literature data and calculated level schemes.

  15. Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Paulsen, Phillip E.; Steuber, Thomas J.

    1989-01-01

    Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests.

  16. Deceleration of the solar wind upstream from the earth's bow shock and the origin of diffuse upstream ions

    NASA Technical Reports Server (NTRS)

    Bame, S. J.; Asbridge, J. R.; Feldman, W. C.; Gosling, J. T.; Paschmann, G.; Skopke, N.

    1980-01-01

    Observations with the Los Alamos Scientific Laboratory/Max-Planck-Institut crossed-fan solar wind ion experiment on ISEE I reveal that the solar wind is decelerated and deflected away from the direction of the earth's bow shock as it enters that portion of the upstream region populated by diffuse bow shock ions and long-period (10-60 s) waves. Typically, the average directed velocity vector changes by 7-10 km/s as it enters the wave region. At times, average speed changes as large as 25-40 km/s are observed. Superposed upon these changes in average flow speed are large amplitude (+ or - 15) fluctuations in flow speed associated with the waves themselves. The observations suggest that the solar wind deceleration is the result of momentum transfer from reflected bow shock ions to the wind via the long-period waves as the reflected ion beams go unstable. The broad angular distributions of the diffuse ions thus appear to be produced as a consequence of the disruption of reflected ion beams.

  17. Solvent extraction of rare-earth ions based on functionalized ionic liquids

    SciTech Connect

    Sun, Xiaoqi; Dai, Sheng; Luo, Huimin

    2012-01-01

    We herein report the achievement of enhanced extractabilities and selectivities for separation of rare earth elements based on functionalized ionic liquids. This work highlights the potential of developing a comprehensive ionic liquid-based extraction strategy for rare earth elements using ionic liquids as both extractant and diluent.

  18. Influence of M2O3 (M = Al, Ga) glass modifiers on structure, thermal and spectroscopic properties of rare earth ions in lead phosphate based systems

    NASA Astrophysics Data System (ADS)

    Sołtys, Marta; Pisarska, Joanna; Żur, Lidia; Goryczka, Tomasz; Pisarski, Wojciech A.

    2014-05-01

    Influence of M2O3 (M = Al, Ga) modifiers oxide on local structure and spectroscopic properties of lead phosphate glasses containing rare earth ions was studied. Among the rare earths, the trivalent europium and erbium ions were selected as an optically active dopants. The thermal properties were examined using DSC, whereas the X-ray diffraction analysis was used in order to verify the structure glass matrix. Luminescence of rare earth ions in lead phosphate glasses was registered in visible and NIR spectral region. The excitation and emission spectra of lead-based systems are presented and discussed in relation to the effect of modifiers oxide M2O3 (M = Al, Ga). Luminescence lifetimes (τm) for the 5D0 state of Eu3+ ions and 4I13/2 state of Er3+ ions were also evaluated.

  19. An investigation into the electrochemical recovery of rare earth ions in a CsCl-based molten salt.

    PubMed

    Jiao, Shuqiang; Zhu, Hongmin

    2011-05-30

    A CsCl-based melt, was used as a supporting electrolyte for a fuel cycle in pyrochemical separation, as it has a high solubility for lanthanide oxide. Cyclic voltammetry and square wave voltammetry were carried out to investigate the cathodic reduction of those rare earth ions. The results prove that the cathodic process of La(III) ions dissolved in a CsCl-based melt, with a one-step reduction La(3+)+3e(-)=La, and is similar to those of other reports which have utilised LiCl-KCl or CaCl(2)-KCl molten salt systems. However, for the Ce(III) ions that dissolved in a CsCl-based melt, there is a significant difference when compared with published literature as there are two reduction steps instead of the reported single step Ce(3+)+e(-)=Ce(2+) and Ce(2+)+2e(-)=Ce. In order to explain the novel result, a detailed investigation was focused on the cathodic process of Ce(III) in a CsCl-based melt. The identification of the M-O (M=La, Ce) compounds that are stable in the electrolyte, as well as the determination of their solubility products, were carried out by potentiometric titration using an oxide ion sensor. Furthermore, the E-pO(2-) (potential-oxide ion) diagram for the M-O stable compound was constructed by combining both theoretical and experimental data.

  20. A scenario for solar wind penetration of earth's magnetic tail based on ion composition data from the ISEE 1 spacecraft

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.

    1992-01-01

    Based on He(2+) and H(-) ion composition data from the Plasma Composition Experiment on ISEE 1, a scenario is proposed for the solar wind penetration of the earth's magnetic tail, which does not require that the solar wind plasma be magnetized. While this study does not take issue with the notion that earth's magnetic field merges with the solar wind magnetic field on a regular basis, it focuses on certain aspects of interaction between the solar wind particles and the earth's field, e.g, the fact that the geomagnetic tail always has a plasma sheet, even during times when the physical signs of magnetic merging are weak or absent. It is argued that the solar plasma enters along slots between the tail lobes and the plasma sheet, even quite close to earth, convected inward along the plasma sheet boundary layer or adjacent to it, by the electric fringe field of the ever present low-latitude magnetopause boundary layer (LLBL). The required E x B drifts are produced by closing LLBL equipotential surfaces through the plasma sheet.

  1. Effect of microsolvation on hydrogen trapping potential of metal ions

    NASA Astrophysics Data System (ADS)

    Das, Ranjita; Bandaru, Sateesh; D'mello, Viola Caroline; Chattaraj, Pratim Kumar

    2013-03-01

    A thorough analysis is carried out to understand how the microsolvation affects the hydrogen adsorbing capacity of metal ions in the presence as well as absence of the counter ions. Calculations are done at different levels of theory by using different functionals and basis sets and also by using the BSSE correction. The Be2+ ion doped systems exhibit stronger interaction with the hydrogen molecule than the other metal doped systems. The extent of interaction is less affected by the method of computation. The reaction free energy values imply that adsorption on alkaline earth metal doped systems is spontaneous at room temperature. Interaction energies are favorable for hydrogen adsorption on the systems containing alkaline earth metal ions and the gravimetric density of adsorbed hydrogen molecule is more in those containing the alkali metal ions.

  2. Chirped dissipative ion-cyclotron solitons in the Earth's low-altitude ionospheric plasma with two ion species

    SciTech Connect

    Kovaleva, I. Kh.

    2013-03-15

    Conditions for the excitation of small-scale nonlinear ion-cyclotron gradient-drift dissipative structures in cold ionospheric plasma are considered. The solution for the wave electric field in this structure in the form of a chirped soliton satisfying the equation of the Ginzburg-Landau type is derived in the electrostatic approach. The dissipative structure as a whole represents the chirped soliton accompanied by the comoving quasineutral plasma hump. The possibility of the excitation of two modes of this type (the high- and low-frequency ones) in plasma containing light and heavy ion impurities is considered. The role of electromagnetic corrections and the possible contribution introduced by these structures to the transport processes in the ionosphere are discussed.

  3. Nobelium: tracer chemistry of the divalent and trivalent ions.

    PubMed

    Maly, J; Sikkeland, T; Silva, R; Ghiorso, A

    1968-06-01

    In the absence of oxidizing or reducing agents the chromatographic and coprecipitation behavior of element 102 is similar to that of the alkaline earth elements. After oxidation with ceric ions, the behavior is that expected of a trivalent actinide. Nobelium is the first actinide for which the +2 oxidation state is the most stable species in aqueous solution.

  4. Nobelium: tracer chemistry of the divalent and trivalent ions.

    PubMed

    Maly, J; Sikkeland, T; Silva, R; Ghiorso, A

    1968-06-01

    In the absence of oxidizing or reducing agents the chromatographic and coprecipitation behavior of element 102 is similar to that of the alkaline earth elements. After oxidation with ceric ions, the behavior is that expected of a trivalent actinide. Nobelium is the first actinide for which the +2 oxidation state is the most stable species in aqueous solution. PMID:17749450

  5. Energy transfer kinetics in oxy-fluoride glass and glass-ceramics doped with rare-earth ions

    SciTech Connect

    Sontakke, Atul D.; Annapurna, K.

    2012-07-01

    An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF{sub 4} nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF{sub 4} nano-crystals in host glass matrix under controlled post heat treatment of precursor oxy-fluoride glasses has been confirmed from XRD, FESEM, and transmission electron microscope (TEM) analysis. Further, the incorporation of dopant ions inside fluoride nano-crystals has been established through optical absorption and TEM-EDX analysis. The noticed decreasing trend in donor to acceptor energy transfer efficiency from precursor glass to glass-ceramics in all three combinations have been explained based on the structural rearrangements that occurred during the heat treatment process. The reduced coupling phonon energy for the dopant ions due to fluoride environment and its influence on the overall phonon assisted contribution in energy transfer process has been illustrated. Additionally, realization of a correlated distribution of dopant ions causing clustering inside nano-crystals has also been reported.

  6. Some Rare Earth Elements Analysis by Microwave Plasma Torch Coupled with the Linear Ion Trap Mass Spectrometry

    PubMed Central

    Xiong, Xiaohong; Jiang, Tao; Qi, Wenhao; Zuo, Jun; Yang, Meiling; Fei, Qiang; Xiao, Saijin; Yu, Aimin; Zhu, Zhiqiang; Chen, Huanwen

    2015-01-01

    A sensitive mass spectrometric analysis method based on the microwave plasma technique is developed for the fast detection of trace rare earth elements (REEs) in aqueous solution. The plasma was produced from a microwave plasma torch (MPT) under atmospheric pressure and was used as ambient ion source of a linear ion trap mass spectrometer (LTQ). Water samples were directly pneumatically nebulized to flow into the plasma through the central tube of MPT. For some REEs, the generated composite ions were detected in both positive and negative ion modes and further characterized in tandem mass spectrometry. Under the optimized conditions, the limit of detection (LOD) was at the level 0.1 ng/mL using MS2 procedure in negative mode. A single REE analysis can be completed within 2~3 minutes with the relative standard deviation ranging between 2.4% and 21.2% (six repeated measurements) for the 5 experimental runs. Moreover, the recovery rates of these REEs are between the range of 97.6%–122.1%. Two real samples have also been analyzed, including well and orange juice. These experimental data demonstrated that this method is a useful tool for the field analysis of REEs in water and can be used as an alternative supplement of ICP-MS. PMID:26421013

  7. Low Temperature Life-Cycle Testing of a Lithium-Ion Battery for Low-Earth-Orbiting Spacecraft

    NASA Technical Reports Server (NTRS)

    Reid, Concha

    2006-01-01

    A flight-qualified, lithium-ion (Li-ion) battery developed for the Mars Surveyor Program 2001 Landeris undergoing life-testing at low temperature under a low-Earth-orbit (LEO) profile to assess its capability to provide long term energy storage for aerospace missions. NASA has embarked upon an ambitious course to return humans to the moon by 2015-2020 in preparation for robotic and human exploration of Mars and robotic exploration of the moons of outer planets. Li-ion batteries are excellent candidates to provide power and energy storage for multiple aspects of these missions due to their high specific energy, high energy density, and excellent low temperature performance. Laboratory testing of Li-ion technology is necessary in order to assess lifetime, characterize multi-cell battery-level performance under aerospace conditions, and to gauge safety aspects of the technology. Life-cycle testing provides an opportunity to examine battery-level performance and the dynamics of individual cells in the stack over the entire life of the battery. Data generated through this testing will be critical to establish confidence in the technology for its widespread use in manned and unmanned missions.

  8. Some Rare Earth Elements Analysis by Microwave Plasma Torch Coupled with the Linear Ion Trap Mass Spectrometry.

    PubMed

    Xiong, Xiaohong; Jiang, Tao; Qi, Wenhao; Zuo, Jun; Yang, Meiling; Fei, Qiang; Xiao, Saijin; Yu, Aimin; Zhu, Zhiqiang; Chen, Huanwen

    2015-01-01

    A sensitive mass spectrometric analysis method based on the microwave plasma technique is developed for the fast detection of trace rare earth elements (REEs) in aqueous solution. The plasma was produced from a microwave plasma torch (MPT) under atmospheric pressure and was used as ambient ion source of a linear ion trap mass spectrometer (LTQ). Water samples were directly pneumatically nebulized to flow into the plasma through the central tube of MPT. For some REEs, the generated composite ions were detected in both positive and negative ion modes and further characterized in tandem mass spectrometry. Under the optimized conditions, the limit of detection (LOD) was at the level 0.1 ng/mL using MS(2) procedure in negative mode. A single REE analysis can be completed within 2~3 minutes with the relative standard deviation ranging between 2.4% and 21.2% (six repeated measurements) for the 5 experimental runs. Moreover, the recovery rates of these REEs are between the range of 97.6%-122.1%. Two real samples have also been analyzed, including well and orange juice. These experimental data demonstrated that this method is a useful tool for the field analysis of REEs in water and can be used as an alternative supplement of ICP-MS. PMID:26421013

  9. COMBUSTION SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE ALKALINE EARTH ALUMINATE Sr4Al14O25:RE(RE = Eu, Dy, Sm)

    NASA Astrophysics Data System (ADS)

    Hedaoo, V. P.; Bhatkar, V. B.; Omanwar, S. K.

    2013-08-01

    Nanoscale phosphors have superior performance characteristics than the bulk phosphors. This paper explains the synthesis and characterization like XRD, FTIR, SEM and photoluminescence properties of nanocrystalline Sr4Al14O25 doped with rare earth elements like europium, dysprosium and samarium by combustion method. XRD showed the nanoscale crystalline nature of as-prepared samples. SEM confirmed size of the particle less than 100 nm. Photoluminescent emission spectra showed strong orange red emission at 593 nm for Sr4Al14O25:Sm3+. The green emission of Eu2+ was observed at around 490 nm for Sr4Al14O25:Eu2+.

  10. Earth's ion upflow associated with polar cap patches: Global and in situ observations

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-He; Zong, Qiu-Gang; Lockwood, Michael; Heelis, Roderick A.; Hairston, Marc; Liang, Jun; McCrea, Ian; Zhang, Bei-Chen; Moen, Jøran; Zhang, Shun-Rong; Zhang, Yong-Liang; Ruohoniemi, J. Michael; Lester, Mark; Thomas, Evan G.; Liu, Rui-Yuan; Dunlop, Malcolm W.; Liu, Yong C.-M.; Ma, Yu-Zhang

    2016-03-01

    We report simultaneous global monitoring of a patch of ionization and in situ observation of ion upflow at the center of the polar cap region during a geomagnetic storm. Our observations indicate strong fluxes of upwelling O+ ions originating from frictional heating produced by rapid antisunward flow of the plasma patch. The statistical results from the crossings of the central polar cap region by Defense Meteorological Satellite Program F16-F18 from 2010 to 2013 confirm that the field-aligned flow can turn upward when rapid antisunward flows appear, with consequent significant frictional heating of the ions, which overcomes the gravity effect. We suggest that such rapidly moving patches can provide an important source of upwelling ions in a region where downward flows are usually expected. These observations give new insight into the processes of ionosphere-magnetosphere coupling.

  11. Interactions of microorganisms with rare earth ions and their utilization for separation and environmental technology.

    PubMed

    Moriwaki, Hiroshi; Yamamoto, Hiroki

    2013-01-01

    In recent years, rare earth elements (REEs) have been widely used in various modern technological devices and the global demand for REE has been increasing. The increased demand for REEs has led to environmental exposure or water pollution from rare earth metal mines and various commercial products. Therefore, the development of a safe technology for the separation and adsorption of REEs is very important from the perspective of green chemistry and environmental pollution. In this review, the application and mechanisms of microorganisms for the removal and extraction of REEs from aqueous solutions are described. In addition, the advantages in using microorganisms for REE adsorption and future studies on this topic are discussed.

  12. Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

    NASA Technical Reports Server (NTRS)

    Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend

    1994-01-01

    Comprehensive energy density studies provide an important measure of the participation of various sources in energization processes and have been relatively rare in the literature. We present a statistical study of the energy density of the near-Earth magnetotail major ions (H(+), O(+), He(++), He(+)) during substorm expansion phase and discuss its implications for the solar wind/magnetosphere/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during substorms through the correlation between the AE indices and the energy density of the major magnetospheric ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active Magnetospheric Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside magnetosphere, at geocentric distances approximately 7 to 9 R(sub E). CHEM provided the opportunity to conduct the first statistical study of energy density in the near-Earth magnetotail with multispecies particle data extending into the higher energy range (greater than or equal to 20 keV/E). the use of 1-min AE indices in this study should be emphasized, as the use (in previous statistical studies) of the (3-hour) Kp index or of long-time averages of AE indices essentially smoothed out all the information on substorms. Most distinct feature of our study is the excellent correlation of O(+) energy density with the AE index, in contrast with the remarkably poor He(++) energy density - AE index correlation. Furthermore, we examined the relation of the ion energy density to the electrojet activity during substorm growth phase. The O(+) energy density is strongly correlated with the pre-onset AU index, that is the eastward electrojet intensity, which represents the growth phase current system. Our investigation shows that the near-Earth magnetotail is increasingly fed with energetic ionospheric ions during periods of enhanced

  13. Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts

    SciTech Connect

    Gao, Feng; Wang, Yilin; Washton, Nancy M.; Kollar, Marton; Szanyi, Janos; Peden, Charles HF

    2015-10-13

    Using a three-step aqueous solution ion-exchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and hydrothermally aged forms, were characterized with several methods including temperature-programmed reduction by H2 (H2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and 27Al solid-state nuclear magnetic resonance (NMR) and diffuse reflectance Infrared Fourier Transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu-ions and the CHA framework making them more readily reducible. By removing a portion of Brønsted acid sites, cocations also help to mitigate hydrolysis of the zeolite catalysts during hydrothermal aging as evidenced from 27Al NMR. Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.

  14. Low Temperature Life-cycle Testing of a Lithium-ion Battery for Low-earth-orbiting Spacecraft

    NASA Technical Reports Server (NTRS)

    Reid, Concha

    2004-01-01

    A flight-qualified, lithium-ion (Li-ion) battery developed for the Mars Surveyor Program 2001 lander is undergoing life-testing at low temperature under a low-Earth-orbit (LEO) profile to assess its capability to provide long term energy storage for aerospace missions. NASA has embarked upon an ambitious course to return humans to the moon by 2015-2020 in preparation for robotic and human exploration of Mars and robotic exploration of the moons of outer planets. Li-ion batteries are excellent candidates to provide power and energy storage for multiple aspects of these missions due to their low specific energy, low energy density, and excellent low temperature performance. Laboratory testing of Li-ion technology is necessary in order to assess lifetime, characterize multi-cell battery-level performance under aerospace conditions, and to gauge safety aspects of the technology. Life-cycle testing provides an opportunity to examine battery-level performance and the dynamics of individual cells in the stack over the entire life of the battery. Data generated through this testing will be critical to establish confidence in the technology for its widespread use in manned and unmanned mission. This paper discusses the performance of the 28 volt, 25 ampere-hour battery through 6000 LEO cycles, which corresponds to one year on LEO orbit. Testing is being performed at 0 C and 40% depth-of-discharge. Individual cell behaviors and their effect on the performance of the battery are described. Capacity, impedance, energy efficiency and end-of-discharge voltage at 1000 cycle intervals are reported. Results from this life-testing will help contribute to the database on battery-level performance of aerospace Li-ion batteries and low temperature cycling under LEO conditions.

  15. Rare earth ion implantation and optical activation in nitride semiconductors for multicolor emission

    NASA Astrophysics Data System (ADS)

    Ruterana, Pierre; Chauvat, Marie-Pierre; Lorenz, Katharina

    2015-04-01

    In order to understand the behavior of nitride semiconductors when submitted to ion implantation, we have used 300 keV europium at fluences from 1012 to above 1017 ions cm-2. Subsequently, Rutherford backscattering (RBS), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to investigate the evolution of damage. The optical properties were investigated prior to and after annealing. It was found that the behavior of the three compounds (AlN, GaN InN) under ion implantation is rather different: whereas InN breaks down at very low fluences (˜1012 ions cm-2), the damage formation mechanisms are similar in AlN and GaN. In both compounds, extended defects such as stacking faults play a critical role. However, they exhibit different stability, as a consequence, GaN transforms to nanocrystalline state from the surface at a fluence of around 2.5 × 1015 ions cm-2, whereas AlN undergoes a chemical amorphization starting at the projected range (Rp), when implanted to extremely high Eu fluences >1017 ionscm-2. As for the optical activation, the formation of highly stable extended defects in these compounds constitutes a real challenge for the annealing of heavily doped layers, and it was noticed that for a substantial optical activation, the implantation fluences should be kept low (<1015 Eu at cm-2).

  16. Ion acceleration at CME-driven shocks near the Earth and the Sun

    SciTech Connect

    Desai, Mihir; Dayeh, Maher; Ebert, Robert; Smith, Charles; Mason, Glenn; Li, G.

    2012-11-20

    We compare the behavior of heavy ion spectra during an Energetic Storm Particle (ESP) event that exhibited clear evidence of wave excitation with that observed during an intense, large gradual Solar Energetic Particle (SEP) event in which the associated <0.2 MeV/nucleon ions are delayed >12 hr. We interpret that the ESP event is an example of the first-order Fermi acceleration process where enhancements in the magnetic field power spectral densities around local ion cyclotron frequency {nu}{sub pc} indicate the presence of Alfven waves excited by accelerated protons streaming away from the in-situ interplanetary shock. The softening or unfolding of the CNO energy spectrum below {approx}200 keV/nucleon and the systematic organization of the Fe and O spectral roll-overs with the E/q ratio during the ESP event are likely due to M/Q-dependent trapping and scattering of the heavy ions by the proton-excited waves. Based on striking similarities in the spectral behavior observed upstream of both, the ESP and the SEP event, we suggest that coupling between proton-generated Alfven waves and energetic ions is also operating at the distant CME shock during the large, gradual SEP event, thereby providing us with a new, powerful tool to remotely probe the roles of shock geometries and wave-particle interactions at near-Sun CME-driven shocks.

  17. Vapor-liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

    NASA Astrophysics Data System (ADS)

    Pester, Nicholas J.; Ding, Kang; Seyfried, William E.

    2015-11-01

    Multi-phase fluid flow is a common occurrence in magmatic hydrothermal systems; and extensive modeling efforts using currently established P-V-T-x properties of the NaCl-H2O system are impending. We have therefore performed hydrothermal flow experiments (360-465 °C) to observe vapor-liquid partitioning of alkaline earth and first row transition metals in NaCl-dominated source solutions. The data allow extraction of partition coefficients related to the intrinsic changes in both chlorinity and density along the two-phase solvus. The coefficients yield an overall decrease in vapor affinity in the order Cu(I) > Na > Fe(II) > Zn > Ni(II) ⩾ Mg ⩾ Mn(II) > Co(II) > Ca > Sr > Ba, distinguished with 95% confidence for vapor densities greater than ∼0.2 g/cm3. The alkaline earth metals are limited to purely electrostatic interactions with Cl ligands, resulting in an excellent linear correlation (R2 > 0.99) between their partition coefficients and respective ionic radii. Though broadly consistent with this relationship, relative behavior of the transition metals is not well resolved, being likely obscured by complex bonding processes and the potential participation of Na in the formation of tetra-chloro species. At lower densities (at/near halite saturation) partitioning behavior of all metals becomes highly non-linear, where M/Cl ratios in the vapor begin to increase despite continued decreases in chlorinity and density. We refer to this phenomenon as "volatility", which is broadly associated with substantial increases in the HCl/NaCl ratio (eventually to >1) due to hydrolysis of NaCl. Some transition metals (e.g., Fe, Zn) exhibit volatility prior to halite stability, suggesting a potential shift in vapor speciation relative to nearer critical regions of the vapor-liquid solvus. The chemistry of deep-sea hydrothermal fluids appears affected by this process during magmatic events, however, our results do not support suggestions of subseafloor halite precipitation

  18. Ion probe determinations of the rare earth concentrations of individual meteoritic phosphate grains

    NASA Technical Reports Server (NTRS)

    Crozaz, G.; Zinner, E.

    1985-01-01

    A new ion probe method for quantitative measurements of the concentrations of all the REE down to the ppm level in 5-20 micron spots is presented. The first application of the method is the determination of REE abundances in meteoritic phosphates. Results are shown to be in good agreement with previous INAA and ion probe determinations. The merrillites in the St. Severin amphoterite are richer in REE than the apatites (the enrichment factors, for various REE, range from 2.3 to 14.2) in contradiction with the results of Ebihara and Honda (1983). Provided good standards for other mineral phases are found or implanted marker ion techniques are used, the method should find a wide range of applications for the study of both terrestrial and extraterrestrial crystals at the microscopic level.

  19. The luminescence properties of rare-earth ions in natural fluorite

    NASA Astrophysics Data System (ADS)

    Czaja, M.; Bodył-Gajowska, S.; Lisiecki, R.; Meijerink, A.; Mazurak, Z.

    2012-09-01

    For the first time, the luminescence properties of Pr3+, Nd3+ and Tm3+ and Yb3+ ions in fluorite crystal have been obtained by steady-state measurements. In addition, the luminescence spectra of Ce3+, Sm2+, Sm3+, Dy3+, Er3+ and Yb3+ were measured. It was pointed out that λexc. = 415 nm is most suitable for measuring the Ho3+ emission beside the Er3+. The emission of trivalent holmium and erbium ions was measured independently using time-resolved measurements and tentative assignment of luminescence lines to C 3v and C 4v symmetry sites was proposed. Besides for natural fluorite crystal, the transitions between Stark energy levels of lanthanide ions were presented.

  20. Alkaline battery, separator therefore

    NASA Technical Reports Server (NTRS)

    Schmidt, George F. (Inventor)

    1980-01-01

    An improved battery separator for alkaline battery cells has low resistance to electrolyte ion transfer and high resistance to electrode ion transfer. The separator is formed by applying an improved coating to an electrolyte absorber. The absorber, preferably, is a flexible, fibrous, and porous substrate that is resistant to strong alkali and oxidation. The coating composition includes an admixture of a polymeric binder, a hydrolyzable polymeric ester and inert fillers. The coating composition is substantially free of reactive fillers and plasticizers commonly employed as porosity promoting agents in separator coatings. When the separator is immersed in electrolyte, the polymeric ester of the film coating reacts with the electrolyte forming a salt and an alcohol. The alcohol goes into solution with the electrolyte while the salt imbibes electrolyte into the coating composition. When the salt is formed, it expands the polymeric chains of the binder to provide a film coating substantially permeable to electrolyte ion transfer but relatively impermeable to electrode ion transfer during use.

  1. Extraction Separation of Rare-Earth Ions via Competitive Ligand Complexations between Aqueous and Ionic-Liquid Phases

    SciTech Connect

    Luo, Huimin; Sun, Xiaoqi; Bell, Jason R; Dai, Sheng

    2011-01-01

    The extraction separation of rare earth elements is the most challenging separation processes in hydrometallurgy and advanced nuclear fuel cycles. The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) is a prime example of these separation processes. The objective of this paper is to explore the use of ionic liquids (ILs) for the TALSPEAK-like process, to further enhance its extraction efficiencies for lanthanides, and to investigate the potential of using this modified TALSPEAK process for separation of lanthanides among themselves. Eight imidazolium ILs ([Cnmim][NTf2] and [Cnmim][BETI], n=4,6,8,10) and one pyrrolidinium IL ([C4mPy][NTf2]) were investigated as diluents using di(2-ethylhexyl)phosphoric acid (HDEHP) as an extractant for separation of lanthanide ions from aqueous solutions of 50 mM glycolic acid or citric acid and 5 mM diethylenetriamine pentaacetic acid (DTPA). The extraction efficiencies were studied in comparison with diisopropylbenzene (DIPB), an organic solvent used as diluent for the conventional TALSPEAK extraction system. Excellent extraction efficiencies and selectivities were found for a number of lanthanide ions using HDEHP as an extractant in these ILs. The effects of different alkyl chain lengths in the cations of ILs and anions on extraction efficiencies and selectivities of lanthanide ions are also presented in this paper.

  2. Energetic heavy ions observed upstream of the Earth's bow shock by the STEP/EPACT instrument on WIND

    NASA Astrophysics Data System (ADS)

    Mason, G. M.; Mazur, J. E.; von Rosenvinge, T. T.

    The Supra-Thermal through Energetic Particle (STEP) subsystem of the EPACT experiment on the WIND spacecraft observed numerous short duration heavy ion enhancements during the ˜9 month period Nov. 1994-Sept. 1995. These enhancements were most frequent and intense when WIND was close to the magnetosphere, but were often observed also during the period when the spacecraft was >100 RE upstream. The events occur in association with high speed solar wind streams that are signatures of corotating interaction regions (CIRs). A typical event observed on January 31, 1995 when WIND was 195 RE upstream showed strong field aligned anisotropies and rapid time variations. Heavy ion abundances near 45 keV/nucleon (nuc) were He:C:O:Fe = 86 : 1.46 : ≡1 ∶ 0.12, similar to those observed at higher energies in CIRs, and distinctly different from magnetospheric ring current abundances measured on the AMPTE spacecraft. We suggest that the CIRs provide the seed population for these heavy ion events, that are then further accelerated in association with the Earth's bow shock.

  3. Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.

    PubMed

    Iannicelli-Zubiani, Elena Maria; Cristiani, Cinzia; Dotelli, Giovanni; Gallo Stampino, Paola; Pelosato, Renato; Mesto, Ernesto; Schingaro, Emanuela; Lacalamita, Maria

    2015-12-01

    Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium.

  4. Energetic ions upstream of the earth's bow shock during an energetic storm particle event

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Ipavich, F. M.

    1983-01-01

    Simultaneous observations of low-energy protons and alpha particles from ISEE 3 far upstream and from ISEE 1 close to the earth's bow shock during the passage of an interplanetary shock wave with its associated energetic storm particles are presented. Intensities, spectra, and anisotropies of the energetic storm particles are modified due to the interaction of these particles with the earth's bow shock. An intensity spike observed at ISEE 1 during the passage of the interplanetary shock is interpreted as being due to postacceleration of energetic storm particles at the bow shock by the first-order Fermi mechanism. The spikes observed at ISEE 1 after the passage of the interplanetary shock are most probably due to reflection of the energetic storm particles at the bow shock.

  5. Distribution pattern of rare earth ions between water and montmorillonite and its relation to the sorbed species of the ions.

    PubMed

    Takahashi, Yoshio; Tada, Akisa; Shimizu, Hiroshi

    2004-09-01

    REE (rare earth element) distribution coefficients (Kd) between the aqueous phase and montmorillonite surface were obtained to investigate the relation between the REE distribution patterns and the species of REE sorbed on the solid-water interface. It was shown that the features in the REE patterns, such as the slope of the REE patterns, the tetrad effect, and the Y/Ho ratio, were closely related to the REE species at the montmorillonite-water interface. In a binary system (REE-montmorillonite) below pH 5, three features (a larger Kd value for a lighter REE, the absence of the tetrad effect, and the Y/Ho ratio being unchanged from its initial value) suggest that hydrated REE are directly sorbed as an outer-sphere complex at the montmorillonite-water interface. Above pH 5.5, the features in the REE patterns, the larger Kd value for heavier REE, the M-type tetrad effect, and the reduced Y/Ho ratio, showed the formation of an inner-sphere complex of REE with -OH group at the montmorillonite surface. In addition, the REE patterns in the presence of humic acid at pH 5.9 were also studied, where the REE patterns became flat, suggesting that the humate complex is dominant as both dissolved and sorbed species of REE in the ternary system. All of these results were consistent with the spectroscopic data (laser-induced fluorescence spectroscopy) showing the local structure of Eu(III) conducted in the same experimental system. The present results suggest that the features in the REE distribution patterns include information on the REE species at the solid-water interface.

  6. Luminescence of rare-earth ions and intrinsic defects in Gd2O3 matrix

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Yu A.; Zatsepin, A. F.; Tselybeev, R. A.; Rychkov, V. N.; Pustovarov, V. A.

    2016-08-01

    The X-ray luminescence and photoluminescence of the ultradispersed Gd2O3 powders with different purity were investigated in 90-360 K temperature range. Both impurity and intrinsic optical active centers were detected. The effect of energy transfer from Gd3+ to RE3+ ions was observed.

  7. Adsorption of rare earth ions onto the cell walls of wild-type and lipoteichoic acid-defective strains of Bacillus subtilis.

    PubMed

    Moriwaki, Hiroshi; Koide, Remi; Yoshikawa, Ritsuko; Warabino, Yuya; Yamamoto, Hiroki

    2013-04-01

    The aim of this study is to investigate the potential of cell walls of wild-type and lipoteichoic acid-defective strains of Bacillus subtilis 168 to adsorb rare earth ions. Freeze-dried cell powders prepared from both strains were used for the evaluation of adsorption ability for the rare earth ions, namely, La(III), Eu(III), and Tm(III). The rare earth ions were efficiently adsorbed onto powders of both wild-type strain (WT powder) and lipoteichoic acid-defective strain (∆LTA powder) at pH 3. The maximum adsorption capacities for Tm(III) by WT and ∆LTA powders were 43 and 37 mg g(-1), respectively. Removal (in percent) of Tm(III), La(III), and Eu(III) from aqueous solution by WT powder was greater than by ∆LTA powder. These results indicate that rare earth ions are adsorbed to functional groups, such as phosphate and carboxyl groups, of lipoteichoic acid. We observed coagulated ∆LTA powder in the removal of rare earth ions (1-20 mg L(-1)) from aqueous solution. In contrast, sedimentation of WT powder did not occur under the same conditions. This unique feature of ∆LTA powder may be caused by the difference of the distribution between lipoteichoic acid and wall teichoic acid. It appears that ∆LTA powder is useful for removal of rare earth ions by adsorption, because aggregation allows for rapid separation of the adsorbent by filtration.

  8. Observation of superconductivity ( Tc = 50 K) in a new tetragonal alkaline-earth cuprate Sr 0.8Ba 1.2CuO 3+δ, synthesised at ambient pressure

    NASA Astrophysics Data System (ADS)

    Hodges, J. P.; Slater, P. R.; Edwards, P. P.; Greaves, C.; Slaski, M.; Van Tendeloo, G.; Amelinckx, S.

    1996-02-01

    The ambient-pressure synthesis of a new tetragonal alkaline-earth superconducting cuprate, Sr 0.8Ba 1.2CuO 3+δ, from a cupro-oxycarbonate is reported. Magnetic-susceptibility measurements show the presence of a superconducting transition ˜50 K in a post-annealed sample. The crystal structure, refined from time-of-flight powder neutron-diffraction data was found to have an oxygen-deficient La 2CuO 4-type tetragonal T structure ( a = 3.8988(3) Å and c = 12.815(3) Å) with oxygen vacancies located within the CuO 2 planes. Ordering of these oxygen vacancies is responsible for the observation of a superlattice in both neutron- and electron-diffraction measurements. An interpretation of the electron-diffraction patterns suggests that the superlattice in Sr 0.8Ba 1.2CuO 3+δ and also in the isostructural superconductor Sr 2CuO 3+δ are of an identical nature.

  9. [Treatment of chronic inflammation of the upper respiratory airways by inhalation thermal therapy with sulfur-sulfate-bicarbonate- carbonate-alkaline earth mineral water: a study of nasal cytology].

    PubMed

    Cristalli, G; Abramo, A; Pollastrini, L

    1996-12-01

    The purpose of the paper is to better characterise changes occurred in nose cytology in a group of 50 subjects affected by chronic inflammation of upper respiratory airway. The patients were random shared in two groups: group A 40 subjects treated using sulphurous thermal water and a group B (control), 10 cases, treated using placebo saline solution. The post-therapy evaluation of nasal cytology showed an improvement of the chronic inflammation in 65% of group A patients (diminution of bacterial dust 65%, diminution of PMN cells in 60% of cases and disappearance of metaplasy notes in all the cases of group A. No statistical modifications were observed in control group. Moreover were observed a increase of plasma-cell number much more in group A. The author conclusion is that a period of thermal therapy using sulphur-sulphate-alkaline-earth metals water in chronic inflammation of the nose, throw pharmacological and physical actions, cause an improvement of the chronic inflammation and a normalisation of nose cytology. PMID:9381939

  10. Electric and magnetic drift of non-adiabatic ions in the earth's geomagnetic tail current sheet

    NASA Technical Reports Server (NTRS)

    Beard, D. B.; Cowley, S. W. H.

    1985-01-01

    It has been shown recently that nonadiabatic particles in the earth's magnetotail drift across the tail roughly as predicted for adiabatic particles with 90 deg pitch angles. In this paper it is shown that this result implies the existence of an approximate invariant of the motion. Adding the effect of convection associated electric fields, the approximate bounce averaged motion of nonadiabatic particles in the magnetotail can be obtained. Thus the particle motion and energization due to combined magnetic and electric drifts in the magnetotail are easily predicted.

  11. The adsorption of rare earth ions using carbonized polydopamine nano shells

    DOE PAGES

    Sun, Xiaoqi; Luo, Huimin; Mahurin, Shannon Mark; Dai, Sheng; Liu, Rui; Hou, Xisen; Dai, Sheng

    2016-01-07

    Herein we report the structure effects of nano carbon shells prepared by carbonized polydopamine for rare earth elements (REEs) adsorption for the first time. The solid carbon sphere, 60 nm carbon shell and 500 nm carbon shell were prepared and investigated for adsorption and desorption of REEs. The adsorption of carbon shells for REEs was found to be better than the solid carbon sphere. The effect of acidities on the adsorption and desorption properties was discussed in this study. The good adsorption performance of carbon shells can be attributed to their porous structure, large specific surface area, amine group andmore » carbonyl group of dopamine.« less

  12. Ion beam sputter-deposited thin film coatings for protection of spacecraft polymers in low earth orbit

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Mirtich, M. J.; Rutledge, S. K.; Swec, D. M.; Nahra, H. K.

    1985-01-01

    Ion beam sputter-deposited thin films at Al2O3, SiO2, and a codeposited mixture of predominantly SiO2 with small amounts of fluoropolymer were evaluated both in laboratory plasma ashing tests and in space on board Shuttle flight STS-8 for effectiveness in preventing oxidation of polyimide Kapton. Measurements of mass loss and optical performance of coated and uncoated polyimide samples exposed to the low earth orbital environment are presented. Optical techniques were used to measure loss rates of protective films exposed to atomic oxygen. Results of the analysis of the space flight exposed samples indicate that thin film metal oxide coatings are very effective in protecting the polyimide. Metal oxide coatings with a small amount of fluoropolymer codeposited have the additional benefit of great flexibility.

  13. Ion beam sputter-deposited thin film coatings for protection of spacecraft polymers in low Earth orbit

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Mirtich, M. J.; Rutledge, S. K.; Swec, D. M.; Nahra, H. K.

    1985-01-01

    Ion beam sputter-deposited thin films of Al2O3, SiO2, and a codeposited mixture of predominantly SiO2 with small amounts of a fluoropolymer were evaluated both in laboratory plasma ashing tests and in space on board shuttle flight STS-8 for effectiveness in preventing oxidation of polyimide Kapton. Measurements of mass loss and optical performance of coated and uncoated polyimide samples exposed to the low Earth orbital environment are presented. Optical techniques were used to measure loss rates of protective films exposed to atomic oxygen. Results of the analysis of the space flight exposed samples indicate that thin film metal oxide coatings are very effective in protecting the polyimide. Metal oxide coatings with a small amount of fluoropolymer codeposited have the additional benefit of great flexibility.

  14. Parity nonconservation in Fr-like actinide and Cs-like rare-earth-metal ions

    NASA Astrophysics Data System (ADS)

    Roberts, B. M.; Dzuba, V. A.; Flambaum, V. V.

    2013-07-01

    Parity-nonconservation (PNC) amplitudes are calculated for the 7s-6d3/2 transitions of the francium isoelectronic sequence (Fr, Ra+, Ac2+, Th3+, Pa4+, U5+, and Np6+) and for the 6s-5d3/2 transitions of the cesium isoelectronic sequence (Cs, Ba+, La2+, Ce3+, and Pr4+). We show in particular that isotopes of La2+, Ac2+, and Th3+ ions have strong potential in the search for new physics beyond the standard model: The PNC amplitudes are large, the calculations are accurate, and the nuclei are practically stable. In addition, 232Th3+ ions have recently been trapped and cooled [Campbell , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.233004 102, 233004 (2009)]. We also extend previous works by calculating the s-s PNC transitions in Ra+ and Ba+ and provide calculations of several energy levels, and electric dipole and quadrupole transition amplitudes for the Fr-like actinide ions.

  15. Influence of yttrium content on the location of rare earth ions in LYSO:Ce crystals

    SciTech Connect

    Ding, Dongzhou; Weng, Linhong; Yang, Jianhua; Ren, Guohao; Wu, Yuntao

    2014-01-15

    Single-crystal X-ray diffraction (SCD), X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray excited luminescence (XEL) measurements were performed to investigate structure details and segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Ce (x=0 at%, 8.7 at%, 25.7 at%, 44.7 at%, 65.7 at%, 87.9 at% and 100 at%). Y{sup 3+} cations were found to have a preferential occupation for RE1 site (7-oxygen-coordinated) over RE2 site (6-oxygen-coordinated), which results in a greater increase of cell parameter c than that of a with increase in Y content due to LYSO's microstructure characteristics. Results presented here revealed that the less the difference in electronegativity and effective ionic radius between the two ions, the easier substitution of one ion by the other, and hence the higher segregation coefficients. Besides, the contribution of luminescence of Ce1 and Ce2 in the whole XEL was evaluated, and the location of Ce{sup 3+} ion was discussed. - Graphical abstract: Segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Cce:italic> at RT/ce:italic>. Display Omitted.

  16. Magnetospheric ions and electrons in the distant magnetosheath at about 50 and 180 earth radii - ISEE-3 observations

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Hovestadt, D.; Klecker, B.; Gloeckler, G.; Ipavich, F. M.; Zwickl, R. D.

    1984-01-01

    Energetic particle data were obtained in the dawn magnetosheath at about 50 earth radii (ER), analyzed, and compared with data taken at 180 ER. Both data sets were acquired during the ISEE-3 geotail mission. The results of analyses of the 16 sec time profiles of 32 and 130 keV protons, 75-115 keV electrons, and some of the 30-36 keV proton angular distributions (PAD) are presented. No temporal dispersions were detected in the particle bursts, implying instead a spatial dispersion. The particles filled flux tubes of 6 ER, with the energetic electrons being beamed along magnetic field lines. PADs displayed anisotropy symmetric relative to the magnetic field. The electrons were not detected at 180 ER. The phenomena are modeled as flux tubes connected to the magnetotail magnetic field in the near-earth magnetopause. The particles leak out along connected field lines. Lion roars scatter the electrons, which escape into interplanetary space. Ions, however, may carry their intensity out to 200 ER, a factor which awaits verification by further data.

  17. Magnetospheric ions and electrons in the distant magnetosheath at about 50 and 180 earth radii - ISEE-3 observations

    NASA Astrophysics Data System (ADS)

    Scholer, M.; Hovestadt, D.; Klecker, B.; Gloeckler, G.; Ipavich, F. M.; Zwickl, R. D.

    1984-10-01

    Energetic particle data were obtained in the dawn magnetosheath at about 50 earth radii (ER), analyzed, and compared with data taken at 180 ER. Both data sets were acquired during the ISEE-3 geotail mission. The results of analyses of the 16 sec time profiles of 32 and 130 keV protons, 75-115 keV electrons, and some of the 30-36 keV proton angular distributions (PAD) are presented. No temporal dispersions were detected in the particle bursts, implying instead a spatial dispersion. The particles filled flux tubes of 6 ER, with the energetic electrons being beamed along magnetic field lines. PADs displayed anisotropy symmetric relative to the magnetic field. The electrons were not detected at 180 ER. The phenomena are modeled as flux tubes connected to the magnetotail magnetic field in the near-earth magnetopause. The particles leak out along connected field lines. Lion roars scatter the electrons, which escape into interplanetary space. Ions, however, may carry their intensity out to 200 ER, a factor which awaits verification by further data.

  18. Solar cycle variation of interstellar neutral He, Ne, O density and pick-up ions along the Earth's orbit

    NASA Astrophysics Data System (ADS)

    Sokół, Justyna M.; Bzowski, Maciej; Kubiak, Marzena A.; Möbius, Eberhard

    2016-06-01

    We simulated the modulation of the interstellar neutral (ISN) He, Ne, and O density and pick-up ion (PUI) production rate and count rate along the Earth's orbit over the solar cycle (SC) from 2002 to 2013 to verify if SC-related effects may modify the inferred ecliptic longitude of the ISN inflow direction. We adopted the classical PUI model with isotropic distribution function and adiabatic cooling, modified by time- and heliolatitude-dependent ionization rates and non-zero injection speed of PUIs. We found that the ionization losses have a noticeable effect on the derivation of the ISN inflow longitude based on the Gaussian fit to the crescent and cone peak locations. We conclude that the non-zero radial velocity of the ISN flow and the energy range of the PUI distribution function that is accumulated are of importance for a precise reproduction of the PUI count rate along the Earth orbit. However, the temporal and latitudinal variations of the ionization in the heliosphere, and particularly their variation on the SC time-scale, may significantly modify the shape of PUI cone and crescent and also their peak positions from year to year and thus bias by a few degrees the derived longitude of the ISN gas inflow direction.

  19. Alkaline sorbent injection for mercury control

    DOEpatents

    Madden, Deborah A.; Holmes, Michael J.

    2003-01-01

    A mercury removal system for removing mercury from combustion flue gases is provided in which alkaline sorbents at generally extremely low stoichiometric molar ratios of alkaline earth or an alkali metal to sulfur of less than 1.0 are injected into a power plant system at one or more locations to remove at least between about 40% and 60% of the mercury content from combustion flue gases. Small amounts of alkaline sorbents are injected into the flue gas stream at a relatively low rate. A particulate filter is used to remove mercury-containing particles downstream of each injection point used in the power plant system.

  20. Alkaline sorbent injection for mercury control

    DOEpatents

    Madden, Deborah A.; Holmes, Michael J.

    2002-01-01

    A mercury removal system for removing mercury from combustion flue gases is provided in which alkaline sorbents at generally extremely low stoichiometric molar ratios of alkaline earth or an alkali metal to sulfur of less than 1.0 are injected into a power plant system at one or more locations to remove at least between about 40% and 60% of the mercury content from combustion flue gases. Small amounts of alkaline sorbents are injected into the flue gas stream at a relatively low rate. A particulate filter is used to remove mercury-containing particles downstream of each injection point used in the power plant system.

  1. Luminescence properties of barium--gadolinium-titanate ceramics doped with rare-earth ions (Eu3+ and Tb3+).

    PubMed

    Hemasundara Raju, S; Muni Sudhakar, B; Sudhakar Reddy, B; Dhoble, S J; Thyagarajan, K; Nageswara Raju, C

    2014-11-01

    Barium-gadolinium-titanate (BaGd2 Ti4 O12) powder ceramics doped with rare-earth ions (Eu(3+) and Tb(3+)) were synthesized by a solid-state reaction method. From the X-ray diffraction spectrum, it was observed that Eu(3+) and Tb(3+):BaGd2 Ti4 O12 powder ceramics are crystallized in the form of an orthorhombic structure. Scanning electron microscopy image shows that the particles are agglomerated and the particle size is about 200 nm. Eu(3+) - and Tb(3+) -doped BaGd2 Ti4 O12 powder ceramics were examined by energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, photoluminescence and thermoluminescence (TL) spectra. Emission spectra of Eu(3+)-doped BaGd2 Ti4 O12 powder ceramics showed bright red emission at 613 nm ((5)D0 →(7)F2) with an excitation wavelength λ(exci)  = 408 nm ((7)F0 → (5)D3) and Tb(3+):BaGd2 Ti4 O12 ceramic powder has shown green emission at 534 nm ((5)D4 → (7)F5) with an excitation wavelength λ(exci)  = 331 nm (((7)F6 → (5)D1). TL spectra show that Eu(3+) and Tb(3+) ions affect TL sensitivity.

  2. Local structure around rare-earth ions in B{sub 2}O{sub 3} glass at high pressure

    SciTech Connect

    Funabiki, Fuji; Matsuishi, Satoru; Hosono, Hideo

    2013-06-14

    Melt quenching of B{sub 2}O{sub 3} with less than 25 mol. % rare-earth oxide (RE{sub 2}O{sub 3}) at ambient pressure results in a milky white glass because of liquid-liquid phase separation into B{sub 2}O{sub 3} and RE{sub 2}O{sub 3}{center_dot}3B{sub 2}O phases. In contrast, we have found that melt quenching under GPa-order pressure realizes a transparent RE-doped B{sub 2}O{sub 3} glass. This study investigates the local structure around the RE ions in the B{sub 2}O{sub 3} glass prepared at 3 GPa using optical measurements and electron-spin-echo envelope modulation spectroscopy. It is shown that the RE-rich microparticles disappear and the RE ions are isolated from each other in a highly symmetric crystal field formed by triangular and tetrahedral boron units. This result is consistent with that extrapolated from the data for RE-doped sodium borate glasses.

  3. White emission materials from glass doped with rare Earth ions: A review

    NASA Astrophysics Data System (ADS)

    Yasaka, P.; Kaewkhao, J.

    2016-03-01

    Solid State Lighting (SSL) based devices are predicted to play a crucial role in the coming years. Development of W-LED, which have an edge over traditional lighting sources due to their compact size, higher reliability, shock resistance, interesting design possibilities, higher transparency and an extremely long lifetime. Over the fifteen trivalent lanthanide ions, Dy3+ ions doped glasses are most appropriate for white light generation because of the fact that it exhibits two intense emission bands corresponds to the 4F9/2→6H15/2 (magnetic dipole) and 4F9/2→6H13/2 (electric dipole) transitions at around 480-500 nm and 580-600 nm pertaining to blue and yellow regions respectively. In this work, the developments of Dy3+ doped in several glass structures for white emitting materials application have reviewed. Properties of Dy3+ doped in glasses were discussed for use as a solid state lighting materials application.

  4. Investigation of thermal diffusivity dependence on temperature in a group of optical single crystals doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.

    2015-07-01

    The group of YAG, YVO4 and GdCOB single crystals was examined to determine the thermal diffusivity as a function of temperature in range from 30 °C to 300 °C. Further investigations concerned on analysis of the influence of dopants on these dependencies. The experimental setup based on thermal wave method with mirage detection was used. The samples represented different crystallographic systems such as cubic (YAG) tetragonal (YVO4) and monoclinic (GdCOB). The anisotropy of thermal conductivity of investigated samples was taken into account in the investigations. The crystals were doped with calcium ions, rare earth ions such as ytterbium, neodymium, and thulium, and also with transition metal vanadium. The results confirmed that influence of doping on the thermal diffusivity of investigated materials strongly depends on temperature. In general the thermal diffusivity decreases with increasing of sample temperature from 30 °C to 300 °C, however the drop in thermal diffusivity is the highest for pure single crystals. Doping is another factor reducing the heat transport in single crystals. Introduction of dopant ions into a crystal lattice leads to a significant decrease in the thermal diffusivity at lower temperatures in comparison with pure crystals. However, the influence of dopants becomes less pronounced with increasing temperature, and in case of weakly doped crystals it becomes negligible at higher temperatures. The interpretation of thermal diffusivity dependence on temperature for single crystals was based on the Debye model of lattice thermal conductivity of solids. The results allowed to conclude that the decrease of thermal diffusivity with temperature and increasing concentration of impurities is caused by shortening of the phonons mean free path due to phonon-phonon and phonon-point defect scatterings.

  5. Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.

    PubMed

    Iannicelli-Zubiani, Elena Maria; Cristiani, Cinzia; Dotelli, Giovanni; Gallo Stampino, Paola; Pelosato, Renato; Mesto, Ernesto; Schingaro, Emanuela; Lacalamita, Maria

    2015-12-01

    Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium. PMID:26403388

  6. Origin and cycle of water on Earth as determined by Ion probe H and D/H measurements

    NASA Astrophysics Data System (ADS)

    Deloule, E.

    2009-12-01

    The question of the origin of water on Earth, and of its abundance has been the object of numerous debates, as well as for the other terrestrial planets. Furthermore the presence and amount of water, or more commonly fluids, in the mantle and continental crust are crucial issues for determining their nature and evolution. Ion probe have been a major tool during the last 3 decades to measure in situ water content, D/H ratio and other elements in various terrestrial and extraterrestrial samples of both hydrous and nominally anhydrous minerals. In a first step, the set up of D/H ratio measurements by ion probe on hydrous minerals [1], often to scarce in peridotite samples to be measurable by conventional mass spectrometry, pointed out variations of δD values in mantle peridotite [2,3] larger than expected (from 0 to -140), both at the mineral grain or regional scales. Such variations point out surface water recycling in the mantle, water exchange during metasomatic reaction and D-H fractionation during mantle processes, and a possible evolution of the Earth mantle D/H ratio through geological time. The determination of D/H ratio in the silicate phases of the matrix and chondrules of primitive meteorites provides new evidences for the source of water in the solar system: the high dD values recorded, up to 3500, implies the uptake of water ice formed in the interstellar media, during the protosolar nebula accretion [3-4]. The D-H budget suggests that up to 10% of Earth and meteorite water originated from interstellar media. The measurements of Martian meteorites [5-6] show contrasted results, with D enriched values associated to the interaction with the Martian surface water and D poor values interpreted as initial values. The development of in situ water content measurements in glasses and nominally anhydrous minerals (NAMs) [7-8] allows a more comprehensive study of the water behavior in the depth Earth. The characterization of its distribution in between the

  7. Tip enhancement of upconversion photoluminescence from rare earth ion doped nanocrystals.

    PubMed

    Mauser, Nina; Piatkowski, Dawid; Mancabelli, Tobia; Nyk, Marcin; Mackowski, Sebastian; Hartschuh, Achim

    2015-04-28

    We present tip-enhanced upconversion photoluminescence (PL) images of Er(3+)- and Yb(3+)-doped NaYF4 nanocrystals on glass substrates with subdiffraction spatial resolution. Tip-sample distance dependent measurements clearly demonstrate the near-field origin of the image contrast. Time-resolved PL measurements show that the tip increases the spontaneous emission rate of the two emission channels of Er(3+) in the visible region. Very efficient enhancement of upconversion PL is discussed in the context of the two-photon nature of the excitation process and homoenergy transfer between the ions within the nanocrystals. Comparison between different nanocrystals and tips shows a strong influence of the tip shape on the image contrast that becomes particularly relevant for the larger dimensions of the investigated nanocrystals.

  8. Rare-earth neutral metal injection into an electron beam ion trap plasma

    SciTech Connect

    Magee, E. W. Beiersdorfer, P.; Brown, G. V.; Hell, N.

    2014-11-15

    We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10{sup −7} Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

  9. Alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 with large nonlinear optical properties in the deep-ultraviolet region

    NASA Astrophysics Data System (ADS)

    Reshak, A. H.; Huang, Hongwei; Kamarudin, H.; Auluck, S.

    2015-02-01

    The linear optical response and second harmonic generation (SHG) in alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 are investigated by means of density functional theory. Calculations are performed using four types of exchange correlations: Ceperley-Alder local density approximation, Perdew Burke and Ernzerhof general gradient approximation, Engel-Vosko generalized gradient approximation, and the recently modified Becke-Johnson potential (mBJ). The mBJ approach brings the calculated band gap (7.20 eV) in excellent agreement with the experimental one (7.28 eV). The calculated values of the uniaxial anisotropy δɛ=-0.076 and the birefringence Δn (0 ) =0.052 indicate considerable anisotropy in the linear optical properties, which makes it favorable for the second harmonic generation. The dominant component of the second harmonic generation is χ111(2)(ω) . The value of |χ111(2)(ω) | is about 1.2 pm/V at λ = 1064 nm in agreement with previous calculations. To analyze the origin of the high SHG of NaSr3Be3B3O9F4 single crystals, we have correlated the features of |χ111(2)(ω) | spectra with the features of ɛ2(ω) spectra as a function of ω/2 and ω. From the calculated dominant component |χ111(2)(ω) | , we find that the microscopic first hyperpolarizability, β111 , the vector components along the dipole moment direction is 0.5 × 10-30 esu at static limit and 0.6 × 10-30 esu at λ = 1064 nm.

  10. CRRES/SPACERAD Heavy Ion Model of the Environment, CHIME For Single Particle Radiation Effects in Space Near Earth User's Guide for Version 3.5

    NASA Astrophysics Data System (ADS)

    Chenette, D. L.; Tobin, J. D.; Geller, S. P.

    1997-02-01

    A new time-dependent model of the heavy ion space radiation environment has been developed which describes the galactic cosmic ray, anomalous component, and solar energetic particle heavy ions fluxes and their temporal and spatial variations in space near earth. This model, the CRRES/SPACERAD Heavy Ion Model of the Environment (CHIME) is incorporated in a set of computer software modules which allow a user to define a model specific to a period of tile or a level of solar activity, and a location or orbit near earth. A brief description of the models forming the basis of CHIME is presented. Documentation, installation, and usage notes specific to the implementation of CHIME on PC-compatible systems are provided in this User's Guide.

  11. Radiative and Nonradiative Transitions of the Rare-Earth Ions Tm(3+) and Ho(3+) in Y3AI5O12 and LiYF4

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Armagan, Guzin; Dibartolo, Baldassare; Modlin, Edward A.

    1995-01-01

    The optical spectra of rare earth ions in solids arise primarily from electric and magnetic dipole transitions between stark split multiplets of the 4f(sup N) electronic configuration. Electric dipole transitions are parity forbidden between levels of the 4f(sup N) configuration, while those of magnetic dipole origin are allowed. It is known from experiment, however, that the significant contributions to the intensities of most transitions are electric dipole in nature. Judd and Ofelt developed the theory of forced electric dipole transitions of rare-earth ions. This study is devoted to determining electric dipole transition probabilities and branching ratios for Tm(3+) and Ho(3+) ions in Yttrium Aluminum Garnet (YAG) and Yttrium Lithium Fluoride (YLF) using the theory of Judd and Ofelt. The radiative rates determined from the Judd-Ofelt analysis are used with measured lifetimes to find nonradiative rates of relaxation.

  12. Stability and oxide ion conductivity in rare-earth aluminium cuspidines

    SciTech Connect

    Martin-Sedeno, M.C.; Marrero-Lopez, D.; Losilla, E.R.; Bruque, S.; Nunez, P.; Aranda, M.A.G. . E-mail: g_aranda@uma.es

    2006-11-15

    RE{sub 4}(Al{sub 2-}{sub x}Ge{sub x}O{sub 7+}{sub x}{sub /2}{open_square}{sub 1-}{sub x}{sub /2})O{sub 2} (RE=Gd{sup 3+} and Nd{sup 3+}) oxy-cuspidine series have been prepared by ceramic method (RE=Gd{sup 3+}) and freeze-dried precursor method (RE=Nd{sup 3+}). The compositional ranges and the high temperature stability have been determined for both series. Gadolinium aluminium cuspidines are stable at very high temperatures but the analogous neodymium compounds are only stable below 1273 K. Joint Rietveld analyses of neutron powder diffraction (NPD) and laboratory X-ray powder diffraction (LXRPD) have been carried out for Nd{sub 4}(Al{sub 2}O{sub 7}{open_square}{sub 1})O{sub 2} and Nd{sub 4}(Al{sub 1.5}Ge{sub 0.5}O{sub 7.25}{open_square}{sub 0.75})O{sub 2} compositions. Furthermore, Rietveld refinement of synchrotron X-ray powder diffraction (SXRPD) data were carried out for Gd{sub 4}(Al{sub 1.0}Ge{sub 1.0}O{sub 7.5}{open_square}{sub 0.5})O{sub 2} composition. The refinements have confirmed the known structural features of the cuspidine framework. These cuspidines series are oxide ion conductors with negligible electronic contribution as determined from impedance spectroscopy at variable oxygen partial pressures. The enhancement in the overall oxide conductivity along the two oxy-cuspidine series is two orders of magnitude. Typical ionic conductivity values for doped samples are around 4x10{sup -5} S cm{sup -1} at 973 K. - Graphical abstract: The attached figure shows the changes in the oxygen distribution of oxy-cuspidines determined by neutron powder diffraction. These oxo-salts are e ion conductors with negligible electronic contribution.

  13. Direct imaging of rare-earth ion clusters in Yb:CaF2

    NASA Astrophysics Data System (ADS)

    Lacroix, B.; Genevois, C.; Doualan, J. L.; Brasse, G.; Braud, A.; Ruterana, P.; Camy, P.; Talbot, E.; Moncorgé, R.; Margerie, J.

    2014-09-01

    The existence and the identification of only one or several coparticipating luminescent Yb3+ centers in the heavily doped Yb :CaF2 laser crystals which are considered in the development of several high intensity laser chains have been examined first by using two complementary and original experimental approaches, i.e., registration of low temperature site-selective laser excitation spectra related to near-infrared and visible cooperative emission processes, on the one hand, and direct imaging at the atomic scale of isolated ions and clusters using a high-resolution scanning transmission electron microscope in the high angle annular dark-field mode, on the other hand, and then correlating the data with simple crystal field calculations. As a consequence, and although all the experimental details could not be accounted for quantitatively, a good overall correlation was found between the experimental and the theoretical data. The results show that at the investigated dopant concentrations, Yb:CaF2 should be considered as a multisite system whose luminescent and lasing properties are dominated by a series of Yb3+ clusters ranging from dimers to tetramers. Hexameric luminescent centers may be dominant at really high dopant concentrations (likely above 20 at. %), as was originally proposed, but certainly not at the intermediate dopant concentrations which are considered for the laser application, i.e., between about 0.5 and 10 at. %.

  14. Rare-earth-ion-doped Al IIO 3 waveguides for active integrated optical devices

    NASA Astrophysics Data System (ADS)

    Bradley, Jonathan D. B.; Ay, Feridun; Blauwendraat, Tom; Wörhoff, Kerstin; Pollnau, Markus

    2007-06-01

    Reactively co-sputtered amorphous Al IIO 3 waveguide layers with low propagation losses have been deposited. In order to define channel waveguides in such Al IIO 3 films, the etching behaviour of Al IIO 3 has been investigated using an inductively coupled reactive ion etch system. The etch rate of Al IIO 3 and possible mask materials was studied by applying various common process gases and combinations of these gases, including CF 4/O II, BCl 3, BCl 3/HBr and Cl II. Based on a comparison of the etch rates and patterning feasibility of the different mask materials, a BCl 3/HBr plasma and and standard resist mask were used to fabricate channel waveguide structures. The etched structures exhibit straight sidewalls with minimal roughness and etch depths of up to 530 nm, sufficient for defining waveguides with strong optical confinement and low bending losses. Low additional propagation losses were measured in single-mode Al IIO 3 ridge waveguides defined using the developed etch process. In initial investigations, Al IIO 3:Er layers fabricated using the same deposition method applied for the undoped layers show typical emission cross-sections, low green upconversion luminescence and lifetimes up to 7 ms.

  15. ALP (Alkaline Phosphatase) Test

    MedlinePlus

    ... known as: ALK PHOS; Alkp Formal name: Alkaline Phosphatase Related tests: AST ; ALT ; GGT ; Bilirubin ; Liver Panel ; Bone Markers ; Alkaline Phosphatase Isoenzymes; Bone Specific ALP All content on Lab ...

  16. Origin, transport, and losses of energetic He(+) and He(2+) ions in the magnetosphere of the Earth - AMPTE/CCE observations

    NASA Technical Reports Server (NTRS)

    Kremser, G.; Wilken, B.; Gloeckler, G.; Hamilton, D. C.; Ipavich, F. M.; Kistler, L. M.; Tanskanen, P.

    1993-01-01

    Data from the ion charge-energy-mass spectrometer CHEM flown on AMPTE/CCE spacecraft are used to investigate the origin, transport, and losses of energetic He(+) and He(2+) ions in the earth's magnetosphere. The L profiles of the average ion phase space density f were determined as a function of the magnetic momentum. It is shown that the L profiles have an inner part, where f increases with L for both He(+) adn He(2+) and where steady-state conditions are fulfilled. The outer boundary L(lim) of this region is located at a distance that depends on the ion species and the geomagnetic activity level. Steady-state conditions continue outside L(lim) for He(+) ions, while the He(2+) ion distribution outside L(lim) is strongly influenced by ion convection causing a lack of steady-state conditions. It is concluded that solar wind is the origin of the He(2+), while a mixed origin is suggested for the He(+) ions, in which the major contribution is from the solar wind via charge exchange production from the He(2+) ions.

  17. Positron elastic scattering from alkaline earth targets

    NASA Astrophysics Data System (ADS)

    Poveda, Luis A.; Assafrão, Denise; Mohallem, José R.

    2016-07-01

    A previously reported model potential approach [Poveda et al., Phys. Rev. A 87, 052702 (2013)] was extended to study low energy positron elastic scattering from beryllium and magnesium. The cross sections were computed for energies ranging from 10-5 eV up to well above the positronium formation threshold. The present results are in good agreement with previous reports, including the prediction of a p-wave resonance in the cross section for magnesium. The emergence of this shape resonance is connected to a trend observed in the evolution of the partial wave cross section in going from Be to Mg target. This trend lead us to speculate that a sharp d-wave resonance should be observed in positron elastic scattering from calcium. The positron-target binding energies are investigated in detail, both using the scattering information and by direct computation of the bound state energies using the model potentials. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70120-y

  18. Alkaline earth stannates: The next silicon?

    SciTech Connect

    Ismail-Beigi, Sohrab Ahn, Charles H.; Walker, Frederick J.; Cheong, Sang-Wook; Rabe, Karin M.

    2015-06-01

    Semiconductor materials are being used in an increasingly diverse array of applications, with new device concepts being proposed each year for solar cells, flat-panel displays, sensors, memory, and spin transport. This rapid progress of invention outpaces the development of new semiconductor materials with the required properties and performance. In many applications, high carrier mobility at room temperature is required in addition to specific functional properties critical to the device concept. We review recent developments on high mobility stannate perovskite oxide materials and devices.

  19. Dramatic effect of rare earth ion on the electrical and magnetic properties of W-type barium hexaferrites

    NASA Astrophysics Data System (ADS)

    Ahmed, M. A.; Okasha, N.; Kershi, R. M.

    2010-08-01

    A series of W-type hexaferrite samples with composition Ba 1- yLa yZn 0.5Mg 0.5CoFe 16O 27; 0≤ y≤0.07 were prepared using the solid state reaction to investigate their magnetic properties, AC and DC electrical conductivity and thermoelectric power as a function of composition and temperature. The X-ray diffraction was studied to identify the formation of the sample properly. Increasing of (a) and decreasing of (c) lattice parameters leads to a constant volume. The data of ac conductivity showed an increase with both temperature and frequency, and it becomes slightly independent of frequency at higher temperature, also the conduction mechanism depends on an La concentration. The results of the charge carrier mobility suggested that the hopping conduction mechanism of holes due to replacement of La 3+ rare earth ions on the expense of Ba 2+ ions is the predominant one. The transition temperature decreases with increasing La content. The values of dc electrical conductivity σdc at room temperature ranged 4.85×10 -6-3.82×10 -6 (Ω -1 cm -1) and the values of the calculated activation energies Edc ranged 0.215-0.137 eV. The highest values of dielectric constant, electrical conductivity and Curie temperature, also the smallest value of porosity and effective magnetic moment are found at y=0.05. The thermoelectric power coefficient showed that the majority of charge carriers are P-type, except at y=0.03, 0.04 and 0.05 negative charge carriers (electrons) takes place at high temperature region.

  20. Integrating biotinylated polyalkylthiophene thin films with biological macromolecules: biosensing organophosphorus pesticides and metal ions with surface immobilized alkaline phosphatase utilizing chemiluminescence measurements

    NASA Astrophysics Data System (ADS)

    Pande, Rajiv; Kamtekar, S.; Ayyagari, Madhu S. R.; Marx, Kenneth A.; Kumar, Jayant; Tripathy, Sukant K.; Kaplan, David L.

    1995-05-01

    We describe a methodology for immobilizing the enzyme alkaline phosphatase onto a glass surface using a novel biotinylated copolymer poly (3-undecylthiophene-co-3- thiophenecarboxaldehyde) 6-biotinamido hexanohydrazide attached hydrophobically to silanized glass. The biotin-streptavidin protein interaction is used to carry out this immobilization. Alkaline phosphatase catalyzes the dephosphorylation of a class of macrocyclic compounds: including CSPD {chloro 3-[4-methoxy spiro(1,2 dioxetane-3-2-trichloro-(3.3.1.1)-decan]-4 yl}phenyl phosphate to a product species which emits energy by chemiluminescence. We can detect this chemiluminescence signal with a photomultiplier tube for both enzymatic catalysis in solution and the surface immobilized enzyme (streptavidin conjugate). This enzyme is inhibited by the organophosphorus class of pesticides as well as nerve agents. The enzyme is also inhibited by Be(II), Bi(III) as well as excess Zn(II), while the apoenzyme is reactivated by Zn(II). We demonstrate in this study that two representative organophosphorus pesticides inhibit the enzymatic production of chemiluminescent products. This is true for the enzyme conjugate both free in solution and immobilized. We can detect pesticides down to about 50 ppb for the enzyme in solution and 500 ppb for surface immobilized enzyme in a 100 (mu) l capillary. Detection of Zn(II) by apoenzyme reactivation occurs down to 3 ppb. Be(II) and Bi(III) are detected by inhibition down to 1 ppm.

  1. Recent Alkaline Lakes: Clues to Understanding the Evolution of Early Planetary Alkaline Oceans and Biogenesis

    NASA Astrophysics Data System (ADS)

    Kempe, S.; Hartmann, J.; Kazmierczak, J.

    2008-09-01

    Abstract New models suggest that terrestrial weathering consumes 0.26GtC/a (72% silicate-, 28% carbonateweathering), equivalent to a loss of one atmospheric C content every 3700a. Rapid weathering leads in volcanic areas to alkaline conditions, illustrated by the crater lake of Niuafo`ou/Tonga and Lake Van/Turkey, the largest soda lake on Earth. Alkaline conditions cause high CaCO3 supersaturation, permineralization of algal mats and growth of stromatolites. Alkaline conditions can nearly depress free [Ca2+] to levels necessary for proteins to function. Therefore early oceans on Earth (and possibly on Mars) should have been alkaline (i.e. "Soda Oceans"). Recent findings of MgSO4 in top soils on Mars may be misleading about the early history of martian oceans.

  2. The effect of oxygen on segregation-induced redistribution of rare-earth elements in silicon layers amorphized by ion implantation

    SciTech Connect

    Aleksandrov, O. V.

    2006-08-15

    A model of segregation-induced redistribution of impurities of rare-earth elements during solid-phase epitaxial crystallization of silicon layers amorphized by ion implantation is developed. This model is based on the assumption that a transition layer with a high mobility of atoms is formed at the interphase boundary on the side of a-Si; the thickness of this layer is governed by the diffusion length of vacancies in a-Si. The Er concentration profiles in Si implanted with both erbium and oxygen ions are analyzed in the context of the model. It shown that, in the case of high doses of implantation of rare-earth ions, it is necessary to take into account the formation of R{sub m} clusters (m = 4), where R denotes the atom of a rare-earth element, whereas, if oxygen ions are also implanted, formation of the complexes RO{sub n} (n = 3-6) should be taken into account; these complexes affect the transition-layer thickness and segregation coefficient.

  3. Optical detection of ultrasound using AFC-based quantum memory technique in cryogenic rare earth ion doped crystals

    NASA Astrophysics Data System (ADS)

    Taylor, Luke R.; McAuslan, David L.; Longdell, Jevon J.

    2013-03-01

    We present results of a novel and highly sensitive technique for the optical detection of ultrasound using the selective storage of frequency shifted photons in an inherently highly efficient and low noise atomic frequency comb (AFC) based quantum memory. The ultrasound `tagged' optical sidebands are absorbed within a pair of symmetric AFCs, generated via optical pumping in a Pr3+:Y2SiO5 sample (tooth separation Δ = 150 kHz, comb finesse fc ~ 2 and optical depth αL ~ 2), separated by twice the ultrasound modulation frequency (1.5 MHz) and centered on either side of a broad spectral pit (1.7 MHz width) allowing transmission of the carrier. The stored sidebands are recovered with 10-20% efficiency as a photon echo (as defined by the comb parameters), and we demonstrate a record 49 dB discrimination between the sidebands and the carrier pulse, high discrimination being important for imaging tissues at depth. We further demonstrate detector limited discrimination (~29 dB) using a highly scattered beam, confirming that the technique is immune to speckle decorrelation. We show that it also remains valid in the case of optically thin samples, and thus represents a significant improvement over other ultrasound detection methods based on rare-earth-ion-doped crystals. These results strongly suggest the suitability of our technique for high-resolution non-contact real-time imaging of biological tissues.

  4. Optical properties and size distribution of the nanocolloids made of rare-earth ion-doped NaYF4

    NASA Astrophysics Data System (ADS)

    Patel, Darayas N.; Lewis, Ashley; Wright, Donald M.; Lewis, Danielle; Valentine, Rueben; Valentine, Maucus; Wessley, Dennis; Sarkisov, Sergey; Darwish, Abdalla M.

    2015-03-01

    In this paper we investigate optical properties and size distribution of the nano-colloids made of trivalent rare-earth ion doped fluorides: holmium and ytterbium, thulium and ytterbium, and erbium and ytterbium co-doped NaYF4. These materials were synthesized by using simple co-precipitation synthetic method. The initially prepared micro-crystals had very weak or no visible upconversion fluorescence signals when being pumped with a 980-nm laser. The fluorescence intensity significantly increased after the crystals were annealed at a temperature of 400°C - 600°C undergoing the transition from cubic alpha to hexagonal beta phase of the fluoride host. Nano-colloids of the crystals were made in polar solvents using the laser ablation and ball milling methods. Size analyses of the prepared nano-colloids were conducted using a dynamic light scatterometer and atomic force microscope. The nano-colloids were filled in holey PCFs and their fluorescent properties were studied and the feasibility of new a type of fiber amplifier/laser was evaluated.

  5. Mechanistic Investigation of Solvent Extraction Based on Anion-Functionalized Ionic Liquids for Selective Separation of Rare-Earth Ions

    SciTech Connect

    Sun, Xiaoqi; Luo, Huimin; Dai, Sheng

    2013-01-01

    In this study, solvation has been found to be a dominant mechanism in a comprehensive ionic liquid based extraction system for rare earth elements (REEs). Trioctylmethylammonium di(2-ethylhexyl)phosphate ([TOMA][DEHP]), an ionic-liquid extractant, was used in 1-alkyl-3-methylimidizolium bis[(trifluoromethyl)sulfonyl]imide ([Cnmim][NTf2], n = 4, 6, 8, 10) and 1-alkyl-3-methylimidizolium bis(perfluoroethanesulfonyl)imide ([Cnmim][BETI], n = 4, 6, 8, 10) for the separation of REEs. Surprisingly, a very similar extraction behavior was observed even as the carbon chain length on the ionic-liquid (IL) cation increased from butyl (C4) to hexyl (C6), to octyl (C8), to decyl (C10). This behavior is in sharp contrast to that exhibited by the conventional neutral extractants, whose extraction efficiencies are strongly dependent on the hydrophobicity of IL cations. Furthermore, the addition of IL cations ([Cnmim]+) or IL anions ([NTf2]- or [BETI]-) to the aqueous phase had little effect on the extraction behavior of the above extraction system, ruling out the strong involvement of the ion-exchange mechanism associated with traditional IL-based extraction systems. Results showed that the extractabilities and selectivities of REEs using [TOMA][DEHP] in [C10mim][NTf2]/[BETI] are several orders of magnitude better than those achieved using conventional organic solvent, diisopropylbenzene (DIPB). This study highlights the potential of developing a comprehensive IL-based extraction strategy for REEs separations.

  6. Pre-selection of optical transitions in rare-earth ions in crystals perspective for quantum information processing

    NASA Astrophysics Data System (ADS)

    Basiev, T. T.; Basieva, I. T.; Kornienko, A. A.; Osiko, V. V.; Pukhov, K. K.; Sekatskii, S. K.

    2012-01-01

    A systematic analysis of decoherence rates due to electron-phonon interactions for optical transitions of rare-earth dopant ions in crystals is presented in the frame of the point charge model. For this model, the large value of any one of the matrix elements of the unit tensor operator U ( k ) of rank k for transitions within the 4f-electronic configuration, viz. U2, U4 or U6, is enough to ensure the strong optical transition between different levels, while the Stark-Stark transitions within the multiplet can be characterized by the matrix element U2 alone, the influence of elements U4, U6 being of much smaller order of magnitude and neglected. The circumstance that exactly such Stark-Stark transitions within the multiplet define the efficiency of electron-phonon interaction and, consequently, the decoherence rate (except for the case of lowest, less than approximately 2-4 K, temperatures), enables selection of optical transitions which are strong enough and at the same time are characterized by relatively small decoherence rates. Correspondingly, these optical transitions, provided that they lie in an appropriate spectral range and the gap to the nearest neighboring energy level is large enough (>500 cm-1) to prevent eventual fast phonon-assisted relaxation, should be considered as prospective for subsequent use in quantum informatics processing and communication. The list of such pre-selected transitions is given; the applicability area and limitations of our approach are discussed.

  7. Chelation ion chromatography as a method for trace elemental analysis in complex environmental and biological samples

    SciTech Connect

    Siriraks, A.; Kingston, H.M. ); Riviello, J.M. )

    1990-06-01

    The development and evaluation of a new method for the determination of trace transition and rare-earth elements based on the combination of chelation and ion chromatography are described. The new method, chelation ion chromatography (Chelation IC), uses a chelating column to concentrate and separate transition and rare-earth elements from the common alkali and alkaline-earth metals, as well as other matrix components, prior to analysis by ion chromatography. The sample fraction from the chelating column contains only the concentrated analyte ions, thus eliminating interfering matrix components from complex matrices such as seawater and digested biological, botanical, and geological materials. This combination of chelation and ion chromatography provides a technique that makes possible the determination of trace elements in complex matrices that have proven to be difficult or impossible to analyze by ion chromatography or conventional atomic spectroscopy techniques.

  8. Fabrication of free-standing NiCo{sub 2}O{sub 4} nanoarrays via a facile modified hydrothermal synthesis method and their applications for lithium ion batteries and high-rate alkaline batteries

    SciTech Connect

    Zheng, Qingyun Zhang, Xiangyang; Shen, Youming

    2015-03-15

    Graphical abstract: Hydrothermal-synthesized NiCo{sub 2}O{sub 4} nanoflake arrays exhibit porous structure and high capacity as well as good cycling life for lithium ion batteries and alkaline batteries. - Highlights: • Self-supported NiCo{sub 2}O{sub 4} nanoflake arrays are prepared by a hydrothermal method. • NiCo{sub 2}O{sub 4} nanoflake arrays show high capacity and good cycling life. • Porous nanoflake arrays structure is favorable for fast ion/electron transfer. - Abstract: Self-supported NiCo{sub 2}O{sub 4} nanoflake arrays on nickel foam are prepared by a facile hydrothermal method. The obtained NiCo{sub 2}O{sub 4} nanoflakes with thicknesses of ∼25 nm grow vertically to the nickel foam substrate and form an interconnected porous network with pore diameters of 50–500 nm. As anode material of LIBs, the NiCo{sub 2}O{sub 4} nanoflake arrays show a high initial coulombic efficiency of 76%, as well as good cycling stability with a capacity of 880 mAh g{sup −1} at 0.5 A g{sup −1}, and 523 mAh g{sup −1} at 1.5 A g{sup −1} after 50 cycles. As the cathode of alkaline batteries, a high capacity of 95 mAh g{sup −1} is achieved at 2 A g{sup −1} and 94% retention is maintained after 10,000 cycles. The superior electrochemical performance is mainly due to the unique nanoflake arrays structure with large surface area and shorter diffusion length for mass and charge transport.

  9. Storage and retrieval of collective excitations on a long-lived spin transition in a rare-earth ion-doped crystal.

    PubMed

    Goldschmidt, E A; Beavan, S E; Polyakov, S V; Migdall, A L; Sellars, M J

    2013-04-22

    Robust, long-lived optical quantum memories are important components of many quantum information and communication protocols. We demonstrate coherent generation, storage, and retrieval of excitations on a long-lived spin transition via spontaneous Raman scattering in a rare-earth ion-doped crystal. We further study the time dynamics of the optical correlations in this system. This is the first demonstration of its kind in a solid and an enabling step toward realizing a solid-state quantum repeater.

  10. Evaluating the role of metal ions in the bathochromic and hyperchromic responses of cyanidin derivatives in acidic and alkaline pH.

    PubMed

    Sigurdson, G T; Robbins, R J; Collins, T M; Giusti, M M

    2016-10-01

    In many food products, colorants derived from natural sources are increasingly popular due to consumer demand. Anthocyanins are one class of versatile and abundant naturally occurring chromophores that produce different hues in nature, especially with metal ions and other copigments assisting. The effects of chelation of metal ions (Mg(2+), Al(3+), Cr(3+), Fe(3+), and Ga(3+)) in factorial excesses to anthocyanin concentration (0-500×) on the spectral characteristics (380-700nm) of cyanidin and acylated cyanidin derivatives were evaluated to better understand the color evolution of anthocyanin-metal chelates in pH 3-8. In all pH, anthocyanins exhibited bathochromic and hyperchromic shifts. Largest bathochromic shifts most often occurred in pH 6; while largest hyperchromic shifts occurred in pH 5. Divalent Mg(2+) showed no observable effect on anthocyanin color while trivalent metal ions caused bathochromic shifts and hue changes. Generally, bathochromic shifts on anthocyanins were greatest with more electron rich metal ions (Fe(3+)≈Ga(3+)>Al(3+)>Cr(3+)).

  11. Evaluating the role of metal ions in the bathochromic and hyperchromic responses of cyanidin derivatives in acidic and alkaline pH.

    PubMed

    Sigurdson, G T; Robbins, R J; Collins, T M; Giusti, M M

    2016-10-01

    In many food products, colorants derived from natural sources are increasingly popular due to consumer demand. Anthocyanins are one class of versatile and abundant naturally occurring chromophores that produce different hues in nature, especially with metal ions and other copigments assisting. The effects of chelation of metal ions (Mg(2+), Al(3+), Cr(3+), Fe(3+), and Ga(3+)) in factorial excesses to anthocyanin concentration (0-500×) on the spectral characteristics (380-700nm) of cyanidin and acylated cyanidin derivatives were evaluated to better understand the color evolution of anthocyanin-metal chelates in pH 3-8. In all pH, anthocyanins exhibited bathochromic and hyperchromic shifts. Largest bathochromic shifts most often occurred in pH 6; while largest hyperchromic shifts occurred in pH 5. Divalent Mg(2+) showed no observable effect on anthocyanin color while trivalent metal ions caused bathochromic shifts and hue changes. Generally, bathochromic shifts on anthocyanins were greatest with more electron rich metal ions (Fe(3+)≈Ga(3+)>Al(3+)>Cr(3+)). PMID:27132820

  12. EMIC-wave-moderated flux limitations of ring current energetic ion intensities in the multi-species plasmas of Earth's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Mauk, B.

    2013-12-01

    One of the early sophisticated integrations of theory and observations of the space age was the development in 1966 of the integral Kennel-Petschek flux limit for trapped energetic electrons and ions within Earth's inner magnetosphere. Specifically, it was proposed that: 1) trapped particle distributions in the magnetic bottle configuration of the inner magnetosphere are intrinsically unstable to the generation various plasma waves and 2) ionospheric reflection of some waves back into the trapped populations leads to runaway growth of the waves and dramatic loss of particles for particle integral intensities that rise above a fairly rigidly specified upper limit. While there has been a long hiatus in utilization of the KP limit in inner magnetospheric research, there have been recent highly successful reconsiderations of more general forms of the KP limit for understanding radiation belt electron intensities and spectral shapes, resulting from improvements in theoretical tools. Such a reconsideration has not happened for energetic trapped ions, perhaps due to the perceived immense complexity of the generation of the Electromagnetic Ion Cyclotron (EMIC) waves, that scatter the energetic ions, for plasmas containing multiple ionic species (H, He, O). Here, a differential Kennel-Petschek (KP) flux limit for magnetospheric energetic ions is devised taking into account multiple ion species effects on the EMIC waves. This new theoretical approach is applied to measured Earth magnetosphere energetic ion spectra (~ keV to ~ 1 MeV) for radial positions (L) 3 to 6.7 RE. The flatness of the most intense spectral shapes for <100 keV indicate sculpting by just such a mechanism, but modifications of traditional KP parameters are needed to account for maximum intensities up to 5 times greater than expected. Future work using the Van Allen Probes mission will likely resolve outstanding uncertainties.

  13. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    SciTech Connect

    Islam, Z.

    1999-05-10

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi{sub 2}Ge{sub 2} (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi{sub 2}Ge{sub 2} compounds. Generalized susceptibility, {chi}{sub 0}(q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi{sub 2}Ge{sub 2}, and the commensurate structure in EuNi{sub 2}Ge{sub 2}. A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T{sub N} in EuNi{sub 2}Ge{sub 2} than that in GdNi{sub 2}Ge{sub 2} is also explained. Next, all the metamagnetic phases in TbNi{sub 2}Ge{sub 2} with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation.

  14. Development of an optical thermal history coating sensor based on the oxidation of a divalent rare earth ion phosphor

    NASA Astrophysics Data System (ADS)

    Yáñez-González, Álvaro; Ruiz-Trejo, Enrique; van Wachem, Berend; Skinner, Stephen; Beyrau, Frank; Heyes, Andrew

    2016-11-01

    The measurement of temperatures in gas turbines, boilers, heat exchangers and other components exposed to hot gases is essential to design energy efficient systems and improve maintenance procedures. When on-line measurements, such as those performed with thermocouples and pyrometers, are not possible or inconvenient, the maximum temperatures of operation can be recorded and measured off-line after operation. Although thermal paints have been used for many years for this purpose, a novel technique based on irreversible changes in the optical properties of thermographic phosphors, can overcome some of the disadvantages of previous methods. In particular, oxidation of the divalent rare earth ion phosphor BaMgAl10O17:Eu (BAM:Eu) has shown great potential for temperature sensing between 700 °C and 1200 °C. The emission spectra of this phosphor change with temperature, which permits to define an intensity ratio between different lines in the spectra that can be used as a measurand of the temperature. In this paper, the study of the sensing capabilities of a sensor coating based on BAM:Eu phosphor material is addressed for the first time. The sensitivity of the intensity ratio is investigated in the temperature range from 800 °C to 1100 °C, and is proved to be affected by ionic diffusion of transition metals from the substrate. The use of an interlayer made of zirconia proves efficient in reducing ionic diffusion and coatings with this diffusion barrier present sensitivity comparable to that of the powder material.

  15. Preparation and Electrochemical Performance of LiNi1/3Co1/3Mn1/3O2 Cathode Materials for Lithium-ion Batteries from Spent Mixed Alkaline Batteries

    NASA Astrophysics Data System (ADS)

    Yang, Li; Xi, Guoxi

    2016-01-01

    LiNi1/3Co1/3Mn1/3O2 cathode materials of lithium-ion batteries were successfully re-synthesized using mixed spent alkaline zinc-manganese batteries and spent lithium-ion batteries as the raw materials. These materials were synthesized by using a combination of dissolution, co-precipitation, calcination, battery preparation, and battery charge-discharge processes. The phase composition, morphology, and electrochemical performance of the products were determined by inductively coupled plasma optical emission spectroscopy, infrared spectra, x-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy, and charge-discharge measurements. The results showed that LiNi1/3Co1/3Mn1/3O2 cathode materials could be successfully re-synthesized at optimal preparation conditions of: co-precipitation, pH value of 8, calcination temperature of 850°C, and calcination time of 10 h. Furthermore, the electrochemical results showed that the re-synthesized sample could deliver an initial discharge capacity of up to 160.2 mAh g-1 and Coulomb efficiency of 99.8%.

  16. Influence of the ionic liquid cation on the solvent extraction of trivalent rare-earth ions by mixtures of Cyanex 923 and ionic liquids.

    PubMed

    Rout, Alok; Binnemans, Koen

    2015-01-21

    Trivalent rare-earth ions were extracted from nitric acid medium by the neutral phosphine oxide extractant Cyanex 923 into ionic liquid phases containing the bis(trifluoromethylsulfonyl)imide anion. Five different cations were considered: 1-butyl-3-methylimidazolium, 1-decyl-3-methylimidazolium, methyltributylammonium, methyltrioctylammonium and trihexyl(tetradecyl)phosphonium. The extraction behavior of neodymium(iii) was investigated as a function of various parameters: pH, extractant concentration, concentration of the neodymium(iii) ion in the aqueous feed and concentration of the salting-out agent. The loading capacity of the ionic liquid phase was studied. The extraction efficiency increased with increasing pH of the aqueous feed solution. The extraction occurred for all ionic liquids via an ion-exchange mechanism and the extraction efficiency could be related to the solubility of the ionic liquid cation in the aqueous phase: high distribution ratios for hydrophilic cations and low ones for hydrophobic cations. Addition of nitrate ions to the aqueous phase resulted in an increase in extraction efficiency for ionic liquids with hydrophobic cations due to extraction of neutral complexes. Neodymium(iii) could be stripped from the ionic liquid phase by 0.5-1.0 M nitric acid solutions and the extracting phase could be reused. The extractability of other rare earths present in the mixture was compared for the five ionic liquids.

  17. Transport, charge exchange and loss of energetic heavy ions in the earth's radiation belts - Applicability and limitations of theory

    NASA Technical Reports Server (NTRS)

    Spjeldvik, W. N.

    1981-01-01

    Computer simulations of processes which control the relative abundances of ions in the trapping regions of geospace are compared with observations from discriminating ion detectors. Energy losses due to Coulomb collisions between ions and exospheric neutrals are considered, along with charge exchange losses and internal charge exchanges. The time evolution of energetic ion fluxes of equatorially mirroring ions under radial diffusion is modelled to include geomagnetic and geoelectric fluctutations. Limits to the validity of diffusion transport theory are discussed, and the simulation is noted to contain provisions for six ionic charge states and the source effect on the radiation belt oxygen ion distributions. Comparisons are made with ion flux data gathered on Explorer 45 and ISEE-1 spacecraft and results indicate that internal charge exchanges cause the radiation belt ion charge state to be independent of source charge rate characteristics, and relative charge state distribution is independent of the radially diffusive transport rate below the charge state redistribution zone.

  18. Synthesis of uniform rare earth fluoride (NaMF4) nanotubes by in situ ion exchange from their hydroxide [M(OH)3] parents.

    PubMed

    Zhang, Fan; Zhao, Dongyuan

    2009-01-27

    In this article, we demonstrate the production of uniform hexagonal sodium rare earth fluoride (beta-NaMF(4)) nanotubes through a hydrothermal in situ ion-exchange reaction by using rare earth hydroxides [M(OH)(3)] as a parent. The trivalent rare earth hydroxides were hydrothermally prepared at 120 degrees C and possessed a quasi-layered structure, which could be formed to be nanotubal morphology through a rolling up process from 2-D sheets. Moreover, the hexagonal structure of rare earth hydroxides [M(OH)(3)] displays a noticeable similarity with beta-NaMF(4). This similarity makes the formation of beta-NaMF(4) with nonlayered structure possible through in situ chemical transformation from M(OH)(3) with a layered structure. The single-crystal beta-NaMF(4) nanotubes were synthesized with well-controlled diameter (80-500 nm), aspect ratio (6-30), wall thickness (25-80 nm), and contents (such as M = Pr, Sm, Gd, Tb, Dy, Er, as well as lanthanide-doped rare earth NaMF(4)). The multicolor upconversion fluorescence has also been successfully realized in the Yb(3+)/Er(3+) (green) and Yb(3+)/Tm(3+) (blue) co-doped beta-NaMF(4) nanotubes by UC excitation in the NIR region. The various UC emission ratios of the samples were investigated as a function of hydrothermal reaction time to research the UC properties of the products and to further demonstrate the hydrothermal in situ ion-exchange process.

  19. Anodes for alkaline electrolysis

    DOEpatents

    Soloveichik, Grigorii Lev

    2011-02-01

    A method of making an anode for alkaline electrolysis cells includes adsorption of precursor material on a carbonaceous material, conversion of the precursor material to hydroxide form and conversion of precursor material from hydroxide form to oxy-hydroxide form within the alkaline electrolysis cell.

  20. Alkaline "Permanent" Paper.

    ERIC Educational Resources Information Center

    Pacey, Antony

    1991-01-01

    Discussion of paper manufacturing processes and their effects on library materials focuses on the promotion of alkaline "permanent" paper, with less acid, by Canadian library preservation specialists. Standards for paper acidity are explained; advantages of alkaline paper are described, including decreased manufacturing costs; and recyclability is…

  1. Redox reactions of actinides in carbonate and alkaline solutions

    NASA Astrophysics Data System (ADS)

    Shilov, Vladimir P.; Yusov, Aleksander B.

    2002-06-01

    Data on redox reactions involving uranium, neptunium, plutonium and americium ions in carbonate and alkaline solutions are generalised. The results of kinetic studies of these reactions are analysed and their mechanisms are discussed. The bibliography includes 169 references.

  2. Sequential injection system with higher dimensional electrochemical sensor signals Part 2. Potentiometric e-tongue for the determination of alkaline ions.

    PubMed

    Cortina, M; Gutés, A; Alegret, S; Del Valle, Manuel

    2005-06-15

    An intelligent, automatic system based on an array of non-specific-response chemical sensors was developed. As a great amount of information is required for its correct modelling, we propose a system generating it itself. The sequential injection analysis (SIA) technique was chosen as it enables the processes of training, calibration, validation and operation to be automated simply. Detection was carried out using an array of potentiometric sensors based on PVC membranes of different selectivity. The diluted standard solutions needed for system learning and response modelling are automatically prepared from more concentrated standards. The electrodes used were characterised with respect to one and two analytes, by means of high-dimensionality calibrations, and the response surface of each was represented; this characterisation enabled an interference study of great practical utility. The combined response was modelled by means of artificial neural networks (ANNs), and thus it was possible to obtain an automated electronic tongue based on SIA. In order to identify the ANN which provided the best model of the electrode responses, some of the network's parameters were optimised and its usefulness in determining NH(4)(+), K(+) and Na(+) ions in synthetic samples was then tested. Finally, it was used to determine these ions in commercial fertilisers, the obtained results being compared with reference methods. PMID:18970109

  3. Hydrogen ion secretion by the collecting duct as a determinant of the urine to blood PCO2 gradient in alkaline urine

    SciTech Connect

    DuBose, T.D. Jr.

    1982-01-01

    Several theories have been advanced to explain the elevation in urinary PCO/sub 2/ during bicarbonate loading and include: (a) H+ secretion, (b) countercurrent system for CO/sub 2/, (c) the ampholyte properties of bicarbonate, and (d) mixing of urine of disparate bicarbonate and butter concentrations. In this study microelectrodes were used to measure in situ and equilibrium pH (pHis and pHeq) and PCO/sub 2/ in control and bicarbonate loaded rats before and after infusion of carbonic anhydrase. The disequilibrium pH method (pHdq . pHis - pHeq) was used to demonstrate H+ secretion. Control rats excreting an acid urine (pH . 6.04 +/- 0.06) failed to display a significant disequilibrium pH at the base (BCD), or tip (TCD) of the papillary collecting duct. Urine pH (7.54 +/- 0.12), and urine to blood (U-B) PCO/sub 2/ increased significantly during NaHCO/sub 3/ loading while PCO/sub 2/ at the BCD and TCD also increased (95 +/- 4 and 122 +/- 4). Furthermore, an acid disequilibrium pH was present at both the BCD and TCD (-0.42 +/- 0.04 and -0.36 +/- 0.03) and was obliterated by carbonic anhydrase. Comparison of the PCO/sub 2/ in the BCD or TCD with the adjacent vasa recta revealed similar values (r . 0.97). It is concluded that H+ secretion by the collecting duct into bicarbonate containing fluid with delayed dehydration of H/sub 2/CO/sub 3/, is the most likely determinant of the U-B PCO/sub 2/ in alkaline urine. Similar values for PCO/sub 2/ in the collecting duct and the adjacent vasa recta suggests trapping of CO/sub 2/ in the medullary countercurrent system. The rise in PCO/sub 2/ occurs both along the collecting duct and after exit from the papilla.

  4. Kinetic studies of the [NpO₂ (CO₃)₃]⁴⁻ ion at alkaline conditions using ¹³C NMR

    SciTech Connect

    Panasci, Adele F.; Harley, Stephen J.; Zavarin, Mavrik; Casey, William H.

    2014-04-21

    Carbonate ligand-exchange rates on the [NpO₂ (CO₃)₃]⁴⁻ ion were determined using a saturation-transfer ¹³C nuclear magnetic resonance (NMR) pulse sequence in the pH range of 8.1 ≤ pH ≤ 10.5. Over the pH range 9.3 ≤ pH ≤ 10.5, which compares most directly with previous work of Stout et al.,1 we find an average rate, activation energy, enthalpy, and entropy of k298ex = 40.6(±4.3) s⁻¹, Ea =45.1(±3.8) kJ mol⁻¹, ΔH = 42.6(±3.8) kJ mol⁻¹, and ΔS = -72(±13) J mol⁻¹ K⁻¹, respectively. These activation parameters are similar to the Stout et al. results at pH 9.4. However, their room-temperature rate at pH 9.4, k298ex = 143(±1.0) s⁻¹, is ~3 times faster than what we experimentally determined at pH 9.3: k298ex = 45.4(±5.3) s⁻¹. Our rates for [NpO₂ (CO₃)₃]⁴⁻ are also faster by a factor of ~3 relative to the isoelectronic [UO₂(CO₃)₃]⁴⁻ as reported by Brucher et al.2 of k298ex = 13(±3) s⁻¹. Consistent with results for the [UO₂(CO₃)₃]⁴⁻ ion, we find evidence for a proton-enhanced pathway for carbonate exchange for the [NpO₂(CO₃)₃]⁴⁻ ion at pH < 9.0.

  5. Control of the visible emission in the SrZrO3 nano-crystals with the rare earth ion doping.

    PubMed

    Kim, Dong Hwan; Kim, Ji Hyun; Chung, Jin Seok; Lee, Yunsang

    2013-11-01

    We investigated the emission property of SrZrO3 nano-crystals (NCs) with the doping of rare earth (RE) ions, Eu3+ and Tm3+, by using 325 nm photo-excitation. SrZrO3 NCs show a sizable violet-blue emission, while the Eu3+ and Tm3+ ions are well known to be good red and blue phosphors, respectively. Combined emissions of the host and the RE ion dopant might suggest a new white luminescent source. The RE ion doped SrZrO3 NCs were initially synthesized by using the combustion method, and then the as-synthesized crystals were annealed at different temperatures from 650 degrees C to 1450 degrees C. The Eu3+-doped SrZrO3 NCs showed the sharp red emission near 600 nm, in addition to a violet-blue emission of the host material in itself. While the red emission is enhanced in the high temperature post-annealing, the blue emission is suppressed in an opposite way. This close relation between the emissions of the host and dopant was observed similarly in the Tm3+-doped NCs. We could control the emission property in the SrZrO3:Eu3+/Tm3+ NCs from blue to red by thermal annealing and RE ion doping.

  6. Winds and Ion Drifts Measured in the Thermospheric Footprint of Earth's Northern Magnetic Cusp During the C-REX Sounding Rocket Mission

    NASA Astrophysics Data System (ADS)

    Conde, M.; Larsen, M. F.; Hampton, D.; Dhadly, M. S.; Ahrns, M. J.; Aruliah, A. L.; Kakinami, Y.; Barker, B.; Kiene, A.; Sigernes, F.; Lorentzen, D. A.

    2015-12-01

    We report here on neutral wind and ion drift measurements recorded during the November 24, 2014, "C-REX" sounding rocket mission into the thermosphere beneath Earth's northern geomagnetic cusp. The rocket released ten tracer clouds, each comprised of a mixture of barium and strontium, at altitudes between 190 and 400 km. The clouds were created by launching rocket-propelled "grenades" at high velocity out from the parent payload, and were dispersed across a 3D volume extending over many tens of km around the main trajectory. Cameras located at Longyearbyen, Ny-Alesund, and aboard an aircraft stationed north of Bear Island were used to image the tracer clouds and to triangulate on their position and 3D motion. Sunlight striking the clouds ionized the barium within a few tens of seconds, whereas the strontium remained neutral. We were thus able to independently measure the flow velocity of both neutrals and ions at the release locations. Here we will present high-resolution maps of the tracer cloud motion, along with the resulting estimates of neutral and ion flow velocities. These results show very substantial ion-neutral velocity differences: the ions' drift direction was roughly perpendicular to that of the neutrals, while the magnitude of their velocity difference was of order 500 meters per second. Combining these data with ground-based measurements of temperature and electron density allows us to estimate that the specific power density for Joule heating at heights above 200 km was very substantial during the time of this experiment. If such Joule heating is typical, it is very likely to play a major role in establishing the (currently poorly understood) permanent enhancements in the neutral mass density of Earth's thermosphere in the geomagnetic cusp regions at altitudes of around 400 km.

  7. Formation of molecular ions by radiative association of cold trapped atoms and ions

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; da Silva, Humberto, Jr.; Aymar, Mireille; Raoult, Maurice

    2015-05-01

    Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca+ , Sr+ , Ba+) and Yb+ are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions show that the final molecular ions are not created in their ground state level. Supported by the Marie-Curie ITN ``COMIQ: Cold Molecular Ions at the Quantum limit'' of the EU (#607491).

  8. Conditions for acceleration of energetic ions greater than 30 keV associated with the earth's bow shock

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Hovestadt, D.; Ipavich, F. M.; Gloeckler, G.

    1980-01-01

    A statistical analysis of particles (greater than 30 keV/charge) upstream of the earth's bow shock is conducted and shows that the rate of occurrence of upstream particle events is relative to the angle between the magnetic field and the shock normal at the shock intersection point as well as relative to the angle between the magnetic field and the radial direction (i.e., the sun-earth line). In addition, the occurrence rate of upstream particle events relative to the bow shock connection time of a field line convected with the solar wind is presented for a model bow shock. A linear dependence of the diffusion coefficient on energy per charge is apparent with the value of the mean free path of a 30-keV proton found to be about 4 earth radii, and the free escape boundary to be at about 30 earth radii in front of the bow shock.

  9. Alkaline battery operational methodology

    DOEpatents

    Sholklapper, Tal; Gallaway, Joshua; Steingart, Daniel; Ingale, Nilesh; Nyce, Michael

    2016-08-16

    Methods of using specific operational charge and discharge parameters to extend the life of alkaline batteries are disclosed. The methods can be used with any commercial primary or secondary alkaline battery, as well as with newer alkaline battery designs, including batteries with flowing electrolyte. The methods include cycling batteries within a narrow operating voltage window, with minimum and maximum cut-off voltages that are set based on battery characteristics and environmental conditions. The narrow voltage window decreases available capacity but allows the batteries to be cycled for hundreds or thousands of times.

  10. Synthesis and phase transitions of oxide-ion conducting compound La{sub 2}Mo{sub 2}O{sub 9} doped with alkaline metals

    SciTech Connect

    Kolesnikova, D. S.; Kharitonova, E. P.; Voronkova, V. I.

    2011-03-15

    The specific features of synthesis, polymorthism, and electric conductivity of oxide-ion conducting compounds La{sub 2-x}Me{sub x}Mo{sub 2}O{sub 9-y}, where Me = Na, K, Rb, or Cs, have been studied. Ceramic samples were obtained by solid-state synthesis in the temperature range of 960-1100 Degree-Sign C. The regions where solid solutions exist have been found to depend on the temperature of the sample firing. According to the calorimetric and electrophysical data, the phase transition from the monoclinic phase ({alpha}) to the cubic phase ({beta}) in samples doped with potassium and rubidium disappears at x = 0.02 and 0.04, respectively. In these cases the only transition from the cubic {beta}{sub ms} phase to the high-temperature cubic {beta} phase is observed near 450 Degree-Sign C. Doping with sodium and cesium does not suppress the {alpha} {yields} {beta} phase transition.

  11. Evaluation and comparison of SuperLig{reg_sign} 644, resorcinol-formaldehyde and CS-100 ion exchange materials for the removal of cesium from simulated alkaline supernate

    SciTech Connect

    Brown, G.N.; Bray, L.A.; Eloviche, R.J.; Bruening, R.L.; Decker, R.M.; Kafka, T.M.; White, L.R.

    1995-03-01

    PNL evaluated three polymeric materials for Cs removal efficiency from a simulated Hanford Neutralized Current Acid Waste (NCAW) supernatant liquid using 200 mL ion exchange columns. Cs loadings (mmole Cs/g resin) were 0.20, 0.18, and 0.039 for Super Lig 644, R-F, and CS-100 (0.045, 0.070, 0.011 mmole Cs/mL resin). Elution of each resin material with 0.5 M HNO{sub 3} required 3.5, 7.0, and 3.2 cv to reach 0.1 C/C{sub 0} for the respective materials, resulting in volume compressions of 27, 20, and 6.9. Peak Cs concentrations during elution was 185, 38.5, and 27.8 C/C{sub 0}. SuperLig 644 had the highest Cs loading per gram in NCAW and the greatest volume compression on aci elution. Because of high density and poor elution, R-F had the highest Cs loading per unit volume and lower volume compression. CS-100, the baseline material for Cs removal at Hanford, was inferior to both SuperLig 644 and R-F in terms of Cs loading and selectivity over sodium.

  12. Acceleration of solar wind ions to 1 MeV by electromagnetic structures upstream of the Earth's bow shock

    NASA Astrophysics Data System (ADS)

    Stasiewicz, K.; Markidis, S.; Eliasson, B.; Strumik, M.; Yamauchi, M.

    2013-05-01

    We present measurements from the ESA/NASA Cluster mission that show in situ acceleration of ions to energies of 1 MeV outside the bow shock. The observed heating can be associated with the presence of electromagnetic structures with strong spatial gradients of the electric field that lead to ion gyro-phase breaking and to the onset of chaos in ion trajectories. It results in rapid, stochastic acceleration of ions in the direction perpendicular to the ambient magnetic field. The electric potential of the structures can be compared to a field of moguls on a ski slope, capable of accelerating and ejecting the fast running skiers out of piste. This mechanism may represent the universal mechanism for perpendicular acceleration and heating of ions in the magnetosphere, the solar corona and in astrophysical plasmas. This is also a basic mechanism that can limit steepening of nonlinear electromagnetic structures at shocks and foreshocks in collisionless plasmas.

  13. VUV spectroscopy of nominally pure and rare-earth ions doped LiCaAIF6 single crystals as promising materials for 157 nm photolithography

    NASA Astrophysics Data System (ADS)

    Cefalas, Alkiviadis C.; Sarantopoulou, Evangelia; Kollia, Z.; Abdulsabirov, R. Y.; Korableva, S. L.; Naumov, A. K.; Semashko, V. V.; Kobe, S.; McGuiness, P. J.

    2002-07-01

    Recently it was found that birefringence is induced in CaF2 crystals when they are illuminated with laser light at 157 nm. Taking into consideration that CaF2 is the only optical material used in 157 nm photolithography today, the possibility to use new wide band gap fluoride crystals as optical elements for 157 nm photolithography, even those of non-cubic symmetry, should be considered. Additionally fluoride dielectric crystals with wide band gaps doped with trivalent rare-earth (RE) ions can be used as passive or active optical elements int eh VUV. For doped crystals, applications depend on the structure of the energy level pattern of the 4fn-15d electronic configuration and RE ion concentration. In this work we are exploiting the use of wide band gap fluoride dielectric crystals doped with RE ions. The laser induced fluorescence spectrum at 157 nm, and the absorption spectra of the LiCaAlF6 crystals, pure and doped with RE ions, were investigated in the VUV region of the spectrum. A new m4tehod for monitoring RE concentration in wide band gap fluoride crystals, that is based on vibrating sample magnetometer measurement is presented as well.

  14. Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

    SciTech Connect

    Daglis, I.A.; Livi, S.; Sarris, E.T.

    1994-04-01

    The authors present a study of hydrogen, oxygen, and helium ions observed in the magnetotail, where measurements of enegy densities were made, and correlated with indexes related to substorm behaviour. The objective is to study relations between the solar wind/magnetosphere/ionosphere. Data were collected using an instrument on the AMPTE/CCE satellite. Strong correlations were observed between different ions and auroral indexes. Energetic ions are found to be increasing in density in the magnetotail in periods when auroral currents are dissipating.

  15. Solar wind contribution to the average population of energetic He(+) and He(++) ions in the Earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Kremser, G.; Rasinkangas, R.; Tanskanen, P.; Wilken, B.; Gloeckler, G.

    1994-01-01

    Measurements with the ion charge-energy-mass spectrometer CHEM on the AMPTE/CCE spacecraft were used to investigate the origin of energetic He(+) and He(++) ions observed in the equatorial plane at 3 less than or equal to L less than or equal to 9. Special emphasis was laid on the dependence of long-term average distributions on magnetic local time (MLT) and the geomagnetic activity index K(sup p). The observations are described in terms of the phase space densities f(sub 1) (for He(+)) and f(sub 2) (for He(++)). They confirm preliminary results from a previous study f(sub 1) is independent of MLT, whereas f(sub 2) is much larger on the nightside than on the dayside. They show, furthermore, that f(sub 1) increases slightly with K(sub p) on intermediate drift shells, but decreases on high drift shells (L greater than or equal to 7). f(sub 2) increases with K(sub p) on all drift shells outside the premidnight sector. Within this sector a decrease is observed on high drift shells. A simple ion tracing code was developed to determine how and from where the ions move into the region of observations. It provides ion trajectories as a function of the ion charge, the magnetic moment and K(sub p). The ion tracing enables a distinction between regions of closed drift orbits (ring current) and open convection trajectories (plasma sheet). It also indicates how the outer part of the observation region is connected to different parts of the more distant plasma sheet. Observations and tracing show that He(++) ions are effectively transported from the plasma sheet on convection trajectories. Their distribution in the observation region corresponds to the distribution of solar wind ions in the plasma sheet. Thus, energetic He(++) ions most likely originate in the solar wind. On the other hand, the plasma sheet is not an important source of energetic He(+) ions. Convection trajectories more likely constitute a sink for He(+) ions, which may diffuse onto them from closed drift orbits

  16. Contamination and purification of alkaline gas treating solutions

    SciTech Connect

    McCullough, J.G.; Nielsen, R.B.

    1996-08-01

    Alkanolamine and potassium carbonate solutions in gas treating units removing carbon dioxide, hydrogen sulfide, or both are contaminated by impurities in the feed gases and makeup water and by the products of the degradation and oxidation of amines occurring in the units themselves. Feed gas impurities include oxygen, carbonyl sulfide, carbon monoxide, hydrogen cyanide, ammonia, brine, solid particles, heavy hydrocarbons, sulfur dioxide, hydrochloric acid, organic acids, and pipeline corrosion inhibitors. Impure makeup water contains sulfate, chloride, alkali metal, and alkaline earth ions (hardness). Reactions causing contamination in the units include oxidation of hydrogen sulfide to sulfate and thiosulfate, oxidation of amines to formic acid and other products, and degradation of amines by carbon dioxide. The resulting heat-stable salts and polymers reduce the gas absorbing capacity of alkanolamine solutions and increase their corrosiveness. Similar problems occur in potassium carbonate solutions, except that degradation products of amine activators are too dilute to be harmful. Contaminants are removed by inlet gas separation, charcoal and mechanical filtration, neutralization of heat-stable salts, reclaiming at both atmospheric and reduced pressure, upstream washing of the feed gas, electrodialysis, use of antioxidants, ion exchange, and blowdown and dumping of the solution.

  17. Alkalinity regulation in soft-water Florida lakes

    SciTech Connect

    Baker, L.A.; Pollman, C.D.; Eilers, J.M.

    1988-01-01

    Major ion chemistry data collected as part of the Environmental Protection Agency (EPA) Eastern Lake Survey was examined to evaluate the mechanisms and extent of alkalinity regulation in 37 undisturbed, soft-water lakes in Florida. Comparison of major ion-Cl ratios in atmospheric deposition and in lake water shows the reactions resulting in retention of sulfate and nitrate are the dominant sources of alkalinity; production of organic acids and ammonium retention are the major alkalinity-consuming processes. Based on average reactions, enrichment of major cations accounted for only 12% of net alkalinity generation in the study lakes. In general, calcium and potassium were depleted in low-ANC lakes, presumably by in-lake sinks, and were enriched in most higher ANC lakes by ground water inputs. Differences in alkalinity among these lakes reflect hydrologic factors and the proximity of clay and carbonate deposits to the lake bed. Overall, net-alkalinity generation nearly balanced H+ predicted from evaporative concentration of atmospheric acid inputs; the close balance suggests that the alkalinity status of these lakes is very sensitive to changes in atmospheric loadings and groundwater alkalinity inputs.

  18. Influence of rare-earth ions on SiO{sub 2}-Na{sub 2}O-RE{sub 2}O{sub 3} glass structure.

    SciTech Connect

    Johnson, J. A.; Benmore, C. J.; Holland, D.; Du, J.; Beuneu, B.; Mekki, A.

    2011-01-27

    Praseodymium and europium sodium silicate glasses of nominal composition (SiO{sub 2}){sub 0.70-x}(Na{sub 2}O){sub 0.30}(RE{sub 2}O{sub 3}){sub x}, where RE is the rare earth and 0 {le} x {le} 0.10, were studied by neutron and high-energy x-ray scattering and classical molecular dynamics simulations. The observation of a significant x-ray intensity in doped as compared to un-doped glasses is indicative of RE-RE correlations at a distance of {approx} 3.7-3.9 {angstrom}, much shorter than would be expected for a homogeneous distribution, suggesting that clustering of the rare-earth cations occurs in both these glass systems at low concentrations. Above x = 0.075 (nominal), minimal changes in this region indicate that the RE atoms are incorporated much more randomly into the glass structure. The molecular dynamics simulations suggest that the rare-earth ions enter the sodium-rich regions in the sodium silicate glasses and act as modifiers. A cluster analysis performed on the model systems indicates that the tendency for clustering is higher in praseodymium-containing glasses than in the europium glasses.

  19. Anomalous momentum and energy transfer rates for electrostatic ion-cyclotron turbulence in downward auroral-current regions of the Earth's magnetosphere. III

    SciTech Connect

    Jasperse, John R.; Basu, Bamandas; Lund, Eric J.; Grossbard, Neil

    2010-06-15

    Recently, a new multimoment fluid theory was developed for inhomogeneous, nonuniformly magnetized plasma in the guiding-center and gyrotropic approximation that includes the effect of electrostatic, turbulent, wave-particle interactions (see Jasperse et al. [Phys. Plasmas 13, 072903 (2006); ibid.13, 112902 (2006)]). In the present paper, which is intended as a sequel, it is concluded from FAST satellite data that the electrostatic ion-cyclotron turbulence that appears is due to the operation of an electron, bump-on-tail-driven ion-cyclotron instability for downward currents in the long-range potential region of the Earth's magnetosphere. Approximate closed-form expressions for the anomalous momentum and energy transfer rates for the ion-cyclotron turbulence are obtained. The turbulent, inhomogeneous, nonuniformly magnetized, multimoment fluid theory given above, in the limit of a turbulent, homogeneous, uniformly magnetized, quasisteady plasma, yields the well-known formula for the anomalous resistivity given by Gary and Paul [Phys. Rev. Lett. 26, 1097 (1971)] and Tange and Ichimaru [J. Phys. Soc. Jpn. 36, 1437 (1974)].

  20. Improvement of the magnetic properties for Mn–Ni–Zn ferrites by rare earth Nd3+ ion substitution

    PubMed Central

    Eltabey, M.M.; Agami, W.R.; Mohsen, H.T.

    2013-01-01

    Single spinel phases of Mn0.5Ni0.1Zn0.4NdxFe2−xO4 ferrite samples (x = 0.0, 0.01, 0.02, 0.05, 0.075, and 0.1) have been prepared by ceramic method and the composition dependence of the physical and magnetic properties has been investigated. SEM micrographs and EDX analysis revealed that there is no considerable effect for the Nd3+ ion substitution on the average grain size or porosity, whereas its concentration in the grain boundaries is higher than that in the grains. Saturation magnetization (MS) increased with the Nd3+ ion concentration (x) and reached a maximum value at x = 0.05. In addition, both the initial permeability and the magnetic homogeneity increased by increasing the Nd3+ ion content. The value of Curie temperature increased due to the substitution by Nd3+ ions to record about 170 K, for the sample with x = 0.05, higher than that of the un-substituted one. PMID:25685529