Showing papers on "Lanthanum published in 1978"

Atomic Energy Levels - The Rare-Earth Elements. The Spectra of Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, and Lutetium,

Abstract: : Energy level data are given for 66 atoms and atomic ions of the 15 elements lanthanum (Z=57) through lutetium (Z=71). These data have been critically compiled from published and unpublished material. Only experimentally determined energy levels are included, the energies being restricted to excitation of outer-shell electrons and to inner-shell excitations up to the soft x-ray range. The levels were taken from analyses of the spectra of atomic gases wherever possible; however, the levels for several of the triply ionized rare earths are from analyses of the spectra of the ions in crystals or solutions. In addition to the level value and the parity, the J value, configuration and term assignments, and the experimental g value are listed wherever available. Leading percentages from the calculated eigenvector are also tabulated for each level if available. The levels are grouped into spectroscopic terms of appropriate coupling schemes where such groups appear meaningful. Ionization potentials are tabulated for most of the spectra. Complete references for the tabulated data are given for each spectrum.

The blood‐testis barrier and its formation relative to spermatocyte maturation in the adult rat: A lanthanum tracer study

Abstract: An electron-opaque substance, lanthanum, was utilized to determine when germ cells of the rat first cross the blood-testis barrier in adult spermatogenesis. Intravascularly perfused lanthanum was shown to surround all spermatogonia. Intravascularly perfused lanthanum was shown to surround all spermatogonia, preleptotene spermatocytes and early leptotene spermatocytes of Stage IX in the adult rat testis. Lanthanum was excluded from the spaces around more mature cells by newly-formed tight junctions between adjoining Sertoli processes. These processes had previously intervened between the leptotene cells and the basal lamina. The results are in close agreement with those of a previous study (Russell, '77a) which indicated that leptotene cells are the first cells of adult spermatogenesis to enter the intermediate compartment and to reside beyond a permeability barrier.

Ground-state properties of f band metals: lanthanum, cerium and thorium

Abstract: Self-consistent relativistic bandstructure calculations for face centred cubic lanthanum, cerium and thorium have been performed using the linear muffin-tin orbital (LMTO) method and the local spin density (LSD) approximation for exchange and correlation. Results are given for equilibrium distance, bulk modulus, spin susceptibility and the electron-phonon matrix element in each case. A significant contribution of f partial waves to the crystal bonding for all three metals has been found. At the atomic volume corresponding to the gamma phase, cerium exhibits a ferromagnetic instability.

Low-velocity electron excited fluorescent display device

Abstract: Fluorescent compositions which contain indium oxide and one phosphor selected from the group hereinafter defined in a weight ratio within the range of 1/9 to 9/1l, and fluorescent display devices having said fluorescent compositions in the form of a fluorescent screen, which can emit green, blue or red light under low-velocity electron excitation, said group consisting of a terbium activated lanthanum oxysulfide phosphor or a terbium activated lanthanum yttrium oxysulfide phosphor [(La 1-x , Y x ) 2 O 2 S:Tb, wherein O≦x <1], a copper and aluminum activated zinc cadmium sulfide phosphor [(Zn 1-x , Cd x )S: Cu, Al, wherein O≧x ≦0.1], a europium activated strontium gallium sulfide phosphor (SrGa 2 S 4 :Eu 2+ ), a cerium activated yttrium aluminum gallate phosphor [Y 3 (Al 1-y , Ga y ) 5 O 12 :Ce, wherein O≦y≦O.5], a manganese activated zinc silicate phosphor (Zn 2 SiO 4 :Mn), a terbium activated yttrium oxysulfide phosphor (Y 2 O 2 S:Tb), a silver activated zinc sulfide phosphor (ZnS:Ag), a europium activated yttrium oxysulfide phosphor (Y 2 O 2 S:Eu), a europium activated yttrium oxide phosphor (Y 2 O 3 :Eu), and a europium activated yttrium vanadate phosphor (YVO 4 :Eu).

Ternary Compounds in the System La-Co-O

Abstract: The compounds LaCoO3, La4Co3Ol0, and La2CoO4 were synthesized and characterized by powder X-ray diffraction. Lanthanum cobaltate, LaCoO3, has the rhombohedra1 modification of the perovskite structure, whereas La4CO3O10 and La2CoO4 have perovskite-related structures based on face-centered orthorhombic lattices. The lattice parameters of these ternary phases are dependent on the conditions of preparation. Six invariant reactions in the system La-Co-O are summarized in a portion of the 1130°C isothermal section.

Catalyst compositions especially useful for preparation of unsaturated acids

Abstract: The present invention is a catalyst composition consisting of oxides or oxide complexes that contains catalytically significant amounts of uranium or thorium plus, tungsten, vanadium and molybdenum plus optionally one or more of Co, Ni, Zn, Cu, Mg, Mn, Bi, Ti, Zr, Sn, P, an alkali metal, an alkaline earth metal, lanthanum or an element of the lanthanoid series. These catalysts are especially useful for producing acrylic acid from acrolein and for producing methacrylic acid from methacrolein.

Dielectric relaxation in yttrium- and lanthanum-doped calcium fluoride

Abstract: The complex dielectric constant has been measured at five audio frequencies over the temperature range 5.5-400 K for 0.1 mol% of yttrium and lanthanum in calcium fluoride. Five relaxations are observed in the yttrium-doped material and one is observed for lanthanum. These results are consistent with trends with ion size observed previously for rare earths in calcium fluoride and emphasize that ion size is the primary factor determining defect formation in calcium fluoride doped with trivalent ions.

Fluorescent lamp containing a green emitting rare earth silicate coactivated phosphor

Abstract: A rare earth silicate phosphor co-activated by cerium and terbium which is expressed by the general structural formula: Ln2(1-x-y) O3.zSiO2 :Ce2x.Tb2y where: Ln is at least one rare earth element selected from the group consisting of yttrium, lanthanum, gadolinium and lutetium, x is 1×10-3 to 3×10-1 gram atom per gram atom of all the rare earth elements, y is 3×10-2 to 3×10-1 gram atom per gram atom of all the rare earth elements, z is 0.8 to 2.2 mol per mol of rare earth oxide, and the phosphor efficiently emits green rays when excited by ultraviolet rays.

Ceramic compositions and articles prepared therefrom

Abstract: A transparent or translucent article of manufacture such as a discharge tube for a metal vapor arc lamp is formed from a high density ceramic composition having a perovskite structure and having the formula: ABO.sub.3 wherein A can be lanthanum, cerium, praseodymium or neodymium and B has a smaller ionic radius and can be aluminium, scandium, lutecium or the like.

Catalyst and process for production of methane-containing gases

Abstract: A catalyst for production of methane-containing gases which is formed from a catalyst precursor composed of a mixed precipitate of hydroxides and/or carbonates of nickel and/or cobalt, lanthanum and/or cerium and aluminum, which is obtained by stepwise addition of solutions of alkaline substances to a solution of an aluminum salt, to a solution of a lanthanum salt and/or a cerium salt and to a nickel salt and/or a cobalt salt is disclosed. This stepwise addition of solutions of alkaline substances is accomplished by (1) first stage addition of a solution of an alkaline substance to a solution of an aluminum salt, (2) second stage addition of a solution of an alkaline substance to a solution of a lanthanum salt and/or a cerium salt in the presence of the precipitate-containing solution formed by the first stage addition and (3) third stage addition of a solution of an alkaline substance to a solution of a nickel salt and/or a cobalt salt in the presence of the precipitate-containing solution formed by the second stage addition.

Chemical separation of molybdenum from uranium and fission product nuclides

Abstract: A very rapid method for the separation of molybdenum(VI) from neutron irradiated uranium and its fission products is described. The procedure is based on the selective extraction of molybdenum(VI) by a 0.1M solution of 2-hexylpyridine in benzene from 4M HCl+0.04M KSCN. Decontamination factors were estimated to be >104 for the radionuclides of niobium, zirconium, ruthenium, lanthanum, cerium, promethium, yttrium, strontium and barium.

Electron Spectroscopy for Chemical Analysis Examination of Rare Earth and Near Rare Earth Species

Abstract: A detailed electron spectroscopy for chemical analysis (ESCA) examination has been performed on a series of very pure rare earth foils, powders, and a sputter-deposited thin film consisting of yttria doped ceria. The foils were studied with their natural passivation layer intact and also sputter etched to provide approximate chemical profiles. The metals examined were cerium, lanthanum, and yttrium. The ESCA spectra of all of the passivated metals experienced charge shifts. Treatment of those shifts with an electron flood gun is an integral part of this study. A semiquantitative analysis of the passivation layer of cerium establishes that the outer mantle is a mixed oxide-hydroxide Ce(IV) system, whereas the inner layers of the oxidative growth are initially mixed oxide-hydroxide Ce(III) systems and finally (close to the virgin metal) a substance believed to be Ce(III) 2 O 3 is exposed. This is the first ESCA spectral analysis of the sesquioxide. Interestingly, sputter etching the ceric oxide/yttrium oxide (CeO 2 /Y 2 O 3 ) film results in a nearly identical chemical development, indicating that some of these results may occur because of sputter reduction. The lanthanum and yttrium systems also display evidence of hydroxide formation on their outer (passivation) surfaces. A unique species which may be La(II)O is detected after sputtering into the passivation layer of lanthanum. The yttrium spectra for the CeO 2 /Y 2 O 3 film exhibit superior resolution compared to that for the yttrium foil. A discussion of the satellite structure of these spectra is included.

Olefin disproportionation over silica-rare earth metal oxide catalysts

Abstract: Olefins, such as n-hexene, are disproportionated under reaction conditions with a catalyst of an oxide of yttrium, lanthanum, cerium, praseodymium, or dysprosium, on a silica support.

Lanthanum indium gallium garnets

Abstract: Congruently melting compositions of gallium garnets containing lanthanum are provided in which trivalent indium is partially substituted for gallium. The lanthanum indium gallium garnets have larger lattice parameters than other rare earth gallium garnets. The lanthanum indium gallium garnets of the invention are represented by the formula La.sub.a In.sub.b Ga.sub.c O.sub.12 where "a" ranges from greater than about 3.24 to less than 3.32, "b" ranges from greater than about 1.84 to less than about 2.24 and "c" ranges from greater than about 2.48 to less than about 2.88, the total of "a" plus "b" plus "c" being 8. The garnets of the invention are useful as single crystal substrates for supporting magneto-optic and magnetic garnet thin films having large lattice parameters approaching 13 A.

Fluorescent inorganic pigment

Abstract: An inorganic fluorescent pigment for use in artificial teeth is provided and a method for producing the same, the pigment having the formula (X.sup.. SE+A.sup.. Ce+B.sup.. Tb+C.sup.. Mn).sub.2 O.sub.3.sup.. SiO.sub.2 wherein Se is at least one of the elements yttrium, gadolinium and lanthanum, Ce is cerium, Tb is terbium, Mn is manganese, A is of from 2 to 10 mol percent, B is of from 2 to 10 mol percent, C is of from 0.5 to 2.5 mol percent, X is 100 -(A+B+C) mol percent. In artificial teeth a product is useful with a particle size according to the Coulter-Counter method of 5 percent of from 0.85 to 1.35 μm, 50 percent of from 2.4 to 4.1 μm and 95 percent of from 7.8 to 18.0 μm. The pigment may be produced by heating a mixture of the SE, Ce- and SiO 2 compounds at a temperature of above 1000° C., grinding the resulting product, mixing it with Tb and Mn compounds and heating it again at a temperature of above 1000° C. in a reducing atmosphere. After grinding the resulting product, the portion having the desired particle size may be selected.

The absorption of deuterium by binary alloys of lanthanum and nickel

Abstract: The variation with temperature (500–700 °C) of the equilibrium pressure of deuterium over four alloys of lanthanum (La 5.25 Ni, La 3 Ni, LaNi and LaNi 2 ) and over lanthanum metal was measured for increasing concentrations up to D / La = 2. In each case the pressure-temperature variation (at constant composition) can be expressed in the form of the equation In P = − A / T + B . Pressure versus concentration isotherms are given for temperatures of 600 and 700 °C. The experimental results can be expressed qualitatively by a model of metastable intermediate compounds.

Influence of calcium, magnesium, lanthanum and A23187 on the aggregation of polymorphonuclear neutrophils.

Abstract: Chemotactic factors transiently aggregate human polymorphonuclear neutrophils. We have found that the aggregation induced by the chemotactic tripeptide, formyl-methionyl-leucyl-phenylalanine, depends on the extracellular calcium and magnesium concentrations and is inhibited by 1 and 10 M lanthanum chloride. The ionophore A23187 and 1 and 0.1 mM lanthanum chloride aggregate the cells. A23187-induced aggregation is dependent on extracellular calcium and magnesium whereas lanthanum-induced aggregation is not.

Zirconium-base alloy structural component for nuclear reactor and method

Abstract: A small amount of lanthanum and praseodymium will substantially improve the slow strain rate ductility of certain zirconium-base alloys and these new alloys and certain other zirconium-base alloys in the irradiated condition can under certain circumstances have surprising load-carrying capacity and service life Such other alloys contain yttrium or calcium instead of lanthanum or praseodymium