Showing papers on "Lanthanum published in 1980"
••
TL;DR: In this article, the crystal structure of LaFe4Sb12 was refined from single-crystal counter data to a residual value of 0.046 for 389 independent structure factors.
Abstract: Fourteen compounds LnT4Sb12 (Ln La, Ce, Pr, Nd, Sm, Eu; T Fe, Ru, Os) were prepared for the first time. Their isotypy with LaFe4P12 (filled CoAs3 structure) is shown by their X-ray powder patterns. LaFe4Sb12 and CeFe4Sb12 show metallic conductivity. The crystal structure of LaFe4Sb12 was refined from single-crystal counter data to a residual value of 0.046 for 389 independent structure factors. A comparison of the structural data for LaFe4Sb12 with those for the previously determined LaFe4P12 and LaFe4As12 structures shows systematic trends in the positional and thermal parameters. The thermal amplitudes of the lanthanum atoms are highest in LaFe4Sb12, indicating that the polymeric [Fe4Sb12]n “framework” is somewhat too large for the lanthanoids. This can also be concluded from an almost non-existent lanthanoid contraction. Systematic trends of the cell volumes suggest that cerium and europium have mixed valencies in most compounds with this structure.
240 citations
••
TL;DR: A ternary phase of composition LnMgB5O10 has been found for Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er.
87 citations
••
TL;DR: The LaB6 (110) and (111) clean surfaces have been studied by angle-resolved XPS, ISS and LEED as discussed by the authors, and the work functions of the (100, (110), (110, and) surfaces were measured from the width of UPS spectra and are ~2.3, 2.5 and 3.3 eV, respectively.
84 citations
••
TL;DR: In this paper, a new compound of lanthanum silicon nitride, LaSi3N5 has been prepared by the reaction between Si3N4 and La2O3 under a 50 atm nitrogen pressure at 2000° C for 2 h.
Abstract: A new compound of lanthanum silicon nitride, LaSi3N5 has been prepared by the reaction between Si3N4 and La2O3 under a 50 atm nitrogen pressure at 2000° C for 2 h. The space group is P212121, Z=4, a=7.838 A, b=11.236 A and c=4.807 A, Dc=4.6 g cm−3. The crystal structure data and X-ray powder diffraction data are given. The characteristics of the structure have been noted and the similarities between LaSi3N5 and Si3N4 have been discussed in terms of the fundamental structural unit of SiN4 tetrahedra.
72 citations
•
01 May 1980
TL;DR: Coatings for iron-, nickel-and cobalt-base superalloys are applied in order to provide good oxidation and/or sulfidation and thermal fatigue resistance for the substrates to which the coatings are applied as mentioned in this paper.
Abstract: Coatings for iron-, nickel- and cobalt-base superalloys The coatings are applied in order to provide good oxidation and/or sulfidation and thermal fatigue resistance for the substrates to which the coatings are applied The coatings consist essentially of, by weight, 10 to 50% chromium, 3 to 15% aluminum, 01 to 10% manganese, up to 8% tantalum, up to 5% tungsten, up to 5% reactive metal from the group consisting of lanthanum, yttrium and other rare earth elements, up to 5 percent of rare earth and/or refractory metal oxide particles, up to 12% silicon, up to 10% hafnium, and the balance selected from the group consisting of nickel, cobalt and iron, and combinations thereof Additions of titanium up to 5% and noble metals up to 15% are also contemplated
64 citations
••
TL;DR: The spin-label results presented here suggest that one mechanism through which calcium and lanthanum mediate their effects on platelet functions may be by decreasing the lipid fluidity of the surface membrane.
Abstract: Previous platelet studies have shown that calcium plays important roles in stimulus-secretion coupling, aggregation, and other membrane-associated functions. In addition, lanthanum induces platelet aggregation and the platelet release reaction and also influences platelet responsiveness to various stimuli. The spin-label results presented here suggest that one mechanism through which calcium and lanthanum mediate their effects on platelet functions may be by decreasing the lipid fluidity of the surface membrane. The structure of platelet membrane lipids was examined with the spin-label method. Washed human platelets were labeled with the 5-, 12- and 16-nitroxide stearic acid spin probes. Order parameters which measure the fluidity of the lipid environment of the incorporated probe may be calculated from the electron spin resonance (ESR) spectra of 5-nitroxide stearate [I(12,3)]-labeled cells. Evidence is presented which indicates that these spectra principally reflect properties of the platelet surface membrane lipids. The membrane fluidity increased with temperature for the range 17 to 37 °C. Either calcium or lanthanum additions to intact cells increased the rigidity of the platelet membranes at 37 °C, although the La3+ effect was larger and occurred at lower concentrations than that of Ca2+. For example, addition of 1mm La3+ or 4mm Ca2+ increased the order parameter of I(12,3)-labeled platelets by 4.3±1.7% or 2.1±0.5%. Preliminary studies conducted on purified platelet plasma membranes labeled with I(12,3) indicated that 1mm LaCl3 or 4mm CaCl2 additions similarly decreased the lipid fluidity at 37 °C. The above cation-induced effects on the fluidity of whole platelets were reversed by the use of the divalent cation-chelating agent ethylene glycol-bis-(β-aminoethyl ether)-N,N′-tetra-acetic acid (EGTA). Lastly, lanthanum (0.2–1mm) caused rapid aggregation of platelets which were suspended in a 50-mm Tris buffer pH 7.4 that did not contain adenosine.
60 citations
•
29 Dec 1980
TL;DR: In this paper, an absorbent comprising at least one inorganic oxide selected from the group consisting of the oxides of aluminum, magnesium, zinc, titanium, and calcium is recovered as a sulfur-containing gas comprising hydrogen sulfide by contacting the spent absorbent with a hydrocarbon in the presence of a catalycarbon cracking catalyst at a temperature from about 375° to about 900° C.
Abstract: Sulfur oxides are removed from a gas by an absorbent comprising at least one inorganic oxide selected from the group consisting of the oxides of aluminum, magnesium, zinc, titanium, and calcium in association with at least one free or combined rare earth metal selected from the group consisting of lanthanum, cerium, praseodymium, samarium, and dysprosium, wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 0.1 to about 30,000. Absorbed sulfur oxides are recovered as a sulfur-containing gas comprising hydrogen sulfide by contacting the spent absorbent with a hydrocarbon in the presence of a hydrocarbon cracking catalyst at a temperature from about 375° to about 900° C. The absorbent can be circulated through a fluidized catalytic cracking process together with the hydrocarbon cracking catalyst to reduce sulfur oxide emissions from the regeneration zone.
58 citations
•
26 Mar 1980
TL;DR: In this article, a process for isomerization of xylenes which comprises contactng an aromatic hydrocarbon stock mainly containing xylene isomers not attaining a thermodynamic equilibrium composition with a catalyst composition containing a crystalline aluminosilicate at an elevated temperature in the vapor phase in the presence of hydrogen, was described.
Abstract: In a process for isomerization of xylenes which comprises contactng an aromatic hydrocarbon stock mainly containing xylene isomers not attaining a thermodynamic equilibrium composition with a catalyst composition containing a crystalline aluminosilicate at an elevated temperature in the vapor phase in the presence of hydrogen, the improvement wherein said catalyst composition comprises a crystalline aluminosilicate having a silica/alumina mole ratio of at least 10 and contains at least two metals which are (a) platinum and (b) at least one metal selected from the group consisting of titanium, chromium, zinc, gallium, germanium, strontium, yttrium, zirconium, molybdenum, palladium, tin, barium, cesium, cerium, tungsten, osmium, lead, cadmium, mercury, indium, lanthanum, beryllium, lithium and rubidium
47 citations
••
39 citations
••
33 citations
••
••
TL;DR: In this article, the electrochemical behavior of ferrites having the composition La 1-x Sr x FeO 3-y in the oxygen reaction has been studied and the catalytic activity of these compounds was compared with that of copper manganite Cu 1.4 Mn 1.6 O 4 and that of lanthanum strontium cobaltite La 0.5 Sr 0.
••
TL;DR: In this article, the ternary phases of alloys of the rare earths with antimony and palladium in the stoichiometric ratio 1:1:1 were studied.
Abstract: We studied the ternary phases of alloys of the rare earths with antimony and palladium in the stoichiometric ratio 1:1:1. The alloys with lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium and terbium proved to be of the hP6 CaIn2 type, whereas those with dysprosium, holmium, erbium, ytterbium and yttrium were of the cF12 MgAgAs type. The trends of the molar volumes are briefly discussed in relation to the molar volumes of isostructural compounds known already.
•
25 Aug 1980
TL;DR: A silicon nitride-based sintered product is a product produced by sintering a powder mixture consisting essentially of silicon oxide, at least one oxide of yttrium, scandium, cerium, lanthanum and the metals of lanthanide series as discussed by the authors.
Abstract: A silicon nitride based sintered product produced by sintering a powder mixture consisting essentially of silicon nitride, at least one oxide of yttrium, scandium, cerium, lanthanum and the metals of lanthanide series and at least one metal or metal oxide of iron, nickel and cobalt.
••
TL;DR: In this paper, a new class of trimethylene bridged biscyclopentadienyl derivatives of lanthanum(III) and cerium (III) with chloride and pentyethynyl ligands is reported.
Abstract: The synthesis of a new class of trimethylene bridged biscyclopentadienyl derivatives of lanthanum(III) and cerium(III) with chloride and pentyethynyl ligands is reported
••
TL;DR: The trivalent cations lanthanum, neodymium and europium were found to have a weak dose-dependent antinociceptive effect as measured on hot plate and tail nick following administration into the lumbar subarachnoid space of rats implanted with chronic intrathecal catheters.
••
•
01 Oct 1980TL;DR: In this article, a semiconducting internal boundary layer ceramic composition having a fine grain structure suitable for use in thin-layer multilayer capacitors is made in one step by firing a mixture comprising a major amount of finely divided strontium titanate, a minor amount of a compound containing either strontia or titanium, or an element functionally equivalent thereto, and a minor amounts of a semiconductor forming ingredient (dopant), the identity of which depends on whether the mixture is rich in strontias or in titanium.
Abstract: A semiconducting internal boundary layer ceramic composition having a fine grain structure suitable for use in thin-layer multilayer capacitors is made in one step by firing a mixture comprising a major amount of finely divided strontium titanate, a minor amount of a compound containing either strontium or titanium, or an element functionally equivalent thereto, a minor amount of a semiconductor forming ingredient (dopant), the identity of which depends on whether the mixture is rich in strontium or in titanium, and a minor amount of a counterdopant selected from cuprous oxide or silver oxide. When the mixture is rich in titanium, the chemical doping agent used to produce semiconductivity is an oxide of a trivalent metal selected from bismuth, boron, iron, antimony, lanthanum and the rare earth and transition metals. When the mixture is rich in strontium, the dopant is an oxide of a pentavalent or hexavalent metal selected from tungsten (+6), niobium (+5), tantalum (+5), and molybdenum (+6).
••
TL;DR: Barium and lanthanum were determined by direct injection of freeze-dried samples (1-15 μg), and magnesium by injection of 2-μl aliquots of a homogenized suspension as mentioned in this paper.
••
TL;DR: In this paper, the thermal decomposition of lanthanum formate was investigated using TG, DTA, GC, IR and X-ray diffraction techniques, and the delineation of La2O(CO3)2 as an intermediate decomposition product is the main new finding.
••
••
TL;DR: In this paper, a solvent extraction with mesityl oxide from sodium sallcylate solution (0.1 M) adjusted to pH 4 was used to separate scandium(III) from iron(III), molybdenum(VI), vanadium(V), chromium (VI), titanium(IV), bismuth (III), zirconium (IV), lanthanum(III, and thorium(IV) was achieved by solvent extraction.
Abstract: Separation of scandium(III) from iron(III), molybdenum(VI), vanadium(V), chromium(VI), titanium(IV), bismuth(III), zirconium(IV), lanthanum(III), and thorium(IV) is achieved by solvent extraction with mesityl oxide from sodium sallcylate solution (0.1 M) adjusted to pH 4. Scandium from the organic phase is stripped with water and determined photometrically as its arsenazo complex at 570 nm. The extracted species is trisolvated, i.e., Sc(HOC/sub 6/H/sub 4/COO)/sub 3/3Me0. 1 figure, 1 table.
•
04 Feb 1980
TL;DR: In this paper, an ion exchange reaction with rare earth ions of the ceria subgroup (viz. cerium, lanthanum, etc.) was used to produce a reaction product containing as little as 0.03 moles of alkalii metal per mole of manganese, and up to one mole of ceria rare earth per six moles in the mixture.
Abstract: Alkali metal delta manganese dioxide hydrate, which is obtained as a by-product in the industrial oxidation of organics by KMnO 4 is subjected to ion exchange reaction with rare earth ions of the ceria subgroup (viz. cerium, lanthanum, etc.). By employing favorable temperature and pH conditions, a reaction product can be produced containing as little as 0.03 moles of alkalii metal per mole of manganese, and up to one mole of ceria rare earth per six moles of manganese. The separated product is prepared for catalytic use in the form of dried porous pellets. The resulting oxidation catalyst has high efficiency, long life, and optimum activity at reasonable temperatures. The catalyst can be used advantageously for applications such as the oxidation and deodorization of exhaust gases from paint drying ovens.
••
TL;DR: Results confirm the limited validity of investigations based on of the "Lanthanum method" and show that lanthanum is carried across the cell membrane and is taken up by subcellular organelles.
Abstract: The present investigation of the cellular distribution of lanthanum was undertaken in order to control the validity of the "Lanthanum method" used for the study of the cell calcium compartments. The presence of lanthanum was evaluated in the isolated guinea-pig heart and its subcellular fractions perfused with a lanthanum-containing Tyrode solution. Lanthanum was determined by instrumental neutron activation analysis. Under the adopted experimental conditions (30-min incubation in the presence of 12.5 microM lanthanum), lanthanum is carried across the cell membrane and is taken up by subcellular organelles. These results confirm the limited validity of investigations based on of the "Lanthanum method".
••
TL;DR: Several La(III)-(hydroxy) carboxylate complexes in aqueous medium have been studied by means of 139La chemical shift and line width measurements as discussed by the authors, and the results show that the carboxylic acidity of carboxyles is positively correlated with the line width.
Abstract: Several La(III)-(hydroxy) carboxylate complexes in aqueous medium have been studied by means of 139La chemical shift and line-width measurements.
••
TL;DR: In this article, two ordered perovskite-type fluorides, Rb2KNdF6 and Cs2KNDF6, have been synthesized and their luminescence properties investigated and their neodymium emission shows weak self-quenching.
••
••
TL;DR: The study indicates that ionic lanthanum injected into the blood circulation of living rabbits, is to a great extent bound to fibrinogen, and that the smallest possible size of the tracer is that of the fibr inogen,molecule (m. w. 330,000).
Abstract: Aqueous solutions of lanthanum nitrate may be used as electron microscopic tracers in vivo to study vascular permeability in the experimental animal. However, with this technique the size of the tracer particles is not known. To gain information about the tracer size, we injected lanthanum nitrate into the blood circulation of living rabbits. The plasma obtained from such animals 30 min later, was studied with the electron microscope. The plasma contained an electron-dense material, readily visible in the electron microscope. A precipitate obtained after centrifugation of the whole blood to separate the cells, also contained the tracer. Lanthanum was found in large amounts in the fibrin clot obtained after treating the plasma with thrombin. The tracer was not detected in the “serum” (i.e. thrombin-treated plasma). The study indicates that ionic lanthanum injected into the blood circulation of living rabbits, is to a great extent bound to fibrinogen, and that the smallest possible size of the tracer is that of the fibrinogen,molecule (m. w. 330,000). Larger particles are present as well.
••
•
22 Jan 1980
TL;DR: In this paper, a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400° K is presented. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon.
Abstract: The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400° K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing bases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.