Showing papers on "Lanthanum published in 1977"
86 citations
TL;DR: In this article, it was shown that the catalytic activity was influenced by the overlap integral between the e g orbital of the transition metal and the sp σ orbital of oxygen, and that the larger overlap integral is, the higher the electrocatalytic activity.
77 citations
TL;DR: Improvement of the previous technique is achieved by phosphate precipitation of lanthanum in the tissue carried out at low temperature, and this method has been successfully applied to bone marrow.
Abstract: A method for obtaining a uniform, dense precipitate of lanthanum nitrate to delineate extracellular space is described. Improvement of the previous technique is achieved by phosphate precipitation of lanthanum in the tissue carried out at low temperature. This method has been successfully applied to bone marrow.
56 citations
TL;DR: In this article, the authors used thermogravimetry in reducing atmospheres to study the oxygen stoichiometry of several Cu-substituted lanthanum manganates.
Abstract: Thermogravimetry in reducing atmospheres was used to study the oxygen Stoichiometry of several Cu-substituted lanthanum manganates. The oxygen content of the samples at various levels of reduction (to La2O3, MnO, and Cu) was calculated from the gravimetric data. Freeze-dried samples prepared by firing at 1100°C in O2 and cooling in O2 had the following composition: LaMnO3.13, LaMn0.7Cuo.3O2.96, LaMn0.5Cu0.5O2.93, and LaMn0.3Cu0.762.71. Single-phase perovskite structure was obtained in all but the last. The lanthanum manganate LaMnO3.13 was reduced to LaMnO3.00, which shows considerable stability. A 50% substitution of Cu for Mn gave LaMn0.5 Cu0.5O2.93, indicating that the ions involved were mostly Mn4+ and Cu2+. This compound could be reduced to LaMng0.5Cu0.5 O2.26 (largely Mn2+ and Cu1+) without destroying the perovskite structure. This reduced phase could be reoxidized to the original oxygen level but subsequent reduction required considerably higher temperatures and was accompanied by the precipitation of Cu-rich phases. Samples with a Cu:Mn ratio 30:70 and 70:30 were O-deficient. The compound LaMn0.7 Cuo.3O2.96 reduced to LaMn0.7Cu0.3O2.54, a relatively stable composition. The highly Cu-rich sample LaMn0.3Cu0.7O2.71 was easily reduced.
55 citations
TL;DR: In this paper, the authors reported the five-peak excitation spectrum expected for the 5d state of Ce3+ in a noncubic crystal field is observed, and the fluorescence quantum yields for LaF3 and LuF3 are 0.9 and 0.82, respectively.
Abstract: Broad‐band uv flurescence is reported for LaF2 : Ce3+ (2760–3120 A) and LuF3 : Ce3+ (2880–3220 A). The five‐peak excitation spectrum expected for the 5d state of Ce3+ in a noncubic crystal field is observed. The fluorescence quantum yields for LaF3 : 1% Ce3+ and LuF3 : 0.1% Ce3+ are 0.9 and 0.82, respectively. Estimates of the threshold power for lasing action suggest that a laser system tunable from 2760 to 3220 A is feasible with noble‐gas–halide lasers as pumping sources.
52 citations
51 citations
Patent•
13 Jul 1977
TL;DR: In this article, a method of producing a single phase ceramic product is described, which comprises the step of forming a powder mixture consisting essentially of a first component consisting of compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportion such that the ratio of the total number of silicon and aluminum atoms to the total amount of oxygen, nitrogen and nitrogen atoms lies in the range 0.735 to 0.77 and such that said compounds react together during the subsequent sintering process to produce a single-phase ceramic material obeying the general formula: Si.sub.z O
Abstract: A method of producing a ceramic product which comprises the step of forming a powder mixture consisting essentially of a first component consisting of compounds containing the elements silicon, aluminum, oxygen and nitrogen in proportion such that the ratio of the total number of silicon and aluminum atoms to the total number of oxygen and nitrogen atoms lies in the range 0.735 to 0.77 and such that said compounds react together during the subsequent sintering process to produce a single phase ceramic material obeying the general formula: Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where z is between 0.38 and 1.5, and between 0.1 and 10% by weight of a second component in the form of an oxide of at least one of the further elements yttrium, scandium, cerium, lanthanum and the metals of the lanthanide series. The mixture is then sintered in a protective environment at a temperature between 1600° C and 2000° C and for a time, decreasing with increasing temperature, of at least 10 minutes to at least 5 hours so as to produce a ceramic material containing at least 80% by volume of said single phase ceramic material together with a second phase containing said at least one further element.
51 citations
TL;DR: In this article, the lanthanum pnictides are divided into a nonmetallic and a metallic group, with the semi-metallic monopnictide lying in between.
Abstract: On the basis of a discussion of their chemical bonding, the lanthanum pnictides are divided into a nonmetallic and a metallic group, with the semi-metallic monopnictides lying in between. With the exception of LaBi2, all the metallic phases were tested for superconductivity. They all show a transition to the superconducting state below 1 K. The anti-Th3P4-type compounds, of which La4As3 was synthesized for the first time, were studied in more detail. A drastic increase in Tc on reduction of the electron concentration was observed in the series La4Bi3−xPbx. Partial substitution of La by Y leads to a decrease in Tc.
43 citations
TL;DR: It is demonstrated that the localization of Lanthanum differed from that shown in previous studies in which hearts were exposed to ionic or colloidal lanthanum during or after fixation.
Abstract: The distribution of ionic lanthanum (La3+) was studied after perfusion of the isolated rat heart with a buffered salt solution containing lanthanum chloride. We have demonstrated that the localization of lanthanum differed from that shown in previous studies in which hearts were exposed to ionic or colloidal lanthanum during or after fixation.
40 citations
Patent•
28 Mar 1977TL;DR: In this article, a sealed electric fuel cell of the type utilizing a reoxidizable compound as the positive electrode and a hexagonal nickel-rare earth metal hydride as the negative electrode is disclosed.
Abstract: A sealed electric fuel cell of the type utilizing a reoxidizable compound as the positive electrode and a hexagonal nickel-rare earth metal hydride as the negative electrode is disclosed. The energy released by the electrochemical oxidation-reduction reaction of the anode appears in the cell as electrical energy.
36 citations
TL;DR: In this paper, a three-component system was proposed for 1-butene isomerization on La 2 O 3, and a reaction scheme for the three component system is proposed.
TL;DR: In this paper, the X-ray crystal and molecular structure of the lanthanum complex has been determined from diffractometer data and the structure was refined by least-squares techniques to R 0.089 for 4 412 observed reflections.
Abstract: A series of diethyldithiocarbamates (Et2dtc) of all the lanthanoids from La to Yb. except Pm, of general formula Na[Ln(Et2dtc)4] have been prepared. The X-ray crystal and molecular structure of the lanthanum complex has been determined from diffractometer data. Crystals are monoclinic, space group P21, with a= 21.154(13). b= 21,445(15), c= 15.584(9)A, β= 101.56(4)°, Z= 8. The structure was refined by least-squares techniques to R 0.089 for 4 412 observed reflections. The structure consists of Na+ and [La(Et2dtc)4]- ions: in the anion the lanthanum atom is co-ordinated by eight sulphur atoms forming a distorted dodecahedron. Conductance and spectral measurements show that the eight-co-ordinate structure persists in methyl cyanide solutions. The electronic spectra have been investigated for methyl cyanide solutions in the spectral range 5–39 kK, and bands attributed to electronic transitions of intraligand, charge-transfer, and f–f type. With the cerium(III) complex, intense bands at ca. 23 kK are attributed to f–d or inverted electron transitions.
TL;DR: In this paper, the conductivity of the oxide is a function of the oxygen concentration due to σ* bond formation, and the resistivity of an oxide electrode was changed depending on polarization potentials.
TL;DR: Lanthanum in combination with electron microscopy confirmed that an intact plasma membrane is necessary for the primary endodermis to control the passage of solutes into the vascular tissues of the stele.
Abstract: Lanthanum in combination with electron microscopy was used to study the functional development of the Casparian strip in the primary root of corn (Zea mays L. WF9 X M14). The Casparian strip was first visible between 13 and 16 mm from the root tip, and was first an effective barrier to lanthanum movement through the apoplast from cortex to stele between 14 and 18 mm from the apex. Until the Casparian strip was formed, lanthanum ion freely penetrated the stelar apoplast. By 18 mm from the apex lanthanum was completely restricted to the extracellular spaces of the cortex. Treatment with 0.02 or 0.03% (v/v) Triton X-100 increased the permeability of the plasma membrane, and allowed lanthanum ion to penetrate the cortical symplast. After the detergent treatment, the endodermis no longer functioned as a barrier to La3+ movement from cortex to stele. This confirms that an intact plasma membrane is necessary for the primary endodermis to control the passage of solutes into the vascular tissues of the stele.
Patent•
25 Feb 1977
TL;DR: In this paper, a composition useful in hydrocarbon conversion processes such as catalytic cracking is disclosed, comprising 0.05 to 10 weight percent lanthanum associated with a refractory support.
Abstract: A composition useful in hydrocarbon conversion processes such as catalytic cracking is disclosed, comprising 0.05 to 10 weight percent lanthanum associated with a refractory support. The composition may also include 0.02 to 10 weight percent iron.
TL;DR: A phase diagram of the lanthanum-bismuth system, which includes five intermetallic compounds, is proposed in this article, and the powder pattern of LaBi 2 has been indexed as an orthorhombic system with unit cell parameters a = 4.737, b = 17.51 and c =4.564 A. The body-centred cubic cell of the γ phase of Lanthanum was found to be tetragonally deformed on forming a solid solution with bismuth.
Abstract: A phase diagram of the lanthanum-bismuth system, which includes five intermetallic compounds, is proposed. Only La 4 Bi 3 melts congruently at 1670 ± 30 ° C ; the other compounds La 2 Bi, La 5 Bi 3 , LaBi and LaBi 2 decompose at 1252 ± 10, 1350 ± 20, 1615 ± 15 and 932 ± 10 ° C , respectively. The structures of La 5 Bi 3 , La 4 Bi 3 and LaBi are already known to be of the Mn 5 Si 3 , anti-Th 3 P 4 and NaCl types, respectively. La 2 Bi has a structure of the La 2 Sb type with I 4 mmm symmetry. The powder pattern of LaBi 2 has been indexed as an orthorhombic system with unit cell parameters a = 4.737, b = 17.51 and c = 4.564 A . The body-centred cubic cell of the γ phase of lanthanum was found to be tetragonally deformed on forming a solid solution with bismuth.
TL;DR: X-ray probe microanalysis indicates that calcium (CA2+) levels are considerably higher in the neural fold region, and the high level of regional La3+ binding is correlated with inherently greater Ca2+ levels in the developing neural axis.
Abstract: Treatment with lanthanum (La3+) after fixation in phosphate (PO4-3)-buffered glutaraldehyde results in the deposition of a cell surface material (CSM) primarily on the developing urodele amphibian neural axis. X-ray probe microanalysis indicates that calcium (CA2+) levels are considerably higher in the neural fold region. La3+ displaces Ca2+ from negatively-charged moieties on biological membranes. Once bound, La3+ likely interacts with residual phosphate(s) resulting in deposition of CSM. Elemental X-ray microanalysis shows CSM contains mostly lanthanum and phosphorus. The high level of regional La3+ binding is correlated with inherently greater Ca2+ levels in the developing neural axis.
Patent•
31 Jan 1977
TL;DR: Novel dimensionally stable electrodes constituted by a film forming metallic material alloyed with at least one member of the group consisting of metal belonging to Groups VIB, VIIB, VIII, IIB, IB, IVA, lanthanum and lanthanide series of the Periodic Table as discussed by the authors.
Abstract: Novel dimensionally stable electrodes constituted by a film forming metallic material alloyed with at least one member of the group consisting of metal belonging to Groups VIB, VIIB, VIII, IIB, IB, IVA, lanthanum and lanthanide series of the Periodic Table, such as chromium, manganese, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, silicon, germanium, tin, lead and lanthanum having an electroconductive and corrosion resistant surface preactivated on the surface thereof, preparation of said electrodes, use of said electrodes as anodes for electrolysis in aqueous and organic solutions or in fused salts as well as for cathodic protection and electrolysis methods using said electrodes.
TL;DR: In this article, the degree of interference from various sulphates in the determination of lead by flameless a.a.s. is high (e.g. the decrease in the signal from lead is 10% for 2 nanomol of sodium sulphate) and decreases in the order sodium ⩾ potassium ⩽ calcium ⩼ magnesium, which can be eliminated by ashing the sample at 870 ± 10°C.
TL;DR: In this paper, the catalytic activities for oxygen reduction of La1−xLnxNiO3 (Ln: Nd, Sm) and of La−NiO 3 prepared by various methods were studied.
TL;DR: In this paper, the anion exchange behavior of scandium was studied in malonate and ascorbate media on Dowex 2×8 colums (1.4×18 cm).
Abstract: The anion-exchange behaviour of scandium was studied in malonate and ascorbate media on Dowex 2×8 colums (1.4×18 cm). It forms anionic complexes with 8% malonic acid at pH 5.0 and 5% ascorbic acid at pH 6.5. Various eluants such as mineral acids and their corresponding salts were tested eluants and their efficiencies evaluated. Scandium was separated from alkali metals, alkaline earth metals Tl(I), Hg(II) and Fe(II). It was separated from Co, Ni, Pd, Mn, Cd and Zn by selective washing of the column and from other elements by selective elution in both systems. The separation of scandium from Y, La, Ce, Pr, Nd, Sm, Gd and Dy were a remarkable feature of the method.
TL;DR: Mesityl oxide was used for the solvent extraction separation of scandium from 0.1 M hydrochloric acid containing 1.5 M ammonium thiocyanate.
Abstract: Mesityl oxide, i.e., 4-methyl-3-pentene-2-one ((CH/sub 3/)/sub 2/C = CHCOCH/sub 3/) was used for the solvent extraction separation of scandium from 0.1 M hydrochloric acid containing 1.5 M ammonium thiocyanate. Scandium from the organic phase was stripped with 0.2 M hydrochloric acid and was determined photometrically as its alizarin red S complex at 520 nm. It was possible to separate scandium from a large number of elements such as yttrium, lanthanum, thorium, uranium, lead, etc. with which it is associated in minerals.
Patent•
18 Jul 1977
TL;DR: A ternary intermetallic compound capable of reversible sorption of hydrogen having the chemical formula LaNi5-x Alx, where x is in the range of about 0.01 to 1.5, was proposed in this paper.
Abstract: A ternary intermetallic compound capable of reversible sorption of hydrogen having the chemical formula LaNi5-x Alx, where x is in the range of about 0.01 to 1.5 and the method of storing hydrogen using the intermetallic compound.
TL;DR: In this article, an attempt is made to understand the reaction for ternary complex formation between sulphonated alizarin fluorine blue (AFBS), lanthanum and the fluoride ion through study of complex-forming reactions between lanthanium and 1-hydroxyanthraquinone-2-sulphonate (HA2S), alizaran-5-sULphonates (A5S), successively.
Abstract: An attempt is made to understand the reaction for ternary complex formation between sulphonated alizarin fluorine blue (AFBS), lanthanum and the fluoride ion through study of complex-forming reactions between lanthanum and 1-hydroxyanthraquinone-2-sulphonate (HA2S), alizarin-5-sulphonate (A5S) and sulphonated alizarin fluorine blue, successively. Comparison of experimental molar-ratio and Job plots with those derived from theory reveals that HA2S forms 1:1 and 1:2 lanthanum-HA2S complexes of K11abs= 1.85 × 107 l mol–1 and K12abs= 1.29 × 107 l mol–1; A5S forms 1:1, 1:2 and 2:2 lanthanum-A5S complexes and AFBS forms 1:1, 2:1 and 2:2 lanthanum-AFBS complexes. Fluoride ions react to form FR and FR2 complexes, where R represents a particular mixture of AFBS-lanthanum complexes. Conditions under which AFBS can best be used for the determination of fluoride are explored and such an analysis is compared statistically with one using the original alizarin fluorine blue; the latter performs well. The use of other lanthanoid ions is investigated.
TL;DR: The thermodynamic stability constants and thermodynamic parameters for complexation reaction of Y3+, La3+, and Ce3+ with tyrosine have been determined pH metrically as mentioned in this paper.
Abstract: The thermodynamic stability constants and thermodynamic parameters for complexation reaction of Y3+, La3+, and Ce3+ with tyrosine have been determined pH metrically. The study reveals the formation of 1∶1 complexes for La3+ and Ce3+ whereas Y3+ yields both 1∶1 and 1∶2 complexes. The values of enthalpy changes (ΔHo) indicate that unionised hydroxy group also participates in complexation.
TL;DR: In this article, the two calcium antagonistic agents lanthanum and tetracaine cause severe disturbances in the secretory process of the exocrine pancreas, including inhibition of the rate of protein synthesis and exocytosis.
Abstract: The two calcium antagonistic agents lanthanum and tetracaine cause severe disturbances in the secretory process of the exocrine pancreas, including inhibition of the rate of protein synthesis and exocytosis. The former effect resulted mainly from the inhibition of amino acid transport. Lanthanum in a concentration up to 1 mM inhibited transport of different species of amino acids in an unspecific way whereas tetracaine interfered specifically with the Na+ -dependent transport system for neutral amino acids (14C-alpha-amino-isobutyric acid). Na+ -dependent transport of neutral amino acids (3H-leucine) was not affected. Transport inhibition was correlated to the acitvity of the Na+, K+ -ATPase system which was measured in isolated plasma membrane fractions. At higher concentrations (5-10 mM) some uptake of lanthanum into the cells by limited endocytosis was observed. At lower concentrations lanthanum seemed to bind exclusively to certain components of the plasms membrane, mainly at the lateral and basal cell surface. Even at a concentration of 5-10 mM no binding to the apical surface occurred. Similarly no binding of lanthanum was observed to the limiting membrane of isolated zymogen granules, while mitochondria, contained in the same fraction showed considerable binding affinity. The action of lanthanum and tetracaine on membrane carrier systems did not affect the interior organization of the plasma membrane. Particle density and distribution in freeze-fracture replicas as well as the submembrane microfilamentous=microtubular system and the junctional elements remained unaffected.