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Lanthanum
Terms modified by Lanthanum Selected AbstractsMixed f-d Metallomesogens with an Extended Rigid CoreEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Koen Binnemans Abstract The liquid-crystalline behaviour of copper(II) and nickel(II) complexes of a mesogenic Schiff-base ligand derived from N,N' -disalicylidene-1,2-phenylenediamine (salophenH2) and of the corresponding trinuclear mixed copper(II)/lanthanum(III) and nickel(II)/lanthanum(III) complexes was investigated. High-temperature X-ray diffraction studies revealed that both the parent transition metal complexes and the mixed f-d complexes exhibit a hexagonal columnar phase (Colh) over an extended temperature range. Complex formation with lanthanum(III) nitrate resulted in an increase of the transition temperatures. The geometrical parameters (lattice parameters and column cross-section) of all the metal complexes are very similar, which indicates that the local organisation in the mesophase is the same despite their structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] 3-D Water-Soluble Reversible Neodymium(III) and Lanthanum(III) Coordination PolymersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2004Tina Vermonden Abstract The formation of soluble supramolecular 3-D coordination polymers with Nd3+ and La3+ in aqueous solution has been studied for two bifunctional ligands consisting of two pyridine-2,6-dicarboxylate groups connected at the 4-position by O(CH2CH2O)4 and O(CH2CH2O)6 spacers (C4 and C6, respectively). Viscosity measurements were used to monitor the network formation as a function of the ligand concentration, and the ratio between metal ions and ligands. For corresponding conditions C4 solutions with Nd3+ always gave much higher viscosities than C6 solutions with Nd3+. C6 is long, and flexible enough to bind with both chelating groups to only one metal ion (ring formation). This causes the polymers to stop growing, resulting in smaller average sizes of the 3-D polymers. The ring-structures could be demonstrated by 1H NMR spectroscopy using C6 and La3+ at low concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Lanthanum(III) Oxide as a Recyclable Catalyst for the Synthesis of Diaryl Sulfides and Diaryl SelenidesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2009Sabbavarapu Narayana Murthy Abstract La2O3 as a new and efficient recyclable catalyst in coupling various aryl halides with aromatic/alkyl thiols and diphenyl diselenide in combination with KOH as a base and DMEDA as a ligand in DMSO at 110 °C is reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Lanthanum Chromite-Based Interconnects as Key Materials for SOFC Stack DevelopmentINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2004Natsuko Sakai The historical investigations on the physicochemical and transport properties of lanthanum chromite-based perovskite oxides are reviewed to evaluate the compatibility as interconnects in solid oxide fuel cells. These materials improve sinterability in air. This has led to investigations on other physicochemical properties of these materials, such as thermal expansion, mechanical strength, and chemical stability. Lanthanum and chromium ion can be substituted by alkaline earths or transition metals, and this translates into a large flexibility in physicochemical properties. However, the formation of oxygen vacancies in a reducing atmosphere can result in an undesirable isothermal expansion or oxygen permeation. The chemical stability of these materials is governed by the fast cation diffusion at the grain boundary of the polycrystals. [source] Lanthanum and its rapidly emerging role as an anti-carcinogenic agentJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2009Shailendra Kapoor No abstract is available for this article. [source] Energetics of Defect Fluorite and Pyrochlore Phases in Lanthanum and Gadolinium HafnatesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Sergey V. Ushakov Aerodynamic levitation combined with laser heating was used to prepare melts in the HfO2,La2O3 (,Gd2O3) systems. All melts crystallized upon quenching in oxygen. Hf2La2O7 pyrochlore and Gd0.5Hf0.5O1.75 fluorite phases were identified. Gd0.5Hf0.5O1.75 fluorite was transformed into the pyrochlore structure by annealing at 1450°C. Pyrochlore that crystallized from HfO2 - La2O3 melts contained 31.6,34.2 mol% La2O3. The unit cell parameter increased linearly with La content from 10.736 to 10.789 Å. Drop solution calorimetric experiments were performed in 3Na2O·4MoO3 melt at 702°C. The enthalpies of formation from the oxides for pyrochlore phases are ,107.0±5.0 kJ/mol for Hf2La2O7 and ,48.8±4.7 kJ/mol for Hf2Gd2O7. The enthalpy of the pyrochlore,fluorite phase transition in Hf2Gd2O7 is 23.6±3.1 kJ/mol. [source] Fiber Strength Retention of Lanthanum- and Cerium Monazite-Coated NextelÔ 720JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2004Emmanuel E. Boakye NextelÔ 720 fibers were coated with LaPO4 and CePO4 monazite. The coatings were applied using washed and unwashed rhabdophane sols derived from La(NO3)3/(NH4)2HPO4 and a washed sol derived from Ce(NO3)3/H3PO4. The coatings were cured in-line at 900°,1300°C. Multiple coatings were also applied. Fiber strength was retained after coating with washed sols, but not with unwashed sols. These results are consistent with earlier work on LaPO4 monazite fiber coatings derived from La(NO3)3/H3PO4. [source] Highly Enantioselective Conjugate Addition of Thioglycolate to Chalcones Catalyzed by Lanthanum: Low Catalyst Loading and Remarkable Chiral Amplification,ANGEWANDTE CHEMIE, Issue 25 2010Yonghai Hui Kleineree,große Wirkung: Mit dem Lanthan(III)-Komplex eines chiralen N,N,-Dioxids als Katalysator verlief die Titelreaktion hoch enantioselektiv und mit hohen Ausbeuten. Besonders bemerkenswert war die große asymmetrische Verstärkung: Das Produkt wurde mit 98,%,ee erhalten, wenn 1,Mol-% L/La(OTf)3 mit 2,%,ee für L eingesetzt wurde. Tf=Trifluormethansulfonyl. [source] ChemInform Abstract: Synthesis, Structure, and Spectroscopic Properties of the New Lanthanum(III) Fluoride Oxomolybdate(VI) La3FMo4O16.CHEMINFORM, Issue 25 2010Ingo Hartenbach Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Solvothermal Synthesis, Crystal Structure and Properties of a New Organic Templated Lanthanum Sulfate [C4N3H16] [La(SO4)3(H2O)].CHEMINFORM, Issue 15 2008Yalin Zhu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of Perovskite-Type Lanthanum Iron Oxide by Glycothermal Reaction of a Lanthanum,Iron Precursor.CHEMINFORM, Issue 51 2002Hiroshi Kominami Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: A New Lanthanum and Calcium Borate La2CaB10O19.CHEMINFORM, Issue 28 2001Yicheng Wu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Biokinetics of cadmium and zinc in a marine bacterium: Influences of metal interaction and pre-exposureENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2008Dongshi Chen Abstract The uptake kinetics of Cd and Zn, as influenced by metal interaction and metal pre-exposure, was examined in the gram-positive marine bacterium Bacillus firmus over a wide range of ambient free-Cd and -Zn concentrations. Bacteria were exposed to experimental media with different concentrations of Cd and Zn over a short, 15-min period. Zinc was found to be an effective competitive inhibitor of Cd uptake when the Zn2+ concentration ([Zn2+]) was increased to 10,8 M, whereas the Cd concentration (ranging from 10,9 to 10,6 M) did not affect Zn uptake. Inhibition of Cd uptake was dependent on [Zn2+] instead of the [Zn2+] to Cd2+ concentration ratio. Cadmium uptake at different [Zn2+] was significantly inhibited by a sulfur ligand (SH) blocker (N -ethylmaleimide) and a Ca-channel blocker (lanthanum), suggesting that competition between Cd and Zn most likely occurred via binding to the same transport sites. Cadmium efflux also was determined in the presence of different [Zn2+]. A biphasic depuration of Cd was found when [Zn2+] was greater than 10,8 M, whereas the calculated Cd efflux rate was independent of [Zn2+]. We further exposed B. firmus at different Cd or Zn concentrations for 24 h, then determined the metal uptake and efflux kinetics as well as the metallothionein (MT) induction. Both the Cd and Zn cellular concentrations increased with greater exposed metal concentration, but the MT levels and efflux were little affected by the elevated metal concentration. To some extent, however, the Cd uptake was reduced with an elevated intracellular Zn concentration, suggesting that at high Cd concentrations, intracellular Zn can suppress the Cd uptake in B. firmus. These results help to understand the interactions of metals in the marine environments. [source] New Insights into the Chemistry of the Antineoplastic Lanthanum Complex Tris(1,10-phenanthroline)tris(thiocyanato-,N)lanthanum(III) (KP772) and Its Interaction with BiomoleculesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2009Florian Biba Abstract The lanthanide complex tris(1,10-phenanthroline)tris(thiocyanato-,N)lanthanum(III) [La(phen)3(NCS)3] (KP772) is a promising anticancer drug candidate, capable of overcoming resistance of tumors to established chemotherapeutics. The compound was characterized by elemental analysis, IR, 1H NMR spectroscopy, TG/DTA measurements, mass spectrometry and X-ray diffraction analysis. The results indicate that KP772 is a neutral, nine-coordinate complex. In addition the behavior in water, important for the application as a chemotherapeutic drug, and the binding to biomolecules was investigated by capillary electrophoresis and ICP-MS.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Syntheses, Crystal Structures, and Characterizations of a Series of New Layered Lanthanide Carboxylate-PhosphonatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2006Si-Fu Tang Abstract Hydrothermal reactions of different lanthanide(III) salts with (H2O3PCH2)2NCH2COOH (H5L1) led to two new layeredlanthanide(III) carboxylate-diphosphonates, namely La(H2L1)(H2O)2·H2O (1) and La(H2L1)(H2O) (2). The structure of compound 1 features a layered architecture in which the nine-coordinate La3+ ions are bridged by phosphonate groups of the ligands. The carboxylate group of the phosphonate ligand remains protonated and is involved in the interlayer hydrogen bonding. Compound 2 features a double layer structure in which the La3+ ion is eight-coordinated and the carboxylate group of the ligand is chelated to a La3+ ion in a bidentate fashion. Hydrothermal reactions of lanthanide(III) salts with 4-HOOC,C6H4,CH2N(CH2PO3H2)2 (H5L2) afforded three new compounds, namely, La(H4L2)(H3L2)(H2O)·2H2O (3), Er(H3L2)(H4L2) (4), and Er(HL3)(H2L3)(H2O) (5) [H2L3 = H2O3PCH2N(CHO)(CH2,C6H4,COOH)]. H2L3 was formed by the in situ oxidation of one P,C bond of the H5L2 ligand. Compound 3 features a (002) lanthanum(III) phosphonate layer in which the seven-coordinate La3+ ions are bridged by diphosphonate moieties of the ligands. The carboxylate group remains protonated and is involved in the interlayer hydrogen bonding. The structure of compound 4 contains a 1D chain along the a axis in which each pair of ErO6 octahedra is bridged by a pair of phosphonate groups. These 1D chains are further interconnected by hydrogen bonds between noncoordinated phosphonate oxygen atoms into a (002) layer with the phenyl carboxylate groups hanging on the interlayer space. The structure of compound 5 is also layered. The interconnection of Er3+ ions by bidentate and tetradentate bridging phosphonate groups resulted in a (002) inorganic layer with the organic groups orientated to the interlayer space. Luminescence properties of compounds 4 and 5 have also been studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Mixed f-d Metallomesogens with an Extended Rigid CoreEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Koen Binnemans Abstract The liquid-crystalline behaviour of copper(II) and nickel(II) complexes of a mesogenic Schiff-base ligand derived from N,N' -disalicylidene-1,2-phenylenediamine (salophenH2) and of the corresponding trinuclear mixed copper(II)/lanthanum(III) and nickel(II)/lanthanum(III) complexes was investigated. High-temperature X-ray diffraction studies revealed that both the parent transition metal complexes and the mixed f-d complexes exhibit a hexagonal columnar phase (Colh) over an extended temperature range. Complex formation with lanthanum(III) nitrate resulted in an increase of the transition temperatures. The geometrical parameters (lattice parameters and column cross-section) of all the metal complexes are very similar, which indicates that the local organisation in the mesophase is the same despite their structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Adducts of Schiff Bases with Tris(,-diketonato)lanthanide(III) Complexes: Structure and Liquid-Crystalline BehaviourEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2003Koen Binnemans Abstract Adducts of the Schiff base 2-hydroxy- N -octadecyloxy-4-tetradecyloxybenzaldimine with tris(,-dibenzoylmethanato)lanthanide(III) complexes are described. The stoichiometry of the complexes is [Ln(dbm)3Lx], where Ln is a trivalent lanthanide ion (all lanthanides except Ce and Pm), Hdbm is dibenzoylmethane and L is the Schiff base; x = 2 for Ln = La,Er and x = 1 for Ln = Tm,Lu. The Schiff-base ligands are in a zwitterionic form and coordinate through the phenolic oxygen only. The X-ray single-crystal structure of [La(dbm)3L,2] with L, = N -butyl-2-hydroxy-4-methoxybenzaldimine is described. The solution structure of lanthanum(III) complexes has been investigated by 1D and 2D 1H NMR techniques. Although the long-chain Schiff-base ligand and the tris(,-dibenzoylmethanato)lanthanide(III) complexes are non-mesomorphic, some of the adducts exhibit a monotropic smectic A phase. The mesomorphic behaviour depends on the lanthanide ion, in the sense that only a mesophase is observed for the series Ln = La,Eu, not for the heavier lanthanides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Lanthanide Formamidinates as Improved Catalysts for the Tishchenko ReactionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2008Agustino Zuyls Abstract The tris(formamidinato)lanthanum(III) complexes [La(o -TolForm)3(thf)2] [1; o -TolForm = N,N, -bis(o -tolyl)formamidinate], [La(XylForm)3(thf)] [2; XylForm = N,N, -bis(2,6-dimethylphenyl)formamidinate], and [La(EtForm)3] [3, EtForm = N,N, -bis(2,6-diethylphenyl)formamidinate] are a new class of precatalysts for the Tishchenko reaction. Their catalytic activity is a result of their high Lewis acidity and the ease with which the ligand spheres can be interchanged. For the dimerization of benzaldehyde to give benzyl benzoate, which is a benchmark reaction, compound 1 is, to the best of our knowledge, the most active catalyst ever reported. On a preparative scale, the reaction can be performed in the absence of solvent. A range of aromatic, heteroaromatic, and aliphatic aldehydes was rapidly converted into the corresponding esters by using catalysts 1,3.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] The chemiionization reactions Ce + O and Ce + O2: Assignment of the observed chemielectron bandsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2009Tanya K. Todorova Abstract Multiconfigurational quantum chemical methods (CASSCF/CASPT2) have been used to study the chemiionization reactions Ce + O , CeO+ + e, and Ce + O2 , CeO + e,. Selected spectroscopic constants for CeOn and CeO (n = 1, 2), as well as reaction enthalpies of the chemiionization reactions of interest, have been computed and compared with experimental values. In contrast to the lanthanum case, for both Ce + O2(X3,) and Ce + O2( a1,g), the Ce + O2 , CeO + e, reaction is shown to be exothermic, and thus, contributes to the experimental chemielectron spectra. The apparent discrepancy between the computed reaction enthalpies and the high kinetic energy offset values measured in the chemielectron spectra is rationalized by arguing that chemielectrons are produced mainly via two sequential reactions (Ce + O2 , CeO + O, followed by Ce + O , CeO+ + e,) as in the case of lanthanum. For Ce + O2 (a1,g), a chemielectron band with higher kinetic energy than that recorded for Ce + O2( X3,) is obtained. This is attributed to production of O( 1D) from the reaction Ce + O2( a1,g) , CeO + O( 1D), followed by chemiionization via the reaction Ce + O( 1D) , CeO+ + e,. Accurate potential energy curves for the ground and a number of excited states of CeO and CeO+ have been computed, and a mechanism for the chemiionization reactions investigated experimentally was proposed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Lanthanide Bis[(trifluoromethyl)sulfonyl]imides as Reusable Catalysts for Mononitration of Substituted Benzenes in Ionic LiquidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Shuojin Wang Abstract Lanthanide bis[(trifluoromethyl)sulfonyl]imides as a kind of effective catalyst were used in quaternary ammonium ionic liquids to afford a useful new method for the nitration of substituted benzenes with concentrated nitric acid (95%) as nitrating agent. The less expensive lanthanum bis[(trifluoromethyl)sulfonyl]imide was found to be the most effective catalyst employed in the ionic liquid tributylammonium bis[(trifluoromethyl)sulfonyl]imide. The lanthanum bis[(trifluoromethyl)sulfonyl]imide/tributylammonium bis[(trifluoromethyl)sulfonyl]imide system demonstrated high catalytic activity for the nitration of halobenzenes and rendered good to excellent yields. This catalyst/ionic liquid system could be recovered by simple procedures and recycled for at least 5 times. [source] Weaning pig performance and faecal microbiota with and without in-feed addition of rare earth elementsJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 9-10 2006M. Kraatz Summary Two 6-week feeding trials were conducted on a total of 112 newly weaned piglets to examine the recently reported growth promoting effects of dietary rare earth elements (REE) in European pig production. Rare earth element-diets were supplemented with a REE-citrate premix of lanthanum and the light lanthanoides cerium, praseodymium and neodymium at 200 mg/kg for 6 weeks after weaning. Overall for both trials, growth performance of REE-citrate and control fed piglets did not differ significantly (p > 0.05). An early enhancive tendency for REE-citrate in trial 1 (feed conversion ratio, FCR ,3%, p = 0.15) proved irreproducible in trial 2. In the late period of trial 1, in-feed addition of REE-citrate significantly impaired piglet performance (FCR + 8%, p =0.01). A cultivation-independent molecular approach, polymerase chain reaction-denaturing gradient gel electrophoresis was further applied to assess REE induced alterations in the predominant faecal microbiota from weaning pigs. Calculation of various ecological characteristics does not indicate (p > 0.05) an often discussed selective effect on local microbial composition of dietary REE. [source] Removal of fluoride using some lanthanum(III)-loaded adsorbents with different functional groups and polymer matricesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2003Luo Fang Abstract Although fluoride is beneficial for human beings in small quantities, it causes dental fluorosis when consumed in larger quantities over a period of time. In recent years, considerable work has been conducted for the purpose of developing new and low cost absorbents for adsorptive removal of fluoride, especially chelating resins loaded with metal ions. In the present study, several types of adsorbents with different functional groups loaded with lanthanum(III) were prepared to be used for fluoride removal from water. The optimum conditions for loading lanthanum(III) on the adsorbents and the effects of pH and initial fluoride concentration as well as shaking time and solid,liquid ratio on the removal of fluoride have been investigated. Based on these fundamental data, the removal of fluoride from actual hot spring water was also tested as a practical application by comparing the efficiency of different adsorbents for the removal of fluoride from hot spring water. The following conclusions were obtained. (1) The different chemical composition and chemical structure of the polymer matrix play the most important role in fluoride adsorption, (2) strongly acidic adsorbents are more effective on fluoride removal at neutral pH than weakly acidic adsorbents, (3) the order of fluoride removal in the neutral pH range of 4.5,8.0 by the different La(III)-loaded adsorbents employed in the present work is as follows: 200CT resin > POJRgel > IR124resin > SOJR gel , CPAgel , WK11 resin. The column experiments showed that the 200CT resin loaded with lanthanum(III) at pH 6.0 can be successfully employed for the removal of fluoride ions from actual hot spring water. Copyright © 2003 Society of Chemical Industry [source] Relative in vitro efficacy of the phosphate binders lanthanum carbonate and sevelamer hydrochlorideJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2007Valerie Autissier Abstract The high tablet burden and poor compliance associated with phosphate-binding drugs has led to a search for more potent agents. In vitro -binding studies were performed on the recently introduced binder, lanthanum carbonate (LC; Fosrenol®), to compare its phosphate-binding affinity with sevelamer hydrochloride (SH; RenagelÔ). Langmuir equilibrium binding affinities (K1) for LC and SH were established using different phosphorus (5,100 mM) and binder (134,670 mg per 50 mL) concentrations at pH 3,7, with or without salts of bile acids present (30 mM). At all pH levels, LC had a higher binding affinity for phosphate than SH. For LC, K1 was 6.1,±,1.0 mM,1 and was independent of pH. For SH, K1 was pH dependent, being 1.5,±,0.8 mM,1 at pH 5,7 and 0.025,±,0.002 mM,1 at pH 3, that is, >200 times lower than for LC. In the presence of 30 mM bile salts, SH lost 50% of its phosphate, whereas no displacement of phosphate occurred for LC. These findings indicate that LC binds phosphate more effectively than SH across the pH range encountered in the gastrointestinal tract, and has a lower propensity for bound phosphate to be displaced by competing anions in the intestine. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2818,2827, 2007 [source] Anomalous concentration dependence of the coordination behavior of Cl, ion to Ln3+ ion (Ln3+ = rare-earth ion) in anhydrous LnCl3 alcohol solutionsJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2007Y. Yoshimura Abstract Raman spectroscopic measurements were carried out for the anhydrous LnCl3·20ROH·XLiCl solutions (Ln3+ = La3+, Lu3+, X = 0,3; ROH = MeOH, EtOH, n -PrOH) in the liquid state. The salt concentration (X) dependence of the wavenumber for the Ln,Cl stretching Raman band (,Ln,Cl) is examined in conjunction with the formation of chloro-rare-earth complexes. We have obtained very intriguing results including the fact that the chloro complexations of the middle rare-earth ions (e.g. gadolinium, holmium ions, etc.) in the MeOH and EtOH solutions show peculiar behavior with regard to the salt concentration dependence: the ,Ln,Cl wavenumber increases with the increasing chloride concentration. However, the ,Ln,Cl wavenumbers of the light and heavy rare-earth (e.g. lanthanum, lutetium, etc.) salt solutions show normal behavior; i.e. ,Ln,Cl decreases with the increasing chloride concentration. On the other hand, in the n -PrOH solutions, the ,Ln,Cl frequency in the solutions of all the rare-earth elements exhibits a normal behavior. We now present a possible mechanism for this anomalous concentration dependence of coordination of Cl, ions to Ln3+ ions in anhydrous LnCl3 alcohol solutions. Copyright © 2007 John Wiley & Sons, Ltd. [source] ORAL PHOSPHATE BINDERS FOR THE MANAGEMENT OF SERUM PHOSPHATE LEVELS IN DIALYSIS PATIENTSJOURNAL OF RENAL CARE, Issue 2009Ismail Mohammed MBBS, MRCP SUMMARY Hyperphosphataemia is an inevitable consequence of end stage chronic kidney disease and is present in the majority of dialysis patients. Hyperphosphataemia is statistically associated with increased cardiovascular mortality among dialysis patients. Dietary restriction of phosphate and current dialysis modalities are not sufficiently effective to maintain serum phosphate levels within the recommended range so that the majority of dialysis patients require oral phosphate binders. However, benefits of achieving the recommended range have yet to be demonstrated prospectively. Unfortunately, conventional phosphate binders are not reliably effective and are associated with a range of limitations and side effects. Aluminium containing agents are highly efficient but no longer widely used because of well-established and proven toxicity. Calcium-based salts are inexpensive, effective and most widely used but there is now concern about their association with hypercalcaemia and vascular calcification. Sevelamer hydrochloride and lanthanum carbonate are non-aluminium, calcium-free phosphate binders. They are effective and reasonably well tolerated, but still do not control phosphate levels in all patients. Patient education programmes have been shown to be a useful and effective method of improving achievement of serum phosphate targets. [source] High-Temperature Stability of Lanthanum Orthophosphate (Monazite) on Silicon Carbide at Low Oxygen Partial PressuresJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Michael K. Cinibulk The stability of lanthanum orthophosphate (LaPO4) on SiC was investigated using a LaPO4 -coated SiC fiber at 1200°,1400°C at low oxygen partial pressures. A critical oxygen partial pressure exists below which LaPO4 is reduced in the presence of SiC and reacts to form La2O3 or La2Si2O7 and SiO2 as the solid reaction products. The critical oxygen partial pressure increases from ,0.5 Pa at 1200°C to ,50 Pa at 1400°C. Above the critical oxygen partial pressure, a thin SiO2 film, which acts as a reaction barrier, exists between the SiC fiber and the LaPO4 coating. Continuous LaPO4 coatings and high strengths were obtained for coated fibers that were heated at or below 1300°C and just above the critical oxygen partial pressure for each temperature. At temperatures above 1300°C, the thin LaPO4 coating becomes morphologically unstable due to free-energy minimization as the grain size reaches the coating thickness, which allows the SiO2 oxidation product to penetrate the coating. [source] Synthesis of Various LaMO3 Perovskites in Molten CarbonatesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2006Toshikatsu Kojima Lanthanum-containing perovskites, LaMO3 (M=Al, Sc, Cr, Mn, Fe, Co, Ni, Ga, and In), have been synthesized in molten carbonates from a mixture of lanthanum carbonate and an M-containing oxide or an acetate, or from a co-precipitation mixture of metal (M) and lanthanum. Metal aluminum, chromium, and iron, immersed in a mixture of molten (Li0.52Na0.48)2CO3 and lanthanum carbonate at 923 K, were covered, respectively, with LaAlO3, LaCrO3, and LaFeO3. Ceramic and single-crystal ,-Al2O3, immersed in molten (Li0.52Na0.48)2CO3 mixed with lanthanum carbonate, were also covered with LaAlO3. In situ X-ray diffractometry revealed that La2O2CO3 reacted with ,-LiAlO2 to yield LaAlO3; the reaction proceeded faster under N2 than under a CO2 atmosphere. [source] Acute Effects of Ethanol on Kainate Receptors in Cultured Hippocampal NeuronsALCOHOLISM, Issue 2 2000Edmar T. Costa Background: Kainate receptors are a subclass of ionotropic glutamate receptors that regulate excitability and mediate synaptic transmission and plasticity in the hippocampus. The acute effects of ethanol on these receptors are not completely understood. Methods: The acute effects of ethanol on pharmacologically isolated kainate receptor-mediated currents were studied in cultured hippocampal neurons obtained from neonatal rats. Whole-cell patch-clamp electrophysiological techniques were used for these studies. LY303070 (GYKI-53784), a potent AMPA (,-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor-selective noncompetitive antagonist, was used to isolate kainate currents. Results: Kainate receptor-mediated currents corresponded to 7% of the total non- N -methyl- d -aspartate (non-NMDA) currents in these neurons and were reduced to 24% of control values in the presence of 15 ,M lanthanum. These kainate receptor-mediated currents were significantly inhibited by ethanol concentrations of 50 mM or more. Under our recording conditions, ethanol inhibited non-NMDA receptor- and NMDA receptor-mediated currents to a similar extent as kainate receptor-mediated currents. Western blot analysis indicated that glutamate receptor-5 and -6/7 subunits, and kainic acid-2 subunits are expressed in these cultured hippocampal neurons. Conclusions: The present results suggest that kainate receptors are important targets for the actions of ethanol in the central nervous system. [source] A modified technique for the impregnation of lanthanum tracer to study the integrity of tight junctions on cells grown on a permeable substrateMICROSCOPY RESEARCH AND TECHNIQUE, Issue 10 2006Harriet Nilsson Abstract Ionic lanthanum is commonly used to trace permeability pathways across epithelia and endothelia in biological electron microscopy. A method for obtaining a uniformly dense precipitate of lanthanum is described. The method, which is a modification of the technique described by Shaklai and Tavassoli (1977) was suitable for fixation of cell cultures grown on permeable filter inserts and was successfully applied to study opening of tight junctions by hypertonic solutions in the airway epithelial cell line 16HBE14o,. The preparation method formed the basis for a semiquantitative morphological determination in which the tight junctions were subdivided as "intact," "weakened," and "open." By using this modified technique, it could be demonstrated that opening of tight junctions in airway epithelial cells increased, with increasing osmolarity with electrolytes having a stronger effect than nonelectrolytes. A significant linear relationship was found between the osmolarity of the medium and the open state of the tight junctions (as determined by the semiquantitative morphological technique) or the transepithelial electrical resistance. Microsc. Res. Tech., 2006. © 2006 Wiley-Liss, Inc. [source] Role of phi cells and the endodermis under salt stress in Brassica oleraceaNEW PHYTOLOGIST, Issue 2 2009N. Fernandez-Garcia Summary ,,Phi cell layers were discovered in the 19th century in a small number of species, including members of the Brassicaceae family. A mechanical role was first suggested for this structure; however, this has never been demonstrated. The main objective of the present work was to analyse the ultrastructure of phi cells, their influence on ion movement from the cortex to the stele, and their contribution to salt stress tolerance in Brassica oleracea. ,,Transmission electron microscopy and X-ray microanalysis studies were used to analyse the subcellular structure and distribution of ions in phi cells and the endodermis under salt stress. Ion movement was analysed using lanthanum as an apoplastic tracer. ,,The ultrastructural results confirm that phi cells are specialized cells showing cell wall ingrowths in the inner tangential cell walls. X-ray microanalysis confirmed a build-up of sodium. Phi thickenings were lignified and lanthanum moved periplasmically at this level. ,,To the best of our knowledge, this is the first study reporting the possible role of the phi cells as a barrier controlling the movement of ions from the cortex to the stele. Therefore, the phi cell layer and endodermis seem to be regulating ion transport in Brassica oleracea under salt stress. [source] | ||||||||||||||||||||||||||||||||||