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1

Dynamic Nuclear Polarization in Samarium Doped Lanthanum Magnesium Nitrate. Ph.D. Thesis - Va. Polytechnic Inst.  

NASA Technical Reports Server (NTRS)

The dynamic nuclear polarization of hydrogen nuclei by the solid effect in single crystals of samarium doped lanthanum magnesium nitrate (Sm:LMN) was studied theoretically and experimentally. The equations of evolution governing the dynamic nuclear polarization by the solid effect were derived in detail using the spin temperature theory and the complete expression for the steady state enhancement of the nuclear polarization was calculated. Experimental enhancements of the proton polarization were obtained for eight crystals at 9.2 GHz and liquid helium temperatures. The samarium concentration ranged from 0.1 percent to 1.1 percent as determined by X-ray fluorescence. A peak enhancement of 181 was measured for a 1.1 percent Sm:LMN crystal at 3.0 K. The maximum enhancements extrapolated with the theory using the experimental data for peak enhancement versus microwave power and correcting for leakage, agree with the ideal enhancement (240 in this experiment) within experimental error for three of the crystals.

Byvik, C. E.

1971-01-01

2

Investigation of the thermal conductivity of selected compounds of lanthanum, samarium and europium  

Microsoft Academic Search

As part of the development of rare earth based ceramic materials for a variety of applications, the thermal conductivities of lanthanum aluminate, samarium zirconate and europium zirconate were investigated, employing the laser flash technique and covering a temperature range from 650–1400 K. Based on the variation of the thermal resistivity as a function of temperature, the heat transport behaviour of

Girija Suresh; G Seenivasan; M. V Krishnaiah; P. Srirama Murti

1998-01-01

3

Europium and samarium doped calcium sulfide thin films grown by PLD S. Christoulakis a,c  

E-print Network

Europium and samarium doped calcium sulfide thin films grown by PLD S. Christoulakis a,c , M Suchea Abstract Europium and samarium doped calcium sulfide thin films (CaS:Eu,Sm) with different thickness were and crystallinity. In this work we present preliminary results related to the deposition of europium and samarium

4

EXTENT OF PARTICULATE MARKER (SAMARIUM, LANTHANUM AND CERIUM) MOVEMENT FROM ONE DIGESTA PARTICLE TO ANOTHER 1'2  

Microsoft Academic Search

SUMMARY An in vitro and in vivo experiment was performed to determine the extent of move- ment of samarium (Sm), cerium (Ce), and lanthanum (La) from the original feedstuff upon which they were adsorbed to other feed particles. The rare-earth elements were demon- strated to be tenaciously bound to the parti- culate phase, with essentially none of the element occuring

Gary F. Hartnell; Larry D. Satter

5

Structural and optical characterization of samarium doped yttrium oxide nanoparticles.  

PubMed

Here we demonstrate the preparation of samarium doped yttrium oxide nanoparticles using samarium chloride as a samarium source by co-precipitation method. The samarium doped yttria nanoparticles are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Fourier transform infra-red spectroscopy (FT-IR). The XRD results revealed that all the synthesized samples exhibit cubic phase with average grain size of the nanoparticles in the order of 9-20 nm, calculated by Scherer's formula. The strain present in the annealed sample is estimated from Williamson-Hall (W-H) plot which is in the order of 3 x 10(-3). SEM and HRTEM results showed that the samples are composed of aggregated nanoparticles with uniform shape and size. The particles are highly crystalline which is also confirmed by XRD results. The position of the absorption peak is shifted towards the lower wavelength side when particles sizes reduced around 10 nm is observed by UV-visible (UV-vis) spectrometer. The direct band gap is estimated from UV-vis absorption spectrum, the calculated value is 5.98 and 5.87 eV for as-prepared and annealed sample (800 degrees C) respectively. The high intense red emission band observed at 608 nm from 4G(5/2)-6H(7/2) transition for Y2O3:Sm3+ under excitation at 214 nm using fluorescence spectrometer. PMID:19908594

Srinivasan, Ramasamy; Yogamalar, Rajeswari; Vinu, Ajayan; Ariga, Katsuhiko; Bose, Arumugam Chandra

2009-11-01

6

Precipitation synthesis and sintering of lanthanum doped yttria transparent ceramics  

NASA Astrophysics Data System (ADS)

Co-precipitation method was used to prepare lanthanum doped yttria nanopowder. After calcinations at 1000 °C, lanthanum ion entered into the yttria lattice. Effect of lanthanum oxide as an equal valent additive on the sintering of yttria was investigated. The addition of lanthanum ions was found to be effective for promoting the densification process during sintering, and make it easier for the ceramic to be transparency at moderate 1700 °C in vacuum. After sintering at 1500 and 1700 °C for 4 h in vacuum, translucent and transparent poly-crystalline ceramics with uniform lanthanum distribution was obtained, respectively. The grain size (75 ± 13 ?m) of 7% lanthanum doped yttria sintered at 1700 °C was about 10 times bigger than that sintered at 1500 °C (7.6 ± 1.9 ?m). The refractive indices of lanthanum ion doped sample were higher than undoped sample in vis-UV light range. The in-line transmittance of 2 mm thick samples sintered at 1700 °C reached 74% at 800 nm (89.7% of theoretical transmittance) wavelength.

Huang, Yihua; Jiang, Dongliang; Zhang, Jingxian; Lin, Qingling

2009-08-01

7

Single-Longitudinal-Mode Lanthanum-Codoped Bismuth-Based Erbium Doped Fiber Ring Laser  

E-print Network

Single-Longitudinal-Mode Lanthanum-Codoped Bismuth-Based Erbium Doped Fiber Ring Laser K. K and demonstrate a stable single-longitudinal-mode lanthanum-codoped bismuth oxide- based erbium doped fiber ring

Wai, Ping-kong Alexander

8

Electrical properties of lanthanum doped barium titanate ceramics  

SciTech Connect

Pure and lanthanum doped barium titanate (BT) ceramics were prepared by sintering pellets at 1300 deg. C for 8 h, obtained from nanopowders synthesized by the polymeric precursor method. XRD results showed formation of a tetragonal structure. The presence of dopants changed the tetragonal structure to pseudo-cubic. The polygonal grain size was reduced up to 300 nm with addition of lanthanum as a donor dopant. Determined dielectric properties revealed that lanthanum modified BT ceramics possessed a diffused ferroelectric character in comparison with pure BT that is a classical ferroelectric material. In doped BT phase transition temperatures were shifted to lower temperatures and dielectric constant values were much higher than in pure BT. A modified Currie Weiss law was used to explore the connection between the doping level and degree of diffuseness of phase transitions. Impedance spectroscopy measurements were carried out at different temperatures in order to investigate electrical resistivity of materials and appearance of a PTCR effect. - Highlights: {yields} Pure and lanthanum doped BaTiO{sub 3} were prepared by polymeric precursors method. {yields} Change of structure from tetragonal to pseudo-cubic. {yields} Lanthanum as a donor dopant influenced on change of ferro-para phase transition. {yields} The diffuseness factor indicated the formation of diffuse ferroelectric material. {yields} Lanthanum affected on PTCR effect appearance in BT ceramics.

Vijatovic Petrovic, M.M., E-mail: miravijat@yahoo.com [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia); Bobic, J.D. [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia); Ramoska, T.; Banys, J. [Faculty of Physics, Vilnius University, Sauletekio al. 9, Vilnius (Lithuania); Stojanovic, B.D. [Institute for Multidisciplinary Research, Belgrade University, Kneza Viseslava 1, Belgrade (Serbia)

2011-10-15

9

FTIR and VSM properties of samarium-doped nickel ferrite  

NASA Astrophysics Data System (ADS)

Nickel Ferrite (NiFe2O4) doped with Samarium (Sm) (0.2, 0.3, 0.4, 0.5 mol.%) was prepared by the conventional solid-state reaction. The crystal structure, surface morphology, infrared spectrum of absorption, and magnetic properties of samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and vibrating sample magnetometer (VSM). XRD patterns were indexed with inverse spinel cubic phase with the space group of Fd-3m of nickel ferrite. The average grain size was about 5-10 ?m. FTIR spectral study on the NiFe2O4 ferrite phase was recorded between 350 cm-1 and 4000 cm-1. Two fundamental absorption bands of the ferrites were appeared at 450 cm-1 and 1000 cm-1 characteristic of metal vibrations. VSM measurements show that the NiFe2O4 doped with Sm 0.3% has the highest value of saturation magnetization. It is also easily demagnetized due to the low value of coercivity field it has. Both NiFe2O4 doped with Sm 0.2 mol.% and 0.4 mol.% materials have same values of coercivity field. However, NiFe2O4 doped with Sm 0.4 mol.% material has the comparatively high value of saturation magnetization than NiFe2O4 doped with Sm 0.2%, also this material was hardly demagnetized, and has highest coercivity field.

?abiko?lu, Israfil; Paral?, Levent

2014-05-01

10

Improved tensile creep properties of yttrium-and lanthanum-doped alumina: a solid solution effect  

E-print Network

Improved tensile creep properties of yttrium- and lanthanum-doped alumina: a solid solution effect- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains

Cho, Junghyun

11

Joining of highly aluminum-doped lanthanum strontium manganese oxide with tetragonal zirconia by plastic deformation  

E-print Network

Joining of highly aluminum-doped lanthanum strontium manganese oxide with tetragonal zirconia February 2008; accepted 24 March 2008 Abstract Aluminum-doped lanthanum strontium manganese oxide, La0.77Sr at the interface. © 2008 Elsevier B.V. All rights reserved. Keywords: Lanthanum strontium aluminum manganese oxide

Dutta, Prabir K.

12

Sinterability and electrical conductivity of calcium-doped lanthanum chromites  

Microsoft Academic Search

Calcium-doped lanthanum chromites, (La1-xCax) (Cr1-y Cay O3, have been synthesized to investigate effects of calcium doping on sinterability and electrical conductivity. X-ray diffractometric results have revealed that in addition to normal perovskites (La1-xCaxCrO3), chromium-deficient perovskites can exist as a single phase in the composition region 0.1 x < 0.3, although the deficit of chromium is small. These chromium-deficient perovskites show

N. Sakai; T. Kawada; H. Yokokawa; M. Dokiya; T. Iwata

1990-01-01

13

Intrinsic and coupling-induced elastic nonlinearity of lanthanum-doped lead magnesium niobatelead titanate electrostrictive ceramic  

E-print Network

Intrinsic and coupling-induced elastic nonlinearity of lanthanum-doped lead magnesium niobate July 2000 The elastic nonlinearity of lanthanum-doped lead magnesium niobate­lead titanate the measurement results on the elastic nonlinearity of PMN-PT and their field dependence. The lanthanum-doped PMN

Cao, Wenwu

14

Magnetoelectric behavior of sodium doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

Nanocrystalline samples of sodium doped manganites with compositional formula La1-xNaxMnO3 (0.025?x?0.25) were prepared by polyvinyl alcohol assisted precursor method. After characterizing the samples by x-ray diffraction and transmission electron microscopy a systematic investigation of electrical, magnetic, and thermopower properties has been undertaken. The resistivity data were analyzed using effective medium approximation. From the analysis it has been found that the metallic fraction is increasing up to x=0.10 and remains constant with further doping. A close examination of the resistivity data clearly indicates that the sodium doped samples are slowly transformed from colossal magnetoresistance behavior to charge ordering behavior. Thermoelectric power data at low temperatures were analyzed by considering the magnon drag concept, while the high temperature data were explained by small polaron conduction mechanism.

Kalyana Lakshmi, Y.; Venkataiah, G.; Reddy, P. Venugopal

2009-07-01

15

Thermal conductivity analysis of lanthanum doped manganites  

NASA Astrophysics Data System (ADS)

The temperature-dependent thermal conductivity of the doped manganites La0.7Ca0.3MnO3 is theoretically analyzed within the framework of Kubo formulae. The Hamiltonian consists of phonon, electron and magnon thermal conductivity contribution term. In this process we took defects, carrier, grain boundary, scattering process term and then calculate phonon, electron and magnon thermal conductivity.

Mansuri, Irfan; Shaikh, M. W.; Khan, E.; Varshney, Dinesh

2014-04-01

16

Lanthanum  

MedlinePLUS

Lanthanum is used to reduce blood levels of phosphate in patients with kidney disease. High levels of phosphate in the blood can cause bone problems. Lanthanum is in a class of medications called phosphate ...

17

Expansion on reduction of calcium doped lanthanum chromite  

SciTech Connect

Doped lanthanum chromites have been considered as interconnect materials for the solid oxide fuel cell (SOFC) because of their favorable chemical and electrical properties under both oxidizing and reducing environments. Several investigators have studied the materials properties of the doped lanthanum chromites to optimize their overall performance as an interconnect material. These properties include electrical conductivity, thermal expansion, sinterability, and chemical compatibility with other cell components. These properties are optimized by the amount of dopants substituted into chromite which are usually Ca or Sr. Figure 1 shows the range of values for these properties. Another important characteristic becoming more of a concern as investigators are building SOFC stacks is that doped lanthanum chromite expands when reduced in a low oxygen partial pressure (pO{sub 2}) (<10{sup -12} atm). Plates used to separate oxidizing and fuel gases can deform because of the pO{sub 2} gradient across the interconnect material. This presentation is a summary of work which will be presented at the Fourth International Symposium on Solid Oxide Fuel Cells. In this article, the possible causes of expansion on reduction of the interconnect will be discussed by using a two-dimensional crystal model. The biaxial strain of the stack is calculated under the assumption that the cell components are forced to remain planar. From this, the maximum stress buildup in the interconnect and electrolyte is estimated. In addition, the effects of thermal expansion mismatch and expansion on reduction of the interconnect are compared, and the optimum interconnect composition from a mechanical standpoint is reported.

Carter, J.D.; Hendriksen, P.V.; Mogensen, M. [Riso National Lab., Roskilde (Denmark). Materials Dept.

1995-07-01

18

Thermal conductivity analysis of lanthanum doped manganites  

SciTech Connect

The temperature-dependent thermal conductivity of the doped manganites La{sub 0.7}Ca{sub 0.3}MnO{sub 3} is theoretically analyzed within the framework of Kubo formulae. The Hamiltonian consists of phonon, electron and magnon thermal conductivity contribution term. In this process we took defects, carrier, grain boundary, scattering process term and then calculate phonon, electron and magnon thermal conductivity.

Mansuri, Irfan, E-mail: dr.irfan.mansuri@gmail.com [Indore Institute of Science and Technology, Pithampur Road Rau, Indore-453331 India and School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001 (India); Shaikh, M. W. [School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001, India and Acropolis Technical Campus, Village Tillore, Indore-453331 (India); Khan, E.; Varshney, Dinesh [School of Physics, Devi Ahilya University, Khandwa Road Campus, Indore-452001 (India)

2014-04-24

19

Spectroscopy of vanadium (III) doped gallium lanthanum sulphide chalcogenide glass  

E-print Network

Vanadium doped gallium lanthanum sulphide glass (V:GLS) displays three absorption bands at 580, 730 and 1155 nm identified by photoluminescence excitation measurements. Broad photoluminescence, with a full width half maximum (FWHM) of 500 nm, is observed peaking at 1500 nm when exciting at 514, 808 and 1064 nm. The fluorescence lifetime and quantum efficiency at 300 K were measured to be 33.4 us and 4 % respectively. From the available spectroscopic data we propose the vanadium ions valence to be 3+ and be in tetrahedral coordination The results indicate potential for development of a laser or optical amplifier based on V:GLS.

Hughes, M; Rutt, H; Hewak, D

2014-01-01

20

Diode pumped white light emission from dysprosium and samarium doped glasses  

NASA Astrophysics Data System (ADS)

Glasses embedded with Dysprosium and Samarium were made by the melt quenching technique. Dy3+ -doped glasses exhibited bright white luminescence under 10 mW of 405 nm diode laser excitation. Color rending index of the glass was improved by adding Sm3+ as a co-dopant to the glass. Spectroscopic results of the glasses are discussed.

Reddy, B. Rami; Edwards, Vernessa M.; Surabhi, Raja

2014-03-01

21

Effect of samarium doping on the dielectric behavior of barium zircomium titanate ceramic  

NASA Astrophysics Data System (ADS)

Samarium doped Barium Zirconium Titanate ceramic with general formula Ba1-xSm2x/3Zr0.05Ti0.95O3 [x=0.0,0.01,0.02,0.03,0.04] has been prepared by high energy ball milling. The X-ray diffraction (XRD) patterns confirmed that these ceramics have a single phase with perovskite-type upto x?0.03 and a small secondary phase exist at x=0.04. The temperature dependent dielectric study shows a ferroelectric phase transition and transition temperature decreases with an increase in the Samarium content.

Badapanda, T.; Sarangi, S.; Behera, B.; Anwar, S.; Sinha, T. P.

2014-04-01

22

Effect of samarium doping on the dielectric behavior of barium zircomium titanate ceramic  

SciTech Connect

Samarium doped Barium Zirconium Titanate ceramic with general formula Ba{sub 1?x}Sm{sub 2x/3}Zr{sub 0.05}Ti{sub 0.95}O{sub 3} [x=0.0,0.01,0.02,0.03,0.04] has been prepared by high energy ball milling. The X-ray diffraction (XRD) patterns confirmed that these ceramics have a single phase with perovskite-type upto x?0.03 and a small secondary phase exist at x=0.04. The temperature dependent dielectric study shows a ferroelectric phase transition and transition temperature decreases with an increase in the Samarium content.

Badapanda, T., E-mail: badapanda.tanmaya@gmail.com [Department of Physics, C.V. Raman College of Engineering, Bhubaneswar, Odisha-752054 (India); Sarangi, S.; Behera, B. [School of Physics, Sambalpur University, Jyoti Vihar Sambalpur, Odisha-768019 (India); Anwar, S. [Colloids and Materials Chemistry, Institute of Minerals and Materials Technology, Bhubaneswar, Odisha-751013 (India); Sinha, T. P. [Department of Physics, Bose Institute, Kolkata-700009 (India)

2014-04-24

23

Synthesis and characterization of cerium-doped lanthanum halide colloidal nanocrystals.  

E-print Network

??Cerium-doped bulk lanthanum halide compounds are attractive in the field of high-energy radiation detection due to their interesting properties that include efficient radiation absorption, highly… (more)

Sankar, Krishnaprasad

2009-01-01

24

Altering the equilibrium condition in Sr-doped lanthanum manganite.  

SciTech Connect

The material of choice for a solid oxide fuel cell cathode based on a yttria-stabilized zirconia (YSZ) electrolyte is doped lanthanum manganite, (La, Sr)MnO{sub 3}. It excels at many of the attributes necessary for a system to work at the required operating temperature and is flexible enough to allow for materials optimization. Although strontium-doping increases the electronic conductivity of the material, the ionic conductivity of the material remains negligible under operating conditions. Studies have shown that the internal equilibrium of the material heavily favors oxidation of the manganese and rather than the loss of lattice oxygen as a charge compensation mechanism. This lack of oxygen vacancies in the structure retards the ability of the material to conduct oxygen ions; thus the optimized system requires a large number of engineered triple point boundary locations to work efficiently. We have successfully doped the host LSM lattice to alter the interred equilibrium of the material to increase its ionic conductivity and thus lower the cathodic overpotential of the system. Our presentation will discuss these new materials, the results of cell tests, and a number of characterization experiments performed.

Carter, J. D.; Krumpelt, M.; Vaughey, J.; Wang, X.

1999-05-28

25

Nickel-and Ruthenium-Doped Lanthanum Chromite Anodes: Effects of Nanoscale Metal Precipitation on Solid Oxide  

E-print Network

Nickel- and Ruthenium-Doped Lanthanum Chromite Anodes: Effects of Nanoscale Metal Precipitation This paper compares the effects of Ni and Ru dopants in lanthanum chromite anodes by correlating structural microscope observations showed that nanoclusters of Ni or Ru metal precipitated onto lanthanum chromite La0

Marks, Laurence D.

26

The evolution mechanism of the dislocation loops in irradiated lanthanum doped cerium oxide  

NASA Astrophysics Data System (ADS)

Cerium dioxide, a non-radioactive surrogate of uranium dioxide, is useful for simulating the radiation responses of uranium dioxide and mixed oxide fuel (MOX). Controlled additions of lanthanum can also be used to form various levels of lattice oxide or anion vacancies. In previous transmission electron microscopy (TEM) experimental studies, the growth rate of dislocation loops in irradiated lanthanum doped ceria was reported to vary with lanthanum concentration. This work reports findings of the evolution mechanisms of the dislocation loops in cerium oxide with and without lanthanum dopants based on a combination of molecular statics and molecular dynamics simulations. These dislocation loops are found to be b=1/3<111> interstitial type Frank loops. Calculations of the defect energy profiles of the dislocation loops with different structural configurations and radii reveal the basis for preference of nucleation as well as the driving force of growth. Frenkel pair evolution simulations and displacement cascade overlaps simulations were conducted for a variety of lanthanum doping conditions. The nucleation and growth processes of the Frank loop were found to be controlled by the mobility of cation interstitials, which is significantly influenced by the lanthanum doping concentration. Competition mechanisms coupled with the mobility of cation point defects were discovered, and can be used to explain the lanthanum effects observed in experiments.

Miao, Yinbin; Aidhy, Dilpuneet; Chen, Wei-Ying; Mo, Kun; Oaks, Aaron; Wolf, Dieter; Stubbins, James F.

2014-02-01

27

Crystal structure of Eu-doped magnetoplumbite-type lanthanum aluminum oxynitride with emission site splitting  

SciTech Connect

Eu-doped lanthanum aluminum oxynitride (LaAl{sub 12}(O,N){sub 19}) with magnetoplumbite structure was prepared by nitridation of the oxide precursor obtained from aluminum glycine gel and subsequent post-annealing. Eu-doped lanthanum aluminum oxynitride exhibited blue light emission at 440 nm with a shoulder at 464 nm under excitation at 254 nm. Isostructural Eu-doped calcium aluminum oxide (CaAl{sub 12}O{sub 19}) exhibited a single emission peak at 415 nm. Structural refinement using neutron powder diffraction indicated that the lanthanum site occupied partially by Eu{sup 2+} splits into 2d and 6h sites in the aluminum oxynitride. The longer emission and the shoulder peak in the former aluminum oxynitride were observed in relation to the increasing covalency as well as crystal field splitting around doped Eu{sup 2+} induced by site splitting involved with the two kinds of anions. - Graphical Abstract: Magnetoplumbite type Eu-doped lanthanum aluminum oxynitride has lanthanum site splitting induced by two kinds of anions, causing two emission peaks. Highlights: > Magnetoplumbite type LaAl{sub 12}(O,N){sub 19} doped with Eu shows emission peak splitting. > ND analysis is performed on La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} and Ca{sub 0.97}Eu{sub 0.03}Al{sub 12}O{sub 19}. > La{sub 0.97}Eu{sub 0.03}Al{sub 12}(O,N){sub 19} has lanthanum site splitting. > The lanthanum site splitting is induced by coexisting of two kinds of anions.

Masubuchi, Yuji, E-mail: yuji-mas@eng.hokudai.ac.jp [Faculty of Engineering, Hokkaido University, N13 W8, Kita-ku, Sapporo 060-8628 (Japan); Hata, Tomoyuki; Motohashi, Teruki; Kikkawa, Shinichi [Faculty of Engineering, Hokkaido University, N13 W8, Kita-ku, Sapporo 060-8628 (Japan)

2011-09-15

28

The pyroelectric properties of the lanthanum-doped ferroelectric plzt ceramics  

Microsoft Academic Search

The pyroelectric properties of hot-pressed lanthanum doped PZT X\\/65\\/35 ferroelectric ceramics have been studied to evaluate their potential as pyroelectric infrared detector materials. The pyroelectric coefficients ranged from 3.5 × 10-8 to 17.0 × 10-8 (coul\\/cm2 °C) for lanthanum compositions from X = 0 to 8. The dielectric properties have also been measured over this compositional range. Thermal noise is

S. T. Liu; J. D. Heaps; O. N. Tufte

1972-01-01

29

Enhancement of ferromagnetic and dielectric properties of lanthanum doped bismuth ferrite nanostructures  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

Chaudhuri, A., E-mail: arka@bose.res.in [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Mandal, K. [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)] [Magnetism Laboratory, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India)

2012-04-15

30

Transport properties of silver-calcium doped lanthanum manganite  

NASA Astrophysics Data System (ADS)

Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0

Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.

2015-01-01

31

YBCO bulk superconductors doped with gadolinium and samarium  

NASA Astrophysics Data System (ADS)

The YBa2Cu3O7-? (YBCO, Y123) bulk single-grain superconductors doped with GdBa2Cu3Oy (Gd123) or SmBa2Cu3Oz (Sm123) were prepared by the Top-seeded melt-growth process. The growth conditions of the samples were optimized for different dopant concentrations. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides dopants also Sm from the seed and Yb from the substrate. The critical temperature, Tc increases with increasing dopant concentration in the studied range. Peak effect in the field dependences of critical current density, Jc(B) at 77 K was observed.

Volochová, Daniela; Piovar?i, Samuel; Radušovská, Monika; Antal, Vitaliy; Ková?, Jozef; Jurek, Karel; Jirsa, Miloš; Diko, Pavel

2013-11-01

32

Mechanochemical preparation of nanocrystalline BaFCl doped with samarium in the 2+ oxidation state.  

PubMed

We report a facile mechanochemical preparation method for nanocrystalline BaFCl doped with samarium in the 2+ oxidation state by ball milling BaCl2, BaF2, and SmI2 under a nitrogen atmosphere. The resulting phosphors were characterized by powder X-ray diffraction; electron microscopy, X-ray photoelectron spectroscopy; and photoluminescence, photoexcitation, cathodoluminescence, and diffuse reflectance spectroscopy. This is the first report of a direct preparation method of Sm(2+) doped alkaline earth fluorohalides at room temperature and points to a significant potential for the preparation of a wide range of related X-ray storage phosphors containing rare earth ions in divalent and trivalent cationic states by mechanochemical methods. PMID:25113662

Wang, Xiang-lei; Liu, Zhi-qiang; Stevens-Kalceff, Marion A; Riesen, Hans

2014-09-01

33

Processing and electrical properties of alkaline earth-doped lanthanum gallate  

Microsoft Academic Search

Oxides exhibiting substantial oxygen ion conductivity are utilized in a number of high-temperature applications, including solid oxide fuel cells, oxygen separation membranes, membrane reactors, and oxygen sensors. Alkaline earth-doped lanthanum gallate powders were prepared by glycine\\/nitrate combustion synthesis. Compacts of powders synthesized under fuel-rich conditions were sintered to densities greater than 97% of theoretical. Appropriate doping with Sr or Ba

J. W. Stevenson; T. R. Armstrong; D. E. McCready; L. R. Pederson; W. J. Weber

1997-01-01

34

Tape casting and sintering of strontium-doped lanthanum chromite for a planar solid oxide fuel cell bipolar plate  

Microsoft Academic Search

Nonagglomerated strontium-doped lanthanum chromite powders were prepared by a modified Pechini resinintermediate process and tape cast to form bipolar plates for a planar solid oxide fuel cell. An air-sintering technique for the strontium-doped lanthanum chromite was developed, which involved placing the green tape between CrâOâ-fired plates. The sintering process was found to be diffusion controlled, with densification beginning at the

Lone-Wen Tai; Paul A. Lessing

1991-01-01

35

Structural studies of lithium boro tellurite glasses doped with praseodymium and samarium oxides  

SciTech Connect

Graphical abstract: [TeO{sub 4}] trigonal bipyramid structural unit, which is formed by two unequivalent pair of oxygen atoms: two equatorial oxygens (O{sub eq}) and two axial oxygens (O{sub ax}). Highlights: ? Pr{sup 3+} and Sm{sup 3+} doped LBT glasses have been prepared and characterized. ? LBT glasses present normal surfaces without metallic clusters. ? Raman spectra revealed the network modifying behaviour of dopant ions. -- Abstract: This paper reports the preparation and structural studies of praseodymium and samarium (0.5, 2 and 4 mol%) oxide doped lithium boro tellurite glasses. These materials were prepared by the quenching technique in a ceramic crucible at 950 °C. Structural characterization was performed by Raman spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy techniques. Results from Raman analysis are in good agreement with those reported in the literature, revealing a normal glass structure for the host material. Understanding on how the glasses internal structure changed when the doping concentration increases was also assessed.

Damas, Pedro [Departamento de Física, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)] [Departamento de Física, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Coelho, João [INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)] [INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Hungerford, Graham [HORIBA Jobin Yvon IBH Ltd., Skypark 5, 45 Finnieston Street, Glasgow G3 8JU (United Kingdom)] [HORIBA Jobin Yvon IBH Ltd., Skypark 5, 45 Finnieston Street, Glasgow G3 8JU (United Kingdom); Hussain, N. Sooraj, E-mail: nandyala.sooraj@fc.up.pt [Departamento de Física, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); INESC Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal)

2012-11-15

36

Controlled size and morphology of EDTMP-doped hydroxyapatite nanoparticles as model for 153Samarium-EDTMP doping.  

PubMed

Hydroxyapatite (HA) nanoparticles have been studied as nano-sized carriers for the delivery of therapeutic agents. One important consideration for these carriers to be used effectively is their bio-distribution in vivo, of which particle size has a significant effect. In this work, HA nanoparticles doped with Ethylene-diamine-tetramethylene-phosphonate (EDTMP) were synthesized via co-precipitation as a model for HA doped with (153)Samarium ((153)Sm) EDTMP. EDTMP has high affinity for radioactive (153)Sm isotopes that can emit both gamma and beta radiation. The effects of synthesis temperature, amount of dopant and hydrothermal treatment on the size of HA-EDTMP nanoparticles were therefore studied. The results showed that the EDTMP ligand was successfully incorporated in the nanoparticles without changing the crystal structure as shown from X-ray diffractometer (XRD) analysis. From the Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) micrographs, it was observed that shorter rod-like nanoparticles, obtained at low synthesis temperatures, became elongated needle-like nanoparticles with increasing temperature. Increasing dopant amount by five fold increases particle size slightly, while a two fold increase in dopant amount has no significant effect. Hydrothermal treatment increases particle crystallinity and results in smooth elongated rod-like structures. The size of HA nanoparticles doped with EDTMP can therefore be manipulated by controlling synthesis temperature and through hydrothermal treatment. PMID:18360794

Han, Yuling Jamie; Loo, Say Chye Joachim; Phung, Ngoc Thao; Ong, Hooi Tin; Russell, Stephen J; Peng, Kah-Whye; Boey, Freddy; Ma, Jan

2008-09-01

37

Optically erasable samarium-doped fluorophosphate glasses for high-dose measurements in microbeam radiation therapy  

SciTech Connect

Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm{sup 3+}) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405?nm to erase the recorded dose information in Sm{sup 3+}-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm{sup 3+}-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm{sup 2+} to Sm{sup 3+} reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm{sup 2+} to Sm{sup 3+} reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT.

Morrell, B.; Okada, G.; Vahedi, S.; Koughia, C., E-mail: cyril.koughia@usask.ca; Kasap, S. O. [Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9 (Canada); Edgar, A.; Varoy, C. [School of Chemical and Physical Sciences and MacDiarmid Institute, Victoria University of Wellington, Wellington 6140 (New Zealand); Belev, G.; Wysokinski, T.; Chapman, D. [Canadian Light Source, Inc., University of Saskatchewan, Saskatoon, Saskatchewan S7N 5C9 (Canada); Sammynaiken, R. [Saskatchewan Structural Sciences Centre, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9 (Canada)

2014-02-14

38

Samarium doped calcium fluoride: A red scintillator and X-ray phosphor  

NASA Astrophysics Data System (ADS)

We report the photoluminescence, X-ray luminescence and scintillation properties of CaF2:Sm2+. Large single crystals of CaF2:Sm2+ were grown by simply slow cooling of the calcium fluorite melt doped with samarium metal. The photoluminescence at room temperature shows a broad red 5d?4f emission band peaked at 725 nm which is well matched to the response of silicon photodetectors, and only a very weak Sm3+ emission is observed. On cooling, the zero phonon lines of the Sm2+ emission can be observed. The lifetime of the broad emission is short at room temperature (46 ns), but temperature dependent, and slows on cooling, reaching a constant value of 1.25 ?s below 180 K. The X-ray luminescence comprises both red Sm2+ and Sm3+ emissions and a blue self-trapped exciton band for low Sm concentrations, but just the broad red emission Sm2+ for highly doped (~1%) samples. The scintillation decay at room temperature shows two components, of 58 ns and 870 ns, in an integrated intensity ratio of 0.7:1 for a 0.1% Sm sample. The light output is around 15,000 photons/MeV when cooled by dry ice, with a scintillation decay time of 1.4 ?s at that temperature. The performance of the material as an X-ray phosphor and scintillator is discussed.

Dixie, Laura Catherine; Edgar, Andrew; Bartle, Colin Murray

2014-07-01

39

Cr(3+)-Doped Lanthanum Gallogermanate Phosphors with Long Persistent IR Emission  

SciTech Connect

Lanthanum gallogermanate co-doped with chromium (La3Ga5GeO14:Cr3+,M, where M=Li, Pb2+, Zn2+, Eu3+, Tm3+, and Dy3+) samples have been prepared using a solid-state chemical reaction method. The phosphor with Dy3+ is observed to have a persistent IR emission for more than 8 h, which is recorded using a spectrometer. The wavelength of the major IR emission is in the range from 700 to 1100 nm. The intensity of the phosphorescence and persistent time can be modified by co-doping proper trapping centers.

Jia, George D [ORNL; Lewis, Linda A [ORNL; Wang, Xiao-jun [Georgia Southern University

2010-01-01

40

Investigation of the influence of strontium carbonate on fluorescence spectra of oxy-fluoride glasses doped with samarium oxide and samarium fluoride  

NASA Astrophysics Data System (ADS)

Oxy-fluoride glasses containing strontium carbonate doped with samarium have been prepared. The glasses are sorted with respect to the quantity of strontium carbonate. The fluorescence spectra recorded for different pumping wavelengths are presented. We have investigated the influence of the excitation on the efficiency of the fluorescence, depending on the quantity of strontium carbonate in the samples for a variety of excitation wavelengths. The results of optical pumping in the range 370 - 490 nm show a typical fluorescence spectrum of Sm3+. When pumped with wavelengths above 500 nm a new peak that has not been reported appeared in the fluorescence spectrum. From the data analysis the range of appearance of the fluorescence peak was determined and the most efficient source for its excitation was found.

Pashova, Teodora; Eftimov, Tinko; Kostova, Irena; Tonchev, Dancho

2015-01-01

41

Preparation and structural characterization of rare-earth doped lead lanthanum zirconate titanate ceramics  

NASA Astrophysics Data System (ADS)

A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y 3+, Nd 3+, Yb 3+), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static 207Pb spin echo NMR spectra, using Fourier Transformation of Carr-Purcell-Meiboom-Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the 207Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y 3+ doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd 3+ dopants differs significantly from that of Yb 3+. While the Nd 3+ ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb 3+ into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase.

de Queiroz, Thiago Branquinho; Mohr, Daniel; Eckert, Hellmut; de Camargo, Andrea S. S.

2009-08-01

42

Comparison of damages in tungsten and tungsten doped with lanthanum-oxide exposed to dense deuterium plasma shots  

NASA Astrophysics Data System (ADS)

Changes in the surface and structure of tungsten and tungsten doped with 1% lanthanum-oxide samples irradiated by powerful deuterium plasma shots are investigated. Comparative analysis of the samples microroughness, the damage factor estimated from SEM images, and the hardness of cross-sections has been carried out. It can be concluded that the doping of tungsten with 1% lanthanum-oxide may decrease the development of a mesh of microcracks on the irradiated surface. However, this doping may increase the microroughness of the sample surface.

Shirokova, V.; Laas, T.; Ainsaar, A.; Priimets, J.; Ugaste, Ü.; Demina, E. V.; Pimenov, V. N.; Maslyaev, S. A.; Dubrovsky, A. V.; Gribkov, V. A.; Scholz, M.; Mikli, V.

2013-04-01

43

Cobalt doped lanthanum chromite material suitable for high temperature use  

DOEpatents

A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25.degree. C. and about 1200.degree. C., capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments.

Ruka, Roswell J. (Churchill, PA)

1986-01-01

44

Cobalt doped lanthanum chromite material suitable for high temperature use  

DOEpatents

A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25 C and about 1,200 C, capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments. 2 figs.

Ruka, R.J.

1986-12-23

45

Crystal structure and physicochemical properties of doped lanthanum manganites  

NASA Astrophysics Data System (ADS)

Substituted lanthanum-strontium manganites La0.7Sr0.3Mn0.9Me0.1O3 ± ? (Me = Ti, Cr, Fe, and Cu) are obtained by standard ceramic and glycerin-nitrate techniques. High-temperature powder X-ray diffraction is employed to study the crystal structure of La0.7Sr0.3Mn0.9Me0.1O3 ± ? oxides. It is shown that in the range 298-1023 K in air, La0.7Sr0.3Mn0.9Me0.103 ± ? manganites crystallized in an orthorhombic cell (space group R-3c). The isobaric temperature dependences of unit cell parameters are determined. Thermal expansion coefficients are calculated for La0.7Sr0.3Mn0.9Me0.103 ± ? oxides. The conductivity of La0.7Sr0.3Mn0.9Me0.103 ± ? is studied as a function of temperature in the range 500 K ? T ? 1200 K in air. It is shown that substituting 3 d metal for manganese considerably lowers the conductivity of basic La0.7Sr0.3Mn0.9O3 ± ?. The chemical stability of iron-substituted manganite La0.7Sr0.3Mn0.9Fe0.1O3 ± ? is studied with respect to the electrolyte material.

Aksenova, T. V.; Gavrilova, L. Ya.; Cherepanov, V. A.

2012-12-01

46

Laser action in Nd(3+)-doped lanthanum oxysulfide powders.  

PubMed

We have investigated the stimulated emission properties of Nd(3+) doped La(2)O(2)S powders at room temperature as a function of pumping energy density, excitation wavelength, and Nd(3+) ion concentration. The absolute stimulated emission energy has been measured. Expressions for the slope efficiencies and lasing thresholds as a function of rare earth concentration and pumping wavelengths, which qualitatively agree with experimental observations, are discussed. PMID:23188335

Iparraguirre, Iñaki; Azkargorta, Jon; Merdrignac-Conanec, Odile; Al-Saleh, Mohamad; Chlique, Christophe; Zhang, Xianghua; Balda, Rolindes; Fernández, Joaquín

2012-10-01

47

Tape casting and sintering of strontium-doped lanthanum chromite for a planar solid oxide fuel cell bipolar plate  

SciTech Connect

Nonagglomerated strontium-doped lanthanum chromite powders were prepared by a modified Pechini resinintermediate process and tape cast to form bipolar plates for a planar solid oxide fuel cell. An air-sintering technique for the strontium-doped lanthanum chromite was developed, which involved placing the green tape between Cr{sub 2}O{sub 3}-fired plates. The sintering process was found to be diffusion controlled, with densification beginning at the surface and proceeding to the interior. A bipolar plate of 2-mm thickness was fired to more than 9.3.5% theoretical density when fired at 1670{degrees}C for 7 h.

Tai, L.W.; Lessing, P.A. (New Mexico Inst. of Mining and Technology, Socorro, NM (US))

1991-01-01

48

Mechanisms of enhanced sulfur tolerance on samarium (Sm)-doped cerium oxide (CeO2) from first principles.  

PubMed

The role of samarium (Sm) 4f states and Sm-perturbed O 2p states in determining the sulfur tolerance of Sm-doped CeO2 was elucidated by using the density functional theory (DFT) + U calculation. We find that the sulfur tolerance of Sm-doped CeO2 is closely related to the modification of O 2p states by the strong interaction between Sm 4f and O 2p states. In particular, the availability of unoccupied O 2p states near the Fermi level is responsible for enhancing the sulfur tolerance of Sm-doped CeO2 compared to the pure CeO2 by increasing the activity of the surface lattice oxygen toward sulfur adsorption, by weakening the interaction between Sm-O, and by increasing the migration tendency of the subsurface oxygen ion toward the surface. PMID:24756238

Lim, Dong-Hee; Kim, Hee Su; Yoon, Sung Pil; Han, Jonghee; Yoon, Chang Won; Choi, Sun Hee; Nam, Suk Woo; Ham, Hyung Chul

2014-06-14

49

Diode-pumped passively mode-locked Yb3+-doped yttrium lanthanum oxide ceramic laser  

NASA Astrophysics Data System (ADS)

A diode-pumped picosecond laser was demonstrated with Yb3+-doped yttrium lanthanum oxide transparent laser ceramic Yb:(Y1-xLax)2O3 (x = 0.1), which was fabricated with nanopowders and sintered in H2 atmosphere. Passive mode-locking was realized for the first time to our knowledge with a semiconductor saturable absorber mirror, generating pulses of 174 ps at the central wavelength 1032.5 nm with the average output power 162 mW under a diode-laser pump power of 3.2 W.

Li, W.; Hao, Q.; Yang, Q.; Zeng, H.

2009-08-01

50

Spectral properties of Ce3+ doped yttrium lanthanum oxide transparent ceramics  

NASA Astrophysics Data System (ADS)

Ce3+-doped yttrium lanthanum oxide (Y0.9La0.1)2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce:(Y0.9La0.1)2O3 transparent ceramics are investigated. There appear two characteristic absorption peaks of Ce3+ ions at 230 nm and 400 nm, separately. It is found that Ce3+ ions can efficiently produce emission at 384 nm from (Y0.9La0.1)2O3 transparent ceramic host, while the emission is completely quenched in Re2O3 (Re = Y, Lu, La) host materials.

Yang, Qiu-Hong; Zhou, Hong-Xu; Lu, Shen-Zhou

2010-02-01

51

Bulk and surface structure characterization of nanoscopic silver doped lanthanum chromites  

NASA Astrophysics Data System (ADS)

Crystalline state of lanthanum chromites with silver as a dopant has been studied by X-ray diffraction and transmission electron microscopy reveals microscopic properties of grain boundaries. X-ray photoelectron spectroscopy has been used to analyze surface states with atomic ratio of La, Cr, O and Ag as a dopant. LaCrO3 shows mixed valence states of chromium while the silver doped samples exhibit differences in chromium concentration with the oxidation of Cr3+ to Cr6+ in presence of chromium nitrate as a precursor salt. Trivalent stable state of chromium is observed for samples synthesized by chromic acetate as a precursor salt.

Desai, P. A.; Joshi, P. N.; Patil, K. R.; Athawale, Anjali A.

2013-01-01

52

Effect of silver nanoparticles incorporated with samarium-doped magnesium tellurite glasses  

NASA Astrophysics Data System (ADS)

Silver nanoparticles (Ag NPs) are incorporated in samarium doped tellurite glass of a composition (89-x)TeO2-10MgO-1Sm2O3-xAgCl, where 0.0?x?0.6 mol%, by a melt quenching technique. It is found that all the glasses are amorphous in nature, and the existence of Ag NPs with an average size of 16.94 nm is confirmed by Transmission Electron Microscopy. Meanwhile, their physical properties such as glass density, molar volume and ionic packing density are computed utilizing the normal method. The density and ionic packing density are observed to decrease with increasing Ag NPs, but increase when the Ag NPs are beyond 0.2 mol%. On the other hand, the molar volume behaves exactly opposite to the increase in Ag NPs content. It decreases when the Ag NPs content value is more than 0.2 mol%. The optical energy band gap and Urbach energy are evaluated from the absorption spectra in the range of 200-900 nm at room temperature. It is also observed that the direct and indirect optical energy band gaps reduce with Ag NPs content, but enhance when the Ag NPs are beyond 0.2 mol%. Meanwhile, the Urbach energy is found to increase as the Ag NPs content is increased but decreases when Ag NPs is 0.2 mol%. The refractive index is deduced from indirect optical energy band gap. Meanwhile, molar refraction and electronic polarizability have been calculated from the Lorentz-Lorentz relation. Refractive index and electronic polarizability are also observed to raise with Ag NPs content, but drop off when Ag NPs content is more than 0.2 mol%. In this paper, all properties are discussed with respect to the Ag NPs concentration.

Yusoff, N. M.; Sahar, M. R.

2015-01-01

53

Effect of doping on surface reactivity and conduction mechanism in samarium-doped ceria thin films.  

PubMed

A systematic study by reversible and hysteretic electrochemical strain microscopy (ESM) in samples of cerium oxide with different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in electrical conduction mechanism and related surface activity, such as water adsorption and dissociation with subsequent proton liberation. We have measured the behavior of the reversible hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first-order reversal curve method. The measurements have been performed in much smaller temperature ranges with respect to alternative measuring techniques. Complementing our study with hard X-ray photoemission spectroscopy and irreversible scanning probe measurements, we find that water incorporation is favored until the doping with Sm is too high to allow the presence of Ce(3+). The influence of doping on the surface reactivity clearly emerges from all of our experimental results. We find that at lower Sm concentration, proton conduction is prevalent, featured by lower activation energy and higher electrical conductivity. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner. PMID:25415828

Yang, Nan; Belianinov, Alex; Strelcov, Evgheni; Tebano, Antonello; Foglietti, Vittorio; Di Castro, Daniele; Schlueter, Christoph; Lee, Tien-Lin; Baddorf, Arthur P; Balke, Nina; Jesse, Stephen; Kalinin, Sergei V; Balestrino, Giuseppe; Aruta, Carmela

2014-12-23

54

Thermopower studies of rare earth doped lanthanum barium manganites  

NASA Astrophysics Data System (ADS)

Influence of rare earth doping on electrical, magnetic and thermopower studies of La0.34Re0.33Ba0.33MnO3 compound was investigated. Ferro to paramagnetic transition and metal to insulator transition temperatures decrease with decreasing ionic radius of the dopant ion. Electrical resistivity in the entire temperature range is explained by phase separation model. The magnitude of Seebeck coefficient increases with increasing dopant ionic radius. A cross over from negative to positive sign has also been observed in thermopower data with decreasing A site ionic radius (). The low temperature thermopower data has been explained using a qualitative model containing diffusion; magnon drag and phonon drag effects while the paramagnetic insulating part has been analyzed using small polaron hopping mechanism.

Reddy, G. Lalitha; Lakshmi, Y. Kalyana; kumar, N. Pavan; Rao, S. Manjunath; Reddy, P. Venugopal

2014-08-01

55

Intrinsic Mobility Limiting Mechanisms in Lanthanum-Doped Strontium Titanate  

NASA Astrophysics Data System (ADS)

The temperature dependent Hall mobility data from La-doped SrTiO3 thin films are analyzed and modeled considering various electron scattering mechanisms. We find that a ˜6 meV transverse optical phonon deformation potential scattering mechanism is necessary to explain the dependence of transport on temperature between 10-200 K. Also, we find that the low temperature electron mobility in intrinsic (nominally undoped) SrTiO3 is limited by acoustic phonon scattering. Adding the above two scattering mechanisms to longitudinal optical phonon and ionized impurity scattering mechanisms, excellent quantitative agreement between mobility measurement and model is achieved in the whole temperature range (2-300 K) and carrier concentrations ranging over a few orders of magnitude (8×1017 -2×1020 cm-3).

Verma, Amit; Kajdos, Adam P.; Cain, Tyler A.; Stemmer, Susanne; Jena, Debdeep

2014-05-01

56

Synthesis and photocatalytic properties of lanthanum doped anatase TiO 2 coated Fe 3 O 4 composites  

Microsoft Academic Search

A composite photocatalyst (La\\/TiO2\\/Fe3O4) with a lanthanum doped TiO2 (La\\/TiO2) shell and a magnetite core was prepared by coating photoactive La\\/TiO2 onto a magnetic Fe3O4 core. The morphological, structural, and optical properties of as-prepared samples were characterized by transmission electron\\u000a microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of lanthanum content on the photocatalytic\\u000a properties was studied,

Zhongliang Shi; Xiaoyan Zhang; Shuhua Yao

2011-01-01

57

Intrinsic inhomogeneities of low-doped lanthanum manganites in the paramagnetic temperature range  

SciTech Connect

The nature of the electrical resistivity for low-doped lanthanum manganites is elucidated. The electrical resistivity is described by the Efros-Shklovskii law (ln{rho} {radical} (T{sub 0}/T){sup -1/2}, where T{sub 0} {radical} 1/R{sub ls}) in the temperature range from T* Almost-Equal-To 300 K Almost-Equal-To T{sub C} (T{sub C} is the Curie temperature for conducting manganites) to their T{sub C} and is explained by the tunneling of carriers between localized states. The magnetoresistance is explained by a change in the size of localized states R{sub ls} in a magnetic field. The patterns of change in R{sub ls} with temperature and magnetic field strength determined from magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a paramagnetic matrix. The sizes R{sub ls} and their temperature dependence have been estimated through magnetic measurements. The results confirm the existence of a Griffith phase. The intrinsic inhomogeneities produced by thermodynamic phase separation determine the electrical resistivity and magnetoresistance of lanthanum manganites.

Solin, N. I., E-mail: solin@imp.uran.ru [Russian Academy of Sciences, Ural Branch, Institute of Metal Physics (Russian Federation)

2012-01-15

58

Enhanced ionic conductivity in pyrochlore and fluorite mixed phase yttrium-doped lanthanum zirconate  

NASA Astrophysics Data System (ADS)

A series of yttrium-doped lanthanum zirconate (La1-xYx)2Zr2O7 (0 ? x ? 1) bulk samples were prepared and their ionic conductivities were studied by impedance spectroscopy. It is found that intermixing of Y and La ions increases the conductivity of the end members pyrochlore-type La2Zr2O7 and fluorite-type Y2Zr2O7. Highest conductivity which is 2-3 orders of magnitude higher than that of La2Zr2O7 and Y2Zr2O7 is achieved in a two-phase sample which consists of both pyrochlore and fluorite phases. The enhanced conductivity in the two-phase sample is attributed to the presence of the pyrochlore-fluorite phase boundary, which has higher conductivity than the pyrochlore and the fluorite phase grains. The effect of the conductive phase boundary has been confirmed by a 2-dimensional finite element modelling.

Yang, Fan; Wang, Yanfei; Zhao, Xiaofeng; Xiao, Ping

2015-01-01

59

Bismuth doped lanthanum ferrite perovskites as novel cathodes for intermediate-temperature solid oxide fuel cells.  

PubMed

Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La(0.8-x)Bi(x)Sr0.2FeO(3-?) (0 ? x ? 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (?), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (?), oxygen chemical surface exchange coefficient (K(chem)), and chemical diffusion coefficient (D(chem)) are explored as a function of bismuth content. While ? decreases with x due to the reduced Fe(4+) content, D(chem) and K(chem) increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 ? cm(2) at 700 °C with Bi doping. The perovskite with x = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance. PMID:24971668

Li, Mei; Wang, Yao; Wang, Yunlong; Chen, Fanglin; Xia, Changrong

2014-07-23

60

Dielectric investigations of polycrystalline samarium bismuth ferrite ceramic  

NASA Astrophysics Data System (ADS)

Results of broadband dielectric investigations of samarium doped bismuth ferrite ceramics are presented in wide temperature range (20-800 K). At temperatures higher than 400 K, the dielectric properties of samarium bismuth ferrite ceramics are governed by Maxwell-Wagner relaxation and electrical conductivity. The DC conductivity increases and activation energy decreases with samarium concentration. In samarium doped bismuth ferrite, the ferroelectric phase transition temperature decreases with samarium concentration and finally no ferroelectric order is observed at x = 0.2. At lower temperatures, the dielectric properties of ferroelectric samarium doped bismuth ferrite are governed by ferroelectric domains dynamics. Ceramics with x = 0.2 exhibit the relaxor-like behaviour.

Palaimiene, E.; Macutkevic, J.; Karpinsky, D. V.; Kholkin, A. L.; Banys, J.

2015-01-01

61

Engineered hydrochar composites for phosphorus removal/recovery: Lanthanum doped hydrochar prepared by hydrothermal carbonization of lanthanum pretreated rice straw.  

PubMed

Engineered hydrochar composites (EHC) were synthesized by hydrothermal carbonization (HTC) of lanthanum pretreated rice straw. The as-prepared composite with about 30% lanthanum content showed greater P removal potential than La(OH)3, indicating the synergistic effect of hydrochar and lanthanum in P removal. The adsorption results showed that EHC showed great P adsorption capacities (>50mgPg(-1)) in the pH range of 2.5-10.5, and the presence of competing anions had little negative effects on P adsorption on EHC. The equilibrium time for P adsorption on EHC was considerably reduced under acid condition (12h) compared to alkaline condition (48h). The maximum adsorption capacity was 61.57mgPg(-1) according to Langmuir isotherms. These results suggested that EHC was highly effective in P adsorption in a wide range of pH and the presence of competing anions, thus EHC could be a promising adsorbent for phosphorus removal/recovery from wastewater. PMID:24727355

Dai, Lichun; Wu, Bo; Tan, Furong; He, Mingxiong; Wang, Wenguo; Qin, Han; Tang, Xiaoyu; Zhu, Qili; Pan, Ke; Hu, Qichun

2014-06-01

62

Photocatalytic conversion of gaseous ethylbenzene on lanthanum-doped titanium dioxide nanotubes.  

PubMed

The photocatalytic properties of titanium dioxide (TiO?) make it an attractive material for environmental remediation. In the present study, lanthanum (La(3+))-doped TiO2 nanotubes with excellent photocatalytic activity were fabricated by a combination of sol-gel method and hydrothermal technique. The optimal preparation parameters were determined by the structural characterization using a range of methods and the photocatalytic degradation of gaseous ethylbenzene (EB). Compared with pure TiO? nanoparticles, 1.2%-La(3+)-doped - titania nanotubes (1.2%-La(3+)-TNTs) exhibited higher activity under 254 nm UV for conversion of EB. The initial EB concentrations and relative humidity (RH) obviously influenced the photocatalytic activity of 1.2%-La(3+)-TNTs. Kinetic analysis showed that surface adsorption and surface reaction controlled the rate-determining step for RH of 40-50% and >80%, respectively. Gas chromatography and mass spectrometry were used to analyze the intermediates generated in the conversion of EB, allowing a tentative decomposition pathway to be proposed. The prepared photocatalyst exhibited enhanced EB conversion compared with undoped TiO?, and showed a promise for the decomposition of recalcitrant compounds before subsequent biopurification. PMID:23643959

Cheng, Zhuo-Wei; Feng, Li; Chen, Jian-Meng; Yu, Jian-Ming; Jiang, Yi-Feng

2013-06-15

63

Crystal structures and magnetic properties of strontium and copper doped lanthanum ferrites  

SciTech Connect

The crystal and magnetic structures of La{sub 0.8}Sr{sub 0.2}Fe{sub 1-x}Cu{sub x}O{sub 3-w} compounds, which exhibit coercive fields larger than any others reported for iron-based perovskites, have been analyzed at room temperature with the neutron powder diffraction technique and the Rietveld method of profile fitting. For x in the range 0.05-0.10 the material is monophasic with orthorhombic symmetry (space group Pnma), and crystallizes in the perovskite-like cell of LaFeO{sub 3}, Fe/Cu cations occupy octahedral sites, La/Sr cations are twelve-fold coordinated. For x=0.20 the material is biphasic, with a main orthorhombic phase (space group Pnma) and a secondary rhombohedral phase with space group R-3c (hexagonal setting). The structural transition from the orthorhombic to the rhombohedral phase reduces the structural distortion of the (Fe/Cu)O{sub 6} octahedron. The average bond distance (Fe/Cu)-O and the pseudo-cubic unit cell volume decrease with increasing Cu content in accordance with the presence of higher valence states of the transition metals. The magnetic structure was modeled for the monophasic samples (x=0.05 and 0.10) assuming an antiferromagnetic interaction between Fe/Cu neighboring cations (G-type): the magnetic moments order antiferromagnetically along the b-axis, with the spin direction along a-axis. The magnetic moments of the Fe/Cu atoms are {mu}{sub x}=2.66(3){mu}{sub B} and 2.43(3){mu}{sub B} for the compositions x=0.05 and 0.10, respectively. By measuring the first magnetization curve and the hysteresis loops, coexisting antiferromagnetic and weak ferromagnetic interactions were observed for all samples. - Graphical abstract: Hysteresis loops measured at room temperature of the sample with x=0.05. Highlights: Black-Right-Pointing-Pointer Iron based perovskites with the largest coercive fields. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites as magnetic materials. Black-Right-Pointing-Pointer Doped lanthanum ferrites show antiferromagnetic and weak ferromagnetic interactions. Black-Right-Pointing-Pointer Sr and Cu lanthanum ferrites show distorted perovkite structure.

Sora, Isabella Natali, E-mail: isabella.natali-sora@unibg.it [INSTM R.U. and Department of Industrial Engineering, University of Bergamo, Dalmine, BG, I-24044 (Italy); Caronna, Tullio; Fontana, Francesca [INSTM R.U. and Department of Industrial Engineering, University of Bergamo, Dalmine, BG, I-24044 (Italy); Julian Fernandez, Cesar de [INSTM R.U. Firenze and Department of Chemistry, University of Florence, I-50019 Sesto Fiorentino (Italy); CNR-Istituto di Scienze e Tecnologie Molecolari (ISTM), 20133 Milano (Italy); Caneschi, Andrea [INSTM R.U. Firenze and Department of Chemistry, University of Florence, I-50019 Sesto Fiorentino (Italy); Green, Mark [Center for Neutron Research, NIST, Gaithersburg, MD (United States); Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742-2115 (United States)

2012-07-15

64

Stability of strontium-doped lanthanum manganite cathode in humidified air  

NASA Astrophysics Data System (ADS)

The stability of strontium-doped lanthanum manganite (LSM) cathode has been studied using symmetric cells (humidified air, LSM/yttria-stabilized zirconia (YSZ)/LSM, humidified air) under a range of humidification levels (0-50%), temperatures (750-850 °C), and cathodic biases (0-0.5 V). Electrochemical impedance spectroscopy revealed an increase in non-ohmic resistance with increasing H2O/O2 ratio, temperature, and cathodic bias. Post-test surface and interface studies showed the segregation of SrO particles on the LSM surface and formation of Mn2O3 and La2Zr2O7 compounds at the cathodic LSM/YSZ interface. The increase in non-ohmic resistance is attributed to surface segregation of SrO and interfacial compound formation, whereas formation and growth of SrO at the LSM surface is attributed to water adsorption. La2Zr2O7 formation is attributed to interfacial reactions.

Hu, Boxun; Keane, Michael; Mahapatra, Manoj K.; Singh, Prabhakar

2014-02-01

65

Blocking effect of crystal–glass interface in lanthanum doped barium strontium titanate glass–ceramics  

SciTech Connect

Graphical abstract: The blocking effect of the crystal–glass interface on the carrier transport behavior in the lanthanum doped barium strontium titanate glass–ceramics: preparation and characterization. - Highlights: • La{sub 2}O{sub 3} addition promotes the crystallization of the major crystalline phase. • The Z? and M? peaks exist a significant mismatch for 0.5 mol% La{sub 2}O{sub 3} addition. • The Z? and M? peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. • Crystallite impedance decreases while crystal–glass interface impedance increases. • La{sub 2}O{sub 3} addition increases blocking factor of the crystal–glass interface. - Abstract: The microstructures and dielectric properties in La{sub 2}O{sub 3}-doped barium strontium titanate glass–ceramics have been investigated by scanning electron microscopy (SEM) and impedance spectroscopy. SEM analysis indicated that La{sub 2}O{sub 3} additive decreases the average crystallite size. Impedance spectroscopy revealed that the positions of Z? and M? peaks are close for undoped samples. When La{sub 2}O{sub 3} concentration is 0.5 mol%, the Z? and M? peaks show a significant mismatch. Furthermore, these peaks separate obviously for 1.0 mol% La{sub 2}O{sub 3} addition. With increasing La{sub 2}O{sub 3} concentration, the contribution of the crystallite impedance becomes smaller, while the contribution of the crystal–glass interface impedance becomes larger. More interestingly, it was found that La{sub 2}O{sub 3} additive increases blocking factor of the crystal–glass interface in the temperature range of 250–450 °C. This may be attributed to a decrease of activation energy of the crystallite and an increase of the crystal–glass interface area.

Wang, Xiangrong [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Zhang, Yong, E-mail: yzhang@tsinghua.edu.cn [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Baturin, Ivan [Ferroelectric Laboratory, Institute of Natural Science, Ural Federal University, Ekaterinburg 620000 (Russian Federation); Liang, Tongxiang [Beijing Fine Ceramics Laboratory, State Key Laboratory of New Ceramics and Fine Processing, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

2013-10-15

66

Magnetic phase transition of nanocrystalline Fe-doped samarium oxide (Sm1.90Fe0.10O3)  

NASA Astrophysics Data System (ADS)

Nanocrystalline Fe3+ doped samarium oxide (Sm1.90Fe0.10O3) has been prepared by the co-precipitation method. The as prepared sample has been annealed at 700 °C for 6 h in an argon atmosphere. The pure crystallographic phase as well as the substitution of Fe3+ ions in the lattice of Sm2O3 is confirmed by Rietveld analysis of the X-ray diffraction patterns. The variation of magnetic susceptibility (?) with temperature (T) is recorded by a Faraday Magnetometer in the temperature range of 300-14 K. The variation of ? vs. T down to ~50 K was successfully fitted by the Curie-Weiss law and below this temperature, susceptibility increases very rapidly, which suggests the presence of ordering at low temperature. To explore this, magnetic measurements are also carried out at different temperatures down to 2 K by using a SQUID Magnetometer. No hysteretic behavior is observed down to 50 K, but a feeble ferromagnetic behavior is observed in the magnetization vs. field curve recorded at ~30 K. A clear hysteresis loop is observed at 2 K with a comparatively high value of maximum magnetization (~3.32 emu/gm). The observed magnetic phase transition is analyzed by using the dipole-dipole interaction among the magnetic nanoparticles at low temperature.

Mandal, J.; Sarkar, B. J.; Deb, A. K.; Chakrabarti, P. K.

2014-12-01

67

Effects of calcination on microscopic and mesoscopic structures in Ca- and Sr-doped nano-crystalline lanthanum chromites  

SciTech Connect

Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-a-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 {sup o}C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages. -- Graphical Abstract: Dopant chromates evolve as intermediate phases during calcination of Ca- and Sr-doped nano-crystalline lanthanum chromites at intermediate temperatures, around 900 {sup o}C, evident from infrared spectroscopy. Such an event results in a modification of the microscopic and mesoscopic structures. Display Omitted Research highlights: {yields} Meso/microscopic structures of La{sub 0.7}Ca{sub 0.3}CrO{sub 3} and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} modify during calcination. {yields} Transient phases CaCrO{sub 4} and SrCrO{sub 4} appear at intermediate temperatures. {yields} Bond length, unit cell volume, etc. modify as intermediate phases evolve and extinct. {yields} Compaction of the agglomerates takes place due to liquid state assisted sintering.

Bhatt, Himal, E-mail: himalphy@gmail.co [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Bahadur, J. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Deo, M.N. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Ramanathan, S. [Materials Processing Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Pandey, K.K. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sen, D.; Mazumder, S. [Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2011-01-15

68

Diode-pumped passively mode-locked Yb3+-doped yttrium lanthanum oxide ceramic sub-picosecond laser  

NASA Astrophysics Data System (ADS)

A diode-pumped sub-picosecond laser is realized with Yb3+-doped yttrium lanthanum oxide transparent ceramic Yb:(Y0.9La0.1)2O3 as the gain medium for the first time. By using Gires-Tournois interferometer mirrors and chirped mirror for dispersion compensation and semiconductor saturable absorber mirror for passive mode-locking, laser pulse as short as 730 fs was obtained at the central wavelength of 1033 nm and repetition rate of 65.5 MHz. Under the maximum pump power of 6 W at 976 nm, the output power is 92 mW.

Wang, Z. L.; Wei, Z. Y.; Wang, Q.; Li, D. H.; Zhang, Z. G.; Zhang, Y. D.; Yang, Q. H.; Zhang, H. J.; Lu, S. Z.

2011-11-01

69

Synthesis, thermal and photoluminescent properties of ZnSe- based oxyfluoride glasses doped with samarium  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doped glasses and glass ceramic materials have recently received considerable attention because of their potential or realized applications as X-ray intensifying screens, phosphors, detectors, waveguides, lasers etc. [1]. In this work, we present a new RE doped ZnO-ZnSe-SrF2-P2O5-B2O3-Sm2O3-SmF3 (ZSPB) glass system synthesized by melt quenching technique. The resulting glasses were visually fully transparent and stable with glass the transition temperatures around 530°C. The thermal properties of this glass system were characterized by Modulated Differential Scanning Calorimetry (MDSC) measurements before and after annealing at 650°C. We have characterized these glasses by Raman spectroscopy and photoluminescence (PL) measurements over the UV-VIS range using light emitting diodes (LED) and laser diodes (LD) excitation sources. We have also irradiated thermally treated and non-treated glass samples by X-rays and have studied the resulting PL. We discuss the results in terms of previously reported models for Sm-doped Zn-borophosphate oxide, oxyfluoride and oxyselenide glasses.

Kostova, I.; Okada, G.; Pashova, T.; Tonchev, D.; Kasap, S.

2014-12-01

70

Determination of the variation of the fluorescence line positions of ruby, strontium tetraborate, alexandrite, and samarium-doped yttrium aluminum garnet with pressure and temperature  

NASA Astrophysics Data System (ADS)

The pressure and temperature dependent fluorescence line-shift of strontium tetraborate has been measured concurrently with x-ray diffraction from the pressure standards sodium chloride or gold. Temperature was found to have a small effect on the fluorescence line-shift under pressure. We found a maximum pressure uncertainty of ±1.8 GPa at 25 GPa (7.2%) and 857 K when making no temperature correction. The fluorescence line-shifts for ruby, Alexandrite, and samarium-doped yttrium aluminum garnet were also determined, using our strontium tetraborate calibration to determine pressure and a thermocouple to measure temperature. Fluorescence measurements were extended up to 800 K for ruby and Alexandrite. Temperature was found to have a small effect on the fluorescence line-shift of samarium-doped yittrium aluminum garnet. We found a maximum uncertainty of ±2.7 GPa at 25 GPa (11.1%) and 857 K when no temperature correction was applied. We determined equations relating to the fluorescence line position from these data, which include a cross derivative term to account for the combined effect of pressure and temperature. We present a method to independently determine pressure and/or temperature from combined fluorescence line-shift measurements of a pair of optical sensors.

Raju, Selva Vennila; Zaug, Joseph M.; Chen, Bin; Yan, Jinyuan; Knight, Jason W.; Jeanloz, Raymond; Clark, Simon M.

2011-07-01

71

Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses  

SciTech Connect

The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm{sup 3+}{yields} Sm{sup 2+} valence conversion in Sm{sup 3+} doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to {approx}5 Gy and saturates at doses exceeding {approx}80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high ''peak-to-valley'' contrast have been observed by means of confocal photoluminescence microscopy.

Okada, Go; Morrell, Brian; Koughia, Cyril; Kasap, Safa [Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Edgar, Andy; Varoy, Chris [School of Chemical and Physical Sciences and MacDiarmid Institute, Victoria University of Wellington, Kelburn Parade (New Zealand); Belev, George; Wysokinski, Tomasz [Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK S7N 0X4 (Canada); Chapman, Dean [Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK S7N 5E5 (Canada)

2011-09-19

72

Spatially resolved measurement of high doses in microbeam radiation therapy using samarium doped fluorophosphate glasses  

NASA Astrophysics Data System (ADS)

The measurement of spatially resolved high doses in microbeam radiation therapy has always been a challenging task, where a combination of high dose response and high spatial resolution (microns) is required for synchrotron radiation peaked around 50 keV. The x-ray induced Sm3+ ? Sm2+ valence conversion in Sm3+ doped fluorophosphates glasses has been tested for use in x-ray dosimetry for microbeam radiation therapy. The conversion efficiency depends almost linearly on the dose of irradiation up to ˜5 Gy and saturates at doses exceeding ˜80 Gy. The conversion shows strong correlation with x-ray induced absorbance of the glass which is related to the formation of phosphorus-oxygen hole centers. When irradiated through a microslit collimator, a good spatial resolution and high "peak-to-valley" contrast have been observed by means of confocal photoluminescence microscopy.

Okada, Go; Morrell, Brian; Koughia, Cyril; Edgar, Andy; Varoy, Chris; Belev, George; Wysokinski, Tomasz; Chapman, Dean; Kasap, Safa

2011-09-01

73

Electronic structure and photocatalytic water splitting of lanthanum-doped Bi{sub 2}AlNbO{sub 7}  

SciTech Connect

Bi{sub 2-x}La{sub x}AlNbO{sub 7} (0 {<=} x {<=} 0.5) photocatalysts were synthesized by the solid-state reaction method and characterized by powder X-ray diffraction (XRD), infrared (IR) spectra and ultraviolet-visible (UV-vis) spectrophotometer. The band gaps of the photocatalysts were estimated from absorption edge of diffuse reflectance spectra, which were increased by the doping of lanthanum. It was found from the electronic band structure study that orbitals of La 5d, Bi 6p and Nb 4d formed a conduction band at a more positive level than Bi 6p and Nb 4d orbitals, which results in increasing the band gap. Photocatalytic activity for water splitting of Bi{sub 1.8}La{sub 0.2}AlNbO{sub 7} was about 2 times higher than that of nondoped Bi{sub 2}AlNbO{sub 7}. The increased photocatalytic activity of La-doped Bi{sub 2}AlNbO{sub 7} was discussed in relation to the band structure and the strong absorption of OH groups at the surface of the catalyst.

Li Yingxuan [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Chen Gang [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: gchen@hit.edu.cn; Zhang Hongjie; Li Zhonghua [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

2009-04-02

74

Dielectric properties and substitution mechanism of samarium-doped Ba{sub 0.68}Sr{sub 0.32}TiO{sub 3} ceramics  

SciTech Connect

Ba{sub 0.68}Sr{sub 0.32}TiO{sub 3} ceramics of perovskite structure are prepared by solid state reaction method with addition of x mol% Sm{sub 2}O{sub 3}, and their dielectric properties are investigated. It is found that, integrating with the lattice parameters and tolerance factor t, there is an alternation of substitution preference of Sm{sup 3+} for the host cations in perovskite lattice. Owing to the replacement of Sm{sup 3+} ions for Ba{sup 2+} ions in the A site, T{sub c} rises with the increase of Sm{sub 2}O{sub 3} doping when the doping content is below 0.1 mol%; meanwhile, when the content is more than 0.1 mol%, Sm{sup 3+} ions tend to occupy the B-site, causing a drop of T{sub c}. Owing to the modifications of Sm{sup 3+} doping, dielectric constant, dissipation factor and temperature stability of dissipation factor are influenced remarkably, making it a superior candidate for environment-friendly applications. Moreover, the creation of oxygen vacancies controls the dielectric constant when the addition is above 0.1 mol%, so the dielectric constant decreases with increasing of samarium.

Li Yuanliang [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)], E-mail: lylll2007@yahoo.cn; Qu Yuanfang [Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China)

2009-01-08

75

Photoluminescence and visible diffuse-reflection spectroscopic evidence of samarium reduction in air-fired samples of mixed samarium: strontium tetraborate precipitates.  

PubMed

Photoluminescence and visible diffuse-reflection spectroscopies have provided evidence of the reduction of samarium to the divalent state in samarium-doped strontium borate and pure samarium borate samples. The samples were prepared by the air firing of homogeneous precipitates of divalent strontium and trivalent samarium ions from aqueous solutions with saturated sodium tetraborate. The use of this method in the preparation of divalent lanthanide ions has not been reported previously. Reduced samarium was observed in fired tetraborate precipitates prepared with solutions containing 1, 5, 10, 25, 50, 75, and 90 mole percent samarium versus strontium. Divalent samarium also was identified in fired precipitates of trivalent samarium solutions precipitated with tetraborate. Sm(2+) was identified as the primary emitting species in each of the eight compositions. However, diffuse-reflection spectroscopy indicated the presence of trivalent samarium in the studied samples, ranging from minimal for samples prepared with low samarium concentrations to nearly exclusive when pure samarium was studied. Quenching of the characteristic emission associated with the trivalent species is believed to result in the absence of the emission features arising from residual samarium(III) in the products. Although the absence of trivalent samarium emission enhanced the ability of emission spectroscopy to identify small amounts of divalent samarium, indicating that reduction had occurred, it limited the ability of this method to determine the extent of the reduction. Diffuse-reflection spectroscopy's ability to look at both species provided a much better analysis of the extent of samarium reduction. PMID:23452491

Brown, Telvin M; Jeffreys, Mareo C; Pehaire, Mario; Stump, Nathan A

2013-03-01

76

Effects of magnetization on hole localization and MnO{sub 6} octahedra disorder in hole-doped lanthanum manganese perovskites  

SciTech Connect

The authors review the distortions of the MnO{sub 6} octahedra reduced by magnetization in hole-doped lanthanum manganese perovskites. The systems they consider include the colossal magnetoresistance (CMR) samples La{sub 1{minus}x}Ca{sub x}MnO{sub 3} (x = 0.21, 0.25, 0.30), La{sub 0.76}Ba{sub 0.33}MnO{sub 3}, and a poorer quality La{sub 0.76}Pb{sub 0.33}MnO{sub 3} sample. They also report preliminary work on three samples of oxygen-doped LaMnO{sub 3+{delta}} and a lanthanum-deficient La{sub 0.9}MnO{sub 3} sample. They find the same exponential relationship between the removal of the distortion and the sample magnetization in the Ba- and Pb-doped CMR samples as was found previously for the Ca doped samples. The MnO{sub 6} distortion in the oxygen-doped materials is found to slightly reduce below the magnetic transition, although much less so than in the CMR samples. Above T{sub C}, the antiferromagnetic LaMnO{sub 3.006} sample shows a softer temperature dependence of the Mn-O bond length distribution broadening. Surprisingly, even this sample shows deviations from thermal (Debye) behavior near T{sub N}, possibly due to FM coupling within MnO planes.

Booth, C.H.; Brosha, E.L.; Kwei, G.H. [Los Alamos National Lab., NM (United States); Bridges, F. [Univ. of California, Santa Cruz, CA (United States). Physics Dept.; Neumeier, J.J. [Florida Atlanta Univ., Boca Raton, FL (United States). Physics Dept.

1998-12-31

77

Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC  

SciTech Connect

Graphical abstract: The figure shows the dependence of conductivity on the Co content. It can be seen that La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest ionic conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, as doping Co weakens the binding energy and aids the migration of the interstitial oxide ions, the ionic conductivity improves. On the other hand, excess dopant of Co (0.8 < x {<=} 1.5) can decrease the number of interstitial oxide ions and reduce the ionic conductivity. Highlights: Black-Right-Pointing-Pointer The unit volumes of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} increase with increasing cobalt content. Black-Right-Pointing-Pointer Doping Co can increase the thermal expansion because of the larger radius of Co{sup 3+} ion. Black-Right-Pointing-Pointer Conductivities of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} first increase and then decrease with cobalt content. Black-Right-Pointing-Pointer Above 550 Degree-Sign C, La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} shows low activation energies of around 0.7 eV. -- Abstract: The thermal expansion and conductivities have been investigated for Co{sup 3+} doped lanthanum silicates. The apatite-type lanthanum silicates with formula La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} (x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.5) were synthesized by sol-gel process. The thermal expansion coefficient (TEC) of La{sub 10}Si{sub 6-x}Co{sub x}O{sub 27-x/2} was improved with increasing cobalt content because of the lower valence and larger radius of Co{sup 3+} ion compared to Si{sup 4+}. Analysis of AC impedance spectroscopy showed that conductivity increased first and then decreased with increasing cobalt content. There is an optimum doping amount of cobalt and La{sub 10}Si{sub 5.2}Co{sub 0.8}O{sub 26.6} exhibits the highest conductivity of 3.33 Multiplication-Sign 10{sup -2} S/cm at 800 Degree-Sign C. When x {<=} 0.8, the local distortion caused by doping with Co{sup 3+} can significantly affect the oxygen channels and assist the migration of the interstitial oxide ions, resulting in the improvement of ionic conductivity. However, excess Co{sup 3+} dopant (0.8 < x {<=} 1.5) reduced the number of interstitial oxide ions and decreased the conductivity.

Shi, Qingle; Lu, Lihua; Jin, Hongjian [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China); Zhang, Hua, E-mail: huazhang@njut.edu.cn [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China); Zeng, Yanwei [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)] [College of Materials Science and Engineering, Nanjing University of Technology, No.5 Xinmofan Road, Nanjing, Jiangsu (China)

2012-03-15

78

Fabrication of Sr- and Co-doped lanthanum chromite interconnectors for SOFC  

SciTech Connect

Graphical abstract: FESEM micrographs of the fresh fracture surfaces for the La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} sintered specimens cast from optimised suspensions with 13.5, 15 and 17.5 vol.% solids loading. Aqueous suspensions were prepared using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h. Highlights: {yields} Optimum casting slips were achieved with 3 wt.% of ammonium polyacrylate and 1 wt.% of tetramethylammonium hydroxide. -- Abstract: Many studies have been performed dealing with the processing conditions of electrodes and electrolytes in solid oxide fuel cells (SOFCs). However, the processing of the interconnector material has received less attention. Lanthanum chromite (LaCrO{sub 3}) is probably the most studied material as SOFCs interconnector. This paper deals with the rheology and casting behaviour of lanthanum chromite based materials to produce interconnectors for SOFCs. A powder with the composition La{sub 0.80}Sr{sub 0.20}Cr{sub 0.92}Co{sub 0.08}O{sub 3} was obtained by combustion synthesis. Aqueous suspensions were prepared to solids loading ranging from 8 to 17.5 vol.%, using ammonium polyacrylate (PAA) as dispersant and tetramethylammonium hydroxide (TMAH) to assure a basic pH and providing stabilization. The influence of the additives concentrations and suspension ball milling time were studied. Suspensions prepared with 24 h ball milling, with 3 wt.% and 1 wt.% of PAA and TMAH, respectively, yielded the best conditions for successful slip casting. Sintering of the green discs was performed in air at 1600 {sup o}C for 4 h leading to relatively dense materials.

Setz, L.F.G. [Departamento de Engenharia de Materiais, Universidade Federal de Sao Carlos - DEMa/UFSCar (Brazil) [Departamento de Engenharia de Materiais, Universidade Federal de Sao Carlos - DEMa/UFSCar (Brazil); Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Santacruz, I. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Universidad de Malaga, 29071 Malaga (Spain)] [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Universidad de Malaga, 29071 Malaga (Spain); Colomer, M.T., E-mail: tcolomer@icv.csic.es [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain); Mello-Castanho, S.R.H. [Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil)] [Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN (Brazil); Moreno, R. [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain)] [Instituto de Ceramica y Vidrio, ICV (CSIC), 28049 Madrid (Spain)

2011-07-15

79

Fission gas transport and its interaction with irradiation induced defects in lanthanum doped ceria  

NASA Astrophysics Data System (ADS)

Combined experimental and modeling efforts have been extremely productive in understanding irradiation-induced displacement damage in metal and metal alloy systems. In order to help understand the fundamental mechanisms of irradiation-induced defect formation and evolution in nuclear fuel, similar combined modeling and experimental efforts have been carried out. Ceria (CeO2) was selected as a surrogate material for Uranium Dioxide (UO2) due to its many similar properties. Lanthanum (La) was chosen as a dopant in CeO 2 to investigate the effect of impurities in a controlled manner. The presence of La in the CeO2 lattice introduces a predictable initial concentration of oxygen vacancies, making it possible to characterize hypo-stoichiometric effects in CeO2. The influence of two La concentrations, 5% and 25%, were examined. Radiation damage was induced using low energy ion implantations and high energy ion irradiation experiments, where the ion beam energy was selected for high displacement damage levels and/or high levels of implanted Xe or Kr. A combination of in situ TEM (Transmission Electron Microscopy) and ex situ TEM experiments were used to study the evolution of defect clusters and the influence of two common fission products, Xe and Kr. The irradiations were performed on thin film, single crystal materials so that the material composition and crystallinity could be directly controlled. The irradiation damage caused the formation of complex microstructures with dislocation loops, voids or bubbles, and dislocation networks at higher doses. The Burgers vectors of the dislocation loops were determined and the loops were found to be mainly [111] type Burgers vector pure edge loops. They have been tentatively identified as interstitial type. La, as an impurity, has revealed a strong defect trapping effect. Various sets of quantitative experimental results were obtained to characterize the dose and temperature effects of irradiation. These results also help to benchmark simulation codes being developed with a kinetic Monte Carlo model. These experimental results include size and size distributions of dislocation loops, voids and gas bubble structures created by irradiation. More importantly, this systematic experimental work has provided key insights into the understanding of the mechanisms of defect evolution in the materials investigated. A model including both defect production and annihilation mechanisms has been proposed to explain the observed defect kinetics in the lower dose regime. A coalescence driven model has been proposed for void/bubble growth in the higher dose regime. Experimental results also revealed that lanthanum trapping has significant influence on the void/bubble growth in the CeO2 lattice. Lattice and kinetic Monte Carlo calculations have provided key insights to the interpretations of experimental results.

Yun, Di

80

Photocatalytic performance of novel samarium-doped spherical-like ZnO hierarchical nanostructures under visible light irradiation for 2,4-dichlorophenol degradation.  

PubMed

A novel samarium-doped spherical-like ZnO hierarchical nanostructure (Sm/ZnO) was synthesized via a facile and surfactant-free chemical solution route. The as-synthesized products were characterized by X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, field emission scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results revealed that Sm ion was successfully doped into ZnO. It was also observed that the Sm doping increased the visible light absorption ability of Sm/ZnO and a red shift for Sm/ZnO appeared when compared to pure ZnO. The photocatalytic studies revealed that the Sm/ZnO exhibited excellent photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) compared with the pure ZnO and commercial TiO2 under visible light irradiation. The photocatalytic enhancement of Sm/ZnO products was attributed to their high charge separation efficiency and ·OH generation ability as evidenced by the photoluminescence spectra. The photocatalytic investigation also showed that various parameters exerted their individual influence on the degradation rate of 2,4-DCP. By using a certain of radical scavengers, ·OH was determined to play a pivotal role for the 2,4-DCP degradation. Moreover, the Sm/ZnO could be easily separated and reused, indicating great potential for practical applications in environmental cleanup. PMID:23618322

Sin, Jin-Chung; Lam, Sze-Mun; Lee, Keat-Teong; Mohamed, Abdul Rahman

2013-07-01

81

Low-temperature thermoluminescence spectra of rare-earth-doped lanthanum fluoride  

SciTech Connect

Lanthanum fluoride consistently shows two strong thermoluminescence glow peaks at low temperature in pure material near 90 and 128 K. A model is proposed in which these thermoluminescence peaks arise from the annealing of halogen defect sites, similar to the H and V{sub k} centers of the alkali halides. Relaxation and decay of these defects in the pure LaF{sub 3} lattice results in broad-band intrinsic luminescence. Addition of rare-earth-impurity ions has two effects. First, the broad-band emission is replaced by narrow-band line emission defined by the trivalent rare-earth dopants. Second, it preferentially determines the formation of the halogen defect sites at impurity lattice sites and such sites appear to increase in thermal stability since the glow peak temperature increases from 128 K in the intrinsic material up to 141 K through the sequence of rare-earth dopants from La to Er. The temperature movement directly correlates with the changes in ionic size of the rare-earth ions, when allowance is made for differences in effective coordination number of the impurity ions. The data suggest two alternative lattice sites can be occupied. The model emphasizes that the intense thermoluminescence signals arise from internal charge rearrangements and annealing of defect complexes, rather than through the more conventional model of separated charge traps and recombination centers. At higher temperatures there is a complex array of glow peaks which depend not only on the dopant concentration but also are specific to each rare earth. Such effects imply defect models giving thermoluminescence within localized complexes and possible reasons are mentioned. {copyright} {ital 1998} {ital The American Physical Society}

Yang, B.; Townsend, P.D.; Rowlands, A.P. [School of Engineering, University of Sussex, Brighton, BN1 9QH (United Kingdom)] [School of Engineering, University of Sussex, Brighton, BN1 9QH (United Kingdom)

1998-01-01

82

Spin Freezing and Recovery of Sublattice Magnetization in Lightly Doped Lanthanum Cuprate  

SciTech Connect

{sup 139}La NQR studies in lightly doped La{sub 2}Cu{sub 1-x}Li{sub x}O{sub 4} and La{sub 1.8-x}Eu{sub 0.2}Sr{sub x}CuO{sub 4} are reviewed. A strong enhancement of the {sup 139}La relaxation rate with a peak accompanied by a sudden increase of the local field at low T has been observed similarly to La{sub 2-x}Sr{sub x}CuO{sub 4}. The anomalous magnetic properties are discussed in the light of the microscopic segregation of doped holes into hole-rich domain walls separating undoped AF domains.

Suh, B.J.; Hammel, P.C.; Sarrao, J.L.; Thompson, J.D.; Fisk, Z.; Hucker, M.; Buchner, B.

1998-10-24

83

Microwave-assisted synthesis of Eu3+ doped lanthanum orthoborates, their characterizations and luminescent properties  

NASA Astrophysics Data System (ADS)

LaBO3 with various particle sizes have been successfully prepared by microwave-assisted combustion and sol-gel synthesis methods. Urea, citric acid and glycine have been used as fuels during the synthesis process. Characterizations were done by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Photoluminescence Excitation and Emission Spectroscopies, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The SEM micrographs show dissimilar morphologies of powders with different particle sizes. Luminescent properties of 2.5%, 5.0%, and 7.5% Eu doped LaBO3 synthesized with three different fuels were compared. The results showed that a 5% level is the critical doping amount for all, and the one synthesized with urea gives rise to the stronger emissions compared to others.

Badan, Cansin; Esenturk, Okan; Y?lmaz, Ay?en

2012-11-01

84

Nuclear magnetic resonance study of superconductivity in strontium-doped lanthanum copper oxides  

SciTech Connect

The goal of this research is to examine a series of copper-oxide based superconductors, La[sub 2[minus]x]Sr[sub x]CuO[sub 4] for 0.10 [<=] x [<=] 0.20, using nuclear magnetic resonance and nuclear quadrupole resonance spectroscopies. Structural and chemical properties of the materials were confirmed by TGA, and powder x-ray diffraction. For each composition, two distinct sites correlates well with the amount of strontium added. The temperature dependence of the [sup 63z]Cu Knight shift of the two sites in La[sub 1.84]Sr[sub 0.16]CuO[sub 4] are identical, indicating that both are in the superconducting phase. Comparison was made between the [sup 63]Cu Knight shifts of La[sub 1.90]Sr[sub 0.10]CuO[sub 4], La[sub 1.84]Sr[sub 0.16]CuO[sub 4] and La[sub 1.80]Sr[sub 0.20]CuO[sub 4] in the normal and superconducting states. These results, combined with magnetic susceptibility measurements, allow the separation of the carrier spin and orbital contributions to the susceptibility. At temperatures just above the superconducting transition, the conduction electron spin susceptibility increases dramatically with strontium doping. The Knight shift of all three compositions converge to the same value of K(0) = 0.17 [+-] 0.04 below T[sub c]. The temperature dependence of the Knight shift at low temperature suggest that the spine susceptibility is zero and the superconducting state is a spin singlet. Differences in the temperature dependence of the spin susceptibility clearly show that under doped, optimally doped and over doped samples are intrinsic superconductors. This work has revealed that the microscopic environment around copper is much more complex than was previously believed.

Kennard, M.A.

1993-01-01

85

Neutron Scattering Study of Magnetism in Pure and Lightly Doped LANTHANUM(2) Copper OXYGEN(4)  

Microsoft Academic Search

We have measured the static and dynamic spin correlations in several undoped and lightly doped La _2CuO_4 single crystals, as well as in two single crystals of YBa_2Cu _3O_{6+x}. We determined the parameters in the spin Hamiltonian of a YBa_2CuO_3O_{6.3} sample and used these their analogues in other lammellar copper oxides to analyze the sublattice magnetization and the transition to

Bernhard Keimer

1991-01-01

86

Nuclear Magnetic Resonance Study of Superconductivity in Strontium-Doped Lanthanum Copper Oxides  

NASA Astrophysics Data System (ADS)

The goal of this research is to examine a series of copper-oxide based superconductors, La_ {rm 2-x}Sr_{ rm x}CuO_4 for 0.10 <= x <= 0.20, using nuclear magnetic resonance and nuclear quadrupolar resonance spectroscopies. Structural and chemical properties of the materials were confirmed by TGA, and powder x-ray diffraction. For each composition, two distinct sites of copper were observed. The relative occupation of the two sites correlates well with the amount of strontium added. The temperature dependence of the ^ {63}Cu Knight shift of the two sites in La_{1.84}Sr_ {0.16}CUO_4 are identical, indicating that both are in the superconducting phase. Comparison was made between the ^ {63}Cu Knight shifts of La_ {1.90}Sr_{0.10} CUO_4, La_ {1.84}Sr_{0.16} CUO_4 and La_ {1.80}Sr_{0.20} CUO_4 in the normal and superconducting states. These results, combined with magnetic susceptibility measurements, allow the separation of the carrier spin and orbital contributions to the susceptibility. At temperatures just above the superconducting transition, the conduction electron spin susceptibility increases dramatically with strontium doping. The Knight shift of all three compositions converge to the same value of K(0) = 0.17 +/- 0.04 below T_{rm c}. The temperature dependence of the Knight shift at low temperature suggest that the spin susceptibility is zero and the superconducting state is a spin singlet. Differences in the temperature dependence of the spin susceptibility clearly show that under doped, optimally doped and over doped samples are intrinsic superconductors. This work has revealed that the microscopic environment around copper is much more complex than was previously believed.

Kennard, Mark Allen

87

Doping and temperature dependence of the Raman spectra lanthanum strontium copper oxide  

NASA Astrophysics Data System (ADS)

Polarized Raman scattering experiments have been carried out on single crystals of La2-xSRxCuO 4 La214x as a function of doping 0?x?0.22 and temperature 15K?T?300K . The polarizations of the incident and scattered light are selected to probe excitations near the axes in k-space ( B1g electronic and magnetic excitations) and near the diagonal directions ( B2g electronic excitations). The low-energy w?800cm-1 B1g Raman response undergoes a strong spectral weight depletion (SWD) as the hole concentration (x) is decreased below the optimum doping level xopt?0.17 . The magnitude of the SWD in underdoped compounds increases slightly with decreasing temperature from 300K to 15K. Furthermore, the low-energy B1g spectral weight of underdoped compounds is transferred to higher frequency region occupied by two-magnon excitations. In contrast to the doping and temperature induced SWD of the B1g spectra, the normal state B2g spectra do not exhibit any obvious variations with temperature and doping. The results are consistent with the existence of a strong anisotropic interaction in underdoped samples that results in a normal state pseudogap on regions of the FS located near the zone axes. The strength of the interaction decreases rapidly with increasing x and the spectral evidence for the pseudogap vanishes for x?xopt . The results suggest that the pseudogap arises from short range antiferromagnetic correlations in the CuO2 planes. The B1g spectra of underdoped compounds is unaffected by the transition to the superconducting state. However, the B1g spectra of optimally and overdoped compounds exhibit a strong renormalization and clear pair-breaking peaks 2D when the samples are cooled below Tc. In contrast to this behavior, the B2g spectra exhibit a superconductivity induced redistribution and 2D peaks for all x studied. The low-energy B2g response functions vary linearly with frequency for all doping levels, suggesting an anisotropic superconducting gap with nodes near the (+/-1, +/-1) directions in k-space. Meanwhile, the low-energy B1g response function changes from w3 in the case of xopt?0.17 to w for the overdoped x = 0.22 crystals. This change in power law is associated with an enhanced residual scattering in the overdoped crystals. The results are in general agreement with many predictions of the nearly antiferromagnetic Fermi liquid model, in which a tendency to order antiferromagnetically competes with a spin-fluctuation mediated pairing. (Abstract shortened by UMI.)

Gharavi-Naeini, Jafar

88

Temperature dependent emission and absorption cross section of Yb3+ doped yttrium lanthanum oxide (YLO) ceramic and its application in diode pumped amplifier.  

PubMed

Temperature dependent absorption and emission cross-sections of 5 at% Yb(3+) doped yttrium lanthanum oxide (Yb:YLO) ceramic between 80K and 300 K are presented. In addition, we report on the first demonstration of ns pulse amplification in Yb:YLO ceramic. A pulse energy of 102 mJ was extracted from a multi-pass amplifier setup. The amplification bandwidth at room temperature confirms the potential of Yb:YLO ceramic for broad bandwidth amplification at cryogenic temperatures. PMID:24104499

Banerjee, Saumyabrata; Koerner, Joerg; Siebold, Mathias; Yang, Qiuhong; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; Loeser, Markus; Zhang, Haojia; Lu, Shenzhou; Hein, Joachim; Schramm, Ulrich; Kaluza, Malte C; Collier, John L

2013-07-01

89

Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films  

PubMed Central

Fourier transform infrared (FTIR) spectrum dielectric constant, ??, loss tangent, tan(?), electric modulus, M*, and ac conductivity, ?ac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300–450?K and 1?kHz–4?MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ? and ? were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, ?-relaxation process splits into ?a and ?c. This splitting is due to the segmental motion in the amorphous (?a) and crystalline (?c) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping. PMID:22933826

Hanafy, Taha A.

2012-01-01

90

Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FTIR) spectrum dielectric constant, ?', loss tangent, tan(?), electric modulus, M*, and ac conductivity, ?ac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ? and ? were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, ?-relaxation process splits into ?a and ?c. This splitting is due to the segmental motion in the amorphous (?a) and crystalline (?c) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

Hanafy, Taha A.

2012-08-01

91

Pulsed laser deposition of rare-earth-doped gallium lanthanum sulphide chalcogenide glass thin films  

NASA Astrophysics Data System (ADS)

Amorphous chalcogenide thin films are of high current interest for technological applications as optical storage media or waveguides for photonic integrated circuits. As part of a larger project including fs, ps and ns pulsed laser deposition regimes, Er- and Pr-doped GLS thin films were deposited by ns PLD, and their structural, chemical and optical properties were analyzed by optical and electronic microscopy, stylus profilometry, X-ray diffraction, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), energy-dispersive X-ray spectroscopy, variable-angle spectroscopic ellipsometry and optical transmission. Films deposited at moderate fluence (~4 J/cm2) in UV (266 nm) presented a good surface quality, while exhibiting acceptable composition uniformity and deviations from stoichiometry in line with the literature. Composition and optical properties dependences on the deposition conditions were investigated and discussed with respect to previous studies on similar systems.

Pompilian, O. G.; Dascalu, G.; Mihaila, I.; Gurlui, S.; Olivier, M.; Nemec, P.; Nazabal, V.; Cimpoesu, N.; Focsa, C.

2014-10-01

92

Dielectric and ferroelectric properties of lanthanum doped SrBi{sub 4}Ti{sub 4}O{sub 15} ferroelectric ceramics  

SciTech Connect

Bismuth layer structure ferroelectrics (BLSFs) have attracted intensive investigation for the potential use in non volatile ferroelectric random access memory (FeRAM) and piezoelectric devices suitable at high temperature. Bismuth layered structured compounds with general formula of (Bi{sub 2}O{sub 2}){sup 2+} (A{sub m-1}B{sub m}O{sub 3m+1}){sup 2-} are firstly found by Aurivillius. The structure of these compounds can be described as pseudo-perovskite (A{sub m-1}B{sub m}O{sub 3m+1}){sup 2-} slabs separated by (Bi{sub 2}O{sub 2}){sup 2+} layers along the crystallographic c-axis. The 12-coordinated A site can be occupied by such cations as La{sup 3+}, Bi{sup 3+}, Ba{sup 2+}, Sr{sup 2+}, Pb{sup 2+}, Ca{sup 2+}, Na{sup +}, etc. While the octahedral-coordinated B site can be occupied by W{sup 6+}, Nb{sup 5+}, Ta{sup 5+}, Ti{sup 4+} etc. Lanthanum substituted BiT (Bi{sub 4}Ti{sub 4}O{sub 12}) known as BLT has been extensively investigated. With this substitution, BLT shows relatively large P{sub r}, low synthesis temperature and good fatigue endurance which makes it a potential candidate for FeRAM application. So, lanthanum doping is an effective way to improve the ferroelectric and fatigue properties of Bi{sub 4}Ti{sub 4}O{sub 12}. Lanthanum doped Bismuth layer structure ferroelectrics (BLSFs) ceramics SrBi{sub 4-x}La{sub x}Ti{sub 4}O{sub 15} (x=0, 0.025, 0.050, 0.075, 0.1) were prepared by solid state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.1. Morphological studies were carried out by SEM analysis. It was found that crystal lattice constant, dielectric and electrical properties of SBT ferroelectrics varied appreciably with amount of doping. Dielectric measurements in the frequency range 100Hz-1MHz were made using an impedance analyzer (Wayne Kerr 6500P) and the measurements were carried out from RT to 600 deg C. The ferroelectric hysteresis loop was traced at room temperature by a standard P-E loop tracer based on sawyer-tower circuit. The values of 2P{sub r} and E{sub c} for pure and lanthanum doped SBT are given. The above results indicate that La{sup 3+} modification is an effective way to improve the ferro electrical properties of SrBi{sub 4}Ti{sub 4}O{sub 15}. The transition temperature (T{sub c}) and dielectric constant for SrBi{sub 4}Ti{sub 4}O{sub 15} are given. It is observed that with the increasing of lanthanum content remnant polarization increases and coercive field decreases. It is believed that these materials are potentially attractive candidates for FeRAM industry.

Ashok, K.; Sarah, P., E-mail: pasala_sarah@yahoo.com [Vardhaman College of Engineering, Shamshabad (India); Raju, V.S. [National Centre for Compositional Characterization of Materials, Bhabha Atomic Research Centre, Hyderabad (India); Chandralingam, S. [Department of Physics, Jawaharlal Nehru Technological University, College of Engineering, Hyderabad (India)

2011-07-01

93

Influence of the lanthanum deficit on electrical resistivity and heat capacity of silver-doped lanthanum manganites La{sub 1-x}Ag{sub y}MnO{sub 3}  

SciTech Connect

The electrical resistivity and heat capacity of the silver-doped lanthanum manganites La{sub 0.80}Ag{sub 0.15}MnO{sub 3} and La{sub 0.85}Ag{sub 0.15}MnO{sub 3} have been investigated. Despite the nonstoichiometry of the composition, the La{sub 0.80}Ag{sub 0.15}MnO{sub 3} manganite exhibits a bulk homogeneity and better physical properties from the applied point of view as compared to the La{sub 0.85}Ag{sub 0.15}MnO{sub 3} manganite, viz., the former compound has a higher spontaneous magnetoresistance and a larger jump of the heat capacity with a small width of the phase transition, and the anomalies of the heat capacity and electrical resistivity in the vicinity of the Curie point of this compound agree with the fluctuation nature of the second-order phase transition. The behavior of the properties of lanthanum-deficient manganites under investigation in the region of the phase transition is consistent with the classical theory of indirect exchange interaction. The behavior of the temperature dependence of the electrical resistivity has been analyzed in terms of two models. One of these models is based on the tunneling of charge carriers between ferrons or polarons, and the other model is based on the polaron hopping conduction. Both approaches lead to consistent results, and their combination has made it possible to estimate the tunneling distance of charge carriers. The origin of the influence of technological parameters characterizing the synthesis of La{sub 1-x}Ag{sub y}MnO{sub 3} ceramic materials on their physical properties has been elucidated.

Abdulvagidov, Sh. B., E-mail: abdulvagidov@iwt.ru; Gamzatov, A. G. [Russian Academy of Sciences, Amirkhanov Institute of Physics, Dagestan Scientific Center (Russian Federation); Mel'nikov, O. V.; Gorbenko, O. Yu. [Moscow State University (Russian Federation)

2009-12-15

94

Localized holes in superconducting lanthanum cuprate P. C. Hammel  

E-print Network

Localized holes in superconducting lanthanum cuprate P. C. Hammel Los Alamos National Laboratory the existence of a second, anomalous copper site in lanthanum cuprate whose character is independent in Sr- and O-doped lanthanum cuprate, yet copper NQR spectra reveal two 63 Cu lines see Fig. 1 and Refs

Hammel, Chris

95

A positron lifetime study of lanthanum and niobium doped Pb(Zr0.6Ti0.4)O3  

NASA Astrophysics Data System (ADS)

A study of vacancy-related defects in lanthanum and niobium doped PbZr0.6Ti0.4O3 with dopant concentrations of 0-6 and 0-4mol%, respectively has been performed using positron annihilation spectroscopy X-ray diffraction, and photoelectron spectroscopy. Positron lifetime as well as coincidence annihilation radiation Doppler line broadening measurements were carried out. It was found that the samples exhibit vacancylike defects that act as positron traps. Two main defect lifetime components were found in both sample sets one at ?150ps and one at ?300ps. These defect trapping sites can be attributed to single oxygen vacancies and A-site vacancies, respectively. Doppler line broadening measurements, however, do not show significant changes as a function of dopant concentrations in terms of shape S and wing W parameters.

Gottschalk, S.; Hahn, H.; Balogh, A. G.; Puff, W.; Kungl, H.; Hoffmann, M. J.

2004-12-01

96

CW blue laser emission by second harmonic generation of 900-nm oscillation of Nd-doped strontium and lanthanum aluminate (ASL)  

NASA Astrophysics Data System (ADS)

Nd-doped strontium and lanthanum (ASL) crystals Sr 1-xLa x-yNd yMg xAl 12-xO 19 (0.05 <= x <= 0.5; y = 0.05) were grown by Czochralski pulling technique. Up to 1.67W of 900nm IR output laser power for an absorbed power of 2.53W was obtained under Ti:sapphire pumping at 792nm. Intracavity second harmonic generation experiments led to 320mW of blue laser power at 450nm with a 10mm-long BiB 3O 6 nonlinear crystal. Other nonlinear crystals were also evaluated such as LBO.

Varona, C.; Loiseau, P.; Aka, G.; Ferrand, B.; Lupei, V.

2006-04-01

97

Development of lanthanum ferrite SOFC cathodes  

Microsoft Academic Search

A number of studies have been conducted concerning compositional\\/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700–800°C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction

Steve P. Simner; Jeff F. Bonnett; Nathan L. Canfield; Kerry D. Meinhardt; Jayne P. Shelton; Vince L. Sprenkle; Jeffry W. Stevenson

2003-01-01

98

Design and fabrication of lanthanum-doped tin-silver-copper lead-free solder for the next generation of microelectronics applications in severe environment  

NASA Astrophysics Data System (ADS)

Tin-Lead solder (Sn-Pb) has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use by the European Rehabilitation of Hazardous Substances (RoHS) directive, and therefore, many researchers are looking to replace it. The urgent need for removing lead from solder alloys led to the very fast introduction of lead-free solder alloys without a deep knowledge of their behavior. Therefore, an extensive knowledge and understanding of the mechanical behavior of the emerging generation of lead-free solders is required to satisfy the demands of structural reliability. Sn-Ag-Cu (SAC) solders are widely used as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) have limited their use in high temperature applications. Many additives are studied to refine the microstructure and improve the mechanical properties of SAC solders including iron (Fe), bismuth (Bi), antimony (Sb) and indium (In) etc. Whereas many researchers studied the impact of novel rare earth (RE) elements like lanthanum (La), cerium (Ce) and lutetium (Lu) on SAC solders. These RE elements are known as “vitamins of metals” because of their special surface active properties. They reduce the surface free energy, refine the grain size and improve the mechanical properties of many lead free solder alloys like Sn-Ag, Sn-Cu and SAC but still a systematic study is required to explore the special effects of “La” on the eutectic SAC alloys. The objective of this PhD thesis is to extend the current knowledge about lead free solders of SAC alloys towards lanthanum doping with varying environmental conditions implemented during service. This thesis is divided into six main parts.

Sadiq, Muhammad

99

Visible light responsive porous Lanthanum-doped Ag3PO4 photocatalyst with high photocatalytic water oxidation activity.  

PubMed

This paper report a facile route of synthesizing Ag3PO4 crystal with smooth surface, and La-doped Ag3PO4 crystal with porous surface by accurately controlling the kinetic parameters during chemical precipitation process. As a result of surface modification induced by La doping, the La-doped Ag3PO4 crystal shows a higher photocatalytic activity than Ag3PO4 crystal in O2 evolution from water splitting. The improved photocatalytic activity of La-doped Ag3PO4 is attributed to the synergistic effects of porous surface structure, abundant surface defects and increased surface area. The result also shows that La doping concentration has a remarkable effect on the photocatalytic activity of Ag3PO4. PMID:24998046

Xie, Ying Peng; Wang, Guo Sheng

2014-09-15

100

Samarium/Cobalt Magnets  

NASA Technical Reports Server (NTRS)

Intrinsic magnetic coercivities of samarium cobalt magnets made to approach theoretical limit of 350 kA/m by carefully eliminating oxygen from finished magnet by hot isostatic pressing (HIP). HIP process viable alternative to currently used sintering process.

Das, D.; Kumar, K.; Frost, R.; Chang, C.

1985-01-01

101

Citrate gel synthesis of aluminum-doped lithium lanthanum titanate solid electrolyte for application in organic-type lithium-oxygen batteries  

NASA Astrophysics Data System (ADS)

Aluminium doped lithium lanthanum titanate (A-LLTO) powders with various excess Li2O content are synthesized using a simple citrate gel method. The obtained A-LLTO powders show an agglomerated form, composed of nano-sized particles of 20-50 nm. The morphology and conductivity of the A-LLTO ceramics are largely affected by the content of excess Li2O. The highest total ionic conductivity of 3.17 × 10-4 S cm-1 is achieved for the A-LLTO sample containing 20% excess Li2O, exhibiting a vacancy content of 6%, and a total activation energy of 0.358 eV. The A-LLTO can act as a membrane to protect lithium metal from oxygen and other contaminants diffused through the oxygen electrode part. The Li-O2 cell employing the A-LLTO solid electrolyte shows a good cycle life of longer than 100 discharge-charge cycles, under the constant capacity mode of 300 mAh g-1.

Le, Hang T. T.; Kalubarme, Ramchandra S.; Ngo, Duc Tung; Jang, Seong-Yong; Jung, Kyu-Nam; Shin, Kyoung-Hee; Park, Chan-Jin

2015-01-01

102

Structure and properties of antimony-doped lanthanum molybdate La{sub 2}Mo{sub 2}O{sub 9}  

SciTech Connect

Polycrystalline samples of the composition La{sub 2}Mo{sub 2-x}Sb{sub x}O{sub 9-y}, where 0 {<=} x {<=} 0.05, were prepared by solid-phase synthesis. Single crystals of La{sub 2}Mo{sub 1.96}Sb{sub 0.04}O{sub 8.17} were obtained by spontaneous crystallization from flux. The structure of the metastable {beta}{sub ms} phase of this compound was determined at room temperature by X-ray diffraction. It was found that the La, Mo, and O1 atoms are displaced from the threefold axis on which they are located in the high-temperature {beta} phase. It was shown that molybdenum atoms in the crystal structure are partially replaced by antimony atoms, which are located on the threefold axis. In antimony-doped crystals, lanthanum atoms partially return to the site on the threefold axis and the coordination environment of molybdenum cations becomes more ordered, thus facilitating the stabilization of the cubic phase at room temperature. Calorimetric measurements (DSC) showed that the introduction of Sb as the dopant into the La{sub 2}Mo{sub 2}O{sub 9} structure leads to a decrease in the temperature of the {alpha} {yields} {beta} phase transition from 570 to 520 Degree-Sign C and to the partial suppression of this transition. The temperature behavior of the conductivity confirms the DSC data. Thus, doping with Sb contributes to the stabilization of the cubic phase at room temperature.

Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Verin, I. A.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Kharitonova, E. P.; Voronkova, V. I. [Moscow State University (Russian Federation)

2011-05-15

103

Structural and magnetic properties of yttrium and lanthanum-doped Ni-Co and Ni-Co-Zn spinel ferrites  

NASA Astrophysics Data System (ADS)

Rare earth doping of Co-rich spinel ferrites is investigated through the preparation of two groups of polycrystalline Ni-Co and Ni-Co-Zn ferrites, where Fe is partly substituted by Y and La. The characterization of the sintered ferrites by means of X-ray powder diffraction and Rietveld profile analysis, indicates the subtle expansion of the spinel unit cell and the cation redistribution in the doped ferrites in order to accommodate the incorporation of Y and La in the lattice. The impurity traces, detected only in the Ni-Co-Zn group, is ascribed to the Zn population in the tetrahedral A-sites impeding the cation transfer. Moreover, the examined microstructure of the doped Ni-Co samples comprises enlarged and more homogeneous grains, whereas grain growth is moderated in the doped Ni-Co-Zn ferrites. The discussed characteristics of the crystal and magnetic structure along with the morphological aspects define the impact of Y and La doping on the static magnetic properties of Ni-Co and Ni-Co-Zn ferrites, saturation magnetization MS and coercivity HC, which were extracted from the respective hysteresis loops.

Stergiou, Charalampos; Litsardakis, George

2014-11-01

104

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode  

DOEpatents

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro.sub.3 particles; (2) dispersing doped LaCrO.sub.3 particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

Richards, Von L. (Murrysville, PA); Singhal, Subhash C. (Murrysville, PA); Pal, Uday B. (Cambridge, MA)

1992-01-01

105

Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode  

DOEpatents

A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

Richards, V.L.; Singhal, S.C.; Pal, U.B.

1992-07-21

106

Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique  

NASA Astrophysics Data System (ADS)

There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ~100?ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti3+. Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material.

Han, Wei; Jiang, Xin; Kajdos, Adam; Yang, See-Hun; Stemmer, Susanne; Parkin, Stuart S. P.

2013-07-01

107

Spin injection and detection in lanthanum- and niobium-doped SrTiO3 using the Hanle technique.  

PubMed

There has been much interest in the injection and detection of spin-polarized carriers in semiconductors for the purposes of developing novel spintronic devices. Here we report the electrical injection and detection of spin-polarized carriers into Nb-doped strontium titanate single crystals and La-doped strontium titanate epitaxial thin films using MgO tunnel barriers and the three-terminal Hanle technique. Spin lifetimes of up to ~100 ps are measured at room temperature and vary little as the temperature is decreased to low temperatures. However, the mobility of the strontium titanate has a strong temperature dependence. This behaviour and the carrier doping dependence of the spin lifetime suggest that the spin lifetime is limited by spin-dependent scattering at the MgO/strontium titanate interfaces, perhaps related to the formation of doping induced Ti(3+). Our results reveal a severe limitation of the three-terminal Hanle technique for measuring spin lifetimes within the interior of the subject material. PMID:23831939

Han, Wei; Jiang, Xin; Kajdos, Adam; Yang, See-Hun; Stemmer, Susanne; Parkin, Stuart S P

2013-01-01

108

Effect of lanthanum doping on tetragonal-like BiFe O3 with mixed-phase domain structures  

NASA Astrophysics Data System (ADS)

The recent discoveries of both chemical-driven and strain-driven morphotropic phase boundaries (MPBs) in BiFe O3 (BFO) thin films have opened up new horizons in developing high-performance lead-free piezoelectrics. An attempt to bridge these two MPBs is made by doping La into highly strained BFO thin films with the coexistence of tetragonal-like and rhombohedral-like phases. The structural, morphological, and ferroelectric properties of such films are investigated. It is observed that La doping changes the energy landscape between the tetragonal-like and the rhombohedral-like polymorphs due to the chemical pressure imposed by the La substitution. Polar instability is found upon increasing La doping for the in-plane polarization component, which correlates with the vanishing of in-plane ferroelectric domain structures. The transition sequence of the in-plane ferroelectric polarization resembles that previously reported for the bulklike rhombohedral phase of BFO under continuous La doping, indicating the universality of the chemical-alloying effect on the ferroelectric order.

You, Lu; Caesario, Petrus; Fang, Liang; Ren, Peng; Wang, Le; Zhou, Yang; Gruverman, Alexei; Wang, Junling

2014-10-01

109

PoS(INTEGRAL2010)107 Development of an Anger camera in lanthanum  

E-print Network

PoS(INTEGRAL2010)107 Development of an Anger camera in lanthanum bromide for gamma-ray space, MA, USA S. Blin, P. Barrillon LAL, IN2P3-CNRS and Univ Paris-Sud, 91898 Orsay cedex, France Lanthanum astronomy in the MeV range Vincent Tatischeff 1. Introduction The recently developed cerium-doped lanthanum

Paris-Sud XI, Université de

110

Development of Lanthanum Ferrite SOFC Cathodes  

SciTech Connect

A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700-800 degrees C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.

Simner, Steve P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

2003-01-01

111

Novel Au/La-SrTiO3 microspheres: superimposed effect of gold nanoparticles and lanthanum doping in photocatalysis.  

PubMed

Novel multielement Au/La-SrTiO(3) microspheres were synthesized by a solvothermal method using monodisperse gold and La-SrTiO(3) nanocrystals as building blocks. The porous Au/La-SrTiO(3) microspheres had a large surface area of 94.6?m(2) ?g(-1). The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare-earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La-SrTiO(3) microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La-SrTiO(3) microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine?B. The photocatalytic activities are in the order of the following: Au/La-SrTiO(3) microspheres>Au/SrTiO(3) microspheres>La-SrTiO(3) microspheres>SrTiO(3) microspheres. PMID:24817580

Wang, Guannan; Wang, Pei; Luo, He-Kuan; Hor, T S Andy

2014-07-01

112

Near-infrared broadband luminescence and energy transfer in Bi-Tm-Er co-doped lanthanum aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The Bi-Tm-Er co-doped SiO2-Al2O3-La2O3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission, were investigated by the optical absorption and photoluminescence spectra. A super broadband NIR emission extending from 0.95 to 1.6 ?m with a full-width at half-maximum (FWHM) of 430 nm which covered the whole O, E, S, C and L bands, was observed in Bi-Tm-Er co-doped samples under 808 nm excitation, as a result of the overlap of the Bi-related emission band (centered at 1270 nm) and the emission from Tm3+3H4?3F4 transition (1450 nm) as well as Er3+4I13/2?4I15/2 transition (1545 nm). In addition, a super broadband emission with amplitude relatively flat from 0.95 to 2.1 ?m has been observed. The possible energy transfer between Bi-related centers, Tm3+ ions and Er3+ ions was proposed.

Minh Hau, Tran; Wang, Rongfei; Yu, Xue; Zhou, Dacheng; Song, Zhiguo; Yang, Zhengwen; He, Xijia; Qiu, Jianbei

2012-09-01

113

Luminescent properties of trivalent praseodymium-doped lanthanum aluminum germanate LaAlGe2O7  

NASA Astrophysics Data System (ADS)

The luminescent characteristics of Pr3+-activated LaAlGe2O7 were investigated. In response to excitement using 448 nm blue light, the emission spectra involved most of the 3P0?3HJ transitions. The dominant emission came from the 3P0?3H4 transition at 487 nm. 1D2 fluorescence quenching was observed in highly doped samples and is related to the cross-relaxation processes among neighboring Pr3+ ions. In contrast with conventional Pr3+-activated phosphors, the extraordinary excitation spectra showed only intense f f transition of Pr3+ ions, while the 4f 5d transition was eliminated. This is ascribed to photoionization. By analyzing absorption and excitation spectra, it is recognized that no efficient energy transfer occurs between Pr3+ and the host lattice in LaAlGe2O7.

Li, Yu-Chun; Chang, Yen-Hwei; Lin, Yu-Feng; Chang, Yee-Shin; Lin, Yi-Jing

2007-10-01

114

Effect of Hydrogen Anneals on Niobium-Doped Lead Zirconate Titanate Capacitors with Lanthanum Strontium Cobalt Oxide/Platinum Electrodes  

NASA Astrophysics Data System (ADS)

Ferroelectric capacitors, being oxide ceramics, are very sensitive to the effects of hydrogen environments at elevated temperatures [H. Ashida et al..: Integr. Ferroelectr. 21 (1998) 97]. After a capacitor has been exposed directly to a annealing hydrogen environment at low hydrogen partial pressures, the electrical properties of the device can deteriorate and leakage currents can increase. At higher hydrogen concentration gradients, such as the formidable forming gas annealing, physical failure of the inter-layer dielectric (ILD) and/or top electrode adhesion can occur. The authors have examined various structural approaches to mitigate the effects of hydrogen damage on integrated ferroelectric lead zirconate titanate (PZT) capacitors. These approaches, including the use of a titanium dioxide barrier layer above the PZT to impede the reducing effect of hydrogen on the ceramic and the use of electrode layers other than platinum to eliminate the generation of free hydrogen ions by catalyst action [S. Aggarwal et al..: Appl. Phys. Lett. 73 (1998) 1973]. The authors have found that niobium-doped PZT capacitors using LSCO/platinum electrodes passivated with titanium dioxide will recover from 1% forming gas annealing within 30 minutes at 450°C in nitrogen.

Evans, Joe; Jr., Jr.; Boyer, Leonard; Velasquez, Geri; Ramesh, Ramamoorthy; Aggarwal, Sanjeev; Keramidas, Vassillis

1999-09-01

115

Microstructure, magnetoresistance, and magnetic properties of pulsed-laser-deposited external, internal, and mixed-doped lanthanum manganite films  

SciTech Connect

In this article we report our studies on the microstructure, magnetoresistance (MR) behavior, and magnetic properties of the La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3] system in thin-film form. By varying the values of [ital x] and [ital y] in La[sub 1[minus]x[minus]y]Ca[sub x]MnO[sub 3], we have synthesized an external- (x=0.3, y=0), an internal- (x=0, y=0.3), and a mixed-doped (x=0.2, y=0.1) system with the same Mn[sup 3+]/Mn[sup 4+] ratio. Thin films of these materials have been grown [ital in situ] on (100) LaAlO[sub 3] substrates using a pulsed-laser-deposition technique. Atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy measurements carried out on these films have shown that the films are smooth, highly crystalline, and epitaxial on the (100) LaAlO[sub 3] substrates. Electrical resistance and magnetoresistance have been measured in the 10[endash]300 K range in magnetic fields up to 5 T using a superconducting quantum interference device magnetometer. The MR ratios (calculated using the expression, [R[sub 0][minus]R[sub H

Pietambaram, S.V.; Kumar, D.; Singh, R.K. (Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611-6400 (United States)); Lee, C.B. (Department of Electrical Engineering, North Carolina AT State University, Greensboro, North Carolina 27411 (United States)); Kaushik, V.S. (MRST Device Engineering Division, Motorola Inc., Austin, Texas (United States))

1999-09-01

116

Modified giant dielectric properties of samarium doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics  

SciTech Connect

Highlights: ? Grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was greatly decreased by doping with Sm{sup 3+}. ? ?? and tan ? decreased with increasing the concentration of Sm{sup 3+} doping. ? Ca{sub 0.925}Sm{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} exhibited ?? ? 10,863 and low tan ? ? 0.043 at 20 °C and 1 kHz. -- Abstract: Effects of Sm{sup 3+} substitution on the microstructure and dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics were investigated. The grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics was greatly decreased by doping with Sm{sup 3+}, resulting from the ability of Sm{sup 3+} to inhibit the grain growth rate. This result can cause a decrease in the dielectric constant (??) and loss tangent (tan ?) of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics. Interestingly, high dielectric permittivity (?? ? 10,863) and low loss tangent (tan ? ? 0.043 at 20 °C and 1 kHz) were observed in the Ca{sub 0.925}Sm{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} ceramic. Nonlinear electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics were modified by doping with Sm{sup 3+}. The dielectric relaxation behavior of Sm-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics can be well ascribed based on the internal barrier layer capacitor model of Schottky barriers at the grain boundaries.

Thongbai, Prasit, E-mail: pthongbai@kku.ac.th [Integrated Nanotechnology Research Center (INRC), and Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand)] [Integrated Nanotechnology Research Center (INRC), and Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Putasaeng, Bundit; Yamwong, Teerapon [National Metal and Materials Technology Center (MTEC), Thailand Science Park, Pathumthani, 12120 (Thailand)] [National Metal and Materials Technology Center (MTEC), Thailand Science Park, Pathumthani, 12120 (Thailand); Maensiri, Santi [School of Physics, Institute of Science, Suranaree University, Nakhon Ratchasima 30000 (Thailand)] [School of Physics, Institute of Science, Suranaree University, Nakhon Ratchasima 30000 (Thailand)

2012-09-15

117

The low-frequency Raman spectra and nanostructure of As-Se-S and As-Se-Te chalcogenide semiconductors doped by samarium  

NASA Astrophysics Data System (ADS)

It has been established that the Raman scattering (RS) of chalcogenide glass-like semiconductors (CGS) materials As-Se-S and As-Se-Te at frequencies below 100 cm-1 consists of two parts: first - which the intensity with increasing frequency up to 30 ÷ 40 cm-1 decreases (quasi-elastic scattering); second - which have been observed a broad band with a maximum at frequencies of ~ 63 ÷ 67 cm-1 (boson peak - BP). Such a case is absent in the respective crystals. The observed features are associated with relaxation and excess density of states of acoustic vibrations in irregularities is localized with nanometer-size of material. It is shown that the contribution of the different types of scattering in a low-frequency range depends on the degree of disorder in the material, which varies with the change of chemical composition and by doping.

Isayeva, G. A.; Alekberov, R. I.; Mekhtiyeva, S. I.; Isayev, A. I.

2014-09-01

118

Effect of samarium substitution on structural and magnetic properties of magnesium ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Samarium doped magnesium ferrite was prepared (MgSmxFe2-xO4) by sol-gel method. X-ray diffraction analysis reveals that the samples are single phasic with crystallite sizes in the 13-25 nm regime. Increase in lattice parameter with doping concentration suggests the expansion in unit cell with Sm3+ doping. Fourier Transform Infrared Spectrum shows substitution of Sm3+ ions in octahedral B site. Transmission Electron Micrograph shows the spherical shape of nano-particles. Magnetic measurement shows a decrease in magnetization with doping which is explained using dependence on particle size.

Thankachan, Smitha; Jacob, Binu P.; Xavier, Sheena; Mohammed, E. M.

2013-12-01

119

Tunable quasi-cw two-micron lasing in diode-pumped crystals of mixed Tm{sup 3+}-doped sodium - lanthanum - gadolinium molybdates and tungstates  

SciTech Connect

Two-micron lasing is obtained for the first time on the {sup 3}F{sub 4} {yields} {sup 3}H{sub 6} transition of Tm{sup 3+} ions in diode-pumped crystals of mixed sodium - lanthanum - gadolinium tungstate Tm:NaLa{sub 1/2}Gd{sub 1/2}(WO{sub 4}){sub 2} (C{sub Tm} = 3.6 at %) (3.6Tm : NLGW) and molybdate Tm:NaLa{sub 1/3}Gd{sub 2/3}(MoO{sub 4}){sub 2} (C{sub Tm} = 4.8 at %) (4.8Tm : NLGM). For the 3.6Tm : NLGW crystal, the quasi-cw laser output power exceeded 200 mW and the slope efficiency (with respect to absorbed pump power) for the {pi}- and {sigma}-polarisations at wavelengths of 1908 and 1918 nm was 34% and 30%, respectively. The laser wavelength of this crystal was continuously tuned within the spectral range of 1860 - 1935 nm. For the 4.8Tm : NLGM crystal, the slope efficiency for the {pi}- and {sigma}-polarisations at wavelengths of 1910 and 1918 nm was 27% and 23%, respectively, and the laser wavelength was tunable within the spectral range of 1870 - 1950 nm. (lasers)

Bol'shchikov, F A; Ryabochkina, P A [N.P. Ogarev Mordovian State University, Saransk (Russian Federation); Zharikov, Evgeny V; Lis, Denis A; Subbotin, Kirill A [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zakharov, N G; Antipov, Oleg L [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2010-12-09

120

Stereospecific and highly stereoselective cyclopropanation reactions promoted by samarium.  

PubMed

Samarium metal and samarium diiodide have become important tools as selective cyclopropanating agents in organic synthesis due to their high chemo- and stereoselectivity. Therefore, Sm and SmI(2) are the ideal reagents to prepare cyclopropane derivatives. This tutorial review highlights C-C multiple bond cyclopropanation processes promoted by samarium or samarium diiodide. PMID:20683534

Concellón, José M; Rodríguez-Solla, Humberto; Concellón, Carmen; del Amo, Vicente

2010-11-01

121

Novel samarium/erbium and samarium/terbium codoped glass phosphor for application in warm white light-emitting-diode  

NASA Astrophysics Data System (ADS)

Tunable polychromatic light emission within the low color correlated temperature range was produced using terbiumand/ or erbium-samarium co-doped PbGeO3:PbF2:CdF2 glass phosphor. The phosphors were synthesized, and their luminescence characteristics were examined under UV-blue light-emitting-diode laser excitation. Luminescence emission around 490, 545, 600, and 645 nm in Tb3+/Sm3+ and 525, 545, 600, and 645 nm in Er3+/Sm3+ co-doped phosphor was obtained and analyzed as a function of the active ions concentration, and excitation wavelength. Color tunability in the red-orange-yellow-green region was achieved combining of Tb3+, Er3+, and Sm3+ ions contents. Results suggest that the color-tunable polychromatic light emitter phosphor herein reported is a promising novel candidate for application in cold white-light LED-based illumination technology

da Silva, Cosmo M.; Gouveia-Neto, Artur S.; Bueno, Luciano A.

2014-02-01

122

Second phases in doped lanthanum gallate perovskites  

Microsoft Academic Search

Synthesis of Lal ? xSrxGal ? yMgyO3 ? ? with 0.098 ? xmol% ? 0.100 and 0.196 ? ymol% ? 0.200 was performed in three ways: according to the solid state route either from oxides, or from oxides and carbonates and from powders prepared by ultrasonic spray pyrolysis. The samples were heterogeneous with a ‘crust’ of a darker color. Impurity

E. Djurado; M. Labeau

1998-01-01

123

Metallic behavior of lanthanum disilicide  

NASA Technical Reports Server (NTRS)

Polycrystalline thin films of LaSi2 were prepared by reaction of sputter-deposited lanthanum layers with silicon wafers. Samples of the low-temperature tetragonal and the high-temperature orthorhombic phases were separately obtained. The room-temperature intrinsic resistivities were 24 and 57 microohm cm for the low- and high-temperature structures, respectively. Although lanthanum disilicide had been previously reported to be a semiconductor, classical metallic behavior was found for both phases.

Long, Robert G.; Bost, M. C.; Mahan, John E.

1988-01-01

124

Lanthanum Bromide Detectors for Safeguards Measurements  

SciTech Connect

Lanthanum bromide has advantages over other popular inorganic scintillator detectors. Lanthanum bromide offers superior resolution, and good efficiency when compared to sodium iodide and lanthanum chloride. It is a good alternative to high purity germanium detectors for some safeguards applications. This paper offers an initial look at lanthanum bromide detectors. Resolution of lanthanum bromide will be compared lanthanum chloride and sodium-iodide detectors through check source measurements. Relative efficiency and angular dependence will be looked at. Nuclear material spectra, to include plutonium and highly enriched uranium, will be compared between detector types.

Wright, J.

2011-05-25

125

Separation of yttrium and neodymium from samarium and the heavier lanthanides by cation-exchange chromatography with hydroxyethylenediaminetriacetate in monochloroacetate buffer.  

PubMed

Trace and mg amounts of yttrium and neodymium are separated from samarium and the heavier lanthanides by elution of the latter with hydroxyethylenediaminetriacetate (HEDTA) in a chloroacetate buffer of pH 2.85 from a column containing 68 ml (20 g) of AG 50W-X4 resin of 200-400 mesh particle size. Yttrium and neodymium (and also praeseodymium, cerium and lanthanum) are retained and can be eluted with 0.01M HEDTA in 0.20M ammonium acetate (pH 6). The separations are reasonably sharp and quantitative: only 3-15 microg of samarium was found in the yttrium fraction and 0.8-3.4 microg of yttrium in the samarium fraction when 4.41 mg of yttrium and 7.12 mg of samarium were present originally. Control of the pH during the column operations is essential because the peak positions are very sensitive to change in pH. The relevant distribution coefficients, elution curves of pairs of elements and results for the analysis of synthetic mixtures are presented. Also included is a method for separating yttrium and the lanthanides from HEDTA and sodium and ammonium ions. PMID:18965088

Strelow, F W; Victor, A H

1990-12-01

126

Influence of samarium doping on electronic and magneto-transport properties of La0.9-xSmxSr0.1MnO3 (0.1?x?0.5) nanoparticles  

NASA Astrophysics Data System (ADS)

We report detailed field dependent electronic- (?-T) and magneto- transport (MR-H) studies of La1-xSmxSr0.1MnO3 (0.1?x?0.5) nanoparticles. Doping induced disorder at La site is observed in field dependent ?-T measurements of the sample. At low doping side, nice metal to insulator transition (MIT) peak appears in ?-T data whereas with increasing of Sm+3 contents, metallic behavior is suppressed under the insulating background although a weak signature of MIT is found. Anomalous resistive nature of the samples with increasing of x can be explained in such a way that doping at nonmagnetic La site with magnetic Sm+3 ion induces an extra magnetic coupling in the system which changes the long range ferromagnetic ordering to spin glass/cluster glass state in antiferromagnetic background. The field dependent magneto resistance (MR) mechanism at different temperatures is investigated using spin polarized tunneling model of conduction electrons between two adjacent grains at the grain boundaries. For the sample of x=0.5, maximum 83 % change in MR is found at 8 T near MIT which leads the colossal magneto resistance effect.

Das, Proloy T.; Gupta, Kajal; Jana, Paresh Chandra; Nath, Tapan Kumar

2014-04-01

127

The distorted-fcc phase of samarium  

NASA Astrophysics Data System (ADS)

Angle-dispersive x-ray powder diffraction experiments were performed on samarium metal up to 50 GPa. We report that the high-pressure distorted-fcc phase has the same hR24 structure observed in praseodymium, but, unlike praseodymium, samarium does not undergo a transition to a second distorted-fcc phase. We also report a path-dependent transition to a new phase, the structure of which has not yet been determined, which occurs on annealing followed by pressure decrease.

Husband, R. J.; Loa, I.; Munro, K.; McMahon, M. I.

2014-05-01

128

Chlorination of lanthanum oxide.  

PubMed

The reactive system La(2)O(3)(s)-Cl(2)(g) was studied in the temperature range 260-950 °C. The reaction course was followed by thermogravimetry, and the solids involved were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that the reaction leads to the formation of solid LaOCl, and for temperatures above 850 °C, the lanthanum oxychloride is chlorinated, producing LaCl(3)(l). The formation of the oxychloride progresses through a nucleation and growth mechanism, and the kinetic analysis showed that at temperatures below 325 °C the system is under chemical control. The influence of diffusive processes on the kinetics of production of LaOCl was evaluated by studying the effect of the reactive gas flow rate, the mass of the sample, and the chlorine diffusion through the boundary layer surrounding the solid sample. The conversion curves were analyzed and fitted according to the Johnson-Mehl-Avrami description, and the reaction order with respect to the chlorine partial pressure was obtained by varying this partial pressure between 10 and 70 kPa. The rate equation was obtained, which includes the influence of the temperature, chlorine partial pressure, and reaction degree. PMID:22280490

Gaviría, Juan P; Navarro, Lucas G; Bohé, Ana E

2012-03-01

129

Growth and characterization of rare earths doped triglycine sulfate crystals  

Microsoft Academic Search

Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in

A. K. Batra; Padmaja Guggilla; Dewanna Cunningham; M. D. Aggarwal; R. B. Lal

2006-01-01

130

Preparation of porous lanthanum phosphate with templates  

SciTech Connect

Malonic acid, propionic acid, glycine, n-butylamine, and urea were added to the preparation of lanthanum phosphate from lanthanum nitrate and phosphoric acid solutions. All additives were taken into lanthanum phosphate particles. The additives that have a basic site were easy to contain in precipitates. The addition of templates improved the specific surface area of lanthanum phosphate. The amount of pore, with radius smaller than 4 nm, increased with the addition of templates. The remained additives had influence on the acidic properties of lanthanum phosphate.

Onoda, Hiroaki, E-mail: onoda@kpu.ac.jp [Department of Informatics and Environmental Sciences, Faculty of Life and Environmental Sciences, Kyoto Prefectural University, 1-5, Shimogamo Nakaragi-cyo, Sakyo-ku, Kyoto 606-8522 (Japan); Ishima, Yuya [Department of Applied Chemistry, Faculty of Life Sciences, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga 525-8577 (Japan); Takenaka, Atsushi [Department of Materials Science, Yonago National College of Technology, 4448, Hikona-cho, Yonago, Tottori 683-8502 (Japan); Tanaka, Isao [Department of Materials Science and Engineering, Faculty of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)

2009-08-05

131

Enhanced red photoluminescence of samarium in zeolite A by interaction with silver ions  

NASA Astrophysics Data System (ADS)

Photosensitization of samarium (Sm) ions by silver (Ag) ions was achieved by simultaneously doping Sm and Ag in zeolite A cages. Photoluminescence (PL) from the 4G2/5 ? 6H2/7 transition of Sm ions at 600 nm was found to be more than 30 times enhanced by the presence of Ag ions. The excitation wavelength dependence of the PL intensity coincided well with the absorption spectra of Ag ions in the ultraviolet region, indicating that Sm ions are excited by the energy transfer from Ag ions.

gui, Sa chu rong; Imakita, Kenji; Fujii, Minoru; Hayashi, Shinji

2014-02-01

132

Lanthanum carbide-based porous materials from carburization of lanthanum oxide and lanthanum oxalate mixtures  

NASA Astrophysics Data System (ADS)

Porous lanthanum carbide (LaC 2) based materials were prepared from lanthanum oxalate (La 2(C 2O 4) 3), lanthanum oxide (La 2O 3) and graphite mixtures. The molar ratio between La 2O 3 and La 2(C 2O 4) 3 was varied in order to detect the effect of starting mixtures on the porosity of the products. Samples structure and morphology were investigated by means of scanning electron microscopy, equipped with the probe for elemental analysis, (SEM-EDS) and X-ray diffraction spectrometry (XRD). As for the porosity characterization, the amount of total porosity was derived from the comparison between the theoretical and the measured density values, whereas a thorough investigation on the amount of open porosity and pore size distribution was carried out by means of Mercury Intrusion Porosimetry, after carburization and sintering. Emissivity measurements were performed upon carburization and sintering in order to verify the effect of porosity on emissivity values.

Biasetto, L.; Zanonato, P.; Carturan, S.; Di Bernardo, P.; Colombo, P.; Andrighetto, A.; Prete, G.

2008-08-01

133

The features of structural transformations in lanthanum manganites La1-xAxMnO3+? (A = Ca, Sr, Ba)  

NASA Astrophysics Data System (ADS)

In this work, the effect of the ionic radius and concentration of a doping element on the features of the structural transformations in polycrystalline lanthanum manganites, La1-xAxMnO3+? (A = Ca, Sr, Ba), has been studied by Mössbauer spectroscopy and X-ray diffraction analysis. For Mössbauer investigations, a small amount of 57Fe (2 at%) Mössbauer isotope was introduced into the samples. It follows from the analysis of the obtained data that both common features of the structural transformations and differences between them exist in lanthanum manganites depending on ionic radius and concentration of a doping element.

Sedykh, Vera D.

2014-10-01

134

Oxidation of a thin samarium film on iridium  

NASA Astrophysics Data System (ADS)

Thermal desorption spectroscopy has been used to study the interaction of oxygen with a thin (<1 nm) samarium film deposited onto a textured iridium ribbon. Desorption of Sm atoms from Ir surface takes place from various states (chemisorbed, condensed, from compound with iridium, and oxide). The formation of samarium oxide is observed already at room temperature. As the temperature increases to T = 1100 K, a compound of samarium with iridium is formed at the first stage and then oxygen interacts with Sm atoms from this compound and "slow" (compared to the first process) growth of samarium oxide takes place.

Afanas'eva, E. Yu.

2014-06-01

135

Ames Lab 101: Lanthanum Decanting  

ScienceCinema

Ames Laboratory scientist Trevor Riedemann explains the process that allows Ames Laboratory to produce some of the purest lanthanum in the world. This and other high-purity rare-earth elements are used to create alloys used in various research projects and play a crucial role in the Planck satellite mission.

Riedemann, Trevor

2012-08-29

136

Ames Lab 101: Lanthanum Decanting  

SciTech Connect

Ames Laboratory scientist Trevor Riedemann explains the process that allows Ames Laboratory to produce some of the purest lanthanum in the world. This and other high-purity rare-earth elements are used to create alloys used in various research projects and play a crucial role in the Planck satellite mission.

Riedemann, Trevor

2010-01-01

137

Isothermal decomposition of ?-irradiated samarium acetate  

NASA Astrophysics Data System (ADS)

Isothermal decomposition of un-irradiated and pre-?-irradiated samarium acetate has been investigated at different temperatures between 613 and 633 K. Irradiation was observed to enhance the rate of decomposition without modifying the mechanism of thermal decomposition. Thermal decomposition of samarium acetate has been shown to proceed by two-dimensional phase-boundary reaction both for un-irradiated and pre-?-irradiated samples. The enhancement of the decomposition was found to increase with an increase in the ?-ray dose applied to the sample and may be attributed to an increase in point defects and formation of additional nucleation centers generated in the host lattice. Thermodynamic values of the main decomposition process were calculated and evaluated.

Mahfouz, R. M.; Monshi, M. A. S.; Alshehri, S. M.; Abd El-Salam, N. M.

2000-10-01

138

Zn²+La³+ Co-Doped TiO2 Photocatalyst for the Purification of Air  

Microsoft Academic Search

The Zn2+-La3+Co-doped TiO2 photocatalysts prepared by doping lanthanum ion and zinc ion into TiO2 structure in a sol-gel process were shown to be efficient photocatalyst for the purification of Indoor air.The catalyst samples were then characterized by XRD and UV-vis analyses. The analytical results demonstrated that the lanthanum- zinc co-doping could inhibit the phase transformation of TiO2 and enhance the

Liu Baojiang; Cheng Xubang; He Jinxin

2009-01-01

139

40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Lanthanum lead titanium zirconium oxide. 721.10601 Section...Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance...substance identified as lanthanum lead titanium zirconium oxide (PMN...

2013-07-01

140

40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.  

...2014-07-01 false Lanthanum lead titanium zirconium oxide. 721.10601 Section...Substances § 721.10601 Lanthanum lead titanium zirconium oxide. (a) Chemical substance...substance identified as lanthanum lead titanium zirconium oxide (PMN...

2014-07-01

141

MAGNETISM AND ELECTRON TRANSPORT IN MAGNETORESISTIVE LANTHANUM CALCIUM  

E-print Network

MAGNETISM AND ELECTRON TRANSPORT IN MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE A DISSERTATION with the large negative magnetoresistance found in lanthanum calcium manganite. Such large magnetoresistances 4, the intrinsic magnetic and electron transport properties of lanthanum calcium manganite

142

Atomic transition probabilities of neutral samarium  

NASA Astrophysics Data System (ADS)

Absolute atomic transition probabilities from a combination of new emission branching fraction measurements using Fourier transform spectrometer data with radiative lifetimes from recent laser induced fluorescence measurements are reported for 299 lines of the first spectrum of samarium (Sm i). Improved values for the upper and lower energy levels of these lines are also reported. Comparisons to published transition probabilities from earlier experiments show satisfactory and good agreement with two of the four published data sets.

Lawler, J. E.; Fittante, A. J.; Den Hartog, E. A.

2013-11-01

143

Rapid Synthesis of Nonstoichiometric Lanthanum Sulfide  

NASA Technical Reports Server (NTRS)

New process relatively fast and simple. Improved method of synthesizing nonstoichiometric lanthanum sulfide faster and simpler. Product purer because some of prior sources of contamination eliminated.

Matsuda, S.; Shapiro, E.; Danielson, L.; Hardister, H.

1987-01-01

144

Thermoelectric Properties of Lanthanum Sulfide  

NASA Technical Reports Server (NTRS)

Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.

Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.

1987-01-01

145

Initial stages of the interaction with oxygen of samarium thin films grown on the iridium surface  

NASA Astrophysics Data System (ADS)

The interaction of thin (<1 nm) samarium films deposited on a textured iridium ribbon has been investigated by thermal desorption spectrometry. Samarium atoms deposited at T = 300 K desorb in three phases associated with the formation of a submonolayer samarium coverage on iridium, a compound of samarium with iridium, and a multilayer samarium film. The interaction with oxygen leads to the appearance of a new desorption phase, which is associated with the formation of samarium oxide. Oxidation of samarium is observed during exposure in oxygen already at room temperature. An increase in temperature of the iridium ribbon, at which exposure in oxygen occurs, to T = 1100 K leads to the formation of the compound of samarium with iridium. Further, the film of the compound decomposes in the course of interaction with oxygen, and samarium oxide grows on the Ir surface.

Afanas'eva, E. Yu.

2014-08-01

146

SOLITONS AND OPTICAL FIBERS: Self-Q-switched ytterbium-doped cladding-pumped fibre laser  

NASA Astrophysics Data System (ADS)

A self-Q-switched ytterbium-doped double-clad fibre laser is described. A samarium-doped fibre is used as a filter for protecting a pump source. A fibre coupler is employed to obtain a nonlinear feedback. The mechanism of pulse formation in the laser is considered, and the dependence of its output pulse on the coupler parameters is studied.

Grukh, Dmitrii A.; Kurkov, Andrei S.; Razdobreev, I. M.; Fotiadi, A. A.

2002-11-01

147

Lanthanum Chloride Scintillator for X-ray Detection  

NASA Astrophysics Data System (ADS)

In this presentation we describe the testing of a new cerium doped Lanthanum Chloride crystal (LaCl3:Ce), which makes an excellent scintillation material for X-ray counting applications. Detailed measurements were taken to determine the properties of the scintillator over an energy range of 5 to 60KeV; the results demonstrate that, when used with an appropriate PMT, the crystal sustains high count rates, minimal dead time and good energy resolution. For example an energy resolution of 35% (FWHM) was achieved at 22KeV and count rates of up to 1MHz are possible without dead-time correction. A comparison of LaCl3:Ce with two conventional scintillation materials, YAP:Ce and NaI(Tl) is also presented, which shows that that LaCl3:Ce offers a good balance of performance parameters for X-ray experiments.

Martin, T.; Allier, C.; Bernard, F.

2007-01-01

148

Field free, directly heated lanthanum boride cathode  

DOEpatents

A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic fields which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

Leung, Ka-Ngo (Hercules, CA); Moussa, David (San Francisco, CA); Wilde, Stephen B. (Pleasant Hill, CA)

1991-01-01

149

Field free, directly heated lanthanum boride cathode  

DOEpatents

A directly heated cylindrical lanthanum boride cathode assembly is disclosed which minimizes generation of magnetic field which would interfere with electron emission from the cathode. The cathode assembly comprises a lanthanum boride cylinder in electrical contact at one end with a central support shaft which functions as one electrode to carry current to the lanthanum boride cylinder and in electrical contact, at its opposite end with a second electrode which is coaxially position around the central support shaft so that magnetic fields generated by heater current flowing in one direction through the central support shaft are cancelled by an opposite magnetic field generated by current flowing through the lanthanum boride cylinder and the coaxial electrode in a direction opposite to the current flow in the central shaft.

Leung, Ka-Ngo; Moussa, D.; Wilde, S.B.

1987-02-02

150

Samarium-monosulfide-based semiconductor strain gages for spacecraft-strain transformation  

NASA Astrophysics Data System (ADS)

The theoretical basis of the measured strain transform by strain gages made of samarium monosulfide and other semiconductors in increments of electrical resistance is considered. Specific structures of semiconductor strain gages based on samarium monosulfide are presented.

Volodin, N. M.; Mishin, Yu. N.; Kaminskii, V. V.; Zakharov, Yu. V.

2013-12-01

151

Compact lanthanum hexaboride hollow cathode.  

PubMed

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB(6) hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current. PMID:20815605

Goebel, Dan M; Watkins, Ronald M

2010-08-01

152

Electromagnetic containerless reaction of samarium with cobalt for the formation of samarium-cobalt alloys  

NASA Technical Reports Server (NTRS)

The electromagnetic levitation technique has been used to obtain nearly stoichiometric SmCo5, with the reaction temperature controlled by a gas jet. The results of several experiments carried out at a 450 kHz, 25 kw RF power levitation facility using different reaction times and cooling rates are presented. It is shown that reaction rates achieved with the levitation technique are larger than the expected diffusion rate in the system liquid samarium-solid cobalt. It is also shown that substantial mixing occurs in the RF-levitated melt.

Chang, C. W.; Das, D. K.; Kumar, K.; Frost, R. T.

1982-01-01

153

Ris-R-1242(EN) Lanthanum Manganate Based Cathodes  

E-print Network

Risø-R-1242(EN) Lanthanum Manganate Based Cathodes for Solid Oxide Fuel Cells Mette Juhl Jørgensen to minimise the voltage drop in the cathode. The electrodes contained a composite layer made from lanthanum

154

Samarium-145 and its use as a radiation source  

DOEpatents

The present invention covers a new radiation source, samarium-145, with radiation energies slightly above those of I-125 and a half-life of 340 days. The samarium-145 source is produced by neutron irradiation of SM-144. This new source is useful as the implanted radiation source in photon activation therapy of malignant tumors to activate the stable I-127 contained in the IdUrd accumulated in the tumor, causing radiation sensitization and Auger cascades that irreperably damage the tumor cells. This new source is also useful as a brachytherapy source.

Fairchild, Ralph G. (Setauket, NY); Laster, Brenda H. (Plainview, NY); Packer, Samuel (Great Neck, NY)

1989-01-01

155

The Basis for Developing Samarium AMS for Fuel Cycle Analysis  

SciTech Connect

Modeling of nuclear reactor fuel burnup indicates that the production of samarium isotopes can vary significantly with reactor type and fuel cycle. The isotopic concentrations of {sup 146}Sm, {sup 149}Sm, and {sup 151}Sm are potential signatures of fuel reprocessing, if analytical techniques can overcome the inherent challenges of lanthanide chemistry, isobaric interferences, and mass/charge interferences. We review the current limitations in measurement of the target samarium isotopes and describe potential approaches for developing Sm-AMS. AMS sample form and preparation chemistry will be discussed as well as possible spectrometer operating conditions.

Buchholz, B A; Biegalski, S R; Whitney, S M; Tumey, S J; Weaver, C J

2008-10-13

156

Determination of lanthanum by flame photometric titration.  

PubMed

The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere. PMID:18960392

Svehla, G; Slevin, P J

1968-09-01

157

Discovery of samarium, europium, gadolinium, and terbium isotopes  

SciTech Connect

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E.; Thoennessen, M., E-mail: thoennessen@nscl.msu.edu

2013-01-15

158

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes  

E-print Network

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

E. May; M. Thoennessen

2012-01-19

159

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes  

E-print Network

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E

2012-01-01

160

Ketyl-allene cyclizations promoted by samarium(II) iodide.  

PubMed

[reaction: see text] Samarium(II) iodide has proven to be an effective reagent for intramolecular reductive coupling reactions. Previous investigations of intramolecular ketyl-olefin coupling reactions provided carbocycles in excellent yield and good diastereoselectivity. This method has been extended to ketyl cyclizations with allenes. Substrates leading to both carbocycles and heterocycles in a selective manner are explored. PMID:15787552

Molander, Gary A; Cormier, Elizabeth Pollina

2005-04-01

161

Investigation into Nanostructured Lanthanum Halides and CeBr3 for Nuclear Radiation Detection  

SciTech Connect

Nanocomposites may enable the use of scintillator materials such as cerium-doped lanthanum fluoride (LaF3:Ce) and cerium bromide (CeBr3) without requiring the growth of large crystals [1]. Nanostructured detectors may allow us to engineer immensely sized detectors of flexible form factors that will have a broad energy range and an energy resolution sufficient to perform isotopic identification. Furthermore, nanocomposites are easy to prepare and very low in cost. It is much less costly to use nanocomposites rather than grow large whole crystals of scintillator materials; with nanocomposites fabricated on an industrial scale, costs are even less. Nanostructured radiation scintillator detectors may improve quantum efficiency and provide vastly improved detector form factors. Quantum efficiencies up to 60% have been seen in photoluminescence from silicon nanocrystals in a densely-packed ensemble [2]. We have fabricated nanoparticles with sizes <10 nm and characterized their nanocomposite radiation detector properties. This work investigates the properties of the nanostructured radiation scintillator in order to extend the gamma energy response on both low- and high-energy regimes by demonstrating the ability to detect low-energy x-rays and relatively high-energy activation prompt gamma rays simultaneously using nanostructured lanthanum bromide, lanthanum fluoride, or CeBr3. Preliminary results of this investigation are consistent with a significant response of these materials to nuclear radiation.

Guss, P. P., Guise, R., Mukhopadhyay, S., Yuan, D.

2011-07-06

162

Strontium and samarium diffusion in diopside  

NASA Astrophysics Data System (ADS)

The volume chemical diffusion of trace amounts of Sr in diopside has been measured as a function of temperature (1100-1300°C), pressure (1 bar-20 kbar), crystallographic direction, and composition. Three experimental/analytical techniques were employed: radiotracer and sectioning; stable tracer and ion microprobe; and Rutherford back-scattering spectroscopy. Comparison of the three yielded excellent agreement. Both natural and synthetic single crystal samples were used with results in the natural diopside giving diffusivities approximately two orders of magnitude greater than those in the man-made crystals. Samarium diffusion in the synthetic crystals was also examined with the ion probe technique with results similar to Sr. Arrhenius relations for diffusion ( D = D0exp[- ?Ha/ RT]) were calculated for different pressures and analytical techniques, and activation volumes (gD Va) were derived from the equation D = D' exp[- P?Va/ RT]. Values of ? Va were negative for Sr diffusion. An empirical relation describing the temperature and pressure dependence of D for Sr in the c direction of the synthetic samples is: D( P, T) = 1200 ( cm2/ sec) exp[-122 ( Kcal/ mol)/ RT (° K)] exp[- P ( bar)/(2.94 T - 4640) R]. The expression for DSr in the natural samples ( c direction) at one atmosphere is: D(0, T) = 54 ( cm2/ sec) exp[-97 ( Kcal/ mol)/ RT (° K)]. A single compensation trend for all the data was evident for all values of D0 and ? Ha in the synthetic crystals. A number of models of geologic processes were investigated in light of the present data. Closure temperatures ( Tc) were calculated for examples of mineral-mineral age-dating and trace element geothermometry. High values of Tc indicate that pyroxenes record emplacement events and are generally not disturbed unless a fluid enters the system. Isotopic equilibration times were examined for lower crustal xenoliths and the mantle source region for MORB using the formula of Hofmann and Hart (1978). Equilibration was shown to be too fast for production of isotopic anomalies in MORB via disequilibrium melting. Also. reasonable residence times at lower crustal temperatures were shown to produce the mineralogical-scale isotopic homogeneity observed in a crustal xenolith from Kilbourne Hole, New Mexico.

Sneeringer, Mark; Hart, Stanley R.; Shimizu, Nobumichi

1984-08-01

163

An experimental analysis of a doped lithium fluoride direct absorption solar receiver  

NASA Technical Reports Server (NTRS)

An experimental analysis of two key elements of a direct absorption solar receiver for use with Brayton solar dynamic systems was conducted. Experimental data are presented on LiF crystals doped with dysprosium, samarium, and cobalt fluorides. In addition, a simulation of the cavity/window environment was performed and a posttest inspection was conducted to evaluate chemical reactivity, transmissivity, and condensation rate.

Kesseli, James; Pollak, Tom; Lacy, Dovie

1988-01-01

164

Self-activating and doped tantalate phosphors.  

SciTech Connect

An ideal red phosphor for blue LEDs is one of the biggest challenges for the solid-state lighting industry. The appropriate phosphor material should have good adsorption and emission properties, good thermal and chemical stability, minimal thermal quenching, high quantum yield, and is preferably inexpensive and easy to fabricate. Tantalates possess many of these criteria, and lithium lanthanum tantalate materials warrant thorough investigation. In this study, we investigated red luminescence of two lithium lanthanum tantalates via three mechanisms: (1) Eu-doping, (2) Mn-doping and (3) self-activation of the tantalum polyhedra. Of these three mechanisms, Mn-doping proved to be the most promising. These materials exhibit two very broad adsorption peaks; one in the UV and one in the blue region of the spectrum; both can be exploited in LED applications. Furthermore, Mn-doping can be accomplished in two ways; ion-exchange and direct solid-state synthesis. One of the two lithium lanthanum tantalate phases investigated proved to be a superior host for Mn-luminescence, suggesting the crystal chemistry of the host lattice is important.

Nyman, May Devan; Rohwer, Lauren Elizabeth Shea

2011-01-01

165

Adsorption of lanthanum to goethite in the presence of gluconate  

SciTech Connect

Adsorption of Lanthanum to Goethite in the Presence of Gluconic Acid L. C. HULL,1 S. E. PEPPER2 AND S. B. CLARK2 1Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (hulllc@inel.gov) 2Washington State University, Pullman, WA (spepper@wsu.edu), (s_clark@wsu.edu) Lanthanide and trivalent-actinide elements in radioactive waste can pose risks to humans and ecological systems for many years. Organic complexing agents, from natural organic matter or the degradation of waste package components, can alter the mobility of these elements. We studied the effect of gluconic acid, as an analogue for cellulose degradation products, on the adsorption of lanthanum, representing lanthanide and trivalent-actinide elments, to goethite, representing natural iron minearals and degradation products of waste packages. Batch pH adsorption edge experiments were conducted with lanthanum alone, and with lanthanum and gluconate at a 1:1 mole ratio. Lanthanum concentrations studied were 0.1, 1, and 10 mM, covering a range from 10% to 1000% of the calculated available adsorption sites on goethite. In the absence of gluconate, lanthanum was primarily present in solution as free lanthanum ion. With gluconate present, free lanthanum concentration in solution decreased with increasing pH as step-wise deprotonation of the gluconate molecule increased the fraction lanthanum complexed with gluconate. Adsorption to the goethite surface was represented with the diffuse double-layer model. The number of adsorption sites and the intrinsic binding constants for the surface complexes were estimated from the pH adsorption edge data using the computer code FITEQL 4.0. Two surface reactions were used to fit the adsorption data in the absence of gluconate. A strong binding site with no proton release and a much higher concentration of weak binding sites with release of two protons per lanthanum adsorbed. The adsorption of lanthanum was not measurably affected by the presence of gluconate below pH 7. At pH values above 7, however, gluconate doubled the maximum amount of lanthanum adsorbed. This was modeled by including a ternary complex with a lanthanum-gluconate complex binding to a lanthanum bound on the surface. No spectroscopic data were obtained to verify the identify of the surface complexes. The presence of gluconate did not appear to affect the formation of solid lanthanum hydroxide at elevated pH and millimolar lanthanum concentrations. The effect of organic molecules on the mobility of lanthanides and trivalent-actinides cannot be simply described with equilibrium thermodynamic models based on currently available data.

Hull, Laurence C.; Sarah Pepper; Sue Clark

2005-05-01

166

Lattice dynamics of the rare-earth element samarium  

NASA Astrophysics Data System (ADS)

The lattice dynamics of samarium is determined by in situ low-temperature nuclear inelastic scattering on a single crystalline (0001)Sm film, a polycrystalline Sm foil, and by first-principles theory. The ab initio calculated phonon dispersion relations and phonon density of states for the Sm-type structure and the double hexagonal-close-packed (dhcp) lattice, characteristic for light lanthanides, are compared. The dhcp unit cell, which is a factor of 2.24 smaller in height, exhibits more pronounced vibrational anisotropy in comparison to the Sm-type structure. The analysis reveals a minor influence of the spin-orbit coupling in the Sm atom on the lattice dynamics. A broadening of the longitudinal peak, not found in the calculations, suggests the influence of electron correlations on lattice dynamics in metallic samarium.

Bauder, Olga; Piekarz, Przemys?aw; Barla, Alessandro; Sergueev, Ilya; Rüffer, Rudolf; ?a?ewski, Jan; Baumbach, Tilo; Parlinski, Krzysztof; Stankov, Svetoslav

2013-12-01

167

Synthesis, structural and spectroscopic investigations of nanostructured samarium oxalate crystals.  

PubMed

Nanostructured samarium oxalate crystals were prepared via microwave assisted co-precipitation method. The crystal structure and morphology of the sample were analyzed using X-ray powder diffraction, Scanning electron microscopy and Transmission electron microscopy. The presence of functional groups is ascertained by Fourier transform infrared spectroscopy. Samarium oxalate nanocrystals of average size 20 nm were aggregated together to form nano-plate structure in sub-microrange. Detailed spectroscopic investigation of the prepared phosphor material was carried out by Judd-Ofelt analysis based on the UV-Visible-NIR absorption spectra and photoluminescence emission spectra. The analysis reveals that the transition from energy level (4)G5/2 to (6)H7/2 of Sm(3+) ion has maximum branching ratio and the corresponding orange emission can be used for display applications. PMID:24334063

Vimal, G; Mani, Kamal P; Biju, P R; Joseph, Cyriac; Unnikrishnan, N V; Ittyachen, M A

2014-03-25

168

Synthesis, structural and spectroscopic investigations of nanostructured samarium oxalate crystals  

NASA Astrophysics Data System (ADS)

Nanostructured samarium oxalate crystals were prepared via microwave assisted co-precipitation method. The crystal structure and morphology of the sample were analyzed using X-ray powder diffraction, Scanning electron microscopy and Transmission electron microscopy. The presence of functional groups is ascertained by Fourier transform infrared spectroscopy. Samarium oxalate nanocrystals of average size 20 nm were aggregated together to form nano-plate structure in sub-microrange. Detailed spectroscopic investigation of the prepared phosphor material was carried out by Judd-Ofelt analysis based on the UV-Visible-NIR absorption spectra and photoluminescence emission spectra. The analysis reveals that the transition from energy level 4G5/2 to 6H7/2 of Sm3+ ion has maximum branching ratio and the corresponding orange emission can be used for display applications.

Vimal, G.; Mani, Kamal P.; Biju, P. R.; Joseph, Cyriac; Unnikrishnan, N. V.; Ittyachen, M. A.

2014-03-01

169

Beta-elimination reactions by using samarium diiodide.  

PubMed

The development of methodologies for the formation of carbon-carbon double bonds could be considered one of the most important challenges in organic synthesis. To this end, beta-elimination reactions in 1,2-difunctionalised substrates have been one of the most important means of generating C=C bonds. This review is intended to highlight the use of SmI2 in beta-elimination procedures, such that the organization of this revision highlights conventional beta-elimination processes which are promoted by samarium diiodide. The synthetic applications of SmI2 will be covered, and 1,2-elimination reactions which are involved in sequential reactions promoted by samarium diiodide, will also be illustrated. These methodologies along with the more recent developments in the area are discussed in this tutorial review. PMID:15592625

Concellón, Jose M; Rodríguez-Solla, Humberto

2004-11-30

170

Ambi-site substitution of Mn in lanthanum germanate apatites  

SciTech Connect

A neutron diffraction study at 4 K of the Mn doped lanthanum germanate apatite-type oxide ion conductor of nominal starting composition 'La{sub 9.5}Mn{sub 0.5}(GeO{sub 4}){sub 6}O{sub 2.75}' is reported. The structure was refined in space group P6{sub 3}/m, although high thermal displacement parameters were observed for the oxide ion sites (particularly O3, and O4). Reduced thermal displacement parameters were obtained by splitting the O3 site, and allowing the O4 oxygen to move off site, which may indicate local regions of lower symmetry within the structure. In addition, the data suggested ambi-site substitution of Mn, with it being present on both the Ge site and the La site. Assuming no change in La:Mn:Ge ratio, a composition of La{sub 9.18}Mn{sub 0.28}(GeO{sub 4}){sub 5.8}(MnO{sub 4}){sub 0.2}O{sub 2} was determined. As such there are nominally no interstitial oxide ions, but rather cation vacancies on the La site. Therefore, the high conductivity for this sample is most likely related to the introduction of Frenkel-type defects at higher temperature, as previously proposed for other apatite-type systems containing vacancies on the La site.

Kendrick, E. [Chemical Sciences, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Knight, K.S. [ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX (United Kingdom); Slater, P.R., E-mail: p.r.slater@bham.ac.uk [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2009-08-05

171

Effects of lanthanum in cellular systems  

Microsoft Academic Search

Lanthanum belongs to the group of elements known as “lanthanons,” which also includes cerium, europium, promethium, and thulium.\\u000a It is the most electropositive element of the rare earth group, is uniformly trivalent, and is similar in its chemical properties\\u000a to the alkaline earth elements. The effects of this element and its compounds on cellular systems are of considerable interest\\u000a because

Tandra Das; Archana Sharma; Geeta Talukder

1988-01-01

172

Microanalysis of a grain boundary's blocking effect in lanthanum silicate electrolyte for intermediate-temperature solid oxide fuel cells.  

PubMed

In order to study the grain boundary's (GB's) blocking effect in lanthanum silicate electrolyte, high density Al-doped apatite-type lanthanum silicate was synthesized and characterized by impedance spectroscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Microstructural characterization indicated that the GB's blocking effect was an intrinsic effect. Further microanalysis shows that the GB region is rich in La and poor in Si in comparing with the grain interior (GI). Our discussion suggested that the chemical variation from GI to GB, on the one hand, could degrade the GB region's conductivity; on the other hand, it introduced a strong space-charge effect at GBs. The latter was believed to play a dominant role in the GB's blocking effect. PMID:23697778

Yan, Pengfei; Mineshige, Atsushi; Mori, Toshiyuki; Wu, Yuanyuan; Auchterlonie, Graeme John; Zou, Jin; Drennan, John

2013-06-12

173

Influence of samarium doping on electronic and magneto-transport properties of La{sub 0.9?x}Sm{sub x}Sr{sub 0.1}MnO{sub 3} (0.1?x?0.5) nanoparticles  

SciTech Connect

We report detailed field dependent electronic- (?-T) and magneto- transport (MR-H) studies of La{sub 1?x}Sm{sub x}Sr{sub 0.1}MnO{sub 3} (0.1?x?0.5) nanoparticles. Doping induced disorder at La site is observed in field dependent ?-T measurements of the sample. At low doping side, nice metal to insulator transition (MIT) peak appears in ?-T data whereas with increasing of Sm{sup +3} contents, metallic behavior is suppressed under the insulating background although a weak signature of MIT is found. Anomalous resistive nature of the samples with increasing of x can be explained in such a way that doping at nonmagnetic La site with magnetic Sm+3 ion induces an extra magnetic coupling in the system which changes the long range ferromagnetic ordering to spin glass/cluster glass state in antiferromagnetic background. The field dependent magneto resistance (MR) mechanism at different temperatures is investigated using spin polarized tunneling model of conduction electrons between two adjacent grains at the grain boundaries. For the sample of x=0.5, maximum 83 % change in MR is found at 8 T near MIT which leads the colossal magneto resistance effect.

Das, Proloy T., E-mail: dasproloy@phy.iitkgp.ernet.in; Nath, Tapan Kumar [Department of Physics and Meteorology, IIT Kharagpur, Kharagpur-721302, W.B. (India); Gupta, Kajal; Jana, Paresh Chandra [Department of Physics and Techno Physics, Vidyasagar University, Midnapore-721102, W.B. (India)

2014-04-24

174

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications  

E-print Network

Atomic layer deposition of lanthanum aluminum oxide nano-laminates for electrical applications 12 March 2004; published online 3 May 2004 Lanthanum aluminum oxide thin films were grown by atomic layer deposition from a lanthanum precursor, tris(N,N -diisopropylacetamidinato lanthanum (La(i PrAMD)3

175

Atomic Layer Deposition of Lanthanum-Based Ternary Oxides Hongtao Wang,a  

E-print Network

Atomic Layer Deposition of Lanthanum-Based Ternary Oxides Hongtao Wang,a Jun-Jieh Wang,b Roy Gordon 02138, USA c Rohm and Haas Electronic Materials, North Andover, Massachusetts 01845, USA LanthanumV , and low leakage.3 Recent reports show that lanthanum-based ternary ox- ides, such as lanthanum scandate La

176

Co-doped Barium Phosphate Glass  

NASA Astrophysics Data System (ADS)

Co-doping of a P2O5:BaO glass matrix with divalent tin and trivalent samarium ions has been realized by the melt-quenching technique with the purpose of investigating the material's luminescent properties. Photoluminescence excitation spectra obtained by monitoring Sm3+ 4G5/2 emission showed a broad excitation band around 290 nm (absent in a Sm3+-doped reference), typical of donor/acceptor energy transfer. Under such excitation, the material exhibits a reddish-white emission. Time-resolved spectra recorded under the 290-nm excitation (non-resonant with Sm3+ excitation peaks) exposed a broad blue-white band characteristic of twofold-coordinated Sn centers and orange-red emission bands of Sm3+ ions, which appeared well separated in time in accord with their emission decay dynamics. Consequently, the data indicate that light absorption occurs at Sn centers (donors) followed by energy transfer to samarium ions (acceptors) which results in populating the 4G5/2 emitting state in Sm3+. Energy transfer pathways likely resulting in the sensitization of Sm3+ photoluminescence are discussed. Results are put into context in terms of the potential of SnO and rare-earth co-doped barium phosphate glasses for use in white light-emitting devices.

Jiménez, J. A.

2014-09-01

177

The Exchange Parameters in Lanthanum Manganites  

E-print Network

The spin-wave spectrum in the metallic ferromagnetic lantha-num cubic manganites was investigated. The interactions with four coordination spheres (32 neighbors) were taken into ac-count. The Heisenberg superexchange between all manganese ions as well as double exchange between the manganese ions with different valence were under consideration. The obtained magnon spectrum permits to investigate dispersion relations along an any crystallographic directions. This possibility was used for the numerical evaluation of the exchange parameters in the compounds La0.75Ca0.25MnO3 and La0.70Ca0.30MnO3 from the inelastic neutron scattering data.

B. V. Karpenko; A. V. Kuznetzov

2008-05-20

178

Lutetium-doped EuO films grown by molecular-beam epitaxy  

SciTech Connect

The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

Melville, A.; Heeg, T. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Mairoser, T.; Schmehl, A. [Zentrum fuer elektronische Korrelationen und Magnetismus, Universitaet Augsburg, Universitaetsstrasse 1, D-86159 Augsburg (Germany); Shai, D. E.; Monkman, E. J.; Harter, J. W. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Hollaender, B.; Schubert, J. [Peter Gruenberg Institute, PGI 9-IT, JARA-FIT, Research Centre Juelich, D-52425 Juelich (Germany); Shen, K. M. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States); Mannhart, J. [Max Planck Institute for Solid State Research, D-70569 Stuttgart (Germany); Schlom, D. G. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States)

2012-05-28

179

Samarium Diiodide-Mediated Reactions in Total Synthesis  

PubMed Central

Introduced by Henri Kagan more than three decades ago, samarium diiodide (SmI2) has found increasing applications in chemical synthesis. This single-electron reducing agent has been particularly useful in C–C bond formations, including those found in total synthesis endeavors. This Review highlights selected applications of SmI2 in total synthesis, with special emphasis on novel transformations and mechanistic considerations. The examples discussed are both illustrative of the power of this reagent in complex molecule construction and inspirational for the design of synthetic strategies toward such targets, both natural and designed. PMID:19714695

Nicolaou, K. C.; Ellery, Shelby P.; Chen, Jason S.

2009-01-01

180

Selective reductive transformations using samarium diiodide-water.  

PubMed

Samarium diiodide (SmI(2)) is one of the most important reductive electron transfer reagents available in the laboratory. Key to the popularity of SmI(2) is the ability of additives and co-solvents to tune the properties of the reagent. Over the last decade water has emerged as a particularly valuable additive, opening up new chemical space and leading to the discovery of unprecedented selectivity and new reactions promoted by SmI(2). In this Feature Article we review recent progress in the application of SmI(2)-H(2)O systems, with an emphasis on mechanistic considerations and the development of new transformations. PMID:21879049

Szostak, Michal; Spain, Malcolm; Parmar, Dixit; Procter, David J

2012-01-11

181

Contamination of YBCO bulk superconductors by samarium and ytterbium  

NASA Astrophysics Data System (ADS)

Y-Ba-Cu-O (YBCO, Y-123) single-grain bulk superconductors with a nominal composition Y1.5Ba2Cu3Ox and 1 wt% CeO2 addition were prepared by the optimized Top-Seeded Melt-Growth process. Small single-crystalline pieces cut from the SmBa2Cu3Oy (Sm-123) bulk were used for seeding of epitaxial growth. Wavelength-dispersive spectrometry (WDS) confirmed that prepared samples contain besides samarium from the seed also ytterbium from the substrate. The influence of maximum melting temperature, Tmax and dwell time on the contamination of the bulk samples was studied. Y2BaCuO5 (Y-211) barriers against samarium diffusion from the seed to melted sample were tested. Using a NdBa2Cu3Oz (Nd-123) seed and a combination of Y2O3 and Yb2O3 substrate led to a high critical temperature (Tc(50%) = 91.54 K) of prepared sample.

Volochova, D.; Jurek, K.; Radusovska, M.; Piovarci, S.; Antal, V.; Kovac, J.; Jirsa, M.; Diko, P.

2014-01-01

182

The energetics of lanthanum tantalate materials  

SciTech Connect

Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta{sub 6}O{sub 19}]{sup 8-}, has yielded a new phase, La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 {sup o}C, which converts to a previously reported LaTaO{sub 4} polymorph at 1200 {sup o}C. The stabilities of La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} (LaTa-OH), the intermediate LaTaO{sub 4} polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for LaTa-OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO{sub 4} and Ln{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases. - Graphical abstract: The energetics of three lanthanum tantalates were investigated by the high-temperature oxide melt solution calorimetry. The enthalpies of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}, LaTaO{sub 4} (850 {sup o}C), and LaTaO{sub 4} (1200 {sup o}C), respectively. These results indicate that the intermediate phase, LaTaO{sub 4} (850 {sup o}C), is the most stable in energy. Display Omitted

Forbes, Tori Z., E-mail: tmforbes@ucdavis.ed [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, CA 95616 (United States); Nyman, May, E-mail: mdnyman@sandia.go [Sandia National Laboratory, POB 5800, Albuquerque, NM 87185 (United States); Rodriguez, Mark A., E-mail: marodri@sandia.go [Sandia National Laboratory, POB 5800, Albuquerque, NM 87185 (United States); Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.ed [Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis, Davis, CA 95616 (United States)

2010-11-15

183

INTERCELLULAR SPACES OF THE HUMAN EPIDERMIS AS DEMONSTRATED WITH LANTHANUM  

Microsoft Academic Search

In normal human epidermis, lanthanum penetrated into the basal lamina-basal cell interspaces, including half-desmosome areas, non-specific intercellular junctions, desmosomes, close approximations and most of the occluding zonules and macules. The majority of what were previously claimed to be tight junctions were permeated by lanthanum, revealing that they were actually gap junctions. Maculae occludentes which follow desmosomes, for instance, were found

Ken Hashimoto

1971-01-01

184

Lanthanum Halide Nanoparticle Scintillators for Nuclear Radiation Detection  

SciTech Connect

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum tribromide, lanthanum trifluoride, or cerium tribromide. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

Guss, P. P., Guise, R., Yuan, D., Mukhopadhyay, S., O'Brien, R., Lowe, D.

2013-02-01

185

Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

Thermionic conversion data obtained from a variable gap cesium diminiode with a hot pressed, sintered lanthanum hexaboride emitter and an arc melted lanthanum hexaboride collector are presented. Performance curves cover a range of temperatures: emitter 1500 to 1700 K, collector 750 to 1000 K, and cesium reservoir 370 to 510 K. Calculated values of emitter and collector work functions and barrier index are also given.

Kroeger, E. W.; Bair, V. L.; Morris, J. F.

1978-01-01

186

Samarium-146 in the early solar system - Evidence from neodymiun in the Allende meteorite  

NASA Technical Reports Server (NTRS)

A carbon-chromite fraction from the Allende C3V chondrite shows strikingly large isotopic enrichments of neodymium-142 (0.47 percent) and neodymium-143 (36 percent). Both apparently formed by alpha decay of samarium-146 and samarium-147 (half-lives 1.03 x 10 to the 8th and 1.06 x 10 to the 11th years), but the isotopic enrichment was greatly magnified by recoil of residual nuclei into a carbon film surounding the samarium-bearing grains. These data provide an improved estimate of the original abundance of extinct samarium-146 in the early solar system, Sm-146/Sm-144 = (4.5 + or - 0.5) x 10 to the -3rd, higher than predicted by some models of p-process nucleosynthesis. It may be possible to use this isotopic pair as a chronometer of the early solar system.

Lugmair, G. W.; Shimamura, T.; Lewis, R. S.; Anders, E.

1983-01-01

187

EUROPIUM, SAMARIUM, AND NEODYMIUM ISOTOPIC FRACTIONS IN METAL-POOR STARS Ian U. Roederer,1  

E-print Network

EUROPIUM, SAMARIUM, AND NEODYMIUM ISOTOPIC FRACTIONS IN METAL-POOR STARS Ian U. Roederer,1 James E Received 2007 August 15; accepted 2007 November 12 ABSTRACT We have derived isotopic fractions of europium

Cowan, John

188

Effect of samarium nanoparticles on the electrical transport properties of polyaniline  

NASA Astrophysics Data System (ADS)

A comprehensive study of the effect of samarium nanoparticles on electrical transport properties of polyaniline has been reported. Samples are prepared by chemical oxidative polymerization of aniline in the presence of samarium nanoparticles and characterized by XRD, FESEM, EDS, HRTEM and UV-Vis spectrometer. When the samarium content in polyaniline matrix increases, energy band gap decreases and conductivity increases by four orders of magnitude. A transformation of negative to positive magnetoconductivity has been observed by incorporating samarium nanoparticles in polyaniline matrix. Two types of activation behavior have been observed from the dielectric relaxation behavior. AC conductivity strongly depends on magnetic field. Although, at present, no theoretical model is found in literature to explain directly the behavior of ac conductivity in the presence of magnetic field, it may be due to the change of grain and interfacial boundary resistances by magnetic field.

Gupta, K.; Mukherjee, P. S.; Meikap, A. K.; Jana, P. C.

2014-06-01

189

Samarium diiodide induced ketyl-(het)arene cyclisations towards novel N-heterocycles.  

PubMed

In this tutorial review we discuss recent advances in the field of ketyl-(het)arene cyclisations promoted by samarium diiodide and related processes. Couplings of samarium ketyls with carbon-carbon multiple bonds are perhaps the most useful reactions to create carbocycles and heterocycles of various ring sizes. They have also successfully been exploited for the synthesis of biologically active compounds or natural products. In this article we intend to summarise our diversity orientated approaches towards nitrogen heterocycles and emphasize other approaches with SmI(2) as well as electrochemical cyclisation methods providing similar N-heterocycles. We also briefly discuss our recently published formal total synthesis of strychnine employing a new samarium diiodide induced cascade reaction as key step. All these examples demonstrate the high synthetic potential of samarium ketyl-(het)arene cyclisations for the preparation of various types of important heterocyclic compounds. PMID:21243132

Beemelmanns, Christine; Reissig, Hans-Ulrich

2011-05-01

190

Sintering aid for lanthanum chromite refractories  

DOEpatents

An electronically conductive interconnect layer for use in a fuel cell or other electrolytic device is formed with sintering additives to permit densification in a monolithic structure with the electrode materials. Additions including an oxide of boron and a eutectic forming composition of Group 2A metal fluorides with Group 3B metal fluorides and Group 2A metal oxides with Group 6B metal oxides lower the required firing temperature of lanthanum chromite to permit densification to in excess of 94% of theoretical density without degradation of electrode material lamina. The monolithic structure is formed by tape casting thin layers of electrode, interconnect and electrolyte materials and sintering the green lamina together under common densification conditions.

Flandermeyer, Brian K. (Bolingbrook, IL); Poeppel, Roger B. (Glen Ellyn, IL); Dusek, Joseph T. (Downers Grove, IL); Anderson, Harlan U. (Rolla, MO)

1988-01-01

191

Lanthanum tetrazinc, LaZn4.  

PubMed

The structure of lanthanum tetrazinc, LaZn(4), has been determined from single-crystal X-ray diffraction data for the first time, approximately 70 years after its discovery. The compound exhibits a new structure type in the space group Cmcm, with one La atom and two Zn atoms occupying sites with m2m symmetry, and one Zn atom occupying a site with 2.. symmetry. The structure is closely related to the BaAl(4), La(3)Al(11), BaNi(2)Si(2) and CaCu(5) structure types, which can be presented as close-packed arrangements of 18-vertex clusters, in this case LaZn(18). The kindred structure types contain related 18-vertex clusters around atoms of the rare earth or alkaline earth metal. PMID:22669182

Oshchapovsky, Igor; Pavlyuk, Volodymyr; Dmytriv, Grygoriy; Griffin, Alexandra

2012-06-01

192

Properties and applications of doped chalcogenide glasses  

NASA Astrophysics Data System (ADS)

The effect of low amounts of antimony, tin, dysprosium, samarium and manganese on structure and optical properties of chalcogenide glassy semiconductors As2S3 and As2Se3 is investigated. The fundamental absorption edge shifts to longer wavelength with doping; the largest shift was observed for doped chalcogenide glasses. Near the edge absorption the impurity affects strongly the slope and the magnitude of the weak absorption tail. The steady-state and transient photoconductivity characteristics are adequately interpreted in frame of the model, in which transport and recombination of non-equilibrium holes are controlled by exponentially distributed hole traps with the distribution parameter T*, depending on the glass composition. Some application of amorphous chalcogenide thin film structures as registration media are presented.

Iovu, Mihai S.

2003-10-01

193

Pulsed laser deposition of lanthanum monosulfide thin films on silicon substrates*  

E-print Network

Pulsed laser deposition of lanthanum monosulfide thin films on silicon substrates* S. Fairchilda; accepted 13 December 2004; published 26 January 2005 Thin films of lanthanum monosulfide LaS have been

Boolchand, Punit

194

Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts  

E-print Network

A 27 Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts actinides (Pu as well as minor actinides). Yttrium and lanthanum has been chosen to simulate actinides

Paris-Sud XI, Université de

195

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 2, FEBRUARY 2005 297 La-Codoped Bismuth-Based Erbium-Doped Fiber  

E-print Network

-Based Erbium-Doped Fiber Ring Laser With 106-nm Tuning Range H. L. Liu, H. Y. Tam, Senior Member, IEEE, W. H lasers using 84.6-cm-long lanthanum-codoped bismuth-based erbium doped fiber and a narrow-band tunable)-codoped bismuth-based erbium-doped fiber (Bi-EDF), laser tuning, microelectromechanical system (MEMS) filter. I

Wai, Ping-kong Alexander

196

The Casparian Strip as a Barrier to the Movement of Lanthanum in Corn Roots  

Microsoft Academic Search

The effectiveness of the Casparian strip as a barrier to apoplastic movement of solutes from cortex to stele of corn roots was investigated by using lanthanum in combination with electron microscopy. Lanthanum deposits were found only in cell walls and on the outside of the plasma membrane of epidermal, cortical, and endodermal cells up to the Casparian strip. Lanthanum was

G. Nagahashi; W. W. Thomson; R. T. Leonard

1974-01-01

197

Elastic constants and high-pressure structural transitions in lanthanum monochalcogenides from experiment and theory  

E-print Network

Elastic constants and high-pressure structural transitions in lanthanum monochalcogenides from 2007 The high-pressure structural behavior of lanthanum monochalcogenides is investigated by theory.1103/PhysRevB.75.184108 PACS number s : 61.50.Ks, 71.15.Nc, 62.20.Dc, 71.20.Gj I. INTRODUCTION The lanthanum

Svane, Axel Torstein

198

Crack tip 90 domain switching in tetragonal lanthanum-modified lead zirconate titanate under an  

E-print Network

Crack tip 90° domain switching in tetragonal lanthanum-modified lead zirconate titanate under) Lanthanum-modified lead zirconate titanate ferroelectric ceramics (Pb0.96La0.04)(Zr0.40Ti0.60)0.99O3 were revealed the residual domain switching in a trans- parent relaxor-type ferroelectric 9.4/65/35 lanthanum

Zhu, Ting

199

Development and Characterization of a Diverging Cusped Field Thruster and a Lanthanum Hexaboride Hollow  

E-print Network

Development and Characterization of a Diverging Cusped Field Thruster and a Lanthanum Hexaboride of a Diverging Cusped Field Thruster and a Lanthanum Hexaboride Hollow Cathode Daniel George Courtney June 2008 and Characterization of a Diverging Cusped Field Thruster and a Lanthanum Hexaboride Hollow Cathode by Daniel George

200

Water Research 39 (2005) 22292236 Effect of counterions on lanthanum biosorption  

E-print Network

Water Research 39 (2005) 2229­2236 Effect of counterions on lanthanum biosorption by Sargassum on the biosorption of La3+ (Lanthanum) using Sargassum polycystum Ca-loaded biomass was studied in this work systems. The presence of chloride ions did not seem to interfere with the lanthanum removal

Volesky, Bohumil

201

Electric-fieldtemperature phase diagram of the relaxor ferroelectric lanthanum-modified lead zirconate titanate  

E-print Network

Electric-field­temperature phase diagram of the relaxor ferroelectric lanthanum-modified lead in the electric-field­temperature phase diagram of 9/65/35 lanthanum-modified lead zirconate titanate ceramics ferroelectrics. S0163-1829 99 00233-7 I. INTRODUCTION Lanthanum-modified lead zirconate titanate ceramics Pb1 x

Bobnar, Vid

202

J. Am. Ceram. Soc., 80 [1] 13341 (1997) Low-Temperature Chemical Synthesis of Lanthanum Monoaluminate  

E-print Network

J. Am. Ceram. Soc., 80 [1] 133­41 (1997) Low-Temperature Chemical Synthesis of Lanthanum substrate In an attempt to prepare LaAlO3 by an aerosol-furnace tech- nique,16 using water-soluble lanthanum and aluminum salts,materials, lanthanum monoaluminate (LaAlO3), was suc- products were formed at furnace

Tas, A. Cuneyt

203

Wave and transport studies utilizing dense plasma filaments generated with a lanthanum hexaboride cathode  

E-print Network

Wave and transport studies utilizing dense plasma filaments generated with a lanthanum hexaboride March 2011; accepted 1 November 2011; published online 27 December 2011) A portable lanthanum hexaboride. Lafferty1 in 1951 first reported on the use of lanthanum hexaboride (LaB6) as a potent electron emitter

California at Los Angles, University of

204

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).  

Code of Federal Regulations, 2012 CFR

...false Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). 721.10370...10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). (a) Chemical...identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN...

2012-07-01

205

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).  

Code of Federal Regulations, 2013 CFR

...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). 721.10370 Section 721...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). (a) Chemical substance...phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS...

2013-07-01

206

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).  

...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). 721.10370 Section 721...Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1). (a) Chemical substance...phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS...

2014-07-01

207

Sonochemical growth of lanthanum conversion films using ultrasonic immersion method for performance improvement of zinc electrodes  

Microsoft Academic Search

The growth of lanthanum conversion coatings on the zinc powder modified by ultrasonic immersion is deeply investigated by Auger electron spectroscopy, X-ray photoelectron spectroscopy, spectrophotometrical and other characterization techniques. The conversion kinetics of La element and the growth mechanism of lanthanum conversion layers are also reported and proposed. The influence of the lanthanum conversion coatings on the discharge properties and

Liqun Zhu; Hui Zhang; Weiping Li; Huicong Liu

2009-01-01

208

Methyl chloride production from methane over lanthanum-based catalysts.  

PubMed

The mechanism of selective production of methyl chloride by a reaction of methane, hydrogen chloride, and oxygen over lanthanum-based catalysts was studied. The results suggest that methane activation proceeds through oxidation-reduction reactions on the surface of catalysts with an irreducible metal-lanthanum, which is significantly different from known mechanisms for oxidative chlorination. Activity and spectroscopic measurements show that lanthanum oxychloride (LaOCl), lanthanum trichloride (LaCl3), and lanthanum phases with an intermediate extent of chlorination are all active for this reaction. The catalyst is stable with no noticeable deactivation after three weeks of testing. Kinetic measurements suggest that methane activation proceeds on the surface of the catalyst. Flow and pulse experiments indicate that the presence of hydrogen chloride is not required for activity, and its role appears to be limited to maintaining the extent of catalyst chlorination. In contrast, the presence of gas-phase oxygen is essential for catalytic activity. Density-functional theory calculations suggest that oxygen can activate surface chlorine species by adsorbing dissociatively and forming OCl surface species, which can serve as an active site for methane activation. The proposed mechanism, thus, involves changing of the formal oxidation state of surface chlorine from -1 to +1 without any changes in the oxidation state of the underlying metal. PMID:17295483

Podkolzin, Simon G; Stangland, Eric E; Jones, Mark E; Peringer, Elvira; Lercher, Johannes A

2007-03-01

209

Cytocompatibility of a free machining titanium alloy containing lanthanum.  

PubMed

Titanium alloys like Ti6Al4V are widely used in medical engineering. However, the mechanical and chemical properties of titanium alloys lead to poor machinability, resulting in high production costs of medical products. To improve the machinability of Ti6Al4V, 0.9% of the rare earth element lanthanum (La) was added. The microstructure, the mechanical, and the corrosion properties were determined. Lanthanum containing alloys exhibited discrete particles of cubic lanthanum. The mechanical properties and corrosion resistance were slightly decreased but are still sufficient for many applications in the field of medical engineering. In vitro experiments with mouse macrophages (RAW 264.7) and human bone-derived cells (MG-63, HBDC) were performed and revealed that macrophages showed a dose response below and above a LaCl3 concentration of 200 microM, while MG-63 and HBDC tolerated three times higher concentrations without reduction of viability. The viability of cells cultured on disks of the materials showed no differences between the reference and the lanthanum containing alloy. We therefore propose that lanthanum containing alloy appears to be a good alternative for biomedical applications, where machining of parts is necessary. PMID:18646202

Feyerabend, Frank; Siemers, Carsten; Willumeit, Regine; Rösler, Joachim

2009-09-01

210

The use of ionic lanthanum as a diffusion tracer and as a marker of calcium binding sites  

Microsoft Academic Search

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.

E. Weihe; W. Hartschuh; J. Metz; U. Brühl

1977-01-01

211

A new nanosensor composed of laminated samarium borate and immobilized laccase for phenol determination.  

PubMed

A new nanosensor composed of laminated samarium borate and immobilized laccase was developed for phenol determination. The laminated samarium borate was synthesized by a mild solid-state-hydrothermal (S-S-H) method without any surfactant or Template. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the samples. The morphology of the as-prepared materials was characterized by SEM, which shows that laminated samarium borate are uniform nanosheets with a layer-by-layer self-assembled single-crystal structure. These laminated samarium borate have typical diameters of 3?~?5 ?m and the thickness of each layer is in the range of 10?~?80 nm. And then, these SmBO3 multilayers were used to immobilize the laccase. The proposed nanosensor composed of laminated samarium borate and immobilized laccase was successfully developed for phenol determination. Cyclic voltammetry were used to study the nanosensor. The proposed nanosensor displayed high sensitivity toward phenolic compounds. The linearity of the nanosensor for the detection of hydroquinone was obtained from 1 to 50 ?M with a detection limit of 3?×?10-7 M (based on the S/N?=?3). PMID:24528570

Hu, Ping; Zhou, Xinlin; Wu, Qingsheng

2014-01-01

212

A new nanosensor composed of laminated samarium borate and immobilized laccase for phenol determination  

PubMed Central

A new nanosensor composed of laminated samarium borate and immobilized laccase was developed for phenol determination. The laminated samarium borate was synthesized by a mild solid-state-hydrothermal (S-S-H) method without any surfactant or Template. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the samples. The morphology of the as-prepared materials was characterized by SEM, which shows that laminated samarium borate are uniform nanosheets with a layer-by-layer self-assembled single-crystal structure. These laminated samarium borate have typical diameters of 3?~?5 ?m and the thickness of each layer is in the range of 10?~?80 nm. And then, these SmBO3 multilayers were used to immobilize the laccase. The proposed nanosensor composed of laminated samarium borate and immobilized laccase was successfully developed for phenol determination. Cyclic voltammetry were used to study the nanosensor. The proposed nanosensor displayed high sensitivity toward phenolic compounds. The linearity of the nanosensor for the detection of hydroquinone was obtained from 1 to 50 ?M with a detection limit of 3?×?10-7 M (based on the S/N?=?3). PMID:24528570

2014-01-01

213

Lanthanum Carbonate for Hyperphosphatemia in Patients on Peritoneal Dialysis  

PubMed Central

? Background: The efficacy of the phosphate binder lanthanum carbonate has been demonstrated for hemodialysis patients, but no studies have focused on patients undergoing continuous ambulatory peritoneal dialysis (CAPD). We evaluated whether lanthanum carbonate could control phosphate levels in patients on CAPD. ? Methods: In this 48-week open-label prospective study, 28 patients on CAPD with a phosphate level of 6 mg/dL or greater were given lanthanum carbonate titrated from 750 mg to 2250 mg daily to achieve a target serum phosphate level of less than 6 mg/dL. The primary efficacy endpoint was reduction of serum phosphate to less than 6 mg/dL. Serum levels of calcium and parathyroid hormone were also evaluated, as were the Ca×P product and adverse effects. ? Results: From week 4 to the end of the study at week 48, we observed a significant reduction of serum phosphate to 5.25 ± 0.97 mg/dL from 6.88 ± 1.06 mg/dL at study start (p < 0.01). At the end of the study, 78.6% of participants had achieved the target of less than 6 mg/dL. Because no change of serum calcium occurred, the Ca×P product declined significantly during the study. Intact parathyroid hormone declined gradually over the study period, but the change had not reached significance at the end of the study (p = 0.11). The mean final dose of lanthanum carbonate was 946 mg daily. The only adverse effect reported was mild nausea in 1 patient. ? Conclusions: Lanthanum carbonate is an effective phosphate binder that can control serum phosphate and Ca×P product in CAPD patients with hyperphosphatemia. Lanthanum carbonate was well tolerated in our population. PMID:23209037

Ohno, Michiya; Ohashi, Hiroshige; Oda, Hiroshi; Yokoyama, Haruko; Okada, Miho; Nagaya, Mayu; Izumi, Kumiko; Ito, Hitomi; Katoh, Shuji

2013-01-01

214

Growth and characterization of rare earths doped triglycine sulfate crystals  

NASA Astrophysics Data System (ADS)

Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in values of dielectric constant and pyroelectric coefficient is observed while the dielectric loss has increased. Using these parameters, figure-of-merits for their use in infrared sensors have also been reported and compared with pure TGS crystal. The Vickers's hardness of doped TGS crystals along (0 1 0) crystallographic face has increased.

Batra, A. K.; Guggilla, Padmaja; Cunningham, Dewanna; Aggarwal, M. D.; Lal, R. B.

2006-01-01

215

XAFS study of gadolinium and samarium bisporphyrinate complexes.  

PubMed

The comparative X-ray absorption spectroscopy study of gadolinium and samarium bisporphyrinate complexes represented by the formulas Gd(III)H(oep)(tpp), Gd(III)(oep)(2), Gd(III)H(tpp)(2) and Sm(III)H(oep)(tpp), Sm(III)(oep)(2), Sm(III)H(tpp)(2) is reported. The XAFS spectra are recorded on the LURE-DCI storage ring (Orsay, France) in transmission mode on the microcrystalline samples at the Gd and Sm L(3) edges. The local environment for Ln(3+) ions has been reconstructed applying one-shell and two-shell XAFS analysis procedures. The protonated and nonprotonated bisporphyrinate complexes present different XAFS features. After our analysis on the title derivatives, the gadolinium ion (at 80 K) is found to be bonded: (i) to eight nitrogen atoms at R(Gd-N) 2.50 A, for Gd(III)(oep)(2) [Debye-Waller (DW) factor 0.004 A(2)]; (ii) to seven nitrogen atoms at R(Gd-N) 2.49 A, for Gd(III)H(oep)(tpp) [DW factor 0.005 A(2)] and one nitrogen at long distance; and (iii) to six nitrogen atoms at R(Gd-N) 2.50 A [DW factor 0.006 A(2)] and two nitrogen atoms at long distance for Gd(III)H(tpp)(2). A similar coordination sphere has been detected for the corresponding Sm derivatives. So, the samarium ion (at room temperature) is bonded: (i) to eight nitrogen atoms at R(Sm-N) 2.53 A, for Sm(III)(oep)(2) [DW factor 0.006 A(2)]; (ii) to seven nitrogen atoms at R(Sm-N) 2.53 A, for Sm(III)H(oep)(tpp) [DW factor 0.006 A(2)] and one nitrogen at long distance; and (iii) to six nitrogen atoms at R(Sm-N) 2.50 A, for Sm(III)H(tpp)(2) [DW factor 0.006 A(2)] and two nitrogen atoms at long distance. As far as concerns Ln(III)(oep)(2) complexes, the increase of Ln-N distance in the series Gd(3+) < Eu(3+) < Sm(3+) reflects an increase in the ionic radii, which are in good agreement with previously published XRD data on Eu(III)(oep)(2). Moreover, the protonated Ln(III)H(oep)(tpp) and Ln(III)H(tpp)(2) complexes possess systematically shorter distances of about 0.02 A between the XAFS and XRD data. This difference is attributed to the asymmetry of the distribution concerning Ln-N distances. PMID:11703105

Agondanou, J H; Spyroulias, G A; Purans, J; Tsikalas, G; Souleau, C; Coutsolelos, A G; Bénazeth, S

2001-11-19

216

Effect of seeding on the formation of lanthanum hexaaluminates synthesized through advanced sol gel process  

NASA Astrophysics Data System (ADS)

Advanced sol gel processing was used to synthesize high purity lanthanum hexaaluminate powders. The effect of seeding on the formation of lanthanum hexaaluminate was also studied by seeding the gel. Dry gel was calcined at various temperatures starting from 1100 °C to 1600 °C for 2 h to study the phase evolution. The combine effects of advanced sol gel processing and the presence of seeds promoted the formation of lanthanum hexaaluminate phase at lower temperature than the conventional routes. Lanthanum hexaaluminate phase was detected at 1201 °C and 1300 °C in seeded and un-seeded gels, respectively. The presence of seed decreases the temperature of formation of lanthanum hexaaluminate by 99 °C. Single phase lanthanum hexaaluminate was formed at 1600 °C in seeded gel whereas trace of lanthanum monoaluminate phase still present in un-seeded gel even at 1600 °C.

Jana, P.; Jayan, P. S.; Mandal, S.; Biswas, K.

2014-12-01

217

Towards the core structure of Strychnos alkaloids using samarium diiodide-induced reactions of indole derivatives.  

PubMed

This report describes the development of a first and second generation approach towards the synthesis of the ABCEG pentacyclic core structure of Strychnos alkaloids. First, we discuss a sequential approach applying a series of functional group transformations to prepare suitable precursors for cyclization reactions. These include attempts of samarium diiodide-induced cyclizations or a Barbier-type reaction of a transient lithium organyl, which successfully led to a tetracyclic key building block earlier used for the synthesis of strychnine. Secondly, we account our first steps towards the development of an atom-economical samarium diiodide-induced cascade reaction using "dimeric" indolyl ketones as cyclization precursors. In this context, we discuss plausible mechanisms for the samarium diiodide-induced cascade reaction as well as transformations of the obtained tetracyclic dihydroindoline derivatives. PMID:24273006

Beemelmanns, Christine; Gross, Steffen; Reissig, Hans-Ulrich

2013-12-23

218

Effects of subchronic samarium exposure on the histopathological structure and apoptosis regulation in mouse testis.  

PubMed

To evaluate the reproductive toxicity of samarium, a widely used rare earth element, male ICR mice were orally exposed to samarium nitrate for 90 days for lesion evaluation in the testis. Decreased organ coefficients, disorganized seminiferous tubules, and decreased spermatogenic cells and sperm of the testis were observed extensively in the treated groups, indicating that the testis is a target organ of samarium. Electron microscopy confirmed that the lesions inside the spermatogenic cells and sperm mainly included mitochondrial swelling, mitochondrial vacuolization, fuzzy nuclear membranes, and marginated chromatin. Increased spermatogenic cell apoptosis rate in the testis was confirmed with a TUNEL assay. And expression up-regulation of p53 and Bax, and down-regulation of Bcl-2 were observed (p<0.05), indicating the apoptosis is related to p53 mediated pathway. PMID:24561534

Zhang, De-Yong; Shen, Xiu-Ying; Ruan, Qin; Xu, Xiao-Lu; Yang, San-Ping; Lu, Yin; Xu, Hui-Ying; Hao, Fei-Lin

2014-03-01

219

Electrical properties of complex perovskite samarium nickel titanate  

NASA Astrophysics Data System (ADS)

The complex perovskite oxide samarium nickel titanate, Sm(Ni1/2Ti1/2)O3 (SNT) is synthesized by solid-state reaction technique. The x-ray diffraction pattern of the sample at room temperature shows monoclinic phase. The microstructure analysis of the sample is performed using scanning electron microscope. Alternating current impedance spectroscopy is used to investigate the electrical properties of SNT in a temperature range from 313 K to 673 K and in a frequency range from 100 Hz to 1 MHz. A peak is observed in the frequency dependence of imaginary part of electric modulus ( M?( ?)) indicating a non-Debye type of relaxation. The relaxation peak of M?( ?) moves towards higher frequencies with the increase of temperature showing the thermally activated nature of the relaxation time. The relaxation times for M?( ?) at different temperatures are found to obey Arrhenius law with an activation energy of 0.57 eV. The scaling behaviour of M?( ?) shows that the relaxation describes the same mechanism at various temperatures. The complex impedance plane plots show that the relaxation mechanism in SNT is purely a bulk effect arising from the semiconductive grains of the sample. The frequency dependent conductivity is found to obey the power law.

Kumar, Nishant; Dutta, Alo; Prasad, S.; Sinha, T. P.

2013-09-01

220

Open ended nitrogen-doped carbon nanotubes for the electrochemical storage of energy in a supercapacitor electrode  

NASA Astrophysics Data System (ADS)

Open ended nitrogen-doped carbon nanotubes (N-doped CNTs) are synthesized by pyrolysis of acetylene/ammonia (C2H2/NH3) mixture over lanthanum nickel (LaNi5) alloy catalyst and subsequent 3M, HNO3:H2SO4 acid mixture treatment. Transmission electron microscopy and X-ray photoelectron spectroscopy evaluations of the acid treated N-doped CNTs reveal that the nanotubes possess an open ended morphology and oxidation of pyridinic-N groups, respectively. The resultant open ended N-doped CNTs tested as a supercapacitor electrode material by cyclic voltammetry and exhibits high specific capacitance of 146 F g-1.

John, Anthuvan Rajesh; Arumugam, Pandurangan

2015-03-01

221

Scintillators with potential to supersede lanthanum bromide  

SciTech Connect

New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high light yield materials: Europium-doped alkaline earth halides and Cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method - SrI{sub 2}, CaI{sub 2}, SrBr{sub 2}, BaI{sub 2} and BaBr{sub 2} - SrI{sub 2} is the most promising. SrI{sub 2}(Eu) emits into the Eu{sup 2+} band, centered at 435 nm, with a decay time of 1.2 {micro}s and a light yield of up to 115,000 photons/MeV. It offers energy resolution better than 3% FWHM at 662 keV, and exhibits excellent light yield proportionality. Transparent ceramics fabrication allows production of Gadolinium- and Terbium-based garnets which are not growable by melt techniques due to phase instabilities. While scintillation light yields of Cerium-doped ceramic garnets are high, light yield non-proportionality and slow decay components appear to limit their prospects for high energy resolution. We are developing an understanding of the mechanisms underlying energy dependent scintillation light yield non-proportionality and how it affects energy resolution. We have also identified aspects of optical design that can be optimized to enhance energy resolution.

Cherepy, Nerine; Payne, Steven; Aszatlos, Steve; Hull, Giulia; Kuntz, J.; Niedermayr, Tom; Pimputkar, S.; Roberts, J.; Sanner, R.; Tillotson, T.; van Loef, Edger; Wilson, Cody; Shah, Kanai; Roy, U.; Hawrami, R.; Burger, Arnold; Boatner, Lynn; Choong, Woon-Seng; Moses, William

2009-06-01

222

Neurotoxicological consequence of long-term exposure to lanthanum  

Microsoft Academic Search

Lanthanides, because of their diversified physical and chemical effects, have been widely used in a number of fields. As a result, more and more lanthanides are entering into the environment and eventually accumulated in human body. Recently, a new medicine, lanthanum carbonate (Fosrenol), has been used to treat chronic renal failure (CRF), and the dosage is much higher than the

Liuxing Feng; Haiqing Xiao; Xiao He; Zijie Li; Fuliang Li; Nianqing Liu; Yuliang Zhao; Yuying Huang; Zhiyong Zhang; Zhifang Chai

2006-01-01

223

Lanthanum reduces the excitation efficiency in fly photoreceptors  

Microsoft Academic Search

Lanthanum (La3+), a known inhibitor of Ca ~÷ binding proteins, was applied to the extracellular space of fly retina. Shot noise analysis indicated that a combination of intense light and La s+ caused a large (down to zero) reduction in the rate of occurrence of the quantal responses to single photons (quantum bumps) which sum to produce the photoreceptor potential.

EDITH SUSS-TOBY; BARUCH MINKE

1991-01-01

224

Discovery of Cesium, Lanthanum, Praseodymium and Promethium Isotopes  

E-print Network

Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E

2011-01-01

225

Discovery of cesium, lanthanum, praseodymium and promethium isotopes  

SciTech Connect

Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

May, E.; Thoennessen, M., E-mail: thoennessen@nscl.msu.edu

2012-09-15

226

Lanthanum Ions abolish the ``Calcium Response'' of Nerve Terminals  

Microsoft Academic Search

IT is well established that, in order to release transmitter, nerve impulses arriving at the terminals require the presence of calcium ions in the external medium1. In the search for other ions which might replace calcium in the process of transmitter release at the neuromuscular junction, it has been found2,3 that lanthanum not only failed to substitute for calcium, but

R. Miledi

1971-01-01

227

Discovery of Cesium, Lanthanum, Praseodymium and Promethium Isotopes  

E-print Network

Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

E. May; M. Thoennessen

2011-09-08

228

Thermophysical Properties of Sulfides of Lanthanum, Praseodymium, Gadolinium, and Dysprosium  

Microsoft Academic Search

The temperature dependence of the thermal conductivity, electrical conductivity, thermoelectromotive force, and thermal expansion coefficient for sulfides of lanthanum, gadolinium, praseodymium and dysprosium of the composition Ln3 – xVxS4 is investigated in the temperature range from 300 to 1200 K. It is shown that the transfer phenomena and thermoelectrical properties of the investigated compositions depend on the concentration of current

G. G. Gadzhiev; Sh. M. Ismailov; M. M. Khamidov; Kh. Kh. Abdullaev; V. V. Sokolov

2000-01-01

229

Ab initio energetics of lanthanum substitution in ferroelectric bismuth titanate.  

PubMed

Using first principles calculations and atomistic thermodynamics the bulk and defect properties of orthorhombic bismuth titanate (Bi?Ti?O??) and bismuth lanthanum titanate (Bi?.??La?.??Ti?O??) have been investigated. Heats of formation, valid chemical conditions for synthesis, lanthanum substitution energies and oxygen and bismuth vacancy formation energies have been computed. The study improves our understanding of how native point defects and substitutional impurities influence the ferroelectric properties of these layered perovskite materials. It is found that lanthanum incorporation could occur on either of the two distinct bismuth sites in the structure and that the effect of substitution is to increase the formation energy of nearby native oxygen vacancies. The results provide direct atomistic evidence over a range of chemical conditions supporting the suggestion that lanthanum incorporation reduces the oxygen vacancy concentration. Oxygen vacancies contribute to ferroelectric fatigue by interacting strongly with domain walls, and therefore a decrease in their concentration is beneficial. The conditions that favor the greatest reduction in oxygen vacancy concentration are described. PMID:21460424

Shah, S H; Bristowe, P D

2011-04-20

230

Lanthanum(III) triflate catalyzed direct amidation of esters.  

PubMed

Lanthanum trifluoromethanesulfonate is an effective single-component catalyst for synthesizing a variety of amides directly from esters and amines under mild conditions. Highly selective amidation of esters and amines, as well as catalyst-controlled amidation of esters, demonstrated the effectiveness of the catalyst system. PMID:24660939

Morimoto, Hiroyuki; Fujiwara, Risa; Shimizu, Yuhei; Morisaki, Kazuhiro; Ohshima, Takashi

2014-04-01

231

The near millimetre wavelength optical constants of calcium lanthanum sulphide  

NASA Astrophysics Data System (ADS)

Spectroscopic measurements at near millimeter wavelengths made on calcium lanthanum sulphide, a potential material for infrared window applications in high speed aircraft, have revealed a region of transparency below 40/cm. The optical constants of the material have been measured from 5 to 40/cm at 293 K, in order to consider its suitability for near millimeters wavelength applications.

Birch, J. R.; Savage, J. A.; Wilson, A. E. J.; Brierley, C. J.

1992-09-01

232

Highly germanium and lanthanum modified silica based glasses in microstructured optical fibers for non-linear applications  

NASA Astrophysics Data System (ADS)

Modified core glass materials in silica-clad microstructured fibers (MOFs) promise efficient conversion of non-linear processes, e.g. for supercontinuum (SC) generation. We used extremely highly germanium-doped silica (max. 36 mol% GeO 2) and lanthanum aluminum silicate glasses with high lanthanum oxide concentration (max. 10 mol% La 2O 3) as core materials. The microstructured optical fibers (Ge-MOFs, La-MOFs) were prepared in five air ring architecture by a stack-and-draw technique using silica for the cladding region. The MOFs show loss minima of about 0.05 dB m -1 (Ge-MOF) and 1.3 dB m -1 (La-MOF) at a wavelength of 1.064 ?m. Such Ge-MOFs and La-MOFs are compatible with conventional silica fibers giving low loss splices with standard single mode fibers. The non-linearity of the La-MOF is approximately two times higher than that of the Ge-MOF, but shows a significantly higher spectral loss. Ge-MOF and La-MOF can both produce similar ultra-broad band supercontinuum spectra from VIS (540 nm and 500 nm) to IR range (2400 nm and 2220 nm) by being pumped with a passively Q-switched Nd:YAG microchip laser.

Kobelke, Jens; Schuster, Kay; Litzkendorf, Doris; Schwuchow, Anka; Kirchhof, Johannes; Tombelaine, Vincent; Bartelt, Hartmut; Leproux, Philippe; Couderc, Vincent; Labruyere, Alexis; Jamier, Raphael

2010-07-01

233

Microstructure Dependence of Oxygen-Ion Conductivity of Samarium-Doped Ceria Ceramics  

NASA Astrophysics Data System (ADS)

Superfine and uniform Ce0.8Sm0.2O1.9 powder was derived from a urea-combustion process with a U/Mn+ ratio of 2.0. The microstructure and oxygen-ion conductivity of the ceramics sintered at 1050-1400 °C were investigated. The relative densities of the ceramics increased with sintering temperature through a maximum at 1200 °C and then slightly declined. The relatively densities of the specimens attained 95.8-98.0% at the sintering temperatures of 1100-1200 °C. The average grain size of the ceramics gradually enhanced from ˜110 to ˜500 nm with the elevation of sintering temperature from 1050 to 1350 °C. The specimens sintered at 1100-1200 °C achieved high oxygen-ion conductivities and low activation energies for the conduction. The results indicate an evident effect of the microstructure on the oxygen-ion conductivity. The superior oxygenion conducting properties of the specimens sintered at 1100-1200 °C are attributed to their low sintering temperatures, high densification levels and fine-grained microstructures.

Huang, Duan-Ping; Xu, Qing; Liu, Han-Xing; Chen, Wen; Zhao, Kai; Kim, Bok-Hee

2013-07-01

234

Parameters estimation for passively all-fiber Q-switched erbium- and samarium-doped laser  

NASA Astrophysics Data System (ADS)

We present a heuristic method for fitting the parameter values of the theoretical model underlying the experimental passively all-fiber Q-switched laser behavior. We use genetic algorithms (GA) to obtain an agreement between the experimental data and the theoretical model throughout simulations of the laser response for several values of the continuous-wave pumping.

Elena Preda, Cristina; Mégret, Patrice

2013-05-01

235

Direct umpolung of glycals and related 2,3-unsaturated N-acetylneuraminic acid derivatives using samarium diiodide.  

PubMed

The umpolung of glycals with samarium diiodide offers a simple route to novel carbohydrate-derived nucleophilic reagents in a single step using a readily available reductant. The corresponding allyl samarium reagent that arises from the hexose series reacts with ketones at the C3?position with high stereoselectivity; carbon-carbon bond formation takes place only anti to the substituent at the C4?position of the dihydropyran ring. For the sialic acid series, the completely regio- and stereoselective coupling process of the samarium reagent occurs at the anomeric carbon atom and provides a new approach to the ?-C-glycosides of N-acetyl neuraminic acid. PMID:24764235

Le, Tien Xuan; Papin, Caroline; Doisneau, Gilles; Beau, Jean-Marie

2014-06-10

236

Mechanisms of magma generation beneath hawaii and mid-ocean ridges: uranium/thorium and samarium/neodymium isotopic evidence.  

PubMed

Measurements of uranium/thorium and samarium/neodymium isotopes and concentrations in a suite of Hawaiian basalts show that uranium/thorium fractionation varies systematically with samarium/neodymium fractionation and major-element composition; these correlations can be understood in terms of simple batch melting models with a garnet-bearing peridotite magma source and melt fractions of 0.25 to 6.5 percent. Midocean ridge basalts shows a systematic but much different relation between uranium/thorium fractionation and samarium/neodymium fractionation, which, although broadly consistent with melting of a garnet-bearing peridotite source, requires a more complex melting model. PMID:17788786

Sims, K W; Depaolo, D J; Murrell, M T; Baldridge, W S; Goldstein, S J; Clague, D A

1995-01-27

237

Preparation of samarium(II) iodide: quantitative evaluation of the effect of water, oxygen, and peroxide content, preparative methods, and the activation of samarium metal.  

PubMed

Samarium(II) iodide (SmI(2)) is one of the most important reducing agents in organic synthesis. Synthetic chemistry promoted by SmI(2) depends on the efficient and reliable preparation of the reagent. Unfortunately, users can experience difficulties preparing the reagent, and this has prevented realization of the full synthetic potential of SmI(2). To provide synthetic chemists with general and reliable methods for the preparation of SmI(2), a systematic evaluation of the factors involved in its synthesis has been carried out. Our studies confirm that SmI(2) is a user-friendly reagent. Factors such as water, oxygen, and peroxide content in THF have little influence on the synthesis of SmI(2). In addition, the use of specialized glovebox equipment or Schlenk techniques is not required for the preparation of SmI(2). However, our studies suggest that the quality of samarium metal is an important factor and that the use of low quality metal is the main cause of failed preparations of the reagent. Accordingly, we report a straightforward method for activation of "inactive" samarium metal and demonstrate the broad utility of this protocol through the electron transfer reductions of a range of substrates using SmI(2) prepared from otherwise "inactive" metal. An investigation into the stability of SmI(2) solutions and an evaluation of commercially available solutions of the reagent is also reported. PMID:22375820

Szostak, Michal; Spain, Malcolm; Procter, David J

2012-04-01

238

Effect of samarium on the temperature induction coefficient of Nd-Dy-Fe-Co-B materials  

NASA Astrophysics Data System (ADS)

Sintered (Nd1 - x - z Dy x Sm2)-(Fe1 - y Co y )-B (atomic fractions x = 0.27, 0.32, 0.39; y = 0.17, 0.23, 0.28; and z = 0.04-0.18) materials have been studied. It is shown that the magnetic moments of samarium ions and the iron-cobalt sublattice are ordered antiferromagnetically and, as the samarium content increases, the content of dysprosium and samarium in the basic A magnetic phase decreases and increases, respectively. As the samarium content ( z) in sintered magnets (Nd0.61 - z Dy0.39Sm z )17.5(Fe0.72Co0.28)76.3B6.2 increases, the thermal induction coefficient is found to decrease monotonically from 0.021 to 0.006%/°C, i.e., by 3.5 times. In this case, residual inductance B r is unchanged (0.8 T).

Kablov, E. N.; Piskorskii, V. P.; Valeev, R. A.

2014-03-01

239

ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.  

PubMed

N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures. PMID:15293392

Ganjali, Mohammad Reza; Rezapour, Morteza; Pourjavid, Mohammad Reza; Haghgoo, Soheila

2004-07-01

240

Sm3+ doped lithium aluminoborate glasses for orange coloured visible laser host material  

NASA Astrophysics Data System (ADS)

Samarium doped lithium aluminium borate glasses have been prepared by conventional melt quench technique and their detailed spectroscopic analysis has been done. The structural analysis has been done by using FTIR studies and density is measured by Archimedes method. The UV-vis-NIR absorption spectra show an increase in intensity of different transitions from the ground level 6H5/2 to various 2S+1LJ levels with an increase in samarium concentration at the expense of aluminium. The fluorescence spectra show several transitions from 4G5/2 to various 6HJ levels along with 4F3/2 to 6HJ and 4G7/2 to 6H5/2.

Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Singh, D. P.

2013-10-01

241

Extensive lanthanum deposition in the gastric mucosa: The first histopathological report.  

PubMed

Lanthanum carbonate is one of the new phosphate binders used for the treatment of hyperphosphatemia in patients with chronic kidney disease. It is poorly absorbed from the gastrointestinal tract, forms insoluble complexes within the lumen, and prevents the absorption of dietary phosphate. A 63-year-old female with a 7-year history of peritoneal dialysis, who was treated with lanthanum carbonate for four years, underwent endoscopic submucosal dissection for intramucosal gastric cancer. Resected specimens showed massive accumulation of macrophages containing fine, granular, brown material in the lamina propria. This was confirmed as lanthanum deposition by scanning electron microscopy with energy dispersive x-ray spectroscopy. Although lanthanum may be poorly absorbed, increased tissue accumulation of lanthanum, particularly in the liver and bone, has been reported in animals with chronic kidney disease. This report indicates enhanced gastrointestinal absorption of lanthanum in some patients or conditions, although its clinical significance awaits further studies. PMID:25413959

Makino, Mutsuki; Kawaguchi, Kenji; Shimojo, Hisashi; Nakamura, Hironori; Nagasawa, Masaki; Kodama, Ryo

2014-11-20

242

Ethanol Gas Sensor Based on Pure and La-Doped Bismuth Vanadate  

NASA Astrophysics Data System (ADS)

Bismuth vanadate (BiVO4) and lanthanum-doped bismuth vanadate (La-doped BiVO4) were prepared via the precipitation method. Their films were produced by simple drop-coating of the initial solutions over gold electrodes, which were coated over a glass substrate. The structural properties of BiVO4 and La-doped BiVO4 samples were studied using x-ray diffractometer, diffuse reflectance spectroscopy, scanning electron microscopy, atomic force microscopy, and compositional analysis. A chamber was designed to install the sensing device and also controllable tools for gas flow rate and temperature. Changes in the resistance of the prepared layers were recorded during exposure to various amounts of ethanol vapor at different temperatures. Both BiVO4 and La-doped BiVO4 layers showed measurable responses in the form of resistance drop (increased conductivity). The higher temperatures up to 450 °C led to stronger signals. The layer containing lanthanum showed signals with shorter recovery times. Introduction of lanthanum caused smaller crystallite sizes in addition to the formation of tetragonal phase of BiVO4. Presence of lanthanum increased the amounts of grain boundaries, magnitude of the response, and sensitivity. Sensitivity of La-doped BiVO4 was almost twice that of the BiVO4 at concentrations of 150-500 ppm of ethanol. Also, the correlation of the response as a function of concentration of ethanol in gas phase was exploited, and two different linear ranges were observed for the lower and higher concentrations.

Golmojdeh, Hosein; Zanjanchi, Mohamad Ali

2014-02-01

243

Fabrication of mesoporous and high specific surface area lanthanum carbide-carbon nanotube composites  

NASA Astrophysics Data System (ADS)

Mesoporous lanthanum carbide-carbon nanotube composites were produced by means of carbothermal reaction of lanthanum oxide, graphite and multi-walled carbon nanotube mixtures under high vacuum. Residual gas analysis revealed the higher reactivity of lanthanum oxide towards carbon nanotubes compared to graphite. After sintering, the composites revealed a specific surface area increasing with the amount of carbon nanotubes introduced. The meso-porosity of carbon nanotubes was maintained after thermal treatment.

Biasetto, L.; Carturan, S.; Maggioni, G.; Zanonato, P.; Di Bernardo, P.; Colombo, P.; Andrighetto, A.; Prete, G.

2009-04-01

244

Investigation into Nanostructured Lanthanum Halides and CeBr{sub 3} for Nuclear Radiation Detection  

SciTech Connect

This slide-show presents work on radiation detection with nanostructured lanthanum halides and CeBr{sub 3}. The goal is to extend the gamma energy response on both low and high-energy regimes by demonstrating the ability to detect low-energy x-rays and relatively high-energy activation prompt gamma rays simultaneously using the nano-structured lanthanum bromide, lanthanum fluoride, cerium bromide, or other nanocrystal material. Homogeneous and nano structure cases are compared.

Guss, P., Guise, R., Mukhopadhyay, S., Yuan, D.

2011-06-22

245

Synthesis and luminescence properties of the lithium-containing lanthanum-oxycarbonate-like borates  

SciTech Connect

The lithium-containing lanthanum-oxycarbonate-like borate, Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7}, has been synthesized by solid-state reactions and was found to be isostructural with the type II lanthanum-oxycarbonate La{sub 2}O{sub 2}(CO{sub 3}). The new compound, lithium-containing lanthanum-oxycarbonate-like borate Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} has been synthesized and its structure characterized by the Rietveld method using powder X-ray diffraction data. It crystallizes in space group P6{sub 3}/mmc with lattice parameters of a=b=4.03396(3) A, c=16.5863(2) A, V=233.746(4) A{sup 3}. The mechanism of the lithium incorporation in the borate is that four Li{sup +} cations replace one (B{sub 2}O){sup 4+} group, i.e. Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} can be described as Li{sub 2x}La{sub 2}O{sub 1.5+2.5x}(BO{sub 3}){sub 1-x}, x=0.3 and the lithium incorporation stabilized the type II borate. The luminescent properties of Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} doped with Eu{sup 3+} were studied, indicating a potential application in white light emitting diodes (WLEDs). - Graphical abstract: The similar compounds of the new compound Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7}. Projections along the b-axes of crystal structures for (a) La{sub 2}O{sub 2}CO{sub 3}-II, (b) A-type La{sub 2}O{sub 3}, (c) Li{sub 0.52}La{sub 2}O{sub 2.52}(CO{sub 3}){sub 0.74}. Highlights: Black-Right-Pointing-Pointer The new compound Li{sub 0.6}La{sub 2}O{sub 2.25}(BO{sub 3}){sub 0.7} has been synthesized. Black-Right-Pointing-Pointer Its structure is characterized by the Rietveld method using powder X-ray diffraction data. Black-Right-Pointing-Pointer This compound crystallizes in space group P6{sub 3}/mmc. Black-Right-Pointing-Pointer The mechanism of lithium incorporation in borate is that two Li{sup +} cations replace one (BO{sub 0.5}){sup 2+} group. Black-Right-Pointing-Pointer The Eu{sup 3+} doped samples have potential application in WLEDs.

Kang, Youjun; Liu, Chunmeng; Kuang, Xiaojun [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)] [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Mi, Jinxiao [Department of Materials Science and Engineering, Xiamen University, Xiamen 361005 (China)] [Department of Materials Science and Engineering, Xiamen University, Xiamen 361005 (China); Liang, Hongbin, E-mail: cesbin@mail.sysu.edu.cn [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)] [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Su, Qiang [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)] [KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

2012-10-15

246

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures  

PubMed Central

This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R.; Smart, Simon; Diniz da Costa, João C.

2015-01-01

247

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures.  

PubMed

This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate. PMID:25644988

Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R; Smart, Simon; Diniz da Costa, João C

2015-01-01

248

Formation of a stratified lanthanum silicate dielectric by reaction with Si(001)  

NASA Astrophysics Data System (ADS)

We have characterized the structure and electrical properties of lanthanum silicate layers formed on Si(001) by reaction of lanthanum oxide with the substrate. Postoxidation of the deposited films results in the formation of a stacked dielectric with a lanthanum silicate layer atop an interfacial layer of SiO2. This structure combines the interfacial properties of SiO2 with the large permittivity of lanthanum silicate. Although the resulting film has leakage properties far superior to an equivalent thickness of SiO2, there is evidence of significant quantities of ionic charge that must be eliminated before use in electronic applications.

Copel, M.; Cartier, E.; Ross, F. M.

2001-03-01

249

Enhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical properties  

NASA Astrophysics Data System (ADS)

Detailed results from field emission studies of lanthanum hexaboride (LaB6) coated multiwalled carbon nanotube (MWCNT) films, pristine LaB6 films, and pristine MWCNT films are reported. The films have been synthesized by a combination of chemical and physical deposition processes. An impressive increase in field enhancement factor and temporal stability as well as a reduction in turn-on field and threshold field are observed in LaB6-coated MWCNTs compared to pristine MWCNT and pristine LaB6 films. Surface morphology of the films has been examined by scanning electron microscopy. Introduction of LaB6 nanoparticles on the outer walls of CNTs LaB6-coated MWCNTs films is confirmed by transmission electron microscopy. The presence of LaB6 was confirmed by X-ray photoelectron spectroscopy results and further validated by the Raman spectra. Raman spectroscopy also shows 67% increase in defect concentration in MWCNTs upon coating with LaB6 and an upshift in the 2D band that could be attributed to p-type doping. Ultraviolet photoelectron spectroscopy studies reveal a reduction in the work function of LaB6-coated MWCNT with respect to its pristine counterpart. The enhanced field emission properties in LaB6-coated MWCNT films are correlated with a change in microstructure and work function.

Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Jha, Menaka; Rodriguez, R. D.; Lehmann, D.; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Hietschold, M.; Zahn, D. R. T.; Schmidt, O. G.

2014-10-01

250

Influence of lanthanum on the optomagnetic properties of zinc ferrite prepared by combustion method  

NASA Astrophysics Data System (ADS)

Pure and lanthanum doped zinc ferrite nanoparticles were synthesized by a combustion method using glycine as fuel. The mechanism of formation of these nanoferrites is discussed briefly. The prepared nanoparticles characterized using powder X-ray diffraction analysis (XRD) revealed the formation of cubic spinel phase with high crystallinity. Average crystallite size, X-ray density and bulk density were found to decrease with an increase in La3+ concentration. The chemical elements and states on the surface of these ferrites were determined using X-ray photoelectron spectroscopy (XPS). The detailed core level spectra of the photoelectron peaks of Zn 2p, Fe 2p, La 3d and O 1s were analyzed. The magnetic behavior of these nanoparticles was studied using a vibrating sample magnetometer (VSM) and corresponding changes in the saturation magnetization (Ms), coercivity (Hc) and remanent magnetization (Mr) were analyzed. The optical behavior of these ferrite nanoparticles was characterized by UV-Diffuse reflectance studies (UV-DRS). From the UV-DRS studies, the optical band gap was found to be in the range of 1.87-1.97 eV. The combustion method significantly produces large amount of products within a short time. Therefore, this method is potentially suitable for manufacturing industries for preparing the magnetic nanoparticles.

Tholkappiyan, R.; Vishista, K.

2014-09-01

251

Effect of pressure on the magnetic properties of lanthanum manganite  

SciTech Connect

The crystalline structure of pure lanthanum manganite under external hydrostatic pressure has been studied. The behavior of magnetic properties and nuclear magnetic resonance (NMR) spectra under these conditions is theoretically predicted. It is shown that an increase in the Neel temperature with pressure is not only caused by the general contraction of the crystal, but is also related to certain peculiarities in the baric behavior of the orbital structure.

Gonchar', L. E., E-mail: Lyudmila.Gonchar@usu.ru; Leskova, Yu. V.; Nikiforov, A. E. [Ural State University (Russian Federation); Kozlenko, D. P. [Joint Institute for Nuclear Research (Russian Federation)

2010-08-15

252

Investigation of lanthanum scintillators for 3-D PET  

Microsoft Academic Search

The main thrust for this work is the investigation and design of a positron emission tomography (PET) scanner based on new Lanthanum Halide scintillators. In three-dimensional (3-D) PET the major limitations are scanner dead-time and ability to reject randoms and scatter. Therefore, to reach the full potential of 3-D PET requires a scintillator with good timing resolution and good energy

S. Surti; J. S. Karp; G. Muehllehner; P. S. Raby

2003-01-01

253

Lanthanum halide nanoparticle scintillators for nuclear radiation detection  

SciTech Connect

Nanoparticles with sizes <10 nm were fabricated and characterized for their nanocomposite radiation detector properties. This work investigated the properties of several nanostructured radiation scintillators, in order to determine the viability of using scintillators employing nanostructured lanthanum trifluoride. Preliminary results of this investigation are consistent with the idea that these materials have an intrinsic response to nuclear radiation that may be correlated to the energy of the incident radiation.

Guss, Paul; Guise, Ronald [Remote Sensing Laboratory, P.O. Box 98521, M/S RSL-48, Las Vegas, Nevada 89193 (United States); Yuan Ding [National Security Technologies, LLC, Los Alamos Operations, P.O. Box 809, M/S LAO/C320, Los Alamos, New Mexico 87544 (United States); Mukhopadhyay, Sanjoy [Remote Sensing Laboratory-Andrews, Building 1783, Arnold Avenue Andrews AFB, Maryland 20762 (United States); O'Brien, Robert; Lowe, Daniel [University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, Nevada 89154 (United States); Kang Zhitao; Menkara, Hisham [Georgia Tech Research Institute, 925 Dalney St., Atlanta, Georgia 30332 (United States); Nagarkar, Vivek V. [RMD, Inc., 44 Hunt Street, Watertown, Massachusetts 02472 (United States)

2013-02-14

254

Yttrium and lanthanum hydride films with switchable optical properties  

Microsoft Academic Search

We discovered that yttrium-, lanthanum- and rare earth-hydride films exhibit remarkable optical properties near their metal–insulator transition: the dihydrides are metallic and shiny while the trihydrides are semiconducting and transparent. The transition between the shiny and transparent state is reversible and can simply be induced by changing the H2 gas pressure or the voltage in an electrolytic cell. No deterioration

R Griessen; J. N Huiberts; M Kremers; A. T. M van Gogh; N. J Koeman; J. P Dekker; P. H. L Notten

1997-01-01

255

Will Lanthanum Halide Scintillators Make NaI(Tl) Obsolete?  

NASA Astrophysics Data System (ADS)

The commercial availability of lanthanum halide scintillators (LaCl3:Ce and LaBr3:Ce) has been much anticipated due to their significantly better resolution (3-4% at 662 keV) relative to NaI(Tl). Unfortunately, our initial investigation of these scintillators revealed significant alpha contamination quite apparent in background spectra. Using measurements of the detector in coincidence with a HPGe detector, we identified the alpha-contaminant as Ac-227. Since this time, the alpha contamination has been substantially reduced so that a second contaminant, La-138 (a beta, gamma, and x-ray source) has become the dominant contaminant in the material. Commercially-available sizes of lanthanum halide scintillators have now reached sizes suitable for handheld Radioactive Isotope Identification Devices (RIIDs). To study the potential of this new material for RIIDs we performed a series of measurements comparing a 1.5'' x 1.5'' LaBr3 detector with an Exploranium GR-135 RIID, which contains a 1.5'' x 2.2'' NaI(Tl) detector. Measurements were taken for short timeframes of seconds to minutes, as typifies RIID usage. Measurements included examples of naturally occurring radioactive material (NORM) typically found in cargo. Of particular interest was the extent to which interference between the La-138 contaminant and K-40, a radioisotope commonly found in NORM, compromise the lanthanum halide performance. Example spectra, detector comparisons and results will be shown.

Milbrath, Brian

2006-05-01

256

Magnetoresistance of lanthanum manganites with activation-type conductivity  

SciTech Connect

The temperature dependence of the resistivity and magnetic moment of La{sub 0.85}Ba{sub 0.15}MnO{sub 3} and La{sub 0.85}Sr{sub 0.15}MnO{sub 3} manganite single crystals in magnetic fields up to 90 kOe is investigated. Analysis of the experimental results shows that the magnetoresistance of lanthanum manganites far from the Curie temperature T{sub C} can be described quantitatively by the s-d model normally used for ferromagnets and taking into account only the exchange interaction between the spins of charge carriers and magnetic moments. These data also show that the features of lanthanum manganites responsible for colossal magnetoresistance (CMR) are manifested in a narrow temperature interval {delta}T Almost-Equal-To 20 K near T{sub C}. Our results suggest a CMR mechanism analogous to the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr-type multilayers with nanometer layer thickness. The nanostratification observed in lanthanum manganites and required for GMR can be described taking into account the spread in T{sub C} in the CMR range {delta}T.

Kurkin, M. I., E-mail: kurkin@imp.uran.ru; Neifeld, E. A.; Korolev, A. V.; Ugryumova, N. A.; Gudin, S. A.; Gapontseva, N. N. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

2013-05-15

257

Adsorption and desorption of samarium atoms on the surface of pure iridium and iridium covered with a graphite monolayer  

NASA Astrophysics Data System (ADS)

Methods of thermionic emission and thermodesorption spectroscopy (TDS) have been used to study the adsorption and condensation of samarium on the surface of pure iridium and iridium covered with a graphite monolayer (valence-saturated neutral substrate) Ir(111)-C. It is shown that at temperatures of 700 < T a < 1200 K the work function ? decreases monotonically from 5.8 to 2.7 eV and during the subsequent deposition of samarium grows slowly to 2.9 eV. It has been found that in all TDS peaks there were observed several phases of samarium. The deposition of samarium onto an Ir-C surface at 700 < T < 1700 K led to a very weak change in the thermionic current in comparison with pure iridium. At temperatures above ˜700 K, samarium is not condensed on the surface of Ir-C, but it is condensed at lower temperatures. By the method of temperature modulation, the heat of samarium desorption was determined to be E ˜ 1.9 eV upon the desorption from an Ir-C surface (at a small coverage) and ˜6 eV upon the desorption from pure Ir.

Orudzhov, A. K.; Dashdemirov, A. O.

2009-01-01

258

A new large area lanthanum hexaboride plasma source C. M. Cooper, W. Gekelman, P. Pribyl, and Z. Lucky  

E-print Network

A new large area lanthanum hexaboride plasma source C. M. Cooper, W. Gekelman, P. Pribyl, and Z July 2010; published online 16 August 2010 A new 18 18 cm2 active area lanthanum hexaboride LaB6 plasma in 1951,1 lanthanum hexaboride LaB6 has been investigated as a source for electron beams, ion sources, ion

California at Los Angles, University of

259

Long-term effects of lanthanum intake on the neurobehavioral development of the rat  

Microsoft Academic Search

The effects of subchronic exposure to lanthanum on rats' physical and neurobehavioral development were investigated. Wistar rats were exposed to lanthanum through oral administration at 0, 0.1, 2, and 40 mg\\/kg concentrations from gestation day 0 through 5 months of age. Prior to weaning of the pups, physical parameters and neurobehaviors were assessed, including body weight gain, pinna detachment, eye

Liuxing Feng; Haiqing Xiao; Xiao He; Zijie Li; Fuliang Li; Nianqing Liu; Zhifang Chai; Yuliang Zhao; Zhiyong Zhang

2006-01-01

260

Cytogenetic and developmental toxicity of cerium and lanthanum to sea urchin embryos  

E-print Network

Cytogenetic and developmental toxicity of cerium and lanthanum to sea urchin embryos Rahime Oral1 was to evaluate the toxicity of two rare earth elements (REE), cerium and lanthanum on sea urchin embryos and sperm. Sea urchin (Paracentrotus lividus) embryos were reared for 72 h in Ce(IV)- or La

Paris-Sud XI, Université de

261

Lanthanum hexaaluminate — novel thermal barrier coatings for gas turbine applications — materials and process development  

Microsoft Academic Search

Lanthanum hexaaluminate (LHA) with a magnetoplumbite structure is a promising competitor to yttria partially stabilized zirconia (Y-PSZ) as a thermal barrier coating (TBC), since most zirconia coatings age significantly, including undesired densification at temperatures exceeding 1100 °C. The microstructure of calcined lanthanum hexaaluminate powders and thermally sprayed coatings show a platelet structure. The magnetoplumbite structure is characterized by the highly

R. Gadow; M. Lischka

2002-01-01

262

Lanthanum permeability of tight junctions along the collecting duct of the rat  

Microsoft Academic Search

Lanthanum permeability of tight junctions along the collecting duct of the rat. The permeability of the tight junctions (zonulae occludentes) was evaluated along the entire length of the collecting duct of the rat using a lanthanum tracer technique. Nine rats with hereditary hypothalamic diabetes insipidus were studied using standard micropuncture and clearance techniques. Glomerular filtration rate (GFR) estimated from inulin

C Craig Tisher; William E Yarger

1975-01-01

263

Humidity sensitivity of composite material of lanthanum ferrite\\/polymer quaternary acrylic resin  

Microsoft Academic Search

The sensing properties of the humidity sensor made of composite material of nanocrystalline lanthanum ferrite (LaFeO3) and polymer quaternary acrylic resin are investigated and compared with those of nanocrystalline lanthanum ferrite, including the sensitivity, the hysteresis, and the response and recover times. The measurement frequency influences both the linearity of the curves of resistance via relative humidity (RH) and the

Jing Wang; Feng-Qing Wu; Kai-He Shi; Xiao-Hua Wang; Peng-Po Sun

2004-01-01

264

Measurement of the triboluminescent properties for europium and samarium tetrakis dibenzoylmethide triethylammonium  

NASA Astrophysics Data System (ADS)

Triboluminescence (TL) is the emission of cold light that is created when materials are fractured. Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is one of the brightest triboluminescent materials that exist. In 2010, efforts began to introduce additives to the synthesis to increase the triboluminescent yield of EuD4TEA. To date, this research has increased the overall emission yield of EuD4TEA by nearly two fold. This paper explores the effects of adding samarium to EuD4TEA. The effects of this additive on the decay time and photoluminescent emission spectra are reported. In addition, the effects of europium on samarium tetrakis dibenzoylmethide triethylammonium are also determined. The effects of europium on the decay time and photoluminescent emission spectra are also reported. Results will show that both additives have an adverse effect on the triboluminescent emission yield. [Figure not available: see fulltext.

Bhat, Kamala N.; Fontenot, Ross S.; Surabhi, Raja; Hollerman, William A.; Aggarwal, Mohan D.; Alapati, Teja R.

2014-11-01

265

Thermo-elastic and ductile properties of Samarium chalcogenides at high pressures  

NASA Astrophysics Data System (ADS)

Samarium chalcogenides crystallize in Fm3m space group at ambient condition and transform to Pm3m space group under high pressure. We have investigated the structural and elastic properties of Samarium chalcogenides using modified charge-transfer potential model. This model incorporates long-range Coulomb effects and charge-transfer (Coulomb screening due to f-electrons of Sm) effect modified by covalency and short-range repulsive interaction extended up to next-nearest neighbours. This model is capable of explaining the Cauchy-discrepancy. We have computed elastic constants, Poisson's ratio and its volume derivative, the ratio of volume thermal expansion coefficient to specific heat, Debye temperature and Grüneisen parameter.

Baraiya, A. K.; Raypuria, G. S.; Gupta, D. C.

2013-02-01

266

Chelating alcohols accelerate the samarium diiodide mediated reduction of 3-heptanone  

Microsoft Academic Search

Initial rate studies of samarium diiodide mediated reduction of 3-heptanone to 3-heptanol are reported. The reduction of 3-heptanone with the polydentate tri(ethylene glycol) methyl ether is 16 times faster than without a proton donor, and 4.3 times faster than methanol. The primary kinetic isotope effect (KIE) was measured as kH\\/kD?2, indicating a rate-determining proton transfer. Diols are superior to mono-alcohols

Anders Dahlén; Göran Hilmersson

2001-01-01

267

Adverse Events in the Long-Term Follow-Up of Patients Treated With Samarium Sm 153 Lexidronam for Osseous Metastases  

SciTech Connect

Purpose: To investigate adverse events after samarium Sm 153 lexidronam and the effect of pre- and post-samarium Sm 153 lexidronam external beam radiation therapy (EBRT) and/or chemotherapy on myelosuppression in patients who received samarium Sm 153 lexidronam for osseous metastases. Methods and Materials: We performed a single-institution retrospective review of 139 patients treated with samarium Sm 153 lexidronam between November 1997 and February 2008. New-onset adverse events after samarium Sm 153 lexidronam were reported. The effect of samarium Sm 153 lexidronam on platelet and peripheral white blood cell counts and the duration of myelosuppression after samarium Sm 153 lexidronam plus EBRT and/or chemotherapy were calculated. Differences in the prevalence of adverse events among patients with varying treatment histories were evaluated with the Pearson chi-square test. Results: Hematologic follow-up was available for 103 patients. Chemotherapy and/or EBRT had no effect on the magnitude or duration of myelosuppression. The most common nonhematologic adverse events were acute lower extremity edema (n = 27) and acute and transient neuropathy (n = 29). Patients treated with chemotherapy after samarium Sm 153 lexidronam had a higher prevalence of lower extremity edema (9 of 18 [50%]) than those who were not treated with chemotherapy after samarium Sm 153 lexidronam (18 of 85 [21.2%]) (p = 0.01, chi-square test). No adverse events were correlated with EBRT. Conclusions: Our observation of new-onset, acute and transient edema and neuropathy after samarium Sm 153 lexidronam and of a relationship between edema and post-samarium Sm 153 lexidronam chemotherapy suggests the need for re-examination of patients in past series or for a prospective investigation with nonhematologic adverse events as a primary endpoint.

Paravati, Anthony J., E-mail: Anthony.J.Paravati@dartmouth.edu [Dartmouth Medical School, Hanover, NH (United States); Russo, Andrea L. [Dartmouth Medical School, Hanover, NH (United States); Aitken, Candice [Dartmouth Medical School, Hanover, NH (United States); Department of Medicine, Section of Radiation Oncology, Dartmouth-Hitchcock Medical Center, Lebanon, NH (Lebanon)

2011-10-01

268

Topological surface state in the Kondo insulator samarium hexaboride  

NASA Astrophysics Data System (ADS)

Topological invariants of electron wavefunctions in condensed matter reveal many intriguing phenomena. A notable example is provided by topological insulators, which are characterized by an insulating bulk coexisting with a metallic boundary state. Although there has been intense interest in Bi-based topological insulators, their behaviour is complicated by the presence of a considerable residual bulk conductivity. Theories predict that the Kondo insulator system SmB6, which is known to undergo a transition from a Kondo lattice metal to a small-gap insulator state with decreasing temperature, could be a topological insulator. Although the insulating bulk and metallic surface separation has been demonstrated in recent transport measurements, these have not demonstrated the topologically protected nature of the metallic surface state. Here we report thickness-dependent transport measurements on doped SmB6, and show that magnetic and non-magnetic doping results in contrasting behaviour that supports the conclusion that SmB6 shows virtually no residual bulk conductivity.

Kim, D. J.; Xia, J.; Fisk, Z.

2014-05-01

269

Topological surface state in the Kondo insulator samarium hexaboride.  

PubMed

Topological invariants of electron wavefunctions in condensed matter reveal many intriguing phenomena. A notable example is provided by topological insulators, which are characterized by an insulating bulk coexisting with a metallic boundary state. Although there has been intense interest in Bi-based topological insulators, their behaviour is complicated by the presence of a considerable residual bulk conductivity. Theories predict that the Kondo insulator system SmB6, which is known to undergo a transition from a Kondo lattice metal to a small-gap insulator state with decreasing temperature, could be a topological insulator. Although the insulating bulk and metallic surface separation has been demonstrated in recent transport measurements, these have not demonstrated the topologically protected nature of the metallic surface state. Here we report thickness-dependent transport measurements on doped SmB6, and show that magnetic and non-magnetic doping results in contrasting behaviour that supports the conclusion that SmB6 shows virtually no residual bulk conductivity. PMID:24658115

Kim, D J; Xia, J; Fisk, Z

2014-05-01

270

RBS ion channeling study of low concentrations of ion implanted samarium in GaN  

NASA Astrophysics Data System (ADS)

The purpose of this work is to determine the location and depth profile of samarium implanted into gallium nitride. The concentrations of the dopant are extremely low (˜100 ppm) which means that the measurements take a large integrated charge to complete so that a pulse pile up system must be employed to enable count rates up to 100 kHz to be used. Although the dopants are more massive than the substrate they are still difficult to resolve with 2 MeV RBS. By taking advantage of the ?-particle energy available from a 4.5 MV tandem, spectra have been obtained where the rare earth dopants are easily visible. Using ion channeling angular scans across more than one axis it is possible to confirm the extent to which an impurity is substitutional, interstitial or randomly located in the host lattice. For the GaN wurtzite lattice with the c-axis <1 0 0 0> perpendicular to the surface the alternative axes are <11¯ 0 1> and the <1 1 2¯ 1>. The data show that samarium is substitutional to a level of about 80% with the remainder randomly located in the lattice. Although there is a higher concentration of the rare earth closer to the surface, the substitutional fraction does not change significantly as a function of depth. The samarium concentration in the sample varied from about 100 ppm at ˜300 nm below the surface to about 300 ppm at the surface.

Ingram, David C.; Lozykowski, Henryk; Jadwisienczak, Wojciech M.

2004-06-01

271

Effect of submicron grains on ionic conductivity of nanocrystalline doped ceria.  

PubMed

Doped ceria has been considered for high oxygen ion conductivity for solid oxide fuel cells. In the present study, 20 mole% samarium doped nano ceria powder was prepared by wet chemical synthesis and sintered at different temperatures to retain submicron grains (> 92-96% density). ionic conductivity of the sintered pellets was measured using impedance spectroscopy as a function of temperature (200-800 degrees C). The total maximum conductivity was 1.0 x 10(-2)S.cm(-1) (at 600 degrees C) for samples sintered at 1200 degrees C. The activation energy at higher test temperature decreases with the decrease in the sintering temperature (by 25%). The grain boundary, grain interior conductivity and activation energy of the electrolyte were correlated to the resulting microstructure. It has been demonstrated that use of doped nano ceria powder as precursor not only reduced the sintering temperature but also provided segregation free grain boundary for engineering higher conductivity dense electrolytes. PMID:21137752

Singh, Virendra; Babu, Suresh; Karakoti, Ajay Singh; Agarwal, Arvind; Seal, Sudipta

2010-10-01

272

Visible emission in Sm3+ and Tb3+ doped phosphate glass excited by UV radiation  

NASA Astrophysics Data System (ADS)

In the article analysis of UV absorption and visible fluorescence of Sm3+ and Tb3+ ions doped phosphate glass with molar composition: 65P2O5 + 8Al2O3 + 10BaO + 17(Na2O + MgO + ZnO) have been investigated. As a result of optical pumping fabricated glass with radiation from a deuterium lamp four luminescence bands were observed near to the wavelength of 600 nm for Sm3+ ions and 550 nm for Tb3+ ions. It was found that larger energy gap between laser and ground levels leads to the strongest emission in the visible range in terbium doped glasses than in glasses doped with samarium ions. Both fabricated glasses are characterized by the ability to selectively detect the radiation in the UV range.

Zmojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Czajkowski, Karol; Ragin, Tomasz

2013-10-01

273

Lanthanum oxide as a new ultraviolet radiation dosimeter  

NASA Astrophysics Data System (ADS)

The sensitivity of thermoluminescence detectors based on commercial lanthanum oxide (La2O3) for beta, gamma, and UV radiation has been investigated. The thermal activation energies were estimated using the Tstop technique. A linear response curve to ultraviolet radiation was obtained over the exposure time ranging from 1 to 120 min. A fading study over a period of 14 days shows that the UV-exposed aliquots faded by 48% when exposed for 30 min. The deep ultraviolet response for ?=254 nm makes La2O3 suitable for photon detectors and dosimeters.

Soliman, C.; Hussein, M. A.

274

Proton-Implanted Planar Waveguide in Gallium Lanthanum Sulphide Glass  

NASA Astrophysics Data System (ADS)

Owing to the remarkable properties of chalcogenide glasses, chalcogenide optical waveguides should play a significant role in the development of integrated optics. This work demonstrates that an optical waveguide can be obtained by a simple proton implantation in gallium lanthanum sulphide (GLS) glass. Two modes exist in the waveguide at a wavelength of 632.8 nm and the refractive index profile of the waveguide is reconstructed. The near-field pattern of the transmitted light is obtained, and the propagation loss is about 3.2 dB/cm for the present waveguide.

Qiu, Feng; Narusawa, Tadashi

2010-09-01

275

Novel borothermal route for the synthesis of lanthanum cerium hexaborides and their field emission properties  

SciTech Connect

The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum-cerium borides were synthesized using hydroxide precursors. These precursors (La{sub 1-x}Ce{sub x}(OH){sub 3}, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 Degree-Sign C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La{sub 0.5}Ce{sub 0.5}B{sub 6} shows excellent field emission characteristics with high field enhancement factor of 4502. - Graphical abstract: Nanostructured lanthanum cerium hexaboride with efficient field emission have fabricated by low temperature hydroxide precursor mediated route. Highlights: Black-Right-Pointing-Pointer New methodology to prepare lanthanum cerium hexaboride at 1300 Degree-Sign C via borothermal route. Black-Right-Pointing-Pointer Nanostructured lanthanum cerium hexaboride film by spin coating process. Black-Right-Pointing-Pointer Nanopyramids based lanthanum cerium hexaboride shows excellent field emission.

Menaka [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)] [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India); Patra, Rajkumar; Ghosh, Santanu [Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)] [Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India); Ganguli, Ashok K., E-mail: ashok@chemistry.iitd.ac.in [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110016 (India)

2012-10-15

276

Optical amplification in disordered electrooptic Tm{sup 3+} and Ho{sup 3+} codoped lanthanum-modified lead zirconate titanate ceramics and study of spectroscopy and communication between cations  

SciTech Connect

Rare earth doped electro-optic (EO) ceramics of lanthanum-modified lead zirconate titanate (PLZT) are promising in building multifunctional optical devices, by taking advantage of both EO effect and optical activity. In this work, the combination of the measured spectra of absorption and photoluminescence, the fluorescent decay, the calculated Judd-Ofelt parameters, and measured single pass gain in Tm{sup 3+}, Ho{sup 3+} codoped PLZT ceramics have marked them out as promising gain media in building electrically controllable lasers/optical amplifiers and other multifunctional devices. Optical energy storage was also observed in the optical amplification dynamics.

Zhao, Hua; Zhang, Kun; Xu, Long; Sun, Fankui; Zhang, Jingwen, E-mail: jingwenz@gmail.com [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Chen, Xuesheng [Department of Physics and Astronomy, Wheaton College, Norton Massachusetts 02766 (United States); Li, Kewen K. [Boston Applied Technologies, Inc., Woburn, Massachusetts 01801 (United States)

2014-02-21

277

Determination of rare earths in lanthanum oxide by inductively-coupled plasma emission derivative spectrometry.  

PubMed

Rare-earth elements (REE) at ppm levels in lanthanum oxide can be determined without prior separation and preconcentration by use of high-resolution inductively-coupled plasma emission derivative spectrometry (ICPEDS). The calibration graphs are all linear and pass through the origin, even in the presence of large amounts of lanthanum, except those for dysprosium, holmium and ytterbium. The detection limit for each REE is 1-10 mug g in lanthanum oxide. Investigation of various physical and/or spectral interferences shows that good selectivity is obtained by ICPEDS. PMID:18963327

Ishii, H; Satoh, K

1983-02-01

278

Radio-opaque fecal impaction and pseudo-occlusion in a dialyzed patient taking lanthanum carbonate.  

PubMed

Lanthanum therapy is an efficient therapy of hyperphosphoremia by chelating phosphore in the digestive tract. Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table. This drug is lightly absorbed and has low water solubility. It should be borne in mind that abdominal X-rays of patients taking lanthanum carbonate may have a radio-opaque appearance typical of imaging agents. This characteristic is suggested to confirm adherence of the patient by doing an abdominal X-ray. We describe in our case a particular good compliant patient with slow digestive transit, which ends by pseudo-occlusion. PMID:22118504

Muller, Clotilde; Muller, Sandrine; Sissoko, Aicha; Klein, Alexandre; Faller, Bernadette; Chantrel, Francois

2012-10-01

279

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments  

DOEpatents

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400/sup 0/K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10 to 30 vol% carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing gases 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.

Holcombe, C.E. Jr.; Kovach, L.; Taylor, A.J.

1980-01-22

280

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments  

DOEpatents

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400.degree. 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.

Holcombe, Cressie E. (Knoxville, TN); Kovach, Louis (Oak Ridge, TN); Taylor, Albert J. (Ten Mile, TN)

1981-01-01

281

Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper  

NASA Astrophysics Data System (ADS)

In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results.

Marwani, Hadi M.; Lodhi, Mazhar Ullah; Khan, Sher Bahadar; Asiri, Abdullah M.

2014-09-01

282

Electrochemical preparation of nanostructured lanthanum using lanthanum chloride as a precursor in 1-butyl-3-methylimidazolium dicyanamide ionic liquid.  

PubMed

Nanostructured lanthanum was electrochemically prepared on a platinum (Pt) substrate in the room temperature ionic liquid 1-butyl-3-methylimidazolium dicyanamide (BMI-DCA) containing anhydrous LaCl3 at 333 K. The electrochemical reduction behavior of La(iii) was investigated using cyclic voltammetry and chronoamperometry techniques. Cyclic voltammogram revealed that the reduction of La(iii) in BMI-DCA involved an irreversible process controlled by diffusion. Chronoamperometric transient analysis confirmed the diffusion controlled electrodeposition process with the diffusion coefficient of La(iii) species in the range of 10(-10) cm(2) s(-1). The strong complexing capability of DCA(-) anions facilitated the displacement of chloride ligands and induced the solubility of LaCl3. The subsequent coordination of La(iii) and DCA(-) anions forming [La(DCA)4](-) complex anions was monitored by designing amperometric titration experiments. Potentiostatically deposited La-deposits with different nanostructures were characterized by SEM, XRD and XPS analyses. The electrodeposition potential was found to play an important role in controlling the nucleation and growth kinetics of the nanocrystal during the electrodeposition process. Depending on the deposition potential, metallic lanthanum with either nanoparticles or nanoporous structures was obtained. PMID:25589210

Zhang, Q B; Yang, C; Hua, Y X; Li, Y; Dong, P

2015-01-28

283

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles  

SciTech Connect

The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO{sub 4} plays a crucial role in determining the particle morphology of La(OH){sub 3}. The reason lies in the fact that KMnO{sub 4} is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the {+-}(1 0 0), {+-}(0 1 0) and {+-}(-110) crystal facets. By adjusting the molar La(OiPr){sub 3}-to-KMnO{sub 4} ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH){sub 3} nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH){sub 3} nanofibers and {beta}-MnOOH nanoparticles at the temperature of 800 deg. C for 8 h yielded polyhedral LaMnO{sub 3} and worm-like La{sub 2}O{sub 3} nanoparticles as final products. - Graphical abstract: Lanthanum hydroxide nanoparticles are synthesized based on a nonaqueous sol-gel process involving the reaction of La(OiPr){sub 3} and KMnO{sub 4} with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. In dependence of the reaction parameters, the La(OH){sub 3} nanoparticles undergo a shape transformation from short nanorods to micron-sized nanofibers.

Djerdj, Igor [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland); Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, P.O. Box 331, 10002 Zagreb (Croatia); Garnweitner, Georg [Max Planck Institute of Colloids and Interfaces, Research Campus Golm, D-14424 Potsdam (Germany); Sheng Su, Dang [Department of Inorganic Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, D-14195 Berlin (Germany); Niederberger, Markus [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)], E-mail: markus.niederberger@mat.ethz.ch

2007-07-15

284

Phase-Transformation-Induced Twins in Lanthanum Gallate Perovskite (LaGaO3).  

E-print Network

??Pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analyzed using X-ray diffractometry (XRD), scanning electron and transmission electron microscopy (SEM and TEM), and electron-backscatter diffraction (EBSD).… (more)

Wang, Wei-Lin

2006-01-01

285

Effect of Adsorbed Nitrogen on the Thermionic Emission from Lanthanum Hexaboride  

NASA Technical Reports Server (NTRS)

The emission properties of lanthanum hexaboride in an atmosphere of nitrogen were investigated. The emitter was not poisoned by adsorbed nitrogen. This result should have application to magnetohydrodynamic devices in which electron flow from channel walls is required.

Carter, Arlen F.; Wood, George P.

1959-01-01

286

METAL INTERACTIONS AT SULFIDE MINERAL SURFACES. PART 2. ADSORPTION AND DESORPTION OF LANTHANUM  

EPA Science Inventory

Batch-type adsorption experiments with four sulfide minerals (chalcocite, galena, pyrite, and sphalerite) were used to investigate the adsorption and desorption behavior of lanthanum (III) in the presence of ethylenediaminetetraacetic acid (EDTA), a model humic substance. Linear ...

287

Synthesis of polycyclic tertiary carbinamines by samarium diiodide mediated cyclizations of indolyl sulfinyl imines.  

PubMed

Samarium diiodide mediated cyclizations of N-acylated indole derivatives bearing sulfinyl imine moieties afforded polycyclic tertiary carbinamines with moderate to excellent diastereoselectivities. Lithium bromide and water turned out to be the best additives to achieve these transformations in good yields. Using enantiopure sulfinyl imines the outcome strongly depends on the reactivity of the indole moiety. Whereas with unactivated indole derivatives desulfinylation and formation of racemic products was observed, indoles bearing electron-withdrawing substituents at C-3 afforded the polycyclic products with intact N-sulfinyl groups and with excellent diastereoselectivity, finally allowing the preparation of enantiopure tertiary carbinamines. The mechanisms of these processes are discussed. PMID:25605534

Rao, Chintada Nageswara; Lentz, Dieter; Reissig, Hans-Ulrich

2015-02-23

288

Evaluation of samarium-153 and holmium-166-EDTMP in the normal baboon model.  

PubMed

Bone-seeking radiopharmaceuticals such as ethylenediaminetetramethylene phosphonate (EDTMP) complexes of samarium-153 and holmium-166 are receiving considerable attention for therapeutic treatment of bone metastases. In this study, using the baboon experimental model, multicompartmental analysis revealed that with regard to pharmacokinetics, biodistribution, and skeletal localisation, 166Ho-EDTMP was significantly inferior to 153Sm-EDTMP and 99mTc-MDP. A more suitable 166Ho-bone-seeking agent should thus be sought for closer similarity to 153Sm-EDTMP to exploit fully the therapeutic potential of its shorter half-life and more energetic beta radiation. PMID:9004281

Louw, W K; Dormehl, I C; van Rensburg, A J; Hugo, N; Alberts, A S; Forsyth, O E; Beverley, G; Sweetlove, M A; Marais, J; Lötter, M G; van Aswegen, A

1996-11-01

289

A novel and efficient samarium iodide-mediated synthesis of neoflavonoids (4-arycloumarins)  

SciTech Connect

Bioactive 4-arylcoumarins (4-aryl-2H-1-benzopyran-2-ones) have been recently isolated from the plants belonging to the families like Leguminosae, Guttiferae, and Compositae, some of which are still used as the traditional folk medicine. Despite many methods reported so far, there appears to be of limited success or of no success in some cases (II{sub b-g}) and, therefore, a simpler and more reliable one remains to be highly desired. Thus, a new and sterling protocol is now presented for the synthesis of neoflavonoids, which involves the intramolecular Reformatsky-type reaction via a one electron transfer process with samarium diiodide as a key step.

Nagasawa, Kazuo; Ryohke, Hirosi; Ohnishi, Makoto; Ito, Keiichi [Hokkaido College of Pharmacy, Otaru (Japan)

1995-12-31

290

Chondrite barium, neodymium, and samarium isotopic heterogeneity and early Earth differentiation.  

PubMed

Isotopic variability in barium, neodymium, and samarium in carbonaceous chondrites reflects the distinct stellar nucleosynthetic contributions to the early solar system. We used 148Nd/144Nd to correct for the observed s-process deficiency, which produced a chondrite 146Sm-142Nd isochron consistent with previous estimates of the initial solar system abundance of 146Sm and a 142Nd/144Nd at average chondrite Sm/Nd ratio that is lower than that measured in terrestrial rocks by 21 +/- 3 parts per million. This result strengthens the conclusion that the deficiency in 142Nd in chondrites relative to terrestrial rocks reflects 146Sm decayand earlyplanetary differentiation processes. PMID:17525335

Carlson, Richard W; Boyet, Maud; Horan, Mary

2007-05-25

291

Samarium(II) promoted stereoselective synthesis of antiproliferative cis-beta-alkoxy-gamma-alkyl-gamma-lactones.  

PubMed

Samarium(II) iodide promotes the stereoselective synthesis of cis-beta-alkoxy-gamma-alkyl-gamma-lactones under mild conditions starting from linear precursors. The in vitro antiproliferative activities were examined in the human solid tumor cell lines from diverse origin A2780, SW1573, and WiDr. From the growth inhibition data a structure-activity relationship was obtained. Overall the results point to the relevant role of cis-beta-alkoxy-gamma-alkyl-gamma-lactones as novel scaffolds for the development of new anticancer drugs. PMID:17055722

Donadel, Osvaldo J; Martín, Tomás; Martín, Víctor S; Padrón, José M

2007-01-01

292

Intramolecular, reductive cyclization of beta-ketoisothiocyanates promoted by using samarium diiodide.  

PubMed

A novel samarium diiodide (SmI2) promoted intramolecular cyclization of beta-ketoisothiocyanate, derived from alpha,beta-unsaturated esters and ammonium thiocyanate led to alpha-hydroxythiolactams and/or thiolactams in high yields. Treatment of beta-ketoisothiocyanate with two equivalents of SmI2 gave a mixture of alpha-hydroxythiolactam and thiolactam. Four equivalents of SmI2 afforded only thiolactam in high yields. The intramolecular cyclization took place with high to complete stereoselectivity. A mechanism to explain this transformation is proposed. PMID:15651025

Cho, Min Seok; Lee, In Sang; Kang, Sung Ho; Kim, Yong Hae

2005-02-18

293

Synthesis of nanocrystalline lanthanum phosphate for low temperature densification to monazite ceramics  

Microsoft Academic Search

Nanocrystalline lanthanum phosphate having average crystallite size 10–12 nm has been prepared by a controlled precipitation reaction from lanthanum nitrate and orthophosphoric acid. The precipitate obtained is washed, dried and calcined in the range 300–800 °C and further sintered as compacted discs at a temperature of 1250 °C. An average grain size of 1–2 ?m was obtained on sintering at

K. Rajesh; B. Sivakumar; P. Krishna Pillai; P. Mukundan; K. G. K. Warrier; V. R. Nair

2004-01-01

294

Dielectric, electromechanical, optical, and mechanical properties of lanthanum-modified lead titanate ceramics  

Microsoft Academic Search

Dielectric, electromechanical, optical, and mechanical properties of hot-pressed lanthanum-modified PbTiOâ ceramics were measured as a function of crystal tetragonality, c\\/a, in a range of tetragonal-to-cubic phases. The results obtained in this study are summarized as follows: The c\\/a changes linearly as a function of lanthanum content. Similarly, Curie point changed linearly and remanent polarization, coercive field, and coupling factors decreased

T. Yamamoto; HIDEJI IGARASHI; KIYOSHI OKAZAKI

1983-01-01

295

Chronic renal failure is associated with increased tissue deposition of lanthanum after 28-day oral administration  

Microsoft Academic Search

Chronic renal failure is associated with increased tissue deposition of lanthanum after 28-day oral administration.BackgroundLanthanum (La) carbonate has recently been proposed as an alternative, calcium- and aluminum-free phosphate binder for the treatment of hyperphosphatemia of chronic renal failure (CRF). However, the extent to which CRF enhances tissue La accumulation induced by oral La overload above that observed under conditions of

BERNARD LACOUR; ANTHONY LUCAS; DANIEL AUCHÈRE; NADYA RUELLAN; NATALIE MARIAUD DE SERRE PATEY; Tilman B. Drueke

2005-01-01

296

Cerium and lanthanum promote floral initiation and reproductive growth of Arabidopsis thaliana  

Microsoft Academic Search

The effects of cerium and lanthanum on the vegetative growth, floral initiation and reproductive growth of Arabidopsis thaliana were studied. Addition of cerium nitrate (0.5–10 ?M) or lanthanum nitrate (0.5–50 ?M) to the culture medium significantly increased the lengths of primary roots, but had no significant effects on the number of rosette leaves produced per plant, plant heights and dry

Ya-Wen He; Chiang-Shiong Loh

2000-01-01

297

Long-Term Efficacy and Tolerability of Lanthanum Carbonate: Results from a 3Year Study  

Microsoft Academic Search

Background: Control of serum phosphate over the long term is essential in patients with end-stage renal disease. Six-month and 2-year extensions to a 6-month study evaluated the long-term safety, tolerability and efficacy of the new phosphate binder lanthanum carbonate. Methods: Patients who participated in a 6-month, randomized trial comparing lanthanum carbonate with calcium carbonate were eligible for a 24-week, open-label

Alastair J. Hutchison; Bart Maes; Johan Vanwalleghem; Gernot Asmus; Elfatih Mohamed; Roland Schmieder; Wolfgang Backs; Rene Jamar; Andre Vosskühler

2006-01-01

298

Lanthanum permeability of the tight junction (zonula occludens) in the renal tubule of the rat  

Microsoft Academic Search

Lanthanum permeability of the tight junction (zonula occludens) in the renal tubule of the rat. The permeability of the tight junctions (zonulae occludentes) in the proximal and distal convoluted tubules and the cortical collecting ducts of the rat were evaluated with a lanthanum tracer. Eight non-expanded and nine volume-expanded rats were studied. Non-expanded animals received 0.02 ml\\/min of isotonic saline.

C Craig Tisher; William E Yarger

1973-01-01

299

Effect of Lanthanum Ions on Function and Structure of Frog Neuromuscular Junctions  

Microsoft Academic Search

1. Electrophysiological and electron-microscopic studies were made of the effect of lanthanum ions on frog neuromuscular junctions. 2. In the presence of 1 mM La2+, nerve impulses continued to invade the nerve terminals but ceased to release transmitter. 3. Lanthanum caused a rapid and large increase in the frequency of miniature end-plate potentials; presumably because La activates the mechanism of

J. Heuser; R. Miledi

1971-01-01

300

Fabrication and spectral properties of Nd 3+-doped yttrium lanthanum oxide transparent ceramics  

NASA Astrophysics Data System (ADS)

Transparent 1 at% Nd 3+:Y 1.9La 0.1O 3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H 2 atmosphere at 1550 °C for 30 h. The Nd 3+:Y 1.9La 0.1O 3 ceramics display uniform grains of about 50 ?m and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820 nm with absorption cross section of 2.48 × 10 -20 cm 2. The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 × 10 -20 cm 2 and broad full width at half maximum (FWHM) of about 6.3 nm. The strongest emission peak was centered at 1078 nm with large stimulated emission cross section of 9.63 × 10 -20 cm 2 and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd 3+:Y 1.9La 0.1O 3 transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively.

Hu, Xiaoman; Yang, Qiuhong; Dou, Chuanguo; Xu, Jun; Zhou, Hongxu

2008-06-01

301

Fabrication and XAFS analysis of Yb3+ doped yttrium lanthanum oxide transparent ceramics  

NASA Astrophysics Data System (ADS)

(YbxY0.90-xLa0.10)2O3 (x = 0.01-0.10) transparent ceramics were fabricated and their structural properties were investigated. The XRD showed our samples exhibited single cubic Y2O3 phase. The lattice parameters were refined with the Rietveld method. The compact structure and an average grain size of 40-50 ?m were revealed by the microstructure. The local fine structure around Yb ions was investigated by using the XAFS (X-ray absorption fine structure) technique. The results showed that: the local structure around Yb ions in the samples with different concentration of Yb ions was basically similar, and Yb ions replaced Y position to form the solid solution. The Yb ions were trivalent. With the concentration of Yb2O3 increased, the coordination number (N) and first shell Yb-O bond length (R) decreased, and the degree of disorder (?) increased.

Jiang, Cen; Yang, Qiuhong; Lu, Qing; Zhang, Haojia

2013-12-01

302

Preparation and laser performance of Nd-doped yttrium lanthanum oxide transparent ceramic  

NASA Astrophysics Data System (ADS)

1.5 at.% Nd:Y 1.8La 0.2O 3 transparent ceramic was fabricated by a solid-state reaction method and sintered at 1650-1700 °C for 40-50 h under H 2 atmosphere. The spectroscopic properties were investigated at room temperature. The transparent ceramic has excellent spectroscopic properties, with the absorption cross section of 1.50 × 10 -20 cm 2 and broad full width at half maximum (FWHM) of about 8 nm at LD wavelength 806 nm, the emission cross section of 2.03 × 10 -20 cm 2 at 1079 nm, and the decay lifetime of 200 ?s. Laser performance was carried out using an uncoated Nd:Y 1.8La 0.2O 3 ceramic plate under laser diode end-pumping without any water cooling device. The room temperature thermal conductivity of this ceramic is 6.20 W/mK. For Nd:Y 1.8La 0.2O 3 ceramic laser, a maximum output power of 62 mW was obtained at 1079 nm under a 808 nm diode pump.

Yang, Qiuhong; Lu, Shenzhou; Zhang, Bin; Zhang, Haojia; Zhou, Jun; Yuan, Zhijun; Qi, Yunfeng; Lou, Qihong

2011-03-01

303

Nuclear Magnetic Resonance Study of Superconductivity in Strontium-Doped Lanthanum Copper Oxides  

Microsoft Academic Search

The goal of this research is to examine a series of copper-oxide based superconductors, La_ {rm 2-x}Sr_{ rm x}CuO_4 for 0.10 <= x <= 0.20, using nuclear magnetic resonance and nuclear quadrupolar resonance spectroscopies. Structural and chemical properties of the materials were confirmed by TGA, and powder x-ray diffraction. For each composition, two distinct sites of copper were observed. The

Mark Allen Kennard

1993-01-01

304

Chemical Preparation of Pure and Strontium and\\/or Magnesium-Doped Lanthanum Gallate Powders  

Microsoft Academic Search

Powder compositions of LaGaO3 ,L a 0.9Sr0.1GaO2.95, and La0.8Sr0.2Ga0.83Mg0.17O2.815 were prepared via a Pechini-type process that uses citric acid and ethylene glycol. The calcina- tion behavior of the precursor powders of the above- mentioned phases was studied in the temperature range of 200°-1400°C in an air atmosphere. Characterization of the powder samples were performed using several processes, including X-ray diffractometry,

A. Cüneyt Ta?; Peter J. Majewski; Fritz Aldinger

2000-01-01

305

Superior oxygen ion conductivity of lanthanum gallate doped with strontium and magnesium  

Microsoft Academic Search

The solid solution range of the La(Sr)Ga(Mg)Oâ perovskite was investigated and the oxygen ion conductivities of corresponding compositions were measured. The solubility of strontium could be extended by the addition of magnesium ions to establish a balance in the oxygen vacancies associated with A and B sites. In this way, the Sr limit in the solid solution was increased to

Peng-nian Huang; A. Petric

1996-01-01

306

Synthesis and Physicochemical Properties of Yttrium Oxide Doped with Neodymium and Lanthanum  

NASA Astrophysics Data System (ADS)

Transparent La0.1Nd0.1Y1.8O3 ceramics were prepared by use of the ethylenediaminetetraacetic acid gel process followed by sintering by hot isostatic pressing. The structure and morphology of the powders and bulk samples and the optical properties of bulk samples were investigated by use of x-ray diffraction (XRD), scanning electron microscopy, visible and near-infrared reflectance spectroscopy, and study of magneto-optic (Faraday) effects. The powders consisted of many agglomerates of fine, oval particles. XRD studies of the powder and bulk sample confirmed their single-phase composition, and spectrophotometric and magneto-optical studies in the range 500-1000 nm revealed their potential for application as an optical materials.

Kruk, A.; Mrózek, M.; Domaga?a, J.; Brylewski, T.; Gawlik, W.

2014-09-01

307

Thermal, electrical, and electrocatalytical properties of lanthanum-doped strontium titanate  

Microsoft Academic Search

Thermal, electrical and electrocatalytical properties of LaxSr1?xTiO3, where x=0.1, 0.2, 0.3, 0.35, and 0.4, perovskite compositions are studied in relation to their potential use as solid oxide fuel cell (SOFC) anode materials. An emphasis is made on the effect of oxidation–reduction cycling on these properties. Depending on the dopant amount, x, and the oxygen partial pressure, LaxSr1?xTiO3 possesses an electrical

Olga A. Marina; Nathan L. Canfield; Jeffry W. Stevenson

2002-01-01

308

Oxygen exchange and diffusion coefficients of strontium-doped lanthanum ferrites by electrical conductivity relaxation  

Microsoft Academic Search

Perovskite-type solid oxide solutions La{sub 1-x}SrâFeO{sub 3-δ} are candidate materials for use as high temperature electrodes and oxygen separation membranes. Electrical conductivity relaxation experiments were performed on thin specimens of La{sub 1-x}SrâFeO{sub 3-δ} (x = 0.1, 0.4) at oxygen partial pressures p{sub Oâ} = 10⁻⁵ to 1 bar in the temperature range 923 to 1,223 K. The transient response of

J. E. ten Elshof; M. H. R. Lankhorst; H. J. M. Bouwmeester

1997-01-01

309

Lanthanum carbonate: a review of its use in lowering serum phosphate in patients with end-stage renal disease.  

PubMed

Orally administered lanthanum carbonate (Fosrenol) dissociates in the acid environment of the upper gastrointestinal tract to release the cation lanthanum, which then binds dietary phosphate. Lanthanum carbonate was effective in reducing levels of serum phosphate and serum calcium x phosphate product and then maintaining these levels within target ranges for up to 6 years in adult patients with end-stage renal disease (ESRD) on haemodialysis or peritoneal dialysis. The reduction in serum phosphate levels with lanthanum carbonate was generally similar to that with calcium carbonate or sevelamer hydrochloride. This agent was generally well tolerated, with the most frequently reported adverse events being gastrointestinal in nature and occurring at a similar rate to that with calcium carbonate. However, lanthanum carbonate was associated with fewer episodes of hypercalcaemia than calcium carbonate. Overall, lanthanum carbonate is a valuable option for the reduction of serum phosphate levels in patients with ESRD on haemodialysis or peritoneal dialysis. PMID:19852531

Curran, Monique P; Robinson, Dean M

2009-11-12

310

Synthesis and characterization of strontium-lanthanum apatites  

SciTech Connect

Two series of strontium-lanthanum apatites, Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}F{sub 2} and Sr{sub 10-x}La {sub x}(PO{sub 4}){sub 6-x}(SiO{sub 4}) {sub x}O with 0 {<=} x {<=} 6, were synthesized by solid state reaction in the temperature range of 1200-1400 deg. C. The obtained materials were characterized by powder X-ray diffraction, infrared absorption spectroscopy and solid {sup 31}P Nuclear Magnetic Resonance. Pure solid solutions were obtained within a limited range of unsubstituted phosphate and silicate apatites. A variation of the lattice parameters was observed, with an increase of a and a decrease of c parameters, related to the radius of the corresponding substituted ions.

Boughzala, K. [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia); Salem, E. Ben [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia); Chrifa, A. Ben [Laboratoire de Thermodynamique Appliquee, Departement de Chimie, Faculte des Sciences de Tunis, Campus Universitaire, 1060 Tunis (Tunisia); Gaudin, E. [Institut de Chimie de la Matiere Condensee, Universite de Bordeaux, CNRS (UPR9048) 87 Avenue du Dr Schweitzer, 33608 Pessac Cedex (France); Bouzouita, K. [U.R. Materiaux Inorganiques, Departement de Chimie, Faculte des Sciences, 5000 Monastir (Tunisia)]. E-mail: khaled.bouzouita@ipeim.rnu.tn

2007-07-03

311

Lanthanum biosorption by a Pseudomonas sp.: equilibrium studies and chemical characterization.  

PubMed

Lanthanum biosorption by a Pseudomonas sp. was characterized in terms of equilibrium metal loading, model fitting, kinetics, effect of solution pH, lanthanum-bacteria interaction mechanism and recovery of sorbed metal. Lanthanum sorption by the bacterium was rapid and optimum at pH 5.0 with equilibrium metal loading as high as 950 mg g(-1) biomass dry wt. Scatchard model and potentiometric titration suggested the presence of at least two types of metal-binding sites, corresponding to a strong and a weak binding affinity. The chemical nature of metal-microbe interaction has been elucidated employing FTIR spectroscopy, energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). FTIR spectroscopy and XRD analysis revealed strong involvement of cellular carboxyl and phosphate groups in lanthanum binding by the bacterial biomass. EDX and the elemental analysis of the sorption solution ascertained the binding of lanthanum with the bacterial biomass via displacement of cellular potassium and calcium. Transmission electron microscopy exhibited La accumulation throughout the bacterial cell with some granular deposits in cell periphery and in cytoplasm. XRD confirmed the presence of LaPO4 crystals onto the bacterial biomass after La accumulation for a long period. A combined ion-exchange-complexation-microprecipitation mechanism could be involved in lanthanum accumulation by the biomass. Almost 98% of biomass-bound La could be recovered using CaCO3 as the desorbing agent. PMID:16598494

Kazy, Sufia K; Das, Susanta K; Sar, Pinaki

2006-09-01

312

Simultaneous determination of lanthanum and cerium in mixed rare earths with p-acetylarsenazo by spectrophotometry.  

PubMed

A new method has been developed for the simultaneous spectrophotometric determination of small amounts of lanthanum and cerium in the presence of large amounts of rare earth elements. Lanthanum (III) and cerium (III) were determined spectrophotometrically with p-acetylarsenazo as the color reagent in the chloroacetic acid medium at pH 3.1 by measuring the absorbances of the complexes at 670 nm. The remained rare earths were masked with ethylenediaminetetracetic acid and ethylenediaminetetracetic acid-zinc during the analysis. The optimum conditions for the simultaneous determination of lanthanum and cerium have been defined. The individual content of lanthanum (III) and cerium (III) were determined by varying the amounts of EDTA and EDTA-Zn used in the analysis and solving the simultaneous absorbance equations based on the Beer's law. The proposed method has been successfully applied to the determination of lanthanum and cerium in Longnan mixed rare earth oxides and other heavy rare earths without preliminary separation with satisfactory results. The relative errors of all analytical results of the method were not more than 2% with good precision. The procedure does not require separation of lanthanum, cerium and the other rare earth elements. PMID:18965986

Zhai, Q Z

1994-05-01

313

Gas permeability of lanthanum oxycarbide targets for the SPES project  

NASA Astrophysics Data System (ADS)

The creation of a porous matrix made of interconnected and permeable paths is a key step for the processing of optimized metal carbide targets in the SPES (Selective Production of Exotic Species) project. Unlike close or non-connected open pores, permeable pores link more efficiently the interior and the surface of target disks, and therefore facilitate the effusion and convection transport mechanisms for a faster extraction of exotic nuclei with short decay times. This work describes the analysis of the interconnected porosity of lanthanum oxycarbide targets through the evaluation of permeability coefficients obtained in argon flow experiments at room and high temperature. Samples were produced by the sacrificial template method using phenolic resin (PR) as source of carbon for the carbothermal reaction of lanthanum oxide, and different amounts of polymethilmetacrylate (PMMA) microbeads as template for the production of porosity. Results showed that conventional targets prepared without sacrificial templates displayed relatively high total porosity (45.6%), but very low permeability coefficients (k1 = 4.21 × 10-17 m2 and k2 = 1.90 × 10-15 m), comparable to other dense ceramic materials. The linear increase in total porosity from 64.8% to 88.9% achieved by the gradual increase of PMMA from 30% to 80 wt.% resulted in a remarkable increase of five orders of magnitude for k1 (2.36 × 10-12 m2) and eight orders for k2 (7.48 × 10-7 m2). The addition of sacrificial fillers was found to be much more efficient to create interconnected and permeable paths in the structure than the carbothermal reduction itself. Preliminary tests with argon flow up to 450 °C revealed that the porous matrix also became more permeable with the increase in the gas temperature due to thermal expansion effects, but the extent of this gain depended on the initial porosity level of the sample.

Biasetto, L.; Innocentini, M. D. M.; Chacon, W. S.; Corradetti, S.; Carturan, S.; Colombo, P.; Andrighetto, A.

2013-09-01

314

Synthesis and characterization of lanthanum dicarbide-carbon targets for radioactive ion beams generation via the carbothermal reaction  

Microsoft Academic Search

In this study, we report the synthesis procedure for the attainment of thin pellets composed of lanthanum dicarbide (LaC2) grains and graphite, as a candidate material for the production of targets for the generation of radioactive ion beams (RIBs). The samples were obtained by thermal treatment of green pellets of lanthanum oxide or lanthanum oxalate (La2O3 and La2(C2O4)3, respectively) mixed

S. Carturan; M. Tonezzer; L. Piga; P. Zanonato; P. Colombo; A. Andrighetto; L. Biasetto; P. Di Bernardo; G. Maggioni; F. Gramegna; G. Prete

2007-01-01

315

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O{9/+}: Synthesis and properties  

NASA Astrophysics Data System (ADS)

Polycrystalline samples in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O{9/+} were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La2Mo2O9) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases ? ? ? and the appearance of the transition ? ms ? ? between two cubic phases. In samples with a high samarium content, the phase transition ? ms ? ? manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La2Mo2O9.

Voronkova, V. I.; Kharitonova, E. P.

2014-07-01

316

Indole synthesis from N-allenyl-2-iodoanilines under mild conditions mediated by samarium(II) diiodide.  

PubMed

A novel method for indole skeleton synthesis under mild conditions mediated by samarium(ii) diiodide has been developed. The reaction of N-allenyl-2-iodoaniline derivatives with SmI2 in the presence of HMPA and i-PrOH at 0 °C afforded indole derivatives in high yields. PMID:25072695

Iwasaki, Hiroki; Suzuki, Kenji; Yamane, Mitsunari; Yoshida, Shohei; Kojima, Naoto; Ozeki, Minoru; Yamashita, Masayuki

2014-09-21

317

Hartree-Fock-Bogoliubov calculations in coordinate space: Neutron-rich sulfur, zirconium, cerium, and samarium isotopes  

E-print Network

Hartree-Fock-Bogoliubov calculations in coordinate space: Neutron-rich sulfur, zirconium, cerium study the properties of neutron-rich zirconium 102,104 Zr , cerium 152 Ce , and samarium 158,160 Sm of nuclear iso- topes still to be explored with new radioactive ion beam facilities [1]. Another limit

Teran, Edgar

318

Bone-seeking radiopharmaceuticals as targeted agents of osteosarcoma: samarium-153-EDTMP and radium-223.  

PubMed

Osteosarcoma is a cancer characterized by formation of bone by malignant cells. Routine bone scan imaging with Tc-99m-MDP is done at diagnosis to evaluate primary tumor uptake and check for bone metastases. At time of relapse the Tc-99m-MDP bone scan also provides a specific means to assess formation of bone by malignant osteosarcoma cells and the potential for bone-seeking radiopharmaceuticals to deliver radioactivity directly into osteoblastic osteosarcoma lesions. This chapter will review and compare a bone-seeking radiopharmaceutical that emits beta-particles, samarium-153-EDTMP, with an alpha-particle emitter, radium-223. The charged alpha particles from radium-223 have far more mass and energy than beta particles (electrons) from Sm-153-EDTMP. Because radium-223 has less marrow toxicity and more radiobiological effectiveness, especially if inside the bone forming cancer cell than samarium-153-EDTMP, radium-223 may have greater potential to become widely used against osteosarcoma as a targeted therapy. Radium-223 also has more potential to be used with chemotherapy against osteosarcoma and bone metastases. Because osteosarcoma makes bone and radium-223 acts like calcium, this radiopharmaceutical could possibly become a new targeted means to achieve safe and effective reduction of tumor burden as well as facilitate better surgery and/or radiotherapy for difficult to resect large, or metastatic tumors. PMID:24924181

Anderson, Peter M; Subbiah, Vivek; Rohren, Eric

2014-01-01

319

Mean-field and density-functional studies of charge ordering and magnetic transitions in lanthanum manganites  

NASA Astrophysics Data System (ADS)

Manganese oxides with perovskite structure exhibit many interesting properties. Recently colossal magnetoresistance (CMR) was observed in these oxides. They show extremely large change in electrical resistance in response to applied magnetic fields. This property has lots of technological relevance for the development of magnetic memory and switching devices. These oxides also show transitions from antiferromagnet to ferromagnet coupled with charge-order to charge-nonorder transition. In this dissertation we examine the electronic origin of these phenomena of lanthanum manganites by studying a model electronic Hamiltonian, which includes double-exchange, super-exchange, and Hubbard terms, using a combination of Hartree-Fock approximation and an exact diagonalization scheme. The existence of "canted" spin order is investigated at zero temperature. We find that the double-exchange mechanism does not always lead to a canted magnetic state, even for small carrier concentration. The canting may be suppressed in these compounds for the typical electronic parameters. We study the charge ordering and magnetic transitions in the perovskites by solving the Hamiltonian both at zero and finite temperature. At zero temperature as we increase the strength of the extended-Hubbard repulsion (Usb1), a first-order transition from a charge-non-ordered metallic ferromagnet (FN) to a charge-ordered, insulating antiferromagnet (AFO) is obtained. The AFO-FN transition is also obtained by increasing the temperature T. The melting of charge ordering as a function of temperature, doping concentration and magnetic field is also examined. Different phases are obtained as a function of temperature and doping concentration. These are in qualitative agreement with experimental data. We study the electronic structures of pyrochlores by the density-functional LMTO method and show that the double-exchange mechanism is relevant for these compounds as well.

Mishra, Snigdharaj Kumar

320

Passively Q-switched Yb- and Sm-doped fiber laser at 1064 nm  

NASA Astrophysics Data System (ADS)

The article describes a simple method of developing a Q-switched fiber laser utilizing the passive Q-switching technique. An ytterbium-doped double-clad fiber was used as the gain medium and a small length of samarium-doped fiber as a saturable absorber to obtain passive Q-switching operation. The laser was capable of operating at continuous wave (CW), Q-switched mode locked, and Q-switched regimes under suitable conditions. Further, the article presented, for the first time, properties of the laser with the orientation of the polarization controller plates inside the cavity. The all fiber laser produces very stable pulses with different energy and repetition rates.

Das, Gautam; Chaboyer, Zachary J.; Navratil, Joseph E.; Drainville, Robert A.

2015-01-01

321

Potentiometric measurement of polymer-membrane electrodes based on lanthanum  

SciTech Connect

Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm{sup ?1}, 1031 cm{sup ?1} and 794.7 cm{sup ?1} for P=O stretching and stretching POC from group ?OP =O. The result showed shift wave number for P =O stretching of the cluster (?OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm{sup ?1} indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R{sub 3}P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10{sup ?3} M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10{sup ?5} and 10{sup ?1} M.

Saefurohman, Asep, E-mail: saefurohman.asep78@Gmail.com; Buchari,, E-mail: saefurohman.asep78@Gmail.com; Noviandri, Indra, E-mail: saefurohman.asep78@Gmail.com [Department of Chemistry, Bandung Institute of Technology (Indonesia); Syoni [Department of Metallurgy Engineering, Bandung Institute of Technology (Indonesia)

2014-03-24

322

Titania-lanthanum phosphate photoactive and hydrophobic new generation catalyst  

SciTech Connect

Titania-lanthanum phosphate nanocomposites with multifunctional properties have been synthesized by aqueous sol-gel method. The precursor sols with varying TiO{sub 2}:LaPO{sub 4} ratios were applied as thin coating on glass substrates in order to be transparent, hydrophobic, photocatalytically active coatings. The phase compositions of the composite powders were identified by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The anatase phase of TiO{sub 2} in TiO{sub 2}-LaPO{sub 4} composite precursors was found to be stable even on annealing at 800 deg. C. The glass substrates, coated with TL1 (TiO{sub 2}-LaPO{sub 4} composition with 1 mol% LaPO{sub 4}) and TL50 (composite precursor containing TiO{sub 2} and LaPO{sub 4} with molar ratio 1:1) sols and annealed at 400 deg. C, produced contact angles of 74 deg. and 92 deg., respectively, though it is only 62 deg. for pure TiO{sub 2} coating. The glass substrates, coated with TL50 sol, produced surfaces with relatively high roughness and uneven morphology. The TL1 material, annealed at 800 deg. C, has shown the highest UV photoactivity with an apparent rate constant, k{sub app}=24x10{sup -3} min{sup -1}, which is over five times higher than that observed with standard Hombikat UV 100 (k{sub app}=4x10{sup -3} min{sup -1}). The photoactivity combined with a moderate contact angle (85.3 deg.) shows that this material has a promise as an efficient self-cleaning precursor. - Graphical abstract: Multifunctional TiO{sub 2}-LaPO{sub 4} composite stabilizes anatase phase with enhanced photocatalytic activity, and moderately higher hydrophobicity is a promising material for self-cleaning application. Highlights: > Titania-lanthanum phosphate nanocomposites were synthesized by aqueous sol-gel method. > Transparent, hydrophobic, photoactive coatings were developed on glass substrates. > The glass substrates, coated with TL1 annealed at 400 deg. C, produced a contact angle of 74 deg. > The TL1 material at 800 deg. C has shown the highest UV photoactivity (k{sub app}=24x10{sup -3} min{sup -1}). > Photoactivity and moderate contact angle show that this is an efficient self-cleaning precursor.

Jyothi, Chembolli K.; Jaimy, Kanakkanmavudi B. [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Sankar, Sasidharan; Smitha, V.S. [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India); Warrier, K.G.K., E-mail: wwarrierkgk@yahoo.co.in [National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum 695019 (India)

2011-07-15

323

Cation-deficient lanthanum manganite oxides: Experimental and theoretical studies  

NASA Astrophysics Data System (ADS)

Cation-deficient lanthanum manganite oxides with 0.8 ? La/Mn ? 1.25 were synthesized using a multi-step decomposition of gel precursors and investigated from experimental and theoretical point of view. The XRD (X-Ray Diffraction) analysis of the mixed LaMnO 3 oxide crystal concludes to a hexagonal structure, space group R-3c, excluding the presence of pure oxides such as La 2O 3, Mn 2O 3, or MnO 2 whatever the ratio La/Mn is. Oxides with nominal formulae La 1- xMnO 3+ y and LaMn 1- x' O 3+ y contain more than one defect structure involving valence defect (holes h rad ), anionic vacancies as well as cationic vacancies in A and B sublattices of the perovskite structure. With the increase of La or Mn non-stoichiometry, the oxygen content y decreases more with La-deficient compositions than with Mn-deficient ones. The La/Mn ratio influences strongly the relationship between [h rad ], [V Orad rad ], [V La?] and [V Mn?]. The DFT-GGA (Density functional Theory, Generalized-Gradient Approximation) simulation of these compounds using VASP (Vienna Ab-initio Simulation Package) concludes that the electronic structure for the optimized stoichiometric La 6Mn 6O 18 is not optimal, relative to that expected considering Mn(III) ions with four alpha electrons each. The non-stoichiometry is the easiest way of reducing the Jahn-Teller instability by depopulating the half-filled e g orbitals. A partial oxidation is then stabilizing. Creation of defects, either an O insertion or a cationic vacancy, allows finding an ideal count. In the case of pure cationic defects (missing a La(III) or a Mn(III) cation), the amount of vacancies is one missing cation upon twelve. The compact nature of lanthanum manganite oxide does not allow oxygen insertion within the bulk structure and oxidation can only be achieved at the surface without O penetration. The formation of antisites is endothermic. The creation of mixed vicinal vacancies, one oxygen and one cationic vacancy (La or Mn), is exothermic for a concentration of defects of one defect per twelve cations.

Hammami, Ramzi; Harrouch Batis, Narjes; Batis, Habib; Minot, Christian

2009-04-01

324

J. Phys. C: Solid State Phys., Vol. 8, 1975.Printed in Great Britain. @ 1975 The metal-insulator transition in lanthanum strontium vanadate  

E-print Network

-insulator transition in lanthanum strontium vanadate M Sayer, R Chent, R Fletcher and A Mansinght Department of Physics cluster formation is of importance. 1. Introduction Lanthanum strontium vanadate La,-xSr,V03 (0 I x VO, was prepared as sintered polycrystalline discs from appro- priate mixtures of lanthanum and strontium oxalates

Chen, Reuven

325

Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium  

SciTech Connect

The purpose of the present work is to accurately measure the neutron cross sections of samarium. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25 meter flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-meter flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multi-level R-matrix Bayesian code SAMMY version M2. The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple scattering corrections to capture yield data and resolution functions specific to the RPI facility. Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture resonance integral to include the strong 0.1 eV resonance in {sup 149}Sm, present measurements agree within estimated uncertainties with EnDF/B-VI release 3. The thermal capture cross-section was calculated from the present measurements of the resonance parameters and also agrees with ENDF within estimated uncertainties. The present measurements reduce the statistical uncertainties in resonance parameters compared to prior measurements.

G. Leinweber; J.A. Burke; H.D. Knox; N.J. Drindak; D.W. Mesh; W.T. Haines; R.V. Ballad; R.C. Block; R.E. Slovacek; C.J. Werner; M.J. Trbovich; D.P. Barry; T. Sato

2001-07-16

326

Silica-lanthanum oxide: pioneer composite of rare-Earth metal oxide in selective phosphopeptides enrichment.  

PubMed

Relying on the successful journey of metal oxides in phosphoproteomics, lanthanum oxide is employed for the engineering of an affinity material for phosphopeptide enrichment. The lanthanum oxide is chemically modified on the surface of silica and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The obtained silica-lanthanum oxide composite is applied for the selective enrichment of phosphopeptides from tryptic digest of standard protein (?-casein, ?-casein, and commercially available casein mixtures from bovine milk). The enriched entities are analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass spectroscopy (MS) results show that the silica-lanthanum oxide composite exhibits enhanced capability for phosphopeptide enrichment with sensitivity assessed to be 50 fmol. Sequence coverage of casein is interpreted showing successful recovery. As a real sample, a protein digest of nonfat milk is applied. Also, the ability of lanthanum in different formats is checked in the selective phosphopeptides enrichment. The composite holds promising future in economic ground as it also possesses the regenerative ability for repetitive use. PMID:23134445

Jabeen, Fahmida; Hussain, Dilshad; Fatima, Batool; Musharraf, S Ghulam; Huck, Christian W; Bonn, G?nther K; Najam-ul-Haq, Muhammad

2012-12-01

327

Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures  

NASA Technical Reports Server (NTRS)

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

2004-01-01

328

Lanthanum carbonate stimulates bone formation in a rat model of renal insufficiency with low bone turnover.  

PubMed

Control of phosphate is important in the management of chronic kidney disease with mineral and bone disorder (CKD-MBD), for which lanthanum carbonate, a non-calcium phosphate-binding agent, has recently been introduced; however, it remains to be determined whether it has any beneficial or deleterious effect on bone remodeling. In the present study, the effects of lanthanum carbonate were examined in an animal model that mimics low turnover bone disease in CKD, i.e., thyroparathyroidectomized (TPTX) and 5/6 nephrectomized (NX) rats undergoing a constant infusion of parathyroid hormone (PTH) and thyroxine injections (TPTX-PTH-5/6NX). Bone histomorphometry at the second lumbar vertebra and tibial metaphysis revealed that both bone formation and resorption were markedly suppressed in the TPTX-PTH-5/6NX model compared with the sham-operated control group, and treatment with lanthanum carbonate was associated with the stimulation of bone formation but not an acceleration of bone resorption. Lanthanum treatment caused a robust stimulation of bone formation with an activation of osteoblasts on the endosteal surface of femoral diaphysis, leading to an increase in cortical bone volume. Thus, lanthanum carbonate has the potential to stimulate bone formation in cases of CKD-MBD with suppressed bone turnover. PMID:24126694

Fumoto, Toshio; Ito, Masako; Ikeda, Kyoji

2014-09-01

329

Investigation on scandium-doped manganate La 0.8Sr 0.2Mn 1? x Sc x O 3? ? cathode for intermediate temperaturesolid oxide fuel cells  

Microsoft Academic Search

Scandium-doped lanthanum strontium manganate La0.8Sr0.2Mn1?xScxO3?? (LSMS) combined with YSZ as composite cathode for anode-supported solid oxide fuel cell is investigated. The LSMS powders are prepared using the modified Pechini method. The XRD and H2-TPR results reveal that non-stoichiometric defects are introduced into the perovskite lattice of LSMS samples as a result of Sc substitution, which leads to increased oxygen ion

Xiangling Yue; Aiyu Yan; Min Zhang; Lin Liu; Yonglai Dong; Mojie Cheng

2008-01-01

330

Photodissociation of yttrium and lanthanum oxide cluster cations.  

PubMed

Transition metal oxide cations of the form M n O m (+) (M = Y, La) are produced by laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. Cluster oxides for each value of n form only a limited number of stoichiometries; MO(M2O3)x(+) species are particularly intense. Cluster cations are mass selected and photodissociated using the third harmonic (355 nm) of a Nd:YAG laser. Multiphoton excitation is required to dissociate these clusters because of their strong bonding. Yttrium and lanthanum oxides exhibit different dissociation channels, but some common trends can be identified. Larger clusters for both metals undergo fission to make certain stable cation clusters, especially MO(M2O3) x (+) species. Specific cations are identified to be especially stable because of their repeated production in the decomposition of larger clusters. These include M3O4(+), M5O7(+), M7O10(+), and M9O13(+), along with Y6O8(+). Density functional theory calculations were performed to investigate the relative stabilities and structures of these systems. PMID:18494453

Reed, Z D; Duncan, M A

2008-06-19

331

Electrical and pyroelectric properties of lanthanum based niobate  

NASA Astrophysics Data System (ADS)

A lanthanum based new tungsten bronze (TB) ferroelectrics (K2Pb2La2W2Ti4Nb4O30) was synthesized by a mixed-oxide method at high temperature. Thermogravimetry analysis (TG) technique was used to decide the material preparation conditions. The formation of desired compound was confirmed by preliminary X-ray structural analysis. The SEM micrograph of the sintered sample exhibits uniform rod-like grain distribution without many voids. Detailed studies of the nature of variation of dielectric parameters with temperature and frequency shows dielectric anomaly at 310 °C. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc) and electrical properties. The dc conductivity follows the Arrhenius equation, and thus its variation with rise in temperature reveals the negative temperature coefficient of resistance (NTCR) behavior of the material. The material obeys Jonscher's universal power law which is evident from the frequency dependence of ac conductivity. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit. Hence the material is useful for pyroelectric sensors.

Padhee, R.; Das, Piyush R.; Parida, B. N.; Choudhary, R. N. P.

2013-02-01

332

Genetics of superionic conductivity in lithium lanthanum titanates.  

PubMed

The self-diffusion of ions is a fundamental mass transport process in solids and has a profound impact on the performance of electrochemical devices such as the solid oxide fuel cell, batteries and electrolysers. The perovskite system lithium lanthanum titanate, La2/3-xLi3xTiO3 (LLTO) has been the subject of much academic interest as it displays very high lattice conductivity for a solid state Li conductor; making it a material of great technological interest for deployment in safe durable mobile power applications. However, so far, a clear picture of the structural features that lead to efficient ion diffusion pathways in LLTO, has not been fully developed. In this work we show that a genetic algorithm in conjunction with molecular dynamics can be employed to elucidate diffusion mechanisms in systems such as LLTO. Based on our simulations we provide evidence that there is a three-dimensional percolated network of Li diffusion pathways. The present approach not only reproduces experimental ionic conductivity results but the method also promises straightforward investigation and optimisation of the properties relating to superionic conductivity in materials such as LLTO. Furthermore, this method could be used to provide insights into related materials with structural disorder. PMID:25372938

Jay, E E; Rushton, M J D; Chroneos, A; Grimes, R W; Kilner, J A

2014-12-01

333

Performance of Lanthanum Strontium Manganite Electrodes at High Pressure  

SciTech Connect

The high-pressure performance of lanthanum strontium manganite (LSM), LSM-zirconia, and LSM/ceria composite electrodes was studied by impedance spectroscopy and dc methods. Electrode resistances decreased in proportion to P(O2)1/2 for the LSM electrode in both cathodic and anodic directions to at least 100 atm, a decrease that was attributed to dissociative oxygen adsorption, surface diffusion, and related phenomena. For the LSM-20/zirconia composite electrode, resistances decreased in proportion to P(O2)1/4 across the entire pressure range considered. Two principal features appeared in the impedance spectra, one that showed a P(O2)1/4 dependence attributed to charge transfer reactions, and one that was nearly pressure-independent, possibly due to transport in the zirconia portion of the composite. For the LSM-20/ceria composite electrode, resistances decreased as P(O2)0.3-0.4 at high pressure, depending on temperature. Two features appeared in the impedance spectra: one at low to intermediate frequency having a P(O2)1/2 dependence and one at high frequency having a P(O2)1/4 dependence. These features are attributed to dissociative oxygen adsorption and to charge transfer reactions, respectively. Results suggest that cathodic losses can be substantially lowered by operation of solid oxide fuel cells at greater than ambient pressure.

Thomsen, Edwin C.; Coffey, Greg W.; Pederson, Larry R.; Marina, Olga A.

2009-06-15

334

Ecotoxicological assessment of lanthanum with Caenorhabditis elegans in liquid medium.  

PubMed

With their widespread applications in industry, agriculture and many other fields, more and more rare earth elements (REEs) are getting into the environment, especially the aquatic systems. Therefore, understanding the aquatic ecotoxicity of REEs has become more and more important. In the present work, Caenorhabditis elegans (C. elegans) was used as a test organism and life-cycle endpoints were chosen along with elemental assay to evaluate the aquatic toxicity of lanthanum (La), a representative of REEs. The results show La³+ had significant adverse effects on the growth and reproduction of worms above a concentration of 10 ?mol L?¹. The elemental mapping by microbeam synchrotron radiation X-ray fluorescence (?-SRXRF) illustrated how La treatment disturbed the metals distribution in the whole body of a single tiny nematode at lower levels. Our results suggested that the high-level REEs in some polluted water bodies would lead to an aquatic ecological crisis. The assessment we performed in the present work could be developed as a standardized test design for aquatic toxicological research. PMID:21510015

Zhang, Haifeng; He, Xiao; Bai, Wei; Guo, Xiaomei; Zhang, Zhiyong; Chai, Zhifang; Zhao, Yuliang

2010-12-01

335

Study of prolonged administration of lanthanum carbonate in dialysis patients.  

PubMed

Data of 36 months were accumulated regarding the effects of lanthanum carbonate (LA) on serum phosphate concentrations in dialysis patients. Fifty-three patients (average age and dialysis history 58.4 years and 9.1 years) were included in this study who have been receiving outpatient treatment since March 2009, and who have been unable to maintain serum phosphate concentrations of ?6.0?mg/dL via traditional therapeutic agents used for hyperphosphatemia. Patients were given dosage of LA in addition to, or instead of, co-hyperphosphatemia treatments already being received. Mean dosages of calcium carbonate (CC) and sevelamer hydrochloride (SH) before starting LA administration were 1301.9?mg and 2462.3?mg, respectively. Dosage of LA for all cases was 750?mg at initial dose; 1528.3?mg at 5 months; and 1416.7?mg at 30 months. Dosage of other phosphate binders were 905.7?mg of CC and 820.8?mg of SH at 5 months; and 687.5?mg of CC and 1031.3?mg of SH at 30 months. Serum phosphorus levels (P levels) were significantly decreased at 1 month of LA administration, and continued until 30 months of La treatment. These results suggest that LA successfully controlled serum P and Ca concentrations simultaneously within target ranges without affecting serum intact parathyroid hormone concentration, although further long-term prospective cohort study on LA would be required. PMID:23586507

Gotoh, Junichi; Kukita, Kazutaka; Tsuchihashi, Seiichiro; Hattori, Masahiro; Iida, Junichi; Horie, Takashi; Onodera, Kazuhiko; Furui, Hidenori; Tamaki, Toru; Meguro, Junichi; Yonekawa, Motoki; Kawamura, Akio

2013-04-01

336

Scintillation properties of SrI_2(Eu^2+) (Strontium iodide doped with europium) for high energy astrophysical detectors: Nonproportionality as a function of temperature and at high gamma-ray energies  

E-print Network

Strontium iodide doped with europium is a new scintillator material being developed as an alternative to lanthanum bromide doped with cerium for use in high energy astrophysical detectors. As with all scintillators, the issue of nonproportionality is important because it affects the energy resolution of the detector. In this study, we investigate how the nonproportionality of strontium iodide doped with europium changes as a function of temperature 16 deg. C to 60 deg. C by heating the strontium iodide doped with europium scintillator separate from the photomultiplier tube. In a separate experiment, we also investigate the nonproportionality at high energies (up to 6 MeV) of strontium iodide doped with europium at a testing facility located at NASA Goddard Space Flight Center. We find that the nonproportionality increases nearly monotonically as the temperature of the strontium iodide doped with europium scintillator is increased, although there is evidence of non-monotonic behavior near 40 deg. C, perhaps du...

Perea, R S; Groza, M; Caudel, D; Nowicki, S; Burger, A; Stassun, K G; Peterson, T E

2014-01-01

337

Soft-X-Ray Lasing down to 6.85 nm in Ni-Like Samarium  

NASA Astrophysics Data System (ADS)

We report on recent progress achieved in X-ray laser research at the Institute of Applied Physics of the University of Bern. Using the 10-TW Nd:glass CPA (chirped-pulse amplification) laser system and the grazing-incidence pumping (GRIP) scheme, intense soft-X-ray lasing has been obtained on the 4d ? 4p, J=0-1 line of samarium (Sm, Z=62) at 7.36 nm, with weak lasing observed at 6.85 nm. This was achieved with main pulse energies of 10-12 J and a pulse duration of 1.5 ps. Crucial to these results was the introduction of a second, relatively intense (22.7 %) prepulse ˜30 ps before the main pulse, in addition to the 13.4 % prepulse incident on target several nanoseconds before the main pulse.

Balmer, J. E.; Staub, F.; Jia, F.

338

Chelating Ligand-Mediated Hydrothermal Synthesis of Samarium Orthovanadate with Decavanadate as Vanadium Source  

PubMed Central

A new ethylenediaminetetraacetic acid- (EDTA-) mediated hydrothermal route to prepare chrysanthemum-shaped samarium orthovanadate (SmVO4) nanocrystals with decavanadate (K6V10O28·9H2O) as vanadium source has been developed. The present hydrothermal approach is simple and reproducible and employs a relatively mild reaction temperature. The EDTA, pH value, and temperature of the reaction systems play important roles in determining the morphologies and growth process of the SmVO4 products. The products have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectra (PL), and UV-Vis spectroscopy. PMID:24068882

Zuo, Wenli

2013-01-01

339

The 23 to 300 C demagnetization resistance of samarium-cobalt permanent magnets  

NASA Technical Reports Server (NTRS)

The influence of temperature on knee point and squareness of the M-H demagnetization characteristic of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperature in demagnetization resistent permanent magnet devices. Composite plots of the knee field and the demagnetizing field required to produce a given magnetic induction swing below remanence were obtained for several commercial Sm2Co17 type magnet samples in the temperature range of 23 to 300 C. Using the knee point to define the limits of operation safe against irreversible demagnetization, such plots are shown to provide an effective overview of the useable regions in the space of temperature-induction swing parameters. The observed second quadrant M-H characteristic squareness is shown, by two measures, to increase gradually with temperature, reaching a peak in the interval 200 to 300 C.

Niedra, Janis M.; Overton, Eric

1991-01-01

340

Preparation of hollow core/shell microspheres of hematite and its adsorption ability for samarium.  

PubMed

Hollow core/shell hematite microspheres with diameter of ca. 1-2 ?m have been successfully achieved by calcining the precursor composite microspheres of pyrite and polyvinylpyrrolidone (PVP) in air. The synthesized products were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) gas sorptometry. Temperature- and time-dependent experiments unveil that the precursor pyrite-PVP composite microspheres finally transform into hollow core/shell hematite microspheres in air through a multistep process including the oxidation and sulfation of pyrite, combustion of PVP occluded in the precursor, desulfation, aggregation, and fusion of nanosized hematite as well as mass transportation from the interior to the exterior of the microspheres. The formation of the hollow core/shell microspheres dominantly depends on the calcination temperature under current experimental conditions, and the aggregation of hematite nanocrystals and the core shrinking during the oxidation of pyrite are responsible for the formation of the hollow structures. Moreover, the adsorption ability of the hematite for Sm(III) was also tested. The results exhibit that the hematite microspheres have good adsorption activity for trivalent samarium, and that its adsorption capacity strongly depends on the pH of the solution, and the maximum adsorption capacity for Sm(III) is 14.48 mg/g at neutral pH. As samarium is a typical member of the lanthanide series, our results suggest that the hollow hematite microspheres have potential application in removal of rare earth elements (REEs) entering the water environment. PMID:24892188

Yu, Sheng-Hui; Yao, Qi-Zhi; Zhou, Gen-Tao; Fu, Sheng-Quan

2014-07-01

341

The role of chemical interactions between thorium, cerium, and lanthanum in lymphocyte toxicity.  

PubMed

Thorium, cerium, and lanthanum are metals present in several types of minerals, the most common of which is monazite. Cerium and lanthanum are elements in the lanthanides series. Thorium, an actinide metal, is a hazardous element due to its radioactive characteristics. There is a lack of information describing the possible chemical interactions among these elements and the effects they may have on humans. Toxicological analyses were performed using cell viability, cell death, and DNA damage assays. Chemical interactions were evaluated based on the Loewe additivity model. The results indicate that thorium and cerium individually have no toxic effects on lymphocytes. However, thorium associated with lanthanum increases the toxicity of this element, thereby reducing the viability of lymphocytes at low concentrations of metals in the mixture. PMID:23930795

Oliveira, Monica S; Duarte, Isabelle M; Paiva, Amanda V; Yunes, Samira N; Almeida, Carlos E; Mattos, Rita C; Sarcinelli, Paula N

2014-01-01

342

Eucalyptus tolerance mechanisms to lanthanum and cerium: Subcellular distribution, antioxidant system and thiol pools.  

PubMed

Guanglin 9 (Eucalyptus grandis×Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200mgkg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200mgkg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis. PMID:25303462

Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

2014-12-01

343

Bifunctional lanthanum phosphate substrates as novel adsorbents and biocatalyst supports for perchlorate removal.  

PubMed

Porous lanthanum phosphate substrates, obtained by an environmentally benign colloidal forming process employing methyl cellulose, are reported here as excellent adsorbents of perchlorate with >98% efficiency and with 100% reusability. Additionally, the effectiveness of such substrates as biocatalyst supports that facilitate biofilm formation of perchlorate reducing microbes (Serratia marcescens NIIST 5) is also demonstrated for the first time. The adsorption of perchlorate ions is attributed to the pore structure of lanthanum phosphate substrate and the microbial attachment is primarily ascribed to its intrinsic hydrophobic property. Lanthanum phosphate thus emerges as a dual functional material that possesses an integrated adsorption/bioremediation property for the effective removal of ClO4(-) which is an increasingly important environmental contaminant. PMID:24872208

Sankar, Sasidharan; Prajeesh, Gangadharan Puthiya Veetil; Anupama, Vijaya Nadaraja; Krishnakumar, Bhaskaran; Hareesh, Padinhattayil; Nair, Balagopal N; Warrier, Krishna Gopakumar; Hareesh, Unnikrishnan Nair Saraswathy

2014-06-30

344

Nanocomposite Lanthanum Zirconate Thermal Barrier Coating Deposited by Suspension Plasma Spray Process  

NASA Astrophysics Data System (ADS)

This work seeks to develop an innovative nanocomposite thermal barrier coating (TBC) exhibiting low thermal conductivity and high durability compared with that of current TBCs. To achieve this objective, nanosized lanthanum zirconate particles were selected for the topcoat of the TBC system, and a new process—suspension plasma spray—was employed to produce desirable microstructural features: the nanocomposite lanthanum zirconate TBC contains ultrafine splats and high volume porosity, for lower thermal conductivity, and better durability. The parameters of plasma spray experiment included two main variables: (i) spray distance varying from 40 to 80 mm and (ii) the concentration of suspension 20, 25, and 30 wt.%, respectively. The microstructure of obtained coatings was characterized with scanning electron microscope and x-ray diffraction. The porosity of coatings is in the range of 6-10%, and the single phase in the as-sprayed coatings was pyrochlore lanthanum zirconate.

Wang, Chaohui; Wang, You; Wang, Liang; Hao, Guangzhao; Sun, Xiaoguang; Shan, Fan; Zou, Zhiwei

2014-10-01

345

High-efficiency, low-temperature cesium diodes with lanthanum-hexaboride electrodes  

NASA Technical Reports Server (NTRS)

Lanthanum hexaboride electrodes in 1700 K cesium diodes may triple power outputs compared with those demonstrated for nuclear thermionic space applications. Still greater relative gains seem possible for emitters below 1700 K. Further improvements in cesium diode performance should result from the lower collector temperatures allowed for earth and low power space duties. Decreased temperatures will lessen thermal transport losses that attend thermionic conversion mechanisms. Such advantages will add to those from collector Carnot and electrode effects. If plasma ignition difficulties impede diode temperature reductions, recycling small fractions of the output power could provide ionization. So high efficiency, low temperature cesium diodes with lanthanum hexaboride electrodes appear feasible.

Morris, J. F.

1974-01-01

346

Combustion synthesis and photoluminescence of Eu3+ doped LaAlO3 nanophosphors  

NASA Astrophysics Data System (ADS)

Eu3+ doped LaAlO3 nanophosphors were successfully synthesized by a combustion process using concentrated solution of lanthanum nitrates and aluminate as oxidiser, and glycine acid as fuel. The powders were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy. Pure LaAlO3 phase was obtained at 800 °C heated for 4 h, without formation of any intermediate phase, with an average crystal size, as determined by TEM, of 60 nm. Intense photoluminescence emission is reported at 616 nm, allowing the use of this material as red phosphor.

Dhahri, A.; Horchani-Naifer, K.; Benedetti, A.; Enrichi, F.; Ferid, M.

2012-09-01

347

Influence of samaria doping on the resistance of ceria thin films and its implications to the planar oxygen sensing devices  

SciTech Connect

In order to evaluate and analyze the effect of samarium (Sm) doping on the resistance of cerium oxide, we have grown highly oriented samaria doped ceria (SDC) thin films on sapphire, Al2O3 (0001) substrates by using oxygen plasma-assisted molecular beam epitaxy (OPA-MBE). The film growth was monitored using reflection high-energy electron diffraction (RHEED) which shows two-dimensional growth throughout the deposition. Following growth, the thin films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution X-ray diffraction (HRXRD), and Rutherford backscattering spectrometry (RBS). XPS depth-profile shows Sm atoms are uniformly distributed in ceria lattice throughout the bulk of the film. The valence states of Ce and Sm in doped thin films are found to be Ce4+ and Sm3+, respectively. HRXRD shows the samaria doped ceria films on Al2O3(0001) exhibit (111) preferred orientation. Ion-channeling in RBS measurements confirms high quality of the thin films. The resistance of the samaria doped ceria films, obtained by two probe measurement capability under various oxygen pressure (1mTorr-100Torr) and temperatures (623K to 973K), is significantly lower than that of pure ceria under same conditions. The 6Sm% doped ceria film is the optimum composition for highest conductivity. This is attributed to the increased oxygen vacant sites in fluorite crystal structure of the epitaxial thin films which facilitate faster oxygen diffusion through hopping process.

Gupta, Shilpi; Kuchibhatla, Satyanarayana V N T; Engelhard, Mark H.; Shutthanandan, V.; Nachimuthu, Ponnusamy; Jiang, Weilin; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Prasad, Shalini

2009-05-27

348

Synthesis, structure and luminescence properties of samarium (III) and dysprosium (III) complexes with a new tridentate organic ligand  

Microsoft Academic Search

A novel organic ligand, 6-diphenylamine carbonyl 2-pyridine carboxylic acid (HDPAP), and the corresponding lanthanide complexes, tris(6-diphenylamine carbonyl 2-pyridine carboxylato) samarium (III) (Sm-DPAP) and tris(6-diphenylamine carbonyl 2-pyridine carboxylato) dysprosium (III) (Dy-DPAP) have been designed and synthesized. The crystal structures and photoluminescence of Sm-DPAP and Dy-DPAP have been studied. The results showed that the lanthanide complexes have electroneutral structures, and the solid

Bao-Li An; Meng-Lian Gong; Ming-Xing Li; Ji-Ming Zhang

2004-01-01

349

Facile synthesis of a benzindenoazepine alkaloid, bulgaramine, via samarium diiodide promoted ring expansion of an alpha-aminocarbonyl compound.  

PubMed

A novel synthetic path to a benzindenoazepine alkaloid was established by employing a samarium diiodide promoted ring expansion reaction of an alpha-aminocarbonyl compound as a key reaction, in which a regioselective carbon-nitrogen bond cleavage followed by ring-closing reactions occurred to give the basic ring skeleton of the target compound. Bulgaramine was synthesized from the known tetrahydroisoquinoline derivative in 5 steps in 50% overall yield. PMID:19296691

Honda, Toshio; Aranishi, Eriko; Kaneda, Kyosuke

2009-04-16

350

Total synthesis of (+)-isoschizandrin utilizing a samarium(II) iodide-promoted 8-endo ketyl-olefin cyclization.  

PubMed

The 13-step synthesis of (+)-isoschizandrin reported herein features a samarium(II) iodide-promoted 8-endo ketyl-olefin coupling to assemble the eight-membered ring present in the target concomitantly with the required functionality and stereochemistry. In constructing (+)-isoschizandrin as a single atropisomer, the synthesis utilizes a kinetic resolution of a seven-membered lactone using a CBS-oxazaborolidine. PMID:14656077

Molander, Gary A; George, Kelly M; Monovich, Lauren G

2003-12-12

351

Preparation and use of samarium diiodide (SmI(2)) in organic synthesis: the mechanistic role of HMPA and Ni(II) salts in the samarium Barbier reaction.  

PubMed

Although initially considered an esoteric reagent, SmI(2) has become a common tool for synthetic organic chemists. SmI(2) is generated through the addition of molecular iodine to samarium metal in THF.(1,2-3) It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI(2) can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.(2-12) One of the fascinating features of SmI-(2)-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.(13-14) Additives commonly utilized to fine tune the reactivity of SmI(2) can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)(2), FeCl(3), etc).(3) Understanding the mechanism of SmI(2) reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.(1,15) Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,(1,3,7,10,12) and have been utilized in key steps of the synthesis of large natural products.(16,17) Previous studies on the effect of additives on SmI(2) reactions have shown that HMPA enhances the reduction potential of SmI(2) by coordinating to the samarium metal center, producing a more powerful,(13-14,18) sterically encumbered reductant(19-21) and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.(22) In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.(23) Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.(24-27) Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI(2) reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.(28) These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI(2) reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI(2)-initiated reactions is described. PMID:23407417

Sadasivam, Dhandapani V; Choquette, Kimberly A; Flowers, Robert A

2013-01-01

352

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction  

PubMed Central

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3 Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23 Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28 These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described. PMID:23407417

Sadasivam, Dhandapani V.; Choquette, Kimberly A.; Flowers, Robert A.

2013-01-01

353

Back bombardment for dispenser and lanthanum hexaboride cathodes  

NASA Astrophysics Data System (ADS)

The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6?s duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.

Bakr, Mahmoud; Kinjo, R.; Choi, Y. W.; Omer, M.; Yoshida, K.; Ueda, S.; Takasaki, M.; Ishida, K.; Kimura, N.; Sonobe, T.; Kii, T.; Masuda, K.; Ohgaki, H.; Zen, H.

2011-06-01

354

Lanthanum lead oxide hydroxide nitrates with a nonlinear optical effect.  

PubMed

Two new lanthanum lead oxide hydroxide nitrates with acentric structure, [LaPb8O(OH)10(H2O)](NO3)7 (1) and [LaPb8O(OH)10(H2O)](NO3)7·2H2O (2), have been prepared under subcritical hydrothermal conditions and crystallize in the space groups of Cc and P212121, respectively. The crystal structure of compound 1 consists of the novel [LaPb8O(OH)10(H2O)](7+) clusters regularly arranged along the ab plane with nitrate ions as the counterions around the clusters by Pb-O bonds, developing into a three-dimensional net framework, while the structure of compound 2 is composed of [LaPb8O(OH)10(H2O)](7+) clusters and [NO3](-) groups as the bridging groups, forming a three-dimensional net framework with crystallized water molecules filling in the gaps. The experiments confirmed that compound 1 is the residue of compound 2 after efflorenscence. Besides, the [LaPb8O(OH)10(H2O)](7+) clusters present mirror symmetry in structures of the two compounds. The second-harmonic-generation (SHG) measurements for the two nitrates indicate that the SHG responses for compounds 1 and 2 are 1.3 and 1.1 times that of KH2PO4, respectively. Theoretical calculations confirmed that the SHG efficiency of compounds 1 and 2 mainly arises from the NO3(-) groups in the structure. PMID:25385570

Wang, Genxiang; Luo, Min; Lin, Chensheng; Ye, Ning; Zhou, Yuqiao; Cheng, Wendan

2014-12-01

355

Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.  

PubMed

DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]·2CH3OH·5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]·2CH3OH·4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery. PMID:24915440

Bao, Fei-Fei; Xu, Xin-Xin; Zhou, Wen; Pang, Chun-Yan; Li, Zaijun; Gu, Zhi-Guo

2014-09-01

356

A new large area lanthanum hexaboride plasma source  

NASA Astrophysics Data System (ADS)

A new 18×18 cm2 active area lanthanum hexaboride (LaB6) plasma source for use in a dc discharge has been developed at UCLA. The cathode consists of four tiled LaB6 pieces indirectly heated to electron emission (1750 °C) by a graphite heater. A molybdenum mesh anode 33 cm in front of the LaB6 accelerates the electrons, ionizing a fill gas to create a 20×20 cm2 nearly square plasma. The source is run in pulsed operation with the anode biased up to +400 V dc with respect to the cathode for up to 100 ms at a 1 Hz repetition rate. Both the cathode and anode "float" electrically with respect to the chamber walls. The source is placed in a toroidal chamber 2 m wide and 3 m tall with a major radius of 5 m. Toroidal and vertical magnetic fields confine the current-free plasma which follows the field in a helix. The plasma starts on the bottom of the machine and spirals around it up to four times (120 m) and can be configured to terminate either on the top wall or on the neutral gas itself. The source typically operates with a discharge current up to 250 A in helium making plasmas with Te<30 eV, Ti<16 eV, and ne<3×1013 cm-3 in a background field of 100 G

Cooper, C. M.; Gekelman, W.; Pribyl, P.; Lucky, Z.

2010-08-01

357

Physical and optical properties of Li2O-MgO-B2O3 doped with Sm3+  

NASA Astrophysics Data System (ADS)

Samarium oxide doped lithium magnesium borate glass has been prepared using conventional melting method. The density and molar volume have been calculated and analyzed while their optical properties were studied by measuring the optical absorption and luminescence spectra at room temperature. From the XRD results, since the patterns do not exhibit any diffraction line thus it confirms their amorphous nature. It was found that the density of the glass samples increased and the molar volume decreased with respect to Sm3+ ions content. Meanwhile, the absorption spectra of this study showed four absorption bands with most outstanding peak at 1230 nm (6H5/2-6F7/2). Three emitted spectra transition were observed in this study which are 4G5/2-6H5/2 (blue), 4G5/2-6H9/2 (green), and 4G5/2-6H11/2(yellowish green). A great enhancement in the PL peaks at green region are observed particularly with the 0.5 mol% concentration, which may attribute to the energy transfer from Mg2+ to the trivalent ions of samarium oxide. Beyond the optimum concentration an opposite effect was remarked. This dwindling is attributed to the concentration quenching phenomenon. The current results agreed with other systematic studies that Sm3+ doped with lithium magnesium borate glasses are attractive solid-state laser materials for generation of various visible lights.

Reduan, S. A.; Hashim, S.; Ibrahim, Z.; Alajerami, Y. S. M.; Mhareb, M. H. A.; Maqableh, M.; Dawaud, R. S. E. S.; Tamchek, N.

2014-02-01

358

Interaction of oxygen with samarium on Al2O3 thin film grown on Ni3Al(111).  

PubMed

The interaction between oxygen and samarium (Sm) on the well-ordered thin Al2O3 film grown on Ni3Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O2(2-)) states and regular samarium oxide (O(2-)) states. By contrast, when exposing O2 to Sm film less than one monolayer on Al2O3, no O2(2-) can be observed. Upon heating to higher temperatures, these metastable O2(2-) states dissociate, supplying active O atoms which can diffuse through the Al2O3 thin film to further oxidize the underlying Ni3Al(111) substrate, leading to the significant increase of the Al2O3 thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni3Al substrate by supplying the active oxygen species at elevated temperatures. PMID:24606375

Cheng, Dingling; Xu, Qian; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa

2014-03-01

359

Interaction of oxygen with samarium on Al2O3 thin film grown on Ni3Al(111)  

NASA Astrophysics Data System (ADS)

The interaction between oxygen and samarium (Sm) on the well-ordered thin Al2O3 film grown on Ni3Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O22-) states and regular samarium oxide (O2-) states. By contrast, when exposing O2 to Sm film less than one monolayer on Al2O3, no O22- can be observed. Upon heating to higher temperatures, these metastable O22- states dissociate, supplying active O atoms which can diffuse through the Al2O3 thin film to further oxidize the underlying Ni3Al(111) substrate, leading to the significant increase of the Al2O3 thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni3Al substrate by supplying the active oxygen species at elevated temperatures.

Cheng, Dingling; Xu, Qian; Han, Yong; Ye, Yifan; Pan, Haibin; Zhu, Junfa

2014-03-01

360

Raman Scattering Study on Vibrational Modes and Structure of Lanthanum Tellurite Glasses  

NASA Astrophysics Data System (ADS)

Raman spectra of xLa2O3-(1-x)TeO2 (x=0, 0.05, 0.10, 0.15, 0.20, and 0.25) lanthanum tellurite glasses were measured and analyzed over the entire glass-forming region in an effort to quantitatively follow the structural changes caused by lanthanum oxide variation. For the first time, systematic intensity measurements have been performed to elucidate the composition induced structural changes in the high-frequency stretching vibration region and a possible mechanism was proposed. The network structure of the glasses is formed by mixing TeO4 trigonal bipyramid and TeO3 trigonal pyramid units. The change of the lanthanum oxide content results in conversion of the TeO4 units to TeO3 units with a varying number of non-bridging oxygen atoms. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged trigonal bipyramid and trigonal pyramid tellurite structural units, allowed to calculate the relative amounts of the species involved in the structural changes with composition. The fraction of the terminal oxygen atoms has been estimated from the Raman intensities with the aid of a structural model concerning the structure of tellurite network systems. The simulation of the experimental density of lanthanum tellurite glasses with modifier content up to 25% revealed that the short range order building units assumed here are sufficient to account for the overall structure in these glasses.

Kalampounias, Angelos G.

2012-10-01

361

Phosphate starvation as an antimicrobial strategy: the controllable toxicity of lanthanum oxide nanoparticles.  

PubMed

Lanthanum oxide nanoparticles were utilized to scavenge phosphate from microbial growth media for the use of targeted nutrient starvation as an antimicrobial strategy. Only in phosphate poor environments a toxic effect was observed. The effect was shown on Escherichia coli, Staphylococcus carnosus, Penicillium roqueforti, and Chlorella vulgaris. PMID:22410707

Gerber, Lukas C; Moser, Nadine; Luechinger, Norman A; Stark, Wendelin J; Grass, Robert N

2012-04-21

362

Separation of carrier free 151,152Tb produced in 16O irradiated lanthanum oxide matrix.  

PubMed

Charged particle activation of natural La2O3 with approximately 78.5 MeV 16O results in the formation of carrier free 151,152Tb isotopes in the matrix. The liquid cation exchanger, HDEHP, has effectively been utilised as an extractant in the quantitative separation of the activation products from the bulk target matrix of lanthanum oxide. PMID:10581678

Nayak, D; Lahiri, S; Ramaswami, A; Manohar, S B; Das, N R

1999-12-01

363

Nonisothermal Thermal Decomposition Reaction Kinetics of Double-base Propellant Catalyzed with Lanthanum Citrate  

Microsoft Academic Search

The decomposition reaction kinetics of the double-base (DB) rocket propellant composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG), and nitrocellulose (NC) with lanthanum citrate as a combustion catalyst was investigated by thermogravimetry and differential thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) under atmospheric pressure and flowing nitrogen gas conditions. The results showed that the thermal decomposition

Jianhua Yi; Fengqi Zhao; Siyu Xu; Hongxu Gao; Rongzu Hu; Haixia Hao; Qing Pei; Yin Gao

2007-01-01

364

Progressive accumulation of lanthanum in the liver of normal and uremic rats  

Microsoft Academic Search

Progressive accumulation of lanthanum in the liver of normal and uremic rats.BackgroundThe loss of renal function in chronic kidney disease (CKD) patients leads to a variety of metabolic disturbances that promote the development of secondary hyperparathyroidism (SH) and bone disease. One of these alterations, hyperphosphatemia, is a persistent problem in patients with CKD and is an important factor in the

EDUARDO SLATOPOLSKY; HELEN LIAPIS; JANE FINCH

2005-01-01

365

Recovery of Zinc, Cadmium, and Lanthanum by Biopolymer Gel Particles of Alginic Acid  

Microsoft Academic Search

Biopolymer gel particles of alginic acid were found to be a useful material for recovering zinc, cadmium, and lanthanum from aqueous solutions. The metals sorbed by the gel particles could be completely eluted by using dilute HCl solution of 0.1 kmol\\/m. The distribution ratios of the individual metals between the gel and liquid phases were measured by using a batch

Yasuhiro Konishi; Satoru Asai; Yuji Midoh; Muneharu Oku

1993-01-01

366

In situ Raman spectroscopy of lanthanum-strontium-cobaltite thin films  

E-print Network

Raman spectroscopy is used to probe the structural change of Lanthanum Strontium Cobaltite (La1.xSrxCoO 3 -8) thin films across change in composition (0%-60% strontium) and temperature (30*C-520°C). Raman shift peaks were ...

Breucop, Justin Daniel

2012-01-01

367

First-principles study of the solid solution of hydrogen in lanthanum  

SciTech Connect

Results from first-principles investigations of the energetical, structural, electronic, and vibrational properties of model structures probing the metal-rich region of the lanthanum-hydrogen system, i.e., the region of the solid solution of hydrogen in lanthanum, are presented. We have studied the site preference and the ordering tendency of hydrogen atoms interstitially bonded in close-packed lanthanum. Spatially separated hydrogen atoms have turned out to exhibit an energetical preference for the occupation of octahedral interstitial sites at low temperature. Indications for a reversal of the site preference in favor of the occupation of tetrahedral interstitial sites at elevated temperature have been found. Linear arrangements consisting of pairs of octahedrally and/or tetrahedrally coordinated hydrogen atoms collinearly bonded to a central lanthanum atom have turned out to be energetically favorable structure elements. Further stabilization is achieved if such hydrogen pairs are in turn linked together so that extended chains of La-H bonds are formed. Pair formation and chain linking counteract the energetical preference for octahedral coordination observed for separated hydrogen atoms.

Schoellhammer, Gunther; Herzig, Peter; Wolf, Walter; Vajda, Peter; Yvon, Klaus [Institut fr Physikalische Chemie, Universitt Wien, Whringer Strasse, A-1090 Vienna (Austria); Materials Design s.a.r.l., 44, avenue F.-A. Bartholdi, F-72000 Le Mans (France); Laboratoire des Solides Irradies, Ecole Polytechnique, F-91128 Palaiseau CEDEX (France); Laboratoire de Crystallographie, Universite de Geneve, Quai Ernest-Ansermet 24, CH-1211 Geneva (Switzerland)

2011-09-01

368

Calcium Influx Requirement for Human Neutrophil Chemotaxis: Inhibition by Lanthanum Chloride  

Microsoft Academic Search

Calcium fluxes of human neutrophils measured in the presence of chemotactically active serum showed a marked stimulation of calcium-45 uptake from the media. Chemotactically inactive serum did not cause an influx of calcium. The magnitude of the calcium influx due to activated serum is sufficient to trigger contractile systems previously described in muscle cells. Lanthanum chloride inhibited the chemotactic response

Mark M. Boucek; Ralph Snyderman

1976-01-01

369

Spacecraft charging control by thermal, field emission with lanthanum-hexaboride emitters  

NASA Technical Reports Server (NTRS)

Thermal, field emitters of lanthanum (or perhaps cerium) hexaboride (LaB6) with temperature variability up to about 1500K are suggested for spacecraft charging control. Such emitters operate at much lower voltages with considerably more control and add plasma-diagnostic versatility. These gains should outweigh the additional complexity of providing heat for the LaB6 thermal, field emitter.

Morris, J. F.

1978-01-01

370

Effects of ultraviolet excitation on the spectroscopic properties of Sm3+ and Tb3+ doped aluminophosphate glasses  

NASA Astrophysics Data System (ADS)

Li2O-BaO-Al2O3-La2O3-P2O5 glasses optically activated with rare earth ions with the 4f5, and 4f8 electronic configuration (Sm3+ and Tb3+, respectively) were analyzed by Raman spectroscopy, absorption, excitation photoluminescence, decay curves and temperature dependent photoluminescence. The spectroscopic characteristics of the as-prepared and heat treated samples at temperatures below and above Tg were studied as well as their room temperature photometric properties under ultraviolet excitation. All the doped glasses exhibit typical signatures of the lanthanides in their trivalent charge state. For the samarium doped glass heat treated at 250 °C (samarium doped glasses have much lower luminance intensity (around 0.3 Cd/m2) when compared with the 6-7 Cd/m2 observed for the terbium doped ones.

Nico, C.; Graça, M. P. F.; Elisa, M.; Sava, B. A.; Monteiro, R. C. C.; Rino, L.; Monteiro, T.

2013-10-01

371

Thickness Dependency of Thin Film Samaria Doped Ceria for Oxygen Sensing  

SciTech Connect

High temperature oxygen sensors are widely used for exhaust gas monitoring in automobiles. This particular study explores the use of thin film single crystalline samaria doped ceria as the oxygen sensing material. Desired signal to noise ratio can be achieved in a material system with high conductivity. From previous studies it is established that 6 atomic percent samarium doping is the optimum concentration for thin film samaria doped ceria to achieve high ionic conductivity. In this study, the conductivity of the 6 atomic percent samaria doped ceria thin film is measured as a function of the sensing film thickness. Hysteresis and dynamic response of this sensing platform is tested for a range of oxygen pressures from 0.001 Torr to 100 Torr for temperatures above 673 K. An attempt has been made to understand the physics behind the thickness dependent conductivity behavior of this sensing platform by developing a hypothetical operating model and through COMSOL simulations. This study can be used to identify the parameters required to construct a fast, reliable and compact high temperature oxygen sensor.

Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Jiang, Weilin; Varga, Tamas; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

2011-01-01

372

Performance Evaluation of an Oxygen Sensor as a Function of the Samaria Doped Ceria Film Thickness  

SciTech Connect

The current demand in the automobile industry is in the control of air-fuel mixture in the combustion engine of automobiles. Oxygen partial pressure can be used as an input parameter for regulating or controlling systems in order to optimize the combustion process. Our goal is to identify and optimize the material system that would potentially function as the active sensing material for such a device that monitors oxygen partial pressure in these systems. We have used thin film samaria doped ceria (SDC) as the sensing material for the sensor operation, exploiting the fact that at high temperatures, oxygen vacancies generated due to samarium doping act as conducting medium for oxygen ions which hop through the vacancies from one side to the other contributing to an electrical signal. We have recently established that 6 atom % Sm doping in ceria films has optimum conductivity. Based on this observation, we have studied the variation in the overall conductivity of 6 atom % samaria doped ceria thin films as a function of thickness in the range of 50 nm to 300 nm at a fixed bias voltage of 2 volts. A direct proportionality in the increase in the overall conductivity is observed with the increase in sensing film thickness. For a range of oxygen pressure values from 1 mTorr to 100 Torr, a tolerable hysteresis error, good dynamic response and a response time of less than 10 seconds was observed

Sanghavi, Rahul P.; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Engelhard, Mark H.; Shutthanandan, V.; Jiang, Weilin; Thevuthasan, Suntharampillai; Kayani, Asghar N.; Prasad, Shalini

2010-12-01

373

Effects of potassium, lanthanum and black widow spider venom on miniature synaptic potentials in the Torpedo electroplax  

Microsoft Academic Search

Using a method of focal drug application it is demonstrated that high potassium concentration, lanthanum, and black widow spider venom accelerate spontaneous transmitter release inTorpedo electric tissue.

Christian Walther; Fachbereich Biologie; UniversitKt Konstanz

1974-01-01

374

Structural phase transitions and superconductivity in lanthanum copper oxides  

SciTech Connect

Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La{sub 2}CuO{sub 4}. This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper.

Crawford, M.K.; Harlow, R.L.; McCarron, E.M. [DuPont, Wilmington, DE (United States)] [and others

1996-12-31

375

Palliative treatment of bone metastases with samarium-153 EDTMP at onset of pain.  

PubMed

We evaluated the pain response and daily discomfort in patients suffering from a borderline degree of bone pain due to breast or lung cancer bone metastases, who had undergone early palliative radionuclide treatment. The results were compared with those from patients who had received standard analgesic therapy. Twenty-one patients (65.7 ± 3 years; 17 women) with metastatic bone cancer underwent samarium-153 (Sm-153) ethylene diamine tetramethylene phosphonate (EDTMP) administration (group A) and 18 patients (64.3 ± 8 years; 16 women)continued to receive standard analgesics (group B; control group). The patients kept a daily pain diary assessing both their discomfort and the pain at specific sites by means of a visual analog scale, rating from 0 (no discomfort–no pain)to 10 (worst discomfort–pain). These diaries were reviewed weekly for 2 months and three physicians rated the pain response on a scale from -2 (considerable deterioration) to +2 (considerable improvement). Baseline characteristics were similar in both groups. The reduction of total discomfort and of bone pain in group A was significantly greater compared to group B (p < 0.0001). A significant improvement of clinical conditions was observed in group A, where the physician rate changed from -1 to 1, compared to group B in which the rate changed from -1 to 0. Sm-153 EDTMP therapy can be considered for patients with bone pain from breast and lung cancer in advance, i.e.,before the establishment of severe pain syndrome. PMID:24122249

Gallicchio, Rosj; Giacomobono, Sabrina; Nardelli, Anna; Pellegrino, Teresa; Simeon, Vittorio; Gattozzi, Domenico; Maddalena, Francesca; Mainenti, Pierpaolo; Storto, Giovanni

2014-07-01

376

Development and evaluation of copper-67 and samarium-153 labeled conjugates for tumor radioimmunotherapy  

SciTech Connect

The potential of utilizing receptor-specific agents such as monoclonal antibodies (MAb), and MAb-derived smaller molecules, as carriers of radionuclides for the selective destruction of tumors has stimulated much research activity. The success of such applications depends on many factors, especially the tumor binding properties of the antibody reagent, the efficiency of labeling and in-vivo stability of the radioconjugate and, on the careful choice of the radionuclide best suited to treat the tumor under consideration. The radiolabeled antibody technique for radioimmunotherapy (RIT), however, has experienced many limitations, and its success has not matched the expectations that were raised more than a decade ago. The problems that have been identified include: (i) degradation of antibody immunoreactivity resulting from chemical manipulations required for labeling; (ii) lack of suitable radioisotopes and methods for stable attachment of the radiolabel; (iii) in-vivo instability of the radioimmunoconjugates; (iv) excessive accumulation of activity in non-target locations; and (v) lack of radioimmunoconjugate accessibility to cells internal to a tumor mass. A careful choice of the radionuclide(s) best suited to treat the tumor under consideration is one of the most important requirements for successful radioimmunotherapy. This study evaluates copper 67 and samarium 153 for tumor radioimmunotherapy.

Srivastava, S.C.; Mausner, L.F.; Mease, R.C.; Meinken, G.E.; Joshi, V.; Kolsky, K.; Sweet, M.; Steplewski, Z.

1995-02-01

377

The effect of electromotive-force generation on electrical properties of thin samarium sulfide films  

SciTech Connect

Electrical properties of thin SmS polycrystalline films with various values of the lattice constant at T = 300-580 K are studied. Specific features of the temperature dependences of electrical conductivity at T > 450 K are revealed. The effect of generation of the electromotive force with magnitude as large as 1.3 V at T = 440-470 K is observed when the films were subjected to the pressure of a spherical indenter. It is shown that it is possible to transform SmS films into a high-resistivity state (with the difference in the resistivity by three orders of magnitude) by applying an electric field with the strength higher than 100 V/cm. All the results obtained are accounted for using a model of the phenomenon of the electromotive-force generation in SmS under uniform heating of the sample and can also be attributed to the variable valence of samarium ions with respect to the lattice defects.

Kaminskii, V. V., E-mail: Vladimir.Kaminski@mail.ioffe.ru; Kazanin, M. M.; Solov'ev, S. M.; Sharenkova, N. V.; Volodin, N. M. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2006-06-15

378

Uranyl sensitization of samarium(III) luminescence in a two-dimensional coordination polymer.  

PubMed

Heterometallic carboxyphosphonates UO(2)(2+)/Ln(3+) have been prepared from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H(3)PPA). Compound 1, (UO(2))(2)(PPA)(HPPA)(2)Sm(H(2)O)·2H(2)O (1) adopts a two-dimensional structure in which the UO(2)(2+) metal ions bind exclusively to the phosphonate moiety, whereas the Ln(3+) ions are coordinated by both phosphonate and carboxylate functionalities. Luminescence studies of 1 show very bright visible and near-IR samarium(III)-centered emission upon direct excitation of the uranyl moiety. The Sm(3+) emissive state exhibits a double-exponential decay with lifetimes of 67.2 ± 6.5 and 9.0 ± 1.3 ?s as measured at 594 nm, after excitation at both 365 and 420 nm. No emission is observed in the region typical of the uranyl cation, indicating that all energy is either transferred to the Sm(3+) center or lost to nonradiative processes. Herein we report the synthesis, crystal structure, and luminescent behavior of 1, as well as those of the isostructural terbium, erbium, and ytterbium analogues. PMID:22171660

Knope, Karah E; de Lill, Daniel T; Rowland, Clare E; Cantos, Paula M; de Bettencourt-Dias, Ana; Cahill, Christopher L

2012-01-01

379

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C  

NASA Technical Reports Server (NTRS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. These quasistatic demagnetization data were obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature.

Niedra, J. M.

1992-01-01

380

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C  

NASA Astrophysics Data System (ADS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. These quasistatic demagnetization data were obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature.

Niedra, J. M.

381

A multicenter study on the effects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients  

Microsoft Academic Search

A multicenter study on the affects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients.BackgroundLanthanum carbonate (LC) (Fosrenol™) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.MethodsNinety-eight patients were randomized to

Patrick C. D'Haese; Goce B. Spasovski; Aleksander Sikole; Alastair Hutchison; Tony J. Freemont; Sylvie Sulkova; Charles Swanepoel; Svetlana Pejanovic; Llubica Djukanovic; Alessandro Balducci; Giorgio Coen; Waldysaw Sulowicz; Anibal Ferreira; Armando Torres; Slobodan Curic; Milan Popovic; Nada Dimkovic; Marc E. De Broe

2003-01-01

382

Diode pumped neodymium doped ASL (Sr1-xLax-yNdyMgxAl12-xO19) laser  

NASA Astrophysics Data System (ADS)

Blue laser based on Neodymium doped strontium lanthanum magnesium aluminoxide (Sr1-xLax-yNdyMgxAl12-xO19) single crystal were constructed by second harmonic generation. Output power of 1.72 W at 900nm was obtained under 792nm laser diode pump. Intra cavity second harmonic generation were performed with non linear crystal LBO leading to output power of 76.6 mW at 450nm with absorbed power of 13.7 W and average absorption efficiency of 61% in Nd:ASL crystal.

Zheng, Lihe; Loiseau, Pascal; Aka, Gérard

2013-07-01

383

Preparation of calcium doped LaCrO 3 fine powders by hydrothermal method and its sintering  

Microsoft Academic Search

The synthesis of fine powders of LaCrO3 and its solid solutions doped with calcium under hydrothermal conditions and the sintering of these powders were investigated. Precursor alkaline coprecipitated lanthanum chromite gels with three different compositions: LaCrO3, La0.9Ca0.1CrO3 and La0.8Ca0.2CrO3, were processed under hydrothermal conditions at low temperatures (350–425°C), for a reaction time between 30 and 120min. Powders of a single

L. P. Rivas-Vázquez; J. C. Rendón-Angeles; J. L. Rodríguez-Galicia; C. A. Gutiérrez-Chavarria; K. J. Zhu; K. Yanagisawa

2006-01-01

384

The extraction of thulium, dysprosium and samarium by di(n-octyl)arsinc acid (HDOAA) in chloroform  

E-print Network

into the organic phase. The maximum E values of 33 for thulium, 15 for dysprosium and a -3 41 for samarium were observed for the 1 x 10 M chloride/1M perchlor- ate, 1 x 10 M chloride/1M nitrate, and 1 x 10 M chloride/1M sulfate systems respectively. The data.... LIST OF FIGURES . INTRODUCTION EXPERIMENTAL ~eee e te Procedures . TABLE OF CONTENTS Page V1 1X X1 Preparation of solutions. Shaking time Determination of pH , . Preparation of the chloride-free Thulium( III) extraction systems Extraction...

El Seoud, Monica Irma

2012-06-07

385

Recent advances in the chemoselective reduction of functional groups mediated by samarium(II) iodide: a single electron transfer approach.  

PubMed

Recently, samarium(II) iodide reductants have emerged as powerful single electron donors for the highly chemoselective reduction of common functional groups. Complete control of the product formation can be achieved on the basis of a judicious choice of a Sm(II) complex/proton donor couple, even in the presence of extremely sensitive functionalities (iodides, aldehydes). In most cases, the reductions are governed by thermodynamic control of the first electron transfer, which opens up new prospects for unprecedented transformations via radical intermediates under mild regio-, chemo- and diastereoselective conditions that are fully orthogonal to hydrogenation or metal-hydride mediated processes. PMID:24013846

Szostak, Michal; Spain, Malcolm; Procter, David J

2013-12-01

386

Sequential elimination-reduction reactions promoted by samarium diiodide: synthesis of 2,3-dideuterioesters or -amides.  

PubMed

A facile and general sequential elimination/reduction process promoted by samarium diiodide provides an efficient method for synthesizing saturated esters or amides 3 from readily available starting materials. The reaction involves a beta-elimination of the starting 2-halo-3-hydroxyesters or -amides 1 and subsequent 1,4-reduction of the obtained alpha,beta-unsaturated esters or amides in the presence of H2O. When D20 is used instead of H2O, 2,3-dideuterioesters or -amides 4 are isolated. A mechanism is proposed to account for this synthesis. PMID:11686607

Concellón, J M; Rodríguez-Solla, H

2001-10-01

387

Measurement of lanthanum and technetium in uranium fuels by inductively coupled plasma atomic emission spectroscopy.  

SciTech Connect

An important parameter in characterizing an irradiated nuclear fuel is determining the amount of uranium fissioned. By determining the amount of uranium fissioned in the fuel a burnup performance parameter can be calculated, and the amount of fission products left in the fuel can be predicted. The quantity of uranium fissioned can be calculated from the amount of lanthanum and technetium present in the fuel. Lanthanum and technetium were measured in irradiated fuel samples using an Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) instrument and separation equipment located in a shielded glove-box. A discussion of the method, interferences, detection limits, quality control and a comparison to other work will be presented.

Carney, K.; Crane, P.; Cummings, D.; Krsul, J.; McKnight, R.

1999-06-10

388

Near fifty percent sodium substituted lanthanum manganites—A potential magnetic refrigerant for room temperature applications  

SciTech Connect

Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering at 300?K and the magnetic isotherms at different temperature ranges were analyzed for estimating magnetic entropy variation. Magnetic entropy change of 1.5?J·kg{sup ?1}·K{sup ?1} was observed near 300?K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300?K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300?K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62?K at 280?K.

Sethulakshmi, N.; Anantharaman, M. R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Al-Omari, I. A. [Department of Physics, Sultan Qaboos University, PC 123 Muscat, Sultanate of Oman (Oman); Suresh, K. G. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

2014-03-03

389

Sensitive and reliable ascorbic acid sensing by lanthanum oxide/reduced graphene oxide nanocomposite.  

PubMed

A simple strategy for the detection and estimation of ascorbic acid (AA), using lanthanum oxide-reduced graphene oxide nanocomposite (LO/RGO) on indium tin oxide (ITO) substrate, is reported. LO/RGO displays high catalytic activity toward the oxidation of AA, and the synergism between lanthanum oxide and reduced graphene oxide was attributed to the successful and efficient detection. Detection mechanism and sensing efficacy of LO/RGO nanocomposite are investigated by electrochemical techniques. Chronoamperometric results under optimal conditions show a linear response range from 14 to 100 ?M for AA detection. Commercially available vitamin C tablets were also analyzed using the proposed LO/RGO sensor, and the remarkable recovery percentage (97.64-99.7) shows the potential application in AA detection. PMID:24879601

Mogha, Navin Kumar; Sahu, Vikrant; Sharma, Meenakshi; Sharma, Raj Kishore; Masram, Dhanraj T

2014-10-01

390

Highly stable, mesoporous mixed lanthanum-cerium oxides with tailored structure and reducibility  

SciTech Connect

Pure and mixed lanthanum and cerium oxides were synthesized via a reverse microemulsion-templated route. This approach yields highly homogeneous and phase-stable mixed oxides with high surface areas across the entire range of La:Ce ratios from pure lanthana to pure ceria. Surprisingly, all mixed oxides show the fluorite crystal structure of ceria, even for lanthanum contents as high as 90%. Varying the La:Ce ratio not only allows tailoring of the oxide morphology (lattice parameter, pore structure, particle size, and surface area), but also results in a fine-tuning of the reducibility of the oxide which can be explained by the creation of oxygen vacancies in the ceria lattice upon La addition. Such finely controlled syntheses, which enable the formation of stable, homogeneous mixed oxides across the entire composition range, open the path towards functional tailoring of oxide materials, such as rational catalyst design via fine-tuning of redox activity.

Liang, Shuang; Broitman, Esteban; Wang, Yanan; Cao, Anmin; Veser, Goetz

2011-05-01

391

Evaluation of kinetic parameters for the thermal decomposition of gamma-irradiated anhydrous lanthanum nitrate  

NASA Astrophysics Data System (ADS)

The thermal decomposition of gamma-irradiated anhydrous lanthanum nitrate was studied by dynamic thermogravimetry. The decomposition proceeds via three consecutive stages characterized by different activation energies. The reaction order, activation energy, frequency factor and entropy of activation were calculated using the Coats-Redfern, Freeman-Carroll and Horowitz-Metzger methods and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with the irradiation dose. The activation energies of all the three stages decrease on irradiation. The mechanism of the decomposition of unirradiated and irradiated anhydrous lanthanum nitrate follows the Mampel model equation,-ln(1-?) for g(?), and the rate-controlling process is random nucleation with the formation of a nucleus on every particle.

James, C.; Samuel, Jadu

392

Relaxor freezing and electric-field induced ferroelectric transition in a lanthanum lead zirconate titanate ceramics  

Microsoft Academic Search

Transition lines between various phases in the electric-field temperature phase diagram of 9\\/65\\/35 lanthanum lead zirconate titanate ceramics were determined by measurements of the temperature and electric-field dependent dielectric constant. Above the critical field (EC) the dc bias electric field induces a transition from the relaxor to the ferroelectric phase, while below EC the system exhibits a freezing transition between

V. Bobnar; Z. Kutnjak; R. Pirc; A. Levstik

1999-01-01

393

Temperature Dependence of Piezoelectric, Dielectric, and Elastic Properties of Lead Lanthanum Zirconate Titanate Ceramics  

Microsoft Academic Search

The piezoelectric resonance and the ferroelectric hysteresis loopin 8\\/65\\/35 lead lanthanum zirconate titanate (PLZT) ceramics were measuredsimultaneously at temperatures ranging from 20 to 140°C. The complexelastic compliance and the complex piezoelectric and dielectric constantswere extracted from the piezoelectric resonance data, while thetemperature-dependent remanent polarization and coercive field were obtainedfrom the ferroelectric hysteresis loops. From the temperature behavior of theabove quantities,

Vid Bobnar; Zdravko Levstik; andAdrijan Levstik

1998-01-01

394

Dielectric properties of partially disordered lanthanum-modified lead zirconate titanate relaxor ferroelectrics  

Microsoft Academic Search

Linear and third-order nonlinear dielectric susceptibilities and the dielectric polarization were measured in 6.5\\/65\\/35 lanthanum lead zirconate titanate (PLZT) hot-pressed ceramics. On cooling linear dielectric data show a transition from an ergodic to a nonergodic relaxor phase, while, on heating, a ferroelectric to ergodic relaxor phase transition appears. The third-order dielectric response is reminiscent of an ergodic to nonergodic relaxor

Boris Vodopivec; Cene Filipic; Adrijan Levstik; Janez Holc; Zdravko Kutnjak; Horst Beige

2004-01-01

395

Electric-field-temperature phase diagram of the relaxor ferroelectric lanthanum-modified lead zirconate titanate  

Microsoft Academic Search

Transition lines between various phases in the electric-field-temperature phase diagram of 9\\/65\\/35 lanthanum-modified lead zirconate titanate ceramics were determined by measurements of the temperature and electric-field-dependent dielectric constant. Above a critical field (EC) the dc bias electric field induces a transition from the relaxor (R) to the long-range ferroelectric (FE) phase. In the temperature direction of the approach to the

Vid Bobnar; Zdravko Kutnjak; Rasa. Pirc; Adrijan Levstik

1999-01-01

396

Development of lanthanum strontium manganite perovskite cathode materials of solid oxide fuel cells: a review  

Microsoft Academic Search

The high-temperature solid oxide fuel cell (SOFC) is the most efficient and environmentally friendly energy conversion technology\\u000a to generate electricity from fuels such as hydrogen and natural gas as compared to the traditional thermal power generation\\u000a plants. In the last 20–30 years, there has been significant progress in the materials development and stack technologies in\\u000a SOFC. Among the electrode materials, lanthanum

San Ping Jiang

2008-01-01

397

Scanning Auger microscopy study of lanthanum partitioning in sphene-based glass?ceramics  

Microsoft Academic Search

Glass-ceramics are being investigated as possible hosts for the radioactive wastes that would result from recycling irradiated nuclear fuels. For a glass?ceramic to be a superior waste form to a single-phase glass, some of the long-lived actinides and fission products must be preferentially incorporated into the lattice of the crystalline phase. The partitioning of lanthanum in sphene-based glass?ceramics has been

W. H. Hocking; P. J. Haywaed; D. G. Watson; G. C. Allen

1984-01-01

398

Chromium and copper substituted lanthanum nano-ferrites: Their synthesis, characterization and application studies  

NASA Astrophysics Data System (ADS)

Nano-crystalline lanthanum ferrites substituted by chromium and copper having formula LaMxFe1-xO3 (M = Cr, Cu; 0.0 ? x ? 0.5) were synthesized using sol-gel auto-combustion method. The formation of ferrite particles was confirmed using Fourier Transform Infra-Red (FT-IR) spectra and powder X-ray Diffraction (XRD) techniques. The entire ferrite compositions were found to be pure phased with same symmetry as LaFeO3. The average crystallite size was calculated to be ?60 nm. The ferrite compositions were observed to behave as semi-conductors, as their resistivity decreased with increasing temperature. These ferrite compositions were employed as catalysts in the decomposition of hydrogen peroxide solution (0.17 M). Pure LaFeO3 was found to have a very low catalytic activity towards the decomposition of hydrogen peroxide solution, while presence of copper in the lanthanum ferrite lattice was found to significantly enhance its catalytic activity. The rate constant in case of reactions catalysed by LaCu0.5Fe0.5O3 was nearly 25 times larger than that obtained from reactions catalysed by pure LaFeO3. However, chromium substitution was not found to influence the catalytic activity of lanthanum ferrites as chromium substituted lanthanum ferrites exhibited very low catalytic activity. This was explained on the basis of relative stability of oxidation states of the substituent ions and the presence of defects in the crystal lattice.

Jauhar, Sheenu; Singhal, Sonal

2014-10-01

399

Slow dynamics and ergodicity breaking in a lanthanum-modified lead zirconate titanate relaxor system  

Microsoft Academic Search

The freezing of the dynamic process in a 9\\/65\\/35 lanthanum lead zirconate-titanate (PLZT) ceramics has been investigated by measurements of the frequency-dependent complex dielectric constant and the quasistatic field-cooled (FC) and zero-field-cooled (ZFC) dielectric susceptibilities. It was found that the aging process is responsible for the difference in temperature variations of the FC static dielectric constant and the static dielectric

Zdravko Kutnjak; Cene Filipic; Rasa. Pirc; Adrijan Levstik; Robert Farhi; Mimoun El Marssi

1999-01-01

400

Fabrication of transparent lead lanthanum zirconate titanate ceramics from fine powders by two-stage sintering  

Microsoft Academic Search

This paper reports that transparent lead lanthanum zirconate titanate (PLZT) ceramics were fabricated from fine powders using an inexpensive two-stage sintering technique. The powders were prepared by hydrolysis from low-cost inorganic precursors. In the two-stage sintering method, uniaxially pressed green pelets were densified to nearly theoretical values in an oxygen gas atmosphere during the first-stage sintering, at 1000[degrees]C for 1

Yoshio Yoshikawa; Kaoru Tsuzuki

1992-01-01

401

Effect of compositional variations in the lead lanthanum zirconate stannate titanate system on electrical properties  

Microsoft Academic Search

The purpose of this work was to evaluate the effect of compositional modifications on the electrical properties of lead lanthanum zirconate stannate titanate (PLZST) ceramics, as well as to examine their electrically induced phase-change behavior. Variations in the Ti:Sn ratio were evaluated. Increased Ti{sup 4+} content produced the following: decreased switching field, related to an increased antiferroelectric-ferroelectric (AFE-FE) transition temperature;

Kelley Markowski; Seung-Eek Park; Shoko Yoshikawa; L. Eric Cross

1996-01-01

402

Design of a lanthanum bromide detector for time-of-flight PET  

Microsoft Academic Search

Recent improvements in the growth and packaging of lanthanum bromide (LaBr3), in addition to its superb intrinsic properties of high light output, excellent energy resolution, and fast decay time, make it a viable detection material for a positron emission tomography (PET) scanner based on time-of-flight (TOF). We have utilized theoretical simulations and experimental measurements to investigate the design and performance

A. Kuhn; S. Surti; J. S. Karp; P. S. Raby; K. S. Shah; A. E. Perkins; G. Muehllehner

2004-01-01

403

Formation and stability of lanthanum oxide thin films deposited from ?-diketonate precursor  

Microsoft Academic Search

Lanthanum oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 180–425°C on soda-lime glass and Si(100) substrates using a ?-diketonate type precursor La(thd)3 and ozone. The chemical constituents of the films were analyzed by TOF-ERDA, RBS and FTIR while XRD and AFM were used to determine the crystallinity and surface morphology. Films grown below 275°C were amorphous

Minna Nieminen; Matti Putkonen; Lauri Niinistö

2001-01-01

404

Room temperature synthesis of high temperature stable lanthanum phosphate–yttria nano composite  

SciTech Connect

Graphical abstract: A facile aqueous sol–gel route involving precipitation–peptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Highlights: ? A novel lanthanum phosphate–Y{sub 2}O{sub 3} nano composite is synthesized for the first time using a modified facile sol gel process. ? The composite becomes crystalline at 600 °C and X-ray diffraction pattern is indexed for monoclinic LaPO{sub 4} and cubic yttria. ? The composite synthesized was tested up to 1300 °C and no reaction between the phases of the constituents is observed with the morphologies of the phases being retained. -- Abstract: A facile aqueous sol–gel route involving precipitation–peptization mechanism followed by electrostatic stabilization is used for synthesizing nanocrystalline composite containing lanthanum phosphate and yttria. Lanthanum phosphate (80 wt%)–yttria (20 wt%) nano composite (LaPO{sub 4}–20%Y{sub 2}O{sub 3}), has an average particle size of ?70 nm after heat treatment of precursor at 600 °C. TG–DTA analysis reveals that stable phase of the composite is formed on heating the precursor at 600 °C. The TEM images of the composite show rod shape morphology of LaPO{sub 4} in which yttria is acquiring near spherical shape. Phase identification of the composite as well as the phase stability up to 1300 °C was carried out using X-ray diffraction technique. With the phases being stable at higher temperatures, the composite synthesized should be a potential material for high temperature applications like thermal barrier coatings and metal melting applications.

Sankar, Sasidharan; Raj, Athira N.; Jyothi, C.K. [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India)] [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India); Warrier, K.G.K., E-mail: wwarrierkgk@yahoo.co.in [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India)] [Material Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, Council of Scientific and Industrial Research, Thiruvananthapuram 695019 (India); Padmanabhan, P.V.A. [Bhabha Atomic Research Centre, Mumbai 400085 (India)] [Bhabha Atomic Research Centre, Mumbai 400085 (India)

2012-07-15

405

Internal stress anisotropies induced by electric field in lanthanum modified PbTiO3 ceramics  

Microsoft Academic Search

Lanthanum modified lead titanate, (Pb0·775La0·15)TiO3 ceramics with a tetragonality of c\\/a = 1·024 were hot-pressed and the anisotropy of internal stress generated by applying a poling field were measured using a microindentation technique. In this specimen with a grain size of Gs=3·0 ?m, the internal stresses in the directions perpendicular and parallel to the DC poling field were 151 and

T. Yamamoto; H. Igarashi; K. Okazaki

1983-01-01

406

Lanthanum Chromite Based Catalysts for Oxidation of Methane Directly on SOFC Anodes  

Microsoft Academic Search

Catalytic properties of substituted lanthanum chromites were investigated for their use as anode materials for direct methane oxidation in solid oxide fuel cell (SOFC) anode materials. Different reaction mixtures were chosen to simulate the various SOFC operating conditions: partial oxidation, CO2 reforming by recycling, and H2O reforming. All experiments were performed in methane-rich atmospheres. Alkaline earth elements such as Ca,

Joseph Sfeir; Philippe A Buffat; Pedro Möckli; Nicolas Xanthopoulos; Ruben Vasquez; Hans Joerg Mathieu; Jan Van herle; K Ravindranathan Thampi

2001-01-01

407

Isolation of hemoglobin from human blood using solid phase extraction with lanthanum(III) modified zeolite  

Microsoft Academic Search

A direct solid-phase extraction procedure for the selective isolation of hemoglobin from complex matrices using lanthanum(III)\\u000a modified zeolite (clinoptilolite) as sorbent was developed. The modified clinoptilolite provides a sorption capacity of 31.8 mg\\u000a g-1 for hemoglobin (Hb). Experimental parameters governing the sorption efficiency, i.e., the pH of sample solution, the ionic\\u000a strength and sorption time, were investigated. A sorption efficiency of

Xuwei Chen; Shuai Chen; Jiawei Liu; Jianhua Wang

2009-01-01

408

Effect of chloride incorporation on the crystallization of zirconium-barium-lanthanum-aluminum fluoride glass  

NASA Technical Reports Server (NTRS)

One aspect of the influence of preparation procedure on the crystallization behavior of a zirconium-barium-lanthanum-aluminum fluoride glass was studied. The crystallization pattern of this glass may be affected by the chlorine concentration within it. In particular, when such glasses are heated at low temperatures, the alpha-Ba-Zr-F6 crystalline phase forms only in those glasses which contain chloride.

Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

1985-01-01

409

Nonaqueous synthesis of metal oxide nanoparticles: Short review and doped titanium dioxide as case study for the preparation of transition metal-doped oxide nanoparticles  

SciTech Connect

The liquid-phase synthesis of metal oxide nanoparticles in organic solvents under exclusion of water is nowadays a well-established alternative to aqueous sol-gel chemistry. In this article, we highlight some of the advantages of these routes based on selected examples. The first part reviews some recent developments in the synthesis of ternary metal oxide nanoparticles by surfactant-free nonaqueous sol-gel routes, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the presentation of structural peculiarities of manganese oxide nanoparticles with an ordered Mn vacancy superstructure. These examples show that nonaqueous systems, on the one hand, allow the preparation of compositionally complex oxides, and, on the other hand, make use of the organic components (initially present or formed in situ) in the reaction mixture to tailor the morphology. Furthermore, obviously even the crystal structure can differ from the corresponding bulk material like in the case of MnO nanoparticles. In the second part of the paper we present original results regarding the synthesis of dilute magnetic semiconductor TiO{sub 2} nanoparticles doped with cobalt and iron. The structural characterization as well as the magnetic properties with special attention to the doping efficiency is discussed. - Graphical abstract: In the first part of this article, nonaqueous sol-gel routes to ternary metal oxide nanoparticles are briefly reviewed, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the appearance of an unprecedented superstructure in MnO nanoparticles. In the second part, doping experiments of TiO{sub 2} with Fe and Co are presented, along with their characterization including magnetic measurements.

Djerdj, Igor [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zuerich (Switzerland)], E-mail: igor.djerdj@mat.ethz.ch; Arcon, Denis [Institute Jozef Stefan, Jamova 39, 1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Jaglicic, Zvonko [Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana (Slovenia); Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova 2, 1000 Ljubljana (Slovenia); Niederberger, Markus [ETH Zuerich, Department of Materials, Wolfgang-Pauli-Strasse 10, 8093 Zuerich (Switzerland)], E-mail: markus.niederberger@mat.ethz.ch

2008-07-15

410

Modification of chitosan by using samarium for potential use in drug delivery system.  

PubMed

In the presence of hydroxyl and amine groups, chitosan is highly reactive; therefore, it could be used as a carrier in drug delivery. For this study, chitosan-Sm complexes with different concentrations of samarium from 2.5 to 25 wt.% have been successfully synthesized by the impregnation method. Chitosan combined with Sm3+ ions produced a drug carrier material with fluorescence properties; thus, it could also be used as an indicator of drug release with ibuprofen (IBU) as a model drug. We evaluated the spectroscopic and interaction properties of chitosan and Sm3+ ions, the interaction of chitosan-Sm matrices with IBU as a model drug, and the effect of Sm3+ ions addition on the chitosan ability to adsorb the drug. The result showed that the hypersensitive fluorescence intensity of chitosan-Sm (2.5 wt.%) is higher than the others, even though the adsorption efficiency of chitosan-Sm 2.5wt.% is lower (29.75%) than that of chitosan-Sm 25 wt.% (33.04%). Chitosan-Sm 25 wt.% showed the highest efficiency of adsorption of ibuprofen (33.04%). In the release process of ibuprofen from the chitosan-Sm-IBU matrix, the intensity of orange fluorescent properties in the hypersensitive peak of 4G5/2?6H7/2 transition at 590 nm was observed. Fluorescent intensity increased with the cumulative amount of IBU released; therefore, the release of IBU from the Sm-modified chitosan complex can be monitored by the changes in fluorescent intensity. PMID:24177873

Kusrini, Eny; Arbianti, Rita; Sofyan, Nofrijon; Abdullah, Mohd Aidil A; Andriani, Fika

2014-01-01

411

Temperature-induced valence transition and associated lattice collapse in samarium fulleride.  

PubMed

The different degrees of freedom of a given system are usually independent of each other but can in some materials be strongly coupled, giving rise to phase equilibria sensitively susceptible to external perturbations. Such systems often exhibit unusual physical properties that are difficult to treat theoretically, as exemplified by strongly correlated electron systems such as intermediate-valence rare-earth heavy fermions and Kondo insulators, colossal magnetoresistive manganites and high-transition temperature (high-T(c)) copper oxide superconductors. Metal fulleride salts-metal intercalation compounds of C60--and materials based on rare-earth metals also exhibit strong electronic correlations. Rare-earth fullerides thus constitute a particularly intriguing system--they contain highly correlated cation (rare-earth) and anion (C60) sublattices. Here we show, using high-resolution synchrotron X-ray diffraction and magnetic susceptibility measurements, that cooling the rare-earth fulleride Sm2.75C60 induces an isosymmetric phase transition near 32 K, accompanied by a dramatic isotropic volume increase and a samarium valence transition from (2 + epsilon) + to nearly 2 +. The negative thermal expansion--heating from 4.2 to 32 K leads to contraction rather than expansion--occurs at a rate about 40 times larger than in ternary metal oxides typically exhibiting such behaviour. We attribute the large negative thermal expansion, unprecedented in fullerene or other molecular systems, to a quasi-continuous valence transition from Sm(2+) towards the smaller Sm((2+epsilon)+), analogous to the valence or configuration transitions encountered in intermediate-valence Kondo insulators like SmS (ref. 3). PMID:14534581

Arvanitidis, J; Papagelis, Konstantinos; Margadonna, Serena; Prassides, Kosmas; Fitch, Andrew N

2003-10-01

412

Europium, Samarium, and Neodymium Isotopic Fractions in Metal-Poor Stars  

E-print Network

We have derived isotopic fractions of europium, samarium, and neodymium in two metal-poor giants with differing neutron-capture nucleosynthetic histories. These isotopic fractions were measured from new high resolution (R ~ 120,000), high signal-to-noise (S/N ~ 160-1000) spectra obtained with the 2dCoude spectrograph of McDonald Observatory's 2.7m Smith telescope. Synthetic spectra were generated using recent high-precision laboratory measurements of hyperfine and isotopic subcomponents of several transitions of these elements and matched quantitatively to the observed spectra. We interpret our isotopic fractions by the nucleosynthesis predictions of the stellar model, which reproduces s-process nucleosynthesis from the physical conditions expected in low-mass, thermally-pulsing stars on the AGB, and the classical method, which approximates s-process nucleosynthesis by a steady neutron flux impinging upon Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with an r-process origin by the classical method and is consistent with either an r- or an s-process origin by the stellar model. Our Sm isotopic fraction in HD 175305 suggests a predominantly r-process origin, and our Sm isotopic fraction in HD 196944 is consistent with an s-process origin. The Nd isotopic fractions, while consistent with either r-process or s-process origins, have very little ability to distinguish between any physical values for the isotopic fraction in either star. This study for the first time extends the n-capture origin of multiple rare earths in metal-poor stars from elemental abundances to the isotopic level, strengthening the r-process interpretation for HD 175305 and the s-process interpretation for HD196944.

Ian U. Roederer; James E. Lawler; Christopher Sneden; John J. Cowan; Jennifer S. Sobeck; Catherine A. Pilachowski

2007-12-16

413

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C  

NASA Technical Reports Server (NTRS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.

1992-01-01

414

M-H characteristics and demagnetization resistance of samarium-cobalt permanent magnets to 300 C  

NASA Astrophysics Data System (ADS)

The influence of temperature on the M-H demagnetization characteristics of permanent magnets is important information for the full utilization of the capabilities of samarium-cobalt magnets at high temperatures in demagnetization-resistant permanent magnet devices. In high temperature space power converters, such as free-piston Stirling engine driven linear alternators, magnet demagnetization can occur as a long-term consequence of thermal agitation of domains and of metallurgical change, and also as an immediate consequence of too large an applied field. Investigated here is the short-term demagnetization resistance to applied fields derived from basic M-H data. This quasistatic demagnetization data was obtained for commercial, high-intrinsic-coercivity, Sm2Co17-type magnets from 5 sources, in the temperature range 23 to 300 C. An electromagnet driven, electronic hysteresigraph was used to test the 1-cm cubic samples. The observed variation of the 2nd quadrant M-H characteristics was a typical rapid loss of M-coercivity and a relatively lesser loss of remanence with increasing temperature. The 2nd quadrant M-H curve knee point is used to define the limits of operation safe against irreversible demagnetization due to an excessive bucking field for a given flux density swing at temperature. Such safe operating area plots are shown to differentiate the high temperature capabilities of the samples from different sources. For most of the samples, their 2nd quadrant M-H loop squareness increased with temperature, reaching a peak or a plateau above 250 C.

Niedra, Janis M.

1992-08-01

415

Microstructured fibers with high lanthanum oxide glass core for nonlinear applications  

NASA Astrophysics Data System (ADS)

We demonstrate a low loss microstructured fiber (MOF) with a high nonlinear glass core and silica holey cladding. The substitution of mostly used silica as core material of microstructured fibers by lanthanum oxide glass promises a high nonlinear conversion efficiency for supercontinuum (SC) generation. The glass composition is optimized in terms of thermochemical and optical requirements. The glass for the MOF core has a high lanthanum oxide concentration (10 mol% La2O3) and a good compatibility with the silica cladding. This is performed by adding a suitable alumina concentration up to 20 mol%. The lanthanum oxide glass preform rods were manufactured by melting technique. Besides purity issues the material homogeneity plays an important role to achieve low optical loss. The addition of fluorides allows the better homogenization of the glass composition in the preform volume by refining. The minimum attenuation of an unstructured fiber drawn from this glass is about 0.6 dB/m. It is mostly caused by decreasing of scattering effects. The microstructured silica cladding allows the considerable shifting of dispersive behavior of the MOF for an optimal pump light conversion. The MOF shows zero dispersion wavelengths (ZDW) of 1140 nm (LP01 mode) and 970 nm (LP11 mode). The supercontinuum generation was investigated with a 1064 nm pump laser (650 ps). It shows a broad band emission between 500 nm and 2200 nm.

Kobelke, J.; Schuster, K.; Litzkendorf, D.; Schwuchow, A.; Kirchhof, J.; Bartelt, H.; Tombelaine, V.; Leproux, P.; Couderc, V.; Labruyere, A.

2009-05-01

416

Facile and efficient one-pot synthesis of benzimidazoles using lanthanum chloride  

PubMed Central

Background We report the synthesis of benzimidazoles using lanthanum chloride as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phenylenediamine and a variety of aldehydes were developed under mild reaction conditions. Results We have examined the effect of different solvents using the same reaction conditions. The yield of the product varied with the nature of the solvents, and better conversion and easy isolation of products were found with acetonitrile. In a similar manner, the reaction with o-phenylenediamine and 3,4,5-trimethoxybenzaldehyde was carried out without any solvents. The observation shows that the reaction was not brought into completion, even after starting for a period of 9 h, and the reaction mixture showed a number of spots in thin-layer chromatography. Conclusions In conclusion, lanthanum chloride has been employed as a novel and efficient catalyst for the synthesis of benzimidazoles in good yields from o-phenylenediamine and a wide variety of aldehydes. All of the reactions were carried out in the presence of lanthanum chloride (10 mol%) in acetonitrile at room temperature. PMID:23919542

2013-01-01

417

Lanthanum halide scintillators for time-of-flight 3-D pet  

DOEpatents

A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

Karp, Joel S. (Glenside, PA); Surti, Suleman (Philadelphia, PA)

2008-06-03

418

Lanthanum silicate coated magnetic microspheres as a promising affinity material for phosphopeptide enrichment and identification.  

PubMed

Novel Fe(3)O(4)@La(x)Si(y)O(5) affinity microspheres consisting of a superparamagnetic Fe(3)O(4) core and an amorphous lanthanum silicate shell have been synthesized. The core-shell-structured Fe(3)O(4)@La(x)Si(y)O(5) microspheres, with a mean size of ca. 480 nm, had rough lanthanum silicate surfaces and displayed relatively strong magnetism (47.2 emu g(-1)). This novel affinity material can be used for selective capture, rapid magnetic separation, and part dephosphorylation (which plays an important role in identifying phosphopeptides in MS) of the phosphopeptides in a peptide mixture. Its ability to selectively trap and magnetically isolate as well as label the phosphopeptides was evaluated using a standard phosphorylated protein (?-casein) and a real sample (human serum). Phosphopeptides and their corresponding label ions were detected for concentrations of ?-casein as low as 1 × 10(-9) M and in mixtures of ?-casein and BSA with molar ratios as low as 1:50. In addition, this affinity material, with its labeling properties, is superior to commercial TiO(2) beads in terms of interference from non-phosphopeptide molecules. These results reveal that the lanthanum silicate coated magnetic microspheres represent a promising affinity material for the rapid purification and recognition of phosphopeptides. PMID:22722743

Cheng, Gong; Liu, Yan-Lin; Zhang, Ji-Lin; Sun, De-Hui; Ni, Jia-Zuan

2012-08-01

419

Efficacy of continuous oral administration of lanthanum carbonate over 24 months.  

PubMed

To examine the efficacy of long-term administration of lanthanum carbonate, changes in serum Ca, phosphate, whole parathyroid hormone (wPTH), and ALP were examined in 40 patients who were able to tolerate dosage of lanthanum carbonate over a continuous period of 24 months. Concurrently, concomitant administration of other phosphate binders, cinacalcet, vitamin D, etc., was also examined. After 24 months, serum phosphorus levels (P levels) had decreased to within management target of guidelines, from 6.16?±?1.44?mg/dL to 5.58?±?1.15?mg/dL, and this effect was maintained for 2 years. There were no changes in Ca level. wPTH did not change significantly but tended to increase at 12 months. The dose of concomitantly administered calcium carbonate and sevelamer hydrochloride was reduced. The P-lowering function of lanthanum carbonate still held steady at 24 months following the start of dosage. Because of the rising trend seen in wPTH, dose of cinacalcet and/or vitamin D need to be modulated. Reducing the number of concomitantly administered phosphate binder tablets was desirable from the standpoint of patient adherence. PMID:23586509

Ishizu, Takashi; Hong, Zhang; Matsunaga, Tsuneaki; Kaneko, Yoko; Taru, Yoshinori

2013-04-01

420

The kinetics of uptake and recovery of lanthanum using freshwater algae as biosorbents: comparative analysis.  

PubMed

In this study, the adsorption and desorption kinetics of lanthanum (La) on micro algal cells was investigated. The internal transcribed spacer (ITS) and 18S ribosomal RNA gene (rRNA) were used for molecular identification of the species. The algal species were found to have 95-98% identities to Desmodesmus multivariabilis, Scenedesmus acuminutus, Chloroidium saccharophilum and Stichococcus bacillaris. The species were cultured and tested independently. D. multivariabilis was found to be the most efficient at adsorbing lanthanum with a maximum sorption capacity (qmax) of 100 mg/g and a high affinity (b) of 4.55 L/g. Desorption of La was also highest in D. multivariabilis with recovery up to 99.63% at initial concentration as high as 100 mg/L. Desorption data fitted best to the modified pseudo second-order with a better correlation coefficient (R(2)) of ?0.98 than first order model. The results showed feasibility of lanthanum recovery using algal sorbents, a cost effective method. PMID:24507581

Birungi, Z S; Chirwa, E M N

2014-05-01

421

JOURNAL DE PHYSIQUE Colloque C5, supplment au n 5, Tome 40, Mai 1979, page C5-83 Density functional theory of f-band metals : lanthanum, cerium and thorium C1  

E-print Network

functional theory of f-band metals : lanthanum, cerium and thorium C1 ) D. Glotzel Institut fur centered cubic lanthanum, cerium and thorium have been performed using the linear muffin tin orbital (LMTO

Paris-Sud XI, Université de

422

Long-term treatment with lanthanum carbonate reduces mineral and bone abnormalities in rats with chronic renal failure  

PubMed Central

Background. Lanthanum carbonate (FOSRENOL®, Shire Pharmaceuticals) is an effective non-calcium, non-resin phosphate binder for the treatment of hyperphosphataemia in patients with chronic kidney disease (CKD). In this study, we used a rat model of chronic renal failure (CRF) to examine the long-term effects of controlling serum phosphorus with lanthanum carbonate treatment on the biochemical and bone abnormalities associated with CKD–mineral and bone disorder (CKD–MBD). Methods. Rats were fed a normal diet (normal renal function, NRF), or a diet containing 0.75% adenine for 3 weeks to induce CRF. NRF rats continued to receive normal diet plus vehicle or normal diet supplemented with 2% (w/w) lanthanum carbonate for 22 weeks. CRF rats received a diet containing 0.1% adenine, with or without 2% (w/w) lanthanum carbonate. Blood and urine biochemistry were assessed, and bone histomorphometry was performed at study completion. Results. Treatment with 0.75% adenine induced severe CRF, as demonstrated by elevated serum creatinine. Hyperphosphataemia, hypocalcaemia, elevated calcium × phosphorus product and secondary hyperparathyroidism were evident in CRF + vehicle animals. Treatment with lanthanum carbonate reduced hyperphosphataemia and secondary hyperparathyroidism in CRF animals (P < 0.05), and had little effect in NRF animals. Bone histomorphometry revealed a severe form of bone disease with fibrosis in CRF + vehicle animals; lanthanum carbonate treatment reduced the severity of the bone abnormalities observed, particularly woven bone formation and fibrosis. Conclusions. Long-term treatment with lanthanum carbonate reduced the biochemical and bone abnormalities of CKD–MBD in a rat model of CRF. PMID:21098011

Damment, Stephen; Secker, Roger; Shen, Victor; Lorenzo, Victor; Rodriguez, Mariano

2011-01-01

423

Optical studies of Sm³? ions doped zinc alumino bismuth borate glasses.  

PubMed

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm(3+)) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm(3+) ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses. The suitable concentration of Sm(3+) ions in these glasses to act as an efficient lasing material has been discussed by measuring the emission cross-section and branching ratios for the emission transitions. The quantum efficiencies were also been estimated from emission decay measurements recorded for the (4)G5/2 level of Sm(3+) ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm(3+) ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers. PMID:24530709

Swapna, K; Mahamuda, Sk; Srinivasa Rao, A; Shakya, S; Sasikala, T; Haranath, D; Vijaya Prakash, G

2014-05-01

424

Optical studies of Sm3+ ions doped Zinc Alumino Bismuth Borate glasses  

NASA Astrophysics Data System (ADS)

Zinc Alumino Bismuth Borate (ZnAlBiB) glasses doped with different concentrations of samarium (Sm3+) ions were prepared by using melt quenching technique and characterized for their lasing potentialities in visible region by using the techniques such as optical absorption, emission and emission decay measurements. Radiative properties for various fluorescent levels of Sm3+ ions were estimated from absorption spectral information using Judd-Ofelt (JO) analysis. The emission spectra and con-focal photoluminescence images obtained by 410 nm laser excitation demonstrates very distinct and intense orange-red emission for all the doped glasses. The suitable concentration of Sm3+ ions in these glasses to act as an efficient lasing material has been discussed by measuring the emission cross-section and branching ratios for the emission transitions. The quantum efficiencies were also been estimated from emission decay measurements recorded for the 4G5/2 level of Sm3+ ions. From the measured emission cross-sections, branching ratios, strong photoluminescence features and CIE chromaticity coordinates, it was found that 1 mol% of Sm3+ ions doped ZnAlBiB glasses are most suitable for the development of visible orange-red lasers.

Swapna, K.; Mahamuda, Sk.; Srinivasa Rao, A.; Shakya, S.; Sasikala, T.; Haranath, D.; Vijaya Prakash, G.

425

Samarium Triflate–Catalyzed Biginelli Condensation: An Improved Method for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones  

Microsoft Academic Search

A simple and efficient method for multicomponant synthesis of 3,4-dihydropyrimidinones has been reported. All the reactions were carried out using samarium triflate as catalyst (10 mol%) at acetonitrile reflux. This procedure is applicable to a variety of substrates such as aliphatic, aromatic, and heterocyclic aldehydes.

A. Venkat Narsaiah; A. Ramesh Reddy; J. S. Yadav

2011-01-01

426

Preparation and Quality Control of the [153Sm]-Samarium Maltolate Complex as a Lanthanide Mobilization Product in Rats  

PubMed Central

Development of lanthanide detoxification agents and protocols is of great importance in management of overdoses. Due to safety of maltol as a detoxifying agent in metal overloads, it can be used as a lanthanide detoxifying agent. In order to demonstrate the biodistribution of final complex, [153Sm]-samarium maltolate was prepared using Sm-153 chloride (radiochemical purity >99.9%; ITLC and specific activity). The stability of the labeled compound was determined in the final solution up to 24h as well as the partition coefficient. Biodistribution studies of Sm-153 chloride, [153Sm]-samarium maltolate were carried out in wild-type rats comparing the critical organ uptakes. Comparative study for Sm3+ cation and the labeled compound was conducted up to 48 h, demonstrating a more rapid wash out for the labeled compound. The effective and biological half lives of 2.3 h and 2.46h were calculated for the complex. The data suggest the detoxification property of maltol formulation for lanthanide overdoses. PMID:21773065

Naseri, Zohreh; Hakimi, Amir; Jalilian, Amir R.; Nemati Kharat, Ali; Bahrami-Samani, Ali; Ghannadi-Maragheh, Mohammad

2011-01-01

427

Lanthanum, cerium, praseodymium and yttrium in waters in an upland acidic and acid sensitive environment, mid-Wales Hydrology and Earth System Sciences, 9(6), 645656 (2005) EGU  

E-print Network

Lanthanum, cerium, praseodymium and yttrium in waters in an upland acidic and acid sensitive environment, mid-Wales 645 Hydrology and Earth System Sciences, 9(6), 645656 (2005) © EGU Lanthanum, cerium@ceh.ac.uk Abstract The less than 0.45mm filterable lanthanum (La), cerium (Ce), praseodymium (Pr) and yttrium (Y

Paris-Sud XI, Université de

428

Comparison of effects of overload on parameters and performance of samarium-cobalt and strontium-ferrite radially oriented permanent magnet brushless DC motors  

SciTech Connect

Effects of high momentary overloads on the samarium-cobalt and strontium-ferrite permanent magnets and the magnetic field in electronically commutated brushless dc machines, as well as their impact on the associated machine parameters were studied. The effect of overload on the machine parameters, and subsequently on the machine system performance was also investigated. This was accomplished through the combined use of finite element analysis of the magnetic field in such machines, perturbation of the magnetic energies to determine machine inductances, and dynamic simulation of the performance of brushless dc machines, when energized from voltage source inverters. These effects were investigated through application of the above methods to two equivalent 15 hp brushless dc motors, one of which was built with samarium-cobalt magnets, while the other was built with strontium- ferrite magnets. For momentary overloads as high as 4.5 p.u. magnet flux reductions of 29% and 42% of the no load flux were obtained in the samarium-cobalt and strontiumferrite machines, respectively. Corresponding reductions in the line to line armature inductances of 52% and 46% of the no load values were reported for the samarium-cobalt and strontium-ferrite cases, respectively. The overload affected the profiles and magnitudes of armature induced back emfs. Subsequently, the effects of overload on machine parameters were found to have significant impact on the performance of the machine systems, where findings indicate that the samarium-cobalt unit is more suited for higher overload duties than the strontium-ferrite machine.

Demerdash, N.A.; Nehl, T.W.; Nyamusa, T.A.

1985-08-01

429

DETERMINATION OF LEAD AND CADMIUM IN FISH AND CLAM TISSUE BY ATOMIC ABSORPTION SPECTROMETRY WITH A MOLYBDENUM AND LANTHANUM TREATED PYROLYTIC GRAPHITE ATOMIZER  

EPA Science Inventory

A molybdenum and lanthanum treated pyrolytically coated graphite tube is employed for the furnace atomic absorption spectrometric determination of lead and cadmium directly in nitric-perchloric acid tissue digests. Lanthanum tends to promote the formation of a smooth lead atomiza...

430

Melt layer erosion of pure and lanthanum doped tungsten under VDE-like high heat flux loads  

NASA Astrophysics Data System (ADS)

Heat loads expected for VDEs in ITER were applied in the neutral beam facility GLADIS at IPP Garching. Several ˜3 mm thick rolled pure W and W-1 wt% La2O3 plates were exposed to pulsed hydrogen beams with a central heat flux of 23 MW/m2 for 1.5-1.8 s. The melting thresholds are determined, and melt layer motion as well as material structure evolutions are shown. The melting thresholds of the two W grades are very close in this experimental setup. Lots of big bubbles with diameters from several ?m to several 10 ?m in the re-solidified layer of W were observed and they spread deeper with increasing heat flux. However, for W-1 wt% La2O3, no big bubbles were found in the corrugated melt layer. The underlying mechanisms referred to the melt layer motion and bubble issues are tentatively discussed based on comparison of the erosion characteristics between the two W grades.

Yuan, Y.; Greuner, H.; Böswirth, B.; Luo, G.-N.; Fu, B. Q.; Xu, H. Y.; Liu, W.

2013-07-01

431

Photoluminescence of cerium fluoride and cerium-doped lanthanum fluoride nanoparticles and investigation of energy transfer to photosensitizer molecules.  

PubMed

CexLa1-xF3 nanoparticles have been proposed for use in nanoscintillator-photosensitizer systems, where excitation of nanoparticles by ionizing radiation would result in energy transfer to photosensitizer molecules, effectively combining the effects of radiotherapy and photodynamic therapy. Thus far, there have been few experimental investigations of such systems. This study reports novel synthesis methods for water-dispersible Ce0.1La0.9F3/LaF3 and CeF3/LaF3 core/shell nanoparticles and an investigation of energy transfer to photosensitizers. Unbound deuteroporphyrin IX 2,4-disulfonic acid was found to substantially quench the luminescence of large (>10 nm diameter) aminocaproic acid-stabilized nanoparticles at reasonable concentrations and loading amounts: up to 80% quenching at 6% w/w photosensitizer loading. Energy transfer was found to occur primarily through a cascade, with excitation of "regular" site Ce(3+) at 252 nm relayed to photosensitizer molecules at the nanoparticle surface through intermediate "perturbed" Ce(3+) sites. Smaller (<5 nm) citrate-stabilized nanoparticles were coated with the bisphosphonate alendronate, allowing covalent conjugation to chlorin e6 and resulting in static quenching of the nanoparticle luminescence: ?50% at ?0.44% w/w. These results provide insight into energy transfer mechanisms that may prove valuable for optimizing similar systems. PMID:24827162

Cooper, Daniel R; Kudinov, Konstantin; Tyagi, Pooja; Hill, Colin K; Bradforth, Stephen E; Nadeau, Jay L

2014-06-28

432

Lanthanum carbonate for the treatment of hyperphosphatemia in CKD 5D: multicenter, double blind, randomized, controlled trial in mainland China  

PubMed Central

Background Serum phosphorus control is critical for chronic kidney disease (CKD) 5D patients. Currently, clinical profile for an oral phosphorus binder in the mainland Chinese population is not available. Objective To establish the efficacy, safety, and tolerability of lanthanum carbonate in CKD 5D patients. Design Multicenter, randomized, double blind, placebo-controlled study. A central randomization center used computer generated tables to allocate treatments. Setting Twelve tertiary teaching hospitals and medical university affiliated hospitals in mainland China. Participants Overall, 258 hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) adult patients were enrolled. Intervention After a 0–3-week washout period and a 4-week lanthanum carbonate dose-titration period, 230 patients were randomized 1:1 to receive lanthanum carbonate (1500 mg-3000 mg) or placebo for a further 4-week maintenance phase. Main outcome measures Efficacy and safety of lanthanum carbonate to achieve and maintain target serum phosphorus concentrations were assessed. Results In the titration phase, serum phosphorus concentrations of all patients decreased significantly. About three-fifths achieved target levels without significantly disturbing serum calcium levels. At the end of the maintenance period, the mean difference in serum phosphorus was significantly different between the lanthanum carbonate and placebo-treated groups (0.63±0.62 mmol/L vs. 0.15±0.52 mmol/L, P < 0.001). The drug-related adverse effects were mild and mostly gastrointestinal in nature. Conclusion Lanthanum carbonate is an efficacious and well-tolerated oral phosphate binder with a mild AE profile in hemodialysis and CAPD patients. This agent may provide an alternative for the treatment of hyperphosphatemia in CKD 5D patients in mainland China. Trial registration No. ChiCTR-TRC-10000817 PMID:23379590

2013-01-01

433

Optical characterization of Sm3+-doped calcium-orthosilicate phosphors prepared using the solid-state reaction method  

NASA Astrophysics Data System (ADS)

Trivalent samarium-doped calcium-orthosilicate (Ca2SiO4:Sm3+) powder is synthesized by varying Sm2O3 amounts and the solid-state reaction method. X-ray diffraction patterns show that the obtained powders formed as orthorhombic-structured Ca2SiO4. Scanning electron microscope images show that the powders have uniform structures of a few micrometers in size. Photophysical features are analyzed by taking absorption, excitation, and emission spectra. Emission spectra exhibit a red-orange luminescence from the 4 G 5/2 ? 6 H 7/2 transition of Sm3+ in all synthesized phosphors. Both the physical and the optical properties show that Ca2SiO4:Sm3+ is an encouraging red-orange emitting phosphor applicable to photonics operating with near ultra-violet excitation.

Ha, Myoung Gyu; Jeong, Jae-Sun; Han, Kyoung-Rim; Bae, Yu Ri; Kim, Ju Sung; Kim, Jong Pil; Hong, K. S.; Yang, Ho-Soon

2013-12-01

434

Preliminary Investigation of Lanthanum-Cerium Bromide Self-Activity Removal  

SciTech Connect

It has been reported that detectors made of lanthanum-cerium halides (LaBr3:Ce and CeBr3) have superior energy resolution for gamma-radiation detection compared to what is offered by conventional sodium iodide (NaI:T1) detectors1–6. Although superior energy resolution may be observed, one major barrier that has hindered the rapid adaptation of lanthanum halides is their self-activity, due primarily to the presence of isotope 138La, and the ? contamination, due to the trace amount of actinides6–8. It has also been observed that the lanthanum-cerium halides contain a substantial amount of self-activity caused by the radioactive isotope 138La. Additionally, LaBr3:Ce spectra are also affected by ? contaminations in the low-energy region. To use either LaBr3:Ce or CeBr3 for high-sensitivity gamma detection, it may be necessary to have the self-activity as well as ? and ? contaminations removed or reduced. This paper describes a novel algorithmic approach for self-activity and contamination reduction for LaBr3:Ce and CeBr3 detectors using a third reference NaI:T1 detector. We present a computational procedure for separating self-activity from the gamma spectra obtained by LaBr3:Ce detectors. With the self-activity spectra precalculated, it is possible to perform real-time self-activity removal. This procedure can be implemented as an automatic self-activity subtraction module for gamma-radiation detectors made of LaBr3:Ce and/or CeBr3 crystals. With this approach, it is possible to develop a new generation of LaBr3:Ce detectors capable of producing spectra as clean as those obtained by conventional NaI:T1 detectors, but with much improved energy resolutions.

Yuan, D., Guss, P.

2011-09-01

435

First-principles calculation on oxygen ion migration in alkaline-earth doped La2GeO5.  

PubMed

By using first-principles calculations based on the density functional theory, we investigated the doping effects of alkaline-earth metals (Ba, Sr and Ca) in monoclinic lanthanum germanate La2GeO5 on its oxygen ion conduction. Although the lattice parameters of the doped systems changed due to the ionic radii mismatch, the crystal structures remained monoclinic. The contribution of each atomic orbital to electronic densities of states was evaluated from the partial densities of states and partial charge densities. It was confirmed that the materials behaved as ionic crystals comprising of cations of La and dopants and anions of oxygen and covalently formed GeO4. The doping effect on the activation barrier for oxygen hopping to the most stable oxygen vacancy site was investigated by the climbing-image nudged elastic band method. By tracing the charge density change during the hopping, it was confirmed that the oxygen motion is governed by covalent interactions. The obtained activation barriers showed excellent quantitative agreements with an experiment for the Ca- and Sr-doped systems in low temperatures as well as the qualitative trend, including the Ba-doped system. PMID:24888249

Linh, Tran Phan Thuy; Sakaue, Mamoru; Meñez Aspera, Susan; Alaydrus, Musa; Wungu, Triati Dewi Kencana; Linh, Nguyen Hoang; Kasai, Hideaki; Mohri, Takahiro; Ishihara, Tatsumi

2014-06-25

436

Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

Biswas, M. [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)] [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India); Bandyopadhyay, S., E-mail: sbando@cgcri.res.in [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)

2012-03-15

437

Annealing of chemical radiation damage in gamma irradiated anhydrous lanthanum nitrate  

NASA Astrophysics Data System (ADS)

The annealing of gamma irradiation damage in anhydrous lanthanum nitrate at different temperatures in the range 383-423 K has been investigated from a viewpoint of reaction kinetics. The annealing data have been analyzed on the basis of models developed for vacancy-interstitial combination and also on the basis of conventional chemical kinetics. Thermal annealing is found to be a combination of a fast first-order process affecting a small proportion of the fragments, followed by a predominantly slow second-order process, with a higher energy of activation, governing the behaviour of the remainder.

James, C.; Samuel, J.

2005-08-01

438

Temperature Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria  

NASA Technical Reports Server (NTRS)

Lanthanum titanate (La2Ti2O7) a layered distorted perovskite (1) with space group Pna2(sub 1) has been shown to have potential as a high temperature piezoelectric (2). However this highly refractory oxide compound must be consolidated at relatively high temperatures approximately 1400 C. Commercial La2Ti207 powders were mechanically alloyed with additions of Y2O3 to lower the consolidation temperature by 300 C and to provide post processing mechanical stability. Temperature dependent electrical, elastic and anelastic behavior were selected as nondestructive means of evaluating the effects of yttria on the properties of this ferroceramic material.

Goldsby, Jon C.

2003-01-01

439

Temperature-Dependent Electrical and Micromechanical Properties of Lanthanum Titanate with Additions of Yttria  

NASA Technical Reports Server (NTRS)

Temperature-dependent elastic properties were determined by establishing continuous flexural vibrations in the material at its lowest resonance frequency of 31tHz. The imaginary part of the complex impedance plotted as a function of frequency and temperature reveals a thermally activated peak, which decreases in magnitude as the temperature increases. Additions of yttria do not degrade the electromechanical in particularly the elastic and anelastic properties of lanthanum titanate. Y2O3/La2Ti2O7 exhibits extremely low internal friction and hence may be more mechanical fatigue-resistant at low strains.

Goldsby, Jon C.

2010-01-01

440

Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple  

NASA Technical Reports Server (NTRS)

The development of more efficient thermoelectric couple technology capable of operating with high-grade heat sources up to 1,275 K is key to improving the performance of radioisotope thermoelectric generators. Lanthanum telluride La3-xTe4 and 14-1-11 Zintls (Yb14MnSb11) have been identified as very promising materials. The fabrication of advanced high-temperature thermoelectric couples requires the joining of several dissimilar materials, typically including a number of diffusion bonding and brazing steps, to achieve a device capable of operating at elevated temperatures across a large temperature differential (up to 900 K). A thermoelectric couple typically comprises a heat collector/ exchanger, metallic interconnects on both hot and cold sides, n-type and ptype conductivity thermoelectric elements, and cold-side hardware to connect to the cold-side heat rejection and provide electrical connections. Differences in the physical, mechanical, and chemical properties of the materials that make up the thermoelectric couple, especially differences in the coefficients of thermal expansion (CTE), result in undesirable interfacial stresses that can lead to mechanical failure of the device. The problem is further complicated by the fact that the thermoelectric materials under consideration have large CTE values, are brittle, and cracks can propagate through them with minimal resistance. The inherent challenge of bonding brittle, high-thermal-expansion thermoelectric materials to a hot shoe material that is thick enough to carry the requisite electrical current was overcome. A critical advantage over prior art is that this device was constructed using all diffusion bonds and a minimum number of assembly steps. The fabrication process and the materials used are described in the following steps: (1) Applying a thin refractory metal foil to both sides of lanthanum telluride. To fabricate the n-type leg of the advanced thermoelectric couple, the pre-synthesized lanthanum telluride coupon was diffusion bonded to the metal foil using a thin adhesion layer. (2) Repeating a similar process for the 14-1-11 Zintl p-type leg of the advanced thermoelectric couple. (3) Bonding thick CTE-matched metal plates on the metallized lanthanum telluride and Yb14MnSb11 to form the hot and cold sides of the thermoelectric couple. The calculated conversion efficiency of such an advanced couple would be about 10.5 percent, about 35 percent better than heritage radioisotope thermoelectric technology that relies on Si-Ge alloys. In addition, unlike Si-Ge alloys, these materials can be combined with many other thermoelectric materials optimized for operation at lower temperatures to achieve conversion efficiency in excess of 15 percent (a factor of 2 increase over heritage technology).

Ravi, Vilupanur A.; Li, Billy Chun-Yip; Fleurial, Pierre; Star, Kurt

2010-01-01

441

Preparation and characterisation of apatite-type lanthanum silicates by a sol-gel process  

Microsoft Academic Search

Recent reports have indicated good fast oxide ion conductivity in apatite silicates. In this article we report on the successful low temperature synthesis of the apatite-type lanthanum silicates, La10(SiO4)6O3 and La9.33(SiO4)6O2, via a sol-gel process. The properties of the resulting apatite phases have been characterised by thermal analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and conductivity measured by

Shanwen Tao; John T. S Irvine

2001-01-01

442

Preparation, phase equilibria, and crystal chemistry of lanthanum, praseodymium, and neodymium hydroxide chlorides  

Microsoft Academic Search

The preparation of hydroxide chlorides of lanthanum, praseodymium, and neodymium has been achieved by hydrothermal methods at 550°C and 1530 atm. Three phases (Ln(OH)â, Ln(OH)â.ââ-Clâ.ââ, and Ln(OH)âCl) have been characterized by analytical and x-ray methods. The observed compositions are closely defined by the x = 0, 0.5, and 1 members of the homologous anion substitution series, Ln(OH)\\/sub 3-x\\/Cl\\/sub x\\/. The

E. T. Lance; J. M. Haschke

1976-01-01

443

Lead lanthanum zirconate stannate titanate based antiferroelectric to ferroelectric phase switching multilayer ceramic actuators  

Microsoft Academic Search

Lead lanthanum zirconate stannate titanate (PLZST) based antiferroelectric to ferroelectric phase switching multilayer ceramic actuators were prepared by the tape casting method. The ceramic powders used were synthesized by a two-step wet chemical method using colloidal processing with a composition of Pb0.97La0.02(Zr0.65Sn0.25Ti0.10)O3. The actuators sintered at 1100°C with Pd\\/Ag internal electrode and consisted of 20 active layer of 40?m thick.

Chen Ming; Yao Xi; Zhang Liangying

2001-01-01

444

Aero dopes and varnishes  

NASA Technical Reports Server (NTRS)

Before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.

Britton, H T S

1927-01-01

445

Photoneutron cross sections for samarium isotopes: Toward a unified understanding of (? ,n ) and (n ,? ) reactions in the rare earth region  

NASA Astrophysics Data System (ADS)

Photoneutron cross sections were measured for the seven stable samarium isotopes 144 ,147 ,148 ,149 ,150 ,152 ,154Sm near the neutron threshold with quasi-monochromatic laser-Compton scattering ? rays . Our photoneutron cross sections are found to be low by 20%-37% relative to existing data. The photoneutron data are analyzed with the talys reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the E 1 ? -ray strength. Using the ? -ray strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse (n ,? ) cross sections including the radioactive nucleus 151Sm with a half-life of 90 yr. The radiative neutron capture cross section for 153Sm with the half-life of 1.928 d is deduced with the ? -ray strength function method.

Filipescu, D. M.; Gheorghe, I.; Utsunomiya, H.; Goriely, S.; Renstrøm, T.; Nyhus, H.-T.; Tesileanu, O.; Glodariu, T.; Shima, T.; Takahisa, K.; Miyamoto, S.; Lui, Y.-W.; Hilaire, S.; Péru, S.; Martini, M.; Koning, A. J.

2014-12-01

446

Formation and characterization of porous silicon-samarium/gadolinium nanocomposites: effect of substrate oxidation and biosynthesis process  

NASA Astrophysics Data System (ADS)

Samarium and gadolinium nanoparticles synthesized by bioreduction process have been incorporated into nanostructured porous silicon template to form a nanocomposite. The structural and optical properties of PS-Gd and PS-Sm nanocomposites have been studied through TEM, SEM and UV-Vis spectroscopy. Extent of infiltration has been verified through reflectance interference Fourier transform spectroscopy as a function of substrate oxidation conditions. The substrates oxidized at 600 °C showed the maximum infiltration and the corresponding change of optical thickness due to nanoparticles. Such biodegradable nanocomposites in the form of particles can have potential applications in localized drug delivery and enhancement of the image contrast and optoelectronic devices. The results here reported open an energy-cheap procedure to take advantages of small rare earth nanoparticles and produced nanocomposites with their immersion in SiO2 substrates, with the perspective to be replied in other similar substrates under controlled conditions.

Perdigon-Lagunes, P.; Ascencio, J. A.; Agarwal, V.

2014-12-01

447

Coproportionation thermodynamics of homoligand solvates of samarium(III) and Yttrium(III) nitrates with neutral organophosphorus compounds  

SciTech Connect

The heats of coproportionation of homoligand solvates of samarium(III) and yttrium(III) nitrates with neutral organophosphorus compounds (tri-n-butyl phosphate, diisooctyl methylphosphonate, and diisoamyl methylphosphonate) in hexane at 298.15 K have been determined calorimetrically. The enthalpies of coproportionation are virtually independent of the nature and concentration of solvates of rare earth metal(III) nitrates in hexane and of the nature of neutral organophosphorus compound and amount to -1.1{plus_minus}0.2 kJ mol{sup -1}. The Gibbs free energy of coproportionation is -5.43 kJ mol{sup -1}, and the entropy is 14.5{plus_minus}0.7 J mol{sup -1} K{sup -1}.

Pyartman, A.K. [St. Petersburg Technological Institute (Russian Federation)

1995-07-01

448

The use of 185 MBq and 740 MBq of 153-samarium hydroxyapatite for knee synovectomy in haemophilia.  

PubMed

The penetration of beta energy of 153-samarium ((153) Sm) (0.8 MeV) is not only appropriate for synovectomy of median articulations but is possible to improve the radiobiological effect using increased activities. The aim of this study was to assess the effectiveness of 185 MBq and 740 MBq of 153-samarium hydroxyapatite ((153) Sm-HA) in knees of haemophilic patients. Thirty-one patients--36 knees, 30 males, were divided into two groups without coinjection of corticosteroid: A - 14 patients (17 knees) treated with intra-articular dose of 185 MBq of (153) Sm-HA, average age 23 years; B--17 patients (19 knees) with 740 MBq of (153) Sm-HA, average age 21.3 years. The evaluation before and after 1 year of synovectomy used the following criteria: reduction in the number of haemarthroses and use of the coagulation factor and improvement in articular motility. Adverse-effects occurrence was considered too. Early and late scintigraphic studies were performed after synoviorthesis and no joint immobilization was recommended. The reduction in haemarthrosis and use of coagulation factor were: group 1--31.3% and 25%; group 2--81.5% and 79% with P < 0.001 respectively; no significant improvement in knees motility was noted for both groups. Four cases of mild reactional synovitis were observed in each group. The scintigraphic control showed homogenous distribution of the radiopharmaceuticals with no articular escape; the material was considered safe by its permanence in the articulation. We have significant improvement in the synovectomy of haemophilic knees with 740 MBq of (153) Sm-HA; the less penetration of its beta radiation was compensated by the increased biological effect with the higher used activity. PMID:24330418

Calegaro, J U M; Machado, J; Furtado, R G; de Almeida, J S C; de Vasconcelos, A V P; de Barboza, M F; de Paula, A P

2014-05-01

449

Samarium-153-ethylene diamine tetramethylene phosphonate, a beta-emitting bone-targeted radiopharmaceutical, useful for patients with osteoblastic bone metastases  

PubMed Central

Bone metastases are prevalent among cancer patients and frequently cause significant morbidity. Oncology providers must mitigate complications associated with bone metastases while limiting therapy-related adverse effects and their impact on quality of life. Multiple treatment modalities, including chemotherapy, surgery, external beam radiation therapy, and radioisotopes, among others, have been recommended and utilized for palliative treatment of bone metastases. Radioisotopes such as samarium-153 are commonly used in the setting of multifocal bone metastases due to their systemic distribution, affinity for osteoblastic lesions, acceptable toxicity profile, and convenience of administration. This review focuses on samarium-153, first defining its radiobiologic and pharmacokinetic properties before describing many clinical trials that support its use as a safe and effective tool in the palliation of patients with bone metastases. PMID:23976864

Longo, John; Lutz, Stephen; Johnstone, Candice

2013-01-01

450

Facile synthesis, characterization and electrical properties of apatite-type lanthanum germanates  

NASA Astrophysics Data System (ADS)

Apatite-type lanthanum germanates La 10- x(GeO 4) 6O 3-1.5 x, have been successfully prepared at room temperature in a planetary ball mill by dry milling for only 6 hours (rotating disc speed =350 rpm), stoichiometric mixtures of hexagonal A sbnd La 2O 3 and GeO 2. As obtained powders are not amorphous and show XRD patterns as well as IR and Raman spectra characteristic of the apatite-type lanthanum germanates. The domain size of the as prepared samples grows gradually with the temperature of post-milling thermal treatment with an activation energy of about 20 kJ mol -1 K -1. The IR and Raman spectra suggest increasing ordering with firing temperature. The electrical properties of the as prepared materials, sintered at temperatures as low as 1200 °C, are similar to those found for the same phases but prepared by conventional solid state reaction and sintered at higher temperatures ( ?=4×10 S cm at 650 °C and 3×10 S cm at 950 °C). Two different regimes are identified in the Arrhenius plots with activation energies of around 1 eV (below 650 °C) and 0.6 eV (above 650 °C).

Rodríguez-Reyna, Evelyn; Fuentes, Antonio F.; Maczka, Miroslaw; Hanuza, Jerzy; Boulahya, Khalid; Amador, Ulises

2006-02-01

451

Biodiesel production by free fatty acid esterification using Lanthanum (La3+) and HZSM-5 based catalysts.  

PubMed

In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller. PMID:23428822

Vieira, Sara S; Magriotis, Zuy M; Santos, Nadiene A V; Saczk, Adelir A; Hori, Carla E; Arroyo, Pedro A

2013-04-01

452

Ultrasonic mediated synthesis of monodispersed lanthanum hydroxide nanorods for possible bioimplant application.  

PubMed

Monodispersed lanthanum hydroxide nano-rods (LaNRs) were synthesized for prospective biomedical application using a microwave heating and ultrasonic agitation methodology which does not require any toxic stabilizing agent. The average length and diameter of the LaNRs thus obtained were 183.4 ± 3.6 and 9.9 ± 0.2 nm respectively, as analyzed by HRTEM. FTIR spectrum confirmed the presence of OH groups. The thermal transformation of lanthanum hydroxide (La(OH)3) was studied by thermogravimetric analysis. The synthesized LaNRs were found to be stable for a period of 1 month at room temperature. They were biocompatible as evaluated by haemocompatibility assay and viability assay using human peripheral blood mononuclear cells. The pro-angiogenic property of LaNRs was demonstrated by in vivo chick chorioallantoic membrane assay. The LaNRs induced osteoblast differentiation of human adipose derived stem cells with significant calcium (Ca(2+)) deposition indicating potential applications in bone tissue engineering. PMID:25601669

Harini, Dhandapani; Rajaram, Anantanarayanan; Rajaram, Rama

2015-01-01

453

Lanthanum chloride impairs spatial learning and memory and downregulates NF-?B signalling pathway in rats.  

PubMed

Exposure to rare earth elements (REEs) is known to impair intelligence in children and cause neurobehavioral abnormalities in animals. However, the mechanisms underlying these phenomena are not clear. Lanthanum is often used to study the effects of REEs. The aim of this study was to investigate the influence of lanthanum chloride (LaCl3) on spatial learning and memory and a possible underlying mechanism involving nuclear factor-kappa B (NF-?B) signalling pathway expression in the hippocampus. The rats were exposed to 0, 0.25, 0.50 or 1.00 % LaCl3 in drinking water during pregnancy and lactation (i.e. while feeding their offspring). After weaning, young rats continued to receive 0, 0.25, 0.50 and 1.00 % LaCl3 in the drinking water for 1 month. LaCl3 exposure impaired the spatial learning and memory of young rats and significantly decreased the expression of phosphorylated I?B kinase complex, phosphorylated I?B?, NF-?B, c-fos, c-jun and brain-derived neurotrophic factor in the hippocampus. These results indicate that LaCl3 exposure impairs spatial learning and memory in rats by inhibiting NF-?B signalling pathway. PMID:23670203

Zheng, Linlin; Yang, Jinghua; Liu, Qiufang; Yu, Fei; Wu, Shengwen; Jin, Cuihong; Lu, Xiaobo; Zhang, Lifeng; Du, Yanqiu; Xi, Qi; Cai, Yuan

2013-12-01

454

Lanthanum Chloride Impairs Spatial Memory Through ERK/MSK1 Signaling Pathway of Hippocampus in Rats.  

PubMed

Rare earth elements (REEs) are used in many fields for their diverse physical and chemical properties. Surveys have shown that REEs can impair learning and memory in children and cause neurobehavioral defects in animals. However, the mechanism underlying these impairments has not yet been completely elucidated. Lanthanum (La) is often selected to study the effects of REEs. The aim of this study was to investigate the spatial memory impairments induced by lanthanum chloride (LaCl3) and the probable underlying mechanism. Wistar rats were exposed to LaCl3 in drinking water at 0 % (control, 0 mM), 0.25 % (18 mM), 0.50 % (36 mM), and 1.00 % (72 mM) from birth to 2 months after weaning. LaCl3 considerably impaired the spatial learning and memory of rats in the Morris water maze test, damaged the synaptic ultrastructure and downregulated the expression of p-MEK1/2, p-ERK1/2, p-MSK1, p-CREB, c-FOS and BDNF in the hippocampus. These results indicate that LaCl3 exposure impairs the spatial learning and memory of rats, which may be attributed to disruption of the synaptic ultrastructure and inhibition of the ERK/MSK1 signaling pathway in the hippocampus. PMID:25316495

Liu, Huiying; Yang, Jinghua; Liu, Qiufang; Jin, Cuihong; Wu, Shengwen; Lu, Xiaobo; Zheng, Linlin; Xi, Qi; Cai, Yuan

2014-12-01