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1

Thermal activation, cathodo- and photoluminescence measurements of rare earth doped (Tm, Tb, Dy, Eu, Sm, Yb) amorphous/nanocrystalline AlN thin films prepared by reactive rf-sputtering  

NASA Astrophysics Data System (ADS)

We present comprehensive cathodo- and photoluminescence measurements from thin amorphous/nanocrystalline (a/nc-) AlN films doped with rare earths. The (a/nc-) AlN films were prepared by reactive rf-sputtering using a high purity (5 N) aluminium disk in high purity nitrogen atmosphere (5 N, pressure ca. 1.3 mbar). The rare earth doping (Tm, Tb, Dy, Eu, Sm, Yb, concentrations were below 1%) was performed by placing respective rare earth metal pieces of appropriate size onto the aluminium disk. The rare earth ion emissions cover the blue (Tm), green (Tb), yellow (Dy), red (Sm, Eu) and infrared (Yb). The optical and related structural properties of the films are correlated by means of high resolution transmission electron microscopy in combination with cathodoluminescence measurements in a scanning electron microscope. In addition, the corresponding compositions are determined by energy-dispersive X-ray analysis. The cathodo- and photoluminescence spectra of the rare earth 3+ ions are recorded in the visible at 300 K in the as-grown condition (Tm, Tb, Dy, Sm, Eu, Yb) and after annealing treatments in the temperature range from 300 to 1100 °C by steps of 150 °C (Tb, Sm, Eu, Yb). The anneal-related changes in the cathodo- and photoluminescence emission spectra and in the microstructure of the films are addressed. The AlN films show nanocrystalline structure almost independent of the annealing treatment. Optimal annealing temperature for emissions of Sm and Eu doped (a/nc-) AlN were derived to be 900 °C whereas Tb 3+ and Yb 3+ emissions increase at least up to 1100 °C.

Weingärtner, R.; Erlenbach, O.; Winnacker, A.; Welte, A.; Brauer, I.; Mendel, H.; Strunk, H. P.; Ribeiro, C. T. M.; Zanatta, A. R.

2006-05-01

2

Multifunctional ScF3:Ln3+ (Ln = Tb, Eu, Yb, Er, Tm and Ho) nano/microcrystals: hydrothermal/solvothermal synthesis, electronic structure, magnetism and tunable luminescence properties  

NASA Astrophysics Data System (ADS)

A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb3+, Eu3+, Yb3+, Tm3+, Er3+ and Ho3+)-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O : EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb3+-Er3+, Yb3+-Tm3+, and Yb3+-Ho3+ codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging.A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb3+, Eu3+, Yb3+, Tm3+, Er3+ and Ho3+)-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O : EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb3+-Er3+, Yb3+-Tm3+, and Yb3+-Ho3+ codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging. Electronic supplementary information (ESI) available: The UV/VUV/CL spectra of nanocrystal defects in ScF3 and the calculation of electron penetration depths. See DOI: 10.1039/c4nr00512k

Han, Lili; Wang, Yuhua; Guo, Linna; Zhao, Lei; Tao, Ye

2014-05-01

3

Large-scale synthesis of Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres and their photoluminescence properties  

SciTech Connect

Graphical abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. Display Omitted Highlights: ? Lu{sub 2}O{sub 3}:Ln{sup 3+} microspheres were prepared by a precipitation followed by a calcination process. ? Lu{sub 2}O{sub 3}:Eu{sup 3+}/Tb{sup 3+} samples exhibit respective red or green emissions. ? Lu{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}/Tm{sup 3+}/Ho{sup 3+} exhibit emissions of green, blue, yellow-green, respectively. ? These finding may find potential applications in bioanalysis and field emission displays. -- Abstract: In this work, multicolor and monodisperse Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+}, Tb{sup 3+}, Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) microspheres were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and cathodoluminescence (CL) spectra were employed to characterize the samples. Upon ultraviolet and low-voltage electron beams excitation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Eu{sup 3+} and Tb{sup 3+}) samples exhibit respective bright red (Eu{sup 3+}, {sup 5}D{sub 0} ? {sup 7}F{sub 2}) and green (Tb{sup 3+}, {sup 5}D{sub 4} ? {sup 7}F{sub 5}) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln{sup 3+} = Yb{sup 3+}/Er{sup 3+}, Yb{sup 3+}/Tm{sup 3+}, and Yb{sup 3+}/Ho{sup 3+}) exhibit characteristic up-conversion (UC) emissions of green (Er{sup 3+}, {sup 4}S{sub 3/2}, {sup 2}H{sub 11/2} ? {sup 4}I{sub 15/2}), blue (Tm{sup 3+}, {sup 1}G{sub 4} ? {sup 3}H{sub 6}) and yellow-green (Ho{sup 3+}, {sup 5}F{sub 4}, {sup 5}S{sub 2} ? {sup 5}I{sub 8}), respectively. These finding may find potential applications in bioanalysis, optoelectronic and nanoscale devices, field emission displays, and so on.

Gao, Yu, E-mail: gaoy777@126.com [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)] [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China); Gong, Jian [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024 (China)] [Key Laboratory of Polyoxometalate Science of Ministry of Education, Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024 (China); Fan, Miaomiao [Department of Medical Pharmaceutical, Shenyang Chemical Industry School, Shenyang 110142 (China)] [Department of Medical Pharmaceutical, Shenyang Chemical Industry School, Shenyang 110142 (China); Fang, Qinghong; Wang, Na; Han, Wenchi; Xu, Zhenhe [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)] [College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142 (China)

2012-12-15

4

Polyoxopalladates encapsulating yttrium and lanthanide ions, [X(III)Pd(II)12(AsPh)8O32]5- (X=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu).  

PubMed

A series of novel yttrium- and lanthanide-containing heteropolyoxopalladates have been prepared and isolated as hydrated sodium salts, Na(5)[X(III)Pd(II)(12)(AsPh)(8)O(32)]y H(2)O (X=Y (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Lu (13); y=15-27). The polyanions [X(III)Pd(II)(12)(AsPh)(8)O(32)](5-) consist of a cuboid framework of twelve Pd(II) ions with eight phenylarsonate heterogroups located at the vertices and a central guest ion X. The compounds 1-13 have been prepared in a simple one-pot self-assembly reaction of Pd(CH(3)COO)(2), phenylarsonic acid and the respective salt of the element X in 0.5 M aqueous sodium acetate solution (pH 6.9), and characterized in the solid state by single-crystal X-ray diffraction, elemental and thermogravimetric (TGA) analyses, and IR spectroscopy. It was demonstrated that small, medium, and also large lanthanide ions can be incorporated in the center of the novel heteropolypalladate [X(III)Pd(II)(12)(AsPh)(8)O(32)](5-). The Ln-O bond lengths follow the expected trend decreasing from left to right in the lanthanide series. This indicates that the {Pd(II)(12)O(32)} shell can adjust to the coordination requirements of the encapsulated guest cation. Compounds 3 and 5 were selected for electrochemical studies. Their cyclic voltammetry in a lithium acetate buffer at pH 5.9 showed a Pd(0) deposition process on the glassy carbon electrode surface. Coulometry indicated that all Pd(II) centers were reduced to Pd(0). The film was stable and could be taken out of the deposition medium and characterized in pure pH 5.9 buffer. Magnetic susceptibility and EPR measurements were carried out on 5 and 6. The former was confirmed to be diamagnetic and the latter strongly paramagnetic with a S=7/2 ground state. DFT calculations for some of the polyoxometalates have been also performed. PMID:20589852

Barsukova, Maria; Izarova, Natalya V; Biboum, Rosa Ngo; Keita, Bineta; Nadjo, Louis; Ramachandran, Vasanth; Dalal, Naresh S; Antonova, Nadya S; Carbó, Jorge J; Poblet, Josep M; Kortz, Ulrich

2010-08-01

5

A new series of lanthanoid containing Keggin-type germanotungstates with acetate chelators: [{ Ln(CH 3COO)GeW 11O 39(H 2O)} 2] 12- { Ln=Eu III, Gd III, Tb III, Dy III, Ho III, Er III, Tm III, and Yb III}  

NASA Astrophysics Data System (ADS)

A series of head-on complexes of lanthanoid containing germanotungstates was isolated from a one pot reaction in an acetate buffer at pH 4.5. This convenient approach brought forward the [{ Ln(CH 3COO)GeW 11O 39(H 2O)} 2] 12- ( Ln=Eu III, Gd III, Tb III, Dy III, Ho III, Er III, Tm III, and Yb III) family with acetate chelators in the rarely observed ?2: ?2- ?1 mode. All compounds were structurally characterized using various solid state analytics, such as single crystal X-ray diffraction, FT-IR spectroscopy, and thermogravimetric analysis. The isostructural polyanions crystallize in the monoclinic system (S.G. P2 1/ c). Temperature-dependent magnetic susceptibility measurements were performed on the Gd III-complex which exhibits near perfect Curie-type behavior.

Hussain, Firasat; Sandriesser, Stefan; Speldrich, Manfred; Patzke, Greta R.

2011-01-01

6

Near-infrared quantum cutting in YPO4:Yb3+, Tm3+ via cooperative energy transfer  

NASA Astrophysics Data System (ADS)

The experimental evidences of the cooperative energy transfer from Tm3+ to Yb3+ have been presented by the photoluminescence properties of YPO4:Yb3+, Tm3+, and the decay lifetime curves of the G14 emission of Tm3+. Near-infrared quantum cutting involving the F25/2?F27/2 emission of Yb3+ (about 970-1010 nm) is achieved upon the excitation of G14 energy level of Tm3+ at 474 nm. Quantum efficiency related to Yb3+ concentration is calculated, and the maximum efficiency reaches 172.8%. Because the energy of Yb3+ transition is matched with the band gap of the crystalline Si, the phosphors could be applied potentially in silicon-based solar cells.

Xie, Lechun; Wang, Yuhua; Zhang, Huijuan

2009-02-01

7

Upconversion emission properties of CeO2: Tm3+, Yb3+ inverse opal photonic crystals  

NASA Astrophysics Data System (ADS)

The ordered and disordered templates were assembled by vertical deposition of polystyrene microspheres. The CeO2: Tm3+, Yb3+ precursor solution was used to infiltrate into the voids of the ordered and disordered templates, respectively. Then the ordered and disordered templates were calcined at 950°C in an air furnace, and the CeO2: Tm3+, Yb3+ inverse opals were obtained. The upconversion emissions from CeO2: Tm3+, Yb3+ inverse opals were suppressed due to the photon trapping caused by Bragg reflection of lattice planes when the upconversion emission band was in the range of the photonic band gaps in the inverse opals.

Cheng, Gong; Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo

2014-10-01

8

Solvothermal syntheses, and characterization of [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce, Pr) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu, Gd, Er, Tm, Yb): The effect of lanthanide contraction on the crystal structures of lanthanide selenidoantimonates(V)  

SciTech Connect

Two types of lanthanide selenidoantimonates [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce(1a), Pr(1b)) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu(2a), Gd(2b), Er(2c), Tm(2d), Yb(2e); en=ethylenediamine) were solvothermally synthesized by reactions of LnCl{sub 3}, Sb and Se with the stoichiometric ratio in en solvent at 140 deg. C. The four-en coordinated lanthanide complex cation [Ln(en){sub 4}]{sup 3+} formed in situ balances the charge of SbSe{sub 4}{sup 3-} anion. In compounds 1a and 1b, the SbSe{sub 4}{sup 3-} anion act as a monodentate ligand to coordinate complex [Ln(en){sub 4}]{sup 3+} and the neutral compound [Ln(en){sub 4}(SbSe{sub 4})] is formed. The Ln{sup 3+} ion has a nine-coordinated environment involving eight N atoms and one Se atom forming a distorted monocapped square antiprism. In 2a-2e the lanthanide(III) ion exists as isolated complex [Ln(en){sub 4}]{sup 3+}, in which the Ln{sup 3+} ion is in a bicapped trigonal prism geometry. A systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series. TG curves show that compounds 1a-1b and 2a-2e remove their organic components in one and two steps, respectively. - Graphical abstract: Two types of lanthanide selenidoantimonates [Ln(en){sub 4}(SbSe{sub 4})] (Ln=Ce, Pr) and [Ln(en){sub 4}]SbSe{sub 4}.0.5en (Ln=Eu, Gd, Er, Tm, Yb; en=ethylenediamine) have been synthesized under the mild solvothermal conditions, and a systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series.

Jia Dingxian [School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123 (China)], E-mail: jiadingxian@suda.edu.cn; Zhu Aimei; Jin Qinyan; Zhang Yong; Jiang Wenqing [School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123 (China)

2008-09-15

9

Dopant distribution in a Tm(3+)-Yb(3+) codoped silica based glass ceramic: an infrared-laser induced upconversion study.  

PubMed

The optically active dopant distribution in a Tm(3+)-Yb(3+) doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm(3+)-Yb(3+) codoped glass and glass ceramic has been performed at room temperature. Tm(3+) and Yb(3+) single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the (3)H(4) level of the Tm(3+) ions a blue upconversion emission is observed, which is drastically increased in the Yb(3+) codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, (3)H(4), (2)F(5/2), and (1)G(4) were interpreted in the glass ceramic samples. The contribution of the optically active Tm(3+) and Yb(3+) ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm(3+) ions in the crystalline phase could be quantified for the 1 mol % Tm(3+)-2.5 mol % Yb(3+) glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm(3+)-Yb(3+) ions in the vitreous phase. PMID:15267504

Lahoz, F; Martin, I R; Mendez-Ramos, J; Nunez, P

2004-04-01

10

Optical properties, fluorescence mechanisms and energy transfer in Tm 3+, Ho 3+ and Tm 3+ Ho 3+ doped near-infrared laser glasses, sensitized by Yb 3+  

Microsoft Academic Search

The optical properties of the rare elements Tm3+, Ho3+ and Yb3+ were systematically investigated in various glasses. The Tm3+ doped aluminozircofluoride glass shows higher quantum efficiency, longer lifetime and stronger fluorescence intensity than Tm3+ doped YSGG crystal and other Tm3+ doped glasses for the 3H4 ? 3H6 transition. Similar quantum efficiency, longer lifetime and stronger fluorescence intensity were also found

B. Peng; Tetsuro Izumitani

1995-01-01

11

Visible-to-infrared quantum cutting by phonon-assisted energy transfer in YPO(4):Tm(3+), Yb(3+) phosphors.  

PubMed

Quantum cutting (QC) of one visible photon into two infrared ones has been reported for the lanthanide ion couple (Tm(3+), Yb(3+)) in a variety of host lattices. The mechanism responsible for QC was assumed to be a cooperative energy transfer (ET) process from Tm(3+) to two Yb(3+) ions, however, no solid evidence was presented. Herein we report visible-to-infrared QC for (Tm(3+), Yb(3+)) in YPO(4) phosphors. The ET process from the excited (1)G(4) level of Tm(3+) to Yb(3+) was investigated in detail by means of optical spectroscopy. By monitoring the steady-state photoluminescence (PL) and PL decay of the intermediate (3)F(4) level of Tm(3+) as a function of the Yb(3+) concentration, we demonstrated the QC of one incident blue photon into one near-infrared emitting photon at 1004 nm from Yb(3+) and simultaneously into one mid-infrared emitting photon at 1791 nm from Tm(3+), rather than two emitting photons from Yb(3+). It was revealed that such visible-to-infrared QC was induced by phonon-assisted ET instead of cooperative ET as previously reported. This kind of QC phosphors may have potential as solar spectral converters to enhance the external quantum efficiency in multi-junction solar cells based on narrow band-gap semiconductors such as Ge, PbS or In(1-x)Ga(x)N. PMID:22441530

Zheng, Wei; Zhu, Haomiao; Li, Renfu; Tu, Datao; Liu, Yongsheng; Luo, Wenqin; Chen, Xueyuan

2012-03-22

12

Nanopatterned PMMA-Yb:Er/Tm:Lu2O3 composites with visible upconversion emissions  

NASA Astrophysics Data System (ADS)

Nanopillars, nanotubes and nanofibers of transparent polymethyl methacrylate (PMMA) polymer with Yb:Ln:Lu2O3 (Ln = Er or Tm) nanoparticles (NPs) (?30-35 nm average size) have been prepared by infiltration of anodized aluminum oxide hexagonally nanopatterned templates. The outer diameter of these nanostructures is in the 330-400 nm range, with lengths up to 50 ?m and a period distance of 430 nm. These nanostructures show visible upconversion (UC) emissions under excitation with 978 nm light. The steady state temperature of the polymer nanostructures is optically evidenced by the Er3+ UC emission and optically controlled around the PMMA glass transition temperature by the excitation light, introducing a new method for NP storage in a solid and potential optically induced particle release. Full color emission is shown in tridoped (Yb:Er:Tm) samples.

Han, X.; Maiz, J.; Mijangos, C.; Zaldo, C.

2014-05-01

13

Laser-like effects and upconversion fluorescence temporal dynamic in Tm3+, Yb3+ doped YF3 single crystals  

NASA Astrophysics Data System (ADS)

A new way of managing fluorescence features in doped bulk and nanosized materials by variation of excitation temporal characteristics is demonstrated. Random laser-like effect on 3H4-3F4 transitions of Tm3+ ions in Yb,Tm:YF3 single crystal was revealed under rectangular pulse train excitation in 930-980 spectral domain.

Kazakov, B. N.; Semashko, V. V.; Lovchev, A. V.; Naumov, A. K.

2014-11-01

14

Solvent Extraction Behavior of Calixarene-Type Cyclophanes Towards Trivalent La, Nd, Eu, Er and Yb  

Microsoft Academic Search

In this paper we describe the solvent extraction behaviour of three calixarene-type cyclophanes towards trivalent lanthanides Ln (Ln = La, Nd, Eu, Er and Yb). By using p-tert-butylcalix\\/6\\/arene hexacarboxylic acid (LI), the lanthanides were extracted from the aqueous phase at pH 2 to 3.5 into chloroform according to a cation exchange mechanism as 1:2 metal:ligand complexes. The extractability is: Nd, Eu >

Rainer Ludwig; Katsutoshi Inoue; Takehiko Yamato

1993-01-01

15

Blue, green and 0.8 ?m Tm 3+, Ho 3+ doped upconversion laser glasses, sensitized by Yb 3+  

Microsoft Academic Search

To obtain efficient upconversion laser glass, the optical properties of Tm3+ and Ho3+ were investigated in various glasses. Fluoride glass was selected as base glass for upconversion. The efficient upconversion fluorescences corresponding to the 1G4?3H6 and 3H4?3H6 transitions of Tm3+ and the 5S2?5I8 transition of Ho3+ were observed in Yb3+-Tm3+ and Yb3+-Ho3+ doped aluminozircofluoride glasses excited at 980 nm. The

Bo Peng; Tetsuro Izumitani

1995-01-01

16

Synthesis, persistent luminescence, and thermoluminescence properties of yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce, Nd, Dy, Ho, Er, Tm, Yb) and orange-red Sr(3-x)Ba(x)SiO5:Eu2+, Dy3+ phosphor.  

PubMed

Sunlight-excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange-red Sr3-xBaxSiO5:Eu(2+),Dy(3+) persistent luminescence phosphor was successfully developed by a two-step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non-equivalent trivalent rare earth co-dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu(2+) in Sr3SiO5 was significantly modified. The yellow persistent emission intensity of Eu(2+) was greatly enhanced by a factor of 4.5 in Sr3SiO5:Eu(2+),Nd(3+) compared with the previously reported Sr3SiO5:Eu(2+), Dy(3+). Furthermore, Sr ions were replaced with equivalent Ba to give Sr3-xBaxSiO5 :Eu(2+),Dy(3+) phosphor, which shows yellow-to-orange-red tunable persistent emissions from ?=570 to 591?nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu(2+) is significantly improved by a factor of 2.7 in Sr3-xBaxSiO5 :Eu(2+),Dy(3+) (x=0.2) compared with Sr3SiO5 :Eu(2+),Dy(3+). A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu(2+) in Sr3-xBaxSiO5:Eu(2+),RE(3+) (RE=rare earth) is also proposed and discussed. PMID:24203579

Li, Ye; Li, Baohong; Ni, Chenchen; Yuan, Shuxia; Wang, Jing; Tang, Qiang; Su, Qiang

2014-02-01

17

Trapping processes in CaS:Eu{sup 2+},Tm{sup 3+}  

SciTech Connect

CaS:Eu{sup 2+},Tm{sup 3+} is a persistent red phosphor. Thermoluminescence was measured under different excitation and thermal treatment conditions. The results reveal that the charge defects, created by substituting Tm{sup 3+} for Ca{sup 2+}, serve as hole traps for the afterglow at room temperature. Tm{sup 3+} plays the role of deep electron trapping centers, capturing electrons either through the conduction band or directly from the excited Eu{sup 2+} ions. These two processes, in which two different sites of Tm{sup 3+} are involved, correspond to two traps with different depths. (c) 2000 American Institute of Physics.

Jia, Dongdong [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China)] [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Jia, Weiyi [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico)] [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Evans, D. R. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)] [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Dennis, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)] [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States); Liu, Huimin [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico)] [Department of Physics, University of Puerto Rico, Mayaguez, Puerto Rico 00681 (Puerto Rico); Zhu, Jing [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China)] [Department of Materials Science and Engineering, Tsinghua University, Beijing, (China); Yen, W. M. [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)] [Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602 (United States)

2000-09-15

18

Passive Q-switching by Tm3+co-doping of a Yb3+-fiber laser  

NASA Astrophysics Data System (ADS)

Q-switching of a wavelength tunable Yb3+-doped double-clad fiber laser by a Tm3+-codoping in the gain fiber is demonstrated. This system showed up to 2.4 W output power, up to 140 kHz repetition rate, a maximum pulse energy of 21.8 µJ and a minimum pulse duration of 1.1 µs. Using a grating pair in Littrow-Littman configuration the emission wavelength was tunable between 1055 nm and 1090 nm. The output radiation showed a maximum spectral linewidth of 4 GHz.

Adel, P.; Auerbach, M.; Fallnich, Carsten; Unger, S.; Müller, H.-R.; Kirchhof, J.

2003-10-01

19

Intrinsic single-band upconversion emission in colloidal Yb/Er(Tm):Na3Zr(Hf)F7 nanocrystals.  

PubMed

Novel Yb/Er(Tm):Na(3)MF(7) (M = Zr, Hf) nanocrystals with intrinsic single-band upconversion emission, in contrast to the routine lanthanide-doped fluoride nanocrystals which show typical multi-band upconversion emissions, are reported for the first time. Specifically, the red upconversion intensity of the Yb/Er:Na(3)ZrF(7) nanocrystals is about 5 times as high as that of the hexagonal Yb/Er:NaYF(4) ones with a similar crystal size. PMID:23010848

Chen, Daqin; Lei, Lei; Zhang, Rui; Yang, Anping; Xu, Ju; Wang, Yuansheng

2012-11-01

20

Solvent extraction behaviour of calixarene-type cyclophanes towards trivalent La, Nd, Eu, Er and Yb  

SciTech Connect

In this paper we describe the solvent extraction behaviour of three calixarene-type cyclophanes towards trivalent lanthanides Ln[sup 3+] (Ln = La, Nd, Eu, Er and Yb). By using p-tert-butylcalix/6/arene hexacarboxylic acid (L1), the lanthanides were extracted from the aqueous phase at pH 2 to 3.5 into chloroform according to a cation exchange mechanism as 1:2 metal:ligand complexes. The extractability is: Nd, Eu > La > Er > Yb. In the presence of excess Na[sup +] in the aqueous phase, this order was not changed but the lanthanides were extracted as 1:1 complexes at low extractant concentration and their extractability decreased. The use of p-tert-butylcalix/4/arene tetracarboxylic acid (L2) with a smaller cavity size dissolved in chloroform or toluene results in lower distribution coefficients, D[sub Ln], compared with L1. The extraction constants of the 1:2 metal:extractant complexes for the water-toluene system follow the order Eu > Nd > Yb > Er > La. Upon addition of excess Na[sup +], both extractability and selectivity increased. The extraction behaviour of a third cyclophane (L3) with a cavity size similar to that of L1 containing four carboxylic acid groups was different from that of L1 with respect to extractability and order of extraction of the lanthanides. 21 refs., 12 figs.

Ludwig, R.; Inoue, Katsutoshi; Yamato, Takehiko (Saga Univ. (Japan))

1993-04-01

21

Synthesis and photoluminescence properties of heteroleptic Eu 3+, Tb 3+ and Tm 3+ complexes  

Microsoft Academic Search

Five Eu(III), four Tb(III) and two Tm(III) multichromophoric complexes (1-Eu, 1-Tb, 2-Eu, 3-Eu, 3-Tb, 3-Tm, 4-Tb, 4-Tm, 5-Eu, 6-Eu and 6-Tb; where 1=tris[dibenzoylmethanido] (4?-chloro-2,2?:6?,2??-terpyridine), 2=tris[dibenzoylmethanido] (4?-(9H-carbazol-9yl)-2,2?:6?,2??-terpyridine), 3=tris(1,1,1,5,5,5-hexafluoroacetylacetonato), 4=tris[1,1,1,5,5,5-hexafluoroacetylacetonato] (tripyridin-2-ylamine), 5=tris[dibenzoylmethanido][N-(4-(9H-carbazol-9-yl)butyl)-N-(dipyridin-2-yl)amine] and 6=tris[dibenzoylmethanido][N-(6-(9H-carbazol-9-yl)hexyl)-N-(dipyridin-2-yl)amine]) emitting in the blue (Tm), green (Tb) and red (Eu) spectral regions, have been synthesized and characterized. The complexes involve five different coordinating (2,2?:6?,2??-terpyridine (terpy); dibenzoylmethane (dbm); 1,1,1,5,5,5-hexafluoroacetylacetonato

Gianluca Accorsi; Nicola Armaroli; François Cardinali; Dong Wang; Youxuan Zheng

2009-01-01

22

Enhanced near-infrared photocatalysis of NaYF4:Yb, Tm/CdS/TiO2 composites.  

PubMed

The previous works by our group (Chem. Commun., 2010, 46, 2304-2306; ACS Catal., 2013, 3, 405-412; Phys. Chem. Chem. Phys., 2013, 15, 14681-14688) have reported the near-infrared-driven photocatalysis of broadband semiconductor TiO2 or ZnO that was combined with upconverting luminescence particles to form a core-shell structure. However, the photocatalytic efficiency is low for this new type of photocatalysts. In this work, NaYF4:Yb,Tm/CdS/TiO2 composites for NIR photocatalysis were prepared by linking CdS and TiO2 nanocrystals on the NaYF4:Yb,Tm microcrystal surfaces. CdS and TiO2 were well interacted to form a heterojunction structure. The energy transfer between NaYF4:Yb,Tm and the semiconductors CdS and TiO2 was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic activities of the as-prepared composites were evaluated by the degradation of methylene blue in aqueous solution upon NIR irradiation. Significantly, it was found that the united adhesions of CdS and TiO2 on the NaYF4:Yb,Tm particle surfaces showed much higher catalytic activities than the individual adhesion of CdS or TiO2 on the NaYF4:Yb,Tm surfaces. This was attributed mainly to the effective separation of the photogenerated electron-hole pairs due to the charge transfer across the CdS-TiO2 interface driven by the band potential difference between them. The presented composite structure of upconverting luminescence materials coupled with narrow/wide semiconductor heterojunctions provides a new model for improved NIR photocatalysis. PMID:24162269

Guo, Xingyuan; Di, Weihua; Chen, Changfeng; Liu, Chunxu; Wang, Xue; Qin, Weiping

2014-01-21

23

White light upconversion emission in Yb3+/ Er3+/ Tm3+ codoped oxy-fluoride lithium tungsten tellurite glass ceramics  

NASA Astrophysics Data System (ADS)

The bright white upconversion emission ( tri-colour UC) is generated in Er/Tm/Yb tri -doped oxy-fluoride lithium tungsten tellurite (TWLOF)glass ceramics containing crystalline phase LiYbF4 under the excitation of 980nm laser diode. The most appropriate combination of rare-earth ions (2mol% YbF3 1mol% ErF3 and 1mol%TmF3 )of glass ceramic sample has been determined to tune the primary colour (RGB and generate white light emission. By varying the pump power, intense and weak blue (487nm, 437nm), green (525nm and 545nm) and red (662nm) emission are simultaneously observed at room temperature. The dependence of upconversion emission intensity suggest that a theephoton process is responsible for the blue emission of Tm3+ ions and red emission due to both Tm3+ and Er3+ ions , while green emission originated from two photon processes in Er3+ ions. Also tri colour upconvesion and energy transfer in this glass ceramics sample were studied under 808nm laser diode excitation. The Upconversion mechanisms and Tm3+ ions plays role of both emitter and activator (transfer energy to Er) were discussed.

Ansari, Ghizal F.; Mahajan, S. K.

2012-02-01

24

Luminescence of YAG doped with Eu, Yb, and Mn ions under VUV excitation  

NASA Astrophysics Data System (ADS)

Hydrothermal synthesis has been successfully used to obtain fine-crystalline powders of yttrium aluminum garnet (YAG) doped with manganese ions and codoped with cerium and manganese ions. Using the method of high-temperature solid-state synthesis, ceramic specimens of YAG that contain europium and ytterbium ions have been obtained. In synthesized YAG:Eu and YAG:Yb ceramics, no luminescence that can be attributed to 5 d-4 f transitions in Eu2+ or Yb2+ ions has been detected, even though the scheme of energy levels of these ions constructed with respect to YAG energy bands indicates that there is a potential possibility of the occurrence of 5 d-4 f luminescence for Eu2+ ions in YAG. At room temperature, the luminescence spectrum of hydrothermally synthesized YAG doped with manganese ions consists of two broad bands with maxima at ˜600 and ˜750 nm and does not contain any narrow bands in the red or IR range. Therefore, the spectrum contradicts to the properties of the luminescence of Mn2+, Mn3+, or Mn4+ ions in YAG described in the literature, even though the obtained hydrothermal specimens can contain noticeable concentrations only of Mn3+ ions.

Makhov, V. N.; Khaidukov, N. M.

2014-05-01

25

Spectral analysis of Er3+-, Er3+\\/Yb3+- and Er3+\\/Tm3+\\/Yb3+-doped TeO2 ZnO WO3 TiO2 Na2O glasses  

Microsoft Academic Search

In this paper, we present the spectroscopic properties of Er3+-, Er3+\\/Yb3+- and Er3+\\/Tm3+\\/Yb3+-doped novel tellurite glasses. From the measured absorption spectra, Judd-Ofelt (JO) intensity parameters (Omega2, Omega4 and Omega6) have been evaluated for the Er3+-doped glass. With 980 nm excitation three strong upconversion emission bands centered at 505, 520 and 630 nm were observed for both Er3+- and Er3+\\/Yb3+-codoped glasses

G. Lakshminarayana; Jianrong Qiu; M. G. Brik; G. A. Kumar; I. V. Kityk

2008-01-01

26

Properties of single crystalline AZn2Sb2 (A=Ca,Eu,Yb)  

SciTech Connect

Single crystals of CaZn{sub 2}Sb{sub 2}, EuZn{sub 2}Sb{sub 2}, and YbZn{sub 2}Sb{sub 2} were grown from melts of nominal composition AZn{sub 5}Sb{sub 5} (A = Ca,Eu,Yb) with the excess melt being removed at 1073 K. The electrical transport properties are consistent with those previously reported for polycrystalline samples. This confirms that the p-type carrier concentrations ranging from 2 x 10{sup 19} cm{sup -3} to -1 x 10{sup 20} cm{sup -3} are intrinsic to these materials. Also consistent with transport in polycrystalline materials, the carrier mobility is found to be lowest in CaZn{sub 2}Sb{sub 2}, suggesting the trends in mobility and thermoelectric efficiency within these compounds are inherent to the material systems and not due to inhomogeneity or impurities in polycrystalline samples. These results suggest CaZn{sub 2}Sb{sub 2} has the strongest coupling between the doping/defects and the electronic framework. Magnetization measurements reveal an antiferromagnetic transition near 13 K in EuZn{sub 2}Sb{sub 2}, and the observed magnetic anisotropy indicates the spins align parallel and anti-parallel to c in the trigonal lattice. Powder neutron diffraction on polycrystalline samples of CaZn{sub 2}Sb{sub 2} and YbZn{sub 2}Sb{sub 2} reveals smooth lattice expansion to 1000 K, with c expanding faster than a. The Debye temperatures calculated from specific heat capacity data and the isotropic displacement parameters are found to correlate with the carrier mobility, with the CaZn{sub 2}Sb{sub 2} displaying the largest Debye temperature and smallest mobility.

May, Andrew F [ORNL; McGuire, Michael A [ORNL; Ma, Jie [ORNL; Delaire, Olivier A [ORNL; Huq, Ashfia [ORNL; Custelcean, Radu [ORNL

2012-01-01

27

Controlled synthesis, photoluminescence, and the quantum cutting mechanism of Eu(3+) doped NaYbF4 nanotubes.  

PubMed

Quantum cutting down-conversion has been the subject of intense research activity due to its wide application in optoelectronic devices. However, the energy transfer mechanism behind this down-conversion process is not fully understood. In this work, monodispersed Eu(3+) doped NaYbF4 nanotubes were synthesized by a hydrothermal route. Simultaneous phase transition from cubic to hexagonal and size modification are controlled by changing the Eu(3+) doping concentration. Excited by 393 nm ultraviolet monochromatic light, Eu(3+) doped NaYbF4 nanotubes show quantum cutting down-conversion involving visible and broadband near-infrared emissions through an energy migration process (5)D2 (Eu(3+)) ? (2)F5/2 (Yb(3+)) + (2)F5/2 (Yb(3+)). Based on the emission spectra of Eu(3+) ions, an improved method is proposed to calculate Judd-Ofelt intensity parameters and radiative transition probability. A comprehensive seven-level rate-equation model is developed to study the energy transfer mechanism. This work offers a method to calculate Judd-Ofelt parameters of opaque powder phosphors and to evaluate the population dynamics of excited states. PMID:24887648

Wang, Xiangfu; Liu, Chun-sheng; Yu, Tonghui; Yan, Xiaohong

2014-07-14

28

Structural properties in RFe2O4 compounds (R=Tm, Yb, and Lu)  

NASA Astrophysics Data System (ADS)

We report a complete characterization of the crystal structure between 400 and 80 K for RFe2O4 (R = Rm, Yb, and Lu) compounds using high resolution x-ray synchrotron powder diffraction. The three samples have a hexagonal structure (space group R3¯m) characterized by a sequence of double layers of mixed valence iron and oxygen atoms forming two-dimensional triangular layers separated by a single R-O layer along the c axis. This structure is stable down to 80 K for TmFe2O4 and YbFe2O4 though a sudden expansion in the c axis is observed at around 300 K coupled to a variation in the electrical properties. However, LuFe2O4 exhibits two structural transitions upon cooling. The splitting of some reflections and the occurrence of superstructure peaks below 320 K reveal a structural phase transition. The unit cell is monoclinic (space group C2/m), and there are four nonequivalent Fe sites with a maximum charge disproportionation of 0.5 e. The hexagonal to monoclinic transition is characterized by a sudden expansion of the c axis on cooling, and it seems to be driven by the condensation of Y2 modes. At lower temperatures (˜170 K) additional splitting of several peaks indicate that the unit cell is no longer monoclinic but triclinic (space group P1¯). This transition is characterized by a contraction of the monoclinic ab plane, while the c axis remains almost unchanged. There are six nonequivalent Fe sites in the triclinic cell, and the charge disproportionation magnitude is little affected.

Blasco, J.; Lafuerza, S.; García, J.; Subías, G.

2014-09-01

29

Effect of Li+ ions on enhancement of near-infrared upconversion emission in Y2O3:Tm3+/Yb3+ nanocrystals  

NASA Astrophysics Data System (ADS)

Near-infrared (NIR) to NIR upconversion emission is investigated in Tm3+/Yb3+/Li+ triply doped Y2O3 nanocrystals. Li+ ions doped in Y2O3:Tm3+/Yb3+ nanocrystals can greatly enhance the NIR upconversion emission intensity of Tm3+ ions. The abnormal shift of the (222) diffraction peak position determined from x-ray diffraction measurements is discussed, by introducing Li+ ions in the Y2O3:Tm3+/Yb3+ nanocrystals. The cause of the enhancement is the modification of the local symmetry induced by the Li+ ions, which increases the intra-4f transitions of Tm3+ ion. Li+ ions doped in Y2O3:Tm3+/Yb3+ nanocrystals also can reduce the OH groups, dissociate the Yb3+ and Tm3+ ion clusters, and create the oxygen vacancies, which are the other reasons for enhancing the upconversion emission intensities. This material may be promising for in vitro and in vivo bioimaging probes.

Li, Dongyu; Wang, Yuxiao; Zhang, Xueru; Dong, Hongxing; Liu, Lu; Shi, Guang; Song, Yinglin

2012-11-01

30

Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (0  

SciTech Connect

The compounds, Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (0Tm was determined from wavelength dispersive microprobe analysis to be x=0.45 (1). Single crystal data are consistent with the Ca{sub 14}AlSb{sub 11} structure type and one formula unit can be described as consisting of 14 Yb{sup 2+} cations, MnSb{sub 4} tetrahedron, Sb{sub 3} linear anion and 4 Sb{sub 3}{sup -} anions. The site occupancy of the Tm atom was not determined because of the small amount and small difference in scattering between Tm and Yb. The difference in bond lengths or angles between the solid solution and pristine Yb{sub 14}MnSb{sub 11} is less than 1%. The magnetic susceptibility of samples prepared by Sn flux with the nominal composition of Yb{sub 14?x}Tm{sub x}MnSb{sub 11} (x=0.1, 0.2, 0.3, and 0.4), show that these phases are ferromagnetic at low temperature with the T{sub C} decreasing from 56 to 39 K with increasing x. Magnetic saturation for the x=0.4 composition at 5 K is consistent with Tm being present as Tm{sup 3+} and a negative magnetoresistance ratio (MR=[(?(H)??(0))/?(H)]×100%) of 18% at 3 T is observed. -- Graphical abstract: Magnetic susceptibility (?) for Yb{sub 14?x}Tm{sub x}MnSb{sub 11} at H{sub a}=0.01 T as a function of temperature along with a view of the structure. Highlights: • New rare earth containing transition metal Zintl phase. • Control of magnetic properties through aliovalent substitution. • Magnetic ordering due to both d and f electrons. • Large magnetoresistance at low temperatures.

Roudebush, John H.; Grebenkemper, Jason; Hu, Yufei; Kazem, Nasrin [Department of Chemistry, University of California, Davis, CA 95616 (United States); Abdusalyamova, M.N. [The Institute of Chemistry of the Tajik Academy of Sciences, 229/2, Aini Street, 734063 Dushanbe (Tajikistan); Kauzlarich, Susan M., E-mail: smkauzlarich@ucdavis.edu [Department of Chemistry, University of California, Davis, CA 95616 (United States)

2014-03-15

31

Field-Induced Magnetic Properties in RCrO 4 Oxides ( R=Pr, Gd, Tb, Tm, and Yb)  

NASA Astrophysics Data System (ADS)

RCrO4 oxides (R=Pr, Gd, Tb, Tm, and Yb) have been synthesized at 773 K using the corresponding nitrates as precursors. X-ray diffraction data reveal that these samples are single phases and crystallize with the zircon-type structure, showing tetragonal symmetry, space group I41/amd. All the compounds are antiferromagnetic and the Néel temperature, which depends on the R3+ ion, takes values lower than 30 K. The presence of a canting appears to be responsible for the negative values of the magnetic susceptibility found below the compensation temperature. This uncommon phenomenon is named reversal of magnetization. It is field-dependent, being suppressed at 500 Oe for the TmCrO4 compound. The highest value of the compensation temperature (24 K) corresponds to the YbCrO4 oxide. A metamagnetic transition has been observed in all cases at critical fields ranging from 225 Oe (GdCrO4) to 1600 Oe (YbCrO4).

Jiménez, E.; Isasi, J.; Sáez-Puche, R.

2002-03-01

32

Infrared-to-visible up-conversion luminescence and energy transfer of RE3+/Yb3+(RE = Ho, Tm) co-doped SrIn2O4  

NASA Astrophysics Data System (ADS)

Near-infrared excited up-conversion phosphors of RE3+/Yb3+(RE = Ho, Tm) co-doped SrIn2O4 were synthesized by a solid-state reaction method. X-ray diffraction analysis revealed the phase composition of those samples, and the up-conversion spectroscopic properties were studied in terms of up-conversion emission spectra. Under 980 nm near-infrared laser excitation, strong green emission with the peak at 546 nm was observed in SrIn2O4: Ho3+/Yb3+, which can be assigned to the characteristic 5S2(5F4) ? 5I8 transition of Ho3+. Furthermore, SrIn2O4: Tm3+/Yb3+ showed bright blue emission with the peak at 486 nm, which is associated with the 1G4 ? 3H6 transition of Tm3+. The UC power studies indicated that the luminescence of SrIn2O4: Ho3+/Yb3+ and SrIn2O4: Tm3+/Yb3+ are attributed to two-photon and three-photon process, respectively. The possible UC luminescence mechanism and energy transfer in SrIn2O4: RE3+/Yb3+ were discussed.

Guan, Ming; Zheng, Hong; Mei, Lefu; Huang, Zhaohui; Yang, Tao; Fang, Minghao; Liu, Yangai

2014-11-01

33

Monodisperse NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals with near-infrared to near-infrared upconversion photoluminescence and magnetic resonance properties  

NASA Astrophysics Data System (ADS)

We report core/shell NaYbF4 : Tm3+/NaGdF4 nanocrystals to be used as probes for bimodal near infrared to near infrared (NIR-to-NIR) upconversion photoluminescence (UCPL) and magnetic resonance (MR) imaging. The NaYbF4 : Tm3+ nanocrystals were previously reported to produce the intense NIR-to-NIR UCPL peaked at ~800 nm under excitation at ~975 nm. We have found that the growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals results in the increase in the intensity of UCPL of Tm3+ ions by about 3 times. Unlike biexponential PL decay of NaYbF4 : Tm3+ nanocrystals, the PL decay of NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals is single exponential and of longer lifetime due to the suppression of surface quenching effects for Tm3+ PL. The growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals also provides high MR relaxivity from paramagnetic Gd3+ ions contained in the shell. The T1-weighted MR signal of the (NaYbF4:2% Tm3+)/NaGdF4 nanoparticles was measured to be about 2.6 mM-1s-1. Due to the combined presence of efficient optical and MR imaging capabilities, nanoprobes based on NaYbF4 : Tm3+/NaGdF4 fluoride nanophosphors can be considered as a promising platform for simultaneous bimodal PL and MR bioimaging.We report core/shell NaYbF4 : Tm3+/NaGdF4 nanocrystals to be used as probes for bimodal near infrared to near infrared (NIR-to-NIR) upconversion photoluminescence (UCPL) and magnetic resonance (MR) imaging. The NaYbF4 : Tm3+ nanocrystals were previously reported to produce the intense NIR-to-NIR UCPL peaked at ~800 nm under excitation at ~975 nm. We have found that the growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals results in the increase in the intensity of UCPL of Tm3+ ions by about 3 times. Unlike biexponential PL decay of NaYbF4 : Tm3+ nanocrystals, the PL decay of NaYbF4 : Tm3+/NaGdF4 core/shell nanocrystals is single exponential and of longer lifetime due to the suppression of surface quenching effects for Tm3+ PL. The growth of a NaGdF4 shell on surface of the NaYbF4 : Tm3+ nanocrystals also provides high MR relaxivity from paramagnetic Gd3+ ions contained in the shell. The T1-weighted MR signal of the (NaYbF4:2% Tm3+)/NaGdF4 nanoparticles was measured to be about 2.6 mM-1s-1. Due to the combined presence of efficient optical and MR imaging capabilities, nanoprobes based on NaYbF4 : Tm3+/NaGdF4 fluoride nanophosphors can be considered as a promising platform for simultaneous bimodal PL and MR bioimaging. Electronic supplementary information (ESI) available: transmission electron images with higher magnification times; histograms of the size distribution of NaYbF4:2% Tm3+ and NaYbF4 : Tm3+/NaGdF4 nanocrystals; d-spacing values of NaYbF4:2% Tm3+ and NaYbF4 : Tm3+/NaGdF4 nanocrystals; mechanisms for upconversion photoluminescence generation. See DOI: 10.1039/c0nr01018a

Chen, Guanying; Ohulchanskyy, Tymish Y.; Law, Wing Cheung; Ågren, Hans; Prasad, Paras N.

2011-05-01

34

SrAl4O7:Tm3+/Yb3+ nanocrystalline blue phosphor: structural, thermal and optical properties  

NASA Astrophysics Data System (ADS)

Strontium aluminate (SrAl4O7) nanophosphor codoped with Tm3+-Yb3+ has been synthesized through the combustion route using urea as the reducing agent. Structural, thermal and optical characterizations have been carried out. Heat treatment of the samples shows a change in the crystallite phases and the relative luminescence intensities for the different bands. The nanocrystalline particles in the as-synthesized sample seem to arrange in rod like shapes of submicrometer length on annealing. A broad (350-550 nm) emission in the UV-green region is observed when 266 nm radiation is used for excitation. Intense upconversion (UC) emissions in blue, red and infrared are seen with excitation by 976 nm radiation. An emission at 364 nm not observed earlier and attributed to 1D2?3H6 transition in Tm3+ is also seen. The blue emission from SrAl4O7:Tm3+/Yb3+ codoped nanophosphor (annealed at 1200°C) exhibits high color purity (89%) and is comparable to phosphors used commercially. The energy transfer mechanisms, responsible for these UC emissions, are proposed and discussed.

Giri, N. K.; Singh, S. K.; Rai, D. K.; Rai, S. B.

2010-04-01

35

Highly improved upconversion luminescence in NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals  

NASA Astrophysics Data System (ADS)

The upconversion luminescence (UCL) of rare earth (RE) ions doped nanomaterials has attracted extensive interest because of its wide and great potential applications. However, the lower UCL efficiency is still an obstacle for real applications. Photonic modulation is a novel way to improve the efficiency of UCL. In this work, NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals (IOPCs) were fabricated through the polymethylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamics of Tm3+ ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL 1D2-3H6/3F4 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. Furthermore, the overall intensity ratio of visible UCL to near-infrared (NIR) down-conversion luminescence (DCL) was 2.8-8 times improved than that of the grinded reference (REF) and independent of the photonic stop band (PSB). The studies on UCL dynamics indicated that the nonradiative transition rate of Tm3+ was considerably suppressed. The facts above indicated that in the IOPCs the UCL efficiency of Tm3+ was largely improved due to the periodic macroporous structure.The upconversion luminescence (UCL) of rare earth (RE) ions doped nanomaterials has attracted extensive interest because of its wide and great potential applications. However, the lower UCL efficiency is still an obstacle for real applications. Photonic modulation is a novel way to improve the efficiency of UCL. In this work, NaGd(WO4)2:Yb3+/Tm3+ inverse opal photonic crystals (IOPCs) were fabricated through the polymethylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamics of Tm3+ ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL 1D2-3H6/3F4 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. Furthermore, the overall intensity ratio of visible UCL to near-infrared (NIR) down-conversion luminescence (DCL) was 2.8-8 times improved than that of the grinded reference (REF) and independent of the photonic stop band (PSB). The studies on UCL dynamics indicated that the nonradiative transition rate of Tm3+ was considerably suppressed. The facts above indicated that in the IOPCs the UCL efficiency of Tm3+ was largely improved due to the periodic macroporous structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05688d

Wang, Yunfeng; Xu, Wen; Cui, Shaobo; Xu, Sai; Yin, Ze; Song, Hongwei; Zhou, Pingwei; Liu, Xiaoyan; Xu, Lin; Cui, Haining

2015-01-01

36

Colloidal synthesis and blue based multicolor upconversion emissions of size and composition controlled monodisperse hexagonal NaYF4 : Yb,Tm nanocrystals  

NASA Astrophysics Data System (ADS)

Monodisperse ?-NaYF4 : Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the ?-NaYF4 : Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the ?-NaYF4 : Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained ?-NaYF4 : Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the ?-NaYF4 : Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for ~50 nm ?-NaYF4 : Yb,Tm nanocrystals than those for the bigger (~150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations.Monodisperse ?-NaYF4 : Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the ?-NaYF4 : Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the ?-NaYF4 : Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained ?-NaYF4 : Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the ?-NaYF4 : Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for ~50 nm ?-NaYF4 : Yb,Tm nanocrystals than those for the bigger (~150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations. Electronic supplementary information (ESI) available: More TEM images and UC results of the ?-NaYF4 : Yb,Tm nanocrystals. See DOI: 10.1039/b9nr00397e

Yin, Anxiang; Zhang, Yawen; Sun, Lingdong; Yan, Chunhua

2010-06-01

37

Luminescence and electroluminescence of Nd, Tm, and Yb doped GaAs and some II-VI compounds  

NASA Astrophysics Data System (ADS)

This report describes the progress accomplished during the three years of research on photoluminescence and electroluminescence properties of Nd, Tm, and Yb doped InP, GaAs, CdS, and ZnS. The results are as follows: We developed the kinetics model of energy transfer from the host lattice to the localized core excited state of rare earth isoelectronic structured traps. The energy transfer processes occur through an Auger mechanism where the recombination energy of the bound electron with a free hole is transferred nonradiatively to the core states (or energy can be transferred from the bound exciton on an REI-trap to the core states). If the initial and final states are not resonant, the energy mismatch must be accommodated by emission or absorption of phonons. Furthermore we discuss details of several quenching processes, which are incorporated into the kinetics equations. The derived two sets of differential equations for semi-insulating and n type semiconductors govern the kinetics of rare earth luminescence. The numerically simulated luminescence rise and decay times show a good quantitative agreement with experimental data obtained for InP: Yb over a wide range of excitation intensity. The photoluminescence spectra and decay time also studied as a function of temperature. The new quenching mechanism of ytterbium luminescence involving Yb and Fe ions is proposed. The electric field quenching of InP: Yb photoluminescence was investigated. The photoluminescence kinetics as a function of excitation intensity in n and p type InP: Yb and GaAs: Nd grown by MOCVD was studied at 1.8 K and 77 K.

Lozykowski, Henryk J.

1994-02-01

38

980 nm laser-diode-excited intense blue upconversion in Tm3+/Yb3+-codoped gallate-bismuth-lead glasses  

NASA Astrophysics Data System (ADS)

Intense blue-upconversion in Tm3+/Yb3+-codoped gallate-bismuth-lead glasses has been achieved under an excitation from a commercially available 980nm laser diode. Energy transfer processes and excited-state absorption account for the population of the G41 emitting level of the Tm3+. Although the addition of GeO2 has enhanced the glass thermal stability, the phonon mode associated with vibration of GeO2 has almost no influence on the blue-upconversion intensity and the radiative lifetime of H43 level. The dependence of the phonon energy of the host on contributions from multiphonon decay on the fluorescence has been discussed. Significant enhancement of the blue-upconversion has also been observed in gallate-bismuth-lead glasses with the incorporation of PbF2 content.

Zhang, Q. Y.; Li, T.; Jiang, Z. H.; Ji, X. H.; Buddhudu, S.

2005-10-01

39

Tunable multicolor and white-light upconversion luminescence in Yb(3+) /Tm(3+) /Ho(3+) tri-doped NaYF4 micro-crystals.  

PubMed

NaYF4 micro-crystals with various concentrations of Yb(3+) /Tm(3+) /Ho(3+) were prepared successfully via a simple and reproducible hydrothermal route using EDTA as the chelating agent. Their phase structure and surface morphology were studied using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns revealed that all the samples were pure hexagonal phase NaYF4 . SEM images showed that Yb(3+) /Tm(3+) /Ho(3+) tri-doped NaYF4 were hexagonal micro-prisms. Upconversion photoluminescence spectra of Yb(3+) /Tm(3+) /Ho(3+) tri-doped NaYF4 micro-crystals with various dopant concentrations under 980?nm excitation with a 665?mW pump power were studied. Tunable multicolor (purple, purplish blue, yellowish green, green) and white light were achieved by simply adjusting the Ho(3+) concentration in 20%Yb(3+) /1%Tm(3+) /xHo(3+) tri-doped NaYF4 micro-crystals. Furthermore, white-light emissions could be obtained using different pump powers in 20%Yb(3+) /1%Tm(3+) /1%Ho(3+) tri-doped NaYF4 micro-crystals at 980?nm excitation. The pump power-dependent intensity relationship was studied and relevant energy transfer processes were discussed in detail. The results suggest that Yb(3+) /Tm(3+) /Ho(3+) tri-doped NaYF4 micro-crystals have potential applications in optoelectronic devices such as photovoltaic, plasma display panel and white-light-emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25377774

Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli

2014-11-01

40

Enhancement of near-infrared to near-infrared upconversion emission in the CeO?: Er³?, Tm³?, Yb³? inverse opals.  

PubMed

In this Letter, CeO?: Er³?, Tm³?, Yb³? inverse opal with near-infrared to near-infrared upconversion emission was prepared by polystyrene colloidal crystal templates, and the influence of photonic bandgap on the upconversion emission was investigated. Comparing with the reference sample, suppression of the blue or red upconversion luminescence was observed in the inverse opals. It is interesting that the near-infrared upconversion emission located at about 803 nm was enhanced due to the inhibition of visible upconversion emission in the inverse opals. Additionally, the variety of upconversion emission mechanisms was observed and discussed in the CeO?: Er³?, Tm³?, Yb³? inverse opals. PMID:24562241

Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo; Yang, Yong; Zhou, Dacheng

2014-02-15

41

Partial Liquid-Phase Hydrogenation of Benzene to Cylohexene on SiO 2 Immobilized Lanthanide (Eu and Yb) Catalysts  

Microsoft Academic Search

SiO2-immobilized Eu and Yb catalysts (=Si–O–Ln–NH2) obtained by the reaction of surface hydroxyl groups on SiO2 with lanthanide metals dissolved in liquid ammonia are active for the partial liquid-phase hydrogenation of benzene to cyclohexene when the reaction was carried out at 423–483 K with hydrogen pressures of 1–5 MPa. Interestingly, only divalent amides are catalytically effective for the partial hydrogenation

Hayao Imamura; Toshiko Kumai; Koji Nishimura; Takayuki Nuruyu; Yoshihisa Sakata

2002-01-01

42

Highly improved upconversion luminescence in NaGd(WO4)2:Yb(3+)/Tm(3+) inverse opal photonic crystals.  

PubMed

The upconversion luminescence (UCL) of rare earth (RE) ions doped nanomaterials has attracted extensive interest because of its wide and great potential applications. However, the lower UCL efficiency is still an obstacle for real applications. Photonic modulation is a novel way to improve the efficiency of UCL. In this work, NaGd(WO4)2:Yb(3+)/Tm(3+) inverse opal photonic crystals (IOPCs) were fabricated through the polymethylmethacrylate (PMMA) template and the modification of the IOPC structure on the emission spectra and dynamics of Tm(3+) ions was systemically studied. It is interesting to observe that in the IOPCs, the high-order UCL (1)D2-(3)H6/(3)F4 was relatively enhanced. At the same time, the local thermal effect induced by laser irradiation was suppressed. Furthermore, the overall intensity ratio of visible UCL to near-infrared (NIR) down-conversion luminescence (DCL) was 2.8-8 times improved than that of the grinded reference (REF) and independent of the photonic stop band (PSB). The studies on UCL dynamics indicated that the nonradiative transition rate of Tm(3+) was considerably suppressed. The facts above indicated that in the IOPCs the UCL efficiency of Tm(3+) was largely improved due to the periodic macroporous structure. PMID:25493336

Wang, Yunfeng; Xu, Wen; Cui, Shaobo; Xu, Sai; Yin, Ze; Song, Hongwei; Zhou, Pingwei; Liu, Xiaoyan; Xu, Lin; Cui, Haining

2015-01-01

43

Preparation and characterization of upconversion luminescent Tm3+/Yb3+ co-doped Y2O3 nanophosphor  

NASA Astrophysics Data System (ADS)

Tm3+/Yb3+ co-doped Y2O3 nanophosphor has been synthesized by the solution combustion technique. Heat treatment of the phosphor materials at higher temperatures modifies the structural and optical properties. At low concentration of Yb3+, an intense upconversion emission is observed in blue region (478 nm) on excitation with 976 nm radiations. Emission has also been observed in the ultraviolet (UV) region viz. at 300 nm. The intensity of blue emission initially increases with dopant concentration as well as with the annealing temperature. However, for higher concentrations of Yb3+ (10 mol%), emission in the blue region is greatly suppressed and NIR emission at 813 nm appears with a large intensity. Intensity ratio of NIR and blue emission ( I NIR/ I B) reaches 74, resulting in almost monochromatic light at 813 nm. To check the suitability of blue emission for display devices, CIE color coordinates ( x, y), color purity and the dominant wavelength ( ? d) for the blue emission have been calculated and the resulting value is found to be close to the coordinates of available standard blue phosphors.

Mishra, K.; Giri, N. K.; Rai, S. B.

2011-06-01

44

Self-assembled RE2(MO4)3:Ln3+ (RE = Y, La, Gd, Lu; M = W, Mo; Ln = Yb/Er, Yb/Tm) hierarchical microcrystals: Hydrothermal synthesis and up-conversion luminescence  

NASA Astrophysics Data System (ADS)

RE2(MO4)3:Ln3+ (RE = Y, La, Gd, Lu; M = W, Mo; Ln = Yb/Er, Yb/Tm) microstructures with uniform shapes and sizes were synthesized via a hydrothermal method in the presence of hexadecyl trimethyl ammonium bromide (CTAB). The structure and morphology of the as-prepared microcrystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The 3D hierarchical architectures of Y2(MoO4)3:Yb3+/Er3+ and Gd2(WO4)3:Yb3+/Er3+ are self-assembled by numerous nanoflakes. The up-conversion (UC) luminescence properties of these samples were investigated. Obvious differences in up-converted emission spectra among the as-obtained products were observed, and possible reasons were discussed. The corresponding up-conversion mechanism was also proposed.

Zhou, You; He, Xiang-Hong; Yan, Bing

2014-01-01

45

Features of the formation of magnetic moments of Tm3+ and Yb3+ rare-earth ions in LuB12 cage glass  

NASA Astrophysics Data System (ADS)

The features of the formation of the magnetic moments of Tm3+ and Yb3+ ions in a metallic matrix of LuB12 cage glass have been studied in measurements of the magnetization and specific heat in the temperature range of 1.9-300 K in magnetic fields up to 90 kOe. It has been shown that a paramagnetic response from the localized moments of isolated ions Tm3+ (7.6?B) and Yb3+ (4.5?B) is observed at temperatures of 150-300 K. A transition to the cage glass phase at low temperatures ( T ? T* ˜ 60 K) is accompanied by disordering in the system of rare-earth ions and by formation of many-body states near Tm3+ and Yb3+ ions. At low temperatures near T m in low magnetic fields, the appearance of an additional spin polarization, which is suppressed with an increase in the field, has been observed. The effective moments and g-factors of Tm and Yb obtained in high fields imply both the binding of a small fraction of magnetic ions to antiferromagnetic dimers and the ?6 ground state of the 2 F 7/2 multiplet of the ytterbium ion. A scenario alternative to the Kondo-type behavior has been proposed to explain the nature of many-body states and the appearance of the spin polarization in rare-earth dodecaborides.

Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Voronov, V. V.; Gavrilkin, S. Yu.; Glushkov, V. V.; Demishev, S. V.; Kuznetsov, A. V.; Mitsen, K. V.; Filippov, V. B.; Shitsevalova, N. Yu.; Gabani, S.; Flachbart, K.

2014-12-01

46

Observation of multi-mode: Upconversion, downshifting and quantum-cutting emission in Tm3+/Yb3+ co-doped Y2O3 phosphor  

NASA Astrophysics Data System (ADS)

Micro-crystalline Y2O3 phosphor co-doped with Yb3+/Tm3+ has been synthesized and characterized. The phosphor material gives efficient multimodal emission via downshifting (DS), upconversion (UC), and downconversion (DC)/quantum cutting (QC) luminescence processes. Cross relaxation and co-operative energy transfer (CET) have been ascribed as the possible mechanism for QC; as result of which a UV/blue photon absorbed by Tm3+ splits into two near infrared photons (wavelength range 950-1050 nm) emitted by Yb3+. The Yb3+ concentration dependent ET efficiency and QC efficiency has also been evaluated. Such multi-mode emitting phosphors could have potential applications in increasing the conversion efficiency of solar cells via spectral modification.

Yadav, Ranvijay; Singh, S. K.; Verma, R. K.; Rai, S. B.

2014-04-01

47

Anomalous Hall effect in three ferromagnetic compounds: EuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30  

NASA Astrophysics Data System (ADS)

The Hall resistivity (?xy) , resistivity (?xx) , and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe4Sb12 (Tc?84K) , Yb14MnSb11 (Tc?53K) , and Eu8Ga16Ge30 (Tc?36K) are Zintl compounds with carrier concentrations between 1×1021 and 3.5×1021cm-3 . The relative decrease in ?xx below Tc [?xx(Tc)/?xx(2K)] is 28, 6.5, and 1.3 for EuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30 , respectively. The low carrier concentrations coupled with low magnetic anisotropies allow a relatively clean separation between the anomalous (?xy') , and normal contributions to the measured Hall resistivity. For each compound the anomalous contribution in the zero field limit is fit to a?xx+?xy?xx2 for temperatures TEuFe4Sb12 , Yb14MnSb11 , and Eu8Ga16Ge30 , respectively, and is independent of temperature for T

Sales, Brian C.; Jin, Rongying; Mandrus, David; Khalifah, Peter

2006-06-01

48

Doxorubicin conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles for therapy and sensing of drug delivery by luminescence resonance energy transfer.  

PubMed

In this study, we report an anticancer drug delivery system based on doxorubicin (DOX)-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles. The as-synthesized nanoparticles consist of uniform spherical nanoparticles with an average diameter of 25 nm. The drug delivery system demonstrates the ability to release DOX by cleavage of the hydrazone bond in mildly acidic environments. The spectra overlap between emission of donor NaYF(4):Yb(3+)/Tm(3+) nanoparticles at 452 nm ((1)D(2)?(3)F(4)) and 477 nm ((1)G(4)?(3)H(6)) and the broad absorbance of acceptor DOX centered at around 480 nm enables energy transfer to occur between the nanoparticles and DOX. The quenching and recovery of the up-conversion luminescence of NaYF(4):Yb(3+)/Tm(3+) by DOX due to luminescence resonance energy transfer (LRET) mechanism are applied as optical probe to confirm the DOX conjunction and monitor the release of DOX. The DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles exhibit an obvious cytotoxic effect on SKOV3 ovarian cancer cells via MTT assay. Meanwhile, the endocytosis process of DOX-conjugated NaYF(4):Yb(3+)/Tm(3+) nanoparticles by SKVO3 cells was demonstrated through confocal laser scanning microscopy (CLSM), flow cytometry and ICP-OES. Such drug delivery system, which combines pH-triggered drug-release and up-converting nanoparticles-based LRET property, has excellent potential applications in cancer therapy and smart imaging. PMID:22938822

Dai, Yunlu; Yang, Dongmei; Ma, Ping'an; Kang, Xiaojiao; Zhang, Xiao; Li, Chunxia; Hou, Zhiyao; Cheng, Ziyong; Lin, Jun

2012-11-01

49

A bifunctional Cr/Yb/Tm:Ca3Ga2Ge3O12 phosphor with near-infrared long-lasting phosphorescence and upconversion luminescence.  

PubMed

Currently, upconversion nanocrystals and long-lasting phosphorescent particles have attracted extensive research interest for their possible applications as bioimaging probes. However, there are few reports concerning the achievement of both upconversion luminescence of lanthanide ions and long-lasting phosphorescence of transition metal ions in a sole host so far. Herein, we demonstrate a novel calcium gallium germanium garnet (Ca3Ga2Ge3O12) host where lanthanide ions such as Tm(3+)/Yb(3+) and transition metal ions such as Cr(3+) can be easily incorporated through substituting the Ca(2+) and Ga(3+) respectively. This Cr/Yb/Tm:Ca3Ga2Ge3O12 phosphor exhibits both broadband near-infrared long-lasting phosphorescence of Cr(3+) with an afterglow time of more than 7000 s and near-infrared to near-infrared upconversion luminescence of Tm(3+). Impressively, it is evidenced that the addition of Yb(3+)/Tm(3+) into Cr:Ca3Ga2Ge3O12 not only results in Tm(3+) upconversion luminescence but also greatly increases Cr(3+) afterglow time. Based on excitation/emission, three-dimensional thermoluminescence, and time-resolved luminescence spectra, the related long-lasting phosphorescence and upconversion luminescent mechanisms are systematically discussed as well. PMID:25068770

Chen, Daqin; Chen, Yan; Lu, Hongwei; Ji, Zhenguo

2014-08-18

50

Ultraviolet upconversion emissions of Gd3+ in beta-NaLuF4:Yb3+,Tm3+,Gd3+ nanocrystals.  

PubMed

Beta-NaLuF4:20%Yb,0.5%Tm,x%Gd (x = 10, 20, 30) nanocrystals were synthesized by high temperature thermal decomposition method. X-ray diffraction (XRD) show the as-prepared samples are characteristic of a pure beta-NaLuF4. Transmission electron microscope (TEM) investigations indicate the nanocrystals have particle size of -85 nm with good monodispersity and well-defined crystallographic facets. Particularly, under 980 nm excitation, upconversion (UC) emissions in the UV range of 270-320 nm were observed in these nanocrystals, which further prove that beta-NaLuF4 is an excellent host for building UV compact solid-state lasers or fiber lasers. PMID:24734621

Song, Weiye; Guo, Xingyuan; He, Guanghui; Qin, Weiping

2014-05-01

51

Near-infrared photocatalysts of BiVO?/CaF?:Er³?, Tm³?, Yb³? with enhanced upconversion properties.  

PubMed

Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO? (BVO)/CaF?:Er(3+), Tm(3+), Yb(3+) (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi(3+) ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). PMID:24302062

Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

2014-01-01

52

Au nanorod decoration on NaYF?:Yb/Tm nanoparticles for enhanced emission and wavelength-dependent biomolecular sensing.  

PubMed

We introduce gold nanorods (GNRs) decoration on NaYF4:Yb/Tm upconversion nanocrystals (UCNCs) by functionalizing the UCNCs with polyamidoamine generation 1 (PAMAM G1) dendrimer, followed by a single-step seed-mediated growth of long-range GNRs to enhance "biological window" upconversion emission. The up-conversion emission of GNR-decorated UCNCs can be enhanced beyond the level typically obtainable using shell-like structures up to 27-fold enhancement. Also, the enhancement can be tuned at different wavelength regions by varying the GNR aspect ratio. The GNR-decorated UCNC is further modified with 2-thiouracil for nonenzymatic detection of uric acid, revealing a detection limit as 1 pM. PMID:23591121

Kannan, Palanisamy; Abdul Rahim, Ferhan; Chen, Rui; Teng, Xue; Huang, Ling; Sun, Handong; Kim, Dong-Hwan

2013-05-01

53

Synthesis, structure, magnetism, and optical properties of theordered mixed-lanthanide sulfides gamma-LnLn'S3 (Ln=La, Ce; Ln'=Er, Tm,Yb)  

SciTech Connect

{gamma}-LnLn{prime}S{sub 3} (Ln = La, Ce; Ln{prime} = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb{sub 2}S{sub 3} flux at 1000 C. This isotypic series of compounds adopts a layered structure that consists of the smaller lanthanides (Er, Tm, and Yb) bound by sulfide in six- and seven-coordinate environments that are connected together by the larger lanthanides (La and Ce) in eight- and nine-coordinate environments. The layers can be broken down into three distinct one-dimensional substructures containing three crystallographically unique Ln{prime} centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln{prime}S{sub 7}] monocapped trigonal prisms that are joined to equivalent chains via edge-sharing to yield ribbons. There are parallel chains of [Ln{prime}S{sub 6}] distorted octahedra that are linked to the first ribbons through corner-sharing. These latter units also share corners with a one-dimensional ribbon composed of parallel chains of [Ln{prime}S{sub 6}] polyhedra that edge-share both in the direction of chain propagation and with adjacent identical chains. Magnetic susceptibility measurements show Curie-Weiss behavior from 2 to 300 K with antiferromagnetic coupling, and no evidence for magnetic ordering. The {theta}{sub p} values range from -0.4 to -37.5 K, and spin-frustration may be indicated for the Yb-containing compounds. All compounds show magnetic moments substantially reduced from those calculated for the free ions. The optical band gaps for {gamma}-LaLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.6 eV, whereas {gamma}-CeLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.3 eV.

Jin, G.B.; Choi, E.S.; Guertin, R.P.; Brooks, J.S.; Bray, T.H.; Booth, C.H.; Albrecht-Schmitt, T.E.

2006-12-12

54

Multifunctional SiO2@Gd2O3:Yb/Tm hollow capsules: controllable synthesis and drug release properties.  

PubMed

A series of hollow and luminescent capsules have been fabricated by covering luminescent Gd2O3:Yb/Tm nanoparticles on the surface of uniform hollow mesoporous silica capsules (HMSCs), which were obtained from an etching process using Fe3O4 as hard templates. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), up-conversion (UC) fluorescence spectra, and N2 adsorption-desorption were used to characterize these samples. It is found that the as-prepared products have mesoporous pores, large specific surface, and high dispersity. In particular, the size, shape, surface area, and interior space of the composites can be finely tuned by adjusting the size and morphology of the magnetic cores. Under 980 nm near-infrared (NIR) laser irradiation, the composites show characteristic blue UC emissions of Tm(3+) even after carrying doxorubicin hydrochloride (DOX). The drug-release test reveals that the capsules showed an apparent sustained release character and released in a pH-sensitive manner. Interestingly, the UC luminescence intensity of the drug-carrying system increases with the released DOX, realizing the possibility to track or monitor the released drug by the change of UC fluorescence simultaneously, which should be highly promising in anticancer drug delivery and targeted cancer therapy. PMID:25285784

Yang, Guixin; Lv, Ruichan; Gai, Shili; Dai, Yunlu; He, Fei; Yang, Piaoping

2014-10-20

55

Near-infrared to visible upconversion in Tm3+ and Yb3+ codoped Lu2O3 nanocrystals synthesized by hydrothermal method.  

PubMed

Lutetium oxide nanocrystals codoped with Tm3+ and Yb3+ have been successfully synthesized via adjusting the pH values of the precursor solution in a hydrothermal method followed by a subsequent calcination process. The samples were systematically characterized by X-ray diffraction, field-emission scanning microscopy, Fourier transform infrared transmittance spectroscopy, and upconversion luminescent spectra. The experimental results show that the pH values of the precursor solution have great effects on the structural, morphological, and upconversion luminescent properties of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals. The as-formed lutetium oxide precursors could transform to cubic Lu2O3 with the same morphology and a slight shrinkage in size after a calcination process. The upconversion emission intensity of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals obtained from the precursor solution with pH = 9 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing the number of OH- groups and the enlarged nanocrystals size. Strong blue and weak red emissions from the prepared nanocrystals were observed under 980 nm laser excitation, which were attributed to the 1G4 --> 3H6 and 1G4 --> 3F4 transitions of Tm3+ ion, respectively. PMID:24738389

Li, Li; Zhang, Xingli; Wei, Xiantao; Wang, Guangchuan; Guo, Changxin

2014-06-01

56

Activation of SO2 with [(?(5) -C5 Me5 )2 Ln(THF)2 ] (Ln=Eu, Yb) leading to dithionite and sulfinate complexes.  

PubMed

The reaction of decamethylytterbocene [(?(5) -C5 Me5 )2 Yb(THF)2 ] with SO2 at low temperature gave two new compounds, namely, the Yb(III) dithionite/sulfinate complex [{(?(5) -C5 Me5 )2 Yb(?3 ,1?(2) O(1,3) ,2?(3) O(2,2',4) -S2 O4 )}2 {(?(5) -C5 Me5 )Yb(?,1?O,2?O'-C5 Me5 SO2 )}2 ] (1) and the Yb(III) dithionite complex [{(?(5) -C5 Me5 )2 Yb}2 (?,1?(2) O(1,3) ,2?(2) O(2,4) -S2 O4 )] (2). After extraction of 1, the mixture was heated to give the dinuclear tetrasulfinate complex [{(?(5) -C5 Me5 )Yb}2 (?,?O,?O'-C5 Me5 SO2 )4 ] (3?a). In contrast, from the reaction of [(?(5) -C5 Me5 )2 Eu(THF)2 ] with SO2 only the tetrasulfinate complex [{(?(5) -C5 Me5 )Eu}2 (?,?O,?O'-C5 Me5 SO2 )4 ] (3?b) was isolated. Two major reaction pathways were observed: 1)?reductive coupling of two SO2 molecules to form the dithionite anion S2 O4 (2-) ; and 2)?nucleophilic attack of one metallocene C5 Me5 ligand on the sulfur atom of SO2 . The compounds presented are the first dithionite and sulfinate complexes of the f-elements. PMID:25196130

Klementyeva, Svetlana V; Gamer, Michael T; Schmidt, Anna-Corina; Meyer, Karsten; Konchenko, Sergey N; Roesky, Peter W

2014-10-13

57

Yellow-orange upconversion emission in Eu(3+)-Yb(3+) codoped BaTiO(3) phosphor.  

PubMed

The Eu(3+)-Yb(3+) codoped BaTiO3 phosphor is prepared via co-precipitation method and its upconversion emission is studied by 980nm diode laser excitation. The X-ray diffraction pattern of the prepared sample showed the tetragonal BaTiO3 phase. The co-doped phosphor showed sharp upconversion emission bands peaking at ?592, ?614, ? 654, ?704 and ?796nm due to the (5)D0?(7)F1, (5)D0?(7)F2, (5)D0?(7)F3, (5)D0?(7)F4 and (5)D0?(7)F6 transitions, respectively of Eu(3+) ions. The sharp band at 489nm is assigned to the (2)F5/2?(2)F7/2 transition of Yb(3+) ion while the broad band around 505nm is assigned to the defect states present in the sample. Based on the available experimental data, the process involved in the UC emissions has been explored and elaborated. PMID:24632162

Kumari, Astha; Rai, Vineet Kumar; Kumar, Kaushal

2014-06-01

58

Yellow-orange upconversion emission in Eu3+-Yb3+ codoped BaTiO3 phosphor  

NASA Astrophysics Data System (ADS)

The Eu3+-Yb3+ codoped BaTiO3 phosphor is prepared via co-precipitation method and its upconversion emission is studied by 980 nm diode laser excitation. The X-ray diffraction pattern of the prepared sample showed the tetragonal BaTiO3 phase. The co-doped phosphor showed sharp upconversion emission bands peaking at ?592, ?614, ? 654, ?704 and ?796 nm due to the 5D0 ? 7F1, 5D0 ? 7F2, 5D0 ? 7F3, 5D0 ? 7F4 and 5D0 ? 7F6 transitions, respectively of Eu3+ ions. The sharp band at 489 nm is assigned to the 2F5/2 ? 2F7/2 transition of Yb3+ ion while the broad band around 505 nm is assigned to the defect states present in the sample. Based on the available experimental data, the process involved in the UC emissions has been explored and elaborated.

Kumari, Astha; Rai, Vineet Kumar; Kumar, Kaushal

2014-06-01

59

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method  

NASA Astrophysics Data System (ADS)

Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from 2H11/2 --> 2I15/2 and 4S3/2 --> 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K-1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.

Gavrilovi?, Tamara V.; Jovanovi?, Dragana J.; Lojpur, Vesna; Drami?anin, Miroslav D.

2014-02-01

60

High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates-Ln(OP-CH-SO) (Ln=Ho, Er, Tm, Yb, Lu, Y)  

Microsoft Academic Search

Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, HOP-CH-SOH (HL), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(OP-CH-SO) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y (6). The syntheses were

Andreas Sonnauer; Norbert Stock

2008-01-01

61

Specific features of magnetoresistance during the antiferromagnet-paramagnet transition in Tm{sub 1-x}Yb{sub x}B{sub 12}  

SciTech Connect

The transverse magnetoresistance {Delta}{rho}/{rho}(H, T) of Tm{sub 1-x}Yb{sub x}B{sub 12} single crystals is studied in the ytterbium concentration range corresponding to the antiferromagnet-paramagnet transition in a magnetic field up to 80 kOe at low temperatures. A magnetic H-T phase diagram is constructed for the antiferromagnetic state of substitutional Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions with x {<=} 0.1. The contributions to the magnetoresistance in the antiferromagnetic and paramagnetic phases of the dodecaborides under study are separated. Along with negative quadratic magnetoresistance -{Delta}{rho}/{rho} {proportional_to} H{sub 2}, the magnetically ordered phase of these compounds is found to have component {Delta}{rho}/{rho} {proportional_to} H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm{sub 1-x}Yb{sub x}B{sub 12} is analyzed in terms of the Yosida model for a local magnetic susceptibility.

Sluchanko, N. E., E-mail: nes@lt.gpi.ru; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Levchenko, A. V.; Filippov, V. B.; Shitsevalova, N. Yu. [National Academy of Sciences of Ukraine, Institute of Problems of Materials Science (Ukraine)

2013-05-15

62

White upconversion of rare-earth doped ZnO nanocrystals and its dependence on size of crystal particles and content of Yb3+ and Tm3+  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doped ZnO nanocrystals were synthesized by chemical combustion method. Bright white upconversion (UC) luminescence with the CIE coordinates close to (0.33, 0.33) was obtained in Er+Tm+Yb tridoped ZnO nanocrystals under the excitation of a cost-effective 980 nm single-wavelength laser diode. The overall and relative UC luminescence intensities of RE doped ZnO nanocrystals were found to be depended highly on the diameter of crystal particles and the concentration of Yb3+ and Tm3+, for which the involved mechanisms were demonstrated. The investigation based on UC spectra, simplified energy level diagram, and excitation power dependence indicated that the remarkable enhancement of the green emission of the RE tridoped sample was due to a dual sensitization of Er3+ by Yb3+ and Tm3+ ions. The RE tridoped ZnO nanocrystals with the CIE coordinates close to (0.33, 0.33) are potentially suitable for the widely realistic application as the multicolor fluorescent labels, due to a fact that they could be cheaply and easily obtained and excited cost effectively.

Liu, Yunxin; Xu, Changfu; Yang, Qibin

2009-04-01

63

White emission from Tm3+/Tb3+/Eu3+ co-doped fluoride zirconate under ultraviolet excitation  

NASA Astrophysics Data System (ADS)

We synthesize Tm3+/Tb3+/Eu3+ triply-doped ZrF4—BaF2—LaF3—AlF3—NaF (ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL'Eclairage (CIE) coordinates of (0.33, 0.33) is achieved at the Eu3+ concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+ ? Eu3+ are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+ ? Eu3+ energy transfer is described with the aid of an energy level diagram.

Sun, Jian; Zhang, Xiao-Song; Yuan, Lin-Lin; Feng, Zhi-Jun; Ling, Zhi; Li, Lan

2014-11-01

64

Additive colouring of CaF2:Yb crystals: determination of Yb2+ concentration in CaF2:Yb crystals and ceramics  

NASA Astrophysics Data System (ADS)

When growing CaF2 crystal doped with rare-earth ions, most of these ions are present in a trivalent state. However, due to contact with graphite crucible, a small proportion of a number of ions (Eu, Sm, Yb and Tm) are reduced to a bivalent state. A similar situation takes place during fabrication of CaF2 ceramics doped with rare-earth metals. This fact is of particular importance for laser CaF2:Yb crystals (ceramics), a promising material for short-pulse, high-power, high-energy diode-pumped solid state lasers since the presence of bivalent Yb ions can be a source of thermal losses. To date, there has been no technique to determine Yb2+ concentration in as-grown crystals. The proposed technique is based on a total reduction of Yb3+ ions via the heating of as-grown CaF2 crystals with known concentration of Yb in the reducing atmosphere of metal vapour and determining the cross section of absorption bands of Yb2+ ions. The knowledge of these parameters allows estimation of the Yb2+ content in CaF2:Yb crystals or ceramics by analysing their absorption spectra. Examples of using this technique are given. The technology of CdF2 crystals reduction (an "additive colouring") and features of colouring of crystals doped with rare-earth ions are considered.

Shcheulin, A. S.; Angervaks, A. E.; Semenova, T. S.; Koryakina, L. F.; Petrova, M. A.; Fedorov, P. P.; Reiterov, V. M.; Garibin, E. A.; Ryskin, A. I.

2013-06-01

65

Er,Yb:ZrO2/Eu:Y2O3 core/shell assemblies as potential temperature sensors in explosions  

NASA Astrophysics Data System (ADS)

We have recently demonstrated the use of nanophase Eu:Y2O3 and Eu:ZrO2 as temperature sensors in explosions. Our previous measurements have shown that each of these materials is suitable for a certain temperature range - Eu:Y2O3 covers the range from about 500 K to about 900 K, and Eu:ZrO2 the range from about 800 K to about 1300 K. In order to have one material that can cover a wider range of temperatures, we have prepared core/shell assemblies of these host materials with different dopants. Here we report on the synthesis and characterization of core/shell assemblies consisting of Er,Yb:ZrO2 cores and Eu:Y2O3 shells. The Er,Yb:ZrO2 core is synthesized via forced hydrolysis and the Eu:Y2O3 shell is synthesized via homogeneous precipitation. Subsequently, these core/shell assemblies are heated for 3 h in a furnace and for 10 s by a pyroprobe at various temperatures. Temperature-induced phase changes in the materials lead to changes in the optical spectra, which can then be correlated with temperature. The Er,Yb:ZrO2 core emits upconverted light in the red and green spectral range when excited with 970 nm, while the Eu:Y2O3 shell emits in the red spectral range when excited with 532 nm. These spectra can be measured separately allowing us to determine temperatures over a wide range.

Gunawidjaja, R.; Myint, T.; Eilers, H.

2014-05-01

66

Synthesis, crystal structures, magnetic and electric transport properties of Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}  

SciTech Connect

Two new rare-earth metal containing Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9} have been synthesized by reactions of the corresponding elements in molten In metal to serve as a self-flux. Their crystal structures have been determined by single crystal X-ray diffraction-both compounds are isostructural and crystallize in the orthorhombic space group Iba2 (No. 45), Z=4 with unit cell parameters a=12.224(2) A, b=12.874(2) A, c=17.315(3) A for Eu{sub 11}InSb{sub 9}, and a=11.7886(11) A, b=12.4151(12) A, c=16.6743(15) A for Yb{sub 11}InSb{sub 9}, respectively (Ca{sub 11}InSb{sub 9}-type, Pearson's code oI84). Both structures can be rationalized using the classic Zintl rules, and are best described in terms of discrete In-centered tetrahedra of Sb, [InSb{sub 4}]{sup 9-}, isolated Sb dimers, [Sb{sub 2}]{sup 4-}, and isolated Sb anions, Sb{sup 3-}. These anionic species are separated by Eu{sup 2+} and Yb{sup 2+} cations, which occupy the empty space between them and counterbalance the formal charges. Temperature-dependent magnetic susceptibility and resistivity measurements corroborate such analysis and indicate divalent Eu and Yb, as well as poorly metallic behavior for both Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed. - Graphical abstract: Reported are the synthesis, the structure and the magnetic and electronic properties of two new rare-earth Zintl phases, Eu{sub 11}InSb{sub 9} and Yb{sub 11}InSb{sub 9}. The close relationships between these structures and those of the monoclinic {alpha}-Ca{sub 21}Mn{sub 4}Sb{sub 18} and Ca{sub 21}Mn{sub 4}Bi{sub 18} are also discussed.

Xia Shengqing [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Hullmann, Jonathan [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)], E-mail: bobev@udel.edu; Ozbay, Arif [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Nowak, Edmund R. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Fritsch, Veronika [Physikalisches Institut, Universitaet Karlsruhe (Thailand), 76128 Karlsruhe (Germany)

2007-07-15

67

Crystal field analysis of Tm/sup 3 +/ and Yb/sup 3 +/ in YPO/sub 4/ and LuPO/sub 4/  

SciTech Connect

The optical and near infrared absorption of dilute Tm/sup 3 +/ and Yb/sup 3 +/ impurities in YPO/sub 4/ and LuPO/sub 4/ single crystals have been measured at liquid helium and nitrogen temperatures. For Tm/sup 3 +/, the spectral region from 5 000 to 38 000 cm/sup -1/ was examined and Zeeman spectra were obtained in the visible region. The observed transitions were assigned and fit to a semiempirical Hamiltonian with adjustable parameters via a least-squares procedure. Satisfactory fits and good agreement between the calculated and measured g values were obtained. For Yb/sup 3 +/, there are more parameters than experimental levels, so zeta, B/sup 2//sub 0/, B/sup 4//sub 0/, and B/sup 4//sub 4/ were adjusted, while B/sup 6//sub 0/ and B/sup 6//sub 4/ were fixed at the values found for Tm/sup 3 +/. Energy levels and Zeeman splittings calculated with these parameters are in good agreement with the measured quantities.

Becker, P.C.; Hayhurst, T.; Shalimoff, G.; Conway, J.G.; Edelstein, N.; Boatner, L.A.; Abraham, M.M.

1984-10-01

68

Stem Cell Labeling using Polyethylenimine Conjugated (?-NaYbF4:Tm3+)/CaF2 Upconversion Nanoparticles  

PubMed Central

We report on a polyethylenimine (PEI) covalently conjugated (?-NaYbF4:Tm3+)/CaF2 upconversion nanoparticle (PEI-UCNP) and its use for labeling rat mesenchymal stem cells (rMSCs). The PEI-UCNPs absorb and emit near-infrared light, allowing for improved in vivo imaging depth over conventional probes. We found that such covalent surface conjugation by PEI results in a much more stable PEI-UCNP suspension in PBS compared to conventional electrostatic layer by layer (LbL) self-assembling coating approach. We systematically examined the effects of nanoparticle dose and exposure time on rat mesenchymal stem cell (rMSC) cytotoxicity. The exocytosis of PEI-UCNPs from labeled rMSCs and the impact of PEI-UCNP uptake on rMSC differentiation was also investigated. Our data show that incubation of 100-µg/mL PEI-UCNPs with rMSCs for 4 h led to efficient labeling of the MSCs, and such a level of PEI-UCNP exposure imposed little cytotoxicity to rMSCs (95% viability). However, extended incubation of PEI-UCNPs at the 100 µg/mL dose for 24 hour resulted in some cytotoxicity to rMSCs (60% viability). PEI-UCNP labeled rMSCs also exhibited normal early proliferation, and the internalized PEI-UCNPs did not leak out to cause unintended labeling of adjacent cells during a 14-day transwell culture experiment. Finally, PEI-UCNP labeled rMSCs were able to undergo osteogenic and adipogenic differentiation upon in vitro induction, although the osteogenesis of labeled rMSCs appeared to be less potent than that of the unlabeled rMSCs. Taken together, PEI-UCNPs are promising agents for stem cell labeling and tracking. PMID:23606911

Zhao, Liang; Kutikov, Artem; Shen, Jie; Duan, Chunying; Song, Jie; Han, Gang

2013-01-01

69

Investigation on up-conversion luminescence properties of novel transparent Ho3+-Tm3+-Yb3+ co-doped oxyfluoride glass ceramics  

NASA Astrophysics Data System (ADS)

In the present letter, the transparent oxyfluoride glass ceramics containing Ho3+-Tm3+-Yb3+:NaYF4 were successfully prepared by melt-quenching at 1400°C and subsequent heating at 650-680°C for 1~2 hours . X-ray diffraction (XRD) with Cu K? radiation (?=0.154nm) investigation revealed that NaYF4 nano-crystals in the glass ceramics was fabricated. Their sizes were determined by Sherrer's equation. The emission spectra red green and blue up-conversion (UC) under 980nm laser diode (LD) pumping and absorption spectra were measured. Luminescence measurements confirmed the partition of RE ions in nano-crystals NaYF4. The blue red and green UC radiations correspond to the transitions 1G4-3H6, 1G4-3H4 of Tm3+, 5F4, 5S2-5I8, 5F5-5I8, of Ho3+ ions, respectively. This is similar to that in Tm3+-Yb3+ and/or Ho3+-Yb3+ co-doped glass ceramics. To obtain upconversion fluorescence mechanisms, upconversion fluorescence intensity versus LD pump power were analyzed in view of energy levels of rare earth. Up-conversion mechanisms were discussed and the ratio between red, green and blue UC emission bands was found to be varied as a function of temperature of heat treatment and pump power. This result could be mainly attributed to the cross-relaxation between Ho3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal and may have potentially applications in tunable visible laser or many other fields.

Liu, Xiao-bo; Han, Wan-lei; Xu, Fang; Song, Ying-lin

2011-06-01

70

Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln = Er, Tm) nanostructures decorated with Ag nanoparticles.  

PubMed

A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells. PMID:24398901

He, Enjie; Zheng, Hairong; Dong, Jun; Gao, Wei; Han, Qingyan; Li, Junna; Hui, Le; Lu, Ying; Tian, Huani

2014-01-31

71

Enhanced near-infrared response of CdS/CdTe solar cell using Tm3+ and Yb3+ co-doped upconverting glass phosphors  

NASA Astrophysics Data System (ADS)

Tm3+ and Yb3+ co-doped upconverting (UC) glass phosphors were used to converting near-infrared to visible light and input to a CdS/CdTe solar cell, therefore to enhance solar cell's response in the near-infrared of the sub-bandgap region. Current-voltage measurements were performed on the solar cell with a UC glass phosphor. A short-circuit photocurrent enhancement of 31 ?A was obtained using a Tm3+and Yb3+ co-doped glass UC phosphor, illuminated by a 980 nm diode laser at 100 mW. This photocurrent response corresponds to external quantum efficiency (EQE) of 0.04 % at 980 nm. For full collection of the UC light in 4? solid angle, the EQE value is expected to reach 1.6 %. The photo-current observed was proportional to the effective UC light intensity from glass UC phosphor. A non-linear relation between the output photo-current and the incident power of the infrared light was observed, similar to the relation between UC intensity and the incident power. UC efficiency of the glass phosphor was calculated using EQE values at both UC wavelengths and at 980 nm.

Pan, Z.; Whyte, D.; Morgan, S. H.; Li, J.; Alaswad, A.; Beach, J. D.; Ohno, T. R.; Wolden, C. A.

2014-10-01

72

Honeycombs of triangles and magnetic frustration in SrL{sub 2}O{sub 4} (L=Gd, Dy, Ho, Er, Tm, and Yb)  

SciTech Connect

The crystal structures, magnetic order, and susceptibility have been investigated for magnetically frustrated SrDy{sub 2}O{sub 4}, SrHo{sub 2}O{sub 4}, SrEr{sub 2}O{sub 4}, SrTm{sub 2}O{sub 4}, and SrYb{sub 2}O{sub 4}. Powder neutron-diffraction structural refinements reveal columns of LO{sub 6} octahedra that run along one crystallographic direction, with Sr-O polyhedra in the interstices. The lanthanide sublattice displays multiple triangular interconnections: one-dimensional strings form the backbones of four types of chains of lanthanide triangles sharing edges arranged in a honeycomb pattern. This crystal structure produces strong geometric frustration for the magnetic system that is evidenced in both magnetic susceptibility and neutron-scattering data at low temperatures. The susceptibility measurements for the series, including SrGd{sub 2}O{sub 4} for which data are also reported, lack the sharp features characteristic of three-dimensional long-range magnetic ordering. Metamagnetic behavior is observed in the magnetization vs applied field data at 1.8 K for the cases of L=Dy, Er, and Ho. Magnetic neutron-scattering studies for the Dy and Er materials show only very broad magnetic scattering at low temperatures, while the Ho system exhibits long-range two-dimensional order. Any magnetic scattering in the Tm and Yb compounds, if present, was too weak to be detected in these measurements.

Karunadasa, H.; Regan, K.A.; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Huang, Q.; Lynn, J.W. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Ueland, B.G.; Schiffer, P. [Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2005-04-01

73

Enhanced performance of Ca2Si5N8:Eu2+, Tm3+ reddish-orange afterglow phosphor by co-doping with Dy3+  

NASA Astrophysics Data System (ADS)

Two types of reddish-orange afterglow emitting nitride phosphors Ca2Si5N8:Eu2+, Tm3+ (CSN:E, T) and Ca2Si5N8:Eu2+, Tm3+, Dy3+ (CSN:E, T, D) were synthesized via a solid-state reaction route and were comparatively investigated. Comparing with the di-doped CSN:E, T phosphor, the tri-doped CSN:E, T, D samples show higher afterglow intensity and longer duration time which can be attributed to the balanced defect micro-environment caused by the presence of Dy3+.

Zhang, Haoran; Dong, Hanwu; Lei, Bingfu; Wang, Peng; Li, Jinfang; Liu, Yingliang; Wang, Jing; Xiao, Yong; Zheng, Mingtao; Meng, Jianxin

2014-09-01

74

An efficient and user-friendly method for the synthesis of hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with controllable shape and upconversion fluorescence  

NASA Astrophysics Data System (ADS)

Hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals are the best IR-to-visible upconverting materials to date, but user-friendly methods for making pure hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence are still lacking. Most of the methods reported so far require excess fluoride reactants in a high-temperature reaction which are very unfriendly to users and raise safety concerns. In this work, an efficient and user-friendly method was developed for the synthesis of uniform hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with upconversion fluorescence, by forming small solid-state crystal nuclei and further growth and ripening of the nuclei. NaYF4:Yb, Er/Tm nanoplates, nanospheres and nanoellipses were also selectively produced by varying the concentration of the surfactant. All the nanocrystals showed strong upconversion fluorescence, and fluorescence from the nanoplates was observed even when the laser power density was reduced to about 50 mW cm-2. These nanocrystals have great potential for use in biology and medicine as fluorescent labels or imaging probes.

Li, Zhengquan; Zhang, Yong

2008-08-01

75

Synthesis, characterisation and properties of rare earth oxyselenides A4O4Se3 (A = Eu, Gd, Tb, Dy, Ho, Er, Yb and Y).  

PubMed

Rare earth oxyselenides A4O4Se3 (A = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Y) were synthesised using solid state reactions and three new structure types (?, ?, and ?) were observed. A4O4Se3 materials adopt either the ? (A = Nd, Sm), ? (A = Eu), ? (A = Gd, Tb) or ? (A = Dy, Ho, Er, Yb, Y) structure depending on the rare earth radius. Each structure type contains alternating [A2O2](2+) and Se(2-)/Se2(2-) layers. Different ordered and disordered arrangements of Se(2-) and [Se-Se](2-) give the Se layer flexibility and lead to the four different structure types observed. The volume coefficients of expansion for A4O4Se3 ranged from +1.746(9) × 10(-5) to +2.237(3) × 10(-5) K(-1) from 12 to 300 K; no structural phase transitions were observed in this temperature range. Diffuse reflection spectra show A4O4Se3 are semiconductors with band gap Eg 1.02-1.46 eV. Gd4O4Se3, Dy4O4Se3, and Tb4O4Se3 samples show antiferromagnetic ordering with Néel temperature, TN, of 7-9 K. DFT calculations confirm the two different valence states of Se(2-) and Se2(2-) in Eu4O4Se3. PMID:25581725

Tuxworth, Andrew J; Wang, Chun-Hai; Evans, John S O

2015-02-01

76

Color-tunable upconversion luminescence of Yb3+, Er3+, and Tm3+ tri-doped ferroelectric BaTiO3 materials  

NASA Astrophysics Data System (ADS)

Tunable upconversion (UC) multicolor luminescence is observed from Yb3+, Er3+, and Tm3+ tri-doped ferroelectric BaTiO3 (BTO) materials. By control of dopant concentrations, the lanthanide-doped BTO powders are capable of generating various UC spectra and color tunability. A white-light emission is achieved through an optimal design. Strong UC luminescence is also observed in the lanthanide-doped BTO thin-films grown on Pt/TiO2/SiO2/Si substrate, which can retain well-defined hysteresis loops with a remnant polarization (2Pr) of 17.8 ?C/cm2. These findings open the possibility of lanthanide-doped BTO as multifunctional materials, in which both luminescent and ferroelectric properties co-exist.

Zhang, Yang; Hao, Jianhua

2013-05-01

77

Development and performance characteristics of flash lamp pumped Yb:YAG, Cr:Tm:Ho:YAG, Er:Tm:Ho:YLF laser sources and investigation of their potential biological applications  

NASA Astrophysics Data System (ADS)

Laser ablation for the formation of apodized patterns on intraocular lenses, as an alternative of the conventional injection molding, has been proved to be a very promising new technique. For the precise lenses ablation, the use of suitable laser wavelength and pulse duration, resulting in a small optical penetration depth in the lens and in confinement of the energy deposition in a small volume, as well as the reduced thermal damage to the surrounding tissue, is essential. Mid-infrared laser wavelengths, at which the organic biological simulators absorption coefficient is large, meet well the above conditions. Towards the complete understanding of the intraocular lens ablation procedure and therefore the choice of the optimum laser beam characteristics for the most accurate, efficient and safe surgical application, the comparative study of various mid-infrared laser sources is of great interest. In this work we investigate the potential of the development of three different mid-infrared laser sources, namely the Yb:YAG, the Cr:Tm:Ho:YAG and the Er:Tm:Ho:YLF laser, operating at 1029 nm, 2060 nm and 2080 nm respectively and their ability in forming patterns on biomaterials. Pumping was achieved with conventional Xe flash lamps in a double elliptical pump chamber. A properly designed Pulse-Forming- Network capable of delivering energy up to 800 J, in variable lamp illumination durations is used. Several hundreds of mJoules were achieved from the Yb:YAG laser oscillator and several Joules from the Ho:YAG and Ho:YLF laser oscillators. Free running and Q-switched laser operation studies and preliminary experiments on laser and biomaterials (biopolymers and animal tissues) interactions will be reported.

Karadimitriou, N.; Klinkenberg, B.; Papadopoulos, D. N.; Serafetinides, A. A.

2007-07-01

78

Up-conversion luminescence in Ho3+ and Tm3+ co-doped Y2O3:Yb3+ fine powders obtained through aerosol decomposition  

NASA Astrophysics Data System (ADS)

Fine yttrium oxide powders doped with Yb3+ and co-doped either with Tm3+ or Ho3+ were synthesized via spray pyrolysis at 900 °C using 0.1 M nitrate precursor. Synthesized powders were additionally thermally treated at 1100 °C for 24 h. The characterization was done through X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and photoluminescent measurements (PL). Generation of cubic bixbyte-structure with space group Ia-3 is confirmed in all samples. Spherical particles with the mean size of ˜400 nm, generated through volume precipitation of much smaller nanograins, expose certain degree of porosity which alters particle morphology during additional thermal treatment. Powders optical characterizations include measurement of up-conversion emission spectra after excitation at 978 nm, as well as determination of emission lifetimes and up-converted emission intensity dependence on excitation power. Dominant green (5F4, 5S2 ? 5I8) and blue (1G4 ? 3H6) emission is found for Ho3+ and Tm3+ samples, respectively. The amplified emission intensities and enhanced lifetime in thermally treated samples are correlated with the powders morphological and structural changes.

Lojpur, V.; Nikoli?, M.; Man?i?, L.; Miloševi?, O.; Drami?anin, M. D.

2012-11-01

79

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance  

NASA Astrophysics Data System (ADS)

Monoclinic potassium rare-earth double tungstates [KRE(WO4)2, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln3+) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb3+- and Tm3+-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

Raghothamachar, B.; Carvajal, J. J.; Pujol, M. C.; Mateos, X.; Solé, R.; Aguiló, M.; Díaz, F.; Dudley, M.

2010-06-01

80

Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+ with enhanced upconversion properties  

NASA Astrophysics Data System (ADS)

Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). Electronic supplementary information (ESI) available: Additional tables and figures. See DOI: 10.1039/c3nr05266d

Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

2014-01-01

81

Ultraviolet-driven white light generation from oxyfluoride glass co-doped with Tm{sup 3+}-Tb{sup 3+}-Eu{sup 3+}  

SciTech Connect

Tm{sup 3+}-Tb{sup 3+}-Eu{sup 3+} co-doped oxyfluoride glasses, doped with about 3.0 mol. % TmF{sub 3}, 0.25 mol. % TbF{sub 3}, and 0.25 mol. % EuF{sub 3}, have been prepared by melt quenching technique. Under excitation at commercial 365 nm, the rare-earth co-dopants are all directly excited and emit in the blue, green, and red, respectively, without appreciable energy transfer amongst the co-dopants. Tint of the white luminescence can be adjusted by changing the ratio of the co-dopants. Properties of the glass host promote excellent dissolution of the co-dopants and low non-radiative decay rate. The white emission at 365 nm excitation is suitable for light emitting diodes applications.

Kuznetsov, A. S.; Nikitin, A.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V. [INPAC-Institute for Nanoscale Physics and Chemistry, KULeuven, Celestijnenlaan 200D, Heverlee, 3001 Leuven (Belgium)] [INPAC-Institute for Nanoscale Physics and Chemistry, KULeuven, Celestijnenlaan 200D, Heverlee, 3001 Leuven (Belgium)

2013-04-22

82

Syntheses, and crystal and electronic structures of the new Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb): Structural relationship with Yb{sub 2}CdSb{sub 2} and the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}  

SciTech Connect

Presented are the details of the syntheses, crystal and electronic structures of a new family of Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb), as well as the solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2}. The structures of Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) were determined to be of a new type with the non-centrosymmetric space group Pmc2{sub 1} (no. 26), Pearson symbol oP12, with lattice parameters a=4.684(1)-4.788(1) A; b=9.099(3)-9.117(2) A; c=7.837(1)-8.057(2) A for the Na{sub 2}ACdSb{sub 2} series, and a=4.6637(9)-5.0368(8) A; b=9.100(2)-9.8183(15) A; and c=7.7954(15)-8.4924(13) A for K{sub 2}ACdSb{sub 2}, respectively. The solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (x{approx}1) are isostructural and isoelectronic to the recently reported Yb{sub 2}CdSb{sub 2} (space group Cmc2{sub 1} (no. 36), Pearson symbol cP20). All discussed structures are based upon CdSb{sub 2}{sup 4-} polyanionic layers, similar to the ones observed in Yb{sub 2}CdSb{sub 2}, with various alkali- and/or alkaline-earth cations coordinated to them. Magnetic susceptibility and Seebeck coefficient measurements on selected Eu{sub 2-x}Yb{sub x}CdSb{sub 2} samples, taken at low temperatures up to 300 K, are also reported. -- Graphical abstract: The quaternary Zintl phases Na{sub 2}ACdSb{sub 2} and K{sub 2}ACdSb{sub 2} (A=Ca, Sr, Ba, Eu, Yb) with novel layered structures have been synthesized for the first time and structurally characterized by single-crystal X-ray diffraction. Reported as well are the results from crystallographic and property studies of the closely related solid solutions Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1Eu, Yb) are new quaternary Zintl phases. {yields} Sr{sub 2-x}A{sub x}CdSb{sub 2}, Ba{sub 2-x}A{sub x}CdSb{sub 2} (x{approx}1), and Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1Eu{sub 2-x}Yb{sub x}CdSb{sub 2} (1

Saparov, Bayrammurad; Saito, Maia [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.ed [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

2011-02-15

83

White up-conversion luminescence power and efficiency in Yb(3+)-, Er(3+)- and Tm(3+)-doped BaIn6Y2O13.  

PubMed

A series of BaIn6Y2O13:Yb(3+), Er(3+), Tm(3+) phosphors with different dopant concentrations have been successfully synthesized by a sol-gel method. In order to obtain efficient white light emitting samples, tri-doped and biphasic samples were prepared. Afterwards, we carried out a systematic study on the up-conversion luminescence (UCL) properties of the samples as functions of doping concentrations and excitation densities. The up-conversion (UC) white light emission powers and efficiencies of samples with different dopant concentrations at different excitation power densities were obtained. The highest white UCL efficiency of up to 0.38% was achieved at excitation densities down to 17.5 W cm(-2) in the biphasic samples. More importantly, we demonstrated that the UC materials with higher efficiency do not necessarily have stronger emission power, and the emission power is the most important parameter. A maximum emission power of up to 1.23 mW was obtained. Furthermore, the impact of temperature on the white UCL was studied, and transparent polymer composites that can emit white light were synthesized by doping BaIn6Y2O13 samples into polymethylmethacrylate (PMMA). PMID:25409772

Zhang, Jiao; Yang, Yanmin; Mi, Chao; Liu, Yanzhou; Yu, Fang; Li, Xiaohong; Mai, Yaohua

2015-01-21

84

Infrared-active optical phonons and magnetic excitations in the hexagonal manganites RMnO3 (R =Ho, Er, Tm, Yb, and Lu)  

NASA Astrophysics Data System (ADS)

Optical properties of hexagonal multiferroic oxides RMnO3, where R=Ho, Er, Tm, Yb, and Lu, have been studied in the far-infrared spectral range between 100 and 2000 cm-1 and temperatures between 1.5 and 300 K by means of several experimental techniques: Mueller matrix spectroscopic ellipsometry, rotating analyzer ellipsometry, and optical transmission spectroscopy. Spectra of the optical phonons are described in terms of the temperature dependencies of their frequency, damping, and oscillator strength. For all studies, oxide materials' clear signatures of the spin-phonon interaction have been found below the temperature of the antiferromagnetic phase transition TN due to magnetic ordering of Mn3+ spins. A decrease of the ionic radius for R3+ ions between Ho3+ and Lu3+ in the corresponding RMnO3 compounds resulted in systematic variation of the frequency for several optical phonons. A magnetic excitation at ˜190 cm-1 was observed at low temperatures below TN and interpreted as resulting from two-magnon absorption.

Basistyy, R.; Stanislavchuk, T. N.; Sirenko, A. A.; Litvinchuk, A. P.; Kotelyanskii, M.; Carr, G. L.; Lee, N.; Wang, X.; Cheong, S.-W.

2014-07-01

85

Structural and thermoelectric properties of BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu)  

SciTech Connect

The structure and thermoelectric properties of a series of barium lanthanide cobaltites, BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu), which were prepared using the spark plasma synthesis technique, have been investigated. The space group of these compounds was re-determined and confirmed to be P31c instead of the reported P6{sub 3}mc. The lattice parameters a and c range from 6.26279(2) Angst to 6.31181(6) Angst , and from 10.22468(6) Angst to 10.24446(15) Angst for R = Lu to Dy, respectively. The crystal structure of BaRCo{sub 4}O{sub 7} is built up from Kagome sheets of CoO{sub 4} tetrahedra, linked by triangular layers of CoO{sub 4} tetrahedra. The values of figure of merit (ZT) of the BaRCo{sub 4}O{sub 7} samples were determined to be around 0.02 at 800 K. X-ray diffraction patterns of these samples have been determined and submitted to the Powder Diffraction File.

Wong-Ng, W.; Yan, Y.; Liu, G. [Ceramics Division, NIST, Gaithersburg, Maryland 20899 (United States); Xie, W.; Tritt, T. [Department of Physics, Clemson University, Greensville, South Carolina 29634 (United States); Kaduk, J. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Thomas, E. [Air Force Research Laboratory, Wright Pattersen, Ohio 45433 (United States)

2011-12-01

86

Preparation and optical characteristics of novel oxynitride phases in the R 3(Ta/Nb)-O-N system (R = La, Eu, Gd, Ho, Y, Yb)  

NASA Astrophysics Data System (ADS)

The synthesis of reactive nitridation precursors prepared by the citrate route has been evidenced with the R 3TaO 7 and R 3NbO 7 stoichiometries (R = La, Eu, Gd, Ho, Y, Yb). Novel oxynitride phases have been isolated in the fluorite-type series R 3Ta(O,N,?) 8 and R 3Nb(O,N,?) 8 where ? represents anionic vacancies. The niobium/tantalum substitution leads to a modification of the absorption properties toward higher wavelengths. The comparison between GdTa, Gd 2Ta and Gd 3Ta-based oxynitride phases highlights a blue shift of the position of the absorption edge with increasing Gd/Ta ratio. Unlike with RTa and R 2Ta stoichiometries, R 3Ta-oxynitride phases generally show a very narrow formation range in temperatures as well as low absorption in the visible.

Ray, Erwan; Tessier, Franck; Cheviré, François

2011-05-01

87

Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2  

SciTech Connect

The thermoelectric transport properties of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were characterized between 2 and 650 K. As synthesized, the polycrystalline samples are found to have lower p-type carrier concentrations than single-crystalline samples of the same empirical formula. These low carrier concentration samples possess the highest mobilities yet reported for materials with the CaAl{sub 2}Si{sub 2} structure type, with a mobility of {approx}740 cm{sup 2}/V/s observed in EuMg{sub 2}Bi{sub 2} at 50 K. Despite decreases in the Seebeck coefficient ({alpha}) and electrical resistivity ({rho}) with increasing temperature, the power factor ({alpha}{sup 2}{rho}) increases for all temperatures examined. This behavior suggests a strong asymmetry in the conduction of electrons and holes. The highest figure of merit (zT) is observed in YbMg{sub 2}Bi{sub 2}, with zT approaching 0.4 at 600 K for two samples with carrier densities of approximately 2 x 10{sup 18} cm{sup -3} and 8 x 10{sup 18} cm{sup -3} at room temperature. Refinements of neutron powder diffraction data yield similar behavior for the structures of CaMg{sub 2}Bi{sub 2} and YbMg{sub 2}Bi{sub 2}, with smooth lattice expansion and relative expansion in c being {approx}35% larger than relative expansion in a at 973 K. First-principles calculations reveal an increasing band gap as Bi is replaced by Sb and then As, and subsequent Boltzmann transport calculations predict an increase in {alpha} for a given n associated with an increased effective mass as the gap opens. The magnitude and temperature dependence of {alpha} suggests higher zT is likely to be achieved at larger carrier concentrations, roughly an order of magnitude higher than those in the current polycrystalline samples, which is also expected from the detailed calculations.

May, Andrew F [ORNL; McGuire, Michael A [ORNL; Ma, Jie [ORNL; Delaire, Olivier A [ORNL; Huq, Ashfia [ORNL; Singh, David J [ORNL; Cai, Wei [ORNL; Wang, Hsin [ORNL

2012-01-01

88

Red persistent and photo-stimulated luminescence properties of SrCaSi5N8: Eu2+, Tm3+ solid solution  

NASA Astrophysics Data System (ADS)

The red persistent and photo-stimulated luminescent (PSL) nitride phosphor, SrCaSi5N8: Eu2+, Tm3+ solid solution, had been synthesized through conventional high temperature solid-state reaction. The SrCaSi5N8: Eu2+, Tm3+ phosphor shows strong photoluminescence (PL) and weak PSL (?em = 647 nm), both originating from the 4f65d-4f7 transition of Eu2+. Thermoluminescence (TL) glow curves measured at various stimulating conditions (UV excitation, in dark, laser stimulation after UV irradiation) show the same peak positions at 345 K and 360 K but great differences in the intensities. The afterglow decay curve presents excellent long-lasting red phosphorescence with a decay time of 30 min (?0.32 mcd/m2) after turning off the activating light. Moreover, the laser stimulated luminescence spectra, which feature sharp rising and falling edges (monitored at 647 nm) as the infrared laser diode (980 nm) excitation was turned on and off periodically, exhibit interesting rapidly responsive, erasable and rewritable abilities.

Wang, Jin; Zhang, Haoran; Lei, Bingfu; Dong, Hanwu; Zhang, Haiming; Liu, Yingliang; Lai, Nuolin; Fang, Yun; Chen, Zhijie

2014-09-01

89

Up-conversion emission tuning in triply-doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate glass and glass-ceramics  

NASA Astrophysics Data System (ADS)

New Yb3+, Er3+ and Tm3+ triply doped fluoro-phosphate glasses belonging to the system NaPO3-YF3-BaF2-CaF2 have been prepared by the classical melt-casting technique. Glasses containing up to 10 wt.% of rare-earth ions fluorides have been obtained and characterized by using differential scanning calorimetry (DSC), UV-visible-near-infrared spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and optically homogeneous glass-ceramics have been reproducibly obtained by appropriate heat treatment in view to manage the red, green and blue emissions upon 975 nm laser excitation. According to the applied thermal heat-treatment, a large enhancement of intensity of the up-conversion emission - from 10 to 160 times higher - has been achieved in the glassceramics compared to that of glasses, suggesting incorporation of the rare-earth ions into the crystalline phase. Furthermore, a large range of color rendering has been observed in these materials by controlling the laser excitation power and material crystallization rate. Time-resolved luminescence experiments as well as X-ray diffractometry and scanning electron microscopy techniques have been employed in order to understand and correlate the multicolor emission changes to the crystallization behavior of this material. A progressive phase transformation of the fluorite-type CaF2-based nanocrystals initially generated was observed along with increasing heat-treatment time, thus modifying the rare earth ions spectroscopic features.

Ledemi, Yannick; Trudel, Andrée.-Anne; Rivera, Victor A. G.; Messaddeq, Younes

2014-03-01

90

Structure, enhancement and white luminescence of multifunctional Lu6O5F8:20%Yb3+,1%Er3+(Tm3+) nanoparticles via further doping with Li+ under different excitation sources  

NASA Astrophysics Data System (ADS)

A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices.A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33577h

Guo, Linna; Wang, Yuhua; Wang, Yanzhao; Zhang, Jia; Dong, Pengyu; Zeng, Wei

2013-02-01

91

Chemical bond parameters and photoluminescence of a natural-white-light Ca9La(VO4)7:Tm3+,Eu3+ with one O2-?V5+ charge transfer and dual f-f transition emission centers  

NASA Astrophysics Data System (ADS)

The relationship between the photoluminescence properties and the crystal structure of undoped, Eu3+ or/ and Tm3+ singly or codoped Ca9La(VO4)7 (CLaVO) samples was discussed. Under the excitation of UV light, CLaVO:Tm3+, CLaVO, and CLaVO:Eu3+ exhibit the characteristic emissions of Tm3+ (1G4?3H6, blue), O2-?V5+ charge transfer (CT), and Eu3+ (5D0?7F2, red), respectively. By adjusting the doping concentration of Tm3+ and Eu3+ ions in CLaVO, a natural white emission in a single composition with the color temperature at 6181 K was obtained. Based on the dielectric theory of complex crystal, the chemical bond parameters of La-O and V-O bonds were quantitatively calculated. The standard deviation of environmental factor of every bond (EFSD), which can be expressed as ? (hei) =?{ (1 / N) ? i = 1 N (hei - ?) 2 } (hei =(fci?bi) 1 / 2QBi and ? = (1 / N) ? i = 1 N hei), was proposed to quantitatively express the distortion degree of VO43- from that of an ideal tetrahedron. The maximum change of EFSD comes from the [VO4]- tetrahedra in CLaVO sample by comparison with that of EFSD of isostructural Ca9Gd(VO4)7. This is possible the key reason that the undoped CLaVO sample has self-activated emission while the self-activated emission of its isostructural Ca9Gd(VO4)7 sample cannot be found. The quantitative calculation also demonstrated that the broad excitation bands at 319 nm in CLaVO:Tm and at 335 nm in CLaVO:Eu were due to the O-V2 and O-V3 (overlap with O-V2) CT, not the CT energy of O2--Eu13+ (O2--Tm13+), O2--Eu23+ (O2--Tm23+), and O2--Eu33+ (O2--Tm33+). The environmental factors surrounding the atoms V1, V2 and V3 were calculated to be 1.577, 1.6379 and 1.7554, respectively. It can be demonstrated that the excitation spectra at 319 nm for CLaVO:Tm and 335 nm for CLaVO:Eu came from the O-V2 and O-V3 CT, respectively.

Li, Ling; Liu, Xiao Guang; Noh, Hyeon Mi; Jeong, Jung Hyun

2015-01-01

92

Turn-on detection of a cancer marker based on near-infrared luminescence energy transfer from NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles to gold nanorods.  

PubMed

A homogeneous immunoassay for the sensitive and selective determination of trace amounts of ?-fetoprotein (AFP, a cancer marker) by detection in the near-infrared (NIR) region based on luminescence energy transfer (LET) from NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles to gold nanorods (GNRs) is presented. The carboxyl-functionalized NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles (UCNPs) were excited by a 980 nm continuous wavelength laser, and its emission peak appeared at a near-infrared wavelength (?804 nm). The carboxyl-functionalized upconverting nanoparticles were conjugated with the anti-AFP (Ab1) and acted as donor. GNRs with a high absorption band around 790 nm, which was overlapped the UCNPs emission, were synthesized and acted as the acceptor. The donor (negatively charged) interacted with the acceptor (positively charged) via electrostatic interactions to bring them into close proximity. LET could occur, producing a quenching phenomenon. When the AFP antigens were added into the system, the binding affinity between AFP and Ab1 was stronger than the electrostatic interactions, which released the energy acceptors from the energy donors, interrupting luminescence energy transfer, and therefore, the luminescence was recovered. On the basis of the restored luminescence, a turn-on optical immunosening system was developed. Under the optimal conditions, the linear range of detection was from 0.18 to 11.44 ng/mL for AFP (R = 0.99), with a detection limit as low as 0.16 ng/mL. The proposed method has also been used to monitor AFP in human serum samples. Therefore, further study based on the NaYF4:Yb,Tm/NaGdF4 core-shell nanoparticles-GNRs construction may open the way for a new class of NIR-LET biosensors with wide applications. PMID:25296290

Chen, Hongqi; Guan, Yingying; Wang, Shaozhen; Ji, Yuan; Gong, Mengqi; Wang, Lun

2014-11-01

93

Hydrothermal synthesis and luminescence properties of hierarchical SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) micro/nanocomposite architectures  

SciTech Connect

Graphical abstract: Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere assembled by numerous nanoplates have been successfully synthesized via a facile hydrothermal process in the presence of chelating reagent. Highlights: Black-Right-Pointing-Pointer Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere were obtained by a simple hydrothermal method. Black-Right-Pointing-Pointer The reaction time, chelating reagent and F source play important roles for the formation of hierarchical microspheres. Black-Right-Pointing-Pointer The luminescence properties of lanthanide ion-doped SrF{sub 2} hierarchical microstructures were discussed. -- Abstract: Highly uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microspheres assembled by 2D nanoplates have been successfully synthesized by a facile and friendly hydrothermal route. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The experimental results indicate that reaction time and chelating reagent play a key role in forming the hierarchical microspheres. The formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The near-infrared luminescence of lanthanide ions (Er, Nd, and Yb) doped SrF{sub 2} microspheres were discussed in detail. In addition, the as-obtained SrF{sub 2}:Eu{sup 3+} sample exhibits orange-red emission centered at 590 nm under excitation at 393 nm, while the SrF{sub 2}:Tb{sup 3+} exhibits a strong green emission at 540 nm. The as-synthesized SrF{sub 2}:Ln{sup 3+} luminescent microspheres might find some potential applications in areas of photoluminescence, telecommunication and laser emission.

Peng, Jing; Hou, Suying; Liu, Xianchun [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Feng, Jing [State Key Laboratory of Rare Earth Resource Utilizations, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)] [State Key Laboratory of Rare Earth Resource Utilizations, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Yu, Xiaodan [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Xing, Yan, E-mail: xingy202@nenu.edu.cn [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Su, Zhongmin [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China)

2012-02-15

94

High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates---Ln(O3P C2H4 SO3) (Ln=Ho, Er, Tm, Yb, Lu, Y)  

Microsoft Academic Search

Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, H2O3P C2H4 SO3H (H3L), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(O3P C2H4 SO3) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y

Andreas Sonnauer; Norbert Stock

2008-01-01

95

High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates— Ln(O 3P–C 2H 4–SO 3) ( Ln=Ho, Er, Tm, Yb, Lu, Y)  

Microsoft Academic Search

Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, H2O3P–C2H4–SO3H (H3L), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(O3P–C2H4–SO3) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y (6). The syntheses were

Andreas Sonnauer; Norbert Stock

2008-01-01

96

Photoluminescence properties of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) activated NaInW{sub 2}O{sub 8} wolframite host lattice  

SciTech Connect

The photoluminescence (PL) studies on NaIn{sub 1-x}RE{sub x}W{sub 2}O{sub 8}, with RE=Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+} phases have shown that the relative contribution of the host lattice and of the intra-f-f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy{sup 3+} and Tm{sup 3+} activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu{sup 3+}, with intense red emission, the host absorption is less pronounced and the intra-f-f transitions of the Eu{sup 3+} ions play a major role, whereas for Tb{sup 3+} intra-f-f transitions are only observed, giving rise to green emission. - Graphical abstract: NaInW{sub 2}O{sub 8} double tungstate doped with Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}and Tm{sup 3+} shows characteristic emission of intense red for Eu{sup 3+}, yellow for Dy{sup 3+}, green for Tb{sup 3+} and blue for Tm{sup 3+}. Highlights: Black-Right-Pointing-Pointer Characteristic emissions of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) are observed NaInW{sub 2}O{sub 8} wolframite. Black-Right-Pointing-Pointer Energy transfer from host to the activators (Eu{sup 3+} Dy{sup 3+} Tm{sup 3+} is observed. Black-Right-Pointing-Pointer PL properties of rare earth ions depend on minor structural variations in the host lattice.

Asiri Naidu, S.; Boudin, S. [Laboratoire de Cristallographie et Sciences des Materiaux, ENSICAEN, Universite de Caen, CNRS, 6 Bd Marechal Juin, F-14050 Caen (France); Varadaraju, U.V. [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India); Raveau, B., E-mail: bernard.raveau@ensicaen.fr [Laboratoire de Cristallographie et Sciences des Materiaux, ENSICAEN, Universite de Caen, CNRS, 6 Bd Marechal Juin, F-14050 Caen (France)

2012-01-15

97

Effects of Bi2O3 on Up-conversion Luminescence Properties of Tm3+/Yb3+-codoped Ga2O3-GeO2-Bi2O3-PbO Glass  

NASA Astrophysics Data System (ADS)

This paper reports on frequency up-conversion (UC) emission properties in Tm3+/Yb3+-codoped Ga2O3-GeO2-Bi2O3-PbO glass upon excitation of 980 nm laser diode. A close correlation is observed between the Bi2O3 substituted content for PbO and UC luminescence properties of Tm3+. It was found that the decreasing PbO and increasing Bi2O3 content improve the blue and red UC emission intensity. The maximum of UC emission intensity is obtained when substituted PbO content is at 35%. In addition, the dependence of the UC emission intensity upon the excitation power has been examined and the involved mechanisms have also been discussed.

Shi, D. M.; Zhao, Y. G.; Wang, X. F.; Liu, J.

98

Highly uniform and monodisperse GdOF:Ln3+ (Ln = Eu, Tb, Tm, Dy, Ho, Sm) microspheres: hydrothermal synthesis and tunable-luminescence properties.  

PubMed

GdOF:Ln(3+) (Ln = Eu, Tb, Tm, Dy, Ho and Sm) microspheres (1.5 ?m) with high uniformity and monodispersity have been synthesized via a facile hydrothermal method followed by heat treatment (600 °C). X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the resulting samples. A series of controlled experiments indicate that sodium citrate (Cit(3-)) as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the dosage of Cit(3-) and pH values in the initial solution. The possible formation mechanism for these microspheres has been presented. Under UV light and low-voltage electron beam excitation, GdOF:Ln(3+) microspheres show the characteristic f-f transitions of Ln(3+) (Eu, Tb/Ho, Tm, Dy and Sm) ions and give bright red, green, blue, yellow and yellowish-orange emission, respectively. In addition, multicolored luminescence containing white emission have been successfully confected for co-doped GdOF:Ln(3+) phosphors by changing the doped Ln(3+) ions and adjusting their doping concentrations due to the simultaneous luminescence of Ln(3+) in the GdOF host, making these materials have potential applications in field-emission display devices. PMID:23942823

Zhang, Yang; Kang, Xiaojiao; Geng, Dongling; Shang, Mengmeng; Wu, Yuan; Li, Xuejiao; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun

2013-10-21

99

Observation of superconductivity at 30?46K in AxFe2Se2 (A = Li, Na, Ba, Sr, Ca, Yb, and Eu)  

PubMed Central

New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30?K in KFe2Se2, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced Tc = 30?46?K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a?3.755–3.831 Å while c?15.99–20.54 Å. Resistivities show the corresponding sharp transitions at 45?K and 39?K for NaFe2Se2 and Ba0.8Fe2Se2, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well. PMID:22645642

Ying, T. P.; Chen, X. L.; Wang, G.; Jin, S. F.; Zhou, T. T.; Lai, X. F.; Zhang, H.; Wang, W. Y.

2012-01-01

100

Electronic structure and electron-phonon coupling in stoichiometric and defective hydrides MPdH3 (M=Ca, Sr, Eu, Yb)  

NASA Astrophysics Data System (ADS)

On the basis of electron transfer from the divalent element to the PdH3 entities, the perovskite structure MPdH3 (M=Sr, Eu, Yb) are expected to have similar electronic states at the Fermi energy as superconducting Pd-Hx and Pd-noble-metal-Hx and thus could be potential candidates for superconductivity. With this motivation, we have investigated the electronic structure and some aspects of the electron-phonon coupling in these hydrides using the ab initio augmented plane-wave method, and the results of the energy bands, the total and partial wave analysis of the density of states, and the electronic contribution, ?H to the electron-phonon coupling are presented. Similar studies for the hydrogen defective material CaPdH2 are also included. We have found that all these compounds are metallic with essentially filled Pd-d bands and a small density of states at Fermi level as in PdH. Nevertheless, the calculated values of ?H, which govern the contribution of the hydrogen atoms to the electron-optical phonon coupling parameter ?, although sizeable, are lower than in PdH. This would indicate that these compounds, if superconducting, would have lower values of the superconducting transition temperatures Tc than in PdH.

Orgaz, Emilio; Mazel, Vincent; Gupta, Michèle

1996-12-01

101

Observation of superconductivity at 30~46 K in A(x)Fe?Se?(A = Li, Na, Ba, Sr, Ca, Yb, and Eu).  

PubMed

New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30?K in KFe?Se?, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced T(c) = 30?46?K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a?3.755-3.831 Å while c?15.99-20.54 Å. Resistivities show the corresponding sharp transitions at 45?K and 39?K for NaFe?Se? and Ba?.?Fe?Se?, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well. PMID:22645642

Ying, T P; Chen, X L; Wang, G; Jin, S F; Zhou, T T; Lai, X F; Zhang, H; Wang, W Y

2012-01-01

102

Separation of the contributions to the magnetization of Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in steady and pulsed magnetic fields  

SciTech Connect

The magnetization of substitutional Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions is studied in the composition range 0 < x {<=} 0.81. The measurements are performed at low temperatures (1.9-300 K) in steady (up to 11 T) and pulsed (up to 50 T, pulse duration of 20-100 ms) magnetic fields. An analysis of the experimental data allowed the contributions to the magnetization of the paramagnetic phase of the Tm{sub 1-x}Yb{sub x}B{sub 12} compounds to be separated. These contributions include a Pauli component, which corresponds to the response of the heavy-fermion manybody states that appears in the energy gap in the vicinity of the Fermi level (density of states (3-4) Multiplication-Sign 10{sup 21} cm{sup -3} meV{sup -1}), and a contribution with saturation in high magnetic fields attributed to the localized magnetic moments ((0.8-3.7){mu}{sub B} per unit cell) of the nanoclusters formed by rare-earth ions with an antiferromagnetic interaction.

Bogach, A. V., E-mail: alex@lt.gpi.ru; Sluchanko, N. E.; Glushkov, V. V.; Demishev, S. V.; Azarevich, A. N.; Filippov, V. B. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Shitsevalova, N. Yu.; Levchenko, A. V. [National Academy of Sciences of Ukraine, Institute of Problems of Materials Science (Ukraine); Vanacken, J.; Moshchalkov, V. V. [Katholieke Universiteit Leuven, Institute of Nanoscale Physics and Chemistry (Belgium); Gabani, S.; Flachbart, K. [Slovak Academy of Sciences, Institute of Experimental Physics (Slovakia)

2013-05-15

103

One-pot solvothermal synthesis of uniform layer-by-layer self-assembled ultrathin hexagonal Gd2O2S nanoplates and luminescent properties from single doped Eu3+ and codoped Er3+, Yb3+.  

PubMed

Uniform Gd(2)O(2)S flower-like nano-assemblies were prepared through one-pot mild solvothermal synthesis. The parallel nanoplates are the building blocks, ?3 nm in thickness and 20-30 in diameter. Ethanediamine, the main solvent, plays an important role in dissolving a large amount of sulphur and producing active S(2-) ions, which results in the direct formation of Gd(2)O(2)S. Oleylamine, the capping agent, controls the growth of the plate-like structure. Under UV excitation, the Gd(2)O(2)S:Eu(3+) nano-phosphor shows good red luminescence with a main emission peak at 627 nm. Under 980 nm laser excitation, Gd(2)O(2)S:xYb(3+),1%Er(3+) nano-phosphors exhibit a tuneable emission, shifting from greenish-yellow to orange-yellow, with increasing Yb(3+) content. PMID:23033159

Liu, Jie; Luo, Hongde; Liu, Pujun; Han, Lixian; Zheng, Xiao; Xu, Bo; Yu, Xibin

2012-12-01

104

High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates-Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) (Ln=Ho, Er, Tm, Yb, Lu, Y)  

SciTech Connect

Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}H (H{sub 3}L), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y (6). The syntheses were scaled-up in glass reactor tubes in order to obtain larger amounts for a detailed characterization. Based on these results all compounds could be also synthesized by microwave-assisted heating and the influence of reaction time and stirring rate during the synthesis was established. For compound 2 the crystal structure was determined by single-crystal X-ray diffraction. The compounds contain isolated slightly distorted LnO{sub 6} octahedra that are connected by the phosphonate and sulfonate groups into a three-dimensional framework. Thermogravimetric investigations demonstrate the high thermal stability of the compounds up to 460 deg. C. - Graphical abstract: A high-throughput and microwave investigation of the System LnX{sub 3}/H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}/NaOH/H{sub 2}O led to six new compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho, Er, Tm, Yb, Lu, Y.

Sonnauer, Andreas [Institute of Inorganic Chemistry, Christian-Albrechts-University, Otto-Hahn-Platz 6/7, D 24118 Kiel (Germany); Stock, Norbert [Institute of Inorganic Chemistry, Christian-Albrechts-University, Otto-Hahn-Platz 6/7, D 24118 Kiel (Germany)], E-mail: stock@ac.uni-kiel.de

2008-11-15

105

NaYF4:Yb,Tm nanocrystals and TiO2 inverse opal composite films: a novel device for upconversion enhancement and solid-based sensing of avidin.  

PubMed

Upconversion luminescence (UCL) detection based on rare-earth doped upconversion nanocrystals (UCNCs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, and no photobleaching. However, it is still a challenge to achieve a stable, reproducible solid-based UCL biosensor because of ineffective UCL of the UCNCs. In this work, we fabricated TiO2 inverse opal photonic crystals (IOPCs)/NaYF4:Yb(3+),Tm(3+) (Er(3+)) UCNC composite films, which can tremendously improve the overall UCL of Tm(3+) as high as 43-fold. Based on the fluorescence resonance energy transfer (FRET) and the specific interaction between biotin and avidin, a novel solid-based UC biosensor is presented for sensing avidin. This solid-based detection system is convenient for detection, and also can offer two parameters for detecting trace amounts of avidin, namely, the emission intensity and the fluorescence decay time. The sensor has a high sensitivity of 34 pmol(-1), a good linear relationship of 0.996 and a low detection limit of 48 pmol. It also exhibits excellent long-time photostability, and the absence of autofluorescence, and thus may have great potential for versatile applications in biodetection. PMID:24752220

Xu, Sai; Xu, Wen; Wang, Yunfeng; Zhang, Shuang; Zhu, Yongsheng; Tao, Li; Xia, Lei; Zhou, Pingwei; Song, Hongwei

2014-06-01

106

NaYF4:Yb,Tm nanocrystals and TiO2 inverse opal composite films: a novel device for upconversion enhancement and solid-based sensing of avidin  

NASA Astrophysics Data System (ADS)

Upconversion luminescence (UCL) detection based on rare-earth doped upconversion nanocrystals (UCNCs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, and no photobleaching. However, it is still a challenge to achieve a stable, reproducible solid-based UCL biosensor because of ineffective UCL of the UCNCs. In this work, we fabricated TiO2 inverse opal photonic crystals (IOPCs)/NaYF4:Yb3+,Tm3+ (Er3+) UCNC composite films, which can tremendously improve the overall UCL of Tm3+ as high as 43-fold. Based on the fluorescence resonance energy transfer (FRET) and the specific interaction between biotin and avidin, a novel solid-based UC biosensor is presented for sensing avidin. This solid-based detection system is convenient for detection, and also can offer two parameters for detecting trace amounts of avidin, namely, the emission intensity and the fluorescence decay time. The sensor has a high sensitivity of 34 pmol-1, a good linear relationship of 0.996 and a low detection limit of 48 pmol. It also exhibits excellent long-time photostability, and the absence of autofluorescence, and thus may have great potential for versatile applications in biodetection.

Xu, Sai; Xu, Wen; Wang, Yunfeng; Zhang, Shuang; Zhu, Yongsheng; Tao, Li; Xia, Lei; Zhou, Pingwei; Song, Hongwei

2014-05-01

107

Ag{sub 2}O dependent up-conversion luminescence properties in Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses  

SciTech Connect

Up-conversion (UC) luminescence properties of Ag/Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses have been studied to assess the effective role of silver nanoparticles as a sensitizer for Tm{sup 3+} and Er{sup 3+} ions. The X-ray diffraction patterns obtained in this work do not reveal any crystalline phase in the glass. However, the absorption spectra reveal that surface plasmons resonance band of Ag undergoes a distinct split with two maxima and a very broad absorption peak with a background that extends toward the near infrared (NIR) with the increasing of Ag{sub 2}O added concentration. Transmission electron microscope images confirm that silver nanoparticles have been precipitated from matrix glasses and show their distribution, size, and shapes. In addition, changes in UC luminescence intensity of four emission bands 476, 524, 546, and 658?nm corresponding to {sup 1}G{sub 4} ? {sup 3}H{sub 6} (Tm{sup 3+}), ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) ? {sup 4}I{sub 15/2} (Er{sup 3+}), and {sup 4}F{sub 9/2} ? {sup 4}I{sub 15/2} (Er{sup 3+}) transitions, respectively, as a function of silver addition to the base composition have been measured under 980?nm excitation. It is confirmed that Ag{sub 2}O added concentration plays an important role in increasing the UC luminescence intensity; however, further increase in Ag{sub 2}O added concentration reduces the intensity.

Hu, Yuebo [Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Qiu, Jianbei, E-mail: qiu@kmust.edu.cn; Song, Zhiguo; Zhou, Dacheng [Key Laboratory of Advanced Materials in Rare and Precious and Non-ferrous Metals, Ministry of Education, Key Laboratory of Advanced Materials of Yunnan Province, Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

2014-02-28

108

Ag-LnBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (Ln = Y, Nd, Sm, Eu, and Yb) superconductor coatings on stainless steel  

SciTech Connect

Ag-doped LnBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (Ln = Y, Nd, Sm, Eu, and Yb) films on two kinds of stainless steel substrate were prepared by the method of direct deposition and heat treatment. The critical temperatures of the samples were evaluated at 91--92 K, independent of silver content and thickness of the coating layer. The resistance of the samples decreased with silver addition. The SEM observation showed a border between the coating layer and the substrate. The elemental analysis by EPMA revealed that aluminum aggregated in the border. The diffusion of iron ions in the coating layer was hindered by the existence of the border and affected by the quantity of aluminum. The width of the border increased with increasing heat-treatment time, governed by the diffusion of metals from the metallic substrate to the coating layer. This fairly agreed with the results of impedance measurements.

Yokogawa, Y. [National Industrial Research Inst., Nagoya (Japan)] [National Industrial Research Inst., Nagoya (Japan); Ansart, F.; Bressolles, J.C.; Roux, P.; Traverse, J.P. [Univ. Paul Sabatier, Toulouse (France). Lab. Materiaux et Energie] [Univ. Paul Sabatier, Toulouse (France). Lab. Materiaux et Energie

1997-07-01

109

The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth-based R{sub 2}Ba{sub 4}Cu{sub 7}O{sub 14-{delta}} (R = Nd, Eu, Tm)  

SciTech Connect

The formation of phases in the (R{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} (Pr-doped R247; R = Nd, Eu, Tm) system with x = 0-1.0 was investigated. Samples of the title series were synthesized at 980-990{degree}C at 25 bar O{sub 2}, followed by annealing at 300{degree}C under 130 bar O{sub 2} for 30 hr. Oxygen content of the samples has been determined by iodometric titration. Single-phased samples has been determined by iodometric titration. Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R = Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements. With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T{sub c}`s) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T{sub c}`s of R247 (R = Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R{sup 3+} radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} samples with x = 0, 0.2, and 0.4, respectively, are also reported.

Teng-Ming Chen; Kao, F.S. [National Chiao-Tung Univ., Taiwan (China)

1997-08-01

110

Direct synthesis of hexagonal NaGdF? nanocrystals from a single-source precursor: upconverting NaGdF? :Yb³? ,Tm³? and its composites with TiO? for near-IR-driven photocatalysis.  

PubMed

A novel single-source precursor NaGd(TFA)4 (diglyme) (TFA=trifluoroacetate) was synthesized, characterized thoroughly, and used to obtain the hexagonal phase of NaGdF4 nanoparticles as an efficient matrix for lanthanide-doped upconverting nanocrystals (NCs) that convert near-infrared radiation into shorter-wavelength UV/visible light. These NCs were then used to prepare well-characterized TiO2@NaGdF4:Yb(3+),Tm(3+) nanocomposites to extend the absorption range of the TiO2 photocatalyst from the UV to the IR region. While the visible/near IR part of the photoluminescent spectra remains almost unaffected by the presence of TiO2, the UV part is strongly quenched due to the absorption of TiO2 above its gap at approximately 380?nm by energy transfer or FRET. Preliminary results on the photocatalytic activity of the above obtained nanocomposites are presented. PMID:24910325

Chen, Ying; Mishra, Shashank; Ledoux, Gilles; Jeanneau, Erwann; Daniel, Marlene; Zhang, Jinlong; Daniele, Stéphane

2014-09-01

111

Electronic states of R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence compounds determined by soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

We here report an investigation of the electronic states in the R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence ferrites by means of soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements together with ab initio theoretical calculations. The presence of Fe+2 and Fe+3 pure ionic species is discarded in the XAS spectra at the O K edge in both experimental data and simulations based on the multiple scattering theory. Similarly, no trace of F e+2/F e+3 contributions is detected in the XMCD spectra at the Fe K edge. On the other hand, the XAS and XMCD spectra at the Fe L2 ,3 edges can be well described in terms of F e+2/F e+3 contributions, and are also supported by multiplet calculations. This finding can be interpreted as the existence of a mixture of 3 d5/3 d6 configurations at the Fe atoms. Alternative ferrimagnetic spin orderings based on a trimodal Fe valence distribution are also proposed and discussed. Finally, a possible explanation for the strong dependence of the Fe L2 ,3 edges XMCD signal magnitude on both the sample surface preparation and detection method is presented.

Lafuerza, Sara; García, Joaquín; Subías, Gloria; Blasco, Javier; Herrero-Martín, Javier; Pascarelli, Sakura

2014-12-01

112

Magnetic properties of the RPO 4(MoO 3) 12 × 30H 2O compounds, R = Ce, Pr, Nd, Tb, Ho, Tm, and Yb  

NASA Astrophysics Data System (ADS)

Magnetic susceptibilities of a number of the rare earth ( R) phosphomolybdates, RPO 4(MoO 3) 12 × 30H 2O, have been measured from 300 K down to ? 10 mK. These materials are cubic, with space group Fd overline3, and are characterized by weak crystalline field splittings. Most can be explained in terms of a lowest order theory for a crystal field with T d ( overline43 m) symmetry, but those of Tb, Ho, and Tm disagree. The discrepancy appears to be due to disorder in the position of the cations about the 8 a sites.

Corruccini, L. R.; van der Noordaa, J. T.; White, Steven J.; Hope, Håkon

1997-09-01

113

Preparation and spectroscopic properties of rare-earth (RE) (RE = Sm, Eu, Tb, Dy, Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) phosphate in vacuum ultraviolet region  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? We report the VUV spectroscopic properties of rare-earth ions in K{sub 2}LnZr(PO{sub 4}){sub 3}. ? The O{sup 2?}-Eu{sup 3+} charge transfer bands at about 220 nm have been observed. ? The 4f–5d spin-allowed and spin-forbidden transitions of Tb{sup 3+} have been observed. ? There is energy transfer between the host and rare-earth activators. -- Abstract: Rare earth (RE = Sm, Eu, Tb, Dy and Tm)-activated K{sub 2}LnZr(PO{sub 4}){sub 3} (Ln = Y, La, Gd and Lu) have been synthesized by solid-state reaction method, and their vacuum ultraviolet (VUV) excitation luminescent characteristics have been investigated. The band in the wavelength range of 130–157 nm and the other one range from 155 to 216 nm with the maximum at about 187 nm in the VUV excitation spectra of these compounds are attributed to the host lattice absorption and O–Zr charge transfer transition, respectively. The charge transfer bands (CTB) of O{sup 2?}-Sm{sup 3+}, O{sup 2?}-Dy{sup 3+} and O{sup 2?}-Tm{sup 3+}, in Sm{sup 3+}, Dy{sup 3+} and Tm{sup 3+}-activated samples, have not been obviously observed probably because the 2p electrons of oxygen are tightly bound to the zirconium ion in the host lattice. For Eu{sup 3+}-activated samples, the relatively weak O{sup 2?}-Eu{sup 3+} CTB at about 220 nm is observed. And for Tb{sup 3+}-activated samples, the bands at 223 and 258 nm are related to the 4f-5d spin-allowed and spin-forbidden transitions of Tb{sup 3+}, respectively. It is observed that there is energy transfer between the host lattice and the luminescent activators (e.g. Eu{sup 3+}, Tb{sup 3+}). From the standpoint of luminescent efficiency, color purity and chemical stability, K{sub 2}GdZr(PO{sub 4}){sub 3}:Sm{sup 3+}, Eu{sup 3+}, Tb{sup 3+} are attractive candidates for novel yellow, red, green-emitting PDP phosphors.

Zhang, Zhi-Jun, E-mail: zhangzj@mail.sic.ac.cn [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Lin, Xiao [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China) [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Graduate School of Chinese Academy of Science, Beijing, 100039 (China); Zhao, Jing-Tai [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China)] [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai, 200050 (China); Zhang, Guo-Bin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, 230026 (China)

2013-02-15

114

Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}: Three new quaternary interlanthanide chalcogenides  

SciTech Connect

Three new ordered quaternary interlanthanide chalcogenides, Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}, have been prepared by direct reaction of the elements in molten NaBr at 900 Degree-Sign C. Each compound forms a new structure-type. The Ce{sub 2}AgYb{sub 5/3}Se{sub 6} structure consists of {infinity}{sup 2}{l_brace} [AgYb{sub 5/6}Se{sub 6}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers are composed of {infinity}{sup 1}{l_brace} [Yb{sub 5/3}Se{sub 6}]{sup 7-}{r_brace} quadruplet ribbons of [YbSe{sub 6}]{sup 9-} octahedra and infinite {infinity}{sup 1}{l_brace} [AgSe{sub 6}]{sup 11-}{r_brace} double chains of [AgSe{sub 5}]{sup 9-}. The La{sub 2}CuErTe{sub 5} structure is made of one-dimensional {infinity}{sup 1}{l_brace} [CuErTe{sub 5}]{sup 6-}{r_brace} ribbons separated by La{sup 3+} cations. These ribbons are formed by cis-edge sharing {infinity}{sup 1}{l_brace} [CuTe{sub 2}]{sup 3-}{r_brace} tetrahedral chains and trans-edge sharing {infinity}{sup 1}{l_brace} [ErTe{sub 4}]{sup 5-}{r_brace} chains. While La{sub 2}CuErTe{sub 5} crystallizes in the orthorhombic space group Pnma, Ce{sub 2}CuTmTe{sub 5} crystallizes in the monoclinic space group C2/m. The latter crystal structure is assembled from {infinity}{sup 2}{l_brace} [CuTmTe{sub 5}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers consist of single {infinity}{sup 1}{l_brace} [TmTe{sub 4}]{sup 5-}{r_brace} chains connected to each other through dimers or pseudo-double chains. - Graphical abstract: [CuTe{sub 4}]{sup 7-} tetrahedra sharing cis-edges to yield chains in the La{sub 2}CuErTe{sub 5}. Highlights: Black-Right-Pointing-Pointer New ordered interlanthanide tellurides. Black-Right-Pointing-Pointer New quaternary chalcogenides. Black-Right-Pointing-Pointer Low-dimensional lanthanide chalcogenide substructures. Black-Right-Pointing-Pointer Flux synthesis of new chalcogenides.

Babo, Jean-Marie [Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: talbrec1@nd.edu [Department of Chemistry and Biochemistry, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States)

2013-01-15

115

Two new ternary lanthanide antimony chalcogenides: Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.68} containing chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anions  

SciTech Connect

Dark red and dark brown crystals of Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 8}Sb{sub 4}Se{sub 11.68}, respectively, were obtained from the reaction of the elements in Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [0 1 0]. The chalcogens in both compounds form chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22 eV for Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.75,} respectively. - Graphical Abstract: The crystal structure of Yb{sub 4}Sb{sub 2}S{sub 11} viewed along the [0 1 0]. Highlights: Black-Right-Pointing-Pointer Lanthanide chalcogenides. Black-Right-Pointing-Pointer Semiconductors. Black-Right-Pointing-Pointer Tunnel structures. Black-Right-Pointing-Pointer Lone-pair effects.

Babo, Jean-Marie [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: talbrec1@nd.edu [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

2012-03-15

116

Mixed cations and structural complexity in (Eu(1-x)Ca(x))(4)In(3)Ge(4) and (Eu(1-x)Ca(x))(3)In(2)Ge(3)--the first two members of the homologous series A(2[n+m])In(2n+m)Ge(2[n+m]) (n, m = 1, 2, ...infinity; A = Ca, Sr, Ba, Eu, or Yb).  

PubMed

Reported are the synthesis and the structural characterization of two members of a new homologous series of polar intermetallic compounds, which exist only with mixed alkaline-earth and rare-earth metal cations. Crystals of (Eu(1-x)Ca(x))(4)In(3)Ge(4) (0.35(1) Eu(1-x)Ca(x))(3)In(2)Ge(3) (0.78(1) Eu(1-x)Ca(x))(4)In(3)Ge(4) adopts the monoclinic Mg(5)Si(6)-type structure (space group C2/m, Z = 2, Pearson symbol mS22) with lattice parameters a = 16.874(1)-17.024(2) A, b = 4.496(3)-4.556(1) A, c = 7.473(4)-7.540(1) A, and beta = 107.306(10)-105.631(3) degrees . (Eu(1-x)Ca(x))(3)In(2)Ge(3) crystallizes with a novel orthorhombic structure (space group Pnma, Z = 4, Pearson symbol oP32) with lattice parameters in the ranges a = 7.382(2)-7.4010(9) A, b = 4.452(1)-4.4640(6) A, and c = 23.684(6)-23.734(3) A, depending on the Eu/Ca ratio. The polyanionic substructures in both cases are related and are based on InGe(4) edge-shared tetrahedra, Ge(2) dimers, and bridging In atoms in a nearly square-planar environment. The (Eu(1-x)Ca(x))(4)In(3)Ge(4) structure can be viewed as a 1:1 intergrowth of Mo(2)FeB(2)-like and TiNiSi-like fragments, whereas (Eu(1-x)Ca(x))(3)In(2)Ge(3) can be rationalized as a 2:1 intergrowth of the same structural motifs. Both phases exhibit fairly wide homogeneity ranges and exist only with mixed cations. The experimental results have been complemented by linear muffin-tin orbital tight-binding band structure calculations, as well as an analysis of the observed cationic site preferences. PMID:20073492

You, Tae-Soo; Tobash, Paul H; Bobev, Svilen

2010-02-15

117

Pure-phase La2(WO4)3:Eu3+ nanocrystals and spindle-like NaLa(WO4)2:Yb3+/Er3+ nano/microcrystals: selective synthesis, morphologies and photoluminescent properties.  

PubMed

The selective synthesis of pure-phase La2(WO4)3 nanocrystals and uniform spindle-like NaLa(WO4)2 nano/microcrystals with tunable size based on one reaction system has been reported for the first time. The sodium ion is crucial for the selective synthesis of La2(WO4)3 and NaLa(WO4)2. An additional hydrothermal treatment has a great effect on the morphology of La2(WO4)3, while the hydrothermal temperature and time, and the amount of glycerine, significantly influence the morphology and size of NaLa(WO4)2. Based on the time-dependent experiments, it is proposed that the Ostwald ripening is the formation mechanism of the spindle-like NaLa(WO4)2. The resultant La2(WO4)3:Er(3+) nanocrystals can emit a bright red color with a high purity under the excitation of 467 nm (blue region) and, more importantly, it can be easily dispersed in distilled water. The up-conversion emission intensity of NaLa(WO4)2:Yb(3+)/Er(3+) is increased rapidly with the Yb(3+) concentration under 980 nm laser excitation, suggesting the efficient energy transfer from Yb(3+) to Er(3+). Moreover, the emission color can be tuned from chartreuse to green by increasing the Yb(3+) concentration. These unique properties of La2(WO4)3 and NaLa(WO4)2 are closely related with their distinctive crystal structures, and it is anticipated that the findings in this work may give an insight into the fabrication and application of the rare earth tungstates. PMID:23824277

Liu, Xiaolin; Hou, Wenhua; Yang, Xiaoyan; Shen, Qingming

2013-08-28

118

Upconversion luminescence enhancement of Yb(3+), Nd(3+) sensitized NaYF4 core-shell nanocrystals on Ag grating films.  

PubMed

Here, we report the wavelength-dependent and angle-dependent upconversion luminescence (UCL) enhancement of NaYF4:Yb(3+),Tm(3+)@NaYF4:Yb(3+),Nd(3+) core-shell nanocrystals (NCs) resulting from Ag grating structures, which provides a novel insight for improving UCL. PMID:25502851

Xu, Wen; Song, Hongwei; Chen, Xu; Wang, Haiyu; Cui, Shaobo; Zhou, Donglei; Zhou, Pingwei; Xu, Sai

2015-01-01

119

R3Au(6+x)Al26T (R = Ca, Sr, Eu, Yb; T = early transition metal): a large family of compounds with a stuffed BaHg11 structure type grown from aluminum flux.  

PubMed

A collection of new quaternary intermetallic compounds with a cubic, stuffed BaHg(11) structure type has been synthesized by the combination of a divalent rare earth or alkaline earth metal R, an early transition metal T, and gold in an excess of molten aluminum. Structural characterization of these R(3)Au(6+x)Al(26)T compounds by powder and single crystal X-ray diffraction indicates that the unit cell varies with the radii of the early transition metal T and the rare earth/alkaline earth R as expected. The element T (where T = group 4, 5, 6, and 7 element) appears to be responsible for the stabilization of up to 43 different members of the R(3)Au(6+x)Al(26)T family of compounds. Varying amounts of disorder and trends in partial occupancies of the Au stuffed site--the site that is vacant in the parent compound BaHg(11)--are also indicated by the diffraction studies of this family of compounds. Magnetic susceptibility data reveals that the transition metal atoms in these materials do not possess local magnetic moments. For the magnetic rare earth containing materials, the europium compounds undergo a ferromagnetic transition at 10 K, and the ytterbium analogues show mixed valent behavior. Band structure calculations also support a mixed valent state for Yb in these compounds. PMID:19146424

Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

2009-02-16

120

EU Business  

NSDL National Science Digital Library

EU Business is provided by Europanet. It aims to provide selected business information to the busy business person. Information available at the site includes European Union (EU) law, business developments in Europe, finance and EU programs. The site also keeps track of European Commission proposals and the progress of draft legislation. Users interested in doing business in Europe will find this site a useful guide to facilitate the process.

1998-01-01

121

Optical study of archetypical valence-fluctuating Eu systems.  

PubMed

We have investigated the optical conductivity of the prominent valence-fluctuating compounds EuIr(2)Si(2) and EuNi(2)P(2) in the infrared energy range to get new insights into the electronic properties of valence-fluctuating systems. For both compounds, we observe upon cooling the formation of a renormalized Drude response, a partial suppression of the optical conductivity below 100 meV, and the appearance of a midinfrared peak at 0.15 eV for EuIr(2)Si(2) and 0.13 eV for EuNi(2)P(2). Most remarkably, our results show a strong similarity with the optical spectra reported for many Ce- or Yb-based heavy-fermion metals and intermediate valence systems, although the phase diagrams and the temperature dependence of the valence differ strongly between Eu systems and Ce- or Yb-based systems. This suggests that the hybridization between 4f and conduction electrons, which is responsible for the properties of Ce and Yb systems, plays an important role in valence-fluctuating Eu systems. PMID:23368375

Guritanu, V; Seiro, S; Sichelschmidt, J; Caroca-Canales, N; Iizuka, T; Kimura, S; Geibel, C; Steglich, F

2012-12-14

122

Two new groups of homoleptic rare earth pyridylbenzimidazolates: (NC12H8(NH)2)[Ln(N3C12H8)4] with Ln = Y, Tb, Yb, and [Ln(N3C12H8)2(N3C12H9)2][Ln(N3C12H8)4](N3C12H9)2 with Ln = La, Sm, Eu.  

PubMed

The compounds (NC(12)H(8)(NH)(2))[Ln(N(3)C(12)H(8))(4)], Ln = Y, Tb, Yb, and [Ln(N(3)C(12)H(8))(2)(N(3)C(12)H(9))(2)][Ln(N(3)C(12)H(8))(4)](N(3)C(12)H(9))(2), with Ln = La, Sm, Eu, were obtained by reactions of the group 3 metals yttrium and lanthanum as well as the lanthanides europium, samarium, terbium, and ytterbium with 2-(2-pyridyl)-benzimidazole. The reactions were carried out in melts of the amine without any solvent and led to two new groups of homoleptic rare earth pyridylbenzimidazolates. The trivalent rare earth atoms have an eightfold nitrogen coordination of four chelating pyridylbenzimidazolates giving an ionic structure with either pyridylbenzimidazolium or [Ln(N(3)C(12)H(8))(2)(N(3)C(12)H(9))(2)](+) counterions. With Y, Eu, Sm, and Yb, single crystals were obtained whereas the La- and Tb-containing compounds were identified by powder methods. The products were investigated by X-ray single crystal or powder diffraction and MIR and far-IR spectroscopy, and with DTA/TG regarding their thermal behavior. They are another good proof of the value of solid-state reaction methods for the formation of homoleptic pnicogenides of the lanthanides. Despite their difference in the chemical formula, both types (NC(12)H(8)(NH)(2))[Ln(N(3)C(12)H(8))(4)], Ln = Y (1), Tb (2), Yb (3), and [Ln(N(3)C(12)H(8))(2)(N(3)C(12)H(9))(2)][Ln(N(3)C(12)H(8))(4)](N(3)C(12)H(9))(2), Ln = La (4), Sm (5), Eu (6), crystallize isotypic in the tetragonal space group I4(1). Crystal data for (1): T = 170(2) K, a = 1684.9(1) pm, c = 3735.0(3) pm, V = 10603.5(14) x 10(6) pm(3), R1 for F(o) > 4sigma(F(o)) = 0.053, wR2 = 0.113. Crystal data for (3): T = 170(2) K, a = 1683.03(7) pm, c = 3724.3(2) pm, V = 10549.4(14) x 10(6) pm(3), R1 for F(o) > 4sigma(F(o)) = 0.047, wR2 = 0.129. Crystal data for (5): T = 103(2) K, a = 1690.1(2) pm, c = 3759.5(4) pm, V = 10739(2) x 10(6) pm(3), R1 for F(o) > 4sigma(F(o)) = 0.050, wR2 = 0.117. Crystal data for (6): T = 170(2) K, a = 1685.89(9) pm, c = 3760.0(3) pm, V = 10686.9(11) x 10(6) pm(3), R1 for F(o) > 4sigma(F(o)) = 0.060, wR2 = 0.144. PMID:12691584

Müller-Buschbaum, Klaus; Quitmann, Catharina C

2003-04-21

123

The series of rare earth complexes [Ln2Cl6 (?-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm-Yb: a molecular model system for luminescence properties in MOFs based on LnCl3 and 4,4'-bipyridine.  

PubMed

A series of 12 dinuclear complexes [Ln2Cl6(?-4,4'-bipy)(py)6], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, (1-12, respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4'-bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl3 and 4,4-bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln-N-MOFs (?)(2)[Ln2Cl6(4,4'-bipy)3]·2(4,4'-bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, (1, 4-8) were determined, showing an antenna effect through a ligand-metal energy transfer. The highest efficiency of luminescence is observed for the terbium-based compound 7 displaying a high quantum yield (QY of 86%). Excitation with UV light reveals typical emission colors of lanthanide-dependent intra 4f-4f-transition emissions in the visible range (Tb(III) : green, Eu(III) : red, Sm(III) : salmon red, Dy(III) : yellow). For the Gd(III)- and Y(III)-containing compounds 6 and 1, blue emission based on triplet phosphorescence is observed. Furthermore, ligand-to-metal charge-transfer (LMCT) states, based on the interaction of Cl(-) with Eu(III), were observed for the Eu(III) compound 5 including energy-transfer processes to the Eu(III) ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln-independent quantum yields in the related MOFs. PMID:24243814

Matthes, Philipp R; Nitsch, Jörn; Kuzmanoski, Ana; Feldmann, Claus; Steffen, Andreas; Marder, Todd B; Müller-Buschbaum, Klaus

2013-12-16

124

TM7TM'6B8 (TM = Ta, Nb; TM' = Ru, Rh, Ir): new compounds with [B6] ring polyanions.  

PubMed

The ternary boron compounds TM(7)TM'(6)B(8) (TM = Ta, Nb; TM' = Ru, Rh, Ir) were prepared by high-temperature thermal treatment of mixtures of the elements. An analysis of the chemical bonding by the electron density/electron localizability approach reveals formation of covalently bonded polyanions [B(6)] and [TM'(6)B(2)]. The cationic part of the structure contains separated TM cations. In agreement with the chemical bonding analysis and band structure calculations, all TM(7)TM'(6)B(8) compounds are metallic Pauli-paramagnets (TM' = Ru, Rh) or diamagnets (TM' = Ir). PMID:22725845

Zheng, Qiang; Kohout, Miroslav; Gumeniuk, Roman; Abramchuk, Nikolay; Borrmann, Horst; Prots, Yurii; Burkhardt, Ulrich; Schnelle, Walter; Akselrud, Lev; Gu, Hui; Leithe-Jasper, Andreas; Grin, Yuri

2012-07-16

125

Power scaling of resonantly pumped Yb-free Er-doped fiber laser  

NASA Astrophysics Data System (ADS)

Even though Yb-doped fiber lasers are known to be the most powerful and most efficient among all fiber lasers, recent successes in the eye-safe ~1.5?m Yb-Er-doped fiber lasers (where Er is excited through Yb-Er energy transfer) are quite impressive. Output power of Yb-Er fiber lasers reached ~300 W level and their optical-to-optical efficiency, for somewhat lower power levels, is exceeding 40% [2]. Nevertheless, as far as real eye safety is concerned, multi-hundred Watt Yb-Er fiber lasers typically carry in their output a significant fraction of competing 1-?m Yb emission, which totally compromises an eye-safe side of the application. Ultimate efficiency and thermal management of Yb-Er approach are also suffering due to: (i), inefficiency of Yb-Er energy transfer and, (ii), gigantic ~40% quantum defect of Er-doped fiber pumped at 9XX-nm. Presented here are very recent and successful results on power scaling of resonantly pumped Yb-free Er-doped fiber lasers and amplifiers. We are reporting an Ybfree Er-doped cladding-pumped fiber power scaling to ~50 W with ~57% optical-tooptical efficiency [6] in a few first experimental steps. This is clear manifestation of scaling potential of this most efficient approach to high power eye-safe fiber laser. The only competing approach to scalable eye-safe fiber laser implements Tm3+-doped fibers pumped at ~790 nm while relying on well known "2-for-1" process leading to quite efficient excitation of the ~2?m Tm3+ laser operation [4]. This approach has operational optical-to-optical efficiency quantum limit of ~75% [4], while resonantly pumped Ybfree Er-doped fiber laser's optical-to-optical efficiency quantum limit exceeds 95% due to its low-quantum-defect (QD) pump-lase scheme. Significant scaling potential of resonantly-pumped Yb-free Er-doped fiber lasers and amplifiers sets a path to an eye-safe fiber laser concept with drastically relaxed thermal management and nearly diffraction limited beam quality at ~kW-=-class power levels as well as high electrical to optical efficiency.

Dubinskii, M.; Zhang, J.; Ter-Mikirtychev, V.

2009-05-01

126

Phase and Size Controllable Synthesis of NaYbF4 Nanocrystals in Oleic Acid/ Ionic Liquid Two-Phase System for Targeted Fluorescent Imaging of Gastric Cancer  

PubMed Central

Upconversion nanocrystals with small size and strong fluorescent signals own great potential in applications such as biomolecule-labeling, in vivo tracking and molecular imaging. Herein we reported that NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with small size and strong fluorescent signals were controllably synthesized by oleic acid (OA)/ ionic liquid (IL) two-phase system for targeted fluorescent imaging of gastric cancer in vivo. The optimal synthesis condition of NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals by OA/IL two-phase system was established, adding more metal ion such as Na+ ion could facilitate the size control and crystal-phase transition, more importantly, markedly enhancing fluorescent intensity of beta-phase nanocrystals compared with traditional methods. Alpha-phase NaYbF4, 2%Tm upconversion nanocrystals with less than 10nm in diameter and beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals with 30 nm or so in diameter and strong fluorescent signals were obtained, these synthesized nanocrystals exhibited very low cytotoxicity. Folic acid-conjugated silica-modified beta-phase NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals were prepared, could actively target gastric cancer tissues implanted into nude mice in vivo, and realized targeted fluorescent imaging. Folic acid-conjugated silica-modified NaYbF4: 25%Gd, 2%Tm upconversion nanocrystals show great potential in applications such as targeted near infared radiation fluorescent imaging, magnetic resonance imaging and targeted therapy of gastric cancer in the near future. PMID:23471455

Pan, Liyuan; He, Meng; Ma, Jiebing; Tang, Wei; Gao, Guo; He, Rong; Su, Haichuan; Cui, Daxiang

2013-01-01

127

Resonant photo-ionization of Yb+ to Yb2+  

E-print Network

We demonstrate the three-step fully-resonant photo-ionization of 174Yb+ with weak continuous-wave lasers at ultra violet wavelengths. Starting from an ion crystal of two laser-cooled Yb+ ions localized in a radio-frequency trap, the verification of the ionization process is performed by characterizing the motional dynamics of the resulting mixed-species ion-crystal.

Simon Heugel; Martin Fischer; Vladimir Elman; Markus Sondermann; Gerd Leuchs

2014-12-21

128

Optical study of Yb(3+)/Yb(2+) conversion in CaF(2) crystals.  

PubMed

Yb(3+) ions with various site symmetries have been observed in the absorption and emission spectra of Yb(3+):CaF(2) crystals, both ?-irradiated and annealed in hydrogen. The absorption intensity value is found to be much higher for the ?-irradiated crystal and strongly dependent on the gamma dose. The UV absorption spectra of ?-irradiated and H(2)-annealed CaF(2):5 at.% Yb(3+) crystals are quite similar. Yb(2+) absorption bands are observed at 360, 315, 271, 260, 227 and 214 nm, which are called A, B, C, D, F and G bands, respectively. For ?-irradiated CaF(2):30 at.% Yb(3+), an additional band at 234 nm can be seen. It is suggested that only a negligible amount of Yb(3+) ions are converted into Yb(2+) under the ?-irradiation. The presence of Yb(2+) is confirmed by the 565 and 540 nm luminescence under 357 nm excitation. It is also suggested that the excitation in the A, C, D and F absorption bands of Yb(2+) gives rise to photo-ionization of Yb(2+) ions and electrons in the conduction band to form the excited Yb(3+) ions which emit IR Yb(3+) luminescence.The UV absorption and emission spectra obtained for ?-irradiated and H(2)-annealed crystals have different structures. This suggests that different mechanisms are responsible for the creation of Yb(2+) ions. ?-irradiation favours Yb(2+) isolated centres by reduction of Yb(3+) ions located at Ca(2+) lattice sites, whereas annealing in hydrogen favours Yb(2+) centres neighbouring Yb(3+) ions when a Yb(3+) ion pair captures a Compton electron. Also, ?-irradiation does not change the position of Yb(3+) ions converted into Yb(2+) in the CaF(2) lattice. In the case of H(2) annealing, a Yb(3+) ion converted to Yb(2+) is shifted to the Ca(2+) position in the lattice. PMID:21690695

Kaczmarek, S?awomir M; Tsuboi, Taiju; Ito, Masahiko; Boulon, Georges; Leniec, Grzegorz

2005-06-29

129

Effect of Yb3+ concentration on optical properties of Yb:CaF2 transparent ceramics  

E-print Network

Effect of Yb3+ concentration on optical properties of Yb:CaF2 transparent ceramics Andréas Lyberis Keywords: CaF2 Ytterbium Transparent ceramics Spectroscopy a b s t r a c t In Yb:CaF2, the coordination, and fluorescence lifetime of 0.1, 1, 5, and 10 at% Yb:CaF2 ceramics to determine whether Yb3+ substitutes

130

Identification of three new Alu Yb subfamilies by source tracking of recently integrated Alu Yb elements  

PubMed Central

Background Alu elements are the most abundant mobile elements in the human genome, with over 1 million copies and constituting more than 10% of the genome. The majority of these Alu elements were inserted into the primate genome 35 to 60 million years ago, but certain subfamilies of Alu elements are relatively very new and suspected to be still evolving. We attempted to trace the source/master copies of all human-specific members of the Alu Yb lineage using a computational approach by clustering similar Yb elements and constructing an evolutionary relation among the members of a cluster. Results We discovered that one copy of Yb8 at 10p14 is the source of several active Yb8 copies, which retrotransposed to generate 712 copies or 54% of all human-specific Yb8 elements. We detected eight other Yb8 elements that had generated ten or more copies, potentially acting as 'stealth drivers’. One Yb8 element at 14q32.31 seemed to act as the source copy for all Yb9 elements tested, having producing 13 active Yb9 elements, and subsequently generated a total of 131 full-length copies. We identified and characterized three new subclasses of Yb elements: Yb8a1, Yb10 and Yb11. Their copy numbers in the reference genome are 75, 8 and 16. We analysed personal genome data from the 1000 Genome Project and detected an additional 6 Yb8a1, 3 Yb10 and 15 Yb11 copies outside the reference genome. Our analysis indicates that the Yb8a1 subfamily has a similar age to Yb9 (1.93 million years and 2.15 million years, respectively), while Yb10 and Yb11 evolved only 1.4 and 0.71 million years ago, suggesting a linear evolutionary path from Yb8a1 to Yb10 and then to Yb11. Our preliminary data indicate that members in Yb10 and Yb11 are mostly polymorphic, indicating their young age. Conclusions Our findings suggest that the Yb lineage is still evolving with new subfamilies being formed. Due to their very young age and the high rate of being polymorphic, insertions from these young subfamilies are very useful genetic markers for studying human population genetics and migration patterns, and the trend for mobile element insertions in the human genome. PMID:24216009

2013-01-01

131

Physics of YbBiPt  

SciTech Connect

YbBiPt has a low temperature linear specific heat coefficient of 8J/mole-Yb K{sup 2} and a small specific-heat anomaly at 0.4K. We discuss new experiments on specific-heat of diluted YbBiPt, and magnetic field dependent effects and electrical resistivity in pure YbBiPt. We argue that in this material the Kondo and crystal-field energy scales are small and of comparable magnitude, placing YbBiPt in the same class as many Uranium heavy-electron compounds.

Thompson, J.D.; Canfield, P.C.; Lacerda, A.; Hundley, M.F.; Fisk, Z. (Los Alamos National Lab., NM (United States)); Ott, H.R.; Felder, E.; Chernikov, M. (Eidgenoessische Technische Hochschule, Zurich (Switzerland)); Maple, M.B.; Visani, P.; Seaman, C.L.; Lopez de la Torre, M.A. (California Univ., San Diego, CA (United States)); Aeppli, G. (AT and T Bell Labs., Murray Hill, NJ (United States))

1992-09-15

132

75 FR 5071 - Lock + TM  

Federal Register 2010, 2011, 2012, 2013

...Commission [Project No. 13649-000] Lock + \\TM\\ Hydro Friends Fund XXXI, LLC; Notice of...22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXI, LLC (Lock + Hydro...1-29-10; 8:45 am] BILLING CODE...

2010-02-01

133

75 FR 5068 - Lock + TM  

Federal Register 2010, 2011, 2012, 2013

...Commission [Project No. 13651-000] Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC; Notice...22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC (Lock...1-29-10; 8:45 am] BILLING CODE...

2010-02-01

134

GEOMAG[TM] Paradoxes  

ERIC Educational Resources Information Center

As often happens, a lot of physics can come out of a toy. What we found interesting is the observation of the magnetic field produced by different configurations built with GEOMAG[TM]. This toy provides small magnetic bars and steel spheres to play with. Amusing 3-D structures can be built; nevertheless, this possibility is not so obvious. Indeed,…

Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

2007-01-01

135

R(5)Pn(3)-type phases of the heavier trivalent rare-earth-metal pnictides (Pn = Sb, Bi): new phase transitions for Er(5)Sb(3) and Tm(5)Sb(3).  

PubMed

The syntheses and distributions of binary R(5)Pn(3) phases among the hexagonal Mn(5)Si(3) (M), and the very similar orthorhombic beta-Yb(5)Sb(3) (Y) and Y(5)Bi(3) (YB) structure types have been studied for R = Y, Gd-Lu and Pn = Sb, Bi. Literature reports of M and YB-type structure distributions among R(5)Pn(3) phases, R = Y, Gd-Ho, are generally confirmed. The reported M-type Er(5)Sb(3) could not be reproduced. Alternate stabilization of Y-type structures by interstitials H or F has been disproved for these nominally trivalent metal pnictides. Single crystal structures are reported for (a) the low temperature YB form of Er(5)Sb(3) (Pnma, a = 7.9646(9) A, b = 9.176(1) A, c = 11.662(1) A), (b) the YB- and high temperature Y-types of Tm(5)Sb(3) (both Pnma, a = 7.9262(5), 11.6034(5) A, b = 9.1375(6), 9.1077(4) A, c = 11.6013(7), 7.9841(4) A, respectively), and (c) the YB structure of Lu(5)Sb(3), a = 7.8847(4) A, b = 9.0770(5) A, c = 11.5055(6) A. Reversible, temperature-driven phase transitions (beta-Yb(5)Sb(3) left arrow over right arrow Y(5)Bi(3) types) for the former Er(5)Sb(3) and Tm(5)Sb(3) around 1100 degrees C and the means of quenching the high temperature Y form, have been esstablished. According to their magnetic susceptibilities, YB-types of Er(5)Sb(3) and Tm(5)Sb(3) contain trivalent cations. Tight-binding linear muffin-tin-orbital method within the atomic sphere approximation (TB-LMTO-ASA) calculations for the two structures of Tm(5)Sb(3) reveal generally similar electronic structures but with subtle Tm-Tm differences supporting their relative stabilities. The ambient temperature YB-Tm(5)Sb(3) shows a deep pseudogap at E(F), approaching that of a closed shell electronic state. Short R-R bonds (3.25-3.29 A) contribute markedly to the structural stabilities of both types. The Y-type structure of Tm(5)Sb(3) shows both close structural parallels to, and bonding contrasts with, the nominally isotypic, stuffed Ca(5)Bi(3)D and its analogues. Some contradictions in the literature are discussed. PMID:19341301

Gupta, Shalabh; León-Escamilla, E Alejandro; Wang, Fei; Miller, Gordon J; Corbett, John D

2009-05-18

136

[Study on ultraviolet upconversion emissions of Gd3+ induced by Tm3+ under 980 nm excitation].  

PubMed

Series of Tm3+/Yb3+ co-doped GdF3 powders were synthesized through an easy and mild hydrothermal method. The phase and purity of powders were characterized by powder X-ray diffraction (XRD) (Rigaku RU-200b). The morphologies of the samples were characterized by field emission scanning electron microscopy (FE SEM) (Hitachi S-4800). The ultraviolet (UV) up-conversion (UC)emission spectra were recorded by a fluorescence spectrophotometer (Hitachi F-4500) with a 980 nm semiconductor continuous wave laser diode as the excitation source. And the luminescent dynamics was measured by excitation with 980 nm using an optical parameter oscillator (OPO) laser pumped by a pulsed Nd : YAG laser with a pulse duration of 10 ns, repetition frequency of 10 Hz, and the signal was recorded by using a monochromator and an oscillograph. Under 980 nm excitation, Gd3+, acting as a kind of host ion in the studied system, and its UV UC emissions were observed and studied. The luminescent dynamics of the characteristic emission of Gd3+ (311.6 nm, 6P7/2 --> 8S7/2) was explored and studied. The luminescent dynamics analysis results indicated that, on UV UC emissions of Gd3+, Yb3+ ions served as primary sensitizer ions successively transferring energy to Tm3+ to populate the 3P2 level. Then, Tm3+ ions served as secondary sensitizer ions transferring energy to populate the multiple 6 I(J) states of Gd3+ 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6 I(J) (Gd3+). Further, 6D(J) levels were populated through other energy transfer processes between Gd3+ and Yb3+ or Tm3+. Finally, UV UC emissions from the excited 6D9/2, 6 I(J), 6P5/2, and 6P7/2 states to the ground state 8S7/2 were observed. Meanwhile, Tm3+ acted as activator in its own UC emissions, and the article did not put emphasis on those except the 3P2 and 1 I6 levels to the ground state 3 H6 transitions. Especially, the dependences of UV UC emissions of Gd3+ on the Yb3+ concentrations, the Tm3+ concentrations, the annealing temperatures, and the excitation power densities of the 980 nm semiconductor continuous wave laser diode were studied, too. PMID:20496672

Cao, Chun-Yan; Yu, Xiao-Guang; Qin, Wei-Ping; Zhang, Ji-Sen

2010-03-01

137

Probing dual mode emission of Eu3+ in garnet phosphor  

NASA Astrophysics Data System (ADS)

Eu3+ doped and Eu3+, Yb3+ co-doped Gd3Ga5O12 phosphors have been developed by facile solid state reaction method which can be easily scaled-up in large quantity. The synthesis has been optimized to get a single phase material at 1300 °C. The phase and crystal parameters have been analyzed by using X-ray diffraction measurement. Photoluminescence excitation (monitored for the 5D0 ? 7F1 transition of Eu3+) depicts that the active ion (Eu3+) can be excited through direct excitation into 4f band of Eu3+, through charge transfer band (Eu3+-O2-) excitation and also through the excitation into 8S7/2 ? 6IJ intra f-f transition of Gd3+ ion, which significantly all together cover a broad excitation region in 200-420 nm. In addition, in the presence of Yb3+ ions, the emission is also achieved by near infrared excitation (976 nm), through a typical upconversion (UC) process. Thus, the material efficiently behaves as a dual mode emitting phosphor (emission is achieved both through normal fluorescence and through UC process). The conversion efficiency of silicon solar cells is only 15% of terrestrial solar energy for 200-400 nm region and also the sub-band gap energy (in infrared region) is lost as heat; therefore, this kind of dual mode phosphors may be used to overcome the above mentioned incomplete utilization of the solar spectrum and can open realm of new possibilities for energy harvesting.

Singh, S. K.; Gi Lee, Dong; Soo Yi, Soung; Jang, Kiwan; Shin, Dong-Soo; Hyun Jeong, Jung

2013-05-01

138

Phase equilibrium and intermediate phases in the Eu-Sb system  

SciTech Connect

Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu-Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor-solid-liquid equilibrium since intermediate phases except Eu{sub 4}Sb{sub 3} evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T-x diagram. Six stable phases were identified: two phases, EuSb{sub 2} and Eu{sub 4}Sb{sub 3}, melt congruently at 1045{+-}10 deg. C and 1600{+-}15 deg. C, the Eu{sub 2}Sb{sub 3}, Eu{sub 11}Sb{sub 10}, Eu{sub 5}Sb{sub 4}, and Eu{sub 5}Sb{sub 3} phases melt incongruently at 850{+-}8 deg. C, 950{+-}10 deg. C, 1350{+-}15 deg. C, and 1445{+-}15 deg. C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu{sub 4}Sb{sub 3}, the most refractory compound, was determined. The topology of the Eu-Sb phase diagram was considered together with that of the Yb-Sb system. - Graphical abstract: The high-temperature range of the T-x phase diagram for the Eu-Sb system. Highlights: > The phase relations in the Eu-Sb system were studied over a large composition and temperature scale. > The liquidus and solidus lines of the T-x diagram were well established using effective techniques. > In the system, six binary phases are stable and they melt incongruently except EuSb{sub 2} and Eu{sub 4}Sb{sub 3}. > Incongruent evaporation was found to be typical of all the phases besides Eu{sub 4}Sb{sub 3}.

Abdusalyamova, M.N. [Institute of Chemistry of Tajik Academy of Sciences, Ajni Str. 299/2, 734063 Dushanbe (Tajikistan); Vasilyeva, I.G., E-mail: kamarz@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Siberian Branch, Lavrentiev Avenue, 3, 630090 Novosibirsk (Russian Federation)

2011-10-15

139

Upconversion emission in (Ln,Yb):KLu(WO4)2 nanocrystals for white light generation  

NASA Astrophysics Data System (ADS)

Optical active lanthanides ions in double tungstates exhibit high emission cross section with low concentration quenching. Production of double tungstates nanocrystals doped with lanthanide ions is suitable for applications in white light emitters if high quantum yield is reached. In this work lanthanide doped (Ln:Yb):KLu(WO4)2 nanocrystals (Ln = Er, Tm, Ho) upconversion emission properties have been study after 980 nm diode laser excitation at 14-334 W/cm2. From CIE chromaticity theory a possible mixture weight ratio to obtain a white light emitter powder was predicted. Luminescence under 980 nm of the (Ln:Yb):KLu(WO4)2 nanocrystals was study and decay times under 460 nm was measured. Reduction of the upconversion quantum yield was observed in the case of physical mixture of nanocrystals.

Barrera, E. W.; Pujol, M. C.; Carvajal, J. J.; Mateos, X.; Solé, R.; Massons, J.; Speghini, A.; Bettinelli, M.; Cascales, C.; Aguiló, M.; Díaz, F.

2014-04-01

140

Thermoluminescence responses of the Yb- and Yb-Tb-doped SiO2 optical fibers to 6-MV photons.  

PubMed

Characteristics of the thermoluminescence (TL) responses of Yb- and Yb-Tb-doped optical fibers irradiated with 6MV photons are reported. The concentration of Yb in the Yb-doped optical fiber was 0.26mol%; the concentrations of Yb and Tb in the Yb-Tb-doped optical fiber were 0.62 and 0.2mol%, respectively. The TL dose responses are linear in the dose range 0.5-4Gy. The radiation sensitivity of the Yb-Tb material is almost two orders of magnitude higher than the sensitivity of the material doped with Yb alone. PMID:24973463

Sahini, M H; Hossain, I; Wagiran, H; Saeed, M A; Ali, H

2014-09-01

141

Facing the Future (TM)  

NSDL National Science Digital Library

Facing the Future(TM) provides educational materials and professional development opportunities for educators that address environmental issues such as population growth, poverty and equity, consumption trends, peace and conflict, health, climate change, and sustainability. These materials include textbooks for students, service learning and action projects, and curriculum units with activities and lesson plans that meet educational standards. The organization's web site provides information on downloading and/or purchasing these materials, information on a featured curriculum unit, news and event announcements, and information on professional development opportunities for in-service and pre-service educators.

142

Effects of quadrupole interactions in rare-earth phosphates RPO 4 (R = Y, Tb-Yb)  

NASA Astrophysics Data System (ADS)

The systematic experimental and theoretical investigations of rare-earth (RE) ion contribution to the temperature dependencies of the Young moduli and lattice parameters were performed for RE phosphates RPO 4 (R = Y, Tb-Yb). An anomalous behavior of the Young moduli and lattice parameters for the investigated phosphates in comparison with YPO 4 and a strong softening of Young's moduli for TbPO 4 and TmPO 4 were discovered. It is shown that anomalies of Young's moduli are well described by the temperature dependencies of strain susceptibilities of RE ions calculated utilizing available crystal-field parameters. The thermal expansion anomalies can be described in terms of temperature dependencies of quadrupole moments. Values of magnetoelastic coefficients were estimated. For Tb and Tm phosphates, the strong softening of Young's moduli is ascribed to the correlation enhancement of relevant strain susceptibilities.

Sokolov, V. I.; Kazei, Z. A.; Kolmakova, N. P.

1992-01-01

143

The Social Context of TM.  

ERIC Educational Resources Information Center

Reports on research which indicates that much of the meaning of transcendental meditation (TM) is constructed from preexisting understandings and expectations. Various influences for the impact of TM are suggested including the language, rules, and world view of the social environment. (RC)

McLeod, John

1981-01-01

144

New intermetallics YbAu2In4 and Yb2Au3In5.  

PubMed

The intermetallic compounds YbAu(2)In(4) and Yb(2)Au(3)In(5) were obtained as single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data of YbAu(2)In(4) showed that it crystallizes as a new structure type in the monoclinic space group P2(1)/m and lattice constants a = 7.6536(19) Å, b = 4.5424(11) Å, c = 9.591(2) Å and ? = 107.838(4)°. The YbAu(2)In(4) compound is composed of a complex [Au(2)In(4)](3-) polyanionic network in which the rare-earth ions are embedded. Yb(2)Au(3)In(5) crystallizes in the polar space group Cmc2(1) with the Y(2)Rh(3)Sn(5) type structure and lattice constants a = 4.5351(9) Å, b = 26.824(5) Å, and c = 7.4641(15) Å. The gold and indium atoms define a complex three-dimensional [Au(3)In(5)] network with a broad range of Au-In (2.751(2) Å-3.0518(16) Å) and In-In (3.062(3) Å-3.3024(19) Å) distances. Magnetic susceptibility measurements of YbAu(2)In(4) revealed a transition at 25 K. Below the transition, the susceptibility of YbAu(2)In(4) follows Curie-Weiss behavior with an effective paramagnetic moment of 0.79 ?(B)/Yb. Magnetic susceptibility measurements on Yb(2)Au(3)In(5) show a mixed valent ytterbium and the magnetic moment within the linear region (<100 K) of 1.95 ?(B)/Yb. Heat capacity data for YbAu(2)In(4) and Yb(2)Au(3)In(5) give Debye temperatures of 185 and 153 K, respectively. PMID:20961134

Sebastian, C Peter; Salvador, James; Martin, Joshua B; Kanatzidis, Mercouri G

2010-11-15

145

K-shell absorption jump factors and jump ratios in elements between Tm ( Z = 69) and Os ( Z = 76) derived from new mass attenuation coefficient measurements  

NASA Astrophysics Data System (ADS)

The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm 2O 3, Yb 2O 3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56-77 keV, were done in a transmission geometry utilizing the K ?1 , K ?2 , K ?1 and K ?2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV ?-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.

Kaya, Necati; T?ra?o?lu, Engin; Apayd?n, Gökhan; Ayl?kc?, Volkan; Cengiz, Erhan

2007-08-01

146

Anomalies in the Young modulus at structural phase transitions in rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu)  

SciTech Connect

The elastic properties of rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80-300 K. The strong softening of the Young modulus {Delta}E(T)/E{sub 0} Almost-Equal-To -(0.1-0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T{sub s} and hysteresis {Delta}T{sub s} increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite is not a 'soft' mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller.

Kazei, Z. A., E-mail: kazei@plms.phys.msu.ru; Snegirev, V. V.; Andreenko, A. S. [Moscow State University (Russian Federation); Kozeeva, L. P. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation)

2011-08-15

147

Monodisperse lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm): morphology controlled synthesis, up-conversion luminescence and in vitro cell imaging  

NASA Astrophysics Data System (ADS)

Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise.Lanthanide oxyfluorides LnOF (Ln = Y, La, Pr-Tm) nano/micro-materials with a variety of well-defined morphologies including nanorods, nanospindles, nanorod-bundles and nanospheres, have been successfully synthesized via a facile precipitation technique followed by a heating treatment. It is found that the pH values, fluoride sources and dosage of urea in the initial reaction systems play critical roles in the morphology determination of the LnOF products and the possible formation mechanism for these diverse architectures has been presented. XRD, FT-IR, TG-DTA, SEM, TEM, as well as up-conversion (UC) luminescence spectra are used to characterize the synthesized samples. Under 980 nm NIR laser excitation, red, green and blue UC luminescence are observed from Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ co-doped YOF nanospheres. The MTT assay indicates that YOF nanospheres exhibit good biocompatibility. Especially, the emission spectrum of YOF: 0.20Yb3+, 0.04Er3+ nanospheres is dominated by a single red emission at 660 nm, which falls into the ``optical window'' of biological tissues. The application of YOF: 0.20Yb3+, 0.04Er3+ nanospheres in the cell imaging is also investigated, which shows a bright-red emission without background noise. Electronic supplementary information (ESI) available: The XRD patterns of GdOF, ErOF, Tm(OF)1.93 and YOF obtained after calcinations at 800 °C for 3 h and the corresponding standard data of GdOF, ErOF, Tm(OF)1.93 and YOF. The accurate amounts of Ln3+ and F- for LaOF, GdOF, ErOF and YOF: 0.20Yb3+, 0.04Er3+, respectively. SEM images of the ErOF precursor under different experimental conditions (a) pH = 2, urea/Ln3+ = 66, with LiF; (b) pH = 2, urea/Ln3+ = 66, with KF; (c) pH = 6, urea/Ln3+ = 66, with NaF; (d) pH = 10, urea/Ln3+ = 66, with NaF; (e) pH = 2, urea/Ln3+ = 80, with NaF and (f) pH = 2, urea/Ln3+ = 100, with NaF. See DOI: 10.1039/c4nr00384e

Zhang, Yang; Li, Xuejiao; Hou, Zhiyao; Lin, Jun

2014-05-01

148

LiquichekTM Diabetes Control  

E-print Network

LiquichekTM Diabetes Control Bio-Rad Laboratories D I A B E T E S / H E M O G L O B I N C O N T R O L S #12;LiquichekTM Diabetes Control Hemoglobin A1C Hemoglobin, Total A liquid human whole blood based product designed to monitor the performance of hemoglobin tests associated with diabetes

Rodriguez, Carlos

149

Near infrared activation of an anticancer Pt(IV) complex by Tm-doped upconversion nanoparticles.  

PubMed

The Pt(IV) complex cis,cis,trans-[Pt(NH3)2(Cl)2(O2CCH2CH2CO2H)2] is photoactivated by near infrared light (980 nm) using NaYF4:Yb(3+)/Tm(3+)@NaYF4 core-shell upconversion nanoparticles. Coupling of this cisplatin precursor with the biocompatible PEGylated phospholipid DSPE-PEG(2000)-NH2 affords a valuable approach to decorate the surface of the nanoparticles, providing novel photoactivatable nanomaterials capable of releasing Pt(II) species upon NIR light excitation. PMID:25536114

Ruggiero, Emmanuel; Hernández-Gil, Javier; Mareque-Rivas, Juan C; Salassa, Luca

2015-01-22

150

YbNiSn, a ferromagnetic Kondo lattice  

Microsoft Academic Search

We present an investigation of the low temperature properties of the ternary intermetallic alloy YbNiSn by X-ray and neutron diffraction, resistivity, magnetisation and 170Yb Mössbauer spectroscopy measurements. It is shown that YbNiSn is a ferromagnet (Tc = 5.65 K) with the Yb3+ magnetic moments lying along the orthorhombic c axis. At low temperatures a strong anisotropy of the interionic exchange

P. Bonville; P. Bellot; J. A. Hodges; P. Imbert; G. Jéhanno; G. Le Bras; J. Hammann; L. Leylekian; G. Chevrier; P. Thuéry; L. D'Onofrio; A. Hamzic; A. Barthélémy

1992-01-01

151

Valencies of Eu in CaS:Eu, La  

NASA Astrophysics Data System (ADS)

Photoluminescence of La and Eu codoped CaS prepared in sodium and potassium polysulfide flux was studied. The emission spectra of CaS:Eu prepared in both fluxes show a broad band at 650 nm due to the f-d transition of Eu 2+. When potassium polysulfide flux is used, the emission from Eu 2+decreases and the line emission of Eu 2+appears with concentration of codoped La 3+. However, when sodium polysulfide flux is used, clear line emission spectra of Eu 3+were observed, in addition to the broad band spectrum from recombination process of defects and vacancies in the host matrix. For the first time at room temperature, sharp line spectrum of Eu 3+is observed and this is a strong indication of La 3+-Eu 3+pairing in CaS:Eu, La. EPR intensity of Eu 2+increases with Eu concentration and decreases with La 3+concentration in CaS:Eu, La prepared in potassium polysulfide flux. However, the result of EPR study suggests that only Eu 3+is doped when CaS:Eu, La is prepared in sodium polysulfide flux.

Choi, Han; Kim, Chang-Hong; Pyun, Chong-Hong; Kim, Sung-Jin

1998-06-01

152

Passively modelocked 50 GHz Er:Yb:glass laser  

E-print Network

Passively modelocked 50 GHz Er:Yb:glass laser S.C. Zeller, L. Krainer, G.J. Spu¨hler, R. Paschotta, M. Golling, D. Ebling, K.J. Weingarten and U. Keller A diode-pumped Er:Yb:glass miniature laser has on power budget and space requirements. We recently presented a passively modelocked Er:Yb:glass laser

Keller, Ursula

153

Semiconducting properties of Tm doped Yb-ZnO films by spray pyrolysis  

NASA Astrophysics Data System (ADS)

In this work, we have investigated the structural, optical and electrical properties of rare earth co-doped zinc oxide thin films prepared by spray pyrolysis technique. X-ray diffraction has shown that the films are polycrystalline and textured with the c-axis of the wurtzite structure along the growth direction. Scanning electronic microscopy and transmission electronic microscopy were used to study the films composition and morphology. Photoluminescence measurements showed that all the films have a strong emission band at around 380 nm. Layers with electrical resistivity values as low as 5.7 × 10-2 ? cm were obtained.

Chaki, Imane; Belayachi, Azzam; El Bahraoui, Toufik; Regragui, Mohamed; Abd-Lefdil, Mohamed

2014-12-01

154

Stability, structural, and electronic properties of atomic chains on Yb/Ge(111)3×2 studied by STM and STS  

NASA Astrophysics Data System (ADS)

By means of scanning tunneling microscopy and spectroscopy (STM/STS), we have investigated the stability and the structure of atomic chains on Yb/Ge(111)3×2 . STM allows the identification of different building blocks of this reconstruction, depending on the bias polarity and voltage, and validates the honeycomb chain-channel (HCC) structure with the Ge?Ge double bond and metal coverage of 1/6 ML for Yb/Ge(111)3×2 , in agreement with the recent photoemission study [Kuzmin , Phys. Rev. B 75, 165305 (2007)]. The Yb atoms are found to be adsorbed on similar sites in the well-defined ×2 rows. Locally, such rows are distorted, leading to the ×4 periodicity, where the Yb atoms are adsorbed on two different sites that are well consistent with T4 and H3 sites. It is also assumed that Yb atoms can fluctuate rapidly between the neighboring T4 and H3 sites, leading to continuous rows observed together with the ×2 rows in STM images. The stability of Ge honeycomb chain is controlled by the presence of Yb atom per two (3×1) surface units in average, which results in the donation of one electron from Yb to the surface per (3×1) unit. When this density is locally changed, the Ge honeycomb chain is found to be broken. The inner structure of the Ge honeycomb chain is visualized in STM and shows dimerized features without any apparent buckling. The STM observations also account for why the double periodicity is missing in the low-energy electron diffraction pattern from Yb/Ge(111)3×2 . The local electronic structure of this reconstruction, namely the Yb rows and Ge honeycomb chains, is studied by STS. The results support the HCC structure with the Ge?Ge double bond. It is believed that the present study elucidates the difference between the (3×2) reconstructions of Yb and Eu on Ge(111) and those of alkaline-earth and rare-earth metals on Si(111).

Kuzmin, M.; Laukkanen, P.; Perälä, R. E.; Punkkinen, M. P. J.; Ahola-Tuomi, M.; Lång, J.; Väyrynen, I. J.

2010-04-01

155

75 FR 78234 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...13764-000; Project No. 13786-000] Lock+ TM Hydro Friends Fund XXXIV; FFP Missouri 5...Emsworth Lock and Dam Projects: Lock+ TM Hydro Friends Fund XXXIV's proposed project...12-14-10; 8:45 am] BILLING CODE...

2010-12-15

156

Optical properties and laser performance of Yb-doped vanadates grown by floating zone method  

NASA Astrophysics Data System (ADS)

We grew high-quality Yb:LuVO4, Yb:GdVO4, and Yb:YVO4 by the floating zone (FZ) method. It was found by measurement that these crystals had favorable optical properties. A maximum absorption coefficient of 27 cm-1 (FWHM) and a fluorescence bandwidth with a 20 nm (FWHM) were observed for Yb:LuVO4 at a Yb doping level of 4 at. %. Finally, we demonstrated the lasing performances of Yb:LuVO4, Yb:GdVO4, and Yb:YVO4. To our knowledge, this is the first time that a Yb-doped vanadate grown by the FZ method has been used as a laser, and 4 at.% Yb doping of the Yb:LuVO4 and Yb:YVO4 is the highest level of doping at which laser oscillation occurs among the Yb-doped vanadates.

Nakamura, Shinki; Agata, Taishi; Ogawa, Takayo; Wada, Satoshi; Higuchi, Mikio

2013-09-01

157

Origin2000TM and Onyx2TM Performance Tuning and Optimization  

E-print Network

Origin2000TM and Onyx2TM Performance Tuning and Optimization Guide Document Number 007-3430-002 #12;Origin2000TM and Onyx2TM Performance Tuning and Optimization Guide Document Number 007, Indy, IRIX, and Onyx are registered trademarks and the Silicon Graphics logo, InfiniteReality, O2, Onyx

Lu, Paul

158

Open minds. Open doors.TM  

E-print Network

Open minds. Open doors.TM John Parmigiani, Director of Industrial Research School of Mechanical for students and faculty John Parmigiani October 17, 2013 #12;Open minds. Open doors.TM John Parmigiani Partnering The Process #12;Open minds. Open doors.TM John Parmigiani, Director of Industrial Research School

Escher, Christine

159

75 FR 2129 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...13625-000] Lock+ TM Hydro Friends Fund XXX, LLC; Notice of Preliminary Permit Application...13, 2009, Lock+ TM Hydro Friends Fund XXX, LLC filed an application, pursuant to...Krouse, Lock+ TM Hydro Friends Fund XXX, LLC, 5090 Richmond Avenue...

2010-01-14

160

76 FR 48840 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...14136-000; 14139-000] Lock+\\TM\\ Hydro Friends Fund XXXV Riverbank...Applications On April 1, 2011, Lock+\\TM\\ Hydro Friends Fund XXXV (Hydro...Managing Partner, Lock+\\TM\\ Hydro Friends Fund XXXV, 5090...45 am] BILLING CODE...

2011-08-09

161

Theoretical analysis of characteristics for 2 ?m Tm3+:Ho3+ co-doped silica fiber laser pumped by a 1550 nm fiber laser  

NASA Astrophysics Data System (ADS)

We established a theoretical model of 2 ?m Tm3+:Ho3+ co-doped silica fiber laser pumped by a 1550 nm fiber laser based on the rate-equation theory and performed the numerical simulation using Runge-Kutta algorithm and Newton-Raphson algorithm. The intracavity power distributions of both pump and laser of the Tm3+:Ho3+ co-doped silica fiber laser based on the Tm3+:Ho3+ co-doped silica fiber supplied by the National Optics Institute in Canada (NOIC) were obtained. The effects of the output reflectivity R4(?s) at the output laser wavelength ?s and the concentrations of Tm3+ and Ho3+ in the fiber on laser output performance were analyzed. In order to achieve a high laser output power, the optimal R4(?s) of 0.13 was verified and the optimal Tm:Ho ratio of 1:2.4 was proposed. Finally, better output performance for the fiber laser based on the optimized Tm3+:Ho3+ co-doped silica fiber was obtained than the laser using the fiber supplied by the NOIC. This theoretical model and numerical simulation results will guide the fabrication of 2 ?m Tm3+:Ho3+ co-doped all-fiber lasers pumped by 1600-nm-band (1500-1750 nm) Er3+:Yb3+ co-doped silica fiber lasers.

Feng, Ting; Yan, Fengping; Peng, Wanjing; Li, Qi; Tan, Siyu; Wang, Jing; Wen, Xiaodong

2012-07-01

162

Luminescence properties of different Eu sites in LiMgPO4:Eu(2+), Eu(3+).  

PubMed

The effect of temperature on the luminescence properties of LiMgPO4 doped with Eu(3+) and Eu(2+) are presented. Depending on the excitation wavelength, luminescence spectra consist of two distinct broad emission bands peaking at 380?nm and 490?nm related to 4f(6)5d(1) ? 4f(7) ((8)S7/2) luminescence of Eu(2+) and to europium-trapped exciton, respectively, and/or several sharp lines between the 580?nm and 710?nm region, ascribed to the (5)D0 ? (7)FJ (J = 0, 1, 2, 3 and 4) transitions in Eu(3+). To explain all the features of the Eu(2+) and Eu(3+) luminescence we discussed the existence of two different Eu sites substituting for Li(+), with short and long distance compensation. The evident effect of increasing the intensity of the Eu(2+) luminescence with increasing temperature was observed. It was considered that the charge compensation mechanism for Eu(3+) and Li(+) as well as Eu(2+) replacing Li(+) in the LiMgPO4 is a long distance compensation that allows for the existence of some of the europium ions either as Eu(3+) at low temperature or as Eu(2+) at high temperature. We concluded that Eu(2+) in the Li(+) site with long distance compensation yields only 4f(6)5d(1) ? 4f(7) luminescence, whereas Eu(2+) in the Li(+) site with short distance compensation yields 4f(6)5d(1) ? 4f(7) luminescence and europium-trapped exciton emission. PMID:25180708

Baran, A; Mahlik, S; Grinberg, M; Cai, P; Kim, S I; Seo, H J

2014-09-24

163

Luminescence properties of different Eu sites in LiMgPO4:Eu2+, Eu3+  

NASA Astrophysics Data System (ADS)

The effect of temperature on the luminescence properties of LiMgPO4 doped with Eu3+ and Eu2+ are presented. Depending on the excitation wavelength, luminescence spectra consist of two distinct broad emission bands peaking at 380?nm and 490?nm related to 4f65d1 ? 4f7 (8S7/2) luminescence of Eu2+ and to europium-trapped exciton, respectively, and/or several sharp lines between the 580?nm and 710?nm region, ascribed to the 5D0 ? 7FJ (J = 0, 1, 2, 3 and 4) transitions in Eu3+. To explain all the features of the Eu2+ and Eu3+ luminescence we discussed the existence of two different Eu sites substituting for Li+, with short and long distance compensation. The evident effect of increasing the intensity of the Eu2+ luminescence with increasing temperature was observed. It was considered that the charge compensation mechanism for Eu3+ and Li+ as well as Eu2+ replacing Li+ in the LiMgPO4 is a long distance compensation that allows for the existence of some of the europium ions either as Eu3+ at low temperature or as Eu2+ at high temperature. We concluded that Eu2+ in the Li+ site with long distance compensation yields only 4f65d1 ? 4f7 luminescence, whereas Eu2+ in the Li+ site with short distance compensation yields 4f65d1 ? 4f7 luminescence and europium-trapped exciton emission.

Baran, A.; Mahlik, S.; Grinberg, M.; Cai, P.; Kim, S. I.; Seo, H. J.

2014-09-01

164

Elastic anomalies of charge ordering in Yb 4As 3  

NASA Astrophysics Data System (ADS)

Elastic constants of the mixed valence compound Yb 4As 3 with extremely low carrier 0.001 per Yb atom have been measured by the ultrasonic method. We found that the transverse C44 mode exhibits a pronounced softening around the structural phase transition point at Tc = 292 K due to the charge ordering of Yb 3+ ions along <111 direction. We interpret the softening of C44 with the coupling of the strain ?yz, ?zx and ?xy to charge fluctuation mode processing the electric quadrupole moment in Yb 3+ linear chain.

Goto, T.; Nemoto, Y.; Nakamura, S.; Ochiai, A.; Suzuki, T.

1997-02-01

165

Double beta decay with large scale Yb-loaded scintillators  

NASA Astrophysics Data System (ADS)

The potential of large scale Yb-loaded liquid scintillators as proposed for solar neutrino spectroscopy are investigated with respect to double beta decay. The potential for ?-?- decay of 176Yb as well as the ?+/EC decay for 168Yb is discussed. Not only getting for the first time an experimental half-life limit on 176Yb decay, this will even be at least comparable or better than existing ones from different isotopes, for the first time a realistic chance to detect ?+/EC decay exists. Effects of MeV-neutrinos are discussed as well.

Zuber, K.

2000-07-01

166

Scaling of Yb-Fiber Frequency Combs  

NASA Astrophysics Data System (ADS)

Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

2010-06-01

167

Melt processing of Yb-123 tapes  

SciTech Connect

The innovation of a simple, scalable process for manufacturing long-length conductors of HTS is essential to potential commercial applications such as power cables, magnets, and transformers. In this paper the authors demonstrate that melt processing of Yb-123 tapes made by the PIT route is an alternative to the coated conductor and Bi-2223 PIT tape fabrication techniques. Ag-clad Yb-123 tapes were fabricated by groove rolling and subsequently, melt processed in different oxygen partial pressures in a zone-melting furnace with a gradient of 140 C/cm. The transition temperatures measured were found to be around 81 K undermost processing conditions. EPMA of the tapes processed under different conditions show the 123 phase to be Ba deficient and Cu and Yb rich. Critical current was measured at various temperatures from 77 K to 4.2 K. The J{sub c} increased with decrease in pO{sub 2}. The highest I{sub c} obtained was 52 A at 4.2 K.

Athur, S. P.; Balachandran, U.; Salama, K.

2000-02-17

168

Interpretation of neutron magnetic scattering in the Kondo lattices YbPd 2 Si 2 and YbAgCu 4  

Microsoft Academic Search

We present an interpretation of published neutron inelastic scattering spectra in the Kondo lattices YbPd2Si2 and YbAgCu4 obtained in terms of the Anderson impurity model, describing the hybridisation of the 4f Yb electrons with the band electrons, and also including the crystal electric field interaction. In YbPd2Si2, the tetragonal crystal field parameters were determined. In YbAgCu4 the crystal field interaction

G. Polatsek; P. Bonville

1992-01-01

169

Eu{sub 3}F{sub 4}S{sub 2}: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF{sub 2}.(EuFS){sub 2}  

SciTech Connect

Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb{sub 3}F{sub 4}S{sub 2} instead. With Eu{sub 3}F{sub 4}S{sub 2} another isotypic representative has now been synthesized. Eu{sub 3}F{sub 4}S{sub 2} (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 deg. C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF{sub 2}-type EuF{sub 2} is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu{sup 2+}) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu{sup 3+}) exhibits a monocapped square antiprismatic coordination sphere with four F{sup -} and five S{sup 2-} anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu{sub 3}F{sub 4}S{sub 2} show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) mu{sub B} per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu{sup II})(Eu{sup III}){sub 2}F{sub 4}S{sub 2} only one third of the europium centers in Eu{sub 3}F{sub 4}S{sub 2} carry permanent magnetic moments. {sup 151}Eu-Moessbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu{sup 2+} and Eu{sup 3+}, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu{sup 2+}/Eu{sup 3+} fraction can be detected. - Graphical abstract: Crystal structure and {sup 151}Eu-Moessbauer spectra of mixed-valent Eu{sub 3}F{sub 4}S{sub 2}.

Grossholz, Hagen; Hartenbach, Ingo [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Kotzyba, Gunter [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Poettgen, Rainer, E-mail: pottgen@uni-muenster.d [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Trill, Henning; Mosel, Bernd D. [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Schleid, Thomas, E-mail: schleid@iac.uni-stuttgart.d [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)

2009-11-15

170

New ternary phosphides and arsenides. Syntheses, crystal structures, physical properties of Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}  

SciTech Connect

Three new europium pnictides Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3} have been synthesized and their structures were determined by single-crystal X-ray diffraction. Eu{sub 2}ZnP{sub 2} is isotypic with Yb{sub 2}CdSb{sub 2} (Cmc2{sub 1} (No. 36); cell parameters a=4.1777(7) Å, b=15.925(3) Å, c=7.3008(12) Å), while the latter two compounds crystallize with the Ba{sub 2}Cd{sub 2}Sb{sub 3} structure type (C2/m (No. 12); cell parameters a=15.653(5)/16.402(1) Å, b=4.127(1)/4.445(4) Å, c=11.552(4)/12.311(1) Å and ?=126.647(4)/126.515(7)° for Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, respectively). Magnetic susceptibility measurements in the interval 5–300 K confirm paramagnetic behavior and effective magnetic moments characteristic of Eu{sup 2+} ([Xe] 4f{sup 7}) ground states. Temperature-dependent electrical conductivity measurements also prove that Eu{sub 2}Cd{sub 2}As{sub 3} is a semiconducting compound with a narrow band gap of 0.059 eV below 100 K. According to TG/DSC analyses, Eu{sub 2}Cd{sub 2}As{sub 3} starts to decompose at about 950 K. - Graphical abstract: A polyhedral view of the crystal structure of new pnictides Eu{sub 2}T{sub 2}Pn{sub 3} (T=Zn or Cd; Pn=P or As). Display Omitted - Highlights: • Three new ternary pnictide Zintl compounds, Eu{sub 2}ZnP{sub 2}, Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}, have been synthesized and characterized. • The europium cations are divalent and ferromagnetically coupled in both Eu{sub 2}Zn{sub 2}P{sub 3} and Eu{sub 2}Cd{sub 2}As{sub 3}. • Eu{sub 2}Cd{sub 2}As{sub 3} has a very small band gap of 0.06 eV and starts to decompose over 950 K.

Wang, Jian [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China); Xia, Sheng-Qing, E-mail: shqxia@sdu.edu.cn [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China); Tao, Xu-Tang [State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China); Schäfer, Marion C. [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

2013-09-15

171

Monodisperse and core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties  

SciTech Connect

The core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles were realized by coating the Lu{sub 2}O{sub 3}:Ln{sup 3+} phosphors onto the surface of non-aggregated, monodisperse and spherical SiO{sub 2} particles by the Pechini sol-gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800 Degree-Sign C annealed sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln{sup 3+} ions under ultraviolet-visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays. - Graphical Abstract: Representative SEM and TEM images of the core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Eu{sup 3+} particles; CIE chromaticity diagram showing the emission colors for SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+}; Multicolor emissions of SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles. Highlights: Black-Right-Pointing-Pointer The core-shell particles were realized by coating the phosphors onto the surface of SiO{sub 2} particles. Black-Right-Pointing-Pointer The sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores. Black-Right-Pointing-Pointer The particles show different light emission colors corresponding to Ln{sup 3+} ions. Black-Right-Pointing-Pointer They have potential applications in fluorescent lamps and field emission displays.

Xu, Zhenhe, E-mail: xuzh056@163.com [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China); Feng, Bin [China National Aviation Fuel Group Corporation, Planning and Development Department, Beijing 100088 (China)] [China National Aviation Fuel Group Corporation, Planning and Development Department, Beijing 100088 (China); Bian, Shasha; Liu, Tao; Wang, Mingli; Gao, Yu; Sun, Di; Gao, Xin [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China); Sun, Yaguang, E-mail: yaguangsun@yahoo.com.cn [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)

2012-12-15

172

Phase formation and melt processing of Yb- 123.  

SciTech Connect

The formation of Yb-123 has been studied at different temperatures in air and in reduced oxygen partial pressure. It is found that the stability and/or the formation kinetics of Yb-123 phase is a major hurdle in manufacturing phase-pure Yb-123 in air. However, under reduced oxygen partial pressure, Yb-123 forms rapidly and more than 90% phase-pure Yb-123 is achieved within three sintering steps. Rods made from this powder were melt-processed in air and showed a T{sub c} of 90 K. Kinetic studies performed by interrupting the growth during the directional solidification of these rods revealed a growth mechanism similar to that of Y-123 and a maximum growth rate of 7.2 mm/h for a stable planar interface. EPMA of the interface showed the liquid to be rich in barium cuprates with a Ba:Cu ratio of 1:3.

Athur, S. P.; Putman, P.; Balachandran, U.; Salama, K.; Energy Technology; Univ. of Houston

1998-01-01

173

Stereocorrelation of Landsat TM images  

NASA Technical Reports Server (NTRS)

A digital elevation model (DEM) developed from Landsat TM images of a rugged terrain area in north Georgia by automated stereocorrelation techniques yielded an rms error (z), RMSE(z), value of + or - 42 m. Based on the B/H ratio of 0.18 for the Landsat data, this Z-error corresponds to a planimetric correlation accuracy of about + or - 0.3 pixels, confirming that precise correlation can be achieved with operational satellite data. Contours at a 100-m interval interpolated from the DEM show a deviation of + or - 33 m from reference contours obtained from existing 1:24,000-scale maps. The 28.5-m pixel resolution and the weak B/H ratio impose limitations on the accuracy that can be achieved with Landsat TM data. However, it is anticipated that RMSE(z) values of + or - 10 m or less can be achieved with SPOT-1 panchromatic stereo images of 10-m resolution recorded at B/H ratios of 0.5 to 1.0. DEMs generated by stereocorrelation techniques can be used to create orthoimages, perspective views, and topographic map products.

Ehlers, Manfred; Welch, R.

1987-01-01

174

170 Yb Mossbauer study of the YbCd 5:7 binary quasi-crystal and related phases  

E-print Network

point), and then water quenched. As YbCd 6 does not melt congruently, this sample had to be further annealed at 575 Ã? C for three hours. The melting point of YbCd (796 Ã? C) lies above the boiling point of Cd

Ryan, Dominic

175

JIS YB Lead Complex Perovskite Ferroelectric Material  

Microsoft Academic Search

Excess WO3 and higher sintering temperature were used for decreasing the temperature dependence of the dielectric constant in Pb(Mg1\\/3Nb2\\/3)O3-PbTiO3-Pb(Mg1\\/2W1\\/2)O3 ternary systems. Under some conditions, materials with both JIS YB specifications (dielectric constant change less than 10% over the temperature range from -25 to 85°C) and high dielectric constant, 5000-7400, were obtained. In the materials, core-shell-like distributions of B-site components were

Fumio Uchikoba; Kentaro Sawamura

1992-01-01

176

Luminescent and scintillation properties of YAG:Tm and YAG:Ce,Tm single crystalline films  

NASA Astrophysics Data System (ADS)

The paper is dedicated to studying the luminescent and scintillation properties of the single crystalline films (SCF) of Tm and Tm-Ce doped Y3Al5O12 garnets grown by the liquid phase epitaxy method. We have found that the effective Tm ? Ce energy transfer is observed in YAG:Ce,Tm SCF. As a result of such transfer, the scintillation light yield of YAG:Ce,Tm SCF under ?-particles excitation can be large in comparison with YAG:Ce SCF counterpart.

Zorenko, Yu.; Gorbenko, V.; Savchyn, V.; Suchocki, A.; Wrzesinski, H.; Walczyk, K.; Fabisiak, K.; Bilski, P.; Twardak, A.

2014-08-01

177

Spectroscopic properties of Eu3+, Dy3+ and Tb3+ ions in lead silicate glasses obtained by the conventional high-temperature melt-quenching technique  

NASA Astrophysics Data System (ADS)

The luminescence properties of selected rare-earth ions in lead silicate glasses have been studied. Europium, dysprosium and terbium ions were chosen as active dopants. Based on excitation and emission measurements as well as luminescence decay analysis, some spectroscopic parameters for these lanthanide ions were determined. In particular, the intensity ratios R/O (Eu3+), Y/B (Dy3+) and G/B (Tb3+) were calculated. Luminescence lifetimes for the 5D0 state of Eu3+ ions, the 4F9/2 state of Dy3+ ions and the 5D4 state of Tb3+ ions were also determined.

?ur, L.; Janek, J.; So?tys, M.; Pisarska, J.; Pisarski, W. A.

2013-11-01

178

77 FR 71590 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...Commission [Project No. 13500-002] Lock+ TM Hydro Friends Fund XI, LLC; Notice of Preliminary...Competing Applications On October 1, 2012, Lock+ TM Hydro Friends Fund XI, LLC filed an application...11-30-12; 8:45 am] BILLING CODE...

2012-12-03

179

75 FR 78233 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...13761-000; Project No. 13770-000] Lock+\\TM\\ Hydro Friends Fund XXXVII; FFP Missouri...Emsworth Back Channel Dam Projects: Lock+ TM Hydro Friends Fund XXXVII's proposed project...12-14-10; 8:45 am] BILLING CODE...

2010-12-15

180

78 FR 26349 - Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...Nos. 13424-002; 14516-000] Lock+\\TM\\ Hydro Friends Fund VI, LLC, FFP Iowa 2...Applications On January 2, 2013, Lock+\\TM\\ Hydro Friends Fund VI, LLC (Hydro Friends...5-3-13; 8:45 am] BILLING CODE...

2013-05-06

181

Crystal growth and luminescence properties of Yb-doped aluminate, gallate, phosphate and vanadate single crystals  

Microsoft Academic Search

(Lu1?xYbx)3Al5O12 (Yb:LuAG), (Y1?xYbx)AlO3 (Yb:YAP), (Y0.9Yb0.1)VO4 (Yb:YVO) and Ca8(La1.98Yb0.02)(PO4)6O2 (Yb:CLPA) single crystals were grown from the melt. Typical double peak spectrum of the Yb3+ Charge Transfer (CT) luminescence was observed in Yb-doped LuAG and YAP. Strong dependence of decay time and intensity on temperature was observed. Concentration quenching effect in Yb-rich Yb:YAP samples results in pronounced 1\\/e decay time shortening below

A. Yoshikawa; M. Nikl; H. Ogino; J. B. Shim; V. V. Kochurikhin; N. Solovieva; T. Fukuda

2005-01-01

182

IBM System pTM Firmware / Microcode Service Strategies and Best Practices IBM System p5TM  

E-print Network

IBM System pTM Firmware / Microcode Service Strategies and Best Practices Page 1 IBM System p5TM Firmware and Microcode Service Strategies and Best Practices IBM CORPORATION® #12;IBM System pTM Firmware.........................................................................................................................................4 Firmware Terminology

183

Heavy Fermion Behavior in Extremely Low Carrier Concentration System Yb4As3  

Microsoft Academic Search

We have investigated the series of Yb pnictides with anti-Th3P4 structure. The valence of Yb varies from about 2 of Yb4Bi3 to 2.25 of Yb4As3 with the decreasing weight of the pnictogen. In the case of Yb4As3, the 4f level is located around the band gap and the charge ordering below about 300 K has been observed. Further, in such

Akira Ochiai; Takashi Suzuki; Tadao Kasuya

1990-01-01

184

Characteristics of amorphous Yb-doped ITO films deposited on polyimide substrate by DC magnetron sputtering  

Microsoft Academic Search

The ITO and Yb-doped ITO (ITO:Yb) films were deposited on polyimide (PI) substrates by DC magnetron sputtering using ITO targets (doped-Yb: 0, 0.57, 3.2 and 7.75at.%) containing different Yb ratios. Film deposition and post-annealing were carried out at room temperature and different temperatures (170°C and 200°C), respectively, in a pure Ar gas atmosphere at 1.0Pa for 1h. The ITO:Yb films

Taedong Jung; Seil Kim; Pungkeun Song

2010-01-01

185

Electronic structure of YbN  

SciTech Connect

Large single crystals of cubic and stoichiometric YbN have been grown. On these crystals we measured the optical reflectivity for photon energies between 1 meV and 12 eV, also at helium temperatures, and performed a Kramers-Kronig analysis to obtain the optical constants. In addition, we measured the Raman effect to obtain further information on the phonon spectra. The electrical conductivity at room and at low temperature and the Hall effect at 300 K served to obtain also the effective mass of the carriers. Also the magnetization and initial susceptibility have been measured. The main important results are that YbN is a self-compensated semimetal with about 10{sup 20} carriers per cm{sup {minus}3}, the occupied 4{ital f}{sup 13} state is about 6 eV below {ital E}{sub {ital F}}, the empty 4{ital f}{sup 14} state is about 0.2 eV above {ital E}{sub {ital F}}, and the effective mass of the carriers is about 2.2{ital m}{sub {ital e}}. In other words the material definitely is not a heavy fermion---but more probably a Kondo system. Nonstoichiometric samples tend to show stronger Kondo features.

Degiorgi, L.; Bacsa, W.; Wachter, P. (Laboratorium fuer Festkoerperphysik, Eidgenoessische Technische Hochschule Zuerich, 8093 Zuerich (Switzerland))

1990-07-01

186

Synthesis and structure of nanocrystalline mixed Ce–Yb silicates  

SciTech Connect

Graphical abstract: - Highlights: • New method of synthesis of nanocrystalline mixed lanthanide silicates is proposed. • Formation of A-type (Ce{sub 1?y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} in well dispersed Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)}–SiO{sub 2} system. • Formation of Yb{sub y}Ce{sub 9.33?y}(SiO{sub 4}){sub 6}O{sub 2} in agglomerated Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)}–SiO{sub 2} system. - Abstract: This work presents results of studies on synthesis and structure of mixed, nanocrystalline Ce–Yb silicates. Using TEM, XRD and FTIR we showed that heat treatment of nanocrystalline Ce{sub 1?x}Yb{sub x}O{sub 2?(x/2)} (x = 0.3, 0.5) mixed oxide supported on amorphous silica in reducing atmosphere, results in formation of Ce–Yb mixed silicates. Dispersion of the oxide on the silica surface and thus a local lanthanide/Si atomic ratio determines the stoichiometry of the silicate. Oxide crystallites uniformly dispersed on the silica surface transformed into A-(Ce{sub 1?y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} disilicate, while the agglomerated nanoparticles converted into Yb{sub y}Ce{sub 9.33?y}(SiO{sub 4}){sub 6}O{sub 2} oxyapatite silicate as an intermediate phase.

Ma?ecka, Ma?gorzata A., E-mail: M.Malecka@int.pan.wroc.pl; K?pi?ski, Leszek

2013-07-15

187

Er and Yb isotope fractionation in planetary materials  

NASA Astrophysics Data System (ADS)

Terrestrial planets are depleted in volatile elements relative to solar abundances. Little is known, however, about volatility at the high temperatures relevant to asteroidal collisions and to the giant lunar impact. Although refractory rare-earth elements have overall similar crystallochemical properties, some differ in their temperatures of condensation from the nebular gas. This is the case for Yb, which condenses at ˜1490K and in the vapor is mostly in elemental form. By contrast, Er, largely present as ErO, condenses at ˜1660K. We analyzed the Er and Yb isotopic compositions in 33 terrestrial basalts, garnets, different classes of chondrites and achondrites, and lunar samples by MC-ICP-MS. The range of mass-dependent isotope fractionation is larger for Yb (0.43‰ per amu) than Er (0.23‰) isotopes. For terrestrial rocks, a positive correlation between ?Yb and La/Yb suggests that the isotopic differences between Er and Yb can be accounted for by the presence of small fractions of Yb2+. Yb is isotopically heavy in kimberlite and light in garnets. Ytterbium behaves similarly to Fe, with Yb3+ being more incompatible than the much less abundant Yb2+. In addition, the coexistence of divalent and trivalent sites in the garnet structure and the preference of heavy isotopes for stable bonds makes Yb in garnet isotopically light. The deficit of heavy Yb isotopes in lunar basaltic samples relative to the Earth, chondrites, and eucrites provides new evidence that the Moon formed by the condensation of silicate vapor in the aftermath of the giant lunar impact. Separation of vapor from melt and of heavy from light isotopes is first expected during the adiabatic expansion of the initial vapor plume. Subsequently, friction between melt and gas tends to further enrich the Moon feeding zone in silicate vapor to compensate the inward migration of melt out of the pre-lunar disk. A major consequence of interpreting the present lunar data by vapor/melt segregation is that the relative abundances of refractory elements in the Moon are unlikely to be chondrite-like or even Earth-like. Erbium isotope ratios in lunar samples reflect the capture of neutrons produced by galactic cosmic rays. The first resonance of 167Er for neutron capture will help cover an energy range poorly covered by other nuclides.

Albalat, Emmanuelle; Telouk, Philippe; Albarède, Francis

2012-11-01

188

YbN: An intrinsic semiconductor with antiferromagnetic exchange  

NASA Astrophysics Data System (ADS)

We present a study of the structural, conducting, magnetic, and optical properties of YbN thin films. Magnetic measurements reveal an antiferromagnetic Curie-Weiss temperature dependence. We find the temperature-dependent resistivity and carrier concentration to be indicative of YbN being semiconducting in nature. Along with this we observe an absorption onset at 1.5 eV, found from optical transmission and reflection measurements. This apparent combination of antiferromagnetism and semiconductivity present in YbN makes it unique among the rare earth nitrides, a series dominated by ferromagnetic semiconductors.

Warring, H.; Ruck, B. J.; McNulty, J. F.; Anton, E.-M.; Granville, S.; Koo, A.; Cowie, B.; Trodahl, H. J.

2014-12-01

189

Magnetic ordering in TmGa.  

PubMed

We have determined the magnetic structure of the intermetallic compound TmGa by high-resolution neutron powder diffraction and (169)Tm Mössbauer spectroscopy. This compound crystallizes in the orthorhombic (Cmcm) CrB-type structure and its magnetic structure is characterized by magnetic order of the Tm sublattice along the a-axis. The initial magnetic ordering occurs at 15(1) K and yields an incommensurate antiferromagnetic structure described by the propagation vector k1 = [0 0.275(2) 0]. At 12 K the dominant ferromagnetic ordering of the Tm sublattice along the a-axis develops in what appears to be a first-order transition. At 3 K the magnetic structure of TmGa is predominantly ferromagnetic but a weakened incommensurate component remains. The ferromagnetic Tm moment reaches 6.7(2) ?B at 3 K and the amplitude of the remaining incommensurate component is 2.7(4) ?B. The (169)Tm hyperfine magnetic field at 5 K is 631(1) T. PMID:24590122

Cadogan, J M; Stewart, G A; Muñoz Pérez, S; Cobas, R; Hansen, B R; Avdeev, M; Hutchison, W D

2014-03-19

190

Preliminary Evaluation of TM for Soils Information  

NASA Technical Reports Server (NTRS)

The capability of the LANDSAT TM for providing information for soil association maps and for detecting soil properties (variability within vegetated fields) was assessed using TM imagery of fields in Mississippi County, Arkansas that were planted with rice, cotton, and soybeans. Results indicate that the TM bands are providing information that is related to the soil properties within the field. Over large areas, these bands also appear to provide information that is related to the soil properties that are important to plant condition. While these results are only an indication of the information that TM can provide, they do indicate the TM data--especially, the mid-TR and thermal bands--show the capability for separating vegetated soil landscapes on a broad basis. The analysis at the field level with a growing crop also indicates that TM, with its additional and narrower bands and improved spatial and radiometric resolution is influenced by within field variability due to soils that has to be accounted for in the analysis of TM data.

Thompson, D. R.; Henderson, K. E.; Houston, A. G.; Pitts, D. E.

1985-01-01

191

Direct elucidation of the effect of building defects on the physical properties of alpha-TmAlB4; An AlB2-type analogous "tiling" compound  

NASA Astrophysics Data System (ADS)

With a counterintuitive approach to crystal growth, single crystals of ?-TmAlB4 were successfully grown, which were indicated from transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements and analysis to be virtually free from the ubiquitous building defects, and their properties investigated. Recent developments in rare earth aluminoboride compounds with two-dimensional boron layers have attracted interest due to the heavy fermion superconductivity in ?-YbAlB4, multiple anomalies manifesting below the Néel temperatures in ?-TmAlB4 attributed to intrinsic building defects, and field stable state in Tm2AlB6. The physical properties of the obtained ?-TmAlB4 crystals show a striking difference from the properties of conventional ?-TmAlB4 crystals containing building defects. TN = 6.8 K is revealed to be higher than the 5.8 K formerly thought, and the multiple anomalies below TN are replaced by a sharp ?-like peak in the specific heat C. The large effect of the building defects on the physical properties could be directly confirmed, and strikingly it is shown how the large peak structure in the specific heat of the high quality sample could be destroyed by the presence of a small amount (one or two percent) of building defects.

Mori, T.; Kuzmych-Ianchuk, I.; Yubuta, K.; Shishido, T.; Okada, S.; Kudou, K.; Grin, Y.

2012-04-01

192

Yb\\/Er-codoped and Yb-doped waveguide lasers in phosphate glass  

Microsoft Academic Search

We present experimental and theoretical results of our recent work on the development of waveguide lasers using rare-earth-doped phosphate glasses. An improvement has been achieved over previously reported waveguide laser results using the process of ion exchange in a commercially available Yb\\/Er-codoped phosphate glass composition. We have demonstrated slope efficiencies near 30% with output powers approaching 200 mW for 1540

David L. Veasey; David S. Funk; Philip M. Peters; Norman A. Sanford; Gregory E. Obarski; Norman Fontaine; Matt Young; Adele P. Peskin; Wei-Chih Liu; S. N. Houde-Walter; Joseph S. Hayden

2000-01-01

193

Epitaxial layer-by-layer growth of Yb:YAG and YbAG PLD-films  

NASA Astrophysics Data System (ADS)

In this contribution, we report on the 2-dimensional (2D) layer-by-layer growth of Yb(10%):Y3Al5O12 (YAG) and Yb3Al5O12 (YbAG) PLD-films on {100}-oriented YAG. The epitaxial growth was observed in situ by Reflection High Energy Electron Diffraction (RHEED) as intensity oscillations of the specularly reflected electron beam. The properties of the films were investigated ex situ by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and optical spectroscopy. The optical emission spectra of the films are similar to those of the corresponding crystalline bulk materials.

Gün, Teoman; Kuzminykh, Yury; Tellkamp, Friedjof; Petermann, Klaus; Huber, Günter

2008-11-01

194

Charge transfer processes and ultraviolet induced absorption in Yb:YAG single crystal laser materials  

NASA Astrophysics Data System (ADS)

Charge transfer (CT) transitions and UV induced color centers in Yb:YAG single crystals have been investigated. A simultaneous pair formation of a stable Yb2+ ion and a hole related (O-) color center (hole polaron) are observed through a CT-process. Slightly different types of hole related color centers are formed in Yb:YAG crystals containing small levels of iron impurities. Furthermore, excitation spectroscopy on the UV irradiated Yb:YAG samples could confirm an energy transfer process between Yb3+ and Yb2+ ions. The findings are important for an increased knowledge of the physical loss mechanisms observed in Yb-doped laser materials, such as the nonlinear decay process in Yb:YAG crystals as well as the photodarkening phenomenon in Yb-doped fiber lasers.

Rydberg, S.; Engholm, M.

2013-06-01

195

Scattering lengths in isotopologues of the RbYb system  

NASA Astrophysics Data System (ADS)

We model the binding energies of rovibrational levels of the RbYb molecule using experimental data from two-color photoassociation spectroscopy in mixtures of ultracold 87Rb with various Yb isotopes. The model uses a theoretical potential based on state-of-the-art ab initio potentials, further improved by least-squares fitting to the experimental data. We have fixed the number of bound states supported by the potential curve, so that the model is mass scaled, that is, it accurately describes the bound-state energies for all measured isotopic combinations. Such a model enables an accurate prediction of the s-wave scattering lengths of all isotopic combinations of the RbYb system. The reduced mass range is broad enough to cover the full scattering lengths range from -? to +?. For example, the 87Rb174Yb system is characterized by a large positive scattering length of +880(120) a.u., while 87Rb173Yb has a=-626(88) a.u. On the other hand 87Rb170Yb has a very small scattering length of -11.5(2.5) a.u. confirmed by the pair's extremely low thermalization rate. For isotopic combinations including 85Rb the variation of the interspecies scattering lengths is much smoother ranging from +39.0(1.6) a.u. for 85Rb176Yb to +230(12) a.u. in the case of 85Rb168Yb. Hyperfine corrections to these scattering lengths are also given. We further complement the fitted potential with interaction parameters calculated from alternative methods. The recommended value of the van der Waals coefficient is C6=2837(13) a.u. agrees with but is more precise than the current state-of-the-art theoretical predictions [M. S. Safronova, S. G. Porsev, and C. W. Clark, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.230802 109, 230802 (2012)].

Borkowski, Mateusz; ?uchowski, Piotr S.; Ciury?o, Roman; Julienne, Paul S.; K?dziera, Dariusz; Mentel, ?ukasz; Tecmer, Pawe?; Münchow, Frank; Bruni, Cristian; Görlitz, Axel

2013-11-01

196

Tightly focused, ultrafast TM01 laser pulses  

NASA Astrophysics Data System (ADS)

Nowadays, the generation of laser pulses focused to a spot size comparable to the wavelength and whose duration is only a few optical cycles of the electric field is achievable. Moreover, TM01 laser pulses are of considerable interest, among other things, because of their remarkable focusing properties. In order to describe theoretically the spatiotemporal behaviour of such nonparaxial, ultrashort TM01 pulses, one needs expressions of their electromagnetic fields. To obtain these expressions, Maxwell's equations must be solved rigorously. The method of the Hertz potential, the complex-source/sink model, and the use of a Poisson-like spectrum are exploited to solve the vectorial wave equation. Closed-form expressions for the electric and the magnetic fields of an isodiffracting TM01 pulse are presented and they can be used to study the behaviour of tightly focused, ultrafast TM pulses.

April, Alexandre

2009-06-01

197

Determination of the 151Eu(n,?)152Eu and 153Eu(n,?)154Eu Reaction Cross Sections at Thermal Neutron Energy  

NASA Astrophysics Data System (ADS)

We have measured partial ?-ray cross sections following neutron capture in enriched 151Eu and 153Eu targets at the cold-neutron-beam facility of the Budapest Research Reactor. The cross sections were standardized using a stoichiometric natEuCl3 target with the well-known 1951-keV ?-ray cross section from the 35Cl(n,?)36Cl reaction at the cold-neutron-beam facility of the Garching Research Reactor. The ?-ray cross sections were corrected for effective g-factors. These data were combined with the structural information of 152Eu and 154Eu given in the Evaluated Nuclear Structure Data File to produce capture ?-ray level schemes. The total radiative capture cross sections of the 151Eu(n,?)152Eu and 153Eu(n,?)154Eu reactions were determined by summing the experimental transition intensities from known levels with simulated intensities of transitions from higher excitations to the ground- or metastable-state. The individual 151Eu(n,?)152Eu and 151Eu(n,?)152gEu reaction cross sections disagree with values in the literature. However, the total cross section of the 151Eu(n,?)152Eu reaction does agree with those values. Also, our deduced cross section for the 153Eu(n,?)154Eu reaction closely follows the data in the literature. These results are supported by an earlier standardization experiment done at the Budapest Research Reactor using a target of Eu2O3 solution in H2SO4.

Basunia, M. S.; Firestone, R. B.; Révay, Zs.; Choi, H. D.; Belgya, T.; Escher, J. E.; Hurst, A. M.; Krti?ka, M.; Szentmiklósi, L.; Sleaford, B.; Summers, N. C.

2014-05-01

198

Unusual weak magnetic exchange in two different structure types: YbPt2Sn and YbPt2In.  

PubMed

We present the structural, magnetic, thermodynamic and transport properties of the two new compounds YbPt(2)Sn and YbPt(2)In. X-ray powder diffraction shows that they crystallize in different structure types, the hexagonal ZrPt(2)Al and the cubic Heusler type, respectively. Despite quite different lattice types, both compounds present very similar magnetic properties: a stable trivalent Yb(3+), no evidence for a sizeable Kondo interaction and very weak exchange interactions with a strength below 1 K as deduced from specific heat C(T). Broad anomalies in C(T) suggest short range magnetic ordering at about 250 mK and 180 mK for YbPt(2)Sn and YbPt(2)In, respectively. The weak exchange and the low ordering temperature result in a large magnetocaloric effect as deduced from the magnetic field dependence of C(T), making these compounds interesting candidates for magnetic cooling. In addition we found in YbPt(2)In evidences for a charge density wave transition at about 290 K. The occurrence of such transitions within several RET2X compound series (RE = rare earth, T = noble metal, X = In, Sn) is analyzed. PMID:25322667

Gruner, T; Jang, D; Steppke, A; Brando, M; Ritter, F; Krellner, C; Geibel, C

2014-12-01

199

Unusual weak magnetic exchange in two different structure types: YbPt2Sn and YbPt2In  

NASA Astrophysics Data System (ADS)

We present the structural, magnetic, thermodynamic and transport properties of the two new compounds YbPt2Sn and YbPt2In. X-ray powder diffraction shows that they crystallize in different structure types, the hexagonal ZrPt2Al and the cubic Heusler type, respectively. Despite quite different lattice types, both compounds present very similar magnetic properties: a stable trivalent Yb3+, no evidence for a sizeable Kondo interaction and very weak exchange interactions with a strength below 1 K as deduced from specific heat C(T). Broad anomalies in C(T) suggest short range magnetic ordering at about 250 mK and 180 mK for YbPt2Sn and YbPt2In, respectively. The weak exchange and the low ordering temperature result in a large magnetocaloric effect as deduced from the magnetic field dependence of C(T), making these compounds interesting candidates for magnetic cooling. In addition we found in YbPt2In evidences for a charge density wave transition at about 290 K. The occurrence of such transitions within several RET2X compound series (RE = rare earth, T = noble metal, X = In, Sn) is analyzed.

Gruner, T.; Jang, D.; Steppke, A.; Brando, M.; Ritter, F.; Krellner, C.; Geibel, C.

2014-12-01

200

Modeling Cr-to-Tm and Cr-to-Tm-to-Ho energy transfer in YAG crystals  

NASA Technical Reports Server (NTRS)

A systematic analysis of energy transfer processes in crystals of YAG doped with varying concentrations of Cr and Tm is described. Both spectral measurements and measurements of the temporal response to pulsed excitation are used to give independent determinations of the microscopic interaction parameter for Cr to Tm transfer. The different factors in influencing the temperature dependence of the Cr to Tm transfer are discussed. The dependence of the Tm cross-relaxation rate on Tm concentration is determined.

Swetits, John J.

1991-01-01

201

HSP60 interacts with YB-1 and affects its polysome association and subcellular localization  

SciTech Connect

YB-1 is a DNA/RNA-binding protein which, in the cytoplasm, associates with polysomes and regulates translation. However, YB-1 has a novel nuclear localization signal, and its nuclear accumulation is correlated with cancer induction. Here we designated the amino-acid sequence as YB-NLS and demonstrated that YB-NLS is necessary for the nuclear translocation of overexpressed YB-1 in NG108-15 cells. In addition, we found that a heat shock protein, HSP60, binds to YB-NLS in the cytoplasm. Interestingly, when HSP60 expression was repressed, an increase of polysome-associated YB-1 was observed in heavy-sedimenting fractions on a sucrose gradient. Overexpression of HSP60 resulted in a decrease of YB-1 in the heavy-sedimenting fractions and suppression of YB-NLS activity. Furthermore, the NLS-deleted YB-1 was apparently associated with the heavy-sedimenting polysomes. These results suggest that HSP60 interacts with YB-1 at the YB-NLS region and acts as a regulator of polysome association and the subcellular distribution of YB-1.

Ohashi, Sachiyo; Atsumi, Megumi [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan); Kobayashi, Shunsuke, E-mail: kobayashi.shunsuke@nihon-u.ac.jp [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)

2009-08-07

202

Anti-Stokes Yb3+ emission--valuable structure information in spectra of rare earth compounds measured with FT-Raman spectrometers.  

PubMed

Raman spectroscopy is a powerful and simple method which proved to be very useful in studies of solids. The most widely used Raman spectrometers are FT-Raman instruments with YAG:Nd(3+) laser as an excitation source. However, in the case of samples containing rare earth elements, the quality of FT-Raman spectra is often low due to strong fluorescence effects. We show that, in such cases, anti-Stokes part of the Raman spectra often contains strong, well resolved bands identified as multiphonon-assisted emission bands of Yb(3+) present as an impurity. We show on several examples that analysis of these bands may provide useful structure information, similar to that obtained by "Eu structure probe" method in optical spectroscopy. The Yb(3+) emission can be also measured using standard luminescence detection systems. However, the application of FT-Raman system allows one to obtain good quality spectra in a much cheaper, easier and faster way (in times as short as a few seconds). Moreover, high-sensitivity of FT-Raman spectrometers allows to detect even very small amounts of Yb(3+) impurity. PMID:16716654

Kepi?ski, Leszek; Maczka, Miros?aw; Hanuza, Jerzy

2006-12-01

203

Gibbs Energy of Formation of Cu 2Yb 2O 5and Thermodynamic Stability of Cu 2R2O 5( R= Tb-Lu)  

NASA Astrophysics Data System (ADS)

The electromotive force (emf) of the solid oxide electrochemical cell,[formula]has been measured between 960 and 1320 K. Based on the measured emf of the above cell as a function of temperature, the Gibbs energy change for the reaction[formula]is obtained as[formula]The Gibbs energy change for the above reaction when combined with that for Cu 2O + CuO equilibrium from the literature gives, for the reaction[formula]It can be seen that the formation of Cu 2Yb 2O 5from the component oxides is endothermic. Since Cu 2Yb 2O 5is an entropy stabilized compound and its formation is endothermic from component oxides, Cu 2Yb 2O 5is thermodynamically unstable relative to its component oxides below 853 K. Earlier we reported the Gibbs energy of formation of Cu 2Dy 2O 5, Cu 2Ho 2O 5, and Cu 2Er 2O 5from CuO and R2O 3( R= Dy, Ho, Er). Since Cu 2Yb 2O 5is also a member of the Cu 2R2O 5family of compounds whose crystal structure belongs to a noncentrosymmetric space group P2 1nb, an attempt has been made to correlate their thermodynamic properties such as enthalpy and entropy of formation with the ionic radius of the trivalent rare-earth cation pressent in octahedral coordination. Based on this correlation, ? H, ? S, and ? Gfor the formation of Cu 2Tb 2O 5, Cu 2Tm 2O 5, and Cu 2Lu 2O 5from the component oxides have been estimated.

Kale, G. M.

1996-08-01

204

Crystal field excitations of YbMn2Si2  

NASA Astrophysics Data System (ADS)

The crystal field excitations of the rare earth intermetallic compound YbMn2Si2 have been measured by inelastic neutron scattering over the temperature range 2.5-50 K. The YbMn2Si2 spectra exhibit three low energy excitations (~3-7 meV) in the antiferromagnetic AFil region above the magnetic phase transition at TN2 = 30(5) K. The crystal field parameters have been determined for YbMn2Si2 in the antiferromagnetic AFil region. A further two inelastic excitations (~9 meV, 17 meV) are observed below TN2=30(5) K, the temperature at which the high temperature antiferromagnetic structure is reported to exhibit doubling of the magnetic cell. Energy level diagrams have been determined for Yb3+ ions in the different sites above (single site) and below the magnetic transition temperature (two sites). The excitation energies for both sites are shown to be temperature independent with the temperature dependences of the transition intensities for the two sites described well by a simple Boltzmann model. The spectra below TN2 cannot be described fully in terms of molecular field models based on either a single Yb3+ site or two Yb3+ sites. This indicates that the magnetic behaviour of YbMn2Si2 is more complicated than previously considered. The inability to account fully for excitations below the magnetic phase transition may be due to an, as yet, unresolved structural transition associated with the magnetic transition.

Mole, R. A.; Hofmann, M.; Adroja, D. T.; Moze, O.; Campbell, S. J.

2013-12-01

205

Synthesis of LiYF4:Yb, Er upconversion nanoparticles and its fluorescence properties.  

PubMed

LiYbF4:Yb, Er nanoparticles have been successfully synthesized by thermal decomposition of multiple trifluoroacetic acid salts. The SEM and TEM results show the size of the LiYF4:Yb, Er nanoparticles is about 100 nm in diagonal line, and the morphology of the LiYF4:Yb, Er nanoparticles is highly uniform with octahedral structure. Under the excitation of 980 nm, the LiYF4:Yb, Er nanoparticles have higher upconversion luminescence efficiency compared with that of NaYF4:Yb, Er. The results indicate that the as-prepared LiYbF4:Yb, Er nanoparticles may have potential applications in bio-probes and displays. PMID:24738451

Zhang, Liming; Wang, Zhixin; Lu, Zhuoxuan; Xia, Kai; Deng, Yan; Li, Song; Zhang, Chuanxiang; Huang, Yuanfu; He, Nongyue

2014-06-01

206

R3Ir4Ge13 ( R=Yb, Lu): Thermal and magnetic properties  

NASA Astrophysics Data System (ADS)

We present the first data of physical properties of the cubic compound Yb3Ir4Ge13. An effective magnetic moment well below the full free-ion Yb+3 value is found. An abrupt rise in the electrical resistivity of Yb3Ir4Ge13 marks the entrance into a charge ordered phase below 60 K. The specific heat of Yb3Ir4Ge13 has a very large peak at low temperatures.

Strydom, A. M.; Oeschler, N.; Steglich, F.

2008-04-01

207

JIS YB Lead Complex Perovskite Ferroelectric Material  

NASA Astrophysics Data System (ADS)

Excess WO3 and higher sintering temperature were used for decreasing the temperature dependence of the dielectric constant in Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 ternary systems. Under some conditions, materials with both JIS YB specifications (dielectric constant change less than 10% over the temperature range from -25 to 85°C) and high dielectric constant, 5000-7400, were obtained. In the materials, core-shell-like distributions of B-site components were observed. These core-shell structures consist of W-rich regions and Ti, Nb-rich regions. In the compositions containing 2% WO3, sintered at 1150°C, core-shell-like domain structures are observed. The fringe pattern corresponded to the Ti, Nb-rich region, and superlattice electron diffraction spots indicating B-site ordering were observed in the W-rich region. In addition, the amounts of WO3 varied the appearance of the core-shell structure.

Uchikoba, Fumio; Sawamura, Kentaro

1992-09-01

208

Interplay between Charge and Magnetic Orderings in YbPd  

NASA Astrophysics Data System (ADS)

The pressure--temperature phase diagram of an intermediate-valence compound YbPd was revealed via simultaneous ac-calorimetry and electrical resistivity measurements. Two successive structural phase transition temperatures, T1 = 125 K and T2 = 110 K, are found to decrease with increasing pressure. The magnetic ordering transition at TN ˜ 1.9 K decreases monotonically up to 1.7 GPa and disappears discontinuously at Pc˜ 1.9 GPa, where the structural phase transition at T2 is also suppressed. At Pc, enhancement of the effective mass and residual resistivity are observed. Another probable magnetic phase transition, however, is found to take place at TML˜ 0.3 K and smoothly varies even when crossing Pc. Structural phase transitions at ambient pressure were also studied by a single crystal X-ray diffraction measurement. Below T2, a tetragonal lattice distortion with doubling of the unit cell along the c-axis is observed, and thus there are two inequivalent Yb-sites below Pc. These results indicate that one Yb-site, having larger valence configuration and thus smaller Kondo temperature, orders at TN. The other phase transition at TML seems to couple to the crystal structure for T2 < T < T1. YbPd is a unique system exhibiting magnetic orderings in metallic charge-ordered Yb systems.

Miyake, Atsushi; Kasano, Kazuki; Kagayama, Tomoko; Shimizu, Katsuya; Takahashi, Ryo; Wakabayashi, Yusuke; Kimura, Tsuyoshi; Ebihara, Takao

2013-08-01

209

Yb3+/Ho3+-codoped antimony-silicate optical fiber  

NASA Astrophysics Data System (ADS)

The emission properties of Yb3+/Ho3+-codoped antimony-silicate optical fiber has been investigated. Luminescence at 2.1 ?m corresponding to 5I7--> 5I8 transition in holmium was obtained by energy transfer between Yb3+ and Ho3+ ions. According to the Dexter-Miyakawa model, the parameters of energy migration CDD of the 2F5/2 (Yb3+) <--> 2F5/2 (Yb3+) transition and direct energy transfer CDA of the 2F5/2 (Yb3+) --> 5I6 (Ho3+) transition was calculated. The optimization of the activator content and the concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of spontaneous emission which formed as a result of energy transfer between ytterbium and holmium ions were observed in the fiber under exciting with radiation at 978 nm wavelength.

?mojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Dorosz, Jan

2012-05-01

210

Yb3+/Ho3+-codoped antimony-silicate optical fiber  

NASA Astrophysics Data System (ADS)

The emission properties of Yb3+/Ho3+-codoped antimony-silicate optical fiber has been investigated. Luminescence at 2.1 ?m corresponding to 5I7--> 5I8 transition in holmium was obtained by energy transfer between Yb3+ and Ho3+ ions. According to the Dexter-Miyakawa model, the parameters of energy migration CDD of the 2F5/2 (Yb3+) <--> 2F5/2 (Yb3+) transition and direct energy transfer CDA of the 2F5/2 (Yb3+) --> 5I6 (Ho3+) transition was calculated. The optimization of the activator content and the concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of spontaneous emission which formed as a result of energy transfer between ytterbium and holmium ions were observed in the fiber under exciting with radiation at 978 nm wavelength.

?mojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Dorosz, Jan

211

TORR TM DE-OILING TECHNOLOGY  

E-print Network

he TORR TM de-oiling technology, with its small footprint and ability to replace less efficient de-oiling equipment, offers the best available process in the treatment of produced water for offshore producers and operators. The TORR TM technology exceeds today’s discharge regulations and will address future regulations. The scaleable technology addresses future increases in water cut. Adding compact TORR TM vessels requires very little real estate when water cuts increase. FEATURES Small footprint and low weight 1000 ppm down to discharge regulation Better polishing for reinjection applications Removes and recovers oil droplets larger than 2 microns Maximum flow rate per vessel of 60,000 BWPF Same high de-oiling efficiency during production start-up periods No additional treatment required for recovered oil Minimal pressure drop and maintenance and minimal operation costs Recovered hydrocarbons can be <0.5 % BSW High flow rate turndown No moving internal parts No added heat or chemicals Operational temperatures up to 90?C Solids handing capabilities Reduced process complexityTECHNOLOGY The TORR TM process consists of two inline pressure vessels, and an optional third vessel can be used as a standby. Produced water enters the TORR TM unit for treatment and then passes through the core of multiple continuous coalescing elements. The continuous coalescing element adsorbs the small oil droplets, coalesces them to large oil globules and then desorbs them. Gravity separation principles remove these large coalesced globules, which then rise to the top of the vessel. Any solution gas accumulating with the oil at the top of the vessel will be safely recovered. The oil and/or gas collected at the top of the vessel are recuperated and returned to a suitable collection unit. The TORR TM technology treated produced water exceeds discharge regulations.

Kompleks Antarabangsa

212

Valence and environment of rare earth ions in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials  

NASA Astrophysics Data System (ADS)

The existence of the different R 2+/R 3+/R IV (R: rare earth) ions as well as the modifications in the structural environment around the dopant and co-dopants in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials was studied by L III edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements at Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) (Hamburg, Germany). The measurements were carried out at 10 and 296 K for selected rare earth (co-)dopants (Eu 2+; Ce 3+, Nd 3+, Sm 3+, and Yb 3+). The XANES results indicated the co-existence of both divalent and trivalent europium in all co-doped CaAl 2O 4:Eu 2+,R 3+ materials, but only divalent europium in CaAl 2O 4:Eu 2+. The measurement temperature did not affect the XANES results. The interatomic distances extracted from the EXAFS data of the CaAl 2O 4:Eu 2+,R 3+ materials indicated that co-doping creates distortions around the Eu 2+ ions suggesting dopant aggregation.

Hölsä, Jorma; Laamanen, Taneli; Lastusaari, Mika; Malkamäki, Marja; Welter, Edmund; Zajac, Dariusz A.

2010-04-01

213

Magnetic transitions in YbCo2Si2  

NASA Astrophysics Data System (ADS)

The results of powder neutron diffraction studies of an antiferromagnet YbCo2Si2with TN,L=0.9 K and TN,H=1.7 K were reported. An appearance of several superlattice peaks was observed at 0.48K, which characterizes the antiferromagnetic ground state in YbCo2Si2. By heating up to 1.1 K, to the intermediate phase, a substantial change in the magnetic reflection from the ground state was revealed. The magnetic peak shifts to lower angle, indicating longer periodicity in the intermediate phase. In addition, the intensity ratio of the magnetic peaks shows significant change between two phases. In contrast to other magnetic RCo2Si2, the simple two-sublattice magnetic structure characterized by an existence of the magnetic 1 00 reflection cannot account for the observed magnetic peaks at both temperatures, which suggests more complex magnetic structures in YbCo2Si2.

Kaneko, Koji; Stockert, Oliver; Mufti, Nandang; Kiefer, Klaus; Klingner, Christoph; Krellner, Cornelius; Geibel, Christoph; Steglich, Frank

2010-01-01

214

Short-wavelength Yb:fiber laser analysis  

NASA Astrophysics Data System (ADS)

Yb:fiber lasers have shown excellent performance in the 980–1100 nm wavelength range. To extend the range below 980 nm, it becomes difficult to reach the transparent condition due to the smaller ratio between emission and absorption cross sections. As a result, a high demand of population inversion is needed, and the selection of pump wavelength as well as other intra-cavity parameters are crucial for lasing in the 920–960 nm wavelength range. To find a feasible solution, the pump wavelength, fiber length, and laser cavity transmittance were systematically studied. Based on the experimental result of a 960 nm Yb:fiber laser, the re-absorption loss and temperature dependent gain can be reliably modeled. The result shows promise in the development of a Yb:fiber laser at a wavelength as short as 920 nm.

Yi, J. Y.; Chang, S. F.; Hsu, C. N.

2013-12-01

215

Magnetism in superconducting EuFe2As1.4P0.6 single crystals studied by local probes  

NASA Astrophysics Data System (ADS)

We have studied the magnetism in superconducting single crystals of EuFe2As1.4P0.6 by using the local probe techniques of zero-field muon spin rotation/relaxation and 151Eu/57Fe Mössbauer spectroscopy. All of these measurements reveal magnetic hyperfine fields below the magnetic ordering temperature TM=18K of the Eu2+ moments. The analysis of the data shows that there is a coexistence of antiferromagnetism, resulting from Eu2+ moments ordered along the crystallographic c-axis, and superconductivity below TSC? 10 K. We find indications for a change in the dynamics of the small Fe magnetic moments (~0.07 ?B) at T*?15K that may be triggering the onset of superconductivity: below T* the Fe magnetic moments seem to be "frozen" within the ab-plane.

Munevar, J.; Micklitz, H.; Alzamora, M.; Argüello, C.; Goko, T.; Ning, F. L.; Munsie, T.; Williams, T. J.; Aczel, A. A.; Luke, G. M.; Chen, G. F.; Yu, W.; Uemura, Y. J.; Baggio-Saitovitch, E.

2014-06-01

216

Measurement of thermal lensing in end-pumped Yb-doped yttrium vanadate crystal and sesquioxide laser ceramics  

NASA Astrophysics Data System (ADS)

The results of theoretical and experimental study of thermal lensing in diode-pumped Yb:YVO4 laser crystal, Yb:Y2O3 and Yb:Sc2O3 laser ceramics are presented. Shown, that influence of thermo-lensing effect is necessary to consider for creation of effective high-intensity femtosecond Yb-doped laser systems.

Pestryakov, E. V.; Petrov, V. V.; Trunov, V. I.; Kirpichnikov, A. V.; Merzliakov, M. A.; Laptev, A. V.; Polyakov, K. V.

2010-09-01

217

Measurement of thermal lensing in end-pumped Yb-doped yttrium vanadate crystal and sesquioxide laser ceramics  

NASA Astrophysics Data System (ADS)

The results of theoretical and experimental study of thermal lensing in diode-pumped Yb:YVO4 laser crystal, Yb:Y2O3 and Yb:Sc2O3 laser ceramics are presented. Shown, that influence of thermo-lensing effect is necessary to consider for creation of effective high-intensity femtosecond Yb-doped laser systems.

Pestryakov, E. V.; Petrov, V. V.; Trunov, V. I.; Kirpichnikov, A. V.; Merzliakov, M. A.; Laptev, A. V.; Polyakov, K. V.

2011-02-01

218

ORNL/TM-2001/164 Prediction of External Corrosion  

E-print Network

ORNL/TM-2001/164 Prediction of External Corrosion for Steel Cylinders--2001 Report Rick Schmoyer States Government or any agency thereof. #12;ORNL/TM-2001/164 PREDICTION OF EXTERNAL CORROSION FOR STEEL

219

ORNL/TM-2002/143 Prediction of External Corrosion  

E-print Network

ORNL/TM-2002/143 Prediction of External Corrosion for Steel Cylinders--2002 Report Rick Schmoyer States Government or any agency thereof. #12;ORNL/TM-2002/143 PREDICTION OF EXTERNAL CORROSION FOR STEEL

220

CCRS proposal for evaluating LANDSAT-4 MSS and TM data  

NASA Technical Reports Server (NTRS)

The measurement of registration errors in LANDSAT MSS data is discussed as well as the development of a revised algorithm for the radiometric calibration of TM data and the production of a geocoded TM image.

Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigators); Guindon, B.; Murphy, J.; Butlin, J. M.; Duff, P.; Fitzgerald, A.; Grieve, G.

1984-01-01

221

Diffusion of Excitation in GGG:Yb3+ Laser Crystal  

NASA Astrophysics Data System (ADS)

The excitation diffusion coefficient DE is measured directly in laser crystals by the optical method of high-frequency dynamic gratings. DE for Gd3Ga5O12:Yb3+ (21 at.%) crystal is found to be 3·10-9 cm3/s at room temperature and 1.2·10-8 cm3/s at 190°C. In KYW:Yb3+ (20 at.%) crystal no excitation diffusion is observed under the same experimental conditions. It is shown that DE is affected by the activator concentration, the temperature, and the probability of radiationless energy exchange between neighboring active impurity ions, which depends on the minimal distance between donor and acceptor.

Kisialiou, I. G.; Ivakin, E. V.

2015-01-01

222

Search for an M0 transition in 170Yb  

NASA Astrophysics Data System (ADS)

We have examined the suggestion that an M0 transition occurs between the 2819.6-keV 0- level of 170Yb and the 0+ ground state by internal-conversion electron emission. Gamma rays, internal-conversion electrons, and internal e+e- pairs were detected from the ?+ and electron capture decay of two-day 170Lu (0+). At an upper limit of 2×10-8 electron per 170Lu decay, no evidence was obtained for M0 decay of the 2819.6-keV level of 170Yb by single-electron emission.

Kuhnert, A.; Henry, E. A.; Wang, T. F.; Brinkman, M. J.; Stoyer, M. A.; Becker, J. A.; Manatt, D. R.; Yates, S. W.

1993-05-01

223

Electron Paramagnetic Resonance of Yb3+ in Scheelite Single Crystals  

Microsoft Academic Search

The electron paramagnetic resonance spectra of the ground state of trivalent ytterbium have been observed in eight single crystals with scheelite structure at 4.2°K and X band frequencies. The crystals used were CdMoO4, CaWO4, CaMoO4, SrWO4, SrMoO4, PbWO4, PbMoO4, and BaWO4. The tetragonal spectra for Yb171, Yb173, and the even isotopes of ytterbium were best fitted with an axial spin

J. P. Sattler; J. Nemarich

1970-01-01

224

Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates  

PubMed Central

Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application. PMID:23618344

2013-01-01

225

Elastic and Dynamical Properties of YB4: First-Principles Study  

NASA Astrophysics Data System (ADS)

We present the elastic and dynamical properties of YB4 from first-principles calculations. It is found that the optimized lattice constants and bulk modulus (182 GPa) agree well with the experimental data. The structural stability of tetragonal YB4 is confirmed by the calculated elastic constants and phonon spectra. YB4 holds a Debye temperature of 874 K and has small elastic anisotropy. The estimated hardness of YB4 is about 17 GPa, indicating that YB4 is a hard solid while not a superhard one.

Fu, Yuan-Yuan; Li, Yin-Wei; Huang, Hong-Mei

2014-11-01

226

Evolution of a magnetic state in YbCu5-xGax  

NASA Astrophysics Data System (ADS)

Substitutions of Cu by Ga in YbCu5 stabilize the hexagonal CaCu5 structure and cause a crossover from a divalent behavior of the Yb-ion in YbCu5 to an almost 3+ state of Yb in YbCu3Ga2. This gain of magnetism is accompanied by a noticeable enhancement of the electronic contribution to the specific heat. External pressure transforms those compounds, exhibiting intermediate valence, to a state which is best described in terms of the Kondo lattice model.

Bauer, E.; Tuan, Le; Hauser, R.; Gratz, E.; Holubar, T.; Hilscher, G.; Michor, H.; Perthold, W.; Godart, C.; Alleno, E.; Hiebl, K.

1995-08-01

227

Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb3+/Tm3+ upconversion particles  

NASA Astrophysics Data System (ADS)

The interaction of UCPs with CT DNA are studied in detail by zeta potential, Energy dispersive spectrometer (EDS) spectroscopy, Thermogravimetric (TGA) analysis, DNA melting determination and various spectroscopic techniques including Ultraviolet-Visible (UV-Vis) absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FTIR) and Raman spectroscopy. The results indicate that CT DNA can assemble on the surface of UCPs mainly by relative stronger hydrophobic force and electrostatic binding, and the predominant interaction site is the deoxyribosyl phosphate backbone of CT DNA. Moreover, after interacting with UCPs, the double helix structure of DNA is undamaged.

Yuan, Xiuxue; Gu, Wenchao; Xiao, Mengsi; Xie, Wenli; Wei, Shaohua; Zhou, Lin; Zhou, Jiahong; Shen, Jian

2015-02-01

228

GAUSS EngineTM Programmer's Manual  

E-print Network

GAUSS EngineTM Programmer's Manual Version 8.0 1 #12;Information in this document is subject one copy of the software for backup purposes. No part of this manual may be reproduced or transmitted Systems, Inc. Microsoft, Visual C/C++, and Visual Basic are either trademarks or registered trademarks

LaFrance, Jeffrey T.

229

August 2002 NASA/TM--2002211612  

E-print Network

August 2002 NASA/TM--2002­211612 Pickup Ions at Dione and Enceladus E. Sittler, R.E. Johnson, S. Jurac, J. Richardson, M. McGrath, F. Crary, D. Young, and J.E. Nordholt #12;The NASA STI Program Office ... in Profile Since its founding, NASA has been dedicated to the advancement of aeronautics and space science

Richardson, John

230

NASA/TM--2001210880 Photographic Analysis Technique  

E-print Network

NASA/TM--2001­210880 Photographic Analysis Technique for Assessing External Tank Foam Loss Events T'Farrell United Space Alliance, Huntsville, Alabama June 2001 #12;Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program

Christian, Eric

231

August 2004 NASA/TM--2004212824  

E-print Network

August 2004 NASA/TM--2004­212824 Stress, Cognition, and Human Performance: A Literature Review and Conceptual Framework Mark A. Staal Ames Research Center, Moffett Field, California #12;The NASA STI Program Office ... in Profile Since its founding, NASA has been dedicated to the advancement of aeronautics

232

ChemagneticsTM Double-Resonance  

E-print Network

ChemagneticsTM Double-Resonance HX CP/MAS NMR Probe Installation Varian NMR Spectrometer Systems Pub. No. 01-999155-00, Rev. A0101 #12;01-999155-00 A0101 Chemagnetcis HX CP/MAS NMR Probes Installation 1 Chemagnetics Double- Resonance HX CP/MAS NMR Probes Installation, Testing, and Specifications

Collins, Gary S.

233

FANTESK**TM PROCESSING AND UTILIZATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fantesk**TM is a stable dispersion of a jet-cooked starch slurry-oil mixture. The jet cooked material can be air- or drum-dried. Jet cooking and shear of the mixture liquefies the starch and lowers its MW. Various oils and fats and different starches can be used to produce Fantesk. Fantesk is a ...

234

The Neuroscience of PowerPoint[TM  

ERIC Educational Resources Information Center

Many concepts have been published relevant to improving the design of PowerPoint[TM] (PP) presentations for didactic purposes, including the redundancy, modality, and signaling principles of multimedia learning. In this article, we review the recent neuroimaging findings that have emerged elucidating the neural structures involved in many of these…

Horvath, Jared Cooney

2014-01-01

235

Introduction to AndroidTM Application Development  

E-print Network

operating system is based on Linux with a Java programming interface. Explore simple GUI applicationsIntroduction to AndroidTM Application Development 21 hours, $945 Create your own Android app and learn how to submit it to market. Discover the basics of Android application development through in

Fork, Richard

236

78 FR 72922 - TSA Pre?TM  

Federal Register 2010, 2011, 2012, 2013

...fee to apply for the program. TSA is establishing the TSA Pre[check] TM Application Program...expended. A. Fee Standards and Guidelines The program fee structure described...notice is designed to fully recover TSA's anticipated costs of the...

2013-12-04

237

Using COS Administrator's WorkbenchTM  

E-print Network

directly to your institution's search interface. Tip: This is the interface all staff and students shouldUsing COS Administrator's WorkbenchTM Tools for Managing COS Expertise and Funding Services http and use your expertise system. This tutorial shows you how to use: COS Administrator's Workbench #12

Ollivier-Gooch, Carl

238

:>':. '*>3 1 /? ORNL/TM-8022  

E-print Network

Division THE STIRLING ENGINE WITH ONE ADIABATIC CYLINDER C. D. West Date Published: March 1982 DISCLAIMER #12;#12;THE STIRLING ENGINE WITH ONE ADIABATIC CYLINDER C. D. West This report shows that integration:>':. '*>3 1 /? ORNL/TM-8022 ^S] ~/ 3)/:: 60g7b6( Contract No. W-7405-eng-26 Engineering Technology

Oak Ridge National Laboratory

239

Painting your home blue [BluetoothTM wireless technology  

Microsoft Academic Search

When looking to network devices in the home, one should look at the BluetoothTM wireless technology. The BluetoothTM wireless technology was designed to be a cable replacement, but is being pushed to be much more. The Bluetooth TM wireless technology consists of two base documents and numerous others, including at least one on testing. The primary is the core specification.

D. Cypher

2002-01-01

240

Principal component analysis of TM images for monitoring inland water quality  

Microsoft Academic Search

TM data have been used by many researchers for remote sensing of monitoring chlorophyll-a concentration, which is strongly correlated with trophic state of surface water. In this paper, principal component analysis (PCA) is employed for extracting alga production in lake water from TM data. Input images are chosen as radiance ratios TM2\\/TM1, TM2\\/TM3 and TM4\\/TM3, instead of four independent band

Xiaozhou Shu; Yin Qiu; Dingbo Kuang

1999-01-01

241

Thermoelectric properties of Yb-filled CoSb3 skutterudites  

NASA Astrophysics Data System (ADS)

Yb-filled skutterudites Yb z Co4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of Yb on the transport and the thermoelectric properties of the skutterudites were examined. In the case of z ? 0.3, a secondary phase (YbSb2) was formed, indicating that the filling fraction limit of Yb was z = 0.2 - 0.3. The intrinsic CoSb3 had a high positive Seebeck coefficient, but Yb-filled CoSb3 exhibited a negative Seebeck coefficient. In the case of z ? 0.1, the maximum absolute value of the Seebeck coefficient was | -231| ?VK-1, and in the case of z ? 0.2, the absolute value of the Seebeck coefficient increased with increasing temperature. The electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling content due to the increased carrier concentration. The thermal conductivity was reduced significantly by Yb filling, mainly due to a decrease in the lattice thermal conductivity. Also, the lattice thermal conductivity decreased with increasing Yb filling content, indicating that the phonon scattering was caused by the rattling of Yb fillers in the voids of the skutterudite structure. Yb0.2Co4Sb12 showed the highest figure of merit of 1.0 at 823 K.

Park, Kwan-Ho; Seo, Won-Seon; Shin, Dong-Kil; Kim, Il-Ho

2014-08-01

242

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

243

YB-1 Acts as a Ligand for Notch-3 Receptors and Modulates Receptor Activation*  

PubMed Central

Y-box (YB) protein-1 is secreted by mesangial and immune cells after cytokine challenge, but extracellular functions are unknown. Here, we demonstrate that extracellular YB-1 associates with outer cell membrane components and interacts with extracellular Notch-3 receptor domains. The interaction appears to be specific for Notch-3, as YB-1-green fluorescent protein binds to the extracellular domains and full-length forms of Notch-3 but not to Notch-1. YB-1-green fluorescent protein and Notch-3 proteins co-localize at cell membranes, and extracellular YB-1 activates Notch-3 signaling, resulting in nuclear translocation of the Notch-3 intracellular domain and up-regulation of Notch target genes. The YB-1/Notch-3 interaction may be of particular relevance for inflammatory mesangioproliferative disease, as both proteins co-localize in an experimental nephritis model and receptor activation temporally and spatially correlates with YB-1 expression. PMID:19640841

Rauen, Thomas; Raffetseder, Ute; Frye, Björn C.; Djudjaj, Sonja; Mühlenberg, Philipp J. T.; Eitner, Frank; Lendahl, Urban; Bernhagen, Jürgen; Dooley, Steven; Mertens, Peter R.

2009-01-01

244

Dielectric relaxation in Yb-doped SrZrO3  

NASA Astrophysics Data System (ADS)

The dielectric constant of the proton conductor SrZr1-xYbxO3 (x = 0-0.1) was measured as a function of temperature and frequency. Two well-defined relaxation peaks were observed in SrZrO3 doped with more than 1 mol% of Yb. The assignment of the two dielectric relaxations is discussed in terms of IR spectra and by free energy calculation for a miscibility of dopant Yb ions. The Yb concentration dependence of the relaxation strength of the two dielectric relaxations is in agreement with the results calculated from the free energy. The two relaxations can be assigned to a reorientation of a single Yb-OH dipole and of Yb-OH dipoles associated with Yb-clusters. The attractive energy for Yb-clustering in SrZrO3 isevaluated at about -85 meV.

Kamishima, O.; Abe, Y.; Ishii, T.; Kawamura, J.; Hattori, T.

2004-07-01

245

High pulse energy multiwatt Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers.  

PubMed

We investigated and compared Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers at repetition rates 5-10 kHz, a frequency range interesting for industrial applications requiring relatively high pulse energy. Both materials allow for pulse energies close to 1 mJ with sub-400-fs pulses. The two laser materials offer comparable performance in the pump power range investigated. The same regenerative amplifiers can be run up to 500 kHz for much faster material processing, with maximum output power of up to 9.4 W. PMID:25321201

Caracciolo, E; Kemnitzer, M; Guandalini, A; Pirzio, F; Agnesi, A; Aus der Au, J

2014-08-25

246

Effect of Yb3+ concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silica-based glasses.  

PubMed

The effect of Yb(3+) concentration on the broadband emission intensity and peak wavelength shift in Yb/Bi ions co-doped silicate glasses is investigated. The optimal Bi(2)O(3) concentration range is about 2.0-2.5 mol% in 65SiO(2)-10Al(2)O(3)-25CaO matrix (SAC glasses). For Yb/Bi codoped SAC glasses, the maximum emission intensity excited by 980 nm LD is ~30 times and 1.5 times higher than that of single Bi-doped SAC glasses excited by 980 nm and 808 nm LD, respectively, the peak emission shows obvious red-shift from 1185 nm to 1235 nm band with the Yb(2)O(3) concentration change from 0 to 3.0 mol%. For the same Yb(2)O(3) concentration in SAC glasses, the measured fluorescence lifetime near 1020 nm of single Yb(3+)-doped glasses is longer than that of Yb/Bi codoping glasses, which implyes the efficient energy transfer from Yb(3+) to Bi(n+) in SAC glasses. The results indicate Yb(2)O(3) can be induced into the bismuth-doped silicate glasses to enhance the emission intensity and control the peak wavelength. PMID:20940756

Dai, Nengli; Xu, Bing; Jiang, Zuowen; Peng, Jingang; Li, Haiqing; Luan, Huaixun; Yang, Luyun; Li, Jinyan

2010-08-30

247

A Revised Periodic Table: With the Lanthanides Repositioned  

Microsoft Academic Search

The lanthanide elements from lanthanum to lutetium inclusive are incorporated into the body of the periodic table. They are\\u000a subdivided into three sub-groups according to their important oxidation states: La to Sm, Eu to Tm, Yb and Lu, so that Eu\\u000a and Yb fall directly below Ba; La, Gd, Lu form a column directly below Y; Ce and Tb fall

Michael Laing

2005-01-01

248

Novel fluorescent chelate for Eu  

NASA Astrophysics Data System (ADS)

Novel high efficient fluorescent chelate for Eu based on diethylenethriaminepentaacetic acid and amino (beta) -diketones is proposed for time-resolved fluorescence immunoassay. The label surpasses all known chelates for europium in major spectral and luminescent characteristics. The proposed label has number of advantages over the well-known europium chelates. The assays with new fluorescent chelate do not require enhancement solution, but the sensitivity of Eu determination is the same as for DELFIA enhancement solution. The assay with new fluorescent chelate is insensitive to contamination of solutions and samples with ions of heavy metals, because the concentration of fluorescent chelate is measured and high excess of Eu prevents dissociation of fluorescent chelate complex. Techniques have been developed for covalent labeling of proteins with the new fluorescent chelate. The labelling proteins can be stored in the lyophilized state or in stabilized solution rather long and retain their immunological properties. Application of the new fluorescent chelate enables the washing step to be avoided and to develop the express non-separation assay.

Savitsky, Alexander P.; Chydinov, Alexander V.; Krilova, Svetlana M.

1995-05-01

249

Governance in EU illicit drugs policy.  

PubMed

This commentary represents the authors' views on EU governance in illicit drug policy, a field in which they were active for more than 10 years between them. EU drug policy has a narrow legal basis in the European Treaties and is mostly non-binding. The main policy instruments are 8-year EU Drug Strategies, underpinned by 4-year Action Plans which set out specific objectives at national, EU or international level. The approach that guides EU drug policy is known as the 'balanced approach'. It is remarkably restrained and reflects the reality that very few Member States have either the socio-political culture or the resources to consistently apply the punitive sanctions foreseen by the UN conventions. An important feature of EU governance in the field of drugs is the proactive support that is provided to non-governmental organisations both within the EU as well as in accession, associated or third countries. At a global level, the EU is a major financial aid donor also in this field. This position is not however reflected in corresponding political clout for the EU within the UN system. EU governance on drugs has made it possible for many of its Member States to accommodate the problem rather than to "solve" what by all the evidence from the last 100 years may well be insoluble, at least by means of criminalisation and prohibition. The big question is where EU drug policy is headed in the next few years. The EU has been promoting measures and practices that target real problems. It has done so without indulging too much in unhelpful rhetoric. However, like all successful formulae this one also has a sell-by date. EU governance in the field of drugs cannot afford to stand still. It needs to find a second wind. PMID:25060612

Edwards, Carel; Galla, Maurice

2014-09-01

250

High-efficiency wavelength and polarization selective grating-waveguide structures for Yb:YAG thin-disk lasers  

NASA Astrophysics Data System (ADS)

We report on Grating Waveguide Structures (GWS) with a high diffraction efficiency used in Littrow configuration to select (and tune) the wavelength of an Yb:YAG thin-disk laser. The structures are composed of a multilayer HR coating, on which an additional low index layer (SiO2) and high index layer (Ta2O5) was deposited. A binary grating with a period of 580 nm is etched on top of the structure with a groove depth of 87 nm for GWS 1 and 72 nm for GWS 2. The simulation results show that the diffraction efficiency in the -1st order can reach a value of 99.99% for TE polarization, whereas it is only about 20% for TM polarization at 1030 nm. The grating was fabricated by standard interference lithography followed by a dry etching process to the desired groove depth. The spectroscopic measurement exhibited a diffraction efficiency of 99.6% for GWS 1 at 1030 nm and 99.7% for GWS 2 at 1048 nm. The devices were placed as end-mirror into the resonator of a Yb:YAG thin-disk laser. An output power of up to 110 W could be obtained from the laser in fundamental-mode operation (M2 ~ 1.2) with GWS 1, corresponding to an optical efficiency of ?oo = 36.2%. In multi-mode operation (M2 ~ 6) a power of 325 W with ?oo = 53.2% could be extracted. The spectral bandwidth of the emitted beam was measured using an Optical Spectrum Analyzer (OSA) to be less than 20 pm in fundamental-mode. We also showed a continuous wavelength tuning range of 46 nm for GWS 1 and of 38 nm for GWS 2. With a commercially available Stokes polarimeter the degree of linear polarization (DOLP) was measured to be higher than 98.6% over the whole power and wavelength tuning range.

Rumpel, Martin; Abdou Ahmed, Marwan; Voss, Andreas; Graf, Thomas

2012-06-01

251

LaVo4: Eu Phosphor Films with Enhanced Eu Solubility  

SciTech Connect

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO{sub 4}:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (< 3 mol %) of Eu in LaVO{sub 4} prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO{sub 4}:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO{sub 4}:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO{sub 4}.

Hwang, Harold

2011-08-11

252

Radioluminescence study in KI(Eu)  

Microsoft Academic Search

The luminous response to alpha, ? and ? rays from radioactive sources and E\\/A ? 20 MeV, 3 ? Z ? 7 heavy ions of KI(Eu) crystals was studied. Measurements include optical spectral response and Eu concentration dependence. When coupled with a transmission Si surface-barrier ?E detector, the light-output response L observed from an optimized KI(Eu) sample is found to

E. Belmont-Moreno; A. Menchaca-Rocha; M. E. Brandan; J. Hernandez A; M. Gonin; K. Hagel; R. Wada; J. B. Natowitz

1991-01-01

253

Preparation and Thermoelectric Properties of YbAl3 Thermoelectric Materials with Excessive Al  

NASA Astrophysics Data System (ADS)

A method to prepare YbAl3 sample with an accurate stoichiometric ratio has been developed by a melting, quenching, annealing and spark plasma sintering (SPS) method. A series of YbAl3 thermoelectric materials with nominal compositions YbAl3+x (x = 0-0.3, ?x = 0.1) have been prepared using the method. We have explored the effects of the excessive Al on phase compositions, microstructure and transport properties. The quenched samples are composed of YbAl3, YbAl2, Yb, and Al. All the annealed samples are composed of main phase YbAl3 and a trace of Al; some annealed samples with x = 0 and x = 0.1 still contain a trace of YbAl2. The SPSed samples with x ? 0.1 are composed of single-phase YbAl3, though a trace of YbAl2 still occured in the SPSed sample with x = 0. The electrical conductivity, Seebeck coefficient, power factor, thermal conductivity and ZT values are first increased with increasing x in the range of 0-0.2 and then decreased when x > 0.2. These thermoelectric properties evolutions originate from the change of densities and chemical composition induced by the excessive Al. The highest ZT value reaches 0.28 at 300 K for the SPSed sample with x = 0.2.

He, Dan-qi; Zhao, Wen-Yu; Mu, Xin; Zhou, Hong-yu; Zhang, Qing-jie

2015-01-01

254

Role of electron transfer in Ce3+ sensitized Yb3+ luminescence in borate glass  

NASA Astrophysics Data System (ADS)

In a Ce3+-Yb3+ system, two mechanisms are proposed so far namely, the quantum cutting mechanism and the electron transfer mechanism explaining Yb3+ infrared luminescence under Ce3+ excitation. Among them, the quantum cutting mechanism, where one Ce3+ photon (ultraviolet/blue) gives rise to two Yb3+ photons (near infrared) is widely sought for because of its huge potential in enhancing the solar cell efficiency. In present study on Ce3+-Yb3+ codoped borate glasses, Ce3+ sensitized Yb3+ luminescence at ˜1 ?m have been observed on Ce3+ 5d state excitation. However, the intensity of sensitized Yb3+ luminescence is found to be very weak compared to the strong quenching occurred in Ce3+ luminescence in Yb3+ codoped glasses. Moreover, the absolute luminescence quantum yield also showed a decreasing trend with Yb3+ codoping in the glasses. The overall behavior of the luminescence properties and the quantum yield is strongly contradicting with the quantum cutting phenomenon. The results are attributed to the energetically favorable electron transfer interactions followed by Ce3+-Yb3+ ? Ce4+-Yb2+ inter-valence charge transfer and successfully explained using the absolute electron binding energies of dopant ions in the studied borate glass. Finally, an attempt has been presented to generalize the electron transfer mechanism among opposite oxidation/reduction property dopant ions using the vacuum referred electron binding energy (VRBE) scheme for lanthanide series.

Sontakke, Atul D.; Ueda, Jumpei; Katayama, Yumiko; Zhuang, Yixi; Dorenbos, Pieter; Tanabe, Setsuhisa

2015-01-01

255

Evaluating LANDSAT-4 MSS and TM data  

NASA Technical Reports Server (NTRS)

Interband line pixel misregistrations were determined for the four MSS bands of the Mistassini, Ontario scene and multitemporal registration of LANDSAT-4 products were tested for two different geocoded scenes. Line and pixel misregistrations are tabulated as determined by the manual ground control points and the digital band to band correlation techniques. A method was developed for determining the spectral information content of TM images for forestry applications.

Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigator); Murphy, J. M.; Grieve, G.; Simard, R.; Horler, D.; Ahern, F. J.

1984-01-01

256

Preliminary Evaluation of TM for Soils Information  

NASA Technical Reports Server (NTRS)

Thematic mapper data acquired over Mississippi County, Arkansas, were examined for utility in separating soil associations within generally level alluvium deposited by the Mississippi River. The 0.76 to 0.90 micron (Band 4) and the 1.55 to 1.75 micron (Band 5) were found to separate the different soil associations fairly well when compared to the USDA-SCS general soil map. The thermal channel also appeared to provide information at this level. A detailed soil survey was available at the field level along with ground observations of crop type, plant height, percent cover and growth stage. Soils within the fields ranged from uniform to soils that occur as patches of sand that stand out strongly against the intermingled areas of dark soil. Examination of the digital values of individual TM bands at the field level indicates that the influence of the soil is greater in TM than it was in MSS bands. The TM appears to provide greater detail of within field variability caused by soils than MSS and thus should provide improved information relating to crop and soil properties. However, this soil influence may cause crop identification classification procedures to have to account for the soil in their algorithms.

Thompson, D. R.; Henderson, K. E.; Houston, A. G.; Pitts, D. E.

1984-01-01

257

Theory of Electric Quadrupole Transition in the XMCD Spectra at the Yb L3 Edge of Mixed Valence Yb Compounds in High Magnetic Fields  

NASA Astrophysics Data System (ADS)

The spectra of X-ray magnetic circular dichroism by the electric quadrupole transition (EQ-XMCD) are theoretically studied at the Yb L3 edge of mixed valence compounds, YbInCu4 and YbAgCu4, around the field-induced valence transition in high magnetic fields. Using a new formulation with a single impurity Anderson model, which directly connects the EQ-XMCD spectra with the weights of the Yb 4f angular momentum jz in the ground state, we show that the EQ-XMCD intensity of YbAgCu4 is more than twice as large as that of YbInCu4. This explains the reason for that the EQ-XMCD spectra was very recently measured successfully for YbAgCu4, whereas no experimental evidence of EQ-XMCD has so far been obtained for YbInCu4. Different EQ-XMCD intensities for the two materials and a peculiar field dependence of EQ-XMCD intensities are discussed on the basis of the weights of jz in the ground state.

Kotani, Akio

2013-04-01

258

Published on Africa EU (http://www.africa-eu-partnership.org) Home > News > Cameroon axes illegal logging > Printer-friendly  

E-print Network

Published on Africa EU (http://www.africa-eu-partnership.org) Home > News > Cameroon axes illegal on the EU side. 9/13/2010 Cameroon axes illegal logging www.africa-eu-partnership.org/print/122 1/2 #12;The goes a long way in supporting the Africa-EU Partnership on Trade, Regional Integration

259

Enhanced thermoelectric power factor in Yb1-xScxAl2 alloys using chemical pressure tuning of the Yb valence  

NASA Astrophysics Data System (ADS)

We have investigated the influence of Sc substitution on the transport and magnetic properties of YbAl2, a well-known intermediate valence compound. Sc substitution provides a chemical pressure that decreases the lattice constant and thereby alters the Yb valence as a function of composition and temperature. We observe a strong correlation between the Seebeck coefficient and the ratio of trivalent to divalent Yb in these compounds, as determined from magnetic susceptibility measurements. This correlation indicates that the largest absolute value of the Seebeck coefficient is achieved when the average Yb valence is near 2.5 (the ratio of divalent to trivalent Yb is 1:1). It is shown that Sc concentration can be used as a means to tune both the magnitude of the maximum of the Seebeck coefficient and the temperature at which this absolute maximum occurs, improving the prospects of the use of these materials in cryogenic Peltier coolers.

Lehr, Gloria J.; Morelli, Donald T.; Jin, Hyungyu; Heremans, Joseph P.

2013-12-01

260

Electronic structure and x-ray magnetic circular dichroism in YbAgCu4 and YbInCu4  

SciTech Connect

X-ray absorption and magnetic circular dichroism spectra at the L3 edge of Yb have been studied theoretically in the mixed-valent compounds YbAgCu4 and YbInCu4 using the fully relativistic Dirac linear muffin-tin orbital band structure method. The effect of the spin-orbit (SO) interaction and Coulomb repulsion U on the electronic structure of YbAgCu4 and YbInCu4 is examined in the frame of the local spin-density approximation (LSDA)+SO+U method. The core-hole effect in the final states as well as the effect of the electric quadrupole E2 and magnetic dipole M1 transitions have been investigated. The calculated results are compared with available experimental data.

Antonov, V. N.; Bekenov, L. V.; Antropov, V. P.

2014-04-01

261

Electronic structure and f-orbital occupancy in Yb-substituted CeCoIn5  

SciTech Connect

The local structure and 4f orbital occupancy have been investigated in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} via Yb L{sub III}-edge extended x-ray absorption fine structure (EXAFS), Ce and Yb L{sub III}-edge x-ray absorption near-edge structure (XANES), and angle-resolved photoemission spectroscopy (ARPES) measurements. Yb(III) (4f{sup 13}) is the hole analog of Ce(III) (4f{sup 1}). Yb is found to be strongly intermediate-valent in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} throughout the entire doping range, including pure YbCoIn{sub 5}, with an f-hole occupancy for Yb of n{sub f} ? 0.3 (i.e. Yb{sup 2.3+}), independent of Yb concentration and independent of temperature down to T = 20 K. In contrast, the f-electron orbital occupancy for Ce remains close to 1 for all Yb concentrations, suggesting that there is no mutual influence on n{sub f} between neighboring Ce and Yb sites. Likewise, ARPES measurements at 12 K have found that the electronic structure along {Gamma} ? X is not sensitive to the Yb substitution, suggesting that the Kondo hybridization of Ce f electrons with the conduction band is not affected by the presence of Yb impurities in the lattice. The emerging picture is that in Ce{sub 1?x}Yb{sub x}CoIn{sub 5} there are two networks, interlaced but independent, that couple to the conduction band: one network of Ce ions in the heavy-fermion limit, one network of Yb ions in the strongly intermediate-valent limit. The robustness of the local and electronic structure to doping suggests the absence of charge transfer between the Ce and Yb ions, and may explain the relative robustness of superconductivity for this Ce-site substitution as compared to the In-site substitution.

Booth, C. H.; Durakiewicz, T.; Capan, C.; Hurt, D.; Bianchi, A. D.; Joyce, J.J.; Fisk, Z.

2011-05-03

262

Structural and magnetic properties of TM-SiO2 (TM = Fe, Co, Ni) films  

NASA Astrophysics Data System (ADS)

TMx-(SiO2)1-x (TM=Fe, Co, Ni) thin films were prepared in a wide concentration range (0.35 ?x?1). Structure was studied with transmission electron microscopy (TEM), X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Magnetic and magnetotransport properties were investigated by means of magnetization and Hall effect measurements. TEM images display nanometric spherical structures embedded in a SiO2 amorphous matrix, with typical sizes increasing from 3 to 5nm when TM volume concentration x is increased. SAXS measurements indicate a complex structure formed by nanosized objects. XRD measurements show that the structure is composed by amorphous SiO2 and TM crystallites. Slightly above the percolation threshold all samples display giant Hall effect. The observed magnetic properties are dependent on x, and display an evolution resulting from the progressive increase of the mean particle size.

Socolovsky, L. M.; Denardin, J. C.; Brandl, A. L.; Knobel, M.; Zhang, X. X.

2003-05-01

263

Neutron Scattering Study of Kondo Lattice Antiferromagnet YbNiSi3  

Microsoft Academic Search

The Kondo lattice antiferromagnet YbNiSi3 was investigated by neutron scattering techniques. The magnetic structure of YbNiSi3 was determined by neutron diffraction techniques on a single-crystalline sample. We revealed that the magnetic moments of Yb atoms align along the b-axis and are composed a ferromagnetic bc plane stacking antiferromagnetically along the a-axis. Inelastic neutron scattering experiments were also performed on a

Yuha Kobayashi; Takahiro Onimaru; Marcos A. Avila; Kenzo Sasai; Minoru Soda; Kazuma Hirota; Toshiro Takabatake

2008-01-01

264

Valence band structure of the icosahedral Ag-In-Yb quasicrystal  

Microsoft Academic Search

The valence band structure of the icosahedral (i) Ag-In-Yb quasicrystal, which is isostructural to the binary i-Cd-Yb system, is investigated by ultraviolet photoemission spectroscopy (UPS). Experimental results are compared with electronic-structure calculations of a cubic approximant of the same phase. UPS spectra from the fivefold, threefold, and twofold i-Ag-In-Yb surfaces reveal that the valence band near to the Fermi level

H. R. Sharma; G. Simutis; V. R. Dhanak; P. J. Nugent; C. Cui; M. Shimoda; R. McGrath; A. P. Tsai; Y. Ishii

2010-01-01

265

Israel-EU Cooperation on Counter Terrorism  

Microsoft Academic Search

This chapter evaluates the nature of counter terrorism cooperation between the EU and Israel in recent years. Counter terrorism policy and cooperation comprise a spectrum of activities ranging from declaratory statements, through intelligence exchange and police operations, to micro interventions and finally the large scale use of military force (Lassse 2002: 43-50). Both in Israel and the EU there are

Limor Nobel

266

Abnormal reduction, Eu(3+) ? Eu(2+), and defect centers in Eu(3+)-doped pollucite, CsAlSi2O6, prepared in an oxidizing atmosphere.  

PubMed

Eu-doped pollucite CsAlSi2O6 was synthesized by the sol-gel method and heated in an air atmosphere. The crystal structure and the microstructure of the phosphors were investigated by X-ray powder diffraction and SEM images, respectively. The photoluminescence spectra and temperature dependent decay curves were measured. An abnormal reduction phenomenon of Eu(3+) ? Eu(2+) was reported when Eu(3+) ions were doped in alkaline metal cation sites in CsAlSi2O6 prepared in an oxidizing atmosphere. The abnormal mechanism was discussed on the basis of the charge compensation model and a rigid three-dimensional framework structure of CsAlSi2O6. The luminescence color centers were investigated by luminescence decay lifetimes and thermal stabilities of Eu(2+) ions. The defect complexes of [(Eu(3+)Cs)(••)-2VCs'] or [(Eu(3+)Cs)(••)-Oi?] induced by the substitution of Eu(3+) on Cs(+) were suggested in the lattices. Eu(2+) ions could be regarded as Eu(3+) ions combining with the released electrons from defects Oi? or VCs' in close vicinity of Eu(3+) (Eu(3+) + e); the electrons cannot enter the atom track of Eu(2+) presenting luminescence of Eu(2+) ions. The results indicate that several defect traps can be attributed to the abnormal reduction mechanism of Eu(3+) to Eu(2+) ions in a matrix. PMID:24364356

Xie, Hongde; Lu, Juan; Guan, Ying; Huang, Yanlin; Wei, Donglei; Seo, Hyo Jin

2014-01-21

267

Spectroscopy of ^161Yb with ATLAS/Gammasphere  

NASA Astrophysics Data System (ADS)

An experiment was performed at Argonne National Laboratory's ATLAS accelerator using the Gammasphere array (˜100 HPGe detectors) whose primary aim was to investigate the collective bands beyond band termination in ^160Yb via the ^120Sn(^44Ca,4n) fusion-evaporation reaction. The high spin yield of the 4n channel was enhanced significantly by selecting a beam energy of 222 MeV and a considerable amount of data of 3n and 5n channels were also obtained. Here is presented the preliminary result of an initial spectroscopic analysis of ^161Yb, the product of the 3n channel. The RadWare (coincidence analysis) software package was utilized and the possibility of revised level placements has been suggested by the analysis, in comparison with previous level schemes.

Gaison, J.; Carroll, J.; Litz, M.; Wang, X.; Riley, M.; Baron, J.; Miller, S.; Simpson, J.; Paul, E.; Boston, A.; Boston, H.; Nolan, J.; Rees, M.; Revill, J.; Janssens, R.; Carpenter, M.; Kondev, F.; Lauritsen, T.; Zhu, S.; Riedinger, L.; Hartley, D.; Ayangeakaa, A.; Garg, U.; Chiara, C.

2012-10-01

268

Charge Fluctuations and the Valence Transition in Yb under Pressure  

SciTech Connect

We present a dynamical mean field theory study of the valence transition (f{sup 14} {yields} f{sup 13}) in elemental, metallic Yb under pressure. Our calculations reproduce the observed valence transition as reflected in the volume dependence of the 4f occupation. The transition is accelerated by heating, and suggests quasiparticle or Kondo-like structure in the spectra of the trivalent end state, consistent with the early lanthanides. Results for the local charge fluctuations and susceptibility, however, show novel signatures uniquely associated with the valence transition itself, indicating that Yb is a fluctuating valence material in contrast to the intermediate valence behavior seen in the early trivalent lanthanides Ce, Pr, and Nd.

Ylvisaker, E R; Kunes, J; McMahan, A K; Pickett, W E

2009-04-21

269

Compact nanosecond pulsed single stage Yb-doped fiber amplifier  

NASA Astrophysics Data System (ADS)

In this work we present a compact, nanosecond pulsed, single frequency, single stage Yb-doped fiber amplifier by using an overall fiber core diameter of 20 ?m. The key component is a custom made, compact, ultra-low noise, single frequency ring-cavity solid state laser (SSL) at 1064 nm used as a master oscillator. The SSL can be designed to provide nanosecond pulses with pulse energies in the sub-mJ range. Our ultimate goal is to develop a compact linearly polarized, single frequency, nanosecond pulsed laser source in an all-fiber format. Short (less than 1m), highly Yb-doped fibers have been used in order to suppress non-linear effects.

Balliu, E.; Engholm, M.; Hellström, J.; Elgcrona, G.; Karlsson, H.

2014-02-01

270

Factors governing Yb magnetism in Yb{sub 0.95}PtIn{sub 2} and other MgCuAl{sub 2}-type structures  

SciTech Connect

The ternary compound 'YbPtIn{sub 2}' has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl{sub 2} structure, a ternary structure type often formed when rare earth metals, Group 10 transition metals, and indium are present in a 1:1:2 ratio. The unit cell is C-centered orthorhombic, space group Cmcm (no. 63) with lattice parameters of a=4.3410(1) A, b=10.3230(2) A, and c=7.8510(2) A. Evidence is found for a substantial non-stoichiometry on the Yb site, in contrast to the Pt and In sites which behave as expected, and it is believed that the stoichiometry of this compound is more properly described as Yb{sub 0.95}PtIn{sub 2}. Magnetic and resistivity measurements reveal that 'YbPtIn{sub 2}' is a weakly interacting, non-magnetic metal exclusively containing Yb{sup 2+}, and with a resistivity ({rho}) varying from 34 {mu}{Omega} cm at room temperature to a residual resistivity {rho}{sub 0} of 23 {mu}{Omega} cm at 1.8 K. Density functional theory calculations suggest that the observed diamagnetic Yb behavior is expected for this compound, but that certain substitutions on the Pt or In site could help stabilize magnetic Yb{sup 3+} and potentially induce heavy fermion behavior. - Graphical abstract: The crystal structure, magnetic behavior, and temperature-dependent resistivity of the new ternary compound Yb{sub 0.95}PtIn{sub 2.} Highlights: Black-Right-Pointing-Pointer Flux growth method used to produce Yb{sub 0.95}PtIn{sub 2} single crystals. Black-Right-Pointing-Pointer Found rare example of non-stoichiometry in a MgCuAl{sub 2}-type structure. Black-Right-Pointing-Pointer The resistivity and diamagnetic response of Yb{sub 0.95}PtIn{sub 2} were modeled. Black-Right-Pointing-Pointer DFT correctly predicts presence of Yb{sup 2+} in Yb{sub 0.95}PtIn{sub 2}. Black-Right-Pointing-Pointer COHP results suggest other MgCuAl{sub 2}-type indides that may contain paramagnetic Yb{sup 3+}.

Malingowski, Andrew C. [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Kim, Moosung [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Liu, Jue [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Wu, Liusuo [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Aronson, Meigan C. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States) [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Khalifah, Peter G., E-mail: kpete@bnl.gov [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

2013-02-15

271

Photoluminescence properties and energy levels of RE (RE = Pr, Sm, Er, Tm) in layered-CaZnOS oxysulfide  

NASA Astrophysics Data System (ADS)

RE3+ (RE = Pr, Sm, Er, Tm)-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. Doping with RE3+ (RE = Pr, Sm, Er, Tm) into layered-CaZnOS resulted in typical RE3+ (RE = Pr, Sm, Er, Tm) f-f line absorptions and emissions, as well as the charge transfer band of Sm3+ at about 3.3 eV. The energy level scheme containing the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaZnOS has been constructed based on the new data presented in this work, together with the data from literature on Ce3+ and Eu2+ doping in CaZnOS. The detailed energy level scheme provides a platform for interpreting the optical spectra and could be used to comment on the valence stability of the lanthanide ions in CaZnOS.

Zhang, Zhi-Jun; Feng, Ang; Chen, Xiang-Yang; Zhao, Jing-Tai

2013-12-01

272

Photoluminescence properties and energy levels of RE (RE?=?Pr, Sm, Er, Tm) in layered-CaZnOS oxysulfide  

SciTech Connect

RE{sup 3+} (RE?=?Pr, Sm, Er, Tm)-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. Doping with RE{sup 3+} (RE?=?Pr, Sm, Er, Tm) into layered-CaZnOS resulted in typical RE{sup 3+} (RE?=?Pr, Sm, Er, Tm) f-f line absorptions and emissions, as well as the charge transfer band of Sm{sup 3+} at about 3.3?eV. The energy level scheme containing the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaZnOS has been constructed based on the new data presented in this work, together with the data from literature on Ce{sup 3+} and Eu{sup 2+} doping in CaZnOS. The detailed energy level scheme provides a platform for interpreting the optical spectra and could be used to comment on the valence stability of the lanthanide ions in CaZnOS.

Zhang, Zhi-Jun, E-mail: zhangzj@mail.sic.ac.cn [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); Feng, Ang; Chen, Xiang-Yang [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Zhao, Jing-Tai, E-mail: jtzhao@mail.sic.ac.cn [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)

2013-12-07

273

Yb-based heavy fermion compounds and field tuned quantum chemistry  

SciTech Connect

The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in {rho}(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT{sub 2}Zn{sub 20} (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT{sub 2}Zn{sub 20} and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, T{sub K}, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum criticality in Yb-based systems.

Mun, Eundeok

2010-07-23

274

Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals.  

PubMed

We investigated the effect of rare earth impurities on the cooling efficiency of Yb³?:LiYF? (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance. PMID:25402099

Di Lieto, Alberto; Sottile, Alberto; Volpi, Azzurra; Zhang, Zhonghan; Seletskiy, Denis V; Tonelli, Mauro

2014-11-17

275

Thermoluminescence properties of ZnO and ZnO:Yb nanophosphors  

SciTech Connect

ZnO and ZnO:Yb thermoluminescence nanophosphors have been developed and tested under beta radiation. Spherical nanoparticles of sizes ranging from 130 to 1200 nm were prepared through a glycol mediated chemical synthesis. The Yb doping had a thermoluminescence quenching effect compared to undoped ZnO. The 5% Yb concentration produced a low fading, a single thermoluminescence glow peak structure, and a dose linearity behavior adequate for thermoluminescence dosimetry applications. The ZnO:Yb nanophosphor has a great potential as a dosimeter for monitoring in ionizing radiation fields.

Pal, U.; Melendrez, R.; Chernov, V.; Barboza-Flores, M. [Instituto Fisica, Universidad Autonoma de Puebla, Apartado Postal J-48, Puebla 72570 (Mexico); Centro de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora 83190 (Mexico)

2006-10-30

276

Cryogenic Yb3+-Doped Solid-State Lasers  

Microsoft Academic Search

Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true for Yb lasers because of their relatively low quantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index

Tso Yee Fan; Daniel J. Ripin; Roshan L. Aggarwal; Juan R. Ochoa; Bien Chann; Michael Tilleman; Joshua Spitzberg

2007-01-01

277

NUCLEAR PHYSICS: Formation Mechanism of Triaxial Superdeformed Nucleus 160Yb  

NASA Astrophysics Data System (ADS)

By using Total Routhian Surface (TRS) method the deformation of the nucleus 160Yb is studied. The result shows that the triaxial superdeformed state exists with deformation parameters in2 = 0.38 and ? = 21°, where proton shell correction energy plays a key role, and the sum of two quasi-proton particle energies gives an additional driving effect. The rotational energy also has an additional role in the formation of triaxial superdeformed.

Dong, Yong-Sheng; Yu, Shao-Ying; Shen, Cai-Wan; Liu, Yan-Xin

2009-10-01

278

Optical Properties of Tm(3+) Ions in Alkali Germanate Glass  

NASA Technical Reports Server (NTRS)

Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

Walsh, Brian M.; Barnes, Norman P.; Reichle, Donald J.; Jiang, Shibin

2006-01-01

279

Charge transfer in cold Yb++Rb collisions  

NASA Astrophysics Data System (ADS)

Charge-transfer cold Yb++ Rb collision dynamics is investigated theoretically using high-level ab initio potential energy curves, dipole moment functions, and nonadiabatic coupling matrix elements. Within the scalar-relativistic approximation, the radiative transitions from the entrance A1?+ to the ground X1?+ state are found to be the only efficient charge-transfer pathway. The spin-orbit coupling does not open other efficient pathways, but alters the potential energy curves and the transition dipole moment for the A-X pair of states. The radiative, as well as the nonradiative, charge-transfer cross sections calculated within the 10-3-10 cm-1 collision energy range exhibit all features of the Langevin ion-atom collision regime, including a rich structure associated with centrifugal barrier tunneling (orbiting) resonances. Theoretical rate coefficients for two Yb isotopes agree well with those measured by immersing Yb+ ions in an ultracold Rb ensemble in a hybrid trap. Possible origins of discrepancy in the product distributions and relations to previously studied similar processes are discussed.

Sayfutyarova, Elvira R.; Buchachenko, Alexei A.; Yakovleva, Svetlana A.; Belyaev, Andrey K.

2013-05-01

280

Mechanism of tantalum adhesion on SiLK{sup TM}  

SciTech Connect

Tantalum adhesion on SiLK{sup TM} was investigated using first-principles method based on density functional theory. Phenylene groups were found to play a major role and the adjacent semi-benzene rings also contribute significantly to Ta adhesion on SiLK{sup TM}. In addition, the degradation effects of H{sub 2}/He reactive plasma clean on Ta adhesion on SiLK{sup TM} was investigated. Based on our findings, argon plasma treatment was suggested and implemented after reactive plasma cleaning process, which resulted in integration of SiLK{sup TM} with Cu up to seven metal layers.

Hu Yue; Yang Shuowang; Chen Xiantong; Lu Dong; Feng Yuanping; Wu Ping [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institute of High Performance Computing, 1 Science Park Road, Singapore 117528 (Singapore); Institute of Microelectronics, 11 Science Park Road, Singapore 117685 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Institute of High Performance Computing, 1 Science Park Road, Singapore 117528 (Singapore)

2005-09-19

281

COMPOSITE TECHNOLOGY DEVELOPMENT INC. CryoCoatTM UltraLightTM  

E-print Network

30 Vacuum [Torr] Apparent ThermalConductivity [mW/M-K] between liquid nitrogen and room temperature density & thermal conductivity of a chemically expanded foam Material lighter than 5 PCF has been 30 40 50 60 70 80 Thermal Conductivity: CTD UltraLightTM UL31xx Temperature [K] ThermalConductivity

McDonald, Kirk

282

Graphing Calculators, the CBL2[TM] and TI-Interactive[TM] in High School Science.  

ERIC Educational Resources Information Center

This collection of activities is designed to show how TI-Interactive[TM] and Calculator-based Laboratories (CBL) can be used to explore topics in high school science. The activities address such topics as specific heat, Boyle's Law, Newton's Law of Cooling, and Antarctic Ozone Levels. Teaching notes and calculator instructions are included as are…

Molnar, Bill

283

Thermoelectric response near a quantum critical point of ?-YbAlB4 and YbRh2Si2: a comparative study.  

PubMed

The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds ?-YbAlB4 and YbRh2Si2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in ?-YbAlB4, but drastically reduced in YbRh2Si2. The ratio of thermopower to specific heat remains constant for ?-YbAlB4, but it is significantly reduced near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds. PMID:23102346

Machida, Y; Tomokuni, K; Ogura, C; Izawa, K; Kuga, K; Nakatsuji, S; Lapertot, G; Knebel, G; Brison, J-P; Flouquet, J

2012-10-12

284

Elevated serum dehydroepiandrosterone sulfate levels in practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs  

Microsoft Academic Search

Serum dehydroepiandosterone sulfate (DHEA-S) levels were measured in 270 men and 153 women who were experienced practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs, mental techniques practiced twice daily, sitting quietly with the eyes closed. These were compared according to sex and 5-year age grouping to 799 male and 453 female nonmeditators. The mean DHEA-S levels in the TM

Jay L. Glaser; Joel L. Brind; Joseph H. Vogelman; Michael J. Eisner; Michael C. Dillbeck; R. Keith Wallace; Deepak Chopra; Norman Orentreich

1992-01-01

285

YB-1 is a Transcription/Translation Factor that Orchestrates the Oncogenome by Hardwiring Signal Transduction to Gene Expression  

PubMed Central

The Y-box Binding Protein-1 (YB-1) is a highly conserved oncogenic transcription/translation factor that is expressed in cancers affecting adults and children. It is now believed that YB-1 plays a causal role in the development of cancer given recent work showing that its expression drives the tumorigenesis in the mammary gland. In human breast cancers, YB-1 is associated with rapidly proliferating tumors that are highly aggressive. Moreover, expression of YB-1 promotes the growth of breast cancer cell lines both in monolayer and anchorage independent conditions. The involvement of YB-1 in breast cancer pathogenesis has made it a putative therapeutic target; however, the mechanism(s) that regulate YB-1 are poorly understood. This review first describes the oncogenic properties of YB-1 in cancer. It also highlights the importance of YB-1 in hardwiring signal transduction pathways to the regulation of genes involved in the development of cancer. PMID:23641145

Wu, Joyce; Stratford, Anna L.; Astanehe, Arezoo; Dunn, Sandra E.

2007-01-01

286

75 FR 56140 - Comment Request for Information Collection for the YouthBuild (YB) Reporting System (OMB Control...  

Federal Register 2010, 2011, 2012, 2013

...YouthBuild (YB) Reporting System (OMB Control No. 1205-0464...about the YB Reporting System which expires on October...Management Information System (MIS) report formats...placements, outcomes, and follow-up status....

2010-09-15

287

Luminescence Properties of Yb-2,4-Dimethoxyhematoporphyrin IX, a Promising Compound for Diagnosis of Malignant Tumors  

NASA Astrophysics Data System (ADS)

The measured quantum yield of Yb-2,4-dimethoxyhematoporphyrin (Yb-DMHP) in DMSO was 0.8%. It was found that molecular oxygen did not quench luminescence of the metal ion in Yb-DMHP, which was a diagnostic advantage while using this complex in practice. The kinetic characteristics of IR luminescence of the Yb porphyrin complex in DMSO/H2O mixtures were measured. The average lifetime of Yb3+ (2F5/2) in DMSO was 9.7 ?s, which was an order of magnitude greater than that of the auto-fluorescence of biological tissues. Water molecules quenched effectively IR luminescence of Yb-DMHP. The integrated luminescence intensity of Yb3+ (2F5/2) depended non-linearly on the fraction of H2O in the DMSO/H2O mixtures. This was indicative of a complex quenching mechanism of Yb luminescence by surrounding molecules.

Stasheuski, A. S.; Knyukshto, V. N.; Ivanov, A. V.; Rumyantseva, V. D.; Shilov, I. P.; Galievsky, V. A.; Dzhagarov, B. M.

2015-01-01

288

Evolution of the 4 f electron localization from YbRh2Si2 to YbRh2Pb studied by electron spin resonance  

NASA Astrophysics Data System (ADS)

We report on electron spin resonance (ESR) experiments on the Heusler alloy YbRh2Pb and compare its spin dynamics with that of several other Yb-based intermetallics. A detailed analysis of the derived ESR parameters indicates the extremely weak hybridization, more localized distribution of the 4 f states, and a smaller RKKY interaction in YbRh2Pb. These findings reveal the important interplay between hybridization effects, chemical substitution, and crystalline electric field interactions that determines the ground state properties of strongly correlated electron systems.

Ivanshin, V. A.; Litvinova, T. O.; Ivanshin, N. A.; Pöppl, A.; Sokolov, D. A.; Aronson, M. C.

2014-05-01

289

High-gain amplification in Yb:CaF2 crystals pumped by a high-brightness Yb-doped 976 nm fiber laser  

NASA Astrophysics Data System (ADS)

We report on high single-pass gain in Yb:CaF2 crystal longitudinally pumped with a 40 W high-brightness fiber laser source based on an ytterbium-doped ultra-large core photonic crystal rod-type fiber operating at 976 nm. A single-pass small-signal gain of 3.2 has been achieved in a 6 % Yb-doped 10-mm-long CaF2 crystal at room temperature, outperforming any CW-diode-pumped scheme and paving the way towards very promising innovative lasers and amplifiers schemes merging the Yb-doped solid-state and fiber technologies.

Machinet, G.; Andriukaitis, G.; Sévillano, P.; Lhermite, J.; Descamps, D.; Pugžlys, A.; Baltuška, A.; Cormier, E.

2013-05-01

290

The temperature gradient technique (TGT) growth and optical properties of Yb-doped YAlO 3 single crystal  

Microsoft Academic Search

The dark-brown colored 5at% Yb-doped YAlO3 (Yb:YAP) single crystal was grown successfully by temperature gradient technique (TGT) for the first time. The TGT-grown Yb:YAP crystal with the perovskite structure and excellent crystallization perfection were confirmed by the X-ray diffractions techniques. The dark-brown color of TGT-Yb:YAP crystal turned into the colorless after annealing in the air at 1200°C for 10h. The

Guangjun Zhao; Hongjun Li; Jiang Zhu; Mingyin Jie; Xiaoming He; Jun Xu

2005-01-01

291

ORNL/TM-2007/224 BIOFUEL FEEDSTOCK ASSESSMENT FOR  

E-print Network

ORNL/TM-2007/224 BIOFUEL FEEDSTOCK ASSESSMENT FOR SELECTED COUNTRIES Keith L. Kline Gbadebo A Government or any agency thereof. #12;ORNL/TM-2007/224 BIOFUEL FEEDSTOCK ASSESSMENT FOR SELECTED COUNTRIES To Support the DOE study of Worldwide Potential to Produce Biofuels with a focus on U.S. Imports Keith L

Pennycook, Steve

292

The EGF-TM7 family: a postgenomic view.  

PubMed

With the human and mouse genome projects now completed, the receptor repertoire of mammalian cells has finally been elucidated. The EGF-TM7 receptors are a family of class B seven-span transmembrane (TM7) receptors predominantly expressed by cells of the immune system. Within the large TM7 superfamily, the molecular structure and ligand-binding properties of EGF-TM7 receptors are unique. Derived from the processing of a single polypeptide, they are expressed at the cell surface as heterodimers consisting of a large extracellular region associated with a TM7 moiety. Through a variable number of N-terminal epidermal growth factor (EGF)-like domains, EGF-TM7 receptors interact with cellular ligands such as CD55 and chondroitin sulfate. Recent in vivo studies demonstrate a role of the EGF-TM7 receptor CD97 in leukocyte migration. The different number of EGF-TM7 genes in man compared with mice, the chimeric nature of EMR2 and the inactivation of human EMR4 point toward a still-evolving receptor family. Here we discuss the currently available information on this intriguing receptor family. PMID:14647991

Kwakkenbos, Mark J; Kop, Else N; Stacey, Martin; Matmati, Mourad; Gordon, Siamon; Lin, Hsi-Hsien; Hamann, Jörg

2004-01-01

293

Utilising eduroam[TM] Architecture in Building Wireless Community Networks  

ERIC Educational Resources Information Center

Purpose: eduroam[TM] has already been proved to be a scalable, secure and feasible way for universities and research institutions to connect their wireless networks into a WLAN roaming community, but the advantages of eduroam[TM] have not yet been fully discovered in the wireless community networks aimed at regular consumers. This aim of this…

Huhtanen, Karri; Vatiainen, Heikki; Keski-Kasari, Sami; Harju, Jarmo

2008-01-01

294

ISI TechnicalManual ISI/TM-88-197  

E-print Network

ISI TechnicalManual ISI/TM-88-197 February1988 University ofSouthern California Gabriel Robins %% ... ... .. The ISI Grapher Manual INFORMATION SCIENCES 213/822-1511 INSTITUTEJ f-"-676 292-t5466Admiralty Way. MONITORING ORGANIZATION REPORT NUMBER(S) ISI/TM-88-197 6a. NAME OF PERFORMING ORGANIZATION USC

Robins, Gabriel

295

Superconducting Wires Enabled by Nanodots wins Nano50TM Award  

E-print Network

. · Awarded the Nano 50TM Award from Nanotech Briefs® Magazine for technology. Developers: · A. Goyal S. KangSuperconducting Wires Enabled by Nanodots wins Nano50TM Award HTS Wires Enabled via 3D Self . · The technology meets performance requirements for most large-scale applications of HTS, including underground

296

Accelerated Math[TM]. What Works Clearinghouse Intervention Report  

ERIC Educational Resources Information Center

"Accelerated Math"[TM], published by Renaissance Learning, is a software tool used to customize assignments and monitor progress in math for students in grades 1-12. The "Accelerated Math"[TM] software creates individualized assignments aligned with state standards and national guidelines, scores student work, and generates reports on student…

What Works Clearinghouse, 2011

2011-01-01

297

Inside Linden Lab: Second Life [TM] for Educators  

ERIC Educational Resources Information Center

A new culture called Second Life [TM] has emerged that promises innovative strategies for everything from social interactions to business. Some educators believe it may hold new and unique opportunities for teaching and learning. Second Life [TM] (SL) is the creation of Linden Labs, a San Francisco-based corporation defined by its creators as "an…

Atkinson, Tom

2008-01-01

298

SpellRead[TM]. What Works Clearinghouse Intervention Report  

ERIC Educational Resources Information Center

"SpellRead"[TM], formerly known as "SpellRead Phonological Auditory Training"[R], is a small-group literacy program for struggling readers in grades 2-12. "SpellRead"[TM] integrates the auditory and visual aspects of the reading process and emphasizes specific skill mastery through systematic and explicit instruction. Students are taught to…

What Works Clearinghouse, 2013

2013-01-01

299

SANDIA CORPORATION SF 6432-TM (01-02)  

E-print Network

of this Contract. TM02 - APPLICABLE LAW The rights and obligations of the parties hereto shall be governed by this Agreement and construed in accordance with federal law of government contracts. TM03 - ASSIGNMENT Contractor shall not assign rights or obligations to third parties without the prior written consent of Sandia

300

Broadband phase noise suppression in a Yb-fiber frequency comb  

E-print Network

Broadband phase noise suppression in a Yb-fiber frequency comb A. Cingöz,1, * D. C. Yost,1 T. K operation and high average power [4,5]. One of the most important applications of frequency combs has been combs with sub- hertz linewidths [6] and Yb combs with submillihertz line- widths [4], suitable

301

Effect of Yb3+ concentration on photoluminescence properties of cubic Gd2O3 phosphor  

NASA Astrophysics Data System (ADS)

Yb3+ doped phosphor of Gd2O3 (Gd2O3:Yb3+) have been prepared by solid state reaction method. The structure and the particle size have been determined by X-ray powder diffraction measurements. The average particle size of the phosphor is in between 35 and 50 nm. The particle size and structure of the phosphor was further confirmed by TEM analysis. The visible and NIR luminescence spectra were recorded under the 980 nm laser excitation. The visible upconversion luminescence of Yb3+ ion was due to cooperative luminescence and the presence of rare earth impurity ions. The cooperative upconversion and NIR luminescence spectra as a function of Yb3+ ion concentration were measured and the emission intensity variation with Yb3+ ion concentration was discussed. Yb3+ energy migration quenched the cooperative luminescence of Gd2O3:Yb3+ phosphor with doping level over 5%, while the NIR emission luminescence continuously increases with increasing Yb3+ ion concentration.

Tamrakar, Raunak Kumar; Bisen, D. P.; Brahme, Nameeta

2015-01-01

302

YB-1 Synthesis Is Regulated by mTOR Signaling Pathway  

PubMed Central

YB-1 is a eukaryotic protein with numerous intra- and extracellular functions based on its ability to interact with RNA, DNA, and many proteins. In spite of achievements in studying its functions, regulation of YB-1 synthesis in the cell remains poorly understood. In the current study Western and Northern blotting were used to determine the amounts of YB-1 and YB-1 mRNA in rabbit organs and several cell lines. As found, in the majority of studied eukaryotic cells a considerable proportion of YB-1 mRNA was stored in free mRNPs, i.e., was poorly translated. Also, we demonstrated that YB-1 synthesis depended on conditions that determined the rate of cell division. Specific suppression of YB-1 synthesis resulted from inhibition of the mTOR signaling pathway with inhibitor PP242, but not rapamycin. Experiments on reporter constructs showed that dependence of YB-1 mRNA translation on activity of the mTOR signaling pathway was dictated by 5? untranslated regions of this mRNA, irrelatively of the TOP-like sequences at the beginning of 5? UTR. PMID:23285076

Lyabin, Dmitry N.; Eliseeva, Irina A.; Ovchinnikov, Lev P.

2012-01-01

303

Evolution of the superconducting properties of CeCoIn5 with Yb substitution  

NASA Astrophysics Data System (ADS)

We report on the evolution of the physical properties of the Yb substitution series starting from the unconventional superconductor (SC) CeCoIn5 to the isostructural normal metal YbCoIn5. This study was motivated by the recent results of Cd or Hg substitution at the percentage level on the In site in CeCoIn5 which for low concentrations first was shown to lead to the coexistence of antiferromagnetism with SC and to a complete suppression of SC at higher concentrations. At the same time, the lattice constant of YbCoIn5 indicates that Yb enters this compound in a partially divalent configuration suggesting that Yb could also be suitable for doping holes into CeCoIn5. In our substitution series we find that that the unit cell volume stays roughly constant up to an Yb concentration of about 40 %, after which the cell volume begins to decrease gradually to the value of YbCoIn5. At the same time we observe a gradual suppression of the transition temperature Tc to zero at an Yb concentration of 60 %. Interestingly, the shape of H-T-phase diagram remains the same when the axis is scaled with the respective Tc and upper critical field Hc2, suggesting that the ratio between Pauli Hp and the orbital critical field Hc20 remains constant.

Hurt, D.; Capan, C.; Fisk, Z.; Bianchi, A. D.

2008-03-01

304

Yb:YAG single crystal fiber power amplifier for femtosecond sources  

E-print Network

-pumped solid-state laser systems have allowed tremendous improvements of their performance, reliabilityYb:YAG single crystal fiber power amplifier for femtosecond sources Xavier Délen,1, * Yoann Zaouter 179807); published January 7, 2013 We demonstrate a versatile femtosecond power amplifier using a Yb

305

POWER WITHOUT INFLUENCE? THE EU AND TRADE DISPUTES WITH RUSSIA  

Microsoft Academic Search

Abstract The gap between,expectations and capabilities in the EU external relations is well known. Perhaps it has nowhere manifested itself as clearly as in the relations between the EU and Russia. Typically, the lack of power of the EU is explained through weak coherence. However, the poor performance of the EU may also depend on other factors such as a

Tuomas Forsberg; Antti Seppo

2008-01-01

306

The effect of conductivity on the Eu153 hyperfine interactions in EuTe  

Microsoft Academic Search

The hyperfine interactions of Eu153 in two well characterized samples of EuTe have been measured at liquid helium temperatures by spin-echo NMR. One of the samples is a conductor and the other one essentially a nonconductor. Our studies indicate that the Eu153 hyperfine interactions are sensitive to the conductivity of the samples. Published magnetization measurements on these samples are used

K. Raj; J. I. Budnick; T. J. Burch

1975-01-01

307

Renal threshold phosphate concentration (TmPO4/GFR).  

PubMed Central

The ratio of maximum rate of renal tubular reabsorption of phosphate to glomerular filtration rate (TmPO4/GFR) was determined in 546 schoolchildren, aged between 6 and 17.9 years, using the nomogram of Walton and Bijvoet.1 TmPO4/GFR correlated with chronological age in girls and boys and in each remained significantly higher than in adults. TmPO4/GFR in the children correlated neither with fasting serum immunoreactive calcitonin and parathyroid hormone levels nor with the urinary cyclic AMP excretion. The study showed a parallel decrease in TmPO4/GFR, excretion of total hydroxyproline and serum alkaline phosphatase activities after puberty, with a significant relationship of both these indices of bone turnover to TmPO4/GFR values. This indicates that the high renal phosphate threshold of children may be an important factor for bone mineralisation by providing high extracellular inorganic phosphate concentrations during normal growth. PMID:6280622

Kruse, K; Kracht, U; Göpfert, G

1982-01-01

308

Registratiom of TM data to digital elevation models  

NASA Technical Reports Server (NTRS)

Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

1984-01-01

309

Eu-doped (Lu/Sc) 2O 3 thin films grown by thermal evaporation  

NASA Astrophysics Data System (ADS)

The sesquioxides Y 2O 3, Sc 2O 3 and Lu 2O 3 are well known hosts for rare-earth-ions, e.g. Eu:Y 2O 3 as red phosphor or Tm:Sc 2O 3 as solid state laser. Sesquioxide thin films on ?-Al 2O 3 substrates allow fabrication of crystalline optical coatings, waveguide lasers and photonic structures. We report on the growth of Eu-doped (Lu 0.19Sc 0.81) 2O 3 thin films on ?-Al 2O 3 by electron-beam evaporation (EBV). The properties of the films are compared with EBV- and PLD-deposited Y 2O 3 films. In contrast to EBV-deposited Y 2O 3 films, the (Lu/Sc) 2O 3 films are chemically stable. The lattice mismatch with respect to the substrate is -1.5% whereas it is +4.7% for Y 2O 3. This leads to films textured along the <1 1 1> direction. The grain size is larger than in EBV-deposited polycrystalline Y 2O 3 films of similar thickness. The local symmetry of the Eu 3+ centers is identical to the symmetry in (Lu/Sc) 2O 3 bulk crystals. Spectral modifications due to surface effects dominate only when the average film thickness is less than 5 nm. Burying EBV-deposited Y 2O 3 films below an amorphous Al 2O 3 cover layer prevents spectral changes and increases the fluorescence quantum yield. The (Lu/Sc) 2O 3 films resemble PLD-deposited Eu:Y 2O 3 films in crystal structure as well as in spectroscopic properties and in quantum yield of the fluorescence. Since EBV is a much simpler—and cheaper—technique than PLD, EBV-deposited (Lu/Sc) 2O 3 films might be favorable for the fabrication of waveguiding and photonic structures for future commercial applications.

Rabisch, L.; Bär, S.; Scheife, H.

2006-05-01

310

Efficient diode-pumped Yb3+:Y2SiO5 and Yb3+:Lu2SiO5 high-power femtosecond laser operation.  

PubMed

We report the mode-locked operation of two new Yb-doped oxyorthosilicates, Y2SiO5 (YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 fs with 410 mW of output power at 1041 nm. More than 2.6 W of average output power, for pulse durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided. These are, to our best knowledge, the highest values ever obtained and the most efficient mode-locked laser in such a classic fiber-coupled diode-pumping configuration. PMID:16642170

Thibault, F; Pelenc, D; Druon, F; Zaouter, Y; Jacquemet, M; Georges, P

2006-05-15

311

Anomalous Eu valence state and superconductivity in undoped Eu3Bi2S4F4.  

PubMed

We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) Å, c = 32.4330(6) Å, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond valence sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, while Eu(2) has an average valence of ??+2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mössbauer and magnetization measurements. The Eu(3+) components donate electrons into the conduction bands that are mainly composed of Bi 6px and 6py states. Consequently, the material itself shows metallic conduction and superconducts at 1.5 K without extrinsic chemical doping. PMID:25314008

Zhai, Hui-Fei; Zhang, Pan; Wu, Si-Qi; He, Chao-Yang; Tang, Zhang-Tu; Jiang, Hao; Sun, Yun-Lei; Bao, Jin-Ke; Nowik, Israel; Felner, Israel; Zeng, Yue-Wu; Li, Yu-Ke; Xu, Xiao-Feng; Tao, Qian; Xu, Zhu-An; Cao, Guang-Han

2014-10-29

312

EPR, ENDOR and optical spectroscopy of Yb3+ ion in KZnF3 single crystals  

NASA Astrophysics Data System (ADS)

The paramagnetic center of tetragonal symmetry formed by the Yb3+ ion in the KZnF3 crystal has been studied using methods of EPR, ENDOR and optical spectroscopy. The location of the impurity ion and the structural model of the complex differing from the model of the Yb3+ center in KMgF3 have been established. The empirical scheme of the energy levels of the Yb3+ ion has been found. The parameters of its interaction with the crystal electrostatic field and the hyperfine interaction with ligands of the nearest environment have been determined. The parameters of the crystal field were used for the analysis of the distortions of the crystal lattice in the vicinity of Yb3+. The parameters of the transferred hyperfine interaction have been calculated for the distances between Yb3+ and F- ions of the nearest environment obtained taking into account the found distortions. They are in good agreement with the experimental values.

Falin, M. L.; Gerasimov, K. I.; Latypov, V. A.; Leushin, A. M.; Schweizer, S.; Spaeth, J.-M.

2015-02-01

313

Enhanced broadband near-infrared luminescence and optical amplification in Yb-Bi codoped phosphate glasses  

NASA Astrophysics Data System (ADS)

Yb-Bi codoped phosphate glass was prepared and its properties were compared with Bi-doped phosphate glass. The broadband infrared luminescence intensity from Yb-Bi codoped glass was ˜32 times stronger than that of Bi-doped glass. The single-pass optical amplification was measured on a traditional two-wave mixing configuration. No optical amplification was observed in Bi-doped glass, while apparent broadband optical amplification between 1272 and 1336nm was observed from Yb-Bi codoped glass with 980nm laser diode excitation. The highest gain coefficient at 1272nm of Yb-Bi codoped glass reached to 2.62cm-1. Yb-Bi codoped phosphate glass is a promising material for broadband optical amplification.

Ruan, Jian; Wu, E.; Zeng, Heping; Zhou, Shifeng; Lakshminarayana, G.; Qiu, Jianrong

2008-03-01

314

Output characteristics of high power cryogenic Yb:YAG TRAM laser oscillator.  

PubMed

We analyzed the output power characteristics of a cryogenically cooled Yb:YAG total-reflection active-mirror (TRAM) laser oscillator including the temperature dependence of the emission cross section and the reabsorption loss of the Yb:YAG TRAM. A CW multi-transverse mode oscillation of a 9.8 at.% doped 0.6 mm thick Yb:YAG ceramic TRAM was investigated for various pump spot sizes and compared with theoretical results. The Yb:YAG temperatures were inferred from the ratio between fluorescence intensities at 1022 nm and 1027 nm which varied significantly with temperature below 200 K. Output power calculations using evaluated temperatures were in good agreement with the experimental data measured between 77 and 200 K, and the output power suppression due to the temperature rise observed above ~140 K. To the best of our knowledge, this is the first evaluation of output power for a cryogenically cooled Yb:YAG TRAM laser. PMID:23037293

Furuse, Hiroaki; Kawanaka, Junji; Miyanaga, Noriaki; Chosrowjan, Haik; Fujita, Masayuki; Takeshita, Kenji; Izawa, Yasukazu

2012-09-10

315

{beta}-decay study of {sup 150}Er, {sup 152}Yb, and {sup 156}Yb: Candidates for a monoenergetic neutrino beam facility  

SciTech Connect

The {beta} decays of {sup 150}Er, {sup 152}Yb, and {sup 156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied the EC decay proceeds mainly to a single state in the daughter nucleus.

Estevez Aguado, M. E.; Algora, A.; Rubio, B.; Bernabeu, J.; Nacher, E.; Tain, J. L.; Gadea, A.; Agramunt, J.; Burkard, K.; Hueller, W.; Doering, J.; Kirchner, R.; Mukha, I.; Plettner, C.; Roeckl, E.; Grawe, H.; Collatz, R.; Hellstroem, M.; Cano-Ott, D.; Karny, M. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); GSI, D-64291 Darmstadt (Germany); CIEMAT, E-28000, Madrid (Spain); Institute of Experimental Physics, University of Warsaw, PL-00-681 Warsaw (Poland); ORNL, Oak Ridge, Tennessee 37831 (United States); PNPI, 188300 Gatchina (Russian Federation); IKP, University of Cologne, D-50937 Cologne (Germany); INFN LNL, I-35020 Legnaro (Padova) (Italy); CFPT-IST, 1049-001 Lisbon (Portugal)

2011-09-15

316

Critical separation for efficient Tm3+ -Tm3+ energy transfer evidenced in nanostructured Tm3+: Al2O3 thin films.  

PubMed

Nanostructured amorphous Al oxide (a-Al2O3) thin films doped with Tm3+ were synthesized by alternate pulsed laser deposition. The Tm3+ ions have been deposited in layers with in-depth separation ranging from 0.75 to 6 nm. The films show two broad emission bands originated from the Tm3+ 3H4-->3F4 and 3F4-->3H6 transitions. Their intensity increases at a similar rate and the lifetimes are not modified as the layer separation decreases down to 1.5 nm, suggesting that there is no concentration quenching. At the critical value of 1.5 nm the onset of Tm3+ -Tm3+ energy transfer is evidenced by a sharp decrease of the emission intensity and lifetime. Below this critical value, the rate at which the intensity increases for the 3F4-->3H6 transition is much higher than that for the 3H4-->3F4 transition, evidencing quenching of the 3H4-->3F4 transition through a cross-relaxation mechanism. The control of the Tm3+ ions in the nanometer scale allows evidencing the onset of energy transfer processes among ions and offers a route to optimize compact photonic gain integrated devices. PMID:18347725

Xiao, Zhisong; Serna, R; Xu, Fei; Afonso, C N

2008-03-15

317

YB-1 represses AP1-dependent gene transactivation and interacts with an AP-1 DNA sequence  

PubMed Central

Involvement of the AP-1 (activator protein-1) transcription factor has been demonstrated previously in the regulation of cell proliferation and cell-cycle progression, in the control of cell migration, invasion and metastasis, and in signal transduction, stress responsiveness, DNA replication and DNA repair. YB-1 (Y-box-binding protein-1) has also been implicated in many of these processes. However, the mechanism by which YB-1 mediates these processes is poorly understood. In the present study, we report that overexpression of a transfected gene encoding YB-1 in human HeLa cervical carcinoma cells significantly represses the transactivation of a minimal AP-1 reporter construct in response to the tumour promoter PMA. YB-1 also represses mRNA expression and PMA-induced promoter transactivation of the endogenous AP-1 target gene encoding matrix metalloproteinase-12 (metalloelastase). YB-1 transrepression of both the minimal and matrix metalloproteinase-12 promoter reporter constructs is dependent on the AP-1 sequence. To identify new nuclear proteins that bind specifically to the AP-1 DNA-binding site, we devised a DNA-affinity-chromatography-based assay termed NAPSTER (nucleotide-affinity preincubation specificity test of recognition) and discovered a 49 kDa protein from human cancer cells that binds in a sequence-specific manner to the AP-1 DNA sequence. By tandem MS fragmentation sequencing analyses we determined that p49 is a YB-1. Immunoblotting of the NAPSTER-purified p49 protein using anti-YB-1 antibodies confirmed YB-1 binding to the AP-1 DNA sequence, as did gel mobility-supershift assays using YB-1 antibodies. This is the first report of YB-1 transrepression and interaction at the AP-1 DNA-binding site. PMID:15702969

2005-01-01

318

EurActiv: EU News and Policy Positions  

NSDL National Science Digital Library

This site is an independent media portal fully dedicated to European Union (EU) affairs. This extensive site is an online platform for EU policies, complementing existing EU media and institutional websites. The site's coverage of EU affairs concentrates on policy positions by EU members, focusing on the policy debates that occur before decisions are made. The website covers many topics such as energy, environmental issues, science and research and sustainable development.

EurActiv

319

Intra-EU migration, citizenship and political union.  

PubMed

"Of the 14.1 million resident aliens living in the European Union (EU), 4.9 million are nationals of EU Member States residing in other Member States.... These resident alien EU nationals present a problem for maintaining democratic inclusiveness while EU Member States undergo integration....I explore this paradox of political integration by focusing on intra-EU migration and the Maastricht Treaty's attempted solution of European citizenship." PMID:12320110

Koslowski, R

1994-09-01

320

Quantum Criticality and Superconductivity in ?-YbAlB4  

NASA Astrophysics Data System (ADS)

Heavy fermion systems have provided a number of prototypical compounds to study unconventional superconductivity and non-Fermi-liquid (NFL) states. A long standing issue in the research of heavy fermion superconductivity in 4f intermetallics is the dramatically different behavior between the electron like Ce (4f^1) and hole like Yb (4f^13) compounds. While superconductivity has been found in a number of Ce based heavy fermion compounds, no superconductivity has been reported for the corresponding Yb systems. In this talk, I present our recent finding of the superconductivity in the new heavy fermion system ?-YbAlB4 [1-3]. The superconducting transition temperature is 80 mK, and above it, the system exhibits pronounced NFL behavior in the transport and thermodynamic properties [2,3]. Furthermore, the magnetic field dependence of the NFL behavior indicates that the system is a rare example of a pure metal that displays quantum criticality at ambient pressure and under zero magnetic field. Using our latest results, we discuss the detailed properties of superconductivity and quantum criticality. This is the work performed in collaboration with K. Kuga, Y. Matsumoto, T. Tomita, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk. [4pt] [1] Robin T. Macaluso, Satoru Nakatsuji, Kentaro Kuga, Evan Lyle Thomas, Yo Machida, Yoshiteru Maeno, Zachary Fisk, and Julia Y. Chan, Chem. Mater. 19 1918 (2007). [0pt] [2] S. Nakatsuji, K.Kuga, Y. Machida, T. Tayama, T. Sakakibara, Y. Karaki, H. Ishimoto, S. Yonezawa, Y. Maeno, E. Pearson, G. G. Lonzarich, L.Balicas, H. Lee, and Z. Fisk, Nature Phys 4, 603-607 (2008). [0pt] [3] K. Kuga, Y. Karaki, Y. Matsumoto, Y. Machida, and S. Nakatsuji, Phys. Rev. Lett. 101, 137004 (2008).

Nakatsuji, Satoru

2009-03-01

321

Water quality mapping using Landsat TM imagery  

NASA Astrophysics Data System (ADS)

Environmental monitoring through the method of traditional ship sampling is time consuming and requires a high survey cost. The objective of this study is to evaluate the feasibility of Landsat TM imagery for total suspended solids (TSS) mapping using a newly developed algorithm over Penang Island. The study area is the seawater region around Penang Island, Malaysia. Water samples were collected during a 3-hour period simultaneously with the satellite image acquisition and later analyzed in the laboratory above the study area. The samples locations were determined using a handheld GPS. The satellite image was geometrically corrected using the second order polynomial transformation. The satellite image also was atmospheric corrected by using ATCOR2 image processing software. The digital numbers for each band corresponding to the sea-truth locations were extracted and then converted into reflectance values for calibration of the water quality algorithm. The proposed algorithm is based on the reflectance model that is a function of the inherent optical properties of water, which can be related to its constituent's concentrations. The generated algorithm was developed for three visible wavelenghts, red, green and blue for this study. Results indicate that the proposed developed algorithm was superior based on the correlation coefficient (R) and root-mean-square deviation (RMS) values. Finally the proposed algorithm was used for TSS mapping at Penang Island, Malaysia. The generated TSS map was colour-coded for visual interpretation and image smoothing was performed on the map to remove random noise. This preliminary study has produced a promising result. This study indicates that the empirical algorithm is suitable for TSS mapping around Penang Island by using satellite Landsat TM data.

Lim, H. S.; MatJafri, M. Z.; Abdullah, K.; Alias, A. N.; Wong, C. J.; Mustapha-Rosli, M. R.; Mohd Saleh, N.

2009-05-01

322

In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications  

NASA Technical Reports Server (NTRS)

The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

2012-01-01

323

Identification of the tropomyosin (HL-Tm) in Haemaphysalis longicornis.  

PubMed

Haemaphysalis longicornis tropomyosin (HL-Tm) was amplified by RT-PCR. The cDNA contained a 825bp open reading frame coding for 274 amino acids with a predicted theoretical isoelectric point (pI) of 4.55 and molecular weight of 31.7kDa. Real-time RT-PCR analysis showed that the expression levels of the HL-Tm in the unfed-females were significantly higher than in other tested developmental stages (eggs, unfed-larvae and unfed-nymphs). Western blot analysis showed that rabbit anti-serum against H. longicornis unfed-adult ticks recognized the recombinant HL-Tm protein (rHL-Tm). Immunization of rabbits with the rHL-Tm resulted in a statistically significant reduction of female engorgement and oviposition. Silencing of HL-Tm by RNAi showed a decrease in tick engorgement and oviposition, which is consistent with the effect of recombinant protein vaccine on the adults. These results showed that tick HL-Tm might be involved in the regulation of ticks blood-feeding, growth and oviposition. PMID:25535026

Tian, Meiyuan; Tian, Zhancheng; Luo, Jin; Xie, Junren; Yin, Hong; Zeng, Qiaoying; Shen, Hui; Chai, Huiping; Yuan, Xiaosong; Wang, Fangfang; Liu, Guangyuan

2015-01-30

324

Quasi four-level Tm:LuAG laser  

NASA Technical Reports Server (NTRS)

A quasi four-level solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG-based host material doped to a final concentration between about 2% and about 7% thulium (Tm) ions. For the more heavily doped final concentrations, the LuAG-based host material is a LuAG seed crystal doped with a small concentration of Tm ions. Laser diode arrays are disposed transversely to the laser crystal for energizing the Tm ions.

Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Hutcheson, Ralph L. (Inventor); Rodriguez, Waldo J. (Inventor)

1997-01-01

325

Review of Tm and Ho Materials; Spectroscopy and Lasers  

NASA Technical Reports Server (NTRS)

A review of Tm and Ho materials is presented, covering some fundamental aspects on the spectroscopy and laser dynamics in both single and co-doped systems. Following an introduction to 2- m lasers, applications and historical development, the physics of quasi-four level lasers, energy transfer and modeling are discussed in some detail. Recent developments in using Tm lasers to pump Ho lasers are discussed, and seen to offer some advantages over conventional Tm:Ho lasers. This article is not intended as a complete review, but as a primer for introducing concepts and a resource for further study.

Walsh, Brian M.

2008-01-01

326

p-wave optical Feshbach resonances in {sup 171}Yb  

SciTech Connect

We study the use of an optical Feshbach resonance to modify the p-wave interaction between ultracold polarized {sup 171}Yb spin-1/2 fermions. A laser exciting two colliding atoms to the {sup 1}S{sub 0}+{sup 3}P{sub 1} channel can be detuned near a purely-long-range excited molecular bound state. Such an exotic molecule has an inner turning point far from the chemical binding region, and thus, three-body recombination in the Feshbach resonance will be highly suppressed in contrast to that typically seen in a ground-state p-wave magnetic Feshbach resonance. We calculate the excited molecular bound-state spectrum using a multichannel integration of the Schroedinger equation, including an external perturbation by a magnetic field. From the multichannel wave functions, we calculate the Feshbach resonance properties, including the modification of the elastic p-wave scattering volume and inelastic spontaneous scattering rate. The use of magnetic fields and selection rules for polarized light yields a highly controllable system. We apply this control to propose a toy model for three-color superfluidity in an optical lattice for spin-polarized {sup 171}Yb, where the three colors correspond to the three spatial orbitals of the first excited p band. We calculate the conditions under which tunneling and on-site interactions are comparable, at which point quantum critical behavior is possible.

Goyal, Krittika; Deutsch, Ivan [Center for Quantum Information and Control, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Reichenbach, Iris [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany)

2010-12-15

327

Low temperature phase diagram of YbBiPt  

SciTech Connect

We report resistivity measurements on the cubic heavy-fermion compound YbBiPt at ambient and hydrostatic pressures to {approx} 19kbars and in magnetic fields to 1 Tesla. The phase transition at T{sub c}, = 0.4K is identified by a sharp rise in resistivity. We use that feature to build low temperature H-T and P-T phase diagrams. The phase boundary in the H-T plane follows the weak coupling BCS expression remarkably well from T{sub c}, to T{sub c}/4, while small hydrostatic pressure of {approx} lkbar suppresses the low temperature phase entirely. These effects of hydrostatic pressure and magnetic field on the phase transition are consistent with an SDW (Spin Density Wave) formation in a very heavy electron band at T = 0.4K. Outside of the SDW phase at low temperature, hydrostatic pressure increases the T{sup 2} Coefficient of resistivity, signaling an increase in heavy-fermion correlations with hydrostatic pressure. The residual resistivity decreases with pressure, contrary to trends in other Yb heavy-fermion compounds.

Movshovich, R.; Lacerda, A.; Canfield, P.C.; Thompson, J.D. [Los Alamos National Lab., NM (United States); Fisk, Z. [Los Alamos National Lab., NM (United States)]|[California Univ., San Diego, La Jolla, CA (United States)

1994-04-01

328

p-wave optical Feshbach resonances in Yb171  

NASA Astrophysics Data System (ADS)

We study the use of an optical Feshbach resonance to modify the p-wave interaction between ultracold polarized Yb171 spin-1/2 fermions. A laser exciting two colliding atoms to the 1S0+3P1 channel can be detuned near a purely-long-range excited molecular bound state. Such an exotic molecule has an inner turning point far from the chemical binding region, and thus, three-body recombination in the Feshbach resonance will be highly suppressed in contrast to that typically seen in a ground-state p-wave magnetic Feshbach resonance. We calculate the excited molecular bound-state spectrum using a multichannel integration of the Schrödinger equation, including an external perturbation by a magnetic field. From the multichannel wave functions, we calculate the Feshbach resonance properties, including the modification of the elastic p-wave scattering volume and inelastic spontaneous scattering rate. The use of magnetic fields and selection rules for polarized light yields a highly controllable system. We apply this control to propose a toy model for three-color superfluidity in an optical lattice for spin-polarized Yb171, where the three colors correspond to the three spatial orbitals of the first excited p band. We calculate the conditions under which tunneling and on-site interactions are comparable, at which point quantum critical behavior is possible.

Goyal, Krittika; Reichenbach, Iris; Deutsch, Ivan

2010-12-01

329

Induced Magnetic Order in Yb2Ti2O7  

NASA Astrophysics Data System (ADS)

Yb2Ti2O7 is part of family of pyrochlore materials with a magnetic rare-earth and a non-magnetic transition metal. In similar compounds containing holmium, erbium, or terbium the geometric frustration results in several exotic ground states including spin-ice, spin-liquid, field-induced ordering, and low-dimensional behavior. The ytterbium-based compound has a strong anomaly in the specific heat at 240 mK [Hodges et al., J Phys Cond Mat 13, 9301 (2001)] but without accompanying long range order. We have made measurements of the elastic and inelastic neutron scattering on a large single crystal of Yb2Ti2O7 over a broad range of the (hhl) scattering plane using the DCS spectrometer at the NIST Center for Neutron Research. Our studies have confirmed the presence of diffuse ``rods'' of scattering along the (111) directions that persist below 100 mK. However, when the sample is field-cooled in fields as low as 0.5 T the rods of scattering are replaced by well-defined magnetic excitations. We will present the results of our studies at a variety of temperatures and fields.

Adams, Carl; Ross, K. A.; Ruff, J. P.; Gaulin, B. D.; Dabkowska, H.; Qiu, Y.; Copley, J. R. D.; Gardner, J. S.

2008-03-01

330

(Gd,Yb,Tb)PO4 up-conversion nanocrystals for bimodal luminescence-MR imaging  

NASA Astrophysics Data System (ADS)

Up-conversion (Gd,Yb,Tb)PO4 materials and their potential for bimodal imaging have received little attention in the literature. Herein, we report the first study on the up-conversion emission of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal method at 150 °C. These materials exhibit ultraviolet, blue and green up-conversion emissions upon excitation with a 980 nm continuous wave laser diode. The intensity of the blue-emission band at 479 nm, ascribed to the cooperative up-conversion emission of a pair of excited Yb3+ ions, depends on the Yb3+/Tb3+ concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb3+ is observed at 543 nm for the 5D4 --> 7F5 transition. Relaxometry measurements reveal that the nanocrystals are efficient T2-weighted (negative) contrast agents which, combined with visible-light emission generated by infrared excitation, affords them considerable potential for being used in bimodal, photoluminescence-magnetic resonance, imaging.Up-conversion (Gd,Yb,Tb)PO4 materials and their potential for bimodal imaging have received little attention in the literature. Herein, we report the first study on the up-conversion emission of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal method at 150 °C. These materials exhibit ultraviolet, blue and green up-conversion emissions upon excitation with a 980 nm continuous wave laser diode. The intensity of the blue-emission band at 479 nm, ascribed to the cooperative up-conversion emission of a pair of excited Yb3+ ions, depends on the Yb3+/Tb3+ concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb3+ is observed at 543 nm for the 5D4 --> 7F5 transition. Relaxometry measurements reveal that the nanocrystals are efficient T2-weighted (negative) contrast agents which, combined with visible-light emission generated by infrared excitation, affords them considerable potential for being used in bimodal, photoluminescence-magnetic resonance, imaging. Electronic supplementary information (ESI) available: A schematic representation for the synthesis of up-conversion monoclinic (Gd,Yb,Tb)PO4 nanocrystals (Fig. S1); XRD patterns of as-synthesized (Gd,Yb,Tb)PO4.2.5H2O and calcined (Gd,Yb,Tb)PO4 samples (Fig. S2) and of dextran-coated and uncoated Gd0.87Yb0.10Tb0.03PO4 nanocrystals (Fig. S3); TEM images of (Gd,Yb,Tb)PO4.2.5H2O and (Gd,Yb,Tb)PO4 samples (Fig. S5 and S6); FT-IR spectra of (Gd,Yb,Tb)PO4.2.5H2O and (Gd,Yb,Tb)PO4 samples (Fig. S7); pump-power dependence of the up-conversion emission intensities (Fig. S8); comparison of the up-conversion emission for dextran-coated and uncoated monoclinic Gd0.87Yb0.10Tb0.03PO4 nanocrystals (Fig. S9); up-conversion emission spectra of monoclinic Gd0.85Yb0.10Tb0.05PO4 nanocrystals calcined for 3 hours at 900 °C and 1200 °C (Fig. S10); relaxivity measurements (Fig. S11 and S12); UV-visible absorption spectra and calibration curve for the Gd3+ leaching test (Fig. S13); steady-state emission/excitation spectra (Fig. S14). See DOI: 10.1039/c2nr31226c

Debasu, Mengistie L.; Ananias, Duarte; Pinho, Sonia L. C.; Geraldes, Carlos F. G. C.; Carlos, Luís D.; Rocha, João

2012-07-01

331

Valence band structure of the icosahedral Ag-In-Yb quasicrystal  

SciTech Connect

The valence band structure of the icosahedral (i) Ag-In-Yb quasicrystal, which is isostructural to the binary i-Cd-Yb system, is investigated by ultraviolet photoemission spectroscopy (UPS). Experimental results are compared with electronic-structure calculations of a cubic approximant of the same phase. UPS spectra from the fivefold, threefold, and twofold i-Ag-In-Yb surfaces reveal that the valence band near to the Fermi level is dominated by Yb 4f-derived states, in agreement with calculations. The spectra also exhibit peaks which are surface core level shifted, caused by changes in the electronic structure in surface layers. Calculations yield a pseudogap in the density of states due to a hybridization of the Yb 5d band with the Ag 5p and In 5p bands. Both experimental and calculated band features are very similar to those of Cd-Yb. The modification of the band structure after surface treatment by sputtering and by oxidation is also studied. Additionally, the work function of i-Ag-In-Yb measured from the width of UPS spectrum is found to be almost unaffected by surface orientation, but increases after sputtering or oxidation.

Sharma, H. R.; Simutis, G.; Dhanak, V. R.; Nugent, P. J.; McGrath, R. [Surface Science Research Centre and Department of Physics, University of Liverpool, Liverpool L69 3BX (United Kingdom); Cui, C. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Shimoda, M. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Tsai, A. P. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Ishii, Y. [Department of Physics, Chuo University, Kasuga, Tokyo 112-8551 (Japan)

2010-03-01

332

Energy transfer mechanisms in Yb3+-doped GdVO4 near-infrared downconversion nanophosphor.  

PubMed

Yb3+-doped GdVO4 nanophosphor was prepared by the co-precipitation method. Under ultraviolet (UV) light excitation, strong near-infrared (NIR) emission of Yb3+ (2F(5/2) --> 2F(7/2)) around 980 nm was observed. Owing to the host absorption of GdVO4, a broad excitation band ranging from 250 to 350 nm was recorded when the Yb3+ emission was monitored, which suggests an efficient energy transfer from the host to the Yb3+ ions. The concentration dependence of the visible vanadate emission and the Yb3+ emission was investigated. The decay curve of the vanadate emission was measured under the excitation of a 266 nm pulsed laser. The decay time of the vanadate emission at 500 nm was remarkably reduced by introducing Yb3+, further verifying that the energy transfer from the vanadate host to the Yb3+ ions was very efficient. Cooperative energy transfer (CET) is discussed as the possible energy transfer process. The temperature dependence of the emission intensity and decay time were also investigated for our further discussion. PMID:22413246

Wei, XianTao; Liu, YuCong; Jiang, GuiCheng; Chen, YongHu; Yin, Min; Xu, Wu

2011-11-01

333

Transfer and back transfer processes in Yb3+-Er3+ codoped fluoroindate glasses  

NASA Astrophysics Data System (ADS)

The kinetics of forward and backward energy transfer processes in fluoroindate glasses double doped with Yb3+ and Er3+ has been studied. It was possible to excite selectively Yb3+ ions and detect emission due only to these ions or combined with the emission coming from the Er3+ ions. At low concentration of Yb3+ (0.1 mol %) the emission decay of these ions is nonexponential when there is back transfer from Er3+ ions; the dynamics is well described using the fluorescence "transfer function" model. Moreover, the evolution of the emission from the 4I11/2 (Er3+) level is in good agreement with the behavior predicted by the model. The critical radii obtained from the fitting for forward and backward energy transfer are compared with those calculated with the Dexter formula. When the Yb3+ concentration is increased, the migration among these ions is very important and the emission decay of the Yb3+ ions is nearly exponential with the lifetime of these ions. This behavior is explained considering that, at high Yb3+ concentration and due to the migration, the transfer from Yb3+ to Er3+ ions is restricted to very closed couples of ions with high back transfer probability. The limitations of the fluorescence "transfer function" model associated with the correlation effect in the excitation of Er3+ ions by energy transfer are discussed.

Martín, I. R.; Rodríguez, V. D.; Lavín, V.; Rodríguez-Mendoza, U. R.

1999-07-01

334

Diode pumped Yb-lasers Q-switched by V:YAG saturable absorber  

NASA Astrophysics Data System (ADS)

V:YAG saturable absorber, developed mainly for 1.3 ?m lasers Q-switching, was used as a passive Q-switch for the 1.03 ?m Yb-doped YAG (10% Yb/Y, 3mm long) and LuAG (15% Yb/Lu, 1mm long) lasers. Longitudinally diode pumped gain medium together with the V:YAG crystal were placed inside the 22mm long hemispherical laser cavity. For Yb-doped crystal excitation fibre-coupled (fibre core diameter 100 ?m) laser diode (max power amplitude 20W, emission wavelength 968 nm) was used. The laser diode was operating in a pulsed regime (repetition rate 10 Hz, pumping pulse width 2 ms) to reduce parasitic thermal effects inside the gain medium. Stable Q-switching was obtained for laser output coupler reflectivity 70% and V:YAG initial transmission 70% at Yb laser emission wavelength. For the both tested active media the parameters of the generated giant pulses were similar. Pulses with duration of 2.5 ns (FWHM), energy about 0.3 mJ, and peak power up to 120kW were generated. The maximal Q-switched pulses repetition rate inside the single pumping pulse was 6.6 kHz in case of Yb:YAG and 8.6 kHz in case of Yb:LuAG. The beam transversal profile was close to the fundamental Gaussian mode. The output was partially polarized.

Šulc, Jan; Kaskow, Mateusz; Jelínková, Helena; Jabczynski, Jan K.

2014-12-01

335

Valence band structure of the icosahedral Ag-In-Yb quasicrystal  

NASA Astrophysics Data System (ADS)

The valence band structure of the icosahedral (i) Ag-In-Yb quasicrystal, which is isostructural to the binary i-Cd-Yb system, is investigated by ultraviolet photoemission spectroscopy (UPS). Experimental results are compared with electronic-structure calculations of a cubic approximant of the same phase. UPS spectra from the fivefold, threefold, and twofold i-Ag-In-Yb surfaces reveal that the valence band near to the Fermi level is dominated by Yb4f -derived states, in agreement with calculations. The spectra also exhibit peaks which are surface core level shifted, caused by changes in the electronic structure in surface layers. Calculations yield a pseudogap in the density of states due to a hybridization of the Yb5d band with the Ag5p and In5p bands. Both experimental and calculated band features are very similar to those of Cd-Yb. The modification of the band structure after surface treatment by sputtering and by oxidation is also studied. Additionally, the work function of i-Ag-In-Yb measured from the width of UPS spectrum is found to be almost unaffected by surface orientation, but increases after sputtering or oxidation.

Sharma, H. R.; Simutis, G.; Dhanak, V. R.; Nugent, P. J.; Cui, C.; Shimoda, M.; McGrath, R.; Tsai, A. P.; Ishii, Y.

2010-03-01

336

First-principles study of one-dimensional sandwich wires [(P)5TM]? (TM = Ti, V, Cr, Mn, Fe, Co)  

NASA Astrophysics Data System (ADS)

Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]?, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]? wires are of large magnetic moment. Among them, we find that [(P)5V]?, [(P)5Cr]? and [(P)5Mn]? display ferromagnetic character, while for [(P)5Ti]?, [(P)5Fe]? and [(P)5Co]?, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]? involves the transfer of one electron from the TM atom to the P5 ligand forming ({P})_{5}^{-} and TM+ alternating structure.

Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

2013-10-01

337

Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same  

DOEpatents

An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises Ytterbium doped apatite (Yb:Ca.sub.5 (PO.sub.4).sub.3 F) or Yb:FAP, or ytterbium doped crystals that are structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.

Krupke, William F. (Pleasanton, CA); Payne, Stephen A. (Castro Valley, CA); Chase, Lloyd L. (Livermore, CA); Smith, Larry K. (Salida, CA)

1994-01-01

338

High-power tunable diode-pumped Yb3+:CaF2 laser.  

PubMed

Results of diode-pumped cw laser operation of an Yb3+:CaF2 single crystal are reported for what is to our knowledge the first time. With a 5-at.% Yb3+ -doped sample we obtained 5.8-W output power at 1053 nm for 15 W of incident power at 980 nm. The laser wavelength could be tuned from 1018 to 1072 nm, and a small-signal gain as high as 1.8 was achieved, showing the great potential of Yb3+:CaF2 as an amplifier medium for femtosecond pulses. PMID:15357346

Lucca, A; Jacquemet, M; Druon, F; Balembois, F; Georges, P; Camy, P; Doualan, J L; Moncorgé, R

2004-08-15

339

Absolute quantum cutting efficiency of Tb3+-Yb3+ co-doped glass  

NASA Astrophysics Data System (ADS)

The absolute quantum cutting efficiency of Tb3+-Yb3+ co-doped glass was quantitatively measured by an integrating sphere detection system, which is independent of the excitation power. As the Yb3+ concentration increases, the near infrared quantum efficiency exhibited an exponential growth with an upper limit of 13.5%, but the visible light efficiency was reduced rapidly. As a result, the total quantum efficiency monotonically decreases rather than increases as theory predicted. In fact, the absolute quantum efficiency was far less than the theoretical value due to the low radiative efficiency of Tb3+ (<61%) and significant cross-relaxation nonradiative loss between Yb3+ ions.

Duan, Qianqian; Qin, Feng; Zhao, Hua; Zhang, Zhiguo; Cao, Wenwu

2013-12-01

340

Effects of Eu concentration control on crystal growth and scintillation properties for Eu:LiSrAlF6 crystals  

NASA Astrophysics Data System (ADS)

Eu doped LiSrAlF6 (Eu:LiSAF) crystals with various Eu concentrations were grown by a micro-pulling-down (?-PD) method and the effects of Eu concentration control on crystal growth and scintillation properties for Eu:LiSAF crystals were investigated as a neutron scintillator. As-grown Eu0.3%:LiSAF crystal had no visible inclusion while milky parts were observed in the crystals with higher Eu contents. The secondary phases with the chemical composition of EuF2 or EuF3 in the Eu:LiSAF matrix were observed for the crystals with high Eu contents while the secondary phase couldn’t be observed in the powder XRD patterns. In the radioluminescence spectra of Eu:LiSAF crystals under ?-ray irradiation, emission peaks around 375 nm originated from 5d-4f transition of Eu2+ ion were observed. The light yields systematically increased with an increase of actual Eu contents in the crystals and the decay times were 1490-1620 ns.

Suzuki, S.; Yokota, Y.; Yamaji, A.; Kurosawa, S.; Kamada, K.; Yoshikawa, A.

2014-10-01

341

bdbiosciences.com 1 BD FalconTM  

E-print Network

., et al., Endothelial cell growth on oxygen-containing films deposited by radio- frequency plasmas,TM the first name in cell culture As the first company to produce sterile, disposable labware more than 50

Wu, Mingming

342

Manufacture of the SEA PowergridTM  

NASA Astrophysics Data System (ADS)

SEA Corporation has completed development of a linear concentrator, the SEA PowergridTM, funded in part by contract with Sandia National Laboratories (DOE 40-8941C). SEA Corporation has also identified low-cost manufacturing techniques for the Powergrid, funded in part by sub-contract with the National Renewable Energy Laboratory (DOE XC-1-10057-21). The Powergrid uses a number of unique features that gives it the potential to be sold at a fraction of the price of flat-plate systems. An important cost saving feature of the Powergrid is that it is designed for automated assembly. SEA Corporation is now establishing facilities for manufacturing the Powergrid. SEA Corporation has completed design and fabrication of an automated receiver assembly station and is planning to install other automated equipment in 1994 with partial funding from the California Energy Commission and Sandia National Laboratories. The first 40 Powergrids will be installed on a building owned by the Sacramento Municipal Utility District (SMUD). The 40 KW system is scheduled for delivery in December, 1993. This paper will describe the manufacturing and assembly equipment and procedures used for the Powergrid. The paper will also describe the current state of manufacturing capacity and plans for the future.

Kaminar, Neil; McEntee, John; Stark, Peter; Lapson, Bill

1994-06-01

343

Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, La–Nd, Sm–Tm)  

SciTech Connect

Single crystals of RCo2Ge2 (R=Y, La–Nd, Sm–Tm) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction; anisotropic, temperature and field dependent magnetization; temperature and field dependent, in-plane resistivity; and specific heat measurements. In this series, the majority of the moment-bearing members order antiferromagnetically; YCo2Ge2 and LaCo2Ge2 are non-moment-bearing. Ce is trivalent in CeCo2Ge2 at high temperatures, and exhibits an enhanced electronic specific heat coefficient due to the Kondo effect at low temperatures. In addition, CeCo2Ge2 shows two low-temperature anomalies in temperature-dependent magnetization and specific heat measurements. Three members (R=Tb–Ho) have multiple phase transitions above 1.8 K. Eu appears to be divalent with total angular momentum L =0. Both EuCo2Ge2 and GdCo2Ge2 manifest essentially isotropic paramagnetic properties consistent with J =S =7/2. Clear magnetic anisotropy for rare-earth members with finite L was observed, with ErCo2Ge2 and TmCo2Ge2 manifesting planar anisotropy and the rest members manifesting axial anisotropy. The experimentally estimated crystal electric field (CEF) parameters B 20 were calculated from the anisotropic paramagnetic ? ab and ? c values and follow a trend that agrees well with theoretical predictions. The ordering temperatures, TNTN, as well as the polycrystalline averaged paramagnetic Curie–Weiss temperature, ?avg, for the heavy rare-earth members deviate from the de Gennes scaling, as the magnitude of both is the highest for Tb, which is sometimes seen for extremely axial systems. Except for SmCo2Ge2, metamagnetic transitions were observed at 1.8 K for all members that ordered antiferromagnetically.

Kong, Tai [Ames Laboratory; Cunningham, Charles E. [Grinnell College; Taufour, Valentin [Iowa State University; Budko, Sergey L. [Ames Laboratory; Buffon, Malinda L.C. [Ames Laboratory; Lin, Xiao [Ames Laboratory; Emmons, Heather [Grinnell College; Canfield, Paul C. [Ames Laboratory

2014-02-04

344

Zeeman relaxation of magnetically trapped Eu atoms  

SciTech Connect

We perform rigorous quantum mechanical calculations for collisions between magnetically trapped Eu atoms to elucidate the results of recent experimental studies. We show that the relaxation from the maximally stretched m{sub s}=7/2 level is entirely determined by the magnetic dipole-dipole interaction and analyze the role of the electronic spin-exchange interaction in transitions from the lower-energy Zeeman levels. The relaxation of the m{sub s}=5/2 state is shown to be very sensitive to the spin-exchange parameter that determines the splitting between the lowest electronic states of the Eu dimer. We suggest that cold collision experiments with trapped atoms can be used as a tool for obtaining accurate information on the electronic spin anisotropy in complex molecules such as Eu{sub 2}.

Suleimanov, Yury V. [Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom)

2010-02-15

345

Diode-pumped thin disk 15% Tm:KYW laser  

NASA Astrophysics Data System (ADS)

We demonstrate high-efficient CW thin disk 15%Tm:KYW laser pumped by a 20W CW laser diode bar at 803nm. Three 15%Tm:KYW b-cut disks of 200, 250 and 300?m thickness are tested, with the maximal laser output being of 4.9W at ~1.9?m. Slope and optical-to-optical conversion efficiencies are reported as well.

Vatnik, S. M.; Vedin, I. A.; Pavljuk, A. A.

2007-06-01

346

Glacier monitoring from Landsat TM: problems and perspectives  

Microsoft Academic Search

Thresholded ratio images from Landsat TM4 \\/ TM5 provide a simple, robust and quite accurate method for classification of clean glacier ice. Automatic retrieval of glacier inventory data is possible by means of GIS-based processing in combination with a DEM of appropriate accuracy. In view of the USGS-led project `Global Land Ice Monitoring from Space' (GLIMS) which aims at a

F. Paul; A. Kaeaeb; M. Maisch; M. Hoelzle; W. Haeberli

2003-01-01

347

Damping parameter and wall velocity of RE-TM films  

Microsoft Academic Search

The temperature dependence of the Gilbert damping parameter and domain wall velocity of ferrimagnetic rare earth-3d transition metal alloy (RE-TM) films are discussed. The Gilbert damping parameter is assumed to be inversely proportional to the net angular momentum of the RE-TM. Under this assumption, wall velocity is simulated. In the case of wall motion utilizing the temperature gradient of wall

T. Kobayashi; H. Hayashi; Y. Fujiwara; S. Shiomi

2005-01-01

348

SafetyNet(TM) -- NPOESS's Low Data Latency Key  

NASA Astrophysics Data System (ADS)

A key feature of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) is the Northrop Grumman Space Technology patent-pending data collection architecture known as 'SafetyNetTM'. The centerpiece of SafetyNetTM is the system of fifteen globally-distributed ground receptors developed by Raytheon Company. These receptors or antennae will collect up to five times as much environmental data approximately four times faster than current polar-orbiting weather satellites. Once collected, these data will be forwarded near-instantaneously to U.S. weather centrals via global fiber optic network for processing and production of data records for use in environmental prediction models. Key system design factors: The NPOESS SafetyNetTM architecture provides: Frequent downlinks and maximizes contact duration (>100% margin) at low cost; Downlink bandwidth margin that allows all Stored Mission Data to be down linked to two separate receptors; and Minimal latency impacts from loss of multiple ground receptors. Other notable characteristics of SafetyNetTM: Simple, receive-only, Ka Band receptor design provides autonomous operations; Fifteen locations in ten countries; full-motion to track polar satellites; Reliable and timely collection, delivery and processing of quality data; 75% of NPOESS data products delivered to the US's weather centrals within 15 minutes; the rest in under 30 minutes. Presentation will show: A graphic of SafetyNetTM within the NPOESS program architecture; A depiction of the NPOESS data download scheme; A map of the worldwide SafetyNetTM receptor locations; A graph of the percent of NPOESS Environmental Data Records (EDRs) versus time from observation to delivery; A example chart of the NPOESS data downlink patterns to SafetyNetTM receptors; Example photos of SafetyNetTM receptor antennae and radomes.

Swearengen, J.; Koster, P. B.; Jamilkowski, M. L.

2008-12-01

349

NPOESS' Key to Low Data Latency: SafetyNet(TM)  

NASA Astrophysics Data System (ADS)

A key feature of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) is the Northrop Grumman Space Technology patent-pending data collection architecture known as 'SafetyNetTM'. The centerpiece of SafetyNetTM is the system of fifteen globally-distributed ground receptors developed by Raytheon Company. These receptors or antennae will collect up to five times as much environmental data approxi-mately four times faster than current polar-orbiting weather satellites. Once collected, these data will be forwarded near-instantaneously to U.S. weather centrals via global fiber optic network for processing and production of data records for use in environmental prediction models. Key system design factors -- The NPOESS SafetyNetTM architecture provides: Frequent downlinks and maximizes contact duration (>100% margin) at low cost; Downlink bandwidth margin that allows all Stored Mission Data to be down linked to two separate receptors; and Minimal latency impacts from loss of multiple ground receptors. Other notable characteristics of SafetyNetTM: Simple, receive-only, Ka Band receptor design provides autonomous operations; Fifteen locations in ten countries; full-motion to track polar satellites; Reliable and timely collection, delivery and processing of quality data; 75% of NPOESS data products delivered to the US's weather centrals within 15 minutes; the rest in under 30 minutes. Presentation will show: A graphic of SafetyNetTM within the NPOESS program architecture; A depiction of the NPOESS data download scheme; A map of the worldwide SafetyNetTM receptor locations; A graph of the percent of NPOESS Environmental Data Records (EDRs) versus time from observation to delivery; A example chart of the NPOESS data downlink patterns to SafetyNetTM receptors; Example photos of SafetyNetTM receptor antennae and radomes.

Koster, P. B.; Swearengen, J.; Jamilkowski, M. L.

2008-12-01

350

Quiet Spike (TM) Build-Up Ground Vibration Testing Approach  

NASA Technical Reports Server (NTRS)

Flight tests of Gulfstream Aerospace Corporation s Quiet Spike(TM) hardware were recently completed on the NASA Dryden Flight Research Center F-15B airplane. NASA Dryden uses a modified F-15B airplane as a testbed aircraft to cost-effectively fly flight research experiments that are typically mounted underneath the F-15B airplane, along the fuselage centerline. For the Quiet Spike(TM) experiment, however, instead of a centerline mounting, a relatively long forward-pointing boom was attached to the radar bulkhead of the F-15B airplane. The Quiet Spike(TM) experiment is a stepping-stone to airframe structural morphing technologies designed to mitigate the sonic-boom strength of business jets over land. The Quiet Spike(TM) boom is a concept in which an aircraft's noseboom would be extended prior to supersonic acceleration. This morphing effectively lengthens the aircraft, thus reducing the peak sonic-boom amplitude, but is also expected to partition the otherwise strong bow shock into a series of reduced-strength, noncoalescing shocklets. Prior to flying the Quiet Spike(TM) experiment on the F-15B airplane several ground vibration tests were required to understand the Quiet Spike(TM) modal characteristics and coupling effects with the F-15B airplane. However, due to the flight hardware availability and compressed schedule requirements, a "traditional" ground vibration test of the mated F-15B Quiet Spike(TM) ready-for-flight configuration did not leave sufficient time available for the finite element model update and flutter analyses before flight testing. Therefore, a "nontraditional" ground vibration testing approach was taken. This paper provides an overview of each phase of the "nontraditional" ground vibration testing completed for the Quiet Spike(TM) project which includes the test setup details, instrumentation layout, and modal results obtained in support of the structural dynamic modeling and flutter analyses.

Spivey, Natalie D.; Herrera, Claudia; Truax, Roger; Pak, Chan-gi; Freund, Donald

2007-01-01

351

YB-1 expression promotes epithelial-to-mesenchymal transition in prostate cancer that is inhibited by a small molecule fisetin.  

PubMed

Epithelial-to-mesenchymal transition (EMT) plays an important role in prostate cancer (PCa) metastasis. The transcription/translation regulatory Y-box binding protein-1 (YB-1) is known to be associated with cancer metastasis. We observed that YB-1 expression increased with tumor grade and showed an inverse relationship with E-cadherin in a human PCa tissue array. Forced YB-1 expression induced a mesenchymal morphology that was associated with down regulation of epithelial markers. Silencing of YB-1 reversed mesenchymal features and decreased cell proliferation, migration and invasion in PCa cells. YB-1 is activated directly via Akt mediated phosphorylation at Ser102 within the cold shock domain (CSD). We next identified fisetin as an inhibitor of YB-1 activation. Computational docking and molecular dynamics suggested that fisetin binds on the residues from ?1 - ?4 strands of CSD, hindering Akt's interaction with YB-1. Calculated free binding energy ranged from -11.9845 to -9.6273 kcal/mol. Plasmon Surface Resonance studies showed that fisetin binds to YB-1 with an affinity of approximately 35 µM, with both slow association and dissociation. Fisetin also inhibited EGF induced YB-1 phosphorylation and markers of EMT both in vitro and in vivo. Collectively our data suggest that YB-1 induces EMT in PCa and identify fisetin as an inhibitor of its activation. PMID:24770864

Khan, Mohammad Imran; Adhami, Vaqar Mustafa; Lall, Rahul Kumar; Sechi, Mario; Joshi, Dinesh C; Haidar, Omar M; Syed, Deeba Nadeem; Siddiqui, Imtiaz Ahmad; Chiu, Shing-Yan; Mukhtar, Hasan

2014-05-15

352

YB-1 expression promotes epithelial-to-mesenchymal transition in prostate cancer that is inhibited by a small molecule fisetin  

PubMed Central

Epithelial-to-mesenchymal transition (EMT) plays an important role in prostate cancer (PCa) metastasis. The transcription/translation regulatory Y-box binding protein-1 (YB-1) is known to be associated with cancer metastasis. We observed that YB-1 expression increased with tumor grade and showed an inverse relationship with E-cadherin in a human PCa tissue array. Forced YB-1 expression induced a mesenchymal morphology that was associated with down regulation of epithelial markers. Silencing of YB-1 reversed mesenchymal features and decreased cell proliferation, migration and invasion in PCa cells. YB-1 is activated directly via Akt mediated phosphorylation at Ser102 within the cold shock domain (CSD). We next identified fisetin as an inhibitor of YB-1 activation. Computational docking and molecular dynamics suggested that fisetin binds on the residues from ?1 - ?4 strands of CSD, hindering Akt's interaction with YB-1. Calculated free binding energy ranged from ?11.9845 to ?9.6273 kcal/mol. Plasmon Surface Resonance studies showed that fisetin binds to YB-1 with an affinity of approximately 35 ?M, with both slow association and dissociation. Fisetin also inhibited EGF induced YB-1 phosphorylation and markers of EMT both in vitro and in vivo. Collectively our data suggest that YB-1 induces EMT in PCa and identify fisetin as an inhibitor of its activation. PMID:24770864

Khan, Mohammad Imran; Adhami, Vaqar Mustafa; Lall, Rahul Kumar; Sechi, Mario; Joshi, Dinesh C.; Haidar, Omar M.; Syed, Deeba Nadeem; Siddiqui, Imtiaz Ahmad; Chiu, Shing-Yan; Mukhtar, Hasan

2014-01-01

353

Structural and magnetic study of Yb3+ in the perovskites Sr2YbMO6 (M=Nb, Ta, Sb)  

NASA Astrophysics Data System (ADS)

The compounds Sr2YbNbO6, Sr2YbTaO6 and Sr2YbSbO6 have been prepared using solid state methods by heating pelleted reagents in air at temperatures up to 1400 °C. Rietveld refinement against room temperature neutron powder diffraction data show that all three compounds crystallise with a cation-ordered variant of the perovskite structure in the P21/n space group. Complete cation ordering occurs between M5+ and Yb3+ over two octahedrally-coordinated sites in the structure and all compounds are stoichiometric in oxygen. The Sb-O bond lengths are similar to related perovskite compounds but differ slightly from those indicated by bond valence sums. Magnetic susceptibility data resemble Curie-Weiss paramagnetic behaviour, but can be better understood as arising from the effect of the octahedral crystal field on the 2F5/2 ground state of Yb3+ leading to a temperature dependent magnetic moment on this ion below 100 K.

Coomer, Fiona C.; Campbell, John; Giordano, Nico; Collins, Oonagh M.; Cussen, Edmund J.

2015-01-01

354

The EU's Dark Hour: Special Report  

NSDL National Science Digital Library

Released on March 15, 1999, a 140-page report by independent experts looked into charges of widespread fraud, nepotism, and corruption in the European Commission, the executive body of the EU, and found numerous cases where "commissioners or the Commission as a whole bear responsibility for instances of fraud, irregularities or mismanagement." In response, the President of the Commission, who is also the chief executive of the EU, and nineteen other senior officials abruptly resigned on March 16. This would be roughly equivalent to the entire US Cabinet resigning. Users interested in further analysis of the crisis and the latest developments will want to visit the BBC Special Report site.

1999-01-01

355

The European Union (EU) Agenda 2000  

NSDL National Science Digital Library

The European Commission released its opinions on the ten applications for EU membership from Central and Eastern Europe in July 1997. They were released with documents outlining the "Agenda 2000" program, which "comprises the Commission's proposals for agricultural, structural and horizontal policies, a reinforced preaccession strategy, and the financial framework beyond 1999." At the EU's US homepage, users can view Commission Opinions on Applicants for Enlargement of the Union and an Executive Summary of the Applicant Opinions. The two volume Agenda 2000 program (459k combined) as well as press notes on both issues are also available.

1997-01-01

356

College of Europe: EU Diplomacy Papers  

NSDL National Science Digital Library

Persons interested in the affairs of Europe will find the College of Europe's Diplomacy Papers site to be most helpful. These working papers are part of a series "dedicated to the interdisciplinary study of the European Union's external relations and external aspects of EU internal policies." Currently, the site contains about two dozen papers that date back to 2006. The papers are authored by a range of experts, including individuals from the University of Dresden, the University of Heidelberg, and the Universite Libre de Bruxelles. Some of the recent papers include "A Misleading Promise? Rethinking European Support for Biofuels" and "The EU and Iran's Nuclear Programme: Testing the Limits of Coercive Diplomacy".

357

Tm3+ and Tm(3+)-Ho3+ co-doped tungsten tellurite glass single mode fiber laser.  

PubMed

We investigated the ~2 ?m spectroscopic and lasing performance of Tm(3+) and Tm(3+)-Ho(3+) co-doped tungsten tellurite glass single mode fibers with a commercial 800 nm laser diode. The double cladding single mode (SM) fibers were fabricated by using rod-in-tube method. The propagation loss of the fiber was ~2.5 dB/m at 1310 nm. The spectroscopic properties of the fibers were analyzed. A 494 mW laser operating at ~1.9 ?m was achieved in a Tm(3+) doped 20 cm long fiber, the slope efficiency was 26%, and the laser beam quality factor M(2) was 1.09. A 35 mW ~2.1 ?m laser output was also demonstrated in a 7 cm long of Tm(3+)-Ho(3+) co-doped tungsten tellurite SM fiber. PMID:22535103

Li, Kefeng; Zhang, Guang; Wang, Xin; Hu, Lili; Kuan, Peiwen; Chen, Danping; Wang, Meng

2012-04-23

358

Chemical pressure effects on magnetism in the quantum spin liquid candidates Yb2X2O7 (X =Sn, Ti, Ge)  

NASA Astrophysics Data System (ADS)

The linear and nonlinear ac susceptibility measurements of Yb-pyrochlores, Yb2X2O7 (X =Sn, Ti, and Ge), show transitions with a ferromagnetic nature at 0.13 and 0.25 K for Yb2Sn2O7 and Yb2Ti2O7, respectively, and an antiferromagnetic ordering at 0.62 K for Yb2Ge2O7. These systematical results (i) provided information about the nature of the unconventional magnetic ground state in Yb2Ti2O7; (ii) realized a distinct antiferromagnetic ordering state in Yb2Ge2O7; and (iii) demonstrated that the application of chemical pressure through the series of Yb-pyrochlores can efficiently perturb the fragile quantum spin fluctuations of the Yb3+ ions and lead to very different magnetic ground states.

Dun, Z. L.; Lee, M.; Choi, E. S.; Hallas, A. M.; Wiebe, C. R.; Gardner, J. S.; Arrighi, E.; Freitas, R. S.; Arevalo-Lopez, A. M.; Attfield, J. P.; Zhou, H. D.; Cheng, J. G.

2014-02-01

359

Loading a planar RF Paul Trap from a cold Yb? source  

E-print Network

In this thesis, we demonstrate a functioning planar radio frequency, three-rod Paul Trap, loaded with Yb+ ions that have been photoionized from a source of neutral atoms, which were cooled in a magneto-optical trap. Planar ...

Shields, Brendan John

2006-01-01

360

New universality class of quantum criticality in Ce- and Yb-based heavy fermions.  

PubMed

A new universality class of quantum criticality emerging in itinerant electron systems with strong local electron correlations is discussed. The quantum criticality of a Ce- or Yb-valence transition gives us a unified explanation for unconventional criticality commonly observed in heavy fermion metals such as YbRh(2)Si(2), ?-YbAlB(4), YbCu(5-x)Al(x), and CeIrIn(5). The key origin is due to the locality of the critical valence fluctuation mode emerging near the quantum critical end point of the first-order valence transition, which is caused by strong electron correlations for f electrons. The wider relevance of this new criticality and important future measurements to uncover its origin are also discussed. PMID:22771583

Watanabe, Shinji; Miyake, Kazumasa

2012-07-25

361

Measurement of the Hyperfine Quenching Rate of the Clock Transition in Yb171  

NASA Astrophysics Data System (ADS)

We report the first experimental determination of the hyperfine quenching rate of the 6s2 S01(F=1/2)-6s6p P03(F=1/2) transition in Yb171 with nuclear spin I =1/2. This rate determines the natural linewidth and the Rabi frequency of the clock transition of a Yb optical frequency standard. Our technique involves spectrally resolved fluorescence decay measurements of the lowest lying P0,13 levels of neutral Yb atoms embedded in a solid Ne matrix. The solid Ne provides a simple way to trap a large number of atoms as well as an efficient mechanism for populating P03. The decay rates in solid Ne are modified by medium effects including the index-of-refraction dependence. We find the P03 hyperfine quenching rate to be (4.42±0.35)×10-2 s-1 for free Yb171, which agrees with recent ab initio calculations.

Xu, C.-Y.; Singh, J.; Zappala, J. C.; Bailey, K. G.; Dietrich, M. R.; Greene, J. P.; Jiang, W.; Lemke, N. D.; Lu, Z.-T.; Mueller, P.; O'Connor, T. P.

2014-07-01

362

Superconductivity of Au–Ge–Yb Approximants with Tsai-Type Clusters  

NASA Astrophysics Data System (ADS)

We report the emergence of bulk superconductivity in Au64.0Ge22.0Yb14.0 and Au63.5Ge20.5Yb16.0 below 0.68 and 0.36 K, respectively. This is the first observation of superconductivity in Tsai-type crystalline approximants of quasicrystals. The Tsai-type cluster center is occupied by Au and Ge ions in the former approximant, and by an Yb ion in the latter. For magnetism, the latter system shows a larger magnetization than the former. To explain this observation, we propose a model that the cluster-center Yb ion is magnetic. The relationship between the magnetism and the superconductivity is also discussed.

Deguchi, Kazuhiko; Nakayama, Mika; Matsukawa, Shuya; Imura, Keiichiro; Tanaka, Katsumasa; Ishimasa, Tsutomu; Sato, Noriaki K.

2015-02-01

363

Enhanced green upconversion luminescence in Yb-Tb co-doped sintered silica nanoporous glass  

NASA Astrophysics Data System (ADS)

We report on a new kind of green-emitting (543 nm) high-silica luminous glass, which is fabricated by sintering of Yb3+-Tb3+ co-doped nanoporous glass. The fluorescence spectra show that there is an energy transfer between Yb3+ and Tb3+. The energy transfer process can be enhanced by addition of Al3+ into the Yb3+-Tb3+ co-doped nanoporous glass, and the energy transfer rate can be enhanced more than three times than that of Yb3+-Tb3+ co-doped porous glass. The role of Al3+ has been discussed, and the fluorescence decay curve reveals that the Al3+ play an important role in the energy transfer process.

Chu, Yingbo; Yang, Yu; Liu, Zijun; Liao, Lei; Wang, Yibo; Li, Jiaming; Li, Haiqing; Peng, Jinggang; Dai, Nengli; Li, Jinyan; Yang, Luyun

2014-11-01

364

Field-dependent Collective ESR Mode in YbRh2Si2  

SciTech Connect

Electron spin resonance (ESR) experiments in YbRh{sub 2}Si{sub 2} Kondo lattice (T{sub K} {approx_equal} 25 K) at different field/frequencies (4.1 {le} v {le} 34.4 GHz) and H{sub {perpendicular}c} revealed: (i) a strong field dependent Yb{sup 3+} spin-lattice relaxation, (ii) a weak field and T-dependent effectiveg-value, (iii) a suppression of the ESR intensity beyond 15% of Lu-doping, and (iv) a strong sample and Lu-doping ({le}15%) dependence of the ESR data. These results suggest that the ESR signal in YbRh{sub 2}Si{sub 2} may be due to a coupled Yb{sup 3+}-conduction electron resonant collective mode with a subtle field-dependent spins dynamic.

Petrovic, C.; Holanda, L.M.; Duque, J.G.S.; Bittar, E.M.; Adriano, C.; Pagliuso, P.G.; Rettori, C.; Hub, R.W.; Maquilon, S.; Fisk, Z.; Huber, D.L.; Oseroff, S.B.

2009-10-15

365

Controlling the 1 ?m spontaneous emission in Er/Yb co-doped fiber amplifiers.  

PubMed

In this paper we present our experimental studies on controlling the amplified spontaneous emission (ASE) from Yb(3+) ions in Er/Yb co-doped fiber amplifiers. We propose a new method of controlling the Yb-ASE by stimulating a laser emission at 1064 nm in the amplifier, by providing a positive 1 ?m signal feedback loop. The results are discussed and compared to a conventional amplifier setup without 1 ?m ASE control and to an amplifier with auxiliary 1064 nm seeding. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output power at 1550 nm and provide stable operation without parasitic lasing at 1 ?m. PMID:21996851

Sobon, Grzegorz; Kaczmarek, Pawel; Antonczak, Arkadiusz; Sotor, Jaroslaw; Abramski, Krzysztof M

2011-09-26

366

Doppler-free Yb spectroscopy with the fluorescence spot technique  

SciTech Connect

We demonstrate a simple technique to measure the resonant frequency of the 398.9-nm {sup 1}S{sub 0}{leftrightarrow}{sup 1}P{sub 1} transition for the different Yb isotopes. The technique, which works by observing and aligning fluorescence spots, has enabled us to measure transition frequencies and isotope shifts with an accuracy of 60 MHz. We provide wavelength measurements for the transition that differ from previously published work. Our technique also allows for the determination of Doppler-shifted transition frequencies for photoionization experiments when the atomic beam and the laser beam are not perpendicular and furthermore allows us to determine the average velocity of the atoms along the direction of the atomic beam.

Nizamani, Altaf H.; McLoughlin, James J.; Hensinger, Winfried K. [Department of Physics and Astronomy, University of Sussex, Falmer, Brighton, East-Sussex, BN1 9QH (United Kingdom)

2010-10-15

367

Precise curvature measurement of Yb:YAG thin disk  

NASA Astrophysics Data System (ADS)

We are developing an Yb:YAG thin disk regenerative amplifier operating at 1 kHz repetition rate which should deliver output of 100 W of average power which corresponds to the pulse energy of 100 mJ. In order to achieve such high output energy, large size mode matching on a thin-disk is required to avoid optical damage but on the other hand, larger mode area is more susceptible to the influence of optical phase distortions (OPD's) thus limits achievable pulse energy and beam quality. We developed a compact setup allowing precise measurement of the thin-disk deformations by implementation of a Hartmann-Shack wavefront sensor and a single mode probe laser diode. In comparison to the interferometric measurement methods, our approach brings a number of advantages like simplicity of alignment, compactness and robustness, at the same time keeping the high precision of measurement in a range of few nanometers.

Muzik, Jiri; Chyla, Michal; Nagisetty, Siva S.; Miura, Taisuke; Mann, Klaus; Endo, Akira; Mocek, Tomas

2015-01-01

368

Coaxial monitoring of keyhole during Yb:YAG laser welding  

NASA Astrophysics Data System (ADS)

In laser remote welding using a scanner, high-speed welding can be achieved by using a 6-axial robot and a galvanometric mirror. In this system, because the laser projection point changes depending on the mirror's position, coaxial monitoring is required to track welding phenomena. This paper presents coaxial monitoring of the keyhole generated by an Yb:YAG laser beam during laser lap welding of steel and Al sheets. A coaxial image camera and a coaxial illumination laser are integrated into the proposed monitoring system. The areas of the keyhole and the full penetration hole were calculated by image processing, and their behaviours were investigated under various welding conditions. The keyhole was monitored using various band-pass filters and a coaxial illumination laser. Adequate filters were suggested for steel and Al alloy welding.

Kim, Cheol-Hee; Ahn, Do-Chang

2012-09-01

369

Graphene Q-switched Yb:KYW planar waveguide laser  

NASA Astrophysics Data System (ADS)

A diode-pumped Yb:KYW planar waveguide laser, single-mode Q-switched by evanescent-field interaction with graphene, is demonstrated for the first time. Few-layer graphene grown by chemical vapor deposition is transferred onto the top of a guiding layer, which initiates stable Q-switched operation in a 2.4-cm-long waveguide laser operating near 1027 nm. Average output powers up to 34 mW and pulse durations as short as 349 ns are achieved. The measured output beam profile, clearly exhibiting a single mode, agrees well with the theoretically calculated mode intensity distribution inside the waveguide. As the pump power is increased, the repetition rate and pulse energy increase from 191 to 607 kHz and from 7.4 to 58.6 nJ, respectively, whereas the pulse duration decreases from 2.09 ?s to 349 ns.

Kim, Jun Wan; Young Choi, Sun; Aravazhi, Shanmugam; Pollnau, Markus; Griebner, Uwe; Petrov, Valentin; Bae, Sukang; Jun Ahn, Kwang; Yeom, Dong-Il; Rotermund, Fabian

2015-01-01

370

The Halting Problem A TM = fhM; wi j M is a TM and w 2 L(M )g  

E-print Network

The Halting Problem Consider A TM = fhM; wi j M is a TM and w 2 L(M )g A TM is Turing-recognizable. Proof Sketch: Simulate M on w. A TM is undecidable. Elements of the proof: TMs can be represented. Construct y such that d(y; i) 6= d(f (i); i). y di#11;ers from every f (i), thus f is not onto

Bylander, Tom

371

Ends of the line for tmRNA-SmpB  

PubMed Central

Genes for the RNA tmRNA and protein SmpB, partners in the trans-translation process that rescues stalled ribosomes, have previously been found in all bacteria and some organelles. During a major update of The tmRNA Website (relocated to http://bioinformatics.sandia.gov/tmrna), including addition of an SmpB sequence database, we found some bacteria that lack functionally significant regions of SmpB. Three groups with reduced genomes have lost the central loop of SmpB, which is thought to improve alanylation and EF-Tu activation: Carsonella, Hodgkinia, and the hemoplasmas (hemotropic Mycoplasma). Carsonella has also lost the SmpB C-terminal tail, thought to stimulate the decoding center of the ribosome. We validate recent identification of tmRNA homologs in oomycete mitochondria by finding partner genes from oomycete nuclei that target SmpB to the mitochondrion. We have moreover identified through exhaustive search a small number of complete, but often highly derived, bacterial genomes that appear to lack a functional copy of either the tmRNA or SmpB gene (but not both). One Carsonella isolate exhibits complete degradation of the tmRNA gene sequence yet its smpB shows no evidence for relaxed selective constraint, relative to other genes in the genome. After loss of the SmpB central loop in the hemoplasmas, one subclade apparently lost tmRNA. Carsonella also exhibits gene overlap such that tmRNA maturation should produce a non-stop smpB mRNA. At least some of the tmRNA/SmpB-deficient strains appear to further lack the ArfA and ArfB backup systems for ribosome rescue. The most frequent neighbors of smpB are the tmRNA gene, a ratA/rnfH unit, and the gene for RNaseR, a known physical and functional partner of tmRNA-SmpB. PMID:25165464

Hudson, Corey M.; Lau, Britney Y.; Williams, Kelly P.

2014-01-01

372

Gamma radiation effects in Yb-doped optical fiber  

NASA Astrophysics Data System (ADS)

Determination of the radiation response of doped-fiber laser materials, systems and components to relevant ionizing radiation fluxes is central to the prediction of long-term fiber-based laser performance/survivability in adverse and/or space-based environments. It is well known that optical elements that are placed into orbit around the Earth experience harsh radiation environments that originate from trapped-particle belts, cosmic rays, and solar events. Of particular interest to optical materials is the continuous flux of gamma photons that the materials encounter. Such radiation exposure commonly leads to the formation of color centers in a broad range of optical materials. Such color center formation gives rise to changes in optical transmission, loss and luminescent band structure, and, thus, impacts long-term optical device performance. In this paper we will present the results of our investigation of gamma-radiation-induced photodarkening on the passive optical transmittance of a number of ytterbium- (Yb-) doped optical fibers. We will discuss the evolution of the optical response of the fiber across the 1.0 to 1.6 micron wavelength window with increasing gamma exposure. Results indicate that these fibers exhibit reasonable radiation resistance to gamma exposures typical of a 5-year, low-earth-orbit environment. Maximum transmittance losses of less than 10% were observed for total gamma exposures of 2-5 krad (Si). In this paper we will present the results of our investigation of gamma-radiation-induced photodarkening on the optical transmittance of a number of ytterbium- (Yb-) doped optical fibers. We will discuss the evolution of the optical response of the fiber across the 1.0 to 1.6 micron wavelength window with increasing gamma exposure. Results indicate that these fibers exhibit reasonable radiation resistance to gamma exposures typical of a 5-year, low-earth orbit environment. Maximum transmittance losses of less than 10% were observed for total gamma exposures of 2-5 krad (Si).

Fox, B. P.; Schneider, Z. V.; Simmons-Potter, K.; Thomes, W. J., Jr.; Meister, D. C.; Bambha, R. P.; Kliner, D. A. V.; Söderlund, M. J.

2007-02-01

373

Traffic at the tmRNA Gene  

PubMed Central

A partial screen for genetic elements integrated into completely sequenced bacterial genomes shows more significant bias in specificity for the tmRNA gene (ssrA) than for any type of tRNA gene. Horizontal gene transfer, a major avenue of bacterial evolution, was assessed by focusing on elements using this single attachment locus. Diverse elements use ssrA; among enterobacteria alone, at least four different integrase subfamilies have independently evolved specificity for ssrA, and almost every strain analyzed presents a unique set of integrated elements. Even elements using essentially the same integrase can be very diverse, as is a group with an ssrA-specific integrase of the P4 subfamily. This same integrase appears to promote damage routinely at attachment sites, which may be adaptive. Elements in arrays can recombine; one such event mediated by invertible DNA segments within neighboring elements likely explains the monophasic nature of Salmonella enterica serovar Typhi. One of a limited set of conserved sequences occurs at the attachment site of each enterobacterial element, apparently serving as a transcriptional terminator for ssrA. Elements were usually found integrated into tRNA-like sequence at the 3? end of ssrA, at subsites corresponding to those used in tRNA genes; an exception was found at the non-tRNA-like 3? end produced by ssrA gene permutation in cyanobacteria, suggesting that, during the evolution of new site specificity by integrases, tropism toward a conserved 3? end of an RNA gene may be as strong as toward a tRNA-like sequence. The proximity of ssrA and smpB, which act in concert, was also surveyed. PMID:12533482

Williams, Kelly P.

2003-01-01

374

Cathode-luminescence property of Er 3+\\/Yb 3+-doped amorphous GeO 2  

Microsoft Academic Search

Luminescence property of erbium (Er)-doped GeO2 has been studied with cathode-luminescence analysis. GeO2 material has exhibited strong luminescence at wavelength 1537nm compared to Er-doped SiOx. By co-doping with ytterbium (Yb), luminescence increased with Er concentration 0.2–0.4mol%. On the other hand, in higher Er concentration, energy could not be transferred between Er and Yb effectively. The fabrication of a single mode

Iku Endo; Nobuhiro Onouchi; Hideyuki Yamaguchi; Atsushi Shimbori; Satoru Matsumoto

2006-01-01

375

Alternative Forms of Y-Box Binding Protein 1 and YB-1 mRNA  

PubMed Central

The multifunctional eukaryotic protein YB-1 (Y-box binding protein 1) plays a role in DNA reparation, transcription regulation, splicing, and mRNA translation, thereby participating in many crucial events in cells. Its effect is dependent mostly on its amount, and hence, on regulation of its synthesis. Published data on regulation of synthesis of YB-1 mediated by its mRNA 5? UTR, and specifically on the 5? UTR length and the presence of TOP-like motifs in this region, are contradictory. Here we report that 5? UTRs of major forms of human, rabbit, and mouse YB-1 mRNAs are about 140 nucleotides long and contain no TOP-like motifs mentioned in the literature. Also, we have found that YB-1 specifically interacts with the 5? UTR of its own mRNA within a region of about 100 nucleotides upstream from the start codon. Apart from YB-1, translation of YB-1 mRNA in a cell free system gives an additional product with an extended N-terminus and lower electrophoretic mobility. The start codon for synthesis of the additional product is AUC at position –(60–58) of the same open reading frame as that for the major product. Also, in the cell there is an alternative YB-1 mRNA with exon 1 replaced by a part of intron 1; YB-1 synthesized in vitro from this mRNA contains, instead of its N-terminal A/P domain, 10–11 amino acids encoded by intron 1. PMID:25116735

Lyabin, Dmitry N.; Doronin, Alexander N.; Eliseeva, Irina A.; Guens, Gelena P.; Kulakovskiy, Ivan V.; Ovchinnikov, Lev P.

2014-01-01

376

High-peak-power tunable laser operation of Yb:SrF2  

NASA Astrophysics Data System (ADS)

Growth, spectroscopic properties, and laser performance of Yb:SrF2 crystals have been investigated. In spatial multimode operation of a diode-pumped Yb:SrF2 laser a slope efficiency of 46% was measured. 180W output power with high beam quality at a pulse duration of 1.5ms was achieved by installing a mode cleaning aperture. A maximum average output power of 270mW and a tuning range of 73nm was observed.

Siebold, Mathias; Hein, Joachim; Kaluza, Malte Christoph; Uecker, Reinhard

2007-07-01

377

Multipulse operation of Yb3+-doped fiber mode-locked laser  

Microsoft Academic Search

The multi-pulse operation of the Yb3+-doped fiber mode-locked laser with a polarization sensitive isolator and two polarization controllers is reported. Dual- and triple-pulse of the Yb3+-doped fiber mode-locked laser in the normal dispersion are achieved as the pumping power is increased. The fiber laser can achieve different multi-pulse outputs by adjusting the polarization controllers or increasing the pump power. The

L. Zh. Yang; Y. C. Wang; G. F. Chen; Y. Sh. Wang; W. Zhao

2007-01-01

378

Effect of L-ascorbic acid on the bioretention of 169 Yb  

Microsoft Academic Search

Studies with L-ascorbic acid as biological complexing agent have been performed to investigate its influence on the uptake and retention of the radionuclide of ytterbium in animals. The experimental results indicate that the retention of169Yb in the investigated organs of mice is affected when169YbCl3 is simultaneously administered to the animal with L-ascorbic acid. L-ascorbic acid has little or no effect

K. Samochocka; J. Konecki; M. Glowacka

1989-01-01

379

Investigations of fiber optic temperature sensors based on Yb:Y3Al5O12  

Microsoft Academic Search

This dissertation presents the development of temperature sensors which employ a fiber-optic probe consisting of single crystal YB3BAlB5BOB12B (YAG) fiber with a phosphor of short length grown directly onto one end using the laser heated pedestal growth method. The response of all the crystalline temperature sensors derives from the temperature-dependent decay time of fluorescence. Yb3+P ions served as the fluorescer,

Jermaine L Kennedy

2006-01-01

380

Fabrication and characterisation of porous silicon nitride ceramics using Yb 2O 3 as sintering additive  

Microsoft Academic Search

Porous Si3N4 ceramics were fabricated by liquid-phase sintering with a Yb2O3 sintering additive, and the microstructure and mechanical properties of the ceramics were investigated, as a function of porosity. Low densification was achieved using a lower Yb2O3 additive content. Fibrous ?-Si3N4 grains developed in the porous microstructure, and the grain morphology and size were affected by different sintering conditions. A

Jian-Feng Yang; Zhen-Yan Deng; Tatsuki Ohji

2003-01-01

381

Diode-pumped regenerative Yb:SrF2 amplifier Sandrine Ricaud1,3,*  

E-print Network

SrF2, SrF2-CaF2, SrF2-BaF2, and YLF," in Advanced Solid-State Photonics, OSA Technical Digest SeriesDiode-pumped regenerative Yb:SrF2 amplifier Sandrine Ricaud1,3,* , Patrick Georges1 , Patrice Camy2 we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier

Boyer, Edmond

382

The EU Dimension to Soil Science in Schools  

ERIC Educational Resources Information Center

The EU as a context for science lessons may be given scant attention but EU decision-making is a vital factor in everyday life. Lessons on the emergence of soil science with Charles Darwin's simple scientific experiments can be linked with competence through action, inclusion and argumentations in science lessons. Decisions about an EU Soil…

Johnson, Sue

2012-01-01

383

Changing governance in the EU milk supply chain  

Microsoft Academic Search

With the 2008 EU's CAP reform the governance of the EU's dairy sector changes. This paper focuses on governance structures between dairy farms and milk processors. To get insight in regional differences within the EU, a literature research and interviews are conducted in three case study areas, namely: the Netherlands, Bulgaria and France. Results show that in these countries both

Noortje Krol; Nico Polman; Jack Peerlings; Dimitre Nikolov

2010-01-01

384

Eu3+ concentration effect on luminescence properties of YAG:Eu3+ nanoparticles  

NASA Astrophysics Data System (ADS)

Nanocrystalline Eu3+-doped YAG powders were prepared by modified Pechini method. The structural properties were investigated with XRD, SEM and Raman spectroscopy. XRD pattern indicated that the phase-pure YAG:Eu3+ crystallites were obtained without the formation of any other phases. Raman spectrum revealed good homogeneity and crystallinity of synthesized nanopowders. The luminescent properties were studied by measurement of excitation and emission spectra, quantum yields and decay curves. The effect of Eu3+ concentration on 5D0 level lifetime was studied. The processes resulting in the relaxation of excited state (5D0 level) were discussed and the probabilities of radiative and nonradiative processes were calculated using the model of f-f transition intensities. It was found that the observed shortening of 5D0 level lifetime with Eu concentration is caused by increase of nonradiative process probability.

Kolesnikov, I. E.; Tolstikova, D. V.; Kurochkin, A. V.; Manshina, A. A.; Mikhailov, M. D.

2014-11-01

385

Structural and spectroscopic properties of Yb³?-doped MgAl?O? nanocrystalline spinel.  

PubMed

Magnesium spinel (MgAl2O4) powders doped with Yb(3+) ions have been synthesized by a sol-gel method and heat-treated in the range of 700-1000 °C for 3 h. XRD patterns indicated that the powders have a cubic structure with high crystallite dispersion. Nanoparticles in the range of 10-30 nm are obtained as a function of the dopant concentration and sintering temperature. The main Yb(3+) zero-phonon line is located at 976 nm. The spectroscopic properties of the Yb(3+) ions are characterized by broad absorption spectroscopy and emission spectroscopy. Even at low temperature, the spectra reveal a strong distorted spinel lattice due to the high inversion rate between Mg(2+) tetrahedral sites and Al(3+) octahedral sites. The substitution of Mg(2+) ions by Yb(3+) ions favors the creation of Yb(3+) ion pairs which are observed in the cooperative luminescence spectra at around 500 nm. The luminescence decays are influenced by both the Yb(3+) content, the energy transfer between ions and by the presence of pairs and aggregates. Detailed analysis of the observed structural and spectroscopic measurements has been described in this manuscript. PMID:24699861

Wiglusz, Rafal J; Boulon, Georges; Guyot, Yannick; Guzik, Malgorzata; Hreniak, Dariusz; Strek, Wieslaw

2014-06-01

386

Structure and unusual magnetic properties of YbMn0.17Si1.88.  

PubMed

YbMn0.17Si1.88 was synthesized from the reaction of ytterbium, manganese, and silicon using indium as a flux. The average structure of YbMn0.17Si1.88 was refined in the monoclinic space group P21, with a = 4.0107(8) Å, b = 3.8380(8) Å, c = 14.458(3) Å, ? = 97.97(3)°, R1/wR2 = 0.0296/0.0720. The structure can be described as the intergrowth of three AlB2-type layers and one BaAl4-type layer. Magnetic susceptibility measurements suggest that the ytterbium atoms in YbMnxSi2-x exist in a mixed valent or intermediate valent state. YbMn0.17Si1.88 shows weak antiferromagnetic ordering below ?4.5 K. The magnetic interactions between the Mn and Yb atoms in YbMn0.17Si1.88 are evident from the magnetic susceptibility measurements performed at low field. A negative magnetization is observed on warming and a positive magnetization on cooling. The heat capacity data suggest moderate heavy fermion behavior. PMID:23617440

Peter, Sebastian C; Malliakas, Christos D; Kanatzidis, Mercouri G

2013-05-01

387

Gain saturation study and measurement of terminal level lifetime for Yb:YAG crystal  

NASA Astrophysics Data System (ADS)

We formulate a set of coupled rate equations describing the dynamic behaviour of a laser extraction based on the energy-level structure of a Yb:YAG crystal. A numerical computation of the energy extraction is carried out which includes the effects of the pulse width and the terminal level lifetime. According to the result of the computation, we formulated an empirical expression for the saturation fluence in Yb:YAG crystals that explicitly depends upon the ratio of the pulse width to the terminal level lifetime. The empirical saturation fluence, when substituted within the Frantz and Nodvik solution for energy extraction, can be used to accurately model the energy extracted from Yb:YAG crystal amplifiers. An experiment is performed in a Yb:YAG disc amplifier to measure the input fluence, output fluence and pulse length. We compare the experimental gain saturation data of the Yb:YAG disc amplifier with our empirical solution and determine the terminal level lifetime from a best fit to the data. The terminal level lifetime of Yb:YAG is found to be 275?ps ± 105?ps.

Yan, Xiongwei; Zheng, Jiangang; Jiang, Xingyin; Li, Mingzhong; Li, Min; Wang, Zhengguo

2014-12-01

388

A Mössbauer investigation of orthorhombic phase YbMnO3  

NASA Astrophysics Data System (ADS)

170Yb- and 57Fe-Mössbauer spectra are reported for orthorhombic phase manganites YbMnO3 and Yb(57Fe0.005Mn0.995)O3, respectively. Point charge model estimates of the electric field gradient agree well with experimental 57Fe-Mössbauer results in terms of both sign and magnitude of the electric quadrupole interaction strength, and the orientation of the magnetic hyperfine field is consistent with an E-type antiferromagnetic order where Mn moments are aligned along the a-axis (Pnma notation). The 170Yb-Mössbauer spectra exhibit pure quadrupole splitting down to 1.8 K, contradicting an earlier report that the Yb sub-lattice orders in it own right at TYb ? 4 K. Nevertheless, there is a slight increase in line broadening with decreasing temperature, probably due to the weak magnetic exchange field arising out of the ordered Mn sub-lattice. The small variation with temperature of the quadrupole interaction strength suggests that the Yb3+ electronic ground state is a well-isolated Kramers doublet.

Stewart, G. A.; Salama, H. A.; Voyer, C. J.; Ryan, D. H.; Scott, D.; O'Neill, H. StC.

2014-11-01

389

Lanthanide near infrared imaging in living cells with Yb3+ nano metal organic frameworks  

PubMed Central

We have created unique near-infrared (NIR)–emitting nanoscale metal-organic frameworks (nano-MOFs) incorporating a high density of Yb3+ lanthanide cations and sensitizers derived from phenylene. We establish here that these nano-MOFs can be incorporated into living cells for NIR imaging. Specifically, we introduce bulk and nano-Yb-phenylenevinylenedicarboxylate-3 (nano-Yb-PVDC-3), a unique MOF based on a PVDC sensitizer-ligand and Yb3+ NIR-emitting lanthanide cations. This material has been structurally characterized, its stability in various media has been assessed, and its luminescent properties have been studied. We demonstrate that it is stable in certain specific biological media, does not photobleach, and has an IC50 of 100 ?g/mL, which is sufficient to allow live cell imaging. Confocal microscopy and inductively coupled plasma measurements reveal that nano-Yb-PVDC-3 can be internalized by cells with a cytoplasmic localization. Despite its relatively low quantum yield, nano-Yb-PVDC-3 emits a sufficient number of photons per unit volume to serve as a NIR-emitting reporter for imaging living HeLa and NIH 3T3 cells. NIR microscopy allows for highly efficient discrimination between the nano-MOF emission signal and the cellular autofluorescence arising from biological material. This work represents a demonstration of the possibility of using NIR lanthanide emission for biological imaging applications in living cells with single-photon excitation. PMID:24108356

Foucault-Collet, Alexandra; Gogick, Kristy A.; White, Kiley A.; Villette, Sandrine; Pallier, Agnès; Collet, Guillaume; Kieda, Claudine; Li, Tao; Geib, Steven J.; Rosi, Nathaniel L.; Petoud, Stéphane

2013-01-01

390

Inhibition of abasic site cleavage in bubble DNA by multifunctional protein YB-1.  

PubMed

Y-box binding protein 1 (YB-1) is widely known to participate in a multiple DNA and RNA processing events in the living cell. YB-1 is also regarded as a putative component of DNA repair. This possibility is supported by relocalization of YB-1 into the nucleus following genotoxic stress. Increased affinity of YB-1 for damaged DNA, especially in its single-stranded form, and its functional interaction with proteins responsible for the initiation of apurinic/apyrimidinic (AP) site repair, namely, AP endonuclease 1 and DNA glycosylase NEIL1, suggest that YB-1 could be involved in the repair of AP sites as a regulatory protein. Here we show that YB-1 has a significant inhibitory effect on the cleavage of AP sites located in single-stranded DNA and in DNA bubble structures. Such interference may be considered as a possible mechanism to prevent single-stranded intermediates of DNA replication, transcription and repair from being converted into highly genotoxic DNA strand breaks, thus allowing the cell to coordinate different DNA processing mechanisms. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25605055

Fomina, Elizaveta E; Pestryakov, Pavel E; Kretov, Dmitry A; Zharkov, Dmitry O; Ovchinnikov, Lev P; Curmi, Patrick A; Lavrik, Olga I

2015-02-01

391

Anion dependent self-assembly of a linear hexanuclear Yb(III) salen complex with enhanced near-infrared (NIR) luminescence properties.  

PubMed

Reactions of H2salen (H2L, N,N'-ethylene bis(salicylideneimine)) with Yb(CF3SO3)3, Yb(OAc)34H2O and Yb(NO3)36H2O in MeOH–EtOH under reflux gave NIR luminescent complexes [Yb6L9(H2L)2] (1), [Yb3L3(HL)(OH)2] (2) and [Yb2L2(H2L)2(NO3)(MeOH)2]NO3 (3), respectively. PMID:24019025

Yang, Xiaoping; Oye, Michael M; Jones, Richard A; Huang, Shaoming

2013-10-25

392

Photoexcitation of Yb-doped aluminosilicate fibers at 250 nm: evidence for excitation transfer from oxygen deficiency centers to Yb{sup 3+}  

SciTech Connect

Emission spectra in the {approx}240-1100 nm wavelength region as well as the temporally resolved decay of Yb{sup 3+} and point defect spontaneous emission have been recorded when aluminosilicate optical fibers doped with Yb are irradiated with {approx}160 fs laser pulses having a central wavelength of {approx}250 nm (({Dirac_h}/2{pi}){omega}=5 eV). Photoexcitation of the fibers in this region of the deep ultraviolet (UV) provides access simultaneously to the Type II Si oxygen deficiency center (ODC), the non-bridging oxygen hole center (NBOHC: an oxygen-excess defect), and the Ge ODC. Emission from all of these defects in the ultraviolet and/or visible is observed, as is intense fluorescence at 976 nm from Yb{sup 3+}. Absorption measurements conducted in the {approx}230-265 nm region with a sequence of UV light-emitting diodes reveal a continuum peaking at {approx}248 nm and having a spectral width of {approx}18 nm (FWHM), confirming that the 250 nm laser pump is photoexciting predominantly the ODC. The temporal histories of the optically active defect and rare earth ion emission waveforms, in combination with time-integrated spectra, suggest that the Si ODC(II) triplet state directly excites Yb{sup 3+} as well as at least one other intrinsic defect in the silica network. Prolonged exposure of the Yb-doped fibers to 250 nm radiation yields increased Yb{sup 3+}, NBOHC, and Si ODC(II) singlet emission which is accompanied by a decline in Si ODC(II) triplet fluorescence, thus reinforcing the conclusion--drawn on the basis of luminescence decay constants--that the triplet state of Si ODC(II) is the immediate precursor to the NBOHC and is partially responsible for Yb ion emission at 976 nm. This conclusion is consistent with the observation that exposure of fiber to 5 eV radiation slightly suppresses ODC absorption in the {approx}240-255 nm region while simultaneously introducing an absorption continuum extending from 260 nm to below 235 nm (({Dirac_h}/2{pi}){omega}{approx_equal}5.28 eV). These results suggest that ODC{yields}E{sup '} center conversion assumes a role in excitation transfer to Yb{sup 3+}.

Carlson, C. G. [Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Present address: Laser and Optics Research Center, USAF Academy, Colorado Springs, Colorado 80840 (United States); Keister, K. E.; Dragic, P. D.; Eden, J. G. [Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Croteau, A. [INO, 2740 Einstein Street, Quebec City, Quebec G1P 4S4 (Canada)

2010-10-15

393

Lu2O3:Yb3+ ceramics - a novel gain material for high-power solid-state lasers  

Microsoft Academic Search

We have developed Yb3+:Lu2O3 ceramics with nanocrystalline technology and a vacuum sintering method. A laser diode end-pumped efficient Yb3+:Lu2O3 ceramic laser was demonstrated. A 0.7 W cw output power was obtained with the slope efficiency of 36% at 1035 nm wavelength, and 0.95 W with the slope efficiency of 53% at 1079 nm. We classify the Lu2O3:Yb3+ ceramics as gain

K. Takaichi; H. Yagi; A. Shirakawa; K. Ueda; S. Hosokawa; T. Yanagitani; A. A. Kaminskii

2005-01-01

394

Mechanically Q-switched codoped Er-Yb glass laser under 1i:sapphire and laser diode  

E-print Network

Mechanically Q-switched codoped Er-Yb glass laser under 1i:sapphire and laser diode pumping E). Codoped Erê", Yb> phosphate glass [2), and a pumped laser diode lead to Ci low-cost, compact microlaser pumping, Q-swi/ching, Solid lasers A simple Qeswitched TEMoo Erl-. Ybê+rglasslaser end-pumped by a Ti:AJ10

Paris-Sud XI, Université de

395

Novel Translational Control through an Iron-Responsive Element by Interaction of Multifunctional Protein YB1 and IRP2  

Microsoft Academic Search

The eukaryotic Y-box-binding protein YB-1 functions in various biological processes, including DNA repair, cell proliferation, and transcriptional and translational controls. To gain further insight into how human YB-1 plays its role in pleiotropic functions, we here used two-hybrid screenings to identify partners of this protein; the results showed that YB-1 itself, iron-regulatory protein 2 (IRP2), and five ribosomal proteins each

Megumi Ashizuka; Takao Fukuda; Takanori Nakamura; Kanemitsu Shirasuna; Kazuhiro Iwai; Hiroto Izumi; Kimitoshi Kohno; Michihiko Kuwano; Takeshi Uchiumi

2002-01-01

396

Crystalline Electric Fields and the Magnetic Ground State for the Heusler Intermetallic YbRh2Pb  

SciTech Connect

We have synthesized an intermetallic compound with a distorted Heusler structure, YbRh2Pb. We present a study of the magnetic, thermal, and transport properties. Heat capacity measurements revealed that YbRh2Pb magnetically orders below TN=0.57 K from a paramagnetic state with substantial crystal electric field splitting. Magnetic field further splits the ground state, which leads to the suppression of magnetic order in YbRh2Pb.

Sokolov,D.; Kim, M.; Aronson, M.; Henderson, C.; Stephens, P.

2008-01-01

397

Spectroscopic properties of Ho3+, Tm3+, and Ho3+/Tm3+ doped tellurite glasses for fiber laser applications  

NASA Astrophysics Data System (ADS)

Several papers were reported on spectroscopic properties of rare earth doped different host glasses. A complete knowledge of fluorescence properties of rare earth ions in laser materials is necessary to achieve efficient, compact and cheap sources of laser radiation for NIR and mid-IR region. Tellurite glasses are potentially useful for generation of NIR and mid-IR laser radiation due to its special features such as lowest phonon energy (750 cm-1) among oxide glasses, reasonably wide transmission region (0.35 - 5?m), good glass stability, good rare earth ion solubility, high linear and non-linear refractive index. In the present work, authors prepared Ho3+ and Tm3+ singly doped and Ho3+/Tm3+ co-doped tellurite glasses using conventional melt-quenching method. Spectroscopic measurements and analysis of energy transfer process in Ho3+, Tm3+ and Ho3+ /Tm3+ co-doped glasses pumped with 785nm and 451 nm excitation wavelengths have been performed. There are some spectroscopic properties which are important in understanding and modeling of rare earth doped laser materials. Using Judd-Ofelt theory, radiative transition rates (Arad), radiative lifetimes (?R) and branching ratios (?) were estimated for certain excited states of Ho3+ and Tm3+ doped tellurite glasses. The emission cross-sections and gain coefficients have been determined from the absorption spectra of Ho3+ and Tm3+ ions in tellurite glasses. The energy transfer process such as ion cross-relaxation, Tm3+-Ho3+ energy transfer and energy transfer upconversion were studied and identified to specific candidate for laser operation.

Seshadri, M.; Ferencz Junior, J. A. P.; Ratnakaram, Y. C.; Barbosa, L. C.

2014-03-01

398

Preparation and up-conversion luminescence properties of LaOBr:Yb3+/Er3+ nanofibers via electrospinning.  

PubMed

LaOBr:Yb(3+)/Er(3+) nanofibers were synthesized for the first time by calcinating electrospun PVP/[La(NO3)3 + Er(NO3)3 + Yb(NO3)3 + NH4 Br] composites. The morphology and properties of the final products were investigated in detail using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffractometry (XRD) and fluorescence spectroscopy. The results indicate that LaOBr:Yb(3+)/Er(3+) nanofibers are tetragonal in structure with a space group of P4/nmm. The diameter of LaOBr:Yb(3+)/Er(3+) nanofibers is ~ 147 nm. Under the excitation of a 980-nm diode laser, LaOBr:Yb(3+)/Er(3+) nanofibers emit strong green and red up-conversion emission centering at 519, 541 and 667 nm, ascribed to the (2)H11/2, (4)S3/2 ? (4) I(15/2) and (4)F9/2 ? (4)I(15/2) energy-level transitions of Er(3+) ions, respectively. The up-conversion luminescent mechanism of LaOBr:Yb(3+)/Er(3+) nanofibers is advanced. Moreover, near-infrared emission of LaOBr:Yb(3+)/Er(3+) nanofibers is obtained under the excitation of a 532-nm laser. The formation mechanism of LaOBr:Yb(3+)/Er(3+) nanofibers is proposed. LaOBr:Yb(3+)/Er(3+) nanofibers could be important up-conversion luminescent materials. PMID:24523144

Ma, Wenwen; Yu, Wensheng; Dong, Xiangting; Wang, Jinxian; Liu, Guixia

2014-11-01

399

Yb{sup 3+}:BaCaBO{sub 3}F: A potential new self-frequency-doubling laser material  

SciTech Connect

Yb:BaCaBO{sub 3}F (Yb:BCBF) has been investigated as a new laser crystal with potential for self-frequency-doubling. An YB:BCBF laser has been pumped at 912 mm, and a measured slope efficiency of 38% has been obtained for the fundamental laser output at 1034 nm. Single crystal powders of BCBF have been compared with K*P for a relative measure of the second harmonic generating potential, yielding d{sub eff}[BCBF]= (0-66)d{sub eff}[K*P]. The growth, spectroscopy, laser performance, and linear and nonlinear optical properties of YB:BCBF are reported here.

Schaffers, K.I.; DeLoach, L.D.; Ebbers, C.A.; Payne, S.A.

1995-03-09

400

Microwave-assisted solvothermal synthesis and upconversion luminescence of CaF2:Yb(3+)/Er(3+) nanocrystals.  

PubMed

Water-dispersible CaF2 and Yb(3+)/Er(3+) codoped CaF2 (CaF2:Yb(3+)/Er(3+)) nanocrystals with different sizes and different Yb(3+) and Er(3+) dopant concentrations were synthesized using ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate as a fluorine source by the rapid microwave-assisted solvothermal method. It was found that the morphology, size and crystallinity of CaF2:Yb(3+)/Er(3+) nanocrystals could be adjusted by using adenosine 5'-triphosphate disodium salt (ATP). Yb(3+) and Er(3+) ions were doped into CaF2 nanocrystals to enable upconversion luminescence emission, and the as-prepared CaF2:Yb(3+)/Er(3+) samples exhibited upconversion luminescence upon excitation at 980nm. Confocal laser scanning microscopy images showed that the CaF2:Yb(3+)/Er(3+) nanocrystals could be used for efficient labeling of human gastric carcinoma cells. Moreover, in vitro cytotoxicity experiments indicated that the as-prepared CaF2:Yb(3+)/Er(3+) nanocrystals had essentially little cytotoxicity. These results indicate that the as-prepared CaF2:Yb(3+)/Er(3+) nanocrystals are promising for the application as a luminescent label material in biological imaging. PMID:25460687

Zhao, Jing; Zhu, Ying-Jie; Wu, Jin; Chen, Feng

2015-02-15

401

Emission behaviors of Yb2O3 nanoparticles pumped by 980 nm laser at different power densities  

NASA Astrophysics Data System (ADS)

Yb2O3 nanoparticles synthesized via Pechini type sol-gel method were characterized by TEM, SAED, EDS, XRD, SEM and Raman spectrometer. Their emission properties were recorded by a fluorescence spectrophotometer with a 980 nm laser as the excitation source. These spectral results indicate that there are two optical bistable emissions at low/high laser power densities, i.e. Yb3+-Yb3+ dimer cooperative upconversion luminescence and thermal emission. Thus, Yb2O3 nanoparticles might be regarded as a candidate for intrinsic optical bistability.

Zheng, Youjin; Lü, Qiang; Wang, Jialiang; Zhang, Guohai; Gao, Yang; Liu, Zhanbo

2014-11-01

402

Rare earth metal oxides: formation, characterization and catalytic activity Thermoanalytical and applied pyrolysis review  

Microsoft Academic Search

This review provides a guide to the recent literature on the characterization of the decomposition routes of different precursors, especially carboxylates of rare earth metals (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Th), and the formation of the final oxide products. It also discusses the effects of 1.(1) the nature of

Gamal A. M. Hussein

1996-01-01

403

Spectroscopic characterization of dynamical processes for Tm,Ho:YAG lasers  

NASA Technical Reports Server (NTRS)

The energy transfer processes in Tm,Ho:YAG lasers were investigated in spectral studies and measurements of the temporal response to pulsed excitation. These processes include the population of the 3H4 pump band of Tm, cross-relaxation in Tm, the transfer of energy from Tm to Ho, and various loss mechanisms. It was found that the Tm cross-relaxation is due to a dipole-dipole interaction between Tm ions and that the rate of this process is a function of temperature and ion concentration.

Armagan, G.; Buoncristiani, A. M.; Edwards, W. C.; Inge, A. T.; Dibartolo, B.

1991-01-01

404

Synthesis and Characterization of Eu-Doped Cadmium Selenide Nanocrystals  

SciTech Connect

Substitution of Cd(II) sites by Eu ions in 5.0 nm {+-} 0.25 nm CdSe, Cd{sub 1-x}Eu{sub x}Se (x=0.374), can be achieved by modification of a lyothermal, single source precursor method. The Eu guest ion occupies a tetrahedral lattice site as a Eu(III) defect ion based on analysis of the XPS and XAS data. XRD and XAS measurements show a linear contraction of the lattice parameters for increasing Eu(III) concentration consistent with statistical substitution at both core and surface sites in the lattice by a random ion displacement mechanism. On the basis of a Vegard's law analysis, the Eu(III) ion is substituted in the tetrahedral cationic lattice site without formation of vacancies or phase segregation of the Eu ion in the lattice.

Raola, O. E.

2002-01-01

405

TM digital image products for applications. [computer compatible tapes  

NASA Technical Reports Server (NTRS)

The image characteristics of digital data generated by LANDSAT 4 thematic mapper (TM) are discussed. Digital data from the TM resides in tape files at various stages of image processing. Within each image data file, the image lines are blocked by a factor of either 5 for a computer compatible tape CCT-BT, or 4 for a CCT-AT and CCT-PT; in each format, the image file has a different format. Nominal geometric corrections which provide proper geodetic relationships between different parts of the image are available only for the CCT-PT. It is concluded that detector 3 of band 5 on the TM does not respond; this channel of data needs replacement. The empty bin phenomenon in CCT-AT images results from integer truncations of mixed-mode arithmetric operations.

Barker, J. L.; Gunther, F. J.; Abrams, R. B.; Ball, D.

1984-01-01

406

Photoluminescence properties of singly doped Tm3+ and co-doped Tm3+/Tb3+ ions in tellurite glasses  

NASA Astrophysics Data System (ADS)

Photoluminescence properties of singly doped Tm3+ and co-doped Tm3+/Tb3+ ions in TZKC glasses with chemical composition of (61.5-x) TeO2 + 25 ZnO + 8 K2O + 5CaO + 0.5Tm2O3 + xTb4O7 (TZKCTm05Tbx; x (in mol%) = 0, 0.5, 1.0, 1.5) have been studied. The experimental oscillator strengths of absorption bands in TZKCTm05 glass were used to determine the host dependent Judd-Ofelt ?2, ?4, ?6 intensity parameters. The effective emission cross-section of 1.8 ?m emission band as a function of wavelength has been deduced by the McCumber's theory. Based on the absorption (?a) and emission cross-sections (?e), the gain co-efficients (G) of 1.8 ?m emission band for various population inversions between the emitting (3F4) and terminating (3H6) levels were evaluated. From the photoluminescence spectra of singly doped Tm3+ and co-doped Tm3+/Tb3+ ions in TZKC glasses, the chromaticity color coordinates (x, y) were estimated.

Sasikala, T.; Rama Moorthy, L.

2014-11-01

407

28 W, 217-fs regenerative bulk amplifier based on Yb:CAlGdO4  

NASA Astrophysics Data System (ADS)

Yb:CaAlGdO4 (Yb:CALGO) is a very promising material for high power ultrashort pulse generation, due to its broad emission bandwidth and good thermal properties. Here we report, to the best of our knowledge, the highest power and shorter pulses ever demonstrated from a Yb:CALGO-based regenerative amplifier. The system layout consists of a Yb:CALGO oscillator seeding a Yb:CALGO regenerative amplifier followed by a folded grating compressor. The Yb:CALGO oscillator provides approximately 650 mW output power in a 63 MHz repetition rate pulse train of 92-fs long pulses. The related spectrum is 12.5 nm wide (FWHM) and centered around 1050 nm. Average output powers as high as 36 W at 500 kHz are achieved out of the regenerative amplifier while pumping with 116 W at approximately 980 nm. A small roll-over in the regenerative output power is observed at maximum pump power. This is mostly due to a drift of the pump wavelength away from the maximum crystal absorption peak with increasing pump current. After compression, we obtained 28 W in a train of 217-fs long pulses, corresponding to a pulse energy higher than 50 ?J per pulse and a peak power above 0.25 GW. The pulse spectrum is centered at 1046 nm and is approximately 11 nm wide, corresponding to a time bandwidth product of 0.69. The beam quality factor stays below M2=1.15 up to the maximum output power level, confirming the outstanding thermal performances of the Yb:CALGO material. Experiments on further power up-scaling are in progress.

Kemnitzer, M.; Caracciolo, E.; Guandalini, A.; Pirzio, F.; Aus der Au, J.; Agnesi, A.

2014-02-01

408

Energy transfer and luminescence studies of Pr 3+ , Yb 3+ co-doped lead borate glass  

NASA Astrophysics Data System (ADS)

Lead borate glass samples doped with the tripositive lanthanide ions Pr 3+ and Yb 3+ were synthesized by the conventional melting-quenching method. The luminescence properties and energy transfer process from Pr 3+ to Yb 3+ were investigated. Upon ultraviolet excitation, the room temperature luminescence decay curve of a sample containing only a low concentration of Pr 3+ exhibited monoexponential decay from 1D 2 with the lifetime 37 ?s, without emission from 3P 0. The room temperature Pr 3+ emission intensity decreased with the increase of Yb 3+ mole ratio in the glass. Under the excitation of 454.5 nm at 10 K, a broad red emission band centered at 605 nm, and an NIR emission band at 995 nm were observed in the co-doped lead borate glass, originating from Pr 3+ and Yb 3+ ions, respectively. The decay curves of the 1D 2 emission from Pr 3+ with addition of Yb 3+ in lead borate glass show non-monoexponential character, and are best described by a stretched exponential function. The average 1D 2 decay time decreases considerably with the addition of Yb 3+ in the glass. Decay curve fitting using a modified Inokuti-Hirayama expression indicates dipole-dipole energy transfer from Pr 3+ to Yb 3+, which is consistent with the expected cross-relaxation scheme. There is a good agreement of the estimated overall energy transfer efficiency obtained from the integrals under the normalized decay curves, or from the lifetimes fitted by the stretched exponential function, or from the average decay times.

Wen, Hongli; Tanner, Peter A.

2011-09-01

409

On the Luminescence Enhancement of Mn2+ By Co-doping of Eu2+ in ZnS:Mn,Eu  

SciTech Connect

The photoluminescence and X-ray luminescence of ZnS:Mn, ZnS:Mn,Eu and ZnS:Eu were investigated and it was found that the luminescence intensity of Mn2+ in ZnS:Mn,Eu co-doped phosphors is highly dependent on the doping concentration of Eu2+. At the optimized Eu2+concentration (0.2%), the photoluminescence of Mn2+ shows about a 5.5 times enhancement and its X-ray luminescence is enhanced by a factor of 2.5. Both wurtzite and zinc blend phases are present in the samples with wurtzite phase dominant. Co-doping of Eu2+ into ZnS:Mn does not change appreciably the ratio of the two phases or the Mn2+ emission luminescence lifetime; however, the doping of Eu2+ into ZnS:Mn does change the phonon activity. Furthermore, it was found that the defect-related blue emission of ZnS:Eu overlaps with the excitation bands of Mn2+ in ZnS:Mn and there is likely energy transfer from these defect states to Mn2+ in ZnS:Mn,Eu. This energy transfer and the phonon modification are considered to be the two main reasons for the luminescence enhancement and the intensity dependence of Mn2+ emission on Eu2+ doping concentration in ZnS:Mn,Eu.

Hossu, Marius; Schaeffer, Roger O.; Ma, Lun; Chen, Wei; Zhu, Yongbin; Sammynaiken, Ramaswami; Joly, Alan G.

2013-06-01

410

Nonparaxial TM and TE beams in free space.  

PubMed

Expressions for the fields of TM and TE laser beams in free space that are rigorous solutions to Maxwell's equations are given in a closed form. The electric and the magnetic fields are both expressed in terms of nonparaxial elegant Laguerre-Gaussian beams that are exact solutions of the Helmholtz equation. These solutions involve well-known functions, such as spherical Bessel and associated Legendre functions. Radially and azimuthally polarized beams of arbitrary order are considered, and the lowest-order radially polarized beam (TM(01) beam) is investigated in detail. PMID:18628798

April, Alexandre

2008-07-15

411

SPACEWAY(TM) Providing Afordable and Versatile Telecommunication Solutions  

NASA Technical Reports Server (NTRS)

This paper presents a summary description of SPACEWAY(TM), a network of Ka band geostationary satellites being developed by Hughes Communications, Inc. to provide worldwide interactive telecommunications services to small, low cost user terminals. By the end of this decade SPACEWAY(TM), using relatively few satellites and tightly focused spot beams, will provide affordable interactive 'bandwidth on demand' communication services on a global basis to consumer and commercial end users. This paper describes the system concept, details the space and ground segment characteristics, and discusses communication links.

Fitzpatrick, Edward James

1996-01-01

412

Ion-exchanged Tm3+:glass channel waveguide laser.  

PubMed

Continuous wave laser action around 1.9 ?m has been demonstrated in a Tm(3+)-doped germanate glass channel waveguide laser fabricated by ion-exchange. Laser action was observed with an absorbed power threshold of only 44 mW and a slope efficiency of up to 6.8% was achieved. Propagation loss at the lasing wavelength was measured to be 0.3 dB/cm. We believe this to be the first ion-exchanged Tm(3+)-doped glass waveguide laser. PMID:23546272

Choudhary, Amol; Kannan, Pradeesh; Mackenzie, Jacob I; Feng, Xian; Shepherd, David P

2013-04-01

413

Enhanced rock discrimination using Landsat-5 Thematic Mapper (TM) data  

NASA Technical Reports Server (NTRS)

The application of TM data to rock discrimination is discussed. Sixteen specific terrains derived from geologic maps are examined on TM images of the Arabian shield obtained on Apr. 14, 1984; visual enhancement procedures are applied to the images. The rock types observed in the test site are described; the major sedimentary formations in the test area are laterite and sandstone. The data reveal that the layered rocks in the outcrop consist of a variety of metamorphosed volcanics, metamorphosed sediments, and amphibolite, and the intrusive complex is composed of several classes of mafic and acidic rocks.

Blodget, H. W.; Andre, C. G.; Marcell, R. F.

1985-01-01

414

Induced spin-polarization of EuS at room temperature in Ni/EuS multilayers  

SciTech Connect

Ni/EuS multilayers with excellent multilayer sequencing are deposited via e-beam evaporation on the native oxide of Si(100) wafers at 4?×?10{sup ?9} millibars. The samples have very small surface and interface roughness and show sharp interfaces. Ni layers are nanocrystalline 4–8?nm thick and EuS layers are 2–4?nm thick and are either amorphous or nanocrystalline. Unlike for Co/EuS multilayers, all Eu ions are in divalent (ferromagnetic) state. We show a direct antiferromagnetic coupling between EuS and Ni layers. At room temperature, the EuS layers are spin-polarized due to the proximity of Ni. Therefore, Ni/EuS is a candidate for room-temperature spintronics applications.

Poulopoulos, P., E-mail: poulop@upatras.gr [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Materials Science Department, University of Patras, 26504 Patras (Greece); Goschew, A.; Straub, A.; Fumagalli, P. [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Kapaklis, V.; Wolff, M. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Delimitis, A. [Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 57001 Thermi, Thessaloniki (Greece); Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), B.P.220, 38043 Grenoble (France); Pappas, S. D. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden)

2014-03-17

415

FERN-the EU Forest Campaign  

NSDL National Science Digital Library

Created by the World Rainforest Movement in 1995, FERN (Forests and the European Union Resource Network) "promotes the conservation and sustainable use of forests and respect for the rights of forest peoples in the policies and practices of the European Union." Presently, the principal FERN campaign areas include Forest Certification; Climate Change; WTO and Trade Agreements; and Aid and Development Cooperation, to name a few. This website contains summaries of current FERN campaigns as well as links to news articles regarding Poverty and EC Aid, Forest Peoples, EU Forests, Trade, and more. The site also offers access to an extensive assortment of publications including Briefings, NGO Statements, EU Documents, and FERN Reports. The website contains a solid collection of related links as well.

416

EU Merger Control in Differentiated Product Industries  

Microsoft Academic Search

EU Merger Control Regulation No 4064\\/89 tended to rely on a dominance test, based on the market share of undertakings, to indicate the level and potential changes in market power. The use of such in differentiated product industries is questionable. New EC Merger Regulation No 139\\/2004 introduces a substantive test to ensure that all post-merger scenarios posing a threat to

Franco Mariuzzo; Patrick Paul Walsh; Ciara Whelan

2004-01-01

417

Banana Split: USA Challenges EU Trade Policies  

NSDL National Science Digital Library

This new research guide from Eldis, the Electronic Development and Environment Information System, (described in the October 9, 1997 Scout Report for Business & Economics) presents background information on the US-EU Banana Trade Dispute (discussed in the March 5, 1999 Scout Report). The guide covers US and Latin American banana producer discontent in addition to perspectives from Caribbean banana exporters, the Commonwealth Secretariat, and the World Trade Organization (WTO).

1999-01-01

418

New ZrO2-Yb2O3 plasma-sprayed coatings for thermal barrier applications  

NASA Technical Reports Server (NTRS)

New thermal barrier coatings, whose compositions were chosen on the basis of a limited study of the ZrO2-Yb2O3 system, were evaluated by cyclic testing in a furnace at 1120 C. On Ni-16.2Cr-5.9Al-0.15Y bond coating, ZrO2-12.4Yb2O3, ZrO2-14.7Yb2O3 and ZrO2-17.4Yb2O3 coatings have respectively 60, 30, and 15 percent longer lives than the near-optimum ZrO2-6.1Y2O3 coating. On Ni-18.3Cr-6.4Al-0.22Yb coating, ZrO2-12.4Yb2O3 has about 40 percent longer life than the ZrO2-6.1Y2O3 coating. The optimum Yb2O3 concentration in ZrO2 at which the maximum life is obtained is believed to be between 12.4 and 14.7 wt pct. The ZrO2-Yb2O3 thermal barrier systems failed through the formation of a crack or cracks in the thermal barrier coating near the bond coating interface. As-received ZrO2-Yb2O3 plasma spray powders had a nonhomogeneous distribution of Yb2O3. Monoclinic, cubic, and tetragonal phases in addition to Zr3Yb4O12 and an unknown phase were present.

Stecura, Stephan

1987-01-01

419

Green EuAlO3:Eu2+ nanophosphor for applications in WLEDs  

NASA Astrophysics Data System (ADS)

Green-emitting aluminate nanophosphors fabricated by a pressure-assisted combustion synthesis (P0 = 1.4, 2.8 and 3.4 MPa) and annealed in pure H2 is reported. The XRD analysis indicates the formation of the EuAlO3 orthorhombic phase. Transmission electron microscopy (TEM) shows coalesced irregular grains with lengths in the range of 35-140 nm. In addition, the nanophosphor synthesized at an initial pressure of 3.4 MPa produced the highest green luminescence centered at 530 nm, which was associated to 4f7-4f65d1 allowed transitions of the Eu2+ located into the EuAlO3:Eu2+ compound. A weak red emission peak corresponding to Eu3+ was also observed by cathodoluminescence. The CIE coordinates for green emission are x = 0.2613 and y = 0.3892, and the luminance produced from nanophosphors when they are excited with a commercial UV-396 nm LED (8.0 ?W) was 285 ± 4.3 Cd/m2.

García, C. R.; Diaz-Torres, L. A.; Oliva, J.; Hirata, G. A.

2014-11-01

420

EuNiGe?, an anisotropic antiferromagnet.  

PubMed

Single crystals of EuNiGe3, crystallizing in the non-centrosymmetric BaNiSn3-type structure, were grown using In flux, enabling us to explore the anisotropic magnetic properties, which was not possible with previously reported polycrystalline samples. The EuNiGe3 single crystalline sample is found to order antiferromagnetically at 13.2 K, as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M (H) is distinctly different for the field parallel to the ab-plane and c-axis; the ab-plane magnetization varies almost linearly with the field before the occurrence of an induced ferromagnetic (FM) phase (spin-flip) at 6.2 Tesla. On the other hand M (H) along the c-axis is accompanied by two metamagnetic transitions followed by a spin-flip at 4.1 T. A model including anisotropic exchange and dipole-dipole interactions reproduces the main features of magnetization plots but falls short of full representation. (H,T) phase diagrams have been constructed for the field applied along the principal directions. From the (151)Eu Mössbauer spectra, we determine that the 13.2 K transition leads to an incommensurate antiferromagnetic (AFM) intermediate phase followed by a transition near 10.5 K to a commensurate AFM configuration. PMID:24787717

Maurya, A; Bonville, P; Thamizhavel, A; Dhar, S K

2014-05-28

421

Nonlinear losses in photoconductive Yb:YAG laser materials: identification of photocarrier properties by non-steady-state photoEMF  

NASA Astrophysics Data System (ADS)

We report on the investigation of the photocarrier sign and the excitation dynamics in Yb:YAG at 940 nm excitation wavelength by non-steady-state photo-electromotive force technique. Annealed crystals with 25 and 50 % Yb-doping concentration demonstrate hole conductivity, while 80 % Yb:YAG displays electron conductivity. A characteristic relaxation time of approximately 1 ms is observed, which corresponds to the lifetime of the excited Yb3+-ion.

Korneev, N.; Rodriguez-Montero, P.; Wolters, U.; Petermann, K.; Huber, G.

2014-07-01

422

Kinematics at the intersection of the Garlock and Death Valley fault zones, California: Integration of TM data and field studies. LANDSAT TM investigation proposal TM-019  

NASA Technical Reports Server (NTRS)

Processing and interpretation of Thematic Mapper (TM) data, extensive field work, and processing of SPOT data were continued. Results of these analyses led to the testing and rejecting of several of the geologic/tectonic hypotheses concerning the continuation of the Garlock Fault Zone (GFZ). It was determined that the Death Valley Fault Zone (DVFZ) is the major through-going feature, extending at least 60 km SW of the Avawatz Mountains. Two 5 km wide fault zones were identified and characterized in the Soda and Bristol Mountains, forming a continuous zone of NW trending faulting. Geophysical measurements indicate a buried connection between the Avawatz and the Soda Mountains Fault Zone. Future work will involve continued field work and mapping at key locations, further analyses of TM data, and conclusion of the project.

Abrams, Michael; Verosub, Ken

1987-01-01

423

YB-1 dependent oncolytic adenovirus efficiently inhibits tumor growth of glioma cancer stem like cells  

PubMed Central

Background The brain cancer stem cell (CSC) model describes a small subset of glioma cells as being responsible for tumor initiation, conferring therapy resistance and tumor recurrence. In brain CSC, the PI3-K/AKT and the RAS/mitogen activated protein kinase (MAPK) pathways are found to be activated. In consequence, the human transcription factor YB-1, knowing to be responsible for the emergence of drug resistance and driving adenoviral replication, is phosphorylated and activated. With this knowledge, YB-1 was established in the past as a biomarker for disease progression and prognosis. This study determines the expression of YB-1 in glioblastoma (GBM) specimen in vivo and in brain CSC lines. In addition, the capacity of Ad-Delo3-RGD, an YB-1 dependent oncolytic adenovirus, to eradicate CSC was evaluated both in vitro and in vivo. Methods YB-1 expression was investigated by immunoblot and immuno-histochemistry. In vitro, viral replication as well as the capacity of Ad-Delo3-RGD to replicate in and, in consequence, to kill CSC was determined by real-time PCR and clonogenic dilution assays. In vivo, Ad-Delo3-RGD-mediated tumor growth inhibition was evaluated in an orthotopic mouse GBM model. Safety and specificity of Ad-Delo3-RGD were investigated in immortalized human astrocytes and by siRNA-mediated downregulation of YB-1. Results YB-1 is highly expressed in brain CSC lines and in GBM specimen. Efficient viral replication in and virus-mediated lysis of CSC was observed in vitro. Experiments addressing safety aspects of Ad-Delo3-RGD showed that (i) virus production in human astrocytes was significantly reduced compared to wild type adenovirus (Ad-WT) and (ii) knockdown of YB-1 significantly reduced virus replication. Mice harboring othotopic GBM developed from a temozolomide (TMZ)-resistant GBM derived CSC line which was intratumorally injected with Ad-Delo3-RGD survived significantly longer than mice receiving PBS-injections or TMZ treatment. Conclusion The results of this study supported YB-1 based virotherapy as an attractive therapeutic strategy for GBM treatment which will be exploited further in multimodal treatment concepts. PMID:24044901

2013-01-01

424

High-pressure effect on the superconductivity of YB6  

NASA Astrophysics Data System (ADS)

Pressure effects on superconducting properties of two YB6 samples (Tc=5.9 and 7.5 K) were investigated by measurements of electrical resistivity, magnetic susceptibility, and x-ray diffraction in the pressure range up to 320 kbar. Magnetoresistivity measurements down to 60 mK and up to 47 kbar have shown a negative pressure effect on Tc as well as on the third critical field Hc3 with the slopes dlnTc/dp =-0.59%/kbar and dlnHc3/dp =-1.1%/kbar, respectively. The magnetic susceptibility measurements evidenced that the slope of dlnTc/dp gradually decreases with pressure reaching a value three times smaller at 112 kbar. The lattice parameter measurements revealed the volume reduction of 14% at 320 kbar. The pressure-volume dependence is described by the Rose-Vinet equation of state. The obtained relative volume dependence dlnTc/dlnV analyzed by the McMillan formula for Tc indicates that the reduction of the superconducting transition temperature is mainly due to hardening of the Einstein-like phonon mode responsible for the superconducting coupling. This is confirmed by the analysis of the resistivity measurements in the normal state up to T =300 K performed at pressures up to 28 kbar.

Gabáni, S.; Taká?ová, I.; Pristáš, G.; Gažo, E.; Flachbart, K.; Mori, T.; Braithwaite, D.; Míšek, M.; Kamenev, K. V.; Hanfland, M.; Samuely, P.

2014-07-01

425

p-Wave Optical Feshbach Resonances in Yb-171  

E-print Network

We study the use of an optical Feshbach resonance to modify the p-wave interaction between ultracold polarized Yb-171 spin-1/2 fermions. A laser exciting two colliding atoms to the 1S_0 + 3P_1 channel can be detuned near a purely-long-range excited molecular bound state. Such an exotic molecule has an inner turning point far from the chemical binding region and thus three-body-recombination in the Feshbach resonance will be highly suppressed in contrast to that typically seen in a ground state p-wave magnetic Feshbach resonance. We calculate the excited molecular bound-state spectrum using a multichannel integration of the Schr\\"{o}dinger equation, including an external perturbation by a magnetic field. From the multichannel wave functions, we calculate the Feshbach resonance properties, including the modification of the elastic p-wave scattering volume and inelastic spontaneous scattering rate. The use of magnetic fields and selection rules for polarized light yields a highly controllable system. We apply th...

Goyal, Krittika; Deutsch, Ivan

2010-01-01

426

Yb:CaF2 thin-disk laser.  

PubMed

We present Ytterbium-doped CaF2 as a laser active material with good prospects for high-power operation in thin-disk laser configuration owing to its favorable thermal properties. Thanks to its broad emission bandwidth the material is also suitable for the generation of ultra-short pulses. The properties of the crystal as well as the challenges related to the coating, polishing, mounting and handling processes which are essential to achieve high power laser oscillation in thin-disk configuration are discussed. A wavelength tunability of 92 nm is demonstrated, which confirms the potential of Yb:CaF2 for the generation of ultra-short pulses. An output power of 250 W with an optical efficiency of ? opt = 47% was measured in CW multimode thin-disk laser operation with a pump spot diameter of 3.6 mm. Using a smaller pump spot diameter of 1 mm the fundamental mode output power was 13 W with an optical efficiency of ? opt = 34%. PMID:24515159

Wentsch, Katrin Sarah; Weichelt, Birgit; Günster, Stefan; Druon, Frederic; Georges, Patrick; Abdou Ahmed, Marwan; Graf, Thomas

2014-01-27

427

78 FR 57149 - Western Minnesota Municipal Power Agency, Lock+TM  

Federal Register 2010, 2011, 2012, 2013

...Western Minnesota Municipal Power Agency, Lock+ TM Hydro Friends Fund III, LLC; Notice of Competing...Power Agency (Western Minnesota) and Lock+ TM Hydro Friends Fund III, LLC (Hydro Friends...9-16-13