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Sample records for eu tm yb

  1. Facile synthesis and luminescence properties of Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), Yb(3+)/Ho(3+)) microspheres.

    PubMed

    Xu, Zhenhe; Zhao, Qian; Ren, Baoyi; You, Lixin; Sun, Yaguang

    2014-08-01

    Multicolor and monodisperse Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Ho(3+)) microspheres were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the samples. The XRD results reveal that the as-prepared spheres can be well indexed to cubic Y2O3 phase with high purity. The SEM and TEM images show the obtained Y2O3:Ln(3+) samples consist of regular nanospheres with the mean diameter of 350 nm. And the possible formation mechanism is also proposed. Upon ultraviolet and low-voltage electron beams excitation, Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+)) samples exhibit respective bright red (Eu(3+), (5)D0 --> (7)F2), green (Tb(3+), (5)D4 --> (7)F5), blue (Dy(3+), (4)F9/2 --> (6)H13/2), yellow (Sm(3+), (4)G5/2 --> (6)H7/2), green (Er(3+), (4)S3/2 --> (4)I15/2), green (Ho(3+), (5)S2 --> (5)I8), blue (Tm(3+), (1)D2 --> (3)F4) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Y2O3:Ln(3+) (Ln(3+) = Yb(3+)/Er(3+), Yb(3+)/Tm(3+) and Yb(3+)/Ho(3+)) exhibit characteristic up-conversion (UC) emissions of green (Er(3+), (2)H11/2, (4)S3/2, (2)H11/2 --> (4)I5/2), blue (Tm(3+), (1)G4 --> (3)H6) and green (Ho(3+), (5)F4, (5)S2 --> (5)I8), respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices. PMID:25936002

  2. Structural and optical properties of lanthanide oxides grown by atomic layer deposition (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb).

    PubMed

    Hansen, Per-Anders; Fjellvåg, Helmer; Finstad, Terje; Nilsen, Ola

    2013-08-14

    Ln2O3 thin films with optically active f-electrons (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) have been grown on Si(100) and soda lime glass substrates by atomic layer deposition (ALD) using Ln(thd)3 (Hthd = 2,2,6,6-tetramethyl-3,5-heptanedione) and ozone as precursors. The temperature range for depositions was 200-400 °C. Growth rates were measured by spectroscopic ellipsometry and a region with a constant growth rate (ALD window) was found for Ln = Ho and Tm. All the compounds are grown as amorphous films at low temperatures, whereas crystalline films (cubic C-Ln2O3) are obtained above a certain temperature ranging from 300 to 250 °C for Nd2O3 to Yb2O3, respectively. AFM studies show that the films were smooth (rms < 1 nm) except for depositions at the highest temperatures. The refractive index was measured by spectroscopic ellipsometry and was found to depend on the deposition temperature. Optical absorption measurements show that the absorption from the f-f transitions depends strongly on the crystallinity of the material. The clear correlation between the degree of crystallinity, optical absorptions and refractive indices is discussed. PMID:23774891

  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

    Gao, Yu; Gong, Jian; Fan, Miaomiao; Fang, Qinghong; Wang, Na; Han, Wenchi; Xu, Zhenhe

    2012-12-15

    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.

  4. Controlled synthesis and luminescence properties of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, Dy, Yb/Er, Yb/Tm, and Yb/Ho) phosphors by hydrothermal method versus pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Chandramohan, Rathinam

    2016-01-01

    Herein, we report on rare-earth (RE) activated Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, Dy, Yb/Er, Yb/Ho, and Yb/Tm) phosphors synthesized using a surfactant-mediated hydrothermal route. Timedependent experiments were performed, and the morphological evolution of the phosphors was studied. From prepared powder samples of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu and Yb/Er), nano-sized thin phosphor films were grown using pulsed laser deposition (PLD). The surface topography of the as-grown thin phosphor films was analyzed. The asprepared phosphors were characterized by structural and optical studies. The powder phosphor exhibited bi pyramid-like micro-architectures. Structural studies indicated that Ca0.5Y1-x(MoO4)2 possesses the scheelite tetragonal crystal structure. The down-conversion luminescence of Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Eu, Pr, Sm, Tb, and Dy) as powder phosphors and Eu3+ doped Ca0.5Y1-x(MoO4)2 thin phosphor film were studied. Upon irradiation with a 980 nm laser, the Ca0.5Y1-x(MoO4)2: xRE3+ (RE = Yb/Er, Yb/Ho, and Yb/Tm) powder phosphors and Ca0.5Y1-x(MoO4)2:xRE3+ (RE = Yb/Er) thin phosphor film showed intense up-converted visible emissions in green, yellow, and blue regions. The fluorescence decay time and color co-ordinates were determined for all synthesized phosphors. From the obtained results, the prepared powder and thin film phosphors are suggested to be suitable candidates for display and electro-luminescence applications. [Figure not available: see fulltext.

  5. Investigation of upconversion and downconversion fluorescence emissions from β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal disk system

    SciTech Connect

    He, Enjie; Zheng, Hairong; Gao, Wei; Tu, Yinxun; Lu, Ying; Li, Guian

    2013-09-01

    Graphical abstract: Well-defined β-NaLn1F4:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) hexagonal thin disks with a simple and user-friendly hydrothermal approach by using sodium citrate as a shape modifier. Much stronger UC and DC fluorescence emissions were observed in NaLuF{sub 4}-based hexagonal disks than that for NaYF{sub 4} counterparts. The strength of hypersensitive transitions is mainly attributed to the decrease of local symmetry Ln-F bond lengths in β-NaLuF{sub 4}. It will show a great potential in improving near-infrared conversion efficiency of silicon solar cells and removable sub-micro luminescent platforms. - Highlights: • Regular hexagonal disks (NaLnF{sub 4}) were synthesized by a simple hydrothermal method. • Much stronger UC and DC emissions were observed in NaLuF{sub 4}-based disks. • Stronger fluorescence emissions in NaLuF{sub 4}-based disks were explained reasonably. • NaLuF{sub 4}-based disks can act as a removable luminescent platform for nano-assembly. • NaLuF{sub 4}-based disks can be applied in improving efficiency of solar cells. - Abstract: Uniform hexagonal β-NaLn1F{sub 4}:Yb{sup 3+}, Ln2{sup 3+} (Ln1 = Y, Lu; Ln2 = Er, Ho, Tm, Eu) disks were synthesized with hydrothermal method in which the sodium citrate was used as a shape modifier. The experimental observation indicated that both upconversion and downconversion fluorescence emissions were significantly stronger in β-NaLuF{sub 4} than that for β-NaYF{sub 4}. It was found that the stronger hypersensitive transitions were mainly due to the increase of J–O parameter (Ω{sub 2}) in β-NaLuF{sub 4} host, while the stronger insensitive transitions were mainly caused by the stronger overlap of electron cloud that was induced by the decrease of Ln-F bond lengths. Additionally, the larger absorption strength in the near-infrared region is another important factor for the stronger fluorescence emissions. The current research has a great potential in improving near-infrared conversion efficiency of silicon solar cells.

  6. Spectroscopic and laser characterization of Yb,Tm:KLu(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Serres, J. M.; Mateos, X.; Demesh, M. P.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2016-01-01

    We report on a comprehensive spectroscopic and laser characterization of monoclinic Yb,Tm:KLu(WO4)2 crystals. Stimulated-emission cross-section spectra corresponding to the 3F4 → 3H6 transition of Tm3+ ions are determined. The radiative lifetime of the 3F4 state of Tm3+ ions is 0.82 ms. The maximum Yb3+ → Tm3+ energy transfer efficiency is 83.9% for 5 at.% Yb - 8 at.% Tm doping. The fractional heat loading for Yb,Tm:KLu(WO4)2 is 0.45 ± 0.05. Using a hemispherical cavity and 5 at.% Yb - 6 at.% Tm doped crystal, a maximum CW power of 227 mW is achieved at 1.983-2.011 μm with a maximum slope efficiency η = 14%. In the microchip laser set-up, the highest slope efficiency is 20% for a 5 at.% Yb- 8 at.% Tm doped crystal with a maximum output power of 201 mW at 1.99-2.007 μm. Operation of Yb,Tm:KLu(WO4)2 as a vibronic laser emitting at 2.081-2.093 μm is also demonstrated.

  7. Possible undercompensation effect in the Kondo insulator (Yb,Tm)B12

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Nemkovski, K. S.; Mignot, J.-M.; Clementyev, E. S.; Ivanov, A. S.; Rols, S.; Bewley, R. I.; Filipov, V. B.; Shitsevalova, N. Yu.

    2014-03-01

    The effects of Tm substitution on the dynamical magnetic response of Yb1-xTmxB12 (x=0, 0.08, 0.15, and 0.75) and Lu0.92Tm0.08B12 compounds have been studied using time-of-flight inelastic neutron scattering. Major changes were observed in the spectral structure and temperature evolution of the Yb contribution to the inelastic response for a rather low content of magnetic Tm ions. A sizable influence of the RB12 host (YbB12, as compared to LuB12 or pure TmB12) on the crystal-field splitting of the Tm3+ ion is also reported. The results point to a specific effect of impurities carrying a magnetic moment (Tm, as compared to Lu or Zr) in a Kondo insulator, which is thought to reflect the "undercompensation" of Yb magnetic moments, originally Kondo screened in pure YbB12. A parallel is made with the strong effect of Tm substitution on the temperature dependence of the Seebeck coefficient in Yb1-xTmxB12, which was reported previously.

  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

    Jia Dingxian Zhu Aimei; Jin Qinyan; Zhang Yong; Jiang Wenqing

    2008-09-15

    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.

  9. Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses

    SciTech Connect

    Zhang Qiang; Zhang Guang; Chen Guorong; Qiu Jianrong; Chen Danping

    2010-01-15

    Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.

  10. Blue Upconversion Luminescence in Tm3+/Yb3+-Codoped Lead Chloride Tellurite Glass

    NASA Astrophysics Data System (ADS)

    Xu, Shi-Qing; Zhang, Jun-Jie; Wang, Guo-Nian; Dai, Shi-Xun; Hu, Li-Li; Jiang, Zhong-Hong

    2004-05-01

    The upconversion properties of Tm3+/Yb3+-codoped lead chloride tellurite glass under 980 nm excitation were investigated. The intense blue (476 nm) emission and weak red (649 nm) emission corresponding to the 1G4rightarrow3H6 and 1G4rightarrow3H4 transitions of Tm3+ ions, respectively, were simultaneously observed at room temperature. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm3+/Yb3+-codoped lead chloride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.

  11. (Ho, Tm, Yb): KLuW nanoparticles, an efficient thermometry sensor in the biological range

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    We studied up-conversion emission of triply doped (Ho,Tm,Yb):KLu(WO4)2 (KLuW) nanocrystals at the range of temperature 296-673 K at different excitation wavelengths. The intensity ratio between two emission lines was used for monitoring the temperature. Pumping Yb3+ at 980 nm provides a good response at relatively high temperatures, while pumping Tm3+ at 802 nm provides an excellent sensitivity in the biological range of temperatures., which make the material also attractive for biological temperature sensors.

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

    PubMed

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

    2014-05-23

    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 μm 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 Er(3+) 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. PMID:24784527

  13. Near-infrared luminescence from Y2O3:Eu3+, Yb3+ prepared by sol-gel method.

    PubMed

    Xie, Ying; Xiao, Lin J; Yan, Feng Q; Chen, Yong J; Li, Wen Z; Geng, Xiu J

    2014-06-01

    Eu3+ and Yb3+ codoped Y2O3 phosphors were synthesized by the sol-gel method. The phosphors possess absorption in the region of 300-550 nm, exhibiting an intense NIR emission of Yb3+ around 1000 nm, which is suitable for matching the maximum spectral response of c-Si solar cells. The optimum composition of Eu3+ and Yb3+ codoped Y2O3 was (Y1.94Yb0.04Eu0.02)2O3. It is observed that two-step energy transfer occurs from the 5D2 level of Eu3+ situated around (466 nm) exciting two neighboring Yb3+ ions to the 2F5/2 level (1000 nm). The down-conversion material based on Eu(3+)- Yb3+ couple may have great potential applications in c-Si solar cells to enhance their photovoltaic conversion efficiency via spectral modification. PMID:24738417

  14. Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses

    NASA Astrophysics Data System (ADS)

    Peng, Shengxi; Yang, Fengjing; Wu, Libo; Qi, Yawei; Zheng, Shichao; Yin, Dandan; Wang, Xunsi; Zhou, Yaxun

    2014-11-01

    A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2-Bi2O3-ZnO-Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980 nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2→4I15/2, 2H11/2(4S3/2)→4I15/2 of Er3+ and 1G4→3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (ΔT=Tx-Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140 °C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.

  15. Optical parameters and upconversion fluorescence in Tm3+/Yb3+-doped alkali-barium-bismuth-tellurite glasses.

    PubMed

    Lin, Hai; Liu, Ke; Lin, Lin; Hou, Yanyan; Yang, Dianlai; Ma, Tiecheng; Pun, Edwin Yun Bun; An, Qingda; Yu, Jiayou; Tanabe, Setsuhisa

    2006-11-01

    Tm(3+)/Yb(3+)-doped alkali-barium-bismuth-tellurite (LKBBT) glasses have been fabricated and characterized. Density, refractive index, optical absorption, absorption and emission cross-sections of Yb(3+), Judd-Ofelt parameters and spontaneous transition probabilities of Tm(3+) have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm(3+) indicate that Tm(3+)/Yb(3+) co-doped LKBBT glasses are promising upconversion optical and laser materials. PMID:16527521

  16. Synthesis and optical properties of transparent glass ceramics with Eu,Yb:PbF2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Rachkovskaya, G. E.; Zakharevich, G. B.; Yumashev, K. V.

    2015-02-01

    Transparent oxyfluoride glass ceramics containing Eu,Yb:PbF2 nanocrystals (average diameter 6.5 nm) is synthesized by secondary heat treatment of the initial SiO2-PbO-PbF2-CdF2 glass doped with YbF3 (1 mol %) and Eu2O3 (1 mol %); the optical absorption and the upconversion luminescence of this ceramics are studied. Intense orange luminescence (the CIE color coordinates are x = 0.602, y = 0.398) is obtained under excitation by a laser diode at a wavelength of 960 nm.

  17. Buffer gas loaded magneto-optical traps for Yb, Tm, Er and Ho

    NASA Astrophysics Data System (ADS)

    Hemmerling, Boerge; Drayna, Garrett K.; Chae, Eunmi; Ravi, Aakash; Doyle, John M.

    2014-06-01

    Direct loading of lanthanide atoms into magneto-optical traps (MOTs) from a very slow cryogenic buffer gas beam source is achieved, without the need for laser slowing. The beam source has an average forward velocity of 60-70\\;m\\;{{s}^{-1}} and a velocity half-width of \\sim 35\\;m\\;{{s}^{-1}}, which allows for direct MOT loading of Yb, Tm, Er and Ho. Residual helium background gas originating from the beam results in a maximum trap lifetime of about 80 ms (with Yb). The addition of a single-frequency slowing laser applied to the Yb in the buffer gas beam increases the number of trapped Yb atoms to 1.3\\left( 0.7 \\right)\\times {{10}^{8}} with a loading rate of 2.0\\left( 1.0 \\right)\\times {{10}^{10}}\\;atoms\\;{{s}^{-1}}. Decay to metastable states is observed for all trapped species and decay rates are measured. Extension of this approach to the loading of molecules into a MOT is discussed.

  18. 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

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

    2014-02-01

    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 λ=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

  19. Three- and two-photon upconversion luminescence switching in Tm/Yb-codoped sodium niobate nanophosphor

    NASA Astrophysics Data System (ADS)

    Kumar, Kagola Upendra; Silva, Wagner Ferreira; Venkata Krishnaiah, Kummara; Jayasankar, Chalicheemalapalli Kulala; Jacinto, Carlos

    2014-01-01

    Intense infrared-to-visible upconversion (UC) emission in Tm/Yb-codoped sodium niobate (NaNbO) nanocrystals under resonant excitation at 976 nm is presented. The results showed that by increasing the pump power/intensity, a strong reduction is observed at the 800/480 nm emitted intensity ratio, characterizing what can be denominated as laser pump power-induced color tunability or luminescent switching. The physical origin is discussed with a focus on tailoring of luminescent switchers to operate at a large pump power range and, indeed, it is intrinsically associated with the competition of the two- and three-photon UC processes and with highly efficient UC emissions in the investigated material. The effect of Yb-ion concentration along with the theoretical aspects on luminescence switching has been investigated. The results obtained here could be useful in the field of sensors and networks for optical processing and optical communications.

  20. Up-conversion luminescence properties and energy transfer of Tm3+/Yb3+ co-doped BaLa2ZnO5

    NASA Astrophysics Data System (ADS)

    Xie, Jing; Mei, Lefu; Deng, Junru; Liu, Haikun; Ma, Bin; Guan, Ming; Liao, Libing; Lv, Guocheng

    2015-11-01

    Tm3+/Yb3+ co-doped BaLa2ZnO5 up-conversion (UC) phosphors were successfully synthesized by high temperature solid-state reaction method. The X-ray diffraction (XRD) results show that synthesized phosphor co-doped with 0.75% Tm/10% Yb has the optimum pure phase of BaLa2ZnO5 among different co-doping concentrations. The structure of BaLa2ZnO5:0.75% Tm/10% Yb phosphor was refined by the Rietveld method and results show the decreased unit cell parameters and cell volume after doping Tm3+/Yb3+, indicating that Tm3+/Yb3+ have successfully replaced La3+. Under excitation at 980 nm, Tm3+/Yb3+ co-doped BaLa2ZnO5 phosphors present bright blue emission near 478 nm generated by the 1G4→3H6 transition and weak red emissions around 653 nm and 692 nm generated by the 1G4→3F4 and 3F3→3H6 transitions of Tm3+, respectively. The UC luminescence properties of BaLa2ZnO5 phosphors co-doped with different Tm3+/Yb3+ concentrations were investigated, and the related UC mechanisms of Tm3+/Yb3+ co-doped BaLa2ZnO5 depending on pump power were studied in detail.

  1. Specific features of magnetoresistance during the antiferromagnet—paramagnet transition in Tm1 - x Yb x B12

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Levchenko, A. V.; Filippov, V. B.; Shitsevalova, N. Yu.

    2013-05-01

    The transverse magnetoresistance Δρ/ρ( H, T) of Tm1 - x Yb x B12 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 Tm1 - x Yb x B12 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 -Δρ/ρ ∝ H 2, the magnetically ordered phase of these compounds is found to have component Δρ/ρ ∝ H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm1 - x Yb x B12 is analyzed in terms of the Yosida model for a local magnetic susceptibility.

  2. Broadband downconversion based infrared quantum cutting by cooperative energy transfer from Eu2+ to Yb3+ in glasses

    NASA Astrophysics Data System (ADS)

    Zhou, Jiajia; Zhuang, Yixi; Ye, Song; Teng, Yu; Lin, Geng; Zhu, Bin; Xie, Junhua; Qiu, Jianrong

    2009-10-01

    Near-infrared quantum cutting involving the emission of near-infrared photons by downconversion cooperative energy transfer from Eu2+ to Yb3+ in borate glasses was reported. Electron spin resonance spectra and absorption spectra were measured to prove the existence of Eu2+ in borate glasses. Excitation, emission, and fluorescence decay measurements were performed to examine the occurrence of cooperative energy transfer from Eu2+ to Yb3+ ions. Yb3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approaches 164.19%.

  3. Quantum sized Ag nanocluster assisted fluorescence enhancement in Tm3+-Yb3+ doped optical fiber beyond plasmonics

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Rik; Haldar, Arindam; Paul, Mukul C.; Das, Shyamal; Bhadra, Shyamal K.

    2015-12-01

    We report a process for enhancing fluorescence emission from conventional rare earth ions in optical fiber by metal nanocluster (MNC) in nonresonant indirect pumping. The process is completely different from formal metal enhanced fluorescence phenomenon as the MNCs are too small in size to support localized surface plasmon and the excitation wavelength is far from plasmon resonance frequency. We used an established theory of two coupled oscillators to explain the simultaneous enhancement of Ytterbium (Yb3+) and Thulium (Tm3+) emission by silver (Ag) NCs under nonresonant pumping in optical fiber. The fiber is pumped with a 980 nm fiber pigtailed laser diode with input power of 20-100 mW to excite the Yb3+. Four times enhancement of Yb3+ emission of 900-1100 nm and Tm3+ upconversion emission around 474 nm, 650 nm, and 790 nm is observed in the fiber with Ag NCs.

  4. Preparation and characterization of upconversion luminescent NaYF4:Yb, Er (Tm)/PS bulk transparent nanocomposites through in situ polymerization.

    PubMed

    Chai, Ruitao; Lian, Hongzhou; Cheng, Ziyong; Zhang, Cuimiao; Hou, Zhiyao; Xu, Zhenhe; Lin, Jun

    2010-05-15

    The in situ polymerization method was applied to synthesize bulk nanocomposites consisting of hydrophobic NaYF(4):Yb, Er (Tm) nanoparticles as the filler and polystyrene (PS) as the host material. The oleic acid stabilized NaYF(4):Yb, Er (Tm) nanoparticles and NaYF(4):Yb, Er (Tm)/PS nanocomposites have been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), the thermogravimetric analysis (TGA), upconversion photoluminescence spectra and luminescence decays. The well-crystallized NaYF(4):Yb, Er (Tm) nanoparticles are spherical with a mean diameter of 40 nm. NaYF(4):Yb, Er/PS and NaYF(4):Yb, Tm/PS nanocomposites exhibit strong green and blue upconversion photoluminescence upon 980 nm laser excitation, due to the integration of luminescent NaYF(4):Yb, Er and NaYF(4):Yb, Tm nanoparticles, respectively. These nanocomposites can be potentially used as 3D display materials. PMID:20172531

  5. Y2O3:Tm,Yb nanophosphors for correlative upconversion luminescence and cathodoluminescence imaging.

    PubMed

    Fukushima, Shoichiro; Furukawa, Taichi; Niioka, Hirohiko; Ichimiya, Masayoshi; Miyake, Jun; Ashida, Masaaki; Araki, Tsutomu; Hashimoto, Mamoru

    2014-12-01

    We present a phosphor nanoparticle that shows both upconversion luminescence (UCL) and cathodoluminescence (CL). With this particle, low-autofluorescence, deep-tissue and wide-field fluorescence imaging can be achieved with nanometer-order high-spatial-resolution imaging. We synthesized Y2O3:Tm,Yb nanophosphors that emit visible and near-infrared UCL under 980 nm irradiation and blue CL via electron beam excitation. The phosphors were applied to fluorescent imaging of HeLa cells. The photostability of the phosphors was superior to that of a conventional organic dye. We show that after uptake by HeLa cells, the particles can be imaged with SEM and CL contrast in a cellular section. This indicates that correlative UCL and CL imaging of biological samples could be realized. PMID:25146422

  6. Size dependent ultraviolet upconversion in single YF3:Yb3+/Tm3+ particles.

    PubMed

    Liu, Zhenyu; Zheng, Kezhi; Zhao, Dan; Liu, Ning; Qin, Weiping

    2011-11-01

    Yb3+-Tm3+ codoped YF3 bulk material was synthesized through a facile high-temperature calcinations method. By grinding and selecting, the particles with different desired sizes in microns were obtained. Under 980 nm excitation, optical upconversion (UC) from near-infrared (NIR) to ultraviolet (UV) was studied for each group of particles for the effect of their size on UC. Comparing with the bulk sample, the micro-size particles exhibited strong ability for NIR-to-UV UC. With the particle size decreasing from 800 microm to 20 microm, their UV emission intensities increased rapidly. Two possible mechanisms were proposed and discussed for clarifying the small size effect (SSE). PMID:22413252

  7. Energy transfer and visible-infrared quantum cutting photoluminescence modification in Tm-Yb codoped YPO(4) inverse opal photonic crystals.

    PubMed

    Wang, Siqin; Qiu, Jianbei; Wang, Qi; Zhou, Dacheng; Yang, Zhengwen

    2015-08-01

    YPO4:  Tm, Yb inverse opal photonic crystals were successfully synthesized by the colloidal crystal templates method, and the visible-infrared quantum cutting (QC) photoluminescence properties of YPO4:  Tm, Yb inverse opal photonic crystals were investigated. We obtained tetragonal phase YPO4 in all the samples when the samples sintered at 950°C for 5 h. The visible emission intensity of Tm3+ decreased significantly when the photonic bandgap was located at 650 nm under 480 nm excitation. On the contrary, the QC emission intensity of Yb3+ was enhanced as compared with the no photonic bandgap sample. When the photonic bandgap was located at 480 nm, the Yb3+ and Tm3+ light-emitting intensity weakened at the same time. We demonstrated that the energy transfer between Tm3+ and Yb3+ is enhanced by the suppression of the red emission of Tm3+. Additionally, the mechanisms for the influence of the photonic bandgap on the energy transfer process of the Tm3+, Yb3+ codoped YPO4 inverse opal are discussed. PMID:26368098

  8. Red, green, blue and white light upconversion emission in Yb3+/Tm3+/Ho3+ co-doped tellurite glasses

    NASA Astrophysics Data System (ADS)

    Desirena, H.; De la Rosa, E.; Salas, P.; Meza, O.

    2011-11-01

    Several Yb3+/Tm3+/Ho3+ co-doped transparent TeO2-ZnO-Na2O-Yb2O3-Ho2O3-Tm2O3 glasses were prepared and luminescence properties were characterized. Simultaneous red, green and blue (RGB) emission were obtained after excitation at 970 nm. Colour emission was tuned from multicolour to white light with colour coordinate (0.32, 0.33) matching very well with the white reference (0.33, 0.33). Changes in colour emission were obtained by varying the intensity ratios between RGB bands that are strongly concentration dependent because of the interaction of co-dopants. The colour tunability, high quality of white light and high intensity of the emitted signal make these transparent glasses excellent candidates for applications in solid-state lighting.

  9. Mechanochemical preparation of nanocrystalline NaYF4:Gd3+/Yb3+/Tm3+: An efficient upconversion phosphor

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Riesen, Hans

    2015-11-01

    We report on a mechanochemical preparation route for NaYF4:Gd3+/Yb3+/Tm3+ nanoparticles by ball-milling NaF, YF3, GdF3, YbF3 and TmF3 at room temperature. An analysis by XRD and TEM demonstrates that the resulting materials are mainly (∼88% after 4 h ball-milling) in the hexagonal phase and are on the nanoscale with an average crystallite size of ∼20 nm. The prepared nanoparticles display efficient upconversion emission; upon excitation by a 980 nm laser diode, bright visible blue light emission can be observed. However, in accord with previous results, the strongest emission is observed in the NIR at 800 nm.

  10. Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation

    NASA Astrophysics Data System (ADS)

    Silva, W. F.; Eliel, G. S. N.; dos Santos, P. V.; de Araujo, M. T.; Vermelho, M. V. D.; Udo, P. T.; Astrath, N. G. C.; Baesso, M. L.; Jacinto, C.

    2010-07-01

    Pump and thermally induced color tunabilities were demonstrated in Yb3+/Tm3+ codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 μm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm2 and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb3+→Tm3+ energy-transfer processes, easy saturations of the Yb3+ and Tm3+ excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information.

  11. Formation enthalpies of LaLn'O3 (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    NASA Astrophysics Data System (ADS)

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra; Navrotsky, Alexandra

    2015-07-01

    High-temperature oxide melt solution calorimetry using 3Na2O·MoO3 at 802 °C was performed for interlanthanide perovskites LaLn'O3 (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La2O3, Ho2O3, Er2O3, Tm2O3 and Yb2O3). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be -8.3±3.4 kJ/mol for LaHoO3, -9.9±3.0 kJ/mol for LaErO3, -10.8±2.7 kJ/mol for LaTmO3 and -12.3±2.9 kJ/mol for LaYbO3. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM3+O3 (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds.

  12. Thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2}

    SciTech Connect

    Zhang, H.; Fang, L.; Tang, M.-B.; Man, Z. Y.; Chen, H. H.; Yang, X. X.; Zhao, J.-T.; Baitinger, M.; Grin, Y.

    2010-11-21

    The thermoelectric performance of EuCd{sub 2}Sb{sub 2} and YbCd{sub 2}Sb{sub 2} was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb{sub 0.5}Eu{sub 0.5}Cd{sub 2}Sb{sub 2} and Yb{sub 0.75}Eu{sub 0.25}Cd{sub 2}Sb{sub 2} at 650 K, respectively.

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

    SciTech Connect

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

    2012-01-01

    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.

  14. Composition Tuning the Upconversion Emission in NaYF4:Yb/Tm Hexaplate Nanocrystals

    PubMed Central

    Zhang, Hua; Li, Yujing; Lin, Yungchen

    2011-01-01

    Single crystal hexagonal NaYF4:Yb/Tm nanocrytstals have been synthesized with uniform size, morphology and controlled chemical composition. Spectroscopic studies show that these nanocrystals exhibit strong energy upconversion emission when excited with a 980 nm diode laser, with two primary emission peaks centered around 452 nm and 476 nm. Importantly, the overall and relative emission intensity at these wavelengths can be readily tuned by controlling the concentration of the trivalent rare earth element dopants at the beginning of the synthesis which has been confirmed by EDX for the first time. Through systematic studies, the optimum rare earth ion doping concentration can be determined for the strongest emission intensity at the selected peak(s). Confocal microscope studies show that the upconversion emission from individual NCs can be readily visualized. These studies demonstrate a rational approach for fine tuning the upconversion properties in rare-earth doped nanostructures, and can broadly impact areas ranging from energy harvesting, energy conversion to biomedical imaging and therapeutics. PMID:21264435

  15. White light upconversion emissions in Er3+/Tm3+/Yb3+ tridoped oxyfluoride glass

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoping; Xu, Wei; Zhu, Shuang; Song, Qiutong; Wu, Xijun; Liu, Hailong

    2015-10-01

    Rare earth ions doped glasses producing visible upconversion emissions are of great interest due to their potential applications in the photonics filed. In fact, practical application of upconversion emissions has been used to obtain color image displays and white light sources. However, there are few reports on the thermal effect on tuning the emission color of the RE doped materials. In this work, the Er3+/Tm3+/Yb3+ tridoped oxyfluoride glasses were prepared through high temperature solid-state method. Under a 980 nm diode laser excitation, the upconversion emissions from the samples were studied. At room-temperature, bright white luminescence, whose CIE chromaticity coordinate was about (0.28, 0.31), can be obtained when the excitation power was 120 mW. The emission color was changed by varying the intensity ratios between RGB bands, which are strongly dependent on the rare earth ions concentration. The temperature dependent color emissions were also investigated. As temperature increased, the intensities for the emission bands presented different decay rates, finally resulting in the changing of the CIE coordinate. When the temperature was 573 K, white light with color coordinate of (0.31, 0.33) was achieved, which matches well with the white reference (0.33, 0.33). The color tunability, high quality of white light and intense emission intensity make the transparent oxyfluoride glasses excellent candidates for applications in solid-state lighting.

  16. Red Eu,Yb:KY(WO4)2 laser at ~702?nm

    NASA Astrophysics Data System (ADS)

    Dashkevich, V. I.; Bagayev, S. N.; Orlovich, V. A.; Bui, A. A.; Loiko, P. A.; Yumashev, K. V.; Yasukevich, A. S.; Kuleshov, N. V.; Vatnik, S. M.; Pavlyuk, A. A.

    2015-08-01

    In this letter, laser operation is demonstrated with a Eu,Yb: KY(WO4)2 crystal on the 5D0?????7F4 transition of the Eu3+ ion. When pumping into the 7F1?????5D1 absorption band by a diode-pumped Nd3+:KGd(WO4)2/KTP laser power-scaled at 533.6?nm up to a watt-level, we achieved 2.5?mW of the continuous wave (CW) red output at ~702.1?nm. At quasi-CW pumping with a duty cycle of 10%, the peak power of the ms-long pulses arrived at ~19?mW, corresponding to a green-to-red conversion efficiency of 0.8%.

  17. Solvent extraction behavior of trivalent Nd, Eu, Ho, and Yb with dibenzoylmethane at 80{degree}C

    SciTech Connect

    Gao, J.; Choppin, G.R.

    1995-05-01

    The extraction behavior of trivalent lanthanide ions (Nd, Eu, Ho and Yb) has been studied with dibenzoylmethane (DBM) at 80{degree}C using molten paraffin wax as diluent. In the range of pH 7 to 8, the extraction of lanthanide cations is greater than 90%. The ratio of Ln:DBM in the extracted species was determined to be 1:3 by the slope analysis method. The pH{sub 1/2} values of extraction and the extraction constants of Nd(III), Eu(III), Ho(III) and Yb(III) are reported. 22 refs., 2 figs., 1 tab.

  18. MOLTEN SALT SYNTHESIS OF YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) MICROSHEETS WITH MULTICOLOR UPCONVERSION LUMINESCENCE

    NASA Astrophysics Data System (ADS)

    Ding, Mingye; Lu, Chunhua; Cao, Linhai; Ni, Yaru; Xu, Zhongzi

    2013-12-01

    In this paper, highly crystalline YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) microsheets were successfully synthesized by a surfactant-free molten salt method for the first time. The results indicated that the as-obtained samples belonged to orthorhombic system and exhibited microsheets morphology with side lengths of 30 to 80 μm and wall thickness from 1 to 1.5 μm. By changing the dopant's species (Ln3+), multicolor (yellow and blue) upconversion emission can be observed in YF3:Yb3+/Ln3+ microsheets under 980 nm laser diode (LD) excitation. The upconversion mechanisms in co-doping YF3 samples were analyzed in detail based on the emission spectra. Importantly, this approach not only proposes a new alternative in synthesizing such materials, but also opens the possibility to meet the increasing commercial demand.

  19. Formation enthalpies of LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) interlanthanide perovskites

    SciTech Connect

    Qi, Jianqi; Guo, Xiaofeng; Mielewczyk-Gryn, Aleksandra

    2015-07-15

    High-temperature oxide melt solution calorimetry using 3Na{sub 2}O·MoO{sub 3} at 802 °C was performed for interlanthanide perovskites LaLn'O{sub 3} (Ln'=Ho, Er, Tm and Yb) and lanthanide oxides (La{sub 2}O{sub 3}, Ho{sub 2}O{sub 3}, Er{sub 2}O{sub 3}, Tm{sub 2}O{sub 3} and Yb{sub 2}O{sub 3}). The enthalpies of formation of these interlanthanide perovskites from binary lanthanide oxides at room temperature (25 °C) were determined to be −8.3±3.4 kJ/mol for LaHoO{sub 3}, −9.9±3.0 kJ/mol for LaErO{sub 3}, −10.8±2.7 kJ/mol for LaTmO{sub 3} and −12.3±2.9 kJ/mol for LaYbO{sub 3}. There is a roughly linear relationships between these enthalpy values and the tolerance factor for these and for other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites, confirming that the distortion of the perovskites as results from ionic radius difference of A-site and B-site cations, is the main factor determining the stability of these compounds. - Graphical abstract: A linear relationship between the enthalpy of formation and the tolerance factor for interlanthanide LaLn'O{sub 3} (Ln'=Ho, Er, Tm, and Yb) and other LaM{sup 3+}O{sub 3} (M=In, Sc, Ga, Al, Fe and Cr) perovskites. - Highlights: • Interlanthanide perovskites were synthesized by solid state reactions. • Their enthalpies of formation were measured by oxide melt solution calorimetry. • ΔH{sub f,ox} shows a linear relationship with tolerance factor.

  20. Upconversion color tunability and white light generation in Tm 3+/Ho 3+/Yb 3+ doped aluminum germanate glasses

    NASA Astrophysics Data System (ADS)

    Gong, Hua; Yang, Dianlai; Zhao, Xin; Yun Bun Pun, Edwin; Lin, Hai

    2010-02-01

    Tm 3+/Ho 3+/Yb 3+ triply doped aluminum germanate glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. Efficient three-photon blue upconversion emission of Tm 3+ and two-photon green and red upconversion fluorescences of Ho 3+ have been observed. The strong red emission of Ho 3+, which is more than eight times higher than that of the green emission, is desirable in achieving high color rendering index. By varying the excitation power of the 974 nm wavelength laser diode, a series of white fluorescences with a large range of correlated color temperature ( CCT) was obtained, and the fluorescence colors can be tuned from yellowish white to warm white, pure white, cool white, and bluish white with different CCT. The upconversion color tunability via pump power adjustment will promote the development of three-dimensional solid-state displays and upconversion illumination devices.

  1. Upconversion luminescent property and EPR study of NaGdF4:Yb3+/Tm3+ synthesized by the hydrothermal method

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Zhang, Jing-Ying; Liu, Kai; Gao, Hong-Jian; Yu, Xiao-Long; Cao, Yang; Liu, Zhong-Xin

    2015-09-01

    Water soluble upconversion (UC) luminescence hexagonal-phase NaGdF4: Yb3+/Tm3+ nanoparticles have been successfully synthesized by the hydrothermal method. XRD, SEM, UC photoluminescence spectra and electron paramagnetic resonance (EPR) spectrum were used to characterize the nanoparticles. The intensity of UC emission region could be controlled through different sodium source and the fluorine source, 6PJ→8S7/2 emission of Gd3+ is also observed at 310 nm. A broad spectrum with a dominant resonance at g of about 2 was observed by the EPR spectrum of the NaGdF4:Yb3+/Tm3+ nanoparticles. The transparent NaGdF4:Yb3+/Tm3+ solution presented naked eye-visible violet-blue light under the 980 nm LD excitation. The current work paves the way for their potential application in infrared tomography and magnetic resonance imaging (MRI).

  2. Synthetic and spectroscopic studies of vanadate glaserites I: Upconversion studies of doubly co-doped (Er, Tm, or Ho):Yb:K3Y(VO4)2

    NASA Astrophysics Data System (ADS)

    Kimani, Martin M.; Chen, Hongyu; McMillen, Colin D.; Anker, Jeffery N.; Kolis, Joseph W.

    2015-03-01

    The synthesis and upconversion properties of trigonal glaserite-type K3Y(VO4)2 co-doped with Er3+/Yb3+, Ho3+/Yb3+, or Tm3+/Yb3+ were studied. Powder samples were synthesized by solid state reactions at 1000 °C for 48 h, while well-formed hexagonal single crystals of the same were grown hydrothermally using 10 M K2CO3 at 560-650 °C. Infrared-to-visible upconversion by Er3+/Yb3+, Ho3+/Yb3+, or Tm3+/Yb3+ codoped-K3Y(VO4)2 glaserite powder and single crystals was observed, and the upconversion spectral properties were studied as a function of different Er3+, Tm3+, Ho3+, and Yb3+ ion concentrations. The process is observed under 980 nm laser diode excitation and leads to strong green (552 nm) and red (659 nm) emission for Er3+/Yb3+, green (549 nm) and red (664 nm) emission for Ho3+/Yb3+, and blue (475 nm) and red (647 nm) emission for Tm3+/Yb3+. The main mechanism that allows for up-conversion is attributed the energy transfer among Yb3+ and the various Er3+/Ho3+/Tm3+ ions in excited states. These results illustrate the large potential of co-doped alkali double vanadates for photonic applications involving optoelectronics devices.

  3. 2.7 μm emission properties of Er3+/Yb3+/Eu3+: SrGdGa3O7 and Er3+/Yb3+/Ho3+: SrGdGa3O7 crystals

    NASA Astrophysics Data System (ADS)

    Xia, Houping; Feng, Jianghe; Ji, Yuexia; Sun, Yijian; Wang, Yan; Jia, Zhitai; Tu, Chaoyang

    2016-04-01

    Er3+/Yb3+/Eu3+: SrGdGa3O7 and Er3+/Yb3+/Ho3+: SrGdGa3O7 crystals were grown by Czochralski technology and detailed spectroscopic analyses were carried out. It was found that the spectra of Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal show weaker near-infrared emission and stronger mid-infrared emission as compared with Er3+/Yb3+: SrGdGa3O7 crystal. Furthermore, the lifetime of the 4I13/2 state decreases from 10.58 ms in Er3+/Yb3+: SrGdGa3O7 crystal to 6.87 ms in Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal, that is, the self-saturation for 2.7 μm laser in Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal is suppressed greatly. These results indicate that the doping of Eu3+ in Er3+/Yb3+: SrGdGa3O7 crystal is beneficial to improve the 2.7 μm laser. In contrast, introducing Ho3+ in Er3+/Yb3+: SrGdGa3O7 crystal is adverse to realize Er3+-activated MIR laser operation. So Er3+/Yb3+/Eu3+: SrGdGa3O7 crystal could be a potential MIR gain media for enhanced 2.7 μm laser.

  4. Tunable multicolor and white-light upconversion luminescence in Yb3+/Tm3+/Ho3+ tri-doped NaYF4 micro-crystals.

    PubMed

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

    2015-09-01

    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. PMID:25377774

  5. Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass.

    PubMed

    Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

    2013-10-01

    Eu(2+)-Yb(3+) co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu(2+) indicated the partition of Eu(2+) into FAP nanocrystals in glass ceramic. NIR emission due to the transition (2)F5/2→(2)F7/2 of Yb(3+) ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu(2+) to Yb(3+), which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu(2+)-Yb(3+) co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells. PMID:23816484

  6. Correlative near-infrared light and cathodoluminescence microscopy using Y2O3:Ln, Yb (Ln = Tm, Er) nanophosphors for multiscale, multicolour bioimaging.

    PubMed

    Fukushima, S; Furukawa, T; Niioka, H; Ichimiya, M; Sannomiya, T; Tanaka, N; Onoshima, D; Yukawa, H; Baba, Y; Ashida, M; Miyake, J; Araki, T; Hashimoto, M

    2016-01-01

    This paper presents a new correlative bioimaging technique using Y2O3:Tm, Yb and Y2O3:Er, Yb nanophosphors (NPs) as imaging probes that emit luminescence excited by both near-infrared (NIR) light and an electron beam. Under 980 nm NIR light irradiation, the Y2O3:Tm, Yb and Y2O3:Er, Yb NPs emitted NIR luminescence (NIRL) around 810 nm and 1530 nm, respectively, and cathodoluminescence at 455 nm and 660 nm under excitation of accelerated electrons, respectively. Multimodalities of the NPs were confirmed in correlative NIRL/CL imaging and their locations were visualized at the same observation area in both NIRL and CL images. Using CL microscopy, the NPs were visualized at the single-particle level and with multicolour. Multiscale NIRL/CL bioimaging was demonstrated through in vivo and in vitro NIRL deep-tissue observations, cellular NIRL imaging, and high-spatial resolution CL imaging of the NPs inside cells. The location of a cell sheet transplanted onto the back muscle fascia of a hairy rat was visualized through NIRL imaging of the Y2O3:Er, Yb NPs. Accurate positions of cells through the thickness (1.5 mm) of a tissue phantom were detected by NIRL from the Y2O3:Tm, Yb NPs. Further, locations of the two types of NPs inside cells were observed using CL microscopy. PMID:27185264

  7. Ultrasmall monodisperse NaYF4:Yb3+/Tm3+ nanocrystals with enhanced near-infrared to near-infrared upconversion photoluminescence

    PubMed Central

    Chen, Guanying; Ohulchanskyy, Tymish Y.; Kumar, Rajiv; Ågren, Hans; Prasad, Prasas N.

    2012-01-01

    Photoluminescent NaYF4:Yb3+/Tm3+ nanocrystals are ideally suited for in vitro and in vivo photoluminescence (PL) bioimaging due to their virtue of near infrared to near infrared (NIR-to-NIR) upconversion (UC); they display PL with peak at ~800 nm if excited at ~980 nm. Here, we report the synthesis of monodisperse NaYF4:Yb3+/Tm3+ nanocrystals of ultrasmall size (7–10 nm) with high UC efficiency. The intensity of their NIR UC emission was demonstrated to increase by up to 43 times along with increase in relative content of Yb3+ ions from 20% to 100%, with a corresponding decrease in the Y3+ content from 80% to 0%. The achieved ultrasmall NaYbF4:2% Tm3+ nanocrystals manifest NIR PL emission, which is 3.6 times more intense than that from 25-30 nm sized NaYF4: 20% Yb3+/2% Tm3+ nanocrystals, previously synthesized and used for in vitro and in vivo bioimaging. An optimization of both size and UC PL efficiency of NIR-to-NIR nanocrystals provides us with highly efficient optical imaging probes for bioapplications. PMID:20509664

  8. Simultaneous size and luminescence control of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) microcrystals via Li+ doping

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    Enhancement of upconversion (UC) luminescence is imperative for the applications of UC microcrystals (MCs). In this work, NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping were successfully prepared by a simple hydrothermal process with the assistance of citric acid. The UC luminescence intensities of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) are significantly enhanced via Li+ doping at different concentrations. Compared to Li+-absent sample, UC luminescence intensities of blue emission (477 nm) and red emission (649 nm) in NaYF4:Yb3+/Tm3+ MCs via 15 mol% Li+ doping are improved by 10 and 9 times, respectively; UC luminescence intensities of green emission (538 nm) and red emission (644 nm) in NaYF4:Yb3+/Ho3+ MCs via 15 mol% Li+ doping are improved by 12 and 3 times, respectively. The mechanism of the enhancement via Li+ doping is discussed in details, which may be attributed to the fact that Li+ doping can cause the distortion of the local symmetry around RE ions. Our results indicate that the enhanced UC luminescence of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping may have potential applications in optoelectronic devices such as solar cells and plasma display panel.

  9. Superconducting EuBa 2Cu 3O 7-δ and YbBa 2Cu 3O 7-δ produced by oxidation of microcrystalline precursor alloys

    NASA Astrophysics Data System (ADS)

    Weiss, F.; Yavari, A. R.; Rouault, A.; Hadar, R.; Senateur, J. P.; Desre, P.

    1988-06-01

    EuBa2Cu3 and YbBa2Cu3 microcrystalltne alloys obtained by rapid solidification have been oxidized completely in flowing oxygen at a temperature higher than 900° C with subsequent slow cooling and have yield the high temperature oxides EuBa2Cu37-δ and YbBa2Cu3O7-δ. The onset of superconductivity occured at 92 K in the case of Eu and at 89 K in the case of Yb. The resistivity in the normal state ( ρ at 100 K) is lower than in sintered powder materials Sue to a better compaction and to a better intergrain coupling.

  10. Uniform NaYF{sub 4}:Yb, Tm hexagonal submicroplates: Controlled synthesis and enhanced UV and blue upconversion luminescence

    SciTech Connect

    Huang, Wenjuan; Ding, Mingye; Huang, Hengming; Jiang, Chenfei; Song, Yan; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ? ?-NaYF{sub 4} phosphors as an excellent upconversion materials. ? Oleic acid can promote the transformation of ? ? ? phase NaYF{sub 4}. ? The shape and size of ?-NaYF{sub 4} submicroplate can be tuned by reactant concentration. ? Enhanced UV and blue peaks can be obtained by varying Yb{sup 3+} and Tm{sup 3+} concentration. -- Abstract: We reported the preparation of cubic (?-) and hexagonal (?-) NaYF{sub 4} particles in high boiling organic solvents 1-octadecene (ODE) and oleic acid (OA), through a thermal decomposition synthesis route. The as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL) spectra. By tuning the OA/ODE volume ratio and reactant concentration, we could manipulate the morphology, size, and crystal structure of the products. Highly uniform ?-NaYF{sub 4} submicroplates were obtained from ?-NaYF{sub 4} nanoparticles by increasing the OA/ODE volume ratio, while the phase kept unchanged with the increasing of reactant concentration. Upconversion emissions from UV to NIR emissions were observed in ?-NaYF{sub 4} hexagonal submicroplates under 980 nm laser diode excitation. In addition, the enhanced UV and blue upconversion emissions were obtained by varying Tm{sup 3+} and Yb{sup 3+} ion concentration.

  11. Hydrothermal synthesis of Yb3+, Tm3+ co-doped Gd6MoO12 and its upconversion properties

    NASA Astrophysics Data System (ADS)

    Di, Qiu-Mei; Sun, Yu-Mei; Xu, Qi-Guang; Han, Liu; Xue, Bing; Sun, Jia-Yue

    2015-06-01

    Yb3+, Tm3+ co-doped Gd6MoO12 phosphors with different morphologies are prepared by the hydrothermal method. The dendrites present different morphologies (including hexagonal prisms, spindles, and spheres) after changing the pH value and edetate disodium (EDTA) usage. It is found that each of the two factors plays a crucial role in forming different morphologies. The up-conversion (UC) luminescence is studied. Under 980-nm semiconductor laser excitation, relatively strong blue emission and weak red emission are observed. Finally, the effect of pumping power on the UC luminescence properties and the level diagram mechanism of Gd6MoO12:Yb3+/Tm3+ phosphor are also discussed. Project supported by the National Natural Science Foundation of China (Grant No. 20976002), the Beijing Natural Science Foundation, China (Grant No. 2122012), the Key Projects for Science and Technology of Beijing Education Commission, China (Grant No. KZ201310011013), and the Education and Research Fund of Guangdong Province, China (Grant No. 2011B090400100).

  12. Hall and transverse even effects in the vicinity of a quantum critical point in Tm{sub 1-x}Yb{sub x}B{sub 12}

    SciTech Connect

    Sluchanko, N. E. Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A.; Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu.

    2012-09-15

    The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x{sub c} Almost-Equal-To 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x{sub c} and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R{sub H}(T) for the Tm{sup 1-x}Yb{sub x}B{sub 12} compounds, in contrast to the invariable behavior R{sub H}(T) Almost-Equal-To const found for TmB{sub 12}. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x {>=} 0.5 with activation energies E{sub g}/k{sub B} Almost-Equal-To 200 K and E{sub a}/k{sub B} 55-75 K, and the sign inversion of R{sub H}(T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm{sub 1-x}Yb{sub x}B{sub 12} cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB{sub 12}.

  13. Hall and transverse even effects in the vicinity of a quantum critical point in Tm1 - x Yb x B12

    NASA Astrophysics Data System (ADS)

    Sluchanko, N. E.; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A.; Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu.

    2012-09-01

    The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm1 - x Yb x B12 solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x c ≈ 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x c and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R H( T) for the Tm1 - x Yb x B12 compounds, in contrast to the invariable behavior R H( T) ≈ const found for TmB12. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x ≥ 0.5 with activation energies E g / k B ≈ 200 K and E a/ k B = 55-75 K, and the sign inversion of R H( T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm1 - x Yb x B12 solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm1 - x Yb x B12 cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB12.

  14. EuTM(2)Ga(8) (TM = Co, Rh, Ir) - a contribution to the chemistry of the CeFe(2)Al(8)-type compounds.

    PubMed

    Sichevych, O; Kohout, M; Schnelle, W; Borrmann, H; Cardoso-Gil, R; Schmidt, M; Burkhardt, U; Grin, Yu

    2009-07-01

    The isostructural compounds EuTM(2)Ga(8) (TM = Co, Rh, Ir) were prepared by direct reaction of the elements by high-frequency thermal treatment. All three phases are isotypic with CeFe(2)Al(8) (space group Pbam, Pearson symbol oP44, Z = 4). The crystal structure was established from single-crystal X-ray diffraction data: a = 12.4322(7) A, b = 14.3814(9) A, and c = 4.0378(2) A for EuCo(2)Ga(8); a = 12.6001(6) A, b = 14.6757(7) A, and c = 4.1172(2) A for EuRh(2)Ga(8); and a = 12.6237(7) A, b = 14.6978(8) A, and c = 4.1486(2) A for EuIr(2)Ga(8), respectively. Analysis of the chemical bonding in EuRh(2)Ga(8) with the electron localizability tools reveals formation of the 3D [Rh(2)Ga(8)] polyanion build by polar covalent bonds. Europium interacts in two ways with the polyanion: mainly as a cation by charge transfer and additionally covalently by means of the electrons of the inner shells. Magnetic susceptibility measurements show Curie-Weiss paramagnetic behavior above 40 K with effective magnetic moments of 7.81, 8.05, and 8.27 micro(B)/f.u. for EuTM(2)Ga(8) (TM = Co, Rh, Ir). Antiferromagnetic ordering of Eu moments is observed in all three compounds below 20 K. Independently on the chemical composition of the coordination sphere, magnetic behavior and, especially, X-ray absorption spectra indicate predominantly the 4f(7) electronic configuration of europium with small admixture of the 4f(6) state. PMID:19469500

  15. Upconversion-luminescent/magnetic dual-functional sub-20 nm core-shell SrF2:Yb,Tm@CaF2:Gd heteronanoparticles.

    PubMed

    Li, Ai-Hua; Lü, Mengyun; Yang, Jun; Chen, Lin; Cui, Xiaohong; Sun, Zhijun

    2016-04-01

    Sub-20 nm core-shell and water-soluble SrF2:Yb,Tm@CaF2:Gd heteronanoparticles with both upconversion luminescence (UCL) and magnetic resonance imaging (MRI) capabilities were designed and synthesized via a two-step hydrothermal method. In the design of the heteronanoparticles, SrF2:Yb,Tm nanoparticles with high UCL efficiency are chosen as the core material for strong UCL output; and by epitaxially coating the SrF2:Yb,Tm core particles with inert and biocompatible shells of CaF2:Gd, the core-shell heteronanoparticles are endowed with a magnetic capability (longitudinal relaxivity of 2.4 mM(-1) s(-1)) for MRI, as well as an enhancement of the near infrared (NIR) UCL by 9.2 times. The aqueous dispersion of SrF2:Yb,Tm@CaF2:Gd heteronanoparticles with a concentration of 2.6 wt% can emit NIR UCL so as to be easily detected with a fiber optical spectrometer under illumination of a 975 nm laser diode with a power density of 8.8 W cm(-2). Such a dispersion with a Gd(3+) concentration of 0.0143 mM in the shell region of the heteronanoparticles can also generate the detectable quickening of longitudinal relaxation. The results promise the strong potential of this nanomaterial for applications in bioimaging as a dual-functional probe. PMID:26934836

  16. Pulsed-laser-assisted synthesis of a Tm3+/Yb3+ co-doped CaMoO4 colloidal nanocrystal and its upconversion luminescence

    NASA Astrophysics Data System (ADS)

    Cho, Kyoungwon; Choi, Jaeha; Lee, Jung-Il; Ryu, Jeong Ho

    2016-01-01

    We report a novel synthetic route for the synthesis of Tm3+/Yb3+ co-doped calcium molybdate (CaMoO4) nanoparticles by using pulsed laser ablation in ethanol. The crystalline phase, particle morphology, particle size distribution, laser ablation mechanism, and upconversion (UC) luminescent properties are investigated. Stable colloidal suspensions consisting of well-dispersed Tm3+/Yb3+ co-doped CaMoO4 nanoparticles with a narrow size distribution could be obtained without any surfactant. Under 980-nm excitation, a Tm3+/Yb3+ co-doped nanocolloidal CaMoO4 suspension showed bright blue emission at a wavelength near 475 nm, which was generated by the 1G4 → 3H6 transition, and a weak red emission at a wavelength near 650 nm due to the 3F2 → 3H6 transition. The Tm3+/Yb3+ co-doped nanocrystalline CaMoO4 suspension exhibited a strong blue emission visible to the naked eyes, and a possible UC mechanism that depends on the pump-power dependence is discussed in detail.

  17. Lasing in a Tm : Yb{sub 3}Al{sub 5}O{sub 12} crystal pumped at 1.678 μm

    SciTech Connect

    Zavartsev, Yu D; Zagumennyi, A I; Kalachev, Yu L; Kutovoi, S A; Mikhailov, V A; Shcherbakov, I A

    2014-10-31

    The Yb{sub 3}Al{sub 5}O{sub 12} (YbAG) crystal is proposed as a matrix of Tm{sup 3+}-doped laser elements for two-micron lasers. A Tm : YbAG crystal of high optical quality is grown by the Czochralski method and its spectral and luminescent characteristics are studied. The luminescence decay time for the upper laser level {sup 3}F{sub 4} is measured to be 4.7 ms. Lasing in this crystal pumped by a 1.678-μm fibre laser is obtained at a wavelength of 2.02 μm for the first time. The total and slope efficiencies of the laser at room temperature and an output power up to 330 mW reach 33% and 41%, respectively. (lasers)

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  19. Yb{sub 14−x}Tm{sub x}MnSb{sub 11} (0

    SciTech Connect

    Roudebush, John H.; Grebenkemper, Jason; Hu, Yufei; Kazem, Nasrin; Abdusalyamova, M.N.

    2014-03-15

    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=[(ρ(H)−ρ(0))/ρ(H)]×100%) of 18% at 3 T is observed. -- Graphical abstract: Magnetic susceptibility (χ) 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.

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

    PubMed

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

    2012-11-01

    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

  1. Frequency upconversion luminescence from Yb{sup +3}-Tm{sup +3} codoped PbO-GeO{sub 2} glasses containing silver nanoparticles

    SciTech Connect

    Assumpcao, Thiago A. A.; Silva, Davinson M. da; Kassab, Luciana R. P.

    2009-09-15

    Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb{sup 3+}-Tm{sup 3+} doped PbO-GeO{sub 2} glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb{sup 3+} transition {sup 2}F{sub 7/2}->{sup 2}F{sub 5/2}) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb{sup 3+} to Tm{sup 3+} ions followed by excited state absorption in the Tm{sup 3+} ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm{sup 3+}:{sup 1}G{sub 4}->{sup 3}H{sub 6}) and at 800 nm (Tm{sup 3+}:{sup 3}H{sub 4}->{sup 3}H{sub 6}).

  2. Investigation on luminescence properties of Er3+-Yb3+-Tm3+ co-doped Gd2O3 hollow microspheres

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    The Gd2O3 hollow microspheres have been successfully fabricated via carbonaceous polysaccharide microspheres as templates and urea as a precipitating agent, which involved the deposition of an inorganic coating on the surface of carbon microsphere, followed by heat treated 800°C for 4h. The obtained high uniform Gd2O3 microspheres with a spherical shape and hollow structure are uniform in size and distribution. The possible mechanism of evolution from glucose to carbonaceous polysaccharide microspheres and the chemical reaction of each step to form the final hollow spheres are proposed. The rare earth ion Ln3+ doped Gd2O3 (Ln = Er, Yb and Tm) hollow microspheres show bright up-conversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which may open new possibilities to synthesize other hollow spherical materials and extend their applications.

  3. van der Waals interactions and dipole polarizabilities of lanthanides: Tm(2F)-He and Yb(1S)-He potentials

    NASA Astrophysics Data System (ADS)

    Buchachenko, Alexei A.; Szczȩśniak, Małgorzata M.; Chałasiński, Grzegorz

    2006-03-01

    Anisotropic dipole polarizabilities of Tm(F2),Tm+2(F2), and Yb(S1) are calculated using the finite-field multireference averaged quadratic coupled cluster (MR-AQCC) (Tm and Tm+2) and RCCSD(T) (Yb) methods with small-core relativistic pseudopotentials ECP28MWB combined with the augmented ANO basis sets. The lanthanide atoms are strongly polarizable with the scalar part originating from the 6s electrons and the tensorial part from the open 4f shells. The adiabatic interaction potentials Σ+2,Π2,Δ2, and Φ2 of Tm(F2)-He and Tm+2(F2)-He were examined by the multireference approaches, multireference configuration interaction and MR-AQCC, using the basis sets designed in the polarizability calculations. A closed-shell lanthanide system Yb(S1)-He was included for comparison. The Tm-He Σ+2,Π2,Δ2, and Φ2 interaction potentials are very shallow and nearly degenerate (within 0.01cm-1), with the well depths in the range of 2.35-2.36cm-1 at R =6.17Å. The basis-set saturated well depths are expected to be larger by ca. 25%, as estimated using the bond-function augmented basis set. The interactions of lanthanide atoms with He are one order of magnitude less anisotropic than those involving first-row transition metal atoms. The suppression of anisotropy is chiefly attributed to the screening effected by the 6s shell. When these electrons are removed as in the di-cation complex Tm+2(F2)-He, the potentials deepen to a thousand wave number range and their anisotropy is enhanced 500-fold.

  4. Photoemission study of reactive rare-earth/semiconductor interfaces: Tm/GaAs(110) and Yb/GaAs(110)

    SciTech Connect

    Prietsch, M.; Laubschat, C.; Domke, M.; Kaindl, G.

    1988-11-15

    The behavior of interfaces formed by growing thin Tm and Yb films on p- and n-type GaAs(110) substrates at room temperature was investigated by photoemission from As 3d, Ga 3d, and metal 4f core levels. At metal coverages THETA<1 A, the core-level binding energies of substrate atoms are found to be shifted to higher and lower values, respectively, for p- and n-type GaAs; this observation is interpreted as a consequence of band bending due to defect states. In addition, photoemission signals from chemically reacted products at the interface are observed, which grow in intensity with metal coverage. In the coverage range 2Tm and 2.5Yb, a further change in band bending occurs, as reflected in additional shifts of all core levels towards lower binding energies. This observation, together with the strongly increasing density of states at the Fermi level around this coverage, indicates that the Schottky barrier is not established until the overlayer assumes metallic character. These observations are interpreted within the concept of metal-induced gap states defining the final Fermi-level position. From the observed variations with metal coverage of binding energies and relative intensities of photoemission signals from the reacted layer, a structure model is proposed for rare-earth/GaAs(110) interfaces that includes a separation of As and Ga atoms into As-rich and Ga-rich rare-earth compounds in the reacted zone.

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

    SciTech Connect

    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

    {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.

  6. Study on upconversion luminescence and luminescent dynamics of 20%Yb3+, 0.5%Tm3+ co-doped YF3 and GdF3 nanocrystals.

    PubMed

    Cao, Chunyan; Qin, Weiping; Zhang, Jisen

    2010-03-01

    20%Yb3+, 0.5%Tm3+ co-doped YF3 and GdF3 were synthesized through a facile hydrothermal method. After annealing under an argon atmosphere, the sizes and morphologies of the two samples were characterized by field emission scanning electron microscopy, and the phase and crystallization were analyzed by X-ray diffraction. With a 980 nm continuous wave laser diode as the excitation source, blue and ultraviolet upconversion emissions in the wavelength range of 260-510 nm of Tm3+ and Gd3+/Tm3+ ions were recorded. Under the same excitation conditions, the upconversion emission spectra of the two nanocrystals were compared and analyzed. Gd3+ in the ground state cannot absorb 980 nm photons directly because of the large energy gap between the ground state 8S7/2 and the first excited state 6P7/2. In the 20%Yb3+, 0.5%Tm3+ co-doped GdF3 nanocrystals, the excited states 6I(J) of Gd3+ can be populated through the energy transfer 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6I(J)(Gd3+), meaning that Yb3+ acted as primary sensitizers and Tm3+ acted as secondary sensitizers, transferred energies to host material Gd3+ and resulted in the ultraviolet upconversion emission of the host ions. In this article, the upconversion luminescent dynamics were studied at the onset of a 980 nm pulsed laser from an optical parametric oscillator pumped by a 10 ns pulsed Nd:YAG laser, too. PMID:20355596

  7. Lasing in a Tm:Ho:Yb3Al5O12 crystal pumped into the 3H6 – 3F4 transition

    NASA Astrophysics Data System (ADS)

    Zavartsev, Yu D.; Zagumennyi, A. I.; Kalachev, Yu L.; Kutovoi, S. A.; Mikhailov, V. A.; Shcherbakov, I. A.

    2016-03-01

    A growth technology has been developed, and a Tm:Ho:Yb3Al5O12 laser crystal of high optical quality has been grown by Czochralski method. Its spectral and luminescent characteristics are studied. Lasing at a wavelength of 2100 nm is obtained under pumping into the absorption line on the 3H6 – 3F4 transition of the Tm3+ ion at a wavelength of 1678 nm. The slope and total (optical) efficiencies of the laser at an output power of up to 320 mW reach 41% and 30%, respectively.

  8. White upconversion luminescence in Tm3+/Ho3+/Yb3+ triply doped K+-Na+ ion-exchanged aluminum germanate glass channel waveguide

    NASA Astrophysics Data System (ADS)

    Liu, Xiao; Chen, Baojie; Pun, Edwin Yue Bun; Lin, Hai

    2013-01-01

    Rare-earth ions doped K+-Na+ ion-exchanged aluminum germanate (NMAG) glass channel waveguides have been designed and fabricated. Under 980 nm laser pumping, an intense upconversion white light transmission trace was observed in Tm3+/Ho3+/Yb3+ triply doped NMAG glass channel waveguide and a high-brightness light spot was achieved from the output end of the fiber connected to the waveguide channel. The fluorescent colors were diverse and located within or near the white region in CIE chromaticity diagram under various pumping powers. These admirable results indicate that Tm3+/Ho3+/Yb3+ triply doped NMAG channel waveguide is a promising light source for medical and high-precision processing illumination.

  9. White upconversion emission in Y{sub 2}O{sub 3}:Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+}phosphor

    SciTech Connect

    Rai, Vineet Kumar; Dey, Riya; Kumar, Kaushal

    2013-06-01

    Graphical abstract: Schematic energy level diagram of Er{sup 3+}–Yb{sup 3+}–Tm{sup 3+} system upon excitation at 980 nm. Highlights: ► Prepared the Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor. ► Excitation of the sample by 980 nm diode laser is studied. ► Explored the possibility of getting white light emission from the synthesized phosphor. ► Colour tunability of the prepared phosphor is studied. ► Temperature sensing behaviour is investigated using FIR studied. - Abstract: Er{sup 3+}–Tm{sup 3+}–Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor has been synthesized by optimized combustion synthesis process and its white light upconversion emission property is investigated using cheap 980 nm diode laser excitation. Efficient red, green and blue light emission bands, necessary for attaining white light emission, are observed in the codoped sample. The concentration of each rare earth ion is adjusted to get the required emission. In this phosphor, interestingly, emission colour coordinates are found to almost independent on the excitation power density. The temperature sensing behaviour of the prepared samples has also been studied using fluorescence intensity ratio (FIR) technique.

  10. Effect of Li{sup +} ions on enhancement of near-infrared upconversion emission in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals

    SciTech Connect

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

    2012-11-01

    Near-infrared (NIR) to NIR upconversion emission is investigated in Tm{sup 3+}/Yb{sup 3+}/Li{sup +} triply doped Y{sub 2}O{sub 3} nanocrystals. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals can greatly enhance the NIR upconversion emission intensity of Tm{sup 3+} ions. The abnormal shift of the (222) diffraction peak position determined from x-ray diffraction measurements is discussed, by introducing Li{sup +} ions in the Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals. The cause of the enhancement is the modification of the local symmetry induced by the Li{sup +} ions, which increases the intra-4f transitions of Tm{sup 3+} ion. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals also can reduce the OH groups, dissociate the Yb{sup 3+} and Tm{sup 3+} 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.

  11. Plasmonic enhanced emissions from cubic NaYF4:Yb: Er/Tm nanophosphors

    PubMed Central

    Sudheendra, L.; Ortalan, Volkan; Dey, Sanchita; Browning, Nigel D.; Kennedy, I.M.

    2011-01-01

    A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF4 nanoparticles, creating a valuable composite material for labeling in biology and other applications use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF4 matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 2040 nm with a gold shell thickness of 48 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancement observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications. PMID:21709812

  12. Plasmonic enhanced emissions from cubic NaYF(4):Yb: Er/Tm nanophosphors.

    PubMed

    Sudheendra, L; Ortalan, Volkan; Dey, Sanchita; Browning, Nigel D; Kennedy, I M

    2011-06-14

    A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF(4) nanoparticles, creating a valuable composite material for labeling in biology and other applications - use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF(4) matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 20-40 nm with a gold shell thickness of 4-8 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancement observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications. PMID:21709812

  13. NIR to blue light upconversion in Tm3+/Yb3+ codoped BaTiO3 tellurite glass

    NASA Astrophysics Data System (ADS)

    Kumari, Astha; Rai, Vineet Kumar

    2015-05-01

    Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm3+-Yb3+ codoped BaTiO3 glass with TeO2 as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ˜ 476 nm, ˜ 653 nm, ˜ 702 nm and one NIR UC band at ˜795 nm are assigned due to the 1G4→ 3H6, 1G4→ 3F4, 3F2→ 3H6 and 3H4→ 3H6 transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.

  14. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm3+ and Yb3+

    NASA Astrophysics Data System (ADS)

    Soares, M. R. N.; Ferro, M.; Costa, F. M.; Monteiro, T.

    2015-11-01

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm3+ and Yb3+ single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm3+ (4f12) under resonant excitation into the high energy 2S+1LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ~800 nm due to the 1G4 --> 3H5/3H4 --> 3H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited 1G4 and 1D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm3+, a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure colour-based sensor characteristics. Moreover, tuning the color of the blackbody radiation in the nanoparticles by harvesting the low energy photons into the visible spectral region was found to be possible by adjusting the excitation power, paving the way for further developments of these nanoparticles for lighting and photovoltaic applications.

  15. Upconversion luminescence and blackbody radiation in tetragonal YSZ co-doped with Tm(3+) and Yb(3+).

    PubMed

    Soares, M R N; Ferro, M; Costa, F M; Monteiro, T

    2015-12-21

    Lanthanide doped inorganic nanoparticles with upconversion luminescence are of utmost importance for biomedical applications, solid state lighting and photovoltaics. In this work we studied the downshifted luminescence, upconversion luminescence (UCL) and blackbody radiation of tetragonal yttrium stabilized zirconia co-doped with Tm(3+) and Yb(3+) single crystals and nanoparticles produced by laser floating zone and laser ablation in liquids, respectively. The photoluminescence (PL) and PL excitation (PLE) were investigated at room temperature (RT). PL spectra exhibit the characteristic lines in UV, blue/green, red and NIR regions of the Tm(3+) (4f(12)) under resonant excitation into the high energy (2S+1)LJ multiplets. Under NIR excitation (980 nm), the samples placed in air display an intense NIR at ∼800 nm due to the (1)G4→(3)H5/(3)H4→(3)H6 transitions. Additionally, red, blue/green and ultraviolet UCL is observed arising from higher excited (1)G4 and (1)D2 multiplets. The power excitation dependence of the UCL intensity indicated that 2-3 low energy absorbed photons are involved in the UCL for low power levels, while for high powers, the identified saturation is dependent on the material size with a enhanced effect on the NPs. The temperature dependence of the UCL was investigated for single crystals and targets used in the ablation. An overall increase of the integrated intensity was found to occur between 12 K and the RT. The thermally activated process is described by activation energies of 10 meV and 30 meV for single crystals and targets, respectively. For the NPs, the UCL was found to be strongly sensitive to pressure conditions. Under vacuum conditions, instead of the narrow lines of the Tm(3+), a wide blackbody radiation was detected, responsible for the change in the emission colour from blue to orange. This phenomenon is totally reversible when the NPs are placed at ambient pressure. The UCL/blackbody radiation in the nanosized material exhibits non-contact pressure colour-based sensor characteristics. Moreover, tuning the color of the blackbody radiation in the nanoparticles by harvesting the low energy photons into the visible spectral region was found to be possible by adjusting the excitation power, paving the way for further developments of these nanoparticles for lighting and photovoltaic applications. PMID:26469333

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    PubMed

    Gavrilović, Tamara V; Jovanović, Dragana J; Lojpur, Vesna; Dramićanin, Miroslav D

    2014-01-01

    Synthesis of Eu(3+)- and Er(3+)/Yb(3+)-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. Eu(3+)-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er(3+)/Yb(3+)-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 (2)H11/2 → (2)I15/2 and (4)S3/2 → (4)I15/2 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. PMID:24572638

  18. "White" phosphor on the basis of Gd2(MoO4)3: Tm,Tb,Eu single crystal

    NASA Astrophysics Data System (ADS)

    Sinitsyn, V. V.; Redkin, B. S.; Kiselev, A. P.; Shmurak, S. Z.; Kolesnikov, N. N.; Kveder, V. V.; Ponyatovsky, E. G.

    2015-08-01

    A single-crystal sample of Gd2(MoO4)3 simultaneously doped with europium, terbium and thulium is grown. The Tm, Tb and Eu dopants are employed as the luminescent centers emitting light in the red, green and blue ranges. Spectroscopy investigation reveals that simultaneous luminescence of the centers of all three types to produce white light occurs only under the sample excitation with ultraviolet (UV) light within the wavelength range 350 < ? < 370 nm. A commercial UV light-emitting diode (LED) with ?LED = 365 nm is applied in order to show that the Gd2(MoO4)3:Tm,Tb,Eu crystal converts its UV flux into white light. So, it is demonstrated that white light may be produced using one matrix with luminous centers of three types.

  19. Quantum sized Ag nanocluster assisted fluorescence enhancement in Tm{sup 3+}-Yb{sup 3+} doped optical fiber beyond plasmonics

    SciTech Connect

    Chattopadhyay, Rik; Haldar, Arindam; Paul, Mukul C.; Das, Shyamal; Bhadra, Shyamal K.

    2015-12-07

    We report a process for enhancing fluorescence emission from conventional rare earth ions in optical fiber by metal nanocluster (MNC) in nonresonant indirect pumping. The process is completely different from formal metal enhanced fluorescence phenomenon as the MNCs are too small in size to support localized surface plasmon and the excitation wavelength is far from plasmon resonance frequency. We used an established theory of two coupled oscillators to explain the simultaneous enhancement of Ytterbium (Yb{sup 3+}) and Thulium (Tm{sup 3+}) emission by silver (Ag) NCs under nonresonant pumping in optical fiber. The fiber is pumped with a 980 nm fiber pigtailed laser diode with input power of 20–100 mW to excite the Yb{sup 3+}. Four times enhancement of Yb{sup 3+} emission of 900–1100 nm and Tm{sup 3+} upconversion emission around 474 nm, 650 nm, and 790 nm is observed in the fiber with Ag NCs.

  20. Synthetic and spectroscopic studies of vanadate glaserites I: Upconversion studies of doubly co-doped (Er, Tm, or Ho):Yb:K{sub 3}Y(VO{sub 4}){sub 2}

    SciTech Connect

    Kimani, Martin M. Chen, Hongyu McMillen, Colin D. Anker, Jeffery N. Kolis, Joseph W.

    2015-03-15

    The synthesis and upconversion properties of trigonal glaserite-type K{sub 3}Y(VO{sub 4}){sub 2} co-doped with Er{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+}, or Tm{sup 3+}/Yb{sup 3+} were studied. Powder samples were synthesized by solid state reactions at 1000 °C for 48 h, while well-formed hexagonal single crystals of the same were grown hydrothermally using 10 M K{sub 2}CO{sub 3} at 560–650 °C. Infrared-to-visible upconversion by Er{sup 3+}/Yb{sup 3+}, Ho{sup 3+}/Yb{sup 3+}, or Tm{sup 3+}/Yb{sup 3+} codoped-K{sub 3}Y(VO{sub 4}){sub 2} glaserite powder and single crystals was observed, and the upconversion spectral properties were studied as a function of different Er{sup 3+}, Tm{sup 3+}, Ho{sup 3+}, and Yb{sup 3+} ion concentrations. The process is observed under 980 nm laser diode excitation and leads to strong green (552 nm) and red (659 nm) emission for Er{sup 3+}/Yb{sup 3+}, green (549 nm) and red (664 nm) emission for Ho{sup 3+}/Yb{sup 3+}, and blue (475 nm) and red (647 nm) emission for Tm{sup 3+}/Yb{sup 3+}. The main mechanism that allows for up-conversion is attributed the energy transfer among Yb{sup 3+} and the various Er{sup 3+}/Ho{sup 3+}/Tm{sup 3+} ions in excited states. These results illustrate the large potential of co-doped alkali double vanadates for photonic applications involving optoelectronics devices. - Graphical abstract: Synthesis and upconversion in vanadate glaserites. - Highlights: • K{sub 3}Y(VO{sub 4}){sub 2} codoped with Er, Tm, or Ho:Yb were synthesized via solid-state and hydrothermal routes. • Upconversion properties are investigated. • The codoped compounds revealed efficient infrared-to-visible upconversion. • The presented compounds are potential host for solid state lighting.

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

    PubMed Central

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

    2013-01-01

    We report on a polyethylenimine (PEI) covalently conjugated (α-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

  2. Lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals: Synthesis, characterization, and photocatalytic properties

    SciTech Connect

    Wang, Wanjun; Liang, Shijing; Bi, Jinhong; Yu, Jimmy C.; Wong, Po Keung; Wu, Ling

    2014-08-15

    Highlights: • Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) are synthesized by hydrothermal method. • Light absorption edge shows red shift with decreasing Ln{sup 3+} radius from Nd{sup 3+} to Yb{sup 3+}. • Ln{sub 2}Sn{sub 2}O{sub 7} shows increasing photocatalytic activity with the decease of Ln{sup 3+} radius. • Electronic configuration reaches 4f{sup 14} under light irradiation may decrease photocatalytic activity. • Hydroxyl radicals are detected to be the major reactive species. - Abstract: A series of lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals have been successfully synthesized via a facile hydrothermal route. With the decrease of Ln{sup 3+} radius, the light absorption edge of the as-prepared Ln{sub 2}Sn{sub 2}O{sub 7} shows a red shift from Nd{sup 3+} to Yb{sup 3+}. Their photocatalytic activities are found to be improved with the decrease of Ln{sup 3+} radius. However, the photocatalytic activity of Yb{sub 2}Sn{sub 2}O{sub 7} is a little lower than Er{sub 2}Sn{sub 2}O{sub 7}, although the Yb{sup 3+} radius is smaller than Er{sup 3+}, which may be attributed to the full-filled electronic configuration (4f{sup 14}) of surface Yb{sup 2+} intermediates (formed by Yb{sup 3+} trapping a photo-excited electron). The crystallite size and surface area play the most important role in determining the activities. Furthermore, hydroxyl radicals are detected to be the major reactive species during the photo-degradation process. Our findings provide insights in the fabrication of highly efficient stannate photocatalysts, thus enlarging the family of photocatalysts available.

  3. Cooperative reduction by Ln(2+) and Cp*(-) ions: synthesis and properties of Sm, Eu, and Yb complexes with 3,6-di-tert-butyl-o-benzoquinone.

    PubMed

    Pushkarevsky, Nikolay A; Ogienko, Mikhail A; Smolentsev, Anton I; Novozhilov, Igor N; Witt, Alexander; Khusniyarov, Marat M; Cherkasov, Vladimir K; Konchenko, Sergey N

    2016-01-21

    The first examples of samarium, europium, and ytterbium complexes with 3,6-di-tert-butyl-o-benzoquinone(3,6-dbbq) in the form of catecholate have been obtained by reactions of the quinone with the corresponding lanthanocenes, [LnCp2*(thf)n] (n = 1 or 2) in solution. In the course of the reactions lanthanide ions lose one or two Cp* ligands, which take part in reduction of a quinone molecule into a catecholate anion (dbcat, 2(-)). As a result of the reactions, Sm and Yb clearly yield dimeric complexes[(LnCp*)2(dbcat)2], where each Ln ion loses one Cp* ligand. Eu forms a trimeric complex [(EuCp*)-(Eu·thf)2(dbcat)3], in which one Eu ion is coordinated by one Cp* ligand, while two Eu ions have lost all Cp* ligands and are coordinated by THF molecules instead. Magnetic properties corroborate the assignment of oxidation states made on the basis of single-crystal X-ray diffraction: all the quinone ligands are present in the catecholate state; both Sm/Yb ions in the dimers are in the +3 oxidation state, whereas the Eu trimer contains two Eu(II) and one Eu(III) ions. Cyclovoltammetry studies show the presence of two reversible oxidation waves for all complexes, presumably concerned with the redox transitions of the dbcat ligands. PMID:26674171

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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 Kα radiation (λ=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.

  5. Optical properties of trigonal single crystals (Yb,Tm)Al{sub 3}(BO{sub 3}){sub 4} grown from fluxes based on the bismuth and lithium molybdates

    SciTech Connect

    Temerov, V. L. Sokolov, A. E.; Sukhachev, A. L.; Bovina, A. F.; Edel'man, I. S.; Malakhovskii, A. V.

    2008-12-15

    The conditions for synthesis of Yb{sub x}Tm{sub 1-x}Al{sub 3}(BO{sub 3}){sub 4} (x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi{sub 2}Mo{sub 3}O{sub 12} and lithium molybdate Li{sub 2}MoO{sub 4} are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K.

  6. Depositing CdS nanoclusters on carbon-modified NaYF4:Yb,Tm upconversion nanocrystals for NIR-light enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    Tou, Meijie; Mei, Yuanyuan; Bai, Song; Luo, Zhenguo; Zhang, Yong; Li, Zhengquan

    2015-12-01

    High-quality hexagonal NaYF4:Yb,Tm upconversion nanocrystals (UCNs) prepared in organic solutions display uniform sizes and strong UC emissions, but they possess a hydrophobic surface which hinders combining them with various semiconductor nanocrystals (NCs) to form a hybrid NIR-activated photocatalyst. Herein we present a facile approach to modify hydrophobic UCNs with a uniform carbon layer and enable them with hydrophilicity and surface functionalization. The carbon shell provides a good substrate for enriching with metal ions and in situ generation of CdS nanoclusters on the particle surface which can utilize both the upconverted UV and visible emissions. The developed NaYF4:Yb,Tm@C@CdS nanoparticles are characterized with TEM, SEM, XRD, PL and UV-Vis spectra and their formation mechanism is elucidated. The products display good photocatalytic activity under visible light and obviously enhanced performance under Vis-NIR light, due to the efficient utilization of UC emissions and the strong adsorption capacity of the carbon shell. The working mechanism of the hybrid photocatalysts is also proposed.High-quality hexagonal NaYF4:Yb,Tm upconversion nanocrystals (UCNs) prepared in organic solutions display uniform sizes and strong UC emissions, but they possess a hydrophobic surface which hinders combining them with various semiconductor nanocrystals (NCs) to form a hybrid NIR-activated photocatalyst. Herein we present a facile approach to modify hydrophobic UCNs with a uniform carbon layer and enable them with hydrophilicity and surface functionalization. The carbon shell provides a good substrate for enriching with metal ions and in situ generation of CdS nanoclusters on the particle surface which can utilize both the upconverted UV and visible emissions. The developed NaYF4:Yb,Tm@C@CdS nanoparticles are characterized with TEM, SEM, XRD, PL and UV-Vis spectra and their formation mechanism is elucidated. The products display good photocatalytic activity under visible light and obviously enhanced performance under Vis-NIR light, due to the efficient utilization of UC emissions and the strong adsorption capacity of the carbon shell. The working mechanism of the hybrid photocatalysts is also proposed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06806a

  7. Les oxydes A2BaCuO 5 ( A = Y, Sm, Eu, Gd, Dy, Ho, Er, Yb)

    NASA Astrophysics Data System (ADS)

    Michel, C.; Raveau, B.

    1982-06-01

    A series of new phases, A2BaCuO 5 ( A = Y, Sm, Eu, Gd, Dy, Ho, Er, Yb), has been isolated. These compounds are orthorhombic, with a ⋍ 7.1, b ⋍ 12.2, and c ⋍ 5.6Å. The probable space groups deduced from the electron diffraction patterns are Pbnm and Pbn2 1. The structure has been resolved from X-ray powder patterns. The framework can be considered as built up from distorted monocapped trigonal prisms AO 7 which share one triangular face forming A2O 11 blocks. The edge-sharing A2O 11 blocks form a three-dimensional network which delimits cavities where Ba 2+ and Cu 2+ are located. Barium is coordinated to 11 oxygen atoms, while the coordination polyhedron of copper is a distorted tetragonal pyramid CuO 5.

  8. Influence of surfactants on the morphology, upconversion emission, and magnetic properties of β-NaGdF4:Yb3+,Ln3+ (Ln = Er, Tm, Ho).

    PubMed

    He, Fei; Niu, Na; Wang, Lin; Xu, Jie; Wang, Yan; Yang, Guixin; Gai, Shili; Yang, Piaoping

    2013-07-21

    In this article, rare earth (RE) ion doped β-NaGdF4 crystals with multicolor up-conversion (UC) emissions and paramagnetic properties were synthesized via a simple one-step precipitation method at room-temperature for the first time. Different surfactants, including Na2EDTA, PVP, SDS, and Na2tar, were introduced to control the crystal size and morphology. It was found that the organic additive can strongly control the size and structure of as-prepared β-NaGdF4:Yb(3+),Ln(3+) samples through absorbing on the surface of primary particles and/or coordinating with RE(3+) ions. Most interestingly, the UC and magnetic properties of the NaGdF4 crystals were also greatly influenced by those additives, which exhibit great distinction. The red emission of (4)F(9/2)→(4)I(15/2) (655 nm) in β-NaGdF4:20%Yb(3+),2%Er(3+), (5)F5→(5)I8 (648 nm) in β-NaGdF4:20%Yb(3+),2%Ho(3+), and NIR emission of (3)H4→(3)H6 (797 nm) in β-NaGdF4:20%Yb(3+),2%Tm(3+) were all markedly enhanced due to abundant organic groups that affect the nonradiative processes. The magnetic properties of β-NaGdF4:Yb(3+),Er(3+) crystals prepared with different surfactants exhibit typical paramagnetic behavior with different intensities due to the different crystal shape anisotropy. PMID:23715476

  9. Multicolour upconversion emission from Ho{sup 3+}-Tm{sup 3+}-Yb{sup 3+} codoped CaMoO{sub 4} phosphor

    SciTech Connect

    Dey, Riya; Rai, Vineet Kumar

    2015-05-15

    The Ho{sup 3+}-Tm{sup 3+}-Yb{sup 3+} codoped CaMoO4 phosphor powder has been synthesized by chemical coprecipitation technique. For the structural investigation the X-ray diffraction analysis has been done. Multicolour upconversion (UC) emission in the visible region from the prepared material has been observed under the 980 nm near infrared (NIR) excitation. The UC emission bands ∼ 474 nm (blue), ∼ 541 nm (green) and ∼ 661 nm (red) region have been assigned as {sup 1}G{sub 4}→{sup 3}H{sub 6} (Tm{sup 3+}), {sup 5}F{sub 4}{sup 5}S{sub 2}→{sup 5}I{sub 8} (Ho{sup 3+}) and {sup 5}F{sub 5}→{sup 5}I{sub 8} (Ho{sup 3+}) transitions respectively.

  10. High Contrast In vitro and In vivo Photoluminescence Bioimaging Using Near Infrared to Near Infrared Up-Conversion in Tm3+ and Yb3+ Doped Fluoride Nanophosphors

    PubMed Central

    Nyk, Marcin; Kumar, Rajiv; Ohulchanskyy, Tymish Y.; Bergey, Earl J.; Prasad, Paras N.

    2012-01-01

    A new approach for photoluminescence imaging in vitro and in vivo has been shown, utilizing near infrared to near infrared (NIR-to-NIR) up-conversion in nanophosphors. This NIR-to-NIR up-conversion process provides deeper light penetration into biological specimen and results in high contrast optical imaging due to absence of an autofluorescence background and decreased light scattering. Aqueous dispersible fluoride (NaYF4) nanocrystals (20–30 nm size) co-doped with the rare earth ions, Tm3+ and Yb3+, were synthesized and characterized by TEM, XRD and photoluminescence (PL) spectroscopy. In vitro cellular uptake was shown by the PL microscopy visualizing the characteristic emission of Tm3+ at ~ 800 nm excited with 975 nm. No apparent cytotoxicity was observed. Subsequent animal imaging studies were performed using Balb-c mice injected intravenously with up-converting nanophosphors, demonstrating the high contrast PL imaging in vivo. PMID:18928324

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

    PubMed

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

    2014-01-31

    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

  12. An experimental design approach for hydrothermal synthesis of NaYF4: Yb3+, Tm3+ upconversion microcrystal: UV emission optimization

    NASA Astrophysics Data System (ADS)

    Kaviani Darani, Masoume; Bastani, Saeed; Ghahari, Mehdi; Kardar, Pooneh

    2015-11-01

    Ultraviolet (UV) emissions of hydrothermally synthesized NaYF4: Yb3+, Tm3+ upconversion crystals were optimized using the response surface methodology experimental design. In these experimental designs, 9 runs, two factors namely (1) Tm3+ ion concentration, and (2) pH value were investigated using 3 different ligands. Introducing UV upconversion emissions as responses, their intensity were separately maximized. Analytical methods such as XRD, SEM, and FTIR could be used to study crystal structure, morphology, and fluorescent spectroscopy in order to obtain luminescence properties. From the photo-luminescence spectra, emissions centered at 347, 364, 452, 478, 648 and 803 nm were observed. Some results show that increasing each DOE factor up to an optimum value resulted in an increase in emission intensity, followed by reduction. To optimize UV emission, as a final result to the UV emission optimization, each design had a suggestion.

  13. Appearance of the crystal field levels with conduction electrons in Tm 0.05La xYb 0.95- xTe

    NASA Astrophysics Data System (ADS)

    Ishida, H.; Matsumura, T.; Shibata, K.

    2004-05-01

    The local electronic states of Tm ions in Tm 0.05La xYb 0.95- xTe have been investigated for x=0.95, 0.75 and 0.55, where the number of conduction electrons and the crystalline electric field (CEF) states varies with x. The results of neutron scattering and specific heat show that the well-defined CEF levels at x=0.95 decays with decreasing x. At x=0.55 the CEF almost vanishes and a quasi-elastic scattering appears. The analysis of the specific heat for x=0.55 also indicates a continuous density of states of the ground state.

  14. Structure and properties of single crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2.

    PubMed

    May, Andrew F; McGuire, Michael A; Singh, David J; Custelcean, Radu; Jellison, Gerald E

    2011-11-01

    Single crystals of CaMg(2)Bi(2), EuMg(2)Bi(2), and YbMg(2)Bi(2) were obtained from a Mg-Bi flux cooled to 650 °C. These materials crystallize in the CaAl(2)Si(2) structure-type (P ̅3m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg(2)Bi(2) displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg(2)Bi(2) reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10(19) cm(-3) for CaMg(2)Bi(2), 1.7(1) × 10(19) cm(-3) for EuMg(2)Bi(2), and 4.6(7) × 10(19) cm(-3) for YbMg(2)Bi(2), which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ρ(300 K)/ρ(10 K) ≤ 1.6 in all cases, indicating significant defect scattering. PMID:21999768

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

    PubMed

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

    2015-01-28

    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

  16. Enhanced photocatalytic activities of the heterostructured upconversion photocatalysts with cotton mediated on TiO2/ZnWO4:Yb3+,Tm3.

    PubMed

    Feng, Kaili; Huang, Shouqiang; Lou, Ziyang; Zhu, Nanwen; Yuan, Haiping

    2015-08-14

    To improve the photocatalytic efficiency and make full use of solar energy, ZnWO(4):Yb(3+),Tm(3+) (ZYT) was introduced as the upconversion luminescence agent on TiO(2) with a cotton template, and novel upconversion photocatalysts of TiO(2)/ZnWO(4):Yb(3+),Tm(3+) (TZYT-C) were synthesized and optimized with 5%-30% of ZYT. The heterostructure between ZYT and TiO(2) was formed in the TZYT-C composites with the presence of tube-like morphologies due to the addition of the cotton template. UV (364 nm) and blue (484 nm) light was emitted from ZYT upon 980 nm NIR irradiation. The BET specific surface areas of all the TZYT-C composites increased from 37 m(2) g(-1) (TiO(2)-C) to the maximum value of 75 m(2) g(-1) on 5%TZYT-C. The photocatalytic activities of the TZYT-C composites were tested using the degradation process of methyl orange (MO). 5%TZYT-C showed the highest degradation efficiency, with a value of 55.6% under sun-like irradiation for 210 min. The same performance was observed on 5%TZYT-C under NIR (λ ≥ 780 nm) irradiation, with a maximum removal rate of 9.02%, since 5%TZYT-C showed the most efficient electron-hole (e(-)/h(+)) pair separation, compared to ZYT and other TZYT-C composites. PMID:26150279

  17. Toward NIR driven photocatalyst: Fabrication, characterization, and photocatalytic activity of β-NaYF4:Yb(3+),Tm(3+)/g-C3N4 nanocomposite.

    PubMed

    Huang, Min-Zhong; Yuan, Baoling; Dai, Leyang; Fu, Ming-Lai

    2015-12-15

    The β-NaYF4:Yb(3+),Tm(3+)/g-C3N4 (NYT/C3N4) photocatalyst has been successfully fabricated by a stepwise method. Firstly, the advanced near-infrared (NIR) driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-Vis-NIR diffuse reflectance spectroscopy. It was found that NYT/C3N4 photocatalyst consisted of uniform hexagonal phase NaYF4 nanocrystals with about 20nm diameter distributed on surface of g-C3N4 sheets, and the NYT/C3N4 composite exhibited strong near-infrared light absorption and the energy transfer from β-NaYF4:Yb(3+),Tm(3+) to g-C3N4 was confirmed. Secondly, the photocatalytic activities of the catalysts were evaluated by the degradation of methyl blue dye and colorless phenol under the irradiation of 980nm laser. The results suggested that NYT/C3N4 nanocomposite is an advanced NIR-driven photocatalyst. Moreover the NYT/C3N4 photocatalyst showed good stability for photocatalytic decoloration of dye in the recycled tests. This study suggested a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on g-C3N4, which will contribute to the utilization of solar energy in the future. PMID:26343979

  18. Effect of temperature on luminescent properties of an antimony-silicate glass co-doped with Yb3+ and Tm3+

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    In the article effect of temperature on luminescent properties of antimony - silicate glass co - doped with 1.0mol%Yb3+/1mol%0.2Tm3+ under 976 nm was investigated. As a result of optical excitation with radiation with the wavelength of 976 nm three luminescence bands were obtained: 477 nm for 1G4?3H6 quantum transition, 650 nm for 1G4?3F4 and 698 nm for 3F2,3?3H6 in thulium ions, formed by the efficient Yb3+ ? Tm3+ energy transfer. It has been found that the increase in temperature of a glass leads to higher probability of phonon transitions from the 1G4 to the 3F2,3 level leading to quenching of luminescence band with the wavelength within the band of 650 nm. The maximum sensitivity to temperature change is 0.02139 [K-1] at 250C. The nature of a change over a range of studied temperature from 5 to 250C is linear. The results of the research indicate that the fabricated glass can be used to construct luminescence temperature sensors.

  19. Separation of the contributions to the magnetization of Tm1 - x Yb x B12 solid solutions in steady and pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Bogach, A. V.; Sluchanko, N. E.; Glushkov, V. V.; Demishev, S. V.; Azarevich, A. N.; Filippov, V. B.; Shitsevalova, N. Yu.; Levchenko, A. V.; Vanacken, J.; Moshchalkov, V. V.; Gabani, S.; Flachbart, K.

    2013-05-01

    The magnetization of substitutional Tm1 - x Yb x B12 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 Tm1 - x Yb x B12 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) × 1021 cm-3 meV-1), and a contribution with saturation in high magnetic fields attributed to the localized magnetic moments ((0.8-3.7)μB per unit cell) of the nanoclusters formed by rare-earth ions with an antiferromagnetic interaction.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  1. Er,Yb:ZrO2 / Eu:Y2O3 Core/Shell Assemblies as Potential Temperature Sensors in Explosions

    NASA Astrophysics Data System (ADS)

    Eilers, Hergen; Gunawidjaja, Ray; Myint, Thandar; Applied Science Laboratory Team

    2013-06-01

    We have recently demonstrated the use of nanophase Eu:Y2O3 and Eu:ZrO2 as temperature sensors in explosions. Initial measurements showed 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 was synthesized via forced hydrolysis and the Eu:Y2O3 shell was synthesized via homogeneous precipitation. Subsequently, these assemblies have been heated by a pyroprobe and a CO2 laser for short periods of time. Heat-induced 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 when excited with 970 nm, while the Eu:Y2O3 shell emits in the red when excited with 532 nm. These spectra can be measured separately allowing us to determine temperatures over a wide range. This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10-1-0005 to Washington State University.

  2. The Crystal Structure of Impurity Centers Tm^{2+} and Eu^{2+} in SrCl2 : Ab Initio Calculations

    NASA Astrophysics Data System (ADS)

    Chernyshev, V. A.; Serdcev, A. V.; Petrov, V. P.; Nikiforov, A. E.

    2016-01-01

    Ab initio calculations of the impurity centers Tm^{2+} thulium and europium Eu^{2+} in SrCl2 and MeF2 (Me = Ca, Sr, Ba) were carried out at low (zero) temperature. The crystal structure of impurity centers was investigated. Charge density maps show that the bonds formed by the rare-earth ions have an ionic character. The crystal structures, lattice dynamics, and band structures of MeF2 and SrCl2 were calculated at low temperature. Ab initio calculations were performed in periodic CRYSTAL code within the framework of the MO LCAO approach by using hybrid DFT functionals.

  3. Effect of C6+ Ion Irradiation on structural and electrical properties of Yb and Eu doped Bi1.5 Zn0.92 Nb1.5 O6.92 pyrochlores

    NASA Astrophysics Data System (ADS)

    Yumak, Mehmet; Mergen, Ayhan; Qureshi, Anjum; Singh, N. L.

    2015-03-01

    Pyrochlore general formula of A2B2X7 where A and B are cations and X is an anion Pyrochlore compounds exhibit semiconductor, metallic or ionic conduction properties, depending on the doping, compositions/ substituting variety of cations and oxygen partial pressure. Ion beam irradiation can induce the structural disordering by mixing the cation and anion sublattices, therefore we aim to inevestigate effects of irradiation in pyrochlore compounds. In this study, Eu and Yb-doped Bi1.5Zn0.92Nb1.5O6.92 (Eu-BZN, Yb-BZN) Doping effect and single phase formation of Eu-BZN, Yb-BZN was characterized by X-ray diffraction technique (XRD). Radiation-induced effect of 85 MeV C6+ ions on Eu-BZN, Yb-BZN was studied by XRD, scanning electron microscopy (SEM) and temperature dependent dielectric measurements at different fluences. XRD results revealed that the ion beam-induced structural amorphization processes in Eu-BZN and Yb-BZN structures. Our results suggested that the ion beam irradiation induced the significant change in the temprature depndent dielectric properties of Eu-BZN and Yb-BZN pyrochlores due to the increased oxygen vacancies as a result of cation and anion disordering. Department of Metallurgical and Materials Eng., Marmara University, Istanbul-81040, Turkey.

  4. Bulk textured Ca 2.5(RE) 0.5Co 4O 9 (RE: Pr, Nd, Eu, Dy and Yb) thermoelectric oxides by sinter-forging

    NASA Astrophysics Data System (ADS)

    Prevel, M.; Perez, O.; Noudem, J. G.

    2007-03-01

    Bulk textured Ca 2.5(RE) 0.5Co 4O 9 (RE, rare-earth element = Pr, Nd, Eu, Dy and Yb) ceramics have been prepared using sinter-forging technique. Both sintered and sinter-forged samples have been prepared and characterized. We present the thermoelectric properties, structural and microstructural investigations of the samples which show a strong degree of crystallite orientation. In addition, the effect of the rare-earth substitution on the properties is discussed.

  5. The action mechanism of TiO{sub 2}:NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} cathode buffer layer in highly efficient inverted organic solar cells

    SciTech Connect

    Liu, Chunyu; Chen, Huan; Zhao, Dan; Shen, Liang; He, Yeyuan; Guo, Wenbin E-mail: chenwy@jlu.edu.cn; Chen, Weiyou E-mail: chenwy@jlu.edu.cn

    2014-08-04

    We report the fabrication and characteristics of organic solar cells with 6.86% power conversion efficiency (PCE) by doping NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} into TiO{sub 2} cathode buffer layer. The dependence of devices performance on doping concentration of NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} is investigated. Results indicate that short-circuit current density (J{sub sc}) has an apparent improvement, leading to an enhancement of 22.7% in PCE for the optimized doping concentration of 0.05 mmol ml{sup −1} compared to the control devices. NaYF{sub 4}:Yb{sup 3+},Tm{sup 3+} nanoparticles (NPs) can play threefold roles, one is that the incident light in visible region can be scattered by NaYF{sub 4} NPs, the second is that solar irradiation in infrared region can be better utilized by Up-conversion effect of Yb{sup 3+} and Tm{sup 3+} ions, the third is that electron transport property in TiO{sub 2} thin film can be greatly improved.

  6. Stokes and anti-Stokes luminescence in Tm(3+)/Yb(3+)-doped Lu3Ga5O12 nano-garnets: a study of multipolar interactions and energy transfer dynamics.

    PubMed

    Rathaiah, Mamilla; Haritha, Pamuluri; Lozano-Gorrín, Antonio Diego; Babu, Palamandala; Jayasankar, Chalicheemalapalli Kulala; Rodríguez-Mendoza, Ulises Ruyman; Lavín, Victor; Venkatramu, Vemula

    2016-06-01

    Nanocrystalline Lu3Ga5O12 garnets doped with Tm(3+)/Yb(3+) ions have been synthesized by a low cost and environmentally benign sol-gel technique and characterized for their structural, Stokes and anti-Stokes luminescence properties. The diffuse reflectance spectra of doped Lu3Ga5O12 nano-garnets have been measured to derive the partial energy level structure of Tm(3+) and Yb(3+) ions and possible energy transfer channels between them. Upon laser excitation at 473 nm, weak red and intense near-infrared Stokes emissions have been observed in the nano-garnets. The decay curves of (3)H4 and (1)G4 levels of Tm(3+) ions and the (2)F5/2 level of Yb(3+) ions have been measured upon resonant laser excitation and are found to be non-exponential in nature due to multipolar interactions. In order to know the kind of multipolar interaction among optically active ions, the decay curves are analyzed through the generalized Yokota-Tanimoto model. Moreover, under 970 nm laser excitation, intense blue anti-Stokes emission is observed by the naked eye in Tm(3+)-Yb(3+) co-doped Lu3Ga5O12 nano-garnets. The results show that as-synthesized nano-garnets may be useful in the field of phosphors and photonics. PMID:27185655

  7. Vacuum ultraviolet and near-infrared excited luminescence properties of Ca{sub 3}(PO{sub 4}){sub 2}:RE{sup 3+}, Na{sup +} (RE=Tb, Yb, Er, Tm, and Ho)

    SciTech Connect

    Zhang Jia; Wang Yuhua; Guo Linna; Zhang Feng; Wen Yan; Liu Bitao; Huang Yan

    2011-08-15

    Tb{sup 3+}, Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2} were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb{sup 3+}-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb{sup 3+} content is comparable with that of the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb{sup 3+}-Ho{sup 3+}, Yb{sup 3+}-Er{sup 3+}, and Yb{sup 3+}-Tm{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, in which the cross-relaxation process between Er{sup 3+} and Tm{sup 3+}, producing the {sup 1}D{sub 2}-{sup 3}F{sub 4} transition of Tm{sup 3+}, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. - Graphical abstract: The CPO:0.25Tb{sup 3+}, 0.25Na{sup +} exhibits a comparable brightness to the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} upon 147 nm excitation. Good white light color is achieved in CPO:Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} under 980 nm excitation. Highlights: > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+},Na{sup +} exhibits a comparable brightness with commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+}. > Red, green and blue colors are achieved in Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2}. > Good white emission is obtained in Yb{sup 3+}-Ho{sup 3+}-Er{sup 3+}-Tm{sup 3+} quadri-doped Ca{sub 3}(PO{sub 4}){sub 2}. > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+}, Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} could be potential phosphors.

  8. Size-Tunable and Monodisperse Tm3+/Gd3+-Doped Hexagonal NaYbF4 Nanoparticles with Engineered Efficient Near Infrared-to-Near Infrared Upconversion for In Vivo Imaging

    PubMed Central

    2015-01-01

    Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd3+) can convert NaYbF4:Tm3+ 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm3+ 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ∼2 nm on the ∼22 nm core of hexagonal NaYbF4:Gd3+ 30%/Tm3+ 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline. PMID:25027118

  9. Controlled growth, intense upconversion emissions and concentration induced luminescence switching of bifunctional Tm3+ doped hexagonal NaYb0.55Gd0.45F4 nanorods

    NASA Astrophysics Data System (ADS)

    Qu, Xilong; Li, Yongchang; Yu, Suixi; Yang, Liwen

    2013-11-01

    Bifunctional hexagonal Tm3+ doped NaYb0.55Gd0.45F4 nanorods with tunable size are prepared via in situ cation-exchange reaction using hydrothermal method. The measured field dependence of magnetization of the NaYb0.55Gd0.45F4 nanorods shows typical paramagnetic characteristics that can be ascribed to the non-interacting localized nature of the magnetic moment of rare-earth ions. When excited by a 980 nm laser, these nanorods exhibit intense multi-color up-conversion (UC) emissions in infrared, red, blue and especially ultraviolet. In addition, luminescent switching between different UC emission wavelengths of 480 nm and 450 nm is observed by adjusting Tm3+ doping concentration. Based on power-dependent spectral analyses, it is found that with the increase of Tm3+ doping concentration, due to the suppressed saturation effect, the dominative UC process redistribute the populations at 1G4 and 1D2(Tm3+) states of Tm3+ ion resulting in the above luminescent switching. Our results indicate that bifunctional hexagonal NaYb1-xGdxF4 nanocrystals have potential applications in miniaturized solid-state light sources, optical processing sensors and fluorescent biolabels.

  10. Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands

    PubMed Central

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-01-01

    Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250 nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980 nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660 nm) and NIR (800 nm) peaks, known as two “optical windows” for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions. PMID:26608870

  11. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe?) for Q-switching Yb-, Er- and Tm-doped fiber lasers.

    PubMed

    Woodward, R I; Howe, R C T; Runcorn, T H; Hu, G; Torrisi, F; Kelleher, E J R; Hasan, T

    2015-07-27

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices. PMID:26367663

  12. [Effect of bivalent alkaline earth fluorides introduction on thermal stability and spectroscopic properties of Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses].

    PubMed

    Hu, Yue-bo; Zhang, Xin-na; Zhou, Da-li; Jiao, Qing; Wang, Rong-fei; Huang, Jin-feng; Long, Xiao-bo; Qiu, Jian-bei

    2012-01-01

    Transparent Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides. PMID:22497127

  13. 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)

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

    2007-07-01

    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.

  14. Real-time, non-invasive monitoring of hydrogel degradation using LiYF4:Yb(3+)/Tm(3+) NIR-to-NIR upconverting nanoparticles.

    PubMed

    Jalani, Ghulam; Naccache, Rafik; Rosenzweig, Derek H; Lerouge, Sophie; Haglund, Lisbet; Vetrone, Fiorenzo; Cerruti, Marta

    2015-07-14

    To design a biodegradable hydrogel as cell support, one should know its in vivo degradation rate. A technique commonly used to track gel degradation is fluorescence spectroscopy. However, the fluorescence from conventional fluorophores quickly decays, and the fluorophores are often moderately cytotoxic. Most importantly, they require ultraviolet or visible (UV-Vis) light as the excitation source, which cannot penetrate deeply through biological tissues. Lanthanide-doped upconverting nanoparticles (UCNPs) are exciting alternatives to conventional fluorophores because they can convert near-infrared (NIR) to UV-Vis-NIR light via a sequential multiphoton absorption process referred to as upconversion. NIR light can penetrate up to few cm inside tissues, thus making these UCNPs much better probes than conventional fluorophores for in vivo monitoring. Also, UCNPs have narrow emission bands, high photoluminescence (PL) signal-to-noise ratio, low cytotoxicity and good physical and chemical stability. Here, we show a nanocomposite system consisting of a biodegradable, in situ thermogelling injectable hydrogel made of chitosan and hyaluronic acid encapsulating silica-coated LiYF4:Yb(3+)/Tm(3+) UCNPs. We use these UCNPs as photoluminescent tags to monitor the gel degradation inside live, cultured intervertebral discs (IVDs) over a period of 3 weeks. PL spectroscopy and NIR imaging show that NIR-to-NIR upconversion of LiYF4:Yb(3+)/Tm(3+)@SiO2 UCNPs allows for tracking of the gel degradation in living tissues. Both in vitro and ex vivo release of UCNPs follow a similar trend during the first 5 days; after this time, ex vivo release becomes faster than in vitro, indicating a faster gel degradation ex vivo. Also, the amount of released UCNPs in vitro increases continuously up to 3 weeks, while it plateaus after 15 days inside the IVDs showing a homogenous distribution of UCNPs throughout the IVD tissue. This non-invasive optical method for real time, live tissue imaging holds great potential for tissue analysis, biomapping and bioimaging applications. PMID:26067274

  15. Blue and NIR emission from nanostructured Tm3+/  Yb3+ co-doped SiO2–Ta2O5 for photonic applications

    NASA Astrophysics Data System (ADS)

    Cardoso Muscelli, Wesley; de Oliveira Lima, Karmel; Thomaz Aquino, Felipe; Rocha Gonçalves, Rogéria

    2016-05-01

    This paper reports on the synthesis of Tm3+/Yb3+ co-doped SiO2–Ta2O5 nanocomposites prepared by a sol–gel route. XRD analysis revealed initial crystallization of the L-Ta2O5 structure dispersed in the silica host, which depended on lanthanide concentration. Vibrational spectroscopy showed low OH groups content, SiO2–Ta2O5 nanocomposite formation, and controlled phase separation characterized by the presence of Ta2O5 nanoparticles. Emission in the near infrared was evident and also depended on lanthanide concentration and excitation wavelength. Direct excitation on the host promoted NIR luminescence; higher intensity emerged at 980 nm, attributed to Yb3+ ions. Excitation of the Tm3+ excited levels elicited energy transfer between Tm3+ and Yb3+ ions. Excitation of the Tm3+ levels (visible range) and the host (UV) promoted emission in the S telecom band for all the samples. Excitation at 980 nm gave rise to upconversion emissions at 476 nm (blue) and 793 nm (NIR). At higher lanthanide concentration, the presence of a dominant cross-relaxation process reduced the blue emission with respect to the NIR emission. The color coordinates were similar to the coordinates of standard blue. All these luminescent properties make the synthesized materials potential candidates for photonic applications like energy converting devices, solar concentrators, and blue emitters.

  16. Impact of codopant ions on 2.5-3.0 ?m emission of Er3+:4I11/2?4I13/2 transition in Yb,Er,Eu:LaYSGG crystal

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Li, Jianfu; Zhu, Zhaojie; You, Zhenyu; Xu, Jinlong; Tu, Chaoyang

    2015-12-01

    The crystal of 1 at% Yb3+, 10 at% Er3+ and 0.1 at% Eu3+ triply doped La0.3Y2.7Sc2Ga3O12 (abbr. as Yb,Er,Eu:LaYSGG) was grown for the first time by using a Czochralski technique. Its absorption, near-infrared and mid-infrared fluorescence spectra, as well as the fluorescence decay curves of Er:4I13/2 and 4I11/2 levels were measured at room temperature. The spectroscopic properties including the absorption and emission cross-sections as well as the fluorescence lifetimes of the title crystal were revealed and compared with 10 at% Er3+:Y3Sc2Ga3O12 crystal. Spectral analyses show that the sensitization of Yb3+ ion leads to an enhanced 2.5-3.0 ?m emission corresponding to Er3+:4I11/2?4I13/2 transition in the grown crystal, meanwhile, the depopulation of Eu3+ ion from Er3+ inhibits the self-termination effect successfully. The energy transfer mechanism was discussed; the energy transfer efficiencies of Yb3+?Er3+ (ET1) and Er3+?Eu3+ (ET2) were estimated to be 94.8% and 93.9%, respectively. The results indicates that Yb,Er,Eu:LaYSGG crystal is a good candidate for LD pumped mid-infrared laser.

  17. Multi-modal luminescence properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphors—upconversion, downshifting and quantum cutting for spectral conversion

    NASA Astrophysics Data System (ADS)

    Dwivedi, A.; Mishra, Kavita; Rai, S. B.

    2015-11-01

    This work investigates the promising multi-modal luminescence (upconversion (UC), downshifting (DS) and quantum cutting (QC)) properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphors synthesized using the well-known solid state reaction method. Structural characterization using x-ray diffraction measurements confirms the formation of the pure phase of the GdNbO4 host with no impurities. The optical band gap (E g) of GdNbO4 (with and without RE3+ ions) calculated from UV-Vis-near-infrared (NIR) measurements was found to be the same ~4.44 eV which indicates that GdNbO4 is a wide band gap material. Further, Bi3+ doping presents an interesting E g tuning of the GdNbO4 phosphor, i.e. E g increases up to 5.38 eV. In terms of luminescence, this material produces intense blue and NIR emission via multi-modal optical processes. On NIR excitation (λ exc  =  980 nm), Gd0.94Tm0.01Yb0.05NbO4 produces intense upconverted blue and NIR and relatively weak red emission. In addition to the UC process, Gd0.94Tm0.01Yb0.05NbO4 also exhibits pump power dependent variation in fluorescence intensity ratio for I 472/I 477 showing the applicability of this material as an optical heater. On UV excitation (λ exc  =  265 nm), Gd0.99Tm0.01NbO4 produces intense DS blue emission due to the Tm3+ ion, overlapped with the emission of the (NbO4)3- ion through strong energy transfer (ET) from (NbO4)3- to Tm3+ ions. Interestingly, NIR QC has also been successfully observed in Gd0.9Yb0.1NbO4, Gd0.89Bi0.01Yb0.1NbO4 and Gd0.79Tm0.01Yb0.2NbO4 phosphors through cooperative ET from the (NbO4)3- group to the Yb3+ ion, Bi(6s)-Nb(4d) to the Yb3+ ion and the Tm3+ ion to the Yb3+ ion, respectively. The mechanisms involved in these processes are explained in detail in this work. The QC efficiency in this work has been found to be ~177%. Thus, the multi-modal luminescence (UC, DS and QC) property of this material makes it a promising candidate for display devices, spectral converters for enhancing the efficiency of silicon solar cells, etc.

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

    PubMed

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

    2015-02-21

    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 (β, γ, and δ) were observed. A4O4Se3 materials adopt either the α (A = Nd, Sm), β (A = Eu), γ (A = Gd, Tb) or δ (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

  19. Triple-layered perovskite niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y): new self-activated oxides.

    PubMed

    Qin, Lin; Wei, Donglei; Huang, Yanlin; Kim, Sun Il; Yu, Young Moon; Seo, Hyo Jin

    2013-09-16

    Niobates CaRNb3O10 (R = La, Sm, Eu, Gd, Dy, Er, Yb, or Y) were prepared by conventional high-temperature solid-state reaction. The formation of a single-phase compound with triple-layered perovskite-type structure was verified through X-ray diffraction (XRD) studies. The luminescence characteristics such as photoluminescence excitation and emission spectra, X-ray-excited luminescence (XEL), Stokes shift, decay curves, and color coordinates were investigated. The niobates can be efficiently excited by UV light and present luminescence behaviors with rich luminescence colors. Under excitation by ultraviolet radiation, CaRNb3O10 (R = La, Gd, Yb, or Y) exhibits strong blue luminescence due to the self-activation center of the octahedral NbO6 groups, even at room temperature. For the materials of composition CaRNb3O10 (R = Sm, Eu, Dy, or Er), the excitation at the host band produces a characteristic luminescence of rare earth ions, indicating a host-guest energy transfer process. CaRNb3O10 (R = Eu) has the strongest luminescence intensity, which can be efficiently excitated by near UV wavelength. It could be suggested to be a potential candidate for the application on near-UV excited white LEDs. PMID:23977903

  20. Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4

    SciTech Connect

    Kyunghan Ahn

    2007-05-09

    The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R{sub 5}Si{sub x}Ge{sub 4-x} systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd{sub 5}Si{sub 4}-type structure. The magnetic properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} materials are nearly composition-independent, reflecting the persistence of the same crystal structure over the whole range of x from 0 to 4. Both the crystallographic and magnetic property data indicate that Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys are mixed valence systems, in which the majority (60%) of Yb atoms is divalent, while the minority (40%) is trivalent. This finding is supported by recent Moessbauer spectroscopy data.

  1. Neutron spectroscopic study of crystal-field excitations and the effect of the crystal field on dipolar magnetism in Li R F4 (R =Gd , Ho, Er, Tm, and Yb)

    NASA Astrophysics Data System (ADS)

    Babkevich, P.; Finco, A.; Jeong, M.; Dalla Piazza, B.; Kovacevic, I.; Klughertz, G.; Krämer, K. W.; Kraemer, C.; Adroja, D. T.; Goremychkin, E.; Unruh, T.; Strässle, T.; Di Lieto, A.; Jensen, J.; Rønnow, H. M.

    2015-10-01

    We present a systematic study of the crystal-field interactions in the Li R F4 (R = Gd , Ho, Er, Tm, and Yb) family of rare-earth magnets. Using detailed inelastic neutron scattering measurements, we have been able to quantify the transition energies and wave functions for each system. This allows us to quantitatively describe the high-temperature susceptibility measurements for the series of materials and make predictions based on a mean-field approach for the low-temperature thermal and quantum phase transitions. We show that coupling between crystal field and phonon states leads to line-shape broadening in LiTmF4 and level splitting in LiYbF4. Furthermore, using high-resolution neutron scattering from LiHoF4, we find anomalous broadening of crystal-field excitations which we attribute to magnetoelastic coupling.

  2. Upconversion Nanophosphors Naluf4:Yb,Tm for Lymphatic Imaging In Vivo by Real-Time Upconversion Luminescence Imaging under Ambient Light and High-Resolution X-ray CT

    PubMed Central

    Sun, Yun; Peng, Juanjuan; Feng, Wei; Li, Fuyou

    2013-01-01

    Lanthanide upconversion nanophosphor (UCNP) has attracted increasing attention for potential applications in bioimaging due to its excellence in deep and high contrast imaging. To date, most upconversion imaging applications were demonstrated in dark surroundings without ambient light for higher signal-to-noise ratio, which hindered the application of optical imaging guided surgery. Herein, the new established NaLuF4-based UCNP (NaLuF4:Yb,Tm, ~17 nm) with bright upconversion emission around 800 nm as imaging signal was used to realize imaging under ambient light to provide more convenient for clinician. Moreover, due to the existance of heavy element lutetium (Lu) in the host lattice, the NaLuF4:Yb,Tm nanoparticles can also be used as an X-ray CT imaging agent to enhance the imaging depth and in vivo imaging resolution. PMID:23650481

  3. Electrocatalytic activities of REMn 2O 5 (RE = Dy, Ho, Er, Tm, Yb, and Lu) and Er 0. 76Zr 0. 11Ca 0. 13Mn 2O 5 for oxygen reduction in alkaline solution

    NASA Astrophysics Data System (ADS)

    Li, Neng; Xu, Xiang; Luo, Dan; Wu, Yishi; Li, Shijie; Lin, Bingxiog

    A series of complex oxides REMn 2O 5 (RE=Dy, Ho, Er, Tm, Yb, and Lu) and Er 0. 76Zr 0. 11Ca 0. 13Mn 2O 5 with large specific areas and nanoscale grain sizes were prepared by an improved amorphous citric precursor method (IACP). Their electrocatalytic performances were characterized by the polarization curves of gas diffusion electrodes employing the oxides. The measurement of polarization curves indicated that the REMn 2O 5 containing different rare earth showed a obviously different electrocatalytic performances for oxygen reduction reaction, being the order Tm>Er>Ho>Dy>Lu>Yb. Temperature-programmed reduction (TPR) analysis revealed that the REMn 2O 5 containing different rare earth showed a significantly different oxygen contents and TPR peak temperatures. Their catalytic activities depended on both the oxygen contents and TPR peak temperatures. These two factors play a plus and a minus role respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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

  5. 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.

    SciTech Connect

    Raghothamachar, B.; Carvajal, J; Pujol, M; Mateos, X; Sole, R; Aguilo, M; Diaz, F; Dudley, M

    2010-01-01

    Monoclinic potassium rare-earth double tungstates [KRE(WO{sub 4}){sub 2}, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln{sup 3+}) 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 Yb{sup 3+}- and Tm{sup 3+}-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.

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

    PubMed

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

    2013-03-21

    A series of Lu6O5F8:20%Yb(3+),1%Er(3+)(Tm(3+)),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%Yb(3+),1%Er(3+)(Tm(3+)),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%Yb(3+),0.3%Er(3+),0.4%Tm(3+),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. PMID:23411671

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

    SciTech Connect

    Kuznetsov, A. S.; Nikitin, A.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

    2013-04-22

    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.

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

    SciTech Connect

    Wong-Ng, W.; Yan, Y.; Liu, G.; Xie, W.; Tritt, T.; Kaduk, J.; Thomas, E.

    2011-12-01

    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.

  9. NIR to blue light upconversion in Tm{sup 3+}/Yb{sup 3+} codoped BaTiO{sub 3} tellurite glass

    SciTech Connect

    Kumari, Astha Rai, Vineet Kumar

    2015-05-15

    Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm{sup 3+}-Yb{sup 3+} codoped BaTiO{sub 3} glass with TeO{sub 2} as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ∼ 476 nm, ∼ 653 nm, ∼ 702 nm and one NIR UC band at ∼795 nm are assigned due to the {sup 1}G{sub 4}→ {sup 3}H{sub 6}, {sup 1}G{sub 4}→ {sup 3}F{sub 4}, {sup 3}F{sub 2}→ {sup 3}H{sub 6} and {sup 3}H{sub 4}→ {sup 3}H{sub 6} transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.

  10. The size confinement effect for Ln3+ (Ln = Tm or Eu) concentration quenching and energy transfer in Y2O3 nanocrystals.

    PubMed

    Wang, Changwen; Meng, Qingyu

    2014-05-01

    Y2O3:Ln (Ln = Tm or Eu) nano-powders with different particle sizes and various doping concentrations were prepared by using a combustion method. The bulk powders doped with the same concentrations were obtained by annealing the nano-powders at high temperatures. Emission spectra of the phosphors were measured. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y2O3:Ln nanocrystal powders were investigated. It is found that the behavior of luminescent concentration quenching for Eu3+ 5D0 --> 7F2 in nano-powders is similar to that in bulk powders. On the contrary, the quenching concentration for Tm3+ 1D2 --> 3H4 is distinctly higher than that in bulk powders. This owes to the size confinement effect which will restrain the electric dipole-dipole interaction as a long-rang interaction (e.g., energy transfer between Tm3+ ions), and will hardly affect the exchange interaction which is a short-rang interaction (e.g., energy transfer between Eu3+ ions). PMID:24734659

  11. Synthesis, Characterization, and Application of Core-Shell Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm) Nanoparticle as Trimodal (MRI, PET/SPECT, and Optical) Imaging Agents.

    PubMed

    Cui, Xianjin; Mathe, Domokos; Kovács, Noémi; Horváth, Ildikó; Jauregui-Osoro, Maite; Torres Martin de Rosales, Rafael; Mullen, Gregory E D; Wong, Wilson; Yan, Yong; Krüger, Dirk; Khlobystov, Andrei N; Gimenez-Lopez, Maria; Semjeni, Mariann; Szigeti, Krisztián; Veres, Dániel S; Lu, Haizhou; Hernández, Ignacio; Gillin, William P; Protti, Andrea; Petik, Katalin Kis; Green, Mark A; Blower, Philip J

    2016-02-17

    Multimodal nanoparticulate materials are described, offering magnetic, radionuclide, and fluorescent imaging capabilities to exploit the complementary advantages of magnetic resonance imaging (MRI), positron emission tomography/single-photon emission commuted tomography (PET/SPECT), and optical imaging. They comprise Fe3O4@NaYF4 core/shell nanoparticles (NPs) with different cation dopants in the shell or core, including Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm). These NPs are stabilized by bisphosphonate polyethylene glycol conjugates (BP-PEG), and then show a high transverse relaxivity (r2) up to 326 mM(-1) s(-1) at 3T, a high affinity to [(18)F]-fluoride or radiometal-bisphosphonate conjugates (e.g., (64)Cu and (99m)Tc), and fluorescent emissions from 500 to 800 nm under excitation at 980 nm. The biodistribution of intravenously administered particles determined by PET/MR imaging suggests that negatively charged Co0.16Fe2.84O4@NaYF4(Yb, Er)-BP-PEG (10K) NPs cleared from the blood pool more slowly than positively charged NPs Fe3O4@NaYF4(Yb, Tm)-BP-PEG (2K). Preliminary results in sentinel lymph node imaging in mice indicate the advantages of multimodal imaging. PMID:26172432

  12. Synthesis, Characterization, and Application of Core–Shell Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm) Nanoparticle as Trimodal (MRI, PET/SPECT, and Optical) Imaging Agents

    PubMed Central

    2015-01-01

    Multimodal nanoparticulate materials are described, offering magnetic, radionuclide, and fluorescent imaging capabilities to exploit the complementary advantages of magnetic resonance imaging (MRI), positron emission tomography/single-photon emission commuted tomography (PET/SPECT), and optical imaging. They comprise Fe3O4@NaYF4 core/shell nanoparticles (NPs) with different cation dopants in the shell or core, including Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm). These NPs are stabilized by bisphosphonate polyethylene glycol conjugates (BP-PEG), and then show a high transverse relaxivity (r2) up to 326 mM–1 s–1 at 3T, a high affinity to [18F]-fluoride or radiometal-bisphosphonate conjugates (e.g., 64Cu and 99mTc), and fluorescent emissions from 500 to 800 nm under excitation at 980 nm. The biodistribution of intravenously administered particles determined by PET/MR imaging suggests that negatively charged Co0.16Fe2.84O4@NaYF4(Yb, Er)-BP-PEG (10K) NPs cleared from the blood pool more slowly than positively charged NPs Fe3O4@NaYF4(Yb, Tm)-BP-PEG (2K). Preliminary results in sentinel lymph node imaging in mice indicate the advantages of multimodal imaging. PMID:26172432

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  14. Heterobinuclear Zn-Ln (Ln = La, Nd, Eu, Gd, Tb, Er and Yb) complexes based on asymmetric Schiff-base ligand: synthesis, characterization and photophysical properties.

    PubMed

    Zhao, Shunsheng; Liu, Xiangrong; Lü, Xingqiang; Wong, Wai-Kwok

    2013-01-01

    With a novel asymmetric Schiff-base zinc complex ZnL (H2 L = N-(3-methoxysalicylidene)-N'-(5-bromo-3-methoxysalicylidene)phenylene-1,2-diamine), obtained from phenylene-1,2-diamine, 3-methoxysalicylaldehyde and 5-bromo-3-methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO3 )3 (CH3 CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO3 )3 ·6H2 O, and characterized by Fourier transform-infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near-infrared luminescence of Nd(3+) , Yb(3+) and Er(3+) with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions. PMID:23001932

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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 (λem = 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.

  16. Broadband down-conversion based near infrared quantum cutting in Eu{sup 2+}–Yb{sup 3+} co-doped SrAl{sub 2}O{sub 4} for crystalline silicon solar cells

    SciTech Connect

    Tai, Yuping; Zheng, Guojun; Wang, Hui; Bai, Jintao

    2015-03-15

    Near infrared (NIR) quantum cutting involving the down conversion of an absorbed visible photon to emission of two NIR photons was achieved in SrAl{sub 2}O{sub 4}:0.01Eu{sup 2+}, xYb{sup 3+} (x=0, 1, 2, 5, 10, 20, 30 mol%) samples. The photoluminescence properties of samples in visible and NIR regions were measured to verify the energy transfer (ET) from Eu{sup 2+} to Yb{sup 3+}. The results demonstrated that Eu{sup 2+} was an efficient sensitizer for Yb{sup 3+} in the SrAl{sub 2}O{sub 4} host lattice. According to Gaussian fitting analysis and temperature-dependent luminescence experiments, the conclusion was drawn that the cooperative energy transfer (CET) process dominated the ET process and the influence of charge transfer state (CTS) of Yb{sup 3+} could be negligible. As a result, the high energy transfer efficiency (ETE) and quantum yield (QY) have been acquired, the maximum value approached 73.68% and 147.36%, respectively. Therefore, this down-conversion material has potential application in crystalline silicon solar cells to improve conversion efficiency. - Graphical abstract: Near infrared quantum cutting was achieved in Eu{sup 2+}–Yb{sup 3+} co-doped SrAl{sub 2}O{sub 4} samples. The cooperative energy transfer process dominated energy transfer process and high energy transfer efficiency was acquired. - Highlights: • The absorption spectrum of Eu{sup 2+} ion is strong in intensity and broad in bandwidth. • The spectra of Eu{sup 2+} in SrAl{sub 2}O{sub 4} lies in the strongest region of solar spectrum. • The cooperative energy transfer (CET) dominated the energy transfer process. • The domination of CET is confirmed by experimental analysis. • SrAl{sub 2}O{sub 4}:Eu{sup 2+},Yb{sup 3+} show high energy transfer efficiency and long lifetime.

  17. Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

    SciTech Connect

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

    2012-01-01

    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.

  18. Spatial distribution of defects and the kinetics of nonequilibrium charge carriers in GaN wurtzite crystals doped with Sm, Eu, Er, Tm, and supplementary Zn impurities

    SciTech Connect

    Mezdrogina, M. M. Krivolapchuk, V. V.; Kozhanova, Yu. V.

    2008-02-15

    By analyzing time-resolved and steady-state photoluminescence spectra, it is established that the spatial distribution of rare-earth ion dopants in wurtzite GaN crystals doped with Sm, Eu, Er, or Tm is governed by the type and concentration of defects in the initial semiconductor matrix as well as by the type of the impurity (its capacity for segregation). Doping with multicharged rare-earth impurities and additionally introduced Zn impurity leads to an intensification of emission. The effect of intensification of emission in the case of n-and p-GaN crystals is considered with the use of the model of isoelectronic traps.

  19. 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

    Asiri Naidu, S.; Boudin, S.; Varadaraju, U.V.; Raveau, B.

    2012-01-15

    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.

  20. Preparation of a novel nanocomposite NaLuF4:Gd,Yb,Tm@SiO2@Ag@TiO2 with high photocatalytic activity driven by simulated solar light.

    PubMed

    Yin, Dongguang; Zhang, Lu; Cao, Xianzhang; Chen, Zhiwen; Tang, Jingxiu; Liu, Yumin; Zhang, Tingting; Wu, Minghong

    2016-01-28

    A novel nanocomposite photocatalyst NaLuF4:Gd,Yb,Tm@SiO2@Ag@TiO2 was developed for the first time. This composite material has a sandwich structure, including a NaLuF4:Gd,Yb,Tm upconversion nanocrystals (UCNCs) core, a media shell of amorphous SiO2 decorated with Ag nanoparticles, and an outer shell of anatase TiO2. The designed new structure takes advantage of the synergetic effect of UCNCs, Ag nanoparticles and TiO2. The UCNCs absorb near-infrared (NIR) light and transfer energy to TiO2, which extends the light responsive range of TiO2 to the NIR region. Ag nanoparticles not only enhance upconversion luminescence of the UCNCs but also enhance light harvesting and improve charge separation of TiO2. The results of photocatalytic applications show that the as-prepared catalyst has high photocatalytic activity. This study provides new insights into the fabrication of TiO2-based nanocomposite photocatalysts with high catalytic efficiency through effective integration of upconversion material, noble metal and TiO2 into a hetero-composite nanostructure. PMID:26673742

  1. [Study on concentration quenching and energy transfer in Ln3+ (Ln = Tb, Tm, Eu) in Y2O3 nanocrystal powders].

    PubMed

    Meng, Qing-Yu; Chen, Bao-Jiu; Xu, Wu; Zhao, Xiao-Xia; Yang, Yan-Min; Di, Wei-Hua; Wang, Xiao-Jun

    2009-01-01

    Nano-powders Y2O3 with various particle sizes and different doping concentrations of Ln (Ln = Tb, Tm, Eu) were prepared by using a combustion technique. The bulky powders doped with concentrations corresponding to nano-powders were obtained by annealing the nano-powders at high temperature. The emission spectra, XRD spectra and TEM were used in the present study. The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y2O3 : Ln nanocrystal powders were investigated. It was found that the behaviors of luminescence concentration quenching for 5D4 --> 7F5 : Tb3+ and 5D0 --> 7F2 : Eu3+ in nano-powders are similar to that in bulky powders. On the contrary, the quenching concentrations for 5D3 --> 7F5 : Tb3+ and 1D2 --> 3H4 : Tm3+ are distinctly higher than that in bulk powders. This owes to the size confinement effect: the interface of nanocrystal particles can stop a portion of the energy transfer, which happens in the bulk ones, between luminescent centers. The size confinement effect can bring different influences to the different types of energy transfer. For instance, it will restrain the energy transfer (governed by electric dipole-dipole interaction) between the ions in long distances, and will hardly affect the energy transfer (governed by exchange interaction) between the ions locating at near intervals. PMID:19385227

  2. EPR study of the ground state of Mn2+ impurity ions in alumoborates MAl3(BO3)4 (M = Y, Eu, Tm)

    NASA Astrophysics Data System (ADS)

    Prokhorov, А А; Prokhorov, A. D.; Chernush, L. F.; Dyakonov, V. P.; Szymczak, H.; Dejneka, A.

    2015-06-01

    New data about the ground state of the Mn2+ impurity ions in a series of single crystals of alumbrados MAl3(BO3)4, where M = Y,Eu,Tm were obtained. The electron paramagnetic resonance (EPR) spectra of the Mn2+ spectra were studied, the parameters of the spin Hamiltonian describing the angular dependence of the spectrum were defined. It was shown that Mn2+ ions substitute trivalent ions of rare earth metals without changing the symmetry of the substitution site. The charge compensation process was found to be a nonlocal one. The cooling of the crystals leads to the increase of the splitting of the ground state, which is associated with the anisotropy of the thermal expansion coefficient. It was shown that an application of the superposition model to explain the distortions induced by an impurity Mn2+ ion has some limitations. The EPR linewidth of the Mn2+ ion in the TmAl3(BO3)4 crystal increases with increasing temperature as a result of the dipole-dipole and exchange interactions with the excited states of the host lattice Tm3+ ion.

  3. 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

    Peng, Jing; Hou, Suying; Liu, Xianchun; Feng, Jing; Yu, Xiaodan; Xing, Yan; Su, Zhongmin

    2012-02-15

    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.

  4. NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}, Er{sup 3+}/Yb{sup 3+}) microspheres: the synthesis and optical properties

    SciTech Connect

    Gao, Zhiyi; Wang, Zhiying; Fu, Linlin; Yang, Xingxing; Fu, Zuoling; Wu, Zhijian; Jeong, Jung Hyun

    2015-10-15

    The strong green upconversion (UC) emission were observed in various Er{sup 3+}, Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} samples synthesized via a hydrothermal route. The UC intensity depends on the dopant concentration, and the optimal UC emission was obtained in NaLa(MoO{sub 4}){sub 2}: 0.02Er{sup 3+}/0.10 Yb{sup 3+}. - Highlights: • The NaLa(MoO{sub 4}){sub 2} microspheres doped with Eu{sup 3+}, Sm{sup 3+} and Er{sup 3+}/Yb{sup 3+} were synthesized by a hydrothermal method. • The effects of the EDTA in the initial solution crystal phase and morphology were studied. • The down-conversion luminescence properties of NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}) were investigated. • The UC luminescence properties and mechanism of Er{sup 3+}/Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} was discussed. - Abstract: NaLa(MoO{sub 4}){sub 2}: RE{sup 3+} (RE{sup 3+} = Eu{sup 3+}, Sm{sup 3+}) microspheres have been synthesized at 180 °C via a facile EDTA-mediated hydrothermal route. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectra were employed to characterize the samples. It was found that the amount of EDTA in the initial solution was responsible for crystal phase and shape determination. The effect of Eu{sup 3+} and Sm{sup 3+} doping concentrations on the luminescent intensity was also investigated in details. Furthermore, the up-conversion (UC) emissions have been observed in a series of Er{sup 3+}/Yb{sup 3+} co-doped NaLa(MoO{sub 4}){sub 2} samples. Concentration dependent studies revealed that the optimal composition was realized for a 2% Er{sup 3+} and 10% Yb{sup 3+}-doping concentration.

  5. Observation of superconductivity at 30~46 K in A(x)Fe₂Se₂(A = Li, Na, Ba, Sr, Ca, Yb, and Eu).

    PubMed

    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

    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 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 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

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

    PubMed Central

    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

    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

  7. Crystal structures of RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) studied by single crystal X-ray diffraction

    SciTech Connect

    Gribanov, Alexander; Grytsiv, Andriy; Rogl, Peter; Seropegin, Yurii; Giester, Gerald

    2009-07-15

    The crystal structures of ternary compounds RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt{sub 3-x}Si{sub 1-y} arises from defects: x{approx}0.20, y{approx}0.14. The crystal structure of RPt{sub 3-x}Si{sub 1-y} can be considered as a packing of four types of building blocks which derive from the CePt{sub 3}B-type unit cell by various degrees of distortion and Pt, Si-defects. - Graphical Abstract: Electron density in RPt{sub 3-x}Si{sub 1-y} at 0, 1/2 , 0.

  8. Doxorubicin-loaded NaYF4:Yb/Tm-TiO2 inorganic photosensitizers for NIR-triggered photodynamic therapy and enhanced chemotherapy in drug-resistant breast cancers.

    PubMed

    Zeng, Leyong; Pan, Yuanwei; Tian, Ying; Wang, Xin; Ren, Wenzhi; Wang, Shouju; Lu, Guangming; Wu, Aiguo

    2015-07-01

    The combination therapy has exhibited important potential for the treatment of cancers, especially for drug-resistant cancers. In this report, bi-functional nanoprobes based on doxorubicin (DOX)-loaded NaYF4:Yb/Tm-TiO2 inorganic photosensitizers (FA-NPs-DOX) were synthesized for invivo near infrared (NIR)-triggered inorganic photodynamic therapy (PDT) and enhanced chemotherapy to overcome the multidrug resistance (MDR) in breast cancers. Using the up-conversion luminescence (UCL) performance of NaYF4:Yb/Tm converting near-infrared (NIR) into ultraviolent (UV) lights, reactive oxygen species (ROS) were triggered from TiO2 inorganic photosensitizers for PDT under the irradiation of a 980nm laser, by which the deep-penetration and low photo-damage could be reached. Moreover, nanocarrier delivery and folic acid (FA) targeting promoted the cellular uptake, and accelerated the release of DOX in drug-sensitive MCF-7 and resistant MCF-7/ADR cells. The toxicity assessment invitro and invivo revealed the good biocompatibility of the as-prepared FA-NPs-DOX nanocomposites. By the combination of enhanced chemotherapy and NIR-triggered inorganic PDT, the viability of MCF-7/ADR cells could decrease by 53.5%, and the inhibition rate of MCF-7/ADR tumors could increase up to 90.33%, compared with free DOX. Therefore, the MDR of breast cancers could be obviously overcome by enhanced chemotherapy and NIR-triggered inorganic PDT of FA-NPs-DOX nanocomposites under the excitation of a 980nm laser. PMID:25913254

  9. New high pressure rare earth tantalates RE{sub x}Ta{sub 2}O{sub 5+1.5x} (RE=La, Eu, Yb)

    SciTech Connect

    Zibrov, Igor P.; Filonenko, Vladimir P.; Zakharov, Nikolai D.; Nikishina, Elena E.; Lebedeva, Elena N.

    2013-07-15

    Rare earth tantalates La{sub 0.075}Ta{sub 2}O{sub 5.113}, Eu{sub 0.089}Ta{sub 2}O{sub 5.134} and Yb{sub 0.051}Ta{sub 2}O{sub 5.077} have been prepared by solid state reaction at P=7.0 GPa and T=1050–1100 °C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F–Ta{sub 2}O{sub 5} [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464–471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La{sub 0.075}Ta{sub 2}O{sub 5.113}, a=10.5099(2), b=7.2679(1), c=6.9765(1) Å, V=532.90(1) Å{sup 3}, Z=6, space group Ibam; Eu{sub 0.089}Ta{sub 2}O{sub 5.134}, a=10.4182(3), b=7.2685(1), c=6.9832(1) Å, V=528.80(2) Å{sup 3}, Z=6, space group Ibam; Yb{sub 0.051}Ta{sub 2}O{sub 5.077}, a=10.4557(2), b=7.3853(1), c=6.8923(1) Å, V=532.21(1) Å{sup 3}, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE{sup +3} compress the unit cell so that its volume becomes less than that of F–Ta{sub 2}O{sub 5}. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer. - Graphical abstract: The structure of RE{sub x}Ta{sub 2}O{sub 5+1.5x} and its HRTEM image (“A” arrows show empty channel, “B” arrows show filled channel). - Highlights: • We synthesized new tantalates of RE under high pressure high temperature conditions. • RE atoms replace water molecules in the channels of the structure. • Aqueous as well as anhydrous tantalates were obtained. • Highly charged cations RE{sup +3} compress the unit cell decreasing RE–O distances.

  10. Low-temperature superstructures of a series of Cd6M (M = Ca, Y, Sr, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) crystalline approximants.

    PubMed

    Nishimoto, Kazue; Sato, Takeru; Tamura, Ryuji

    2013-06-12

    The low-temperature (LT) superstructure and the phase transition temperature have been investigated for a series of Cd6M crystalline approximants by transmission electron microscopy as well as electrical resistivity measurements. Except for M = Lu, Cd6M is found to undergo a phase transition to a monoclinic phase at a low temperature and the transition temperature (Tc) scales well with the size of the M atom. For M = Ca, Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm the LT superstructure is explained by a ?2a a ?2a lattice with the space group C2/c, and for M = Sr and Yb a ?2a 2a ?2a monoclinic lattice with P2/m. On the other hand, no phase transition is observed for M = Lu, indicating that a Cd4 tetrahedron at the cluster center remains disordered down to the lowest temperature, i.e. 16 K. It is shown that the volume inside the Cd20 dodecahedron plays a crucial role in the occurrence of the phase transition, and long-term aging in particular promotes the phase transition for late rare-earth elements such as Ho, Er and Tm, suggesting that the transition is sensitive to and is even hindered by disorder such as atomic vacancies. The absence of the transition for M = Lu is attributed to the highest activation energy for the transition due to the smallest volume inside the Cd20 dodecahedron. PMID:23685563

  11. 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)

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

    2014-05-01

    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.

  12. 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

    Hu, Yuebo; Qiu, Jianbei Song, Zhiguo; Zhou, Dacheng

    2014-02-28

    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.

  13. Up/down conversion luminescence and charge compensation investigation of Ca0.5Y1-x(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors

    NASA Astrophysics Data System (ADS)

    Mahalingam, Venkatakrishnan; Thirumalai, Jagannathan; Krishnan, Rajagopalan; Mantha, Srinivas

    2016-01-01

    Microstructures of Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors were prepared via the solid-state reaction method. X-ray diffraction, scanning electron microscopy and photoluminescence were used to characterize the prepared phosphor samples. The results reveal that the phosphor samples have single phase scheelite structures with tetragonal symmetry of I41/a. The down/up conversion photoluminescence of the Ca0.5Y(1-x)(WO4)2:xLn3+ (Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er) phosphors properties reveal characteristic visible emissions. The energy transfer process, fluorescence lifetime and color coordinates are discussed in detail. Furthermore, the phosphor Ca0.5Y(1-x)(WO4)2:xPr3+ co-doped with alkali chlorides shows the enhancement of luminescence, which was found in the sodium chloride co-doped powder phosphor. The photometric characteristics indicate the suitability of the inorganic powder phosphors for solid-state lighting and display applications.

  14. Synthetic and spectroscopic studies of vanadate glaserites II: Photoluminescence studies of Ln:K{sub 3}Y(VO{sub 4}){sub 2} (Ln=Eu, Er, Sm, Ho, or Tm)

    SciTech Connect

    Kimani, Martin M. McMillen, Colin D. Kolis, Joseph W.

    2015-03-15

    Glaserite-type potassium yttrium double vanadates (K{sub 3}Y(VO{sub 4}){sub 2}) doped with Eu{sup 3+}, Er{sup 3+}, Sm{sup 3+}, Ho{sup 3+}, or Tm{sup 3+} have been synthesized by solid state reactions at 1000 °C for 48 h and their photoluminescence properties investigated. Efficient energy transfer from the vanadate group to the rare earth ion has been established by photoluminescence investigation. Ultraviolet excitation into the metal to ligand charge transfer band of the vanadate groups results in orange-red, blue and green emissions from Eu{sup 3+} (592 nm), Sm{sup 3+} (602 nm), Tm{sup 3+} (475 nm), Er{sup 3+} (553 nm), and Ho{sup 3+} (541–551 nm) dopant ions. The emission intensities of the lanthanide-doped K{sub 3}Y(VO{sub 4}){sub 2} powders were studied as a function of dopant ion concentrations. Over the concentration ranges studied, no emission quenching was observed for Eu{sup 3+} or Ho{sup 3+} dopants, while Er{sup 3+}, Sm{sup 3+} and Tm{sup 3+} dopants did exhibit such effects for dopant ion concentrations greater than 5%, probably due to cross relaxation processes. - Graphical abstract: Synthesis and photoluminescence in vanadate glaserites. - Highlights: • K{sub 3}Y(VO{sub 4}){sub 2} doped with Eu, Er, Tm, Sm, or Ho were synthesized via solid-state reactions. • Photoluminescence properties are investigated. • The lanthanide doped K{sub 3}Y(VO{sub 4}){sub 2} compounds revealed efficient energy transfer from the vanadate group to the rare earth ions. • The presented compounds are promising materials for light display systems, lasers, and optoelectronic devices.

  15. 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)

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

    1997-09-01

    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.

  16. NIR-responsive silica-coated NaYbF4:Er/Tm/Ho upconversion fluorescent nanoparticles with tunable emission colors and their applications in immunolabeling and fluorescent imaging of cancer cells

    PubMed Central

    Wang, Meng; Mi, Congcong; Zhang, Yixin; Liu, Jinling; Li, Feng; Mao, Chuanbin; Xu, Shukun

    2009-01-01

    NaYbF4: RE upconversion (UC) fluorescent nanoparticles (NPs) were synthesized with variable rare-earth dopants (RE= Er3+, Tm3+, or Ho3+, or a combination of these ions), from rare-earth stearate precursors in a water-ethanol-oleic acid system by using a two-phase solvothermal method. The NPs were shown to emit visible light such as orange, yellow, green, cyan, blue or pink light in response to near infrared (NIR) irradiation, and their emission colors could be simply tuned by changing either the co-dopant concentration or dopant species. The UC NPs were well-dispersed and spherical with an average size of 15~35 nm. They emitted strong UC fluorescence under the 980 nm NIR excitation. The effects of solvothermal reaction time and temperature on nanoparticle size and phase structure as well as UC fluorescence intensity were systematically studied. Water dispersibility was achieved by forming a silica coat on the surface of the UC NPs. After animo-functionalization, the silica-coated UC NPs were chemically conjugated with the rabbit anti-CEA8 antibody and then used as fluorescent biolabels for the immunolabeling and imaging of HeLa cells. The NIR-responsive multicolor visible light emission of these UC NPs will enable potential applications in biolabeling and multiplexed analysis because NIR light can penetrate tissue as deep as several inches and is safe to human body. PMID:20160878

  17. (α-NaYbF4:Tm3+)/CaF2 Core/Shell Nanoparticles with Efficient Near-Infrared to Near-Infrared Upconversion for High-Contrast Deep Tissue Bioimaging

    PubMed Central

    Chen, Guanying; Shen, Jie; Ohulchanskyy, Tymish Y.; Patel, Nayan J.; Kutikov, Artem; Li, Zhipeng; Song, Jie; Pandey, Ravindra K.; Ågren, Hans; Prasad, Paras N.; Han, Gang

    2012-01-01

    We describe the development of novel and biocompatible core/shell (α-NaYbF4:Tm3+)/CaF2 nanoparticles which exhibit highly efficient NIRin-NIRout upconversion (UC) for high contrast and deep bioimaging. When excited at ~980 nm, these nanoparticles emit photoluminescence (PL) peaked at ~800 nm. The quantum yield of this UC PL under low power density excitation (~0.3 W/cm2) is 0.6±0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via hetero-epitaxial growth of a biocompatible CaF2 shell which results in a 35-fold increase in the intensity of UC PL from the core. Small animal whole-body UC PL imaging with exceptional contrast (signal-to-background ratio of 310) is shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles (700 pmol/kg). High-contrast UC PL imaging of deep tissues is also demonstrated, using a nanoparticle-loaded synthetic fibrous mesh wrapped around rat femoral bone, and a cuvette with nanoparticle aqueous dispersion - covered with a 3.2-cm thick animal tissue (pork). PMID:22928629

  18. Structure determination of KScS₂, RbScS₂ and KLnS₂ (Ln = Nd, Sm, Tb, Dy, Ho, Er, Tm and Yb) and crystal-chemical discussion.

    PubMed

    Havlák, Lubomír; Fábry, Jan; Henriques, Margarida; Dušek, Michal

    2015-07-01

    The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α-NaFeO2 structure type in agreement with the ratio of the ionic radii r(3+)/r(+). KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S-S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S(2-)) and the bond-valence sums. PMID:26146403

  19. Evolution of the crystal and magnetic structure of the R2MnRuO7 (R = Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) family of pyrochlore oxides.

    PubMed

    Martínez-Coronado, R; Retuerto, M; Fernández, M T; Alonso, J A

    2012-07-28

    The members of the family of pyrochlore oxides with the formula R(2)MnRuO(7) (R = Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have been synthesized and characterized. Polycrystalline samples were prepared by a soft chemistry procedure involving citrates of the different metal ions, followed by thermal treatments in air or O(2) pressure. The crystallographic and magnetic structures have been analysed from X-ray diffraction (XRD) and neutron powder diffraction (NPD) data, in complement with magnetic measurements; the evolution along the series of the crystallographic parameters (unit-cell parameters, bond distances and angles) is discussed. In R(2)MnRuO(7) pyrochlores, Mn and Ru ions statistically occupy the 16c sites in a cubic unit cell with space group Fd ̅3m, which defines an intrinsic frustrated three-dimensional system. In all the cases, the low-temperature NPD data unveils an antiferromagnetic coupling of two subsets of Mn(4+)/Ru(4+) spins, indicating that the magnetic frustration is partially relieved by the random distribution of Mn and Ru over the 16c sites. At lower temperatures there is a polarization of the R(3+) magnetic moments, which also participate in the magnetic structure, when a magnetic rare earth is present. PMID:22669397

  20. Novel light-conversion hybrids of SBA-16 functionalized with rare earth (Eu3+, Nd3+, Yb3+) complexes of modified 2-methyl-9-hydroxyphenalenone and 1,10-phenanthroline

    NASA Astrophysics Data System (ADS)

    Gu, Yan-Jing; Yan, Bing; Qiao, Xiao-Fei

    2013-03-01

    Novel rare earth complex-functionalized mesoporous SBA-16-type hybrid materials are synthesized by the co-condensation of modified 2-methyl-9-hydroxyphenalenone (MHPOSi), from modified 3-(triethoxysilyl)-propyl isocyanate (TEPIC), and tetraethoxysilane (TEOS) in the presence of Pluronic F127 as a template. These inorganic-organic mesoporous hybrids are characterized by FT-IR spectra, small-angle X-ray diffraction (SAXRD), N2 adsorption-desorption measurements, thermal analysis and spectroscopy. Their photophysical properties, which show novel light conversion properties, are discussed in detail. The Eu3+ hybrid system shows ultraviolet excitation and visible emission, and the Nd+ and Yb3+ hybrids exhibit visible excitation and NIR emission.

  1. 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

    Babo, Jean-Marie; Albrecht-Schmitt, Thomas E.

    2013-01-15

    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.

  2. 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

    Zhang, Zhi-Jun; Lin, Xiao; Graduate School of Chinese Academy of Science, Beijing, 100039 ; Zhao, Jing-Tai; Zhang, Guo-Bin

    2013-02-15

    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.

  3. Near infrared emission of TbAG:Ce3+,Yb3+ phosphor for solar cell applications

    NASA Astrophysics Data System (ADS)

    Meshram, N. D.; Yadav, P. J.; Pathak, A. A.; Joshi, C. P.; Moharil, S. V.

    2016-05-01

    Luminescent materials doped with rare earth ions are used for many devices such as optical amplifiers in telecommunication, phosphors for white light emitting diodes (LEDs), displays, and so on. Recently, they also have attracted a great interest for photovoltaic applications to improve solar cell efficiency by modifying solar spectrum. Crystal silicon (c-Si) solar cells most effectively convert photons of energy close to the semiconductor band gap. The mis-match between the incident solar spectrum and the spectral response of solar cells is one of the main reasons to limit the cell efficiency. The efficiency limit of the c-Si has been estimated to be 29% by Shockley and Queisser. However, this limit is estimated to be improved up to 38.4% by modifying the solar spectrum by a quantum cutting (down converting) phosphor which converts one photon of high energy into two photons of lower energy. The phenomenon such as the quantum cutting or the down conversion of rare earth ions have been investigated since Dexter reported the possibility of a luminescent quantum yield greater than unity in 1957. In the past, the quantum cutting from a vacuum ultraviolet photon to visible photons for Pr3+, Gd3+,Gd3+-Eu3+, and Er3+-Tb3+ had been studied. Recently, a new quantum cutting phenomenon from visible photon shorter than 500 nm to two infrared photons for Tb3+-Yb3+, Pr3+-Yb3+, and Tm3+-Yb3+ has been reported. The Yb3+ ion is suitable as an acceptor and emitter because luminescent quantum efficiency of Yb3+ is close to 100% and the energy of the only excited level of Yb3+ (1.2 eV) is roughly in accordance with the band gap of Si (1.1 eV). In addition, the Ce3+-doped Tb3Al5O12 (TbAG), used as a phosphor for white LED, has broad absorption bands in the range of 300-500 nm due to strong ligand field and high luminescent quantum efficiency. Therefore, the Ce3+ ions in the TbAG can be suitable as an excellent sensitizing donor for down conversion materials of Si solar cells. In this paper, Ce3+ -Yb3+-codoped TbAG ceramics were prepared and the energy transfer (ET) including down conversion mechanism in Ce3+ - Yb3+ codoped TbAG ceramics have been evaluated by the photoluminescence (PL), the photoluminescence excitation (PLE), the lifetime and the quantum yield (QY), which was measured directly using an integrating sphere.

  4. Green upconversion in Y2O3:Yb nanopowder

    NASA Astrophysics Data System (ADS)

    Horvat, Darja; Lazar, Dušan; Možina, Janez; Križan, Janez; Diaci, Janez; Terzić, Mira

    2015-01-01

    Green emission lines, in addition to the blue and the red, were observed upon 980 nm excitation in yttrium oxide (Y2O3) nanopowder codoped with Yb and Tm, synthesized by the chemical combustion method. Upconversion emission studies suggest that the number and characteristics of the green lines are influenced by the annealing temperature as well as by the Yb/Tm concentration ratio, opening possibilities for new customized applications. The chromaticity properties of the upconversion spectra were quantified by the Commission Internationale de l'éclairage coordinate analysis.

  5. Chemical bond parameters and photoluminescence of a natural-white-light Ca{sub 9}La(VO{sub 4}){sub 7}:Tm{sup 3+},Eu{sup 3+} with one O{sup 2−}→V{sup 5+} charge transfer and dual f-f transition emission centers

    SciTech Connect

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

    2015-01-15

    The relationship between the photoluminescence properties and the crystal structure of undoped, Eu{sup 3+} or/ and Tm{sup 3+} singly or codoped Ca{sub 9}La(VO{sub 4}){sub 7} (CLaVO) samples was discussed. Under the excitation of UV light, CLaVO:Tm{sup 3+}, CLaVO, and CLaVO:Eu{sup 3+} exhibit the characteristic emissions of Tm{sup 3+} ({sup 1}G{sub 4}→{sup 3}H{sub 6}, blue), O{sup 2−}→V{sup 5+} charge transfer (CT), and Eu{sup 3+} ({sup 5}D{sub 0}→{sup 7}F{sub 2}, red), respectively. By adjusting the doping concentration of Tm{sup 3+} and Eu{sup 3+} 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 σ(h{sub e{sub i}})=√((1/N)∑{sub i=1}{sup N}(h{sub e{sub i}}−μ){sup 2}) (h{sub e{sub i}}=(f{sub c{sub i}}α{sub b{sub i}}){sup 1/2}Q{sub B{sub i}} and μ=(1/N)∑{sub i=1}{sup N}h{sub e{sub i}}), was proposed to quantitatively express the distortion degree of VO{sub 4}{sup 3−} from that of an ideal tetrahedron. The maximum change of EFSD comes from the [VO{sub 4}]{sup −} tetrahedra in CLaVO sample by comparison with that of EFSD of isostructural Ca{sub 9}Gd(VO{sub 4}){sub 7}. This is possible the key reason that the undoped CLaVO sample has self-activated emission while the self-activated emission of its isostructural Ca{sub 9}Gd(VO{sub 4}){sub 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 O{sup 2−}-Eu1{sup 3+} (O{sup 2−}-Tm1{sup 3+}), O{sup 2−}-Eu2{sup 3+} (O{sup 2−}-Tm2{sup 3+}), and O{sup 2−}-Eu3{sup 3+} (O{sup 2−}-Tm3{sup 3+}). 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. - Graphical abstracts: The relationship between the photoluminescence properties and the crystal structure of undoped, Eu{sup 3+} or/ and Tm{sup 3+} singly or codoped Ca{sub 9}La(VO{sub 4}){sub 7} (CLaVO) samples was discussed experimentally and theoretically. - Highlights: ●The photoluminescence properties of Ca{sub 9}La(VO{sub 4}){sub 7}:Eu, Tm were measured. ●The tunable color including white emission can be obtained. ●The important chemical bond parameters of O-V were calculated quantitatively. ●The standard deviation of environmental factor of every bond was proposed. ●The theoretical analysis of the self-activated emission for Ca{sub 9}La(VO{sub 4}){sub 7} was given.

  6. Direct synthesis of hexagonal NaGdF₄ nanocrystals from a single-source precursor: upconverting NaGdF₄ :Yb³⁺ ,Tm³⁺ and its composites with TiO₂ for near-IR-driven photocatalysis.

    PubMed

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

    2014-09-01

    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

  7. Triaxial strongly deformed bands in {sup 160,161}Tm

    SciTech Connect

    Teal, C.; Lagergren, K.; Aguilar, A.; Riley, M. A.; Hartley, D. J.; Simpson, J.; Joss, D. T.; Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; Zhu, S.; Garg, U.; Kondev, F. G.; Wang, X.; Ragnarsson, I.

    2008-07-15

    High-spin states in {sup 160,161}Tm were populated using the {sup 128}Te({sup 37}Cl, 5n and 4n) reactions at a beam energy of 170 MeV. Emitted {gamma} rays were detected in the Gammasphere spectrometer. Two rotational bands with high moments of inertia were discovered, one assigned to {sup 160}Tm, while the other tentatively assigned to {sup 161}Tm. These sequences display features similar to bands observed in neighboring Er, Tm, Yb, and Lu nuclei which have been discussed in terms of triaxial strongly deformed structures. Cranked Nilsson Strutinsky calculations have been performed that predict well-deformed triaxial shapes at high spin in {sup 160,161}Tm.

  8. Yb14-xTmxMnSb11 (0

    NASA Astrophysics Data System (ADS)

    Roudebush, John H.; Grebenkemper, Jason; Hu, Yufei; Kazem, Nasrin; Abdusalyamova, M. N.; Kauzlarich, Susan M.

    2014-03-01

    The compounds, Yb14-xTmxMnSb11 (0Tm was determined from wavelength dispersive microprobe analysis to be x=0.45 (1). Single crystal data are consistent with the Ca14AlSb11 structure type and one formula unit can be described as consisting of 14 Yb2+ cations, MnSb4 tetrahedron, Sb3 linear anion and 4 Sb3- 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 Yb14MnSb11 is less than 1%. The magnetic susceptibility of samples prepared by Sn flux with the nominal composition of Yb14-xTmxMnSb11 (x=0.1, 0.2, 0.3, and 0.4), show that these phases are ferromagnetic at low temperature with the TC 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 Tm3+ and a negative magnetoresistance ratio (MR=[(ρ(H)-ρ(0))/ρ(H)]×100%) of 18% at 3 T is observed.

  9. Resonant photo-ionization of Yb+ to Yb2+

    NASA Astrophysics Data System (ADS)

    Heugel, Simon; Fischer, Martin; Elman, Vladimir; Maiwald, Robert; Sondermann, Markus; Leuchs, Gerd

    2016-01-01

    We demonstrate the controlled creation of a {}174{{Yb}}2+ ion by photo-ionizing {}174{{Yb}}+ with weak continuous-wave lasers at ultraviolet wavelengths. The photo-ionization is performed by resonantly exciting transitions of the {}174{{Yb}}+ ion in three steps. Starting from an ion crystal of two laser-cooled {}174{{Yb}}+ ions localized in a radio-frequency trap, the verification of the ionization process is performed by characterizing the properties of the resulting mixed-species ion-crystal. The obtained results facilitate fundamental studies of physics involving {{Yb}}2+ ions.

  10. OncoLogicTM

    EPA Science Inventory

    OncoLogicTM - A Computer System to Evaluate the Carcinogenic Potential of Chemicals
    OncoLogicTM is a software program that evaluates the likelihood that a chemical may cause cancer. OncoLogicTM has been peer reviewed and is being rele...

  11. Amphiphilic silane modified NaYF4:Yb,Er loaded with Eu(TTA)3(TPPO)2 nanoparticles and their multi-functions: dual mode temperature sensing and cell imaging

    NASA Astrophysics Data System (ADS)

    Chen, Boting; Dong, Biao; Wang, Jing; Zhang, Shuang; Xu, Lin; Yu, Wei; Song, Hongwei

    2013-08-01

    Rare-earth upconversion nanophosphors (UCNPs) have become one of the most promising luminescent materials for bio-applications, but their use still meets some limitations by difficulties in obtaining biocompatible UCNPs. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into hydrophilic ones by amphiphilic silane modification with ultrathin thickness at room temperature (RT). In this strategy, the coating layers can also afford the place for loading with Eu(TTA)3(TPPO)2 complex which displays down conversion luminescence (DCL). Due to the UC and DC properties, we achieved the dual mode physiological range temperature sensing and dual mode cell imaging. Such novel nanomaterials offer a new surface modification strategy for the NPs that are formed in the oil phase for bio-applications.Rare-earth upconversion nanophosphors (UCNPs) have become one of the most promising luminescent materials for bio-applications, but their use still meets some limitations by difficulties in obtaining biocompatible UCNPs. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into hydrophilic ones by amphiphilic silane modification with ultrathin thickness at room temperature (RT). In this strategy, the coating layers can also afford the place for loading with Eu(TTA)3(TPPO)2 complex which displays down conversion luminescence (DCL). Due to the UC and DC properties, we achieved the dual mode physiological range temperature sensing and dual mode cell imaging. Such novel nanomaterials offer a new surface modification strategy for the NPs that are formed in the oil phase for bio-applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02670a

  12. Tm, Pr, and Tb impurities in a metallic host

    NASA Astrophysics Data System (ADS)

    Lustfeld, H.

    1980-05-01

    Starting with a generalized Anderson Hamiltonian and a Schrieffer-Wolff transformation for R.E. systems a Hamiltonian H r is derived which is appropriate for Tm, Pr and to a lesser extent for Tb impurities in a metallic host. It is shown that this Hamiltonian contains the Kondo Hamiltonian and that of Cocqblin and Schrieffer (which is valid for Ce and Yb impurities) as special cases. To investigate the properties of the Hamiltonian, crystal field effects are neglected and the equation-of-motion-method is applied. The corresponding system of 6 or 8 coupled integral equations is solved. The solution allows a discussion of the ferromagnetic and antiferromagnetic couplings which normally both occur. The condition for only ferromagnetic coupling of H r is given. This condition is fulfilled in Tb 4+ impurities. The resistivity is calculated for Pr 2+, Pr 3+, Tm 2+, Tm 3+ and Tb 3+ impurities.

  13. Ultraviolet upconversion luminescence of Gd{sup 3+} and Eu{sup 3+} in nano-structured glass ceramics

    SciTech Connect

    Lin, Hang; Chen, Daqin; Yu, Yunlong; Yang, Anping; Zhang, Rui; Wang, Yuansheng

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Ultraviolet upconversion emissions of Eu{sup 3+} and Gd{sup 3+} are rarely studied. Black-Right-Pointing-Pointer Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. Black-Right-Pointing-Pointer Ultraviolet upconversion signal are found greatly enhanced after crystallization. Black-Right-Pointing-Pointer It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu{sup 3+} ({sup 5}H{sub 3-7}, {sup 5}G{sub 2-6}, {sup 5}L{sub 6} {yields} {sup 7}F{sub 0}) and Gd{sup 3+} ({sup 6}I{sub J}, {sup 6}P{sub J} {yields} {sup 8}S{sub 7/2}) are studied in the Eu{sup 3+} (or Gd{sup 3+}) doped SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} precursor glasses and glass ceramics containing {beta}-YF{sub 3} nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb{sup 3+} to Tm{sup 3+}, then further to Eu{sup 3+} or Gd{sup 3+} is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of {beta}-YF{sub 3} nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.

  14. Continuous wave diode pumped Yb:LLF and Yb:NYF lasers

    NASA Astrophysics Data System (ADS)

    Yasukevich, A. S.; Kisel, V. E.; Kurilchik, S. V.; Grigoriev, S. V.; Kuleshov, N. V.; Gordeev, E. Yu.; Korableva, S. L.; Naumov, A. K.; Semashko, V. V.

    2009-11-01

    Experimental and theoretical results of investigation of CW Yb:LiLuF 4 (Yb:LLF) and Yb:Na 4Y 6F 22 (Yb:NYF) lasers under longitudinal diode laser pump are reported. Slope efficiencies of 41%, 58% with 0.21, 0.53 W of output powers were obtained for the Yb:LLF and Yb:NYF lasers, correspondingly. The Yb:NYF laser demonstrated tunability in the region from 1005 to 1061 nm. The mathematical modelling of CW laser operation predicts under optimized laser parameters optical to optical efficiencies of about 55% and 51% for Yb:LLF and Yb:NYF lasers, respectively.

  15. CLOMP_TM

    Energy Science and Technology Software Center (ESTSC)

    2012-06-01

    The CLOMP_TM benchmark was developed to measure the overheads of various mechanisms used to guarantee the generation of correct results in threaded code even when multiple threads might be accessing and/or updating the same memory location at the same time. This includes widely supported mechanisms like OpenMP Atomic and Open MP Critical as well as new mechanisms like Transactional Memory (TM) and Speculative Execution (SE) of threads. The CLOMP_TM benchmark is highly configurable to allowmore » a variety of problem sizes, atomic update region sizes, and potential race condition opportunities to be studied. A wide variety of checks are done on the results to verify the expected answer was actuallyl generated. Thus CLOMP_TM can be used both to measure the overhead for various mechanisms and to check the correctness of their implementation.« less

  16. 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

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

    2013-01-01

    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

  17. A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer

    NASA Astrophysics Data System (ADS)

    Marciniak, L.; Prorok, K.; Francés-Soriano, L.; Pérez-Prieto, J.; Bednarkiewicz, A.

    2016-02-01

    The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ~980 to the more relevant ~808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd --> Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ~808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale. Electronic supplementary information (ESI) available: Characterization, structural and morphological characterization of nanocrystals, the measurement setup. See DOI: 10.1039/c5nr08223d

  18. High power ytterbium (Yb(3+))-doped fibre laser operating in the 1.12 micron region

    NASA Astrophysics Data System (ADS)

    Mackechnie, C. J.; Barnes, W. L.; Hanna, D. C.; Townsend, J. E.

    1993-01-01

    Results are presented for high power (greater than 0.5 W) Yb(3+) fiber lasers operating at a wavelength of around 1120 nm pumped either by Nd:YAG (1.064 micron) or Nd:YLF (1.047 micron) lasers. The use of this laser as a single-wavelength pump for a Tm(3+) ZBLAN upconversion fiber laser is also demonstrated.

  19. Valences of dopants in Eu2+ persistent luminescence materials

    NASA Astrophysics Data System (ADS)

    Lastusaari, M.; Brito, H. F.; Carlson, S.; Hölsä, J.; Laamanen, T.; Rodrigues, L. C. V.; Welter, E.

    2014-04-01

    The existence and effect of different rare earth (R2+/3+/IV) ions in SrAl2O4:Eu2+,R3+ and M2MgSi2O7:Eu2+,R3+ (M: Sr, Ba) persistent luminescence materials was studied with XANES (x-ray absorption near edge structure) measurements at HASYLAB/DESY (Hamburg, Germany) and MAX-lab (Lund, Sweden). The experiments were carried out at 298 K for selected rare earth (co-)dopants (Eu2+; Ce3+, Nd3+, Sm3+, Dy3+ and Yb3+). The co-existence of Eu2+ and Eu3+ was observed in all materials. The co-dopants were always in the trivalent form.

  20. GEOMAG[TM] Paradoxes

    ERIC Educational Resources Information Center

    Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

    2007-01-01

    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,

  1. GEOMAG[TM] Paradoxes

    ERIC Educational Resources Information Center

    Defrancesco, Silvia; Logiurato, Fabrizio; Karwasz, Grzegorz

    2007-01-01

    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,…

  2. Structure and Properties of YbZnSn, YbAgSn, and Yb 2Pt 2Pb

    NASA Astrophysics Data System (ADS)

    Pttgen, Rainer; Arpe, Petra E.; Felser, Claudia; Kumann, Dirk; Mllmann, Ralf; Mosel, Bernd D.; Knnen, Bernd; Kotzyba, Gunter

    1999-07-01

    YbZnSn, YbAgSn, and Yb2Pt2Pb were synthesized by reacting the elements in sealed tantalum tubes in a high-frequency furnace. The structures of YbAgSn and Yb2Pt2Pb were refined from single crystal X-ray data: YbAgPb type, Poverline6m2, a=479.2(2) pm, c=1087.3(3) pm, wR2=0.050, BASF=0.34(8), 509 F2 values, 18 variables for YbAgSn and Er2Au2Sn type, a=776.0(1) pm, c=701.8(2) pm, wR2=0.072, 426 F2 values, 18 variables for Yb2Pt2Pb. The lattice constants of YbZnSn are confirmed: NdPtSb type, P63mc, a=464.7(1) pm, c=747.7(2) pm. The stannides YbZnSn and YbAgSn crystallize with superstructures of the AlB2 type. The zinc (silver) and tin atoms form ordered Zn3Sn3 and Ag3Sn3 hexagons, respectively. The stacking sequences for the differently oriented hexagons are AB, AB for YbZnSn and ABC, ABC for YbAgSn. While exclusively Zn-Sn intralayer interactions were observed in YbZnSn, intralayer Ag-Sn and significant Sn-Sn interlayer interactions at 318 pm occur in YbAgSn. The [ZnSn] and [AgSn] polyanions in YbZnSn and YbAgSn, respectively, have a pronounced two-dimensional character. This picture of chemical bonding in YbAgSn is confirmed by TB-LMTO-ASA band structure calculations. The partial densities-of-states and the valence charge densities are discussed. The magnetic (no long-range ordering, Yb2+) and the resistivity measurements (metallic behavior) are in excellent agreement with the electronic structure calculations. Yb2Pt2Pb crystallizes with the Er2Au2Sn structure, a ternary derivative of the Zr3Al2 type. This structure is composed of distorted AlB2 and CsCl related slabs of compositions YbPt2 and YbPb. Yb2Pt2Pb shows paramagnetic behavior (4.30.4 ?B/Yb) indicating trivalent ytterbium. Magnetic susceptibility measurements on YbZnSn and YbAgSn show Pauli paramagnetism with room temperature susceptibilities of 2.5(1)10-9 and 4.6(1)10-9 m3/mol. Electrical resistivity measurements indicate metallic conductivity with specific resistivities of 44040 ??cm (YbZnSn) and 49040 ??cm (YbAgSn) at 300 K. 119Sn Mssbauer spectra of YbZnSn show a single signal at room temperature with an isomer shift of ?=1.85(1) mm/s. YbAgSn shows two superimposed signals at 78 K: a singlet at ?=1.94(1) mm/s and a second signal at ?=1.99(1) mm/s subjected to quadrupole splitting of ?EQ=1.35(1) mm/s, in agreement with the two crystallographically different tin sites.

  3. Analysis of the Petunia TM6 MADS box gene reveals functional divergence within the DEF/AP3 lineage.

    PubMed

    Rijpkema, Anneke S; Royaert, Stefan; Zethof, Jan; van der Weerden, Gerard; Gerats, Tom; Vandenbussche, Michiel

    2006-08-01

    Antirrhinum majus DEFICIENS (DEF) and Arabidopsis thaliana APETALA3 (AP3) MADS box proteins are required to specify petal and stamen identity. Sampling of DEF/AP3 homologs revealed two types of DEF/AP3 proteins, euAP3 and TOMATO MADS BOX GENE6 (TM6), within core eudicots, and we show functional divergence in Petunia hybrida euAP3 and TM6 proteins. Petunia DEF (also known as GREEN PETALS [GP]) is expressed mainly in whorls 2 and 3, and its expression pattern remains unchanged in a blind (bl) mutant background, in which the cadastral C-repression function in the perianth is impaired. Petunia TM6 functions as a B-class organ identity protein only in the determination of stamen identity. Atypically, Petunia TM6 is regulated like a C-class rather than a B-class gene, is expressed mainly in whorls 3 and 4, and is repressed by BL in the perianth, thereby preventing involvement in petal development. A promoter comparison between DEF and TM6 indicates an important change in regulatory elements during or after the duplication that resulted in euAP3- and TM6-type genes. Surprisingly, although TM6 normally is not involved in petal development, 35S-driven TM6 expression can restore petal development in a def (gp) mutant background. Finally, we isolated both euAP3 and TM6 genes from seven solanaceous species, suggesting that a dual euAP3/TM6 B-function system might be the rule in the Solanaceae. PMID:16844905

  4. A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer.

    PubMed

    Marciniak, L; Prorok, K; Francés-Soriano, L; Pérez-Prieto, J; Bednarkiewicz, A

    2016-02-25

    The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ∼980 to the more relevant ∼808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd → Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ∼808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale. PMID:26865210

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

    PubMed

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

    2010-03-01

    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

  6. Lifetime measurement in ^170Yb

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Krücken, R.; Beausang, C. W.; Casten, R. F.; Cooper, J. R.; Cederkäll, J.; Caprio, M.; Novak, J. R.; Zamfir, N. V.; Barton, C.

    1999-10-01

    The nature of the low lying K^π=0^+ excitations in deformed nuclei have recently been subject of intense discussion. In this context we present results from a Coulomb excitation experiment on ^170Yb using a 70MeV ^16O beam on a gold backed, 1.5 mg/cm^2 thick ^170Yb target. The beam was delivered by the ESTU tandem accelerator of WNSL at Yale University. Gamma rays were detected by the YRAST Ball array in coincidence with back-scattered ^16O particles, which were detected in an array of 8 solar cells. Lineshapes were observed for several transitions from collective states in ^170Yb and the lifetimes for those states were extracted using a standard DSAM analysis. The results will be presented together with a short introduction to the solar cell array at Yale (SCARY) that was used to make angular selection of the excited ^170Yb nuclei. This work is supported by the US-DOE under grant numbers DE-FG02-91ER-40609 and DE-FG02-88ER-40417.

  7. Fabrication of Yb-123 Tapes

    SciTech Connect

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

    2000-11-15

    While Bi-2223 tapes have been the workhorses of the superconductor industry, their poor performance in applied magnetic fields restrict their use to below 30 K. Melt-processing of Ag-clad Yb-123 PIT tapes offers a simple and scalable technique for fabricating long-length HTS conductors capable of being used at 77 K. Under reduced oxygen partial pressure, the peritectic temperature of Yb-123 is below the melting point of Ag, and this facilitates the adaptation of melt-texturing methods for fabricating these tapes. The effect of melt-processing temperature on current density was also explored; a temperature of 965 C yielded optimal critical current values. The critical current density achieved at 4.2 K was 20,000 A/cm{sup 2}, corresponding to a critical current of 52 A. Based on the above results, an optimal processing zone for melt-processing of Ag-clad Yb-123 tapes was determined. These results hold promise for melt-processing of Ag-clad Yb-123 tapes as an alternative to Bi-2223 PIT technology.

  8. Synthesis, crystal structure, and magnetism of A2Co12As7 (A=Ca, Y, Ce-Yb)

    NASA Astrophysics Data System (ADS)

    Tan, Xiaoyan; Ovidiu Garlea, V.; Chai, Ping; Geondzhian, Andrey Y.; Yaroslavtsev, Alexander A.; Xin, Yan; Menushenkov, Alexey P.; Chernikov, Roman V.; Shatruk, Michael

    2016-04-01

    Ternary intermetallics, A2Co12As7 (A=Ca, Y, Ce-Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P63/m variant of the Zr2Fe12P7 structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A2Co12As7 is generally characterized by ferromagnetic ordering of Co 3d moments at 100-140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr-Sm to ferromagnetic for A=Ce and Eu-Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce2Co12As7 and Nd2Co12As7, respectively.

  9. Effects of Yb concentration on the spectroscopic properties of Yb: Y3Al5O12.

    PubMed

    Wang, Xiaodan; Xu, Xiaodong; Zeng, Xionghui; Zhao, Zhiwei; Jiang, Benxue; He, Xiaoming; Xu, Jun

    2006-01-01

    Yb:YAG single crystals with Yb doping concentration 5.4, 16.3, 27.1, 53.6, and 100 at.% were grown by the Czochralski process. The effects of Yb concentration on the absorption spectra (190-1100 nm), fluorescence spectra under 940 nm and X-ray excitation were studied. The concentration quenching of fluorescence was observed when the Yb doping concentration reaches to as high as 27.1at.% for Yb:YAG. Under 940 nm excitation, the influence of the self-absorption at 969 and 1029 nm on the fluorescence spectra is not evident when the Yb doping concentration is as high as 27.1at.%. However, it can greatly change the shape of fluorescence spectra of Yb:YAG when the Yb doping concentration reaches to above 53.6 at.%. PMID:16344242

  10. YB48 the metal rich boundary of YB66; crystal growth and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Hossain, M. Anwar; Tanaka, Isao; Tanaka, Takaho; Khan, A. Ullah; Mori, Takao

    2015-12-01

    It was discovered that the well-known higher boride YB66, one of the first reported phonon glass electron crystals (PGEC), could be obtained in a much more metal-rich composition than previously thought possible. Using the floating zone growth method, YB48 single crystals with YB66 crystal structure could be obtained, and their thermoelectric properties measured. This expansion of the homogeneity range of the well-known YB66 compound is surprising and a new Y atomic site was discovered. YB48 exhibits much higher power factors than YB66 which increase rapidly with increasing temperature. The obtained dimensionless figure of merit of this compound at 990 K is approximately 30 times higher than that of previously reported YB66 samples, and higher than any other pristine higher boride. This discovery reveals YB48 as a promising high temperature thermoelectric material.

  11. Mode instability thresholds for Tm-doped fiber amplifiers pumped at 790 nm.

    PubMed

    Smith, Arlee V; Smith, Jesse J

    2016-01-25

    We use a detailed numerical model of stimulated thermal Rayleigh scattering to compute mode instability thresholds in Tm(3+)-doped fiber amplifiers. The fiber amplifies 2040 nm light using a 790 nm pump. The cross-relaxation process is strong, permitting power efficiencies of 60%. The predicted instability thresholds are compared with those in similar Yb(3+)-doped fiber amplifiers with 976 nm pump and 1060 nm signal, and are found to be higher, even though the heat load is much higher in Tm-doped amplifiers. The higher threshold in the Tm-doped fiber is attributed to its longer signal wavelength, and to stronger gain saturation, due in part to cross-relaxation heating. PMID:26832480

  12. Optical refrigeration of Yb3+:YAG nanocrystals

    NASA Astrophysics Data System (ADS)

    Nemova, Galina; Kashyap, Raman

    2015-03-01

    We have theoretically investigated the laser cooling process in Yb3+:YAG nanocrystals. We have developed an approach, which permits not only estimate the cooling process in Yb3+:YAG nanocrystals but compare this process with the laser cooling of the Yb3+:YAG bulk samples. The temperature dependences of all parameters of the system are taken into account. The cooperative effects such as re-absorption, the energy migration and cooperative luminescence have been considered.

  13. 75 FR 5071 - Lock + TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-01

    ... Energy Regulatory Commission Lock + \\TM\\ Hydro Friends Fund XXXI, LLC; Notice of Preliminary Permit... January 22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXI, LLC (Lock + Hydro) filed an... Lewis County, Missouri. The project would be located at the existing Mississippi River Lock and Dam...

  14. 75 FR 5068 - Lock + TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-01

    ... Energy Regulatory Commission Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC; Notice of Preliminary Permit... January 22, 2010. On January 8, 2010, Lock + \\TM\\ Hydro Friends Fund XXXIII, LLC (Lock + Hydro) filed an..., and Ralls County, Missouri. The project would to be located at the existing Mississippi River Lock...

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  16. The tmRNA website

    DOE PAGESBeta

    Hudson, C. M.; Williams, K. P.

    2014-11-05

    The transfer-messenger RNA (tmRNA) and its partner protein SmpB act together in resolving problems arising when translating bacterial ribosomes reach the end of mRNA with no stop codon. Their genes have been found in nearly all bacterial genomes and in some organelles. The tmRNA Website serves tmRNA sequences, alignments and feature annotations, and has recently moved to http: //bioinformatics.sandia.gov/tmrna/. New features include software used to find the sequences, an update raising the number of unique tmRNA sequences from 492 to 1716, and a database of SmpB sequences which are served along with the tmRNA sequence from the same organism.

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

    PubMed

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

    2014-09-01

    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

  18. EPR study of Yb-doped irradiated glasses

    NASA Astrophysics Data System (ADS)

    Ollier, N.; Planchais, R.; Boizot, B.

    2008-06-01

    Yb3+ reduction under β and γ irradiation has been studied in aluminoborosilicate glasses by EPR spectroscopy. From the Yb3+ EPR line variation, we demonstrate that more than one Yb3+ sites coexist in the pristine Yb-doped glasses. Reduction of Yb3+ into Yb2+ is observed for all integrated doses and Yb doping contents. For doses higher than 108 Gy, an Yb3+ ion environment change occurs, this change is correlated with a stabilization of the reduced Yb2+ state. The paramagnetic defect concentration displays a linear variation as a function of the logarithm of the dose. The glass doping with Yb2O3 leads to a substantial decrease of the defect concentration as well as a modification in the relative proportion of the defects produced. In particular, Yb doping tends to increase the relative content of Oxy defects.

  19. Thermoelectric properties of the Zintl phases Yb5M2Sb6 (M = Al, Ga, In).

    PubMed

    Aydemir, Umut; Zevalkink, Alex; Ormeci, Alim; Wang, Heng; Ohno, Saneyuki; Bux, Sabah; Snyder, G Jeffrey

    2015-04-21

    Zintl compounds with chemical formula Yb5M2Sb6 (M = Al, Ga, and In) form one of two known A5M2Pn6 structure types characterized by double chains of corner-linked MPn4 tetrahedra bridged by Pn2 dumbbells. High temperature electronic and thermal transport measurements were used to characterize the thermoelectric properties of Yb5M2Sb6 compounds. All samples were found to exhibit similar high p-type carrier concentrations, low resistivity and low Seebeck coefficients in agreement with the band structure calculations. These results, combined with previous studies, suggest that Yb5M2Sb6 compounds are semimetals (i.e., they lack an energy gap between the valence and conduction bands), in contrast to the semiconducting alkaline earth (Ca, Sr, Ba) and Eu based A5M2Sb6 compounds. Yb5M2Sb6 compounds have very low lattice thermal conductivity, comparable to other closely related A5M2Sb6 and A3MSb3 phases. However, due to the semimetallic behaviour, the figure of merit of investigated samples remains low (zT < 0.15). PMID:25670617

  20. Optical waveguides in Yb:SBN crystals fabricated by swift C3+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Guiyuan; Dong, Ningning; Wang, Jun; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

    2016-01-01

    We report on the fabrication of optical planar waveguides supporting both the TE and TM confinements in Yb:SBN crystal by swift C3+ ions irradiation. A combination of the micro-photoluminescence and micro-Raman investigations have evidenced the presence of lattice distortion, damage and disordering of the SBN network along the ion irradiation path, with these effects being at the basis of the refractive index modification. The enhanced micro-photoluminescence and micro-Raman intensity in the waveguide volumes show the potential application of the obtained waveguides as active laser gain media.

  1. Definition of an intramolecular Eu-to-Eu energy transfer within a discrete [Eu2L] complex in solution.

    PubMed

    Nonat, Aline; Regueiro-Figueroa, Martín; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos; Charbonnière, Loïc J

    2012-06-25

    Ligand L, based on two do3a moieties linked by the methylene groups of 6,6'-dimethyl-2,2'-bipyridine, was synthesized and characterized. The addition of Ln salts to an aqueous solution of L (0.01 M Tris-HCl, pH 7.4) led to the successive formation of [LnL] and [Ln(2)L] complexes, as evidenced by UV/Vis and fluorescence titration experiments. Homodinuclear [Ln(2)L] complexes (Ln = Eu, Gd, Tb, Yb, and Lu) were prepared and characterized. The (1)H and (13)C NMR spectra of the Lu and Yb complexes in D(2)O solution (pD = 7.0) showed C(1) symmetry of these species in solution, pointing to two different chemical environments for the two lanthanide cations. The analysis of the chemical shifts of the Yb complex indicated that the two coordination sites present square antiprismatic (SAP) coordination environments around the metal ions. The spectroscopic properties of the [Tb(2)L] complex upon ligand excitation revealed conventional behavior with τ(H2O) = 2.05(1) ms and ϕ(H2O) = 51%, except for the calculation of the hydration number obtained from the luminescent lifetimes in H(2)O and D(2)O, which pointed to a non-integer value of 0.6 water molecules per Tb(III) ion. In contrast, the Eu complex revealed surprising features such as: 1) the presence of two and up to five components in the (5)D(0)→(7)F(0) and (5)D(0)→(7)F(1) emission bands, respectively; 2) marked differences between the normalized spectra obtained in H(2)O and D(2)O solutions; and 3) unconventional temporal evolution of the luminescence intensity at certain wavelengths, the intensity profile first displaying a rising step before the occurrence of the expected decay. Additional spectroscopic experiments performed on [Gd(2-x)Eu(x)L] complexes (x = 0.1 and 1.9) confirmed the presence of two distinct Eu sites with hydration numbers of 0 (site I) and 2 (site II), and showed that the unconventional temporal evolution of the emission intensity is the result of an unprecedented intramolecular Eu-to-Eu energy-transfer process. A mathematical model was developed to interpret the experimental data, leading to energy-transfer rates of 0.98 ms(-1) for the transfer from the site with q=0 to that with q=2 and vice versa. Hartree-Fock (HF) and density functional theory (DFT) calculations performed at the B3LYP level were used to investigate the conformation of the complex in solution, and to estimate the intermetallic distance, which provided Förster radii (R(0)) values of 8.1 Å for the energy transfer from site I to site II, and 6.8 Å for the reverse energy transfer. These results represent the first evidence of an intramolecular energy-transfer equilibrium between two identical lanthanide cations within a discrete molecular complex in solution. PMID:22614945

  2. Phase equilibrium and intermediate phases in the Eu-Sb system

    SciTech Connect

    Abdusalyamova, M.N.

    2011-10-15

    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}.

  3. 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)

    Kaya, Necati; Tıraşoğlu, Engin; Apaydın, Gökhan; Aylıkcı, Volkan; Cengiz, Erhan

    2007-08-01

    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 α1 , K α2 , K β1 and K β2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV γ-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.

  4. CaF2:Yb laser ceramics

    NASA Astrophysics Data System (ADS)

    Akchurin, M. Sh.; Basiev, T. T.; Demidenko, A. A.; Doroshenko, M. E.; Fedorov, P. P.; Garibin, E. A.; Gusev, P. E.; Kuznetsov, S. V.; Krutov, M. A.; Mironov, I. A.; Osiko, V. V.; Popov, P. A.

    2013-01-01

    CaF2:Yb fluoride laser ceramics, prepared by hot-forming, exhibit the same optical properties as starting single crystals. Slope efficiency of the Сa0.95Yb0.05F2.05 is equal to 35% in the pulsed mode of laser operation. Decrease of ytterbium concentration in CaF2:Yb samples down to 3 mol.% resulted in the essential improvement of Сa0.97Yb0.03F2.03 thermal conductivity from 3.5 to 4.5 W/m K, but slightly decreased (down to 30%) slope efficiency of the samples under both pulsed and CW mode of operation. Alternative hot-pressing synthesis of CaF2:Yb fluoride laser ceramics provided materials with superior mechanical properties (microhardness Н = 3.2 GPa and fracture toughness К1С = 0.65 МPа m1/2) in comparison with hot-formed and/or single crystal CaF2:Yb specimens. For the first time, lasing has been observed for the novel aforementioned hot-pressed CaF2:Yb ceramics.

  5. Collapse dynamics of a {sup 176}Yb-{sup 174}Yb Bose-Einstein condensate

    SciTech Connect

    Chaudhary, G. K.; Ramakumar, R.

    2010-06-15

    In this paper, we present a theoretical study of a two-component Bose-Einstein condensate composed of ytterbium (Yb) isotopes in a three-dimensional anisotropic harmonic potential. The condensate consists of a mixture of {sup 176}Yb atoms which have a negative s-wave scattering length and {sup 174}Yb atoms having a positive s-wave scattering length. We study the ground-state as well as dynamic properties of this two-component condensate. Due to the attractive interactions between {sup 176}Yb atoms, the condensate of {sup 176}Yb undergoes a collapse when the particle number exceeds a critical value. The critical number and the collapse dynamics are modified due to the presence of {sup 174}Yb atoms. We use coupled two-component Gross-Pitaevskii equations to study the collapse dynamics. The theoretical results obtained are in reasonable agreement with the experimental results of Fukuhara et al. [Phys. Rev. A 79, 021601(R) (2009)].

  6. New intermetallics YbAu2In4 and Yb2Au3In5.

    PubMed

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

    2010-11-15

    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 β = 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 μ(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 μ(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

  7. 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

    Kazei, Z. A. Snegirev, V. V.; Andreenko, A. S.; Kozeeva, L. P.

    2011-08-15

    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.

  8. Growth of YbF 3-doped CaF 2 crystals and characterization of Yb 3+/Yb 2+ conversion

    NASA Astrophysics Data System (ADS)

    Nicoara, Irina; Stef, Marius; Pruna, Andreea

    2008-04-01

    Calcium fluoride crystals doped with YbF 3 and PbF 2-, NaF- and LiF-codoped were grown using the vertical Bridgman method. Transparent, high quality, with various high Yb 2+ contents in the as-grown crystals has been obtained using a special procedure. The optical absorption spectra reveal the characteristic ultraviolet (UV) absorption bands of the divalent Yb ions. Influence of the codoping with Pb 2+, Li + and Na + ions on the absorption spectra and on the Yb 2+ ions content has been studied. High-intensity emission bands in the near-UV spectral region, not reported before, have been observed for excitation by 230 nm. A comparison of our results with those obtained by other authors is also given.

  9. 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)

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

    2014-05-01

    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

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

    PubMed

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

    2015-02-01

    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

  11. Are there non-statistical effects in /sup 173/Yb(n,gamma)/sup 174/Yb

    SciTech Connect

    Pospisil, S.; Becvar, F.; Chrien, R.E.; Kopecky, J.

    1987-01-01

    The resonance-averaged capture of neutrons in /sup 173/Yb has been studied at energy of 2 keV. With a statistical significance of 99.5% an enhancement of E1-transition to the neutron 2QP levels in /sup 174/Yb is observed. 8 refs.

  12. Low temperature magnetism in YbPtBi by {sup 170}Yb Moessbauer spectroscopy

    SciTech Connect

    Le Bras, G.; Bonville, P.; Hodges, J.A.; Imbert, P.; Canfield, P.C.

    1994-05-24

    The authors report on {sup 170}Yb Moessbauer spectroscopy data in the cubic fcc alloy YbPtBi, in the temperature range 0.06--30 K. The zero field spectra show a two component structure above 1.5 K, which can be analyzed as due to 85% of Yb{sup 3+} ions at a site with cubic symmetry and 15% at a site with non-cubic symmetry. Below 0.3 K, the spectra are resolved and can also be interpreted in terms of two sites, but with a dominant non-cubic site ({approximately} 60%) with Yb ions bearing small magnetic moments. The spectra with a large applied magnetic field give information on the Yb{sup 3+} C.E.F. level scheme and on the exchange interaction. The relation of the Moessbauer data with the results of {micro}SR measurements is discussed.

  13. Valence fluctuation and magnetic ordering in EuNi2(P1-x Ge x )2 single crystals.

    PubMed

    Paramanik, U B; Bar, A; Das, Debarchan; Caroca-Canales, N; Prasad, R; Geibel, C; Hossain, Z

    2016-04-27

    Unusual phases and phase transitions are seen at the magnetic-nonmagnetic boundary in Ce-, Eu- and Yb-based compounds. EuNi2P2 is a very unusual valence fluctuating Eu system, because at low temperatures the Eu valence stays close to 2.5 instead of approaching an integer value. The Eu valence, and thus the magnetic property in this system, can be tuned by Ge substitution in the P site as EuNi2Ge2 is known to exhibit the antiferromagnetc (AFM) ordering of divalent Eu moments with [Formula: see text] K. We have grown EuNi2(P1-x Ge x )2 ([Formula: see text]) single crystals and studied their magnetic, thermodynamic and transport properties. Increasing Ge doping to x  >  0.4 results in a well-defined AFM ordered state with [Formula: see text] K for x  =  0.5. Moreover, the reduced value of magnetic entropy for x  =  0.5 at T N suggests the presence of valance fluctuation/the Kondo effect in this compound. Interestingly, the specific heat exhibits an enhanced Sommerfeld coefficient upon Ge doping. Subsequently, electronic structure calculations lead to a non-integral valence in EuNi2P2 but a stable divalent Eu state in EuNi2Ge2, which is in good agreement with the experimental results. PMID:26988385

  14. Listening and Legos[TM

    ERIC Educational Resources Information Center

    Morris, Pamela

    2012-01-01

    This simple exercise, performed in teams, gives students practice in listening to instructions, particularly when there are restrictions for the communication. The teams compete in a limited amount of time to build a Lego[TM] structure based on the instructions of one team member. Which team listens the best and is most successful?

  15. Resonantly pumped amplification in a Tm-doped large mode-area photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Sincore, Alex; Shah, Lawrence; Wysmolek, Mateusz; Ryan, Robert; Abdulfattah, Ali; Richardson, Martin

    2015-03-01

    Ultra-large mode area thulium-doped photonic crystal fibers (Tm:PCF) have enabled the highest peak powers in 2 micron fiber laser systems to date. However, Tm:PCFs are limited by slope efficiencies of <50% when pumped with 790 nm laser diodes. A well-known alternative is pumping at 1550 nm with erbium/ytterbium-doped fiber (Er/Yb:fiber) lasers for efficiencies approaching ~70%. However, these 1550 nm pump lasers are also relatively inefficient themselves. A recently demonstrated and more attractive approach to enable slope efficiencies over 90% in thuliumdoped step-index fibers is resonant pumping (or in-band pumping). This utilizes a high power thulium fiber laser operating at a shorter wavelength as the pump. In this manuscript, we describe an initial demonstration of resonant pumping in Tm:PCF. While the extracted power was still in the exponential regime due to pump power limitations, slope efficiencies in excess of ~64 have been observed, and there is still room for improvement. These initial results show promise for applying resonant pumping in Tm:PCF to improve efficiencies and facilitate high power scaling in ultralarge mode area systems.

  16. 75 FR 2129 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-14

    ... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XXX, LLC; Notice of Preliminary Permit... January 6, 2010. On November 13, 2009, Lock+ TM Hydro Friends Fund XXX, LLC filed an application, pursuant...,018 megawatt-hours. Applicant Contact: Wayne F. Krouse, Lock+ TM Hydro Friends Fund XXX, LLC,...

  17. 75 FR 78234 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XXXVIII, FFP Missouri 12, LLC, et al.; Notice of... Intervene December 8, 2010. Lock+TM Hydro Friends Fund XXXVIII........ Project No. 13744-000 FFP Missouri 12... No. 13780-000 On May 18, 2010, Lock+ TM Hydro Friends Fund XXXVIII, FFP Missouri 12, LLC, Allegheny...

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 Ω cm were obtained.

  19. Evidence from Tm anomalies for non-CI refractory lithophile element proportions in terrestrial planets and achondrites

    NASA Astrophysics Data System (ADS)

    Barrat, J. A.; Dauphas, N.; Gillet, P.; Bollinger, C.; Etoubleau, J.; Bischoff, A.; Yamaguchi, A.

    2016-03-01

    Thulium is a heavy rare earth element (REE) whose geochemical behavior is intermediate between Er and Yb, and that is not expected to be decoupled from these elements during accretion of planetary bodies and geological processes. However, irregularities in REE volatilities at higher temperature could have decoupled the REEs relative to one another during the early stages of condensation of the solar nebula. Indeed, positive Tm anomalies are found in some refractory inclusions from carbonaceous chondrites, and it is possible that large scale nebular reservoirs displaying positive or negative Tm anomalies were formed during the early history of the solar system. We analyzed a series of meteorites and terrestrial rocks in order to evaluate the existence of Tm anomalies in planetary materials. Relative to CIs (Ivuna-type carbonaceous chondrites), carbonaceous chondrites display unresolved or positive Tm anomalies, while most of the noncarbonaceous chondrites show slightly negative Tm anomalies. Quantification of these anomalies in terrestrial samples is complicated when samples display fractionated heavy REE patterns. Taking this effect into account, we show that the Earth, Mars, Vesta, the aubrite and ureilite parent bodies display small negative anomalies (Tm/Tm∗ ≈ 0.975), very similar to those found in ordinary and enstatite chondrites. We suggest that a slight negative Tm anomaly relative to CI is a widespread feature of the materials from the inner solar system. This finding suggests that CI chondrites may not be appropriate for normalizing REE abundances of most planetary materials as they may be enriched in a high-temperature refractory component with non-solar composition. The presence of Tm anomalies at a bulk planetary scale is, to this day, the strongest piece of evidence that refractory lithophile elements are not present in constant CI proportions in planetary bodies.

  20. Yb3AuGe2In3: an ordered variant of the YbAuIn structure exhibiting mixed-valent Yb behavior.

    PubMed

    Chondroudi, Maria; Peter, Sebastian C; Malliakas, Christos D; Balasubramanian, Mali; Li, Qing'An; Kanatzidis, Mercouri G

    2011-02-21

    Yb(3)AuGe(2)In(3) was obtained as large single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data show that Yb(3)AuGe(2)In(3) is an ordered variant of YbAuIn with lattice constants, a = b = 7.3153(8) Å and c = 4.4210(5) Å, and space group P(6)2m. The parent compound YbAuIn was also studied for comparison. YbAuIn crystallizes in the ZrNiAl structure type, hexagonal, P(6)2m space group with lattice parameters a = b = 7.7127(11) Å and c = 4.0294(8) Å. In Yb(3)AuGe(2)In(3), Ge substitutes for one of the two Au positions in the ternary compound Yb(3)Au(3)In(3). The structure can be described as alternating [Ge(2)In(3)] and [Yb(3)Au] slabs that stack along the c-axis. The magnetic susceptibility data follow a modified Curie-Weiss law. The effective magnetic moment μ(eff) of 0.52 μ(B)/Yb atom was deduced from the Curie constant and Curie-Weiss constant of θ(p) = -1.5 K indicating antiferromagnetic interactions in Yb(3)AuGe(2)In(3). X-ray absorption near edge spectroscopy (XANES) measurements indicate intermediate valency for Yb in both compounds. The metallic nature of both compounds was confirmed by the resistivity measurements. Specific heat data for Yb(3)AuGe(2)In(3) and YbAuIn give an electronic γ term of 31 and 84 mJ/mol·K(2), respectively, suggesting that the ternary analog is a "light" heavy fermion compound. PMID:21247072

  1. An Yb-Raman cascaded fiber laser with temporal stability

    NASA Astrophysics Data System (ADS)

    Wenliang, Wang; Jinyong, Leng; Yang, Gao; Shaofeng, Guo; Zongfu, Jiang

    2015-07-01

    We report a new structure of fiber laser, which has the advantages of temporal stability and wavelength agility. An Yb-Raman cascaded fiber oscillator generating 168 mW 1137 nm stable CW signal with 18.2% slope efficiency is demonstrated. In this fiber oscillator, the gain from both Yb ion and SRS effect is utilized. By comparison, the characteristics of the 1137 nm Yb-doped fiber laser are studied. The results show that the serious self-pulsation effect in the Yb-doped fiber laser is suppressed in the Yb-Raman cascaded fiber oscillator.

  2. Applications of TM polarized illumination

    NASA Astrophysics Data System (ADS)

    Smith, Bruce; Zhou, Jianming; Xie, Peng

    2008-03-01

    The use of transverse electric (TE) polarization has dominated illumination schemes as selective polarization is used for high-NA patterning. The benefits of TE polarization are clear - the interference of diffracted beams remains absolute at oblique angles. Transverse magnetic (TM) polarization is usually considered less desirable as imaging modulation from interference at large angle falls off rapidly as the 1/cosθ. Significant potential remains, however, for the use of TM polarization at large angles when its reflection component is utilized. By controlling the resist/substrate interface reflectivity, high modulation for TM polarization can be maintained for angles up to 90° in the resist. This can potentially impact the design of illumination away from most recent TE-only schemes for oblique imaging angles (high NA). We demonstrate several cases of TM illumination combined with tuned substrate reflectivity for 0.93NA, 1.20NA, and 1.35NA and compare results to TE and unpolarized cases. The goal is to achieve a flat response through polarization at large imaging angles. An additional application of TM illumination is its potential use for double patterning. As double patterning and double exposure approaches are sought in order to meet the needs of 32nm device generations and beyond, materials and process engineering challenges become prohibitive. We have devised a method for frequency doubling in a single exposure using an unconventional means of polarization selection and by making use of the reflective component produced at the photoresist/substrate interface. In doing so, patterns can be deposited into a photoresist film with double density. As an example, using a projection system numerical aperture of 1.20, with water as an immersion fluid, and a conventional polyacrylate 193nm photoresist, pattern resolution at 20nm half-pitch are obtainable (which is 0.125lambda/NA). The process to transfer this geometry into a hardmask layer uses conventional materials, including the photoresist layer and thin film silicon oxide based materials.

  3. Synthesis and Thermoelectric Properties of the YbTe-YbSb System

    NASA Astrophysics Data System (ADS)

    Kawamura, Airi; Hu, Yufei; Kauzlarich, Susan M.

    2016-01-01

    The syntheses of YbTe1- x Sb x ( x = 0, 0.05, 0.2, 0.5, 0.8, 1) were investigated by solid state reactions and formed into dense pellets by spark plasma sintering. X-ray powder diffraction and microprobe analysis indicated no solubility of Sb in YbTe, and these phases are better described as composite phases (YbTe)1- x (YbSb) x ( x = 0, 0.05, 0.2, 0.5, 0.8, 1). Thermal conductivity, electrical resistivity, and Seebeck coefficients were acquired for the larger values of x ( x = 0.2, 0.5, 0.8, 1) from room temperature to 773 K, and the figure of merit was calculated. Thermal conductivities for x = 0, 0.05 are also reported; however, measurements of Seebeck coefficients and electrical resistivity were not possible due to large resistivity. The figure of merit for all samples was low, and the maximum zT measured was zT 791K = 0.018 for YbSb. Low figures of merit were primarily the result of very high resistivity in YbTe rich samples, and high thermal conductivity, and a small Seebeck coefficient in all samples.

  4. The tmRNA ribosome rescue system

    PubMed Central

    Janssen, Brian D.; Hayes, Christopher S.

    2012-01-01

    The bacterial tmRNA quality control system monitors protein synthesis and recycles stalled translation complexes in a process termed ribosome rescue. During rescue, tmRNA acts first as a transfer RNA to bind stalled ribosomes, then as a messenger RNA to add the ssrA peptide tag to the C-terminus of the nascent polypeptide chain. The ssrA peptide targets tagged peptides for proteolysis, ensuring rapid degradation of potentially deleterious truncated polypeptides. Ribosome rescue also facilitates turnover of the damaged messages responsible for translational arrest. Thus, tmRNA increases the fidelity of gene expression by promoting the synthesis of full-length proteins. In addition to serving as a global quality control system, tmRNA also plays important roles in bacterial development, pathogenesis and environmental stress responses. This review focuses on the mechanism of tmRNA-mediated ribosome rescue and the role of tmRNA in bacterial physiology. PMID:22243584

  5. Tunability of Yb:glass laser

    NASA Astrophysics Data System (ADS)

    Å ulc, Jan; Krivosudský, Ondrej; Jelínková, Helena; Stepien, Ryszard

    2013-03-01

    Ytterbium doped phosphate glass (5 mol% of Yb2O3, thickness 1 and 2 mm, uncoated), developed for fibre laser, was tested in bulk form as a laser active medium. For Yb:glass pumping a fibre coupled (fibre core diameter 100 μm, NA = 0.22) laser diode with emission at wavelength 975nm was used. The laser diode was operating in pulsed regime (pulse length 1.5 ms, repetition rate 5 Hz, maximum pulse energy 22 mJ) with low duty cycle to reduce a heat accumulation inside the active medium (Yb:glass was only air-cooled). Longitudinally pumped Yb:glass samples were placed inside the 145mm long semi-hemispherical resonator formed by a flat pumping mirror (HR @ 1.0 - 1.1 μm, HT @ 0.97 μm) and by curved output coupler (r = 150 mm). Set of output couplers with reflectivity 91 - 97% @ 1.0 - 1.1 μm was used. Tuning of the Yb:glass laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler (reflectivity 97%) and laser active medium. In untuned regime the energy up to 2.4mJ was obtained at wavelength 1050 nm. Slope efficiency up to 17% in respect to absorbed pumping was reached with the 2mm sample. In tuned regime the smooth laser tuning curve, limited by used Lyot filter, extended from 1005nm up to 1080nm (FWHM 48 nm). The maximum output energy of 1.65mJ was obtained at 1060nm for the absorbed energy 16 mJ.

  6. Influence of rare earth cation size on the crystal structure in rare earth silicates, Na2RESiO4(OH) (RE = Sc, Yb) and NaRESiO4 (RE = La, Yb)

    NASA Astrophysics Data System (ADS)

    Latshaw, Allison M.; Wilkins, Branford O.; Chance, W. Michael; Smith, Mark D.; zur Loye, Hans-Conrad

    2016-01-01

    Crystals of Na2ScSiO4(OH) and Na2YbSiO4(OH) were synthesized at low temperatures using a sodium hydroxide based hydroflux, while crystals of NaLaSiO4 and NaYbSiO4 were grown at high temperatures using a sodium fluoride/sodium chloride eutectic flux. Both structure types were crystallized under reaction conditions that, when used for medium sized rare earths (RE = Pr, Nd, Sm - Tm) yield the Na5RE4X[SiO4]4 structure type, where X is OH in the hydroflux conditions and F in the eutectic flux conditions. Herein, we report the synthesis, structure, size effect, and magnetic properties of these compositions and introduce the new structure type of Na2RESiO4(OH), which crystallizes in the orthorhombic space group Pca21, of NaLaSiO4, which crystallizes in the orthorhombic space group Pna21, and of NaYbSiO4, which crystallizes in the orthorhombic space group Pnma, where both NaRESiO4 compounds have one silicon structural analog.

  7. Harmonic mode-locking in a Tm-doped fiber laser: Characterization of its timing jitter and ultralong starting dynamics

    NASA Astrophysics Data System (ADS)

    Bao, Chengying; Yang, Changxi

    2015-12-01

    We report an experimental characterization on harmonic mode-locking in a Tm-doped fiber laser, which exhibits pump related timing jitter and ultralong mode-locking starting dynamics. The laser is pumped by a laser diode seeded EDFA. Harmonic mode-locking is initiated by nonlinear polarization rotation and showed a good long term stability. Timing jitter is found to be significantly influenced by the properties of laser diode seed for the EDFA. When switching the seed from a Fabry-Perot cavity laser diode to a distributed feedback (DFB) laser diode, timing jitter decreases from 16 ps to 6 ps. It also takes the laser an ultralong self-starting time (> 100 s), 3 order of magnitude longer than typical Er-doped or Yb-doped fiber lasers, to reach a steady harmonic mode-locking in some cases. These experimental evidences can contribute to a better understanding of Tm-doped fiber lasers.

  8. Strategy for thermometry via Tm³⁺-doped NaYF₄ core-shell nanoparticles.

    PubMed

    Zhou, Shaoshuai; Jiang, Guicheng; Li, Xinyue; Jiang, Sha; Wei, Xiantao; Chen, Yonghu; Yin, Min; Duan, Changkui

    2014-12-01

    Optical thermometers usually make use of the fluorescence intensity ratio of two thermally coupled energy levels, with the relative sensitivity constrained by the limited energy gap. Here we develop a strategy by using the upconversion (UC) emissions originating from two multiplets with opposite temperature dependences to achieve higher relative temperature sensitivity. We show that the intensity ratio of the two UC emissions, ³F(2,3) and ¹G₄, of Tm³⁺ in β-NaYF₄:20%Yb³⁺, 0.5%Tm³⁺/NaYF₄:1%Pr³⁺ core-shell nanoparticles under 980 nm laser excitation exhibits high relative temperature sensitivity between 350 and 510 K, with a maximum of 1.53%  K⁻¹ at 417 K. This demonstrates the validity of the strategy, and that the studied material has the potential for high-performance optical thermometry. PMID:25490653

  9. Magnetic properties of EuLn{sub 2}O{sub 4} (Ln=rare earths)

    SciTech Connect

    Hirose, Keiichi; Doi, Yoshihiro; Hinatsu, Yukio

    2009-07-15

    Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) were prepared. They crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. {sup 151}Eu Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. From the positive Weiss constant and the saturation of magnetization for EuLu{sub 2}O{sub 4}, it is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel. When Ln=Gd-Tm, ferromagnetically aligned Eu{sup 2+} ions interact with the Ln{sup 3+} ions, which would overcome the magnetic frustration of triangularly aligned Ln{sup 3+} ions and the EuLn{sub 2}O{sub 4} compounds show a simple antiferromagnetic behavior. - Graphical abstract: Ternary rare earth oxides EuLn{sub 2}O{sub 4} (Ln=Gd, Dy-Lu) crystallized in an orthorhombic CaFe{sub 2}O{sub 4}-type structure with space group Pnma. Moessbauer spectroscopic measurements show that the Eu ions are in the divalent state. All these compounds show an antiferromagnetic transition at 4.2-6.3 K. It is considered that ferromagnetic chains of Eu{sup 2+} are aligned along the b-axis of the orthorhombic unit cell, with neighboring Eu{sup 2+} chains antiparallel.

  10. Neutron scattering studies on Yb3Pt4

    NASA Astrophysics Data System (ADS)

    Janssen, Y.; Bennett, M. C.; Marques, C.; Wu, L.; Kim, M. S.; Park, K. S.; Huang, Q.; Li, J. Y.; Chen, Y.; Lynn, J. W.; Aronson, M. C.

    2009-03-01

    The antiferromagnetic (AF) intermetallic compound Yb3Pt4 shows a magnetic phase diagram which includes a quantum critical point, but is different from other Yb-containing quantum critical compounds. We elucidated the zero-field behavior by neutron scattering on both polycrystal and single-crystal samples. The magnetic structure due to the single-site-low-symmetry Yb moments was determined by diffraction. The AF unit cell coincides with the crystallographic unit cell, and shows pairs of Yb nearest-neighbor moments pointing directly towards each other. The order parameter is consistent with a continuous transition at the N'eel temperature (2.4 K) and can be described by a simple mean-field model. The ordered moment amounts to ˜ 1.2 μB/Yb at 0 K. Inelastic neutron scattering reveals that the crystal electric field lifts the degeneracy of the Yb 4f ground state into 4 doublets, consistent with specific heat results.

  11. Dysfunction of Rice Mitochondrial Membrane Induced by Yb3+.

    PubMed

    Gao, Jia-Ling; Wu, Man; Liu, Wen; Feng, Zhi-Jiang; Zhang, Ye-Zhong; Jiang, Feng-Lei; Liu, Yi; Dai, Jie

    2015-12-01

    Ytterbium (Yb), a widely used rare earth element, is treated as highly toxic to human being and adverseness to plant. Mitochondria play a significant role in plant growth and development, and are proposed as a potential target for ytterbium toxicity. In this paper, the biological effect of Yb(3+) on isolated rice mitochondria was investigated. We found that Yb(3+) with high concentrations (200 ~ 600 μM) not only induced mitochondrial membrane permeability transition (mtMPT), but also disturbed the mitochondrial ultrastructure. Moreover, Yb(3+) caused the respiratory chain damage, ROS formation, membrane potential decrease, and mitochondrial complex II activity reverse. The results above suggested that Yb(3+) with high concentrations could induce mitochondrial membrane dysfunction. These findings will support some valuable information to the safe application of Yb-based agents. PMID:26305923

  12. Nd3+, Yb3+ and Nd3+/Yb3+: doped borosilicate glasses for luminescent thermometry

    NASA Astrophysics Data System (ADS)

    Bykowski, Kamil; Bruszewski, Artur; Cimaszewski, Dominik; Zmojda, Jacek; Kochanowicz, Marcin; Dorosz, Dominik

    2014-11-01

    The article presents influence of temperature on luminescent properties of borosilicate glasses with molar composition: SiO2-B2O3-Al2O3-Na2O-K2O doped with Nd3+, Yb3+ and co-doped with Nd3+/Yb°3+ ions. In the range from 60 to 300°C the quenching of luminescence signal versus increase of temperature was observed. In case of glasses doped with Nd3+ and Yb3+ ions the sensitivity was determinated to be 0.0016 [1/K] at 1.06μm and 0.001 [1/K] at 1.02μm, respectively. Fabricated glass co-doped with Nd3+/Yb3+ ions is characterized by the highest sensitivity and maximum value 0.003 [1/K] was observed at the wavelength of 1020nm, corresponding to the Yb3+: 2F5/2 --> 2F7/2 transition in energy levels structure of ions.

  13. A Review of "Integrity[TM]"

    ERIC Educational Resources Information Center

    Veldkamp, Bernard P.

    2008-01-01

    Integrity[TM], an online application for testing both the statistical integrity of the test and the academic integrity of the examinees, was evaluated for this review. Program features and the program output are described. An overview of the statistics in Integrity[TM] is provided, and the application is illustrated with a small simulation study.…

  14. 78 FR 72922 - TSA Pre✓TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-04

    ...The Transportation Security Administration (TSA) announces the establishment of a fee for applicants of the TSA Pre[check]TM Application Program. Members of the public may apply to this TSA program by voluntarily providing biometric and biographic information and paying a fee. TSA will use these fees from applicants to fund selected activities of the TSA Pre[check]TM......

  15. 77 FR 71590 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-03

    ... Energy Regulatory Commission Lock+ TM Hydro Friends Fund XI, LLC; Notice of Preliminary Permit... October 1, 2012, Lock+ TM Hydro Friends Fund XI, LLC filed an application for a preliminary permit, pursuant to section 4(f) of the Federal Power Act (FPA), proposing to study the feasibility of the Lock...

  16. 76 FR 48840 - Lock+TM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-09

    ... Energy Regulatory Commission Lock+\\TM\\ Hydro Friends Fund XXXV Riverbank Hydro No. 4, LLC; Notice of..., and Competing Applications On April 1, 2011, Lock+\\TM\\ Hydro Friends Fund XXXV (Hydro Friends) and... Corps of Engineers' (Corps) Lock and Dam No. 5, located on the Mississippi River near Minnesota...

  17. Diode-pumped regenerative Yb:SrF2 amplifier

    NASA Astrophysics Data System (ADS)

    Ricaud, S.; Georges, P.; Camy, P.; Doualan, J.-L.; Moncorgé, R.; Courjaud, A.; Mottay, E.; Druon, F.

    2012-03-01

    We report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed.

  18. RbYb(PO3)4

    PubMed Central

    Zhu, Jing; Chen, Hui

    2013-01-01

    Rubidium ytterbium(III) tetra­kis­(polyphosphate), RbYb(PO3)4, was synthesized by solid-state reaction. It adopts structure type IV of the MRE(PO3)4 (M = alkali metal and RE = rare earth metal) family of compounds. The structure is composed of a three-dimensional framework made up from double spiral polyphosphate chains parallel to [10-1] and irregular [YbO8] polyhedra. There are eight PO4 tetra­hedra in the repeat unit of the polyphosphate chains. The Rb+ cation is located in channels extending along [100] that are delimited by the three-dimensional framework. It is surrounded by 11 O atoms, defining an irregular polyhedron. PMID:23476312

  19. Scaling of Yb-Fiber Frequency Combs

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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).

  20. 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

    Xu, Zhenhe; Feng, Bin; Bian, Shasha; Liu, Tao; Wang, Mingli; Gao, Yu; Sun, Di; Gao, Xin; Sun, Yaguang

    2012-12-15

    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.

  1. Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)

    SciTech Connect

    Myers, Kenneth D.

    1999-11-08

    This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.

  2. Constitutive and functional expression of YB-1 in microglial cells.

    PubMed

    Keilhoff, G; Titze, M; Esser, T; Langnaese, K; Ebmeyer, U

    2015-08-20

    Y-box-binding protein (YB-1) is a member of the cold-shock protein family and participates in a wide variety of DNA/RNA-dependent cellular processes including DNA repair, transcription, mRNA splicing, packaging, and translation. At the cellular level, YB-1 is involved in cell proliferation and differentiation, stress responses, and malignant cell transformation. A general role for YB-1 during inflammation has also been well described; however, there are minimal data concerning YB-1 expression in microglia, which are the immune cells of the brain. Therefore, we studied the expression of YB-1 in a clinically relevant global ischemia model for neurological injury following cardiac arrest. This model is characterized by massive neurodegeneration of the hippocampal CA1 region and the subsequent long-lasting activation of microglia. In addition, we studied YB-1 expression in BV-2 cells, which are an accepted microglia culture model. BV-2 cells were stressed by oxygen/glucose deprivation (OGD), OGD-relevant mediators, lipopolysaccharide (LPS), and phagocytosis-inducing cell debris and nanoparticles. Using quantitative polymerase chain reaction (PCR), we show constitutive expression of YB-1 transcripts in unstressed BV-2 cells. The functional upregulation of the YB-1 protein was demonstrated in microglia in vivo and in BV-2 cells in vitro. All stressors except for LPS were potent enhancers of the level of YB-1 protein, which appears to be regulated primarily by proteasomal degradation and, to a lesser extent, by the activation (phosphorylation) of the translation initiation factor eIF4E. The proteasome of BV-2 cells is impaired by OGD, which results in decreased protein degradation and therefore increased levels of YB-1 protein. LPS induces proteasome activity, which enables the level of YB-1 protein to remain at control levels despite enhanced protein ubiquitination. The proteasome inhibitor MG-132 was able to increase YB-1 protein levels in control and LPS-treated cultures. YB-1 upregulation was not accompanied by its translocation from the cytoplasm to the nucleus. YB-1 induction appeared to be related to microglial proliferation because it was partially co-regulated with Ki67. In addition, YB-1 protein levels correlated with microglia phagocytic activity because its upregulation could also be induced by inert NPs. PMID:26102006

  3. Valence fluctuation and magnetic ordering in EuNi2(P1-x Ge x )2 single crystals

    NASA Astrophysics Data System (ADS)

    Paramanik, U. B.; Bar, A.; Das, Debarchan; Caroca-Canales, N.; Prasad, R.; Geibel, C.; Hossain, Z.

    2016-04-01

    Unusual phases and phase transitions are seen at the magnetic-nonmagnetic boundary in Ce-, Eu- and Yb-based compounds. EuNi2P2 is a very unusual valence fluctuating Eu system, because at low temperatures the Eu valence stays close to 2.5 instead of approaching an integer value. The Eu valence, and thus the magnetic property in this system, can be tuned by Ge substitution in the P site as EuNi2Ge2 is known to exhibit the antiferromagnetc (AFM) ordering of divalent Eu moments with {{T}\\text{N}}=30 K. We have grown EuNi2(P1-x Ge x )2 (0.0≤slant x≤slant 0.5 ) single crystals and studied their magnetic, thermodynamic and transport properties. Increasing Ge doping to x  >  0.4 results in a well-defined AFM ordered state with {{T}\\text{N}}=12 K for x  =  0.5. Moreover, the reduced value of magnetic entropy for x  =  0.5 at T N suggests the presence of valance fluctuation/the Kondo effect in this compound. Interestingly, the specific heat exhibits an enhanced Sommerfeld coefficient upon Ge doping. Subsequently, electronic structure calculations lead to a non-integral valence in EuNi2P2 but a stable divalent Eu state in EuNi2Ge2, which is in good agreement with the experimental results.

  4. The GEMnet (TM) global data communication

    NASA Technical Reports Server (NTRS)

    Yi, Byung K.; Chitty, Richard; Walters, Dave; Howard, Regan

    1995-01-01

    The GEMnet(TM) (Global Electronics Message network) will provide global digital data communications anywhere in the world at any time for minimum cost. GEMnet(TM) is an end-to-end Non-Voice Non-Geostationary Mobile Satellite (NVNG) (sometimes dubbed 'Little LEO') System which consists of a constellation of 38 low Earth orbiting small satellites and a ground segment. The GEMnet(TM) ground segment will consist of subscriber user terminals, gateway stations, a Network Operational Center(NOC), and a backbone network interconnecting the NOC and gateways. This paper will describe the GEMnet(TM) system concept including ground and space segments, system heritage, data communication services, and protocols.

  5. Tightly focused, ultrafast TM01 laser pulses

    NASA Astrophysics Data System (ADS)

    April, Alexandre

    2009-06-01

    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.

  6. Level structure of /sup 174/Yb from the /sup 173/Yb(n,. gamma. ) reaction

    SciTech Connect

    Greenwood, R.C.; Reich, C.W.

    1981-01-01

    The level structure of /sup 174/Yb has been studied using the /sup 173/Yb(n,..gamma..) reaction with both thermal and 2-keV neutrons. Measurements of ..gamma..-ray energies and intensities were made using Ge(Li) detectors. From these data a neutron separation energy of 7464.8 +- 0.5 keV has been determined for /sup 174/Yb. A level scheme is proposed for /sup 174/Yb which contains 47 excited states, with identified de-excitation modes, below 2.35 MeV. Features of the proposed level scheme include: the K/sup ..pi../=2/sup -/, 0/sup -/, and 3/sup -/ octupole-vibrational bands with band-head energies of 1318, 1710, and 1851 keV, respectively; the ..gamma..-vibrational band at 1634 keV; three excited K/sup ..pi../=0/sup +/ bands with band-head energies of 1487, 1885, and 2100 keV; and, several two-quasiparticle bands with band-head energies in keV (and K/sup ..pi../ assignments) of 1606(3/sup +/), 1624(1/sup +/), 2016(3/sup +/), and 2049(3/sup -/). Configuration assignments for these two-quasiparticle bands are discussed. The available data for the K/sup ..pi../=3/sup +/ band at 1606 keV are not inconsistent with the assumption that it has collective character; and it is suggested that it, together with the lowest-lying 3/sup +/ band in /sup 172/Yb (at 1172 keV), might represent, in the framework of the interacting boson approximation model, examples of g-boson excitations.

  7. Ternary rare earth-lanthanide sulfides. [Re = Eu, Sm or Yb

    DOEpatents

    Takeshita, Takuo; Gschneidner, K.A. Jr.; Beaudry, B.J.

    1986-03-06

    Disclosed is a new ternary rare earth sulfur compound having the formula La/sub 3-x/M/sub x/S/sub 4/, where M is europium, samarium, or ytterbium, with x = 0.15 to 0.8. The compound has good high-temperature thermoelectric properties and exhibits long-term structural stability up to 1000/sup 0/C.

  8. Nanosecond cryogenic Yb:YAG disk laser

    SciTech Connect

    Perevezentsev, E A; Mukhin, I B; Kuznetsov, I I; Vadimova, O L; Palashov, O V

    2014-05-30

    A cryogenic Yb:YAG disk laser is modernised to increase its average and peak power. The master oscillator unit of the laser is considerably modified so that the pulse duration decreases to several nanoseconds with the same pulse energy. A cryogenic disk laser head with a flow-through cooling system is developed. Based on two such laser heads, a new main amplifier is assembled according to an active multipass cell scheme. The total small-signal gain of cryogenic cascades is ∼10{sup 8}. (lasers)

  9. 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

    Grossholz, Hagen; Hartenbach, Ingo; Kotzyba, Gunter; Poettgen, Rainer; Trill, Henning; Mosel, Bernd D.; Schleid, Thomas

    2009-11-15

    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}.

  10. 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

    Wang, Jian; Xia, Sheng-Qing; Tao, Xu-Tang; Schäfer, Marion C.; Bobev, Svilen

    2013-09-15

    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 β=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.

  11. Photoluminescence properties of Yb(2+) ions doped in the perovskites CsCaX3 and CsSrX3 (X = Cl, Br, and I) - a comparative study.

    PubMed

    Suta, Markus; Urland, Werner; Daul, Claude; Wickleder, Claudia

    2016-05-21

    The Yb(2+)-doped perovskite derivatives CsMX3 (M = Ca and Sr; X = Cl, Br, and I) are ideal systems for obtaining a detailed insight into the structure-luminescence relationship of divalent lanthanides. The investigation of the respective photoluminescence properties yielded two emission bands in the violet and blue spectral range for all compounds, which are assigned to the spin-allowed and spin-forbidden 5d-4f transitions, respectively. The impact on their energetic positions is dependent on both the covalency of the Yb(2+)-halide bond and the corresponding bond length in agreement with expectations. The excitation spectra provide a detailed fine structure at low temperatures and can be partly interpreted separating the 4f(13) core from the 5d electron in the excited state. The local crystal field in CsSrI3:Yb(2+) provides a special case due to the trigonal distortion induced by the crystal structure that is clearly evident in the luminescence features of Yb(2+). The structure-property relationship of several spectroscopic key quantities of Yb(2+) in this series of halides is analyzed in detail and parallels the properties of Eu(2+) ions doped in the given perovskites. PMID:26894637

  12. Electrochemical formation of Al-Tm intermetallics in eutectic LiCl-KCl melt containing Tm and Al ions

    NASA Astrophysics Data System (ADS)

    Li, Xing; Yan, Yong-De; Zhang, Mi-Lin; Tang, Hao; Ji, De-Bin; Han, Wei; Xue, Yun; Zhang, Zhi-Jian

    2014-09-01

    This work focuses on investigating the electrochemical formation of Al-Tm and Al-Li-Tm alloys in LiCl-KCl-AlCl3-Tm2O3 melt on both W and Al electrodes. Thermodynamic calculation and electrochemical behavior of LiCl-KCl melt containing both AlCl3 and Tm2O3 showed that AlCl3 can chlorinate Tm2O3 to release Tm(III) ions. Three kinds of Al-Tm intermetallics at about -1.26, -1.32 and -1.43 V were detected by means of various electrochemical measurement techniques, i.e. cyclic voltammetry, square wave voltammetry and open circuit chronopotentiometry. Potentiostatic and galvanostatic electrolysis were carried out on Al and W electrodes to prepare Al-Tm and Al-Li-Tm alloys, respectively. The composition of Al-Li-Tm alloys was analyzed by inductive coupled plasma atomic emission spectrometer (ICP-AES).

  13. Concurrent Validity of LibQUAL+[TM] Scores: What Do LibQUAL+[TM] Scores Measure?

    ERIC Educational Resources Information Center

    Thompson, Bruce; Cook, Colleen; Kyrillidou, Martha

    2005-01-01

    The present study investigated the validity of LibQUAL+[TM] scores, and specifically how total and subscale LibQUAL+[TM] scores are associated with self-reported, library-related satisfaction and outcomes scores. Participants included 88,664 students and faculty who completed the American English (n[AE] = 69,494) or the British English (n[BE] =…

  14. QCD For Intel(R) Xeon Phi(tm) and Xeon(tm) processors

    SciTech Connect

    Joo, Balint

    2014-09-11

    This library provides a library containing highly optimized Wilson-Dslash, Wilson Clover operator and Krylov subspace solvers for Lattice QCD simulations. The library is targeted at Intel(R) Xeon Phi(tm), and Intel(R) Xeon(tm) processors.

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

    NASA Technical Reports Server (NTRS)

    Swetits, John J.

    1991-01-01

    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.

  16. EU pharmaceutical expenditure forecast

    PubMed Central

    Urbinati, Duccio; Rémuzat, Cécile; Kornfeld, Åsa; Vataire, Anne-Lise; Cetinsoy, Laurent; Aballéa, Samuel; Mzoughi, Olfa; Toumi, Mondher

    2014-01-01

    Background and Objectives With constant incentives for healthcare payers to contain their pharmaceutical budgets, forecasting has become critically important. Some countries have, for instance, developed pharmaceutical horizon scanning units. The objective of this project was to build a model to assess the net effect of the entrance of new patented medicinal products versus medicinal products going off-patent, with a defined forecast horizon, on selected European Union (EU) Member States’ pharmaceutical budgets. This model took into account population ageing, as well as current and future country-specific pricing, reimbursement, and market access policies (the project was performed for the European Commission; see http://ec.europa.eu/health/healthcare/key_documents/index_en.htm). Method In order to have a representative heterogeneity of EU Member States, the following countries were selected for the analysis: France, Germany, Greece, Hungary, Poland, Portugal, and the United Kingdom. A forecasting period of 5 years (2012–2016) was chosen to assess the net pharmaceutical budget impact. A model for generics and biosimilars was developed for each country. The model estimated a separate and combined effect of the direct and indirect impacts of the patent cliff. A second model, estimating the sales development and the risk of development failure, was developed for new drugs. New drugs were reviewed individually to assess their clinical potential and translate it into commercial potential. The forecast was carried out according to three perspectives (healthcare public payer, society, and manufacturer), and several types of distribution chains (retail, hospital, and combined retail and hospital). Probabilistic and deterministic sensitivity analyses were carried out. Results According to the model, all countries experienced drug budget reductions except Poland (+€41 million). Savings were expected to be the highest in the United Kingdom (−€9,367 million), France (−€5,589 million), and, far behind them, Germany (−€831 million), Greece (−€808 million), Portugal (−€243 million), and Hungary (−€84 million). The main source of savings came from the cardiovascular, central nervous system, and respiratory areas and from biosimilar entries. Oncology, immunology, and inflammation, in contrast, lead to additional expenditure. The model was particularly sensitive to the time to market of branded products, generic prices, generic penetration, and the distribution of biosimilars. Conclusions The results of this forecast suggested a decrease in pharmaceutical expenditure in the studied period. The model was sensitive to pharmaceutical policy decisions.

  17. Fabrication and laser properties of transparent Yb:YAG ceramics

    NASA Astrophysics Data System (ADS)

    Luo, Dewei; Zhang, Jian; Xu, Changwen; Qin, Xianpeng; Tang, Dingyuan; Ma, Jan

    2012-04-01

    High optical quality transparent Yb:YAG laser ceramics have been successfully fabricated by a vacuum reactive sintering method. Commercial Al2O3 powder and co-precipitated Y2O3 and Yb2O3 powders were used as the raw materials. In-line transmittances at 1300 nm and 400 nm were measured to be 83.6% and 81.8% respectively for a 3 mm thick mirror polished Yb:YAG ceramics sample. Continuous wave (CW) lasing at the wavelength of 1030 nm was achieved when pumped by a 940 nm fiber coupled laser diode. A slope efficiency as high as 62.7% was obtained.

  18. Yb:YAG enhanced Cr,Yb:YAG self-Q-switched microchip laser under QCW laser-diode pumping

    NASA Astrophysics Data System (ADS)

    Wang, Guangyu; Chen, Dimeng; Cheng, Ying; Dong, Jun

    2015-05-01

    Enhanced Cr,Yb:YAG self-Q-switched microchip lasers by bonding Yb:YAG crystal have been studied under quasi-continuous-wave (QCW) laser-diode pumping for the first time to our best knowledge. The effects of the pump pulse duration and pump power of the QCW laser-diode on the performance of Yb:YAG/Cr,Yb:YAG microchip lasers have been investigated. The optical efficiency, pulse energy and peak power of the Yb:YAG/Cr,Yb:YAG self-Q-switched laser increase with the pump pulse duration and pump power, and tend to be constant when the pump pulse duration is longer than 1 ms, which is comparable to the fluorescence lifetime of Yb:YAG crystal. Output energy of over 11.7 mJ was obtained at input pump energy of 48.2 mJ; corresponding optical-to-optical efficiency of 24.3% was obtained. Laser pulses with pulse energy of 31 μJ and peak power of 13.3 kW were obtained. The multi-longitudinal modes oscillation around 1030 nm was dominant within the available input pump energy.

  19. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    DOE PAGESBeta

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squaredmore » Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.« less

  20. From the Ternary Eu(Au/In)2 and EuAu4(Au/In)2 with Remarkable Au/In Distributions to a New Structure Type: The Gold-Rich Eu5Au16(Au/In)6 Structure.

    PubMed

    Steinberg, Simon; Card, Nathan; Mudring, Anja-Verena

    2015-09-01

    The ternary Eu(Au/In)2 (EuAu(0.46)In(1.54(2))) (I), EuAu4(Au/In)2 (EuAu(4+x)In(2-x) with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au(17.29)In(4.71(3))) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squared Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au(17.29)In(4.71(3))) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2-"EuAu4In2". The site preferences of the disordered Au/In positions in II were investigated for different hypothetical "EuAu4(Au/In)2" models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au-In contacts. A chemical bonding analysis on two "EuAu5In" and "EuAu4In2" models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems. PMID:26270622

  1. Bulk and surface valence in YbPd/sub x/ compounds

    SciTech Connect

    Domke, M.; Laubschat, C.; Sampathkumaran, E.V.; Prietsch, M.; Mandel, T.; Kaindl, G.; Middelmann, H.U.

    1985-12-15

    The bulk and surface valence v-bar of Yb is investigated for YbPd/sub x/ intermetallic compounds (with x = 1,1.33,3) by photoemission using synchrotron radiation. YbPd is found to be of intermediate valence (v-barapprox. =2.75), while Yb/sub 3/Pd/sub 4/ and YbPd/sub 3/ are identified as bulk trivalent systems. The outermost atomic surface layer of both YbPd and Yb/sub 3/Pd/sub 4/ is found to be divalent, while only a fraction of Yb surface atoms turns divalent in YbPd/sub 3/. The results are compared with bremsstrahlung isochromat spectroscopy measurements and predictions based on Miedema's scheme.

  2. Competition between the inter- and intra-sublattice interactions in Yb2V2O7

    NASA Astrophysics Data System (ADS)

    Dun, Z. L.; Ma, J.; Cao, H. B.; Qiu, Y.; Copley, J. R. D.; Hong, T.; Matsuda, M.; Cheng, J. G.; Lee, M.; Choi, E. S.; Johnston, S.; Zhou, H. D.

    2015-02-01

    We studied the magnetic properties of single-crystal Yb2V2O7 using dc and ac susceptibility measurements, elastic and inelastic neutron-scattering measurements, and linear spin-wave theory. The experimental data show a ferromagnetic ordering of V4 + ions at 70 K, a short-range ordering of Yb3 + ions below 40 K, and finally a long-range noncollinear ordering of Yb3 + ions below 15 K. With external magnetic field oriented along the [111] axis, the Yb sublattice experiences a spin flop transition related to the "three-in one-out" spin structure. By modeling the spin-wave excitations, we extract the Hamiltonian parameters. Our results confirm that although the extra inter-sublattice Yb-V interactions dramatically increase the Yb ordering temperature to 15 K, the intra-sublattice Yb-Yb interactions, based on the pyrochlore lattice, still stabilize the Yb ions' noncollinear spin structure and spin flop transition.

  3. Competition between the inter- and intra-sublattice interactions in Yb2V2O7

    NASA Astrophysics Data System (ADS)

    Dun, Zhiling; Ma, Jie; Cao, Huibo; Hong, Tao; Matsuda, Masaaki; Qiu, Yiming; Copley, John; Cheng, Jinguang; Lee, Minseong; Choi, Eunsang; Johnston, Steve; Zhou, Haidong

    2015-03-01

    We studied single crystals of Yb2V2O7 using dc and ac susceptibility measurements, elastic and inelastic neutron scattering measurements, and linear spin wave theory. The experimental data shows a ferromagnetic ordering of V4+ ions at 70 K, a short-range ordering of Yb3+ ions below 40 K, and finally a long-range non-collinear ordering of Yb3+ ions below 15 K. With external magnetic field oriented along the [111] axis, the Yb-sublattice experiences a spin flop transition related to the ``three-in one-out'' spin structure. By modeling the spin wave excitations, we extract the Hamiltonian parameters. Our results confirm that although the extra inter-sublattice Yb-V interactions dramatically increases the Yb ordering temperature to 15 K, the intra-sublattice Yb-Yb interactions, based on the pyrochlore lattice, still stabilize the Yb ions' non-collinear spin structure and spin flop transition.

  4. Multimodal bioimaging using rare earth doped Gd2O2S: Yb/Er phosphor with upconversion luminescence and magnetic resonance properties

    PubMed Central

    Ajithkumar, G.; Yoo, Benjamin; Goral, Dara E.; Hornsby, Peter J.; Lin, Ai-Ling; Ladiwala, Uma; Dravid, Vinayak P.; Sardar, Dhiraj K

    2013-01-01

    While infrared upconversion imaging using halide nanoparticles are so common the search for a very efficient halide free upconverting phosphors is still lacking. In this article we report Gd2O2S:Yb/Er,YbHo,YbTm systems as a very efficient alternative phosphors that show upconversion efficiency comparable or even higher than existing halide phosphors. While the majority of rare earth dopants provide the necessary features for optical imaging, the paramagnetic Gd ion also contributes to the magnetic imaging,thereby resulting in a system with bimodal imaging features. Results from imaging of the nanoparticles together with aggregates of cultured cells have suggested that imaging of the particles in living animals may be possible. In vitro tests revealed no signficant toxicity because no cell death was observed when the nanoparticles were in the presence of growing cells in culture. Measurement of the magnetization of the phosphor shows that the particles are strongly magnetic, thus making them suitable as an MRI agent. PMID:25191618

  5. Landsat TM and ETM+ Thermal Band Calibration

    NASA Technical Reports Server (NTRS)

    Barsi, Julia A.; Hook, Simon J.; Palluconi, Frank D.; Schott, John R.; Raqueno, Nina G.

    2006-01-01

    Landsat-5 Thematic Mapper (TM) has been imaging the Earth since March 1984 and Landsat-7 Enhanced Thematic Mapper Plus (ETM+) was added to the series of Landsat instruments in April 1999. The stability and calibration of the ETM+ has been monitored extensively since launch. Though not monitored for many years, TM now has a similar system in place to monitor stability and calibration. University teams have been evaluating the on-board calibration of the instruments through ground-based measurements since 1999. This paper considers the calibration efforts for the thermal band, Band 6, of both the Landsat-5 and Landsat-7 instruments.

  6. Application of Yb:YAG short pulse laser system

    DOEpatents

    Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Crane, John K.; Telford, Steve; Perry, Michael D.

    2004-07-06

    A diode pumped, high power (at least 20W), short pulse (up to 2 ps), chirped pulse amplified laser using Yb:YAG as the gain material is employed for material processing. Yb:YAG is used as the gain medium for both a regenerative amplifier and a high power 4-pass amplifier. A single common reflective grating optical device is used to both stretch pulses for amplification purposes and to recompress amplified pulses before being directed to a workpiece.

  7. Indirect excitation of Eu3+ in GaN codoped with Mg and Eu

    NASA Astrophysics Data System (ADS)

    Yamaga, M.; Watanabe, H.; Kurahashi, M.; O'Donnell, K. P.; Lorenz, K.; Boćkowski, M.

    2015-06-01

    Temperature-dependent Eu3+ luminescence spectra in GaN(Mg):Eu can be assigned to, at least, two distinct Eu3+ centres, denoted by Eu0 and Eu1. The splitting energy levels of the 7FJ (J=1,2) multiplets for the Eu0 and Eu1 centres have been calculated using the equivalent operator Hamiltonian for C3v crystal field with the addition of an odd parity distortion.

  8. Physical properties of superbulky lanthanide metallocenes: synthesis and extraordinary luminescence of [Eu(II)(Cp(BIG))2] (Cp(BIG) = (4-nBu-C6H4)5-cyclopentadienyl).

    PubMed

    Harder, Sjoerd; Naglav, Dominik; Ruspic, Christian; Wickleder, Claudia; Adlung, Matthias; Hermes, Wilfried; Eul, Matthias; Pöttgen, Rainer; Rego, Daniel B; Poineau, Frederic; Czerwinski, Kenneth R; Herber, Rolfe H; Nowik, Israel

    2013-09-01

    The superbulky deca-aryleuropocene [Eu(Cp(BIG))2], Cp(BIG) = (4-nBu-C6H4)5-cyclopentadienyl, was prepared by reaction of [Eu(dmat)2(thf)2], DMAT = 2-Me2N-α-Me3Si-benzyl, with two equivalents of Cp(BIG)H. Recrystallizyation from cold hexane gave the product with a surprisingly bright and efficient orange emission (45% quantum yield). The crystal structure is isomorphic to those of [M(Cp(BIG))2] (M = Sm, Yb, Ca, Ba) and shows the typical distortions that arise from Cp(BIG)⋅⋅⋅Cp(BIG) attraction as well as excessively large displacement parameter for the heavy Eu atom (U(eq) = 0.075). In order to gain information on the true oxidation state of the central metal in superbulky metallocenes [M(Cp(BIG))2] (M = Sm, Eu, Yb), several physical analyses have been applied. Temperature-dependent magnetic susceptibility data of [Yb(Cp(BIG))2] show diamagnetism, indicating stable divalent ytterbium. Temperature-dependent (151)Eu Mössbauer effect spectroscopic examination of [Eu(Cp(BIG))2] was examined over the temperature range 93-215 K and the hyperfine and dynamical properties of the Eu(II) species are discussed in detail. The mean square amplitude of vibration of the Eu atom as a function of temperature was determined and compared to the value extracted from the single-crystal X-ray data at 203 K. The large difference in these two values was ascribed to the presence of static disorder and/or the presence of low-frequency torsional and librational modes in [Eu(Cp(BIG))2]. X-ray absorbance near edge spectroscopy (XANES) showed that all three [Ln(Cp(BIG))2] (Ln = Sm, Eu, Yb) compounds are divalent. The XANES white-line spectra are at 8.3, 7.3, and 7.8 eV, for Sm, Eu, and Yb, respectively, lower than the Ln2O3 standards. No XANES temperature dependence was found from room temperature to 100 K. XANES also showed that the [Ln(Cp(BIG))2] complexes had less trivalent impurity than a [EuI2(thf)x] standard. The complex [Eu(Cp(BIG))2] shows already at room temperature strong orange photoluminescence (quantum yield: 45 %): excitation at 412 nm (24,270 cm(-1)) gives a symmetrical single band in the emission spectrum at 606 nm (νmax =16495 cm(-1), FWHM: 2090 cm(-1), Stokes-shift: 2140 cm(-1)), which is assigned to a 4f(6)5d(1) → 4f(7) transition of Eu(II). These remarkable values compare well to those for Eu(II)-doped ionic host lattices and are likely caused by the rigidity of the [Eu(Cp(BIG))2] complex. Sharp emission signals, typical for Eu(III), are not visible. PMID:23907896

  9. Beta-Decay Study of ^{150}Er, ^{152}Yb, and ^{156}Yb: Candidates for a Monoenergetic Neutrino Beam Facility

    SciTech Connect

    Estevez Aguado, M. E.; Algora, A.; Rubio, B.; Bernabeu, J.; Nacher, E.; Tain, J. L.; Gadea, A.; Agramunt, J.; Burkard, K.; Hueller, W.; Doring, J.; Kirchner, R.; Mukha, I.; Plettner, C.; Roeckl, E.; Grawe, H.; Collatz, R.; Hellstrom, M.; Cano-Ott, D.; Karny, M.; Janas, Z.; Gierlik, M.; Plochocki, A.; Rykaczewski, Krzysztof Piotr; Batist, L.; Moroz, F.; Wittman, V.; Blazhev, A.; Valiente, J. J.; Espinoza, C.

    2011-01-01

    The beta decays of ^{150}Er, ^{152}Yb, and ^{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.

  10. 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 ...

  11. The Neuroscience of PowerPoint[TM

    ERIC Educational Resources Information Center

    Horvath, Jared Cooney

    2014-01-01

    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…

  12. C-Print[TM]. PEPNet Tipsheet

    ERIC Educational Resources Information Center

    Francis, Pam

    2000-01-01

    C-Print[TM] is a computer-aided speech-to-print transcription system developed at the National Technical Institute for the Deaf (NTID) as a support service option for some deaf and hard-of-hearing students in mainstream educational environments. It was developed by NTID researchers eager to improve the classroom experience for students at both the…

  13. Defying Gravity Using Jenga[TM] Blocks

    ERIC Educational Resources Information Center

    Tan, Yin-Soo; Yap, Kueh-Chin

    2007-01-01

    This paper describes how Jenga[TM] blocks can be used to demonstrate the physics of an overhanging tower that appears to defy gravity. We also propose ideas for how this demonstration can be adapted for the A-level physics curriculum. (Contains 8 figures and 1 table.)

  14. Biosimilar regulation in the EU.

    PubMed

    Kurki, Pekka; Ekman, Niklas

    2015-01-01

    In the EU, the EMA has been working with biosimilars since 1998. This experience is crystallized in the extensive set of guidelines, which range from basic principles to details of clinical trials. While the guidance may appear complicated, it has enabled the development of biosimilars, of which 21 have managed to get marketing authorization. Currently marketed biosimilars in the EU have a good track record in safety and traceability. No biosimilars have been withdrawn from the market because of safety concerns. The most controversial issues with biosimilars are immunogenicity and extrapolation of therapeutic indications. The available data for these topics do not raise concerns among EU regulators. Interchangeability and substitution are regulated by individual EU member states. PMID:26294076

  15. CCRS proposal for evaluating LANDSAT-4 MSS and TM data

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  16. Creation of Yb2O3 Nanoprecipitates Through an Oxidation Process in Bulk Yb-Filled Skutterudites

    NASA Astrophysics Data System (ADS)

    Ding, Juan; Gu, Hui; Qiu, Pengfei; Chen, Xihong; Xiong, Zhen; Zheng, Qiang; Shi, Xun; Chen, Lidong

    2013-03-01

    An approach to introduce in situ nanoprecipitates into bulk filled skutterudites is developed through controlling the oxidation process of the fillers. Yb0.3Co4Sb12 is selected as the base material, and prolonged oxidation at high temperatures in sealed quartz tubes under a low pressure of oxygen leads to the formation of Yb2O3 nanoinclusions. Transmission electron microscopy shows that the Yb2O3 nanoprecipitates are created within the skutterudite crystal grains through an internal oxidation mechanism. With increased time of oxidation, the amount of Yb2O3 nanoprecipitates is increased and the nanoprecipitates are more uniformly distributed in the matrix. For the samples oxidized for 10 days, the lattice thermal conductivity is reduced by about 19% at 850 K compared with the Yb0.3Co4Sb12 matrix. The reduction in the lattice thermal conductivity originates from additional phonon scattering by the Yb2O3 nanoprecipitates, leading to a maximum ZT of 1.3.

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

    PubMed

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

    2014-12-01

    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

  18. Variation in luminescence behavior of Yb3+ doped GdAlO3 phosphor with gradual increase in Yb3+ concentration

    NASA Astrophysics Data System (ADS)

    Tamrakar, Raunak Kumar; Upadhyay, Kanchan; Bisen, D. P.

    2016-03-01

    The present paper reports the combustion synthesis of Yb3+ doped GdAlO3 phosphors. The structural characterization and luminescence spectra of Yb3+ doped GdAlO3 phosphors have been discussed. The effects of variable concentration of Yb3+ on Photoluminescence (PL) behavior were studied. The structural characterization was done by X-ray diffraction (XRD) and Transmission electron microscope technique (TEM). The good connectivity with grains and the semi-sphere line structure was found by TEM. The functional group analysis was carried out by Fourier transform infrared (FTIR) spectroscopic techniques. The prepared phosphor gives emission spectra in visible as well as NIR region. Both emissions were studied as a function of Yb3+ concentration. The emission intensity variation with Yb3+ ion concentration for visible and NIR region were discussed separately. The NIR emission luminescence of GdAlO3:Yb3+ phosphor luminescence continuously increases with increasing Yb3+ ion concentration.

  19. Investigation of loss processes of Tm and Tm,Ho in YAG

    NASA Technical Reports Server (NTRS)

    Armagan, G.; Buoncristiani, A. M.; Bair, C. H.; Inge, A. T.; Hess, R. V.

    1991-01-01

    The loss of excitation from various manifolds of Tm and Tm,Ho in YAG as a function of temperature and concentration is studied. Two probable loss mechanisms - a Tm up-conversion and a Ho up-conversion - are identified. A 785-nm CW diode laser with 400-nW peak power was focused to a small spot on the sample. The emission from the sample observed at 90 deg was monitored through a monochromator with slits open to 3 mm. Intensity of emission was measured by varying the power of the excitation source using a set of neutral density filters. Power is reported as the percentage of the peak power, and the intensity curves were normalized below 20 percent of transmission. The fact that there is emission above the pump energy indicates an up-conversion from excited manifolds. Nonlinear changes in the intensity of the emission from the Tm 3F4 manifold with the pump power reveals a loss of excitation from this manifold. The linear dependence of the 5I7 manifold emission with pump power at low Tm and high Ho concentrations and the gain of energy in the 5I6 manifold of Ho indicate that the 5I7 manifold loss is due to the coupling of Tm and Ho ions.

  20. Pioneers--The "Engineering byDesign[TM]" Network

    ERIC Educational Resources Information Center

    Burke, Barry N.

    2006-01-01

    This article discusses the standards-based instruction model, Engineering byDesign[TM] (EbD), and a network of teachers called the Engineering byDesign[TM] Network. Engineering byDesign[TM] is the only standards-based national model for Grades K-12 that delivers technological literacy which was developed by the International Technology Education…

  1. Radiative lifetime measurements of some Tm I and Tm II levels by time-resolved laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Tian, Yanshan; Wang, Xinghao; Yu, Qi; Li, Yongfan; Gao, Yang; Dai, Zhenwen

    2016-04-01

    Radiative lifetimes of 88 levels of Tm I in the energy range 22 791.176-48 547.98 cm-1 and 29 levels of Tm II in the range 27 294.79-65 612.85 cm-1 were measured by time-resolved laser-induced fluorescence spectroscopy in laser-ablation plasma. The lifetime values obtained are in the range from 15.4 to 7900 ns for Tm I and from 36.5 to 1000 ns for Tm II. To the best of our knowledge, 77 lifetimes of Tm I and 22 lifetimes of Tm II are reported for the first time. Good agreements between the present results and the previous experimental values were achieved for both Tm I and Tm II.

  2. YB-1 promotes microtubule assembly in vitro through interaction with tubulin and microtubules

    PubMed Central

    Chernov, Konstantin G; Mechulam, Alain; Popova, Nadezhda V; Pastre, David; Nadezhdina, Elena S; Skabkina, Olga V; Shanina, Nina A; Vasiliev, Victor D; Tarrade, Anne; Melki, Judith; Joshi, Vandana; Baconnais, Sonia; Toma, Flavio; Ovchinnikov, Lev P; Curmi, Patrick A

    2008-01-01

    Background YB-1 is a major regulator of gene expression in eukaryotic cells. In addition to its role in transcription, YB-1 plays a key role in translation and stabilization of mRNAs. Results We show here that YB-1 interacts with tubulin and microtubules and stimulates microtubule assembly in vitro. High resolution imaging via electron and atomic force microscopy revealed that microtubules assembled in the presence of YB-1 exhibited a normal single wall ultrastructure and indicated that YB-1 most probably coats the outer microtubule wall. Furthermore, we found that YB-1 also promotes the assembly of MAPs-tubulin and subtilisin-treated tubulin. Finally, we demonstrated that tubulin interferes with RNA:YB-1 complexes. Conclusion These results suggest that YB-1 may regulate microtubule assembly in vivo and that its interaction with tubulin may contribute to the control of mRNA translation. PMID:18793384

  3. Nanobulges on surface of silicon film and Si-Yb quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Qi; Liu, Shirong; Huang, Zhong-Mei; Miao, Xin-Jian; Qin, Chao-Jian; Lv, Quan

    2014-07-01

    Nanosilicon provides pumping levels and the localized states produced from Si-Yb bond on bulge surface of silicon film generate stimulated emission, in which a four-level system is built for chip-laser. The Si-Yb nanobulges on Si film cause a remarkable increase of the surface area and make a buffering layer for mismatch between Si and Yb lattices. Dynamics of photoluminescence and electroluminescence on nanosilicon coated by Yb is investigated. Stimulated peaks near 700 nm are observed on silicon quantum dots coated by Yb. Enhanced EL peaks in the wavelength region from 1300 nm to 1650 nm are measured on the Si film coated by Yb. Si-Yb quantum cascade laser is designed, in which emission wavelength could be manipulated into the window of optical communication by Si-Yb bonding on bulge surface of Si film.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  5. Near-IR photoactivation using mesoporous silica-coated NaYF4:Yb,Er/Tm upconversion nanoparticles.

    PubMed

    Gnanasammandhan, Muthu Kumara; Idris, Niagara Muhammad; Bansal, Akshaya; Huang, Kai; Zhang, Yong

    2016-04-01

    Photoactivation is a process in which light is used to 'activate' photolabile therapeutics. As a therapeutic strategy, its advantages are that it is noninvasive and that a high degree of spatial and temporal control is possible. However, conventional photoactivation techniques are hampered by the limited penetration depth of the UV and visible lights to which the photosensitive compounds are responsive. Here we describe a protocol for the use of upconversion nanoparticles (UCNs) as light transducers to convert deeply penetrating near-infrared (NIR) light to UV-visible wavelengths matching that of the absorption spectrum of photosensitive therapeutics. This allows the use of deep-penetrating and biologically friendly NIR light instead of low-penetrating and/or toxic visible or UV lights for photoactivation. In this protocol, we focus on two photoactivation applications: photodynamic therapy (PDT) and photoactivated control of gene expression. We describe how to prepare and characterize the UCNs, as well as how to check their function in biochemical assays and in cells. For both applications, the UCNs are coated with mesoporous silica for easy loading of the therapeutics. For PDT, the UCNs are coated with polyethylene glycol (PEG) for stabilization and folic acid for tumor targeting and then loaded with photosensitizers that would be expected to kill cells by singlet oxygen production; the nanoparticles are injected intravenously. For photoactivated control of gene expression, knockdown of essential tumor genes is achieved using UCNs loaded with caged nucleic acids, which are injected intratumorally. The whole process from nanoparticle synthesis to animal studies takes ∼36 d. PMID:26963631

  6. Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb(3+)/Tm(3+) upconversion particles.

    PubMed

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

    2015-02-25

    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. PMID:25305602

  7. Ultrasensitive polarized up-conversion of Tm(3+)-Yb3+ doped ?-NaYF4 single nanorod.

    PubMed

    Zhou, Jiajia; Chen, Gengxu; Wu, E; Bi, Gang; Wu, Botao; Teng, Yu; Zhou, Shifeng; Qiu, Jianrong

    2013-05-01

    Up-conversion luminescence in rare earth ions (REs) doped nanoparticles has attracted considerable research attention for the promising applications in solid-state lasers, three-dimensional displays, solar cells, biological imaging, and so forth. However, there have been no reports on REs doped nanoparticles to investigate their polarized energy transfer up-conversion, especially for single particle. Herein, the polarized energy transfer up-conversion from REs doped fluoride nanorods is demonstrated in a single particle spectroscopy mode for the first time. Unique luminescent phenomena, for example, sharp energy level split and singlet-to-triplet transitions at room temperature, multiple discrete luminescence intensity periodic variation with polarization direction, are observed upon excitation with 980 nm linearly polarized laser. Furthermore, nanorods with the controllable aspect ratio and symmetry are fabricated for analysis of the mechanism of polarization anisotropy. The comparative experiments suggest that intraions transition properties and crystal local symmetry dominate the polarization anisotropy, which is also confirmed by density functional theory calculations. Taking advantage of the REs based up-conversion, potential application in polarized microscopic multi-information transportation is suggested for the polarization anisotropy from REs doped fluoride single nanorod or nanorod array. PMID:23611309

  8. Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise

    ERIC Educational Resources Information Center

    Hailstone, Jono; Kilding, Andrew E.

    2011-01-01

    The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim of

  9. Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise

    ERIC Educational Resources Information Center

    Hailstone, Jono; Kilding, Andrew E.

    2011-01-01

    The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim of…

  10. High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}

    SciTech Connect

    Haberer, Almut; Huppertz, Hubert

    2009-04-15

    Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.

  11. TE/TM decomposition of electromagnetic sources

    NASA Technical Reports Server (NTRS)

    Lindell, Ismo V.

    1988-01-01

    Three methods are given by which bounded EM sources can be decomposed into two parts radiating transverse electric (TE) and transverse magnetic (TM) fields with respect to a given constant direction in space. The theory applies source equivalence and nonradiating source concepts, which lead to decomposition methods based on a recursive formula or two differential equations for the determination of the TE and TM components of the original source. Decompositions for a dipole in terms of point, line, and plane sources are studied in detail. The planar decomposition is seen to match to an earlier result given by Clemmow (1963). As an application of the point decomposition method, it is demonstrated that the general exact image expression for the Sommerfeld half-space problem, previously derived through heuristic reasoning, can be more straightforwardly obtained through the present decomposition method.

  12. Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent

    SciTech Connect

    Moore, Evan G.; Seitz, Michael; Raymond, Kenneth N.

    2008-06-09

    It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to the Solomon-Bloembergen-Morgan equations or, where sufficiently soluble in aqueous solution, studies on the temperature dependence of the paramagnetic contribution to the water {sup 17}O NMR transverse relaxation rate. Recently, Beeby et al reported on a qualitative equation to determine inner sphere hydration based on the change in lifetimes for Yb(III) in going from H{sub 2}O to D{sub 2}O solution, and we reasoned that the lower energy accepting state of Yb(III) may lie below the LMCT state which quenches Eu(III) emission, and hence may facilitate sensitized emission from Yb(III). This hypothesis was borne out experimentally, and herein we describe for the first time sensitized luminescence in the Near Infra-Red (NIR) region from a [Yb(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] complex, and hence the direct measurement of q for the archetypical member of this family of compounds.

  13. Evaluating LANDSAT-4 MSS and TM data

    NASA Technical Reports Server (NTRS)

    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

    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.

  14. Preliminary Evaluation of TM for Soils Information

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  15. TM/LANDSAT thermal image unmixing

    NASA Astrophysics Data System (ADS)

    Zhukov, Boris; Oertel, Dieter; Lehner, Manfred

    1997-08-01

    The multi-sensor multi-resolution technique (MMT) is applied to unmix a TM/LANDSAT-5 thermal image of a typical agricultural scene using higher-resolution images in the reflective TM channels. The technique allows to retrieve the mean thermal radiance for the multispectral classes which can be recognized in the higher-resolution reflective images. As a result, the unmixed thermal image can be restored with the pixel size of 30 m and merged with the reflective images for combined data analysis. Moving-window processing, as well as low-pass correction are used to reduce the effect of mixing the thermal features which can not be recognized in the reflective images. The accuracy of the technique is tested by comparing the unmixed TM thermal image with the airborne thermal images of the same scene, which were obtained by the DAIS-7915 imaging spectrometer shortly after the LANDSAT-5 fly-by, as well as with on- ground temperature measurements. The technique can be applied for unmixing thermal images of multi-resolution sensors in the near-future spaceborne Earth observation missions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    We have measured partial γ-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 γ-ray cross section from the 35Cl(n,γ)36Cl reaction at the cold-neutron-beam facility of the Garching Research Reactor. The γ-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 γ-ray level schemes. The total radiative capture cross sections of the 151Eu(n,γ)152Eu and 153Eu(n,γ)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,γ)152Eu and 151Eu(n,γ)152gEu reaction cross sections disagree with values in the literature. However, the total cross section of the 151Eu(n,γ)152Eu reaction does agree with those values. Also, our deduced cross section for the 153Eu(n,γ)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.

  17. Absolute calibration accuracy of L4 TM and L5 TM sensor image pairs

    USGS Publications Warehouse

    Chander, G.; Micijevic, E.

    2006-01-01

    The Landsat suite of satellites has collected the longest continuous archive of multispectral data of any land-observing space program. From the Landsat program's inception in 1972 to the present, the Earth science user community has benefited from a historical record of remotely sensed data. However, little attention has been paid to ensuring that the data are calibrated and comparable from mission to mission, Launched in 1982 and 1984 respectively, the Landsat 4 (L4) and Landsat 5 (L5) Thematic Mappers (TM) are the backbone of an extensive archive of moderate resolution Earth imagery. To evaluate the "current" absolute accuracy of these two sensors, image pairs from the L5 TM and L4 TM sensors were compared. The approach involves comparing image statistics derived from large common areas observed eight days apart by the two sensors. The average percent differences in reflectance estimates obtained from the L4 TM agree with those from the L5 TM to within 15 percent. Additional work to characterize the absolute differences between the two sensors over the entire mission is in progress.

  18. Yb:YAG Lasers for Space Based Remote Sensing

    NASA Technical Reports Server (NTRS)

    Ewing, J.J.; Fan, T. Y.

    1998-01-01

    Diode pumped solid state lasers will play a prominent role in future remote sensing missions because of their intrinsic high efficiency and low mass. Applications including altimetry, cloud and aerosol measurement, wind velocity measurement by both coherent and incoherent methods, and species measurements, with appropriate frequency converters, all will benefit from a diode pumped primary laser. To date the "gold standard" diode pumped Nd laser has been the laser of choice for most of these concepts. This paper discusses an alternate 1 micron laser, the YB:YAG laser, and its potential relevance for lidar applications. Conceptual design analysis and, to the extent possible at the time of the conference, preliminary experimental data on the performance of a bread board YB:YAG oscillator will be presented. The paper centers on application of YB:YAG for altimetry, but extension to other applications will be discussed.

  19. Laser performance of Yb3+ doped oxyorthosilicates LYSO and GYSO.

    PubMed

    Brickeen, Brian K; Geathers, Eliot

    2009-05-11

    Ytterbium offers a number of advantages as the active ion in solid-state laser crystals, but is hindered by the disadvantages of a three level lasing scheme. Yb(3+)-doped oxyorthosilicates have emerged in recent years as potentially quasi-four level laser materials. Two such crystals, Yb:GdYSiO(5) and Yb:LuYSiO(5), are investigated to determine the extent of four-level behavior. It is shown that these crystals demonstrate a significant reduction in the pump intensity required to reach threshold, but still exhibit three-level effects in terms of self-absorption, population inversion, and thermal sensitivity. The important material properties such as the coefficient of thermal expansion and the thermo-optic coefficient are measured. PMID:19434180

  20. Preparation and characterization of Yb-doped YAG ceramics

    NASA Astrophysics Data System (ADS)

    Hostaša, Jan; Esposito, Laura; Alderighi, Daniele; Pirri, Angela

    2013-02-01

    This work presents the results of the preparation of polycrystalline Yb:YAG ceramics for laser sources with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray dried mixture of pure oxide powders with TEOS as a sintering aid. Sintering was conducted under high vacuum and clean atmosphere. Various sintering cycles were tested, so that optimum conditions could be selected in dependence on Yb concentration. Samples with optical transmittance higher than 80% were prepared and their laser performance was examined. Slope efficiency as high as 73% and a maximum output power of 6 W were obtained for the sample doped with 10% Yb. Final microstructure of prepared samples was analyzed via optical microscopy, scanning and transmission electron microscopy, and EDS.

  1. Evolution of collectivity to very high spins in 160Yb

    NASA Astrophysics Data System (ADS)

    Johnson, N. R.; McGowan, F. K.; Winchell, D. F.; Baktash, C.; Garrett, J. D.; Lee, I. Y.; Wells, J. C.; Chaturvedi, L.; Gao, W. B.; Ma, W. C.; Pilotte, S.; Yu, C.-H.

    1996-02-01

    Lifetimes of 160Yb yrast states at high rotational frequencies have been measured by the Doppler broadened line shape technique. Excited states in 160Yb were populated by the reaction 120Sn(44Ca,4n)160Yb at a beam energy of 200 MeV and the experimental measurements were carried out in the coincidence mode with an array of Compton-suppressed germanium detectors. The results for the 24+ to 32+ yrast states led to values of the transition quadrupole moments similar to those obtained for the lower members (ħω<=0.29 MeV) of the ground band in previous recoil-distance measurements. The trend of reducing Qt values found for the I=34+ and 36+ states are suggestive of band termination. The results are discussed in the light of current theoretical predictions.

  2. Sequential growth of sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell-shell nanoparticles for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Peng, Huang-Yong; Ding, Bin-Bin; Ma, Yin-Chu; Sun, Shi-Qi; Tao, Wei; Guo, Yan-Chuan; Guo, Hui-Chen; Yang, Xian-Zhu; Qian, Hai-Sheng

    2015-12-01

    Upconversion (UC) nanostructures have attracted much interest for their extensive biological applications. In this work, we describe a sequential synthetic route to prepare sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell upconversion nanoparticles. The as-prepared products were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM, JEM 2100F), respectively. The as-prepared core-shell nanoparticles of NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb are composed of elliptical nanoparticles with a length of 80 nm and width of 42 nm, which show efficient upconversion fluorescence excited at 808 nm indicating the formation of core-shell-shell sandwiched nanostructures. In addition, the as-prepared sandwiched NaYF4:Yb/Er@NaYF4:Yb@NaNdF4:Yb core-shell upconversion nanoparticles also show strong upconversion fluorescence excited at 980 nm. Amphiphilic mPEG2k-b-PEBEP6K copolymers (denoted as PPE) were chosen to transfer these hydrophobic UCNPs into the aqueous phase for biological application. In vitro photodynamic therapy of cancer cells show that the viability of cells incubated with the nanoparticles loaded with MC 540 was significantly lower as compared to the nanoparticles without photosensitizers exposed to NIR laser.

  3. EU Space Awareness: Initial implemenation

    NASA Astrophysics Data System (ADS)

    Russo, Pedro

    2015-08-01

    EU Space Awareness uses the excitement of space to attract young people into science and technology and stimulate European and global citizenship. The project will show children and teenagers the opportunities offered by space science and engineering and inspire primary-school children when their curiosity is high and their value systems are being formed. EU Space Awareness, a 3-year project, has started in March 2015 with 10 partner organisations and 15 network nodes in 17 European countries and the IAU Office of Astronomy for Development. During this talk we will give a update about the intial implementation of the project and its relevant for astronomy for development.

  4. Tertiary phosphine complexes of the f-block metals. Preparation of pentamethylcyclopentadienyl-tertiary phosphine complexes of ytterbium(II), ytterbium(III), and europium(II). Crystal structure of Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/)

    SciTech Connect

    Tilley, T.D.; Andersen, R.A.; Zalkin, A.

    1983-03-16

    The diphosphine, Me/sub 2/PCH/sub 2/CH/sub 2/PMe/sub 2/, reacts with M(Me/sub 5/C/sub 5/)/sub 2/(OEt/sub 2/) to give insoluble M(Me/sub 5/C/sub 5/)/sub 2/(Me/sub 2/PCH/sub 2/CH/sub 2/PMe/sub 2/), where M is Eu or Yb. In contrast, Me/sub 2/PCH/sub 2/PMe/sub 2/ gives the hydrocarbon-soluble complexes M(Me/sub 5/C/sub 5/)/sub 2/(Me/sub 2/PCH/sub 2/PMe/sub 2/), where M is Eu or Yb. The ytterbium complex reacts with YbCl/sub 3/ in toluene to give Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/), and the crystal structure shows that the phosphine is acting as a monodentate ligand. Yb(Me/sub 5/C/sub 5/)/sub 2/Cl(Me/sub 2/PCH/sub 2/PMe/sub 2/) crystallizes in the monoclinic space group P2/sub 1//c with a = 16.358 (6) A, b = 8.595 (4) A, c - 20.712 (7) A, ..beta.. = 104.75 (4)/sup 0/, V = 2816 A/sup 3/, and d(calcd) = 1.45 g cm/sup -3/ for Z = 4 and mol wt = 615.15. Diffraction data were collected with a CAD-4 automated diffractometer, and the structure was refined to R = 0.054 for 3309 reflections with 4/sup 0/ < 2theta < 45/sup 0/ (Mo K..cap alpha.. radiation). The Yb is coordinated to the two Me/sub 5/C/sub 5/ groups, to the chlorine atom, and to one phosphorus atom of the bis(dimethylphosphino)methane ligand. The Yb-P and Yb-Cl distances are 2.94 and 2.53 A, respectively. The centroids of the C/sub 5/Me/sub 5/ ligands and the Cl and P atoms are in an approximate tetrahedral arrangement about the Yb atom.

  5. Identification and characterization of NF-YB family genes in tung tree.

    PubMed

    Yang, Susu; Wang, Yangdong; Yin, Hengfu; Guo, Haobo; Gao, Ming; Zhu, Huiping; Chen, Yicun

    2015-12-01

    The NF-YB transcription factor gene family encodes a subunit of the CCAAT box-binding factor (CBF), a highly conserved trimeric activator that strongly binds to the CCAAT box promoter element. Studies on model plants have shown that NF-YB proteins participate in important developmental and physiological processes, but little is known about NF-YB proteins in trees. Here, we identified seven NF-YB transcription factor-encoding genes in Vernicia fordii, an important oilseed tree in China. A phylogenetic analysis separated the genes into two groups; non-LEC1 type (VfNF-YB1, 5, 7, 9, 11, 13) and LEC1-type (VfNF-YB 14). A gene structure analysis showed that VfNF-YB 5 has three introns and the other genes have no introns. The seven VfNF-YB sequences contain highly conserved domains, a disordered region at the N terminus, and two long helix structures at the C terminus. Phylogenetic analyses showed that VfNF-YB family genes are highly homologous to GmNF-YB genes, and many of them are closely related to functionally characterized NF-YBs. In expression analyses of various tissues (root, stem, leaf, and kernel) and the root during pathogen infection, VfNF-YB1, 5, and 11 were dominantly expressed in kernels, and VfNF-YB7 and 9 were expressed only in the root. Different VfNF-YB family genes showed different responses to pathogen infection, suggesting that they play different roles in the pathogen response. Together, these findings represent the first extensive evaluation of the NF-YB family in tung tree and provide a foundation for dissecting the functions of VfNF-YB genes in seed development, stress adaption, fatty acid synthesis, and pathogen response. PMID:26037219

  6. Is YbAs a heavy Fermion system

    SciTech Connect

    Monnier, R.; Degiorgi, L.; Delley, B.; Koelling, D.D. . Lab. fuer Festkoerperphysik; Paul Scherrer Inst. , Villigen; Argonne National Lab., IL )

    1989-08-01

    Using parameters extracted from a tight binding fit to an ab initio band structure, the specific heat anomaly observed in YbAs around 5 K is computed within the infinite U limit of the degenerate Anderson impurity model. Applying the renormalization procedure derived in variational treatments of the periodic Anderson model, a quasiparticle Fermi surface with strong nesting features and small mass enhancements is obtained. The results suggest that YbAs is not a classical'' heavy Fermion system. 28 refs., 3 figs., 1 tab.

  7. Laser brackets debonding: Tm:YAP and ClarityTM SL self-ligating appliance system

    NASA Astrophysics Data System (ADS)

    Dostálová, Tatjana; Jelínková, Helena; Šulc, Jan; Koranda, Petr; Němec, Michal; Jelínek, Michal; Fibrich, Martin; Michalik, Pavel; Miyagi, Mitsunobu

    2010-02-01

    The study demonstrates the possibility of using Tm:YAP laser radiation for the removing ceramic brackets. The amount of enamel loss and residual resin on teeth has been evaluated. A diode-pumped Tm:YAP microchip laser generating at wavelength 1.9 μm was used for the debonding process. The transmission and absorption measurement of the basic elements - bracket, adhesive resin, and enamel was analyzed to explain the source of the heat and bracket debonding. Quantitative measurements are made for visualizing enamel surface before and after a self-ligating bonding technique. Temperature rise observation during the debonding procedure - from 0.5 to 2 W power - has improved the accuracy of assessment. The results were evaluated by CCD camera and scanning electron microscope. From the measurements it is possible to conclude that continuously running small diode pumped Tm:YAP microchip laser having output power 1W can remove the ceramic bracket without enamel iatrogenic damage.

  8. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    DOE PAGESBeta

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; et al

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  9. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    SciTech Connect

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; Zhao, Zhongxian

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  10. Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Xiong, Liangming; Sekiya, Edson H.; Saito, Kazuya

    2009-01-01

    A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb2O3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb3+-derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets.

  11. Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties.

    PubMed

    Xiong, Liangming; Sekiya, Edson H; Saito, Kazuya

    2009-01-01

    A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb2O3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb3+-derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets. PMID:19417259

  12. Thermal analysis on grad-doped active-mirror Yb:YAG ceramic lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaojin; Wang, Jianlei; Jiang, Benxue

    2015-11-01

    Heat conduction, temperature distribution, thermal stress, and thermally induced refractive index of a diode-pumped active-mirror grad-doped Yb:YAG ceramic laser are analyzed and compared to a uniform-doped Yb:YAG ceramic laser. It is found that a rationally designed grad-doped Yb:YAG ceramic has a smaller temperature gradient than a uniform-doped Yb:YAG ceramic with the same absorption pump power, which results in higher output energy in the grad-doped Yb:YAG ceramic laser.

  13. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub2}.

    SciTech Connect

    Peter, S. C.; Malliakas, C. D.; Nakotte, H.; Kothapilli, K.; Rayaprol, S.; Schultz, A. J.; Kanatzidis, M. G.

    2012-03-01

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a = 12.2261(20) {angstrom}, b = 10.7447(20) {angstrom}, c = 8.4754(17) {angstrom} and {beta} = 110.288(30){sup o} (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge)n. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a = b = 5.9874(6) {angstrom} and c = 15.1178(19) {angstrom}. The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{alpha}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures.

  14. Measurement of thermal neutron cross-section and resonance integral for the 174Yb(n,γ) 175Yb reaction by the cadmium ratio method

    NASA Astrophysics Data System (ADS)

    Karadag, Mustafa; Yücel, Haluk

    2008-06-01

    The thermal-neutron cross-section and the resonance integral for the 174Yb(n,γ)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am-Be neutron sources. The gamma-ray spectra from the activated samples were measured with a calibrated n-type high-purity Ge detector. The experimental results were corrected for the correction factors calculated for thermal and epithermal neutron self-shielding effects, epithermal neutron spectrum shape and gamma-ray self attenuation. Thus, the thermal neutron cross-section for the 174Yb(n,γ)175Yb reaction is found to be 126.5 ± 6.6 b, relative to that of the 55Mn monitor. The resonance integral value for the 174Yb(n,γ)175Yb reaction is found to be 59.6 ± 8.5 b, at cadmium cut-off energy of a 0.55 eV. Using the measured cadmium ratios of 55Mn and 174Yb, the result for resonance integral of the 174Yb(n,γ)175Yb reaction has also been obtained relative to the reference value of the 55Mn monitor. The present results for the 174Yb(n,γ)175Yb reaction agree well only with the recent experimental ones obtained by Kafala et al. [1] and De Corte and Simonits [2] within uncertainty limits. However, the previously reported experimental data for the thermal neutron cross-section for this reaction are distributed between 24 and 141 b, and similarly the experimental values for the resonance integral value also show a large scatter in the range of 30-69 b.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    (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 μm 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 (σ) increased.

  16. In situ observation of the Yb2+ emission in the radiodarkening process of Yb-doped optical preform.

    PubMed

    Ollier, N; Corbel, C; Duchez, J-B; Cavani, O; Benabdesselam, M; Mady, F

    2016-05-01

    This Letter relates the clear evidence of Yb2+ formation under 2.5 MeV electron irradiation in optical fiber preforms showing a darkening of the core. We thus detected by in situ photoluminescence measurements the green emission of divalent Yb2+ under the 355 nm excitation. Moreover, we showed the existence of two types of Yb2+ ion species with different stabilities. We demonstrated that the radiodarkening mechanism is based on a pair association of Yb2+ with aluminum oxygen hole center point defects. PMID:27128065

  17. Influence of the melting atmosphere on Yb3+/Al3+ co-doped silica glass with powder melting technology

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Zhou, Guiyao; Xia, Changming; Han, Ying; Zhao, Xingtao; Zhang, Wei; Wang, Wei

    2014-03-01

    We demonstrated the formation of Yb2+ ions in Yb3+/Al3+ co-doped silica glass using the powder melting technology based on the high-frequency plasma furnace. The Yb3+ ions can be deoxidated into Yb2+ ions under the atmosphere of N2 or Ar. The appearance and optical properties of the Yb3+/Al3+ co-doped silica glass are also changed.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  19. Fiber amplifiers and lasers in Yb:silica

    SciTech Connect

    Wilcox, R.B.; Browning, D.F.; Feit, M.D.; Nyman, B.

    1996-11-15

    We have measured gain and saturation in sing;e mode Yb:silica fiber, and developed fiber lasers and amplifiers at 1053 nm. The lasers are tunable over 10`s of nanometers, with amplifier gain flattened by fiber gratings or dielectric filters.

  20. Fluorescence and Spectroscopic Properties of Yb3+-Doped Phosphate Glasses

    NASA Astrophysics Data System (ADS)

    Krishnaiah, K. Venkata; Kumar, K. Upendra; Agarwal, V.; Murali, C. G.; Chaurasia, S.; Dhareshwar, L. J.; Jayasankar, C. K.; Lavin, Victor

    The concentration dependent Yb3+: phosphate (P2O5 + K2O + MgO + Al2O3 + Yb2O3) glasses have been prepared and characterized their fluorescence and laser properties. The stimulated emission cross-section and laser performance parameters were determined from the measured absorption spectra using the method of reciprocity. The refractive index, absorption and emission cross-sections and fluorescence lifetimes varied with Yb3+ ion concentration. The higher emission cross-section was found to be 1.01 × 10-20 cm2 at the extraction wavelength of 1005 nm. The fluorescence lifetime of 2F5/2 level decreases from 1.04 ms to 0.28 ms with increase of Yb2O3 concentration from 0.05 to 6.0 mol %. The gain cross-section spectra can be obtained from the measured absorption and emission cross-sections with different population levels. The values of emission cross-section, fluorescence lifetime, minimum pulse duration, pump power, extraction efficiency and gain coefficients suggest that these glasses can be used as a laser gain media for the generation of ultrashort pulse and high power laser applications.

  1. Universal dynamic magnetism in Yb pyrochlores with disparate ground states

    NASA Astrophysics Data System (ADS)

    Hallas, A. M.; Gaudet, J.; Butch, N. P.; Tachibana, M.; Freitas, R. S.; Luke, G. M.; Wiebe, C. R.; Gaulin, B. D.

    2016-03-01

    The ytterbium pyrochlore magnets, Yb2B2O7 (B =Sn ,Ti ,Ge ) are well described by Seff=1 /2 quantum spins decorating a network of corner-sharing tetrahedra and interacting via anisotropic exchange. Structurally, only the nonmagnetic B -site cation, and hence primarily the lattice parameter, changes across the series. Nonetheless, a range of magnetic behaviors is observed: the low-temperature magnetism in Yb2Ti2O7 and Yb2Sn2O7 has a ferromagnetic character, while Yb2Ge2O7 displays an antiferromagnetically ordered Néel state at low temperatures. While the static properties of the ytterbium pyrochlores are distinct, inelastic neutron scattering measurements reveal a common character to their exotic spin dynamics. All three ytterbium pyrochlores show a gapless continuum of spin excitations, resembling overdamped ferromagnetic spin waves at low Q . Furthermore, the specific heat of the series also follows a common form, with a broad, high-temperature anomaly followed by a sharp low-temperature anomaly at TC or TN. The novel spin dynamics we report correlate strongly with the broad specific heat anomaly only, remaining unchanged across the sharp anomaly. This result suggests that the primary order parameter in the ytterbium pyrochlores associated with the sharp anomaly is "hidden" and not simple magnetic dipole order.

  2. Ionizing radiation detection by Yb-doped silica optical fibers

    NASA Astrophysics Data System (ADS)

    De Mattia, Cristina; Veronese, Ivan; Fasoli, Mauro; Chiodini, Norberto; Mones, Eleonora; Cantone, Marie Claire; Cialdi, Simone; Gargano, Marco; Ludwig, Nicola; Bonizzoni, Letizia; Vedda, Anna

    2015-08-01

    Rare earths-doped silica optical fibers have shown promising results for ionizing radiation monitoring, thanks to their radio-luminescence (RL) properties. However, the use of these systems for accurate and precise dosimetric measurements in radiation fields above the Cerenkov energy threshold, like those employed in radiation therapy, is still challenging, since a spurious luminescence, namely the "stem effect," is also generated in the passive fiber portion exposed to radiation. The spurious signal mainly occurs in the UV-VIS region, therefore a dopant emitting in the near infrared may be suitable for an optical discrimination of the stem effect. In this work, the RL and dosimetric properties of Yb-doped silica optical fibers, produced by sol-gel technique, are studied, together with the methods and instruments to achieve an efficient optical detection of the Yb3+ emission, characterized by a sharp line at about 975 nm. The results demonstrate that the RL of Yb3+ is free from any spectral superposition with the spurious luminescence. This aspect, in addition with the suitable linearity, reproducibility, and sensitivity properties of the Yb-doped fibers, paves the way to their use in applications where an efficient stem effect removal is required.

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

    ERIC Educational Resources Information Center

    Molnar, Bill

    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…

  4. Unusual Yb magnetic properties in YbMn6Ge1.8-xSn4.2Gax and YbMn6Ge1.8Sn4.2-yGay

    NASA Astrophysics Data System (ADS)

    Eichenberger, L.; Malaman, B.; Mazet, T.

    2016-05-01

    We investigate the magnetic properties of the new HfFe6Ge6-type (P6/mmm) YbMn6Ge1.8-xSn4.2Gax (x=0.05, 0.4 and 0.9) and YbMn6Ge1.8Sn4.2-yGay (y=0.05, 0.5 and 1.0) alloys from DC magnetization and powder neutron diffraction experiments. The electronic structure modifications induced by the Ga substitution are found to promote the ferromagnetic order of the Mn sublattice, to enhance the Yb ordering temperature (up to TYb∼170 K) and to strongly increase the low-temperature coercive field (up to μ0Hc∼1 T). By contrast, the changes in the Yb magnetic moment magnitude upon Ga substitution are analyzed to be mainly driven by chemical pressure effects. The reduced Yb magnetic moment (1.0 μBYb<1.8 μB) compared with the free ion value (4 μB) is interpreted as resulting from Kondo screening. There are strong indirect indications that the high temperature Yb magnetic ordering likely involves intermediate valent Yb.

  5. Mechanism of tantalum adhesion on SiLK{sup TM}

    SciTech Connect

    Hu Yue; Yang Shuowang; Chen Xiantong; Lu Dong; Feng Yuanping; Wu Ping

    2005-09-19

    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.

  6. Nanocrystallization in Yb3+-doped oxyfluoride glasses for laser cooling

    NASA Astrophysics Data System (ADS)

    Kummara, Venkata Krishaniah; Ledemi, Yannick; Soares de Lima Filho, Elton; Messaddeq, Younes; Kashyap, Raman

    2015-03-01

    Glass-ceramics are composite materials consisting of crystals which are controllably grown within a glass matrix usually by applying an appropriate heat treatment. They possess outstanding optical properties with applications in solid state lasers, optical amplifiers, and now, laser induced cooling. For laser cooling, the material should exhibit specific properties like low phonon energy environment around the lanthanide ions, low background losses, high transparency and high photoluminescence quantum yield. In the present study, oxyfluoride glasses and ultra-transparent nano glassceramics doped with different concentrations (2, 5, 8, 12, 16 and 20 mol %) of Yb 3+ ions have been prepared by conventional melt-quenching and subsequent thermal treatments at different temperatures, respectively. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements have been performed to characterize the thermal properties of the glass and the structural changes in the glass-ceramics, respectively. The XRD patterns confirm the growth of β-PbF2 nanocrystals as well as progressive incorporation of Yb 3+ ions. This enhances the Yb 3+ ion emission intensity which depends on the doping concentration and ceramization temperatures. The size (20 nm) of the nanocrystallites was estimated from the Sherrer's formula and found to increase with increasing ceramization temperature, small enough to avoid scattering losses and ensure an excellent transparency of the glass-ceramics comparable with that of the parent glass. An enhancement of the luminescence properties of Yb 3+ ions surrounded by a crystalline low phonon environment is observed. Finally, the utilization of these heavily Yb 3+-doped ultra-transparent materials for laser cooling and solid state laser applications is discussed.

  7. Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi

    2012-09-01

    In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 × 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 ± 1 °C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 ± 1 °C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the functional groups but also as a substrate inducing the nucleation of phosphate nanoparticles. Stable nano-sized Yb phosphate precipitates formed on yeast cell surfaces in the present study, which implies that this post-adsorption nano-particle formation process caused by microbial cells should be one of the important processes governing the long-term migration of heavy rare earth elements and presumably trivalent actinides in geological repository.

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

    PubMed Central

    2013-01-01

    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

  9. YB-1, a new biomarker of glioma progression, is associated with the prognosis of glioma patients.

    PubMed

    Zheng, Jin; Dong, Weijiang; Zhang, Jiangwei; Li, Guangyue; Gong, Huilin

    2016-04-01

    Y box protein 1 (YB-1) is a multifunctional cellular protein expressed in various cancers, and is a potential target in cancer therapy. Although there is evidence showing that YB-1 plays a role in human cancers, the clinical significance of YB-1 expression in glioma has not been established. In the present study, we investigated the YB-1 level in glioma tumors and analyzed the relationship between the YB-1 level and the grade of malignant glioma, with the aim of providing new ideas for the diagnosis and treatment of gliomas in clinical and basic research settings. A total of 108 patients, comprising 14, 31, 30, and 33 with gliomas of Grades I, II, III, and IV, respectively, were included in this study. The mRNA and protein levels of YB-1 were found to be significantly different between Grade IV and lower-grade tumors. The YB-1 levels in cerebrospinal fluid were significantly higher in Grades III and IV glioma patients than in Grades I and II patients. Immunofluorescence staining was used to detect the levels of YB-1 in the cytoplasm and the nucleus, and results indicated that the intracellular distribution was significantly associated with the pathological grade of glioma. A higher level of YB-1 was associated with shortened survival, suggesting that YB-1 plays a role in the progression of human glioma. PMID:26936129

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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 μm 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.

  11. Novel fluorescent chelate for Eu

    NASA Astrophysics Data System (ADS)

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

    1995-05-01

    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.

  12. Development of the HiLight TM scintillator for computed tomography medical imaging

    NASA Astrophysics Data System (ADS)

    Duclos, Steven J.; Greskovich, Charles D.; Lyons, Robert J.; Vartuli, James S.; Hoffman, David M.; Riedner, Robert J.; Lynch, Michael J.

    2003-06-01

    The image quality of computed tomography (CT) medical scanners is extremely sensitive to afterglow, radiation damage and optical non-uniformities of scintillators used in X-ray detectors. This represents a tough challenge in the design of scintillator materials with optimum properties. Discussion will center on the development and properties of the first commercialized transparent ceramic scintillator, the (Y,Gd) 2O 3:Eu-based HiLight TM scintillator used in GE Medical System's CT products. The flexibility of the ceramic scintillator platform has enabled it to be engineered to satisfy the changing needs of CT imaging, which is demonstrated by its successful incorporation into over 8000 CT systems worldwide since 1988. The ceramic process makes possible uniform co-doping at ppm levels to control electronic defects responsible for afterglow, reducing it to levels below detectibility in CT images. Annealing of the material in controlled oxygen atmospheres, combined with rapid oxygen diffusion along grain boundaries in the ceramic, reduces radiation damage to negligible values. Transient thermoluminescence of these materials will be discussed as a diagnostic of electronic trap levels responsible for both afterglow and radiation damage. Finally, with the increased scan speed requirements of modern CT systems, energy transfer between the Eu activator and other rare-earth ions can be used to speed the radiative decay of the scintillator, ensuring the material's continued viability in future CT systems.

  13. Efficient sensitization of Yb3+ emission by Nd3+ in Y2O3 transparent ceramics and the prospect for high-energy Yb lasers.

    PubMed

    Lupei, Voicu; Lupei, Aurelia; Gheorghe, Cristina; Hau, Stefania; Ikesue, Akio

    2009-07-15

    Very efficient energy transfer from Nd3+ to Yb3+ in transparent Y2O3 ceramics in the temperature range 10-300 K is demonstrated. It is inferred that this shows potential for the construction of high-energy Yb3+ lasers under diode or flash-lamp excitation of Nd3+. PMID:19823528

  14. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  15. YB-1 overexpression promotes a TGF-β1-induced epithelial–mesenchymal transition via Akt activation

    SciTech Connect

    Ha, Bin; Lee, Eun Byul; Cui, Jun; Kim, Yosup; Jang, Ho Hee

    2015-03-06

    The Y-box binding protein-1 (YB-1) is a transcription/translation regulatory protein, and the expression thereof is associated with cancer aggressiveness. In the present study, we explored the regulatory effects of YB-1 during the transforming growth factor-β1 (TGF-β1)-induced epithelial-to-mesenchymal transition (EMT) in lung adenocarcinoma cells. Downregulation of YB-1 increased E-cadherin promoter activity, and upregulation of YB-1 decreased promoter activity, suggesting that the YB-1 level may be correlated with the EMT. TGF-β1 induced YB-1 expression, and TGF-β1 translocated cytosolic YB-1 into the nucleus. YB-1 overexpression promoted TGF-β1-induced downregulation of epithelial markers, upregulation of mesenchymal markers, and cell migration. Moreover, YB-1 overexpression enhanced the expression of E-cadherin transcriptional repressors via TGF-β1-induced Akt activation. Our findings afford new insights into the role played by YB-1 in the TGF-β1 signaling pathway. - Highlights: • YB-1 regulates E-cadherin expression in A549 cells. • TGF-β1 induces upregulating and nuclear localization of YB-1. • YB-1 overexpression accelerates TGF-β1-induced EMT and cell migration. • YB-1 regulates Snail and Slug expression via Akt activation.

  16. SpellRead[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2013

    2013-01-01

    "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…

  17. Relative radiometric calibration of LANDSAT TM reflective bands

    NASA Technical Reports Server (NTRS)

    Barker, J. L.

    1984-01-01

    A common scientific methodology and terminology is outlined for characterizing the radiometry of both TM sensors. The magnitude of the most significant sources of radiometric variability are discussed and methods are recommended for achieving the exceptional potential inherent in the radiometric precision and accuracy of the TM sensors.

  18. Notes from ERIC/TM: Educational Measurement Productivity.

    ERIC Educational Resources Information Center

    Rudner, Lawrence M.; And Others

    1991-01-01

    During a 28-month period beginning in January 1988, the ERIC Clearinghouse on Tests, Measurement, and Evaluation (ERIC/TM) selected documents submitted by over 800 organizations for entry into the ERIC database. Twenty-three organizations, which submitted 595 (31 percent) of the 1,904 documents accepted by ERIC/TM during that period, are

  19. Utilising eduroam[TM] Architecture in Building Wireless Community Networks

    ERIC Educational Resources Information Center

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

    2008-01-01

    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…

  20. 75 FR 61479 - Western Passage OCGenTM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Western Passage OCGen\\TM\\ Power Project; Notice of Preliminary Permit... consist of: (1) 2 OCGen\\TM\\ hydrokinetic tidal devices each consisting of four 150-kilowatt...

  1. Full Immersive Virtual Environment Cave[TM] in Chemistry Education

    ERIC Educational Resources Information Center

    Limniou, M.; Roberts, D.; Papadopoulos, N.

    2008-01-01

    By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualize…

  2. Accelerated Math[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2010

    2010-01-01

    "Accelerated Math"[TM], published by Renaissance Learning, is a software tool used to customize assignments and monitor progress in mathematics for students in grades 1-12. "Accelerated Math"[TM] creates individualized assignments that align with state standards and national guidelines, scores student work, and generates formative feedback through…

  3. Accelerated Math[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2011

    2011-01-01

    "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…

  4. Accelerated Reader[TM]. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2010

    2010-01-01

    "Accelerated Reader"[TM] is a guided reading intervention used to supplement regular reading instruction in K-12 classrooms. Its aim is to improve students' reading skills through reading practice and quizzes on the books students read. The "Accelerated Reader"[TM] program calls for students to select and read a book and then take a computerized…

  5. Social Stories[TM] for Children with Disabilities

    ERIC Educational Resources Information Center

    Reynhout, Georgina; Carter, Mark

    2006-01-01

    A review of the empirical research literature on Social Stories[TM] is presented, including a descriptive review and single-subject meta-analysis of appropriate studies. Examination of data suggests the effects of Social Stories[TM] are highly variable. Interpretations of extant studies are frequently confounded by inadequate participant…

  6. Social Stories[TM]: A Possible Theoretical Rationale

    ERIC Educational Resources Information Center

    Reynhout, Georgina; Carter, Mark

    2011-01-01

    Social Stories[TM] are an intervention widely used with individuals with autism spectrum disorders (ASD). This paper discusses a possible theoretical rationale that might account for the purported efficacy of Social Stories[TM]. Attributes of individuals with ASD in relation to Social Story intervention including difficulties with theory of mind…

  7. Disability Awareness Night[TM]: 2006 Honorees, Sponsors, Teams

    ERIC Educational Resources Information Center

    Exceptional Parent, 2006

    2006-01-01

    This article presents the 2006 honorees, sponsors, and teams for the Disability Awareness Night[TM]. Disability Awareness Night[TM] is a unique and powerful community outreach program. Its vision is to continue to raise awareness outside of the community of individuals with disabilities to continue the goal that this program will open doors to…

  8. Full Immersive Virtual Environment Cave[TM] in Chemistry Education

    ERIC Educational Resources Information Center

    Limniou, M.; Roberts, D.; Papadopoulos, N.

    2008-01-01

    By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualize

  9. Inside Linden Lab: Second Life [TM] for Educators

    ERIC Educational Resources Information Center

    Atkinson, Tom

    2008-01-01

    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…

  10. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}

    SciTech Connect

    Peter, Sebastian C.; Malliakas, Christos D.; Nakotte, Heinze; Kothapilli, Karunakar; Rayaprol, Sudhindra; Schultz, Arthur J.; Kanatzidis, Mercouri G.

    2012-03-15

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.

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

    SciTech Connect

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

    2014-04-01

    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.

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

    SciTech Connect

    Antonov, VN; Bekenov, LV; Antropov, VP

    2014-04-08

    X-ray absorption and magnetic circular dichroism spectra at the L-3 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 E-2 and magnetic dipole M-1 transitions have been investigated. The calculated results are compared with available experimental data.

  13. Identification of proteins specifically interacting with YB-1 mRNA 3' UTR and the effect of hnRNP Q on YB-1 mRNA translation.

    PubMed

    Lyabin, D N; Nigmatullina, L F; Doronin, A N; Eliseeva, I A; Ovchinnikov, L P

    2013-06-01

    In this study, proteins specifically interacting with the 3' untranslated region (UTR) of mRNA of the multifunctional Y-box-binding protein 1 (YB-1) were identified. One of these, hnRNP Q, was shown to specifically interact with the regulatory element (RE) in YB-1 mRNA 3' UTR and to inhibit translation of this mRNA. Its binding to the RE was accompanied by displacement from this element of the poly(A)-binding protein (PABP), a positive regulator of YB-1 mRNA translation, and by enhanced binding of the negative YB-1 mRNA translation regulator - YB-1 itself. PMID:23980891

  14. Governance in EU illicit drugs policy.

    PubMed

    Edwards, Carel; Galla, Maurice

    2014-09-01

    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

  15. Spectrum and energy levels of the Yb4+ free ion (Yb V)

    NASA Astrophysics Data System (ADS)

    Meftah, Ali; Wyart, Jean-François; Tchang-Brillet, Wan-Ü. Lydia; Blaess, Christophe; Champion, Norbert

    2013-10-01

    The spectrum of ionized ytterbium produced by a sliding spark source was recorded on the 10 m high resolution vacuum ultraviolet normal-incidence spectrograph of the Meudon Observatory. About 1080 lines attributed to Yb V, hitherto unknown, have been identified. The analysis of this spectrum established all the energy levels of the ground configuration 4f12 and, respectively 174, 12 and 43 levels of the excited configurations 4f115d,4f116s and 4f116p. The theoretical calculations by means of the Cowan codes included a least-squares optimization of the relevant radial parameters by minimizing the differences between calculated and experimental level energies, which led to mean errors of 55 cm-1 for the 56 even parity levels and 51 cm-1 for the 186 odd parity ones. Interactions with the unknown core-excited configurations 5p54f13, 5p54f126p, 5p54f125d and 5p54f126s were taken into account.

  16. Optical properties of Tm 3+ ions in lithium borate glasses

    NASA Astrophysics Data System (ADS)

    Jayasankar, C. K.; Renuka ^Devi, A.

    1996-09-01

    Optical properties of Tm 3+ ions are investigated in the following lithium borate (LBO) glasses: Li 2CO 3 + H 3BO 3 and MCO 3 + Li 2CO 3 + H 3BO 3 (M = Mg, Ca, Sr and Ba). The assigned energy level data of Tm 3+ (4f 12) in these borate glasses as well as the data that are available for some other systems in the literature are analysed in terms of a parametrized Hamiltonian model that includes 14 free-ion parameters. The absorption linestrengths are measured for Tm 3+:LBO glasses. Using these data, intensity parameters (Ω λ, λ = 2, 4, 6), radiative transition probabilities, radiative lifetimes, fluorescence branching ratios and integrated absorption cross-sections for fluorescent levels of Tm 3+:LBO glasses are calculated by applying Judd-Ofelt theory. The effect of glass network formers and glass modifiers on the optical properties of Tm 3+:glasses are discussed.

  17. Structural features of the tmRNA–ribosome interaction

    PubMed Central

    Bugaeva, Elizaveta Y.; Surkov, Serhiy; Golovin, Andrey V.; Öfverstedt, Lars-Göran; Skoglund, Ulf; Isaksson, Leif A.; Bogdanov, Alexey A.; Shpanchenko, Olga V.; Dontsova, Olga A.

    2009-01-01

    Trans-translation is a process which switches the synthesis of a polypeptide chain encoded by a nonstop messenger RNA to the mRNA-like domain of a transfer-messenger RNA (tmRNA). It is used in bacterial cells for rescuing the ribosomes arrested during translation of damaged mRNA and directing this mRNA and the product polypeptide for degradation. The molecular basis of this process is not well understood. Earlier, we developed an approach that allowed isolation of tmRNA–ribosomal complexes arrested at a desired step of tmRNA passage through the ribosome. We have here exploited it to examine the tmRNA structure using chemical probing and cryo-electron microscopy tomography. Computer modeling has been used to develop a model for spatial organization of the tmRNA inside the ribosome at different stages of trans-translation. PMID:19861420

  18. Water quality mapping using Landsat TM imagery

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    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.

  19. 76 FR 38618 - Proposed Information Collection; Comment Request; StormReadyTM

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ...Ready\\TM\\, TsunamiReady\\TM\\ and StormReady/TsunamiReady\\TM\\ Application Forms AGENCY: National Oceanic... TsunamiReady and StormReady/TsunamiReady programs also in this information collection, is a...

  20. Structure of Tm2 and Tm2C2 encapsulated in low-symmetry C82(Cs(6)) fullerene cage by single crystal X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Sado, Yuki; Aoyagi, Shinobu; Izumi, Noriko; Kitaura, Ryo; Kowalczyk, Tim; Wang, Jian; Irle, Stephan; Nishibori, Eiji; Sugimoto, Kunihisa; Shinohara, Hisanori

    2014-04-01

    The molecular structures of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are determined by means of single crystal X-ray diffraction using the co-crystals with nickel octaethylporphyrin (Ni(OEP)). The molecular orientations and Tm positions of Tm2@C82(Cs(6)) and Tm2C2@C82(Cs(6)) are basically the same each other. One of the two Tm positions is very close to the Tm position of Tm@C82(Cs(6)). These facts demonstrate that the stable endohedral Tm positions are not fundamentally affected by the addition of the other Tm atoms but dependent on the kind of the fullerene cage structure.

  1. Cryogenically-cooled Yb:YGAG ceramic mode-locked laser.

    PubMed

    Muk, J; Jelnek, M; Jambunathan, V; Miura, T; Smr, M; Endo, A; Mocek, T; Kube?ek, V

    2016-01-25

    This work reports on a liquid-nitrogen-cooled, SESAM mode-locked Yb:YGAG (Yb:Y3Ga2Al3O12) ceramic laser. The Yb:YGAG has a similar structure to Yb:YAG, but its emission spectrum at low temperature remains much broader, which is suitable for ultrashort pulse generation and amplification. A stable pulse train with 119-MHz repetition rate was obtained at a wavelength of 1026 nm. The measured pulse duration is 2.4 ps, which is more than four times shorter than that achieved with a cryogenically-cooled Yb:YAG. Furthermore, laser performance of the Yb:YGAG ceramics in continuous-wave operation and wavelength tunability at 80 K was investigated. PMID:26832521

  2. Synthesis and characterization of Er:Yb3Al5O12 nanopowder

    NASA Astrophysics Data System (ADS)

    Li, Chun; Xu, Jialin; Liu, Wang; Lin, Hai; Liu, Yu; Wang, Dan; Zhai, Jian; Fu, Tiehan; Zhou, Hu; Li, Yusheng; Liu, Jinghe; Zeng, Fanming

    2015-12-01

    Er:Yb1Al5O12 (Er:YbAG) nanopowder was prepared by carbonate coprecipitation method. Highpurity Er:YbAG powder was obtained after calcination at as low as 1000°C with an average particle size of 70 nm. The Al-O-Yb phonon vibrations were investigated and the absorption band arisen from interaction between lattice vibration and photon in YbAG is located around 610 cm-1. A strong emission peak of powder was observed at 1.53 µm with 980 nm laser excitation. An energy transfer mechanism between Yb3+ and Er3+ states responsible for the peak emission was proposed. An optimum Er3+ dopant concentration was determined.

  3. Down conversion of Er3+-Yb3+ couple in Y2BaZnO5

    NASA Astrophysics Data System (ADS)

    Xia, Wenbin; Jin, Xiangliang; Yang, Xiaoliang; Xiao, Siguo

    2016-04-01

    Er3+-Yb3+ co-doped Y2BaZnO5 phosphors were synthesized via high temperature solid-state reaction method. The quantum cutting properties for Er3+-Yb3+ co-doped Y2BaZnO5 phosphors have been detailedly exploited under different wavelength excitation. Unlike in fluoride host, only the Er(4S3/2) + Yb(2F7/2) → Er(4I13/2) + Yb(2F5/2) energy transfer process in Y2BaZnO5 effectively performs the down-conversion, which can split an absorbed high-energy photon into two photons of 1000 nm and 1550 nm radiations. The quantum cutting properties of Er3+-Yb3+ couple in Y2BaZnO5 provides meaningful reference in search of new efficient Er3+-Yb3+ co-doped quantum cutting phosphors.

  4. Links between the Oncoprotein YB-1 and Small Non-Coding RNAs in Breast Cancer

    PubMed Central

    Blenkiron, Cherie; Hurley, Daniel G.; Fitzgerald, Sandra; Print, Cristin G.; Lasham, Annette

    2013-01-01

    Background The nucleic acid-binding protein YB-1, a member of the cold-shock domain protein family, has been implicated in the progression of breast cancer and is associated with poor patient survival. YB-1 has sequence similarity to LIN28, another cold-shock protein family member, which has a role in the regulation of small noncoding RNAs (sncRNAs) including microRNAs (miRNAs). Therefore, to investigate whether there is an association between YB-1 and sncRNAs in breast cancer, we investigated whether sncRNAs were bound by YB-1 in two breast cancer cell lines (luminal A-like and basal cell-like), and whether the abundance of sncRNAs and mRNAs changed in response to experimental reduction of YB-1 expression. Results RNA-immunoprecipitation with an anti-YB-1 antibody showed that several sncRNAs are bound by YB-1. Some of these were bound by YB-1 in both breast cancer cell lines; others were cell-line specific. The small RNAs bound by YB-1 were derived from various sncRNA families including miRNAs such as let-7 and miR-320, transfer RNAs, ribosomal RNAs and small nucleolar RNAs (snoRNA). Reducing YB-1 expression altered the abundance of a number of transcripts encoding miRNA biogenesis and processing proteins but did not alter the abundance of mature or precursor miRNAs. Conclusions YB-1 binds to specific miRNAs, snoRNAs and tRNA-derived fragments and appears to regulate the expression of miRNA biogenesis and processing machinery. We propose that some of the oncogenic effects of YB-1 in breast cancer may be mediated through its interactions with sncRNAs. PMID:24260353

  5. XRD and IR Studies of Yb3+ Doped Tellurite Glass

    NASA Astrophysics Data System (ADS)

    Sahar, M. R.; Isa, H. Noor

    2011-03-01

    Ytterbium doped sodium-tellurite glasses having composition of (80-x) TeO2-20Na2O-(x)Yb2O3 (where x = 0.0-2.0 mol%) are prepared by melt quenching technique. The crystallinity of the glass has been examined using X-ray diffraction technique. All glass are found to be amorphous in nature. Meanwhile the transmission spectroscopy is determine by using Infrared Spectroscopy. It is found that the absorption vibrational spectra occurs at range 3405-3423 cm-1, 1632-1643 cm-1, 1377-1382 cm-1, 721-732 cm-1 and 589-606 cm-1 peaks. The predominant peaks around 700 cm-1 is due to the Te-O-Te vibration while peak at 600 cm-1 is due to the vibration of Yb3+ ions.

  6. Charge Fluctuations and the Valence Transition in Yb under Pressure

    SciTech Connect

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

    2009-04-21

    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.

  7. Quantum Critical Behavior in YbRh_2Si_2

    NASA Astrophysics Data System (ADS)

    Steglich, F.

    2002-03-01

    Single crystals of the ``heavy-fermion'' metal YbRh_2Si2 show pronounced non-Fermi-liquid (NFL) phenomena at p = 0 and B = 0. These are related to a weak antiferromagnetic (AF) transition at TN ≈ 70 mK. By doping with 5at% Ge, the Néel temperature is depressed to below T = 10 mK, i.e., the system is pushed toward the quantum critical point (TN arrow 0). For the YbRh_2(Si_0.95Ge_0.05)2 single crystal the resistivity ρ is found to depend linearly on T over more than three decades for T >= 10 mK, reminiscent of the prediction for the frequently adopted spin-density-wave scenario (assuming 2D AF spinfluctuations). Recent results of magnetic and thermodynamic measurements are in striking conflict with this scenario.

  8. Diffusion of Excitation in GGG:Yb3+ Laser Crystal

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  9. First principle investigations on structural, mechanical, spin polarized electronic and magnetic properties of TmZn and TmCd

    NASA Astrophysics Data System (ADS)

    Chand, Satish; Singh, R. P.; Govindan, A.

    2015-09-01

    Structural, mechanical, spin polarized electronic and magnetic properties of TmZn and TmCd intermetallic compounds have been studied using the full-potential linearize augmented plane-wave plus local orbital method. The structural and mechanical properties have been studied in terms of lattice parameter ( a 0), bulk modulus ( B 0) and its first-order pressure derivative (B0^' }), elastic constants ( C ij ), Young's modulus ( Y), shear modulus ( G) and Poisson's ratio (\\upsilon) in equilibrium state which are found to be consistent with available experimental/theoretical values. Spin polarized electronic properties have been investigated in terms of band structure and density of state histograms for spin up and spin down channel. Electronic behavior of TmZn and TmCd shows that studied materials are metallic ferromagnets with high spin polarization in which Tm-f state electrons have dominant character.

  10. NUCLEAR PHYSICS: Formation Mechanism of Triaxial Superdeformed Nucleus 160Yb

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    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 γ = 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.

  11. Efficient lasing in Yb:(YLa)2O3 ceramics

    NASA Astrophysics Data System (ADS)

    Snetkov, I. L.; Mukhin, I. B.; Balabanov, S. S.; Permin, D. A.; Palashov, O. V.

    2015-02-01

    A high-optical-quality sample of Yb0.1Y1.7La0.2O3 ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate - nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%.

  12. The Cold Shock Domain of YB-1 Segregates RNA from DNA by Non-Bonded Interactions

    PubMed Central

    Kljashtorny, Vladislav; Nikonov, Stanislav; Ovchinnikov, Lev; Lyabin, Dmitry; Vodovar, Nicolas; Curmi, Patrick; Manivet, Philippe

    2015-01-01

    The human YB-1 protein plays multiple cellular roles, of which many are dictated by its binding to RNA and DNA through its Cold Shock Domain (CSD). Using molecular dynamics simulation approaches validated by experimental assays, the YB1 CSD was found to interact with nucleic acids in a sequence-dependent manner and with a higher affinity for RNA than DNA. The binding properties of the YB1 CSD were close to those observed for the related bacterial Cold Shock Proteins (CSP), albeit some differences in sequence specificity. The results provide insights in the molecular mechanisms whereby YB-1 interacts with nucleic acids. PMID:26147853

  13. Interplay between YB-1 and IL-6 promotes the metastatic phenotype in breast cancer cells

    PubMed Central

    Castellana, Bàrbara; Aasen, Trond; Moreno-Bueno, Gema; Dunn, Sandra E.; Ramón y Cajal, Santiago

    2015-01-01

    Epithelial to mesenchymal transition (EMT) induces cell plasticity and promotes metastasis. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) and the pleiotropic cytokine interleukin 6 (IL-6) have both been implicated in tumor cell metastasis and EMT, but via distinct pathways. Here, we show that direct interplay between YB-1 and IL-6 regulates breast cancer metastasis. Overexpression of YB-1 in breast cancer cell lines induced IL-6 production while stimulation with IL-6 increased YB-1 expression and YB-1 phosphorylation. Either approach was sufficient to induce EMT features, including increased cell migration and invasion. Silencing of YB-1 partially reverted the EMT and blocked the effect of IL-6 while inhibition of IL-6 signaling blocked the phenotype induced by YB-1 overexpression, demonstrating a clear YB-1/IL-6 interdependence. Our findings describe a novel signaling network in which YB-1 regulates IL-6, and vice versa, creating a positive feed-forward loop driving EMT-like metastatic features during breast cancer progression. Identification of signaling partners or pathways underlying this co-dependence may uncover novel therapeutic opportunities. PMID:26512918

  14. YbPtGe2: A multivalent charge-ordered system with an unusual spin pseudogap

    NASA Astrophysics Data System (ADS)

    Gumeniuk, Roman; Sarkar, Rajib; Geibel, Christoph; Schnelle, Walter; Paulmann, Carsten; Baenitz, Michael; Tsirlin, Alexander A.; Guritanu, Violeta; Sichelschmidt, Jrg; Grin, Yuri; Leithe-Jasper, Andreas

    2012-12-01

    We performed a study of the structural and physical properties of YbPtGe2. This compound is a multivalent charge-ordered system presenting an unusual spin pseudogap below 200 K. The crystal structure of YbPtGe2 is refined from single-crystal and powder high-resolution synchrotron x-ray diffraction data at different temperatures. Analysis of the structural features of YbPtGe2, together with a combined study of Yb LIII x-ray absorption spectroscopy, magnetic susceptibility ?(T), thermopower S(T), and 171Yb and 195Pt NMR indicate half of the Yb atoms to be in an intermediate valence state with an electronic configuration close to 4f13 (Yb3+), while for the remaining Yb atoms the 4f14 (Yb2+) configuration with almost no valence fluctuations is most likely. A drastic drop of the magnetic susceptibility and a decrease of the isotropic shift 195Kiso(T) with decreasing temperature in the temperature range of 50-200 K evidence the opening of a spin pseudogap with an activation energy of ?/kB 200 K. Surprisingly, transport properties do not show clear evidence for the opening of a charge gap, thus excluding a standard Kondo-insulator scenario. Possible origins for this unusual electronic (valence) behavior are discussed.

  15. Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

    SciTech Connect

    Wang, Xinshun Liu, Yang; Zhao, Panjuan; Guo, Zhongyi; Li, Yan; Qu, Shiliang

    2015-04-21

    The broad band upconversion luminescence in Yb{sup 3+}:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb{sup 2+} ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb{sup 2+}-F{sup +}) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb{sup 3+} to Yb{sup 2+} and (Yb{sup 2+}-F{sup +}) centers have been induced by infrared femtosecond laser irradiation in Yb{sup 3+}:YAG crystal.

  16. Yb-based heavy fermion compounds and field tuned quantum chemistry

    SciTech Connect

    Mun, Eundeok

    2010-07-23

    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.

  17. Optical properties of Yb-doped LaB6 from first-principles calculation

    NASA Astrophysics Data System (ADS)

    Chao, Luomeng; Bao, Lihong; Wei, Wei; Tegus, O.

    2016-03-01

    The optical properties of Yb-doped LaB6 have been investigated by first-principles calculations within the framework of density functional theory. The results show that the Yb 4f states at near Fermi surface affect their optical properties and the Yb-doping leads to a reduction of the plasmon energy of LaB6, i.e. a redshift of the position of transmission peak in the visible-near infrared region. This study offers a theoretical prediction for the design and application of Yb-doped LaB6 as an optoelectronic material.

  18. Broadband infrared luminescence in Yb-doped Bi2O3-GeO2 glasses

    NASA Astrophysics Data System (ADS)

    Yu, Pingsheng; Su, Liangbi; Cheng, Junhua; Xu, Jun

    2016-01-01

    The Yb-doped Bi2O3-GeO2 glasses were prepared by the conventional melt quenching technique. Near-infrared (NIR) broadband emission was found at about 1024 nm, and 1330 nm (under 785 nm excitation), and the measured fluorescent lifetime was about several hundred microseconds. The emission intensity of Yb-doped Bi2O3-GeO2 glasses increased with increasing of Yb dopant in our experiments. The NIR emission should be related to Yb3+ and lower valence Bi ions.

  19. X-RAY ABSORPTION SPECTROSCOPY OF YB3+-DOPED OPTICAL FIBERS

    SciTech Connect

    Citron, Robert; Kropf, A.J.

    2008-01-01

    Optical fibers doped with Ytterbium-3+ have become increasingly common in fiber lasers and amplifiers. Yb-doped fibers provide the capability to produce high power and short pulses at specific wavelengths, resulting in highly effective gain media. However, little is known about the local structure, distribution, and chemical coordination of Yb3+ in the fibers. This information is necessary to improve the manufacturing process and optical qualities of the fibers. Five fibers doped with Yb3+ were studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES), in addition to Yb3+ mapping. The Yb3+ distribution in each fiber core was mapped with 2D and 1D intensity scans, which measured X-ray fluorescence over the scan areas. Two of the five fibers examined showed highly irregular Yb3+ distributions in the core center. In four of the five fibers Yb3+ was detected outside of the given fiber core dimensions, suggesting possible Yb3+ diffusion from the core, manufacturing error, or both. X-ray absorption spectroscopy (XAS) analysis has so far proven inconclusive, but did show that the fibers had differing EXAFS spectra. The Yb3+ distribution mapping proved highly useful, but additional modeling and examination of fiber preforms must be conducted to improve XAS analysis, which has been shown to have great potential for the study of similar optical fi bers.

  20. Akt-Mediated YB-1 Phosphorylation Activates Translation of Silent mRNA Species

    PubMed Central

    Evdokimova, Valentina; Ruzanov, Peter; Anglesio, Michael S.; Sorokin, Alexey V.; Ovchinnikov, Lev P.; Buckley, Jonathan; Triche, Timothy J.; Sonenberg, Nahum; Sorensen, Poul H. B.

    2006-01-01

    YB-1 is a broad-specificity RNA-binding protein that is involved in regulation of mRNA transcription, splicing, translation, and stability. In both germinal and somatic cells, YB-1 and related proteins are major components of translationally inactive messenger ribonucleoprotein particles (mRNPs) and are mainly responsible for storage of mRNAs in a silent state. However, mechanisms regulating the repressor activity of YB-1 are not well understood. Here we demonstrate that association of YB-1 with the capped 5′ terminus of the mRNA is regulated via phosphorylation by the serine/threonine protein kinase Akt. In contrast to its nonphosphorylated form, phosphorylated YB-1 fails to inhibit cap-dependent but not internal ribosome entry site-dependent translation of a reporter mRNA in vitro. We also show that similar to YB-1, Akt is associated with inactive mRNPs and that activated Akt may relieve translational repression of the YB-1-bound mRNAs. Using Affymetrix microarrays, we found that many of the YB-1-associated messages encode stress- and growth-related proteins, raising the intriguing possibility that Akt-mediated YB-1 phosphorylation could, in part, increase production of proteins regulating cell proliferation, oncogenic transformation, and stress response. PMID:16354698

  1. Quasi-millimeter-wave absorption behavior in Y/Yb-stabilized zirconia ceramics

    NASA Astrophysics Data System (ADS)

    Teranishi, Takashi; Akiyama, Naoki; Ayano, Keiko; Hayashi, Hidetaka; Kishimoto, Akira; Fujimori, Kazuhiro; Hoshina, Takuya; Takeda, Hiroaki; Tsurumi, Takaaki

    2012-06-01

    Broadband dielectric spectra from 10 to 1014 Hz were acquired for 8 mol. % Y2O3/Yb2O3-stabilized zirconia (8YSZ and 8YbSZ) ceramics that related the dipole and ionic polarization losses to the absorption efficiency of electromagnetic irradiation. For 24 GHz irradiation, 8YSZ exhibited a higher absorption efficiency than 8YbSZ, resulting in a higher dielectric loss. The difference in the dielectric loss was interpreted as the difference in the loss of the dipoles originating from the fluctuations in the defect associations (Y'ZrVo ¨ and Yb'ZrVo ¨).

  2. Flux growth of Yb(6.6)Ir(6)Sn(16) having mixed-valent ytterbium.

    PubMed

    Peter, Sebastian C; Subbarao, Udumula; Rayaprol, Sudhindra; Martin, Joshua B; Balasubramanian, Mahalingam; Malliakas, Christos D; Kanatzidis, Mercouri G

    2014-07-01

    The compound Yb6.6Ir6Sn16 was obtained as single crystals in high yield from the reaction of Yb with Ir and Sn run in excess indium. Single-crystal X-ray diffraction analysis shows that Yb6.6Ir6Sn16 crystallizes in the tetragonal space group P42/nmc with a = b = 9.7105(7) Å and c = 13.7183(11) Å. The crystal structure is composed of a [Ir6Sn16] polyanionic network with cages in which the Yb atoms are embedded. The Yb sublattice features extensive vacancies on one crystallographic site. Magnetic susceptibility measurements on single crystals indicate Curie-Weiss law behavior <100 K with no magnetic ordering down to 2 K. The magnetic moment within the linear region (<100 K) is 3.21 μB/Yb, which is ∼70% of the expected value for a free Yb(3+) ion suggesting the presence of mixed-valent ytterbium atoms. X-ray absorption near edge spectroscopy confirms that Yb6.6Ir6Sn16 exhibits mixed valence. Resistivity and heat capacity measurements for Yb6.6Ir6Sn16 indicate non-Fermi liquid metallic behavior. PMID:24921221

  3. Measurement of the γ emission probability of 173Yb using surrogate reactions

    NASA Astrophysics Data System (ADS)

    Delaune, O.; Blanc, A.; Burke, J. T.; Casperson, R.; Chau Huu-Tai, P.; McCleskey, E.; McCleskey, M.; Méot, V.; Roig, O.; Saastamoinen, A.

    2015-05-01

    We performed the 174Yb(p,d) reaction in order to measure the gamma-emission probability of 173Yb. The identification of the ejectiles — allowing us to tag the production of 173Yb nuclei — was performed using the STARLiTeR detector system. Unusually, the "statistical" γ-rays were used to determined the gammaemission probability and a spin distribution was extracted from it. A comparison with the spin distribution from the 174Yb(3He,α) reaction shows that the transferred angular momentum is similar in both reactions.

  4. Intracellular distribution of TM4SF1 and internalization of TM4SF1-antibody complex in vascular endothelial cells

    SciTech Connect

    Sciuto, Tracey E.; Merley, Anne; Lin, Chi-Iou; Richardson, Douglas; Liu, Yu; Li, Dan; Dvorak, Ann M.; Dvorak, Harold F.; Jaminet, Shou-Ching S.

    2015-09-25

    Transmembrane-4 L-six family member-1 (TM4SF1) is a small plasma membrane-associated glycoprotein that is highly and selectively expressed on the plasma membranes of tumor cells, cultured endothelial cells, and, in vivo, on tumor-associated endothelium. Immunofluorescence microscopy also demonstrated TM4SF1 in cytoplasm and, tentatively, within nuclei. With monoclonal antibody 8G4, and the finer resolution afforded by immuno-nanogold transmission electron microscopy, we now demonstrate TM4SF1 in uncoated cytoplasmic vesicles, nuclear pores and nucleoplasm. Because of its prominent surface location on tumor cells and tumor-associated endothelium, TM4SF1 has potential as a dual therapeutic target using an antibody drug conjugate (ADC) approach. For ADC to be successful, antibodies reacting with cell surface antigens must be internalized for delivery of associated toxins to intracellular targets. We now report that 8G4 is efficiently taken up into cultured endothelial cells by uncoated vesicles in a dynamin-dependent, clathrin-independent manner. It is then transported along microtubules through the cytoplasm and passes through nuclear pores into the nucleus. These findings validate TM4SF1 as an attractive candidate for cancer therapy with antibody-bound toxins that have the capacity to react with either cytoplasmic or nuclear targets in tumor cells or tumor-associated vascular endothelium. - Highlights: • Anti-TM4SF1 antibody 8G4 was efficiently taken up by cultured endothelial cells. • TM4SF1–8G4 internalization is dynamin-dependent but clathrin-independent. • TM4SF1–8G4 complexes internalize along microtubules to reach the perinuclear region. • Internalized TM4SF1–8G4 complexes pass through nuclear pores into the nucleus. • TM4SF1 is an attractive candidate for ADC cancer therapy.

  5. Phase stability of AlYB(14) sputtered thin films.

    PubMed

    Kölpin, Helmut; Music, Denis; Henkelman, Graeme; Emmerlich, Jens; Munnik, Frans; Schneider, Jochen M

    2009-09-01

    AlYB(14) (Imma) thin films were synthesized by magnetron sputtering. On the basis of x-ray diffraction, no phases other than crystalline AlYB(14) could be identified. According to electron probe microanalysis, energy dispersive x-ray analysis and elastic recoil detection analysis, the Al and Y occupancies vary in the range of 0.73-1.0 and 0.29-0.45, respectively. Density functional theory based calculations were carried out to investigate the effect of occupancy on the stability of Al(x)Y(y)B(14) (x,y = 0.25, 0.5, 0.75, 1). The mean effective charge per icosahedron and the bulk moduli were also calculated. It is shown that the most stable configuration is Al(0.5)YB(14), corresponding to a charge transfer of two electrons from the metal atoms to the boron icosahedra. Furthermore, it is found that the stability of a configuration is increased as the charge is homogeneously distributed within the icosahedra. The bulk moduli for all configurations investigated are in the range between 196 and 220 GPa, rather close to those for known hard phases such as α- Al(2)O(3). PMID:21828627

  6. Thermoelectric nanocrystalline YbCoSb laser prepared layers

    NASA Astrophysics Data System (ADS)

    Jelínek, Miroslav; Zeipl, Radek; Kocourek, Tomáš; Remsa, Jan; Navrátil, Jiří

    2016-03-01

    Filled thermoelectric Yb x Co4Sb12 layers were prepared by pulsed laser deposition method. The Yb0.19Co4Sb12 target was fabricated by hot pressing. Various deposition conditions were tested: target—substrate distance d T-S (4 or 6 cm), ambient argon pressure (from 0.5 to 13 Pa), laser repetition rate (from 3 to 10 Hz), substrate temperature (from 250 to 400 °C) and laser fluence (in region from 0.8 to 5 J cm-2). Film roughness was determined by mechanical profilometer and by AFM. For d T-S = 4 cm we observed a deficit of Yb and surplus of Co. Sb was transferred from target to film roughly stoichiometrically (as measured by EDX). Films created at 0.8 J cm-2 exhibited generally poor stoichiometry and mechanical properties. Optimal conditions and stoichiometric transport were found for d T-S = 6 cm and 13 Pa of Ar. XRD shows that the films were nanocrystalline with CoSb3 structure. Grain size was in the range of ~50-80 nm. Temperature dependence of Seebeck coefficient and power factor was measured. Thermoelectric efficiency ZT ~ 0.04-0.05 was measured at room temperature using Harman method. In dependence on layers quality, we calculated thermal conductivity λ ~ 0.4-1.3 W K-1 m-1.

  7. Composite Yb:YAG/SiC-prism thin disk laser.

    PubMed

    Newburgh, G A; Michael, A; Dubinskii, M

    2010-08-01

    We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk. PMID:20721095

  8. Contribution of Eu 4f states to the magnetic anisotropy of EuO

    SciTech Connect

    Arenholz, E.; Schmehl, A.; Schlom, D.G.; van der Laan, G.

    2008-09-11

    Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shell-, and symmetry-selective techniques to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu2+ M4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.

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

    PubMed

    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

    Haemaphysalis longicornis tropomyosin (HL-Tm) was amplified by RT-PCR. The cDNA contained a 825 bp open reading frame coding for 274 amino acids with a predicted theoretical isoelectric point (pI) of 4.55 and molecular weight of 31.7 kDa. 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

  10. Monodisperse core-shell structured up-conversion Yb(OH)CO₃@YbPO₄:Er³+ hollow spheres as drug carriers.

    PubMed

    Xu, Zhenhe; Ma, Ping'an; Li, Chunxia; Hou, Zhiyao; Zhai, Xuefeng; Huang, Shanshan; Lin, Jun

    2011-06-01

    In this work, we report a facile solution-phase synthesis of monodisperse core-shell structured Yb(OH)CO₃@YbPO₄ hollow spheres (size around 380 nm) by utilizing the colloidal sphere of Yb(OH)CO₃ as the sacrificial template via the Kirkendall effect. The Er³+ doped Yb(OH)CO₃@YbPO₄ core-shell hollow spheres can be prepared similarly, which exhibit strong green emission under 980 nm NIR laser excitation even after loading with drug molecules. Most importantly, the sample can be used as an effective drug delivery carrier. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. A typical anticancer drug, doxorubicin hydrochloride (DOX), is used for drug loading, and the release properties, cytotoxicity, uptake behavior and therapeutic effects were examined. It is found that DOX is shuttled into cell by core-shell hollow spheres carrier and released inside cells after endocytosis, and the DOX-loaded spheres exhibited greater cytotoxicity than free DOX. These results indicate that the core-shell Er³+ doped Yb(OH)CO₃@YbPO₄ hollow spheres have potential for drug loading and delivery into cancer cells to induce cell death. PMID:21435712

  11. Ends of the line for tmRNA-SmpB

    DOE PAGESBeta

    Hudson, Corey M.; Lau, Britney Y.; Williams, Kelly P.

    2014-08-13

    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. We validate recent identification of tmRNA homologs in oomycete mitochondria by finding partner genes from oomycete nuclei that target SmpB to the mitochondrion. Exhaustive search now identifies a small number of complete, often highly derived, bacterial genomes that appear to lack a functional copy of one or the other partner gene (but not both). Three groups with reduced genomes have lost the central loop of SmpB, which is thought to improve alanylation andmore » EF-Tu activation: Carsonella, Hodgkinia and the hemplasmas (hemotropic Mycoplasma). Carsonella has also lost the SmpB C-terminal tail, thought to stimulate the decoding center of the ribosome. Carsonella moreover exhibits gene overlap such that tmRNA maturation should produce a non-stop smpB mRNA, and one isolate exhibits complete degradation of the tmRNA gene yet its smpB shows no evidence for relaxed selective constraint. After loss of the SmpB central loop in the hemoplasmas, a subclade apparently lost tmRNA. 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. The tmRNA Website has moved and been updated, adding an SmpB sequence database (http://bioinformatics.sandia.gov/tmrna).« less

  12. Ends of the line for tmRNA-SmpB

    SciTech Connect

    Hudson, Corey M.; Lau, Britney Y.; Williams, Kelly P.

    2014-08-13

    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. We validate recent identification of tmRNA homologs in oomycete mitochondria by finding partner genes from oomycete nuclei that target SmpB to the mitochondrion. Exhaustive search now identifies a small number of complete, often highly derived, bacterial genomes that appear to lack a functional copy of one or the other partner gene (but not both). 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 hemplasmas (hemotropic Mycoplasma). Carsonella has also lost the SmpB C-terminal tail, thought to stimulate the decoding center of the ribosome. Carsonella moreover exhibits gene overlap such that tmRNA maturation should produce a non-stop smpB mRNA, and one isolate exhibits complete degradation of the tmRNA gene yet its smpB shows no evidence for relaxed selective constraint. After loss of the SmpB central loop in the hemoplasmas, a subclade apparently lost tmRNA. 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. The tmRNA Website has moved and been updated, adding an SmpB sequence database (http://bioinformatics.sandia.gov/tmrna).

  13. Stimulated Raman adiabatic passage in Tm{sup 3+}:YAG

    SciTech Connect

    Alexander, A. L.; Lauro, R.; Louchet, A.; Chaneliere, T.; Le Goueet, J. L.

    2008-10-01

    We report on the experimental demonstration of stimulated Raman adiabatic passage in a Tm{sup 3+}:YAG crystal. Tm{sup 3+}:YAG is a promising material for use in quantum information processing applications, but as yet there are few experimental investigations of coherent Raman processes in this material. We investigate the effect of inhomogeneous broadening and Rabi frequency on the transfer efficiency and the width of the two-photon spectrum. Simulations of the complete Tm{sup 3+}:YAG system are presented along with the corresponding experimental results.

  14. Tm:germanate Fiber Laser: Tuning And Q-switching

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.

  15. Review of Tm and Ho Materials; Spectroscopy and Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2008-01-01

    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.

  16. Quasi four-level Tm:LuAG laser

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  17. Influence of undoped YAG cap on diode-pumped composite YAG/Er:Yb:glass laser

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Jelínková, Helena; Nejezchleb, Karel; Škoda, Václav

    2012-03-01

    Two samples of Er-Yb doped phosphate glass were tested as a gain medium of longitudinally diode pumped laser. One sample was a simple Er:Yb:glass rod (length 2.8 mm), second sample was composite rod consisting of 2.8mm long Er:Yb:glass and 6mm long YAG crystal. Diameter of both samples was 6 mm. Dopant concentration for Er:Yb:glass was 0.75 × 1020 cm-3 Er and 1.7 × 1021 cm-3 Yb. The goal of the experiment was to investigate an effect of the undoped YAG cap on the Er:Yb:glass laser operation. The active medium, fixed in cupreous heatsink, was placed inside the 150mm long resonator consisted of a flat pumping mirror (HR @ 1.52-1.65 μm, HT @ 0.97 μm) and curved output coupler (r = 150 mm, R = 97% @ 1.52-1.61 μm). For Er:Yb:glass pumping a fiber coupled laser diode, operating in pulsed regime, was used. The pumping pulse width, energy, and wavelength were 1 ms, 10 mJ, and 975 nm, respectively. The decrease of Er:Yb:glass laser output pulse energy with increasing pumping repetition rate was observed for both samples. In case of simple Er:Yb:glass the energy dropped from 1.4mJ to 0.6mJ after pumping duty cycle increase from 0.5% to 6 %. In case of composite YAG/Er:Yb:glass active medium the relative output energy decrease was only 20% for pumping duty cycle increase from 0.5% to 10%. This result showed that the slope of the output energy decrease with increasing duty cycle was approximately four times slower for composite active media in comparison with simple Er:Yb:glass.

  18. Fabrication and photoluminescence properties of Cr:YAG and Yb,Cr:YAG transparent ceramic

    NASA Astrophysics Data System (ADS)

    Chen, Xingtao; Lu, Tiecheng; Wei, Nian; Lu, Zhongwen; Chen, Lijia; Zhang, Qinghua; Cheng, Gang; Qi, Jianqi

    2015-11-01

    Cr:YAG and Yb/Cr:YAG transparent ceramics containing Ca as charge counter element were fabricated by vacuum sintering technique using the co-precipitation synthesis of raw powders. Their spectral and luminescence properties as well as the influence of Cr3+ concentration on the optical properties of Yb,Cr:YAG ceramic were investigated. Results show the transmittance of 10 at.% Yb, 0.25 at.% Cr:YAG and 0.25 at.% Cr:YAG reaches 83% at 1200 nm and 81% at 1400 nm, respectively. And the Yb,Cr:YAG ceramics exhibit a pore free structure with an average grain size of about 5 μm. After annealing, most of Cr3+ ions transform into Cr4+. In the case of excitation wavelength of 440 nm, a sharp emission peak of 694 nm appeared in the Yb,Cr:YAG ceramic before annealing and the band enhanced with the increase of the Cr3+ concentration, which is attributed to the 4T2g-4A2g fluorescence transition. The emission spectrums and fluorescence decays manifest that both the luminescent intensity and the lifetimes of Yb,Cr:YAG are lower than Yb:YAG ceramic and the lifetimes of Yb,Cr:YAG and Yb:YAG are 0.93 and 2.38 ms, respectively. This results demonstrate the existence of the ground state absorption of Cr4+ in the Yb,Cr:YAG ceramic. Experimental evidence proved that Yb,Cr:YAG transparent ceramics could be a potential material for passive self-Q-switched solid-state laser.

  19. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    SciTech Connect

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squared Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.

  20. Photoelectron spectra of thulium atoms encapsulated C82 fullerene, Tm2@C82 (III) and Tm2C2@C82 (III)

    NASA Astrophysics Data System (ADS)

    Miyazaki, Takafumi; Tokumoto, Youji; Sumii, Ryohei; Yagi, Hajime; Izumi, Noriko; Shinohara, Hisanori; Hino, Shojun

    2014-03-01

    Ultraviolet photoelectron spectra (UPS) and X-ray photoelectron spectra (XPS) of two thulium atoms and thulium-carbide cluster entrapped fullerenes, Tm2@C82 (III) and Tm2C2@C82 (III), were measured using synchrotron radiation and MgKα X-ray light sources. The UPS spectral onset energy of these endohedral fullerenes is around 0.9 eV, which is smaller than that of 1.2 eV of empty C82. The UPS of Tm2@C82 (III) and Tm2C2@C82 (III) resemble each other. Further, the UPS of Tm2@C82 (III), Y2@C82-C3v and Er2@C82-C3v are almost identical and as well as are Tm2C2@C82 (III), Y2C2@C82-C3v and Er2C2@C82-C3v. The XPS Tm4d5/2 peaks of Tm2@C82 and Tm2C2@C82 appear at higher binding energy region than that of Tm@C82, which suggests the oxidation states of Tm atoms in Tm2@C82 (III) and Tm2C2@C82 are higher than that in Tm@C82.

  1. ASTROCULTURE (TM) root metabolism and cytochemical analysis.

    PubMed

    Porterfield, D M; Barta, D J; Ming, D W; Morrow, R C; Musgrave, M E

    2000-01-01

    Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure. PMID:11543169

  2. ASTROCULTURE (TM) root metabolism and cytochemical analysis

    NASA Technical Reports Server (NTRS)

    Porterfield, D. M.; Barta, D. J.; Ming, D. W.; Morrow, R. C.; Musgrave, M. E.

    2000-01-01

    Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.

  3. Resonant tandem pumping of Tm-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Creeden, Daniel; Johnson, Benjamin R.; Rines, Glen A.; Setzler, Scott D.

    2014-06-01

    We have demonstrated efficient lasing of a Tm-doped fiber when pumped with another Tm-doped fiber. In these experiments, we use a 1908 nm Tm-doped fiber laser as a pump source for another Tm-doped fiber laser, operating at a slightly longer wavelength (~2000 nm). Pumping in the 1900 nm region allows for very high optical efficiencies, low heat generation, and significant power scaling potential due to the use of fiber laser pumping. The trade-off is that the ground-state pump absorption at 1908 nm is ~37 times lower than at 795nm. However, the absorption cross-section is still sufficiently high enough to achieve effective pump absorption without exceedingly long fiber lengths. This may also be advantageous for distributing the thermal load in higher power applications.

  4. Syntheses, Crystal Structures, and Properties of EuRhIn, EuIr 2, and EuIrSn 2

    NASA Astrophysics Data System (ADS)

    Pöttgen, Rainer; Hoffmann, Rolf-Dieter; Möller, Manfred H.; Kotzyba, Gunter; Künnen, Bernd; Rosenhahn, Carsten; Mosel, Bernd D.

    1999-06-01

    The title compounds were prepared from the elements by reactions in sealed tantalum tubes in a high-frequency furnace. Their structures were refined from single crystal X-ray diffractometer data: Pnma, a=744.4(1) pm, b=434.15(9) pm, c=845.5(1) pm, wR2=0.0433, 658 F2 values, 20 variables for EuRhIn, Fd3m, a=756.5(1) pm, wR2=0.0349, 94 F2 values, 5 variables for EuIr2, and Cmcm, a=434.78(3) pm, b=1124.0(1) pm, c=751.20(5) pm, wR2=0.0561, 565 F2 values, 16 variables for EuIrSn2. EuRhIn crystallizes with a TiNiSi type structure that consists of strongly puckered Rh3In3 hexagons. The europium atoms fill the channels within the three-dimensional [RhIn] polyanion. EuRhIn orders ferromagnetically at 22.0(5) K with a saturation magnetic moment of 6.7(1) μB/Eu at 4 K and 5.5 T. The divalent character of the europium atoms in EuRhIn was determined from temperature dependent susceptibility (7.9 μB/Eu in the high-temperature part) and 151Eu Mössbauer spectroscopic experiments. The latter show an isomer shift of δ=-8.30(2) mm/s at 78 K. At 4.2 K full magnetic hyperfine field splitting subjected to significant quadrupole splitting of ΔEQ=8 mm/s is observed. EuRhIn is a metallic conductor with a room temperature value of 58 μΩcm for the specific resistivity. The structure of the Laves phase EuIr2 is confirmed on the basis of single crystal X-ray data. The iridium atoms form a tetrahedral network with Ir-Ir distances of 268 pm. EuIrSn2 adopts a MgCuAl2 type structure that may be described as an iridium-filled variant of a distorted CaIn2-like sublattice of composition EuSn2. The tin atoms in the distorted and puckered hexagonal network have shorter (303 and 322 pm) and longer (343 pm) tin-tin contacts.

  5. Measurements of isotope shift in Eu II

    NASA Astrophysics Data System (ADS)

    Broström, Lars; Mannervik, Sven; Royen, Peder; Wännström, Anders

    1995-03-01

    The isotope shift between singly-charged 151Eu and 153Eu in the 4f7(8So)6s 9So4 - 4f7(8So)6p1/2 J = 4 transition at 4129 Å has been measured using fast ion beam-laser technique. This Eu line has attracted interest in connection with efforts of obtaining a cosmochronometer based on observed Th/Eu abundance ratios. Knowledge of the isotope shift is of importance in order to check that contaminations from line blends do not contribute to the line intensity of Eu II. The measured value of the isotope shift -0.1527 (2) cm-1 is consistent with the old spectroscopic value of Krebs and Winkler (-0.1503 (25)cm-1) using a Fabry-Perot interferometer, while the accuracy is improved substantially.

  6. Preparation, Biological Evaluation and Dosimetry Studies of 175Yb-Bis-Phosphonates for Palliative Treatment of Bone Pain

    PubMed Central

    Fakhari, Ashraf; Jalilian, Amir R.; Yousefnia, Hassan; Shanehsazzadeh, Saeed; Samani, Ali Bahrami; Daha, Fariba Johari; Ardestani, Mehdi Shafiee; Khalaj, Ali

    2015-01-01

    Objective: Optimized production and quality control of ytterbium-175 (Yb-175) labeled pamidronate and alendronate complexes as efficient agents for bone pain palliation has been presented. Methods: Yb-175 labeled pamidronate and alendronate (175Yb-PMD and 175Yb-ALN) complexes were prepared successfully at optimized conditions with acceptable radiochemical purity, stability and significant hydroxyapatite absorption. The biodistribution of complexes were evaluated up to 48 h, which demonstrated significant bone uptake ratios for 175Yb-PAM at all-time intervals. It was also detected that 175Yb-PAM mostly washed out and excreted through the kidneys. Results: The performance of 175Yb-PAM in an animal model was better or comparable to other 175Yb-bone seeking complexes previously reported. Conclusion: Based on calculations, the total body dose for 175Yb-ALN is 40% higher as compared to 175Yb-PAM (especially kidneys) indicating that 175Yb-PAM is probably a safer agent than 175Yb-ALN.

  7. Feasibility study for production of 175Yb: a promising therapeutic radionuclide.

    PubMed

    Chakraborty, Sudipta; Unni, P R; Venkatesh, Meera; Pillai, M R A

    2002-09-01

    Owing to its favourable decay characteristics 175Yb (T1/2 = 4.2 d, E beta(max) = 480 keV) can be regarded as a potential radionuclide for therapeutic applications. Production of 175Yb using (174Yb(n, gamma)175Yb) reaction by thermal neutron bombardment on natural ytterbium target is described. The activity of 175Yb produced as well as its radionuclidic purity under different irradiation conditions were determined by gamma-ray spectrometry using an HPGe 4 K MCA system and compared with theoretically calculated values. The radiochemical purity after chemical processing was determined by paper chromatography as well as paper electrophoresis techniques. It is found that 31 Ci/g (1145 GBq/g) of 175Yb can be produced with > 95% radionuclidic purity (with approximately 3% of 169Yb and approximately 2% of 177Lu) by irradiating natural Yb2O3 target at a thermal neutron flux of 3 x 10(13) n/cm2/s for a period of 5 d. PMID:12201133

  8. Roles of critical valence fluctuations in Ce- and Yb-based heavy fermion metals.

    PubMed

    Watanabe, Shinji; Miyake, Kazumasa

    2011-03-01

    The roles of critical valence fluctuations of Ce and Yb are discussed as a key origin of several anomalies observed in Ce- and Yb-based heavy fermion systems. Recent development of the theory has revealed that a magnetic field is an efficient control parameter to induce the critical end point of the first-order valence transition. Metamagnetism and non-Fermi liquid behavior caused by this mechanism are discussed by comparing favorably with CeIrIn5, YbAgCu4 and YbIr2Zn20. The interplay of the magnetic order and valence fluctuations offers a key concept for understanding Ce- and Yb-based systems. It is shown that suppression of the magnetic order by enhanced valence fluctuations gives rise to the coincidence of the magnetic-transition point and valence crossover point at absolute zero as a function of pressure or magnetic field. The interplay is shown to resolve the outstanding puzzle in CeRhIn5 in a unified way. The broader applicability of this newly clarified mechanism is discussed by surveying promising materials such as YbAuCu4, β-YbAlB4 and YbRh2Si2. PMID:21339570

  9. Spectroscopic and lasing properties of Ho:Tm:LuAG

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Filer, Elizabeth D.; Naranjo, Felipe L.; Rodriguez, Waldo J.; Kokta, Milan R.

    1993-01-01

    Ho:Tm:LuAG has been grown, examined spectroscopically, and lased at 2.1 microns. Ho:Tm:LuAG was selected for this experimental investigation when quantum-mechanical modeling predicted that it would be a good laser material for Ho laser operation on one of the 5I7 to 5I8 transitions. Lasing was achieved at 2.100 microns, one of the three wavelengths predicted to be most probable for laser action.

  10. Flashlamp-pumped Ho:Tm:Cr:LuAG laser

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Murray, Keith E. (Inventor); Kokta, Milan R. (Inventor)

    1997-01-01

    A room temperature solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG host material doped with a concentration of about 0.35% Ho ions, about 5.57% Tm ions and at least about 1.01% Cr ions. A broadband energizing source such as a flashlamp is disposed transversely to the laser crystal to energize the Ho ions, Tm ions and Cr ions.

  11. Quiet Spike (TM) Build-Up Ground Vibration Testing Approach

    NASA Technical Reports Server (NTRS)

    Spivey, Natalie D.; Herrera, Claudia; Truax, Roger; Pak, Chan-gi; Freund, Donald

    2007-01-01

    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.

  12. Measurement of the 169Tm (n ,3 n ) 167Tm cross section and the associated branching ratios in the decay of 167Tm

    NASA Astrophysics Data System (ADS)

    Champine, B.; Gooden, M. E.; Krishichayan, Norman, E. B.; Scielzo, N. D.; Stoyer, M. A.; Thomas, K. J.; Tonchev, A. P.; Tornow, W.; Wang, B. S.

    2016-01-01

    The cross section for the 169Tm(n ,3 n ) 167Tm reaction was measured from 17 to 22 MeV using quasimonoenergetic neutrons produced by the 2H(d ,n ) 3He reaction. This energy range was studied to resolve the discrepancy between previous (n ,3 n ) cross-section measurements. In addition, the absolute γ -ray branching ratios following the electron-capture decay of 167Tm were measured. These results provide more reliable nuclear data for an important diagnostic that is used at the National Ignition Facility to estimate the yield of reaction-in-flight neutrons produced via the inertial-confinement-fusion plasma in deuterium-tritium capsules.

  13. YB-1, the E2F Pathway, and Regulation of Tumor Cell Growth

    PubMed Central

    Samuel, Weini; Cao, Helen; Patel, Rachna; Mehta, Reena; Stern, J. Lewis; Reid, Glen; Woolley, Adele G.; Miller, Lance D.; Black, Michael A; Shelling, Andrew N.; Print, Cristin G.; Braithwaite, Antony W.

    2012-01-01

    Background Y-box binding factor 1 (YB-1) has been associated with prognosis in many tumor types. Reduced YB-1 expression inhibits tumor cell growth, but the mechanism is unclear. Methods YB-1 mRNA levels were compared with tumor grade and histology using microarray data from 771 breast cancer patients and with disease-free survival and distant metastasis–free survival using data from 375 of those patients who did not receive adjuvant therapy. Microarrays were further searched for genes that had correlated expression with YB-1 mRNA. Small interfering RNA (siRNA) was used to study the effects of reduced YB-1 expression on growth of three tumor cell lines (MCF-7 breast, HCT116 colon, and A549 lung cancer cells), on tumorigenesis by A549 cells in nude mice, and on global transcription in the three cancer cell lines. Reporter gene assays were used to determine whether YB-1 siRNAs affected the expression of E2F1, and chromatin immunoprecipitation was used to determine whether YB-1 bound to various E2F promoters as well as E2F1-regulated promoters. All P values were from two-sided tests. Results YB-1 levels were elevated in more aggressive tumors and were strongly associated with poor disease-free survival and distant metastasis–free survival. YB-1 expression was often associated with the expression of genes with E2F sites in their promoters. Cells expressing YB-1 siRNA grew substantially more slowly than control cells and formed tumors less readily in nude mice. Transcripts that were altered in cancer cell lines with YB-1 siRNA included 32 genes that are components of prognostic gene expression signatures. YB-1 regulated expression of an E2F1 promoter–reporter construct in A549 cells (eg, relative E2F1 promoter activity with control siRNA = 4.04; with YB-1 siRNA = 1.40, difference= −2.64, 95% confidence interval = −3.57 to −1.71, P < .001) and bound to the promoters of several well-defined E2F1 target genes. Conclusion YB-1 expression is associated with the activity of E2F transcription factors and may control tumor cell growth by this mechanism. PMID:22205655

  14. High-energy diode-pumped D2O-cooled multislab Yb:YAG and Yb:QX-glass lasers.

    PubMed

    Siebold, Mathias; Loeser, Markus; Harzendorf, Gunter; Nehring, Harald; Tsybin, Igor; Roeser, Fabian; Albach, Daniel; Schramm, Ulrich

    2014-06-15

    We investigated the lasing performance of a multislab Yb:QX and Yb:YAG laser amplifiers using a facet-cooled design. Di-deuterium oxide (D2O) was used as the coolant flowing between the active slabs with the pump and laser light passing through the very low absorbing heavy-water films. A square pump profile at a maximum intensity of 40  kW/cm2 drove the amplifier with a peak fluence of 5.5  J/cm2 and a pulse duration of 6 ns. We demonstrated a maximum pulse energy of 1 J for each gain medium as well as a repetition rate of 10 Hz for Yb:YAG and 1 Hz for Yb:QX glass, thus showing the feasibility and scalability of directly water-cooled, diode-pumped, high-energy short-pulse lasers. PMID:24978549

  15. Radiochemical separation of no-carrier-added 177Lu as produced via the 176Yb(n,gamma)177Yb-->177Lu process.

    PubMed

    Lebedev, N A; Novgorodov, A F; Misiak, R; Brockmann, J; Rösch, F

    2000-09-01

    The 176Yb(n,gamma)177Yb-beta(-)-->177Lu process was investigated to provide no-carrier-added (nca) 177Lu. The radiochemical separation of the 177Lu from the macro-amounts of the ytterbium target based on the cementation process, i.e. the selective extraction of Yb by Na(Hg) amalgam from Cl-/CH3COO- electrolytes, followed by a final cation exchange purification. The cementation separation process provides a decontamination factor of Yb(III) of 10(4), the cation exchange purification adding a decontamination factor of > 10(2). The nca 177Lu is available in radiochemically pure form despite the chemical similarity of the lanthanides with 75 +/- 5% overall separation yield within 4-5 h. It can be used to synthesise nca 177Lu labelled radiotherapeuticals. PMID:10972147

  16. [Studies on the properties of energy upconversion of the rare earth ErYb and HoYb in the oxyfluoride glass].

    PubMed

    Yuan, F C; Yang, X L; Liu, Z W

    2001-12-01

    Er and Yb, Ho and Yb codoped in the oxyfluoride were burnt on in the specific temperature, and got two kinds of samples. Using 930 nm as an exciting light, the emitting fluorescent spectra of two kinds of the samples were measured, and observed the red band and green band fluorescent spectra, respectively. According to the detected absorption spectra of Er2O3, Ho2O3, Yb2O3 and the rule of energy jump, the mechanism and the properties of the energy upconversion of two kinds of the samples were explained. As can be seen, energy upconversion properties were determined mainly by the absorbtion spectra of Er2O3, Yb2O3. Energy upconversion efficiency were determined by excitative photons. PMID:12958886

  17. Upconversion of SrWO4:Er3+/Yb3+: Improvement by Yb3+ codoping and temperature sensitivity for optical temperature sensors

    NASA Astrophysics Data System (ADS)

    Wei, Zhen; Zheng, Wei; Zhu, Zhiyong; Guo, Xiongfei

    2016-05-01

    SrWO4:Er3+/Yb3+ phosphors are synthesized by a solid state reaction. The XRD patterns indicate that the doping ions will not change the phase of SrWO4. Under the excitation at 980 nm, SrWO4:Er3+/Yb3+ phosphors show emission bands in green and red regions. The temperature-dependence of upconversion efficiency and temperature-sensing properties of SrWO4:Er3+/Yb3+ phosphors have been discussed according to the fluorescence intensity ratio of green emissions from 2H11/2/4S3/2 → 4I15/2 transitions of Er3+ in the range of 95-775 K under the excitation at 980 nm. The maximum sensitivity of SrWO4:1%Er3+/6%Yb3+ phosphor is found to be 0.01282 K-1 at 489 K.

  18. Passive Q-switching of Yb bulk lasers by a graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Serres, J. M.; Mateos, X.; Liu, J.; Zhang, H.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2016-04-01

    Compact Yb:KLu(WO4)2 and Yb:LuVO4 lasers diode-pumped at 978 nm are passively Q-switched by a single-layer graphene saturable absorber. The Yb:KLu(WO4)2 laser generated 165 ns/0.49 μJ pulses at 1030 nm with 170 mW average output power and 12 % slope efficiency. With the Yb:LuVO4 laser, 152 ns/0.83 μJ pulses were achieved. The output power reached 300 mW at 1024 nm, and the slope efficiency was 10 %. Laser operation in a plano-plano cavity is achieved with both crystals with thermal lensing playing a key role in their performance. A model describing graphene Q-switched Yb lasers is developed. Our results indicate the potential of graphene for passive Q-switching of ~1 μm bulk lasers.

  19. Processing and properties of Yb-doped BiFeO{sub 3} ceramics

    SciTech Connect

    Yan, Z.; Wang, K. F.; Qu, J. F.; Wang, Y.; Song, Z. T.; Feng, S. L.

    2007-08-20

    The authors prepared Yb-doped bismuth iron oxide ceramics (Bi{sub 1-x}Yb{sub x}FeO{sub 3}, with 0{<=}x{<=}0.20) by rapid liquid phase sintering method and investigated the material's structures and electrical properties. The x-ray diffraction measurements showed that the doping of Yb has induced noticeable lattice distortion in the ceramics, and a largest distortion was observed when the concentration of Yb was 15%. By doping electrical resistivity, ferroelectric and dielectric properties of the ceramics were improved. Among all samples, BiFeO{sub 3} doped with 15% Yb was found to have the smallest leakage current density (<10{sup -7} A/cm{sup 2}) and the largest remnant polarization (8.5 {mu}C/cm{sup 2})

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  1. Site-selective 11B NMR studies on YbAlB4

    NASA Astrophysics Data System (ADS)

    Takano, S.; Grbic, M. S.; Kimura, K.; Yoshida, M.; Takigawa, M.; Farrell, E. C. T. O.; Kuga, K.; Nakatsuji, S.; Harima, H.

    2016-02-01

    β-YbAlB4 is a distinctive heavy fermion superconductor that exhibits unconventional quantum criticality without tuning in a strongly intermediate valence state. In this paper, we report the result of 11B NMR measurements on the single crystals of, β-YbAlB4 and α- YbAlB4, the locally isostructural polymorph of β-YbAlB4. All 11B NMR lines for both samples were successfully assigned to inequivalent crystallographic sites by comparing the experimental results and the ab-initio calculation of the electric field gradient. In both compounds, the anisotropy of the Knight shift exhibits a characteristic radial pattern, indicating approximate axial symmetry of the hybridization between the Yb-4f electrons and the conduction electrons.

  2. Enhancement of Tb-Yb quantum cutting emission by inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Qiu, Jianbei; Song, Zhiguo; Yang, Zhengwen; Yin, Zhaoyi; Zhou, Dacheng; Wang, Siqin

    2016-04-01

    Yb3+, Tb3+ co-doped YPO4 inverse opal photonic crystal was prepared directly by sol-gel technique in combination with self-assembly method. With the influence of the photonic band gap, quantum cutting emission of Tb3+, Yb3+ was investigated in photonic crystals by photoluminescence and fluorescence lifetime. The result clearly shows that, when the spontaneous emission of donor Tb3+ is inhibited by photonic band gap, Tb3+-Yb3+ quantum cutting quantum efficiency from Tb3+ to Yb3+ could be enhanced from 131.2% to 140.5%. The mechanisms for the influence of the photonic band gap on quantum cutting process of Tb3+ and Yb3+ are discussed. We believe that the present work will be valuable for the foundational study of quantum cutting energy transfer process and application of quantum cutting optical devices in spectral modification materials for silicon solar cells.

  3. Traffic at the tmRNA Gene

    PubMed Central

    Williams, Kelly P.

    2003-01-01

    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

  4. Structural and magnetic study of Yb{sup 3+} in the perovskites Sr{sub 2}YbMO{sub 6} (M=Nb, Ta, Sb)

    SciTech Connect

    Coomer, Fiona C.; Campbell, John; Giordano, Nico; Collins, Oonagh M.; Cussen, Edmund J.

    2015-01-15

    The compounds Sr{sub 2}YbNbO{sub 6}, Sr{sub 2}YbTaO{sub 6} and Sr{sub 2}YbSbO{sub 6} 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 P2{sub 1}/n space group. Complete cation ordering occurs between M{sup 5+} and Yb{sup 3+} 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 {sup 2}F{sub 5/2} ground state of Yb{sup 3+} leading to a temperature dependent magnetic moment on this ion below 100 K. - Graphical abstract: The magnetic susceptibility of the face-centred cubic Yb{sup 3+} lattice is dominated by the temperature dependent single-ion moment below 100 K. - Highlights: • Cation-ordered perovskites are studied using neutron diffraction and magnetometry. • Yb{sup 3+} cations form a pseudo face centred cubic lattice in a distorted structure. • Sb{sup 5+} cation is slightly overbonded as observed in related perovskites. • Crystal field splitting of 4f{sup 13} Yb{sup 3+} giving a temperature dependent moment. • Magnetic susceptibility reproduces theoretical predictions below 100 K.

  5. Laser desorption/ionization mass spectrometry on nanostructured semiconductor substrates: DIOS(TM) and QuickMass(TM)

    NASA Astrophysics Data System (ADS)

    Law, K. P.

    2010-02-01

    In the era of systems biology, new analytical platforms are under demand. Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a promising high throughput laser mass spectrometry approach that has attracted a lot of attention, and has been commercialized. Another substrate material manufactured by physical method has also been made commercially available under the trade name of QuickMass(TM). These two commercial substrates, DIOS(TM) and QuickMass(TM), were investigated independently from the manufacturers and were characterized by a number of advanced surface techniques. This work determined (1) the correlation between the substrate physicochemical properties and their LDI activity, (2) the feasibility of metabolic profiling from complex biological matrices and (3) the laser desorption/ionization mechanism. The DIOS(TM) substrate was characterized with a thick nano-sized porous layer, a high surface concentration of fluorocarbon and silicon oxides and super-hydrophobicity. In contrast, the QuickMass(TM) substrate consisted of a non-porous germanium thin-film. The relatively high ionization efficiency obtained from the DIOS(TM) substrate was contributed to the fluorosilane manufacturing processes and its porous morphology. Despite the QuickMass(TM) substrate being less effective, it was noted that the use of germanium affords a self-cleaning mechanism and suppresses background interference of mass spectra. The suitability of DIOS(TM) substrates for metabolic profiling of complex biological matrices was demonstrated. DIOS mass spectra of human blood plasma, human urine and animal liver tissue extracts were produced. Suitable extraction methods were found to be important, but relatively simplified approaches were sufficient. Further investigations of the DIOS desorption/ionization mechanism were carried out. The previously proposed sub-surface state reaction could be a molten-solid interfacial state reaction of the substrate and this had a significant effect toward the protonation reaction of amines.

  6. Genome-wide analysis of YB-1-RNA interactions reveals a novel role of YB-1 in miRNA processing in glioblastoma multiforme.

    PubMed

    Wu, Shuai-Lai; Fu, Xing; Huang, Jinyan; Jia, Ting-Ting; Zong, Feng-Yang; Mu, Shi-Rong; Zhu, Hong; Yan, Yong; Qiu, Shuwei; Wu, Qun; Yan, Wei; Peng, Ying; Chen, Juxiang; Hui, Jingyi

    2015-09-30

    Altered miRNA expression is believed to play a crucial role in a variety of human cancers; however, the mechanisms leading to the dysregulation of miRNA expression remain elusive. In this study, we report that the human Y box-binding protein (YB-1), a major mRNA packaging protein, is a novel modulator of miRNA processing in glioblastoma multiforme (GBM). Using individual nucleotide-resolution crosslinking immunoprecipitation coupled to deep sequencing (iCLIP-seq), we performed the first genome-wide analysis of the in vivo YB-1-RNA interactions and found that YB-1 preferentially recognizes a UYAUC consensus motif and binds to the majority of coding gene transcripts including pre-mRNAs and mature mRNAs. Remarkably, our data show that YB-1 also binds extensively to the terminal loop region of pri-/pre-miR-29b-2 and regulates the biogenesis of miR-29b-2 by blocking the recruitment of microprocessor and Dicer to its precursors. Furthermore, we show that down-regulation of miR-29b by YB-1, which is up-regulated in GBM, is important for cell proliferation. Together, our findings reveal a novel function of YB-1 in regulating non-coding RNA expression, which has important implications in tumorigenesis. PMID:26240386

  7. In Situ Growth of a Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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 (˜3 × 10-3 g/cm2 h) 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.

  8. Interplay of chemical expansion, Yb valence, and low temperature thermoelectricity in the YbCu2Si2-xGex solid solution

    NASA Astrophysics Data System (ADS)

    Lehr, Gloria J.; Morelli, Donald T.

    2015-04-01

    YbCu2Si2 is a promising low temperature thermoelectric material because of the large broad peak in the Seebeck coefficient near 100 K combined with a low electrical resistivity. This behavior is thought to arise from fluctuating, or intermediate, valence effects due to partial occupation of Yb 4f energy states near the Fermi level. Previous studies of the magnetic properties under pressure have demonstrated that the average Yb valence is sensitive to the contraction of unit cell volume. By forming a solid solution of YbCu2Si2 with YbCu2Ge2, an isostructural compound with a larger unit cell volume, here we examine the subtle effects of lattice expansion on the transport properties and average Yb valence. We observe a shift in the peak of the Seebeck coefficient towards higher temperatures, as well as an enhanced power factor in the solid solutions. At the same time, a reduction in thermal conductivity due to alloy scattering enhances the thermoelectric figure of merit. Chemical pressure effects may thus be utilized to control and optimize the thermoelectric properties of these alloys in the cryogenic temperature range.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  10. Genome-wide analysis of YB-1-RNA interactions reveals a novel role of YB-1 in miRNA processing in glioblastoma multiforme

    PubMed Central

    Wu, Shuai-Lai; Fu, Xing; Huang, Jinyan; Jia, Ting-Ting; Zong, Feng-Yang; Mu, Shi-Rong; Zhu, Hong; Yan, Yong; Qiu, Shuwei; Wu, Qun; Yan, Wei; Peng, Ying; Chen, Juxiang; Hui, Jingyi

    2015-01-01

    Altered miRNA expression is believed to play a crucial role in a variety of human cancers; however, the mechanisms leading to the dysregulation of miRNA expression remain elusive. In this study, we report that the human Y box-binding protein (YB-1), a major mRNA packaging protein, is a novel modulator of miRNA processing in glioblastoma multiforme (GBM). Using individual nucleotide-resolution crosslinking immunoprecipitation coupled to deep sequencing (iCLIP-seq), we performed the first genome-wide analysis of the in vivo YB-1-RNA interactions and found that YB-1 preferentially recognizes a UYAUC consensus motif and binds to the majority of coding gene transcripts including pre-mRNAs and mature mRNAs. Remarkably, our data show that YB-1 also binds extensively to the terminal loop region of pri-/pre-miR-29b-2 and regulates the biogenesis of miR-29b-2 by blocking the recruitment of microprocessor and Dicer to its precursors. Furthermore, we show that down-regulation of miR-29b by YB-1, which is up-regulated in GBM, is important for cell proliferation. Together, our findings reveal a novel function of YB-1 in regulating non-coding RNA expression, which has important implications in tumorigenesis. PMID:26240386

  11. Magnetostriction of the dilute amorphous alloy Yb Au

    NASA Astrophysics Data System (ADS)

    Trieu, Duong hai

    1988-11-01

    In this paper the shape magnetostriction of one percent dilute amorphous alloy of Yb in Au metal is calculated. We obtain λ ≈ -4 × 10 -5 for the case of saturated magnetization. The dominant mixing interaction ( Hmix) between the f holes and conduction holes has been taken into account. The canonical transformation is applied to the total Hamiltonian H = H0 + Hmix + Hd to obtain the expression for the magnetoelastic energy Fme. Three contributions to magnetostriction have been considered. Among them the crystal field contribution is the dominant one.

  12. Pressure dependence of the Fermi surface of hcp Yb

    NASA Astrophysics Data System (ADS)

    Schirber, J. E.; Beaudry, B. J.; Jepsen, O.

    1981-06-01

    The pressure dependence of Fermi-surface cross sections for principal symmetry directions has been investigated using solid He pressure generation techniques. Careful searches for de Haas-van Alphen signals were conducted from 2 to 9 kbar in both virgin fcc crystals and samples transformed from hcp to fcc. No sign of the frequency reported by Ribault was detected. Results are discussed in terms of theoretically calculated pressure-induced changes in the band structure and Fermi surface of the hcp phase of Yb.

  13. Characterization of Yb:YAG ceramics as laser media

    NASA Astrophysics Data System (ADS)

    Alderighi, Daniele; Pirri, Angela; Toci, Guido; Vannini, Matteo; Esposito, Laura; Costa, Anna Luisa; Piancastelli, Andreana; Serantoni, Marina

    2010-12-01

    We report the preparation and characterization of 9.8 at.% Yb 3+ doped YAG polycrystalline ceramics for laser applications. Reactive sintering of commercial powders in a clean atmosphere and under high vacuum has been used to achieve the YAG phase. The selected experimental conditions for the powder treatment, shaping and sintering are described and their influence on the optical quality of the obtained samples has been discussed. Microstructural, optical and laser characterization of the ceramics have been performed. In particular the influence of the pre-sintering (calcination) and sintering cycles has been investigated by laser characterization allowing to find unexpected loss mechanisms that cannot be revealed by standard optical characterization.

  14. Front-end system for Yb : YAG cryogenic disk laser

    NASA Astrophysics Data System (ADS)

    Perevezentsev, E. A.; Mukhin, I. B.; Kuznetsov, I. I.; Vadimova, O. L.; Palashov, O. V.

    2015-05-01

    A new front-end system for a cryogenic Yb : YAG laser is designed. The system consists of a femtosecond source, a stretcher and a regenerative amplifier with an output energy of 25 μJ at a pulse repetition rate of 49 kHz, a pulse duration of ~2 ns and a bandwidth of ~1.5 nm. After increasing the pump power of the regenerative amplifier, it is expected to achieve a pulse energy of ~1 mJ at the input to cryogenic amplification stages, which will allow one to obtain laser pulses with a duration of several picoseconds at the output of the cryogenic laser after compression.

  15. Magnetic structures and physical properties of Tm3Cu4Ge4 and Tm3Cu4Sn4.

    PubMed

    Baran, S; Kaczorowski, D; Szytuła, A; Gil, A; Hoser, A

    2013-02-13

    Tm(3)Cu(4)Ge(4) crystallizes in the orthorhombic Gd(3)Cu(4)Ge(4)-type crystal structure (space group Immm) whereas Tm(3)Cu(4)Sn(4) crystallizes in a distorted variant of this structure (monoclinic space group C2/m). The compounds were studied by means of neutron diffraction, specific heat, electrical resistivity and magnetic measurements. Analysis of experimental data revealed the presence of an antiferromagnetic order below 2.8 K in both compounds. In Tm(3)Cu(4)Ge(4) the magnetic unit cell is doubled in respect to the crystal unit cell and the magnetic structure can be described by a propagation vector k = [0, 1/2, 0]. A larger magnetic unit cell was found in Tm(3)Cu(4)Sn(4), given by a propagation vector k = [1/2, 1/2, 0] (for simplicity the orthorhombic description is used for both the germanide and the stannide). Close to 2 K, in each compound an incommensurate antiferromagnetic order develops. This low-temperature magnetic phase is characterized by a propagation vector k = [1/4, 0, k(z)], where k(z) is close to 0.49 and 0.47 in Tm(3)Cu(4)Ge(4) and Tm(3)Cu(4)Sn(4), respectively. The antiferromagnetic phase transitions are clearly seen in the bulk magnetic and specific heat data of both compounds. PMID:23334319

  16. Deposition of luminescent NaCl:Tm2+ thin films with a Tm concentration gradient using RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    de Jong, M.; Kesteloo, W.; van der Kolk, E.

    2015-08-01

    Luminescent thin films were deposited using magnetron sputtering of a NaCl single crystal and Tm-metal. By using a combinatorial approach, a single film with a thickness ranging from 3.1 ?m to 6.9 ?m and a Tm to Na ratio varying from 0.05 to 0.26 was obtained. XRD shows the formation of the simple cubic NaCl structure and SEM images display a mix of 0.50-0.75 ?m and 2-3 ?m cubic and needle-like structures when the substrate is not rotating during deposition. NIR transmission spectra reveal narrow absorption lines at 1134 nm and 1218 nm caused by 4f-4f absorption of divalent and trivalent Tm, respectively. Photoluminescence excitation and UV-VIS transmission spectra show broad bands between 275 nm and 700 nm, caused by the Tm2+ 4f13 ? 4f125d1 transitions. Excitation into these bands results in 2F5/2 ? 2F7/2 line emission by Tm2+ at 1134 nm. The broad absorption range covering the entire UV and VIS part of the solar spectrum and the absence of self-absorption of the sharp emission line makes NaCl:Tm2+ a promising material for luminescent solar concentrators as thin films on glass provided light scattering can be minimised.

  17. Study of Eu{sup 3+} → Eu{sup 2+} reduction in BaAl{sub 2}O{sub 4}:Eu prepared in different gas atmospheres

    SciTech Connect

    Rezende, Marcos V. dos S.; Valerio, Mário E.G.; Jackson, Robert A.

    2015-01-15

    Highlights: • The effect of different gas atmospheres on the Eu reduction process was studied. • The Eu reduction was monitored analyzing XANES region at the Eu L{sub III}-edge. • Hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization. • Only a part of the Eu ions can be stabilized in the divalent state. • A model of Eu reduction process is proposed. - Abstract: The effect of different gas atmospheres such as H{sub 2}(g), synthetic air, carbon monoxide (CO) and nitrogen (N{sub 2}) on the Eu{sup 3+} → Eu{sup 2+} reduction process during the synthesis of Eu-doped BaAl{sub 2}O{sub 4} was studied using synchrotron radiation. The Eu{sup 3+} → Eu{sup 2+} reduction was monitored analyzing XANES region when the sample are excited at the Eu L{sub III}-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu{sup 2+} stabilization in BaAl{sub 2}O{sub 4} and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.

  18. Ultrafast Transparent Ceramic Scintillators Using the Yb3+ Charge Transfer Luminescence in RE2O3 Host

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Fujimoto, Yutaka; Kurosawa, Shunsuke; Watanabe, Kenichi; Yagi, Hideki; Yanagitani, Takagimi; Jary, Vitezslav; Futami, Yoshisuke; Yokota, Yuui; Yoshikawa, Akira; Uritani, Akira; Iguchi, Tetsuo; Nikl, Martin

    2011-12-01

    We report a new discovery of Yb3+-doped ultrafast scintillators based on the Yb3+ charge transfer luminescence. Transparent ceramic Yb3+-doped Y2O3, Sc2O3, Lu2O3, and Yb2O3 were prepared by sintering. When irradiated by γ- and X-rays, they showed a well detectable photoabsorption peak in the pulse height spectra and ultrafast scintillation decay dominated by the decay time of about 1 ns. For the first time, the Yb3+-doped oxide materials show detectable scintillation in the pulse height measurement at room temperature with ultrafast scintillation decay.

  19. Studies on the development of ¹⁶⁹Yb-brachytherapy seeds: New generation brachytherapy sources for the management of cancer.

    PubMed

    Saxena, Sanjay Kumar; Kumar, Yogendra; Jagadeesan, K C; Nuwad, Jitendra; Bamankar, Y R; Dash, Ashutosh

    2015-07-01

    This paper describes development of (169)Yb-seeds by encapsulating 0.6-0.65 mm (ϕ) sized (169)Yb2O3 microspheres in titanium capsules. Microspheres synthesized by a sol-gel route were characterized by XRD, SEM/EDS and ICP-AES. Optimization of neutron irradiation was accomplished and (169)Yb-seeds up to 74 MBq of (169)Yb could be produced from natural Yb2O3 microspheres, which have the potential for use in prostate brachytherapy. A protocol to prepare (169)Yb-brachytherapy sources (2.96-3.7 TBq of (169)Yb) with the use of enriched targets was also formulated. PMID:25846454

  20. Glacier Mapping With Landsat Tm: Improvements and Accuracy

    NASA Astrophysics Data System (ADS)

    Paul, F.; Huggel, C.; Kaeaeb, A.; Maisch, M.

    The new Swiss Glacier Inventory for the year 2000 (SGI 2000) is presently derived from Landsat TM data. Glacier areas were obtained by segmentation of a ratio image from TM band 4 and 5. This method has proven to be very simple and highly accurate - an essential requirement for world-wide application within the project GLIMS (Global Land Ice Measurements from Space). Mis-classification using TM4 / TM 5 results for lakes, forests and areas with vegetation in cloud shadows. Digital image processing techniques are used to classify these regions separately and eliminate them from the glacier map. Automatic mapping of debris-covered glacier ice is difficult due to the spectral similarity with the surrounding terrain. For the SGI 2000, an attempt has been made to obtain the debris-covered area on glaciers by a combination of pixel- based image classification, digital terrain modelling, an object-oriented procedure and change detection analysis. First results of these improvements are presented. The accuracy of the TM derived glacier outlines is assessed by a comparison with manually derived outlines of higher resolution data sets (pan bands from SPOT, IRS- 1C and Ikonos). The overlay of outlines show very good correspondence (within the georeferencing accuracy) and the comparison of glacier areas reveals differences smaller than 5% for debris-free ice. Since acquisition of IRS-1C and Ikonos imagery is one year before and after the TM scene, respectively, small differences are also a result of glacier retreat. The automatically mapped debris-covered glacier areas are compared to the areas assigned manually on the TM image by visual interpretation. For most glaciers only a few pixels have to be corrected, for some others larger modi- fications are required.

  1. Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, La–Nd, Sm–Tm)

    SciTech Connect

    Kong, Tai; Cunningham, Charles E.; Taufour, Valentin; Budko, Sergey L.; Buffon, Malinda L.C.; Lin, Xiao; Emmons, Heather; Canfield, Paul C.

    2014-05-01

    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 θ ab and θ 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, Θavg, 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.

  2. Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, La-Nd, Sm-Tm)

    NASA Astrophysics Data System (ADS)

    Kong, Tai; Cunningham, Charles E.; Taufour, Valentin; Bud'ko, Sergey L.; Buffon, Malinda L. C.; Lin, Xiao; Emmons, Heather; Canfield, Paul C.

    2014-05-01

    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 B20 were calculated from the anisotropic paramagnetic θab and θc values and follow a trend that agrees well with theoretical predictions. The ordering temperatures, TN, as well as the polycrystalline averaged paramagnetic Curie-Weiss temperature, Θavg, 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.

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

    SciTech Connect

    Goyal, Krittika; Deutsch, Ivan; Reichenbach, Iris

    2010-12-15

    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.

  4. Microwave sintering of Yb:YAG transparent laser ceramics

    NASA Astrophysics Data System (ADS)

    Esposito, Laura; Piancastelli, Andreana; Bykov, Yury; Egorov, Sergei; Eremeev, Anatolii

    2013-02-01

    Reactive sintering of YAG based ceramics is generally performed under high vacuum in graphite-free furnaces in order to guarantee the elimination of pores and absence of any contamination. An alternative densification technique is the field assisted process such as spark plasma sintering and microwave sintering. Both of these methods are characterized by very fast heating rates, low sintering temperatures and short sintering times. The microwave sintering process is different from electric resistance heating since heat is generated in the bulk of the powder compact through electromagnetic radiation absorption and creates within its body uniform temperature distribution. Microwave sintering of laser ceramics is advantageously distinguished by the absence of any elements having high temperature such as electric heaters or dies which materials can contaminate the sintered parts. In addition, the inverse temperature distribution that exists within the body under volumetric microwave heating is favorable for elimination of porosity. Microwave sintering of Yb:YAG samples were tested and the obtained results are presented. The samples were sintered on a gyrotron-based system operating at a frequency of 24 GHz with microwave power up to 6 kW. Reactive sintering of YAG doped with 1.0, 5.0, and 9.8 at.% Yb2O3 was performed in different temperature-time regimes. The microstructure and the optical transmittance of the obtained samples were compared to those of samples obtained by conventional high vacuum sintering.

  5. Optical Lattice Induced Light Shifts in an Yb Atomic Clock

    SciTech Connect

    Barber, Z. W.; Stalnaker, J. E.; Lemke, N. D.; Poli, N.; Oates, C. W.; Fortier, T. M.; Diddams, S. A.; Hollberg, L.; Hoyt, C. W.; Taichenachev, A. V.; Yudin, V. I.

    2008-03-14

    We present an experimental study of the lattice-induced light shifts on the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} optical clock transition ({nu}{sub clock}{approx_equal}518 THz) in neutral ytterbium. The 'magic' frequency {nu}{sub magic} for the {sup 174}Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p{sup 3}P{sub 0}{yields}6s8p{sup 3}P{sub 0}, 6s8p{sup 3}P{sub 2}, and 6s5f{sup 3}F{sub 2} two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 {mu}K deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10{sup -17}.

  6. Miniature Microwave Frequency Standard with Trapped 171Yb+

    NASA Astrophysics Data System (ADS)

    Schwindt, Peter; Jau, Yuan-Yu; Casias, Adrian; Serkland, Darwin; Manginell, Ronald; Moorman, Matthew; Prestage, John; Yu, Nan; Kellogg, James; Boschen, Dan; Kosvin, Igor

    2014-05-01

    We report the development of a low-power, miniature 171Yb trapped ion clock at Sandia National Laboratories. The ultimate goal of this development effort is to construct a frequency standard that has a frequency stability comparable to a commercial Cs beam standard, but with 100 to 1000 times smaller size and power consumption. The 171Yb ion has a ground state hyperfine splitting of 12.6 GHz that we use as the ``clock'' transition, and the linewidth of the clock resonance is expected to be less than 10-3 Hz, which leads to a very high-Q clock resonance. An atomic clock using trapped ions is an excellent candidate for miniaturization because ions are well isolated from the environment independent of the size of the trap. We have successfully developed miniature ion-trap vacuum packages with sizes ranging from 1 to 10 cubic centimeters. A few microTorr of He buffer gas is introduced into each of our miniature vacuum packages for collisional cooling of the trapped ions. The vacuum packages are sealed and passively pumped by non-evaporable getters. Using a sealed 3 cm3 ion-trap vacuum package in combination with miniaturized lasers, optics, and electronics, we constructed a miniature clock prototype that demonstrated excellent long-term stability reaching the 10-14 range after a few days of integration.

  7. Formation of LiYb Molecules by Photoassocation

    NASA Astrophysics Data System (ADS)

    Roy, Richard; Shrestha, Rajendra; Green, Alaina; Gupta, Subhadeep

    2015-05-01

    Combining ultracold alkali and alkaline-earth (or earth-like) gases to form ground state doublet sigma molecules offers a paramagnetic degree of freedom, which is attractive for quantum information and simulation applications and studies of controlled chemical reactions. However, the spinless ground electronic state of alkaline-earth atoms renders magnetoassociation techniques infeasible. Instead, coherent Raman techniques may be used to couple free atoms in an ultracold mixture to rovibrational states in the ground electronic manifold. To this end, we perform photoassociation (PA) spectroscopy of 6Li and multiple Yb isotopes in a dual-species MOT on the Li D line (671 nm) and resolve multiple features in the exited electronic YbLi* potentials. We plan to utilize these excited molecular states to perform 2-photon PA spectroscopy of the ground doublet sigma potential. Subsequently, the states with the most favorable Franck-Condon overlap will be targeted for coherent production of ground state molecules in a 3 dimensional optical lattice. We gratefully acknowledge funding from the NSF, AFOSR, and ARO-MURI.

  8. β-YbAlB4: a critical vortex metal

    NASA Astrophysics Data System (ADS)

    Ramires, Aline; Coleman, Piers; Tsvelik, Alexei

    2012-02-01

    β-YbAlB4 is the first Yb based heavy fermion superconductor and has a non Fermi Liquid behavior in the normal state that develops without external tuning by pressure or doping, making it intrinsically quantum critical [1]. Application of a magnetic field is found to drive the development of a Fermi Liquid in which the Fermi temperature is determined by the Zeeman energy [2]. Here we present a theory for the intrinsic quantum criticality in which the main ingredient is an anisotropic hybridization matrix with line nodes in momentum space that carry a vorticity and resemble topological defects. Our theory predicts that the application of a field induces a novel Lifshitz transition, in which a quasi-two dimensional Fermi Liquid with density of states N^*(B) 1/√B nucleates around the line node in momentum space. We also discuss how the vortex metal picture can account for the ESR anomalies observed in this system [3]. 0.3truein [1] S. Nakatsuji et al., Nature Phys. 4, 603 (2008). [2] Y. Matsumoto et al., Science 21, 316 (2011). [3] L. M. Holanda et al., Phys Rev. Lett. 107, 026402 (2011).

  9. Synthesis and tunable luminescent properties of Eu-doped Ca2NaSiO4F - Coexistence of the Eu2+ and Eu3+ centers

    NASA Astrophysics Data System (ADS)

    Xie, Mubiao; Li, Dongyu; Zhu, Guoxian; Pan, Rongkai; Fu, Xionghui

    Novel phosphors Ca2NaSiO4F:Eu were synthesized successfully by the conventional solid-state method in CO atmosphere, and their spectroscopic properties in UV-vis region were investigated. The photoluminescence properties show that Eu3+ ions were partially reduced to Eu2+ in Ca2NaSiO4F. As a result of radiation and re-absorption energy transfer from Eu2+ to Eu3+, both Eu2+ bluish-green emission at around 520 nm and Eu3+ red emission are observed in the emission spectra under the n-UV light excitation. Furthermore, the ratio between Eu2+ and Eu3+ emissions varies with increasing content of overall Eu. Because relative intensity of the red component from Eu3+ became systematically stronger, white light emission can be realized by combining the emission of Eu2+ and Eu3+ in a single host lattice under n-UV light excitation. These results indicate that the Ca2NaSiO4F:Eu phosphors have potential applications as a n-UV convertible phosphor for light-emitting diodes.

  10. High-spin structure, K isomers, and state mixing in the neutron-rich isotopes 173Tm and 175Tm

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; Nieminen, P. H.; Watanabe, H.; Carpenter, M. P.; Chowdhury, P.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Seweryniak, D.; Zhu, S.

    2012-11-01

    High-spin states in the odd-proton thulium isotopes 173Tm and 175Tm have been studied using deep-inelastic reactions and γ-ray spectroscopy. In 173Tm, the low-lying structure has been confirmed and numerous new states have been identified, including a three-quasiparticle Kπ= 19/2- isomer with a lifetime of τ=360(100) ns at 1906 keV and a five-quasiparticle Kπ=35/2- isomer with a lifetime of τ= 175(40) ns at 4048 keV. The Kπ=35/2- state is interpreted as a t-band configuration that shows anomalously fast decays. In 175Tm, the low-lying structure has been reevaluated, a candidate state for the 9/2-[514] orbital has been identified at 1175 keV, and the 7/2-[523] bandhead has been measured to have a lifetime of τ= 460(50) ns. Newly identified high-K structures in 175Tm include a Kπ=15/2- isomer with a lifetime of τ= 64(3) ns at 947 keV and a Kπ= 23/2+ isomer with a lifetime of τ= 30(20) μs at 1518 keV. The Kπ=15/2- isomer shows relatively enhanced decays to the 7/2-[523] band that can be explained by chance mixing with the 15/2- member of the 7/2- band. Multiquasiparticle calculations have been performed for 173Tm and 175Tm, the results of which compare well with the experimentally observed high-spin states.

  11. Loading rate of Yb+ loaded through photoionization in radiofrequency ion trap

    NASA Astrophysics Data System (ADS)

    Onoda, Y.; Sugiyama, K.; Ikeda, M.; Kitano, M.

    2011-12-01

    We investigate the loading rate of Yb+ ions loaded through photoionization in a radiofrequency trap. The absolute or relative number of the loaded trapped ions is measured by use of an electric resonance of the secular motion. This method is applicable even in the presence of anharmonicity. In two-color photoionization, where the first-excitation laser drives the 1S0-1P1 transition in the Yb atom and the second one ionizes the atom from the 1P1 state, the loading rate is at its highest by the excitation of the ionization potential. A similar loading rate is observed at the second-laser wavelength around 369.5 nm, which is the wavelength for the cooling transition of Yb+. We estimate the loading cross section to be 40(15) Mb for the two-color excitation of the ionization potential. The excitation of the Yb atoms in the Rydberg states is detected by the enhancement of the loading rate. By irradiation with only the first-excitation laser, Yb+ is produced at a rate three orders of magnitude smaller than that when the non-resonant two-photon absorption from the 1P1 state is the dominant process. We also measure the charge-exchange rate between Yb+ and Yb, and discuss its effect on isotope-selective photoionization loading.

  12. Yb-substituted clathrates Ba8-xYbxGa16Ge30

    NASA Astrophysics Data System (ADS)

    Liu, L. H.; Wei, Y. P.; Yang, S. W.; Zhu, J.; Li, Y.

    2014-06-01

    Exploration of new rare-earth captured clathrates is an important field of clathrate application. Study on the second phases produced in the synthesis process is crucial for confirming the incorporation of rare earth atoms into the clathrate lattice. In the current study, the Yb-doped clathrate samples with nominal composition of Ba6Yb2Ga16Ge30 were prepared by combining arc melting (ARC), melt spinning (MS) and spark plasma sintering (SPS) techniques. By using the TEM with EDS analysis and X-ray diffraction refinement, phase analysis was systemically performed in different steps of the preparation process. Although the clathrate was the main phase in obtained samples, the Yb content in the clathrate phase was found to be much lower than the nominal composition as the Yb atoms strongly tend to create other byproduct phases including Yb2O3 — which is the main obstacle in the synthesis of Yb-substituted clathrates. For the dilute Yb-doped germanium clathrate sample a decrease in the thermal conductivity and electrical conductivity was simultaneously observed, therefore, no expected improvement of ZT occurred.

  13. Thermal neutron decay time /SUP TM/ log applications in California

    SciTech Connect

    Wiese, H.C.

    1983-02-01

    The Thermal Neutron Decay Time /SUP TM/ (TDT) log has had wide applications throughout the world for many years. Recent improvements in equipment design, combined with the effect of the presence of trace elements in the low-salinity formation waters of California, have extended the TDT's use to these reservoirs. Interpretation of TDT logs employs the dual water model concept. The dual water model concept is explained and an example of its use is shown in this paper. The TDT logs run in California are processed through the Schlumberger Computing Center using the Cased Reservoir Analysis /SUP TM/ (CRA) program. The CRA program uses the dual water model. An example is shown including pass 1 EDIT output, parameter selection, and CRA output. Example of California applications are presented, including selection of zones for recompletion, location of zones of high GOR, evaluation of diatomite, monitoring of reservoir performance and production, and logging of TDT through drillpipe. With the introduction of the Schlumberger Cyber Service Units /SUP TM/ (CSU's) to the field, the scope of wellsite Quicklook /SUP TM/ computations has increased greatly. Recently introduced to the field is Cyberscan, /SUP TM/ a Quicklook wellsite computation. The process is described, and an example is presented. Also shown is a comparison of the Cyberscan example and the CRA computed on the same well.

  14. Formation, optical properties, and electronic structure of thin Yb silicide films on Si(111)

    NASA Astrophysics Data System (ADS)

    Galkin, N. G.; Maslov, A. M.; Polyarnyi, V. O.

    2005-06-01

    Continuous very thin (2.5-3.0 nm) and thin (16-18 nm) ytterbium suicide films with some pinhole density (3×107- 1×108 cm-2) have been formed on Si(111) by solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE) growth methods on templates. The stoichiometric ytterbium suicide (YbSi2) formation has shown in SPE grown films by AES and EELS data. Very thin Yb suicide films grown by RDE method had the silicon enrichment in YbSi2 suicide composition. The analysis of LEED data and AFM imaging has shown that ytterbium suicide films had non-oriented blocks with the polycrystalline structure. The analysis of scanning region length dependencies of the root mean square roughness deviation (σR(L)) for grown suicide films has shown that the formation of ytterbium suicide in SPE and RDE growth methods is determined by the surface diffusion of Yb atoms during the three-dimensional growth process. Optical functions (n, k, α, ɛ1, ɛ2, Im ɛ1-1, neff, ɛeff) of ytterbium silicide films grown on Si(1 1 1) have been calculated from transmittance and reflectance spectra in the energy range of 0.1-6.2 eV. Two nearly discrete absorption bands have been observed in the electronic structure of Yb silicide films with different composition, which connected with interband transitions on divalent and trivalent Yb states. It was established that the reflection coefficient minimum in R-spectra at energies higher 4.2 eV corresponds to the state density minimum in Yb suicide between divalent and trivalent Yb states. It was shown from optical data that Yb silicide films have the semi-metallic properties with low state densities at energies less 0.4 eV and high state densities at 0.5-2.5 eV.

  15. Efficient Nd3+→Yb3+ energy transfer processes in high phonon energy phosphate glasses for 1.0 μm Yb3+ laser

    NASA Astrophysics Data System (ADS)

    Rivera-López, F.; Babu, P.; Basavapoornima, Ch.; Jayasankar, C. K.; Lavín, V.

    2011-06-01

    Efficient Nd3+→Yb3+ resonant and phonon-assisted energy transfer processes have been observed in phosphate glasses and have been studied using steady-state and time-resolved optical spectroscopies. Results indicate that the energy transfer occurs via nonradiative electric dipole-dipole processes and is enhanced with the concentration of Yb3+ acceptor ions, having an efficiency higher than 75% for the glass doped with 1 mol% of Nd2O3 and 4 mol% of Yb2O3. The luminescence decay curves show a nonexponential character and the energy transfer microscopic parameter calculated with the Inokuti-Hirayama model gives a value of 240 × 10-40 cm6 s-1, being one of the highest reported in the literature for Nd3+-Yb3+ co-doped matrices. From the steady-state experimental absorption and emission cross-sections, a general expression for estimating the microscopic energy transfer parameter is proposed based upon the theoretical methods developed by Miyakawa and Dexter and Tarelho et al. This expression takes into account all the resonant mechanisms involved in an energy transfer processes together with other phonon-assisted nonvanishing overlaps. The value of the Nd3+→Yb3+ energy transfer microscopic parameter has been calculated to be 200 × 10-40 cm6 s-1, which is in good agreement with that obtained from the Inokuti-Hirayama fitting. These results show the importance of the nonresonant phonon-assisted Nd3+→Yb3+ energy transfer processes and the great potential of these glasses as active matrices in the development of multiple-pump-channel Yb3+ lasers.

  16. Expression of tmRNAin Mycobacteria is Increased by Antimicrobial Agents that Target the Ribosome

    PubMed Central

    Andini, Nadya; Nash, Kevin A.

    2011-01-01

    The specialized RNA, tmRNA, is a central component of prokaryote trans-translation; a process that salvages stalled translational complexes. Evidence from other bacteria, suggested that exposure to ribosome inhibitors elevated tmRNA levels, although it was unclear whether such changes resulted from increased tmRNA synthesis. Consequently, this study was initiated to determine the effect of ribosome inhibitors on the expression tmRNA in mycobacteria. Exposure of Mycobacterium smegmatis to ribosome-targeting antimicrobial agents was associated with increased in the levels of the tmRNA precursor, pre-tmRNA, and mature tmRNA. For example, exposure to 16 μg mL−1 erythromycin for 3 h increased pre-tmRNA and tmRNA by 18 and 6-fold, respectively. Equivalent results were found following exposure of Mycobacterium bovis BCG to streptomycin. Exposure to antimicrobial agents with non-ribosome targets did not affect tmRNA levels. The increased tmRNA levels were associated with increased output from the ssrA promoter, which controls tmRNA transcription, without evidence of a change in tmRNA degradation. Thus, these results suggested that the upregulation of tmRNA expression was an important response of bacteria to exposure to ribosome-inhibiting antimicrobial agents. PMID:21718348

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

    SciTech Connect

    Krupke, W.F.; Payne, S.A.; Chase, L.L.; Smith, L.K.

    1991-12-31

    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 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.

  18. Dissipative soliton operation of a diode pumped Yb:NaY(WO₄)₂ laser.

    PubMed

    Ma, Jie; Wang, Jun; Shen, Deyuan; Yu, Haohai; Zhang, Huaijin; Tang, Dingyuan

    2015-12-14

    We report on the dissipative soliton operation of a diode pumped Yb:NaY(WO₄)₂ (Yb:NYW) solid-state laser. The dissipative solitons and their features as the net cavity group velocity dispersion is changed from the normal to the anomalous dispersion regime are experimentally investigated. Taking advantage of the dissipative soliton shaping of the mode-locked pulses we have generated stable near transform-limited pulses as short as 54 fs. To our knowledge, this is so far the shortest pulse directly obtained from the mode-locked Yb:NYW oscillator. PMID:26699021

  19. Missing metallofullerene Yb@C72: A density functional theory survey

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Zhao, Xiang

    2013-09-01

    With density functional theory calculations, Yb@C72 isomers are determined to utilize two fullerene cages violating the isolated pentagon rule. Both endohedral fullerenes show high thermodynamic stability in fullerene formation temperature region. Detailed calculations on the properties such as ionization energies and electron affinities of Yb@C72 provide a profoundly understanding of these two novel molecules. In addition, electronic absorption spectra and infrared spectra of two Yb@C72 isomers have also been simulated theoretically to assist future experiments.

  20. Continuous wave Yb:YCOB cyan lasers with KTP as the sum-frequency converter

    NASA Astrophysics Data System (ADS)

    Lan, Ruijun; Cheng, Hao; Yang, Guang

    2015-12-01

    All-solid-state cyan laser at 500 nm range are reported based on a Yb:YCa4O(BO3)3 (Yb:YCOB) crystal and a type-II phase matched KTiOPO4 (KTP) crystal. The 503 nm cyan laser is obtained by the sum-frequency mixing (SFM) of 974 nm pump wave and 1042 nm fundamental wave. To the best of our knowledge, this is the first cyan laser demonstrated with Yb-doped YCOB crystal. A dual-wavelength laser at 505 and 525 nm is also obtained, which origins from the simultaneous SFM and self-frequency doubling.

  1. Ultralow-threshold Yb(3+):SiO(2) glass laser fabricated by the solgel process.

    PubMed

    Ostby, Eric P; Yang, Lan; Vahala, Kerry J

    2007-09-15

    A Yb-doped silica microcavity laser on a silicon chip is fabricated from a solgel thin film. The high-Q micro-toroid cavity, which has a finesse of 10,000, is evanescently coupled to an optical fiber taper. We report a threshold of 1.8 microW absorbed power that is, to the best of our knowledge, the lowest published threshold to date for any Yb-doped laser. The effect of Yb(3+) concentration on laser threshold is experimentally quantified. PMID:17873923

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

    DOEpatents

    Krupke, William F.; Payne, Stephen A.; Chase, Lloyd L.; Smith, Larry K.

    1994-01-01

    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.

  3. Mode-locked operation of a diode-pumped femtosecond Yb:SrF2 laser.

    PubMed

    Druon, F; Papadopoulos, D N; Boudeile, J; Hanna, M; Georges, P; Benayad, A; Camy, P; Doualan, J L; Ménard, V; Moncorgé, R

    2009-08-01

    Femtosecond mode-locked operation is demonstrated for the first time, to our knowledge, with a Yb:SrF(2) crystal. The shortest pulse duration is 143 fs for an average power of 450 mW. The highest average power is 620 mW for a pulse duration of 173 fs. Since Yb:SrF(2) corresponds to the longest-lifetime Yb-doped crystal with which the mode-locking operation has been achieved, a detailed analysis is carried out to characterize the quality of the solitonlike regime. PMID:19649095

  4. The spectroscopic properties of Yb3+ doped α-BBO crystal

    NASA Astrophysics Data System (ADS)

    Yu, Pingsheng; Su, Liangbi; Wu, Feng; Xu, Jun

    2012-05-01

    2.0 mol% (relative to Ba2+) Yb3+ doped α-BaB2O4 (α-BBO) crystal was obtained by the Czochralski method. The doped crystal structure was determined by means of an X-ray diffraction analysis. The absorption, near-infrared (NIR) luminescence spectra and fluorescence decay curve of Yb3+ doped α-BBO crystal were investigated. NIR emission under 940 nm and 980 nm LDs (laser diodes) excitation was observed in the Yb doped α-BBO crystal.

  5. Hydrological planning studies using Landsat-4 Thematic Mapper (TM)

    NASA Technical Reports Server (NTRS)

    Gervin, J. C.; Mulligan, P. J.; Lu, Y. C.; Marcell, R. F.

    1984-01-01

    NASA, in cooperation with the U.S. Army Corps of Engineers, is evaluating the capabilities of Landsat 4 Thematic Mapper (TM) data for environmental and hydrological applications. Attention is given to the results of studies conducted at the Clinton River Basin in Michigan and the eastern shore of the Chesapeake Bay in Maryland. In the former, the evaluation conducted was for the band combinations: (1) 2, 3, and 4; (2) 3, 4, and 5; (3) 3, 4, 5, and 6; and (4) all seven bands. In the latter case, Multispectral Scanner (MSS) and TM data were classified for combinations (1), (3) and (4). Wetland classification accuracy for the 7-band TM data in this study was found to be 9 percent higher than with MSS data, allowing more reliable and accurate monitoring.

  6. Analysis of forest disturbance using TM and AVHRR data

    NASA Technical Reports Server (NTRS)

    Spanner, Michael A.; Hlavka, Christine A.; Pierce, Lars L.

    1989-01-01

    A methodology that will be used to determine the proportions of undisturbed, successional vegetation and recently disturbed land cover within coniferous forests using remotely sensed data from the advanced very high resolution radiometer (AVHRR) is presented. The method uses thematic mapper (TM) data to determine the proportions of the three stages of forest disturbance and regrowth for each AVHRR pixel in the sample areas, and is then applied to interpret all AVHRR imagery. Preliminary results indicate that there are predictable relationships between TM spectral response and the disturbance classes. Analysis of ellipse plots from a TM classification of the disturbed forested landscape indicates that the forest classes are separable in the red (0.63-0.69 micron) and near-infrared (0.76-0.90 micron) bands, providing evidence that the proportion of disturbance classes may be determined from AVHRR data.

  7. TM digital image products for applications. [computer compatible tapes

    NASA Technical Reports Server (NTRS)

    Barker, J. L.; Gunther, F. J.; Abrams, R. B.; Ball, D.

    1984-01-01

    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.

  8. Growth and spectral properties of Tm:BaY2F8 crystals with different Tm3+ concentration

    NASA Astrophysics Data System (ADS)

    Liu, Wang; Li, Chun; Xu, Jialin; Zhou, Yao; Xie, Huishuang; Gao, Meiling; Yin, Ru; Zheng, Dongyang; Lin, Hai; Liu, Jinghe; Zeng, Fanming

    2016-01-01

    Tm3+:BaY2F8 (Tm:BYF) laser crystals with different doping concentrations were successfully grown by Czochralski method. The optimal growth parameters obtained are as follows: the pulling rate is 0.5 mm/h; the rotation speed is 5 rpm; the cooling rate is 10°C/h. Phase composition, absorption spectra, and fluorescence properties of crystals were studied by XRD and spectral methods. XRD analysis indicates that the crystal belongs to monoclinic system with the C2/ m space group. The lattice parameters were calculated and the anisotropy of the crystals was studied, confirming that the a axis is the best growth direction. The absorption peaks around 790 nm became larger with increase of Tm3+ concentration. The cross section of 15% Tm:BYF crystal around 791 nm is 9.47 × 10-21 cm2. The 10% Tm:BYF crystal has the strongest emission peak around 1879.6 nm with the FWHM of 79 nm and the emission cross-section of 2.13 × 10-21 cm2, which is favorable for the 1.88 μm laser output.

  9. Electronic structure of YbGa1.15Si0:85 and YbGaxGe2-x probed by resonant x-ray emission and photoelectron spectroscopies

    SciTech Connect

    Yamaoka, Hitoshi; Jarrige, Ignace; Tsujii, Naohito; Imai, Motoharu; Lin, Jung-Fu; Matsunami, Masaharu; Eguchi, Ritsuko; Arita, Masashi; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki; Taguchi, Munetaka; Senba, Yasunori; Ohashi, Haruhiko; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding

    2011-03-31

    We performed an x-ray spectroscopic study combining resonant x-ray emission spectroscopy (RXES) and photoelectron spectroscopy on the superconducting ternary silicide YbGa 1.15 Si 0.85 and nonsuperconducting ternary germanide YbGax Ge2-x (x = 1.0 and 1.1). The Yb valence for all three compounds is found to be about 2.3. In YbGa1.15 Si0.85 no temperature dependence of the Yb valence is observed in the RXES spectra in the temperature range of 7–300 K, while the valence shows a drastic increase under pressure from the Yb2+ state partially including itinerant electrons to the localized Yb3+ state. Differences are observed in the valence-band spectra of the photoelectron spectroscopy between YbGa1.15 Si0.85 and YbGax Ge2-x , which may be attributed to the difference of crystal structure. We conclude that both the crystal structure of the planar GaSi layer in YbGa1.15 Si0.85 and the resultant electronic structure may have a crucial role in the occurrence of superconductivity.

  10. 151Eu Mössbauer measurements of CuLa1 - x Eu x O2 with luminescent property

    NASA Astrophysics Data System (ADS)

    Fujishiro, Fumito; Hashimoto, Takuya; Takahashi, Masashi

    2012-03-01

    An increase of the asymmetric ratio of photoluminescence lines from CuLa1 - x Eu x O2 was observed under 100 K, suggesting a lower site symmetry for the Eu cation. Mössbauer spectra of CuLa0.8Eu0.2O2 measured at 77 K revealed that the valence of Eu is trivalent and that the crystal structure of CuLa1 - x Eu x O2 might contain a EuO6 octahedron with lower symmetry. The thermodynamic stability of the valence of Cu and Eu was calculated, showing agreement with Mössbauer spectra.

  11. Spectroscopic characterization of dynamical processes for Tm,Ho:YAG lasers

    NASA Technical Reports Server (NTRS)

    Armagan, G.; Buoncristiani, A. M.; Edwards, W. C.; Inge, A. T.; Dibartolo, B.

    1991-01-01

    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.

  12. Enhanced rock discrimination using Landsat-5 Thematic Mapper (TM) data

    NASA Technical Reports Server (NTRS)

    Blodget, H. W.; Andre, C. G.; Marcell, R. F.

    1985-01-01

    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.

  13. SPACEWAY(TM) Providing Afordable and Versatile Telecommunication Solutions

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Edward James

    1996-01-01

    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.

  14. 152 W average power Tm-doped fiber CPA system.

    PubMed

    Stutzki, Fabian; Gaida, Christian; Gebhardt, Martin; Jansen, Florian; Wienke, Andreas; Zeitner, Uwe; Fuchs, Frank; Jauregui, Cesar; Wandt, Dieter; Kracht, Dietmar; Limpert, Jens; Tünnermann, Andreas

    2014-08-15

    A high-power thulium (Tm)-doped fiber chirped-pulse amplification system emitting a record compressed average output power of 152 W and 4 MW peak power is demonstrated. This result is enabled by utilizing Tm-doped photonic crystal fibers with mode-field diameters of 35 μm, which mitigate detrimental nonlinearities, exhibit slope efficiencies of more than 50%, and allow for reaching a pump-power-limited average output power of 241 W. The high-compression efficiency has been achieved by using multilayer dielectric gratings with diffraction efficiencies higher than 98%. PMID:25121845

  15. Crossover from a heavy fermion to intermediate valence state in noncentrosymmetric Yb2Ni12(P,As)7

    PubMed Central

    Jiang, W. B.; Yang, L.; Guo, C. Y.; Hu, Z.; Lee, J. M.; Smidman, M.; Wang, Y. F.; Shang, T.; Cheng, Z. W.; Gao, F.; Ishii, H.; Tsuei, K. D.; Liao, Y. F.; Lu, X.; Tjeng, L. H.; Chen, J. M.; Yuan, H. Q.

    2015-01-01

    We report measurements of the physical properties and electronic structure of the hexagonal compounds Yb2Ni12Pn7 (Pn = P, As) by measuring the electrical resistivity, magnetization, specific heat and partial fluorescence yield x-ray absorption spectroscopy (PFY-XAS). These demonstrate a crossover upon reducing the unit cell volume, from an intermediate valence state in Yb2Ni12As7 to a heavy-fermion paramagnetic state in Yb2Ni12P7, where the Yb is nearly trivalent. Application of pressure to Yb2Ni12P7 suppresses TFL, the temperature below which Fermi liquid behavior is recovered, suggesting the presence of a quantum critical point (QCP) under pressure. However, while there is little change in the Yb valence of Yb2Ni12P7 up to 30 GPa, there is a strong increase for Yb2Ni12As7 under pressure, before a near constant value is reached. These results indicate that any magnetic QCP in this system is well separated from strong valence fluctuations. The pressure dependence of the valence and lattice parameters of Yb2Ni12As7 are compared and at 1 GPa, there is an anomaly in the unit cell volume as well as a change in the slope of the Yb valence, indicating a correlation between structural and electronic changes. PMID:26626431

  16. Crossover from a heavy fermion to intermediate valence state in noncentrosymmetric Yb2Ni12(P,As)7

    NASA Astrophysics Data System (ADS)

    Jiang, W. B.; Yang, L.; Guo, C. Y.; Hu, Z.; Lee, J. M.; Smidman, M.; Wang, Y. F.; Shang, T.; Cheng, Z. W.; Gao, F.; Ishii, H.; Tsuei, K. D.; Liao, Y. F.; Lu, X.; Tjeng, L. H.; Chen, J. M.; Yuan, H. Q.

    2015-12-01

    We report measurements of the physical properties and electronic structure of the hexagonal compounds Yb2Ni12Pn7 (Pn = P, As) by measuring the electrical resistivity, magnetization, specific heat and partial fluorescence yield x-ray absorption spectroscopy (PFY-XAS). These demonstrate a crossover upon reducing the unit cell volume, from an intermediate valence state in Yb2Ni12As7 to a heavy-fermion paramagnetic state in Yb2Ni12P7, where the Yb is nearly trivalent. Application of pressure to Yb2Ni12P7 suppresses TFL, the temperature below which Fermi liquid behavior is recovered, suggesting the presence of a quantum critical point (QCP) under pressure. However, while there is little change in the Yb valence of Yb2Ni12P7 up to 30 GPa, there is a strong increase for Yb2Ni12As7 under pressure, before a near constant value is reached. These results indicate that any magnetic QCP in this system is well separated from strong valence fluctuations. The pressure dependence of the valence and lattice parameters of Yb2Ni12As7 are compared and at 1 GPa, there is an anomaly in the unit cell volume as well as a change in the slope of the Yb valence, indicating a correlation between structural and electronic changes.

  17. YB-1 expression promotes epithelial-to-mesenchymal transition in prostate cancer that is inhibited by a small molecule fisetin.

    PubMed

    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

    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 β1 - β4 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

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

    SciTech Connect

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

    2013-12-07

    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.

  19. 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)

    Abrams, Michael; Verosub, Ken

    1987-01-01

    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.

  20. Graphene Q-switched Yb:KYW planar waveguide laser

    SciTech Connect

    Kim, Jun Wan; Young Choi, Sun; Jun Ahn, Kwang; Yeom, Dong-Il E-mail: rotermun@ajou.ac.kr; Rotermund, Fabian E-mail: rotermun@ajou.ac.kr; Aravazhi, Shanmugam; Pollnau, Markus; Griebner, Uwe; Petrov, Valentin; Bae, Sukang

    2015-01-15

    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 μs to 349 ns.

  1. Progress toward 174Yb BEC realization for Quantum Simulation

    NASA Astrophysics Data System (ADS)

    Mun, Jongchul; Lee, Jeongwon; Lee, Jae Hoon; Noh, Jiho

    2015-05-01

    We report the progress in building our experimental setup for 174Yb BEC. The experimental setup consists of the conventional Zeeman slower and new type of magneto-optical trap(MOT), which we propose and demonstrate for alkaline-earth-metal-like atoms. This new type of MOT, which we call core-shell MOT, utilizes both the broad 1S0 -->1P1 transition and the narrow 1S0 -->3P1 transition in two spatialy seperated regions. Experimental implementation of this scheme showed both faster loading and high atom numbers, by more than two orders and one order of magnitude respectively, compared to conventional MOT schemes. We plan to further cool and transfer the atomic sample into a science chamber by displacing an optical dipole trap using an optically compensated zoom-lens. The atoms will be loaded into an optical lattice for quantum simulations.

  2. [Investigation on spectroscopic properties of Yb3+ -doped laser glasses].

    PubMed

    Li, Wei-nan; Ding, Guang-lei; Lu, Min; Xiang, Li-bin

    2006-10-01

    Yb3+ -doped borosilicate glasses were prepared at high tempreture. The absorption spectra and fluorescence spectra were measured at room temperature. The integrated absorption cross section, stimulated emission cross section and fluorescent time were calculated. The results showed that the main peak wavelength was 975.15 nm in absorption spectra with one subpeak near 937.17 nm; emission peak was at 977.15 nm in fluorescence spectra with one subpeak near 997.42 nm; with increasing the sample thickness from 0.5 to 5 mm, luminescence intensity became greater, and the peak shifted to longer wavelength from 995.79 to 999.02 nm. The effective line width of fluorescence increased from 34.64 to 54.50 nm; Fluorescence lifetime decreased from 1.04 to 1.00 ms. PMID:17205719

  3. Injection locking of Yb-fiber based optical frequency comb.

    PubMed

    Kuse, Naoya; Ozawa, Akira; Nomura, Yutaka; Ito, Isao; Kobayashi, Yohei

    2012-05-01

    We demonstrated the synchronization of offset and repetition frequency between two independent Yb-doped fiber mode-locked lasers by injection locking. By injecting master-laser pulse-train into slave laser cavity, stability and accuracy of master frequency comb are transferred to slave comb. Passive stabilization of frequency comb offers robust and convenient way to duplicate frequency comb that can be applied to long-distance comb transfer. Injecting master pulse would also help to initiate and stabilize mode-locking of high repetition rate or ultrabroadband frequency combs. Additionally, we also demonstrated even more robust synchronization of combs can be achieved with the help of active stabilization of relative offset frequency difference. PMID:22565676

  4. Discrete-fibre subpicosecond oscillator-amplifier based on a Yb:KYW laser

    SciTech Connect

    Kobtsev, S M; Kukarin, S V

    2007-11-30

    A hybrid subpicosecond system based on a Yb:KYW laser and a Yb fibre amplifier made by using the GTWave technology is studied. The system pumped by the 980-nm, 12-W cw radiation emits 0.9-ps, 40-nJ pulses at a pulse repetition rate of 100 MHz and an average power of 4 W. The central emission wavelength of the system can be tuned in the pulsed regime from 1038 to 1053 nm and from 1030 to 1070 nm in the cw regime. The gain of the Yb fibre GTWave amplifier is measured for the first time within the tuning range of the Yb:KYW laser. (lasers)

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

    PubMed

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

    2014-11-17

    We investigated the effect of rare earth impurities on the cooling efficiency of Yb³⁺:LiYF₄ (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

  6. Large core Yb-doped optical fiber through vapor phase doping technique

    NASA Astrophysics Data System (ADS)

    Saha, Maitreyee; Pal, Atasi; Pal, Mrinmay; Sen, Ranjan

    2013-05-01

    Rare earth (RE) doped optical fibers have shown tremendous progress for producing high power fiber lasers for industrial, medical and strategic applications. However, fabrication of large core, high Yb-doped fiber is still a challenge through conventional process due to poor repeatability and limitation regarding core size. This paper presents successful fabrication of Yb-doped fibers through vapor phase doping technique. Preform fabrication was carried out using a specially constructed MCVD system containing High Temperature Vapor Delivery Unit with sublimators for Al and Yb precursors. The novelty of the present work lies in deposition of Al2O3 and Yb2O3 in vapor phase simultaneously with silica during formation of sintered core layer which result in uniform dopants distribution in the preform. The fibers exhibited lasing efficiency of 76% with low `photodarkening effect'.

  7. Laser performance parameters of Yb3+ doped UV-transparent phosphate glasses

    NASA Astrophysics Data System (ADS)

    Pinheiro, A. S.; Freitas, A. M.; Silva, G. H.; Bell, M. J. V.; Anjos, V.; Carmo, A. P.; Dantas, N. O.

    2014-01-01

    We report on optical investigation of phosphate glasses doped with Yb2O3. UV-Vis and FT-NIR optical absorption, photoluminescence, time-resolved photoluminescence and refractometry techniques are used. Cluster formation of Yb3+ was not observed as well as, no evidence of cooperative luminescence among Yb3+. An exponential decay of the 2F5/2 → 2F7/2 lifetime of ytterbium was found when the interionic distance decreases. The quantum efficiency and laser performance were also investigated. Relatively high figure of merit was found, 0.33 × 10-20 cm2 ms. The values of the minimum fraction of Yb3+ for minimum laser gain, pump saturation intensity and minimum absorbed pumping intensity were estimated.

  8. Analysis of upconversion luminescence in Yb3+/Er3+ co-doped tellurite optical fiber

    NASA Astrophysics Data System (ADS)

    Mazerski, Wojciech; Kochanowicz, Marcin; Dorosz, Dominik

    2013-10-01

    In the paper the analysis of upconversion luminescence in Yb3+/Er3+ co-doped tellurite glass and optical fiber has been investigated. Upconversion luminescence at 525 nm, 546 nm, 651 nm corresponding to the Er3+: 2H11/2→4I15/2, 4S3/2→4I15/2, (4F9/2→4I15/2) transitions, respectively was obtained as a result of energy transfer between Yb3+ and Er3+ ions. Developed tellurite glass characterized by highest intensity of upconversion luminescence (0.5mol% Yb2O3/0.1mol% Er2O3) was used as core of optical fiber. The analysis of influence of Yb3+/Er3+ co-doped tellurite optical fiber length on upconversion emission spectra was examinated.

  9. Optimization of the cooling profile to achieve crack-free Yb:S-FAP crystals

    SciTech Connect

    Fang, H; Qiu, S; Kheng, L; Schaffers, K; Tassano, J; Caird, J; Zhang, H

    2007-08-20

    Yb:S-FAP [Yb{sup 3+}:Sr{sub 5}(PO{sub 4}){sub 3}F] crystals are an important gain medium for diode-pumped laser applications. Growth of 7.0 cm diameter Yb:S-FAP crystals utilizing the Czochralski (CZ) method from SrF{sub 2}-rich melts often encounter cracks during the post growth cool down stage. To suppress cracking during cool down, a numerical simulation of the growth system was used to understand the correlation between the furnace power during cool down and the radial temperature differences within the crystal. The critical radial temperature difference, above which the crystal cracks, has been determined by benchmarking the simulation results against experimental observations. Based on this comparison, an optimal three-stage ramp-down profile was implemented and produced high quality, crack-free Yb:S-FAP crystals.

  10. Single linearly polarized, widely and freely tunable two wavelengths Yb3+-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Dongfeng; Wang, Chinhua

    2010-01-01

    We report a novel single linearly polarized, widely, freely and continuously tunable two wavelengths Yb3+-doped fiber laser. The laser generates stable arbitrary two wavelengths output between 1003.1 and 1080.7 nm peak wavelengths simultaneously with a 346.0 mW CW power by using polarization beam splitting (PBS) for separation of two wavelengths. Each lasing line shows a single polarization with a polarization extinction ratio of >20 dB under different pump levels. The central and the interval of the two wavelengths can be tuned smoothly and independently in the entire gain region of >70 nm of PM Yb3+-doped single mode fiber. Strongly enhanced polarization-hole burning (PHB) phenomena in polarization maintain (PM) Yb3+-doped fiber was observed in the tunable two wavelengths Yb3+-doped fiber laser.

  11. Centrosome maturation requires YB-1 to regulate dynamic instability of microtubules for nucleus reassembly

    PubMed Central

    Kawaguchi, Atsushi; Asaka, Masamitsu N.; Matsumoto, Ken; Nagata, Kyosuke

    2015-01-01

    Microtubule formation from the centrosome increases dramatically at the onset of mitosis. This process is termed centrosome maturation. However, regulatory mechanisms of microtubule assembly from the centrosome in response to the centrosome maturation are largely unknown. Here we found that YB-1, a cellular cancer susceptibility protein, is required for the centrosome maturation. Phosphorylated YB-1 accumulated in the centrosome at mitotic phase. By YB-1 knockdown, microtubules were found detached from the centrosome at telophase and an abnormal nuclear shape called nuclear lobulation was found due to defective reassembly of nuclear envelope by mis-localization of non-centrosomal microtubules. In conclusion, we propose that YB-1 is important for the assembly of centrosomal microtubule array for temporal and spatial regulation of microtubules. PMID:25740062

  12. Alumina Paste Layer as a Sublimation Suppression Barrier for Yb14MnSb11

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Caillat, Thierry

    2010-01-01

    Sublimation is a major cause of degradation of thermoelectric power generation systems. Most thermoelectric materials tend to have peak values at the temperature where sublimation occurs. A sublimation barrier is needed that is stable at operating temperatures, inert against thermoelectric materials, and able to withstand thermal cycling stress. A porous alumina paste layer is suitable as a sublimation barrier for Yb14MnSb11. It can accommodate stress generated by the thermal expansion discrepancy between the suppression layer and thermoelectric materials. Sublimation suppression is achieved by filling pores naturally with YbO2, a natural byproduct of sublimation. YbO2 generated during the sublimation of Yb14MnSb11 fills the porous structure of the alumina paste, causing sublimation to decrease with time as the pores become filled.

  13. Do supranational EU institutions make a difference? EU asylum law before and after ‘communitarization’

    PubMed Central

    Ripoll Servent, Ariadna; Trauner, Florian

    2014-01-01

    ABSTRACT This article examines whether the empowerment of the European Union's (EU) supranational institutions has had an impact on the development of EU asylum. By systematically investigating EU asylum law before and after ‘communitarization’, it argues that its ‘policy core’ has maintained a high degree of continuity. An advocacy coalition under the leadership of the interior ministers managed to co-opt pivotal actors in the newly empowered European Commission and European Parliament. By contenting themselves with changes of secondary order, these EU institutions accepted and institutionalized the restrictive and weakly integrated core of EU asylum set by the Council in the first negotiation round. Their role and decisions were driven not only by the negotiation dynamics and political expediency, but also by new inter- and intra-institutional norms fostering consensual practices. PMID:26924934

  14. Diode pumped tunable lasers based on Tm:CaF2 and Tm:Ho:CaF2 ceramics

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Němec, Michal; Jelinková, Helena; Doroshenko, Maxim E.; Fedorov, Pavel P.; Osiko, Vyacheslav V.

    2014-02-01

    The Tm:CaF2 (4% of TmF3) and Tm:Ho:CaF2 (2% of TmF3, 0.3% of HoF3) ceramics, prepared using hot pressing, and hot formation technique had been used as an active medium of diode pumped mid-infrared tunable laser. A fibre (core diameter 400 μm, NA = 0.22) coupled laser diode (LIMO, HLU30F400-790) was used to longitudinal pumping. The laser diode was operating in the pulsed regime (6 ms pulse length, 10 Hz repetition rate). The duty-cycle 6% ensures a low thermal load even under the maximum diode pumping power amplitude 25W (ceramics samples were only air-cooled). The laser diode emission wavelength was 786 nm. The 80mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.85 - 2.15 μm, HT @ 0.78 μm) and a curved (r = 150mm) output coupler with a reflectivity of ˜ 98% @ 1.85 - 2.0 μm for Tm:CaF2 laser or ˜ 99.5% @ 2.0 - 2.15 μm for Ho:Tm:CaF2. Tuning of the laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle. Both samples offered broad and smooth tuning possibilities in mid-IR spectral range and the lasers were continuously tunable over ˜ 100 nm. The obtained Tm:CaF2 tunability ranged from 1892 to 1992nm (the maximum output energy 1.8mJ was reached at 1952nm for absorbed pumping energy 78 mJ). In case of Tm:Ho:CaF2 laser tunability from 2016 to 2111nm was reached (the maximum output energy 1.5mJ was reached at 2083nm for absorbed pumping energy 53 mJ). Both these material are good candidates for a future investigation of high energy, ultra-short, laser pulse generation.

  15. High thermoelectric performance of In, Yb, Ce multiple filled CoSb3 based skutterudite compounds

    NASA Astrophysics Data System (ADS)

    Ballikaya, Sedat; Uzar, Neslihan; Yildirim, Saffettin; Salvador, James R.; Uher, Ctirad

    2012-09-01

    Filling voids with rare earth atoms is an effective way to lowering thermal conductivity which necessarily enhances thermoelectric properties of skutterudite compounds. Yb atom is one of the most effective species among the rare earth atoms for filling the voids in the skutterudite structure due to a large atomic mass, radius and it is intermediate valence state. In this work, we aim to find the best filling partners for Yb using different combinations of Ce and In as well as to optimize actual filling fraction in order to achieve high values of ZT. The traditional method of synthesis relying on melting-annealing and followed by spark plasma sintering was used to prepare all samples. The thermoelectric properties of four samples of Yb0.2In0.2Co4Sb12, Yb0.2Ce0.15Co4Sb12, Yb0.2Ce0.15In0.2Co4Sb12, and Yb0.3Ce0.15In0.2Co4Sb12 (nominal) were examined based on the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. Hall coefficient and Seebeck coefficient signs confirm that all samples are n-type skutterudite compounds. Carrier density increases with the increasing Yb+Ce content. A high power factor value of 57.7 μW/K2/cm for Yb0.2Ce0.15Co4Sb12 and a lower thermal conductivity value of 2.82 W/m/K for Yb0.2Ce0.15In0.2Co4Sb12 indicate that small quantities of Ce with In may be a good partner to Yb to reduce the thermal conductivity further and thus enhance the thermoelectric performance of skutterudites. The highest ZT value of 1.43 was achieved for Yb0.2Ce0.15In0.2Co4Sb12 triple-filled skutterudite at 800 K.

  16. Alternative forms of Y-box binding protein 1 and YB-1 mRNA.

    PubMed

    Lyabin, Dmitry N; Doronin, Alexander N; Eliseeva, Irina A; Guens, Gelena P; Kulakovskiy, Ivan V; Ovchinnikov, Lev P

    2014-01-01

    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

  17. Optimizing Yb concentration of fiber amplifiers in the presence of transverse modal instabilities and photodarkening.

    PubMed

    Lægsgaard, Jesper

    2016-03-10

    The Yb concentration of double-clad optical fiber amplifiers is numerically optimized with respect to maximizing the transverse modal instability threshold in the presence of absorption arising from photodarkening. The pump cladding area is scaled with the Yb concentration to approximately maintain the pump absorption in operation. It is found that approximate analytical expressions can predict the optimized concentration levels found in numerical simulations with sufficient accuracy to be useful in fiber design. PMID:26974790

  18. The EU sustainable energy policy indicators framework.

    PubMed

    Streimikiene, Dalia; Sivickas, Gintautas

    2008-11-01

    The article deals with indicators framework to monitor implementation of the main EU (European Union) directives and other policy documents targeting sustainable energy development. The main EU directives which have impact on sustainable energy development are directives promoting energy efficiency and use of renewable energy sources, directives implementing greenhouse gas mitigation and atmospheric pollution reduction policies and other policy documents and strategies targeting energy sector. Promotion of use of renewable energy sources and energy efficiency improvements are among priorities of EU energy policy because the use of renewable energy sources and energy efficiency improvements has positive impact on energy security and climate change mitigation. The framework of indicators can be developed to establish the main targets set by EU energy and environmental policies allowing to connect indicators via chain of mutual impacts and to define policies and measures necessary to achieve established targets based on assessment of their impact on the targeted indicators representing sustainable energy development aims. The article discusses the application of indicators framework for EU sustainable energy policy analysis and presents the case study of this policy tool application for Baltic States. The article also discusses the use of biomass in Baltic States and future considerations in this field. PMID:18538845

  19. Synthesis, Structure, and Transport Properties of YbSb2Te4 and YbSb4Te7 for Thermoelectric Applications

    NASA Technical Reports Server (NTRS)

    Guloy, Amado S.

    2005-01-01

    Very little work has been done in the Yb-Sb-Te system of compounds. Exploratory synthesis of various compounds in the system has been performed in the search for new thermoelectric materials. The compounds in the system were examined due to the fact that the system is known to act as a concentrated Kondo system, a heavy fermion. Heavy fermions are known to possess high densities of state which are useful in thermoelectric applications. TWO compounds in the system, YbSb2Te4 and YbSb4Te7, have been successfully synthesized in bulk by two methods: low temperature mechanical alloying and high temperature direct synthesis. The Hall mobility, Seebeck coefficient, electrical resistivity, and thermal conductivity were measured on both the unannealed and annealed compounds up to 550 C to determine the dimensionless thermoelectric figure of merit, ZT. The results indicate that both compounds make promising candidates for use in thermoelectric devices.

  20. Information Retention from PowerPoint[TM] and Traditional Lectures

    ERIC Educational Resources Information Center

    Savoy, April; Proctor, Robert W.; Salvendy, Gavriel

    2009-01-01

    The benefit of PowerPoint[TM] is continuously debated, but both supporters and detractors have insufficient empirical evidence. Its use in university lectures has influenced investigations of PowerPoint's effects on student performance (e.g., overall quiz/exam scores) in comparison to lectures based on overhead projectors, traditional lectures