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Sample records for gadolinium gallium garnet

  1. Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet

    SciTech Connect

    Murphy, R.W.

    1994-12-01

    Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.

  2. Modification of the crystal structure of gadolinium gallium garnet by helium ion irradiation

    SciTech Connect

    Ostafiychuk, B. K.; Yaremiy, I. P. Yaremiy, S. I.; Fedoriv, V. D.; Tomyn, U. O.; Umantsiv, M. M.; Fodchuk, I. M.; Kladko, V. P.

    2013-12-15

    The structure of gadolinium gallium garnet (GGG) single crystals before and after implantation by He{sup +} ions has been investigated using high-resolution X-ray diffraction methods and the generalized dynamic theory of X-ray scattering. The main types of growth defects in GGG single crystals and radiation-induced defects in the ion-implanted layer have been determined. It is established that the concentration of dislocation loops in the GGG surface layer modified by ion implantation increases and their radius decreases with an increase in the implantation dose.

  3. Longitudinal Spin Seebeck Effect in Bi-substituted Neodymium Iron Garnet on Gadolinium Gallium Garnet Substrate Prepared by MOD Method

    NASA Astrophysics Data System (ADS)

    Asada, H.; Kuwahara, A.; Sueyasu, K.; Ishibashi, T.; Liu, Q.; Lou, G.; Kishimoto, K.; Koyanagi, T.

    Bi-substituted Neodymium Iron Garnet (Nd3-xBixFe5O12, Bi:NIG) thin films with the Bi composition x=0-1.0 are prepared on both the (001) and (111) oriented gadolinium gallium garnet (GGG) substrates by a metal organic decomposition method. Crystalline qualities and magnetic properties of these films are examined by X-ray diffraction, atomic force microscopy and vibrating sample magnetometer. Longitudinal spin Seebeck effects (LSSEs) are investigated by means of the inverse spin Hall effect in a Pt film. The increase of LSSE voltage in Bi:NIG(x=0-1.0)/Pt bilayers on GGG(001) is observed with the increase of Bi composition. In the case of GGG(111), the LSSE voltage for Bi:NIG(x=1.0) is also larger than that for NIG.

  4. Optical properties of color centers in calcium-stabilized gadolinium gallium garnets

    SciTech Connect

    Pogatshnik, G.J. ); Cain, L.S. ); Chen, Y. ); Evans, B.D. )

    1991-01-15

    The addition of small amounts of calcium during the crystal growth of large-diameter, gadolinium gallium garnet (GGG) crystals creates color centers that absorb in the near-uv region of the spectrum. Ultraviolet and {gamma}-ray irradiation of the crystals produced changes in the intensities of the uv color-center bands along with a broad absorption throughout the visible spectrum. The color center that gives rise to an absorption band at 350 nm serves as a photoionizable donor center so that uv excitation results in a visible coloration of the crystals. The effects of oxidation and reduction treatments on the strength of the color-center bands and on the radiation response of the material were examined. Photoluminescence bands were observed in both reduced GGG crystals as well as crystals that were irradiated with neutrons. Visible coloration is likely to occur during flashlamp pumping of laser rods that utilize large-diameter GGG crystals as the laser host. The changes in the optical properties of the material under uv excitation indicate that the addition of small amounts of calcium to assist in the growth of large-diameter crystals is likely to result in the degradation of laser performance.

  5. Enhancement of the electron electric dipole moment in gadolinium garnets

    SciTech Connect

    Mukhamedjanov, T.N.; Dzuba, V.A.; Sushkov, O.P.

    2003-10-01

    Effects caused by the electron electric dipole moment (EDM) in gadolinium garnets are considered. Experimental studies of these effects could improve the current upper limit on the electron EDM by several orders of magnitude. We suggest a consistent theoretical model and perform calculations of observable effects in gadolinium gallium garnet and gadolinium iron garnet. Our calculation accounts for both direct and exchange diagrams.

  6. Evidence of multicenter structure of cerium ions in gadolinium gallium garnet crystals studied by infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Przybylińska, H.; Ma, Chong-Geng; Brik, M. G.; Kamińska, A.; Szczepkowski, J.; Sybilski, P.; Wittlin, A.; Berkowski, M.; Jastrzębski, W.; Suchocki, A.

    2013-01-01

    Low temperature, infrared absorption spectra of gadolinium gallium garnet crystals doped with Ce are presented. In the region of intraconfigurational 4f-4f transitions the spectra exhibit existence of at least two different, major Ce3+ related centers in the GGG crystals and also some other centers at lower concentration. The spectrum of 4f-4f intrashell transitions of Ce3+ ions extends up to about 3700 cm-1 due to the large splitting of the 2F7/2 excited state. In the visible region the absorption spectrum shows influence of symmetry-related selection rules. The absorption coefficient changes in the region of 4f1-5d1 transitions due to thermal population of the second level, belonging to the 2F5/2 ground state. This suggests that the symmetry of the site occupied by Ce3+ ions, which substitute Gd3+, is higher than D2 expected for garnet hosts.

  7. Thermal, spectroscopic and laser properties of Nd3+ in gadolinium scandium gallium garnet crystal produced by optical floating zone method

    NASA Astrophysics Data System (ADS)

    Tian, Li; Wang, Shuxian; Wu, Kui; Wang, Baolin; Yu, Haohai; Zhang, Huaijin; Cai, Huaqiang; Huang, Hui

    2013-12-01

    A neodymium-doped gadolinium scandium gallium garnet (Nd:GSGG) single crystal with dimensions of Φ 5 × 20 mm2 has been grown by means of optical floating zone (OFZ). X-ray powder diffraction (XRPD) result shows that the as-grown Nd:GSGG crystal possesses a cubic structure with space group Ia3d and a cell parameter of a = 1.2561 nm. Effective elemental segregation coefficients of the Nd:GSGG as-grown crystal were calculated by using X-ray fluorescence (XRF). The thermal properties of the Nd:GSGG crystal were systematically studied by measuring the specific heat, thermal expansion and thermal diffusion coefficient, and the thermal conductivity of this crystal was calculated. The absorption and luminescence spectra of Nd:GSGG were measured at room temperature (RT). By using the Judd-Ofelt (J-O) theory, the theoretical radiative lifetime was calculated and compared with the experimental result. Continuous wave (CW) laser performance was achieved with the Nd:GSGG at the wavelength of 1062 nm when it was pumped by a laser diode (LD). A maximum output power of 0.792 W at 1062 nm was obtained with a slope efficiency of 11.89% under a pump power of 7.36 W, and an optical-optical conversion efficiency of 11.72%.

  8. Band-gap modulation via gallium substitution in cerium doped gadolinium aluminum garnet using a mixed fuel combustion approach

    SciTech Connect

    Tyagi, Mohit; Pitale, Shreyas S.; Ghosh, Manoranjan; Shinde, Seema

    2014-04-24

    Cerium doped Gadolinium garnets (Gd{sub 3}Al{sub x}Ga{sub 5−x}O{sub 12} where 0≤x≤5) are synthesized via combustion synthesis using mixture of urea and glycine fuels. A 4h Post annealing at 1400 oC is found to be necessary for pure phase formation. Lattice spacing variation as a result of partial or total Ga substitution at Al site was mapped by X-ray diffraction. Photoluminescence emission of Ce shifts as a consequence of Ga substitution and therefore suggests a local re-adjustment of crystal field around activator site.

  9. Longitudinal spin Seebeck effect in Nd2BiFe5-xGaxO12 prepared on gadolinium gallium garnet (001) by metal organic decomposition method

    NASA Astrophysics Data System (ADS)

    Asada, H.; Kuwahara, A.; Sakata, N.; Ono, T.; Ishibashi, T.; Meguro, A.; Hashinaka, T.; Kishimoto, K.; Koyanagi, T.

    2015-05-01

    Nd2BiFe5-xGaxO12 thin films with the Ga composition x = 0, 0.5, and 1.0 are prepared on (001) oriented gadolinium gallium garnet substrates by a metal organic decomposition method. Only (001) peaks are observed in x-ray diffraction patterns for all the films, suggesting that the highly oriented Nd2BiFe5-xGaxO12 thin films were formed. Increasing Ga composition, the saturation magnetization decreases, and the perpendicular easy axis is enhanced due to the decrease of the shape anisotropy. Longitudinal spin Seebeck effects (LSSEs) in Nd2BiFe5-xGaxO12 thin films with a Pt layer of 10 nm in thickness were investigated. Magnetic field dependence of the thermoelectric voltage caused by the LSSE in Nd2BiFe5-xGaxO12 films indicates the hysteresis loop with the small coercivity reflecting the magnetization curve. The decrease of LSSE voltage in Nd2BiFe5-xGaxO12 is clearly observed with the decrease of Fe composition.

  10. Longitudinal spin Seebeck effect in Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} prepared on gadolinium gallium garnet (001) by metal organic decomposition method

    SciTech Connect

    Asada, H. Kuwahara, A.; Sakata, N.; Ono, T.; Kishimoto, K.; Koyanagi, T.; Ishibashi, T.; Meguro, A.; Hashinaka, T.

    2015-05-07

    Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} thin films with the Ga composition x = 0, 0.5, and 1.0 are prepared on (001) oriented gadolinium gallium garnet substrates by a metal organic decomposition method. Only (001) peaks are observed in x-ray diffraction patterns for all the films, suggesting that the highly oriented Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} thin films were formed. Increasing Ga composition, the saturation magnetization decreases, and the perpendicular easy axis is enhanced due to the decrease of the shape anisotropy. Longitudinal spin Seebeck effects (LSSEs) in Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} thin films with a Pt layer of 10 nm in thickness were investigated. Magnetic field dependence of the thermoelectric voltage caused by the LSSE in Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} films indicates the hysteresis loop with the small coercivity reflecting the magnetization curve. The decrease of LSSE voltage in Nd{sub 2}BiFe{sub 5−x}Ga{sub x}O{sub 12} is clearly observed with the decrease of Fe composition.

  11. Growth of epitaxial bismuth and gallium substituted lutetium iron garnet films by pulsed laser deposition

    SciTech Connect

    Leitenmeier, Stephan; Heinrich, Andreas; Lindner, Joerg K. N.; Stritzker, Bernd

    2006-04-15

    Epitaxial bismuth and gallium substituted lutetium iron garnet thin films have been grown on (100) oriented gadolinium gallium garnet Gd{sub 3}Ga{sub 5}O{sub 12} substrates by pulsed laser deposition. The films have been studied using x-ray diffraction, high resolution x-ray diffraction, Rutherford backscattering spectroscopy, transmission electron microscopy, and electron diffraction. We obtained smooth films with thicknesses between 0.3 and 1.0 {mu}m showing good crystalline quality and epitaxial growth.

  12. Thermal effects on cavity stability of chromium- and neodymium-doped gadolinium scandium gallium garnet laser under solar-simulator pumping

    NASA Technical Reports Server (NTRS)

    Kim, Kyong H.; Venable, Demetrius D.; Brown, Lamarr A.; Lee, Ja H.

    1991-01-01

    Results are presented on testing a Cr- and Nd-codoped Gd-Sc-Ga-garnet (Cr:Nd:GSGG) crystal and a Nd:YAG crystal (both of 3.2 mm diam and 76-mm long) for pulsed and CW laser operations using a flashlamp and solar simulator as pumping sources. Results from experiments with the flashlamp show that, at pulse lengths of 0.11, 0.28, and 0.90 ms, the slope efficiency of the Cd:Nd:GSGG crystal was higher than that of the Nd:YAG crystal and increased with pulse width. With the solar simulator, however, the CW laser operation of the Cr:Nd:GSGG crystal was limited to intensities not greater than 1500 solar constants, while the Nd:YAG laser successfully performed for all pump beam intensities available. It was found that the exposure for several minutes of the Cr:Nd:GSGG crystal to pump beam intensity of 3000 solar constants led to its damage by thermal cracking, indicating that a better solar-pumped CW laser performance may be difficult to realize with rod geometry.

  13. Origin of color centers in the flux-grown europium gallium garnet

    SciTech Connect

    Aleksandrovsky, A. S.; Arkhipkin, V. G.; Bezmaternykh, L. N.; Gudim, I. A.; Krylov, A. S.; Vagizov, F.

    2008-04-15

    Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Moessbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Moessbauer isotope shifts and quadrupole splitting for EuGG are determined.

  14. Magnetization and coercivity of nanocrystalline gadolinium iron garnet

    NASA Astrophysics Data System (ADS)

    Nguyet, Dao Thi Thuy; Duong, Nguyen Phuc; Satoh, Takuya; Anh, Luong Ngoc; Hien, Than Duc

    2013-04-01

    Gadolinium iron garnet (GdIG) nanoparticles with mean particle size of about 37 nm have been synthesized by citrate precursor gel formation followed by annealing at 800 °C for 2 hours. Magnetic behavior of clustered GdIG nanoparticles was studied in temperature range from 5 K to above Curie temperature. The sample shows a magnetization compensation temperature Tcomp˜286.5 K and a Curie temperature TC˜560 K. In comparison with the bulk saturation magnetization, the sample exhibits lower spontaneous magnetization in the temperature region from 5 K to Tcomp whereas higher spontaneous magnetization is observed at higher temperatures up to near the Curie point. The magnetization curves show a differential susceptibility in high fields which increases sharply below 50 K. At very low temperatures, irreversibility was observed in the magnetization loops, enduring in the fields up to ˜12.5 kOe. The spontaneous magnetization, high-field susceptibility and low-temperature irreversible effect were discussed based on a model for the interacting particles consisting of ferrimagnetically aligned core spins and disordered spins in surface layer which become frozen at low temperatures. We proposed a mechanism for the enhancement of the spontaneous magnetization above Tcomp in which the Gd and Fe spins in the surface layer are largely decoupled at high temperatures and the surface Fe spins realign to the magnetic moment of the core. The magnetic coercivity Hc at low temperatures is governed by the effective anisotropy whereas in the vicinity of the compensation point a peak in the coercive force shows up as a result of the so-called paraprocess with the maximum value of 1.2 kOe at Tcomp and by further increasing temperature the coercivity decreases and eventually vanishes at about 500 K. The interparticle interactions were found to play an important role in the hysteresis behavior of the sample.

  15. Electronic Raman scattering from terbium gallium garnet excited with a picosecond laser

    NASA Astrophysics Data System (ADS)

    Koningstein, J. A.; Lemaire, H.; Atkinson, G. H.

    1987-09-01

    The electronic Raman (ER) spectrum of terbium gallium garnet, recorded using picosecond radiation from the frequency-doubled output of a Nd:YAG laser is reported. The observed spectral bands with frequency shifts up to 6000 cm-1 are the result of the effect of a strong crystal field which causes J-mixing between the 7F 6,5,....,0 states. The site symmetry of Tb 3+ in the garnet can be confirmed from this spectroscopy.

  16. Ferromagnetic resonance of gadolinium doped calcium vanadium garnets

    SciTech Connect

    Srivastava, A.K.; Patni, M.J.

    1997-02-01

    The ferromagnetic resonance (FMR) line shapes of Gd-substituted calcium vanadium garnets Y{sub 1.6{minus}z}Ca{sub 1.4}Gd{sub z}Fe{sub 4}V{sub 0.4}Zr{sub 0.6}O{sub 12} (0.8{le}{ital z}{le}1.4) have been studied as the function of the Gd content. The samples had been synthesized by two different routes, with porosities varying from 0.23{percent} to 8.9{percent}. The FMR linewidth, {Delta}H, in low porosity samples is small (15{endash}20 Oe) and becomes seven to eight times higher in high porosity samples. The linewidth can be explained on the basis of Schloemann{close_quote}s theory of anisotropy and porosity broadening in polycrystalline materials. The line shape is Lorentzian for low porosity and Gaussian for high porosity samples. This variation of the FMR line shape with porosity is explained on the basis of the stochastic theory. {copyright} {ital 1997 American Institute of Physics.}

  17. Defects in laser crystals of rare-earth aluminum and gallium garnets

    SciTech Connect

    Vorob`ev, Yu.P.; Goncharov, O.Yu.

    1994-12-01

    Using thermodynamic and crystallochemical analysis of garnets R{sub 3}Ga{sub 5}O{sub 12}(R=Sm - Lu, Y) and R{sub 3}Al{sub 5}O{sub 12} (R = Gd - Lu, Y) and their solid solutions, we characterized point defects present in their structure and, for the first time, estimated their contents. We showed that the garnets under consideration contain cationic defects and oxygen vacancies: (1) In aluminum garnets R{sub 3}Al{sub 5}O{sub 12}, improper-valence ions form at octahedral sites. (2) In gallium garnets R{sub 3}Ga{sub 5}O{sub 12} and Ga-containing solid solutions, there are Ga vacancies at octahedral sites. (3) In Dy{sub 3}(Ga{sub c}Al{sub 1-c}){sub 5}O{sub 12} solid solutions, in addition to the above-mentioned defects typical of gallium garnets, antistructural, substitutional defects (Ga{sup 3+}{sub IV}) are present. The Ga{sup 3+}ions occupy preferentially octahedra; that is, they exhibit a higher affinity for octahedral coordination than Alk{sup 3+} ions, in agreement with Goldschmidt`s crystallochemical approach. The refined solid-solution ranges for R{sub 3}Ga{sub c}Al{sub 1-c}{sub 5}O{sub 12}(R=Nd,Sm,Eu,Gd) are 0.75 {le}c{le} 1 for Nd, 0.5 {le}c{le} 1 for Sm, 0.4 {le}c{le} 1 for Eu, and 0.25 {le}c{le} 1 for Gd.

  18. Dramatic impact of the giant local magnetic fields on spin-dependent recombination processes in gadolinium based garnets

    SciTech Connect

    Romanov, N. G. Tolmachev, D. O.; Gurin, A. S.; Uspenskaya, Yu. A.; Asatryan, H. R.; Badalyan, A. G.; Baranov, P. G.; Wieczorek, H.; Ronda, C.

    2015-06-29

    A giant magnetic field effect on spin-dependent recombination of the radiation-induced defects has been found in cerium doped gadolinium based garnet crystals and ceramics, promising materials for scintillator applications. A sharp and strong increase in the afterglow intensity stimulated by external magnetic field and an evidence of the magnetic field memory have been discovered. The effect was ascribed to huge Gd-induced internal magnetic fields, which suppress the recombination, and cross-relaxation with Gd{sup 3+} ions leading to reorientation of the spins of the electron and hole centers. Thus, the spin system of radiation-induced defects in gadolinium garnet based scintillator materials was shown to accumulate significant energy which can be released in external magnetic fields.

  19. Luminescence properties and electronic structure of Ce{sup 3+}-doped gadolinium aluminum garnet

    SciTech Connect

    Dotsenko, V.P.; Berezovskaya, I.V.; Voloshinovskii, A.S.; Zadneprovski, B.I.; Efryushina, N.P.

    2015-04-15

    Highlights: • The luminescence properties of Ce{sup 3+} ions in (Y, Gd){sub 3}Al{sub 5}O{sub 12} are analyzed. • The Gd{sup 3+} → Y{sup 3+} substitution leads to increasing of Ce{sup 3+} noncubic crystal field splitting parameter. • The excitation spectra for the Ce{sup 3+} emission in GdAG contain bands at 6.67, 7.75, and 9.76 eV. • These features are due to the Ce{sup 3+}-bound exciton formation and O 2p → Al 3s, 3p transitions. • Contributions from Al atoms to the conduction-band density of states are quite essential. - Abstract: Yttrium-gadolinium aluminum garnets (YGdAG) doped with Ce{sup 3+} ions have been prepared by co-precipitation method. The luminescent properties of Ce{sup 3+} ions in Gd{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12} (x = 0.01) have been studied upon excitation in the 2–20 eV region. The substitution of Gd{sup 3+} for Y{sup 3+} in the garnet structure results in broadening the emission band and shifting its maximum towards the longer wavelengths. It was found that in addition to the 4f → 5d excitation bands of Ce{sup 3+} ions, the excitation spectra for the Ce{sup 3+} emission contain bands at 6.67, 7.75, and 9.76 eV. These bands are attributed to the Ce{sup 3+}-bound exciton formation and O 2p → Al 3s, 3p transitions, respectively. Although gadolinium states dominate near the bottom of the conduction band of Gd{sub 3}Al{sub 5}O{sub 12}, contributions from Al{sub tetr} and Al{sub oct} atoms to the conduction-band density of states are evaluated as quite essential.

  20. Faraday effect improvement by Dy{sup 3+}-doping of terbium gallium garnet single crystal

    SciTech Connect

    Chen, Zhe Yang, Lei; Hang, Yin; Wang, Xiangyong

    2016-01-15

    Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy{sup 3+} in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy{sup 3+}-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS–NIR) at room temperature. The Verdet constants increase at measured wavelengths and high thermal stability was found in Dy{sup 3+}-doped TGG, as compared to the properties of pure TGG, indicating that Dy{sup 3+}-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS–NIR wavelengths. - Graphical abstract: Highly transparent Dy{sup 3+}-doped terbium gallium garnet (TGG) and pure TGG single crystals were grown by Czochralski method. The Dy{sup 3+}-doped TGG possesses 20–30% higher Verdet values in reference to TGG independently on wavelength.

  1. Faraday effect improvement by Dy3+-doping of terbium gallium garnet single crystal

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Yang, Lei; Hang, Yin; Wang, Xiangyong

    2016-01-01

    Highly transparent Dy3+-doped terbium gallium garnet (TGG) single crystal was grown by Czochralski (Cz) method. Phase composition of the crystal was tested by XRD measurements. The distribution coefficient of Dy3+ in the crystal was obtained. The optical and magneto-optical properties were analyzed in detail, and magnetic properties of the Dy3+-TGG crystal were studied. The paramagnetic behavior is observed down to 10 K. The as-grown crystal exhibited high optical transmittance, particularly in the visible region. The Faraday rotation was investigated over visible and near-infrared regions (VIS-NIR) at room temperature. The Verdet constants increase at measured wavelengths and high thermal stability was found in Dy3+-doped TGG, as compared to the properties of pure TGG, indicating that Dy3+-doped crystals are preferable for magneto-active materials used in Faraday devices at VIS-NIR wavelengths.

  2. Optical constants of yttrium-iron garnet single-crystal film structures

    NASA Astrophysics Data System (ADS)

    Sobol, V. R.; Volchik, T. V.; Arabei, S. M.; Korzun, B. V.; Kalanda, N. A.

    2009-03-01

    Light-attenuation spectra of yttrium-iron garnet single-crystal film structures grown on a gallium-gadolinium garnet substrate by liquid-phase epitaxy from the undercooled solution in the melt have been studied and compared with those of bulk yttrium-iron garnet samples. The calculated optical constants are discussed taking into account the influence of crystal field on the splitting of the energy states of iron ions in the film samples.

  3. Magnetic properties of gadolinium and carbon co-doped gallium nitride

    NASA Astrophysics Data System (ADS)

    Syed Kaleemullah, N.; Ramsubramanian, S.; Mohankumar, R.; Munawar Basha, S.; Rajagopalan, M.; Kumar, J.

    2017-01-01

    Investigations have been carried out to study the ferromagnetic properties of Gadolinium (Gd) Carbon (C) co-doped wurtzite Gallium Nitride (GaN) using full-potential linear augmented plane wave (FP-LAPW) method within the density functional theory. The system shows half-metallic nature when single Gd is substituted in Ga36N36 supercell. The presence of carbon in GaN supercell is found to generate weak magnetic moment (Ms) in the neighbouring atoms. When Carbon is codoped in the Gd-GaN, it increased the total magnetic moment of the system (Mtot). The cause of ferromagnetism in the Gd and C co-doped GaN has been explained by Zener's p-d exchange mechanism. The role of defects in the magnetic property of this system is also investigated. The results indicate the gallium vacancy influences the magnetic moment of the Gd and C codoped GaN more than the nitrogen vacancy. The presence of holes is effective than electrons in achieving the ferromagnetism in the considered system.

  4. Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation

    NASA Astrophysics Data System (ADS)

    Chun-Xiao, Liu; Meng, Chen; Li-Li, Fu; Rui-Lin, Zheng; Hai-Tao, Guo; Zhi-Guang, Zhou; Wei-Nan, Li; She-Bao, Lin; Wei, Wei

    2016-04-01

    In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet (Nd:CNGG) crystal are reported. The waveguide is produced by proton (H+) implantation at 480 keV and a fluence of 1.0×1017 ions/cm2. The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8 nm. The reflectivity calculation method (RCM) is used to reconstruct the refractive index profile. The finite-difference beam propagation method (FD-BPM) is employed to calculate the guided mode profile of the waveguide. The stopping and range of ions in matter 2010 (SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation. Project supported by the National Natural Science Foundation of China (Grant Nos. 11405041, 61405240, 61077070, 61177086, 51002181, and 61177084), the Scientific Research Starting Foundation for New Teachers of Nanjing University of Posts and Telecommunications (NUPTSF) (Grant No. NY214159), and the Research Center of Optical Communications Engineering & Technology, Jiangsu Province, China (Grant No. ZSF0401).

  5. Interaction of Er{sup 3+} ions in Er-doped calcium - niobium - gallium garnet crystals

    SciTech Connect

    Malov, A V; Popov, A V; Ryabochkina, P A; Bol'shakov, E V

    2010-08-03

    The processes of nonradiative energy transfer in calcium - niobium - gallium garnet (CNGG) crystals doped with Er{sup 3+} ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations C{sub Er}=6% and 11% is transferred via the nonradiative co-operative processes {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 11/2{yields}} {sup 4}F{sub 7/2}, {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}F{sub 9/2}; and {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 9/2}, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes {sup 4}S{sub 3/2{yields}}{sup 4}I{sub 9/2}, {sup 4}I{sub 15/2{yields}}{sup 4}I{sub 13/2}, whose intensity depends on the concentration of Er{sup 3+} ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%. (active media)

  6. Adhesion after erbium, chromium:yttrium-scandium-gallium-garnet laser application at three different irradiation conditions.

    PubMed

    Botta, Sérgio Brossi; da Ana, Patricia Aparecida; Zezell, Denise Maria; Powers, John M; Matos, Adriana Bona

    2009-01-01

    The aim of this study was to investigate whether distinct cooling of low fluence erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation would influence adhesion. Main factors tested were: substrates (two), irradiation conditions (three), and adhesives (three). A 750 microm diameter tip was used, for 50 s, 1 mm from the surface, with a 0.25 W power output, 20 Hz, energy density of 2.8 J/cm(2) with energy per pulse of 12.5 mJ. When applied, water delivery rate was 11 ml/min. The analysis of variance (ANOVA) showed that laser conditioning significantly decreased the bond strength of all adhesive systems applied on enamel. On dentin, laser conditioning significantly reduced bond strength of etch-and-rinse and one-step self-etch systems; however, laser irradiation under water cooling did not alter bonding of two-step self-etching. It may be concluded that the irradiation with Er,Cr:YSGG laser at 2.8 J/cm(2) with water coolant was responsible for a better adhesion to dentin, while enamel irradiation reduced bond strength, irrespective of cooling conditions.

  7. Evaluation of mineral content of enamel prepared by erbium, chromium:yttrium-scandium-gallium-garnet laser.

    PubMed

    Secilmis, Asli; Usumez, Aslihan; Usumez, Serdar; Berk, Gizem

    2010-07-01

    The aim of this study was to evaluate the mineral content of enamel etched at two different power settings with an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser. Buccal, lingual and mesial or distal surfaces of five premolar teeth were cut, and three enamel slabs were obtained from each tooth. Fifteen enamel specimens were divided into three groups (1 W, 2 W and control) of five specimens each and subjected to Er,Cr:YSGG laser. The mean percentage weights of the five elements [calcium (Ca), potassium (K), magnesium (Mg), sodium (Na) and phosphorus (P)] in each slab were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). One way analysis of variance (ANOVA) was used to analyze differences among the groups (1 W, 2 W and control). There were no significant differences among the groups (1 W, 2 W and control) for Ca, K, Mg, Na, or P, or for the Ca/P ratio (P > 0.05). Scanning electron microscopy (SEM) photographs indicated that the surface irregularities increased with increased power setting. Laser treatment did not affect the mean percentage weights of Ca, K, Mg, Na, and P, or the Ca/P ratio, in any group.

  8. Preparation and characterization of highly transparent Ce3+ doped terbium gallium garnet single crystal

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Yang, Lei; Hang, Yin; Wang, Xiangyong

    2015-09-01

    A Ce3+ doped terbium gallium garnet crystal (TCGG) with 30 mm in diameter and 25 mm in length has been grown by the Czochralski (Cz) method. The cation distributions in the TCGG crystal and thermal expansion coefficient have been investigated. Absorption spectrum was evaluated in the visible and near-infrared region (VIS-NIR) at room temperature, which indicated the crystal had low absorption coefficient at 500-1500 nm. The specific Faraday rotation of single crystal was measured at room temperature in 532, 633, and 1064 nm. The Verdet constant of the crystal at 633 nm comes up to 164.3 rad m-1 T-1, 26.3% larger than that of TGG at 633 nm. The thermal conductivity and laser induced damage threshold (LIDT) were also measured. Overall, the TCGG single crystal studied here exhibits superior properties than the commercial TGG so far, therefore it has potential to cover the increasing demand for new and improved Faraday rotators in the VIS-NIR region.

  9. The effect of gallium substitution on the microstructure and magnetic properties of yttrium iron garnet

    SciTech Connect

    Zaini, N. Z. M. Ibrahim, N. B.

    2015-09-25

    Y{sub 3}Fe{sub (5-y)}Ga{sub y}O{sub 12} (y = 0, 0.4, 1.4 and 2,4) thin films were prepared by sol-gel method and annealed for 2h in oxygen. The thin film’s characteristic were studied by an X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM) and a vibration sample magnetometer (VSM). The XRD show that all films have the garnet phase structure. The grain size particles measured using FESEM were between 45.08 nm to 51.58 nm, and the thickness were between 42 nm to 90 nm. The magnetic properties measured using VSM showed that result was shown with hysteresis loop. The magnetization saturation decreased from 144.26 to 2.76 emu/cm{sup 3} with the increasing substitution gallium. The substitution for y = 2.4 was shown the saturation magnetization was very low. The coercivity increased 35 to 75 Oe due the the increasing grain size.

  10. Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

    PubMed Central

    Li, Ji-Guang; Sakka, Yoshio

    2015-01-01

    This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd3+ to the activator. Ce3+ doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out. PMID:27877750

  11. Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12).

    PubMed

    Li, Ji-Guang; Sakka, Yoshio

    2015-02-01

    This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd(3+) to the activator. Ce(3+) doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out.

  12. Symmetry reduction due to gallium substitution in the garnet Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12

    PubMed Central

    Robben, Lars; Merzlyakova, Elena; Heitjans, Paul; Gesing, Thorsten M.

    2016-01-01

    Single-crystal structure refinements on lithium lanthanum zirconate (LLZO; Li7La3Zr2O12) substituted with gallium were successfully carried out in the cubic symmetry space group I 3d. Gallium was found on two lithium sites as well as on the lanthanum position. Due to the structural distortion of the resulting Li6.43(2)Ga0.52(3)La2.67(4)Zr2O12 (Ga–LLZO) single crystals, a reduction of the LLZO cubic garnet symmetry from Ia d to I 3d was necessary, which could hardly be analysed from X-ray powder diffraction data. PMID:27006788

  13. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

  14. Magneto-optical properties of magnetic photonic crystal fiber of terbium gallium garnet filled with magnetic fluid

    NASA Astrophysics Data System (ADS)

    Otmani, Hamza; Bouchemat, Mohamed; Bouchemat, Touraya; Lahoubi, Mahieddine; Pu, Shengli; Deghdak, Rachid

    2016-11-01

    We present in this work, magneto-optical (MO) properties of a magnetophotonic crystal fiber (MPCF) based on terbium gallium garnet Tb3Ga5O12 or TGG. The air holes of a periodic triangular lattice are filled with magnetic fluid (MF). With a light which can be confined in the core area of this MF filled MPCF we obtain a confinement corresponding to the propagation of the single mode by assuming an effective index (neff). The variations of neff as a function of the gyrotropy parameter (g) and magnetic nanoparticle volume fraction concentrations are well established at the telecommunication wavelength λ = 1.55 μm. The TE-TM mode conversion based on the Faraday rotation and modal birefringence are then numerically simulated. Faraday rotation exhibits largest value of 8700.08°/cm at MF concentration of 0.25% and g = 0.0144, whereas the modal birefringence is reduced to 0.00177 at the same conditions. These results could be helpful for experimentally designing and realizing isolators with these filled MF-MPCFs based on this TGG material. They appear to possess significant potential for the practical applications due to their unique MO properties.

  15. Application of reflectance confocal microscopy to evaluate skin damage after irradiation with an yttrium-scandium-gallium-garnet (YSGG) laser.

    PubMed

    Yue, Xueping; Wang, Hongwei; Li, Qing; Li, Linfeng

    2017-02-01

    The objective of this study was to observe the characteristics of the skin after irradiation with a 2790-nm yttrium-scandium-gallium-garnet (YSGG) laser using reflectance confocal microscopy (RCM). A 2790-nm YSGG laser was used to irradiate fresh foreskin (four doses, at spot density 3) in vitro. The characteristics of microscopic ablative columns (MAC), thermal coagulation zone (TCZ), and microscopic treatment zones (MTZ) were observed immediately after irradiation using digital microscope and RCM. The characteristics of MAC, TCZ, and MTZ with variations in pulse energy were comparatively analyzed. After irradiation, MAC, TCZ, and MTZ characteristics and undamaged skin between MTZs can be observed by RCM. The depth and width of MTZ obviously increased with the increase in pulse energy. At 80, 120, and 160 mJ/microbeam (MB), the MTZ actual area and proportion were about two times that of the theoretical value and three times at 200 mJ/MB. With increases in depth, the single MAC gradually decreased in a fingertip-shaped model, with TCZ slowly increasing, and MTZ slightly decreasing in a columnar shape. RCM was able to determine the characteristics of thermal injury on the skin after the 2790-nm YSGG laser irradiation with different pulse energies. Pulse energy higher than 200 mJ/MB may have much larger thermal injury and side effect. RCM could be used in the clinic in future.

  16. Gallium

    SciTech Connect

    1996-01-01

    Discovered in 1875 through a study of its spectral properties, gallium was the first element to be uncovered following the publication of Mendeleev`s Periodic Table. French chemist, P.E. Lecoq de Boisbaudran, named his element discovery in honor of his native country; gallium is derived from the Latin word for France-{open_quotes}Gallia.{close_quotes}. This paper describes the properties, sources, and market for gallium.

  17. Gain in pulsed x-ray irradiated Cr,Nd:GdScGa-garnet

    SciTech Connect

    Brannon, P.J. )

    1995-01-09

    The transmission properties of gadolinium scandium gallium garnet doped with chromium and neodymium have been studied during and after a 20 ns high-energy x-ray pulse. Gain is observed in the transmission which indicates a small signal gain of 0.175/cm. About 5% of the absorbed dose is converted to inversion, which is comparable to flash-lamp-pumped inversion. The small signal gain scales with dose.

  18. Tunable Microwave Transversal Filters and Dispersive Delay Lines Based on Oblique Incidence Reflection of Magnetostatic Wave Propagating in Epitaxial Garnets.

    DTIC Science & Technology

    1986-09-30

    based on Epitaxial Ferrites . This final report summarizes the results of viable realizations of these goals. Transversal filters at microwave ...DISPLACEMENT IN DIELECTRIC IMAGE GUIDES At microwave or millimeter wave frequency range, ferrite materials play important roles in the design of...isolators utilizing epitaxial YIG on gadolinium Gallium Garnet at 90-100GHz. These experiments have shown that the concept is feasible but that ferrite

  19. Coupling Single-Mode Fiber to Uniform and Symmetrically Tapered Thin-Film Waveguide Structures Using Gadolinium Gallium Garnet

    NASA Technical Reports Server (NTRS)

    Gadi, Jagannath; Yalamanchili, Raj; Shahid, Mohammad

    1995-01-01

    The need for high efficiency components has grown significantly due to the expanding role of fiber optic communications for various applications. Integrated optics is in a state of metamorphosis and there are many problems awaiting solutions. One of the main problems being the lack of a simple and efficient method of coupling single-mode fibers to thin-film devices for integrated optics. In this paper, optical coupling between a single-mode fiber and a uniform and tapered thin-film waveguide is theoretically modeled and analyzed. A novel tapered structure presented in this paper is shown to produce perfect match for power transfer.

  20. Absolute excited-state absorption cross section and fluorescence quantum efficiency of Cr/sup 3 +/: gadolinium scandium gallium garnet

    SciTech Connect

    Seelert, W.; Strauss, E.

    1987-10-01

    Excited-state properties of the laser material Cr/sup 3 +/:Gd/sub 3/Sc/sub 2/(GaO/sub 4/)/sub 3/ were determined by a photocaloric technique. The excited-state absorption cross section at 650 nm is (3.6 +- 0.6)10/sup -20/ cm/sup 2/, and the fluorescence quantum efficiency at ambient temperature is (91 +- 1)%.

  1. Terbium gallium garnet ceramic-based Faraday isolator with compensation of thermally induced depolarization for high-energy pulsed lasers with kilowatt average power

    SciTech Connect

    Yasuhara, Ryo; Snetkov, Ilya; Starobor, Alexey; Palashov, Oleg

    2014-12-15

    A scalable aperture Faraday isolator for high-energy pulsed lasers with kW-level average power was demonstrated using terbium gallium garnet ceramics with water cooling and compensation of thermally induced depolarization in a magnetic field. An isolation ratio of 35 dB (depolarization ratio γ of 3.4 × 10{sup −4}) was experimentally observed at a maximum laser power of 740 W. By using this result, we estimated that this isolator maintains an isolation ratio of 30 dB for laser powers of up to 2.7 kW. Our results provide the solution for achieving optical isolation in high-energy (100 J to kJ) laser systems with a repetition rate greater than 10 Hz.

  2. Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components.

    PubMed

    Benetti, Carolina; Ana, Patricia Aparecida; Bachmann, Luciano; Zezell, Denise Maria

    2015-12-01

    The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm(2)), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

  3. Low-temperature synthesis and characterization of yttrium-gallium garnet Y{sub 3}Ga{sub 5}O{sub 12} (YGG)

    SciTech Connect

    Mathur, Sanjay; Shen Hao; Leleckaite, Asta; Beganskiene, Aldona; Kareiva, Aivaras . E-mail: aivaras.kareiva@chf.vu.lt

    2005-03-08

    To obtain yttrium-gallium garnet (Y{sub 3}Ga{sub 5}O{sub 12}, YGG) a simple 'chimie douce' method has been developed. This sol-gel method yielded excellent starting gel precursor for the fabrication of YGG phase, which could be used as host material for optical applications. The pattern of X-ray diffraction analysis of the ceramic sample sintered for 10 h at 1000 deg. C showed the formation of monophasic Y{sub 3}Ga{sub 5}O{sub 12} phase. The phase transformations, composition and micro-structural features in the gels and polycrystalline sample were studied by thermoanalytical methods (TGA/DTA), powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The quality of the resulting products (homogeneity, crystallisation temperature, grain size, grain size distribution, etc.) is discussed.

  4. Surface plasmon resonance system with magneto-optic garnet

    NASA Astrophysics Data System (ADS)

    Vlček, Jaroslav; Pištora, Jaromír.; Halagačka, Lukáš

    2016-12-01

    We demonstrate the model specification of the MO-SPR coupling-prism system consisting of the Ag film deposited between two garnet layers; the water is supposed as an analyte. The bismuth-doped gallium-gadolinium iron garnet offers low optical losses as well as strong MO response from visible to near infrared optical region. We apply two different response functions that detect a change of analyte refractive index that operate either directly with reflectance change at appropriate incidence angle or with the magneto-optically highlighted SP resonance dip shift. Suggested sensitivity criteria lead to the sensitivity about 120 1/RIU or 75 deg/RIU with the resolution of the order 10-5 RIU by experimentally acceptable variation of response factors.

  5. Garnet-to-perovskite transition in Gd3Sc2Ga3O12 at high pressure and high temperature.

    PubMed

    Lin, Chuanlong; Liu, Jing; Lin, Jung-Fu; Li, Xiaodong; Li, Yanchun; Zhang, Qingli; Xiong, Lun; Li, Rui

    2013-01-07

    The structural phase transition of gadolinium-scandium-gallium garnet (Gd(3)Sc(2)Ga(3)O(12), GSGG) has been studied at high pressure and high temperature using the synchrotron X-ray diffraction technique in a laser-heated diamond anvil cell. The GSGG garnet transformed to an orthorhombic perovskite structure at approximately 24 GPa after laser heating to 1500-2000 K. The garnet-to-perovskite phase transition is associated with an ∼8% volume reduction and an increase in the coordination number of the Ga(3+) or Sc(3+) ion. The orthorhombic perovskite GSGG has bulk modulus B(0) = 194(15) GPa with B(0)' = 5.3(8), exhibiting slightly less compression than the cubic garnet structure of GSGG with B(0) = 157(15) GPa and B(0)' = 6.5(10). Upon compression at room temperature, the cubic GSGG garnet became amorphous at ∼65 GPa. Coupled with the amorphous-to-perovskite phase transition in Y(3)Fe(5)O(12) and Gd(3)Ga(5)O(12) at high-pressure-temperature conditions, we conclude that amorphization should represent a new thermodynamic state resulting from hindrance of the garnet-to-perovskite phase transition, whereas the garnet-to-amorphous transition in rare-earth garnets should be kinetically hindered at room temperature.

  6. Developmental competence of mouse embryos following zona drilling using a non-contact holmium:yttrium scandian gallium garnet (Ho:YSGG) laser system.

    PubMed

    Schiewe, M C; Neev, J; Hazeleger, N L; Balmaceda, J P; Berns, M W; Tadir, Y

    1995-07-01

    The purpose of this study was to assess the efficacy of the holmium:yttrium scandian gallium garnet (Ho:YSGG) laser, operating in a pipette-free, non-contact mode, to assist hatching and sustain normal embryonic development. Two-cell mouse embryos were recovered and assigned to laser-assisted hatching (LAH) treatment or control human tubal fluid (HTF) culture with or without serum (HTF-s, HTF-o) or with late serum supplementation (HTF-o/s). The basic experimental apparatus for LAH consisted of a stationary 2.1 microns Ho:YSGG laser beam directed through a mechanical shutter into an input port of a Zeiss Axiomat inverted microscope. Fewer (P < 0.05) embryos developed to the blastocyst stage in the HTF-s group (81%) than in the LAH (90%), HTF-o (94%) and HTF-o/s (92%) groups. The level of hatching was significantly increased (P < 0.01) after the LAH treatment (57%) compared to HTF-o/s (32%), HTF-s (18%) or HTF-o (5%). Implantation rates were not significantly impaired following the LAH treatment (21%). These data demonstrate that LAH using the Ho:YSGG laser is a simple, accurate and effective procedure for assisted hatching.

  7. Implant Bed Preparation with an Erbium, Chromium Doped Yttrium Scandium Gallium Garnet (Er,Cr: YSGG) Laser Using Stereolithographic Surgical Guide

    PubMed Central

    Seymen, Gülin; Turgut, Zeynep; Berk, Gizem; Bodur, Ayşen

    2013-01-01

    Background: Implant bed preparation with laser is taken into consideration owing to the increased interest in use of lasers in hard tissue surgery. The purpose of this study is to determine the deviations in the position and inclination between the planned and prepared implant beds with Erbium, Chromium doped Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) laser using stereolithographic (SLA) surgical guides. Methods: After 3-dimensional (3D) imaging of six sheep lower jaws, computed tomography (CT) images were transformed into 3D models. Locations of implant beds were determined on these models. Two implant beds in each half jaw were prepared with an Er,Cr:YSGG laser system and a conventional drilling method using a total of 12 SLA surgical guides. A new CT was taken to analyze the deviation values between planned and prepared implant beds. Finally, a software program was used to superimpose the images on 3D models, then the laser and conventional drilling groups were compared. Results: Differences of mean angular deviations between the planned and prepared implant beds were 5.17±4.91° in the laser group and 2.02±1.94° in the conventional drilling group.The mean coronal deviation values were found to be 0.48±0.25 mm and 0.23±0.14 mm in the laser group and conventional drilling group, respectively. While the mean deviation at the apex between the planned and prepared implant beds were 0.70±0.26 mm and 0.26±0.08 ,the mean vertical deviations were 0.06±0.15 mm and 0.02±0.05 mm for the laser group and the conventional drilling group, respectively. Conclusion: It is possible to prepare an implant bed properly with the aid of Er,Cr:YSGGlaser by using SLA surgical guide. PMID:25606303

  8. Comparative evaluation of surface topography of tooth prepared using erbium, chromium: Yttrium, scandium, gallium, garnet laser and bur and its clinical implications

    PubMed Central

    Verma, Mahesh; Kumari, Pooja; Gupta, Rekha; Gill, Shubhra; Gupta, Ankur

    2015-01-01

    Background: Erbium, chromium: Yttrium, scandium, gallium, garnet (Er, Cr: YSGG) laser has been successfully used in the ablation of dental hard and soft tissues. It has been reported that this system is also useful for preparing tooth surfaces and etching, but no consensus exist in the literature regarding the advantage of lasers over conventional tooth preparation technique. Materials and Methods: Labial surfaces of 25 extracted human maxillary central incisors were divided into two halves. Right half was prepared with diamond bur and left half with Er, Cr; YSGG laser and a reduction of 0.3–0.5 mm was carried out. Topography of prepared surfaces of five teeth were examined under scanning electron microscope (SEM). The remaining samples were divided into 4 groups of 10 specimens each based on the surface treatment received: One group was acid etched and other was nonetched. Composite resin cylinders were bonded on prepared surfaces and shear bond strength was assessed using a universal testing machine. Results: The SEM observation revealed that the laser prepared surfaces were clean, highly irregular and devoid of a smear layer. Bur prepared surfaces were relatively smooth but covered with smear layer. Highest bond strength was shown by laser prepared acid etched group, followed by bur prepared the acid etched group. The bur prepared nonacid etched group showed least bond strength. Conclusions: Er, Cr: YSGG laser can be used for preparing tooth and bond strength value achieved by laser preparation alone without surface treatment procedure lies in the range of clinical acceptability. PMID:26929482

  9. Erbium, chromium:yttrium scandium gallium garnet laser for caries removal: influence on bonding of a self-etching adhesive system.

    PubMed

    Tachibana, Arlene; Marques, Márcia Martins; Soler, Julia Maria Pavan; Matos, Adriana Bona

    2008-10-01

    This study evaluated the influence of the dental substrates obtained after the use of different caries removal techniques on bonding of a self-etching system. Forty, extracted, carious, human molars were ground to expose flat surfaces containing caries-infected dentine surrounded by sound dentine. The caries lesions of the specimens were removed or not (control--G1) either by round steel burs and water-cooled, low speed, handpiece (G2), or by irradiation with an erbium, chromium:yttrium scandium gallium garnet (Er,Cr:YSGG) laser (2W, 20 Hz, 35.38 J/cm(2), fiber G4 handpiece with 0.2826 mm(2), non-contact mode at a 2 mm distance, 70% air/20% water--G3) or using a chemo-mechanical method (Carisolv--G4). Caries-infected, caries-affected and sound dentines were submitted to a bonding system followed by construction of a resin-based composite crown. Hour-glass shaped samples were obtained and submitted to a micro-tensile bond test. The bond strength data were compared by analysis of variance (ANOVA), complemented by Tukey's test (P

  10. The Adjunctive Use of the Erbium, Chromium: Yttrium Scandium Gallium Garnet Laser in Closed Flap Periodontal Therapy. A Retrospective Cohort Study

    PubMed Central

    Al-Falaki, Rana; Cronshaw, Mark; Parker, Steven

    2016-01-01

    Objectives: The current periodontal literature has been inconsistent in finding an added advantage to using lasers in periodontal therapy. The aim of this study was to compare treatment outcomes following root surface instrumentation alone (NL group), or with adjunctive use of Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) laser (L group). Material and Methods: Patients diagnosed with generalized chronic periodontitis, having a minimum of 1 year follow up were selected by a blinded party for inclusion in a retrospective analysis from patients treated prior to and after integration of laser in a single clinic setting. Probing depths (PD) of all sites ≥5 mm and full mouth bleeding scores were analyzed. Further analysis was carried out on the treatment outcomes of only the molar teeth and of pockets >6mm. Results: 53 patients were included (25 NL,28 L). There was no significant difference between baseline PDs (NL=6.19mm, L=6.27mm, range 5-11mm). The mean PD after one year was 2.83mm (NL) 2.45mm (L), with the mean PD reductions being 3.35mm (NL) and 3.82mm (L) (p<0.002). The mean PD reduction for the molars were 3.32mm (NL) and 3.86mm (L) (p< 0.007), and for ≥7mm group were 4.75mm (NL) compared to 5.14mm (L) (p< 0.009). There was significantly less bleeding on probing in the laser group after one year (p<0.001) Conclusion: Both treatment modalities were effective in treating chronic periodontitis, but the added use of laser may have advantages, particularly in molar tooth sites and deeper pockets. Further research with RCTs is needed to test this hypothesis further. PMID:27350796

  11. Phase stable rare earth garnets

    DOEpatents

    Kuntz, Joshua D.; Cherepy, Nerine J.; Roberts, Jeffery J.; Payne, Stephen A.

    2013-06-11

    A transparent ceramic according to one embodiment includes a rare earth garnet comprising A.sub.hB.sub.iC.sub.jO.sub.12, where h is 3.+-.10%, i is 2.+-.10%, and j is 3.+-.10%. A includes a rare earth element or a mixture of rare earth elements, B includes at least one of aluminum, gallium and scandium, and C includes at least one of aluminum, gallium and scandium, where A is at a dodecahedral site of the garnet, B is at an octahedral site of the garnet, and C is at a tetrahedral site of the garnet. In one embodiment, the rare earth garment has scintillation properties. A radiation detector in one embodiment includes a transparent ceramic as described above and a photo detector optically coupled to the rare earth garnet.

  12. Platinum/yttrium iron garnet inverted structures for spin current transport

    NASA Astrophysics Data System (ADS)

    Aldosary, Mohammed; Li, Junxue; Tang, Chi; Xu, Yadong; Zheng, Jian-Guo; Bozhilov, Krassimir N.; Shi, Jing

    2016-06-01

    30-80 nm thick yttrium iron garnet (YIG) films are grown by pulsed laser deposition on a 5 nm thick sputtered Pt atop gadolinium gallium garnet substrate (GGG) (110). Upon post-growth rapid thermal annealing, single crystal YIG(110) emerges as if it were epitaxially grown on GGG(110) despite the presence of the intermediate Pt film. The YIG surface shows atomic steps with the root-mean-square roughness of 0.12 nm on flat terraces. Both Pt/YIG and GGG/Pt interfaces are atomically sharp. The resulting YIG(110) films show clear in-plane uniaxial magnetic anisotropy with a well-defined easy axis along <001> and a peak-to-peak ferromagnetic resonance linewidth of 7.5 Oe at 9.32 GHz, similar to YIG epitaxially grown on GGG. Both spin Hall magnetoresistance and longitudinal spin Seebeck effects in the inverted bilayers indicate excellent Pt/YIG interface quality.

  13. Thickness- and temperature-dependent magnetodynamic properties of yttrium iron garnet thin films

    SciTech Connect

    Haidar, M. Ranjbar, M.; Balinsky, M.; Dumas, R. K.; Khartsev, S.; Åkerman, J.

    2015-05-07

    The magnetodynamical properties of nanometer-thick yttrium iron garnet films are studied using ferromagnetic resonance as a function of temperature. The films were grown on gadolinium gallium garnet substrates by pulsed laser deposition. First, we found that the damping coefficient increases as the temperature increases for different film thicknesses. Second, we found two different dependencies of the damping on film thickness: at room temperature, the damping coefficient increases as the film thickness decreases, while at T = 8 K, we find the damping to depend only weakly on the thickness. We attribute this behavior to an enhancement of the relaxation of the magnetization by impurities or defects at the surfaces.

  14. Crystal field disorder effects in the optical spectra of Nd{sup 3+} and Yb{sup 3+}-doped calcium lithium niobium gallium garnets laser crystals and ceramics

    SciTech Connect

    Lupei, V.; Lupei, A.; Gheorghe, C.; Gheorghe, L.; Achim, A.; Ikesue, A.

    2012-09-15

    The optical spectroscopic properties of RE{sup 3+} (Nd, 1 at. % or Yb, 1 to 10 at. %)-doped calcium-lithium-niobium-gallium garnet (CLNGG) single crystals and ceramics in the 10 K-300 K range are analyzed. In these compositionally disordered materials, RE{sup 3+} substitute Ca{sup 2+} in dodecahedral sites and the charge compensation is accomplished by adjusting the proportion of Li{sup +}, Nb{sup 5+}, and Ga{sup 3+} to the doping concentration. The crystals and ceramics show similar optical spectra, with broad and structured (especially at low temperatures) bands whose shape depends on temperature and doping concentration. At 10 K, the Nd{sup 3+4}I{sub 9/2}{yields}{sup 4}F{sub 3/2,5/2} and Yb{sup 3+2}F{sub 7/2}{yields}{sup 2}F{sub 5/2} absorption bands, which show prospect for diode laser pumping, can be decomposed in several lines that can be attributed to centers with large differences in the crystal field. The positions of these components are the same, but the relative intensity depends on the doping concentration and two main centers dominate the spectra. Non-selective excitation evidences broad emission bands, of prospect for short-pulse laser emission, whereas the selective excitation reveals the particular emission spectra of the various centers. The modeling reveals that the nonequivalent centers correspond to RE{sup 3+} ions with different cationic combinations in the nearest octahedral and tetrahedral coordination spheres, and the most abundant two centers have 4Nb and, respectively, 3Nb1Li in the nearest octahedral sphere. At 300 K, the spectral resolution is lost. It is then inferred that the observed optical bands are envelopes of the spectra of various structural centers, whose resolution is determined by the relative contribution of the temperature-dependent homogeneous broadening and the effects of crystal field disordering (multicenter structure, inhomogeneous broadening). The relevance of spectroscopic properties for selection of pumping

  15. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2001-01-01

    A general overview of the industrial garnet industry is provided. About 20 percent of global industrial garnet production takes place in the U.S. During 2000, an estimated 300 kt of industrial garnets were produced worldwide. The U.S. is the world's largest consumer of industrial garnet, consuming 56.9 kt in 2000.

  16. Pulsed laser deposition of epitaxial yttrium iron garnet films with low Gilbert damping and bulk-like magnetization

    SciTech Connect

    Onbasli, M. C. Kim, D. H.; Ross, C. A.; Kehlberger, A.; Jakob, G.; Kläui, M.; Chumak, A. V.; Hillebrands, B.

    2014-10-01

    Yttrium iron garnet (YIG, Y {sub 3}Fe{sub 5}O{sub 12}) films have been epitaxially grown on Gadolinium Gallium Garnet (GGG, Gd{sub 3}Ga{sub 5}O{sub 12}) substrates with (100) orientation using pulsed laser deposition. The films were single-phase, epitaxial with the GGG substrate, and the root-mean-square surface roughness varied between 0.14 nm and 0.2 nm. Films with thicknesses ranging from 17 to 200 nm exhibited low coercivity (<2 Oe), near-bulk room temperature saturation moments (∼135 emu cm{sup −3}), in-plane easy axis, and damping parameters as low as 2.2 × 10{sup −4}. These high quality YIG thin films are useful in the investigation of the origins of novel magnetic phenomena and magnetization dynamics.

  17. Effective lattice stabilization of gadolinium aluminate garnet (GdAG) via Lu3+ doping and development of highly efficient (Gd,Lu)AG:Eu3+ red phosphors

    PubMed Central

    Li, Jinkai; Li, Ji-Guang; Zhang, Zhongjie; Wu, Xiaoli; Liu, Shaohong; Li, Xiaodong; Sun, Xudong; Sakka, Yoshio

    2012-01-01

    The metastable garnet lattice of Gd3Al5O12 is stabilized by doping with smaller Lu3+, which then allows an effective incorporation of larger Eu3+ activators. The [(Gd1−xLux)1−yEuy]3Al5O12 (x = 0.1–0.5, y = 0.01–0.09) garnet solid solutions, calcined from their precursors synthesized via carbonate coprecipitation, exhibit strong luminescence at 591 nm (the 5D0 → 7F1 magnetic dipole transition of Eu3+) upon UV excitation into the charge transfer band (CTB) at ∼239 nm, with CIE chromaticity coordinates of x = 0.620 and y = 0.380 (orange-red). The quenching concentration of Eu3+ was estimated at ∼5 at.% (y = 0.05), and the quenching was attributed to exchange interactions. Partial replacement of Gd3+ with Lu3+ up to 50 at.% (x = 0.5) while keeping Eu3+ at the optimal content of 5 at.% does not significantly alter the peak positions of the CTB and 5D0 → 7F1 emission bands but slightly weakens both bands owing to the higher electronegativity of Lu3+. The effects of processing temperature (1000–1500 °C) and Lu/Eu contents on the intensity, quantum efficiency, lifetime and asymmetry factor of luminescence were thoroughly investigated. The [(Gd0.7Lu0.3)0.95Eu0.05]3Al5O12 phosphor processed at 1500 °C exhibits a high internal quantum efficiency of ∼83.2% under 239 nm excitation, which, in combination with the high theoretical density, favors its use as a new type of photoluminescent and scintillation material. PMID:27877495

  18. RBS and XRD Characterization of Yttrium Iron Garnet Thin Films

    NASA Astrophysics Data System (ADS)

    Mansour, M.; Roumie, M.; Abdel Samad, B.; Basma, H.; Korek, M.

    2015-03-01

    Magnetic materials such as yttrium iron garnet (YIG or Y3Fe5O12) present a great importance for their magneto-optic properties. They are potential materials used for applications in the domain of optical telecommunications for example. In this work, we have investigated YIG thin films deposited on substrates of quartz and GGG (gadolinium gallium garnet or Gd3Ga5O12). Using Rutherford backscattering spectrometry (RBS) we characterized the performed layers (thickness and stoichiometry) in order to correlate the films preparation conditions with the quality of the final material. We determined the optimal energy of the alpha particles beam used for RBS measurements and we fitted the experimental spectra using the SIMNRA simulated code. Our RBS results showed that the films have a stoichiometry close to that of the starting material. In addition, we found that the film thickness is proportional to deposition time but inversely proportional to the substrate temperature. Moreover, using x-ray diffraction (XRD) we determined the annealing effect on the structure of the profile of our thin films.

  19. X-Ray Fluorescence Analysis of Yttrium-Iron-Gadolinium Solutions Used to Prepare Spray Dried Powders.

    DTIC Science & Technology

    IRON, * GADOLINIUM , *X RAY SPECTROSCOPY, *YTTRIUM, COMPUTER PROGRAMS, SOLUTIONS(MIXTURES), QUALITY CONTROL, NITRIC ACID, RARE EARTH ELEMENTS, CHEMICAL ANALYSIS, FERRITES , PHASE SHIFT CIRCUITS, YTTRIUM IRON GARNET.

  20. Ce-doped single crystal and ceramic garnets for γ ray detection

    SciTech Connect

    Hull, G; Roberts, J; Kuntz, J; Fisher, S; Sanner, R; Tillotson, T; Drobshoff, A; Payne, S; Cherepy, N

    2007-07-30

    Ceramic and single crystal Lutetium Aluminum Garnet scintillators exhibit energy resolution with bialkali photomultiplier tube detection as good as 8.6% at 662 keV. Ceramic fabrication allows production of garnets that cannot easily be grown as single crystals, such as Gadolinium Aluminum Garnet and Terbium Aluminum Garnet. Measured scintillation light yields of Cerium-doped ceramic garnets indicate prospects for high energy resolution.

  1. Magnetic properties of epitaxial bismuth ferrite-garnet mono- and bilayers

    NASA Astrophysics Data System (ADS)

    Semuk, E. Yu.; Berzhansky, V. N.; Prokopov, A. R.; Shaposhnikov, A. N.; Karavainikov, A. V.; Salyuk, O. Yu.; Golub, V. O.

    2015-11-01

    Magnetic properties of Bi1.5Gd1.5Fe4.5Al0.5O12 (84 nm) and Bi2.8Y0.2Fe5O12 (180 nm) films epitaxially grown on gallium-gadolinium garnet (GGG) single crystal (111) substrate as well as Bi1.5Gd1.5Fe4.5Al0.5O12/Bi2.8Y0.2Fe5O12 bilayer were investigated using ferromagnetic resonance technique. The mismatch of the lattice parameters of substrate and magnetic layers leads to formation of adaptive layers which affect on the high order anisotropy constant of the films but practically do not affect on uniaxial perpendicular magnetic anisotropy The magnetic properties of the bilayer film were explained in supposition of strong exchange coupling between magnetic layers taking into account film-film and film-substrate elastic interaction.

  2. Effects of processing on the low-voltage performance of cathodoluminescent garnet phosphors

    SciTech Connect

    Phillips, M.L.F.; Shea, L.E.

    1995-08-01

    Field emission flat panel displays place new demands on the performance of cathodoluminescent phosphors. In particular, such phosphors must be efficient at lower voltages (ca. 100-1000 V), and must withstand higher current densities than are present on cathode ray tube screens. ZnO:Zn has been studied extensively as a low-voltage phosphor, but problems such as poor chromatic saturation and temperature sensitivity of emission remain. In this work the use of terbium-doped garnet phases such as yttrium aluminum garnet (YAG) and gadolinium gallium garnet (GGG) as low voltage green-emitting phosphors is evaluated. Hydrothermal synthesis yields well-faceted YAG grains with particle diameters of less than 1 {mu}m. Cathodoluminescent efficiency at a particular voltage was not affected by synthetic route, though the hydrothermally synthesized material was less susceptible to damage at high power densities. An efficiency of 3.5 lm/W was observed for GGG:Tb at 800 V. Deposition of the phosphors onto conducting screens increased their efficiencies at very low voltages (< 200 V). These materials may be considered alternatives to reduced zinc oxide as green-emitting phosphors.

  3. Advantages and esthetic results of erbium, chromium:yttrium-scandium-gallium-garnet laser application in second-stage implant surgery in patients with insufficient gingival attachment: a report of three cases.

    PubMed

    Arnabat-Domínguez, Josep; Bragado-Novel, Mercedes; España-Tost, Antonio Jesús; Berini-Aytés, Leonardo; Gay-Escoda, Cosme

    2010-05-01

    Traditional implant placement involves two surgical stages. Although the second stage is comparatively less aggressive for the patient, postoperative pain and swelling can be further reduced by the use of laser instead of a scalpel. Correct handling of peri-implant soft tissue is of major importance in obtaining adequate gingival tissue attachment around implants. The presence of this keratinized gingiva ensures adequate esthetic results and maintains implant health. We report on three patients with implants in the anterior area who were operated on under the above conditions. Traditionally, the tissue overlying the implants is removed and eliminated. In seeking a way to preserve the attached gingiva, we raised a trapezoidal flap, uncovering each implant and allowing apical repositioning and transpositioning of keratinized gingiva to the buccal side. The results obtained were compared with those from other patients operated on by conventional scalpel. The erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser minimized postoperative pain, and the time to prosthetic rehabilitation was also shortened. The esthetic results were far superior, and no complications were recorded.

  4. Ferrimagnetism in the rare-earth iron garnets: a Monte Carlo study.

    PubMed

    Oitmaa, J; Falk, Thomas

    2009-03-25

    We investigate classical vector spin models of the rare-earth iron garnet ferrimagnets yttrium iron garnet (YIG) and gadolinium iron garnet (GdIG) using Monte Carlo simulations. Critical temperatures agree well with experiment. A compensation point is observed in GdIG, again in good agreement with experiment.

  5. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2010-01-01

    In 2009, U.S. production of crude garnet concentrate for industrial use was estimated to be 56.5 kt (62,300 st), valued at about $8.85 million. This was a 10-percent decrease in quantity compared with 2008 production. Refined garnet material sold or used was 28 kt (31,000 st) valued at $7.96 million.

  6. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2011-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet's angular fractures, relatively high hardness and specific gravity, chemical inertness and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  7. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2012-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet's angular fractures, relatively high hardness and specific gravity, chemical inertness, and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  8. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2006-01-01

    In 2005, US production of crude garnet concentrate for industrial use was 28.4 kt valued at $3.05 million. Refined garnet material sold or used was 30.4 kt valued at $10 million. For the year, the US was one of the world's leading consumers of industrial garnet. Domestic values for crude concentrates for different applications ranged from about $53 to $120/t. In the short term, excess production capacity, combined with suppliers that vary in quality, grain size and mineral type, will keep prices down.

  9. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2000-01-01

    The state of the global industrial garnet industry in 1999 is discussed. Industrial garnet mined in the U.S., which accounts for approximately one-third of the world's total, is usually a solid-solution of almandine and pyrope. The U.S. is the largest consumer of industrial garnet, using an estimated 47,800 st in 1999 as an abrasive and as a filtration medium in the petroleum industry, filtration plants, aircraft and motor vehicle manufacture, shipbuilding, wood furniture finishing operations, electronic component manufacture, ceramics manufacture, and glass production. Prices for crude concentrates ranged from approximately $50 to $110/st and refined garnet from $50 to $215/st in 1999, depending on type, source, quantity purchased, quality, and application.

  10. Effects of post-deposition annealing on the structure and magnetization of PLD grown yttrium iron garnet films

    NASA Astrophysics Data System (ADS)

    Kumar, Ravinder; Hossain, Z.; Budhani, R. C.

    2017-03-01

    We report on the recrystallization of 200 nm thick as-grown Yttrium Iron Garnet ( Y 3.4 Fe 4.6 O 12 ) films on the (111) face of gadolinium gallium garnet single crystals by post-deposition annealing. Epitaxial conversion of the as-grown microcrystalline yttrium iron garnet films was seen after annealing at 800 °C for more than 30 min both in ambient oxygen and in air. The as-grown oxygen annealed samples at 800 °C for 60 min crystallize epitaxially and show excellent figure-of-merit for saturation magnetization (MS = 3.3 μB/f.u., comparable to the bulk value) and coercivity (HC ˜ 1.1 Oe). The ambient air annealing at 800 °C with a very slow rate of cooling (2 °C/min) results in a double layer structure with a thicker unstrained epitaxial top layer having the MS and HC of 2.9 μB/f.u. and 0.12 Oe, respectively. The symmetric and asymmetric reciprocal space maps of both the samples reveal a locking of the in-plane lattice of the film to the in-plane lattice of the substrate, indicating a pseudomorphic growth. The residual stress calculated by the sin 2 ψ technique is compressive in nature. The lower layer in the air annealed sample is highly strained, whereas the top layer has negligible compressive stress.

  11. Gallium scan

    MedlinePlus

    ... material called gallium and is a type of nuclear medicine exam. A related test is gallium scan ... Brown ML, Forstrom LA, et al. Society of nuclear medicine procedure guideline for gallium scintigraphy in inflammation. ...

  12. Giant Zeeman shifts in the optical transitions of yttrium iron garnet thin films

    NASA Astrophysics Data System (ADS)

    Vidyasagar, R.; Alves Santos, O.; Holanda, J.; Cunha, R. O.; Machado, F. L. A.; Ribeiro, P. R. T.; Rodrigues, A. R.; Mendes, J. B. S.; Azevedo, A.; Rezende, S. M.

    2016-09-01

    We report the observation of giant Zeeman shifts in the optical transitions of high-quality very thin films of yttrium iron garnet (YIG) grown by rf sputtering on gadolinium gallium garnet substrates. The optical absorption profile measured with magneto-optical absorption spectroscopy shows dual optical transition in the UV-visible frequency region attributed to transitions from the O-2p valence band to the Fe-3d conduction band and from the O-2p valence band to Fe-2p53d6 excitonic states at the Γ-symmetry point of the YIG band structure. The application of a static magnetic field of only 0.6 kOe produces giant Zeeman shifts of ˜100 meV in the YIG band structure and ˜60 meV in the excitonic states corresponding to effective g-factors on the order of 104. The giant Zeeman effects are attributed to changes in energy levels by the large exchange fields of the Fe-3d orbitals during the magnetization process.

  13. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2013-01-01

    Garnet has been used as a gemstone since the Bronze Age. However, garnet’s angular fractures, relatively high hardness and specific gravity, chemical inertness and nontoxicity make it ideal for many industrial applications. It is also free of crystalline silica and can be recycled.

  14. Influence of erbium, chromium-doped: Yttrium scandium-gallium-garnet laser etching and traditional etching systems on depth of resin penetration in enamel: A confocal laser scanning electron microscope study

    PubMed Central

    Vijayan, Vishal; Rajasigamani, K.; Karthik, K.; Maroli, Sasidharan; Chakkarayan, Jitesh; Haris, Mohamed

    2015-01-01

    Objective: This study was performed to assess the resin tag length penetration in enamel surface after bonding of brackets to identify which system was most efficient. Methodology: Our study was based on a more robust confocal microscopy for visualizing the resin tags in enamel. Totally, 100 extracted human first and second premolars have been selected for this study and were randomly divided into ten groups of 10 teeth each. In Group 1, the buccal enamel surface was etched with 37% phosphoric acid (3M ESPE), Group 2 with 37% phosphoric (Ultradent). In Groups 5, 6, and 7, erbium, chromium-doped: Yttrium scandium-gallium-garnet (Er, Cr: YSGG) laser (Biolase) was used for etching the using following specifications: Group 5 (1.5 W/20 Hz, 15 s), Group 6 (2 W/10 Hz, 15 s), and Group 7 (2 W/20 Hz, 15 s). In Groups 8, 9, and 10, Er, Cr: YSGG laser (Biolase) using same specifications and additional to this step, conventional etching on the buccal enamel surface was etched with 37% (3M ESPE) after laser etching. In Groups 1, 5, 6, 7, 8, 9, and 10 3M Unitek Transbond XT primer was mixed with Rhodamine B dye (Sigma-Aldrich, Germany) to etched surface and then cured for 20 s. In Group 2, Ultradents bonding agent was mixed with Rhodamine B. In Group 3, 3M Unitek Transbond PLUS, Monrovia, USA, which was mixed with Rhodamine B dye (Sigma-Aldrich, Germany). Group 4, with self-etching primer (Ultradent-Peak SE, USA) was mixed with Rhodamine B dye (Sigma-Aldrich, Germany). Later (3M Unitek, Transbond XT, Monrovia USA) [Figure 1] was used to bond the modified Begg brackets (T. P. Orthodontics) in Groups 1, 3, 5, 6, 7, 8, 9, and 10. In Groups 2, 4 Ultradent-Peak LC Bond was used to bond the modified brackets. After curing brackets were debonded, and enamel depth penetration was assessed using confocal laser scanning microscope. Results: Group J had a mean maximum depth of penetration of 100.876 μm, and Group D was the least having a maximum value of 44.254 μm. Conclusions: Laser

  15. Magnetostatic Waves-Based Integrated Optic Bragg Cell Modules With Applications To RF Signal Processing

    DTIC Science & Technology

    1992-06-30

    magnetooptic (MO) interactions between guided-optical waves (GOW) and magnetostatic waves (MSW) in Yttrium Iron Garnet- Gadolinium Gallium Garnet (YIG...Yittrium Iron Garnet- Gadolinium Gallium Garnet Waveguide," Appl. Phys. Lett., Vol.47, pp.651-654, 1985. [4] C.S. Tsai, "Guided-wave Acoustooptic Bragg...5] D. Young and C.S. Tsai, "GHz Bandwidth Magneto-Optic Interaction in Yittrium Iron Garnet- Gadolinium Gallium Garnet Using Magnetostatic Forward

  16. Industrial garnet

    USGS Publications Warehouse

    Olson, D.W.

    2007-01-01

    World production of industrial garnet was about 326 kt in 2006, with the U.S. producing about 11 percent of this total. U.S. consumption, imports, and exports were estimated at 74.3 kt, 52.3 kt, and 13.2 kt, respectively. The most important exporters are Australia, China, and India. Although demand is expected to rise over the next 5 years, prices are expected to remain low in the short term.

  17. Temperature dependence of the magnon spin diffusion length and magnon spin conductivity in the magnetic insulator yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Cornelissen, L. J.; Shan, J.; van Wees, B. J.

    2016-11-01

    We present a systematic study of the temperature dependence of diffusive magnon spin transport using nonlocal devices fabricated on a 210-nm yttrium iron garnet film on a gadolinium gallium garnet substrate. In our measurements, we detect spin signals arising from electrical and thermal magnon generation, and we directly extract the magnon spin diffusion length λm for temperatures from 2 to 293 K. Values of λm obtained from electrical and thermal generation agree within the experimental error with λm=9.6 ±0.9 μ m at room temperature to a minimum of λm=5.5 ±0.7 μ m at 30 K. Using a two-dimensional finite element model to fit the data obtained for electrical magnon generation we extract the magnon spin conductivity σm as a function of temperature, which is reduced from σm=3.7 ±0.3 ×105S /m at room temperature to σm=0.9 ±0.6 ×104S /m at 5 K. Finally, we observe an enhancement of the signal originating from thermally generated magnons for low temperatures where a maximum is observed around T =7 K . An explanation for this low-temperature enhancement is however still missing and requires additional investigation.

  18. Transparent ceramic garnet scintillator optimization via composition and co-doping for high-energy resolution gamma spectrometers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Beck, Patrick R.; Swanberg, Erik L.; Hunter, Steven L.

    2016-09-01

    Breakthrough energy resolution, R(662keV) <4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce), by optimizing fabrication conditions. Here we describe the dependence of scintillation light yield and energy resolution on several variables: (1) Stoichiometry, in particular Gd/Y and Ga/Al ratios which modify the bandgap energy, (2) Processing methods, including vacuum vs. oxygen sintering, and (3) Trace co-dopants that influence the formation of Ce4+ and modify the intra-bandgap trap distribution. To learn about how chemical composition influences the scintillation properties of transparent ceramic garnet scintillators, we have measured: scintillation decay component amplitudes; intensity and duration of afterglow; thermoluminescence glow curve peak positions and amplitudes; integrated light yield; light yield non-proportionality, as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI); and energy resolution for gamma spectroscopy. Optimized GYGAG(Ce) provides R(662 keV) =3.0%, for 0.05 cm3 size ceramics with Silicon photodiode readout, and R(662 keV) =4.6%, at 2 in3 size with PMT readout.

  19. Thin yttrium iron garnet films grown by pulsed laser deposition: Crystal structure, static, and dynamic magnetic properties

    SciTech Connect

    Sokolov, N. S. Fedorov, V. V.; Korovin, A. M.; Suturin, S. M.; Baranov, D. A.; Gastev, S. V.; Krichevtsov, B. B.; Bursian, V. E.; Lutsev, L. V.; Maksimova, K. Yu.; Grunin, A. I.; Tabuchi, M.

    2016-01-14

    Pulsed laser deposition has been used to grow thin (10–84 nm) epitaxial layers of Yttrium Iron Garnet Y{sub 3}Fe{sub 5}O{sub 12} (YIG) on (111)–oriented Gadolinium Gallium Garnet substrates at different growth conditions. Atomic force microscopy showed flat surface morphology both on micrometer and nanometer scales. X-ray diffraction measurements revealed that the films are coherent with the substrate in the interface plane. The interplane distance in the [111] direction was found to be by 1.2% larger than expected for YIG stoichiometric pseudomorphic film indicating presence of rhombohedral distortion in this direction. Polar Kerr effect and ferromagnetic resonance measurements showed existence of additional magnetic anisotropy, which adds to the demagnetizing field to keep magnetization vector in the film plane. The origin of the magnetic anisotropy is related to the strain in YIG films observed by XRD. Magneto-optical Kerr effect measurements revealed important role of magnetization rotation during magnetization reversal. An unusual fine structure of microwave magnetic resonance spectra has been observed in the film grown at reduced (0.5 mTorr) oxygen pressure. Surface spin wave propagation has been demonstrated in the in-plane magnetized films.

  20. Nonreciprocity of spin waves in magnonic crystals created by surface acoustic waves in structures with yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Kryshtal, R. G.; Medved, A. V.

    2015-12-01

    Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW - magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW - magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW - magnonic crystals are promising for signal processing in the GHz range.

  1. Band-gap and band-edge engineering of multicomponent garnet scintillators from first principles

    DOE PAGES

    Yadav, Satyesh K.; Uberuaga, Blas P.; Nikl, Martin; ...

    2015-11-24

    Complex doping schemes in R3Al5O12 (where R is the rare-earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band gap is altered in a manner that facilitates the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density-functional theory and hybrid density-functional theory (HDFT) are used to survey potential admixing candidates that modify either the conduction-band minimum (CBM) or valence-bandmore » maximum (VBM). We consider two sets of compositions based on Lu3B5O12 where B is Al, Ga, In, As, and Sb, and R3Al5O12, where R is Lu, Gd, Dy, and Er. We find that admixing with various R cations does not appreciably affect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sb decrease the band gap by raising the VBM, the relative change in band gap is quantitatively validated by HDFT. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. Furthermore, this approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.« less

  2. Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering

    NASA Astrophysics Data System (ADS)

    Boudiar, T.; Payet-Gervy, B.; Blanc-Mignon, M.-F.; Rousseau, J.-J.; Le Berre, M.; Joisten, H.

    2004-12-01

    Thin films of yttrium iron garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system. Thin films are crystallised by heat-treatment to obtain magneto-optical properties. On quartz substrate, the network of cracks observed on the annealed samples can be explained by the difference between the thermal expansion coefficient of substrate and YIG. Physico-chemical analysis shown that the obtained material has a correct stoichiometry and is crystallised as FCC. The Faraday rotation of thin films is measured with a classical ellipsometric system based on transmission which allows us to obtained an accuracy of 0.01 ° . The variation of Faraday rotation is studied on the one hand versus radio frequency power applied to the cathode during the deposition and on the other hand versus the applied magnetic field. The results are compared with those obtained by vibrating sample magnetometer analysis in perpendicular configuration. A maximum Faraday rotation is observed to be 1900 ° / cm at the wavelength of 594 nm for a YIG thin film formed on quartz substrate and annealed at 740 ° C . The values of the Faraday rotation coefficients obtained in the study versus the wavelength are comparable to those of the literature for the bulk material. In order to eliminate the stress due to the heat-treatment, we made some films on single crystals of gadolinium gallium garnet (1 1 1) substrates for which thermal expansion coefficient is near than the YIG one. The material crystallises with no crackles and the Faraday effect is equivalent.

  3. Swift heavy ion-beam induced amorphization and recrystallization of yttrium iron garnet.

    PubMed

    Costantini, Jean-Marc; Miro, Sandrine; Beuneu, François; Toulemonde, Marcel

    2015-12-16

    Pure and (Ca and Si)-substituted yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers and amorphous films on gadolinium gallium garnet (Gd3Ga5O12, or GGG) single crystal substrates were irradiated by 50 MeV (32)Si and 50 MeV (or 60 MeV) (63)Cu ions for electronic stopping powers larger than the threshold value (~4 MeV μm(-1)) for amorphous track formation in YIG crystals. Conductivity data of crystalline samples in a broad ion fluence range (10(11)-10(16) cm(-2)) are modeled with a set of rate equations corresponding to the amorphization and recrystallization induced in ion tracks by electronic excitations. The data for amorphous layers confirm that a recrystallization process takes place above ~10(14) cm(-2). Cross sections for both processes deduced from this analysis are discussed in comparison to previous determinations with reference to the inelastic thermal-spike model of track formation. Micro-Raman spectroscopy was also used to follow the related structural modifications. Raman spectra show the progressive vanishing and randomization of crystal phonon modes in relation to the ion-induced damage. For crystalline samples irradiated at high fluences (⩾10(14) cm(-2)), only two prominent broad bands remain like for amorphous films, thereby reflecting the phonon density of states of the disordered solid, regardless of samples and irradiation conditions. The main band peaked at ~660 cm(-1) is assigned to vibration modes of randomized bonds in tetrahedral (FeO4) units.

  4. Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

    PubMed Central

    Onbasli, Mehmet C.; Beran, Lukáš; Zahradník, Martin; Kučera, Miroslav; Antoš, Roman; Mistrík, Jan; Dionne, Gerald F.; Veis, Martin; Ross, Caroline A.

    2016-01-01

    Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices. PMID:27025269

  5. Bi-substituted iron garnet films for one-dimensional magneto-photonic crystals: Synthesis and properties

    SciTech Connect

    Shaposhnikov, A.N.; Karavainikov, A.V.; Prokopov, A.R.; Berzhansky, V.N.; Salyuk, O.Y.

    2012-06-15

    Graphical abstract: Faraday hysteresis loops for Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12} film on glass-ceramic substrate (a), Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} film on gallium–gadolinium garnet (b) and for glass-ceramic/SiO{sub 2}/Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12}/Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} structure (c). Highlights: ► Bismuth-substituted iron garnet films as magneto-optical layers in magneto-photonic crystals. ► It is impossible to crystallize the films with high Bi content on amorphous substrates. ► The crystallization of the films can be achieved by their deposition on buffer layer with low bismuth content. -- Abstract: The crystallization processes in Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12}, Bi{sub 2.5}Gd{sub 0.5}Fe{sub 3.8}Al{sub 1.2}O{sub 12}, Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12} and Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12} garnet films deposited by reactive ion beam sputtering on (1 1 1) gadolinium–gallium garnet substrates, optical glass-ceramic and SiO{sub 2} films have been studied. Films were annealed at low pressure in oxygen atmosphere and in the air. The possibility of preparation of crystalline garnet films with high concentration of bismuth on the SiO{sub 2} films using a buffer layer with low concentration of Bi has been shown. This allows to produce one-dimensional magneto-photonic crystals with high effective Faraday rotation (several tens of°/μm for the visible optical spectrum).

  6. Electrospun cellulose acetate-garnet nanocomposite magnetic fibers for bioseparations.

    PubMed

    Munaweera, Imalka; Aliev, Ali; Balkus, Kenneth J

    2014-01-08

    Cellulose acetate fibers with magnetic properties have recently attracted much attention because of their potential novel applications in biomedicine such as for cell and protein separations, magnetic resonance imaging contrast agents, and magnetic filters. In this work, as synthesized yttrium iron garnet and gadolinium substituted yttrium iron garnet nanoparticles have been used to generate magnetic filter paper. Garnet nanoparticles dispersed in cellulose acetate polymer solutions were electrospun as free-standing nonwoven fiber mats as well as on cellulose filter paper substrates resulting in magnetic filter papers. The magnetic fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and superconducting quantum interference device (SQUID) magnetic property measurements. The resulting magnetic polymer nanocomposites can be easily picked up by an external magnet from a liquid medium. Fluorescein isothiocyanate (FITC) labeled bovine serum albumin (BSA) was separated from solution by using the magnetic filter paper.

  7. Relationship between the magnetizations of sublattices in gadolinium iron garnet

    SciTech Connect

    Brezgunov, M.M.; Petrov, A.E.

    1984-04-01

    The results of magnetic and structural studies of Gd/sub 3/F/sub 5/O/sub 12/ and Y/sub 3/Fe/sub 5/O/sub 12/ before and after interaction with neutrons, which were carried out to determine the role played by each magnetic sublattice in changes observed in the physical properties of Gd/sub 3/Fe/sub 5/O/sub 12/ are reported. (AIP)

  8. Gadolinium photoionization process

    DOEpatents

    Paisner, Jeffrey A.; Comaskey, Brian J.; Haynam, Christopher A.; Eggert, Jon H.

    1993-01-01

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  9. Gadolinium photoionization process

    DOEpatents

    Paisner, J.A.; Comaskey, B.J.; Haynam, C.A.; Eggert, J.H.

    1993-04-13

    A method is provided for selective photoionization of the odd-numbered atomic mass gadolinium isotopes 155 and 157. The selective photoionization is accomplished by circular or linear parallel polarized laser beam energy effecting a three-step photoionization pathway.

  10. Rare-Earth Garnets and Perovskites for Space-Based ADR Cooling at High T and Low H

    NASA Technical Reports Server (NTRS)

    King, T. T.; Rowlett, B. A.; Ramirez, R. A.; Shirron, P. J.; Canavan, E. R.; DiPirro, M. J.; Panek, J. S.; Tuttle, J. G.; Shull, R. D.; Fry, R. A.; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    Future NASA satellite detector systems must be cooled to the 0.1 K temperature range to meet the stringent energy resolution and sensitivity requirements demanded by mid-term astronomy missions. The development of adiabatic demagnetization refrigeration (ADR) materials that can efficiently cool from the passive radiative cooling limit of approx. 30 K down to sub-Kelvin under low magnetic fields (H less than or equal to 3 T) would represent a significant improvement in space-based cooling technology. Governed by these engineering goals, our efforts have focused on quantifying the change in magnetic entropy of rare-earth garnets and perovskites. Various compositions within the gadolinium gallium iron garnet solid solution series (GGIG, Gd3Ga(5-x)Fe(x)O12, 0.00 less than or equal to X less than or equal to 5.00) and gadolinium aluminum perovskite (GAP, GdAlO3) have been synthesized via an organometallic complex approach and confirmed with powder x-ray diffraction. The magnetization of the GGIG and GAP materials has been measured as a function of composition (0.00 less than or equal to X less than or equal to 5.00), temperature (2 K less than or equal to T less than or equal to 30 K) and applied magnetic field (0 T less than or equal to H less than or equal to 3 T). The magnetic entropy change (DeltaS(sub mag)) between 0 T and 3 T was determined from the magnetization data. In the GGIG system, DeltaS(sub mag) was compositionally dependent; Fe(sup 3+) additions up to X less than or equal to 2.44 increased DeltaS(sub mag) at T > 5 K. For GAP, DeltaS(sub mag) was similar to that of GGIG, X = 0.00, both in terms of magnitude and temperature dependence at T > 10 K. However, the DeltaS(sub mag) of GAP at T < 10 K was less than the endmember GGIG composition, X = 0.00, and exhibited maximum approx. 5 K.

  11. Band-gap and band-edge engineering of multicomponent garnet scintillators from first principles

    SciTech Connect

    Yadav, Satyesh K.; Uberuaga, Blas P.; Nikl, Martin; Jiang, Chao; Stanek, Christopher R.

    2015-11-24

    Complex doping schemes in R3Al5O12 (where R is the rare-earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band gap is altered in a manner that facilitates the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density-functional theory and hybrid density-functional theory (HDFT) are used to survey potential admixing candidates that modify either the conduction-band minimum (CBM) or valence-band maximum (VBM). We consider two sets of compositions based on Lu3B5O12 where B is Al, Ga, In, As, and Sb, and R3Al5O12, where R is Lu, Gd, Dy, and Er. We find that admixing with various R cations does not appreciably affect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sb decrease the band gap by raising the VBM, the relative change in band gap is quantitatively validated by HDFT. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. Furthermore, this approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.

  12. Gadolinium-Induced Fibrosis.

    PubMed

    Todd, Derrick J; Kay, Jonathan

    2016-01-01

    Gadolinium-based contrast agents (GBCAs), once believed to be safe for patients with renal disease, have been strongly associated with nephrogenic systemic fibrosis (NSF), a severe systemic fibrosing disorder that predominantly afflicts individuals with advanced renal dysfunction. We provide a historical perspective on the appearance and disappearance of NSF, including its initial recognition as a discrete clinical entity, its association with GBCA exposure, and the data supporting a causative relationship between GBCA exposure and NSF. On the basis of this body of evidence, we propose that the name gadolinium-induced fibrosis (GIF) more accurately reflects the totality of knowledge regarding this disease. Use of high-risk GBCAs, such as formulated gadodiamide, should be avoided in patients with renal disease. Restriction of GBCA use in this population has almost completely eradicated new cases of this debilitating condition. Emerging antifibrotic therapies may be useful for patients who suffer from GIF.

  13. Mineral of the month: garnet

    USGS Publications Warehouse

    Olson, Donald

    2005-01-01

    Garnet is the general name given to a group of complex silicate minerals, all with isometric crystal structure, similar properties and chemical compositions. Garnet occurs in every color of the spectrum except blue, but it is most commonly red, purple, brown and green. Garnet necklaces dating from the Bronze Age have been found in graves and also among the ornaments adorning the oldest Egyptian mummies.

  14. Mantle garnets: A cracking yarn

    NASA Astrophysics Data System (ADS)

    Matthews, M.; Harte, B.; Prior, D.

    1992-07-01

    Garnets showing variation in chemical composition occur in the metasomatised peridotitic wallrocks to intrusive pyroxenitic "dikes" in mantle xenoliths from the Matsoku kimberlite pipe. They have been examined by scanning electron microscope (SEM) and imaged using both high contrast and electron channelling backscattered electron (BSE) methods. The images revealed intricate variation in the backscatter coefficient, η, across garnets. The pattern of variation is one of very slightly diffuse "brightwhite" (high η) lines surrounded by paler diffuse auras, grading into darker (lower η.) areas away from the bright lines. The bright lines are usually irregular in detail and show branching and braiding; but in some cases they form regularly spaced parallel to subparallel sets which reflect crystallographic orientation. Electron and ion microprobe analyses, including a highly exhaustive 40,000 data point electron microprobe survey across one garnet, have correlated the change in the backscatter coefficient with compositional variation. The compositional changes largely involve enrichment in Fe and Ti and decrease in Mg of the garnet forming the bright lines and pale auras and are consistent with those of metasomatic garnets identified by previous work on an extensive suite of Matsoku xenoliths. The high Ti and Fe garnet is also enriched in Y, Zr, MREEs and HREEs and is considered to have formed by direct crystallisation from the melt causing metasomatism, whilst areas away from the high η lines show compositions similar to those of garnets in unmetasomatised rock. The bright (high η) lines are interpreted as delineating a pattern of fractures along which the metasomatising melt was able to penetrate the garnet and from this melt new garnet crystallised to heal the fractures and form the high Fe-Ti garnet. Diffusion of elements outward from these melt-filled and subsequently healed fractures into the main body of the garnet produced the more diffuse zonation pattern

  15. Gallium nitride optoelectronic devices

    NASA Technical Reports Server (NTRS)

    Chu, T. L.; Chu, S. S.

    1972-01-01

    The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

  16. Investigations in gallium removal

    SciTech Connect

    Philip, C.V.; Pitt, W.W.; Beard, C.A.

    1997-11-01

    Gallium present in weapons plutonium must be removed before it can be used for the production of mixed-oxide (MOX) nuclear reactor fuel. The main goal of the preliminary studies conducted at Texas A and M University was to assist in the development of a thermal process to remove gallium from a gallium oxide/plutonium oxide matrix. This effort is being conducted in close consultation with the Los Alamos National Laboratory (LANL) personnel involved in the development of this process for the US Department of Energy (DOE). Simple experiments were performed on gallium oxide, and cerium-oxide/gallium-oxide mixtures, heated to temperatures ranging from 700--900 C in a reducing environment, and a method for collecting the gallium vapors under these conditions was demonstrated.

  17. Magnetostatic Wave Transducers, Resonators and Dispersion Control

    DTIC Science & Technology

    1990-05-01

    propagating at microwave frequencies in magnetically biased, liquid phase epitaxial films of Yttrium Iron Garnet (YIG) grown on Gadolinium Gallium Garnet... microwave energy for MSSW propagation along the YIG film. A 25 um-thick 3mm- wide YIG film and 15 um-thick Gadolinium Gallium Garnet (GGG) substrate was...stretching. Methods for providing these time delays include an assortment of fixed cables. ferrite loaded cables. surface acoustic wave iSA W) devices

  18. Epitaxial Garnets and Hexagonal Ferrites.

    DTIC Science & Technology

    1983-12-01

    Ferrites Lithium Ferrite Magnetostatic Wave Garnets Epitaxy Yttrium Iron Garnet Liquid Phase Epitaxy Hexagonal Ferrite Microwave Signal Processing...epitaxial ferrit ( materials for use in microwave and millirreter-wave signal processing devices. The major emphasis has been on multiple layer...overall objective of this research is to develop epitaxial single crystal ferrite films suitable for microwave and millimeter-wave signal processing at

  19. Crystal Chemistry of Melanite Garnet

    NASA Technical Reports Server (NTRS)

    Nguyen, Dawn Marie

    1999-01-01

    This original project resulted in a detailed crystal chemical data map of a titanium rich garnet (melanite) suite that originates from the Crowsnest Volcanics of Alberta Canada. Garnet is typically present during the partial melting of the earth's mantle to produce basalt. Prior studies conducted at Youngstown State University have yielded questions as to the crystal structure of the melanite. In the Studies conducted at Youngstown State University, through the use of single crystal x-ray diffraction, the c-axis appears to be distorted creating a tetragonal crystal instead of the typical cubic crystal of garnets. The micro probe was used on the same suite of titanium rich garnets as used in the single crystal x-ray diffraction. The combination of the single crystal x-ray research and the detailed microprobe research will allow us to determine the exact crystal chemical structure of the melanite garnet. The crystal chemical data was gathered through the utilization of the SX100 Electron Probe Micro Analyzer. Determination of the exact chemical nature may prove useful in modeling the ultramafic source rock responsible for the formation of the titanium rich lunar basalts.

  20. Preventing Supercooling Of Gallium

    NASA Technical Reports Server (NTRS)

    Massucco, Arthur A.; Wenghoefer, Hans M.; Wilkins, Ronnie

    1994-01-01

    Principle of heterogeneous nucleation exploited to prevent gallium from supercooling, enabling its use as heat-storage material that crystallizes reproducibly at its freezing or melting temperature of 29 to 30 degrees C. In original intended application, gallium used as heat-storage material in gloves of space suits. Terrestrial application lies in preparation of freezing-temperature reference samples for laboratories. Principle of heterogeneous nucleation also exploited similarly in heat pipes filled with sodium.

  1. Mineral resource of the month: garnet

    USGS Publications Warehouse

    Olson, Donald W.

    2011-01-01

    Garnet, the birthstone for the month of January, has been used as a gemstone for centuries. Garnet necklaces dating from the Bronze Age have been found in graves, and garnet is found among the ornaments adorning the oldest Egyptian mummies. However, garnet’s characteristics, such as its relatively high hardness and chemical inertness, make it ideal for many industrial applications.

  2. Electrodeposition of gallium for photovoltaics

    SciTech Connect

    Bhattacharya, Raghu N.

    2016-08-09

    An electroplating solution and method for producing an electroplating solution containing a gallium salt, an ionic compound and a solvent that results in a gallium thin film that can be deposited on a substrate.

  3. Thermodynamic properties of gadolinium disilicide

    SciTech Connect

    Lukashenko, G.M.; Polotskaya, R.I.

    1986-11-01

    The authors determine the Gibbs energy, enthalpy, formation heat, and other thermodynamic properties of gadolinium disilicide by measuring the electromotive force in the 830-960 K temperature range in electrolytes consisting of molten tin and various chlorides. The relationship of these properties to crystal structure is briefly discussed.

  4. Experience with gadolinium at yankee

    SciTech Connect

    Cacciapouti, R.J.; Sironen, M.A.; Kaptiz, D.M.; Potter, R.C.

    1985-11-01

    The Vermont Yankee nuclear power station, a boiling water reactor, has been operating with gadolinium in the fuel bundles since 1973. The gadolinium has ranged from 2.0 to 4.0 wt% in 7 x 7, 8 x 8, and retrofit 8 x 8 bundle designs. When Yankee Atomic Electric Company initiated its program in 1978 to perform reload licensing analysis, these bundles and the core designs had to be modeled accurately. The basic calculational model consists of the cross section generation code, CASMO, and the three-dimensional nodal code, SIMULATE. The gadolinium cross sections for use in CASMO were generated using MICBURN to model each gadolinium pin individually. This combination of codes has been used to calculate 11 cycles of operation at Vermont Yankee. The model has been depleted each cycle using explicit plant conditions at equilibrium xenon. At various state points, the eigenvalues, hot and cold, were calculated and tabulated for each cycle. Comparisons were made between plant-measured and SIMULATE-calculated TIP values and between process computer and SIMULATE thermal margins. The model is also used to predict future cycle operating conditions and thermal margins based on past comparisons.

  5. Chapter L: U.S. Industrial Garnet

    USGS Publications Warehouse

    Evans, James G.; Moyle, Phillip R.

    2006-01-01

    The United States presently consumes about 16 percent of global production of industrial garnet for use in abrasive airblasting, abrasive coatings, filtration media, waterjet cutting, and grinding. As of 2005, domestic garnet production has decreased from a high of 74,000 t in 1998, and imports have increased to the extent that as much as 60 percent of the garnet used in the United States in 2003 was imported, mainly from India, China, and Australia; Canada joined the list of suppliers in 2005. The principal type of garnet used is almandite (almandine), because of its specific gravity and hardness; andradite is also extensively used, although it is not as hard or dense as almandite. Most industrial-grade garnet is obtained from gneiss, amphibolite, schist, skarn, and igneous rocks and from alluvium derived from weathering and erosion of these rocks. Garnet mines and occurrences are located in 21 States, but the only presently active (2006) mines are in northern Idaho (garnet placers; one mine), southeastern Montana (garnet placers; one mine), and eastern New York (unweathered bedrock; two mines). In Idaho, garnet is mined from Tertiary and (or) Quaternary sedimentary deposits adjacent to garnetiferous metapelites that are correlated with the Wallace Formation of the Proterozoic Belt Supergroup. In New York, garnet is mined from crystalline rocks of the Adirondack Mountains that are part of the Proterozoic Grenville province, and from the southern Taconic Range that is part of the northern Appalachian Mountains. In Montana, sources of garnet in placers include amphibolite, mica schist, and gneiss of Archean age and younger granite. Two mines that were active in the recent past in southwestern Montana produced garnet from gold dredge tailings and saprolite. In this report, we review the history of garnet mining and production and describe some garnet occurrences in most of the Eastern States along the Appalachian Mountains and in some of the Western States where

  6. New perspective in garnet phosphor: low temperature synthesis, nanostructures, and observation of multimodal luminescence.

    PubMed

    Mishra, Kavita; Singh, Sunil Kumar; Singh, Akhilesh Kumar; Rai, Monika; Gupta, Bipin Kumar; Rai, Shyam Bahadur

    2014-09-15

    Herein, we report a new concept for garnet materials in terms of the synthesis of nanocrystalline structure at low temperatures and its multimodal luminescence processes. Terbium- and ytterbium-ion-codoped yttrium gallium garnet nanophosphors have been synthesized via solution combustion technique; nearly pure phase nanophosphor samples were obtained. The synthesized nanophosphor shows efficient multimodal upconversion (UC), downshifting (DS), and quantum cutting (QC)/downconversion (DC) luminescence, which is a new paradigm in garnet material. The garnet nanophosphor shows strong green emission through DS and UC processes both. Furthermore, cooperative energy transfer (CET) has been described in detail, and a possible mechanism for the QC process is also proposed. A UV/blue photon absorbed by Tb(3+) ion splits into two near-infrared photons (wavelength range 900-1040 nm), emitted by a Yb(3+) ion pair, with an efficiency of more than 100%. The Yb(3+) concentration dependent ET from Tb(3+) to Yb(3+) has been verified using time domain analysis. An ET efficiency as high as 28% and a corresponding QC efficiency of about 128% (for 15 mol % of Yb(3+) concentration) have been attained. Such a multimode emitting nanophosphor could be very useful in display devices and for enhancing the conversion efficiency of next generation solar cells via spectral modification etc.

  7. Tumor growth suppression by gadolinium-neutron capture therapy using gadolinium-entrapped liposome as gadolinium delivery agent.

    PubMed

    Dewi, Novriana; Yanagie, Hironobu; Zhu, Haito; Demachi, Kazuyuki; Shinohara, Atsuko; Yokoyama, Kazuhito; Sekino, Masaki; Sakurai, Yuriko; Morishita, Yasuyuki; Iyomoto, Naoko; Nagasaki, Takeshi; Horiguchi, Yukichi; Nagasaki, Yukio; Nakajima, Jun; Ono, Minoru; Kakimi, Kazuhiro; Takahashi, Hiroyuki

    2013-07-01

    Neutron capture therapy (NCT) is a promising non-invasive cancer therapy approach and some recent NCT research has focused on using compounds containing gadolinium as an alternative to currently used boron-10 considering several advantages that gadolinium offers compared to those of boron. In this study, we evaluated gadolinium-entrapped liposome compound as neutron capture therapy agent by in vivo experiment on colon-26 tumor-bearing mice. Gadolinium compound were injected intravenously via tail vein and allowed to accumulate into tumor site. Tumor samples were taken for quantitative analysis by ICP-MS at 2, 12, and 24 h after gadolinium compound injection. Highest gadolinium concentration was observed at about 2 h after gadolinium compound injection with an average of 40.3 μg/g of wet tumor tissue. We performed neutron irradiation at JRR-4 reactor facility of Japan Atomic Energy Research Institute in Tokaimura with average neutron fluence of 2×10¹² n/cm². The experimental results showed that the tumor growth suppression of gadolinium-injected irradiated group was revealed until about four times higher compared to the control group, and no significant weight loss were observed after treatment suggesting low systemic toxicity of this compound. The gadolinium-entrapped liposome will become one of the candidates for Gd delivery system on NCT.

  8. Epitaxial Garnets and Hexagonal Ferrites.

    DTIC Science & Technology

    1982-04-20

    Iron Garnet Liquid Phase Epitaxy Hexagonal Ferrite microwave Signal Processing Millimeter-Wave 20. ABSTRACT (Continue ani revee arde if necoeermy and...le.’uIfy by block rns.) e objective of this research is to develop new and improved epitauial ferrite materials for use in microwave and millimeter... ferrite films suitable for microwave and millimeter-wave signal processing at frequencies above 1 GHz. The specific tasks are: a. Analyze and develop

  9. GADOLINIUM SOLUBILITY AND VOLATILITY DURING DWPF PROCESSING

    SciTech Connect

    Reboul, S

    2008-01-30

    Understanding of gadolinium behavior, as it relates to potential neutron poisoning applications at the DWPF, has increased over the past several years as process specific data have been generated. Of primary importance are phenomena related to gadolinium solubility and volatility, which introduce the potential for gadolinium to be separated from fissile materials during Chemical Process Cell (CPC) and Melter operations. Existing data indicate that gadolinium solubilities under moderately low pH conditions can vary over several orders of magnitude, depending on the quantities of other constituents that are present. With respect to sludge batching processes, the gadolinium solubility appears to be highly affected by iron. In cases where the mass ratio of Fe:Gd is 300 or more, the gadolinium solubility has been observed to be low, one milligram per liter or less. In contrast, when the ratio of Fe:Gd is 20 or less, the gadolinium solubility has been found to be relatively high, several thousands of milligrams per liter. For gadolinium to serve as an effective neutron poison in CPC operations, the solubility needs to be limited to approximately 100 mg/L. Unfortunately, the Fe:Gd ratio that corresponds to this solubility limit has not been identified. Existing data suggest gadolinium and plutonium are not volatile during melter operations. However, the data are subject to inherent uncertainties preventing definitive conclusions on this matter. In order to determine if gadolinium offers a practical means of poisoning waste in DWPF operations, generation of additional data is recommended. This includes: Gd solubility testing under conditions where the Fe:Gd ratio varies from 50 to 150; and Gd and Pu volatility studies tailored to quantifying high temperature partitioning. Additional tests focusing on crystal aging of Gd/Pu precipitates should be pursued if receipt of gadolinium-poisoned waste into the Tank Farm becomes routine.

  10. Gallium-containing anticancer compounds.

    PubMed

    Chitambar, Christopher R

    2012-06-01

    There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin's lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks crossresistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed.

  11. Gadolinium Deposition in Humans: When Did We Learn That Gadolinium Was Deposited In Vivo?

    PubMed

    Huckle, James E; Altun, Ersan; Jay, Michael; Semelka, Richard C

    2016-04-01

    Recently, there have been numerous major peer-reviewed publications reporting deposition of gadolinium in the dentate nucleus and globus pallidus in subjects with normal renal function. This review takes a retrospective look back through the development of gadolinium-based contrast agents to describe the historical evidence of gadolinium deposition in vivo and shows that deposition in the basal ganglia should come as no surprise. Evidence for gadolinium deposition in both animal models and human patients is described. Stability differences among gadolinium contrast agents have long been recognized in vitro, and deposition of gadolinium in tissues has been described in animal models since at least 1984. The first major study that showed deposition in humans appeared in 1998 regarding patients with renal failure and in 2004 in patients with normal renal function. The historical literature indicates that gadolinium retention in healthy patients is occurring, although the clinical consequences of deposition remain unknown.

  12. Gadolinium deposition in nephrogenic fibrosing dermopathy.

    PubMed

    Boyd, Alan S; Zic, John A; Abraham, Jerrold L

    2007-01-01

    There is growing recognition of the association between the use of gadolinium-containing radiocontrast agents for magnetic resonance imaging and the serious dermal and systemic disease nephrogenic fibrosing dermopathy/nephrogenic systemic fibrosis (NFD/NSF). The pathogenesis of this entity remains unclear; however, our recent observations suggest a likely mechanism for the initial dermal manifestations of this gadolinium toxicity.

  13. Metals Fact Sheet: Gadolinium GD

    SciTech Connect

    1992-10-01

    Gadolinium is a silvery-white, malleable, ductile metallic element used to improve the high-temperature characteristics of iron, chromium, and related metallic alloys. It was named after the French chemist, Gadolin, discoverer of yttrium. This article discusses sources of the element, the world supply and demand, and also a number of applications. With the largest thermal neutron absorption cross section of any element, one of these applications is as a burnable poison in reactors and as neutron absorbers in other nuclear devices.

  14. Bulk Cubic Gallium Nitride

    DTIC Science & Technology

    1999-02-09

    microcrysta. form at bottom of «he reaction vessel. The objective of the second step is the solvothermal transport of the gallium nitride residing in the...system using pressure pumps can be used to gain precise control of the pressure. High pressure is typically used for the solvothermal transport. The...takes place in the reaction vessel during heating is a solvothermal reaction that is conducted at or above the critical point of the solvent The

  15. Gallium interactions with Zircaloy

    SciTech Connect

    Woods, A.L.; West, M.K.

    1999-01-01

    This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

  16. Development of gallium compounds for treatment of lymphoma: gallium maltolate, a novel hydroxypyrone gallium compound, induces apoptosis and circumvents lymphoma cell resistance to gallium nitrate.

    PubMed

    Chitambar, Christopher R; Purpi, David P; Woodliff, Jeffrey; Yang, Meiying; Wereley, Janine P

    2007-09-01

    Clinical studies have shown gallium nitrate to have significant antitumor activity against non-Hodgkin's lymphoma and bladder cancer, thus indicating that gallium-based drugs have potential for further development as antineoplastic agents. In this study, we compared the cytotoxicity of gallium maltolate, a novel gallium compound, with gallium nitrate in lymphoma cell lines, including p53 variant and unique gallium nitrate-resistant cells. We found that gallium maltolate inhibited cell proliferation and induced apoptosis through the mitochondrial pathway at lower concentrations and more rapidly than gallium nitrate. Gallium maltolate produced an increase in intracellular reactive oxygen species (ROS) within 2 h of incubation with cells; this effect could be blocked by mitoquinone, a mitochondria-targeted antioxidant. The role of the transferrin receptor (TfR) in gallium maltolate's action was examined using monoclonal antibody (MoAb) 42/6 to block TfR function. However, although MoAb 42/6 reduced gallium maltolate-induced caspase-3 activity, it had only a minor effect on cell growth inhibition. Importantly, gallium maltolate induced apoptosis in cells resistant to gallium nitrate, and, unlike gallium nitrate, its cytotoxicity was not affected by cellular p53 status. Cellular gallium uptake was greater with gallium maltolate than with gallium nitrate. We conclude that gallium maltolate inhibits cell proliferation and induces apoptosis more efficiently than gallium nitrate. Gallium maltolate is incorporated into lymphoma cells to a greater extent than gallium nitrate via both TfR-independent and -dependent pathways; it has significant activity against gallium nitrate-resistant cells and acts independently of p53. Further studies to evaluate its antineoplastic activity in vivo are warranted.

  17. Oxidative dissolution of gallium arsenide and separation of gallium from arsenic

    SciTech Connect

    Coleman, J.P.; Monzyk, B.F.

    1988-07-26

    The method of dissociating gallium arsenide into a gallium-containing component and an arsenic-containing component, is described which comprises contacting the gallium arsenide with an oxidizing agent and a liquid comprising hydroxamic acid to convert the gallium to a gallium-hydroxamic acid complex and to oxidize the arsenic to a positive valence state.

  18. Magnetic and electronic properties of nanocrystalline Gd{sub 3}Fe{sub 5}O{sub 12} garnet

    SciTech Connect

    Lassri, H.; Hlil, E.K.; Prasad, S.; Krishnan, R.

    2011-12-15

    The Gd{sub 3}Fe{sub 5}O{sub 12} nanocrystalline Gadolinium Iron Garnet (GdIG) obtained from a sintered block was milled in a high energy ball mill. We measured the magnetization at 5 K under applied fields up to 12 T. We report here our study of approach to saturation magnetization. The results have been interpreted within the framework of random anisotropy model. From an analysis of the approach to saturation magnetization some fundamental parameters have been extracted. We have determined the anisotropy field H{sub r} and the local magnetic anisotropy constant K{sub L}. In addition, first-principles spin-density functional calculations, using the Full potential Linear Augmented Plane Waves (FLAPW) method are performed to investigate electronic and magnetic structures. All computed parameters are discussed and compared to available experimental data. - Graphical abstract: Random anisotropy fields, random anisotropy constant, substantial interstitial magnetism as well as magnetic quadrupolar feature on oxygen are determined from magnetization, theoretical random magnetic anisotropy model and FLAPW calculations in nanocrystalline Gadolinium Iron Garnet (GdIG). Highlights: Black-Right-Pointing-Pointer Nanocrystalline Gadolinium Iron Garnet (GdIG) prepared by a high energy ball mill. Black-Right-Pointing-Pointer Random magnetic anisotropy model developed for amorphous is used for Nanocrystalline GdIG. Black-Right-Pointing-Pointer Random anisotropy fields and random anisotropy constant are determined. Black-Right-Pointing-Pointer FLAPW calculations performed to investigate both magnetic and electronic structures. Black-Right-Pointing-Pointer Substantial interstitial magnetism and magnetic quadrupolar feature on oxygen are revealed.

  19. Gallium--A smart metal

    USGS Publications Warehouse

    Foley, Nora; Jaskula, Brian W.

    2013-01-01

    Gallium is a soft, silvery metallic element with an atomic number of 31 and the chemical symbol Ga. The French chemist Paul-Emile Lecoq de Boisbaudran discovered gallium in sphalerite (a zinc-sulfide mineral) in 1875 using spectroscopy. He named the element "gallia" after his native land of France (formerly Gaul; in Latin, Gallia). The existence of gallium had been predicted in 1871 by Dmitri Mendeleev, the Russian chemist who published the first periodic table of the elements. Mendeleev noted a gap in his table and named the missing element "eka-aluminum" because he determined that its location was one place away from aluminum in the table. Mendeleev thought that the missing element (gallium) would be very much like aluminum in its chemical properties, and he was right. Solid gallium has a low melting temperature (~29 degrees Celsius, or °C) and an unusually high boiling point (~2,204 °C). Because of these properties, the earliest uses of gallium were in high-temperature thermometers and in designing metal alloys that melt easily. The development of a gallium-based direct band-gap semiconductor in the 1960s led to what is now one of the most well-known applications for gallium-based products--the manufacture of smartphones and data-centric networks.

  20. Limit on the Electron Electric Dipole Moment in Gadolinium-Iron Garnet

    SciTech Connect

    Heidenreich, B.J.; Elliott, O.T.; Charney, N.D.; Virgien, K.A.; Bridges, A.W.; McKeon, M.A.; Peck, S.K.; Krause, D. Jr.; Gordon, J.E.; Hunter, L.R.; Lamoreaux, S.K.

    2005-12-16

    A new method for the detection of the electron electric dipole moment (EDM) using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the sample's magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron EDM of 5x10{sup -24}e cm, which is a factor of 40 below the limit obtained from the only previous solid-state EDM experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.

  1. Chemical properties of Garnets from Garnet Ridge, Navajo volcanic field in the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Koga, I.; Ogasawara, Y.

    2012-12-01

    Significant amounts of garnet crystals have derived from kimberlitic diatremes at Garnet Ridge in northern Arizona. These garnets are chemically diverse and their origins have been still controversial. The diatremes at Garnet Ridge were dated at 30Ma (Smith et al., 2004). Coesite-bearing lawsonite eclogite reported by Usui et al., (2003) is important evidence for subduction of the Fallaron Plate below the Colorado plateau. This study characterized various kinds of garnets with several origins by petrographical observations and electron microprobe analyses (JXA-8900 WDS mode and JXA-733 EDS mode). On the basis of the chemical compositions and other features, the garnets were classified into the following 8 groups (A to H). Inclusions and exsolved phases were identified by laser Raman spectroscopy. (A) Garnet crystals (5-8 mm) with purple color are called ''Navajo Ruby''. A significant amount of Cr2O3 is a typical feature (up to ~5.9 wt. %). These garnet were rich in pyrope (66-78 mol. %). Olivine, Cpx, and exsolved lamellae of rutile were contained. (B) Reddish brown garnets were Pyp-rich (60-75 mol. %), and contained a minor amount of Cr2O3 (less than ~1 wt. %). The inclusions were rod-shaped rutile , Cpx, Opx, zircon, olivine and exsolved lamellae of apatite. (C) Garnet megacrysts (8-12 cm) were plotted near the center of Prp-Alm-Grs triangle (Pyp30-35 Alm28-33 Grs29-35). Exsolved apatite lamellae were confirmed. (D) Some of reddish brown garnets were plotted on same area as the Type-C. (E) Garnets in eclogite have Alm-rich composition (Pyp6-22 Alm52-65 Grs16-42). They clearly showed prograde chemical zonation; MgO: 1.4 to 5.4 wt. %, CaO: 14.0 to 5.6 wt. % both from core to rim. (F) Garnets in altered or metasomatized eclogite had a wide range of chemical composition (Pyp7-38 Alm52-69 Grs4-31) with similar prograde zonation. The cores were plotted near the rim of Type-E garnet. (G) Garnets in unidentified rock (strongly altered) had Alm-rich composition near Alm

  2. Status of gadolinium enrichment technology at LLNL

    SciTech Connect

    Haynam, C.; Comaskey, B.; Conway, J.; Eggert, J.; Glaser, J.; Ng, E.; Paisner, J.; Solarz, R.; Worden, E.

    1993-01-01

    A method based on,polarization selectivity and three step laser photoionization is presented for separation of the odd isotopes of gadolinium. Measurements of the spectroscopic parameters needed to quantify the excitation pathway are discussed. Model results are presented for the efficiency of photoionization. The vapor properties of electron beam vaporized gadolinium are presented which show dramatic cooling during the expansion of the hot dense vapor into a vacuum. This results in a significant increase in the efficiency of conversion of natural feed into enriched product in the AVLIS process. Production of enriched gadolinium for use in commercial power reactors appears to be economically viable using technology in use at LLNL.

  3. Raman spectroscopy of garnet-group minerals

    USGS Publications Warehouse

    Mingsheng, P.; Mao, Ho-kwang; Dien, L.; Chao, E.C.T.

    1994-01-01

    The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the internal modes, translational and rotatory modes of SiO4 tetrahedra, as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe garnet series. ?? 1994 Institute of Geochemistry, Chinese Academy of Sciences.

  4. Brain gadolinium deposition after administration of gadolinium-based contrast agents.

    PubMed

    Kanda, Tomonori; Oba, Hiroshi; Toyoda, Keiko; Kitajima, Kazuhiro; Furui, Shigeru

    2016-01-01

    Gadolinium-based contrast agents (GBCAs) consist of gadolinium ions and a chelating agent that binds the gadolinium ion tightly so that its toxicity is not manifested. However, in 2013, an association between brain MRI abnormalities and a history of GBCA administration was first reported. Even in patients with normal renal function, increased signal intensity in the dentate nucleus and globus pallidus on unenhanced T1-weighted images showed a positive correlation with previous exposure to linear chelate type GBCAs, but not to macrocyclic chelate type ones. This difference of GBCAs is speculated to reflect the stability of GBCAs, and de-chelated gadolinium deposition has been strongly suspected. Using inductively coupled plasma mass spectroscopy, gadolinium was detected from patients' brains with a history of repeated GBCA administration. In some cases, the gadolinium concentration of a patient's brain with normal renal function exceeded the gadolinium concentration of the skin in nephrogenic systemic fibrosis patients, but without any histological change. The actual risk has not been documented yet, but it seems important to consider the potential unknown risks of residual gadolinium in our decisions regarding GBCA administration, and to make efforts to minimize any residual gadolinium in the patient's body.

  5. Gallium Arsenide Domino Circuit

    NASA Technical Reports Server (NTRS)

    Yang, Long; Long, Stephen I.

    1990-01-01

    Advantages include reduced power and high speed. Experimental gallium arsenide field-effect-transistor (FET) domino circuit replicated in large numbers for use in dynamic-logic systems. Name of circuit denotes mode of operation, which logic signals propagate from each stage to next when successive stages operated at slightly staggered clock cycles, in manner reminiscent of dominoes falling in a row. Building block of domino circuit includes input, inverter, and level-shifting substages. Combinational logic executed in input substage. During low half of clock cycle, result of logic operation transmitted to following stage.

  6. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; DiNetta, Louis C.; DuganCavanagh, K.; Goetz, M. A.

    1996-01-01

    Betavoltaic power supplies based on gallium phosphide can supply long term low-level power with high reliability. Results are presented for GaP devices powered by Ni-63 and tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/cm(exp 2) have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. A small demonstration system has been assembled that generates and stores enough electricity to light up an LED.

  7. Gallium nitride nanotube lasers

    DOE PAGES

    Li, Changyi; Liu, Sheng; Hurtado, Antonio; ...

    2015-01-01

    Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

  8. Rare Earth Garnet Selective Emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional

  9. Deuterium implantation in magnetic garnets

    SciTech Connect

    Wilts, C.H.; Urai, A.

    1988-11-01

    The magnetic effects of deuterium implantation and subsequent annealing were measured in Gd, Tm, and Ga-substituted yttrium iron garnet films for comparison with measurements made earlier with hydrogen implantation. Implantation energy was 60 keV and the dose ranged from 0.5 to 3 x 10/sup 16/ ions/cm/sup 2/ for D/sup +//sub 2/ ions, as compared to an energy of 120 keV and a dose from 0.3 to 4 x 10/sup 16/ ions/cm/sup 2/ for H/sup +//sub 2/ in the earlier study. Measurements made included x-ray rocking curves and ferromagnetic resonance spectra measured at 9.5 GHz. For all doses the implanted layer remained crystalline. Implanted layer thickness was about 4200 A and peak strain occured at a depth of 2600 A. Peak strain increased monotonically, but departed from a linear relation with dose. For the highest dose, the peak strain was 2.5%. Relaxation of strain with annealing was intermediate between that found earlier for hydrogen and neon implantation. As compared to all other implant elements, both deuterium and hydrogen show a large anomalous magnetic anisotropy which can exceed 10 000 Oe for either ion. The absence of this effect for He, Ne, and other ions supports the conjecture that the effect is chemical and related to electronic bonding rather than strain or disorder. The anomalous anisotropy for deuterium decreases and shifts location with annealing. It has largely disappeared at temperatures of 300--350 /sup 0/C. The shape of the profile is consistent with the hypothesis that the shift in anisotropy is associated with diffusion of the deuterium atoms to the surface of the garnet film. At the highest dose, crystalline damage in the region of highest strain is sufficient to radically alter magnetic properties and in particular reduces even the excess anisotropy so that a two-peak profile results until modified by annealing.

  10. Evaluation of garnet discrimination diagrams using geochemical data of garnets derived from various host rocks

    NASA Astrophysics Data System (ADS)

    Krippner, Anne; Meinhold, Guido; Morton, Andrew C.; von Eynatten, Hilmar

    2014-06-01

    This work is an attempt to evaluate six different garnet discrimination diagrams (one binary diagram and five ternary diagrams) commonly used by many researchers. The mineral chemistry of detrital garnet is a useful tool in sedimentary provenance studies, yet there is no clear-cut understanding of what garnet type originates from which host lithology. Several discrimination diagrams exist for garnet showing distinct compositional fields, separated by strict boundaries that are thought to reflect specific types of source rocks. For this study, a large dataset was compiled (N = 3532) encompassing major element compositions of garnets derived from various host lithologies, including metamorphic, igneous, and mantle-derived rocks, in order to test the applicability of the various discrimination schemes. The dataset contains mineral chemical data collected from the literature complemented with some new data (N = 530) from garnet-bearing metamorphic and ultramafic rocks in Austria and Norway. Discrimination of the tested diagrams only works for a small group of garnets derived from mantle rocks, granulite-facies metasedimentary rocks, and felsic igneous rocks. For other garnet types, the assignment to a certain type of host rock remains ambiguous. This is considered insufficient and therefore the evaluated diagrams should be used with great care. We further apply compositional biplot analysis to derive some hints towards future perspectives in detrital garnet discrimination.

  11. Intercomparison of garnet barometers and implications for garnet mixing models

    SciTech Connect

    Anovitz, L.M.; Essene, E.J.

    1985-01-01

    Several well-calibrated barometers are available in the system Ca-Fe-Ti-Al-Si-O, including: Alm+3Ru-3Ilm+Sil+2Qtz (GRAIL), 2Alm+Grreverse arrow6Ru=6Ilm+3An+3Qtz (GRIPS); 2Alm+Gr=3Fa+3An (FAG); 3AnGr+Ky+Qtz (GASP); 2Fs-Fa+Qtz (FFQ); and Gr+Qtz=An+2Wo (WAGS). GRIPS, GRAIL and GASP form a linearly dependent set such that any two should yield the third given an a/X model for the grossular/almandine solid-solution. Application to barometry of garnet granulite assemblages from the Grenville in Ontario yields average pressures 0.1 kb lower for GRIPS and 0.4 kb higher for FAGS using our mixing model. Results from Parry Island, Ontario, yield 8.7 kb from GRAIL as opposed to 9.1 kb using Ganguly and Saxena's model. For GASP, Parry Island assemblages yield 8.4 kb with the authors calibration. Ganguly and Saxena's model gives 5.4 kb using Gasparik's reversals and 8.1 kb using the position of GASP calculated from GRIPS and GRAIL. These corrections allow GRIPS, GRAIL, GASP and FAGS to yield consistent pressures to +/- 0.5 kb in regional metamorphic terranes. Application of their mixing model outside of the fitted range 700-1000 K is not encouraged as extrapolation may yield erroneous results.

  12. Gallium Safety in the Laboratory

    SciTech Connect

    Cadwallader, L.C.

    2003-05-07

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  13. Gallium Safety in the Laboratory

    SciTech Connect

    Lee C. Cadwallader

    2003-06-01

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  14. Garnet ships in a quartzite sea

    NASA Astrophysics Data System (ADS)

    Rogowitz, Anna; Rice, A. Hugh N.; Grasemann, Bernhard; Huet, Benjamin

    2016-04-01

    During progressive deformation, a strong inclusion in a weaker matrix causes a stress concentration that may result in strain localization, seen in a matrix grain-size reduction. A superb example of this phenomena, but rather more complex, has been observed in north Norwegian Caledonides. A probably subvertical metadolerite dyke has been rotated to lie parallel to the penetrative regional low-angled foliation during the emplacement of the overlying nappe. The metadolerite, now only ~1.4 cm thick and lying between two quartzite layers has been retrogressed to a biotite schist with an assemblage of biotite, titanite, epidote group, garnet and quartz. Garnets are from 0.2 mm to 4 cm in size, subhedral and have two growth zones, with inclusions of predominantly titanite and rare amphibole. The country-rock metasedimentary schists contain staurolite, indicating mid-amphibolite-facies conditions (~550 °C and 6 kbar). During late deformation, some garnets were forced into the quartzite, resulting in the development of pronounced gouges (tectoglyphs), up to 70 mm long, 14 mm wide and 14 mm deep, deepening in the direction of movement. Quartz was pushed up at the sides of the gouges and forms a pronounced bow-wave at the front of the garnets. Where garnets are gouged into the quartzite, intense strain localization occurs. Both in front of and under the garnet, a up to 18 mm wide zone of quartz mylonite developed. The mylonitic foliation curves around the garnet, with a relatively sharp boundary to the adjacent quartzite that preserves an older random fabric. Deformation in the mylonite, which shows a strong crystallographic preferred orientation, seems to have occurred by (1) intense dislocation glide followed by (2) subgrain rotation resulting in an almost foam-like fabric. The grain size of the mylonite (at the quartzite-biotite schist interface) increases with increasing distance behind the present position of the garnets. This observation is consistent with an expected

  15. Rare earth garnet selective emitter

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

    1994-01-01

    Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approximately equal to 0.74, ((4)l(sub 15/2)) - ( (4)l(sub13/2)), for Er-YAG and epsilon(sub lambda) approximately equal to 0.65, ((5)l(sub 7))-((5)l(sub 8)) for Ho-YAG) at excellent candidates for high efficiency selective emitters in the thermophotovoltaics (TPV) systems operating at moderate temperatures (1200-1500K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. This paper presents normal spectral emittance, epsilon(sub lambda), measurements of holmium (Ho), and erbium (Er) doped YAG thin film selective emitters at 1500 K, and compares those results with the theoretical spectral emittance.

  16. Water contents of garnets from the Garnet Ridge, northern Arizona: H2O behavior underneath the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Ogasawara, Y.; Sakamaki, K.; Sato, Y.

    2013-12-01

    Kimberlitic volcanism at the Garnet Ridge delivered a wide variety of garnets and garnet-associated rocks in large vertical range from the deep mantle to shallow depths underneath the Colorado Plateau (Smith et al., 2004). Koga and Ogasawara (2012) classified the garnets at the Garnet Ridge into the following nine groups; (a) Cr and pyrope-rich garnet, (b) pyrope-rich reddish brown garnet, (c) reddish brown garnet, (d) garnet in eclogite, (e) garnet in metasomatized eclogite, (f) garnet aggregate, (g) garnet megacryst, (h) garnet in metasomatic rock I, (i) garnet in metasomatic rock II. They regarded these garnets as the four origins: mantle peridotite (a, b), subducted oceanic crust (d, e), high-pressure metasomatism (c, f, g), low-pressure metasomatism (h, i). On the garnets (a, b, d), Sakamaki et al. (2012) preliminary reported OH qualitatively using micro FT-IR spectroscopy. In garnets (a, b), OH was detected clearly, but in garnet (d) OH was below detection limit because the thickness of a doubly polished section of garnet (d) was too small (thickness: ~70 μm) and the concentration was too low. Using micro FT-IR method, this study conducted the quantitative analysis of H2O for 20 grains of group (a), 18 grains of group (b) and 6 grains of group (d). The garnet samples were prepared as doubly polished thick sections (thicknesses of 0.1-1.3 mm). An IR absorption coefficient of 8770 L/mol/cm2 (Katayama et al., 2005) for garnets was used. Significant amounts of hydroxyl were detected in garnets (a, b, d); clear OH bands were identified in garnets (a, b), but very week and extremely broad OH bands in garnet (d). In the analyzed garnets, no zonal distribution of OH was identified. Garnet (a): the IR spectra have a main OH band at 3575 cm-1 and often with a week band at 3675 cm-1. The resultant H2O contents range from the below detection limit to 119 ppm wt. and are distributed at 0~10 and at ca. 100 ppm wt., bimodally. Garnet (b): the IR spectra have a main OH band

  17. Evaluation of absorbed dose in Gadolinium neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Abdullaeva, Gayane; Djuraeva, Gulnara; Kim, Andrey; Koblik, Yuriy; Kulabdullaev, Gairatulla; Rakhmonov, Turdimukhammad; Saytjanov, Shavkat

    2015-02-01

    Gadolinium neutron capture therapy (GdNCT) is used for treatment of radioresistant malignant tumors. The absorbed dose in GdNCT can be divided into four primary dose components: thermal neutron, fast neutron, photon and natural gadolinium doses. The most significant is the dose created by natural gadolinium. The amount of gadolinium at the irradiated region is changeable and depends on the gadolinium delivery agent and on the structure of the location where the agent is injected. To de- fine the time dependence of the gadolinium concentration ρ(t) in the irradiated region the pharmacokinetics of gadolinium delivery agent (Magnevist) was studied at intratumoral injection in mice and intramuscular injection in rats. A polynomial approximation was applied to the experimental data and the influence of ρ(t) on the relative change of the absorbed dose of gadolinium was studied.

  18. Structural, optical and magnetic properties of gadolinium sesquioxide nanobars synthesized via thermal decomposition of gadolinium oxalate

    SciTech Connect

    Manigandan, R.; Giribabu, K.; Suresh, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2013-10-15

    Graphical abstract: - Highlights: • The cubic Gd{sub 2}O{sub 3} nanobars are synthesized by decomposition of C{sub 6}H{sub 20}Gd{sub 2}O{sub 22}. • The nanoparticles are rectangular bar shape with high porous surface. • The combination of magnetic and optical properties within a single particle. • The Gd{sub 2}O{sub 3} nanobars have tailorable nanostructure, wide bandgap and are paramagnetic. - Abstract: Gadolinium oxide nanobars were obtained by thermal decomposition of gadolinium oxalate, which was synthesized by the chemical precipitation method along with glycerol. The functional group analysis and formation of gadolinium oxide from gadolinium oxalate were characterized by the Fourier transform infrared spectroscopy and thermo gravimetric analyzer. The crystal structure, average crystallite size, and lattice parameter were analyzed by X-ray diffraction technique. Moreover, Raman shifts, elemental composition and morphology of the gadolinium oxide was widely investigated by the laser Raman microscope, X-ray photoelectron spectroscopy, FE-SEM-EDAX and HR-TEM, respectively. Furthermore, the optical properties like band gap, absorbance measurement of the gadolinium oxide were extensively examined. In addition, the paramagnetic property of gadolinium oxide nanobars was explored by the vibrating sample magnetometer.

  19. GALLIUM ARSENIDE DENDRITE SINGLE CRYSTAL PROGRAM

    DTIC Science & Technology

    ARSENIDES, *GALLIUM COMPOUNDS, *LABORATORY FURNACES, * SOLAR CELLS , CRUCIBLES, DESIGN, DIFFUSION, EXPLOSIONS, INTERMETALLIC COMPOUNDS, MATERIALS, PHOSPHORUS, SINGLE CRYSTALS, TEMPERATURE CONTROL, ZINC

  20. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Gallium. 173.162 Section 173.162 Transportation... PACKAGINGS Non-bulk Packaging for Hazardous Materials Other Than Class 1 and Class 7 § 173.162 Gallium. (a) Except when packaged in cylinders or steel flasks, gallium must be packaged in packagings which meet...

  1. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Gallium. 173.162 Section 173.162 Transportation... PACKAGINGS Non-bulk Packaging for Hazardous Materials Other Than Class 1 and Class 7 § 173.162 Gallium. (a) Except when packaged in cylinders or steel flasks, gallium must be packaged in packagings which meet...

  2. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Gallium. 173.162 Section 173.162 Transportation... PACKAGINGS Non-bulk Packaging for Hazardous Materials Other Than Class 1 and Class 7 § 173.162 Gallium. (a) Except when packaged in cylinders or steel flasks, gallium must be packaged in packagings which meet...

  3. 49 CFR 173.162 - Gallium.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Gallium. 173.162 Section 173.162 Transportation... PACKAGINGS Non-bulk Packaging for Hazardous Materials Other Than Class 1 and Class 7 § 173.162 Gallium. (a) Except when packaged in cylinders or steel flasks, gallium must be packaged in packagings which meet...

  4. Progress in gallium arsenide semiconductors

    SciTech Connect

    Brodsky, M.H. )

    1990-02-01

    After almost 30 years as the technology of the future, gallium arsenide has begun to make a place for itself, not by supplanting silicon but by complementing it in new applications. The inherent advantages of the material lie in the speed with which electrons move through it, in weak-signal operations and in the generation and detection of light. These advantages suit it for roles in computing, television reception and the optoelectronic transmission of data through optical-fiber networks. Gallium arsenide light-emitting diodes and lasers used in visual-display technologies and audio-disk players already account for more than $1 billion in sales annually. Hundreds of thousands of satellite-receiving dishes that use gallium arsenide detectors are sold every year, and high-speed circuits using gallium arsenide transistors are projected to reach a similar turnover in a few years. In an economy and society that depend on the rapid exchange of information as well as on the processing of it, many silicon-dominated processors will require a considerable admixture of gallium arsenide components in order to do their jobs.

  5. Magnetodielectric coupling in multiferroic holmium iron garnets

    NASA Astrophysics Data System (ADS)

    Malar Selvi, M.; Chakraborty, Deepannita; Venkateswaran, C.

    2017-02-01

    Single phase magneto-electric multiferroics require a large magnetic or electric field for producing magneto-electric (ME) and magnetodielectric (MD) effects. For utilizing these effects in devices investigations on the room temperature and low field MD studies are necessary. Recently, efforts have been largely devoted to the investigation of rare earth iron garnets. In the physical method, the preparation of rare earth iron garnet requires high sintering temperature and processing time. To solve these problems, ball milling assisted microwave sintering technique is used to prepare nanocrystalline holmium iron garnets (Ho3Fe5O12). Magnetic and dielectric properties of the prepared sample are investigated. These properties get enhanced in nanocrystalline form when compared to the bulk. The MD coupling of the prepared sample is evident from the anomaly in the temperature dependent dielectric constant plot and the ME coupling susceptibility is derived from the room temperature MD measurements.

  6. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

    1995-01-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  7. Medical applications and toxicities of gallium compounds.

    PubMed

    Chitambar, Christopher R

    2010-05-01

    Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use.

  8. Combinatorial pulsed laser deposition of doped yttrium iron garnet films on yttrium aluminium garnet

    NASA Astrophysics Data System (ADS)

    Sposito, A.; Gregory, S. A.; de Groot, P. A. J.; Eason, R. W.

    2014-02-01

    We investigate the crystalline growth of yttrium iron garnet (YIG) films doped with bismuth (Bi) and cerium (Ce) by combinatorial pulsed laser deposition, co-ablating a YIG target and either a Bi2O3 or a CeO2 target, for applications in microwave and optical communications. Substrate temperature is critical for crystalline growth of YIG with simultaneous inclusion of Bi in the garnet lattice, whereas Ce is not incorporated in the garnet structure, but forms a separate CeO2 phase.

  9. Combinatorial pulsed laser deposition of doped yttrium iron garnet films on yttrium aluminium garnet

    SciTech Connect

    Sposito, A. Eason, R. W.; Gregory, S. A.; Groot, P. A. J. de

    2014-02-07

    We investigate the crystalline growth of yttrium iron garnet (YIG) films doped with bismuth (Bi) and cerium (Ce) by combinatorial pulsed laser deposition, co-ablating a YIG target and either a Bi{sub 2}O{sub 3} or a CeO{sub 2} target, for applications in microwave and optical communications. Substrate temperature is critical for crystalline growth of YIG with simultaneous inclusion of Bi in the garnet lattice, whereas Ce is not incorporated in the garnet structure, but forms a separate CeO{sub 2} phase.

  10. Micro-Raman spectra of ugrandite garnet.

    PubMed

    Moroz, T; Ragozin, A; Salikhov, D; Belikova, G; Puchkov, V; Kagi, H

    2009-08-01

    The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X(3)Y(2)(SiO(4))(3), X = Ca(2+), Y = Al(3+), Fe(3+), Cr(3+), according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.

  11. Micro-Raman spectra of ugrandite garnet

    NASA Astrophysics Data System (ADS)

    Moroz, T.; Ragozin, A.; Salikhov, D.; Belikova, G.; Puchkov, V.; Kagi, H.

    2009-08-01

    The natural garnets from chromite ores associated with pegmatoid pyroxenites of Sangalyk area (Uchaly ore district, southern Urals, Russia) were studied by means of micro-Raman spectroscopy. The compositions of these garnets were close to ugrandite, an isomorphous intermediate group of uvarovite-grossularite-andradite, X 3Y 2(SiO 4) 3, X = Ca 2+, Y = Al 3+, Fe 3+, Cr 3+, according to Raman spectra and X-ray microprobe analyses. An assignment of most of the observed bands in visible and near infrared Raman spectra is reported.

  12. Gallium and Reactor Neutrino Anomalies

    NASA Astrophysics Data System (ADS)

    Acero, M. A.; Giunti, C.; Laveder, M.

    2009-03-01

    The observed deficit in the Gallium radioactive source experiments may be interpreted as a possible indication of active-sterile ν mixing. In the effective framework of two-neutrino mixing we obtain sin2ϑ≳0.03 and Δm≳0.1 eV. The compatibility of this result with the data of the Bugey reactor ν disappearance experiments is studied. It is found that the Bugey data present a hint of neutrino oscillations with 0.02≲sin2ϑ≲0.08 and Δm≈1.8 eV, which is compatible with the Gallium allowed region of the mixing parameters. This hint persists in the combined analysis of Gallium, Bugey, and Chooz data.

  13. Microwave filter based on Lamb modes for optoelectronic generator

    NASA Astrophysics Data System (ADS)

    Vitko, V. V.; Nikitin, A. A.; Kondrashov, A. V.; Nikitin, A. A.; Ustinov, A. B.; Belyavskiy, P. Yu; Kalinikos, B. A.; Butler, J. E.

    2015-12-01

    Experimental results for narrowband filter based on yttrium iron garnet film epitaxially grown on gadolinium gallium garnet substrate have been shown. The principle of operation of the filter is based on excitation of Lamb modes in the substrate. We demonstrated also that the use of single crystal diamond as a substrate will significantly reduce the phase noise of the designed optoelectronic microwave generator.

  14. Mineral resource of the month: gallium

    USGS Publications Warehouse

    Jaskula, Brian W.

    2009-01-01

    The metal element gallium occurs in very small concentrations in rocks and ores of other metals — native gallium is not known. As society gets more and more high-tech, gallium becomes more useful. Gallium is one of only five metals that are liquid at or close to room temperature. It has one of the longest liquid ranges of any metal (29.8 degrees Celsius to 2204 degrees Celsius) and has a low vapor pressure even at high temperatures. Ultra-pure gallium has a brilliant silvery appearance, and the solid metal exhibits conchoidal fracture similar to glass.

  15. Gadolinium: Central Metal of the Lanthanoids

    ERIC Educational Resources Information Center

    Laing, Michael

    2009-01-01

    The physical and chemical properties of gadolinium are compared with those of the other lanthanoids. Some properties are intermediate between those of lanthanum and lutetium; some between those of barium and hafnium; and others (unexpectedly) between those of ytterbium and lutetium. Both the remarkably high molar heat capacity of the metal and the…

  16. A toxicological study of gadolinium nitrate

    SciTech Connect

    London, J.E.

    1988-05-01

    The sensitization study in the guinea pig did not show gadolinium nitrate to have potential sensitizing properties. Skin application studies in the rabbit demonstrated that it was cutaneously a severe irritant. This material was considered an irritant in the rabbit eye application studies. 3 refs., 1 tab.

  17. Renal amyloidosis. Evaluation by gallium imaging

    SciTech Connect

    Lee, V.W.; Skinner, M.; Cohen, A.S.; Ngai, S.; Peng, T.T.

    1986-09-01

    A study has been performed to evaluate the efficacy of gallium imaging in the detection of renal amyloidosis. Ten of the 11 patients who had biopsy-proven renal amyloidosis demonstrated marked uptake in both kidneys. One patient revealed moderate gallium uptake in his kidneys. None of the patients had underlying renal or extrarenal pathology other than amyloidosis, which could account for renal gallium uptake (renal infection, neoplasm, hepatic failure or frequent blood transfusions). Four patients also had extrarenal foci of abnormal gallium uptake, suggesting other sites of amyloid deposits. Our data strongly suggest that gallium imaging has a high sensitivity for detection of renal amyloidosis. Its specificity is enhanced significantly by careful review of the clinical history to exclude other known causes of renal gallium uptake. Potentially, gallium imaging may be used to monitor the progress of patients under experimental therapy.

  18. Potential effects of gallium on cladding materials

    SciTech Connect

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  19. Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide.

    PubMed

    Tanaka, Akiyo

    2004-08-01

    Gallium arsenide (GaAs), indium arsenide (InAs), and aluminium gallium arsenide (AlGaAs) are semiconductor applications. Although the increased use of these materials has raised concerns about occupational exposure to them, there is little information regarding the adverse health effects to workers arising from exposure to these particles. However, available data indicate these semiconductor materials can be toxic in animals. Although acute and chronic toxicity of the lung, reproductive organs, and kidney are associated with exposure to these semiconductor materials, in particular, chronic toxicity should pay much attention owing to low solubility of these materials. Between InAs, GaAs, and AlGaAs, InAs was the most toxic material to the lung followed by GaAs and AlGaAs when given intratracheally. This was probably due to difference in the toxicity of the counter-element of arsenic in semiconductor materials, such as indium, gallium, or aluminium, and not arsenic itself. It appeared that indium, gallium, or aluminium was toxic when released from the particles, though the physical character of the particles also contributes to toxic effect. Although there is no evidence of the carcinogenicity of InAs or AlGaAs, GaAs and InP, which are semiconductor materials, showed the clear evidence of carcinogenic potential. It is necessary to pay much greater attention to the human exposure of semiconductor materials.

  20. Hydrous Na-garnet from Garnet Ridge; products of mantle metasomatism underneath the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Sakamaki, Kunihiko; Sato, Yuto; Ogasawara, Yoshihide

    2016-12-01

    This is the first report on amphibole exsolution in pyrope from the Colorado Plateau. Pyrope crystals delivered from mantle depths underneath the Colorado Plateau by kimberlitic volcanism at 30 Ma were collected at Garnet Ridge, northern Arizona. The garnet grains analyzed in this study occur as discrete crystals (without adjacent rock matrix) and are classified into two major groups, Cr-rich pyrope and Cr-poor pyrope. The Cr-poor pyrope group is divided into four subgroups based on exsolved phases: amphibole lamella type, ilmenite lamella type, dense lamellae type, and clinopyroxene/amphibole lamellae type. Exsolved amphibole occurs in amphibole lamella type, dense lamellae type, and clinopyroxene/amphibole lamellae type of Cr-poor pyrope. The amphibole crystals tend to have preferred orientations in their garnet hosts and occur as monomineralic hexagonal or rhombic prisms and tablets, and as multimineralic needles or blades with other exsolved phases. Exsolved amphibole has pargasitic compositions (Na2O up to 1.6 apfu based on 23 oxygen). Garnet host crystals that have undergone amphibole exsolution have low OH contents (2-42 ppmw H2O) compared to garnets that do not have amphibole lamellae (up to 115 ppmw H2O). The low OH contents of garnets hosting amphibole lamellae suggest loss of OH from garnet during amphibole exsolution. Amphibole exsolution from pyrope resulted from breakdown of a precursor "hydrous Na-garnet" composition (Mg,Na+ x)3(Al2 - x, Mgx)2Si3O12 - 2x(OH)2x. Exsolution of amphibole and other phases probably occurred during exhumation to depths shallower than 100 km prior to volcanic eruption.

  1. Major element chemistry and inclusion/lamella mineralogy of garnets from the Garnet Ridge in the Colorado Plateau, northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Koga, I.; Ogasawara, Y.

    2014-12-01

    Various garnets with diverse features and origins occur in the Garnet Ridge. These were transported from upper mantle to crustal depths underneath the Colorado Plateau by a kimberlitic diatreme (ca. 30 Ma) as xenocrysts and xenoliths. On the basis of major element chemistry, inclusion/lamella mineralogy, color, and host rocks of garnets, the Garnet Ridge garnets were classified into the following ten groups (Table) using 495 analyzed grains: A. Cr and pyrope-rich garnet, B. pyrope-rich reddish brown garnet, C. garnet aggregate, D. garnet megacryst, E. garnet in eclogite, F. garnet in metasomatized eclogite, G. quartz lamellae-bearing garnet, H. garnet in metasomatic rock I, I. garnet in metasomatic rock II, J. almandine-rich garnet. A and B are of mantle peridotite origins. Both garnets were characterized by Cr-Spl lamellae for A, and Cpx/Amp lamellae for B, respectively. B is subdivided into 2 types by lamellae and inclusions: (Prp 49-66, Grs 16-26 mol%) lamellae of Rt, Ilm, Cpx, Amp, and Chl, and (Prp 47-66, Grs 11-24 mol%) lamellae of Ilm and fluid inclusions. C and D have similar chemistry and inclusion/lamella mineralogy. The chemistry (Prp 22-53, Grs 11-41, Alm 26-50 mol%) and the wide variation suggest metasomatism at mantle depths. E includes Rt, Omp, Zrn, Ap, Kfs, and simplectite of Zo + Ab. F contains Rt, Omp, and Ap. Both E and F have chemical zonation from core to rim in Alm component. These garnets are of subducted oceanic slab origins, probably Fallaron plate. G includes Cpx, Zrn, and fluid, and oriented lamellae of Rt, Ap, and Qtz. Oriented Qtz lamellae characterize this group. The host rock of H is of metasomatism origin at crustal depths. H has Grs-rich composition and inclusions of Mt, Zo, Ttn, Ap and fluid. I has lamellae of Rt and crichtonites, and includes Qtz and Zrn. The host rock of I was strongly altered. J shows chemical zonation from core to rim in Alm component. This garnet includes Pl, Qtz, Ilm with Mt lamellae, and Rt lamella. The

  2. Inhibitors in LPE growth of garnets

    NASA Astrophysics Data System (ADS)

    De Roode, W. H.; Robertson, J. M.

    1983-09-01

    The growth rate of LPE growth garnets can be reduced considerably by the addition of small amounts of group II oxides. This effect can be helpful for the controlled growth of very thin garnet films for sub-micron bubbles and optical devices. The largest effect was found with the addition of Mg 2+ and Ca 2+, resulting in a maximum decrease of the growth rate of approximately 70%. A semi-empirical formula was used to describe the growth rate as a function of the dipping temperature. The change in the growth rate on the addition of the inhibitor ion at constant temperature was found to be proportional to ( aMO)/( aMO+2 Ln 2O 3), where M is a group II element, Ln 2O 2 is the sum of the yttrium and RE oxides in the melt, and a is the inhibitor factor. The value of the inhibitor factor depends on both the inhibitor ion as well as the composition of the garnet. The lowering of the growth rate on the addition of an inhibitor ion is explained by the introduction of an extra growth resistance due to the charge compensation mechanism of the divalent ions. The influence of the different charge compensation possibilities in the garnet system is examined and the relative importance of these possibilities for charge compensation is discussed.

  3. Quantification of water in majoritic garnet

    SciTech Connect

    Thomas, Sylvia -Monique; Wilson, Kathryn; Koch-Muller, Monika; Hauri, Erik H.; McCammon, Catherine; Jacobsen, Steven D.; Lazarz, John; Rhede, Dieter; Ren, Minghua; Blair, Neal; Lenz, Stephan

    2015-05-01

    Majoritic garnet, characterized by an excess of silicon (>3 Si per formula unit), is considered one of the major phases of the Earth’s transition zone from 410-660 km depth. Quantifying the H2O content of nominally anhydrous mantle minerals is necessary to evaluate their water storage capacity from experiments and modeling the Earth’s deep water cycle. We present mineral-specific infrared absorption coefficients for the purpose of quantifying the amount of water incorporated into majorite as hydroxyl point defects. A suite of majoritic garnet samples with varying proportions of Si, Fe, Al, Cr and H2O was synthesized at conditions of 18-19 GPa and 1500-1800°C. Single-crystals were characterized using X-ray diffraction, electron microprobe analysis, secondary Ion Mass spectrometry (SIMS), IR, Raman and Mössbauer spectroscopy. We utilize SIMS and Raman spectroscopy in combination with IR spectroscopy to provide IR absorption coefficients for water in majoritic garnets with the general mineral formula (Mg,Fe)3(Si,Mg,Fe,Al,Cr)2[SiO4]3. Furthermore, the IR absorption coefficient for majoritic garnet in the OH stretching region is frequency-dependent and ranges from 10 470 ± 3100 Lmol-1cm-2 to 23 400 ± 2300 Lmol-1cm-2.

  4. Quantification of water in majoritic garnet

    DOE PAGES

    Thomas, Sylvia -Monique; Wilson, Kathryn; Koch-Muller, Monika; ...

    2015-05-01

    Majoritic garnet, characterized by an excess of silicon (>3 Si per formula unit), is considered one of the major phases of the Earth’s transition zone from 410-660 km depth. Quantifying the H2O content of nominally anhydrous mantle minerals is necessary to evaluate their water storage capacity from experiments and modeling the Earth’s deep water cycle. We present mineral-specific infrared absorption coefficients for the purpose of quantifying the amount of water incorporated into majorite as hydroxyl point defects. A suite of majoritic garnet samples with varying proportions of Si, Fe, Al, Cr and H2O was synthesized at conditions of 18-19 GPamore » and 1500-1800°C. Single-crystals were characterized using X-ray diffraction, electron microprobe analysis, secondary Ion Mass spectrometry (SIMS), IR, Raman and Mössbauer spectroscopy. We utilize SIMS and Raman spectroscopy in combination with IR spectroscopy to provide IR absorption coefficients for water in majoritic garnets with the general mineral formula (Mg,Fe)3(Si,Mg,Fe,Al,Cr)2[SiO4]3. Furthermore, the IR absorption coefficient for majoritic garnet in the OH stretching region is frequency-dependent and ranges from 10 470 ± 3100 Lmol-1cm-2 to 23 400 ± 2300 Lmol-1cm-2.« less

  5. Oligonuclear gallium nitrogen cage compounds: molecular intermediates on the way from gallium hydrazides to gallium nitride.

    PubMed

    Uhl, Werner; Abel, Thomas; Hagemeier, Elke; Hepp, Alexander; Layh, Marcus; Rezaeirad, Babak; Luftmann, Heinrich

    2011-01-03

    Gallium hydrazides are potentially applicable as facile starting compounds for the generation of GaN by thermolysis. The decomposition pathways are, however, complicated and depend strongly on the substituents attached to the gallium atoms and the hydrazido groups. This paper describes some systematic investigations into the thermolysis of the gallium hydrazine adduct Bu(t)(3)Ga←NH(2)-NHMe (1a) and the dimeric gallium hydrazides [R(2)Ga(N(2)H(2)R')](2) (2b, R = Bu(t), R' = Bu(t); 2c, R = Pr(i), R' = Ph; 2d, R = Me, R' = Bu(t)) which have four- or five-membered heterocycles in their molecular cores. Heating of the adduct 1a to 170 °C gave the heterocyclic compound Bu(t)(2)Ga(μ-NH(2))[μ-N(Me)-N(=CH(2))]GaBu(t)(2) (3) by cleavage of N-N bonds and rearrangement. 3 was further converted at 400 °C into the tetrameric gallium cyanide (Bu(t)(2)GaCN)(4) (4). The thermolysis of the hydrazide (Bu(t)(2)Ga)(2)(NH-NHBu(t))(2) (2b) at temperatures between 270 and 420 °C resulted in cleavage of all N-N bonds and the formation of an octanuclear gallium imide, (Bu(t)GaNH)(8) (6). The trimeric dialkylgallium amide (Bu(t)(2)GaNH(2))(3) (5) was isolated as an intermediate. Thermolysis of the hydrazides (Pr(i)(2)Ga)(2)(NH-NHPh)(NH(2)-NPh) (2c) and (Me(2)Ga)(2)(NH-NHBu(t))(2) (2d) proceeded in contrast with retention of the N-N bonds and afforded a variety of novel gallium hydrazido cage compounds with four gallium atoms and up to four hydrazido groups in a single molecule: (Pr(i)Ga)(4)(NH-NPh)(3)NH (7), (MeGa)(4)(NH-NBu(t))(4) (8), (MeGa)(4)(NH-NBu(t))(3)NBu(t) (9), and (MeGa)(4)(NHNBu(t))(3)NH (10). Partial hydrolysis gave reproducibly the unique octanuclear mixed hydrazido oxo compound (MeGa)(8)(NHNBu(t))(4)O(4) (11).

  6. P-type gallium nitride

    DOEpatents

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  7. P-type gallium nitride

    DOEpatents

    Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

    1997-01-01

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

  8. Gallium scan in intracerebral sarcoidosis

    SciTech Connect

    Makhija, M.C.; Anayiotos, C.P.

    1981-07-01

    Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

  9. Liquid gallium rotary electric contract

    NASA Technical Reports Server (NTRS)

    Przybyszewski, J. S.

    1969-01-01

    Due to its low vapor pressure, gallium, when substituted for mercury in a liquid slip ring system, transmits substantial amounts of electrical current to rotating components in an ultrahigh vacuum. It features low electrical loss, little or no wear, and long maintenance-free life.

  10. Wavelength dependence of Verdet constant of Pr doped terbium gallium garnet crystal

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Yang, Lei; Wang, Xiangyong; Hang, Yin

    2016-12-01

    Samples of the magneto-active material - Pr3+: Tb3Ga5O12 crystals with Pr3+ ion concentration of 1%, 2%, 3% and 5%. The Verdet constant measurement has been carried out at room temperature in the 400-1500 nm range for all crystal samples and was compared with a pure Tb3Ga5O12 material. A high value of the Verdet constant for 5% Pr3+: Tb3Ga5O12 crystal was obtained at room temperature - namely, 324.5, 200.1 and 68.7 rad/(T·m) for 532, 632.8 and 1064 nm, respectively. The Verdet constant of Pr doped TGG crystal at 1064 nm is much more higher than that of TGG. The superior performance of the materials indicates that Pr3+: Tb3Ga5O12 crystals have great potential to meet the increasing demand for magneto-optical devices in the VIS-NIR wavelength.

  11. Gallium nitride electronics

    NASA Astrophysics Data System (ADS)

    Rajan, Siddharth; Jena, Debdeep

    2013-07-01

    In the past two decades, there has been increasing research and industrial activity in the area of gallium nitride (GaN) electronics, stimulated first by the successful demonstration of GaN LEDs. While the promise of wide band gap semiconductors for power electronics was recognized many years before this by one of the contributors to this issue (J Baliga), the success in the area of LEDs acted as a catalyst. It set the field of GaN electronics in motion, and today the technology is improving the performance of several applications including RF cell phone base stations and military radar. GaN could also play a very important role in reducing worldwide energy consumption by enabling high efficiency compact power converters operating at high voltages and lower frequencies. While GaN electronics is a rapidly evolving area with active research worldwide, this special issue provides an opportunity to capture some of the great advances that have been made in the last 15 years. The issue begins with a section on epitaxy and processing, followed by an overview of high-frequency HEMTs, which have been the most commercially successful application of III-nitride electronics to date. This is followed by review and research articles on power-switching transistors, which are currently of great interest to the III-nitride community. A section of this issue is devoted to the reliability of III-nitride devices, an area that is of increasing significance as the research focus has moved from not just high performance but also production-worthiness and long-term usage of these devices. Finally, a group of papers on new and relatively less studied ideas for III-nitride electronics, such as interband tunneling, heterojunction bipolar transistors, and high-temperature electronics is included. These areas point to new areas of research and technological innovation going beyond the state of the art into the future. We hope that the breadth and quality of articles in this issue will make it

  12. Method of separating and purifying gadolinium-153

    DOEpatents

    Bray, Lane A [Richland, WA; Corneillie, Todd M [Davis, CA

    2001-01-01

    The present invention is an improvement to the method of separating and purifying gadolinium from a mixture of gadolinium and europium having the steps of (a) dissolving the mixture in an acid; (b) reducing europium+3 to europium+2; and (c) precipitating the europium+2 with a sulfate ion in a superstoichiometric amount; wherein the improvement is achieved by using one or more of the following: (i) the acid is an anoic acid; (ii) the reducing is with zinc metal in the absence of a second metal or with an amount of the second metal that is ineffective in the reducing; (iii) adding a group IIA element after step (c) for precipitating the excess sulfate prior to repeating step (c); (iv) the sulfate is a sulfate salt with a monovalent cation; (v) adding cold europium+3 prior to repeating step (c).

  13. Construction of Gallium Point at NMIJ

    NASA Astrophysics Data System (ADS)

    Widiatmo, J. V.; Saito, I.; Yamazawa, K.

    2017-03-01

    Two open-type gallium point cells were fabricated using ingots whose nominal purities are 7N. Measurement systems for the realization of the melting point of gallium using these cells were built. The melting point of gallium is repeatedly realized by means of the measurement systems for evaluating the repeatability. Measurements for evaluating the effect of hydrostatic pressure coming from the molten gallium existing during the melting process and the effect of gas pressure that fills the cell were also performed. Direct cell comparisons between those cells were conducted. This comparison was aimed to evaluate the consistency of each cell, especially related to the nominal purity. Direct cell comparison between the open-type and the sealed-type gallium point cell was also conducted. Chemical analysis was conducted using samples extracted from ingots used in both the newly built open-type gallium point cells, from which the effect of impurities in the ingot was evaluated.

  14. Running droplets of gallium from evaporation of gallium arsenide.

    PubMed

    Tersoff, J; Jesson, D E; Tang, W X

    2009-04-10

    High-temperature annealing of gallium arsenide in vacuum causes excess evaporation of arsenic, with accumulation of gallium as liquid droplets on the surface. Using real-time in situ surface electron microscopy, we found that these droplets spontaneously run across the crystal surface. Running droplets have been seen in many systems, but they typically require special surface preparation or gradient forces. In contrast, we show that noncongruent evaporation automatically provides a driving force for running droplets. The motion is predicted and observed to slow and stop near a characteristic temperature, with the speed increasing both below and above this temperature. The same behavior is expected to occur during the evaporation of similar III-V semiconductors such as indium arsenide.

  15. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  16. Garnet phosphors prepared via hydrothermal synthesis

    SciTech Connect

    Phillips, M.L.F.; Walko, R.J.; Shea, L.E.

    1996-05-01

    This project studied hydrothermal synthesis as a route to producing green-emitting cathodoluminescent phosphorus isostructural with yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, or YAG). Aqueous precipitation of Y, Gd, Al, Ga, and Tb salts produced amorphous gels, which were heated with water at 600 C and 3,200 bar to produce crystalline YAG:Tb, Y{sub 3}Ga{sub 5}O{sub 12}:Tb, Y{sub 3}Al{sub 3}Ga{sub 2}O{sub 12}:Tb, and Gd{sub 3}Ga{sub 5}O{sub 12}:Tb powders. Process parameters were identified that yielded submicron YAG:Tb and Y{sub 3}Ga{sub 5}O{sub 12}:Tb powders without grinding. Cathodoluminescent efficiencies were measured as functions of power density at 600 V, using both the hydrothermal garnets and identical phosphor compositions synthesized at high temperatures. Saturation behavior was independent of synthetic technique, however, the hydrothermal phosphorus were less susceptible to damage (irreversible efficiency loss) at very high power densities (up to 0.1 W/cm{sup 2}). The fine grain sizes available with hydrothermal synthesis make it an attractive method for preparing garnet phosphorus for field emission, projection, and head-up displays.

  17. Garnets from the Camafuca-Camazambo kimberlite (Angola).

    PubMed

    Correia, Eugénio A; Laiginhas, Fernando A T P

    2006-06-01

    This work presents a geochemical study of a set of garnets, selected by their colors, from the Camafuca-Camazambo kimberlite, located on northeast Angola. Mantle-derived garnets were classified according to the scheme proposed by Grütter et al. (2004) and belong to the G1, G4, G9 and G10 groups. Both sub-calcic (G10) and Ca-saturated (G9) garnets, typical, respectively, of harzburgites and lherzolites, were identified. The solubility limit of knorringite molecule in G10D garnets suggests they have crystallized at a minimum pressure of about 40 to 45 kbar (4-4.5 GPa). The occurrence of diamond stability field garnets (G10D) is a clear indicator of the potential of this kimberlite for diamond. The chemistry of the garnets suggests that the source for the kimberlite was a lherzolite that has suffered a partial melting that formed basaltic magma, leaving a harzburgite as a residue.

  18. Hepatocellular carcinoma detection by gallium scan and subsequent treatment by gallium maltolate: rationale and case study.

    PubMed

    Bernstein, Lawrence R; van der Hoeven, Jacobus J M; Boer, Robbert O

    2011-07-01

    Gallium is antiproliferative to many types of cancer, due primarily to its ability to act as a non-functional mimic of ferric iron (Fe(3+)). Because Fe(3+) is needed for ribonucleotide reductase activity--and thus DNA synthesis--gallium can inhibit DNA production and cell division. Diagnostic gallium scans have shown that hepatocellular carcinoma (HCC) is commonly avid for gallium. Furthermore, in vitro studies have found that gallium nitrate, and particularly gallium maltolate (GaM), have dose-dependent antiproliferative activity against HCC cell lines. Rationale thus exists to use GaM, an orally active compound that has been well tolerated in Phase I clinical trials, to treat patients whose HCC is gallium-avid in a gallium scan. Because gallium absorbed from orally administered GaM is bound predominately to serum transferrin, which travels to all tissues in the body, GaM has the potential to treat even distant metastases. A patient with advanced HCC (20 × 10 cm primary tumor, ascites around liver and spleen, resistant to Nexavar(®) (sorafenib)), whose cancer was highly gallium-avid in a (67)Ga-scan, was treated with oral gallium maltolate at 1500 mg/day q.d. After four weeks of treatment, the patient had a large reduction in pain, with greatly increased mobility and quality of life, and significantly lowered serum bilirubin and inflammation-related liver enzymes. At eight weeks, CT scans showed apparent necrosis of the tumor.

  19. Growth and characterization of (Y[sub 3]Fe[sub 5]O[sub 12]--Bi[sub 3]Fe[sub 5]O[sub 12]) heterostructures by pulsed laser deposition

    SciTech Connect

    Simion, B.M.; Thomas, G. ); Ramesh, R.; Keramidas, V.G. ); Pfeffer, R.L. )

    1995-02-13

    Superlattice heterostructures consisting of alternating single crystalline ferrimagnetic yttrium--iron--garnet (YIG) and bismuth--iron--garnet (BIG) thin film layers on gadolinium--gallium--garnet substrates show an increased saturation magnetization with respect to that of the monolayered structures grown under the same conditions. The observed effect is attributed to the distortions introduced in the YIG layers by the adjacent BIG layers. In this letter, we report our growth approach, by pulsed laser deposition, of these unusually performing thin film heterostructures.

  20. Creep of Oxide Single Crystals

    DTIC Science & Technology

    1990-08-01

    literature data on Gd 3Ga5O1 2 (8) indicate that garnets may be highly deformation resistant at temperatures very close to their melting points...Data for Yttrium Aluminum Garnet Single Crystals Temperature Stress Creep Rate (sec 1 ) for Given Stress Direction (0C) (MPa) [111] [110] [100] 1650...Gadolinium Gallium Garnet Single Crystals," J.Mat.Sci., 17, 878-884 (1982). 9. B.M. Wanklyn, Clarendon Laboratory, personal communicaticn. 10. S.B. Austerman

  1. Cost and availability of gadolinium for nuclear fuel reprocessing plants

    SciTech Connect

    Klepper, O.H.

    1985-06-01

    Gadolinium is currently planned for use as a soluble neutron poison in nuclear fuel reprocessing plants to prevent criticality of solutions of spent fuel. Gadolinium is relatively rare and expensive. The present study was undertaken therefore to estimate whether this material is likely to be available in quantities sufficient for fuel reprocessing and at reasonable prices. It was found that gadolinium, one of 16 rare earth elements, appears in the marketplace as a by-product and that its present supply is a function of the production rate of other more prevalent rare earths. The potential demand for gadolinium in a fuel reprocessing facility serving a future fast reactor industry amounts to only a small fraction of the supply. At the present rate of consumption, domestic supplies of rare earths containing gadolinium are adequate to meet national needs (including fuel reprocessing) for over 100 years. With access to foreign sources, US demands can be met well beyond the 21st century. It is concluded therefore that the supply of gadolinium will quite likely be more than adequate for reprocessing spent fuel for the early generation of fast reactors. The current price of 99.99% pure gadolinium oxide lies in the range $50/lb to $65/lb (1984 dollars). By the year 2020, in time for reprocessing spent fuel from an early generation of large fast reactors, the corresponding values are expected to lie in the $60/lb to $75/lb (1984 dollars) price range. This increase is modest and its economic impact on nuclear fuel reprocessing would be minor. The economic potential for recovering gadolinium from the wastes of nuclear fuel reprocessing plants (which use gadolinium neutron poison) was also investigated. The cost of recycled gadolinium was estimated at over twelve times the cost of fresh gadolinium, and thus recycle using current recovery technology is not economical. 15 refs., 4 figs., 11 tabs.

  2. Inclusion/lamella mineralogy and chemical characteristics of garnets from the Garnet Ridge in the Colorado Plateau, northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Ogasawara, Y.

    2013-12-01

    A wide variety of garnets as xenocrysts and those in xenoliths, come from kimberlitic diatreme (Smith et al. 2004), occurs at the Garnet Ridge. Koga and Ogasawara (2012) classified these garnets into 9 groups: (a) Cr and pyrope-rich garnet, (b) pyrope-rich reddish brown garnet, (c) reddish brown garnet, (d) garnet in eclogite, (e) garnet in metasomatized eclogite, (f) garnet aggregate, (g) garnet megacryst, (h) garnet in metasomatic rock I, (i) garnet in metasomatic rock II. They divided genetically these groups into four: mantle peridotite (a, b), subducted oceanic crust (d, e), high-pressure metasomatism (c, f, g), low-pressure metasomatism (h, i).In this study, the following 4 groups (a, b, f, g) were chose for inclusion mineralogy by laser Raman spectroscopy. Groups (a) and (b): pyrope-rich garnets (a: 45-82, b: 61-80 Prp mol%) both Cr-rich and Cr-poor (a: 1.0-5.9, b: 0.0-1.0 wt.% Cr2O3) are Ca-poor (1.5-7.0 wt.% CaO) and single-crystals of 5-15 mm in diameter. Group (a) is identical to chrome-pyrope based on the classification of kimberlitic garnets by Dawson and Stephens (1975). CaO-Cr2O3 ratio of (a, b) indicates lherzorite origin (Turkin and Sobolev 2009). Wang et al. (1999) have reported the detailed inclusion and lamella mineralogy of pyrope-rich garnets from the Garnet Ridge. We identified inclusions of Chl (OH: 3450, 3582, 3679 cm-1), Amp (OH: 3685, 3711 cm-1), Ol, Opx, Cpx, Rt (OH: 3295 cm-1), Mgs, Dol, Cal, sulfides, fluid (OH: 3445 cm-1) and spherical composite inclusions of Amp, Ap, Dol, Mgs, Rt and sulfides, and oriented lamellae (presumable exsolution) of Qz, Ol, Opx, Cpx, Amp, Chl, Rt, Ilm, crichtonite (6-7 Peaks at 120-820 cm-1), carmichaelite (710-782 cm-1, OH: 3340 cm-1), Ap (OH: 3570 cm-1) and Ti-Chn (OH: 3404, 3527, 3564 cm-1) adjacent to the oriented Ol. The mineral assemblages of the inclusion and lamella show a correlation with the host garnet compositions; inclusions: (a, b) Ol + Opx + Cpx × composite, (b, low Mg) Opx + Cpx + Amp

  3. Pure spin current transport in gallium doped zinc oxide

    NASA Astrophysics Data System (ADS)

    Althammer, Matthias; Mukherjee, Joynarayan; Geprägs, Stephan; Goennenwein, Sebastian T. B.; Opel, Matthias; Ramachandra Rao, M. S.; Gross, Rudolf

    2017-01-01

    We study the flow of a pure spin current through zinc oxide by measuring the spin Hall magnetoresistance (SMR) in thin film trilayer samples consisting of bismuth-substituted yttrium iron garnet (Bi:YIG), gallium-doped zinc oxide (Ga:ZnO), and platinum. We investigate the dependence of the SMR magnitude on the thickness of the Ga:ZnO interlayer and compare to a Bi:YIG/Pt bilayer. We find that the SMR magnitude is reduced by almost one order of magnitude upon inserting a Ga:ZnO interlayer and continuously decreases with increasing interlayer thickness. Nevertheless, the SMR stays finite even for a 12 nm thick Ga:ZnO interlayer. These results show that a pure spin current indeed can propagate through a several nm-thick degenerately doped zinc oxide layer. We also observe differences in both the temperature and the field dependence of the SMR when comparing tri- and bilayers. Finally, we compare our data to the predictions of a model based on spin diffusion. This shows that interface resistances play a crucial role for the SMR magnitude in these trilayer structures.

  4. Atomistic simulation of trace element incorporation into garnets - comparison with experimental garnet-melt partitioning data

    NASA Astrophysics Data System (ADS)

    van Westrenen, W.; Allan, N. L.; Blundy, J. D.; Purton, J. A.; Wood, B. J.

    2000-05-01

    We have studied the energetics of trace element incorporation into pure almandine (Alm), grossular (Gros), pyrope (Py) and spessartine (Spes) garnets (X 3Al 2Si 3O 12, with X = Fe, Ca, Mg, Mn respectively), by means of computer simulations of perfect and defective lattices in the static limit. The simulations use a consistent set of interatomic potentials to describe the non-Coulombic interactions between the ions, and take explicit account of lattice relaxation associated with trace element incorporation. The calculated relaxation (strain) energies Urel are compared to those obtained using the Brice (1975) model of lattice relaxation, and the results compared to experimental garnet-melt trace element partitioning data interpreted using the same model. Simulated Urel associated with a wide range of homovalent (Ni, Mg, Co, Fe, Mn, Ca, Eu, Sr, Ba) and charge-compensated heterovalent (Sc, Lu, Yb, Ho, Gd, Eu, Nd, La, Li, Na, K, Rb) substitutions onto the garnet X-sites show a near-parabolic dependence on trace element radius, in agreement with the Brice model. From application of the Brice model we derived apparent X-site Young's moduli EX(1+, 2+, 3+) and the 'ideal' ionic radii r0(1+, 2+, 3+), corresponding to the minima in plots of Urel vs. radius. For both homovalent and heterovalent substitutions r0 increases in the order Py-Alm-Spes-Gros, consistent with crystallographic data on the size of garnet X-sites and with the results of garnet-melt partitioning studies. Each end-member also shows a marked increase in both the apparent EX and r0 with increasing trace element charge ( Zc). The increase in EX is consistent with values obtained by fitting to the Brice model of experimental garnet-melt partitioning data. However, the increase in r0 with increasing Zc is contrary to experimental observation. To estimate the influence of melt on the energetics of trace element incorporation, solution energies ( Usol) were calculated for appropriate exchange reactions between

  5. Extraction-chromatographic affinage in gadolinium-153 preparation production technology

    SciTech Connect

    Melnik, M.I.; Karelin, E.A.; Kuznetsov, R.A.

    1993-12-31

    The gadolinium 153 preparation is used for production of medical gamma-sources which are applicable in bone densimeters for early diagnostics of osteoporosis. This preparation must meet strict requirements with respect to the content of europium radionuclides and specific activity. In The Research Institute of Atomic Reactors (RIAR) the gadolinium 153 is produced by neutron irradiation of Europium 151. This process is described.

  6. Resonance parameter measurements and analysis of gadolinium

    SciTech Connect

    Leinweber, G.; Barry, D. P.; Trbovich, M. J.; Burke, J. A.; Drindak, N. J.; Knox, H. D.; Ballad, R. V.; Block, R. C.; Danon, Y.; Severnyak, L. I.

    2006-07-01

    The purpose of the present work is to measure the neutron cross sections of gadolinium accurately. Gd has the highest thermal absorption cross section of any natural element. Therefore it is an important element for thermal reactor applications Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Inst. (RPI) LINAC facility using metallic and liquid Gd samples. The liquid samples were isotopically-enriched in either {sup 155}Gd or {sup 157}Gd. The capture measurements were made at the 25-m flight station with a sodium iodide detector, and the transmission measurements were performed at 15- and 25-m flight stations with {sup 6}Li glass scintillation detectors. The multilevel R-matrix Bayesian code SAMMY was used to extract resonance parameters. The results of the thermal region analysis are significant. Resonance parameters for the low energy doublet, at 0.025 and 0.032 eV, are presented. The thermal (2200 m/s) capture cross section of {sup 157}Gd has been measured to be 11% smaller than that calculated from ENDF/B-VI updated through release 8. Thermal capture cross sections and capture resonance integrals for each isotope as well as elemental gadolinium are presented. In the epithermal region, natural metal samples were measured in capture and transmission. Neutron interaction data up to 300 eV have been analyzed. Substantial improvement to the understanding of gadolinium cross sections is presented, particularly above 180 eV where the ENDF resolved region for {sup 155}Gd ends. (authors)

  7. Magma, Magma, Quite Contaminated, How Does Your Garnet Grow?

    NASA Astrophysics Data System (ADS)

    Lackey, J.; Romero, G. A.; Valley, J. W.

    2010-12-01

    Garnet in granitoid rocks has drawn considerable attention and discussion because of uncertainty surrounding its origins. For example, enrichment of Al, resulting in peraluminous magmas capable of crystallizing garnets, may be controlled by contamination or extreme differentiation; Mn enrichment in aplitic and pegmatitic phases suggests garnet may appear only at relatively low, near solidus temperatures. Peritectic garnet, grown by magma-wallrock reaction, may be confused with magmatic garnet, and xenocrysts of metamorphic garnet, entrained from wallrocks, further complicate interpretation. We address these uncertainties with the SIMS analysis of oxygen isotope variations in single garnet crystals and crystal populations in granitic rocks. Values of δ18O were measured on a CAMECA IMS 1280 using a 10 µm spot size and typical precision of ± 0.3 at 2 standard deviations. Analyses were corrected for instrumental mass fractionation according to the newly solved bias correction protocol for garnet (Page et al. 2010). Samples were collected from the Devonian Togus and Hallowell plutons in the south central Maine. These plutons are an ideal site for this study because they are peraluminous and contain pervasive garnet, they locally intrude pelitic, garnet-bearing wallrocks, and they have field evidence of xenolith entrainment and peritectic reaction of xenoliths and the host magmas. Garnet δ18O values of 7.5-10.5‰ show a large range of crustal input to host magmas. Crystal-to-crystal variation of δ18O in hand-samples varies up to 2‰, confirming that garnet populations have complex origins. Traverses (20-50 spots) of single crystals show that δ18O varies up to 1‰, with rims of crystals (outer 50-100µm) being up to 1‰ higher or lower than interiors. Increases of δ18O are interpreted as late-stage contamination, whereas lower δ18O rims, with correspondence to decreasing Fe/Mg ratio, suggest growth during falling magma temperature (50-100°C). Some garnet

  8. Substitution of gadolinium ethylenediaminetetraacetate with phosphites: towards gadolinium deposit in nephrogenic systemic fibrosis.

    PubMed

    Gao, Song; Chen, Mao-Long; Zhou, Zhao-Hui

    2014-01-14

    In neutral media, reactions of gadolinium ethylenediaminetetraacetates with phosphorous acid result in the formation of the mixed-ligand polymeric complex K3n[Gd(EDTA)(HPO3)]n·7nH2O () and dimeric complex Na6[Gd2(EDTA)2(HPO3)2]·2.5NaCl·21H2O () (H4EDTA = ethylenediaminetetraacetic acid) in warm solution. Further substitution with citric acid gives the monomeric gadolinium citrate with EDTA (NH4)2Na[Gd(EDTA)(H2cit)]·4H2O (). The compounds were characterized by elemental analysis, single crystal X-ray diffraction, FT-IR, ESI-MS and thermogravimetric analysis. Structural analysis indicates that three coordinated water molecules in the gadolinium ethylenediaminetetraacetate trihydrates are replaced by phosphite ions (HPO3(2-)) in the compounds and . Gadolinium atoms are octa-coordinated by EDTA and the phosphite ion, the latter links adjacent Gd-EDTA units to generate an infinite one-dimensional chain in compound and a dimeric octatomic ring in . In complex , coordinated water molecules were substituted by the α-hydroxy, α-carboxy and β-carboxy groups of citrate. Citrate is favourable for inhibiting the formation of Gd-EDTA phosphite. All the complexes are very easily soluble in water. The solution behavior of the isostructural lanthanum complexes was probed with (13)C and (31)P NMR spectra in D2O for comparison. ESI-MS analysis and recrystallization proved that complexes and dissociate to the monomeric unit of Gd-EDTA and free HPO3(2-) in aqueous solution. Substitutions of gadolinium ethylenediaminetetraacetates to and are attributed to be the cause of nephrogenic systemic fibrosis in some way.

  9. Gallium Electromagnetic (GEM) Thrustor Concept and Design

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Markusic, Thomas E.

    2006-01-01

    We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

  10. Towards modeling gadolinium-lead-borate glasses

    SciTech Connect

    Rada, S.; Ristoiu, T.; Rada, M.; Coroiu, I.; Maties, V.; Culea, E.

    2010-01-15

    Infrared spectra of gadolinium-lead-borate glasses of the xGd{sub 2}O{sub 3}.(100 - x)[3B{sub 2}O{sub 3}.PbO] system, where x = 0, 5, 10, 15, 25, 35 and 50 mol.%, have been recorded to explore the role of content of gadolinium ions behaving as glass modifier. The FTIR spectroscopy data for the xGd{sub 2}O{sub 3}.(1 - x)[3B{sub 2}O{sub 3}.PbO] glasses show the structural role of lead ions as a network-formers and of the gadolinium ions network modifiers. Adding of the rare earth ion up to 35 mol.% into the glass matrix, the IR bands characteristic to the studied glasses become sharper and more pronounced. Structural changes, as recognized by analyzing band shapes of IR spectra, revealed that Gd{sub 2}O{sub 3} causes a change from the continuous borate network to the continuous lead-borate network interconnected through Pb-O-B and B-O-B bridges and the transformation of some tetrahedral [BO{sub 4}] units into trigonal [BO{sub 3}] units. Then, gadolinium ions have affinity towards [BO{sub 3}] structural units which contain non-bridging oxygens necessary for the charge compensation because the more electronegative [BO{sub 3}] structural units were implied in the formation of B-O-Gd bonds and the transformation of glass network into a glass ceramic. We propose a possible structural model of building blocks for the formation of continuous random 3B{sub 2}O{sub 3}.PbO network glass used by density functional theory (DFT) calculations. DFT calculations show that lead atoms occupy three different sites in the proposed model. The first is coordinated with six oxygen atoms forming distorted octahedral geometries. The second lead atom has an octahedral oxygen environment and the five longer Pb-O bonds are considered as participating in the metal coordination scheme. The third lead atom has ionic character. In agreement with the results offered by the experimental FTIR data, the theoretical IR data confirm that our proposed structure is highly possible.

  11. Light deflection in gadolinium molybdate ferroelastic crystals

    NASA Astrophysics Data System (ADS)

    Staniorowski, Piotr; Bornarel, Jean

    2000-02-01

    The deflection of a He-Ne light beam by polydomain gadolinium molybdate (GMO) crystals has been studied with respect to incidence angle icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> i on the sample at room temperature. The A and B deflected beams do not cross each other during the icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> i variation, in contrast to results and calculations previously published. The model using the Fresnel equation confirms this result. The model presented is more accurate for numerical calculation than that using the Huygens construction.

  12. Thermal Spin Dynamics of Yttrium Iron Garnet

    NASA Astrophysics Data System (ADS)

    Barker, Joseph; Bauer, Gerrit E. W.

    2016-11-01

    The magnetic insulator yttrium iron garnet can be grown with near perfection and is therefore and ideal conduit for spin currents. It is a complex material with 20 magnetic moments in the unit cell. In spite of being a ferrimagnet, YIG is almost always modeled as a simple ferromagnet with a single spin wave mode. We use the method of atomistic spin dynamics to study the temperature evolution of the full spin wave spectrum, in quantitative agreement with neutron scattering experiments. The antiferromagnetic or optical mode is found to suppress the spin Seebeck effect at room temperature and beyond due to thermally pumped spin currents with opposite polarization to the ferromagnetic mode.

  13. Majorite Garnet and Lithosphere Evolution: Kaapvaal Craton

    NASA Astrophysics Data System (ADS)

    Griffin, W. L.; Tessalina, S.; O'Reilly, S. Y.

    2013-12-01

    The uppermost 50-70 km of the subcontinental lithospheric mantle (SCLM) beneath the Kaapvaal Craton (S. Africa) consists largely of highly-depleted chromite harzburgites. These rocks are understudied, mainly because of their uniformity and their lack of indicator minerals such as garnet and clinopyroxene (cpx). Kimberlite-borne xenoliths of these rocks contain rare volumes of cpx-spinel (modal 76/24) symplectite, with smooth grain boundaries; many studies have suggested that these might represent low-pressure breakdown products of garnet (majorite + olivine → cpx + spinel). Our reconstruction of a suite of these grains, using element mapping and EMP analysis of constituent minerals, gives a majoritic garnet with mean composition 21.8% CaO, 15.8% Cr2O3, 9.22% Al2O3, Si=3.118, mg#=0.93. The majorite contents suggest formation at depths of 250-280 km. Ni contents imply temperatures ≥1500 °C, but have large uncertainties related to the subtraction of olivine (ca 20%) during the reconstruction calculation. LAM-ICPMS analyses show strongly sinuous REE patterns with CN Dy/Lu <0.1 and Ce/Dy >100. Most analyses have negative Eu anomalies, consistent with chromite compositions that indicate strongly reducing conditions (ΔfO2(FMQ) = -4 to -5). Melt modeling suggests that the harzburgites are products of 30-40% melting of asthenospheric mantle at 250 km depth, leaving residues of ol+opx+chromite. The presence of the majorites and their overall LREE enrichment are ascribed to the introduction of carbonatitic metasomatic fluids, similar to those recorded by diamond-inclusions (subcalcic garnets), shortly after the depletion. We suggest that the melting, the metasomatism and the ultimate breakdown of the majorite track a process of mantle upwelling, with melt-extraction at depth providing the buoyancy that allowed the residual harzburgites to rise to shallow levels and stabilize the SCLM. Os-isotope analyses of sulfides associated with the majorites give TRD = 2.5-3.4 Ga

  14. Unconventional Superfluidity in Yttrium Iron Garnet Films

    NASA Astrophysics Data System (ADS)

    Sun, Chen; Nattermann, Thomas; Pokrovsky, Valery L.

    2016-06-01

    We argue that the magnon condensate in yttrium iron garnet may display experimentally observable superfluidity at room temperature despite the 100 times dominance of the normal density over superfluid ones. The superfluidity has a more complicated nature than in known superfluids since the U(1) symmetry of the global phase shift is violated by the dipolar interaction leading to the exchange of spin moment between the condensate and the crystal lattice. It produces periodic inhomogeneity in the stationary superfluid flow. We discuss the manner of observation and possible applications of magnon superfluidity. It may strongly enhance the spin-torque effects and reduce the energy consumption of the magnonic devices.

  15. Elastic moduli of pyrope rich garnets

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Pandey, A. K.; Singh, C. K.

    2013-06-01

    The elastic properties of minerals depend on its composition, crystal structure, temperature and level of defects. The elastic parameters are important for the interpretation of the structure and composition of the garnet rich family. In present work we have calculated the elastic moduli such as isothermal bulk modulus, Young's modulus and Shear modulus over a wide range of temperature from 300 K to 1000 K by using Birch EOS and Poirrier Tarantola equation of state. The obtained results are compared with the experimental results obtained by measuring the elastic moduli of single crystal. The calculated results show that the logarithmic isothermal EOS does not cooperate well with experimental results.

  16. Very high-pressure orogenic garnet peridotites

    PubMed Central

    Liou, J. G.; Zhang, R. Y.; Ernst, W. G.

    2007-01-01

    Mantle-derived garnet peridotites are a minor component in many very high-pressure metamorphic terranes that formed during continental subduction and collision. Some of these mantle rocks contain trace amounts of zircon and micrometer-sized inclusions. The constituent minerals exhibit pre- and postsubduction microstructures, including polymorphic transformation and mineral exsolution. Experimental, mineralogical, petrochemical, and geochronological characterizations using novel techniques with high spatial, temporal, and energy resolutions are resulting in unexpected discoveries of new phases, providing better constraints on deep mantle processes. PMID:17519341

  17. Imaging Domains In Magnetic Garnets By Use Of TSMFM

    NASA Technical Reports Server (NTRS)

    Katti, Romney R.; Wu, Jiin-Chuan; Stadler, Henry L.; Rice, Paul

    1994-01-01

    Tunneling-stabilized magnetic-force microscopy (TSMFM) demonstrated to yield images of magnetic domains in low-coercivity magnetic garnets with perpendicular anisotropy. Ability to generate images of domain walls and minute vertical Bloch lines aids study of vertical-Bloch-line magnetic memory devices that contain garnets. TSMFM provides desired resolution because its resolution not limited by diffraction.

  18. The Garnet to Majorite Transformation in Mafic Compositions

    NASA Technical Reports Server (NTRS)

    Xirouchakis, D.; Draper, David S.; Agee, C. B.

    2002-01-01

    The garnet to majorite transformation in mafic compositions is controlled by bulk composition and the presence of silicate melt, clinopyroxene, and silicate perovskite as well as pressure. Thus, the use of empirical geobarometers based on garnet Si(4+) and/or [Al(3+) +/- Cr(3+)] (p.f.u) seems unjustified. Additional information is contained in the original extended abstract.

  19. Chemistry and mineralogy of garnet pyroxenites from Sabah, Malaysia

    USGS Publications Warehouse

    Morgan, B.A.

    1974-01-01

    Garnet pyroxenites and corundum-garnet amphibolites from the Dent peninsula of eastern Sabah (North Borneo) occur as blocks in a slump breccia deposit of late Miocene age. The earliest formed minerals include pyrope-almandine garnet, tschermakitic augite, pargasite, and rutile. Cumulate textures are present in two of the six specimens studied. The earlier fabric has been extensively brecciated and partly replaced by plagioclase, ilmenite, and a fibrous amphibole. The bulk composition and mineralogy of these rocks are similar to those of garnet pyroxenite lenses within ultramafic rocks. Estimated temperature and pressure for the origin of the Sabah garnet pyroxenites is 850??150?? C and 19??4 kbar. ?? 1974 Springer-Verlag.

  20. Chemical zonation in garnet: kinetics or chemical equilibrium?

    NASA Astrophysics Data System (ADS)

    Ague, Jay; Chu, Xu; Axler, Jennifer

    2015-04-01

    Chemical zonation in garnet is widely used to reconstruct the pressure (P), temperature (T), time (t), and fluid (f) histories of mountain belts. Zonation is thought to result largely from changing P - T - t - f conditions during growth as well as post-growth intracrystalline diffusion. Chemical zonation is conventionally interpreted to mean that at least some of the garnet interior was out of chemical equilibrium with the matrix during metamorphism. In this case, thermally-activated diffusion in garnet is too slow to equalize chemical potentials. However, in their groundbreaking paper, Tajčmanová et al. (2014) postulate that in high-grade rocks, chemical zonation may actually reflect attainment of equilibrium. In this scenario, diffusion is fast but viscous relaxation is slow such that the zonation patterns directly mirror internal pressure gradients within garnet. Such zoning would likely be very different than typical concentric growth zonation. Furthermore, Baumgartner et al. (2010) hypothesize that given significant variations in the molar volumes of garnet endmembers, diffusional relaxation may produce internal pressure gradients if the garnet behaves as a near constant-volume system. Consequently, growth zoning could be preserved by pressure variations within the garnet that equalize chemical potentials and slow or stop diffusion (i.e., the garnet is chemically heterogeneous but maintains internal chemical equilibrium due to the pressure variations). This mechanism predicts that areas of garnet with small compositional contrasts would undergo more diffusional relaxation than areas with large contrasts. Moreover, generation of large internal pressure gradients approaching 1 GPa would be expected to induce deformation (e.g., fracturing) in regions of large compositional gradients. Strongly growth-zoned amphibolite facies garnet from the Barrovian zones, Scotland (Ague and Baxter, 2007) shows neither of these features. The sharp compositional gradients are

  1. Electrospun Gallium Nitride Nanofibers (abstract)

    NASA Astrophysics Data System (ADS)

    Meléndez, Anamaris; Morales, Kristle; Ramos, Idalia; Campo, Eva; Santiago, Jorge J.

    2009-04-01

    The high thermal conductivity and wide bandgap of gallium nitride (GaN) are desirable characteristics in optoelectronics and sensing applications. In comparison to thin films and powders, in the nanofiber morphology the sensitivity of GaN is expected to increase as the exposed area (proportional to the length) increases. In this work we present electrospinning as a novel technique in the fabrication of GaN nanofibers. Electrospinning, invented in the 1930s, is a simple, inexpensive, and rapid technique to produce microscopically long ultrafine fibers. GaN nanofibers are produced using gallium nitrate and dimethyl-acetamide as precursors. After electrospinning, thermal decomposition under an inert atmosphere is used to pyrolyze the polymer. To complete the preparation, the nanofibers are sintered in a tube furnace under a NH3 flow. Both scanning electron microscopy and profilometry show that the process produces continuous and uniform fibers with diameters ranging from 20 to a few hundred nanometers, and lengths of up to a few centimeters. X-ray diffraction (XRD) analysis shows the development of GaN nanofibers with hexagonal wurtzite structure. Future work includes additional characterization using transmission electron microscopy and XRD to understand the role of precursors and nitridation in nanofiber synthesis, and the use of single nanofibers for the construction of optical and gas sensing devices.

  2. Clinical applications of Gallium-68.

    PubMed

    Banerjee, Sangeeta Ray; Pomper, Martin G

    2013-06-01

    Gallium-68 is a positron-emitting radioisotope that is produced from a (68)Ge/(68)Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. (68)Ga-DOTATOC, (8)Ga-DOTATATE, (68)Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with (68)Ga over the past few years around the world, including within the United States. An estimated ∼10,000 scans are being performed yearly in Europe at about 100 centers utilizing (68)Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied (68)Ga-labeled imaging agents used in nuclear medicine.

  3. The surface tension of liquid gallium

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.

    1985-01-01

    The surface tension of liquid gallium has been measured using the sessile drop technique in an Auger spectrometer. The experimental method is described. The surface tension in mJ/sq m is found to decrease linearly with increasing temperature and may be represented as 708-0.66(T-29.8), where T is the temperature in centigrade. This result is of interest because gallium has been suggested as a model fluid for Marangoni flow experiments. In addition, the surface tension is of technological significance in the processing of compound semiconductors involving gallium.

  4. Status of gallium-67 in tumor detector

    SciTech Connect

    Hoffer, P.

    1980-04-01

    The efficacy of gallium-67 citrate in detecting specific tumors is discussed. Tumors in which gallium-67 imaging is useful as a diagnostic tool include Hodgkin's disease, histiocystic lymphoma, Burkitt's lymphoma, hepatoma melanoma, and leukemia. It has not been found to be effective in diagnosing head and neck tumors, gastrointestinal tumors, genitourinary tract tumors, breast tumors, and pediatric tumors. Gallium may be useful in the evaluation of non-Hodgkin's lymphoma, testicular carcinoma, mesothelioma, and carcinoma of the lung. It may also be useful for determining response to treatment and prognosis in some neoplasms.

  5. Alkali metal and alkali earth metal gadolinium halide scintillators

    DOEpatents

    Bourret-Courchesne, Edith; Derenzo, Stephen E.; Parms, Shameka; Porter-Chapman, Yetta D.; Wiggins, Latoria K.

    2016-08-02

    The present invention provides for a composition comprising an inorganic scintillator comprising a gadolinium halide, optionally cerium-doped, having the formula A.sub.nGdX.sub.m:Ce; wherein A is nothing, an alkali metal, such as Li or Na, or an alkali earth metal, such as Ba; X is F, Br, Cl, or I; n is an integer from 1 to 2; m is an integer from 4 to 7; and the molar percent of cerium is 0% to 100%. The gadolinium halides or alkali earth metal gadolinium halides are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

  6. Comparison of gadolinium depletion in CASMO-4 and CASMO-3

    SciTech Connect

    Knott, D.; Edenius, M.

    1995-12-31

    Since the mid-1980s, CASMO-3 has been used to generate two-group nodal data for SIMULATE-3. Development of CASMO-3 was based on the accuracy needed to analyze {approximately} 12-month cycle lengths. Fuel designs for these annual cycles contained low gadolinium loadings in only a few pins. As cycle lengths increased from 12 to 24 months, gadolinium loadings doubled and tripled, as did the number of pins containing gadolinium. The use of heavy burnable absorber loadings has been a driving force behind the development of CASMO-4.

  7. Survey of the market, supply, and availability of gallium

    SciTech Connect

    Rosi, F.D.

    1980-01-01

    The present and potential availability of gallium metal in connection with materials evaluation recommendations for satellite power systems is examined in the following areas: (1) market considerations - the present and emerging uses of gallium, as well as the consumption and price of gallium; (2) supply considerations - present sources of gallium, commercial and new methods for extracting gallium from bauxite, and summary comments; (3) methods for purifying gallium to satisfy market demands; (4) principal suppliers of gallium; and (5) gallium availability from bauxite on the basis of primary aluminum production; and bauxite production, reserves and resources. The study was based on published information as well as information derived from private communications with both major and potential suppliers and users of gallium, and with staff members at the Bureau of Mines. 16 references, 3 figures, 6 tables.

  8. Removal of gadolinium nitrate from heavy water

    SciTech Connect

    Wilde, E.W.

    2000-03-22

    Work was conducted to develop a cost-effective process to purify 181 55-gallon drums containing spent heavy water moderator (D2O) contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS). These drums also contain low level radioactive contamination, including tritium, which complicates treatment options. Presently, the drums of degraded moderator are being stored on site. It was suggested that a process utilizing biological mechanisms could potentially lower the total cost of heavy water purification by allowing the use of smaller equipment with less product loss and a reduction in the quantity of secondary waste materials produced by the current baseline process (ion exchange).

  9. Radiochemical separation of gallium by amalgam exchange

    USGS Publications Warehouse

    Ruch, R.R.

    1969-01-01

    An amalgam-exchange separation of radioactive gallium from a number of interfering radioisotopes has been developed. A dilute (ca. 0.3%) gallium amalgam is agitated with a slightly acidic solution of 72Ga3+ containing concentrations of sodium thiocyanate and either perchlorate or chloride. The amalgam is then removed and the radioactive gallium stripped by agitation with dilute nitric acid. The combined exchange yield of the perchlorate-thiocyanate system is 90??4% and that of the chloride-thiocyanate system is 75??4%. Decontamination yields of most of the 11 interfering isotopes studied were less than 0.02%. The technique is applicable for use with activation analysis for the determination of trace amounts of gallium. ?? 1969.

  10. Materials synthesis: Two-dimensional gallium nitride

    NASA Astrophysics Data System (ADS)

    Koratkar, Nikhil A.

    2016-11-01

    Graphene is used as a capping sheet to synthesize 2D gallium nitride by means of migration-enhanced encapsulation growth. This technique may allow the stabilization of 2D materials that are not amenable to synthesis by traditional methods.

  11. Magnetic phase transitions in samarium iron garnet

    SciTech Connect

    Geller, S.; Balestrino, G.

    1980-05-01

    Moessbauer spectroscopy has shown that there are at least three magnetic phases of samarium iron garnet and possibly five, if spin reorientations that are not abrupt are assumed to occur between these phases. The easy magnetic axes are: (111), 560>T> or approx. =60 K; (110), approx. 45>T> or approx. =18 K; (100), approx. 10>T > or = 5 K. The spin reorientations are estimated to occur between approx. 60 and approx. 45 K and between approx. 18 and approx. 10 K. While the phases with the (111) and (110) easy magnetic axis have been reported before, this is the first report of the lowest-temperature phase with (100) easy magnetic axis, and of the possible spin reorientations. If the latter exist, the lowest-temperature phase can not be tetragonal; it is most likely orthorhombic. The sequence of magnetic space groups is: R3c', (111) ..-->.. F2'/d' ..-->.. Fdd'd', (110) ..-->.. I2'/c' ..-->.. Ibc'a', (100).

  12. Magnetic phase transitions in samarium iron garnet

    NASA Astrophysics Data System (ADS)

    Geller, S.; Balestrino, G.

    1980-05-01

    Mössbauer spectroscopy has shown that there are at least three magnetic phases of samarium iron garnet and possibly five, if spin reorientations that are not abrupt are assumed to occur between these phases. The easy magnetic axes are: [111], 560>T>~60 K; [110], ~45>T>~18 K; [100], ~10>T>=5 K. The spin reorientations are estimated to occur between ~60 and ~45 K and between ~18 and ~10 K. While the phases with the [111] and [110] easy magnetic axis have been reported before, this is the first report of the lowest-temperature phase with [100] easy magnetic axis, and of the possible spin reorientations. If the latter exist, the lowest-temperature phase cannot be tetragonal; it is most likely orthorhomic. The sequence of magnetic space groups is: R3¯c',[111]-->F2'd'-->Fdd'd', [110]-->I2'c'-->Ibc'a', [100].

  13. Generator for gallium-68 and compositions obtained therefrom

    DOEpatents

    Neirinckx, Rudi D.; Davis, Michael A.

    1981-01-01

    A generator for obtaining radioactive gallium-68 from germanium-68 bound in a resin containing unsubstituted phenolic hydroxyl groups. The germanium-68 is loaded into the resin from an aqueous solution of the germanium-68. A physiologically acceptable solution of gallium-68 having an activity of 0.1 to 50 millicuries per milliliter of gallium-68 solution is obtained. The solution is obtained from the bound germanium-68 which forms gallium-68 in situ by eluting the column with a hydrochloric acid solution to form an acidic solution of gallium-68. The acidic solution of gallium-68 can be neutralized.

  14. Thermochromism in yttrium iron garnet compounds.

    PubMed

    Serier-Brault, Hélène; Thibault, Lucile; Legrain, Magalie; Deniard, Philippe; Rocquefelte, Xavier; Leone, Philippe; Perillon, Jean-Luc; Le Bris, Stéphanie; Waku, Jean; Jobic, Stéphane

    2014-12-01

    Polycrystalline yttrium iron garnet (Y3Fe5O12, hereafter labeled YIG) has been synthesized by solid-state reaction, characterized by X-ray diffraction, Mössbauer spectroscopy, and UV-vis-NIR diffuse reflectance spectroscopy, and its optical properties from room temperature (RT) to 300 °C are discussed. Namely, its greenish color at RT is assigned to an O(2-) → Fe(3+) ligand-to-metal charge transfer at 2.57 eV coupled with d-d transitions peaking at 1.35 and 2.04 eV. When the temperature is raised, YIG displays a marked thermochromic effect; i.e., the color changes continuously from greenish to brownish, which offers opportunities for potential application as a temperature indicator for everyday uses. The origin of the observed thermochromism is assigned to a gradual red shift of the ligand-to-metal charge transfer with temperature while the positioning in energy of the d-d transitions is almost unaltered. Attempts to achieve more saturated colors via doping (e.g., Al(3+), Ga(3+), Mn(3+), ...) remained unsuccessful except for chromium. Indeed, Y3Fe5O12:Cr samples exhibit at RT the same color than the undoped garnet at 200 °C. The introduction of Cr(3+) ions strongly impacts the color of the Y3Fe5O12 parent either by an inductive effect or, more probably, by a direct effect on the electronic structure of the undoped material with formation of a midgap state.

  15. Garnet: featured mineral group at the 1993 Tucson Show

    USGS Publications Warehouse

    Modreski, P.J.

    1993-01-01

    The garnets are a common but complex group of minerals. They are perhaps the mineral kingdom's best example of solid solution: a relationship in which minerals have chemical compositions that are intermediate between two or more ideal end-member species. In garnet, we deal with a complex group of solid-solution series between as many as 14 end-member minerals. The varying intergradations of solid solution between these different end-members help to explain the garnet group's variety of color, environment of occurrence, gem use, and variation in such physical properties as specific gravity, refractive index, and hardness. -from Author

  16. Characterization of gadolinium and lanthanum oxide films on Si (100)

    NASA Astrophysics Data System (ADS)

    Wu, X.; Landheer, D.; Sproule, G. I.; Quance, T.; Graham, M. J.; Botton, G. A.

    2002-05-01

    High-resolution transmission electron microscopy, electron energy loss spectroscopy, and Auger electron spectroscopy, were used to study gadolinium and lanthanum oxide films deposited on Si (100) substrates using electron-beam evaporation from pressed-powder targets. As-deposited films consist of a crystalline oxide layer and an amorphous interfacial layer. A complicated distinct multilayer structure consisting of oxide layers, silicate layers, and SiO2-rich layers in thick (~30 nm) annealed films has been observed for both gadolinium and lanthanum films. For thinner annealed films (~8 nm), there is no longer a crystalline oxide layer but an amorphous gadolinium or lanthanum silicate layer and an interfacial SiO2-rich layer. The formation of the lanthanum silicate by annealing lanthanum oxide is found to be thermodynamically more favorable than the formation of gadolinium silicate.

  17. Gadolinium loaded plastic scintillators for high efficiency neutron detection

    NASA Astrophysics Data System (ADS)

    Ovechkina, Lena; Riley, Kent; Miller, Stuart; Bell, Zane; Nagarkar, Vivek

    2009-08-01

    Gadolinium has the highest thermal neutron absorption cross section of any naturally occurring element, and emits conversion electrons as well as atomic X-rays in over 50% of its neutron captures, which makes it a useful dopant in scintillators for detecting thermal neutrons. Gadolinium isopropoxide was studied as a possible dopant for styrene-based plastic scintillators as a convenient and inexpensive method to produce high-efficiency thermal neutron detectors. Plastic scintillators with gadolinium weight concentrations of up to 3% were transparent, uniform and defect-free and were characterized with spectral measurements performed under x-ray and neutron irradiation. The new material has the same characteristic emission of styrene with a maximum at approximately 425 nm, and a light output of 76% relative to the undoped plastic. A 13 mm thick sample containing 0.5% gadolinium by weight detected 46% of incident thermal neutrons, which makes this an attractive material for a variety of applications.

  18. Gallium poisoning: a rare case report.

    PubMed

    Ivanoff, Chris S; Ivanoff, Athena E; Hottel, Timothy L

    2012-02-01

    The authors present a case of a college student who suffered acute gallium poisoning as a result of accidental exposure to gallium halide complexes. This is extremely rare and has never been reported in the literature. Acute symptoms after the incident, which initially presented as dermatitis and appeared relatively not life-threatening, rapidly progressed to dangerous episodes of tachycardia, tremors, dyspnea, vertigo, and unexpected black-outs. Had there been effective emergency medical care protocols, diagnostic testing, treatment and antidotes, the latent manifestations of irreversible cardiomyopathy may have been prevented. Given how quickly exposure led to morbidity, this article aims to raise an awareness of the toxic potential of gallium. This has particular relevance for workers involved in the production of semiconductors where there is a potential for accidental exposure to gallium by-products during device processing. It may also have implications for dentists who use gallium alloys to replace mercury containing amalgam. In the absence of threshold limit values and exposure limits for humans, as well as emergency medical guidelines for treatment of poisoning, the case calls on the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration to establish guidelines and medical management protocols specific for gallium.

  19. Gallium Arsenide wafer scale integration

    NASA Astrophysics Data System (ADS)

    McDonald, J. F.; Taylor, G.; Steinvorth, R.; Donlan, B.; Bergendahl, A. S.

    1985-08-01

    Gallium Arsenide (GaAs) digital MESFET technology has recently begun to appear in the semiconductor marketplace. The initial commercial offerings are at the small to medium scale integration levels. The high speed of these parts would seem to be very attractive for designers of high performance signal processing equipment. Persistent yield problems, however, have prevented the appearance of large scale integrated circuits. As a result, intrapackage and interpackage signal propagation problems such as coupling, parasitics and delay are likely to negate much of the benefits of the fast MESFET logic devices for large systems constructed with such small scale building blocks. An early packaging concept, Wafer Scale Integration (WSI), which could possibly be used to address some of these limitations is reexamined.

  20. Vacuum annealed cerium-substituted yttrium iron garnet films on non-garnet substrates for integrated optical circuits

    SciTech Connect

    Goto, Taichi; Ross, C. A.; Eto, Yu; Kobayashi, Keiichi; Haga, Yoji; Inoue, Mitsuteru

    2013-05-07

    Polycrystalline cerium-substituted yttrium iron garnet (CeYIG) showing large Faraday rotation (FR) in the near-IR region was grown on non-garnet (synthetic fused silica, Si, and Si-on-insulator) substrates by sputtering followed by thermal annealing in vacuum. The FR of the films is comparable to the single crystal value. Structural characterization, magnetic properties, refractive index, extinction coefficient, surface topography, and FR vs. wavelength were measured and the magnetooptical figure of merit was compared with that of CeYIG films on garnet substrates.

  1. Magneto-Optical Experiments on Rare Earth Garnet Films.

    ERIC Educational Resources Information Center

    Tanner, B. K.

    1980-01-01

    Describes experiments in which inexpensive or standard laboratory equipment is used to measure several macroscopic magnetic properties of thin rare earth garnet films used in the manufacture of magnetic bubble devices. (Author/CS)

  2. Window structure for passivating solar cells based on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Barnett, Allen M. (Inventor)

    1985-01-01

    Passivated gallium arsenide solar photovoltaic cells with high resistance to moisture and oxygen are provided by means of a gallium arsenide phosphide window graded through its thickness from arsenic rich to phosphorus rich.

  3. Garnet--An Essential Industrial Mineral and January's Birthstone

    USGS Publications Warehouse

    Evans, James G.; Moyle, Phillip R.; Frank, David G.; Olson, Donald W.

    2006-01-01

    Garnet is one of the most common minerals in the world. Occurring in almost any color, it is most widely known for its beauty as a gem stone. Because of its hardness and other properties, garnet is also an essential industrial mineral used in abrasive products, non-slip surfaces, and filtration. To help manage our Nation's resources of such essential minerals, the U.S. Geological Survey (USGS) provides crucial data and scientific information to industry, policymakers, and the public.

  4. Indus Basin sediment provenance constrained using garnet geochemistry

    NASA Astrophysics Data System (ADS)

    Alizai, Anwar; Clift, Peter D.; Still, John

    2016-08-01

    The chemical and mineralogical diversity of western Himalayan rivers is the result of each of them draining different tectonic and lithologic units, whose character is partly transferred to the sediments carried by those rivers. Garnet geochemistry was employed to discriminate provenance in the Indus River system. We characterized the geochemistry of garnet sediment grains from the modern Indus and all its major tributaries, as well as the related but ephemeral Ghaggar-Hakra River and dune sand from the Thar Desert. Garnet geochemistry displays a unique signature for the Himalayan rivers on the east of the Indus drainage compared to those in the western drainage. The trunk Indus remains distinct because of the dominant arc-type pyrope-garnet derived from Kohistan and the Karakoram. The Jhellum, which lies just east of the modern Indus has modest concentrations of arc-type pyrope garnets, which are more depleted in the other eastern tributaries. Their presence in the Jhellum reflects recycling of trunk Indus garnets through the Miocene Siwalik Group foreland sedimentary rocks. The Thar Desert dune sample contains significant numbers of grains similar to those in the trunk Indus, likely reworked by monsoon winds from the SW. Our data further indicate the presence of a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. Sands from this channel cannot be distinguished from the Indus on the basis of their garnet geochemistry alone but we favour their sedimentation from an Indus channel rather than reworking of desert sands by another stream. The garnet geochemistry shows some potential as a provenance tool, but cannot be used alone to uniquely discriminate Indus Basin provenance.

  5. Garnet polycrystals and the significance of clustered crystallization

    NASA Astrophysics Data System (ADS)

    Whitney, Donna L.; Seaton, Nicholas C. A.

    2010-10-01

    Polycrystalline garnets are common in metamorphic rocks and may form as a result of close spacing of nuclei (if clustering is early) or impingement of larger grains (if clustering occurs later in the growth history). The timing of clustering relative to garnet growth is relevant to understanding the formation and evolution of porphyroblasts and evaluating the significance (if any) of clustering. Electron backscattered diffraction (EBSD) analysis of garnet-bearing metamorphic rocks reveals the presence of polycrystalline garnet in nine localities examined in this study: the northern Appalachians (Vermont, Maine, New York, USA); North American Cordillera (North Cascades Range, Washington; Snake Range, Nevada, USA); western Rocky Mountains (British Columbia, Canada); southern Menderes Massif (Turkey); Santander Massif (Colombia); and the Sanandaj-Sirjan zone (Hamadan, Iran). In some samples, polycrystals comprise ~20-30% of garnets analyzed, and chemical and textural evidence suggests that early coalescence of garnet polycrystals is common. Some early-coalescing polycrystals exhibit growth zoning that is concentric about the geometric center of the polycrystal. In thin section, these garnets may be undetectable as polycrystals based on morphology or zoning. In some polycrystals, zoning is unrelated to the location of internal grain boundaries; in others, Fe-Mn-Mg zoning has a different pattern than that of Ca; zoning patterns may vary on the scale of a single thin section. In addition, some polycrystals are characterized by high-angle misorientation boundaries that may be in special (non-random) orientations, an observation that indicates that these polycrystals are not random clusters of grains. The presence of internal grain boundaries may affect diffusion pathways and length scales, and may facilitate communication of porphyroblast interiors with matrix phases, thereby influencing reaction history of the rock and the composition/zoning of garnet.

  6. Correction: Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

    PubMed

    Sarkar, Sujoy; Sampath, S

    2016-05-28

    Correction for 'Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control' by Sujoy Sarkar et al., Chem. Commun., 2016, 52, 6407-6410.

  7. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Copper gallium indium selenide. 721... Substances § 721.10391 Copper gallium indium selenide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as copper gallium indium selenide (PMN...

  8. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Copper gallium indium selenide. 721... Substances § 721.10391 Copper gallium indium selenide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as copper gallium indium selenide (PMN...

  9. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Copper gallium indium selenide. 721... Substances § 721.10391 Copper gallium indium selenide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as copper gallium indium selenide (PMN...

  10. High Performance Anion Chromatography of Gadolinium Chelates.

    PubMed

    Hajós, Peter; Lukács, Diana; Farsang, Evelin; Horváth, Krisztian

    2016-11-01

    High performance anion chromatography (HPIC) method to separate ionic Gd chelates, [Formula: see text], [Formula: see text], [Formula: see text] and free matrix anions was developed. At alkaline pHs, polydentate complexing agents such as ethylene-diamine-tetraacetate, diethylene-triamine pentaacetate and trans-1,2-diamine-cyclohexane-tetraacetate tend to form stable Gd chelate anions and can be separated by anion exchange. Separations were studied in the simple isocratic chromatographic run over the wide range of pH and concentration of carbonate eluent using suppressed conductivity detection. The ion exchange and complex forming equilibria were quantitatively described and demonstrated in order to understand major factors in the control of selectivity of Gd chelates. Parameters of optimized resolution between concurrent ions were presented on a 3D resolution surface. The applicability of the developed method is represented by the simultaneous analysis of Gd chelates and organic/inorganic anions. Inductively coupled plasma atomic emission spectroscopy  (ICP-AES) analysis was used for confirmation of HPIC results for Gd. Collection protocols for the heart-cutting procedure of chromatograms were applied. SPE procedures were also developed not only to extract traces of free gadolinium ions from samples, but also to remove the high level of interfering anions of the complex matrices. The limit of detection, the recoverability and the linearity of the method were also presented.

  11. Studies of narrow autoionizing resonances in gadolinium

    SciTech Connect

    Bushaw, Bruce A.; Nortershauser, W.; Blaum, K.; Wendt, Klaus

    2003-06-30

    The autoionization (AI) spectrum of gadolinium between the first and second limits has been investigated by triple-resonance excitation with high-resolution cw lasers. A large number of narrow AI resonances have been observed and assigned total angular momentum J values. The resonances are further divided into members of AI Rydberg series converging to the second limit or other ''interloping'' levels. Fine structure in the Rydberg series has been identified and interpreted in terms of Jc j coupling. A number of detailed studies have been performed on the interloping resonances: These include lifetime determination by lineshape analysis, isotope shifts, hyperfine structure, and photoionization saturation parameters. The electronic structure of the interloping levels is discussed in terms of these studies. Linewidths generally decrease with increasing total angular momentum and the J = 7 resonances are extremely narrow with Lorentzian widths ranging from < 1 MHz up to 157 MHz. The strongest resonances are found to have cross-sections of {approx}10-12 cm{sup 2} and photoionization can be saturated with powers available from cw diode lasers.

  12. Distribution profile of gadolinium in gadolinium chelate-treated renally-impaired rats: role of pharmaceutical formulation.

    PubMed

    Fretellier, Nathalie; Salhi, Mariem; Schroeder, Josef; Siegmund, Heiko; Chevalier, Thibaut; Bruneval, Patrick; Jestin-Mayer, Gaëlle; Delaloge, Francette; Factor, Cécile; Mayer, Jean-François; Fabicki, Jean-Michel; Robic, Caroline; Bonnemain, Bruno; Idée, Jean-Marc; Corot, Claire

    2015-05-25

    While not acutely toxic, chronic hepatic effect of certain gadolinium chelates (GC), used as contrast agent for magnetic resonance imaging, might represent a risk in renally-impaired patients due to free gadolinium accumulation in the liver. To answer this question, this study investigated the consequences of the presence of small amounts of either a soluble gadolinium salt ("free" Gd) or low-stability chelating impurity in the pharmaceutical solution of gadoteric acid, a macrocyclic GC with high thermodynamic and kinetic stabilities, were investigated in renally-impaired rats. Renal failure was induced by adding 0.75% adenine in the diet for three weeks. The pharmaceutical and commercial solution of gadoteric acid was administered (5 daily intravenous injections of 2.5 mmol Gd/kg) either alone or after being spiked with either "free" gadolinium (i.e., 0.04% w/v) or low-stability impurity (i.e., 0.06 w/v). Another GC, gadodiamide (low thermodynamic and kinetic stabilities) was given as its commercial solution at a similar dose. Non-chelated gadolinium was tested at two doses (0.005 and 0.01 mmol Gd/kg) as acetate salt. Gadodiamide induced systemic toxicity (mortality, severe epidermal and dermal lesions) and substantial tissue Gd retention. The addition of very low amounts of "free", non-chelated gadolinium or low thermodynamic stability impurity to the pharmaceutical solution of the thermodynamically stable GC gadoteric acid resulted in substantial capture of metal by the liver, similar to what was observed in "free" gadolinium salt-treated rats. Relaxometry studies strongly suggested the presence of free and soluble gadolinium in the liver. Electron microscopy examinations revealed the presence of free and insoluble gadolinium deposits in hepatocytes and Kupffer cells of rats treated with gadoteric acid solution spiked with low-stability impurity, free gadolinium and gadodiamide, but not in rats treated with the pharmaceutical solution of gadoteric acid. The

  13. Use of a Mixture of Gadolinium and Iodinated Contrast for Angiography

    SciTech Connect

    Badiola, Carlos M.

    2004-03-15

    The purpose of this study was to determine if the image quality of gadolinium digital subtraction angiography (DSA) can be improved by the addition of small quantities of iodinated contrast to gadolinium. The optical density (OD) of a mixture of four parts gadolinium-based contrast to one part iodinated contrast was measured through a phantom study and compared to that of full-strength gadolinium, full strength iodinated contrast, and a 20% solution of iodinated contrast. We also compared the clinical image quality of the mixture of gadolinium-based contrast and iodinated contrast relative to full-strength gadolinium and full strength iodinated contrast during DSA. The DSA image quality of the gadolinium-iodinated contrast mixture was significantly improved relative to images obtained with full-strength gadolinium and compared favorably to that obtained with full-strength iodinated contrast. The phantom data showed that the OD of the gadolinium-iodinated contrast mixture was much greater than that of full strength gadolinium and the 20% iodinated contrast solution. The increase in OD was greater than that expected from a simple additive effect of the OD of the contrast agents. Adding a small amount of iodinated contrast to gadolinium results in a significant improvement in the radiographic density and DSA image quality of gadolinium. This simple technique appears to overcome one of the major limitations of gadolinium-based angiography-poor radiographic density-while continuing to minimize the volume of administered iodinated contrast.

  14. Gallium Zeolites for Light Paraffin Aromatization

    SciTech Connect

    Price, G.L.; Dooley, K.M.

    1999-02-10

    The primary original goal of this project was to investigate the active state of gallium-containing MFI catalysts for light paraffin aromatization, in particular the state of gallium in the active material. Our original hypothesis was that the most active and selective materials were those which contained gallium zeolitic cations, and that previously reported conditions for the activation of gallium-containing catalysts served to create these active centers. We believed that in high silica materials such as MFI, ion-exchange is most effectively accomplished with metals in their 1+ oxidation state, both because of the sparsity of the anionic ion-exchange sites associated with the zeolite, and because the large hydration shells associated with aqueous 3+ cations hinder transport. Metals such as Ga which commonly exist in higher oxidation states need to be reduced to promote ion-exchange and this is the reason that reduction of gallium-containing catalysts for light paraffin aromatization often yields a dramatic enhancement in catalytic activity. We have effectively combined reduction with ion-exchange and we term this combined process ''reductive solid-state ion-exchange''. Our hypothesis has largely been proven true, and a number of the papers we have published directly address this hypothesis.

  15. Garnet: a key to unraveling Earth's dynamic lithosphere

    NASA Astrophysics Data System (ADS)

    Smit, M. A.; Scherer, E. E.; Mezger, K.; Lee, J.; Ratschbacher, L.; Kooijman, E.; Stearns, M. A.

    2015-12-01

    Garnet enables constraints on all parameters relevant to lithosphere studies: pressure, temperature, strain, and time. This aspect, in combination with its widespread occurrence in metamorphic rocks and ability to resist retrogression, make the mineral a prime target in research into the dynamics of mountain belts. Garnet-based petrological and geochemical tools have diversified and improved as a result of recent advancements in spatial and analytical resolution. In particular, our ability to obtain precise age constraints using garnet Lu-Hf and Sm-Nd geochronology, and interpret these in a geological context has greatly improved. This contribution highlights a series of recent enhancements to the garnet toolkit and demonstrates its versatility in two case studies set in an archetypal collisional orogen: the Pamir-Himalaya-Tibet mountain chain. To enable a more effective use of garnet geochronology, we investigated the retentiveness of Lu-Hf and Sm-Nd isotope signatures in naturally metamorphosed garnet. Diffusive re-equilibration of these signatures is shown to occur to a minor, if not insignificant, extent during crustal metamorphism, thus firmly establishing these methods as reliable geochronometers. Diffusive major-element zoning analysis of the same garnet led to the development of a new thermometric tool, which was shown to provide reliable temperature estimates for a wide variety of rocks and terranes. We used Lu-Hf garnet geochronology to show that mid-crustal flow and 'Barrovian-type' metamorphism of rocks now exposed in the North Himalayan Gneiss Domes in Central Tibet commenced in the early Eocene. This result is the first to confirm that crustal thickening and contraction in the Tibetan Himalaya was broadly synchronous with the collision between Greater India and Eurasia. Garnet dating and thermometry, and rutile U-Pb thermochronology in the Pamir revealed a history of heating to 750-830 °C, commencing at 37 Ma in the South Pamir and occurring

  16. Multistep sintering to synthesize fast lithium garnets

    NASA Astrophysics Data System (ADS)

    Xu, Biyi; Duan, Huanan; Xia, Wenhao; Guo, Yiping; Kang, Hongmei; Li, Hua; Liu, Hezhou

    2016-01-01

    A multistep sintering schedule is developed to synthesize Li7La3Zr2O12 (LLZO) doped with 0.2 mol% Al3+. The effect of sintering steps on phase, relative density and ionic conductivity of Al-doped LLZO has been evaluated using powder X-Ray diffraction (XRD), scanning electron microscopy (SEM), 27Al magic spinning nuclear magnetic resonance (NMR) spectroscopy and electrochemical impedance spectroscopy (EIS). The results show that by holding the sample at 900 °C for 6 h, the mixture of tetragonal and cubic garnet phases are obtained; by continuously holding at 1100 °C for 6 h, the tetragonal phase completely transforms into cubic phase; by holding at 1200 °C, the relative density increases without decomposition of the cubic phase. The Al-LLZO pellets after multistep sintering exhibit cubic phase, relative density of 94.25% and ionic conductivity of 4.5 × 10-4 S cm-1 at room temperature. Based on the observation, a sintering model is proposed and discussed.

  17. Fabrication of transparent yttrium aluminum garnet ceramic

    NASA Astrophysics Data System (ADS)

    Li, Xia

    2009-03-01

    In this paper, the synthesis of Nd-doped yttrium aluminum garnet (Nd:YAG) spherical nano-crystallites was investigated by using the solvothermal method, and the optimum processing conditions for processing the transparent ceramic preparation was determined. Powder consisting of nanosized particles obtained by the solvothermal method displays significantly less crystallite agglomeration, indicating a high degree of sinterability. The phase structure and the morphology of the YAG crystallites were depended on the reaction conditions, the optimum temperature is 300 centigrade for 1h, at which the pure phase of spherically shaped YAG nanoparticles can be obtained. Microstructure evolution at different sintering stages demonstrated that fully transparent YAG ceramic can be fabricated by vacuum sintering at 1750 centigrade for 5h by using the as-synthesized powders. The ceramic has a relative density of about 99.98% of the theoretical value, and an average grain size of about 3-5μm. The transmittance of the ceramic is 55% in the visible range, and 70% in the infrared range.

  18. Evaluation of thermobarometers for garnet peridotites

    NASA Technical Reports Server (NTRS)

    Finnerty, A. A.; Boyd, F. R.

    1984-01-01

    Twenty-one geothermometers and six geobarometers are evaluated for accuracy and precision for garnet lherzolites, with a suite of well-equilibrated xenoliths from kimberlites of northern Lesotho. Accuracy was tested by comparison of P-T estimates for a diamond-bearing and a graphite-bearing xenolith with the experimentally determined diamond-graphite univariant curve and by comparison of P-T estimates for phlogopite-bearing xenoliths to the high-temperature stability limit of phlogopite. Precision was evaluated by measuring the scatter of P-T estimates for each of four xenoliths from a wide range of P and T when many point analyses of the constituent minerals are used for P-T estimation. Most satisfactory is a thermobarometer composed of the uncorrected diopside-enstatite miscibility gap of Lindsley and Dixon (1976), combined with the uncorrected isopleths for aluminum in enstatite coexisting with pyrope of MacGregor (1974). The inflection observed in the northern Lesotho paleogeotherm cannot be an artifact of the method of temperature estimation.

  19. Ambient temperature deposition of gallium nitride/gallium oxynitride from a deep eutectic electrolyte, under potential control.

    PubMed

    Sarkar, Sujoy; Sampath, S

    2016-05-11

    A ternary, ionically conducting, deep eutectic solvent based on acetamide, urea and gallium nitrate is reported for the electrodeposition of gallium nitride/gallium indium nitride under ambient conditions; blue and white light emitting photoluminescent deposits are obtained under potential control.

  20. Single gallium nitride nanowire lasers.

    PubMed

    Johnson, Justin C; Choi, Heon-Jin; Knutsen, Kelly P; Schaller, Richard D; Yang, Peidong; Saykally, Richard J

    2002-10-01

    There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.

  1. PARTITIONING OF GADOLINIUM IN THE CHEMICAL PROCESSING CELL

    SciTech Connect

    Reboul, S.; Best, D.; Stone, M.; Click, D.

    2011-04-27

    A combination of short-term beaker tests and longer-duration Sludge Receipt and Adjustment Tank (SRAT) simulations were performed to investigate the relative partitioning behaviors of gadolinium and iron under conditions applicable to the Chemical Processing Cell (CPC). The testing was performed utilizing non-radioactive simple Fe-Gd slurries, non-radioactive Sludge Batch 6 simulant slurries, and a radioactive real-waste slurry representative of Sludge Batch 7 material. The testing focused on the following range of conditions: (a) Fe:Gd ratios of 25-100; (b) pH values of 2-6; (c) acidification via addition of nitric, formic, and glycolic acids; (d) temperatures of {approx}93 C and {approx}22 C; and (e) oxalate concentrations of <100 mg/kg and {approx}10,000 mg/kg. The purpose of the testing was to provide data for assessing the potential use of gadolinium as a supplemental neutron poison when dispositioning excess plutonium. Understanding of the partitioning behavior of gadolinium in the CPC was the first step in assessing gadolinium's potential applicability. Significant fractions of gadolinium partitioned to the liquid-phase at pH values of 4.0 and below, regardless of the Fe:Gd ratio. In SRAT simulations targeting nitric and formic acid additions of 150% acid stoichiometry, the pH dropped to a minimum of 3.5-4.0, and the maximum fractions of gadolinium and iron partitioning to solution were both {approx}20%. In contrast, in a SRAT simulation utilizing a nitric and formic acid addition under atypical conditions (due to an anomalously low insoluble solids content), the pH dropped to a minimum of 3.7, and the maximum fractions of gadolinium and iron partitioning to solution were {approx}60% and {approx}70%, respectively. When glycolic acid was used in combination with nitric and formic acids at 100% acid stoichiometry, the pH dropped to a minimum of 3.6-4.0, and the maximum fractions of gadolinium and iron partitioning to solution were 60-80% and 3-5%, respectively

  2. Presumed Multiple Metasomatism underneath the Colorado Plateau; Decoding from Chemistry and Inclusion/Lamella Mineralogy of Diverse Garnets from the Garnet Ridge, Northern Arizona

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Ogasawara, Y.

    2015-12-01

    Various garnets containing the information on mantle petrology and related metasomatism occur at the Garnet Ridge, Colorado Plateau. The origins of garnets range from deep mantle to shallow continental crust. These garnets were delivered by kimberlitic diatreme of 30 Ma (Smith et al. 2004). We have classified the garnets into 10 groups (A to J, see figure) by naked eye observation, major chemistry, minor Na-Ti-P, inclusion/lamella mineralogy. Among them, groups A to D are of mantle origin, E to G of subducted oceanic crust origin, and H to J of continental crust origin. We summarized results as in the followings. A: Cr and pyrope-rich garnet has Cr2O3(0.8-6.3 wt.%) and inclusions of Ol, Cpx, Opx, Ti-Chu/Chn and carbonates, indicating carbonated garnet lherzolites as host. Cr contents negatively correlates with Na-Ti-P contents and occurrence of exsolved Rt, Ilm and crichtonite. This indicates Cr-rich end-member is the most "primitive" mantle garnet before metasomatism. B: Pyrope-rich reddish brown garnet of peridotitic origins was subdivided into 4 subgroups (B1 to B4, see figure). Compositional range in Ca-Mg-Fe triangle expands to Fe-rich side from group A. Exsolved Na-bearing amphibole and inclusions of Ap, carbonates and fluid were identified. These indicate metasomatism of group A. C: Garnet megacryst is coarse-grained garnet (2-10 cm across) with crystal faces. This garnet has wide chemical variation plotted in the center area of Ca-Mg-Fe triangle. D: Garnet aggregate has similar chemistry of group C and is composed of several grains. Grain boundaries of garnet were recognized by Rt, Ilm and other minerals and oscillatory zonings of Ca, Mg, Fe and Na-Ti-P. Fluid inclusions of groups C and D suggest these garnets might crystalized from fluid. E: Garnet in eclogite and F: Garnet in metasomatized eclogite are xenolith samples (the Fallaron Plate origin?). Aggregate of Zo+Ab contained in group E indicates decomposed precursor lawsonite inclusion. G: Quartz

  3. Structure and thermodynamics of uranium-containing iron garnets

    DOE PAGES

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; ...

    2016-09-15

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2–xFe3O12 (x = 0.5–0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation statesmore » and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+. U substitution had a significant effect on local environments, the extent of U substitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were first time determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Furthermore, our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2–xFe3O12 as viable waste form phases for U and other actinides.« less

  4. Structure and thermodynamics of uranium-containing iron garnets

    SciTech Connect

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; Engelhard, Mark H.; Lanzirotti, Antonio; Newville, Matthew; Ilton, Eugene S.; Sutton, Stephen R.; Xu, Hongwu

    2016-09-01

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2-xFe3O12 (x = 0.5 - 0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation states and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+ (x = 0 and substituted sample), U substitution had a significant effect on local environments, the extent of U isubstitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2-xFe3O12 as viable waste form phases for U and other actinides.

  5. Structure and thermodynamics of uranium-containing iron garnets

    SciTech Connect

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; Engelhard, Mark H.; Lanzirotti, Antonio; Newville, Matthew; Ilton, Eugene S.; Sutton, Stephen R.; Xu, Hongwu

    2016-09-15

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2–xFe3O12 (x = 0.5–0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation states and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+. U substitution had a significant effect on local environments, the extent of U substitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were first time determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Furthermore, our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2–xFe3O12 as viable waste form phases for U and other actinides.

  6. Structure and thermodynamics of uranium-containing iron garnets

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofeng; Navrotsky, Alexandra; Kukkadapu, Ravi K.; Engelhard, Mark H.; Lanzirotti, Antonio; Newville, Matthew; Ilton, Eugene S.; Sutton, Stephen R.; Xu, Hongwu

    2016-09-01

    Use of crystalline garnet as a waste form phase appears to be advantageous for accommodating actinides from nuclear waste. Previous studies show that large amounts of uranium (U) and its analogues such as cerium (Ce) and thorium (Th) can be incorporated into the garnet structure. In this study, we synthesized U loaded garnet phases, Ca3UxZr2-xFe3O12 (x = 0.5-0.7), along with the endmember phase, Ca3(Zr2)SiFe3+2O12, for comparison. The oxidation states of U were determined by X-ray photoelectron and absorption spectroscopies, revealing the presence of mixed pentavalent and hexavalent uranium in the phases with x = 0.6 and 0.7. The oxidation states and coordination environments of Fe were measured using transmission 57Fe-Mössbauer spectroscopy, which shows that all iron is tetrahedrally coordinated Fe3+. U substitution had a significant effect on local environments, the extent of U substitution within this range had a minimal effect on the structure, and unlike in the x = 0 sample, Fe exists in two different environments in the substituted garnets. The enthalpies of formation of garnet phases from constituent oxides and elements were first time determined by high temperature oxide melt solution calorimetry. The results indicate that these substituted garnets are thermodynamically stable under reducing conditions. Our structural and thermodynamic analysis further provides explanation for the formation of natural uranium garnet, elbrusite-(Zr), and supports the potential use of Ca3UxZr2-xFe3O12 as viable waste form phases for U and other actinides.

  7. New SMU Gallium Fixed-Point Cells

    NASA Astrophysics Data System (ADS)

    Ranostaj, Juraj; Ďuriš, Stanislav; Knorová, Renáta; Kaskötö, Mariana; Vyskočilová, Irena

    2011-08-01

    In the framework of the European research project EURAMET 732, the Slovak Institute of Metrology (SMU) built three primary gallium fixed-point cells of different designs. The cells are designed for the calibration of the long-stem SPRT. In regard to the procedure commonly used at SMU when realizing the gallium point, the cells are designed for use in a stirred liquid bath. This article provides information about the cell designs, materials used, method of filling, and results of the performed experiments. The experiments were focused on the study of the cells' metrological characteristics, some effects that could influence the melting-point temperature and the effect of the melted metal fraction on the immersion profile. New cells were compared with the SMU reference gallium cell.

  8. /sup 67/Gallium lung scans in progressive systemic sclerosis

    SciTech Connect

    Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

    1983-08-01

    /sup 67/Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the /sup 67/Gallium Uptake Index. The mean total pulmonary /sup 67/Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the /sup 56/Gallium uptake. Increased pulmonary /sup 67/Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity.

  9. Gadolinium metallo nanocongregates as potential magnetosensors for detecting early stage cancers

    SciTech Connect

    Dutta, Ranu; Pandey, Avinash C.

    2015-04-27

    Gadolinium chelates and gadolinium based inorganic nanoparticles have been extensively studied, because of the high magnetic moment of gadolinium. Here, metallic gadolinium nanocongregates have been developed. Upon injecting these nanoparticles in the mice, they initially circulate in the blood stream and are localized at the cancer site, which could be visualized upon application of magnetic field hence acting as small magnetic nanosensors searching for even small cancers, detecting cancers at a very early stage.

  10. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Joslin, D.; Garlick, J.; Lillington, D.; Gillanders, M.; Cavicchi, B.; Scott-Monck, J.; Kachare, R.; Anspaugh, B.

    1987-01-01

    High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.

  11. Zonation patterns of skarn garnets: Records of hydrothermal system evolution

    NASA Astrophysics Data System (ADS)

    Jamtveit, Bjørn; Wogelius, Roy A.; Fraser, Donald G.

    1993-02-01

    Chemically zoned skarn garnets provide a continuous record of hydrothermal processes in lower Paleozoic sedimentary rocks within the contact aureole around the Drammen granite in the Oslo rift, southern Norway. Major and trace element zonation profiles, the latter obtained using a scanning high-resolution proton microprobe, reveal early infiltration-controlled growth of relatively grossular rich garnets, the major and trace elements compositions being buffered by local mineral dissolution. Subsequent rapid, epitaxial growth of andradite-rich garnet on grossular-rich cores marks the onset of vigorous and focused fluid flow along high-permeability zones. During this later stage, the hydrothermal fluid composition was to a large extent externally controlled, and the andradite precipitating from these fluids was characterized by high As and W contents. The zonation patterns of the andradite-rich garnets record at least five intermittent growth periods, with rapid andradite precipitation from fluid batches with high fO2, and progressively decreasing As and W contents. Thin layers, poor in Fe, As, and W, but relatively high in Al and Mn, represent periods of slow growth rates between the major pulses of hydrothermal fluids. The marked rimward decrease in the As and W contents of the garnets may reflect influx of meteoric waters or exhaustion of these elements in the hydrothermal fluid reservoir caused by boiling-controlled distillation processes at depth.

  12. Four Terminal Gallium Nitride MOSFETs

    NASA Astrophysics Data System (ADS)

    Veety, Matthew Thomas

    All reported gallium nitride (GaN) transistors to date have been three-terminal devices with source, drain, and gate electrodes. In the case of GaN MOSFETs, this leaves the bulk of the device at a floating potential which can impact device threshold voltage. In more traditional silicon-based MOSFET fabrication a bulk contact can be made on the back side of the silicon wafer. For GaN grown on sapphire substrates, however, this is not possible and an alternate, front-side bulk contact must be investigated. GaN is a III-V, wide band gap semiconductor that as promising material parameters for use in high frequency and high power applications. Possible applications are in the 1 to 10 GHz frequency band and power inverters for next generation grid solid state transformers and inverters. GaN has seen significant academic and commercial research for use in Heterojunction Field Effect Transistors (HFETs). These devices however are depletion-mode, meaning the device is considered "on" at zero gate bias. A MOSFET structure allows for enhancement mode operation, which is normally off. This mode is preferrable in high power applications as the device has lower off-state power consumption and is easier to implement in circuits. Proper surface passivation of seminconductor surface interface states is an important processing step for any device. Preliminary research on surface treatments using GaN wet etches and depletion-mode GaN devices utilizing this process are discussed. Devices pretreated with potassium pursulfate prior to gate dielectric deposition show significant device improvements. This process can be applied to any current GaN FET. Enhancement-mode GaN MOSFETs were fabricated on magnesium doped p-type Wurtzite gallium nitride grown by Metal Organic Chemical Vapor Deposition (MOCVD) on c-plane sapphire substrates. Devices utilized ion implant source and drain which was activated under NH3 overpressure in MOCVD. Also, devices were fabricated with a SiO2 gate dielectric

  13. Synchrotron X-ray fluorescence microscopy of gallium in bladder tissue following gallium maltolate administration during urinary tract infection.

    PubMed

    Ball, Katherine R; Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L; Blyth, Robert I R; Sham, Tsun-Kong; Dowling, Patricia M; Thompson, Julie

    2013-11-01

    A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 μg/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli.

  14. Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection

    PubMed Central

    Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L.; Blyth, Robert I. R.; Sham, Tsun-Kong; Dowling, Patricia M.; Thompson, Julie

    2013-01-01

    A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 μg/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli. PMID:23877680

  15. Phase noise management of spin-wave delay-line oscillators

    NASA Astrophysics Data System (ADS)

    Drozdovskii, A. V.; Ustinov, A. B.

    2015-12-01

    A phase noise of microwave oscillators having an active ring circuitry with a spin- wave delay line is theoretically and experimentally investigated. The delay line was made with yttrium iron garnet (YIG) film epitaxially grown on gadolinium gallium garnet substrate. Obtained results demonstrate a management of the oscillator phase noise with a variation of the distance between antennas used for excitation and reception of spin waves in the YIG film.

  16. Bibliography of Soviet Laser Developments, Number 72, July - August 1984.

    DTIC Science & Technology

    1985-11-01

    Method for modeling the flux and spectral brightness of microwave radiation fields in absorbing and scattering atmospheres. CVSLAZAt, 8th. Tezisy...a phase transition method to determine the constant of anisotropy for epitaxial ferrite -garnet films with various crystallographic orientations...color centers in gadolinium -scandium-gallium garnet crystals. IANFA, no. 7, 1984, 1343-1345. 3. Babin, A.A.; Belyayeva, N.N.; Beiyayev, Yu.N

  17. Tunable Microwave Transversal Filters.

    DTIC Science & Technology

    1984-05-01

    GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER AFOSR-TR. 84-0977 S4. TI TLE (and Subtitle) 5. TYP ?FE&T&PEO OEE U!NABLE MICROWAVE TRANSVERSAL FILTERS...this goal through magnetostatic waves MSW propagating at microwave frequency in magnetically biased, liquid phase epitaxial films of yttrium iron...garnet (YIG) grown on gadolinium gallium garnet (GGG). This technology has a number of advantages; low loss (greater than 30db/usec at xband), tunable by

  18. Two-garnet rodingite from Amador County, California

    USGS Publications Warehouse

    Duffield, W.A.; Beeson, M.H.

    1973-01-01

    Two distinct phases of garnet have been discovered in rodingite from Amador County, Calif. The two garnets are hydrogrossular and (hydro?) grossular-andradite. Only one, generally hydrogrossular, has been reported in rodingitcs studied by other workers. The rodingite of this study formed from a mafic dike with abundant euhedral plagioclase laths. The hydrogrossular is concentrated within the areas of these laths and is volumetrically about as abundant. The (hydro?) grossular-andradite is concentrated in the groundmass and as incursions into the plagioclase laths. The garnets apparently grew during one general episode of metasomatism, and their spatial distribution and compositions were controlled principally by the unequal distribution of iron and aluminum caused by the presence of plagioclase laths (and mafic minerals?) in the original unaltered dike.

  19. Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; Pal, AnnaMarie T.; Patton, Martin O.; Jenkins, Phillip P.

    1999-01-01

    As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study presents a spectral emittance model for films and cylinders of rare earth doped yttrium aluminum garnets. Good agreement between experimental and theoretical film spectral emittances was found for erbium and holmium aluminum garnets. Spectral emittances of films are sensitive to temperature differences across the film. For operating conditions of interest, the film emitter experiences a linear temperature variation whereas the cylinder emitter has a more advantageous uniform temperature. Emitter efficiency is also a sensitive function of temperature. For holminum aluminum garnet film the efficiency is 0.35 at 1446K but only 0.27 at 1270 K.

  20. Gadolinium accumulation in organs of Sprague-Dawley® rats after implantation of a biodegradable magnesium-gadolinium alloy.

    PubMed

    Myrissa, Anastasia; Braeuer, Simone; Martinelli, Elisabeth; Willumeit-Römer, Regine; Goessler, Walter; Weinberg, Annelie Martina

    2017-01-15

    Biodegradable magnesium implants are under investigation because of their promising properties as medical devices. For enhancing the mechanical properties and the degradation resistance, rare earth elements are often used as alloying elements. In this study Mg10Gd pins were implanted into Sprague-Dawley® rats. The pin volume loss and a possible accumulation of magnesium and gadolinium in the rats' organs and blood were investigated in a long-term study over 36weeks. The results showed that Mg10Gd is a fast disintegrating material. Already 12weeks after implantation the alloy is fragmented to smaller particles, which can be found within the intramedullary cavity and the cortical bones. They disturbed the bone remodeling until the end of the study. The results concerning the elements' distribution in the animals' bodies were even more striking, since an accumulation of gadolinium could be observed in the investigated organs over the whole time span. The most affected tissue was the spleen, with up to 3240μgGd/kg wet mass, followed by the lung, liver and kidney (up to 1040, 685 and 207μgGd/kg). In the brain, muscle and heart, the gadolinium concentrations were much smaller (less than 20μg/kg), but an accumulation could still be detected. Interestingly, blood serum samples showed no accumulation of magnesium and gadolinium. This is the first time that an accumulation of gadolinium in animal organs was observed after the application of a gadolinium-containing degradable magnesium implant. These findings demonstrate the importance of future investigations concerning the distribution of the constituents of new biodegradable materials in the body, to ensure the patients' safety.

  1. Gallium-67 imaging in pulmonary eosinophilic granuloma

    SciTech Connect

    Makhija, M.C.; Davis, G.

    1984-03-01

    Gallium-67 citrate has been known to localize in the lungs in a variety of pulmonary diseases. Abnormal lung activity implies active underlying disease. Serial Ga-67 lung scans may be helpful when steroids are used as therapeutic agents. A case of pulmonary eosinophic granuloma is reported here with diffuse bilateral Ga-67 pulmonary activity.

  2. Gallium Electromagnetic (GEM) Thruster Performance Measurements

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Polzin, K. A.

    2009-01-01

    Discharge current, terminal voltage, and mass bit measurements are performed on a coaxial gallium electromagnetic thruster at discharge currents in the range of 7-23 kA. It is found that the mass bit varies quadratically with the discharge current which yields a constant exhaust velocity of 20 km/s. Increasing the electrode radius ratio of the thruster from to 2.6 to 3.4 increases the thruster efficiency from 21% to 30%. When operating with a central gallium anode, macroparticles are ejected at all energy levels tested. A central gallium cathode ejects macroparticles when the current density exceeds 3.7 10(exp 8) A/square m . A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma. The spectra show that neutral, singly, and doubly ionized gallium species are present in the discharge, as well as annular electrode species at higher energy levels. Axial Langmuir triple probe measurements yield electron temperatures in the range of 0.8-3.8 eV and electron densities in the range of 8 x 10(exp )20 to 1.6 x 10(exp 21) m(exp -3) . Triple probe measurements suggest an exhaust plume with a divergence angle of 9 , and a completely doubly ionized plasma at the ablating thruster cathode.

  3. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  4. Solar cell with a gallium nitride electrode

    DOEpatents

    Pankove, Jacques I.

    1979-01-01

    A solar cell which comprises a body of silicon having a P-N junction therein with a transparent conducting N-type gallium nitride layer as an ohmic contact on the N-type side of the semiconductor exposed to solar radiation.

  5. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  6. Anisotropy of the magnetic susceptibility of gallium

    USGS Publications Warehouse

    Pankey, T.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  7. SPECT gallium imaging in abdominal lymphoma

    SciTech Connect

    Adcock, K.A.; Friefeld, G.D.; Waldron, J.A. Jr.

    1986-05-01

    A case of non-Hodgkin's lymphoma of the abdomen studied by gallium SPECT imaging is reported. The tomographic slices accurately demonstrated the location of residual disease after chemotherapy in the region of the transverse mesocolon. Previous transmission CT had shown considerable persistent retroperitoneal lymphadenopathy, but was not helpful in determining the presence of viable lymphoma.

  8. A Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott; Greeff, Carl

    2009-06-01

    A new SESAME multiphase gallium equation of state (EOS) has been developed. The equation of state includes two of the solid phases (Ga I, Ga III) and a fluid phase. The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We will also explore refreezing via isentropic release and compression.

  9. Gallium-positive Lyme disease myocarditis

    SciTech Connect

    Alpert, L.I.; Welch, P.; Fisher, N.

    1985-09-01

    In the course of a work-up for fever of unknown origin associated with intermittent arrhythmias, a gallium scan was performed which revealed diffuse myocardial uptake. The diagnosis of Lyme disease myocarditis subsequently was confirmed by serologic titers. One month following recovery from the acute illness, the abnormal myocardial uptake completely resolved.

  10. Gallium Nitride Crystals: Novel Supercapacitor Electrode Materials.

    PubMed

    Wang, Shouzhi; Zhang, Lei; Sun, Changlong; Shao, Yongliang; Wu, Yongzhong; Lv, Jiaxin; Hao, Xiaopeng

    2016-05-01

    A type of single-crystal gallium nitride mesoporous membrane is fabricated and its supercapacitor properties are demonstrated for the first time. The supercapacitors exhibit high-rate capability, stable cycling life at high rates, and ultrahigh power density. This study may expand the range of crystals as high-performance electrode materials in the field of energy storage.

  11. Development of gallium aluminum phosphide electroluminescent diodes

    NASA Technical Reports Server (NTRS)

    Chicotka, R. J.; Lorenz, M. R.; Nethercot, A. H.; Pettit, G. D.

    1972-01-01

    Work done on the development of gallium aluminum phosphide alloys for electroluminescent light sources is described. The preparation of this wide band gap semiconductor alloy, its physical properties (particularly the band structure, the electrical characteristics, and the light emitting properties) and work done on the fabrication of diode structures from these alloys are broadly covered.

  12. Hydrogen chemisorption on gallium oxide polymorphs.

    PubMed

    Collins, Sebastián E; Baltanás, Miguel A; Bonivardi, Adrian L

    2005-02-01

    The chemisorption of H(2) over a set of gallia polymorphs (alpha-, beta-, and gamma-Ga(2)O(3)) has been studied by temperature-programmed adsorption equilibrium and desorption (TPA and TPD, respectively) experiments, using in situ transmission infrared spectroscopy. Upon heating the gallium oxides above 500 K in 101.3 kPa of H(2), two overlapped infrared signals developed. The 2003- and 1980-cm(-1) bands were assigned to the stretching frequencies of H bonded to coordinatively unsaturated (cus) gallium cations in tetrahedral and octahedral positions [nu(Ga(t)-H) and nu(Ga(o)-H), respectively]. Irrespective to the gallium cation geometrical environment, (i) a linear relationship between the integrated intensity of the whole nu(Ga-H) infrared band versus the Brunauer-Emmett-Teller surface area of the gallia was found and (ii) TPA and TPD results revealed that molecular hydrogen is dissociatively chemisorbed on any bulk gallium oxide polymorph following two reaction pathways. An endothermal, homolytic dissociation occurs over surface cus-gallium sites at T > 450 K, giving rise to Ga-H(I) bonds. The heat and entropy of this type I hydrogen adsorption were determined by the Langmuir's adsorption model as Deltah(I) = 155 +/- 25 kJ mol(-1) and Deltas(I) = 0.27 +/- 0.11 kJ mol(-1) K(-1). In addition, another exothermic, heterolytic adsorption sets in already in the low-temperature region. This type of hydrogen chemisorption involves surface Ga-O-Ga species, originating GaO-H and Ga-H(II) bonds which can only be removed from the gallia surface after heating under evacuation at T > 650 K. The measured desorption energy of this last, second-order process was equal to 77 +/- 10 kJ mol(-1). The potential of the H(2) chemisorption as a tool to measure or estimate the specific surface area of gallia and to discern the nature and proportion of gallium cation coordination sites on the surface of bulk gallium oxides is also analyzed.

  13. Analysis of garnets from the archaeological sites in Slovenia

    NASA Astrophysics Data System (ADS)

    Šmit, Ž.; Fajfar, H.; Jeršek, M.; Knific, T.; Lux, J.

    2014-06-01

    Garnets (62 individual stones) originating from the Migration Period cemeteries and hilltop settlements in Slovenia were analyzed by the combined PIXE/PIGE method for their chemical composition. Typologically, the analyzed stones may be classified as almandines originating from the sites in India, belonging to types I and II according to Calligaro. A smaller group of pyraldines intermediate between almandines and pyropes was also determined; identified as type III, their source is most likely in Sri Lanka. No garnets from Bohemia (Czech Republic) have been discovered, which may be related to important political changes in the 7th c. AD, induced by Slavic and Avaric migrations.

  14. Electronic structure of Ce3+ multicenters in yttrium aluminum garnets

    NASA Astrophysics Data System (ADS)

    Przybylińska, H.; Ma, Chong-Geng; Brik, M. G.; Kamińska, A.; Sybilski, P.; Wittlin, A.; Berkowski, M.; Zorenko, Yu.; Gorbenko, V.; Wrzesinski, H.; Suchocki, A.

    2013-06-01

    Low temperature, infrared, and visible-ultraviolet absorption spectra of yttrium aluminum garnet (YAG) bulk crystals and epitaxial layers doped with Ce are presented. In the region of intra-configurational 4f-4f transitions, the spectra of the bulk YAG crystals exhibit existence of at least two different Ce3+ related centers, a major one associated with Ce in regular positions substituting yttrium and also additional center, due to so called antisite positions in the garnet host, i.e., ions in the Al positions. Crystal field analysis based on exchange charge model exhibit excellent agreement with the experimental data for major Ce3+ center.

  15. Chemistry and pharmacokinetics of gallium maltolate, a compound with high oral gallium bioavailability.

    PubMed

    Bernstein, L R; Tanner, T; Godfrey, C; Noll, B

    2000-01-01

    Gallium maltolate, tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium (GaM), is an orally active gallium compound for therapeutic use. It is moderately soluble in water (10.7 +/- 0.9 mg/mL at 25 composite functionC) with an octanol partition coefficient of 0.41+/-0.08. The molecule is electrically neutral in aqueous solution at neutral pH; a dilute aqueous solution (2.5 x10-(-5) M) showed little dissociation at pH 5.5-8.0. Single crystal X-ray diffraction analysis found the GaM molecule to consist of three maltolate ligands bidentately bound to a central gallium atom in a propeller-like arrangement, with one of the ligands disordered in two possible orientations. The compound is orthorhombic, space group Pbca, unit cell a = 16.675(3), b = 12.034(2), c = 18.435(2) A at 158K. GaM was administered to healthy human volunteers at single doses of 100, 200, 300, and 500 mg (three subjects per dose). GaM was very well tolerated. Oral absorption of Ga into plasma was fairly rapid (absorption half life = 0.8-2.0h), with a central compartment excretion half life of 17-21h. Absorption appeared dose proportional over the dosage range studied. Estimated oral gallium bioavailability was approximately 25-57%, based on comparison with published data on intravenous gallium nitrate. Urinary Ga excretion following oral GaM administration was approximately 2% of the administered dose over 72h, in contrast to 49-94% urinary Ga excretion over 24h following i.v. gallium nitrate administration. We suggest that oral administration of GaM results in nearly all plasma gallium being bound to transferrin, whereas i.v. administration of gallium nitrate results in formation of considerable plasma gallate [Ga(OH)(4) (-)], which is rapidly excreted in the urine. These data support the continued investigation of GaM as an orally active therapeutic gallium compound.

  16. Chemistry and Pharmacokinetics of Gallium Maltolate, a Compound With High Oral Gallium Bioavailability

    PubMed Central

    Tanner, Trevor; Godfrey, Claire; Noll, Bruce

    2000-01-01

    Gallium maltolate, tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium (GaM), is an orally active gallium compound for therapeutic use. It is moderately soluble in water (10.7 ± 0.9 mg/mL at 25∘C) with an octanol partition coefficient of 0.41±0.08. The molecule is electrically neutral in aqueous solution at neutral pH; a dilute aqueous solution (2.5 ×10−-5 M) showed little dissociation at pH 5.5-8.0. Single crystal X-ray diffraction analysis found the GaM molecule to consist of three maltolate ligands bidentately bound to a central gallium atom in a propeller-like arrangement, with one of the ligands disordered in two possible orientations. The compound is orthorhombic, space group Pbca, unit cell a = 16.675(3), b = 12.034(2), c = 18.435(2) Å at 158K. GaM was administered to healthy human volunteers at single doses of 100, 200, 300, and 500 mg (three subjects per dose). GaM was very well tolerated. Oral absorption of Ga into plasma was fairly rapid (absorption half life = 0.8-2.0h), with a central compartment excretion half life of 17-21h. Absorption appeared dose proportional over the dosage range studied. Estimated oral gallium bioavailability was approximately 25-57%, based on comparison with published data on intravenous gallium nitrate. Urinary Ga excretion following oral GaM administration was approximately 2% of the administered dose over 72h, in contrast to 49-94% urinary Ga excretion over 24h following i.v. gallium nitrate administration. We suggest that oral administration of GaM results in nearly all plasma gallium being bound to transferrin, whereas i.v. administration of gallium nitrate results in formation of considerable plasma gallate [Ga(OH)4−], which is rapidly excreted in the urine. These data support the continued investigation of GaM as an orally active therapeutic gallium compound. PMID:18475921

  17. Gallium 67 scintigraphy in glomerular disease

    SciTech Connect

    Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

    1988-12-01

    To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

  18. Discovery of samarium, europium, gadolinium, and terbium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2013-01-15

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

  19. Gadolinium chloride pretreatment ameliorates acute cadmium-induced hepatotoxicity.

    PubMed

    Kyriakou, Loukas G; Tzirogiannis, Konstantinos N; Demonakou, Maria D; Kourentzi, Kalliopi T; Mykoniatis, Michael G; Panoutsopoulos, Georgios I

    2013-08-01

    Cadmium is a known industrial and environmental pollutant. It causes hepatotoxicity upon acute administration. Features of cadmium-induced acute hepatoxicity encompass necrosis, apoptosis, peliosis and inflammatory infiltration. Gadolinium chloride (GdCl3) may prevent cadmium-induced hepatotoxicity by suppressing Kupffer cells. The effect of GdCl3 pretreatment on a model of acute cadmium-induced liver injury was investigated. Male Wistar rats 4-5 months old were injected intraperitoneally with normal saline followed by cadmium chloride (CdCl2; 6.5 mg/kg) or GdCl3 (10 mg/kg) followed by CdCl2 (6.5 mg/kg; groups I and II, respectively). Rats of both the groups were killed at 9, 12, 16, 24, 48 and 60 h after cadmium intoxication. Liver sections were analyzed for necrosis, apoptosis, peliosis and mitoses. Liver regeneration was also evaluated by tritiated thymidine incorporation into hepatic DNA. Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also determined. Hepatic necrosis, hepatocyte and nonparenchymal cell apoptosis and macroscopic and microscopic types of peliosis hepatis were minimized by gadolinium pretreatment. Serum levels of AST and ALT were also greatly diminished in rats of group II. Tritiated thymidine incorporation into hepatic DNA was increased in gadolinium pretreatment rats. Kupffer cell activation was minimal in both the groups of rats. Gadolinium pretreatment attenuates acute cadmium-induced liver injury in young Wistar rats, with mechanisms other than Kupffer cell elimination.

  20. Purification of cerium, neodymium and gadolinium for low background experiments

    NASA Astrophysics Data System (ADS)

    Boiko, R. S.; Barabash, A. S.; Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Tretyak, V. I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  1. Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

    SciTech Connect

    Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; Vohra, Yogesh K.

    2014-11-07

    High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Smtype→ dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GP and a temperature of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.

  2. Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

    DOE PAGES

    Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

    2014-11-07

    High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Smtype→ dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GP and a temperaturemore » of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.« less

  3. Lu-Hf geochronology on cm-sized garnets using microsampling: New constraints on garnet growth rates and duration of metamorphism during continental collision (Menderes Massif, Turkey)

    NASA Astrophysics Data System (ADS)

    Schmidt, Alexander; Pourteau, Amaury; Candan, Osman; Oberhänsli, Roland

    2015-12-01

    This study shows Lu-Hf geochronology of zoned garnet crystals contained in mica schists from the southern Menderes Massif, Turkey. Selected samples are four 3-5 cm large garnet megacrysts of which several consecutive garnet shells have been sampled with a micro-saw and analyzed for dating. The results are used to extract growth rates of garnet, and also to improve the time constraint for Alpine-aged overprint of the Pan-African basement in the Menderes Massif. Lu-Hf ages of the sampled garnet shells are determined by two-point garnet-only isochrons using the garnets' Lu-depleted rim compositions. This yields a consistent decrease of age information from core to rim segments of individual garnet crystals and the calculated isochron ages propose a time frame of growth between 42.6 ± 1.9 and 34.8 ± 3.1 Ma. Major element profiles in the investigated garnets characterize zoning patterns indicative of prograde conditions: Rayleigh fractionated bell-shaped Mn and decreasing Fe/(Fe + Mg) are recorded by the garnets' core to rim compositions. Therefore the obtained Lu-Hf ages record timing of early prograde growth for the cores of the garnets. Two of the large garnet crystals also yield isochron ages of 58.83 ± 0.69 and 50.16 ± 0.84 Ma in their innermost cores, which appear to record an early nucleation event. This view, however, is not in concordance with the observed major element profiles of these garnets, and therefore is interpreted with caution. Termination of the garnet growth period is determined through the calculation of radial growth rates based on the size of the garnets and the Lu-Hf ages obtained for consecutive shells. Extrapolation of these rates potentially constrains the total duration for garnet growth terminating at 31 ± 6 Ma. Comparison of the growth rates calculated for individual crystals shows a variety of slow and fast growing garnets, and similar results have been previously obtained with the Rb-Sr and Sm-Nd isotope systems. The new data

  4. Europium gallium garnet (Eu3Ga5O12) and Eu3GaO6: Synthesis and material properties

    NASA Astrophysics Data System (ADS)

    Sawada, Kenji; Nakamura, Toshihiro; Adachi, Sadao

    2016-10-01

    Eu-Ga-O ternary compounds were synthesized from a mixture of cubic (c-) Eu2O3 and monoclinic Ga2O3 (β-Ga2O3) raw powders using the solid-state reaction method by calcination at Tc = 1200 °C. The structural and optical properties of the Eu-Ga-O ternary compounds were investigated using X-ray diffraction analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and Raman scattering measurements. Stoichiometric compounds such as cubic Eu3Ga5O12 (EGG) and orthorhombic Eu3GaO6 were synthesized using molar ratios of x = 0.375 and 0.75 [x≡Eu2O3/(Eu2O3 + Ga2O3)], respectively, together with the end-point binary compounds β-Ga2O3 (x = 0) and monoclinic (m-) Eu2O3 (x = 1.0). The structural change from "cubic" to "monoclinic" in Eu2O3 is due to the structural phase transition occurring at Tc ≥ 1050 °C. In principle, the perovskite-type EuGaO3 and monoclinic Eu4Ga2O9 can also be synthesized at x = 0.5 and 0.667, respectively; however, such stoichiometric compounds could not be synthesized in this study. The PL and PLE properties of EGG and Eu3GaO6 were studied in detail. The temperature dependence of the PL spectra was observed through measurements carried out between T = 20 and 300 K and explained using a newly developed model. Raman scattering measurements were also performed on the Eu-Ga-O ternary systems over the entire composition range from x = 0 (β-Ga2O3) to 1.0 (m-Eu2O3).

  5. Luminescent properties of Cr-doped gallium garnet crystals grown by the micro-pulling-down method

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Suzuki, Akira; Yamaji, Akihiro; Kamada, Kei; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Chani, Valery Ivanovich; Yoshikawa, Akira

    2016-10-01

    Cr-doped (GdxY1-x)3Ga5O12 crystals (x=0.00, 0.25, 0.50, 0.75 and 1.00) were grown by the micro-pulling-down method and examined for their possible application as red and infrared scintillating detectors in medical field. Although Cr:(Gd0.75Y0.25)3Ga5O12 and Cr:Gd3Ga5O12 had similar X-ray diffraction patterns, other samples showed some change in lattice constant. All the crystals had broad emission bands in the red and infrared region when excited by either 450 nm photons or X rays. These bands were associated with 4T2→A2 transitions. Moreover, redshift of the emission-peak wavelengths (4T2→4A2) and absorption peaks (4A2→4T1 and 4T2) was observed with increase of Gd content (x) in Cr-doped (GdxY1-x)3Ga5O12 due to the change of the crystal fields. The crystals had scintillation emissions in the wavelength region suitable for the real time dose monitoring in radiation therapy.

  6. Fragmentation of wall rock garnets during deep crustal earthquakes

    PubMed Central

    Austrheim, Håkon; Dunkel, Kristina G.; Plümper, Oliver; Ildefonse, Benoit; Liu, Yang; Jamtveit, Bjørn

    2017-01-01

    Fractures and faults riddle the Earth’s crust on all scales, and the deformation associated with them is presumed to have had significant effects on its petrological and structural evolution. However, despite the abundance of directly observable earthquake activity, unequivocal evidence for seismic slip rates along ancient faults is rare and usually related to frictional melting and the formation of pseudotachylites. We report novel microstructures from garnet crystals in the immediate vicinity of seismic slip planes that transected lower crustal granulites during intermediate-depth earthquakes in the Bergen Arcs area, western Norway, some 420 million years ago. Seismic loading caused massive dislocation formations and fragmentation of wall rock garnets. Microfracturing and the injection of sulfide melts occurred during an early stage of loading. Subsequent dilation caused pervasive transport of fluids into the garnets along a network of microfractures, dislocations, and subgrain and grain boundaries, leading to the growth of abundant mineral inclusions inside the fragmented garnets. Recrystallization by grain boundary migration closed most of the pores and fractures generated by the seismic event. This wall rock alteration represents the initial stages of an earthquake-triggered metamorphic transformation process that ultimately led to reworking of the lower crust on a regional scale. PMID:28261660

  7. Fragmentation of wall rock garnets during deep crustal earthquakes.

    PubMed

    Austrheim, Håkon; Dunkel, Kristina G; Plümper, Oliver; Ildefonse, Benoit; Liu, Yang; Jamtveit, Bjørn

    2017-02-01

    Fractures and faults riddle the Earth's crust on all scales, and the deformation associated with them is presumed to have had significant effects on its petrological and structural evolution. However, despite the abundance of directly observable earthquake activity, unequivocal evidence for seismic slip rates along ancient faults is rare and usually related to frictional melting and the formation of pseudotachylites. We report novel microstructures from garnet crystals in the immediate vicinity of seismic slip planes that transected lower crustal granulites during intermediate-depth earthquakes in the Bergen Arcs area, western Norway, some 420 million years ago. Seismic loading caused massive dislocation formations and fragmentation of wall rock garnets. Microfracturing and the injection of sulfide melts occurred during an early stage of loading. Subsequent dilation caused pervasive transport of fluids into the garnets along a network of microfractures, dislocations, and subgrain and grain boundaries, leading to the growth of abundant mineral inclusions inside the fragmented garnets. Recrystallization by grain boundary migration closed most of the pores and fractures generated by the seismic event. This wall rock alteration represents the initial stages of an earthquake-triggered metamorphic transformation process that ultimately led to reworking of the lower crust on a regional scale.

  8. William Herschel and the 'garnet' stars: μ Cephei and more

    NASA Astrophysics Data System (ADS)

    Steinicke, Wolfgang

    2015-07-01

    Although William Herschel's 'Garnet Star' (μ Cephei) is a prominent object, the story of the discovery of this famous red star is not well documented. Prior to and after Herschel, the identification of this star was the subject of confusion in various catalogues and atlases. The case is complex and involves other stars in southern Cepheus, including double stars, found by Herschel in the course of his star surveys. It is also fascinating to learn that μ Cephei is not the only star called 'garnet' by him. This study reveals that there are 21 in all, resulting in a 'Herschel Catalogue of Garnet Stars' - the first historical catalogue of red stars. Among them are prominent objects, which in the literature are credited to later observers. This misconception is corrected here, for Herschel was the true discoverer of all of them. The most interesting cases are Hind's 'Crimson Star', Secchi's 'La Superba', John Herschel's 'Ruby Star' and Schmidt's V Aquilae. Finally, we discussed whether Herschel speculated about the physical nature of his garnet stars, many of which are now known to be variable.

  9. On fabrication procedures of Li-ion conducting garnets

    NASA Astrophysics Data System (ADS)

    Hanc, Emil; Zając, Wojciech; Lu, Li; Yan, Binggong; Kotobuki, Masashi; Ziąbka, Magdalena; Molenda, Janina

    2017-04-01

    Ceramic oxides exhibiting high lithium-ion mobility at room temperature receive broad attention as candidate electrolytes for lithium batteries. Lithium-stuffed garnets from the Li7La3Zr2O12 group seem to be especially promising because of their high ionic conductivity at room temperature and their electrochemical stability. In this work, we discuss factors that affect formation of the garnet in its bulk form or in the form of thick and thin films. We demonstrate that zinc oxide can be applied as a sintering aid that facilitate the formation of the highly conducting cubic Li7La3Zr2O12 garnet phase in a single-step sintering procedure. Based on our experience with the single-step sintering experiments, we successfully fabricated a thick-film membrane consisting of a garnet solid electrolyte using the tape casting technique. In order to reduce the thickness of the electrolyte even further we investigated the fabrication of a thin-film Li7La3Zr2O12 electrolyte by means of the pulsed laser deposition technique.

  10. Lowest-temperature magnetic phase transition of samarium iron garnet

    NASA Astrophysics Data System (ADS)

    Balestrino, G.; Geller, S.; Antonini, B.; Paroli, P.; Tucciarone, A.

    1984-10-01

    New Mössbauer spectroscopic analysis confirms the spin reorientation below 18 K of samarium iron garnet first reported by Geller and Balestrino. However, both the Mössbauer spectroscopic analysis and measurements with an easy-axis monitor indicate that the axis of easy magnetization at the end of the spin reorientation region is along a <740> direction.

  11. Survey of the market, supply and availability of gallium

    SciTech Connect

    Rosi, F.D.

    1980-07-01

    The objective of this study was to assess the present consumption and supply of gallium, its potential availability in the satellite power system (SPS) implementation time frame, and commercial and new processing methods for increasing the production of gallium. Findings are reported in detail. The findings strongly suggest that with proper long range planning adequate gallium would be available from free-enterprise world supplies of bauxite for SPS implementation.

  12. Magnetostriction and Magnetic Heterogeneities in Iron-Gallium

    DTIC Science & Technology

    2010-07-08

    REPORT Magnetostriction and Magnetic Heterogeneities in Iron-Gallium 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Iron-gallium alloys Fe1-xGax exhibit...an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe0.81Ga0.19 single...magnetic heterogeneities in the mechanism for magnetostriction in this material. 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES

  13. Surface photovoltage spectroscopy applied to gallium arsenide surfaces

    NASA Technical Reports Server (NTRS)

    Bynik, C. E.

    1975-01-01

    The experimental and theoretical basis for surface photovoltage spectroscopy is outlined. Results of this technique applied to gallium arsenide surfaces, are reviewed and discussed. The results suggest that in gallium arsenide the surface voltage may be due to deep bulk impurity acceptor states that are pinned at the Fermi level at the surface. Establishment of the validity of this model will indicate the direction to proceed to increase the efficiency of gallium arsenide solar cells.

  14. Inflammatory pseudotumor: A gallium-avid mobile mesenteric mass

    SciTech Connect

    Auringer, S.T.; Scott, M.D.; Sumner, T.E. )

    1991-08-01

    An 8-yr-old boy with a 1-mo history of culture-negative fever and anemia underwent gallium, ultrasound, and computed tomography studies as part of the evaluation of a fever of unknown origin. These studies revealed a mobile gallium-avid solid abdominal mass subsequently proven to be an inflammatory pseudotumor of the mesentery, a rare benign mass. This report documents the gallium-avid nature of this rare lesion and discusses associated characteristic clinical, pathologic, and radiographic features.

  15. Gallium Nitride (GaN) High Power Electronics (FY11)

    DTIC Science & Technology

    2012-01-01

    Gallium Nitride (GaN) High Power Electronics (FY11) by Kenneth A. Jones, Randy P. Tompkins, Michael A. Derenge, Kevin W. Kirchner, Iskander...Army Research Laboratory Adelphi, MD 20783-1197 ARL-TR-5903 January 2012 Gallium Nitride (GaN) High Power Electronics (FY11) Kenneth A...DSI 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Gallium Nitride (GaN) High Power Electronics (FY11) 5a. CONTRACT NUMBER 5b. GRANT

  16. Interactions of Zircaloy cladding with gallium: 1998 midyear status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

    1998-06-01

    A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  17. Interactions of zircaloy cladding with gallium -- 1997 status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

    1997-11-01

    A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  18. Diamond-garnet geobarometry: The role of garnet compressibility and expansivity

    NASA Astrophysics Data System (ADS)

    Milani, S.; Nestola, F.; Alvaro, M.; Pasqual, D.; Mazzucchelli, M. L.; Domeneghetti, M. C.; Geiger, C. A.

    2015-06-01

    We report P-V and T-V Equations of State (EoS) for synthetic single crystal pyrope (Py, Mg3Al2Si3O12) and the P-V EoS for synthetic single crystals of almandine (Alm, Fe3Al2Si3O12) as well as an intermediate composition (Py60Alm40) as measured by in-situ high-pressure and high-temperature X-ray diffraction experiments. The unit-cell volumes of the three samples were measured at room temperature and different pressures and up to about 8 GPa in a diamond-anvil cell. The high-temperature experiment was carried out using a micro-furnace. The pressure-volume data were fitted to a third order Birch-Murnaghan EoS giving the following coefficients: V0 = 1506.15(16) Å3, KT0 = 163.7(1.7) GPa and K‧ = 6.4(4) for pyrope, V0 = 1533.52(10) Å3, KT0 = 172.6(1.5) GPa and K‧ = 5.8(5) for almandine and V0 = 1516.32(13) Å3, KT0 = 167.2(1.7) GPa and K‧ = 5.6(5) for the intermediate Py60Alm40 composition. The unit-cell volume along the pyrope-almandine join changes linearly within the error of measurement indicating ideality in the volume of mixing behaviour for the solid solution. The first pressure derivative, K‧, for all three garnets is similar within experimental uncertainty with an average value of K‧ = 6.0(4). The thermal expansion parameters for end-member pyrope, as described using to the Kroll-type EoS, with the Einstein temperature, θE, fixed to 320 K, are α(303 K, 1 bar) = 2.543(5) ∗ 10- 5 K- 1 and V0 = 1504.64(4) Å3. The determined thermoelastic parameters were combined in a thermal-pressure type EoS (thermal-P type EoS) to calculate the entrapment pressures, Pe, for natural garnet inclusions in diamonds at mantle temperatures. A calculated pressure of 5.8 GPa at T = 1500 K using our newly determined thermoelastic parameters appears to be more consistent with diamond-forming conditions compared to the higher pressures that range up to 6.8 GPa at T = 1500 K, which are obtained using thermoelastic data in the literature.

  19. Calculation of the Energetics of Water Incorporation in Majorite Garnet

    NASA Astrophysics Data System (ADS)

    Pigott, J. S.; Wright, K.; Gale, J. D.; Panero, W. R.

    2013-12-01

    Global-scale mantle processes, such as subduction and plume ascent, are linked to surface processes through plate tectonics. Subduction rates, plume buoyancy, and rheology are among the properties associated with a convective mantle that are strongly affected by the volatile budget of the Earth's upper mantle and transition zone (410 km - 660 km). Therefore understanding of the role of hydrogen in mantle minerals is of importance when modeling mantle convection throughout Earth history into the Hadean. Garnet is found in the Earth's upper mantle and transition zone (~60 km - 710 km) with majorite garnet accounting for as much as 40 percent of the rock volume at 500 km. Given the potential of nominally anhydrous minerals, including garnet, to store H2O in the form of OH defects, constraining the hydrogen incorporation mechanism in majorite is crucial to an accurate interpretation of mantle processes. The water storage capacity of majorite is controlled by pressure, temperature, composition and the mechanism by which it incorporates hydrogen. Estimates of the potential of mantle garnets to be major water storage minerals, as well as the mechanics of hydrogen incorporation in majorite, are variable based on experimental evidence. This study addresses the deep-Earth water budget by calculating the defect energetics associated with hydrogen incorporation into tetragonal MgSiO3 (majorite) garnet between 0 and 20 GPa using atomistic simulations. At the pressure conditions of the Earth's mantle, hydrogen is most likely to be associated with protonation of oxygen adjacent to cation vacancies. At both P = 10 GPa and P = 20 GPa, our calculations show that of the six distinct oxygen positions, only three are likely to be protonated. Hydroxyl groups are predicted to be bound to Mg vacancies as [VMg(OH)2]X defect complexes, where the Mg vacancies are located at both the octahedral and dodecahedral sites.

  20. A comparison of microstructural and chemical patterns in garnet from the Fleur de Lys Supergroup, Newfoundland

    NASA Astrophysics Data System (ADS)

    Stallard, Aaron; Hickey, Ken

    2002-07-01

    This study uses compositional analyses of garnet porphyroblasts to test a previously published microstructure-based model of garnet growth in the Fleur de Lys Supergroup. X-ray maps reveal significant compositional anomalies within garnet, including zoning reversals and steepened compositional gradients. These anomalies occur at the margin of the proposed first stage of garnet growth (G 1), and coincide with truncations of inclusion trails and changes in the inclusion assemblage. Intervals of reversed composition zoning and steepened compositional gradients across this boundary are interpreted to represent a hiatus in garnet growth, possibly accompanied by garnet consumption, during which changes in the garnet-forming reaction, P- T conditions and deformation kinematics occurred. The junction of the proposed second and third stages of garnet growth (G 2 and G 3) coincides with the transition between successive crenulation cleavages, without substantial microstructural truncations or changes in the inclusion assemblage. The G 2-G 3 boundary is generally marked by uninterrupted normal zoning, with subtle compositional anomalies in some samples. This boundary may in fact record continuous garnet growth, or alternatively mark a relatively short intra-orogenic pause in garnet growth with minimal affect on zoning patterns. Individual porphyroblasts with contrasting inclusion trail microstructures also have different zoning patterns, and this supports the previous recognition of contrasting growth histories between individual porphyroblasts. A combined structural-metamorphic model is presented that integrates the timing of garnet growth and foliation development, reaction history and the P- T- t path in the Fleur de Lys Supergroup.

  1. Efficient water reduction with gallium phosphide nanowires

    NASA Astrophysics Data System (ADS)

    Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A.; van Dam, Dick; Cui, Yingchao; Notten, Peter H. L.; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.

    2015-07-01

    Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires.

  2. Efficient water reduction with gallium phosphide nanowires

    PubMed Central

    Standing, Anthony; Assali, Simone; Gao, Lu; Verheijen, Marcel A.; van Dam, Dick; Cui, Yingchao; Notten, Peter H. L.; Haverkort, Jos E. M.; Bakkers, Erik P. A. M.

    2015-01-01

    Photoelectrochemical hydrogen production from solar energy and water offers a clean and sustainable fuel option for the future. Planar III/V material systems have shown the highest efficiencies, but are expensive. By moving to the nanowire regime the demand on material quantity is reduced, and new materials can be uncovered, such as wurtzite gallium phosphide, featuring a direct bandgap. This is one of the few materials combining large solar light absorption and (close to) ideal band-edge positions for full water splitting. Here we report the photoelectrochemical reduction of water, on a p-type wurtzite gallium phosphide nanowire photocathode. By modifying geometry to reduce electrical resistance and enhance optical absorption, and modifying the surface with a multistep platinum deposition, high current densities and open circuit potentials were achieved. Our results demonstrate the capabilities of this material, even when used in such low quantities, as in nanowires. PMID:26183949

  3. Combined external-beam PIXE and /μ-Raman characterisation of garnets used in Merovingian jewellery

    NASA Astrophysics Data System (ADS)

    Calligaro, T.; Colinart, S.; Poirot, J.-P.; Sudres, C.

    2002-04-01

    Red garnets were the dominant gemstones used for jewels in Europe during the Early Middle Ages. We have studied over 350 garnets set on 12 jewels unearthed in the royal necropolis of the Saint-Denis Basilica, close to Paris. This famous collection of "cloisonné" style artefacts dates from the Merovingian period (late fifth century AD to early seventh century AD). The archaeological issue addressed is the identification of the geographical origin of these garnets, in view to establish the gem trading routes during the Dark Ages. External beam PIXE was used to determine the major constituents (Mg, Al, Si, Ca, Mn, Fe), specifying the garnet type (composition in various mineralogical end-members, e.g. almandine, pyrope, spessartite, …), and the trace element content (Cr, Y). Three sorts of garnets were identified. Ten jewels are adorned with almandine garnets (Fe-rich). One jewel has intermediate almandine-pyrope garnets ("rhodolite"). The last and most recent jewel is inlaid with pyrope (Mg-rich) garnets. Trace element content and slight differences in major composition allowed to distinguish five different sources: two sources for pyrope garnets (with and without chromium), and two sources for almandine garnets (distinctive calcium, magnesium and yttrium contents). A preliminary comparison with literature data suggested that almandine garnets may have been mined from India while the "rhodolite" garnets may have been imported from Sri Lanka. The sources of pyrope garnets could be the Bohemian deposits (Czech republic). In addition, μ-Raman spectrometry was used to identify most of the mineral inclusions (apatite, zircon, ilmenite, monazite, calcite, quartz) present in almandine garnets. Even if two specific types of inclusions were not identified, due to the lack of corresponding reference spectra in our database, the Raman spectra collected provided an interesting inclusion fingerprint.

  4. A Gallium multiphase equation of state

    SciTech Connect

    Crockett, Scott D; Greeff, Carl

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

  5. Gallium-67 radionuclide imaging in acute pyelonephritis

    SciTech Connect

    Mendez, G.; Morillo, G.; Alonso, M.; Isikoff, M.B.

    1980-01-01

    The symptoms and clinical course of patients with acute pyelonephritis are variable; likewise, urinalysis, blood cultures, and excretory urography may be normal or equivocal. The ability of gallium-67 to accumulate in areas of active inflammation was useful in the diagnosis of acute pyelonephritis in 12 cases. A multiplane tomographic scanner was used for imaging four of these patients. Initial experience with this scanner is also discussed.

  6. a Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott D.; Greeff, Carl W.

    2009-12-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. It includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression. We predict an unusual spontaneous spreading of low pressure shocks from STP.

  7. Positron study of annealing of gallium arsenide

    SciTech Connect

    Rice-Evans, P.C.; Smith, D.L.; Evans, H.E.; Gledhill, G.A. )

    1991-02-01

    A positron beam has been used to investigate the sub-surface changes in semi-insulating gallium arsenide which had been annealed to a range of temperatures. The variations of the Doppler S parameter as a function of positron implantation energy, when subjected to a diffusion analysis, indicate variations in positron trapping at different depths. The results indicate the changes in the type of point defect that accompany the annealing.

  8. High-dose gallium imaging in lymphoma

    SciTech Connect

    Anderson, K.C.; Leonard, R.C.; Canellos, G.P.; Skarin, A.T.; Kaplan, W.D.

    1983-08-01

    The role of gallium-67 imaging in the management of patients with lymphoma, traditionally assessed using low tracer doses and the rectilinear scanner, was assessed when using larger doses (7 to 10 mCi) and a triple-peak Anger camera. Gallium scan results in 51 patients with non-Hodgkin's lymphoma and 21 patients with Hodgkin's disease were compared with simultaneous radiologic, clinical, and histopathologic reports. Subsequent disease course was also evaluated in light of radionuclide findings. Sensitivity and specificity of the scans were 0.90 or greater for both non-Hodgkin's lymphoma and Hodgkin's disease, and overall accuracy by site was 96 percent. Although there are insufficient numbers of pretreatment scans to allow any conclusions, our data suggest that newer approaches to gallium scanning in treated patients are (1) highly specific in all lymphomas and most sensitive in high-grade non-Hodgkin's lymphoma and Hodgkin's disease; (2) valuable in assessing the mediastinum in both non-Hodgkin's lymphoma and Hodgkin's disease; and (3) helpful adjuncts to computed tomographic scanning and ultrasonography in assessing abdominal node disease.

  9. About a Gadolinium-doped Water Cherenkov LAGUNA Detector

    SciTech Connect

    Labarga, Luis

    2010-11-24

    Water Cherenkov (wC) detectors are extremely powerful apparatuses for scientific research. Nevertheless they lack of neutron tagging capabilities, which translates, mainly, into an inability to identify the anti-matter nature of the reacting incoming anti-neutrino particles. A solution was proposed by R. Beacon and M. Vagins back in 2004: by dissolving in the water a compound with nucleus with very large cross section for neutron capture like the Gadolinium, with a corresponding emission of photons of enough energy to be detected, they can tag thermal neutrons with an efficiency larger than 80%. In this talk we detail the technique and its implications in the measurement capabilities and, as well, the new backgrounds induced. We discuss the improvement on their physics program, also for the case of LAGUNA type detectors. We comment shortly the status of the pioneering R and D program of the Super-Kamiokande Collaboration towards dissolving a Gadolinium compound in its water.

  10. [Gadolinium-based contrast agents for magnetic resonance imaging].

    PubMed

    Carrasco Muñoz, S; Calles Blanco, C; Marcin, Javier; Fernández Álvarez, C; Lafuente Martínez, J

    2014-06-01

    Gadolinium-based contrast agents are increasingly being used in magnetic resonance imaging. These agents can improve the contrast in images and provide information about function and metabolism, increasing both sensitivity and specificity. We describe the gadolinium-based contrast agents that have been approved for clinical use, detailing their main characteristics based on their chemical structure, stability, and safety. In general terms, these compounds are safe. Nevertheless, adverse reactions, the possibility of nephrotoxicity from these compounds, and the possibility of developing nephrogenic systemic fibrosis will be covered in this article. Lastly, the article will discuss the current guidelines, recommendations, and contraindications for their clinical use, including the management of pregnant and breast-feeding patients.

  11. Gadolinium-enhanced magnetic resonance angiography in brain death

    NASA Astrophysics Data System (ADS)

    Luchtmann, M.; Beuing, O.; Skalej, M.; Kohl, J.; Serowy, S.; Bernarding, J.; Firsching, R.

    2014-01-01

    Confirmatory tests for the diagnosis of brain death in addition to clinical findings may shorten observation time required in some countries and may add certainty to the diagnosis under specific circumstances. The practicability of Gadolinium-enhanced magnetic resonance angiography to confirm cerebral circulatory arrest was assessed after the diagnosis of brain death in 15 patients using a 1.5 Tesla MRI scanner. In all 15 patients extracranial blood flow distal to the external carotid arteries was undisturbed. In 14 patients no contrast medium was noted within intracerebral vessels above the proximal level of the intracerebral arteries. In one patient more distal segments of the anterior and middle cerebral arteries (A3 and M3) were filled with contrast medium. Gadolinium-enhanced MRA may be considered conclusive evidence of cerebral circulatory arrest, when major intracranial vessels fail to fill with contrast medium while extracranial vessels show normal blood flow.

  12. Compensation and Characterization of Gallium Arsenide

    NASA Astrophysics Data System (ADS)

    Roush, Randy Allen

    1995-01-01

    The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow silicon donors are compensated by deep acceptors. Copper is an example of a transition metal that forms deep acceptors in GaAs, and therefore this work will focus on the compensation and characterization of GaAs:Si:Cu. The compensation of the material has shown that the lower diffusion temperatures (500-600^ circC) form primarily the well-known Cu _{rm B} centers whereas the higher temperature anneals (>750 ^circC) result in the formation of CU_{rm A}. Using compensation curves, the copper density is found by comparing the compensation temperature with copper solubility curves given by others. These curves also show that the formation of CU_{rm B}, EL2, and CU_{rm A} can be manipulated by varying processing parameters such as annealing temperature and arsenic pressure. The compensation results are confirmed using Temperature-Dependent Hall (TDH) measurements to detect the copper levels. Also, the photoconductive properties of the material under illumination from 1.06 and 2.1 μm wavelength laser pulses have been used to demonstrate the effects of the different processing procedures. The persistent photoconductivity inherent to these devices under illumination from the 1.06 μm laser pulse is used to predict the concentration of the Cu_ {rm B

  13. Dressler's syndrome demonstrated by late gadolinium enhancement cardiovascular magnetic resonance

    PubMed Central

    Steadman, Christopher D; Khoo, Jeffrey; Kovac, Jan; McCann, Gerry P

    2009-01-01

    A 49-year old patient presented late with an anterolateral ST-elevation myocardial infarction and was treated with rescue angioplasty to an occluded left anterior descending artery. Her recovery was complicated by low-grade pyrexia and raised inflammatory markers. Cardiovascular magnetic resonance 5 weeks after the acute presentation showed transmural infarction and global late gadolinium enhancement of the pericardium in keeping with Dressler's syndrome. PMID:19627595

  14. Magnons as a Bose-Einstein Condensate in Nanocrystalline Gadolinium

    SciTech Connect

    Kaul, S. N.; Mathew, S. P.

    2011-06-17

    The recent observation [S. P. Mathew et al., J. Phys. Conf. Ser. 200, 072047 (2010)] of the anomalous softening of spin-wave modes at low temperatures in nanocrystalline gadolinium is interpreted as a Bose-Einstein condensation (BEC) of magnons. A self-consistent calculation, based on the BEC picture, is shown to closely reproduce the observed temperature variations of magnetization and specific heat at constant magnetic fields.

  15. Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy (abstract)

    NASA Astrophysics Data System (ADS)

    Lee, Dongkyu; Maeng, Inhee; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol; Son, Joo-Hiuk

    2009-04-01

    The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd2O3) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

  16. Progress in the use of gadolinium for NCT.

    PubMed

    Cerullo, N; Bufalino, D; Daquino, G

    2009-07-01

    The evaluation of possible improvement in the use of Gd in cancer therapy, in reference to gadolinium in cancer therapy (GdNCT), has been analysed. At first the problem of the gadolinium compounds toxicity was reviewed identifying the Motexafin Gadolinium as the best. Afterwards, the spectrum of IC and Auger electrons was calculated using a special method. Afterwards, this electron source has been used as input of the PENELOPE code and the energy deposit in DNA was well defined. Taking into account that the electron yield and energy distribution are related to the neutron beam spectrum and intensity, the shaping assembly architecture was optimised through computational investigations. Finally the study of GdNCT was performed from two different points of view: macrodosimetry using MCNPX, with calculation of absorbed doses both in tumour and healthy tissues, and microdosimetry using PENELOPE, with the determination of electron RBE through the energy deposit. The equivalent doses were determined combining these two kinds of data, introducing specific figures of merit to be used in treatment planning system (TPS). According to these results, the GdNCT appears to be a fairly possible tumour therapy.

  17. Type of MRI contrast, tissue gadolinium, and fibrosis.

    PubMed

    Do, Catherine; Barnes, Jeffrey L; Tan, Chunyan; Wagner, Brent

    2014-10-01

    It has been presupposed that the thermodynamic stability constant (K(therm)) of gadolinium-based MRI chelates relate to the risk of precipitating nephrogenic systemic fibrosis. The present study compared low-K(therm) gadodiamide with high-K(therm) gadoteridol in cultured fibroblasts and rats with uninephrectomies. Gadolinium content was assessed using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy in paraffin-embedded tissues. In vitro, fibroblasts demonstrated dose-dependent fibronectin generation, transforming growth factor-β production, and expression of activated myofibroblast stress fiber protein α-smooth muscle actin. There were negligible differences with respect to toxicity or proliferation between the two contrast agents. In the rodent model, gadodiamide treatment led to greater skin fibrosis and dermal cellularity than gadoteridol. In the kidney, both contrast agents led to proximal tubule vacuolization and increased fibronectin accumulation. Despite large detectable gadolinium signals in the spleen, skin, muscle, and liver from the gadodiamide-treated group, contrast-induced fibrosis appeared to be limited to the skin and kidney. These findings support the hypothesis that low-K(therm) chelates have a greater propensity to elicit nephrogenic systemic fibrosis and demonstrate that certain tissues are resistant to these effects.

  18. Magnetization of 2.6 T in gadolinium thin films

    NASA Astrophysics Data System (ADS)

    Scheunert, G.; Hendren, W. R.; Ward, C.; Bowman, R. M.

    2012-10-01

    There is renewed interest in rare-earth elements and gadolinium in particular for a range of studies in coupling physics and applications. However, it is still apparent that synthesis impacts understanding of the intrinsic magnetic properties of thin gadolinium films, particularly for thicknesses of topicality. We report studies on 50 nm thick nanogranular polycrystalline gadolinium thin films on SiO2 wafers that demonstrate single-crystal like behavior. The maximum in-plane saturation magnetization at 4 K was found to be 4πMS4 K = (2.61 ± 0.26) T with a coercivity of HC4 K = (160 ± 5) Oe. A maximum Curie point of TC = (293 ± 2) K was measured via zero-field-cooled-field-cooled magnetization measurements in close agreement with values reported in bulk single crystals. Our measurements revealed magnetic transitions at T1 = (12 ± 2) K (as deposited samples) and T2 = (22 ± 2) K (depositions on heated substrates) possibly arising from the interaction of paramagnetic face-centred cubic grains with their ferromagnetic hexagonal close-packed counterparts.

  19. Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy

    SciTech Connect

    Lee, Dongkyu; Maeng, Inhee; Son, Joo-Hiuk; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol

    2009-04-19

    The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

  20. Repurposing of gallium-based drugs for antibacterial therapy.

    PubMed

    Bonchi, Carlo; Imperi, Francesco; Minandri, Fabrizia; Visca, Paolo; Frangipani, Emanuela

    2014-01-01

    While the occurrence and spread of antibiotic resistance in bacterial pathogens is vanishing current anti-infective therapies, the antibiotic discovery pipeline is drying up. In the last years, the repurposing of existing drugs for new clinical applications has become a major research area in drug discovery, also in the field of anti-infectives. This review discusses the potential of repurposing previously approved gallium formulations in antibacterial chemotherapy. Gallium has no proven function in biological systems, but it can act as an iron-mimetic in both prokaryotic and eukaryotic cells. The activity of gallium mostly relies on its ability to replace iron in redox enzymes, thus impairing their function and ultimately hampering cell growth. Cancer cells and bacteria are preferential gallium targets due to their active metabolism and fast growth. The wealth of knowledge on the pharmacological properties of gallium has opened the door to the repurposing of gallium-based drugs for the treatment of infections sustained by antibiotic-resistant bacterial pathogens, such as Acinetobacter baumannii or Pseudomonas aeruginosa, and for suppression of Mycobacterium tuberculosis growth. The promising antibacterial activity of gallium both in vitro and in different animal models of infection raises the hope that gallium will confirm its efficacy in clinical trials, and will become a valuable therapeutic option to cure otherwise untreatable bacterial infections.

  1. Gallium scintigraphy in bone infarction. Correlation with bone imaging

    SciTech Connect

    Armas, R.R.; Goldsmith, S.J.

    1984-01-01

    The appearance of gallium-67 images in bone infarction was studied in nine patients with sickle cell disease and correlated with the bone scan findings. Gallium uptake in acute infarction was decreased or absent with a variable bone scan uptake, and normal in healing infarcts, which showed increased uptake on bone scan. The significance of these findings is discussed.

  2. Strengthened solid-state laser materials

    SciTech Connect

    Marion, J.

    1985-10-01

    The tensile fracture strength of crystalline materials for high average power lasers has been increased by a factor of 15 using deep chemical polishing. Samples of gadolinium scandium gallium garnet, gadolinium gallium garnet, and yttrium aluminum garnet, which were prepared by conventional mechanical techniques to a high quality polish, were found to contain subsurface damage up to 50 ..mu..m in depth. When this damage was removed by deep chemical etching, the mean strength of small, four-point flexure specimens increased from 155 to 2280 MPa; however, these samples were no longer optically flat after etching. Specimens in which the optical figure was restored by polishing after the etch had an intermediate strength of 630 MPa.

  3. Laser photochemistry of gallium-containing compounds. [Trimethylgallium

    SciTech Connect

    Baughcum, S.L.; Oldenborg, R.C.

    1986-01-01

    The production of gas-phase gallium atoms in the photolysis of trimethylgallium has been investigated at 193 nm and at other laser wavelengths. Ground state (4 /sup 2/P/sup 0//sub 1/2) and metastable (4 /sup 2/P/sup 0//sub 3/2/) gallium atoms are detected using laser-induced fluorescence techniques. Our results indicate that gallium atoms continue to be produced at long times after the laser pulse. The observed dependence on photolysis laser fluence, trimethylgallium pressure, and buffer gas pressure are consistent with a mechanism in which highly excited gallium methyl radicals undergo unimolecular decomposition to produce gallium atoms. Since this process is observed to happen on the time scale of hundreds of microseconds, these results have important implications for studies of metal deposition and direct laser writing by laser photolysis of organometallic compounds. 31 refs., 5 figs.

  4. Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys

    NASA Astrophysics Data System (ADS)

    Maltsev, Dmitry S.; Volkovich, Vladimir A.; Yamshchikov, Leonid F.; Chukin, Andrey V.

    2016-09-01

    Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys were studied. Temperature dependences of gadolinium activity in the studied alloys were determined at 573-1073 K employing the EMF method. Solubility of gadolinium in the Ga-Sn and Ga-Zn alloys was measured at 462-1073 K using IMCs sedimentation method. Activity coefficients as well as partial and excess thermodynamic functions of gadolinium in the studied alloys were calculated on the basis of the obtained experimental data.

  5. Gadolinium-based contrast agents: did we miss something in the last 25 years?

    PubMed

    Beomonte Zobel, Bruno; Quattrocchi, Carlo Cosimo; Errante, Yuri; Grasso, Rosario Francesco

    2016-06-01

    In the last 24 months, several clinical and experimental studies, suggested first and demonstrated later, a progressive concentration of Gadolinium in the brain of normal renal function patients, following repeated injections of some of the commercially approved Gadolinium-Based Contrast Agents. Although, till now, Gadolinium brain deposits have not been associated to any kind of neurological signs or symptoms, they oblige the radiology community to modify the actual approach in using Gadolinium contrast media in daily practice, to reduce unknown possible risks for patients.

  6. [CT contrast administration of iodine, gadolinium and ytterbium. In-vitro studies and animal experiments].

    PubMed

    Zwicker, C; Langer, M; Urich, V; Felix, R

    1993-03-01

    The absorption of the elements iodine, gadolinium and ytterbium in various dilutions was studied in relation to CT. Regression analysis and specific CT density measurements showed that absorption decreases from gadolinium to ytterbium and iodine. These results were confirmed by experiments using ten dogs. Boli of 0.5 molar gadolinium used for angio-CT without table movement showed the largest increase in density in the aorta and liver with an average of 190HU and 21HU respectively compared with iodine which gave 157HU and 12HU respectively. The animal experimental studies suggest that gadolinium and ytterbium are suitable contrast media for dynamic CT investigations.

  7. Combination of boron and gadolinium compounds for neutron capture therapy. An in vitro study.

    PubMed

    Matsumura, A; Zhang, T; Nakai, K; Endo, K; Kumada, H; Yamamoto, T; Yoshida, F; Sakurai, Y; Yamamoto, K; Nose, T

    2005-03-01

    In neutron capture therapy, the therapeutic effect of the boron compound is based on alpha particles produced by the B(n, alpha) reaction while with the gadolinium compound the main radiation effect is from gamma rays derived from the Gd(n, gamma) reaction. The uptake and distribution within the tumor may be different among these compounds. Thus, the combination of the boron and gadolinium compounds may be beneficial for enhancing the radiation dose to the tumor. Chinese hamster fibroblast V79 cells were used. For the neutron targeting compounds, 10B (BSH) at 0, 5, 10, and 15 ppm, and 157Gd (Gd-BOPTA) at 0, 800, 1600, 2400, 3200, and 4800 ppm, were combined. The neutron irradiation was performed with thermal neutrons for 30 min. (neutron flux: 0.84 x 10(8) n/cm2/s in free air). The combination of the boron and gadolinium compounds showed an additive effect when the gadolinium concentration was lower than 1600 ppm. This additive effect decreased as a function of gadolinium concentration at 2400 ppm and resulted in no additive effect at more than 3200 ppm of gadolinium. In conclusion, the combination of the boron and gadolinium compounds can enhance the therapeutic effect with an optimum concentration ratio. When the gadolinium concentration is too high, it may weaken the boron neutron capture reaction due to the high cross-section of gadolinium compound against neutrons.

  8. Optical isolator based on mode conversion in magnetic garnet films.

    PubMed

    Hemme, H; Dötsch, H; Menzler, H P

    1987-09-15

    Calculations are presented describing a novel optical isolator which works by complete TE(0)-TM(0) mode conversion in magnetic garnet films caused by stress-induced optical anisotropy (50%) and by Faraday rotation (50%). These conversions take place along two different, perpendicular light paths in the same crystal that are connected by an integrated mirror. Possible tolerances of the film parameters are given so that a 30-dB isolation is still guaranteed.

  9. Multicolor filter all-garnet magneto-optical photonic crystals.

    PubMed

    Ansari, N; Khartsev, S I; Grishin, A M

    2012-09-01

    We demonstrate a multicolor optical filter and isolator based on a double-cavity magneto-optical (MO) photonic crystal. Being grown as a heteroepitaxial all-garnet multilayer, it compromises a strong MO response and high optical transmittance. Low-loss, high Faraday rotation passbands as well as strong light rejection within the stop band were achieved by optimization of distance between cavities and repetition number of distributed Bragg reflectors.

  10. Measurement of magnetostriction coefficients of epitaxial garnet films.

    PubMed

    Vella-Coleiro, G P

    1979-09-01

    A technique for measuring the magnetostriction coefficients of epitaxial garnet films on 50-mm-diam wafers is described. The measurement is based on the shift of the microwave ferrimagnetic resonance produced by stressing the film, which is achieved by supporting the wafer around its circumference and reducing the atmospheric pressure on one side. A simple, nonresonant transmission microwave spectrometer which is well suited for measurements on large wafers is also described.

  11. Thermal Plasma Synthesis of Crystalline Gallium Nitride Nanopowder from Gallium Nitrate Hydrate and Melamine

    PubMed Central

    Kim, Tae-Hee; Choi, Sooseok; Park, Dong-Wha

    2016-01-01

    Gallium nitride (GaN) nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC) non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO3)3∙xH2O) was used as a raw material and NH3 gas was used as a nitridation source. Additionally, melamine (C3H6N6) powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga2O3). Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C3H6N6. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing.

  12. Wear performance of garnet aluminium composites at high contact pressure

    NASA Astrophysics Data System (ADS)

    Sharma, Anju; Arora, Rama; Kumar, Suresh; Singh, Gurmel; Pandey, O. P.

    2016-05-01

    To satisfy the needs of the engineering sector, researchers and material scientists in this area adopted the development of composites with tailor made properties to enhance efficiency and cost savings in the manufacturing sector. The technology of the mineral industry is shaping the supply and demand of minerals derived materials. The composites are best classified as high performance materials have high strength-to-weight ratios, and require controlled manufacturing environments for optimum performance. Natural mineral garnet was used as the reinforcement of composite because of satisfactory mechanical properties as well as an attractive ecological alternative to others ceramics. For this purpose, samples have been prepared with different sizesof the garnet reinforcement using the mechanical stirring method to achieve the homogeneously dispersed strengthening phase. A systematic study of the effect of high contact pressure on the sliding wear behaviour of garnet reinforced LM13 alloy composites is presented in this paper. The SEM analysis of the worn samples and debris reveals the clues about the wear mechanism. The drastic improvement in the wear resistance of the composites at high contact pressure shows the high potential of the material to be used in engineering applications.

  13. Sublattice Magnetic Relaxation in Rare Earth Iron Garnets

    SciTech Connect

    McCloy, John S.; Walsh, Brian

    2013-07-08

    The magnetic properties of rare earth garnets make them attractive materials for applications ranging from optical communications to magnetic refrigeration. The purpose of this research was to determine the AC magnetic properties of several rare earth garnets, in order to ascertain the contributions of various sublattices. Gd3Fe5O¬12, Gd3Ga5O12, Tb3Fe5O12, Tb3Ga5O12, and Y3Fe5O12 were synthesized by a solid state reaction of their oxides and verified by x-ray diffraction. Frequency-dependent AC susceptibility and DC magnetization were measured versus temperature (10 – 340 K). Field cooling had little effect on AC susceptibility, but large effect on DC magnetization, increasing magnetization at the lowest temperature and shifting the compensation point to lower temperatures. Data suggest that interaction of the two iron lattices results in the two frequency dependent magnetic relaxations in the iron garnets, which were fit using the Vogel-Fulcher and Arrhenius laws.

  14. Ferroelectricity of domain walls in rare earth iron garnet films

    NASA Astrophysics Data System (ADS)

    Popov, A. I.; Zvezdin, K. A.; Gareeva, Z. V.; Mazhitova, F. A.; Vakhitov, R. M.; Yumaguzin, A. R.; Zvezdin, A. K.

    2016-11-01

    In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.

  15. Lattice and Magnetic Effects on Multiferroic Transitions in Garnets

    NASA Astrophysics Data System (ADS)

    Louca, Despina; Kamazawa, K.; Proffen, T.

    2007-03-01

    The possible presence of ferroelectricity in a magnetically ordered state has attracted considerable attention particularly in ABO3 and AB2O5 systems with B = Mn. Evidence for strong coupling of the two order parameters has been provided in the so-called multiferroics, where the field-induced polarization leads to a giant magnetoelectric effect and a magneto-dielectric effect. It was recently shown that the ferrimagnetic garnet crystal of Tb3Fe5O12 exhibits a large magnetodielectric response as well when a very small magnetic field is applied (1). To understand the origin of the high sensitivity of the dielectric effect in garnets, we investigated the crystal and magnetic structures of Tb3(Fe/Ga)5O12 using pulsed neutron diffraction. The garnet crystal appears to be very close to a lattice instability and high-resolution diffraction showed that the lattice gradually changes symmetry from cubic to rhombohedral with cooling over a wide temperature range. At the same time, magnetic diffuse scattering is observed that goes away by 15 K. The role of the lattice and of local distortions in the magnetic polarization and the coupling of the magnetostriction to the dielectric effect will be discussed. (1) N. Hur et al, Appl. Phys. Lett. 87, 042901 (2005).

  16. Ferroelectricity of domain walls in rare earth iron garnet films.

    PubMed

    Popov, A I; Zvezdin, K A; Gareeva, Z V; Mazhitova, F A; Vakhitov, R M; Yumaguzin, A R; Zvezdin, A K

    2016-11-16

    In this paper, we report on electric polarization arising in a vicinity of Bloch-like domain walls in rare-earth iron garnet films. The domain walls generate an intrinsic magnetic field that breaks an antiferroelectric structure formed in the garnets due to an exchange interaction between rare earth and iron sublattices. We explore 180° domain walls whose formation is energetically preferable in the films with perpendicular magnetic anisotropy. Magnetic and electric structures of the 180° quasi-Bloch domain walls have been simulated at various relations between system parameters. Singlet, doublet ground states of rare earth ions and strongly anisotropic rare earth Ising ions have been considered. Our results show that electric polarization appears in rare earth garnet films at Bloch domain walls, and the maximum of magnetic inhomogeneity is not always linked to the maximum of electric polarization. A number of factors including the temperature, the state of the rare earth ion and the type of a wall influence magnetically induced electric polarization. We show that the value of polarization can be enhanced by the shrinking of the Bloch domain wall width, decreasing the temperature, and increasing the deviations of magnetization from the Bloch rotation that are regulated by impacts given by magnetic anisotropies of the films.

  17. Two chain gallium fluorodiphosphates: synthesis, structure solution, and their transient presence during the hydrothermal crystallisation of a microporous gallium fluorophosphate.

    PubMed

    Millange, Franck; Walton, Richard I; Guillou, Nathalie; Loiseau, Thierry; O'Hare, Dermot; Férey, Gérard

    2002-04-21

    Two novel gallium fluorodiphosphates have been isolated and their structures solved ab initio from powder X-ray diffraction data; the materials readily interconvert under hydrothermal conditions, and are metastable with respect to an open-framework zeolitic gallium fluorophosphate, during the synthesis of which they are present as transient intermediates.

  18. Timing and duration of garnet granulite metamorphism in magmatic arc crust, Fiordland, New Zealand

    USGS Publications Warehouse

    Stowell, H.; Tulloch, A.; Zuluaga, C.; Koenig, A.

    2010-01-01

    Pembroke Granulite from Fiordland, New Zealand provides a window into the mid- to lower crust of magmatic arcs. Garnet Sm-Nd and zircon U-Pb ages constrain the timing and duration of high-P partial melting that produced trondhjemitic high Sr/Y magma. Trace element zoning in large, euhedral garnet is compatible with little post growth modification and supports the interpretation that garnet Sm-Nd ages of 126.1??2.0 and 122.6??2.0. Ma date crystal growth. Integration of the garnet ages with U-Pb zircon ages elucidates a history of intrusion(?) and a protracted period of high-temperature metamorphism and partial melting. The oldest zircon ages of 163 to 150. Ma reflect inheritance or intrusion and a cluster of zircon ages ca. 134. Ma date orthopyroxene-bearing mineral assemblages that may be magmatic or metamorphic in origin. Zircon and garnet ages from unmelted gneiss and garnet reaction zones record garnet granulite facies metamorphism at 128 to 126. Ma. Peritectic garnet and additional zircon ages from trondhjemite veins and garnet reaction zones indicate that garnet growth and partial melting lasted until ca. 123. Ma. Two single fraction garnet ages and young zircon ages suggest continued high-temperature re-equilibration until ca. 95. Ma. Phase diagram sections constrain orthopyroxene assemblages to <0.6 GPa @ 650??C, peak garnet granulite facies metamorphic conditions to 680-815??C @ 1.1-1.4. GPa, and a P-T path with a P increase of???0.5. GPa. These sections are compatible with water contents???0.28wt.%, local dehydration during garnet granulite metamorphism, and <0.3. GPa P increases during garnet growth. Results demonstrate the utility of integrated U-Pb zircon and Sm-Nd garnet ages, and phase diagram sections for understanding the nature, duration, and conditions of deep crustal metamorphism and melting. Geochronologic and thermobarometric data for garnet granulite indicate that thickening of arc crust, which caused high-pressure metamorphism in northern

  19. The Preparation and Structural Characterization of Three Structural Types of Gallium Compounds Derived from Gallium (II) Chloride

    NASA Technical Reports Server (NTRS)

    Gordon, Edward M.; Hepp, Aloysius F.; Duraj. Stan A.; Habash, Tuhfeh S.; Fanwick, Phillip E.; Schupp, John D.; Eckles, William E.; Long, Shawn

    1997-01-01

    The three compounds Ga2Cl4(4-mepy)2 (1),[GaCl2(4-mepy)4]GaCl4x1/2(4-mepy); (2) and GaCl2(4-mepy)2(S2CNEt2); (3) (4-mepy= 4-methylpyridine) have been prepared from reactions of gallium (II) chloride in 4-methylpyridine and characterized by single-crystal X-ray analysis. Small variations in the reaction conditions for gallium(II) chloride can produce crystals with substantially different structural properties. The three compounds described here encompass a neutral gallium(II) dimer in which each gallium is four-coordinate, an ionic compound containing both anionic and cationic gallium complex ions with different coordination numbers and a neutral six-coordinate heteroleptic

  20. Free carrier absorption in self-activated PbWO4 and Ce-doped Y3(Al0.25Ga0.75)3O12 and Gd3Al2Ga3O12 garnet scintillators

    NASA Astrophysics Data System (ADS)

    Auffray, E.; Korjik, M.; Lucchini, M. T.; Nargelas, S.; Sidletskiy, O.; Tamulaitis, G.; Tratsiak, Y.; Vaitkevičius, A.

    2016-08-01

    Nonequilibrium carrier dynamics in the scintillators prospective for fast timing in high energy physics and medical imaging applications was studied. The time-resolved free carrier absorption investigation was carried out to study the dynamics of nonequilibrium carriers in wide-band-gap scintillation materials: self-activated led tungstate (PbWO4, PWO) ant two garnet crystals, GAGG:Ce and YAGG:Ce. It was shown that free electrons appear in the conduction band of PWO and YAGG:Ce crystals within a sub-picosecond time scale, while the free holes in GAGG:Ce appear due to delocalization from Gd3+ ground states to the valence band within a few picoseconds after short-pulse excitation. The influence of Gd ions on the nonequilibrium carrier dynamics is discussed on the base of comparison the results of the free carrier absorption in GAGG:Ce containing gadolinium and in YAGG without Gd in the host lattice.

  1. Electrical characterization of germanium implanted gallium arsenide

    NASA Astrophysics Data System (ADS)

    Pedrotti, F. L.

    1980-06-01

    The amphoteric electrical properties of germanium single implants into gallium arsenide, and of dual implants of germanium with either gallium or arsenic into gallium arsenide, have been studied. Room temperature implantation was performed for all implanted ions at 120 keV, with doses ranging from 5E12 to 3E15 ions per square centimeter. Implanted samples were annealed with pyrolytic silicon nitride encapsulants at temperatures ranging from 700 to 1000 degrees Celsius. Both p- and n-type layers were observed. Type of conductivity, electrical activation, and carrier mobility were found to depend critically upon ion dose and anneal temperature. The general electrical behavior suggests that in samples of lower dose and anneal temperature, the implanted Ge ions go into As sites preferentially, producing p-type activity, whereas in samples of higher dose and anneal temperature, more Ge ions go into Ga sites, producing n-type activity. Conductivity was found to change from p- to n-type at an intermediate dose of 3E14 ions per square centimeter and at an anneal temperature between 900 and 950 degrees Celsius. It has been determined that additional implantation of As into GaAs Ge favors Ge occupancy of Ga sites and an enhancement of n-type activity, whereas the additional implantation of Ga encourages Ge occupancy of As sites and an enhancement of p-type activity. Enhancement factors of as much as 8 for p-type activations, and as much as 50 for n-type activations have been measured.

  2. Gallium scintigraphic pattern in lung CMV infections

    SciTech Connect

    Ganz, W.I.; Cohen, D.; Mallin, W.

    1994-05-01

    Due to extensive use of prophylactic therapy for Pneumonitis Carinii Pneumonia (PCP), Cytomegalic Viral (CMV) infection may now be the most common lung infection in AIDS patients. This study was performed to determine Gallium-67 patterns in AIDS patients with CMV. Pathology reports were reviewed in AIDS patients who had a dose of 5 to 10 mCi of Gallium-67 citrate. Analysis of images were obtained 48-72 hours later of the entire body was performed. Gallium-67 scans in 14 AIDS patients with biopsy proven CMV, were evaluated for eye, colon, adrenal, lung and renal uptake. These were compared to 40 AIDS patients without CMV. These controls had infections including PCP, Mycobacterial infections, and lymphocytic interstitial pneumonitis. 100% of CMV patients had bowel uptake greater than or equal to liver. Similar bowel activity was seen in 50% of AIDS patients without CMV. 71% had intense eye uptake which was seen in only 10% of patients without CMV. 50% of CMV patients had renal uptake compared to 5% of non-CMV cases. Adrenal uptake was suggested in 50%, however, SPECT imaging is needed for confirmation. 85% had low grade lung uptake. The low grade lung had perihilar prominence. The remaining 15% had high grade lung uptake (greater than sternum) due to superimposed PCP infection. Colon uptake is very sensitive indicator for CMV infection. However, observing eye, renal, and or adrenal uptake improved the diagnostic specificity. SPECT imaging is needed to confirm renal or adrenal abnormalities due to intense bowel activity present in 100% of cases. When high grade lung uptake is seen superimposed PCP is suggested.

  3. Martian mantle primary melts - An experimental study of iron-rich garnet lherzolite minimum melt composition

    NASA Technical Reports Server (NTRS)

    Bertka, Constance M.; Holloway, John R.

    1988-01-01

    The minimum melt composition in equilibrium with an iron-rich garnet lherzolite assemblage is ascertained from a study of the liquidus relations of iron-rich basaltic compositions at 23 kb. The experimentally determined primary melt composition and its calculated sodium content reveal that Martian garnet lherzolite minimum melts are picritic alkali olivine basalts. Martian primary melts are found to be more picritic than terrestrial garnet lherzolite primary melts.

  4. Processing and Characterization of Polycrystalline Yag (Yttrium Aluminum Garnet) Core-Clad Fibers - Postprint

    DTIC Science & Technology

    2015-01-01

    AFRL-RY-WP-TP-2014-0296 PROCESSING AND CHARACTERIZATION OF POLYCRYSTALLINE YAG ( YTTRIUM ALUMINUM GARNET) CORE-CLAD FIBERS -POSTPRINT...April 2013 – 1 April 2014 4. TITLE AND SUBTITLE PROCESSING AND CHARACTERIZATION OF POLYCRYSTALLINE YAG ( YTTRIUM ALUMINUM GARNET) CORE-CLAD FIBERS...of polycrystalline YAG ( Yttrium Aluminum Garnet) core-clad fibers Hyun Jun Kima,b, Geoff E. Faira*, Santeri A

  5. Sodium Flux Growth of Bulk Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Von Dollen, Paul Martin

    This dissertation focused on development of a novel apparatus and techniques for crystal growth of bulk gallium nitride (GaN) using the sodium flux method. Though several methods exist to produce bulk GaN, none have been commercialized on an industrial scale. The sodium flux method offers potentially lower cost production due to relatively mild process conditions while maintaining high crystal quality. But the current equipment and methods for sodium flux growth of bulk GaN are generally not amenable to large-scale crystal growth or in situ investigation of growth processes, which has hampered progress. A key task was to prevent sodium loss or migration from the sodium-gallium growth melt while permitting N2 gas to access the growing crystal, which was accomplished by implementing a reflux condensing stem along with a reusable sealed capsule. The reflux condensing stem also enabled direct monitoring and control of the melt temperature, which has not been previously reported for the sodium flux method. Molybdenum-based materials were identified from a corrosion study as candidates for direct containment of the corrosive sodium-gallium melt. Successful introduction of these materials allowed implementation of a crucible-free containment system, which improved process control and can potentially reduce crystal impurity levels. Using the new growth system, the (0001) Ga face (+c plane) growth rate was >50 mum/hr, which is the highest bulk GaN growth rate reported for the sodium flux method. Omega X-ray rocking curve (?-XRC) measurements indicated the presence of multiple grains, though full width at half maximum (FWHM) values for individual peaks were <100 arcseconds. Oxygen impurity concentrations as measured by secondary ion mass spectroscopy (SIMS) were >1020 atoms/cm3, possibly due to reactor cleaning and handling procedures. This dissertation also introduced an in situ technique to correlate changes in N2 pressure with dissolution of nitrogen and precipitation of

  6. Gallium Lanthanum Sulphide Fibers for Infrared Transmission

    NASA Astrophysics Data System (ADS)

    West, Y. D.; Schweizer, T.; Brady, D. J.; Hewak, D. W.

    Gallium lanthanum sulphide (GLS) glass and fiber have potential for use in both active and passive infrared applications. In this paper the optical, thermal, and other key properties, which are essential for understanding the applications and crucial in the quest for practical fibres, are discussed. Glass preparation by melt-quenchingand subsequent fibre fabrication is described using both rod-in-tube and extruded preforms. Absorptive and scattering losses are explored as they could represent a fundamental limitation to successful device fabrication. Potential passive and active applications are reported and the prospects for a future generation of sulphide fiber-based devices examined.

  7. Patterned gallium surfaces as molecular mirrors.

    PubMed

    Bossi, Alessandra; Rivetti, Claudio; Mangiarotti, Laura; Whitcombe, Michael J; Turner, Anthony P F; Piletsky, Sergey A

    2007-09-30

    An entirely new means of printing molecular information on a planar film, involving casting nanoscale impressions of the template protein molecules in molten gallium, is presented here for the first time. The metallic imprints not only replicate the shape and size of the proteins used as template. They also show specific binding for the template species. Such a simple approach to the creation of antibody-like properties in metallic mirrors can lead to applications in separations, microfluidic devices, and the development of new optical and electronic sensors, and will be of interest to chemists, materials scientists, analytical specialists, and electronic engineers.

  8. Understanding garnet variability: Application of geometallurgy to diamonds and exploration

    NASA Astrophysics Data System (ADS)

    Hoal, K. O.; Appleby, S. K.; Stammer, J. G.

    2009-05-01

    Peridotitic and eclogitic garnets are a fundamental component in understanding mantle petrology, diamond petrogenesis, and the ascent of mantle materials in kimberlites. They are also critical in exploration programs, as the presence of mantle garnets at the earth's surface provides an indication of dispersion from a deeply derived magmatic carrier. The composition of these garnets further is used as an indicator of diamond prospectivity, on the basis of comparison with garnet compositions known to be in some degree of equilibrium with diamonds. For mantle xenoliths and kimberlites, optical microscopy, electron microprobe analysis (EPMA), and scanning electron microscopy (SEM) are the main tools used for understanding key mineralogical and textural variability relationships. Mineralogy and texture reflect diamond genesis, metasomatic alteration, fluid migration and manifestation, volcanological processes, peridotite disaggregation, and other manifestations of mantle processes that are observable, describable, and applicable in exploration and mining. Mineralogy and texture studies lead to further questions that are better addressed by higher resolution chemical analysis of isotopes and rare earth elements, or luminescence. Understanding mineralogical and textural variability is the primary geological input for geometallurgy (geomet), the field integrating the earth sciences with the extractive industries. The framework for geomet encompasses geology, mineralogy, deposit modeling and extraction methods for the optimum value return of resources, and it relies on the fact that the mineralogy and texture of rocks influence subsequent interpretation and downstream applications. Developments in this area have been made possible by the new generation of high-speed SEM-based quantitative mineralogical instruments, enabling the statistical assessment of thousands of grains or particles, or samples, and their application to models for exploration, ore deposits, or geomet

  9. Garnet separation system water jet cutter B321 Weld Shop, MFD

    SciTech Connect

    Vercelli, T.M.

    1991-12-01

    Presently there is one Water Jet cutter in use in the B321 Weld Shop with the possibility of one to three more jet machines being installed in the near future. The water jet machine uses a high pressure water jet to cut various materials. Depending on the material to be cut a garnet abrasive is sometimes added to the water jet to enhance it's cutting capability. The jet is captured in a water bath tank below the cutting surface. The water bath absorbs the energy of the water jet while acting as a collection tank for the water and garnet emitting from the water jet nozzle, and any excess material and kerff from the cutting operation. The garnet and excess material must be removed from the tank periodically. The method of water and garnet separation is inefficient, requires manual operation, does not control the water level in the water bath tank, and requires weekly filter changes. The original system is replaced by automatic continuous recirculating water-garnet separation system. The system pumps the water and garnet from the water bath tank through a Hydrocyclone Separator'' and back to the water bath tank. This system is capable of depositing the garnet into 55 gallon drums while automatically separating the garnet from the water. This eliminates having to manually shovel the garnet from the water bath tank, reduces filter changes, reduces machines down time, and automatically maintains the water level of the water bath tank. This document describes the design details of this system.

  10. Garnet separation system water jet cutter B321 Weld Shop, MFD

    SciTech Connect

    Vercelli, T.M.

    1991-12-01

    Presently there is one Water Jet cutter in use in the B321 Weld Shop with the possibility of one to three more jet machines being installed in the near future. The water jet machine uses a high pressure water jet to cut various materials. Depending on the material to be cut a garnet abrasive is sometimes added to the water jet to enhance it`s cutting capability. The jet is captured in a water bath tank below the cutting surface. The water bath absorbs the energy of the water jet while acting as a collection tank for the water and garnet emitting from the water jet nozzle, and any excess material and kerff from the cutting operation. The garnet and excess material must be removed from the tank periodically. The method of water and garnet separation is inefficient, requires manual operation, does not control the water level in the water bath tank, and requires weekly filter changes. The original system is replaced by automatic continuous recirculating water-garnet separation system. The system pumps the water and garnet from the water bath tank through a ``Hydrocyclone Separator`` and back to the water bath tank. This system is capable of depositing the garnet into 55 gallon drums while automatically separating the garnet from the water. This eliminates having to manually shovel the garnet from the water bath tank, reduces filter changes, reduces machines down time, and automatically maintains the water level of the water bath tank. This document describes the design details of this system.

  11. A COMPARISON OF FAR INFRARED AND RAMAN SPECTRA OF SOME RARE EARTH GARNET SINGLE CRYSTALS,

    DTIC Science & Technology

    RARE EARTH COMPOUNDS, *INFRARED SPECTRA), (*GARNET, RARE EARTH COMPOUNDS), (* RAMAN SPECTROSCOPY, RARE EARTH COMPOUNDS), SINGLE CRYSTALS, ALUMINATES...PHONONS, YTTRIUM COMPOUNDS, YTTERBIUM COMPOUNDS, TERBIUM COMPOUNDS, DYSPROSIUM COMPOUNDS, CANADA

  12. Gallium induces the production of virulence factors in Pseudomonas aeruginosa.

    PubMed

    García-Contreras, Rodolfo; Pérez-Eretza, Berenice; Lira-Silva, Elizabeth; Jasso-Chávez, Ricardo; Coria-Jiménez, Rafael; Rangel-Vega, Adrián; Maeda, Toshinari; Wood, Thomas K

    2014-02-01

    The novel antimicrobial gallium is a nonredox iron III analogue with bacteriostatic and bactericidal properties, effective for the treatment of Pseudomonas aeruginosa in vitro and in vivo in mouse and rabbit infection models. It interferes with iron metabolism, transport, and presumably its homeostasis. As gallium exerts its antimicrobial effects by competing with iron, we hypothesized that it ultimately will lead cells to an iron deficiency status. As iron deficiency promotes the expression of virulence factors in vitro and promotes the pathogenicity of P. aeruginosa in animal models, it is anticipated that treatment with gallium will also promote the production of virulence factors. To test this hypothesis, the reference strain PA14 and two clinical isolates from patients with cystic fibrosis were exposed to gallium, and their production of pyocyanin, rhamnolipids, elastase, alkaline protease, alginate, pyoverdine, and biofilm was determined. Gallium treatment induced the production of all the virulence factors tested in the three strains except for pyoverdine. In addition, as the Ga-induced virulence factors are quorum sensing controlled, co-administration of Ga and the quorum quencher brominated furanone C-30 was assayed, and it was found that C-30 alleviated growth inhibition from gallium. Hence, adding both C-30 and gallium may be more effective in the treatment of P. aeruginosa infections.

  13. The effect of gallium nitrate on synoviocyte MMP activity.

    PubMed

    Panagakos, F S; Kumar, E; Venescar, C; Guidon, P

    2000-02-01

    Gallium, a group IIIa metal salt, has been demonstrated to be an effective immunosuppressive agent. Gallium has also been shown to inhibit the production of inflammatory cytokines, such as IL-1beta, produced by macrophage-like cells in vitro. To further characterize the effects of gallium on the inflammatory process, we examined the effects of gallium nitrate on matrix metalloproteinase (MMP) activity utilizing the rabbit synoviocyte cell line HIG-82. HIG-82 cells were incubated with IL-1beta and TPA, with and without increasing concentrations of gallium nitrate. Conditioned medium was collected and assayed for MMP activity using a synthetic substrate and substrate gel zymography. IL-1beta and TPA alone induced MMP activity in HIG-82 cells. A dose-dependent inhibition of IL-1beta and TPA stimulated MMP activity by gallium nitrate at increasing concentrations was observed. This study demonstrates that gallium nitrate can inhibit the activity of MMPs and may be useful as a modulator of inflammation in arthritis.

  14. Compatibility of ITER candidate structural materials with static gallium

    SciTech Connect

    Luebbers, P.R.; Michaud, W.F.; Chopra, O.K.

    1993-12-01

    Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400{degrees}C, corrosion rates are {approx}4.0, 0.5, and 0.03 mm/yr for type 316 SS, Inconel 625, and Nb-5 Mo- 1 Zr alloy, respectively. The pure metals react rapidly with gallium. In contrast to findings in earlier studies, pure iron shows greater corrosion than nickel. The corrosion rates at 400{degrees}C are {ge}88 and 18 mm/yr, respectively, for Armco iron and Nickel 270. The results indicate that at temperatures up to 400{degrees}C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The solubility data for pure metals and oxygen in gallium are reviewed. The physical, chemical, and radioactive properties of gallium are also presented. The supply and availability of gallium, as well as price predictions through the year 2020, are summarized.

  15. Behavior of Zircaloy Cladding in the Presence of Gallium

    SciTech Connect

    DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

    1998-09-28

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

  16. Some interesting features of the Tb3+ magnetooptics in the paramagnetic garnets

    NASA Astrophysics Data System (ADS)

    Valiev, Uygun V.; Gruber, John B.; Burdick, Gary W.; Mukhammadiev, Anvar K.; Fu, Dejun; Pelenovich, Vasiliy O.

    2014-05-01

    The spectra of the absorption, luminescence, magnetic circular dichroism (MCD) and magnetic circular polarization of luminescence (MCPL) in the terbium-yttrium gallium garnet Tb3+:Y3Ga5O12 (Tb:YGG) have been studied within the visible and near ultraviolet (UV) spectral range for temperatures T = 85 and 300 K. The MCD spectrum observed within the UV absorption band for Tb:YGG is associated with spin- and parity-allowed electric-dipole 4f → 5d transitions occurring between levels of the ground 7F6 multiplet and the 7D state of the excited 4f(7)5d configuration of the Tb3+ ion. Analysis of the spectral and the temperature dependences of the magnetooptical and optical spectra has made it possible to identify magneto-optically-active 4f → 4f transitions occurring between Stark sublevels of the 5D4 and 7F5 multiplets in Tb3+:YGG. Quantum mechanical "mixing" of the three lowest energy Stark singlets in the excited 5D4 multiplet by an external magnetic field H leads to the change of the circularly polarized luminescence line intensities. The Zeeman effect in the UV absorption band 7F6 → 5L10 of Tb3+:YGG at T = 85 K was also studied. The magnetic field dependence of the Zeeman splitting of some absorption lines is found to exhibit unusual behavior: as the magnetic field increases, the band splitting decreases rather than increases. A parameterized Hamiltonian defined to operate within the entire 4f(8) ground electronic configuration of Tb3+ was used to model the experimental Stark levels, their irreducible representations (irreps.) and wave functions. The crystal-field parameters were determined using a Monte-Carlo method in which nine independent crystal-field parameters, were given random initial values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 101 calculated and experimental Stark levels is 16.7 cm-1.

  17. Use of Gadolinium as a Primary Criticality Control in Disposing Waste Containing Plutonium at SRS

    SciTech Connect

    Andrew, Vincent

    2005-01-04

    Use of gadolinium as a neutron poison has been proposed for disposing of several metric tons of excess plutonium at the Savannah River Site (SRS). The plutonium will first be dissolved in nitric acid in small batches. Gadolinium nitrate will then be added to the plutonium nitrate solution. The Gd-poisoned plutonium solution will be neutralized and transferred to large under-ground tanks. The pH of small batches of neutralized plutonium solution will be adjusted prior to addition of the glass frit for eventual production as glass logs. The use of gadolinium as the neutron poison would minimize the number of glass logs generated from this disposition. The primary criticality safety concerns regarding the disposal process are: (1) maintaining neutron moderation under all processing conditions since gadolinium has a very large absorption cross section for thermal neutrons, (2) characteristics of plutonium and gadolinium precipitation during the neutralization process, (3) mixing characteristics of the precipitate to ensure that plutonium would remain homogeneously mixed with gadolinium, and (4) potential separation of plutonium and gadolinium during nitric and formic acids addition. A number of experiments were conducted at the Savannah River National Laboratory to study the behavior of plutonium and gadolinium at various stages of the disposition process.

  18. Gallium scanning in lymphoid interstitial pneumonitis of children with AIDS

    SciTech Connect

    Schiff, R.G.; Kabat, L.; Kamani, N.

    1987-12-01

    Lymphoid interstitial pneumonitis (LIP) is a frequent pulmonary complication in the child with the acquired immune deficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection. We report the gallium scan findings in two children with AIDS and LIP. Gallium scintigraphy in both children demonstrated increased radionuclide concentration throughout the lungs, a pattern indistinguishable scintigraphically from that of Pneumocystis carinii pneumonia (PCP). This should alert nuclear medicine practitioners and referring physicians to another cause of diffusely increased gallium uptake in the lungs of patients with AIDS.

  19. Electrical and optical properties of gadolinium doped bismuth ferrite nanoparticles

    SciTech Connect

    Mukherjee, A. Banerjee, M. Basu, S.; Pal, M.

    2014-04-24

    Multiferroic bismuth ferrite (BFO) and gadolinium (Gd) doped bismuth ferrite had been synthesized by a sol-gel method. Particle size had been estimated by Transmission electron microscopy (TEM) and found to decrease with Gd doping. We studied the temperature and frequency dependence of impedance and electric modulus and calculated the grain and grain boundary resistance and capacitance of the investigated samples. We observed that electrical activation energy increases for all the doped samples. Optical band gap also increases for the doped samples which can be used in photocatalytic application of BFO.

  20. Dual-Energy X-Radiography With Gadolinium Filter

    NASA Technical Reports Server (NTRS)

    Rutt, Brian

    1987-01-01

    Image resolution increased, and cost reduced. Proposed dual-energy x-ray imaging system, continuous bremsstrahlung spectrum from x-ray tube filtered by foil of nonradioactive gadolinium or another rare-earth metal to form two-peaked energy spectrum. After passing through patient or object under examination, filtered radiation detected by array of energy-discriminating, photon-counting detectors. Detector outputs processed to form x-ray image for each peak and possibly enhanced image based on data taken at both peaks.

  1. Gadolinium-based nanoparticles for theranostic MRI-radiosensitization.

    PubMed

    Lux, François; Sancey, Lucie; Bianchi, Andrea; Crémillieux, Yannick; Roux, Stéphane; Tillement, Olivier

    2015-01-01

    A rapid development of gadolinium-based nanoparticles is observed due to their attractive properties as MRI-positive contrast agents. Indeed, they display high relaxivity, adapted biodistribution and passive uptake in the tumor thanks to enhanced permeability and retention effect. In addition to these imaging properties, it has been recently shown that they can act as effective radiosensitizers under different types of irradiation (radiotherapy, neutron therapy or hadron therapy). These new therapeutic modalities pave the way to therapy guided by imaging and to personalized medicine.

  2. Magnetoresistance of polycrystalline gadolinium with varying grain size

    SciTech Connect

    Chakravorty, Manotosh Raychaudhuri, A. K.

    2015-01-21

    In this paper, we report a study of evolution of low field magnetoresistance (MR) of Gadolinium as the grain size in the sample is changed from few microns (∼4 μm) to the nanoscopic regime (∼35 nm). The low field MR has a clear effect on varying grain size. In large grain sample (few μm), the magnetic domains are controlled by local anisotropy field determined mainly by the magnetocrystalline anisotropy. The low field MR clearly reflects the temperature dependence of the magnetocrystalline anisotropy. For decreasing gain size, the contribution of spin disorder at the grain boundary increases and enhances the local anisotropy field.

  3. Electrical and optical properties of gadolinium doped bismuth ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Mukherjee, A.; Banerjee, M.; Basu, S.; Pal, M.

    2014-04-01

    Multiferroic bismuth ferrite (BFO) and gadolinium (Gd) doped bismuth ferrite had been synthesized by a sol-gel method. Particle size had been estimated by Transmission electron microscopy (TEM) and found to decrease with Gd doping. We studied the temperature and frequency dependence of impedance and electric modulus and calculated the grain and grain boundary resistance and capacitance of the investigated samples. We observed that electrical activation energy increases for all the doped samples. Optical band gap also increases for the doped samples which can be used in photocatalytic application of BFO.

  4. Antitumor effect of novel gallium compounds and efficacy of nanoparticle-mediated gallium delivery in lung cancer.

    PubMed

    Wehrung, Daniel; Oyewumi, Moses O

    2012-02-01

    The widespread application of gallium (Ga) in cancer therapy has been greatly hampered by lack of specificity resulting in poor tumor accumulation and retention. To address the challenge, two lipophilic gallium (III) compounds (gallium hexanedione; GaH and gallium acetylacetonate; GaAcAc) were synthesized and antitumor studies were conducted in human lung adenocarcinoma (A549) cells. Nanoparticles (NPs) containing various concentrations of the Ga compounds were prepared using a binary mixture of Gelucire 44/14 and cetyl alcohol as matrix materials. NPs were characterized based on size, morphology, stability and biocompatibility. Antitumor effects of free or NP-loaded Ga compounds were investigated based on cell viability, production of reactive oxygen species and reduction of mitochondrial potential. Compared to free Ga compounds, cytotoxicity of NP-loaded Ga (5-150 microg/ml) was less dependent on concentration and incubation time (exposure) with A549 cells. NP-mediated delivery (5-150 microg Ga/ml) enhanced antitumor effects of Ga compounds and the effect was pronounced at: (i) shorter incubation times; and (ii) at low concentrations of gallium (approximately 50 microg/ml) (p < 0.0006). Additional studies showed that NP-mediated Ga delivery was not dependent on transferrin receptor uptake mechanism (p > 0.13) suggesting the potential in overcoming gallium resistance in some tumors. In general, preparation of stable and biocompatible NPs that facilitated Ga tumor uptake and antitumor effects could be effective in gallium-based cancer therapy.

  5. Interactions of Zircaloy Cladding with Gallium: Final Report

    SciTech Connect

    D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

    1998-09-01

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS

  6. Sensitivity of alanine dosimeters with gadolinium exposed to 6 MV photons at clinical doses.

    PubMed

    Marrale, M; Longo, A; Spanò, M; Bartolotta, A; D'Oca, M C; Brai, M

    2011-12-01

    In this study we analyzed the ESR signal of alanine dosimeters with gadolinium exposed to 6 MV linear accelerator photons. We observed that the addition of gadolinium brings about an improvement in the sensitivity to photons because of its high atomic number. The experimental data indicated that the addition of gadolinium increases the sensitivity of the alanine to 6 MV photons. This enhancement was better observed at high gadolinium concentrations for which the tissue equivalence is heavily reduced. However, information about the irradiation setup and of the radiation beam features allows one to correct for this difference. Monte Carlo simulations were carried out to obtain information on the expected effect of the addition of gadolinium on the dose absorbed by the alanine molecules inside the pellets. These results are compared with the experimental values, and the agreement is discussed.

  7. Gadolinium Thin Foils in a Plasma Panel Sensor as an Alternative to 3He

    SciTech Connect

    Varner Jr, Robert L; Beene, James R; Friedman, Dr. Peter S.

    2010-01-01

    Gadolinium has long been investigated as a detector for neutrons. It has a thermal neutron capture cross-section that is unparalleled among stable elements, because of the isotopes $^{155,157}$Gd. As a replacement for $^3$He, gadolinium has a significant defect, it produces many gamma-rays with an energy sum of 8 MeV. It also produces conversion electrons, mostly 29 keV in energy. The key to replacing $^3$He with gadolinium is using a gamma-blind electron detector to detect the conversion electrons. We suggest that coupling a layer of gadolinium to a Plasma Panel Sensor (PPS) can provide highly efficient, nearly gamma-blind detection of the conversion. The PPS is a proposed detector under development as a dense array of avalanche counters based on plasma display technology. We will present simulations of the response of prototypes of this detector and considerations of the use of gadolinium in the PPS.

  8. Cation Distribution and Magnetic Interactions in Substituted Iron-Containing Garnets: Characterization by Iron-57 Mössbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Berry, Frank J.; Dávalos, Juan Z.; Gancedo, J. Ramón; Greaves, Colin; Marco, José F.; Slater, Peter; Vithal, Muga

    1996-02-01

    Some new compounds with garnet-related structures have been examined by57Fe Mössbauer spectroscopy. The results show that in compounds of the type YCa2SbFe4-xGaxO12(x= 2, 3) the gallium is distributed over both the octahedral and tetrahedral sites. In these compounds, together with materials of composition Y3-2xCa2xSbxFe5-xO12(x= 1.25, 1.5) and Y3-xCaxSnxFe5-xO12(x= 1, 2), the results show evidence of more than one tetrahedral environment for the Fe3+ions. The quadrupole splitting data for the Fe3+ions in tetrahedral sites in some of these compounds are significantly larger than those previously reported for Fe3+in tetrahedral sites in other garnets. The compounds YCa2SbFe4O12and Y2CaSnFe4O12magnetically order at similar temperatures and show comparable octahedral- and tetrahedral-hyperfine magnetic fields at 18 K. The substitution of Fe3+by diamagnetic Sb5+on the octahedral sites results in a considerable lowering of the magnetic ordering temperature. The compounds Y0.5Ca2.5Sb1.25Fe3.75O12and Ca3Sb1.5Fe3.5O12show magnetic ordering on both the octahedral and tetrahedral sublattices at 18 K. A similar effect is observed in the compound YCa2SbFe3GaO12where 33% of the Fe3+ions located at the tetrahedral sites are substituted by diamagnetic Ga3+ions. The importance ofa-dantiferromagnetic superexchange interactions is demonstrated in compounds of the type YCa2SbFe2Ga2O12and YCa2SbFeGa3O12where the Ga3+ions substitute the Fe3+ions on both the octahedral and tetrahedral sites. In these compounds the dilution of the magnetic ions at the tetrahedral sites results in the frustration of magnetic ordering on both thed- anda-sublattices. The compound YCa2Sn2Fe3O12which does not contain Fe3+on the octahedral sites shows magnetic ordering on thed-sublattice in the absence of magnetic ions on theasublattice. The result demonstrates the importance ofd-dantiferromagnetic superexchange interactions.

  9. Vibrational spectra of tellurates with the garnet structure

    NASA Astrophysics Data System (ADS)

    Rulmont, A.; Tarte, P.; Choisnet, J.

    1992-07-01

    The IR and Raman spectra of tellurates Ln 3Te 2Li 3O 12 (Ln=Pr…Lu, Y), Ca 3Te 2Zn 3O 12 and Na 3Te 2M 3+3O 12 (M 3+ = Al, Ga, Fe) with the garnet structure are presented and discussed on the basis of a group theoretical analysis, and of 6Li— 7Li isotopic frequency shifts. The assignment of the high-frequency bands to stretching vibrations of the TeO 6 octahedra is only an approximation whose validity depends on the nature of the tetrahedral cation (Li, Zn or M 3+) and of the symmetry properties of the vibrations: cationic mass effects play an important role in the antisymmetric, IR-active vibrations, whereas the bonding forces are the determining factor in the totally symmetric, Raman active vibrations. For the Na 3Te 2M 3+3O 12 garnets, the (TeO 6) internal modes approximation is unacceptable since the stretching frequencies of the TeO 6 and M 3+O 4 groups are of the same order of magnitude. No detailed assignments are available for the medium-frequency bands: they are due in part to the bending vibrations of the TeO 6 octahedra, but the contribution of the tetrahedral cation Zn 2+ or M 3+ to this region of the spectrum remains largely unknown. The translational frequencies of the dodecahedral Ln 3+ cations have been identified in the low frequency region (below 250 cm -1) by comparison of the frequencies of the Ln and Y garnets.

  10. Silicon ring isolators with bonded nonreciprocal magneto-optic garnets.

    PubMed

    Tien, Ming-Chun; Mizumoto, Tetsuya; Pintus, Paolo; Kromer, Herbert; Bowers, John E

    2011-06-06

    A ring isolator is demonstrated for the first time by directly bonding a cerium-substituted yttrium iron garnet (Ce:YIG) onto a silicon ring resonator using oxygen plasma enhanced bonding. The silicon waveguide is 600 nm wide and 295 nm thick with 500-nm-thick Ce:YIG on the top to have reasonable nonreciprocal effect and low optical loss. With a radial magnetic field applied to the ring isolator, it exhibits 9-dB isolation at resonance in the 1550 nm wavelength regime.

  11. The compression mechanism of garnets based on in situ observations

    NASA Astrophysics Data System (ADS)

    Dymshits, Anna; Sharygin, Igor; Litasov, Konstantin; Shatskiy, Anton

    2014-05-01

    Previously it was showed that the bulk modulus of garnet is strongly affected by the bulk modulus of the dodecahedra, while compressibility of other individual polyhedra displays no correlation with the compressibility of the structure as a whole (Milman et al., 2001). If so, Na-majorite (Na-maj) would have the smallest bulk modulus of all silicate garnets, as a phase with a predicted dodecahedral bulk modulus of approximately 70 GPa (Hazen et al., 1994). In fact Na-maj has the largest bulk modulus among the silicate garnets. This behavior must reflect the all-mineral framework of Na-maj with very small cell volume and silicon in the octahedral position. Thus, we conclude that not only the dodecahedral sites, but also the behavior of the garnet framework and relative sizes of the 8- and 6-coordinated cations, control garnet compression. The octahedral site in Na-maj is quite small (1.79 Å) and contains only silicon in comparison to the pyrope (1.85 Å) or majorite (1.88 Å). The small and highly charged octahedra shares four edges with the dodecahedra and thus restrict the volume of the large and low charged dodecahedra. In spite Na-maj has a large average X-cation radius (RNa = 1.07 Å) its dodecahedral volume is relatively small (V = 21.23 and 21.26 Å3). Pacalo et al. (1992) suggested that XO8 polyhedra act as braces and controls the amount of rotation between tetrahedra and octahedra within the corner-linked chains. In case of pyrope XO8 cite is not filled up and polyhedra within the corner-linked chains can rotate freely to accommodate applied stress. In case of Na-maj the dodecahedral site is filled up and rotational freedom is minimized. The dodecahedral site in knorringite (Knr) contains cation with a small radius (Mg-O = 2.22 and 2.34 Å), so XO8 polyhedra is not filled up and can rotate freely to accommodate applied stress. In case of uvarovite not only octahedral but the dodecahedral site is also large (Ca-O = 2.35 and 2.51 Å), so the rotational

  12. Fabrication of Aluminum Gallium Nitride/Gallium Nitride MESFET And It's Applications in Biosensing

    NASA Astrophysics Data System (ADS)

    Alur, Siddharth

    Gallium Nitride has been researched extensively for the past three decades for its application in Light Emitting Diodes (LED's), power devices and UV photodetectors. With the recent developments in crystal growth technology and the ability to control the doping there has been an increased interest in heterostructures formed between Gallium nitride and it's alloy Aluminium Gallium Nitride. These heterostructures due to the combined effect of spontaneous and piezoelectric effect can form a high density and a high mobility electron gas channel without any intentional doping. This high density electron gas makes these heterostructures ideal to be used as sensors. Gallium Nitride is also chemically very stable. Detection of biomolecules in a fast and reliable manner is very important in the areas of food safety and medical research. For biomolecular detection it is paramount to have a robust binding of the probes on the sensor surface. Therefore, in this dissertation, the fabrication and application of the AlGaN/GaN heterostructures as biological sensors for the detection of DNA and Organophosphate hydrolase enzyme is discussed. In order to use these AlGaN/GaN heterostructures as biological sensors capable of working in a liquid environment photodefinable polydimethyl-siloxane is used as an encapsulant. The immobilization conditions for a robust binding of thiolated DNA and the catalytic receptor enzyme organophosphate hydrolase on gold surfaces is developed with the help of X-ray photoelectron spectroscopy. DNA and OPH are detected by measuring the change in the drain current of the device as a function of time.

  13. Measurement of arsenic and gallium content of gallium arsenide semiconductor waste streams by ICP-MS.

    PubMed

    Torrance, Keith W; Keenan, Helen E; Hursthouse, Andrew S; Stirling, David

    2010-01-01

    The chemistry of semiconductor wafer processing liquid waste, contaminated by heavy metals, was investigated to determine arsenic content. Arsenic and gallium concentrations were determined for waste slurries collected from gallium arsenide (GaAs) wafer processing at three industrial sources and compared to slurries prepared under laboratory conditions. The arsenic and gallium content of waste slurries was analyzed using inductively coupled plasma mass-spectrometry (ICP-MS) and it is reported that the arsenic content of the waste streams was related to the wafer thinning process, with slurries from wafer polishing having the highest dissolved arsenic content at over 1,900 mgL(-1). Lapping slurries had much lower dissolved arsenic (< 90 mgL(-1)) content, but higher particulate contents. It is demonstrated that significant percentage of GaAs becomes soluble during wafer lapping. Grinding slurries had the lowest dissolved arsenic content at 15 mgL(-1). All three waste streams are classified as hazardous waste, based on their solids content and dissolved arsenic levels and treatment is required before discharge or disposal. It is calculated that as much as 93% of material is discarded through the entire GaAs device manufacturing process, with limited recycling. Although gallium can be economically recovered from waste slurries, there is little incentive to recover arsenic, which is mostly landfilled. Options for treating GaAs processing waste streams are reviewed and some recommendations made for handling the waste. Therefore, although the quantities of hazardous waste generated are miniscule in comparison to other industries, sustainable manufacturing practices are needed to minimize the environmental impact of GaAs semiconductor device fabrication.

  14. Crystallization of pegmatites: Insights from chemistry of garnet, Jacumba pegmatites, San Diego County, California

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Sirbescu, M. C.

    2013-12-01

    Systematic mineral and textural variations from the border zone to the core of a zoned pegmatite sheet may reflect the kinetic or equilibrium fractionation processes that occurred during sequential crystallization of the pegmatite magma. Rhythmic layering, also named 'line rock', is a salient textural feature of world famous San Diego Co. pegmatites, that consists of alternating garnet × tourmaline layers and albite - quartz layers, mm's to cm's thick. Slowly diffusing, incompatible elements in the felsic magma including B, Fe, and Mn may become enriched in boundary layers formed ahead of rapidly crystallized quartzo-felspathic assemblages. This study explores whether the chemistry of garnet concentrated in the border and foot-wall zones and dispersed in the graphic feldspar, core, and pocket zones of Garnet Ledge pegmatite, Jacumba district, might fingerprint the diffusion-controlled oscillatory boundary layers. The lithium-cesium-tantalum (LCT) Jacumba pegmatite district, late product of the Eastern Peninsular Ranges Batholith, consists of numerous subparallel dikes, 3 to 7 m thick, intruding pre-batholitic metasedimentary rocks. The composite aplite-pegmatite dikes are texturally diverse. Comb-textured tourmaline, other unidirectional textures, garnet × tourmaline 'line rock', and coarse graphic K-feldspar crystals occur in the outer zones, followed by massive feldspar-quartz cores, vuggy cleavlandite- euhedral garnet, and miarolitic cavities. The Jacumba pegmatites have produced gem spodumene, beryl, and garnet from several open cuts such as the Beebe Hole and Pack Rat - Garnet Ledge workings. Systematic mineralogical and textural variations, and SEM-EDS garnet compositions were recorded from border to core at Garnet Ledge outcrop and thin section scale, focusing on continuous traverses across the line rock. Garnet from Garnet Ledge belongs to the spessartine-almandine series (Sp42 to Sp65) with minor contents of Mg, Ca, and Ti, consistent with garnet

  15. The dimeric nature of bonding in gallium: from small clusters to the α-gallium phase.

    PubMed

    Tonner, Ralf; Gaston, Nicola

    2014-11-28

    We consider the structural similarity of small gallium clusters to the bulk structure of α-gallium, which has been previously described as a molecular metal, via density functional theory-based computations. Previous calculations have shown that the tetramer, the hexamer, and the octamer of gallium are all structurally similar to the α-phase. We perform an analysis of the bonding in these clusters in terms of the molecular orbitals and atoms in molecules description in order to assess whether we can see similarities at these sizes to the bonding pattern, which is ascribed to the co-existence of covalent and metallic bonding in the bulk. The singlet Ga4 and Ga8 clusters can be constructed in a singlet ground state from the Ga-dimers in the first excited triplet state of the Ga2-molecule, the (3)Σg(-) state. Molecular orbital (MO) analysis confirms that the dimer is an essential building block of these small clusters. Comparison of the AIM characteristics of the bonds within the clusters to the bonds in the bulk α-phase supports the identification of the covalent bond in the bulk as related to the (3)Σg(-) state of the dimer.

  16. Computer simulation of radiation damage in gallium arsenide

    NASA Technical Reports Server (NTRS)

    Stith, John J.; Davenport, James C.; Copeland, Randolph L.

    1989-01-01

    A version of the binary-collision simulation code MARLOWE was used to study the spatial characteristics of radiation damage in proton and electron irradiated gallium arsenide. Comparisons made with the experimental results proved to be encouraging.

  17. Gallium accumulation in early pulmonary Pneumocystis carinii infection

    SciTech Connect

    Stevens, D.A.; Allegra, J.C.

    1986-09-01

    The accumulation of gallium 67 citrate in pulmonary Pneumocystis carinii is well known. The sensitivity of gallium uptake in detecting early inflammatory processes, even when conventional roentgenograms are normal, would seem to make it possible in immunocompromised patients to make a presumptive diagnosis of this serious infection early in its course without using invasive techniques to demonstrate the organism. However, the presence of gallium uptake in radiation pneumonitis, pulmonary drug toxicity, and other processes that also occur in this group limit its usefulness. In our two patients--a young woman with Hodgkin's disease and an elderly woman with small cell lung cancer--this technique proved helpful. Although the latter patient was successfully treated empirically, such empiric treatment should be reserved for patients unable or unwilling to undergo invasive tests. Pulmonary gallium uptake in patients with respiratory symptoms, even with a normal chest film, should prompt attempts to directly demonstrate the organism.

  18. Preliminary Experimental Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    A low-energy gallium plasma source is used to perform a spatially and temporally broad spectroscopic survey in the 220-520 nm range. Neutral, singly, and doubly ionized gallium are present in a 20 J, 1.8 kA (peak) arc discharge operating with a central cathode. When the polarity of the inner electrode is reversed the discharge current and arc voltage waveforms remain similar. Utilizing a central anode configuration, multiple Ga lines are absent in the 270-340 nm range. In addition, neutral and singly ionized Fe spectral lines are present, indicating erosion of the outer electrode. With graphite present on the insulator to facilitate breakdown, line emission from the gallium species is further reduced and while emissions from singly and doubly ionized carbon atoms and molecular carbon (C2) radicals are observed. These data indicate that a significant fraction of energy is shifted from the gallium and deposited into the various carbon species.

  19. Ellipsometric study of silicon nitride on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Bu-Abbud, G. H.; Woollam, J. A.; Liu, D.; Chung, Y.; Langer, D.

    1982-01-01

    A method for optimizing the sensitivity of ellipsometric measurements for thin dielectric films on semiconductors is described in simple physical terms. The technique is demonstrated for the case of sputtered silicon nitride films on gallium arsenide.

  20. Dielectric and magnetic properties of some gadolinium silica nanoceramics

    SciTech Connect

    Coroiu, I. Pascuta, P. Bosca, M. Culea, E.

    2013-11-13

    Some nanostructure gadolinium silica glass-ceramics were obtained undergoing a sol gel method and a heat-treatment at 1000°C about two hours. The magnetic and dielectric properties of these samples were studied. The magnetic properties were evidenced performing susceptibility measurements in the 80-300K temperature range. A Curie-Weiss behavior has acquired. The values estimated for paramagnetic Curie temperature being small and positive suggest the presence of weak ferromagnetic interactions between Gd{sup 3+} ions. The dielectric properties were evaluated from dielectric permittivity (ε{sub r}) and dielectric loss (tanδ) measurements at the frequency 1 kHz, 10 kHz and 100 kHz, in the 25-225°C temperature range and dielectric dispersion at room temperature for 79.5 kHz - 1GHz frequency area. The dielectric properties suggest that the main polarization mechanism corresponds to interfacial polarization, characteristic for polycrystalline-structured dielectrics. The polycrystalline structure of the samples is due to the polymorphous transformations of the nanostructure silica crystallites in the presence of gadolinium oxide. They were highlighted by SEM micrographs.

  1. Gadolinium-hydrogen ion exchange of zirconium phosphate

    NASA Technical Reports Server (NTRS)

    Liu, D. C.; Power, J. L.

    1972-01-01

    The Gd(+3)/H(+) ion exchange on a commercial zirconium phosphate ion exchanger was investigated in chloride, sulfate, and phosphate solutions of Gd(+3) at gadolinium concentrations of 0.001 to 1 millimole per cc and in the pH range of 0 to 3.5. Relatively low Gd(+3) capacities, in the range of 0.01 to 0.1 millimole per g of ion exchanger were found at room temperature. A significant difference in Gd(+3) sorption was observed, depending on whether the ion exchanger was converted from initial conditions of greater or lesser Gd(+3) sorption than the specific final conditions. Correlations were found between decrease in Gd(+3) capacity and loss of exchanger phosphate groups due to hydrolysis during washing and between increase in capacity and treatment with H3PO4. Fitting of the experimental data to ideal ion exchange equilibrium expressions indicated that each Gd(+3) ion is sorbed on only one site of the ion exchanger. The selectivity quotient was determined to be 2.5 + or - 0.4 at room temperature on gadolinium desorption in chloride solutions.

  2. MRI gadolinium enhancement precedes neuroradiological findings in acute necrotizing encephalopathy.

    PubMed

    Yoshida, Takeshi; Tamura, Takuya; Nagai, Yuhki; Ueda, Hiroyuki; Awaya, Tomonari; Shibata, Minoru; Kato, Takeo; Heike, Toshio

    2013-11-01

    We report a 2-year-old Japanese boy with acute necrotizing encephalopathy (ANE) triggered by human herpes virus-6, who presented insightful magnetic resonance imaging (MRI) findings. He was admitted due to impaired consciousness and a convulsion, 2 days after the onset of an upper respiratory infection. At admission, cranial MRI showed marked gadolinium enhancement at the bilateral thalami, brainstem and periventricular white matter without abnormal findings in noncontrast MRI sequences. On the following day, noncontrast computed tomography demonstrated homogeneous low-density lesions in the bilateral thalami and severe diffuse brain edema. The patient progressively deteriorated and died on the 18th day of admission. The pathogenesis of ANE remains mostly unknown, but it has been suggested that hypercytokinemia may play a major role. Overproduced cytokines cause vascular endothelial damage and alter the permeability of the vessel wall in the multiple organs, including the brain. The MRI findings in our case demonstrate that blood-brain barrier permeability was altered prior to the appearance of typical neuroradiological findings. This suggests that alteration of blood-brain barrier permeability is the first step in the development of the brain lesions in ANE, and supports the proposed mechanism whereby hypercytokinemia causes necrotic brain lesions. This is the first report demonstrating MRI gadolinium enhancement antecedent to typical neuroradiological findings in ANE.

  3. Magnetic Force Microscopy Images of Magnetic Garnet With Thin-Film Magnetic Tip

    NASA Technical Reports Server (NTRS)

    Wadas, A.; Moreland, J.; Rice, P.; Katti, R.

    1993-01-01

    We present magnetic force microscopy images of YGdTmGa/YSmTmGa magnetic garnet, usinga thin Fe film deposited on Si_3N_5 tips. We have found correlations between the topography andthe magnetic domain structure. We have observed the domain wall contrast with a iron thin-film tip. We report on domain wall imaging of garnet with magnetic force microscopy.

  4. Influence of powerful laser irradiation on electromagneto-optical dependences of yttrium iron garnets

    SciTech Connect

    Koronovskyy, V. E.

    2009-09-15

    Electromagneto-optical properties of yttrium iron garnets have been investigated in a longitudinal geometry by using optical polarimetry method. It is revealed that irradiation of yttrium iron garnet films by powerful laser impulse leads to essential increase in the electromagneto-optical effect value, which can be due to the elimination of the local mechanical strain or nonuniform pressure in them.

  5. Variations in Ti coordination and concentration in garnet in response to temperature, pressure and composition

    NASA Astrophysics Data System (ADS)

    Ackerson, M. R.; Tailby, N.; Watson, E. B.; Spear, F. S.

    2013-12-01

    Titanium concentrations in garnet vary over several orders of magnitude in natural systems-- from trace-element levels in continental metamorphic systems to several weight percent in garnets from mantle xenoliths. Broadly speaking the wide range of concentrations is due to crystallization from diverse environments. Understanding the crystallographic site and Ti-substitution mechanism in garnet is crucial to deciphering concentration trends and how these relate to the petrogenetic history. This study uses XANES spectroscopy to measure Ti coordination in natural and synthetic garnets known to crystallize over a wide range of conditions to investigate whether changes in Ti coordination and concentration correlate with changes T, P and bulk composition. Ti XANES spectroscopy utilizes shifts in the 1s-3d pre-edge feature, which shows systematic shifts in intensity and energy with coordination. Natural and synthetic garnets grown at >800 oC and >1 GPa incorporate Ti almost entirely on the octahedral site in garnet. It is possible that a small amount of Ti substitutes on the tetrahedral site in these garnets, but the concentration is too low to be observed in the spectra. The most feasible mechanism for octahedral substitution involves charge-balanced coupled substitution with an M2+ cation (where M2+=Mg, Fe, Ca, or Mn) resulting in a net loss of two Al for every Ti gained. Substitution of Al onto the tetrahedral site and Ti on the octahedral site is an other feasible mechanism, although the stoichiometric deficit of Al in experimental garnets suggests this mechanism could only account for a small percentage of Ti. Increases in Ti concentration correlate best with increasing Ca content in experimental garnets. Ti solubility also changes in response to T and P. These observations suggest that Ti incorporation on the octahedral site is dependent on the activities of Ti, Al and other M2+ cation system components. This helps to explain some of the differences in Ti

  6. Complexometric determination of gallium with calcein blue as indicator

    USGS Publications Warehouse

    Elsheimer, H.N.

    1967-01-01

    A metalfluorechromic indicator, Calcein Blue, has been used for the back-titration of milligram amounts of EDTA in presence of gallium complexes. The indicator was used in conjunction with an ultraviolet titration assembly equipped with a cadmium sulphide detector cell and a microammeter for enhanced end-point detection. The result is a convenient and rapid method with an accuracy approaching 0.1 % and a relative standard deviation of about 0.4% for 10 mg of gallium. ?? 1967.

  7. Generator for ionic gallium-68 based on column chromatography

    DOEpatents

    Neirinckx, Rudi D.; Davis, Michael A.

    1981-01-01

    A physiologically acceptable solution of gallium-68 fluorides, having an activity of 0.1 to 50 millicuries per milliliter of solution is provided. The solution is obtained from a generator comprising germanium-68 hexafluoride bound to a column of an anion exchange resin which forms gallium-68 in situ by eluting the column with an acid solution to form a solution containing .sup.68 Ga-fluorides. The solution then is neutralized prior to administration.

  8. Mineral inclusions in garnet crystals and their application in studies of high and ultrahigh pressure rocks

    NASA Astrophysics Data System (ADS)

    Perchuk, Alexei

    2010-05-01

    Mineral inclusions in crystals like garnet, zircon or clinopyroxene play a key role in identifying ultrahigh-pressure (UHP) metamorphic rocks and in deciphering their metamorphic (P) - temperature (T) history. In this contribution, we address the questions related to the modification of garnet interiors mediated by H2O and/or CO2 fluids released either from the mineral inclusions or from the exterior source. The data presented are based on experimental studies of eclogitic garnets containing various mineral inclusions and on petrologic studies of natural rocks from several HP and UHP complexes. An experimental study on eclogitic garnets with different min¬eral inclusions (including hydrous phases and carbonates) from several subduction-related complexes reveals considerable modification of garnet interiors at temperatures of 700-1100˚C and a pressure of 3-4 GPa, representative of different diamond-bearing metamorphic UHP terranes. Epidote, amphibole, and chlorite inclusions in the garnets underwent dehydration melting over the entire experimental PT range. In the presence of aqueous fluids, carbonate minerals in the inclusions began to melt at 800 °C and 3 GPa. Melting gave rise to new garnet, with the composition controlled by the chemistry of the primary inclusions and by PT run conditions. Garnet either grew directly from the melt or formed by metasomatic replacement of host garnet walls, leaving residual melt at the substitution front in the latter case. Partial melting of inclusions decreased the mechanical strength of the garnet host and led to local shearing. The following diagnostic criteria for melt in metamorphic garnet may be formulated on the basis of the experimental study: (1) (sub-) euhedral garnet grows within the inclusion and/or xenomorphic garnet replaces the garnet host; (2) newly formed garnet is characterized by a composition different from the garnet host; (3) the inclusion surface is features characteristic wedge-shaped ledges or radial

  9. Method of fabricating germanium and gallium arsenide devices

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzban (Inventor)

    1990-01-01

    A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

  10. Inhalation developmental toxicology studies: Gallium arsenide in mice and rats

    SciTech Connect

    Mast, T.J.; Greenspan, B.J.; Dill, J.A.; Stoney, K.H.; Evanoff, J.J.; Rommereim, R.L.

    1990-12-01

    Gallium arsenide is a crystalline compound used extensively in the semiconductor industry. Workers preparing solar cells and gallium arsenide ingots and wafers are potentially at risk from the inhalation of gallium arsenide dust. The potential for gallium arsenide to cause developmental toxicity was assessed in Sprague- Dawley rats and CD-1 (Swiss) mice exposed to 0, 10, 37, or 75 mg/m{sup 3} gallium arsenide, 6 h/day, 7 days/week. Each of the four treatment groups consisted of 10 virgin females (for comparison), and {approx}30 positively mated rats or {approx}24 positively mated mice. Mice were exposed on 4--17 days of gestation (dg), and rats on 4--19 dg. The day of plug or sperm detection was designated as 0 dg. Body weights were obtained throughout the study period, and uterine and fetal body weights were obtained at sacrifice (rats, 20 dg; mice, 18 dg). Implants were enumerated and their status recorded. Live fetuses were sexed and examined for gross, visceral, skeletal, and soft-tissue craniofacial defects. Gallium and arsenic concentrations were determined in the maternal blood and uterine contents of the rats (3/group) at 7, 14, and 20 dg. 37 refs., 11 figs., 30 tabs.

  11. Radiation effects in Zr and Hf containing garnets

    NASA Astrophysics Data System (ADS)

    Whittle, Karl R.; Blackford, Mark G.; Smith, Katherine L.; Zaluzec, Nestor J.; Weyland, Matthew; Lumpkin, Gregory R.

    2015-07-01

    Garnets have been considered as host phases for the safe immobilisation of high-level nuclear waste, as they have been shown to accommodate a wide range of elements across three different cation sites, such as Ca, Y, Mn on the a-site, Fe, Al, U, Zr, and Ti on the b-site, and Si, Fe, Al on the c-site. Garnets, due to their ability to have variable composition, make ideal model materials for the examination of radiation damage and recovery in nuclear materials, including as potential waste forms. Kimzeyite, Ca3Zr2FeAlSiO12, has been shown naturally to contain up to 30 wt% Zr, and has previously been examined to elucidate both the structure and ordering within the lattice. This study examines the effects of radiation damage and recovery using in-situ ion beam irradiation with 1 MeV Kr ions at the IVEM-TANDEM facility, Argonne National Laboratory. The complementary Hf containing system Ca3Hf2FeAlSiO12 was also examined, and found to have a different response to irradiation damage. A sample of irradiated Ca3Zr2FeAlSiO12, at 1000 K, was characterised using aberration corrected (S)TEM and found to contain discreet, nano-sized, crystalline Fe rich particles, indicating a competing process during recovery is occurring.

  12. Thermal Decomposition of Almandine Garnet: Mössbauer Study

    NASA Astrophysics Data System (ADS)

    Barcova, K.; Mashlan, M.; Zboril, R.; Martinec, P.; Kula, P.

    2001-07-01

    The thermal decomposition of almandine garnet from Zoltye Vody, Ukraine, has been studied using57Fe Mössbauer spectroscopy. Room temperature Mössbauer spectrum of the initial powdered sample is characterised by one doublet corresponding to Fe2+ in dodecahedral position 24c. In the room temperature spectra of all heated almandine samples, a doublet corresponding to γ-Fe2O3 nanoparticles appeared. Depending on experimental conditions (heating temperature and time), the additional spectral lines of α-Fe2O3 and ɛ-Fe2O3 were observed in Mössbauer spectra. It is obvious that the thermal transformation of almandine garnet in air is related to the primary formation of γ-Fe2O3 superparamagnetic nanoparticles. γ-Fe2O3 nanoparticles are transformed into ɛ-Fe2O3 and consequently into α-Fe2O3 at higher temperatures. The mechanism and kinetics of the individual structural transformations depend on experimental conditions — mainly on the heating temperature and size of the particles.

  13. Influence of deuterium implantation on bubble garnet properties

    SciTech Connect

    Gerard, P.; Capra, T.; Magnin, J.

    1985-12-15

    A classical (Y Sm Lu Ca)/sub 3/ (Fe Ge)/sub 5/ O/sub 12/ bubble garnet, supporting 1.8-..mu..m bubbles, has been implanted with 1.5 x 10/sup 16/ D/sup +//sub 2/ cm/sup 2/ at 60 keV either directly or through a predeposited 100-A-thick silica layer. Nuclear techniques such as D (/sup 3/He, ..cap alpha..) p nuclear reaction and Rutherford backscattering combined with channeling measurements were used to determine the implant and damage profiles, respectively. Double-crystal x-ray diffraction was used to measure the maximum strain and magnetic properties were obtained from ferromagnetic resonance. The evolution of these parameters has been studied as a function of annealing treatments. It follows that, as compared to hydrogen, deuterium also interacts at damage-level inducing within the garnet new magnetic phenomena. A higher annealing temperature is required for bubble memory applications. The silica overlayer which is useful for increasing the anisotropy field change, somewhat affects the magnetic properties of the implanted layer.

  14. Direct Band Gap Wurtzite Gallium Phosphide Nanowires

    PubMed Central

    2013-01-01

    The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

  15. Producing gallium arsenide crystals in space

    NASA Technical Reports Server (NTRS)

    Randolph, R. L.

    1984-01-01

    The production of high quality crystals in space is a promising near-term application of microgravity processing. Gallium arsenide is the selected material for initial commercial production because of its inherent superior electronic properties, wide range of market applications, and broad base of on-going device development effort. Plausible product prices can absorb the high cost of space transportation for the initial flights provided by the Space Transportation System. The next step for bulk crystal growth, beyond the STS, is planned to come later with the use of free flyers or a space station, where real benefits are foreseen. The use of these vehicles, together with refinement and increasing automation of space-based crystal growth factories, will bring down costs and will support growing demands for high quality GaAs and other specialty electronic and electro-optical crystals grown in space.

  16. The interaction of gold with gallium arsenide

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar-cell contact materials, are known to react readily with gallium arsenide. Experiments designed to identify the mechanisms involved in these GaAs-metal interactions have yielded several interesting results. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are also explained by invoking this mechanism.

  17. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Garlick, G. F. J.

    1987-01-01

    High-efficiency gallium arsenide cells, made by the liquid epitaxy method (LPE), have been irradiated with 1-MeV electrons up to fluences of 10 to the 16th e/sq cm. Measurements have been made of cell spectral response and dark and light-excited current-voltage characteristics and analyzed using computer-based models to determine underlying parameters such as damage coefficients. It is possible to use spectral response to sort out damage effects in the different cell component layers. Damage coefficients are similar to other reported in the literature for the emitter and buffer (base). However, there is also a damage effect in the window layer and possibly at the window emitter interface similar to that found for proton-irradiated liquid-phase epitaxy-grown cells. Depletion layer recombination is found to be less than theoretically expected at high fluence.

  18. Contact formation in gallium arsenide solar cells

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1988-01-01

    Gold and gold-based alloys, commonly used as solar cell contact materials, are known to react readily with gallium arsenide. Experiments were performed to identify the mechanisms involved in these GaAs-metal interactions. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are explained by invoking this mechanism.

  19. Cathodoluminescence spectra of gallium nitride nanorods

    PubMed Central

    2011-01-01

    Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio. PMID:22168896

  20. Cavity optomechanics in gallium phosphide microdisks

    SciTech Connect

    Mitchell, Matthew; Barclay, Paul E.; Hryciw, Aaron C.

    2014-04-07

    We demonstrate gallium phosphide (GaP) microdisk optical cavities with intrinsic quality factors >2.8 × 10{sup 5} and mode volumes <10(λ/n){sup 3}, and study their nonlinear and optomechanical properties. For optical intensities up to 8.0 × 10{sup 4} intracavity photons, we observe optical loss in the microcavity to decrease with increasing intensity, indicating that saturable absorption sites are present in the GaP material, and that two-photon absorption is not significant. We observe optomechanical coupling between optical modes of the microdisk around 1.5 μm and several mechanical resonances, and measure an optical spring effect consistent with a theoretically predicted optomechanical coupling rate g{sub 0}/2π∼30 kHz for the fundamental mechanical radial breathing mode at 488 MHz.

  1. Gallium Arsenide solar cell radiation damage experiment

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

    1991-01-01

    Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

  2. Gallium arsenide solar array subsystem study

    NASA Technical Reports Server (NTRS)

    Miller, F. Q.

    1982-01-01

    The effects on life cycle costs of a number of technology areas are examined for a gallium arsenide space solar array. Four specific configurations were addressed: (1) a 250 KWe LEO mission - planer array; (2) a 250 KWe LEO mission - with concentration; (3) a 50 KWe GEO mission planer array; (4) a 50 KWe GEO mission - with concentration. For each configuration, a baseline system conceptual design was developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies were then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance, and hence life cycle costs.

  3. Gallium arsenide - Solar panel assembly technology

    NASA Astrophysics Data System (ADS)

    Zemmrich, D.; Mardesich, N.; Macfarlane, B.; Loo, R.

    Gallium arsenide (GaAs) solar cell devices are maturing at 18 percent AM0 efficiencies for liquid phase epitaxy (LPE) technology, and efforts must be intensified placing necessary focus on the development of panel assembly techniques, and ultimately panel manufacturing methods capable of maintaining these high efficiencies for on-panel operation. Key problems and solutions are described which were experienced during the assembly of flight qualified solar panels using Spectrolab's mature (silicon) panel manufacturing processes for assembly of LPE GaAs solar cells. These cells were produced by Hughes Malibu (supplied by the U.S. Air Force WPAFB) ranging in efficiency from 15 to 17 percent, air mass zero (AM0) 28 C. Cell assembly methods for coverglass installation, submodule, and circuit soldering, as well as panel bonding are discussed. The LIPS II satellite, using a GaAs solar cell panel was successfully launched in 1983.

  4. Cathodoluminescence spectra of gallium nitride nanorods.

    PubMed

    Tsai, Chia-Chang; Li, Guan-Hua; Lin, Yuan-Ting; Chang, Ching-Wen; Wadekar, Paritosh; Chen, Quark Yung-Sung; Rigutti, Lorenzo; Tchernycheva, Maria; Julien, François Henri; Tu, Li-Wei

    2011-12-14

    Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio.

  5. Thickness dependent thermal conductivity of gallium nitride

    NASA Astrophysics Data System (ADS)

    Ziade, Elbara; Yang, Jia; Brummer, Gordie; Nothern, Denis; Moustakas, Theodore; Schmidt, Aaron J.

    2017-01-01

    As the size of gallium nitride (GaN) transistors is reduced in order to reach higher operating frequencies, heat dissipation becomes the critical bottleneck in device performance and longevity. Despite the importance of characterizing the physics governing the thermal transport in thin GaN films, the literature is far from conclusive. In this letter, we report measurements of thermal conductivity in a GaN film with thickness ranging from 15-1000 nm grown on 4H-SiC without a transition layer. Additionally, we measure the thermal conductivity in the GaN film when it is 1 μm-thick in the temperature range of 300 < T < 600 K and use a phonon transport model to explain the thermal conductivity in this film.

  6. The potential of detrital garnet as a provenance proxy in the Central Swiss Alps

    NASA Astrophysics Data System (ADS)

    Stutenbecker, Laura; Berger, Alfons; Schlunegger, Fritz

    2017-04-01

    Detrital garnet is a promising candidate to reliably fingerprint sediment sources in the Alps, which has so far been complicated by the wide range and similarity of some of the lithologies. Garnet is present in most Alpine sediments, is easy to identify, is fairly stable and, most importantly, reflects the type and the metamorphic grade of its source rock in its chemical composition. This study aims to establish fingerprints based on detrital garnet composition for the most important tectonic units of the Central Alps, including European, Penninic and Adriatic basement rocks and their respective metasedimentary covers. Sediments collected from modern rivers, which drain representative portions of the individual tectonic units, contain a natural mixture of the various garnet populations present in each unit. We selected six catchments in southwestern Switzerland draining the External massifs, Helvetic sediments and the Penninic nappe stack at the transition of Alpine greenschist- to amphibolite-facies metamorphism in order to test the variability of Alpine garnets and the role of inherited (pre-Alpine) garnets. Extraordinary grossular- and spessartine-rich garnets of the External massifs, which experienced greenschist facies metamorphism, are clearly distinguishable from generally almandine-rich garnets supplied by the higher-grade metamorphic Penninic nappe stack. The variable pyrope, grossular and spessartine components of these almandine-rich garnets can be used to further distinguish pre-Alpine, Alpine eclogite-facies and low-grade metasedimentary garnets. This provenance proxy has the potential to be used for reconstructing sediment sources, transport and dispersal patterns in a variety of settings throughout the Alpine sedimentary record.

  7. Growth control in colon epithelial cells: gadolinium enhances calcium-mediated growth regulation.

    PubMed

    Attili, Durga; Jenkins, Brian; Aslam, Muhammad Nadeem; Dame, Michael K; Varani, James

    2012-12-01

    Gadolinium, a member of the lanthanoid family of transition metals, interacts with calcium-binding sites on proteins and other biological molecules. The overall goal of the present investigation was to determine if gadolinium could enhance calcium-induced epithelial cell growth inhibition in the colon. Gadolinium at concentrations as low as 1-5 μM combined with calcium inhibits proliferation of human colonic epithelial cells more effectively than calcium alone. Gadolinium had no detectable effect on calcium-induced differentiation in the same cells based on change in cell morphology, induction of E-cadherin synthesis, and translocation of E-cadherin from the cytosol to the cell surface. When the colon epithelial cells were treated with gadolinium and then exposed to increased calcium concentrations, movement of extracellular calcium into the cell was suppressed. In contrast, gadolinium treatment had no effect on ionomycin-induced release of stored intracellular calcium into the cytoplasm. Whether these in vitro observations can be translated into an approach for reducing abnormal proliferation in the colonic mucosa (including polyp formation) is not known. These results do, however, provide an explanation for our recent findings that a multi-mineral supplement containing all of the naturally occurring lanthanoid metals including gadolinium are more effective than calcium alone in preventing colon polyp formation in mice on a high-fat diet.

  8. Structural and magnetic properties of yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrites prepared by microemulsion method

    NASA Astrophysics Data System (ADS)

    Akhtar, Majid Niaz; Bakar Sulong, Abu; Khan, Muhammad Azhar; Ahmad, Mukhtar; Murtaza, Ghulam; Raza, M. R.; Raza, R.; Saleem, M.; Kashif, M.

    2016-03-01

    Yttrium iron garnet (YIG) and yttrium aluminum iron garnet (YAIG) nanoferrite samples were synthesized by microemulsion method. The effect of sintering was examined by heating the samples at 900, 1000, and 1100 °C. The YIG and YAIG samples were then characterized using X-ray diffraction and field-emission scanning electron microscopy. Static and dynamic magnetic properties were measured by evaluating initial permeability, Q factor, and vibrating sample magnetometry properties of YIG and YAIG samples. YIG samples sintered at 1100 °C showed higher initial permeability and Q factor compared with YAIG samples. However, hysteresis loops also showed variations in the saturation magnetization, remanence, and coercivity of YIG and YAIG samples sintered at 900, 1000, and 1100 °C. The observed magnetic parameter such as saturation magnetization, coercivity and initial permeability are strongly affected by increasing temperature. The saturation magnetization and coercivity of YIG and YAIG nanoferrites were found in the range 11.56-19.92 emu/g and 7.30-87.70 Oe respectively. Furthermore, the decreasing trends in the static and magnetic properties of YAIG samples may be due to the introduction of Al ions in the YIG crystal lattice. Thus, YIG and YAIG sintered at 1100 °C can be used for wide-ranging frequency applications.

  9. Gadolinium nanoparticles and contrast agent as radiation sensitizers.

    PubMed

    Taupin, Florence; Flaender, Mélanie; Delorme, Rachel; Brochard, Thierry; Mayol, Jean-François; Arnaud, Josiane; Perriat, Pascal; Sancey, Lucie; Lux, François; Barth, Rolf F; Carrière, Marie; Ravanat, Jean-Luc; Elleaume, Hélène

    2015-06-07

    The goal of the present study was to evaluate and compare the radiosensitizing properties of gadolinium nanoparticles (NPs) with the gadolinium contrast agent (GdCA) Magnevist(®) in order to better understand the mechanisms by which they act as radiation sensitizers. This was determined following either low energy synchrotron irradiation or high energy gamma irradiation of F98 rat glioma cells exposed to ultrasmall gadolinium NPs (GdNPs, hydrodynamic diameter of 3 nm) or GdCA. Clonogenic assays were used to quantify cell survival after irradiation in the presence of Gd using monochromatic x-rays with energies in the 25 keV-80 keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. Radiosensitization was demonstrated with both agents in combination with X-irradiation. At the same concentration (2.1 mg mL(-1)), GdNPS had a greater effect than GdCA. The maximum sensitization-enhancement ratio at 4 Gy (SER4Gy) was observed at an energy of 65 keV for both the nanoparticles and the contrast agent (2.44   ±   0.33 and 1.50   ±   0.20, for GdNPs and GdCA, respectively). At a higher energy (1.25 MeV), radiosensitization only was observed with GdNPs (1.66   ±   0.17 and 1.01   ±   0.11, for GdNPs and GdCA, respectively). The radiation dose enhancements were highly 'energy dependent' for both agents. Secondary-electron-emission generated after photoelectric events appeared to be the primary mechanism by which Gd contrast agents functioned as radiosensitizers. On the other hand, other biological mechanisms, such as alterations in the cell cycle may explain the enhanced radiosensitizing properties of GdNPs.

  10. Gadolinium nanoparticles and contrast agent as radiation sensitizers

    NASA Astrophysics Data System (ADS)

    Taupin, Florence; Flaender, Mélanie; Delorme, Rachel; Brochard, Thierry; Mayol, Jean-François; Arnaud, Josiane; Perriat, Pascal; Sancey, Lucie; Lux, François; Barth, Rolf F.; Carrière, Marie; Ravanat, Jean-Luc; Elleaume, Hélène

    2015-06-01

    The goal of the present study was to evaluate and compare the radiosensitizing properties of gadolinium nanoparticles (NPs) with the gadolinium contrast agent (GdCA) Magnevist® in order to better understand the mechanisms by which they act as radiation sensitizers. This was determined following either low energy synchrotron irradiation or high energy gamma irradiation of F98 rat glioma cells exposed to ultrasmall gadolinium NPs (GdNPs, hydrodynamic diameter of 3 nm) or GdCA. Clonogenic assays were used to quantify cell survival after irradiation in the presence of Gd using monochromatic x-rays with energies in the 25 keV-80 keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. Radiosensitization was demonstrated with both agents in combination with X-irradiation. At the same concentration (2.1 mg mL-1), GdNPS had a greater effect than GdCA. The maximum sensitization-enhancement ratio at 4 Gy (SER4Gy) was observed at an energy of 65 keV for both the nanoparticles and the contrast agent (2.44   ±   0.33 and 1.50   ±   0.20, for GdNPs and GdCA, respectively). At a higher energy (1.25 MeV), radiosensitization only was observed with GdNPs (1.66   ±   0.17 and 1.01   ±   0.11, for GdNPs and GdCA, respectively). The radiation dose enhancements were highly ‘energy dependent’ for both agents. Secondary-electron-emission generated after photoelectric events appeared to be the primary mechanism by which Gd contrast agents functioned as radiosensitizers. On the other hand, other biological mechanisms, such as alterations in the cell cycle may explain the enhanced radiosensitizing properties of GdNPs.

  11. Ages of Sevier thrusting from dating of metamorphic garnet using the Lu-Hf method

    NASA Astrophysics Data System (ADS)

    Cruz-Uribe, A. M.; Hoisch, T. D.; Wells, M. L.; Vervoort, J. D.

    2008-12-01

    Combined thermodynamic modeling of garnet growth zoning and Lu-Hf dating of garnet yield well-constrained pressure-temperature-time (PTt) paths. Here we present PTt paths from amphibolite-facies pelitic garnet from the Raft River-Albion-Grouse Creek metamorphic core complex that constrain the timing of thrusting in the hinterland of the Sevier thrust belt. Three general times of thrust burial are indicated: 150, 138, and 85 Ma. Lu-Hf garnet dating of burial-related garnet growth in the Raft River Mountains yielded a Late Jurassic age of 149.9 ± 1.2 Ma (2σ, MSWD = 1.1) based on three garnet fractions and a whole rock. A PT path from the schist of Mahogany Peaks in the Albion Range, Idaho, records an isothermal pressure increase indicating growth during thrusting. Lu-Hf dating of garnet from the same rock yielded an Early Cretaceous age of 138.7 ± 0.7 Ma (2σ, MSWD = 1.6) based on seven garnet fractions. An additional PT path from a nearby outcrop also records an isothermal pressure increase and a similar Lu-Hf garnet age of 132.1 ± 5.1 Ma (2σ, MSWD = 9.5) based on three garnet fractions and a whole rock. PT paths of multiple garnet grains from the schist of Stevens Spring in the Grouse Creek Mountains, Utah, exhibit isothermal pressure increases and yielded a Lu-Hf garnet age of 85.5 ± 1.9 Ma (2σ, MSWD = 3.9) based on five garnet fractions and a whole rock. The Late Jurassic burial event recorded in the Raft River Mountains is older than the ages of inception of thrusting of the western thrusts of the Sevier fold-thrust belt including the Canyon Range and Paris - Willard thrusts, but consistent with an eastward progression in initial shortening in the orogenic wedge and development of an inferred thrust load responsible for the retroarc Morrison Formation basin. Early Cretaceous hinterland burial recorded in the Albion Range is permissively coeval with activity on the Willard and Canyon Range thrusts. Finally, renewed hinterland thrust burial during the Late

  12. Samarium- and ytterbium-promoted oxidation of silicon and gallium arsenide surfaces

    SciTech Connect

    Franciosi, A.

    1989-02-21

    A method is described for promoting oxidation of a silicon or gallium arsenide surface comprising: depositing a ytterbium overlayer on the silicon or gallium arsenide surface prior to the oxidation of the surface.

  13. Epiphyseal and physeal cartilage: normal gadolinium-enhanced MR imaging.

    PubMed

    Li, Xiaoming; Wang, Renfa; Li, Yonggang; Tang, Lihua; Hu, Junwu; Xu, Anhui

    2005-01-01

    To evaluate the normal appearance of epiphyseal and physeal cartilage on Gadolinium (Gd)-enhanced MR imaging. The appearance and enhancement ratios of 20 proximal and distal femoral epiphyses in 10 normal piglets were analyzed on Gd-enhanced MR images. The correlation of the MR imaging appearance with corresponding histological findings of immature epiphyses was examined. Our results showed that Gd-enhanced MRI could differentiate the differences in enhancement between physeal and epiphyseal cartilage and show vascular canals within the epiphyseal cartilage. Enhanced ratios in the physeal were greater than those in the epiphyseal cartilage (P < 0.005). It is concluded that Gd-enhanced MR imaging reveals epiphyseal vascular canals and shows difference in enhancement of physeal and epiphyseal cartilage.

  14. The structural response of gadolinium phosphate to pressure

    NASA Astrophysics Data System (ADS)

    Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; Boatner, Lynn A.

    2016-09-01

    Accurate elastic constants for gadolinium phosphate (GdPO4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO4 determined under hydrostatic conditions, 128.1(8) GPa (Kʹ=5.8(2)), is markedly different from that obtained with GdPO4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. High pressure Raman and diffraction analysis indicate that the PO4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO4 structure is facilitated by bending/twisting of the Gd-O-P links that result in increased distortion in the GdO9 polyhedra.

  15. Defect induced mobility enhancement: Gadolinium oxide (100) on Si(100)

    SciTech Connect

    Sitaputra, W.; Tsu, R.

    2012-11-26

    Growth of predominantly single crystal (100)-oriented gadolinium oxide (Gd{sub 2}O{sub 3}) on a p-type Si(100) and growth of a polycrystal with a predominant Gd{sub 2}O{sub 3}(100) crystallite on a n-type Si(100) was performed using molecular beam epitaxy. Despite a poorer crystal structure than Gd{sub 2}O{sub 3}(110), an enhancement in carrier mobility can be found only from the Gd{sub 2}O{sub 3}(100)/n-type Si(100) interface. The mobility of 1715-1780 cm{sup 2}/V {center_dot} s was observed at room temperature, for carrier concentration >10{sup 20} cm{sup -3}. This accumulation of the electrons and the mobility enhancement may arise from the two-dimensional confinement due to charge transfer across the interface similar to transfer doping.

  16. Mechanism of inhibition of ribonucleotide reductase with motexafin gadolinium (MGd)

    SciTech Connect

    Zahedi Avval, Farnaz; Berndt, Carsten; Pramanik, Aladdin; Holmgren, Arne

    2009-02-13

    Motexafin gadolinium (MGd) is an expanded porphyrin anticancer agent which selectively targets tumor cells and works as a radiation enhancer, with promising results in clinical trials. Its mechanism of action is oxidation of intracellular reducing molecules and acting as a direct inhibitor of mammalian ribonucleotide reductase (RNR). This paper focuses on the mechanism of inhibition of RNR by MGd. Our experimental data present at least two pathways for inhibition of RNR; one precluding subunits oligomerization and the other direct inhibition of the large catalytic subunit of the enzyme. Co-localization of MGd and RNR in the cytoplasm particularly in the S-phase may account for its inhibitory properties. These data can elucidate an important effect of MGd on the cancer cells with overproduction of RNR and its efficacy as an anticancer agent and not only as a general radiosensitizer.

  17. The structural response of gadolinium phosphate to pressure

    DOE PAGES

    Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; ...

    2016-06-16

    In this study, accurate elastic constants for gadolinium phosphate (GdPO4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO4 structure is facilitated by bending/twisting of the Gd–O–P links that result in increased distortion in the GdO9more » polyhedra.« less

  18. The structural response of gadolinium phosphate to pressure

    SciTech Connect

    Heffernan, Karina M.; Ross, Nancy L.; Spencer, Elinor C.; Boatner, Lynn A.

    2016-06-16

    In this study, accurate elastic constants for gadolinium phosphate (GdPO4) have been measured by single-crystal high-pressure diffraction methods. The bulk modulus of GdPO4 determined under hydrostatic conditions, 128.1(8) GPa (K'=5.8(2)), is markedly different from that obtained with GdPO4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. Finally, high pressure Raman and diffraction analysis indicate that the PO4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO4 structure is facilitated by bending/twisting of the Gd–O–P links that result in increased distortion in the GdO9 polyhedra.

  19. Gallium Potentiates the Antibacterial Effect of Gentamicin against Francisella tularensis.

    PubMed

    Lindgren, Helena; Sjöstedt, Anders

    2015-10-26

    The reasons why aminoglycosides are bactericidal have not been not fully elucidated, and evidence indicates that the cidal effects are at least partly dependent on iron. We demonstrate that availability of iron markedly affects the susceptibility of the facultative intracellular bacterium Francisella tularensis strain SCHU S4 to the aminoglycoside gentamicin. Specifically, the intracellular depots of iron were inversely correlated to gentamicin susceptibility, whereas the extracellular iron concentrations were directly correlated to the susceptibility. Further proof of the intimate link between iron availability and antibiotic susceptibility were the findings that a ΔfslA mutant, which is defective for siderophore-dependent uptake of ferric iron, showed enhanced gentamicin susceptibility and that a ΔfeoB mutant, which is defective for uptake of ferrous iron, displayed complete growth arrest in the presence of gentamicin. Based on the aforementioned findings, it was hypothesized that gallium could potentiate the effect of gentamicin, since gallium is sequestered by iron uptake systems. The ferrozine assay demonstrated that the presence of gallium inhibited >70% of the iron uptake. Addition of gentamicin and/or gallium to infected bone marrow-derived macrophages showed that both 100 μM gallium and 10 μg/ml of gentamicin inhibited intracellular growth of SCHU S4 and that the combined treatment acted synergistically. Moreover, treatment of F. tularensis-infected mice with gentamicin and gallium showed an additive effect. Collectively, the data demonstrate that SCHU S4 is dependent on iron to minimize the effects of gentamicin and that gallium, by inhibiting the iron uptake, potentiates the bactericidal effect of gentamicin in vitro and in vivo.

  20. Application of ultrasound in solvent extraction of nickel and gallium

    SciTech Connect

    Pesic, B.

    1996-07-01

    The effects of ultrasound on the rate of solvent extraction of nickel with Lix 65N and Lix 70, and gallium with Kelex 100 were investigated. These solvent extraction systems are noted by their sluggish nature. Low frequency (20 kHz) ultrasound increased the rates of extraction of nickel by factors of four to seven. The ultrasound had no effect on the final chemical equilibrium. Gallium extraction rates were enhanced with the use of ultrasound by as much as a factor of 15. Again, the ultrasound had no effect on extraction equilibrium. For both nickel and gallium, the enhanced rates were attributed to increased interfacial surface area associated with ultrasonically induced cavitation and microdroplet formation. The stability of the microdroplets permitted intermittent application of ultrasound with corresponding decreases in ultrasonic energy requirements. The lowest energy consumption was observed with short (0.25 to 5 s) bursts of high power (41 to 61 W) ultrasonic inputs. The study also provided insight into the factors that affect the complex extraction of gallium from sodium aluminate solutions. The rate controlling step was found to be the dehydration of the gallate ion, Ga(OH)4, and the first complex formation between gallium and Kelex 100. Sodium was found to enhance the extraction rate up to a point, beyond which increased concentration was detrimental. Increasing aluminum concentration was found to slow extraction rates. Modifiers and diluents were shown to markedly affect extraction rates even without ultrasound. Ketone modifiers, particularly 2-undecanone, when used with Kermac 470B or Escaid 200 diluents enhanced extraction rates of gallium to the point that the use of ultrasound provided no additional benefits. The positive effects of ketone modifiers for the solvent extraction of gallium had not been previously reported.

  1. Gallium Potentiates the Antibacterial Effect of Gentamicin against Francisella tularensis

    PubMed Central

    Lindgren, Helena

    2015-01-01

    The reasons why aminoglycosides are bactericidal have not been not fully elucidated, and evidence indicates that the cidal effects are at least partly dependent on iron. We demonstrate that availability of iron markedly affects the susceptibility of the facultative intracellular bacterium Francisella tularensis strain SCHU S4 to the aminoglycoside gentamicin. Specifically, the intracellular depots of iron were inversely correlated to gentamicin susceptibility, whereas the extracellular iron concentrations were directly correlated to the susceptibility. Further proof of the intimate link between iron availability and antibiotic susceptibility were the findings that a ΔfslA mutant, which is defective for siderophore-dependent uptake of ferric iron, showed enhanced gentamicin susceptibility and that a ΔfeoB mutant, which is defective for uptake of ferrous iron, displayed complete growth arrest in the presence of gentamicin. Based on the aforementioned findings, it was hypothesized that gallium could potentiate the effect of gentamicin, since gallium is sequestered by iron uptake systems. The ferrozine assay demonstrated that the presence of gallium inhibited >70% of the iron uptake. Addition of gentamicin and/or gallium to infected bone marrow-derived macrophages showed that both 100 μM gallium and 10 μg/ml of gentamicin inhibited intracellular growth of SCHU S4 and that the combined treatment acted synergistically. Moreover, treatment of F. tularensis-infected mice with gentamicin and gallium showed an additive effect. Collectively, the data demonstrate that SCHU S4 is dependent on iron to minimize the effects of gentamicin and that gallium, by inhibiting the iron uptake, potentiates the bactericidal effect of gentamicin in vitro and in vivo. PMID:26503658

  2. Lithospheric roots beneath western Laurentia: The geochemical signal in mantle garnets

    USGS Publications Warehouse

    Canil, D.; Schulze, D.J.; Hall, D.; Hearn, B.C.; Milliken, S.M.

    2003-01-01

    This study presents major and trace element data for 243 mantle garnet xenocrysts from six kimberlites in parts of western North America. The geochemical data for the garnet xenocrysts are used to infer the composition, thickness, and tectonothermal affinity of the mantle lithosphere beneath western Laurentia at the time of kimberlite eruption. The garnets record temperatures between 800 and 1450??C using Ni-in-garnet thermometry and represent mainly lherzolitic mantle lithosphere sampled over an interval from about 110-260 km depth. Garnets with sinuous rare-earth element patterns, high Sr, and high Sc/V occur mainly at shallow depths and occur almost exclusively in kimberlites interpreted to have sampled Archean mantle lithosphere beneath the Wyoming Province in Laurentia, and are notably absent in garnets from kimberlites erupting through the Proterozoic Yavapai Mazatzal and Trans-Hudson provinces. The similarities in depths of equilibration, but differing geochemical patterns in garnets from the Cross kimberlite (southeastern British Columbia) compared to kimberlites in the Wyoming Province argue for post-Archean replacement and (or) modification of mantle beneath the Archean Hearne Province. Convective removal of mantle lithosphere beneath the Archean Hearne Province in a "tEctonic vise" during the Proterozoic terminal collisions that formed Laurentia either did not occur, or was followed by replacement of thick mantle lithosphere that was sampled by kimberlite in the Triassic, and is still observed there seismically today.

  3. Ce(3+)-Doped garnet phosphors: composition modification, luminescence properties and applications.

    PubMed

    Xia, Zhiguo; Meijerink, Andries

    2017-01-03

    Garnets have the general formula of A3B2C3O12 and form a wide range of inorganic compounds, occurring both naturally (gemstones) and synthetically. Their physical and chemical properties are closely related to the structure and composition. In particular, Ce(3+)-doped garnet phosphors have a long history and are widely applied, ranging from flying spot cameras, lasers and phosphors in fluorescent tubes to more recent applications in white light LEDs, as afterglow materials and scintillators for medical imaging. Garnet phosphors are unique in their tunability of the luminescence properties through variations in the {A}, [B] and (C) cation sublattice. The flexibility in phosphor composition and the tunable luminescence properties rely on design and synthesis strategies for new garnet compositions with tailor-made luminescence properties. It is the aim of this review to discuss the variation in luminescence properties of Ce(3+)-doped garnet materials in relation to the applications. This review will provide insight into the relation between crystal chemistry and luminescence for the important class of Ce(3+)-doped garnet phosphors. It will summarize previous research on the structural design and optical properties of garnet phosphors and also discuss future research opportunities in this field.

  4. Investigation of the growth of garnet films by liquid phase epitaxy

    NASA Technical Reports Server (NTRS)

    Moody, J. W.; Shaw, R. W.; Sandfort, R. M.

    1974-01-01

    Liquid phase expitaxy was investigated to determine its applicability to fabricating magnetic rare earth garnet films for spacecraft data recording systems. Two mixed garnet systems were investigated in detail: (1) Gd-Y and (2) Eu-Yb-Y. All films were deposited on Gd3Ga5012 substrates. The uniaxial anisotropy of the Gd-Y garnets is primarily stress-induced. These garnets are characterized by high-domain wall mobility, low coercivity and modest anisotropy. Characteristic length was found to be relatively sensitive to temperature. The Eu-Yb-Y garnets exhibit acceptable mobilities, good temperature stability and reasonable quality factors. The uniaxial anisotropy of these garnets is primarily growth-induced. The system is well suited for compositional "tailoring" to optimize specific desirable properties. Liquid phase epitaxy can be used to deposit Gd3Ga5012 spacing layers on magnetic garnet films and this arrangement possesses certain advantages over more conventional magnetic filmspacing layer combinations. However, it cannot be used if the magnetic film is to be ion implanted.

  5. Study of the provenance of Belgian Merovingian garnets by PIXE at IPNAS cyclotron

    NASA Astrophysics Data System (ADS)

    Mathis, F.; Vrielynck, O.; Laclavetine, K.; Chêne, G.; Strivay, D.

    2008-05-01

    Recent archaeological excavation in Belgium reveals one of the biggest Merovingian necropolis ever found in this country. This necropolis contains 436 tombs with a period of occupation of almost two centuries. Some of these tombs were very rich, especially two of them, and delivered an important funerary furniture. About 60 jewels inlaid with red garnets have been found, most of them of "cloisonné" style (namely about 450 garnets). The new extracted beam set-up of the IPNAS cyclotron (University of Liège, Belgium) has been improved in order to analyse by PIXE these garnets and try to determine their provenance. These analyses reveal that the garnets found in the necropolis of Grez-Doiceau are very homogeneous in composition (almandine garnets) and are coming almost from a unique source. These results have been compared to previous studies led in France during these past five years. This permits to identify the source of almandine garnet situated in India and to highlight differences in garnet supply between France and Belgium in Merovingian times.

  6. Fabrication and Characterization of Gadolinium Phosphate Neutron Absorber

    SciTech Connect

    Lessing, Paul Alan; Erickson, Arnold Wendell

    2003-12-01

    Hydrated gadolinium phosphate (GdPO4·1H2O) was synthesized by reacting high purity dissolved salts (gadolinium nitrates or chlorides) with phosphoric acid. The hydrated powders were shown to be extremely insoluble in water with a Ksp measured to be between 2.07 E-14 and 4.76 E-13. Calcination to between 800 and 1000 °C resulted in the formation of GdPO4 in a monazite (monoclinic) crystal structure. This was correlated with the first exothermic differential thermal analysis (DTA) peak (864.9–883.4 °C). The DTA also showed small peaks in the 1200–1250 °C range, that could be associated with a change from the monazite (monoclinic) crystal structure to the xenotime (tetragonal) crystal structure. However, calcination of a sample to 1400 °C, followed by relatively rapid cooling and XRD, showed the structure was still monazite (monoclinic). DTA results showed a melting point at 1899–1920 °C (endothermic peak). It was therefore concluded that the melting point probably was the melting of the monazite (monoclinic) phase, but may have been xenotime if a phase change at 1200–1250 °C was reversible and very rapid. The higher part of the melting range was achieved with material derived using the slightly higher purity nitrate salt. The results show that GdPO4 is an excellent candidate for a chemically stable, water-insoluble neutron absorber for inclusion in spent nuclear fuel canisters.

  7. Gallium a unique anti-resorptive agent in bone: Preclinical studies on its mechanisms of action

    SciTech Connect

    Bockman, R.; Adelman, R.; Donnelly, R.; Brody, L.; Warrell, R. ); Jones, K.W. )

    1990-01-01

    The discovery of gallium as a new and unique agent for the treatment of metabolic bone disorders was in part fortuitous. Gallium is an exciting new therapeutic agent for the treatment of pathologic states characterized by accelerated bone resorption. Compared to other therapeutic metal compounds containing platinum or germanium, gallium affects its antiresorptive action without any evidence of a cytotoxic effect on bone cells. Gallium is unique amongst all therapeutically available antiresorptive agents in that it favors bone formation. 18 refs., 1 fig.

  8. Effectiveness of ion implantation of iron garnet films

    SciTech Connect

    Tikhonov, A.N.; Fedichkin, G.M.; Yurchenko, S.E.; Suslin, L.A.; Smirnov, I.S.; Shlenov, Yu.V.

    1986-01-01

    The authors seek to determine experimentally what changes of the magnetic bubble properties and of the iron garnet film characteristics resulting from implantation of Ne/sup +/ ions can be used as criteria for assessing the effectiveness of this process in the production of bubble devices. For the experiments, the authors used (YBi)/sub 3/(FeGa)/sub 5/O/sub 12/; (TmBi)/sub 3/(FeGa)/sub 5/O/sub 12/; and (YSmLuCa)/sub 3/(FeGe)/sub 5/O/sub 12/. The orientation of the Gd/sub 3/Ga/sub 5/O/sub 12/ substrate is (111) in all cases. The current density of the H/sup +/ proton beam did not exceed 0.5 micro-A/cm/sup 2/.

  9. Tunable negative index metamaterial using yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    He, Yongxue; He, Peng; Dae Yoon, Soack; Parimi, P. V.; Rachford, F. J.; Harris, V. G.; Vittoria, C.

    2007-06-01

    A magnetic field tunable, broadband, low-loss, negative refractive index metamaterial is fabricated using yttrium iron garnet (YIG) and a periodic array of copper wires. The tunability is demonstrated from 18 to 23 GHz under an applied magnetic field with a figure of merit of 4.2 GHz/kOe. The tuning bandwidth is measured to be 5 GHz compared to 0.9 GHz for fixed field. We measure a minimum insertion loss of 4 dB (or 5.7 dB/cm) at 22.3 GHz. The measured negative refractive index bandwidth is 0.9 GHz compared to 0.5 GHz calculated by the transfer function matrix theory and 1 GHz calculated by finite element simulation.

  10. Radiative Performance of Rare Earth Garnet Thin Film Selective Emitters

    NASA Technical Reports Server (NTRS)

    Lowe, Roland A.; Chubb, Donald L.; Good, Brian S.

    1994-01-01

    In this paper we present the first emitter efficiency results for the thin film 40 percent Er-1.5 percent Ho YAG (Yttrium Aluminum Garnet, Y3Al5O12) and 25 percent Ho YAG selective emitter at 1500 K with a platinum substrate. Spectral emittance and emissive power measurements were made (1.2 less than lambda less than 3.2 microns). Emitter efficiency and power density are significantly improved with the addition of multiple rare earth dopants. Predicted efficiency results are presented for an optimized (equal power density in the Er, (4)I(sub 15/2)-(4)I(sub 13/2) at 1.5 microns, and Ho, (5)I(sub 7)-(5)I(sub 8) at 2.0 micron emission bands) Er-Ho YAG thin film selective emitter.

  11. Process for forming pure silver ohmic contacts to N- and P-type gallium arsenide materials

    DOEpatents

    Hogan, S.J.

    1983-03-13

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components a n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffuse layer and the substrate layer wherein the n-type layer comprises a substantially low doping carrier concentration.

  12. Pure silver ohmic contacts to N- and P- type gallium arsenide materials

    DOEpatents

    Hogan, Stephen J.

    1986-01-01

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

  13. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  14. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  15. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  16. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  17. 40 CFR 421.180 - Applicability: Description of the primary and secondary germanium and gallium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary and secondary germanium and gallium subcategory. 421.180 Section 421.180 Protection of Environment... POINT SOURCE CATEGORY Primary and Secondary Germanium and Gallium Subcategory § 421.180 Applicability: Description of the primary and secondary germanium and gallium subcategory. The provisions of this subpart...

  18. Gallium nitrate inhibits alkaline phosphatase activity in a differentiating mesenchymal cell culture.

    PubMed

    Boskey, A L; Ziecheck, W; Guidon, P; Doty, S B

    1993-02-01

    The effect of gallium nitrate on alkaline phosphatase activity in a differentiating chick limb-bud mesenchymal cell culture was monitored in order to gain insight into the observation that rachitic rats treated with gallium nitrate failed to show the expected increase in serum alkaline phosphatase activity. Cultures maintained in media containing 15 microM gallium nitrate showed drastically decreased alkaline phosphatase activities in the absence of significant alterations in total protein synthesis and DNA content. However, addition of 15 microM gallium nitrate to cultures 18 h before assay for alkaline phosphatase activity had little effect. At the light microscopic and electron microscopic level, gallium-treated cultures differed morphologically from gallium-free cultures: with gallium present, there were fewer hypertrophic chondrocytes and cartilage nodules were flatter and further apart. Because of altered morphology, staining with an antibody against chick cartilage alkaline phosphatase appeared less extensive; however, all nodules stained equivalently relative to gallium-free controls. Histochemical staining for alkaline phosphatase activity was negative in gallium-treated cultures, demonstrating that the alkaline phosphatase protein present was not active. The defective alkaline phosphatase activity in cultures maintained in the presence of gallium was also evidenced when cultures were supplemented with the alkaline phosphatase substrate, beta-glycerophosphate (beta GP). The data presented suggest that gallium inhibits alkaline phosphatase activity in this culture system and that gallium causes alterations in the differentiation of mesenchymal cells into hypertrophic chondrocytes.

  19. Electroluminescence Studies on Longwavelength Indium Arsenide Quantum Dot Microcavities Grown on Gallium Arsenide

    DTIC Science & Technology

    2011-12-01

    ELECTROLUMINESCENCE STUDIES ON LONG WAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE THESIS John C...11-46 ELECTROLUMINESCENCE STUDIES ON LONGWAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE THESIS...58 1 ELECTROLUMINESCENCE STUDIES ON LONGWAVELENGTH INDIUM ARSENIDE QUANTUM DOT MICROCAVITIES GROWN ON GALLIUM ARSENIDE I

  20. Theoretical study of structure and stability of small gadolinium carboxylate complexes in liquid scintillator solvents.

    PubMed

    Huang, Pin-Wen

    2014-09-01

    The structural properties of three small gadolinium carboxylate complexes in three liquid scintillator solvents (pseudocumene, linear alkylbenzene, and phenyl xylylethane) were theoretically investigated using density functional theory (B3LYP/LC-RECP) and polarizable continuum model (PCM). The average interaction energy between gadolinium atom and carboxylate ligand (E(int)) and the energy difference of the highest singly occupied molecular orbital and lowest unoccupied molecular orbital (Δ(SL)) were calculated to evaluate and compare the relative stability of these complexes in solvents. The calculation results show that the larger (with a longer alkyl chain) gadolinium carboxylate complex has greater stability than the smaller one, while these gadolinium carboxylates in linear alkylbenzene were found to have greater stability than those in the other two solvents.

  1. Gallium based low-interaction anions

    DOEpatents

    King, Wayne A.; Kubas, Gregory J.

    2000-01-01

    The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

  2. Correlation by Rb-Sr geochronology of garnet growth histories from different structural levels within the Tauern Window, Eastern Alps

    SciTech Connect

    Christensen, John N.; Selverstone, Jane; Rosenfeld, John L.; Depaolo, Donald J.

    1993-06-01

    In order to evaluate rates of tectonometamorphic processes, growth rates of garnets from metamorphic rocks of the Tauern Window, Eastern Alps were measured using Rb-Sr isotopes. The garnet growth rates were determined from Rb-Sr isotopic zonation of single garnet crystals and the Rb-Sr isotopic compositions of their associated rock matrices. Garnets were analyzed from the Upper Schieferhulle (USH) and Lower Schieferhulle (LSH) within the Tauern Window. Two garnets from the USH grew at rates of 0.67(-0.13)+0.19 mm/million years and 0.88(-0.19)+0.34 mm/million years, respectively, indicating an average growth duration of 5.4 +- 1.7 million years. The duration of growth coupled with the amount of rotation recorded by inclusion trails in the USH garnets yields an average shear-strain rate during garnet growth of 2.7(-0.7)+1.2 x 10(-14) s-1 . Garnet growth in the sample from the USH occurred between 35.4 +- 0.6 and 30 +- 0.8 Ma. The garnet from the LSH grew at a rate of 0.23 +- 0.015 mm/mil lion years, between 62 +- 1.5 Ma and 30.2 +- 1.5 Ma. Contemporaneous cessation of garnet growth in both units at approximately 30 Ma is in accord with previous dating of the thermal peak of metamorphism in the Tauern Window. Correlation with previously published pressure-temperature paths for garnets from the USH and LSH yields approximate rates of burial, exhumation and heating during garnet growth. Assuming that these P - T paths are applicable to the garnets in this study, the contemporaneous exhumation rates recorded by garnet in the USH and LSH were approximately 4(-2)+3 mm/year and 2 +- 1 mm/year, respectively. [References: 34

  3. Density of Gadolinium Nitrate Solutions for the High Flux Isotope Reactor

    SciTech Connect

    Taylor, Paul Allen; Lee, Denise L

    2009-05-01

    In late 1992, the High Flux Isotope Reactor (HFIR) was planning to switch the solution contained in the poison injection tank from cadmium nitrate to gadolinium nitrate. The poison injection system is an emergency system used to shut down the reactor by adding a neutron poison to the cooling water. This system must be able to supply a minimum of 69 pounds of gadolinium to the reactor coolant system in order to guarantee that the reactor would become subcritical. A graph of the density of gadolinium nitrate solutions over a concentration range of 5 to 30 wt% and a temperature range of 15 to 40{sup o}C was prepared. Routine density measurements of the solution in the poison injection tank are made by HFIR personnel, and an adaptation of the original graph is used to determine the gadolinium nitrate concentration. In late 2008, HFIR personnel decided that the heat tracing that was present on the piping for the poison injection system could be removed without any danger of freezing the solution; however, the gadolinium nitrate solution might get as cold as 5{sup o}C. This was outside the range of the current density-concentration correlation, so the range needed to be expanded. This report supplies a new density-concentration correlation that covers the extended temperature range. The correlation is given in new units, which greatly simplifies the calculation that is required to determine the pounds of gadolinium in the tank solution. The procedure for calculating the amount of gadolinium in the HFIR poison injection system is as follows: (1) Calculate the usable volume in the system; (2) Measure the density of the solution; (3) Calculate the gadolinium concentration using the following equation: Gd(lb/ft{sup 3}) = measured density (g/mL) x 34.681 - 34.785; (4) Calculate the amount of gadolinium in the system using the following equation: Amount of Gd(lb) = Gd concentration (lb/ft{sup 3}) x usable volume (ft{sup 3}). The equation in step 3 is exact for a temperature of

  4. High temperature garnet growth in New England: regional temperature-time trends revealed

    NASA Astrophysics Data System (ADS)

    Sullivan, N.; Ostwald, C.; Chu, X.; Baxter, E. F.; Ague, J. J.; Eckert, J. O.

    2013-12-01

    A series of localized ultrahigh-temperature (UHT)/high-temperature (HT) granulite facies regions have been identified within the regional amphibolite facies metamorphic zone of the Central Maine Terrane stretching from north-central New Hampshire, through central Massachusetts, and into northeastern Connecticut. Here, we aim to constrain the age and peak temperature of metamorphism at three localities within this region: Bristol, NH, Phillipston, MA and Willington, CT. Garnet-forming reactions are linked directly to peak metamorphic temperatures through thermodynamic modeling and/or Zr-in-rutile thermometry. Precise garnet geochronology allows us to identify the timing of these peak temperatures, as well as the duration of garnet growth. Geochronologic and thermodynamic work was done on 12 samples collected throughout a ~5 km2 metamorphic 'hotspot' previously identified in Bristol, NH (Chamberlain and Rumble, 1988; Journal of Petrology). The highest temperature assemblage within this hotspot is characterized by the presence of garnet + sillimanite + K-feldspar + cordierite and reached temperatures >820οC. The lowest temperature periphery of the hotspot is characterized by sillimanite + muscovite + K-feldspar + minor garnet and reached a maximum temperature of 650οC. Bulk garnet ages from samples within the hotspot range significantly from at least 400.0 × 2.5 Ma to 352.7 × 1.8 Ma with the youngest ages associated with the lower temperature samples. This collection of ages indicates a prolonged period (~50 Ma) of >650οC temperatures interspersed by period(s) of garnet growth. Zoned garnet geochronology will help reveal whether garnet growth and related heating was continuous or episodic. Further south, in Phillipston, MA, zoned garnet geochronology performed on a 2.5 cm diameter garnet porphyroblast indicates garnet growth spanning 389 - 363 Ma, reaching peak temperatures at the end of that time span of 920-940οC, followed by a younger event recorded in

  5. Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

  6. Gadolinium Use in Spine Pain Management Procedures for Patients with Contrast Allergies: Results in 527 Procedures

    SciTech Connect

    Safriel, Yair Ang, Roberto; Ali, Muhammed

    2008-03-15

    Introduction. To review the safety and efficacy of gadolinium in spine pain management procedures in patients at high risk for a contrast reaction and who are not suitable candidates for the use of standard non-ionic contrast. Methods. We reviewed records over a 61-month period of all image-guided spinal pain management procedures where patients had allergies making them unsuitable candidates for standard non-ionic contrast and where gadolinium was used to confirm needle tip placement prior to injection of medication. Results. Three hundred and four outpatients underwent 527 procedures. A spinal needle was used in all but 41 procedures. Gadolinium was visualized using portable C-arm fluoroscopy in vivo allowing for confirmation of needle tip location. The gadolinium dose ranged from 0.2 to 10 ml per level. The highest dose received by one patient was 15.83 ml intradiscally during a three-level discogram. Three hundred and one patients were discharged without complication or known delayed complications. One patient had documented intrathecal injection but without sequelae and 2 patients who underwent cervical procedures experienced seizures requiring admission to the intensive care unit. Both the latter patients were discharged without any further complications. Conclusion. Based on our experience we recommend using gadolinium judiciously for needle tip confirmation. We feel more confident using gadolinium in the lumbar spine and in cervical nerve blocks. Gadolinium should probably not be used as an injectate volume expander. The indications for gadolinium use in cervical needle-guided spine procedures are less clear and use of a blunt-tipped needle should be considered.

  7. Application of extracellular gadolinium-based MRI contrast agents and the risk of nephrogenic systemic fibrosis.

    PubMed

    Heverhagen, J T; Krombach, G A; Gizewski, E

    2014-07-01

    Nephrogenic systemic fibrosis (NSF) is a serious, sometimes fatal disease. Findings in recent years have shown that a causal association between gadolinium containing contrast media and NSF is most likely. Therefore, the regulatory authorities have issued guidelines on the use of gadolinium-containing contrast media which have reduced the number of new cases of NSF to almost zero. However, it is for precisely this reason that the greatest care must still be taken to ensure that these guidelines are complied with. The most important factors are renal function, the quantity of gadolinium administered and coexisting diseases such as inflammation. All of these factors crucially influence the quantity of gadolinium released from the chelat in the body. This free gadolinium is thought to be the trigger for NSF. Other important factors are the stability of the gadolinium complex and furthermore the route of its elimination from the body. Partial elimination via the liver might be an additional protective mechanism. In conclusion, despite the NSF risk, contrast-enhanced MRI is a safe diagnostic procedure which can be used reliably and safely even in patients with severe renal failure, and does not necessarily have to be replaced by other methods.

  8. Gadolinium contrast agent-induced CD163+ ferroportin+ osteogenic cells in nephrogenic systemic fibrosis.

    PubMed

    Swaminathan, Sundararaman; Bose, Chhanda; Shah, Sudhir V; Hall, Kimberly A; Hiatt, Kim M

    2013-09-01

    Gadolinium-based contrast agents are linked to nephrogenic systemic fibrosis in patients with renal insufficiency. The pathology of nephrogenic systemic fibrosis is characterized by abnormal tissue repair: fibrosis and ectopic ossification. The mechanisms by which gadolinium could induce fibrosis and ossification are not known. We examined in vitro the effect of a gadolinium-based contrast agent on human peripheral blood mononuclear cells for phenotype and function relevant to the pathology of nephrogenic systemic fibrosis using immunofluorescence, flow cytometry, real-time PCR, and osteogenic assays. We also examined tissues from patients with nephrogenic systemic fibrosis, using IHC to identify the presence of cells with phenotype induced by gadolinium. Gadolinium contrast induced differentiation of human peripheral blood mononuclear cells into a unique cellular phenotype--CD163(+) cells expressing proteins involved in fibrosis and bone formation. These cells express fibroblast growth factor (FGF)23, osteoblast transcription factors Runt-related transcription factor 2, and osterix, and show an osteogenic phenotype in in vitro assays. We show in vivo the presence of CD163(+)/procollagen-1(+)/osteocalcin(+) cells in the fibrotic and calcified tissues of nephrogenic systemic fibrosis patients. Gadolinium contrast-induced CD163(+)/ferroportin(+)/FGF23(+) cells with osteogenic potential may play a role in systemic fibrosis and ectopic ossification in nephrogenic systemic fibrosis.

  9. Gallium plasmonics: deep subwavelength spectroscopic imaging of single and interacting gallium nanoparticles.

    PubMed

    Knight, Mark W; Coenen, Toon; Yang, Yang; Brenny, Benjamin J M; Losurdo, Maria; Brown, April S; Everitt, Henry O; Polman, Albert

    2015-02-24

    Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tunability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tunability in single Ga NPs and demonstrates that the plasmonic modes of interacting Ga nanoparticles can hybridize to produce strong hot spots in the ultraviolet. The controlled, robust UV plasmonic resonances of gallium nanoparticles are applicable to energy- and phase-specific applications such as optical memory, environmental remediation, and simultaneous fluorescence and surface-enhanced Raman spectroscopies.

  10. Native gallium adatoms discovered on atomically-smooth gallium nitride surfaces at low temperature.

    PubMed

    Alam, Khan; Foley, Andrew; Smith, Arthur R

    2015-03-11

    In advanced compound semiconductor devices, such as in quantum dot and quantum well systems, detailed atomic configurations at the growth surfaces are vital in determining the structural and electronic properties. Therefore, it is important to investigate the surface reconstructions in order to make further technological advancements. Usually, conventional semiconductor surfaces (e.g., arsenides, phosphides, and antimonides) are highly reactive due to the existence of a high density of group V (anion) surface dangling bonds. However, in the case of nitrides, group III rich growth conditions in molecular beam epitaxy are usually preferred leading to group III (Ga)-rich surfaces. Here, we use low-temperature scanning tunneling microscopy to reveal a uniform distribution of native gallium adatoms with a density of 0.3%-0.5% of a monolayer on the clean, as-grown surface of nitrogen polar GaN(0001̅) having the centered 6 × 12 reconstruction. Unseen at room temperature, these Ga adatoms are strongly bound to the surface but move with an extremely low surface diffusion barrier and a high density saturation coverage in thermodynamic equilibrium with Ga droplets. Furthermore, the Ga adatoms reveal an intrinsic surface chirality and an asymmetric site occupation. These observations can have important impacts in the understanding of gallium nitride surfaces.

  11. Simulation studies on the evolution of gallium nitride on a liquid gallium surface under plasma bombardment.

    PubMed

    Vasquez, M R; Flauta, R E; Wada, M

    2008-02-01

    Monte Carlo simulations were conducted to study the formation of gallium-nitride (GaN) layer on liquid gallium (Ga) sputtering target immersed in nitrogen (N(2)) plasma. In the simulation model, N ions were assumed to possess energy equal to the bias voltage applied to the sputtering target with respect to the plasma. The results showed the surface morphology of GaN changed from a relatively smooth GaN on Ga surface at 50 eV N ion energy to a rough surface with GaN dendrites on liquid Ga at 500 eV ion energy. Further increase in N ion energy up to 1 keV resulted in smaller density of GaN dendrites on surface. Increasing surface coverage of Ga by GaN substantially reduced the sputtering yield of Ga from the target. These simulation results were correlated with previously reported experimental observations on liquid Ga surface immersed in the nitrogen plasma of a plasma-sputter-type ion source.

  12. Gallium nitride photocathodes for imaging photon counters

    NASA Astrophysics Data System (ADS)

    Siegmund, Oswald H. W.; Hull, Jeffrey S.; Tremsin, Anton S.; McPhate, Jason B.; Dabiran, Amir M.

    2010-07-01

    Gallium nitride opaque and semitransparent photocathodes provide high ultraviolet quantum efficiencies from 100 nm to a long wavelength cutoff at ~380 nm. P (Mg) doped GaN photocathode layers ~100 nm thick with a barrier layer of AlN (22 nm) on sapphire substrates also have low out of band response, and are highly robust. Opaque GaN photocathodes are relatively easy to optimize, and consistently provide high quantum efficiency (70% at 120 nm) provided the surface cleaning and activation (Cs) processes are well established. We have used two dimensional photon counting imaging microchannel plate detectors, with an active area of 25 mm diameter, to investigate the imaging characteristics of semitransparent GaN photocathodes. These can be produced with high (20%) efficiency, but the thickness and conductivity of the GaN must be carefully optimized. High spatial resolution of ~50 μm with low intrinsic background (~7 events sec-1 cm-2) and good image uniformity have been achieved. Selectively patterned deposited GaN photocathodes have also been used to allow quick diagnostics of optimization parameters. GaN photocathodes of both types show great promise for future detector applications in ultraviolet Astrophysical instruments.

  13. Gallium nitride photocathode development for imaging detectors

    NASA Astrophysics Data System (ADS)

    Siegmund, Oswald H. W.; Tremsin, Anton S.; Vallerga, John V.; McPhate, Jason B.; Hull, Jeffrey S.; Malloy, James; Dabiran, Amir M.

    2008-07-01

    Recent progress in Gallium Nitride (GaN, AlGaN, InGaN) photocathodes show great promise for future detector applications in Astrophysical instruments. Efforts with opaque GaN photocathodes have yielded quantum efficiencies up to 70% at 120 nm and cutoffs at ~380 nm, with low out of band response, and high stability. Previous work with semitransparent GaN photocathodes produced relatively low quantum efficiencies in transmission mode (4%). We now have preliminary data showing that quantum efficiency improvements of a factor of 5 can be achieved. We have also performed two dimensional photon counting imaging with 25mm diameter semitransparent GaN photocathodes in close proximity to a microchannel plate stack and a cross delay line readout. The imaging performance achieves spatial resolution of ~50μm with low intrinsic background (below 1 event sec-1 cm-2) and reasonable image uniformity. GaN photocathodes with significant quantum efficiency have been fabricated on ceramic MCP substrates. In addition GaN has been deposited at low temperature onto quartz substrates, also achieving substantial quantum efficiency.

  14. Evaluation of the carcinogenicity of gallium arsenide.

    PubMed

    Bomhard, Ernst M; Gelbke, Heinz-Peter; Schenk, Hermann; Williams, Gary M; Cohen, Samuel M

    2013-05-01

    Gallium arsenide (GaAs) is an important semiconductor material. In 2-year inhalation studies, GaAs increased the incidence of lung tumors in female rats, but not in male rats or male and female mice. Alveolar proteinosis followed by chronic active inflammation was the predominant non-neoplastic pulmonary findings. IARC classified GaAs as carcinogenic to humans (group 1) based on the assumption that As and Ga ions are bioavailable. The European Chemical Agency Risk Assessment Committee concluded that GaAs should be classified into Carcinogenicity Category 1B (presumed to have carcinogenic potential for humans; ECHA). We evaluate whether these classifications are justified. Physico-chemical properties of GaAs particles and the degree of mechanical treatment are critical in this evaluation. The available data on mode of action (MOA), genotoxicity and bioavailability do not support the contribution of As or Ga ions to the lung tumors in female rats. Most toxicological studies utilized small particles produced by strong mechanical treatment, destroying the crystalline structure. The resulting amorphous GaAs is not relevant to crystalline GaAs at production and processing sites. The likely tumorigenic MOA is lung toxicity related to particulate-induced inflammation and increased proliferation. It is concluded that there is no evidence for a primary carcinogenic effect of GaAs.

  15. Gallium-based avalanche photodiode optical crosstalk

    NASA Astrophysics Data System (ADS)

    Blazej, Josef; Prochazka, Ivan; Hamal, Karel; Sopko, Bruno; Chren, Dominik

    2006-11-01

    Solid-state single photon detectors based on avalanche photodiode are getting more attention in various areas of applied physics: optical sensors, quantum key distribution, optical ranging and Lidar, time-resolved spectroscopy, X-ray laser diagnostics, and turbid media imaging. Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAsP, and InGaP/InGaAs at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Trends in demand are focused on detection array construction recently. Even extremely small arrays containing a few cells are of great importance for users. Electrical crosstalk between individual gating and quenching circuits and optical crosstalk between individual detecting cells are serious limitation for array design and performance. Optical crosstalk is caused by the parasitic light emission of the avalanche which accompanies the photon detection process. We have studied in detail the optical emission of the avalanche photon counting structure in the silicon- and gallium-based photodiodes. The timing properties and spectral distribution of the emitted light have been measured for different operating conditions to quantify optical crosstalk. We conclude that optical crosstalk is an inherent property of avalanche photodiode operated in Geiger mode. The only way to minimize optical crosstalk in avalanche photodiode array is to build active quenching circuit with minimum response time.

  16. Investigation on gallium ions impacting monolayer graphene

    SciTech Connect

    Wu, Xin; Zhao, Haiyan Yan, Dong; Pei, Jiayun

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  17. Gallium nitride T-ray transmission characteristics

    NASA Astrophysics Data System (ADS)

    Ferguson, Bradley; Mickan, Samuel P.; Hubbard, Seth; Pavlidis, Dimitris; Abbott, Derek

    2001-11-01

    T-ray imaging and spectroscopy both exploit the terahertz (THz) region of the spectrum. This gives rise to very promising industrial and biomedical applications, where non-invasive and sensitive identification of a substance is achievable, through a material's distinct absorption features in the THz band. Present T-ray systems are limited by low output power, and the race is now on to find more efficient THz emitters. We discuss the feasibility of a novel high-power gallium nitride emitter for terahertz generation. This paper details the advantages of such an emitter, primarily by virtue of its high-voltage capability, and evaluates the benefits of sapphire and silicon carbide substrates. The far-infrared transmission spectra for thin samples of GaN, sapphire and SiC are reported. A high-power THz emitter, that operates at room temperature and is potentially low-cost will open up a host of new possibilities and applications. The central result in this paper demonstrates that sapphire is the better choice over SiC, for the GaN supporting substrate, as we show that it has superior THz transmission characteristics.

  18. IBIC analysis of gallium arsenide Schottky diodes

    NASA Astrophysics Data System (ADS)

    Vittone, E.; Fizzotti, F.; Mirri, K.; Gargioni, E.; Polesello, P.; LoGiudice, A.; Manfredotti, C.; Galassini, S.; Rossi, P.; Vanni, P.; Nava, F.

    1999-10-01

    Semi-insulating (SI) gallium arsenide (GaAs) devices operating as a reverse biased Schottky diode offer an attractive choice as radiation detector at room temperature both in high energy physics experiments and as X-ray image sensors. However, SI GaAs devices contain a high concentration of traps, which decreases the charge collection efficiency (cce), and affects the energy resolution of such detectors working as nuclear spectrometers. In this paper we present a detailed investigation of the spatial uniformity of the cce carried out by analysing ion beam induced charge (IBIC) space maps obtained by scanning a focused 2 MeV proton microbeam on a SI n-GaAs Schottky diode. The microbeam irradiated both the front (Schottky) and back (ohmic) contacts in order to evaluate the transport properties of both electrons and holes generated by ionisation. The IBIC space maps show a clear non-uniformity of the cce. The poor energy resolution previously observed in such detectors working as alpha particle spectrometers is ascribed to the presence of two different "phases" in the material, which produce two distinct collection efficiency spectra. Such "phases" show different behaviour as a function of the applied bias voltage which is most likely due to the different electric field dependence of the relevant capture cross sections of the trapping centres for both charge carriers.

  19. Electrical characterization of magnesium implanted gallium nitride

    NASA Astrophysics Data System (ADS)

    Krtschil, A.; Kielburg, A.; Witte, H.; Christen, J.; Krost, A.; Wenzel, A.; Rauschenbach, B.

    2002-01-01

    Gallium nitride layers grown by molecular beam epitaxy on c axis oriented sapphire substrates were implanted with 180 keV magnesium ions with ion doses between 1×1014 and 1×1016cm-2. The implantation induced defect states were investigated by temperature dependent conductivity (TDC) as well as by thermal and optical admittance spectroscopy (TAS, OAS) measurements. Dominant carrier emissions having thermal activation energies between 360 and 800 meV were found in TAS and TDC. These states are assigned to implantation induced electron traps since they do not appear in the nonimplanted reference sample. Defect states with similar transition energies were also observed in OAS resulting in an enhancement of defect-to-band transitions in the near band-gap region around 3.45 eV, in the blue band around 3.0 eV, as well as in the midgap range for photon energies between 2.5 and 1.80 eV, respectively. In addition, new transitions were found at 2.1 and 1.95 eV. Furthermore, transitions from implantation induced shallow states were observed, i.e., the magnesium acceptor as well as a new donor level at about 70 meV, tentatively discussed as nitrogen vacancy. The critical ion dose for amorphization was determined to be between 5×1015 and 1×1016Mg+ cm-2 using x-ray diffraction.

  20. Funneling electron beams from gallium arsenide photocathodes

    NASA Astrophysics Data System (ADS)

    Rahman, Omer Habib

    Gallium Arsenide (GaAs) is the most widely used source of polarized electrons around the world. Electrons are extracted from a GaAs surface, terminated by a cesium-oxygen layer. The electrons are accelerated to form a beam by a DC electric field. This beam can ionize residual gas in the chamber, and the DC field accelerates the resulting ions into the cathode surface, damaging the Cesium- Oxygen layer. This process, called Ion Back Bombardment, is the dominant mechanism for limiting photocathode lifetime. As a result, high average current operation yields charge lifetimes too low to be used in a collider design. One idea to extend the charge lifetime is to funnel the beams from multiple cathodes using a rotating magnetic field-if operation of one cathode does not affect the operation of another cathode in the same chamber, then the source's lifetime can be extended by simply adding more cathodes. This dissertation presents the design, construction and commissioning of a unique electron gun capable of operating twenty cathodes. Results of funneling two electron beams with a rotating magnetic field are also presented. For average currents at 175 nA and 350 nA, the charge lifetimes for individual cathodes and two-cathode operation were measured, showing that the charge lifetime for two beam funneling is the sum of the individual ion back bombardment charge lifetimes. The addition of charge lifetime implies that beam funneling can be used to increase charge lifetime by an order of magnitude.

  1. Gallium Nitride Based Logpile Photonic Crystal

    SciTech Connect

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J.; Wang, George T.; Fischer, Arthur J.

    2011-11-09

    A nine-layer logpile three-dimensional photonic crystal (3DPC) is demonstrated composed of single crystalline gallium nitride (GaN) nanorods, ~ 100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a ''line-defect'' cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25–30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride-based optoelectronic devices.

  2. Gallium nitride based logpile photonic crystals.

    PubMed

    Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

    2011-11-09

    We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.

  3. Determination of gallium originated from a gallium-based anticancer drug in human urine using ICP-MS.

    PubMed

    Filatova, Darya G; Seregina, Irina F; Foteeva, Lidia S; Pukhov, Vladimir V; Timerbaev, Andrei R; Bolshov, Mikhail A

    2011-05-01

    Urine analysis gives an insight into the excretion of the administered drug which is related to its reactivity and toxicity. In this work, the capability of inductively coupled plasma mass spectrometry (ICP-MS) to measure ultratrace metal levels was utilized for rapid assaying of gallium originating from the novel gallium anticancer drug, tris(8-quinolinolato)gallium(III) (GaQ(3)), in human urine. Sample dilution with 1% (v/v) HNO(3) as the only required pre-treatment was shown to prevent contamination of the sample introduction system and to reduce polyatomic interferences from sample components. The origin of the blank signal at masses of gallium isotopes, 71 and 69, was investigated using high-resolution ICP-MS and attributed, respectively, to the formation of (36)Ar(35)Cl(+) and (40)Ar(31)P(+) ions and, tentatively, to a triplet of doubly charged ions of Ba, La, and Ce. The accuracy and precision performance was tested by evaluating a set of parameters for analytical method validation. The developed assay has been applied for the determination of gallium in urine samples spiked with GaQ(3). The achieved recoveries (95-102%) and quantification limit of 0.2 μg L(-1) emphasize the practical applicability of the presented analytical approach to monitor renal elimination of GaQ(3) at all dose levels in clinical trials that are currently in progress.

  4. Antibacterial effect of gallium and silver on Pseudomonas aeruginosa treated with gallium-silver-phosphate-based glasses.

    PubMed

    Valappil, Sabeel P; Higham, Susan M

    2014-01-01

    Gallium and silver incorporated phosphate-based glasses were evaluated for antibacterial effect on the growth of Pseudomonas aeruginosa, which is a leading cause of opportunistic infections. The glasses were produced by conventional melt quenching methods at 1100°C for 1 h. Glass degradation studies were conducted by weight loss method. Disc diffusion assay and cell viability assay displayed statistically significant (p ≤ 0.0005) effect on P. aeruginosa growth which increased with decreasing calcium content in the glasses. The gallium ion release rates (1.83, 0.69 and 0.48 ppm·h(-1)) and silver ion release rates (2.97, 2.84 and 2.47 ppm·h(-1)) were found to account for this variation. Constant depth film fermentor was used to evaluate the anti-biofilm properties of the glasses. Both gallium and silver in the glass contributed to biofilm growth inhibitory effect on P. aeruginosa (up to 2.68 reduction in log 10 values of the viable counts compared with controls). The glasses were found to deliver gallium and silver in a controlled way and exerted cumulative antibacterial action on planktonic and biofilm growth of P. aeruginosa. The antibacterial, especially anti-biofilm, properties of the gallium and silver incorporated phosphate-based glasses make them a potential candidate to combat infections caused by P. aeruginosa.

  5. The Soviet-American gallium experiment at Baksan

    SciTech Connect

    Abazov, A. I.; Abdurashitov, D. N.; Anosov, O. L.; Danshin, S. N.; Eroshkina, L. A.; Faizov, E. L.; Gavrin, V. N.; Kalikhov, A. V.; Knodel, T. V.; Knyshenko, I. I.; Kornoukhov, V. N.; Mezentseva, S. A.; Mirmov, I. N.; Ostrinsky, A. I.; Petukhov, V. V; Pshukov, A. M.; Revzin, N. Ye; Shikhin, A. A.; Slyusareva, Ye. D.; Timofeyev, P. V.; Veretenkin, E. P.; Vermul, V. M.; Yantz, V. E.; Zakharov, Yu.; Zatsepin, G. T.; Zhandarov, V. I.

    1990-01-01

    A gallium solar neutrino detector is sensitive to the full range of the solar neutrino spectrum, including the low-energy neutrinos from the fundamental proton-proton fusion reaction. If neutrino oscillations in the solar interior are responsible for the suppressed {sup 8}B flux measured by the Homestake {sup 37}Cl experiment and the Kamiokande water Cherenkov detector, then a comparison of the gallium, chlorine, and water results may make possible a determination of the neutrino mass difference and mixing angle. A 30-ton gallium detector is currently operating in the Baksan laboratory in the Soviet Union, with a ratio of expected solar signal to measured background (during the first one to two {sup 71}Ge half lives) of approximately one. 28 refs.

  6. Interaction of sodium with tellurium in gallium melts

    SciTech Connect

    Dergacheva, M.B.; Sarsekeeva, R.Zh.; Kozin, L.F.

    1988-09-20

    The purpose of this work was to study interaction of sodium with admixtures of tellurium and to determine the composition and phase state of the intermetallic compounds formed. The investigations were carried out by a potentiometric method with measurement of emf of the concentration cells. Sodium was introduced into the original gallium-tellurium binary alloy by electrolysis. The results of measurements of the emf of the cell were used for plotting potentiometric curves. The emf values found on the horizontal region of the potentiometric were subjected to mathematical analysis for determination of deviations from the regression line of the results of three parallel series of measurement. The emf of concentration cells with a solid electrolyte, based on melts of the gallium-sodium-tellurium ternary system, deviate from the theoretical values at 855 K; this is attributed to formation of the intermetallic compound, sparingly soluble in gallium, the free energy of formation of which is -266 +/- 15 kJ/mole.

  7. Fluorian garnets from the host rocks of the Skaergaard intrusion: implications for metamorphic fluid composition

    USGS Publications Warehouse

    Manning, C.E.; Bird, D.K.

    1990-01-01

    Zoned, silica-deficient, calcic garnets containing up to 5 mol% F substitution for O formed during contact metamorphism of basalts by the Skaergaard intrusion in East Greenland. Fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30-70 m from the intrusion. The F content of garnet is extremely sensitive to minor changes in fluid composition. The calculations show that a decrease in pH or an increase in log aF- of 0.3 at constant pressure and temperature will decrease the F concentration in garnet from 5 to 0 mol%. The results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities of F species in coexisting metamorphic and hydrothermal fluids. -from Authors

  8. Using garnet peridotites as tools to reconstruct paleo-geodynamic settings of fossil continental collision zones

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; van Roermund, Herman; Zhang, Lifei

    2010-05-01

    Orogenic garnet peridotites (metamorphic rocks containing the characteristic HP garnet-olivine mineral assemblage) form volumetrically minor, but important components of (ultra)high pressure (UHP) metamorphic terranes. Such terranes form along convergent plate margins where two adjacent plates collide and one of the plates is subducted below the other. After eduction back to the surface such fossil continental subduction/collision zones form the basic components of exposed (U)HP metamorphic terranes. In the absence of significant amounts of tectonic overpressure (Vrijmoed et al., 2010), the discovery of diamond and majoritic garnet in (U)HP metamorphic terranes provide evidence that subduction of continental crust into the mantle was deep enough to reach the garnet stability field in the overlying mantle wedge above the subduction zone. Brueckner (1998) was the first author who noticed that garnet peridotite bodies, present in such mantle wedges, could be transferred during collision from the mantle wedge into the subducted continental crust. Subsequent buoyancy, most likely generated by slab break off of previously subducted oceanic crust, is the most likely candidate to enable the subducted continental crust and its garnet peridotite "cargo" to return back to (sub)crustal levels. During the latter process mantle wedge garnet peridotite may recrystallize (partly or completely) into what will be called here subduction zone garnet peridotite. Alternatively subduction zone garnet peridotite may be formed by prograde subduction of ultramafic protoliths (serpentinites, Fe-Ti peridotite) that may be present in subducting continental crust prior to subduction. Subdivision between these two basic types of orogenic garnet peridotites (mantle wedge - versus subduction zone peridotite) allows however that in mantle wedge garnet peridotite the subcontinental lithospheric mantle (SCLM) - versus crustal-incorporation processes can be identified which a.o. has lead to the recent

  9. Luminescence properties of Lu3Al5O12:Tb3+ nano-garnet

    NASA Astrophysics Data System (ADS)

    Praveena, R.; Shim, Jae Jeong; Cai, Peiqing; Seo, Hyo Jin; Chung, Wan-Young; Kwon, Tae Ha; Jayasankar, C. K.; Haritha, P.; Venkatramu, V.

    2014-06-01

    Trivalent terbium-doped lutetium-aluminate nano-garnet (Lu3Al5O12:Tb3+) powder was prepared by using the Pechini sol-gel process. The structure and crystallinity of the Lu3Al5O12:Tb3+ nano-garnet were characterized by using X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. The green emission of Tb3+ ions is observed at 545 nm corresponding to the 5D4 → 7F5 transition under the 271-nm excitation. The temperature dependent luminescence properties of the Lu3Al5O12:Tb3+ nano-garnet are investigated. The results show that the present garnet exhibits better thermal stability than the other green emitting phosphors, hence, the Lu3Al5O12:Tb3+ phosphor is a promising candidate for light-emitting devices.

  10. Promise and Pitfalls of Lu/Hf-Sm/Nd Garnet Geochronology

    NASA Astrophysics Data System (ADS)

    King, R. L.; Vervoort, J. D.; Kohn, M. J.; Zirakparvar, N. A.; Hart, G. L.; Corrie, S. L.; Cheng, H.

    2007-12-01

    Our ability to routinely measure Lu-Hf and Sm-Nd isotopes in garnet allows broad new applications in geochronology, petrology, and tectonics. However, applications of these data can be limited by challenges in interpreting the petrologic record and preparing garnets for analysis. Here, we examine petrologic and chemical pitfalls encountered in garnet geochronology. Petrologic factors influencing trace element compositions in garnet include reactions that modify REE availability and partitioning (1,2), kinetically limited transfer of REEs to garnet (3), and bulk compositional heterogeneities (4). Interpreting the effects of these processes on Sm/Nd and Lu/Hf ages requires characterizing REE zonation prior to isotope analysis and age interpretation. Because garnet fractions are traditionally picked from crushed samples without regard to intracrystalline origins or chemistries, isochrons will represent mixtures derived to varying degrees from all periods of garnet growth. While measured zoning might generally indicate what garnet portion dominates the Lu/Hf or Sm/Nd budget, traditional mineral separation will rarely realize the chronologic potential afforded by high precision Hf and Nd isotope measurements. The potential use of alternative techniques, such as microsampling, necessitates selective digestion and/or leaching to eliminate inclusions within garnet. For Sm/Nd geochronology, H2SO4 leaching removes LREE-rich phosphates (e.g. apatite), but not silicates (e.g. epidote), precluding Sm-Nd dating of some rocks. For Lu/Hf geochronology, ubiquitous zircon microinclusions (c. 1 μm) can significantly disrupt age determinations. Microinclusions cannot be detected optically or separated physically, requiring selective chemical digestion. If complete digestion methods, such as bomb digestion, are used for garnet fractions, then "common Hf" from zircon will be contained in final solutions. These mixed analyses are of dubious utility and will fall into one of two

  11. Extremely-efficient, miniaturized, long-lived alpha-voltaic power source using liquid gallium

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Patel, Jagdishbhai (Inventor); Fleurial, Jean-Pierre (Inventor)

    2004-01-01

    A power source converts .alpha.-particle energy to electricity for use in electrical systems. Liquid gallium or other liquid medium is subjected to .alpha.-particle emissions. Electrons are freed by collision from neutral gallium atoms to provide gallium ions. The electrons migrate to a cathode while the gallium ions migrate to an anode. A current and/or voltage difference then arises between the cathode and anode because of the work function difference of the cathode and anode. Gallium atoms are regenerated by the receiving of electrons from the anode enabling the generation of additional electrons from additional .alpha.-particle collisions.

  12. Phase separation in garnet solid solutions and its effect on optical properties.

    PubMed

    Kaveh, Shakiba; Tremblay, Clément P; Norhashim, Nurhakimah; Curry, Richard J; Cheetham, Anthony K

    2013-11-26

    Phase behavior is studied in erbium-doped Y3 Al5 O12 (YAG) garnets synthesized by solid-state reactions. High resolution synchrotron XRD and SEM-EDX studies reveal phase separation at an erbium content between 8 and 50 at%, depending upon the processing conditions. Similar results are found in closely-related garnet systems. The phase separation has a striking effect on the optical properties of YAG:Er(3+) .

  13. Calcium diffusivity in alumino-silicate garnets: an experimental and ATEM study

    NASA Astrophysics Data System (ADS)

    Vielzeuf, D.; Baronnet, A.; Perchuk, A. L.; Laporte, D.; Baker, M. B.

    2007-08-01

    Concentration gradients in calcium are common in metamorphic or magmatic garnets and can be used to determine the timescales of geological processes. However, the kinetics of Ca diffusion in garnet is poorly constrained and experimental studies have to date yielded widely varying diffusion coefficients. In this paper, we describe a new method for generating diffusion profiles in garnet. We incorporated polished and compositionally homogeneous garnet seeds in a finely ground powder of clinopyroxene and garnet. During the experiments (1.3 GPa, 1,050-1,250°C, and ƒO2 ≤ the graphite-O2 buffer), the mineral powder partially melted, recrystallized, and formed a 10-50 μm wide overgrowth zone of compositionally distinct garnet around the seeds. Long duration experiments generated measurable relaxation profiles at these seed/overgrowth interfaces. We performed analytical transmission electron microscope traverses across the interfaces in each experiment. Thirteen usable compositional profiles were obtained with characteristic distances of diffusion ranging from 300 to 1,000 nm. From these profiles, Ca-(Fe, Mg) interdiffusion coefficients were retrieved using an analytical solution for the diffusion equation and the data were cast in an Arrhenius relation. Linear regression of the data yields an activation energy Q Ca-(Fe, Mg) equal to 188 ± 48 kJ mol-1 and a frequency factor D 0 equal to 6.6 × 10-14 m2 s-1. Within the compositional range studied, the composition of garnet has no major effect on the Ca-(Fe, Mg) interdiffusion coefficient. The very slow diffusion rate of Ca is in agreement with natural observations indicating that Ca diffuses more slowly than Fe and Mg. The Ca diffusion coefficients derived from this study are not model-dependent and can be used to determine the durations of geological events from Ca relaxation profiles in natural garnets.

  14. Growth of metamorphic and peritectic garnets in ultrahigh-pressure metagranite during continental subduction and exhumation in the Dabie orogen

    NASA Astrophysics Data System (ADS)

    Xia, Qiong-Xia; Wang, Hao-Zheng; Zhou, Li-Gang; Gao, Xiao-Ying; Zheng, Yong-Fei; Van Orman, James Ashton; Xu, Haijun; Hu, Zhaochu

    2016-12-01

    Two generations of garnet are recognized in ultrahigh-pressure (UHP) metagranite from the Dabie orogen by a combined study of petrography, major and trace element profiles in garnet, and phase equilibrium modeling for metagranite. The results enable distinction between metamorphic and peritectic garnet on the basis of BSE images, and major and trace element compositions. Our research provides new insights into the growth of anatectic garnet due to dehydration melting of UHP metamorphic rocks during exhumation from mantle depths. The first generation of garnet (Grt-I) occurs as a broad domain in the center, which is related to metamorphic growth during prograde subduction. This garnet is dark in BSE images, rich in grossular and poor in almandine and pyrope. The chondrite-normalized rare earth element (REE) patterns show LREE depletion and flat MREE-HREE patterns. The second generation of garnet (Grt-II) occurs as a rim of euhedral garnet, or as patches in Grt-I domains, recrystallized after dissolution of preexisting metamorphic garnet in the presence of anatectic melts during exhumation. It is bright in BSE images, poor in grossular, and rich in almandine and pyrope contents. Trace element analyses on Grt-II domains yield high contents of Sc, Cr, Y and HREE and low contents of Ti and MREE. The chondrite-normalized REE patterns exhibit LREE depletion, and steep MREE-HREE patterns. Based on REE partitioning between garnet and zircon/titanite, the last growth times for metamorphic and anatectic garnets are constrained by zircon and titanite U-Pb ages to be 240 Ma and 220 Ma, respectively. Based on anatectic microstructures and a modeled P-T pseudosection, it is suggested that dehydration melting occurred at 2.0-2.5 GPa during exhumation. Melting occurred through the breakdown of phengite via the peritectic reaction: garnet (I) + phengite + plagioclase + quartz → garnet (II) + biotite + K-feldspar + melt.

  15. Chemical and mass spectrographic analysis of nuclear-grade gadolinium oxide (Gd/sub 2/O/sub 3/) powder

    SciTech Connect

    Not Available

    1981-01-01

    Analytical procedures to determine compliance of gadolinium oxide powders with specifications are presented. The following methods are described in detail: carbon by direct combustion - thermal conductivity method; total chlorine and fluorine by pyrohydrolysis ion-selective electrode method; loss of weight on ignition; sulfur by combustion - iodometric titration method; impurity elements by a spark-source mass spectrographic method; and gadolinium content in gadolinium oxide by impurity correction method. (JMT)

  16. MSW (Magnetostatic Wave) Variable Time-Delay Techniques.

    DTIC Science & Technology

    1983-09-01

    Epitaxial Transducers Arrays Microwaves Films GGG Antenna s0. ABSTRACT (Continue on reverse side If necessn and Identify by block number) >Studies of...describes work performed in the course of a program to investigate magnetostatic wave (FSW) device techniques for phased array antennas and microwave ...plane component in epitaxial YIG films grown on >-oriented gadolinium gallium garnet (GGG) substrates. Several other explanations were considered and

  17. Design and Fabrication of Submicron Magnetic Bubble Device Technology.

    DTIC Science & Technology

    1986-10-31

    each K.. -rare-earth product. (i.e, KG = ij X XLu for Y-Lu pair). Anisotropy results from the pair ordering of Samarium and Europium with other rare...in the rate of decrease in the field values of most commercially available Barium ferrite permanent magnets, which is the source of the bias field...on (111) substrates of gadolinium -gallium garnet and subsequently exposed to various doses of oxygen and/or deutenum ions. At moderate implantation

  18. Reciprocating Magnetic Refrigerator

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.

    1985-01-01

    Unit cools to 4 K by adiabatic demagnetization. Two porous matrices of paramagnetic material gadolinium/gallium/garnet held in long piston called displacer, machined out of Micarta (phenol formaldehyde polymer). Holes in side of displacer allow heat-exchange fluid to flow to and through matrices within. Piston seals on displacer prevent substantial mixing of fluid in two loops. Magnetic refrigerator provides continuous rather than "one-shot" cooling.

  19. Magnetostriction and magnetic heterogeneities in iron-gallium.

    PubMed

    Laver, M; Mudivarthi, C; Cullen, J R; Flatau, A B; Chen, W-C; Watson, S M; Wuttig, M

    2010-07-09

    Iron-gallium alloys Fe(1-x)Ga(x) exhibit an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe(0.81)Ga(0.19) single crystal. We uncover heterogeneities with an average spacing of 15 nm and with magnetizations distinct from the matrix. The moments in and around the heterogeneities are observed to reorient with an applied magnetic field or mechanical strain. We discuss the possible roles played by nanoscale magnetic heterogeneities in the mechanism for magnetostriction in this material.

  20. Magnetostriction and Magnetic Heterogeneities in Iron-Gallium

    SciTech Connect

    Laver, M.; Mudivarthi, C.; Cullen, J. R.; Wuttig, M.; Flatau, A. B.; Chen, W.-C.; Watson, S. M.

    2010-07-09

    Iron-gallium alloys Fe{sub 1-x}Ga{sub x} exhibit an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe{sub 0.81}Ga{sub 0.19} single crystal. We uncover heterogeneities with an average spacing of 15 nm and with magnetizations distinct from the matrix. The moments in and around the heterogeneities are observed to reorient with an applied magnetic field or mechanical strain. We discuss the possible roles played by nanoscale magnetic heterogeneities in the mechanism for magnetostriction in this material.

  1. Absence of gallium-67 avidity in diffuse pulmonary calcification

    SciTech Connect

    Lecklitner, M.L.; Foster, R.W.

    1985-09-01

    Diffuse pulmonary uptake by bone-seeking radiopharmaceuticals has been reported previously but, in the same patient, would pulmonary uptake of Ga-67 citrate yield clinically meaningful results. A patient with hypercalcemia and renal failure in whom bone scintigraphy demonstrated striking diffuse bilateral pulmonary uptake, but subsequent gallium imaging demonstrated no evidence of pulmonary uptake greater than body background, is discussed. We conclude that pulmonary uptake of gallium cannot be attributed to calcium deposition and should carry the same clinical significance in regard to inflammatory and malignant lesions as would be assigned to patients without pulmonary calcific deposits.

  2. Renal lymphoma imaged by ultrasound and Gallium-67

    SciTech Connect

    Shirkhoda, A.; Staab, E.V.; Mittelstaedt, C.A.

    1980-10-01

    Lymphomatous involvement of the kidneys, usually a secondary process, may be seen as single or multiple sonolucent or weakly echogenic masses on ultrasound. The majority of these patients have a known diagnosis of lymphoma and are being evaluated for change in nodal mass size, flank pain, and/or deteriorating renal function. Occasionally, these masses are discovered on an excretory urogram and are further investigated with ultrasound. The ultrasound findings may be confirmed with gallium scanning. Five such cases are presented along with the ultrasonic and gallium scan findings.

  3. Gallium-based anti-infectives: targeting microbial iron-uptake mechanisms.

    PubMed

    Kelson, Andrew B; Carnevali, Maia; Truong-Le, Vu

    2013-10-01

    Microbes have evolved elaborate iron-acquisition systems to sequester iron from the host environment using siderophores and heme uptake systems. Gallium(III) is structurally similar to iron(III), except that it cannot be reduced under physiological conditions, therefore gallium has the potential to serve as an iron analog, and thus an anti-microbial. Because Ga(III) can bind to virtually any complex that binds Fe(III), simple gallium salts as well as more complex siderophores and hemes are potential carriers to deliver Ga(III) to the microbes. These gallium complexes represent a new class of anti-infectives that is different in mechanism of action from conventional antibiotics. Simple gallium salts such as gallium nitrate, maltolate, and simple gallium siderophore complexes such as gallium citrate have shown good antibacterial activities. The most studied complex has been gallium citrate, which exhibits broad activity against many Gram negative bacteria at ∼1-5μg/ml MICs, strong biofilm activity, low drug resistance, and efficacy in vivo. Using the structural features of specific siderophore and heme made by pathogenic bacteria and fungi, researchers have begun to evaluate new gallium complexes to target key pathogens. This review will summarize potential iron-acquisition system targets and recent research on gallium-based anti-infectives.

  4. Construction of an electrode modified with gallium(III) for voltammetric detection of ovalbumin.

    PubMed

    Sugawara, Kazuharu; Okusawa, Makoto; Takano, Yusaku; Kadoya, Toshihiko

    2014-01-01

    Electrodes modified with gallium(III) complexes were constructed to detect ovalbumin (OVA). For immobilization of a gallium(III)-nitrilotriacetate (NTA) complex, the electrode was first covered with collagen film. After the amino groups of the film had reacted with isothiocyanobenzyl-NTA, the gallium(III) was then able to combine with the NTA moieties. Another design featured an electrode cast with a gallium(III)-acetylacetonate (AA) complex. The amount of gallium(III) in the NTA complex was equivalent to one-quarter of the gallium(III) that could be utilized from an AA complex. However, the calibration curves of OVA using gallium(III)-NTA and gallium(III)-AA complexes were linear in the ranges of 7.0 × 10(-11) - 3.0 × 10(-9) M and 5.0 × 10(-10) - 8.0 × 10(-9) M, respectively. The gallium(III) on the electrode with NTA complex had high flexibility due to the existence of a spacer between the NTA and the collagen film, and, therefore, the reactivity of the gallium(III) to OVA was superior to that of the gallium(III)-AA complex with no spacer.

  5. The origin of garnet in the anorthosite-charnockite suite of the Adirondacks

    USGS Publications Warehouse

    McLelland, J.M.; Whitney, P.R.

    1977-01-01

    Detailed analysis of textural and chemical criteria in rocks of the anorthosite-charnockite suite of the Adirondack Highlands suggests that development of garnet in silica-saturated rocks of the suite occurs according to the reaction: {Mathematical expression}, where ?? is a function of the distribution of Fe and Mg between the several coexisting ferromagnesian phases. Depending upon the relative amounts of Fe and Mg present, quartz may be either a reactant or a product. Using an aluminum-fixed reference frame, this reaction can be restated in terms of a set of balanced partial reactions describing the processes occurring in spatially separated domains within the rock. The fact that garnet invariably replaces plagioclase as opposed to the other reactant phases indicates that the aluminum-fixed model is valid as a first approximation. This reaction is univariant and produces unzoned garnet. It differs from a similar equation proposed by de Waard (1965) for the origin of garnet in Adirondack metabasic rocks, i.e. 6 Orthopyroxene+2 Anorthite = Clinopyroxene+Garnet+2 Quartz, the principle difference being that iron oxides (ilmenite and/or magnetite) are essential reactant phases in the present reactions. The product assemblage (garnet+clinopyroxene+plagioclase ?? orthopyroxene ?? quartz) is characteristic of the clinopyroxene-almandine subfacies of the granulite facies. ?? 1977 Springer-Verlag.

  6. Raman imaging of fluid inclusions in garnet from UHPM rocks (Kokchetav massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Dieing, Thomas; Golovin, Aleksandr V; Toporski, Jan

    2011-10-01

    Confocal Raman imaging of fluid inclusions in garnet porphyroblasts from diamond-grade metamorphic calc-silicate rocks from the Kumdy-Kol microdiamond deposit (Kokchetav Massif, Northern Kazakhstan) reveals that these fluid inclusions consist of almost pure water with different step-daughter phases (e.g., calcite, mica and rare quartz). These fluid inclusions are characterized by negative crystal shape of the host-garnet and they exclusively occur within the core of garnet porphyroblasts. These observations are consistent with their primary origin, most likely at ultrahigh-pressure (UHP) metamorphic conditions. The euhedral newly formed garnet, different in color and composition, was found to be associated with these fluid inclusions. It is proposed that newly formed garnet and water fluid inclusions appear by reaction between the hydrous fluid and the garnet-host. These fluid inclusions provide an unequivocal record of almost pure H(2)O fluids, indicating water-saturated conditions within subducted continental crust during prograde stage and/or ultrahigh-P metamorphism.

  7. Metastable garnet in oceanic crust at the top of the lower mantle.

    PubMed

    Kubo, Tomoaki; Ohtani, Eiji; Kondo, Tadashi; Kato, Takumi; Toma, Motomasa; Hosoya, Tomofumi; Sano, Asami; Kikegawa, Takumi; Nagase, Toshiro

    As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account.

  8. Unintentional gallium incorporation in InGaN layers during epitaxial growth

    NASA Astrophysics Data System (ADS)

    Zhou, Kun; Ren, Huaijin; Ikeda, Masao; Liu, Jianping; Ma, Yi; Gao, Songxin; Tang, Chun; Li, Deyao; Zhang, Liquan; Yang, Hui

    2017-01-01

    Unintentional gallium incorporation was observed and investigated in the epitaxial growth of InGaN by metalorganic vapor phase epitaxy. InGaN was grown without intentional gallium precursor and the gallium incorporation rate was found not dependent on TEGa source but was significantly influenced by temperature and TMIn source flow. The source of the unintentional gallium incorporation is confirmed to be from the flow distributor of the reactor. The incorporation mechanism was analyzed to be the diffusion of resultant of transmetalation reaction between TMIn or its decomposed products (for example DMIn) and residual gallium. Due to the unintentional gallium incorporation, the growth rate and indium content of InGaN layer are determined by indium source, gallium source and the growth temperature.

  9. Method for improving the growth of cadmium telluride on a gallium arsenide substrate

    SciTech Connect

    Reno, J.L.

    1990-12-31

    A method for preparing a gallium arsenide substrate, prior to growing a layer of cadmium telluride on a support surface thereof. The preparation includes the steps of cleaning the gallium arsenide substrate and thereafter forming prepatterned shapes on the support surface of the gallium arsenide substrate. The layer of cadmium telluride then grown on the prepared substrate results in dislocation densities of approximately 1{times}10{sup 6}/cm{sup 2} or less. The prepatterned shapes on the support surface of the gallium arsenide substrate are formed by reactive ion etching an original outer surface of the gallium arsenide substrate and into the body of the gallium arsenide substrate to a depth of at least two microns. The prepatterned shapes have the appearance of cylindrical mesas each having a diameter of at lease twelve microns. After the mesas are formed on the support surface of the gallium arsenide substrate, the substrate is again cleaned.

  10. Gallium-67 uptake by the thyroid associated with progressive systemic sclerosis

    SciTech Connect

    Sjoberg, R.J.; Blue, P.W.; Kidd, G.S.

    1989-01-01

    Although thyroidal uptake of gallium-67 has been described in several thyroid disorders, gallium-67 scanning is not commonly used in the evaluation of thyroid disease. Thyroidal gallium-67 uptake has been reported to occur frequently with subacute thyroiditis, anaplastic thyroid carcinoma, and thyroid lymphoma, and occasionally with Hashimoto's thyroiditis and follicular thyroid carcinoma. A patient is described with progressive systemic sclerosis who, while being scanned for possible active pulmonary involvement, was found incidentally to have abnormal gallium-67 uptake only in the thyroid gland. Fine needle aspiration cytology of the thyroid revealed Hashimoto's thyroiditis. Although Hashimoto's thyroiditis occurs with increased frequency in patients with progressive systemic sclerosis, thyroidal uptake of gallium-67 associated with progressive systemic sclerosis has not, to our knowledge, been previously described. Since aggressive thyroid malignancies frequently are imaged by gallium-67 scintigraphy, fine needle aspiration cytology of the thyroid often is essential in the evaluation of thyroidal gallium-67 uptake.

  11. Gallium arsenide processing for gate array logic

    NASA Technical Reports Server (NTRS)

    Cole, Eric D.

    1989-01-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  12. Gallium arsenide processing for gate array logic

    NASA Astrophysics Data System (ADS)

    Cole, Eric D.

    1989-09-01

    The development of a reliable and reproducible GaAs process was initiated for applications in gate array logic. Gallium Arsenide is an extremely important material for high speed electronic applications in both digital and analog circuits since its electron mobility is 3 to 5 times that of silicon, this allows for faster switching times for devices fabricated with it. Unfortunately GaAs is an extremely difficult material to process with respect to silicon and since it includes the arsenic component GaAs can be quite dangerous (toxic) especially during some heating steps. The first stage of the research was directed at developing a simple process to produce GaAs MESFETs. The MESFET (MEtal Semiconductor Field Effect Transistor) is the most useful, practical and simple active device which can be fabricated in GaAs. It utilizes an ohmic source and drain contact separated by a Schottky gate. The gate width is typically a few microns. Several process steps were required to produce a good working device including ion implantation, photolithography, thermal annealing, and metal deposition. A process was designed to reduce the total number of steps to a minimum so as to reduce possible errors. The first run produced no good devices. The problem occurred during an aluminum etch step while defining the gate contacts. It was found that the chemical etchant attacked the GaAs causing trenching and subsequent severing of the active gate region from the rest of the device. Thus all devices appeared as open circuits. This problem is being corrected and since it was the last step in the process correction should be successful. The second planned stage involves the circuit assembly of the discrete MESFETs into logic gates for test and analysis. Finally the third stage is to incorporate the designed process with the tested circuit in a layout that would produce the gate array as a GaAs integrated circuit.

  13. Impedance spectroscopic characterization of gadolinium substituted cobalt ferrite ceramics

    SciTech Connect

    Rahman, Md. T. Ramana, C. V.

    2014-10-28

    Gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}, referred to CFGO) with variable Gd content (x = 0.0–0.4) have been synthesized by solid state ceramic method. The crystal structure and impedance properties of CFGO compounds have been evaluated. X-ray diffraction measurements indicate that CFGO crystallize in the inverse spinel phase. The CFGO compounds exhibit lattice expansion due to substitution of larger Gd ions into the crystal lattice. Impedance spectroscopy analysis was performed under a wide range of frequency (f = 20 Hz–1 MHz) and temperature (T = 303–573 K). Electrical properties of Gd incorporated Co ferrite ceramics are enhanced compared to pure CoFe{sub 2}O{sub 4} due to the lattice distortion. Impedance spectroscopic analysis illustrates the variation of bulk grain and grain-boundary contributions towards the electrical resistance and capacitance of CFGO materials with temperature. A two-layer heterogeneous model consisting of moderately conducting grain interior (ferrite-phase) regions separated by insulating grain boundaries (resistive-phase) accurately account for the observed temperature and frequency dependent electrical characteristic of CFGO ceramics.

  14. Late Gadolinium Enhancement in Patients with Nonischemic Dilated Cardiomyopathy.

    PubMed

    Memon, Sarfaraz; Ganga, Harsha V; Kluger, Jeffrey

    2016-07-01

    One-third of all patients with heart failure have nonischemic dilated cardiomyopathy (NIDM). Five-year mortality from NIDM is as high as 20% with sudden cardiac death (SCD) as the cause in 30% of the deaths. Currently, the left ventricular ejection fraction (LVEF) is used as the main criteria to risk stratify patients requiring an implantable cardioverter defibrillator (ICD) to prevent SCD. However, LVEF does not necessarily reflect myocardial propensity for electrical instability leading to ventricular tachycardia (VT) or ventricular fibrillation (VF). Due to the differential risk in various subgroups of patients for arrhythmic death, it is important to identify appropriate patients for ICD implantation so that we can optimize healthcare resources and avoid the complications of ICDs in individuals who are unlikely to benefit. We performed a systematic search and review of clinical trials of NIDM and the use of ICDs and cardiac magnetic resonance imaging with late gadolinium enhancement (LGE) for risk stratification. LGE identifies patients with NIDM who are at high risk for SCD and enables optimized patient selection for ICD placement, while the absence of LGE may reduce the need for ICD implantation in patients with NIDM who are at low risk for future VF/VT or SCD.

  15. Gadolinium-loaded gel scintillators for neutron and antineutrino detection

    SciTech Connect

    Riddle, Catherine Lynn; Akers, Douglas William; Demmer, Ricky Lynn; Paviet, Patricia Denise; Drigert, Mark William

    2016-11-29

    A gadolinium (Gd) loaded scintillation gel (Gd-ScintGel) compound allows for neutron and gamma-ray detection. The unique gel scintillator encompasses some of the best features of both liquid and solid scintillators, yet without many of the disadvantages associated therewith. Preferably, the gel scintillator is a water soluble Gd-DTPA compound and water soluble fluorophores such as: CdSe/ZnS (or ZnS) quantum dot (Q-dot) nanoparticles, coumarin derivatives 7-hydroxy-4-methylcoumarin, 7-hydroxy-4-methylcoumarin-3-acetic acid, 7-hydroxycoumarin-3-carboxylic acid, and Alexa Fluor 350 as well as a carbostyril compound, carbostyril 124 in a stable water-based gel, such as methylcellulose or polyacrylamide polymers. The Gd-loaded ScintGel allows for a homogenious distribution of the Gd-DTPA and the fluorophores, and yields clean fluorescent emission peaks. A moderator, such as deuterium or a water-based clear polymer, can be incorporated in the Gd-ScintGel. The gel scintillators can be used in compact detectors, including neutron and antineutrino detectors.

  16. DNA surface modified gadolinium phosphate nanoparticles as MRI contrast agents.

    PubMed

    Dumont, Matthieu F; Baligand, Celine; Li, Yichen; Knowles, Elisabeth S; Meisel, Mark W; Walter, Glenn A; Talham, Daniel R

    2012-05-16

    Oligonucleotide modified gadolinium phosphate nanoparticles have been prepared and their magnetic resonance relaxivity properties measured. Nanoparticles of GdPO4·H2O were synthesized in a water/oil microemulsion using IGEPAL CO-520 as surfactant, resulting in 50 to 100 nm particles that are highly dispersible and stable in water. Using surface modification chemistry previously established for zirconium phosphonate surfaces, the particles are directly modified with 5'-phosphate terminated oligonucleotides, and the specific interaction of the divalent phosphate with Gd(3+) sites at the surface is demonstrated. The ability of the modified nanoparticles to act as MRI contrast agents was determined by performing MR relaxivity measurements at 14.1 T. Solutions of nanopure water, Feridex, and Omniscan (FDA approved contrast agents) in 0.25% agarose were used for comparison and control purposes. MRI data confirm that GdPO4·H2O nanoparticles have relaxivities (r1, r2) comparable to those of commercially available contrast agents. In addition, the data suggest that biofunctionalization of the surface of the nanoparticles does not prevent their function as MRI contrast agents.

  17. Electronic transport in gadolinium atomic-size contacts

    NASA Astrophysics Data System (ADS)

    Olivera, B.; Salgado, C.; Lado, J. L.; Karimi, A.; Henkel, V.; Scheer, E.; Fernández-Rossier, J.; Palacios, J. J.; Untiedt, C.

    2017-02-01

    We report on the fabrication, transport measurements, and density functional theory (DFT) calculations of atomic-size contacts made of gadolinium (Gd). Gd is known to have local moments mainly associated with f electrons. These coexist with itinerant s and d bands that account for its metallic character. Here we explore whether and how the local moments influence electronic transport properties at the atomic scale. Using both scanning tunneling microscope and lithographic mechanically controllable break junction techniques under cryogenic conditions, we study the conductance of Gd when only few atoms form the junction between bulk electrodes made of the very same material. Thousands of measurements show that Gd has an average lowest conductance, attributed to single-atom contact, below 2/e2 h . Our DFT calculations for monostrand chains anticipate that the f bands are fully spin polarized and insulating and that the conduction may be dominated by s , p , and d bands. We also analyze the electronic transport for model nanocontacts using the nonequilibrium Green's function formalism in combination with DFT. We obtain an overall good agreement with the experimental results for zero bias and show that the contribution to the electronic transport from the f channels is negligible and that from the d channels is marginal.

  18. Analytical Interference in Serum Iron Determination Reveals Iron Versus Gadolinium Transmetallation With Linear Gadolinium-Based Contrast Agents

    PubMed Central

    Fretellier, Nathalie; Poteau, Nathalie; Factor, Cécile; Mayer, Jean-François; Medina, Christelle; Port, Marc; Idée, Jean-Marc; Corot, Claire

    2014-01-01

    Objectives The purposes of this study were to evaluate the risk for analytical interference with gadolinium-based contrast agents (GBCAs) for the colorimetric measurement of serum iron (Fe3+) and to investigate the mechanisms involved. Materials and Methods Rat serum was spiked with several concentrations of all molecular categories of GBCAs, ligands, or “free” soluble gadolinium (Gd3+). Serum iron concentration was determined by 2 different colorimetric methods at pH 4.0 (with a Vitros DT60 analyzer or a Cobas Integra 400 analyzer). Secondly, the cause of interference was investigated by (a) adding free soluble Gd3+ or Mn2+ to serum in the presence of gadobenic acid or gadodiamide and (b) electrospray ionization mass spectrometry. Results Spurious decrease in serum Fe3+ concentration was observed with all linear GBCAs (only with the Vitros DT60 technique occurring at pH 4.0) but not with macrocyclic GBCAs or with free soluble Gd3+. Spurious hyposideremia was also observed with the free ligands present in the pharmaceutical solutions of the linear GBCAs gadopentetic acid and gadodiamide (ie, diethylene triamine pentaacetic acid and calcium-diethylene triamine pentaacetic acid bismethylamide, respectively), suggesting the formation of Fe-ligand chelate. Gadobenic acid-induced interference was blocked in a concentration-dependent fashion by adding a free soluble Gd3+ salt. Conversely, Mn2+, which has a lower affinity than Gd3+ and Fe3+ for the ligand of gadobenic acid (ie, benzyloxypropionic diethylenetriamine tetraacetic acid), was less effective (interference was only partially blocked), suggesting an Fe3+ versus Gd3+ transmetallation phenomenon at pH 4.0. Similar results were observed with gadodiamide. Mass spectrometry detected the formation of Fe-ligand with all linear GBCAs tested in the presence of Fe3+ and the disappearance of Fe-ligand after the addition of free soluble Gd3+. No Fe-ligand chelate was found in the case of the macrocyclic GBCA gadoteric

  19. Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

    SciTech Connect

    Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R.

    2008-02-11

    Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO{sub 2} layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO{sub 2} pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO{sub 2} thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated.

  20. Graphical representations of the chemistry of garnets in a three-dimensional MATLAB based provenance plot

    NASA Astrophysics Data System (ADS)

    Knierzinger, Wolfgang; Palzer, Markus; Wagreich, Michael; Meszar, Maria; Gier, Susanne

    2016-04-01

    A newly developed, MATLAB based garnet provenance plot allows a three-dimensional tetrahedral representation of the chemistry of garnets for the endmembers almandine, pyrope, spessartine and grossular. Based on a freely accessible database of Suggate & Hall (2013) and additional EPMA-data on the internet, the chemistry of more than 2500 garnets was evaluated and used to create various subfields that correspond to different facies conditions of metapelitic, metasomatic and metaigneous rocks as well as granitic rocks. These triangulated subfields act as reference structures within the tetrahedron, facilitating assignments of garnet chemistries to different lithologies. In comparison with conventional tenary garnet discrimination diagrams by Mange & Morton (2007), Wright/Preston et al. (1938/2002) and Aubrecht et al. (2009), this tetrahedral provenance plot enables a better assessment of the conditions of formation of garnets by reducing the overlapping of certain subfields. In particular, a clearer distinction between greenschist facies rocks, amphibolite facies rocks and granitic rocks can be achieved. First applications of the tetrahedral garnet plot provided new insights on sedimentary processes during the Lower Miocene in the pre-Alpine Molasse basin. Bibliography Aubrecht, R., Meres, S., Sykora, M., Mikus, T. (2009). Provenance of the detrital garnets and spinels from the Albian sediments of the Czorsztyn Unit (Pieniny Klippen Belt , Western Carpathians, Slovakia). In: Geologica Carpathica, Dec. 2009, 60, 6, pp. 463-483. Mange, M.A., Morton, A.C. (2007). Geochemistry of Heavy Minerals. In: Mange, M.A. & Wright, D.T.(2007).Heavy Minerals in Use, Amsterdam, pp. 345-391. Preston, J., Hartley, A., Mange-Rajetzky, M., Hole, M., May, G., Buck, S., Vaughan, L. (2002). The provenance of Triassic continental sandstones from the Beryl Field, northern North Sea: Mineralogical, geochemical and sedimentological constraints. In: Journal of Sedimentary Research, 72, pp. 18