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Sample records for gd si planar

  1. The isothermal section of Gd-Ni-Si system at 1070 K

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Manfrinetti, P.; Pani, M.; Provino, A.; Nirmala, R.; Quezado, S.; Malik, S. K.

    2016-03-01

    The Gd-Ni-Si system has been investigated at 1070 K by X-ray and microprobe analyses. The existence of the known compounds, i.e.: GdNi10Si2, GdNi8Si3, GdNi5Si3, GdNi7Si6, GdNi6Si6, GdNi4Si, GdNi2Si2, GdNiSi3, Gd3Ni6Si2, GdNiSi, GdNiSi2, GdNi0.4Si1.6, Gd2Ni2.35Si0.65, Gd3NiSi2, Gd3NiSi3 and Gd6Ni1.67Si3, has been confirmed. Moreover, five new phases have been identified in this system. The crystal structure for four of them has been determined: Gd2Ni16-12.8Si1-4.2 (Th2Zn17-type), GdNi6.6Si6 (GdNi7Si6-type), Gd3Ni8Si (Y3Co8Si-type) and Gd3Ni11.5Si4.2(Gd3Ru4Ga12-type). The compound with composition ~Gd2Ni4Si3 still remains with unknown structure. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi5, GdNi3, GdNi2, GdNi, GdSi2 and GdSi1.67; while no appreciable solubility was observed for the other binary compounds of the Gd-Ni-Si system. Magnetic properties of the GdNi6Si6, GdNi6.6Si6 and Gd3Ni11.5Si4.2 compounds have also been investigated and are here reported.

  2. Designer hydride routes to 'Si-Ge'/(Gd,Er)2O3/Si(1 1 1) semiconductor-on-insulator heterostructures

    NASA Astrophysics Data System (ADS)

    Watkins, Tylan; Jiang, Liying; Smith, D. J.; Chizmeshya, A. V. G.; Menendez, J.; Kouvetakis, J.

    2011-12-01

    We demonstrate Si-Ge integration on engineered M2O3/Si(1 1 1) (M = Gd,Er) dielectric buffer layers using non-traditional chemical precursors that provide new levels of functionality within the deposition process. Stoichiometric Si0.50Ge0.50 alloys and pure Si heterostructures are grown epitaxially via ultra-low-temperature chemical vapor deposition using SiH3GeH3 and Si3H8/Si4H10, respectively. In the case of Si on Gd2O3, an optimal growth processing window in the range of 500-600 °C was found to yield planar layers with monocrystalline structures via a proposed coincidence lattice matching mechanism (2aSi-aGd2O3), while for the SiGe system (2% lattice mismatch) comparable quality films with fully relaxed strain states are deposited at a lower temperature range of 420-450 °C. Extension of this growth process to Si on Er2O3 yields remarkably high-quality layers in spite of the even larger ~3% lattice mismatch. In all cases, the Si-Ge overlayers are found to primarily adopt an A-B-A epitaxial alignment with respect to the M2O3 buffered Si(1 1 1). A comparative study of the Si growth using Si3H8 and Si4H10 indicates that both compounds provide an efficient and straightforward process for semiconductor growth on Gd2O3/Si(1 1 1), which appears to be more viable than conventional approaches from the point of view of scalability and volume.

  3. Planar CMOS analog SiPMs: design, modeling, and characterization

    NASA Astrophysics Data System (ADS)

    Zou, Yu; Villa, Federica; Bronzi, Danilo; Tisa, Simone; Tosi, Alberto; Zappa, Franco

    2015-11-01

    Silicon photomultipliers (SiPMs) are large area detectors consisting of an array of single-photon-sensitive microcells, which make SiPMs extremely attractive to substitute the photomultiplier tubes in many applications. We present the design, fabrication, and characterization of analog SiPMs in standard planar 0.35 μm CMOS technology, with about 1 mm × 1 mm total area and different kinds of microcells, based on single-photon avalanche diodes with 30 μm diameter reaching 21.0% fill-factor (FF), 50 μm diameter (FF = 58.3%) or 50 μm square active area with rounded corner of 5 μm radius (FF = 73.7%). We also developed the electrical SPICE model for CMOS SiPMs. Our CMOS SiPMs have 25 V breakdown voltage, in line with most commercial SiPMs and higher gain (8.8 × 106, 13.2 × 106, and 15.0 × 106, respectively). Although dark count rate density is slightly higher than state-of-the-art analog SiPMs, the proposed standard CMOS processing opens the feasibility of integration with active electronics, for switching hot pixels off, drastically reducing the overall dark count rate, or for further on-chip processing.

  4. Growth and scintillation properties of Ce doped Gd2Si2O7/SiO2 eutectics

    NASA Astrophysics Data System (ADS)

    Kamada, Kei; Kurosawa, Shunsuke; Murakami, Rikito; Yokota, Yuui; Pejchal, Jan; Ohashi, Yuji; Yoshikawa, Akira

    2015-06-01

    Ce:Gd2Si2O7/SiO2 eutectic was grown by the μ-PD method. The square-shape sample with a side of 5 mm and a length of 15 mm was obtained. Two phases of orthorhombic Gd2Si2O7 and SiO2 was observed. Rod-phase was SiO2 and matrix phase was Gd2Si2O7. Ce3+ 4f5d emission have been observed at 400nm. The sample showed light yield of around 16,000 photons/MeV. Scintillation decay time was 46.3ns(21%) 249ns(79%).

  5. Crystal structure of the ternary silicide Gd2Re3Si5

    PubMed Central

    Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

    2014-01-01

    A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta­silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo­octa­hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti­prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5) Å and isolated squares with an Re—Re distance of 2.9683 (6) Å. PMID:25552967

  6. Crystal structure of the ternary silicide Gd2Re3Si5.

    PubMed

    Fedyna, Vitaliia; Kozak, Roksolana; Gladyshevskii, Roman

    2014-12-01

    A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta-silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo-octa-hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti-prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re-Re distance of 2.78163 (5) Å and isolated squares with an Re-Re distance of 2.9683 (6) Å. PMID:25552967

  7. Analysis of Gd5(Si2Ge2) Microstructure and Phase Transition

    SciTech Connect

    John Scott Meyers

    2002-06-27

    With the recent discovery of the giant magnetocaloric effect and the beginning of extensive research on the properties of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, a necessity has developed for a better understanding of the microstructure and crystal structure of this family of rare earth compounds with startling phenomenological properties. The aim of this research is to characterize the microstructure of the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, with X {approx_equal} 2 and its phase change by using both transmission and electron microscopes. A brief history of past work on Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} is necessary to understand this research in its proper context.

  8. Effect of Milling Time on the Blocking Temperature of Nanoparticles of Magnetocaloric Gd5Si4

    NASA Astrophysics Data System (ADS)

    Hadimani, Ravi; Gupta, Shalbh; Harstad, Shane; Pecharsky, Vitalij; Jiles, David; David C Jiles Team; Vitalij Pecharsky Collaboration

    Extensive research has been done on giant magnetocaloric material Gd5(SixGe1-x)4 to improve adiabatic temperature/isothermal entropy change. However, there have been only a few reports on fabrication of nanostructure/nanoparticles that can be used to tune various properties by changing the length scale. Recently we have reported fabrication of room temperature ferromagnetic nanoparticles of Gd5Si4 using high energy ball milling. These nanoparticles have potential applications in biomedical engineering such as better T2 MRI contrast agents and in hypothermia. Here we report the effect of milling time on the blocking temperature, micro-structure, crystal structure, and magnetic properties of these nanoparticles. Magnetization vs. temperature at an applied field of 100 Oe is measured for all the ball milled samples. Bulk Gd5Si4 has a transition temperature of ~340 K. There are two phase transitions observed in the nanoparticles, one near 300 K corresponding to the Gd5Si4 phase and another between 75-150 K corresponding to Gd5Si3. Zero Field Cooling (ZFC) and Field Cooling (FC) were measured. The blocking temperatures for the nanoparticles increase with decrease in milling time.

  9. Synthesis and luminescent properties of nanoscale Gd2Si2O7:Eu3+ phosphors.

    PubMed

    Li, Yong; Wang, Chao-Nan; Wei, Xian-Tao; Zhao, Jiang-Bo; Zhang, Wei-Ping; Yin, Min

    2010-03-01

    Gd2Si2O7:Eu3+ nanoparticles were prepared by the sol-gel method with citric acid as an additive in the precursor solutions. The crystal structure was analyzed by means of X-ray diffraction (XRD). The results indicate that the alpha-Gd2Si2O7 powders in size 35 nm are obtained at a synthesis temperature of 1,100 degrees C, and the doping ion contents do not influence the crystal structure. The excitation and emission spectra of samples were measured. The dependence of photoluminescence intensity and lifetime of level on Eu3+ concentration and synthesis temperature of samples are also discussed. PMID:20355659

  10. Electron spin resonance g shift in Gd{sub 5}Si{sub 4}, Gd{sub 5}Ge{sub 4}, and Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}

    SciTech Connect

    Pires, M. J. M.; Mansanares, A. M.; Silva, E. C. da; Carvalho, A. Magnus G.; Gama, S.; Coelho, A. A.

    2006-04-01

    Gd{sub 5}Si{sub 4}, Gd{sub 5}Ge{sub 4}, and Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88} compounds were studied by electron spin resonance. The arc-melted samples were initially characterized by optical metallography, x-ray diffraction, and static magnetization measurements. The electron spin resonance results show a negative paramagnetic g shift for Gd{sub 5}Si{sub 4} and Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}, and a smaller positive one for Gd{sub 5}Ge{sub 4}. The values of the exchange parameter (j) between the localized Gd-4f spins and the conduction electrons are obtained from the g shifts. These values are positive and of the same order of magnitude for Gd{sub 5}Si{sub 4} and Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}, and negative one order of magnitude smaller for Gd{sub 5}Ge{sub 4}. The electron spin resonance data were interpreted considering the strongly bottlenecked solution of the coupled Bloch-Hasegawa equations.

  11. Temperature and Field Induced Strain Measurements in Single Crystal Gd5Si2Ge2

    NASA Astrophysics Data System (ADS)

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-06-01

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of -8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of -8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.

  12. Atomic configuration of irradiation-induced planar defects in 3C-SiC

    SciTech Connect

    Lin, Y. R.; Ho, C. Y.; Hsieh, C. Y.; Chang, M. T.; Lo, S. C.; Chen, F. R.; Kai, J. J.

    2014-03-24

    The atomic configuration of irradiation-induced planar defects in single crystal 3C-SiC at high irradiation temperatures was shown in this research. A spherical aberration corrected scanning transmission electron microscope provided images of individual silicon and carbon atoms by the annular bright-field (ABF) method. Two types of irradiation-induced planar defects were observed in the ABF images including the extrinsic stacking fault loop with two offset Si-C bilayers and the intrinsic stacking fault loop with one offset Si-C bilayer. The results are in good agreement with images simulated under identical conditions.

  13. Electronic structure and spectral properties of RCuSi (R=Nd,Gd) compounds

    NASA Astrophysics Data System (ADS)

    Knyazev, Yu. V.; Lukoyanov, A. V.; Kuz'min, Yu. I.; Gupta, Sachin; Suresh, K. G.

    2016-04-01

    We report a joint experimental and theoretical investigation of optical properties and electronic structure of NdCuSi and GdCuSi compounds. Optical characteristics have been studied employing ellipsometry in a spectral range 0.22-15 μm. Spin-polarized calculations of the electronic structure have been performed using LSDA+U method accounting for electronic correlations in the 4f shell of rare earth elements. Additionally, we probe our electronic structures by calculating the interband optical conductivities and comparing them with spectral measurement. We find that all main features of the experimental curves have been qualitative interpreted using the calculated densities of states.

  14. Preparation and effect of thermal treatment on Gd2O3:SiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Ahlawat, Rachna

    2015-04-01

    Rare earth oxides have been extensively investigated due to their fascinating properties such as enhanced luminescence efficiency, lower lasing threshold, high-performance luminescent devices, drug-carrying vehicle, contrast agent in magnetic resonance imaging (MRI), up-conversion materials, catalysts and time-resolved fluorescence (TRF) labels for biological detection etc. Nanocomposites of silica gadolinium oxide have been successfully synthesized by sol-gel process using hydrochloric acid as a catalyst. Gd(NO3)3ṡ6H2O and tetraethyl orthosilicate (TEOS) were used as precursors to obtain powdered form of gadolinum oxide:silica (Gd2O3:SiO2) composite. The powdered samples having 2.8 mol% Gd2O3 were annealed at 500°C and 900°C temperature for 6 h and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effect of annealing on the phase evolution of the composite system has been discussed in detail. It was found that the sintering of gadolinium precursor plays a pivotal role to obtain crystalline phase of Gd2O3. Cubic phase of gadolinium oxide was developed for annealed sample at 900°C (6 h) with an average grain size 12 nm.

  15. A current modulation in the Gd{sub 2}O{sub 3}/Si/Gd{sub 2}O{sub 3} quantum well structure as a mean to monitor oxygen vacancies

    SciTech Connect

    Sitaputra, Wattaka; Hudak, John A.; Tsu, Raphael

    2014-05-15

    The Gd{sub 2}O{sub 3} layer grown by electron beam evaporation system normally leads to oxygen deficient sites unless the oxygen partial pressure is provided. These oxygen vacancies were monitored through their current modulating effect. This modulation controlled the current within a Si well of the Gd{sub 2}O{sub 3}/Si/Gd{sub 2}O{sub 3} quantum well structure through the migration of the oxygen vacancies. Such behavior were not found in the structure that contains far less oxygen vacancy such as SiO{sub 2}/Si/SiO{sub 2} structure.

  16. Investigation of room temperature ferromagnetic nanoparticles of Gd5Si4

    DOE PAGESBeta

    Hadimani, R. L.; Gupta, S.; Harstad, S. M.; Pecharsky, V. K.; Jiles, D. C.

    2015-07-06

    Gd5(SixGe1-x)4 compounds undergo first-order phase transitions close to room temperature when x ~ = 0.5, which are accompanied by extreme changes of properties. We report the fabrication of the nanoparticles of one of the parent compounds-Gd5Si4-using high-energy ball milling. Crystal structure, microstructure, and magnetic properties have been investigated. Particles agglomerate at long milling times, and the particles that are milled >20 min lose crystallinity and no longer undergo magnetic phase transition close to 340 K, which is present in a bulk material. The samples milled for >20 min exhibit a slightly increased coercivity. As a result, magnetization at a highmore » temperature of 275K decreases with the increase in the milling time.« less

  17. Atomically sharp 318 nm Gd:AlGaN ultraviolet light emitting diodes on Si with low threshold voltage

    SciTech Connect

    Kent, Thomas F.; Carnevale, Santino D.; Myers, Roberto C.

    2013-05-20

    Self-assembled Al{sub x}Ga{sub 1-x}N polarization-induced nanowire light emitting diodes (PINLEDs) with Gd-doped AlN active regions are prepared by plasma-assisted molecular beam epitaxy on Si substrates. Atomically sharp electroluminescence (EL) from Gd intra-f-shell electronic transitions at 313 nm and 318 nm is observed under forward biases above 5 V. The intensity of the Gd 4f EL scales linearly with current density and increases at lower temperature. The low field excitation of Gd 4f EL in PINLEDs is contrasted with high field excitation in metal/Gd:AlN/polarization-induced n-AlGaN devices; PINLED devices offer over a three fold enhancement in 4f EL intensity at a given device bias.

  18. Method of making active magnetic refrigerant materials based on Gd-Si-Ge alloys

    DOEpatents

    Pecharsky, Alexandra O.; Gschneidner, Jr., Karl A.; Pecharsky, Vitalij K.

    2006-10-03

    An alloy made of heat treated material represented by Gd.sub.5(Si.sub.xGe.sub.1-x).sub.4 where 0.47.ltoreq.x.ltoreq.0.56 that exhibits a magnetic entropy change (-.DELTA.S.sub.m) of at least 16 J/kg K, a magnetostriction of at least 2000 parts per million, and a magnetoresistance of at least 5 percent at a temperature of about 300K and below, and method of heat treating the material between 800 to 1600 degrees C. for a time to this end.

  19. Studies of relativistic electron scattering at planar alignment in a thin Si crystal

    NASA Astrophysics Data System (ADS)

    Takabayashi, Y.; Pivovarov, Yu. L.; Tukhfatullin, T. A.

    2014-04-01

    Experiments on 255-MeV electron scattering under (220) planar channeling conditions in a Si crystal were carried out at the linac of the SAGA Light Source. The spatial and angular distributions of electrons penetrating through a 20-μm thick Si crystal at different incident angles with respect to the (220) plane were measured, and features characteristic of the planar alignment were identified. The experimental results were compared with computer simulations, and showed a reasonable agreement. A comparison with doughnut scattering at axial channeling in the same crystal was also performed. It was confirmed that the planar alignment effect is weaker than the axial alignment effect. These studies are important for understanding the basic mechanism of electron scattering and radiation processes in a crystal.

  20. Photoluminescence properties of MgY4Si3O13:Gd3+, Tb3+ under vacuum ultraviolet excitation

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; An, Shengli; Fan, Bin; Li, Songbo

    2013-07-01

    Gd3+ and Tb3+ co-doped MgY4Si3O13 green phosphors were prepared by a solid-state reaction. The photoluminescence properties in vacuum ultraviolet-visible (VUV-vis) range and decay properties were investigated in details. The f-d transition of Gd3+ ions and spin-allowed f-d transition of Tb3+ ions locate at about 134 nm and 239 nm, respectively. Two charge transfer bands of O2- → Gd3+ and O2- → Tb3+ overlap at about 155 nm. Some f-f transition of Tb3+ and Gd3+ ions are confirmed in VUV-vis range. Upon excitation at 172 nm, the optimal composition of MgY3.3Si3O13:0.5Gd3+, 0.2Tb3+ phosphor exhibits the characteristic transitions of Gd3+ and Tb3+ with chromaticity coordinate of (0.2849, 0.5843). The phosphor has a shorter decay time (2.13 ms) than that of Zn2SiO4:Mn2+ (4.56 ms). The results suggest that this green phosphor is a potential candidate for mercury-free luminescence lamps and plasma display panels (PDPs) application.

  1. Illumination Effect on Bipolar Switching Properties of Gd:SiO2 RRAM Devices Using Transparent Indium Tin Oxide Electrode.

    PubMed

    Chen, Kai-Huang; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Liang, Shu-Ping; Young, Tai-Fa; Syu, Yong-En; Sze, Simon M

    2016-12-01

    To discuss the optoelectronic effect on resistive random access memory (RRAM) devices, the bipolar switching properties and electron-hole pair generation behavior in the transparent indium tin oxide (ITO) electrode of Gd:SiO2 thin films under the ultraviolet (λ = 400 nm) and red-light (λ = 770 nm) illumination for high resistance state (HRS)/low resistance state (LRS) was observed and investigated. In dark environment, the Gd:SiO2 RRAM devices exhibited the ohmic conduction mechanism for LRS, exhibited the Schottky emission conduction and Poole-Frankel conduction mechanism for HRS. For light illumination effect, the operation current of the Gd:SiO2 RRAM devices for HRS/LRS was slightly increased. Finally, the electron-hole pair transport mechanism, switching conduction diagram, and energy band of the RRAM devices will be clearly demonstrated and explained. PMID:27117634

  2. Illumination Effect on Bipolar Switching Properties of Gd:SiO2 RRAM Devices Using Transparent Indium Tin Oxide Electrode

    NASA Astrophysics Data System (ADS)

    Chen, Kai-Huang; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Liang, Shu-Ping; Young, Tai-Fa; Syu, Yong-En; Sze, Simon M.

    2016-04-01

    To discuss the optoelectronic effect on resistive random access memory (RRAM) devices, the bipolar switching properties and electron-hole pair generation behavior in the transparent indium tin oxide (ITO) electrode of Gd:SiO2 thin films under the ultraviolet ( λ = 400 nm) and red-light ( λ = 770 nm) illumination for high resistance state (HRS)/low resistance state (LRS) was observed and investigated. In dark environment, the Gd:SiO2 RRAM devices exhibited the ohmic conduction mechanism for LRS, exhibited the Schottky emission conduction and Poole-Frankel conduction mechanism for HRS. For light illumination effect, the operation current of the Gd:SiO2 RRAM devices for HRS/LRS was slightly increased. Finally, the electron-hole pair transport mechanism, switching conduction diagram, and energy band of the RRAM devices will be clearly demonstrated and explained.

  3. Forced Volume Magnetostriction in Composite Gd5Si2Ge2

    SciTech Connect

    Choe, W; McCall, S K; Radousky, H B; Nersessian, N; Or, S W; Carman, G P; Pecharsky, V K; Pecharsky, A O

    2004-04-01

    A -1200 ppm forced volume magnetostriction has been obtained in a [0-3], resin binder, Gd{sub 5}Si{sub 2}Ge{sub 2} particulate composite. The strain is a result of a magnetically induced phase transformation from a high volume (high temperature, low magnetic field) monoclinic phase to a low volume (low temperature, high magnetic field) orthorhombic phase. The particles used in the composite were ball-milled from a bulk sample and were sieved to obtain a size distribution of {approx}> 600 {micro}m. Bulk Gd{sub 5}Si{sub 2}Ge{sub 2} was manufactured via arc melting and subsequently annealed at 1300 C for 1 hour to produce a textured, polycrystalline sample. The transformation temperatures of the bulk sample, as measured using a Differential Scanning Calorimeter (DSC), were M{sub s}= -9.3 C, M{sub f}=-14.6 C, A{sub s}=-4.4 C, and A{sub f}=-1.2 C. The composite and the bulk samples were magnetically characterized using a SQUID magnetometer, and found to undergo a paramagnetic to ferromagnetic transition during the phase transformation, consistent with published results. The bulk sample was also found to possess a maximum linear magnetostriction -2500 ppm.

  4. Temperature and field induced strain measurements in single crystal Gd5Si2Ge2

    DOE PAGESBeta

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-03-29

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of –8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of –8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Furthermore,more » using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.« less

  5. Magnetic ordering in Sc2CoSi2-type R2FeSi2 (R=Gd, Tb) and R2CoSi2 (R=Y, Gd-Er) compounds

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Pani, M.; Nirmala, R.; Quezado, S.; Malik, S. K.

    2016-09-01

    Magnetic and magnetocaloric properties of Sc2CoSi2-type R2TSi2 (R=Gd-Er, T=Fe, Co) compounds have been studied using magnetization data. These indicate the presence of mixed ferromagnetic and antiferromagnetic interactions in these compounds. One observes a ferromagnetic transition followed by an antiferromagnetic order and a further possible spin-reorientation transition at low temperatures. Compared to Gd2{Fe, Co}Si2, the Tb2FeSi2 and {Tb-Er}2CoSi2 compounds exhibit remarkable hysteresis (for e.g. Tb2FeSi2 shows residual magnetization Mres/Tb=2.45 μB, coercive field Hcoer=14.9 kOe, and critical field Hcrit 5 kOe at 5 K) possibly due to the magnetocrystalline anisotropy of the rare earth. The R2{Fe, Co}Si2 show relatively small magnetocaloric effect (i.e. isothermal magnetic entropy change, ΔSm) around the magnetic transition temperature: the maximal value of MCE is demonstrated by Ho2CoSi2 (ΔSm=-8.1 J/kg K at 72 K and ΔSm=-9.4 J/kg K at 23 K in field change of 50 kOe) and Er2CoSi2 (ΔSm=-13.6 J/kg K at 32 K and ΔSm=-8.4 J/kg K at 12 K in field change of 50 kOe).

  6. RNi8Si3 (R=Gd,Tb): Novel ternary ordered derivatives of the BaCd11 type

    NASA Astrophysics Data System (ADS)

    Pani, M.; Morozkin, A. V.; Yapaskurt, V. O.; Provino, A.; Manfrinetti, P.; Nirmala, R.; Malik, S. K.

    2016-01-01

    The title compounds have been synthesized and characterized both from the structural and magnetic point of view. Both crystallize in a new monoclinic structure strictly related to the tetragonal BaCd11 type. The structure was solved by means of X-ray single-crystal techniques for GdNi8Si3 and confirmed for TbNi8Si3 on powder data; the corresponding lattice parameters (obtained from Guinier powder patterns) are a=6.3259(2), b=13.7245(5), c=7.4949(3) Å, β=113.522(3)°, Vcell=596.64(3) Å3 and a=6.3200(2), b=13.6987(4), c=7.4923(2) Å, β=113.494(2)°, Vcell=594.88(2) Å3. The symmetry relationship between the tI48-I41/amd BaCd11 aristotype and the new ordered mS48-C2/c GdNi8Si3 derivative is described via the Bärnighausen formalism within the group theory. The large Gd-Gd (Tb-Tb) distances, mediated via Ni-Si network, likely lead to weak magnetic interactions. Low-field magnetization vs temperature measurements indicate weak and field-sensitive antiferromagnetic ground state, with ordering temperatures of 3 K in GdNi8Si3 and about 2-3 K in TbNi8Si3. On the other hand, the isothermal field-dependent magnetization data show the presence of competing interactions in both compounds, with a field-induced ferromagnetic behavior for GdNi8Si3 and a ferrimagnetic-like behavior in TbNi8Si3 at the ordering temperature TC/N of about (or slightly higher than) 3K. The magnetocaloric effect, quantified in terms of isothermal magnetic entropy change ΔSm, has the maximum values of -19.8 J(kg K)-1 (at 4 K for 140 kOe field change) and -12.1 J(kg K)-1 (at 12 K for 140 kOe field change) in GdNi8Si3 and TbNi8Si3, respectively.

  7. Phase equilibria and elements partitioning in zirconolite-rich region of Ca-Zr-Ti-Al-Gd-Si-O system

    SciTech Connect

    Knyazev, O.A.; Stefanovsky, S.V.; Ioudintsev, S.V.; Nikonov, B.S.; Omelianenko, B.I.; Mokhov, A.V.; Yakushev, A.I.

    1997-12-31

    Zirconolite-rich ceramics were produced by the cold crucible melting technique in an air atmosphere, at 1550 {+-} 50 C and 1 atm. Four samples with overall composition (in wt.%): 4.9-14.3 CaO; 19.0-41.3 ZrO{sub 2}; 24.1-42.6 TiO{sub 2}; 1.3-11.3 Al{sub 2}O{sub 3}; 6.8-30.0 Gd{sub 2}O{sub 3}; and 1.1-8.5 SiO{sub 2} have been studied. Total phases in the ceramics consist of major zirconolite and minor rutile, perovskite, zirconia, aluminium titanate, and glass. The Gd{sub 2}O{sub 3} content in zirconolite reaches up to 31.4 wt.% corresponding to the formula: (Ca{sub 0.4},Gd{sub 0.7})Zr{sub 1.0}(Ti{sub 1.4},Al{sub 0.5})O{sub 7.0}. The data on the phase composition agree well with coupled Gd incorporation into the mineral structure: Ca(II) + Ti(IV) = Gd(III) + Al(III), and 2Gd(III) = Ca(II) + Zr(IV). The highest Gd contents observed in the other phases are 25.4% for zirconia, 12.6% in glass, 8.8% in perovskite, and 1.4% for rutile. The rest of the elements` distribution in the samples are analyzed.

  8. Second order phase transition temperature of single crystals of Gd5Si1.3Ge2.7 and Gd5Si1.4Ge2.6

    DOE PAGESBeta

    Hadimani, R. L.; Melikhov, Y.; Schlagel, D. L.; Lograsso, T. A.; Dennis, K. W.; McCallum, R. W.; Jiles, D. C.

    2015-01-30

    Gd5(SixGe1–x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3Ge2.7 and Gd5Si1.4Ge2.6. In this study, we have investigated the first order and second order phase transition temperatures of these samples using magnetic moment vs. temperature and magnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.

  9. Bonding, aromaticity, and planar tetracoordinated carbon in Si2CH 2 and Ge 2CH 2.

    PubMed

    Vogt-Geisse, Stefan; Wu, Judy I-Chia; Schleyer, Paul v R; Schaefer, Henry F

    2015-08-01

    Natural bond orbital (NBO) analyses and dissected nucleus-independent chemical shifts (NICS π z z ) were computed to evaluate the bonding (bond type, electron occupation, hybridization) and aromatic character of the three lowest-lying Si2CH2 (1-Si, 2-Si, 3-Si) and Ge2CH2 (1-Ge, 2-Ge, 3-Ge) isomers. While their carbon C3H2 analogs favor classical alkene, allene, and alkyne type bonding, these Si and Ge derivatives are more polarizable and can favor "highly electron delocalized"? and "non-classical"? structures. The lowest energy Si 2CH2 and Ge 2CH2 isomers, 1-Si and 1-Ge, exhibit two sets of 3-center 2-electron (3c-2e) bonding; a π-3c-2e bond involving the heavy atoms (C-Si-Si and C-Ge-Ge), and a σ-3c-2e bond (Si-H-Si, Ge-H-Ge). Both 3-Si and 3-Ge exhibit π and σ-3c-2e bonding involving a planar tetracoordinated carbon (ptC) center. Despite their highly electron delocalized nature, all of the Si2CH2 and Ge2CH2 isomers considered display only modest two π electron aromatic character (NICS(0) π z z =--6.2 to -8.9 ppm, computed at the heavy atom ring center) compared to the cyclic-C 3H2 (-13.3 ppm). Graphical Abstract The three lowest Si2CH2 and Ge2CH2 isomers. PMID:26232183

  10. Method of making active magnetic refrigerant, colossal magnetostriction and giant magnetoresistive materials based on Gd-Si-Ge alloys

    DOEpatents

    Gschneidner, Jr., Karl A.; Pecharsky, Alexandra O.; Pecharsky, Vitalij K.

    2003-07-08

    Method of making an active magnetic refrigerant represented by Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4 alloy for 0.ltoreq.x.ltoreq.1.0 comprising placing amounts of the commercially pure Gd, Si, and Ge charge components in a crucible, heating the charge contents under subambient pressure to a melting temperature of the alloy for a time sufficient to homogenize the alloy and oxidize carbon with oxygen present in the Gd charge component to reduce carbon, rapidly solidifying the alloy in the crucible, and heat treating the solidified alloy at a temperature below the melting temperature for a time effective to homogenize a microstructure of the solidified material, and then cooling sufficiently fast to prevent the eutectoid decomposition and improve magnetocaloric and/or the magnetostrictive and/or the magnetoresistive properties thereof.

  11. Active magnetic refrigerants based on Gd-Si-Ge material and refrigeration apparatus and process

    DOEpatents

    Gschneidner, K.A. Jr.; Pecharsky, V.K.

    1998-04-28

    Active magnetic regenerator and method using Gd{sub 5} (Si{sub x}Ge{sub 1{minus}x}){sub 4}, where x is equal to or less than 0.5, as a magnetic refrigerant that exhibits a reversible ferromagnetic/antiferromagnetic or ferromagnetic-II/ferromagnetic-I first order phase transition and extraordinary magneto-thermal properties, such as a giant magnetocaloric effect, that renders the refrigerant more efficient and useful than existing magnetic refrigerants for commercialization of magnetic regenerators. The reversible first order phase transition is tunable from approximately 30 K to approximately 290 K (near room temperature) and above by compositional adjustments. The active magnetic regenerator and method can function for refrigerating, air conditioning, and liquefying low temperature cryogens with significantly improved efficiency and operating temperature range from approximately 10 K to 300 K and above. Also an active magnetic regenerator and method using Gd{sub 5} (Si{sub x} Ge{sub 1{minus}x}){sub 4}, where x is equal to or greater than 0.5, as a magnetic heater/refrigerant that exhibits a reversible ferromagnetic/paramagnetic second order phase transition with large magneto-thermal properties, such as a large magnetocaloric effect that permits the commercialization of a magnetic heat pump and/or refrigerant. This second order phase transition is tunable from approximately 280 K (near room temperature) to approximately 350 K by composition adjustments. The active magnetic regenerator and method can function for low level heating for climate control for buildings, homes and automobile, and chemical processing. 27 figs.

  12. Active magnetic refrigerants based on Gd-Si-Ge material and refrigeration apparatus and process

    DOEpatents

    Gschneidner, Jr., Karl A.; Pecharsky, Vitalij K.

    1998-04-28

    Active magnetic regenerator and method using Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4, where x is equal to or less than 0.5, as a magnetic refrigerant that exhibits a reversible ferromagnetic/antiferromagnetic or ferromagnetic-II/ferromagnetic-I first order phase transition and extraordinary magneto-thermal properties, such as a giant magnetocaloric effect, that renders the refrigerant more efficient and useful than existing magnetic refrigerants for commercialization of magnetic regenerators. The reversible first order phase transition is tunable from approximately 30 K to approximately 290 K (near room temperature) and above by compositional adjustments. The active magnetic regenerator and method can function for refrigerating, air conditioning, and liquefying low temperature cryogens with significantly improved efficiency and operating temperature range from approximately 10 K to 300 K and above. Also an active magnetic regenerator and method using Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4, where x is equal to or greater than 0.5, as a magnetic heater/refrigerant that exhibits a reversible ferromagnetic/paramagnetic second order phase transition with large magneto-thermal properties, such as a large magnetocaloric effect that permits the commercialization of a magnetic heat pump and/or refrigerant. This second order phase transition is tunable from approximately 280 K (near room temperature) to approximately 350 K by composition adjustments. The active magnetic regenerator and method can function for low level heating for climate control for buildings, homes and automobile, and chemical processing.

  13. Graphene as a transparent conducting and surface field layer in planar Si solar cells

    PubMed Central

    2014-01-01

    This work presents an experimental and finite difference time domain (FDTD) simulation-based study on the application of graphene as a transparent conducting layer on a planar and untextured crystalline p-n silicon solar cell. A high-quality monolayer graphene with 97% transparency and 350 Ω/□ sheet resistance grown by atmospheric pressure chemical vapor deposition method was transferred onto planar Si cells. An increase in efficiency from 5.38% to 7.85% was observed upon deposition of graphene onto Si cells, which further increases to 8.94% upon SiO2 deposition onto the graphene/Si structure. A large increase in photon conversion efficiency as a result of graphene deposition shows that the electronic interaction and the presence of an electric field at the graphene/Si interface together play an important role in this improvement and additionally lead to a reduction in series resistance due to the conducting nature of graphene. PMID:25114642

  14. Self-assembly of SiO2/Gd-DTPA-polyethylenimine nanocomposites as magnetic resonance imaging probes.

    PubMed

    Luo, Kui; Tian, Jing; Liu, Gang; Sun, Jiayu; Xia, Chunchao; Tang, Hehan; Lin, Ling; Miao, Tianxin; Zhao, Xuna; Gao, Fabao; Gong, Qiyong; Song, Bin; Shuai, Xintao; Ai, Hua; Gu, Zhongwei

    2010-01-01

    Controlled self-assembly of organic/inorganic magnetic hybrid materials have important applications in magnetic resonance imaging (MRI). In this study, a widely used polycation polyethylenimine was conjugated with gadopentetic acid (Gd-DTPA) as a gadolinium bearing polyelectrolyte (Gd-DTPA-PEI). Next, multilayers of Gd-DTPA-PEI were coated on silica nanoparticles through layer-by-layer (LbL) self-assembly with polyanions as monitored by dynamic light scattering, zeta-potential, and scanning electron microscopy. The thickness of the multilayer film was estimated from quartz crystal microbalance based on counting frequency change of each adsorbed layer. The magnetic relaxation of SiO2/(Gd-DTPA-PEl/polyanion), core-shell nanocomposite was tested at 1.5 T magnetic field in a clinical MRI scanner, and a 3-fold increase in T1 relaxivity to 15.1 Gd mM(-1)s(-1) was noticed comparing to Gd-DTPA small molecules. Dextran sulfate was coated as the outermost layer on the nanocomposite for better biocompatibility as verified by in vitro cytotoxicity studies. This formulation provides good signal intensity enhancement of mouse liver in vivo with only 1/25 dose of clinical standard at 30 and 60 minutes after intravenous injection. This sensitive imaging probe with unique core-shell structures may find broad applications in cellular and molecular imaging. PMID:20352889

  15. Generation of planar defects caused by the surface diffusion of Au atoms on SiNWs

    SciTech Connect

    Lee, Woo-Jung; Ma, Jin Won; Bae, Jung Min; Cho, Mann-Ho; Ahn, Jae Pyung

    2012-10-15

    The generation of planar defects in silicon nanowires (SiNWs) synthesized by means of a vapor–liquid–solid (VLS) procedure using Au as a catalyst in an ultra-high vacuum chemical vapor deposition (UHV-CVD) system was investigated. Faceting, the formation of planar defects and the diffusion of Au in SiNWs occurred simultaneously, proportional to the growth temperature and the ratio of the H{sub 2} precursor gas. The planes located on the sidewalls of the wire after Au diffusion were faceted (1 1 1) and (1 0 0) surfaces, which represent equilibrium configurations of Si due to surface energy minimization during rapid wire growth under unstable conditions. Moreover, (1 1 1) twin defects were formed on the sidewalls of the faceted boundaries where the Au clusters were mainly located, due to the surface tension of the Au atoms, resulting in clusters at the liquid/solid interfaces in SiNWs with a 〈1 1 1〉 growth direction.

  16. SiO2 nanofluid planar jet impingement cooling on a convex heated plate

    NASA Astrophysics Data System (ADS)

    Asghari Lafmajani, Neda; Ebrahimi Bidhendi, Mahsa; Ashjaee, Mehdi

    2016-02-01

    The main objective of this paper is to investigate the heat transfer coefficient of a planar jet of SiO2 nanofluid that impinges vertically on the middle of a convex heated plate for cooling purposes. The planar jet issues from a rectangular slot nozzle. The convex aluminum plate has a thickness, width and length of 0.2, 40 and 130 mm, respectively, and is bent with a radius of 200 mm. A constant heat-flux condition is employed. 7 nm SiO2 particles are added to water to prepare the nanofluid with 0.1, 1 and 2 % (ml SiO2/ml H2O) concentrations. The tests are also performed at different Reynolds numbers from 1803 to 2782. Results indicate that adding the SiO2 nanoparticles can effectively increase both local and average heat transfer coefficients up to 39.37 and 32.78 %, respectively. These positive effects often are more pronounced with increasing Reynolds numbers. This enhancement increases with ascending the concentration of nanofluid, especially from 0.1 to 1 %.

  17. Anomalous Hall effect in the prospective spintronic material Eu1-x Gd x O integrated with Si.

    PubMed

    Parfenov, Oleg E; Averyanov, Dmitry V; Tokmachev, Andrey M; Taldenkov, Alexander N; Storchak, Vyacheslav G

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm(-1) in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies. PMID:27165844

  18. Anomalous Hall effect in the prospective spintronic material Eu1‑x Gd x O integrated with Si

    NASA Astrophysics Data System (ADS)

    Parfenov, Oleg E.; Averyanov, Dmitry V.; Tokmachev, Andrey M.; Taldenkov, Alexander N.; Storchak, Vyacheslav G.

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm‑1 in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.

  19. Unusual magnetic behavior in Gd{sub 5}(Si{sub 1.5}Ge{sub 2.5}) and Gd{sub 5}(Si{sub 2}Ge{sub 2})

    SciTech Connect

    Levin, E. M.; Pecharsky, V. K.; Gschneidner, K. A.

    2000-12-01

    The coexistence of ferromagnetic and paramagnetic phases in the 4f-electron systems Gd{sub 5}(Si{sub 1.5}Ge{sub 2.5}) and Gd{sub 5}(Si{sub 2}Ge{sub 2}) during the magnetic-martensitic phase transition have been observed. A dc magnetic field reversibly changes both the magnetic and crystal structures of the alloys above their respective Curie temperatures. A negative imaginary component of the ac magnetic susceptibility for both alloys has been observed in the ferromagnetic state. The results are discussed in terms of indirect Ruderman-Kittel-Kasuya-Yosida and direct superexchange interactions, and anomalies of the relaxation process.

  20. X-ray photoelectron spectroscopy and diffraction investigation of a metal-oxide-semiconductor heterostructure: Pt/Gd2O3/Si(111)

    NASA Astrophysics Data System (ADS)

    Ferrah, D.; El Kazzi, M.; Niu, G.; Botella, C.; Penuelas, J.; Robach, Y.; Louahadj, L.; Bachelet, R.; Largeau, L.; Saint-Girons, G.; Liu, Q.; Vilquin, B.; Grenet, G.

    2015-04-01

    Platinum thin films deposited by physical vapor deposition (PVD) on Gd2O3/Si(111) templates are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray photoelectron diffraction (XPD). Both XRD and XPD give clear evidence that Gd2O3 grows (111)-oriented and single-domain on Si(111) with mirror epitaxial relationship viz., [1bar10] Gd2O3(111)//[11bar0] Si(111). On Gd2O3/Si(111), Pt is partially crystallized with (111) orientation. There are two epitaxial domains and a slightly visible (111) fiber texture. The in-plane relationships of these Pt(111) domains with Gd2O3(111) are a direct one: [11bar0] Pt(111)//[11bar0] Gd2O3(111) and a mirror one: [1bar10] Pt(111)//[11bar0] Gd2O3(111). XPS reveals that Pt4f exhibits a metallic behavior even for small amounts of Pt but very small chemical shifts suggest that Pt environment is different at the interface with Gd2O3. These XPS chemical shifts have been correlated with features in XPD azimuth curves, which could be related with the existence of hexagonal α-PtO2(0001)layer.

  1. High-temperature scintillation properties of orthorhombic Gd2Si2O7 aiming at well logging

    NASA Astrophysics Data System (ADS)

    Tsubota, Youichi; Kaneko, Junichi H.; Higuchi, Mikio; Nishiyama, Shusuke; Ishibashi, Hiroyuki

    2015-06-01

    Scintillation and luminescence properties of orthorhombic Gd2Si2O7:Ce (GPS:Ce) single-crystal scintillators were investigated for temperatures ranging from room temperature (RT) to 573 K. Orthorhombic GPS crystals were grown by using a top-seeded solution growth (TSSG) method. The scintillation light yield of the orthorhombic GPS at RT was ∼2.9 times higher than that of Gd2SiO5:Ce (GSO). The light yield values of the orthorhombic GPS (Ce = 2.5%) were almost unchanged for temperatures ranging from RT to 523 K, and at 523 K, were higher than twice the light yield of GSO at RT. These GPS scintillators are expected to contribute to oil exploration at greater depths.

  2. Investigation of room temperature ferromagnetic nanoparticles of Gd5Si4

    SciTech Connect

    Hadimani, R. L.; Gupta, S.; Harstad, S. M.; Pecharsky, V. K.; Jiles, D. C.

    2015-07-06

    Gd5(SixGe1-x)4 compounds undergo first-order phase transitions close to room temperature when x ~ = 0.5, which are accompanied by extreme changes of properties. We report the fabrication of the nanoparticles of one of the parent compounds-Gd5Si4-using high-energy ball milling. Crystal structure, microstructure, and magnetic properties have been investigated. Particles agglomerate at long milling times, and the particles that are milled >20 min lose crystallinity and no longer undergo magnetic phase transition close to 340 K, which is present in a bulk material. The samples milled for >20 min exhibit a slightly increased coercivity. As a result, magnetization at a high temperature of 275K decreases with the increase in the milling time.

  3. Electrospun SiO2 "necklaces" on unglazed ceramic tiles: a planarizing strategy

    NASA Astrophysics Data System (ADS)

    Di Mauro, Alessandro; Fragalà, Maria Elena

    2015-05-01

    Silica based nanofibres have been deposited on unglazed ceramic tiles by combining electrospinning and sol-gel processes. Poly(vinyl pyrrolidone) (PVP) alcoholic solutions and commercial spin on glass (Accuglass) mixtures have been used to obtain composite fibrous non-woven mats totally converted, after thermal annealing at 600 °C, to SiO2 microsphere "necklaces". The possibility to get an uniform fibres coverage onto the tile surface confirms the validity of electrospinning (easily scalable to large surface samples) as coating strategy to cover the macroscopic defects typical of the polished unglazed tile surface and improve surface planarization.

  4. Robust and tunable itinerant ferromagnetism at the silicon surface of the antiferromagnet GdRh2Si2

    NASA Astrophysics Data System (ADS)

    Güttler, M.; Generalov, A.; Otrokov, M. M.; Kummer, K.; Kliemt, K.; Fedorov, A.; Chikina, A.; Danzenbächer, S.; Schulz, S.; Chulkov, E. V.; Koroteev, Yu. M.; Caroca-Canales, N.; Shi, M.; Radovic, M.; Geibel, C.; Laubschat, C.; Dudin, P.; Kim, T. K.; Hoesch, M.; Krellner, C.; Vyalikh, D. V.

    2016-04-01

    Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated.

  5. Robust and tunable itinerant ferromagnetism at the silicon surface of the antiferromagnet GdRh2Si2

    PubMed Central

    Güttler, M.; Generalov, A.; Otrokov, M. M.; Kummer, K.; Kliemt, K.; Fedorov, A.; Chikina, A.; Danzenbächer, S.; Schulz, S.; Chulkov, E. V.; Koroteev, Yu. M.; Caroca-Canales, N.; Shi, M.; Radovic, M.; Geibel, C.; Laubschat, C.; Dudin, P.; Kim, T. K.; Hoesch, M.; Krellner, C.; Vyalikh, D. V.

    2016-01-01

    Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated. PMID:27052006

  6. Robust and tunable itinerant ferromagnetism at the silicon surface of the antiferromagnet GdRh2Si2.

    PubMed

    Güttler, M; Generalov, A; Otrokov, M M; Kummer, K; Kliemt, K; Fedorov, A; Chikina, A; Danzenbächer, S; Schulz, S; Chulkov, E V; Koroteev, Yu M; Caroca-Canales, N; Shi, M; Radovic, M; Geibel, C; Laubschat, C; Dudin, P; Kim, T K; Hoesch, M; Krellner, C; Vyalikh, D V

    2016-01-01

    Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated. PMID:27052006

  7. Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystals

    PubMed Central

    Li, Haifeng; Xiao, Yinguo; Schmitz, Berthold; Persson, Jörg; Schmidt, Wolfgang; Meuffels, Paul; Roth, Georg; Brückel, Thomas

    2012-01-01

    Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to ~415%, accompanied by a large negative thermal volume expansion (NTVE). Around TN the PMRV translates to negative, down to ~−10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices. PMID:23087815

  8. Study of radiation hardness of Gd2SiO5 scintillator for heavy ion beam

    NASA Astrophysics Data System (ADS)

    Kawade, K.; Fukatsu, K.; Itow, Y.; Masuda, K.; Murakami, T.; Sako, T.; Suzuki, K.; Suzuki, T.; Taki, K.

    2011-09-01

    Gd2SiO5 (GSO) scintillator has very excellent radiation resistance, a fast decay time and a large light yield. Because of these features, GSO scintillator is a suitable material for high radiation environment experiments such as those encountered at high energy accelerators. The radiation hardness of GSO has been measured with Carbon ion beams at the Heavy Ion Medical Accelerator in Chiba (HIMAC). During two nights of irradiation the GSO received a total radiation dose of 7 × 105 Gy and no decrease of light yield was observed. On the other hand an increase of light yield by 25% was observed. The increase is proportional to the total dose, increasing at a rate of 0.025%/Gy and saturating at around 1 kGy. Recovery to the initial light yield was also observed during the day between two nights of radiation exposure. The recovery was observed to have a slow exponential time constant of approximately 1.5 × 104 seconds together with a faster component. In case of the LHCf experiment, a very forward region experiment on LHC (pseudo-rapidity η > 8.4), the irradiation dose is expected to be approximately 100 Gy for 10 nb-1 of data taking at (s)1/2 = 14TeV. The expected increase in light yield of less than a few percent will not affect the LHCf measurement.

  9. Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystals.

    PubMed

    Li, Haifeng; Xiao, Yinguo; Schmitz, Berthold; Persson, Jörg; Schmidt, Wolfgang; Meuffels, Paul; Roth, Georg; Brückel, Thomas

    2012-01-01

    Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to ~415%, accompanied by a large negative thermal volume expansion (NTVE). Around T(N) the PMRV translates to negative, down to ~-10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5d bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4f spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices. PMID:23087815

  10. Magnetic Entropy and Interactions in a-Gd_xSi_1-x

    NASA Astrophysics Data System (ADS)

    Zink, B. L.; Sappey, R.; Revaz, B.; Hellman, F.

    2001-03-01

    In the last several years many dramatic phenomena have been observed in amorphous gadolinium-silicon alloys. Among these are enormous negative magnetoresistance(F. Hellman et al., PRL 77, 4652 (1996))^,(P. Xiong et al., PRB 59, R3929 (1999)), a resulting field-tunable metal-insulator transition(W. Teizer et al., PRL 85, 848 (2000)), and unique and fascinating spin-glass behavior(F. Hellman et al., PRL 84, 5411 (2000)). The zero field specific heat of these films indicates that localized electrons cooperate with the local gadolinium moments in the magnetic freezing(B. L. Zink et al., PRL 83, 2266 (1999)). Recent specific heat measurements in magnetic fields up to 8 Tesla show a shift of magnetic entropy to higher temperatures which is small relative to that seen in the canonical spin-glasses such as CuMn. The size of this shift raises questions about the strength and nature of magnetic interactions in a-Gd_xSi_1-x.

  11. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    NASA Astrophysics Data System (ADS)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  12. Solvothermal synthesis and luminescence properties of monodisperse Gd{sub 2}O{sub 3}:Eu{sup 3+} and Gd{sub 2}O{sub 3}:Eu{sup 3+}SiO{sub 2} nanospheres

    SciTech Connect

    Wang, Yu; Bai, Xue; Liu, Tong; Dong, Biao; Xu, Lin; Liu, Qiong; Song, Hongwei

    2010-12-15

    A series of uniform, monodispersed Gd(OH){sup 3}:Eu{sup 3+} nanospheres less than 100 nm were successfully synthesized with iron ions as catalyst and DMF as solvent under the solvothermal condition. Cetyltrimethyl ammonium bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as co-surfactant during this facile procedure should be changed as A series of uniform, monodisperse Gd(OH){sup 3}:Eu{sup 3+} nanospheres less than 100 nm in diameter were successfully synthesized with solvothermal method. Iron ion was used as catalyst and Dimethylformamide (DMF) as solvent, Cetyltrimethyl Ammonium Bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as surfactants. Further calcination process was applied to prepare Gd{sub 2}O{sub 3}:Eu{sup 3+} nanoshpheres during this facile procedure. -- Graphical abstract: Uniform and monodisperse Gd{sub 2}O{sub 3}:Eu{sup 3+} and Gd{sub 2}O{sub 3}:Eu{sup 3+}SiO{sub 2} monodisperse were synthesized by annealed relative parent's Gd(OH){sub 3}:Eu{sup 3+} and Gd(OH){sub 3}:Eu{sup 3+}SiO{sub 2}, respectively. Their morphology and luminescence properties all strongly depended on the iron concentration. Display Omitted

  13. Channeling energy loss and dechanneling of He along axial and planar directions of Si

    NASA Astrophysics Data System (ADS)

    Shafiei, S.; Lamehi-Rachti, M.

    2016-01-01

    In the present work, the energy loss and the dechanneling of He ions in the energy of 1.5 MeV and 2 MeV along the <1 0 0> and <1 1 0> axial directions as well as the {1 0 0} and {1 1 0} planar directions of Si were studied by the simulation of the channeling Rutherford backscattering spectra. The simulation was done based on the considerations that a fraction of the aligned beam enters the sample as a random component due to the ions scattering from the surface, and the dechanneling starts at the greater penetration depths, xDech. It was presumed that the dechanneling process follows a simple exponential law with a parameter λ which is proportional to the half-thickness. The Levenberg-Marquardt algorithm was used to set the best parameters of energy loss ratio, xDech and λ. The experimental results are well reproduced by this simulation. Differences between various axial and planar channels in the Si crystal and their influence on the energy loss ratio and dechanneling of He ions are described. Moreover, the energy dependence of energy loss ratio and dechanneling of He ions were investigated. It is shown that the dechanneling behavior of ions depends on the energy and energy loss of the ions along a channel. The channeled to random energy loss increases by decreasing ions energy.

  14. Role of Ge in bridging ferromagnetism in the giant magnetocaloric Gd{sub 5}(Ge{sub 1-x}Si{sub x}){sub 4} alloys.

    SciTech Connect

    Haskel, D.; Lee, Y. B.; Harmon, B. N.; Islam, Z.; Lang, J. C.; Srajer, G.; Mudryk, Ya.; Gschneidner, K. A., Jr.; Pecharsky, V. K.; X-Ray Science Division; Iowa State Univ.

    2007-06-15

    X-ray magnetic circular dichroism (XMCD) measurements and density functional theory (DFT) are used to study the electronic conduction states in Gd{sub 5}(Ge{sub 1-x}Si{sub x}){sub 4} materials through the first-order bond-breaking magnetostructural transition responsible for their giant magnetocaloric effect. Spin-dependent hybridization between Ge 4p and Gd 5d conduction states, which XMCD senses through the induced magnetic polarization in Ge ions, enables long-range Ruderman-Kittel-Kasuya-Yosida ferromagnetic interactions between Gd 4f moments in adjacent Gd slabs connected by Ge(Si) bonds. These interactions are strong below but weaken above the Ge(Si) bond-breaking transition that destroys 3D ferromagnetic order.

  15. Performance of very thin Gd2SiO5 scintillator bars for the LHCf experiment

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Kasahara, K.; Kawade, K.; Murakami, T.; Masuda, K.; Sako, T.; Torii, S.

    2013-01-01

    To increase the radiation resistivity of the calorimeter, the LHCf group plans to replace its plastic scintillator with Gd2SiO5 (GSO) scintillator. In this report, we present the basic performance of very thin GSO scintillator bars that will replace the scintillating fibers employed as the position sensitive part of the current LHCf detector. The size of a bar is 1 mm × 1 mm × 40 mm. White acrylic paint was painted on one group of GSO bars and a second group was unpainted. After observing a clear peak of cosmic ray muons corresponding to 3 to 4 photoelectrons, a quantitative test was performed by using a 290 MeV/n carbon beam at HIMAC in Japan. The non-painted bars have less position dependence of light collection efficiency (effective attenuation length is about 140 mm) and less piece-to-piece variation. The unpainted bars show about 8% cross talk between adjacent bars which is larger than the painted ones. However, for estimating the center of a cascade shower inside the calorimeter, uniformity of light collection is more important than cross talk, so we have decided to use non-painted bars in the LHCf detector. A simulation of a 100 GeV electron injected in the center of the detector shows that position dependence and cross talk cause only a 0.04 mm shift of the shower centroid without any correction applied. This shows that these effects are relatively small compared to the uncertainty of the beam center position which was 1 mm for the LHCf experiments already performed at √s =7 TeV.

  16. High-Pressure Rare Earth Disilicates REE2Si 2O 7( REE=Nd, Sm, Eu, Gd): Type K

    NASA Astrophysics Data System (ADS)

    Fleet, Michael E.; Liu, Xiaoyang

    2001-10-01

    A new structure type (K) is reported for the disilicates of Nd, Sm, Eu, and Gd made at high pressure. Crystals of type K were synthesized at 10 GPa, 1600-1700°C in an MA6/8 superpress and used for single-crystal X-ray structure study by Kappa CCD diffractometry at room temperature. Crystal data are: monoclinic, space group P21/n, Z=4; Nd2Si2O7-a=6.6658(2), b=6.7234(3), c=12.3975(6) Å, β=102.147(3)°, V=543.2 Å3, R=0.029, and Dx=5.584 g/cm3; Sm2Si2O7-a=6.6039(3), b=6.6849(3), c=12.3069(5) Å, β=102.489(3)°, V=530.4 Å3, R=0.038, and Dx=5.871 g/cm3; Eu2Si2O7-a=6.5777(3), b=6.6652(4), c=12.2668(8) Å, β=102.671(4)°, V=524.7 Å3, R=0.030, and Dx=5.976 g/cm3; Gd2Si2O7-a=6.5558(4), b=6.6469(4), c=12.2394(6) Å, β=102.844(3)°, V=520.0 Å3, R=0.026, and Dx=6.166 g/cm3. The type K structure is built from a diorthosilicate group [Si2O7] interconnected by REE3+ cations in eightfold coordination with oxygen. The bridging oxygen (Si-O-Si) bond angle of the diorthosilicate group of rare earth disilicates stable at 1 bar (types A to G) is related to spatial accommodation of the REE3+ cation and ranges from 130 to 135° in the light rare earth disilicates (types A, F, G) to 180° in Lu2Si2O7 (type C). Volume reduction in the high-pressure type K structure is achieved largely by closure of the Si-O-Si bond angle to 122.7-124.4°, through rigid body rotation of the two SiO4 tetrahedra. This also permits a marginal increase in the average coordination of the REE3+ cation.

  17. Magnetic order of Y3NiSi3-type R3NiSi3 (R=Gd-DY) compounds

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Yapaskurt, V. O.; Nirmala, R.; Malik, S. K.; Quezado, S.; Yao, Jinlei; Mozharivskyj, Y.; Nigam, A. K.; Isnard, O.

    2016-01-01

    Magnetic measurements and neutron powder diffraction investigations on the Y3NiSi3-type R3NiSi3 compounds (R=Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd3NiSi3, Tb3NiSi3 and Dy3NiSi3 indicate antiferromagnetic-like transition at temperatures 260 K, 202 K and 140 K, respectively. Also, the Tb3NiSi3 and Dy3NiSi3 compounds show spin-reorientation transition at 132 K and 99 K, respectively. Below the spin-reorientation transition, the isothermal magnetization curves indicate the metamagnetic-like behavior of Tb3NiSi3 and Dy3NiSi3. The magnetocaloric effect of Dy3NiSi3 is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of -1.2 J/kg K and -1.1 J/kg K for a field change of 50 kOe near 146 K and 92 K, respectively. The neutron diffraction studies of Tb3NiSi3 suggest the magnetic ordering of the Tb2 4j sublattice and no magnetic ordering of the Tb1 2a sublattice. Tb3NiSi3 transforms from the high temperature paramagnetic state to the commensurate high-temperature a- and c-axis antiferromagnet of I‧2/m magnetic space group below 250 K. Below 150 K, the high-temperature antiferromagnet transforms into the low-temperature a-, b- and c-axis antiferromagnet of I‧i magnetic space group. At 1.5 K, the terbium magnetic moment in Tb2 sublattice and its a-, b- and c-axis components reach the values of MTb2=8.2(1) μB, MaTb2=5.9(1) μB, MbTb2=4.3(2) μB and McTb2=3.7(2) μB, respectively.

  18. Investigation of band offsets and direct current leakage properties of nitrogen doped epitaxial Gd{sub 2}O{sub 3} thin films on Si

    SciTech Connect

    Roy Chaudhuri, Ayan; Osten, H. J.; Fissel, A.

    2013-05-14

    Dielectric properties of epitaxial Gd{sub 2}O{sub 3} thin films grown on Si have been found to improve significantly by incorporation of suitable dopants. However, in order to achieve optimum electrical properties from such doped oxides, it is important to understand the correlation between doping and the electronic structure of the material. In the present article, we report about the effect of nitrogen doping on the electronic structure and room temperature dc leakage properties of epitaxial Gd{sub 2}O{sub 3} thin films. Epitaxial Gd{sub 2}O{sub 3}:N thin films were grown on p-type Si (111) substrates by solid source molecular beam epitaxy technique using molecular N{sub 2}O as the nitridation agent. First investigations confirmed the presence of substitutional N in the Gd{sub 2}O{sub 3}:N layers. Incorporation of nitrogen did not affect the structural quality of the oxide layers. X ray photoelectron spectroscopy investigations revealed band gap narrowing in epitaxial Gd{sub 2}O{sub 3} due to nitrogen doping, which leads to reduction in the valence band offset of the Gd{sub 2}O{sub 3}:N layers with Si. DC leakage current measured at room temperature revealed that despite reduction in the band gap and valence band offsets due to N doping, the Gd{sub 2}O{sub 3}:N layers remain sufficiently insulating. A significant reduction of the leakage current densities in the Gd{sub 2}O{sub 3}:N layers with increasing nitrogen content suggests that doping of epitaxial Gd{sub 2}O{sub 3} thin films with nitrogen can be an effective route to eliminate the adverse effects of the oxygen vacancy induced defects in the oxide layers.

  19. Magnetic nanoparticles induced dielectric enhancement in (La, Gd)2O3: SiO2 composite systems

    NASA Astrophysics Data System (ADS)

    Kao, T. H.; Mukherjee, S.; Yang, H. D.

    2013-11-01

    Magnetic Gd2O3 and non-magnetic La2O3 nanoparticles (NPs) have been synthesized together with different doping concentrations in SiO2 matrix via sol-gel route calcination at 700 °C and above. Properly annealed NP-glass composite systems show enhancement of dielectric constant and magnetodielectric effect (MDE) near room temperature, depending on superparamagnetic NPs concentrations. From application point of view, the enhancement of dielectric constant along with MDE can be achieved by tuning the NPs size through varying calcination temperature and/or increasing the doping concentration of magnetic rare earth oxide.

  20. Study on energy transfer and energy migration of Ca2Gd8(SiO4)6O2:Dy3+ phosphor films.

    PubMed

    Wang, X Q; Han, X M; Zhen, C M

    2011-11-01

    Being a kind of rare-earth-metal silicate with oxidapatite structure, Ca2R8(SiO4)6O2 (R = Y, Gd, La) is a promising material doped with rare earth, and widely used as phosphors. In this thesis, Ca2Gd8(SiO4)6O2:Dy3+ films were prepared by the sol-gel method. X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. AFM study indicated that the phosphor films consisted of 120 nm homogeneous particles. By combining the model of Burshtein for donor-donor migration and the V-F-B model for donor-acceptor energy transfer, the experimental luminescence decay curve of 6P(J) state of Gd3+ was re-simulated. It is found that concentration quenching of Gd3+ can be due to the result of the joint action of donor-donor (Gd3+-Gd3+) energy migration and donor-acceptor (Gd3+-Dy3+) energy transfer. PMID:22413278

  1. Performance of Ce-doped (La, Gd)2Si2O7 scintillator with an avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Shishido, Toetsu; Suzuki, Akira; Pejchal, Jan; Yokota, Yuui; Yoshikawa, Akira

    2014-04-01

    Scintillation properties of Ce-doped (La, Gd)2Si2O7 (Ce:La-GPS) crystal were measured with Si avalanche photodiode (APD, Hamamatsu S8664-55). Since Ce:La-GPS is a novel scintillator, its scintillation properties have been evaluated using the APD for the first time. This crystal grown by floating zone method had a good light output of 41,000±1000 photons/MeV and FWHM energy resolution at 662 keV was 4.4±0.1% at 23.0±0.2 °C. The photon non-proportional response (PNR) of Ce:La-GPS was approximately 65% at 32 keV, where light output at 662 keV was normalized to 100%. Moreover, the temperature dependence of the light outputs was determined to be approximately 0.15%/°C from -10 to 30 °C.

  2. Low field magneto caloric effect in (Gd1-x Prx)5 Si3.2 Sn0.8 alloys

    NASA Astrophysics Data System (ADS)

    Xavier, J.; Saban, K. V.

    2015-02-01

    The structural, thermal and magnetic properties of the arc melted (Gd1-x Prx)5 Si3.2 Sn0.8 alloys with x = 0, 0.05, 0.1 and 0.15 were studied. A maximum magnetic entropy change of 1.2034 J/kgK occurs for the x = 0.1 alloy at 299 K for a low magnetic field change of 1.58 T. The Arrott plot technique confirms a second order ferromagnetic to paramagnetic phase transition in all these Si rich orthorhombic samples. Tuneable Tc around room temperature, moderate values of ΔSm in low magnetic fields and absence of magnetic hysteresis make these alloys useful with regard to room temperature magnetic refrigeration.

  3. Superior dielectric properties for template assisted grown (100) oriented Gd{sub 2}O{sub 3} thin films on Si(100)

    SciTech Connect

    Roy Chaudhuri, Ayan Osten, H. J.; Fissel, A.

    2014-01-06

    We report about the single crystalline growth and dielectric properties of Gd{sub 2}O{sub 3}(100) thin films on Si(100) surface. Using a two step molecular beam epitaxy growth process, we demonstrate that controlled engineering of the oxide/Si interface is a key step to achieve the atypical (100) oriented growth of Gd{sub 2}O{sub 3}. Unusually, high dielectric constant values (∼23–27) were extracted from capacitance voltage measurements. Such effect can be understood in terms of a two dimensional charge layer at the Gd{sub 2}O{sub 3}/Si interface (W. Sitaputra and R. Tsu, Appl. Phys. Lett. 101, 222903 (2012)) which can influence the dielectric properties of the oxide layer by forming an additional negative quantum capacitance.

  4. Improvement of Bipolar Switching Properties of Gd:SiOx RRAM Devices on Indium Tin Oxide Electrode by Low-Temperature Supercritical CO2 Treatment

    NASA Astrophysics Data System (ADS)

    Chen, Kai-Huang; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Liang, Shu-Ping; Young, Tai-Fa; Syu, Yong-En; Sze, Simon M.

    2016-02-01

    Bipolar switching resistance behaviors of the Gd:SiO2 resistive random access memory (RRAM) devices on indium tin oxide electrode by the low-temperature supercritical CO2-treated technology were investigated. For physical and electrical measurement results obtained, the improvement on oxygen qualities, properties of indium tin oxide electrode, and operation current of the Gd:SiO2 RRAM devices were also observed. In addition, the initial metallic filament-forming model analyses and conduction transferred mechanism in switching resistance properties of the RRAM devices were verified and explained. Finally, the electrical reliability and retention properties of the Gd:SiO2 RRAM devices for low-resistance state (LRS)/high-resistance state (HRS) in different switching cycles were also measured for applications in nonvolatile random memory devices.

  5. Improvement of Bipolar Switching Properties of Gd:SiOx RRAM Devices on Indium Tin Oxide Electrode by Low-Temperature Supercritical CO2 Treatment.

    PubMed

    Chen, Kai-Huang; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Liang, Shu-Ping; Young, Tai-Fa; Syu, Yong-En; Sze, Simon M

    2016-12-01

    Bipolar switching resistance behaviors of the Gd:SiO2 resistive random access memory (RRAM) devices on indium tin oxide electrode by the low-temperature supercritical CO2-treated technology were investigated. For physical and electrical measurement results obtained, the improvement on oxygen qualities, properties of indium tin oxide electrode, and operation current of the Gd:SiO2 RRAM devices were also observed. In addition, the initial metallic filament-forming model analyses and conduction transferred mechanism in switching resistance properties of the RRAM devices were verified and explained. Finally, the electrical reliability and retention properties of the Gd:SiO2 RRAM devices for low-resistance state (LRS)/high-resistance state (HRS) in different switching cycles were also measured for applications in nonvolatile random memory devices. PMID:26831690

  6. Fabrication of a novel nanocomposite Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for large enhancement upconversion luminescence.

    PubMed

    Yin, Dongguang; Cao, Xianzhang; Zhang, Lu; Tang, Jingxiu; Huang, Wenfeng; Han, Yanlin; Wu, Minghong

    2015-06-28

    Upconversion nanocrystals have a lot of advantages over other fluorescent materials. However, their applications are still limited due to their comparatively low upconversion luminescence (UCL). In the present study, a novel nanocomposite of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er for enhancing UCL was fabricated successfully, and its morphology, crystalline phase, composition, and fluorescent property were investigated. It is interesting to find that the Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er and Ag@SiO2-NaLuF4:Yb,Gd,Er nanocomposites showed high UCL enhancements of 52- and 10-fold compared to the control of Ag-free nanocomposite SiO2-NaLuF4:Yb,Gd,Er, respectively. The enhancement of 52-fold is greater than those reported in our previous studies and some papers. Moreover, the measured life times of the Ag-presented nanocrystals were longer than that of Ag-absent counterparts. These enhancements of UCL can be ascribed to the effect of metal-enhanced fluorescence, which is caused by the enhancement of the local electric field. The UCL intensity of Ag/graphene@SiO2-NaLuF4:Yb,Gd,Er was 5.2-fold higher than that of Ag@SiO2-NaLuF4:Yb,Gd,Er, indicating that graphene presented in the fabricated nanocomposite structure favors metal-enhanced UCL. The small-sized Ag nanoparticles anchored on the graphene sheet mutually enhanced each other's polarizability and surface plasmon resonance, resulting in a big metal-enhanced UCL. This study provides a new strategy for effectively enhancing the UCL of upconversion nanocrystals. The enhancement potentially increases the overall upconversion nanocrystal detectability for highly sensitive biological, medical, and optical detections. PMID:25999289

  7. Epitaxial growth of Sc2O3 films on Gd2O3-buffered Si substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Paulraj, Joseph; Wang, Rongping; Sellars, Matthew; Luther-Davies, Barry

    2016-04-01

    We investigated the optimal conditions to prepare high-quality Sc2O3 films on Gd2O3-buffered Si wafers using pulsed laser deposition technique with an aim at developing waveguide devices that can transform the performance of the gradient echo quantum memory based on bulk crystals. Under the optimal conditions, only oxide and Si (2 2 2) peaks appeared in the X-ray diffraction pattern. The Sc2O3 (2 2 2) diffraction peak was located at 2 θ = 31.5° with a full width at half maxima (FWHM) of 0.16°, and its rocking curve had a FWHM of 0.10°. In-plane epitaxial relationship was confirmed by X-ray pole figure where Sc2O3 (1 1 1) was parallel to Si (1 1 1). High-resolution TEM images indicated clear interfaces and perfect lattice images with sharp electron diffraction dots. All these results confirm that the oxide films on Si were single crystalline with high quality.

  8. Planar SiC MEMS flame ionization sensor for in-engine monitoring

    NASA Astrophysics Data System (ADS)

    Rolfe, D. A.; Wodin-Schwartz, S.; Alonso, R.; Pisano, A. P.

    2013-12-01

    A novel planar silicon carbide (SiC) MEMS flame ionization sensor was developed, fabricated and tested to measure the presence of a flame from the surface of an engine or other cooled surface while withstanding the high temperature and soot of a combustion environment. Silicon carbide, a ceramic semiconductor, was chosen as the sensor material because it has low surface energy and excellent mechanical and electrical properties at high temperatures. The sensor measures the conductivity of scattered charge carriers in the flame's quenching layer. This allows for flame detection, even when the sensor is situated several millimetres from the flame region. The sensor has been shown to detect the ionization of premixed methane and butane flames in a wide temperature range starting from room temperature. The sensors can measure both the flame chemi-ionization and the deposition of water vapour on the sensor surface. The width and speed of a premixed methane laminar flame front were measured with a series of two sensors fabricated on a single die. This research points to the feasibility of using either single sensors or arrays in internal combustion engine cylinders to optimize engine performance, or for using sensors to monitor flame stability in gas turbine applications.

  9. [U(III) {N(SiMe2 tBu)2 }3 ]: a structurally authenticated trigonal planar actinide complex.

    PubMed

    Goodwin, Conrad A P; Tuna, Floriana; McInnes, Eric J L; Liddle, Stephen T; McMaster, Jonathan; Vitorica-Yrezabal, Inigo J; Mills, David P

    2014-11-01

    We report the synthesis and characterization of the uranium(III) triamide complex [U(III) (N**)3 ] [1, N**=N(SiMe2 tBu)2 (-) ]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three-coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [U(III) (N**)3 ] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [U(III) (N")3 ] (N"=N(SiMe3 )2 (-) ), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [U(III) (N")3 ], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of U(III) single-molecule magnets. PMID:25241882

  10. [UIII{N(SiMe2tBu)2}3]: A Structurally Authenticated Trigonal Planar Actinide Complex

    PubMed Central

    Goodwin, Conrad AP; Tuna, Floriana; McInnes, Eric JL; Liddle, Stephen T; McMaster, Jonathan; Vitorica-Yrezabal, Inigo J; Mills, David P

    2014-01-01

    We report the synthesis and characterization of the uranium(III) triamide complex [UIII(N**)3] [1, N**=N(SiMe2tBu)2−]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three-coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [UIII(N**)3] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [UIII(N“)3] (N”=N(SiMe3)2−), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [UIII(N“)3], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of UIII single-molecule magnets. PMID:25241882

  11. The electronic structure and spin polarization of Co2Mn0.75(Gd, Eu)0.25Z (Z=Si, Ge, Ga, Al) quaternary Heusler alloys

    NASA Astrophysics Data System (ADS)

    Berri, Saadi

    2016-03-01

    A first-principles approach is used to study the electronic and magnetic properties of Co2Mn0.75(Gd, Eu)0.25Z(Z=Si, Ge, Ga, Al) quaternary Heusler alloys. The investigation was done using the (FP-LAPW) method where the exchange-correlation potential was calculated with the frame of GGA-WC. At ambient conditions our calculated results of band structures reveal that for Co2Mn0.75(Gd, Eu)0.25Z(Z=Si, Ge) has a half-metallic (HM) band structure profile showing 100% spin polarization at the Fermi level. In contrast, Co2Mn0.75(Gd, Eu)0.25Z(Z=Ga, Al) alloys are found to be metallic. Finally, the half metallic compounds found in some structures of this series might be useful in spintronic devices.

  12. Annealing influence on the magnetostructural transition in Gd5Si1.3Ge2.7 thin films

    DOE PAGESBeta

    Pires, A. L.; Belo, J. H.; Gomes, I. T.; Hadimani, R. L.; Jiles, D. C.; Fernandes, L.; Tavares, P. B.; Araújo, J. P.; Lopes, A. M. L.; Pereira, A. M.

    2015-05-19

    Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 500ºC, the samples showed a typical paramagnetic behavior. On the other hand, thermal treatments below 500ºC promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition around 249 Kmore » is not affected. This magnetostructural transition extinction was reflected in the magnetocaloric behavior and resulted in a drastic decrease in the entropy change peak value (of about 68%). An increase in TC was reported, proving that at the nanoscale, heat treatments may be a useful tool to optimize the magnetocaloric properties in Gd5(SixGe1-x)4 thin films.« less

  13. Light coupling between vertical III-As nanowires and planar Si photonic waveguides for the monolithic integration of active optoelectronic devices on a Si platform.

    PubMed

    Giuntoni, Ivano; Geelhaar, Lutz; Bruns, Jürgen; Riechert, Henning

    2016-08-01

    We present a new concept for the optical interfacing between vertical III-As nanowires and planar Si waveguides. The nanowires are arranged in a two-dimensional array which forms a grating structure on top of the waveguide. This grating enables light coupling in both directions between the components made from the two different material classes. Numerical simulations show that this concept permits a light extraction efficiency from the waveguide larger than 45% and a light insertion efficiency larger than 35%. This new approach would allow the monolithic integration of nanowire-based active optoelectronics devices, like photodetectors and light sources, on the Si photonics platform. PMID:27505805

  14. White light emitting LaGdSiO5:Dy3+ nanophosphors for solid state lighting applications

    NASA Astrophysics Data System (ADS)

    Ogugua, Simon N.; Swart, Hendrik C.; Ntwaeaborwa, Odireleng M.

    2016-01-01

    Powdered dysprosium (Dy3+) doped Lanthanum gadolinium oxyorthosilicate (LaGdSiO5) mixed phosphors were synthesized using urea-assisted solution combustion method. The X-ray diffractometer analysis showed that the samples crystalized in the pure monoclinic mixed phase of LaGdSiO5. The crystallite size and the lattice strain calculated from the X-ray diffraction peaks using Williamson-Hall equation varied from 12 nm to 16 nm and 1.6 ×10-2 to 2.43 ×10-2 respectively. The photoluminescence (PL) emission spectra recorded using 425, 454 and 475 nm excitation wavelengths exhibit characteristic similar to the YAG:Ce phosphor pumped InGaN LED system, by absorbing portion of the excitation energy and re-emitting it. The emission spectra were characterized by radiative recombination at 425, 454, 475, 485 and 575 nm depending on the excitation wavelength. These emission line are ascribed to the f→f transitions of Dy3+. The peak intensity and hence the color of the emitted visible light were dependent on the concentration of Dy3+. The International Commission on Illumination (CIE) color coordinates of (0.336, 0.313) and (0.359, 0.361) were obtained for Dy3+ molar concentration of 0.05 and 3.0 mol% when the emission was monitored using 454 nm and 475 nm respectively. The band gap measured from the reflectance curve using Tauc plot initially decreased with increasing Dy3+ concentration, but at higher concentration, it started to increase. These materials were evaluated for solid state lighting application.

  15. Properties of planar Nb/{alpha}-Si/Nb Josephson junctions with various degrees of doping of the {alpha}-Si layer

    SciTech Connect

    Gudkov, A. L.; Kupriyanov, M. Yu.; Samus', A. N.

    2012-05-15

    The properties of Nb/{alpha}-Si/Nb planar Josephson junctions with various degrees of doping of the amorphous silicon layer are experimentally studied. Tungsten is used as a doping impurity. The properties of the Josephson junctions are shown to change substantially when the degree of doping of the {alpha}-Si layer changes: a current transport mechanism and the shape of the current-voltage characteristic of the junctions change. Josephson junctions with SNS-type conduction are formed in the case of a fully degenerate {alpha}-Si layer. The properties of such junctions are described by a classical resistive model. Josephson junctions with a resonance mechanism of current transport through impurity centers are formed at a lower degree of doping of the {alpha}-Si layer. The high-frequency properties of such junctions are shown to change. The experimental results demonstrate that these junctions are close to SINIS-type Josephson junctions.

  16. Enhanced luminescence intensity and color purity of the red emitting LnVO{sub 4}:Eu{sup 3+}@ SiO{sub 2} (Ln = Gd, Y and Gd/Y) powder phosphors

    SciTech Connect

    Rambabu, U.; Han, Sang-Do

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Tetragonal phase lanthanide vanadates doped with Eu{sup 3+} were synthesized. ► Luminescence enhancement was done by optimizing the host (Gd,Y) and SiO{sub 2} coatings. ► SiO{sub 2} coating was characterized by SEM-EDAX, FT-IR and PL techniques. ► {sup 5}D{sub 0} → {sup 7}F{sub 2} domination over {sup 5}D{sub 0} → {sup 7}F{sub 1} indicates the absence of an inversion symmetry. ► Y{sub 0.95}VO{sub 4}:Eu{sup 3+}@ SiO{sub 2}(10 vol.%) is found to be a novel enhanced red emitting phosphor. -- Abstract: An attempt was made to enhance the luminescence properties of LnVO{sub 4}:Eu{sup 3+}@ SiO{sub 2} (Ln = Gd, Y and Gd/Y) powder phosphors. Pure phase with tetragonal structure of the produced phosphors was confirmed by XRD profiles. Sub-micron sized phosphors have shown 35% more PL intensity than the bulk, which was further improved 20.22% with SiO{sub 2} shell coating. SiO{sub 2} shell coating was optimized by SEM-EDAX, FT-IR, PL and TEM measurements. Emission intensities of the transition, {sup 5}D{sub 0} → {sup 7}F{sub 2} have dominated {sup 5}D{sub 0} → {sup 7}F{sub 1}, which indicated the lowering of an inverse symmetry in the vicinity of Eu{sup 3+} ions. Luminescence intensity and color purity were enhanced with the host modification by substituting Gd{sup 3+} with Y{sup 3+} sites, followed by SiO{sub 2} coating. Based on the systematic investigations carried out, the phosphor Y{sub 0.95}VO{sub 4}:Eu{sup 3+}{sub 0.05}@ SiO{sub 2} is suggested to be a novel contender for its suitable red emission in certain displays or lighting.

  17. Second order phase transition temperature of single crystals of Gd5Si1.3Ge2.7 and Gd5Si1.4Ge2.6

    SciTech Connect

    Hadimani, R. L.; Melikhov, Y.; Schlagel, D. L.; Lograsso, T. A.; Dennis, K. W.; McCallum, R. W.; Jiles, D. C.

    2015-01-30

    Gd5(SixGe1–x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3Ge2.7 and Gd5Si1.4Ge2.6. In this study, we have investigated the first order and second order phase transition temperatures of these samples using magnetic moment vs. temperature and magnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.

  18. Selected AB₄²-/- (A = C, Si, Ge; B = Al, Ga, In) Ions: a Battle Between Covalency and Aromaticity, and Prediction of Square Planar Si in SiIn₄²-/-

    SciTech Connect

    Alexandrova, Anastassia N.; Nayhouse, Michael J.; Huynh, Mioy T.; Kuo, Jonathan L.; Melkonian, Arek V.; Chavez, Gerardo; Hernando, Nina M.; Kowal, Matthew D.; Liu, Chi-Ping

    2012-11-21

    CAl₄²-/- (D₄h, ¹A₁g) is is a cluster ion that has been established to be planar, aromatic, and contain a tetracoordinate planar C atom. Valence isoelectronic substitution of C with Si and Ge in this cluster leads to a radical change of structure toward distorted pentagonal species. We find that this structural change goes together with the cluster acquiring partial covalency of bonding between Si/Ge and Al₄, facilitated by hybridization of the atomic orbitals (AOs). Counter intuitively, for the AAl₄²-/- (A = C, Si, Ge) clusters, hybridization in the dopant atom is strengthened from C, to Si, and to Ge, even though typically AOs are more likely to hybridize if they are closer in energy (i.e. in earlier elements in the Periodic Table). The trend is explained by the better overlap of the hybrids of the heavier dopants with the orbitals of Al₄. From the thus understood trend, it is inferred that covalency in such clusters can be switched off, by varying the relative sizes of the AOs of the main element and the dopant. Using this mechanism, we then successfully killed covalency in Si, and predicted a new aromatic cluster ion containing a tetracoordinate square planar Si, SiIn₄²-/-.

  19. Structural, electronic, and magnetic properties of heterofullerene C(58)Si with odd number of atoms and a near planar tetracoordinate Si atom.

    PubMed

    Liu, Feng-Ling; Jalbout, Abraham F

    2008-06-01

    Density functional calculations and minimization techniques have been employed to characterize the structural and electronic properties of [5,6]-heterofullerene-C(58)Si-C(2v). Since it has odd number of atoms and a near planar tetracoordinate Si atom on the skeleton of the cage, it has odd number of atoms assembling a cage and is a novel molecule. Vibrational frequencies of the molecule have been calculated at the B3LYP/6-31G* level of theory. The absence of imaginary vibrational frequency confirms that the molecule corresponds to a true minimum on the potential energy hypersurface. Sixteen (13)C nuclear magnetic resonance (NMR) spectral signals of C(58)Si are characterized, and its heat of formation was estimated in this work. PMID:18328755

  20. Magnesium substitutions in rare-earth metal germanides with the Gd5Si4 type. Synthesis, structure determination and magnetic properties of RE5-xMgxGe4 (RE=Gd-Tm, Lu and Y)

    SciTech Connect

    Sarrao, J L; Thompson, Joe D; Tobash, P H; Bobev, S

    2009-01-01

    A series of magnesium-substituted rare-earth metal germanides with a general formula RE{sub 5-x}Mg{sub x}Ge{sub 4} (x {approx} 1.0-2.3; RE =Gd-Tm, Lu, Y) have been synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. These compounds crystallize with the common Gd{sub 5}Si{sub 4} type in the orthorhombic space group Pnma (No. 62; Z =4; Pearson's code oP36) and do not appear to undergo temperature-induced crystallographic phase transitions down to 120 K. Replacing rare-earth metal atoms with Mg, up to nearly 45 % at., reduces the valence electron count and is clearly expressed in the subtle changes of the Ge-Ge and metal-metal bonding. Magnetization measurements as a function of the temperature and the applied field reveal complex magnetic structures at cryogenic temperatures, and Curie-Weiss paramagnetic behavior at higher temperatures. The observed local moment magnetism is consistent with RE+ ground states in all cases. In the magnetically ordered phases, the magnetization cannot reach saturation in fields up to 50 kOe. The structural trends across the series and the variations of hte magnetic properties as a function of the Mg content are also discussed. KEYWORDS: Rare-earth intermetallics, germanides, crystal structure,Gd{sub 5}Si{sub 4} type.

  1. Characterization of 3D and planar Si diodes with different neutron converter materials

    NASA Astrophysics Data System (ADS)

    Mendicino, R.; Boscardin, M.; Carturan, S.; Betta, G.-F. Dalla; Palma, M. Dalla; Maggioni, G.; Quaranta, A.; Ronchin, S.

    2015-10-01

    In this paper, we report on the characterization of silicon 3D and planar sensors, coupled with different neutron converter materials, such as 10B, B104 C and 6LiF, with different deposition thickness. Selected results from the electrical and functional characterization of the devices are shown and comparatively discussed with the aid of SRIM and Geant4 simulations. The limited neutron detection efficiency, on the order of ≃ 1% (planar) and ≃ 8% (3D) from simulations, is understood, and hints for the optimization of the devices have been derived.

  2. Magnetic Field Induced Phase Transitions in Gd5(Si1.95Ge2.05)Single Crystal and the Anisotropic Magnetocaloric Effect

    SciTech Connect

    H. Tang; V.K. Pecharsky; A.O. Pecharsky; D.L. Schlagel; T.A. Lograsso; K.A. Gschneidner,jr.

    2004-09-30

    The magnetization measurements using a Gd{sub 5}(Si{sub 1.95}Ge{sub 2.05}) single crystal with the magnetic field applied along three crystallographic directions, [001], [010] and [100], were carried out as function of applied field (0-56 kOe) at various temperatures ({approx}5-320 K). The magnetic-field induced phase transformations at temperature above the zero-field critical temperature, i.e. the paramagnetic (PM) {leftrightarrow} ferromagnetic (FM) transitions with application or removal of magnetic field, are found to be temperature dependent and hysteretic. The corresponding critical fields increase with increasing temperature. The magnetic field (H)-temperature (T) phase diagrams have been constructed for the Gd{sub 5}(Si{sub 1.95}Ge{sub 2.05}) single crystal with field along the three directions. A small anisotropy has been observed. The magnetocaloric effect (MCE) has been calculated from the isothermal magnetization data, and the observed anisotropy correlates with H-T phase diagrams. The results are discussed in connection with the magnetic-field induced martensitic-like structural transition observed in the Gd{sub 5}(Si{sub 2}Ge{sub 2})-type compounds.

  3. A comparative investigation of Lu2SiO5:Ce and Gd2O2S:Eu powder scintillators for use in x-ray mammography detectors

    NASA Astrophysics Data System (ADS)

    Michail, C. M.; Fountos, G. P.; David, S. L.; Valais, I. G.; Toutountzis, A. E.; Kalyvas, N. E.; Kandarakis, I. S.; Panayiotakis, G. S.

    2009-10-01

    The dominant powder scintillator in most medical imaging modalities for decades has been Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Apart from Gd2O2S:Tb, there are alternative powder phosphor scintillators such as Lu2SiO5:Ce and Gd2O2S:Eu that have been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital mammography detectors such as CCDs. Lu2SiO5:Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purposes of the present study, two scintillating screens, one from Lu2SiO5:Ce and the other from Gd2O2S:Eu powders, were prepared using the method of sedimentation. The screen coating thicknesses were 25.0 and 33.1 mg cm-2 respectively. The screens were investigated by evaluating the following parameters: the output signal, the modulation transfer function, the noise equivalent passband, the informational efficiency, the quantum detection efficiency and the zero-frequency detective quantum efficiency. Furthermore, the spectral compatibility of those materials with various optical detectors was determined. Results were compared to published data for the commercially employed 'Kodak Min-R film-screen system', based on a 31.7 mg cm-2 thick Gd2O2S:Tb phosphor. For Gd2O2S:Eu, MTF data were found comparable to those of Gd2O2S:Tb, while the MTF of Lu2SiO5:Ce was even higher resulting in better spatial resolution and image sharpness properties. On the other hand, Gd2O2S:Eu was found to exhibit higher output signal and zero-frequency detective quantum efficiency than Lu2SiO5:Ce.

  4. A promising RVO4:Eu(3+), Li(+)@SiO2 (R = Gd, Y and Gd/Y) red-emitting phosphor with improved luminescence (cd/m(2)) and colour purity for optical display applications.

    PubMed

    Rambabu, Urlagaddala; Munirathnam, Nagegownivari Ramachandra; Reddy, Busireddy Sudhakar; Chatterjee, Sandip

    2016-02-01

    Red emission intensity was optimized in three stages, by investigating the effects of: (i) host composition (Gd, Y and Gd/Y), (ii) codoping Li(+) as a sensitizer and, finally, (iii) with a SiO2 shell coating as a protecting layer. Lanthanide vanadate powder phosphors were synthesized using a modified colloidal precipitation technique. The effects of SiO2 coating on phosphor particles were characterized using scanning electron microscopy (SEM)-EDAX, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and photoluminescence (PL) measurements. An improvement in the PL intensity on Li codoping was due to improved crystallinity, which led to higher oscillating strengths for the optical transitions, and also a lowering of the inversion symmetry of Eu(3+) ions. Red emission intensity due to (5)D0  → (5)D2 transition of the phosphor Y0.94VO4:Eu(3+)0.05, Li(+)0.01 was enhanced by 22.28% compared with Y0.95VO4:Eu(3+)0.05, and was further improved by 58.73% with SiO2 coating. The luminescence intensity (I) and colour coordinates (x, y) of the optimized phosphor Y0.94VO4:Eu(3+)0.05, Li(+)0.01@SiO2, where I = 13.07 cd/m(2) and (x = 0.6721, y = 0.3240), were compared with values for a commercial red phosphor (Y2O2S:Eu(3+)), where I = 27 cd/m(2) and (x = 0.6522, y = 0.3437). The measured colour coordinates are superior to those of the commercial red phosphor, and moreover, match well with standard NTSC values (x = 0.67, y = 0.33). PMID:25989734

  5. Determination of energy loss of 1200 keV deuterons along axial and planar channels of Si

    NASA Astrophysics Data System (ADS)

    Shafiei, S.; Lamehi-Rachti, M.

    2015-02-01

    In this paper, the energy loss of 1200 keV deuterons along the <1 0 0> and <1 1 0> axes as well as the {1 0 0} and {1 1 0} planes of Si were determined by the simulation of the channeling Rutherford backscattering spectra. The simulation was done by taking two considerations into account: (i) a minimum random component of the beam which enters the sample because of the scattering ions from the surface, (ii) the dechanneling starts at greater penetration depths, xDech. Moreover, it was assumed that the dechanneling follows a Gompertz type sigmoidal function with two parameters k and xc which present the dechanneling rate and range, respectively. The best simulation parameters, penetration depth at which the dechanneling starts, energy loss and dechanneling rate and range, were chosen by using the Levenberg-Marquardt algorithm. The experimental results are well reproduced by this simulation. The ratio of channeling energy loss to the random is changed from 0.63 ± 0.02 along the <1 1 0> axial channel to the 0.91 ± 0.02 along the {1 0 0} planar direction. The differences in the energy loss and the dechanneling process along the axial and planar channels are attributed to the potential barrier and the fractional area of each channel blocked by atoms. The ratio of channeling to random energy loss of deuterons along the <1 0 0> axial direction is in agreement with another reference.

  6. Superconductivity above 90 K in the square-planar compound system ABa2Cu3O(6 + x) with A = Y, La, Nd, Sm, Eu, Gd, Ho, Er, and Lu

    NASA Technical Reports Server (NTRS)

    Hor, P. H.; Meng, R. L.; Wang, Y. Q.; Gao, L.; Huang, Z. J.

    1987-01-01

    Superconductivity has been found in the 90-K range in ABa2Cu3O(6 + x) with A = La, Nd, Sm, Eu, Gd, Ho, Er, and Lu in addition to Y. The results suggest that the unique square-planar Cu atoms, each surrounded by four or six oxygen atoms, are crucial to the superconductivity of oxides in general. In particular, the high Tc of ABa2Cu3O(6 + x) is attributed mainly to the quasi-two-dimensional assembly of the CuO2-Ba-CuO(2 + x)Ba-CuO2 layers sandwiched between two A layers, with particular emphasis in the CuO(2 + x) layers. Higher-Tc oxides are predicted for compounds with bigger assemblies of CuO2 layers coupled by Ba layers.

  7. Planar electron-tunneling Si/Si0.7Ge0.3 triple-barrier resonant tunneling diode formed on undoped strain-relaxed buffer with flat surface

    NASA Astrophysics Data System (ADS)

    Okubo, Takafumi; Tsukamoto, Takahiro; Suda, Yoshiyuki

    2014-03-01

    We demonstrated a planar electron-tunneling Si/Si0.7Ge0.3 triple-barrier (TB) resonant tunneling diode (RTD) formed via a channel layer on an undoped strain-relaxed quadruple-Si1-xGex-layer (QL) buffer. Compared with a conventional vertical Si/Si0.7Ge0.3 TB RTD formed on a heavily doped QL buffer, the dislocation density is low, the surface is flat, and the resonance current density is much larger. These observations, together with analyses of current-voltage (I-V) curve fitting to the physics-based analytical expression, suggest that the enhanced I-V characteristics in the planar RTD are related to decreases in the number of crystalline defect states and the structural and potential fluctuations.

  8. New tetragonal derivatives of cubic NaZn13-type structure: RNi6Si6 compounds, crystal structure and magnetic ordering (R=Y, La, Ce, Sm, Gd-Yb)

    NASA Astrophysics Data System (ADS)

    Pani, M.; Manfrinetti, P.; Provino, A.; Yuan, Fang; Mozharivskyj, Y.; Morozkin, A. V.; Knotko, A. V.; Garshev, A. V.; Yapaskurt, V. O.; Isnard, O.

    2014-02-01

    Novel RNi6Si6 compounds adopt the new CeNi6Si6-type structure for R=La-Ce (tP52, space group P4/nbm N 125-1) and new YNi6Si6-type structure for R=Y, Sm, Gd-Yb (tP52, space group P4barb2N 117) that are tetragonal derivative of NaZn13-type structure, like LaCo9Si4-type. The CeNi6Si6, GdNi6Si6, TbNi6Si6, DyNi6Si6 and HoNi6Si6 compounds are Curie-Weiss paramagnets down to ~30 K, and do not order magnetically down to 5 K. However, the inverse paramagnetic susceptibility of LaNi6Si6 does not follow Curie-Weiss law. The DyNi6Si6 shows ferromagnetic-like saturation behaviour at 5 K in applied fields of 50 kOe, giving rise to a magnetic moment value of 6.5 μB/f.u. in 50 kOe. The powder neutron diffraction study in zero applied filed indicates square modulated the c-collinear antiferromagnetic ordering of TbNi6Si6 with K=[±1/4, ±1/4, 0] wave vector below ~10 K. The CeNi6Si6, GdNi6Si6, TbNi6Si6, DyNi6Si6 and HoNi6Si6 compounds are Curie-Weiss paramagnets down to ~30 K, and do not order magnetically down to 4.2 K. The powder neutron diffraction study in zero applied filed indicates square modulated the c-collinear antiferromagnetic ordering of TbNi6Si6 with K=[±1/4, ±1/4, 0] wave vector below ~10 K.

  9. Investigation of crystallinity and planar defects in the Si nanowires grown by vapor-liquid-solid mode using indium catalyst for solar cell applications

    NASA Astrophysics Data System (ADS)

    Ajmal Khan, Muhammad; Ishikawa, Yasuaki; Kita, Ippei; Tani, Ayumi; Yano, Hiroshi; Fuyuki, Takashi; Konagai, Makoto

    2016-01-01

    Stacking-fault-free and planar defect (twinning plane)-free In-catalyzed Si nanowires (NWs) are essential for carrier transport and nanoscale device applications. In this article, In-catalyzed, vertically aligned, and cone-shaped Si NWs on Si(111) were grown successfully, in the vapor-liquid-solid (VLS) mode. In particular, the influences of substrate temperature (TS) and cooling rate (ΔTS/Δt) on the formation of planar defects, twinning planes along the [112] direction, and stacking faults in Si NWs were investigated. When TS was decreased from 600 °C to room temperature at a rate of 100 °C/240 s after Si NW growth, twinning plane defects perpendicular to the substrate and along different segments of (111)-oriented Si NWs were observed. Finally, one simple model was proposed to explain the stacking fault formation as well as Si NW length limitation due to the In-nanoparticle (In-NP) migration, and root causes of the twinning plane defects in the Si-NWs.

  10. Annealing influence on the magnetostructural transition in Gd5Si1.3Ge2.7 thin films

    SciTech Connect

    Pires, A. L.; Belo, J. H.; Gomes, I. T.; Hadimani, R. L.; Jiles, D. C.; Fernandes, L.; Tavares, P. B.; Araújo, J. P.; Lopes, A. M. L.; Pereira, A. M.

    2015-05-19

    Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 500ºC, the samples showed a typical paramagnetic behavior. On the other hand, thermal treatments below 500ºC promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition around 249 K is not affected. This magnetostructural transition extinction was reflected in the magnetocaloric behavior and resulted in a drastic decrease in the entropy change peak value (of about 68%). An increase in TC was reported, proving that at the nanoscale, heat treatments may be a useful tool to optimize the magnetocaloric properties in Gd5(SixGe1-x)4 thin films.

  11. Designed synthesis of multi-functional PEGylated Yb2O3:Gd@SiO2@CeO2 islands core@shell nanostructure.

    PubMed

    Li, Junqi; Yao, Shuang; Song, Shuyan; Wang, Xiao; Wang, Yinghui; Ding, Xing; Wang, Fan; Zhang, Hongjie

    2016-07-28

    Nanomaterials that can restrain or reduce the production of excessive reactive oxygen species such as H2O2 to defend and treat against Alzheimer's disease (AD) have attracted much attention. In this paper, we adopt the strategy of layer-by-layer deposition; namely, first synthesizing available gadolinium-doped ytterbia nanoparticles (Yb2O3:Gd NPs) as cores, and then coating them with silica via the classical Stöber method to prevent leakage and act as a carrier for subsequent ceria deposition and PEGylation, and finally obtain the expected core@shell-structured nanocomposite of PEGylated Yb2O3:Gd@SiO2@CeO2 islands. The nanomaterial has proved not only to be a high-performance dual-modal contrast agent for use in MRI and CT, but also to exhibit excellent catalase mimetic activity, which may help the prognosis, diagnosis and treatment of AD in the future. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy characterization have revealed the successful design and synthesis of the cores with remarkable size uniformity, with well-distributed CeO2 islands decorated on the surface of SiO2 shells, and tightly immobilized PEG. PMID:27351951

  12. Planar versus puckered nets in the polar intermetallic series EuGaTt (Tt = Si, Ge, Sn).

    PubMed

    You, Tae-Soo; Grin, Yuri; Miller, Gordon J

    2007-10-15

    The ternary polar intermetallic compounds EuGaTt (Tt = Si, Ge, Sn) have been synthesized and characterized experimentally, as well as theoretically. EuGaSi crystallizes in the hexagonal AlB(2)-type structure (space group P6/mmm, Z = 1, Pearson symbol hP3) with randomly distributed Ga and Si atoms on the graphite-type planes: a = 4.1687(6) A, c = 4.5543(9) A. On the other hand, EuGaGe and EuGaSn adopt the hexagonal YPtAs-type structure (space group P6(3)/mmc, Z = 4, Pearson symbol hP12): a = 4.2646(6) A and c = 18.041(5) A for EuGaGe; a = 4.5243(5) A and c = 18.067(3) A for EuGaSn. The three crystal structures contain formally [GaTt](2-) polyanionic 3-bonded, hexagonal networks, which change from planar to puckered and exhibit a significant decrease in interlayer Ga-Ga distances as the size of Tt increases. Magnetic susceptibility measurements of this series of compounds show Curie-Weiss behavior above 86(5), 95(5), and 116(5) K with magnetic moments of 7.93, 7.97, and 7.99 mu(B) for EuGaSi, EuGaGe, and EuGaSn, respectively, indicating a 4f(7) electronic configuration (Eu(2+)) for Eu atoms. X-ray absorption spectra (XAS) are also consistent with these magnetic properties. Electronic structure calculations supplemented by a crystal orbital Hamilton population (COHP) analysis identifies the synergy between atomic sizes, from both Eu and Tt atoms, and the orbital contributions from Eu toward influencing the structural features of EuGaTt. A multicentered interaction between planes of Eu atoms and the [GaTt](2-) layers rather than through-space Ga-Ga bonding is seen in ELF distributions. PMID:17880208

  13. Template-assisted selective epitaxy of III–V nanoscale devices for co-planar heterogeneous integration with Si

    SciTech Connect

    Schmid, H. Borg, M.; Moselund, K.; Cutaia, D.; Riel, H.; Gignac, L.; Breslin, C. M.; Bruley, J.

    2015-06-08

    III–V nanoscale devices were monolithically integrated on silicon-on-insulator (SOI) substrates by template-assisted selective epitaxy (TASE) using metal organic chemical vapor deposition. Single crystal III–V (InAs, InGaAs, GaAs) nanostructures, such as nanowires, nanostructures containing constrictions, and cross junctions, as well as 3D stacked nanowires were directly obtained by epitaxial filling of lithographically defined oxide templates. The benefit of TASE is exemplified by the straightforward fabrication of nanoscale Hall structures as well as multiple gate field effect transistors (MuG-FETs) grown co-planar to the SOI layer. Hall measurements on InAs nanowire cross junctions revealed an electron mobility of 5400 cm{sup 2}/V s, while the alongside fabricated InAs MuG-FETs with ten 55 nm wide, 23 nm thick, and 390 nm long channels exhibit an on current of 660 μA/μm and a peak transconductance of 1.0 mS/μm at V{sub DS} = 0.5 V. These results demonstrate TASE as a promising fabrication approach for heterogeneous material integration on Si.

  14. Influence of Gd{sup 3+} on the visible quantum cutting in green-emitting silicate Na{sub 3}Gd{sub 0.9−x}Y{sub x}Si{sub 3}O{sub 9}:0.1Tb{sup 3+} phosphors

    SciTech Connect

    Han, Lili; Wang, Yuhua; Zhao, Lei; Zhang, Jia; Wang, Yanzhao; Tao, Ye

    2013-06-01

    Highlights: ► The visible quantum cutting between Tb{sup 3+} in silicate Na{sub 3}Gd{sub 0.9−x}Y{sub x}Si{sub 3}O{sub 9}:0.1Tb{sup 3+} phosphors are firstly investigated. ► Gd{sup 3+} plays an important intermediate role during the QC process and reinforces the cross relaxation efficiency. ► Na{sub 3}Gd{sub 0.9}Tb{sub 0.1}Si{sub 3}O{sub 9} has potential application for 3D-PDPs and Hg-free lamps for the total QE of 151.2%. - Abstract: The visible quantum cutting via cross-relaxation between Tb{sup 3+} ions in Na{sub 3}Gd{sub 0.9−x}Y{sub x}Si{sub 3}O{sub 9}:0.1Tb{sup 3+} phosphors are identified for the first time. It has also been found that with the increase of the ratio of Gd{sup 3+}/Y{sup 3+}, the quantum cutting efficiency increases, which indicates the Gd{sup 3+} plays an important intermediate role in energy transfer to convert vacuum ultraviolet light to visible light and reinforces the cross relaxation efficiency during the quantum cutting process. In addition, the energy transfer process from Gd{sup 3+} to Tb{sup 3+} is also investigated and discussed in terms of luminescence spectra.

  15. Optical properties and chemical composition analyses of mixed rare earth oxyorthosilicate (R2SiO5, R=La, Gd and Y) doped Dy3+ phosphors prepared by urea-assisted solution combustion method

    NASA Astrophysics Data System (ADS)

    Ogugua, S. N.; Shaat, S. K. K.; Swart, H. C.; Ntwaeaborwa, O. M.

    2015-08-01

    Dysprosium (Dy3+) doped lanthanum gadolinium oxyorthosilicate (LaGdSiO5), lanthanum yttrium oxyorthosilicate (LaYSiO5) and gadolinium yttrium oxyorthosilicate (GdYSiO5) phosphors (in powder form) were synthesized by urea-assisted combustion method. The X-ray diffractometer analysis confirmed that the LaGdSiO5, LaYSiO5 and GdYSiO5 crystalized in monoclinic phases. The chemical composition of the phosphors was analyzed by measuring the atomic and molecular ionic species using the time of flight secondary ion mass spectroscopy (ToF SIMS). In addition, ToF SIMS imaging technique was used to determine the distribution of the Dy3+ dopant ions on the surface on the phosphors. The average crystallite sizes and lattice strains of the phosphor were increased by Dy3+ doping. The field emission scanning electron microscope images showed that the powders were made up of an agglomeration of particles with no regular shape. The photoluminescence data showed narrow line emission peaks at the wavelengths of 485 nm (minor emission) and 573 nm (major emission) associated with the f→f transitions of Dy3+. The photoluminescence (PL) measurements showed that the emission peak of LaGdSiO5:Dy3+ was ~3× more intense than those of LaYSiO5:Dy3+ and GdYSiO5:Dy3+ when excited using monochromatic xenon lamp with a wavelength of 241 nm. However, when the powders were excited using a 325 nm He-Cd laser, the highest PL emission intensity was observed from GdYSiO5:Dy3+.

  16. In Vivo Immunotoxicity of SiO2@(Y0.5Gd0.45Eu0.05)2O3 as Dual-Modality Nanoprobes

    PubMed Central

    Tian, Xiumei; Li, Ermao; Yang, Fanwen; Peng, Ye; Zhu, Jixiang; He, Fupo; Chen, Xiaoming

    2014-01-01

    We have successfully synthesized SiO2@(Y0.5Gd0.45Eu0.05)2O3 nanocomposites as a potential dual-modality nanoprobe for molecular imaging in vitro. However, their immunotoxicity assessment in vivo remains unknown. In this article, the in vitro biocompatibility of our dual-modality nanoprobes was assayed in terms of cell viability and apoptosis. In vivo immunotoxicity was investigated by monitoring the generation of reactive oxygen species (ROS), cluster of differentiation (CD) markers and cytokines in Balb/c mice. The data show that the in vitro biocompatibility was satisfactory. In addition, the immunotoxicity data revealed there are no significant changes in the expression levels of CD11b and CD71 between the nanoprobe group and the Gd in a diethylenetriaminepentaacetic acid (DTPA) chelator (Gd-DTPA) group 24 h after injection in Balb/c mice (p > 0.05). Importantly, there are significant differences in the expression levels of CD206 and CD25 as well as the secretion of IL-4 and the generation of ROS 24 h after injection (p < 0.05). Transmission electron microscopy (TEM) images showed that few nanoprobes were localized in the phagosomes of liver and lung. In conclusion, the toxic effects of our nanoprobes may mainly result from the aggregation of particles in phagosomes. This accumulation may damage the microstructure of the cells and generate oxidative stress reactions that further stimulate the immune response. Therefore, it is important to evaluate the in vivo immunotoxicity of these rare earth-based biomaterials at the molecular level before molecular imaging in vivo. PMID:25105724

  17. Enhanced upconversion multicolor and white light luminescence in SiO2-coated lanthanide-doped GdVO4 hydrothermal nanocrystals.

    PubMed

    Calderón-Villajos, Rocío; Zaldo, Carlos; Cascales, Concepción

    2012-12-21

    Tetragonal zircon-type codoped Yb, Ln-GdVO(4) (Ln=Tm, Ho, Er) upconverting nanocrystals with square and rectangular sections were prepared through an efficient low-temperature hydrothermal synthesis. Further processing that combined annealing at 600 °C followed by coating of the surface with a uniform 5 nm-shell of SiO(2) resulted in a significant improvement of the intensity of the upconverted emitted visible light following near-infrared (~980 nm) diode laser excitation with respect to raw hydrothermal nanocrystals. Strong tunable color and bright visible light composed of red-green, blue and green emissions from Ho(3+), Tm(3+) and Er(3+), respectively, were generated by adjusting the Yb-Ln composition of these silica-coated nanocrystals. Based on calculations of CIE color coordinates, nearly ideal white upconversion light was achieved for samples of composition Gd(0.829)Yb(0.15)Tm(0.01)Ho(0.009)Er(0.002)VO(4). PMID:23196274

  18. Interfacial bonding distribution and energy band structure of (Gd 2O 3) 1 - x(SiO 2) x ( x = 0.5)/GaAs (0 0 1) system

    NASA Astrophysics Data System (ADS)

    Yang, Jun-Kyu; Kang, Min-Gu; Kim, Woo Sik; Park, Hyung-Ho

    2004-10-01

    A (Gd 2O 3) 1 - x(SiO 2) x ( x = 0.5) gate dielectric film was deposited on an n-GaAs (0 0 1) substrate at various substrate temperatures. Bonding distribution of interfacial Ga and As was characterized by comparing the 3d and 3p photoelectron lines. Surface passivation using (NH 4) 2S was employed to preserve a stable interface. Interfacial GaAs oxide was not formed after the deposition, since bonding transition from AsS to GaS bonds provides thermal stability and protective effect against oxidation. While, without the passivation, interfacial GaAs-oxides were continuously grown as the substrate temperature was increased. The energy band gap of (Gd 2O 3) 0.5(SiO 2) 0.5 was defined as 6.8 eV using energy loss spectra of O 1s photoelectrons. The valence band maximum energy ( EVBM) of (Gd 2O 3) 0.5(SiO 2) 0.5 was determined to be 3.7 eV. By arrangement of the measured energy bandgap and EVBM, the energy band structure of (Gd 2O 3) 0.5(SiO 2) 0.5/GaAs system was demonstrated and an enhanced conduction band offset was observed.

  19. Experimental and Computational Analysis of Emission from Highly Ionized Si, Kr, Mo, Gd, and Tb Plasmas at 6.6 nm

    NASA Astrophysics Data System (ADS)

    Parchamy, Homaira; Szilagyi, John; Masnavi, Majid; Richardson, Martin; One Team

    2013-10-01

    There is increasing interest in high-power extreme-ultraviolet (EUV) laser-based lamps for sub-10 nm lithography operating in the region of 6.6 nm based on the LaN/B4C multilayer mirrors for manufacturing the next generation of microelectronics. A detailed multilevel non-LTE atomic model is developed to investigate emissivity and absorption properties of highly ionized Si, Kr, Mo, Gd, and Tb plasmas at 6.6 nm. Experimental spectra are presented together with analysis based on calculations using the relativistic Flexible Atomic Code. We will present the optimum regions for conversion efficiency of mass-limited targets against target density and laser parameters by means of 1D hydrodynamic coupled to a developed population kinetics codes.

  20. Investigation of continuous wave and pulsed laser performance based on Nd3+:Gd0.6Y1.4SiO5 crystal

    NASA Astrophysics Data System (ADS)

    Feng, Chao; Liu, Zhaojun; Cong, Zhenhua; Shen, Hongbin; Li, Yongfu; Wang, Qingpu; Fang, Jiaxiong; Xu, Xiaodong; Xu, Jun; Zhang, Xingyu

    2015-12-01

    We systematically investigated a laser diode (LD) pumped Nd:GYSO (Nd3+:Gd0.6Y1.4SiO5) laser. The output power of the continuous wave laser was as high as 3.5 W with a slope efficiency of 31.8%. In the Q-switched operation; the laser exhibited dual-wavelengths output (1073.6 nm and 1074.7 nm) synchronously with a Cr4+:YAG as the saturable absorber (SA). Additionally, a passively mode-locked laser was demonstrated using a semiconductor SA mirror with a maximum average output power of 510 mW at a central wavelength of 1074 nm, while the pulse width of the laser was as short as 5 ps. Our experiment proved that the Nd:GYSO mixed crystal was a promising material for a solid-state laser.

  1. Nd:(Gd0.3Y0.7)2SiO5 crystal: A novel efficient dual-wavelength continuous-wave medium

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

    2016-05-01

    Efficient dual-wavelength continuous-wave (CW) and passively Q-switched laser operation of Nd:(Gd0.3Y0.7)2SiO5 crystal were investigated for the first time to our knowledge. Maximum CW output power of 2.3 W was obtained under the absorbed pump power of 4.6 W, corresponding to the slope efficiency of 55%. Dual-wavelength CW laser with respective wavelengths around 1074 nm and 1078 nm were achieved. With Cr4+:YAG as the saturable absorber, passive Q-switched performance was obtained. The slope efficiency of passively Q-switched operation was 45%. The shortest pulse width, the corresponding pulse energy and peak power were calculated to be 13.1 ns, 50.2 μJ and 3.8 kW, respectively.

  2. Optical, scintillation properties and defect study of Gd2Si2O7:Ce single crystal grown by floating zone method

    NASA Astrophysics Data System (ADS)

    Feng, He; Xu, Wusheng; Ren, Guohao; Yang, Qiuhong; Xie, Jianjun; Xu, Jun; Xu, Jiayue

    2013-02-01

    Single crystal of Gd2Si2O7:Ce (GPS) presenting attractive scintillation performance was grown by the floating zone method. The vacuum ultra-violet (VUV) excitation and emission, ultra-violet (UV) excitation and emission spectra and fluorescent decay time at 77 K and RT were measured and discussed. Relative energy levels of 5d sublevels of Ce3+ in GPS:Ce are detected by the VUV excitation spectrum. The UV emission curve of GPS:1%Ce peaks around 382 nm at 77 K and moves towards longer wavelength direction as temperature increases. Thermally stimulated luminescence (TSL) was employed to investigate the defects in GPS:1%Ce. Energy depths of two traps detected in GPS:1%Ce are 0.64 and 1.00 eV.

  3. Electron spin resonance and magnetic characterization of the Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}

    SciTech Connect

    Pires, M.J.M.; Carvalho, A. Magnus G.; Gama, S.; Silva, E.C. da; Coelho, A.A.; Mansanares, A.M.

    2005-12-01

    Electron spin resonance was applied on samples of Gd{sub 5.09}Ge{sub 2.03}Si{sub 1.88}. The results are discussed under the scope of magnetization measurements, optical metallography, and wavelength dispersive spectroscopy. Polycrystalline arc-melted samples submitted to different heat treatments were investigated. The correlation of the electron spin resonance and magnetization results permitted a characterization of the present phases and their transitions. Two coexisting phases in the temperature range between two phase transitions have been identified and associated to distinct crystallographic phases. Additionally, the magnetic moment at high temperatures has been estimated from the measured effective g factor. A peak value of 21.5 J/kg K for the magnetocaloric effect was obtained for a sample heat treated at 1500 deg. C for 16 h.

  4. Preparation of translucent Gd2Si2O7:Ce polycrystalline thin plates and their scintillation performance for α-particles

    NASA Astrophysics Data System (ADS)

    Nishikata, Mami; Ueda, Aki; Higuchi, Mikio; Kaneko, Junichi H.; Tsubota, Youichi; Ishibashi, Hiroyuki

    2015-07-01

    Translucent Gd2Si2O7:Ce (GPS:Ce) polycrystalline plates were prepared via liquid-phase sintering using SiO2 as a self-flux, and their scintillation performances for α-particles were investigated. Dense sintered compacts comprising large grains, some of which were larger than 100 μm in diameter, were successfully prepared by sintering at 1690 °C for 100 h. The best result was obtained with the powder comprising only <40 μm particles. Any combination of powders of <40 μm and <15 μm resulted in inhomogeneous structures with smaller grains of about 50 μm. A translucent GPS:Ce thin plate was fabricated by grinding the sintered compact that contained excess SiO2 of 8 mol%. Since the plate was composed of large grains, scattering at the grain boundaries was effectively suppressed and many of the grains virtually act as single crystals when the plate thickness was less than 100 μm. Therefore, the decrease in the plate thickness brought increase in the total transmission, and light yield and energy resolution were consequently improved. When the plate thickness was 50 μm, light yield was 82% as compared with that of a GPS:Ce single crystal as a reference, and energy resolution attained to 13%.

  5. A luminescent and mesoporous core-shell structured Gd2O3 : Eu(3+)@nSiO2@mSiO2 nanocomposite as a drug carrier.

    PubMed

    Xu, Zhenhe; Gao, Yu; Huang, Shanshan; Ma, Ping' an; Lin, Jun; Fang, Jiye

    2011-05-14

    In this paper, Gd(2)O(3) : Eu(3+) nanospheres have been encapsulated with nonporous silica and further layer of ordered mesoporous silica through a simple sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N(2) adsorption/desorption, photoluminescence (PL) spectra, and kinetic decay were used to characterize the sample. The results indicate that the nanocomposite with general 50 nm shell thickness and 270 nm core size shows typical ordered mesoporous characteristics (2.4 nm) and has spherical morphology with a smooth surface and narrow size distribution. Additionally, the obtained inorganic nanocomposite shows the characteristic emission of Eu(3+) ((5)D(0)→(7)F(1-4)) even after the loading of drug molecules. The biocompatibility test on L929 fibroblast cells using MTT assay reveals low cytotoxicity of the system. Most importantly, the nanocomposite can be used as an effective drug delivery carrier. A typical anticancer drug, doxorubicin hydrochloride (DOX), was used for drug loading, and the DOX release, cytotoxicity, uptake behavior and therapeutic effects were examined. It was found that DOX is shuttled into the cell by the nanocomposite and released inside cells after endocytosis and that the DOX-loaded nanocomposite exhibited greater cytotoxicity than free DOX. These results indicate that core-shell structured Gd(2)O(3) : Eu(3+)@nSiO(2)@mSiO(2) nanocomposite has potential for drug loading and delivery into cancer cells to induce cell death. PMID:21431226

  6. Toward Design Principles for Diffusionless Transformations: The Frustrated Formation of Co-Co Bonds in a Low-Temperature Polymorph of GdCoSi2.

    PubMed

    Vinokur, Anastasiya I; Fredrickson, Daniel C

    2016-06-20

    Diffusionless (or displacive) phase transitions allow inorganic materials to show exquisite responsiveness to external stimuli, as is illustrated vividly by the superelasticity, shape memory, and magnetocaloric effects exhibited by martensitic materials. In this Article, we present a new diffusionless transition in the compound GdCoSi2, whose origin in frustrated bonding points toward generalizable design principles for these transformations. We first describe the synthesis of GdCoSi2 and the determination of its structure using single crystal X-ray diffraction. While previous studies based on powder X-ray diffraction assigned this compound to the simple CeNi1-xSi2 structure type (space group Cmcm), our structure solution reveals a superstructure variant (space group Pbcm) in which the Co sublattice is distorted to create zigzag chains of Co atoms. DFT-calibrated Hückel calculations, coupled with a reversed approximation Molecular Orbital (raMO) analysis, trace this superstructure to the use of Co-Co isolobal bonds to complete filled 18 electron configurations on the Co atoms, in accordance with the 18-n rule. The formation of these Co-Co bonds is partially impeded, however, by a small degree of electron transfer from Si-based electronic states to those with Co-Co σ* character. The incomplete success of Co-Co bond creation suggests that these interactions are relatively weak, opening the possibility of them being overcome by thermal energy at elevated temperatures. In fact, high-temperature powder and single crystal X-ray diffraction data, as well as differential scanning calorimetry, indicate that a reversible Pbcm to Cmcm transition occurs at about 380 K. This transition is diffusionless, and the available data point toward it being first-order. We expect that similar cases of frustrated interactions could be staged in other rare earth-transition metal-main group phases, providing a potentially rich source of compounds exhibiting diffusionless transformations

  7. (1)H relaxivity of water in aqueous suspensions of Gd(3+)-loaded NaY nanozeolites and AlTUD-1 mesoporous material: the influence of Si/Al ratio and pore size.

    PubMed

    Norek, Małgorzata; Neves, Isabel C; Peters, Joop A

    2007-07-23

    The results of a (1)H nuclear magnetic relaxation dispersion (NMRD) and EPR study on aqueous suspensions of Gd(3+)-loaded NaY nanozeolites and AlTUD-1 mesoporous material are described. Upon increase of the Si/Al ratio from 1.7 to 4.0 in the Gd(3+)-loaded zeolites, the relaxation rate per mM Gd(3+) (r1) at 40 MHz and 25 degrees C increases from 14 to 27 s(-)1 mM(-1). The NMRD and EPR data were fitted with a previously developed two-step model that considers the system as a concentrated aqueous solution of Gd(3+) in the interior of the zeolite that is in exchange with the bulk water outside the zeolite. The results show that the observed increase in relaxivity can mainly be attributed to the residence lifetime of the water protons in the interior of the material, which decreased from 0.3 to 0.2 micros, upon the increase of the Si/Al ratio. This can be explained by the decreased interaction of water with the zeolite walls as a result of the increased hydrophobicity. The importance of the exchange rate of water between the inside and the outside of the material was further demonstrated by the relatively high relaxivity (33 s(-1) mM(-1) at 40 MHz, 25 degrees C) observed for a suspension of the Gd(3+)-loaded mesoporous material AlTUD-1. Unfortunately, Gd(3+) leaches rather easily from that material, but not from the Gd(3+)-loaded NaY zeolites, which may have potential as contrast agents for magnetic resonance imaging. PMID:17589991

  8. Interface investigation of planar hybrid n-Si/PEDOT:PSS solar cells with open circuit voltages up to 645 mV and efficiencies of 12.6 %

    NASA Astrophysics Data System (ADS)

    Pietsch, Matthias; Jäckle, Sara; Christiansen, Silke

    2014-06-01

    We have studied interface formation properties of hybrid n-Si/PEDOT:PSS solar cells on planar substrates by varying the silicon substrate doping concentration ( N D). Final power conversion efficiencies (PCE) of 12.6 % and open circuit voltages ( V oc) comparable to conventional diffused emitter pn junction solar cells have been achieved. It was observed, that an increase of N D leads to an increase of V oc with a maximal value of 645 mV, which is, to our knowledge, the highest reported value for n-Si/PEDOT:PSS interfaces. The dependence of the solar cell characteristics on N D is analyzed and similarities to minority charge carrier drift-diffusion limited solar cells are presented. The results point out the potential of hybrid n-Si/PEDOT:PSS interfaces to fabricate high performance opto-electronic devices with cost-effective fabrication technologies.

  9. Superstructure in RE2-xFe4Si14-y (RE = Y, Gd-Lu) characterized by diffraction, electron microscopy, and Mössbauer spectroscopy.

    PubMed

    Han, Mi-Kyung; Wu, Ya-Qiao; Kramer, Matthew; Vatovez, Benjamin; Grandjean, Fernande; Long, Gary J; Miller, Gordon J

    2006-12-25

    Ternary rare-earth iron silicides RE(2-x)Fe4Si(14-y) (RE = Y, Gd-Lu; x approximately equal to 0.8; y approximately equal to 4.1) crystallize in the hexagonal system with a approximately equal to 3.9 A, c approximately equal to 15.3 A, Pearson symbol hP20-4.9. Their structures involve rare-earth silicide planes with approximate compositions of "RE1.2Si1.9" alternating with beta-FeSi2-derived slabs and are part of a growing class of rare-earth/transition-metal/main-group compounds based on rare-earth/main-group element planes interspersed with (distorted) fluorite-type transition-metal/main-group element layers. The rare-earth silicide planes in the crystallographic unit cells show partial occupancies of both the RE and Si sites because of interatomic distance constraints. Transmission electron microscopy reveals a 4a x 4b x c superstructure for these compounds, whereas further X-ray diffraction experiments suggest ordering within the ab planes but disordered stacking along the c direction. A 4a x 4b structural model for the rare-earth silicide plane is proposed, which provides good agreement with the electron microscopy results and creates two distinct Fe environments in a 15:1 ratio. Fe-57 Mössbauer spectra confirm these two different iron environments in the powder samples. Magnetic susceptibilities suggest weak (essentially no) magnetic coupling between rare-earth elements, and resistivity measurements indicate poor metallic behavior with a large residual resistivity at low temperatures, which is consistent with disorder. First-principles electronic-structure calculations on model structures identify a pseudogap in the densities of states for specific valence-electron counts that provides a basis for a useful electron-counting scheme for this class of rare-earth/transition-metal/main-group compounds. PMID:17173406

  10. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3Si2 and Zr3Al2 Structure Types

    SciTech Connect

    Sean William McWhorter

    2006-05-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} several new compounds were synthesized with different crystal structures, but similar structural features. In Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} can be thought of as being formed from two 3{sup 2}434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd{sub 2}MgGe{sub 2} and Gd{sub 2}InGe{sub 2} both possess the same 3{sup 2}434 nets of Gd atoms as Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, but these nets are connected differently, forming the Mo{sub 2}FeB{sub 2} crystal structure. A search of the literature revealed that compounds with the composition R{sub 2}XM{sub 2} (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo{sub 2}FeB{sub 2}, Zr{sub 3}Al{sub 2}, Mn{sub 2}AlB{sub 2} and W{sub 2}CoB{sub 2} crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd{sub 2}AlGe{sub 2} forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how electrons can be accounted for. A series of electronic structure calculations were performed on models with the U{sub 3}Si{sub 2} and Zr{sub 3}Al{sub 2} structures, using Zr and A1 as

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

    PubMed

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

    2014-10-20

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

  12. Magnetic and Electrical Properties of a New Series of Rare Earth Silicide Carbides with the Composition R3Si 2C 2( R=Y, La-Nd, Sm, Gd-Tm)

    NASA Astrophysics Data System (ADS)

    Gerdes, Martin H.; Witte, Anne M.; Jeitschko, Wolfgang; Lang, Arne; Künnen, Bernd

    1998-07-01

    The 12 title compounds have been prepared by arc-melting cold-pressed pellets of the elemental components and subsequent annealing. They crystallize with an orthorhombic structure and with cell dimensions varying betweena=403.9(1) pm,b=1688.4(2) pm, andc=450.6(1) pm for La3Si2C2anda=379.6(1) pm,b=1532.8(2) pm, andc=414.5(1) pm for Tm3Si2C2. The magnetic properties of these compounds were determined with a SQUID magnetometer between 2 and 300 K with magnetic flux densities up to 5.5 T. Y3Si2C2is a Pauli paramagnet. The cerium atoms in Ce3Si2C2are trivalent; at low temperatures this compound is ferro- or ferrimagnetic with an ordering temperature of 10(±3) K. Pr3Si2C2and Nd3Si2C2are ferromagnetic (TC=25(±3) and 30(±3) K, respectively), whereas the silicide carbidesR3Si2C2withR=Sm and Gd-Tm are antiferromagnetic. Ho3Si2C2, Er3Si2C2, and Tm3Si2C2show metamagnetic transitions. The highest ordering temperature occurs for Gd3Si2C2with a Néel temperatureTN=50(±1) K. The electrical conductivities of several compounds were determined between 5 and 300 K. They indicate metallic behavior, and in several cases they reflect the magnetic ordering temperatures.

  13. Study of Rayleigh–Taylor growth in laser irradiated planar SiO{sub 2} targets at ignition-relevant conditions

    SciTech Connect

    Hager, J. D.; Collins, T. J. B.; Knauer, J. P.; Meyerhofer, D. D.; Sangster, T. C.; Smalyuk, V. A.

    2013-07-15

    Rayleigh–Taylor (RT) growth experiments were performed on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar SiO{sub 2} targets seeded with a single mode 60-μm wavelength perturbation driven at peak laser intensities up to 9 × 10{sup 14} W/cm{sup 2}. These are the first RT measurements in SiO{sub 2} at conditions relevant to direct-drive inertial confinement fusion ignition. The measured average modulation growth rates agree with the 2-D hydrodynamics code DRACO, providing an important step in the development of target ablators that are robust to RT growth and hot- electron preheat considerations when driven at the intensities required to achieve thermonuclear ignition.

  14. Plasma Deposited SiO2 for Planar Self-Aligned Gate Metal-Insulator-Semiconductor Field Effect Transistors on Semi-Insulating InP

    NASA Technical Reports Server (NTRS)

    Tabory, Charles N.; Young, Paul G.; Smith, Edwyn D.; Alterovitz, Samuel A.

    1994-01-01

    Metal-insulator-semiconductor (MIS) field effect transistors were fabricated on InP substrates using a planar self-aligned gate process. A 700-1000 A gate insulator of Si02 doped with phosphorus was deposited by a direct plasma enhanced chemical vapor deposition at 400 mTorr, 275 C, 5 W, and power density of 8.5 MW/sq cm. High frequency capacitance-voltage measurements were taken on MIS capacitors which have been subjected to a 700 C anneal and an interface state density of lxl0(exp 11)/eV/cq cm was found. Current-voltage measurements of the capacitors show a breakdown voltage of 107 V/cm and a insulator resistivity of 10(exp 14) omega cm. Transistors were fabricated on semi-insulating InP using a standard planar self-aligned gate process in which the gate insulator was subjected to an ion implantation activation anneal of 700 C. MIS field effect transistors gave a maximum extrinsic transconductance of 23 mS/mm for a gate length of 3 microns. The drain current drift saturated at 87.5% of the initial current, while reaching to within 1% of the saturated value after only 1x10(exp 3). This is the first reported viable planar InP self-aligned gate transistor process reported to date.

  15. The layered antimonides RELi3Sb2 (RE=Ce-Nd, Sm, Gd-Ho). Filled derivatives of the CaAl2Si2 structure type

    NASA Astrophysics Data System (ADS)

    Schäfer, Marion C.; Suen, Nian-Tzu; Raglione, Michaella; Bobev, Svilen

    2014-02-01

    Reported are the synthesis and the structural characterization of an extended family of rare-earth metal-lithium-antimonides with the formula RELi3Sb2 (RE=Ce-Nd, Sm, Gd-Ho). They crystallize in the trigonal space group P3barm1 (No. 164, Pearson symbol hP6) with a structure, best viewed as a filled derivative of the common CaAl2Si2 structure type (ternary variant of α-La2O3). Across the series, the lattice parameters monotonically decrease, following the lanthanide contraction. Temperature-dependent magnetic susceptibility measurements for CeLi3Sb2, PrLi3Sb2 and TbLi3Sb2 reveal paramagnetic behavior in the high temperature range, and the obtained effective moments are consistent with the expected ones for the free-ion RE3+ ground state. Possible ferromagnetic ordering for PrLi3Sb2 and antiferromagnetic ordering for TbLi3Sb2 are observed in the low temperature range (below 20 K). Tight-binding muffin-tin orbital electronic band structure calculations for LaLi3Sb2 are presented and discussed as well.

  16. Lasing characteristics of Yb-doped gadolinium yttrium mixed oxyorthosilicate Yb:(Gd0.1Y0.9)2SiO5

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Dechun; Li, Guiqiu; Li, Tao; Qiao, Wenchao; Xu, Xiaodong; Zheng, Lihe; Xu, Jun

    2015-07-01

    A continuous wave (CW) tunable laser based on an alloyed oxyorthosilicate Yb:(Gd0.1Y0.9)2SiO5 was demonstrated for the first time. With an output coupler (OC) of T = 10%, a maximum output power of 958 mW was obtained with a slope efficiency of 18.2%. Simultaneous multi-wavelength operation was also observed with an OC of T = 4%. The M2 factor of the CW laser beam was measured to be 1.06. The thermo-optic coefficient was estimated to be 7.1 × 10-6/K. By using a 400 μm-thick GaAs wafer as saturable absorber, a stably Q-switched laser at 1080.4 nm was also firstly realized. A minimum pulse duration of 60.2 ns was obtained with a repetition rate of 47.6 kHz under an absorbed pump power of 11.25 W. The corresponding highest pulse energy and peak power were 5.3 μJ and 88 W, respectively. By using a V-type cavity and an OC of T = 4%, the laser can be tuned in the range from 1021 to 1094 nm.

  17. Influence of core size on the upconversion luminescence properties of spherical Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}@SiO{sub 2} particles with core-shell structures

    SciTech Connect

    Zheng, Kezhi; Liu, Zhenyu; Liu, Ye; Song, Weiye; Qin, Weiping

    2013-11-14

    Spherical SiO{sub 2} particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+}@SiO{sub 2} particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO{sub 2} cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er{sup 3+} ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO{sub 2} particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO{sub 2} cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO{sub 2} core sizes.

  18. Influence of core size on the upconversion luminescence properties of spherical Gd2O3:Yb3+/Er3+@SiO2 particles with core-shell structures

    NASA Astrophysics Data System (ADS)

    Zheng, Kezhi; Liu, Zhenyu; Liu, Ye; Song, Weiye; Qin, Weiping

    2013-11-01

    Spherical SiO2 particles with different sizes (30, 80, 120, and 180 nm) have been coated with Gd2O3:Yb3+/Er3+ layers by a heterogeneous precipitation method, leading to the formation of core-shell structural Gd2O3:Yb3+/Er3+@SiO2 particles. The samples were characterized by using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, upconversion (UC) emission spectra, and fluorescent dynamical analysis. The obtained core-shell particles have perfect spherical shape with narrow size distribution. Under the excitation of 980 nm diode laser, the core-shell samples showed size-dependent upconversion luminescence (UCL) properties. The inner SiO2 cores in core-shell samples were proved to have limited effect on the total UCL intensities of Er3+ ions. The UCL intensities of core-shell particles were demonstrated much higher than the values obtained in pure Gd2O3:Yb3+/Er3+ with the same phosphor volume. The dependence of the specific area of a UCL shell on the size of its inner SiO2 particle was calculated and analyzed for the first time. It was confirmed that the surface effect came from the outer surfaces of emitting shells is dominant in influencing the UCL property in the core-shell samples. Three-photon UC processes for the green emissions were observed in the samples with small sizes of SiO2 cores. The results of dynamical analysis illustrated that more nonradiative relaxation occurred in the core-shell samples with smaller SiO2 core sizes.

  19. Selective MOVPE of InGaN-based LED structures on non-planar Si (111) facets of patterned Si (100) substrates

    NASA Astrophysics Data System (ADS)

    Reuters, B.; Strate, J.; Hahn, H.; Finken, M.; Wille, A.; Heuken, M.; Kalisch, H.; Vescan, A.

    2014-04-01

    The growing interest in modern energy-saving illuminants for general lighting, multimedia applications and automotive industry demands for alternative low-cost substrates for MOVPE LED growth. Nitride MOVPE growth is possible on the Si (111) plane, which makes Si substrates attractive as an alternative to sapphire substrates. A novel technology is presented using patterned Si (100) substrates, in which MOVPE-grown LED structures are fabricated on Si {111} facets tilted by 54.7°. Structural and optical properties are discussed and correlated to epitaxial growth conditions. It is shown that crystal quality reaches already a reasonable level for preliminary LED operation.

  20. Spectroscopy of Gd153 and Gd157 using the (p,dγ) reaction

    DOE PAGESBeta

    Ross, T. J.; Hughes, R. O.; Allmond, J. M.; Beausang, C. W.; Angell, C. T.; Basunia, M. S.; Bleuel, D. L.; Burke, J. T.; Casperson, R. J.; Escher, J. E.; et al

    2014-10-31

    Low-spin single quasineutron levels in 153Gd and 157Gd have been studied following the 154Gd(p,d-γ )153Gd and 158Gd(p,d-γ )157Gd reactions. A combined Si telescope and high-purity germanium array was utilized, allowing d-γ and d-γ-γ coincidence measurements. Almost all of the established low-excitation-energy, low-spin structures were confirmed in both 153Gd and 157Gd. Several new levels and numerous new rays are observed in both nuclei, particularly for Ex ≥1 MeV. Lastly, residual effects of a neutron subshell closure at N = 64 are observed in the form of a large excitation energy gap in the single quasineutron level schemes.

  1. Growth conditions, structure, Raman characterization and optical properties of Sm-doped (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5} single crystals grown by the Czochralski method

    SciTech Connect

    GLowacki, MichaL; Runka, Tomasz; Drozdowski, MirosLaw; Domukhovski, Viktor; Berkowski, Marek

    2012-02-15

    The (Lu{sub x}Gd{sub 0.995-x}Sm{sub 0.005}){sub 2}SiO{sub 5} single crystals with x=0.095, 0.11, 0.15, 0.17, 0.19 0.35 and 0.5 were grown by the Czochralski method. Structural properties were investigated by X-ray diffraction measurements. Unit cell parameters and cell volume were determined by the Rietveld refinement of the collected X-ray powder spectra. The segregation features between Gd and Lu were estimated and analyzed. Vibrational properties of the solid solutions were analyzed on the basis of polarized Raman spectra acquired at 300-875 K temperature range. Absorption and emission spectra of Sm{sup 3+} ion in the crystals with different composition were analyzed in the terms of dopant energy levels, oscillator strengths of transitions and spectral features of luminescence bands in the visible range. Both structural and optical investigations revealed that change of Lu{sup 3+} content in (Lu{sub x}Gd{sub 0.995-x}Sm{sub 0.005}){sub 2}SiO{sub 5} solid solution crystals induces the phase transition from C2/c (Lu{sub 2}SiO{sub 5}) to P2{sub 1}/c (Gd{sub 2}SiO{sub 5}) structure. It was found that the break of LSO to GSO-type structure occurs at 0.15Gd{sub 1-x}){sub 2}SiO{sub 5} solid solutions have been grown by Czochralski method and characterized by various techniques. Crystal structure changes from C2/c to P2{sub 1}/c for composition with 0.15Gd{sub 1-x}){sub 2}SiO{sub 5} crystals are an alternative to LSO and GSO hosts for applications. Black-Right-Pointing-Pointer The break of the P2{sub 1}/c to C2/c structure in (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5}:Sm occurs for 0.15

  2. Fabrication and optical testing of hybrid SiO2: azo-polymer based planar waveguides for NLO/SHG laser emission

    NASA Astrophysics Data System (ADS)

    Torres-Zúñiga, V.; Morales-Saavedra, O. G.; Pérez-Martínez, A. L.

    2015-01-01

    Predesigned push-pull azo-dye polymers were homogeneously dispersed within a SiO2 sol-gel matrix synthesized via the sonogel (SG) route. High-quality spin-coated films were obtained with these hybrid structures in the liquid sol-phase. The spectroscopic UV- Vis analyses reveal the appropriate insertion of these organic compounds within the highly pure SG-environment whereas the thermal (DSC) analysis and photoacoustic measurements evidence the thermomechanical stability of the amorphous hybrid layers. As the optical attenuation, refractive index and film thickness values of the obtained films are adequate for opto-electronic applications; these hybrid films were implemented to fabricate optical waveguiding prototypes. In this sense, functional planar waveguides were fabricated for nonlinear optical (NLO) applications after performing a molecular ordering via a corona DC-poling procedure in order to achieve a macroscopic polar order (ferroelectric and noncentrosymmetric arrangement of the organic chromophores). The poled films were then able to exhibit stable NLO-waveguiding effects as excited with a Nd:YAG laser system in order to generate second harmonic waves travelling within the planar layer.

  3. Fabrication and characterization of Er+3 doped SiO2/SnO2 glass-ceramic thin films for planar waveguide applications

    NASA Astrophysics Data System (ADS)

    Guddala, S.; Chiappini, A.; Armellini, C.; Turell, S.; Righini, G. C.; Ferrari, M.; Narayana Rao, D.

    2015-02-01

    Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2-xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 μm communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

  4. Novel Dy{sup 3+}-doped Ca{sub 2}Gd{sub 8}(SiO{sub 4}){sub 6}O{sub 2} white light phosphors for Hg-free lamps application

    SciTech Connect

    Wang, Yuhua; Wen, Yan; Zhang, Feng

    2010-11-15

    The luminescent properties of Ca{sub 2}Gd{sub 8(1-x)}(SiO{sub 4}){sub 6}O{sub 2}:xDy{sup 3+} (1% {<=} x {<=} 5%) powder crystals with oxyapatite structure were investigated under vacuum ultraviolet excitation. In the excitation spectrum, the peaks at 166 nm and 191 nm of the vacuum ultraviolet region can be assigned to the O{sup 2-} {yields} Gd{sup 3+}, and O{sup 2-} {yields} Dy{sup 3+} charge transfer band respectively, which is consistent with the theoretical calculated value using J{phi}rgensen's empirical formula. While the peaks at 183 nm and 289 nm are attributed to the f-d spin-allowed transitions and the f-d spin-forbidden transitions of Dy{sup 3+} in the host lattice with Dorenbos's expression. According to the emission spectra, all the samples exhibited excellent white emission under 172 nm excitation and the best calculated chromaticity coordinate was 0.335, 0.338, which indicates that the Ca{sub 2}Gd{sub 8}(SiO{sub 4}){sub 6}O{sub 2}:Dy{sup 3+} phosphor could be considered as a potential candidate for Hg-free lamps application.

  5. High-pressure synthesis and single-crystal structure refinement of gadolinium holmium silicate hydroxyapatite Gd{sub 4.33}Ho{sub 4.33}(SiO{sub 4}){sub 6}(OH){sub 2}

    SciTech Connect

    Wang Chao; Liu Xiaoyang . E-mail: liuxy@jlu.edu.cn; Fleet, M.E.; Feng, Shouhua; Xu Ruren

    2006-07-15

    Single crystals of gadolinium holmium silicate hydroxyapatite Gd{sub 4.33}Ho{sub 4.33}(SiO{sub 4}){sub 6}(OH){sub 2} have been synthesized at 2.0GPa and 1450 deg. C using a piston-cylinder-type high-pressure apparatus. The crystal symmetry by single-crystal X-ray diffraction analysis is hexagonal, space group P6{sub 3}/m (No. 176), with a=9.3142(5)A, c=6.7010(4)A, Z=1. Gadolinium and Ho are disordered over the two large cation positions, A(1) and A(2), and charge balance in this silicate apatite is maintained by cation vacancies in A(1). Two other apatite-structure crystals investigated have P3-bar and Imma symmetry, and represent either partially ordered Gd-Ho distributions or crystal strain induced during quenching.

  6. A planar Al-Si Schottky barrier metal–oxide–semiconductor field effect transistor operated at cryogenic temperatures

    SciTech Connect

    Purches, W. E.; Rossi, A.; Zhao, R.; Kafanov, S.; Duty, T. L.; Dzurak, A. S.; Rogge, S.; Tettamanzi, G. C.

    2015-08-10

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  7. A planar Al-Si Schottky barrier metal-oxide-semiconductor field effect transistor operated at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Purches, W. E.; Rossi, A.; Zhao, R.; Kafanov, S.; Duty, T. L.; Dzurak, A. S.; Rogge, S.; Tettamanzi, G. C.

    2015-08-01

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  8. Crystal and electronic structures of CaAl 2Si 2-type rare-earth copper zinc phosphides RECuZnP 2 ( RE=Pr, Nd, Gd-Tm, Lu)

    NASA Astrophysics Data System (ADS)

    Blanchard, Peter E. R.; Stoyko, Stanislav S.; Cavell, Ronald G.; Mar, Arthur

    2011-01-01

    The quaternary rare-earth phosphides RECuZnP 2 ( RE=Pr, Nd, Gd-Tm, Lu) have been prepared by reaction of the elements at 900 °C, completing this versatile series which forms for nearly all RE metals. They adopt the trigonal CaAl 2Si 2-type structure (Pearson symbol hP5, space group P3¯ m1, Z=1), as confirmed by single-crystal X-ray diffraction analysis on ErCuZnP 2 and powder X-ray diffraction analysis on the remaining members. The Cu and Zn atoms are assumed to be disordered over the single transition-metal site. Band structure calculations on a hypothetically ordered YCuZnP 2 model suggest a semimetal, with a zero band gap between the valence and conduction bands. This electronic structure is supported by XPS valence band spectra for RECuZnP 2 ( RE=Gd-Er), in which the intensity drops off smoothly at the Fermi edge. The absence of a band gap permits the electron count to deviate from the precise value of 16 e - per formula unit, as demonstrated by the formation of a solid solution in GdCu xZn 2- xP 2 (1.0≤ x≤1.3), while still retaining the CaAl 2Si 2-type structure. Because the Cu 2 p XPS spectra indicate that the Cu atoms are always monovalent, the substitution of Cu for Zn leads to a decrease in electron count and a lowering of the Fermi level in the valence band. The magnetic susceptibility of RECuZnP 2 ( RE=Gd-Er), which obeys the Curie-Weiss law, confirms the presence of trivalent RE atoms.

  9. Electrochemical planarization

    DOEpatents

    Bernhardt, A.F.; Contolini, R.J.

    1993-10-26

    In a process for fabricating planarized thin film metal interconnects for integrated circuit structures, a planarized metal layer is etched back to the underlying dielectric layer by electropolishing, ion milling or other procedure. Electropolishing reduces processing time from hours to minutes and allows batch processing of multiple wafers. The etched back planarized thin film interconnect is flush with the dielectric layer. 12 figures.

  10. Electrochemical planarization

    DOEpatents

    Bernhardt, Anthony F.; Contolini, Robert J.

    1993-01-01

    In a process for fabricating planarized thin film metal interconnects for integrated circuit structures, a planarized metal layer is etched back to the underlying dielectric layer by electropolishing, ion milling or other procedure. Electropolishing reduces processing time from hours to minutes and allows batch processing of multiple wafers. The etched back planarized thin film interconnect is flush with the dielectric layer.

  11. Crystal and electronic structures of CaAl{sub 2}Si{sub 2}-type rare-earth copper zinc phosphides RECuZnP{sub 2} (RE=Pr, Nd, Gd-Tm, Lu)

    SciTech Connect

    Blanchard, Peter E.R.; Stoyko, Stanislav S.; Cavell, Ronald G.; Mar, Arthur

    2011-01-15

    The quaternary rare-earth phosphides RECuZnP{sub 2} (RE=Pr, Nd, Gd-Tm, Lu) have been prepared by reaction of the elements at 900 {sup o}C, completing this versatile series which forms for nearly all RE metals. They adopt the trigonal CaAl{sub 2}Si{sub 2}-type structure (Pearson symbol hP5, space group P3-bar m1, Z=1), as confirmed by single-crystal X-ray diffraction analysis on ErCuZnP{sub 2} and powder X-ray diffraction analysis on the remaining members. The Cu and Zn atoms are assumed to be disordered over the single transition-metal site. Band structure calculations on a hypothetically ordered YCuZnP{sub 2} model suggest a semimetal, with a zero band gap between the valence and conduction bands. This electronic structure is supported by XPS valence band spectra for RECuZnP{sub 2} (RE=Gd-Er), in which the intensity drops off smoothly at the Fermi edge. The absence of a band gap permits the electron count to deviate from the precise value of 16 e{sup -} per formula unit, as demonstrated by the formation of a solid solution in GdCu{sub x}Zn{sub 2-x}P{sub 2} (1.0{<=}x{<=}1.3), while still retaining the CaAl{sub 2}Si{sub 2}-type structure. Because the Cu 2p XPS spectra indicate that the Cu atoms are always monovalent, the substitution of Cu for Zn leads to a decrease in electron count and a lowering of the Fermi level in the valence band. The magnetic susceptibility of RECuZnP{sub 2} (RE=Gd-Er), which obeys the Curie-Weiss law, confirms the presence of trivalent RE atoms. -- Graphical abstract: The absence of a band gap in the semimetallic quaternary rare-earth phosphides RECuZnP{sub 2} permits the formation of a solid solution such as GdCu{sub x}Zn{sub 2-x}P{sub 2} through hole-doping of the valence band. Display Omitted

  12. Ferromagnetic properties of fcc Gd thin films

    SciTech Connect

    Bertelli, T. P. Passamani, E. C.; Larica, C.; Nascimento, V. P.; Takeuchi, A. Y.

    2015-05-28

    Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature T{sub S} and film thickness x. Gd fcc samples were obtained when T{sub S} = 763 K and x = 10 nm, while the hcp structure was stabilized for lower T{sub S} (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fcc Gd layer as a consequence of the lattice relaxation process. Spin reorientation phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm{sup 3}, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fcc structure, as a soft ferromagnetic material.

  13. Pressure tuning of the magnetic transition in Gd{sub5}(Si{sub 0.375} Ge{sub 0.625}){sub 4}giant magnetocaloric effect material.

    SciTech Connect

    Tseng, Y. C.; Haskel, D.; Lang, J. C.; Mudryk, Ya.; Pecharsky, V. K.; Gschneidner, K. A.; Northwestern Univ.; Iowa State Univ.

    2008-04-01

    The effect of hydrostatic pressure on the ferromagnetic ordering transition of the monoclinic Gd{sub 5}(Si{sub 0.375}Ge{sub 0.625}){sub 4} giant magnetocaloric effect compound was investigated using x-ray magnetic circular dichroism measurements in a diamond anvil cell. The Curie temperature T{sub C} increases linearly with applied pressure up to {approx}7.2 GPa, at which point a discontinuity in dT{sub c}/dP occurs. This discontinuity, which appears when T{sub C} reaches {approx}277 K, is also observed when the unit cell volume is reduced by Si doping and is associated with the volume-driven monoclinic (M) to orthorhombic [O(I)] structural transition.

  14. Mo2NiB2-type {Gd, Tb, Dy)2Ni2.35Si0.65 and La2Ni3-type {Dy, Ho}2Ni2.5Si0.5 compounds: Crystal structure and magnetic properties

    NASA Astrophysics Data System (ADS)

    Morozkin, A. V.; Isnard, O.; Nirmala, R.; Malik, S. K.

    2015-05-01

    The crystal structure of new Mo2NiB2-type {Gd, Tb, Dy}2Ni2.35Si0.65 (Immm, No. 71, oI10) and La2Ni3-type {Dy, Ho}2Ni2.5Si0.5 (Cmce No. 64, oC20) compounds has been established using powder X-ray diffraction studies. Magnetization measurements show that the Mo2NiB2-type Gd2Ni2.35Si0.65 undergoes a ferromagnetic transition at 66 K, whereas isostructural Tb2Ni2.35Si0.65 shows an antiferromagnetic transition at 52 K and a field-induced metamagnetic transition at low temperatures. Neutron diffraction study shows that, in zero applied field, Tb2Ni2.35Si0.65 exhibits c-axis antiferromagnetic order with propagation vector K=[1/2, 0, 1/2] below its magnetic ordering temperature and Tb magnetic moment reaches a value of 8.32(5) μB at 2 K. The La2Ni3-type Dy2Ni2.5Si0.5 exhibits ferromagnetic like transition at 42 K with coexisting antiferromagnetic interactions and field induced metamagnetic transition below 17 K. The magnetocaloric effect of Gd2Ni2.35Si0.65, Tb2Ni2.35Si0.65 and Dy2Ni2.5Si0.5 is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of -14.3 J/kg K, -5.3 J/kg K and -10.3 J/kg K for a field change of 50 kOe near 66 K, 52 K and 42 K, respectively. Low temperature magnetic ordering with enhanced anisotropic effects in Tb2Ni2.35Si0.65 and Dy2Ni2.35Si0.65 is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +12.8 J/kg K and +9.9 J/kg K, respectively at 7 K for a field change of 50 kOe.

  15. Synthesis and characterization of monodisperse spherical SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

    SciTech Connect

    Wang, H.; Yang, J.; Zhang, C.M.; Lin, J.

    2009-10-15

    Spherical SiO{sub 2} particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO{sub 2}-RE{sub 2}O{sub 3} (RE=rare earth elements) and SiO{sub 2}-Gd{sub 2}O{sub 3}:Ln{sup 3+} (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, Sm{sup 3+}, Er{sup 3+}, Ho{sup 3+}) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln{sup 3+} ion mainly shows its characteristic emissions in the core-shell particles from Gd{sub 2}O{sub 3}:Ln{sup 3+} (Eu{sup 3+}, Tb{sup 3+}, Sm{sup 3+}, Dy{sup 3+}, Er{sup 3+}, Ho{sup 3+}) shells. - Graphical abstract: The advantages of core-shell phosphors are the easy availability of homogeneous spherical morphology in different size, and its corresponding luminescence color can change from red, yellow to green.

  16. Mo{sub 2}NiB{sub 2}-type (Gd, Tb, Dy){sub 2}Ni{sub 2.35}Si{sub 0.65} and La{sub 2}Ni{sub 3}-type (Dy, Ho){sub 2}Ni{sub 2.5}Si{sub 0.5} compounds: Crystal structure and magnetic properties

    SciTech Connect

    Morozkin, A.V.; Isnard, O.; Nirmala, R.; Malik, S.K.

    2015-05-15

    The crystal structure of new Mo{sub 2}NiB{sub 2}-type (Gd, Tb, Dy){sub 2}Ni{sub 2.35}Si{sub 0.65} (Immm, No. 71, oI10) and La{sub 2}Ni{sub 3}-type (Dy, Ho){sub 2}Ni{sub 2.5}Si{sub 0.5} (Cmce No. 64, oC20) compounds has been established using powder X-ray diffraction studies. Magnetization measurements show that the Mo{sub 2}NiB{sub 2}-type Gd{sub 2}Ni{sub 2.35}Si{sub 0.65} undergoes a ferromagnetic transition at ~66 K, whereas isostructural Tb{sub 2}Ni{sub 2.35}Si{sub 0.65} shows an antiferromagnetic transition at ~52 K and a field-induced metamagnetic transition at low temperatures. Neutron diffraction study shows that, in zero applied field, Tb{sub 2}Ni{sub 2.35}Si{sub 0.65} exhibits c-axis antiferromagnetic order with propagation vector K=[1/2, 0, 1/2] below its magnetic ordering temperature and Tb magnetic moment reaches a value of 8.32(5) μ{sub B} at 2 K. The La{sub 2}Ni{sub 3}-type Dy{sub 2}Ni{sub 2.5}Si{sub 0.5} exhibits ferromagnetic like transition at ~42 K with coexisting antiferromagnetic interactions and field induced metamagnetic transition below ~17 K. The magnetocaloric effect of Gd{sub 2}Ni{sub 2.35}Si{sub 0.65}, Tb{sub 2}Ni{sub 2.35}Si{sub 0.65} and Dy{sub 2}Ni{sub 2.5}Si{sub 0.5} is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of −14.3 J/kg K, −5.3 J/kg K and −10.3 J/kg K for a field change of 50 kOe near 66 K, 52 K and 42 K, respectively. Low temperature magnetic ordering with enhanced anisotropic effects in Tb{sub 2}Ni{sub 2.35}Si{sub 0.65} and Dy{sub 2}Ni{sub 2.35}Si{sub 0.65} is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +12.8 J/kg K and ~+9.9 J/kg K, respectively at 7 K for a field change of 50 kOe. - Graphical abstract: The (Gd, Tb, Dy){sub 2}Ni{sub 2.35}Si{sub 0.65} supplement the series of Mo{sub 2}NiB{sub 2}-type rare earth compounds, whereas the (Dy, Ho){sub 2}Ni{sub 2.5}Si{sub 0.5} supplement the series of La{sub 2}Ni{sub 3}-type rare

  17. Study on the low-temperature properties of pyrochlores Gd2Hf2O7 and Gd2Zr2O7, using crystal-field theory

    NASA Astrophysics Data System (ADS)

    Ali Biswas, Aksar; Jana, Yatramohan

    2011-07-01

    The geometrically frustrated pyrochlores Gd2Hf2O7 (GdH) and Gd2Zr2O7 (GdZ) are easy planar anisotropic systems in which considerable single-ion crystal-field anisotropies of D3d symmetry are found in the ground multiplet 8S7/2 due to admixture of higher Russell-Saunders terms. The 8S7/2 splits into 4 doublets with total CF splitting 9.9 K in GdH and 9.4 K in GdZ. The magnetic specific heat Cmag follows a conventional T3 behavior in GdH and an unconventional T4.6 behavior in GdZ down to 0.4 K.

  18. Planar micromixer

    DOEpatents

    Fiechtner, Gregory J.; Singh, Anup K.; Wiedenman, Boyd J.

    2008-03-18

    The present embodiment describes a laminar-mixing embodiment that utilizes simple, three-dimensional injection. Also described is the use of the embodiment in combination with wide and shallow sections of channel to affect rapid mixing in microanalytical systems. The shallow channel sections are constructed using all planar micromachining techniques, including those based on isotropic etching. The planar construction enables design using minimum dispersion concepts that, in turn, enable simultaneous mixing and injection into subsequent chromatography channels.

  19. Analysis of the refractive index and film thickness of Eu doped gadolinium oxide (Gd2O3) planar waveguides fabricated by the sol-gel and dip coating methods

    NASA Astrophysics Data System (ADS)

    Johnson, Quianna S.; Edwards, Matthew; Curley, Michael

    2013-09-01

    The present research focused on the systematic study of the fabrication of gadolinium oxide (Gd2O3) and gadolinium oxide:europium (Gd2O3:Eu3+) thin films via the sol-gel and dip coating methods under normal laboratory conditions in a methanol solvent medium to determine if thin films of comparable quality could be produced. The thin films were synthesized via the sol-gel method by the hydrolysis of gadolinium acetylacetate in two different solvent mediums, absolute ethanol and methanol. The europium doped gadolinium oxide sol-­-gels were prepared to have a final concentration of 0.01 M europium nitrate. Ordinary microscope glass slides (borosilicate glass or BSG) were used as the substrate. The substrates were cleaned and coated using the dip coating apparatus to prepare thin films that consisted of 5, 10, 30 and 50 layers. The cast films were annealed at 300°C and 500°C by direct insertion in a furnace operated under atmospheric conditions. The resulting film thickness and effective refractive indices were determined and compared. Finally, we present the introductory results of gadolinium oxide thin films as a waveguide.

  20. Spectroscopic, structural and in vitro cytotoxicity evaluation of luminescent, lanthanide doped core@shell nanomaterials GdVO4:Eu(3+)5%@SiO2@NH2.

    PubMed

    Szczeszak, Agata; Ekner-Grzyb, Anna; Runowski, Marcin; Szutkowski, Kosma; Mrówczyńska, Lucyna; Kaźmierczak, Zuzanna; Grzyb, Tomasz; Dąbrowska, Krystyna; Giersig, Michael; Lis, Stefan

    2016-11-01

    The luminescent GdVO4:Eu(3+)5%@SiO2@NH2 core@shell nanomaterials were obtained via co-precipitation method, followed by hydrolysis and co-condensation of silane derivatives: tetraethyl orthosilicate and 3-aminopropyltriethoxysilane. Their effect on human erythrocytes sedimentation and on proliferation of human lung microvascular endothelial cells was examined and discussed. The luminescent nanoparticles were synthesized in the presence of polyacrylic acid or glycerin in order to minimalize the agglomeration and excessive growth of nanostructures. Surface coating with amine functionalized silica shell improved their biocompatibility, facilitated further organic conjugation and protected the internal core. Magnetic measurements revealed an enhanced T1-relaxivity for the synthesized GdVO4:Eu(3+)5% nanostructures. Structure, morphology and average grain size of the obtained nanomaterials were determined by X-ray diffraction, transmission electron microscopy and dynamic light scattering analysis. The qualitative elemental composition of the nanomaterials was established using energy-dispersive X-ray spectroscopy. The spectroscopic characteristic of red emitting core@shell nanophosphors was completed by measuring luminescence spectra and decays. The emission spectra revealed characteristic bands of Eu(3+) ions related to the transitions (5)D0-(7)F0,1,2,3,4 and (5)D1-(7)F1. The luminescence lifetimes consisted of two components, associated with the presence of Eu(3+) ions located at the surface of the crystallites and in the bulk. PMID:27478979

  1. CaO-MgO-Al2O3-SiO2 (CMAS) corrosion of Gd2Zr2O7 and Sm2Zr2O7

    DOE PAGESBeta

    Wang, Honglong; Bakal, Ahmet; Zhang, Xingxing; Tarwater, Emily; Sheng, Zhizhi; Fergus, Jeffrey W.

    2016-08-08

    Ceramic thermal barrier coatings are applied to superalloys used in gas turbine engineering to increase the operating temperature and the energy conversion efficiency. However, dust consisting of CaO-MgO-Al2O3-SiO2 (CMAS) from the air can be injected into the engines and corrode the thermal barrier coatings. Lanthanide zirconates are promising materials in thermal barrier coatings due to their low thermal conductivities, good phase stability and good corrosion resistance. However, the corrosion resistance mechanism of CMAS on lanthanide zirconates is still not clearly understood. In this work, the corrosion mechanism of Gd2Zr2O7 and Sm2Zr2O7 in CMAS is studied. Here, the results show thatmore » the CMAS can easily react with lanthanide zirconate thermal barrier coatings to form a dense layer, which can resist further corrosion« less

  2. The lanthanoid(III) chloride cyclo-tetrasilicates M{sub 6}Cl{sub 10}[Si{sub 4}O{sub 12}] (M=Sm, Gd-Dy): Synthesis, structure and IR investigations

    SciTech Connect

    Hartenbach, Ingo . E-mail: hartenbach@iac.uni-stuttgart.de; Jagiella, Stefan; Schleid, Thomas . E-mail: schleid@iac.uni-stuttgart.de

    2006-08-15

    The chloride derivatized lanthanoid(III) cyclo-tetrasilicates of the composition M{sub 6}Cl{sub 10}[Si{sub 4}O{sub 12}] (M=Sm, Gd-Dy) crystallize monoclinically in space group C2/m (a=1062-1065, b=1036-1052, c=1163-1187pm, {beta}{approx}103{sup o}, Z=2). They are obtained by the reaction of the sesquioxides M{sub 2}O{sub 3} (or the combination of Tb{sub 4}O{sub 7} and Tb in 3:2-molar ratio for the terbium case), the corresponding trichlorides MCl{sub 3}, and SiO{sub 2} (silica gel) in stoichiometric ratios with double the amount of MCl{sub 3} as flux in evacuated silica tubes (7d at 850deg. C) as transparent, pseudo-octagonal, pillar-shaped single crystals with the colour of the respective lanthanoid trication M{sup 3+}. Their crystal structure can be considered as a layered arrangement in which cationic {sub {approx}}{sup 2}{l_brace}[(M2){sub 5}Cl{sub 9}]{sup 6+}{r_brace} layers are alternatingly piled with anionic ones of the kind {sub {approx}}{sup 2}{l_brace}[(M1)Cl[Si{sub 4}O{sub 12}

  3. Electrochemical planarization for microelectronic circuits

    SciTech Connect

    Contolini, R.J.; Mayer, S.T.; Bernhardt, A.F.

    1993-03-25

    The need for flatter and smoother surfaces (planarization) in microelectronic circuits increases as the number of metal levels in ultra large scale integrated (ULSI) circuits increases. At Lawrence Livermore National Laboratory, the authors have developed an electrochemical planarization process that fills vias and trenches with metal (without voids) and subsequently planarizes the surface. Use is made of plasma-enhanced chemical vapor deposition (PECVD) of SiO[sub 2] for the dielectric layers and electroplated copper for the metalization. This report describes the advantages of this process over existing techniques, possibilities for collaboration, and previous technology transfer.

  4. Electrochemical planarization for microelectronic circuits

    NASA Astrophysics Data System (ADS)

    Contolini, R. J.; Mayer, S. T.; Bernhardt, A. F.

    1993-03-01

    The need for flatter and smoother surfaces (planarization) in microelectronic circuits increases as the number of metal levels in ultra large scale integrated (ULSI) circuits increases. At Lawrence Livermore National Laboratory, the authors have developed an electrochemical planarization process that fills vias and trenches with metal (without voids) and subsequently planarizes the surface. Use is made of plasma-enhanced chemical vapor deposition (PECVD) of SiO2 for the dielectric layers and electroplated copper for the metalization. This report describes the advantages of this process over existing techniques, possibilities for collaboration, and previous technology transfer.

  5. Thermopower and electrical resistivity behavior near the martensitic transition in Gd 5(Si xGe 1-x) 4 magnetocaloric compounds

    NASA Astrophysics Data System (ADS)

    Pinto, R. P.; Sousa, J. B.; Correia, F. C.; Araújo, J. P.; Braga, M. E.; Pereira, A. M.; Morellon, L.; Algarabel, P. A.; Magen, C.; Ibarra, M. R.

    2005-04-01

    Recently, the Gd5(SixGe1-x)4 system exhibits fascinating physical properties, namely giant magnetocaloric, magnetoresistance and magnetostriction effects near a first-order (martensitic like; T =TS) magneto-structural transition. We report the thermopower behavior S (T) between 10 and 300 K for compounds with x = 0 , 0.10 and 0.45, belonging to three distinct regions of the magnetic/structural phase diagram. Large thermopower changes are observed near TS for x = 0 .10 (TS = 78 K ; AFM-Orthorhombic II/FM-Ortho.I) and for x = 0.45 (TS = 242 K ; PM-Monoc/FM-Ortho.I) with a Gaussian distribution in d S / d T , characteristic of a first-order phase transition. Near the purely magnetic transitions (PM/AFM) for x = 0 (TN = 122 K) and x = 0.10 (TN = 127 K) we observe d S / d T peaks governed by spin fluctuation effects. A comparative analysis between d S / d T and the resistivity derivative d ρ / d T near TS is made. At low temperatures S (T) behaves similarly in the ferromagnetic x = 0.10 and 0.45 compounds (S ≈ AT + BT2) , the anomalous B term being related to the mean internal field (spin wave excitations). For x = 0 (AFM phase at low T) one has S = AT (no B term; zero mean internal field).

  6. Si

    NASA Astrophysics Data System (ADS)

    Fiameni, S.; Famengo, A.; Agresti, F.; Boldrini, S.; Battiston, S.; Saleemi, M.; Johnsson, M.; Toprak, M. S.; Fabrizio, M.

    2014-06-01

    Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion in the middle-high temperature range. The detrimental effect of the presence of MgO on the TE properties of Mg2Si based materials is widely known. For this reason, the conditions used for synthesis and sintering were optimized to limit oxygen contamination. The effect of Bi doping on the TE performance of dense Mg2Si materials was also investigated. Synthesis was performed by ball milling in an inert atmosphere starting from commercial Mg2Si powder and Bi powder. The samples were consolidated, by spark plasma sintering, to a density >95%. The morphology, and the composition and crystal structure of samples were characterized by field-emission scanning electronic microscopy and x-ray diffraction, respectively. Moreover, determination of Seebeck coefficients and measurement of electrical and thermal conductivity were performed for all the samples. Mg2Si with 0.1 mol% Bi doping had a ZT value of 0.81, indicative of the potential of this method for fabrication of n-type bulk material with good TE performance.

  7. Biogeochemistry of Mariana Islands coastal sediments: terrestrial influence on /gd13, Ash, CaCO3, Al, Fe, Si and P

    NASA Astrophysics Data System (ADS)

    Matson, Ernest A.

    1989-01-01

    Stable C isotope ratios (δ13C-PDB), percentages of organic matter, and HCl insoluble ash and soluble carbonates, extractable Fe, Al, Si and P were used to determine the distribution and accumulation of terrestrial material in reef-flat moats and lagoons of two high islands (Guam and Saipan) in the western tropical Pacific. Carbonate sediments of a reef-flat moat infiltrated by seepage of aquifer waters (but without surface runoff) were depleted in both P (by 38%) and 13C (by 41%) and enriched in Si (by 100%) relative to offshore lagoon sediments. Iron and ash accumulated in depositional regimes regardless of the occurrence of runoff but was depleted from coarse-grained carbonates in turbulent regimes. Aluminum (>ca. 10 to 20 μmol g-1), Fe (>ca. 1 to 3 μmol g-1) and ash (>0.5%) indicated terrigenous influence which was corroborated by depletions in both 13C and P. Low-salinity geochemical segregation, natural biochemical accumulation, as well as long-shore currents and eddies help sequester these materials nearshore.

  8. Synthesis, crystal structure and properties of Mg3B36Si9C and related rare earth compounds RE3-xB36Si9C (RE=Y, Gd-Lu)

    NASA Astrophysics Data System (ADS)

    Ludwig, Thilo; Pediaditakis, Alexis; Sagawe, Vanessa; Hillebrecht, Harald

    2013-08-01

    We report on the synthesis and characterisation of Mg3B36Si9C. Black single crystals of hexagonal shape were yielded from the elements at 1600 °C in h-BN crucibles welded in Ta ampoules. The crystal structure (space group R3barm, a=10.0793(13) Å, c=16.372(3) Å, 660 refl., 51 param., R1(F)=0.019; wR2(F2)=0.051) is characterized by a Kagome-net of B12 icosahedra, ethane like Si8-units and disordered SiC-dumbbells. Vibrational spectra show typical features of boron-rich borides and Zintl phases. Mg3B36Si9C is stable against HF/HNO3 and conc. NaOH. The micro-hardness is 17.0 GPa (Vickers) and 14.5 GPa (Knoop), respectively. According to simple electron counting rules Mg3B36Si9C is an electron precise compound. Band structure calculations reveal a band gap of 1.0 eV in agreement to the black colour. Interatomic distances obtained from the refinement of X-ray data are biased and falsified by the disorder of the SiC-dumbbell. The most evident structural parameters were obtained by relaxation calculation. Composition and carbon content were confirmed by WDX measurements. The small but significant carbon content is necessary by structural reasons and frequently caused by contaminations. The rare earth compounds RE3-xB36Si9C (RE=Y, Dy-Lu) are isotypic. Single crystals were grown from a silicon melt and their structures refined. The partial occupation of the RE-sites fits to the requirements of an electron-precise composition. According to the displacement parameters a relaxation should be applied to obtain correct structural parameters.

  9. Ganglioside GD2 in reception and transduction of cell death signal in tumor cells

    PubMed Central

    2014-01-01

    Background Ganglioside GD2 is expressed on plasma membranes of various types of malignant cells. One of the most promising approaches for cancer immunotherapy is the treatment with monoclonal antibodies recognizing tumor-associated markers such as ganglioside GD2. It is considered that major mechanisms of anticancer activity of anti-GD2 antibodies are complement-dependent cytotoxicity and/or antibody-mediated cellular cytotoxicity. At the same time, several studies suggested that anti-GD2 antibodies are capable of direct induction of cell death of number of tumor cell lines, but it has not been investigated in details. In this study we investigated the functional role of ganglioside GD2 in the induction of cell death of multiple tumor cell lines by using GD2-specific monoclonal antibodies. Methods Expression of GD2 on different tumor cell lines was analyzed by flow cytometry using anti-GD2 antibodies. By using HPTLC followed by densitometric analysis we measured the amount of ganglioside GD2 in total ganglioside fractions isolated from tumor cell lines. An MTT assay was performed to assess viability of GD2-positive and -negative tumor cell lines treated with anti-GD2 mAbs. Cross-reactivity of anti-GD2 mAbs with other gangliosides or other surface molecules was investigated by ELISA and flow cytometry. Inhibition of GD2 expression was achieved by using of inhibitor for ganglioside synthesis PDMP and/or siRNA for GM2/GD2 and GD3 synthases. Results Anti-GD2 mAbs effectively induced non-classical cell death that combined features of both apoptosis and necrosis in GD2-positive tumor cells and did not affect GD2-negative tumors. Anti-GD2 mAbs directly induced cell death, which included alteration of mitochondrial membrane potential, induction of apoptotic volume decrease and cell membrane permeability. This cytotoxic effect was mediated exclusively by specific binding of anti-GD2 antibodies with ganglioside GD2 but not with other molecules. Moreover, the level of GD2

  10. Modification of Mg{sub 2}Si in Mg–Si alloys with gadolinium

    SciTech Connect

    Ye, Lingying; Hu, Jilong Tang, Changping; Zhang, Xinming; Deng, Yunlai; Liu, Zhaoyang; Zhou, Zhile

    2013-05-15

    The modification effect of gadolinium (Gd) on Mg{sub 2}Si in the hypereutectic Mg–3 wt.% Si alloy has been investigated using optical microscope, scanning electron microscope, X-ray diffraction and hardness measurements. The results indicate that the morphology of the primary Mg{sub 2}Si is changed from coarse dendrite into fine polygon with the increasing Gd content. The average size of the primary Mg{sub 2}Si significantly decreases with increasing Gd content up to 1.0 wt.%, and then slowly increases. Interestingly, when the Gd content is increased to 4.0 and 8.0 wt.%, the primary and eutectic Mg{sub 2}Si evidently decrease and even disappear. The modification and refinement of the primary Mg{sub 2}Si is mainly attributed to the poisoning effect. The GdMg{sub 2} phase in the primary Mg{sub 2}Si is obviously coarsened as the Gd content exceeds 2.0 wt.%. While the decrease and disappearance of the primary and eutectic Mg{sub 2}Si are ascribed to the formation of vast GdSi compound. Therefore, it is reasonable to conclude that proper Gd (1.0 wt.%) addition can effectively modify and refine the primary Mg{sub 2}Si. - Highlights: ► Proper Gd (1.0 wt.%) addition can effectively modify and refine the primary Mg{sub 2}Si. ► We studied the reaction feasibility between Mg and Si, Gd and Si in Mg–Gd–Si system. ► We explored the modification mechanism of Gd modifier on Mg{sub 2}Si.

  11. Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

    NASA Astrophysics Data System (ADS)

    Cipro, R.; Baron, T.; Martin, M.; Moeyaert, J.; David, S.; Gorbenko, V.; Bassani, F.; Bogumilowicz, Y.; Barnes, J. P.; Rochat, N.; Loup, V.; Vizioz, C.; Allouti, N.; Chauvin, N.; Bao, X. Y.; Ye, Z.; Pin, J. B.; Sanchez, E.

    2014-06-01

    Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO2 cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

  12. SiO 2-CaO-B 2O 3-Al 2O 3 ceramic glaze as sealant for planar ITSOFC

    NASA Astrophysics Data System (ADS)

    Zheng, R.; Wang, S. R.; Nie, H. W.; Wen, T.-L.

    A series of ceramic glazes based on the SiO 2-CaO-B 2O 3-Al 2O 3 system as sealant for intermediate temperature solid oxide fuel cell (ITSOFC) were investigated. Different ratios of B 2O 3/SiO 2 and Al 2O 3/CaO were investigated to control softening process, phase separation, and crystallization. When B 2O 3/SiO 2 ratio was in the range of 0.14-0.27, the glazes showed good wetting and bonding behavior with both 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte and stainless steel interconnect which could satisfy the sealing demand at 850 °C. And the dimension stability can be kept for over 100 h by introducing ceramic felt and controlling the glazes viscosity in the range of 10 4 to 10 6 Pa s. By means of controlling Al 2O 3/CaO ratio in the range of 0.4-0.68, phase separation and crystallization were restrained effectively. After holding at 850 °C for 100 h, non-crystalline network in the glazes could be found, and a suitable viscous flow could well relax thermal stress. The sealing was effective even after 10 thermal cycles. Element analysis showed a good chemical stability at the ceramic glazes/stainless steel interconnect and ceramic glazes/8YSZ electrolyte interfaces.

  13. The morphology of GM1 x/SM 0.6-x/Chol 0.4 planar bilayers supported on SiO 2 surfaces

    NASA Astrophysics Data System (ADS)

    Mao, Yanli; Tero, Ryugo; Imai, Yosuke; Hoshino, Tyuji; Urisu, Tsuneo

    2008-07-01

    Ganglioside GM1 (GM1), sphingomyelin (SM) and cholesterol (Chol) are dominant lipid components of rafts in plasma membranes. The morphology of GM1 x/SM 0.6-x/Chol 0.4 SPBs on SiO 2 surfaces has been studied by atomic force microscopy and fluorescence microscopy at various ratios of GM1/SM ( x = 0-0.25). The unique changes in morphology depending on the GM1 concentrations are qualitatively explained by hydrogen bonding and the hydrophobic interactions between SM and Chol, and by hydrogen bonding and the steric effects between bulky GM1 headgroups under Ca 2+ existing conditions and the electrostatic repulsion between the negative charges of GM1 headgroups under Ca 2+ nonexisting conditions.

  14. High-pressure synthesis of a La orthosilicate and Nd, Gd, and Dy disilicates

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyang; Fleet, Michael E.

    2002-11-01

    Several rare-earth silicates have been synthesized at 10 GPa and 1600-1700 °C: a La orthosilicate (La4Si3O12) with a defect Ba3(PO4)2-type, a new structure type (K) for Nd and Gd disilicates (Nd2Si2O7 and Gd2Si2O7) with a diorthosilicate structure, and a new structure type (L) for Dy disilicate (Dy2Si2O7) with a structure containing linear triple tetrahedral groups [Si3O10], but having one in six atoms distributed with 50% occupancy over two tetrahedral positions.

  15. Electrochromatography Methods: Planar Electrochromatography

    NASA Astrophysics Data System (ADS)

    Chomicki, Adam; Dzido, Tadeusz H.; Płocharz, Paweł; Polak, Beata

    Planar electrochromatography is a technique in which mixture components are separated in adsorbent layer of a chromatographic plate placed in electric field. In such separation system a mobile phase movement stems from electroosmosis phenomenon. Partition and electrophoresis mechanisms are involved in separation of mixture components with this technique. Two principal modes of planar electrochromatography are described: planar electrochromatography in an open system (PEC) and planar electrochromatography in a closed system (pressurized planar electrochromatography, PPEC). The development of both modes is presented beginning with the first paper on electrochromatography by Pretorius et al. in 1974 and finishing with the last papers by Dzido et al. in 2010. Constructional development of equipment to planar electrochromatography is provided and influence of operating variables on separation efficiency as well. The advantages and challenges of PPEC technique are especially discussed.

  16. Perpendicular Magnetic Anisotropy of Tb/Fe and Gd/Fe Multilayers Studied with Torque Magnetometer

    NASA Astrophysics Data System (ADS)

    Chowdhury, Ataur

    Perpendicular magnetic anisotropy (PMA) of multilayers critically depend on the magnetic and structural ordering of the interface. To study the effect of interface on PMA, Tb/Fe and Gd/Fe multilayers with varying Fe (0.8-9.0 nm) and Gd (0.5-2.8 nm) or Tb (0.3-6.3 nm) layer thicknesses were fabricated by planar magnetron sputtering. The magnetometer results of spin orientation clearly reveals that samples with Gd or Tb layer thickness of more than 1.2 nm display no PMA, regardless of the Fe layer thickness. Tb/Fe and Gd/Fe multilayers with thin (<1.2 nm) Tb or Gd layers display large PMA, but no PMA is observed when the Fe layer thickness is increased to 4.0 nm and higher. The bulk magnetization and anisotropy energy constant of the samples are found to increase with increasing Fe layer thickness. Torque measurement also reveals that there are two distinctly different axes of spin alignment at different energy. Tb/Fe and Gd/Fe multilayers with similar composition reveal similar magnetic and structural characteristics, and it may imply that single-ion-anisotropy of rare-earth element, which is quite large for Tb ions and very small for Gd ions, may not be the dominating cause of PMA in Td/Fe and Gd/Fe multilayers. A detailed explanation of the results will be provided based on exchange interaction at the interface.

  17. Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Caurant, D.

    2010-07-01

    Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

  18. Tuning interfacial domain walls in GdCo/Gd/GdCo' spring magnets

    NASA Astrophysics Data System (ADS)

    Blanco-Roldán, C.; Choi, Y.; Quirós, C.; Valvidares, S. M.; Zarate, R.; Vélez, M.; Alameda, J. M.; Haskel, D.; Martín, J. I.

    2015-12-01

    Spring magnets based on GdCo multilayers have been prepared to study the nucleation and evolution of interfacial domain walls (iDWs) depending on layer composition and interlayer coupling. GdCo alloy compositions in each layer were chosen so that their net magnetization aligns either with the Gd (G d35C o65 ) or Co (G d11C o89 ) sublattices. This condition forces an antiparallel arrangement of the layers' net magnetization and leads to nucleation of iDWs above critical magnetic fields whose values are dictated by the interplay between Zeeman and exchange energies. By combining x-ray resonant magnetic scattering with Kerr magnetometry, we provide detailed insight into the nucleation and spatial profile of the iDWs. For strong coupling (GdCo/GdCo' bilayer), iDWs are centered at the interface but with asymmetric width depending on each layer magnetization. When interlayer coupling is weakened by introducing a thin Gd interlayer, the exchange spring effect becomes restricted to a lower temperature and field range than observed in the bilayer structure. Due to the ferromagnetic alignment between the high magnetization G d35C o65 layer and the Gd interlayer, the iDW shrinks and moves into the lower exchange Gd interlayer, causing a reduction of iDW energy.

  19. Epitaxial Si encapsulation of highly misfitting SiC quantum dot arrays formed on Si (001)

    SciTech Connect

    Petz, C. W.; Floro, J. A.; Yang, D.; Levy, J.; Myers, A. F.

    2014-01-06

    This work examines Si overgrowth to encapsulate 3C-SiC quantum dot arrays epitaxially grown on Si substrates. Using transmission electron microscopy, we show how the crystalline quality of the Si cap depends on the growth conditions. Overgrowth at 300 °C leads to a planar, epitaxial Si cap, but with small crystallographic rotations in the cap above each quantum dot. At 400 °C growth temperature, Si exhibits reduced sticking to the SiC, leading to a non-planar cap. However, a two-step process, with thin layer grown at 250 °C followed by growth at 500 °C, leads to a planar cap with a much-reduced density of defects.

  20. Learning planar ising models

    SciTech Connect

    Johnson, Jason K; Chertkov, Michael; Netrapalli, Praneeth

    2010-11-12

    Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus our attention on the class of planar Ising models, for which inference is tractable using techniques of statistical physics [Kac and Ward; Kasteleyn]. Based on these techniques and recent methods for planarity testing and planar embedding [Chrobak and Payne], we propose a simple greedy algorithm for learning the best planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. We present the results of numerical experiments evaluating the performance of our algorithm.

  1. Peculiarities of thermoelectric half-Heusler phase formation in Gd-Ni-Sb and Lu-Ni-Sb ternary systems

    NASA Astrophysics Data System (ADS)

    Romaka, V. V.; Romaka, L.; Horyn, A.; Rogl, P.; Stadnyk, Yu; Melnychenko, N.; Orlovskyy, M.; Krayovskyy, V.

    2016-07-01

    The phase equilibria in the Gd-Ni-Sb and Lu-Ni-Sb ternary systems were studied at 873 K by X-ray and metallographic analyses in the whole concentration range. The interaction of the elements in the Gd-Ni-Sb system results the formation of five ternary compounds at investigated temperature: Gd5Ni2Sb (Mo5SiB2-type), Gd5NiSb2 (Yb5Sb3-type), GdNiSb (MgAgAs-type), Gd3Ni6Sb5 (Y3Ni6Sb5-type), and GdNi0.72Sb2 (HfCuSi2-type). At investigated temperature the Lu-Ni-Sb system is characterized by formation of the LuNiSb (MgAgAs-type), Lu5Ni2Sb (Mo5SiB2-type), and Lu5Ni0.56Sb2.44 (Yb5Sb3-type) compounds. The disordering in the crystal structure of half-Heusler GdNiSb and LuNiSb was revealed by EPMA and studied by means of Rietveld refinement and DFT modeling. The performed electronic structure calculations are in good agreement with electrical transport property studies.

  2. Spectroscopy of Gd153 and Gd157 using the (p,dγ) reaction

    SciTech Connect

    Ross, T. J.; Hughes, R. O.; Allmond, J. M.; Beausang, C. W.; Angell, C. T.; Basunia, M. S.; Bleuel, D. L.; Burke, J. T.; Casperson, R. J.; Escher, J. E.; Fallon, P.; Hatarik, R.; Munson, J.; Paschalis, S.; Petri, M.; Phair, L. W.; Ressler, J. J.; Scielzo, N. D.

    2014-10-31

    Low-spin single quasineutron levels in 153Gd and 157Gd have been studied following the 154Gd(p,d-γ )153Gd and 158Gd(p,d-γ )157Gd reactions. A combined Si telescope and high-purity germanium array was utilized, allowing d-γ and d-γ-γ coincidence measurements. Almost all of the established low-excitation-energy, low-spin structures were confirmed in both 153Gd and 157Gd. Several new levels and numerous new rays are observed in both nuclei, particularly for Ex ≥1 MeV. Lastly, residual effects of a neutron subshell closure at N = 64 are observed in the form of a large excitation energy gap in the single quasineutron level schemes.

  3. Observations on the Influence of Secondary Me Oxides Additives (Me=Si,Al, Mg) on the Microstructural Evolution and Mechanical Behavior of Silicon Nitride Ceramics Containing RE2O3 (RE=La, Gd, Lu)

    SciTech Connect

    Becher, Paul F; Averill, Frank; Lin, Hua-Tay; Waters, Shirley B; Shibata, Naoya; Painter, Gayle S; van Benthem, Klaus

    2010-01-01

    The evolution of β Si3N4 microstructures is influenced by the adsorption of rare earth elements at grain surfaces and by the viscosity of the intergranular phases. Theoretical and STEM studies show that the RE atoms exhibit different tendencies to segregate from the liquid phase to grain surfaces and different binding strengths at these surfaces. When combined with MgO (or Al2O3) secondary additions, the rare earth additives are combined in low viscosity intergranular phases during densification and the α to β phase transformation and microstructural evolution are dominated by the RE adsorption behavior. On the other hand, a much higher viscosity intergranular phase forms when the RE2O3 are combined with SiO2. While the rare earth adsorption behavior remains the same, the phase transformation and microstructure are now dominated by Si3N4 solubility and transport in the high liquid phase. By understanding these additive effects, one can develop reinforced microstructures leading silicon nitride ceramics with greatly improved mechanical behavior.

  4. Glass-ceramic nuclear waste forms obtained from SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): study of internal crystallization

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Caurant, D.; Baffier, N.; Mazerolles, L.; Fillet, C.

    2004-10-01

    Glass-ceramic waste forms such as zirconolite (nominally CaZrTi 2O 7) based ones can be envisaged as good candidates for minor actinides or Pu immobilization. Such materials, in which the actinides (or lanthanides used as actinide surrogates) would be preferentially incorporated into zirconolite crystals homogeneously dispersed in a durable glassy matrix, can be prepared by controlled crystallization (nucleation + crystal growth) of parent glasses belonging to the SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 system. In this work we present the effects of the nature of the minor actinide surrogate (Ce, Nd, Eu, Gd, Yb, Th) on the structure, the microstructure and the composition of the zirconolite crystals formed in the bulk of the glass-ceramics. The amount of lanthanides and thorium incorporated into zirconolite crystals is discussed in relation with the capacity of the glass to accommodate these elements and of the crystals to incorporate them in the calcium and zirconium sites of their structure.

  5. Enjoyment of Euclidean Planar Triangles

    ERIC Educational Resources Information Center

    Srinivasan, V. K.

    2013-01-01

    This article adopts the following classification for a Euclidean planar [triangle]ABC, purely based on angles alone. A Euclidean planar triangle is said to be acute angled if all the three angles of the Euclidean planar [triangle]ABC are acute angles. It is said to be right angled at a specific vertex, say B, if the angle ?ABC is a right angle…

  6. Planar plasmonic chiral nanostructures.

    PubMed

    Zu, Shuai; Bao, Yanjun; Fang, Zheyu

    2016-02-21

    A strong chiral optical response induced at a plasmonic Fano resonance in a planar Au heptamer nanostructure was experimentally and theoretically demonstrated. The scattering spectra show the characteristic narrow-band feature of Fano resonances for both left and right circular polarized lights, with a chiral response reaching 30% at the Fano resonance. Specifically, we systematically investigate the chiral response of planar heptamers with gradually changing the inter-particle rotation angles and separation distance. The chiral spectral characteristics clearly depend on the strength of Fano resonances and the associated near-field optical distributions. Finite element method simulations together with a multipole expansion method demonstrate that the enhanced chirality is caused by the excitation of magnetic quadrupolar and electric toroidal dipolar modes. Our work provides an effective method for the design of 2D nanostructures with a strong chiral response. PMID:26818746

  7. Planar electrochemical device assembly

    DOEpatents

    Jacobson; Craig P. , Visco; Steven J. , De Jonghe; Lutgard C.

    2010-11-09

    A pre-fabricated electrochemical device having a dense electrolyte disposed between an anode and a cathode preferably deposited as thin films is bonded to a porous electrically conductive support. A second porous electrically conductive support may be bonded to a counter electrode of the electrochemical device. Multiple electrochemical devices may be bonded in parallel to a single porous support, such as a perforated sheet to provide a planar array. Planar arrays may be arranged in a stacked interconnected array. A method of making a supported electrochemical device is disclosed wherein the method includes a step of bonding a pre-fabricated electrochemical device layer to an existing porous metal or porous metal alloy layer.

  8. Dielectric Covered Planar Antennas

    NASA Technical Reports Server (NTRS)

    Llombart Juan, Nuria (Inventor); Lee, Choonsup (Inventor); Chattopadhyay, Goutam (Inventor); Gill, John J. (Inventor); Skalare, Anders J. (Inventor); Siegel, Peter H. (Inventor)

    2014-01-01

    An antenna element suitable for integrated arrays at terahertz frequencies is disclosed. The antenna element comprises an extended spherical (e.g. hemispherical) semiconductor lens, e.g. silicon, antenna fed by a leaky wave waveguide feed. The extended spherical lens comprises a substantially spherical lens adjacent a substantially planar lens extension. A couple of TE/TM leaky wave modes are excited in a resonant cavity formed between a ground plane and the substantially planar lens extension by a waveguide block coupled to the ground plane. Due to these modes, the primary feed radiates inside the lens with a directive pattern that illuminates a small sector of the lens. The antenna structure is compatible with known semiconductor fabrication technology and enables production of large format imaging arrays.

  9. Planar electrochemical device assembly

    DOEpatents

    Jacobson, Craig P.; Visco, Steven J.; De Jonghe, Lutgard C.

    2007-06-19

    A pre-fabricated electrochemical device having a dense electrolyte disposed between an anode and a cathode preferably deposited as thin films is bonded to a porous electrically conductive support. A second porous electrically conductive support may be bonded to a counter electrode of the electrochemical device. Multiple electrochemical devices may be bonded in parallel to a single porous support, such as a perforated sheet to provide a planar array. Planar arrays may be arranged in a stacked interconnected array. A method of making a supported electrochemical device is disclosed wherein the method includes a step of bonding a pre-fabricated electrochemical device layer to an existing porous metal or porous metal alloy layer.

  10. Planar triode pulser socket

    DOEpatents

    Booth, R.

    1994-10-25

    A planar triode is mounted in a PC board orifice by means of a U-shaped capacitor housing and anode contact yoke removably attached to cathode leg extensions passing through and soldered to the cathode side of the PC board by means of a PC cathode pad. A pliant/flexible contact attached to the orifice make triode grid contact with a grid pad on the grid side of the PC board, permitting quick and easy replacement of bad triodes. 14 figs.

  11. Planar triode pulser socket

    DOEpatents

    Booth, Rex

    1994-01-01

    A planar triode is mounted in a PC board orifice by means of a U-shaped capacitor housing and anode contact yoke removably attached to cathode leg extensions passing through and soldered to the cathode side of the PC board by means of a PC cathode pad. A pliant/flexible contact attached to the orifice make triode grid contact with a grid pad on the grid side of the PC board, permitting quick and easy replacement of bad triodes.

  12. Planar waveguide optical immunosensors

    NASA Astrophysics Data System (ADS)

    Choquette, Steven J.; Locascio-Brown, Laurie E.; Durst, Richard A.

    1991-03-01

    Monoclonal antibodies were covalently bonded to the surfaces of planar waveguides to confer immunoreacth''ity. Silver-ion diffused waveguides were used to measure theophylline concentrations in a fluorescence immunoassay and silicon nitride waveguides were used to detect theophylline in an absorbance-based immunoassay. Liposomes were employed in both assays as the optically detectable label in a competitive reaction to monitor antigen-antibody complexation. Regeneration of the active antibody site will be discussed.

  13. Lattice distortions in layered type arsenides LnTAs 2 ( Ln=La-Nd, Sm, Gd, Tb; T=Ag, Au): Crystal structures, electronic and magnetic properties

    NASA Astrophysics Data System (ADS)

    Rutzinger, D.; Bartsch, C.; Doerr, M.; Rosner, H.; Neu, V.; Doert, Th.; Ruck, M.

    2010-03-01

    The lanthanide coinage-metal diarsenides LnTAs 2 ( Ln=La, Ce-Nd, Sm; T=Ag, Au) have been reinvestigated and their structures have been refined from single crystal X-ray data. Two different distortion variants of the HfCuSi 2 type are found: PrAgAs 2, NdAgAs 2, SmAgAs 2, GdAgAs 2, TbAgAs 2, NdAuAs 2 and SmAuAs 2 crystallize as twofold superstructures in space group Pmcn with the As atoms of their planar layers forming zigzag chains, whereas LaAgAs 2, CeAgAs 2 and PrAuAs 2 adopt a fourfold superstructure (space group Pmca) with cis-trans chains of As atoms. The respective atomic positions can be derived from the HfCuSi 2 type by group-subgroup relations. The compounds with zigzag chains of As atoms exhibit metallic behaviour while those with cis-trans chains are semiconducting as measured on powder pellets. The majority of the compounds including 4 f elements show antiferromagnetic ordering at TN<20 K.

  14. Crystal growth and optical properties of Ce:(La,Gd)2Ge2O7 grown by the floating zone method

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Shishido, Toetsu; Sugawara, Takamasa; Yubuta, Kunio; Jan, Pejchal; Suzuki, Akira; Yokota, Yuui; Shoji, Yasuhiro; Kamada, Kei; Yoshikawa, Akira

    2014-05-01

    Some pyrosilicate scintillators such as Ce:Gd2Si2O7 and Ce:Lu2Si2O7 have a good light output, and especially Ce:(Gd,La)2Si2O7 has an excellent light output of over 36,000 ph/MeV. In order to search novel scintilators, we have developed a pyrogermanate-based scintillation material (Ce0.01,Gd0.90,La0.09)2Ge2O7 using the floating zone method. Although the light output was decreased due to quenching, 5d-4f transition of Ce3+ was observed around 480 nm in photo- and radio-luminescence spectra. This emission wavelength was longer than that of (Ce0.01,Gd0.90,La0.09)2Si2O7 with an emission wavelength of 390 nm.

  15. Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd5(SixGe1-x)4

    SciTech Connect

    Mangui Han

    2004-12-19

    Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} for x 0 {approx} 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd{sub 5}(Si{sub 1.95}Ge{sub 2.05}), Gd{sub 5}(Si{sub 2}Ge{sub 2}), Gd{sub 5}(Si{sub 2.09}Ge{sub 1.91}), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd{sub 5}(Si{sub 0.15}Ge{sub 3.85}), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd{sub 5}(Si{sub 2.3}Ge{sub 1.7}) and Gd{sub 5}(Si{sub 3}Ge{sub 1}), it was a second order transformation between the paramagnetic and ferromagnetic state, because no {Delta}T have been found. Giant magnetostriction was only found on Gd{sub 5}(Si{sub 1.95}Ge{sub 2.05}), Gd{sub 5}(Si{sub 2}Ge{sub 2}), Gd{sub 5}(Si{sub 2.09}Ge{sub 1.91}) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd{sub 5}(Si{sub 2.09}Ge{sub 1.91}) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally-induced strain higher in the sample made from lower purity level Gd starting materials compared with the sample made from high purity Gd metal. TE, MS, MFM and VSM measurements

  16. Instantaneous planar visualization of reacting supersonic flows using silane seeding

    NASA Technical Reports Server (NTRS)

    Smith, Michael W.; Northam, G. B.

    1991-01-01

    A new visualization technique for reacting flows has been developed. This technique, which is suitable for supersonic combustion flows, has been demonstrated on a scramjet combustor model. In this application, gaseous silane (SiH4) was added to the primary hydrogen fuel. When the fuel reacted, so did the (SiH4), producing silica (SiO2) particles in situ. The particles were illuminated with a laser sheet formed from a frequency-doubled Nd:YAG laser (532 nm) beam and the Mie scattering signal was imaged. These planar images of the silica Mie scattering provided instantaneous 'maps' of combustion progress within the turbulent reacting flowfield.

  17. Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

    SciTech Connect

    Cipro, R.; Gorbenko, V.; Baron, T. Martin, M.; Moeyaert, J.; David, S.; Bassani, F.; Bogumilowicz, Y.; Barnes, J. P.; Rochat, N.; Loup, V.; Vizioz, C.; Allouti, N.; Chauvin, N.; Bao, X. Y.; Ye, Z.; Pin, J. B.; Sanchez, E.

    2014-06-30

    Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO{sub 2} cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

  18. Planar elliptic growth

    SciTech Connect

    Mineev, Mark

    2008-01-01

    The planar elliptic extension of the Laplacian growth is, after a proper parametrization, given in a form of a solution to the equation for areapreserving diffeomorphisms. The infinite set of conservation laws associated with such elliptic growth is interpreted in terms of potential theory, and the relations between two major forms of the elliptic growth are analyzed. The constants of integration for closed form solutions are identified as the singularities of the Schwarz function, which are located both inside and outside the moving contour. Well-posedness of the recovery of the elliptic operator governing the process from the continuum of interfaces parametrized by time is addressed and two examples of exact solutions of elliptic growth are presented.

  19. Planar electroluminescent panel techniques

    NASA Technical Reports Server (NTRS)

    Kerr, C.; Kell, R. E.

    1973-01-01

    Investigations of planar electroluminescent multipurpose displays with latch-in memory are described. An 18 x 24 in. flat, thin address panel with elements spacing of 0.100 in. was constructed which demonstrated essentially uniform luminosity of 3-5 foot lamberts for each of its 43200 EL cells. A working model of a 4-bit EL-PC (electroluminescent photoconductive) electrooptical decoder was made which demonstrated the feasibility of this concept. A single-diagram electroluminescent display device with photoconductive-electroluminescent latch-in memory was constructed which demonstrated the conceptual soundness of this principle. Attempts to combine these principles in a single PEL multipurpose display with latch-in memory were unsuccessful and were judged to exceed the state-of-the-art for close-packed (0.10 in. centers) photoconductor-electroluminescent cell assembly.

  20. Elevated overview of Piers GD1 and GD2, showing rail lines, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Elevated overview of Piers GD-1 and GD-2, showing rail lines, GD-2 Quay Wall of Dry Dock No. 2 on left - U.S. Naval Base, Pearl Harbor, Dry Dock No. 1, Approach Pier & Caisson Docking Wharf, Ocean end of Fifth Street between Dry Dock Nos. 1 & 2, Pearl City, Honolulu County, HI

  1. Si(hhm) surfaces: Templates for developing nanostructures

    SciTech Connect

    Bozhko, S. I. Ionov, A. M.; Chaika, A. N.

    2015-06-15

    The fabrication of ordered low-dimensional structures on clean and metal-atom-decorated stepped Si(557) and Si(556) surfaces is discussed. The formation conditions and atomic structure of regular step systems on clean Si(557) 7 × 7 and Si(556) 7 × 7 surfaces are studied. The atomic structure of stepped Si(hhm), Ag/Si(557), and Gd/Si(557) surfaces is studied using high-resolution scanning tunneling microscopy and low-energy electron diffraction. The possibility of fabricating 1D and 2D structures of gadolinium and silver atoms on the Si(557) surface is demonstrated.

  2. Registration of heavy metal ions and pesticides with ATR planar waveguide enzyme sensors

    NASA Astrophysics Data System (ADS)

    Nabok, Alexei; Haron, Saharudin; Ray, Asim

    2004-11-01

    The proposed novel type of enzyme optical sensors is based on a combination of SiO2/Si3N4/SiO2 planar waveguide ATR (attenuated total reflection) transducer, fabricated by standard silicon planar technology, with the composite polyelectrolyte self-assembled coating containing both organic chromophores and enzyme molecules. Such devices were deployed to monitor typical industrial and agricultural water pollutants, such as heavy metal ions and pesticides, acting as inhibitors of enzyme reactions. The sensitivity of registration of these pollutants in the range of 1 ppb was achieved. The use of different enzymes in the sensitive membrane provides a background for pattern recognition of the above pollutants.

  3. Magnetic ordering in Gd5Ir2Bi and Gd5Ir2Sb

    NASA Astrophysics Data System (ADS)

    Ryan, D. H.; Mas, Nadejda; Rejali, Rasa; Miller, T.; Gerke, Birgit; Heying, Birgit; Pöttgen, Rainer; Flacau, Roxana

    2016-05-01

    155Gd Mössbauer spectroscopy and neutron powder diffraction have been used to study magnetic ordering in Gd5Ir2Bi and Gd5Ir2Sb. Despite the hyperfine fields (Bhf) at the two Gd sites differing by more than a factor of two for both compounds, the moments derived from neutron diffraction are essentially equal in Gd5Ir2Bi. This implies an unusual departure from the commonly assumed scaling between B hf G d and μGd. Neutron powder diffraction shows that Gd5Ir2Bi is a c-axis ferromagnet at 3.6 K. We find no evidence for a FM → AF transition.

  4. 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.

  5. GD2-targeted immunotherapy and radioimmunotherapy

    PubMed Central

    Dobrenkov, Konstantin; Cheung, Nai-Kong

    2014-01-01

    Ganglioside GD2 is a tumor-associated surface antigen found in a broad spectrum of human cancers and stem cells. They include pediatric embryonal tumors (neuroblastoma, retinoblastoma, brain tumors, osteosarcoma, Ewing’s sarcoma, rhabdomyosarcoma), as well as adult cancers (small cell lung cancer, melanoma, soft tissue sarcomas). Because of its restricted normal tissue distribution, GD2 has been proven safe for antibody targeting. Anti-GD2 antibody is now incorporated into the standard of care for the treatment of high risk metastatic neuroblastoma. Building on this experience, novel combinations of antibody, cytokines, cells and genetically engineered products all directed at GD2 are rapidly moving into the clinic. In the review, past and present immunotherapy trials directed at GD2 will be summarized, highlighting the lessons learned and the future directions. PMID:25440605

  6. Non-planar chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Adkins, Douglas R.; Sokolowski, Sara S.; Lewis, Patrick R.

    2006-10-10

    A non-planar chemical preconcentrator comprises a high-surface area, low mass, three-dimensional, flow-through sorption support structure that can be coated or packed with a sorptive material. The sorptive material can collect and concentrate a chemical analyte from a fluid stream and rapidly release it as a very narrow temporal plug for improved separations in a microanalytical system. The non-planar chemical preconcentrator retains most of the thermal and fabrication benefits of a planar preconcentrator, but has improved ruggedness and uptake, while reducing sorptive coating concerns and extending the range of collectible analytes.

  7. Ab initio quantum chemical investigation of several isomers of anionic Si 6

    NASA Astrophysics Data System (ADS)

    Takahashi, Masae; Kawazoe, Yoshiyuki

    2006-02-01

    Eight isomers (planar hexagon, benzvalene, Dewar benzene, triangular prismane, bicyclopropenyl, octahedron, chair form, and twist boat form) of Si 6, Si62-, Si64-, and Si66-, have been searched for by the MP2 and B3LYP electronic structure calculations. Totally 14 isomers were found: two Si 6, six Si62-, five Si64-, and one Si66-. Two of them are different from the eight isomers: deformed triangle Si62-; pentagonal pyramidal Si64-. We discovered that the predicted stable shapes of Si62-, Si64-, and Si66- are octahedral, pentagonal pyramidal, and hexagonal, respectively, which agrees well with Wade rule.

  8. Improving dielectric properties of epitaxial Gd{sub 2}O{sub 3} thin films on silicon by nitrogen doping

    SciTech Connect

    Roy Chaudhuri, Ayan; Osten, H. J.; Fissel, A.; Archakam, V. R.

    2013-01-14

    We report about the effect of nitrogen doping on the electrical properties of epitaxial Gd{sub 2}O{sub 3} thin films. Epitaxial Gd{sub 2}O{sub 3}:N thin films were grown on Si (111) substrates by solid source molecular beam epitaxy using nitrous oxide as the nitridation agent. Substitutional nitrogen incorporation into the dielectric layer was confirmed by secondary ion mass spectroscopy and X-ray photoelectron spectroscopy analysis. Substantial reduction of the leakage current density and disappearance of hysteresis in capacitance-voltage characteristics observed in the Gd{sub 2}O{sub 3}:N layers indicate that nitrogen incorporation in Gd{sub 2}O{sub 3} effectively eliminates the adverse effects of the oxygen vacancy induced defects in the oxide layer.

  9. Process for forming planarized films

    DOEpatents

    Pang, Stella W.; Horn, Mark W.

    1991-01-01

    A planarization process and apparatus which employs plasma-enhanced chemical vapor deposition (PECVD) to form plarnarization films of dielectric or conductive carbonaceous material on step-like substrates.

  10. Object Classification via Planar Abstraction

    NASA Astrophysics Data System (ADS)

    Oesau, Sven; Lafarge, Florent; Alliez, Pierre

    2016-06-01

    We present a supervised machine learning approach for classification of objects from sampled point data. The main idea consists in first abstracting the input object into planar parts at several scales, then discriminate between the different classes of objects solely through features derived from these planar shapes. Abstracting into planar shapes provides a means to both reduce the computational complexity and improve robustness to defects inherent to the acquisition process. Measuring statistical properties and relationships between planar shapes offers invariance to scale and orientation. A random forest is then used for solving the multiclass classification problem. We demonstrate the potential of our approach on a set of indoor objects from the Princeton shape benchmark and on objects acquired from indoor scenes and compare the performance of our method with other point-based shape descriptors.

  11. Flat panel planar optic display

    SciTech Connect

    Veligdan, J.T.

    1994-11-01

    A prototype 10 inch flat panel Planar Optic Display, (POD), screen has been constructed and tested. This display screen is comprised of hundreds of planar optic class sheets bonded together with a cladding layer between each sheet where each glass sheet represents a vertical line of resolution. The display is 9 inches wide by 5 inches high and approximately 1 inch thick. A 3 milliwatt HeNe laser is used as the illumination source and a vector scanning technique is employed.

  12. The Precataclysmic Variable GD 245

    NASA Astrophysics Data System (ADS)

    Schmidt, Gary D.; Smith, Paul S.; Harvey, David A.; Grauer, Albert D.

    1995-07-01

    A combined photometric/spectroscopic study has been carried out of the evolved binary GD 245. The system is shown to consist of a DA2 white dwarf plus M3-5 secondary in a 4.17 h orbit. From model fitting to the white dwarf spectral features, the primary star is found to have log g=7.77±0.02 and Teff=22170 K, leading to M1 (g)=0.48 Msun and R1=0.015 Rsun. Radial velocity analysis of the double-lined system implies M2=0.22 Msun. The distance is computed to be 61 pc and the orbital inclination is i≍69°. These parameters are consistent with the companion being a main-sequence object, in which case Teff=3S60 K, R2=0.27 Rsun, and the binary just escapes being an eclipsing system. A rich spectrum of emission lines phased in strength and radial velocity with the orbital motion is testimony to irradiation of a corotating secondary star by the white dwarf. However, the strength of this spectral component exceeds the intercepted Lyman continuum from the white dwarf, implying that alternate heating mechanisms are important. The companion underfills its Roche lobe by less than 25% in radius, and for current estimates of the angular momentum loss rate in close binaries will require less than 108 yr to evolve into contact. At the inception of mass transfer, the cataclysmic variable GD 245 will appear as one of the rare objects in the 2-3 h orbital period gap.

  13. Trade-Off Relationship between Si Recess and Defect Density Formed by Plasma-Induced Damage in Planar Metal-Oxide-Semiconductor Field-Effect Transistors and the Optimization Methodology

    NASA Astrophysics Data System (ADS)

    Eriguchi, Koji; Nakakubo, Yoshinori; Matsuda, Asahiko; Kamei, Masayuki; Takao, Yoshinori; Ono, Kouichi

    2011-08-01

    Physical damage induced by high-energy ion bombardment during plasma processing is characterized from the viewpoint of the relationship between surface-damaged layer (silicon loss) and defect site underneath the surface. Parameters for plasma-induced damage (PID), Si recess depth (dR) and residual (areal) defect density after wet-etch treatment (Ndam), are calculated on the basis of a modified range theory, and the trade-off relationship between dR and Ndam is presented. We also model their effects on device parameters such as off-state leakage (Ioff) and drain saturation current (Ion) of n-channel metal-oxide-semiconductor field effect transistors (MOSFETs). Based on the models, we clarify the relationship among plasma process parameters (ion energy and ion flux), dR, Ndam, Ioff, and Ion. Then we propose a methodology optimizing ion energy and ion flux under the constraints defined by device specifications Ioff and Ion, via dR and Ndam. This procedure is regarded as so-called optimization problems. The proposed methodology is applicable to optimizing plasma parameters that minimize degradation of MOSFET performance by PID.

  14. All-metal superconducting planar microwave resonator

    NASA Astrophysics Data System (ADS)

    Horsley, Matt; Pereverzev, Sergey; Dubois, Jonathon; Friedrich, Stephan; Qu, Dongxia; Libby, Steve; Lordi, Vincenzo; Carosi, Gianpaolo; Stoeffl, Wolfgang; Chapline, George; Drury, Owen; Quantum Noise in Superconducting Devices Team

    There is common agreement that noise and resonance frequency jitter in superconducting microwave planar resonators are caused by presence of two-level systems, or fluctuators, in resonator materials- in dielectric substrate, in superconducting and dielectric layers and on the boundaries and interfaces. Scaling of noise with device dimensions indicate that fluctuators are likely concentrated around boundaries; physical nature of those fluctuators remains unclear. The presence of dielectrics is not necessary for the superconducting device functionality, and one can ask question about properties of all-metal device, where dielectric substrate and oxide films on metal are absent. Resonator made from of thin conducting layer with cuts in it is usually called slot line resonator. We report on the design, fabrication and initial testing of multiple split rings slot line resonator made out of thin molybdenum plate. This work is being funded as part of a three year strategic initiative (LDRD 16-SI-004) to better understand noise in superconducting devices.

  15. pH-Dependent biodegradable silica nanotubes derived from Gd(OH)3 nanorods and their potential for oral drug delivery and MR imaging.

    PubMed

    Hu, Kuo-Wei; Hsu, Kang-Che; Yeh, Chen-Sheng

    2010-09-01

    We report a pH dependence of degradable silica nanotubes, which dissolved to the biodegradation product monosilicic acid, Si(OH)(4). The silica nanotubes, potentially acting as oral-based administration carriers, were resistant to dissolution in the extreme acidic condition of pH 1, but degraded quickly at pH 8, and the degradation rate can be tuned by tailoring the thickness of silica nanotubes with thicker nanotubes dissolving more slowly. Because Gd(OH)(3) nanorods were used as templates, the silica nanotubes could be further developed as MR imaging contrast agents as well as drugs carriers. The released Gd(3+) ions resulting from the etching of Gd(OH)(3) nanorods were chelated by the pre-modified DOTA, yielding Gd-DOTA complexes grafted onto silica nanotubes. The Gd-DOTA grafted silica nanotubes loaded with doxorubicin revealed enhanced T(1) imaging contrast and anticancer activity. PMID:20542331

  16. Magnetic properties of RE5Ir2X (RE = Y, Gd-Ho, X = Sn, Sb, Pb, Bi) and magnetocaloric characterization of Gd5Ir2X

    NASA Astrophysics Data System (ADS)

    Schäfer, Konrad; Schwickert, Christian; Niehaus, Oliver; Winter, Florian; Pöttgen, Rainer

    2014-09-01

    Systematic phase analytical studies of the systems RE-Ir-X (X = Sn, Pb, Sb, Bi) led to 15 new stannides, plumbides, antimonides and bismuthides with the composition RE5Ir2X. The compounds have been synthesized and characterized by X-ray powder diffraction. The structures of Gd5Ir2Sb and Dy5Ir2Bi have been refined from single crystal X-ray diffractometer data: Mo5SiB2 type, I4/mcm, a = 775.2(2), c = 1361.3(5) pm, wR2 = 0.0933, 404 F2 values, 16 variables for Gd5Ir2Sb and a = 767.5(1), c = 1368.9(3) pm, wR2 = 0.0694, 571 F2 values, 16 variables for Dy5Ir2Bi. Magnetic measurements of Gd5Ir2X (X = Sn, Pb, Sb, Bi), Tb5Ir2X (X = Sn, Pb, Sb, Bi), Dy5Ir2Pb, Dy5Ir2Bi and Ho5Ir2Pb indicate ferromagnetic transitions at TC = 154.3, 159.3, 124.4, 119.3, 99.2, 98.2, 65.5, 68.6, 45.1, 35.6 and 23.5 K, respectively. Gd5Ir2Bi and Gd5Ir2Sb show an additional antiferromagnetic transition at TN = 118.5 and 91.0 K. The magnetocaloric effect of Gd5Ir2X (X = Sn, Pb, Sb, Bi) in terms of the isothermal entropy change ΔSm is -7.3(3), -6.5(3), -8.7(3) and -9.0(3) J kg-1 K-1 at temperatures of 153, 157, 120 and 126 K for a 5 T field change. 119Sn Mössbauer spectra of Gd5Ir2Sn at 78 K show a huge transferred hyperfine field of 21.9(1) T and an isomer shift of 1.94(1) mm s-1, typical for stannides. 121Sb Mössbauer spectra of Gd5Ir2Sb at 78 K show a transferred hyperfine field of 14.2(3) T and an isomer shift of -7.45(8) mm s-1 reflecting the antimonide character.

  17. Planar photovoltaic solar concentrator module

    DOEpatents

    Chiang, Clement J.

    1992-01-01

    A planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor.

  18. Planar photovoltaic solar concentrator module

    DOEpatents

    Chiang, C.J.

    1992-12-01

    A planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor. 5 figs.

  19. Planar immersion lens with metasurfaces

    NASA Astrophysics Data System (ADS)

    Ho, John S.; Qiu, Brynan; Tanabe, Yuji; Yeh, Alexander J.; Fan, Shanhui; Poon, Ada S. Y.

    2015-03-01

    The solid immersion lens is a powerful optical tool that allows light entering material from air or a vacuum to focus to a spot much smaller than the free-space wavelength. Conventionally, however, the lenses rely on semispherical topographies and are nonplanar and bulky, which limits their integration in many applications. Recently, there has been considerable interest in using planar structures, referred to as metasurfaces, to construct flat optical components for manipulating light in unusual ways. Here, we propose and demonstrate the concept of a planar immersion lens based on metasurfaces. The resulting planar device, when placed near an interface between air and dielectric material, can focus electromagnetic radiation incident from air to a spot in the material smaller than the free-space wavelength. As an experimental demonstration, we fabricate an ultrathin and flexible microwave lens and further show that it achieves wireless energy transfer in material mimicking biological tissue.

  20. Effect of the control of global planarity of intermetal dielectric layers on the lithographic process window

    NASA Astrophysics Data System (ADS)

    Keysar, Shani; Markowitz, Leah; Ben-Gigi, Corin; Tweg, Rama; Margalit-Ilovich, Ayelet; Kepten, Avishai; Wachs, Amir; Shaviv, Roey

    1999-06-01

    The sensitivity of lithographic process window to global planarity of the inter metal dielectric layers is established in this work. The inter metal dielectric layers, between the metal layers, were prepared by utilizing the H2O2/SiH4 chemistry known as the 'Advanced Planarity Layer (APL)'. Four degrees of global planarity were tested within the APL process window, utilizing different H2O2 stabilization pressures. SEM cross sections were used to determine the degree of planarity in the CMOS product and at lithographic test structures. The lithographic process window and the effect of the stepper leveling system were defined for typical high and low topographies. The results how a strong link between the lithographic process window to degree of global planarity of the APL. Good global planarity enlarged depth of focus and energy latitude, allowing a wider lithographic process window. Also, in cases of improved APL planarity, the stepper leveling system had only a limited contribution to a lithographic process window. This control over the global planarity of the inter metal dielectric layers and the wide lithographic process window that results eliminate the need for CMP at 0.5 (mu) technology.

  1. Glycolipid GD3 and GD3 synthase are key drivers for glioblastoma stem cells and tumorigenicity.

    PubMed

    Yeh, Shih-Chi; Wang, Pao-Yuan; Lou, Yi-Wei; Khoo, Kay-Hooi; Hsiao, Michael; Hsu, Tsui-Ling; Wong, Chi-Huey

    2016-05-17

    The cancer stem cells (CSCs) of glioblastoma multiforme (GBM), a grade IV astrocytoma, have been enriched by the expressed marker CD133. However, recent studies have shown that CD133(-) cells also possess tumor-initiating potential. By analysis of gangliosides on various cells, we show that ganglioside D3 (GD3) is overexpressed on eight neurospheres and tumor cells; in combination with CD133, the sorted cells exhibit a higher expression of stemness genes and self-renewal potential; and as few as six cells will form neurospheres and 20-30 cells will grow tumor in mice. Furthermore, GD3 synthase (GD3S) is increased in neurospheres and human GBM tissues, but not in normal brain tissues, and suppression of GD3S results in decreased GBM stem cell (GSC)-associated properties. In addition, a GD3 antibody is shown to induce complement-dependent cytotoxicity against cells expressing GD3 and inhibition of GBM tumor growth in vivo. Our results demonstrate that GD3 and GD3S are highly expressed in GSCs, play a key role in glioblastoma tumorigenicity, and are potential therapeutic targets against GBM. PMID:27143722

  2. Oblique view of GD5 taken from Pier GD4 U.S. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Oblique view of GD-5 taken from Pier GD-4 - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  3. GD4 with GD3 at oblique view on left U.S. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GD-4 with GD-3 at oblique view on left - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  4. Pier GD3, oblique view taken from Pier GD2, Caisson of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Pier GD-3, oblique view taken from Pier GD-2, Caisson of Dry Dock No. 2 to left - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  5. Overview of GD2 and GD3 with Caisson of Dry Dock ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of GD-2 and GD-3 with Caisson of Dry Dock No. 2 in center - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  6. Oblique of GD4 and GD5, Dry Dock No. 3 Caisson ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Oblique of GD-4 and GD-5, Dry Dock No. 3 Caisson between piers - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  7. GD2 and GD3 synthase: novel drug targets for cancer therapy

    PubMed Central

    Sphyris, Nathalie; Sarkar, Tapasree Roy; Battula, Venkata L; Andreeff, Michael; Mani, Sendurai A

    2015-01-01

    Our recent study suggests that targeting GD3 synthase (also known as ST8SIA1)—the rate-limiting enzyme in biosynthesis of the breast cancer stem cell marker GD2—abrogates metastasis and depletes the cancer stem cell populations within a tumor, thus providing an effective therapeutic strategy against metastatic breast cancers. PMID:27308452

  8. Magnetic resonance imaging of the pancreas in streptozotocin-induced diabetic rats: Gadofluorine P and Gd-DOTA

    PubMed Central

    Cho, Hye Rim; Lee, Youkyung; Doble, Philip; Bishop, David; Hare, Dominic; Kim, Young-Jae; Kim, Kwang Gi; Jung, Hye Seung; Park, Kyong Soo; Choi, Seung Hong; Moon, Woo Kyung

    2015-01-01

    AIM: To investigate the performance of Gadofluorine P-enhanced magnetic resonance imaging (MRI) on the diagnosis of diabetes in a streptozotocin (STZ) -induced diabetic rat model. METHODS: Fischer 344 rats were treated with STZ. Rats not treated with STZ served as controls. T1-weighted MRI was performed using a 3T scanner before and after the injection of Gd-DOTA or Gadofluorine P (6 diabetic rats, 5 controls). The normalized signal intensity (SI) and the enhancement ratio (ER) of the pancreas were measured at each time point, and the values were compared between the normal and diabetic rats using the Mann-Whitney test. In addition, the values were correlated with the mean islet number. Optimal cut-off values were calculated using a positive test based on receiver operating characteristics. Intrapancreatic Gd concentration after the injection of each contrast media was measured using laser ablation-inductively coupled plasma-mass spectrometry in a separate set of rats (4 diabetic rats, 4 controls for Gadofluorine P; 2, 2 for Gd-DOTA). RESULTS: The normalized SI and ER of the pancreas using Gd-DOTA were not significantly different between diabetic rats and controls. With Gadofluorine P, the values were significantly higher in the diabetic rats than in the control rats 30 min after injection (P < 0.05). The area under the receiver operating characteristic curve that differentiated diabetic rats from the control group was greater for Gadofluorine P than for Gd-DOTA (0.967 vs 0.667, P = 0.085). An increase in normalized SI 30 min after Gadofluorine P was correlated with a decrease in the mean number of islets (r2 = 0.510, P = 0.014). Intra-pancreatic Gd was higher in rats with Gadofluorine P injection than Gd-DOTA injection (Gadofluorine P vs Gd-DOTA, 7.37 vs 0.00, P < 0.01). A significant difference in the concentration of intrapancreatic Gd was observed between the control and diabetic animals that were sacrificed 30 min after Gadofluorine P injection (control vs

  9. Inorganic photosensitizer coupled Gd-based upconversion luminescent nanocomposites for in vivo magnetic resonance imaging and near-infrared-responsive photodynamic therapy in cancers.

    PubMed

    Zhang, Ling'e; Zeng, Leyong; Pan, Yuanwei; Luo, Song; Ren, Wenzhi; Gong, An; Ma, Xuehua; Liang, Hongze; Lu, Guangming; Wu, Aiguo

    2015-03-01

    Inorganic photosensitizer coupled Gd-based upconversion luminescent (UCL) nanocomposites have potential application for both magnetic resonance imaging (MRI) and photodynamic therapy (PDT) of cancers using the light stability and biocompatibility of TiO2 inorganic photosensitizer. However, TiO2 inorganic photosensitizer could only be excited by ultraviolet (UV) light, which was harmful and weakly penetrable in tissues. In this work, folic acid (FA)-targeted NaGdF4:Yb/Tm@SiO2@TiO2 nanocomposites (FA-Gd-Si-Ti NPs) were constructed and synthesized for both in vivo MRI and near infrared (NIR)-responsive inorganic PDT, in which TiO2 component could be excited by NIR light due to the UCL performance of NaGdF4:Yb/Tm component converting NIR to UV light. The results showed the as-prepared FA-Gd-Si-Ti NPs had good biocompatibility in vitro and in vivo. Moreover, MR study indicated that FA-Gd-Si-Ti NPs were good T1-weighted MRI contrast agents with high longitudinal relaxivity (r1) of 4.53 mm(-1) s(-1), also in vivo MRI of nude mice showed "bright" signal in MCF-7 tumor. Under the irradiation of 980 nm laser at the power density of 0.6 W/cm(2) for 20 min, the viability of HeLa and MCF-7 cells incubated with FA-Gd-Si-Ti NPs could decrease from about 90 % to 35 % and 31%, respectively. Furthermore, in vivo PDT of MCF-7 tumor-bearing nude mice model showed that the inhibition ratio of tumors injected with FA-Gd-Si-Ti NPs reached up to 88.6% after 2-week treatment, compared with that of nude mice in control group. Based on the deep penetration of NIR light and the good biocompatibility of TiO2 inorganic photosensitizer, the as-prepared FA-Gd-Si-Ti NPs could have potential applications in both MRI and NIR-responsive PDT of cancers in deep tissues. PMID:25617128

  10. Transfer of Excitation Energy from Pr3+ to Gd3+ in YF3:Pr3+,Gd3+

    NASA Astrophysics Data System (ADS)

    Hirai, Takeshi; Yoshida, Hisashi; Sakuragi, Shiro; Hashimoto, Satoshi; Ohno, Nobuhito

    2007-02-01

    Luminescence and excitation spectra for YF3:Gd3+, YF3:Pr3+, and YF3:Pr3+,Gd3+ have been studied in the vacuum ultraviolet (VUV) spectral region at room temperature. In YF3:Gd3+, Gd3+ ions absorb VUV light ranging from 150 to 200 nm due to 4 f-4 f transitions, yielding an ultraviolet (UV) luminescence line at 311 nm originating from the 4 f-4 f transition (6P7/2→8S7/2 state). In YF3:Pr3+,Gd3+, Pr3+ ions absorb the VUV light (150-200 nm) due to 4 f-5d transitions, and the absorption gives rise to the UV luminescence of Gd3+ ions that is much stronger than that of YF3:Gd3+. In this paper, we discuss the energy transfer process from Pr3+ to Gd3+ ions in YF3:Pr3+,Gd3+ excited by VUV light.

  11. Room temperature table-like magnetocaloric effect in amorphous Gd50Co45Fe5 ribbon

    NASA Astrophysics Data System (ADS)

    Liu, G. L.; Zhao, D. Q.; Bai, H. Y.; Wang, W. H.; Pan, M. X.

    2016-02-01

    Gd50Co45Fe5 amorphous alloy ribbon with a table-like magnetocaloric effect (MCE) suitable for the ideal Ericsson cycle at room temperature has been developed. In addition to a high magnetic transition temperature of 289 K very close to that of Gd (294 K), a relatively large value of refrigerant capacity (~521 J kg-1) has been achieved under a field change of 5 T. This value of refrigerant capacity (RC) is about 27% and 70% larger than those of Gd (~410 J kg-1) and Gd5Si2Ge2 (~306 J kg-1). More importantly, the peak value of magnetic entropy change (-Δ S\\text{M}\\max ) approaches a nearly constant value of ~3.8 J  ṡ  kg-1  ṡ  K-1 under an applied field change of 0~5 T in a wide temperature span over 40 K around room temperature, which could be used as the candidate working material in the Ericsson-cycle magnetic regenerative refrigerator around room temperature.

  12. Development of a pMOSFET sensor with a Gd converter for low energy neutron dosimetry.

    PubMed

    Lee, N H; Kim, S H; Youk, G U; Park, I J; Kim, Y M

    2004-01-01

    A pMOSFET having a 10 microm thick Gadolinium (Gd) layer has been invented as a slow neutron sensor. When slow neutrons are incident to the Gd layer, conversion electrons, which generate electron-hole pairs in the SiO2 layer of the pMOSFET, are generated by a neutron capture process. The holes are easily trapped in the oxide and act as positive-charge centres in the oxide. Due to the induced charges, the threshold turn-on voltage of the pMOSFET is changed. The developed sensors were tested at a neutron beam port of the HANARO research reactor and a 60Co irradiation facility to investigate slow neutron response and gamma ray contamination, respectively. The resultant voltage change was proportional to the accumulated neutron dose and it was very sensitive to slow neutrons. Moreover, ionising radiation contamination was negligible. It can also be used in a mixed radiation field by subtracting the voltage change of a pMOSFET without Gd from that of the Gd-pMOSFET. PMID:15353659

  13. Spectroscopic properties of transparent Er-doped oxyfluoride glass-ceramics with GdF₃.

    PubMed

    Środa, Marcin; Szlósarczyk, Krzysztof; Różański, Marek; Sitarz, Maciej; Jeleń, Piotr

    2015-01-01

    Optically active glass-ceramics (GC) with the low-phonon phases of fluorides, doped with Er(3+) was studied. Glass based on SiO₂-Al₂O₃-Na₂F₂-Na₂O-GdF₃-BaO system was obtained. Dopant were introduced to the glass in an amount of 0.01 mol Er₂O₃ per 1 mol of glass. DTA/DSC study shows multi-stage crystallization. XRD identification of obtained phases did not confirm the presence of pure GdF₃ phase. Instead of that ceramization process led to formation of NaGdF₄ and BaGdF₅. The structural changes were studied using FT-IR spectroscopic method. The study of luminescence of the samples confirmed that optical properties of the obtained GC depend on crystallizing phases during ceramization. Time resolved spectroscopy of Er-doped glass showed the 3 and 8 times increase of lifetime of emission from (4)S₃/₂ and (4)F₉/₂ states, respectively. It confirms the erbium ions have ability to locate in the low phonon gadolinium-based crystallites. The results give possibility to obtain a new material for optoelectronic application. PMID:25049170

  14. Lifetime Measurements of Levels in 160Gd

    NASA Astrophysics Data System (ADS)

    Casarella, Clark; Aprahamian, Ani; Crider, Ben; Lesher, Shelly; Marsh, Ian; Peters, Erin; Prados-Estevez, Francisco; Smith, Mallory; Vanhoy, Jeffrey; Yates, Steven

    2013-10-01

    The rare earth region of nuclei has been well established as a region of deformation for decades. However, the nature of vibrations built on a deformed ground state remain far from understood and present an oustanding challenge to nuclear structure physics. Studies of 158Gd has shown a preponderance of excited 0+ states with varying degrees of collectivity. We have measured level lifetimes, reduced transition probabilities and angular distributions of gamma-rays excited by inelastic neutron scattering and the use of the Doppler Shift Attenuation Method (DSAM) at the University of Kentucky 7 MV Van de Graaff Accelerator Facility. Low lying excited states of 160Gd were populated up to an excitation energy of E < 2 MeV. We will present and discuss the measured level lifetimes of 160Gd and their implied degrees of collectivity. This work was supported by the NSF under contract numbers PHY-1068192, PHY-12-05412, and PHY-0956310.

  15. Pulsating White Dwarf Star GD99

    NASA Astrophysics Data System (ADS)

    Chynoweth, K. M.; Thompson, S.; Mullally, F.; Yeates, C.

    2004-12-01

    We present 15 hours of time-series photometry of the variable white dwarf star GD99. These data were obtained at the McDonald Observatory 2.1m Otto Struve Telescope in January 2003, using the Argos CCD photometer. We achieved a noise level as low as 0.07 %, as measured from the power spectrum of our first night. Our observations confirm that GD99 is a unique pulsating white dwarf whose modes show characteristics of both the hot and cold type of DA variable stars. Additionally, GD99 has a large number of modes, making it a good candidate for asteroseismological study. Our preliminary results indicate that this star merits further study to decipher its abundant set of unusual modes. With such a rich period structure, longer continuous data sets will be required to fully resolve the pulsation spectrum.

  16. Planar tetranuclear lanthanide clusters with the Dy4 analogue displaying slow magnetic relaxation.

    PubMed

    Langley, Stuart K; Chilton, Nicholas F; Gass, Ian A; Moubaraki, Boujemaa; Murray, Keith S

    2011-12-21

    Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar 'butterfly' arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour. PMID:22031449

  17. Manufacturing of planar ceramic interconnects

    SciTech Connect

    Armstrong, B.L.; Coffey, G.W.; Meinhardt, K.D.; Armstrong, T.R.

    1996-12-31

    The fabrication of ceramic interconnects for solid oxide fuel cells (SOFC) and separator plates for electrochemical separation devices has been a perennial challenge facing developers. Electrochemical vapor deposition (EVD), plasma spraying, pressing, tape casting and tape calendering are processes that are typically utilized to fabricate separator plates or interconnects for the various SOFC designs and electrochemical separation devices. For sake of brevity and the selection of a planar fuel cell or gas separation device design, pressing will be the only fabrication technique discussed here. This paper reports on the effect of the characteristics of two doped lanthanum manganite powders used in the initial studies as a planar porous separator for a fuel cell cathode and as a dense interconnect for an oxygen generator.

  18. Planar Multilayer Circuit Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Minev, Z. K.; Serniak, K.; Pop, I. M.; Leghtas, Z.; Sliwa, K.; Hatridge, M.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.

    2016-04-01

    Experimental quantum information processing with superconducting circuits is rapidly advancing, driven by innovation in two classes of devices, one involving planar microfabricated (2D) resonators, and the other involving machined three-dimensional (3D) cavities. We demonstrate that circuit quantum electrodynamics can be implemented in a multilayer superconducting structure that combines 2D and 3D advantages. We employ standard microfabrication techniques to pattern each layer, and rely on a vacuum gap between the layers to store the electromagnetic energy. Planar qubits are lithographically defined as an aperture in a conducting boundary of the resonators. We demonstrate the aperture concept by implementing an integrated, two-cavity-mode, one-transmon-qubit system.

  19. Window defect planar mapping technique

    NASA Technical Reports Server (NTRS)

    Minton, F. R.; Minton, U. O. (Inventor)

    1976-01-01

    A method of planar mapping defects in a window having an edge surface and a planar surface. The method is comprised of steps for mounting the window on a support surface. Then a light sensitive paper is placed adjacent to the window surface. A light source is positioned adjacent to the window edge. The window is then illuminated with the source of light for a predetermined interval of time. Defects on the surface of the glass, as well as in the interior of the glass are detected by analyzing the developed light sensitive paper. The light source must be in the form of optical fibers or a light tube whose light transmitting ends are placed near the edge surface of the window.

  20. Summing Planar Bosonic Open Strings

    SciTech Connect

    Bardakci, Korkut

    2006-02-16

    In earlier work, planar graphs of massless {phi}{sup 3} theory were summed with the help of the light cone world sheet picture and the mean field approximation. In the present article, the same methods are applied to the problem of summing planar bosonic open strings. They find that in the ground state of the system, string boundaries form a condensate on the world sheet, and a new string emerges from this summation. Its slope is always greater than the initial slope, and it remains non-zero even when the initial slope is set equal to zero. If they assume the initial string tends to a field a theory in the zero slope limit, this result provides evidence for string formation in field theory.

  1. Compact planar microwave blocking filters

    NASA Technical Reports Server (NTRS)

    U-Yen, Kongpop (Inventor); Wollack, Edward J. (Inventor)

    2012-01-01

    A compact planar microwave blocking filter includes a dielectric substrate and a plurality of filter unit elements disposed on the substrate. The filter unit elements are interconnected in a symmetrical series cascade with filter unit elements being organized in the series based on physical size. In the filter, a first filter unit element of the plurality of filter unit elements includes a low impedance open-ended line configured to reduce the shunt capacitance of the filter.

  2. Enjoyment of Euclidean planar triangles

    NASA Astrophysics Data System (ADS)

    Srinivasan, V. K.

    2013-09-01

    This article adopts the following classification for a Euclidean planar ?, purely based on angles alone. A Euclidean planar triangle is said to be acute angled if all the three angles of the Euclidean planar ? are acute angles. It is said to be right angled at a specific vertex, say B, if the angle ? is a right angle with the two remaining angles as acute angles. It is said to be obtuse angled at the vertex B if ? is an obtuse angle, with the two remaining angles as acute angles. In spite of the availability of numerous text books that contain our human knowledge of Euclidean plane geometry, softwares can offer newer insights about the characterizations of planar geometrical objects. The author's characterizations of triangles involve points like the centroid G, the orthocentre H of the ?, the circumcentre S of the ?, the centre N of the nine-point circle of the ?. Also the radical centre rc of three involved diameter circles of the sides BC, AC and AB of the ? provides a reformulation of the orthocentre, resulting in an interesting theorem, dubbed by the author as 'Three Circles Theorem'. This provides a special result for a right-angled ?, again dubbed by the author as 'The Four Circles Theorem'. Apart from providing various inter connections between the geometrical points, the relationships between shapes of the triangle and the behaviour of the points are reasonably explored in this article. Most of these results will be useful to students that take courses in Euclidean Geometry at the college level and the high school level. This article will be useful to teachers in mathematics at the high school level and the college level.

  3. PANEL CODE FOR PLANAR CASCADES

    NASA Technical Reports Server (NTRS)

    Mcfarland, E. R.

    1994-01-01

    The Panel Code for Planar Cascades was developed as an aid for the designer of turbomachinery blade rows. The effective design of turbomachinery blade rows relies on the use of computer codes to model the flow on blade-to-blade surfaces. Most of the currently used codes model the flow as inviscid, irrotational, and compressible with solutions being obtained by finite difference or finite element numerical techniques. While these codes can yield very accurate solutions, they usually require an experienced user to manipulate input data and control parameters. Also, they often limit a designer in the types of blade geometries, cascade configurations, and flow conditions that can be considered. The Panel Code for Planar Cascades accelerates the design process and gives the designer more freedom in developing blade shapes by offering a simple blade-to-blade flow code. Panel, or integral equation, solution techniques have been used for several years by external aerodynamicists who have developed and refined them into a primary design tool of the aircraft industry. The Panel Code for Planar Cascades adapts these same techniques to provide a versatile, stable, and efficient calculation scheme for internal flow. The code calculates the compressible, inviscid, irrotational flow through a planar cascade of arbitrary blade shapes. Since the panel solution technique is for incompressible flow, a compressibility correction is introduced to account for compressible flow effects. The analysis is limited to flow conditions in the subsonic and shock-free transonic range. Input to the code consists of inlet flow conditions, blade geometry data, and simple control parameters. Output includes flow parameters at selected control points. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 series computer with a central memory requirement of approximately 590K of 8 bit bytes. This program was developed in 1982.

  4. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1989-03-21

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration. 6 figs.

  5. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1985-08-23

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  6. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, D.B.

    1985-06-24

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping lase pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  7. NMR planar microcoil for microanalysis

    NASA Astrophysics Data System (ADS)

    Sorli, B.; Chateaux, J. F.; Quiquerez, L.; Bouchet-Fakri, L.; Briguet, A.; Morin, P.

    2006-11-01

    This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity. It is a real challenging task to develop microsystem for NMR spectrum extraction for smaller and smaller sample volume. Moreover, it is advantageous that these microsystems could be integrated in a Micro Total Analysing System (μ -TAS) as an analysing tool. In this paper, NMR theory, description, fabrication process and electrical characterization of planar microcoils receiver are described. Results obtained on NMR microspectroscopy experiments have been performed on water and ethanol, using a 1 mm diameter planar coil. This microcoil is tuned and matched at 85.13 MHz which is the Larmor frequency of proton in a 2 T magnetic field. This paper has been presented at “3e colloque interdisciplinaire en instrumentation (C2I 2004)”, École Normale Supérieure de Cachan, 29 30 janvier 2004.

  8. Reinvestigation of the Cd–Gd phase diagram

    PubMed Central

    Reichmann, Thomas L.; Ipser, Herbert

    2014-01-01

    The complete Cd–Gd equilibrium phase diagram was investigated by a combination of powder-XRD, SEM and DTA. All previously reported phases, i.e., CdGd, Cd2Gd, Cd3Gd, Cd45Gd11, Cd58Gd13, and Cd6Gd, could be confirmed. In addition, a new intermetallic compound with a stoichiometric composition corresponding to “Cd8Gd” was found to exist. It was obtained that “Cd8Gd” decomposes peritectically at 465 °C. Homogeneity ranges of all intermetallic compounds were determined at distinct temperatures. In addition, the maximum solubilities of Cd in the low- and high-temperature modifications of Gd were determined precisely as 4.6 and 22.6 at.%, respectively. All invariant reaction temperatures (with the exception of the formation of Cd58Gd13) as well as liquidus temperatures were determined, most probably, Cd58Gd13 is formed in a peritectoid reaction from Cd45Gd11 and Cd6Gd at a temperature below 700 °C. PMID:25544803

  9. Resonant Photoemission in f Electron Systems: Pu& Gd

    SciTech Connect

    Tobin, J G; Chung, B W; Schulze, R K; Terry, J; Farr, J D; Shuh, D K; Heinzelman, K; Rotenberg, E; Waddill, G D; van der Laan, G

    2003-03-07

    Resonant photoemission in the Pu5f and Pu6p states is compared to that in the Gd4f and Gd5p states. Spectral simulations, based upon and atomic model with angular momentum coupling, are compared to the Gd and Pu results. Additional spectroscopic measurements of Pu, including core level photoemission and x-ray absorption are also presented.

  10. Enhanced cathodoluminescence from an amorphous AlN:holmium phosphor by co-doped Gd{sup +3} for optical devices applications

    SciTech Connect

    Maqbool, Muhammad; Kordesch, Martin E.; Kayani, A.

    2009-05-15

    Sputter-deposited thin films of amorphous AlN:Ho (1 at. %) emits in the green (549 nm) region of the visible spectrum under electron excitation. The addition of Gd (1 at. %) in the film enhances the green emission linearly after thermal activation at 900 deg. C for 40 min in a nitrogen atmosphere. The luminescence enhancement saturates when the gadolinium concentration reaches four times the holmium concentration. The optical bandgap of amorphous AlN is about 210 nm, so that the film is transparent in the ultraviolet, allowing us to observe the ultraviolet emission at 313 nm from Gd. No significant quenching of the Gd emission is observed. Energy dispersive x-ray (EDX) spectra confirm the increasing concentration of Gd. X-ray diffraction (XRD) analysis shows no peaks other than those arising from the Si (111) substrate, confirming that the films are amorphous. The enhanced luminescence can be used to make high-efficiency optical devices.

  11. Dispersion-engineered tapered planar waveguide for coherent supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Hu, Hongyu; Li, Wenbo; Dutta, Niloy K.

    We have designed a tapered planar rib waveguide and numerically studied supercontinuum generation by the propagation of input pulses at 1.55 μm. The Air-SF57 glass-SiO2 waveguide is 2 cm long, with a varying etch depth to manage the total dispersion. This proposed waveguide geometry significantly broadens the output spectrum caused by continuous modification of the phase matching condition for dispersive wave emission. The coherence property has also been investigated, demonstrating that fully coherent supercontinuum extending from ~1 μm to ~4.6 μm can be obtained with proper pumping conditions.

  12. Electrochemical phase analysis of powders in the GdB4-GdB system

    SciTech Connect

    Tkach, A.V.; Masyuk, T.V.; Paderno, Y.B.

    1985-05-01

    In recent years solid-phase voltammetric analysis with a carbon paste electrode has been employed successfully for the determination of the phase composition of a number of oxide and sulfide materials. This is a rapid and highly sensitive method of quantitative analysis, offering many possibilities. In this paper the authors study the feasibility of using voltammetric analysis with a carbon paste electrode for investigating the phase composition of powders in the GdB4-GdB6 system.

  13. Structural, magnetic, and thermal characteristics of the phase transitions in Gd{sub 5}Ga{sub x}Ge{sub 4-x} magnetocaloric materials

    SciTech Connect

    Misra, Sumohan; Mozharivskyj, Yurij; Tsokol, Alexandra O.; Schlagel, Deborah L.; Lograsso, Thomas A.; Miller, Gordon J.

    2009-11-15

    Temperature-dependent, single crystal and powder X-ray diffraction studies as well as magnetization, and heat capacity measurements were carried out on two phases of the Gd{sub 5}Ga{sub x}Ge{sub 4-x} system: for x=0.7 and 1.0. Gd{sub 5}Ga{sub 0.7}Ge{sub 3.3} shows three structure types as a function of temperature: (i) from 165 K to room temperature, the orthorhombic Sm{sub 5}Ge{sub 4}-type structure exists; (ii) below 150 K, it transforms to a orthorhombic Gd{sub 5}Si{sub 4}-type structure; and (iii) a monoclinic Gd{sub 5}Si{sub 2}Ge{sub 2}-type component is observed for the intermediate temperature range of 150 K<=T<=165 K. This is the first time that all these three structure types have been observed for the same composition. For Gd{sub 5}Ga{sub 1.0}Ge{sub 3.0}, the room temperature phase belongs to the orthorhombic Pu{sub 5}Rh{sub 4}-type structure with interslab contacts between main group atoms of 2.837(4) A. Upon heating above 523 K, it transforms to a Gd{sub 5}Si{sub 4}-type structure with this distance decreasing to 2.521(7) A before decomposing above 573 K. - Graphical Abstract: Phase transformations in Gd{sub 5}Ga{sub x}Ge{sub 4-x} magnetocaloric materials as a function of temperature.

  14. Shock-ignition relevant experiments with planar targets on OMEGA

    SciTech Connect

    Hohenberger, M.; Hu, S. X.; Anderson, K. S.; Boehly, T. R.; Sangster, T. C.; Seka, W.; Stoeckl, C.; Yaakobi, B.; Theobald, W.; Lafon, M.; Nora, R.; Betti, R.; Meyerhofer, D. D.; Casner, A.; Fratanduono, D. E.; Ribeyre, X.; Schurtz, G.

    2014-02-15

    We report on laser-driven, strong-shock generation and hot-electron production in planar targets in the presence of a pre-plasma at shock-ignition (SI) relevant laser and pre-plasma conditions. 2-D simulations reproduce the shock dynamics well, indicating ablator shocks of up to 75 Mbar have been generated. We observe hot-electron temperatures of ∼70 keV at intensities of 1.4 × 10{sup 15} W/cm{sup 2} with multiple overlapping beams driving the two-plasmon decay instability. When extrapolated to SI-relevant intensities of ∼10{sup 16} W/cm{sup 2}, the hot electron temperature will likely exceed 100 keV, suggesting that tightly focused beams without overlap are better suited for launching the ignitor shock.

  15. Pointed drawings of planar graphs☆

    PubMed Central

    Aichholzer, Oswin; Rote, Günter; Schulz, André; Vogtenhuber, Birgit

    2012-01-01

    We study the problem how to draw a planar graph crossing-free such that every vertex is incident to an angle greater than π. In general a plane straight-line drawing cannot guarantee this property. We present algorithms which construct such drawings with either tangent-continuous biarcs or quadratic Bézier curves (parabolic arcs), even if the positions of the vertices are predefined by a given plane straight-line drawing of the graph. Moreover, the graph can be drawn with circular arcs if the vertices can be placed arbitrarily. The topic is related to non-crossing drawings of multigraphs and vertex labeling. PMID:23471372

  16. Terahertz super thin planar lenses

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Ye, Jiasheng; Hu, Dan; Wang, Xinke; Feng, Shengfei; Sun, Wenfeng

    2012-12-01

    Terahertz (THz) radiation is an under developing range in the electromagnetic spectrum. It has attracted a lot of attentions due to its various potential applications. However, THz systems are difficult to be integrated into a smart size due to the limitation of its long wavelength. In this presentation, we propose a new approach to design planar lenses with a thickness of several hundred nanometers in the THz range. The fabricated lenses are characterized with a focal plane imaging system and it is found that they can focus the THz light and image an object well. It is expected that this new approach can pave a way for smart THz systems integration.

  17. Gd{sub 3+}-ESR and magnetic susceptibility of GdCu{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8}

    SciTech Connect

    Coldea, R.; Coldea, M.; Pop, I.

    1994-03-01

    Gd ESR of GdCu{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} and magnetic susceptibility of GdCu{sub 4}Al{sub 8}, GdMn{sub 4}Al{sub 8}, and YMn{sub 4}Al{sub 8} were measured in the temperature range of 290K--460K and 90K--1050K, respectively. The occurrence of the Mn moment in YMn{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} is strongly correlated with the critical value of d{approx}2.6{angstrom} of the Mn-Mn distance below which the Mn moment is not stable. The experimental data for GdMn{sub 4}Al{sub 8}, compared with the data for the isostructural compounds GdCu{sub 4}Al{sub 8} and YMn{sub 4}Al{sub 8}, show that near the critical value of d, the existence of Mn moment depends not only on the value of d, but also on the local magnetic surroundings. It has been revealed that the magnetic character of Mn moment in YMn{sub 4}Al{sub 8} and GdMn{sub 4}Al{sub 8} changes from an itinerant electron type to a local-moment type with increasing temperature.

  18. Planar Be-implanted GaAs junction formation using swept-line electron beam annealing

    SciTech Connect

    Banerjee, S.K.; De Jule, R.Y.; Soda, K.J.

    1983-12-01

    Comparative studies of swept-line electron beam annealing and furnace annealing of Be implanted in n-GaAs doped with Si are presented. Electron beam annealing causes less Be redistribution and results in fewer traps than furnace annealing, but causes site mixing of amphoteric Si. Planar Be-implanted junctions result in a p(+)-nu-n structure for the electron beam annealed samples, similar to thermally quenched samples. It is believed that this is caused by the incorporation of amphoteric Si on Ga and As sites during transient annealing, which produces results similar to thermal quenching. 14 references.

  19. Liftings and stresses for planar periodic frameworks

    PubMed Central

    Borcea, Ciprian; Streinu, Ileana

    2015-01-01

    We formulate and prove a periodic analog of Maxwell’s theorem relating stressed planar frameworks and their liftings to polyhedral surfaces with spherical topology. We use our lifting theorem to prove deformation and rigidity-theoretic properties for planar periodic pseudo-triangulations, generalizing features known for their finite counterparts. These properties are then applied to questions originating in mathematical crystallography and materials science, concerning planar periodic auxetic structures and ultrarigid periodic frameworks. PMID:26973370

  20. Theory of non-planar orbits

    SciTech Connect

    Antillon, A.; Month, M.

    1985-01-01

    The basic dynamics of a planar accelerator is extended to the non-planar case. This is done using the geometrical concept of torsion and extending the Hamiltonian formalism. A generalized non-planar reference orbit is adopted which introduces torsion in appropriately chosen drift spaces. The parameters of the reference orbit are associated with uncoupled and coupled betatron parameters currently in use. 6 refs.

  1. Scan registration using planar features

    NASA Astrophysics Data System (ADS)

    Previtali, M.; Barazzetti, L.; Brumana, R.; Scaioni, M.

    2014-06-01

    Point cloud acquisition by using laser scanners provides an efficient way for 3D as-built modelling of indoor/outdoor urban environments. In the case of large structures, multiple scans may be required to cover the entire scene and registration is needed to merge them together. In general, the identification of corresponding geometric features among a series of scans can be used to compute the 3D rigid-body transformation useful for the registration of each scan into the reference system of the final point cloud. Different automatic or semi-automatic methods have been developed to this purpose. Several solutions based on artificial targets are available, which however may not be suitable in any situations. Methods based on surface matching (like ICP and LS3D) can be applied if the scans to align have a proper geometry and surface texture. In the case of urban and architectural scenes that present the prevalence of a few basic geometric shapes ("Legoland" scenes) the availability of many planar features is exploited here for registration. The presented technique does not require artificial targets to be added to the scanned scene. In addition, unlike other surface-based techniques (like ICP) the planar feature-based registration technique is not limited to work in a pairwise manner but it can handle the simultaneous alignment of multiple scans. Finally, some applications are presented and discussed to show how this technique can achieve accuracy comparable to a consolidated registration method.

  2. Planar waveguide sensor of ammonia

    NASA Astrophysics Data System (ADS)

    Rogoziński, Roman; Tyszkiewicz, Cuma; Karasiński, Paweł; Izydorczyk, Weronika

    2015-12-01

    The paper presents the concept of forming ammonia sensor based on a planar waveguide structure. It is an amplitude sensor produced on the basis of the multimode waveguide. The technological base for this kind of structure is the ion exchange method and the sol-gel method. The planar multimode waveguide of channel type is produced in glass substrate (soda-lime glass of Menzel-Glaser company) by the selective Ag+↔Na+ ion exchange. On the surface of the glass substrate a porous (~40%) silica layer is produced by the sol-gel method. This layer is sensitized to the presence of ammonia in the surrounding atmosphere by impregnation with Bromocresol Purple (BCP) dye. Therefore it constitutes a sensor layer. Spectrophotometric tests carried out showed about 50% reduction of cross-transmission changes of such sensor layer for a wave λ=593 nm caused by the presence of 25% ammonia water vapor in its ambience. The radiation source used in this type of sensor structure is a light emitting diode LED. The gradient channel waveguide is designed for frontal connection (optical glue) with a standard multimode telecommunications waveguide 62.5/125μm.

  3. Planar Hall effect bridge magnetic field sensors

    SciTech Connect

    Henriksen, A. D.; Dalslet, B. T.; Skieller, D. H.; Lee, K. H.; Okkels, F.; Hansen, M. F.

    2010-07-05

    Until now, the planar Hall effect has been studied in samples with cross-shaped Hall geometry. We demonstrate theoretically and experimentally that the planar Hall effect can be observed for an exchange-biased ferromagnetic material in a Wheatstone bridge topology and that the sensor signal can be significantly enhanced by a geometric factor. For the samples in the present study, we demonstrate an enhancement of the sensor output by a factor of about 100 compared to cross-shaped sensors. The presented construction opens a new design and application area of the planar Hall effect, which we term planar Hall effect bridge sensors.

  4. Planarized fiber-FHD optical composite

    NASA Astrophysics Data System (ADS)

    Holmes, C.; Carpenter, L. G.; Gates, J. C.; Gawith, C. B. E.; Smith, P. G. R.

    2015-03-01

    We demonstrate the fabrication of a mechanically robust planarised fibre-FHD optical composite. Fabrication is achieved through deposition and consolidation of optical grade silica soot on to both an optical fibre and planar substrate. The consolidated silica acts in joining the fibre and planar substrate both mechanically and optically. The concept lends itself to applications where long interaction lengths (order of tens of centimetres) and optical interaction via a planar waveguide are required, such as pump schemes, precision layup of fibre optics and hybrid fibre-planar devices. This paper considers the developments in fabrication process that enable component development.

  5. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, David B.

    1987-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  6. Planarization of metal films for multilevel interconnects

    DOEpatents

    Tuckerman, David B.

    1989-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is anarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  7. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, Allan; Boozer, Allen H.

    1987-01-01

    A helical axis stellarator using only noninterlocking planar, non-circular coils, generates magnetic fields having a magnetic well and large rotational transform with resultant large equilibrium beta.

  8. GD SDR Automatic Gain Control Characterization Testing

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer M.; Briones, Janette C.

    2013-01-01

    The General Dynamics (GD) S-Band software defined radio (SDR) in the Space Communications and Navigation (SCAN) Testbed on the International Space Station (ISS) will provide experimenters an opportunity to develop and demonstrate experimental waveforms in space. The GD SDR platform and initial waveform were characterized on the ground before launch and the data will be compared to the data that will be collected during on-orbit operations. A desired function of the SDR is to estimate the received signal to noise ratio (SNR), which would enable experimenters to better determine on-orbit link conditions. The GD SDR does not have an SNR estimator, but it does have an analog and a digital automatic gain control (AGC). The AGCs can be used to estimate the SDR input power which can be converted into a SNR. Tests were conducted to characterize the AGC response to changes in SDR input power and temperature. This purpose of this paper is to describe the tests that were conducted, discuss the results showi ng how the AGCs relate to the SDR input power, and provide recommendations for AGC testing and characterization.

  9. GD SDR Automatic Gain Control Characterization Testing

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer M.; Briones, Janette C.

    2013-01-01

    The General Dynamics (GD) S-Band software defined radio (SDR) in the Space Communications and Navigation (SCAN) Testbed on the International Space Station (ISS) will provide experimenters an opportunity to develop and demonstrate experimental waveforms in space. The GD SDR platform and initial waveform were characterized on the ground before launch and the data will be compared to the data that will be collected during on-orbit operations. A desired function of the SDR is to estimate the received signal to noise ratio (SNR), which would enable experimenters to better determine on-orbit link conditions. The GD SDR does not have an SNR estimator, but it does have an analog and a digital automatic gain control (AGC). The AGCs can be used to estimate the SDR input power which can be converted into a SNR. Tests were conducted to characterize the AGC response to changes in SDR input power and temperature. This purpose of this paper is to describe the tests that were conducted, discuss the results showing how the AGCs relate to the SDR input power, and provide recommendations for AGC testing and characterization.

  10. A bioinspired planar superhydrophobic microboat

    NASA Astrophysics Data System (ADS)

    Yong, Jiale; Yang, Qing; Chen, Feng; Zhang, Dongshi; Du, Guangqing; Si, Jinhai; Yun, Feng; Hou, Xun

    2014-03-01

    In nature, a frog can easily rest on a lotus leaf even though the frog's weight is several times the weight of the lotus leaf. Inspired by the lotus leaf, we fabricated a planar superhydrophobic microboat (SMB) with a superhydrophobic upper surface on a PDMS sheet which was irradiated by a focused femtosecond laser. The SMB can not only float effortlessly over the water surface but can also hold up some heavy objects, exhibiting an excellent loading capacity. The water surface is curved near the edge of the upper surface and the SMB's upper edge is below the water level, greatly enhancing the displacement. Experimental results and theoretical analysis demonstrate that the superhydrophobicity on the edge of the upper surface is responsible for the SMB's large loading capacity. Here, we call it the ‘superhydrophobic edge effect’.

  11. Ten inch Planar Optic Display

    SciTech Connect

    Beiser, L.; Veligdan, J.

    1996-04-01

    A Planar Optic Display (POD) is being built and tested for suitability as a high brightness replacement for the cathode ray tube, (CRT). The POD display technology utilizes a laminated optical waveguide structure which allows a projection type of display to be constructed in a thin (I to 2 inch) housing. Inherent in the optical waveguide is a black cladding matrix which gives the display a black appearance leading to very high contrast. A Digital Micromirror Device, (DMD) from Texas Instruments is used to create video images in conjunction with a 100 milliwatt green solid state laser. An anamorphic optical system is used to inject light into the POD to form a stigmatic image. In addition to the design of the POD screen, we discuss: image formation, image projection, and optical design constraints.

  12. The simplicity of planar networks

    NASA Astrophysics Data System (ADS)

    Viana, Matheus P.; Strano, Emanuele; Bordin, Patricia; Barthelemy, Marc

    2013-12-01

    Shortest paths are not always simple. In planar networks, they can be very different from those with the smallest number of turns - the simplest paths. The statistical comparison of the lengths of the shortest and simplest paths provides a non trivial and non local information about the spatial organization of these graphs. We define the simplicity index as the average ratio of these lengths and the simplicity profile characterizes the simplicity at different scales. We measure these metrics on artificial (roads, highways, railways) and natural networks (leaves, slime mould, insect wings) and show that there are fundamental differences in the organization of urban and biological systems, related to their function, navigation or distribution: straight lines are organized hierarchically in biological cases, and have random lengths and locations in urban systems. In the case of time evolving networks, the simplicity is able to reveal important structural changes during their evolution.

  13. Planar microresonators for EPR experiments.

    PubMed

    Narkowicz, R; Suter, D; Stonies, R

    2005-08-01

    EPR resonators on the basis of standing-wave cavities are optimised for large samples. For small samples it is possible to design different resonators that have much better power handling properties and higher sensitivity. Other parameters being equal, the sensitivity of the resonator can be increased by minimising its size and thus increasing the filling factor. Like in NMR, it is possible to use lumped elements; coils can confine the microwave field to volumes that are much smaller than the wavelength. We discuss the design and evaluation of EPR resonators on the basis of planar microcoils. Our test resonators, which operate at a frequency of 14 GHz, have excellent microwave efficiency factors, achieving 24 ns pi/2 EPR pulses with an input power of 17 mW. The sensitivity tests with DPPH samples resulted in the sensitivity value 2.3 x 10(9) spins.G(-1) Hz(-1/2) at 300 K. PMID:15939642

  14. Planar microresonators for EPR experiments

    NASA Astrophysics Data System (ADS)

    Narkowicz, R.; Suter, D.; Stonies, R.

    2005-08-01

    EPR resonators on the basis of standing-wave cavities are optimised for large samples. For small samples it is possible to design different resonators that have much better power handling properties and higher sensitivity. Other parameters being equal, the sensitivity of the resonator can be increased by minimising its size and thus increasing the filling factor. Like in NMR, it is possible to use lumped elements; coils can confine the microwave field to volumes that are much smaller than the wavelength. We discuss the design and evaluation of EPR resonators on the basis of planar microcoils. Our test resonators, which operate at a frequency of 14 GHz, have excellent microwave efficiency factors, achieving 24 ns π/2 EPR pulses with an input power of 17 mW. The sensitivity tests with DPPH samples resulted in the sensitivity value 2.3 × 10 9 spins · G -1Hz -1/2 at 300 K.

  15. Novel gold nanocluster electrochemiluminescence immunosensors based on nanoporous NiGd-Ni2O3-Gd2O3 alloys.

    PubMed

    Lv, Xiaohui; Ma, Hongmin; Wu, Dan; Yan, Tao; Ji, Lei; Liu, Yixin; Pang, Xuehui; Du, Bin; Wei, Qin

    2016-01-15

    Herein, three-dimensional nanoporous NiGd alloy (NP-NiGd) was prepared by selectively dealloy Al from NiGdAl alloy in mild alkaline solution, then Ni2O3 and Gd2O3 grew further on the surface of NP-NiGd to obtain the NP-NiGd-Ni2O3-Gd2O3. On this basis, NP-NiGd-Ni2O3-Gd2O3 was further functionalized with gold nanoparticles (NP-NiGd-Ni2O3-Gd2O3@Au) and acted as sensor platform to fabricate a novel electrochemiluminescence (ECL) immunosensor. Bovine serum albumin protected gold nanoclusters (AuNCs@BSA) were prepared and acted as illuminant. AuNCs@BSA modified graphene oxide (GO/AuNCs@BSA) were used as labels of second antibody. In order to characterize the performance of the ECL immunosensor, carcino embryonie antigen (CEA) was used as the model to complete the experiments. Due to the good performances of NP-NiGd-Ni2O3-Gd2O3@Au (high surface area, excellent electron conductivity) and AuNCs@BSA (low toxicity, biocompatibility, easy preparation and good water solubility), the ECL immunosensor exhibited a wide range from 10(-4) to 5ng/mL with a detection limit of 0.03pg/mL (S/N=3). The immunosensor with excellent stability, acceptable repeatability and selectivity provided a promising method to detect CEA in human serum sample sensitively. PMID:26318782

  16. Abnormal thermal expansion, multiple transitions, magnetocaloric effect, and electronic structure of Gd{sub 6}Co{sub 4.85}

    SciTech Connect

    Zhang, Jiliang; Zheng, Zhigang; Shan, Guangcun E-mail: bobev@udel.edu; Bobev, Svilen E-mail: bobev@udel.edu; Shek, Chan Hung E-mail: bobev@udel.edu

    2015-10-07

    The structure of known Gd{sub 4}Co{sub 3} compound is re-determined as Gd{sub 6}Co{sub 4.85}, adopting the Gd{sub 6}Co{sub 1.67}Si{sub 3} structure type, which is characterized by two disorder Co sites filling the Gd octahedral and a short Gd-Gd distance within the octahedra. The compound shows uniaxial negative thermal expansion in paramagnetic state, significant negative expansion in ferromagnetic state, and positive expansion below ca. 140 K. It also exhibits large magnetocaloric effect, with an entropy change of −6.4 J kg{sup −1} K{sup −1} at 50 kOe. In the lattice of the compound, Co atoms at different sites show different spin states. It was confirmed by the X-ray photoelectron spectra and calculation of electronic structure and shed lights on the abnormal thermal expansion. The stability of such compound and the origin of its magnetism are also discussed based on measured and calculated electronic structures.

  17. Improved double planar probe data analysis technique

    SciTech Connect

    Ghim, Young-chul; Hershkowitz, Noah

    2009-03-15

    Plasma electron number density and ion number density in a dc multidipole weakly collisional Ar plasma are measured with a single planar Langmuir probe and a double planar probe, respectively. A factor of two discrepancy between the two density measurements is resolved by applying Sheridan's empirical formula [T. E. Sheridan, Phys. Plasmas 7, 3084 (2000)] for sheath expansion to the double probe data.

  18. Positron Emission Mammotomography with Dual Planar Detectors

    SciTech Connect

    Mark Smith; Raymond Raylman; Stanislaw Majewski

    2003-06-29

    Positron emission mammography (PEM) is usually performed with two stationary planar detectors above and below a compressed breast. There is image blurring normal to the detectors due to the limited angular range of the lines of response. Positron emission mammotomography (PEM-T) with dual planar detectors rotating about the breast can obtain complete angular sampling and has the potential to improve activity estimation.

  19. Magnetostructural transition in Gd5Sb0.5Ge3.5

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. S.; Mudryk, Ya.; Paudyal, D.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Schlagel, D. L.; Lograsso, T. A.

    2009-11-01

    Magnetic and crystallographic properties of Gd5Sb0.5Ge3.5 were investigated using dc magnetization, ac magnetic susceptibility, and heat capacity of an oriented single crystal, combined with temperature and magnetic field dependent x-ray powder diffraction. The compound undergoes an unusual magnetostructural transition at 40 K and a nonmagnetic second-order transition around 63 K. The detailed crystallographic study of Gd5Sb0.5Ge3.5 shows that contrary to the R5(SixGe1-x)4 systems ( R is a rare-earth metal), the structural transition occurs without shear displacements of the [R5T4]∞2 slabs ( T=Si , Ge, and Sb), and a substantial volume change (-0.5%) does not lead to a change in crystallographic symmetry. The first-principles electronic structure calculations show higher interslab than intraslab ferromagnetic exchange interaction indicating that Sm5Ge4 type of structure supports a ferromagnetic ground state in Gd5Sb0.5Ge3.5 .

  20. Strong magnetic coupling in the hexagonal R5Pb3 compounds (R=Gd-Tm)

    NASA Astrophysics Data System (ADS)

    Marcinkova, Andrea; de la Cruz, Clarina; Yip, Joshua; Zhao, Liang L.; Wang, Jiakui K.; Svanidze, E.; Morosan, E.

    2015-06-01

    We have synthesized the R5Pb3 (R=Gd-Tm) compounds in polycrystalline form and performed neutron scattering and magnetization measurements. For all R5Pb3 reported here the Weiss temperatures θW are several times smaller than the ordering temperatures TORD, while the latter are remarkably high (TORD up to 275 K for R=Gd) compared to other known R-M binaries (M=Si, Ge, Sn and Sb). The magnetic order changes from ferromagnetic (FM) in R=Gd, Tb to antiferromagnetic (AFM) in R=Dy-Tm. Below TORD, the magnetization measurements together with neutron powder diffraction show complex magnetic behaviors and reveal the existence of up to three additional phase transitions, believed to be a result of large anisotropic exchange and/or crystal electric field effects, induced high anisotropy. The R5Pb3 magnetic unit cells for R=Tb-Tm can be described with incommensurate magnetic wave vectors with spin modulation either along the c axis in R=Tb, Er and Tm, or within the ab plane in R=Dy and Ho.

  1. Ferroelectric and ferromagnetic properties of Gd substituted nickel ferrite

    NASA Astrophysics Data System (ADS)

    Kamala Bharathi, K.; Markandeyulu, G.

    2008-04-01

    Ferromagnetic and ferroelectric characteristics of Gd substituted nickel ferrite (NiOṡFe1.925Gd0.075O3) were investigated. The material formed in the cubic inverse spinel phase and in addition, a small amount of GdFeO3 phase was identified. A small distortion of the cubic lattice was observed upon the substitution of Fe by Gd in the B site. Substitution of Gd for Fe lowered the saturation magnetization. However, the saturation magnetostriction is seen not to change significantly by the substitution of Gd. From the temperature variation of dielectric constant measurement, the ferroelectric transition temperature was found to be 512K. The existence of the ferroelectricity was confirmed from the ferroelectric loop. The (high) dielectric constant with frequency is seen to reveal a dispersion of relaxation times.

  2. [Gd-doped natural thenardite: Eu photoluminescence properties of europium].

    PubMed

    Guzaliayi, Juman; Tuerxun, Aidilibike; Aizitiaili, Abulizi; Aierken, Sidike

    2012-06-01

    The authors prepared Na2SO4: Eu, Gd, and Na2Gd2 (SO4)4: Eu phosphors by heating, the mixed powder of GdF3, EuF3 and natural mirabilite with muffle furnace at 1 000 degrees C for 30 min and continually heating it with microwave at 750 degrees C for 10 min. With increasing the concentrations of Gd ion, the 610 nm emission intensity due to Eu3+ was strengthened. Gd3+ probably formed a bridge between substrate and the activator so that the energy is able to be transferred efficiently. The luminescence intensity, along with colorimetric purity, reaches the top with 21 mol% Gd3+ doping in the thenardite (Na2SO4: Eu) lattices, eventually coming up the quenching effects of concentration. PMID:22870627

  3. Gd(III)-Gd(III) distance measurements with chirp pump pulses

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Qi, Mian; Wili, Nino; Pribitzer, Stephan; Godt, Adelheid; Jeschke, Gunnar

    2015-10-01

    The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S = 7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero

  4. Photoluminescence of Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 under vacuum ultraviolet excitation

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Wang, Yuhua; Huang, Yan

    2011-06-01

    Novel Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 phosphors were synthesized by solid-state reaction and their photoluminescence properties in vacuum ultraviolet region were investigated for the first time. It can be observed from the excitation spectra that the host-related absorption band is located around 170 nm, and it overlaps the O 2- → Tb 3+ charge transfer band of Ca 8MgGd(PO 4) 7:Tb 3+ around 161 nm and the 3d 5 → 3d 44s transition band of Ca 8MgGd(PO 4) 7:Mn 2+ near 200 nm. The 4f-4f 5d spin-allowed and spin-forbidden transitions of Tb 3+ are verified to be located at 170-250 and 257-271 nm, respectively. Upon 147 nm excitation, the dominant emission peak intensity of the Ca 8MgGd 0.1(PO 4) 7:0.9Tb 3+ phosphor is about 2.7 times stronger than that of the commercial Zn 2SiO 4:Mn 2+ green phosphor, and the brightness of the former with a short decay time of 2.5 ms is about 98% of the latter's. The Ca 8MgGd(PO 4):Mn 2+ phosphor excited at 147 nm exhibits a deep red emission around 650 nm, which could be attributed to the 4T 1 → 6A 1 transition of Mn 2+, with the CIE index (0.679, 0.321). In a word, the results above indicate that both Tb 3+ and Mn 2+ activated Ca 8MgGd(PO 4) 7 phosphors could be promising for PDP or Hg-free lamp applications.

  5. The Dy–Ni–Si system as a representative of the rare earth–Ni–Si family: Its isothermal section and new rare-earth nickel silicides

    SciTech Connect

    Yuan, Fang; Mozharivskyj, Y.; Morozkin, A.V.; Knotko, A.V.; Yapaskurt, V.O.; Pani, M.; Provino, A.; Manfrinetti, P.

    2014-11-15

    The Dy–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analysis. The system contains the 12 known compounds DyNi{sub 10}Si{sub 2}, DyNi{sub 5}Si{sub 3}, DyNi{sub 6}Si{sub 6}, DyNi{sub 4}Si, DyNi{sub 2}Si{sub 2}, Dy{sub 2}Ni{sub 3}Si{sub 5}, DyNiSi{sub 3}, Dy{sub 3}Ni{sub 6}Si{sub 2}, DyNiSi{sub 2}, DyNiSi, Dy{sub 3}NiSi{sub 3}, Dy{sub 3}NiSi{sub 2}, and the new compounds Dy{sub 34}Ni{sub 16−27}Si{sub 50−39} (AlB{sub 2}-type), Dy{sub 2}Ni{sub 15.2−14.1}Si{sub 1.8−2.9} (Th{sub 2}Zn{sub 17}-type), ∼Dy{sub 11}Ni{sub 65}Si{sub 24}, ∼Dy{sub 16}Ni{sub 62}Si{sub 22} (unknown structures), DyNi{sub 7}Si{sub 6} (GdNi{sub 7}Si{sub 6}-type), Dy{sub 3}Ni{sub 8}Si (Ce{sub 3}Co{sub 8}Si-type), DyNi{sub 2}Si (YPd{sub 2}Si-type), ∼Dy{sub 40}Ni{sub 47}Si{sub 13} and ∼Dy{sub 5}Ni{sub 2}Si{sub 3} (unknown structures). Quasi–binary solid solutions were detected at 1070 (870 K) for Dy{sub 2}Ni{sub 17}, DyNi{sub 5}, DyNi{sub 7}, DyNi{sub 3}, DyNi{sub 2}, DyNi, DySi{sub 2} and DySi{sub 1.67}. No detectable solubility is observed for the other binary compounds of the Dy–Ni–Si system. The crystal structures of new phases RNi{sub 7}Si{sub 6} (GdNi{sub 7}Si{sub 6}-type), R{sub 3}Ni{sub 8}Si (Ce{sub 3}Co{sub 8}Si-type), RNi{sub 2}Si (YPd{sub 2}Si-type) and R{sub 3}Ni{sub 12}Si{sub 4} (Gd{sub 3}Ru{sub 4}Al{sub 12}-type), with R=Y, Gd–Tm, has been studied. Magnetic properties of few representative compounds are also reported. - Graphical abstract: The Dy–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analysis. The system contains the 12 known compounds DyNi{sub 10}Si{sub 2}, DyNi{sub 5}Si{sub 3}, DyNi{sub 6}Si{sub 6}, DyNi{sub 4}Si, DyNi{sub 2}Si{sub 2}, Dy{sub 2}Ni{sub 3}Si{sub 5}, DyNiSi{sub 3}, Dy{sub 3}Ni{sub 6}Si{sub 2}, DyNiSi{sub 2}, DyNiSi, Dy{sub 3}NiSi{sub 3}, Dy{sub 3}NiSi{sub 2}, and the new compounds Dy{sub 34}Ni{sub 16−27}Si{sub 50−39}, Dy{sub 2}Ni{sub 15.2−14.1}Si{sub 1.8−2.9}, ∼Dy{sub 11}Ni{sub 65

  6. High Temperature Ferromagnetism in a GdAg2 Monolayer.

    PubMed

    Ormaza, M; Fernández, L; Ilyn, M; Magaña, A; Xu, B; Verstraete, M J; Gastaldo, M; Valbuena, M A; Gargiani, P; Mugarza, A; Ayuela, A; Vitali, L; Blanco-Rey, M; Schiller, F; Ortega, J E

    2016-07-13

    Materials that exhibit ferromagnetism, interfacial stability, and tunability are highly desired for the realization of emerging magnetoelectronic phenomena in heterostructures. Here we present the GdAg2 monolayer alloy, which possesses all such qualities. By combining X-ray absorption, Kerr effect, and angle-resolved photoemission with ab initio calculations, we have investigated the ferromagnetic nature of this class of Gd-based alloys. The Curie temperature can increase from 19 K in GdAu2 to a remarkably high 85 K in GdAg2. We find that the exchange coupling between Gd atoms is barely affected by their full coordination with noble metal atoms, and instead, magnetic coupling is effectively mediated by noble metal-Gd hybrid s,p-d bands. The direct comparison between isostructural GdAu2 and GdAg2 monolayers explains how the higher degree of surface confinement and electron occupation of such hybrid s,p-d bands promote the high Curie temperature in the latter. Finally, the chemical composition and structural robustness of the GdAg2 alloy has been demonstrated by interfacing them with organic semiconductors or magnetic nanodots. These results encourage systematic investigations of rare-earth/noble metal surface alloys and interfaces, in order to exploit them in magnetoelectronic applications. PMID:27247988

  7. Gd3TCAS2: An Aquated Gd(3+)-Thiacalix[4]arene Sandwich Cluster with Extremely Slow Ligand Substitution Kinetics.

    PubMed

    Iki, Nobuhiko; Boros, Eszter; Nakamura, Mami; Baba, Ryo; Caravan, Peter

    2016-04-18

    In aqueous solution, Gd(3+) and thiacalix[4]arene-p-tetrasulfonate (TCAS) form the complex [Gd3TCAS2](7-), in which a trinuclear Gd(3+) core is sandwiched by two TCAS ligands. Acid-catalyzed dissociation reactions, as well as transmetalation and ligand exchange with physiological concentrations of Zn(2+) and phosphate, showed [Gd3TCAS2](7-) to be extremely inert compared to other Gd complexes. Luminescence lifetime measurements of the Tb analogue Tb3TCAS2 allowed estimation of the mean hydration number q to be 2.4 per Tb ion. The longitudinal relaxivity of [Gd3TCAS2](7-) (per Gd(3+)) was r1 = 5.83 mM(-1) s(-1) at 20 Hz (37 °C, pH 7.4); however, this relaxivity was limited by an extremely slow water exchange rate that was 5 orders of magnitude slower than the Gd(3+) aqua ion. Binding to serum albumin resulted in no relaxivity increase owing to the extremely slow water exchange kinetics. The slow dissociation and water exchange kinetics of [Gd3TCAS2](7-) can be attributed to the very rigid coordination geometry. PMID:27018719

  8. Ferromagnetism at room temperature of c- and m-plane GaN : Gd films grown on different substrates by reactive molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ranchal, R.; Yadav, B. S.; Trampert, A.

    2013-02-01

    We report the magnetic properties of c- and m-plane GaN : Gd films grown on different substrate materials. Additionally, we have investigated the magnetic behaviour of the bare substrates in order to analyse their possible contribution on the properties of this material system. For the growth of c-phase GaN : Gd we have used 6H-SiC(0 0 0 1) and GaN/Al2O3 templates. Whereas templates only exhibit a diamagnetic behaviour, the SiC substrates show clear signatures of ferromagnetism at room temperature. Rutherford backscattering spectroscopy and secondary ions mass spectrometry have revealed traces of Fe in the SiC substrates. This Fe contamination seems to be related to the ferromagnetic ordering observed in these substrates. LiAlO2(0 0 1) is a good choice for growth of m-plane diluted nitrides due to its diamagnetic behaviour. The hysteresis loops of c- and m-phase GaN : Gd deposited on template and LiAlO2, respectively, show coercivity and magnetic saturation. These characteristics together with the magnetization curves are indications of an intrinsic ferromagnetic behaviour in the GaN : Gd.

  9. Polysilicon planarization and plug recess etching in a decoupled plasma source chamber using two endpoint techniques

    NASA Astrophysics Data System (ADS)

    Kaplita, George A.; Schmitz, Stefan; Ranade, Rajiv; Mathad, Gangadhara S.

    1999-09-01

    The planarization and recessing of polysilicon to form a plug are processes of increasing importance in silicon IC fabrication. While this technology has been developed and applied to DRAM technology using Trench Storage Capacitors, the need for such processes in other IC applications (i.e. polysilicon studs) has increased. Both planarization and recess processes usually have stringent requirements on etch rate, recess uniformity, and selectivity to underlying films. Additionally, both processes generally must be isotropic, yet must not expand any seams that might be present in the polysilicon fill. These processes should also be insensitive to changes in exposed silicon area (pattern factor) on the wafer. A SF6 plasma process in a polysilicon DPS (Decoupled Plasma Source) reactor has demonstrated the capability of achieving the above process requirements for both planarization and recess etch. The SF6 process in the decoupled plasma source reactor exhibited less sensitivity to pattern factor than in other types of reactors. Control of these planarization and recess processes requires two endpoint systems to work sequentially in the same recipe: one for monitoring the endpoint when blanket polysilicon (100% Si loading) is being planarized and one for monitoring the recess depth while the plug is being recessed (less than 10% Si loading). The planarization process employs an optical emission endpoint system (OES). An interferometric endpoint system (IEP), capable of monitoring lateral interference, is used for determining the recess depth. The ability of using either or both systems is required to make these plug processes manufacturable. Measuring the recess depth resulting from the recess process can be difficult, costly and time- consuming. An Atomic Force Microscope (AFM) can greatly alleviate these problems and can serve as a critical tool in the development of recess processes.

  10. Hybrid Si nanocones/PEDOT:PSS solar cell

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Wang, Jianxiong; Rusli, ᅟ

    2015-04-01

    Periodic silicon nanocones (SiNCs) with different periodicities are fabricated by dry etching of a Si substrate patterned using monolayer polystyrene (PS) nanospheres as a mask. Hybrid Si/PEDOT:PSS solar cells based on the SiNCs are then fabricated and characterized in terms of their optical, electrical, and photovoltaic properties. The optical properties of the SiNCs are also investigated using theoretical simulation based on the finite element method. The SiNCs reveal excellent light trapping ability as compared to a planar Si substrate. It is found that the power conversion efficiency (PCE) of the hybrid cells decreases with increasing periodicity of the SiNCs. The highest PCE of 7.1% is achieved for the SiNC hybrid cell with a 400-nm periodicity, due to the strong light trapping near the peak of the solar spectrum and better current collection efficiency.

  11. Planar doped barrier subharmonic mixers

    NASA Technical Reports Server (NTRS)

    Lee, T. H.; East, J. R.; Haddad, G. I.

    1992-01-01

    The Planar Doped Barrier (PDB) diode is a device consisting of a p(+) doping spike between two intrinsic layers and n(+) ohmic contacts. This device has the advantages of controllable barrier height, diode capacitance and forward to reverse current ratio. A symmetrically designed PDB has an anti-symmetric current vs. voltage characteristic and is ideal for use as millimeter wave subharmonic mixers. We have fabricated such devices with barrier heights of 0.3, 0.5 and 0.7 volts from GaAs and InGaAs using a multijunction honeycomb structure with junction diameters between one and ten microns. Initial RF measurements are encouraging. The 0.7 volt barrier height 4 micron GaAs devices were tested as subharmonic mixers at 202 GHz with an IF frequency of 1 GHz and had 18 dB of conversion loss. The estimated mismatch loss was 7 dB and was due to higher diode capacitance. The LO frequency was 100.5 GHz and the pump power was 8 mW.

  12. Piezo Voltage Controlled Planar Hall Effect Devices

    NASA Astrophysics Data System (ADS)

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-06-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

  13. Planar Hall effect in Y{sub 3}Fe{sub 5}O{sub 12}/IrMn films

    SciTech Connect

    Zhang, X. Zou, L. K.

    2014-12-29

    The planar Hall effect of IrMn on an yttrium iron garnet (YIG = Y{sub 3}Fe{sub 5}O{sub 12}) was measured in the magnetic field rotating in the film plane. The magnetic field angular dependence of planar Hall resistance (PHR) was observed in YIG/IrMn bilayer at different temperatures, while the Gd{sub 3}Ga{sub 5}O{sub 12}/IrMn film shows constant PHR for different magnetic field angles at both 10 K and 300 K. This provides evidence that IrMn has interfacial spins which can be led by ferrimagnetic layer in YIG/IrMn structure. A hysteresis can be observed in PHR-magnetic field angle loop of YIG/IrMn film at 10 K, indicative of the irreversible switching of IrMn interfacial spins at low temperature.

  14. Room-temperature near-infrared high-Q perovskite whispering-gallery planar nanolasers.

    PubMed

    Zhang, Qing; Ha, Son Tung; Liu, Xinfeng; Sum, Tze Chien; Xiong, Qihua

    2014-10-01

    Near-infrared (NIR) solid-state micro/nanolasers are important building blocks for true integration of optoelectronic circuitry. Although significant progress has been made in III-V nanowire lasers with achieving NIR lasing at room temperature, challenges remain including low quantum efficiencies and high Auger losses. Importantly, the obstacles toward integrating one-dimensional nanowires on the planar ubiquitous Si platform need to be effectively tackled. Here we demonstrate a new family of planar room-temperature NIR nanolasers based on organic-inorganic perovskite CH3NH3PbI(3-a)X(a) (X = I, Br, Cl) nanoplatelets. Their large exciton binding energies, long diffusion lengths, and naturally formed high-quality planar whispering-gallery mode cavities ensure adequate gain and efficient optical feedback for low-threshold optically pumped in-plane lasing. We show that these remarkable wavelength tunable whispering-gallery nanolasers can be easily integrated onto conductive platforms (Si, Au, indium tin oxide, and so forth). Our findings open up a new class of wavelength tunable planar nanomaterials potentially suitable for on-chip integration. PMID:25118830

  15. The new structure type Gd3Ni7Al14.

    PubMed

    Pukas, Svitlana; Gladyshevskii, Roman

    2015-11-01

    The crystal structure of Gd3Ni7Al14 (trigadolinium heptanickel tetradecaaluminide) belongs to a family of two-layer structures and can be described as an assembly of interpenetrating centred straight prisms. For the Ni atoms, trigonal prisms (Al4Gd2 and Al6) are observed, the Al atoms are inside tetragonal (Ni2Al2Gd4, Ni2Al4Gd2, Al4Gd4, Ni4Al4 and Al8) and pentagonal (Ni4Al6 and Al10) prisms, while the Gd atoms are at the centres of pentagonal (Ni4Al6) and hexagonal (Ni4Al8) prisms. In each case, the true coordination polyhedron is a capped prism, also including atoms from the same layer. The structural features of Gd3Ni7Al14 are similar to those of the intermetallides PrNi2Al3 and ZrNiAl. In all these structures, Ni-centred trigonal prisms form infinite columns via common triangular faces. The columns share prism edges and form a three-dimensional framework with six-membered rings in the (001) plane in the case of the PrNi2Al3 and ZrNiAl types. In the case of Gd3Ni7Al14, six-membered rings are also observed, but only two-thirds of the rings are interconnected via prism edges. PMID:26524174

  16. Electronic transitions in GdN band structure

    SciTech Connect

    Vidyasagar, R. Kita, T.; Sakurai, T.; Ohta, H.

    2014-05-28

    Using the near-infrared (NIR) absorbance spectroscopy, electronic transitions and spin polarization of the GdN epitaxial film have been investigated; and the GdN epitaxial film was grown by a reactive rf sputtering technique. The GdN film exhibited three broad bands in the NIR frequency regimes; and those bands are attributable primarily to the minority and majority spin transitions at the X-point and an indirect transition along the Γ-X symmetric direction of GdN Brillouin zone. We experimentally observe a pronounced red-shift of the indirect band gap when cooling down below the Curie temperature which is ascribed to the orbital-dependent coulomb interactions of Gd-5dxy electrons, which tend to push-up the N-2p bands. On the other hand, we have evaluated the spin polarization of 0.17 (±0.005), which indicates that the GdN epitaxial film has almost 100% spin-polarized carriers. Furthermore, the experimental result of GdN electronic transitions are consistent with the previous reports and are thus well-reproduced. The Arrott plots evidenced that the Curie temperature of GdN film is 36 K and the large spin moment is explained by the nitrogen vacancies and the intra-atomic exchange interaction.

  17. Linear dichroism and resonant photoemission in Gd 011

    SciTech Connect

    Mishra, S.R.; Cummins, T.R.; Gammon, W.J.; van der Laan, G.; Goodman, K.W.; Tobin, J.G.

    1998-05-13

    Magnetic Linear Dichroism in Angular Distributions (MLDAD) from Photoelectron Emission was used to probe the nature of Resonant Photoemission. Gd 5p and Gd 4f emission were investigated. Using novel theoretical simulations, we were able to show that temporal matching is a requirement for ``True`` Resonant Photoemission, where the Resonant Photoemission retains the characteristics of Photoelectron Emission.

  18. On linear area embedding of planar graphs

    NASA Astrophysics Data System (ADS)

    Dolev, D.; Trickey, H.

    1981-09-01

    Planar embedding with minimal area of graphs on an integer grid is one of the major issues in VLSI. Valiant (V) gave an algorithm to construct a planar embedding for trees in linear area; he also proved that there are planar graphs that require quadratic area. An algorithm to embed outerplanar graphs in linear area is given. This algorithm is extended to work for every planar graph that has the following property: for every vertex there exists a path of length less than K to the exterior face, where K is a constant. Finally, finding a minimal embedding area is shown to be NP-complete for forests, and hence more general types of graphs.

  19. Non-planar microfabricated gas chromatography column

    DOEpatents

    Lewis, Patrick R.; Wheeler, David R.

    2007-09-25

    A non-planar microfabricated gas chromatography column comprises a planar substrate having a plurality of through holes, a top lid and a bottom lid bonded to opposite surfaces of the planar substrate, and inlet and outlet ports for injection of a sample gas and elution of separated analytes. A plurality of such planar substrates can be aligned and stacked to provide a longer column length having a small footprint. Furthermore, two or more separate channels can enable multi-channel or multi-dimensional gas chromatography. The through holes preferably have a circular cross section and can be coated with a stationary phase material or packed with a porous packing material. Importantly, uniform stationary phase coatings can be obtained and band broadening can be minimized with the circular channels. A heating or cooling element can be disposed on at least one of the lids to enable temperature programming of the column.

  20. Novel Planar and Integrated Microwave Antennas

    NASA Technical Reports Server (NTRS)

    Saed, Mohammad A.

    2000-01-01

    This project dealt with design, analysis, and testing of new types of planar and integrated antennas operating in the microwave frequency range. The following was accomplished during this project period:

  1. [3D-MR-angiography using Gd-DTPA].

    PubMed

    Seiderer, M; Bauer, W M; Villringer, A; Einhäupl, K

    1990-03-01

    Projection angiograms similar to DSA can be obtained via 3D-gradient echo techniques by subtraction of data sets acquired before and after the intravenous administration of Gd-DTPA (0.1-0.2 mmol/kg body weight). As Gd-DTPA does not penetrate the blood-brain barrier, image subtraction results in complete cancellation of non vascular tissue. In organs without blood-brain barrier Gd-DTPA induced signal enhancement results in modest background superposition of vascular anatomy. With Gd-DTPA angiography vessels are imaged favouring the venous system because of the more constant flow velocity and the lack of ECG synchronization. Gd-DTPA angiography results in high signal-to-noise angiograms and can even be performed with MR imagers which do not meet the hardware requirements for angiography based on flow compensated gradients. PMID:2157258

  2. Geometrical structure and spin order of Gd13 cluster

    NASA Astrophysics Data System (ADS)

    Yuan, H. K.; Chen, H.; Kuang, A. L.; Wu, B.

    2011-09-01

    The spin-polarized generalized gradient approximation to the density-functional theory has been used to determine the lowest energy structure, electronic structure, and magnetic property of Gd13 cluster. Our results show that the ionic bonding is combined with the covalent characteristics in stabilizing the Gd cluster. The ferrimagnetic icosahedron is found to be the lowest energy configuration, in which the centered Gd atom couples antiferromagnetically with the rest Gd atoms surrounding it. No spin non-collinear evidence has been detected in our calculations. It is identified that the local magnetic moments of Gd atom are about 8 μB regardless of geometrical structure. Finally, the comprehensive electronic structure analyses show that the indirect long-range magnetic coupling between the polarized 4f is mediated by the polarization of 5d, 6s, and 6p conduction electrons, which is the typical Ruderman-Kittel-Kasuya-Yosida interactions.

  3. The influence of impurities and planar defects on the infrared properties of silicon carbide films

    SciTech Connect

    Rajasekhara, S.; Ferreira, P. J.; Kovar, D.; Neuner, B. H. III; Shvets, G.; Zorman, C. A.; Jegenyes, N.; Ferro, G.

    2011-05-09

    Two cubic, single crystal silicon carbide (3C-SiC) films with similar thickness are shown to exhibit significantly different optical properties at mid-infrared wavelengths. Depth profiling by time-of-flight secondary ion mass spectroscopy indicates that these two films have substantially different n-type impurity concentrations that are responsible for the observed differences in optical absorption. The influence of impurities manifests as substantially different planar defect morphologies.

  4. Planar electrical-substitution carbon nanotube cryogenic radiometer

    NASA Astrophysics Data System (ADS)

    Tomlin, N. A.; White, M.; Vayshenker, I.; Woods, S. I.; Lehman, J. H.

    2015-04-01

    We have developed a fully-lithographic electrical-substitution planar bolometric-radiometer (PBR) that employs multiwall vertically-aligned carbon nanotubes (VACNT) as the absorber and thermistor, micro-machined Si as the weak thermal link and thin-film Mo as the electrical heater. The near-unity absorption of the VACNT over a broad wavelength range permits a planar geometry, compatible with lithographic fabrication. We present performance results on a PBR with an absorption of 0.999 35 at 1550 nm, a thermal conductance of 456 µW K-1 at 4 K and a time constant (1/e) of 7.7 ms. A single measurement of approximately 100 µW optical power at 1550 nm achieved in less than 100 s yields an expanded uncertainty of 0.14% (k = 2). We also observe an elevated superconducting transition temperature of 3.884 K for the Mo heater, which opens the possibility of future devices incorporating more sensitive thermistors and superconducting thin-film wiring. Contribution of an agency of the US government; not subject to copyright

  5. Improved double planar probe data analysis technique.

    PubMed

    Ghim Kim, Young-Chul; Hershkowitz, Noah

    2009-03-01

    Plasma electron number density and ion number density in a dc multidipole weakly collisional Ar plasma are measured with a single planar Langmuir probe and a double planar probe, respectively. A factor of two discrepancy between the two density measurements is resolved by applying Sheridan's empirical formula [T. E. Sheridan, Phys. Plasmas 7, 3084 (2000)] for sheath expansion to the double probe data. PMID:19334917

  6. The Planar Gauge in a New Formalism

    NASA Astrophysics Data System (ADS)

    Leibbrandt, George; Nyeo, Su-Long

    The main feature of the planar gauge, apart from the decoupling of ghosts, is the nontransversality of the Yang-Mills self-energy with the resulting appearance of a pincer diagram in the Ward identity. We employ the general prescription for axial-type gauges, recently developed by one of the authors, to check this Ward identity and derive BRS-invariant counterterms in the planar gauge.

  7. The planar gauge in a new formalism

    SciTech Connect

    Leibbrandt, G.; Nyeo, S.L.

    1988-09-01

    The main feature of the planar gauge, apart from the decoupling of ghosts, is the nontransversatility of the Yang-Mills self-energy with the resulting appearance of a pincer diagram in the Ward identity. The authors employ the general prescription for axial-type gauges, recently developed by one of the authors, to check this Ward identity and derive BRS-invariant counterterms in the planar gauge.

  8. Magnetization of planar four-fermion systems

    SciTech Connect

    Caldas, Heron; Ramos, Rudnei O.

    2009-09-15

    We consider a planar system of fermions, at finite temperature and density under a static magnetic field parallel to the two-dimensional plane. This magnetic field generates a Zeeman effect and then a spin polarization of the system. The critical properties are studied from the Landau's free energy. The possible observable consequences of the magnetization of planar systems such as polymer films and graphene are discussed.

  9. Planar prism spectrometer based on adiabatically connected waveguiding slabs

    NASA Astrophysics Data System (ADS)

    Civitci, F.; Hammer, M.; Hoekstra, H. J. W. M.

    2016-04-01

    The device principle of a prism-based on-chip spectrometer for TE polarization is introduced. The spectrometer exploits the modal dispersion in planar waveguides in a layout with slab regions having two different thicknesses of the guiding layer. The set-up uses parabolic mirrors, for the collimation of light of the input waveguide and focusing of the light to the receiver waveguides, which relies on total internal reflection at the interface between two such regions. These regions are connected adiabatically to prevent unwanted mode conversion and loss at the edges of the prism. The structure can be fabricated with two wet etching steps. The paper presents basic theory and a general approach for device optimization. The latter is illustrated with a numerical example assuming SiON technology.

  10. Thermochemical investigations in the system Cd–Gd

    PubMed Central

    Reichmann, Thomas L.; Ganesan, Rajesh; Ipser, Herbert

    2014-01-01

    Vapour pressure measurements were performed in terms of a non-isothermal isopiestic method to determine vapour pressures of Cd in the system Cd–Gd between 693 and 1045 K. From these results thermodynamic activities of Cd were derived as a function of temperature for the composition range 52–86 at.% Cd. By employing an adapted Gibbs–Helmholtz equation, partial molar enthalpies of mixing of Cd were obtained for the corresponding composition range, which were used to convert the activity values of Cd to a common average sample temperature of 773 K. The relatively large variation of the activity across the homogeneity ranges of the phases Cd2Gd and Cd45Gd11 indicates that they probably belong to the most stable intermetallic compounds in this system. An activity value of Gd for the two phase field Cd6Gd+L was available from literature and served as an integration constant for a Gibbs–Duhem integration. Integral Gibbs energies are presented between 51 and 100 at.% Cd at 773 K, referred to Cd(l) and α-Gd(s) as standard states. Gibbs energies of formation for the exact stoichiometric compositions of the phases Cd58Gd13, Cd45Gd11, Cd3Gd and Cd2Gd were obtained at 773 K as about −19.9, −21.1, −24.8, and −30.0 kJ g atom−1, respectively. PMID:25328283

  11. Optimized planar micro-optic concentrator design

    NASA Astrophysics Data System (ADS)

    Pan, Jui-Wen; Su, Yu-Chung; Lee, Sheng-Yi

    2016-06-01

    The structural parameters of a planar micro-optic concentrator are optimized. First, the direct-loss is minimized by altering the relationship between the f-number of the lenslet, the angle of the micro-structure and the ray paths in the planar micro-optic concentrator. Second, the size of the micro-structure is made equal to the mini-blur size of the lenslet in order to reduce the non-direct loss. Last, the f-number and the entrance pupil diameter of the lenslet are determined by the relationships among the f-number, the entrance pupil diameter, the optical efficiency, the acceptance angle and the thickness of the planar micro-optic concentrator from the optical simulation results. For an optimized planar micro-optic concentrator with a 300× concentration, the f-number of the lenslet, the EPD of the lenslet, the angle of the micro-structure and the thickness of the planar micro-optic concentrator are 2.6, 1.49 mm, 120 degrees and 5.97 mm, respectively. For micro-structures 28.95 μm, 51.24 μm and 88.29 μm in size, the half acceptance angles of the planar micro-optic concentrator are 0.115 degrees, 0.275 degrees and 0.55 degrees, respectively, and the optical efficiencies are 81.23%, 71.92% and 50.02%, respectively.

  12. Electron-optical systems for planar gyrotrons

    NASA Astrophysics Data System (ADS)

    Manuilov, V. N.; Zaslavsky, V. Yu.; Ginzburg, N. S.; Glyavin, M. Yu.; Kuftin, A. N.; Zotova, I. V.

    2014-02-01

    The methodology of designing an electron-optical system (EOS) that forms sheet helical electron beams (HEBs) for high-power gyrotrons is developed. As an example, we consider the EOS for a 140-GHz gyrotron operated at the first harmonic of the cyclotron frequency with an accelerating voltage of 50 kV, a beam current of 30 A, and a magnetic field compression of 36. A planar geometry of the magnetron-injection gun (MIG) is suggested. The adiabatic theory of MIGs modified for the planar geometry of EOS is used for preliminary estimations of MIG parameters. Numerical simulation of the HEB properties based on the CST STUDIO SUITE 3D code is performed to find the optimal configuration of a planar MIG. The accuracy of the calculated data is discussed. The main factors that affect the HEB quality are considered. It is shown that a sheet HEB with a pitch-factor of 1.3 and velocity spread not exceeding 25%-30% can be formed; this is quite acceptable for high-efficiency operation of modern gyrotrons. Calculation of the beam-wave interaction with the obtained HEB parameters proved that a high output power with a sufficiently good efficiency of about 20% can be reached. Simulations show the feasibility of the experimental implementation of a novel planar EOS and its use in short-wave planar gyrotrons. The developed technique can be used for the study and optimization of planar gyrotrons of different frequency bands and power levels.

  13. Coherent growth of GaGdN layers with high Gd concentration on GaN(0001)

    SciTech Connect

    Higashi, K.; Hasegawa, S.; Abe, D.; Mitsuno, Y.; Komori, S.; Ishimaru, M.; Asahi, H.; Ishikawa, F.

    2012-11-26

    We report on the coherent growth of GaGdN with high Gd concentration on a GaN template using radio-frequency plasma-assisted molecular beam epitaxy under elevated growth conditions. X-ray diffraction and cross-sectional transmission electron microscopy observations revealed that at a growth temperature of 700 {sup Degree-Sign }C or below, GaGdN layers are coherently grown on the GaN templates without segregation of the secondary phases. As the GdN mole fraction x was increased to 0.08, the c-axis lattice parameter in Ga{sub 1-x}Gd{sub x}N increased linearly. Increasing the growth temperature to 750 {sup Degree-Sign }C causes lattice relaxation in GaGdN. All GaGdN samples exhibited photoluminescence emissions near the band-edge, a blue luminescence band emission, and a green luminescence band emission. The origin of the green luminescence band emission is discussed in relation to the compressive strain existing in the GaGdN layers coherently grown on GaN.

  14. Advanced high-k dielectric amorphous LaGdO3 based high density metal-insulator-metal capacitors with sub-nanometer capacitance equivalent thickness

    NASA Astrophysics Data System (ADS)

    Pavunny, S. P.; Misra, P.; Scott, J. F.; Katiyar, R. S.

    2013-06-01

    Planar metal-insulator-metal (MIM) mono-dielectric layer stacks were fabricated using pulsed laser deposited thin films of high-k dielectric LaGdO3. These stacks showed high capacitance density ˜43.5 fF/μm2 with sub-nanometer capacitance equivalent thicknesses of ˜0.66 nm, large breakdown field of ˜6 MV/cm, greater energy storage density of ˜40 J/cm3, smaller voltage coefficient of capacitance, and lower dependence of it on layer thickness α ∝ d-1 and frequency. All these features make LaGdO3 a material of interest for next generation MIM structures for radio frequency, analog/mixed-signal, and dynamic random access memory applications.

  15. Micropipes and voids at β¨SiC/Si(100) interfaces: an electron microscopy study

    NASA Astrophysics Data System (ADS)

    Scholz, R.; Gösele, U.; Niemann, E.; Wischmeyer, F.

    The microstructure of β-SiC/Si(100) interfaces generated by carbonization and subsequent growth in a chemical vapor deposition (CVD) reactor was investigated by transmission electron microscopy (TEM). Differently prepared cross section and planar specimens allowed a detailed characterization of interface defects. Besides pyramidal voids, which were frequently reported to appear at SiC/Si interfaces within the substrate, recently discovered micropipes are of special interest. Both kinds of defects form by outdiffusion of silicon during the carbonization process. In contrast to voids. which initially remain empty, micropipes develop by simultaneous ingrowth of SiC. The area densities of micropipes were found to be orders of magnitude higher than those of voids. Micropipe formation may be due to a high density of SiC nuclei preexisting on the substrate surfaces after pretreatments. The simultaneous development of voids and micropipes is discussed on the basis of results obtained from a short-time carbonization experiment.

  16. Improved memory characteristics by NH{sub 3}-nitrided GdO as charge storage layer for nonvolatile memory applications

    SciTech Connect

    Liu, L.; Xu, J. P.; Ji, F.; Chen, J. X.; Lai, P. T.

    2012-07-16

    Charge-trapping memory capacitor with nitrided gadolinium oxide (GdO) as charge storage layer (CSL) is fabricated, and the influence of post-deposition annealing in NH{sub 3} on its memory characteristics is investigated. Transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction are used to analyze the cross-section and interface quality, composition, and crystallinity of the stack gate dielectric, respectively. It is found that nitrogen incorporation can improve the memory window and achieve a good trade-off among the memory properties due to NH{sub 3}-annealing-induced reasonable distribution profile of a large quantity of deep-level bulk traps created in the nitrided GdO film and reduction of shallow traps near the CSL/SiO{sub 2} interface.

  17. Morphology and electrical conduction of Si:P δ-doped layers on vicinal Si(001)

    NASA Astrophysics Data System (ADS)

    Reusch, T. C. G.; Goh, K. E. J.; Pok, W.; Lo, W.-C. N.; McKibbin, S. R.; Simmons, M. Y.

    2008-09-01

    We present a combined scanning tunneling microscopy (STM) and low-temperature magnetotransport study of Si:P δ-doped layers on vicinal Si(001) substrates. The substrates were misoriented 4° toward [110] resulting in a high step density on the starting growth surface. Atomically resolved STM was used to study all stages of the fabrication. We find only a weak influence of the high step density and discuss the implications for the fabrication δ-doped layers and planar nanoscale Si:P devices by scanning tunneling lithography.

  18. Fracture Toughness Properties of Gd123 Superconducting Bulks

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Murakami, A.

    Fracture toughness properties of melt growth GdBa2Cu3Ox (Gd123) large single domain superconducting bulks with Ag2O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, KIC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

  19. Integration of planar transformer and/or planar inductor with power switches in power converter

    DOEpatents

    Chen, Kanghua; Ahmed, Sayeed; Zhu, Lizhi

    2007-10-30

    A power converter integrates at least one planar transformer comprising a multi-layer transformer substrate and/or at least one planar inductor comprising a multi-layer inductor substrate with a number of power semiconductor switches physically and thermally coupled to a heat sink via one or more multi-layer switch substrates.

  20. {NiLn} (Ln = Gd, Dy) rod-like nano-sized heteronuclear coordination clusters with a double carbonate bridge skeleton and remarkable MCE behaviour.

    PubMed

    Guarda, Eliana; Bader, Katharina; van Slageren, Joris; Alborés, Pablo

    2016-05-17

    The newly obtained complexes [NiLn(Piv)16(teaH)6(OCH3)2(CO3)2(H2O)2] Ln = Gd, Dy, show a remarkable μ5-carbonate bridged octanuclear planar {Ni4Ln4} core further capped with embedded {Ni3Ln} cubane motifs to afford a rod shaped nano-sized molecule of about 1.2 × 2.8 nm. Unusual MCE behaviour has been found due to multiple low lying excited states arising from competing ferromagnetic and anti-ferromagnetic Ni-Ni and Ni-Ln exchange interactions. PMID:27126965

  1. Hydrogenation induced structure and property changes in GdGa

    NASA Astrophysics Data System (ADS)

    Nedumkandathil, Reji; Kranak, Verina F.; Johansson, Robert; Ångström, Jonas; Balmes, Oliver; Andersson, Mikael S.; Nordblad, Per; Scheicher, Ralph H.; Sahlberg, Martin; Häussermann, Ulrich

    2016-07-01

    Hydrides GdGaHx were obtained by exposing the Zintl phase GdGa with the CrB structure to a hydrogen atmosphere at pressures from 1.5 to 50 bar and temperatures from 50 to 500 °C. Structural analysis by powder X-ray diffraction suggests that conditions with hydrogen pressures in a range between 15 and 50 bar and temperatures below 500 °C afford a uniform hydride phase with the NdGaH1.66 structure (Cmcm, a=3.9867(7) Å, b=12.024(2) Å, c=4.1009(6) Å) which hosts H in two distinct positions, H1 and H2. H1 is coordinated in a tetrahedral fashion by Gd atoms, whereas H2 atoms are inserted between Ga atoms. The assignment of the NdGaH1.66 structure is corroborated by first principles DFT calculations. Modeling of phase and structure stability as a function of composition resulted in excellent agreement with experimental lattice parameters when x=1.66 and revealed the presence of five-atom moieties Ga-H2-Ga-H2-Ga in GdGaH1.66. From in situ powder X-ray diffraction using synchrotron radiation it was established that hydrogenation at temperatures above 200 °C affords a hydride with x≈1.3, which is stable up to 500 °C, and that additional H absorption, yielding GdGaH1.66, takes place at lower temperatures. Consequently, GdGaH1.66 desorbs H above T=200 °C. Without the presence of hydrogen, hydrides GdGaHx decompose at temperatures above 300 °C into GdH2 and an unidentified Gd-Ga intermetallics. Thus the hydrogenation of GdGa is not reversible. From magnetic measurements the Curie-Weiss constant and effective magnetic moment of GdGaH1.66 were obtained. The former indicates antiferromagnetic interactions, the latter attains a value of ~8 μB which is typical for compounds containing Gd3+ions.

  2. Heat capacity of RVO4 ( R = La-Gd) orthovanadates

    NASA Astrophysics Data System (ADS)

    Denisova, L. T.; Chumilina, L. G.; Denisov, V. M.

    2015-05-01

    The data on the molar heat capacity of GdVO4 and SmVO4 as a function of the temperature have been obtained. The thermodynamic properties of the oxide compounds have been calculated from the experimental data. It has been shown that the specific heat capacity of La-Gd oxides and their orthovanadates change regularly depending on the ionic radius R 3+ within the first and second tetrads (La-Nd, Pm-Gd). The values of C p 0 (298 K) have been evaluated for PmVO4 and CeVO4.

  3. Electron microscopy of a Gd-Ba-Cu-O superconductor

    NASA Technical Reports Server (NTRS)

    Ramesh, R.; Thomas, G.; Meng, R. L.; Hor, P. H.; Chu, C. W.

    1989-01-01

    An electron microscopy study has been carried out to characterize the microstructure of a sintered Gd-Ba-Cu-O superconductor alloy. The GdBa2Cu3O(7-x) phase in the oxygen annealed sample is orthorhombic, while in the vacuum annealed sample it is tetragonal. It is shown that the details of the fine structure in the 001-line zone axis convergent beam patterns can be used to distinguish between the orthorhombic form and the tetragonal form. In addition to this matrix phase, an amorphous phase is frequently observed at the triple grain junctions. Gd-rich inclusions have been observed inside the matrix phase.

  4. SI Notes.

    ERIC Educational Resources Information Center

    Nelson, Robert A.

    1983-01-01

    Discusses legislation related to SI (International Systems of Units) in the United States. Indicates that although SI metric units have been officially recognized by law in the United States, U.S. Customary Units have never received a statutory basis. (JN)

  5. Generation of core-shell structures and segregation of dopants in Si/SiO2 nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Sunghyun; Park, Ji-Sang; Chang, K. J.

    2013-03-01

    Oxidized Si nanowires (SiNWs) are usually synthesized by subsequent thermal annealing of as-grown SiNWs. It has been observed that B diffusivity is enhanced during thermal annealing in SiNWs, similar to the phenomena called transient enhanced diffusion or oxidation enhanced diffusion in planar Si/SiO2 interfaces. However, previous theoretical studies have been focused on hydrogen or hydroxyl terminated SiNWs. In this work, we generate realistic atomic models for oxidized SiNWs in which crystalline Si core is sheathed by amorphous SiO2 by using a combined approach of classical molecular dynamics simulations with first-principles density functional calculations. For realistic core-shell structures, we investigate the stability and segregation behavior of B and P dopants. A single substitutional B is more stable in the Si core, with a very small energy variation with the radial position of B. On the other hand, B dopants easily segregate to the oxide shell with the aid of Si self-interstitials generated during thermal oxidation. In contrast to B dopants, P dopants prefer to reside in the Si core even in the presence of Si self-interstitials but tend to aggregate in the Si region near the interface, forming nearest-neighbor donor pairs which are electrically inactive.

  6. Fast three-dimensional proton spectroscopic imaging of the human brain at 3 T by combining spectroscopic missing pulse steady-state free precession and echo planar spectroscopic imaging.

    PubMed

    Dreher, Wolfgang; Erhard, Peter; Leibfritz, Dieter

    2011-12-01

    The combination of the principles of two fast spectroscopic imaging (SI) methods, spectroscopic missing pulse steady-state free precession and echo planar SI (EPSI) is described as an approach toward fast 3D SI. This method, termed missing pulse steady-state free precession echo planar SI, exhibits a considerably reduced minimum total measurement time T(min), allowing a higher temporal resolution, a larger spatial matrix size, and the use of k-space weighted averaging and phase cycling, while maintaining all advantages of the original spectroscopic missing pulse steady-state free precession sequence. The minor signal-to-noise ratio loss caused by using oscillating read gradients can be compensated by applying k-space weighted averaging. The missing pulse steady-state free precession echo planar SI sequence was implemented on a 3 T head scanner, tested on phantoms and applied to healthy volunteers. PMID:21574181

  7. Microstructure and rolling capability of modified AZ31-Ce-Gd alloys

    SciTech Connect

    Li Wenping; Zhou Hong; Lin Pengyu; Zhao Shizhe

    2009-11-15

    AZ31-Ce-Gd alloys were studied and the influence of cerium (Ce) and gadolinium (Gd) on the microstructure and rolling capability of AZ31 alloy was investigated. The results indicated that the grains of AZ31 alloy were refined with Ce and Gd addition. Ce and Gd addition resulted in the formation of Al{sub 4}Ce, Al{sub 2}Gd and Mg{sub 3}Gd. After homogenization and rolling, the Al{sub 4}Ce, Al{sub 2}Gd and Mg{sub 3}Gd still existed. The rolling capability of AZ31 alloy was improved obviously with Ce and Gd addition. However, once Gd content increased to a certain value, the rolling capability of the modified alloy declined but still better than that of AZ31 alloy.

  8. Piezo Voltage Controlled Planar Hall Effect Devices.

    PubMed

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials. PMID:27329068

  9. Planar quantum squeezing and atom interferometry

    SciTech Connect

    He, Q. Y.; Drummond, P. D.; Reid, M. D.; Peng Shiguo

    2011-08-15

    We obtain a lower bound on the sum of two orthogonal spin component variances in a plane. This gives a planar uncertainty relation which holds even when the Heisenberg relation is not useful. We investigate the asymptotic, large-J limit and derive the properties of the planar quantum squeezed states that saturate this uncertainty relation. These states extend the concept of spin squeezing to any two conjugate spin directions. We show that planar quantum squeezing can be achieved experimentally as the ground state of a Bose-Einstein condensate in two coupled potential wells with a critical attractive interaction. These states reduce interferometric phase noise at all phase angles simultaneously. This is useful for one-shot interferometric phase measurements where the measured phase is completely unknown. Our results can also be used to derive entanglement criteria for multiple spins J at separated sites, with applications in quantum information.

  10. Piezo Voltage Controlled Planar Hall Effect Devices

    PubMed Central

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials. PMID:27329068

  11. The Feynman Identity for Planar Graphs

    NASA Astrophysics Data System (ADS)

    da Costa, G. A. T. F.

    2016-08-01

    The Feynman identity (FI) of a planar graph relates the Euler polynomial of the graph to an infinite product over the equivalence classes of closed nonperiodic signed cycles in the graph. The main objectives of this paper are to compute the number of equivalence classes of nonperiodic cycles of given length and sign in a planar graph and to interpret the data encoded by the FI in the context of free Lie superalgebras. This solves in the case of planar graphs a problem first raised by Sherman and sets the FI as the denominator identity of a free Lie superalgebra generated from a graph. Other results are obtained. For instance, in connection with zeta functions of graphs.

  12. A catastrophe theory model of planar orientation

    SciTech Connect

    Wright, M.W.; Deacon, G.E.

    2000-06-01

    The manipulation of planar objects using linear fences is of interest in robotics and parts feeding applications. The global behavior of such systems can be characterized graphically using Brost's push stability diagram (PSD). Previously, the authors have shown specifically under what conditions this representation undergoes qualitative, topological transitions corresponding to globally distinct behavioral regimes. In this paper, they show that these insights form a united whole when viewed from the perspective of catastrophe theory. The key result is that a planar object being pushed by a fence under the assumption of Coulomb friction is functionally equivalent to a gravitational catastrophe machine. Qualitative changes in global behavior are thus explained as catastrophes as singularities are encountered on a discriminant surface due to smooth changes in parameters. Catastrophe theory thus forms part of a computational theory of planar orientation, the aim of which is to understand such systems and make predictions about their behavior.

  13. Pinning of flux lines by planar defects

    NASA Astrophysics Data System (ADS)

    Petković, Aleksandra; Emig, Thorsten; Nattermann, Thomas

    2009-06-01

    The influence of randomly distributed point impurities and planar defects on order and transport in type-II superconductors and related systems is studied. It is shown that the Bragg glass phase is unstable with respect to planar defects. Even a single weak defect plane oriented parallel to the magnetic field as well as to one of the main axes of the Abrikosov flux-line lattice is a relevant perturbation in the Bragg glass. A defect that is aligned with the magnetic field restores the flux density oscillations, which decay algebraically with the distance from the defect. The theory exhibits striking similarities to the physics of a Luttinger liquid with a frozen impurity. The exponent for the flux-line creep in the direction perpendicular to a relevant defect is derived. We find that the flux-line lattice exhibits in the presence of many randomly distributed parallel planar defects aligned to the magnetic field a glassy phase which we call planar glass. The planar glass is characterized by diverging shear and tilt moduli, a transverse Meissner effect, and resistance against shear deformations. We also obtain sample-to-sample fluctuations of the longitudinal magnetic susceptibility and an exponential decay of translational long-range order in the direction perpendicular to the defects. The flux creep perpendicular to the defects leads to a nonlinear resistivity ρ(J→0)˜exp[-(JD/J)3/2] . Strong planar defects enforce arrays of dislocations that are located at the defects with a Burgers vector parallel to the defects in order to relax shear strain.

  14. Electron-optical systems for planar gyrotrons

    SciTech Connect

    Manuilov, V. N.; Zaslavsky, V. Yu.; Ginzburg, N. S.; Glyavin, M. Yu.; Kuftin, A. N.; Zotova, I. V.

    2014-02-15

    The methodology of designing an electron-optical system (EOS) that forms sheet helical electron beams (HEBs) for high-power gyrotrons is developed. As an example, we consider the EOS for a 140-GHz gyrotron operated at the first harmonic of the cyclotron frequency with an accelerating voltage of 50 kV, a beam current of 30 A, and a magnetic field compression of 36. A planar geometry of the magnetron-injection gun (MIG) is suggested. The adiabatic theory of MIGs modified for the planar geometry of EOS is used for preliminary estimations of MIG parameters. Numerical simulation of the HEB properties based on the CST STUDIO SUITE 3D code is performed to find the optimal configuration of a planar MIG. The accuracy of the calculated data is discussed. The main factors that affect the HEB quality are considered. It is shown that a sheet HEB with a pitch-factor of 1.3 and velocity spread not exceeding 25%–30% can be formed; this is quite acceptable for high-efficiency operation of modern gyrotrons. Calculation of the beam-wave interaction with the obtained HEB parameters proved that a high output power with a sufficiently good efficiency of about 20% can be reached. Simulations show the feasibility of the experimental implementation of a novel planar EOS and its use in short-wave planar gyrotrons. The developed technique can be used for the study and optimization of planar gyrotrons of different frequency bands and power levels.

  15. Recirculating planar magnetrons: simulations and experiment

    SciTech Connect

    Franzi, Matthew; Gilgenbach, Ronald; French, David; Lau, Y.Y.; Simon, David; Hoff, Brad; Luginsland, John W.

    2011-07-01

    The Recirculating Planar Magnetron (RPM) is a novel crossed-field device whose geometry is expected to reduce thermal load, enhance current yield as well as ease the geometric limitations in scaling to high RF frequencies as compared to the conventional cylindrical magnetrons. The RPM has two different adaptations: A. Axial B field and radial E field; B. Radial B field and axial E field. The preliminary configuration (A) to be used in experiments at the University of Michigan consists of two parallel planar sections which join on either end by cylindrical regions to form a concentric extruded ellipse. Similar to conventional magnetrons, a voltage across the AK gap in conjunction with an axial magnetic field provides the electrons with an ExB drift. The device is named RPM because the drifting electrons recirculate from one planar region to the other. The drifting electrons interact with the resonantly tuned slow wave structure on the anode causing spoke formation. These electron spokes drive a RF electric field in the cavities from which RF power may be extracted to Waveguides. The RPM may be designed in either a conventional configuration with the anode on the outside, for simplified extraction, or as an inverted magnetron with the anode at the inner conductor, for fast start-up. Currently, experiments at the Pulsed Power and Microwave Laboratory at the University of Michigan are in the setup and design phase. A conventional RPM with planar cavities is to be installed on the Michigan Electron Long Beam Accelerator (MELBA) and is anticipated to operate at -200kV, 0.2T with a beam current of 1-10 kA at 1GHz. The conventional RPM consists of 12 identical planar cavities, 6 on each planar side, with simulated quality factor of 20.

  16. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  17. Strong atomic ordering in Gd-doped GaN

    SciTech Connect

    Ishimaru, Manabu; Higashi, Kotaro; Hasegawa, Shigehiko; Asahi, Hajime; Sato, Kazuhisa; Konno, Toyohiko J.

    2012-09-03

    Gd-doped GaN (Ga{sub 1-x}Gd{sub x}N) thin films were grown on a GaN(001) template by radio frequency plasma-assisted molecular beam epitaxy and characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM). Three samples with a different Gd composition were prepared in this study: x = 0.02, 0.05, and 0.08. XRD and TEM results revealed that the low Gd concentration GaN possesses the wurtzite structure. On the other hand, it was found that an ordered phase with a quadruple-periodicity along the [001] direction in the wurtzite structure is formed throughout the film with x = 0.08. We proposed the atomistic model for the superlattice structure observed here.

  18. A pseudo-icosahedral cage {Gd12} based on aminomethylphosphonate.

    PubMed

    Zhang, Ze-Min; Zangana, Karzan H; Kostopoulos, Andreas K; Tong, Ming-Liang; Winpenny, Richard E P

    2016-05-31

    Reaction of (aminomethyl)phosphonic acid (ampH2) with a mixture of gadolinium and cobalt pivalates under solvothermal conditions, led to a pseudo-icosahedral cage {Gd12}, which shows a large magnetocaloric effect (MCE). PMID:27188600

  19. Gd3+ complex-modified NaLuF4-based upconversion nanophosphors for trimodality imaging of NIR-to-NIR upconversion luminescence, X-Ray computed tomography and magnetic resonance.

    PubMed

    Xia, Ao; Chen, Min; Gao, Yuan; Wu, Dongmei; Feng, Wei; Li, Fuyou

    2012-07-01

    Multimodality molecular imaging has recently attracted much attention, because it can take advantage of individual imaging modalities by fusing together information from several molecular imaging techniques. Herein, we report a multifunctional lanthanide-based nanoparticle for near-infrared to near-infrared (NIR-to-NIR) upconversion luminescence (UCL), X-ray computed tomography (CT) and T(1)-enhanced magnetic resonance (MR) trimodality in-vivo imaging. By careful selection of the lanthanide elements, core-shell structured lanthanide-based nanoparticles, NaLuF(4):Yb(3+),Tm(3+)@SiO(2)-GdDTPA nanoparticles (UCNP@SiO(2)-GdDTPA) have been designed and synthesized. We also prove that the application of UCNP@SiO(2)-GdDTPA for NIR-to-NIR UCL, CT and MRI multi-modality in-vivo imaging can be established successfully. In addition, the biological toxicity of UCNP@SiO(2)-GdDTPA is evaluated by the methyl thiazolyl tetrazolium (MTT) assay and histological analysis of viscera sections. PMID:22560666

  20. Large-scale planar lightwave circuits

    NASA Astrophysics Data System (ADS)

    Bidnyk, Serge; Zhang, Hua; Pearson, Matt; Balakrishnan, Ashok

    2011-01-01

    By leveraging advanced wafer processing and flip-chip bonding techniques, we have succeeded in hybrid integrating a myriad of active optical components, including photodetectors and laser diodes, with our planar lightwave circuit (PLC) platform. We have combined hybrid integration of active components with monolithic integration of other critical functions, such as diffraction gratings, on-chip mirrors, mode-converters, and thermo-optic elements. Further process development has led to the integration of polarization controlling functionality. Most recently, all these technological advancements have been combined to create large-scale planar lightwave circuits that comprise hundreds of optical elements integrated on chips less than a square inch in size.

  1. Laser direct write of planar alkaline microbatteries

    NASA Astrophysics Data System (ADS)

    Arnold, C. B.; Kim, H.; Piqué, A.

    We are developing a laser engineering approach to fabricate and optimize alkaline microbatteries in planar geometries. The laser direct-write technique enables multicapability for adding, removing and processing material and provides the ability to pattern complicated structures needed for fabricating complete microbattery assemblies. In this paper, we demonstrate the production of planar zinc-silver oxide alkaline cells under ambient conditions. The microbattery cells exhibit 1.55-V open-circuit potentials, as expected for the battery chemistry, and show a flat discharge behavior under constant-current loads. High capacities of over 450 μAhcm-2 are obtained for 5-mm2 microbatteries.

  2. Planar Inlet Design and Analysis Process (PINDAP)

    NASA Technical Reports Server (NTRS)

    Slater, John W.; Gruber, Christopher R.

    2005-01-01

    The Planar Inlet Design and Analysis Process (PINDAP) is a collection of software tools that allow the efficient aerodynamic design and analysis of planar (two-dimensional and axisymmetric) inlets. The aerodynamic analysis is performed using the Wind-US computational fluid dynamics (CFD) program. A major element in PINDAP is a Fortran 90 code named PINDAP that can establish the parametric design of the inlet and efficiently model the geometry and generate the grid for CFD analysis with design changes to those parameters. The use of PINDAP is demonstrated for subsonic, supersonic, and hypersonic inlets.

  3. The magnetic entropy changes in Gd 1- xB x alloys

    NASA Astrophysics Data System (ADS)

    Dunhui, Wang; Songling, Huang; Zhida, Han; Zhenghua, Su; Yi, Wang; Youwei, Du

    2004-07-01

    A series of Gd (1- x) B x alloys have been prepared by arc melting method. After introducing small quantity of B atom in Gd, the Curie temperature of these alloys increase while the magnetic entropy changes are almost same as that of Gd. The refrigerant capacities of these alloys are also greater than that of Gd. These results suggest that Gd (1- x) B x alloys may be utilized as refrigerant in household magnetic refrigeration.

  4. Mechanical properties of Gd123 superconducting bulks at 77 K

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Murakami, A.

    2012-05-01

    Mechanical properties of melt-grown GdBa2Cu3Ox (Gd123) large single-domain superconducting bulks with 10 wt% of Ag2O and 0.5 wt% of Pt have been evaluated at 77 K through flexural tests, on specimens cut from the samples, in order to estimate the mechanical properties of the Gd123 material without metal substrates, buffer layers or stabilization layers. The densified bulk was 46 mm in diameter and 25 mm in thickness, with low void density, and the standard bulk was around the same size, with voids. The results show that the mechanical properties of the densified Gd123 bulk with low void density are better than those of the standard Gd123 bulk with voids. We also compared the mechanical properties of as-grown bulks with those of annealed bulks. The relations between the microstructure and the flexural strength or the fracture toughness of the densified Gd123 bulk have been shown.

  5. Evaluation of the aromaticity of non-planar and bowl-shaped molecules by NICS criterion.

    PubMed

    Reisi-Vanani, Adel; Rezaei, Ali Asghar

    2015-09-01

    Nucleus independent chemical shift (NICS) criterion was used to gauge the amount of aromaticity in a lot of publications in two last decades. Non-planar molecules with many polygons in different sheets that make angle together have not been studied by this criterion. Perhaps, one ascribes this deficiency to NICS index, but we think it is concern to depauperation in evaluation methods. Therefore, in this work, we try to evaluate aromaticity of two fullerene substructures bowl-shaped molecules, namely corannulene and sumanene as typical non-planar molecules by using of the NICSzz-scan method. The gauge-independent atomic orbital (GIAO) NMR calculations were done at B3LYP/6-311+G(d) level of theory. Energetic criterion as another tool for evaluation of the aromaticity of compounds was used and discussed. Results shows that pentagon and hexagon rings in corannulene have antiaromatic and aromatic character, respectively and in sumanene, pentagon and outer hexagon rings have antiaromatic and aromatic character, respectively. However, the picture obtained based on the NICS computations did not provide any insight towards the real nature of current density in the corannulene and sumanene. PMID:26188797

  6. Continuum {gamma} rays feeding normal and superdeformed states in Gd nuclei

    SciTech Connect

    Zhu, L.H.; Cinausero, M.; de Angelis, G.; De Poli, M.; Gadea, A.; Napoli, D.R.; Bazzacco, D.; Lunardi, S.; Viesti, G.; Petrache, C.M.; Rossi Alvarez, C.

    1997-03-01

    The feeding mechanism of the superdeformed bands in {sup 147}Gd and {sup 148}Gd has been studied via the {sup 124}Sn + {sup 29}Si reaction at a beam energy of 157 MeV. Using the BGO inner ball of the GASP array, high-energy {gamma} rays have been detected in coincidence with discrete transitions deexciting normal-deformed (ND) and superdeformed (SD) states in the final product nuclei. The slope of the measured high-energy {gamma}-ray spectra depends strongly on the number of emitted neutrons and is somewhat lower for spectra in coincidence with SD bands than for those in coincidence with ND structures. Both observations are qualitatively reproduced by statistical model Monte Carlo calculations, which point out the importance of angular momentum effects in the emission of energetic {gamma} rays. The present data exclude the enhanced population of SD bands when fed through high-energy E1 transitions. {copyright} {ital 1997} {ital The American Physical Society}

  7. Obtaining strong ferromagnetism in diluted Gd-doped ZnO thin films through controlled Gd-defect complexes

    SciTech Connect

    Roqan, I. S. Venkatesh, S.; Zhang, Z.; Hussain, S.; Bantounas, I.; Flemban, T. H.; Schwingenschlogl, U.; Franklin, J. B.; Zou, B.; Petrov, P. K.; Ryan, M. P.; Alford, N. M.; Lee, J.-S.

    2015-02-21

    We demonstrate the fabrication of reproducible long-range ferromagnetism (FM) in highly crystalline Gd{sub x}Zn{sub 1−x}O thin films by controlling the defects. Films are grown on lattice-matched substrates by pulsed laser deposition at low oxygen pressures (≤25 mTorr) and low Gd concentrations (x ≤ 0.009). These films feature strong FM (10 μ{sub B} per Gd atom) at room temperature. While films deposited at higher oxygen pressure do not exhibit FM, FM is recovered by post-annealing these films under vacuum. These findings reveal the contribution of oxygen deficiency defects to the long-range FM. We demonstrate the possible FM mechanisms, which are confirmed by density functional theory study, and show that Gd dopants are essential for establishing FM that is induced by intrinsic defects in these films.

  8. Polymer films as planarization and sacrificial layers for uncooled infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Liu, Weiguo; Cai, Changlong; Zhou, Shun

    2010-10-01

    This paper presents a planarization procedure using polymer films to achieve a flat CMOS surface of Readout Integrated Circuit (ROIC) for the integration between uncooled infrared focal plane arrays and ROIC. At the same time, the polymer film is also used as the sacrificial layers. After amorphous Silicon (a-Si) film was deposited using plasma enhanced chemical vapor deposition (PECVD), and patterned using inductively coupled plasma (ICP), the polymer sacrificial layer should be removed to form a-Si self-supporting micro-bridge structure. So the thickness of polymer film determine the height of the micro-bridge; the soft curing temperature determines if the contact hole can be etched by developer during the first photolithography; and the rate of dry etching determines whether the sacrificial layers of the structure can be released successfully. In this paper, the curing temperature, surface roughness, etching process of polymer films are systematically researched. On this basis, polymer film as planarization successfully reduces the 2μm height of the bumps on ROIC to less than 83 nm, over the planarized polymer mesas, bolometer arrays are fabricated. Then the polymer film as sacrificial are removed by ICP and 160x120 self-supporting micro-bridge structure arrays are successfully fabricated.

  9. Polymer films as planarization and sacrificial layers for uncooled infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Liu, Weiguo; Cai, Changlong; Zhou, Shun

    2011-02-01

    This paper presents a planarization procedure using polymer films to achieve a flat CMOS surface of Readout Integrated Circuit (ROIC) for the integration between uncooled infrared focal plane arrays and ROIC. At the same time, the polymer film is also used as the sacrificial layers. After amorphous Silicon (a-Si) film was deposited using plasma enhanced chemical vapor deposition (PECVD), and patterned using inductively coupled plasma (ICP), the polymer sacrificial layer should be removed to form a-Si self-supporting micro-bridge structure. So the thickness of polymer film determine the height of the micro-bridge; the soft curing temperature determines if the contact hole can be etched by developer during the first photolithography; and the rate of dry etching determines whether the sacrificial layers of the structure can be released successfully. In this paper, the curing temperature, surface roughness, etching process of polymer films are systematically researched. On this basis, polymer film as planarization successfully reduces the 2μm height of the bumps on ROIC to less than 83 nm, over the planarized polymer mesas, bolometer arrays are fabricated. Then the polymer film as sacrificial are removed by ICP and 160x120 self-supporting micro-bridge structure arrays are successfully fabricated.

  10. Experimental investigation of planar ion traps

    SciTech Connect

    Pearson, C. E.; Leibrandt, D. R.; Bakr, W. S.; Mallard, W. J.; Brown, K. R.; Chuang, I. L.

    2006-03-15

    Chiaverini et al. [Quantum Inf. Comput. 5, 419 (2005)] recently suggested a linear Paul trap geometry for ion-trap quantum computation that places all of the electrodes in a plane. Such planar ion traps are compatible with modern semiconductor fabrication techniques and can be scaled to make compact, many-zone traps. In this paper we present an experimental realization of planar ion traps using electrodes on a printed circuit board to trap linear chains of tens of charged particles of 0.44 {mu}m diameter in a vacuum of 15 Pa (10{sup -1} torr). With these traps we address concerns about the low trap depth of planar ion traps and develop control electrode layouts for moving ions between trap zones without facing some of the technical difficulties involved in an atomic ion-trap experiment. Specifically, we use a trap with 36 zones (77 electrodes) arranged in a cross to demonstrate loading from a traditional four-rod linear Paul trap, linear ion movement, splitting and joining of ion chains, and movement of ions through intersections. We further propose an additional dc-biased electrode above the trap which increases the trap depth dramatically, and a planar ion-trap geometry that generates a two-dimensional lattice of point Paul traps.

  11. Duality analysis on random planar lattices.

    PubMed

    Ohzeki, Masayuki; Fujii, Keisuke

    2012-11-01

    The conventional duality analysis is employed to identify a location of a critical point on a uniform lattice without any disorder in its structure. In the present study, we deal with the random planar lattice, which consists of the randomized structure based on the square lattice. We introduce the uniformly random modification by the bond dilution and contraction on a part of the unit square. The random planar lattice includes the triangular and hexagonal lattices in extreme cases of a parameter to control the structure. A modern duality analysis fashion with real-space renormalization is found to be available for estimating the location of the critical points with a wide range of the randomness parameter. As a simple test bed, we demonstrate that our method indeed gives several critical points for the cases of the Ising and Potts models and the bond-percolation thresholds on the random planar lattice. Our method leads to not only such an extension of the duality analyses on the classical statistical mechanics but also a fascinating result associated with optimal error thresholds for a class of quantum error correction code, the surface code on the random planar lattice, which is known as a skillful technique to protect the quantum state. PMID:23214752

  12. A Planar Calculus for Infinite Index Subfactors

    NASA Astrophysics Data System (ADS)

    Penneys, David

    2013-05-01

    We develop an analog of Jones' planar calculus for II 1-factor bimodules with arbitrary left and right von Neumann dimension. We generalize to bimodules Burns' results on rotations and extremality for infinite index subfactors. These results are obtained without Jones' basic construction and the resulting Jones projections.

  13. Duality analysis on random planar lattices

    NASA Astrophysics Data System (ADS)

    Ohzeki, Masayuki; Fujii, Keisuke

    2012-11-01

    The conventional duality analysis is employed to identify a location of a critical point on a uniform lattice without any disorder in its structure. In the present study, we deal with the random planar lattice, which consists of the randomized structure based on the square lattice. We introduce the uniformly random modification by the bond dilution and contraction on a part of the unit square. The random planar lattice includes the triangular and hexagonal lattices in extreme cases of a parameter to control the structure. A modern duality analysis fashion with real-space renormalization is found to be available for estimating the location of the critical points with a wide range of the randomness parameter. As a simple test bed, we demonstrate that our method indeed gives several critical points for the cases of the Ising and Potts models and the bond-percolation thresholds on the random planar lattice. Our method leads to not only such an extension of the duality analyses on the classical statistical mechanics but also a fascinating result associated with optimal error thresholds for a class of quantum error correction code, the surface code on the random planar lattice, which is known as a skillful technique to protect the quantum state.

  14. COMPUTER ANALYSIS OF PLANAR GAMMA CAMERA IMAGES

    EPA Science Inventory



    COMPUTER ANALYSIS OF PLANAR GAMMA CAMERA IMAGES

    T Martonen1 and J Schroeter2

    1Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. EPA, Research Triangle Park, NC 27711 USA and 2Curriculum in Toxicology, Unive...

  15. Piecewise-Planar Parabolic Reflectarray Antenna

    NASA Technical Reports Server (NTRS)

    Hodges, Richard; Zawadzki, Mark

    2009-01-01

    The figure shows a dual-beam, dualpolarization Ku-band antenna, the reflector of which comprises an assembly of small reflectarrays arranged in a piecewise- planar approximation of a parabolic reflector surface. The specific antenna design is intended to satisfy requirements for a wide-swath spaceborne radar altimeter, but the general principle of piecewise-planar reflectarray approximation of a parabolic reflector also offers advantages for other applications in which there are requirements for wideswath antennas that can be stowed compactly and that perform equally in both horizontal and vertical polarizations. The main advantages of using flat (e.g., reflectarray) antenna surfaces instead of paraboloidal or parabolic surfaces is that the flat ones can be fabricated at lower cost and can be stowed and deployed more easily. Heretofore, reflectarray antennas have typically been designed to reside on single planar surfaces and to emulate the focusing properties of, variously, paraboloidal (dish) or parabolic antennas. In the present case, one approximates the nominal parabolic shape by concatenating several flat pieces, while still exploiting the principles of the planar reflectarray for each piece. Prior to the conception of the present design, the use of a single large reflectarray was considered, but then abandoned when it was found that the directional and gain properties of the antenna would be noticeably different for the horizontal and vertical polarizations.

  16. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, A.; Boozer, A.H.

    1984-03-06

    The present invention generates stellarator fields having favorable properties (magnetic well and large rotational transform) by a simple coil system consisting only of unlinked planar non-circular coils. At large rotational transform toroidal effects on magnetic well and rotational transform are small and can be ignored. We do so herein, specializing in straight helical systems.

  17. Strain-induced phase variation and dielectric constant enhancement of epitaxial Gd2O3

    NASA Astrophysics Data System (ADS)

    Shekhter, P.; Schwendt, D.; Amouyal, Y.; Wietler, T. F.; Osten, H. J.; Eizenberg, M.

    2016-07-01

    One of the approaches for realizing advanced high k insulators for metal oxide semiconductor field effect transistors based devices is the use of rare earth oxides. When these oxides are deposited as epitaxial thin films, they demonstrate dielectric properties that differ greatly from those that are known for bulk oxides. Using structural and spectroscopic techniques, as well as first-principles calculations, Gd2O3 films deposited on Si (111) and Ge (111) were characterized. It was seen that the same 4 nm thick film, grown simultaneously on Ge and Si, presents an unstrained lattice on Ge while showing a metastable phase on Si. This change from the cubic lattice to the distorted metastable phase is characterized by an increase in the dielectric constant of more than 30% and a change in band gap. The case in study shows that extreme structural changes can occur in ultra-thin epitaxial rare earth oxide films and modify their dielectric properties when the underlying substrate is altered.

  18. Structures and stabilities of small silicon clusters: Ab initio molecular-orbital calculations of Si7-Si11

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaolei; Zeng, X. C.

    2003-02-01

    Ab initio all-electron molecular-orbital calculations have been carried out to study the structure and relative stability of small silicon clusters (Sin, n=7-11). A number of low-energy geometric isomers are optimized at the second-order Møller-Plesset (MP2) MP2/6-31G(d) level. Harmonic vibrational analysis has been performed to assure that the optimized geometries are stable. The total energies of stable isomers are computed at the coupled-cluster single and double substitutions (including triple excitations) [CCSD(T)] CCSD(T)/6-31G(d) level. The calculated binding energies per atom at both the MP2/6-31G(d) and CCSD(T)/6-31G(d) levels agree with the experiments. For Si7, Si8, and Si10, the lowest-energy structures are the same as those predicted previously from the all-electron optimization at the Hartree-Fock (HF) HF/6-31G(d) level [Raghavachari and Rohlfing, J. Chem. Phys. 89, 2219 (1988)]. For Si9, the lowest-energy isomer is same as that predicted based on density-functional plane-wave pseudopotential method [Vasiliev, Ogut, and Chelikowsky, Phys. Rev. Lett. 78, 4805 (1997)]. Particular attention has been given to Si11 because several low-energy geometric isomers were found nearly isoenergetic. On the basis of MP2/6-311G(2d)//CCSD(T)/6-311G(2d) calculation, we identified that the C2v isomer, a tricapped trigonal prism with two additional caps on side trigonal faces, is most likely the global-minimum structure. However, another competitive geometric isomer for the global minimum is also found on basis of the MP2/6-311G(2d)//CCSD(T)/6-311G(2d) calculation. Additionally, calculations of the binding energy and the cluster polarizability offer more insights into relatively strong stability of two magic-number clusters Si6 and Si10.

  19. Coated Si microwire array solar cells for better light trapping

    NASA Astrophysics Data System (ADS)

    Lee, Eunsongyi; Gwon, Minji; Cho, Yunae; Kim, Dong-Wook

    2013-09-01

    We investigated optical properties of planar Si wafers and Si microwire (MW) arrays with and without ZnO thin films using the finite-difference time-domain (FDTD) method. Reflectance of the MW array (diameter: 4 μm and period: 12 μm) was smaller than that of the planar wafer in the wavelength range from 400 to 1100 nm, which could be originated from antireflection effects due to low optical density and guided-mode-assisted field enhancement. The reflectance of ZnO (thickness: 50 and 80 nm)-coated MW array was drastically reduced compared with the bare array but somewhat larger than that of the coated planar wafer. This could be attributed to less-confined guided modes in the wires, which was supported by the field distribution simulation results. Our results provide some insights into possible roles of transparent conducting layers on MW arrays for photovoltaic applications.

  20. Silica-coated Gd(DOTA)-loaded protein nanoparticles enable magnetic resonance imaging of macrophages

    PubMed Central

    Bruckman, Michael A.; Randolph, Lauren N.; Gulati, Neetu M.; Stewart, Phoebe L.; Steinmetz, Nicole F.

    2015-01-01

    The molecular imaging of in vivo targets allows non-invasive disease diagnosis. Nanoparticles offer a promising platform for molecular imaging because they can deliver large payloads of imaging reagents to the site of disease. Magnetic resonance imaging (MRI) is often preferred for clinical diagnosis because it uses non-ionizing radiation and offers both high spatial resolution and excellent penetration. We have explored the use of plant viruses as the basis of for MRI contrast reagents, specifically Tobacco mosaic virus (TMV), which can assemble to form either stiff rods or spheres. We loaded TMV particles with paramagnetic Gd ions, increasing the ionic relaxivity compared to free Gd ions. The loaded TMV particles were then coated with silica maintaining high relaxivities. Interestingly, we found that when Gd(DOTA) was loaded into the interior channel of TMV and the exterior was coated with silica, the T1 relaxivities increased by three-fold from 10.9 mM−1 s−1 to 29.7 mM−1s−1 at 60 MHz compared to uncoated Gd-loaded TMV. To test the performance of the contrast agents in a biological setting, we focused on interactions with macrophages because the active or passive targeting of immune cells is a popular strategy to investigate the cellular components involved in disease progression associated with inflammation. In vitro assays and phantom MRI experiments indicate efficient targeting and imaging of macrophages, enhanced contrast-to-noise ratio was observed by shape-engineering (SNP > TMV) and silica-coating (Si-TMV/SNP > TMV/SNP). Because plant viruses are in the food chain, antibodies may be prevalent in the population. Therefore we investigated whether the silica-coating could prevent antibody recognition; indeed our data indicate that mineralization can be used as a stealth coating option to reduce clearance. Therefore, we conclude that the silica-coated protein-based contrast agent may provide an interesting candidate material for further investigation

  1. Combinatorial growth of Si nanoribbons

    PubMed Central

    2011-01-01

    Silicon nanoribbons (Si NRs) with a thickness of about 30 nm and a width up to a few micrometers were synthesized. Systematic observations indicate that Si NRs evolve via the following sequences: the growth of basal nanowires assisted with a Pt catalyst by a vapor-liquid-solid (VLS) mechanism, followed by the formation of saw-like edges on the basal nanowires and the planar filling of those edges by a vapor-solid (VS) mechanism. Si NRs have twins along the longitudinal < 110 > growth of the basal nanowires that also extend in < 112 > direction to edge of NRs. These twins appear to drive the lateral growth by a reentrant twin mechanism. These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction. These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth. PMID:21794158

  2. "Finite part" electric and magnetic stored energies for planar antennas

    NASA Technical Reports Server (NTRS)

    Cockrell, C. R.

    1981-01-01

    A pair of formulas representing the time-average "finite part" electric and magnetic stored energies for planar antennas are derived. It is also shown that the asymptotic reciprocal relationship between quality factor and relative bandwidth exists for planar antennas.

  3. Accidental formation of Gd₄(SiO₄)₂OTe: crystal structure and spectroscopic properties.

    PubMed

    Daszkiewicz, Marek; Gulay, Lubomir D

    2015-07-01

    Designing new functional materials with increasingly complex compositions is of current interest in science and technology. Complex rare-earth-based chalcogenides have specific thermal, electrical, magnetic and optical properties. Tetragadolinium bis[tetraoxidosilicate(IV)] oxide telluride, Gd4(SiO4)2OTe, was obtained accidentally while studying the Gd2Te3-Cu2Te system. The crystal structure was determined by means of single-crystal X-ray diffraction. The compound crystallizes in the space group Pnma. Three symmetry-independent gadolinium sites were determined. The excitation and emission spectra were collected at room temperature and at 10 K. Gd4(SiO4)2OTe appears to be a promising optical material when doped with rare-earth ions. PMID:26146399

  4. Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

    SciTech Connect

    Jongik Park

    2004-12-19

    EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} are two members of the RT{sub 2}X{sub 2} (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr{sub 2}Si{sub 2} structure are known for their wide variety of magnetic properties, Extensive studies of the RT{sub 2}X{sub 2} series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi{sub 2}Ge{sub 2} were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds.

  5. A therapeutic trial of human melanomas with combined small interfering RNAs targeting adaptor molecules p130Cas and paxillin activated under expression of ganglioside GD3.

    PubMed

    Makino, Yusuke; Hamamura, Kazunori; Takei, Yoshifumi; Bhuiyan, Robiul Hasan; Ohkawa, Yuki; Ohmi, Yuhsuke; Nakashima, Hideyuki; Furukawa, Keiko; Furukawa, Koichi

    2016-08-01

    We previously demonstrated that focal adhesion kinase (FAK), p130Cas and paxillin are crucially involved in the enhanced malignant properties under expression of ganglioside GD3 in melanoma cells. Therefore, molecules existing in the GD3-mediated signaling pathway could be considered as suitable targets for therapeutic intervention in malignant melanoma. The aim of this study was to determine whether blockade of p130Cas and/or paxillin by RNAi suppresses melanoma growth. We found a suitable dose (40 μM siRNA, 25 μl/tumor) of the siRNA to suppress p130Cas in the xenografts generated in nu/nu mice. Based on these results, we performed intratumoral (i.t.) treatment with anti-p130Cas and/or anti-paxillin siRNAs mixed with atelocollagen as a drug delivery system in a xenograft tumor of a human melanoma cell line, SK-MEL-28. Mixture of atelocollagen (1.75%) and an siRNA (500 or 1000 pmol/tumor) was injected into the tumors every 3 days after the first injection. An siRNA against human p130Cas markedly suppressed tumor growth of the xenograft in a dose-dependent manner, whereas siRNA against human paxillin slightly inhibited the tumor growth. A control siRNA against firefly luciferase showed no effect. To our surprise, siRNA against human p130Cas (500 or 1000 pmol/tumor) combined with siRNA against human paxillin dramatically suppressed tumor growth. In agreement with the tumor suppression effects of the anti-p130Cas siRNA, reduction in Ki-67 positive cell number as well as in p130Cas expression was demonstrated by immunohistostaining. These results suggested that blockade of GD3-mediated growth signaling pathways by siRNAs might be a novel and promising therapeutic strategy against malignant melanomas, provided signaling molecules such as p130Cas and paxillin are significantly expressed in individual cases. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc. PMID:27068854

  6. Overcoming artificial broadening in Gd(3+)-Gd(3+) distance distributions arising from dipolar pseudo-secular terms in DEER experiments.

    PubMed

    Cohen, Marie Ramirez; Frydman, Veronica; Milko, Petr; Iron, Mark A; Abdelkader, Elwy H; Lee, Michael D; Swarbrick, James D; Raitsimring, Arnold; Otting, Gottfried; Graham, Bim; Feintuch, Akiva; Goldfarb, Daniella

    2016-05-14

    By providing accurate distance measurements between spin labels site-specifically attached to bio-macromolecules, double electron-electron resonance (DEER) spectroscopy provides a unique tool to probe the structural and conformational changes in these molecules. Gd(3+)-tags present an important family of spin-labels for such purposes, as they feature high chemical stability and high sensitivity in high-field DEER measurements. The high sensitivity of the Gd(3+) ion is associated with its high spin (S = 7/2) and small zero field splitting (ZFS), resulting in a narrow spectral width of its central transition at high fields. However, under the conditions of short distances and exceptionally small ZFS, the weak coupling approximation, which is essential for straightforward DEER data analysis, becomes invalid and the pseudo-secular terms of the dipolar Hamiltonian can no longer be ignored. This work further explores the effects of pseudo-secular terms on Gd(3+)-Gd(3+) DEER measurements using a specifically designed ruler molecule; a rigid bis-Gd(3+)-DOTA model compound with an expected Gd(3+)-Gd(3+) distance of 2.35 nm and a very narrow central transition at the W-band (95 GHz). We show that the DEER dipolar modulations are damped under the standard W-band DEER measurement conditions with a frequency separation, Δν, of 100 MHz between the pump and observe pulses. Consequently, the DEER spectrum deviates considerably from the expected Pake pattern. We show that the Pake pattern and the associated dipolar modulations can be restored with the aid of a dual mode cavity by increasing Δν from 100 MHz to 1.09 GHz, allowing for a straightforward measurement of a Gd(3+)-Gd(3+) distance of 2.35 nm. The increase in Δν increases the contribution of the |-5/2〉→|-3/2〉 and |-7/2〉→|-5/2〉 transitions to the signal at the expense of the |-3/2 〉→|-1/2〉 transition, thus minimizing the effect of dipolar pseudo-secular terms and restoring the validity of the weak

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

    SciTech Connect

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

    2012-02-15

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

  8. Gd-HOPO Based High Relaxivity MRI Contrast Agents

    SciTech Connect

    Datta, Ankona; Raymond, Kenneth

    2008-11-06

    Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd{sup 3+}, especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd{sup 3+} in which all he donor atoms are oxygen. Because Gd{sup 3+} favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water olecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd{sup 3+} binding. The Gd- HOPO-based contrast agents surpass current commercially available agents ecause of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast gents, which are based on polyaminocarboxylate ligands.

  9. A thermo-sensitive polymeric gel containing a gadolinium (Gd) compound encapsulated into liposomes significantly extended the retention of the Gd in tumors.

    PubMed

    Le, Uyen Minh; Shaker, Dalia S; Sloat, Brian R; Cui, Zhengrong

    2008-04-01

    Gadolinium neutron capture therapy (Gd-NCT) is a promising approach to fight cancer. One key factor for the success of Gd-NCT is to deliver and maintain a sufficient amount of Gd inside tumors. A large amount of Gd can be readily introduced into tumors by direct intratumor injection. However, an innovative approach is needed to maintain the Gd in the tumors. We encapsulated a Gd compound into a liposome formulation and then dispersed the liposomes into a thermo-sensitive polymeric gel. In murine tumor models, we showed that this liposome-in-thermo-sensitive gel system significantly extended the retention of the Gd compound in tumors. This similar concept may be applied to prolong the retention of other cytotoxic chemicals in tumors, and thus, improve their anti-tumor efficacy. PMID:18401783

  10. Study on luminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors prepared by co-precipitation.

    PubMed

    Meng, Qingyu; Hua, Ruinian; Chen, Baojiu; Tian, Yue; Lu, Shuchen; Sun, Linan

    2011-01-01

    Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors with different concentrations have been prepared by co-precipitation. XRD (X-ray diffraction) and SEM (scanning electron microscopy) were used to investigate the structure and morphology. The emission spectra, excitation spectra and fluorescence decay curves were measured, and partial J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated. Furthermore, concentration quenching curves of Eu3+ in different hosts were drawn. The photoluminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors have been studied. The results indicate that Eu3+ 5D0-7F2 red luminescence can be effectively excited by 395 nm and 465 nm in Gd2WO6 and Gd2W2O9 hosts, similar to the familiar Gd2(WO4)3:Eu. Especially Gd2W2O9:Eu has strong red emission and high quenching concentration, so it has potential applications for trichromatic white LED as red fluorescent materials. PMID:21446424

  11. Regular shock refraction in planar ideal MHD

    NASA Astrophysics Data System (ADS)

    Delmont, P.; Keppens, R.

    2010-03-01

    We study the classical problem of planar shock refraction at an oblique density discontinuity, separating two gases at rest, in planar ideal (magneto)hydrodynamics. In the hydrodynamical case, 3 signals arise and the interface becomes Richtmyer-Meshkov unstable due to vorticity deposition on the shocked contact. In the magnetohydrodynamical case, on the other hand, when the normal component of the magnetic field does not vanish, 5 signals will arise. The interface then typically remains stable, since the Rankine-Hugoniot jump conditions in ideal MHD do not allow for vorticity deposition on a contact discontinuity. We present an exact Riemann solver based solution strategy to describe the initial self similar refraction phase. Using grid-adaptive MHD simulations, we show that after reflection from the top wall, the interface remains stable.

  12. Constant field gradient planar cavity structure

    SciTech Connect

    Kang, Yoon W.; Kustom, R.L.

    1997-12-01

    A cavity structure is described having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam.

  13. Constant field gradient planar coupled cavity structure

    DOEpatents

    Kang, Yoon W.; Kustom, Robert L.

    1999-01-01

    A cavity structure having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam.

  14. Constant field gradient planar coupled cavity structure

    DOEpatents

    Kang, Y.W.; Kustom, R.L.

    1999-07-27

    A cavity structure is disclosed having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam. 16 figs.

  15. Stable planar mesoscopic photonic crystal cavities.

    PubMed

    Magno, G; Monmayrant, A; Grande, M; Lozes-Dupuy, F; Gauthier-Lafaye, O; Calò, G; Petruzzelli, V

    2014-07-15

    Mesoscopic self-collimation (MSC) in mesoscopic photonic crystals with high reflectivity is exploited to realize a novel high Q-factor cavity by means of mesoscopic PhC planar mirrors. These mirrors efficiently confine a mode inside a planar Fabry-Perot-like cavity, that results from a beam focusing effect that stabilizes the cavity even for small beam sizes, resembling the focusing behavior of curved mirrors. Moreover, they show an improved reflectivity with respect to their standard distributed Bragg reflector counterparts that allows higher compactness. A Q-factor higher than 10⁴ has been achieved for an optimized 5-period-long mirror cavity. The optimization of the Q-factor and the performances in terms of energy storage, field enhancement, and confinement are detailed. PMID:25121692

  16. Gd12Co5.3Bi and Gd12Co5Bi, Crystalline Doppelgänger with Low Thermal Conductivities.

    PubMed

    Oliynyk, Anton O; Sparks, Taylor D; Gaultois, Michael W; Ghadbeigi, Leila; Mar, Arthur

    2016-07-01

    Attempts to prepare Gd12Co5Bi, a member of the rare-earth (RE) intermetallics RE12Co5Bi, which were identified by a machine-learning recommendation engine as potential candidates for thermoelectric materials, led instead to formation of the new compound Gd12Co5.3Bi with a very similar composition. Phase equilibria near the Gd-rich corner of the Gd-Co-Bi phase diagram were elucidated by both lab-based and variable-temperature synchrotron powder X-ray diffraction, suggesting that Gd12Co5.3Bi and Gd12Co5Bi are distinct phases. The higher symmetry structure of Gd12Co5.3Bi (cubic, space group Im3̅, Z = 2, a = 9.713(6) Å), as determined from single-crystal X-ray diffraction, is closely related to that of Gd12Co5Bi (tetragonal, space group Immm). Single Co atoms and Co-Co dumbbells are disordered with occupancies of 0.78(2) and 0.22(2), respectively, in Gd12Co5.3Bi, but they are ordered in Gd12Co5Bi. Consistent with this disorder, the electrical resistivity shows less dependence on temperature for Gd12Co5.3Bi than for Gd12Co5Bi. The thermal conductivity is low and reaches 2.8 W m(-1) K(-1) at 600 °C for both compounds; however, the temperature dependence of the thermal conductivity differs, decreasing for Gd12Co5.3Bi and increasing for Gd12Co5Bi as the temperature increases. The unusual trends in thermal properties persist in the heat capacity, which decreases below 2R, and in the thermal diffusivity, which increases at higher temperatures. PMID:27299657

  17. Displacement of the C Terminus of Herpes Simplex Virus gD Is Sufficient To Expose the Fusion-Activating Interfaces on gD

    PubMed Central

    Gallagher, John R.; Saw, Wan Ting; Atanasiu, Doina; Lou, Huan; Eisenberg, Roselyn J.

    2013-01-01

    Viral entry by herpes simplex virus (HSV) is executed and tightly regulated by four glycoproteins. While several viral glycoproteins can mediate viral adhesion to host cells, only binding of gD to cellular receptor can activate core fusion proteins gB and gH/gL to execute membrane fusion and viral entry. Atomic structures of gD bound to receptor indicate that the C terminus of the gD ectodomain must be displaced before receptor can bind to gD, but it is unclear which conformational changes in gD activate membrane fusion. We rationally designed mutations in gD to displace the C terminus and observe if fusion could be activated without receptor binding. Using a cell-based fusion assay, we found that gD V231W induced cell-cell fusion in the absence of receptor. Using recombinant gD V231W protein, we observed binding to conformationally sensitive antibodies or HSV receptor and concluded that there were changes proximal to the receptor binding interface, while the tertiary structure of gD V231W was similar to that of wild-type gD. We used a biosensor to analyze the kinetics of receptor binding and the extent to which the C terminus blocks binding to receptor. We found that the C terminus of gD V231W was enriched in the open or displaced conformation, indicating a mechanism for its function. We conclude that gD V231W triggers fusion through displacement of its C terminus and that this motion is indicative of how gD links receptor binding to exposure of interfaces on gD that activate fusion via gH/gL and gB. PMID:24049165

  18. Photophysical Property and Photocatalytic Activity of New Gd2InSbO7 and Gd2FeSbO7 Compounds under Visible Light Irradiation

    PubMed Central

    Luan, Jingfei; Xu, Yong

    2013-01-01

    Gd2InSbO7 and Gd2FeSbO7 were synthesized first, and their structural and photocatalytic properties were studied. The lattice parameters and the band gaps for Gd2InSbO7 and Gd2FeSbO7 were 10.449546 Å, 10.276026 Å, 2.897 eV and 2.151 eV. The photocatalytic degradation of rhodamine B was performed with Gd2InSbO7 and Gd2FeSbO7 under visible light irradiation. Gd2InSbO7 and Gd2FeSbO7 had higher catalytic activity compared with Bi2InTaO7. Gd2FeSbO7 exhibited higher catalytic activity than Gd2InSbO7. The photocatalytic degradation of rhodamine B followed with the first-order reaction kinetics, and the first-order rate constant k was 0.01606, 0.02220 or 0.00329 min−1 with Gd2InSbO7, Gd2FeSbO7 or Bi2InTaO7 as photocatalyst. Complete removal of rhodamine B was observed after visible light irradiation for 225 min or 260 min with Gd2FeSbO7 or Gd2InSbO7 as photocatalyst. The evolution of CO2 was realized, and it indicated continuous mineralization of rhodamine B during the photocatalytic process. The possible photocatalytic degradation pathway of rhodamine B was proposed. PMID:23296275

  19. Planar graphical models which are easy

    SciTech Connect

    Chertkov, Michael; Chernyak, Vladimir

    2009-01-01

    We describe a rich family of binary variables statistical mechanics models on planar graphs which are equivalent to Gaussian Grassmann Graphical models (free fermions). Calculation of partition function (weighted counting) in the models is easy (of polynomial complexity) as reduced to evaluation of determinants of matrixes linear in the number of variables. In particular, this family of models covers Holographic Algorithms of Valiant and extends on the Gauge Transformations discussed in our previous works.

  20. Planar Poincare Charts For Polarization Calculations

    NASA Technical Reports Server (NTRS)

    Tedjojuwono, Ken K.; Hunter, William W.; Ocheltree, Stewart L.

    1993-01-01

    New type of stereographic projection of Poincare sphere makes flat charts for use in graphical analyses of polarization-transformation characteristics of optical components or systems. Charts used to predict polarization state at output of birefringent material for any arbitrary input polarization state. Analyses of some polarization-dependent optical components or systems reduced to simple graphical procedures. Planar charts more practical to use and store.

  1. Experiments in Planar Multipole Ion Traps

    NASA Astrophysics Data System (ADS)

    Clark, Rob; Burke, Timothy; Green, Dylan

    2016-05-01

    We present the design and demonstration of multipole ion traps based on concentric rings. We have developed both surface-electrode and layered planar trap designs which enable one to null the quadratic term in the electric potential to a high degree. Experiments demonstrating frequency upconversion of an applied signal demonstrate the nonlinear dynamics present in the trap. Applications include quantum chaos, ultracold chemistry, and, potentially, mass spectrometry. We acknowledge support from the Research Corporation for Science Advancement and from The Citadel Foundation.

  2. Circular dichroism of planar chiral magnetic metamaterials.

    PubMed

    Decker, M; Klein, M W; Wegener, M; Linden, S

    2007-04-01

    We propose, fabricate, and study a double-layer chiral planar metamaterial that exhibits pronounced circular dichroism at near-infrared wavelengths. The antisymmetric oscillation modes of the two coupled layers allow local magnetic-dipole moments and enhanced polarization effects compared with similar single-layer systems where only electric-dipole moments occur. Experiment and rigorous theoretical calculations are in good agreement. PMID:17339960

  3. Microstructures of Si surface layers implanted with Cu

    SciTech Connect

    Follstaedt, D.M.; Myers, S.M.

    1993-12-31

    Microstructures of Si ion-implanted with Cu have been characterized by TEM after annealing. For 1.2 at.%, the Cu is trapped at planar defects, but for 10 at.%, {eta}-Cu{sub 3}Si forms and Cu diffuses at its equilibrium solubility. These observations allow proper evaluation of the binding energies of Cu to previously formed internal cavities (2.2 eV) and {eta}-Cu{sub 3}Si (1.7 eV). The 10 at.% Cu layer promotes oxidation of Si catalyzed by {eta}-Cu{sub 3}Si. The microstructures also indicate that Si implanted with {approximately}2 at.% Cu reforms epitaxially with embedded defects after 8 hr at 700C, but for {approximately}10 at.% Cu, epitaxy is not recovered after 6 hours at 600C.

  4. Energy-transfer from Gd(III) to Tb(III) in (Gd,Yb,Tb)PO4 nanocrystals.

    PubMed

    Debasu, Mengistie L; Ananias, Duarte; Rocha, João; Malta, Oscar L; Carlos, Luís D

    2013-10-01

    The photoluminescence properties of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal route at 150 °C are reported. Energy-transfer from Gd(3+) to Tb(3+) is witnessed by the detailed analyses of excited-state lifetimes, emission quantum yields, and emission and excitation spectra at room temperature, for Tb(3+) concentrations ranging from 0.5 to 5.0 mol%. Absolute-emission quantum yields up to 42% are obtained by exciting within the (6)I7/2-17/2 (Gd(3+)) manifold at 272 nm. The room temperature emission spectrum is dominated by the (5)D4 → (7)F5 (Tb(3+)) transition at 543 nm, with a long decay-time (3.95-6.25 ms) and exhibiting a rise-time component. The (5)D3 → (7)F6 (Tb(3+)) rise-time (0.078 ms) and the (6)P7/2 → (8)S7/2 (Gd(3+)) decay-time (0.103 ms) are of the same order, supporting the Gd(3+) to Tb(3+) energy-transfer process. A remarkably longer lifetime of 2.29 ms was measured at 11 K for the (6)P7/2 → (8)S7/2 (Gd(3+)) emission upon excitation at 272 nm, while the emission spectrum at 11 K is dominated by the (6)P7/2 → (8)S7/2 transition line, showing that the Gd(3+) to Tb(3+) energy-transfer process is mainly phonon-assisted with an efficiency of ~95% at room temperature. The Gd(3+) to Tb(3+) energy transfer is governed by the exchange mechanism with rates between 10(2) and 10(3) s(-1), depending on the energy mismatch conditions between the (6)I7/2 and (6)P7/2 levels of Gd(3+) and the Tb(3+ 5)I7, (5)F2,3 and (5)H5,6,7 manifolds and the radial overlap integral values. PMID:23942992

  5. Si Wire-Array Solar Cells

    NASA Astrophysics Data System (ADS)

    Boettcher, Shannon

    2010-03-01

    Micron-scale Si wire arrays are three-dimensional photovoltaic absorbers that enable orthogonalization of light absorption and carrier collection and hence allow for the utilization of relatively impure Si in efficient solar cell designs. The wire arrays are grown by a vapor-liquid-solid-catalyzed process on a crystalline (111) Si wafer lithographically patterned with an array of metal catalyst particles. Following growth, such arrays can be embedded in polymethyldisiloxane (PDMS) and then peeled from the template growth substrate. The result is an unusual photovoltaic material: a flexible, bendable, wafer-thickness crystalline Si absorber. In this paper I will describe: 1. the growth of high-quality Si wires with controllable doping and the evaluation of their photovoltaic energy-conversion performance using a test electrolyte that forms a rectifying conformal semiconductor-liquid contact 2. the observation of enhanced absorption in wire arrays exceeding the conventional light trapping limits for planar Si cells of equivalent material thickness and 3. single-wire and large-area solid-state Si wire-array solar cell results obtained to date with directions for future cell designs based on optical and device physics. In collaboration with Michael Kelzenberg, Morgan Putnam, Joshua Spurgeon, Daniel Turner-Evans, Emily Warren, Nathan Lewis, and Harry Atwater, California Institute of Technology.

  6. Recirculating Planar Magnetron Modeling and Experiments

    NASA Astrophysics Data System (ADS)

    Franzi, Matthew; Gilgenbach, Ronald; Hoff, Brad; French, Dave; Lau, Y. Y.

    2011-10-01

    We present simulations and initial experimental results of a new class of crossed field device: Recirculating Planar Magnetrons (RPM). Two geometries of RPM are being explored: 1) Dual planar-magnetrons connected by a recirculating section with axial magnetic field and transverse electric field, and 2) Planar cathode and anode-cavity rings with radial magnetic field and axial electric field. These RPMs have numerous advantages for high power microwave generation by virtue of larger area cathodes and anodes. The axial B-field RPM can be configured in either the conventional or inverted (faster startup) configuration. Two and three-dimensional EM PIC simulations show rapid electron spoke formation and microwave oscillation in pi-mode. Smoothbore prototype axial-B RPM experiments are underway using the MELBA accelerator at parameters of -300 kV, 1-20 kA and pulselengths of 0.5-1 microsecond. Implementation and operation of the first RPM slow wave structure, operating at 1GHz, will be discussed. Research supported by AFOSR, AFRL, L-3 Communications, and Northrop Grumman. Done...processed 1830 records...17:52:57 Beginning APS data extraction...17:52:57

  7. Planar geometry inertial electrostatic confinement fusion device

    NASA Astrophysics Data System (ADS)

    Knapp, Daniel R.

    2015-03-01

    In the classic gridded inertial electrostatic confinement (IEC) fusion reactor, ion bombardment of the grid leads to heating, thermionic electron emission, significant power loss, and ultimately melting of the grid. Gridless IEC devices have sought to overcome these limitations. Klein reported a gridless device in which ions are circulated as a linear beam in an electrostatic analogue of an optical resonator. To overcome limits of stored ions due to space charge effects at the turning regions, the device employed multiple overlapping traps. The work reported here seeks to further increase the turning region space in a gridless trap by employing a planar geometry. Ion trapping in the planar device was examined by simulating trajectories of 2H+ ions with SIMION 8.1 software. Simulations were carried out using multiple potentials as in Klein's device and for a single potential trap as a planar analogue of the anharmonic ion trap. Scattering by background gas was simulated using a hard sphere collision model, and the results suggested the device will require operation at low pressure with a separate ion source.

  8. Fast planar segmentation of depth images

    NASA Astrophysics Data System (ADS)

    Javan Hemmat, Hani; Pourtaherian, Arash; Bondarev, Egor; de With, Peter H. N.

    2015-03-01

    One of the major challenges for applications dealing with the 3D concept is the real-time execution of the algorithms. Besides this, for the indoor environments, perceiving the geometry of surrounding structures plays a prominent role in terms of application performance. Since indoor structures mainly consist of planar surfaces, fast and accurate detection of such features has a crucial impact on quality and functionality of the 3D applications, e.g. decreasing model size (decimation), enhancing localization, mapping, and semantic reconstruction. The available planar-segmentation algorithms are mostly developed using surface normals and/or curvatures. Therefore, they are computationally expensive and challenging for real-time performance. In this paper, we introduce a fast planar-segmentation method for depth images avoiding surface normal calculations. Firstly, the proposed method searches for 3D edges in a depth image and finds the lines between identified edges. Secondly, it merges all the points on each pair of intersecting lines into a plane. Finally, various enhancements (e.g. filtering) are applied to improve the segmentation quality. The proposed algorithm is capable of handling VGA-resolution depth images at a 6 FPS frame-rate with a single-thread implementation. Furthermore, due to the multi-threaded design of the algorithm, we achieve a factor of 10 speedup by deploying a GPU implementation.

  9. Planar Tunneling Spectroscopy of Graphene Nanodevices

    NASA Astrophysics Data System (ADS)

    Wang, Joel I.-Jan; Bretheau, Landry; Pisoni, Riccardo; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo

    2-D Van-der-Waals mesoscopic physics have seen a rapid development in the last 10 years, with new materials each year added to the toolbox. Stacking them like Lego enables the combination of their individual electronic properties. In particular, hexagonal boron nitride, which is an insulator, gives the possibility to perform planar (2-D to 2-D) tunneling spectroscopy within this type of heterostructures. Unlike standard transport measurements, tunneling spectroscopy enables to probe the electronic properties in the energy domain. Moreover, since planar tunneling probes a large area of the system, global quantum features such as quantum Hall effect, superconducting proximity effect or quantum confinement can be investigated. In this talk, we will present implementation of heterostructures consisting of graphene, hexagonal boron nitride, and graphite, fabricated for planar tunneling spectroscopy. In order to reveal the intrinsic properties of materials, the fabrication scheme aims at preserving the pristine nature of the 2-DEGS as well as minimizing the doping introduced by external probes. As a demonstration, measurements of these devices in normal states, high magnetic field environment, and induced superconducting state will be presented.

  10. Spontaneous Planar Chiral Symmetry Breaking in Cells

    NASA Astrophysics Data System (ADS)

    Hadidjojo, Jeremy; Lubensky, David

    Recent progress in animal development has highlighted the central role played by planar cell polarity (PCP) in epithelial tissue morphogenesis. Through PCP, cells have the ability to collectively polarize in the plane of the epithelium by localizing morphogenetic proteins along a certain axis. This allows direction-dependent modulation of tissue mechanical properties that can translate into the formation of complex, non-rotationally invariant shapes. Recent experimental observations[1] show that cells, in addition to being planar-polarized, can also spontaneously develop planar chirality, perhaps in the effort of making yet more complex shapes that are reflection non-invariant. In this talk we will present our work in characterizing general mechanisms that can lead to spontaneous chiral symmetry breaking in cells. We decompose interfacial concentration of polarity proteins in a hexagonal cell packing into irreducible representations. We find that in the case of polar concentration distributions, a chiral state can only be reached from a secondary instability after the cells are polarized. However in the case of nematic distributions, we show that a finite-amplitude (subcritical, or ``first-order'') nematic transition can send the system from disorder directly to a chiral state. In addition, we find that perturbing the system by stretching the hexagonal packing enables direct (supercritical, or ``second-order'') chiral transition in the nematic case. Finally, we do a Landau expansion to study competition between stretch-induced chirality and the tendency towards a non-chiral state in packings that have retained the full 6-fold symmetry.

  11. Non-planar on-shell diagrams

    NASA Astrophysics Data System (ADS)

    Franco, Sebastián; Galloni, Daniele; Penante, Brenda; Wen, Congkao

    2015-06-01

    We initiate a systematic study of non-planar on-shell diagrams in SYM and develop powerful technology for doing so. We introduce canonical variables generalizing face variables, which make the d log form of the on-shell form explicit. We make significant progress towards a general classification of arbitrary on-shell diagrams by means of two classes of combinatorial objects: generalized matching and matroid polytopes. We propose a boundary measurement that connects general on-shell diagrams to the Grassmannian. Our proposal exhibits two important and non-trivial properties: positivity in the planar case and it matches the combinatorial description of the diagrams in terms of generalized matroid polytopes. Interestingly, non-planar diagrams exhibit novel phenomena, such as the emergence of constraints on Plücker coordinates beyond Plücker relations when deleting edges, which are neatly captured by the generalized matching and matroid polytopes. This behavior is tied to the existence of a new type of poles in the on-shell form at which combinations of Plücker coordinates vanish. Finally, we introduce a prescription, applicable beyond the MHV case, for writing the on-shell form as a function of minors directly from the graph.

  12. Spectroscopic characteristics of GdVO4: Dy3+ crystal

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; He, Xiaoming; Zhang, Lianhan; Liu, Youchen; Yin, Jigang; Zhang, Peixing; Chen, Guangzhu; Wang, Xiangyong; Chen, Zhe; Shi, Chunjun; Hong, Jiaqi; Hang, Yin

    2014-11-01

    Room temperature optical absorption, emission spectrum of GdVO4: Dy3+ crystal grown by Czochralski (CZ) method were measured and analyzed. Spectral parameters were calculated in the framework of the Judd-Ofelt theory. The GdVO4: Dy3+ crystal showed two intense and relatively broad absorption bands in UV wavelength range centered at 390 and 453 nm and two prominent emission peaks located at blue 485 and yellow 575 nm. The corresponding absorption and emission cross sections were estimated and the luminescence decay curve was analyzed. Optical spectroscopy investigations indicate that GdVO4: Dy3+ crystal would be a promising blue and yellow solid state laser material.

  13. Spectroscopic study of Gd nanostructures quantum confined in Fe corrals

    SciTech Connect

    Cao, R. X.; Sun, L.; Miao, B. F.; Li, Q. L.; Zheng, C.; Wu, D.; You, B.; Zhang, W.; Han, P.; Bader, S. D.; Zhang, W. Y.; Ding, H. F.

    2015-07-10

    Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. As a result, this demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.

  14. Vapor pressure measurements of LaGd alloys

    NASA Astrophysics Data System (ADS)

    Shoji, Yoshiyuki; Matsui, Tsuneo; Nakamura, Kinya; Inoue, Tadashi

    1997-08-01

    The vapor pressures of La(g) and Gd(g) over La xGd 1- x alloys ( x = 0.00, 0.12, 0.22, 0.45, 0.70, 0.74, 0.85, 1.00) were measured with a time-of-flight mass spectrometer equipped with a tungsten Knudsen cell over the temperature range 1588 to 1797 K. The chemical activities of lanthanum and gadolinium in the alloys were determined by comparing the vapor pressures of La(g) and Gd(g) over the alloys with those over the pure metals. The chemical activities, thus obtained, showed positive deviations from Raoult's law over the entire compositional range. The interatomic force between gadolinium and lanthanum was thought to be repulsive. The partial molar Gibbs free energy and the Gibbs free energy, enthalpy and entropy of formation were calculated from the activity values.

  15. Spectroscopic study of Gd nanostructures quantum confined in Fe corrals

    DOE PAGESBeta

    Cao, R. X.; Sun, L.; Miao, B. F.; Li, Q. L.; Zheng, C.; Wu, D.; You, B.; Zhang, W.; Han, P.; Bader, S. D.; et al

    2015-07-10

    Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of themore » corrals and Gd structures trapped inside, are supported by tight-binding calculations. As a result, this demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.« less

  16. Effect of Gd polarization on the large magnetocaloric effect of GdCrO4 in a broad temperature range

    NASA Astrophysics Data System (ADS)

    Palacios, E.; Tomasi, C.; Sáez-Puche, R.; Dos santos-García, A. J.; Fernández-Martínez, F.; Burriel, R.

    2016-02-01

    The ferromagnetic zircon-type phase of GdCrO4 presents high values for the magnetocaloric (MC) parameters. This compound has large isothermal entropy changes Δ ST under the magnetic field action in a wide temperature range, from 5 to 35 K, reaching a maximum |Δ ST|=29.0 ±0.1 J /kg K at 22 K, for a field increment Δ B =9 T. It orders ferromagnetically at TC=21.3 K via the Cr-Cr exchange interaction and shows a second transition at 4.8 K due to the ordering of the Gd sublattice. The large MC effect is enhanced by the polarization of the Gd3 + ions by the Cr5 + ones via a weaker Gd-Cr interaction. This effect is an interesting feature to be considered in the search for new compounds with a high MC effect in the range of liquid hydrogen or natural gas, regarding the liquefaction of gases by magnetization-demagnetization cycles. This paper contains experimental measurements of magnetization, heat capacity, and direct determinations of the MC effect. The magnetic contribution to the heat capacity Cm has been obtained after subtracting the lattice component. Approximate values for the exchange constants J1 (Cr-Cr) and J3 (Gd-Cr) have been deduced from Cm.

  17. Enhanced upconversion luminescence in NaGdF4:Yb,Er nanocrystals by Fe3+ doping and their application in bioimaging

    NASA Astrophysics Data System (ADS)

    Ramasamy, Parthiban; Chandra, Prakash; Rhee, Seog Woo; Kim, Jinkwon

    2013-08-01

    The visible green and red upconversion emissions in Er3+/Yb3+ doped β-NaGdF4 nanoparticles were enhanced by tridoping with Fe3+ ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe3+ ions in NaGdF4:Yb3+/Er3+ nanoparticles. The effect of Fe3+ tridoping on the upconversion luminescence in NaGdF4:Yb3+/Er3+ NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe3+ ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells.The visible green and red upconversion emissions in Er3+/Yb3+ doped β-NaGdF4 nanoparticles were enhanced by tridoping with Fe3+ ions (0-40 mol%). XRD, XPS, ICP-AES and EDS data demonstrated successful incorporation of Fe3+ ions in NaGdF4:Yb3+/Er3+ nanoparticles. The effect of Fe3+ tridoping on the upconversion luminescence in NaGdF4:Yb3+/Er3+ NPs was investigated in detail. The green and red emission intensities were enhanced by 34 and 30 times, respectively. The maximum emission was observed in a sample containing 30 mol% Fe3+ ions. A possible mechanism for the enhanced upconversion emission is proposed. In addition, a layer of silica was coated onto the surface of UCNPs to improve the biocompatibility. Folic acid was covalently linked to the silica coated UCNPs to form UCNP@SiO2-FA nanoprobes, which have been successfully applied to the fluorescent imaging HeLa cells. Electronic supplementary information (ESI) available: EDS spectrum, mechanism of enhanced UC emission, XPS data, and TEM images and PL spectra of UCNPs@SiO2 NPs. See DOI: 10.1039/c3nr01608k

  18. Tunneling Spectroscopy of Amorphous Magnetic Rare Earth-Si Alloys near the Metal-Insulator Transition

    NASA Astrophysics Data System (ADS)

    Xiong, P.; Zink, B. L.; Tran, M. Q.; Gebala, A. E.; Wilcox, E. M.; Hellman, F.; Dynes, R. C.

    1997-03-01

    Amorphous dilute magnetic semiconductors exhibit striking differences in the electrical and magneto-transport behavior from their crystalline or nonmagnetic analogs.(F. Hellman et al., Phys. Rev. Lett. 77, 4652 (1996).) Magnetic impurities cause a large suppression of conductivity below 50 K in a-Si_xGd_1-x and a-Si_xTb_1-x relative to the nonmagnetic a-Si_xY_1-x (x ~ 0.85-0.9). Application of a magnetic field increases the conductivity by orders of magnitude. We have fabricated good quality tunnel junctions on a-Si:Gd and the nonmagnetic a-Si:Y to probe the electronic density of states in these two systems. We present the results of the tunneling spectroscopy and its magnetic field dependence for a series of the two alloys at different compositions. We will discuss the correlation between the tunneling spectra and the transport properties and its implications on the possible origin of the magnetic field tuned insulator-metal transition in a-Si:Gd. Research Supported by ONR Grant No. N000149151320 and NSF Grant No. DMR-9208599.

  19. The preparation of high-J c Gd0.5Y0.5Ba2Cu3O7‑δ thin films by the MOCVD process

    NASA Astrophysics Data System (ADS)

    Zhao, R. P.; Zhang, F.; Liu, Q.; Xia, Y. D.; Lu, Y. M.; Cai, C. B.; Tao, B. W.; Li, Y. R.

    2016-06-01

    A home-designed metal organic chemical vapor deposition (MOCVD) system has been employed to prepare high critical current density (J c) Gd0.5Y0.5Ba2Cu3O7‑δ (GdYBCO) thin films on LaMnO3/epitaxial MgO/ion beam assisted deposition (IBAD)-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes; the thin films were directly heated by the Joule effect after applying an heating current (I h ) through the Hastelloy tapes. The effect of the mole ratio of the metal organic sources has been systematically investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that the GdYBCO films crystallized better and became denser with the increasing of the Cu/Ba ratio from 1.0 to 1.1, yielding a J c at 77 K and 0 T of 200 nm GdYBCO film increasing from 2.5 MA cm‑2 to 7 MA cm‑2. In addition, SEM and energy dispersive spectrometer (EDS) characterizations revealed that more and more outgrowths appeared and the density of the film was reduced with an increase in the Cu/Ba ratio from 1.1 to 1.2. When the I h was 26.8 A and the mole ratio of Gd(tmhd)3, Y(tmhd)3, Ba(tmhd)2 and Cu(tmhd)2 in the precursor was 0.55:0.55:2:2.2, the critical current (I c) of the deposited 200 nm-thick GdYBCO film reached a 140 A cm‑1 width (77 K, 0 T), corresponding to the J c 7 MA cm‑2 (77 K, 0 T).

  20. Strain and stability of ultrathin Ge layers in Si/Ge/Si axial heterojunction nanowires

    SciTech Connect

    Ross, Frances M.; Stach, Eric A.; Wen, Cheng -Yen; Reuter, Mark C.; Su, Dong

    2015-02-05

    The abrupt heterointerfaces in the Si/Ge materials system presents useful possibilities for electronic device engineering because the band structure can be affected by strain induced by the lattice mismatch. In planar layers, heterointerfaces with abrupt composition changes are difficult to realize without introducing misfit dislocations. However, in catalytically grown nanowires, abrupt heterointerfaces can be fabricated by appropriate choice of the catalyst. Here we grow nanowires containing Si/Ge and Si/Ge/Si structures respectively with sub-1nm thick Ge "quantum wells" and we measure the interfacial strain fields using geometric phase analysis. Narrow Ge layers show radial strains of several percent, with a corresponding dilation in the axial direction. Si/Ge interfaces show lattice rotation and curvature of the lattice planes. We conclude that high strains can be achieved, compared to what is possible in planar layers. In addition, we study the stability of these heterostructures under heating and electron beam irradiation. The strain and composition gradients are supposed to the cause of the instability for interdiffusion.

  1. Strain and stability of ultrathin Ge layers in Si/Ge/Si axial heterojunction nanowires

    DOE PAGESBeta

    Ross, Frances M.; Stach, Eric A.; Wen, Cheng -Yen; Reuter, Mark C.; Su, Dong

    2015-02-05

    The abrupt heterointerfaces in the Si/Ge materials system presents useful possibilities for electronic device engineering because the band structure can be affected by strain induced by the lattice mismatch. In planar layers, heterointerfaces with abrupt composition changes are difficult to realize without introducing misfit dislocations. However, in catalytically grown nanowires, abrupt heterointerfaces can be fabricated by appropriate choice of the catalyst. Here we grow nanowires containing Si/Ge and Si/Ge/Si structures respectively with sub-1nm thick Ge "quantum wells" and we measure the interfacial strain fields using geometric phase analysis. Narrow Ge layers show radial strains of several percent, with a correspondingmore » dilation in the axial direction. Si/Ge interfaces show lattice rotation and curvature of the lattice planes. We conclude that high strains can be achieved, compared to what is possible in planar layers. In addition, we study the stability of these heterostructures under heating and electron beam irradiation. The strain and composition gradients are supposed to the cause of the instability for interdiffusion.« less

  2. CHEMICAL ABUNDANCES IN THE EXTERNALLY POLLUTED WHITE DWARF GD 40: EVIDENCE OF A ROCKY EXTRASOLAR MINOR PLANET

    SciTech Connect

    Klein, B.; Jura, M.; Zuckerman, B.; Melis, C.; Koester, D. E-mail: jura@astro.ucla.ed E-mail: cmelis@ucsd.ed

    2010-02-01

    We present Keck/High Resolution Echelle Spectrometer data with model atmosphere analysis of the helium-dominated polluted white dwarf GD 40, in which we measure atmospheric abundances relative to helium of nine elements: H, O, Mg, Si, Ca, Ti, Cr, Mn, and Fe. Apart from hydrogen, whose association with the other contaminants is uncertain, this material most likely accreted from GD 40's circumstellar dust disk whose existence is demonstrated by excess infrared emission. The data are best explained by accretion of rocky planetary material, in which heavy elements are largely contained within oxides, derived from a tidally disrupted minor planet at least the mass of Juno, and probably as massive as Vesta. The relatively low hydrogen abundance sets an upper limit of 10% water by mass in the inferred parent body, and the relatively high abundances of refractory elements, Ca and Ti, may indicate high-temperature processing. While the overall constitution of the parent body is similar to the bulk Earth being over 85% by mass composed of oxygen, magnesium, silicon, and iron, we find n(Si)/n(Mg) = 0.30 +- 0.11, significantly smaller than the ratio near unity for the bulk Earth, chondrites, the Sun, and nearby stars. This result suggests that differentiation occurred within the parent body.

  3. Spin-on-dielectrics: Planarity modeling

    NASA Astrophysics Data System (ADS)

    Smythe, John A.

    2009-12-01

    The idea of replacing chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), and sputter oxide materials, among others, with a spin-on approach has been of interest in the Semiconductor industry for the last two decades. The technique draws from the planarizing nature of a liquid when applied to surface topography. The method, initially known as Spin-On-Glass (SOG), has more recently taken on the more general term Spin-On-Dielectric (SOD). Prior works have addressed issues including, crack resistance, etch rate, resistance to photo resist stripping conditions, film stress, defectivity and planarity. Planarity characteristics have not been addressed with the rigor needed to predict the interaction between variable topography in terms of the degree of local and global planarization. In this work, experimental results for film thickness as a function of viscosity and spin speed are presented. Experimental results for percent trench fill are presented for different trench depth, width and coating thickness. Models have been developed using level-set two-phase flow and Arbitrary Lagrangian-Eulerian (ALE) interface tracking methods as implemented in COMSOL(TM) to describe the movement of an initial interface in time. Droplet spreading and capillary rise cases were used to validate the level-set two-phase flow application mode treatment of variable viscosity, surface tension and contact angle. This work presents model results for film thinning on 200 mm wafer and local planarization characteristics at the nanometer scale of present day semiconductor device features. The film thinning model is based on a set of equations derived to represent flow, evaporation and diffusion for variable rotational velocity, solvent concentration and initial profile. Model results for full wafer thinning include the effects of variable evaporation with radius on final film height profile given differing initial profiles. A simple and a complex evaporation

  4. Magnetic properties of Eu doped BiGdO3

    NASA Astrophysics Data System (ADS)

    Nithya, R.; Yadagiri, K.; Shukla, Neeraj

    2016-05-01

    Bulk Bismuth Gadolinium Oxide, BiGdO3 and Eu doped BiGdO3 compounds were synthesized by the conventional solid state reaction in air. Phase formation of these compounds was tracked using powder X-ray characterization technique since single phase formation was found to be sensitive to thermal treatment parameters such as cooling and heating rates. Analysis of X-ray diffraction patterns revealed cubic structure with Pm-3m symmetry. An antiferromagnetic transition around 3.8K was observed in the pristine compound whereas doped samples showed paramagnetic nature in the whole measured temperature range.

  5. Oxygen modified growth of Gd on Mo(110)

    NASA Astrophysics Data System (ADS)

    Mozley, S.; Nicklin, C. L.; James, M. A.; Steadman, P.; Norris, C.; Lohmeier, M.

    1995-07-01

    X-ray diffraction measurements have been made in real time during deposition of the rare earth Gd on the non-magnetic substrate Mo(110). For the clean surface at 300 K, the variation of the specularly reflected X-ray intensity with deposition time is consistent with the completion of a close-packed monolayer followed by increasingly disordered, multilayer, growth. Exposure of the Mo surface to 0.25 langmuir of oxygen prior to Gd deposition produced better defined intensity oscillations characteristic of improved layerwise growth. It is suggested that the oxygen creates nucleation sites which increases interlayer mass transport.

  6. Nanoscale dielectric microscopy of non-planar samples by lift-mode electrostatic force microscopy.

    PubMed

    Van Der Hofstadt, M; Fabregas, R; Biagi, M C; Fumagalli, L; Gomila, G

    2016-10-01

    Lift-mode electrostatic force microscopy (EFM) is one of the most convenient imaging modes to study the local dielectric properties of non-planar samples. Here we present the quantitative analysis of this imaging mode. We introduce a method to quantify and subtract the topographic crosstalk from the lift-mode EFM images, and a 3D numerical approach that allows for extracting the local dielectric constant with nanoscale spatial resolution free from topographic artifacts. We demonstrate this procedure by measuring the dielectric properties of micropatterned SiO2 pillars and of single bacteria cells, thus illustrating the wide applicability of our approach from materials science to biology. PMID:27597315

  7. Modeling the optical response of grating-profiled PtSi/Si infrared detectors

    NASA Astrophysics Data System (ADS)

    Rea, Chris J. T.; Cairns, Gerald F.; Dawson, Paul

    1997-10-01

    Modeling the optical response of grating profiled PtSi/Si structures is examined to demonstrate the potential of microstructuring in optimizing the absorption of infrared detectors. Coupling to angularly broad surface plasmon polariton resonances near normal incidence is, in fact, achieved at both Si/PtSi and SiO2/PtSi interfaces for the same grating parameters in the wavelength ranges 3.0 - 4.4 micrometer and 1.3 - 1.9 micrometer respectively. These ranges correspond to two infrared, atmospheric transmission windows, and demonstrate the potential for a single device geometry to operate optimally in two different spectral bands. It is also shown that, throughout these spectral bands, it is possible to attain reflectance significantly lower than that of the planar structure counterparts in the angle range 0 degrees to plus or minus 20 degrees (corresponding to the use of F1.4 optics), along with containment of low reflectance to that angle range. Absorption mediated by the PtSi/Si surface plasmon polariton mode may be of particular interest in these Schottky barrier structures, since there would be considerable enhancement in the generation of hot carriers in the near barrier region where they have a better chance of direct or indirect (via elastic scattering) promotion over the barrier to give rise to a detectable charge.

  8. Transport Properties of Closely-Packed Carbon Nanotubes Film on SiC Tuned by Si-Doping

    NASA Astrophysics Data System (ADS)

    Norimatsu, Wataru; Maruyama, Takehiro; Yoshida, Kenta; Takase, Koichi; Kusunoki, Michiko

    2012-10-01

    Here, we reveal origins of the planar electrical transport of closely-packed carbon nanotubes (CNTs) and silicon-doped CNTs (Si-CNTs) films. Their electrical resistivities increased with decreasing temperature, but exhibit a plateau below 60 K. This phenomenon can be well described using the simple-two-band model, which is often used to understand the electronic properties of graphite. Cryogenic energy-filtered transmission electron microscopy visualizes Si atoms dispersed finely in CNTs, preserving the structural features of CNTs. These Si atoms induced effective carriers above 150 K, while three-dimensional variable range hopping and weak localization are dominant in their transport below 50 and 10 K, respectively.

  9. First principle identification of SiC monolayer as an efficient catalyst for CO oxidation

    SciTech Connect

    Sinthika, S. E-mail: sinthika90@gmail.com; Thapa, Ranjit E-mail: sinthika90@gmail.com; Reddy, C. Prakash

    2015-06-24

    Using density functional theory, we investigated the electronic properties of SiC monolayer and tested its catalytic activity toward CO oxidation. The planar nature of a SiC monolayer is found to stable and is a high band gap semiconductor. CO interacts physically with SiC surface, whereas O{sub 2} is adsorbed with moderate binding. CO oxidation on SiC monolayer prefers the Eley Rideal mechanism over the Langmuir Hinshelwood mechanism, with an easily surmountable activation barrier during CO{sub 2} formation. Overall metal free SiC monolayer can be used as efficient catalyst for CO oxidation.

  10. First principle identification of SiC monolayer as an efficient catalyst for CO oxidation

    NASA Astrophysics Data System (ADS)

    Sinthika, S.; Reddy, C. Prakash; Thapa, Ranjit

    2015-06-01

    Using density functional theory, we investigated the electronic properties of SiC monolayer and tested its catalytic activity toward CO oxidation. The planar nature of a SiC monolayer is found to stable and is a high band gap semiconductor. CO interacts physically with SiC surface, whereas O2 is adsorbed with moderate binding. CO oxidation on SiC monolayer prefers the Eley Rideal mechanism over the Langmuir Hinshelwood mechanism, with an easily surmountable activation barrier during CO2 formation. Overall metal free SiC monolayer can be used as efficient catalyst for CO oxidation.

  11. Microstructure and property of directionally solidified Ni-Si hypereutectic alloy

    NASA Astrophysics Data System (ADS)

    Cui, Chunjuan; Tian, Lulu; Zhang, Jun; Yu, Shengnan; Liu, Lin; Fu, Hengzhi

    2016-03-01

    This paper investigates the influence of the solidification rate on the microstructure, solid/liquid interface, and micro-hardness of the directionally solidified Ni-Si hypereutectic alloy. Microstructure of the Ni-Si hypereutectic alloy is refined with the increase of the solidification rate. The Ni-Si hypereutectic composite is mainly composed of α-Ni matrix, Ni-Ni3Si eutectic phase, and metastable Ni31Si12 phase. The solid/liquid interface always keeps planar interface no matter how high the solidification rate is increased. This is proved by the calculation in terms of M-S interface stability criterion. Moreover, the Ni-Si hypereutectic composites present higher micro-hardness as compared with that of the pure Ni3Si compound. This is caused by the formation of the metastable Ni31Si12 phase and NiSi phase during the directional solidification process.

  12. Rare-earth substitution in (BiYCa)3(FeSiGe)5O12 bubble films

    NASA Technical Reports Server (NTRS)

    Luther, L. C.; Slusky, S. E. G.; Brandle, C. D.; Norelli, M. P.

    1987-01-01

    The substitution of Y by Sm, Tb, Gd, and Ho in (BiYCa)3 FeSiGe)5O12 bubble garnet is shown to have large effects on the growth-induced anisotropy (GIA). The presently accepted film composition intended for 6-or 8-micron-period bubble memory devices demands partial substitution of Y by Gd and Ho. However, comparing films grown under the same growth conditions, it is observed that YGdHoBilG films posess less (GIA) than their Gd, Ho-free counterparts. Thus, to satisfy (GIA) requirements, the supercooling during growth must be increased by 20 K to 80 K with undesirable effects on defect densities. A new film composition containing Sm, Tb, and Gd has been formulated to satisfy all known material property specifications for 6- or 8-micron-period memory devices. It can be grown with only 45-50 K supercooling.

  13. Evaluation of gadolinium compounds potentially suitable for magnetic resonance using Gd-153 scintigraphy

    SciTech Connect

    Engelstad, B.; Huberty, J.; White, D.; Wynne, C.; Ramos, E.; Goldberg, H.

    1985-05-01

    Gd-153 is not customarily considered for scintigraphy, yet it: 1) is available at acceptable cost, 2) has a 242 day half-life suitable for prolonged animal studies and 3) has 97 keV (40%) and 103 keV (59%) photopeaks suitable for conventional scintigraphy. Gd-153 (10-15 ..mu..Ci; 370-555 kBq) was administered to normal rats in 5 forms: 1) carrier 0.1 mmole/kg Gd-EIDA (diethyl iminodiacetic acid), 2) tracer (<.1 umole/kg) Gd-EIDA, 3) tracer Gd-ISIDA (diisopropyl iminodiacetic acid), 4) tracer GdCl/sub 3/, and 5) tracer Gd-DTPA. Scintigraphy, performed continuously for 90 minutes following intravenous injection and at intervals at up to 2 weeks, depicted: 1) rapid, partial hepatobiliary and renal clearance of tracer Gd-EIDA and Gd-ISIDA; 2) slow blood clearance and partial hepatobiliary clearance of carrier Gd-EIDA; and 3) prolonged reticuloendothelial retention of all IDA complexes, similar to GdCl3. Whole body and tissue distribution data paralleled the scintigraphic findings. Gd-153 scintigraphy provides a simple method to assess balance, distribution, kinetics, and stability of new paramagnetic contrast agents, and bis-iminodiacetate gadolinium complexes, unlike technetium analogues, lack effective stability to prevent gadolinium hydrolysis or translocation.

  14. High relaxivity Gd(III)-DNA gold nanostars: investigation of shape effects on proton relaxation.

    PubMed

    Rotz, Matthew W; Culver, Kayla S B; Parigi, Giacomo; MacRenaris, Keith W; Luchinat, Claudio; Odom, Teri W; Meade, Thomas J

    2015-03-24

    Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)-DNA), followed by surface conjugation onto gold nanostars (DNA-Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM(-1) s(-1). Additionally, DNA-Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA-Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA-Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)-DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)-DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs. PMID:25723190

  15. Pier GD5, view of top of deck and looking toward ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Pier GD-5, view of top of deck and looking toward GD-4, concrete leg jutting out to the west of GD-5 in foreground - U.S. Naval Base, Pearl Harbor, Pier & Quay Walls, Entrance to Dry Dock No. 2 & Repair Wharfs, east & west sides of Dry Dock No. 2 & west side of Dry Dock No. 3, Pearl City, Honolulu County, HI

  16. Mapping the magnetic hyperfine field in GdCo5

    NASA Astrophysics Data System (ADS)

    Krylov, V. I.; Bosch-Santos, B.; Cabrera-Pasca, G. A.; Delyagin, N. N.; Carbonari, A. W.

    2016-05-01

    The magnetic hyperfine field (Bhf) in ferrimagnetic GdCo5 compound has been investigated as a function of temperature by Mössbauer effect (ME) spectroscopy and perturbed angular correlation (PAC) spectroscopy using 119Sn and 111Cd probe nuclei, respectively. Results show that the non-magnetic probe atoms 119Sn and 111Cd substitute all three non-equivalent positions in GdCo5: Gd, CoI, and CoII. For 119Sn and 111Cd probes at Gd sites, the saturation magnetic hyperfine fields are very different with values of Bhf1 = 57.0(1) T and Bhf1= 20.7(1) T, respectively. For 119Sn and 111Cd atoms localized at CoI and CoII sites the magnetic hyperfine fields are practically identical and, in saturation, reach the values of Bhf2 = 11.6(1) T and Bhf2 = 11.1(2) T, and Bhf3 = 14.8(1) T and Bhf3 = 14.4(2) T, respectively.

  17. Gd uptake experiments for preliminary set of functionalized adsorbents

    SciTech Connect

    Clinton Noack

    2015-03-16

    These data summarize adsorption experiments conducted with Gd in 0.5 M NaCl. Results represent preliminary, proof-of-concept data utilizing fine-powder silica gel as the adsorbent support. Future testing will focus on larger, application-appropriate beads.

  18. Infrared spectroscopy and the ferromagnetic transition in Gd.

    PubMed

    Obied, L H; Crandles, D A; Antonov, V N; Bose, S K; Jepsen, O

    2013-01-23

    The low energy electronic structure of Gd has been investigated experimentally by infrared reflectance spectroscopy, and theoretically from first principles, using the fully relativistic Dirac linear-muffin-tin-orbital (LMTO) method in the local spin density approximation (LSDA) as well as within the LSDA + U approach. The reflectance of a Gd single crystal was measured with the electric field in the plane perpendicular to the c-axis for temperatures between 50 K and slightly above the Curie temperature (293 K) in the frequency range between 100 and 12 000 cm(-1) (0.013-1.5 eV). As Gd enters the ferromagnetic state, the dissipative part of the optical conductivity exhibits interesting spectral weight transfers over the whole spectral range measured. It is shown that the ab initio calculations reproduce well the experimental spectra for the ferromagnetic state and allow one to explain the microscopic origin of the optical response of Gd in terms of interband transitions. PMID:23221360

  19. Buffer layer between a planar optical concentrator and a solar cell

    SciTech Connect

    Solano, Manuel E.; Barber, Greg D.; Lakhtakia, Akhlesh; Faryad, Muhammad; Monk, Peter B.; Mallouk, Thomas E.

    2015-09-15

    The effect of inserting a buffer layer between a periodically multilayered isotropic dielectric (PMLID) material acting as a planar optical concentrator and a photovoltaic solar cell was theoretically investigated. The substitution of the photovoltaic material by a cheaper dielectric material in a large area of the structure could reduce the fabrication costs without significantly reducing the efficiency of the solar cell. Both crystalline silicon (c-Si) and gallium arsenide (GaAs) were considered as the photovoltaic material. We found that the buffer layer can act as an antireflection coating at the interface of the PMLID and the photovoltaic materials, and the structure increases the spectrally averaged electron-hole pair density by 36% for c-Si and 38% for GaAs compared to the structure without buffer layer. Numerical evidence indicates that the optimal structure is robust with respect to small changes in the grating profile.

  20. Buffer layer between a planar optical concentrator and a solar cell

    NASA Astrophysics Data System (ADS)

    Solano, Manuel E.; Barber, Greg D.; Lakhtakia, Akhlesh; Faryad, Muhammad; Monk, Peter B.; Mallouk, Thomas E.

    2015-09-01

    The effect of inserting a buffer layer between a periodically multilayered isotropic dielectric (PMLID) material acting as a planar optical concentrator and a photovoltaic solar cell was theoretically investigated. The substitution of the photovoltaic material by a cheaper dielectric material in a large area of the structure could reduce the fabrication costs without significantly reducing the efficiency of the solar cell. Both crystalline silicon (c-Si) and gallium arsenide (GaAs) were considered as the photovoltaic material. We found that the buffer layer can act as an antireflection coating at the interface of the PMLID and the photovoltaic materials, and the structure increases the spectrally averaged electron-hole pair density by 36% for c-Si and 38% for GaAs compared to the structure without buffer layer. Numerical evidence indicates that the optimal structure is robust with respect to small changes in the grating profile.

  1. Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits

    PubMed Central

    Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

    2014-01-01

    Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells. PMID:24810591

  2. Implosion characteristics and applications of combined tungsten-aluminum Z-pinch planar arrays

    NASA Astrophysics Data System (ADS)

    Osborne, G. C.; Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Weller, M. E.; Shrestha, I.; Williamson, K. M.; Shlyaptseva, V. V.

    2013-12-01

    An exploration of the implosion properties and X-ray radiation pulses from tungsten-based planar wire array Z-pinch experiments is presented, with an emphasis on loads mixed with aluminum. These experiments were carried out on Zebra, the 1.0 MA pulse power generator at the Nevada Terawatt Facility. A suite of diagnostics was used to study these plasmas, including X-ray and EUV Si diodes, optical imaging, laser shadowgraphy, and time-gated and time-integrated X-ray pinhole imagers and spectrometers. Specifically, loads with relatively large inter-wire gaps where tungsten is placed in the center of a planar configuration composed primarily of aluminum showed unusual characteristics. These loads are shown to generate a "bubbling" effect in which plasma from the ablation of outer aluminum wires is temporarily hindered from converging at the center of the array where the tungsten wire is located. Reproduction of these experiments with variations to load geometry, materials, and mass distribution are also presented and discussed in an attempt to better understand the phenomenon. In addition, a theoretical model has also been applied to better understand the dynamics of the implosions of these loads. Applications of this effect to radiation pulse shaping, particularly with multi-planar arrays, are also discussed.

  3. High voltage planar multijunction solar cell

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.; Chai, A. T.; Goradia, C. P. (Inventor)

    1982-01-01

    A high voltage multijunction solar cell is provided wherein a plurality of discrete voltage generating regions or unit cells are formed in a single generally planar semiconductor body. The unit cells are comprised of doped regions of opposite conductivity type separated by a gap or undiffused region. Metal contacts connect adjacent cells together in series so that the output voltages of the individual cells are additive. In some embodiments, doped field regions separated by a overlie the unit cells but the cells may be formed in both faces of the wafer.

  4. Planar graphical models which are easy

    NASA Astrophysics Data System (ADS)

    Chernyak, Vladimir Y.; Chertkov, Michael

    2010-11-01

    We describe a rich family of binary variables statistical mechanics models on a given planar graph which are equivalent to Gaussian Grassmann graphical models (free fermions) defined on the same graph. Calculation of the partition function (weighted counting) for such a model is easy (of polynomial complexity) as it is reducible to evaluation of a Pfaffian of a matrix of size equal to twice the number of edges in the graph. In particular, this approach touches upon holographic algorithms of Valiant and utilizes the gauge transformations discussed in our previous works.

  5. The cell biology of planar cell polarity

    PubMed Central

    2014-01-01

    Planar cell polarity (PCP) refers to the coordinated alignment of cell polarity across the tissue plane. Key to the establishment of PCP is asymmetric partitioning of cortical PCP components and intercellular communication to coordinate polarity between neighboring cells. Recent progress has been made toward understanding how protein transport, endocytosis, and intercellular interactions contribute to asymmetric PCP protein localization. Additionally, the functions of gradients and mechanical forces as global cues that bias PCP orientation are beginning to be elucidated. Together, these findings are shedding light on how global cues integrate with local cell interactions to organize cellular polarity at the tissue level. PMID:25349257

  6. Theoretical analysis of planar pulse microwiggler

    SciTech Connect

    Qing-Xiang Liu |; Yong Xu

    1995-12-31

    The Magnetic field distributions of a planar pulse microwiggler are studied analytically and numerically. Exact solutions of two-dimensional magnetic fields are derived, which show that along the electron axis the fields have a variation close enough to a sine wave. We also investigate wiggler field errors due to machining tolerance and effects of the field errors on trajectories of electron with the help numerical simulations. The results are critical for successful operation of CAEP compact free-electron laser experiment under preparation.

  7. Conceptual Design for Superconducting Planar Helical Undulator

    NASA Astrophysics Data System (ADS)

    Sasaki, Shigemi

    2004-05-01

    A preliminary consideration was made on a short-period superconducting planar helical undulator (SCHU) for circularly polarized radiation. The SCHU consists of coils and iron poles/yokes. There is no magnetic structure in the horizontal plane of the electron orbit. The SCHU would provide the large horizontal aperture needed to allow injection into the storage ring. The expected field strength is at least 30% larger than that by an APPLE-type permanent-magnet device with the same gap and the same period.

  8. Walls and chains of planar Skyrmions

    SciTech Connect

    Harland, Derek; Ward, R. S.

    2008-02-15

    In planar (baby) Skyrme systems, there may be extended linear structures which resemble either domain walls or chains of skyrmions, depending on the choice of potential and boundary conditions. We show that systems with a single vacuum, for example, with potential V=1-{phi}{sub 3}, admit chain solutions, whereas walls are ruled out by the uniqueness of the vacuum. On the other hand, in double-vacuum systems such as V=(1/2)(1-{phi}{sub 3}{sup 2}), one has stable wall solutions, but there are no stable chains; the walls may be viewed as the primary objects in such systems, with skyrmions being made out of them.

  9. Optical planar waveguide for cell counting

    PubMed Central

    LeBlanc, John; Mueller, Andrew J.; Prinz, Adrian; Butte, Manish J.

    2012-01-01

    Low cost counting of cells has medical applications in screening, military medicine, disaster medicine, and rural healthcare. In this report, we present a shallow, buried, planar waveguide fabricated by potassium ion exchange in glass that enables low-cost and rapid counting of metal-tagged objects that lie in the evanescent field of the waveguide. Laser light transmitted through the waveguide was attenuated proportionately to the presence of metal-coated microstructures fabricated from photoresist. This technology enables the low-cost enumeration of cells from blood, urine, or other biofluids. PMID:22331960

  10. Vortex gyroscope imaging of planar superfluids.

    PubMed

    Powis, A T; Sammut, S J; Simula, T P

    2014-10-17

    We propose a robust imaging technique that makes it possible to distinguish vortices from antivortices in quasi-two-dimensional Bose-Einstein condensates from a single image of the density of the atoms. Tilting the planar condensate prior to standard absorption imaging excites a generalized gyroscopic mode of the condensate, revealing the sign and location of each vortex. This technique is anticipated to enable experimental measurement of the incompressible kinetic energy spectrum of the condensate and the observation of a negative-temperature phase transition of the vortex gas, driven by two-dimensional superfluid turbulence. PMID:25361263

  11. Broadband Planar 5:1 Impedence Transformer

    NASA Technical Reports Server (NTRS)

    Ehsan, Negar; Hsieh, Wen-Ting; Moseley, Samuel H.; Wollack, Edward J.

    2015-01-01

    This paper presents a broadband Guanella-type planar impedance transformer that transforms so 50 omega to 10 omega with a 10 dB bandwidth of 1-14GHz. The transformer is designed on a flexible 50 micrometer thick polyimide substrate in microstrip and parallel-plate transmission line topologies, and is Inspired by the traditional 4:1 Guanella transformer. Back-to-back transformers were designed and fabricated for characterization in a 50 omega system. Simulated and measured results are in excellent agreement.

  12. Transparent conductor-Si pillars heterojunction photodetector

    SciTech Connect

    Yun, Ju-Hyung; Kim, Joondong; Park, Yun Chang

    2014-08-14

    We report a high-performing heterojunction photodetector by enhanced surface effects. Periodically, patterned Si substrates were used to enlarge the photo-reactive regions and yield proportionally improved photo-responses. An optically transparent indium-tin-oxide (ITO) was deposited on a Si substrate and spontaneously formed an ITO/Si heterojunction. Due to an electrical conductive ITO film, ITO/Si heterojunction device can be operated at zero-bias, which effectively suppresses the dark current, resulting in better performances than those by a positive or a negative bias operation. This zero-bias operating heterojunction device exhibits a short response time (∼ 22.5 ms) due to the physical reaction to the incident light. We revealed that the location of the space charge region (SCR) is crucial for a specific photon-wavelength response. The SCR space has the highest collection efficiency of the photo-generated carriers. The photo-response can be maximized when we design the photodetector by superposing the SCR space over a corresponding photon-absorption length. The surface enhanced Si pillar devices significantly improved the photo-responses ratios from that of a planar Si device. According to this design scheme, a high photo-response ratio of 5560% was achieved at a wavelength of 600 nm. This surfaced-enhanced heterojunction design scheme would be a promising approach for various photoelectric applications.

  13. Comparative Study on the Corrosion Resistance of Fe-Based Amorphous Metal, Borated Stainless Steel and Ni-Cr-Mo-Gd Alloy

    SciTech Connect

    Lian, Tiangan; Day, Daniel; Hailey, Phillip; Choi, Jor-Shan; Farmer, Joseph

    2007-07-01

    Iron-based amorphous alloy Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} was compared to borated stainless steel and Ni-Cr-Mo-Gd alloy on their corrosion resistance in various high-concentration chloride solutions. The melt-spun ribbon of this iron-based amorphous alloy have demonstrated a better corrosion resistance than the bulk borated stainless steel and the bulk Ni-Cr-Mo-Gd alloy, in high-concentration chloride brines at temperatures 90 deg. C or higher. (authors)

  14. Structure and growth morphology of Gd 2O 3-doped CeO 2 thin films

    NASA Astrophysics Data System (ADS)

    Jiang, Xuening; Hao, Binkui

    2010-05-01

    Gd 2O 3-doped CeO 2 (Gd 0.1Ce 0.9O 1.95, GDC) thin films were synthesized on (1 0 0) Si single crystal substrates by a reactive radio frequency magnetron sputtering technique. Structures and surface morphologies were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and one-dimensional power spectral density (1DPSD) analysis. The XRD patterns indicated that, in the temperature range of 200-700 °C, f.c.c. structured GDC thin films were formed with growth orientations varying with temperature—random growth at 200 °C, (2 2 0) textures at 300-600 °C and (1 1 1) texture at 700 °C. GDC film synthesized at 200 °C had the smoothest surface with roughness of Rrms=0.973 nm. Its 1DPSD plot was characterized with a constant part at the low frequencies and a part at the high frequencies that could be fitted by the f-2.4 power law decay. Such surface feature and scaling behavior were probably caused by the high deposition rate and random growth in the GDC film at this temperature. At higher temperatures (300-700 °C), however, an intermediate frequency slope (- γ2≈-2) appeared in the 1DPSD plots between the low frequency constant part and the high frequency part fitted by f-4 power law decay, which indicated a roughing mechanism dominated by crystallographic orientation growth that caused much rougher surfaces in GDC films ( Rrms>4 nm).

  15. Analysis and design of planar and non-planar wings for induced drag minimization

    NASA Technical Reports Server (NTRS)

    Mortara, Karl W.; Straussfogel, Dennis M.; Maughmer, Mark D.

    1992-01-01

    The goal of the work reported herein is to develop and validate computational tools to be used for the design of planar and non-planar wing geometries for minimum induced drag. Because of the iterative nature of the design problem, it is important that, in addition to being sufficiently accurate for the problem at hand, these tools need to be reasonably fast and computationally efficient. Toward this end, a method of predicting induced drag in the presence of a free wake has been coupled with a panel method. The induced drag prediction technique is based on the application of the Kutta-Joukowski law at the trailing edge. Until now, the use of this method has not been fully explored and pressure integration and Trefftz-plane calculations favored. As is shown in this report, however, the Kutta-Joukowski method is able to give better results for a given amount of effort than the more commonly used techniques, particularly when relaxed wakes and non-planar wing geometries are considered. Using these methods, it is demonstrated that a reduction in induced drag can be achieved through non-planar wing geometries. It remains to determine what overall drag reductions are possible when the induced drag reduction is traded-off against increased wetted area. With the design methodology that is described herein, such trade studies can be performed in which the non-linear effects of the free wake are taken into account.

  16. A study of the interfacial resistive switching mechanism by proton exchange reactions on the SiO(x) layer.

    PubMed

    Zhou, Fei; Chang, Yao-Feng; Chen, Ying-Chen; Wu, Xiaohan; Zhang, Ye; Fowler, Burt; Lee, Jack C

    2016-01-14

    In this work, we investigated SiO(x)-based interfacial resistive switching in planar metal-insulator-metal structures using physical/chemical/electrical analyses. This work helps clarify the interfacial reaction process and mechanism in SiO(x), and also shows the potential for high temperature operation in future nonvolatile memory applications. PMID:26659556

  17. Separation of Gd-humic complexes and Gd-based magnetic resonance imaging contrast agent in river water with QAE-Sephadex A-25 for the fractionation analysis.

    PubMed

    Matsumiya, Hiroaki; Inoue, Hiroto; Hiraide, Masataka

    2014-10-01

    Gadolinium complexed with naturally occurring, negatively charged humic substances (humic and fulvic acids) was collected from 500 mL of sample solution onto a column packed with 150 mg of a strongly basic anion-exchanger (QAE-Sephadex A-25). A Gd-based magnetic resonance imaging contrast agent (diethylenetriamine-N,N,N',N″,N″-pentaacetato aquo gadolinium(III), Gd-DTPA(2-)) was simultaneously collected on the same column. The Gd-DTPA complex was desorbed by anion-exchange with 50mM tetramethylammonium sulfate, leaving the Gd-humic complexes on the column. The Gd-humic complexes were subsequently dissociated with 1M nitric acid to desorb the humic fraction of Gd. The two-step desorption with small volumes of the eluting agents allowed the 100-fold preconcentration for the fractionation analysis of Gd at low ng L(-1) levels by inductively coupled plasma-mass spectrometry (ICP-MS). On the other hand, Gd(III) neither complexed with humic substances nor DTPA, i.e., free species, was not sorbed on the column. The free Gd in the effluent was preconcentrated 100-fold by a conventional solid-phase extraction with an iminodiacetic acid-type chelating resin and determined by ICP-MS. The proposed analytical fractionation method was applied to river water samples. PMID:25059192

  18. Phase Stability and Pressure Dependence of Defect Formation in Gd2Ti2O7 and Gd2Zr2O7 Pyrochlore

    SciTech Connect

    Zhang,F.; Wang, J.; Lian, J.; Lang, M.; Becker, U.; Ewing, R.

    2008-01-01

    We report dramatically different behaviors between isostructural Gd2Ti2O7 and Gd2Zr2O7 pyrochlore at pressures up to 44 GPa, in which the substitution of Ti for Zr significantly increases structural stability. Upon release of pressure, the Gd2Ti2O7 becomes amorphous. In contrast, the high-pressure phase of Gd2Zr2O7 transforms to a disordered defect-fluorite structure. First-principle calculations for both compositions revealed that the response of pyrochlore to high pressure is controlled by the intrinsic energetics of defect formation.

  19. Percent Infarct Mapping for Delayed Contrast Enhancement MR Imaging to Quantify Myocardial Viability by Gd(DTPA)

    PubMed Central

    Simor, Tamás; Surányi, Pál; Ruzsics, Balázs; Tóth, Attila; Tóth, Levente; Kiss, Pál; Brott, Brigitta C.; Varga-Szemes, Ákos; Elgavish, Ada; Elgavish, Gabriel A.

    2010-01-01

    Purpose To demonstrate the advantages of Signal Intensity Percent-Infarct-Mapping (SI-PIM) using the standard delayed enhancement (DE) acquisition in assessing viability following myocardial infarction (MI). SI-PIM quantifies MI density with a voxel-by-voxel resolution in clinically used DE images. Materials and Methods In canines (n=6), 96h after reperfused MI and administration of 0.2mmol/kg Gd(DTPA), ex-vivo DE images were acquired and SI-PIMs calculated. SI-PIM data were compared with data from DE images analyzed with several thresholding levels using SIremote+2SD, SIremote+6SD, SI full width half maximum (SIFWHM), and with triphenyl-tetrazolium-chloride (TTC) staining. SI-PIM was also compared to R1 percent infarct mapping (R1-PIM). Results Left ventricular infarct volumes (IV) in DE images, IVSIremote+2SD and IVSIremote+6SD overestimated (p<0.05) TTC by medians of 13.21ml [10.2; 15.2] and 6.2ml [3.79; 8.23], respectively. SIFWHM, SI-PIM and R1-PIM, however, only non-significantly underestimated TTC, by medians of −0.10ml [−0.12, −0.06], −0.86ml [−1.04; 1.54] and −1.30ml [−4.99; −0.29], respectively. The Infarct-Involved Voxel Volume (IIVV) of SI-PIM, 32.4ml [21.2, 46.3] is higher (p<0.01) than IIVVs of SIFWHM 8.3ml [3.79, 19.0]. SI-PIMFWHM, however, underestimates TTC (−5.74ml [−11.89; −2.52] (p<0.01)). Thus SI-PIM outperforms SIFWHM because larger IIVVs are obtained, and thus PIs both in the rim and the core of the infarcted tissue are characterized, in contradistinction from DE-SIFWHM which shows mainly the infarct core. Conclusion We have shown here, ex vivo, that SI-PIM has the same advantages as R1-PIM, but it is based on the scanning sequences of DE imaging, and thus it is obtainable within the same short scanning time as DE. This makes it a practical method for clinical studies. PMID:20882616

  20. Magnetism and Raman spectroscopy of the dimeric lanthanide iodates Ln(IO3)3 (Ln Gd, Er) and magnetism of Yb(IO3)3.

    SciTech Connect

    Sykora, Richard E.; Khalifah, Peter; Assefa, Zerihun; Albrecht-Schmitt, Thomas E.; Haire, Richard G.

    2008-01-01

    Colorless single crystals of Gd(IO3)3 or pale pink single crystals of Er(IO3)3 have been formed from the reaction of Gd metal with H5IO6 or Er metal with H5IO6 under hydrothermal reaction conditions at 180 1C. The structures of both materials adopt the Bi(IO3)3 structure type. Crystallographic data are (MoKa, l 0.71073 A ): Gd(IO3)3, monoclinic, space group P21/n, a 8.7615(3) A , b 5.9081(2) A , c 15.1232(6) A , b 96.980(1)1, V 777.03(5) Z 4, R(F) 1.68% for 119 parameters with 1930 re ections with I42s(I); Er(IO3)3, monoclinic, space group P21/n, a 8.6885(7) A , b 5.9538(5) A , c 14.9664(12) A , b 97.054(1)1, V 768.4(1) Z 4, R(F) 2.26% for 119 parameters with 1894 re ections with I42s(I). In addition to structural studies, Gd(IO3)3, Er(IO3)3, and the isostructural Yb(IO3)3 were also characterized by Raman spectroscopy and magnetic property measurements. The results of the Raman studies indicated that the vibrational pro les are adequately sensitive to distinguish between the structures of the iodates reported here and other lanthanide iodate systems. The magnetic measurements indicate that only in Gd(IO3)3 did the 3+ lanthanide ion exhibit its full 7.9 mB Hund s rule moment; Er3+ and Yb3+ exhibited ground state moments and gap energy scales of 8.3 mB/70 K and 3.8 mB/160 K, respectively. Er(IO3)3 exhibited extremely weak ferromagnetic correlations (+0.4 K), while the magnetic ions in Gd(IO3)3 and Yb(IO3)3 were fully non-interacting within the resolution of our measurements ("'0.2 K).

  1. General lossless planar coupler design algorithms.

    PubMed

    Vance, Rod

    2015-08-01

    This paper reviews and extends two classes of algorithms for the design of planar couplers with any unitary transfer matrix as design goals. Such couplers find use in optical sensing for fading free interferometry, coherent optical network demodulation, and also for quantum state preparation in quantum optical experiments and technology. The two classes are (1) "atomic coupler algorithms" decomposing a unitary transfer matrix into a planar network of 2×2 couplers, and (2) "Lie theoretic algorithms" concatenating unit cell devices with variable phase delay sets that form canonical coordinates for neighborhoods in the Lie group U(N), so that the concatenations realize any transfer matrix in U(N). As well as review, this paper gives (1) a Lie theoretic proof existence proof showing that both classes of algorithms work and (2) direct proofs of the efficacy of the "atomic coupler" algorithms. The Lie theoretic proof strengthens former results. 5×5 couplers designed by both methods are compared by Monte Carlo analysis, which would seem to imply atomic rather than Lie theoretic methods yield designs more resilient to manufacturing imperfections. PMID:26367295

  2. Coordination chemistry of Si5Cl10 with organocyanides.

    PubMed

    Dai, Xuliang; Anderson, Kenneth J; Schulz, Douglas L; Boudjouk, Philip

    2010-12-14

    Organocyanides readily coordinate to decachlorocyclopentasilane (Si(5)Cl(10)) to form "inverse sandwich" compounds 1-3 with a planar Si(5) ring. The products were isolated in high yield and fully characterized by elemental analysis, multinuclear NMR, IR and UV-Vis spectroscopy. While the spectroscopic data suggests the presence of a fairly weak interaction between the Si(5) ring and the coordinative organocyanide ligands, single-crystal X-ray diffraction studies of compound 1 and 2 show μ(5)-coordination of the apical cyano nitrogen atoms to the silicon atoms in the Si(5) ring. Distances between silicon atoms and nitrogen atoms are significantly shorter than a Si-N van der Waals bond but longer than the sum of their covalent radii. Multiple interactions between the cyano groups and equatorial Cl atoms, and intermolecular interactions were observed in the solid state for both compounds 1 and 2. PMID:20967378

  3. Low Activation Joining of SiC/SiC Composites for Fusion Applications

    SciTech Connect

    Henager, Charles H.; Kurtz, Richard J.; Ferraris, Monica

    2011-06-30

    The use of SiC composites in fusion environments likely requires joining of plates using reactive joining or brazing. One promising reactive joining method uses solid-state displacement reactions between Si and TiC to produce Ti3SiC2 + SiC. We continue to explore the processing envelope for this joint for the Titan collaboration in order to produce optimal joints to undergo irradiation studies in HFIR. The TITAN collaboration has designed miniature torsion joints for preparation, testing, and irradiation in HFIR. PNNL synthesized 40 miniature torsion joints and several were tested for shear strength prior to irradiation testing in HFIR. The resulting tests indicated that 1) joint fixture alignment problems cause joint strengths to be lower than optimal, 2) that non-planar torsion test failures may limit the effectiveness of the miniature specimen design, and 3) that several joints that were well aligned had high shear strengths and promising mechanical properties. In summary, it appears that high joint strengths cause non-planar shear fracture and complicate strength analysis for miniature torsion specimens.

  4. Planar silicon nitride mid-infrared devices

    NASA Astrophysics Data System (ADS)

    Tai Lin, Pao; Singh, Vivek; Kimerling, Lionel; Murthy Agarwal, Anuradha

    2013-06-01

    Integrated mid-infrared devices including (i) straight/bent waveguides and (ii) directional couplers are demonstrated on silicon nitride (SiN) thin films prepared by optimized low-pressure chemical vapor deposition. The deposited SiN film has a broad spectral transparency from visible up to a wavelength of λ = 8.5 μm (as seen from Fourier transform infrared spectroscopy). Our SiN waveguide shows a dominant fundamental mode with an optical loss of 2.1 dB/cm at λ = 3.7 μm. In addition, we demonstrate an efficient SiN directional coupler between λ = 3.55 μm to λ = 3.75 μm where an 8 dB extinction ratio is achieved within each channel upon wavelength scanning. With the inherent advantage of complementary metal-oxide-semiconductor compatibility, our SiN platform paves the way to create sophisticated photonic circuits that are desired for mid-infrared nonlinear light generation and chip-scale biochemical sensors.

  5. Planar Particle Imaging Doppler Velocimetry Developed

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.

    2000-01-01

    Two current techniques exist for the measurement of planar, three-component velocity fields. Both techniques require multiple views of the illumination plane in order to extract all three velocity components. Particle image velocimetry (PIV) is a high-resolution, high accuracy, planar velocimetry technique that provides valuable instantaneous velocity information in aeropropulsion test facilities. PIV can provide three-component flow-field measurements using a two-camera, stereo viewing configuration. Doppler global velocimetry (DGV) is another planar velocimetry technique that can provide three component flow-field measurements; however, it requires three detector systems that must be located at oblique angles from the measurement plane. The three-dimensional configurations of either technique require multiple (DGV) or at least large (stereo PIV) optical access ports in the facility in which the measurements are being conducted. Optical access is extremely limited in aeropropulsion test facilities. In many cases, only one optical access port is available. A hybrid measurement technique has been developed at the NASA Glenn Research Center, planar particle image and Doppler velocimetry (PPIDV), which combines elements from both the PIV and DGV techniques into a single detection system that can measure all three components of velocity across a planar region of a flow field through a single optical access port. In the standard PIV technique, a pulsed laser is used to illuminate the flow field at two closely spaced instances in time, which are recorded on a "frame-straddling" camera, yielding a pair of single-exposure image frames. The PIV camera is oriented perpendicular to the light sheet, and the processed PIV data yield the two-component velocity field in the plane of the light sheet. In the standard DGV technique, an injection-seeded Nd:YAG pulsed laser light sheet illuminates the seeded flow field, and three receiver systems are used to measure three components

  6. Research on planar antennas and arrays - 'Structures Rayonnantes'

    NASA Astrophysics Data System (ADS)

    Daniel, J. P.; Dubost, G.; Terret, C.; Citerne, J.; Drissi, M.

    1993-02-01

    Radiating antenna structures related to flat and wire antennas developed by the laboratory 'Structures Rayonnantes' of the University of Rennes I (France) are discussed with emphasis on flat antennas and arrays studied during the last three years and on their typical applications. Particular attention is given to basic planar radiating sources including patches with coaxial or microstrip feed, printed slots, slot-fed patches, slot-loaded patches, and electromagnetic coupled dipoles and patches; planar arrays including planar phased and planar passive arrays and dual-beam printed antennas; and arrays of microstrip dipoles.

  7. Planarization of topography with spin-on carbon hard mask

    NASA Astrophysics Data System (ADS)

    Noya, Go; Hama, Yusuke; Ishii, Maki; Nakasugi, Shigemasa; Kudo, Takanori; Padmanaban, Munirathna

    2016-03-01

    Spin-on-carbon hard mask (SOC HM) has been used in semiconductor manufacturing since 45nm node as an alternative carbon hard mask process to chemical vapor deposition (CVD). As advancement of semiconductor to 2X nm nodes and beyond, multiple patterning technology is used and planarization of topography become more important and challenging ever before. In order to develop next generation SOC, one of focuses is planarization of topography. SOC with different concepts for improved planarization and the influence of thermal flow temperature, crosslink, film shrinkage, baking conditions on planarization and filling performance are described in this paper.

  8. Synthesis and Magnetic Properties of Gd Doped EuS Nanocrystals with Enhanced Curie Temperatures

    SciTech Connect

    Selinsky, Rachel S.; Han, Jae Hyo; Perez, Elvin A. Morales; Guzei, Ilia A.; Jin, Song

    2010-12-07

    EuS nanocrystals (NCs) were doped with Gd resulting in an enhancement of their magnetic properties. New EuS and GdS single source precursors (SSPs) were synthesized, characterized, and employed to synthesize Eu{sub 1-x}Gd{sub x}S NCs by decomposition in oleylamine and trioctylphosphine at 290 C. The doped NCs were characterized using X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, which support the uniform distribution of Gd dopants through electron energy loss spectroscopy (EELS) mapping. X-ray absorption spectroscopy (XAS) revealed the dopant ions in Eu{sub 1-x}Gd{sub x}S NCs to be predominantly Gd{sup 3+}. NCs with a variety of doping ratios of Gd (0 {le} x < 1) were systematically studied using vibrating sample magnetometry and the observed magnetic properties were correlated with the Gd doping levels (x) as quantified with ICP-AES. Enhancement of the Curie temperature (T{sub C}) was observed for samples with low Gd concentrations (x {le} 10%) with a maximum T{sub C} of 29.4 K observed for NCs containing 5.3% Gd. Overall, the observed T{sub C}, Weiss temperature ({theta}), and hysteretic behavior correspond directly to the doping level in Eu{sub 1-x}Gd{sub x}S NCs and the trends qualitatively follow those previously reported for bulk and thin film samples.

  9. Gd(III)-DOTA-modified sonosensitive liposomes for ultrasound-triggered release and MR imaging

    NASA Astrophysics Data System (ADS)

    Jung, Suk Hyun; Na, Kyunga; Lee, Seul A.; Cho, Sun Hang; Seong, Hasoo; Shin, Byung Cheol

    2012-08-01

    Ultrasound-sensitive (sonosensitive) liposomes for tumor targeting have been studied in order to increase the antitumor efficacy of drugs and decrease the associated severe side effects. Liposomal contrast agents having Gd(III) are known as a nano-contrast agent system for the efficient and selective delivery of contrast agents into pathological sites. The objective of this study was to prepare Gd(III)-DOTA-modified sonosensitive liposomes (GdSL), which could deliver a model drug, doxorubicin (DOX), to a specific site and, at the same time, be capable of magnetic resonance (MR) imaging. The GdSL was prepared using synthesized Gd(III)-DOTA-1,2-distearoyl- sn-glycero-3-phosphoethanolamine lipid. Sonosensitivity of GdSL to 20-kHz ultrasound induced 33% to 40% of DOX release. The relaxivities ( r 1) of GdSL were 6.6 to 7.8 mM-1 s-1, which were higher than that of MR-bester®. Intracellular uptake properties of GdSL were evaluated according to the intensity of ultrasound. Intracellular uptake of DOX for ultrasound-triggered GdSL was higher than that for non-ultrasound-triggered GdSL. The results of our study suggest that the paramagnetic and sonosensitive liposomes, GdSL, may provide a versatile platform for molecular imaging and targeted drug delivery.

  10. Synthesis and magnetic properties of Gd doped EuS nanocrystals with enhanced Curie temperatures.

    PubMed

    Selinsky, Rachel S; Han, Jae Hyo; Morales Pérez, Elvin A; Guzei, Ilia A; Jin, Song

    2010-11-17

    EuS nanocrystals (NCs) were doped with Gd resulting in an enhancement of their magnetic properties. New EuS and GdS single source precursors (SSPs) were synthesized, characterized, and employed to synthesize Eu(1-x)Gd(x)S NCs by decomposition in oleylamine and trioctylphosphine at 290 °C. The doped NCs were characterized using X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, which support the uniform distribution of Gd dopants through electron energy loss spectroscopy (EELS) mapping. X-ray absorption spectroscopy (XAS) revealed the dopant ions in Eu(1-x)Gd(x)S NCs to be predominantly Gd(3+). NCs with a variety of doping ratios of Gd (0 ≤ x < 1) were systematically studied using vibrating sample magnetometry and the observed magnetic properties were correlated with the Gd doping levels (x) as quantified with ICP-AES. Enhancement of the Curie temperature (T(C)) was observed for samples with low Gd concentrations (x ≤ 10%) with a maximum T(C) of 29.4 K observed for NCs containing 5.3% Gd. Overall, the observed T(C), Weiss temperature (θ), and hysteretic behavior correspond directly to the doping level in Eu(1-x)Gd(x)S NCs and the trends qualitatively follow those previously reported for bulk and thin film samples. PMID:20964293

  11. Electrical and optical characterization of green synthesized Gd2S3

    NASA Astrophysics Data System (ADS)

    Paul, Somnath; Sarkar, A.

    2016-05-01

    Gadolinium sulphide (Gd2S3) is a magnetic semiconductor with large band gap. Gd2S3 was synthesized following chemical and green techniques. Later process provides good stability of the nano clusters (NC) due to in-situ capping of Gd2S3 NC. It has been found that the optical band gap in Gd2S3 developed by green synthesis is lowered considerably over that in chemically synthesized Gd2S3. The green agencies used in this work are Jatropha Latex and dilute Garlic extract; both are enriched in sulphur and other organic polymer molecules. Simple observation shows that Gd2S3 NC retains residual magnetization. In this work optical and electrical characterization of the developed Gd2S3 specimens are carried out. The overall results obtained are good.

  12. Tuning optical and ferromagnetic properties of thin GdN films by nitrogen-vacancy centers

    NASA Astrophysics Data System (ADS)

    Vidyasagar, Reddithota; Kitayama, Shinya; Yoshitomi, Hiroaki; Kita, Takashi; Sakurai, Takahiro; Ohta, Hitoshi

    2013-02-01

    AlN/GdN/AlN double heterostructures were grown on c-sapphire substrates using a reactive rf sputtering method under high vacuum conditions. The optical absorption spectrum of the GdN shows a clear fundamental band edge of GdN around 800 nm; this transition is attributed to the minority spin band energy of GdN at the X point. Nitrogen vacancy centers cause a blue-shift of the optical band edge of GdN, which could be ascribed to both the band filling, and the electron-hole interactions resulting from the free carriers generated by nitrogen vacancies. Temperature-dependent magnetization measurements demonstrate a clear change in the magnetization values of GdN with respect to the N2 partial pressure. Nitrogen vacancy centers in the thin GdN film raise the Curie temperature from 31 K to 39 K, which has been accurately measured by the Arrott plots.

  13. Synthesis and characterization of the novel monoamide derivatives of Gd-TTDA.

    PubMed

    Wang, Yun-Ming; Li, Cha-Ru; Huang, Yu-Chin; Ou, Ming-Hung; Liu, Gin-Chung

    2005-01-24

    For this study, the N'-monoamide derivatives of TTDA (3,6,10-tri(carboxymethyl)-3,6,10-triazadodecanedioic acid), N'-methylamide (TTDA-MA), N'-benzylamide (TTDA-BA), and N'-2-methoxybenzylamide (TTDA-MOBA), were synthesized. Their protonation constants and stability constants (log K(ML)'s) formed with Ca(2+), Zn(2+), Cu(2+), and Gd(3+) were determined by potentiometric titration in 0.10 M Me(4)NCl at 25.0 +/- 0.1 degrees C. The relaxivity values of [Gd(TTDA-MA)](-), [Gd(TTDA-BA)](-), and [Gd(TTDA-MOBA)](-) remained constant with respect to pH changes over the range 4.5-12.0. The (17)O NMR chemical shift of H(2)O induced by [Dy(TTDA-MA)(H(2)O)](-) at pH 6.80 showed 0.9 inner-sphere water molecules. Water proton relaxivity values for [Gd(TTDA-MA)(H(2)O)](-), [Gd(TTDA-BA)(H(2)O)](-), and [Gd(TTDA-MOBA)(H(2)O)](-) at 37.0 +/- 0.1 degrees C and 20 MHz are 3.89, 4.21, and 4.25, respectively. The water-exchange lifetime (tau(M)) and rotational correlation time (tau(R)) of [Gd(TTDA-MA)(H(2)O)](-), [Gd(TTDA-BA)(H(2)O)](-), and [Gd(TTDA-MOBA)(H(2)O)](-) are obtained from reduced the (17)O relaxation rate and chemical shifts of H(2)(17)O. The (2)H NMR longitudinal relaxation rates of the deuterated diamagnetic lanthanum complexes for the rotational correlation time were also thoroughly investigated. The water-exchange rates (K(298)(ex) for [Gd(TTDA-MA)(H(2)O)](-), [Gd(TTDA-BA)(H(2)O)](-), and [Gd(TTDA-MOBA)(H(2)O)](-) are lower than that of [Gd(TTDA)(H(2)O)](2)(-) but significantly higher than those of [Gd(DTPA)(H(2)O)](2)(-) and [Gd(DTPA-BMA)(H(2)O)]. The rotational correlation times for [Gd(TTDA-BA)(H(2)O)](-) and [Gd(TTDA-MOBA)(H(2)O)](-) are significantly longer than those of [Gd(TTDA)(H(2)O)](2)(-) and [Gd(DTPA)(H(2)O)](2)(-) complexes. The marked increase of the relaxivity of [Gd(TTDA-BA)(H(2)O)](-) and [Gd(TTDA-MOBA)(H(2)O)](-) results mainly from their longer rotational correlation time. The noncovalent interaction between human serum albumin (HSA) and [Gd

  14. Sol-precipitation-hydrothermal synthesis and luminescence of GdPO4:Tb3+ submicron cubes

    NASA Astrophysics Data System (ADS)

    Cao, Yanyan; Sun, Peng; Liang, Yingmin; Wang, Rongrong; Zhang, Xiao

    2016-05-01

    GdPO4:Tb3+ submicron cubes were synthesized by a sol-precipitation-hydrothermal process. The XRD result indicated that GdPO4:Tb3+ submicron cubes have pure hexagonal phase. The SEM and TEM images confirmed the formation of cubic morphology. Under the excitation at 273 nm, GdPO4:Tb3+ submicron cubes show emission bands corresponding to Gd3+ and Tb3+. With the increasing Tb3+ concentration, the emission intensities originating from Gd3+ and 5D3 → 7Fj transition of Tb3+ decrease, but the emission intensities originating from 5D4 → 7Fj transition of Tb3+ increase. These results suggested energy transfer from Gd3+ to Tb3+ and the occurrence of cross-relaxation processes in GdPO4:Tb3+ submicron cubes.

  15. Materials Data on Gd(SiIr)2 (SG:139) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Materials Data on GdSi2 (SG:141) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  17. Materials Data on Gd(SiPd)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  18. Materials Data on Gd(SiCu)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  19. Materials Data on Gd(MnSi)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Materials Data on GdSiRu (SG:129) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Materials Data on Gd(SiPt)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  2. Materials Data on Gd(SiOs)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on Gd2Al6Si4Pt (SG:166) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on Gd(SiRh)2 (SG:139) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on GdSi2Rh3 (SG:191) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Materials Data on GdMnSi (SG:129) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Assessing the potential roles of silicon and germanium phthalocyanines in planar heterojunction organic photovoltaic devices and how pentafluoro phenoxylation can enhance π-π interactions and device performance.

    PubMed

    Lessard, Benoît H; White, Robin T; Al-Amar, Mohammad; Plint, Trevor; Castrucci, Jeffrey S; Josey, David S; Lu, Zheng-Hong; Bender, Timothy P

    2015-03-11

    In this study, we have assessed the potential application of dichloro silicon phthalocyanine (Cl2-SiPc) and dichloro germanium phthalocyanine (Cl2-GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. We have determined that Cl2-SiPc can act as an electron donating material when paired with C60 and that Cl2-SiPc or Cl2-GePc can also act as an electron acceptor material when paired with pentacene. These two materials enabled the harvesting of triplet energy resulting from the singlet fission process in pentacene. However, contributions to the generation of photocurrent were observed for Cl2-SiPc with no evidence of photocurrent contribution from Cl2-GePc. The result of our initial assessment established the potential for the application of SiPc and GePc in PHJ OPV devices. Thereafter, bis(pentafluoro phenoxy) silicon phthalocyanine (F10-SiPc) and bis(pentafluoro phenoxy) germanium phthalocyanine (F10-GePc) were synthesized and characterized. During thermal processing, it was discovered that F10-SiPc and F10-GePc underwent a reaction forming small amounts of difluoro SiPc (F2-SiPc) and difluoro GePc (F2-GePc). This undesirable reaction could be circumvented for F10-SiPc but not for F10-GePc. Using single crystal X-ray diffraction, it was determined that F10-SiPc has significantly enhanced π-π interactions compared with that of Cl2-SiPc, which had little to none. Unoptimized PHJ OPV devices based on F10-SiPc were fabricated and directly compared to those constructed from Cl2-SiPc, and in all cases, PHJ OPV devices based on F10-SiPc had significantly improved device characteristics compared to Cl2-SiPc. PMID:25665015

  8. Gd(III)-Gd(III) EPR distance measurements--the range of accessible distances and the impact of zero field splitting.

    PubMed

    Dalaloyan, Arina; Qi, Mian; Ruthstein, Sharon; Vega, Shimon; Godt, Adelheid; Feintuch, Akiva; Goldfarb, Daniella

    2015-07-28

    Gd(III) complexes have emerged as spin labels for distance determination in biomolecules through double-electron-electron resonance (DEER) measurements at high fields. For data analysis, the standard approach developed for a pair of weakly coupled spins with S = 1/2 was applied, ignoring the actual properties of Gd(III) ions, i.e. S = 7/2 and ZFS (zero field splitting) ≠ 0. The present study reports on a careful investigation on the consequences of this approach, together with the range of distances accessible by DEER with Gd(III) complexes as spin labels. The experiments were performed on a series of specifically designed and synthesized Gd-rulers (Gd-PyMTA-spacer-Gd-PyMTA) covering Gd-Gd distances of 2-8 nm. These were dissolved in D2O-glycerol-d8 (0.03-0.10 mM solutions) which is the solvent used for the corresponding experiments on biomolecules. Q- and W-band DEER measurements, followed by data analysis using the standard data analysis approach, used for S = 1/2 pairs gave the distance-distribution curves, of which the absolute maxima agreed very well with the expected distances. However, in the case of the short distances of 2.1 and 2.9 nm, the distance distributions revealed additional peaks. These are a consequence of neglecting the pseudo-secular term in the dipolar Hamiltonian during the data analysis, as is outlined in a theoretical treatment. At distances of 3.4 nm and above, disregarding the pseudo-secular term leads to a broadening of a maximum of 0.4 nm of the distance-distribution curves at half height. Overall, the distances of up to 8.3 nm were determined, and the long evolution time of 16 μs at 10 K indicates that a distance of up to 9.4 nm can be accessed. A large distribution of the ZFS parameter, D, as is found for most Gd(III) complexes in a frozen solution, is crucial for the application of Gd(III) complexes as spin labels for distance determination via Gd(III)-Gd(III) DEER, especially for short distances. The larger ZFS of Gd-PyMTA, in

  9. Water Permeability of Asymmetric Planar Lipid Bilayers

    PubMed Central

    Krylov, Andrey V.; Pohl, Peter; Zeidel, Mark L.; Hill, Warren G.

    2001-01-01

    To understand how plasma membranes may limit water flux, we have modeled the apical membrane of MDCK type 1 cells. Previous experiments demonstrated that liposomes designed to mimic the inner and outer leaflet of this membrane exhibited 18-fold lower water permeation for outer leaflet lipids than inner leaflet lipids (Hill, W.G., and M.L. Zeidel. 2000. J. Biol. Chem. 275:30176–30185), confirming that the outer leaflet is the primary barrier to permeation. If leaflets in a bilayer resist permeation independently, the following equation estimates single leaflet permeabilities: 1/PAB = 1/PA + 1/PB (Eq. l), where PAB is the permeability of a bilayer composed of leaflets A and B, PA is the permeability of leaflet A, and PB is the permeability of leaflet B. Using for the MDCK leaflet–specific liposomes gives an estimated value for the osmotic water permeability (Pf) of 4.6 × 10−4 cm/s (at 25°C) that correlated well with experimentally measured values in intact cells. We have now constructed both symmetric and asymmetric planar lipid bilayers that model the MDCK apical membrane. Water permeability across these bilayers was monitored in the immediate membrane vicinity using a Na+-sensitive scanning microelectrode and an osmotic gradient induced by addition of urea. The near-membrane concentration distribution of solute was used to calculate the velocity of water flow (Pohl, P., S.M. Saparov, and Y.N. Antonenko. 1997. Biophys. J. 72:1711–1718). At 36°C, Pf was 3.44 ± 0.35 × 10−3 cm/s for symmetrical inner leaflet membranes and 3.40 ± 0.34 × 10−4 cm/s for symmetrical exofacial membranes. From , the estimated permeability of an asymmetric membrane is 6.2 × 10−4 cm/s. Water permeability measured for the asymmetric planar bilayer was 6.7 ± 0.7 × 10−4 cm/s, which is within 10% of the calculated value. Direct experimental measurement of Pf for an asymmetric planar membrane confirms that leaflets in a bilayer offer independent and additive resistances to

  10. MCM Polarimetric Radiometers for Planar Arrays

    NASA Technical Reports Server (NTRS)

    Kangaslahti, Pekka; Dawson, Douglas; Gaier, Todd

    2007-01-01

    A polarimetric radiometer that operates at a frequency of 40 GHz has been designed and built as a prototype of multiple identical units that could be arranged in a planar array for scientific measurements. Such an array is planned for use in studying the cosmic microwave background (CMB). All of the subsystems and components of this polarimetric radiometer are integrated into a single multi-chip module (MCM) of substantially planar geometry. In comparison with traditional designs of polarimetric radiometers, the MCM design is expected to greatly reduce the cost per unit in an array of many such units. The design of the unit is dictated partly by a requirement, in the planned CMB application, to measure the Stokes parameters I, Q, and U of the CMB radiation with high sensitivity. (A complete definition of the Stokes parameters would exceed the scope of this article. In necessarily oversimplified terms, I is a measure of total intensity of radiation, while Q and U are measures of the relationships between the horizontally and vertically polarized components of radiation.) Because the sensitivity of a single polarimeter cannot be increased significantly, the only way to satisfy the high-sensitivity requirement is to make a large array of polarimeters that operate in parallel. The MCM includes contact pins that can be plugged into receptacles on a standard printed-circuit board (PCB). All of the required microwave functionality is implemented within the MCM; any required supporting non-microwave ("back-end") electronic functionality, including the provision of DC bias and control signals, can be implemented by standard PCB techniques. On the way from a microwave antenna to the MCM, the incoming microwave signal passes through an orthomode transducer (OMT), which splits the radiation into an h + i(nu) beam and an h - i(nu) beam (where, using complex-number notation, h denotes the horizontal component, nu denotes the vertical component, and +/-i denotes a +/-90deg phase

  11. Ultrasensitive Si phototransistors with a punchthrough base

    SciTech Connect

    Luo, Hailin; Chang, Yuchun; Wong, K. S.; Wang, Y.

    2001-08-06

    Si phototransistors with a punchthrough base were fabricated with regular planar technology. Optical conversion gains larger than 15000 were observed. In addition to very high gain, the unique structure of the device also resulted in a fast transient response as well as low output noise. The measured full width at half maximum of the device transient response is 1.6 ns and a -3 dB bandwidth of 300 MHz. The measured output noises at different currents can be well fitted by the relation i{sub n}{sup 2}=2qI{sub C}. {copyright} 2001 American Institute of Physics.

  12. Rare-earth metal gallium silicides via the gallium self-flux method. Synthesis, crystal structures, and magnetic properties of RE(Ga1-xSix)2 (RE=Y, La-Nd, Sm, Gd-Yb, Lu)

    NASA Astrophysics Data System (ADS)

    Darone, Gregory M.; Hmiel, Benjamin; Zhang, Jiliang; Saha, Shanta; Kirshenbaum, Kevin; Greene, Richard; Paglione, Johnpierre; Bobev, Svilen

    2013-05-01

    Fifteen ternary rare-earth metal gallium silicides have been synthesized using molten Ga as a molten flux. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with three different structures—the early to mid-late rare-earth metals RE=La-Nd, Sm, Gd-Ho, Yb and Y form compounds with empirical formulae RE(GaxSi1-x)2 (0.38≤x≤0.63), which crystallize with the tetragonal α-ThSi2 structure type (space group I41/amd, No. 141; Pearson symbol tI12). The compounds of the late rare-earth crystallize with the orthorhombic α-GdSi2 structure type (space group Imma, No. 74; Pearson symbol oI12), with refined empirical formula REGaxSi2-x-y (RE=Ho, Er, Tm; 0.33≤x≤0.40, 0.10≤y≤0.18). LuGa0.32(1)Si1.43(1) crystallizes with the orthorhombic YbMn0.17Si1.83 structure type (space group Cmcm, No. 63; Pearson symbol oC24). Structural trends are reviewed and analyzed; the magnetic susceptibilities of the grown single-crystals are presented.

  13. Metamodels for Planar 3R Workspace Optimization.

    SciTech Connect

    Turner, C. J.

    2002-01-01

    Robotic workspace optimization is a central element of robot system design. To formulate the optimization problem, the complex relationships between design variables, tuning parameters, and performance indices need to be accurately and efficiently represented. The nature of the relationships suggests that metamodels, or models of the models, should be used to derive suitable objective functions. A comparison of two metamodeling techniques for robotic workspace optimization problems for several trial cases suggests that non-uniform rational B-spline models, derived from computer graphics and computer-aided design techniques, are as suitable as response surface models to solve planar 3R workspace optimization problems. Promising nonlinear modeling results with B-spline models suggest future work is justified and performance gains can be realized.

  14. Development of Osaka gas type planar SOFC

    SciTech Connect

    Iha, M.; Shiratori, A.; Chikagawa, O.

    1996-12-31

    Osaka Gas Co. has been developing a planar type SOFC (OG type SOFC) which has a suitable structure for stacking. Murata Mfg. Co. has begun to develop the OG type SOFC stack through joint program since 1993. Figure 1 shows OG type cell structure. Because each cell is sustained by cell holders acting air manifold, the load of upper cell is not put on the lower cells. Single cell is composed of 3-layered membrane and LaCrO{sub 3} separator. 5 single cells are mounted on the cell holder, connected with Ni felt electrically, and bonded by glassy material sealant. We call the 5-cell stack a unit. Stacking 13 units, we succeeded 870 W generation in 1993. But the power density was low, 0.11 Wcm{sup -2} because of crack in the electrolyte and gas leakage at some cells.

  15. Planarity of nitro-substituted phenothiazines.

    PubMed

    Brock, C P; DeLaLuz, P J; Golinski, M; Lloyd, M A; Vanaman, T C; Watt, D S

    1996-08-01

    The structures of three nitro-substituted phenothiazines [1,3,4-trifluoro-2-nitrophenothiazine, 10-(4-chlorobutyl)-1,3,4-trifluoro-2-nitrophenothiazine and 10-(4-chlorobutyl)-3-nitrophenothiazine] have been determined. The first of these red compounds forms infinite stacks in the solid state, in which donor and acceptor regions of the approximately planar molecules alternate. The molecules of the other two compounds, which have folded, or 'butterfly', conformations in the solid state, do not form stacks, presumably because the bulky chlorobutyl substituents cannot be accommodated. The very dark color of solid 3-nitrophenothiazine suggests the presence of extended molecular stacks, but crystals suitable for a structure determination could not be obtained. PMID:8810494

  16. Planar-constructed spatial micro-stage

    DOEpatents

    Jokiel, Jr., Bernhard; Benavides, Gilbert L.; Bieg, Lothar F.; Allen, James J.

    2004-01-13

    A multiple degree of freedom platform assembly formed from a plurality of thin films on a substrate can, when activated, move out of the plane of the substrate without additional manufacturing steps. The platform is connected to the substrate by at least three linkages, each linkage being pivotally connected to the platform and the base. At least two of the base connections are to powered traveling devices that are manufactured at one end of a path and which may be moved to locations along the path to cause the platform to move to predetermined positions. The entire assembly, including hinges, is manufactured as planar structures; preferably by a thin film technology such as MEMS.

  17. Multi-axis planar slide system

    DOEpatents

    Bieg, Lothar F.

    2002-01-01

    An apparatus for positioning an item that provides two-dimensional, independent orthogonal motion of a platform in a X-Y plane. A pair of master and slave disks engages opposite sides of the platform. Rotational drivers are connected to master disks so the disks rotate eccentrically about axes of rotation. Opposing slave disks are connected to master disks on opposite sides of the platform by a timing belt, or are electronically synchronized together using stepper motors, to effect coordinated motion. The coordinated eccentric motion of the pairs of master/slave disks compels smooth linear motion of the platform in the X-Y plane without backlash. The apparatus can be a planar mechanism implemented in a MEMS device.

  18. Photonic bandgap structures in planar waveguides.

    PubMed

    Ctyroký, J

    2001-02-01

    If a one-dimensional (1D) or two-dimensional (2D) photonic bandgap (PBG) structure is incorporated into a planar optical waveguide, the refractive-index nonuniformity in the direction perpendicular to the waveguide plane responsible for waveguiding may affect its behavior detrimentally. Such influence is demonstrated in the paper by numerical modeling of a deeply etched first-order waveguide Bragg grating. On the basis of physical considerations, a simple condition for the design of 1D and 2D waveguide PBG structures free of this degradation is formulated; it is, in fact the separability condition for the wave equation. Its positive effect is verified by numerical modeling of a modified waveguide Bragg grating that fulfills the separability condition. PMID:11205991

  19. Electrodynamics of planar Archimedean spiral resonator

    NASA Astrophysics Data System (ADS)

    Maleeva, N.; Averkin, A.; Abramov, N. N.; Fistul, M. V.; Karpov, A.; Zhuravel, A. P.; Ustinov, A. V.

    2015-07-01

    We present a theoretical and experimental study of electrodynamics of a planar spiral superconducting resonator of a finite length. The resonator is made in the form of a monofilar Archimedean spiral. By making use of a general model of inhomogeneous alternating current flowing along the resonator and specific boundary conditions on the surface of the strip, we obtain analytically the frequencies fn of resonances which can be excited in such system. We also calculate corresponding inhomogeneous RF current distributions ψ n ( r ) , where r is the coordinate across a spiral. We show that the resonant frequencies and current distributions are well described by simple relationships f n = f 1 n and ψ n ( r ) ≃ sin [ π n ( r / R e ) 2 ] , where n = 1 , 2... and Re is the external radius of the spiral. Our analysis of electrodynamic properties of spiral resonators' is in good agreement with direct numerical simulations and measurements made using specifically designed magnetic probe and laser scanning microscope.

  20. Planar optics with patterned chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Kobashi, Junji; Yoshida, Hiroyuki; Ozaki, Masanori

    2016-06-01

    Reflective metasurfaces based on metallic and dielectric nanoscatterers have attracted interest owing to their ability to control the phase of light. However, because such nanoscatterers require subwavelength features, the fabrication of elements that operate in the visible range is challenging. Here, we show that chiral liquid crystals with a self-organized helical structure enable metasurface-like, non-specular reflection in the visible region. The phase of light that is Bragg-reflected off the helical structure can be controlled over 0–2π depending on the spatial phase of the helical structure; thus planar elements with arbitrary reflected wavefronts can be created via orientation control. The circular polarization selectivity and external field tunability of Bragg reflection open a wide variety of potential applications for this family of functional devices, from optical isolators to wearable displays.

  1. Organic hybrid planar-nanocrystalline bulk heterojunctions

    DOEpatents

    Forrest, Stephen R.; Yang, Fan

    2011-03-01

    A photosensitive optoelectronic device having an improved hybrid planar bulk heterojunction includes a plurality of photoconductive materials disposed between the anode and the cathode. The photoconductive materials include a first continuous layer of donor material and a second continuous layer of acceptor material. A first network of donor material or materials extends from the first continuous layer toward the second continuous layer, providing continuous pathways for conduction of holes to the first continuous layer. A second network of acceptor material or materials extends from the second continuous layer toward the first continuous layer, providing continuous pathways for conduction of electrons to the second continuous layer. The first network and the second network are interlaced with each other. At least one other photoconductive material is interspersed between the interlaced networks. This other photoconductive material or materials has an absorption spectra different from the donor and acceptor materials.

  2. Organic hybrid planar-nanocrystalline bulk heterojunctions

    DOEpatents

    Forrest, Stephen R.; Yang, Fan

    2013-04-09

    A photosensitive optoelectronic device having an improved hybrid planar bulk heterojunction includes a plurality of photoconductive materials disposed between the anode and the cathode. The photoconductive materials include a first continuous layer of donor material and a second continuous layer of acceptor material. A first network of donor material or materials extends from the first continuous layer toward the second continuous layer, providing continuous pathways for conduction of holes to the first continuous layer. A second network of acceptor material or materials extends from the second continuous layer toward the first continuous layer, providing continuous pathways for conduction of electrons to the second continuous layer. The first network and the second network are interlaced with each other. At least one other photoconductive material is interspersed between the interlaced networks. This other photoconductive material or materials has an absorption spectra different from the donor and acceptor materials.

  3. A planar quasi-optical SIS receiver

    NASA Technical Reports Server (NTRS)

    Stimson, Philip A.; Dengler, Robert J.; Leduc, Henry G.; Cypher, Scott R.; Siegel, Peter H.

    1993-01-01

    A planar, quasi-optical SIS receiver operating at 230 GHz is described. The receiver consists of a 2 x 5 array of half wave dipole antennas with ten niobium-aluminum oxide-niobium SIS junctions on a quartz dielectric-filled parabola. The 1.4 GHz intermediate frequency is coupled from the mixer via coplanar strip transmission lines and 4:1 balun transformers. The receiver is operated at 4.2 K in a liquid helium immersion cryostat. We report accurate measurements of the performance of single receiver elements. A mixer noise temperature of 89 K DSB, receiver noise temperature of 156 K DSB, and conversion loss of 3 dB into a matched load have been obtained.

  4. Exact formation of hairy planar black holes

    NASA Astrophysics Data System (ADS)

    Fan, Zhong-Ying; Chen, Bin

    2016-04-01

    We consider Einstein gravity minimally coupled to a scalar field with a given potential in general dimensions. We obtain large classes of static hairy planar black holes which are asymptotic to anti-de Sitter (AdS) space-times. In particular, for a special case μ =(n -2 )/2 , we obtain new classes of exact dynamical solutions describing black hole formation. We find there are two classes of collapse solutions. The first class of solutions describes the evolution start from AdS space-time with a naked singularity at the origin. The space-time is linearly unstable and evolves into stationary black hole states even under small perturbation. The second class of solutions describes the space-time spontaneously evolving from AdS vacua into stationary black hole states undergoing nonlinear instability. We also discuss the global properties of all these dynamical solutions.

  5. Planar dipolar polymer brush: field theoretical investigations

    NASA Astrophysics Data System (ADS)

    Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby

    2015-03-01

    Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.

  6. Photoemission spectroscopy of planar and nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Gervasoni, J. L.

    2016-02-01

    In this paper, I present some results for the process of excitation of bulk and surface plasmons during the emission of electrons in the proximity of surfaces of different shapes and dimensions. I describe in detail the effects due to the interaction between an electron and a stationary positive ion (or atomic hole) in the neighborhood of a metallic surface, paying special attention to the results obtained by my research group. We used the dielectric response of the metal and the specular reflection model for the case of planar surfaces, and the second quantization theory for nanostructured surfaces. In particular, we studied how the electron-hole pair interaction can influence the energy loss of the emerging electron. We investigated the importance of surface effects in the analysis of photoelectron spectroscopy. The method described here is useful for studying multiple plasmon excitations in nanostructures and for understanding the excited electron spectra of these nanostructures (different from those of the same bulk material).

  7. Planar electrostatic gradiometer for airborne geodesy

    NASA Astrophysics Data System (ADS)

    Foulon, B.; Christophe, B.; Lebat, V.; Boulanger, D.

    2011-12-01

    The knowledge of the gravity field of the Earth has been considerably improved for the last decades, thanks to satellites, in particular, both for gravity measurements and positioning. Gravity, and especially gravity gradiometry data are then of great interest to the study of the structure of the continental margins. Space gravity measurements, in particular with the GOCE satellite in orbit since 2009, provide an absolute gravity reference and should contribute to estimate the systematic effects that would affect the surface datasets. But the spatial resolution of those data essentially addresses the large and medium wavelengths of the field (down to a resolution of 90km) and it is therefore essential to complete them at the shorter wavelengths in particular in the littoral area. To this aim, gravity gradiometry systems may be particularly suitable by covering the land/sea transition zone with a uniform precision, and a spatial resolution higher than from gravimetry. The GREMLIT instrument is taking advantage of technologies, formerly developed by ONERA for the GRACE and GOCE space missions, by adapting them to an airborne environment, using a planar configuration for the gradiometer and designing and building a dedicated stabilized platform controlled by the common mode outputs of the instrument itself similarly to the drag free control of the GOCE satellite. The mains interests of the planar configuration are: - its definition, optimized for levitation in the Earth's gravity field ; - its intrinsic linearity, which minimizes the aliasing due to high frequency vibrations or motions generated outside the measurement bandwidth ; - its compactness, ensuring an excellent dimensional stability, a better thermal homogeneity and making the realization of the decoupling platform easier. The performance objective is 0.1 Eötvös. This lowered performance level with respect to a one hundred times better GOCE-type instrument, takes into account the difficulty of measurements

  8. Polymer planar Bragg grating for sensing applications

    NASA Astrophysics Data System (ADS)

    Rosenberger, M.; Hartlaub, N.; Koller, G.; Belle, S.; Schmauss, B.; Hellmann, R.

    2013-05-01

    Bragg gratings have become indispensable as optical sensing elements and are already used for a variety of technical applications. Mainly silica fiber Bragg gratings (FBGs) have been extensively studied over the last decades and are nowadays commercially available. Bragg grating sensors consisting of other materials like polymers, however, have only recently come into the focus of fundamental and applied research. Polymers exhibit significantly different properties advantageous for many sensing applications and therefore provide a good alternative to silica based devices. In addition, polymer materials are inexpensive, simple to handle as well as available in various forms like liquid resists or bulk material. Accordingly, polymer integrated optics attract increasing interest and can serve as a substitute for optical fibers. We report on the fabrication of a planar Bragg grating sensor in bulk Polymethylmethacrylate (PMMA). The sensor consists of an optical waveguide and a Bragg grating, both written simultaneously into a PMMA chip by a single writing step, for which a phase mask covered by an amplitude mask is placed on top of the PMMA and exposed to the UV radiation of a KrF excimer laser. Depending on the phase mask period, different Bragg gratings reflecting in the telecommunication wavelength range are fabricated and characterized. Reflection and transmission measurements show a narrow reflection band and a high reflectivity of the polymer planar Bragg grating (PPBG). After connecting to a single mode fiber, the portable PPBG based sensor was evaluated for different measurands like humidity and strain. The sensor performance was compared to already existing sensing systems. Due to the obtained results as well as the rapid and cheap fabrication of the sensor chip, the PPBG qualifies for a low cost sensing element.

  9. Unsteady planar diffusion flames: Ignition, travel, burnout

    NASA Technical Reports Server (NTRS)

    Fendell, F.; Wu, F.

    1995-01-01

    In microgravity, a thin planar diffusion flame is created and thenceforth travels so that the flame is situated at all times at an interface at which the hydrogen and oxygen meet in stoichiometric proportion. If the initial amount of hydrogen is deficient relative to the initial amount of oxygen, then the planar flame will travel further and further into the half volume initially containing hydrogen, until the hydrogen is (virtually) fully depleted. Of course, when the amount of residual hydrogen becomes small, the diffusion flame is neither vigorous nor thin; in practice, the flame is extinguished before the hydrogen is fully depleted, owing to the finite rate of the actual chemical-kinetic mechanism. The rate of travel of the hydrogen-air diffusion flame is much slower than the rate of laminar flame propagation through a hydrogen-air mixture. This slow travel facilitates diagnostic detection of the flame position as a function of time, but the slow travel also means that the time to burnout (extinction) probably far exceeds the testing time (typically, a few seconds) available in earth-sited facilities for microgravity-environment experiments. We undertake an analysis to predict (1) the position and temperature of the diffusion flame as a function of time, (2) the time at which extinction of the diffusion flame occurs, and (3) the thickness of quench layers formed on side walls (i.e., on lateral boundaries, with normal vectors parallel to the diffusion-flame plane), and whether, prior to extinction, water vapor formed by burning will condense on these cold walls.

  10. Gd-DTPA Adsorption on Chitosan/Magnetite Nanocomposites.

    PubMed

    Pylypchuk, Ie V; Kołodyńska, D; Kozioł, M; Gorbyk, P P

    2016-12-01

    The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods. PMID:27030468

  11. Growth and properties of epitaxial GdN

    SciTech Connect

    Ludbrook, B. M.; Kuebel, M.; Ruck, B. J.; Preston, A. R. H.; Trodahl, H. J.; Farrell, I. L.; Reeves, R. J.; Durbin, S. M.; Ranno, L.

    2009-09-15

    Epitaxial gadolinium nitride films with well-oriented crystallites of up to 30 nm have been grown on yttria-stabilized zirconia substrates using a plasma-assisted pulsed laser deposition technique. We observe that the epitaxial GdN growth proceeds on top of a gadolinium oxide buffer layer that forms via reaction between deposited Gd and mobile oxygen from the substrate. Hall effect measurements show the films are electron doped to degeneracy, with carrier concentrations of 4x10{sup 20} cm{sup -3}. Magnetic measurements establish a T{sub C} of 70 K with a coercive field that can be tuned from 200 Oe to as low as 10 Oe.

  12. Carrier-dependent magnetic anisotropy of Gd-adsorbed graphene

    NASA Astrophysics Data System (ADS)

    Lu, Yuan; Zhou, Tie-ge; Shao, Bin; Zuo, Xu; Feng, Min

    2016-05-01

    Using first-principles calculation based on density functional theory, we study the magnetic anisotropy of Gd-adsorbed graphene and its dependence on carrier accumulation. We show that carrier accumulation not only impacts the magnitude of magnetic anisotropy but also switches its sign. Hole accumulation enhances the perpendicular anisotropy up to ˜16 meV per Gd atom, while electron accumulation switches the anisotropy from perpendicular to in-plane direction. Moreover, we find that the first order perturbation of spin-orbit coupling interaction induces a pseudo-gap at Γ for the perpendicular magnetization, which leads to the the anomalous magnetic anisotropy for the neutral composite. Our findings pave the way for magneto-electric materials based on rare-earth-decorated graphene for voltage-controlled spintronics.

  13. Thermally induced magnetization switching in Gd/Fe multilayers

    NASA Astrophysics Data System (ADS)

    Xu, C.; Ostler, T. A.; Chantrell, R. W.

    2016-02-01

    A theoretical model of Gd/Fe multilayers is constructed using the atomistic spin dynamics formalism. By varying the thicknesses and number of layers we have shown that a strong dependence of the energy required for thermally induced magnetization switching (TIMS) is present; with a larger number of interfaces, lower energy is required. The results of the layer resolved dynamics show that the reversal process of the multilayered structures, similar to that of a GdFeCo alloy, is driven by the antiferromagnetic interaction between the transition-metal and rare-earth components. Finally, while the presence of the interface drives the reversal process, we show here that the switching process does not initiate at the surface but from the layers furthest from it, a departure from the alloy behavior which expands the classes of material types exhibiting TIMS.

  14. Ground state and constrained domain walls in Gd /Fe multilayers

    NASA Astrophysics Data System (ADS)

    Van Aken, Bas B.; Prieto, José L.; Mathur, Neil D.

    2005-03-01

    The magnetic ground state of antiferromagnetically coupled Gd /Fe multilayers and the evolution of in-plane domain walls is modeled with micromagnetics. The twisted state is characterized by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios MFe:MGd, the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio MFe:MGd but also by the thicknesses of the layers; that is by the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe-aligned and the Gd-aligned state in favor of the twisted state. On the other hand, ultrathin layers exclude the twisted state, since wider domain walls cannot form in these ultrathin layers.

  15. Structure of Gd2O3 nanoparticles at high temperature

    NASA Astrophysics Data System (ADS)

    Jamnezhad, H.; Jafari, M.

    2016-06-01

    The present study aimed to investigate the structure of Gd2O3 nanoparticles by X-ray diffraction between 25 °C and 1000 °C and compare it with the bulk sample. For the nanoparticles at room temperature, the structure was monoclinic; with an increase in temperature, mixed phases containing the monoclinic and cubic phases were observe between 500 °C and 1000 °C, whereas the bulk sample was transformed from cubic (at room temperature) into hexagonal structures at high pressure. The trends observed for nanoparticles and bulk materials may be different. The scanning electron microscope (SEM) analyses confirmed the existence of Gd2O3 nanoparticles. Moreover, since this material has the magnetic properties, especially during the phase transition, so it was one of the point of our attention in this paper.

  16. Amplitude Modulation in the ZZ Ceti Star GD 244

    NASA Astrophysics Data System (ADS)

    Bognár, Zs.; Paparó, M.; Molnár, L.; Plachy, E.; Sódor, Á.

    2015-06-01

    Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation of the long-term pulsational behaviour of GD 244. We found that the 307.1 s period component of one of the doublets show long-term, periodic amplitude modulation with a time scale of ˜ 740 days. Possible explanations are that nonlinear resonant mode coupling is operating among the rotationally split frequency components, or two modes, unresolved in the yearly data are excited at ˜ 307.1 s. This is the first time that such long-term periodic amplitude modulation is published on a ZZ Ceti star.

  17. Current status of SK-Gd project and EGADS

    NASA Astrophysics Data System (ADS)

    Xu, Chenyuan; Super-Kamiokande Collaboration

    2016-05-01

    Supernova Relic Neutrino (SRN) has not been observed yet because of its low event rate and high background. By adding gadolinium into water Cherenkov detector, inverse beta decay will have two signals, the prompt one is positron signal and the delayed one is a ~8 MeV gamma cascade from neutron capture on gadolinium. By this way, background for SRN can be largely reduced by detecting prompt and delayed signals coincidently, and Super-K will also have the ability to distinguish neutrino and anti-neutrino. SK-Gd is a R&D project proposed to dissolve gadolinium into Super-K. As a part of it, EGADS, a 200 ton water Cherenkov detector was built in Kamioka mine. Current status of SK-Gd project and the physics work being performed in EGADS will be presented here.

  18. Gd-DTPA Adsorption on Chitosan/Magnetite Nanocomposites

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie. V.; Kołodyńska, D.; Kozioł, M.; Gorbyk, P. P.

    2016-03-01

    The synthesis of the chitosan/magnetite nanocomposites is presented. Composites were prepared by co-precipitation of iron(II) and iron(III) salts by aqueous ammonia in the 0.1 % chitosan solution. It was shown that magnetite synthesis in the chitosan medium does not affect the magnetite crystal structure. The thermal analysis data showed 4.6 % of mass concentration of chitosan in the hybrid chitosan/magnetite composite. In the concentration range of initial Gd-DTPA solution up to 0.4 mmol/L, addition of chitosan to magnetite increases the adsorption capacity and affinity to Gd-DTPA complex. The Langmuir and Freundlich adsorption models were applied to describe adsorption processes. Nanocomposites were characterized by scanning electron microscopy (SEM), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and specific surface area determination (ASAP) methods.

  19. Electronic structure, magnetism, and Fermi surfaces of Gd and Tb

    NASA Astrophysics Data System (ADS)

    Ahuja, R.; Auluck, S.; Johansson, B.; Brooks, M. S. S.

    1994-08-01

    We report on local-spin-density calculations for the ferromagnetic rare-earth metals Gd and Tb using the relativistic first-principles linear-muffin-tin-orbital method in the atomic-sphere approximation. We have used a method which treats simultaneously the localized 4f and the conduction-electron spin magnetism. The 4f magnetic moments are obtained from the Russel-Saunders scheme but the radial 4f spin density is a part of the self-consistent density-functional calculations. The calculated conduction-electron moment for Gd is in very good agreement with the measured value. The calculated de Haas-von Alphen frequencies are in agreement with available data.

  20. Semi-Euclidean quasi-elliptic planar motion

    NASA Astrophysics Data System (ADS)

    Bekar, Murat; Yayli, Yusuf

    2016-06-01

    The aim of this paper is to study the algebra of split semi-quaternions with their basic properties. Also, the results of the Euclidean planar motion given by Blaschke and Grünwald is generalized to semi-Euclidean planar motion by using the algebra of split semi-quaternions.

  1. Beam-pointing errors of planar-phased arrays.

    NASA Technical Reports Server (NTRS)

    Carver, K. R.; Cooper, W. K.; Stutzman, W. L.

    1973-01-01

    Using both analytical and Monte Carlo techniques, beam-pointing errors of planar-phased arrays are analyzed. The obtained simple formulas for rms pointing errors are applicable to uniform planar arrays with both uniform and Gaussian uncorrelated phase-error distributions and for any arbitrary scan angle.

  2. Synthesizing skyrmion bound pairs in Fe-Gd thin films

    NASA Astrophysics Data System (ADS)

    Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; Shi, X.; Tamura, N.; Mishra, S. K.; Fischer, P.; McMorran, B. J.; Sinha, S. K.; Fullerton, E. E.; Kevan, S. D.; Roy, S.

    2016-07-01

    We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

  3. Magnetic and thermodynamic properties of GdCu4Au

    NASA Astrophysics Data System (ADS)

    Bashir, Aiman K.; Tchoula Tchokonté, Moise B.; Britz, Douglas; Sondezi, B. M.; Strydom, André M.

    2015-03-01

    The results of magnetic susceptibility, χ(T), magnetization, σ(μ0H), and specific heat, CP(T), for GdCu4Au are presented. The room temperature powder X-ray diffraction studies indicate a cubic MgCu4Sn - type crystal structure with space group Fbar 43m (No.216). The low field dc χ(T) data shows an antiferromagnetic - like (AFM) anomaly associated with a Néel temperature TN = 10.8 K for GdCu4Au. In the paramagnetic region above TN, χ(T) data follows the Curies - Weiss law with an effective magnetic moment μeff = 7.444(1) μB and paramagnetic Weiss temperature θP = -15.01(2) K. The experimental value of is close to the calculated value of 7.94 μB expected for the free Gd3+-ion. The field-cooled (FC) and zero-field-cooled (ZFC) χ(T) data provide evidence for the formation of spin-glass state with a freezing temperature Tf = 15 K. σ(μ0H) measured in the ordering region (below TN) shows that GdCu4Au undergoes metamagnetic transition above 0.7 T, characterized by a slight upward curvature above this field. Measurement of σ(μ0H) in the paramagnetic regions show a linear behaviour up to 0.7 T and a downward curvature at high fields. CP(T) data shows an AFM - like phase transition at TN = 10.4 K close to the phase transition observed in χ(T) results. The 4f-electron entropy reaches the value of Rln2 close to TN at 9.02 K and reaches the value of Rln(2J + 1) at T = 180 K.

  4. Synthesizing skyrmion bound pairs in Fe-Gd thin films

    DOE PAGESBeta

    Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; Shi, X.; Tamura, N.; Mishra, S. K.; Fischer, P.; McMorran, B. J.; Sinha, S. K.; Fullerton, E. E.; et al

    2016-07-11

    Here, we show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

  5. Temperature dependence of the magnetic excitations in Gd

    SciTech Connect

    Cable, J.W.; Nicklow, R.M.; Wakabayashi, N.

    1985-08-01

    Magnetic excitation spectra were measured for Gd in the and directions over the temperature range from 9 to 320/sup 0/K (T/sub c/ = 292.7/sup 0/K). Spin-wave-like modes are observed at T greater than or equal to T/sub c/. The critical wavevector for the appearance of these modes is proportional to the inverse correlation length.

  6. Gd-TEMDO: Design, Synthesis, and MRI Application.

    PubMed

    Boltjes, André; Shrinidhi, Annadka; van de Kolk, Kees; Herdtweck, Eberhardt; Dömling, Alexander

    2016-05-23

    A simple Ugi tetrazole multicomponent reaction allows the synthesis of a novel macrocyclic cyclen derivative with four appendant tetrazole arms in just two steps in excellent yields. This ligand, called TEMDO, turns out to have a high complexation affinity with lanthanoid metals. Here we describe the design, synthesis, solid-state structure, binding constant, and some MRI applications of the Gd-TEMDO complex as the first example of a congeneric family of oligo-amino tetrazoles. PMID:26991633

  7. Synthesis, crystal structure, and physical properties of the Gd3BiO3 and Gd8Bi3O8 phases

    NASA Astrophysics Data System (ADS)

    Forbes, Scott; Yuan, Fang; Kosuda, Kosuke; Kolodiazhnyi, Taras; Mozharivskyj, Yurij

    2016-01-01

    The second and third known rare-earth bismuthide oxides, Gd3BiO3 and Gd8Bi3O8, have been discovered via high temperature reactions at 1300 °C. Like its Gd-Sb-O counterparts, the Gd3BiO3 and Gd8Bi3O8 phases crystallize in the monoclinic C2/m space group, with the latter containing disordered Bi atoms along the b direction of the unit cell. Unlike the RE8Sb3O8 series, the formation of the Gd3BiO3 phase does not necessarily precede the formation of Gd8Bi3O8, which is likely due to the difficulty of accommodating bismuth in the RE-O framework due to its larger size. Physical property measurements performed on a pure Gd8Bi3O8 sample reveal semiconducting behavior. Although electronic structure calculations predict metallic behavior due to an unbalanced electron count, the semiconducting behavior originates from the Anderson localization of the Bi p states near the Fermi level as a result of atomic disorder.

  8. Structural and topographical analysis of Nd:Gd2O3 nanorods

    NASA Astrophysics Data System (ADS)

    Boopathi, G.; Raj, S. Gokul; Kumar, G. Ramesh; Mohan, R.

    2013-06-01

    Nanocrystalline form of pure and Nd doped gadolinium hydroxide [Nd:Gd(OH(3] nanorods were successfully synthesized at 60 °C through simple co-precipitation method of Gd(NO3)3.6H2O and Nd(NO3)3.6H2O solutions with a specified pH, adjusted using NH3 as buffer solution. The dopant percentage was maintained at 5%. The as-synthesized Gd(OH)3 and Nd:Gd(OH(3 nanorods were annealed at 500 °C for 1 h to form the respective Gd2O3 and Nd:Gd2O3 nanorods. Powder X-ray diffraction (XRD) pattern, scanning electron microscopy with energy dispersive X-ray (SEM/EDX) and high-resolution transmission electron microscopy (HRTEM) analyses were used to characterize these as-synthesized [Gd(OH)3 and Nd:Gd(OH(3] and annealed [Gd2O3 and Nd:Gd2O3] nanorods.

  9. Structural and topographical analysis of Nd:Gd{sub 2}O{sub 3} nanorods

    SciTech Connect

    Boopathi, G.; Mohan, R.; Raj, S. Gokul; Kumar, G. Ramesh

    2013-06-03

    Nanocrystalline form of pure and Nd doped gadolinium hydroxide [Nd:Gd(OH({sub 3}] nanorods were successfully synthesized at 60 Degree-Sign C through simple co-precipitation method of Gd(NO{sub 3}){sub 3}.6H{sub 2}O and Nd(NO{sub 3}){sub 3}.6H{sub 2}O solutions with a specified pH, adjusted using NH{sub 3} as buffer solution. The dopant percentage was maintained at 5%. The as-synthesized Gd(OH){sub 3} and Nd:Gd(OH({sub 3} nanorods were annealed at 500 Degree-Sign C for 1 h to form the respective Gd{sub 2}O{sub 3} and Nd:Gd{sub 2}O{sub 3} nanorods. Powder X-ray diffraction (XRD) pattern, scanning electron microscopy with energy dispersive X-ray (SEM/EDX) and high-resolution transmission electron microscopy (HRTEM) analyses were used to characterize these as-synthesized [Gd(OH){sub 3} and Nd:Gd(OH({sub 3}] and annealed [Gd{sub 2}O{sub 3} and Nd:Gd{sub 2}O{sub 3}] nanorods.

  10. Gd{sup 3+} incorporated ZnO nanoparticles: A versatile material

    SciTech Connect

    Kumar, Surender Sahare, P.D.

    2014-03-01

    Graphical abstract: - Highlights: • Chemically synthesized Gd{sup 3+} doped ZnO nanoparticles. • The broad visible emission of the ZnO is dependent on the surface defects and can be tailored by Gd{sup 3+} doing. • PL and magnetic properties are modified by Gd{sup 3+} doping. • Photocatalysis experiment reveals that the ZnO: Gd{sup 3+} degrades the Rh B dye faster than the undoped ZnO. - Abstract: Gd{sup 3+} doped ZnO nanoparticles are synthesized by wet chemical route method and investigated through structural, optical, magnetic and photocatalytic properties. Transmission Electron Microscopy technique has been performed on undoped and Gd{sup 3+} doped ZnO nanoparticles. X-ray diffraction, X-ray photoelectron spectroscopy and Raman analyses are carried out in order to examine the desired phase formation and substitution of Gd{sup 3+} in the ZnO matrix. Gd{sup 3+} doped ZnO nanoparticles show enhanced photoluminescent and ferromagnetic properties as compared to undoped ZnO. The broad visible emission of ZnO is found to be largely dependent on the surface defects and these surface defects can be tailored by Gd{sup 3+} doping concentration. Furthermore, Gd{sup 3+} doped ZnO nanoparticles also show improved photocatalytic properties as compared with undoped ZnO nanoparticles under ultraviolet irradiation.

  11. Ferromagnetism in Gd doped ZnO nanowires: A first principles study

    SciTech Connect

    Aravindh, S. Assa; Schwingenschloegl, Udo E-mail: iman.roqan@kaust.edu.sa; Roqan, Iman S. E-mail: iman.roqan@kaust.edu.sa

    2014-12-21

    In several experimental studies, room temperature ferromagnetism in Gd-doped ZnO nanostructures has been achieved. However, the mechanism and the origin of the ferromagnetism remain controversial. We investigate the structural, magnetic, and electronic properties of Zn{sub 48}O{sub 48} nanowires doped with Gd, using density functional theory. Our findings indicate that substitutionally incorporated Gd atoms prefer occupying the surface Zn sites. Moreover, the formation energy increases with the distance between Gd atoms, signifying that no Gd-Gd segregation occurs in the nanowires within the concentration limit of ≤2%. Gd induces ferromagnetism in ZnO nanowires with magnetic coupling energy up to 21 meV in the neutral state, which increases with additional electron and O vacancy, revealing the role of carriers in magnetic exchange. The potential for achieving room temperature ferromagnetism and high T{sub C} in ZnO:Gd nanowires is evident from the large ferromagnetic coupling energy (200 meV) obtained with the O vacancy. Density of states shows that Fermi level overlaps with Gd f states with the introduction of O vacancy, indicating the possibility of s-f coupling. These results will assist in understanding experimental findings in Gd-doped ZnO nanowires.

  12. Modeling GD-1 Gaps in a Milky Way Potential

    NASA Astrophysics Data System (ADS)

    Carlberg, R. G.

    2016-03-01

    The GD-1 star stream is currently the best available for identifying density fluctuations, “gaps,” along its length as a test of the LCDM prediction of large numbers of dark matter sub-halos orbiting in the halo. Density variations of some form are present, since the variance of the density along the stream is three times that expected from the empirically estimated variation in the filtered mean star counts. The density variations are characterized with filters that approximate the shape of sub-halo, gravitationally induced stream gaps. The filters locate gaps and measure their amplitude, leading to a measurement of the distribution of gap widths. To gain an understanding of the factors influencing the gap width distribution, a suite of collisionless n-body simulations for a GD-1-like orbit in a Milky-Way-like potential provides a dynamically realistic statistical prediction of the gap distribution. The simulations show that every location in the stream has been disturbed to some degree by a sub-halo. The small gaps found via the filtering are largely noise. Larger gaps, those longer than 1 kpc, or 10° for GD-1, are the source of the excess variance. The suite of stream simulations shows that sub-halos at the predicted inner halo abundance or possibly somewhat higher can produce the required large-scale density variations.

  13. Magnetic structure and magnetocalorics of GdPO4

    DOE PAGESBeta

    Palacios, E; Rodr´ıguez-Velamaz´an,,; Evangelisti, Marco; McIntyre, G; Lorusso, G; Visser, Dirk; De Jongh, L. Jos; Boatner, Lynn A

    2014-01-01

    The magnetic ordering structure of GdPO4 is determined at T = 60 mK by diffraction of hot neutrons with wavelength = 0.4696 A. It corresponds to a non-collinear antiferromagnetic arrangement of the Gd moments with propagation vector k = (1/2, 0, 1/2). This arrangement is found to minimize the dipole-dipole interaction and the crystal field anisotropy energy, the magnetic superexchange being much smaller. The intensity of the magnetic reflections decreases with increasing temperature and vanishes at T 0.8 K, in agreement with the magnetic ordering temperature TN = 0.77 K, as reported in previous works based on heat capacity andmore » magnetic susceptibility measurements. The magnetocaloric parameters have been determined from heat capacity data at constant applied fields up to 7 T, as well as from isothermal magnetization data. The magnetocaloric effect reaches ST = 375.8 mJ cm3 K 1 at T = 2.1 K, largely exceeding the maximum values reported to date for Gd-based magnetic refrigerants.« less

  14. Magnetic structure and magnetocalorics of GdPO4

    SciTech Connect

    Palacios, E; Rodr´ıguez-Velamaz´an,,; Evangelisti, Marco; McIntyre, G; Lorusso, G; Visser, Dirk; De Jongh, L. Jos; Boatner, Lynn A

    2014-01-01

    The magnetic ordering structure of GdPO4 is determined at T = 60 mK by diffraction of hot neutrons with wavelength = 0.4696 A. It corresponds to a non-collinear antiferromagnetic arrangement of the Gd moments with propagation vector k = (1/2, 0, 1/2). This arrangement is found to minimize the dipole-dipole interaction and the crystal field anisotropy energy, the magnetic superexchange being much smaller. The intensity of the magnetic reflections decreases with increasing temperature and vanishes at T 0.8 K, in agreement with the magnetic ordering temperature TN = 0.77 K, as reported in previous works based on heat capacity and magnetic susceptibility measurements. The magnetocaloric parameters have been determined from heat capacity data at constant applied fields up to 7 T, as well as from isothermal magnetization data. The magnetocaloric effect reaches ST = 375.8 mJ cm3 K 1 at T = 2.1 K, largely exceeding the maximum values reported to date for Gd-based magnetic refrigerants.

  15. Toxics testing performance evaluation for GB and GD

    SciTech Connect

    O`Neill, H.J.; Schneider, J.F.; Brubaker, K.L.; Kimmell, T.A.; Anderson, A.W.

    1997-10-01

    Residues resulting from demilitarization, treatment, cleanup, and testing of military chemical agents at Dugway Proving Ground (DPG), Utah, are currently listed as hazardous wastes by the State of Utah Department of Environmental Quality. The US Army Test and Evaluation Command believes that certain categories of waste generated at DPG are not hazardous. To demonstrate this, analytical methods capable of quantitatively measuring the concentrations of chemical agents, including GB and GD, in the different waste media must be available. Argonne National Laboratory has developed methods to analyze metal substrate, spent hypochlorite decontamination fluid, and soil matrices for GB and GD. These methods involve the use of sorbent cartridge preconcentration and thermal desorption combined with gas chromatography using flame photometric detection to achieve the desired sensitivity and specificity. This report describes the methods and presents results for these three common waste matrices. The test results indicate that these methods can be used to quantitatively determine concentrations of GB and GD in the low parts-per-billion range in all sample media tested.

  16. Potential dual imaging nanoparticle: Gd2O3 nanoparticle

    PubMed Central

    Ahmad, Md. Wasi; Xu, Wenlong; Kim, Sung June; Baeck, Jong Su; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok; Park, Ji Ae; Kim, Tae Jeong; Lee, Gang Ho

    2015-01-01

    Gadolinium (Gd) is a unique and powerful element in chemistry and biomedicine which can be applied simultaneously to magnetic resonance imaging (MRI), X-ray computed tomography (CT), and neutron capture therapy for cancers. This multifunctionality can be maximized using gadolinium oxide (Gd2O3) nanoparticles (GNPs) because of the large amount of Gd per GNP, making both diagnosis and therapy (i.e., theragnosis) for cancers possible using only GNPs. In this study, the T1 MRI and CT dual imaging capability of GNPs is explored by synthesizing various iodine compound (IC) coated GNPs (IC-GNPs). All the IC-GNP samples showed stronger X-ray absorption and larger longitudinal water proton relaxivities (r1 = 26–38 s−1mM−1 and r2/r1 = 1.4–1.9) than the respective commercial contrast agents. In vivo T1 MR and CT images of mice were also acquired, supporting that the GNP is a potential dual imaging agent. PMID:25707374

  17. Magnetic structures in potential multiferroic GdCrO3

    NASA Astrophysics Data System (ADS)

    Manuel, Pascal; Chapon, Laurent; Khalyavin, Dmitry; Xueyun, Wang; Cheong, Sang-Wook

    2015-03-01

    For the past decade, multiferroics materials have atracted a lot of attention in the condensed matter community because of potential applications for devices. A somewhat ambiguous addition to the multiferroics family was recently reported in the peroskite based GdCrO3 in both bulk and thin film samples. Indeed, ferroelectricity was evidenced by a strong enhancement of the capacitance in a field but significant leakage and no well developed P-E hysteresis blurred the picture. Our own measurements clearly indicate the existence of a polar phase below 2K. To complete the understanding of this material, the determination of the magnetic structure is required but is hampered by the fact Gd is a strong neutron absorber. We will present some neutron diffraction data collected on an isotopic 160GdCrO3 sample at the WISH diffractometer at ISIS which confirm the presence of three successive magnetic phases, previously only seen by magnetization, as a function of temperature. We will compare our determined structures against predictions based on group theoretical considerations and experimental work on other rare-earth ortho-chromates and discuss the mechanism for multiferroicity.

  18. Gd2O3 nanoparticles stabilized by hydrothermally modified dextrose for positive contrast magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Babić-Stojić, Branka; Jokanović, Vukoman; Milivojević, Dušan; Požek, Miroslav; Jagličić, Zvonko; Makovec, Darko; Arsikin, Katarina; Paunović, Verica

    2016-04-01

    Gd2O3 nanoparticles of a few nm in size and their agglomerates dispersed in dextrose derived polymer template were synthesized by hydrothermal treatment. The produced nanosized material was investigated by TEM, FTIR spectroscopy, SQUID measurements and NMR relaxometry. Biological evaluation of this material was done by crystal violet and MTT assays to determine the cell viability. Longitudinal and transverse NMR relaxivities of water diluted Gd2O3 nanoparticle dispersions measured at the magnetic field of 1.5 T, estimated to be r1(Gd2O3)=9.6 s-1 mM-1 in the Gd concentration range 0.1-30 mM and r2(Gd2O3)=17.7 s-1 mM-1 in the lower concentration range 0.1-0.8 mM, are significantly higher than the corresponding relaxivities measured for the standard contrast agent r1(Gd-DTPA)=4.1 s-1 mM-1 and r2(Gd-DTPA)=5.1 s-1 mM-1. The ratio of the two relaxivities for Gd2O3 nanoparticles r2/r1=1.8 is suitable for T1-weighted imaging. Good MRI signal intensities of the water diluted Gd2O3 nanoparticle dispersions were recorded at lower Gd concentrations 0.2-0.8 mM. The Gd2O3 samples did not exert any significant cytotoxic effects at Gd concentrations of 0.2 mM and below. These properties of the produced Gd2O3 nanoparticles in hydrothermally modified dextrose make them promising for potential application in MRI for the design of a positive MRI contrast agent.

  19. S-shaped decanuclear heterometallic [Ni8Ln2] complexes [Ln(III) = Gd, Tb, Dy and Ho]: theoretical modeling of the magnetic properties of the gadolinium analogue.

    PubMed

    Hossain, Sakiat; Das, Sourav; Chakraborty, Amit; Lloret, Francesc; Cano, Joan; Pardo, Emilio; Chandrasekhar, Vadapalli

    2014-07-14

    The reaction of 8-quinolinol-2-carboaldoxime (LH2) with Ni(II) and Ln(III) salts afforded the heterometallic decanuclear compounds [Ni8Dy2(μ3-OH)2(L)8(LH)2(H2O)6](ClO4)2·16H2O (1), [Ni8Gd2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](NO3)2·12H2O (2), [Ni8Ho2(μ3-OH)2(L)8(LH)2(H2O)4(MeOH)2](ClO4)2·2MeOH·12H2O (3) and [Ni8Tb2 (μ3-OH)2(L)8(LH)2(MeOH)4(OMe)2]·2CH2Cl2·8H2O (4). While compounds 1-3 are dicationic, compound 4 is neutral. These compounds possess an S-shaped architecture and comprise a long chain of metal ions bound to each other. In all the complexes, the eight Ni(II) and two Ln(III) ions of the multimetallic ensemble are hold together by two μ3-OH, eight dianionic (L(2-)) and two monoanionic oxime ligands (LH(-)) whereas compound 4 has two μ3-OH, eight dianionic (L(2-)), two monoanionic oxime ligands (LH(-)) and two terminal methoxy (MeO(-)) ligands. The central portion of the S-shaped molecular wire is made up of an octanuclear Ni(II) ensemble which has at its two ends the Ln(III) caps. Magnetic studies on 1-4 reveal that the magnetic interactions between neighboring metal ions are negligible at room temperature. On the other hand, at lower temperatures in all the compounds anti-ferromagnetic interactions seem to be dominated. Analysis of the magnetic data for the Gd(III) derivative indicates Ni(II)-Ni(II) anti-ferromagnetic interactions and Gd(III)-Ni(II) ferromagnetic interactions at low temperatures. A theoretical density functional study on the magnetic behavior of the Gd(III) derivative suggests that while the weak ferromagnetic interaction between Gd(III) and Ni(II) is in line with the expectation of the magnetic interactions between orthogonal d and f orbitals, antiferromagnetic Ni(II)-Ni(II) interactions are related to the wide Ni-O-Ni angles (∼102°) and quasi-planar conformation of the Ni2O2 core. PMID:24876072

  20. Yangian-type symmetries of non-planar leading singularities

    NASA Astrophysics Data System (ADS)

    Frassek, Rouven; Meidinger, David

    2016-05-01

    We take up the study of integrable structures behind non-planar contributions to scattering amplitudes in {N}=4 super Yang-Mills theory. Focusing on leading singularities, we derive the action of the Yangian generators on color-ordered subsets of the external states. Each subset corresponds to a single boundary of the non-planar on-shell diagram. While Yangian invariance is broken, we find that higher-level Yangian generators still annihilate the non-planar on-shell diagram. For a given diagram, the number of these generators is governed by the degree of non-planarity. Furthermore, we present additional identities involving integrable transfer matrices. In particular, for diagrams on a cylinder we obtain a conservation rule similar to the Yangian invariance condition of planar on-shell diagrams. To exemplify our results, we consider a five-point MHV on-shell function on a cylinder.