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Sample records for earth doped integrated

  1. Plasma synthesis of rare earth doped integrated optical waveguides

    SciTech Connect

    Raoux, S.; Anders, S.; Yu, K.M.; Brown, I.G.; Ivanov, I.C.

    1995-03-01

    We describe a novel means for the production of optically active planar waveguides. The makes use of a low energy plasma deposition. Cathodic-arc-produced metal plasmas the metallic components of the films and gases are added to form compound films. Here we discuss the synthesis of Al{sub 2{minus}x}ER{sub x}O{sub 3} thin films. The erbium concentration (x) can vary from 0 to 100% and the thickness of the film can be from Angstroms to microns. In such material, at high active center concentration (x=l% to 20%), erbium ions give rise to room temperature 1.53{mu}m emission which has minimum loss in silica-based optical fibers. With this technique, multilayer integrated planar waveguide structures can be grown, such as Al{sub 2}O{sub 3}/Al{sub 2{minus}x}Er{sub x}O{sub 3}/Al{sub 2}O{sub 3}/Si, for example.

  2. Monolithically integrated active waveguides and lasers using rare-earth doped spin-on glass

    SciTech Connect

    Ashby, C.I.H.; Sullivan, C.T.; Vawter, G.A.

    1996-09-01

    This LDRD program No. 3505.230 explored a new approach to monolithic integration of active waveguides and rare-earth solid state lasers directly onto III-V substrates. It involved selectively incorporating rare-earth ions into spin-on glasses (SOGs) that could be solvent cast and then patterned with conventional microelectronic processing. The patterned, rare-earth spin-on glasses (RESOGs) were to be photopumped by laser diodes prefabricated on the wafer and would serve as directly integrated active waveguides and/or rare-earth solid state lasers.

  3. Rare earth doping of zirconia optical waveguides

    NASA Astrophysics Data System (ADS)

    Berglund, William Ruben

    The understanding of the optical physics of rare earth ions doped in an host material transparent in the infrared is an important foundation for improving and developing new applications in active optical devices. With pumping a rare earth doped device can provide large gains at wavelengths in the luminescence bands from transitions in its (4f)n states. Many of these bands are in wavelengths that are useful in the field of optical telecommunications and laser applications. In this work, we investigated the rare earth doping characteristics of ion beam sputtered thin films of ZrO 2 (zirconia) in planar waveguides. Three properties of sputtered zirconia that make it an interesting candidate for rare earth doping includes a high range of infrared transmission, low phonon energy, and high index of refraction. Waveguides were fabricated as a three layer ZrO2/SO2 loaded ridge structure, where the percentage of silica was varied in the films in order to obtain a desired index contrast of the middle guide layer with the cladding. These films and structures were shown to be completely amorphous with low loss and good optical gain. Ion beam sputtered films of rare earth doped zirconia showed potential of greater brightness and higher gains than that of silica based optical amplifiers. But it may suffer from ``bottlenecks'' of states with longer lifetimes and excited state absorption, and increased ion-ion interaction effects with higher doping levels. A simulation model on the performance of highly doped waveguides with upconversion was developed and included was an improved calculation of losses due to waveguide bends based on the WKB method. Judd Ofelt calculations based on absorption and lifetime measurements were used to find the quantum efficiency of radiative emissions of Er3+ and Pr3+ in zirconia. This work shows that there is great potential for the use of zirconia in both passive and active waveguide structures.

  4. Fabrication and characterization of rare earth-doped silicon nanocrystals and rare earth-doped silicon dioxide nanostructures

    NASA Astrophysics Data System (ADS)

    St. John, John Vincent

    The intrinsic indirect bandgap of Si limits the applicability of Si as an optoelectronic device due to the lack of efficient light emission. Several strategies exist to overcome the inefficient photoluminescence (PL) of Si, including the formation of nanophase Si in a quantum confined size regime and the integration of luminescent rare-earth ions with SiO2 layers on Si. Until this point it has not been possible to study the properties of discrete silicon nanoclusters which have been doped with a luminescent rare earth center. Studies of Er3+ in Si with nanoscale dimensions has been restricted to Er3+ and Si nanostructures co-deposited as thin films. This research represents the first reported synthesis of discrete Er3+-doped Si nanocrystals. Erbium-doped Si nanoparticles are prepared by the co-pyrolysis of disilane and an Er3+ precursor in a He carrier gas with collection of the aerosol in an ethylene glycol bubbler. Analysis of the reaction products indicates that the Er3+-doped Si nanoparticles aggregate, and that the size distributions of those aggregates can be controlled by varying the length of the oven used for pyrolysis. The Er3+-doped Si nanocrystals are composed of crystalline Si. Er3+-doped Si nanoparticles show characteristic 1.54 mum PL ascribed to Er3+. The excitation mechanism for the Er3+ PL is thought to arise through carrier-mediated energy transfer from electron-hole pair recombination in the Si lattice. A hybrid approach to the formation of luminescent Si involves a technique, called spark processing. Spark processing uses the high energy arc from a Tesla coil to ablate and oxidize a Si surface that has been coated with a layer of a rare earth salt. Studies of spark processing using Eu3+ salt layers on Si suggest that the rare earth ions are incorporated in the growing SiO2 layer. Spark processing can also be applied to the formation of luminescent Er3+-doped spark processed SiO2 layers on Si. The luminescent intensity of the Er3+ PL is controlled to some extent through the initial concentration of Er3+ ions before spark processing. High resolution photoluminescence measurements indicate that the Er3+ is in fact trapped in the SiO2 layer and does not form a separate oxide phase.

  5. Enhanced photoluminescence from porous silicon microcavities by rare earth doping

    NASA Astrophysics Data System (ADS)

    Sun, Di-fei; Jia, Zhen-hong; Zhou, Jun

    2016-01-01

    The photoluminescence (PL) properties of porous silicon microcavities (PSMs) in the visible range at room temperature are improved by doping the rare earth ytterbium (Yb) into PSMs prepared by the electrochemical etching method. It is observed that PSMs doped with the rare earth have an emission band around 630 nm. Compared with the single-layer porous silicon (PS) film, the PSMs doped with Yb have narrower and stronger PL spectrum.

  6. Rare-earth-doped polymer optical waveguide amplifiers

    NASA Astrophysics Data System (ADS)

    Gao, Renyuan; Norwood, Robert A.; Teng, C. C.; Garito, Anthony F.

    2000-05-01

    The optical properties and characteristics of rare earth- doped polymers have been studied to evaluate their viability for use in optical amplifiers. Rare earth ions are encapsulated in organic, covalently bonded chromophores. The optical properties of various rare earth chromophores doped into polymers are measured and calculated and are then used in numerical simulations of amplifiers and lasers. The result provide an estimate of their potential device performance and establish the fundamental bases for applications in photonics. Owing to their distinct advantages, such as chromophore energy transfer effects, high rare earth ion concentrations, shielding of the ion form high energy vibrations of the host, enhanced optical transition moments and controllable decay rates and branching ratios, rare earth-doped polymers are found to be promising candidates for various device applications. Numerical simulations for samarium and europium doped polymers indicate that gains about 10 dB and greater are achievable in relatively short polymer optical fiber and waveguide amplifiers. Studies of the dependence of metastable state lifetime of rare earth doped polymer systems on doping concentrations reveal that rare earth chromophores dissociation occurs at low concentrations. These results are used to optimize the parameters of our rare earth doped polymer optical waveguide amplifiers.

  7. Tunable, rare earth-doped solid state lasers

    DOEpatents

    Emmett, John L.; Jacobs, Ralph R.; Krupke, William F.; Weber, Marvin J.

    1980-01-01

    Laser apparatus comprising combinations of an excimer pump laser and a rare earth-doped solid matrix, utilizing the 5d-4f radiative transition in a rare earth ion to produce visible and ultra-violet laser radiation with high overall efficiency in selected cases and relatively long radiative lifetimes.

  8. Radiation-induced loss of rare earth doped silica fibers

    SciTech Connect

    Henschel, H.; Koehn, O.; Schmidt, H.U.; Kirchhof, J.; Unger, S.

    1998-06-01

    Eighteen single mode fibers doped with different rare earth elements are exposed to {sup 60}Co gamma radiation in order to estimate the radiation sensitivity of fiber amplifiers or fiber lasers and to find fibers with extremely high loss increase that are suited for dosimetry of low radiation levels. Induced loss measurements with varying dose rate confirmed the applicability of a simple dose rate transformation method also to rare earth doped fibers. Operation of a distributed fiber optic radiation sensor is demonstrated at a dose rate of less than 0.1 Gy/d.

  9. 40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... earth doped (generic). 721.10423 Section 721.10423 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10423 Complex strontium aluminate, rare earth doped... substances identified generically as complex strontium aluminate, rare earth doped (PMNs P-12-22, P-12-23,...

  10. Rare-earth-doped polymers for optical amplification and lasing

    NASA Astrophysics Data System (ADS)

    Gao, Renyuan; Koeppen, C.; Zheng, G.; Garito, Anthony F.

    1998-04-01

    The optical properties and characteristics of rare earth- doped polymers have been studied to evaluate their viability for use in amplifier and laser applications. Rare earth ions are encapsulated in organic, covalent bonded chromophores. The optical properties of various rare earth chromophores doped into polymers are measured and calculated and are then used in numerical simulations of amplifiers and lasers. The result provide an estimate of their potential device performance and establish the fundamental bases for these applications in photonics. Owing to their distinct and important advantages, such as chromophore energy transfer effects, high rare earth ion concentrations, shielding of the ion from high energy vibrations of the host, enhanced optical transition moments, and controllable decay rates and branching ratios, rare earth-doped polymers are found to be promising candidates for various device applications. Numerical simulations for samarium chromophore, for example, indicate that gains about 10 dB and greater are achievable in relatively short polymer optical fiber amplifiers operating at 650 nm.

  11. Photo darkening of rare earth doped silica.

    PubMed

    Mattsson, Kent E

    2011-10-10

    The photo darkening (PD) absorption spectra from unseeded amplifier operation (by 915 nm pumping) of ytterbium / aluminum and co-doped silica fibers is after prolonged operation observed to develop a characteristic line at 2.6 eV (477 nm). This line is proposed to be due to inter center excitation transfer from type II oxygen deficiency centers ODC(II) to Tm3+ trace impurities. The ODC(II) is proposed to be the result of a displacive transition of a 4-fold silica ring hosting two 3-fold silicon units that presents two non-bridging oxygen to Yb3+ (as part of its 6-fold coordination by oxygen). The displacive transition is initiated by a charge disproportionation process which leads to NBO transfer in forming dioxasilirane (2-fold coordinated silicon with two NBO attached) next to silylene (2-fold coordinated silicon with a lone electron pair). In collaboration with a valence electron of Yb3+ a new / 1 chemical bond is formed on dioxasilirane which comprises the PD color center for the visible and near-infrared. Difference in solid acidity of the silica material co-doped with Yb/Al and Yb/P may explain the observed difference in spectral shapes by change of bond order to the formed chemical bond. PMID:21996988

  12. Magnetic property improvement of niobium doped with rare earth elements

    NASA Astrophysics Data System (ADS)

    Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin

    2014-05-01

    A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

  13. Rare Earth Doped High Temperature Ceramic Selective Emitters

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    As a result of their electron structure, rare earth ions in crystals at high temperature emit radiation in several narrow bands rather than in a continuous blackbody manner. This study develops a spectral emittance model for films of rare earth containing materials. Although there are several possible rare earth doped high temperature materials, this study was confined to rare earth aluminum garnets. Good agreement between experimental and theoretical spectral emittances was found for erbium, thulium and erbium-holmium aluminum garnets. Spectral emittances of these films are sensitive to temperature differences across the film. Emitter efficiency is also a sensitive function of temperature. For thulium aluminum garnet the efficiency is 0.38 at 1700 K but only 0.19 at 1262 K.

  14. Rare earth doped zinc oxide varistors

    DOEpatents

    McMillan, A.D.; Modine, F.A.; Lauf, R.J.; Alim, M.A.; Mahan, G.D.; Bartkowiak, M.

    1998-12-29

    A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2--4.0% oxide of at least one rare earth element, 0.5--4.0% Co{sub 3}O{sub 4}, 0.05--0.4% K{sub 2}O, 0.05--0.2% Cr{sub 2}O{sub 3}, 0--0.2% CaO, 0.00005--0.01% Al{sub 2}O{sub 3}, 0--2% MnO, 0--0.05% MgO, 0--0.5% TiO{sub 3}, 0--0.2% SnO{sub 2}, 0--0.02% B{sub 2}O{sub 3}, balance ZnO. 4 figs.

  15. Rare earth doped zinc oxide varistors

    DOEpatents

    McMillan, April D.; Modine, Frank A.; Lauf, Robert J.; Alim, Mohammad A.; Mahan, Gerald D.; Bartkowiak, Miroslaw

    1998-01-01

    A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO.

  16. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films.

    PubMed

    Figueroa, A I; van der Laan, G; Harrison, S E; Cibin, G; Hesjedal, T

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi(3+) in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  17. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films

    PubMed Central

    Figueroa, A. I.; van der Laan, G.; Harrison, S. E.; Cibin, G.; Hesjedal, T.

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  18. Rare Earth Doped Fiber Amplifiers for the First Telecommunication Window

    NASA Astrophysics Data System (ADS)

    Sridhar, Balakrishnan

    A complete experimental and theoretical study of rare earth doped fiber-optic amplifiers for the first tele-communication window has been made. The thulium doped fluoride fiber amplifier is shown to provide amplification in the 800nm-820nm signal region. A complete steady state theoretical model has been presented and the model has been experimentally verified. The model predicts the gain, noise figure and the amplified spontaneous emission in the 800nm, 1470nm, 1900nm and 2300nm bands. The effect of population trapping at the ^3F_4 energy level of thulium ion is also shown with the help of the model. It has been shown that about 5 -15%o of the population is trapped at the ^3F _4 energy level. We have also shown theoretically, the expected gain and noise performance of Thulium doped fluoride fiber amplifiers pumped in the 680nm absorption band. The maximum gain at 806nm is slightly lower than with comparable 780 nm pumping. The gain bandwidth is however found to increase with 680nm pumping. The higher ASE at shorter wavelengths (<806nm) reduces the gain at the peak wavelength (806nm). This is a result of the better inversion with three level pumping at 680nm as compared to two level resonant pumping at 780nm. We report an efficient single mode erbium doped flouride fiber amplifier in the 850nm signal band for the first time. The amplification is through an up-conversion process. The erbium doped flouride fiber amplifier was pumped with an estimated pump power of 35mW at 792nm. We have also considered a theoretical model for a single mode erbium doped fluoride fiber amplifier. Efficient amplification occurs because of the strong excited state absorption at the pump wavelength from the ^4I_{13/2} energy level.

  19. Rare earth doped upconverting particles for different photonic applications

    NASA Astrophysics Data System (ADS)

    Pokhrel, Madhab; Gangadharan, Ajith Kumar; Sardar, Dhiraj Kumar

    2013-03-01

    Trivalent rare earth ions especially erbium (Er3+) and ytterbium (Yb3+) co-doped in various host nanoparticles are known for their extraordinary spectroscopic properties. A thorough optical characterization including the absolute upconversion quantum yield (QY) measurement is of critical importance in evaluating their potential for various photonic applications. In this paper, we will be presenting a measured absolute upconversion QYs for Yb3+ and Er3+ doped in La2O2S under 980 and 1550 nm excitation at various power densities. Comparison of absolute QYs for different concentrations of Yb3+ and Er3+ doped in La2O2S will be made for all the upconversion emissions with respect to reported most efficient upconverting phosphor NaYF4 doped with 20% Yb3+ and 2% Er3+. Furthermore, applications of these phosphors in different areas such as bio-imaging, solar cell, security, etc. will be explored depending on the measured absolute upconversion quantum yields. In addition, preliminary results on in vitro imaging using upconverting nanoparticles as a contrast agent will be reported. This work was supported by the National Science Foundation Partnerships for Research and Education in Materials (PREM) Grant No. DMR-0934218.

  20. Rare Earth doped nanoparticles in imaging and PDT

    NASA Astrophysics Data System (ADS)

    Yust, Brian G.; Sardar, Dhiraj K.; Mimun, Lawrence C.; Gangadharan, Ajith K.; Tsin, Andrew T.

    2013-02-01

    Nanoparticles doped with rare earth ions for biomedical imaging and infrared photodynamic therapy (IRPDT) have been synthesized, characterized, and compared. Specifically, these nanoparticles utilize two primary modalities: near infrared excitation and emission for imaging, and near infrared upconversion for photodynamic therapy. These nanoparticles are optimized for both their infrared emission and upconversion energy transfer to a photoactive agent conjugated to the surface. Finally, these nanoparticles are tested for toxicity, imaged in cells using the near infrared emission pathway, and used for selective killing of cells through the upconversion driven IRPDT.

  1. Rare Earth doped nanoparticles in imaging and PDT.

    PubMed

    Yust, Brian G; Sardar, Dhiraj K; Mimun, Lawrence C; Gangadharan, Ajith K; Tsin, Andrew T

    2013-02-19

    Nanoparticles doped with rare earth ions for biomedical imaging and infrared photodynamic therapy (IRPDT) have been synthesized, characterized, and compared. Specifically, these nanoparticles utilize two primary modalities: near infrared excitation and emission for imaging, and near infrared upconversion for photodynamic therapy. These nanoparticles are optimized for both their infrared emission and upconversion energy transfer to a photoactive agent conjugated to the surface. Finally, these nanoparticles are tested for toxicity, imaged in cells using the near infrared emission pathway, and used for selective killing of cells through the upconversion driven IRPDT. PMID:25429335

  2. Rare Earth doped nanoparticles in imaging and PDT

    PubMed Central

    Yust, Brian G.; Sardar, Dhiraj K.; Mimun, Lawrence C.; Gangadharan, Ajith K.; Tsin, Andrew T.

    2014-01-01

    Nanoparticles doped with rare earth ions for biomedical imaging and infrared photodynamic therapy (IRPDT) have been synthesized, characterized, and compared. Specifically, these nanoparticles utilize two primary modalities: near infrared excitation and emission for imaging, and near infrared upconversion for photodynamic therapy. These nanoparticles are optimized for both their infrared emission and upconversion energy transfer to a photoactive agent conjugated to the surface. Finally, these nanoparticles are tested for toxicity, imaged in cells using the near infrared emission pathway, and used for selective killing of cells through the upconversion driven IRPDT. PMID:25429335

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  4. Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.; Zhu, Dongming

    2005-01-01

    Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttria-partially stabilized zirconia. As used here, "thermal-barrier coatings" (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components. A TBC as deposited has some porosity, which is desirable in that it reduces the thermal conductivity below the intrinsic thermal conductivity of the fully dense form of the material. Undesirably, the thermal conductivity gradually increases because the porosity gradually decreases as a consequence of sintering during high-temperature service. Because of these and other considerations such as phase transformations, the maximum allowable service temperature for yttria-partially stabilized zirconia TBCs lies in the range of about 1,200 to 1,300 C. In contrast, the present multicomponent, rare-earth-doped, perovskite-type TBCs can withstand higher temperatures.

  5. Engineering broadband and anisotropic photoluminescence emission from rare earth doped tellurite thin film photonic crystals.

    PubMed

    Lin, Pao T; Vanhoutte, Michiel; Patel, Neil S; Singh, Vivek; Hu, Juejun; Cai, Yan; Camacho-Aguilera, Rodolfo; Michel, Jurgen; Kimerling, Lionel C; Agarwal, Anu

    2012-01-30

    Broadband and anisotropic light emission from rare-earth doped tellurite thin films is demonstrated using Er3+-TeO2 photonic crystals (PhCs). By adjusting the PhC parameters, photoluminescent light can be efficiently coupled into vertical surface emission or lateral waveguide propagation modes. Because of the flexibility of light projection direction, Er3+-TeO2 is a potential broadband light source for integration with three-dimensional photonic circuits and on-chip biochemical sensors. PMID:22330453

  6. White light emission from GaN stack layers doped by different rare-earth metals

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Liu, Chang

    2015-02-01

    Experimental progress of electroluminescence devices (ELDs) employing GaN doped with rare-earth metals had been significantly made targeting RGB displays. However, reports on the theoretical models to design the devices and the applications were limited. Our previous paper proposed a device model using the quantum collision theory and Judd-Ofelt approximation to design the ELDs for white light illumination. In the present study, the model is modified by considering the light extraction efficiency and optical loss during propagating in the films. To improve the luminous efficiency, an ELD with three stack layers of GaN:Tm/GaN:Er/GaN:Eu is proposed and designed. The model predicts that the color of the integrated light can be controlled by applied voltage, thickness of each doping layer and doping concentrations of the rare earth metals. The luminous efficacy of white light emission at a bias of -100 V is calculated to be 274 lm/W, which is much higher than that of fluorescent lumps. The proposed ELD will open a door to efficient solid-state lighting.

  7. Rare-earth doped polymer waveguides and light emitting diodes

    NASA Astrophysics Data System (ADS)

    Slooff, L. H.

    2000-11-01

    Polymer-based optical waveguide amplifiers offer a low-cost alternative for inorganic waveguide amplifiers. Due to the fact that their refractive index is almost similar to that of standard optical fibers, they can be easily coupled with existing fibers at low coupling losses. Doping the polymer with rare-earth ions that can yield optical gain is not straightforward, as the rare-earth salts are poorly soluble in the polymer matrix. This thesis studies two different approaches to dope a polymer waveguide with rare-earth ions. The first one is based on organic cage-like complexes that encapsulate the rare-earth ion and are designed to provide enough coordination sites to bind the rare-earth ion and to shield it from the surrounding matrix. Chapter 2 describes the optical properties of Er-doped organic polydentate cage complexes. The complexes show clear photoluminescence at 1.54 mm with a bandwidth of 70 nm, the highest reported for an erbium-doped material so far. The luminescence lifetime is very short (~1 ms) due to coupling to vibrational overtones of O-H and C-H bonds. Due to this short luminescence lifetime, high pump powers (~1 W) are needed for optical gain in a waveguide amplifier based on these complexes. The pump power can be reduced if the Er is excited via the aromatic part of the complex, which has a higher absorption cross section. In Chapter 3 a lissamine-functionalised neodymium complex is studied in which the highly absorbing lissamine acts as a sensitiser. The lissamine is first excited into the singlet state from which intersystem crossing to the triplet state can take place. From there it can transfer its energy to the Nd ion by a Dexter transfer mechanism. Room-temperature photoluminescence at 890, 1060, and 1340 nm from Nd is observed, together with luminescence from the lissamine sensitiser at 600 nm. Photodegradation of the lissamine sensitiser is observed, which is studied in more detail in Chapter 4. The observed change in time of the spectral shape of the lissamine luminescence can be explained by assuming that two types of complexes exist. One type in which energy transfer to the Nd3+ ion can take place, and one that is not coupled to Nd. The highly absorbing sensitiser makes the standard butt-end coupling of the pump light into a waveguide amplifier impractical. The pump power can be used more efficiently by using a novel coupled waveguide system as described in Chapter 5. This employs gradual evanescent field coupling between parallel pump and signal waveguides. An alternative approach to make a rare-earth doped polymer waveguide is by combining the excellent properties of SiO2 as a host for the rare-earth with the easy processing of polymers. The optical properties of Er-doped silica films made by an acid-catalysed sol-gel synthesis are reported in Chapter 6. The Er exhibits long luminescence lifetimes of 10-12 ms, which indicates that OH from the wet chemical synthesis is successfully removed during the vacuum anneal treatment. Using a base-catalysed sol-gel synthesis, silica colloidal spheres with diameters of 175 and 340 nm were grown. Chapter 7 describes the luminescence properties of the 340 nm spheres, implanted with Er up to concentrations of 1.0 at.%. The Er shows a very long luminescence lifetime of 17 ms, and the radiative lifetime is estimated to be 20-22 ms, indicating a high quantum efficiency. This long luminescence lifetime is partly due to the low local optical density of states (DOS) in the free standing silica colloids. Optical gain calculations are made for the colloid/polymer waveguide that predicts a net gain of 8.7 dB at a pump power of 30 mW, for a 15 cm long waveguide. Such a length can be rolled up on an area of 16 mm2. In Chapter 8, calculations of the DOS are described for thin films as well as the spherical colloids. By comparing the calculation with experimentally probed decay rates, radiative and non-radiative components in the decay of Er are determined. Besides optical pumping of planar waveguide amplifiers it would be interesting if electrical pumping could b

  8. Integrated Instrument Simulator Suites for Earth Science

    NASA Technical Reports Server (NTRS)

    Tanelli, Simone; Tao, Wei-Kuo; Matsui, Toshihisa; Hostetler, Chris; Hair, Johnathan; Butler, Carolyn; Kuo, Kwo-Sen; Niamsuwan, Noppasin; Johnson, Michael P.; Jacob, Joseph C.; Tsang, Leung; Shams, Khawaja; Jaruwatanadilok, Sermsak; Oveisgharan, Shadi; Simard, Marc; Turk, Francis J.

    2012-01-01

    The NASA Earth Observing System Simulators Suite (NEOS3) is a modular framework of forward simulations tools for remote sensing of Earth's Atmosphere from space. It was initiated as the Instrument Simulator Suite for Atmospheric Remote Sensing (ISSARS) under the NASA Advanced Information Systems Technology (AIST) program of the Earth Science Technology Office (ESTO) to enable science users to perform simulations based on advanced atmospheric and simple land surface models, and to rapidly integrate in a broad framework any experimental or innovative tools that they may have developed in this context. The name was changed to NEOS3 when the project was expanded to include more advanced modeling tools for the surface contributions, accounting for scattering and emission properties of layered surface (e.g., soil moisture, vegetation, snow and ice, subsurface layers). NEOS3 relies on a web-based graphic user interface, and a three-stage processing strategy to generate simulated measurements. The user has full control over a wide range of customizations both in terms of a priori assumptions and in terms of specific solvers or models used to calculate the measured signals.This presentation will demonstrate the general architecture, the configuration procedures and illustrate some sample products and the fundamental interface requirements for modules candidate for integration.

  9. Feasibility of Integrated Insulation in Rammed Earth

    NASA Astrophysics Data System (ADS)

    Stone, C.; Balintova, M.; Holub, M.

    2015-11-01

    Building Codes in Europe stipulate strict thermal performance criteria which any traditional rammed earth recipe cannot meet. This does not infer that the material itself is inferior; it has many other face saving attributes such as low embodied energy, high workability, sound insulation, fire resistance, aesthetics, high diffusivity and thermal accumulation properties. Integrated insulation is experimented with, to try achieve a 0.22 [W/(m2.K)] overall coefficient of heat transfer for walls required by 2015 Slovak standards, without using external insulation or using technologically complex interstitial insulation. This has the added aesthetic benefit of leaving the earth wall exposed to the external environment. Results evaluate the feasibility of this traditional approach.

  10. Pressure studies of alkali, alkaline earth and rare earth doped C{sub 60} superconductors

    SciTech Connect

    Schirber, J.E.; Bayless, W.R.; Kortan, A.R.; Ozdas, E.; Zhou, O.; Murphy, D.; Fischer, J.E.

    1994-06-01

    Pressure studies of the superconducting transition temperature T{sub c} of the alkali metal doped C{sub 60} compounds helped to establish a universal curve of T{sub c} versus lattice constant upon which nearly all of these materials lie. Various theoretical schemes incorporate this finding and suggest that only the lattice parameter and not the details of the dopant determine T{sub c}. Ca{sub 5}C{sub 60}, the highest T{sub c} member of the alkaline earth doped C{sub 60} superconductor has a T{sub c} which lies on this universal curve so this material, from these considerations, should have the same large negative pressure derivative as the alkali doped superconductors. We have measured dT{sub c}/dP for Ca{sub 5}C{sub 60} and for Yb{sub x}C{sub 60} (x near 3) and find small and positive values indicating that the theoretical models must be expanded to include band structure effects.

  11. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    SciTech Connect

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-15

    The effect of partial substitution of alkaline earth (AE) ions, Sr{sup 2+} and Ca{sup 2+}, for the rare earth (RE) ions, La{sup 3+}, Ce{sup 3+}, Pr{sup 3+}, and Sm{sup 3+}, on the physical properties of REVO{sub 4} compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO{sub 4}-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H{sub 2} fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode. - Graphical abstract: Coulometric titration isotherms for ({open_square}) LaVO{sub 4}, ( White-Circle ) PrVO{sub 4}, ( Lozenge ) CeVO{sub 4}, ( Black-Up-Pointing-Triangle ) Ce{sub 0.7}Sr{sub 0.3}VO{sub 3.85}, and ( Black-Square ) Ce{sub 0.7}Ca{sub 0.3}VO{sub 3.85}, at 973 K. Highlights: Black-Right-Pointing-Pointer Infiltration procedures were used to prepare SOFC anodes from various vanadates. Black-Right-Pointing-Pointer Doping of Alkaline Earth to Rare Earth Vanadates showed to improve conductivity and chemical stability. Black-Right-Pointing-Pointer Alkaline Earth Doped Rare Earth Vanadates-YSZ composites showed conductivities as high as 5 S cm{sup -1} at 973 K. Black-Right-Pointing-Pointer As with other ceramic anodes, the addition of a catalyst was required to achieve low anode impedance.

  12. Health Sensing Functions in Thermal Barrier Coatings Incorporating Rare-Earth-Doped Luminescent Sublayers

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Singh, J.; Wolfe, D. E.

    2004-01-01

    Great effort has been directed towards developing techniques to monitor the health of thermal barrier coatings (TBCs) that would detect the approach of safety-threatening conditions. An unconventional approach is presented here where health sensing functionality is integrated into the TBC itself by the incorporation of rare-earth-doped luminescent sublayers to monitor erosion as well as whether the TBC is maintaining the underlying substrate at a sufficiently low temperature. Erosion indication is demonstrated in electron-beam physical vapor deposited (EB-PVD) TBCs consisting of 7wt% yttria-stabilized zirconia (7YSZ) with europium-doped and terbium-doped sublayers. Multiple ingot deposition produced sharp boundaries between the doped sublayers without interrupting the columnar growth of the TBC. The TBC-coated specimens were subjected to alumina particle jet erosion, and the erosion depth was then indicated under ultraviolet illumination that excited easily visible luminescence characteristic of sublayer that was exposed by erosion. In addition, temperature measurements from a bottom-lying europium-doped sublayer in a TBC produced by multiple ingot EB-PVD were accomplished by measuring the temperature-dependent decay time from the 606 nm wavelength emission excited in that sublayer with a 532 nm wavelength laser that was selected for its close match to one of the europium excitation wavelengths as well as being at a wavelength where the TBC is relatively transparent. It is proposed the low dopant levels and absence of interruption of the TBC columnar growth allow the addition of the erosion and temperature sensing functions with minimal effects on TBC performance.

  13. Energetics of Rare Earth Doped Uranium Oxide Solid Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Lei

    The physical and chemical properties of UO2 nuclear fuels are affected as fission products accumulate during irradiation. The lanthanides, a main group of fission products, form extensive solid solutions with uranium oxide in the fluorite structure. Thermodynamic studies of such solid solutions had been performed to obtain partial molar free energies of oxygen as a function of dopant concentration and temperature; however, direct measurement of formation enthalpies was hampered by the refractory nature of these oxides. In this work, high temperature oxide melt solution calorimetry was utilized to study the thermochemistry of various rare earth doped uranium oxide LnxU 1-xO2-0.5x+y (Ln = La, Y, Nd) over a wide range of dopant concentrations and oxygen contents. The sintered solid solutions were carefully characterized to determine their phase purity, chemical composition, and uranium oxidation state, with most of the materials in the oxygen excess regime. The enthalpies of formation of LnxU1-xO2-0.5x+y were calculated from the calorimetric data. The oxidation enthalpies of these solid solutions are similar to that of UO2. The formation enthalpies from constituent oxides (LnO1.5, UO2, and UO3) become increasingly negative with addition of dopant cations and appear relatively independent of the uranium oxidation state (oxygen content) when the type and concentration of the dopants are the same. This is valid in the oxygen excess regime; thus an estimation of formation enthalpies of LnxU1-xO2 materials can be made. The formation enthalpies from elements of hyperstoichiometric LnxU1-xO 2-0.5x+y materials obtained from calorimetric measurements are in good agreement with those calculated from free energy data. A direct comparison between the formation enthalpies from calorimetric study and computational research using density functional theory was also performed. The experimental and computational energies of LnxU 1-xO2 (Ln = La, Y, Nd) generally agree within 10 kJ/mol. Since all the other doped fluorite oxides based on zirconia, hafnia, ceria, and thoria are in the oxygen deficit (oxygen vacancy formation) regime, a systematic study of these rare earth doped fluorite oxides (LnxA 1-xO2-0.5x) was made comparing experimental and computational results. A consistent trend suggested by both calorimetry and computation, was found for all oxygen vacancy containing systems (actinide and non-actinide oxide systems). Larger size mismatch between the smaller host cation (A 4+) and the larger rare earth dopant cation (Ln3+) generally produces more stable solid solutions. The energetics of these systems is the result of competition between strain energy arising from size mismatch (endothermic) and defect association (exothermic). The formation enthalpies of LnxU1-xO2-0.5x obtained from calculation are slightly positive.

  14. Mixedness determination of rare earth-doped ceramics

    NASA Astrophysics Data System (ADS)

    Czerepinski, Jennifer H.

    The lack of chemical uniformity in a powder mixture, such as clustering of a minor component, can lead to deterioration of materials properties. A method to determine powder mixture quality is to correlate the chemical homogeneity of a multi-component mixture with its particle size distribution and mixing method. This is applicable to rare earth-doped ceramics, which require at least 1-2 nm dopant ion spacing to optimize optical properties. Mixedness simulations were conducted for random heterogeneous mixtures of Nd-doped LaF3 mixtures using the Concentric Shell Model of Mixedness (CSMM). Results indicate that when the host to dopant particle size ratio is 100, multi-scale concentration variance is optimized. In order to verify results from the model, experimental methods that probe a mixture at the micro, meso, and macro scales are needed. To directly compare CSMM results experimentally, an image processing method was developed to calculate variance profiles from electron images. An in-lens (IL) secondary electron image is subtracted from the corresponding Everhart-Thornley (ET) secondary electron image in a Field-Emission Scanning Electron Microscope (FESEM) to produce two phases and pores that can be quantified with 50 nm spatial resolution. A macro was developed to quickly analyze multi-scale compositional variance from these images. Results for a 50:50 mixture of NdF3 and LaF3 agree with the computational model. The method has proven to be applicable only for mixtures with major components and specific particle morphologies, but the macro is useful for any type of imaging that produces excellent phase contrast, such as confocal microscopy. Fluorescence spectroscopy was used as an indirect method to confirm computational results for Nd-doped LaF3 mixtures. Fluorescence lifetime can be used as a quantitative method to indirectly measure chemical homogeneity when the limits of electron microscopy have been reached. Fluorescence lifetime represents the compositional fluctuations of a dopant on the nanoscale while accounting for billions of particles in a fast, non-destructive manner. The significance of this study will show how small-scale fluctuations in homogeneity limit the optimization of optical properties, which can be improved by the proper selection of particle size and mixing method.

  15. Sensing using rare-earth-doped upconversion nanoparticles.

    PubMed

    Hao, Shuwei; Chen, Guanying; Yang, Chunhui

    2013-01-01

    Optical sensing plays an important role in theranostics due to its capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental psychological processes. Rare-earth (RE) doped upconversion nanoparticles (UCNPs) are promising for these endeavors due to their unique frequency converting capability; they emit efficient and sharp visible or ultraviolet (UV) luminescence via use of ladder-like energy levels of RE ions when excited at near infrared (NIR) light that are silent to tissues. These features allow not only a high penetration depth in biological tissues but also a high detection sensitivity. Indeed, the energy transfer between UCNPs and biomolecular or chemical indicators provide opportunities for high-sensitive bio- and chemical-sensing. A temperature-sensitive change of the intensity ratio between two close UC bands promises them for use in temperature mapping of a single living cell. In this work, we review recent investigations on using UCNPs for the detection of biomolecules (avidin, ATP, etc.), ions (cyanide, mecury, etc.), small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as for in vitro temperature sensing. We also briefly summarize chemical methods in synthesizing UCNPs of high efficiency that are important for the detection limit. PMID:23650480

  16. Sensing Using Rare-Earth-Doped Upconversion Nanoparticles

    PubMed Central

    Hao, Shuwei; Chen, Guanying; Yang, Chunhui

    2013-01-01

    Optical sensing plays an important role in theranostics due to its capability to detect hint biochemical entities or molecular targets as well as to precisely monitor specific fundamental psychological processes. Rare-earth (RE) doped upconversion nanoparticles (UCNPs) are promising for these endeavors due to their unique frequency converting capability; they emit efficient and sharp visible or ultraviolet (UV) luminescence via use of ladder-like energy levels of RE ions when excited at near infrared (NIR) light that are silent to tissues. These features allow not only a high penetration depth in biological tissues but also a high detection sensitivity. Indeed, the energy transfer between UCNPs and biomolecular or chemical indicators provide opportunities for high-sensitive bio- and chemical-sensing. A temperature-sensitive change of the intensity ratio between two close UC bands promises them for use in temperature mapping of a single living cell. In this work, we review recent investigations on using UCNPs for the detection of biomolecules (avidin, ATP, etc.), ions (cyanide, mecury, etc.), small gas molecules (oxygen, carbon dioxide, ammonia, etc.), as well as for in vitro temperature sensing. We also briefly summarize chemical methods in synthesizing UCNPs of high efficiency that are important for the detection limit. PMID:23650480

  17. Rare earth doping of gallium nitride by RF-MBE

    NASA Astrophysics Data System (ADS)

    Birkhahn, Ronald H.

    The objective of my dissertation research was to incorporate rare earth (RE) elements, specifically Er, into GaN while preserving growth rates and maintaining or improving crystal quality of the homo- or heteroepitaxial thin films. The purpose of this research was to investigate the visible and infrared light emission characteristics of RE elements in conjunction with the electrical properties of semiconductors for the potential of light emitting devices and optical memory. These GaN films were grown on many types of substrates (e.g. Si, SiC, GaN, Al2O3, etc.) for comparison purposes in a gas and solid source molecular beam epitaxy (MBE) system manufactured by Riber Instruments SA. Solid source Knudsen cells provided the group III and RE precursors and a RF-plasma source cracked and provided the atomic nitrogen species. My research focus concerned establishing growth conditions by MBE and analysis of the resulting undoped and Er-doped GaN films using various materials techniques. Structural properties were examined by optical microscope, x-ray diffraction, SIMS, AFM, and SEM. Optical properties were tested by photoluminscence (PL) (UV to IR), and absorption. Electrical properties included determination of carrier concentration and mobility. The growth and demonstration of devices from these films is also shown. In addition, another RE (Pr) is also incorporated and the resulting film properties are found to behave similarly to GaN:Er. A theory of GaN:Er growth is presented based on currently available data.

  18. Multilayer Thermal Barrier Coating (TBC) Architectures Utilizing Rare Earth Doped YSZ and Rare Earth Pyrochlores

    NASA Technical Reports Server (NTRS)

    Schmitt, Michael P.; Rai, Amarendra K.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

    2014-01-01

    To allow for increased gas turbine efficiencies, new insulating thermal barrier coatings (TBCs) must be developed to protect the underlying metallic components from higher operating temperatures. This work focused on using rare earth doped (Yb and Gd) yttria stabilized zirconia (t' Low-k) and Gd2Zr2O7 pyrochlores (GZO) combined with novel nanolayered and thick layered microstructures to enable operation beyond the 1200 C stability limit of current 7 wt% yttria stabilized zirconia (7YSZ) coatings. It was observed that the layered system can reduce the thermal conductivity by approximately 45 percent with respect to YSZ after 20 hr of testing at 1316 C. The erosion rate of GZO is shown to be an order to magnitude higher than YSZ and t' Low-k, but this can be reduced by almost 57 percent when utilizing a nanolayered structure. Lastly, the thermal instability of the layered system is investigated and thought is given to optimization of layer thickness.

  19. Nonlinear refractive index of a rare-earth-doped fiber laser.

    PubMed

    Bochove, Erik

    2004-10-15

    An expression is derived for the intensity-dependent index of refraction of a rare-earth-doped fiber laser by use of a Kramers-Kronig relation and simple rate equations. The solution is applied to examine the properties of the nonlinear index of an ytterbium-doped silicate fiber laser at 975-nm pump and 1080-nm laser wavelengths. PMID:15532284

  20. Fluorescence properties of rare-earth doped sol-gel silica glasses

    NASA Astrophysics Data System (ADS)

    Stone, Brandon Thomas

    Rare earth doped silica glasses find numerous applications ranging from fiber amplifiers for optical communications to high power lasers for inertial confinement fusion research. The performance of rare earth doped optical devices would be improved by better understanding of relationships among glass structure, composition and dopant ion optical properties. The specific problem of rare earth ion clustering limits the efficiency of rare earth optical devices by limiting optimal rare earth ion concentrations. The fluorescence properties of rare earth ions were studied in sol-gel silica in order to determine the mechanism of rare earth ion clustering and evaluate synthesis procedures designed to prevent clustering. Fluorescence line narrowing measurements were used to identify rare earth clustering. While aluminum co-doping in rare earth doped silica has been found to eliminate rare earth ion clusters, it has also been found to increase the residual hydroxyl content and hydroxyl quenching. The use of an alternate aluminum precursor expected to reduce the hydroxyl content in sol-gel silica and the use of other co-dopant ions to reduce rare earth ion clustering were considered. Hydroxyl quenching due to the large residual hydroxyl content in sol-gel silica lowers optical efficiencies through non-radiative decay of ions in excited states. Excited state lifetime measurements were used to qualitatively assess the hydroxyl content of rare earth doped sol-gel silica with different compositions and prepared with different procedures. Fluorinated dopant ion precursors were used to produce in situ dehydroxylation in rare earth doped sol-gel silica. Additionally, rare earth doped hybrid organic/inorganic gels were prepared in an effort to reduce the hydroxyl content of the final silica glass. The influence of these synthesis schemes on rare earth ion clustering was also determined. The effects of energy transfer between rare earth ions in sol-gel silica were examined with lifetime, fluorescence, and upconversion measurements. Rare earth ion clustering was expected to have a beneficial effect on upconversion. Green and red upconversion fluorescence was detected, and models of the upconversion processes were developed.

  1. Earths Nearest Neighbors: Dynamical integrations of NEO-Earth approaches in support of MANOS

    NASA Astrophysics Data System (ADS)

    Endicott, Thomas; Moskovitz, Nicholas; Binzel, Richard; Polishook, David; Burt, Brian

    2014-11-01

    The Mission Accessible Near-Earth Object Survey (MANOS) began in August 2013 as a multi-year physical characterization survey that was awarded large survey status by NOAO. MANOS will target several hundred mission-accessible NEOs across visible and near-infrared wavelengths, ultimately providing a comprehensive catalog of physical properties (astrometry, light curves, spectra). In support of this telescopic survey, we are performing a suite of orbital integrations to investigate the dynamical evolution of the near-Earth asteroid population.Using orbital information from the Lowell Observatory AstOrb database and the swift orbital integration package, we compute the orbital history of every known NEO from present day to five hundred thousand years in the past. This orbital history is used to identify the temporal evolution of each NEO's minimum orbital intersection distance (MOID) value, quantifying the physical distance between the orbits of a given NEO and that of a terrestrial planet. Due to the non-deterministic behavior of many NEO orbits beyond a few hundred years, these integrated MOIDs do not uniquely determine whether an NEO and a planet will actually encounter one another, bur rather provide a probabilistic metric for the proximity in which two objects can encounter one another. Integrated MOIDs can be a useful tool for correlating measured physical properties with high probabilities of planetary encounters (e.g. Binzel et al. 2010, Nature 463, 331).We will present the status of these orbital integrations. These integrations show a variety of dynamical histories, from objects that are stable over the integration limits to those that show chaotic behavior after approximately fifty to one hundred thousand years. These orbital integrations are being used to track the potentially hazardous object (PHA) population over time, to evaluate dynamical history for both specific objects and NEO sub-populations, and to estimate the evolution of NEO surface temperatures due to changing perihelion distances.

  2. Rare-earth-ion-doped waveguide lasers on a silicon chip

    NASA Astrophysics Data System (ADS)

    Pollnau, Markus

    2015-03-01

    Rare-earth-ion-doped materials are of high interest as amplifiers and lasers in integrated optics. Their longer excited-state lifetimes and the weaker refractive-index change accompanied with rare-earth-ion excitation compared to electron-hole pairs in III-V semiconductors provide spatially and temporally stable optical gain, allowing for high-speed amplification and narrow-linewidth lasers. Amorphous Al2O3 deposited onto thermally oxidized silicon wafers offers the advantage of integration with silicon photonics and electronics. Layer deposition by RF reactive co-sputtering and micro-structuring by chlorine-based reactive-ion etching provide low-loss channel waveguides. With erbium doping, we improved the gain to 2 dB/cm at 1533 nm and a gain bandwidth of 80 nm. The gain is limited by migration-accelerated energy-transfer upconversion and a fast quenching process. Since stimulated emission is even faster than this quenching process, lasers are only affected in terms of their threshold, allowing us to demonstrate diode-pumped micro-ring, distributed-feedback (DFB), and distributed-Bragg-reflector (DBR) lasers in Al2O3:Er3+ and Al2O3:Yb3+ on a silicon chip. Surface-relief Bragg gratings were patterned by laser-interference lithography. Monolithic DFB and DBR cavities with Q-factors of 1.35×106 were realized. In an Er-doped DFB laser, single-longitudinal-mode operation at 1545 nm was achieved with a linewidth of 1.7 kHz, corresponding to a laser Q-factor of 1.14×1011. Yb-doped DFB and DBR lasers were demonstrated at 1020 nm with output powers of 55 mW and a slope efficiency of 67% versus launched pump power. A dual-phaseshift, dual-wavelength laser was achieved and a stable microwave signal at ~15 GHz was created via the heterodyne photo-detection of the two laser wavelengths.

  3. Influence of Rare Earth Doping on the Structural and Catalytic Properties of Nanostructured Tin Oxide

    PubMed Central

    2008-01-01

    Nanoparticles of tin oxide, doped with Ce and Y, were prepared using the polymeric precursor method. The structural variations of the tin oxide nanoparticles were characterized by means of nitrogen physisorption, carbon dioxide chemisorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The synthesized samples, undoped and doped with the rare earths, were used to promote the ethanol steam reforming reaction. The SnO2-based nanoparticles were shown to be active catalysts for the ethanol steam reforming. The surface properties, such as surface area, basicity/base strength distribution, and catalytic activity/selectivity, were influenced by the rare earth doping of SnO2and also by the annealing temperatures. Doping led to chemical and micro-structural variations at the surface of the SnO2particles. Changes in the catalytic properties of the samples, such as selectivity toward ethylene, may be ascribed to different dopings and annealing temperatures.

  4. Integrating Live Access Server into Google Earth

    NASA Astrophysics Data System (ADS)

    Li, J.; Schweitzer, R.; Hankin, S.; O'Brien, K.

    2006-12-01

    The Live Access Server (LAS) is a highly configurable Web server designed to provide flexible access to visualization and analysis products generated from geo-referenced scientific data sets. Now at version 7.0, LAS has been in operation since 1994. The current ~{!0~}Armstrong?release of LAS V7 consists of a set of modular components in a three tiered architecture -- user interface, workflow orchestration and services to access data and generate scientific products. The LAS user interface (UI) helps the user make requests, preventing requests that are impossible or unreasonable. The UI communicates with the LAS Product Server (LPS the workflow orchestration component) via an XML string with an HTTP GET. When a request is received by the LPS, business logic converts this request into a series of Web Service requests invoked via SOAP. The SOAP services perform data access and generate products (visualizations, data subsets, analyses, etc.). LPS packages these outputs into final products via Jakarta Velocity templates for delivery to the end user. Back-end services are most often a legacy application wrapped in a Java class. The Java wrapper classes are deployed as Web Services accessible via SOAP using the AxisServlet and a custom Web Services Deployment Descriptor file. Ferret is the default visualization application used by LAS, though other applications (e.g. Matlab, CDAT, and GrADS) can also be used. This application demonstrates how Keyhole Markup Language (KML) can be used to provide simple integration of LAS and Google Earth. KML makes access to "Virtual Globe" capabilities so simple that it can be added as an option to existing systems. This application is one such example. The ability to package an image in KML was added to the LAS as a new SOAP service. On the LAS user interface, users can select a Google Earth product in the same manner that any other LAS product is requested. The server will dynamically generate a KML file, which contains the 2D plot requested by the user. Then, the plot can be viewed in the Google Earth desktop application.

  5. Thermoluminescent spectra of rare earth doped MgB4O7 dosemeters.

    PubMed

    Karali, T; Rowlands, A P; Prokic, M; Townsend, P D; Halmagean, E

    2002-01-01

    This paper presents X ray excited TL spectra of magnesium borate doped with either single rare earth ions Dy or Tm, or co-doped with Dy/Tm, Tm/Mn or Dy/Tb. Intrinsic emission from the host material is in the UV/blue region at approximately 375 nm, with a tail extending to 200 nm. The main dosimetric peak is detected at approximately 180 degrees C but slight differences are noted between the glow peak maxima from the different rare earth ions and there were changes following thermal treatments. The results are discussed according to the interaction between trapping and rare earth sites. PMID:12382891

  6. Origin of enhanced magnetization in rare earth doped multiferroic bismuth ferrite

    SciTech Connect

    Nayek, C.; Thirmal, Ch.; Murugavel, P.; Tamilselvan, A.; Balakumar, S.

    2014-02-21

    We report structural and magnetic properties of rare earth doped Bi{sub 0.95}R{sub 0.05} FeO{sub 3} (R?=?Y, Ho, and Er) submicron particles. Rare earth doping enhances the magnetization and the magnetization shows an increasing trend with decreasing dopant ionic radii. In contrast to the x-ray diffraction pattern, we have seen a strong evidence for the presence of rare earth iron garnets R{sub 3}Fe{sub 5}O{sub 12} in magnetization measured as a function of temperature, in selected area electron diffraction, and in Raman measurements. Our results emphasised the role of secondary phases in the magnetic property of rare earth doped BiFeO{sub 3} compounds along with the structural distortion favoring spin canting by increase in Dzyaloshinskii-Moriya exchange energy.

  7. Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium

    SciTech Connect

    Page, R.H.; Schaffers, K.I.; Waide, P.A.; Tassano, J.B.; Payne, S.A.; Kruplce, W.F.; Bischel, W.K.

    1997-07-26

    We discuss the upconversion luminescence efficiencies of phosphors that generate red, green, and blue light. The phosphors studied are single crystals and powders co-doped with Er{sup 3+} and Yb{sup 3+}, and with Tm{sup 3+} and Yb{sup 3+}. The Yb ions are pumped near 980 nm; transfers of two or three quanta to the co-doped rare earth ion generate visible luminescence. The main contribution embodied in this work is the quantitative measurement of this upconversion efficiency, based on the use of a calibrated integrating sphere, determination of the fraction of pump light absorbed, and careful control of the pump laser beam profile. The green phosphors are the most efficient, yielding efficiency values as high as 4 %, with the red and blue materials giving 1 - 2 %. Saturation was observed in all cases, suggesting that populations of upconversion steps of the ions are maximized at higher power. Quasi-CW modeling of the intensity- dependent upconversion efficiency was attempted; input data included level lifetimes, transition cross sections, and cross-relaxation rate coefficients. The saturation of the Yb,Er:fluoride media is explained as the pumping of Er{sup 3+} ions into a bottleneck (long-lived state)- the {sup 4}I{sub 13/2} metastable level, making them unavailable for further excitation transfer. 32 refs., 5 figs., 3 tabs.

  8. Synthesis and Photoresponse of Rare-Earth-Doped Phosphosilicates

    SciTech Connect

    Cao, Z.; Lee, Burtrand I.; Samuels, William D.; Exarhos, Gregory J.

    1998-12-14

    Phosphate ceramics doped with Tb3+ ions were synthesized through Sol-Gel process (SGP). the emission intensity as a function of various factors such as matrix composition, crystal structure, particle size, dopant concentration, and synthesis conditions was investigated.

  9. NIR persistent luminescence of lanthanide ion-doped rare-earth oxycarbonates: the effect of dopants.

    PubMed

    Caratto, Valentina; Locardi, Federico; Costa, Giorgio Andrea; Masini, Roberto; Fasoli, Mauro; Panzeri, Laura; Martini, Marco; Bottinelli, Emanuela; Gianotti, Enrica; Miletto, Ivana

    2014-10-22

    A series of luminescent rare-earth ion-doped hexagonal II-type Gd oxycarbonate phosphors Gd2-xRExO2CO3 (RE = Eu(3+), Yb(3+), Dy(3+)) have been successfully synthesized by thermal decomposition of the corresponding mixed oxalates. The Yb(3+) doped Gd-oxycarbonate has evidenced a high persistent luminescence in the NIR region, that is independent from the temperature and makes this materials particular attractive as optical probes for bioimaging. PMID:25285437

  10. The alkali and alkaline earth metal doped ZnO nanotubes: DFT studies

    NASA Astrophysics Data System (ADS)

    Peyghan, Ali Ahmadi; Noei, Maziar

    2014-01-01

    Doping of several alkali and alkaline earth metals into sidewall of an armchair ZnO nanotube has been investigated by employing the density functional theory in terms of energetic, geometric, and electronic properties. It has been found that doping processes of the alkali and alkaline metals are endothermic and exothermic, respectively. Based on the results, contrary to the alkaline metal doping, the electronic properties of the tube are much more sensitive to alkali metal doping so that it is transformed from intrinsic semiconductor with HOMO-LUMO energy gap of 3.77 eV to an extrinsic semiconductor with the energy gap of ~1.11-1.95 eV. The doping of alkali and alkaline metals increases and decreases the work function of the tube, respectively, which may influence the electron emission from the tube surface.

  11. Influence of rare earth doping on thermoelectric properties of SrTiO{sub 3} ceramics

    SciTech Connect

    Liu, J. Wang, C. L.; Li, Y.; Su, W. B.; Zhu, Y. H.; Li, J. C.; Mei, L. M.

    2013-12-14

    Thermoelectric properties of SrTiO{sub 3} ceramics, doped with different rare earth elements, were investigated in this work. It's found that the ionic radius of doping elements plays an important role on thermoelectric properties: SrTiO{sub 3} ceramics doped with large rare earth ions (such as La, Nd, and Sm) exhibit large power factors, and those doped with small ions (such as Gd, Dy, Er, and Y) exhibit low thermal conductivities. Therefore, a simple approach for enhancing the thermoelectric performance of SrTiO{sub 3} ceramics is proposed: mainly doped with large ions to obtain a large power factor and, simultaneously, slightly co-doped with small ions to obtain a low thermal conductivity. Based on this rule, Sr{sub 0.8}La{sub 0.18}Yb{sub 0.02}TiO{sub 3} ceramics were prepared, whose ZT value at 1?023?K reaches 0.31, increasing by a factor of 19% compared with the single-doped counterpart Sr{sub 0.8}La{sub 0.2}TiO{sub 3} (ZT?=?0.26)

  12. Interfacing Superconducting Qubits and Telecom Photons via a Rare-Earth-Doped Crystal

    NASA Astrophysics Data System (ADS)

    O'Brien, Christopher; Lauk, Nikolai; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

    2014-08-01

    We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of ? pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered ? pulses. We predict total transfer efficiencies on the order of 90%.

  13. Laser induced breakdown spectroscopy diagnosis of rare earth doped optical glasses

    SciTech Connect

    Dwivedi, Y.; Thakur, S. N.; Rai, S. B.

    2010-05-01

    In the present work, rare earth (Nd, Eu, Er, Ho) doped oxyfluoroborate glasses were studied using laser induced breakdown spectroscopy (LIBS) technique. It has been observed that rare earth elements other than the doped one also reveal their presence in the spectrum. In addition the spectral lines of elements constituting the glass matrix have also been observed. Different plasma parameters such as plasma temperature and electron density have been estimated. It is concluded that the LIBS is a potential technique to identify simultaneously the light elements (B, O, F) as well as the heavy elements (Fe, Ba, Ca, Eu, Nd, Ho, Er) present in optical glasses.

  14. Earth System Science: An Integrated Approach.

    ERIC Educational Resources Information Center

    Environment, 2001

    2001-01-01

    Details how an understanding of the role played by human activities in global environmental change has emerged. Presents information about the earth system provided by research programs. Speculates about the direction of future research. (DDR)

  15. Growth and characterization of rare earths doped triglycine sulfate crystals

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  16. Numerical simulations of the optical gain of crystalline fiber doped by rare earth and transition ion

    NASA Astrophysics Data System (ADS)

    Daoui, A. K.; Boubir, B.; Adouane, A.; Demagh, N.; Ghoumazi, M.

    2015-02-01

    A fiber laser is a laser whose gain medium is a doped fiber, although lasers whose cavity is made wholly of fibers have also been called fiber lasers. The gain media in a fiber laser is usually fiber doped with rare-earth ions, such as erbium (Er), neodymium (Nd), ytterbium (Yb), thulium (Tm), or praseodymium (Pr), which is doped into the core of the optical fiber, similar to those used to transmit telecommunications signals. Fiber lasers find many applications in materials processing, including cutting, welding, drilling, and marking metal. To maximize their market penetration, it is necessary to increase their output power. In this work, we present a detailed study based on the numerical simulation using MATLAB, of one of the principal characteristics of a fiber laser doped with rare earth ions and transition ion. The gain depends on several parameters such as the length of the doped fiber, the density, the pump power, noise, etc.). The used program resolves the state equations in this context together with those governing the light propagation phenomena. The developed code can also be used to study the dynamic operating modes of a doped fiber laser.

  17. Modifications in the electronic structure of Rare-Earth doped BiFeO3 multiferroic

    NASA Astrophysics Data System (ADS)

    Trivedi, Priyanka; Katba, Savan; Jethva, Sadaf; Udeshi, Malay; Vyas, Brinda; Vagadia, Megha; Gautam, S.; Chae, K. H.; Asokan, K.; Kuberkar, D. G.

    2015-11-01

    We report the modifications in the electronic structure of Rare Earth (RE) doped polycrystalline BiFeO3 (Bi0.9RE0.1FeO3 (RE= La, Pr, and Er)) synthesized using conventional solid state reaction method. Structural studies using XRD shows that all the samples possess rhombohedral symmetry. As compared to Er and Pr-doped BiFeO3, La-doping results in the improvement in P-E behavior. X-ray absorption studies at Fe L-edge shows the presence of mixed valence state of Fe ions in all the samples. Interestingly, O K-edge spectra of La-doped BiFeO3 shows enhancement in the intensity of the feature 'b' assigned to the hybridization of Bi 6s and O 2p orbital.

  18. Structure and distortion of lead fluoride nanocrystals in rare earth doped oxyfluoride glass ceramics.

    PubMed

    Ge, Jin; Zhao, Lijuan; Guo, Hui; Lan, Zijian; Chang, Lifen; Li, Yiming; Yu, Hua

    2013-10-28

    A series of rare earth (RE) doped oxyfluoride glasses with the composition of (45-x) SiO2-5Al2O3-40PbF2-10CdF2-xRe2O3 (x = 1, 5, 10, 15) (mol%) were prepared by a traditional melt-quenching method. Glass ceramics (GCs) were obtained after thermal treatment and characterized by X-ray diffraction (XRD) to investigate the nanocrystal structure and distortion. Both the dopant type and the doping level play an important role in the distortion of the PbF2-RE lattice. It is found that a cubic Pb3REF9 phase forms in low doping GCs, a tetragonal PbREF5 phase forms in middle doping GCs and cubic PbRE3F11 forms in high doping GCs. Accordingly, the site symmetry of RE(3+) dopants in ?-PbF2 nanocrystal undergoes a transition of OhD4hOh with the increase of doping level. The change in the ligands coordinating the RE(3+) ions was further illustrated by the optical changes in Yb-doped GCs. This paper provides insights on the nanocrystal structure of RE at the atomic level and tries to make a complete description of the nanocrystal structure and distortion in these glass-ceramic materials, which will benefit the optimization of optical properties. PMID:24019159

  19. Visible to infrared low temperature photoluminescence of rare earth doped bismuth germanate crystals.

    PubMed

    Canimoglu, A; Ayvacikli, M; Karabulut, Y; Karali, T; Can, N

    2016-05-01

    In this paper, the influence of a series of rare earth (Eu, Tm, Nd) and Cr ion doping on the optical properties of BGO was investigated by means of photoluminescence (PL) from visible to IR region in the 10-300K temperature range using different types of detectors, namely, photomultiplier tube (PMT), InGaAs (IGA), and Si. Several samples were investigated having dopants concentrations of 0.3wt%Nd, 0.4wt%Tm, 0.06wt% Cr and 3ppm Eu. The PL spectra of the samples showed different luminescence behaviour which is assigned to the 4f intra shell transition from rare earth ions. The temperature dependence of the PL from rare earth doped BGO crystals is also examined. PMID:26943903

  20. Nanophotonic photon echo memory based on rare-earth-doped crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Tian; Kindem, Jonathan; Miyazono, Evan; Faraon, Andrei; Caltech nano quantum optics Team

    2015-03-01

    Rare earth ions (REIs) are promising candidates for implementing solid-state quantum memories and quantum repeater devices. Their high spectral stability and long coherence times make REIs a good choice for integration in an on-chip quantum nano-photonic platform. We report the coupling of the 883 nm transition of Neodymium (Nd) to a Yttrium orthosilicate (YSO) photonic crystal nano-beam resonator, achieving Purcell enhanced spontaneous emission by 21 times and increased optical absorption. Photon echoes were observed in nano-beams of different doping concentrations, yielding optical coherence times T2 up to 80 ?s that are comparable to unprocessed bulk samples. This indicates the remarkable coherence properties of Nd are preserved during nanofabrication, therefore opening the possibility of efficient on-chip optical quantum memories. The nano-resonator with mode volume of 1 . 6(? / n) 3 was fabricated using focused ion beam, and a quality factor of 3200 was measured. Purcell enhanced absorption of 80% by an ensemble of ~ 1 106 ions in the resonator was measured, which fulfills the cavity impedance matching condition that is necessary to achieve quantum storage of photons with unity efficiency.

  1. Luminescent dye-doped or rare-earth-doped monodisperse silica nanospheres as efficient labels in DNA microarrays

    NASA Astrophysics Data System (ADS)

    Enrichi, F.; Ricc, R.; Meneghello, A.; Pierobon, R.; Marinello, F.; Schiavuta, P.

    2009-08-01

    Luminescent nanoparticles are gaining more and more interest in bio-labeling and bio-imaging applications, like for example DNA microarray. This is a high-throughput technology used for detection and quantification of nucleic acid molecules and other ones of biological interest. The analysis is resulting by specific hybridization between probe sequences deposited in array and a target ss-DNA usually expressed by PCR and functionalized by a fluorescent dye. These organic labels have well known disadvantages like photobleaching and limited sensitivity. Quantum dots may be used as alternatives, but they present troubles like blinking, toxicity and excitation wavelengths out of the usual range of commercial instruments, lowering their efficiency. Therefore in this work we investigate a different strategy, based on the use of inorganic silica nanospheres incorporating standard luminescent dyes or rare earth doped nanocrystals. In the first case it is possible to obtain a high luminescence emission signal, due to the high number of dye molecules that can be accommodated into each nanoparticle, reduced photobleaching and environmental protection of the dye molecules thanks to the encapsulation in the silica matrix. In the second case, rare earths exhibit narrow emission bands (easy identification), large Stokes shifts (efficient discrimination of excitation and emission) and long luminescence lifetimes (possibility to perform time-delayed analysis) which can be efficiently used for the improvement of signal to noise ratio. The synthesis and characterization of good luminescent silica spheres either by organic dye-doping or by rare-earth-doping are investigated and reported. Moreover, their application in the DNA microarray technology in comparison to the use of standard molecular fluorophores or commercial quantum dots is discussed. The cheap and easy synthesis of these luminescent particles, the stability in water, the surface functionalization and bio-compatibility makes them very promising for present and future applications in bio-labeling and bio-imaging.

  2. Radioluminescence and thermoluminescence of rare earth element and phosphorus-doped zircon

    SciTech Connect

    Karali, T.; Can, N.; Townsend, P.D.; Rowlands, A.P.; Hanchar, J.M.

    2000-06-01

    The radioluminescence and thermoluminescence spectra of synthetic zircon crystals doped with individual trivalent rare earth element (REE) ions (Pr, Sm, Eu, Gd, Dy, Ho, Er, and Yb) and P are reported in the temperature range 25 to 673 K. Although there is some intrinsic UV/blue emission from the host lattice, the dominant signals are from the rare-earth sites, with signals characteristic of the REE{sup 3+} states. The shapes of the glow curves are different for each dopant, and there are distinct differences between glow peak temperatures for different rare-earth lines of the same element. Within the overall set of signals there are indications of linear trends in which some glow peak temperatures vary as a function of the ionic size of the rare earth ions. The temperature shifts of the peaks are considerable, up to 200{degree}, and much larger than those cited in other rare-earth-doped crystals of LaF{sub 3} and Bi{sub 4}Ge{sub 3}O{sub 12}. The data clearly suggest that the rare-earth ions are active both in the trapping and luminescence steps, and hence the TL occurs within localized defect complexes that include REE{sup 3+} ions.

  3. Integrating Models and Datasets with Earth System Curator

    NASA Astrophysics Data System (ADS)

    Deluca, C.; Middleton, D.; Balaji, V.

    2008-05-01

    The central goal of the NSF-funded Earth System Curator project is to develop an integrated portal in which datasets and complex, multi-component Earth System models can be described, archived, browsed, distributed, and compared. To this end, the Curator team has partnered with the established Community Data Portal (CDP) and Earth System Grid (ESG) efforts. This presentation outlines ontology extensions, user interface considerations, metadata acquisition strategies, and other activities and issues in the development of the extended capability. It also describes a first deployment of the extended portal for a summer workshop focused on the comparison of a collection of atmospheric dynamical cores.

  4. PAL spectroscopy of rare-earth doped Ga-Ge-Te/Se glasses

    NASA Astrophysics Data System (ADS)

    Shpotyuk, Ya.; Ingram, A.; Shpotyuk, O.

    2016-04-01

    Positron annihilation lifetime (PAL) spectroscopy was applied for the first time to study free-volume void evolution in chalcogenide glasses of Ga-Ge-Te/Se cut-section exemplified by glassy Ga10Ge15Te75 and Ga10Ge15Te72Se3 doped with 500 ppm of Tb3+ or Pr3+. The collected PAL spectra reconstructed within two-state trapping model reveal decaying tendency in positron trapping efficiency in these glasses under rare-earth doping. This effect results in unchanged or slightly increased defect-related lifetimes τ2 at the cost of more strong decrease in I2 intensities, as well as reduced positron trapping rate in defects and fraction of trapped positrons. Observed changes are ascribed to rare-earth activated elimination of intrinsic free volumes associated mainly with negatively-charged states of chalcogen atoms especially those neighboring with Ga-based polyhedrons.

  5. Ab initio Disordered Local Moment Approach for a Doped Rare-Earth Magnet

    NASA Astrophysics Data System (ADS)

    Matsumoto, Munehisa; Banerjee, Rudra; Staunton, Julie B.

    Following the finite-temperature ab initio calculation framework based on the relativistic disordered local moments [J. B. Staunton et al., Phys. Rev. Lett. 93, 257204 (2004); Phys. Rev. B 74, 144411 (2006)], we computationally demonstrate the possibility of doping-enhanced coercivity at high-temperatures, taking YCo5 as a working material in order to extract the 3d-electron part of the electronic structure of the rare-earth permanent magnets. Alkaline-earth dopants are shown to be the candidates to realize the proposed phenomenon.

  6. Electronic structures and magnetic properties of rare-earth-atom-doped BNNTs

    NASA Astrophysics Data System (ADS)

    Ren, Juan; Zhang, Ning-Chao; Wang, Peng; Ning, Chao; Zhang, Hong; Peng, Xiao-Juan

    2016-04-01

    Stable geometries, electronic structures, and magnetic properties of (8,0) and (4,4) single-walled BN nanotubes (BNNTs) doped with rare-earth (RE) atoms are investigated using the first-principles pseudopotential plane wave method with density functional theory (DFT). The results show that these RE atoms can be effectively doped in BNNTs with favorable energies. Because of the curvature effect, the values of binding energy for RE-atom-doped (4,4) BNNTs are larger than those of the same atoms on (8,0) BNNTs. Electron transfer between RE-5 d, 6 s, and B-2 p, N-2 p orbitals was also observed. Furthermore, electronic structures and magnetic properties of BNNTs can be modified by such doping. The results show that the adsorption of Ce, Pm, Sm, and Eu atoms can induce magnetization, while no magnetism is observed when BNNTs are doped with La. These results are useful for spintronics applications and for developing magnetic nanostructures.

  7. The tetragonal structure of nanocrystals in rare-earth doped oxyfluoride glass ceramics.

    PubMed

    Hu, Nan; Yu, Hua; Zhang, Ming; Zhang, Pan; Wang, Yazhou; Zhao, Lijuan

    2011-01-28

    Rare-earth doped oxyfluoride glasses and nanocrystalline glass ceramics have been prepared and studied by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) aiming at investigating the structure and the symmetry of the nanocrystal as well as the site of the rare-earth ion. To solve the problem encountered by previous researchers due to glass host interference, we etched off glass matrix and released the fluoride nanocrystal, which is more convenient for EDS measurement. A tetragonal phase model with the chemical formula as PbREF(5) proved by quantitative EDS and XRD analyses has been proposed in this paper for the first time. Two specific crystalline phases with the same space group have been observed at 460 °C-500 °C and 520 °C-560 °C, respectively. Moreover, a super "pseudo-cubic" cell based on our tetragonal model may give a good explanation to the probable previous cubic-symmetry misunderstanding by researchers. Additionally, the thermodynamic mechanism of phase transition and the thermal stability related to the structure of nanocrystals in glass ceramics have been studied and supported by ab initio calculations and experimental methods. The structure and thermal stability of the nanocrystal and clear environment of the rare-earth ion reported here have far-reaching significance with respect to the optical investigations and further applications of rare-earth doped oxyfluoride glass ceramics. PMID:21152548

  8. Rare earth doped ring-shaped luminescent micro-composites on patterned ferroelectrics.

    PubMed

    Garca-Santizo, J V; Molina, P; Ramrez, M O; Lemanski, K; Strek, W; Dere?, P J; Baus, L E

    2010-08-16

    Ferroelectric domain patterns are used as templates on which rare earth doped high refractive index nanoparticles activated with trivalent rare earth ions (RE(3+)) are selectively assembled on domain surfaces with a specific polarization. Two-dimensional luminescent heterostructures, with sizes and geometries defined by the ferroelectric patterning are achieved. The process of incorporation and consolidation of the optically active nanoparticles into the alternate domain structures leads to luminescent ring-shaped arrangements with innovative geometries and to a micrometer spatial control of the trivalent rare earth ion emitters. Multicolor emission systems and the possibility of chromatic switching at the micrometer scale among the three different compounds forming the two dimensional structure is demonstrated. PMID:20721219

  9. Integrated computational materials discovery of silver doped tin sulfide as a thermoelectric material.

    PubMed

    Bera, Chandan; Jacob, Stephane; Opahle, Ingo; Gunda, N S Harsha; Chmielowski, Radoslaw; Dennler, Gilles; Madsen, Georg K H

    2014-10-01

    Accelerating the discovery of new materials is crucial for realizing the vision of need-driven materials development. In the present study we employ an integrated computational and experimental approach to search for new thermoelectric materials. High-throughput first principles calculations of thermoelectric transport coefficients are used to screen sulfide compounds conforming to the boundary conditions of abundant and innocuous components. A further computational screening step of substitutional defects is introduced, whereby SnS doped with monovalent cations is identified as having favorable transport properties. By silver doping of SnS under S-rich conditions an electric conductivity more than an order of magnitude higher than reported previously is realized. The obtained thermoelectric power-factor at room temperature is comparable to the state of the art for thermoelectric materials based on earth abundant, non-toxic elements. The high-throughput screening of extrinsic defects solves a long standing bottleneck in search of new thermoelectric materials. We show how the intrinsic carrier concentration in the low-temperature phase of SnSe is two orders of magnitude higher than in SnS. We furthermore find that the carrier concentration in SnSe can still be further optimized by silver doping. PMID:25115284

  10. Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

    NASA Astrophysics Data System (ADS)

    Adijanto, Lawrence; Balaji Padmanabhan, Venu; Holmes, Kevin J.; Gorte, Raymond J.; Vohs, John M.

    2012-06-01

    The effect of partial substitution of alkaline earth (AE) ions, Sr2+ and Ca2+, for the rare earth (RE) ions, La3+, Ce3+, Pr3+, and Sm3+, on the physical properties of REVO4 compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO4-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H2 fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode.

  11. Addressing the Electrical Transport Behavior of Rare Earth Doped Multiferroic Bismuth Ferrite

    NASA Astrophysics Data System (ADS)

    Pradhan, Sangram K.; Rout, Prajna P.; Das, Sangram K.; Roul, Binod K.

    2011-11-01

    Frequently observed deformation of P-E hysteresis loops of multiferroic BiFeO3 (BFO) and doped BFO by leakage currents hindered potential applications of BFO. Apart from the increased power consumption and heating due to leakage current, charge injection associated with the electrical transport properties (I-V) is also believed to be involved in accelerating fatigue as well as raising other reliability issues for real applications. Suitable thin film structure with selection of proper contacts as well as incorporating dopants in BFO, promising results were observed which significantly suppress the leakage current. However, bulk BFO specimen possesses appreciable difficulties for I-V measurements. In this paper, we have carried out electrical transport measurements on sub-millimeter thick bulk BFO and rare earth doped BFO applying different electrical contacts under high voltage biasing configuration. Gd and Ho doped BFO specimens were measured which were processed by slow step sintering schedule. Our experimental findings revealed that Gd & Ho doping in Fe deficient BFO promotes the suppression of oxygen vacancies and in turn reduce leakage current which support the P-E loop. Attempt has been made to explain above results by common transport models which includes Schottky, space charge limited conduction and Poole-Frenkel effect.

  12. Multi-color fluorescence in rare earth acetylacetonate hydrate doped poly methyl methacrylate

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Shen, L. F.; Pun, E. Y. B.; Chen, B. J.; Lin, H.

    2013-01-01

    Europium and terbium acetylacetonate hydrates were doped into poly methyl methacrylate (PMMA). Efficient purplish-red and green fluorescence was obtained from europium acetylacetonate hydrates (EAH) and terbium acetylacetonate hydrates (TAH) doped PMMA respectively. Judd-Ofelt parameters ?2 (19.7310-20 cm2) and ?4 (2.1910-20 cm2) indicate a high inversion asymmetric and strong covalent environment in PMMA. The maximum stimulated emission cross-sections for the 5D0?7FJ (J=1, 2 and 4) transitions in EAH doped PMMA were calculated to be 0.3810-21, 4.9010-21 and 0.3610-21 cm2, respectively. Variable fluorescence color can be efficiently achieved from the cooperation of three fluorescence colors offered by red (Eu3+), green (Tb3+) and blue (ligand) in EAH/TAH codoped PMMA by adjusting the excitation wavelength. These results indicate that PMMA is an effective photoluminescence co-sensitizer and PMMA doped with rare earth acetylacetonate hydrates is a promising candidate for a series of optoelectronic functional devices.

  13. Integrating the Earth, Atmospheric, and Ocean Sciences at Millersville University

    NASA Astrophysics Data System (ADS)

    Clark, R. D.

    2005-12-01

    For nearly 40 years, the Department of Earth Sciences at Millersville University (MU-DES) of Pennsylvania has been preparing students for careers in the earth, atmospheric, and ocean sciences by providing a rigorous and comprehensive curricula leading to B.S. degrees in geology, meteorology, and oceanography. Undergraduate research is a hallmark of these earth sciences programs with over 30 students participating in some form of meritorious research each year. These programs are rich in applied physics, couched in mathematics, and steeped in technical computing and computer languages. Our success is measured by the number of students that find meaningful careers or go on to earn graduate degrees in their respective fields, as well as the high quality of faculty that the department has retained over the years. Student retention rates in the major have steadily increased with the introduction of a formal learning community and peer mentoring initiatives, and the number of new incoming freshmen and transfer students stands at an all-time high. Yet until recently, the disciplines have remained largely disparate with only minor inroads made into integrating courses that seek to address the Earth as a system. This is soon to change as the MU-DES unveils a new program leading to a B.S. in Integrated Earth Systems. The B.S. in Integrated Earth Systems (ISS) is not a reorganization of existing courses to form a marketable program. Instead, it is a fully integrated program two years in development that borrows from the multi-disciplinary backgrounds and experiences of faculty, while bringing in resources that are tailored to visualizing and modeling the Earth system. The result is the creation of a cross-cutting curriculum designed to prepare the 21st century student for the challenges and opportunities attending the holistic study of the Earth as a system. MU-DES will continue to offer programs leading to degrees in geology, meteorology, and ocean science, but in addition, the B.S. in Integrated Earth Systems will serve those students who find excitement at the boundaries of these disciplines, and prepare them for careers in this emerging field. The ISS program will target high school students of the highest caliber who demonstrate strong aptitude in mathematics and the physical sciences, who will need a minimum amount of remedial work. These select students will be exposed to courses in Earth Systems: Cycles and Interactions, Geophysical Fluid Dynamics, Air-Sea Interaction, Boundary Layers and Turbulence, Climate Variability and Global Change, Atmosphere-Ocean Modeling, Solar-Terrestrial Interactions, Weather Systems Science, Earth Observing Systems, Remote Sensing and more, as part of the ISS curriculum. This paper will highlight the MU-DES programs and learning initiatives and expand and elaborate on the new program in ISS.

  14. Optical properties of rare earth doped strontium aluminate (SAO) phosphors: A review

    NASA Astrophysics Data System (ADS)

    Kshatri, D. S.; Khare, A.

    2014-11-01

    After the first news on rare earth (RE) doped strontium aluminate (SAO) phosphors in late 1990s, researchers all over the world geared up to develop stable and efficient persistent phosphors. Scientists studied various features of long lasting phosphors (LLP) and tried to earmark appropriate mechanism. However, about two decades after the discovery of SrAl2O4: Eu2+, Dy3+, the number of persistent luminescent materials is not significant. In this review, we present an overview of the optical characteristics of RE doped SAO phosphors in terms of photoluminescence (PL), thermoluminescence (TL) and afterglow spectra. Also, we refresh the work undertaken to study diverse factors like dopant concentration, temperature, surface energy, role of activator, etc. Simultaneously, some of our important findings on SAO are reported and discussed in the end.

  15. Design of rare-earth-ion doped chalcogenide photonic crystals for enhancing the fluorescence emission

    NASA Astrophysics Data System (ADS)

    Zhang, Peiqing; Dai, Shixun; Niu, Xueke; Xu, Yinsheng; Zhang, Wei; Wu, Yuehao; Xu, Tiefeng; Nie, Qiuhua

    2014-07-01

    Rare-earth-ion doped chalcogenide glass is a promising material for developing mid-infrared light sources. In this work, Tm3+-doped chalcogenide glass was prepared and photonic crystal structures were designed to enhance its fluorescence emission at approximately 3.8 ?m. By employing the finite-difference time-domain (FDTD) simulation, the emission characteristics of the luminescent centers in the bulk material and in the photonic crystals were worked out. Utilizing analysis of the photon excitation inside the sample and the photon extraction on the sample surface, it was found that fluorescence emission can be significantly enhanced 260-fold with the designed photonic crystal structure. The results of this work can be used to realize high-efficiency mid-infrared light sources.

  16. Spectroscopic and electrical properties of Mg Ti ferrite doped with different rare-earth elements

    NASA Astrophysics Data System (ADS)

    Ahmed, M. A.; Ateia, E.; Salem, F. M.

    2006-05-01

    The dielectric constant ( ??), and the electric conductivity ( ?) for Mg 1+xTi xR yFe 2-2x-yO 4, 0.025? y?0.15 doped with different rare-earth ions, R=Er, Ce and Nd, were measured in the temperature range 300-750 K. The measurements were carried out as a function of frequency 50-1000 kHz X-ray diffractograms and IR spectra revealed that all the investigated samples posses the spinel structure. More than one conduction mechanism is used to interpret the electrical measurements. The most predominant one is the hopping mechanism that occurs between the ions of different valences existing on the same and different sites. All the ionic radii of the rare-earth used are too large to occupy the octahedral site. They form secondary phases on the grain boundaries. The electrical properties show that the pure sample has a larger dielectric constant as well as a larger valence exchange with respect to any doped one. This means that introducing rare-earth ions into the samples decreases ?? and increases the resistivity, owing to the decreasing Fe-Fe interaction. This feature can help to obtain well applicable ferrites.

  17. Influence of doping with alkaline earth metals on the optical properties of thermochromic VO2

    NASA Astrophysics Data System (ADS)

    Dietrich, Marc K.; Kramm, Benedikt G.; Becker, Martin; Meyer, Bruno K.; Polity, Angelika; Klar, Peter J.

    2015-05-01

    Thin films of doped VO2 were deposited, analyzed, and optimized with regard to their solar energy transmittance (Tsol) and visible/luminous light transmittance (Tlum) which are important parameters in the context of smart window applications in buildings. The doping with alkaline earth metals (AEM) like Mg, Ca, Sr, or Ba increased both Tsol and Tlum due to a bandgap widening and an associated absorption edge blue-shift. Thereby, the brown-yellowish color impression of pure VO2 thin films, which is one major hindrance limiting the usage of VO2 as thermochromic window coating, was overcome. Transparent thin films with excellent switching behavior were prepared by sputtering. Highly doped V1-xMexO2 (Me = Ca, Sr, Ba) kept its excellent thermochromic switching behavior up to x(Me) = Me/(Me + V) = 10 at. % doping level, while the optical bandgap energy was increased from 1.64 eV for undoped VO2 to 2.38 eV for x(Mg) = 7.7 at. %, 1.85 eV for x(Ca) = 7.4 at. %, 1.84 eV for x(Sr) = 6.4 at. % and 1.70 eV for x(Ba) = 6.8 at. %, as well as the absorption edge is blue shifted by increasing AEM contents. Also, the critical temperature ?c, at which the semiconductor-to-metal transition (SMT) occurs, was decreased by AEM doping, which amounted to about -0.5 K/at. % for all AEM on average. The critical temperature was determined by transmittance-temperature hysteresis measurements. Furthermore, Tsol and Tlum were calculated and were found to be significantly enhanced by AEM doping. Tlum increased from 32.0% in undoped VO2 to 43.4% in VO2 doped with 6.4 at. % Sr. Similar improvements were found for other AEM. The modulation of the solar energy transmittance ?Tsol, which is the difference of the Tsol values in the low and high temperature phase, was almost constant or even slightly increased when the doping level was increased up to about 10 at. % Ca, Sr, or Ba.

  18. Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO? fiber.

    PubMed

    Katsumata, Toru; Morita, Kentaro; Komuro, Shuji; Aizawa, Hiroaki

    2014-08-01

    Visible light thermal radiation from SiO2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO2 fibers are smaller than those from SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO2 are potentially applicable for the fiber-optic thermometry above 900 K. PMID:25173299

  19. Properties and Applications of Laser-Induced Gratings in Rare Earth Doped Glasses.

    NASA Astrophysics Data System (ADS)

    Behrens, Edward Grady

    Scope and method of study. Four-wave-mixing techniques were used in an attempt to create permanent laser-induced grating in Pr^{3+}-, Nd ^{3+}-, Eu^ {3+}-, and Er^{3+ }-doped glasses. The permanent laser-induced grating signal intensity and build-up and erase times were investigated as function of the write beam crossing angle, write beam power, and temperature. Thermal lensing measurements were conducted on Eu^{3+} - and Nd^{3+}-doped glasses and room temperature Raman and resonant Raman spectra were obtained for Eu^{3+}-doped glasses. The permanent laser-induced grating signal intensity was studied in Eu^{3+} -doped alkali-metal glasses as a function of the alkali -metal network modifier ion and a model was developed by treating the sample as a two-level system. Optical device applications of the permanent laser-induced gratings were studied by creating some simple devices. Findings and conclusions. Permanent laser-induced gratings were created in the Pr^{3+ }- and Eu^{3+} -doped glasses. The permanent laser-induced grating is associated with a structural phase change of the glass host. The structural change is produced by high energy phonons which are emitted by radiationless relaxation processes of the rare earth ion. Nd^{3+} and Er^{3+} relax nonradiatively by the emission of phonons of much lower energy which are unable to produce the structural phase change needed to form a permanent laser-induced grating. The difference in energy of the emitted phonons is responsible for the differing characteristics of the thermal lensing experiments. The model does a good job of predicting the experimental results for the asymmetry and other parameters of the two-level system. The application of these laser -induced gratings for optical devices demonstrates their importance to optical technology.

  20. Thermally induced mode coupling in rare-earth doped fiber amplifiers.

    PubMed

    Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard; Broeng, Jes; Lgsgaard, Jesper

    2012-06-15

    We present a simple semianalytical model of thermally induced mode coupling in multimode rare-earth doped fiber amplifiers. The model predicts that power can be transferred from the fundamental mode to a higher-order mode when the operating power exceeds a certain threshold, and thus provides an explanation of recently reported mode instability in such fiber amplifiers under high average-power operation. We apply our model to a simple step-index fiber design, and investigate how the power threshold depends on various design parameters of the fiber. PMID:22739915

  1. Fibre Tip Sensors for Localised Temperature Sensing Based on Rare Earth-Doped Glass Coatings

    PubMed Central

    Schartner, Erik P.; Monro, Tanya M.

    2014-01-01

    We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium:ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.10.3 C to be recorded over the biologically relevant range of temperatures from 2339 C. PMID:25407907

  2. Synthesis of rare earth doped TiO2 nanorods as photocatalysts for lignin degradation

    NASA Astrophysics Data System (ADS)

    Song, Liang; Zhao, Xueyuan; Cao, Lixin; Moon, Ji-Won; Gu, Baohua; Wang, Wei

    2015-10-01

    A two-step process is developed to synthesize rare earth doped titania nanorods (RE-TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE-TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu-TiO2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10-3 s-1. The La3+, Sm3+, Eu3+ and Er3+ doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. We further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products.A two-step process is developed to synthesize rare earth doped titania nanorods (RE-TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE-TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu-TiO2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10-3 s-1. The La3+, Sm3+, Eu3+ and Er3+ doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. We further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03537f

  3. Fibre tip sensors for localised temperature sensing based on rare earth-doped glass coatings.

    PubMed

    Schartner, Erik P; Monro, Tanya M

    2014-01-01

    We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium:ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.1-0.3 C to be recorded over the biologically relevant range of temperatures from 23-39 C. PMID:25407907

  4. Progress in rare-earth-doped mid-infrared fiber lasers.

    PubMed

    Seddon, Angela B; Tang, Zhuoqi; Furniss, David; Sujecki, Slawomir; Benson, Trevor M

    2010-12-01

    The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested. PMID:21165021

  5. High quality factor nanophotonic resonators in bulk rare-earth doped crystals.

    PubMed

    Zhong, Tian; Rochman, Jake; Kindem, Jonathan M; Miyazono, Evan; Faraon, Andrei

    2016-01-11

    Numerous bulk crystalline materials exhibit attractive nonlinear and luminescent properties for classical and quantum optical applications. A chip-scale platform for high quality factor optical nanocavities in these materials will enable new optoelectronic devices and quantum light-matter interfaces. In this article, photonic crystal nanobeam resonators fabricated using focused ion beam milling in bulk insulators, such as rare-earth doped yttrium orthosilicate and yttrium vanadate, are demonstrated. Operation in the visible, near infrared, and telecom wavelengths with quality factors up to 27,000 and optical mode volumes close to one cubic wavelength is measured. These devices enable new nanolasers, on-chip quantum optical memories, single photon sources, and non-linear devices at low photon numbers based on rare-earth ions. The techniques are also applicable to other luminescent centers and crystal. PMID:26832284

  6. High quality factor nanophotonic resonators in bulk rare-earth doped crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Tian; Rochman, Jake; Kindem, Jonathan M.; Miyazono, Evan; Faraon, Andrei

    2016-01-01

    Numerous bulk crystalline materials exhibit attractive nonlinear and luminescent properties for classical and quantum optical applications. A chip-scale platform for high quality factor optical nanocavities in these materials will enable new optoelectronic devices and quantum light-matter interfaces. In this article, photonic crystal nanobeam resonators fabricated using focused ion beam milling in bulk insulators, such as rare-earth doped yttrium orthosilicate and yttrium vanadate, are demonstrated. Operation in the visible, near infrared, and telecom wavelengths with quality factors up to 27,000 and optical mode volumes close to one cubic wavelength is measured. These devices enable new nanolasers, on-chip quantum optical memories, single photon sources, and non-linear devices at low photon numbers based on rare-earth ions. The techniques are also applicable to other luminescent centers and crystals.

  7. The integrated Earth System Model Version 1: formulation and functionality

    SciTech Connect

    Collins, William D.; Craig, Anthony P.; Truesdale, John E.; Di Vittorio, Alan; Jones, Andrew D.; Bond-Lamberty, Benjamin; Calvin, Katherine V.; Edmonds, James A.; Kim, Son H.; Thomson, Allison M.; Patel, Pralit L.; Zhou, Yuyu; Mao, Jiafu; Shi, Xiaoying; Thornton, Peter E.; Chini, Louise M.; Hurtt, George C.

    2015-07-23

    The integrated Earth System Model (iESM) has been developed as a new tool for pro- jecting the joint human/climate system. The iESM is based upon coupling an Integrated Assessment Model (IAM) and an Earth System Model (ESM) into a common modeling in- frastructure. IAMs are the primary tool for describing the human–Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species, land use and land cover change, and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. The iESM project integrates the economic and human dimension modeling of an IAM and a fully coupled ESM within a sin- gle simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore- omitted feedbacks between natural and societal drivers, we can improve scientific under- standing of the human–Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper de- scribes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.

  8. The integrated Earth system model version 1: formulation and functionality

    DOE PAGESBeta

    Collins, W. D.; Craig, A. P.; Truesdale, J. E.; Di Vittorio, A. V.; Jones, A. D.; Bond-Lamberty, B.; Calvin, K. V.; Edmonds, J. A.; Kim, S. H.; Thomson, A. M.; et al

    2015-07-23

    The integrated Earth system model (iESM) has been developed as a new tool for projecting the joint human/climate system. The iESM is based upon coupling an integrated assessment model (IAM) and an Earth system model (ESM) into a common modeling infrastructure. IAMs are the primary tool for describing the human–Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species (SLS), land use and land cover change (LULCC), and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. Themore » iESM project integrates the economic and human-dimension modeling of an IAM and a fully coupled ESM within a single simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore-omitted feedbacks between natural and societal drivers, we can improve scientific understanding of the human–Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper describes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.« less

  9. The integrated Earth system model version 1: formulation and functionality

    NASA Astrophysics Data System (ADS)

    Collins, W. D.; Craig, A. P.; Truesdale, J. E.; Di Vittorio, A. V.; Jones, A. D.; Bond-Lamberty, B.; Calvin, K. V.; Edmonds, J. A.; Kim, S. H.; Thomson, A. M.; Patel, P.; Zhou, Y.; Mao, J.; Shi, X.; Thornton, P. E.; Chini, L. P.; Hurtt, G. C.

    2015-07-01

    The integrated Earth system model (iESM) has been developed as a new tool for projecting the joint human/climate system. The iESM is based upon coupling an integrated assessment model (IAM) and an Earth system model (ESM) into a common modeling infrastructure. IAMs are the primary tool for describing the human-Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species (SLS), land use and land cover change (LULCC), and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. The iESM project integrates the economic and human-dimension modeling of an IAM and a fully coupled ESM within a single simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore-omitted feedbacks between natural and societal drivers, we can improve scientific understanding of the human-Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper describes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.

  10. The EPOS Architecture: Integrated Services for solid Earth Science

    NASA Astrophysics Data System (ADS)

    Cocco, Massimo; Consortium, Epos

    2013-04-01

    The European Plate Observing System (EPOS) represents a scientific vision and an IT approach in which innovative multidisciplinary research is made possible for a better understanding of the physical processes controlling earthquakes, volcanic eruptions, unrest episodes and tsunamis as well as those driving tectonics and Earth surface dynamics. EPOS has a long-term plan to facilitate integrated use of data, models and facilities from existing (but also new) distributed research infrastructures, for solid Earth science. One primary purpose of EPOS is to take full advantage of the new e-science opportunities coming available. The aim is to obtain an efficient and comprehensive multidisciplinary research platform for the Earth sciences in Europe. The EPOS preparatory phase (EPOS PP), funded by the European Commission within the Capacities program, started on November 1st 2010 and it has completed its first two years of activity. EPOS is presently mid-way through its preparatory phase and to date it has achieved all the objectives, milestones and deliverables planned in its roadmap towards construction. The EPOS mission is to integrate the existing research infrastructures (RIs) in solid Earth science warranting increased accessibility and usability of multidisciplinary data from monitoring networks, laboratory experiments and computational simulations. This is expected to enhance worldwide interoperability in the Earth Sciences and establish a leading, integrated European infrastructure offering services to researchers and other stakeholders. The Preparatory Phase aims at leveraging the project to the level of maturity required to implement the EPOS construction phase, with a defined legal structure, detailed technical planning and financial plan. We will present the EPOS architecture, which relies on the integration of the main outcomes from legal, governance and financial work following the strategic EPOS roadmap and according to the technical work done during the first two years in order to establish an effective implementation plan guaranteeing long term sustainability for the infrastructure and the associated services. We plan to describe the RIs to be integrated in EPOS and to illustrate the initial suite of integrated and thematic core services to be offered to the users. We will present examples of combined data analyses and we will address the importance of opening our research infrastructures to users from different communities. We will describe the use-cases identified so far in order to allow stakeholders and potential future users to understand and interact with the EPOS infrastructure. In this framework, we also discuss the global perspectives for data infrastructures in order to verify the coherency of the EPOS plans and present the EPOS contributions. We also discuss the international cooperation initiatives in which EPOS is involved emphasizing the implications for solid Earth data infrastructures. In particular, EPOS and the satellite Earth Observation communities are collaborating in order to promote the integration of data from in-situ monitoring networks and satellite observing systems. Finally, we will also discuss the priorities for the third year of activity and the key actions planned to better involve users in EPOS. In particular, we will discuss the work done to finalize the design phase as well as the activities to start the validation and testing phase of the EPOS infrastructure.

  11. An OpenEarth Framework (OEF) for Integrating and Visualizing Earth Science Data

    NASA Astrophysics Data System (ADS)

    Moreland, J. L.; Nadeau, D. R.; Baru, C.; Crosby, C. J.

    2009-12-01

    The integration of data is essential to make transformative progress in understanding the complex processes operating at the Earths surface and within its interior. While our current ability to collect massive amounts of data, develop structural models, and generate high-resolution dynamics models is well developed, our ability to quantitatively integrate these data and models into holistic interpretations of Earth systems is poorly developed. We lack the basic tools to realize a first-order goal in Earth science of developing integrated 4D models of Earth structure and processes using a complete range of available constraints, at a time when the research agenda of major efforts such as EarthScope demand such a capability. Among the challenges to 3D data integration are data that may be in different coordinate spaces, units, value ranges, file formats, and data structures. While several file format standards exist, they are infrequently or incorrectly used. Metadata is often missing, misleading, or relegated to README text files along side the data. This leaves much of the work to integrate data bogged down by simple data management tasks. The OpenEarth Framework (OEF) being developed by GEON addresses these data management difficulties. The software incorporates file format parsers, data interpretation heuristics, user interfaces to prompt for missing information, and visualization techniques to merge data into a common visual model. The OEFs data access libraries parse formal and de facto standard file formats and map their data into a common data model. The software handles file format quirks, storage details, caching, local and remote file access, and web service protocol handling. Heuristics are used to determine coordinate spaces, units, and other key data features. Where multiple data structure, naming, and file organization conventions exist, those heuristics check for each conventions use to find a high confidence interpretation of the data. When no convention or embedded data yields a suitable answer, the user is prompted to fill in the blanks. The OEFs interaction libraries assist in the construction of user interfaces for data management. These libraries support data import, data prompting, data introspection, the management of the contents of a common data model, and the creation of derived data to support visualization. Finally, visualization libraries provide interactive visualization using an extended version of NASA WorldWind. The OEF viewer supports visualization of terrains, point clouds, 3D volumes, imagery, cutting planes, isosurfaces, and more. Data may be color coded, shaded, and displayed above, or below the terrain, and always registered into a common coordinate space. The OEF architecture is open and cross-platform software libraries are available separately for use with other software projects, while modules from other projects may be integrated into the OEF to extend its features. The OEF is currently being used to visualize data from EarthScope-related research in the Western US.

  12. Rare earth elements in synthetic zircon. 1. synthesis, and rare earth element and phosphorus doping.

    SciTech Connect

    Hanchar, J. M.; Finch, R. J.; Hoskin, W. O.; Watson, E. B.; Cherniak, D. J.; Mariano, A. N.; Chemical Engineering; George Washington Univ.; Univ. of Canterbury; Australian National Univ.; Rensselaer Polytechnic Inst.

    2001-05-01

    Sedimentary mineral assemblages commonly contain detrital zircon crystals as part of the heavy-mineral fraction. Age spectra determined by U-Pb isotopic analysis of single zircon crystals within a sample may directly image the age composition--but not the chemical composition--of the source region. Rare earth element (REE) abundances have been measured for zircons from a range of common crustal igneous rock types from different tectonic environments, as well as kimberlite, carbonatite, and high-grade metamorphic rocks, to assess the potential of using zircon REE characteristics to infer the rock types present in sediment source regions. Except for zircon with probable mantle affinities, zircon REE abundances and normalized patterns show little intersample and intrasample variation. To evaluate the actual variation in detrital zircon REE composition in a true sediment of known mixed provenance, zircons from a sandstone sample from the Statfjord Formation (North Sea) were analyzed. Despite a provenance including high-grade metasediment and granitoids and a range in zircon age of 2.82 b.y., the zircon REEs exhibit a narrow abundance range with no systematic differences in pattern shape. These evidences show zircon REE patterns and abundances are generally not useful as indicators of provenance.

  13. Demonstrating the possibility of implementing the Toffoli gate in crystals doped by rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, R. A.; Gushchin, L. A.; Zelensky, I. V.; Malakyan, Yu. P.; Sobgaida, D. A.

    2015-07-01

    A scheme for the implementation of the Toffoli gate in inorganic crystals doped by rare-earth metal ions is proposed. A numerical analysis of the factors affecting the fidelity of the Toffoli gate implementation is carried out, and estimates for the available experimental parameters are obtained. A demonstration experiment is set up in which behavior similar to the Toffoli gate is shown for ensembles of Pr3+ ions doped into a LaF3 crystal.

  14. Nanophotonic coherent light–matter interfaces based on rare-earth-doped crystals

    PubMed Central

    Zhong, Tian; Kindem, Jonathan M.; Miyazono, Evan; Faraon, Andrei

    2015-01-01

    Quantum light–matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent 4I9/2–4F3/2 optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2∼100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light–matter interfaces. PMID:26364586

  15. Nanophotonic coherent light-matter interfaces based on rare-earth-doped crystals.

    PubMed

    Zhong, Tian; Kindem, Jonathan M; Miyazono, Evan; Faraon, Andrei

    2015-01-01

    Quantum light-matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent (4)I(9/2)-(4)F(3/2) optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2∼100 μs) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light-matter interfaces. PMID:26364586

  16. Nanophotonic coherent light-matter interfaces based on rare-earth-doped crystals

    NASA Astrophysics Data System (ADS)

    Zhong, Tian; Kindem, Jonathan M.; Miyazono, Evan; Faraon, Andrei

    2015-09-01

    Quantum light-matter interfaces connecting stationary qubits to photons will enable optical networks for quantum communications, precise global time keeping, photon switching and studies of fundamental physics. Rare-earth-ion-doped crystals are state-of-the-art materials for optical quantum memories and quantum transducers between optical photons, microwave photons and spin waves. Here we demonstrate coupling of an ensemble of neodymium rare-earth-ions to photonic nanocavities fabricated in the yttrium orthosilicate host crystal. Cavity quantum electrodynamics effects including Purcell enhancement (F=42) and dipole-induced transparency are observed on the highly coherent 4I9/2-4F3/2 optical transition. Fluctuations in the cavity transmission due to statistical fine structure of the atomic density are measured, indicating operation at the quantum level. Coherent optical control of cavity-coupled rare-earth ions is performed via photon echoes. Long optical coherence times (T2~100 ?s) and small inhomogeneous broadening are measured for the cavity-coupled rare-earth ions, thus demonstrating their potential for on-chip scalable quantum light-matter interfaces.

  17. Synthesis of rare earth doped TiO2 nanorods as photocatalysts for lignin degradation.

    PubMed

    Song, Liang; Zhao, Xueyuan; Cao, Lixin; Moon, Ji-Won; Gu, Baohua; Wang, Wei

    2015-10-28

    A two-step process is developed to synthesize rare earth doped titania nanorods (RE-TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE-TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu-TiO2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10(-3) s(-1). The La(3+), Sm(3+), Eu(3+) and Er(3+) doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. We further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products. PMID:26400095

  18. Catholuminescence properties of rare earth doped CaSnO3 phosphor.

    PubMed

    Canimoglu, A; Garcia-Guinea, J; Karabulut, Y; Ayvacikli, M; Jorge, A; Can, N

    2015-05-01

    The present study describes cathodoluminescence (CL) properties of CaSnO3 phosphors doped with Eu(3+), Tb(3+) and Dy(3+) synthesized by a solid-state method. X-ray diffraction (XRD) patterns confirm that CaSnO3 sintered at 1200C exhibits orthorhombic structure. The evidence and rationale for two strong broad emission bands appeared at 360 and 780nm for undoped CaSnO3 are presented. The CL measurements exhibit that the 4f-4f emissions from (5)D4?(7)F6 (490nm), (5)D4 ?(7)F5 (544nm), (5)D4 ?(7)F4 (586nm) and (5)D4 ?(7)F3 (622nm), assigned to possible transitions of Tb(3+) ions are seen. The strongest one, observed at 544nm, due to its probability of both magnetic and electric transitions make the sample emission green. Emissions at 480, 574, 662 and 755nm were detected for the CaSnO3:Dy(3+) and attributed to the transitions from the (4)F9/2 to various energy levels (6)H15/2, (6)H13/2, (6)H11/2 and (6)H9/2+(6)F11/2 of Dy(3+), respectively. CL spectra of Eu doped CaSnO3 reveal that there is a strong emission peak appeared at 615nm due to the electric dipole transition (5)D0?(7)F2 (red). Finally, our results show that the rare earth doped CaSnO3 have remarkable potential for applications as optical materials since it exhibits efficient and sharp emission due to rare earth ions. PMID:25766113

  19. Observational data preparation and availability for Integrated Earth System modeling

    NASA Astrophysics Data System (ADS)

    Corrigan, A.; Kleese van Dam, K.; Hibbard, K. A.; Williams, D. N.

    2010-12-01

    High-quality and well-characterized observational data sets form the foundation for assessing the current state of the climate, enabling reliable climate predictions, and supporting policy decisions. Many different observational data sources are used for developing parameters and for validating each of the major components of current climate models (e.g., atmosphere model, land-surface model, ocean model, and sea-ice model) as well as formulating extensive integrated assessment models (e.g. land-surface, impact assessment) for the study, analysis, and prediction of the Earths climate. As simulations grow both in complexity, number and size, it will be essential to automate many of the testing and parameterization tasks to keep up with (in particular) analysis and verification demands. With observational data playing a pivotal role in the process, it is therefore necessary that observational data is easily available and consumable within these simulation and testing environments. The major challenges in utilizing observational data for model evaluation are however: significant variability in spatial scale (remote sensing, area coverage, point observation, trajectories), temporal scales (minutes to hours, long term time series to intermittent or time limited observations), different data formats and variable names (between different observational data collections), structure (e.g. multiple independent streams versus gridded values) and representations (between simulation and observation). Solutions have to be found to overcome these differences, speed up the integration process, and enable the simulation community to flexibly assemble the required verification and parameterization data sets within their computational environment. The Program for Climate Model Diagnosis and Intercomparison (PCMDI) and PNNLs integrated Regional Earth Systems Modeling Initiative (iRESM) are collaborating to develop Earth System Grid (ESG) extensions related to regional work such as e.g. coastal river estuary modeling, land usage/coverage, ecological processes. Hereby they will investigate the flexible creation of observational data sets for iRESMs modeling requirements and their publication into ESG, integration of observational data into the model testing and parameterization cycle through the ESG infrastructure and publication of modeling results back into the community utilizing the ESG infrastructure. This work will build on ongoing developments of the ESG Federation (including DOE, NASA, NOAA, BADC, DKRZ, etc.) on incorporating a range of specific observational data needs into the CF metadata convention.

  20. Structural transition in rare earth doped zirconium oxide: A positron annihilation study

    SciTech Connect

    Chakraborty, Keka; Bisoi, Abhijit

    2012-11-15

    Graphical abstract: New microstructural analysis and phase transition of rare earth doped mixed oxide compounds such as: Sm{sub 2?x}Dy{sub x}Zr{sub 2}O{sub 7} (where x = 0.0 ? x ? 2.0) that are potentially useful as solid oxide fuels, ionic conductors, optoelectronic materials and most importantly as radiation resistant host for high level rad-waste disposal, structural transition in the system is reported through positron annihilation spectroscopy as there is an indication in the X-ray diffraction analysis. Highlights: ? Zirconium oxide material doped with rare earth ions. ? The method of positron annihilation spectroscopy suggests a phase transition in the system. ? The crystal structure transformation from pure pyrochlore to defect fluorite type of structure is shown by X-ray diffraction results. -- Abstract: A series of compounds with the general composition Sm{sub 2?x}Dy{sub x}Zr{sub 2}O{sub 7} (where 0 ? x ? 2.0) were synthesized by chemical route and characterized by powder X-ray diffraction (XRD) analysis. The rare earth ion namely Sm{sup +3} in the compound was gradually replaced with another smaller and heavier ion, Dy{sup +3} of the 4f series, there by resulting in orderdisorder structural transition, which has been studied by positron annihilation lifetime and Doppler broadening spectroscopy. This study reveals the subtle electronic micro environmental changes in the pyrochlore lattice (prevalent due to the oxygen vacancy in anti-site defect structure of the compound) toward its transformation to defect fluorite structure as found in Dy{sub 2}Zr{sub 2}O{sub 7}. A comparison of the changes perceived with PAS as compared to XRD analysis is critically assayed.

  1. The OpenEarth Framework (OEF) for the 3D Visualization of Integrated Earth Science Data

    NASA Astrophysics Data System (ADS)

    Nadeau, David; Moreland, John; Baru, Chaitan; Crosby, Chris

    2010-05-01

    Data integration is increasingly important as we strive to combine data from disparate sources and assemble better models of the complex processes operating at the Earth's surface and within its interior. These data are often large, multi-dimensional, and subject to differing conventions for data structures, file formats, coordinate spaces, and units of measure. When visualized, these data require differing, and sometimes conflicting, conventions for visual representations, dimensionality, symbology, and interaction. All of this makes the visualization of integrated Earth science data particularly difficult. The OpenEarth Framework (OEF) is an open-source data integration and visualization suite of applications and libraries being developed by the GEON project at the University of California, San Diego, USA. Funded by the NSF, the project is leveraging virtual globe technology from NASA's WorldWind to create interactive 3D visualization tools that combine and layer data from a wide variety of sources to create a holistic view of features at, above, and beneath the Earth's surface. The OEF architecture is open, cross-platform, modular, and based upon Java. The OEF's modular approach to software architecture yields an array of mix-and-match software components for assembling custom applications. Available modules support file format handling, web service communications, data management, user interaction, and 3D visualization. File parsers handle a variety of formal and de facto standard file formats used in the field. Each one imports data into a general-purpose common data model supporting multidimensional regular and irregular grids, topography, feature geometry, and more. Data within these data models may be manipulated, combined, reprojected, and visualized. The OEF's visualization features support a variety of conventional and new visualization techniques for looking at topography, tomography, point clouds, imagery, maps, and feature geometry. 3D data such as seismic tomography may be sliced by multiple oriented cutting planes and isosurfaced to create 3D skins that trace feature boundaries within the data. Topography may be overlaid with satellite imagery, maps, and data such as gravity and magnetics measurements. Multiple data sets may be visualized simultaneously using overlapping layers within a common 3D coordinate space. Data management within the OEF handles and hides the inevitable quirks of differing file formats, web protocols, storage structures, coordinate spaces, and metadata representations. Heuristics are used to extract necessary metadata used to guide data and visual operations. Derived data representations are computed to better support fluid interaction and visualization while the original data is left unchanged in its original form. Data is cached for better memory and network efficiency, and all visualization makes use of 3D graphics hardware support found on today's computers. The OpenEarth Framework project is currently prototyping the software for use in the visualization, and integration of continental scale geophysical data being produced by EarthScope-related research in the Western US. The OEF is providing researchers with new ways to display and interrogate their data and is anticipated to be a valuable tool for future EarthScope-related research.

  2. Integrating LiDAR Data into Earth Science Education

    NASA Astrophysics Data System (ADS)

    Robinson, S. E.; Arrowsmith, R.; de Groot, R. M.; Crosby, C. J.; Whitesides, A. S.; Colunga, J.

    2010-12-01

    The use of high-resolution topography derived from Light Detection and Ranging (LiDAR) in the study of active tectonics is widespread and has become an indispensable tool to better understand earthquake hazards. For this reason and the spectacular representation of the phenomena the data provide, it is appropriate to integrate these data into the Earth science education curriculum. A collaboration between Arizona State University, the OpenTopography Facility, and the Southern California Earthquake Center are developing, three earth science education products to inform students and other audiences about LiDAR and its application to active tectonics research. First, a 10-minute introductory video titled LiDAR: Illuminating Earthquakes was produced and is freely available online through the OpenTopography portal and SCEC. The second product is an update and enhancement of the Wallace Creek Interpretive Trail website (www.scec.org/wallacecreek). LiDAR topography data products have been added along with the development of a virtual tour of the offset channels at Wallace Creek using the B4 LiDAR data within the Google Earth environment. The virtual tour to Wallace Creek is designed as a lab activity for introductory undergraduate geology courses to increase understanding of earthquake hazards through exploration of the dramatic offset created by the San Andreas Fault (SAF) at Wallace Creek and Global Positioning System-derived displacements spanning the SAF at Wallace Creek . This activity is currently being tested in courses at Arizona State University. The goal of the assessment is to measure student understanding of plate tectonics and earthquakes after completing the activity. Including high-resolution topography LiDAR data into the earth science education curriculum promotes understanding of plate tectonics, faults, and other topics related to earthquake hazards.

  3. EC-EARTH: an Earth System Model based on the ECWMF Integrated Forecasting System

    NASA Astrophysics Data System (ADS)

    Selten, F.; Bintanja, R.; Yang, S.; Severijns, C.; Semmler, T.; Wyser, K.; Wang, X.; Hazeleger, W.

    2009-04-01

    EC-EARTH is the name of an Earth system model that is being developed by a number of institutes in Europe. It is based on the Integrated Forecast System of the European Centre for Medium Range Weather Forecasts (ECWMF). The ECMWF model delivers the best weather forecasts in the world by an objective measure. However, when applied to climate time scales, the performance is not better than the state-of-art climate models by an objective metrics. In the Numerical Weather Prediction version, the top of the atmosphere fluxes (TOA) are not balanced with observed sea surface temperatures as a lower boundary condition. After consultation of experts at ECMWF, a set of parameters was identified that could be used to reduce the model biases and close the TOA heat budget. We describe a set of tuning experiments and show the subsequent improvements in the simulated climate by an objective metrics. The adjusted model at T159L62 resolution coupled to the NEMO2/ORCA1 ocean model outperforms the mean CMIP3 model using this metrics. Additional transient integrations show the extent to which 'fast processes' contribute to the errors in the mean state and variance.

  4. Toward an integrative model of doping use: an empirical study with adolescent athletes.

    PubMed

    Lazuras, Lambros; Barkoukis, Vassileios; Tsorbatzoudis, Haralambos

    2015-02-01

    The present study assessed adolescent athletes' intentions toward doping by using an integrative theoretical model. Overall, 650 adolescent athletes from team and individual sports completed an anonymous structured questionnaire including demographic information, social desirability, achievement goals, motivational regulations, sportspersonship orientations, social cognitive variables, and anticipated regret. Hierarchical regression analysis showed that the integrative model predicted 57.2% of the variance in doping intentions. Social cognitive variables and anticipated regret directly predicted doping intentions. Anticipated regret added 3% incremental variance on top of other predictors. Multiple mediation analyses showed that the effects of achievement goals on intentions were mediated by self-efficacy beliefs, whereas the effects of sportspersonship were mediated by attitudes and anticipated regret. The present study confirmed the dual structure of an integrative model of doping intentions and further highlighted the role of anticipated regret in the study of adolescent doping use. PMID:25730890

  5. An Integrated Concept on Earth and Environmental Sciences Postgraduate Education

    NASA Astrophysics Data System (ADS)

    Grosfeld, Klaus; Lohmann, Gerrit; Ladstätter-Weißenmayer, Annette; Burrows, John; Sprengel, Claudia; Bijma, Jelle

    2010-05-01

    Today's graduate and postgraduate education in the field of Earth System and Environmental Science is a highly interdisciplinary and inter-institutional challenge. The integration of observations, palaeoclimate data, and climate modelling requires networks and collaborations of experts and specialists in order to better understand natural climate variations over a broad range of timescales and disciplines, and to cope with the challenges of recent climate change. The existing research infrastructure at the Alfred-Wegener-Institut Bremerhaven (AWI), University of Bremen, and Jacobs University Bremen offers a unique research environment in north-western Germany to study past, present and future changes of the climate system, with special focus on high latitudinal processes. It covers all kind of disciplines, climate science, geosciences and biosciences, and provides a consistent framework for education and qualification of a new generation of expertly trained, internationally competitive master and PhD students. On postgraduate level, the Postgraduate Programme Environmental Physics (PEP) at the University of Bremen (www.pep.uni-bremen.de) educates the participants on the complex relationship between atmosphere, hydrosphere (ocean), cryosphere (ice region) and solid earth (land). Here, the learning of experimental methods in environmental physics at the most advanced level, numerical data analysis using supercomputers, and data interpretation via sophisticated methods prepare students for a scientific career. Within cooperation with the Ocean University of China (OUC) students are participating one year in the PEP programme during their master studies since 2006, to get finally a double degree of both universities. Based on this successful cooperation a similar programme is in preparation with the Lulea University of Technology, Sweden. The Earth System Science Research School (ESSReS) (www.earth-system-science.org) at the AWI enables PhD students from a variety of disciplines to cooperate and exchange views on the common theme of ‘linking data and modelling', leading to a better understanding of local processes within a global context. Computational and conceptual models of the Earth system provide the ability to investigate different scenarios in biogeochemistry, such as the carbon cycle, the structure of marine sediments, and isotope distribution in climate components. Training and education, especially in time-series and data analysis, is a common key component for all participants. The Helmholtz Graduate School for Polar and Marine Research (POLMAR) (polmar.awi.de), beyond the aforementioned programmes in further cooperation with the Max Planck Institute for Marine Microbiology, Bremen, the University of Potsdam, Bremerhaven University of Applied Science and the Institute for Marine Resources (IMARE), provides a consistent framework for education and qualification for PhD students in general. Developing all categories of skills needed for analysing complex climate and environmental systems and the development of integrated solutions in a supportive network of collaborating research institutions fosters outstanding career options. Structured scientific training and supervision supported by a broad range of transferable skills development courses is indicative for the entire concept. This structured and integrated educational concept provides a strong basis for qualifying the next generation of excellent scientists for the challenging questions in Earth System Science and Polar and Marine Research.

  6. Low temperature CO sensor based on cataluminescence from plasma-assisted catalytic oxidation on Ag doped alkaline-earth nanomaterials.

    PubMed

    Han, Jiaying; Han, Feifei; Ouyang, Jin; He, Lixin; Zhang, Yantu; Na, Na

    2014-03-21

    Based on cataluminescence from plasma-assisted catalytic oxidation, a low temperature CO sensor was fabricated. With Ag doped alkaline-earth catalyst as sensing element, air as discharge gas, carrier gas and oxidant supplier, significant cataluminescence was achieved at low temperature, demonstrating a potential low-consumption and portable sensor of CO. PMID:24519492

  7. The relationship between magnetism and magneto-optical effects in rare earth doped aluminophosphate glasses

    NASA Astrophysics Data System (ADS)

    Valeanu, M.; Sofronie, M.; Galca, A. C.; Tolea, F.; Elisa, M.; Sava, B.; Boroica, L.; Kuncser, V.

    2016-02-01

    Aluminophosphate glasses from the Li2O-BaO-Al2O3-P2O5 system with the addition of nonmagnetic and paramagnetic rare earth ions, were prepared using a wet nonconventional method to process the raw materials, followed by a meltingquenching procedure. The glasses obtained were characterized with respect to their magnetic and magneto-optical properties using superconducting quantum interference device magnetometry and spectroscopic ellipsometry. The assumption of a linear dependence of the Verdet constant on the magnetic susceptibility, with a proportionality constant dependent on the type of vitreous matrix and doping ion, is critically discussed. The diamagnetic and paramagnetic contributions to the Faraday rotation were separately analyzed and specific designs for optimal active and passive elements are proposed.

  8. Interfacing Superconducting Qubits and Telecom Photons via a Rare-Earth Doped Crystal

    NASA Astrophysics Data System (ADS)

    Lauk, Nikolai; O'Brien, Christopher; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

    2014-05-01

    Superconducting qubits (SCQ) are promising candidates for scalable quantum computation. However, they are essentially stationary, which makes them less suitable for quantum information transport. Interfacing short telecom photons with SCQ's would enable the combination of SCQ with low loss optical fiber networks and a fast, reliable quantum network could be realized. To this end, we propose and theoretically analyze a scheme for coupling optical photons to a SCQ, using a rare earth doped crystal (REDC) coupled to the microwave cavity as an interface. The idea is first to store an optical photon by mapping it to a spin excitation in a REDC and then transfer this excitation to a SCQ via a microwave cavity. Due to intrinsic and engineered inhomogeneous broadening of the optical and spin transitions employed in REDC for the storage of short optical photon pulses, we suggest and optimize a special transfer protocol using staggered ?-pulses.

  9. Coherent spectroscopy of rare-earth-metal-ion-doped whispering-gallery-mode resonators

    SciTech Connect

    McAuslan, D. L.; Korystov, D.; Longdell, J. J.

    2011-06-15

    We perform an investigation into the properties of Pr{sup 3+}:Y{sub 2}SiO{sub 5} whispering-gallery-mode resonators as a first step toward achieving the strong coupling regime of cavity QED with rare-earth-metal-ion-doped crystals. Direct measurement of cavity QED parameters are made using photon echoes, giving good agreement with theoretical predictions. By comparing the ions at the surface of the resonator to those in the center, it is determined that the physical process of making the resonator does not negatively affect the properties of the ions. Coupling between the ions and resonator is analyzed through the observation of optical bistability and normal-mode splitting.

  10. Compensation for effects of ambient temperature on rare-earth doped fiber optic thermometer

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sotomayor, J. L.; Krasowski, M. J.; Eustace, J. G.

    1990-01-01

    Variations in ambient temperature have a negative effect on the performance of any fiber optic sensing system. A change in ambient temperature may alter the design parameters of fiber optic cables, connectors, sources, detectors, and other fiber optic components and eventually the performance of the entire system. The thermal stability of components is especially important in a system which employs intensity modulated sensors. Several referencing schemes have been developed to account for the variable losses that occur within the system. However, none of these conventional compensating techniques can be used to stabilize the thermal drift of the light source in a system based on the spectral properties of the sensor material. The compensation for changes in ambient temperature becomes especially important in fiber optic thermometers doped with rare earths. Different approaches to solving this problem are searched and analyzed.

  11. Compensation for effects of ambient temperature on rare-earth doped fiber optic thermometer

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Sotomayor, J. L.; Krasowski, M. J.; Eustace, J. G.

    1989-01-01

    Variations in ambient temperature have a negative effect on the performance of any fiber optic sensing system. A change in ambient temperature may alter the design parameters of fiber optic cables, connectors, sources, detectors, and other fiber optic components and eventually the performance of the entire system. The thermal stability of components is especially important in a system which employs intensity modulated sensors. Several referencing schemes have been developed to account for the variable losses that occur within the system. However, none of these conventional compensating techniques can be used to stabilize the thermal drift of the light source in a system based on the spectral properties of the sensor material. The compensation for changes in ambient temperature becomes especially important in fiber optic thermometers doped with rare earths. Different approaches to solving this problem are searched and analyzed.

  12. Spectroscopic analyses of trivalent rare-earth ions doped in different host materials

    NASA Astrophysics Data System (ADS)

    Chandrasekharan, Sreerenjini

    2011-12-01

    Trivalent rare-earth (RE3+) ions of 4f n electronic configurations are found to possess potential applications in the field of optoelectronic and biophotonic technologies owing to their unique optical properties. They have been used as optical activators in a large number of solid-state laser host materials due to their rich energy level structure. This work focuses on the spectroscopic study of two RE 3+ ions, namely, trivalent erbium and neodymium (Er3+ and Nd3+, respectively), embedded in some important single crystal and nanocrystalline host materials including yttrium orthoaluminate (YAlO3), erbium oxide (Er2O3), yttrium oxide (Y2O3) and a combined host system of Y2O 3 and a vinyl polymer named Polymethyl Methacrylate (PMMA). Each one of these host materials are known to be unique for their characteristic properties such as chemical durability, thermal stability, optical clarity, wide band gaps, biocompatibility, and success as phosphors in various optoelectronic devices. The complete material characterization has been performed through morphology analyses using advanced microscopy techniques and spectroscopic analyses of the characteristic absorption and emission spectra by applying phenomenological crystal-field splitting and Judd-Ofelt techniques. The important spectroscopic parameters such as line strengths, radiative decay rates, and branching ratios have been obtained for the intermanifold transitions from the upper multiplets to the corresponding lower-lying multiplet manifolds 2S+1LJ of RE3+ ions doped in various host systems. Using the radiative decay rates, radiative life times are obtained and the experimental analyses of the fluorescent spectra yield the measured lifetimes of emitting metastable states. Finally, the results are compared with the previously published set of values for the same ions doped in similar type of host systems. Detailed analyses of the spectroscopic properties show that the studied systems RE3+ doped single crystals and nanocrystals can have tremendous applications in optoelectronic and biomedical research.

  13. Potential rare earth free permanent magnet: interstitial boron doped FeCo

    NASA Astrophysics Data System (ADS)

    Khan, Imran; Hong, Jisang

    2014-10-01

    Using the full potential linearized augmented plane wave method, we investigated the structural and the magnetic properties of boron doped FeCo. After fully relaxing the lattice structure, the interatomic distances between boron and Fe atoms were found to be greatly enhanced and the tetragonal distortion was realized due to this increased interatomic distance. Nonetheless, both the unit cell volume and the total magnetic moment of the tetragonally distorted FeCo structure were weakly suppressed compared with those of ideal bulk FeCo. We found a magnetocrystalline anisotropy constant of 0.8 MJ m-3 and this was mainly due to the tetragonal distortion induced by boron impurity, not from the hybridization effect with Fe or Co, because no essential change in the magnetocrystalline anisotropy constant was found even without boron impurity in the lattice distorted system. Additionally, the estimated maximum energy product and coercive field were 100 MGOe and 745 kA m-1, respectively. These results may imply that the interstitial boron doped FeCo can be used for a potential rare earth free permanent magnet although those values are likely to be suppressed in real samples due to micromagnetic factors.

  14. Sol-gel-derived hybrid materials multi-doped with rare-earth metal ions

    NASA Astrophysics Data System (ADS)

    Zelazowska, E.; Rysiakiewicz-Pasek, E.; Borczuch-Laczka, M.; Cholewa-Kowalska, K.

    2012-06-01

    Four different hybrid organic-inorganic materials based on TiO2-SiO2 matrices with organic additives and doped with rare-earth metal ions (III) from the group of europium, cerium, terbium, neodymium, dysprosium and samarium, were synthesized by sol-gel method. Tetraethyl orthosilicate, titanium (IV) isopropoxide and organic compounds, such as butyl acrylate, butyl methacrylate, ethyl acetoacetate, ethylene glycol dimethacrylate, ethyl acetate, propylene carbonate, organic solvents and certain inorganic salts were used in the synthesis. The inorganic part of the sols, which were used in the synthesis of all the hybrid materials, was prepared separately and then the organic parts were added. The materials obtained were aged for three weeks at room temperature and then heated in an electric oven for three hours at temperatures of 80 °C-150 °C. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDX); X-ray diffraction (XRD); Fourier transform infrared spectroscopy (KBr technique); 29Si magic-angle spinning nuclear magnetic resonance; and fluorescence spectroscopy were used for the examination of morphology, microstructure and luminescence properties, respectively. Photoluminescence properties with relatively intense narrow emission lines of Tb, Eu, Dy, Nd, Sm respectively to the RE-ions doping, were observed for all the hybrid materials.

  15. Coherency strain enhanced dielectric-temperature property of rare-earth doped BaTiO{sub 3}

    SciTech Connect

    Jeon, Sang-Chae; Kang, Suk-Joong L.

    2013-03-18

    Core/shell-grained BaTiO{sub 3} samples were prepared with addition of rare earth elements. The core/shell interface was semi-coherent, and many misfit dislocations formed in Dy-doped samples. In contrast, a coherent interface and few dislocations were observed in Ho- and Er-doped samples. Dy-doped samples exhibited poor temperature stability, showing a peak with no frequency dispersion. Ho- and Er-doped samples exhibited a broad curve with frequency dispersion. This improved temperature stability is attributed to the coherency strain, which leads to the formation of polar nano-regions in the shell. Coherency at the core/shell interface is critical to improve the temperature stability of core/shell-structured BaTiO{sub 3}.

  16. Development of an Integrated Earth System Model on the Earth Simulator

    NASA Astrophysics Data System (ADS)

    Kawamiya, M.

    2005-12-01

    Frontier Research Center for Global Change (FRCGC) launched in FY 2002 a project to develop an integrated earth system model that operates on the Earth Simulator, in collaboration with the Center for Climate System Research of the University of Tokyo, National Institute of Environmental Studies. The project aims at development of a model where biological and chemical processes important for the global environment are included to interact with climate changes. The model is developed by adding individual component models to atmospheric and oceanic general circulation models (GCMs). The component models are terrestrial and oceanic carbon cycle models and an atmospheric chemistry model. Improvements of the physical climate model are required in order to extend the model top to the middle atmosphere. Preliminary results with fully-coupled climate - carbon cycle model show a significant positive feedback between climate change and carbon cycle, while another preceding model exhibits an even stronger feedback. Other foci of the project include: experiments with the atmospheric chemistry component model, which demonstrate that impact of climate change on other green house gases such as tropospheric ozone and methane could be significant; examination of resolution-dependence of momentum transfer to the stratosphere by gravity waves using high resolution Atmospheric GCMs which explicitly resolve gravity waves.

  17. An integrated view of data quality in Earth observation

    PubMed Central

    Yang, X.; Blower, J. D.; Bastin, L.; Lush, V.; Zabala, A.; Mas, J.; Cornford, D.; Daz, P.; Lumsden, J.

    2013-01-01

    Data quality is a difficult notion to define precisely, and different communities have different views and understandings of the subject. This causes confusion, a lack of harmonization of data across communities and omission of vital quality information. For some existing data infrastructures, data quality standards cannot address the problem adequately and cannot fulfil all user needs or cover all concepts of data quality. In this study, we discuss some philosophical issues on data quality. We identify actual user needs on data quality, review existing standards and specifications on data quality, and propose an integrated model for data quality in the field of Earth observation (EO). We also propose a practical mechanism for applying the integrated quality information model to a large number of datasets through metadata inheritance. While our data quality management approach is in the domain of EO, we believe that the ideas and methodologies for data quality management can be applied to wider domains and disciplines to facilitate quality-enabled scientific research. PMID:23230156

  18. An integrated view of data quality in Earth observation.

    PubMed

    Yang, X; Blower, J D; Bastin, L; Lush, V; Zabala, A; Mas, J; Cornford, D; Daz, P; Lumsden, J

    2013-01-28

    Data quality is a difficult notion to define precisely, and different communities have different views and understandings of the subject. This causes confusion, a lack of harmonization of data across communities and omission of vital quality information. For some existing data infrastructures, data quality standards cannot address the problem adequately and cannot fulfil all user needs or cover all concepts of data quality. In this study, we discuss some philosophical issues on data quality. We identify actual user needs on data quality, review existing standards and specifications on data quality, and propose an integrated model for data quality in the field of Earth observation (EO). We also propose a practical mechanism for applying the integrated quality information model to a large number of datasets through metadata inheritance. While our data quality management approach is in the domain of EO, we believe that the ideas and methodologies for data quality management can be applied to wider domains and disciplines to facilitate quality-enabled scientific research. PMID:23230156

  19. Integrated Thermal Response Tool for Earth Entry Vehicles

    NASA Technical Reports Server (NTRS)

    Chen, Y.-K.; Milos, F. S.; Partridge, Harry (Technical Monitor)

    2001-01-01

    A system is presented for multi-dimensional, fully-coupled thermal response modeling of hypersonic entry vehicles. The system consists of a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), a commercial finite-element thermal and mechanical analysis code (MARC), and a high fidelity Navier-Stokes equation solver (GIANTS). The simulations performed by this integrated system include hypersonic flow-field, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the ablating and charring heatshield material is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of both the heatshield and the structure can be obtained simultaneously. Representative computations for a proposed blunt body earth entry vehicle are presented and discussed in detail.

  20. The MCVD synthesis and characterization of water tolerant fiber optic waveguides based on alkaline earth-doped silicas

    NASA Astrophysics Data System (ADS)

    Farley, Kevin F.

    Optical fibers that transmit throughout the entire telecommunications spectrum (1.2--1.7 mum) are presently manufactured by the removal of hydrogen or OH from the host preform glass. Hydrogen-oxygen torches are utilized in the conventional preform manufacturing process, but result in the formation of hydroxyls in germanium-doped silica fiber. The hydroxyl species generate unacceptably high losses for long haul telecommunications systems. This thesis has explored an alternative strategy for reducing OH-related absorption in silica-based glasses. Alkaline earth modifiers have been introduced via the modified chemical vapor deposition (MCVD) process to successfully damp out and dramatically reduce the extrinsic attenuation associated with both water and hydrogen. Specifically, alkaline earth ions were introduced into alumino-silicate glasses to form MgO-Al2O3-SiO2, CaO-Al 2O3-SiO2, and SrO-Al2O3-SiO 2 compositions. The utilization of halide precursors based on the vapor delivery of rare earths was incorporated into the existing MCVD set-up to fabricate these optical preforms. Both the bulk preforms and fibers drawn from them were characterized to determine relevant optical properties, including the attenuation, index profiles and extinction coefficients arising from OH in each host. The data indicate that modification of the silica glass structure through the additions of modifying ions can significantly reduce OH related absorption. For example, the doping of alkaline earth ions decreased the extinction coefficient measured at the 1.39 mum) OH overtone, to values < 0.2 L/(mol*cm). Prompt gamma activation analysis (PGAA) measurements conducted at the National Institute of Standards and Technology (NIST) found OH concentrations in the glasses in the range from 10 to 27.5 ppm. The alkaline earth-doped fibers exhibited lower OH absorption at 1.39 mum) than germanium and aluminum-doped reference fibers. Fibers doped with either magnesium, calcium or strontium displayed up to a 92% reduction in OH absorption at 1.39 mum) as compared to the standard fibers. This was achieved without the imposition of any drying techniques. Moreover, the superior performance of the alkaline earth-doped silica fibers was further reinforced by a series of experiments documenting their resistance to hydrogen induced losses.

  1. Synthesis, characterization and processing of active rare earth-doped chalcohalide glasses

    NASA Astrophysics Data System (ADS)

    Debari, Roberto Mauro

    Applications for infrared-transmitting non-oxide glass fibers span a broad range of topics. They can be used in the military, the medical field, telecommunications, and even in agriculture. Rare earth ions are used as dopants in these glasses in order to stimulate emissions in the infrared spectral region. In order to extend the host glass transmission further into the infrared, selenium atoms were substituted for sulfur in the established Ge-S-I chalcohalide glass system and the fundamental properties of these latter glasses were explored. Over 30 different compositions in the Ge-Se-I glass system were investigated as to their thermal and optical properties. The resulting optimum host with a composition of Ge15Se80I5 has a broad transmission range from 0.7 mum to 17.0 mum and a high working range over 145C. The host glass also exhibited a Tg of 125C, making rotational casting of a cladding tube for rod-and-tube fiberization a possibility. The base glass was doped with 1000 to 4000 ppm/wt of erbium, dysprosium, or neodymium. When doped with Er3+-ions, absorptions at 1.54 mum and 3.42 mum were observed. Nd3+-doping resulted in an absorption peak near 4.24 mum and Dy3+ ions caused absorption at 1.30 mum. Fluorescence emissions were found for neodymium at 1.396 mum with a FWHM of 74 nm, and for dysprosium at 1.145 mum with a FWHM of 75 nm, at 1.360 mum with a FWHM of 98 rim and at 1.674 mum with a FWHM of 60 nm. High optical quality tubes of the host glass could be formed using rotational casting in silica ampoules. Glass tubes, 4 to 6 cm long with a 1 cm outer diameter and a tailored inner-hole diameter ranging from 0.4 to 0.6 cm could be synthesized by this process with excellent dimensional tolerances around the circumference as well as along the length. A preform of this size provided 25 continuous meters of unclad fiber with diameters ranging from 140 to 200 mum. A UV-curable acrylate cladding was applied via an external coating cup. An x-ray analysis of the resulting fiber verified the constituents of the fiber. Due to tradeoffs between thermal properties, optical properties and rare earth solubility, the Ge-Se-I glass system must still be optimized prior to use as an active fiber device. Nevertheless, the viability of this host system has been demonstrated in this investigation. Some very promising advantages to adding halides to chalcogenide glass systems have been confirmed, including the tailoring of glass transition temperatures, enhancement of rare earth solubility, expanded fluorescence emissions in the IR, and suppression of some impurity absorption bands. Also, the potential for rod-and-tube fiberization utilizing the rotational casting method for tube synthesis has been established along with its resulting pristine core-clad interface. This research provides a foundation for active fiber device applications in the 2 to 10 mum spectral region.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  3. Structure and superconductivity of rare earth doped La 2-xSr xCuO 4

    NASA Astrophysics Data System (ADS)

    Bchner, B.; Breuer, M.; Schlabitz, W.; Viack, A.; Schfer, W.; Freimuth, A.; Kampf, A. P.

    1994-12-01

    We present results of a detailed investigation of the structural phase transitions and their influence on superconductivity in rare earth doped La 2-xSr xCuO 4. The structural transitions are predominantly determined by size differences of the atoms in alternating layers of the structure. In contrast to the findings in Ba-doped La2CuO4 the influence of the low temperature transition on the electronic properties is not restricted to a narrow hole doping around x ? {1}/{8}. Our data show a strong influence of the buckling of the planar (Cu?O?Cu) bonds on the electronic properties. In particular, superconductivity disappears in the low temperature tetragonal phase if the buckling exceeds a critical strength.

  4. Spectroscopic characterizations of rare earth doped ceramics, nanocrystals, nanocrystal embedded polymeric hosts and their potential applications

    NASA Astrophysics Data System (ADS)

    Nash, Kelly Latrice

    Trivalent rare earth (RE3+) ions have been used as an activator in laser host materials and in a wide variety of photonic applications. Of the competing hosts, one of the most well studied and successful host has been yttrium aluminum garnet Y3Al5O12 (YAG). In comparison to YAG, yttrium oxide (Y2O3) has shown promise as a potential laser medium due to its excellent optical, thermal and mechanical properties. As single crystals, Y2O3 system can be extremely difficult to grow due to the high melting temperature (2200C) of the host. Alternatively, ceramic and nanocrystalline forms of Y2O3 have contributed to renewed interest in the material as laser host and more recently in biological and other photonic applications due to simplicity of fabrication. This work focuses on four RE 3+ ions, namely erbium, neodymium, holmium, europium doped into Y 2O3 and are selected due to their multi-frequency absorption properties and visible to near infrared emission characteristics. The chosen nanocrystalline material are embedded or coated in polymers that are biocompatible resulting in visible to near infrared fluorescent polymers. These materials are characterized through morphology studies and spectroscopic analyses of the absorption and emission spectra. Judd-Ofelt (J-O) and Crystal-Field (CF) techniques are applied to the systems and the results are compared to single crystal and ceramic forms and in some cases these analyses are reported for the first time for this host. Results of these analyses show that the addition of near infrared emitting rare earth nanocrystals to these polymers offers an attractive application to their existing biological applications.

  5. Effect of transition element doping on crystal structure of rare earth borosilicides REB44Si 2

    NASA Astrophysics Data System (ADS)

    Berthebaud, D.; Sato, A.; Michiue, Y.; Mori, T.; Nomura, A.; Shishido, T.; Nakajima, K.

    2011-07-01

    On a previous study on samples of doped-YB 44Si 2, an improvement of thermoelectric properties has been achieved. Regarding the interesting effect of the doping of transition elements on the thermoelectric properties, a single crystal study has been carried out on Zn doped, Rh doped and Ni doped samples to assess how the transition element doping affects the crystal structure. Refinements were carried out based on the structural model solution of YB 44Si 2 reported in a previous study. Variations in the silicon contents were found in the doped single crystals. Splitting of partially occupied sites has also been detected for some of the doped samples. In this paper we present differences in the partial occupations of boron and silicon sites. Possibility of transition elements insertions based on the differences in crystal structures will be presented.

  6. Intense luminescence emission from rare-earth-doped MoO3 nanoplates and lamellar crystals for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Vila, M.; Daz-Guerra, C.; Jerez, D.; Lorenz, K.; Piqueras, J.; Alves, E.

    2014-09-01

    Strong and stable room-temperature photoluminescence (PL) emission is achieved in MoO3 nanoplates and lamellar crystals doped with Er and Eu by ion implantation and subsequent annealing. Micro-Raman and PL spectroscopy reveal that optical activation of the rare earth ions and recovery of the original MoO3 structure are achieved for shorter annealing treatments and for lower temperatures in nanoplates, as compared with lamellar crystals. Er seems to be more readily incorporated into optically active sites in the oxide lattice than Eu. The influence of the dimensionality of the host sample on the characteristics of the PL emission of both rare earth dopants is addressed.

  7. Ultraviolet absorption and excitation spectroscopy of rare-earth-doped glass fibers derived from glassy and crystalline preforms

    NASA Astrophysics Data System (ADS)

    Dragic, Peter D.; Liu, Yuh-Shiuan; Galvin, Thomas C.; Eden, J. G.

    2012-02-01

    Ultraviolet absorption and laser excitation spectroscopy (LES) measurements are presented for rare-earth-doped optical fibers produced from both glassy and crystalline preforms. Absorption spectra are obtained via broad-spectrum UV LEDs emitting in the 250nm region. LES measurements are obtained utilizing a tunable UV laser source. The tunable laser employed is a frequency-doubled titanium:sapphire laser-pumped optical parametric amplifier (OPA) operating down to a minimum wavelength of about 225nm. Our results indicate a roughly linear relationship between the concentration of oxygen deficiency centers (ODC) and rare-earth content, regardless of the preform type, and the slope of the line is found to vary significantly with the rare earth. Additionally, LES measurements are used to elucidate the energy transfer mechanism from pumping in the UV to emission by the rare-earth. In all cases the fibers are Al codoped and those produced from glassy preforms are manufactured via standard methods. Fibers produced from crystalline preforms start with a pure silica-sleeved rare-earth doped YAG crystal rod that becomes glassy (amorphous) post-draw.

  8. The Characterization of Eu2+-Doped Mixed Alkaline-Earth Iodide Scintillator Crystals

    SciTech Connect

    Neal, John S; Boatner, Lynn A; Ramey, Joanne Oxendine; Wisniewski, D.; Kolopus, James A; Cherepy, Nerine; Payne, Stephen A.

    2011-01-01

    The high-performance inorganic scintillator, SrI2:Eu2+, when activated with divalent europium in the concentration range of 3 to 6%, has shown great promise for use in applications that require high-energy-resolution gamma-ray detection. We have recently grown and tested crystals in which other alkaline-earth ions have been partially substituted for Sr ions. Specifically, europium-doped single crystals have been grown in which up to 30 at % of the strontium ions have been substituted for either by barium, magnesium, or calcium ions. In the case of the strontium iodide scintillator host, a material that is characterized by an orthorhombic crystal structure, there are three other column IIA elements that are obvious choices for investigations whose purpose is to realize potential improvements in the performance of SrI2:Eu2+-based scintillators via the replacement of strontium ions with either Mg2+, Ca2+, or Ba2+. Light yields of up to 81,400 photons/MeV with an associated energy resolution of 3.7% (fwhm for 662 keV gamma-rays) have been observed in the case of a partial substitution of Ba2+ for Sr2+. The measured decay times ranged from 1.1 to 2.0 s, while the peak emission wavelengths ranged from 432 to 438 nm.

  9. Rare-earth doped colour tuneable up-conversion ZBLAN phosphor for enhancing photocatalysis

    NASA Astrophysics Data System (ADS)

    Méndez-Ramos, J.; Acosta-Mora, P.; Ruiz-Morales, J. C.; Sierra, M.; Redondas, A.; Ruggiero, E.; Salassa, L.; Borges, M. E.; Esparza, P.

    2015-03-01

    Rare-earth doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride glasses have been successfully synthesized showing outstanding UV-VIS up-conversion luminescence of Er3+ and Tm3+, sensitized by Yb3+ ions, under near-infrared excitation at 980 nm. The ratio between blue, green and red up-conversion emission bands can be adjusted by varying the pump power density of the incident infrared radiation, resulting in a controlled tuneability of the overall emitting colour from greenish to yellowish. Additionally, the observed high energy UV intense up-conversion emissions are suitable to enhance photocatalytic activity of main water-splitting semiconductor electrodes (such as TiO2) used in sustainable production of hydrogen. Photocatalysis and photolysis degradation of methylene blue in water under sun-like irradiation using benchmark photocatalyst (TiO2 Degussa P25) have been boosted by 20% and by a factor of 2.5 respectively, due to the enhancement of UV radiation that reaches the TiO2 particles by the addition of ZBLAN powder into a slurry-type photo-reactor. Hence, up-conversion ZBLAN phosphors contribute to demonstrate the possibility of transforming the incoming infrared radiation into the UV region needed to bridge the gap of photocatalytic semiconductors.

  10. Rare-earth-doped nanophosphors for multicolor cathodoluminescence nanobioimaging using scanning transmission electron microscopy.

    PubMed

    Furukawa, Taichi; Fukushima, Shoichiro; Niioka, Hirohiko; Yamamoto, Naoki; Miyake, Jun; Araki, Tsutomu; Hashimoto, Mamoru

    2015-05-01

    We describe rare-earth-doped nanophosphors (RE-NPs) for biological imaging using cathodoluminescence(CL) microscopy based on scanning transmission electron microscopy (STEM). We report the first demonstration of multicolor CL nanobioimaging using STEM with nanophosphors. The CL spectra of the synthesized nanophosphors (Y2O3∶Eu, Y2O3∶Tb) were sufficiently narrow to be distinguished. From CL images of RE-NPs on an elastic carbon-coated copper grid, the spatial resolution was beyond the diffraction limit of light.Y2O3∶Tb and Y2O3∶Eu RE-NPs showed a remarkable resistance against electron beam exposure even at high acceleration voltage (80 kV) and retained a CL intensity of more than 97% compared with the initial intensity for 1 min. In biological CL imaging with STEM, heavy-metal-stained cell sections containing the RE-NPs were prepared,and both the CL images of RE-NPs and cellular structures, such as mitochondria, were clearly observed from STEM images with high contrast. The cellular CL imaging using RE-NPs also had high spatial resolution even though heavy-metal-stained cells are normally regarded as highly scattering media. Moreover, since theRE-NPs exhibit photoluminescence (PL) excited by UV light, they are useful for multimodal correlative imaging using CL and PL. PMID:26000793

  11. Synthesis and structure of some nano-sized rare-earth metal ions doped potassium hexacyanoferrates

    NASA Astrophysics Data System (ADS)

    Narayan, Himanshu; Alemu, Hailemichael; Nketsa, Pusetso F.; Manatha, Toka J.; Madhavi Thakurdesai, And

    2015-05-01

    Rare-earth ions doped potassium hexacyanoferrates (KR-HCF); with the general formula KRFe(CN)6 3H2 O [with, R?Y, Gd and Yb] nanoparticles were synthesized through precipitation. Characterization was done through particle-size analyzer, scanning electron microscopy (SEM), Fourier Transform infra-red (FTIR) and Raman spectroscopy, and powder X-ray diffraction (XRD). The XRD data was analyzed on FullProf Software Suite program and the unit-cell structure and lattice parameters of KR-HCF samples were determined from scratch and refined further. All the three KR-HCF nanoparticles seem to crystallize in the orthorhombic primitive PMMM space-group. Reasonably good agreement was found with the previously reported lattice constants of KGd-HCF and KYb-HCF orthorhombic single-crystals, except that they assume different space-groups. The observed dissimilarity of space-groups may be attributed to the different time scales involved in the synthesis process. Moreover, the crystal structure of KYFe(CN)6 3H2 O nanoparticles is being reported for the very first time.

  12. Rare-earth-doped nanophosphors for multicolor cathodoluminescence nanobioimaging using scanning transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Furukawa, Taichi; Fukushima, Shoichiro; Niioka, Hirohiko; Yamamoto, Naoki; Miyake, Jun; Araki, Tsutomu; Hashimoto, Mamoru

    2015-05-01

    We describe rare-earth-doped nanophosphors (RE-NPs) for biological imaging using cathodoluminescence (CL) microscopy based on scanning transmission electron microscopy (STEM). We report the first demonstration of multicolor CL nanobioimaging using STEM with nanophosphors. The CL spectra of the synthesized nanophosphors (Y2O3:Eu, Y2O3:Tb) were sufficiently narrow to be distinguished. From CL images of RE-NPs on an elastic carbon-coated copper grid, the spatial resolution was beyond the diffraction limit of light. Y2O3:Tb and Y2O3:Eu RE-NPs showed a remarkable resistance against electron beam exposure even at high acceleration voltage (80 kV) and retained a CL intensity of more than 97% compared with the initial intensity for 1 min. In biological CL imaging with STEM, heavy-metal-stained cell sections containing the RE-NPs were prepared, and both the CL images of RE-NPs and cellular structures, such as mitochondria, were clearly observed from STEM images with high contrast. The cellular CL imaging using RE-NPs also had high spatial resolution even though heavy-metal-stained cells are normally regarded as highly scattering media. Moreover, since the RE-NPs exhibit photoluminescence (PL) excited by UV light, they are useful for multimodal correlative imaging using CL and PL.

  13. Structure-property-composition relationships in doped zinc oxides: enhanced photocatalytic activity with rare earth dopants.

    PubMed

    Goodall, Josephine B M; Illsley, Derek; Lines, Robert; Makwana, Neel M; Darr, Jawwad A

    2015-02-01

    In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases. PMID:25602735

  14. Engineering rare-earth-doped heavy metal oxide glasses for 2-5 ?m lasers

    NASA Astrophysics Data System (ADS)

    Richards, Billy D. O.; Jha, Animesh; Dorofeev, Vitaly; Manzur, Tariq

    2010-04-01

    The electronic states in trivalent rare-earth ions offer an excellent opportunity for designing efficient fibre and bulk lasers for atmospheric remote sensing and LIDAR technology. The first part of this review article focuses on engineering passive fibres for 2-5 ?m transmission. The fabrication of single-mode tungsten tellurite optical fibres from high purity bulk glass rods is described. Fibres with a numerical aperture of 0.1 and core diameter of 10+/-2 ?m have been drawn using suction and rod-in-tube techniques of fibre preform fabrication. Losses of 2.3 dBm-1 at 974 nm have been measured. These fibres are of interest for use as passive transmission fibre or active fibres for lasing in the 2-5 ?m spectral region. The use of heavy metal oxides in the fabrication of glass leads to extended infrared transmission. In the 2nd part of the review we compare the slope efficiencies of Tm3+ and Tm3+/Ho3+ doped glasses and fibres for 1950-2080 nm lasers using a range of pumping schemes in tellurite and germanium oxide hosts. We also explain the importance of choosing 1950-2080 nm tunable lasers as a pump source for stimulated emission at longer wavelengths.

  15. Structures, Stabilities, and Electronic Properties for Rare-Earth Lanthanum Doped Gold Clusters

    NASA Astrophysics Data System (ADS)

    Zhao, Ya-Ru

    2015-02-01

    The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La2Aun (n = 1-9) and pure gold Aun (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La2Aun clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La2Au6 isomer possesses higher stability for small-sized La2Aun clusters (n = 1-9). The charges in the La2Aun clusters transfer from La atoms to the Aun host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La2Aun clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

  16. LiYF4 (YLF) single crystals doped with rare-earth elements

    NASA Astrophysics Data System (ADS)

    Kowalczyk, E.; Kowalczyk, Z.; Grasza, K.; Gala, M.; Lukasiewicz, Tadeusz

    1995-10-01

    LiYF4 (YLF) is a very promising host material for lasers. Investigation of the spectroscopic and physical properties of YLF:Nd has suggested that this material may be a better candidate than Nd:YAG for generating short pulses with high peak power. This is a distinct advantage for many applications. Stimulated emission is attained at 1053 nm and 1047 nm. Also upconservation laser action in YLF and YLF:Er crystals is reported. More recently YLF doped with rare-earth elements has gained some attention. Pulsed room-temperature laser action at 2.06 micrometer has been achieved using YLF:Ho sensitized with Er and Tm. Using YLF:Pr blue light emission at 479 nm at room temperature was observed. Growth experiments of YLF:Nd crystals were carried by the Bridgman method. A vacuum furnace with cylindrical molybdenum heater and graphite crucible have been used. The temperature gradient of 25 degrees Celsius/cm has been achieved by using a stainless steel liner in the lower part of the furnace. The growth was performed in a nitrogen atmosphere. First crystals of YLF:Nd have been obtained.

  17. Synthesis and characterization of rare earth doped novel optical materials and their potential applications

    NASA Astrophysics Data System (ADS)

    Pokhrel, Madhab

    There are many application of photonic materials but selection of photonic materials are always constrained by number of factors such as cost, availability of materials, thermal and chemical stability, toxicity, size and more importantly ease of synthesis and processing along with the efficient emission. For example, quantum dots are efficient emitter but they are significantly toxic, whereas dyes are also efficient emitters but they are chemically unstable. On the other hand, display and LED requires the micron size particles but bio application requires the nano-sized particles. On the other hand, laser gain media requires the ceramics glass or single crystal not the nanoparticles. So, realization of practical optical systems critically depends on suitable materials that offer specific combinations of properties. Solid-state powders such as rare-earth ions doped nano and micron size phosphors are one of the most promising candidates for several photonic applications discussed above. In this dissertation, we investigate the upconversion (UC) fluorescence characteristics of rare earth (RE) doped M2O2S (M = Y, Gd, La) oxysulphide phosphors, for near-infrared to visible UC. Both nano and micron size phosphors were investigated depending on their applications of interest. This oxysulphide phosphor possesses several excellent properties such as chemical stability, low toxicity and can be easily mass produced at low cost. Mainly, Yb3+, Er3+, and Ho3+ were doped in the host lattice, resulting in bright red, green, blue and NIR emissions under 980 nm and 1550 nm excitation at various excitation power densities. Maximum UC quantum yields (QY) up to 6.2 %, 5.8%, and 4.6% were respectively achieved in Yb3+/Er3+ :La2O2S, Y2O2S, and Gd2O 2S. Comparisons have been made with respect to reported most efficient upconverting phosphors beta-NaYF4:20 % Yb/ 2% Er. We believe that present phosphors are the most efficient and lower excitation threshold upconverting phosphors at 980 and 1550 nm excitation reported to date for UV, green, red and NIR emissions, which makes them potential candidates for many photonic applications. In addition, UC mechanisms were proposed in these phosphors based on the time resolved spectroscopic measurements, including concentration, and power dependence studies. Potential applications of these phosphors in different areas such as solar cells, displays, etc. have been explored depending on the measured absolute quantum yield as well as color coordinate measurements. In addition, the application of nanophosphors for bioimaging application has been explored. Results from imaging of the nanoparticles together with aggregates of cultured cells have been studied. In vitro toxicity tests were conducted too. Nanoparticles internalization into the nucleus and cytoplasm were conformed using 3D reconstruction of the Z-stack images collected using the confocal mode of the two photon microscope. Measurement of the magnetization of the phosphor was conducted to study the paramagnetic strength of these Gd based nanoparticles. Magnetic resonance imaging with better contrast was also collected using these particles. Finally, the application of these UC phosphors for solar cell and display has been discussed briefly.

  18. Spintronics: Towards room temperature ferromagnetic devices via manganese and rare earth doped gallium nitride

    NASA Astrophysics Data System (ADS)

    Luen, Melvyn Oliver

    Spintronics is a multidisciplinary field aimed at the active manipulation of spin degrees of freedom in solid-state systems. The goal being the understanding of the interaction between the particle spin and its solid-state environment, and the making of useful devices based on the acquired knowledge. If Moore's law is to continue, then we need to find alternatives to conventional microelectronics. Where conventional electronic devices rely on manipulating charge to produce desired functions, spintronic devices would manipulate both the charge flow and electron spin within that flow. This would add an extra degree of freedom to microelectronics and usher in the era of truly nanoelectronic devices. Research aimed at a whole new generation of electronic devices is underway by introducing electron spin as a new or additional physical variable, and semiconductor devices that exploit this new freedom will operate faster and more efficiently than conventional microelectronic devices and offer new functionality that promises to revolutionize the electronics industry. Long recognized as the material of choice for next-generation solid-state lighting, gallium nitride (GaN) also has proven uses in the field of high power, high frequency field-effect transistors (FETs). But its promise as a material system for spintronic applications may be its ultimate legacy. In this dissertation, the growth of gallium-manganese-nitride (GaMnN) compound semiconductor alloy was investigated through the use of an in-house built metal-organic chemical vapor deposition (MOCVD) reactor. Building on previous investigations of ferromagnetic mechanisms in GaMnN, where ferromagnetism was shown to be carrier mediated, a above room temperature ferromagnetic GaMnN i-p-n diode structure was conceived. This device proved to be the first of its kind in the world, where ferromagnetic properties are controlled via proximity of the mediating holes, upon voltage bias of adjacent structure layers. Simultaneously, post-growth diffusion of ferromagnetic, rare earth species into GaN template thin films also was investigated. Structural, electrical, optical and magnetic characterization of diffused films grown on sapphire was performed. Optimization of the conditions leading to the first successful diffusion of neodymium into GaN thin films, and the magnetic and optical studies that followed are detailed. A mechanism governing and conditions promoting ferromagnetism in rare earth (RE) doped GaN is proposed. The magnetic relationship between two similar and dissimilar rare earth elements, in a single GaN crystal are investigated. Finally, spin valve and magnetic tunnel junction devices based on the magnetic properties of RE-GaN thin films are investigated.

  19. First-principles calculation on oxygen ion migration in alkaline-earth doped La2GeO5.

    PubMed

    Linh, Tran Phan Thuy; Sakaue, Mamoru; Meñez Aspera, Susan; Alaydrus, Musa; Wungu, Triati Dewi Kencana; Linh, Nguyen Hoang; Kasai, Hideaki; Mohri, Takahiro; Ishihara, Tatsumi

    2014-06-25

    By using first-principles calculations based on the density functional theory, we investigated the doping effects of alkaline-earth metals (Ba, Sr and Ca) in monoclinic lanthanum germanate La2GeO5 on its oxygen ion conduction. Although the lattice parameters of the doped systems changed due to the ionic radii mismatch, the crystal structures remained monoclinic. The contribution of each atomic orbital to electronic densities of states was evaluated from the partial densities of states and partial charge densities. It was confirmed that the materials behaved as ionic crystals comprising of cations of La and dopants and anions of oxygen and covalently formed GeO4. The doping effect on the activation barrier for oxygen hopping to the most stable oxygen vacancy site was investigated by the climbing-image nudged elastic band method. By tracing the charge density change during the hopping, it was confirmed that the oxygen motion is governed by covalent interactions. The obtained activation barriers showed excellent quantitative agreements with an experiment for the Ca- and Sr-doped systems in low temperatures as well as the qualitative trend, including the Ba-doped system. PMID:24888249

  20. INTEGRATED EARTH OBSERVATIONS: APPLICATION TO AIR QUALITY AND HUMAN HEALTH

    EPA Science Inventory

    In February 2005, ministers from 60 countries and the European Commission met in Brussels, Belgium to endorse the 10-year plan for a Global Earth Observation System of Systems(GEOSS) prepared by the Group on Earth Observations (GEO), a partnership of nations and international org...

  1. Rare-Earth Doped Wide Bandgap Oxide Semiconductor Materials and Devices

    NASA Astrophysics Data System (ADS)

    Wellenius, Ian Patrick

    Amorphous oxide semiconductors composed of indium gallium zinc oxide are transparent to visible light and have higher electron mobilities than conventional amorphous semiconductors, such as amorphous silicon. The advantages of higher switching speed, lack of dangling bonds leading to good electronic stability and visible spectrum transparency of amorphous oxide semiconductor devices are expected to lead to numerous applications, including transparent displays and flexible electronics. In this thesis the integration of transparent thin film transistors with transparent electroluminescent pixels was investigated. Compared with display technologies employing organic semiconductors that degrade with exposure to moisture and ultraviolet light, the all-oxide structure of this device is expected to be environmentally robust. This is believed to be the first demonstration of an integrated active matrix pixel using amorphous oxide semiconductor materials as both the light emitter and addressing circuit elements. The transparent active matrix pixel was designed, fabricated and characterized, that integrated amorphous indium gallium zinc oxide (IGZO) thin film transistors (TFTs) with a europium-doped IGZO thin film electroluminescent (TFEL) device. The integrated circuits were fabricated using room temperature pulsed laser deposition (PLD) of IGZO and ITO thin films onto substrates of Corning 7059 glass, sputter coated with an ITO back contact and subsequent atomic layer deposited ATO high-k dielectric. A second ITO layer is deposited by PLD as a contact and interconnect layer. All deposition steps were carried out at room temperature. In addition to the integration task, an important part of this thesis concerns the investigation of europium as a dopant in different oxide hosts including gallium oxide, gadolinium oxide, and amorphous IGZO. Amorphous IGZO was chosen for the integration task since it could be deposited at room temperature, however it was found that the emission intensity of Eu:IGZO thin films was strongly dependent on the oxygen pressure during deposition. It was determined that Eu3+ emission only occurs when the films are insulating, the result of increased oxygen pressure during deposition. Relatively low concentrations of Eu3+ of 1 mole percent were used for this study, with the intensity of these first generation pixels at 6 cd/m 2. Both gadolinium and gallium oxide films were investigated at higher substrate temperatures with a range of europium dopant concentrations. It was found that the both cubic and monoclinic phases of gadolinium oxide could be deposited, with the phase determined by deposition oxygen pressure. The film structure was analyzed by x-ray diffraction and transmission electron microscopy and optical spectra were obtained using time resolved photoluminescence (performed by a collaborator). These results were found to be in agreement with Stark-split energy levels calculated by another collaborator. Using 2.5 mole percent europium-doped gallium oxide as a host, bright thin film electroluminescent devices with intensities of 221 cd/m2 observed for a TFEL device excited by a symmetric +/-100 V max square pulse train at 1 kHz. This compares favorably with other red TFEL devices in the literature. Comparison with cathodoluminescence and photoluminescence data suggests that these performance metrics can be improved since the optimal concentration of europium by those experimental techniques was found to be near 10 mole percent. Time resolved photoluminescence revealed that radiative relaxation of the Eu3+ dopant could be modeled by two exponential decay components. Comparison of the intensity versus frequency of the electroluminescent data with time resolved photoluminescence data suggests that the faster component dominates the emission of the TFEL device.

  2. Visualization of melanoma tumor with lectin-conjugated rare-earth doped fluoride nanocrystals

    PubMed Central

    Dumych, Tetiana; Lutsyk, Maxym; Banski, Mateusz; Yashchenko, Antonina; Sojka, Bartlomiej; Horbay, Rostyslav; Lutsyk, Alexander; Stoika, Rostyslav; Misiewicz, Jan; Podhorodecki, Artur; Bilyy, Rostyslav

    2014-01-01

    Aim To develop specific fluorescent markers for melanoma tumor visualization, which would provide high selectivity and reversible binding pattern, by the use of carbohydrate-recognizing proteins, lectins, combined with the physical ability for imaging deep in the living tissues by utilizing red and near infrared fluorescent properties of specific rare-earth doped nanocrystals (NC). Methods B10F16 melanoma cells were inoculated to C57BL/6 mice for inducing experimental melanoma tumor. Tumors were removed and analyzed by lectin-histochemistry using LABA, PFA, PNA, HPA, SNA, GNA, and NPL lectins and stained with hematoxylin and eosin. NPL lectin was conjugated to fluorescent NaGdF4:Eu3+-COOH nanoparticles (5 nm) via zero length cross-linking reaction, and the conjugates were purified from unbound substances and then used for further visualization of histological samples. Fluorescent microscopy was used to visualize NPL-NaGdF4:Eu3+ with the fluorescent emission at 600-720 nm range. Results NPL lectin selectively recognized regions of undifferentiated melanoblasts surrounding neoangiogenic foci inside melanoma tumor, PNA lectin recognized differentiated melanoblasts, and LCA and WGA were bound to tumor stroma regions. NPL-NaGdF4:Eu3+ conjugated NC were efficiently detecting newly formed regions of melanoma tumor, confirmed by fluorescent microscopy in visible and near infrared mode. These conjugates possessed high photostability and were compatible with convenient xylene-based mounting systems and preserved intensive fluorescent signal at samples storage for at least 6 months. Conclusion NPL lectin-NaGdF4:Eu3+ conjugated NC permitted distinct identification of contours of the melanoma tissue on histological sections using red excitation at 590-610 nm and near infrared emission of 700-720 nm. These data are of potential practical significance for development of glycans-conjugated nanoparticles to be used for in vivo visualization of melanoma tumor. PMID:24891277

  3. Polarization dependence of two-photon transition intensities in rare-earth doped crystals

    SciTech Connect

    Le Nguyen, An-Dien

    1996-05-01

    A polarization dependence technique has been developed as a tool to investigate phonon scattering (PS), electronic Raman scattering (ERS), and two-photon absorption (TPA) transition intensities in vanadate and phosphate crystals. A general theory for the polarization dependence (PD) of two-photon transition intensities has been given. Expressions for the polarization dependent behavior of two-photon transition intensities have been tabulated for the 32 crystallographic point groups. When the wavefunctions for the initial and final states of a rare-earth doped in crystals are known, explicit PD expressions with no unknown parameters can be obtained. A spectroscopic method for measuring and interpreting phonon and ERS intensities has been developed to study PrVO{sub 4}, NdVO{sub 4}, ErVO{sub 4}, and TmVO{sub 4} crystals. Relative phonon intensities with the polarization of the incident and scattered light arbitrarily varied were accurately predicted and subsequently used for alignment and calibration in ERS measurements in these systems for the first time. Since ERS and PS intensities generally follow different polarization curves as a function of polar angles, the two can be uniquely identified by comparing their respective polarization behavior. The most crucial application of the technique in ERS spectroscopy is the establishment of a stringent test for the Axe theory. For the first time, the F{sub 1}/F{sub 2} ratio extracted from the experimental fits of the ERS intensities were compared with those predicted by theories which include both the second- and third-order contributions. Relatively good agreement between the fitted values of F{sub 1}/F{sub 2} and the predicted values using the second-order theory has been found.

  4. Ultralow doping profiles for applications in 3D integrated varactor tuned oscillators grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Gyuro, I.; Scheffer, F.; Joseph, M.; Roth, B.; Heuken, M.; Heime, K.

    1991-01-01

    We report on the growth of GaAs/AlGaAs multilayers for three-dimensional (3D) monolithic microwave integrated circuits (MMICs). In this contribution, the experimental fabrication of a varactor tuned FET oscillator is shown with emphasis on the MOVPE requirements. The key to 3D integration is the growth of an AlAs/GaAs superlattice as a high performance insulating layer which enables the stacking of independently optimized structures such as highly doped MESFET layer and a varactor diode layer with a controlled doping profile from n = 8 10 14 cm -3 up to n = 2 10 17 cm -3.

  5. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources.

    PubMed

    Ganem, Joseph; Bowman, Steven R

    2013-01-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence. PMID:24180684

  6. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

    NASA Astrophysics Data System (ADS)

    Ganem, Joseph; Bowman, Steven R.

    2013-11-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence.

  7. Use of thulium-sensitized rare earth-doped low phonon energy crystalline hosts for IR sources

    PubMed Central

    2013-01-01

    Crystalline hosts with low phonon energies enable novel energy transfer processes when doped with rare earth ions. Two applications of energy transfer for rare earth ions in thulium-sensitized low phonon energy crystals that result in infrared luminescence are discussed. One application is an endothermic, phonon-assisted cross-relaxation process in thulium-doped yttrium chloride that converts lattice phonons to infrared emission, which raises the possibility of a fundamentally new method for achieving solid-state optical cooling. The other application is an optically pumped mid-IR phosphor using thulium-praseodymium-doped potassium lead chloride that converts 805-nm diode light to broadband emission from 4,000 to 5,500 nm. These two applications in chloride crystals are discussed in terms of critical radii calculated from Forster-Dexter energy transfer theory. It is found that the critical radii for electric dipole-dipole interactions in low phonon energy chloride crystals are comparable to those in conventional oxide and fluoride crystals. It is the reduction in multi-phonon relaxation rates in chloride crystals that enable these additional energy transfer processes and infrared luminescence. PMID:24180684

  8. Microstructure and properties of in-flight rare-earth doped thermal barrier coatings prepared by suspension plasma spray

    NASA Astrophysics Data System (ADS)

    Gong, Stephanie

    Thermal barrier coatings with lower thermal conductivity improve the efficiency of gas turbine engines by allowing higher operating temperatures. Recent studies were shown that coatings containing a pair of rare-earth oxides with equal molar ratio have lower thermal conductivity and improved sintering resistance compared to the undoped 4-4.5 mol.% yttria-stabilized zirconia (YSZ). In the present work, rare-earth doped coatings were fabricated via suspension plasma spray by spraying YSZ powder-ethanol suspensions that contained dissolved rare-earth nitrates. The compositions of the coatings determined by inductively coupled plasma mass spectroscopy verified that 68 +/- 8% of the rare-earth nitrates added into the suspension was incorporated into the coatings. Two coatings containing different concentrations of the same dopant pair (Nd2O3/Yb2O3), and three coatings having similar concentrations of different dopant pairs (Nd 2O3/Yb2O3, Nd2O3/Gd 2O3, and Gd2O3/Yb2O 3) were produced and compared. The effect of dopant concentration and dopant pair type on the microstructure and properties of the coatings in the as-sprayed and heat treated conditions were investigated using XRD, SEM, TEM, STEM-EDX, and the laser flash method. The cross-sectional morphology of all coatings displayed columnar structure. The porosity content of the coating was found to increase with increasing dopant concentration, but did not significantly change with dopant pairs. Similarly, increasing the Nd2O3/Yb2O 3 concentration lowered the thermal conductivity of the as-sprayed coatings. Although the effect of changing dopant pair type is not as significant as increasing the dopant concentration, the coating that contained Gd2O 3/Yb2O3 exhibited the lowest conductivity compared to coatings that had other dopant pairs. Thermal conductivity measurement performed on the heat treated coatings indicated a larger conductivity increase for the rare-earth doped coatings. A detailed study on the microstructural change of the coatings after various heat treatments at 1200°C and 1300°C showed evidence of crack healing and grain growth. Comparison between the rare-earth dopant distribution of a selected coating before and after a 1300°C/50 hr heat treatment suggests the possibility of dopant rearrangement, which can further increase the thermal conductivity. An explanation on the difference in the properties of the rare-earth doped coatings produced by SPS and conventional processes was discussed.

  9. Information Technology Infusion Case Study: Integrating Google Earth into the A-Train Data Depot

    NASA Astrophysics Data System (ADS)

    Smith, P. M.; Kempler, S. J.; Leptoukh, G. G.; Chen, A.

    2010-12-01

    The purpose of the NASA funded project, Utilizing 3 Dimensional Data Views to Access Data and Discover Relationships Between Multiple Heterogeneous Data Sets Along the A-Train Tracks (Kempler, PI, NASA ROSES NNH07ZDA001N ACCESS Proposal) was to employ the latest 3 dimensional visualization technology to explore and provide direct data access to heterogeneous A-Train datasets, operationally, along, and on either side of the A-Train tracks. Google Earth (tm) provides the foundation for organizing, visualizing, publishing, and synergizing Earth science data in virtual 3 dimensions, for this project. Successful integration of Google Earth (tm) into the A-Train Data Depot (ATDD), resulted in: a) visualizing two-, three- and four-dimensional Earth science data on Google Earth (tm); b) visualizing and synergizing analyzed results derived from the Giovanni online analysis system; and c) visualizing results derived from other standard web services (e.g. OGC WMS). These implementations produce KMZ files that can be opened and visualized via a Google Earth (tm). Integrating A-Train data on Google Earth (tm) through ATDD (http://disc.gsfc.nasa.gov/atdd) affords users the ability to more efficiently discover, access, manipulate and analyze A-Train atmospheric data. The integration of Google Earth (tm) into the ATDD came with anticipated and unanticipated challenges, and solutions, insulated far beneath the easily obtainable ATDD Google Earth (tm) images and data downloads. In addition, some components of integration went rather smoothly. This presentation will discuss the challenges and non-challenges encountered and innovative solutions implemented to enable displaying NASA vertical and horizontal Earth science data within Google Earth (tm) technology. Findings discussed, include: - Interoperability between ATDD and Google Earth (tm) - Required enhancements to existing systems - Reuse of infused technology - Making the total greater than the some of the parts It is hoped that lessons learned and presented can be directly applied or extrapolated to better understanding and overcoming information technology infusion roadblocks.

  10. An Integrated and Collaborative Approach for NASA Earth Science Data

    NASA Technical Reports Server (NTRS)

    Murphy, K.; Lowe, D.; Behnke, J.; Ramapriyan, H.; Behnke, J.; Sofinowski, E.

    2012-01-01

    Earth science research requires coordination and collaboration across multiple disparate science domains. Data systems that support this research are often as disparate as the disciplines that they support. These distinctions can create barriers limiting access to measurements, which could otherwise enable cross-discipline Earth science. NASA's Earth Observing System Data and Information System (EOSDIS) is continuing to bridge the gap between discipline-centric data systems with a coherent and transparent system of systems that offers up to date and engaging science related content, creates an active and immersive science user experience, and encourages the use of EOSDIS earth data and services. The new Earthdata Coherent Web (ECW) project encourages cohesiveness by combining existing websites, data and services into a unified website with a common look and feel, common tools and common processes. It includes cross-linking and cross-referencing across the Earthdata site and NASA's Distributed Active Archive Centers (DAAC), and by leveraging existing EOSDIS Cyber-infrastructure and Web Service technologies to foster re-use and to reduce barriers to discovering Earth science data (http://earthdata.nasa.gov).

  11. Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO{sub 2} fiber

    SciTech Connect

    Katsumata, Toru Morita, Kentaro; Komuro, Shuji; Aizawa, Hiroaki

    2014-08-15

    Visible light thermal radiation from SiO{sub 2} glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO{sub 2} fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO{sub 2} fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO{sub 2} fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO{sub 2} fibers are smaller than those from SiO{sub 2} fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO{sub 2} are potentially applicable for the fiber-optic thermometry above 900 K.

  12. Program for integrating multizonal photographs of the Earth, taken by MKF-6 camera, in a computer

    NASA Technical Reports Server (NTRS)

    Agapov, A. V.; Mosin, S. T.

    1980-01-01

    An algorithm and program are described, for integrating up to 6 simultaneously exposed photographs in different spectral ranges of the surface of the Earth, taken by MKF-6 cameras aboard Soyuz-22. Three of the reference marks are identified on 1 photograph and then are used to integrate the other photographs with the first. The program was compiled for the ES-1040 computer, as a standard subprogram in a system for computer processing of data of study of the Earth from space.

  13. Effects of varying base glass composition on the optical properties of lead borate glasses doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Heidorn, William D.

    Rare Earth (RE) doped lead borate glasses are expected to exhibit a compositional dependence in their optical properties due to the changes induced by variations in the structure of the base glass with increasing lead oxide content. A series of lead borate glasses with the composition xPbO:(99.5 - x)B2O 3 (x = 29.5 to 69.5 in steps of 10 mol%) doped with 0.5 mol% Sm2O3, Er2O3, and Ho2O3 were prepared using the melt quench technique followed by 3 hours of annealing near the glass transition temperature. Optical absorption and fluorescence spectra of these RE doped lead borate glasses were analyzed using Judd-Ofelt theory. The compositional dependence of Judd-Ofelt intensity parameters, O t (t = 2, 4, 6), were determined and were then used to calculate the radiative transition probability of the excited states, the total radiative transition probability, branching ratios, and radiative lifetime of the glasses. From the fluorescence spectra the stimulated emission cross section, and Stark splitting of the excited states were calculated as a function of glass composition. A fourth set of samples with composition xPbO:(99 - x)B2O 3(x = 29 to 69 in steps of 10 mol%) co-doped with 0.5 mol% Er2 O3 and Ho2O3 were also prepared and the effects of co-doping on the absorption and fluorescence were analyzed. In all the glass systems studied, it was found that the optical properties are strongly influenced by structural changes arising from compositional variation. Er3+ transitions exhibit large stimulated cross section suggesting the possible utilization of these materials in laser applications. Keywords: Lead and bismuth borate glasses, fluorescence, optical absorption, Sm3+, Ho3+, Er3+ ions, Judd-Ofelt intensity parameters, stimulated emission cross section.

  14. Time-resolved spectroscopy of 5d-4f transitions in Pr3+ doped alkali-earth fluorides

    NASA Astrophysics Data System (ADS)

    Shendrik, R.; Radzhabov, E.; Nagirnyi, V.

    2010-11-01

    We measured time-resolved spectra and emission decay times under pulsed X-ray and synchrotron excitation in alkali-earth fluorides doped with Pr3+ ions. Two fast decay components were found in the emission spectra of BaF2-Pr3+ and SrF2-Pr3+ . These were 4 ns and 21 ns in BaF2-Pr3+ and 8 and 24 ns in SrF2-Pr3+. The intensity of the faster components 4 ns and 8 ns depended on concentration of Pr3+. Thus, the presence of aggregates might be the cause of such faster components.

  15. Spatially resolved in-core temperature measurement in rare-earth doped fibers during pumping

    NASA Astrophysics Data System (ADS)

    Fiebrandt, Julia; Leich, Martin; Unger, Sonja; Schwuchow, Anka; Jger, Matthias; Rothhardt, Manfred; Bartelt, Hartmut

    2014-03-01

    We demonstrate a spatially distributed measurement technique to observe temperature changes along a pumped Ybdoped fiber. The technique is based on an array of fiber Bragg gratings acting as temperature sensor line. The Bragg gratings are inscribed directly into the actively doped fiber core using high intensity laser pulses and an interferometric setup. We studied the temperature evolution in differently doped fibers under pumping conditions and find different effects contributing to the observed temperature increase. To avoid an additional heating caused by pump-induced photodarkening, we measure the spatially resolved temperature profile during pumping along a photodarkening-reduced, cerium co-doped fiber.

  16. Reduction of magnetic damping constant of FeCo films by rare-earth Gd doping

    SciTech Connect

    Guo, Xiaobin; Xi, Li Li, Yue; Han, Xuemeng; Li, Dong; Wang, Zhen; Zuo, Yalu

    2014-08-18

    Magnetic damping constant (α) is one of the key parameters to determine the critical current density of spin-transfer-torque devices and the switching time of magnetization for ultra-high-frequency devices. In this work, Gd doped FeCo films were fabricated to investigate α based on the ferromagnetic resonance technique. Gd doping not only can efficiently decrease the magnetic inhomogeneity and the extrinsic part of α but also the Landé g-factor and intrinsic part of α. The obtained α was roughly proportional to (g-2){sup 2} and the magnetic anisotropic constant, indicating that the decreased spin-orbit interaction decreases α by Gd doping.

  17. Chalcogenide glasses for infrared applications: New synthesis routes and rare earth doping

    NASA Astrophysics Data System (ADS)

    Hubert, Mathieu

    Chalcogenide glasses and glass-ceramics present a high interest for the production of thermal imaging lenses transparent in the 3--5 microm and 8--12 microm windows. However, chalcogenide glasses are conventionally synthesized utilizing expensive and single use silica ampoules sealed under vacuum. The present work addresses the development of innovative synthesis methods for chalcogenide glasses that can present an alternative to the silica tube route. The first approach assessed by melting the raw starting elements in reusable silica containers appears inadequate for synthesis of glasses from the system Ge-Ga-Se. The second synthesis approach consists of the preparation of amorphous chalcogenide powders by ball milling of raw elements (mechanosynthesis) followed by consolidation of the as-prepared powders. Hot Uniaxial Pressing is suitable for sintering of powders with compositions stable against crystallization but uncontrolled crystallization occurs for the unstable compositions. In contrast, consolidation through Spark Plasma Sintering (SPS) allows production of bulk glasses with large dimensions in a short duration and at relatively low temperatures. Moreover, increased SPS treatment duration yields infrared transparent glass-ceramics with enhanced mechanical properties. This innovative synthesis method combining mechanosynthesis and SPS has been patented in the framework if this study. The controlled etching of 80GeSe2-20Ga2Se 3 glass-ceramics in acid solution yields nanoporous materials with enhanced surface area. The porous layer created on the surface of the glass-ceramic plays the role of anti-reflection coating and increases the optical transmission in the infrared range by 10%. These materials present potential for the production of sensors with increased sensitivity. The influence of indium and lead addition on the thermal and optical properties of the 80GeSe2-20Ga2Se3 glass is also assessed. Increased In or Pb contents tend to decrease the Tg and shift the optical band gap toward higher wavelengths. A systematic ceramization study emphasizes the difficulty of controlling the crystallization for glasses in the systems GeSe2-Ga2Se3-In2Se 3 and GeSe2-Ga2Se3-PbSe. No crystallization of the In2Se3 and PbSe crystalline phase was obtained. Finally, the possibility of producing rare-earth doped 80GeSe2 -20Ga2Se3 glass-ceramics transparent in the infrared region up to 16 microm is demonstrated. Enhanced photoluminescence intensity and reduced radiative lifetimes are observed with increased crystallinity in these materials.

  18. Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

    NASA Astrophysics Data System (ADS)

    Chen, Daqin; Wang, Yuansheng; Yu, Yunlong; Huang, Ping; Weng, Fangyi

    2008-10-01

    Transparent SiO 2-Al 2O 3-NaF-YF 3 bulk nano-composites triply doped with Ho 3+, Tm 3+ and Yb 3+ were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the β-YF 3 crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb 3+ to Ho 3+ or Tm 3+. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%.

  19. Rare-earth doped sol-gel materials for optical waveguides

    NASA Astrophysics Data System (ADS)

    Locher, Martin; Romano, Valerio; Weber, Heinz P.

    2005-03-01

    Neodymium doped SiO2-Al2O3 samples have been produced by the sol-gel method and characterized by refraction index and fluorescence measurements. TiO2 co-doping has been used to control the refraction index n up to a concentration of TiO2:SiO2 of 1:1 where n has increased from 1.46 to 1.73. Refraction index measurements of thin films have been done by white light interferometry. The fluorescence spectra and lifetimes upon 808 nm excitation have been measured. The results show that TiO2 co-doping of Nd3+:SiO2-Al2O3 sample does not lead to a significant decrease of the fluorescence lifetime. A fiber preform with a neodymium doped sol-gel core has been manufactured and successfully drawn to a fiber, which showed laser action.

  20. Earth

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1984-01-01

    The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

  1. Characterizing the Purple Earth: Modeling the globally integrated spectral variability of the Archean Earth

    SciTech Connect

    Sanromá, E.; Pallé, E.; López, R.; Montañés-Rodríguez, P.; Kiang, N. Y.; Gutiérrez-Navarro, A. M.

    2014-01-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. However, the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3.0 Gyr ago. At that time, one of the more widespread life forms on the planet was purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and purple bacteria concentration/distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  2. Characterizing the Purple Earth: Modeling the Globally Integrated Spectral Variability of the Archean Earth

    NASA Astrophysics Data System (ADS)

    Sanrom, E.; Pall, E.; Parenteau, M. N.; Kiang, N. Y.; Gutirrez-Navarro, A. M.; Lpez, R.; Montas-Rodrguez, P.

    2014-01-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. However, the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3.0 Gyr ago. At that time, one of the more widespread life forms on the planet was purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and purple bacteria concentration/distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  3. Luminescence and scintillation properties of rare-earth-doped LuF3 scintillation crystals

    NASA Astrophysics Data System (ADS)

    Pejchal, Jan; Fukuda, Kentaro; Kurosawa, Shunsuke; Yokota, Yuui; Yoshikawa, Akira

    2015-03-01

    The Nd-doped and Er-doped LuF3 single crystals were grown by the micro-pulling-down method to study their scintillation properties in the vacuum-ultraviolet (VUV) region. The doubly Nd-Er codoped single crystal was grown to study possibility of scintillation performance improvement by energy transfer from Er3+ to Nd3+ ions. The LiF flux was to avoid phase transition below melting temperature. The 1%Nd-doped sample showed the highest overall scintillation efficiency under X-ray excitation which was 7 times as high as that of the LaF3:Nd 8% standard. The leading Nd3+ 5d-4f emission was situated at 176 nm, while the Er3+ 5d-4f emission for Er-doped samples was observed at 163 nm, which better matches the sensitivity of some VUV-sensitive photodetectors. The optimum Er concentration was determined to be around 1-3 mol%. No Er3+ 5d-4f emission was observed for the doubly Er,Nd-codoped sample due to energy transfer from the Er3+ to Nd3+ ions. Slight improvement of the light yield was observed in the doubly-doped sample with respect to the Nd-only doped one.

  4. Towards mid-infrared fiber-lasers: rare earth ion doped, indium-containing, selenide bulk glasses and fiber

    NASA Astrophysics Data System (ADS)

    Sakr, H.; Tang, Z.; Furniss, D.; Sojka, L.; Moneim, N. A.; Barney, E.; Sujecki, S.; Benson, T. M.; Seddon, A. B.

    2014-02-01

    Chalcogenide glasses are promising materials for mid-infrared (IR) fiber lasers (i.e. 3 - 25 μm wavelength range). These glasses exhibit low phonon energies, together with large refractive indices, rare earth (RE-) ion solubility and sufficient mechanical and chemical robustness. Optical quality of the fiber is key. Gallium is known to promote RE-ion solubility in chalcogenide glasses, probably forming a [Pr(III)] - Se - [Ga(III)] associated type complex. Here, indium is investigated as an alternative additive to gallium in Pr3+-doped Ge-As-Se chalcogenide glasses. Indium has the same outer electronic structure as gallium. Moreover, indium has the advantage of being heavier than gallium, potentially promoting a lower phonon-energy, local environment of the RE-dopant. Zero to ~2000 ppmw (nominal parts per million by weight) Pr3+- doped Ge-As-In-Se bulk glasses are prepared using the melt-quench method. ~500 ppmw Pr3+- doped Ge-As-In-Se, optically-clad fiber is realized via fiber-drawing of extruded fiberoptic preforms. Fiber absorption and emission spectra are collected and compared with those of the bulk glasses.

  5. Synthesis and characterization of BaAl2O4:Eu2+ co-doped with different rare earth ions

    NASA Astrophysics Data System (ADS)

    Lephoto, M. A.; Ntwaeaborwa, O. M.; Pitale, Shreyas S.; Swart, H. C.; Botha, J. R.; Mothudi, B. M.

    2012-05-01

    Combustion method was used in this study to prepare BaAl2O4:Eu2+ phosphors co-doped with different trivalent rare-earths (Re3+=Dy3+, Nd3+, Gd3+, Sm3+, Ce3+, Er3+, Pr3+ and Tb3+) ions at an initiating temperature of 600 C. The phosphors were annealed at 1000 C for 3 h. As confirmed from the X-ray diffraction (XRD) data, both as prepared and post annealed samples crystallized in the well known hexagonal structure of BaAl2O4. All samples exhibited bluish-green emission associated with the 4f65d1?4f7 transitions of Eu2+ at ?500 nm. Although the highest intensity was observed from Er3+ co-doping, the longest afterglow (due to trapping and detrapping of charge carriers) was observed from Nd3+ followed by Dy3+ co-doping. The traps responsible for the long afterglow were studied using thermoluminescence (TL) spectroscopy.

  6. Composition-driven structural phase transitions in rare-earth-doped BiFeO3 ceramics: a review.

    PubMed

    Arnold, Donna C

    2015-01-01

    Bismuth ferrite suffers from high leakage currents and the presence of a complex incommensurate spin cycloidal magnetic ordering, which has limited its commercial viability and has led researchers to investigate the functionality of doped BiFeO3 ceramics. In particular, the substitution of rare earths onto the Bi(3+) site of the perovskite lattice have been shown to lead to improved functional properties, including lower leakage currents and the suppression of the magnetic spin cycloid. There is particular interest in materials with compositions close to structural morphotropic phase boundaries, because these may lead to materials with enhanced electronic and magnetic properties analogous to the highly relevant PbZrO3- PbTiO3 solid solution. However, many contradictory crystal structures and physical behaviors are reported within the literature. To understand the structure-property relationships in these materials, it is vital that we first unravel the complex structural phase diagrams. We report here a comprehensive review of structural phase transitions in rare-earth-doped bismuth ferrite ceramics across the entire lanthanide series. We attempt to rationalize the literature in terms of the perovskite tool kit and propose an updated phase diagram based on an interpretation of the literature. PMID:25585391

  7. Bridging the Gap between Earth Science and Students: An Integrated Approach using NASA Earth Science Climate Data

    NASA Technical Reports Server (NTRS)

    Alston, Erica J.; Chambers, Lin H.; Phelps, Carrie S.; Oots, Penny C.; Moore, Susan W.; Diones, Dennis D.

    2007-01-01

    Under the auspices of the Department of Education's No Child Left Behind (NCLB) Act, beginning in 2007 students will be tested in the science area. There are many techniques that educators can employ to teach students science. The use of authentic materials or in this case authentic data can be an engaging alternative to more traditional methods. An Earth science classroom is a great place for the integration of authentic data and science concepts. The National Aeronautics and Space Administration (NASA) has a wealth of high quality Earth science data available to the general public. For instance, the Atmospheric Science Data Center (ASDC) at NASA s Langley Research Center houses over 800 Earth science data sets related to Earth's radiation budget, clouds, aerosols and tropospheric chemistry. These data sets were produced to increase academic understanding of the natural and anthropogenic factors that influence global climate; however, a major hurdle in using authentic data is the size of the data and data documentation. To facilitate the use of these data sets for educational purposes, the Mentoring and inquirY using NASA Data on Atmospheric and Earth science for Teachers and Amateurs (MY NASA DATA) project has been established to systematically support educational activities at all levels of formal and informal education. The MY NASA DATA project accomplishes this by reducing these large data holdings to microsets that are easily accessible and explored by K-12 educators and students though the project's Web page. MY NASA DATA seeks to ease the difficulty in understanding the jargon-heavy language of Earth science. This manuscript will show how MY NASA DATA provides resources for NCLB implementation in the science area through an overview of the Web site, the different microsets available, the lesson plans and computer tools, and an overview of educational support mechanisms.

  8. Enhancement of thermopower of TAGS-85 high-performance thermoelectric materials by doping with the rare earth Dy

    SciTech Connect

    Levin, Evgenii; Budko, Serfuei; Schmidt-Rohr, Klaus

    2012-04-10

    Enhancement of thermopower is achieved by doping the narrow-band semiconductor Ag{sub 6.52}Sb{sub 6.52}Ge{sub 36.96}Te{sub 50} (acronym TAGS-85), one of the best p-type thermoelectric materials, with 1 or 2% of the rare earth dysprosium (Dy). Evidence for the incorporation of Dy into the lattice is provided by X-ray diffraction and increased orientation-dependent local fields detected by {sup 125}Te NMR spectroscopy. Since Dy has a stable electronic configuration, the enhancement cannot be attributed to 4f-electron states formed near the Fermi level. It is likely that the enhancement is due to a small reduction in the carrier concentration, detected by {sup 125}Te NMR spectroscopy, but mostly due to energy filtering of the carriers by potential barriers formed in the lattice by Dy, which has large both atomic size and localized magnetic moment. The interplay between the thermopower, the electrical resistivity, and the thermal conductivity of TAGS-85 doped with Dy results in an enhancement of the power factor (PF) and the thermoelectric figure of merit (ZT) at 730 K, from PF = 28 ?W cm{sup ?1} K{sup ?2} and ZT ? 1.3 in TAGS-85 to PF = 35 ?W cm{sup ?1} K{sup ?2} and ZT ? 1.5 in TAGS-85 doped with 1 or 2% Dy for Ge. This makes TAGS-85 doped with Dy a promising material for thermoelectric power generation.

  9. In-volume waveguides by fs-laser direct writing in rare-earth-doped fluoride glass and phosphate glass

    NASA Astrophysics Data System (ADS)

    Esser, D.; Wortmann, D.; Gottmann, J.

    2009-02-01

    Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er- and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (?=500fs, ?=1045nm, f=0.1-5MHz) from an Ybfiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50?m in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.

  10. Investigation of thermal diffusivity dependence on temperature in a group of optical single crystals doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.

    2015-07-01

    The group of YAG, YVO4 and GdCOB single crystals was examined to determine the thermal diffusivity as a function of temperature in range from 30 °C to 300 °C. Further investigations concerned on analysis of the influence of dopants on these dependencies. The experimental setup based on thermal wave method with mirage detection was used. The samples represented different crystallographic systems such as cubic (YAG) tetragonal (YVO4) and monoclinic (GdCOB). The anisotropy of thermal conductivity of investigated samples was taken into account in the investigations. The crystals were doped with calcium ions, rare earth ions such as ytterbium, neodymium, and thulium, and also with transition metal vanadium. The results confirmed that influence of doping on the thermal diffusivity of investigated materials strongly depends on temperature. In general the thermal diffusivity decreases with increasing of sample temperature from 30 °C to 300 °C, however the drop in thermal diffusivity is the highest for pure single crystals. Doping is another factor reducing the heat transport in single crystals. Introduction of dopant ions into a crystal lattice leads to a significant decrease in the thermal diffusivity at lower temperatures in comparison with pure crystals. However, the influence of dopants becomes less pronounced with increasing temperature, and in case of weakly doped crystals it becomes negligible at higher temperatures. The interpretation of thermal diffusivity dependence on temperature for single crystals was based on the Debye model of lattice thermal conductivity of solids. The results allowed to conclude that the decrease of thermal diffusivity with temperature and increasing concentration of impurities is caused by shortening of the phonons mean free path due to phonon-phonon and phonon-point defect scatterings.

  11. The Role of Defect Complexes in the Magneto-Optical Properties of Rare Earth Doped Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Mitchell, Brandon

    Wide band gap semiconductors doped with rare earth ions (RE) have shown great potential for applications in optoelectronics, photonics, and spintronics. The 1.54mum Erbium (Er) emission has been extensively utilized in optical fiber communications, and Europium (Eu) is commonly used as a red color component for LEDs and fluorescence lamps. For the realization of spintronic-type devices, a dilutely doped semiconductor that exhibits room temperature ferromagnetic behavior would be desirable. Such behavior has been observed in GaN:Er. Furthermore, it was demonstrated that strain may play an important role in the control of this ferromagnetism; however, this requires further investigation. One motivation of this work is the realization of an all solid state white light source monolithically integrated into III/V nitride semiconductor materials, ideally GaN. For this, the current AlGaAs-based LEDs need to be replaced. One approach for achieving efficient red emission from GaN is dilute doping with fluorescent ions. In this regard, Eu has consistently been the most promising candidate as a dopant in the active layer for a red, GaN based, LED due to the sharp 5D0 to 7F2 transitions that result in red emission around 620nm. The success of GaN:Eu as the active layer for a red LED is based on the ability for the Eu ions to be efficiently excited by electron hole pairs. Thus, the processes by which energy is transferred from the host to the Eu ions has been studied. Complications arise, however, from the fact that Eu ions incorporate into multiple center environments, the structures of which are found to have a profound influence on the excitation pathways and efficiencies of the Eu ion. Therefore the nature of Eu incorporation and the resulting luminescence efficiency in GaN has been extensively investigated. By performing a comparative study on GaN:Eu samples grown under a variety of controlled conditions and using a variety of experimental techniques, the majority site has been concluded to contain a nitrogen vacancy (V N) in its immediate structure. The nitrogen vacancy can appear in two symmetries, which has a profound impact on the luminescence and magnetic properties of the sample. The structure of the minority site has also been identified. For both sites, we give substantial evidence that the excitation efficiency of the red Eu emission is improved by the presence of donor-acceptor pairs in the vicinity of the Eu. Furthermore, when Mg was co-doped into GaN:Eu, additional incorporation environments were discovered that show high excitation efficiency at room temperature. These have been attributed to the coupling of Mg-H complexes to the majority Eu site. Electron beam irradiation, indirect and resonant (direct) laser excitation were found to modify these complexes, indicating that vibrational energy alone can trigger the migration of the H, while the presence of additional charges and excess energy controls the type of reconfiguration and the activation of non-radiative decay channels. We identify, experimentally, a two-step process in the dissociation of Mg-H complexes and propose, based on density functional theory, that the presence of minority carriers and the resulting charge states of complexes can also influence this process. In GaN:Er, we have given a more thorough overview of the optical and magneto-optical properties by extending to the 800nm excitation range and drastically improving the signal-to-noise ratio in the magnetic measurements, as well as applying a perpendicular magnetic field. This has allowed us to calculate g-factors for the parallel case, but revealed that the Zeeman interaction is not quite linear for perpendicular magnetic fields. We were able to assign crystal field numbers of mu = 3/2 to two crystal field levels. We have also given strong evidence that the strain in the sample, which results from lattice mismatch, enhances its magnetization, as seen through fluorescence line narrowing and asymmetry between the Zeeman transition intensities, under application of magnetic fields in anti-paralle

  12. Cyberinfrastructure at IRIS: Challenges and Solutions Providing Integrated Data Access to EarthScope and Other Earth Science Data

    NASA Astrophysics Data System (ADS)

    Ahern, T. K.; Barga, R.; Casey, R.; Kamb, L.; Parastatidis, S.; Stromme, S.; Weertman, B. T.

    2008-12-01

    While mature methods of accessing seismic data from the IRIS DMC have existed for decades, the demands for improved interdisciplinary data integration call for new approaches. Talented software teams at the IRIS DMC, UNAVCO and the ICDP in Germany, have been developing web services for all EarthScope data including data from USArray, PBO and SAFOD. These web services are based upon SOAP and WSDL. The EarthScope Data Portal was the first external system to access data holdings from the IRIS DMC using Web Services. EarthScope will also draw more heavily upon products to aid in cross-disciplinary data reuse. A Product Management System called SPADE allows archive of and access to heterogeneous data products, presented as XML documents, at the IRIS DMC. Searchable metadata are extracted from the XML and enable powerful searches for products from EarthScope and other data sources. IRIS is teaming with the External Research Group at Microsoft Research to leverage a powerful Scientific Workflow Engine (Trident) and interact with the web services developed at centers such as IRIS to enable access to data services as well as computational services. We believe that this approach will allow web- based control of workflows and the invocation of computational services that transform data. This capability will greatly improve access to data across scientific disciplines. This presentation will review some of the traditional access tools as well as many of the newer approaches that use web services, scientific workflow to improve interdisciplinary data access.

  13. Integration of Earth System Models and Workflow Management under iRODS for the Northeast Regional Earth System Modeling Project

    NASA Astrophysics Data System (ADS)

    Lengyel, F.; Yang, P.; Rosenzweig, B.; Vorosmarty, C. J.

    2012-12-01

    The Northeast Regional Earth System Model (NE-RESM, NSF Award #1049181) integrates weather research and forecasting models, terrestrial and aquatic ecosystem models, a water balance/transport model, and mesoscale and energy systems input-out economic models developed by interdisciplinary research team from academia and government with expertise in physics, biogeochemistry, engineering, energy, economics, and policy. NE-RESM is intended to forecast the implications of planning decisions on the region's environment, ecosystem services, energy systems and economy through the 21st century. Integration of model components and the development of cyberinfrastructure for interacting with the system is facilitated with the integrated Rule Oriented Data System (iRODS), a distributed data grid that provides archival storage with metadata facilities and a rule-based workflow engine for automating and auditing scientific workflows.

  14. The optical antenna system design research on earth integrative network laser link in the future

    NASA Astrophysics Data System (ADS)

    Liu, Xianzhu; Fu, Qiang; He, Jingyi

    2014-11-01

    Earth integrated information network can be real-time acquisition, transmission and processing the spatial information with the carrier based on space platforms, such as geostationary satellites or in low-orbit satellites, stratospheric balloons or unmanned and manned aircraft, etc. It is an essential infrastructure for China to constructed earth integrated information network. Earth integrated information network can not only support the highly dynamic and the real-time transmission of broadband down to earth observation, but the reliable transmission of the ultra remote and the large delay up to the deep space exploration, as well as provide services for the significant application of the ocean voyage, emergency rescue, navigation and positioning, air transportation, aerospace measurement or control and other fields.Thus the earth integrated information network can expand the human science, culture and productive activities to the space, ocean and even deep space, so it is the global research focus. The network of the laser communication link is an important component and the mean of communication in the earth integrated information network. Optimize the structure and design the system of the optical antenna is considered one of the difficulty key technologies for the space laser communication link network. Therefore, this paper presents an optical antenna system that it can be used in space laser communication link network.The antenna system was consisted by the plurality mirrors stitched with the rotational paraboloid as a substrate. The optical system structure of the multi-mirror stitched was simulated and emulated by the light tools software. Cassegrain form to be used in a relay optical system. The structural parameters of the relay optical system was optimized and designed by the optical design software of zemax. The results of the optimal design and simulation or emulation indicated that the antenna system had a good optical performance and a certain reference value in engineering. It can provide effective technical support to realize interconnection of earth integrated laser link information network in the future.

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

    PubMed

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

    2012-01-01

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

  16. Integrated Modular Avionics for Spacecraft: Earth Observation Use Case Demonstrator

    NASA Astrophysics Data System (ADS)

    Deredempt, Marie-Helene; Rossignol, Alain; Hyounet, Philippe

    2013-08-01

    Integrated Modular Avionics (IMA) for Space, as European Space Agency initiative, aimed to make applicable to space domain the time and space partitioning concepts and particularly the ARINC 653 standard [1][2]. Expected benefits of such an approach are development flexibility, capability to provide differential V&V for different criticality level functionalities and to integrate late or In-Orbit delivery. This development flexibility could improve software subcontracting, industrial organization and software reuse. Time and space partitioning technique facilitates integration of software functions as black boxes and integration of decentralized function such as star tracker in On Board Computer to save mass and power by limiting electronics resources. In aeronautical domain, Integrated Modular Avionics architecture is based on a network of LRU (Line Replaceable Unit) interconnected by AFDX (Avionic Full DupleX). Time and Space partitioning concept is applicable to LRU and provides independent partitions which inter communicate using ARINC 653 communication ports. Using End System (LRU component) intercommunication between LRU is managed in the same way than intercommunication between partitions in LRU. In such architecture an application developed using only communication port can be integrated in an LRU or another one without impacting the global architecture. In space domain, a redundant On Board Computer controls (ground monitoring TM) and manages the platform (ground command TC) in terms of power, solar array deployment, attitude, orbit, thermal, maintenance, failure detection and recovery isolation. In addition, Payload units and platform units such as RIU, PCDU, AOCS units (Star tracker, Reaction wheels) are considered in this architecture. Interfaces are mainly realized through MIL-STD-1553B busses and SpaceWire and this could be considered as the main constraint for IMA implementation in space domain. During the first phase of IMA SP project, ARINC653 impact was analyzed. Requirements and architecture for space domain were defined [3][4] and System Executive platforms (based on Xtratum, Pike OS, and AIR) were developed with RTEMS as Guest OS. This paper focuses on the demonstrator developed by Astrium as part of IMA SP project. This demonstrator has the objective to confirm operational software partitioning feasibility above Xtratum System Executive Platform with acceptable CPU overhead.

  17. Integrating Diverse Geophysical and Geological Data to Construct Multi-Dimensional Earth Models: The Open Earth Framework

    NASA Astrophysics Data System (ADS)

    Baru, C.; Keller, R.; Wallet, B.; Crosby, C.; Moreland, J.; Nadeau, D.

    2008-12-01

    Currently, many large geoscientific efforts (e.g., EarthScope, Continental Dynamics, and GeoSwath) have emphasized that a crucial need in advancing our understanding of the structure and evolution of the continents is high-resolution, 3-D models of lithospheric structure. In addition, the geoscience community recognizes that our ultimate goal is the addition of the dimension of time to make the problem 4-D. Adding the dimension of time is a complex problem that is strongly dependent on the integration of a variety of geological data into our analyses (e.g., geochronology, paleontology, stratigraphy, pressure-time histories, structural geology, paleogeography, etc.). The geoscience community also recognizes that solutions to the scientific and societal questions that they seek to answer require innovative integration of many types of data so that many physical properties (x, y, z, P-wave velocity, S-wave velocity, density, electrical conductivity, etc.) are measured and included in 3-D models. The problem is, therefore, truly multidimensional in nature. We are developing an Open Earth Framework (OEF) as an open data model for integration of such multidimensional Earth Sciences data. In our work and interactions with the community on building and visualizing complex earth models, several issues have emerged on which there is consensus. First of all, integration efforts should work from the surface down because we have the most data there (e.g., geologic maps, remote sensing data such as LIDAR and ASTER, digital elevation models, gravity and magnetic measurements, etc.) and because the complex conditions near surface always have a potential to mask deeper features. Secondly since we cannot expect uniform coverage of a variety of high-resolution data in anything but special circumstances, a data integration effort should first establish a regional context using lower resolution (and usually wide coverage) data and then proceed to modeling the data sets with the highest spatial resolution. Finally, formal quantitative integration would logically begin with employing accepted relationships between physical properties (e.g., there are widely used empirical relationships between Vp and density) and then proceed to producing integrated models that facilitate the search for anomalies. Our workshops and community interactions have shown that both raster (voxels) and vector (surfaces) 3D data structures would be involved if we are to produce integrated models that have all of the properties that the community desires. These interactions also quickly revealed a consensus that building such models can only be achieved through a highly integrated approach that takes advantage of all of the geological and geophysical constraints available. Conceptually, the modeling would begin with a voxel-based approach of building a highly-integrated 3-D model at Time=0 by deriving physical properties such as Vp, Vs, density, magnetic properties, electrical properties, anisotropy, attenuation (Q), temperature, etc. for volume elements that could take on several forms. Then, interfaces that represent features such as the Moho, major faults, crystalline basement surface beneath sedimentary basins, magmatic bodies, etc. would be inserted into the model in order to properly characterize the region geologically.

  18. Structural and optical properties of rare-earth doped lithium niobate waveguides formed by MeV helium ion implantation

    SciTech Connect

    Herreros, B.; Lifante, G.; Cusso, F.; Kling, A.; Soares, J.C.; Silva, M.F. da; Townsend, P.D.; Chandler, P.J.

    1996-12-31

    Results of investigations of optical waveguides formed by high energy helium implantation into lithium niobate codoped with 5 mol% MgO and 1 mol% Tm{sup 3+} or 1 mol% Er{sup 3+} are reported. A comparative study of structural and luminescence properties between implanted and untreated samples has been performed by means of Rutherford backscattering (RBS) combined with channeling and photoluminescence methods, respectively in order to investigate residual lattice damage and the incorporation of the optical active rare earths. For the case of Tm a full substitutional incorporation of the optical active rare earths. For the case of Tm a full substitutional incorporation on the lithium site and a high crystal quality in both bulk and implanted waveguide material has been found. For Er doped lithium niobate the channeling results show a fraction of Er randomly incorporated or forming precipitates and a deterioration of the waveguide`s lattice. The optical investigations show in both cases only a slight broadening of the emission lines of the rare earths in the waveguides compared to the bulk material.

  19. Random lattice deformations in rare-earth-doped cubic hexafluoroelpasolites: High-resolution optical spectroscopy and theoretical studies

    NASA Astrophysics Data System (ADS)

    Malkin, B. Z.; Pytalev, D. S.; Popova, M. N.; Baibekov, E. I.; Falin, M. L.; Gerasimov, K. I.; Khaidukov, N. M.

    2012-10-01

    High-resolution Fourier spectroscopy is used to study the low-temperature (3-10 K) optical absorption spectra of Cs2NaYF6 and Cs2NaScF6 crystals doped with rare-earth ions, which substitute for Y3+ or Sc3+ ions at sites with cubic Oh symmetry. Splitting of some absorption lines corresponding to doublet (?6 or ?7)-quadruplet (?8) transitions in the Kramers Yb3+, Er3+, and Sm3+ ions and a singlet (?1)-triplet (?4) transition in the non-Kramers Tm3+ ion is observed. In the vicinity of these lines, additional spectral satellites with intensities depending nonlinearly on the concentration of the rare-earth ions are present. We argue that the observed splitting is caused by low-symmetry components of the crystal field induced by random lattice strains. An explicit expression for the generalized distribution function of local strains produced by random point defects in the elastic continuum is derived and used to simulate the line shapes. A satisfactorily agreement with the measured spectra is achieved. The observed satellite transitions are ascribed to pairs of the nearest-neighbor rare-earth ions interacting through the dynamic lattice deformations.

  20. Monolithic integration of rare-earth oxides and semiconductors for on-silicon technology

    SciTech Connect

    Dargis, Rytis Clark, Andrew; Erdem Arkun, Fevzi; Grinys, Tomas; Tomasiunas, Rolandas; O'Hara, Andy; Demkov, Alexander A.

    2014-07-01

    Several concepts of integration of the epitaxial rare-earth oxides into the emerging advanced semiconductor on silicon technology are presented. Germanium grows epitaxially on gadolinium oxide despite lattice mismatch of more than 4%. Additionally, polymorphism of some of the rare-earth oxides allows engineering of their crystal structure from hexagonal to cubic and formation of buffer layers that can be used for growth of germanium on a lattice matched oxide layer. Molecular beam epitaxy and metal organic chemical vapor deposition of gallium nitride on the rare-earth oxide buffer layers on silicon is discussed.

  1. Integrated planning and scheduling for Earth science data processing

    NASA Technical Reports Server (NTRS)

    Boddy, Mark; White, Jim; Goldman, Robert; Short, Nick, Jr.

    1995-01-01

    Several current NASA programs such as the EOSDIS Core System (ECS) have data processing and data management requirements that call for an integrated planning and scheduling capability. In this paper, we describe the experience of applying advanced scheduling technology operationally, in terms of what was accomplished, lessons learned, and what remains to be done in order to achieve similar successes in ECS and other programs. We discuss the importance and benefits of advanced scheduling tools, and our progress toward realizing them, through examples and illustrations based on ECS requirements. The first part of the paper focuses on the Data Archive and Distribution (DADS) V0 Scheduler. We then discuss system integration issues ranging from communication with the scheduler to the monitoring of system events and re-scheduling in response to them. The challenge of adapting the scheduler to domain-specific features and scheduling policies is also considered. Extrapolation to the ECS domain raises issues of integrating scheduling with a product-generation planner (such as PlaSTiC), and implementing conditional planning in an operational system. We conclude by briefly noting ongoing technology development and deployment projects being undertaken by HTC and the ISTB.

  2. Integrating Research Infrastructures for solid Earth Science: the EPOS preparatory phase roadmap and achievements

    NASA Astrophysics Data System (ADS)

    Cocco, M.; EPOS Consortium

    2012-04-01

    The European Plate Observing System (EPOS) is a long-term integrated research infrastructure plan to promote innovative approaches for a better understanding of the physical processes controlling earthquakes, volcanic eruptions, unrest episodes and tsunamis as well as those driving tectonics and Earth surface dynamics. The EPOS plan aims at integrating the currently scattered, but highly advanced European facilities into one, distributed, but coherent multidisciplinary Research Infrastructure (RI) allowing sustainable long-term Earth science research strategies and an effective coordinated European-scale monitoring facility for solid Earth dynamics taking full advantage of new e-science opportunities. The EPOS preparatory phase (EPOS PP), funded by the European Commission within the Capacities program, started on November 1st 2010 and it has completed its first year of activity. The EPOS mission is to integrate the existing research infrastructures (RIs) in solid Earth science in order to increase the accessibility and usability of multidisciplinary data from monitoring networks, laboratory experiments and computational simulations enhancing worldwide interoperability in Earth Science by establishing a leading integrated European infrastructure and services. We will present the EPOS PP roadmap for the long-term solid Earth observation strategies as well as the e-science implementation plan envisioned to establish an innovative integrated e-infrastructure component necessary to create an effective service to users. Moreover, we will show the preliminary outcomes from the first inventory of the RIs we are going to integrate in EPOS. We also plan to discuss the outreach and dissemination actions and the strategy designed to meet the specific user needs. More recently the EPOS and the satellite Earth Observation communities are collaborating in order to promote the integration of data from in-situ monitoring networks and satellite observing systems. The goal is to coordinate the access to data relevant for geohazard research for selected "Supersites" locations in Europe as well as to contribute to the global supersite initiative in the framework of the GEO work program. Making observations of solid Earth dynamic processes controlling natural phenomena immediately available and promoting their comparison with numerical simulations and their interpretation through theoretical analyses will represent a multidisciplinary platform for discoveries which will foster scientific excellence in solid Earth research. Finally, we will also discuss the priorities for the second year of activity and the key actions planned to better involve users in EPOS. In particular, we will discuss the work done to finalize the identification of the mission needs as well as the activities to start the design phase of the EPOS infrastructure.

  3. Integrating research infrastructures for solid Earth science in Europe: the European Plate Observing System

    NASA Astrophysics Data System (ADS)

    Cocco, M.; Giardini, D.; EPOS-PP Consortium

    2011-12-01

    The European Plate Observing System (EPOS) coordinates and integrates the research infrastructures in the European-Mediterranean region, to promote innovative approaches for a better understanding of the physical processes controlling earthquakes, volcanic eruptions, tsunamis as well as those driving tectonics and Earth surface dynamics. The EPOS 30-year plan aims at integrating the currently scattered, but highly advanced European facilities into one distributed, coherent multidisciplinary Research Infrastructure allowing sustainable long-term Earth science research strategies and an effective coordinated European-scale monitoring facility for solid Earth dynamics taking full advantage of new e-science opportunities. EPOS has been approved by ESFRI (the European Scientific Forum for Research Infrastructures) as one of the critical European Research Infrastructures, and the EPOS Preparatory Phase is supported by the European Commission FP7 program. The cooperation between EPOS and similar US infrastructures (i.e. Earthscope) will be ensured by dedicated NSF-EC funding. EPOS is integrating data from permanent national and regional geophysical monitoring networks (seismological, GPS), with the observations from "in-situ" observatories (volcano observatories, in-situ fault zone test sites) and temporary-monitoring and laboratory experiments through a cyber-infrastructure for data mining and processing, and facilities for data integration, archiving and exchange. The vision is to integrate these existing research infrastructures in order to increase the accessibility and usability of multidisciplinary data from monitoring networks, laboratory experiments and computational simulations enhancing worldwide interoperability in Earth Science by establishing a leading integrated European infrastructure and services. More recently the EPOS and the satellite Earth Observation communities are collaborating in order to promote the integration of data from in-situ monitoring networks and remote sensing. The goal is to coordinate the access to data relevant for geohazard research for selected "Supersites" locations in Europe as well as to contribute to the global supersite initiative. Making observations of solid Earth dynamic processes controlling natural phenomena immediately available and promoting their comparison with numerical simulations and their interpretation through theoretical analyses will represent a multidisciplinary platform for discoveries which will foster scientific excellence in solid Earth research. We will present the key actions needed to: i) develop sustainable long-term Earth observation strategies preceding and following earthquakes and volcanic eruptions; ii) develop an innovative integrated e-infrastructure component necessary to create an effective service to users; iii) promote the strategic and outreach actions to meet the specific user needs; iv) develop expertise in the use and interpretation of Supersites data in order to promote capacity building and timely transfer of scientific knowledge. This will facilitate new scientific discoveries through the availability of unprecedented data sets and it will increase resilience and preparedness in the society.

  4. Estimation of cut-off wavelength of rare earth doped single-mode fibers

    NASA Astrophysics Data System (ADS)

    Kaur, Jagneet; Thyagarajan, K.; Pal, B. P.

    1999-11-01

    A new empirical relation is proposed describing spectral variation of mode-field radius (MFR) as inferred from measurements in the far-field of the fiber. It is shown that using this relation, it is possible to estimate the cut-off wavelength ( ?c) of the fiber. The proposed technique is successfully tested through measurements made on two standard step index single-mode fibers, as well as on an erbium doped fiber (EDF) having ?c falling within its strong absorption band around 980 nm. This empirical formula is more accurate than the widely used Marcuse's formula to describe spectral dependence of MFR determined through measurements made in the fiber's far-field. The proposed technique is especially suited for estimation of ?c of doped fibers in which ?c falls within an absorption band.

  5. Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

    NASA Astrophysics Data System (ADS)

    Kunkel, Nathalie; Ferrier, Alban; Thiel, Charles W.; Ramrez, Mariola O.; Baus, Luisa E.; Cone, Rufus L.; Ikesue, Akio; Goldner, Philippe

    2015-09-01

    Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu3+ doped Y 2O3 transparent ceramics. This result is obtained on the 7F0?5D0 transition in Eu3+ doped Y 2O3 ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of 15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu3+ concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.

  6. DECADE Web Portal: Integrating MaGa, EarthChem and GVP Will Further Our Knowledge on Earth Degassing

    NASA Astrophysics Data System (ADS)

    Cardellini, C.; Frigeri, A.; Lehnert, K. A.; Ash, J.; McCormick, B.; Chiodini, G.; Fischer, T. P.; Cottrell, E.

    2014-12-01

    The release of gases from the Earth's interior to the exosphere takes place in both volcanic and non-volcanic areas of the planet. Fully understanding this complex process requires the integration of geochemical, petrological and volcanological data. At present, major online data repositories relevant to studies of degassing are not linked and interoperable. We are developing interoperability between three of those, which will support more powerful synoptic studies of degassing. The three data systems that will make their data accessible via the DECADE portal are: (1) the Smithsonian Institution's Global Volcanism Program database (GVP) of volcanic activity data, (2) EarthChem databases for geochemical and geochronological data of rocks and melt inclusions, and (3) the MaGa database (Mapping Gas emissions) which contains compositional and flux data of gases released at volcanic and non-volcanic degassing sites. These databases are developed and maintained by institutions or groups of experts in a specific field, and data are archived in formats specific to these databases. In the framework of the Deep Earth Carbon Degassing (DECADE) initiative of the Deep Carbon Observatory (DCO), we are developing a web portal that will create a powerful search engine of these databases from a single entry point. The portal will return comprehensive multi-component datasets, based on the search criteria selected by the user. For example, a single geographic or temporal search will return data relating to compositions of emitted gases and erupted products, the age of the erupted products, and coincident activity at the volcano. The development of this level of capability for the DECADE Portal requires complete synergy between these databases, including availability of standard-based web services (WMS, WFS) at all data systems. Data and metadata can thus be extracted from each system without interfering with each database's local schema or being replicated to achieve integration at the DECADE web portal. The DECADE portal will enable new synoptic perspectives on the Earth degassing process. Other data systems can be easily plugged in using the existing framework. Our vision is to explore Earth degassing related datasets over previously unexplored spatial or temporal ranges.

  7. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    NASA Astrophysics Data System (ADS)

    Li, Jiawei; Huo, Juntao; Law, Jiayan; Chang, Chuntao; Du, Juan; Man, Qikui; Wang, Xinmin; Li, Run-Wei

    2014-08-01

    The effects of heavy rare earth (RE) additions on the Curie temperature (TC) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune TC in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (?SM) and refrigerant capacity (RC) of the alloys. The observed values of ?SM and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd5Ge1.9Si2Fe0.1. The tunable TC and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

  8. Effect of temperature and rare-earth doping on charge-carrier mobility in indium-monoselenide crystals

    SciTech Connect

    Abdinov, A. Sh.; Babayeva, R. F.; Amirova, S. I.; Rzayev, R. M.

    2013-08-15

    In the temperature range T = 77-600 K, the dependence of the charge-carrier mobility ({mu}) on the initial dark resistivity is experimentally investigated at 77 K ({rho}d{sub 0}), as well as on the temperature and the level (N) of rare-earth doping with such elements as gadolinium (Gd), holmium (Ho), and dysprosium (Dy) in n-type indium-monoselenide (InSe) crystals. It is established that the anomalous behavior of the dependences {mu}(T), {mu}({rho}d{sub 0}), and {mu}(N) found from the viewpoint of the theory of charge-carrier mobility in crystalline semiconductors is related, first of all, to partial disorder in indium-monoselenide crystals and can be attributed to the presence of random drift barriers in the free energy bands.

  9. Nitrogen-Doped Carbon Nanocoil Array Integrated on Carbon Nanofiber Paper for Supercapacitor Electrodes.

    PubMed

    Choi, Won Ho; Choi, Mi Jin; Bang, Jin Ho

    2015-09-01

    Integrating a nanostructured carbon array on a conductive substrate remains a challenging task that presently relies primarily on high-vacuum deposition technology. To overcome the problems associated with current vacuum techniques, we demonstrate the formation of an N-doped carbon array by pyrolysis of a polymer array that was electrochemically grown on carbon fiber paper. The resulting carbon array was investigated for use as a supercapacitor electrode. In-depth surface characterization results revealed that the microtextural properties, surface functionalities, and degree of nitrogen incorporated into the N-doped carbon array can be delicately controlled by manipulating carbonization temperatures. Furthermore, electrochemical measurements showed that subtle changes in these physical properties resulted in significant changes in the capacitive behavior of the N-doped carbon array. Pore structures and nitrogen/oxygen functional groups, which are favorable for charge storage, were formed at low carbonization temperatures. This result showed the importance of having a comprehensive understanding of how the surface characteristics of carbon affect its capacitive performance. When utilized as a substrate in a pseudocapacitive electrode material, the N-doped carbon array maximizes capacitive performance by simultaneously achieving high gravimetric and areal capacitances due to its large surface area and high electrical conductivity. PMID:26264641

  10. White emission materials from glass doped with rare Earth ions: A review

    NASA Astrophysics Data System (ADS)

    Yasaka, P.; Kaewkhao, J.

    2016-03-01

    Solid State Lighting (SSL) based devices are predicted to play a crucial role in the coming years. Development of W-LED, which have an edge over traditional lighting sources due to their compact size, higher reliability, shock resistance, interesting design possibilities, higher transparency and an extremely long lifetime. Over the fifteen trivalent lanthanide ions, Dy3+ ions doped glasses are most appropriate for white light generation because of the fact that it exhibits two intense emission bands corresponds to the 4F9/2→6H15/2 (magnetic dipole) and 4F9/2→6H13/2 (electric dipole) transitions at around 480-500 nm and 580-600 nm pertaining to blue and yellow regions respectively. In this work, the developments of Dy3+ doped in several glass structures for white emitting materials application have reviewed. Properties of Dy3+ doped in glasses were discussed for use as a solid state lighting materials application.

  11. Rare-earth-doped materials with application to optical signal processing, quantum information science, and medical imaging technology

    NASA Astrophysics Data System (ADS)

    Cone, R. L.; Thiel, C. W.; Sun, Y.; Bttger, Thomas; Macfarlane, R. M.

    2012-02-01

    Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.

  12. Optical properties and size distribution of the nanocolloids made of rare-earth ion-doped NaYF4

    NASA Astrophysics Data System (ADS)

    Patel, Darayas N.; Lewis, Ashley; Wright, Donald M.; Lewis, Danielle; Valentine, Rueben; Valentine, Maucus; Wessley, Dennis; Sarkisov, Sergey; Darwish, Abdalla M.

    2015-03-01

    In this paper we investigate optical properties and size distribution of the nano-colloids made of trivalent rare-earth ion doped fluorides: holmium and ytterbium, thulium and ytterbium, and erbium and ytterbium co-doped NaYF4. These materials were synthesized by using simple co-precipitation synthetic method. The initially prepared micro-crystals had very weak or no visible upconversion fluorescence signals when being pumped with a 980-nm laser. The fluorescence intensity significantly increased after the crystals were annealed at a temperature of 400°C - 600°C undergoing the transition from cubic alpha to hexagonal beta phase of the fluoride host. Nano-colloids of the crystals were made in polar solvents using the laser ablation and ball milling methods. Size analyses of the prepared nano-colloids were conducted using a dynamic light scatterometer and atomic force microscope. The nano-colloids were filled in holey PCFs and their fluorescent properties were studied and the feasibility of new a type of fiber amplifier/laser was evaluated.

  13. Novel kinds of down/up-conversion luminescent rare earth doped fluoride BaMgF{sub 4}: RE{sup 3+} microcrystals

    SciTech Connect

    Yan, Zhi-Yuan; Yan, Bing Jia, Li-Ping

    2013-10-15

    Graphical abstract: We achieve the liquid phase chemical synthesis of rare earth fluoride system BaMgF4: RE{sup 3+} microphosphors, which realize down/up-conversion luminescence. - Highlights: • Doped BaMgF{sub 4} microphosphors are firstly prepared by hydrothermal process. • Doped BaMgF{sub 4} nanosheets are firstly prepared by high temperature solution reaction. • The down-conversion luminescence is realized in the rare earth doped BaMgF{sub 4}. • The upconversion luminescence is realized in the rare earth doped BaMgF{sub 4}. - Abstract: In this paper, we realize the liquid-phase chemical synthesis of high-quality orthorhombic polycrystalline BaMgF{sub 4}: RE{sup 3+} (RE = Eu, Tb, Sm, Dy, Yb–Er/Tm) compounds with hydrothermal and high-temperature solution methods, respectively. The products from hydrothermal technology show the micrometer size while the products from hydrothermal technology present nanosheet morphology. The rare earth ions doped BaMgF{sub 4} from hydrothermal synthesis are discussed in details, which can realize the downconversion luminescence for doped Eu{sup 3+} or Tb{sup 3+} and upconversion luminescence for Yb{sup 3+}/Er{sup 3+} (Tm{sup 3+}), respectively. To our knowledge, the hydrothermal or high temperature solution synthesis and photoluminescence (Eu{sup 3+}, Tb{sup 3+} or Yb{sup 3+}/Er{sup 3+}(Tm{sup 3+})) of these fluoride systems are firstly reported.

  14. The EPOS Implementation Phase: building thematic and integrated services for solid Earth sciences

    NASA Astrophysics Data System (ADS)

    Cocco, Massimo; Epos Consortium, the

    2015-04-01

    The European Plate Observing System (EPOS) has a scientific vision and approach aimed at creating a pan-European infrastructure for Earth sciences to support a safe and sustainable society. To follow this vision, the EPOS mission is integrating a suite of diverse and advanced Research Infrastructures (RIs) in Europe relying on new e-science opportunities to monitor and understand the dynamic and complex Earth system. To this goal, the EPOS Preparatory Phase has designed a long-term plan to facilitate integrated use of data and products as well as access to facilities from mainly distributed existing and new research infrastructures for solid Earth Science. EPOS will enable innovative multidisciplinary research for a better understanding of the Earth's physical processes that control earthquakes, volcanic eruptions, ground instability and tsunami as well as the processes driving tectonics and Earth surface dynamics. Through integration of data, models and facilities EPOS will allow the Earth Science community to make a step change in developing new concepts and tools for key answers to scientific and socio-economic questions concerning geo-hazards and geo-resources as well as Earth sciences applications to the environment and to human welfare. Since its conception EPOS has been built as "a single, Pan-European, sustainable and distributed infrastructure". EPOS is, indeed, the sole infrastructure for solid Earth Science in ESFRI and its pan-European dimension is demonstrated by the participation of 23 countries in its preparatory phase. EPOS is presently moving into its implementation phase further extending its pan-European dimension. The EPOS Implementation Phase project (EPOS IP) builds on the achievements of the successful EPOS preparatory phase project. The EPOS IP objectives are synergetic and coherent with the establishment of the new legal subject (the EPOS-ERIC in Italy). EPOS coordinates the existing and new solid Earth RIs within Europe and builds the integrating RI elements. This integration requires a significant coordination between, among others, disciplinary (thematic) communities, national RIs policies and initiatives, as well as geo- and IT-scientists. The RIs that EPOS is coordinating include: i) regionally-distributed geophysical observing systems (seismological and geodetic networks); ii) local observatories (including geomagnetic, near-fault and volcano observatories); iii) analytical and experimental laboratories; iv) integrated satellite data and geological information services v) new services for natural and anthropogenic hazards. Here we present the successful story of the EPOS Preparatory Phase and the progress towards the implementation of both integrated core services (ICS) and thematic core services (TCS) for the different communities participating to the integration plan. We aim to discuss the achieved results and the approach followed to design the implementation phase. The goal is to present and discuss the strategies adopted to foster the implementation of TCS, clarifying their crucial role as domain-specific service hubs for coordinating and harmonizing national resources/plans with the European dimension of EPOS, and their integration to develop the new ICS. We will present the prototype of the ICS central hub as a key contribution for providing multidisciplinary services for solid Earth sciences as well as the glue to keep ICT aspects integrated and rationalized across EPOS. Finally, we will discuss the well-defined role of the EPOS-ERIC Headquarter to coordinate and harmonize national RIs and EPOS services (through ICS and TCS) looking for an effective commitment by national governments. It will be an important and timely opportunity to discuss the EPOS roadmap toward the operation of the novel multidisciplinary platform for discoveries to foster scientific excellence in solid Earth sciences.

  15. A Special Assignment from NASA: Understanding Earth's Atmosphere through the Integration of Science and Mathematics

    ERIC Educational Resources Information Center

    Fox, Justine E.; Glen, Nicole J.

    2012-01-01

    Have your students ever wondered what NASA scientists do? Have they asked you what their science and mathematics lessons have to do with the real world? This unit about Earth's atmosphere can help to answer both of those questions. The unit described here showcases "content specific integration" of science and mathematics in that the lessons meet…

  16. A Special Assignment from NASA: Understanding Earth's Atmosphere through the Integration of Science and Mathematics

    ERIC Educational Resources Information Center

    Fox, Justine E.; Glen, Nicole J.

    2012-01-01

    Have your students ever wondered what NASA scientists do? Have they asked you what their science and mathematics lessons have to do with the real world? This unit about Earth's atmosphere can help to answer both of those questions. The unit described here showcases "content specific integration" of science and mathematics in that the lessons meet

  17. InP HEMT Integrated Circuits for Submillimeter Wave Radiometers in Earth Remote Sensing

    NASA Technical Reports Server (NTRS)

    Deal, William R.; Chattopadhyay, Goutam

    2012-01-01

    The operating frequency of InP integrated circuits has pushed well into the Submillimeter Wave frequency band, with amplification reported as high as 670 GHz. This paper provides an overview of current performance and potential application of InP HEMT to Submillimeter Wave radiometers for earth remote sensing.

  18. Effects of rare-earth doping on femtosecond laser waveguide writing in zinc polyphosphate glass

    SciTech Connect

    Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil; Krol, Denise M.; Reis, Signo T.; Brow, Richard K.

    2012-07-15

    We have investigated waveguide writing in Er-Yb doped zinc polyphosphate glass using a femtosecond laser with a repetition rate of 1 KHz. We find that fabrication of good waveguides requires a glass composition with an O/P ratio of 3.25. The dependence on laser writing parameters including laser fluence, focusing conditions, and scan speed is reported. Waveguide properties together with absorption and emission data indicate that these glasses can be used for the fabrication of compact, high gain amplifying devices.

  19. Multiphonon transitions in LaAlO 3 doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Dere?, Przemys?aw J.; Mahiou, Rachid; Goldner, Philippe

    2009-01-01

    From radiative transitions rates in praseodymium, neodymium, erbium, holmium and thulium ions doped LaAlO 3 and measured emission decay times multiphonon nonradiative transitions rates WMNR have been calculated. Radiative transition rates were determined in the frame of Judd-Ofelt theory. The data obtained were plotted in the function of energy gap ? E and fitted by exponential function WMNR = B exp(- ? ? E), where B = 1.02 10 9 and ? = 3.61 10 -3. Fitting results show that multiphonon nonradiative transition rates are low comparing to other oxide crystals being similar to those of YAG.

  20. Investigation of thermophysical characteristics of SrMoO4 crystals, nominally pure and doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Skrobov, S. A.; Matovnikov, A. V.; Ivleva, L. I.; Dunaeva, E. E.; Shekhovtsov, A. N.; Kosmyna, M. B.

    2015-11-01

    Thermophysical characteristics of SrMoO4 crystals (grown by the Czochralski method from intrinsic melts), nominally pure and doped with rare earth ions, have been investigated. The temperature and concentration dependences of the thermal conductivity are obtained for SrMoO4 samples containing Nd3+ (0.28, 0.56, 0.84, and 1.33 at %), Pr3+ (0.01 and 0.41 at %), Ho3+ (0.01 and 0.06 at %), and Ho3+ (0.13 at %) + Tm3+ (0.13 at %) in a temperature range of 50-300 K. The thermal conductivities are measured in the directions parallel and/or perpendicular to the crystal optical axis. The thermal conductivity of nominally pure SrMoO4 at 300 K in the direction perpendicular to the c axis has been found to be 4.2 W/(m K). The introduction of impurities of rare earth metals reduces the thermal conductivity of SrMoO4 crystals. The anisotropy of the thermal conductivity is weak. The measured molar specific heat C P ( T) of a nominally pure SrMoO4 crystal is 116.2 J/(mol K) at 300 K. The temperature dependence of the phonon mean free path l( T) in a SrMoO4 crystal is calculated for the temperature range of 80-300 K based on experimental data.

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

    SciTech Connect

    Yang, B.; Townsend, P.D.; Rowlands, A.P.

    1998-01-01

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

  2. Measuring and analyzing excitation-induced decoherence in rare-earth-doped optical materials

    NASA Astrophysics Data System (ADS)

    Thiel, C. W.; Macfarlane, R. M.; Sun, Y.; Bttger, T.; Sinclair, N.; Tittel, W.; Cone, R. L.

    2014-10-01

    A method is introduced for quantitatively analyzing photon echo decay measurements to characterize excitation-induced decoherence resulting from the phenomenon of instantaneous spectral diffusion. Detailed analysis is presented that allows fundamental material properties to be extracted that predict and describe excitation-induced decoherence for a broad range of measurements, applications and experimental conditions. Motivated by the need for a method that enables systematic studies of ultra-low decoherence systems and direct comparison of properties between optical materials, this approach employs simple techniques and analytical expressions that avoid the need for difficult to measure and often unknown material parameters or numerical simulations. This measurement and analysis approach is demonstrated for the 3H6 to 3H4 optical transition of three thulium-doped crystals, Tm3+:YAG, Tm3+:LiNbO3 and Tm3+:YGG, that are currently employed in quantum information and classical signal processing demonstrations where minimizing decoherence is essential to achieve high efficiencies and large signal bandwidths. These new results reveal more than two orders of magnitude variation in sensitivity to excitation-induced decoherence among the materials studied and establish that the Tm3+:YGG system offers the longest optical coherence lifetimes and the lowest levels of excitation-induced decoherence yet observed for any known thulium-doped material.

  3. Rare-Earth Doped Particles as Dual-Modality Contrast Agent for Minimally-Invasive Luminescence and Dual-Wavelength Photoacoustic Imaging

    NASA Astrophysics Data System (ADS)

    Sheng, Yang; Liao, Lun-De; Thakor, Nitish; Tan, Mei Chee

    2014-10-01

    Multi-modal imaging is an emerging area that integrates multiple imaging modalities to simultaneously capture visual information over many spatial scales. Complementary contrast agents need to be co-developed in order to achieve high resolution and contrast. In this work, we demonstrated that rare-earth doped particles (REDPs) can be employed as dual-modal imaging agents for both luminescence and photoacoustic (PA) imaging to achieve intrinsic high contrast, temporal and spatial resolution, reaching deeper depth. REDPs synthesized with different surfactants (citric acid, polyacrylic acid, ethylenediaminetetraacetic acid and sodium citrate) exhibit tunable emission properties and PA signal amplitudes. Amongst these samples, sodium citrate-modified REDPs showed the strongest PA signals. Furthermore, since REDPs have multiple absorption peaks, they offer a unique opportunity for multi-wavelength PA imaging (e.g. PA signals were measured using 520 and 975 nm excitations). The in vivo PA images around the cortical superior sagittal sinus (SSS) blood vessel captured with enhanced signal arising from REDPs demonstrated that in addition to be excellent luminescent probes, REDPs can also be used as successful PA contrast agents. Anisotropic polyacrylic acid-modified REDPs were found to be the best candidates for dual-modal luminescence and PA imaging due to their strong luminescence and PA signal intensities.

  4. Rare-Earth Doped Particles as Dual-Modality Contrast Agent for Minimally-Invasive Luminescence and Dual-Wavelength Photoacoustic Imaging

    PubMed Central

    Sheng, Yang; Liao, Lun-De; Thakor, Nitish; Tan, Mei Chee

    2014-01-01

    Multi-modal imaging is an emerging area that integrates multiple imaging modalities to simultaneously capture visual information over many spatial scales. Complementary contrast agents need to be co-developed in order to achieve high resolution and contrast. In this work, we demonstrated that rare-earth doped particles (REDPs) can be employed as dual-modal imaging agents for both luminescence and photoacoustic (PA) imaging to achieve intrinsic high contrast, temporal and spatial resolution, reaching deeper depth. REDPs synthesized with different surfactants (citric acid, polyacrylic acid, ethylenediaminetetraacetic acid and sodium citrate) exhibit tunable emission properties and PA signal amplitudes. Amongst these samples, sodium citrate-modified REDPs showed the strongest PA signals. Furthermore, since REDPs have multiple absorption peaks, they offer a unique opportunity for multi-wavelength PA imaging (e.g. PA signals were measured using 520 and 975 nm excitations). The in vivo PA images around the cortical superior sagittal sinus (SSS) blood vessel captured with enhanced signal arising from REDPs demonstrated that in addition to be excellent luminescent probes, REDPs can also be used as successful PA contrast agents. Anisotropic polyacrylic acid-modified REDPs were found to be the best candidates for dual-modal luminescence and PA imaging due to their strong luminescence and PA signal intensities. PMID:25297843

  5. MT+, integrating magnetotellurics to determine earth structure, physical state, and processes

    USGS Publications Warehouse

    Bedrosian, P.A.

    2007-01-01

    As one of the few deep-earth imaging techniques, magnetotellurics provides information on both the structure and physical state of the crust and upper mantle. Magnetotellurics is sensitive to electrical conductivity, which varies within the earth by many orders of magnitude and is modified by a range of earth processes. As with all geophysical techniques, magnetotellurics has a non-unique inverse problem and has limitations in resolution and sensitivity. As such, an integrated approach, either via the joint interpretation of independent geophysical models, or through the simultaneous inversion of independent data sets is valuable, and at times essential to an accurate interpretation. Magnetotelluric data and models are increasingly integrated with geological, geophysical and geochemical information. This review considers recent studies that illustrate the ways in which such information is combined, from qualitative comparisons to statistical correlation studies to multi-property inversions. Also emphasized are the range of problems addressed by these integrated approaches, and their value in elucidating earth structure, physical state, and processes. ?? Springer Science+Business Media B.V. 2007.

  6. Rare-earth-doped biological composites as in vivo shortwave infrared reporters

    PubMed Central

    Naczynski, D.J.; Tan, M.C.; Zevon, M.; Wall, B.; Kohl, J.; Kulesa, A.; Chen, S.; Roth, C.M.; Riman, R.E.; Moghe, P.V.

    2013-01-01

    The extension of in vivo optical imaging for disease screening and image-guided surgical interventions requires brightly-emitting, tissue-specific materials that optically transmit through living tissue and can be imaged with portable systems that display data in real-time. Recent work suggests that a new window across the short wavelength infrared region can improve in vivo imaging sensitivity over near infrared light. Here we report on the first evidence of multispectral, real-time short wavelength infrared imaging offering anatomical resolution using brightly-emitting rare-earth nanomaterials and demonstrate their applicability toward disease-targeted imaging. Inorganic-protein nanocomposites of rare-earth nanomaterials with human serum albumin facilitated systemic biodistribution of the rare-earth nanomaterials resulting in the increased accumulation and retention in tumor tissue that was visualized by the localized enhancement of infrared signal intensity. Our findings lay the groundwork for a new generation of versatile, biomedical nanomaterials that can advance disease monitoring based on a pioneering infrared imaging technique. PMID:23873342

  7. Narrow inhomogeneous and homogeneous optical linewidths in a rare earth doped transparent ceramic

    NASA Astrophysics Data System (ADS)

    Ferrier, A.; Thiel, C. W.; Tumino, B.; Ramirez, M. O.; Baus, L. E.; Cone, R. L.; Ikesue, A.; Goldner, Ph.

    2013-01-01

    Inhomogeneous and homogeneous linewidth are reported in a Eu3+ doped transparent Y2O3 ceramic for the 7F0-5D0 transition, using high-resolution coherent spectroscopy. The 8.7-GHz inhomogeneous linewidth is close to that of single crystals, as is the 59-kHz homogeneous linewidth at 3 K (T2 = 5.4 ?s). The homogeneous linewidth exhibits a temperature dependence that is typical of a crystalline environment, and additional dephasing observed in the ceramic is attributed to magnetic impurities or defects introduced during the synthesis process. The absence of Eu3+segregation at the grain boundaries, evidenced through confocal microfluorescence, further indicates that the majority of Eu3+ions in the ceramic experience an environment comparable to a single crystal. The obtained results suggest that ceramic materials can be competitive with single crystals for applications in quantum information and spectral hole burning devices, beyond their current applications in lasers and scintillators.

  8. Characterization of rare-earth-doped nanophosphors for photodynamic therapy excited by clinical ionizing radiation beams

    NASA Astrophysics Data System (ADS)

    Darafsheh, Arash; Najmr, Stan; Paik, Taejong; Tenuto, Michael E.; Murray, Christopher B.; Finlay, Jarod C.; Friedberg, Joseph S.

    2015-03-01

    We investigated the optical properties of novel terbium (Tb3+)-doped nanophosphors with various host compounds irradiated by clinical electron, photon, and proton beams for their potential as optical probes. The emission spectra of nanophosphors embedded in tissue-mimicking phantoms were collected by an optical fiber connected to a CCD-coupled spectrograph while the samples were irradiated with electron and photon beams generated by a medical linear accelerator and proton beams generated by a clinical cyclotron. We characterized the luminescence of such nanophosphors as a function of the beam energy and observed a dose dependency of the luminescence signal. We demonstrated x-ray luminescence, cathodoluminescence, and ionoluminescence of the nanophosphors in clinical ionizing radiation fields, which indicates their potential as downconverters of high-energy radiation into visible light.

  9. Using the Earth as an Effective Model for Integrating Space Science Into Education Outreach Programs

    NASA Astrophysics Data System (ADS)

    Morris, P. A.; Allen, J.; Galindo, C.; McKay, G.; Obot, V.; Reiff, P.

    2005-05-01

    Our methods of teaching Earth and space science as two disciplines do not represent the spirit of earlier scientists such as Aristotle, da Vinci, and Galileo. We need to re-evaluate these methods and take advantage of the excitement created in the general public over the recent space science exploration programs. The information that we are obtaining from both the Mars missions and Cassini-Huygens focuses on interpreting geomorphology, mineral compositions and gas identification based on Earth as a baseline for data evaluation. This type of evaluation is an extension of Hutton's 18th century principle of Uniformitarianism, the present is the key to the past, or Earth is the key for understanding extraterrestrial bodies. Geomorphological examples are volcanic activity, meteoritic impacts, and evidence of water altering surface features. The Hawaiian, or shield, type volcanoes are analogues for Olympus Mons and the other volcanoes on Mars. Other examples include comparing sand dunes on Earth with possible Martian dunes, known stream patterns on Earth with potential stream patterns on Mars, and even comparing meteoritic impact features on Mars, the Earth, Moon and Mercury. All of these comparisons have been developed into inquiry-based activities and are available through NASA publications. Each of these activities is easily adapted to emphasize either Earth science or space science or both. Beyond geomorphology, solar storms are an excellent topic for integrating Earth and space science. Solar storms are traditionally part of space science studies, but most students do not understand their effect on Earth or the intense effects they could have on humans, whether traveling through space or exploring the surfaces of the Moon or Mars. Effects are not only limited to space travel and other planetary surfaces but also include Earth's magnetosphere, which in turn, affect radio transmission and potentially climate. Like geomorphology courses, there are extensive NASA programs available via either the Internet or CD (e.g., those distributed by P. Reiff, Rice University) that provide inquiry-based activities for students. There is great potential to share the connections of Earth and space science by using NASA developed education materials. The materials can be adapted for the classroom, after school programs, family outreach events, and summer science enrichment programs.

  10. Evidence of dilute ferromagnetism in rare-earth doped yttrium aluminium garnet

    NASA Astrophysics Data System (ADS)

    Farr, Warrick G.; Goryachev, Maxim; le Floch, Jean-Michel; Bushev, Pavel; Tobar, Michael E.

    2015-09-01

    This work demonstrates strong coupling regime between an erbium ion spin ensemble and microwave hybrid cavity-whispering gallery modes in a yttrium aluminium garnet dielectric crystal. Coupling strengths of 220 MHz and mode quality factors in excess of 106 are demonstrated. Moreover, the magnetic response of high-Q modes demonstrates behaviour which is unusual for paramagnetic systems. This behaviour includes hysteresis and memory effects. Such qualitative change of the system's magnetic field response is interpreted as a phase transition of rare earth ion impurities. This phenomenon is similar to the phenomenon of dilute ferromagnetism in semiconductors. The clear temperature dependence of the phenomenon is demonstrated.

  11. Time-frequency-domain dispersion measurement in rare earth doped large effective mode area multicore fibers

    NASA Astrophysics Data System (ADS)

    Baselt, T.; Taudt, Ch.; Hartmann, P.

    2014-03-01

    Ytterbium doped multicore fibers have been recently employed in the field of high power and Quasi-Gaussian beam lasers to design truly single-mode multicore fiber lasers. The special design of these fibers offers low bending loss even for compact high power lasers and amplifiers. Moreover, the Multi-core fiber amplifier possesses a large effective mode area which results in a significant decrease of the related nonlinear effects. In the paper, modal resolved group-velocity dispersion measurements in active multicore fibers are performed using time-frequency-domain white-light interferometry. A Mach-Zehnder-type interferometer with dual-channel detection in the spectral range from 0.4 ?m up to 1.7 ?m and a home-made supercontinuum source are used. Temporally resolved spectrograms recorded at distinct delay positions enable the detection of interference fringes for the equalizationwavelength. The group-velocity dispersion can be derived by applying a Sellmeier polynomial fit to the wavelength dependent differential group delay function. The dispersion parameters for several LMA fibers are investigated over a broad spectral range of about 1.3 ?m.

  12. Refinement and design of rare earth doped photonic crystal fibre amplifier using an ANN approach

    NASA Astrophysics Data System (ADS)

    Mescia, Luciano; Fornarelli, Girolamo; Magarielli, Donato; Prudenzano, Francesco; De Sario, Marco; Vacca, Francesco

    2011-10-01

    A number of numerical and analytical methods with different complexity can be exploited to analyse fibre amplifiers. Conventional approaches make the refinement and design of the devices extremely time consuming, especially when several design parameters have to be simultaneously optimised to obtain the desired performance in terms of gain and noise figure. In order to tackle this issue, a method based on an artificial neural network to perform the refinement and design of erbium doped photonic crystal fibre amplifiers is proposed in this paper. The capability of the neural network to capture the nonlinear functional link among the physical and geometrical characteristics of the fibre amplifier and its gain and noise figure is exploited. In the refinement it is employed to determine the optimal values of the parameters maximising the gain. In the design, it is used to develop an inverse problem solver in order to determine the values of the parameters corresponding to the known values of gain. Numerical results show that the proposed approach finds the refinement/design parameters in good accordance with respect to the conventional one.

  13. Multicolor upconversion luminescence of rare-earth doped Y2CaZnO5 nanophosphors for white lighting-emitting diodes

    NASA Astrophysics Data System (ADS)

    Rajeswari, R.; Surendra Babu, S.; Jayasankar, C. K.

    2014-02-01

    Rare earth doped Y2CaZnO5 nanophosphors were synthesized via the citrate-gel combustion method. Transmission electron microscopy measurements reveal that the particles are distributed uniformly within the size range of 10-30 nm. The Er3+-doped Y2CaZnO5 nanophosphors show strong green upconversion luminescence, which is visible to the naked eye even at 20 mW excitation power of 980 nm diode laser. When these phosphors are codoped with Yb3+ ions, the emission changed to reddish color at higher Yb3+ ion concentrations. Moreover, these phosphors emitted bright white light luminescence when it is triply doped with Er3+/Tm 3+/Yb3+ ions, indicates Y2CaZnO5 nanophosphors are an ideal candidate for phosphor converted white light emitting diodes.

  14. Transition metal and rare earth quad-doped photovoltaic phosphate glasses toward raising a-SiC:H solar cell performance

    NASA Astrophysics Data System (ADS)

    Song, P.; Zhang, C. M.; Zhu, P. F.

    2016-01-01

    Efficiency enhancement of a hydrogenated amorphous-silicon carbide (a-SiC:H) solar cell using downshifting and upconversion of photovoltaic (PV) glasses doped with transition metal (TM) ions and rare earth (RE) ions are investigated. P2O5-Li2O-Al2O3-Sb2O3-MnO-Yb2O3-Er2O3 glass doped with Sb3+-Mn2+-Yb3+-Er3+ ions is prepared and the PV glass is placed on an a-SiC:H solar cell. The performance of the cell in combination with the PV glass is simulated and measured, and the results show that the theoretical and experimental efficiencies are both enhanced compared to the bare one. The potential of TM-RE quad-doped glasses for improving the efficiency of a-SiC:H PV modules are explored.

  15. Theoretical investigation of the structures, stabilities, and NLO responses of calcium-doped pyridazine: alkaline-earth-based alkaline salt electrides.

    PubMed

    Wang, Yin-Feng; Huang, Jiangen; Jia, Li; Zhou, Guangpei

    2014-02-01

    Currently, whether alkaline-earth-doped compounds with electride characteristics are novel candidates for high-performance nonlinear optical (NLO) materials is unknown. In this paper, using quantum chemical computations, we show that: when doping calcium atoms into a family of alkaline-substituted pyridazines, alkaline-earth-based alkaline salt electrides M-H?C?N??Ca (M=H, Li, and K) with distended excess electron clouds are formed. Interestingly, from the triplet to the singlet state, the chemical valence of calcium atom changes from +1 to 0, and the dipole moment direction (??) of the molecule reverses for each M-H?C?N??Ca. Changing pyridazine from without (H?C?N??Ca) to with one alkaline substituent (M-H?C?N??Ca, M=Li and K), the ground state changes from the triplet to the singlet state. The alkaline earth metal doping effect (electride effect) and alkaline salt effect on the static first hyperpolarizabilities (??) demonstrates that (1) the ?? value is increased approximately 1371-fold from 2 (pyridazine, H?C?N?) to 2745au (Ca-doped pyridazine, H?C?N??Ca), (2) the ?? value is increased approximately 1146-fold from 2 in pyridazine (H?C?N?) to 2294au in an Li-substituted pyridazine (Li-H?C?N?), and (3) the ?? value is increased 324-(M=Li) and 106-(M=K) fold from 826 (MLi) and 2294au (MK) to 268,679 (M=Li) and 245,878au (M=K), respectively, from the alkalized pyridazine (M-H?C?N?) to the Ca-doped pyridazine (M-H?C?N??Ca). These results may provide a new means for designing high-performance NLO materials. PMID:24361791

  16. Fluorescence in nanocomposites based on polyethylene oxides and block copolymers of polyethylene oxide-polypropylene oxide loaded with rare earth doped fluorides

    NASA Astrophysics Data System (ADS)

    Yust, Brian; Pedraza, Francisco; Sardar, Dhiraj; Saenz, Aaron; Chipara, Mircea

    2015-03-01

    Rare earth doped fluoride nanoparticles with a size of about 25 nm have been synthesized by a solvothermal process. Polymer-based nanocomposites, containing various weight fraction of nanofillers, have been obtained by dissolving the polymeric matrix (polyethylene oxide) within a solvent (deionized water), adding the nanoparticles, sonicating the mixture, and finally removing the solvent. The complete removal of the solvent has been confirmed by Thermogravimetric Analysis. Additional information about the thermal features have been obtained by Differential Scanning Calorimetry, Wide Angle X-Ray Scattering, FTIR, UV-Visible, and Raman. The effect of the loading with nanoparticles on the glass, crystallization, and melting transition temperatures of the polymeric matrix are reported. Fluorescence of rare earth doped nanoparticles dispersed within the polymeric matrix has been tested by laser spectroscopy. The dependence of fluorescence intensity on the concentration of nanofillers and on temperature in the range 300 to 400 K is analyzed.

  17. Concentration of dependence of radiative and nonradiative energy transfers in rare-earth-doped laser crystals grown from a new method based on gradient concentration fiber single crystals

    NASA Astrophysics Data System (ADS)

    Boulon, Georges; Laversenne, L.; Goutaudier, C.; Guyot, Y.; Cohen-Adad, Marie-Therese

    2003-04-01

    New and original monocrystalline samples having a continuous longitudinal concentration gradient are used to study dynamical processes of resonant transitions in rare earth doped laser crystals like Y2O3 sesquioxide and YAG garnet. This fast and simple method allows to measure the radiative lifetime, the influence of radiation trapping, impurity quenching and RE pairs or clusters on the excited-state lifetime as a functon of the dopant concentration. Examples in Yb3+, Er3+ and Ho3+ rare earth ions are presented.

  18. Composition dependence of the magnetic properties of strontium hexaferrite doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Singh, Taminder; Batra, M. S.; Singh, Iqbal; Katoch, Arun

    2014-09-01

    Rare earth substituted ferrite Sr1-xRExFe12O19 (where RE = La, Gd and Dy, x = 0.0, 0.10, 0.20 and 0.30), have been prepared by employing the ceramic technique and subsequent heat treatment. The magnetic properties of the calcined samples were characterized with a Vibrating Sample Magnetometer (VSM). The samples were sintered at 1150C for 8 hours. The samples were characterized for magnetic properties such as specific saturation magnetization MS, specific remanence magnetization Mr, and coercivity Hc as well as microstructure. It has been observed that all these parameters depend on the composition and heat treatment of the prepared samples. The coercively Hc exhibits an increase as the RE content increases in Sr1-xRExFe12O19 ferrite. With increasing RE content the MS and Mr decrease due to dissolution of RE ion into hexaferrite lattice.

  19. Progress toward a negative refractive index in an atomic system: Spectroscopy and simulations of a rare-earth doped crystal

    NASA Astrophysics Data System (ADS)

    Simmons, Zachary J.

    A material with a negative index of refraction would have interesting properties including: light refracting the 'wrong' way, [special characters omitted] and [special character omitted] forming a left-handed triad, and the prospect of lenses that could harness evanescent waves and beat the diffraction limit. Although there has been progress toward this in artificial materials, we seek an optical negative index in an atomic system. A necessary ingredient of an atomic negative index is a strong magnetic response. This work describes our project to investigate an optical magnetic dipole transition in a rare-earth doped crystal. The document discusses relevant background material including the atomic structure of Eu:YSO and crystal-related issues, as well as construction of the experimental apparatus. The response of the 7F0 → 5D1 transition in Eu:YSO is relatively strong and a great system for exploring optical magnetic dipole physics. Initial results from optical pumping experiments are described as well as simulation results for coherent effects including Rabi flopping and electromagnetically induced transparency (EIT). There is also discussion of current experimental issues and prospects. This system may be one of the most promising atomic systems in which to pursue experimental realization of left-handed wave phenomena.

  20. Energy transfer kinetics in oxy-fluoride glass and glass-ceramics doped with rare-earth ions

    SciTech Connect

    Sontakke, Atul D.; Annapurna, K.

    2012-07-01

    An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF{sub 4} nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF{sub 4} nano-crystals in host glass matrix under controlled post heat treatment of precursor oxy-fluoride glasses has been confirmed from XRD, FESEM, and transmission electron microscope (TEM) analysis. Further, the incorporation of dopant ions inside fluoride nano-crystals has been established through optical absorption and TEM-EDX analysis. The noticed decreasing trend in donor to acceptor energy transfer efficiency from precursor glass to glass-ceramics in all three combinations have been explained based on the structural rearrangements that occurred during the heat treatment process. The reduced coupling phonon energy for the dopant ions due to fluoride environment and its influence on the overall phonon assisted contribution in energy transfer process has been illustrated. Additionally, realization of a correlated distribution of dopant ions causing clustering inside nano-crystals has also been reported.

  1. Enhancement of single particle rare earth doped NaYF4: Yb, Er emission with a gold shell

    NASA Astrophysics Data System (ADS)

    Li, Ling; Green, Kory; Hallen, Hans; Lim, Shuang Fang

    2015-01-01

    Upconversion of infrared light to visible light has important implications for bioimaging. However, the small absorption cross-section of rare earth dopants has limited the efficiency of these anti-Stokes nanomaterials. We present enhanced excitation absorption and single particle fluorescent emission of sodium yttrium fluoride, NaYF4: Yb, Er based upconverting nanoparticles coated with a gold nanoshell through surface plasmon resonance. The single gold-shell coated nanoparticles show enhanced absorption in the near infrared, enhanced total emission intensity, and increased green relative to red emission. We also show differences in enhancement between single and aggregated gold shell nanoparticles. The surface plasmon resonance of the gold-shell coated nanoparticle is shown to be dependent on the shell thickness. In contrast to other reported results, our single particle experimental observations are corroborated by finite element calculations that show where the green/red emission enhancement occurs, and what portion of the enhancement is due to electromagnetic effects. We find that the excitation enhancement and green/red emission ratio enhancement occurs at the corners and edges of the doped emissive core.

  2. Synthesis and upconversion emission of rare earth-doped olive-like YF{sub 3} micro-particles

    SciTech Connect

    Lin, Hang; Chen, Daqin; Niu, Mutong; Yu, Yunlong; Huang, Ping; Wang, Yuansheng

    2010-01-15

    The olive-like YF{sub 3} micro-particles were fabricated via a two-step route. The precursor NH{sub 4}Y{sub 3}F{sub 10} nano-cages sized 8 nm with hollow interiors were first synthesized in a solid reaction at room temperature. In the course of subsequent hydrothermal treating, the unstable NH{sub 4}Y{sub 3}F{sub 10} nano-cages were decomposed, resulted in the formation of Y(OH){sub 1.63}F{sub 1.37} micro-tubes. Prolonging the hydrothermal reaction induced the further decomposition of Y(OH){sub 1.63}F{sub 1.37} to produce YF{sub 3} nano-crystals, which then aggregated together forming the final olive-like YF{sub 3} micro-particles. For the Er{sup 3+}/Yb{sup 3+} co-doped olive-like YF{sub 3} micro-particles, intense visible upconversion emissions were measured under 976 nm excitation owing to the partition of rare earth ions in the lattice, indicating this material a promising luminescent host.

  3. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    SciTech Connect

    Li, Jiawei; Huo, Juntao; Chang, Chuntao E-mail: dujun@nimte.ac.cn; Du, Juan E-mail: dujun@nimte.ac.cn; Man, Qikui; Wang, Xinmin; Li, Run-Wei; Law, Jiayan

    2014-08-14

    The effects of heavy rare earth (RE) additions on the Curie temperature (T{sub C}) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T{sub C} in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔS{sub M}) and refrigerant capacity (RC) of the alloys. The observed values of ΔS{sub M} and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd{sub 5}Ge{sub 1.9}Si{sub 2}Fe{sub 0.1}. The tunable T{sub C} and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

  4. Calcination-free micropatterning of rare-earth-ion-doped nanoparticle films on wettability-patterned surfaces of plastic sheets.

    PubMed

    Watanabe, Satoshi; Hamada, Yudai; Hyodo, Hiroshi; Soga, Kohei; Matsumoto, Mutsuyoshi

    2014-05-15

    We demonstrate a patterning technique of rare-earth-ion-doped (RE) nanoparticle films directly on wettability-patterned surfaces fabricated on plastic sheets in one step. Self-assembled monolayers consisting of silane-coupling agent with hydrophobic groups were fabricated on plastic sheets. UV-ozone treatments were performed through a metal mask to selectively remove the self-assembled monolayers in a patterned manner, resulting in the formation of wettability-patterned surfaces on plastic sheets. Using a water dispersion of Er(3+) and Yb(3+)-codoped Y2O3 nanoparticles at a diameter of 100 nm, RE-nanoparticle films were fabricated on the wettability-patterned surfaces by a dip-coating technique. By adjusting the concentration of RE-nanoparticle dispersion, withdrawal speed, and withdrawal angle, amount of RE-nanoparticles, we were able to control the structures of the RE-nanoparticle films. Fluorescence microscope observations demonstrate that visible upconversion luminescence and near-infrared fluorescence were emitted from the RE-nanoparticle films on the wettability-patterned surfaces. This technique allows for the fabrication of flexible emitting devices with long-operating life time with minimized material consumption and few fabrication steps, and for the application to sensors, emitting devices, and displays in electronics, photonics, and bionics in the future. PMID:24655829

  5. Optical clock transition in a rare-earth-ion-doped crystal: coherence lifetime extension for quantum storage applications

    NASA Astrophysics Data System (ADS)

    Tongning, Robert-Christopher; Chanelière, Thierry; Le Gouët, Jean-Louis; Florencia Pascual-Winter, María

    2015-04-01

    Atomic clock transitions are desirable for quantum information storage and processing thanks to the protection from decoherence they provide. In the context of rare- earth-ion-doped crystals for quantum information storage, clock Zeeman or hyperfine transitions have been identified and exploited for long-lived storage in spin degrees of freedom. We present a theoretical and experimental analysis on the existence of an optical clock transition in Tm3+:YAG, in view of storage in optical coherences. The combination of a Zeeman-like term and a quadratic electronic Zeeman term in the Hamiltonian, lead to the existence of a magnetic field amplitude (12 mT) for which the derivative of the optical transition energy with respect to the field amplitude vanishes, regardless of the magnetic field orientation. We have verified this prediction through hole-burning spectroscopy experiments. In addition to that, a study of the behavior of the Hamiltonian as a function of the magnetic field orientation yields the direction for which both derivatives with respect to the magnetic field angular coordinates also vanish. The condition for an optical clock transition with three vanishing partial derivatives is met.

  6. Optical detection of ultrasound using AFC-based quantum memory technique in cryogenic rare earth ion doped crystals

    NASA Astrophysics Data System (ADS)

    Taylor, Luke R.; McAuslan, David L.; Longdell, Jevon J.

    2013-03-01

    We present results of a novel and highly sensitive technique for the optical detection of ultrasound using the selective storage of frequency shifted photons in an inherently highly efficient and low noise atomic frequency comb (AFC) based quantum memory. The ultrasound `tagged' optical sidebands are absorbed within a pair of symmetric AFCs, generated via optical pumping in a Pr3+:Y2SiO5 sample (tooth separation ? = 150 kHz, comb finesse fc ~ 2 and optical depth ?L ~ 2), separated by twice the ultrasound modulation frequency (1.5 MHz) and centered on either side of a broad spectral pit (1.7 MHz width) allowing transmission of the carrier. The stored sidebands are recovered with 10-20% efficiency as a photon echo (as defined by the comb parameters), and we demonstrate a record 49 dB discrimination between the sidebands and the carrier pulse, high discrimination being important for imaging tissues at depth. We further demonstrate detector limited discrimination (~29 dB) using a highly scattered beam, confirming that the technique is immune to speckle decorrelation. We show that it also remains valid in the case of optically thin samples, and thus represents a significant improvement over other ultrasound detection methods based on rare-earth-ion-doped crystals. These results strongly suggest the suitability of our technique for high-resolution non-contact real-time imaging of biological tissues.

  7. Infrared and visible emissions of rare-earth-doped CeO2 phosphor.

    PubMed

    Chandrakar, D; Kaur, J; Dubey, V; Suryanarayana, N S; Parganiha, Y

    2015-12-01

    This paper reports the synthesis and characterization of Er(3+) -doped CeO2 phosphor with variable concentrations of erbium. The sample was synthesized using a solid-state reaction method, which is useful for the large-scale production of phosphors and is also eco-friendly. The prepared sample was characterized using an X-ray diffraction (XRD) technique. The XRD pattern confirmed that sample has the pure cubic fluorite crystal structure of CeO2 . The crystallite size of the prepared phosphor was determined by Scherer's formula and the crystallite size giving an intense XRD peak is 40.06?nm. The surface morphology of the phosphor was determined by field emission gun scanning electron microscopy (FEGSEM). From the FEGSEM image, good surface morphology with some agglomerates was found. The functional group in the prepared sample was analysed by Fourier transform infrared (FTIR) spectroscopy. All samples prepared with variable concentrations of Er(3+) (0.1-2?mol%) were studied by photoluminescence analysis and it was found that the excitation spectra of the prepared phosphor shows broad excitation centred at 251?nm. Emission spectra at different concentrations of Er(3+) show strong peaks at 413 and 470?nm and a weaker peak at 594?nm. The dominant peaks at 413 and 470?nm are caused by the allowed electronic transition (4) S3/2 ???(4) I15/2 and the weaker transition at 594?nm is due to the transition (4) ?F9/2 ???(4) I15/2 . Spectrophotometric determinations of peaks were evaluated using the Commission Internationale de I'Eclairage (CIE) technique. The emission spectra were also observed using an infrared (IR) laser 980?nm source, and three distinct peaks were found in the IR region at 848, 870 and 980?nm. The prepared phosphor has utility for application in display devices. Copyright 2015 John Wiley & Sons, Ltd. PMID:25810371

  8. Thermochemistry of rare earth doped uranium oxides LnxU1-xO2-0.5x+y (Ln = La, Y, Nd)

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Navrotsky, Alexandra

    2015-10-01

    Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10-50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

  9. Information Requirements for Integrating Spatially Discrete, Feature-Based Earth Observations

    NASA Astrophysics Data System (ADS)

    Horsburgh, J. S.; Aufdenkampe, A. K.; Lehnert, K. A.; Mayorga, E.; Hsu, L.; Song, L.; Zaslavsky, I.; Valentine, D. L.

    2014-12-01

    Several cyberinfrastructures have emerged for sharing observational data collected at densely sampled and/or highly instrumented field sites. These include the CUAHSI Hydrologic Information System (HIS), the Critical Zone Observatory Integrated Data Management System (CZOData), the Integrated Earth Data Applications (IEDA) and EarthChem system, and the Integrated Ocean Observing System (IOOS). These systems rely on standard data encodings and, in some cases, standard semantics for classes of geoscience data. Their focus is on sharing data on the Internet via web services in domain specific encodings or markup languages. While they have made progress in making data available, it still takes investigators significant effort to discover and access datasets from multiple repositories because of inconsistencies in the way domain systems describe, encode, and share data. Yet, there are many scenarios that require efficient integration of these data types across different domains. For example, understanding a soil profile's geochemical response to extreme weather events requires integration of hydrologic and atmospheric time series with geochemical data from soil samples collected over various depth intervals from soil cores or pits at different positions on a landscape. Integrated access to and analysis of data for such studies are hindered because common characteristics of data, including time, location, provenance, methods, and units are described differently within different systems. Integration requires syntactic and semantic translations that can be manual, error-prone, and lossy. We report information requirements identified as part of our work to define an information model for a broad class of earth science data - i.e., spatially-discrete, feature-based earth observations resulting from in-situ sensors and environmental samples. We sought to answer the question: "What information must accompany observational data for them to be archivable and discoverable within a publication system as well as interpretable once retrieved from such a system for analysis and (re)use?" We also describe development of multiple functional schemas (i.e., physical implementations for data storage, transfer, and archival) for the information model that capture the requirements reported here.

  10. Control of the visible emission in the SrZrO3 nano-crystals with the rare earth ion doping.

    PubMed

    Kim, Dong Hwan; Kim, Ji Hyun; Chung, Jin Seok; Lee, Yunsang

    2013-11-01

    We investigated the emission property of SrZrO3 nano-crystals (NCs) with the doping of rare earth (RE) ions, Eu3+ and Tm3+, by using 325 nm photo-excitation. SrZrO3 NCs show a sizable violet-blue emission, while the Eu3+ and Tm3+ ions are well known to be good red and blue phosphors, respectively. Combined emissions of the host and the RE ion dopant might suggest a new white luminescent source. The RE ion doped SrZrO3 NCs were initially synthesized by using the combustion method, and then the as-synthesized crystals were annealed at different temperatures from 650 degrees C to 1450 degrees C. The Eu3+-doped SrZrO3 NCs showed the sharp red emission near 600 nm, in addition to a violet-blue emission of the host material in itself. While the red emission is enhanced in the high temperature post-annealing, the blue emission is suppressed in an opposite way. This close relation between the emissions of the host and dopant was observed similarly in the Tm3+-doped NCs. We could control the emission property in the SrZrO3:Eu3+/Tm3+ NCs from blue to red by thermal annealing and RE ion doping. PMID:24245294

  11. Rare earth ion (La, Ce, and Eu) doped ZnO nanoparticles synthesized via sol-gel method: Application in dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Pandey, Padmini; Kurchania, Rajnish; Haque, Fozia Z.

    2015-10-01

    Dye-sensitized solar cells (DSSCs) were fabricated by using ZnO nanoparticles as working electrode material synthesized via simple and cost effective sol-gel method. Crystallography and morphology was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM), respectively. Among various rare earth ions, 1.0 mol % La, Ce, and Eu doped ZnO nanoparticles based photoanodes were used to test DSSC performance. Lower efficiency (? = 1.14%) for La ion doped ZnO nanoparticles based cell was observed. A much lower photocurrent J sc = 2.52 mA/cm2 with 0.60% efficiency ( ?) for the Ce ion doped ZnO nanoparticles based prototype was observed as compared to that ( J sc = 3.86 mA/cm2 with ? = 1.24%) of the undoped one which may be due to the formation of opposite internal electric potential difference in the cell. Furthermore, the improvement in efficiency (? = 1.36%) and J sc = 3.99 mA/cm2 for Eu ion doped ZnO can be attributed to enhanced electron injection and transport abilities. This indicates that 1.0 mol % Eu ion doped ZnO film possesses better electrical conductivity probably due to the existence of high-valance Eu ions in the ZnO matrix which might be promising in ZnO-based dye sensitized solar cell.

  12. Synthesis and characterization of rare earth doped barium fluoride nanoparticles and derivatized copper phthalocyanine nanoparticles

    NASA Astrophysics Data System (ADS)

    Bender, Christopher Mark

    1998-12-01

    Nanoparticles of neodymium doped barium fluoride (Nd:BaFsb2) were synthesized for use as the inorganic component of an optical amplifier composite. Microemulsions were used to maintain domain size in the nano-regime (100 nm), and decreasing the volume fraction of the aqueous content, while simultaneously increasing the volume fraction of the cosurfactant (methanol), gave a linear relationship between decreasing domain size and increasing volume fraction of alcohol. As Nd was added to the BaFsb2 host, direct incorporation was observed at low dopant levels (0-10 mol-%), a two-phase mixture was observed at intermediate dopant levels (10-50 mol-%), and a nearly amorphous product resulted with very high Nd-dopant levels (>50 mol-%). Fluorescence measurements of the solids showed that concentration quenching was delayed until unusually high levels, probably as a result of the lost crystallinity. Praseodymium and ytterbium codoped barium fluoride (Pr,Yb:BaFsb2) were also synthesized in microemulsions. Though as-prepared powders did not fluoresce, treatment with high temperatures (900spC) and dynamic vacuum resulted in products which would fluoresce at 1.3 mum. Lower temperature treatments (500-750spC) were used to decrease sintering, however this resulted in Ybsp{3+} products in which Ybsp{3+} fluorescence was quenched by exposure to air. Contamination due to water and hydroxide is believed to be the reason. Ethanolic microemulsions were used to make copper phthalocyanine (CuPc), which was modified with either zinc phthalocyanine (ZnPc) or copper phthalcyaninesulfonic acid by means of a flow system. The sulfonic acid derivative was lost upon aqueous washing. The zinc derivatized product gave a dispersion in n-hexylamine, which was stable for seven days. The mole ratio of Cu:Zn was 1:1 for the solids dispersed in n-hexylamine, and was 6:1 for the solids that were not dispersed. Because underivatized CuPc formed by the same method did not result in a dispersed product, the dispersion mechanism is postulated to be due to interaction between the ZnPc on the surface and the n-hexylamine.

  13. Fundamentals of laser cooling of rare-earth-ion doped solids and its enhancement using nanopowders

    NASA Astrophysics Data System (ADS)

    Ruan, Xiulin

    The Fermi golden rule is applied as the primary theory for laser cooling of solids, by recognizing that the absorption is a photon-induced, phonon-assisted, electronic transition. The limiting factors are identified as the coupling and population of the energy carriers (photon, electron, and phonon), which include the photon-electron coupling, electron-phonon coupling, ion-dopant concentration, phonon density of states, and the photon population. The photon-electron and electron-vibration coupling rates for ion-doped materials are calculated using ab initio methods for the first time. Using the calculated first-principle wavefunctions, the electric transition dipole moment between the ground and excited states is determined by its definition. The electron-phonon coupling is calculated by taking into account the modification of the electronic wavefunction in response to the nuclei motion, and the modifications of the vibrational modes before and after the transition. This ab initio approach does not require any fitting to experiment, providing a theoretical foundation for the optimal selection of laser cooling materials (both dopant and host). Nanostructure is proposed for the first time to enhance laser cooling performance, through the optimization of carrier populations using nanopowders. The concept of optimum dopant concentration is established and determined using the energy transfer theory, and is found to be larger than that currently used. The phonon density of states of nanopowders, calculated using molecular dynamics simulations, exhibits broadened modes, and extended tails at low and high frequencies. This is advantageous over the bulk material since more phonon modes are available in the desired range. The pumping field energy is calculated by solving the Maxwell equations in random nanopowder media. Photons are multiply scattered and do not propagate through the medium, and large field enhancement is observed. This leads to the trapping of more photons in nanopowder media, compared to the bulk material, implying more efficient absorption and cooling performance. Due to these enhancement effects, thermal predictions show that nanopowders can be cooled to the cryogenic temperature range, for the first time.

  14. The integrated Earth System Model (iESM): formulation and functionality

    DOE PAGESBeta

    Collins, W. D.; Craig, A. P.; Truesdale, J. E.; Di Vittorio, A. V.; Jones, A. D.; Bond-Lamberty, B.; Calvin, K. V.; Edmonds, J. A.; Kim, S. H.; Thomson, A. M.; et al

    2015-01-21

    The integrated Earth System Model (iESM) has been developed as a new tool for projecting the joint human/climate system. The iESM is based upon coupling an Integrated Assessment Model (IAM) and an Earth System Model (ESM) into a common modeling infrastructure. IAMs are the primary tool for describing the human–Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species, land use and land cover change, and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. The iESM projectmore » integrates the economic and human dimension modeling of an IAM and a fully coupled ESM within a single simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore-omitted feedbacks between natural and societal drivers, we can improve scientific understanding of the human–Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper describes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.« less

  15. The integrated Earth System Model (iESM): formulation and functionality

    NASA Astrophysics Data System (ADS)

    Collins, W. D.; Craig, A. P.; Truesdale, J. E.; Di Vittorio, A. V.; Jones, A. D.; Bond-Lamberty, B.; Calvin, K. V.; Edmonds, J. A.; Kim, S. H.; Thomson, A. M.; Patel, P.; Zhou, Y.; Mao, J.; Shi, X.; Thornton, P. E.; Chini, L. P.; Hurtt, G. C.

    2015-01-01

    The integrated Earth System Model (iESM) has been developed as a new tool for projecting the joint human/climate system. The iESM is based upon coupling an Integrated Assessment Model (IAM) and an Earth System Model (ESM) into a common modeling infrastructure. IAMs are the primary tool for describing the human-Earth system, including the sources of global greenhouse gases (GHGs) and short-lived species, land use and land cover change, and other resource-related drivers of anthropogenic climate change. ESMs are the primary scientific tools for examining the physical, chemical, and biogeochemical impacts of human-induced changes to the climate system. The iESM project integrates the economic and human dimension modeling of an IAM and a fully coupled ESM within a single simulation system while maintaining the separability of each model if needed. Both IAM and ESM codes are developed and used by large communities and have been extensively applied in recent national and international climate assessments. By introducing heretofore-omitted feedbacks between natural and societal drivers, we can improve scientific understanding of the human-Earth system dynamics. Potential applications include studies of the interactions and feedbacks leading to the timing, scale, and geographic distribution of emissions trajectories and other human influences, corresponding climate effects, and the subsequent impacts of a changing climate on human and natural systems. This paper describes the formulation, requirements, implementation, testing, and resulting functionality of the first version of the iESM released to the global climate community.

  16. VARIABILITY OF WATER AND OXYGEN ABSORPTION BANDS IN THE DISK-INTEGRATED SPECTRA OF EARTH

    SciTech Connect

    Fujii, Yuka; Suto, Yasushi; Turner, Edwin L.

    2013-03-10

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H{sub 2}O and O{sub 2} bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H{sub 2}O and O{sub 2} bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H{sub 2}O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

  17. Variability of Water and Oxygen Absorption Bands in the Disk-integrated Spectra of Earth

    NASA Astrophysics Data System (ADS)

    Fujii, Yuka; Turner, Edwin L.; Suto, Yasushi

    2013-03-01

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H2O and O2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H2O and O2 bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H2O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

  18. Earth science information: Planning for the integration and use of global change information

    NASA Technical Reports Server (NTRS)

    Lousma, Jack R.

    1992-01-01

    The Consortium for International Earth Science Information Network (CIESIN) was founded in 1989 as a non-profit corporation dedicated to facilitating access to, use and understanding of global change information worldwide. The Consortium was created to cooperate and coordinate with organizations and researchers throughout the global change community to further access the most advanced technology, the latest scientific research, and the best information available for critical environmental decision making. CIESIN study efforts are guided by Congressional mandates to 'convene key present and potential users to assess the need for investment in integration of earth science information,' to 'outline the desirable pattern of interaction with the scientific and policy community,' and to 'develop recommendations and draft plans to achieve the appropriate level of effort in the use of earth science data for research and public policy purposes.' In addition, CIESIN is tasked by NASA to develop a data center that would extend the benefits of Earth Observing System (EOS) to the users of global change information related to human dimensions issues. For FY 1991, CIESIN focused on two main objectives. The first addressed the identification of information needs of global change research and non-research user groups worldwide. The second focused on an evaluation of the most efficient mechanisms for making this information available in usable forms.

  19. PHOTOMETRIC VARIABILITY OF THE DISK-INTEGRATED THERMAL EMISSION OF THE EARTH

    SciTech Connect

    Gomez-Leal, I.; Selsis, F.; Palle, E. E-mail: selsis@obs.u-bordeaux1.fr

    2012-06-10

    Here we present an analysis of the global-integrated mid-infrared emission flux of the Earth based on data derived from satellite measurements. We have studied the photometric annual, seasonal, and rotational variability of the thermal emission of the Earth to determine which properties can be inferred from the point-like signal. We find that the analysis of the time series allows us to determine the 24 hr rotational period of the planet for most observing geometries, due to large warm and cold areas, identified with geographic features, which appear consecutively in the observer's planetary view. However, the effects of global-scale meteorology can effectively mask the rotation for several days at a time. We also find that orbital time series exhibit a seasonal modulation, whose amplitude depends strongly on the latitude of the observer but weakly on its ecliptic longitude. As no systematic difference of brightness temperature is found between the dayside and the nightside, the phase variations of the Earth in the infrared range are negligible. Finally, we also conclude that the phase variation of a spatially unresolved Earth-Moon system is dominated by the lunar signal.

  20. Integrated microfluidic flowmeter based on a micro-FBG inscribed in Co?-doped optical fiber.

    PubMed

    Liu, Zhengyong; Tse, Ming-Leung Vincent; Zhang, A Ping; Tam, Hwa-Yaw

    2014-10-15

    A novel microfluidic flowmeter integrated with microfiber Bragg grating (FBG) is presented. Two glass capillaries and a short length of high-light-absorption Co?-doped optical fiber were stacked inside a larger outer capillary tube. The stack was then drawn into a tapered device. Two microchannels with the diameter of ~50???m were formed inside the capillaries for flowing of microfluidics. An FBG was inscribed in the tapered Co?-doped fiber with waist diameter of ~70???m, and acts as a flow-rate sensor. A pump laser with wavelength of 1480 nm was utilized to locally heat the FBG, rendering the FBG as miniature "hot-wire" flowmeter. The flow rate of the liquid in the microchannels is determined by the induced wavelength shift of the FBG. The experimental results achieve a minimum detectable change of ~16??nL/s in flow rate, which is very promising in the use as part of biochips. PMID:25361108

  1. Practices of Integrating the Earth Charter into Education Activities in German Federal States of Hessen and Rheinland-Pfalz

    ERIC Educational Resources Information Center

    Mathar, Reiner

    2010-01-01

    The integration of Earth Charter into everyday practice of schools in Germany has to be combined with the curriculum development in different subjects. Two states of Germany started this process by organizing inservice training for primary and secondary teachers. Additionally they translated and adopted the Earth Charter Teachers Guidebook to…

  2. Practices of Integrating the Earth Charter into Education Activities in German Federal States of Hessen and Rheinland-Pfalz

    ERIC Educational Resources Information Center

    Mathar, Reiner

    2010-01-01

    The integration of Earth Charter into everyday practice of schools in Germany has to be combined with the curriculum development in different subjects. Two states of Germany started this process by organizing inservice training for primary and secondary teachers. Additionally they translated and adopted the Earth Charter Teachers Guidebook to

  3. INTEGRATION OF THE ROTATION OF AN EARTH-LIKE BODY AS A PERTURBED SPHERICAL ROTOR

    SciTech Connect

    Ferrer, Sebastian; Lara, Martin E-mail: mlara@roa.e

    2010-05-15

    For rigid bodies close to a sphere, we propose an analytical solution that is free from elliptic integrals and functions, and can be fundamental for application to perturbed problems. After reordering the Hamiltonian as a perturbed spherical rotor, the Lie-series solution is generated up to an arbitrary order. Using the inertia parameters of different solar system bodies, the comparison of the approximate series solution with the exact analytical one shows that the precision reached with relatively low orders is at the same level of the observational accuracy for the Earth and Mars. Thus, for instance, the periodic errors of the mathematical solution are confined to the microarcsecond level with a simple second-order truncation for the Earth. On the contrary, higher orders are required for the mathematical solution to reach a precision at the expected level of accuracy of proposed new theories for the rotational dynamics of the Moon.

  4. Advancing Coupled Human-Earth System Models: The Integrated Ecosystem Demography Model (iED) Project

    NASA Astrophysics Data System (ADS)

    Hurtt, G. C.; Chini, L. P.; Clarke, L.; Calvin, K. V.; Chambers, J. Q.; Dubayah, R.; Dolan, K.; Edmonds, J. A.; Fisk, J. P.; Flanagan, S.; Frolking, S.; Janetos, A. C.; LePage, Y.; Morton, D. C.; Patel, P.; Rourke, O.; Sahajpal, R.; Thomson, A. M.; Wise, M.; Ying, Q.

    2012-12-01

    Recent studies with integrated assessment models, models linking human and natural systems at a global scale, highlight the importance of terrestrial systems in climate stabilization efforts. Here we introduce a new modeling framework iED, designed to link advanced remote sensing data (active and passive.), height-structured terrestrial ecosystem dynamics (ED), gridded land-use change projections (GLM), and integrated assessment modeling (GCAM) into a single coupled modeling framework with unprecedented spatial resolution and process-level detail. Our research aims to reduce uncertainties associated with forest modeling within integrated assessments, and to quantify the impacts of climate change on forest growth, mortality, and productivity for integrated assessments of terrestrial carbon management. iED is being used to address key science questions including: (1) What are the opportunities for land-use strategies such as afforestation or woody bioenergy crop production to contribute to stabilization of atmospheric CO2 concentrations? (2) How could potentially altered disturbance rates from tropical cyclones and Amazonian fires affect vegetation, carbon stocks and fluxes, and the development of climate change mitigation strategies? (3) What are the linked remote sensing/ecosystem modeling requirements for improving integrated assessments of climate mitigation strategies? With its strong connections to data and conceptual linkages to other models in development, iED is also designed to inform the next generation of remote sensing and integrated Earth system modeling efforts.

  5. Facile fabrication and photoluminescence properties of rare-earth-doped Gd?O? hollow spheres via a sacrificial template method.

    PubMed

    Gao, Yu; Zhao, Qian; Fang, Qinghong; Xu, Zhenhe

    2013-08-21

    Rare-earth-doped gadolinium oxide (Gd?O?) hollow spheres were successfully fabricated on a large scale by using PS spheres as sacrificed templates and urea as a precipitating agent, which involved the deposition of an inorganic coating Gd(OH)CO3 on the surface of PS spheres and subsequent calcination in the air. Various approaches including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), as well as photoluminescence spectroscopies were used to characterize the samples. The results indicate that the sample is composed of uniform hollow Gd?O? spheres with a mean particle size of about 2.3 ?m and these hollow spheres have the mesoporous shell that are composed of a large amount of nanoparticles. The possible mechanism of evolution from PS spheres to the amorphous precursor and to the final hollow Gd?O? spheres have been proposed. The as-obtained samples show strong light emission with different colors corresponding to different Ln? ions under ultraviolet-visible light and electron-beam excitation. Under 980 nm NIR irradiation, Gd?O?:Ln? (Ln? = Yb?/Er?, Yb?/Tm? and Yb?/Ho?) exhibit characteristic up-conversion (UC) emissions of red (Er?, H11/2, ?S3/2, ?F9/2 ? ?I15/2), blue (Tm?, G? ? H?) and green (Ho?, ?F?, ?S? ? ?I?), respectively. These merits of multicolor emissions in the visible region endow these kinds of materials with potential applications in the field of light display systems, lasers, optoelectronic devices, and MRI contrast agents. PMID:23801272

  6. Solid state NMR as a new approach for the structural characterization of rare-earth doped lead lanthanum zirconate titanate laser ceramics

    NASA Astrophysics Data System (ADS)

    Mohr, Daniel; de Camargo, Andrea S. S.; Schneider, Jos F.; Queiroz, Thiago B.; Eckert, Hellmut; Botero, riton R.; Garcia, Ducinei; Eiras, Jos A.

    2008-10-01

    To facilitate the design of laser host materials with optimized emission properties, detailed structural information at the atomic level is essential, regarding the local bonding environment of the active ions (distribution over distinct lattice sites) and their extent of local clustering as well as their population distribution over separate micro- or nanophases. The present study explores the potential of solid state NMR spectroscopy to provide such understanding for rare-earth doped lead lanthanum zirconate titanate (PLZT) ceramics. As the NMR signals of the paramagnetic dopant species cannot be observed directly, two complementary approaches are utilized: (1) direct observation of diamagnetic mimics using 45Sc NMR and (2) study of the paramagnetic interaction of the constituent host lattice nuclei with the rare-earth dopant, using 207Pb NMR lineshape analysis. 45Sc MAS NMR spectra of scandium-doped PLZT samples unambiguously reveal scandium to be six-coordinated, suggesting that this rare-earth ion substitutes in the B site. Static 207Pb spin echo NMR spectra of a series of Tm-doped PLZT samples reveal a clear influence of paramagnetic rare-earth dopant concentration on the NMR lineshape. In the latter case high-fidelity spectra can be obtained by spin echo mapping under systematic incrementation of the excitation frequency, benefiting from the signal-to-noise enhancement afforded by spin echo train Fourier transforms. Consistent with XRD data, the 207Pb NMR lineshape analysis suggests that statistical incorporation into the PLZT lattice occurs at dopant levels of up to 1 wt.% Tm 3+, while at higher levels the solubility limit is reached.

  7. A Terrestrial Integrated Modeling System (TIMS) at a catchment scale - implications for Earth System Modeling

    NASA Astrophysics Data System (ADS)

    Niu, G. Y.; Fang, Y.; Wu, R.; Mathias, A.; Paniconi, C.; Troch, P. A. A.; Zeng, X.; Chorover, J.; Monson, R. K.

    2014-12-01

    To enhance our predictive understandings of the interactions between the soil, plants, and air and their integrated behavior at hillslope and catchment scales, we have been developing a Terrestrial Integrated Modeling System (TIMS). TIMS aims to numerically simulate various physical and chemical processes that occur over the Earth's terrestrial surface, e.g., exchanges and flows of energy, water, carbon and other chemicals between and within the soil, plants, and air. TIMS is being compiled from existing models that have arisen from individual scientific communities, including 1) a surface energy, water, and carbon exchange scheme (NoahMP), 2) a 3-dimensional physically-based hydrological model (CATHY), 3) a reactive transport model (CrunchFlow), and 4) an individual-based vegetation dynamics model (ECOTONE). TIMS also integrates newly developed components, e.g., a microbial enzyme based soil organic carbon decomposition model and a solar radiation correction scheme accounting for the effects of terrain shading and slope angle and aspect. We will present the current state of TIMS development and some validations against measurements at various scales, the challenges for developing and evaluating such a complex modeling system, and implications for scaling-up plot-scale processes (e.g., AmeriFlux) to global-scale land surface models for use in Earth System Models (ESMs).

  8. Broadband tunable integrated optical ratch-reel ring laser in doped aluminium oxide

    NASA Astrophysics Data System (ADS)

    Schoer, Gerrit; Mahnke, Matthias; Schober, Marc; Herrmann, Alexander; Müller, Jörg

    2006-04-01

    In this paper an optically pumped tunable ring-laser system based on low-loss integrated optic titanium doped sapphirelike waveguides on silicon is presented including simulation results and a characterisation of the realised system. The Al IIO 3 thin film layers are doped in situ with titanium in a PECVD deposition from metal-organic precursors. The waveguides are patterned by reactive ion etching (RIE) to obtain high quality, low-loss waveguides. Afterwards the wafer is annealed by RTP (Rapid Thermal Processing). Thereby the layers change to a sapphire-like morphology and the titanium becomes optically activated without the formation of larger crystallites so that higher losses due to scattering are prevented. For tuning the laser, two solutions are presented. The first is a ZnO based electro-optically tunable etalon which is integrated in the active ring; the second is an also ZnO based coupled ring resonator which can be tuned either by the electro-optical effect or elasto-optically by placing it on a membrane. The required directional element that ensures the propagation in only one direction of the ring is realised by a new "ratch-reel structure" which acts as an optical diode. As the optical field is shifted to the outer periphery of the ring, it is possible to realise a structure that scatters the optical field in one propagation direction, whereas in the other direction it propagates with low loss. The system is pumped by a frequency doubled Nd-YAG-laser at 532 nm which is coupled to the ring via a SiON waveguide. The output power is coupled to a tangential waveguide where the coupling coefficient is determined by distance and refractive indices.

  9. Earth Systems Science in an Integrated Science Content and Methods Course for Elementary Education Majors

    NASA Astrophysics Data System (ADS)

    Madsen, J. A.; Allen, D. E.; Donham, R. S.; Fifield, S. J.; Shipman, H. L.; Ford, D. J.; Dagher, Z. R.

    2004-12-01

    With funding from the National Science Foundation, we have designed an integrated science content and methods course for sophomore-level elementary teacher education (ETE) majors. This course, the Science Semester, is a 15-credit sequence that consists of three science content courses (Earth, Life, and Physical Science) and a science teaching methods course. The goal of this integrated science and education methods curriculum is to foster holistic understandings of science and pedagogy that future elementary teachers need to effectively use inquiry-based approaches in teaching science in their classrooms. During the Science Semester, traditional subject matter boundaries are crossed to stress shared themes that teachers must understand to teach standards-based elementary science. Exemplary approaches that support both learning science and learning how to teach science are used. In the science courses, students work collaboratively on multidisciplinary problem-based learning (PBL) activities that place science concepts in authentic contexts and build learning skills. In the methods course, students critically explore the theory and practice of elementary science teaching, drawing on their shared experiences of inquiry learning in the science courses. An earth system science approach is ideally adapted for the integrated, inquiry-based learning that takes place during the Science Semester. The PBL investigations that are the hallmark of the Science Semester provide the backdrop through which fundamental earth system interactions can be studied. For example in the PBL investigation that focuses on energy, the carbon cycle is examined as it relates to fossil fuels. In another PBL investigation centered on kids, cancer, and the environment, the hydrologic cycle with emphasis on surface runoff and ground water contamination is studied. In a PBL investigation that has students learning about the Delaware Bay ecosystem through the story of the horseshoe crab and the biome that swirls around this remarkable arthropod, students are exposed to interactions between the hydrosphere, atmosphere, and geosphere and they examine ways in which climate change can affect this ecosystem.

  10. Enhanced Electroresponse of Alkaline Earth Metal-Doped Silica/Titania Spheres by Synergetic Effect of Dispersion Stability and Dielectric Property.

    PubMed

    Yoon, Chang-Min; Lee, Seungae; Cheong, Oug Jae; Jang, Jyongsik

    2015-09-01

    A series of alkaline earth metal-doped hollow SiO2/TiO2 spheres (EM-HST) are prepared as electrorheological (ER) materials via sonication-mediated etching method with various alkaline earth metal hydroxides as the etchant. The EM-HST spheres are assessed to determine how their hollow interior and metal-doping affects the ER activity. Both the dispersion stability and the dielectric properties of these materials are greatly enhanced by the proposed one-step etching method, which results in significant enhancement of ER activity. These improvements are attributed to increased particle mobility and interfacial polarization originating from the hollow nature of the EM-HST spheres and the effects of EM metal-doping. In particular, Ca-HST-based ER fluid exhibits ER performance which is 7.1-fold and 3.1-fold higher than those of nonhollow core/shell silica/titania (CS/ST) and undoped hollow silica/titania (HST)-based ER fluids, respectively. This study develops a versatile and simple approach to enhancing ER activity through synergetic effects arising from the combination of dispersion stability and the unique dielectric properties of hollow EM-HST spheres. In addition, the multigram scale production described in this experiment can be an excellent advantage for practical and commercial ER application. PMID:26266695

  11. ESTREAMS and EarthScapes: Integrating Teacher Professional Development Into a Science and Technology Center

    NASA Astrophysics Data System (ADS)

    Campbell, K.; Dalbotten, D.

    2004-12-01

    The National Center for Earth-surface Dynamics (NCED) has developed three inter-locking programs to integrate Teacher Professional Development into the Center. These programs address teachers at two stages of professional development: post-baccalaureate pre-service teachers enrolled in masters programs and in-service teachers. Formal and informal methods are used to involve teachers in NCED research and in NCED's informal public education programs, exhibits and outdoor park at the Science Museum of Minnesota. This session will present the methods we are developing and our results to date. It will also introduce materials we currently make available through our online Education Portal.

  12. Integrating emerging earth science technologies into disaster risk management: an enterprise architecture approach

    NASA Astrophysics Data System (ADS)

    Evans, J. D.; Hao, W.; Chettri, S. R.

    2014-12-01

    Disaster risk management has grown to rely on earth observations, multi-source data analysis, numerical modeling, and interagency information sharing. The practice and outcomes of disaster risk management will likely undergo further change as several emerging earth science technologies come of age: mobile devices; location-based services; ubiquitous sensors; drones; small satellites; satellite direct readout; Big Data analytics; cloud computing; Web services for predictive modeling, semantic reconciliation, and collaboration; and many others. Integrating these new technologies well requires developing and adapting them to meet current needs; but also rethinking current practice to draw on new capabilities to reach additional objectives. This requires a holistic view of the disaster risk management enterprise and of the analytical or operational capabilities afforded by these technologies. One helpful tool for this assessment, the GEOSS Architecture for the Use of Remote Sensing Products in Disaster Management and Risk Assessment (Evans & Moe, 2013), considers all phases of the disaster risk management lifecycle for a comprehensive set of natural hazard types, and outlines common clusters of activities and their use of information and computation resources. We are using these architectural views, together with insights from current practice, to highlight effective, interrelated roles for emerging earth science technologies in disaster risk management. These roles may be helpful in creating roadmaps for research and development investment at national and international levels.

  13. The surface temperatures of the earth: steps towards integrated understanding of variability and change

    NASA Astrophysics Data System (ADS)

    Merchant, C. J.; Matthiesen, S.; Rayner, N. A.; Remedios, J. J.; Jones, P. D.; Olesen, F.; Trewin, B.; Thorne, P. W.; Auchmann, R.; Corlett, G. K.; Guillevic, P. C.; Hulley, G. C.

    2013-06-01

    Surface temperature is a key aspect of weather and climate, but the term may refer to different quantities that play interconnected roles and are observed by different means. In a community-based activity in June 2012, the EarthTemp Network brought together 55 researchers from five continents to improve the interaction between scientific communities who focus on surface temperature in particular domains, to exploit the strengths of different observing systems and to better meet the needs of different communities. The workshop identified key needs for progress towards meeting scientific and societal requirements for surface temperature understanding and information which are presented in this community paper. A "whole-Earth" perspective is required with more integrated, collaborative approaches to observing and understanding Earth's various surface temperatures. It is necessary to build understanding of the relationships between different surface temperatures, where presently inadequate, and undertake large-scale systematic intercomparisons. Datasets need to be easier to obtain and exploit for a wide constituency of users, with the differences and complementarities communicated in readily understood terms, and realistic and consistent uncertainty information provided. Steps were also recommended to curate and make available data that are presently inaccessible, develop new observing systems and build capacities to accelerate progress in the accuracy and usability of surface temperature datasets.

  14. The Surface Temperatures of the Earth: Steps towards Integrated Understanding of Variability and Change

    NASA Astrophysics Data System (ADS)

    Matthiesen, Stephan; Merchant, Chris; Rayner, Nick; Remedios, John; Høyer, Jacob L.; Jones, Phil; Olesen, Folke; Roquet, Hervé; Sobrino, José; Thorne, Peter

    2013-04-01

    Surface temperature is a key aspect of weather and climate, relevant to human health, agriculture and leisure, ecosystem services, infrastructure development and economic activity. In a community-based activity, the EarthTemp Network brought together 55 researchers from 5 continents to improve the interaction between scientific communities who focus on particular domains, to exploit the strengths of different observing systems and to better meet the needs of different communities. The Network idenitified key needs for progress towards meeting societal needs for surface temperature understanding and information, which will be reviewed and discussed in this contribution. A "whole-Earth" perspective is required with more integrated, collaborative approaches to observing and understanding Earth's various surface temperatures. It is necessary to build understanding of the relationships of different surface temperatures, where presently inadequate, and undertake large-scale systematic intercomparisons. Datasets need to be easier to obtain and exploit for a wide constituency of users, with the differences and complementarities communicated in readily understood terms, and realistic and consistent uncertainty information. Steps are also recommended to curate and make available data that are presently inaccessible, develop new observing systems and build capacities to accelerate progress in the accuracy and usability of surface temperature datasets.

  15. The surface temperatures of Earth: steps towards integrated understanding of variability and change

    NASA Astrophysics Data System (ADS)

    Merchant, C. J.; Matthiesen, S.; Rayner, N. A.; Remedios, J. J.; Jones, P. D.; Olesen, F.; Trewin, B.; Thorne, P. W.; Auchmann, R.; Corlett, G. K.; Guillevic, P. C.; Hulley, G. C.

    2013-12-01

    Surface temperature is a key aspect of weather and climate, but the term may refer to different quantities that play interconnected roles and are observed by different means. In a community-based activity in June 2012, the EarthTemp Network brought together 55 researchers from five continents to improve the interaction between scientific communities who focus on surface temperature in particular domains, to exploit the strengths of different observing systems and to better meet the needs of different communities. The workshop identified key needs for progress towards meeting scientific and societal requirements for surface temperature understanding and information, which are presented in this community paper. A "whole-Earth" perspective is required with more integrated, collaborative approaches to observing and understanding Earth's various surface temperatures. It is necessary to build understanding of the relationships between different surface temperatures, where presently inadequate, and undertake large-scale systematic intercomparisons. Datasets need to be easier to obtain and exploit for a wide constituency of users, with the differences and complementarities communicated in readily understood terms, and realistic and consistent uncertainty information provided. Steps were also recommended to curate and make available data that are presently inaccessible, develop new observing systems and build capacities to accelerate progress in the accuracy and usability of surface temperature datasets.

  16. Spherical-earth gravity and magnetic anomaly modeling by Gauss-Legendre quadrature integration

    NASA Technical Reports Server (NTRS)

    Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J.

    1981-01-01

    Gauss-Legendre quadrature integration is used to calculate the anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical earth. The procedure involves representation of the anomalous source as a distribution of equivalent point gravity poles or point magnetic dipoles. The distribution of equivalent point sources is determined directly from the volume limits of the anomalous body. The variable limits of integration for an arbitrarily shaped body are obtained from interpolations performed on a set of body points which approximate the body's surface envelope. The versatility of the method is shown by its ability to treat physical property variations within the source volume as well as variable magnetic fields over the source and observation surface. Examples are provided which illustrate the capabilities of the technique, including a preliminary modeling of potential field signatures for the Mississippi embayment crustal structure at 450 km.

  17. Earth science information: Planning for the integration and use of global change information

    NASA Technical Reports Server (NTRS)

    Lousma, Jack R.

    1992-01-01

    Activities and accomplishments of the first six months of the Consortium for International Earth Science Information Network (CIESIN's) 1992 technical program have focused on four main missions: (1) the development and implementation of plans for initiation of the Socioeconomic Data and Applications Center (SEDAC) as part of the EOSDIS Program; (2) the pursuit and development of a broad-based global change information cooperative by providing systems analysis and integration between natural science and social science data bases held by numerous federal agencies and other sources; (3) the fostering of scientific research into the human dimensions of global change and providing integration between natural science and social science data and information; and (4) the serving of CIESIN as a gateway for global change data and information distribution through development of the Global Change Research Information Office and other comprehensive knowledge sharing systems.

  18. Theoretical model and experimental demonstration of frequency control in rare-earth-doped fiber lasers with a 3{times}3 nonplanar fused-fiber coupler

    SciTech Connect

    Gloag, A.; Forster, R.J.; Langford, N.

    1997-04-01

    We present a numerical analysis that illustrates the potential of 3{times}3 nonplanar fused-fiber couplers for inhibiting longitudinal mode hops in rare-earth-doped-fiber lasers. A unidirectional erbium-doped ring-fiber laser is configured that contains a single 3{times}3 fused-fiber coupler. Narrow linewidth operation without any evidence of longitudinal mode hops is observed. The oscillating linewidth is 14 kHz with a rms frequency jitter {approximately}2 kHz. The relative intensity noise is measured in both the frequency stabilized and the frequency unstabilized cases. An average 15-dB reduction in the relative intensity noise over the 0{endash}200 Hz frequency range is observed when the laser is stabilized. {copyright} 1997 Optical Society of America

  19. 56.6 DB High Gain L-Band Edfa Utilizing Short-Length Highly-Doped Erbium Rare-Earth Material

    NASA Astrophysics Data System (ADS)

    Al-Mansoori, M. H.; Al-Ghaithi, W. S.

    2014-07-01

    In this paper, we experimentally investigate the performance of an efficient high gain L-band erbium-doped fiber (EDF) amplifier structure utilizing short-length highly-doped erbium rare-earth material with a single pump source. The amplifier gain and noise figure variation for different amplifier structures have been investigated. A filter is used to reduce the self-saturation effect and suppress the C-band amplified spontaneous emission (ASE) noise. The amplifier achieves a signal gain of 56.6 dB with a low noise figure of 4.8 dB at -50 dBm input signal power using only 8 m of EDF length. The amplifier gain shows significant improvement of 6 dB with C/L band coupler and 13 dB with tunable-band pass filter compared to amplifier structure without ASE suppression.

  20. Towards a comprehensive model of Earth's disk-integrated Stokes vector

    NASA Astrophysics Data System (ADS)

    Garca Muoz, A.

    2015-07-01

    A significant body of work on simulating the remote appearance of Earth-like exoplanets has been done over the last decade. The research is driven by the prospect of characterizing habitable planets beyond the Solar System in the near future. In this work, I present a method to produce the disk-integrated signature of planets that are described in their three-dimensional complexity, i.e. with both horizontal and vertical variations in the optical properties of their envelopes. The approach is based on Pre-conditioned Backward Monte Carlo integration of the vector Radiative Transport Equation and yields the full Stokes vector for outgoing reflected radiation. The method is demonstrated through selected examples inspired by published work at wavelengths from the visible to the near infrared and terrestrial prescriptions of both cloud and surface albedo maps. I explore the performance of the method in terms of computational time and accuracy. A clear strength of this approach is that its computational cost does not appear to be significantly affected by non-uniformities in the planet optical properties. Earth's simulated appearance is strongly dependent on wavelength; both brightness and polarization undergo diurnal variations arising from changes in the planet cover, but polarization yields a better insight into variations with phase angle. There is partial cancellation of the polarized signal from the northern and southern hemispheres so that the outgoing polarization vector lies preferentially either in the plane parallel or perpendicular to the planet scattering plane, also for non-uniform cloud and albedo properties and various levels of absorption within the atmosphere. The evaluation of circular polarization is challenging; a number of one-photon experiments of 109 or more is needed to resolve hemispherically integrated degrees of circular polarization of a few times 10-5. Last, I introduce brightness curves of Earth obtained with one of the Messenger cameras at three wavelengths (0.48, 0.56 and 0.63 ?m) during a flyby in 2005. The light curves show distinct structure associated with the varying aspect of the Earth's visible disk (phases of 98-107) as the planet undergoes a full 24 h rotation; the structure is reasonably well reproduced with model simulations.

  1. Earth Science Research Discovery, Integration, 3D Visualization and Analysis using NASA World Wind

    NASA Astrophysics Data System (ADS)

    Alameh, N.; Hogan, P.

    2008-12-01

    NASA plays a leadership role in the world of Advanced Information Technologies. Part of our mission is to leverage those technologies to increase the usability of the growing amount of earth observation produced by the science community. NASA World Wind open source technology provides a complete 3D visualization platform that is being continually advanced by NASA, its partners and the open source community. The technology makes scientific data and observations more accessible to Earth scientists and offers them a standards-based extensible platform to manipulate and analyze that data. The API-centric architecture of World Wind's SDK allows others to readily extend or embed this technology (including in web pages). Such multiple approaches to using the technology accelerate opportunities for the research community to provide "advances in fundamental understanding of the Earth system and increased application of this understanding to serve the nation and the people of the world" (NRC Decadal Survey). The opportunities to advance this NASA Open Source Agreement (NOSA) technology by leveraging advances in web services, interoperability, data discovery mechanisms, and Sensor Web are unencumbered by proprietary constraints and therefore provide the basis for an evolving platform that can reliably service the needs of the Earth Science, Sensor Web and GEOSS communities. The ability for these communities to not only use this technology in an unrestricted manner but to also participate in advancing it leads to accelerated innovation and maximum exchange of information. 3 characteristics enable World Wind to push the frontier in Advanced Information Systems: 1- World Wind provides a unifying information browser to enable a variety of 3D geospatial applications. World Wind consists of a coherent suite of modular components to be used selectively or in concert with any number of programs. 2- World Wind technology can be embedded as part of any application and hence makes it more possible to include virtual globe capability in support of any Earth science objective. 3- With the source code being fully accessible, anyone can advance this technology (including in a commercial or other proprietary manner). Such features enable World Wind to provide easy discovery, access and 3D integration/visualization/analysis of Earth observation data in a flexible, customizable open source tool. This positions World Wind to become a key part of an Advanced Information Systems infrastructure supporting a collaborative decision-making environment for a variety of applications.

  2. From LACIE to GEOGLAM: Integrating Earth Observations into Operational Agricultural Monitoring Systems

    NASA Astrophysics Data System (ADS)

    Becker-Reshef, I.; Justice, C. O.

    2012-12-01

    Earth observation data, owing to their synoptic, timely and repetitive coverage, have long been recognized as an indispensible tool for agricultural monitoring at local to global scales. Research and development over the past several decades in the field of agricultural remote sensing has led to considerable capacity for crop monitoring within the current operational monitoring systems. These systems are relied upon nationally and internationally to provide crop outlooks and production forecasts as the growing season progresses. This talk will discuss the legacy and current state of operational agricultural monitoring using earth observations. In the US, the National Aeronautics and Space Administration (NASA) and the US Department of Agriculture (USDA) have been collaborating to monitor global agriculture from space since the 1970s. In 1974, the USDA, NASA and National Oceanic and Atmospheric Administration (NOAA) initiated the Large Area Crop Inventory Experiment (LACIE) which demonstrated that earth observations could provide vital information on crop production, with unprecedented accuracy and timeliness, prior to harvest. This experiment spurred many agencies and researchers around the world to further develop and evaluate remote sensing technologies for timely, large area, crop monitoring. The USDA and NASA continue to closely collaborate. More recently they jointly initiated the Global Agricultural Monitoring Project (GLAM) to enhance the agricultural monitoring and the crop-production estimation capabilities of the USDA Foreign Agricultural Service by using the new generation of NASA satellite observations including from MODIS and the Visible Infrared Imaging Radiometer Suite (VIIRS) instruments. Internationally, in response to the growing calls for improved agricultural information, the Group on Earth Observations (partnership of governments and international organizations) developed the Global Agricultural Monitoring (GEOGLAM) initiative which was adopted by the G20 as part of the action plan on food price volatility and agriculture. The goal of GEOGLAM is to enhance agricultural production estimates through leveraging advances in the research domain and in satellite technologies, and integrating these into the existing operational monitoring systems.

  3. Integrating Authentic Earth Science Data in Online Visualization Tools and Social Media Networking to Promote Earth Science Education

    NASA Astrophysics Data System (ADS)

    Carter, B. L.; Campbell, B.; Chambers, L.; Davis, A.; Riebeek, H.; Ward, K.

    2008-12-01

    The Goddard Space Flight Center (GSFC) is one of the largest Earth Science research-based institutions in the nation. Along with the research comes a dedicated group of people who are tasked with developing Earth science research-based education and public outreach materials to reach the broadest possible range of audiences. The GSFC Earth science education community makes use of a wide variety of platforms in order to reach their goals of communicating science. These platforms include using social media networking such as Twitter and Facebook, as well as geo-spatial tools such as MY NASA DATA, NASA World Wind, NEO, and Google Earth. Using a wide variety of platforms serves the dual purposes of promoting NASA Earth Science research and making authentic data available to educational communities that otherwise might not otherwise be granted access. Making data available to education communities promotes scientific literacy through the investigation of scientific phenomena using the same data that is used by the scientific community. Data from several NASA missions will be used to demonstrate the ways in which Earth science data are made available for the education community.

  4. Comparing morphologies of drainage basins on Mars and Earth using integral-geometry and neural maps

    NASA Technical Reports Server (NTRS)

    Stepinski, T. F.; Coradetti, S.

    2004-01-01

    We compare morphologies of drainage basins on Mars and Earth in order to confine the formation process of Martian valley networks. Basins on both planets are computationally extracted from digital topography. Integral-geometry methods are used to represent each basin by a circularity function that encapsulates its internal structure. The shape of such a function is an indicator of the style of fluvial erosion. We use the self-organizing map technique to construct a similarity graph for all basins. The graph reveals systematic differences between morphologies of basins on the two planets. This dichotomy indicates that terrestrial and Martian surfaces were eroded differently. We argue that morphologies of Martian basins are incompatible with runoff from sustained, homogeneous rainfall. Fluvial environments compatible with observed morphologies are discussed. We also construct a similarity graph based on the comparison of basins hypsometric curves to demonstrate that hypsometry is incapable of discriminating between terrestrial and Martian basins. INDEX TERMS: 1824 Hydrology: Geomorphology (1625); 1886 Hydrology: Weathering (1625); 5415 Planetology: Solid Surface Planets: Erosion and weathering; 6225 Planetology: Solar System Objects Mars. Citation: Stepinski, T. F., and S. Coradetti (2004), Comparing morphologies of drainage basins on Mars and Earth using integral-ge

  5. Integration of Google Maps/Earth with microscale meteorology models and data visualization

    NASA Astrophysics Data System (ADS)

    Wang, Yansen; Huynh, Giap; Williamson, Chatt

    2013-12-01

    The Google Maps/Earth GIS has been integrated with a microscale meteorological model to improve the system's functionality and ease of use. Almost all the components of the model system, including the terrain data processing, morphological data generation, meteorological data gathering and initialization, and displaying/visualizing the model results, have been improved by using this approach. Different from the traditional stand-along model system, this novel system takes advantages of enormous resources in map and image data retrieving/handling, four-dimensional (space and time) data visualization, overlaying, and many other advanced GIS features that the Google Maps/Earth platform has to offer. We have developed modular components for all of the model system controls and data processing programs which are glued together with the JavaScript language and KML/XML data. We have also developed small modular software using the Google application program interface to convert the model results and intermediate data for visualizations and animations. Capabilities such as high-resolution image, street view, and 3D buildings in the Google Earth/Map are also used to quickly generate small-scale vegetation and building morphology data that are required for the microscale meteorological models. This system has also been applied to visualize the data from other instruments such as Doppler wind lidars. Because of the tight integration of the internet based GIS and a microscale meteorology model, the model system is more versatile, intuitive, and user-friendly than a stand-along system we had developed before. This kind of system will enhance the user experience and also help researchers to explore new phenomena in fine-scale meteorology.

  6. Novel δ-doped partially insulated junctionless transistor for mixed signal integrated circuits

    NASA Astrophysics Data System (ADS)

    Patil, Ganesh C.; Bonge, Vijaysinh H.; Malode, Mayur M.; Jain, Rahul G.

    2016-02-01

    In this paper, δ-doped partially insulated junctionless transistor (δ-Pi-OXJLT) has been proposed which shows that, employing highly doped δ-region below the channel not only reduces the off-state leakage current (IOFF) and short channel effects (SCEs) but also reduce the requirements of scaling channel thickness of junctionless transistor (JLT). The comparative analysis of digital and analog circuit performance of proposed δ-Pi-OXJLT, bulk planar (BP) JLT and silicon-on-insulator (SOI) JLT has also been carried out. The digital parameters analyzed in this work are, on-state drive current (ION), IOFF, ION/IOFF ratio, static power dissipation (PSTAT) whereas the analog parameters analyzed includes, transconductance (GM), transconductance generation factor (GM/IDS), intrinsic gain (GMRO) and cut-off frequency (fT) of the devices. In addition, scaling behavior of the devices is studied for various channel lengths by using the parameters such as drain induced barrier lowering (DIBL) and sub-threshold swing (SS). It has been found that, the proposed δ-Pi-OXJLT shows significant reduction in IOFF, DIBL and SS over BPJLT and SOIJLT devices. Further, ION and ION/IOFF ratio in the case of proposed δ-Pi-OXJLT also improves over the BPJLT device. Furthermore, the improvement in analog figures of merit, GM, GM/IDS, GMRO and fT in the case of proposed δ-Pi-OXJLT clearly shows that the proposed δ-Pi-OXJLT is the promising device for mixed signal integrated circuits.

  7. Microstructural and ferroelectric properties of rare earth (Ce, Pr, and Tb)-doped Na0.5Bi4.5Ti3O15 thin films

    NASA Astrophysics Data System (ADS)

    Raghavan, Chinnambedu Murugesan; Kim, Jin Won; Song, Tae Kwon; Kim, Sang Su

    2015-11-01

    Pure Na0.5Bi4.5Ti4O15 and rare earth-doped Na0.5Bi4RE0.5Ti4O15 (RE = Ce, Pr, and Tb) thin films were prepared on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by using a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies revealed that the thin films are crystallized in a single-phase Aurivillius structure with no additional phases. The rare earth-doped Na0.5Bi4RE0.5Ti4O15 thin films exhibited improved electrical and ferroelectric properties. Among the studied rare earth metal ions, the Tb3+ ion leads to a remarkable improvement in the ferroelectric properties. The use of the Tb3+ ion for doping resulted in a well-saturated ferroelectric hysteresis loop with a large remnant polarization (2Pr) of 40 μC/cm2 and a low coercive electric field (2Ec) of 176 kV/cm, measured at an applied electric field of 475 kV in the Na0.5Bi4Tb0.5Ti4O15 thin film. Furthermore, the leakage current density of the Na0.5Bi4Tb0.5Ti4O15 thin film was one order of magnitude lower than that of the Na0.5Bi4.5Ti4O15 thin film.

  8. Department of Energy's Virtual Lab Infrastructure for Integrated Earth System Science Data

    NASA Astrophysics Data System (ADS)

    Williams, D. N.; Palanisamy, G.; Shipman, G.; Boden, T.; Voyles, J.

    2014-12-01

    The U.S. Department of Energy (DOE) Office of Biological and Environmental Research (BER) Climate and Environmental Sciences Division (CESD) produces a diversity of data, information, software, and model codes across its research and informatics programs and facilities. This information includes raw and reduced observational and instrumentation data, model codes, model-generated results, and integrated data products. Currently, most of this data and information are prepared and shared for program specific activities, corresponding to CESD organization research. A major challenge facing BER CESD is how best to inventory, integrate, and deliver these vast and diverse resources for the purpose of accelerating Earth system science research. This talk provides a concept for a CESD Integrated Data Ecosystem and an initial roadmap for its implementation to address this integration challenge in the "Big Data" domain. Towards this end, a new BER Virtual Laboratory Infrastructure will be presented, which will include services and software connecting the heterogeneous CESD data holdings, and constructed with open source software based on industry standards, protocols, and state-of-the-art technology.

  9. Effect of transition element doping on crystal structure of rare earth borosilicides REB{sub 44}Si{sub 2}

    SciTech Connect

    Berthebaud, D.; Sato, A.; Michiue, Y.; Mori, T.; Nomura, A.; Shishido, T.; Nakajima, K.

    2011-07-15

    On a previous study on samples of doped-YB{sub 44}Si{sub 2}, an improvement of thermoelectric properties has been achieved. Regarding the interesting effect of the doping of transition elements on the thermoelectric properties, a single crystal study has been carried out on Zn doped, Rh doped and Ni doped samples to assess how the transition element doping affects the crystal structure. Refinements were carried out based on the structural model solution of YB{sub 44}Si{sub 2} reported in a previous study. Variations in the silicon contents were found in the doped single crystals. Splitting of partially occupied sites has also been detected for some of the doped samples. In this paper we present differences in the partial occupations of boron and silicon sites. Possibility of transition elements insertions based on the differences in crystal structures will be presented. - Graphical Abstract: New transition elements doped YB{sub 44}Si{sub 2} were synthesized and have nominal compositions YB{sub 41.1}Si{sub 1.1}Rh{sub 0.02} and YB{sub 41}Si{sub 1.3}Ni{sub 0.06}. Insertion of transition elements into the crystal structure of YB{sub 44}Si{sub 2} leads to the transformation of B{sub 12} icosahedra into B{sub 11} polyhedrons for a few percent of them. Highlights: > Differences in the partial occupations of boron and silicon sites{yields}Possibility of transition elements insertions. > Mixed occupancy of split positions. > Insertion of transition elements between B{sub 12} icosahedra.

  10. Discovery, Integration, and Analysis (DIA) Engine for Ontologically Registered Earth Science Data

    NASA Astrophysics Data System (ADS)

    Sinha, A.; Malik, Z.; Rezgui, A.; Dalton, A.; Lin, K.

    2006-12-01

    A newly developed DIA engine within the NSF supported GEON program utilizes an ontologic cyberinfrastructure framework for discovery, integration, and analysis of earth science data. Data discovery, is commonly challenging because of the use of personalized acronyms, notations, conventions, etc., but can be simplified through ontologic registration. Data integration enables users to extract new information, called data products, by jointly considering and correlating several ontologically registered data sets. We have developed ontology packages as well as accessed ontologies such as SWEET, which provide concepts, concept taxonomies, relationships between concepts, and properties, as an initial step towards the development of complete heavyweight ontologies (with axioms and constraints) for earth science. The primary objective is to allow researchers to associate ontology to their data, so that a unique and definite meaning is associated with each data item. This facilitates data discovery and integration by relating data items with similar semantics across various repositories. The DIA engine provides a Web accessible graphical user interface (GUI) comprising of map services and query menus. Users can specify a "geological region of interest" by making selections on geologic maps which are part of the GUI. Moreover, interactive menus enable filtering, discovery and integration of data (geospatial as well as aspatial), using many tools, including those developed by the community. We support the Web services technology to share these tools since web services hide the tool implementation details and only provide the required invocation details (input/output parameters, etc.). Thus, geoscientists can build tools that access ontologically registered data and provide invocation details publicly. Therefore, any tool that is developed as a Web service can be plugged in the DIA engine. The DIA engine supports dynamic data product creation which requires "on-the-fly" discovery and integration of different ontologic data classes. The integration can either occur between the "same" ontologic class or across "different" ontologic classes. We also provide the capability to track all stages in the development of products, so other users can readily accept data products and may proceed into a data analysis phase (e.g., to verify hypothesis) . The development of DIA engine is guided by generating data products that can be analyzed to evaluate scientific hypotheses, such as "Do A-type plutons in Virginia mark the trace of a Neoproterozoic hot- spot?"

  11. The EPOS e-Infrastructure: Integrating Solid Earth Science in Europe

    NASA Astrophysics Data System (ADS)

    Trani, L.; Bailo, D.; Jeffery, K. G.

    2014-12-01

    The European Plate Observing System (EPOS) is an ambitious long term integration plan addressing the major solid-earth research infrastructures in Europe. For its large scale and extent it is a unique initiative which will foster new scientific discoveries and enable scientists to investigate the solid earth system in unprecedented ways. A key aspect of EPOS is to provide end-users with homogeneous access to services and multidisciplinary data collected by monitoring infrastructures and experimental facilities as well as access to processing and visualization tools. Such a complex system requires a solid, scalable and reliable architecture in order to accommodate innovative features and to meet the evolving expectations of the heterogeneous communities involved. Within the FP7 EU project EPOS PP1 (Preparatory Phase), which is approaching its completion in October 2014, the goal of the infrastructure and virtual community working group (WG7) was to design and test a preliminary architecture. The EPOS e-infrastructure architecture has been systematically developed based on collected primary (user) and secondary (interoperation with other systems) requirements and through three distinct design refinement phases (Strawman, Woodman and Ironman). The EPOS architecture is constituted of Integrated Core Services (ICS), which provide access to thematic (domain-specific) services (Thematic Core Services - TCS) integrating national research infrastructures. The key component of the architecture is the metadata catalogue, which utilizes the CERIF2(Common European Research Information Format) standard. The metadata catalogue is conceived to effectively capture all the information needed and to make large (re-)use of existing domain specific standards. In this contribution we will present the lessons learned and the technical achievements of the EPOS Preparatory Phase. 1www.epos-eu.org 2www.eurocris.org

  12. Integral Earth-System Properties Observed from Space: Introducing the "Lidar Albedo"

    NASA Astrophysics Data System (ADS)

    Charlson, R. J.

    2006-12-01

    Radiometric observations from space inherently integrate over all atmospheric and surface phenomena within the view volume. This has disadvantages in terms of diagnostic capability. On the other hand, a high-leverage use of satellite observations is to characterize the variation of Earth-system properties, thereby providing integral constraints to be explained by theoretical models in conjunction with more detailed, sub-orbital measurement programs. Spaceborne lidar observations from LITE (1994), GLAS (2003-present), and now CALIPSO (launched April, 2006) offer the prospect of global-scale assessments of the vertical distribution of aerosols and thin clouds. We suggest that these lidar data sets provide, as well, a diagnostic proxy for variations in local planetary albedo (A) associated with these phenomena. We dub this proxy - previously known as integrated attentuated backscatter - the "lidar albedo" (AL). AL is a natural lidar product that represents the fraction of laser energy returned to the receiving telescope, out to a given range. It has units of (1/sr) and can be thought of as a single vector in the middle of the upscatter phase function characterizing the Earth's atmosphere at a given location and time. Thus, it is reasonable to propose that variations in AL will be closely correlated with variations in A. Factors that may cause a non-linear relationship between A and AL include the following: (i) different types of features (gases, aerosol, droplets, crystals) have different scattering phase functions; (ii) a portion of 180 reflectance arises from multiple scattering, much of which will fall outside the field of view of the receiving telescope, and (iii) AL is expected to saturate at lower optical depths than A. Despite these weaknesses, measurements of AL by nadir-pointing lidars offer these advantages: (i) better spatial resolution than broadband flux radiometers, (ii) a simple retrieval with well known accuracy of about 2 percent, and (iii) vertical resolution, which means the ability to diagnose the atmospheric causes of albedo variations without interference from the underlying surface.

  13. Self-Guided Field Explorations: Integrating Earth Science into Students' Lives

    NASA Astrophysics Data System (ADS)

    Kirkby, K. C.; Kirkby, S.

    2013-12-01

    Self-guided field explorations are a simple way to transform an earth science class into a more pedagogically effective experience. Previous experience demonstrated that self-guided student explorations of museum and aquarium exhibits were both extremely popular and remarkably effective. That success led our program to test an expansion of the concept to include self-guided student explorations in outdoor field settings. Preliminary assessment indicates these self-guided field explorations are nearly as popular with students as the museum and aquarium explorations and are as pedagogically effective. Student gains on post-instruction assessment match or exceed those seen in instructor-assisted, hands-on, small group laboratory activities and completely eclipse gains achieved by traditional lecture instruction. As importantly, self-guided field explorations provide a way to integrate field experiences into large enrollment courses where the sheer scale of class trips makes them logistically impossible. This expands course breadth, integrating new topics that could not be as effectively covered by the original class structure. Our introductory program assessed two models of self-guided field explorations. A walking/cycling exploration of the Saint Anthony Falls area, a mile from campus, focuses on the intersections of geological processes with human history. Students explore the geology behind the waterfalls' evolution as well as its subsequent social and economic impacts on human history. A second exploration focuses on the campus area geology, including its building stones as well as its landscape evolution. In both explorations, the goal was to integrate geology with the students' broader understanding of the world they live in. Although the explorations' creation requires a significant commitment, once developed, self-guided explorations are surprisingly low maintenance. These explorations provide a model of a simple, highly effective pedagogical tool that is easily adapted to almost any campus setting. A number of factors contribute to self-guided explorations' success. For most students, these are novel, particularly memorable experiences. Interactive in nature, self-guided explorations are also relaxed, self-paced instruction without the pressures that can dominate other educational settings. Well designed explorations build on students' prior knowledge, allowing them to integrate new earth science concepts with familiar ideas and settings. By creating connections between geology and human society, these explorations also make earth science more relevant to students who had not previously considered their world from a geological perspective. By their very nature, explorations are place-centered education which helps ground instruction and makes it more relevant to students without strong science backgrounds. Further these explorations give students control over, and responsibility for, their own learning, which is always a pedagogically sound approach. Finally, self-guided explorations can integrate earth science education into students' social lives as most students choose to complete the explorations in groups, often with friends and family who are not enrolled in the course.

  14. Crystal growth, characterization and theoretical studies of alkaline earth metal-doped tetrakis(thiourea)nickel(II) chloride.

    PubMed

    Agilandeshwari, R; Muthu, K; Meenatchi, V; Meena, K; Rajasekar, M; Aditya Prasad, A; Meenakshisundaram, S P

    2015-02-25

    The influence of Sr(II)-doping on the properties of tetrakis(thiourea)nickel(II) chloride (TTNC) has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies of doped specimens confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the Sr(II) are observed by scanning electron microscopy. The incorporation of metal into the host crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The nonlinear optical properties of the doped and undoped specimens were studied. Theoretical calculations were performed using the Density functional theory (DFT) method with B3LYP/LANL2DZ as the basis set. The molecular geometry and vibrational frequencies of TTNC in the ground state were calculated and the observed structural parameters of TTNC are compared with parameters obtained from single crystal X-ray studies. The atomic charge distributions are obtained by Mulliken charge population analysis. The first-order molecular hyperpolarizability, polarizability and dipole moment were derived. PMID:25233030

  15. Effect of knowledge integration activities on students' perception of the earth's crust as a cyclic system

    NASA Astrophysics Data System (ADS)

    Kali, Yael; Orion, Nir; Eylon, Bat-Sheva

    2003-08-01

    Systems thinking is regarded as a high-order thinking skill required in scientific, technological, and everyday domains. However, little is known about systems thinking in the context of science education. In the current research, students' understanding of the rock cycle system after a learning program was characterized, and the effect of a concluding knowledge integration activity on their systems thinking was studied. Answers to an open-ended test were interpreted using a systems thinking continuum, ranging from a completely static view of the system to an understanding of the system's cyclic nature. A meaningful improvement in students' views of the rock cycle toward the higher side of the systems thinking continuum was found after the knowledge integration activity. Students became more aware of the dynamic and cyclic nature of the rock cycle, and their ability to construct sequences of processes representing material transformation in relatively large chunks significantly improved. Success of the knowledge integration activity stresses the importance of postknowledge acquisition activities, which engage students in a dual process of differentiation of their knowledge and reintegration in a systems context. We suggest including such activities in curricula involving systems-based contents, particularly in earth science, in which systems thinking can bring about environmental literacy.

  16. Integration of external metadata into the Earth System Grid Federation (ESGF)

    NASA Astrophysics Data System (ADS)

    Berger, Katharina; Levavasseur, Guillaume; Stockhause, Martina; Lautenschlager, Michael

    2015-04-01

    International projects with high volume data usually disseminate their data in a federated data infrastructure, e.g.~the Earth System Grid Federation (ESGF). The ESGF aims to make the geographically distributed data seamlessly discoverable and accessible. Additional data-related information is currently collected and stored in separate repositories by each data provider. This scattered and useful information is not or only partly available for ESGF users. Examples for such additional information systems are ES-DOC/metafor for model and simulation information, IPSL's versioning information, CHARMe for user annotations, DKRZ's quality information and data citation information. The ESGF Quality Control working team (esgf-qcwt) aims to integrate these valuable pieces of additional information into the ESGF in order to make them available to users and data archive managers by (i) integrating external information into ESGF portal, (ii) integrating links to external information objects into the ESGF metadata index, e.g. by the use of PIDs (Persistent IDentifiers), and (iii) automating the collection of external information during the ESGF data publication process. For the sixth phase of CMIP (Coupled Model Intercomparison Project), the ESGF metadata index is to be enriched by additional information on data citation, file version, etc. This information will support users directly and can be automatically exploited by higher level services (human and machine readability).

  17. Release of AGAP Aerogeophysical Data through the Integrated Earth Data Applications Facility

    NASA Astrophysics Data System (ADS)

    O'hara, S. H.; Abdi, A.; Bonczkowski, J.; Bell, R. E.; Frearson, N.; Ferraccioli, F.; Corr, H.; Jordan, T. A.; Rose, K. C.; Studinger, M.; Gogineni, P. S.; Braaten, D. A.; Damaske, D.

    2011-12-01

    During the International Polar Year 2007 - 2009, scientists from six nations collaborated on a multi-disciplinary investigation of the Gamburtsevs, the least explored mountain range on Earth buried beneath the East Antarctic Ice Sheet, as part of the Antarctic Gamburtsev Province (AGAP) project. The AGAP project collected more than 120,000 line km of new aerogeophysical data using two Twin Otter aircraft. Data included ice penetrating radar, magnetometer, gravimeter and laser altimeter measurements. The main AGAP survey grid included north-south lines spaced 5 km apart, with crossing lines every 33 km and transects over the Vostok Subglacial Highlands, South Pole and southern Recovery lakes region. 150-MHz ice penetrating radars with bandwidths of 15 to 20 MHz measured ice thickness, bedrock topography, sub-ice hydrology, and produced high-resolution images of the internal structure of the East Antarctic Ice Sheet. Magnetic data map geologic structures across the mountain range, while gravity data provide new insights into the tectonic evolution and crustal thickness of the region. A swath-scanning laser altimeter with a spatial resolution of 2 meters measured elevation and details of the ice surface. Complete AGAP datasets are now in the process of becoming publicly available and freely accessible through the Java-based data visualization tool GeoMapApp (http://www.geomapapp.org), and the Antarctic & Southern Ocean Data Portal (http://www.marine-geo.org/tools/search/entry.php?id=AGAP_GAMBIT), both part of the Integrated Earth Data Applications (IEDA) Data Facility (http://www.iedadata.org) based at the Lamont-Doherty Earth Observatory of Columbia University. AGAP data will also be accessible through the Natural Environment Research Council (NERC) Polar Data Center, based at the British Antarctic Survey (http://www.antarctica.ac.uk/bas_research/data/index.php) and at the Center for the Remote Sensing of Ice Sheets (https://www.cresis.ku.edu/research/gambit).

  18. Integrating Earth System Science Data Into Tribal College and University Curricula

    NASA Astrophysics Data System (ADS)

    Tilgner, P. J.; Perkey, D. J.

    2007-12-01

    Universities Space Research Association and Sinte Gleska University (SGU) have teamed with eight Tribal Colleges and Universities (TCUs) to participate in a NASA Earth Science funded project, TRibal Earth Science and Technology Education (TRESTE) project which focuses on TCU faculty teaching undergraduate Earth science courses to non-science and science students, with particular attention to TCU faculty teaching K-12 pre- and in- service teachers. The eight partner TCUs are: Blackfeet Community College (BCC), Browning, MT, Fond du Lac Tribal and Community College, Cloquet, MN, Fort Berthold Community College, New Town, ND, Little Priest Tribal College, Winnebago, NE, Oglala Lakota College, Pine Ridge, SD, Sitting Bull College, Fort Yates, ND, Turtle Mountain Community College, Belcourt, ND, United Tribes Technical College (UTTC), Bismarck, ND. The goal of this 3-year project is to promote the use of NASA Earth science data and products in the classroom thereby enabling faculty to inspire undergraduate students to careers in Earth system science, the physical sciences, and related fields of science and engineering. To accomplish this goal we are targeting three areas: (1) course content - enhance the utilization of Earth system science and physical science concepts, (2) teaching methodology - develop problem-based learning (PBL) methods, and (3) tools and technology - increase the utilization of GIS and remote sensing in the classroom. We also have enlisted ESRI, NativeView and the USGS as collaborators. To date we have held an introductory "needs" workshop at the USGS EROS Data Center and two annual workshops, one at UTTC and the second at BCC. During these annual workshops we have divided our time among the three areas. We have modeled the workshops using the PBL or Case Study approach by starting with a story or current event. Topics for the annual workshops have been Drought and Forest and Grassland Fires. These topics led us into the solar radiation budget, surface energy budgets, climate and climate change, impacts, etc. GIS and remote sensing training has focused on importing, converting and displaying data sets related to drought and fires. The Integrated Science courses at SGU, designed primarily for pre-service elementary teachers, have incorporated physical science concepts and teaching approaches presented at the TRESTE annual workshops. The content of the courses follows the PBL teaching approach and is organized around a relevant, local problem such as prairie dog control and prairie management. Concepts from Earth, life and physical sciences are included in the course design. The fall course is introduced using recent news articles on legislation to control prairie dogs. After expressing their ideas based solely on experience and emotion, students determine what knowledge they will need to write an informed opinion on the issue. One of the instructional units for the course includes instruction and practice in interpreting satellite images of the local reservation to determine impact of prairie dog towns on vegetation. Students also conduct soil studies in the disturbed areas and nearby undisturbed areas. Data is gathered on soil chemistry, soil temperatures, and surface temperatures, measured with an infrared sensor provided by the TRESTE grant. Additional topics covered in the course that contain information from the annual workshops, include prairie fires, climate and climate change, and effects of the drought on local bodies of water.

  19. Theoretical investigation of the more suitable rare earth to achieve high gain in waveguide based on silica containing silicon nanograins doped with either Nd+ or Er+ ions.

    PubMed

    Fafin, Alexandre; Cardin, Julien; Dufour, Christian; Gourbilleau, Fabrice

    2014-05-19

    We present a comparative study of the gain achievement in a waveguide whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd3+) or erbium ions (Er3+). By means of an auxiliary differential equation and finite difference time domain (ADE-FDTD) approach that we developed, we investigate the steady states regime of both rare earths ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 104 mW/mm2. Moreover, the achievable gain has been estimated in this pumping range. The Nd3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm). Taking into account the experimental background losses we demonstrate that a significant positive net gain can only be achieved with the Nd3+ doped waveguide. PMID:24921348

  20. Documenting the NASA Armstrong Flight Research Center Oblate Earth Simulation Equations of Motion and Integration Algorithm

    NASA Technical Reports Server (NTRS)

    Clarke, R.; Lintereur, L.; Bahm, C.

    2016-01-01

    A desire for more complete documentation of the National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC), Edwards, California legacy code used in the core simulation has led to this e ort to fully document the oblate Earth six-degree-of-freedom equations of motion and integration algorithm. The authors of this report have taken much of the earlier work of the simulation engineering group and used it as a jumping-o point for this report. The largest addition this report makes is that each element of the equations of motion is traced back to first principles and at no point is the reader forced to take an equation on faith alone. There are no discoveries of previously unknown principles contained in this report; this report is a collection and presentation of textbook principles. The value of this report is that those textbook principles are herein documented in standard nomenclature that matches the form of the computer code DERIVC. Previous handwritten notes are much of the backbone of this work, however, in almost every area, derivations are explicitly shown to assure the reader that the equations which make up the oblate Earth version of the computer routine, DERIVC, are correct.

  1. CIM-EARTH: Community integrated model of economic and resource trajectories for humankind.

    SciTech Connect

    Elliott, J.; Foster, I.; Judd, K.; Moyer, E.; Munson, T.; Univ. of Chicago; Hoover Inst.

    2010-01-01

    Climate change is a global problem with local climatic and economic impacts. Mitigation policies can be applied on large geographic scales, such as a carbon cap-and-trade program for the entire U.S., on medium geographic scales, such as the NOx program for the northeastern U.S., or on smaller scales, such as statewide renewable portfolio standards and local gasoline taxes. To enable study of the environmental benefits, transition costs, capitalization effects, and other consequences of mitigation policies, we are developing dynamic general equilibrium models capable of incorporating important climate impacts. This report describes the economic framework we have developed and the current Community Integrated Model of Economic and Resource Trajectories for Humankind (CIM-EARTH) instance.

  2. Spherical-earth Gravity and Magnetic Anomaly Modeling by Gauss-legendre Quadrature Integration

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J. (Principal Investigator)

    1981-01-01

    The anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical Earth for an arbitrary body represented by an equivalent point source distribution of gravity poles or magnetic dipoles were calculated. The distribution of equivalent point sources was determined directly from the coordinate limits of the source volume. Variable integration limits for an arbitrarily shaped body are derived from interpolation of points which approximate the body's surface envelope. The versatility of the method is enhanced by the ability to treat physical property variations within the source volume and to consider variable magnetic fields over the source and observation surface. A number of examples verify and illustrate the capabilities of the technique, including preliminary modeling of potential field signatures for Mississippi embayment crustal structure at satellite elevations.

  3. Integrated optical amplifiers and microspherical lasers based on erbium-doped oxide glasses

    NASA Astrophysics Data System (ADS)

    Righini, G. C.; Arnaud, C.; Berneschi, S.; Bettinelli, M.; Brenci, M.; Chiasera, A.; Feron, P.; Ferrari, M.; Montagna, M.; Nunzi Conti, G.; Pelli, S.; Portales, H.; Siligardi, C.; Speghini, A.; Zampedri, L.

    2005-10-01

    Er3+-doped glasses have been a subject of great interest in the recent years for their application in the areas of guided wave optical amplifiers and lasers. Oxide-glass matrices, in particular, offer the advantage of relatively simple fabrication processes-both for bulk glasses and optical fibers-and have demonstrated quite good properties in the 1.5 ?m wavelength band. Here we present some results we have obtained in the development of different silica-based glasses and in their application to the production of integrated optical amplifiers and microspherical lasers. As to the former application, two classes of silica glasses have been produced and investigated, namely a melted soda-lime-alumino-silicate glass and a sol-gel silica-hafnia glass. Both of them exhibit a wide emission bandwidth and seem quite promising for broadband optical amplifiers. We also demonstrated low-threshold microlasers, based on whispering gallery mode spherical resonators, fabricated in different oxide glasses.

  4. A Hybrid Neuro-Fuzzy Model For Integrating Large Earth-Science Datasets

    NASA Astrophysics Data System (ADS)

    Porwal, A.; Carranza, J.; Hale, M.

    2004-12-01

    A GIS-based hybrid neuro-fuzzy approach to integration of large earth-science datasets for mineral prospectivity mapping is described. It implements a Takagi-Sugeno type fuzzy inference system in the framework of a four-layered feed-forward adaptive neural network. Each unique combination of the datasets is considered a feature vector whose components are derived by knowledge-based ordinal encoding of the constituent datasets. A subset of feature vectors with a known output target vector (i.e., unique conditions known to be associated with either a mineralized or a barren location) is used for the training of an adaptive neuro-fuzzy inference system. Training involves iterative adjustment of parameters of the adaptive neuro-fuzzy inference system using a hybrid learning procedure for mapping each training vector to its output target vector with minimum sum of squared error. The trained adaptive neuro-fuzzy inference system is used to process all feature vectors. The output for each feature vector is a value that indicates the extent to which a feature vector belongs to the mineralized class or the barren class. These values are used to generate a prospectivity map. The procedure is demonstrated by an application to regional-scale base metal prospectivity mapping in a study area located in the Aravalli metallogenic province (western India). A comparison of the hybrid neuro-fuzzy approach with pure knowledge-driven fuzzy and pure data-driven neural network approaches indicates that the former offers a superior method for integrating large earth-science datasets for predictive spatial mathematical modelling.

  5. New Data Services for Polar Investigators from Integrated Earth Data Applications (IEDA)

    NASA Astrophysics Data System (ADS)

    Nitsche, F. O.; Ferrini, V.; Morton, J. J.; Arko, R. A.; McLain, K.; O'hara, S. H.; Carbotte, S. M.; Lehnert, K. A.; IEDA Team, I.

    2013-12-01

    Accessibility and preservation of data is needed to support multi-disciplinary research in the key environmentally sensitive Polar Regions. IEDA (Integrated Earth Data Applications) is a community-based data facility funded by the US National Science Foundation (NSF) to support, sustain, and advance the geosciences by providing data services for observational solid earth data from the Ocean, Earth, and Polar Sciences. IEDA tools and services relevant to the Polar Research Community include the Antarctic and Southern Ocean Data System (ASODS), the U.S. Antarctic Program Data Coordination Center (USAP-DCC), GeoMapApp, as well as a number of services for sample-based data (SESAR and EarthChem). In addition to existing tools, which assist Polar investigators in archiving their data, and creating DIF records for global searches in AMD, IEDA recently added several new tools and services that will provide further support for investigators with the data life cycle process. These include a data management plan (http://www.iedadata.org/compliance/plan) and data compliance reporting tool (http://www.iedadata.org/compliance/report) that will help investigators comply with the requirements of funding agencies such as the National Science Foundation (NSF). Data, especially from challenging Polar Regions, are likely to be used by other scientists for future studies. Therefore, data acknowledgment is an important concern of many investigators. To encourage data acknowledgments by data users, we link references of publications (when known) to datasets and cruises registered within the ASODS system as part of our data curation services (http://www.marine-geo.org/portals/antarctic/references.php). In addition, IEDA offers a data publication service to register scientific data with DOI's, making data sets citable as publications with attribution to investigators as authors. IEDA is a publication agent of the DataCite consortium. Offering such services provides additional incentives for making data available through data centers. Such tools and services are important building blocks of a coherent and comprehensive (cyber) data support structure for Polar investigators.

  6. [Ce3⁺/Tb3⁺ Doped Alkaline-Earth Borate Glasses Employed in Enhanced Solar Cells].

    PubMed

    Yang, Peng; Zhao, Xin; Wang, Zhi-qiang; Lin, Hai

    2015-12-01

    Ce³⁺ and Tb³⁺ doped alkaline earth borate (LKZBSB) glasses and the photoluminescence properties of glass system have been fabricated and investigated, and the observed violet and green fluorescences are originated from Ce³⁺ and Tb³⁺ emit- ting centers, respectively. Four emission bands peaked at 487, 543, 586 and 621 nm are attributed to the emission transitions ⁵D₄-->⁷F₆, ⁵D₄-->⁷F₅, ⁵D₄-->⁷F₄ and ⁵D₄-->⁷F₃ of Tb³⁺, respectively, and consists of a broad emission band peaking at 389 nm attributed to 5d--4ƒ electric dipole allowed transition of Ce³⁺. With the introduction of Ce³⁺, the effective excitation wavelength range of Tb³⁺ in LKZBSB glasses are remarkably expanded, and the enhanced factor of green fluorescence of Tb³⁺ in Ce³⁺/Tb³⁺ co-doped LKZBSB glasses is up to 73 times in medium-wavelength ultraviolet (UVB) excitation region, compared with that in Tb³⁺ single-doped case. The results show that the conversion from ultraviolet (UV) radiation to visible light is efficient in Ce³⁺/ Tb³⁺ doped LKZBSB glasses, demonstrating that the glasses have potential values in developing enhanced solar cell as a conver- sion layer. PMID:26964196

  7. DECADE web portal: toward the integration of MaGa, EarthChem and VOTW data systems to further the knowledge on Earth degassing

    NASA Astrophysics Data System (ADS)

    Cardellini, Carlo; Frigeri, Alessandro; Lehnert, Kerstin; Ash, Jason; McCormick, Brendan; Chiodini, Giovanni; Fischer, Tobias; Cottrell, Elizabeth

    2015-04-01

    The release of volatiles from the Earth's interior takes place in both volcanic and non-volcanic areas of the planet. The comprehension of such complex process and the improvement of the current estimates of global carbon emissions, will greatly benefit from the integration of geochemical, petrological and volcanological data. At present, major online data repositories relevant to studies of degassing are not linked and interoperable. In the framework of the Deep Earth Carbon Degassing (DECADE) initiative of the Deep Carbon Observatory (DCO), we are developing interoperability between three data systems that will make their data accessible via the DECADE portal: (1) the Smithsonian Institutionian's Global Volcanism Program database (VOTW) of volcanic activity data, (2) EarthChem databases for geochemical and geochronological data of rocks and melt inclusions, and (3) the MaGa database (Mapping Gas emissions) which contains compositional and flux data of gases released at volcanic and non-volcanic degassing sites. The DECADE web portal will create a powerful search engine of these databases from a single entry point and will return comprehensive multi-component datasets. A user will be able, for example, to obtain data relating to compositions of emitted gases, compositions and age of the erupted products and coincident activity, of a specific volcano. This level of capability requires a complete synergy between the databases, including availability of standard-based web services (WMS, WFS) at all data systems. Data and metadata can thus be extracted from each system without interfering with each database's local schema or being replicated to achieve integration at the DECADE web portal. The DECADE portal will enable new synoptic perspectives on the Earth degassing process allowing to explore Earth degassing related datasets over previously unexplored spatial or temporal ranges.

  8. A comprehensive view on climate change: coupling of earth system and integrated assessment models

    NASA Astrophysics Data System (ADS)

    van Vuuren, Detlef P.; Batlle Bayer, Laura; Chuwah, Clifford; Ganzeveld, Laurens; Hazeleger, Wilco; van den Hurk, Bart; van Noije, Twan; O'Neill, Brian; Strengers, Bart J.

    2012-06-01

    There are several reasons to strengthen the cooperation between the integrated assessment (IA) and earth system (ES) modeling teams in order to better understand the joint development of environmental and human systems. This cooperation can take many different forms, ranging from information exchange between research communities to fully coupled modeling approaches. Here, we discuss the strengths and weaknesses of different approaches and try to establish some guidelines for their applicability, based mainly on the type of interaction between the model components (including the role of feedback), possibilities for simplification and the importance of uncertainty. We also discuss several important areas of joint IA-ES research, such as land use/land cover dynamics and the interaction between climate change and air pollution, and indicate the type of collaboration that seems to be most appropriate in each case. We find that full coupling of IA-ES models might not always be the most desirable form of cooperation, since in some cases the direct feedbacks between IA and ES may be too weak or subject to considerable process or scenario uncertainty. However, when local processes are important, it could be important to consider full integration. By encouraging cooperation between the IA and ES communities in the future more consistent insights can be developed.

  9. Creation of integrated analytical GIS-system on the Earth Sciences

    NASA Astrophysics Data System (ADS)

    Ryakhovsky, V.; Aladyshev, O.; Shulga, N.

    2004-12-01

    The program-technological complex is created on the basis of integrated geoinformation systems (GIS) as which are understood as three dimensional representations of various earths' layers in vector and raster form with the variable dimension. For the management, the distributed access and data processing of such volume the system of meta-computing GRID is used. For a prototype of meta-computing GRID environment the Globes system will be conducted, which is created and used in leading US scientific and computing centers. Execution and analysis of proposed model will be realized by parallel program, written by high-level language with MPI (Message Parsing Interface) using. This parallel program will be executed with user's parameters corresponding to requirements of modern computing clusters. Network components of parallel access and preview of data will be realized in the framework of multi-level model of the corporative server software and J2EE www-service, advanced by Sun Microsystems. At each investigation phase the user carries out processing and multimedia visualization of the received results in time in two and three-dimensional space. The developed multiplanimetric geoinformation system will allow to carry out the integrated analysis of geoinformation streams in an interactive mode, in particular, to reveal laws of existential distribution and dynamics of development of the basic structural lithosphere's elements, and also to establish relationship of stages of their development with epoch of formation of large and superlarge mineral deposits. Funded by RFBR (grants 02-07-90140 and 04-07-90304).

  10. Integrated earth system dynamic modeling for life cycle impact assessment of ecosystem services.

    PubMed

    Arbault, Damien; Rivire, Mylne; Rugani, Benedetto; Benetto, Enrico; Tiruta-Barna, Ligia

    2014-02-15

    Despite the increasing awareness of our dependence on Ecosystem Services (ES), Life Cycle Impact Assessment (LCIA) does not explicitly and fully assess the damages caused by human activities on ES generation. Recent improvements in LCIA focus on specific cause-effect chains, mainly related to land use changes, leading to Characterization Factors (CFs) at the midpoint assessment level. However, despite the complexity and temporal dynamics of ES, current LCIA approaches consider the environmental mechanisms underneath ES to be independent from each other and devoid of dynamic character, leading to constant CFs whose representativeness is debatable. This paper takes a step forward and is aimed at demonstrating the feasibility of using an integrated earth system dynamic modeling perspective to retrieve time- and scenario-dependent CFs that consider the complex interlinkages between natural processes delivering ES. The GUMBO (Global Unified Metamodel of the Biosphere) model is used to quantify changes in ES production in physical terms - leading to midpoint CFs - and changes in human welfare indicators, which are considered here as endpoint CFs. The interpretation of the obtained results highlights the key methodological challenges to be solved to consider this approach as a robust alternative to the mainstream rationale currently adopted in LCIA. Further research should focus on increasing the granularity of environmental interventions in the modeling tools to match current standards in LCA and on adapting the conceptual approach to a spatially-explicit integrated model. PMID:24291626

  11. Absolute Light Yield Measurements on SrF_2 and BaF_2 Doped With Rare Earth Ions

    NASA Astrophysics Data System (ADS)

    Shendrik, Roman; Radzhabov, Evgeny

    2014-02-01

    Results of absolute light output measurements on strontium and barium fluoride doped with PrF$_3$ and CeF$_3$ are presented and compared with scintillators having well-known light output (NaI-Tl, CsI-Tl, BGO). For pure SrF$_2$ crystal we obtain a value of about 28600 photons/MeV.

  12. RIMS: An Integrated Mapping and Analysis System with Applications to Earth Sciences and Hydrology

    NASA Astrophysics Data System (ADS)

    Proussevitch, A. A.; Glidden, S.; Shiklomanov, A. I.; Lammers, R. B.

    2011-12-01

    A web-based information and computational system for analysis of spatially distributed Earth system, climate, and hydrologic data have been developed. The System allows visualization, data exploration, querying, manipulation and arbitrary calculations with any loaded gridded or vector polygon dataset. The system's acronym, RIMS, stands for its core functionality as a Rapid Integrated Mapping System. The system can be deployed for a Global scale projects as well as for regional hydrology and climatology studies. In particular, the Water Systems Analysis Group of the University of New Hampshire developed the global and regional (Northern Eurasia, pan-Arctic) versions of the system with different map projections and specific data. The system has demonstrated its potential for applications in other fields of Earth sciences and education. The key Web server/client components of the framework include (a) a visualization engine built on Open Source libraries (GDAL, PROJ.4, etc.) that are utilized in a MapServer; (b) multi-level data querying tools built on XML server-client communication protocols that allow downloading map data on-the-fly to a client web browser; and (c) data manipulation and grid cell level calculation tools that mimic desktop GIS software functionality via a web interface. Server side data management of the system is designed around a simple database of dataset metadata facilitating mounting of new data to the system and maintaining existing data in an easy manner. RIMS contains "built-in" river network data that allows for query of upstream areas on-demand which can be used for spatial data aggregation and analysis of sub-basin areas. RIMS is an ongoing effort and currently being used to serve a number of websites hosting a suite of hydrologic, environmental and other GIS data.

  13. Integrated Earth Data Applications (IEDA) Tools for Data Management Plans and Data Compliance Reporting

    NASA Astrophysics Data System (ADS)

    Morton, J.; Ferrini, V.; Carbotte, S. M.; Lehnert, K. A.

    2012-12-01

    An important step in data stewardship is planning not only for how data will be acquired, processed and analyzed, but how data will be documented, preserved and shared. The Integrated Earth Data Applications (IEDA) Facility has developed multi-tiered web applications that assist investigators in both planning for data curation and demonstrating that their data has been made available. The IEDA Data Management Plan Tool is designed to help investigators create Data Management Plans for NSF proposals. It guides users through all relevant steps and allows them to provide relevant information about expected data types and products and select appropriate repositories for data curation. The product of the tool is a PDF that can be added to NSF proposals. A list of potential data repositories for a broad range of geoscience data types (geophysical, geochemical, climate, oceanographic, biological) is provided, but users can enter other repositories if desired. A dashboard interface allows users to manage multiple data management plans, retrieve previous versions, create new plans based on previous submissions, and link submitted plans to their funded NSF awards. A fully featured implementation of this tool is available at http://www.iedadata.org/compliance/plan. With an increasing focus on data compliance, IEDA is also developing a Data Compliance Reporting Tool. The Data Compliance Reporting Tool allows users to search for data inventoried within IEDA data systems (EarthChem and Marine Geoscience Data System) by award number and provides basic metadata and links to those data sets. In addition, links are provided to underway data acquired aboard the U.S. Academic Research Fleet (handled by the Rolling Deck to Repository Program), as well as related data that has been registered through the U.S. Antarctic Program Data Coordination Center. Future developments of this tool will include the ability for investigators to directly contribute additional information to update their Data Compliance Report.

  14. Integration of Earth Remote Sensing into the NOAA/NWS Damage Assessment Toolkit

    NASA Technical Reports Server (NTRS)

    Molthan, Andrew; Burks, Jason; Camp, Parks; McGrath, Kevin; Bell, Jordan

    2014-01-01

    Following the occurrence of severe weather, NOAA/NWS meteorologists are tasked with performing a storm damage survey to assess the type and severity of the weather event, primarily focused with the confirmation and assessment of tornadoes. This labor-intensive process requires meteorologists to venture into the affected area, acquire damage indicators through photos, eyewitness accounts, and other documentation, then aggregation of data in order to make a final determination of the tornado path length, width, maximum intensity, and other characteristics. Earth remote sensing from operational, polar-orbiting satellites can support the damage assessment process by helping to identify portions of damage tracks that are difficult to access due to road limitations or time constraints by applying change detection techniques. In addition, higher resolution commercial imagery can corroborate ground-based surveys by examining higher-resolution commercial imagery. As part of an ongoing collaboration, NASA and NOAA are working to integrate near real-time Earth remote sensing observations into the NOAA/NWS Damage Assessment Toolkit, a handheld application used by meteorologists in the survey process. The team has recently developed a more streamlined approach for delivering data via a web mapping service and menu interface, allowing for caching of imagery before field deployment. Near real-time products have been developed using MODIS and VIIRS imagery and change detection for preliminary track identification, along with conduits for higher-resolution Landsat, ASTER, and commercial imagery as they become available. In addition to tornado damage assessments, the team is also investigating the use of near real-time imagery for identifying hail damage to vegetation, which also results in large swaths of damage, particularly in the central United States during the peak growing season months of June, July, and August. This presentation will present an overview of recent activities, challenges and successes, best practices, and opportunities for future work and collaboration.

  15. Integration of Earth Remote Sensing into the NOAA/NWS Damage Assessment Toolkit

    NASA Astrophysics Data System (ADS)

    Molthan, A.; Burks, J. E.; Camp, P.; McGrath, K.; Bell, J. R.

    2014-12-01

    Following the occurrence of severe weather, NOAA/NWS meteorologists are tasked with performing a storm damage survey to assess the type and severity of the weather event, primarily focused with the confirmation and assessment of tornadoes. This labor-intensive process requires meteorologists to venture into the affected area, acquire damage indicators through photos, eyewitness accounts, and other documentation, then aggregation of data in order to make a final determination of the tornado path length, width, maximum intensity, and other characteristics. Earth remote sensing from operational, polar-orbiting satellites can support the damage assessment process by helping to identify portions of damage tracks that are difficult to access due to road limitations or time constraints by applying change detection techniques. In addition, higher resolution commercial imagery can corroborate ground-based surveys by examining higher-resolution commercial imagery. As part of an ongoing collaboration, NASA and NOAA are working to integrate near real-time Earth remote sensing observations into the NOAA/NWS Damage Assessment Toolkit (DAT), a suite of applications used by meteorologists in the survey process. The DAT includes a handheld application used by meteorologists in the survey process. The team has recently developed a more streamlined approach for delivering data via a web mapping service and menu interface, allowing for caching of imagery before field deployment. Near real-time products have been developed using MODIS and VIIRS imagery and change detection for preliminary track identification, along with conduits for higher-resolution Landsat, ASTER, and commercial imagery as they become available. In addition to tornado damage assessments, the team is also investigating the use of near real-time imagery for identifying hail damage to vegetation, which also results in large swaths of damage, particularly in the central United States during the peak growing season months of June, July, and August. This presentation will present an overview of recent activities, challenges and successes, best practices, and opportunities for future work and collaboration.

  16. CIM-EARTH: Community Integrated Model of Economic and Resource Trajectories for Humankind

    NASA Astrophysics Data System (ADS)

    Foster, I.; Elliott, J.; Munson, T.; Judd, K.; Moyer, E. J.; Sanstad, A. H.

    2010-12-01

    We report here on the development of an open source software framework termed CIM-EARTH that is intended to aid decision-making in climate and energy policy. Numerical modeling in support of evaluating policies to address climate change is difficult not only because of inherent uncertainties but because of the differences in scale and modeling approach required for various subcomponents of the system. Economic and climate models are structured quite differently, and while climate forcing can be assumed to be roughly global, climate impacts and the human response to them occur on small spatial scales. Mitigation policies likewise can be applied on scales ranging from the better part of a continent (e.g. a carbon cap-and-trade program for the entire U.S.) to a few hundred km (e.g. statewide renewable portfolio standards and local gasoline taxes). Both spatial and time resolution requirements can be challenging for global economic models. CIM-EARTH is a modular framework based around dynamic general equilibrium models. It is designed as a community tool that will enable study of the environmental benefits, transition costs, capitalization effects, and other consequences of both mitigation policies and unchecked climate change. Modularity enables both integration of highly resolved component sub-models for energy and other key systems and also user-directed choice of tradeoffs between e.g. spatial, sectoral, and time resolution. This poster describes the framework architecture, the current realized version, and plans for future releases. As with other open-source models familiar to the climate community (e.g. CCSM), deliverables will be made publicly available on a regular schedule, and community input is solicited for development of new features and modules.

  17. Svalbard Integrated Arctic Earth Observing System - A New Coordinated Foundation for Environmental Services in and around Svalbard

    NASA Astrophysics Data System (ADS)

    Lilja Bye, Bente

    2015-04-01

    Svalbard Integrated Earth Observing System (SIOS) is an international infrastructure project. There were 28 partners from Europe and Asia involved in the preparatory phase of this ESFRI project. The essential objectives are to establish a mechanism for integration among the existing research institutions in Svalbard to create a joint state-of-the-art observing system in Earth System Science, and better coordinated services for the International Research community with respect to access, data and knowledge management, logistics and training. In addition to the SIOS members various data services, SIOS itself will provide a few new services such as processed satellite data (from Copernicus' Sentinels as well as others) and combined in-situ and satellite data. All in all SIOS represent a new capacity and foundation for more Earth System Science, including climate and environment, data services in and around Svalbard. A presentation of SIOS including time schedule for implementation of the basic services will be given.

  18. Integration of lessons from recent research for “Earth to Mars” life support systems

    NASA Astrophysics Data System (ADS)

    Nelson, M.; Dempster, W. F.; Allen, J. P.

    Development of reliable and robust strategies for long-term life support for planetary exploration must be built from real-time experimentation to verify and improve system components. Also critical is incorporating a range of viable options to handle potential short-term life system imbalances. This paper revisits some of the conceptual framework for a Mars base prototype which has been developed by the authors along with others previously advanced ("Mars on Earth ®") in the light of three years of experimentation in the Laboratory Biosphere, further investigation of system alternatives and the advent of other innovative engineering and agri-ecosystem approaches. Several experiments with candidate space agriculture crops have demonstrated the higher productivity possible with elevated light levels and improved environmental controls. For example, crops of sweet potatoes exceeded original Mars base prototype projections by an average of 46% (53% for best crop) ultradwarf (Apogee) wheat by 9% (23% for best crop), pinto bean by 13% (31% for best crop). These production levels, although they may be increased with further optimization of lighting regimes, environmental parameters, crop density etc. offer evidence that a soil-based system can be as productive as the hydroponic systems which have dominated space life support scenarios and research. But soil also offers distinct advantages: the capability to be created on the Moon or Mars using in situ space resources, reduces long-term reliance on consumables and imported resources, and more readily recycling and incorporating crew and crop waste products. In addition, a living soil contains a complex microbial ecosystem which helps prevent the buildup of trace gases or compounds, and thus assist with air and water purification. The atmospheric dynamics of these crops were studied in the Laboratory Biosphere adding to the database necessary for managing the mixed stands of crops essential for supplying a nutritionally adequate diet in space. This paper explores some of the challenges of small bioregenerative life support: air-sealing and facility architecture/design, balance of short-term variations of carbon dioxide and oxygen through staggered plantings, options for additional atmospheric buffers and sinks, lighting/energy efficiency engineering, crop and waste product recycling approaches, and human factor considerations in the design and operation of a Mars base. An "Earth to Mars" project, forging the ability to live sustainably in space (as on Earth) requires continued research and testing of these components and integrated subsystems; and developing a step-by-step learning process.

  19. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2003-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi-component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma-sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), electron energy-loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia- yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging from 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  20. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    1990-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi- component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma- sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia-yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging fiom 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  1. Time-integrated photoluminescence and pump-probe reflection spectroscopy of Si doped InN thin films

    SciTech Connect

    Mohanta, Antaryami; Jang, Der-Jun Wang, Ming-Sung; Tu, L. W.

    2014-01-28

    Temperature and excitation power dependent time-integrated photoluminescence of Si doped InN thin films are investigated. Photoluminescence (PL) spectra at low temperatures are described by single emission peak ensued due to free-to-bound recombination; whereas PL spectra at higher temperatures above 150?K are characterized by both band-to-band and free-to-bound transition. Carrier dynamics of Si doped InN thin films is studied using pump-probe reflection spectroscopy at room temperature. The hot electron cooling process is well described by electron-electron scattering. The dependence of the hot electron cooling rate on total electron density shows sublinear to linear behavior with increase of background electron density. The variation of the carrier recombination lifetime with total electron density implicates the dominance of the defect-related nonradiative recombination channel over other recombination processes.

  2. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    PubMed

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, Ren; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are suitable for probing, manipulating, sculpting, and sensing at single digit nanoscale. PMID:21534601

  3. Comparative study of pure and alkaline earth metallic doped cadmium mercury thiocyanate single crystalsGel technique

    NASA Astrophysics Data System (ADS)

    Kalainathan, S.; Kumari, P. Nisha Santha

    2009-07-01

    Growth aspects of Ba and Ca doped cadmium mercury thiocyanate (CMTC) single crystals from silica gel by the process of diffusion are discussed. The incorporation of dopants in the crystal has been confirmed by inductively coupled plasma (ICP) analysis. Single crystal X-ray diffraction studies reveal the structures of the doped crystals to be tetragonal implying that the incorporation of the dopants has not changed the structure of the parent crystal. The diffraction planes were identified and indexed by powder diffraction analysis. High-resolution X-ray diffraction analyses were carried out to investigate the crystalline perfection of the grown crystals. The grown crystals were characterized by Fourier transform infrared and transmission spectral analyses. Vickers microhardness studies on the grown crystals reveal that they belong to soft material category. Employing powder Kurtz method, their second harmonic generation efficiencies were measured in comparison with urea.

  4. CEOS WGISS Integrated Catalog, A Catalog for Earth Observation Satellite Data

    NASA Astrophysics Data System (ADS)

    Enloe, Y.; Yapur, M.

    2011-12-01

    The Committee on Earth Observation Satellites (CEOS) was formed in 1984 to coordinate the world's civil space-borne observations of the Earth. More recently, CEOS and its member agencies have committed to provide the implementation of the space-based component of the Group on Earth Observation (GEO) Global Earth Observation System of Systems (GEOSS) Common Infrastructure (GCI). In the case of CEOS, there are a number of challenges in directly connecting the components and services of its member agencies to the GCI. In many cases, the existing catalog systems of the member agencies do not support the OGC Catalog Service for the Web (CSW) that has been selected as the standard for the GCI. Another challenge is related to the fact that collections of satellite data products are extremely large and constantly growing with millions of individual products. Harvesting the associated metadata into the clearinghouse of the GCI is not a practical alternative. In addition, the collection/granule hierarchy and unique spatial/temporal characteristics of satellite data and the user registration and asynchronous access requirements of the agency systems pose additional challenges. The CEOS approach has been to design and implement a CEOS WGISS Integrated Catalog (CWIC) that will serve as a community catalog of the products and services that are offered through its member's systems. CWIC will be based on a distributed search architecture and serve as a gateway between the GEO portal or community portals and clients and the CEOS agency systems. CWIC will receive standard search queries from these portals or clients all using the GEO supported catalog standard, the OGC CSW 2.0.2 and the WGISS Search Criteria for granule search and translate them into the native protocols of the underlying catalogs. Likewise, the result sets from the CEOS agency catalogs will be converted to the form that will be compatible with the portals and clients. The CWIC data provider partners include NOAA, NASA, USGS, INPE (Brazil), and two Chinese data centers coordinated by the Chinese Academy of Science have joined the engineering team and their systems are accessible via CWIC. In addition, multiple other CEOS agencies are or plan to be members of the teams developing community portals and clients that will access CWIC. Recently, NASA initiated development of a prototype client to access CWIC. The ultimate goal of the CEOS WGISS effort is to make the satellite data and services of its member agencies more accessible and useful to the broad set of GEO research programs and applications and this is most effectively approached by harmonization within the satellite community. This kind of community-based development with the harmonization occurring first within the community and then being offered to the broader GEO systems fits the original GEO vision of becoming "a system of systems", clearly representing a contribution towards achieving full interoperability in a standards-based manner.

  5. Chemical environment of rare earth ions in Ge28.125Ga6.25S65.625 glass-ceramics doped with Dy3+

    NASA Astrophysics Data System (ADS)

    Wang, Rongping; Yan, Kunlun; Zhang, Mingjie; Shen, Xiang; Dai, Shixun; Yang, Xinyu; Yang, Zhiyong; Yang, Anping; Zhang, Bin; Luther-Davies, Barry

    2015-10-01

    We have annealed Ge28.125Ga6.25S65.625 glasses doped with 0.5% Dy to create glass-ceramics in order to examine the local chemical environment of the rare earth ions (REI). More than 12 times enhancement of the emission at 2.9 and 3.5 ?m was achieved in glass-ceramics produced using prolonged annealing time. Elemental mapping showed clear evidence that Ga2S3 crystalline grains with a size of 50 nm were dispersed in a Ge-S glass matrix in the glass-ceramics, and the REI could only be found near the Ga2S3 crystalline grains. From the unchanged lineshape of the emissions at 2.9 and 3.5 ?m and lack of splitting of the absorption peaks, we concluded that the REI were bonded to Ga on the surface of the Ga2S3 crystals.

  6. 5d-4f emission of Eu2+ and electron-vibrational interaction in several alkaline earth sulfides doped with Eu2+ and Er3+

    NASA Astrophysics Data System (ADS)

    Kumar, G. A.; Liu, D.-X.; Tian, Y.; Brik, M. G.; Sardar, D. K.

    2015-12-01

    Several alkaline earth sulfides doped with Eu2+ and Er3+ ions have been synthesized and shown to be potential phosphors for applications in the visible spectral range. The excitation and emission spectra corresponding to the 4f-5d interconfigurational transitions of Eu2+ were analyzed with an aim of extraction of the main parameters of the electron-vibrational interaction. The values of the Huang-Rhys factor, effective phonon energies, and zero-phonon line positions were systematically compared for all studied materials; physical trends were discussed. As a test for the validity of the obtained parameters, the Eu2+ 5d-4f emission bands were modeled to yield good agreement with the experimental spectra.

  7. Using laser ablation to study the microhomogeneity and composition of rare-earth doped Ta2O5 Precursors and a LiTaO3 charge

    NASA Astrophysics Data System (ADS)

    Elizarova, I. R.; Masloboeva, S. M.

    2015-09-01

    The possibilities and aspects of using laser ablation (LA) to study the microhemogeneity and composition of tantalum pentoxides and a Ta2O5-based lithium tantalate charge doped with small concentrations of rare earth elements (TRs) are studied. It is shown that LA can be performed for Ta2O5 precursor and LiTaO3?TR> charge samples pelletized without a binder. The detection limits of TR are determined via inductively coupled plasma mass spectrometry (ICP-MS), and the conditions for quantitative analysis are found. Based on the calculated values of root-mean-square deviation S r , it is proved that the distribution of the dopant in the studied samples is chemically homogeneous.

  8. Preparation, Analysis and Behaviors of Ti-Based SnO2 Electrode and the Function of Rare-Earth Doping in Aqueous Wastes Treatment

    NASA Astrophysics Data System (ADS)

    Feng, Yujie; Liu, Junfeng; Ding, Haiyang

    Electrocatalytic anodes act as key function of electrocatalytic oxidation process for the removal of toxic or biorefractory materials. The characteristics of the anodes, such as potential for oxygen evolution, electric resistance, crystal size of the coating or the service life etc., have important impacts on the behavior of the electrodes. Titaniumbased tin dioxides electrode Ti / SnO2 found a kind of catalytic material with high oxygen evolution potential which related to the catalytic ability with the degradation of toxic material for aqueous wastes removal Four kinds of rare earth (Dy, Eu, Nd and Gd) were selected as doping agents to research the relationship between the electrocatalytic properties and the degradation pathway for organics degradation with the inner structure of the SnO2 crystals. The crystal structure of the electrode materials influence the properties of the anodes in many aspects and should be very important to understand the interplay mechanism for developing new kinds of catalytic electrodes.

  9. Integrating Parallel and Distributed Data Mining Algorithms into the NASA Earth Exchange (NEX)

    NASA Astrophysics Data System (ADS)

    Oza, N.; Kumar, V.; Nemani, R. R.; Boriah, S.; Das, K.; Khandelwal, A.; Matthews, B.; Michaelis, A.; Mithal, V.; Nayak, G.; Votava, P.

    2014-12-01

    There is an urgent need in global climate change science for efficient model and/or data analysis algorithms that can be deployed in distributed and parallel environments because of the proliferation of large and heterogeneous data sets. Members of our team from NASA Ames Research Center and the University of Minnesota have been developing new distributed data mining algorithms and developing distributed versions of algorithms originally developed to run on a single machine. We are integrating these algorithms together with the Terrestrial Observation and Prediction System (TOPS), an ecological nowcasting and forecasting system, on the NASA Earth Exchange (NEX). We are also developing a framework under which data mining algorithm developers can make their algorithms available for use by scientists in our system, model developers can set up their models to run within our system and make their results available, and data source providers can make their data available, all with as little effort as possible. We demonstrate the substantial time savings and new results that can be derived through this framework by demonstrating an improvement to the Burned Area (BA) data product on a global scale. Our improvement was derived through development and implementation on NEX of a novel spatiotemporal time series change detection algorithm which will also be presented.

  10. Refluxing synthesis, photoluminescence and binding ability to deoxyribonucleic acid of water-soluble rare earth ion-doped LaF3 nanoparticles.

    PubMed

    Wang, Zhenling; Zhang, Yi; Li, Chunyang; Zhang, Xinlei; Chang, Jiazhong; Xie, Jianping; Li, Chengwei

    2014-06-01

    Water-soluble rare earth ion (Ce3+, Tb3+)-doped LaF3 nanoparticles with the ability to bind to deoxyribonucleic acid (DNA) were prepared by the refluxing method in a glycerol/water mixture and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and so on. The obtained LaF3:Ce3+, LaF3:Tb3+ and LaF3:Ce3+, Tb3+ nanoparticles are well crystallized with a hexagonal structure and composed of spherical particles with an average size from 11 to 19 nm. The as-prepared samples can be dispersed into water to form a colloidal solution. Under ultraviolet (UV) light irradiation, the emission lines of Tb3+ in the co-doped LaF3:Ce3+, Tb3+ are evidently strengthened compared to those in the single-doped LaF3:Tb3+ nanoparticles, which is due to the energy transfer from Ce3+ to Tb3+ ions in the LaF3:Ce3+, Tb3+ samples. The biological experiment confirms that the water-soluble LaF3:Ce3+, Tb3+ nanoparticles can be bonded to the DNA molecules and emit visible light under UV irradiation. These luminescent nanoparticles could be used similarly to ethidium bromide (EtBr), which has been used extensively as a DNA staining reagent. The advantage that LaF3:Ce3+, Tb3+ nanoparticles have lower toxicity than EtBr makes them a potential reagent instead of EtBr in the DNA staining in biological experiments. PMID:24738421

  11. Efficient Dual-Modal NIR-to-NIR Emission of Rare Earth Ions Co-doped Nanocrystals for Biological Fluorescence Imaging.

    PubMed

    Zhou, Jiajia; Shirahata, Naoto; Sun, Hong-Tao; Ghosh, Batu; Ogawara, Makoto; Teng, Yu; Zhou, Shifeng; Sa Chu, Rong Gui; Fujii, Minoru; Qiu, Jianrong

    2013-02-01

    A novel approach has been developed for the realization of efficient near-infrared to near-infrared (NIR-to-NIR) upconversion and down-shifting emission in nanophosphors. The efficient dual-modal NIR-to-NIR emission is realized in a ?-NaGdF4/Nd(3+)@NaGdF4/Tm(3+)-Yb(3+) core-shell nanocrystal by careful control of the identity and concentration of the doped rare earth (RE) ion species and by manipulation of the spatial distributions of these RE ions. The photoluminescence results reveal that the emission efficiency increases at least 2-fold when comparing the materials synthesized in this study with those synthesized through traditional approaches. Hence, these core-shell structured nanocrystals with novel excitation and emission behaviors enable us to obtain tissue fluorescence imaging by detecting the upconverted and down-shifted photoluminescence from Tm(3+) and Nd(3+) ions, respectively. The reported approach thus provides a new route for the realization of high-yield emission from RE ion doped nanocrystals, which could prove to be useful for the design of optical materials containing other optically active centers. PMID:26281731

  12. An Integrated Approach to Modeling Solar Electric Propulsion Vehicles During Long Duration, Near-Earth Orbit Transfers

    NASA Technical Reports Server (NTRS)

    Smith, David A.; Hojnicki, Jeffrey S.; Sjauw, Waldy K.

    2014-01-01

    Recent NASA interest in utilizing solar electronic propulsion (SEP) technology to transfer payloads, e.g. from low-Earth orbit (LEO) to higher energy geostationary-Earth orbit (GEO) or to Earth escape, has necessitated the development of high fidelity SEP vehicle models and simulations. These models and simulations need to be capable of capturing vehicle dynamics and sub-system interactions experienced during the transfer trajectories which are typically accomplished with continuous-burn (potentially interrupted by solar eclipse), long duration "spiral out" maneuvers taking several months or more to complete. This paper presents details of an integrated simulation approach achieved by combining a high fidelity vehicle simulation code with a detailed solar array model. The combined simulation tool gives researchers the functionality to study the integrated effects of various vehicle sub-systems (e.g. vehicle guidance, navigation and control (GN&C), electric propulsion system (EP)) with time varying power production. Results from a simulation model of a vehicle with a 50 kW class SEP system using the integrated tool are presented and compared to the results from another simulation model employing a 50 kW end-of-life (EOL) fixed power level assumption. These models simulate a vehicle under three degree of freedom dynamics (i.e. translational dynamics only) and include the effects of a targeting guidance algorithm (providing a "near optimal" transfer) during a LEO to near Earth escape (C (sub 3) = -2.0 km (sup 2) / sec (sup -2) spiral trajectory. The presented results include the impact of the fully integrated, time-varying solar array model (e.g. cumulative array degradation from traversing the Van Allen belts, impact of solar eclipses on the vehicle and the related temperature responses in the solar arrays due to operating in the Earth's thermal environment, high fidelity array power module, etc.); these are used to assess the impact on vehicle performance (i.e. propellant consumption) and transit times.

  13. Charge Compensation in RE3+ (RE = Eu, Gd) and M+ (M = Li, Na, K) Co-Doped Alkaline Earth Nanofluorides Obtained by Microwave Reaction with Reactive Ionic Liquids Leading to Improved Optical Properties

    SciTech Connect

    Lorbeer, C; Behrends, F; Cybinska, J; Eckert, H; Mudring, Anja -V

    2014-01-01

    Alkaline earth fluorides are extraordinarily promising host matrices for phosphor materials with regard to rare earth doping. In particular, quantum cutting materials, which might considerably enhance the efficiency of mercury-free fluorescent lamps or SC solar cells, are often based on rare earth containing crystalline fluorides such as NaGdF4, GdF3 or LaF3. Substituting most of the precious rare earth ions and simultaneously retaining the efficiency of the phosphor is a major goal. Alkaline earth fluoride nanoparticles doped with trivalent lanthanide ions (which are required for the quantum cutting phenomenon) were prepared via a microwave assisted method in ionic liquids. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect was thoroughly studied by powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR spectroscopy. Monovalent alkali ions were codoped with the trivalent lanthanide ions to relieve stress and achieve a better crystallinity and higher quantum cutting abilities of the prepared material. 19F-magic angle spinning (MAS)-NMR-spectra, assisted by 19F{23Na} rotational echo double resonance (REDOR) studies, reveal distinct local fluoride environments, the populations of which are discussed in relation to spatial distribution and clustering models. In the co-doped samples, fluoride species having both Na+ and La3+ ions within their coordination sphere can be identified and quantified. This interplay of mono- and trivalent ions in the CaF2 lattice appears to be an efficient charge compensation mechanism that allows for improved performance characteristics of such co-doped phosphor materials.

  14. Rare earth doped LiYbF{sub 4} phosphors with controlled morphologies: Hydrothermal synthesis and luminescent properties

    SciTech Connect

    Huang, Wenjuan; Lu, Chunhua; Jiang, Chenfei; Jin, Junyang; Ding, Mingye; Ni, Yaru; Xu, Zhongzi

    2012-06-15

    Highlights: ? LiYbF{sub 4} microparticles as an excellent upconverting materials. ? High temperature and long time can favor high crystalline LiYbF{sub 4} microparticles. ? The shape of LiYbF{sub 4} microparticles can be tuned by the molar ratio of EDTA to Yb{sup 3+}. ? Bright green emission can be obtained by changing the doping concentration of Er{sup 3+}. -- Abstract: High quality monodisperse LiYbF{sub 4} microparticles with shape of octahedron had been prepared via a facile hydrothermal route. The crystalline phase, size, morphology and luminescence properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra and Commission Internationale de LEclairage (CIE 1931) chromaticity coordinates, respectively. The influences of reaction temperature, reaction time and the molar ratio of EDTA to Yb{sup 3+} on the crystal phases and shapes of as-prepared products had been investigated in detail. The upconversion (UC) luminescence properties of LiYb{sub 1?x}F{sub 4}:xEr{sup 3+} (x =0.1, 0.2, 0.5, 1, 2, 5 and 10 mol%) particles with octahedral microstructures were studied under 976 nm excitation. The results showed that the luminescence colors of the corresponding products could be tuned to bright green by changing the doping concentration of Er{sup 3+} ion. The luminescence mechanisms for the doped Er{sup 3+} ion were thoroughly analyzed, showing great potential in applications such as biolabels, displays and other optical technologies.

  15. Photon management properties of rare-earth (Nd,Yb,Sm)-doped CeO2 films prepared by pulsed laser deposition.

    PubMed

    Balestrieri, Matteo; Colis, Silviu; Gallart, Mathieu; Schmerber, Guy; Bazylewski, Paul; Chang, Gap Soo; Ziegler, Marc; Gilliot, Pierre; Slaoui, Abdelilah; Dinia, Aziz

    2016-01-20

    CeO2 is a promising material for applications in optoelectronics and photovoltaics due to its large band gap and values of the refractive index and lattice parameters, which are suitable for silicon-based devices. In this study, we show that trivalent Sm, Nd and Yb ions can be successfully inserted and optically activated in CeO2 films grown at a relatively low deposition temperature (400 C), which is compatible with inorganic photovoltaics. CeO2 thin films can therefore be efficiently functionalized with photon-management properties by doping with trivalent rare earth (RE) ions. Structural and optical analyses provide details of the electronic level structure of the films and of their energy transfer mechanisms. In particular, we give evidence of the existence of an absorption band centered at 350 nm from which energy transfer to rare earth ions occurs. The transfer mechanisms can be completely explained only by considering the spontaneous migration of Ce(3+) ions in CeO2 at a short distance from the RE(3+) ions. The strong absorption cross section of the f-d transitions in Ce(3+) ions efficiently intercepts the UV photons of the solar spectrum and therefore strongly increases the potential of these layers as downshifters and downconverters. PMID:26699802

  16. Investigating the Near-Earth Object Population Using Numerical Integration Methods and LINEAR Data

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Morbidelli, A.; Jedicke, R.; Stuart, J. S.; Evans, J. B.; Stokes, G.

    2004-11-01

    The remarkable progress made in finding near-Earth objects (NEOs) over the last decade by dedicated NEO surveys has been accompanied by substantial numerical and theoretical work. Together, these advances have given us a much more profound understanding of the NEO population than we have had at any time in the past. Recent models of the NEO orbital and size distributions have been made using different techniques (e.g., Bottke et al. 2000, 2002; Stuart 2001). In Bottke et al., an NEO model was produced by combining numerical integration work with computations of observational biases. This model was calibrated by fitting model parameters to a relatively small sample of 138 NEOs detected by Spacewatch. In Stuart (2001), a NEO model was computed more directly by debiasing the more extensive NEO observations provided by LINEAR. While the results from each model were similar overall, we found that the Bottke et al. model could not reproduce several features of the Stuart model (e.g., specific bumps in the NEO inclination distribution; its somewhat ``flat" shape). To explore this mismatch, we modified our NEO model in two important ways: (i) we added several high inclination sources of NEOs that were excluded by Bottke et al. (2002) (e.g., Hungarias, Phocaeas), and (ii) we joined forces with the LINEAR survey team to explore their extensive NEO data set within our model. While our new results are consistent with previous work, they also indicate that the high inclination asteroid sources contribute to the NEO population at the 10% level; this may be enough to explain some of the features observed in Stuart (2001). Our latest results, as well as the implications of this work, will be discussed in our talk.

  17. Incorporating Stakeholder Decision Support Needs into an Integrated Regional Earth System Model

    SciTech Connect

    Rice, Jennie S.; Moss, Richard H.; Runci, Paul J.; Anderson, K. L.; Malone, Elizabeth L.

    2012-03-21

    A new modeling effort exploring the opportunities, constraints, and interactions between mitigation and adaptation at regional scale is utilizing stakeholder engagement in an innovative approach to guide model development and demonstration, including uncertainty characterization, to effectively inform regional decision making. This project, the integrated Regional Earth System Model (iRESM), employs structured stakeholder interactions and literature reviews to identify the most relevant adaptation and mitigation alternatives and decision criteria for each regional application of the framework. The information is used to identify important model capabilities and to provide a focus for numerical experiments. This paper presents the stakeholder research results from the first iRESM pilot region. The pilot region includes the Great Lakes Basin in the Midwest portion of the United States as well as other contiguous states. This geographic area (14 states in total) permits cohesive modeling of hydrologic systems while also providing gradients in climate, demography, land cover/land use, and energy supply and demand. The results from the stakeholder research indicate that iRESM should prioritize addressing adaptation alternatives in the water resources, urban infrastructure, and agriculture sectors, such as water conservation, expanded water quality monitoring, altered reservoir releases, lowered water intakes, urban infrastructure upgrades, increased electric power reserves in urban areas, and land use management/crop selection changes. Regarding mitigation alternatives, the stakeholder research shows a need for iRESM to focus on policies affecting the penetration of renewable energy technologies, and the costs and effectiveness of energy efficiency, bioenergy production, wind energy, and carbon capture and sequestration.

  18. Potential Uses of EarthSLOT (an Earth Science, Logistics, and Outreach Terrainbase) for Education and Integration in the International Polar Year

    NASA Astrophysics Data System (ADS)

    Nolan, M.

    2004-12-01

    EarthSLOT is an internet-based, 3D, interactive terrain and data visualization system that may have many potential uses as an education and integration tool for International Polar Year projects. Recently funded by NSF's Office of Polar Programs for use in the Arctic, the global nature of the application lends itself well for use at both poles and everywhere in between. The application allows one to start with a spinning earth and zoom down to surface level. The highest resolution digital elevation models available provide the necessary 3D topographic perspective and a variety of possible high-resolution satellite and aerial imagery layers add surface realism; resolution can be down to the centimeter level for either type of data, and frequently acquired satellite imagery may be updated automatically as it arrives. Superimposed on this can be nearly any form of vector or annotation layers, such as shapefiles, polygons, point data, and 3D models (still and moving), which can be easily imported from existing GIS applications or spreadsheets. External databases can also be queried and the results served seamlessly. The entire application is served over the internet, and any connection with speeds over 300kps allows one to interactively fly with a minimum of performance lag. EarthSLOT stands for Earth Science, Logistics, and Outreach Terrainbase, targeting the user-groups of scientists, logisticians, and the public. Approved scientific users can add their own vector content to the application on their own, such that they can create their own custom applications featuring their data but using our underlying earth model with a minimum of interaction with us. For example, an oceanographer can add ship tracks or buoy locations to the model with links to data, host the link on his or her own web page, and invite collaborators to view the spatial relationship of their data to underlying bathymetry. Logisticians or program managers interested in understanding the spatial relationships between different projects for the purposes of coordinating or facilitating cost sharing of logistics can add layers that show the locations and timing of their projects. Educators or principle investigators interested in outreach can design and implement custom applications to share the motivation, rationale, and results of their work in a large variety of ways. Each of these applications can be freely-shared or password-protected, depending on their nature, on either project home pages or on a central IPY-EarthSLOT site. Our prototype application can be found on-line at www.earthslot.org. We already have substantial Landsat coverage of the Arctic, and in the near future plan to incorporate high resolution mosaics of Greenland and Antarctica. With modest additional funding, we propose that EarthSLOT could be used a central integration tool for projects related to the International Polar Year.

  19. Double Rare-Earth Oxides Co-doped Strontium Zirconate as a New Thermal Barrier Coating Material

    NASA Astrophysics Data System (ADS)

    Ma, Wen; Wang, Dongxing; Dong, Hongying; Lun, Wenshan; He, Weiyan; Zheng, Xuebin

    2013-03-01

    Y2O3 and Yb2O3 co-doped strontium zirconate with chemistry of Sr(Zr0.9Y0.05Yb0.05)O2.95 (SZYY) was synthesized and had a minor second phase of Yb2O3. The SZYY showed good phase stability not only from room temperature to 1400 C but also at high temperature of 1450 C for a long period, analyzed by thermogravimetry-differential scanning calorimetry and x-ray diffraction, respectively. The coefficients of thermal expansion (CTEs) of the sintered bulk SZYY were recorded by a high-temperature dilatometer and revealed a positive influence on phase transitions of SrZrO3 by co-doping with Y2O3 and Yb2O3. The thermal conductivities of SZYY were at least ~30% lower in contrast to that of SrZrO3 and 8YSZ in the whole tested temperature range. Good chemical compatibility was observed for SZYY with 8YSZ or Al2O3 powders after a 24 h heat treatment at 1250 C. The phase stability and the microstructure evolution of the as-sprayed SZYY coating during annealing at 1400 C were also investigated.

  20. An integrated study of earth resources in the state of California using remote sensing techniques. [water and forest management

    NASA Technical Reports Server (NTRS)

    Colwell, R. N.

    1974-01-01

    Progress and results of an integrated study of California's water resources are discussed. The investigation concerns itself primarily with the usefulness of remote sensing of relation to two categories of problems: (1) water supply; and (2) water demand. Also considered are its applicability to forest management and timber inventory. The cost effectiveness and utility of remote sensors such as the Earth Resources Technology Satellite for water and timber management are presented.

  1. Nanocrystalline semiconductor doped rare earth oxide for the photocatalytic degradation studies on Acid Blue 113: A di-azo compound under UV slurry photoreactor.

    PubMed

    Suganya Josephine, G A; Mary Nisha, U; Meenakshi, G; Sivasamy, A

    2015-11-01

    Preventive measures for the control of environmental pollution and its remediation has received much interest in recent years due to the world-wide increase in the contamination of water bodies. Contributions of these harmful effluents are caused by the leather processing, pharmaceutical, cosmetic, textile, agricultural and other chemical industries. Nowadays, advanced oxidation processes considered to be better option for the complete destruction of organic contaminants in water and wastewater. Acid Blue 113 is a most widely used di-azo compound in leather, textile, dying and food industry as a color rending compound. In the present study, we have reported the photo catalytic degradation of Acid Blue 113 using a nanocrystalline semiconductor doped rare earth oxide as a photo catalyst under UV light irradiation. The photocatalyst was prepared by a simple precipitation technique and were characterized by XRD, FT-IR, UV-DRS and FE-SEM analysis. The experimental results proved that the prepared photo catalyst was nanocrystalline and highly active in the UV region. The UV-DRS results showed the band gap energy was 3.15eV for the prepared photo catalyst. The photodegradation efficiency was analyzed by various experimental parameters such as pH, catalyst dosage, variation of substrate concentration and effect of electrolyte addition. The photo degradation process followed a pseudo first order kinetics and was continuously monitored by UV-visible spectrophotometer. The experimental results proved the efficacy of the nanocrystalline zinc oxide doped dysprosium oxide which are highly active under UV light irradiations. It is also suggested that the prepared material would find wider applications in environmental remediation technologies to remove the carcinogenic and toxic moieties present in the industrial effluents. PMID:26025644

  2. Empowering Rural Appalachian Youth Through Integrated Inquiry-based Earth Science

    NASA Astrophysics Data System (ADS)

    Cartwright, T. J.; Hogsett, M.

    2009-05-01

    Science education must be relevant and inspiring to keep students engaged and receptive to learning. Reports suggest that science education reform can be advanced by involving students in active research (NSF 1996). Through a 2-year Geoscience Education award from the National Science Foundation, a program called IDGE (Integrated Design for Geoscience Education) has targeted low-income, under-represented, and minority high school students in rural Appalachia in inquiry-based projects, international collaboration, and an international environmental expedition incorporating the GLOBE program protocols. This program targeted Upward Bound students at Marshall University in Huntington, West Virginia. The Upward Bound is a federally-supported program targeting low-income, under-represented, and minority students for inclusion in a summer academic- enrichment program. IDGE builds on the mission of Upward Bound by encouraging underprivileged students to investigate science and scientific careers. This outreach has proven to be successful in enhancing positive attitudes and understanding about science and increasing the number of students considering science careers. IDGE has found that students must be challenged to observe the world around them and to consider how their decisions affect the future of our planet, thus making geoscience relevant and interesting to the students. By making the geoscience course inquiry-based and incorporating field research that is relevant to local environmental issues, it becomes possible for students to bridge the gap between science in theory and science in practice while remaining engaged. Participants were able to broaden environmental connections through an ecological expedition experience to Costa Rica, serving as an opportunity to broaden the vision of students as members of an international community of learners and scientists through their experiences with a diverse natural environment. This trip, in coordination with the inclusion of scientific instruments such as GPS and probeware, fostered additional student interest in earth science. IDGE has shown to have a lasting effect on the participating students who learn from the experience that science is a dynamic field in need of creative minds who want to make discoveries. Through relevant inquiry, the quality of geoscience instruction is inspiring a new generation of geoscientists. This work was supported in part by the National Science Foundation under award 0735596. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.

  3. Space-Based Sensor Web for Earth Science Applications: An Integrated Architecture for Providing Societal Benefits

    NASA Technical Reports Server (NTRS)

    Habib, Shahid; Talabac, Stephen J.

    2004-01-01

    There is a significant interest in the Earth Science research and user remote sensing community to substantially increase the number of useful observations relative to the current frequency of collection. The obvious reason for such a push is to improve the temporal, spectral, and spatial coverage of the area(s) under investigation. However, there is little analysis available in terms of the benefits, costs and the optimal set of sensors needed to make the necessary observations. Classic observing system solutions may no longer be applicable because of their point design philosophy. Instead, a new intelligent data collection system paradigm employing both reactive and proactive measurement strategies with adaptability to the dynamics of the phenomena should be developed. This is a complex problem that should be carefully studied and balanced across various boundaries including: science, modeling, applications, and technology. Modeling plays a crucial role in making useful predictions about naturally occurring or human-induced phenomena In particular, modeling can serve to mitigate the potentially deleterious impacts a phenomenon may have on human life, property, and the economy. This is especially significant when one is interested in learning about the dynamics of, for example, the spread of forest fires, regional to large-scale air quality issues, the spread of the harmful invasive species, or the atmospheric transport of volcanic plumes and ash. This paper identifies and examines these challenging issues and presents architectural alternatives for an integrated sensor web to provide observing scenarios driving the requisite dynamic spatial, spectral, and temporal characteristics to address these key application areas. A special emphasis is placed on the observing systems and its operational aspects in serving the multiple users and stakeholders in providing societal benefits. We also address how such systems will take advantage of technological advancement in small spacecraft and emerging information technologies, and how sensor web options may be realized and made affordable. Specialized detector subsystems and precision flying techniques may still require substantial innovation, development time and cost: we have presented the considerations for these issues. Finally, data and information gathering and compression techniques are also briefly described.

  4. Structural characterization of rare-earth doped soda magnesia alumina silica glasses for holographic storage: Brillouin, Raman and NMR spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Utegulov, Zhandos Nurpeisovich

    Scope and method of study. This work was directed to perform (Brillouin and Raman) light scattering and (29Si, 27Al, 23Na) MAS NMR spectroscopies to study structural, vibrational, elastic, photoelastic and magnetic properties of Eu3+ -doped soda magnesia alumina silica (EDSMAS) glasses as a function of content of individual components: Eu2O3, Al 2O3 and Na2O to provide new knowledge related to the mechanism underlying the formation of holographic gratings in these materials. Findings and conclusions. Europium doping and alumina substitution for silica causes glass to become harder but at the same time more polarizable. In both glass series the enhanced hardness is due to reduction of the free space. In addition, in the former case the europiums have high coordination and enhanced field strength with oxygen atoms. In the latter one, the aluminums entering the glass recover Si-O-Si bridges by attracting charge balancing modifiers from depolymerized SiO4 network. Growing polarizability in Eu- and Al-series is mostly due to depolymerization by Eu 3+ doping and the appearance of AlO4 tetrahedral groups weakly bound to sodium ions, respectively. The Eu3+ ions form the broad distribution of Qn species with possible clustering of rare-earths at large Eu3+ ion concentration, while sodium ions entering the glass cause the formation of rather distinct Qn species. In Na-series the glass becomes more depolymerized although less compressible in the volumetric sense . In this series Na environment is sensitive to the first neighbor Na+ network-modifiers. The overall bonding in all three EDSMAS glass series becomes more polarizable compared to fused silica. The depolymerization (polymerization) of the EDSMAS glass is mainly characterized by the presence of NBOs (BOs) and three (four) member silicate and aluminosilicate rings. Si and Al atoms were found to be in tetrahedrally coordinated sites. No Al was observed in 6- or 5-fold coordinated sites. Lorentz-Lorentz effect was the dominant contribution to the photoelastic constant P 12. The strength of the holographic storage signal is defined by many factors among which the number of the excited Eu3+ ions, the high-energy phonons associated with Si-NBO vibrations, weakly bound Na+ ions charge balancing [AlO4]- complexes and the stability of the traps for the mobile light ions play very important roles.

  5. Laboratory Earth Under the Lens: Diachronic Evaluation of an Integrated Graduate-Level On-Line Earth System Science Course Series for K-12 Educators

    NASA Astrophysics Data System (ADS)

    Low, R.; Gosselin, D. C.; Haney, C.; Larson-Miller, C.; Bonnstetter, R.; Mandryk, C.

    2012-12-01

    Educational research strives to identify the pedagogies that promote student learning. However, the body of research identifying the characteristics of effective teacher preparation is "least strong for science," and is largely based on studies of the effectiveness of individual courses or workshops (NRC 2010). The National Research Council's "Preparing Teachers: Building Evidence for Strong Policy," (2010) provides a mandate for teacher education providers to conduct research on program-scale effectiveness. The high priority research agenda identified by the NRC is expected to elicit understanding of the aspects of teacher preparation that critically impact classroom student learning outcomes. The Laboratory Lens project is designed to identify effective practices in a teacher education program, with specific reference to the content domain of Earth science. Now in its fifth year, the Masters of Applied Science (MAS) program at UNL offers a variety of science courses, ranging from entomology to food science. The six-course Lab Earth series serves as the backbone of the Specialization for Science Educators within the MAS program, and provides comprehensive content coverage of all Earth science topics identified in the AAAS Benchmarks. "How People Learn," (NRC 2009) emphasizes that expert knowledge includes not only factual knowledge, but also the well-developed conceptual framework critical to the ability to, "remember, reason, and solve problems." A focus of our research is to document the process by which the transition from novice to expert takes place in Lab Earth's on-line teacher participants. A feature of our research design is the standardization of evaluation instruments across the six courses. We have used data derived from implementation of the Community of Inquiry Survey (COI) in pilot offerings to ensure that the course sequence is effective in developing a community of learners, while developing their content knowledge. A pre- and post- course Wilcoxan Signed Ranks Test is included in the battery of assessments to ensure that the courses achieve a statistically significant increase in participants' beliefs about their personal science teaching efficacy. The research design also includes the analysis of concept maps and content mastery assignments to assist in documentation of a teacher's transition from mastery of novice to expert knowledge. Content-based, course-specific pre and post knowledge surveys are included in the battery of assessments. In the analysis of on-line discussions, the project employs a textual analysis technique outlined in "The Rhetoric of Social Intervention," (RSI) (Opt and Gring 2009). RSI provides a promising analytical framework, especially when examining the development of understanding of scientific topics with societal implications, such as sustainability and climate change. The session provides a description of the integrated research design and data collection and analysis in the first year of this project.

  6. A Synergy Framework for the integration of Earth Observation technologies into Disaster Risk Reduction

    NASA Astrophysics Data System (ADS)

    Gaetani, Francesco; Petiteville, Ivan; Pisano, Francesco; Rudari, Roberto; St Pierre, Luc

    2015-04-01

    Earth observations and space-based applications have seen a considerable advance in the last decade, and such advances should find their way in applications related to DRR, climate change and sustainable development, including in the indicators to monitor advances in these areas. The post-2015 framework for disaster risk reduction, as adopted by the 3rd WCDRR is a action-oriented framework for disaster risk reduction that builds on modalities of cooperation linking local, national, regional and global efforts. Earth observations from ground and space platforms and related applications will play a key role in facilitating the implementation of the HFA2 and represent a unique platform to observe and assess how risks have changed in recent years, as well as to track the reduction in the level of exposure of communities. The proposed white paper focuses mainly on Earth Observation from space but it also addresses the use of other sources of data ( airborne, marine, in-situ, socio-economic and model outputs) in combination to remote sensing data. Earth observations (EO) and Space-based technologies can play a crucial role in contributing to the generation of relevant information to support informed decision-making regarding risk and vulnerability reduction and to address the underlying factors of disaster risk. For example, long series of Earth observation data collected over more than 30 years already contribute to track changes in the environment and in particular, environmental degradation around the world. Earth observation data is key to the work of the scientific community. Whether due to inadequate land-use policies, lack of awareness or understanding regarding such degradation, or inadequate use of natural resources including water and the oceans; Earth observation technologies are now routinely employed by many Ministries of Environment and Natural Resources worldwide to monitor the extent of degradation and a basis to design and enact new environmental management policies. This White Paper is the premise of a global partnership as a way to enhance the use of Earth observation and Space-based technologies worldwide in the context of the post-2015 disaster risk reduction framework. This document outlines several issues pertaining to such a global partnership including efforts conducted by international stakeholders, recent advances in the use of Earth observation and Space-based technologies, challenges that need to be addressed, policies, and potential aims.

  7. Photoemission from In-situ Rare-Earth-Doped GaN Grown by MBE and MOCVD

    NASA Astrophysics Data System (ADS)

    Steckl, Andrew; Lee, Don; Pan, Ming; Heikenfeld, Jason

    2003-03-01

    of excited RE ions. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. This represents an interesting multi-color emission alternative to conventional bandgap engineering. The deposition of in-situ doped GaN (and AlxGa1-xN:RE ) layers was carried out by MBE and MOCVD. The MBE growth is performed with solid (effusion) sources for group III (Ga, Al) and RE elements (Er, Eu, Tm) and a N2 gas (plasma) source. The MOCVD growth is carried out with MO sources for group III and RE elements and with a hydride (NH3) for group V. The complex relationship between growth mechanisms and RE emission in the GaN layers is becoming better understood. The study of the effects of RE concentration, growth temperature, and III-V ratio on materials properties and on resulting photoemission has led to different models of the relation between growth and RE-based emission mechanisms for MBE- and MOCVD-grown films.

  8. Superconductivity by rare earth doping in the 1038-type compounds (Ca1-xREx) 10(FeAs)10(Pt3As8) with RE=Y, La-Nd, Sm-Lu

    NASA Astrophysics Data System (ADS)

    Strzer, Tobias; Derondeau, Gerald; Bertschler, Eva-Maria; Johrendt, Dirk

    2015-01-01

    We report superconductivity in polycrystalline samples of the 1038-type compounds (Ca1-xREx) 10(FeAs)10(Pt3As8) up to Tc=35 K with RE=Y, La-Nd, Sm, Gd-Lu. The critical temperatures are nearly independent of the trivalent rare earth element used, yielding a common Tc(xRE) phase diagram for electron doping in all these systems. The absence of superconductivity in Eu2+ doped samples, as well as the close resemblance of (Ca1-xREx) 10(FeAs)10(Pt3As8) to the 1048 compound substantiate that the electron doping scenario in the RE-1038 and 1048 phases is analogous to other iron-based superconductors with simpler crystal structures.

  9. Few-mode erbium-doped fiber amplifier design method based on the signal-pump overlap integral

    NASA Astrophysics Data System (ADS)

    Herbster, Adolfo F.; Romero, Murilo A.

    2014-09-01

    Space-division multiplexing allows an increase of link capacity by using either multicore or single-core few-mode (FM) optical fibers. In the case of FM systems, each mode carries its own data stream and long-haul transmission can be hampered by the use of conventional erbium-doped fiber amplifiers (EDFAs), since because of distinct field profile configurations, each mode experiences a different value of optical gain. The role of the FM-EDFA designer, usually done by solving rate and propagation equations, is to define both the fiber cross-section and the pumping configuration to provide the best possible mode equalization of optical gain and noise figure. An optimization method is proposed here based on the definition of a figure of merit related to the equalization of the pump-mode signal overlap integral, significantly reducing computation time and allowing a multiobjective optimization approach. The results obtained were validated against the solution provided by the full set of rate and propagation equations and we conducted an FM-EDFA optimization case study. Our double-ring Er doping profile design requires a single 180-mW LP11 pump to provide a mean gain of 21.3 dB, within 0.6 dB of equalization for each of the four modes considered.

  10. An integrative 'omics' solution to the detection of recombinant human erythropoietin and blood doping.

    PubMed

    Pitsiladis, Yannis P; Durussel, Jérôme; Rabin, Olivier

    2014-05-01

    Administration of recombinant human erythropoietin (rHumanEPO) improves sporting performance and hence is frequently subject to abuse by athletes, although rHumanEPO is prohibited by the WADA. Approaches to detect rHumanEPO doping have improved significantly in recent years but remain imperfect. A new transcriptomic-based longitudinal screening approach is being developed that has the potential to improve the analytical performance of current detection methods. In particular, studies are being funded by WADA to identify a 'molecular signature' of rHumanEPO doping and preliminary results are promising. In the first systematic study to be conducted, the expression of hundreds of genes were found to be altered by rHumanEPO with numerous gene transcripts being differentially expressed after the first injection and further transcripts profoundly upregulated during and subsequently downregulated up to 4 weeks postadministration of the drug; with the same transcriptomic pattern observed in all participants. The identification of a blood 'molecular signature' of rHumanEPO administration is the strongest evidence to date that gene biomarkers have the potential to substantially improve the analytical performance of current antidoping methods such as the Athlete Biological Passport for rHumanEPO detection. Given the early promise of transcriptomics, research using an 'omics'-based approach involving genomics, transcriptomics, proteomics and metabolomics should be intensified in order to achieve improved detection of rHumanEPO and other doping substances and methods difficult to detect such a recombinant human growth hormone and blood transfusions. PMID:24627340

  11. Integrated porous-silicon light-emitting diodes: A fabrication process using graded doping profiles

    SciTech Connect

    Barillaro, G.; Diligenti, A.; Pieri, F.; Fuso, F.; Allegrini, M.

    2001-06-25

    A fabrication process, compatible with an industrial bipolar+complementary metal{endash}oxide{endash}semiconductor (MOS)+diffusion MOS technology, has been developed for the fabrication of efficient porous-silicon-based light-emitting diodes. The electrical contact is fabricated with a double n{sup +}/p doping, achieving a high current injection efficiency and thus lower biasing voltages. The anodization is performed as the last step of the process, thus reducing potential incompatibilities with industrial processes. The fabricated devices show yellow-orange electroluminescence, visible with the naked eye in room lighting. A spectral characterization of light emission is presented and briefly discussed. {copyright} 2001 American Institute of Physics.

  12. The EPOS e-Infrastructure: metadata driven integration of data products and services in solid Earth Science

    NASA Astrophysics Data System (ADS)

    Bailo, Daniele; Jeffery, Keith

    2015-04-01

    The European Plate Observing System (EPOS) is an ambitious long term integration plan addressing the major solid-earth research infrastructures in Europe. For its large scale and extent it is an unique initiative which will foster new scientific discoveries and enable scientists to investigate the solid earth system with unprecedented ways. A key aspect of EPOS is to provide end-users with homogeneous access to services and multidisciplinary data collected by monitoring infrastructures and experimental facilities as well as access to software, processing and visualization tools. Such a complex system requires a solid, scalable and reliable architecture in order to accommodate innovative features and to meet the evolving expectations of the heterogeneous communities involved.

  13. Magnetization dynamics in rare earth Gd3+ doped Mn(0.5)Zn(0.5)Fe2O4 magnetic fluid: electron spin resonance study.

    PubMed

    Parekh, Kinnari; Upadhyay, R V

    2012-12-01

    The electron spin resonance (ESR) technique has been applied to study the spin dynamics in broad temperature range for rare earth doped Mn(0.5)Zn(0.5)Fe(1.9)Gd(0.1)O(4) (MZG5) magnetic fluid. Zero field cooled (ZFC) ESR spectra of MZG5 fluid exhibit an isotropic shift in the resonance field below 40 K, while the field cooled (FC) ESR spectra show a deviation from sin(2)? behavior and an angle dependent hysteresis, this unambiguously points to the dominating unidirectional freezing of surface spins below 40 K. Above 60 K, the resonance field exhibits sin(2)? behavior, indicating the uniaxial anisotropy contribution of core spin. This indicates that surface spin freezing temperature is around 40 K. The presence of surface spin freezing and the coupling between core and surface spins are further supported by cycle dependent FC ESR spectra measured at 20 K, which show the systematic increase in resonance field (H(res)) and intensity. The double peak behavior of blocking temperature distribution retrieved from ZFC-FC magnetization measurement is an additional corroboration of the existence of surface spin glass like layer. PMID:23123769

  14. Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

    2002-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

  15. Calcium tetraboride-does it exist? Synthesis and properties of a carbon-doped calcium tetraboride that is isotypic with the known rare earth tetraborides.

    PubMed

    Schmitt, Ruth; Blaschkowski, Bjrn; Eichele, Klaus; Meyer, H-Jrgen

    2006-04-01

    Crystalline samples of carbon-doped CaB4 were synthesized by solid-state reactions in sealed niobium ampules from the elements Ca, B, and C. The structure was determined by single-crystal X-ray diffraction (P4/mbm, Z = 4, a = 7.0989(7) A, c = 4.1353(5) A, R1 = 0.026, and wR2 = 0.058) revealing an atom arrangement containing a three-dimensional boron network built up from B6 octahedra and B2 dumbbells which is well-known from the structures of rare earth tetraborides. Crystals of CaB(4-x)Cx are black with a metallic luster and behave stable against mineral acids. Band structure calculations indicate that CaB4 is a stable semiconducting compound with a narrow band gap and that carbon should not necessarily be required for the stability of this compound. The presence of carbon in the crystalline samples of CaB(4-x)Cx was indicated by electron energy loss spectroscopy, but the carbon content in the samples was estimated to be less than 5% according to inductively coupled plasma-atomic emission spectrometry measurements. The distribution of boron and carbon atoms in the structure was investigated by means of 11B and 13C solid-state magic angle spinning NMR. Measurements of the magnetic susceptibility indicate a temperature-independent paramagnetism down to 20 K. PMID:16562963

  16. Continuous monitoring of a large active earth flow using an integrated GPS - automatic total station approach

    NASA Astrophysics Data System (ADS)

    Corsini, A.

    2009-04-01

    Landslide monitoring has evolved as a crucial tool in civil protection to mitigate and prevent disasters. The research presents an approach to continuous monitoring of a large-scale active earth flow using a system that integrates surface measurements obtained by a GPS and an automatic total station. With the data obtained from the system the landslide can be monitored in near-real-time and surface displacements can be directly utilized to provide early warning of slope movements and to study the behavior of the landslide, e.g. to predict timing and mechanisms of future failure. The Valoria landslide located in the northern Apennines of Italy was reactivated in 2001, 2005 and 2007 damaging roads and endangering houses. A monitoring system was installed in 2007-2008 in the frame of a civil protection plan aimed at risk mitigation. The system consists of an automatic total station measuring about 40 prisms located in the landslide to a maximum distance of 1.800 km; one double-frequency GPS receiver connects in streaming by wireless communication with 4 single-frequency GPS in side the flow. Until December 2007 the monitoring network was operated with periodic static surveying followed by the data post-processing. From September 2007 until March 2008 the landslide deformation was evaluated by periodic surveys with the total station and the GPS system. This first measure showed that the displacements were influenced by the rainfall events and by the snow melting. The total displacements measured vary from centimeter scale in the crown zone, where retrogressive movements were in progress, to over 50 m in the flow track zone. Starting in March 2008 data acquisition by the total station system and GPS were automated in order to allow continuous and near-real-time data processing. The displacement data collected in one and a half year of continuous operation show different acceleration and deceleration phases as a result of the pore water pressure distribution inside the landslide. From March 2008, the total station and the GPS receiver were predisposed for the continuous monitoring. The successive deformation continued constantly and some monitored points recorded decimeter of cumulative displacements in May. In June the displacements progressively decreased due to the absence of the precipitation. Abundant rainfalls in July 2008 (200 mm of rainfall in 50 days) drove a new instability in the landslide. As a result some landslide sectors experienced accelerations measuring total displacements between one decimeter and ten meters in 20 days. Following this event acceleration was recorded at the end of October 2008, when 550 mm of cumulative rain fell in 40 days. During this event the velocity of the material varied between cm/day to m/day and the maximum reacted displacement was 15 m. Through the monitoring with data acquisition every 3 hours it was also possible to evaluate the continuous transfer of mass from the upper part of the slope to lower part. Measurements showed the reactivation of a downslope portion only one day after reactivation occurred upslope at a distance 200 m. The utilized monitoring system has proven reliable for continuous monitoring of an active earth flow with large deformations ranging up to meters for day also during the paroxysmal phases. Moreover, the complex behavior of the flow in the active phase and in each acceleration and deceleration phase was highlighted. For instance, the timing and intensity of movement propagation downslope as an effect of mass transfer and successive loading of lower slope portions was evidenced many times. This information cannot be obtained with borehole monitoring systems which are normally damaged when displacement exceeds some decimeters, nor can it be computed with comparable spatial coverage and data availability timing using other high precision methods, such as laser scanners or ground-based SAR. Another advantage of the adopted monitoring approach over other techniques is the wide angle of operation provided by the strategically beneficial location of the master

  17. CVT/GPL phase 2 integrated testing. [in earth observations, space physics, and material sciences

    NASA Technical Reports Server (NTRS)

    Shurney, R. E.; Maybee, G.; Schmitt, S.

    1974-01-01

    Experiments representing earth observations, space physics, and material sciences disciplines were installed in the General Purpose Laboratory (GPL). The experiments and the GPL are described. The experiments interfaces the GPL and GPL support systems are assessed. The experiments were cloud physics, ionospheric disturbances, material sciences, high energy astronomy, and superfluid helium.

  18. Learning in the Middle School Earth Science Classroom: Students Conceptually Integrate New Knowledge Using Intelligent Laserdiscs.

    ERIC Educational Resources Information Center

    Freitag, Patricia K.; Abegg, Gerald L.

    A study was designed to describe how middle school students select, link, and determine relationships between textual and visual information. Fourteen authoring groups were formed from both eighth-grade earth science classes of one veteran teacher in one school. Each group was challenged to produce an informative interactive laservideodisc project

  19. "Space on Earth:" A Learning Community Integrating English, Math, and Science

    ERIC Educational Resources Information Center

    Fortna, Joanna; Sullivan, Jim

    2010-01-01

    Imagine a mathematics instructor and English instructor sharing an office; scribbled equations litter one desk, snatches of poetry the other. Our learning community, "Space on Earth," grew from conversations in just such an office where we bridged our own disciplinary gap and discovered a shared passion for helping students apply the concepts and

  20. Use of Persistent Identifiers to link Heterogeneous Data Systems in the Integrated Earth Data Applications (IEDA) Facility

    NASA Astrophysics Data System (ADS)

    Hsu, L.; Lehnert, K. A.; Carbotte, S. M.; Arko, R. A.; Ferrini, V.; O'hara, S. H.; Walker, J. D.

    2012-12-01

    The Integrated Earth Data Applications (IEDA) facility maintains multiple data systems with a wide range of solid earth data types from the marine, terrestrial, and polar environments. Examples of the different data types include syntheses of ultra-high resolution seafloor bathymetry collected on large collaborative cruises and analytical geochemistry measurements collected by single investigators in small, unique projects. These different data types have historically been channeled into separate, discipline-specific databases with search and retrieval tailored for the specific data type. However, a current major goal is to integrate data from different systems to allow interdisciplinary data discovery and scientific analysis. To increase discovery and access across these heterogeneous systems, IEDA employs several unique IDs, including sample IDs (International Geo Sample Number, IGSN), person IDs (GeoPass ID), funding award IDs (NSF Award Number), cruise IDs (from the Marine Geoscience Data System Expedition Metadata Catalog), dataset IDs (DOIs), and publication IDs (DOIs). These IDs allow linking of a sample registry (System for Earth SAmple Registration), data libraries and repositories (e.g. Geochemical Research Library, Marine Geoscience Data System), integrated synthesis databases (e.g. EarthChem Portal, PetDB), and investigator services (IEDA Data Compliance Tool). The linked systems allow efficient discovery of related data across different levels of granularity. In addition, IEDA data systems maintain links with several external data systems, including digital journal publishers. Links have been established between the EarthChem Portal and ScienceDirect through publication DOIs, returning sample-level objects and geochemical analyses for a particular publication. Linking IEDA-hosted data to digital publications with IGSNs at the sample level and with IEDA-allocated dataset DOIs are under development. As an example, an individual investigator could sign up for a GeoPass account ID, write a proposal to NSF and create a data plan using the IEDA Data Management Plan Tool. Having received the grant, the investigator then collects rock samples on a scientific cruise from dredges and registers the samples with IGSNs. The investigator then performs analytical geochemistry on the samples, and submits the full dataset to the Geochemical Resource Library for a dataset DOI. Finally, the investigator writes an article that is published in Science Direct. Knowing any of the following IDs: Investigator GeoPass ID, NSF Award Number, Cruise ID, Sample IGSNs, dataset DOI, or publication DOI, a user would be able to navigate to all samples, datasets, and publications in IEDA and external systems. Use of persistent identifiers to link heterogeneous data systems in IEDA thus increases access, discovery, and proper citation of hard-earned investigator datasets.

  1. Modeling the globally-integrated spectral variability of the Archean Earth: The purple planet

    NASA Astrophysics Data System (ADS)

    Palle, E.; Sanroma, E.; Parenteau, M. N.; Kiang, N. Y.; Gutierrez-Navarro, A. M.; Lopez, R.; Montaes-Rodrguez, P.

    2014-03-01

    Ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected and the efforts of future missions are aimed at the discovery, and perhaps characterization, of small rocky exoplanets within the habitable zone of their stars. Clearly, what we know about our planet will be our guideline for the characterization of such planets. But the Earth has been inhabited for at least 3.8 Gyr and its appearance has changed with time. Here, we have studied the Earth during the Archean eon, 3 Gyr ago. At that time, one of the more widespread life forms on the planet were purple bacteria. These bacteria are photosynthetic microorganisms and can inhabit both aquatic and terrestrial environments. Here, we use a radiative transfer model to simulate the visible and near-infrared radiation reflected by our planet, taking into account several scenarios regarding the possible distribution of purple bacteria over continents and oceans. We find that purple bacteria have a reflectance spectrum that has a strong reflectivity increase, similar to the red edge of leafy plants, although shifted redward. This feature produces a detectable signal in the disk-averaged spectra of our planet, depending on cloud amount and bacteria concentration/ distribution. We conclude that by using multi-color photometric observations, it is possible to distinguish between an Archean Earth in which purple bacteria inhabit vast extensions of the planet and a present-day Earth with continents covered by deserts, vegetation, or microbial mats.

  2. Gamma ray spectroscopy employing divalent europium-doped alkaline earth halides and digital readout for accurate histogramming

    DOEpatents

    Cherepy, Nerine Jane; Payne, Stephen Anthony; Drury, Owen B; Sturm, Benjamin W

    2014-11-11

    A scintillator radiation detector system according to one embodiment includes a scintillator; and a processing device for processing pulse traces corresponding to light pulses from the scintillator, wherein pulse digitization is used to improve energy resolution of the system. A scintillator radiation detector system according to another embodiment includes a processing device for fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times and performing a direct integration of fit parameters. A method according to yet another embodiment includes processing pulse traces corresponding to light pulses from a scintillator, wherein pulse digitization is used to improve energy resolution of the system. A method in a further embodiment includes fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times; and performing a direct integration of fit parameters. Additional systems and methods are also presented.

  3. Mitochondrial potential (??m) changes in single rat hepatocytes: the effect of orthovanadate nanoparticles doped with rare-earth elements.

    PubMed

    Kavok, Nataliya S; Averchenko, Katherine A; Klochkov, Vladimir K; Yefimova, Svetlana L; Malyukin, Yuri V

    2014-12-01

    Rare-earth-based nanoparticles (NPs) are widely used as fluorescent probes for imaging in vitro and in vivo. One of the challenges that restrain NPs applications in biomedical research is their effect on subcellular structures. In this paper, the ability of lanthanide NPs to affect the cellular oxidative balance and alter the mitochondrial function was analyzed. Since size and shape mutually affect the cellular internalization and intracellular distribution of NPs, the investigations were performed with NPs of spherical (GdYVO4:Eu(3+), spindle-(GdVO4: Eu(3+) and rod-like (LaVO4: Eu(3+) shapes. Quantitative microfluorimetry with JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine iodide) as a mitochondrial probe was used for monitoring of the mitochondrial transmembrane potential (?? m) in single living cells. Changes in the ratio of the JC-1 probe fluorescence were used to analyze the NPs effect on ??(m). The fastest suppressive effect (within 1 hour) was found for spherical NPs. Gradual lowering of ??(m) was observed at the exposure of cells within 24 hours for all types of NPs. Exogenous thiols were required for ??(m) protection. The protective role of exogenous glutathione (GSH) proves that the increase of reactive oxygen species (ROS) formation with depletion of GSH can mediate NPs toxicity. The dynamics of the shape-dependent effect can be explained by the features of NPs transportation into cells. PMID:25533054

  4. Enhancement of Cerenkov Luminescence Imaging by Dual Excitation of Er3+, Yb3+-Doped Rare-Earth Microparticles

    PubMed Central

    Xu, Feng; Feng, Ailing; Zhao, Ying; Lu, Tianjian; Yang, Weidong; Wang, Zhe; Lin, Min; Wang, Jing

    2013-01-01

    Cerenkov luminescence imaging (CLI) has been successfully utilized in various fields of preclinical studies; however, CLI is challenging due to its weak luminescent intensity and insufficient penetration capability. Here, we report the design and synthesis of a type of rare-earth microparticles (REMPs), which can be dually excited by Cerenkov luminescence (CL) resulting from the decay of radionuclides to enhance CLI in terms of intensity and penetration. Methods: Yb3+- and Er3+- codoped hexagonal NaYF4 hollow microtubes were synthesized via a hydrothermal route. The phase, morphology, and emission spectrum were confirmed for these REMPs by power X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectrophotometry, respectively. A commercial CCD camera equipped with a series of optical filters was employed to quantify the intensity and spectrum of CLI from radionuclides. The enhancement of penetration was investigated by imaging studies of nylon phantoms and nude mouse pseudotumor models. Results: the REMPs could be dually excited by CL at the wavelengths of 520 and 980 nm, and the emission peaks overlaid at 660 nm. This strategy approximately doubled the overall detectable intensity of CLI and extended its maximum penetration in nylon phantoms from 5 to 15 mm. The penetration study in living animals yielded similar results. Conclusions: this study demonstrated that CL can dually excite REMPs and that the overlaid emissions in the range of 660 nm could significantly enhance the penetration and intensity of CL. The proposed enhanced CLI strategy may have promising applications in the future. PMID:24205030

  5. Integration of multi-discipline data processing for earth observing systems

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph; Chase, Robert

    1987-01-01

    The first steps taken to ensure the controlled evolution of existing facilities toward greater interoperability and sharing of resources among NASA-supported earth science and applications data systems (ESADS) are described. Recommendations made by the various panels during the 1987 ESADS Workshop are presented. The panels were concerned with directories and catalogs, data archives, data manipulation software, computational facilities, data storage media, database management, and networking. Consideration was also given to the tracking and tuning of overall development and management coordination issues.

  6. Sun-, Earth- and Moon-integrated simulation ray tracing for observation from space using ASAP

    NASA Astrophysics Data System (ADS)

    Breault, Robert P.; Kim, Sug-Whan; Yang, Seul-Ki; Ryu, Dongok

    2014-09-01

    The Space Optics Laboratory at Yonsei University, Korea, in cooperation with Breault Research Organization (BRO) in Tucson, Arizona, have invested significant research and development efforts into creating large scale ray tracing techniques for simulating "reflected" light from the earth with an artificial satellite. This presentation describes a complex model that combines the sun, the earth and an orbiting optical instrument combined into a real scale nonsequential ray tracing computation using BRO's Advanced Systems Analysis Program, ASAP. The Sun is simulated as a spherically emitting light source of 695,500 km in diameter. The earth also is simulated as a sphere with its characteristics defined as target objects to be observed and defined with appropriate optical properties. They include the atmosphere, land and ocean elements, each having distinctive optical properties expressed by single or combined characteristics of refraction, reflection and scattering. The current embodiment has an atmospheric model consisting of 33 optical layers, a land model with 6 different albedos and the ocean simulated with sun glint characteristics. A space-based optical instrument, with an actual opto-mechanical prescription, is defined in an orbit of several hundreds to thousands of miles in altitude above the earth's surface. The model allows for almost simultaneous evaluations of the imaging and radiometric performances of the instrument. Several real-life application results are reported suggesting that this simulation approach not only provides valuable information that can greatly improve the space optical instrument performance but also provides a simulation tool for scientists to evaluate all phases of a space mission.

  7. [Study on CuO-CeO2 catalysts doped with alkali and alkaline earth metal oxides by in-situ DRIFTS].

    PubMed

    Zou, Han-Bo; Chen, Sheng-Zhou; Wang, Qi-Ying; Liu, Zi-Li; Lin, Wei-Ming

    2010-03-01

    CuO-CeO2 series catalysts are the effective catalysts for the selective CO oxidation in hydrogen-rich gas. The adsorption species on the CuO-CeO2 catalysts doped with alkali and alkaline earth metal oxides were investigated with in situ diffuse reflectance FTIR spectroscopy (in-situ DRIFTS) technique. The results showed that a bane at 2 106 cm(-1), due to the carbonyl species, appeared on the CuO-CeO2 catalysts. In the reaction atmosphere, the intensity of this band increased first and then decreased with increasing the temperatures. It was noted that the main active adsorption sites of the CuO-CeO2 catalysts were Cu+ species. At lower temperatures, the carbonyl species were desorbed from the surface of CuO-CeO2 catalysts in the reversible form, while they were desorbed mainly in the irreversible form at the higher temperatures. A sharp peak at 3 660 cm(-1), attributed to the geminal Ce(OH)2 group, was also apparent on the surface of reduced CuO-CeO2 catalyst. The peaks at 1 568, 2 838 and 2 948 cm(-1) were attributed to formate species and the peaks centered at 1 257 and 1 633 cm(-1) were assigned to carbonate species. CO could react with the active hydroxyl species and generate formate species. At higher temperatures, the C-H bond of formate species could break and form carbonate species. These two species would decrease the performance of CuO-CeO2 catalysts at higher temperatures. The stronger IR peaks attributed to CO2 and formate species were observed, moreover there was still a weak IR peak assigned to carbonyl species for Cu1 Li1 Ce9Odelta catalyst when the temperature was above 180 degrees C. It was shown that as the electron donor, the doping of Li2 O on CuO-CeO2 catalyst could contribute to the irreversible desorption of CO at lower temperatures and inhibit the adsorption of H2 on the catalytic surface, and benefit the formation of formate species as well. Although the amounts of CO adsorption on Cu1 Mg1 Ce9 Odelta and Cu1 Ba1 Ce9 Odelta catalysts were much more than other catalysts at lower temperatures, they were mainly desorbed in the reversible form, which had no contribution to the selective CO oxidation. PMID:20496684

  8. Integrated Earth Science Research in Deep Underground Science and Engineering Laboratories

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Hazen, T. C.; Conrad, M. E.; Johnson, L. R.; Salve, R.

    2004-12-01

    There are three types of sites being considered for deep-underground earth science and physics experiments: (1) abandoned mines (e.g., the Homestake Gold Mine, South Dakota; the Soudan Iron Mine, Minnesota), (2) active mines/facilities (e.g., the Henderson Molybdenum Mine, Colorado; the Kimballton Limestone Mine, Virginia; the Waste Isolation Pilot Plant [in salt], New Mexico), and (3) new tunnels (e.g., Icicle Creek in the Cascades, Washington; Mt. San Jacinto, California). Additional sites have been considered in the geologically unique region of southeastern California and southwestern Nevada, which has both very high mountain peaks and the lowest point in the United States (Death Valley). Telescope Peak (along the western border of Death Valley), Boundary Peak (along the California-Nevada border), Mt. Charleston (outside Las Vegas), and Mt. Tom (along the Pine Creek Valley) all have favorable characteristics for consideration. Telescope Peak can site the deepest laboratory in the United States. The Mt. Charleston tunnel can be a highway extension connecting Las Vegas to Pahrump. The Pine Creek Mine next to Mt. Tom is an abandoned tungsten mine. The lowest levels of the mine are accessible by nearly horizontal tunnels from portals in the mining base camp. Drainage (most noticeable in the springs resulting from snow melt) flows (from the mountain top through upper tunnel complex) out of the access tunnel without the need for pumping. While the underground drifts at Yucca Mountain, Nevada, have not yet been considered (since they are relatively shallow for physics experiments), they have undergone extensive earth science research for nearly 10 years, as the site for future storage of nation's spent nuclear fuels. All these underground sites could accommodate different earth science and physics experiments. Most underground physics experiments require depth to reduce the cosmic-ray-induced muon flux from atmospheric sources. Earth science experiments can be spatially extensive, from sub-room-size scale to ten-kilometer scale. The DUSEL sites with vertical depth and lateral extent can accommodate many different experiments. Hydrologic studies can characterize the in-flow along drifts, ramps, and shafts. Geophysical and rock mechanics studies can have seismic and electromagnetic sensors stationed on site, for both local monitoring of excavations and long-term stability, and mine-scale network of sensors to form a large aperture for tomography imaging. The geo-biochemical studies can include the ecological evaluation of the effects of introduced materials and the search for the origin of life in isolated fluid pockets at depth. The muon flux can be measured underground to detect empty space (or lack of it) above detectors, as demonstrated at the Chephren pyramid, Egypt, in the 1970s and currently at the Pyramid of the Sun, Mexico. Conventional geophysical tomography, with wave propagation through rock mass, can be extended to include particle rays, with high-energy muon flux as an example. Muons interacting with atoms have implications for both geochemical and biological processes. This type of research can further promote collaboration between earth scientists with physicists. A deep laboratory can accommodate a deep campus for suites of physics detectors, and several campuses at different depths within the same site for earth science experiments in rock mechanics, hydrology, geochemistry, ecology, geo-microbiology, coupled processes, and many other branches of earth and planetary sciences.

  9. Integrating Real-time, Real-world Geoscience Experiences into Classroom Instruction with EarthLabs and the JOIDES Resolution

    NASA Astrophysics Data System (ADS)

    Mote, A. S.; Lockwood, J.; Ellins, K. K.; Haddad, N.; Cooper, S. K.; Ledley, T. S.

    2013-12-01

    Inspiring the next generation of geoscientists and preparing students for the 21st century workforce requires lifting science outside of the classroom and giving learners the opportunity to think critically about real-world geoscience problems. The EarthLabs suite of climate science modules challenges students with a variety of learning experiences including current scientific data analysis, computer visualizations, satellite imagery, and engaging videos. Each module includes a series of hands-on activities to allow students to explore Earth's complex and dynamic climate history, leading to a deeper understanding of present and future changes to our planet. A new EarthLabs module in development 'Climate Detectives: An Expedition on board the JOIDES Resolution," focuses on Integrated Ocean Drilling Program (IODP) Expedition 341 to Southern Alaska. The module is structured to allow students to work collaboratively, mimicking scientific research groups on the JOIDES Resolution. As students assume the role of a scientist, learn about data collection methods, and analyze authentic data, they learn about the climate history and tectonic processes of the Southern Alaska continental margin, as well as explore the relationship between climate, sedimentation, and tectonics. The Project Based Learning (PBL) approach used in the module teaches students how to analyze data and solve problems like scientists, strengthening the development of higher order thinking skills and preparing them for college coursework. The 'Climate Detectives' Module also provides students with opportunities to interact with scientists through live video conferencing and pre-recorded video presentations by scientists. In this presentation, Expedition 341 Education Officer, Alison Mote, describes the new module, which takes students on an educational journey as they learn about the scientific objectives, methods, and data collection tools scientists use to conduct research on sediment cores retrieved from beneath the seafloor in the Gulf of Alaska during summer 2013. Students discover how we know what we know about the Earth through the lens of scientific ocean drilling.

  10. Electrically tunable fiber-integrated Yb-doped laser covering 74 nm based on a fiber Bragg grating array

    NASA Astrophysics Data System (ADS)

    Tiess, T.; Rothhardt, M.; Chojetzki, C.; Jger, M.; Bartelt, H.

    2015-03-01

    Fiber lasers provide the foundation to combine an excellent beam quality in single mode operation with a robust and highly efficient design. Based on fiber-integrated configurations, they are employed in many different applications ranging from industry over research to medical technology. However, there is lots of potential to approach even new fields of applications e.g. in spectroscopy based on tunable systems with an adjustable emission wavelength. We present a novel tuning concept for pulsed fiber-integrated laser systems using an array of fiber Bragg gratings (FBGs) as discrete spectral filter. Based on stacking many standard FBGs, the bandwidth and filter properties are easy to scale by increasing the number of gratings allowing huge tuning ranges as well as tailored tuning characteristics. In this work, we demonstrate the potential of this electrically controlled tuning concept. Using an Ytterbium (Yb)-doped fiber laser, we investigate the general tuning characteristics. With variable pulse durations in the nanosecond regime, we demonstrate high signal contrast (~45 dB), excellent wavelength stability and narrow linewidth (<15 GHz). In order to highlight the great spectral freedom, a tuning range of 74 nm in the Yb band is realized which, to the best of our knowledge, is the largest bandwidth reported based on a monolithic filter design.

  11. On an improved sub-regional water resources management representation for integration into earth system models

    SciTech Connect

    Voisin, Nathalie; Li, Hongyi; Ward, Duane L.; Huang, Maoyi; Wigmosta, Mark S.; Leung, Lai-Yung R.

    2013-09-30

    Human influence on the hydrologic cycle includes regulation and storage, consumptive use and overall redistribution of water resources in space and time. Representing these processes is essential for applications of earth system models in hydrologic and climate predictions, as well as impact studies at regional to global scales. Emerging large-scale research reservoir models use generic operating rules that are flexible for coupling with earth system models. Those generic operating rules have been successful in reproducing the overall regulated flow at large basin scales. This study investigates the uncertainties of the reservoir models from different implementations of the generic operating rules using the complex multi-objective Columbia River Regulation System in northwestern United States as an example to understand their effects on not only regulated flow but also reservoir storage and fraction of the demand that is met. Numerical experiments are designed to test new generic operating rules that combine storage and releases targets for multi-purpose reservoirs and to compare the use of reservoir usage priorities, withdrawals vs. consumptive demand, as well as natural vs. regulated mean flow for calibrating operating rules. Overall the best performing implementation is the use of the combined priorities (flood control storage targets and irrigation release targets) operating rules calibrated with mean annual natural flow and mean monthly withdrawals. The challenge of not accounting for groundwater withdrawals, or on the contrary, assuming that all remaining demand is met through groundwater extractions, is discussed.

  12. Integrated Solid Earth Science: the right place and time to discover the unexpected? (Arthur Holmes Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Cloetingh, Sierd

    2013-04-01

    The fascination of learning more about the way system Earth operates has driven generations of Earth scientists. This has been the case for early pioneers such as Arthur Holmes, focusing on the geological record in continental settings, as well as for the founding fathers of plate tectonics, who built upon the results of exploring the ocean floor. Two years ago we celebrated the centenary of the discovery by Mohorovicic of the seismic discontinuity that separates the crust from the mantle, which now carries his name. Reading the rocks and mapping the (sub)surface of the Earth has provided the foundation for a great deal of what we conceptually pursue today in developing and validating coupled deep Earth and surface processes. The unexpected is probably characterizing most of my scientific career. It started in 1968 when, as a student, entering the geology program of Groningen University headed by Professor Philip Kuenen, a pioneer in marine geology and sedimentology, the textbook of Arthur Holmes just happened to be my first purchase. It was during those years that plate tectonics drastically changed everything we were learning. I was also privileged to enter a few years later as an MSc student the Utrecht geophysics school at a time where Nico Vlaar as a young professor was developing a vigorous research program with a focus on seismology, attracting and stimulating many talented students. When he and Rinus Wortel started research on Tectonophysics in Utrecht, I decided to go for a PhD research project tackling the problem of the initiation of subduction, a first order problem in geodynamics, with still many aspects to be resolved. This research and the joint work with Rinus Wortel on modeling intraplate stresses in the Faralon, Nazca and Indo-Australian plates led quite unexpectedly to exploring, together with Kurt Lambeck, intraplate stress fluctuations in the lithosphere as possible tectonic causes for the origin of third-order cycles in relative sea-level. Those cycles were detected as a result of the pioneering work on the stratigraphic record of sedimentary basins and continental margins from all over the world by Peter Vail, Bilal Haq and others from Exxon. It was at this time, that sedimentary basins became a frontier in the integration of quantitative geology and geophysics. Sedimentary basins do not only provide a powerful source of information on the evolution of the underlying lithosphere and climate fluctuations, but also contain mankind's main reservoirs of geo-energy and geo-resources. It was Peter Ziegler, head of global geology at Shell International, who was the prime mentor in my somewhat unexpected scientific journey in sedimentary basins. These became the main research target of the Tectonics research group I established in 1988 in Amsterdam. In these years it became increasingly evident that the rheology of the lithosphere exerts a crucial control on the evolution of basins, but also on continental topography. It is on this topic that the cooperation over more than two decades with Evgenii Burov, addressing issues like the rheological structure of Europe's lithosphere, rift shoulder uplift and the interplay of lithospheric folding and mantle-lithosphere interactions, has, been very fruitful. Another unexpected milestone has been the opportunity to build up, parallel to the research efforts in field studies and numerical modeling, an analogue tectonic laboratory in our group. This brings me to another issue, also completely unforeseen: the integration of earth science in Europe, particularly taking off after the disappearance of the Iron Curtain. For my group, the latter marked the beginning of a very fruitful cooperation in particular with the groups of Frank Horvath in Budapest and Cornel Dinu in Bucharest, addressing the fascinating solid Earth dynamics of the Carpathians and Pannonian basin. Over the last few years, it has been become evident that integration in the solid earth science is the way to go. Not only on a national level, such as pursued by the Netherlands Research School of Integrated Solid Earth Science (ISES), but also on a full European scale, such as the TOPO-EUROPE research program. This goes hand in hand with setting the stage for a pan-European research infrastructure for solid earth science by the European Plate Observing System (EPOS). Much of the unexpected remains to be discovered. The Holmes medal awarded by the European Geosciences Union, itself an example of the immense progress European earth scientists have made in joining forces, means a lot to me. I share it with my co-workers in my group, the close to 70 PhD students who worked with us, and other numerous colleagues and friends that all contributed immensely to the unexpected.

  13. Discover Earth

    NASA Technical Reports Server (NTRS)

    Steele, Colleen

    1998-01-01

    Discover Earth is a NASA-sponsored project for teachers of grades 5-12, designed to: (1) enhance understanding of the Earth as an integrated system; (2) enhance the interdisciplinary approach to science instruction; and (3) provide classroom materials that focus on those goals. Discover Earth is conducted by the Institute for Global Environmental Strategies in collaboration with Dr. Eric Barron, Director, Earth System Science Center, The Pennsylvania State University; and Dr. Robert Hudson, Chair, the Department of Meteorology, University of Maryland at College Park. The enclosed materials: (1) represent only part of the Discover Earth materials; (2) were developed by classroom teachers who are participating in the Discover Earth project; (3) utilize an investigative approach and on-line data; and (4) can be effectively adjusted to classrooms with greater/without technology access. The Discover Earth classroom materials focus on the Earth system and key issues of global climate change including topics such as the greenhouse effect, clouds and Earth's radiation balance, surface hydrology and land cover, and volcanoes and climate change. All the materials developed to date are available on line at (http://www.strategies.org) You are encouraged to submit comments and recommendations about these materials to the Discover Earth project manager, contact information is listed below. You are welcome to duplicate all these materials.

  14. Effect of Knowledge Integration Activities on Students' Perception of the Earth's Crust as a Cyclic System.

    ERIC Educational Resources Information Center

    Kali, Yael; Orion, Nir; Eylon, Bat-Sheva

    2003-01-01

    Characterizes students' understanding of the rock cycle system. Examines effects of a knowledge integration activity on their system thinking. Interprets answers to an open-ended test using a systems thinking continuum ranging from a completely static view of the system to an understanding of the system's cyclic nature. Reports meaningful

  15. Effect of Knowledge Integration Activities on Students' Perception of the Earth's Crust as a Cyclic System.

    ERIC Educational Resources Information Center

    Kali, Yael; Orion, Nir; Eylon, Bat-Sheva

    2003-01-01

    Characterizes students' understanding of the rock cycle system. Examines effects of a knowledge integration activity on their system thinking. Interprets answers to an open-ended test using a systems thinking continuum ranging from a completely static view of the system to an understanding of the system's cyclic nature. Reports meaningful…

  16. MEOS Microsatellite Earth Observation using Miniature Integrated-Optic IR Spectrometers

    NASA Astrophysics Data System (ADS)

    Kruzelecky, Roman

    Our planetary atmosphere helps to regulate the Earth's thermal budget and the resulting global climate by controlling the energy balance between the incident solar radiation and the thermal emission to space from the Earth's atmosphere and surface. Certain atmospheric gases, most importantly H2 O vapour and CO2 , can absorb some of the Earth's emitted IR radiation and trap it in the atmosphere to provide an atmospheric greenhouse effect that currently adds about 38 K to the Earth's mean surface temperature. The associated greenhouse gas (GHG) and water cycles are a complex balance of interactions among surface ecosystems and atmospheric processes. The natural water and carbon cycles are being measurably disrupted by anthropogenic activities. Since the industrial revolution, significant anthropogenic sources of greenhouse gases and aerosols have evolved, while natural sinks, such as forests and wetlands, are being destroyed. Changes in the land cover affect the balance of GHG sources and sinks, as well as the Albedo and resultant surface temperature. Water vapour, the most abundant GHG, is affected indirectly though the influence of aerosols on cloud formation and precipitation patterns, and directly through the influence of surface temperatures on the water evaporation rates. There is also positive feedback between the water and carbon cycles. For example, drought can result in desertification with subsequent release of stored carbon. It is clear that the common thread in all of these climate-related effects is the interaction between the surface ecosystems and the carbonand nitrogen-containing gases in the lower troposphere. Uptake of CO2 by growing vegetation, release of CH4 and N2 O by soil processes, and the effects of carbon and water cycle chemistry all interact strongly in a system that is both ex-tremely complex and poorly understood at the present time. In order to quantify these processes and provide a clearer prediction of their likely effects in the future, the MEOS Miniature Earth Observing Satellite will innovatively combine remote atmospheric/land-cover measurements with ecosystem modelling in near real-time to obtain simultaneous variations in lower tropospheric GHG mixing ratios and the resulting responses of surface ecosystems. MEOS will provide lower tropospheric CO2 , CH4 , CO, N2 O, H2 O and aerosol mixing ratios over natural sources and sinks using two kinds of synergistic observations; a forward limb measurement and a follow-on nadir measurement over the same geographical tangent point. The measurements will be accomplished using separate limb and nadir suites of miniature lineimaging spectrometers and will be spatially coordinated such that the same air mass is observed in both views within a few minutes. The limb data will consist of 16-pixel vertical spectral line imaging to provide 2.5-km vertical resolution, while the corresponding nadir measurements will view sixteen 5 by 10 km2 ground pixels with a 160-km East-West swath width. The separate limb and nadir instrument suites each feature two complementary NIR miniature spectrometers that will operate in parallel, alternating the collected optical signal between the high-resolution Fabry-Perot guided-wave FP-IOSPEC spectrometer with simultaneous multiple microchannels at 0.03 FWHM with SNR>400 and the 1220 to 2450 nm broad-band spectrometer with 1.2 nm FWHM such that one undergoes the illuminated segment of the processing while the other spectrometer undergoes its dark signal processing. This spectral region provides several harmonic optical absorption bands associated with CO2 , CH4 , CO, H2 O and N2 O. The innovative data synergy of the coarse resolution broad-band spectra with the scanned spectral measurements of the trace-gas fine features at 0.03 nm FWHM in multiple microchannels will be used to improve the accuracy of the trace gas retrievals relative to current missions. In addition, the mission will retrieve cloud top pressures to better than 0.1 kPa from measurements of the 0.76 mm O2 A band with 0.02 nm resolution and will conta

  17. Integrated propulsion for near-Earth space missions. Volume 2: Technical

    NASA Technical Reports Server (NTRS)

    Dailey, C. L.; Meissinger, H. F.; Lovberg, R. H.; Zafran, S.

    1981-01-01

    The calculation approach is described for parametric analysis of candidate electric propulsion systems employed in LEO to GEO missions. Occultation relations, atmospheric density effects, and natural radiation effects are presented. A solar cell cover glass tradeoff is performed to determine optimum glass thickness. Solar array and spacecraft pointing strategies are described for low altitude flight and for optimum array illumination during ascent. Mass ratio tradeoffs versus transfer time provide direction for thruster technology improvements. Integrated electric propulsion analysis is performed for orbit boosting, inclination change, attitude control, stationkeeping, repositioning, and disposal functions as well as power sharing with payload on orbit. Comparison with chemical auxiliary propulsion is made to quantify the advantages of integrated propulsion in terms of weight savings and concomittant launch cost savings.

  18. Combining sky and earth: desert ants (Melophorus bagoti) show weighted integration of celestial and terrestrial cues.

    PubMed

    Legge, Eric L G; Wystrach, Antoine; Spetch, Marcia L; Cheng, Ken

    2014-12-01

    Insects typically use celestial sources of directional information for path integration, and terrestrial panoramic information for view-based navigation. Here we set celestial and terrestrial sources of directional information in conflict for homing desert ants (Melophorus bagoti). In the first experiment, ants learned to navigate out of a round experimental arena with a distinctive artificial panorama. On crucial tests, we rotated the arena to create a conflict between the artificial panorama and celestial information. In a second experiment, ants at a feeder in their natural visually-cluttered habitat were displaced prior to their homing journey so that the dictates of path integration (feeder to nest direction) based on a celestial compass conflicted with the dictates of view-based navigation (release point to nest direction) based on the natural terrestrial panorama. In both experiments, ants generally headed in a direction intermediate to the dictates of celestial and terrestrial information. In the second experiment, the ants put more weight on the terrestrial cues when they provided better directional information. We conclude that desert ants weight and integrate the dictates of celestial and terrestrial information in determining their initial heading, even when the two directional cues are highly discrepant. PMID:25324340

  19. The NASA A-Train and the Next Generation of Earth Science Data Integration

    NASA Astrophysics Data System (ADS)

    Vicente, G. A.; Kempler, S.; Smith, P.; Tewari, K.; Kummerer, R.; Leptoukh, G.; Stephens, G.; Partain, P.; Reinke, D.

    2005-12-01

    The A-Train is a succession of six U.S. and international sun-synchronous orbit satellites seconds to minutes apart across the 1:30 p.m. local afternoon equator crossing time according to the sequence: Orbiting Carbon Observatory (OCO), EOS Aqua, CloudSat, Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL), CALIPSO, and EOS Aura. Flying in such a formation increases the number of observations and enables coordination between science observations, resulting in a more complete virtual science platform. The A-Train formation will allow for synergistic measurements where data from several different satellites can be used together to obtain comprehensive information about various key atmospheric components or processes. This combined information from several sources will give a more complete answer to many questions than would be possible from any single satellite. In order to take advantage of this unique opportunity, the NASA Goddard Space Flight Center (GSFC) Earth Sciences (GES), Data and Information Services Center (DISC) is building an A-Train Data Depot (ATDD) to process, archive, access, visualize, analyze and correlate distributed atmosphere measurements from various instruments along A-Train tracks. The ATDD will enable the seamless access to remotely located A-Train data, so that they can be combined to create a consolidated vertical view of the Earth's Atmosphere along the flying tracks. Once the infrastructure of the ATDD is in place, it can be easily evolved to serve data from all A-Train data measurements as a one-stop shopping that will save time and improve efficiency. Users interest in Atmospheric Chemistry, and Water and Energy Science will have a clear connection with their data of interest by being able to access the specific subset (parameter, spatial, and temporal) of interest. This presentation will describe the initial efforts at the GES/DISC in the development of the ATDD portal beginning with the CloudSat products and subsetting services from the CloudSat data processing facility at the Cooperative Institute for Research in the Atmosphere (CIRA). The project combines data from the AQUA MODIS instrument with the CloudSat 94 GHz cloud imaging radar and serves as a benchmark to the challenges facing the full development and implementation of the ATDD. The main issues to be discussed include ground track matching to determine the MODIS pixel closest to the CloudSat ground track, management of pixel resolution differences, compensation for orbital variations, etc.

  20. An integrated study of earth resources in the state of California based on ERTS-1 and supporting aircraft data

    NASA Technical Reports Server (NTRS)

    Colwell, R. N.; Thorley, G. A.; Burgy, R. H.; Schubert, G.; Estes, J. E.; Bowden, L. W.; Algazi, V. R.; Wildman, W. E.; Huntington, G. L. (Principal Investigator)

    1972-01-01

    There are no author-identified significant results in this report. Results of an integrated study of earth resources in the state of California using ERTS-1 and supporting aircraft data are presented. Areas of investigation cover (1) regional agricultural surveys; (2) solving water resource management problems; (3) resource management in Northern California using ERTS-1 data; (4) analysis of river meanders; (5) assessment and monitoring change in west side of the San Joaquin Valley and central coastal zone of state; (6) assessment and monitoring of changes in Southern California environment; (7) digital handling and processing of ERTS-1 data; (8) use of ERTS-1 data in educational and applied research programs of the Agricultural Extension Service; and (9) identification, classification, and mapping of salt affected soils.

  1. Path Integral Monte Carlo Study Confirms a Highly Ordered Snowball in 4He Nanodroplets Doped with an Ar+ Ion

    NASA Astrophysics Data System (ADS)

    Tramonto, F.; Salvestrini, P.; Nava, M.; Galli, D. E.

    2015-07-01

    By means of the Path Integral Monte Carlo method, we have performed a detailed microscopic study of 4He nanodroplets doped with an argon ion, Ar, at K. We have computed density profiles, energies, dissociation energies, and characterized the local order around the ion for nanodroplets with a number of 4He atoms ranging from 10 to 64 and also 128. We have found the formation of a stable solid structure around the ion, a "snowball", consisting of three concentric shells in which the 4He atoms are placed at the vertices of platonic solids: the first inner shell is an icosahedron (12 atoms); the second one is a dodecahedron with 20 atoms placed on the faces of the icosahedron of the first shell; the third shell is again an icosahedron composed of 12 atoms placed on the faces of the dodecahedron of the second shell. The "magic numbers" implied by this structure, 12, 32, and 44 helium atoms, have been observed in a recent experimental study (Bartl et al., J Phys Chem A 118:8050, 2014) of these complexes; the dissociation energy curve computed in the present work shows jumps in correspondence with those found in the nanodroplets abundance distribution measured in that experiment, strengthening the agreement between theory and experiment. The same structures were predicted in Galli et al. (J Phys Chem A 115:7300, 2011) in a study regarding Na+@4He when ; a comparison between Ar+@4He and Na+@4He complexes is also presented.

  2. An integrated multifunctional platform based on biotin-doped conducting polymer nanowires for cell capture, release, and electrochemical sensing.

    PubMed

    Hong, Woo Young; Jeon, Seung Hyun; Lee, Eun Sook; Cho, Youngnam

    2014-12-01

    Here, we propose an integrated multifunctional system constructed by conductive disulfide-biotin-doped polypyrrole nanowires (SS-biotin-Ppy NWs) for capture, release, and in situ quantification of circulating tumor cells (CTCs). A well-ordered three-dimensional nanowire structure equipped with a monoclonal antibody offers a significant impact on the cell-capture efficiency, as well as on electrical- or glutathione (GSH)-mediated release of the captured cells. In addition, the electrochemical identification/detection of the captured cancer cells can be directly conducted on the same Ppy NW platform by using horseradish peroxidase (HRP)-labeled and anti-EpCAM-conjugated nanoparticles (HRP/anti-EpCAM Ppy NPs), showing very high sensitivity and specificity. The signal amplification can be clearly attributed to the catalytic response resulting from enzymatic reduction of hydrogen peroxide on Ppy NWs, consequently generating a greatly increased amperometric response with a detection range of 10 to 1נ10(4)cells and a detection limit of as low as 10cells. Overall, the proposed Ppy NWs not only present a promising platform for effective cell capture and release but also permit cytosensing capability for on-site analysis. PMID:25192586

  3. Distributed Earth observation data integration and on-demand services based on a collaborative framework of geospatial data service gateway

    NASA Astrophysics Data System (ADS)

    Xie, Jibo; Li, Guoqing

    2015-04-01

    Earth observation (EO) data obtained by air-borne or space-borne sensors has the characteristics of heterogeneity and geographical distribution of storage. These data sources belong to different organizations or agencies whose data management and storage methods are quite different and geographically distributed. Different data sources provide different data publish platforms or portals. With more Remote sensing sensors used for Earth Observation (EO) missions, different space agencies have distributed archived massive EO data. The distribution of EO data archives and system heterogeneity makes it difficult to efficiently use geospatial data for many EO applications, such as hazard mitigation. To solve the interoperable problems of different EO data systems, an advanced architecture of distributed geospatial data infrastructure is introduced to solve the complexity of distributed and heterogeneous EO data integration and on-demand processing in this paper. The concept and architecture of geospatial data service gateway (GDSG) is proposed to build connection with heterogeneous EO data sources by which EO data can be retrieved and accessed with unified interfaces. The GDSG consists of a set of tools and service to encapsulate heterogeneous geospatial data sources into homogenous service modules. The GDSG modules includes EO metadata harvesters and translators, adaptors to different type of data system, unified data query and access interfaces, EO data cache management, and gateway GUI, etc. The GDSG framework is used to implement interoperability and synchronization between distributed EO data sources with heterogeneous architecture. An on-demand distributed EO data platform is developed to validate the GDSG architecture and implementation techniques. Several distributed EO data achieves are used for test. Flood and earthquake serves as two scenarios for the use cases of distributed EO data integration and interoperability.

  4. Integration of lessons from recent research for "Earth to Mars" life support systems

    NASA Astrophysics Data System (ADS)

    Nelson, M.; Allen, J. P.; Alling, A.; Dempster, W. F.; Silverstone, S.; van Thillo, M.

    Development of reliable and robust strategies for long-term life support for mbox planetary exploration needs to be built on real-time experimentation to verify and improve system components Also critical is the incorporation of a range of viable options to handle potential short-term life system imbalances This paper revisits some of the conceptual framework for a Mars base prototype previously advanced Mars on Earth in the light of three years of experimentation by the authors in the Laboratory Biosphere further investigation of system alternatives and the advent of other innovative engineering and agri-ecosystem approaches Several experiments with candidate space agriculture crops have demonstrated the higher productivity possible with elevated light levels and improved environmental controls For example crops of sweet potatoes exceeded original Mars base prototype projections by 83 ultradwarf Apogee wheat by 27 pinto bean by 240 and cowpeas slightly exceeded anticipated dry bean yield These production levels although they may be increased with further optimization of lighting regimes environmental parameters crop density etc offer evidence that a soil-based system can be as productive as the hydroponic systems which have dominated space life support scenarios and research Soil also offers several distinct advantages the capability to be created using in-situ space resources reducing reliance on consumables and imported resources and more easily recycling and

  5. Towards an Integrated Model of Earth's Thermo-Chemical Evolution and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Tackley, P. J.; Xie, S.

    2001-05-01

    It has long been a challenge for geodynamicists, who have typically modeled homogeneous mantles, to explain the geochemical evidence for the existence of several distinct chemical reservoirs, in terms of a dynamically and chemically self-consistent model. While the mixing behavior of generalized tracers has received much attention in the modeling community, a recent trend has been towards mantle convection models that track the evolution of specific chemical species, both major and minor, and can thus be related to geochemical observations. However, obtaining realistic chemical evolution in such models is dependent on their having a reasonable representation of plate tectonic behavior since the recycling of oceanic crust and complementary depleted residuum is a key process in Earth that other terrestrial planets may lack. In general, this has required inserting plate motions by hand in models. In recent years, however, we have learned how to perform numerical simulations of mantle convection in which plate tectonic behavior is introduced self-consistently through plastic yielding of the lithosphere. In this presentation, models of mantle convection that combine a treatment of geochemical evolution with self-consistently generated plate tectonics, will be presented. Preliminary results indicate that the system can self-consistently evolve regions which have a HIMU-like signature as well as regions with a high He3/He4 ratio.

  6. Towards Designing an Integrated Earth Observation System for the Provision of Solar Energy Resource and Assessment

    NASA Technical Reports Server (NTRS)

    Stackouse, Paul W., Jr.; Renne, D.; Beyer, H.-G.; Wald, L.; Meyers, R.; Perez, R.; Suri, M.

    2006-01-01

    The GEOSS strategic plan specifically targets the area of improved energy resource management due to the importance of these to the economic and social viability of every nation of the world. With the world s increasing demand for energy resources, the need for new alternative energy resources grows. This paper overviews a new initiative within the International Energy Agency that addresses needs to better manage and develop solar energy resources worldwide. The goal is to provide the solar energy industry, the electricity sector, governments, and renewable energy organizations and institutions with the most suitable and accurate information of the solar radiation resources at the Earth's surface in easily-accessible formats and understandable quality metrics. The scope of solar resource assessment information includes historic data sets and currently derived data products using satellite imagery and other means. Thus, this new task will address the needs of the solar energy sector while at the same time will serve as a model that satisfies GEOSS objectives and goals.

  7. Efficient self-phase modulation in low loss, high index doped silica glass integrated waveguides.

    PubMed

    Duchesne, David; Ferrera, Marcello; Razzari, Luca; Morandotti, Roberto; Little, Brent E; Chu, Sai T; Moss, David J

    2009-02-01

    We demonstrate efficient self phase modulation, as well as negligible nonlinear absorption, in low loss (<0.06 dB/cm), high index silica glass-based waveguides. Using approximately 1 ps pulses near 1560 nm we achieve a 1.5pi nonlinear phase shift in an integrated 45 cm long spiral waveguide with <60 W of peak input power, corresponding to a large nonlinearity (gamma) of 220 W(-1)km(-1). Further, we observe negligible nonlinear absorption for input intensities > 25 GW/cm(2). The high nonlinearity and low linear and nonlinear losses of these waveguides make them promising for nonlinear all-optical signal processing applications. PMID:19189017

  8. Entrainment of bed material by Earth-surface mass flows: review and reformulation of depth-integrated theory

    USGS Publications Warehouse

    Iverson, Richard M.; Chaojun Ouyang

    2015-01-01

    Earth-surface mass flows such as debris flows, rock avalanches, and dam-break floods can grow greatly in size and destructive potential by entraining bed material they encounter. Increasing use of depth-integrated mass- and momentum-conservation equations to model these erosive flows motivates a review of the underlying theory. Our review indicates that many existing models apply depth-integrated conservation principles incorrectly, leading to spurious inferences about the role of mass and momentum exchanges at flow-bed boundaries. Model discrepancies can be rectified by analyzing conservation of mass and momentum in a two-layer system consisting of a moving upper layer and static lower layer. Our analysis shows that erosion or deposition rates at the interface between layers must in general satisfy three jump conditions. These conditions impose constraints on valid erosion formulas, and they help determine the correct forms of depth-integrated conservation equations. Two of the three jump conditions are closely analogous to Rankine-Hugoniot conditions that describe the behavior of shocks in compressible gasses, and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries. Grain-fluid mixtures commonly behave as compressible materials as they undergo entrainment, because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow. If no bulk density change occurs, then only the shear-traction jump condition applies. Even for this special case, however, accurate formulation of depth-integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion.

  9. Entrainment of bed material by Earth-surface mass flows: Review and reformulation of depth-integrated theory

    NASA Astrophysics Data System (ADS)

    Iverson, Richard M.; Ouyang, Chaojun

    2015-03-01

    Earth-surface mass flows such as debris flows, rock avalanches, and dam-break floods can grow greatly in size and destructive potential by entraining bed material they encounter. Increasing use of depth-integrated mass and momentum conservation equations to model these erosive flows motivates a review of the underlying theory. Our review indicates that many existing models apply depth-integrated conservation principles incorrectly, leading to spurious inferences about the role of mass and momentum exchanges at flow-bed boundaries. Model discrepancies can be rectified by analyzing conservation of mass and momentum in a two-layer system consisting of a moving upper layer and static lower layer. Our analysis shows that erosion or deposition rates at the interface between layers must, in general, satisfy three jump conditions. These conditions impose constraints on valid erosion formulas, and they help determine the correct forms of depth-integrated conservation equations. Two of the three jump conditions are closely analogous to Rankine-Hugoniot conditions that describe the behavior of shocks in compressible gasses, and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries. Grain-fluid mixtures commonly behave as compressible materials as they undergo entrainment, because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow. If no bulk density change occurs, then only the shear traction jump condition applies. Even for this special case, however, accurate formulation of depth-integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion.

  10. Visual-vestibular integration as a function of adaptation to space flight and return to Earth

    NASA Technical Reports Server (NTRS)

    Reschke, Millard R.; Bloomberg, Jacob J.; Harm, Deborah L.; Huebner, William P.; Krnavek, Jody M.; Paloski, William H.; Berthoz, Alan

    1999-01-01

    Research on perception and control of self-orientation and self-motion addresses interactions between action and perception . Self-orientation and self-motion, and the perception of that orientation and motion are required for and modified by goal-directed action. Detailed Supplementary Objective (DSO) 604 Operational Investigation-3 (OI-3) was designed to investigate the integrated coordination of head and eye movements within a structured environment where perception could modify responses and where response could be compensatory for perception. A full understanding of this coordination required definition of spatial orientation models for the microgravity environment encountered during spaceflight.

  11. Structural and optical properties of rare earth-doped (Ba{sub 0.77}Ca{sub 0.23}){sub 1-x}(Sm, Nd, Pr, Yb){sub x}TiO{sub 3}

    SciTech Connect

    Moraes, A. P. A.; Filho, A. G. Souza; Freire, P. T. C.; Filho, J. Mendes; M'Peko, J. C.; Hernandes, A. C.; Antonelli, E.; Blair, Michael W.; Muenchausen, Ross E.; Jacobsohn, Luiz G.; Paraguassu, W.

    2011-06-15

    The structural, dielectric, and vibrational properties of pure and rare earth (RE)-doped Ba{sub 0.77}Ca{sub 0.23}TiO{sub 3} (BCT23; RE = Nd, Sm, Pr, Yb) ceramics obtained via solid-state reaction were investigated. The pure and RE-doped BCT23 ceramics sintered at 1450 deg. C in air for 4 h showed a dense microstructure in all ceramics. The use of RE ions as dopants introduced lattice-parameter changes that manifested in the reduction of the volume of the unit cell. RE-doped BCT23 samples exhibit a more homogenous microstructure due to the absence of a Ti-rich phase in the grain boundaries as demonstrated by scanning electron microscopy imaging. The incorporation of REs led to perturbations of the local symmetry of TiO{sub 6} octahedra and the creation of a new Raman mode. The results of Raman scattering measurements indicated that the Curie temperature of the ferroelectric phase transition depends on the RE ion and ion content, with the Curie temperature shifting toward lower values as the RE content increases, with the exception of Yb{sup 3+} doping, which did not affect the ferroelectric phase transition temperature. The phase transition behavior is explained using the standard soft mode model. Electronic paramagnetic resonance measurements showed the existence of Ti vacancies in the structure of RE-doped BCT23. Defects are created via charge compensation mechanisms due to the incorporation of elements with a different valence state relative to the ions of the pure BCT23 host. It is concluded that the Ti vacancies are responsible for the activation of the Raman mode at 840 cm{sup -1}, which is in agreement with lattice dynamics calculations.

  12. MAPS (My Atlas and Plot Service) for Integrated Earth Observation Data

    NASA Astrophysics Data System (ADS)

    Ichino, M.; Fukuda, K.; Sugiura, N.; Funakoshi, R.

    2010-12-01

    DIAS (Data integration and Analysis System) is one of the activities of GEOSS, and also one of Japanese National Key Technology activities. JAMSTEC collaborates with the University of Tokyo, the main contractor of the project. It is a five-year project until March 2011. We at JAMSTEC also have developed a data distribution system toward long-term sustainable services as part of DIAS. We launched the early website at 2007. It provided six integration and analysis datasets in the fields of Ocean & Fishery Resources, Water Cycle and Land Ecosystem. We also investigated users needs through an online questionnaire and through interviews regarding the types and quality of required data, data formats, website functions and so on. Accordingly, our new website, MAPS, which is short for My Atlas and Plot Service has been remodeled with four new datasets and new functions to meet users needs since the fall in 2010. We have provided online mapping and plotting services with MapServer, and download services with functions of extracting digital data by selected attribute and of converting into another file type. These services provide a powerful visualization and analysis capabilities for the data products. The input items and forms in online questionnaire and Contact-Us page in our website have been refined to collect feedbacks and comments about the new website functions. We are continuously researching the further future needs in order to promote the wider usage of the datasets.

  13. Integrated propulsion for near-Earth space missions. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    Dailey, C. L.; Meissinger, H. F.; Lovberg, R. H.; Zafran, S.

    1981-01-01

    Tradeoffs between electric propulsion system mass ratio and transfer time from LEO to GEO were conducted parametrically for various thruster efficiency, specific impulse, and other propulsion parameters. A computer model was developed for performing orbit transfer calculations which included the effects of aerodynamic drag, radiation degradation, and occultation. The tradeoff results showed that thruster technology areas for integrated propulsion should be directed towards improving primary thruster efficiency in the range from 1500 to 2500 seconds, and be continued towards reducing specific mass. Comparison of auxiliary propulsion systems showed large total propellant mass savings with integrated electric auxiliary propulsion. Stationkeeping is the most demanding on orbit propulsion requirement. At area densities above 0.5 sq m/kg, East-West stationkeeping requirements from solar pressure exceed North-South stationkeeping requirements from gravitational forces. A solar array pointing strategy was developed to minimize the effects of atmospheric drag at low altitude, enabling electric propulsion to initiate orbit transfer at Shuttle's maximum cargo carrying altitude. Gravity gradient torques are used during ascent to sustain the spacecraft roll motion required for optimum solar array illumination. A near optimum cover glass thickness of 6 mils was established for LEO to GEO transfer.

  14. TIGER-NET- Enabling An Earth Observation Capacity For Integrated Water Resource Management In Africa

    NASA Astrophysics Data System (ADS)

    Walli, A.; Tttrup, C.; Naeimi, V.; Bauer-Gottwein, P.; Bila, M.; Mufeti, P.; Tumbulto, J. W.; Rajah, C.; Moloele, LS.; Koetz, B.

    2013-12-01

    As part of the TIGER initiative [1] the TIGER-NET project aims to support the assessment and monitoring of water resources from watershed to transboundary basin level delivering indispensable information for Integrated Water Resource Management in Africa through: 1. Development of an open-source Water Observation and Information Systems (WOIS) for monitoring, assessing and inventorying water resources in a cost- effective manner; 2. Capacity building and training of African water authorities and technical centers to fully exploit the increasing observation capacity offered by current and upcoming generations of satellites, including the Sentinel missions. Dedicated application case studies have been developed and demonstrated covering all EO products required by and developed with the participating African water authorities for their water resource management tasks, such as water reservoir inventory, water quality monitoring, water demand planning as well as flood forecasting and monitoring.

  15. Research priorities in land use and land-cover change for the Earth system and integrated assessment modelling

    SciTech Connect

    Hibbard, Kathleen A.; Janetos, Anthony C.; Van Vuuren, Detlef; Pongratz, Julia; Rose, Steven K.; Betts, Richard; Herold, Martin; Feddema, Johannes J.

    2010-11-15

    This special issue has highlighted recent and innovative methods and results that integrate observations and AQ3 modelling analyses of regional to global aspect of biophysical and biogeochemical interactions of land-cover change with the climate system. Both the Earth System and the Integrated Assessment modeling communities recognize the importance of an accurate representation of land use and land-cover change to understand and quantify the interactions and feedbacks with the climate and socio-economic systems, respectively. To date, cooperation between these communities has been limited. Based on common interests, this work discusses research priorities in representing land use and land-cover change for improved collaboration across modelling, observing and measurement communities. Major research topics in land use and land-cover change are those that help us better understand (1) the interaction of land use and land cover with the climate system (e.g. carbon cycle feedbacks), (2) the provision of goods and ecosystem services by terrestrial (natural and anthropogenic) land-cover types (e.g. food production), (3) land use and management decisions and (4) opportunities and limitations for managing climate change (for both mitigation and adaptation strategies).

  16. Thermal neutron imaging with rare-earth-ion-doped LiCaAlF 6 scintillators and a sealed 252Cf source

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Noriaki; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Kamada, Kei; Fukuda, Kentaro; Suyama, Toshihisa; Watanabe, Kenichi; Yamazaki, Atsushi; Chani, Valery; Yoshikawa, Akira

    2011-10-01

    Thermal neutron imaging with Ce-doped LiCaAlF 6 crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF 6 scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF 6 single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 502 mm 2 was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The 252Cf source (<1 MBq) was sealed with 43 mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2 mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF 6.

  17. A technique for modelling p- n junction depletion capacitance of multiple doping regions in integrated circuits

    NASA Astrophysics Data System (ADS)

    Pinkham, Raymond; Anderson, Daniel F.

    1986-08-01

    The continuing advancements in integrated circuit technology have placed new burdons on the circuit design engineer, who must rely extensively upon computer simulation to correctly predict circuit behavior. One challenge is to develop better modelling techniques to more accurately deal with complex p- n junction structures often used in modern VLSI designs. This paper presents an easily implemented method for deriving parameters which accurately model the behavior of MOS VLSI structures containing complex p- n junction capacitance components. The methodology is applicable to both planar and laterally diffused junctions, whether formed by direct ion implantation or by diffusion from a finite or infinite source. The theories behind the equations used and results of the application of this new technique are discussed. A flow chart for a fitter program based on the new method is presented and described. The corresponding program written for the TI-59 scientific programmable calculator is available. Final model parameters are given and are shown to produce a numerical capacitance model which is accurate to within 2%.

  18. Durability of glasses from the Hg-doped Integrated DWPF Melter System (IDMS) campaign

    SciTech Connect

    Jantzen, C.M.

    1992-08-30

    The Integrated DWPF Melter System (IDMS) for the vitrification of high-level radioactive wastes is designed and constructed to be a 1/9th scale prototype of the full scale Defense Waste Processing Facility (DWPF) melter. The IDMS facility is the first engineering scale melter system capable of processing mercury, and flowsheet levels of halides and noble metals. In order to determine the effects of mercury on the feed preparation process, the off-gas chemistry, glass melting behavior, and glass durability, a three-run mercury (Hg) campaign was conducted. The glasses produced during the Hg campaign were composed of Batch 1 sludge, simulated precipitate hydrolysis aqueous product (PHA) from the Precipitate Hydrolysis Experimental Facility (PHEF), and Frit 202. The glasses were produced using the DWPF process/product models for glass durability, viscosity, and liquidus. The durability model indicated that the glasses would all be more durable than the glass qualified in the DWPF Environmental Assessment (EA). The glass quality was verified by performing the Product Consistency Test (PCT) which was designed for glass durability testing in the DWPF.

  19. Earth tides

    SciTech Connect

    Harrison, J.C.

    1984-01-01

    Nineteen papers on gravity, tilt, and strain tides are compiled into this volume. Detailed chapters cover the calculation of the tidal forces and of the Earth's response to them, as well as actual observations of earth tides. Partial Contents: On Earth tides. The tidal forces: Tidal Forces. New Computations of the Tide-Generating Potential. Corrected Tables of Tidal Harmonics. The Theory of Tidal Deformations. Body Tides on an Elliptical, Rotating, Elastic and Oceanless Earth, Deformation of the Earth by Surface Loads. Gravimetric Tidal Loading Computed from Integrated Green's Functions. Tidal Friction in the Solid Earth. Loading Tides Versus Body Tides. Lunar Tidal Acceleration from Earth Satellite Orbit Analysis. Observations: gravity. Tidal Gravity in Britain: Tidal Loading and the Spatial Distribution of the Marine Tide. Tidal Loading along a Profile Europe-East Africa-South Asia-Australia and the Pacific Ocean. Detailed Gravity-Tide Spectrum between One and Four Cycles per Day. Observations: tilt and strain. Cavity and Topographic Effects in Tilt and Strain Measurement. Observations of Local Elastic Effects on Earth Tide Tilts and Strains.

  20. Geo-Semantic Framework for Integrating Long-Tail Data and Model Resources for Advancing Earth System Science

    NASA Astrophysics Data System (ADS)

    Elag, M.; Kumar, P.

    2014-12-01

    Often, scientists and small research groups collect data, which target to address issues and have limited geographic or temporal range. A large number of such collections together constitute a large database that is of immense value to Earth Science studies. Complexity of integrating these data include heterogeneity in dimensions, coordinate systems, scales, variables, providers, users and contexts. They have been defined as long-tail data. Similarly, we use "long-tail models" to characterize a heterogeneous collection of models and/or modules developed for targeted problems by individuals and small groups, which together provide a large valuable collection. Complexity of integrating across these models include differing variable names and units for the same concept, model runs at different time steps and spatial resolution, use of differing naming and reference conventions, etc. Ability to "integrate long-tail models and data" will provide an opportunity for the interoperability and reusability of communities' resources, where not only models can be combined in a workflow, but each model will be able to discover and (re)use data in application specific context of space, time and questions. This capability is essential to represent, understand, predict, and manage heterogeneous and interconnected processes and activities by harnessing the complex, heterogeneous, and extensive set of distributed resources. Because of the staggering production rate of long-tail models and data resulting from the advances in computational, sensing, and information technologies, an important challenge arises: how can geoinformatics bring together these resources seamlessly, given the inherent complexity among model and data resources that span across various domains. We will present a semantic-based framework to support integration of "long-tail" models and data. This builds on existing technologies including: (i) SEAD (Sustainable Environmental Actionable Data) which supports curation and preservation of long-tail data during its life-cycle; (ii) BrownDog, which enhances the machine interpretability of large unstructured and uncurated data; and (iii) CSDMS (Community Surface Dynamics Modeling System), which "componentizes" models by providing plug-and-play environment for models integration.

  1. Building Capacity to Integrate NASA Earth Science into Water Resources Management Applications in the Context of a Changing Climate

    NASA Astrophysics Data System (ADS)

    Prados, A. I.; Mehta, A. V.

    2011-12-01

    The NASA Applied Sciences program provides technical capacity building activities to enable decision-makers to integrate NASA Earth Science into environmental management activities. This includes workshops tailored to end-user needs by working directly with agencies to 1) identify environmental management activities that could benefit from NASA Earth Science and 2) conducting workshops that teach the NASA products and decision-support tools best suited to the identified application area. Building on a successful 3-year effort on air pollution monitoring for environmental applications, the project has expanded into water resources. Climate Change has dramatically increased demand for observational and predictive data in support of decision making activities related to water supply and demand. However, a gap remains between NASA products and applied research and the entities who stand to benefit from their utilization. To fill this gap, the project has developed short courses on 1) impacts of climate change on water resources 2) hands-on exercises on access and interpretation of NASA imagery relevant to water resources management via the use of decision-support web tools and software and 3) case studies on the application of NASA products in the field. The program is currently focused on two areas 1) precipitation products over the central and southern U.S. that help communities and agencies improve flooding forecasts and 2) snow and snow/water equivalent products over the western U.S and Latin America that can provide end-users with improved stream flow prediction in Spring within a framework of decreasing snow availability.

  2. Expedition Earth and Beyond: Using NASA Data Resources and Integrated Educational Strategies to Promote Authentic Research in the Classroom

    NASA Technical Reports Server (NTRS)

    Graffi, Paige Valderrama; Stefanov, William; Willis, Kim; Runco, Sue

    2009-01-01

    Teachers in today s classrooms are bound by state required skills, education standards, and high stakes testing. How can they gain skills and confidence to replace units or individual activities with curriculum that incorporates project and inquiry-based learning and promotes authentic research in the classroom? The key to promoting classroom authentic research experiences lies in educator professional development that is structured around teacher needs. The Expedition Earth and Beyond Program is a new geosciences program based at the NASA Johnson Space Center designed to engage, inspire and educate teachers and students in grades 5-14. The program promotes authentic research experiences for classrooms and uses strategies that will help NASA reach its education goals while still allowing educators to teach required standards. Teachers will have access to experts in terrestrial and planetary remote sensing and geoscience; this will enhance their use of content, structure, and relevant experiences to gain the confidence and skills they need to actively engage students in authentic research experiences. Integrated and powerful educational strategies are used to build skills and confidence in teachers. The strategies are as follows: 1) creating Standards-aligned, inquiry-based curricular resources as ready-to-use materials that can be modified by teachers to fit their unique classroom situation; 2) providing ongoing professional development opportunities that focus on active experiences using curricular materials, inquiry-based techniques and expanding content knowledge; 3) connecting science experts to classrooms to deepen content knowledge and provide relevance to classroom activities and real world applications; 4) facilitating students sharing research with their peers and scientists reinforcing their active participation and contributions to research. These components of the Expedition Earth and Beyond Education Program will be enhanced by providing exciting and diverse research opportunities that are inspired by views of Earth from space taken by astronauts on board the International Space Station. The interest and connection to viewing our home planet from space will inevitably spark questions that will drive students to pursue their research investigations, as well as forming a basis for comparisons to the exploration of other planetary bodies in our solar system.

  3. Svalbard Integrated Arctic Earth Observing System (sios): Facilitating Easy Access to Multidisciplinary Arctic Data Through the Brokering Approach.

    NASA Astrophysics Data System (ADS)

    Bye, B. L.; Godøy, Ø.

    2014-12-01

    Environmental and climate changes are important elements of our global challenges. They are observed at a global scale and in particular in the Arctic. In order to give better estimates of the future changes, the Arctic has to be monitored and analyzed by a multi-disciplinary observation system that will improve Earth System Models. The best chance to achieve significant results within a relatively short time frame is found in regions with a large natural climate gradient, and where processes sensitive to the expected changes are particularly important. Svalbard and the surrounding ocean areas fulfil all these criteria. The vision for SIOS is to be a regional observational system for long term acquisition and proliferation of fundamental knowledge on global environmental change within an Earth System Science perspective in and around Svalbard. SIOS will systematically develop and implement methods for how observational networks are to be construed. The distributed SIOS data management system (SDMS) will be implemented through a combination of technologies tailored to the multi-disciplinary nature of the Arctic data. One of these technologies is The Brokering approach or "Framework". The Brokering approach provides a series of services such as discovery, access, transformation and semantics support to enable translation from one discipline/culture to another. This is exactly the challenges the SDMS will have to handle and thus the Brokering approach is integrated in the design of the system. A description of the design strategy for the SDMS that includes The Brokering approach will be presented. The design and implementation plans for the SDMS are based on research done in the EU funded ESFRI project SIOS and examples of solutions for interoperable systems producing Arctic datasets and products coordinated through SIOS will be showcased. The reported experience from SIOS brokering approach will feed into the process of developing a sustainable brokering governance in the framework of Research Data Alliance. It will also support the Global Earth Observation System of Systems (GEOSS). This is a contribution to increase our global capacity to create interoperable systems that provide multi-disciplinary dataset and products.

  4. A Critical Path for Data Integration in the U.S. Earth Sciences

    NASA Astrophysics Data System (ADS)

    Gallagher, K. T.; Allison, M. L.

    2011-12-01

    Development efforts for the U.S. Geoscience Information Network (US GIN) have crystallized around the Community for Data Integration (CDI) at the USGS, and the 50-state AASG State Geothermal Data project. The next step in developing a USGS-AASG community is to bring these two efforts into closer alignment through greater participation in CDI activities by geoinformatics practitioners from state geological surveys, and implementation of test bed activities by the USGIN partners. Test bed activities in the geological survey community will define a scope and provide a foundation to promote the use of specifications developed by the larger geoinformatics community. Adoption of some of these specifications as 'standards' by USGS and AASG for use by those organizations will lend authority and motivate wider adoption. The arc from use case to test bed to production deployments to agreement on 'standard' specifications for data discovery and access must be propelled by active interest from the user communities who have a stake in the outcome. The specifications developed will benefit the organizations involved in development, testing and deployment, which motivates participation -- a model that has worked successfully for standards organizations such as OGC, ISO and OASIS. The governance structure to support such a community process should promote grass root nucleation of interest groups that are the core of development efforts. Some mechanism for community agreement on priorities is desirable because geological survey agencies will need to allocate resources to support development. Loosely knit organizations such as ESIP and the current CDI provide models for this kind of structure. Because many geological surveys have data archive and dissemination functions as part of their portfolio, some support for the system can be built into the operating expenses and overhead. Sharing of resources and reuse of components can reduce the cost. Wide adoption of similar software, protocols and practices increases the number of stake holders with an interest in supporting the system.

  5. Modeling of optical amplifier waveguide based on silicon nanostructures and rare earth ions doped silica matrix gain media by a finite-difference time-domain method: comparison of achievable gain with Er3+ or Nd3+ ions dopants

    NASA Astrophysics Data System (ADS)

    Cardin, Julien; Fafin, Alexandre; Dufour, Christian; Gourbilleau, Fabrice

    2015-03-01

    A comparative study of the gain achievement is performed in a waveguide optical amplifier whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd3+) or erbium ions (Er3+). Due to the large difference between population levels characteristic times (ms) and finite-difference time step (10-17s), the conventional auxiliary differential equation and finite-difference time-domain (ADE-FDTD) method is not appropriate to treat such systems. Consequently, a new two loops algorithm based on ADE-FDTD method is presented in order to model this waveguide optical amplifier. We investigate the steady states regime of both rare earth ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 104 mW/mm2 . Furthermore, the three dimensional distribution of achievable gain per unit length has been estimated in this pumping range. The Nd3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm-1) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm-1). Considering the experimental background losses found on those waveguides we demonstrate that a significant positive net gain can only be achieved with the Nd3+ doped waveguide. The developed algorithm is stable and applicable to optical gain materials with emitters having a wide range of characteristic lifetimes.

  6. MODELING THE DYNAMICS OF THE INTEGRATED EARTH SYSTEM AND THE VALUE OF GLOBAL ECOSYSTEM SERVICES USING THE GUMBO MODEL. (R827169)

    EPA Science Inventory

    A global unified metamodel of the biosphere (GUMBO) was developed to simulate the integrated earth system and assess the dynamics and values of ecosystem services. It is a `metamodel' in that it represents a synthesis and a simplification of several existing dynamic gl...

  7. INTEGRATING EARTH OBSERVATION AND FIELD DATA INTO A LYME DISEASE MODEL TO MAP AND PREDICT RISKS TO BIODIVERSITY AND HUMAN HEALTH

    EPA Science Inventory

    DW-75-92243901
    Title: Integrating Earth Observation and Field Data into a Lyme Disease Model to Map and Predict Risks to Biodiversity and Human HealthDurland Fish, Maria Diuk-Wasser, Joe Roman, Yongtao Guan, Brad Lobitz, Rama Nemani, Joe Piesman, Montira J. Pongsiri, F...

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

    SciTech Connect

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

    2010-01-01

    Monoclinic potassium rare-earth double tungstates [KRE(WO{sub 4}){sub 2}, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln{sup 3+}) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb{sup 3+}- and Tm{sup 3+}-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

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

    NASA Astrophysics Data System (ADS)

    Raghothamachar, B.; Carvajal, J. J.; Pujol, M. C.; Mateos, X.; Sol, R.; Aguil, M.; Daz, F.; Dudley, M.

    2010-06-01

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

  10. An integrated, open-source set of tools for urban vulnerability monitoring from Earth observation data

    NASA Astrophysics Data System (ADS)

    De Vecchi, Daniele; Harb, Mostapha; Dell'Acqua, Fabio; Aurelio Galeazzo, Daniel

    2015-04-01

    Aim: The paper introduces an integrated set of open-source tools designed to process medium and high-resolution imagery with the aim to extract vulnerability indicators [1]. Problem: In the context of risk monitoring [2], a series of vulnerability proxies can be defined, such as the extension of a built-up area or buildings regularity [3]. Different open-source C and Python libraries are already available for image processing and geospatial information (e.g. OrfeoToolbox, OpenCV and GDAL). They include basic processing tools but not vulnerability-oriented workflows. Therefore, it is of significant importance to provide end-users with a set of tools capable to return information at a higher level. Solution: The proposed set of python algorithms is a combination of low-level image processing and geospatial information handling tools along with high-level workflows. In particular, two main products are released under the GPL license: source code, developers-oriented, and a QGIS plugin. These tools were produced within the SENSUM project framework (ended December 2014) where the main focus was on earthquake and landslide risk. Further development and maintenance is guaranteed by the decision to include them in the platform designed within the FP 7 RASOR project . Conclusion: With the lack of a unified software suite for vulnerability indicators extraction, the proposed solution can provide inputs for already available models like the Global Earthquake Model. The inclusion of the proposed set of algorithms within the RASOR platforms can guarantee support and enlarge the community of end-users. Keywords: Vulnerability monitoring, remote sensing, optical imagery, open-source software tools References [1] M. Harb, D. De Vecchi, F. Dell'Acqua, "Remote sensing-based vulnerability proxies in the EU FP7 project SENSUM", Symposium on earthquake and landslide risk in Central Asia and Caucasus: exploiting remote sensing and geo-spatial information management, 29-30th January 2014, Bishkek, Kyrgyz Republic. [2] UNISDR, "Living with Risk", Geneva, Switzerland, 2004. [3] P. Bisch, E. Carvalho, H. Degree, P. Fajfar, M. Fardis, P. Franchin, M. Kreslin, A. Pecker, "Eurocode 8: Seismic Design of Buildings", Lisbon, 2011. (SENSUM: www.sensum-project.eu, grant number: 312972 ) (RASOR: www.rasor-project.eu, grant number: 606888 )

  11. Thermal stress anomaly in rare-earth-doped fiber materials for high-power fiber lasers codoped with aluminum and phosphorus

    NASA Astrophysics Data System (ADS)

    Just, F.; Unger, S.; Kirchhof, J.; Reichel, V.; Bartelt, H.

    2010-05-01

    It is well known that thermal stress can significantly influence the properties of optical fibers. These stresses are caused by variations in the coefficient of thermal expansion (CTE) of the differently doped areas in the fiber, like the core and the cladding. On the one hand, the stress has a strong effect on the mechanical stability of fibers. On the other hand, the stress also modifies the most essential property of a fiber, the refractive index distribution, and therefore also the propagation properties. Similar to the effect of generation of birefringence in polarisation maintaining fibers, thermal stress also generates changes in the refractive index of the differently doped regions in the fiber. We report on results of non-destructive polarimetric stress measurements in ytterbium doped fiber preforms, that are codoped with aluminum as well as with phosphorus. Simple models of changes in the CTE for samples doped with multiple elements assume an additive superposition of the changes caused by each dopant. In contrast to such simple models, our investigations have shown that the induced stress cannot be explained by an additive change in the CTE of the glass material. The occurring stresses turn out to be smaller than the simple sum of the effects generated by the respective dopants. This result is also in agreement with measurements of the refractive index profile of these samples. The changes in the index are again not additive for doping with both aluminum and phosphorus.

  12. A net-centric system of services model for the Integrated Earth Observation System (IEOS) and the Integrated Ocean Observing System (IOOS)

    NASA Astrophysics Data System (ADS)

    Ardanuy, Philip; Bensman, Ed; Bergen, Bill; Chen, Bob; Griffith, Frank; Sutton, Cary; Hood, Carroll; Ritchie, Adrian; Tarro, Andre

    2006-08-01

    This paper considers an evolved technique for significantly enhanced enterprise-level data processing, reprocessing, archival, dissemination, and utilization. There is today a robust working paradigm established with the Advanced Weather Interactive Processing System (AWIPS)-NOAA/NWS's information integration and fusion capability. This process model extends vertically, and seamlessly, from environmental sensing through the direct delivery of societal benefit. NWS, via AWIPS, is the primary source of weather forecast and warning information in the nation. AWIPS is the tested and proven "the nerve center of operations" at all 122 NWS Weather Forecast Offices (WFOs) and 13 River Forecast Centers (RFCs). However, additional line organizations whose role in satisfying NOAA's five mission goals (ecosystems, climate, weather & water, commerce & transportation, and mission support) in multiple program areas might be facilitated through utilization of AWIPS-like functionalities, including the National Marine Fisheries Service (NMFS); National Environmental Satellite, Data, and Information Service (NESDIS); Office of Oceanic & Atmospheric Research (OAR); and the National Ocean Service (NOS). In addition to NOAA's mission goals, there are nine diverse, recommended, and important societal benefit areas in the US Integrated Earth Observation System (IEOS). This paper shows how the satisfaction of this suite of goals and benefit areas can be optimized by leveraging several key ingredients: (1) the evolution of AWIPS towards a net-centric system of services concept of operations; (2) infusion of technologies and concepts from pathfinder systems; (3) the development of new observing systems targeted at deliberate, and not just serendipitous, societal benefit; and (4) the diverse, nested local, regional, national, and international scales of the different benefits and goal areas, and their interoperability and interplay across the system of systems.

  13. Google Earth as a Vehicle to Integrating Multiple Layers of Environmental Satellite Data for Weather and Science Applications

    NASA Astrophysics Data System (ADS)

    Turk, F. J.; Miller, S. D.

    2007-12-01

    One of the main challenges facing current and future environmental satellite systems (e.g, the future National Polar Orbiting Environmental Satellite System (NPOESS)) is reaching and entraining the diverse user community via communication of how these systems address their particular needs. A necessary element to meeting this challenge is effective data visualization: facilitating the display, animation and layering of multiple satellite imaging and sounding sensors (providing complementary information) in a user-friendly and intuitive fashion. In light of the fact that these data are rapidly making their way into the classroom owing to efficient and timely data archival systems and dissemination over the Internet, there is a golden opportunity to leverage existing technology to introduce environmental science to wide spectrum of users. Google Earth's simplified interface and underlying markup language enables access to detailed global geographic information, and contains features which are both desirable and advantageous for geo-referencing and combining a wide range of environmental satellite data types. Since these satellite data are available with a variety of horizontal spatial resolutions (tens of km down to hundreds of meters), the imagery can be sub-setted (tiled) at a very small size. This allows low-bandwidth users to efficiently view and animate a sequence of imagery while zoomed out from the surface, whereas high-bandwidth users can efficiently zoom into the finest image resolution when viewing fine-scale phenomena such as fires, volcanic activity, as well as the details of meteorological phenomena such as hurricanes, rainfall, lightning, winds, etc. Dynamically updated network links allow for near real-time updates such that these data can be integrated with other Earth-hosted applications and exploited not only in the teaching environment, but also for operational users in the government and private industry sectors. To conceptualize how environmental satellite data would be utilized within a geobrowser in a near real-time setting, we present a demonstration from the 2007 hurricane season, developed within the Google Earth framework. A menu of imagery based sequential satellite overpasses (GOES and other geostationary satellites, TRMM, CloudSat, Terra, Aqua, DMSP, NOAA, QuikScat) during the storm lifecycle, are presented to the Earth client in an structured folder format. The remapping of these satellite data follows the hurricane track, enabling the user to view, animate, zoom, overlay and combine visible, infrared and passive microwave imagery and combine with other data (surface reports, forecasts, surface winds, ground and spaceborne radars, etc.) at various stages of the hurricane lifecycle. Pop-up balloons provide training that explains the properties and capabilities of the satellite datasets and what components of the underlying weather are represented. Future satellite overpass tracks are provided so that the user can anticipate imagery updates several days in advance (e.g., as a hurricane approaches landfall). This combination of geo-navigable data provides a convenient framework for efficiently demonstrating meteorological, oceanographic and weather and climate concepts to students, planners, and the public at large.

  14. The key role of Satellite Laser Ranging towards the integrated estimation of geometry, rotation and gravitational field of the Earth

    NASA Astrophysics Data System (ADS)

    Blossfeld, Mathis

    2015-01-01

    In 2007, the Global Geodetic Observing System (GGOS) was installed as a full component of the International Association of Geodesy (IAG). One primary goal of GGOS is the integration of geometric and gravimetric observation techniques to estimate consistent geodetic-geophysical parameters. Thereby, GGOS is based on the data and services of the IAG. Besides the combination of different geodetic techniques, also the common estimation of the station coordinates (TRF), Earth Orientation Parameters (EOP) and coefficients of the Earth's gravitational field (Stokes coefficients) is necessary in order to reach this goal. However, the combination of all geometric and gravimetric observation techniques is not yet fully realized. A major step towards the GGOS idea of parameter integration would be the understanding of the existing correlations between the above mentioned fundamental geodetic parameter groups. This topic is the major objective of this thesis. One possibility to study the interactions is the use of Satellite Laser Ranging (SLR) in an intertechnique combination with Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) or the intra-technique combination of multiple SLR-tracked satellites. SLR plays a key role in this thesis since it is the unique technique which is sensitive to all parameter groups and allows an integrated parameter estimation with very high accuracy. The present work is based on five first-author publications which are supplemented by four co-author publications. In this framework, for the first time an extensive discussion of a refined global Terrestrial Reference Frame (TRF) estimation procedure, the estimation of so-called Epoch Reference Frames (ERFs) is presented. In contrast to the conventional linear station motion model, the ERFs provide frequently estimated station coordinates and Earth Orientation Parameters (EOP) which allow to approximate not modeled non-linear station motions very accurately. Thereby, SLR provides the origin information for the frequently estimated ERFs. The neglected non-linear station motions in the conventional TRF realizations are forced via the correlation of translations and rotations (due to a non-optimal ground station network) into the terrestrial pole coordinates. In contrast to this, the pole coordinates of the Epoch Reference Frame (ERF)s are only partly biased. However, due to the sparse and varying ground station network, the ERFs have a more unstable datum than the conventional TRFs. One possibility to improve the ERF datum stability is to enlarge the sampling interval (e.g., from one week to four weeks) which results in a decreased ability of the ERFs to monitor short-term station motions. Besides the pole coordinates, also significantly corrupted satellite-derived Length Of Day (LOD) values have been found. The reason for this systematic error is investigated in this thesis on the basis of SLR estimates. The theoretical relationship between the orbital elements, LOD and the Stokes coefficient C20 is worked out. To quantify this interaction, several time series using different a priori models for the Earth's gravitational field and different satellite constellations have been computed and compared. Furthermore, secular effects on the nodal precession due to relativistic effects and empirical accelerations are analyzed. In addition to the separate estimation of station coordinates and EOP, also the estimation of Stokes coefficients is analyzed. In order to further decorrelate the orbital elements and Stokes coefficients, the combination of up to ten different SLR-tracked satellites have been studied. Thereby, the impact of each satellite on the decorrelation of satellite orbit parameters and C20 is investigated. Afterwards, the resulting second-degree Stokes coefficients are validated w.r.t. other external state-of-the-art time series and datasets (e.g., equatorial excitation functions of polar motion, Antarctic ice mass trends). The last part of this thesis discusses in detail the interactions and correlations which have to be considered if the fundamental geodetic parameters are estimated in one common adjustment. The understanding and correct handling of these interactions is essential for the integrated estimation. Based on the findings of the SLR singletechnique multi-parameter solution, the achieved understandings of the parameter interactions can be transferred to other geodetic space techniques and might support the combination of geometric and gravimetric observations in future.

  15. Structural and spectroscopic properties of rare-earth (Nd3+, Er3+, and Yb3+) doped transparent lead lanthanum zirconate titanate ceramics

    NASA Astrophysics Data System (ADS)

    de Camargo, Andrea S. S.; de O. Nunes, Luiz Antonio; Santos, Ivair A.; Garcia, Ducinei; Eiras, Jos Antonio

    2004-02-01

    This work presents the structural and spectroscopic characterization of transparent lead lanthanum zirconate titanate ceramics doped with Nd3+, Er3+, or Yb3+ ions. High optical quality samples presenting the perovskite structure were prepared through a mixed oxides method followed by conventional sintering or uniaxial hot pressing. Absorption and luminescence spectra were measured, and radiative emission parameters were calculated for Nd3+- and Er3+-doped samples. The results indicate the potential of these polycrystalline host-ion combinations for the construction of diode-pumped lasers in the near-infrared region.

  16. Selective Emitter Pumped Rare Earth Laser

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L. (Inventor); Patton, Martin O. (Inventor)

    2001-01-01

    A selective emitter pumped rare earth laser provides an additional type of laser for use in many laser applications. Rare earth doped lasers exist which are pumped with flashtubes or laser diodes. The invention uses a rare earth emitter to transform thermal energy input to a spectral band matching the absorption band of a rare earth in the laser in order to produce lasing.

  17. Earth: Earth Science and Health

    NASA Technical Reports Server (NTRS)

    Maynard, Nancy G.

    2001-01-01

    A major new NASA initiative on environmental change and health has been established to promote the application of Earth science remote sensing data, information, observations, and technologies to issues of human health. NASA's Earth Sciences suite of Earth observing instruments are now providing improved observations science, data, and advanced technologies about the Earth's land, atmosphere, and oceans. These new space-based resources are being combined with other agency and university resources, data integration and fusion technologies, geographic information systems (GIS), and the spectrum of tools available from the public health community, making it possible to better understand how the environment and climate are linked to specific diseases, to improve outbreak prediction, and to minimize disease risk. This presentation is an overview of NASA's tools, capabilities, and research advances in this initiative.

  18. Earth materials and earth dynamics

    SciTech Connect

    Bennett, K; Shankland, T.

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  19. Synthesis and characterization of rare-earth doped SrBi{sub 2}Nb{sub 2}O{sub 9} phase in lithium borate based nanocrystallized glasses

    SciTech Connect

    Harihara Venkataraman, B.; Fujiwara, Takumi; Komatsu, Takayuki

    2009-06-15

    Glass composites comprising of un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites are fabricated in the glass system 16.66SrO-16.66[(1-x)Bi{sub 2}O{sub 3}-xSm{sub 2}O{sub 3}]-16.66Nb{sub 2}O{sub 5}-50Li{sub 2}B{sub 4}O{sub 7} (0<=x<=0.5, in mol%) via the melt quenching technique. The glassy nature of the as-quenched samples is established by differential thermal analyses. Transmission electron microscopic studies reveal the presence of about 15 nm sized spherical crystallites of the fluorite-like SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} phase in the samples heat treated at 530 deg. C. The formation of layered perovskite-type un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites with an orthorhombic structure through the intermediate fluorite phase is confirmed by X-ray powder diffraction and micro-Raman spectroscopic studies. The influence of samarium doping on the lattice parameters, lattice distortions, and the Raman peak positions of SrBi{sub 2}Nb{sub 2}O{sub 9} perovskite phase is clarified. The dielectric constants of the perovskite SrBi{sub 2}Nb{sub 2}O{sub 9} and SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} nanocrystals are relatively larger than those of the corresponding fluorite-like phase and the precursor glass. - Graphical Abstract: This figure shows the XRD patterns at room temperature for the as-quenched and heat treated samples in Sm{sub 2}O{sub 3}-doped (x=0.1) glass. Based on these results, it is concluded that the formation of samarium-doped perovskite SBN phase takes place via an intermediate fluorite-like phase in the crystallization of this glass.

  20. The EOS Aqua/Aura Experience: Lessons Learned on Design, Integration, and Test of Earth-Observing Satellites

    NASA Technical Reports Server (NTRS)

    Nosek, Thomas P.

    2004-01-01

    NASA and NOAA earth observing satellite programs are flying a number of sophisticated scientific instruments which collect data on many phenomena and parameters of the earth's environment. The NASA Earth Observing System (EOS) Program originated the EOS Common Bus approach, which featured two spacecraft (Aqua and Aura) of virtually identical design but with completely different instruments. Significant savings were obtained by the Common Bus approach and these lessons learned are presented as information for future program requiring multiple busses for new diversified instruments with increased capabilities for acquiring earth environmental data volume, accuracy, and type.

  1. The Use of the Integrated Medical Model for Forecasting and Mitigating Medical Risks for a Near-Earth Asteroid Mission

    NASA Technical Reports Server (NTRS)

    Kerstman, Eric; Saile, Lynn; Freire de Carvalho, Mary; Myers, Jerry; Walton, Marlei; Butler, Douglas; Lopez, Vilma

    2011-01-01

    Introduction The Integrated Medical Model (IMM) is a decision support tool that is useful to space flight mission managers and medical system designers in assessing risks and optimizing medical systems. The IMM employs an evidence-based, probabilistic risk assessment (PRA) approach within the operational constraints of space flight. Methods Stochastic computational methods are used to forecast probability distributions of medical events, crew health metrics, medical resource utilization, and probability estimates of medical evacuation and loss of crew life. The IMM can also optimize medical kits within the constraints of mass and volume for specified missions. The IMM was used to forecast medical evacuation and loss of crew life probabilities, as well as crew health metrics for a near-earth asteroid (NEA) mission. An optimized medical kit for this mission was proposed based on the IMM simulation. Discussion The IMM can provide information to the space program regarding medical risks, including crew medical impairment, medical evacuation and loss of crew life. This information is valuable to mission managers and the space medicine community in assessing risk and developing mitigation strategies. Exploration missions such as NEA missions will have significant mass and volume constraints applied to the medical system. Appropriate allocation of medical resources will be critical to mission success. The IMM capability of optimizing medical systems based on specific crew and mission profiles will be advantageous to medical system designers. Conclusion The IMM is a decision support tool that can provide estimates of the impact of medical events on human space flight missions, such as crew impairment, evacuation, and loss of crew life. It can be used to support the development of mitigation strategies and to propose optimized medical systems for specified space flight missions. Learning Objectives The audience will learn how an evidence-based decision support tool can be used to help assess risk, develop mitigation strategies, and optimize medical systems for exploration space flight missions.

  2. Information Technology Infusion Case Study: Integrating Google Earth(Trademark) into the A-Train Data Depot

    NASA Technical Reports Server (NTRS)

    Smith, Peter; Kempler, Steven; Leptoukh, Gregory; Chen, Aijun

    2010-01-01

    This poster paper represents the NASA funded project that was to employ the latest three dimensional visualization technology to explore and provide direct data access to heterogeneous A-Train datasets. Google Earth (tm) provides foundation for organizing, visualizing, publishing and synergizing Earth science data .

  3. On the formulation of gravitational potential difference between the GRACE satellites based on energy integral in Earth fixed frame

    NASA Astrophysics Data System (ADS)

    Zeng, Y. Y.; Guo, J. Y.; Shang, K.; Shum, C. K.; Yu, J. H.

    2015-09-01

    Two methods for computing gravitational potential difference (GPD) between the GRACE satellites using orbit data have been formulated based on energy integral; one in geocentric inertial frame (GIF) and another in Earth fixed frame (EFF). Here we present a rigorous theoretical formulation in EFF with particular emphasis on necessary approximations, provide a computational approach to mitigate the approximations to negligible level, and verify our approach using simulations. We conclude that a term neglected or ignored in all former work without verification should be retained. In our simulations, 2 cycle per revolution (CPR) errors are present in the GPD computed using our formulation, and empirical removal of the 2 CPR and lower frequency errors can improve the precisions of Stokes coefficients (SCs) of degree 3 and above by 1-2 orders of magnitudes. This is despite of the fact that the result without removing these errors is already accurate enough. Furthermore, the relation between data errors and their influences on GPD is analysed, and a formal examination is made on the possible precision that real GRACE data may attain. The result of removing 2 CPR errors may imply that, if not taken care of properly, the values of SCs computed by means of the energy integral method using real GRACE data may be seriously corrupted by aliasing errors from possibly very large 2 CPR errors based on two facts: (1) errors of bar C_{2,0} manifest as 2 CPR errors in GPD and (2) errors of bar C_{2,0} in GRACE data-the differences between the CSR monthly values of bar C_{2,0} independently determined using GRACE and SLR are a reasonable measure of their magnitude-are very large. Our simulations show that, if 2 CPR errors in GPD vary from day to day as much as those corresponding to errors of bar C_{2,0} from month to month, the aliasing errors of degree 15 and above SCs computed using a month's GPD data may attain a level comparable to the magnitude of gravitational potential variation signal that GRACE was designed to recover. Consequently, we conclude that aliasing errors from 2 CPR errors in real GRACE data may be very large if not properly handled; and therefore, we propose an approach to reduce aliasing errors from 2 CPR and lower frequency errors for computing SCs above degree 2.

  4. Investigation of Interactions between the Doped Rare Earth Ions and Encaged Radicals in C12A7:RE3 + Using Optical and EPR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Layfield, Carter; Ma, Li; Wang, Xiao-Jun

    2015-03-01

    Doped calcium aluminates (C12A7) (C12A7:Eu3 + and C12A7:Mn2 +) have been prepared using solid state reaction methods. The Eu3 + and Mn2 + dopants can both occupy the Ca2 + positions in C12A7.The unique cage-like structure of C12A7 allows different anions, such as oxygen, hydrogen to be trapped in cage by modifying the sample preparation or treatment conditions. The effects of these encaged anions/radicals on the local symmetries of Ca2 + have been studied using photoluminescence from C12A7 doped with Eu3 +, which is a sensitive environmental probe. The effects can also be independently observed from the hyperfine structure of electron paramagnetic resonance spectra in C12A7 doped with Mn2 +. Our results showed: 1) the presence of 5D0 to 7F0 transition implies that Eu3 + is at a non-centrosymmetric site in all caged radical centers; 2) this singlet transition is doubled when superoxides are encaged in C12A7, indicating that the sites of calcium (or Eu2 +) ions are not identical due to the distortion of the encaged anions; 3) a blue shift of the transition occurred due to nephelauxetic effects in asymmetry sites. We have also observed double sets of EPR signals of sextet hyperfine splitting for Mn2 + in C12A7-O but single sets in C12A7-H. We conclude that the local symmetry around Ca2 + positions are distorted more when superoxide is encaged in C12A7. Finally, RE3 + doped C12A7 samples have been systematically prepared and the interactions between the encaged ions and RE3 + emission centers studied using EPR spectroscopy.

  5. Rare-earth-ion-doped ultra-narrow-linewidth lasers on a silicon chip and applications to intra-laser-cavity optical sensing

    NASA Astrophysics Data System (ADS)

    Bernhardi, E. H.; de Ridder, R. M.; Wörhoff, K.; Pollnau, M.

    2013-03-01

    We report on diode-pumped distributed-feedback (DFB) and distributed-Bragg-reflector (DBR) channel waveguide lasers in Er-doped and Yb-doped Al2O3 on standard thermally oxidized silicon substrates. Uniform surface-relief Bragg gratings were patterned by laser-interference lithography and etched into the SiO2 top cladding. The maximum grating reflectivity exceeded 99%. Monolithic DFB and DBR cavities with Q-factors of up to 1.35×106 were realized. The Erdoped DFB laser delivered 3 mW of output power with a slope efficiency of 41% versus absorbed pump power. Singlelongitudinal- mode operation at a wavelength of 1545.2 nm was achieved with an emission line width of 1.70 0.58 kHz, corresponding to a laser Q-factor of 1.14×1011. Yb-doped DFB and DBR lasers were demonstrated at wavelengths near 1020 nm with output powers of 55 mW and a slope efficiency of 67% versus launched pump power. An Yb-doped dualwavelength laser was achieved based on the optical resonances induced by two local phase shifts in the DFB structure. A stable microwave signal at ~15 GHz with a -3-dB width of 9 kHz and a long-term frequency stability of +/- 2.5 MHz was created via the heterodyne photo-detection of the two laser wavelengths. By measuring changes in the microwave beat signal as the intra-cavity evanescent laser field interacts with micro-particles on the waveguide surface, we achieved real-time detection and accurate size measurement of single micro-particles with diameters ranging between 1 μm and 20 μm, which represents the typical size of many fungal and bacterial pathogens. A limit of detection of ~500 nm was deduced.

  6. Tin oxide thick film by doping rare earth for detecting traces of CO{sub 2}: Operating in oxygen-free atmosphere

    SciTech Connect

    Xiong, Ya; Zhang, Guozhu; Zhang, Shunping; Zeng, Dawen; Xie, Changsheng

    2014-04-01

    Highlights: • La, Gd, and Lu doped SnO{sub 2} with their sensing properties toward CO{sub 2} were compared. • The microstructures of SnO{sub 2}-based nanoparticles were elaborately characterized. • La-SnO{sub 2} thick film shows superior response toward trace ppm CO{sub 2}. • Our sensing material can be recommended to employ in oxygen-free environment. - Abstract: SnO{sub 2} thick films doped with atomic ratios ranging from 0 up to 8 at.% La, 8 at.% Gd, 8 at.% Lu were fabricated, respectively, via hydrothermal and impregnation methods. The crystal phase, morphology, and chemical composition of the SnO{sub 2}-based nanoparticles were characterized by XRD, FE-SEM, EDX, HRTEM and XPS. Sensing properties of La-SnO{sub 2}, Gd-SnO{sub 2}, Lu-SnO{sub 2} films, as well as the pure SnO{sub 2} film, were analyzed toward CO{sub 2} in the absence of O{sub 2}. It was found that the optimal doping element was La and the best doping ratio was 4 at.%. The maximum response appeared at an operating temperature of 250 °C, on which condition the 4 at.% La-SnO{sub 2} exhibited a remarkable improvement of response from 5.12 to 29.8 when increasing CO{sub 2} concentration from 50 to 500 ppm. Furthermore, the working mechanism underlying such enhancement in CO{sub 2}-sensing functions by La additive in the absence of O{sub 2} was proposed and discussed.

  7. Effects of some rare earth and carbonate-based co-dopants on structural and electrical properties of samarium doped ceria (SDC) electrolytes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Anwar, Mustafa; Khan, Zuhair S.; Mustafa, Kamal; Rana, Akmal

    2015-09-01

    In the present study, samarium doped ceria (SDC) and SDC-based composite with the addition of K2CO3 were prepared by co-precipitation route and effects of pH of the solution and calcination temperature on microstructure of SDC and SDC-K2CO3, respectively, were investigated. Furthermore, experimentation was performed to investigate into the ionic conductivity of pure SDC by co-doping with yttrium i.e., YSDC, XRD and SEM studies show that the crystallite size and particle size of SDC increases with the increase in pH. The SEM images of all the samples of SDC synthesized at different pH values showed the irregular shaped and dispersed particles. SDC-K2CO3 was calcined at 600?C, 700?C and 800?C for 4 h and XRD results showed that crystallite size increases while lattice strain, decreases with the increase in calcination temperature and no peaks were detected for K2CO3 as it is present in an amorphous form. The ionic conductivity of the electrolytes increases with the increase in temperature and SDC-K2CO3 shows the highest value of ionic conductivity as compared to SDC and YSDC. Chemical compatibility tests were performed between the co-doped electrolyte and lithiated NiO cathode at high temperature. It revealed that the couple could be used up to the temperature of 700?C.

  8. Rare earth ions doped polyaniline/cobalt ferrite nanocomposites via a novel coordination-oxidative polymerization-hydrothermal route: Preparation and microwave-absorbing properties

    NASA Astrophysics Data System (ADS)

    Yang, Chunming; Jiang, Junjun; Liu, Xiaohua; Yin, Chengjie; Deng, Cuifen

    2016-04-01

    Polyaniline/CoRExFe2-xO4 (RE=La, Ce, Y, x=0.05-0.25) nanocomposites were successfully synthesized by a novel coordination-oxidative polymerization-hydrothermal method, and doped by sulfosalicylic acid. The resultant nanocomposites were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and electromagnetic measurements. The composites mainly showed nanofibers with a diameter of ca. 70 nm and a length longer than 2 μm. The surface of composites was uniformly covered with numerous nanoparticles with an average size of ca. 10-20 nm. Microwave absorption properties of polyaniline/CoRExFe2-xO4 nanocomposites doped with La ion were found to be better than those doped with Ce and Y ions. For the polyaniline/CoLaxFe2-xO4 nanocomposite, the optimal microwave absorption performance is at x=0.15, that is, the mass ratio of La in CoLaxFe2-xO4 is 7.5%, with the conductivity of the composite about 0.833 S/cm. Furthermore, when the layer thickness is 2 mm, the maximum reflection loss achieves the maximum number of -42.65 dB at 15.91 GHz with a bandwidth of 6.14 GHz above -10 dB loss, suggesting that these nanocomposites are excellent in microwave absorbing capacity.

  9. Large research infrastructure for Earth-Ocean Science: Challenges of multidisciplinary integration across hardware, software, and people networks

    NASA Astrophysics Data System (ADS)

    Best, M.; Barnes, C. R.; Johnson, F.; Pautet, L.; Pirenne, B.; Founding Scientists Of Neptune Canada

    2010-12-01

    NEPTUNE Canada is operating a regional cabled ocean observatory across the northern Juan de Fuca Plate in the northeastern Pacific. Installation of the first suite of instruments and connectivity equipment was completed in 2009, so this system now provides the continuous power and bandwidth to collect integrated data on physical, chemical, geological, and biological gradients at temporal resolutions relevant to the dynamics of the earth-ocean system. The building of this facility integrates hardware, software, and people networks. Hardware progress to date includes: installation of the 800km powered fiber-optic backbone in the Fall of 2007; development of Nodes and Junction Boxes; acquisition/development and testing of Instruments; development of mobile instrument platforms such as a) a Vertical Profiler and b) a Crawler (University of Bremmen); and integration of over a thousand components into an operating subsea sensor system. Nodes, extension cables, junction boxes, and instruments were installed at 4 out of 5 locations in 2009; the fifth Node is instrumented in September 2010. In parallel, software and hardware systems are acquiring, archiving, and delivering the continuous real-time data through the internet to the world - already many terabytes of data. A web environment (Oceans 2.0) to combine this data access with analysis and visualization, collaborative tools, interoperability, and instrument control is being released. Finally, a network of scientists and technicians are contributing to the process in every phase, and data users already number in the thousands. Initial experiments were planned through a series of workshops and international proposal competitions. At inshore Folger Passage, Barkley Sound, understanding controls on biological productivity help evaluate the effects that marine processes have on fish and marine mammals. Experiments around Barkley Canyon allow quantification of changes in biological and chemical activity associated with nutrient and cross-shelf sediment transport around the shelf/slope break and through the canyon to the deep sea. There and north along the mid-continental slope, instruments on exposed and shallowly buried gas hydrates allow monitoring of changes in their distribution, structure, and venting, particularly related to earthquakes, slope failures and regional plate motions. Circulation obviation retrofit kits (CORKs) at mid-plate ODP 1026-7 monitor real-time changes in crustal temperature and pressure, particularly as they relate to events such as earthquakes, hydrothermal convection or regional plate strain. At Endeavour Ridge, complex interactions among volcanic, tectonic, hydrothermal and biological processes are quantified at the western edge of the Juan de Fuca plate. Across the network, high resolution seismic information elucidates tectonic processes such as earthquakes, and a tsunami system allows determination of open ocean tsunami amplitude, propagation direction, and speed. The infrastructure has further capacity for experiments to expand from this initial suite. Further information and opportunities can be found at http://www.neptunecanada.ca

  10. Characterizing an Integrated Annual Global Measure of the Earth's Maximum Land Surface Temperatures from 2003 to 2012 Reveals Strong Biogeographic Influences

    NASA Astrophysics Data System (ADS)

    Mildrexler, D. J.; Zhao, M.; Running, S. W.

    2014-12-01

    Land Surface Temperature (LST) is a good indicator of the surface energy balance because it is determined by interactions and energy fluxes between the atmosphere and the ground. The variability of land surface properties and vegetation densities across the Earth's surface changes these interactions and gives LST a unique biogeographic influence. Natural and human-induced disturbances modify the surface characteristics and alter the expression of LST. This results in a heterogeneous and dynamic thermal environment. Measurements that merge these factors into a single global metric, while maintaining the important biophysical and biogeographical factors of the land surface's thermal environment are needed to better understand integrated temperature changes in the Earth system. Using satellite-based LST we have developed a new global metric that focuses on one critical component of LST that occurs when the relationship between vegetation density and surface temperature is strongly coupled: annual maximum LST (LSTmax). A 10 year evaluation of LSTmax histograms that include every 1-km pixel across the Earth's surface reveals that this integrative measurement is strongly influenced by the biogeographic patterns of the Earth's ecosystems, providing a unique comparative view of the planet every year that can be likened to the Earth's thermal maximum fingerprint. The biogeographical component is controlled by the frequency and distribution of vegetation types across the Earth's land surface and displays a trimodal distribution. The three modes are driven by ice covered polar regions, forests, and hot desert/shrubland environments. In ice covered areas the histograms show that the heat of fusion results in a convergence of surface temperatures around the melting point. The histograms also show low interannual variability reflecting two important global land surface dynamics; 1) only a small fraction of the Earth's surface is disturbed in any given year, and 2) when considered at the global scale, the positive and negative climate forcings resulting from the aggregate effects of the loss of vegetation to disturbances and the regrowth from natural succession are roughly in balance. Changes in any component of the histogram can be tracked and would indicate a major change in the Earth system.

  11. Geometries and electronic properties of the neutral and charged rare earth Yb-doped Si(n) (n = 1-6) clusters: a relativistic density functional investigation.

    PubMed

    Zhao, Run-Ning; Ren, Zhao-Yu; Guo, Ping; Bai, Jin-Tao; Zhang, Chong-Hui; Han, Ju-Guang

    2006-03-23

    The neutral and charged YbSi(n) (n = 1-6) clusters considering different spin configurations have been systematically investigated by using the relativistic density functional theory with generalized gradient approximation. The total bonding energies, equilibrium geometries, Mulliken populations (MP), Hirshfeld charges (HC), fragmentation energies, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps are calculated and discussed. The optimized geometries indicate that the most stable YbSi(n) (n = 1-6) clusters keep basically the analogous frameworks as the low-lying Si(n)(+1) clusters, while the charged species deviate from their neutral counterparts, and that the doped Yb tends to occupy the substitutional site of the neutral and charged YbSi(n) isomers. The relative stabilities are investigated in terms of the calculated fragmentation energies, exhibiting enhanced stabilities for the remarkably stable neutral and charged YbSi2 and YbSi5 clusters. Furthermore, the calculated MP and HC values show that the charges of the neutral and charged YbSi(n) clusters transfer from the Yb atom to Si(n) atoms and the Yb atom acts as an electron donor, and that the f orbitals of the Yb atom in the neutral and charged YbSi(n) clusters behave as core without involvement in chemical bonding. The calculated HOMO-LUMO gaps indicate that the YbSi2 and YbSi4+ clusters have stronger chemical stabilities. Comparisons of the Yb-doped Si(n) (n = 1-6) with available theoretical results of transition-metal-doped silicon clusters are made. The growth pattern is investigated also. PMID:16539431

  12. Ambient Large-Scale Template-Mediated Synthesis of High-Aspect Ratio Single-Crystalline, Chemically Doped Rare-Earth Phosphate Nanowires for Bioimaging

    SciTech Connect

    Zhang, F.; Wong, S.

    2009-12-30

    A simple and effective template-mediated protocol has been developed for the large-scale, room-temperature preparation of high-aspect-ratio, single-crystalline Tb-doped CePO{sub 4} nanowires, measuring {approx}12 nm in diameter and over 10 {mu}m in length. Moreover, we also isolated sheaf-like bundles of nanostructures. The synthesis mechanism likely involved a crystal splitting step. The resulting nanowires demonstrated an intense redox-sensitive green photoluminescence, which was exploited, in addition to their inherently high biocompatibility and low toxicity, for potential applications in biological imaging and labeling of cells.

  13. Blue, yellow and orange color emitting rare earth doped BaCa2Al8O15 phosphors prepared by combustion method

    NASA Astrophysics Data System (ADS)

    Yerpude, A. N.; Dhoble, S. J.; Reddy, B. Sudhakar

    2014-12-01

    Eu2+, Dy3+, Sm3+ activated BaCa2Al8O15 phosphors were prepared by the combustion method. The phosphor powders were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectrophotometer. Photoluminescence spectra of BaCa2Al8O15:Eu2+ phosphors show emission wavelength at 435 nm that corresponds to 4f65d1→4f7 transition of Eu2+ ion by keeping excitation wavelength extending broad-band from 270 to 400 nm centered at 334 nm. The Dy3+ doped BaCa2Al8O15 phosphors shows blue emission (485 nm) and yellow emission (566 nm) under the excitation of 347 nm, corresponding to the 4F9/2→6H15/2 transition and 4F9/2→6H13/2 transition of Dy3+ ions, respectively. The Sm3+ doped BaCa2Al8O15 phosphors have shown strong orange emission at 604 nm corresponding to the 4G5/2→6H7/2 transition of Sm3+ with intense excitation wavelength at 406 nm. Scanning electron microscopy has been used for exploring the size and morphological properties of the prepared phosphors. The obtained results show that the phosphors have potential application in the field of solid state lighting.

  14. The boundary integral method for the D.C. geoelectric problem in the 3-layered earth with a prismoid inhomogeneity in the second layer

    NASA Astrophysics Data System (ADS)

    Hvoždara, Milan

    2012-12-01

    The paper presents algorithm and numerical results for the boundary integral equations (BIE) method of the forward D.C. geoelectric problem for the three-layered earth which contains the prismoidal body with sloped faces in the second layer. This situation occurs in the sedimentary basins. Although the numerical calculations are more complicated in comparison with faces orthogonal to the x, y, z axes, the generalization to the sloped faces enables treatment of the anomalous fields for the bodies of more general shapes as rectangular prisms. The graphs with numerical results present isoline maps of the perturbing potential as well as the resistivity profiles when the source field is due to the pair of D.C. electrodes at the surface of the earth. Also presented apparent resistivity curves for the Schlumberger array AMNB sounding.

  15. Distributed Infrastructure Enabling Effective Integration of Earth Observation Information Resources for Collective Solution of Archiving, Searching, Processing and EO Data Analyzing Tasks

    NASA Astrophysics Data System (ADS)

    Savorskiy, V. P.; Lupyan, E. A.; Kaevitser, V. I.; Smirnov, M. T.; Ermakov, D. M.; Balashov, I. V.; Bourtsev, M. A.; Efremov, V. Yu; Proshin, A. A.; Tolpin, V. A.; Uvarov, L. A.; Flitman, E. V.

    2012-07-01

    Numerous applications of Earth observation (EO) data for Earth resource exploration both for land use management purposes and for fundamental research goals require as much as possible independent EO data sets provided for a number of data consumers, i.e. for collective (shared) data usage. In addition data distribution procedures should be accompanied with sophisticated information services enabling correct interpretation and application of provided data. As a result data providers should be able to convert data in a lot of consumer-proper formats and in some cases it should require additional data processing before data shipping. Presented work proposes basic infrastructure for collective (shared) EO data usage that enables above mentioned integration of information resources contained in typical Russian EO centers. Paper reveals architecture design, description of basic infrastructure elements, and examples of real implementations.

  16. Defect Clustering and Nano-phase Structure Characterization of Multicomponent Rare Earth-Oxide-Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2004-01-01

    Advanced thermal barrier coatings (TBCs) have been developed by incorporating multicomponent rare earth oxide dopants into zirconia-based thermal barrier coatings to promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nanophases within the coating systems. In this paper, the defect clusters, induced by Nd, Gd, and Yb rare earth dopants in the zirconia-yttria thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The TEM lattice imaging, selected area diffraction (SAD), and electron energy-loss spectroscopy (EELS) analyses demonstrated that the extensive nanoscale rare earth dopant segregation exists in the plasma-sprayed and electron-physical-vapor-deposited (EB PVD) thermal barrier coatings. The nanoscale concentration heterogeneity and the resulting large lattice distortion promoted the formation of parallel and rotational defective lattice clusters in the coating systems. The presence of the 5-to 100-nm-sized defect clusters and nanophases is believed to be responsible for the significant reduction of thermal conductivity, improved sintering resistance, and long-term high temperature stability of the advanced thermal barrier coating systems.

  17. Supramolecular recognition control of polyethylene glycol modified N-doped graphene quantum dots: tunable selectivity for alkali and alkaline-earth metal ions.

    PubMed

    Yang, Siwei; Sun, Jing; Zhu, Chong; He, Peng; Peng, Zheng; Ding, Guqiao

    2016-02-01

    The graphene quantum dot based fluorescent probe community needs unambiguous evidence about the control on the ion selectivity. In this paper, polyethylene glycol modified N-doped graphene quantum dots (PN-GQDs) were synthesized by alkylation reaction between graphene quantum dots and organic halides. We demonstrate the tunable selectivity and sensitivity by controlling the supramolecular recognition through the length and the end group size of the polyether chain on PN-GQDs. The relationship formulae between the selectivity/detection limit and polyether chains are experimentally deduced. The polyether chain length determines the interaction between the PN-GQDs and ions with different ratios of charge to radius, which in turn leads to a good selectivity control. Meanwhile the detection limit shows an exponential growth with the size of end groups of the polyether chain. The PN-GQDs can be used as ultrasensitive and selective fluorescent probes for Li(+), Na(+), K(+), Mg(2+), Ca(2+) and Sr(2+), respectively. PMID:26730814

  18. Practicing ESD at School: Integration of Formal and Nonformal Education Methods Based on the Earth Charter (Belarusian Experience)

    ERIC Educational Resources Information Center

    Savelava, Sofia; Savelau, Dmitry; Cary, Marina Bakhnova

    2010-01-01

    The Earth Charter represents the philosophy and ethics necessary to create a new period of human civilization. Understanding and adoption of this new vision is the most important mission of education for sustainable development (ESD). This article argues that for successful implementation of ESD principles at school, the school education system…

  19. Nonlinear single-crystal fibers of undoped and rare earth-doped niobates: growth by LHPG, spectroscopy and second harmonic generation

    NASA Astrophysics Data System (ADS)

    Foulon, Gisele; Ferriol, Michel; Brenier, Alain; Cohen-Adad, Marie-Therese; Boulon, Georges

    1997-11-01

    The renewal of second order non-linear crystals is very strong in laser materials optics. We are involved in the search of new systems based upon highly non-linear niobate crystal family. Among these crystals, Ba2NaNb5O15 (BNN) and K3Li2-xNb5+xO15+2x (KLN, 0.15 < x < 0.5) with a tungsten bronze-type structure are very efficient materials for the obtention of respectively green and blue laser light by frequency doubling or by self-frequency doubling after doping by Nd3+ ions. Unfortunately, BNN and KLN are difficult to grow by conventional techniques such as Czochralski without cracks caused by a strong lattice change occurring during cooling of the crystals. In addition, microtwins in BNN crystals and compositional inhomogeneities in KLN ones are often encountered. The obtention of good quality and crackless BNN and KLN single crystals doped with different amounts of Nd2O3 is reported. The crystals were grown by the laser heated pedestal growth technique. This method allowed to obtain good quality and homogeneous crystals of BNN and KLN overcoming the problems encountered with other growth techniques. More particularly, for BNN crystals, a structural transition between orthohombic and tetragonal symmetry was found to occur for a Nd3+ amount between 2 and 3 atomic percent avoiding the microtwinning which disturbs the optical properties of the crystals. Low temperature spectroscopy revealed that Nd3+ ions substitute both Ba2+ and Na+ ions in the pentagonal and square sites of the tungsten bronze-type structure of BNN whereas they substitute only K+ ions in the pentagonal sites of that of KLN. Non- critical phase matching at room temperature was also investigated for both materials.

  20. Why are the Tcs so high in rare-earth doped CaFe2As2 single crystals and ultrathin FeSe epi-films?

    NASA Astrophysics Data System (ADS)

    Chu, C. W.

    2015-03-01

    Recent reports of non-bulk superconductivity with unexpectedly high onset-Tcs up to 49 K in the Pr-doped CaFe2As2 [(Ca,Pr)122] single crystals and up to 100 K in one-unit-cell (1UC) FeSe epi-films, respectively, offer an unusual opportunity to seek an answer to the question posed in the title. Through systematic compositional, structural, resistive, and magnetic investigations on (Ca,R)122 single crystals with R = La, Ce, Pr, and Nd, we have observed a doping-level-independent Tc, a large magnetic anisotropy, and the existence of mesoscopic-2D structures in these crystals, thus providing evidence consistent with the proposed interface-enhanced Tc in these naturally assembled Fe-based superconductors. Similar resistive and magnetic measurements were also made on the 1-4UC FeSe ultra thin epi-films. We have detected a Meissner state below 1 Oe with extensive weak-links up to ~ 20 K, unconnected small superconducting patches up to ~ 40 K, and an unusual dispersion of diamagnetic moment with frequency up to 80 K. The unusual frequency dependences of the diamagnetic moment observed in the films at different temperature ranges suggest that collective excitations of electron and/or spin nature may exist in the FeSe films below 20 K and 40-80 K. The experimental results will be presented and the implications discussed. Collaborators: Liangzi Deng, Bing Lv, Fengyan Wei, and Yu-Yi Xue, University of Houston; Li-Li Wang, Xu-Cun Ma, and Qi-Kun Xue, Tsinghua University, Beijing.

  1. Constructing one-dimensional silver nanowire-doped reduced graphene oxide integrated with CdS nanowire network hybrid structures toward artificial photosynthesis

    NASA Astrophysics Data System (ADS)

    Liu, Siqi; Weng, Bo; Tang, Zi-Rong; Xu, Yi-Jun

    2014-12-01

    A ternary hybrid structure of one-dimensional (1D) silver nanowire-doped reduced graphene oxide (RGO) integrated with a CdS nanowire (NW) network has been fabricated via a simple electrostatic self-assembly method followed by a hydrothermal reduction process. The electrical conductivity of RGO can be significantly enhanced by opening up new conduction channels by bridging the high resistance grain-boundaries (HGBs) with 1D Ag nanowires, which results in a prolonged lifetime of photo-generated charge carriers excited from the CdS NW network, thus making Ag NW-RGO an efficient co-catalyst with the CdS NW network toward artificial photosynthesis.A ternary hybrid structure of one-dimensional (1D) silver nanowire-doped reduced graphene oxide (RGO) integrated with a CdS nanowire (NW) network has been fabricated via a simple electrostatic self-assembly method followed by a hydrothermal reduction process. The electrical conductivity of RGO can be significantly enhanced by opening up new conduction channels by bridging the high resistance grain-boundaries (HGBs) with 1D Ag nanowires, which results in a prolonged lifetime of photo-generated charge carriers excited from the CdS NW network, thus making Ag NW-RGO an efficient co-catalyst with the CdS NW network toward artificial photosynthesis. Electronic supplementary information (ESI) available: Experimental details, photographs of the experimental setups for photocatalytic activity testing, SEM images of Ag NWs and CdS NWs, Zeta potential, Raman spectra, DRS spectra, PL spectra and PL decay time evolution, and photocatalytic performances of samples for reduction of 4-NA and recycling test. See DOI: 10.1039/c4nr04229h

  2. Integrating Science Content and Pedagogy in the Earth, Life, and Physical Sciences: A K-8 Pre-Service Teacher Preparation Continuum at the University of Delaware

    NASA Astrophysics Data System (ADS)

    Madsen, J.; Allen, D.; Donham, R.; Fifield, S.; Ford, D.; Shipman, H.; Dagher, Z.

    2007-12-01

    University of Delaware faculty in the geological sciences, biological sciences, and the physics and astronomy departments have partnered with faculty and researchers from the school of education to form a continuum for K- 8 pre-service teacher preparation in science. The goal of the continuum is to develop integrated understandings of content and pedagogy so that these future teachers can effectively use inquiry-based approaches in teaching science in their classrooms. Throughout the continuum where earth science content appears an earth system science approach, with emphasis on inquiry-based activities, is employed. The continuum for K-8 pre-service teachers includes a gateway content course in the earth, life, or physical sciences taken during the freshman year followed by integrated science content and methods courses taken during the sophomore year. These integrated courses, called the Science Semester, were designed and implemented with funding from the National Science Foundation. During the Science Semester, traditional content and pedagogy subject matter boundaries are crossed to stress shared themes that teachers must understand to teach standards-based science. Students work collaboratively on multidisciplinary problem-based learning (PBL) activities that place science concepts in authentic contexts and build learning skills. They also critically explore the theory and practice of elementary science teaching, drawing on their shared experiences of inquiry learning during the Science Semester. The PBL activities that are the hallmark of the Science Semester provide the backdrop through which fundamental earth system interactions can be studied. For example in a PBL investigation that focuses on kids, cancer, and the environment, the hydrologic cycle with emphasis on surface runoff and ground water contamination is studied. Those students seeking secondary certification in science will enroll, as a bridge toward their student teaching experience, in an additional content course within a science discipline that is concurrently taught with a science methods course. Emphasizing inquiry-based activities, these bridge courses also focus on developing integrated understandings of the sciences. The continuum extends beyond the student teaching experience by tracking cohorts of science teachers during their in-service years. With funding from the National Science Foundation's Teacher Professional Continuum program, we are conducting research on this inquiry-based professional development approach for K-8 teachers across this continuum.

  3. BaY{sub 2}F{sub 8} single crystals doped with rare-earth ions as promising up-conversion media for UV and VUV lasers

    SciTech Connect

    Pushkar', A A; Uvarova, T V; Molchanov, V N

    2008-04-30

    BaY{sub 2}F{sub 8} crystals are studied as promising active media for UV and VUV lasers. The up-conversion pumping of rare-earth activators is proposed to solve problems related to the solarisation of the medium and the selection of pump sources. The technology of growing oriented BaY{sub 2}F{sub 8} single crystals is developed and the influence of the crystal orientation on the growth rate and quality of single crystals is determined. (active media)

  4. EarthScope's Plate Boundary Observatory in Alaska: Building on Existing Infrastructure to Provide a Platform for Integrated Research and Hazard-monitoring Efforts

    NASA Astrophysics Data System (ADS)

    Boyce, E. S.; Bierma, R. M.; Willoughby, H.; Feaux, K.; Mattioli, G. S.; Enders, M.; Busby, R. W.

    2014-12-01

    EarthScope's geodetic component in Alaska, the UNAVCO-operated Plate Boundary Observatory (PBO) network, includes 139 continuous GPS sites and 41 supporting telemetry relays. These are spread across a vast area, from northern AK to the Aleutians. Forty-five of these stations were installed or have been upgraded in cooperation with various partner agencies and currently provide data collection and transmission for more than one group. Leveraging existing infrastructure normally has multiple benefits, such as easier permitting requirements and costs savings through reduced overall construction and maintenance expenses. At some sites, PBO-AK power and communications systems have additional capacity beyond that which is needed for reliable acquisition of GPS data. Where permits allow, such stations could serve as platforms for additional instrumentation or real-time observing needs. With the expansion of the Transportable Array (TA) into Alaska, there is increased interest to leverage existing EarthScope resources for station co-location and telemetry integration. Because of the complexity and difficulty of long-term O&M at PBO sites, however, actual integration of GPS and seismic equipment must be considered on a case-by-case basis. UNAVCO currently operates two integrated GPS/seismic stations in collaboration with the Alaska Earthquake Center, and three with the Alaska Volcano Observatory. By the end of 2014, PBO and TA plan to install another four integrated and/or co-located geodetic and seismic systems. While three of these are designed around existing PBO stations, one will be a completely new TA installation, providing PBO with an opportunity to expand geodetic data collection in Alaska within the limited operations and maintenance phase of the project. We will present some of the design considerations, outcomes, and lessons learned from past and ongoing projects to integrate seismometers and other instrumentation at PBO-Alaska stations. Developing the PBO network as a platform for ongoing research and hazard monitoring equipment may also continue to serve the needs of the research community and the public beyond the sun-setting and completion of EarthScope science plan in 2018.

  5. Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films

    PubMed Central

    Zhang, Huairuo; Reaney, Ian M.; Marincel, Daniel M.; Trolier-McKinstry, Susan; Ramasse, Quentin M.; MacLaren, Ian; Findlay, Scott D.; Fraleigh, Robert D.; Ross, Ian M.; Hu, Shunbo; Ren, Wei; Mark Rainforth, W.

    2015-01-01

    Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.6Bi0.25Nd0.15)3+ Fe3+O3, formed within epitaxial Ti and Nd doped BiFeO3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe2O3-rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe2O3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe2O3. This finding is therefore significant not only to the thin film but also to the high-pressure community. PMID:26272264

  6. Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films.

    PubMed

    Zhang, Huairuo; Reaney, Ian M; Marincel, Daniel M; Trolier-McKinstry, Susan; Ramasse, Quentin M; MacLaren, Ian; Findlay, Scott D; Fraleigh, Robert D; Ross, Ian M; Hu, Shunbo; Ren, Wei; Rainforth, W Mark

    2015-01-01

    Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.6Bi0.25Nd0.15)(3+) Fe(3+)O3, formed within epitaxial Ti and Nd doped BiFeO3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe2O3-rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe2O3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe2O3. This finding is therefore significant not only to the thin film but also to the high-pressure community. PMID:26272264

  7. Synthesis and characterization of visible emission from rare-earth doped aluminum nitride, gallium nitride and gallium aluminum nitride powders and thin films

    NASA Astrophysics Data System (ADS)

    Tao, Jonathan Huai-Tse

    A three-step solution-based process had been used synthesize powders of GaN, AlN and their alloys. The complete solid solubility and tunable nature of these nitride band gaps in the visible spectrum were the motivation of these studies due to their application in solid state lighting. Energy dispersive X-ray spectroscopy confirmed the reduction in oxygen content for the GaN powders to as low as 4 atom % with an 8 % oxygen to nitrogen ratio. Relative to commercial GaN powders, the bandedge of the powders synthesized by such approach also shifted to higher energy, which indicated fewer defects, as observed from reflectance measurements. Inspired by the use of rare-earth elements as color emitters in fluorescent lamp phosphors, these elements were also used as activators in our nitride material. Visible emission was demonstrated through photoluminescence measurements in AlN powders activated with rare-earth elements Eu3+, Tb3+, Tm3+. These ions showed emission in the red, green and blue regions of the visible spectrum, respectively. Eu3+ and Tb3+ co-activation was also observed in an AlN sample that indicated successful energy transfer from the host to sensitizer, and subsequently to another activator. Tb3+ emission was observed under cathodoluminescence in GaN powders synthesized by the same method, and a concentration study showed no effect of concentration quenching up to 8 atom %. Using the same source powder, a pulsed-laser deposited thin film was fabricated that showed both band gap emission and activator-related emission, suggesting a reduction of defects when the powders were deposited as thin films. Additionally, GaN:Tb3+ films were also fabricated using metallorganic vapor phase epitaxy using precursors with and without oxygen ligands. Tb3+ emission was only observed in the sample fabricated from the precursor with oxygen ligand, suggestion that oxygen may be required for effective rare earth luminescence. Finally, Ga1-xAl xN alloy powders (x=0.5) and Ga1-x-yAlxDy yN (x=0.10, 0.30, y=0.01) powders were synthesized using the solution method while incorporating a stainless steel pressure vessel, which increased the synthesis pressure and aided the formation of a single phase hydroxide precursor. This in turn produced a single phase alloy nitride in the final step. Dy3+ emission that was not observed in GaN powders was also observed in the Ga1-x-yAlxDyyN powder. This suggested that the incorporation of aluminum enabled rare-earth emission in the nitrides synthesized for these experiments. However, attempts to sputter nitride alloy thin films via radio frequency sputtering were unsuccessful; only very minor peak shifts in the X-ray diffraction patterns were observed. Nevertheless, energy dispersive X-ray spectroscopy indicates the presence of Al in the Ga0.5Al0.5N film deposited on a Si substrate. This suggested that Al atoms may have segregated from the alloy lattice during the deposition process, with only a small amount of Al atoms incorporated into the GaN lattice.

  8. Magnetic and microwave absorption properties of rare earth ions (Sm3+, Er3+) doped strontium ferrite and its nanocomposites with polypyrrole

    NASA Astrophysics Data System (ADS)

    Luo, Juhua; Xu, Yang; Mao, Hongkai

    2015-05-01

    M-type strontium ferrite substituted by RE (RE=Sm3+, Er3+) were prepared via a sol-gel method. Polypyrrole (PPy)/ferrite nanocomposites (with 20 wt% ferrite) were prepared by in situ polymerization method in the presence of ammonium persulfate. Effect of the substituted RE ions on structure, magnetic properties and microwave absorption properties were investigated by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and vector network analyzer. All XRD patterns show the single phase of strontium hexaferrite without other intermediate phases. The crystallite size of synthesized particle is within the range of 22.2-38.1 nm. The structural in character of the composites were investigated with FT-IR analysis. It shows that the ferrite successfully packed by PPy. TEM photographs show that the particle size had grown up to 50-100 nm after coating with PPy. In the magnetization for the PPy/SrSm0.3Fe11.7O19 (SrEr0.3Fe11.7O19) composites, the coercivity (Hc) of the composites both increased compared with the undoped composite while the saturation magnetization (Ms) appeared opposite change with different RE ions. Considering the electromagnetic loss and impedance matching comprehensively, the Er-doped ferrite/PPy composite got the better microwave absorption performance with the maximum RL value of -24.01 dB in 13.8 GHz at 3.0 mm. And its width (<-10 dB) has reached 7.2 GHz which has covered the whole Ku band.

  9. Study the structural and magnetic properties of rare-earth ions (La and Gd) doped Ba0.9575Ca0.0025Ti0.80685Mn0.002475Nb0.002475Zr0.1782O3 (BCTMNZ) ceramics

    NASA Astrophysics Data System (ADS)

    Rai, Radheshyam; Kumari, Poonam; Valente, M. A.

    2015-12-01

    In this paper, we investigated the influence of rare earth (RE=La and Gd) doped Ba0.9575RE0.04Ca0.0025Ti0.80685 Mn0.002475Nb0.002475Zr0.1782O3 (BCTMNZ) ceramics were fabricated by using a conventional solid-state reaction method. The doping effects of La and Gd on the structural and magnetic properties were studied. The structural pattern of the ceramic samples were investigated by X-ray diffraction and the results indicated that both samples shows an orthorhombic structure with pure phase. Strain and crystalline size values for Gd and La doped were 0.31-0.33% and 0.154-0.181μm, respectively. The room temperature hysteresis loops were obtained by using a vibrating sample magnetometer. La doped ceramic showed the higher value of magnetization i.e., 0.369μB/f.u. as compared to Gd doped BLTMNZ ceramics.

  10. Influence of rare-earth elements doping on thermoelectric properties of Ca0.98Dy0.02MnO3 at high temperature

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanhu; Wang, Chunlei; Su, Wenbin; Liu, Jian; Li, Jichao; Zhang, Xinhua; Mei, Liangmo

    2015-05-01

    Ca0.98Dy0.02MnO3 and Ca0.96Dy0.02Re0.02MnO3 (Re=La, Pr, Sm, Eu, Ho, and Yb) have been synthesized by the solid state reaction method. Samples with relative densities all over 96% have been obtained. Thermoelectric properties are evaluated between 300 and 1000 K. The electrical resistivity shows a typical metal-like conductivity behavior, and at high temperature, 973 K, decreases from 36.1 m? cm for Ca0.98Dy0.02MnO3 to 8.6 m? cm for Ca0.96Dy0.02Yb0.02MnO3. Both the absolute values of Seebeck coefficient and thermal conductivity are reduced by the introduction of second rare-earth element. The highest power factor of 415 ?W/(K2m) is obtained for Ca0.96Dy0.02Yb0.02MnO3 sample, resulting in the highest dimensionless figure of merit (ZT) 0.25 at 973 K. This value shows an improvement of 144% compared with that of Ca0.98Dy0.02MnO3 ceramics at the same temperature.

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

    PubMed Central

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

    2013-01-01

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

  12. The need and potential for building a integrated knowledge-base of the Earth-Human system

    NASA Astrophysics Data System (ADS)

    Jacobs, Clifford

    2011-03-01

    The pursuit of scientific understanding is increasingly based on interdisciplinary research. To understand more deeply the planet and its interactions requires a progressively more holistic approach, exploring knowledge coming from all scientific and engineering disciplines including but not limited to, biology, chemistry, computer sciences, geosciences, material sciences, mathematics, physics, cyberinfrastucture, and social sciences. Nowhere is such an approach more critical than in the study of global climate change in which one of the major challenges is the development of next-generation Earth System Models that include coupled and interactive representations of ecosystems, agricultural working lands and forests, urban environments, biogeochemistry, atmospheric chemistry, ocean and atmospheric currents, the water cycle, land ice, and human activities.

  13. Ray-tracing studies and path-integrated gains of ELF unducted whistler mode waves in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Huang, C. Y.; Goertz, C. K.

    1983-01-01

    Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.

  14. Incubational domain characterization in lightly doped ceria

    SciTech Connect

    Li Zhipeng; Mori, Toshiyuki; John Auchterlonie, Graeme; Zou Jin; Drennan, John

    2012-08-15

    Microstructures of both Gd- and Y-doped ceria with different doping level (i.e., 10 at% and 25 at%) have been comprehensively characterized by means of high resolution transmission electron microscopy and selected area electron diffraction. Coherent nano-sized domains can be widely observed in heavily doped ceria. Nevertheless, it was found that a large amount of dislocations actually exist in lightly doped ceria instead of heavily doped ones. Furthermore, incubational domains can be detected in lightly doped ceria, with dislocations located at the interfaces. The interactions between such linear dislocations and dopant defects have been simulated accordingly. As a consequence, the formation mechanism of incubational domains is rationalized in terms of the interaction between intrinsic dislocations of doped ceria and dopant defects. This study offers the insights into the initial state and related mechanism of the formation of nano-sized domains, which have been widely observed in heavily rare-earth-doped ceria in recent years. - Graphical abstract: Interactions between dislocations and dopants lead to incubational domain formation in lightly doped ceria. Highlights: Black-Right-Pointing-Pointer Microstructures were characterized in both heavily and light Gd-/Y-doped ceria. Black-Right-Pointing-Pointer Dislocations are existed in lightly doped ceria rather than heavily doped one. Black-Right-Pointing-Pointer Interactions between dislocations and dopant defects were simulated. Black-Right-Pointing-Pointer Formation of dislocation associated incubational domain is rationalized.

  15. Temperature-dependent structure of Tb-doped magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rice, Katherine P.; Russek, Stephen E.; Geiss, Roy H.; Shaw, Justin M.; Usselman, Robert J.; Evarts, Eric R.; Silva, Thomas J.; Nembach, Hans T.; Arenholz, Elke; Idzerda, Yves U.

    2015-02-01

    High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High-angle annular dark-field microscopy shows that the dopant is well-distributed throughout the particle, and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming weak coupling between Fe and Tb spins at room temperature. The Gilbert damping constant, ?, is remarkably low for the Tb-doped nanoparticles, with ? = 0.024 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high-relaxivity T1 and T2 MRI agents with integrated optical signatures.

  16. Temperature-dependent structure of Tb-doped magnetite nanoparticles

    SciTech Connect

    Rice, Katherine P.; Russek, Stephen E. Shaw, Justin M.; Usselman, Robert J.; Evarts, Eric R.; Silva, Thomas J.; Nembach, Hans T.; Geiss, Roy H.; Arenholz, Elke; Idzerda, Yves U.

    2015-02-09

    High quality 5 nm cubic Tb-doped magnetite nanoparticles have been synthesized by a wet-chemical method to investigate tailoring of magnetic properties for imaging and biomedical applications. We show that the Tb is incorporated into the octahedral 3+ sites. High-angle annular dark-field microscopy shows that the dopant is well-distributed throughout the particle, and x-ray diffraction measurements show a small lattice parameter shift with the inclusion of a rare-earth dopant. Magnetization and x-ray magnetic circular dichroism data indicate that the Tb spins are unpolarized and weakly coupled to the iron spin lattice at room temperature, and begin to polarize and couple to the iron oxide lattice at temperatures below 50 K. Broadband ferromagnetic resonance measurements show no increase in magnetic damping at room temperature for Tb-doped nanoparticles relative to undoped nanoparticles, further confirming weak coupling between Fe and Tb spins at room temperature. The Gilbert damping constant, α, is remarkably low for the Tb-doped nanoparticles, with α = 0.024 ± 0.003. These nanoparticles, which have a large fixed moment, a large fluctuating moment and optically active rare-earth elements, are potential high-relaxivity T1 and T2 MRI agents with integrated optical signatures.

  17. Early Earth

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2015-05-01

    Earth has continents, subduction and mobile lid plate tectonics, but details of the early evolution are poorly understood. Here I summarize the Hadean-Archean record, review evidence for a hotter Earth and consider geodynamic models for early Earth.

  18. Airplane dopes and doping

    NASA Technical Reports Server (NTRS)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  19. Expedition Earth and Beyond: Engaging Classrooms in Student-Led Research Using NASA Data, Access to Scientists, and Integrated Educational Strategies

    NASA Technical Reports Server (NTRS)

    Graff, P. V.; Stefanov, W. L.; Willis, K. J.; Runco, S.; McCollum, T.; Baker, M.; Lindgren, C.; Mailhot, M.

    2011-01-01

    Classroom teachers are challenged with engaging and preparing today s students for the future. Activities are driven by state required skills, education standards, and high-stakes testing. Providing educators with standards-aligned, inquiry-based activities that will help them engage their students in student-led research in the classroom will help them teach required standards, essential skills, and help inspire their students to become motivated learners. The Astromaterials Research and Exploration Science (ARES) Education Program, classroom educators, and ARES scientists at the NASA Johnson Space Center created the Expedition Earth and Beyond education program to help teachers promote student-led research in their classrooms (grades 5-14) by using NASA data, providing access to scientists, and using integrated educational strategies.

  20. Development of response models for the Earth Radiation Budget Experiment (ERBE) sensors. Part 2: Analysis of the ERBE integrating sphere ground calibration

    NASA Technical Reports Server (NTRS)

    Halyo, Nesim; Taylor, Deborah B.

    1987-01-01

    An explicit solution of the spectral radiance leaving an arbitrary point on the wall of a spherical cavity with diffuse reflectivity is obtained. The solution is applicable to spheres with an arbitrary number of openings of any size and shape, an arbitrary number of light sources with possible non-diffuse characteristics, a non-uniform sphere wall temperature distribution, non-uniform and non-diffuse sphere wall emissivity and non-uniform but diffuse sphere wall spectral reflectivity. A general measurement equation describing the output of a sensor with a given field of view, angular and spectral response measuring the sphere output is obtained. The results are applied to the Earth Radiation Budget Experiment (ERBE) integrating sphere. The sphere wall radiance uniformity, loading effects and non-uniform wall temperature effects are investigated. It is shown that using appropriate interpretation and processing, a high-accuracy short-wave calibration of the ERBE sensors can be achieved.

  1. Three-dimensional cavity quantum electrodynamics with a rare-earth spin ensemble

    NASA Astrophysics Data System (ADS)

    Probst, S.; Tkal?ec, A.; Rotzinger, H.; Rieger, D.; Le Floch, J.-M.; Goryachev, M.; Tobar, M. E.; Ustinov, A. V.; Bushev, P. A.

    2014-09-01

    We present cavity QED experiments with an Er3+:Y2SiO5 crystal magnetically coupled to a three-dimensional (3D) cylindrical sapphire loaded copper resonator. Such waveguide cavities are promising for the realization of a superconducting quantum processor. Here, we demonstrate the coherent integration of a rare-earth spin ensemble with the 3D architecture. The collective coupling strength of the Er3+ spins to the 3D cavity is 21 MHz. The cylindrical sapphire loaded resonator allowed us to explore the anisotropic collective coupling between the rare-earth doped crystal and the cavity. This work shows the potential of spin doped solids in 3D quantum circuits for application as microwave quantum memories as well as for prospective microwave to optical interfaces.

  2. Design of broadband erbium-doped fiber amplifier using very high-speed integrated circuit hardware description language for next-generation optical network

    NASA Astrophysics Data System (ADS)

    Goel, Aditya; Mishra, Ravi Shankar

    2011-01-01

    We mainly concentrate on the problem of gain broadening and flattening of erbium-doped fiber amplifier (EDFA) using dual forward-pumping configuration in which we use pumping both at 980 and 1480 nm wavelengths. The gain cascading of two EDFAs pumped separately at 980 and 1480 nm combines the advantage of high gain characteristics of 980 nm pumping and broad bandwidth characteristics of 1480 nm pumping. The use of increased number of channels in the present dense wavelength division multiplexing (DWDM) optical network requires a flat gain spectrum across the whole usable bandwidth. The use of very high-speed integrated circuit hardware description language (VHDL-AMS) in lightwave system modeling has been explored. Its application in designing wideband EDFA has not been reported thus far. This work facilitates to design broadband EDFA operating in both the C-band and L-band regions with VHDL-AMS. The amplifier design is made of a dual stage, copumped at 980 and 1480 nm, which delivers an average output power of -16 dBm over the entire 3-dB bandwidth of 80 nm.

  3. Peru Water Resources: Integrating NASA Earth Observations into Water Resource Planning and Management in Perus La Libertad Region

    NASA Technical Reports Server (NTRS)

    Padgett-Vasquez, Steve; Steentofte, Catherine; Holbrook, Abigail

    2014-01-01

    Developing countries often struggle with providing water security and sanitation services to their populations. An important aspect of improving security and sanitation is developing a comprehensive understanding of the country's water budget. Water For People, a non-profit organization dedicated to providing clean drinking water, is working with the Peruvian government to develop a water budget for the La Libertad region of Peru which includes the creation of an extensive watershed management plan. Currently, the data archive of the necessary variables to create the water management plan is extremely limited. Implementing NASA Earth observations has bolstered the dataset being used by Water For People, and the METRIC (Mapping EvapoTranspiration at High Resolution and Internalized Calibration) model has allowed for the estimation of the evapotranspiration values for the region. Landsat 8 imagery and the DEM (Digital Elevation Model) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor onboard Terra were used to derive the land cover information, and were used in conjunction with local weather data of Cascas from Peru's National Meteorological and Hydrological Service (SENAMHI). Python was used to combine input variables and METRIC model calculations to approximate the evapotranspiration values for the Ochape sub-basin of the Chicama River watershed. Once calculated, the evapotranspiration values and methodology were shared Water For People to help supplement their decision support tools in the La Libertad region of Peru and potentially apply the methodology in other areas of need.

  4. The EarthCARE space-borne Doppler 94 GHz radar simulator: correction of multiple scattering, aliasing and NUBF and effects of variable along track integration

    NASA Astrophysics Data System (ADS)

    Augustynek, T.; Battaglia, A.; Kollias, P.

    2011-12-01

    The primary goal of this work is to address several challenges related to spaceborne Doppler radars like future the EarthCARE mission and recent developments of data simulation, correction and processing. The 94 GHz Cloud Profiling Radar onboard the ESA EarthCARE mission will be the first radar in space with Doppler capability allowing mean Doppler velocity measurements. This will enable more accurate characterization of clouds and precipitation (classification, retrieval accuracy, dynamics). It is the only instrument of this kind planned for the immediate post-CloudSat era and represents an irreplaceable asset in regards to climate change studies. Meeting the scientific accuracy requirements of vertical motions of 1 m/s, with a horizontal resolution of 1 km, is very challenging. The five key factors that control the performance of spaceborne radar will be discussed, such as: contribution of multiple scattering (MS), attenuation, velocity folding, non uniform beam filling (NUBF) and effects of along track integration of the signal. The research utilizes an end-to-end simulator for spaceborne Doppler radars. The simulator uses a Monte Carlo module which accounts for MS and produces ideal Doppler spectra as measured by a spaceborne radar flying over 3D highly resolved scenes produced via WRF Model simulations. The estimates of the Doppler moments (reflectivity, mean Doppler velocity and spectrum width) are achieved via the pulse pair technique. The objective method for identification of MS-contaminated range-bins based purely on the reflectivity-derived variables is described, with most important one, cumulative integrated reflectivity, found to be 41 dBZ_int which serves as the threshold value for identification of radar range gates contaminated by MS. This is further demonstrated in a CloudSat case study with the threshold value for CloudSat is found to be 41.9 dBZ_int. The unfolding procedure of Doppler velocities will be presented. Then we will describe the effects of the along track integration and achieved accuracy and biases of Doppler velocity for integration distance of 0.5, 1, 5 and 10 km. This will be complemented by correction of NUBF effect utilizing the along tract reflectivity gradient and velocity bias dependence.

  5. An integrated modeling system for estimating glacier and snow melt driven streamflow from remote sensing and earth system data products in the Himalayas

    NASA Astrophysics Data System (ADS)

    Brown, M. E.; Racoviteanu, A. E.; Tarboton, D. G.; Gupta, A. Sen; Nigro, J.; Policelli, F.; Habib, S.; Tokay, M.; Shrestha, M. S.; Bajracharya, S.; Hummel, P.; Gray, M.; Duda, P.; Zaitchik, B.; Mahat, V.; Artan, G.; Tokar, S.

    2014-11-01

    Quantification of the contribution of the hydrologic components (snow, ice and rain) to river discharge in the Hindu Kush Himalayan (HKH) region is important for decision-making in water sensitive sectors, and for water resources management and flood risk reduction. In this area, access to and monitoring of the glaciers and their melt outflow is challenging due to difficult access, thus modeling based on remote sensing offers the potential for providing information to improve water resources management and decision making. This paper describes an integrated modeling system developed using downscaled NASA satellite based and earth system data products coupled with in-situ hydrologic data to assess the contribution of snow and glaciers to the flows of the rivers in the HKH region. Snow and glacier melt was estimated using the Utah Energy Balance (UEB) model, further enhanced to accommodate glacier ice melt over clean and debris-covered tongues, then meltwater was input into the USGS Geospatial Stream Flow Model (GeoSFM). The two model components were integrated into Better Assessment Science Integrating point and Nonpoint Sources modeling framework (BASINS) as a user-friendly open source system and was made available to countries in high Asia. Here we present a case study from the Langtang Khola watershed in the monsoon-influenced Nepal Himalaya, used to validate our energy balance approach and to test the applicability of our modeling system. The snow and glacier melt model predicts that for the eight years used for model evaluation (October 2003-September 2010), the total surface water input over the basin was 9.43 m, originating as 62% from glacier melt, 30% from snowmelt and 8% from rainfall. Measured streamflow for those years were 5.02 m, reflecting a runoff coefficient of 0.53. GeoSFM simulated streamflow was 5.31 m indicating reasonable correspondence between measured and model confirming the capability of the integrated system to provide a quantification of water availability.

  6. An Integrated Modeling System for Estimating Glacier and Snow Melt Driven Streamflow from Remote Sensing and Earth System Data Products in the Himalayas

    NASA Technical Reports Server (NTRS)

    Brown, M. E.; Racoviteanu, A. E.; Tarboton, D. G.; Sen Gupta, A.; Nigro, J.; Policelli, F.; Habib, S.; Tokay, M.; Shrestha, M. S.; Bajracharya, S.

    2014-01-01

    Quantification of the contribution of the hydrologic components (snow, ice and rain) to river discharge in the Hindu Kush Himalayan (HKH) region is important for decision-making in water sensitive sectors, and for water resources management and flood risk reduction. In this area, access to and monitoring of the glaciers and their melt outflow is challenging due to difficult access, thus modeling based on remote sensing offers the potential for providing information to improve water resources management and decision making. This paper describes an integrated modeling system developed using downscaled NASA satellite based and earth system data products coupled with in-situ hydrologic data to assess the contribution of snow and glaciers to the flows of the rivers in the HKH region. Snow and glacier melt was estimated using the Utah Energy Balance (UEB) model, further enhanced to accommodate glacier ice melt over clean and debris-covered tongues, then meltwater was input into the USGS Geospatial Stream Flow Model (Geo- SFM). The two model components were integrated into Better Assessment Science Integrating point and Nonpoint Sources modeling framework (BASINS) as a user-friendly open source system and was made available to countries in high Asia. Here we present a case study from the Langtang Khola watershed in the monsoon-influenced Nepal Himalaya, used to validate our energy balance approach and to test the applicability of our modeling system. The snow and glacier melt model predicts that for the eight years used for model evaluation (October 2003-September 2010), the total surface water input over the basin was 9.43 m, originating as 62% from glacier melt, 30% from snowmelt and 8% from rainfall. Measured streamflow for those years were 5.02 m, reflecting a runoff coefficient of 0.53. GeoSFM simulated streamflow was 5.31 m indicating reasonable correspondence between measured and model confirming the capability of the integrated system to provide a quantification of water availability.

  7. Effects of rare-earth (Tb, Yb, and Lu)-doping on the structural, electrical and ferroelectric properties of K0.5Bi4.5Ti4O15 thin films

    NASA Astrophysics Data System (ADS)

    Kim, J. W.; Raghavan, C. M.; Choi, J. Y.; Kim, S. S.

    2015-10-01

    The electrical and the ferroelectric properties of pure K0.5Bi4.5Ti4O15 and a series of rare-earth-doped K0.5 RE 0.5Bi4Ti4O15 (RE = Tb, Yb, and Lu) thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method have been investigated. Compared to the pure K0.5Bi4.5Ti4O15 thin film, there were no structural changes in the K0.5 RE 0.5Bi4Ti4O15 thin films while the leakage current and the ferroelectric properties were significantly improved. Among the thin films, the K0.5Lu0.5Bi4Ti4O15 thin film exhibited wellsaturated hysteresis loops with a large remnant polarization (2 P r) of 32 ?C/cm2 and a coercive field (2 E c) of 307 kV/cm at an applied electric field of 886 kV/cm. Furthermore, a low leakage current density of 2.95 10-9 A/cm2, which is about two orders of magnitude lower than that of the K0.5Bi4.5Ti4O15 thin film, was measured in the K0.5Lu0.5Bi4Ti4O15 thin film at an applied electric field of 100 kV/cm. The enhanced electrical and ferroelectric properties observed in the rare-earthdoped K0.5 RE 0.5Bi4Ti4O15 thin films can be correlated to a decrease in the number of ionic defects, such as bismuth and oxygen vacancies, structural distortion, and improved microstructure.

  8. A stand-alone tree demography and landscape structure module for Earth system models: integration with global forest data

    NASA Astrophysics Data System (ADS)

    Haverd, V.; Smith, B.; Nieradzik, L. P.; Briggs, P. R.

    2014-02-01

    Poorly constrained rates of biomass turnover are a key limitation of Earth system models (ESM). In light of this, we recently proposed a new approach encoded in a model called Populations-Order-Physiology (POP), for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity. POP is suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any ESM. POP bridges the gap between first generation Dynamic Vegetation Models (DVMs) with simple large-area parameterisations of woody biomass (typically used in current ESMs) and complex second generation DVMs, that explicitly simulate demographic processes and landscape heterogeneity of forests. The key simplification in the POP approach, compared with second-generation DVMs, is to compute physiological processes such as assimilation at grid-scale (with CABLE or a similar land surface model), but to partition the grid-scale biomass increment among age classes defined at sub grid-scale, each subject to its own dynamics. POP was successfully demonstrated along a savanna transect in northern Australia, replicating the effects of strong rainfall and fire disturbance gradients on observed stand productivity and structure. Here, we extend the application of POP to a range of forest types around the globe, employing paired observations of stem biomass and density from forest inventory data to calibrate model parameters governing stand demography and biomass evolution. The calibrated POP model is then coupled to the CABLE land surface model and the combined model (CABLE-POP) is evaluated against leaf-stem allometry observations from forest stands ranging in age from 3 to 200 yr. Results indicate that simulated biomass pools conform well with observed allometry. We conclude that POP represents a preferable alternative to large-area parameterisations of woody biomass turnover, typically used in current ESMs.

  9. Polar Misunderstandings: Earth's Dynamic Dynamo

    ERIC Educational Resources Information Center

    DiSpezio, Michael A.

    2011-01-01

    This article discusses the movement of Earth's north and south poles. The Earth's poles may be a bit more complex and dynamic than what many students and teachers believe. With better understanding, offer them up as a rich landscape for higher-level critical analysis and subject integration. Possible curriculum tie-ins include magnets, Earth

  10. Use of geochemical signatures, including rare earth elements, in mosses and lichens to assess spatial integration and the influence of forest environment

    NASA Astrophysics Data System (ADS)

    Gandois, L.; Agnan, Y.; Leblond, S.; Sjalon-Delmas, N.; Le Roux, G.; Probst, A.

    2014-10-01

    In order to assess the influence of local environment and spatial integration of Trace Metals (TM) by biomonitors, Al, As, Cd, Cr, Cs, Cu, Fe, Mn, Ni, Pb, Sb, Sn, V and Zn and some rare earth element (REE) concentrations have been measured in lichens and mosses collected in three French forest sites located in three distinct mountainous areas, as well as in the local soil and bedrock, and in both bulk deposition (BD) and throughfall (TF). Similar enrichment factors (EF) were calculated using lichens and mosses and local bedrock for most elements, except for Cs, Mn, Ni, Pb, and Cu which were significantly (KW, p < 0.05) more enriched in mosses. Similar REE ratios were measured in soils, bedrock, lichens and mosses at each study sites, indicating a regional integration of atmospheric deposition by both biomonitors. Both TM signature and REE composition of mosses revealed that this biomonitor is highly influenced by throughfall composition, and reflect atmospheric deposition interaction with the forest canopy. This explained the higher enrichment measured in mosses for elements which concentration in deposition were influenced by the canopy, either due to leaching (Mn), direct uptake (Ni), or dry deposition dissolution (Pb, Cu, Cs).

  11. From land use to land cover: Restoring the afforestation signal in a coupled integrated assessment - earth system model and the implications for CMIP5 RCP simulations

    SciTech Connect

    Di Vittorio, Alan V.; Chini, Louise M.; Bond-Lamberty, Benjamin; Mao, Jiafu; Shi, Xiaoying; Truesdale, John E.; Craig, Anthony P.; Calvin, Katherine V.; Jones, Andrew D.; Collins, William D.; Edmonds, James A.; Hurtt, George; Thornton, Peter E.; Thomson, Allison M.

    2014-11-27

    Climate projections depend on scenarios of fossil fuel emissions and land use change, and the IPCC AR5 parallel process assumes consistent climate scenarios across Integrated Assessment and Earth System Models (IAMs and ESMs). To facilitate consistency, CMIP5 used a novel land use harmonization to provide ESMs with seamless, 1500-2100 land use trajectories generated by historical data and four IAMs. However, we have identified and partially addressed a major gap in the CMIP5 land coupling design. The CMIP5 Community ESM (CESM) global afforestation is only 22% of RCP4.5 afforestation from 2005 to 2100. Likewise, only 17% of the Global Change Assessment Model’s (GCAM’s) 2040 RCP4.5 afforestation signal, and none of the pasture loss, were transmitted to CESM within a newly integrated model. This is a critical problem because afforestation is necessary for achieving the RCP4.5 climate stabilization. We attempted to rectify this problem by modifying only the ESM component of the integrated model, enabling CESM to simulate 66% of GCAM’s afforestation in 2040, and 94% of GCAM’s pasture loss as grassland and shrubland losses. This additional afforestation increases vegetation carbon gain by 19 PgC and decreases atmospheric CO2 gain by 8 ppmv from 2005 to 2040, implying different climate scenarios between CMIP5 GCAM and CESM. Similar inconsistencies likely exist in other CMIP5 model results, primarily because land cover information is not shared between models, with possible contributions from afforestation exceeding model-specific, potentially viable forest area. Further work to harmonize land cover among models will be required to adequately rectify this problem.

  12. The Quickest, Lowest-cost Lunar Resource Assessment Program: Integrated High-tech Earth-based Astronomy

    NASA Technical Reports Server (NTRS)

    Pieters, Carle M.

    1992-01-01

    Science and technology applications for the Moon have not fully kept pace with technical advancements in sensor development and analytical information extraction capabilities. Appropriate unanswered questions for the Moon abound, but until recently there has been little motivation to link sophisticated technical capabilities with specific measurement and analysis projects. Over the last decade enormous technical progress has been made in the development of (1) CCD photometric array detectors; (2) visible to near-infrared imaging spectrometers; (3)infrared spectroscopy; (4) high-resolution dual-polarization radar imaging at 3.5, 12, and 70 cm; and equally important (5) data analysis and information extraction techniques using compact powerful computers. Parts of each of these have been tested separately, but there has been no programmatic effort to develop and optimize instruments to meet lunar science and resource assessment needs (e.g., specific wavelength range, resolution, etc.) nor to coordinate activities so that the symbiotic relation between different kinds of data can be fully realized. No single type of remotely acquired data completely characterizes the lunar environment, but there has been little opportunity for integration of diverse advanced sensor data for the Moon. Two examples of technology concepts for lunar measurements are given. Using VIS/near-IR spectroscopy, the mineral composition of surface material can be derived from visible and near-infrared radiation reflected from the surface. The surface and subsurface scattering properties of the Moon can be analyzed using radar backscattering imaging.

  13. Path integral Monte Carlo simulations of H2 adsorbed to lithium-doped benzene: A model for hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Lindoy, Lachlan P.; Kolmann, Stephen J.; D'Arcy, Jordan H.; Crittenden, Deborah L.; Jordan, Meredith J. T.

    2015-11-01

    Finite temperature quantum and anharmonic effects are studied in H2-Li+-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ΔUads, and enthalpy, ΔHads, for H2 adsorption onto Li+-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling—coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li+-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ΔUads and ΔHads are -13.3 ± 0.1 and -14.5 ± 0.1 kJ mol-1, respectively.

  14. Path integral Monte Carlo simulations of H2 adsorbed to lithium-doped benzene: A model for hydrogen storage materials.

    PubMed

    Lindoy, Lachlan P; Kolmann, Stephen J; D'Arcy, Jordan H; Crittenden, Deborah L; Jordan, Meredith J T

    2015-11-21

    Finite temperature quantum and anharmonic effects are studied in H2-Li(+)-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ?Uads, and enthalpy, ?Hads, for H2 adsorption onto Li(+)-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling-coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li(+)-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ?Uads and ?Hads are -13.3 0.1 and -14.5 0.1 kJ mol(-1), respectively. PMID:26590532

  15. From land use to land cover: restoring the afforestation signal in a coupled integrated assessment-earth system model and the implications for CMIP5 RCP simulations

    NASA Astrophysics Data System (ADS)

    Di Vittorio, A. V.; Chini, L. P.; Bond-Lamberty, B.; Mao, J.; Shi, X.; Truesdale, J.; Craig, A.; Calvin, K.; Jones, A.; Collins, W. D.; Edmonds, J.; Hurtt, G. C.; Thornton, P.; Thomson, A.

    2014-11-01

    Climate projections depend on scenarios of fossil fuel emissions and land use change, and the Intergovernmental Panel on Climate Change (IPCC) AR5 parallel process assumes consistent climate scenarios across integrated assessment and earth system models (IAMs and ESMs). The CMIP5 (Coupled Model Intercomparison Project Phase 5) project used a novel "land use harmonization" based on the Global Land use Model (GLM) to provide ESMs with consistent 1500-2100 land use trajectories generated by historical data and four IAMs. A direct coupling of the Global Change Assessment Model (GCAM), GLM, and the Community ESM (CESM) has allowed us to characterize and partially address a major gap in the CMIP5 land coupling design: the lack of a corresponding land cover harmonization. For RCP4.5, CESM global afforestation is only 22% of GCAM's 2005 to 2100 afforestation. Likewise, only 17% of GCAM's 2040 afforestation, and zero pasture loss, were transmitted to CESM within the directly coupled model. This is a problem because GCAM relied on afforestation to achieve RCP4.5 climate stabilization. GLM modifications and sharing forest area between GCAM and GLM within the directly coupled model did not increase CESM afforestation. Modifying the land use translator in addition to GLM, however, enabled CESM to include 66% of GCAM's afforestation in 2040, and 94% of GCAM's pasture loss as grassland and shrubland losses. This additional afforestation increases CESM vegetation carbon gain by 19 PgC and decreases atmospheric CO2 gain by 8 ppmv from 2005 to 2040, which demonstrates that CESM without additional afforestation simulates a different RCP4.5 scenario than prescribed by GCAM. Similar land cover inconsistencies exist in other CMIP5 model results, primarily because land cover information is not shared between models. Further work to harmonize land cover among models will be required to increase fidelity between IAM scenarios and ESM simulations and realize the full potential of scenario-based earth system simulations.

  16. A New Northern Eurasia Earth Science Partnership Initiative (NEESPI): Science Plan of Integrated Approach to Regional Climate and Environment Change Studies

    NASA Astrophysics Data System (ADS)

    Groisman, P. Y.; Bartalev, S. A.

    2004-12-01

    The Northern Eurasia Earth Science Partnership Initiative (NEESPI) is an international large-scale, integrated, regional program of research focusing on the area of Northern Eurasia initiated by NASA and Russian Academy of Sciences. A brief introduction of the NEESPI Science Plan (SP) will be presented. While extensive and diverse, Northern Eurasia has common (and unique) features, the studying of which in a corroborated fashion under the NEESPI umbrella will produce synergetic effects. SP specifically addresses the reasons to look on the region as a "single" piece: transitional economies and land use (the legacy of the former USSR), geographical features (largest landmass in the extratropics mostly isolated from humid air masses), one of the world highest sensitivities to climatic and environmental changes with feedbacks of global concern and extensive and fluent transitional zones between ecosystems. The major NEESPI science question is: How do Northern Eurasia's terrestrial ecosystems dynamics interact with and alter the biosphere, atmosphere, and hydrosphere of the Earth? These dynamics have several facets: Biogeochemical Cycles, Surface Energy and Water Cycles, and Interactions with Human Society, each of which have to be studied in their interactions and complexity. Studying of Ecosystem-Climate Interactions mechanisms and Modeling component became a centerpiece of the SP. These studies can be conducted within a suite of models that are considered as a major instrument to assess our predictive capabilities of environmental changes and ecosystem sustainability in Northern Eurasia to support numerous applications and decision making. The creation of such a suite of models and providing it with an appropriate input data stream emerges as a focus of the Initiative. Remote sensing has an important role in the NEESPI science program, providing up to date and historical, spatially explicit information to inventory and quantify changes in the land surface and in the coastal zone for use in process and modeling studies. Social aspects of the NEESPI SP include the Education and land use components.

  17. From land use to land cover: Restoring the afforestation signal in a coupled integrated assessment - earth system model and the implications for CMIP5 RCP simulations

    NASA Astrophysics Data System (ADS)

    Di Vittorio, Alan; Chini, Louise; Bond-Lamberty, Ben; Mao, Jiafu; Shi, Xiaoying; Truesdale, John; Craig, Anthony; Calvin, Kate; Jones, Andrew; Collins, William; Edmonds, Jae; Hurtt, George; Thornton, Peter; Thomson, Allison

    2015-04-01

    Climate projections depend on scenarios of fossil fuel emissions and land use change, and the IPCC AR5 parallel process assumes consistent climate scenarios across Integrated Assessment and Earth System Models (IAMs and ESMs). The CMIP5 project used a novel "land use harmonization" based on the Global Land use Model (GLM) to provide ESMs with consistent 1500-2100 land use trajectories generated by historical data and four IAMs. A direct coupling of the Global Change Assessment Model (GCAM), GLM, and the Community ESM (CESM) has allowed us to characterize and partially address a major gap in the CMIP5 land coupling design: the lack of a corresponding land cover harmonization. For RCP4.5, CESM global afforestation is only 22% of GCAM's 2005 to 2100 afforestation. Likewise, only 17% of GCAM's 2040 afforestation, and zero pasture loss, were transmitted to CESM within the directly coupled model. This is a problem because GCAM relied on afforestation to achieve RCP4.5 climate stabilization. GLM modifications and sharing forest area between GCAM and GLM within the directly coupled model did not increase CESM afforestation. Modifying the land use translator in addition to GLM, however, enabled CESM to include 66% of GCAM's afforestation in 2040, and 94% of GCAM's pasture loss as grassland and shrubland losses. This additional afforestation increases CESM vegetation carbon gain by 19 PgC and decreases atmospheric CO2 gain by 8 ppmv from 2005 to 2040, which demonstrates that CESM without additional afforestation simulates a different RCP4.5 scenario than prescribed by GCAM. Similar land cover inconsistencies exist in other CMIP5 model results, primarily because land cover information is not shared between models. Further work to harmonize land cover among models will be required to increase fidelity between IAM scenarios and ESM simulations and realize the full potential of scenario-based earth system simulations.

  18. Integration of Multiple OGC Standards for Delivery of Earth Science Information - Presentation of Time-Enabled WMS Through KML as Implemented by the PHAiRS Project

    NASA Astrophysics Data System (ADS)

    Hudspeth, W. B.; Benedict, K. K.

    2008-12-01

    Since 2004 the Earth Data Analysis Center has, in collaboration with researchers from the University of Arizona and George Mason University, with funding from NASA, developed a services oriented architecture (SOA) designed for the delivery of historic and current dust forecast data products to the public health user community. This system has generated nearly three years of daily 48-hour dust forecasts, ultimately representing over 289,000 individual hourly forecast rasters for ground surface dust concentrations in four model particle size classes and PM 2.5 and PM 10 size classes. This large collection of model outputs is published as a time-enabled Open Geospatial Consortium (OGC) Web Map Service (WMS) that allows for the efficient retrieval of a single hourly forecast map image for each of these particle size classes, for the entire collection of model outputs. While this WMS service has proven effective in meeting the specific project goals of providing services that support the integration of project products into existing public health decision support systems, the development of an alternative visualization capability that takes advantage of virtual globe technologies was also seen as a valuable complementary capability for making these model outputs accessible to a greater audience of environmental public health users. This paper presents the results of a development effort that produced a system that automatically generates time-enabled KML that enables sequential acquisition of hourly model outputs (via time-enabled WMS) in time-enabled virtual globe applications (e.g. Google Earth). While this effort has proven very successful, it has also highlighted areas where support for time-enabled WMS could be improved, both within the KML standard, and within clients that implement time-enabled viewers.

  19. Integration of light attenuation measurements from Earth Observation into 3D Geobiochemical models of the North Sea.

    NASA Astrophysics Data System (ADS)

    van der Woerd, Hans; Blaas, Meinte; Peters, Steef W. M.; Eleveld, Marieke; Garcia Triana, Ivan D. T. F.

    2013-04-01

    The FP7 CoBiOS project aims to develop a near-real-time information system to diagnose high-biomass blooms in the Baltic Sea and North Sea. The core information in such a system will result from integration of ocean colour remote sensing with 3D geobiochemical modelling. A key parameter is the description of available solar energy in these complex waters, where optically active substances such as silt, algae and dissolved organic material all contribute to the light extinction. A new approach is presented to consistently define the light extinction coefficient Kd of the downward irradiance over PAR from an EO perspective and a numerical modelling perspective. An analysis of a few hundred in-situ Kd-profiles in the North Sea demonstrates that irradiance extinction by the various substances as a function of their PAR-representative absorption and scattering properties works better than a linear model of 'specific extinction' coefficients. In addition to adopting consistent coefficients, it is recommended to apply a nonlinear approach to couple absorption and scattering properties for deriving Kd [1,2]. This approach enables obtaining a consistently defined set of Kd values that will facilitate assimilation of geobiochemical models with ocean colour observations. [1] Lee, Z.P., Du, K.P., Arnone, R. 2005. A model for the diffuse attenuation coefficient of downwelling irradiance J. Geophys. Res., 110, C02016, doi:10.1029/2004JC002275, 2005 [2] Van der Woerd, H.J., Pasterkamp, R. 2008. HYDROPT: A fast and flexible method to retrieve chlorophyll-a from multi-spectral satellite observation of optical-complex coastal waters. Rem. Sens. Env. 112, 1795-1807

  20. Assessing environmental drivers of vegetation greenness by integrating multiple earth observation data in the LPJmL dynamic global vegetation model

    NASA Astrophysics Data System (ADS)

    Forkel, Matthias; Carvalhais, Nuno; Schaphoff, Sibyll; von Bloh, Werner; Thurner, Martin; Thonicke, Kirsten

    2014-05-01

    Recently produced satellite datasets of vegetation greenness demonstrate a widespread greening of the earth in the last three decades. These positive trends in vegetation greenness are related to changes in leaf area, vegetation cover and photosynthetic activity. Climatic changes, CO2 fertilization, disturbances and other land cover changes are potential drivers of these greening trends. Nevertheless, different satellite datasets show different magnitudes and trends in vegetation greenness. This fact raises the question about the reliability of these datasets. On the other hand, global vegetation models can be potentially used to assess the effects of environmental drivers on vegetation greenness and thus to explore the environme