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1

Rare earth-doped integrated glass components: modeling and optimization  

Microsoft Academic Search

For the integrated optic erbium-doped phosphate silica-amplifier, a comprehensive model is presented which includes high-concentration dissipative ion-ion interactions. Based on actual waveguide parameters, the model is seen to reproduce measured gains closely. A rigorous design optimization is performed, and the influence of variations in the launched pump power, the core cross section, the waveguide length, the erbium concentration, and the

Ole Lumholt; Anders Bjarklev; Thomas Rasmussen; G. Lester

1995-01-01

2

Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices  

Microsoft Academic Search

We report on optical properties and prospect applications on rare-earth doped oxyfluoride precursor glass and ensuing nano-glass-ceramics. We find out the spectral optical gain of the nano-glass-ceramics and show that its flatness and breadth are advantageous as compared to contemporary used erbium doped optical amplifiers. We present the possibility of flat gain cross-section erbium doped waveguide amplifiers as short 'chip',

Vicente Daniel Rodrguez-Armas; Victor K. Tikhomirov; Jorge Mndez-Ramos; Angel C. Yanes; Javier Del-Castillo; David Furniss; Angela B. Seddon

2007-01-01

3

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

Microsoft Academic Search

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

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

1996-01-01

4

Modeling and fabrication of rare-earth-doped integrated optical waveguide amplifiers  

Microsoft Academic Search

This thesis addresses modeling and fabrication issues related to erbium\\/ytterbium-doped glass waveguide amplifiers. Compact optical waveguides which amplify light in the 1.55 mum wavelength window will play an important role in complementing other integrated optic devices such as modulators and switches. In designing waveguide amplifiers, two features are of utmost importance: (1) high signal gain over short distances. (2) compatibility

Madhu Krishnaswamy

1998-01-01

5

Path integral Monte Carlo study of 4He clusters doped with alkali and alkali-earth ions.  

PubMed

Path integral Monte Carlo calculations of (4)He nanodroplets doped with alkali (Na(+), K(+) and Cs(+)) and alkali-earth (Be(+) and Mg(+)) ions are presented. We study the system at T = 1 K and between 14 and 128 (4)He atoms. For all studied systems, we find that the ion is well localized at the center of the droplet with the formation of a "snowball" of well-defined shells of localized (4)He atoms forming solid-like order in at least the first surrounding shell. The number of surrounding helium shells (two or three) and the number of atoms per shell and the degree of localization of the helium atoms are sensitive to the type of ion. The number of (4)He atoms in the first shell varies from 12 for Na(+) to 18 for Mg(+) and depends weakly on the size of the droplet. The study of the density profile and of the angular correlations shows that the local solid-like order is more pronounced for the alkali ions with Na(+) giving a very stable icosahedral order extending up to three shells. PMID:21568337

Galli, D E; Ceperley, D M; Reatto, L

2011-06-30

6

Rare earth doped polymer optical fiber and waveguide amplifiers  

Microsoft Academic Search

We present the results of our studies on the optical properties, doping mechanisms, and optical signal amplification processes of rare earth doped polymer optical fiber and waveguide amplifiers. First, we develop our rare earth doped polymers and investigate the rare earth doping mechanisms. Second, we experimentally measure the optical properties of these materials and optimize these properties by designing the

Renyuan Gao

1999-01-01

7

Rare earth doping of zirconia optical waveguides  

NASA Astrophysics Data System (ADS)

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.

Berglund, William Ruben

8

Rare earth doped tellurite glasses  

NASA Astrophysics Data System (ADS)

Glasses based on TeO2-BaO-MgO-ZnO-Na2O have been made successfully. The Raman scattering and the transmission properties were measured, and the photoluminescence properties of Pr3+ doped tellurite glasses were studied. Tellurite glasses exhibit an IR transmission cut- off beyond approximately 6 micrometers . The maximum-phonon band is at 745 cm-1. The emission from the Pr3+:1G4 yields 3H5 transition is at 1.295 micrometers wavelength with a spectral bandwidth of 30 nm. Pr3+ doped tellurite glasses appear to be a promising candidate for waveguide amplifiers in the 1.3 micrometers telecommunication window.

Man, S. Q.; Liu, H. W.; Pun, Edwin Y.; Chung, Po Sheun

1998-12-01

9

Novel waveguide techniques and devices in rare-earth doped glass and rare-earth indiffused lithium niobate  

Microsoft Academic Search

The research described in this thesis focuses on the development of novel fabrication techniques and new devices in rare-earth doped glasses and lithium niobate substrates. These two substrate are among the most promising materials for the development of complex, highly efficient, integrated optical devices. We demonstrate the first Yb-doped glass waveguide laser fabricated using the ion exchange technique. Characterization of

Catalin Mihai Florea

2002-01-01

10

Rare earth-doped glass microbarcodes  

PubMed Central

The development of ultraminiaturized identification tags has applications in fields ranging from advanced biotechnology to security. This paper describes micrometer-sized glass barcodes containing a pattern of different fluorescent materials that are easily identified by using a UV lamp and an optical microscope. A model DNA hybridization assay using these microbarcodes is described. Rare earth-doped glasses were chosen because of their narrow emission bands, high quantum efficiencies, noninterference with common fluorescent labels, and inertness to most organic and aqueous solvents. These properties and the large number (>1 million) of possible combinations of these microbarcodes make them attractive for use in multiplexed bioassays and general encoding.

Dejneka, Matthew J.; Streltsov, Alexander; Pal, Santona; Frutos, Anthony G.; Powell, Christy L.; Yost, Kevin; Yuen, Po Ki; Muller, Uwe; Lahiri, Joydeep

2003-01-01

11

Rare Earth Doped LiNbO 3 Waveguide Amplifiers and Lasers  

Microsoft Academic Search

\\u000a Rare earth doping (above all by Nd3+ and Er3+) mainly of silica-based optical fibers has been applied to develop fiber optical amplifiers and lasers of excellent properties\\u000a [1-3]. Moreover, it can also be an attractive method to fabricate active devices on the planar substrates of integrated optics.\\u000a In particular, rare earth doping of LiNbO3 will significantly increase the potential of

Wolfgang Sohler

1991-01-01

12

Aluminophosphate-doped glasses with rare-earth ions  

Microsoft Academic Search

Aluminophosphate glasses doped with rare-earth ions have recently attracted a large interest owing to their relevant non-linear optical properties. Until now, all studies were done over the glasses doped with rare-earth ions, in which the rare-earth ions were into a vitreous silica matrix. Our study was made as for rare-earth ions into a vitreous aluminophosphate matrix. In the first step,

Rodica Rogojan; Paul E. Sterian; Mihai Elisa

2000-01-01

13

Rare-earth doped polymers for planar optical amplifiers  

NASA Astrophysics Data System (ADS)

Optical waveguide amplifiers based on polymer materials offer a low-cost alternative for inorganic waveguide amplifiers. Due to the fact that their refractive index is similar to that of standard optical fibers, they can be easily coupled to existing fibers with low coupling losses. Doping the polymer with rare-earth ions that yield optical gain is not straightforward, as the rare-earth salts are poorly soluble in the polymer matrix. This review article focuses on two different approaches to dope a polymer waveguide with rare-earth ions. The first approach is based on organic cage-like complexes that encapsulate the rare-earth ion and are designed to provide coordination sites to bind the rare-earth ion and to shield it from the surrounding matrix. These complexes also offer the possibility of attaching a highly absorbing antenna group, which increases the pump efficiency significantly. The second approach to fabricate rare-earth doped polymer waveguides is obtained by combining the excellent properties of SiO2 as a host for rare-earth ions with the easy processing of polymers. This is done by doping polymers with Er-doped silica colloidal spheres.

Slooff, L. H.; van Blaaderen, A.; Polman, A.; Hebbink, G. A.; Klink, S. I.; van Veggel, F. C. J. M.; Reinhoudt, D. N.; Hofstraat, J. W.

2002-04-01

14

Electronphonon interaction in rare earth doped nanocrystals  

Microsoft Academic Search

Nanoscale materials exhibit properties which differ considerably from their bulk counterparts due to modifications of their phonon density of states due to finite size effects. Rare earth doped insulating nanoparticles provide an ideal model system for studying the fundamental interactions between electronic states and phonons since the narrow lines due to rare earth 4fn?4fn transitions provide a high-resolution probe, while

Ho-Soon Yang; K. S Hong; S. P Feofilov; Brian M Tissue; R. S Meltzer; W. M Dennis

1999-01-01

15

Crystallization behavior of rare-earth doped fluorochlorozirconate glasses.  

PubMed

A series of fluorochlorozirconate (FCZ) glasses, each doped with a different rare-earth, was prepared and examined to determine thermal stability and activation energy, Ea , of the dopant dependent BaCl2 crystallization. Non-isothermal differential scanning calorimetry (DSC) measurements were done to investigate the endothermic and exothermic reactions upon heat treatment of the glass samples. In comparison to the rare-earth free FCZ glass, significant changes in the Hruby constant, Hr , and Ea were found due to the addition of a rare-earth and also between the individual dopants. PMID:23493406

Palick, C; Ahrens, B; Henke, B; Johnson, J A; Schweizer, S

2011-06-01

16

Study of rare-earth-doped scintillators  

NASA Astrophysics Data System (ADS)

Scintillators are widely used in radiation detection applications in basic science and industry. Scintillators are generally solids and consist of an emission center and a host lattice. Especially in medical applications that detect high-energy photons, the emission centers are rare-earth (RE) ions, mostly Ce3+. However, recently Pr3+ also exhibited fast 5d-4f emission and became an alternative to Ce3+. In X-ray computed tomography, a scintillation decay time on the order of microseconds is acceptable, and other rare-earth ions such as Nd3+, Eu2+, Ho3+, Er3+, and Tm3+ are candidates for the emission center. The characteristics of these inorganic materials and their advantages and disadvantages for scintillators will be discussed.

Yanagida, Takayuki

2013-09-01

17

Rare Earth Doped High Temperature Ceramic Selective Emitters  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

18

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

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.

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

19

Twin-Core Rare-Earth Doped Nonlinear Fiber Devices  

Microsoft Academic Search

Twin-core rare-earth doped nonlinear optical fiber devices, including optical fiber switches, optical fiber filters and optical fiber amplifiers, are explored in this thesis. An analytical method resorting to the energy E of an oscillator with perturbed nonlinear potential is proposed and demonstrated for investigating the bifurcation and the near-separatrix-crossing of a nonlinear fiber coupler with loss and saturable nonlinearity. Two

Bin Wu

1994-01-01

20

Rare-earth doped optical fibers for temperature sensing  

Microsoft Academic Search

The feasibility of using a variety of rare-earth doped optical fibers for measuring spatially averaged temperatures from ~0 to ~100C over distances of 10 to 20 m is discussed. Such distributed temperature sensors would be particularly well-suited for building climate control systems and industrial processing applications. The temperature-dependent absorption spectra of 6 MCVD processed fibers containing different concentrations of Nd3+,

Kathryn W. Quoi; Robert A. Lieberman; Leonard G. Cohen; D. Scott Shenk; Jay R. Simpson

1992-01-01

21

Rare earth doped zinc oxide varistors  

DOEpatents

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.

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

1998-12-29

22

Rare earth doped zinc oxide varistors  

DOEpatents

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.

McMillan, April D. (Knoxville, TN); Modine, Frank A. (Oak Ridge, TN); Lauf, Robert J. (Oak Ridge, TN); Alim, Mohammad A. (Medina, OH); Mahan, Gerald D. (Oak Ridge, TN); Bartkowiak, Miroslaw (Oak Ridge, TN)

1998-01-01

23

Luminescence studies of rare-earth doped and Co-doped hydroxyapatite  

NASA Astrophysics Data System (ADS)

Rare-earth doped and co-doped hydroxyapatite (Eu: HA, Eu-Y: HA) were prepared by wet precipitation method by using CTAB as the organic modifier. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Photoluminescence spectra (PL). Upon excitation at 350 nm the samples Eu: HA and Eu-Y: HA shows the emission band in the visible region, which makes it suitable for potential application such as bio-imaging.

Vasugi, G.; Thamizhavel, A.; Girija, E. K.

2012-06-01

24

Rare Earth Doped Fiber Amplifiers for the First Telecommunication Window  

NASA Astrophysics Data System (ADS)

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.

Sridhar, Balakrishnan

25

Rare earth doped upconverting particles for different photonic applications  

NASA Astrophysics Data System (ADS)

Trivalent rare earth ions especially erbium (Er^3+) and ytterbium (Yb^3+) 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 Yb^3+ and Er^3+ doped in La2O2S under 980 and 1550 nm excitation at various power densities. Comparison of absolute QYs for different concentrations of Yb^3+ and Er^3+ doped in La2O2S will be made for all the upconversion emissions with respect to reported most efficient upconverting phosphor NaYF4 doped with 20% Yb^3+ and 2% Er^3+. 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.

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

2013-03-01

26

Persistent luminescence phenomena in materials doped with rare earth ions  

NASA Astrophysics Data System (ADS)

The luminescent efficiency of rare earth ions is usually drastically lowered when defects are present in the host lattice. Persistent luminescence is the most recent rare earth application based on lattice defects. Typical materials are the Eu 2+-doped alkaline earth aluminates, MAl 2O 4:Eu 2+ ( M=Ca and Sr). The trivalent R 3+ ions as co-dopants enhance greatly the duration and intensity of persistent luminescence. As a result of very slow thermal bleaching of the excitation energy from the lattice defects acting as traps, the new persistent luminescent materials yield luminescence still visible to naked eye for more than 10 h. Despite the seemingly simple stoichiometry and structure of these materials, the determination of persistent luminescence mechanism(s) presents a very complicated problem. This report presents in detail some of the factors affecting the luminescence properties of the Eu 2+-, R 3+-doped MAl 2O 4. The possible mechanisms involved with different defect centers and interactions between them and the emitting Eu 2+ ion are discussed based on the results of systematic investigations carried out on the preparation, composition, structure and different luminescence properties.

Aitasalo, T.; Dere?, P.; Hls, J.; Jungner, H.; Krupa, J.-C.; Lastusaari, M.; Legendziewicz, J.; Niittykoski, J.; Str?k, W.

2003-02-01

27

Rare Earth Doped Magnetic Clusters of Gold for Medical Application  

NASA Astrophysics Data System (ADS)

In recent years gold clusters have been studied extensively due to their unusual properties and applications in cancer treatment and catalysis. Small gold clusters having up to 15 atoms are planar as shown in figure 1. Thereafter a transition occurs to 3D structures but the atomic structures continue to have high dispersion. Doping of these clusters could transform them in to new structures and affect the properties. Gold clusters with cage structures such as W@Au12 can be prepared with large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gap by doping with a transition metal atom such as W. By changing the transition metal atom, cage structures of different sizes as well as different HOMO-LUMO gaps can be formed which could be useful in different optical applications. In these structures gold clusters are generally non-magnetic. However, it is also possible to form magnetic clusters of gold such as Gold clusters have been found to be good for cancer treatment. We have performed ab initio calculations on doping of rare earths in small gold clusters to obtain magnetic clusters using projector augmented wave pseudopotential method within generalized gradient approximation for the exchange-correlation energy. Elemental gold clusters having up to 15 atoms are planar and thereafter 3D structures become favorable. We have explored the changes in the growth behavior when a rare earth atom is doped and studied the variation in the magnetic behavior as a function of size. Our results suggest that gold clusters may have twin advantage of treating cancer as well as be helful in magnetic imaging such as by MRI.

Deo Yadav, Brahm; Kumar, Vijay

2011-03-01

28

Rare Earth doped nanoparticles in imaging and PDT  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

29

Rare Earth Doped Yttrium Aluminum Garnet (YAG) Selective Emitters  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

30

Transmission and absorption spectra of aluminophosphate-doped glasses with rare-earth ions  

Microsoft Academic Search

Aluminophosphate glasses doped with rare-earth ions have recently attracted a large interest owing to their relevant non-linear optical properties. Until now, all studies were done over the glasses doped with rare-earth ions in which the rare-earth ions were into a vitreous silica matrix. Our study was made as for rare-earth ions into a vitreous aluminophosphate matrix. In the first step,

Rodica Rogojan; Paul E. Sterian; Mihai Elisa

1998-01-01

31

Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings  

NASA Technical Reports Server (NTRS)

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.

Miller, Robert A.; Zhu, Dongming

2005-01-01

32

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

PubMed

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

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

33

Integrated instrument simulator suites for Earth science  

NASA Astrophysics Data System (ADS)

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.

Tanelli, Simone; Tao, Wei-Kwo; Matsui, Toshihisa; Hostetler, Chris A.; Hair, Johnathan W.; 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.

2012-11-01

34

FLUORESCENCE PROPERTIES OF As2S3 GLASS DOPED WITH RARE-EARTH ELEMENTS  

Microsoft Academic Search

Chalcogenide glasses doped with various rare-earth ions are extensively studied as potential materials for fiber optic amplifiers operating at 1.3 and 1.5 ?m telecommunication windows. The experimental results on optical absorption and photoluminescence of arsenic sulfide glasses and optical fibers doped with rare-earth elements (Pr3+, Sm3+, Er3+ and Dy3+) are presented. Near the absorption edge the rare-earth impurities affect strongly

M. Iovu; A. Andriesh; I. Culeac

35

Photoluminescence in rare-earth doped As2S3 glasses  

Microsoft Academic Search

Chalcogenide glasses doped with various rare-earth ions are extensively studied as potential materials for fiber optic amplifiers operating at 1.3 and 1.5 mum telecommunication windows. The experimental results on optical absorption and photoluminescence of arsenic sulfide glasses and optical fibers doped with rare-earth elements (Pr3+, Sm3+, Er3+ and Dy3+) are presented. Near the absorption edge the rare-earth impurities affect strongly

Mihai S. Iovu; Andrei M. Andriesh; Ion P. Culeac

2005-01-01

36

Rare-earth doped high-power fiber lasers and amplifiers  

Microsoft Academic Search

Rare-earth doped high power fibers lasers and amplifiers are important for applications in telecommunications, laser ranging, materials processing, imaging, and medical systems. The commonly used rare-earth dopants are Er, Nd, and Yb. Both theoretical and experimental investigations of rare-earth doped high power fiber lasers and amplifiers have been conducted in this work. In the first part of my thesis research,

Kunzhong Lu

2001-01-01

37

Thermopower studies of rare earth doped lanthanum barium manganites  

NASA Astrophysics Data System (ADS)

Influence of rare earth doping on electrical, magnetic and thermopower studies of La0.34Re0.33Ba0.33MnO3 compound was investigated. Ferro to paramagnetic transition and metal to insulator transition temperatures decrease with decreasing ionic radius of the dopant ion. Electrical resistivity in the entire temperature range is explained by phase separation model. The magnitude of Seebeck coefficient increases with increasing dopant ionic radius. A cross over from negative to positive sign has also been observed in thermopower data with decreasing A site ionic radius (). The low temperature thermopower data has been explained using a qualitative model containing diffusion; magnon drag and phonon drag effects while the paramagnetic insulating part has been analyzed using small polaron hopping mechanism.

Reddy, G. Lalitha; Lakshmi, Y. Kalyana; kumar, N. Pavan; Rao, S. Manjunath; Reddy, P. Venugopal

2014-08-01

38

Rare-earth-doped materials for applications in quantum information storage and signal processing  

Microsoft Academic Search

Realization of practical quantum memory and optical signal processing systems critically depends on suitable materials that offer specific combinations of properties. Solid-state materials such as rare-earth ions doped into dielectric crystals are one of the most promising candidates for several quantum information storage protocols, including quantum storage of single photons. This article provides an overview of rare-earth-doped material properties and

C. W. Thiel; Thomas Bttger; R. L. Cone

2011-01-01

39

Persistent luminescence in rare earth ion-doped gadolinium oxysulfide phosphors  

Microsoft Academic Search

A series of rare-earth ion-doped gadolinium oxysulfide phosphors Gd2O2S:RE3+, Ti, Mg (RE=Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb) were synthesized by solid-state reaction. The excitation and photoluminescence spectra, afterglow spectra, afterglow decay curves and thermoluminescence spectra of the phosphors were examined. According to the afterglow spectra, gadolinium oxysulfide doped with rare-earth ions were classified into three

Bingfu Lei; Yingliang Liu; Junwen Zhang; Jianxin Meng; Shiqing Man; Shaozao Tan

2010-01-01

40

Crystallization Behavior of Rare?earth Doped Luminous Pigment\\/Polyamide 6 Composites  

Microsoft Academic Search

The crystallization behavior of well?dispersed rare?earth doped luminous pigment\\/polyamide 6 (PA6) composites prepared through in situ polymerization was investigated by DSC. The rare?earth doped luminous pigments could accelerate the forming of ? form crystals and also had a great effect on the crystallinity and crystallization rate of PA6 composites. The Ozawa, Jeziorny, and Mo methods were used to analyze the

W. J. L; X. L. Zhu; Y. M. Zhang; H. P. Wang; C. S. Wang; Y. T. Ye

2007-01-01

41

Rare-Earth Doping of Silica Based Optical Fiber by the Sol-Gel Method  

Microsoft Academic Search

Using a sol-gel process for rare earth doping, a minimum background loss of less than 2 dB\\/km at 1.1 mum has been achieved in erbium doped Al:SiO_2 single-mode fibers. The long lifetime for fluorescence of 520 mu sec for neodymium in an Al:SiO_2 glass host prepared by the sol-gel method suggested that this approach provides a very uniform doping of

Fengqing Wu

1995-01-01

42

Sensing using rare-earth-doped upconversion nanoparticles.  

PubMed

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

Hao, Shuwei; Chen, Guanying; Yang, Chunhui

2013-01-01

43

Sensing Using Rare-Earth-Doped Upconversion Nanoparticles  

PubMed Central

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.

Hao, Shuwei; Chen, Guanying; Yang, Chunhui

2013-01-01

44

Rare earth doping of gallium nitride by RF-MBE  

NASA Astrophysics Data System (ADS)

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.

Birkhahn, Ronald H.

45

Integrating Live Access Server into Google Earth  

NASA Astrophysics Data System (ADS)

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.

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

2006-12-01

46

In vivo demonstration of enhanced radiotherapy using rare earth doped titania nanoparticles  

NASA Astrophysics Data System (ADS)

Radiation therapy is often limited by damage to healthy tissue and associated side-effects; restricting radiation to ineffective doses. Preferential incorporation of materials into tumour tissue can enhance the effect of radiation. Titania has precedent for use in photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon photoexcitation, but is limited by the penetration depth of UV light. Optimization of a nanomaterial for interaction with X-rays could be used for deep tumour treatment. As such, titania nanoparticles were doped with gadolinium to optimize the localized energy absorption from a conventional medical X-ray, and further optimized by the addition of other rare earth (RE) elements. These elements were selected due to their large X-ray photon interaction cross-section, and potential for integration into the titania crystal structure. Specific activation of the nanoparticles by X-ray can result in generation of ROS leading to cell death in a tumour-localized manner. We show here that intratumoural injection of RE doped titania nanoparticles can enhance the efficacy of radiotherapy in vivo.Radiation therapy is often limited by damage to healthy tissue and associated side-effects; restricting radiation to ineffective doses. Preferential incorporation of materials into tumour tissue can enhance the effect of radiation. Titania has precedent for use in photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon photoexcitation, but is limited by the penetration depth of UV light. Optimization of a nanomaterial for interaction with X-rays could be used for deep tumour treatment. As such, titania nanoparticles were doped with gadolinium to optimize the localized energy absorption from a conventional medical X-ray, and further optimized by the addition of other rare earth (RE) elements. These elements were selected due to their large X-ray photon interaction cross-section, and potential for integration into the titania crystal structure. Specific activation of the nanoparticles by X-ray can result in generation of ROS leading to cell death in a tumour-localized manner. We show here that intratumoural injection of RE doped titania nanoparticles can enhance the efficacy of radiotherapy in vivo. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr30769c

Townley, Helen E.; Kim, Jeewon; Dobson, Peter J.

2012-07-01

47

Special glassy materials doped with rare-earth elements for fiber optics  

Microsoft Academic Search

Lead-bismuth-gallium-cadmium glasses doped with rare earths elements have been investigated. Certain optical properties of the glasses have been determined. The results of luminescence investiations in the form of absorption and luminescence spectra are presented, and the quantum yields as well as the calculated and measured luminescence lifetimes of the particular rare earths elements in the matrix of the examined glasses

Jan Wasylak; Dominik Dorosz; Jan Kucharski; Jan Kityk

2003-01-01

48

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

NASA Astrophysics Data System (ADS)

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 SnO2 and also by the annealing temperatures. Doping led to chemical and micro-structural variations at the surface of the SnO2 particles. Changes in the catalytic properties of the samples, such as selectivity toward ethylene, may be ascribed to different dopings and annealing temperatures.

Fajardo, Humberto V.; Longo, Elson; Probst, Luiz F. D.; Valentini, Antoninho; Carreo, Neftal L. V.; Nunes, Michael R.; Maciel, Adeilton P.; Leite, Edson R.

2008-05-01

49

Water-soluble conjugated polyelectrolyte brush encapsulated rare-earth ion doped nanoparticles with dual-upconversion properties for multicolor cell imaging.  

PubMed

A concise route to prepare water-soluble rare-earth ion doped upconversion nanoparticles (UCNPs) by encapsulation of grafted cationic conjugated polyelectrolyte brushes (PFNBr) is reported. Integrating two kinds of upconversion materials effectively addresses multicolor fluorescence by introducing the concept of dual-upconversion. PMID:23969491

Hu, Wenbo; Lu, Xiaomei; Jiang, Rongcui; Fan, Quli; Zhao, Hui; Deng, Weixing; Zhang, Lei; Huang, Ling; Huang, Wei

2013-10-11

50

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

SciTech Connect

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.

Page, R.H.; Schaffers, K.I.; Waide, P.A.; Tassano, J.B.; Payne, S.A.; Kruplce, W.F.; Bischel, W.K. [Gemfire Corporation, Palo Alto, CA (United States)

1997-07-26

51

Optimization of rare-earth-doped fluorides for infrared lasers  

NASA Astrophysics Data System (ADS)

The rare-earth-doped fluoride crystals Tm,Dy:BaY2F8 (Tm,Dy:BYF), Yb,Pr:NaYF4 (Yb,Pr:NYF), and Nd:NYF show considerable promise as infrared laser materials, operating at 3 ?m, 1.3 ?m, and 1.06 ?m respectively. Lasing has been reported previously on all three ionic transitions, but not in these crystals. Optimization of these materials for laser applications requires a more complete spectroscopic characterization than is currently available, particularly with regard to the key parameters of fluorescence lifetime and stimulated emission cross section. To further the optimization process, polarized absorption and emission have been measured for Tm,Dy:BYF, Yb,Pr:NYF, and Nd:NYF, and relevant fluorescence lifetimes have been measured or estimated. For Tm,Dy:BYF and Yb,Pr:NYF which rely upon sensitization, energy transfer parameters were calculated. Results were used in a mathematical model to determine the conditions in which lasing may be obtained. The long upper laser level lifetime in Tm,Dy:BYF translates into low threshold pump intensity, but the ability to reach threshold depends strongly on active ion concentration. The short lifetime in Yb,Pr:NYF leads to much higher threshold pump intensities, but lasing is still attainable if resonator loss is minimized. In Nd:NYF lasing was demonstrated, with a maximum of 60 mW output from an absorbed pump power of 345 mW, and a slope efficiency of 21%. Thresholds were high owing to resonator losses near 9%. Two chief issues involving the optimization of these laser materials were identified and explored. First, identification of the orientation for which emission cross section is highest is complicated in Tm,Dy:BYF by the presence of strong magnetic dipole radiation on the 3 ?m transition. This effect makes it necessary to account for the polarization of both the electric and magnetic fields of the emitted radiation when determining an optimal crystal orientation, an accounting further complicated by the low symmetry of the monoclinic BYF host crystal. Second, the effect of host crystal on fluorescence lifetime was considered by comparing lifetime values for the same ionic manifolds in BYF, NYF, and other host crystals. NYF has especially low phonon energies, which leads to longer lifetimes on the longer wavelength transitions which are susceptible to multiphonon relaxation. This advantage is especially needed for lasing at 1.3 ?m in Pr where the upper level lifetime is very short. On the shorter wavelength transitions in Tm and Nd, however, the role of phonons is negligible and lifetimes are somewhat shorter than in other fluoride hosts.

Peterson, Rita Dedomenico

2000-11-01

52

Dopant-host relationships in rare-earth oxides and garnets doped with trivalent rare-earth ions  

Microsoft Academic Search

The dopant-host interactions were considered in the Eu3+- and R3+-doped cubic C-type rare-earth oxides (R2O3) as well as in nondoped R3Ga5O12 and R3+-doped yttrium gallium garnets (Y3Ga5O12:R3+). The investigations were based mainly on the analyses of optical absorption and luminescence spectra using both new and previously published data. The concept of the crystal field (CF) strength parameter Nv was used

Elisabeth Antic-Fidancev; Jorma Hls; Mika Lastusaari; Aurelia Lupei

2001-01-01

53

Earth System Science: An Integrated Approach.  

ERIC Educational Resources Information Center

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)

Environment, 2001

2001-01-01

54

Multiferroism in rare earth metals-doped BiFeO3 nanowires  

NASA Astrophysics Data System (ADS)

Nanowires are the key multifunctional materials for the development towards device miniaturization and high-density data storage systems for future nanoelectronics. In the present report, multifunctional undoped and rare earth metals ions (Gd3+, Tb3+, Dy3+)-doped BiFeO3 nanowires with 20 nm diameter, have been synthesized by template-assisted colloidal dispersion technique. The effect of the size of synthesized nanowires, as well as, the doping of rare earth ions on the structural, magnetic, dielectric and magnetodielectric properties have been studied. The doping of rare earth metals ions leads to structural transition from rhombohedral to orthorhombic BiFeO3 nanowires. The synthesized nanowires exhibit ferromagnetic nature with high value of saturation magnetization, dielectric constant and magnetodielectric coefficient.

Lotey, Gurmeet Singh; Verma, N. K.

2013-08-01

55

Synthesis and Photoresponse of Rare-Earth-Doped Phosphosilicates  

SciTech Connect

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.

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

1998-12-14

56

Luminescence properties of Ce 3+ and Tb 3+ doped rare earth borate glasses  

Microsoft Academic Search

Ce3+- and Tb3+-doped rare earth borate glasses were synthesized and their luminescence properties have been studied. The sample containing Ce3+ ions has a strong purplish-blue emission and that doped with Tb3+ emits a green light under UV excitation. The Ce3+ ions in the host form two kinds of emission centers, owing to different lattice sites occupied by Ce3+ in the

Lihui Huang; Xiaojun Wang; Hai Lin; Xingren Liu

2001-01-01

57

Investigation of pumping dynamics in rare earth doped solid state laser materials  

Microsoft Academic Search

The pumping dynamics of rare earth-doped solid-state laser materials are discussed here with an emphasis on the effects occurring in laser-pumped laser systems. A tunable alexandrite laser is used as the pump source for Nd(3+)-doped laser materials. It is found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump

Richard C. Powell; Michael L. Kliewer

1989-01-01

58

Molecular beam epitaxy (MBE) growth of rare earth doped gallium nitride for laser diode application  

Microsoft Academic Search

The goal of this dissertation is to demonstrate the visible laser emission from rare earth doped GaN grown on sapphire and silicon substrate. The research presented in this dissertation focused on exploration of RE's physics and laser characteristics and investigating site selective laser emission. In this study, the first visible (red) lasing emission from Eu-doped GaN thin films grown on

Jeongho Park

2006-01-01

59

Giant optical gain in a rare-earth-ion-doped waveguide amplifier  

Microsoft Academic Search

For optical amplification, typically rare-earth-ion (RE) doped fiber amplifiers (RDFA) or semiconductor optical amplifiers (SOAs) are selected. Despite the weak transition cross-sections of RE ions and their low doping level in silica fibers, resulting in very low gain per unit length, the extremely long interaction lengths realized in fibers can lead to significant overall gain. SOAs can deliver similarly high

D. Geskus; S. Aravazhi; S. M. Garcia Blanco; M. Pollnau

2011-01-01

60

Fluorescence Spectroscopy of Polymer Systems Doped with Rare-Earth Metal Ions and Their Complexes  

Microsoft Academic Search

There has been an increased attention to explore the possibility of using polymer materials with rare-earth (RE) metal ions and their complexes as potential optical materials due to their capability of exhibiting novel and unusual properties. The fluorescence characteristics of polymer systems doped with RE metal ions and\\/or their complexes were analyzed and the effects of the doping metal ion\\/metal

K. S. V. Krishna Rao; Hong-Guo Liu; Yong-Ill Lee

2010-01-01

61

Photoluminescence spectra of rare earth doped CaGa 2S 4 single crystals  

Microsoft Academic Search

Six kind CaGa2S4 single crystals doped with different rare earth (RE) elements are grown by the horizontal Bridgman method, and their photoluminescence (PL) spectra are measured in the temperature range from 10 to 300K. The PL spectra of Ce or Eu doped crystals have broad line shapes due to the phonon assisted 4f5d transitions. On the other hand, those of

C. Hidaka; E. Yamagishi; T. Takizawa

2005-01-01

62

Synthesis and optical properties of sub-micron sized rare earth-doped zirconia particles  

Microsoft Academic Search

Sub-micron sized crystalline particles of Eu3+ and Er3+-doped zirconia (ZrO2) were prepared via a wet chemical solgel route and post synthesis annealing. The doping was achieved by introduction of the respective rare earth salts into the zirconia precursor solution, with insitu generation of sodium chloride for stabilization of the particle surface during growth. A series of materials with differing europium

I. Freris; P. Riello; F. Enrichi; D. Cristofori; A. Benedetti

2011-01-01

63

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

NASA Astrophysics Data System (ADS)

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.

Peyghan, Ali Ahmadi; Noei, Maziar

2014-01-01

64

Laser induced breakdown spectroscopy diagnosis of rare earth doped optical glasses  

SciTech Connect

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.

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

2010-05-01

65

Fabrication of ordered magnetite-doped rare earth fluoride nanotube arrays by nanocrystal self-assembly  

Microsoft Academic Search

We describe a nanocrystal self-assembly method for the preparation of rare earth fluoride nanotube (ReF-NT) arrays and magnetite-doped\\u000a rare earth fluoride nanotubes (Fe3O4-ReF-NTs) by using porous anodic aluminum oxide (AAO) as a hard template. The ReF-NTs can be simply prepared by the impregnation\\u000a of ?-NaYF4 nanocrystals doped with Yb and Er into the channels of the porous AAO and show

Fan Zhang; Dongyuan Zhao

2009-01-01

66

Development of an Integrated Earth System Model on the Earth Simulator  

Microsoft Academic Search

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

Michio Kawamiya; Chisato Yoshikawa; Tomomichi Kato; Hisashi Sato; Kengo Sudo; Shingo Watanabe; Taroh Matsuno

2005-01-01

67

Influence of rare earth doping on thermoelectric properties of SrTiO3 ceramics  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of SrTiO3 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: SrTiO3 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 SrTiO3 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, Sr0.8La0.18Yb0.02TiO3 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 Sr0.8La0.2TiO3 (ZT = 0.26).

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

2013-12-01

68

Internal and External Radiative Decay Engineering of Rare Earth Doped Nanocrystalline Sesquioxides  

NASA Astrophysics Data System (ADS)

Rare earth (RE) based sesquioxide structures (RE2O3), when doped judiciously with trivalent RE ions, are not susceptible to photobleaching and offer many sharp electronic transitions with excited state lifetimes on the order of milliseconds. Additionally, internal lattice engineering of the host offers several distinct crystal phases which may be synthesized easily by tuning the host RE. Similarly, the proximity of noble metals to trivalent rare earth ions has shown promise as a sensitizer that greatly enhances the photoluminescence of the rare earth ion. More recently, results have been reported for gold coated silica dielectric nanoparticles which have been modeled extensively and shown to act as a nano-antenna, enhancing the electric field inside the dielectric core. This short range antenna effect offers radiative decay engineering at the external level. Here, we report the internal and external radiative decay engineering of several rare earth doped sesquioxide and metallic hetero-nanostructures and discuss the nanoscale physics of these systems.

Dennis, Robert; Nash, Kelly; Zhang, Maogen; Gorski, Waldemar; Sardar, Dhiraj

2010-10-01

69

Creation of trapped electrons and holes in alkaline-earth fluoride crystals doped by rare-earth ions  

Microsoft Academic Search

Defects in Ce3+- and Eu2+-doped alkaline-earth fluorides, created by vacuum ultraviolet (UV) photons at energies lower than at the bandgap, were investigated by various methods: thermostimulated luminescence, photostimulated luminescence and optical absorption. The CaF2:Eu2+ thermoluminescence curves in the range of 60-330 K due to various types of trapped holes were the same after vacuum UV illumination as after x-irradiation. Thermoluminescence

E. Radzhabov

2001-01-01

70

Creation of trapped electrons and holes in alkaline-earth fluoride crystals doped by rare-earth ions  

Microsoft Academic Search

Defects in Ce3+- and Eu2+-doped alkaline-earth fluorides, created by vacuum ultraviolet (VUV) photons with energy lower than that of the band gap, were investigated by various methods: thermostimulated luminescence, photostimulated luminescence and optical absorption. The CaF2:Eu2+ thermoluminescence curves in the range of 60330K due to various types of trapped holes were the same after VUV illumination as after X-ray irradiation.

E. Radzhabov

2002-01-01

71

Modeling rare-earth doped microfiber ring lasers.  

PubMed

We propose a compact laser configuration based on resonating both the pump and signal light along a microfiber ring doped with active ions. We estimate the minimum Q-factor to obtain lasing and find that values already demonstrated in passive microfiber rings will be sufficient. We model the performance of this device in steady state using rate equations and show that pump resonance can significantly reduce the threshold and increase the quantum efficiency, especially for rings made of materials with weak active ion absorption. Numerical examples for erbium and ytterbium doped devices are presented. Taking into account scattering and coupling losses the optimum pump coupling factor is calculated. The dependences of the quantum efficiency and threshold power on the coupling losses are also investigated. We predict that efficient ytterbium-doped lasers can be obtained with a ring diameter down to a few tens of micrometers. PMID:19529078

Li, Yuhang; Vienne, Guillaume; Jiang, Xiaoshun; Pan, Xinyun; Liu, Xu; Gu, Peifu; Tong, Limin

2006-08-01

72

Electroluminescence spectra of rare-earth-doped ZnS 1-XSe X thin films  

NASA Astrophysics Data System (ADS)

Electroluminescence has been measured for ZnS 1- XSe X thin films doped with rare-earth ions. As X increases the band-gap energy of the host decreases. The emission levels of trivalent rare-earth ions are not observed when the band-gap energy is narrower than the excitation levels. This is because of the energy transfer between the host and the emission center.

Miura, Noboru; Ogawa, Kiyoshi; Kobayashi, Shuko; Matsumoto, Hironaga; Nakano, Ryotaro

1994-04-01

73

Luminescence and charge compensation in SnO2 doped with rare-earth ions  

Microsoft Academic Search

Tin oxide has been doped with several of the rare-earth ions, namely europium, terbium, thulium, holmium and neodymium. The effects of coactivators such as lithium, phosphorus and niobium have been investigated as well. Of the rare-earth ions, only europium, terbium and thulium plus coactivator, when added to tin oxide, caused the characteristic RE3+ lines in the visible region of the

D. F. Crabtree

1978-01-01

74

UV and gamma-ray excited luminescence of cerium-doped rare-earth oxyorthosilicates  

Microsoft Academic Search

Gamma-ray and UV-excitation of cerium-doped rare-earth oxyorthosilicates (RE = Y, Gd, and Lu) has been used to investigate the emission mechanism for this family of scintillators. The data clearly indicate the presence of two different luminescence centers, which are attributed to cerium substitution in the two different rare-earth crystallographic sites. While this model explains much of the present and previous

H. Suzuki; T. A. Tombrello; C. L. Melcher; J. S. Schweitzer

1992-01-01

75

Rare Earth Doped Magnetic Clusters of Gold for Medical Application  

Microsoft Academic Search

In recent years gold clusters have been studied extensively due to their unusual properties and applications in cancer treatment and catalysis. Small gold clusters having up to 15 atoms are planar as shown in figure 1. Thereafter a transition occurs to 3D structures but the atomic structures continue to have high dispersion. Doping of these clusters could transform them in

Brahm Deo Yadav; Vijay Kumar

2011-01-01

76

Strong mechanoluminescence induced by elastic deformation of rare-earth-doped strontium aluminate phosphors  

Microsoft Academic Search

When rare-earth-doped strontium aluminate phosphor mixed in an epoxy resin, is deformed elastically by applying a uniaxial pressure, then initially the mechanoluminescence (ML) intensity increases with time, attains a peak value Im at a particular time tm, and later on it decreases with time. After tm, initially, the ML intensity decreases exponentially at a fast rate and then it decreases

B. P. Chandra; R. N. Baghel; A. K. Luka; T. R. Sanodiya; R. K. Kuraria; Shashi R. Kuraria

2009-01-01

77

Intensities of optical transitions in the spectra of Eu 3+ -doped rare-earth formates  

Microsoft Academic Search

Europium formate, as well as the formates of La, Gd, Tb, and Y doped with Eu ~+ (C~5 mole %), were synthesized by reacting the respective rare-earth oxides with solutions of formic acid at a temperature of 80~ The solutions obtained were evaporated. The crystalline precipitates formed were separated and dried at a temperature not greater than 200~ until all

Yu. I. Atrashevskii; G. G. Novitskii; A. S. Yasyukevich; Yu. I. Krasilov; S. M. Portnova

1985-01-01

78

VUV spectroscopy of wide band-gap crystals doped with rare earth ions  

Microsoft Academic Search

Spectral and kinetic properties of vacuum ultraviolet (VUV) luminescence from different fluoride crystals doped with Nd3+, Er3+ or Tm3+ are discussed. Concentration quenching of VUV luminescence, the impact mechanism of the energy transfer from the matrix to the emission centers as well as nonradiative relaxation processes in the rare earth ions have been detected and studied. The crystal properties are

V. N. Makhov; N. M. Khaidukov; N. Yu. Kirikova; M. Kirm; J. C. Krupa; T. V. Ouvarova; G. Zimmerer

2001-01-01

79

Optical and structural investigation on rare-earth-doped aluminophosphate glasses  

NASA Astrophysics Data System (ADS)

Aluminophosphate glasses belonging to the oxide system Li 2O-BaO-Al 2O 3-La 2O 3-P 2O 5, un-doped and doped with rare-earth metal ions (Ce 4+, Nd 3+, Sm 3+) were obtained by a wet non-conventional method. The influence of the doping ions on the optical properties of the phosphate glasses has been investigated in relation with structural features of the vitreous matrix. The optical behavior has been studied by ultra-violet-visible-near-infra-red (UV-VIS-NIR) spectroscopy, revealing electronic transitions specific for rare-earth ions. Structural information via optical phonons was provided by infrared (IR) absorption spectra in the range 400-4000 cm -1. Raman and fluorescence spectroscopy measurements have been performed. A strong fluorescence was observed in the visible spectrum, using 514.5 nm and 633 nm laser excitation.

Elisa, M.; Cristina Vasiliu, I.; Grigorescu, Cristiana E. A.; Grigoras, Bogdan; Niciu, Horatiu; Niciu, Daniela; Meghea, Aurelia; Iftimie, Nicoleta; Giurginca, Maria; Trodahl, H. J.; Dalley, M.

2006-05-01

80

[Study on rare earth doped long luminescence glass].  

PubMed

A luminosilicate glass samples doped with Eu203 and Dy2O3 were prepared under the air and reducing atmosphere respectively. The excitation spectra, emission spectra and thermal luminescence spectra of the samples prepared under different atmosphere were measured. Luminescence mechanism of the afterglow glasses wa s analyzed. The results showed that the sample prepared under an ambient atmosphere has no afterglow. Its excitation and emission spectra showed the typical transitions of (5)Di( i = 0, 1) --> (7)Fj (j = 0-4) from Eu3+ but the sample reheated at a reducing atmosphere has afterglow. The sample doped with Eu2+ shows luminescence peaking at 462 nm. And the sample codoped with Eu2+ and Dy3+ shows luminescence peaking at 457 nm. The afterglowluminescence can last more than 12 h. PMID:16499036

Zhang, Xi-yan; Mi, Xiao-yun; Xiao, Zhi-yi; Liu, Quan-sheng

2005-11-01

81

Sensitized red luminescence from Ce 3+, Mn 2+-doped glaserite-type alkaline-earth silicates  

NASA Astrophysics Data System (ADS)

Bright red luminescence is observed from Ce, Mn-doped glaserite-type alkaline-earth silicates with M2BaMgSi 2O 8 ( M: Ba, Sr, Ca) chemical composition. Under UV excitation, Ce-doped M2BaMgSi 2O 8 exhibits strong near-UV emission with asymmetric peak shape. UV-excited Mn-doped M2BaMgSi 2O 8 compounds show visible red emission only when Ce 3+ ions are doped together. These results indicate that Mn 2+-derived red emission is caused by an efficient energy transfer from Ce 3+ to Mn 2+. The red emission becomes intense with an increase in Ba-amount. This trend originates from the relaxation of the selection rule for 3 d-3 d transition in Mn 2+ ions, which is caused by the structural deformation due to Ba 2+ occupation for layer-pockets.

Yonesaki, Yoshinori; Takei, Takahiro; Kumada, Nobuhiro; Kinomura, Nobukazu

2010-06-01

82

Dielectric spectrum of rare-earth-doped calcium fluoride crystals  

Microsoft Academic Search

Calcium fluoride crystals doped with ErF3 and YbF3 have been grown using the vertical Bridgman method. The real and imaginary parts of the complex dielectric constant, ?? and ??, have been measured at five audio-frequencies (1100kHz) over the temperature range 150300K. From the observed relaxation processes the activation energy for dipole reorientation and the relaxation time constant,?0, have been determined.

I. Nicoara; M. Munteanu; N. Pecingina-Girjioaba; Marius Stef; L. Lighezan

2006-01-01

83

Enhanced superconductivity by rare-earth metal doping in phenanthrene  

NASA Astrophysics Data System (ADS)

We successfully synthesized La- and Sm-doped phenanthrene powder samples and observed superconductivity in them at Tc around 6 K. The Tcs are 6.1 K for La1 phenanthrene and 6.0 K for Sm1 phenanthrene, which are enhanced by about 1 and 0.5 K compared to those in A3 phenanthrene (A = K and Rb) and in Ae1.5 phenanthrene (Ae = Sr and Ba) superconductors, respectively. The superconductive shielding fractions for La1 phenanthrene and Sm1 phenanthrene are 46.1% and 49.8% at 2 K, respectively. The small effect of doping with the magnetic ion Sm3+ on Tc and the positive pressure dependence coefficient of Tc strongly suggest unconventional superconductivity in the doped phenanthrene superconductors. The charge transfer to organic molecules from dopants of La and Sm induces a redshift of 7 cm-1 per electron for the mode at 1441 cm-1 in the Raman spectra, which is almost the same as those observed in A3 phenanthrene (A = K and Rb) and Ae1.5 phenanthrene (Ae = Sr and Ba) superconductors.

Wang, X. F.; Luo, X. G.; Ying, J. J.; Xiang, Z. J.; Zhang, S. L.; Zhang, R. R.; Zhang, Y. H.; Yan, Y. J.; Wang, A. F.; Cheng, P.; Ye, G. J.; Chen, X. H.

2012-08-01

84

Creation of trapped electrons and holes in alkaline-earth fluoride crystals doped by rare-earth ions  

NASA Astrophysics Data System (ADS)

Defects in Ce 3+- and Eu 2+-doped alkaline-earth fluorides, created by vacuum ultraviolet (VUV) photons with energy lower than that of the band gap, were investigated by various methods: thermostimulated luminescence, photostimulated luminescence and optical absorption. The CaF 2:Eu 2+ thermoluminescence curves in the range of 60-330 K due to various types of trapped holes were the same after VUV illumination as after X-ray irradiation. Thermoluminescence curves of Ce 3+-doped alkaline-earth fluorides created by VUV illumination or X-ray irradiation were generally similar. However, Vk thermoluminescence peaks were absent in VUV-illuminated CaF 2:Ce 3+ and SrF 2:Ce 3+ crystals. Creation of Ce 2+ characteristic bands was observed in photostimulated luminescence spectra as well as in optical absorption spectra of vacuum ultraviolet-illuminated or X-ray-irradiated Ce 3+-doped crystals. The proposed mechanism of creation of trapped hole and trapped electron defects by vacuum ultraviolet illumination involves charge transfer-type transitions, in which the electron transfers from valence band to an impurity level, lying in the band gap. Comparison of all involved energies of transitions in the crystals investigated shows that the sum of all transition energies is less than that of the band gap by 1-3 eV. This energy difference can be considered as the energy of lattice relaxation around created Ce 2+ or Eu + ions.

Radzhabov, E.

2002-06-01

85

Molodensky's theory of the Earth's figure determination using topographic reductions and integration over the Earth's surface.  

NASA Astrophysics Data System (ADS)

Molodensky's theory is developed with due regard for the topographic gravity reduction, which can lead to the Earth's mass center displacement from the rotation axis. The possibility of integration over the Earth's surface without transfer to the telluroid is shown. Various measurement data can be used to provide a single solution of this problem, for example land gravity anomalies and results of sea altimetric and gravimetric surveying.

Yurkina, M. I.

1989-01-01

86

Ferromagnetism and Photoluminescence in Rare-Earth doped GaN via Diffusion  

NASA Astrophysics Data System (ADS)

Rare-earth doped GaN is attracting attention both as a diluted magnetic semiconductor (DMS) material and for optical devices useful in communications and multi-color semiconductor display technology. GaN's large band gap (3.4 eV) gives rise to optical transparency over a wide spectral range, from the infrared (IR) to the ultraviolet. These properties make it an optimum host for the various emissions that are possible from rare-earth (RE) ions. Recently, rare-earth doped GaN also has demonstrated above room temperature ferromagnetism. In this study, we report the diffusion of RE (Nd, Sm, Gd and Er) into undoped, Mg-doped and Si-doped GaN templates. Room temperature optical and ferromagnetic properties were studied using photoluminescence (PL) and alternating gradient magnetometer, respectively. Ferromagnetic properties show a preference for undoped and n-type GaN. PL spectra exhibit RE ion inner shell transitions in the visible and infrared regions. The mechanisms for above room temperature ferromagnetism and emission intensity related to the RE concentration, is discussed.

Luen, M. Oliver; Nepal, N.; Bedair, S. M.; Zavada, J. M.; Brown, Ei Ei; Hommerich, U.; Frajtag, P.; El-Masry, N. A.

2009-03-01

87

Optical properties of rare earth doped transparent oxyfluoride glass ceramics  

NASA Astrophysics Data System (ADS)

Optical properties of Eu3+ ions in oxyfluoride glasses and glass ceramics doped with low concentration (0.1 mol%) have been analysed and compared with previous results for high concentrated samples (2.5 mol%). The Eu3+ ions in the low dopant concentration glass ceramics are diluted into like crystalline environments with higher symmetry and lower coupled phonons energy than in the precursor glasses. Fluorescence line narrowing measurements indicate the presence of two main fluoride site distributions for the Eu3+ ions in these low concentrated glass ceramics.

Mendez-Ramos, J.; Lavin, V.; Martin, I. R.; Rodriguez-Mendoza, U. R.; Rodriguez, V. D.; Lozano-Gorrin, A. D.; Nunez, P.

2003-01-01

88

Preparation of rare-earth element doped Mg2Si by FAPAS  

NASA Astrophysics Data System (ADS)

Rare-earth elements (Re) Sc and Y doped Mg2Si thermoelectric materials were made via a field-activated and pressure-assisted synthesis (FAPAS) method at 1023-1073 K, 50 MPa for 15 min. The samples created using this method have uniform and compact structures. The average grain size was about 1.5-2 ?m, the micro-content of Re did not change the matrix morphology. The sample with 2500 ppm Sc obtained the best See-beck coefficient absolute value, about 1.93 times of that belonging to non-doped Mg2 Si at about 408 K. The electric conductivity of the sample doped with 2000 ppm Y becomes 1.69 times of that of pure Mg2Si at 468 K, while the former had a better comprehensive electrical performance. Their thermal conductivity was reduced to 70% and 84% of that of non-doped Mg2Si. Thus, the figure of merit and ZT of these two samples were enhanced visibly, which were 3.3 and 2.4 times of the non-doped samples at 408 K and 468 K, respectively. The maximal ZT belonging to samples doped with 2500 ppm Sc went up to 0.42 at about 498 K, higher than 0.40 of sample doped with 2000 ppm Y at 528 K and 0.25 of non-doped Mg2Si at 678 K, and the samples doped with Sc seemed to get the best thermoelectric performances at lower temperature.

Liqi, Wang; Qingsen, Meng; Wenhao, Fan

2012-11-01

89

A combined DFT + U and Monte Carlo study on rare earth doped ceria.  

PubMed

We investigate the dopant distribution and its influence on the oxygen ion conductivity of ceria doped with rare earth oxides by combining density functional theory and Monte Carlo simulations. We calculate the association energies of dopant pairs, oxygen vacancy pairs and between dopant ions and oxygen vacancies by means of DFT + U including finite size corrections. The cation coordination numbers from ensuing Metropolis Monte Carlo simulations show remarkable agreement with experimental data. Combining Metropolis and Kinetic Monte Carlo simulations we find a distinct dependence of the ionic conductivity on the dopant distribution and predict long term degradation of electrolytes based on doped ceria. PMID:24477833

Grieshammer, Steffen; Grope, Benjamin O H; Koettgen, Julius; Martin, Manfred

2014-06-01

90

Optical absorption and photoluminescence in Sm 3+- and Eu 3+-doped rare-earth borate glasses  

Microsoft Academic Search

Sm3+- and Eu3+-doped rare-earth borate glasses (Li2OBaOLa2O3B2O3) have been fabricated and characterized optically. The density, refractive index, optical absorption, Judd-Ofelt parameters, and spontaneous transition probabilities have been measured, calculated and analyzed. Sm3+ and Eu3+ emit intense reddish-orange and red lights under blue and UV light excitations, respectively. In Sm3+ and Eu3+ co-doped glasses, the excitation wavelength range of Eu3+ emission

Hai Lin; Dianlai Yang; Guishan Liu; Tiecheng Ma; Bin Zhai; Qingda An; Jiayou Yu; Xiaojun Wang; Xingren Liu; Edwin Yue-Bun Pun

2005-01-01

91

Doping alkaline-earth: a strategy of stabilizing hexagonal GdF3 at room temperature.  

PubMed

Hexagonal GdF3 is a more efficient phosphor host compared with the traditional orthorhombic form but the hexagonal phase is thermodynamically unstable at room temperature. Herein, we present a strategy to stabilize hexagonal GdF3 by doping with alkaline-earth ions in a mild hydrothermal reaction system. The selection of the dopant, effect of the dopant amount and the mechanism of the phase transition was discussed in detail. The luminescence variation of GdF3:Eu was demonstrated to verify the phase transformation. Furthermore, the upconversion luminescence of the Sr-doped and undoped GdF3:Yb/Er was investigated. PMID:24026018

Zhao, Qi; Shao, Baiqi; L, Wei; Jia, Yongchao; Lv, Wenzhen; Jiao, Mengmeng; You, Hongpeng

2013-11-21

92

Dopant-host relationships in rare-earth oxides and garnets doped with trivalent rare-earth ions  

NASA Astrophysics Data System (ADS)

The dopant-host interactions were considered in the Eu3+- and R3+-doped cubic C-type rare-earth oxides (R2O3) as well as in nondoped R3Ga5O12 and R3+-doped yttrium gallium garnets (Y3Ga5O12:R3+). The investigations were based mainly on the analyses of optical absorption and luminescence spectra using both new and previously published data. The concept of the crystal field (CF) strength parameter Nv was used in the considerations. When a R3+ dopant different from the host cation is embedded into the host lattice, a decrease in the R3+ site symmetry, distortions, and/or stresses are usually introduced. These local effects were found to affect significantly the strength of the crystal field in both R3+-doped Y2O3 and Y3Ga5O12 when compared to nondoped R2O3 and R3Ga5O12. With increasing positive size mismatch between the dopant and the host cation, the CF effect was found to be enhanced. The origin of this effect may be of electrostatic or covalent nature due to the decrease in dopant-oxygen distances or the delocalization of the 4f electrons, respectively. High-pressure investigations on Eu3+-doped R2O3 support the present conclusions. The formation of neighbor R3+-R3+ pairs in doped garnets induces additional lines in the optical spectra. For large ions such as Pr3+ and Nd3+ in Y3Al5O12 or Gd3Ga5O12, the pair lines compared to isolated ions result from modifications in the CF effect due to local distortions. The superexchange interaction for near-neighbor Pr3+ and Nd3+ pairs is manifested in dynamical behavior.

Antic-Fidancev, Elisabeth; Hls, Jorma; Lastusaari, Mika; Lupei, Aurelia

2001-11-01

93

Integrated Optical Pumping of Cr & Ti-Doped Sapphire Substrates With III-V Nitride Materials.  

National Technical Information Service (NTIS)

The goal of this proposal was to investigate the potential advantages of integrating III-V nitride structures on doped sapphire substrates and doped sapphire waveguide structures. III-V Nitride structures are typically grown on undoped synthetic sapphire ...

J. Muth

2005-01-01

94

IR and UV spectral studies for rare earths-doped tellurite glasses  

Microsoft Academic Search

Infrared absorption spectra were measured for pure TeO2 glasses and doped with 10-wt% of different rare-earth oxides, La2O3, CeO2, Pr2O3, Sm2O3, Nd2O3, and Yb2O3. The recorded bands were attributed to the different modes of vibrations of TeO band. Rare earths connected to the chains of TeO4 groups are identified on the basis of the simultaneous presence of the bands at

L. M. Sharaf El-Deen; M. S. Al Salhi; Meawad M. Elkholy

2008-01-01

95

Optical properties of rare-earth doped Sr 3Al 2O 6  

NASA Astrophysics Data System (ADS)

This paper describes a computational study of extrinsic defect of Sr 3Al 2O 6 induced by trivalent rare-earth dopants. Solution energies for a range of possible doping mechanisms are calculated, and predictions made of doping sites and charge-compensation schemes. It is shown that there are definite trends going along the rare-earth series. Atomistic modeling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the system. The transition levels are then calculated for the Eu 3+-substituted material, and comparisons with the experimental results were done.

Rezende, M. V. S.; Arajo, R. M.; Montes, P. J. R.; Valerio, M. E. G.

2010-08-01

96

Spectroscopy and laser performance of some rare earth and transition-metal-doped garnets  

NASA Astrophysics Data System (ADS)

Investigation of the spectroscopic properties and laser performance of rare earth and transition metal ions doped crystals (garnets) is presented. Recent spectroscopic results of energy transfer and back transfer mechanism in Cr:Tm:Ho:YAG, Cr:Tm:Ho:LuAG (Lu3Al5O12) at a variety of temperatures (10K-300K) will be reported. A direct energy transfer from Tm3+ excited states to Ho3+ 5I7 lasing level was observed and analyzed. Multipolar interaction between special sites of Cr3+ and rare earth lasing ions (Tm3+, Ho3+), which results from a strong correlation placement distribution was found and analyzed. The effect of this interaction on the enhancement of laser efficiency will be discussed. The room temperature performance and the laser parameters of broadly tunable solid state lasers (at 1150-1600 nm), based on Cr4+ doped different garnets will be presented and discussed as well.

Kalisky, Yehoshua Y.; Zhang, Jiamin; Rotman, Stanley R.; Kokta, Milan R.

1995-04-01

97

Temperature and dose-rate effects in gamma irradiated rare-earth doped fibers  

NASA Astrophysics Data System (ADS)

Rare-earth-doped fibers, such as Er3+- and Yb3+-doped aluminosilicates can be advantageous in space-based systems due to their stability, their high-bandwidth transmission properties and their lightweight, small-volume properties. In such environments the effect of ionizing-radiation on the optical transmission of these fibers is of paramount importance. For the present work, gamma-radiation experiments were conducted in which un-pumped Yb3+ and Er3+ doped sample fibers were irradiated with a Cobalt-60 source under different dose-rate and temperature conditions. In-situ spectral transmittance data over the near IR was monitored during the irradiations for total doses of up to tens of krad (Si). It was found that there was a dose-rate dependence in which higher rates resulted in more photodarkening. Higher temperatures were not found to significantly affect the rate of photodarkening at the dose rates used.

Fox, B. P.; Simmons-Potter, K.; Thomes, W. J., Jr.; Meister, D. C.; Bambha, R. P.; Kliner, D. A. V.

2008-08-01

98

Photoluminescence spectra of rare earth doped CaGa2S4 single crystals  

NASA Astrophysics Data System (ADS)

Six kind CaGa2S4 single crystals doped with different rare earth (RE) elements are grown by the horizontal Bridgman method, and their photoluminescence (PL) spectra are measured in the temperature range from 10 to 300 K. The PL spectra of Ce or Eu doped crystals have broad line shapes due to the phonon assisted 4f 5d transitions. On the other hand, those of Pr3+, Tb3+, Er3+ or Tm3+ doped samples show narrow ones owing to the 4f 4f transitions. The assignments of the electronic levels are made in reference to the reported data of RE 4f multiplets observed in same materials.

Hidaka, C.; Yamagishi, E.; Takizawa, T.

2005-11-01

99

Rare-earth doped glass scintillators effective to spent nuclear fuels through photocatalyst  

Microsoft Academic Search

New rare-earth doped scintillators were grown to change radioactive energies of spent nuclear fuels exhausted out of atomic power plants to UV-light, followed by making absorb into photocatalyst soaked in water to get yield hydrogen gas available to fuel cells and oxygen gas for medical usages. This project requires that the scintillating light should exist in the absorption edge 380nm

K. Kawano; H. Tasaki; B.-C. Hong; T. Ishitsuka

2008-01-01

100

Preparation and laser induced damage properties of rare earth doped BAS glass  

Microsoft Academic Search

Rare earth doped B2O3-Al2O3-SiO2 glass (RExBAS, x=5, 10, 20; RE=La, Sm) were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1064 nm laser induced damage performance was investigated through the method of 1-on-1. The results indicated that there was a strong absorptive peak near 1064 nm in SmxBAS glass, the

Yaru NI; Zhongzi XU; Chunhua LU; Yan ZHANG; Qitu ZHANG

2008-01-01

101

Cathodoluminescence of synthetic (doped with rare-earth elements) and natural anhydrites  

Microsoft Academic Search

In order to interpret cathodoluminescence (CL) spectra of natural anhydrites, synthetic crystals were indirectly obtained by precipitation of gypsum from solutions containing doping rare-earth elements (REE), and by transformation into anhydrite by dehydration at 800C during 3 h. Analyses by ICP-MS of several anhydrites obtained from solutions containing 130 ppm of REE clearly showed that light REE (LREE) can be

A. Baumer; Ph. Blanc; F. Cesbron; D. Ohnenstetter

1997-01-01

102

Microemulsion synthesis, characterization of highly visible light responsive rare earth-doped Bi2O3.  

PubMed

In this paper, Bi(2)O(3) and rare earth (La, Ce)-doped Bi(2)O(3) visible-light-driven photocatalysts were prepared in a Triton X-100/n-hexanol/cyclohexane/water reverse microemulsion. The resulting materials were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, photoluminescence spectra (PLS) and UV-Vis diffuse reflectance spectroscopy. The XRD patterns of the as-prepared catalysts calcined at 500 C exhibited only the characteristic peaks of monoclinic ?-Bi(2)O(3). PLS analysis implied that the separation efficiency for electron-hole has been enhanced when Bi(2)O(3) was doped with rare earth. UV-Vis diffuse reflectance spectroscopy measurements presented an extension of light absorption into the visible region. The photocatalytic activity of the samples was evaluated by degradation of methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP). The results displayed that the photocatalytic activity of rare earth-doped Bi(2)O(3) was higher than that of dopant-free Bi(2)O(3). The optimal dopant amount of La or Ce was 1.0 mol%. And the mechanisms of influence on the photocatalytic activity of the catalysts were discussed. PMID:22530926

Wu, Shuxing; Fang, Jianzhang; Xu, Xiaoxin; Liu, Zhang; Zhu, Ximiao; Xu, Weicheng

2012-01-01

103

Classical spin model of the relaxation dynamics of rare-earth doped permalloy  

NASA Astrophysics Data System (ADS)

In this paper, the ultrafast dynamic behavior of rare-earth doped permalloy is investigated using an atomistic spin model with Langevin dynamics. In line with experimental work, the effective Gilbert damping is calculated from transverse relaxation simulations, which shows that rare-earth doping causes an increase in the damping. Analytic theory suggests that this increase in damping would lead to a decrease in the demagnetization time. However, longitudinal relaxation calculations show an increase with doping concentration instead. The simulations are in a good agreement with previous experimental work of Radu [Radu , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.117201 102, 117201 (2009)]. The longitudinal relaxation time of the magnetization is shown to be driven by the interaction between the transition metal and the laser-excited conduction electrons, whereas the effective damping is predominantly determined by the slower interaction between the rare-earth elements and the phonon heat bath. We conclude that for complex materials, it is evidently important not to expect a single damping parameter but to consider the energy transfer channel relevant to the technique and time scale of the measurement.

Ellis, M. O. A.; Ostler, T. A.; Chantrell, R. W.

2012-11-01

104

Synthesis and properties of fluorizirconate rare-earth-doped glasses  

NASA Astrophysics Data System (ADS)

The entire reaction processes of the synthesizing technologies of ZrF4 synthesized from ZrO2 as the raw material and NH4HF2 as fluorinating agent were studied in considerable detail, and the produce of an analytical reagent ZrF4 was prepared. The glasses of a series of ZBLAN with and without rare-earth ions were fabricated using the self-prepared starting materials. The phenomena of the cloud-sheets in the glass sample and the cricoid arenaceous bands generated in the glass surface layer were analyzed, and the resolving phenomena measures were pointed out. The glass-forming ability is analyzed by the (Delta) T or HR parameter measured in the experiment.

Cao, Wanghe; Kan, Shidong; Zang, Chuanyi

1998-08-01

105

Rare-earth doped sol-gel silicate glasses for scintillator applications  

NASA Astrophysics Data System (ADS)

Radio-, photo- and thermally stimulated - luminescence (RL, PL, TSL) measurements have been performed on SiO2 sol-gel glasses doped by 0.1 mol% Ce and 3 mol% Gd, and on (0.1 mol% Ce, 3 mol% Gd) co-doped samples. Ce3+ 5d-4f emission F caking at about 2.7 eV has been observed in the RL of SiO2: 0.1 mol% CC, while the typical (6)p-S-8 emission of Gd3+ centred at 3.97 eV has been detected in SiO2: 3 mol% Gd. The co-doped sample displays both 5d-4f Ce3+ and P-6-S-8 Gd3+ emissions with reduced intensities with respect to those observed in the singly doped glasses. Moreover, in co-doped glasses the PL time decay patterns of both rare earth ions show a non exponential dependence and are significantly shortened. To explain such an effect non radiative de-excitation of both RE ions excited states involving energy transfers to defect levels is suggested. Bidirectional Gd3+ <-> Ce3+ energy transfers could also occur. Complementary TSL measurements put in evidence the existence of broad glow peaks at about 100 K and 220 K. The TSL spectra feature the RE ions emissions.

Chiodini, N.; Fasoli, M.; Martini, M.; Morazzoni, E.; Rosetta, E.; Scotti, R.; Spinolo, G.; Vedda, A.; Nikl, M.; Solovieva, N.; Baraldi, A.; Capelletti, R.; Francini, R.

2003-01-01

106

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

NASA Astrophysics Data System (ADS)

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.

Clark, R. D.

2005-12-01

107

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

PubMed

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

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

2010-08-16

108

Visible and near infrared emitting thin film electroluminescent gallium nitride doped with rare earths  

NASA Astrophysics Data System (ADS)

Visible and near-infrared (NIR) light-emitting thin-film electroluminescent gallium nitride (GaN) doped with rare earth (RE) elements was studied. The rare-earth-doped GaN thin films were prepared by radio frequency (RF) planar magnetron co-sputtering of separate targets consisting of a GaN compound target and a metallic rare earth target in a pure nitrogen atmosphere. The luminescence of rare-earth-doped GaN was shown to be a strong function of its structure and properties, and growth parameters affected the structure and properties of the GaN host films. A phase transition from the thermodynamically stable wurtzite to the metastable zinc-blende structure at room temperature in GaN host films was observed upon increasing the impact energy of the bombarding species, thereby increasing the compressive stress in the GaN film. The switch from wurtzite to zinc-blende GaN occurred at a compressive internal stress of 1 GPa. The internal compressive stress above this threshold value apparently stabilizes the zinc-blende GaN phase at room temperature. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) showed that the impact by hyperthermal species yielded a highly condensed fibrous GaN microstructure with a smooth surface morphology due to annihilation of porosity by knock-on and bombardment-induced adatom mobility. X-ray diffraction and texture analyses showed that the GaN films deposited at a low pressure had a predominant cubic phase with a preferred crystallographic orientation of the [111] direction perpendicular to the surface of the film. X-ray rocking curve data revealed that cubic GaN films grown with a lower growth rate exhibited a more highly [111]-textured structure. Alternating-current thin-film electroluminescent (ACTFEL) devices were fabricated based on GaN doped with rare earth (RE) elements. Visible electroluminescent light emission peaks at 475 (blue), 530 (green), and 614 nm (red) were demonstrated at room temperature from GaN doped with thulium (Tm), erbium (Er), and europium (Eu), respectively. The near-infrared electroluminescent light emissions at 800, 1082, and 1550 nm were obtained at room temperature from GaN doped with Tm, neodymium (Nd), and Er, respectively. The emitted power densities of the fabricated ACTFEL devices were 1.53, 0.71, and 3.48 muW/cm2 for the GaN doped with 1 at.% of Er, 1.5 at.% of Tm, and 1.2 at.% of Nd, respectively. The dominant electroluminescence excitation mechanism for RE-doped GaN was found to be direct impact-excitation of the trivalent RE ions by hot electrons.

Kim, Joo Han

109

Towards integrated Earth sensing: advanced technologies for in situ sensing in the context of Earth observation  

NASA Astrophysics Data System (ADS)

Over the next few years, the nature of remote and in situ sensing and their relationship with the Internet will change drastically. A growing perspective is that significant advancements in Earth observation are expected to come about only by developing more systematic capabilities for fusing remote sensing observations and in situ measurements for use in models, at relevant scales, to generate geophysical and biospheric information products. This paper presents the concept of integrated Earth sensing, which encompasses remote, proximal and in situ sensing. It endeavours to take advantage of the converging technologies of micro-sensors and telecommunications, as well as the converging technologies of geospatial information and information technology. It has the potential to significantly expand the scope of remote sensing and make it more viable by providing solid underpinnings for the quality, robustness, and reliability of the information derived from satellite-based Earth sensing in many contexts, including the monitoring of remote environments, hazards and disasters, and natural resources. As a first step towards integrated Earth sensing, a prototype in-situ sensorweb has been developed and deployed for remote operation complete with telepresence in the context of applications such as watershed monitoring. The paper describes the sensor and telecommunications components of an experimental six-node sensorweb that includes measurements of various optical, hydrological and meteorological quantities in a flood plain. The in-situ measurements are combined with optical and radar satellite image data to produce geospatial maps of key surface parameters for assimilation into stream flow and flood forecast models.

Teillet, P.; Gauthier, R.; Pultz, T.

110

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

Microsoft Academic Search

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

J. M. Hanchar; R. J. Finch; W. O. Hoskin; E. B. Watson; D. J. Cherniak; A. N. Mariano

2001-01-01

111

NOAA's Global Earth Observation - Integrated Data Environment (GEO-IDE)  

NASA Astrophysics Data System (ADS)

The international Group on Earth Observation (GEO) and the U.S. coordination group, USGEO, have identified nine societal benefit areas that require environmental data of a wide range of types and from many diverse sources. GEO has called on the nations of the world to ensure that the relevant data that they hold is made accessible and useful to these applications. In response, nations and their environmental agencies are addressing the challenges associated with data integration of these distributed and diverse data types. The National Oceanic and Atmospheric Administration (NOAA) holds extremely large collections of data describing the physical and biological properties of the Earth's environment. To date, the data collections and the systems that support them have been acquired by individually funded and managed programs with differing requirements, standards, interfaces and conventions, mirroring the data integration issues faced at the national and international level. The Global Earth Observation - Integrated Data Environment (GEO-IDE) has been initiated by NOAA to address these issues for its own interdisciplinary applications as well as those of the the broader national and international iniatives. The concept and initial plans for GEO-IDE have been developed by the Data Management Integration Team (DMIT), a group of data management professionals representing all NOAA's Line Offices, Goal Teams and the office of the CIO. The goal of GEO-IDE is to define an architecture and the associated processes necessary to establish the required standards and guidelines that allow NOAA's data providers to make their products available as a set of interoperable services. GEO-IDE is addressing the integration of existing data services while at the same time providing guidance to future data system development activities. It is intended to meet an important NOAA need while also supporting NOAA's contribution to USGEO and GEO.

McDonald, K. R.

2007-12-01

112

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

113

The EPOS Architecture: Integrated Services for solid Earth Science  

NASA Astrophysics Data System (ADS)

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.

Cocco, Massimo; Consortium, Epos

2013-04-01

114

Crystallization studies on rare-earth co-doped fluorozirconate-based glasses  

PubMed Central

This work focuses on the structural changes of barium chloride (BaCl2) nanoparticles in fluorochlorozirconate-based glass ceramics when doped with two different luminescent activators, in this case rare-earth (RE) ions, and thermally processed using a differential scanning calorimeter. In a first step, only europium in its divalent and trivalent oxidation states, Eu2+ and Eu3+, is investigated, which shows no significant influence on the crystallization of hexagonal phase BaCl2. However, higher amounts of Eu2+ increase the activation energy of the phase transition to an orthorhombic crystal structure. In a second step, nucleation and nanocrystal growth are influenced by changing the structural environment of the glasses by co-doping with Eu2+ and trivalent Gd3+, Nd3+, Yb3+, or Tb3+, due to the different atomic radii and electro-negativity of the co-dopants.

Passlick, C.; Johnson, J.A.; Schweizer, S.

2013-01-01

115

Electrostatic tuning of Kondo effect in a rare-earth-doped wide-band-gap oxide  

NASA Astrophysics Data System (ADS)

As a long-lived theme in solid-state physics, the Kondo effect reflects the many-body physics involving the short-range Coulomb interactions between itinerant electrons and localized spins in metallic materials. Here we show that the Kondo effect is present in ZnO, a prototypical wide-band-gap oxide, doped with a rare-earth element (Gd). The localized 4f electrons of Gd ions do not produce remanent magnetism, but interact strongly with the host electrons, giving rise to a saturating resistance upturn and negative magnetoresistance at low temperatures. Furthermore, the Kondo temperature and resistance can be electrostatically modulated using electric-double-layer gating with liquid ionic electrolyte. Our experiments provide the experimental evidence of tunable Kondo effect in ZnO, underscoring the magnetic interactions between localized and itinerant electrons and the emergent transport behaviors in such doped wide-band-gap oxides.

Li, Yongfeng; Deng, Rui; Lin, Weinan; Tian, Yufeng; Peng, Haiyang; Yi, Jiabao; Yao, Bin; Wu, Tom

2013-04-01

116

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

117

Optical properties of oxide glasses with semiconductor nanoparticles co-doped with rare earth ions  

NASA Astrophysics Data System (ADS)

This letter investigates PZABP glasses with nominal composition, 60P2O5. 15ZnO. 5Al2O3. 10BaO. 10PbO, doped with tellurium and co-doped with different concentrations of rare earth ions, ytterbium and europium. AFM, optical absorption, photoluminescence (PL) and time-resolved photoluminescence (TRPL) techniques characterized the vitreous systems. The formation of semiconductor nanoclusters ZnTe bulk-like and ZnTe quantum dots were identified. PL and TRPL show the energy transfer from the ZnTe nanocrystals and Eu3+ ions to Yb3+ ions. The optical properties presented qualify the system as potentially useful for light emission devices in the infrared region from 920 to 1060 nm.

Neto, M. C.; Silva, G. H.; Carmo, A. P.; Pinheiro, A. S.; Dantas, N. O.; Bell, M. J. V.; Anjos, V.

2013-11-01

118

Persistent luminescence of Eu2+ and Na+ doped alkaline earth aluminates  

NASA Astrophysics Data System (ADS)

The luminescence and afterglow properties of the Eu2+ and Na+ doped alkaline earth aluminates, stoichiometric and non-stoichiometric (MxAl2O4:Eu2+, Na+, M=Ca or Sr, x=0.97, 1.00 or 1.03, X-Na=0.02), were studied. Broad band luminescence and afterglow of the Eu2+ ion were observed in the blue (lambda(max) = 440 nm) and green (lambda(max)=520 nm) region for the calcium and strontium aluminates, respectively Both Na+ co-doping and strontium excess quenched the afterglow efficiently The results supported the mechanism of the persistent luminescence where the cation vacancies act as traps. The results for the calcium aluminates were ambiguous, probably due to the slightly larger ionic radius of the Na+ with respect to that of Ca2+. The sodium ions may not fit into the calcium sites and thus form (an) independent compound(s).

Aitasalo, T.; Holsa, J.; Lastusaari, M.; Legendziewicz, J.; Niittykoski, J.

2003-01-01

119

Scintillation property of rare earth-free SnO-doped oxide glass  

NASA Astrophysics Data System (ADS)

The authors have demonstrated scintillation of rare earth (RE)-free Sn-doped oxide glass by excitation of ionizing radiation. It is notable that light emission is attained for RE-free transparent glass due to s2-sp transition of Sn2+ centre and the emission correlates with the excitation band at 20 eV. We have also demonstrated that excitation band of emission centre can be tuned by the chemical composition of the host glass. The present result is valuable not only for design of RE-free inorganic amorphous oxide scintillator but also for revealing the band structure of oxide glass by irradiation of ionizing radiation.

Masai, Hirokazu; Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Yoko, Toshinobu

2012-11-01

120

Optical properties of alkali and alkaline-earth lead borate glasses doped with Nd 3+ Ions  

Microsoft Academic Search

Spectroscopic and physical properties of Nd3+-doped alkali lead borate glasses of type 20R\\u000a 2O 30PbO 49.5B2O3 0.5Nd2O3 (R = Li and K) and alkaline-earth lead borate glasses 20RO 30PbO 49.5B2O3 0.5Nd2O3 (R = Ca, Ba, and Pb) have been investigated. Optical absorption spectra have been used to determine the Slater-Condon (F2, F4, and F6),

S. Mohan; K. S. Thind; D. Singh; L. Gerward

2008-01-01

121

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

NASA Astrophysics Data System (ADS)

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.

Behrens, Edward Grady

122

Fabrication of photonic crystals in rare-earth doped chalcogenide glass films for enhanced upconversion  

NASA Astrophysics Data System (ADS)

Gallium lanthanum oxysulfide (GLSO) is a promising host material for observing strong upconversion emission from trivalent rare-earth ions such as erbium (Er3+). Its attractive properties include high rare-earth solubility due to the lanthanum content of the glass former, a high refractive index (n = 2.2 at 550nm) for high radiative efficiency, and a low maximum phonon energy of approximately 425cm -1. Photonic crystals meanwhile can provide controlled light extraction, and may be capable of suppressing unwanted IR emission from lower lying metastable states. Here, we describe the fabrication of photonic crystals in annealed films of Er3+-doped GLSO deposited by RF sputtering. The most intense visible upconversion emission is observed in films annealed at 550C, close to the bulk glass transition temperature. Hexagonal lattice photonic crystals are subsequently milled into the films using a focused ion beam (FIB). The milling parameters are optimized to produce the most vertical sidewall profile.

Pollard, M. E.; Knight, K. J.; Parker, G. J.; Hewak, D. W.; Charlton, M. D. B.

2012-02-01

123

Fluorescence and atomic defect properties of rare earth doped barium titanate  

NASA Astrophysics Data System (ADS)

Rare earth doped barium titanate was studied by laser induced fluorescence. Trivalent erbium and europium were used as dopant ions. Rare earth ions primarily entered the crystal with a distant charge compensation, though a small amount were associated with other defects in the crystal. There were thirteen spectroscopically distinct erbium sites characterized and ten distinct europium sites characterized. The crystals were annealed at 800C in air and in a mixture of CO and CO2 gas to cause oxygen vacancies to react with the rare earth ions. They were also annealed at 1250C in air to allow cation motion so that cation defect reactions with rare earth ions could be studied as well. It was found that some erbium ion sites were stable at lower temperatures, but could only be formed during crystal growth. Some erbium sites also seem to be associations with oxygen vacancies in the crystal. A defect model of barium titanate was also developed to help explain defect reactions. Europium sites did not show reproducible results with the annealing experiments, but the ionization energy of divalent to trivalent europium ions in a barium titanate host crystal was estimated at 1.1 eV due to a change in the characteristics of the europium sites at about 0.06mol% europium dopant.

Bak, John D.

124

Wide band gap fluoride dielectric crystals doped with trivalent rare earth ions as optical materials for 157 nm photolithography  

Microsoft Academic Search

We investigate the possibility to use a new class of wide band gap fluoride dielectric crystals as optical elements for 157 nm photolithography. The rare earth doped or non-doped crystals can be used as passive or active optical elements in the VUV. Applications are depending on the structure of the levels of the 4fn?15d electronic configuration and the strength of

E. Sarantopoulou; Z. Kollia; A. C. Cefalas

2000-01-01

125

Effect of alkaline earth metal doping on thermal, optical, magnetic and dielectric properties of BiFeO3 nanoparticles  

Microsoft Academic Search

Substrate-free pure-phase BiFeO3 (BFO) nanoparticles doped with alkaline earth metals (Ba, Sr and Ca) have been synthesized by a sol-gel route and their thermal, optical, dielectric and magnetic properties are discussed. The characteristic structural phase transitions of BFO nanoparticles are found to occur at much lower temperatures. A reduction of the Nel temperature has been observed in the doped samples

B. Bhushan; A. Basumallick; S. K. Bandopadhyay; N. Y. Vasanthacharya; D. Das

2009-01-01

126

High-bandwidth quantum memory protocol for storing single photons in rare-earth doped crystals  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of a high-bandwidth quantum memory protocol for storing single photons in a rare-earth-ion doped crystal. The basic idea is to benefit from a coherent free-induced decay type re-emission which occurs naturally when a photon with a broadband spectrum is absorbed by a narrow atomic transition in an optically dense ensemble. This allows for a high-bandwidth memory for realistic material parameters. Long storage time and on-demand readout are obtained by means of spin states in a lambda-type configuration, through the transfer of the optical coherence to a spin coherence (so-called spin-wave storage). We give explicit formulae and show numerical results which make it possible to gain insight into the dependence of the memory efficiency on the optical depth and on the width and the shape of stored photons. We present a feasibility study in rare-earth doped crystals and show that high efficiencies and high bandwidth can be obtained with realistic parameters. High-bandwidth memories using spin-wave storage offers the possibility of very high time-bandwidth products, which is important for experiments where high repetition rates are needed.

Caprara Vivoli, Valentina; Sangouard, Nicolas; Afzelius, Mikael; Gisin, Nicolas

2013-09-01

127

Excess modes and enhanced scattering in rare-earth-doped amorphous silicon thin films  

NASA Astrophysics Data System (ADS)

We report specific heat and thermal conductivity of gadolinium- and yttrium-doped amorphous silicon thin films measured using silicon-nitride membrane-based microcalorimeters. Addition of gadolinium or yttrium to the amorphous silicon network reduces the thermal conductivity over a wide temperature range while significantly increasing the specific heat. This result indicates that a large number of nonpropagating states are added to the vibrational spectrum that are most likely caused either by localized vibration of the dopant atom in a Si cage or softening of the material forming the cage structures. High-resolution cross-sectional electron micrographs reveal columnar features in Gd-doped material which do not appear in pure amorphous silicon. Scattering from both the nanoscaled columns and the filled-cage structures play a role in the reduced thermal conductivity in the rare-earth-doped amorphous semiconductor. The overall result is an amorphous solid with a large bump in C/T3 and no plateau in thermal conductivity.

Zink, B. L.; Islam, R.; Smith, David J.; Hellman, F.

2006-11-01

128

Synthesis and photoluminescent behavior of Eu3+-doped alkaline-earth tungstates  

NASA Astrophysics Data System (ADS)

Eu3+-doped alkaline-earth tungstates MWO4 (M=Ca2+, Sr2+, Ba2+) were prepared by a polymeric precursor method based on the Pechini process. The polymeric precursors were calcined at 700 C for 2 h in order to obtain well-crystallized powders and then characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and photoluminescence spectroscopy (PL). All prepared samples showed a pure crystalline phase with scheelite-type structure confirmed by XRD. It was noted that the charge-transfer band shifted from 260 to 283 nm when calcium is replaced by strontium. However, this band was not observed for Eu3+-doped barium tungstate. Upon excitation at 260 nm, the emission spectra are dominated by the red 5D0?7F2 transition at 618 nm. By analyzing of the emission lines, it was inferred that Eu3+ ions occupy low symmetry sites in the host lattice. It was also found that Eu3+-doped SrWO4 displays better chromaticity coordinates and greater luminescence intensity than the other samples.

Barros, B. S.; de Lima, A. C.; da Silva, Z. R.; Melo, D. M. A.; Alves-Jr, S.

2012-05-01

129

Microwave study of photoconductivity induced by laser pulses in rare-earth-doped dielectric crystals  

NASA Astrophysics Data System (ADS)

Transient responses of the dielectric permittivity ?=?1-i?2 of rare-earth-doped dielectric crystals under pulsed laser excitation were studied by the 8-mm microwave resonator technique at room temperature. The fluorite-type crystals (CaF2, SrF2, and BaF2) which contained divalent ions of Sm, Eu, and Tm, as well as Lu2(SiO4)O and Y3Al5O12 doped with trivalent Ce ions were investigated. The dielectric response to a laser pulse contains two different types of signals: electronic and heating ones. The electronic peak, which is quite fast (from 40 to 100 ns or more), is the signature of electrons released into the conduction band following an impurity photoionization. The prolonged heating signal has a sawtooth form on which oscillations are imposed. It is due to modulation of the dielectric constant by a sudden temperature rise and subsequent elastic vibrations of the sample caused by the energy absorbed from the laser pulse. In different crystals the electronic peak was caused by the transient response of either ?1, ?2, or a mixture of the two. The modulation of the dielectric loss factor ?2 corresponds to conventional photoconductivity, i.e., the photoexcitation of mobile electrons. The modulation of the dielectric constant ?1 corresponds to the photoexcitation of bound electrons, probably captured by traps. The threshold energies of photons at which the photoionization of rare-earth ions may occur, were determined for CaF2:Sm2+ (3.3 eV) and Lu2(SiO4)O:Ce3+ (3.1 eV). In fluorite-type crystals doped with Sm2+ or Tm2+ ions, the significant reduction of a lifetime of electrons in a conduction band was revealed with an increase in energy of laser pulses. In SrF2:Eu crystal the record-high signals of photoconductivity were observed upon excitation by VIS light in the optical region of transparency of this crystal. The microwave resonant technique may be used for detail studying the photoionization dynamics of rare-earth ions and finding the location of their energy levels with respect to the host conduction band in doped insulators.

Joubert, M.-F.; Kazanskii, S. A.; Guyot, Y.; Gcon, J.-C.; Pdrini, C.

2004-04-01

130

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

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

131

Integrating LiDAR Data into Earth Science Education  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

132

Rare-earth metal oxide doped transparent mesoporous silica plates under non-aqueous condition as a potential UV sensor.  

PubMed

Transparent mesoporous silica plates doped with rare-earth metal oxide were prepared using solvent-evaporation method based on the self-organization between structure-directing agent and silicate in a non-aqueous solvent. A triblock copolymer, Pluronic (F127 or P123), was used as the structure-directing agent, while tetraethyl orthosilicate (TEOS) was used as a silica source. The pore diameter and the surface area of the mesoporous silica plate prepared with the optimized conditions were ca 40 A and 600 m2 g(-1), respectively, for both structure-directing agent. Rare-earth metal oxides (Eu, Tb, Tm oxide) in mesochannel were formed via one-step synthetic route based on the preparation method of a silica plate. Optical properties of rare-earth metal oxide-doped mesoporous silica plates were investigated by UV irradiation and photoluminescence (PL) spectroscopy. Under the exitation wavelength of 254 nm, the doped mesoporous silica plates emitted red, green and blue for Eu, Tb and Tm oxides, respectively. Rare-earth metal oxide-doped mesoporous silica plates showed enhanced PL intensity compared to that of the bulk rare-earth metal oxide. PMID:24245274

Lee, Sang-Joon; Park, Sung Soo; Lee, Sang Hyun; Hong, Sang-Hyun; Ha, Chang-Sik

2013-11-01

133

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

SciTech Connect

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.

Chakraborty, Keka [Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)] [Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bisoi, Abhijit [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)] [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Ganguly, Bichitra Nandi, E-mail: bichitra.ganguly@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Grover, Vinita; Sayed, Farheen Nasir; Tyagi, A.K. [Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)] [Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2012-11-15

134

Systematics of 4f electron energies relative to host bands by resonant photoemission of rare earth doped optical materials  

Microsoft Academic Search

Relative energies of 4fn electronic states and crystal band states are important for a fundamental understanding of rare-earth-doped optical materials and a practical understanding of each material's potential performance in specific applications. With this motivation, the 4fn ground state binding energies of rare earth ions have been studied in the gallium garnets using resonant photoemission spectroscopy and compared with the

C. W. Thiel; H. Cruguel; Y. Sun; G. J. Lapeyre; R. M. Macfarlane; R. W. Equall; R. L. Cone

2001-01-01

135

Investigating material trends and lattice relaxation effects for understanding electron transfer phenomena in rare-earth-doped optical materials  

Microsoft Academic Search

Rare-earth-doped insulators and semiconductors play an important role in a wide range of modern optical technologies. Knowledge of the relative energies of rare-earth ions localized electronic states and the band states of the host crystal is important for understanding the properties of these materials and for determining the potential material performance in specific applications such as lasers, phosphors, and optical

C. W. Thiel; R. L. Cone

2011-01-01

136

Fabrication by H+ or He+ ion implantation in lithium niobates and tantalates doped with rare earths and optical characterization  

Microsoft Academic Search

By using a Van de Graaff accelerator, optical waveguides are fabricated in rare earth ions-doped LiNbO3, LiNbO3 (MgO) and LiTaO3 crystals, by thermally controlled He+ or H+ implantation. The Rare earth ions used as dopants are either the Nd3+ laser ion or the Eu3+ structural probe. The mode spectra of the various waveguides are investigated by dark lines spectroscopy. The

C. Mignotte; P. Moretti; K. E. Lipinska-Kalita; G. Boulon; J. Mugnier

1996-01-01

137

Er-doped integrated optical devices in LiNbO3  

Microsoft Academic Search

The state-of-the-art of Er-doped integrated optical devices in LiNbO3 is reviewed starting with a brief discussion of the technology of Er-indiffusion. This technique yields high-quality waveguides and allows a selective surface doping necessary to develop optical circuits of higher complexity. Doped waveguides have been used as single- and double-pass optical amplifiers for the wavelength range 1530 nm

I. Baumann; S. Bosso; R. Brinkmann; R. Corsini; M. Dinand; A. Greiner; K. Schafer; J. Sochtig; W. Sohler; H. Suche; R. Wessel

1996-01-01

138

Hydrothermal Synthesis, Microstructure and Photoluminescence of Eu3+-Doped Mixed Rare Earth Nano-Orthophosphates  

PubMed Central

Eu3+-doped mixed rare earth orthophosphates (rare earth = La, Y, Gd) have been prepared by hydrothermal technology, whose crystal phase and microstructure both vary with the molar ratio of the mixed rare earth ions. For LaxY1xPO4: Eu3+, the ion radius distinction between the La3+ and Y3+ is so large that only La0.9Y0.1PO4: Eu3+ shows the pure monoclinic phase. For LaxGd1xPO4: Eu3+ system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires. Similarly, YxGd1xPO4: Eu3+, Y0.1Gd0.9PO4: Eu3+ and Y0.5Gd0.5PO4: Eu3+ samples present the pure hexagonal phase and nanorods microstructure, while Y0.9Gd0.1PO4: Eu3+ exhibits the tetragonal phase and nanocubic micromorphology. The photoluminescence behaviors of Eu3+ in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

2010-01-01

139

Optical spectroscopy of rare earth ion-doped TiO2 nanophosphors.  

PubMed

Trivalent rare-earth (RE3+) ion-doped TiO2 nanophosphors belong to one kind of novel optical materials and have attracted increasing attention. The luminescence properties of different RE3+ ions in various TiO2 nanomaterials have been reviewed. Much attention is paid to our recent progresses on the luminescence properties of RE3+ (RE = Eu, Er, Sm, Nd) ions in anatase TiO2 nanoparticles prepared by a sol-gel-solvothermal method. Using Eu3+ as a sensitive optical probe, three significantly different luminescence centers of Eu3+ in TiO2 nanoparticles were detected by means of site-selective spectroscopy at 10 K. Based on the crystal-field (CF) splitting of Eu3+ at each site, C2v and D2 symmetries were proposed for Eu3+ incorporated at two lattice sites. A structural model for the formation of multiple sites was proposed based on the optical behaviors of Eu3+ at different sites. Similar multi-site luminescence was observed in Sm(3+)- or Nd(3+)-doped TiO2 nanoparticles. In Eu(3+)-doped TiO2 nanoparticles, only weak energy transfer from the TiO2 host to the Eu3+ ions was observed at 10 K due to the mismatch of energy between the TiO2 band-gap and the Eu3+ excited states. On the contrary, efficient host-sensitized luminescences were realized in Sm(3+)- or Nd(3+)-doped anatase TiO2 nanoparticles due to the match of energy between TiO2 band-gap and the Sm3+ and Nd3+ excited states. The excitation spectra of both Sm(3+)- and Nd(3+)-doped samples exhibit a dominant broad peak centered at approximately 340 nm, which is associated with the band-gap of TiO2, indicating that sensitized emission is much more efficient than direct excitation of the Sm3+ and Nd3+ ions. Single lattice site emission of Er3+ in TiO2 nanocrystals can be achieved by modifying the experimental conditions. Upon excitation by a Ti: sapphire laser at 978 nm, intense green upconverted luminescence was observed. The characteristic emission of Er3+ ions was obtained both in the ultraviolet-visible (UV-vis) and near-infrared regions through the high-resolution experiments at 10 K. The CF experienced by Er3+ in TiO2 nanocrystal was systematically studied by means of the energy level fitting. PMID:20355538

Chen, Xueyuan; Luo, Wenqin

2010-03-01

140

Invited Paper Spectral control of optical gain in a rare earth-doped optical fiber using novel triple layered structures  

Microsoft Academic Search

Novel techniques to control the effective emission cross section of a rare earth-doped optical fiber with a functional cladding structure are reviewed for applications in active fiber devices. We discuss evanescent wave filtering (EWF) technique based on the overlap in the radiative transition cross sections between the emitting ion in the core and the absorbing ion in the inner cladding.

Kyungwhan Oh; Seongwoo Yoo; Uh-Chan Ryu; Seungtaek Kim; Un-Chul Paek; Daniel B. S. Soh; Jayanta K. Sahu; Johan Nilsson

141

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

PubMed

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

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

2014-03-21

142

Photon-pair source with controllable delay based on shaped inhomogeneous broadening of rare-earth-metal-doped solids  

SciTech Connect

Spontaneous Raman emission in atomic gases provides an attractive source of photon pairs with a controllable delay. We show how this technique can be implemented in solid state systems by appropriately shaping the inhomogeneous broadening. Our proposal is eminently feasible with current technology and provides a realistic solution to entangle remote rare-earth-metal-doped solids in a heralded way.

Sekatski, Pavel; Sangouard, Nicolas; Gisin, Nicolas; Afzelius, Mikael [Group of Applied Physics, University of Geneva, CH-1211 Geneva 4 (Switzerland); Riedmatten, Hugues de [Group of Applied Physics, University of Geneva, CH-1211 Geneva 4 (Switzerland); ICFO-Institute of Photonic Sciences, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08015 Barcelona (Spain)

2011-05-15

143

Co-doping of glasses with rare earth ions and metallic nanoparticles for frequency up-conversion  

Microsoft Academic Search

We explore different approaches to achieve co-doping of glasses with rare earth ions and metallic nanoparticles, and to manipulate the spectral position of the particles' surface plasmon resonance. The final goal is to find a composite material with improved efficiency of frequency up-conversion of light for photovoltaic applications. The potential for improvement has been shown by theoretical calculations predicting that

S. Wackerow; G. Seifert

2010-01-01

144

Thermoanalytical studies of coprecipitated hydroxides of yttrium and aluminum for preparation of rare-earth doped YAG phosphors  

Microsoft Academic Search

Yttrium-aluminum garnets (YAG) doped with a rare-earth element, including terbium (Tb), thulium (Tm), and Erbium (Er) produce the phosphorescence. YAGs may be synthesized by baking hydroxides of their constituents at a high temperature. No flux is required and the temperature of the solid state synthesis may be decreased to only 1150 degrees Celsius when the hydroxides are coprecipitated. We report

Marija S. Scholl

1996-01-01

145

Advancing coupled human-earth system models: The integrated Earth System Model Project  

NASA Astrophysics Data System (ADS)

As human and biogeophysical models develop, opportunities for connections between them evolve and can be used to advance our understanding of human-earth systems interaction in the context of a changing climate. One such integration is taking place with the Community Earth System Model (CESM) and the Global Change Assessment Model (GCAM). A multi-disciplinary, multi-institution team has succeeded in integrating the GCAM integrated assessment model of human activity into CESM to dynamically represent the feedbacks between changing climate and human decision making, in the context of greenhouse gas mitigation policies. The first applications of this capability have focused on the feedbacks between climate change impacts on terrestrial ecosystem productivity and human decisions affecting future land use change, which are in turn connected to human decisions about energy systems and bioenergy production. These experiments have been conducted in the context of the RCP4.5 scenario, one of four pathways of future radiative forcing being used in CMIP5, which constrains future human-induced greenhouse gas emissions from energy and land activities to stabilize radiative forcing at 4.5 W/m2 (~650 ppm CO2 -eq) by 2100. When this pathway is run in GCAM with the climate feedback on terrestrial productivity from CESM, there are implications for both the land use and energy system changes required for stabilization. Early findings indicate that traditional definitions of radiative forcing used in scenario development are missing a critical component of the biogeophysical consequences of land use change and their contribution to effective radiative forcing. Initial full coupling of the two global models has important implications for how climate impacts on terrestrial ecosystems changes the dynamics of future land use change for agriculture and forestry, particularly in the context of a climate mitigation policy designed to reduce emissions from land use as well as energy systems. While these initial experiments have relied on offline coupling methodologies, current and future experiments are utilizing a single model code developed to integrate GCAM into CESM as a component of the land model. This unique capability facilitates many new applications to scientific questions arising from human and biogeophysical systems interaction. Future developments will further integrate the energy system decisions and greenhouse gas emissions as simulated in GCAM with the appropriate climate and land system components of CESM.

Thomson, A. M.; Edmonds, J. A.; Collins, W.; Thornton, P. E.; Hurtt, G. C.; Janetos, A. C.; Jones, A.; Mao, J.; Chini, L. P.; Calvin, K. V.; Bond-Lamberty, B. P.; Shi, X.

2012-12-01

146

Mars for Earthlings: A Higher Educational Terrestrial Analog Approach for Teaching Integrated Earth and Planetary Science  

NASA Astrophysics Data System (ADS)

"Mars for Earthlings" teaching modules use Earth analogs to explore Mars at an introductory college level. This integrated approach increases science literacy and attracts students to STEM disciplines.

Chan, M. A.; Robinson, J. K.

2012-03-01

147

Integration of satellite fire products into MPI Earth System Model  

NASA Astrophysics Data System (ADS)

Fires are the ubiquitous phenomenon affecting all natural biomes. Since the beginning of the satellite Era, fires are being continuously observed from satellites. The most interesting satellite parameter retrieved from satellite measurements is the burned area. Combined with information on biomass available for burning the burned area can be translated into climate relevant carbon emissions from fires into the atmosphere. In this study we integrate observed burned area into a global vegetation model to derive global fire emissions. Global continuous burned area dataset is provided by the Global Fire Emissions Dataset (GFED). GFED products were obtained from MODIS (and pre-MODIS) satellites and are available for the time period of 14 years (1997-2011). This dataset is widely used, well documented and supported by periodical updates containing new features. We integrate the global burned area product into the land model JSBACH, a part of the Earth-System model developed at the Max Plank Institute for Meteorology. The land model JSBACH simulates land biomass in terms of carbon content. Fire is an important disturbance process in the Earth's carbon cycle and affects mainly the carbon stored in vegetation. In the standard JSBACH version fire is represented by process based algorithms. Using the satellite data as an alternative we are targeting better comparability of modeled carbon emissions with independent satellite measurements of atmospheric composition. The structure of burned vegetation inside of a biome can be described as the balance between woody and herbaceous vegetation. GFED provides in addition to the burned area satellite derived information of the tree cover distribution within the burned area. Using this dataset, we can attribute the burned area to the respective simulated herbaceous or woody biomass within the vegetation model. By testing several extreme cases we evaluate the quantitative impact of vegetation balance between woody and herbaceous vegetation on fire carbon emissions. The integration procedure of satellite observed burned area into JSBACH is developed in a way that it can be easily adapted to future satellite fire datasets (e.g. expected ESA CCI Fire-ECV products). Here we will also discuss further possibilities for the integration of satellite fire data into vegetation models.

Khlystova, Iryna G.; Kloster, Silvia

2013-04-01

148

Upconversion fluorescence spectroscopy in rare earth doped sol-gel nano-glass ceramics  

NASA Astrophysics Data System (ADS)

There has recently been a great deal of interest in searching for new materials for application as hosts in infrared-tovisible light upconverters or optical amplifiers based upon rare-earth doped systems. Some of their many applications include: color displays, high density optical recording, biomedical diagnostics, infrared laser viewers and indicators, fiber lasers and amplifiers. Fluorosilicate based sol gel glass ceramics have recently emerged as auspicious candidates for such photonic devices applications. These glasses are advantageous because they present low temperature of preparation, better mechanical strength, chemical durability, and thermal stability than fluoride-based glasses. The present work involves the investigation of optical transitions and upconversion fluorescence spectroscopy of trivalent lanthanide ions Er3+ codoped with Yb3+ in ?-PbF2 nanocrystals dispersed in silica glassy matrix, excited with nearinfrared diode lasers. The dependence of the upconversion luminescence upon diode laser power, and the upconversion excitation mechanisms involved are also investigated.

Bueno, Luciano A.; da Gouveia-Neto, Artur S.; da Silva, Andria F.; Moura, Digenes S.; da Silva, Elias A.; Costa, Ernande B.

2010-02-01

149

Electron paramagnetic resonance of vanadyl doped mixed alkaline earth borate glasses  

NASA Astrophysics Data System (ADS)

The ``mixed alkaline effect'' is one of the classical anomalies of glass science. We report here an interesting phenomenon ``Mixed Alkaline earth oxide Effect'' observed in a series of VO2+ ions doped in xMgO-(30-x)BaO-68B2O3-2V2O5 glass system. Glasses are investigated by EPR technique at X-band frequencies. The EPR spectra of all the glasses exhibited resonance signals characteristic of VO2+ ions in octahedral coordination with tetragonal compression and have C4V symmetry with ground state dxy. Tetragonality (?gll/?g?) of V4+ ion sites exhibited non-linear variation with MgO content, which indicated change in the ligand field at the site of V4+.

Samdani; Chandrasekhar, K.; Shareefuddin, Md.; Chary, M. Narasimha

2013-06-01

150

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

151

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

152

Enhancement of ferroelectricity and ferromagnetism in rare earth element doped BiFeO3  

NASA Astrophysics Data System (ADS)

Rare earth element doped BiFeO3 thin films were fabricated using the pulsed laser deposition method and various targets made from different starting Fe2O3 and Fe3O4 iron source materials. The films fabricated using the targets made from Fe3O4 exhibit great enhancement in their ferroelectricity, due to greatly reduced electrical leakage, as well as enhanced magnetization compared to those films deposited using targets from Fe2O3. It is suggested that the Fe2+ ion plays an important role in compensating for the charge imbalance and reducing current leakage, as well as enhancing the magnetic moment through the introduction of antiferrimagnetic ordering at Fe2+ site.

Cheng, Z. X.; Wang, X. L.; Dou, S. X.; Kimura, H.; Ozawa, K.

2008-12-01

153

c-axis transport in rare-earth doped CaFe2As2  

NASA Astrophysics Data System (ADS)

The discovery of a low volume fraction phase of superconductivity in rare-earth doped Ca1-xRxFe2As2 with Tc= 47 K has sparked controversy over the nature of the observed superconductivity. However, an important aspect to understanding the behavior in these systems lies in understanding the role of the structural collapse wherein interlayer As atoms abruptly form a bond at sufficiently low temperatures, resulting in a 10% reduction of the c-axis through a first-order transition. We will present measurements of electrical transport with currents directed along the crystallographic c-axis, discussing the implications for the superconducting phase and the nature of the band structure change through the structural collapse transition.

Paglione, Johnpierre; Drye, T.; Hu, R.; Saha, S. R.

2013-03-01

154

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

NASA Astrophysics Data System (ADS)

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.

Chandrasekharan, Sreerenjini

155

Superparamagnetism and interfacial superconductivity in rare earth Pr-doped Ca122  

NASA Astrophysics Data System (ADS)

To better understand the origin of the non-bulk superconductivity with an unusually high onset-Tc (49 K) and its superconducting behavior in the rare earth Pr-doped Ca122 [(Ca1-xPrx)Fe2As2], detailed chemical analyses and magnetization measurements on both the as-synthesized and annealed single crystals were carried out. A small but non-negligible As-deficiency and superparamagnetic clusters (SPCs) were detected in the superconducting as-synthesized crystals, suggesting that the SPCs originate from the As vacancies. The magnetic moment of the SPC were found to be insensitive to the doping level x, while the SPC density (n) is zero for x 0.05 in the non-superconducting region and increases monotonically with x for x 0.1 in the superconducting region. The superconducting volume fraction (f) was shown to be very closely related with n. Noticeable inter-cluster interactions, from antiferromagnetic for x 0.05 (non -SC region) to weakly ferromagnetic for x 0.1 (SC region) were found, suggesting that the defects are ordered. Systematically annealing the crystals over 500-920^o simultaneously suppress both n and f. Therefore, we propose that the ordered vacancies, and the associated interfaces, are responsible for the rather high onset-Tc.

Deng, L. Z.; Lv, B.; Wei, F. Y.; Xue, Y. Y.; Chu, C. W.

2013-03-01

156

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

157

High-density frequency domain storage in alkaline earth sulfides double doped with lanthanide  

NASA Astrophysics Data System (ADS)

Previously we have reported the largest number of photon- gated spectral holes ever burned in a solid. This has interest in their applications in optical storage. However, multiple holeburning in MgS:Eu resulted in noticeable erasure of the previously burned holes. This was attributed to the mechanism of holeburning in this material where both Eu2+ and Eu3+ are stable ions. In gated holeburning, Eu2+ ions are ionized. Eu3+ that form deep traps, capture the electrons generated during the holeburning and are converted to Eu2+. The Zero Phonon Line (ZPL) of these newly formed Eu2+ ions are randomly distributed across the inhomogeneous line causing a partial erasure of the holes burned earlier. This reduces the efficiency of holeburning. Co-doping of MgS:Eu and CaS:Eu with different rare earth (RE) ions has been investigated to provide deep electron traps other than Eu3+. Furthermore, co-doping provides the opportunity to burn holes in multiple ZPLs belonging to different REs, thus increasing the storage density many folds.

Aly, M. F.; Biyikli, Levent; Dardona, Sameh; Hasan, Zameer U.

2000-11-01

158

High-density frequency domain storage in alkaline earth sulfides double-doped with lanthanide*  

NASA Astrophysics Data System (ADS)

Previously we have reported the largest number of photon-gated spectral holes ever burned in a solid. This has revived interest for their applications in optical storage. However, multiple holeburning in MgS:Eu resulted in noticeable erasure of the previously burned holes. This was attributed to the mechanism of holeburning in this material where both Eu2+ and Eu3+ are stable ions. In gated holeburning, Eu2+ ions are ionized. Eu3+ ions, that form deep traps, capture the electrons generated during the holeburning and are converted to Eu2+. The Zero Phonon Line (ZPL) of these newly formed Eu2+ ions are randomly distributed across the inhomogeneous line causing a partial erasure of the holes burned earlier. This reduces the efficiency of holeburning. Co-doping of MgS:Eu and CaS:Eu with different rare earth (RE) ions has been investigated to provide deep electron traps other than Eu 3+. Furthermore, co-doping provides the opportunity to burn holes in multiple ZPLs belonging to different REs, thus increasing the storage density many folds.

Aly, M. F.; Biyikli, L.; Dardona, S. I.; Hasan, Zameer

2000-03-01

159

Monte Carlo simulation of radiation pattern for rare earth ions doped luminescent glasses under violet LED excitation  

NASA Astrophysics Data System (ADS)

Rare earth ions doped luminescence glasses are promising phosphor candidates in the fabrication of LEDs in the future due to their specific advantages such as higher thermal stability, higher transparency, compared to current commercial LEDs. While radiation patterns of luminescent glasses are different from current commercial LEDs fabricated by phosphors, luminescent glasses play roles both in emitting light and adjusting light distribution. In order to investigate radiation pattern of luminescent glasses, luminescence physical model of flat glasses doped with single rare earth ion was presented. Process of photons acting on rare earth ions and transporting in the luminescent glasses, and output light distribution from luminescent glasses were analyzed based on violet LED. At last, the simulating of radiation pattern for luminescent glasses based on Monte Carlo ray-tracing method was proved by experiment.

Lei, Xiaohua; Feng, Yong'an; Chen, Weimin; Zhang, Peng; Ren, Linjiao; Du, Xiaoqing

2013-09-01

160

An integrated view of data quality in Earth observation  

PubMed Central

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.

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

2013-01-01

161

Optical spectra of un-doped and rare-earth-(=Pr, Nd, Eu, and Er) doped transparent ceramic Y3Al5O12  

Microsoft Academic Search

Undoped and rare-earth- (Pr, Nd, Eu, and Er) doped transparent Y3Al5O12 ceramics have been prepared, and their optical spectra have been measured. It is found that absorption coefficient of the undoped ceramic Y3Al5O12 is almost independent of wavelength with 0.258 cm?1, which gives transmittance of the undoped ceramic Y3Al5O12 to be, for example, 95% for a 2-mm height. Peaks in

H. Haneda M. Sekita; S. Shirasaki

1991-01-01

162

Structural collapse and superconductivity in rare-earth-doped CaFe2As2  

NASA Astrophysics Data System (ADS)

Aliovalent rare-earth substitution into the alkaline-earth site of CaFe2As2 single crystals is used to fine tune structural, magnetic, and electronic properties of this iron-based superconducting system. Neutron and single-crystal x-ray scattering experiments indicate that an isostructural collapse of the tetragonal unit cell can be controllably induced at ambient pressures by the choice of substituent ion size. This instability is driven by the interlayer As-As anion separation, resulting in an unprecedented thermal expansion coefficient of 18010-6 K-1. Electrical transport and magnetic susceptibility measurements reveal abrupt changes in the physical properties through the collapse as a function of temperature, including a reconstruction of the electronic structure. Superconductivity with onset transition temperatures as high as 47 K is stabilized by the suppression of antiferromagnetic order via chemical pressure, electron doping, or a combination of both. Extensive investigations are performed to understand the observations of partial volume-fraction diamagnetic screening, ruling out extrinsic sources such as strain mechanisms, surface states, or foreign phases as the cause of this superconducting phase that appears to be stable in both collapsed and uncollapsed structures.

Saha, S. R.; Butch, N. P.; Drye, T.; Magill, J.; Ziemak, S.; Kirshenbaum, K.; Zavalij, P. Y.; Lynn, J. W.; Paglione, J.

2012-01-01

163

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

Microsoft Academic Search

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

R. D. Clark

2005-01-01

164

Effect of rare earth doping on thermo-physical properties of lanthanum zirconate ceramic for thermal barrier coatings  

Microsoft Academic Search

The effect of rare earth doping on thermo-physical properties of lanthanum zirconate was investigated. Oxide powders of various compositions La2Zr2O7 were synthesized by coprecipitation-calcination method. High-temperature dilatometer, DSC, and laser thermal diffusivity methods were used to analyze thermal expansion coefficient (TEC), specific heat, and thermal diffusivity. The results showed that CeO2 doped pyrochlores La2(Zr1.8Ce0.2)2O7 and La1.7(DyNd)0.15(Zr0.8Ce0.2)2O7 had higher TEC than

Hongming ZHOU; Danqing YI

2008-01-01

165

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

NASA Astrophysics Data System (ADS)

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.

Farley, Kevin F.

166

Synthesis and characterization of alkali/alkaline earth-doped fiber optic silica preforms  

NASA Astrophysics Data System (ADS)

The search for an ultra-low loss optical fiber has been driven by the discovery that certain multicomponent glasses possessed lower Rayleigh scattering losses than silica. Typically, these glasses cannot be employed in fiber optic applications because they are fabricated by conventional melting and processing techniques that introduce large amounts of impurities into the materials. High purity processing techniques such as chemical vapor deposition are required to truly realize the potential of these glasses as fiber optic materials. The Modified Chemical Vapor Deposition (MCVD) process was employed in the thesis work because of the flexibility and species confinement available with this processing method. The multicomponent glass compositions investigated in the thesis work include: Na2O-Al2O3-SiO 2, CaO-Al2O3, & MgO-Al2O3 -SiO2. Novel vapor delivery approaches, based on the current organometallic and chloride vapor delivery of rare earth metals, were devised to fabricate the multicomponent glasses evaluated in this work. Thermodynamic data were used to predict the feasibility of the MCVD processing of the glasses. Initial work on the Na2O-Al2O3-SiO2 system was unsatisfactory. The minimal amounts, <0.40 mol%, of sodium achievable in doped preforms proved that the Na2OAl2O 3-SiO2 system could not be adequately synthesized by MCVD processing. However, the moderately high dopant levels, 1--5 mol% CaO & MgO, achieved in the MCVD fabrication of CaO-Al2O3-SiO 2 & MgO-Al2O3-SiO2, demonstrated the suitability of these latter systems as fiber optic materials. The first successful MCVD fabrication and fiberization of the alkaline earth doped silica glasses achieved in this thesis work represents a milestone in ultra-low loss glass research. The modification of the silica glass structure with minor dopant levels, <10 mol%, resulted in noticeable changes in the optical properties of the glass. The CaO-Al2O3-SiO 2 glass system produced waveguide properties superior to the current GeO2-SiO2 glass fiber including a smooth index profile, improved ability to tailor the index profile, comparable scattering losses, and a rare earth host glass with enhanced solubility. The MgO-Al2O 3-SiO2 possessed lower OH absorption at 1.39 mum than the Rutgers GeO2-SiO2 glass fiber due to the dampening of the fundamental OH vibration. The demonstration of alkaline earth aluminosilicate glass compositions as viable optical fiber compositions offers many areas of opportunity for future applications.

Homa, Daniel Scott

167

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

168

Glass-forming ability and chemical stability of magneto-optical glass heavily doped with rare earth oxide  

Microsoft Academic Search

The glass-forming region of B2O3-Al2O3-SiO2 (BAS) glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was\\u000a investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of\\u000a the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with

Hairong Yin; Chunxiang Zhang; Liying Liu; Guoping Chen; Baojun Tang

2009-01-01

169

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

NASA Astrophysics Data System (ADS)

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.

Nash, Kelly Latrice

170

A novel technique for doping silicate glasses with transition metals and rare-earth for waveguides applications  

Microsoft Academic Search

Field-Assisted Solid-State Ion-Exchange (FASSIE) technique for doping silicate glasses with either transition metals or rare earths has been attracting much attention for its potential application in light waveguides, luminescent materials and for the possibility to realize systems in which formation of metal nanoclusters is controlled by suitable post-exchange techniques. In this framework, metallic films of either silver or gold are

S. Ali; F. Gonella; E. Cattaruzza; A. Quaranta

2010-01-01

171

Highly transparent and conductive rare earth-doped ZnO thin films prepared by magnetron sputtering  

Microsoft Academic Search

Highly transparent and conductive thin films of ZnO doped with a rare-earth element, Sc or Y, have been prepared by d.c. magnetron sputtering using a powder target. The resistivity of the ZnO:Sc thin films was always lower than that of the ZnO:Y thin films; a resistivity in the order of 10?4 ? cm was obtained in these films. The resistivity

Tadatsugu Minami; Takashi Yamamoto; Toshihiro Miyata

2000-01-01

172

Single-crystal rare-earth doped YAG fiber lasers grown by the laser-heated pedestal growth technique  

NASA Astrophysics Data System (ADS)

High concentrations of the rare-earth elements erbium, holmium and thulium have been successfully doped into single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) fibers by use of the laser heated pedestal growth (LHPG) method. The spontaneous emission spectra and fluorescence were measured in the near-infrared (NIR). The results show progress towards forming a solid state laser able to produce a wavelength in the NIR, for high power applications.

Nie, Craig D.; Harrington, James A.; Li, Yuan; Johnson, Eric G.; Cloos, Elizabeth F.; Rand, Stephen C.; Machado, Pedro; Shori, Ramesh K.

2014-03-01

173

Crystal Growth and Radiation-Induced Defects of Rare Earth Doped Lithium Yttrium Fluoride Laser Host Materials  

Microsoft Academic Search

Scope of study. Single crystals of undoped and rare-earth doped lithium yttrium fluoride (YLF) crystals were grown using the Czochralski and vertical Bridgman techniques. This material has an incongruent melting point and as a consequence the growth material must contain excess LiF. Single crystals of undoped YLF were irradiated with 1.75 MeV electrons. This irradiation was found to create defects

David Wayne Hart

1991-01-01

174

Characterization of rare-earth doped Lu 2O 3 nanopowders prepared with polymer complex solution synthesis  

Microsoft Academic Search

We explored a synthesis route based on the polymer complex solution method for the production of the rare-earth doped Lu2O3 crystalline nanopowders. In this type of synthesis polyethylene glycol is used both as fuel for the combustion reaction, and as nucleation agent for the crystallization process. Synthesized materials were characterized with X-ray diffraction technique, scanning and transmission electron microscopy, EDX

Radenka Krsmanovi?; eljka Anti?; Barbora Brtov; Miroslav D. Drami?anin

2010-01-01

175

Fluorescence enhancement in rare earth doped sol-gel glass by N , N dimethylformamide as a drying control chemical additive  

Microsoft Academic Search

Studies of terbium fluorescence intensity as a function of annealing temperature reveal the cause of increased fluorescence yields observed in rare earth doped sol-gel silicates prepared using N,N-dimethylformamide (DMF) as a drying control chemical additive (DCCA). While gels prepared with DMF actually have lower fluorescence yields than gels prepared without DMF at lower annealing temperatures, DMF gels can be annealed

A. P. Beyler; D. M. Boye; K. R. Hoffman; A. J. Silversmith

2011-01-01

176

Rare earth doping into optical nonlinear nanocrystalline phase in transparent TeO 2-based glass-ceramics  

Microsoft Academic Search

Optically transparent rare earth (Ln)-doped glass-ceramics based on the system K2ONb2O5TeO2 have been prepared, and the effect of Ln additions on crystallization behaviors and optical properties has been examined. The lattice constant of the TeO2-based metastable optical nonlinear nanocrystalline phase (average particle size: <60nm) with basically a cubic structure in the glass-ceramics decreases due to Ln additions, and the incorporation

K. Hirano; Y. Benino; T. Komatsu

2001-01-01

177

Preparation of Eu-doped alkaline-earth silicate phosphor particles by using liquid-phase synthesis method  

Microsoft Academic Search

The liquid-phase synthesis method for preparing Eu-doped alkaline-earth silicate phosphor particles, which is expected to be applied for lighting apparatuses, such as mercury-free fluorescent lamps and flat-plane displays, such as PDP, was investigated. The sols, as the phosphor particle precursors, were synthesized by solgel processes under various conditions in the liquid-phase. The particle sizes of the sols were almost uniform,

Yoshihiro Nishisu; Mikio Kobayashi; Hitoshi Ohya; Toshiyuki Akiya

2006-01-01

178

Enhancement of up-conversion efficiency by combining rare earth-doped phosphors with PbS quantum dots  

Microsoft Academic Search

This paper aims to enhance the up-conversion phenomena observed in silicon solar cells by combining a rare earth-doped phosphor with PbS quantum dots. Two different ways of adhering the up-converter and the fluorescent material to a bifacial solar cell are implemented: dissolving the powder in a spin-on oxide and by dissolving it in a silicone gel. Characterization is carried out

A. C. Pan; C. del Caizo; E. Cnovas; N. M. Santos; J. P. Leito; A. Luque

2010-01-01

179

Structure and optical properties under VUV\\/UV excitation of Eu2+ doped Alkaline Earth Aluminate Phosphors  

Microsoft Academic Search

Polycrystalline hexagonal alkaline earth aluminates M3Al16O27 doped by divalent europium were prepared by solid state reaction. The crystal structure and optical properties at room temperature were investigated. The structure parameters were refined using Rietveld refinement procedures. The space group of the materials is P63\\/mmc. Eu2+ ions occupy the 2d cation position of the large cation in the unit cell. The

D. Ntzold; H. Wulff; S. Jilg; L. Kantz; L. Schwarz

2006-01-01

180

Crystal growth of rare-earth-doped ternary potassium lead chloride single crystals by the Bridgman method  

Microsoft Academic Search

High optical quality pure and rare-earth-doped ternary-potassium-lead-chloride (KPb2Cl5) single crystals have been grown using the Bridgman technique in a two-zone transparent vertical furnace. Combining the chlorination of the melt, to eliminate oxygen impurities, with a horizontal zone-refining, followed by the Bridgman growth itself using sealed silica ampoules, we successfully grew non-moisture-sensitive crystals of a high optical quality. The moisture content

M. Voda; M. Al-Saleh; G. Lobera; R. Balda; J. Fernandez

2004-01-01

181

Thermoanalytical studies of coprecipitated hydroxides of yttrium and aluminum for preparation of rare-earth doped YAG phosphors  

NASA Astrophysics Data System (ADS)

Yttrium-aluminum garnets (YAG) doped with a rare-earth element, including terbium (Tb), thulium (Tm), and Erbium (Er) produce the phosphorescence. YAGs may be synthesized by baking hydroxides of their constituents at a high temperature. No flux is required and the temperature of the solid state synthesis may be decreased to only 1150 degrees Celsius when the hydroxides are coprecipitated. We report here on the results of the thermoanalytical studies of the coprecipitated hydroxides in the YAG solid state synthesis.

Scholl, Marija S.

1996-02-01

182

Influence of rare earths doping on the structure and electro-catalytic performance of Ti\\/SbSnO 2 electrodes  

Microsoft Academic Search

Rare earth Ce, Eu, Gd and Dy doped Ti\\/SbSnO2 electrodes were prepared by thermal decomposition and the performance of electrodes for the electro-catalytic decomposition of a model pollutant (phenol) was investigated. Phenol degradation and TOC removal followed pseudo-first-order kinetics in the experimental range, with the maximum rate achieved using Gd-doped electrode and the minimum rate obtained by Ce-doped electrode. Electrodes

Yu-Hong Cui; Yu-Jie Feng; Zheng-Qian Liu

2009-01-01

183

Doping Effect of Rare-Earth Ions on Electrical Properties of BiFeO3 Thin Films Fabricated by Chemical Solution Deposition  

Microsoft Academic Search

Rare-earth-ion (La and Nd)-doped BiFeO3 (BFO) thin films were fabricated by depositing sol-gel solutions on Pt\\/Ti\\/SiO2\\/Si(100) structures. It was found from X-ray diffraction analysis that BFO thin films were polycrystalline and 5 at. % La and Nd ion dopings did not cause structural changes in the BFO thin films. By 5 at. % La doping in BFO thin films, breakdown

Sushil K. Singh; Hiroshi Ishiwara

2006-01-01

184

Using the earth system for integrating the science curriculum  

Microsoft Academic Search

Content and process instruction from the earth sciences has gone unrepresented in the world's science curricula, especially at the secondary level. As a result there is a serious deficiency in public understanding of the planet on which we all live. This lack includes national and international leaders in politics, business, and science. The earth system science effort now engaging the

Victor J. Mayer

1995-01-01

185

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...

186

Features of an intermetallic n-ZrNiSn semiconductor heavily doped with atoms of rare-earth metals  

SciTech Connect

The crystal structure, density of electron states, electron transport, and magnetic characteristics of an intermetallic n-ZrNiSn semiconductor heavily doped with atoms of rare-earth metals (R) have been studied in the ranges of temperatures 1.5-400 K, concentrations of rare-earth metal 9.5 x 10{sup 19}-9.5 x 10{sup 21} cm{sup -3}, and magnetic fields H {<=} 15 T. The regions of existence of Zr{sub 1-x}R{sub x}NiSn solid solutions are determined, criteria for solubility of atoms of rare-earth metals in ZrNiSn and for the insulator-metal transition are formulated, and the nature of 'a priori doping' of ZrNiSn is determined as a result of redistribution of Zr and Ni atoms at the crystallographic sites of Zr. Correlation between the concentration of the R impurity, the amplitude of modulation of the bands of continuous energies, and the degree of occupation of potential wells of small-scale fluctuations with charge carriers is established. The results are discussed in the context of the Shklovskii-Efros model of a heavily doped and compensated semiconductor.

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua [National Academy of Sciences of Ukraine, Ya. Pidstryhach Institute for Applied Problems of Mechanics and Mathematics (Ukraine); Fruchart, D.; Hlil, E. K. [CNRS, Institute Neel (France); Gladyshevskii, R. E. [Ivan Franko Lviv National University (Ukraine); Gignoux, D. [CNRS, Institute Neel (France); Romaka, V. V.; Kuzhel, B. S. [Ivan Franko Lviv National University (Ukraine); Krayjvskii, R. V. [Lvivska Politechnika National University (Ukraine)

2010-03-15

187

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

NASA Astrophysics Data System (ADS)

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.

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

2010-04-01

188

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

NASA Astrophysics Data System (ADS)

Sol-gel derived organic-inorganic hybrid materials doped with rare earth metal ions (Pr 3+) and small amounts of lithium ions (0.1-0.2 wt.%) were produced from the tetraethyl orthosilicate (TEOS), AlCl 36H 2O (about 10 mol%), ethyl methacrylate, butyl methacrylate and some other organic additions (ca. 35-40 wt.% of organics in the fresh gels) to obtain hybrid organic-inorganic hosts. The gel and hybrid materials obtained were aged at room temperature for three weeks, then heated in an electric drier for 3 h at temperature of 125 C and investigated for morphology, structure and luminescence properties by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), 29Si and 27Al MAS nuclear magnetic resonance and fluorescence spectroscopy. An influence of the organic additions and inorganic dopants on microstructure of the materials obtained and their luminescence properties has been examined. Under excitation with UV radiation in a range of 210-350 nm, the sharp and relatively intense luminescence emission lines due to 3P 0 ? 3H 4 (blue) and 3P 0 ? 3F 3 (red) transitions of Pr 3+ ions were observed in the luminescence spectra of gel and hybrid materials of SA-series.

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

2011-10-01

189

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

NASA Astrophysics Data System (ADS)

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.

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

1995-10-01

190

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

NASA Astrophysics Data System (ADS)

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.

Pokhrel, Madhab

191

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

NASA Astrophysics Data System (ADS)

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.

Luen, Melvyn Oliver

192

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

193

Numerical integration routines for near-earth operations  

NASA Technical Reports Server (NTRS)

Two general purpose numerical integration schemes were built into the NASA-JSC computer system. The state-of-the-art of numerical integration, the particular integrators built into the JSC computer system, and the use of the new integration packages are described. Background information about numerical integration and the variable-order, variable-stepsize Adams numerical integration technique is discussed. Results concerning the PEACE parameter optimization program are given along with recommendations and conclusions.

Powers, W. F.

1973-01-01

194

Astro-Venture: An Integrated Earth and Space Science Curriculum Supplement Focused on Astrobiology  

Microsoft Academic Search

Astro-Venture is an example of a NASA educational product that successfully integrates Earth and space science by engaging students in grades 5-8 in the search for and design of a planet with the necessary characteristics for human habitation. Students study the Earth to understand how it meets human needs for survival in the areas of astronomy, geology, biology and atmospheric

C. M. O'Guinn; K. L. Wilmoth; L. K. Coe

2005-01-01

195

Integrated visualization of remote sensing data using Google Earth  

NASA Astrophysics Data System (ADS)

The need for advanced visualization tools for meteorological data has lead in the last years to the development of sophisticated software packages either by observing systems manufacturers or by third-party solution providers. For example, manufacturers of remote sensing systems such as weather radars or lightning detection systems include zoom, product selection, archive access capabilities, as well as quantitative tools for data analysis, as standard features which are highly appreciated in weather surveillance or post-event case study analysis. However, the fact that each manufacturer has its own visualization system and data formats hampers the usability and integration of different data sources. In this context, Google Earth (GE) offers the possibility of combining several graphical information types in a unique visualization system which can be easily accessed by users. The Meteorological Service of Catalonia (SMC) has been evaluating the use of GE as a visualization platform for surveillance tasks in adverse weather events. First experiences are related to the integration in real-time of remote sensing data: radar, lightning, and satellite. The tool shows the animation of the combined products in the last hour, giving a good picture of the meteorological situation. One of the main advantages of this product is that is easy to be installed in many computers and does not need high computational requirements. Besides this, the capability of GE provides information about the most affected areas by heavy rain or other weather phenomena. On the opposite, the main disadvantage is that the product offers only qualitative information, and quantitative data is only available though the graphical display (i.e. trough color scales but not associated to physical values that can be accessed by users easily). The procedure developed to run in real time is divided in three parts. First of all, a crontab file launches different applications, depending on the data type (satellite, radar, or lightning) to be treated. For each type of data, the time of launching is different, and goes from 5 (satellite and lightning) to 6 minutes (radar). The second part is the use of IDL and ENVI programs, which search in each archive file the last images in one hour. In the case of lightning data, the files are generated for the procedure, while for the others the procedure searches for existing imagery. Finally, the procedure generates metadata information required by GE, kml files, and sends them to the internal server. At the same time, in the local computer where GE is running, there exists kml files which update the information referring to the server ones. Another application that has been evaluated is the analysis of past events. In this sense, further work is devoted to develop access procedures to archived data via cgi scripts in order to retrieve and convert the information in a format suitable for GE. The presentation includes examples of the evaluation of the use of GE, and a brief comparison with other existing visualization systems available within the SMC.

Castella, M.; Rigo, T.; Argemi, O.; Bech, J.; Pineda, N.; Vilaclara, E.

2009-09-01

196

Piezoelectric/photoluminescence effects in rare-earth doped lead-free ceramics  

NASA Astrophysics Data System (ADS)

In the present work, we report the environmentally-friendly multifunctional effectspiezoelectric/photoluminescence effects, which originated from the combination of the electromechanical properties and the photoluminescence effect through introducing the rare-earth elements (Pr and Eu) into the (Bi0.5Na0.5)TiO3-BaTiO3 ceramics with the composition around the morphotropic phase boundary. Compared to the pure piezoelectric ceramic, the proposed system simultaneously exhibited enhanced ferroelectric, piezoelectric, dielectric properties along with strong photoluminescence effects, which exhibited potential applications in sensor, and electro-mechano-optical integration. In addition, the present work also provides a promising path for us to fabricate multifunctional composites.

Yao, Qirong; Wang, Feifei; Jin, Chengchao; Tang, Yanxue; Wang, Tao; Shi, Wangzhou

2013-10-01

197

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

PubMed

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:Eu(3+)-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:Eu(3+) 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:Eu(3+) 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:Eu(3+) 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

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

2014-06-01

198

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

PubMed Central

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.

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

199

An Integrated and Collaborative Approach for NASA Earth Science Data  

NASA Technical Reports Server (NTRS)

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).

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

2012-01-01

200

Characterization of the rare earth orthophosphates and Ce-doped LaPO4 by x ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d(sup 10)4f (yields) 3d(sup 9)4f(sup n+1) (M(sub 4,5)) transitions that contain a wealth of spectroscopic features. XAS is a useful technique for the characterization of 4f-occupancy, 4f-hybridization, and valence in RE-containing materials. The XAS measurements of the single crystal RE-orthophosphates, as well as a range of Ce doped (approximately 1-30%) LaPO4 hosts were performed at the 3d edge in the total electron yield mode at beamline 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble that of the corresponding RE metal and emphasize the major contribution of the trivalent state to the electronic transitions occurring at the 3d edge. There is no energy shift of the La and Ce absorption peaks with Ce doping and furthermore, no additional transitions are observed in either spectral region. However, accompanying the Ce doping there is a significant narrowing of the La absorption peak full width half maximum that contrasts to the Ce features that exhibit no contraction. The La and Ce spectra indicate that the Ce-doping of LaPO4 is purely substitutional.

Shuh, D. K.; Perry, D.; Terminello, L. J.; Boatner, L. A.; Abraham, M. M.

201

Comparison of various organic compounds destruction on rare earths doped Ti/Sb-SnO2 electrodes.  

PubMed

Ti/Sb-SnO2 and three kinds of rare earths (REs), namely Ce, Gd, and Eu doped Ti/Sb-SnO2 electrodes were prepared and tested for their capacity on electrocatalytic degradation of three kinds of basal aromatic compounds (benzoquinone, hydroquinone and catechol) and six kinds of aliphatic acids (maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid and acetic acid). The elimination of selected organics as well as their TOC removal with different doped Ti/Sb-SnO2 electrodes was described by first-order kinetics. Compared with Ti/Sb-SnO2, the Gd and Eu doped electrodes show better performance on the degradation of most of the selected organics, while Ce doped electrode shows either closely or lower efficiency on the degradation of these selected organics. Besides electrode material, the molecular structure of organic compound has obvious effect on its degradation in the electrocatalytic process. Catechol is more resistant to the electrophilic attack by hydroxyl radicals than benzoquinone and hydroquinone. The compound with more complicate molecular structure or longer carbon chain is more difficult to be mineralized. The aliphatic acid with higher oxygen content or more double bonds is more readily to be oxidized in the electrocatalytic process. PMID:23022412

Cui, Yu-Hong; Feng, Yu-Jie; Liu, Junfeng; Ren, Nanqi

2012-11-15

202

Higher permittivity rare earth doped HfO2 for sub-45-nm metal-insulator-semiconductor devices  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doping (Gd, Er, Dy) of HfO2 reduces leakage current by three orders of magnitude compared with pure HfO2. The key to reducing HfO2 leakage current and equivalent oxide thickness (EOT) is stabilization of the higher permittivity tetragonal phase. RE doping of 10-20 at. % stabilizes tetragonal HfO2 and increases permittivity. The maximum permittivity achieved for HfREOx is 28. The maximum permittivity for ZrREO is 32. HfGdO metal-insulator-semiconductor capacitors with EOT=1.93 nm and leakage current <110-8 A/cm2 after 1070 C have been demonstrated.

Govindarajan, S.; Bscke, T. S.; Sivasubramani, P.; Kirsch, P. D.; Lee, B. H.; Tseng, H.-H.; Jammy, R.; Schrder, U.; Ramanathan, S.; Gnade, B. E.

2007-08-01

203

Properties of Oxygen Deficient Thin Films of Hole doped Rare Earth Manganites: Correlation with the Cation Stoichiometry  

NASA Astrophysics Data System (ADS)

Alkaline-earth doped rare earth manganese oxides RE1-xAExMnO3 exhibit a wide array of electrical and magnetic properties depending on the cation composition stoichiometry. The composition x=0.33 is known to exhibit insulator-metal transition accompanied by a ferromagnetic transition and ``colossal magnetoresistance.'' The transition temperatures depend on the choice of rare earth and alkaline earth cations, the parameter governing this dependence being the average ionic size at the rare earth site (A-site). In thin films of these materials, the oxygen stoichiometry is also a variable which influences the electrical and magnetic properties through changes in the mixed valence state of Mn, i.e. the ratio of Mn^3+ to Mn^4+ ions. Based on our studies on several manganite systems, we will present results correlating the effects of oxygen deficiency with the cation stoichiometry at the A site. Properties of interest include structural parameters, electrical and magneto-transport and surface morphology.

Keshavarz, Camron; Sharma, Prakash; Goehringer, Tyler; Tanyi, E. Kevin; Hobbs, Erik; Watson, Michael; Yong, Grace; Schaefer, David; Kolagani, Rajeswari

2013-03-01

204

Novel rare earth doped tellurite glasses for fiber lasers in the 2-micron wavelength region  

NASA Astrophysics Data System (ADS)

In this paper Tm-doped tellurite glasses (75TeO II-20ZnO-5 Na IIO, mol%) were prepared and characterized, and codoping with Yb was investigated in order to improve pump efficiency and wavelength emission range. Emission spectra and lifetime measurements were obtained by pumping Tm-doped tellurite glasses at 800 nm and Yb-Tm co-doped tellurite glasses at 980 nm, thus exploiting the Yb-Tm energy transfer mechanism. Highly Yb-doped Tm-tellurite glasses were investigated (Yb IIO 3 concentrations up to 5 wt%) and an increase in 3F 4 lifetime with Yb IIO 3 concentrations higher than 3% was observed. This showed that high amounts of Yb do not affect lifetime of the metastable state, thus allowing investigation of lasers in this range of doping concentrations.

Milanese, Daniel; Vota, Monica; Liao, Guihua; Ferraris, Monica; Coluccelli, Nicola; Taccheo, Stefano

2007-03-01

205

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

206

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

Microsoft Academic Search

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

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

2004-01-01

207

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

Microsoft Academic Search

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

R. Shendrik; E. Radzhabov; V. Nagirnyi

2010-01-01

208

Rare-earth-doped LiNbO3 and KTiOPO4 (KTP) for waveguide quantum memories  

Microsoft Academic Search

Optical waveguides in rare-earth-doped crystals are one of the most promising systems for practical implementations of quantum memory. To further develop these systems, detailed understanding of these materials is required. We report experimental studies of the optical properties and decoherence for Tm3+:LiNbO3, Pr3+:LiNbO3, Er3+:LiNbO3 and Er3+:KTiOPO4 (KTP) bulk crystals for quantum memory applications and discuss potential differences between the properties

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

2012-01-01

209

Effect of soaking temperature on concentrations of rare-earth ions in optical fiber core in solution doping process  

NASA Astrophysics Data System (ADS)

Effect of soaking temperature on concentration of rare-earth ions in the optical fiber core during solution doping process was investigated. The dopant concentration of Er3+ and Ho3+ in the preforms and the fibers measured by the electron probe microanalysis and the optical spectrum analyzer was found to increase with decreasing the soaking temperature. The increase in the concentration of the Er3+ and the Ho3+ was attributed to the precipitation of the dopants due to the decrease in the solubility by decreasing the temperature.

Kim, Yune H.; Paek, Un-Chul T.; Han, Won-Taek

2001-04-01

210

Robust quantum gates and a bus architecture for quantum computing with rare-earth-ion-doped crystals  

SciTech Connect

We present a composite pulse controlled phase gate which, together with a bus architecture, improves the feasibility of a recent quantum computing proposal based on rare-earth-ion-doped crystals. The proposed gate operation is tolerant to variations between ions of coupling strengths, pulse lengths, and frequency shifts. In the absence of decoherence effects, it achieves worst case fidelities above 0.999 with relative variations in coupling strength as high as 10% and frequency shifts up to several percent of the resonant Rabi frequency of the laser used to implement the gate. We outline an experiment to demonstrate the creation and detection of maximally entangled states in the system.

Wesenberg, Janus; Moelmer, Klaus [QUANTOP, Danish Research Foundation Center for Quantum Optics, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, (Denmark)

2003-07-01

211

Crystal growth of rare-earth-doped ternary potassium lead chloride single crystals by the Bridgman method  

NASA Astrophysics Data System (ADS)

High optical quality pure and rare-earth-doped ternary-potassium-lead-chloride (KPb 2Cl 5) single crystals have been grown using the Bridgman technique in a two-zone transparent vertical furnace. Combining the chlorination of the melt, to eliminate oxygen impurities, with a horizontal zone-refining, followed by the Bridgman growth itself using sealed silica ampoules, we successfully grew non-moisture-sensitive crystals of a high optical quality. The moisture content in the raw materials determines the quality of the resulting crystals.

Voda, M.; Al-Saleh, M.; Lobera, G.; Balda, R.; Fernndez, J.

2004-09-01

212

Transforming Water Management: an Emerging Promise of Integrated Earth Observations  

NASA Astrophysics Data System (ADS)

Throughout its history, civilization has relied on technology to facilitate many of its advances. New innovations and technologies have often provided strategic advantages that have led to transformations in institutions, economies and ultimately societies. Observational and information technologies are leading to significant developments in the water sector. After a brief introduction tracing the role of observational technologies in the areas of hydrology and water cycle science, this talk explores the existing and potential contributions of remote sensing data in water resource management around the world. In particular, it outlines the steps being undertaken by the Group on Earth Observations (GEO) and its Water Task to facilitate capacity building efforts in water management using Earth Observations in Asia, Africa and Latin and Caribbean America. Success stories on the benefits of using Earth Observations and applying GEO principles are provided. While GEO and its capacity building efforts are contributing to the transformation of water management through interoperability, data sharing, and capacity building, the full potential of these contributions has not been fully realized because impediments and challenges still remain.

Lawford, R. G.

2011-12-01

213

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

NASA Astrophysics Data System (ADS)

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.

Hubert, Mathieu

214

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

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

215

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

216

Micro Infrared Earth Sensor project: an integrated IR camera for Earth remote sensing  

Microsoft Academic Search

MEMS technology now makes possible to produce active microdevices combining detection, signal processing, and data storage with accuracy and compactness. In view of their characteristics, it can be expected that such microsensors will be used extensively in space applications dedicated to micro and nano satellites. The advanced architecture of a MicroInfraRedEarthSensor generic system based on a Vox microbolometer array associated

Georges Soto-Romero; Francis Bony; Jean-Jacques Simonne; Jean-Yves Fourniols

2001-01-01

217

Improving visible-light photocatalytic activity for hydrogen evolution over ZnIn2S4: A case study of alkaline-earth metal doping  

NASA Astrophysics Data System (ADS)

A series of alkaline-earth metal doped ZnIn2S4 photocatalysts were prepared by the microwave-assisted hydrothermal method, and characterized using various analysis techniques, such as XRD, Raman, UV-vis spectra, photoluminescence spectra and SEM. The successful incorporation of Ca, Sr and Ba into the lattices of ZnIn2S4 was proved by Raman spectra. Photocatalytic results demonstrated that Ca doping could greatly enhance the activity of ZnIn2S4, with about two times higher than undoped ZnIn2S4, while Sr and Ba doping could not. The varied photocatalytic activities of doped ZnIn2S4 as a function of alkaline-earth metals as dopants were discussed on the basis of the sophisticated photoluminescence process.

Shen, Shaohua; Zhao, Liang; Guan, Xiangjiu; Guo, Liejin

2012-01-01

218

Anomalous Pressure Dependence of Dipolar Relaxation Times in Rare Earth Doped Lead Fluoride.  

National Technical Information Service (NTIS)

Electrical relaxation measurements at high pressures have been carried out on lead fluoride doped with lanthanum and cerium. A single, strong relaxation peak is observed and the relaxation time decreases with pressure. This is contrary to the behavior exh...

J. J. Fontanella M. C. Wintersgill D. R. Figueroa A. V. Chadwick C. G. Andeen

1984-01-01

219

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

220

[Infrared photostimulated luminescence and optical storage compares in alkaline earth sulphide doped with Mn].  

PubMed

The phosphors SrS: Eu and CaS: Eu doped with Mn were prepared by sulfurization flux method (SFM). Infrared photostimulated luminescence (PSL) of both the phosphors were measured. The PSL peak wavelength of SrS: Eu, Mn is 610 nm. Comparing the storage intensities, SrS has better optical properties. The doping of Mn2+ increases photon amount and improves the storage properties. PMID:16379271

Zhang, Lin; Wang, Yong-sheng; Sun, Li; Lu, Cheng-zhu

2005-09-01

221

Role of charge transfer state and host matrix in Eu3+-doped alkali and earth alkali fluoro-aluminoborate glasses  

NASA Astrophysics Data System (ADS)

Judd-Ofelt parameters of Eu3+-doped alkali and earth alkali fluoro-aluminoborate glasses are determined from the fluorescence spectra. The dependence of these parameters on the compositional changes of the materials is discussed. The glass containing sulphate component shows the larger values of ? compared with the fluoro-aluminoborate glasses because of higher ?CT (Eu3+-F-) values. The difference of ionic radius and electronegativity between Na and Ca lead to higher ?2 parameter of CaF2-Al2O3-B2O3:Eu3+ glass. Persistent spectral hole burning has been observed in Eu3+ ions doped alkali-and earth alkali fluoro-aluminoborate glasses with the compositions of 16NaF73B2O38Al2O33Eu2O3 and 16CaF273B2O38Al2O33Eu2O3, which have been prepared using conventional melting technique.

Thanh, N. T.; Quang, V. X.; Tuyen, V. P.; Tam, N. V.; Hayakawa, T.; Huy, B. T.

2012-06-01

222

Frequency dependence of Verdet constant of Bismuth-Doped Rare-Earth Iron Garnets for Magneto-Optic Sensor Applications  

NASA Astrophysics Data System (ADS)

There is growing interest in applying magneto-optic materials toward sensor applications. One of these applications is to exploit the Faraday Effect to measure magnetic fields. Bismuth-doped rare-earth iron garnets have proven to be highly sensitive Faraday rotators, but their frequency response and dynamic range to magnetic fields require further study. The Faraday Effect was studied in two samples of bismuth-doped rare-earth iron garnets grown in different conditions, and experiments were performed in a static field as well as in a RF field. Static magnetic fields up to 3 kG were used, and we found that the Faraday rotation became saturated at high fields, indicating that the field dependence follows the hyperbolic tangent function. We extracted each sample's Verdet constant from the Faraday rotation at low magnetic fields of 0.1 kG. These experiments were repeated using different laser probe beam wavelengths, ranging from 405 nm to 2000 nm. We measured the transmission coefficient and the Verdet constant for each sample for different probe beam wavelengths and for an external magnetic field at various frequencies. We will discuss the implication of our experimental results.

Shinn, Mannix; Tao, Rongjia; Wu, Dong Ho; Garzarella, Anthony

2013-03-01

223

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

NASA Astrophysics Data System (ADS)

Chalcogenide glasses are promising materials for mid-infrared (IR) fiber lasers (i.e. 3 - 25 ?m 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.

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

2014-02-01

224

Intense visible fluorescence and energy transfer in Dy 3+, Tb 3+, Sm 3+ and Eu 3+ doped rare-earth borate glasses  

Microsoft Academic Search

Tb3+\\/Dy3+ and Eu3+\\/Sm3+ doped rare-earth borate glasses have been synthesized and characterized. Under UV excitation, Dy3+, Tb3+, Sm3+ and Eu3+ emit intense yellowish white, green, reddish orange and red lights, respectively. In Tb3+\\/Dy3+ co-doped glasses, the enhancement of Tb3+ green emission is observed, and the sensitization is related to the efficient energy transfer from Dy3+ to Tb3+. In Eu3+\\/Sm3+ co-doped

Hai Lin; Edwin Yue-Bun Pun; Xiaojun Wang; Xingren Liu

2005-01-01

225

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

NASA Astrophysics Data System (ADS)

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.

Cocco, M.; EPOS Consortium

2012-04-01

226

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

NASA Astrophysics Data System (ADS)

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.

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

2009-02-01

227

Integrated planning and scheduling for Earth science data processing  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

228

Energy Transfer in Rare Earth Ion Clusters and Fluorescence from Rare Earth Doped LANTHANUM(1.85)STRONTIUM(0.15)COPPER -OXYGEN(4) Superconductors.  

NASA Astrophysics Data System (ADS)

Laser spectroscopy of rare earth ions in solids was used to study mechanisms of non-resonant energy transfer within rare earth clusters, and to detect insulating, impurity phases in rare earth doped La_{1.85 }Sr_{0.15}CuO _4 superconductors. The mechanisms of phonon-assisted, non-resonant energy transfer were studied in well-defined dimer sites in Er^{3+ }:SrF_2 and Pr ^{3+}:CaF_2. Application of a magnetic field to Er^{3+} :SrF_2 greatly increased the energy transfer rate. The magnetic field dependence in Er^{3+}:SrF _2 indicates that the mechanism of non-resonant energy transfer is a two-phonon, resonant process (Orbach process). Application of a magnetic field to Pr ^{3+}:CaF_2 had no effect on the energy transfer rate because no significant Zeeman splittings occurred. The temperature dependence of the energy transfer rate in Pr^{3+ }:CaF_2 showed the mechanism to be a one-phonon-assisted process at low temperatures and predominantly an Orbach process above 10 K. In the second part of this thesis, laser spectroscopy of a Eu ^{3+} probe ion is developed to detect impurity phases in La_{1.85 }Sr_{0.15}CuO _4 superconductors. Two impurity phases were found in polycrystalline La_ {1.85}Sr_{0.15} CuO_4: unreacted La _2O_3 starting material, and a La-silicate phase, which formed from contamination during sintering. The spectroscopic technique was found to be more than 100 times more sensitive than powder x -ray diffraction to detect minor impurity phases. In preparing the superconductors, several studies were made on the effect of Pr^{3+}, Eu ^{3+}, Bi^{3+ }, and fluorine dopants on the superconducting properties of La_{1.85}Sr _{0.15}CuO_4 and La_2Cuo_4 . Pr^{3+}, Eu ^{3+}, Bi^ {3+}, and F_2 doping all decreased the superconductivity in La_ {1.85}Sr^{0.15} CuO_4. Treating semi-conducting La_2CuO_4 in F_2 gas converted it to a superconductor with an onset T_{rm c} of 30-35 K.

Tissue, Brian Max

1988-12-01

229

Energy transfer in rare earth ion clusters and fluorescence from rare-earth-doped La sub 1. 85 Sr sub 0. 15 CuO sub 4 superconductors  

SciTech Connect

Laser spectroscopy of rare earth ions in solids was used to study mechanisms of non-resonant energy transfer within rare earth clusters, and to detect insulating, impurity phases in rare-earth-doped La{sub 1.85}Sr{sub 0.15}CuO{sub 4} superconductors. The mechanisms of phonon-assisted, non-resonant energy transfer were studied in well-defined dimer sites in Er{sup 3+}:SrF{sub 2} and Pr{sup 3+}:CaF{sub 2}. Application of a magnetic field to Er{sup 3+}:SrF{sub 2} greatly increased the energy-transfer rate. The magnetic field dependence in Er{sup 3+}:SrF{sub 2} indicates that the mechanism of non-resonant energy transfer is a two-phonon, resonant process (Orbach process). Application of a magnetic field to Pr{sup 3+}:CaF{sub 2} had no effect on the energy-transfer rate because no significant Zeeman splittings occurred. The temperature dependence of the energy-transfer rate in Pr{sup 3+}:CaF{sub 2} showed the mechanism to be a one-phonon-assisted process at low temperatures and predominantly an Orbach process above 10 K. In the second part of this thesis, laser spectroscopy of a Eu{sup 3+} probe ion is developed to detect impurity phases in La{sub 1.85}Sr{sub 0.15}CuO{sub 4} superconductors. Two impurity phases were found in polycrystalline La{sub 1.85}Sr{sub 0.15}CuO{sub 4}: unreacted La{sub 2}O{sub 3} starting material, and a La-silicate phase, which formed from contamination during sintering.

Tissue, B.M.

1988-01-01

230

Non-rare earth white emission phosphor: Ti-doped MgAl2O4  

NASA Astrophysics Data System (ADS)

White emission produced by Ti-doped MgAl2O4 phosphor powder is reported, which is in contrast to blue emission from most Ti-doped single crystals of MgAl2O4. The white emission peak consists of four deconvoluted peaks: 440, 490, 550, and 620 nm, when was excited by 260 nm wavelength. Ti4+ in octahedral sites was found to contribute mostly to greenish blue emissions at 490 and 550 nm. The red emission at 620 nm was produced by abundant Mg2+ and O2- vacancies in the spinel powder.

Lim, J. H.; Kim, B. N.; Kim, Y.; Kang, S.; Xie, R. J.; Chong, I. S.; Morita, K.; Yoshida, H.; Hiraga, K.

2013-01-01

231

Photoinduced second-harmonic generation in rare-earth-doped aluminosilicate optical fibers.  

PubMed

The presence of defect states in the band gap is an essential ingredient of recent models of photoinduced second-harmonic generation (SHG) in fibers. We have created such states by doping aluminosilicate glass fibers that do not contain Ge with Ce or Eu and observed SHG from 1.06-microm light after preparation of the fibers with 0.532- and 1.06-microm light. In an aluminosilicate fiber doped with 0.008 wt. % Ce, the SHG conversion efficiency is as high as 1.5% at infrared (1.06-microm) peak powers of 200 W. PMID:19784097

Krol, D M; Simpson, J R

1991-11-01

232

Diurnal variability of the Earth Radiation Budget: Sampling requirements, time integration aspects and error estimates for the Earth Radiation Budget Experiment (ERBE)  

Microsoft Academic Search

The diurnal variation of the Earth Radiation Budget and its components require for sparsely temporal sampling a high amount of modeling for the derivation of precise daily averages. In the present study the time integration errors of the regional monthly averages of the Earth Radiation Budget Experiment (Barkstrom, 1984) are estimated for April 1985. For this error assessment we made

M. Rieland; E. Raschke

1991-01-01

233

GPS\\/INS integrated measurement system on Earth-circling spacecraft  

Microsoft Academic Search

This paper proposes GPS\\/INS integrated to implement the positioning and the attitude determination of the Earth-circling spacecraft. Observability analysis shows that the integration system, in which only GPS pseudo-range and delta pseudo-range are the observable, cannot assure favorable observability of the attitude error angles. The GPS carrier phase observable can be introduced to enhance the reliability and the precision in

Feng Wen-jiang; Yu Ping; Yang Shi-zhong

2001-01-01

234

Energy Transfer Under Strong Pumping in High Concentration Rare Earth Doped Laser Crystals.  

National Technical Information Service (NTIS)

The weak interaction between isolated Er ions, and between Er and Pr ions, has been quantitatively measured in the host crystal BaY2F8. Fluorescent decay data from samples doped with 1%-100% Er and 0.05%-0.5% Pr show the decay rate is linearly proportiona...

D. S. Knowles

1991-01-01

235

Optical Characterization of Rare Earth-doped Wide Band Gap Semiconductors.  

National Technical Information Service (NTIS)

Comprehensive spectroscopic studies of Er implanted GaN and in-situ Er doped AlN and GaN prepared by metalorganic molecular beam epitaxy were carried out. Each investigated sample exhibited strong 1.54 um luminescence at room temperature. it was found, ho...

U. Hommerich

1999-01-01

236

Low-threshold integrated microlaser emitting in the blue formed from thulium doped silica  

NASA Astrophysics Data System (ADS)

While there are several methods for creating a blue microlaser, most have very high lasing thresholds and are not integrated on a silicon substrate. The present work demonstrates a blue laser based on the upconversion of thulium in a doped silica sol-gel microtoroid resonant cavity integrated on a silicon wafer. The thulium is pumped at 1060nm, and emission occurs near 780nm and 450nm. The high intensity of the circulating optical field in the microcavity increases the photon interaction pathlength and interaction time with the thulium atoms, enabling sub-mW thresholds at both blue and near-IR lasing emissions.

Mehrabani, Simin; Armani, Andrea M.

2014-03-01

237

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

ERIC Educational Resources Information Center

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

Fox, Justine E.; Glen, Nicole J.

2012-01-01

238

Wideband Approximate Solutions for the Sommerfeld Integrals Arising in the Wire over Earth Problem  

Microsoft Academic Search

Approximate solutions for the spatial Fourier transform (in the axial direction) of the Sommerfeld type integrals for the axial and vertical electric fields from a current on a thin wire of infinite length above lossy earth are derived. These solutions are valid over a wide band of frequencies (1 Hz - 1 GHz) and for distances from field points to

M. Wu; R. G. Olsen; S. W. Plate

1990-01-01

239

Development of a portable integrating sphere source for the Earth Observing System's calibration validation programme  

Microsoft Academic Search

We have designed and built a portable integrating sphere source for use at the National Aeronautics and Space Administration (NASA) satellite sensor calibration facilities in support of the Earth Observing System (EOS) calibration programme. The source is designed to complement existing detector-based validation methodologies over the spectral range 400-2500 nm, affording extra flexibility in implementing the programme. Details of the

S. W. Brown; B. C. Johnson

2003-01-01

240

Multiphonon Relaxation and Excitation Transfer in Rare-Earth Doped Glasses.  

National Technical Information Service (NTIS)

The theory of multiphononon relaxation for rare-earth ions in crystals is extended to nonradiative relaxation in glasses. The expected exponential dependence of the multiphonon rates on energy gaps was verified for 5 oxide glass compositions; the active p...

C. B. Layne

1975-01-01

241

Earth  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant Earth. There is a section about water on earth and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.

2008-10-03

242

Structure and properties of rare earth-doped lead borate glasses  

Microsoft Academic Search

Influence of rare earth oxide (Nd2O3, Er2O3) addition on structure and glass properties has been investigated in PbOB2O3Al2O3WO3 system. With an increasing of rare earth concentration, intensity of OH band drastically decreases and IR transparency is slightly shifted to the longer wavelengths. The ErBO3 crystalline phase has been identified basing on X-ray diffraction analysis. In opposite to the neodymium oxide,

W. A. Pisarski; T. Goryczka; B. Wodecka-Du?; M. P?o?ska; J. Pisarska

2005-01-01

243

Rare earth doped silicate-oxyfluoride glass ceramics incorporating LaF3 nano-crystals for UV-LED color conversion  

NASA Astrophysics Data System (ADS)

Rare earth doped oxyfluoride glass ceramics with LaF3 nano-crystals formed inside were fabricated for color converter of UV-LED. Among various rare earth ions, Dy3+ and Eu3+ showed practically utilizable visible emissions under UV-LED excitation of 365 nm. The visible emission has been improved by the formation of LaF3 brought by heat treatment. X-ray diffraction and transmission electron microscopy along with its energy dispersive spectra confirmed the formation of LaF3 nano-crystals. Compositional dependence and the effects of heat treatment conditions on the visible emissions have been investigated. The CIE chromaticity coordinates of the glasses were also examined for Dy3+ singly doped and co-doped samples. The effect of LaF3 nano-crystals and co-dopants on the visible emission properties of Dy3+ was discussed.

Bae, Suk-Rok; Choi, Yong Gyu; Im, Won Bin; Lee, Ki Seok; Chung, Woon Jin

2013-09-01

244

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

Microsoft Academic Search

We present comprehensive cathodo- and photoluminescence measurements from thin amorphous\\/nanocrystalline (a\\/nc-) AlN films doped with rare earths. The (a\\/nc-) AlN films were prepared by reactive rf-sputtering using a high purity (5N) aluminium disk in high purity nitrogen atmosphere (5N, pressure ca. 1.3mbar). The rare earth doping (Tm,Tb,Dy,Eu,Sm,Yb, concentrations were below 1%) was performed by placing respective rare earth metal pieces

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

2006-01-01

245

Radiation hardness of PbWO 4 Cherenkov radiators heavily doped with trivalent rare-earth ions  

NASA Astrophysics Data System (ADS)

PbWO 4 single crystals heavily doped with trivalent rare-earth (RE) ions were proposed a few years ago as one of the heaviest Cherenkov radiators. We have found that their radiation damage due to 60Co ?-rays are almost saturated at 10 3 Gy (1 Gy=100 rad). The radiation-induced absorption coefficient ?ir at 420 nm slightly above the short-wavelength cutoff was 3.1, 5.4 and 7.2 m -1 at 10 5 Gy in PbWO 4:Gd 3+(3 at%), PbWO 4:La 3+(5 at%) and PbWO 4:La 3+(8 at%), respectively.

Kobayashi, M.; Sugimoto, S.; Usuki, Y.

2004-05-01

246

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

SciTech Connect

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.

Abdinov, A. Sh., E-mail: abdinov-axmed@yandex.ru [Baku State University (Azerbaijan); Babayeva, R. F., E-mail: Babaeva-Rena@yandex.ru [Azerbaijan State Economic University (Azerbaijan); Amirova, S. I.; Rzayev, R. M. [Baku State University (Azerbaijan)] [Baku State University (Azerbaijan)

2013-08-15

247

Effect of thermal annealing treatments on the optical properties of rare-earth-doped AlN films  

NASA Astrophysics Data System (ADS)

Aluminium-nitrogen (AlN) films doped with samarium, europium or ytterbium have been prepared by conventional radio frequency sputtering. Because of the deposition method and conditions the as-deposited films are amorphous with Sm, Eu or Yb concentrations at low 0.5 at%. After deposition the films were submitted to cumulative isochronal thermal annealing (TA) treatments and investigated by optical transmission spectroscopy, photo- (PL) and cathodoluminescence (CL) measurements. For comparison purposes one undoped AlN film was also prepared and investigated in detail. The experimental results indicate that (a) all samples exhibit PL and CL at room temperature, (b) the main spectral features present in the AlN samples are due to defect-related transitions (undoped film) or the rare-earth (RE) ions, (c) in both cases (undoped and Sm-, Eu- or Yb-doped films) the luminescence intensity scales with the temperature of TA and (d) for the present AlN samples, there is a clear relationship between their luminescence intensity and respective energy of optical bandgaps. Finally, the effect of TA on the excitation-recombination mechanisms involving the RE ions is presented and discussed.

Zanatta, A. R.

2009-01-01

248

Rare-earth ions doped heavy metal germanium tellurite glasses for fiber lighting in minimally invasive surgery.  

PubMed

In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers. PMID:20940794

Yang, D L; Gong, H; Pun, E Y B; Zhao, X; Lin, H

2010-08-30

249

Laser cooling with rare-earth doped direct band gap semiconductors  

NASA Astrophysics Data System (ADS)

We present a theoretical scheme for laser cooling with ytterbium doped indium phosphide (Yb3+:InP). Yb3+:InP is a rareearth doped direct band-gap semiconductor. The cooling process in our system is based on thermal quenching of excited ytterbium ions. The mechanism of cooling in our system consists of laser excitation of ytterbium ions in the long wavelength tail of the Yb3+absorption spectrum followed by thermal quenching of excited ions accompanied by phonon absorption providing cooling. The band-to-band radiative recombination completing the cooling cycle removes energy from the system. This new approach to laser cooling of solids permits an increase in the efficiency of the cooling cycle approximately by the order, to accelerate the cooling process considerably, and allows cooling with pump wavelengths shorter than the mean fluorescence wavelength.

Nemova, Galina; Kashyap, Raman

2013-02-01

250

Room temperature ferromagnetism with large magnetic moment at low field in rare-earth-doped BiFeO? thin films.  

PubMed

Thin films of rare earth (RE)-doped BiFeO3 (where RE=Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using the pulsed laser deposition technique. All the films show a single phase of rhombohedral structure with space group R3c. The saturated magnetization in the Ho- and Sm-doped films is much larger than the values reported in the literature, and is observed at quite a low field of 0.2 T. For Ho and Sm doping, the magnetization increases as the film becomes thinner, suggesting that the observed magnetism is mostly due to a surface effect. In the case of Nd doping, even though the thin film has a large magnetic moment, the mechanism seems to be different. PMID:23615045

Kim, Tae-Young; Hong, Nguyen Hoa; Sugawara, T; Raghavender, A T; Kurisu, M

2013-05-22

251

Multiple Energy Transfers in Rare Earth Complex-Doped SiO 2 Spheres  

Microsoft Academic Search

Silica spheres doped with Eu(TTFA)3 and\\/or Sm(TTFA)3 were synthesized by using the modified Stober method. The transmission electron microscope image reveals that the hybrid spheres have smooth surfaces and an average diameter of about 210 nm. Fluorescence spectrometer was used to analyze the fluorescence properties of hybrid spheres. The results show that multiple energy transfer processes are simultaneously achieved in

Changqing Huang; Ting Sun; Weijian Tian; Baoping Zhao

2006-01-01

252

Properties of rare earth doped thin film dielectric layers for upconversion laser waveguides  

Microsoft Academic Search

Thin films of erbium doped tantalum pentoxide were prepared on unheated orientated silicon substrates with a thermally grown 2 mum thick SiO2 layer using reactive sputtering in an oxygen rich environment for upconversion laser experiments. Tantalum and Erbium metal targets were co-sputtered using an ion beam assisted reactive process to produce the high quality amorphous thin film layers. The Erbium

S. J. Pearce; M. D. B. Charlton; G. J. Parker; J. S. Wilkinson

2011-01-01

253

Electron-phonon interaction and charge carrier mass enhancement in electron doped alkali earth titanate semiconductors  

Microsoft Academic Search

We have studied the electron-phonon coupling in electron doped SrTiO3 for which the carrier concentration ranges from a dilute gas of polarons to a polaron liquid. Here we report a comprehensive THz, infrared and optical study together with DC conductivity, Hall effect and specific heat measurements. Our THz spectra at 7 K show the presence of a very narrow (<

Dook van Mechelen; Dirk van der Marel; Claudio Grimaldi; Peter Armitage; Alexey Kuzmenko; Hans Hagemann; Nicolas Reyren; Rolf Lortz; Igor Mazin

2008-01-01

254

Study of newly discovered two dimensional cobalt based perovskite compounds doped with various rare earth elements  

Microsoft Academic Search

This thesis focuses on the study of a newly discovered two-dimensional CoO2 layer structured peroskite compound, Sr2CoO4. To explore doping effects on the physical properties of the new compound, a systematic and detailed experimental study has been carried out, relating to the aspects of synthesis, structure, transport and magneto-transport behaviour, magnetism, and dielectricity. Theoretical investigations have also been carried out

Qi Wen Yao

2008-01-01

255

X-ray absorption spectroscopy and photoluminescence study of rare earth ions doped strontium sulphide phosphors  

NASA Astrophysics Data System (ADS)

We present here the electronic structure and photoluminescence properties of Sm (0.1-1.0 mol%) doped SrS phosphors. The doping in SrS was probed by near-edge X-ray absorption fine structure (NEXAFS) at M5,4-edges of Sm in total electron yield mode. The simulated absorption edges using atomic multiplet calculations were correlated with experimental results, which clearly reveal the presence of trivalent state of Sm in SrS matrix. However, for Sm (1 mol%), very minor traces of Sm2+ were also observed, which have been explained by comparing the NEXAFS spectra in total electron and florescence yield mode. The PL emission of SrS:Sm comprises of three sharp bands at 567, 602 and 650 nm owing to the well-known intra 4f transitions from 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2) levels of Sm3+ ions in SrS host. The effect of Ce co-doping on SrS:Sm phosphors was also investigated, which exhibits characteristic PL emission of independent ions at their respective excitation wavelengths. However, at an excitation wavelength of 393 nm, SrS:Ce,Sm exhibits the simultaneous characteristic PL emission of both ions spanning into blue-green-red region. The CIE chromaticity coordinates also clearly show the influence of excitation wavelengths on the emission colour of SrS:Ce,Sm.

Vij, Ankush; Gautam, Sanjeev; Kumar, Vinay; Brajpuriya, R.; Kumar, Ravi; Singh, Nafa; Chae, Keun Hwa

2013-01-01

256

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

USGS Publications Warehouse

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.

Bedrosian, P. A.

2007-01-01

257

Development of a new doping principle for manufacturing of rare earth ion activated silica preforms for optical fibers and study of their spectroscopic properties  

NASA Astrophysics Data System (ADS)

A new doping principle for the fabrication of optical waveguides has been proposed and developed. The principle involves the use of a "building block" approach, when a doping precursor, which includes some or all chemical elements necessary for the formation of an optical waveguide, also contains optically active rare earth ions that are spatially organized in a desired manner on a molecular level. This research has been concerned with the use of precursors that potentially have large minimum distances between rare earth ions in order to increase resulting minimum distances in the final glass made from such precursors and therefore decrease the rate of cooperative energy transfers between rare earth ions leading to quenching of luminescence. Aluminosilicate molecular sieves, zeolites X and Y, with rare earth loading levels not exceeding 16 ions per unit cell in the network of small cages have been proposed and investigated as "building block", large minimum distance precursors for the fabrication of silica optical fibers. Zeolite derived optical preforms and fibers with ultra-high rare earth concentrations up to 1.2 1021 ion/cm 3 have been fabricated for the first time using methods developed in this work. A new acid-free low-water neutral pH sol-gel process has been developed for the deposition of sol-gel films containing zeolite powders. Luminescent properties of neodymium doped zeolite derived preforms have been studied as a function of the total rare earth concentration and levels of rare earth loading of zeolites. Luminescent properties of zeolite-doped sol-gel films at various stages of vitrification have also been studied to evaluate rare earth ion quantum yield and the ion arrangement at different fabrication stages. It has been demonstrated that the lifetime of the Nd3+ metastable level in dehydrated unsintered zeolite-doped sol-gel films strongly increases when zeolite loading becomes less than 16 neodymium ions per unit cell in the network of small pores in both zeolite X and Y. It has also been determined that zeolites with rare earth loading levels between 12 and 25 ions per unit cell allow fabrication of optical preforms with luminescent properties comparable to those obtained by other known approaches.

Shubochkin, Roman Leonidovich

258

Earth  

NSDL National Science Digital Library

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Earth. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions show Earth features such as the Ross Ice Shelf in Antarctica, Simpson Desert in Australia, Mt. Etna in Sicily, the Cassiar Mountains in Canada, the Strait of Gibraltar, Mississippi River, Grand Canyon, Wadi Kufra Oasis in Libya, and Moon images such as Hadley Rille, Plum Crater, massifs and Moon rocks. These images were taken with the Galileo Spacecraft and by the Apollo missions.

259

Combinatorial study of cofluorescence of rare earth organic complexes doped in the poly(methyl methacrylate) matrix.  

PubMed

The luminescence enhancement effect of different kinds and contents of rare earth complexe (RE(DBM)3Phen, RE = Dy, La, Gd, Sm, Y; DBM = dibenzoylmethane; Phen = 1,10-phenanthroline) sensitized Eu(DBM)3Phen doped in poly(methyl methacrylate) (PMMA) matrix was investigated using the combinatorial method. The efficiency of the luminescence enhancement increases with a decrease in the weight percentage of the Eu(DBM)3Phen and an increase in the molecular weight of the PMMA in the systems. Among these sensitization ion complexes, La(DBM)3Phen shows the highest sensitization efficiency. At the optimal content of 5 wt % Eu(DBM)3Phen and 350,000 g/mol weight average molecular weight (Mw) of PMMA, the maximum sensitization efficiency of La(DBM)3Phen is approximately 20 times. We believe that the PMMA with high molecular weight enwraps the rare earth complexes and keeps the donors and acceptors close, which results in the effective intermolecular energy transfer and, consequently, the high sensitization efficiency. PMID:15638482

Ding, Jian Jun; Jiu, Hong Fang; Bao, Jun; Lu, Jie Cheng; Gui, Wan Ru; Zhang, Qi Jin; Gao, Chen

2005-01-01

260

Laser-induced generation of micrometer-sized luminescent patterns on rare-earth-doped amorphous films  

SciTech Connect

Room-temperature photoluminescence has been achieved from rare-earth-doped amorphous (a-) GeN films. The samples were prepared by the radio-frequency-sputtering method, and light emission from the rare-earth (RE) centers was obtained after irradiating the films with a highly focused laser beam. As a result of this laser annealing procedure, almost circular holes with approximately 1-{mu}m diameter were produced on the surface of the a-GeN films. The area nearby these holes correspond to crystalline Ge and coincide with the regions, where relatively strong RE-related luminescence takes place. These laser-annealed areas can be easily and conveniently managed in order to generate different microscopic luminescent patterns. Depending on the RE ion employed, visible and near-infrared light emission were obtained from the patterns so produced. The development of these micrometer-sized luminescent centers, as well as their probable mechanisms of excitation-recombination, will be presented and discussed. The importance of the current experimental results to future technological applications such as microdevices, for example, will also be outlined.

Zanatta, A.R.; Ribeiro, C.T.M. [Laboratorio de Filmes Finos, Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, P.O. Box 369, Sao Carlos 13560-250 (Brazil)

2004-12-01

261

Robust Visible and Infrared Light Emitting Devices Using Rare-Earth- Doped GaN.  

National Technical Information Service (NTIS)

Rare earth (RE) dopants (such as Er, Eu, Tm) in the wide bandgap semiconductor (WBGS) GaN are investigated for the fabrication of robust visible and infrared light emitting devices at a variety of wavelengths. GaN:RE devices are extremely versatile emitte...

A. Steckl

2006-01-01

262

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

Microsoft Academic Search

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

Roberto Mauro Debari

2002-01-01

263

Synthesis of rare earth doped yttrium-vanadate nanoparticles encapsulated within apoferritin.  

PubMed

Luminescent europium (Eu) and dysprosium (Dy) doped yttrium-vanadate (Y-V) nanoparticles (NPs) were synthesized in the cavity of the protein, apoferritin. Y-V NPs were synthesized by incubating a solution of apoferritin with Y(3+) and VO3(-) ions in the presence of ethylene diamine-N-N'-diacetic acid (EDDA). EDDA plays an important role in preventing Y-vanadate precipitation in bulk solution by chelating the Y(3+) ions. Using high resolution electron microscopy, the obtained NPs in the apoferritin cavities were confirmed to be amorphous, and to consist of Y and V. Eu-doped Y-V (Y-V:Eu) NPs were synthesized by the same procedure as Y-V NPs, except that Eu(NO3)3 was added. Y-V:Eu NPs exhibited a strong absorption peak due to the O-V charge transfer transition and remarkable luminescence at 618 nm due to the (5)D0 ? (7)F2 transition. The luminescence lifetime of Y:Eu and Y-V:Eu NPs measured in H2O and D2O solution showed reduction of non-radiative transition to the O-H vibration in Y-V:Eu NPs. Accordingly, Y-V NPs showed strong luminescence compared to Y:Eu NPs. Dy-doped Y-V NPs were also synthesized in apoferritin cavities and showed luminescence peaks at 482 nm and 572 nm, corresponding to (4)F9/2 ? (6)H15/2 and (4)F9/2 ? (6)H13/2 transitions. These NPs stably dispersed in water solution since their aggregation was prevented by the protein shell. NPs encapsulated in the protein are likely to be biocompatible and would have significant potential for biological imaging applications. PMID:24930497

Harada, Tomoaki; Yoshimura, Hideyuki

2014-06-25

264

Transport properties and anisotropy in rare-earth doped CaFe2As2 single crystals with Tc above 40 K  

NASA Astrophysics Data System (ADS)

In this paper we report the superconductivity above 40 K in the electron doping single crystals Ca1-xRxFe2As2 (R = La, Ce, Pr). The x-ray diffraction patterns indicate high crystalline quality and c-axis orientation. The resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by partial replacement of Ca with rare-earth elements and the superconducting transition reaches as high as 46 K, which is higher than the value in electron doping FeAs-122 compounds formed by substituting Fe ions with transition metal, and even surpasses the highest value observed in hole doping systems with a transition temperature up to 38 K. The upper critical fields have been determined with the magnetic field along the ab-plane and c-axis, yielding an anisotropy of 2-3. Hall effect measurements indicate that the conduction in this material is dominated by electron-like charge carriers. Our results confirm the feasibility of inducing superconductivity in Ca122 compounds via electron doping using aliovalent rare-earth substitution into the alkaline earth site, which should add more ingredients to the underlying physics of the iron-based superconductors.

Qi, Yanpeng; Gao, Zhaoshun; Wang, Lei; Wang, Dongliang; Zhang, Xianping; Yao, Chao; Wang, Chunlei; Wang, Chengduo; Ma, Yanwei

2012-04-01

265

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

SciTech Connect

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.

Fletcher, Luke B.; Witcher, Jon J.; Troy, Neil; Krol, Denise M. [Department of Applied Science, University of California Davis, Davis, California 95616 (United States); Reis, Signo T.; Brow, Richard K. [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

2012-07-15

266

Growth and microstructural analysis of nanosized Y 2O 3 doped with rare-earths  

Microsoft Academic Search

Nanosized cubic Y2O3 samples, undoped and doped with 10mol% Nd2O3, Eu2O3, Gd2O3, Tb2O3, Ho2O3 and Er2O3 (Y1.8Ln0.2O3, where Ln=Nd, Eu, Gd, Tb, Ho or Er), were prepared by means of a controlled hydrolysis method in an aqueous solution containing ammonia, Y(NO3)3 and Ln(NO3)3 as precursors, and a surface modifier. The microstrain and the average size of the diffraction domains have

Brigida Allieri; Laura E Depero; Alessandra Marino; Luigi Sangaletti; Lucia Caporaso; Adolfo Speghini; Marco Bettinelli

2000-01-01

267

Ultraslow Light Propagation in an Inhomogeneously Broadened Rare-Earth Ion-Doped Crystal  

NASA Astrophysics Data System (ADS)

We show that coherent population oscillations effect allows us to burn a narrow spectral hole (26 Hz) within the homogeneous absorption line of the optical transition of an erbium ion-doped crystal. The large dispersion of the index of refraction associated with this hole permits us to achieve a group velocity as low as 2.7m/s with a transmission of 40%. We especially benefit from the inhomogeneous absorption broadening of the ions to tune both the transmission coefficient, from 40% to 90%, and the light group velocity from 2.7m/s to 100m/s.

Baldit, E.; Bencheikh, K.; Monnier, P.; Levenson, J. A.; Rouget, V.

2005-09-01

268

Fabrication of rare-earth doped sol-gel based composite planar optical waveguides on glass  

NASA Astrophysics Data System (ADS)

Incorporation of active materials, such as Neodymium (Nd3+) and Erbium (Er3+) in suitable host media has potential applications in lasers and amplifiers. We have fabricated composite planar waveguides on glass substrates doped with Nd3+ and Er3+ ions using the sol-gel process. The composite sol-gel was prepared using polyvinylpyrrolidone as the organic part, while Tetraethyl orthosilicate and Titanium isopropoxide formed the inorganic part. The samples were prism coupled and it was found that they supported single mode at (lambda) equals 633 nm. Gain measurement of the Nd3+ samples have also been carried out.

Natarajan, S. R.; Srinivas, Talabuttala; Joseph, M. J.; Selvarajan, Ananth

1998-12-01

269

Synthesis, luminescence and scintillation of rare earth doped lanthanum fluoride nanoparticles  

NASA Astrophysics Data System (ADS)

Scintillation from nanoparticles is a nascent field but offers valuable fundamental insights and practical utilities. In this work, the scintillation response of LaF 3:Eu nanoparticles is reported. Core/multi-shell nanoparticles were prepared using a modified solution precipitation method that takes advantage of the organic ligand ammonium di- n-octadecyldithiophosphate (ADDP) to simultaneously achieve shelling of doped core nanoparticles while avoiding agglomeration. Nanoparticles were characterized on their structure, morphology, luminescence, and scintillation behavior by means of X-ray diffraction, transmission electron microscopy, photoluminescence, and radioluminescence (RL) measurements, respectively. Analysis of the scintillation process revealed that the unique aspect of scintillation in nanoparticles when compared to bulk materials is related to the migration of carriers within the nanoparticle. Cladding of the Eu-doped core with an undoped shell was found to increase scintillation intensity by a factor of 3, and further shelling leads to a continuous decrease in RL intensity. Surface passivation, together with the decreasing probability of radiative recombination of carriers at the luminescent centers in the core with increasing number of shells grown around the core are suggested to describe the observed RL intensity behavior. Scintillation enhancement by means of shelling is a promising pathway to enhance the use of scintillator nanoparticles in detection devices.

Jacobsohn, L. G.; Sprinkle, K. B.; Kucera, C. J.; James, T. L.; Roberts, S. A.; Qian, H.; Yukihara, E. G.; DeVol, T. A.; Ballato, J.

2010-12-01

270

Amplifying four-wavelength combiner, based on erbium\\/ytterbium-doped waveguide amplifiers and integrated splitters  

Microsoft Academic Search

We report the successful system demonstration of a four-wavelength integrated-optics amplifying combiner. The arrangement consists of an all-connectorized 41 glass splitter followed by a 4.5-cm-long Er\\/Yb-doped waveguide amplifier. When injecting 120 mW of 975-nm laser diode pump, we record, in the amplifying section, 11.6 dB of net gain in the single pass configuration and 23 dB in the double pass

D. Barbier; M. Rattay; F. Saint Andre; G. Clauss; M. Trouillon; A. Kevorkian; J.-M. P. Delavaux; E. Murphy

1997-01-01

271

Integrated ray tracing simulation of spectral bio-signatures from full 3D earth model  

NASA Astrophysics Data System (ADS)

Accurate identification and understanding of spectral bio-signatures from possible extra terrestrial planets have received an ever increasing attention from both astronomy and space science communities in recent years. In pursuance of this subject, one of the most important scientific breakthroughs would be to obtain the detailed understanding on spectral biosignatures of the Earth, as it serves as a reference datum for accurate interpretation of collapsed (in temporal and spatial domains) information from the spectral measurement using TPF instruments. We report a new Integrated Ray Tracing (IRT) model capable of computing various spectral bio-signatures as they are observed from the Earth surface. The model includes the Sun, the full 3-D Earth, and an optical instrument, all combined into single ray tracing environment in real scale. In particular, the full 3-D Earth surface is constructed from high resolution coastal line data and defined with realistic reflectance and BSDF characteristics depending on wavelength, vegetation types and their distributions. We first examined the model validity by confirming the imaging and radiometric performance of the AmonRa visible channel camera, simulating the Earth observation from the L1 halo orbit. We then computed disk averaged spectra, light curves and NDVI indexes, leading to the construction of the observed disk averaged spectra at the AmonRa instrument detector plane. The model, computational procedure and the simulation results are presented. The future plan for the detailed spectral signature simulation runs for various input conditions including seasonal vegetation changes and variable cloud covers is discussed.

Ryu, Dongok; Seong, Sehyun; Lee, Jae-Min; Hong, Jinsuk; Jeong, Soomin; Jeong, Yukyeong; Kim, Sug-Whan

2009-08-01

272

Rare-earth doped oxyfluoride glass-ceramics and fluoride ceramics: Synthesis and optical properties  

Microsoft Academic Search

Ultra-transparent glass-ceramics are synthesized in the GeO2PbOPbF2 system by rare-earth heterogeneous nucleation of PbF2. The influence of YbF3 on the nucleation process is studied through differential thermal analysis (DTA) and the morphology is observed by transmission electron microscopy (TEM). The optical properties of the glass-ceramics are compared to those of the starting glass as well as to those of a

M. Mortier; A. Bensalah; G. Dantelle; G. Patriarche; D. Vivien

2007-01-01

273

VUVUV Photoluminescence Spectra of Strontium Orthophosphate Doped with Rare Earth Ions  

Microsoft Academic Search

The measurements of VUVUV photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra of rare earth ions activated strontium orthophosphate [Sr3(PO4)2:RE, RE = Ce, Sm, Eu, Tb] are performed. Whenever the samples are excited by VUV or UV light, the typical emission of Ce3+, Sm3+, Eu3+, Eu2+ and Tb3+ ions can be observed in PL spectra, respectively. The charge transfer bands

Hongbin Liang; Ye Tao; Qiang Su; Shubin Wang

2002-01-01

274

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

PubMed Central

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.

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

275

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

PubMed

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 tumour 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

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

276

Crystallization kinetics of AlF 3-based glasses doped with rare earth ions  

Microsoft Academic Search

Different concentrations of NdF3, PrF3, and PrF3, codoped with YbF3, ranging from 0.25 to 2.0 wt%, have been added to an AlF3-base glass with composition (mol%) 30.2AlF310.6BaF220.2CaF28.3YF33.5MgF23.8NaF13.2SrF210.2ZrF4. The Avrami exponent, n, and activation energy, E, for the base glass, as well as the doped glasses, have been calculated by analyzing the differential scanning calorimetry curves, according to the amended OzawaChen

Tariq Iqbal; A. N Kayani; M. R Shariari; G. Sigeljr

1997-01-01

277

The optical properties of trivalent rare earth ions (Er3+) doped borotellurite glass  

NASA Astrophysics Data System (ADS)

Erbium doped borotellurite glass has been fabricated by using conventional melting method. The density and molar volume have been calculated and analyzed while their optical properties were studied by measuring the optical absorption and luminescence spectra at room temperature. From the XRD results, since the patterns do not exhibit any diffraction line thus it confirms their amorphous nature. It is found that the density of the glass samples increased and the molar volume decreased with respect to Er ions content. Meanwhile, the upconversion emissions centered at 487, 523, 558, 642, 695 and 782 nm have been observed under the 650 nm excitation in the 4 F 9/2 level. Some other results will be analysed and discussed in details.

Nurbaisyatul, E. S.; Azman, K.; Azhan, H.; Razali, W. A. W.; Noranizah, A.; Hashim, S.; Alajerami, Y. S. M.

2014-03-01

278

Luminescence properties of Sm3+-doped alkaline earth ortho-stannates  

NASA Astrophysics Data System (ADS)

A series of Sm3+ doped M2SnO4 (M = Ca, Sr and Ba) samples were prepared by a conventional high temperature solid-state reaction route. All samples were characterized by powder X-ray diffraction (XRD) analysis, photoluminescence (PL), photoluminescence thermal quenching (TQ) and fluorescence lifetime (FL) measurements. The morphology of synthesized phosphor powders was examined by scanning electron microscopy (SEM). Moreover, luminous efficacies (LE) and color points of the CIE 1931 color space diagram were calculated and discussed. Synthesized powders showed bright orange-red emission under UV excitation. Based on the results obtained we demonstrate that Sm3+ ions occupy Ca and Sr sites in the Ca2SnO4 and Sr2SnO4 ortho-stannate structures, respectively. In contrast, Sm3+ substitutes Sn in the barium ortho-stannate Ba2SnO4 structure.

Stanulis, Andrius; Katelnikovas, Art?ras; Enseling, David; Dutczak, Danuta; akirzanovas, Simas; Bael, Marlies Van; Hardy, An; Kareiva, Aivaras; Jstel, Thomas

2014-05-01

279

Rare earth (Sm3+ and Dy3+)-doped gadolinium oxide nanomaterials for luminescence thermometry  

NASA Astrophysics Data System (ADS)

The possibility of using Sm3+- and Dy3+-doped Gd2O3 nanopowders as thermographic phosphor materials was studied. Both samples were synthesized by a combustion method. The crystalline structure of synthesized samples was confirmed by x-ray diffraction measurements. Photoluminescence measurements were recorded in the temperature range from 298 to 773 K. The photoluminescence spectrum of Sm3+ showed peaks that originate from 4G5/2 ? 6HJ transitions, while in the case of Dy3+ 4F7/2 ? 6HJ transitions were observed. The fluorescence intensity ratio of the prepared nanomaterials was studied as a function of temperature using the 4G5/2 ? 6H5/2 and 4G5/2 ? 6H7/2 transitions of Sm3+ ions and the 4F7/2 ? 6H13/2 and 4F7/2 ? 6H15/2 transitions of Dy3+ ions. Both doped Gd2O3 samples proved to have good potential for the development of thermographic phosphors. The maximum sensitivity was approximately 1.744 10-3 K-1 for the sample with 1 mol% Sm3+ at 701 K and 2.48 10-3 K-1 for the sample with 1 mol% Dy3+ at 773 K. The lifetime measurements were recorded in the same temperature region for the 606 and 572 nm lines of samarium and dysprosium, respectively. The lifetime at room temperature was found to be about 0.395 ms for Sm3+ and 0.123 ms for Dy3+ and it decreased as the temperature increased.

Al-Juboori, Ayad Zwayen M.

2013-11-01

280

Far-Infrared Studies of Vibrational Spectra of the Rare Earth Doped Fluorite Crystals.  

NASA Astrophysics Data System (ADS)

A zero-phonon assisted 4f-5d electronic transition of a trivalent rare earth in a fluorite host is accompanied by a vibronic sideband. This sideband resembles the single phonon density of states of the crystalline host with notable exceptions. A strong feature above the omega _{rm LO}(k = O) frequency of the host lattice is present, and is attributed to a local phonon mode feature of the defect crystal. The frequency of this local mode is weakly dependent on the trivalent rare earth and depends on the fluorite host chosen. The presence of this mode in the ultraviolet absorption spectrum of a XF_{rm 2}:RE ^{rm +3} system is due to the excited 4f^{rm n-1 }5d state of the trivalent rare earth ion interacting with the defect lattice to excite a local mode. Electric dipole vibronic transitions specify that it must be an even symmetry mode (assuming a predominantly cubic crystal field environment for the substitutional rare earth ion) and has been attributed to the symmetric breathing mode (A_{rm 1g}). The host fluorite lattice is represented by a rigid ion model and the dynamics of the defect lattice due to a single substitutional impurity at one of the Ca ^{rm +2} lattice sites is determined via the evaluation of a defect matrix which specifies the interaction of the defect ion with its neighboring ions. The direct effect of an interstitial charge compensating fluorine has been neglected, (ie., the remotely compensated case), allowing us to work in a defect subspace with O_{rm h} point group symmetry. The conditions required to sustain local phonon modes in the defect lattice with A_{rm 1g} and F _{rm 1u} symmetries are then determined. These modes are found to be insensitive to mass variations corresponding to the full range of RE ^{rm +3} substitutional impurities, but require a large change in the original Ca-F and F-F force constant values of the host lattice about the Ca^{rm +2} substitutional impurity site. The change in the local mode frequency of both symmetries (A_{ rm 1g} and F_{rm 1u}) is sensitive to variations in the RE -F and F-F force constants connected to the impurity site. This suggests that the interaction between the 5d orbitals of the excited trivalent rare earth ion and the defect lattice is the most probable mechanism giving rise to the local modes. The force constants needed to sustain the F _{rm 1u} symmetry mode suggests that infrared absorption corresponding to the presence of an infrared active local mode may be possible in a CaF _{rm 2}:Ce ^{rm +3} system where the trivalent cerium has undergone a 4f-5d electronic transition. Infrared studies of BaF_{ rm 2}:Ce^{rm +3} and SrF_{rm 2}:Er^{rm +3} with the rare earth ion in its ground state revealed no infrared absorption that could be assigned to any of the local phonon modes, lending credence to the excited state interaction picture.

Demsky, Juergen

281

Astro-Venture: An Integrated Earth and Space Science Curriculum Supplement Focused on Astrobiology  

NASA Astrophysics Data System (ADS)

Astro-Venture is an example of a NASA educational product that successfully integrates Earth and space science by engaging students in grades 5-8 in the search for and design of a planet with the necessary characteristics for human habitation. Students study the Earth to understand how it meets human needs for survival in the areas of astronomy, geology, biology and atmospheric sciences. They then extend these ideas in simulated searches and analyses of stellar and planetary data sets to determine whether other planets or moons might be habitable. Astro-Venture uses online multimedia activities and off-line inquiry explorations to engage students in guided inquiry aligned with the 5 E inquiry model. For each core science area, students engage in an online training module in which they isolate variables and observe the affects on Earth. They then draw conclusions about which characteristics allow Earth to remain habitable. Following this experience, students engage in classroom, hands-on activities that teach them core standards-based concepts and focus on why the identified characteristics are vital to human habitability. These concepts include: states of matter, flow of energy, chemical properties, planetary geology, plate tectonics, human health and systems theory. With an understanding of the "whats" and the "whys" students then engage in a mission module in which they simulate the methods scientists would use to go about finding a planet with these characteristics. This helps them to understand the "hows". By meeting education standards, teachers can easily integrate this product into their classroom curriculum. Students apply all that they've learned to design a planet that meets the requirements for human habitability in all areas. Through this process, they learn about the Earth within the context of the solar system and how all parts work as a system in meeting our needs.

O'Guinn, C. M.; Wilmoth, K. L.; Coe, L. K.

2005-05-01

282

Coupling earth system and integrated assessment models: the problem of steady state  

NASA Astrophysics Data System (ADS)

Human activities are significantly altering biogeochemical cycles at the global scale, posing a significant problem for earth system models (ESMs), which may incorporate static land-use change inputs but do not actively simulate policy or economic forces. One option to address this problem is to couple an ESM with an economically oriented integrated assessment model. Here we have implemented and tested a coupling mechanism between the carbon cycles of an ESM (CESM, the Community Earth System Model) and an integrated assessment (GCAM) model, examining the best proxy variables to share between the models, and quantifying our ability to distinguish climate- and land-use-driven flux changes. The net primary production and heterotrophic respiration outputs of the Community Land Model (CLM), the land component of CESM, were found to be the most robust proxy variables by which to manipulate GCAM's assumptions of long-term ecosystem steady state carbon, with short-term forest production strongly correlated with long-term biomass changes in climate-change model runs. Carbon-cycle effects of anthropogenic land-use change are short-term and spatially limited relative to widely distributed climate effects, and as a result we were able to distinguish these effects successfully in the model coupling, passing only the latter to GCAM. By allowing climate effects from a full earth system model to dynamically modulate the economic and policy decisions of an integrated assessment model, this work provides a foundation for linking these models in a robust and flexible framework capable of examining two-way interactions between human and earth system processes.

Bond-Lamberty, B.; Calvin, K.; Jones, A. D.; Mao, J.; Patel, P.; Shi, X.; Thomson, A.; Thornton, P.; Zhou, Y.

2014-02-01

283

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

SciTech Connect

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.

Fujii, Yuka; Suto, Yasushi [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Turner, Edwin L., E-mail: yuka.fujii@utap.phys.s.u-tokyo.ac.jp [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2013-03-10

284

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

285

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

286

A path-integral Langevin equation treatment of low-temperature doped helium clusters.  

PubMed

We present an implementation of path integral molecular dynamics for sampling low temperature properties of doped helium clusters using Langevin dynamics. The robustness of the path integral Langevin equation and white-noise Langevin equation [M. Ceriotti, M. Parrinello, T. E. Markland, and D. E. Manolopoulos, J. Chem. Phys. 133, 124104 (2010)] sampling methods are considered for those weakly bound systems with comparison to path integral Monte Carlo (PIMC) in terms of efficiency and accuracy. Using these techniques, convergence studies are performed to confirm the systematic error reduction introduced by increasing the number of discretization steps of the path integral. We comment on the structural and energetic evolution of He(N)-CO(2) clusters from N = 1 to 20. To quantify the importance of both rotations and exchange in our simulations, we present a chemical potential and calculated band origin shifts as a function of cluster size utilizing PIMC sampling that includes these effects. This work also serves to showcase the implementation of path integral simulation techniques within the molecular modelling toolkit [K. Hinsen, J. Comp. Chem. 21, 79 (2000)], an open-source molecular simulation package. PMID:22713049

Ing, Christopher; Hinsen, Konrad; Yang, Jing; Zeng, Toby; Li, Hui; Roy, Pierre-Nicholas

2012-06-14

287

A path-integral Langevin equation treatment of low-temperature doped helium clusters  

NASA Astrophysics Data System (ADS)

We present an implementation of path integral molecular dynamics for sampling low temperature properties of doped helium clusters using Langevin dynamics. The robustness of the path integral Langevin equation and white-noise Langevin equation [M. Ceriotti, M. Parrinello, T. E. Markland, and D. E. Manolopoulos, J. Chem. Phys. 133, 124104 (2010)] sampling methods are considered for those weakly bound systems with comparison to path integral Monte Carlo (PIMC) in terms of efficiency and accuracy. Using these techniques, convergence studies are performed to confirm the systematic error reduction introduced by increasing the number of discretization steps of the path integral. We comment on the structural and energetic evolution of HeN-CO2 clusters from N = 1 to 20. To quantify the importance of both rotations and exchange in our simulations, we present a chemical potential and calculated band origin shifts as a function of cluster size utilizing PIMC sampling that includes these effects. This work also serves to showcase the implementation of path integral simulation techniques within the molecular modelling toolkit [K. Hinsen, J. Comp. Chem. 21, 79 (2000)], an open-source molecular simulation package.

Ing, Christopher; Hinsen, Konrad; Yang, Jing; Zeng, Toby; Li, Hui; Roy, Pierre-Nicholas

2012-06-01

288

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

PubMed

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

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

2014-02-01

289

High Temperature Electrical Properties and Defect Structures of Alkaline Earth-Doped Lanthanum Cuprate Superconductors.  

NASA Astrophysics Data System (ADS)

Existing oxygen nonstoichiometry data of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} have been fitted by defect structure models featuring isolated oxygen vacancies, neutral associates and singly charged associates, respectively. The associate models fit the data acceptably well up to x = 0.4 while the isolated vacancy model does not fit the data as satisfactorily. Therefore, the oxygen deficiency in both systems is attributed to dopant-vacancy associates rather than isolated oxygen vacancies. However, all three models are unable to reproduce the flattening of electrical properties at high doping levels. Jonker plots reveal that the flattening is caused by degeneracy. The oxygen partial pressure dependence of the electrical properties indicates that the associates are not neutral but singly charged. Thermoelectric power and electrical conductivity have been measured in situ for rm La_ {2-x}Ca_{x}CuO_{4 -y} with x = 0-0.16 in P(O_2 ) = 10^{-5} { -1} atm at T = 700-1000^circ C. The results are similar to those of rm La_{2-x}Ba_{x}CuO _{4-y} and rm La _{2-x}Sr_{x}CuO_ {4-y} yet significant magnitudes of oxygen deficiency reportedly occur in rm La_ {2-x}Ca_{x}CuO_{4 -y} at much lower doping levels. Defect structure models involving charged oxygen vacancies cannot simultaneously fit both properties. Neutral oxygen vacancies and their association with dopants were invoked to reconcile both electrical property and oxygen nonstoichiometry data. The proposed defect structure models have been rationalized based on the bond-length mismatch first observed by Goodenough and his coworkers. The Cu-O bonds in the CuO_2 layers are longer than the La-O bonds in the (LaO)_2 layers. Substitution of larger Ba or Sr for La relieves the mismatch by lengthening the La-O bonds. Holes created for charge compensation contribute to the relief by shortening the Cu-O bonds. Once the mismatch is completely relieved, charged oxygen vacancies are formed in the (LaO)_2 layers, to minimize further expansions. The electrostatic attraction leads to the association of oppositely charged dopants and vacancies. Substitution of smaller Ca for La aggravates the mismatch by further shortening the La-O bonds. Neutral oxygen vacancies, together with holes, form in the CuO _2 layers to shorten Cu-O bonds to compensate the shortening of the La-O bonds. The association of dopants and vacancies can be explained by the preference of Ca for eight-fold coordination.

Shen, Li.

1995-01-01

290

A review of visible, near-IR, and mid-IR transitions in rare-earth doped glass waveguides for remote sensing and lidar  

Microsoft Academic Search

In the review article we explain the recent investigations on rare-earth doped glass and optical fibres for designing lasers which may be suitable for remote sensing and LIDAR applications. The paper explains the importance of engineering efficient lasing transitions in visible (480-650 nm) for generating UV lasers via one-stage harmonic generation. Besides visible transitions, we also demonstrate the transitions in

Animesh Jha

2006-01-01

291

Development of the FTIR properties of nano-structure silica gel doped with different rare earth elements, prepared by sol-gel route  

Microsoft Academic Search

Structural characteristics of pure silica gel (silica-xerogel, SiO2) and silica gel doped with some rare earth elements (REEs) such as, praseodymium Pr3+, and Europium Eu3+, Erbium Er3+ and Holmium Ho3+ ions, with different concentrations ranging from 1 up to 6%, in the form of monolith materials were prepared by sol-gel technique,\\u000a Using tetra-ethoxysilane as precursor materials, which are of particular

I. K. Battisha; A. El Beyally; S. Abd El Mongy; A. M. Nahrawi

2007-01-01

292

Optical spectra of undoped and rare-earth-(=Pr, Nd, Eu, and Er) doped transparent ceramic Y sub 3 Al sub 5 O sub 12  

Microsoft Academic Search

Undoped and rare-earth- (Pr, Nd, Eu, and Er) doped transparent YAlO ceramics have been prepared, and their optical spectra have been measured. It is found that absorption coefficient of the undoped ceramic YAlO is almost independent of wavelength with 0.258 cm⁻¹, which gives transmittance of the undoped ceramic YAlO to be, for example, 95% for a 2-mm height. Peaks in

M. Sekita; H. Haneda; S. Shirasaki; T. Yanagitani

1991-01-01

293

VUV spectroscopic properties of rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) type phosphate  

Microsoft Academic Search

The excitation spectra of pure and rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) in the vacuum ultraviolet (VUV) regions are investigated. The results indicate that these samples show strong absorption in the VUV range. The band ranging from 130 to 160 nm is due to the absorption band of host lattice or PO4 groups; the

Zhi-Jun Zhang; Hao-Hong Chen; Xin-Xin Yang; Jing-Tai Zhao; Guo-Bin Zhang; Chao-Shu Shi

2008-01-01

294

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

ERIC Educational Resources Information Center

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

Mathar, Reiner

2010-01-01

295

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

296

Properties of rare earth doped thin film dielectric layers for upconversion laser waveguides  

NASA Astrophysics Data System (ADS)

Thin films of erbium doped tantalum pentoxide were prepared on unheated <100> orientated silicon substrates with a thermally grown 2 ?m thick SiO2 layer using reactive sputtering in an oxygen rich environment for upconversion laser experiments. Tantalum and Erbium metal targets were co-sputtered using an ion beam assisted reactive process to produce the high quality amorphous thin film layers. The Erbium dopant concentration was adjusted by varying the relative deposition rate. Slab waveguide loss before high temperature annealing was measured to be 0.8 dB/cm at 633 nm which reduced to 0.5 dB/cm after annealing at 500 C. Micron scale waveguides were etched into the deposited thin film slab waveguides using photolithography and reactive ion etching. Finally a silicon dioxide buffer layer was deposited on top of the ridge waveguides to help constrict the laser mode and to add a protective layer. 2 cm long waveguide samples were cleaved and polished to achieve good optical quality end facets for laser experiments. Upconversion efficiency and laser gain measurements were performed on the final waveguides. Waveguide losses of 6.35 dB/cm were measured for the final ridge waveguides and a coupling efficiency of 48 % was obtained. A positive net gain of 0.25 dB was measured for upconversion to 551 nm using a pump probe optical setup.

Pearce, S. J.; Charlton, M. D. B.; Parker, G. J.; Wilkinson, J. S.

2011-02-01

297

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

SciTech Connect

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.

Gomez-Leal, I.; Selsis, F. [Univ. Bordeaux, LAB, UMR 5804, F-33270 Floirac (France); Palle, E., E-mail: gomezleal@obs.u-bordeaux1.fr, E-mail: selsis@obs.u-bordeaux1.fr, E-mail: epalle@iac.es [Instituto de Astrofisica de Canarias, Via Lactea s/n, La Laguna E-38205, Tenerife (Spain)

2012-06-10

298

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

NASA Technical Reports Server (NTRS)

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.

Lousma, Jack R.

1992-01-01

299

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

SciTech Connect

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.

Sontakke, Atul D.; Annapurna, K. [Glass Science and Technology Section, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Road, Kolkata - 700 032 (India)

2012-07-01

300

Infrared-to-visible upconversion fluorescence spectroscopy in trivalent rare-earth-doped lead-magnesium-fluorophosphate glass  

NASA Astrophysics Data System (ADS)

There has recently been a great deal of interest in searching for new vitreous materials for application as hosts in infrared-to-visible light upconverters or optical amplifiers based upon rare-earth doped systems. Some of their many applications include: color displays, high density optical recording, biomedical diagnostics, infrared laser viewers and indicators, fiber lasers and amplifiers. Fluorophosphate-based glasses have recently emerged as auspicious candidates for such photonic devices applications. These glasses are advantageous because they present low nonlinear refractive indeces, better mechanical strength, chemical durability, and thermal stability than fluoride-based glasses and are suitable for developing low-loss, high strength, and low-cost optical fibers. It has recently been shown also that the fluorophosphate-based glass is an excellent candidate for high power lasers and broadband amplifiers in the eye-safe region around 1.5 ?m for applications in communication, medicine, and meteorology. The present work involves the investigation of optical transitions and upconversion fluorescence spectroscopy of trivalent lanthanide ions Er3+ and Tm3+ codoped with Yb3+ in P2O5-PbO-MgF2 glass, excited with near-infrared diode lasers. The dependence of the upconversion luminescence upon the Yb3+-concentration and diode laser power, and the upconversion excitation mechanisms involved are also investigated. The viability of using these glasses as host for practical applications in optical temperature sensors will also be presented.

Bueno, Luciano A.; Gouveia-Neto, Artur da S.; Fonseca do Nascimento, Raphael; Arcanjo da Silva, Elias; do Nascimento, Valberes B.; Barbosa da Costa, Ernande

2008-03-01

301

Structural and optical properties of rare-earth-doped Y2O3 waveguides grown by pulsed-laser deposition  

NASA Astrophysics Data System (ADS)

Crystalline rare-earth-doped yttrium oxide thin films were grown by pulsed-laser deposition (PLD) on SiO2/Si substrates. The structural and morphological features of these films were studied, as a function of the growth conditions (temperature from 200 to 800 degC and oxygen pressure from 10-6 to 0.5 mbar), by using Rutherford backscattering spectroscopy, x-ray diffraction, and atomic force microscopy. The related optical properties were investigated by m-lines spectroscopy at 633 nm and 1.3 mum. The optimal conditions were found to be a temperature and a pressure of 700 degC and 10-6 mbar, respectively. In that case, the Y2O3 films are stoichiometric with controlled erbium and europium rates, and present a well-crystallized, (111) textured cubic phase and a low surface roughness of about 10 A. Moreover, the PLD films show good waveguiding properties with a high refractive index (1.92 at 633 nm), a step-index structure, and low optical losses around 1 dB/cm in the near infrared region, promising for a planar amplifier function.

Pons-Y-Moll, Olivier; Perriere, Jacques; Millon, Eric; Defourneau, Reine Marie; Defourneau, Daniel; Vincent, Brice; Essahlaoui, Abdel; Boudrioua, Azzedine; Seiler, Wilfrid

2002-11-01

302

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

303

Correlation of XANES features with the scintillation efficiencies of Ce doped alkaline earth lithium silicate glasses  

SciTech Connect

Cerium-activated, lithium-silicate glasses are widely used as thermal neutron detectors because of their versatility, robustness and low cost. The glasses convert the energy of the neutrons to visible light pulses that may be counted. This process, scintillation, is generally thought to be composed of three steps: ionization, energy transfer, and luminescence. If defects are present, they can trap the excitations, altering the scintillation output. These features have been discussed previously. The presence of magnesium in these glasses increases scintillation efficiency, but as previously observed the effect drops by a factor greater than 2.5 with substitution through the series of alkaline earths. Here, cerium activated glasses of composition 20Li{sub 2}O{center_dot}15MO{center_dot}64.4SiO{sub 2}{center_dot}0.6Ce{sub 3}O{sub 3} (where m is Mg, Ca, Sr, or Ba) exhibit scintillation efficiencies that vary by more than a factor of 2.5 with the alkaline earth. Previous work has suggested a correlation between the microstructure of these glasses and scintillation efficiency. Measurements of the Ce L{sub III} x-ray absorption edge in the Mg, Ca and Sr glasses display a feature near the absorption edge that is suggestive of the presence of Ce{sup 4+}. The area of this peak is, in fact, correlated with the scintillation efficiency of the glass. The amount of Ce{sup 4+} indicated by the intensity of this feature is, however, too high to be a permanent population. The authors suspect that the feature is a transient phenomenon related to creation of Ce{sup 4+} and trapped electrons due to photoionization by the x-ray beam.

Blanchard, D.L.; Sunberg, D.S.; Craig, R.A.; Bliss, M. [Pacific Northwest Lab., Richland, WA (United States); Weber, M.J. [Lawrence Livermore National Lab., CA (United States)

1994-11-01

304

Lanthanide Contraction Effect In Magnetic Thermoelectric Materials Of Rare Earth-doped Bi1.5Pb0.5Ca2Co2O8  

NASA Astrophysics Data System (ADS)

We report in this paper the result of synthesis and crystal structure characterization of magnetic thermoelectric materials of rare-earth-doped Bi1.5Pb0.5Ca2Co2O8, namely Bi1.5Pb0.5Ca1.9RE0.1Co2O8 (RE = La, Pr, Sm, Eu, Gd, Ho). Single phase samples have been prepared by solid state reaction process using precursors of Bi2O3, PbO, CaCO3, RE2O3, and Co3O4. The precursors were pulverized, calcinated, and sintered in air at various temperatures for several hours. Analysis of XRD data shows that Bi1.5Pb0.5Ca1.9RE0.1Co2O8 compound is a layered system consisting of an alternate stack of CoO2 layer and Bi2Sr2O4 block along the c-axis. The misfit structure along b-direction is revealed from the difference of the b-axis length belonging to two sublattices, namely hexagonal CdI2-type CoO2 layer and rock-salt (RS) NaCl-type Bi2Sr2O4 block, while they possess the common a- and c-axis lattice parameters and ? angles. The overall crystal structure parameters (a, b, and c) increases with type of doping from La to Ho, namely by decreasing the ionic radii of rare-earth ion. We discuss this phenomenon in terms of the lanthanide contraction, an effect commonly found in the rare-earth compound, results from poor shielding of nuclear charge by 4f electrons. In addition, the values of b-lattice parameters in these rare-earth doped samples are almost the same with those belongs to undoped parent compound (Bi1.5Pb0.5Sr2Co2O8) and its related Y-doped (Bi1.5Pb0.5Ca1.9Y0.1Co2O8) samples, while the c-values reduced significantly in rare-earth doped samples, with opposite trend with those of variation of a-axis length. Morevover, the misfit degree in rare-earth doped compound is higher in compared to parent compound and Y-doped samples. We argue that these structural changes induced by rare-earth doping may provide information for the variation of electronic structure of Co-ions (Co3+ and Co4+), in particular their different spin states of low-spin, intermediate-spin, and high-spin. This, in turn, will affect the thermoelectric properties (Seebeck coefficient) of the system.

Sutjahja, Inge Magdalena; Akbar, Taufik; Nugroho, Agung

2010-12-01

305

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

PubMed

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

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

2013-11-01

306

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

NASA Astrophysics Data System (ADS)

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.

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

307

Development of Uncooled Micro-bolometer Arrays Based on Hole-doped Rare-Earth Manganites  

NASA Astrophysics Data System (ADS)

Material properties indicate that rare earth manganites have a competitive advantage over VOx which is a material commonly employed as bolometric sensors in state of the art uncooled imaging arrays. We will present the results of our work on developing manganite thin films for uncooled micro-bolometer arrays. By fine tuning the cation composition and stoichiometry, we have identified material compositions suitable for uncooled bolometer operation and developed thin films of these materials by Pulsed Laser Deposition (PLD) on Si. For hetero-epitaxy on Si, we employ lattice engineering schemes to circumvent problems such as chemical incompatibility and amorphization of the substrate surface due to the native oxide. We are in the process of fabricating single test bolometers and micro-bolometer arrays. We will discuss the results of materials development and device fabrication efforts and will present performance parameters and estimated figures of merit for test bolometers. We will also discuss efforts towards understanding and alleviating material problems such as the residual stresses in the thin film heterostructures which are of critical importance for the fabrication of suspended microstructures.

Tanyi, E. Kevin; Yong, Grace; Keshavarz, Camron; Sharma, Prakash; Rubin, Christopher; Kolagani, Rajeswari; Gross, Steven

2013-03-01

308

VUV-UV Photoluminescence Spectra of Strontium Orthophosphate Doped with Rare Earth Ions  

NASA Astrophysics Data System (ADS)

The measurements of VUV-UV photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra of rare earth ions activated strontium orthophosphate [Sr 3(PO 4) 2: RE, RE = Ce, Sm, Eu, Tb] are performed. Whenever the samples are excited by VUV or UV light, the typical emission of Ce 3+, Sm 3+, Eu 3+, Eu 2+ and Tb 3+ ions can be observed in PL spectra, respectively. The charge transfer bands (CTBs) of Sm 3+ and Eu 3+ are found, respectively, peaking at 206 and 230 nm. The absorption bands peaking in the region of 150-160 nm are assigned to the host lattice sensitization bands, i.e., the band-to-band transitions of PO 43- grouping in Sr 3(PO 4) 2. It is speculated that the first f- d transitions of Sm 3+ (Eu 3+), and the CTB of Tb 3+are, respectively, located around 165 (1 4 3) and 167 nm by means of VUV-UV PLE spectra and relational empirical formula, these f-d transitions or CT bands are included in the bands with the maxima at 150-160 nm, respectively. The valence change of europium from trivalent to divalent in strontium orthophosphate prepared in air is observed by VUV-UV PL and PLE spectra.

Liang, Hongbin; Tao, Ye; Su, Qiang; Wang, Shubin

2002-09-01

309

Excitation and luminescence of rare earth-doped lead phosphate glasses  

NASA Astrophysics Data System (ADS)

Excitation and luminescence properties of Eu3+, Tb3+ and Er3+ ions in lead phosphate glasses have been studied. From excitation spectra of Eu3+ ions, the electron-phonon coupling strength and phonon energy of the glass host were calculated and compared to that obtained by Raman spectroscopy. Main intense and long-lived luminescence bands are related to the 5D0-7F2 (red) transition of Eu3+, the 5D4-7F5 (green) transition of Tb3+ and the 4I13/2-4I15/2 (near-infrared) transition of Er3+. The critical transfer distances, the donor-acceptor interaction parameters and the energy transfer probabilities were calculated using the fitting of the luminescence decay curves from 5D0 (Eu3+), 5D4 (Tb3+) and 4I13/2 (Er3+) excited states. The energy transfer probabilities for Eu3+ (5D0), Tb3+ (5D4) and Er3+ (4I13/2) are relatively small, which indicates low self-quenching luminescence of rare earth ions in lead phosphate glasses.

Pisarska, J.; So?tys, M.; ?ur, L.; Pisarski, W. A.; Jayasankar, C. K.

2014-03-01

310

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

NASA Astrophysics Data System (ADS)

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.

Bender, Christopher Mark

1998-12-01

311

Prospects for projecting the impact of Earth system processes on Integrated Assessment  

NASA Astrophysics Data System (ADS)

We discuss the prospects for advancing the quantitative exploration of climate mitigation strategies using the integrated Earth System Model (iESM). The iESM leverages existing investments by DOE in community simulation capabilities including the Community Earth System Model (CESM) together with the Global Change Assessment Model (GCAM) and the Global Land-use Model (GLM). GCAM and GLM are the foundation for one of the Representative Concentration Pathways (RCPs) evaluated in the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). The distinguishing features of iESM are the incorporation of integrated assessment capabilities into a full ESM and the provision for two-way interactions between the energy sector and climate change. Initial experiments using this new modeling system have demonstrated the need to revisit the conceptual design of the RCP scenarios [Moss, et al., 2010]. The iESM team has shown that feedbacks from climate change to the energy sector, an important class of interactions omitted from the current IPCC scenarios, can significantly alter the future allocation of land for energy and food production. Because human and biogeophysical Earth systems are closely coupled in the iESM, it is now possible to rapidly explore climate implications of new scenarios for future assessments and likewise to quantify the effects of improved treatments of major climatic processes on those scenarios. We discuss the progress towards significantly enhanced treatments of aerosols, carbon cycles, and methane feedbacks in CESM. We conclude with the potential applications of these capabilities in integrated assessment on decadal to centennial timescales using iESM.

Collins, W.; Edmonds, J. A.; Thornton, P. E.; Craig, A.; Hurtt, G. C.; Janetos, A. C.; Jones, A.; Koven, C. D.; Riley, W. J.; Truesdale, J.

2012-12-01

312

Using the Collaborative Sun-Earth Connector for integrating data systems  

NASA Astrophysics Data System (ADS)

We demonstrate the coupling of disjoint data systems into virtual collaborative operations using the Collaborative Sun-Earth Connector (CoSEC). In addition to demonstrating possible interactions between Virtual observatories, we will present how individual missions and researchers can integrate their systems with space science services already incorporated into CoSEC. We present more advanced concepts of how to create collaborative data environments using upcoming solar missions as examples. This research has been supported through NASA contract NNH04CC00C.

Hurlburt, N.; Freeland, S.; Slater, G.; Bentley, R.; Hill, F.; Bose, P.

2005-05-01

313

Integrating EarthScope seismic, GPS, and other active Earth observations into informal education programs in parks and museums  

Microsoft Academic Search

EarthScope is a National Science Foundation program that uses seismic, GPS, and other geophysical devices to explore the structure and evolution of the North American continent and to understand the physical processes that cause earthquakes and volcanic eruptions. Two challenges facing the EarthScope community include providing the public with access to timely science results and presenting complex data and related

R. J. Lillie; C. Goddard; J. Braunmiller; A. M. Trehu

2008-01-01

314

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

NASA Astrophysics Data System (ADS)

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 Al2O3 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.

Schoer, Gerrit; Mahnke, Matthias; Schober, Marc; Herrmann, Alexander; Mller, Jrg

2006-05-01

315

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

NASA Astrophysics Data System (ADS)

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.

Matthiesen, Stephan; Merchant, Chris; Rayner, Nick; Remedios, John; Hyer, Jacob L.; Jones, Phil; Olesen, Folke; Roquet, Herv; Sobrino, Jos; Thorne, Peter

2013-04-01

316

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

NASA Technical Reports Server (NTRS)

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.

Lousma, Jack R.

1992-01-01

317

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)

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.

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

318

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

PubMed

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

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

2013-08-21

319

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

NASA Astrophysics Data System (ADS)

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.

Alameh, N.; Hogan, P.

2008-12-01

320

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

321

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

NASA Technical Reports Server (NTRS)

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

Stepinski, T. F.; Coradetti, S.

2004-01-01

322

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

NASA Astrophysics Data System (ADS)

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.

Wang, Yansen; Huynh, Giap; Williamson, Chatt

2013-12-01

323

1 kW peak power passively Q-switched Nd(3+)-doped glass integrated waveguide laser.  

PubMed

Embedded optical sensors always require more compact, stable, and powerful laser sources. In this Letter, we present a fully integrated passively Q-switched laser, which has been realized by a Ag(+)/Na(+) ion exchange on a Nd(3+)-doped phosphate glass. A BDN-doped cellulose acetate thick film is deposited on the waveguide, acting as an upper cladding and providing a distributed saturable absorption. At ?=1054 nm, the device emits pulses of 1.3 ns FWHM with a repetition rate of 28 kHz. These performances, coupled with the 1 kW peak power, are promising for applications such as supercontinuum generation. PMID:21633424

Charlet, B; Bastard, L; Broquin, J E

2011-06-01

324

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

NASA Astrophysics Data System (ADS)

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?"

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

2006-12-01

325

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

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

Gloag, A.; Forster, R.J.; Langford, N. [Department of Physics and Applied Physics, University of Strathclyde, 107 Rottenrow East, Glasgow G4 ONG (United Kingdom)

1997-04-01

326

Integrating EarthScope seismic, GPS, and other active Earth observations into informal education programs in parks and museums  

NASA Astrophysics Data System (ADS)

EarthScope is a National Science Foundation program that uses seismic, GPS, and other geophysical devices to explore the structure and evolution of the North American continent and to understand the physical processes that cause earthquakes and volcanic eruptions. Two challenges facing the EarthScope community include providing the public with access to timely science results and presenting complex data and related principles in language and formats accessible to varied audiences. A series of workshops for park and museum educators combines scientific observations with interpretive methods to convey stories of the dynamic landscape of the western United States. The initial workshop, held at the Mt. Rainier National Park Education Center, focused on how EarthScope data and scientific results enhance the "sense of place" represented by the coastlines, valleys, and mountains of the Cascadia Subduction Zone. Participants learned how seismic and GPS instruments monitor earthquakes, volcanoes, and tsunamis that reveal the power of Earth's forces in the Pacific Northwest. A second workshop, held at the University of Nevada-Reno, related EarthScope observations to active continental rifting in the Basin and Range Province. Future workshops will focus on the San Andreas Fault, Colorado Plateau, Rio Grande Rift, and other regions. The workshops are helping interpretive professionals learn how observations of dynamic landscapes can be used to connect various audiences to many of the physical, historical, and cultural aspects of a park or museum site.

Lillie, R. J.; Goddard, C.; Braunmiller, J.; Trehu, A. M.

2008-12-01

327

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

NASA Astrophysics Data System (ADS)

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.

Kirkby, K. C.; Kirkby, S.

2013-12-01

328

Unusual superconductivity up to 49 K in single crystalline R-doped CaFe2As2 (Ca122) at ambient with R = rare earth  

NASA Astrophysics Data System (ADS)

The discovery in 2008 of the Fe-pnictide and Fe-chalcogenide superconductors has generated immense interest. They crystallize in four different structures, namely, the 1111-phase (RFeAsO, where R = rare earth) with the ZrCuSiAs structure (P4/nmm); the 122-phase (AeFe2As2 and AFe2As2, where Ae = alkaline earth and A = alkaline) with the ThCr2Si2 structure (I4/mmm); the 111-phase (AFeAs, where A = alkaline) with the PbFCl structure (P4/nmm); and the 11-phase (FeSe1-x) with the PbO structure (P4/nmm). The highest Tc's of these compounds are 57 K, 38 K, 20 K and 10 K for the 1111, 122, 111 and 11 structure classes with different electron or hole- ping at ambient. Until now, no effort has been successful to raise the maximum Tc of Fe-pnictides or -chalcogenides to above the 60's K as predicted. In view of the unsettled superconducting behavior of Ca122 under pressure, we have investigated the electron-doping effect on Ca122, in contrast to previous studies on the 122 class where only hole-doping has been carried out. We have detected superconductivity up to 49 K in single crystalline CaFe2As2 via electron-doping by partial replacement of Ca by rare-earth. The superconducting transition observed suggests the possible existence of two phases: one starts at ~ 49 K with a low critical field ~ 4 Oe, and the other at ~ 21 K, with a much higher critical field > 5 T. Our observations are in strong contrast to previous reports of doping or pressurizing layered compounds AeFe2As2 (or Ae122), where Ae = Ca, Sr or Ba. In Ae122, hole-doping has been previously observed to generate superconductivity with a transition temperature (Tc) only up to 38 K and pressurization has been reported to produce superconductivity with a Tc up to 30 K. The unusual 49 K phase observed appears to be filamentary or interfacial in nature. The associated superconducting transition at 49 K behaves as Josephson-Junctioncoupled-like, suggesting the existence of a superconducting phase above 49 K in the R-Ca-Fe-As compound system. The results will be presented and the implications discussed.

Chu, C. W.

2012-03-01

329

Luminescence property of rare-earth-doped bismuth-borate glasses with different concentrations of bismuth and rare-earth material  

NASA Astrophysics Data System (ADS)

Bismuth-borate glass scintillators have high density and good radiation hardness. Thus, if they are highly luminescent, they can be applied in astrophysics, high-energy and nuclear physics, homeland security, radiation detection and medical imaging. Bismuth-borate glasseswith the formula xBi2O3:(100 - x)B2O3 ( x = 30, 50, and 66.7 mol%) were fabricated and doped with Nd, Er, Dy, Pr, Sm, Ho, Gd, and Ce in different dopant concentrations by using the melt-quenching technique. The X-ray emission spectra for the bismuth-borate glasses were measured and showed that only Sm-, Dy-, and Nd-doped glass scintillators had noticeable luminescence. Also, we measured the photo-luminescence and the proton-induced emission spectra. We obtained the result that Sm- and Dy- doped glass scintillators emitted luminescence. The emission peaks of the Sm- doped glass were 569, 598, 641, and 708 nm and were due to (4G5/2 ? 6H J ) ( J = 5/2, 7/2, 9/2, 11/2) transitions, respectively. The emission peaks of the Dy- doped glass were at 485 nm (4F9/2 ? 6H15/2), 575 nm (4F9/2 ? 6H13/2), 660 nm (4F9/2 ? 6H11/2), and 755 nm (4F9/2 ? 6H9/2 + 6H11/2), and that of the Nd-doped glass was at 895 nm due to the (4F3/2 ? 4I9/2) transition. The luminescence intensities were compared in terms of different Bi concentrations and dopant concentrations.

Park, J. M.; Kim, H. J.; Limsuwan, P.; Kaewkhao, J.

2012-07-01

330

Proton solubility for La 2Zr 2O 7 with a pyrochlore structure doped with a series of alkaline-earth ions  

Microsoft Academic Search

Alkaline-earth ion doped La2Zr2O7 samples with a pyrochlore structure, i.e., (La2?xMx)Zr2O7?? and La2(Zr2?xMx)O7?? (M=Mg, Ca, Sr and Ba), were prepared by conventional ceramic methods. The quantity of protons dissolved in the crystal was evaluated by evolved H2O gas, which was detected by a quadrupole mass spectrometer. The relationship between the proton solubility of the La2Zr2O7-based high temperature proton conductor and

Takahisa Omata; Katsuhiko Ikeda; Ryoji Tokashiki; Shinya Otsuka-Yao-Matsuo

2004-01-01

331

Coherent magnon and acoustic phonon dynamics in tetragonal and rare-earth-doped BiFeO3 multiferroic thin films  

NASA Astrophysics Data System (ADS)

Coherent magnons and acoustic phonons were impulsively excited and probed in thin films of the room temperature multiferroic Bi1-x-yDyxLayFeO3 using femtosecond laser pulses. The elastic moduli of rhombohedral, tetragonal, and rare-earth doped BiFeO3 were determined from acoustic-mode frequencies in conjunction with spectroscopic ellipsometry. A weak ferromagnetic order, induced alternately by magnetization in the growth direction or by tetragonality, created a magnon oscillation at 75 GHz, indicative of a Dzyaloshinskii-Moriya interaction energy of 0.31 meV.

Doig, K. I.; Aguesse, F.; Axelsson, A. K.; Alford, N. M.; Nawaz, S.; Palkar, V. R.; Jones, S. P. P.; Johnson, R. D.; Synowicki, R. A.; Lloyd-Hughes, J.

2013-09-01

332

Storage and retrieval of collective excitations on a long-lived spin transition in a rare-earth ion-doped crystal.  

PubMed

Robust, long-lived optical quantum memories are important components of many quantum information and communication protocols. We demonstrate coherent generation, storage, and retrieval of excitations on a long-lived spin transition via spontaneous Raman scattering in a rare-earth ion-doped crystal. We further study the time dynamics of the optical correlations in this system. This is the first demonstration of its kind in a solid and an enabling step toward realizing a solid-state quantum repeater. PMID:23609713

Goldschmidt, E A; Beavan, S E; Polyakov, S V; Migdall, A L; Sellars, M J

2013-04-22

333

Wide frequencies range of spin excitations in a rare-earth Bi-doped iron garnet with a giant Faraday rotation  

NASA Astrophysics Data System (ADS)

Ultrafast magnetization dynamics of a rare-earth Bi-doped garnet were studied using an optical pump-probe technique via the inverse Faraday effect. We observed a wide range of frequency modes of the magnetization precession, covering two orders of magnitude. The excitation efficiency of low-frequency precessions in the GHz range, together with a significant beating effect, strongly depended on the amplitude of the external magnetic field. On the contrary, high-frequency precession was independent of the external magnetic field. The obtained results may be exploited in the development of wide class of microwave and magneto-optical devices.

Parchenko, Sergii; Stupakiewicz, Andrzej; Yoshimine, Isao; Satoh, Takuya; Maziewski, Andrzej

2013-10-01

334

Point-charge and induced-dipole model analysis of spin-Hamiltonian parameters for Gd3+ doping single crystals of rare-earth-metal trichloride hexahydrates  

NASA Astrophysics Data System (ADS)

Spin-Hamiltonian parameters are calculated for Gd3+ doping single crystals of rare-earth-metal trichloride hexahydrates R Cl3.6H2O (RTH): R = Nd, Sm, Eu, Tb, Dy, Ho, Er, and Tm, with the use of the point-charge plus induced-dipole model, with variable anisotropic tensor polarizabilities. It is found that the parameters can all be computed to be within experimental error by suitable choices of polarizability tensors. Conclusions about the polarizability values of the various ions in the RTH crystals are drawn.

Lewis, Norman R.; Misra, Sushil K.

1982-04-01

335

An Integrated Small Satellite Approach for Measurements of the Near-Earth Space Environment  

NASA Astrophysics Data System (ADS)

Small satellites are well suited to making measurements of the near-Earth space environment especially since there is variability in the space environment on scales ranging from centimeters to thousand of kilometers and fractions of a second to years. Space weather is the day-to-day (or shorter) variation about that mean condition for the space environment parameters. In this paper we discuss some of the factors that must be considered when designing a system for space weather monitoring or the scientific investigation of the near-Earth environment. Some examples of important near-Earth space environment parameters are: 1) the number flux and energy of energetic particles in the auroral region and/or the radiation belts, 2) the number density temperature and composition of neutrals and ions in the upper atmosphere (the thermosphere and ionosphere, respectively), 3) the wind speed in the upper atmosphere (above 200 km), 4) the ion drift velocity and/or DC component of the electric field, and 5) small scale fluctuations in the ionosphere that lead to radio scintillation. The upper atmosphere is fundamentally different from the lower atmosphere because it is a weakly ionized plasma and, consequently, reacts to drivers from above (the magnetospheric electric field) and wave and tidal forcing from the stratosphere and mesosphere. Because of this the timescales for changes are much shorter than in the lower atmosphere and a purely dynamical description is not adequate. Measurements from many local solar times are required in order to characterize the normal variability in the upper atmosphere. Recent advances in the maturity and development of microelectromechanical systems (MEMS) for sensor and spacecraft component applications have enabled new capabilities for advancing space weather understanding. In this paper the development of an integrated solution by JHU/APL will be discussed. Details will be provided regarding the range of potential science objectives, enabling sensor technologies, triple-cubesat (< 5kg) and nanosatellite (< 50kg) system design, launch, and mission operations.

Rogers, A. Q.; Paxton, L. J.; Darrin, A.

2009-12-01

336

Integrating Earth System Science Data Into Tribal College and University Curricula  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

337

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

NASA Astrophysics Data System (ADS)

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.

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

2004-12-01

338

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

NASA Astrophysics Data System (ADS)

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.

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

339

The WADA Proficiency Testing Program as an integral part of the fight against doping in sport  

Microsoft Academic Search

This article provides a brief perspective of the World Anti-Doping Agency (WADA) in the context of the fight against doping\\u000a in sport and of the WADA Proficiency Testing Program as an essential element of the World Anti-Doping Program. The WADA Proficiency\\u000a Testing Program exists within the framework of the WADA-accredited laboratories and is aimed at improving the effectiveness\\u000a of the

Victoria Ivanova; Thierry Boghosian; Olivier Rabin

2007-01-01

340

Integrating EarthScope Research and Education on a National Scale  

Microsoft Academic Search

EarthScope's education and outreach mission is to ensure the EarthScope experiment creates as its legacy a public more knowledgeable and understanding of the scientific and societal contributions made by the EarthScope experiment and Earth science. It will fulfill this commitment by developing and disseminating products that utilize the data, models, technology and discoveries of EarthScope and that support existing education

M. K. Hall-Wallace; T. Boyd; G. Richard; K. Ellins; C. Meertens; S. Semken; J. Taber; M. Benthien; L. Wald; R. Marvinney

2002-01-01

341

Enhancing the phase stability and ionic conductivity of scandia stabilized zirconia by rare earth co-doping  

NASA Astrophysics Data System (ADS)

Effect of co-doping Yb, Gd and Ce in scandia stabilized zirconia (SSZ) on the phase stability, high temperature aging behavior and ionic conductivity was studied. Both binary (10 mol% SSZ) and the ternary (co-doped) compositions were found to be in single cubic phase in the as-processed condition. However, the binary composition exhibited the rhombohedral ? phase after sintering whereas the ternary compositions remained in the single cubic phase. The sintered pellets were aged at 900 C for 500 h in air to study the phase stability at high temperature. Transmission electron microscopy revealed that the aged samples of Yb and Gd co-doped compositions contain small amount of the tetragonal phase which resulted in considerable degradation in conductivity (more than 20%). The Ce co-doped sample, on the other hand, was in single cubic phase after aging and this ensured that conductivity reduction was minimal in this composition. The co-doped samples however, showed higher conductivity before and after aging compared to the binary composition. The rhombohedral ? phase was absent in all the co-doped ternary compositions even after high temperature aging.

Shyam Kumar, C. N.; Bauri, Ranjit

2014-05-01

342

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

NASA Astrophysics Data System (ADS)

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.

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

343

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

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

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

2014-05-19

344

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

345

Density-functional study on the robust ferromagnetism in rare-earth element Yb-doped SnO2  

NASA Astrophysics Data System (ADS)

So far, little has been known about the ferromagnetism induced by pf hybridization. We investigate the magnetic properties of Yb-doped SnO2 by first-principles calculations. We find that the doped system favors the ferromagnetic state and a room-temperature ferromagnetism can be expected in it. The origin of ferromagnetism can be attributed to the pf hybridization between Yb impurity and its surrounding oxygen atoms. The formation energy of defect complex is calculated and the magnetic mediation of intrinsic vacancies is studied. Our results reveal that the formation energy of the defect complex with Sn vacancy is about 7.3 eV lower in energy than that with oxygen vacancy. This means Sn vacancy is much easier to form than oxygen vacancy in the presence of Yb substitution. The ferromagnetism of the doped system is greatly enhanced in the presence of Sn vacancies.

Zhang, Kai-Cheng; Li, Yong-Feng; Liu, Yong; Chi, Feng

2014-06-01

346

Infrared-to-visible upconversion of rare-earth doped glass ceramics containing CaF 2 crystals  

Microsoft Academic Search

Oxy-fluoride glass ceramics containing CaF2 crystals doped with YbF3LnF3 (Ln=Er, Tm) were prepared by heat-treatment from SiO2Al2O3CaOCaF2 glasses. The upconversion emission spectra of Er3+ and Tm3+ ions in the visible range were measured by 970nm pumping. In the spectrum of the Er doped sample, 540nm upconversion band due to the 4S3\\/24I15\\/2 and 660nm band due to the 4F9\\/24I15\\/2 were observed.

Yuki Kishi; Setsuhisa Tanabe

2006-01-01

347

Integrated ray tracing simulation of annual variation of spectral bio-signatures from cloud free 3D optical Earth model  

NASA Astrophysics Data System (ADS)

Understanding the Earth spectral bio-signatures provides an important reference datum for accurate de-convolution of collapsed spectral signals from potential earth-like planets of other star systems. This study presents a new ray tracing computation method including an improved 3D optical earth model constructed with the coastal line and vegetation distribution data from the Global Ecological Zone (GEZ) map. Using non-Lambertian bidirectional scattering distribution function (BSDF) models, the input earth surface model is characterized with three different scattering properties and their annual variations depending on monthly changes in vegetation distribution, sea ice coverage and illumination angle. The input atmosphere model consists of one layer with Rayleigh scattering model from the sea level to 100 km in altitude and its radiative transfer characteristics is computed for four seasons using the SMART codes. The ocean scattering model is a combination of sun-glint scattering and Lambertian scattering models. The land surface scattering is defined with the semi empirical parametric kernel method used for MODIS and POLDER missions. These three component models were integrated into the final Earth model that was then incorporated into the in-house built integrated ray tracing (IRT) model capable of computing both spectral imaging and radiative transfer performance of a hypothetical space instrument as it observes the Earth from its designated orbit. The IRT model simulation inputs include variation in earth orientation, illuminated phases, and seasonal sea ice and vegetation distribution. The trial simulation runs result in the annual variations in phase dependent disk averaged spectra (DAS) and its associated bio-signatures such as NDVI. The full computational details are presented together with the resulting annual variation in DAS and its associated bio-signatures.

Ryu, Dongok; Kim, Sug-Whan; Kim, Dae Wook; Lee, Jae-Min; Lee, Hanshin; Park, Won Hyun; Seong, Sehyun; Ham, Sun-Jeong

2010-08-01

348

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

349

Thermoluminescent response of rare earth doped nanocrystalline Ba0.97Ca0.03SO4  

NASA Astrophysics Data System (ADS)

The effects of Ce co-doping on the thermoluminescence (TL) characteristics of nanocrystalline Ba0.97Ca0.03SO4:Eu phosphor are studied. Formation of the compound and particle size was confirmed by XRD with particle size around 45 nm. The Eu doped phosphor has a simple TL glow curve structure with a single prominent peak at around 187C with a small hump at around 250C. Ce co-doping, decreases the TL intensity considerably, though the shape of the glow curve remains same. The photoluminescence (PL) emission spectrum has been examined and studied for the Co-doped sample to get an insight into the emission mechanism of the phosphor which involves transfer of energy from Eu2+ to Ce3+ to examine the decrease in peak intensity of the phosphor. The TL response for different doses has also been reported to check the linearity range and it is found that the phosphor is quite suitable for use in dosimetry of ionizing radiations.

Bahl, Shaila; Lochab, S. P.; Pandey, Anant; Kumar, Pratik

2013-02-01

350

Hydrothermal synthesis and luminescence behavior of rare-earth-doped NaLa(WO{sub 4}){sub 2} powders  

SciTech Connect

NaLa(WO{sub 4}){sub 2} powders doped with Eu{sup 3+}, Nd{sup 3+}, and Er{sup 3+} have been synthesized by a mild hydrothermal method and a crystal of exclusive scheelite phase could be obtained at low temperature. From the spectrum of Eu{sup 3+} it has been concluded that the dopant Eu{sup 3+} ion occupies a La{sup 3+} site and mainly takes the site with C{sub 2} symmetry. The higher quenching concentration can be observed in the Eu{sup 3+}-doped NaLa(WO{sub 4}){sub 2} powders. The Er{sup 3+}- and Nd{sup 3+}-doped NaLa(WO{sub 4}){sub 2} powders exhibit luminescence in the near infrared (Er{sup 3+} at 1550nm, and Nd{sup 3+} at 1060nm). The transition mechanism of the up-conversion luminescence of the Er{sup 3+}-doped NaLa(WO{sub 4}){sub 2} powders can be ascribed to two photons absorption process.

Wang Feng [Institute of Inorganic Materials, Department of Materials Science and Engineering, Zhejiang University, No. 38, Zheda Road, Hangzhou City, Zhejiang province 310027 (China); Fan Xianping [Institute of Inorganic Materials, Department of Materials Science and Engineering, Zhejiang University, No. 38, Zheda Road, Hangzhou City, Zhejiang province 310027 (China)]. E-mail: fanxp@cmsce.zju.edu.cn; Pi Daibo [Institute of Inorganic Materials, Department of Materials Science and Engineering, Zhejiang University, No. 38, Zheda Road, Hangzhou City, Zhejiang province 310027 (China); Wang Zhiyu [Institute of Inorganic Materials, Department of Materials Science and Engineering, Zhejiang University, No. 38, Zheda Road, Hangzhou City, Zhejiang province 310027 (China); Wang Minquan [Institute of Inorganic Materials, Department of Materials Science and Engineering, Zhejiang University, No. 38, Zheda Road, Hangzhou City, Zhejiang province 310027 (China)

2005-03-15

351

Synthesis and Characterization of Alkaline-Earth Metal (Ca, Sr, and Ba) Doped Nanodimensional LaMnO3 Rare-Earth Manganites  

NASA Astrophysics Data System (ADS)

The substitution of divalent cations of alkaline-earth elements in nanodimensional structures of rare-earth manganites produces advanced materials with potential electrical and magnetic functionalities. A systematic investigation of La0.65A0.35MnO3 (A = Ca, Sr, Ba) materials synthesized with a modified citrate route adopting ethanol dehydration has been undertaken. The structural and morphological analyses are carried out by using x-ray diffraction and scanning electron microscopy, respectively. Resistivity measurements are performed in variation with temperature to study the electrical transport properties which are found to vary with the size of the A-site cationic radius. Room temperature magnetic measurements are carried out to investigate the type of magnetic phase present in materials. The stability of the magnetic phase and coercivity are found to be dependent on the size of nanocrystallites.

Asma, Khalid; Saadat, Anwar Siddiqi; Affia, Aslam

2013-07-01

352

Dual function of rare earth doped nano Bi2O3: white light emission and photocatalytic properties.  

PubMed

Undoped Bi(2)O(3) and single and double doped Bi(2)O(3) : M (where M = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS, diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have a rod-like shape. Energy transfer was observed from host to the dopant ions. Characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. Interestingly, the Commission International de l'Eclairage (CIE) coordinates of the double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods lie in the white light region of the chromaticity diagram and it has a quantum efficiency of 51%. The undoped Bi(2)O(3) showed a band gap of 3.98 eV which is red shifted to 3.81eV in the case of double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods. The photocatalytic activities of undoped nano Bi(2)O(3) and double doped nano Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) were evaluated for the degradation of Rhodamine B under UV irradiation of 310 nm. The results showed that Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) had better photocatalytic activity compared to undoped nano Bi(2)O(3). The evolution of CO(2) was realized and these results indicated the continuous mineralization of rhodamine B during the photocatalytic process. Thus double doped Bi(2)O(3) : Eu(3+)(0.8%) : Tb(3+)(1.2%) nanorods can be termed as a bifunctional material exhibiting both photocatalytic properties and white light emission. PMID:22791072

Dutta, Dimple P; Roy, Mainak; Tyagi, A K

2012-09-14

353

Luminescence properties of B2O3-GeO2-Gd2O3 scintillating glass doped with rare-earth and transition-metal ions  

NASA Astrophysics Data System (ADS)

Novel B2O3-GeO2-Gd2O3 ternary scintillating glasses doped with 1 mol% rare-earth and transition-metal activators were synthesized by melt-quenching method. Their transmittance, photoluminescence (PL) and X-ray excited luminescence (XEL) spectra were investigated. The results suggest that a high content of Gd2O3 is of significance for designing dense glass with density of 6.0 g/cm3. And energy transfer from Gd3+ to the incorporated activators can be realized in the borogermanate glasses. The emission position and decay time can be efficiently tuned by incorporating various kinds of activators. All results imply the developed borogermanate scintillating glass is potential for scintillating fields.

Sun, Xin-Yuan; Jiang, Da-Guo; Wang, Wen-Feng; Cao, Chun-Yan; Li, Yu-Nong; Zhen, Guo-Tai; Wang, Hong; Yang, Xin-Xin; Chen, Hao-Hong; Zhang, Zhi-Jun; Zhao, Jing-Tai

2013-07-01

354

Synthesis and characterization of A-site deficient rare-earth doped BaZr xTi 1- xO 3 perovskite-type compounds  

NASA Astrophysics Data System (ADS)

A-site deficient rare-earth doped BaZr xTi 1- xO 3 (BZT) ceramics were prepared from a soft-chemistry route and by solid-state reaction (SSR). Perovskite-like single-phase diagrams for the BaTiO 3-La 2/3TiO 3-BaZrO 3 system were constructed for each method of synthesis. Infrared spectroscopy on (Ba 1- yLa 2 y/3 )Zr xTi 1- xO 3 solid solution revealed a dramatic stress on the M-O (M = Ti, Zr) bonds due to the combined effect of A-site vacancies and the lower ionic radius of La 3+ than that of Ba 2+. A relationship between the M-O stretching vibration ( ?) and the tolerance factor ( t) was determined. (Ba 1- yLn 2 y/3 )Zr 0.09Ti 0.91O 3 (Ln = La, Pr, Nd) samples synthesized by SSR were selected for detailed studies. X-ray diffraction data were refined by the Rietveld method. Scanning electron microscopy on sintered compacts detected abnormal crystal growth and grain sizes in the range of about 1 ?m up to 10 ?m when the dopant concentration is 6.7 at. %. Impedance measurements exhibited that ferroelectric to paraelectric phase-transition temperature shifted to lower values as increasing rare-earth content. (Ba 1- yLn 2 y/3 )Zr 0.09Ti 0.91O 3 system showed a diffuse phase transition with a relaxor-like ferroelectric behaviour. Furthermore, the dielectric constant was enhanced with respect to non-doped BZT system.

Ostos, C.; Mestres, L.; Martnez-Sarrin, M. L.; Garca, J. E.; Albareda, A.; Perez, R.

2009-05-01

355

Refluxing synthesis, photoluminescence and binding ability to deoxyribonucleic acid of water-soluble rare earth ion-doped LaF3 nanoparticles.  

PubMed

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

Wang, Zhenling; Zhang, Yi; Li, Chunyang; Zhang, Xinlei; Chang, Jiazhong; Xie, Jianping; Li, Chengwei

2014-06-01

356

Influence of Rare Earth Ho3+ Doping on Structural, Microstructure and Magnetic Properties of ZnO Bulk and Thin Film Systems  

NASA Astrophysics Data System (ADS)

We have investigated the doping behavior of rare earth element holmium (Ho3+) in ZnO semiconductor. The structural, microstructure, and magnetic properties of Zn1-xHoxO (x=0.0, 0.04, and 0.05) thin films deposited on Si(100) substrate by thermal evaporation technique were studied. The ceramic targets were prepared by conventional solid state ceramic technique. The pallets used as target were final sintered at 900 C in the presence of N2 atmosphere. The experimental results of X-ray diffraction (XRD) spectra, surface morphology, and magnetic properties show that the Ho3+ doped ZnO thin films has a strong influence on the materials properties. The higher angle shift in peak position and most preferred (101) orientation were observed in XRD pattern. These spectra confirmed the substitution of Ho3+ in ZnO lattice. The surface morphology and stoichiometry for both bulk and thin films were analyzed by scanning electron microscopy and energy dispersive spectroscopy. It was observed that grain size decreases with the increase of Ho3+. Room temperature ferromagnetism was observed for Zn0.95Ho0.05O films. The ferromagnetism might be attributed to the substitution of Ho ions for Zn2+ in ZnO lattices.

Murtaza Rai, Ghulam; Azhar Iqbal, Muhammad; Xu, Yongbing; Will, Iain Gordon; Zhang, Wen

2011-06-01

357

Two-Photon Excited Fluorescence in Rare-Earth Doped Optical Fiber for Applications in Distributed Sensing of Temperature  

Microsoft Academic Search

Distributed temperature sensing based on time-cor- related two-photon excited fluorescence (TPF) in doped optical fiber is described. Counter-propagating laser pulses generate a TPF flash at the position of their overlap which is scanned along the fiber by a variable relative time delay. The flash is transmitted to one end where it is detected and analyzed to yield the temperature from

Craig J. Dalzell; Thomas P. J. Han; Ivan S. Ruddock; David B. Hollis

2012-01-01

358

Rare-earth doped gadolinia based phosphors for potential multicolor and white light emitting deep UV LEDs  

NASA Astrophysics Data System (ADS)

Gadolinium oxide host and europium/dysprosium/terbium doped gadolinium oxide nanoparticles were synthesized using the sonochemical technique. Gadolinium oxide nanocrystals were also co-doped with total 2 mol% of Eu3+/Dy3+,Eu3+/Tb3+,Dy3+/Tb3+, and also Eu3+/Dy3+/Tb3+ ions, by the same method. The nanoparticles obtained were characterized using powder x-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. The size of the particles ranged from 15 to 30 nm. The triple doped samples showed multicolor emission on single wavelength excitation. The photoluminescence results were correlated with the lifetime data to get an insight into the luminescence and energy transfer processes taking place in the system. On excitation at 247 nm, the novel nanocrystalline Gd2O3:RE (RE = Dy, Tb) phosphor resulted in having very impressive CIE chromaticity coordinates of x = 0.315 and y = 0.316, and a correlated color temperature of 6508 K, which is very close to standard daylight.

Bedekar, Vinila; Dutta, Dimple P.; Mohapatra, M.; Godbole, S. V.; Ghildiyal, R.; Tyagi, A. K.

2009-03-01

359

Incorporating Stakeholder Decision Support Needs into an Integrated Regional Earth System Model  

SciTech Connect

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.

Rice, Jennie S.; Moss, Richard H.; Runci, Paul J.; Anderson, K. L.; Malone, Elizabeth L.

2012-03-21

360

The Svalbard Integrated Arctic Earth Observing System (SIOS) ESFRI Initiative - A possible future cornerstone of European Arctic research  

NASA Astrophysics Data System (ADS)

The Norwegian initiative "Svalbard Integrated Arctic Earth Observing System (SIOS) was included in the Revised Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) in 2009; an application to perform a preparatory phase project is currently under evaluation. The main aim of the SIOS initiative is to establish an Earth System observation platform in the European Arctic that is capable to match the whole scope of Earth System Models (ESM) on the observational side, ranging from solar/space-terrestrial interaction via atmosphere-ocean land-cryosphere coupling at the ground to geosphere-biosphere coupling. To this end, it is planned to integrate and upgrade all Arctic research stations on- and offshore in the Svalbard region which are currently operated by 15 nations, both European and worldwide. The initiative will also include the comprehensive marine and airborne monitoring and research activities and utilize the easy access to remote sensing data emerging from the satellite receiving activities at Longyearbyen. The already very comprehensive activity - though with limited international coordination - on Svalbard preconditions, as a first step, a thorough gap analysis of existing infrastructure in light of the needs of the modeling community and a careful design of the future overarching infrastructure. The interdisciplinary scientific character of SIOS makes the initiative well-suited to serve as a catalyser and integrator of the environmental ESFRI initiatives in the Arctic, while the truly global composition of the consortium may serve as a model for the envisaged pan-Arctic observing system SAON.

Hansen, Georg H.; Refsnes, Karin

2010-05-01

361

Preparation and up-conversion fluorescence of rare earth (Er{sup 3+} or Yb{sup 3+}/Er{sup 3+})-doped TiO{sub 2} nanobelts  

SciTech Connect

Anatase TiO{sub 2} nanobelts doped with rare earth (RE) ions Yb{sup 3+}, Er{sup 3+} or Yb{sup 3+}/Er{sup 3+} have been prepared using layered titanate nanobelts (LTO NBs) with RE ions as the precursor obtained by ion-exchange between LTO NBs and RE ions under hydrothermal process. Various measurement results demonstrate that the RE ions have doped into the lattice of TiO{sub 2}, and the Er{sup 3+} or Yb{sup 3+}/Er{sup 3+} doped nanobelts show strong visible up-conversion (UC) fluorescence under 980 nm excitation. The UC emission intensity of LTO NBs embedded with Er{sup 3+} or Yb{sup 3+}/Er{sup 3+} is slightly higher than that of the corresponding TiO{sub 2} nanobelts doped with RE ions, whereas higher RE doping content leads to the decrease of UC emission intensity due to the concentration-quenching effect. - Graphical abstract: Anatase TiO{sub 2} nanobelts doped with Er{sup 3+} or Yb{sup 3+}/Er{sup 3+} cations were simply synthesized using two-step preparation proceedings of ion-exchange and hydrothermal treatment, and their upconversion emissions were also investigated. SEM images of TiO{sub 2} nanobelts (NBs) doped with Er{sup 3+} (the left) and codoped with Yb{sup 3+}/Er{sup 3+} (the right).

Ji Tianhao, E-mail: jitianhao@th.btbu.edu.c [College of Chemical and Environmental Engineering, Beijing Technology and Business University, 11 Fucheng Road, Beijing 100048 (China); Liu Yang; Zhao Hui; Du Haiyan; Sun Jiayue [College of Chemical and Environmental Engineering, Beijing Technology and Business University, 11 Fucheng Road, Beijing 100048 (China); Ge Guanglu [National Center for Nanoscience and Technology, Beijing 100190 (China)

2010-03-15

362

Advancing Access, Attribution, and Integration of Earth & Ocean Science Data: Integrated Services of the Marine Geoscience Data System and the Geoinformatics for Geochemistry Program  

NASA Astrophysics Data System (ADS)

Development and operation of digital data collections are needed across all areas of the earth and ocean sciences to ensure access and preservation of data sets collected in support of earth and ocean sciences in order to maximize the return on research investments, while enabling verification of research results and contributing to new science initiatives. This is particularly true for data sets that are acquired at high cost, particularly in the marine environment, and that contain irreplaceable observations made of earths dynamic properties. The Marine Geoscience Data System (MGDS, www.marine-geo.org) and the Geoinformatics for Geochemistry Program (GfG, www.geoinfogeochem.org) have over the past decade developed, maintained, and operated community-driven data collections that support the preservation, discovery, retrieval, and analysis of a wide range of observational field and analytical data types from the marine and terrestrial environments, among them the PetDB database, the EarthChem data network, the Ridge2000 and MARGINS databases, the Antarctic and Southern Ocean Data System (ASODS), the Global Multi Resolution Topography Synthesis, and the System for Earth Sample Registration (SESAR). MGDS and GfG systems have been developed based on an active understanding of the practices, needs, and concerns of their user communities. They have engaged investigators in the design of the systems, seeking their feedback, and educating the community about responsibilities and benefits of scientific data management and sharing, and worked with funding agencies, editors, publishers, professional societies, and researchers to achieve broad community support, to proactively drive the development of community standards and best practices for data submission, data publication, data documentation, and data archiving, and to advance implementation. In a new formal partnership named IEDA (Integrated Earth Data Applications), the MGDS and GfG will be funded by the US National Science Foundation under a Cooperative Agreement to continue the operation of all MGDS and GfG data systems, while providing new integrated data services that will substantially enhance the utility of all data collection components, and improve data curation, interoperability and efficiency of operations. These will include an on-line service to improve ease of data submission across our user communities, a data publication service for scientists to publish their datasets with citable universal identifiers (DOIs), partnerships with institutions to ensure long-term archiving of data holdings, an authentication service for single sign-on to all systems, and operational services for shared vocabularies and to ease registration of common expeditions and geochemical datasets across our two systems.

Lehnert, K. A.; Carbotte, S. M.; Ferrini, V.; Arko, R. A.; Chan, S.; Ryan, W. B.

2010-12-01

363

Empowering Rural Appalachian Youth Through Integrated Inquiry-based Earth Science  

NASA Astrophysics Data System (ADS)

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.

Cartwright, T. J.; Hogsett, M.

2009-05-01

364

Space-Based Sensor Web for Earth Science Applications: An Integrated Architecture for Providing Societal Benefits  

NASA Technical Reports Server (NTRS)

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.

Habib, Shahid; Talabac, Stephen J.

2004-01-01

365

Double Rare-Earth Oxides Co-doped Strontium Zirconate as a New Thermal Barrier Coating Material  

NASA Astrophysics Data System (ADS)

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.

Ma, Wen; Wang, Dongxing; Dong, Hongying; Lun, Wenshan; He, Weiyan; Zheng, Xuebin

2013-03-01

366

Surface effect of nanocrystals doped with rare-earth ions enriched on surface and its application in upconversion luminescence  

NASA Astrophysics Data System (ADS)

By employing a certain proportion of hydrogen peroxide, ammonia, ammonium fluoride, and ethylene diamine tetraacetic acid (EDTA) as precipitator, well-crystallized LaOF:Eu3+ and LaOF:Yb3+, Er3+ nanocrystals are synthesized by using the chemical co-precipitation method. The structural properties of these samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) spectra. The results show that all the samples have an average size below 70 nm, which decreases gradually with the increase of the EDTA content, and a certain number of EDTA molecules are coupled with doped ions on the surfaces of nanocrystals. Most of the doped ions are proved to be enriched on the surfaces of nanocrystals and surrounded by the high energy vibration groups and bonds in EDTA molecules. The observed differences in upconversion emission spectrum among the different LaOF:Yb3+, Er3+ nanocrystals are explained by the different two-photon upconversion mechanisms. Especially, in the LaOF:Yb3+, Er3+ nanocrystals with EDTA, the two-photon processes that contain several special cross-relaxation processes are introduced to analyse the corresponding upconversion mechanisms.

He, En-Jie; Liu, Ning; Zhang, Mao-Lian; Qin, Yan-Fu; Guan, Bang-Gui; Li, Yong; Guo, Ming-Lei

2012-07-01

367

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)

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.

Low, R.; Gosselin, D. C.; Haney, C.; Larson-Miller, C.; Bonnstetter, R.; Mandryk, C.

2012-12-01

368

Expedition Earth and Beyond: Engaging Classrooms in Student-Led Research Using NASA Data, Access to Scientists, and Integrated Educational Strategies  

Microsoft Academic Search

Expedition Earth and Beyond, facilitated by the ARES Education Program at NASA JSC, is designed to help teachers promote student-led classroom research by using NASA data, providing access to scientists and using integrated educational strategies.

P. V. Graff; W. L. Stefanov; K. J. Willis; S. Runco; T. McCollum; M. Baker; C. Lindgren; M. Mailhot

2011-01-01

369

38.5% optical-to-optical efficiency neodymium-doped yttrium vanadate/magnesium-oxide-doped periodically poled lithium niobate integrated green module with watt-level output power for laser display applications  

NASA Astrophysics Data System (ADS)

In this paper, 1.15 W linearly polarized continuous-wave green laser is achieved from a novel neodymium-doped yttrium vanadate/magnesium-oxide-doped periodically poled lithium niobate (Nd:YVO4/MgO:PPLN) integrated packaging module (namely, mGreen) with an optical-to-optical efficiency as high as 38.5%. The presented package module is designed for mass production of green lasers at low cost to overcome the "Green" bottleneck in laser display industry.

Gan, Yi; Lu, Yang; Xu, Qing-yang; Xu, Chang-qing

2012-11-01

370

Time-resolved luminescent VUV-spectroscopy of pure and doped by rare earth ions crystals of strontium fluoride  

NASA Astrophysics Data System (ADS)

The spectroscopic properties SrF 2-Eu(1%), SrF 2-Er(1%) and nominal pure SrF 2 crystals have been studied using time-resolved vacuum ultraviolet (VUV) spectroscopy under pulsed synchrotron radiation excitation. The 4f k?4f k-15d (f-d) and 4f k?4f k (f-f) excitation spectra and emission spectra (with and without of time resolution) have been investigated in the wide energy region at 8 and 295 K. Moreover, the emission and excitation behaviors of intrinsic luminescence SrF 2 have been studied at 8 K, when the fast and slow components given by singlet and triplet relaxation of self-trapped excitons (STE) are observed. Special attention is devoted to VUV emission of Er 3+-doped SrF 2 due to spin-allowed and spin-forbidden 4f 105d?4f 11 transitions.

Ivanovskikh, K. V.; Pustovarov, V. A.; Shulgin, B. V.

2005-05-01

371

Monolithically integrated dye-doped PDMS long-pass filters for disposable on-chip fluorescence detection.  

PubMed

We report the fabrication of high quality monolithically integrated optical long-pass filters, for use in disposable diagnostic microchips. The filters were prepared by incorporating dye molecules directly into the microfluidic chip substrate, thereby providing a fully integrated solution that removes the usual need for discrete optical filters. In brief, lysochrome dyes were added to a poly(dimethylsiloxane) (PDMS) monomer prior to moulding of the microchip from a structured SU-8 master. Optimum results were obtained using 1 mm layers of PDMS doped with 1200 microg mL(-1) Sudan II, which resulted in less than 0.01% transmittance below 500 nm (OD 4), >80% above 570 nm, and negligible autofluorescence. These spectral characteristics compare favourably with commercially available Schott-glass long-pass filters, indicating that high quality optical filters can be straightforwardly integrated into the form of PDMS microfluidic chips. The filters were found to be robust in use, showing only slight degradation after extended illumination and negligible dye leaching after prolonged exposure to aqueous solutions. The provision of low cost high quality integrated filters represents a key step towards the development of high-sensitivity disposable microfluidic devices for point-of-care diagnostics. PMID:16874366

Hofmann, Oliver; Wang, Xuhua; Cornwell, Alastair; Beecher, Stephen; Raja, Amal; Bradley, Donal D C; Demello, Andrew J; Demello, John C

2006-08-01

372

Ultrathin Ca-PO4-CO3 solid-solution nanowires: a controllable synthesis and full-color emission by rare-earth doping.  

PubMed

It was found that calcium carbonate (CaCO(3)) and hydroxyapatite (Ca(10)(OH)(2)(PO(4))(6)), which are two crucial constituents of the most abundant minerals in nature and very important bioinorganic components in the tissues of mineralizing organisms, can form solid solutions in a wide range of PO(4)(3-)/CO(3)(2-) (P/C) ratios at low temperature when prepared as ultrathin nanowire structures. This is due to the special reactivity of ultrasmall nanocrystals, which can effectively lower the synthetic temperature and promote the formation of solid solutions. The as-prepared ultrathin nanowires with suitable P/C ratios presented strong blue luminescence due to the existence of abundant defects strengthened by CO(3)(2-). If used as the matrix, the as-prepared ultrathin nanowires demonstrated bright green or red luminescent properties when doped with Tb(3+) or Eu(3+) ions, and simultaneously retained their original morphologies. These three kinds of fluorescent nanowires could reproduce a full range of luminescence colors based on additive color mixtures of the three primary colors (red, green, and blue). In addition, under the same reaction system, ultrafine rare-earth-doped (Ce(3+), Tb(3+), Eu(3+)) nanowires (about 1 nm in diameter) were synthesized by using a one-step hydrothermal process, which further pushed the size of the Ca-PO(4)-CO(3) nanobuilding blocks to one unit cell region. These ultrafine nanowires displayed excellent film-forming properties and the ability to absorb UV radiation. PMID:22968988

Hui, Junfeng; Yu, Qiyu; Long, Yong; Zhang, Zhicheng; Yang, Yong; Wang, Pengpeng; Xu, Biao; Wang, Xun

2012-10-22

373

Use of Persistent Identifiers to link Heterogeneous Data Systems in the Integrated Earth Data Applications (IEDA) Facility  

NASA Astrophysics Data System (ADS)

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.

Hsu, L.; Lehnert, K. A.; Carbotte, S. M.; Arko, R. A.; Ferrini, V.; O'hara, S. H.; Walker, J. D.

2012-12-01

374

Observations from Integrated Ground Motion Using EarthScope's USArray Transportable Array  

NASA Astrophysics Data System (ADS)

Integrated Ground Motion (IGM) is a new method for visualizing and investigating long-term changes in seismic background levels. These new time series present an opportunity to evaluate variations in background seismic levels on intermediate time scales longer than those usually considered in processing seismic event data, but shorter than the time scales typically utilized when measuring the power spectral density (PSD) function of a seismic channel or instrument. Example uses for this new method include determining relationships between weather and seismic noise, detection of uncataloged small seismic and slow slip events, detection and characterization of remotely triggered seismicity, detection and monitoring of induced seismicity and detection of non-seismic signals. Here we apply the IGM processing method to broadband seismic data from the EarthScope USArray Transportable Array (TA) [www.usarray.org], and present some preliminary observations of the observed patterns in seismicity. We generate IGM time series from raw broadband seismic data by filtering and evaluating the envelope of a sliding time window. We further process the resulting IGM time series to remove peaks from short-duration seismic events by clipping the series at the 95th percentile value and normalizing each resulting series on a 0-1 scale. For this initial evaluation, we process IGM from overlapping 15-minute windows sampled every 5 minutes from four weeks of TA data for the western US in early 2008, bandpass filtering over four different ranges: 7-19 Hz, 1-8 Hz, 1-20 sec, and 20-100 sec. We create a series of animations overlaying the IGM values on a map of the western US and compressing the time scale to 2 hours/second. We observe that IGM in the 7-19 Hz and 1-8 Hz bands is primarily influenced by diurnal variations in background seismic levels, which generally overwhelm the signals from small (M<1.5) local earthquakes. Small earthquakes are somewhat more visible in the 1-8 Hz band. In our test data set, both the 1-8 Hz and 7-19 Hz IGM series also show a series of signal sources which appear to move at ~200 m/s and are visible over only a few stations; we speculate that these sources represent low-flying military test flights. IGM in the 1-20 second band appears to be influenced by a combination of local and teleseismic earthquakes plus large, long-term variations in background levels. Since this is the frequency band occupied by primary and secondary microseism, we hypothesize that the longer-term variations are mainly weather and oceanic wave related, and plan to test for correlation with weather and wave-height data. IGM in the 20-100 second band appears to be primarily related to large-magnitude (M>5) teleseismic events, although we observe some longer-term elevated IGM levels in the Pacific Northwest which may be due to either low-frequency slip events or oceanic winter storm-related noise sources.

West, J. D.; Fouch, M. J.

2012-12-01

375

Learning in the Middle School Earth Science Classroom: Students Conceptually Integrate New Knowledge Using Intelligent Laserdiscs.  

ERIC Educational Resources Information Center

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

Freitag, Patricia K.; Abegg, Gerald L.

376

Effect of rare-earth ion doping on the multiferroic properties of BiFeO3 thin films grown epitaxially on SrTiO3(1?0?0)  

NASA Astrophysics Data System (ADS)

High-quality epitaxial Bi1-xRExFeO3 (RE=La, Nd, Gd; x = 0, 0.05, 0.15) thin films were prepared on SrTiO3(1?0?0) substrates using pulsed laser deposition. X-ray diffraction and RBS-channelling spectroscopy showed that the films are single-phase perovskite, free of additional phases and textured with preferential orientation along the [1?0?0] direction. The dependences of magnetization on temperature and field showed that the films exhibit weak ferromagnetic properties. Among the studied rare-earth doping ions, Bi3+ substitution by Gd3+ most considerably enhanced the ferromagnetic properties. Substitution by La3+ smoothened out the surface morphology, which is important for different potential applications. Both undoped and doped films showed clear ferroelectric response in piezoresponse force microscopy, thus confirming their multiferroic nature. The doping was found to promote a preferential ferroelectric poling of the domains.

Lazenka, V. V.; Lorenz, M.; Modarresi, H.; Brachwitz, K.; Schwinkendorf, P.; Bntgen, T.; Vanacken, J.; Ziese, M.; Grundmann, M.; Moshchalkov, V. V.

2013-05-01

377

An integrative 'omics' solution to the detection of recombinant human erythropoietin and blood doping.  

PubMed

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

Pitsiladis, Yannis P; Durussel, Jrme; Rabin, Olivier

2014-05-01

378

Integrated porous-silicon light-emitting diodes: A fabrication process using graded doping profiles  

SciTech Connect

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.

Barillaro, G.; Diligenti, A.; Pieri, F.; Fuso, F.; Allegrini, M.

2001-06-25

379

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

NASA Astrophysics Data System (ADS)

We report on the enhancement in emission of NaYF4: Yb, Er upconverting nanoparticles (UCNPs) coated with a gold nanoshell. We have synthesized a doped NaYF4 core of 350 nm, with a sufficiently thick undoped NaYF4 shell of 65 nm thickness to minimize contact with the gold surface plasmons, and effectively minimizing luminescence quenching. Absorption and fluorescence emission measurements of single NaYF4 particles show enhanced absorption in the near infrared and a 1.5 times overall enhanced emission intensity. A relative increase in green/red emission was observed for both gold seed attachment and shell growth, of approximately 1.9 and 2.3 times respectively. Both Au seed attachment and shell growth has been shown to double the green/red emission ratio. The surface plasmon resonance of the UCNP core/Au shell composite is shown to be dependent on the gold shell thickness. Our experimental results are corroborated by finite element calculations.

Lim, Shuang; Li, Ling; Hallen, Hans

2013-03-01

380

Structural and luminescence investigations on Sm 3+ doped sodium fluoroborate glasses containing alkali/alkaline earth metal oxides  

NASA Astrophysics Data System (ADS)

Structural and luminescence behavior of the Sm 3+ doped 49B 2O 3+25 xCO 3+25NaF+1Sm 2O 3, (where x=Li 2, Na 2, K 2, Ca and Mg) glasses have been studied and reported. Structural analysis of the prepared glasses was made through FTIR spectra and their optical properties were studied using optical absorption, luminescence and lifetime measurements. The bonding parameters and the oscillator strengths were determined from the absorption spectra. These parameters have been used to obtain the Judd-Ofelt parameters. Using the Judd-Ofelt parameters, radiative properties such as transition probability ( A), stimulated emission cross section (?PE) and branching ratio's ( ?R) for the trivalent samarium ions corresponding to their 4G 5/2? 6H J ( J=5/2, 7/2, 9/2 and 11/2) excited state transitions have been calculated and reported. The decay curve of the 4G 5/2? 6H 7/2 transition exhibits non-exponential behavior. The non-exponential behavior has been attributed to the energy transfer through cross-relaxation between adjacent Sm 3+ ions. The lifetime of the 4G 5/2 level is found to be comparatively less than that of the reported Sm 3+ glasses and the same is due to the presence of OH groups, which is confirmed through the FTIR spectral studies.

Arul Rayappan, I.; Selvaraju, K.; Marimuthu, K.

2011-02-01

381

Optical properties of macroporous Y 3Al 5O 12 crystals doped with rare earth ions synthesized via sol-gel process from ionic precursors  

NASA Astrophysics Data System (ADS)

We have prepared macroporous Y 3Al 5O 12 (YAG) monoliths doped with rare earth (RE) ions (RE = Ce, Eu, Sm, and Pr) via the ionic precursor-derived sol-gel reaction accompanied by phase separation and investigated their fluorescence and scattering properties. YAG monoliths with well-defined bicontinuous macropores and skeletons were synthesized from the mixture of water and ethanol containing yttrium(III), aluminum(III), and RE(III) salts using propylene oxide as a gelation initiator and poly(ethylene oxide) as a phase separation inducer. X-ray diffraction measurements reveal that the sample as-dried and that heat-treated at 700 C are amorphous, while a single crystalline phase of YAG is precipitated in the samples heat-treated at temperatures between 800 and 1100 C. The macroporous YAG:RE ceramics heat-treated at 800 C and higher temperatures exhibit fluorescence due to 4f-5d (Ce 3+) and 4f-4f (Eu 3+, Sm 3+, Pr 3+) electronic transitions characteristic of the RE ions occupying the eight-coordinated dodecahedral sites in YAG lattice. Coherent backscattering experiments indicate that the scattering strength is enhanced by the densification of skeletons in macroporous YAG monoliths, depending on the heat treatment temperature.

Murai, Shunsuke; Fujita, Koji; Iwata, Koji; Tanaka, Katsuhisa

2010-12-01

382

Superconductivity of metal nitride chloride ?-MNCl (M = Zr, Hf) with rare-earth metal RE (RE = Eu, Yb) doped by intercalation  

NASA Astrophysics Data System (ADS)

Electrons were doped into the ?-form layered metal nitride chloride MNCl (M = Zr, Hf) by intercalation of rare-earth metals RE (RE = Eu, Yb) using liquid ammonia solutions. The intercalated compounds REx(NH3)yMNCl show superconductivity with transition temperatures Tc of 13 and 24.3 K for M = Zr and Hf, respectively, quite similar to the alkali metal intercalated analogs. The paramagnetic characteristics for Eu2+ and Yb3+ can coexist with superconductivity. The magnetic resistance measured on the uniaxially oriented Eu0.08(NH3)yHfNCl with the magnetic field parallel to the ab plane (? ab) and the c axis (? c) shows a strong anisotropic effect on the upper critical field Hc2; a large anisotropic parameter \\gamma ={H}_{{c}2}^{\\parallel a b}/{H}_{{c}2}^{\\parallel c}\\sim 4 suggests a pseudo-two-dimensional superconductivity. The Tc of Eu0.13(THF)yHfNCl is shifted toward a higher value of 25.8 K upon expansion of the interlayer spacing from 11.9 to 17.5 by co-intercalation of voluminous organic molecules such as tetrahydrofuran.

Zhang, Shuai; Tanaka, Masashi; Onimaru, Takahiro; Takabatake, Toshiro; Isikawa, Yosikazu; Yamanaka, Shoji

2013-04-01

383

Dielectric and nonlinear current-voltage characteristics of rare-earth doped CaCu3Ti4O12 ceramics  

NASA Astrophysics Data System (ADS)

CaCu3Ti4O12 (CCTO) ceramics doped with rare earth (RE) oxides, including Y2O3, La2O3, Eu2O3, and Gd2O3, were prepared by the traditional solid-state reaction method in order to investigate the effect of RE oxide dopants on the electrical properties as a varistor. The phase identification and morphology of the ceramics were investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. A high voltage measuring unit and precision impedance analyzer were used to determine the nonohmic (J-E) behaviors and measure the dielectric properties and impedance spectroscopy of the ceramics, respectively. The results showed that RE oxides enhanced greatly the breakdown electric flied but reduced the nonlinear coefficient and the mean grain size of CCTO ceramics. There was a good linear relationship between ln J and E1/2, which demonstrated that the Schottky barrier should exist at the grain boundary. A double Schottky barrier model composed of a depletion layer and a negative charge sheet was proposed, analogous to the barrier model for ZnO varistors. The depletion layer width determined by diffusion distance of RE ions and the effective surface states played important roles on the electrical properties of the ceramics.

Liu, Laijun; Fang, Liang; Huang, Yanmin; Li, Yunhua; Shi, Danping; Zheng, Shaoying; Wu, Shuangshuang; Hu, Changzheng

2011-11-01

384

Fabrication and Characterization of Fluorescent Rare-Earth-Doped Glass-Particle-Based Tips for Near-Field Optical Imaging Applications  

NASA Astrophysics Data System (ADS)

Fluorescent rare-earth-doped glass particles glued to the end of an atomic force microscope tip have been used to perform scanning near-field optical measurements on nanostructured samples. The fixation procedure of the fluorescent fragment at the end of the tip is described in detail. The procedure consists of depositing a thin adhesive layer on the tip. Then a tip approach is performed on a fragment that remains stuck near the tip extremity. To displace the particle and position it at the very end of the tip, a nanomanipulation is achieved by use of a second tip mounted on piezoelectric scanners. Afterward, the particle size is reduced by focused ion beam milling. These particles exhibit a strong green luminescence where excited in the near infrared by an upconversion mechanism. Images obtained near a metallic edge show a lateral resolution in the 180-200-nm range. Images we obtained by measuring the light scattered by 250-nm holes show a resolution well below 100 nm. This phenomenon can be explained by a local excitation of the particle and by the nonlinear nature of the excitation.

Aigouy, Lionel; de Wilde, Yannick; Mortier, Michel; Girak, Jacques; Bourhis, Eric

2004-07-01

385

Calcium tetraboride-does it exist? Synthesis and properties of a carbon-doped calcium tetraboride that is isotypic with the known rare earth tetraborides.  

PubMed

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

Schmitt, Ruth; Blaschkowski, Bjrn; Eichele, Klaus; Meyer, H-Jrgen

2006-04-01

386

Integrated Borehole Geodetic and Seismic Networks: A Developing Tool for Earth Science  

Microsoft Academic Search

The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the continuous three-dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. A component of this observatory is a network of 78 borehole observatories consisting of some combination of borehole strainmeters, borehole

David Mencin; Mike Jackson; Kathleen Hodgkinson; Adrian Borsa

2010-01-01

387

Formation of an integrated holding company to produce rare-earth metal articles  

NASA Astrophysics Data System (ADS)

The possibility of formation of a Russian holding company for the production of rare-earth metal articles under conditions of its increasing demand on the world market is considered. It is reasonable to ensure stable business operation on the market under conditions of state-private partnership after the fraction of soled products is determined and supported by the competitive advantages of Russian products.

Bogdanov, S. V.; Grishaev, S. I.

2013-12-01

388

Integrated Earth Science Research in Deep Underground Science and Engineering Laboratories  

Microsoft Academic Search

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

J. S. Wang; T. C. Hazen; M. E. Conrad; L. R. Johnson; R. Salve

2004-01-01

389

Thermophysical Properties of Rare-Earth-Stabilized Zirconia and Zirconate Pyrochlores as Surrogates for Actinide-Doped Zirconia  

NASA Astrophysics Data System (ADS)

Thermophysical properties of rare-earth-stabilized zirconia and zirconate pyrochlores, A2Zr2O7 (A = La, Nd, Sm, Gd, Dy, Y), were evaluated by X-ray diffractometry, Raman spectroscopy, and the ultrasound pulse-echo method. Crystallographic analyses elucidated that La2Zr2O7, Nd2Zr2O7, Sm2Zr2O7, and Gd2Zr2O7 had the pyrochlore structure, whereas Dy2Zr2O7 and Y2Zr2O7 had the defect fluorite structure. For lanthanide pyrochlores, the thermal expansion became smaller with increasing ionic radius of A and increasing crystal binding energy. The elastic moduli and Debye temperature evaluated using longitudinal and transverse sound velocities also depend on the ionic radius and binding energy, and hence these values related to mechanical properties increase with the ionic radius of A. On the other hand, Poissons ratio was almost comparable among these pyrochlores. In addition, thermophysical properties of actinide pyrochlore are discussed in this study.

Shimamura, Keiichi; Arima, Tatsumi; Idemitsu, Kazuya; Inagaki, Yaohiro

2007-06-01

390

Towards an integrated model of Earth's crustal density structure: gravity and topography effects on global scale  

NASA Astrophysics Data System (ADS)

An accurate knowledge of the Earth's crustal density structure plays a central role in our understanding of its composition and thermal conditions and it is also crucial to obtain a correct seismic interpretation of the Earth's mantle. The goal this work is to improve our understanding of the crust's physical parameters using a multidisciplinary approach based on different kinds of geophysical and geodynamical observations and with a stress on the importance of mineral properties. Starting from the most updated and used global crustal model, CRUST 2.0 (Bassin et al., 2000), in which the density structure of the crust is inferred by interpreting data coming from seismic reflection profiles through Vp-density empirical relationship (Christensen and Mooney, 1995), we have explored the effect of phase transitions and different chemical compositions on the crust physical properties, surface topography and gravity potential field. Our first step is to compute the crustal density structure through a self-consistent thermodynamical modeling of average compositions for upper, middle and lower crust (Rudnick and Gao, 2003), taking in to account both anhydrous and hydrated conditions. This way, the relationship between Vp and density exploits further petrological constraints and knowledge of mineral properties. We also build a density model where we use a 3-D thermal structure based on heat-flow measurements. Subsequently we determine the influence on gravity, geoid and topography of the CRUST2.0 and the computed density distributions by using the same mantle structure. For this purpose, we perform an instantaneous mantle-flow computation using the code StagYY (Tackley, 2008). The comparison between computed results and measured data permitted us to assess the importance of taking into account information coming from mineral physics and gravity field measurements in order to produce a well constrained and physically reliable global crustal model. Our preliminary result shows the strong potential of such an interdisciplinary approach to study the Earth's interior.

Guerri, Mattia; Cammarano, Fabio; Tackley, Paul

2013-04-01

391

Integrating EarthScope Data Into Interactive Visualizations, Movies and High-Resolution Static Images  

NASA Astrophysics Data System (ADS)

What is EarthScope? The answer to this question can best be addressed through images, movies and interactive visualizations. Using these types of visual tools the temporal evolution and spatial scales of the various EarthScope data (e.g., earthquakes, sediment thickness, aquifers, focal mechanisms, topography, moho depth, mines, geology, magnetics, faults and gravity) can be more easily understood. Working with EarthScope researchers we have developed visualizations to assist with data quality (i.e., from SAFOD, USArray and PBO), hypothesis testing and the presentation of final results. Through this process we have identified 6 key areas of interest: (1) Depicting temporal evolution of data; (2) The ability to toggle on/off and color-code data sub-sets for complex high-density data; (3) Developing end-products that can be used as on-line supplements to journal articles; (4) Creating multi-use end-products that benefit researchers, emergency response personnel and education programs; (5) Quality assessing and geo-referencing newly collected data; and (6) Making difficult subjects more understandable. The visualizations we create can be accessed from our website (we get ~4,000 unique visitors to our pages each month) through the visual objects library at the Scripps Institution of Oceanography's Visualization Center (http://siovizcenter.ucsd.edu/library.php). These include 3D interactive visualizations, Quicktime movies and online tools and can be explored using freeware that runs on multiple platforms (e.g., Windows, Mac OS X, Linux, SGI Irix).

Kilb, D.

2008-12-01

392

Discover Earth  

NASA Technical Reports Server (NTRS)

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.

Steele, Colleen

1998-01-01

393

On an improved sub-regional water resources management representation for integration into earth system models  

SciTech Connect

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.

Voisin, Nathalie; Li, Hongyi; Ward, Duane L.; Huang, Maoyi; Wigmosta, Mark S.; Leung, Lai-Yung R.

2013-09-30

394

On an improved sub-regional water resources management representation for integration into earth system models  

NASA Astrophysics Data System (ADS)

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 options of not accounting for groundwater withdrawals, or on the contrary, of assuming that all remaining demand is met through groundwater extractions, are discussed.

Voisin, N.; Li, H.; Ward, D.; Huang, M.; Wigmosta, M.; Leung, L. R.

2013-03-01

395

Silica-based sol-gel films doped with active elements  

Microsoft Academic Search

The preparation of glassy films doped with rare earth ions is important for planar waveguide fabrication in active integrated optic devices. The sol-gel process is a promising route for the preparation of such films and the eventual overcoming of the problem of rare earth clustering. In the present work, both SiO2 and 90SiO2-10TiO2 films were prepared by spin coating on

R. M. Almeida; X. Orignac; D. Barbier

1994-01-01

396

Quantitative determination of site occupancy of multi-rare-earth elements doped into Ca{sub 2}SnO{sub 4} phosphor by electron channeling microanalysis  

SciTech Connect

X-ray fluorescence analysis based on electron channeling effects in transmission electron microscopy (TEM) was performed on Ca{sub 2}SnO{sub 4} phosphor materials doped with Eu{sup 3+}/Y{sup 3+} at various concentrations, which showed red photoluminescence associated with the {sup 5}D{sub 0}-{sup 7}F{sub 2} electric dipole transition of Eu{sup 3+} ions. The method provided direct information on which host element site dopant elements occupy, the results of which were compared with those of X-ray diffraction (XRD)-Rietveld analysis. The obtained results indicated that while it is not favorable for a part of Eu{sup 3+} to occupy the smaller Sn{sup 4+} site, this is still energetically better than creating Ca vacancies or any other of the possible charge balance mechanisms. The local lattice distortions associated with dopant impurities with different ionic radii were also examined by TEM-electron energy-loss spectroscopy (TEM-EELS). The change in PL intensity as a function of dopant concentration is discussed based on the experimental results, although the general concept of concentration quenching applies. - Abstract: The composition of Ca{sub 1.8}Eu{sub 0.2}Y{sub 0.2}Sn{sub 0.8}O{sub 4} determined by electron channeling microanalysis is graphically shown, where the rare-earth dopants, Eu and Y preferentially occupy the Ca and Sn sites, respectively, to maintain the local charge neutrality.

Fujimichi, Y. [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Muto, S., E-mail: s-mutoh@nucl.nagoya-u.ac.j [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Tatsumi, K. [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kawano, T.; Yamane, H. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan)

2010-09-15

397

Earth Observation Remote Sensing and GIS Services for Monitoring of Integration Systems  

Microsoft Academic Search

Today availability of using the high resolution of space imagery creates a positive environment on application of space technology for monitoring of integrated systems in different areas of industry and commercial purposes. They are an airborne, unmanned aerial vehicles (UAV) and satellite Synthetic Aperture Radar and LIDAR multi-spectral and hyper-spectral sensors. One of the advance methods of feasibility study of

S. Kurnaz; R. B. Rustamov

2007-01-01

398

Er-doped light emitting slot waveguides monolithically integrated in a silicon photonic chip.  

PubMed

An integrated erbium-based light emitting diode has been realized in a waveguide configuration allowing 1.54?m light signal routing in silicon photonic circuits. This injection device is based on an asymmetric horizontal slot waveguide where the active slot material is Er(3+) in SiO2 or Er(3+) in Si-rich oxide. The active horizontal slot waveguide allows optical confinement, guiding and lateral extraction of the light for on-chip distribution. Light is then coupled through a taper section to a passive Si waveguide terminated by a grating which extracts (or inserts) the light signal for measuring purposes. We measured an optical power density in the range of tens of ?W/cm(2) which follows a super-linear dependence on injected current density. When the device is biased at high current density, upon a voltage pulse (pump signal), free-carrier and space charge absorption losses become large, attenuating a probe signal by more than 60 dB/cm and thus behaving conceptually as an electro-optical modulator. The integrated device reported here is the first example, still to be optimized, of a fundamental block to realize an integrated silicon photonic circuit with monolithic integration of the light emitter. PMID:23449309

Ramrez, J M; Ferrarese Lupi, F; Berencn, Y; Anopchenko, A; Colonna, J P; Jambois, O; Fedeli, J M; Pavesi, L; Prtljaga, N; Rivallin, P; Tengattini, A; Navarro-Urrios, D; Garrido, B

2013-03-22

399

Er-doped light emitting slot waveguides monolithically integrated in a silicon photonic chip  

NASA Astrophysics Data System (ADS)

An integrated erbium-based light emitting diode has been realized in a waveguide configuration allowing 1.54 ?m light signal routing in silicon photonic circuits. This injection device is based on an asymmetric horizontal slot waveguide where the active slot material is Er3+ in SiO2 or Er3+ in Si-rich oxide. The active horizontal slot waveguide allows optical confinement, guiding and lateral extraction of the light for on-chip distribution. Light is then coupled through a taper section to a passive Si waveguide terminated by a grating which extracts (or inserts) the light signal for measuring purposes. We measured an optical power density in the range of tens of ?W/cm2 which follows a super-linear dependence on injected current density. When the device is biased at high current density, upon a voltage pulse (pump signal), free-carrier and space charge absorption losses become large, attenuating a probe signal by more than 60 dB/cm and thus behaving conceptually as an electro-optical modulator. The integrated device reported here is the first example, still to be optimized, of a fundamental block to realize an integrated silicon photonic circuit with monolithic integration of the light emitter.

Ramrez, J. M.; Ferrarese Lupi, F.; Berencn, Y.; Anopchenko, A.; Colonna, J. P.; Jambois, O.; Fedeli, J. M.; Pavesi, L.; Prtljaga, N.; Rivallin, P.; Tengattini, A.; Navarro-Urrios, D.; Garrido, B.

2013-03-01

400

An integrated study of earth resources in the state of California based on ERTS-1 and supporting aircraft data  

NASA Technical Reports Server (NTRS)

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.

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 investigators)

1972-01-01

401

Large-scale three-dimensional inversion of EarthScope MT data using the integral equation method  

NASA Astrophysics Data System (ADS)

In this paper we apply 3D inversion to MT data collected in the Northwestern United States as a part of the EarthScope project. By the end of 2009 MT data had been collected from 262 stations located throughout Oregon, Washington, Idaho, and most of Montana and Wyoming. We used data from 139 MT stations in this analysis. We developed fully parallelized rigorous 3D MT inversion software based on the integral equation method with variable background conductivity. We also implemented a receiver footprint approach which considerably reduced the computational resources needed to invert the large volumes of data covering vast areas. The data set used in the inversion was obtained through the Incorporated Research Institutions for Seismology (IRIS). The inversion domain was divided into 2.7 M cells. The inverted electrical conductivity distribution agrees reasonably well with geological features of the region.

Zhdanov, M. S.; Green, A.; Gribenko, A.; Cuma, M.

2010-08-01

402

MEOS Microsatellite Earth Observation using Miniature Integrated-Optic IR Spectrometers  

NASA Astrophysics Data System (ADS)

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

Kruzelecky, Roman

403

Path integral Monte Carlo study of SF6-doped helium clusters  

Microsoft Academic Search

The path-integral Monte Carlo technique is applied to study the SF6He39 cluster at low temperatures. The method employs as input only pair potentials, the number of atoms, and the temperature, and is thus independent of the trial function bias which can affect calculation of structural quantities in variational and diffusion Monte Carlo. We thereby obtain an unambiguous answer to the

Yongkyung Kwon; David M. Ceperley; K. Birgitta Whaley

1996-01-01

404

Preparation conditions and optical properties of rare earth ion (Er{sup 3+} and Eu{sup 3+})-doped alumina films by the aqueous sol{endash}gel method  

SciTech Connect

Transparent alumina and rare earth ion (Er{sup 3+} and Eu{sup 3+}) highly doped alumina films (15 mol%) were prepared by the aqueous sol{endash}gel method, in order to examine the effects of various preparation conditions on the structure and optical properties of doped films. The results showed that when the gel was heat treated, it lost free and bound water and was converted into the oxide by way of a series of intermediate phases although the oxide as a whole remained structureless. The thermogravimetric analysis curve showed a marked weight loss in the temperature range of 100{endash}500{degree}C and the slow loss continuing at higher temperature of 800{degree}C. High doping may reflect noncrystalline structure of alumina. The fluorescence of Eu{sup 3+} sensitive of microstructure increased especially corresponding to this weight loss with treatment. The {Omega}{sub 2} indicative of the asymmetric environment of Er{sup 3+} showed a similar increase. Concentration quenching for doped films treated at 800{degree}C was not significant in this concentration range. Lifetimes increased with increasing treatment temperature, similar to above increase. {copyright} 2001 American Institute of Physics.

Ishizaka, T.; Kurokawa, Y.

2001-07-01

405

Integrated Solid Earth Science: the right place and time to discover the unexpected? (Arthur Holmes Medal Lecture)  

NASA Astrophysics Data System (ADS)

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 Integrate

Cloetingh, Sierd

2013-04-01

406

The variation of the cryosphere in the Last Millennium simulation using integrated Earth System Model  

NASA Astrophysics Data System (ADS)

In this study, we analyze the result of Last Millennium (LM) Experiment using GCM and ESM, to verify the response of the cryosphere to the hundereds-year-scale climate change. In addition to the sensitivity analysis between the forcing conditions, comparison with existing climate/paleoclimate data. The period of the LM experiment covers the Little Ice Age and Medieval Climate Anomaly, and responses of the cryosphere during those periods are of interest. The models used in this study are the Atmosphere-Land-Ocean General Circulation Model MIROC and the Earth System Model MIROC-ESM. Resolution of atmosphere/land components are T42 (ca 2.8?) in horizontal, 80 layers in vertical. Ocean component has a resolution of 1.4? (longitude) by variable 0.56-1.4? (latitude) in the horizontal and 44 levels in the vertical. As an ESM, MIROC-ESM has a carbon-cycle components for the land and ocean ecosystems. Setup of the experiments follow the protocol of model inter-comparison CMIP5/PMIP3. As preliminary results, temporal variations in surface air temperature, snow amount, and snow/rain ratio for Siberia region was analyzed. Winter warming during 20th century is clear. Signatures are shown in rise of February Temperarure, decrease in snow amount, increase in runoff during spring. Ratio of snow fall over total precipitation is sensitive to the temperature, which may caused the above-mentioned trends in snow.

Sueyoshi, Tetsuo; Ohgaito, Rumi; Yamamoto, Akitomo; Chikamoto, Megumi O.; Hajima, Tomohiro; Okajima, Hideki; Yoshimori, Masakazu; Abe, Manabu; O'ishi, Ryota; Saito, Fuyuki; Watanabe, Shingo; Kawamiya, Michio; Abe-Ouchi, Ayako

2013-04-01

407

Integration of lessons from recent research for "Earth to Mars" life support systems  

NASA Astrophysics Data System (ADS)

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

Nelson, M.; Allen, J. P.; Alling, A.; Dempster, W. F.; Silverstone, S.; van Thillo, M.

408

Tunable Second Harmonic Generation in a Nd 3 + -Doped Fiber Laser Using a LiNbO 3Integrated MachZehnder  

Microsoft Academic Search

We report on a tunable neodymium-doped fiber laser using an intracavity lithium niobate-integrated tuner. The device is a low-voltage asymmetric LiNbO3MachZehnder interferometer working as a tunable spectral filter. Laser emission occurs simultaneously at two wavelengths, ?0=1088 nm and ?2=544 nm, due to the nonlinear properties of the crystal. The lasing wavelengths are tuned over ranges of 12 nm in the

Pascal Mollier; Henri Porte; Benoit Grappe; Jrme Hauden; Jean-Pierre Goedgebuer

1998-01-01

409