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1

Plasma synthesis of rare earth doped integrated optical waveguides  

SciTech Connect

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

Raoux, S.; Anders, S.; Yu, K.M.; Brown, I.G. [Lawrence Berkeley Lab., CA (United States); Ivanov, I.C. [Charles Evans & Associates, Redwood City, CA (United States)

1995-03-01

2

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

SciTech Connect

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

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

1996-09-01

3

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

4

Rare-earth-doped transparent glass ceramics  

Microsoft Academic Search

Glass ceramics are a known class of polycrystalline ceramic materials, where, depending on the glass matrix and the particular crystalline phases, one can obtain materials with improved mechanical, thermal, electrical or optical properties. The characteristics and applications of optical glass ceramics are reviewed, with particular emphasis on rare-earth-doped transparent glass ceramics for photonics, including the search for new transparent glass

M Clara Gonçalves; Luís F Santos; Rui M Almeida

2002-01-01

5

Luminescence in rare-earth-doped thiospinels  

Microsoft Academic Search

Narrow line optical absorption and emission spectra have been observed in Nd3+- and Er3+-doped In2S3, CdIn2S4, and ZnIn2S4. All three spectra show essentially the same structure, and this indicates that the rare-earth ions occupy the same type of environment in the three lattices. The sites most probably have octohedral symmetry, since electron spin resonance results show that the site for

M. Brown; W. Shand

1968-01-01

6

Mechanical Properties of Alkaline-Earth Doped Lanthanum Gallate  

SciTech Connect

Report on mechanical properties of Lanthanum Gallate. Lanthanum gallate doped with alkaline earths was prepared from combustion-synthesized powders. Mechanical properties of the doped gallates were evaluated as a function of composition and temperature.

Baskaran, Suresh; Lewinsohn, Charles A.; Chou, Y S.; Qian, Maoxu; Stevenson, Jeffry W.; Armstrong, Timothy R.

1999-08-01

7

Scintillation of rare earth doped fluoride nanoparticles  

SciTech Connect

The scintillation response of rare earth (RE) doped core/undoped (multi-)shell fluoride nanoparticles was investigated under x-ray and alpha particle irradiation. A significant enhancement of the scintillation response was observed with increasing shells due: (i) to the passivation of surface quenching defects together with the activation of the REs on the surface of the core nanoparticle after the growth of a shell, and (ii) to the increase of the volume of the nanoparticles. These results are expected to reflect a general aspect of the scintillation process in nanoparticles, and to impact radiation sensing technologies that make use of nanoparticles.

Jacobsohn, L. G.; McPherson, C. L.; Sprinkle, K. B.; Ballato, J. [Center for Optical Materials Science and Engineering Technologies (COMSET), and School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Yukihara, E. G. [Physics Department, Oklahoma State University, Stillwater, Oklahoma 74078-3072 (United States); DeVol, T. A. [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, South Carolina 29634-0905 (United States)

2011-09-12

8

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

9

Rare earth doped fibre for structural damage assessment  

Microsoft Academic Search

A technique that uses laser excited fluorescence in rare earth doped optical fibres to determine the location of structural damage is demonstrated. It has been shown experimentally that the position of a 'fracture' in a sensing erbium doped optical fiber can be evaluated by measuring the backward fluorescence power (BFP) from this erbium doped optical fiber (EDOF). This sensor can

N. Y. Fan; S. Huang; A. T. Alavie

1995-01-01

10

Magnetism of silicon doped with alkaline earth elements  

Microsoft Academic Search

It would be highly desirable to fashion spintronic materials based on silicon because of the vital importance of silicon in semiconductor technology. Since it is very difficult to experimentally dope transition metals into silicon, we explore the possibility of ferromagnetism in silicon doped with alkaline earth atoms using first-principle calculations. It is found that the energy needed for doping a

Bang-Gui Liu; Li-Jie Shi; Steven G. Louie

2005-01-01

11

Energetics of Rare-earth-doped Hafnia  

SciTech Connect

The enthalpies of formation of rare-earth (RE)-doped Hf{sub 1-}xRExO{sub 2-}x{sub /2} solid solutions (RE = Sm, Gd, Dy, Yb; x = 0.25 to 0.62) with respect to the oxide end members, monoclinic HfO{sub 2} and C-type REO{sub 1.5}, were determined using oxide melt solution calorimetry. The enthalpies of formation fit a function quadratic in composition. The strongly negative interaction parameters in all solid solutions confirm a strong tendency for short-range order. Though strongly negative for all systems, the interaction parameters become less negative with increasing ionic potential (decreasing RE radius). Crystallization energetics were investigated for amorphous coprecipitation products with x = 0.4. The energy difference between the crystalline (fluorite and pyrochlore) and amorphous phases decreases with decreasing dopant radius. This suggests that systems doped with small RE ions have more similar local structures in the fluorite and amorphous phases. These observations may result in a smaller kinetic barrier to recrystallization and account for the greater radiation resistance of materials with smaller RE cations.

Simoncic,P.; Navrotsky, A.

2007-01-01

12

Hydrothermal synthesis and characterization of rare earth doped ceria nanoparticles  

Microsoft Academic Search

Ceria (CeO2) and rare earth doped ceria (RE=Pr, Gd and Sm) of different doping concentration (10, 20 and 30mol%) were synthesized by hydrothermal synthesis method, achieving nano-particles with weak agglomeration. The nano-particles were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), BET specific surface area measurement and thermal analysis. The size of all doped nano-particles was in the range

A. I. Y. Tok; S. W. Du; F. Y. C. Boey; W. K. Chong

2007-01-01

13

Tunable, rare earth-doped solid state lasers  

DOEpatents

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

Emmett, John L. (Pleasanton, CA); Jacobs, Ralph R. (Livermore, CA); Krupke, William F. (Pleasanton, CA); Weber, Marvin J. (Danville, CA)

1980-01-01

14

Magnetism of silicon doped with alkaline earth elements  

NASA Astrophysics Data System (ADS)

It would be highly desirable to fashion spintronic materials based on silicon because of the vital importance of silicon in semiconductor technology. Since it is very difficult to experimentally dope transition metals into silicon, we explore the possibility of ferromagnetism in silicon doped with alkaline earth atoms using first-principle calculations. It is found that the energy needed for doping a calcium atom into silicon is approximately equivalent to the formation energy of a vacancy in silicon. Neither silicon nor any alkaline earth metal alone is magnetic, but our calculations indicate that ferromagnetism may be obtained by appropriately doping silicon with alkaline earth atoms such as calcium. This is intriguing for basic understanding of magnetism and for possible future applications.

Liu, Bang-Gui; Shi, Li-Jie; Louie, Steven G.

2005-03-01

15

Radiative and non-radiative processes in heteroepitaxial rare earth doped barium titanate thin films for photonic applications  

Microsoft Academic Search

Rare earth doped barium titanate thin films were investigated as a potential material for use as an infrared optical gain media in integrated optical and electro-optical applications. To obtain large optical amplification, high concentrations of radiatively active rare earth ions are necessary. Additionally, low absorptive and scattering losses in the thin films are required to maximize the gain. Metalorganic chemical

Gregory Matthew Ford

1998-01-01

16

Photosensitivity of rare-earth-doped ZBLAN fluoride glasses  

Microsoft Academic Search

We have performed experiments to elucidate the mechanism of photosensitivity in rare-earth-doped fluorozirconate (ZBLAN) glasses. Glasses doped with Ce, Tb, Tm, and Pr were studied. Permanent holographic gratings were written in bulk samples using 248 nm light, with the strongest gratings observed in Ce:ZBLAN. Ultraviolet (UV) induced changes in both absorption and electron spin resonance (ESR) spectra were observed. In

Glen M. Williams; Tsung-Ein Tsai; Celia I. Merzbacher; E. Joseph Friebele

1997-01-01

17

Rare-earth-doped fiber designs for superluminescent sources  

NASA Astrophysics Data System (ADS)

The use of rare-earth-doped fiber section working in amplified spontaneous emission regime for different emission wavelengths is analyzed theoretically. From simulation results, the design of all-fiber superluminescent sources employing different rare earths as dopants for new optical windows and different applications is proposed. Results on different pump and signal powers in forward and backward propagation direction with respect to fiber length are presented.

Pérez-Sánchez, Grethell G.; Bertoldi-Martins, Indayara; Gallion, Philippe; Alvarez-Chávez, Jose A.

2013-08-01

18

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

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

2010-12-18

19

Crystallization behavior of rare-earth doped fluorochlorozirconate glasses  

PubMed Central

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.

Passlick, C.; Ahrens, B.; Henke, B.; Johnson, J.A.; Schweizer, S.

2012-01-01

20

Electrical Transport Properties of Rare Earth Doped Pentatellurides  

NASA Astrophysics Data System (ADS)

The transition metal pentatellurides HfTe5 and ZrTe5 exhibit a broad resistive anomaly as a function of temperature. This anomaly is also seen in the thermopower as it changes from a large positive value below room temperature to a large negative value at lower temperatures with the zero crossing corresponding well with the peak temperature of the resistive anomaly. The magnitude of the resistive peak and the peak temperature are highly sensitive to doping as well as external influences such as magnetic field and pressure. We have synthesized a series of rare-earth doped pentatellurides (Ce, Dy, etc.) and performed a series of measurements of the temperature dependence of the resistivity and thermopower in these samples. In this study we show the effect that doping with rare earth elements has on this anomaly in both HfTe5 and ZrTe_5.

Lowhorn, Nathan D.; Tritt, Terry M.; Abbott, Edward E.; Kolis, J. W.

2002-10-01

21

Production and Rare Earth Doping of Aerogels  

NASA Astrophysics Data System (ADS)

We present recent studies into several methods for making Aerogels. We used both critical point drying methods and chemical dehydroxylation to achieve low density glasses. We used an SEM to characterize the increased pore sizes in these glass materials. In addition, we will present preliminary results of our efforts to add rare earth ions to the glass structure. We are attempting to add the rare earth ions to the glass while avoiding the clustering problems normally encountered in the sol-gel synthesis technique.

Montejo, Genderzon; Sanchez, Freddy; Wenzlau, Dylan; Hoffman, Kurt

2010-10-01

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. 4 figs.

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

1998-12-29

23

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

24

Thermal expansion and Debye temperature of rare earth-doped ceria  

Microsoft Academic Search

Thermal expansions of un-doped ceria and rare earth-doped ceria (Ce1?xMxO2?x\\/2, M=La, Sm, Dy, Yb) were measured in the temperature range from 100 to 800K by TMA. Debye temperatures of these compounds were measured at room temperature by an ultrasonic pulse method. The thermal expansion coefficients of rare earth-doped CeO2 increased with increasing ionic radius of doped ions and its M

Tetsuo Hisashige; Yasuhisa Yamamura; Toshihide Tsuji

2006-01-01

25

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

26

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

27

Pressure studies of alkali, alkaline earth and rare earth doped C60 superconductors  

NASA Astrophysics Data System (ADS)

Pressure studies of the superconducting transition temperature T(sub c) of the alkali metal doped C60 compounds helped to establish a universal curve of T(sub c) versus lattice constant upon which nearly all of these materials lie. Various theoretical schemes incorporate this finding and suggest that only the lattice parameter and not the details of the dopant determine T(sub c). Ca5C60, the highest T(sub c) member of the alkaline earth doped C60 superconductor has a T(sub c) which lies on this universal curve so this material, from these considerations, should have the same large negative pressure derivative as the alkali doped superconductors. We have measured dT(sub c)/dP for Ca5C60 and for Yb(sub x)C60 (x near 3) and find small and positive values indicating that the theoretical models must be expanded to include band structure effects.

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

28

Blue photoluminescence in Ti-doped alkaline-earth stannates  

SciTech Connect

Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A {sub 2}(Sn{sub 1-} {sub x} Ti {sub x} )O{sub 4} (A=Ca, Sr, Ba) (x=0.005-0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca{sub 2}SnO{sub 4}, at 410 nm for Sr{sub 2}SnO{sub 4}, and at 425 nm for Ba{sub 2}SnO{sub 4} under UV excitation. Emission intensities were relatively insensitive to Ti concentration and no sharp concentration quenching was observed. Mixing alkaline-earth ions in the crystal structures did not increase the emission intensities in the A {sub 2}(Sn{sub 1-} {sub x} Ti {sub x} )O{sub 4} system. The excitation spectra of these stannates exhibited broad bands just below the fundamental absorption edges, implying that luminescence centers do not consist of the component elements in the host materials. It was suggested that the isolated TiO{sub 6} complexes are possible luminescence centers in these materials, as previously proposed in other Ti-doped stannates such as Mg{sub 2}SnO{sub 4} and Y{sub 2}Sn{sub 2}O{sub 7}. - Graphical abstract: Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A {sub 2}(Sn{sub 1-} {sub x} Ti {sub x} )O{sub 4} (A=Ca, Sr, Ba) (x=0.005-0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca{sub 2}SnO{sub 4}, at 410 nm for Sr{sub 2}SnO{sub 4}, and at 425 nm for Ba{sub 2}SnO{sub 4} under UV excitation.

Yamashita, Takahiro [Department of Materials Science, Faculty of Engineering, Kyushu Institute of Technology, 1-1 Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan); Ueda, Kazushige [Department of Materials Science, Faculty of Engineering, Kyushu Institute of Technology, 1-1 Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan)], E-mail: kueda@che.kyutech.ac.jp

2007-04-15

29

Modelling the concentration dependence of rare earth doping in inorganic materials for optical applications: Application to rare earth doped barium aluminate  

NASA Astrophysics Data System (ADS)

This paper reports a method for modelling the concentration dependence of rare earth doping in inorganic materials. The method is applied to barium aluminate, which when doped with rare earth ions has important optical applications as a phosphor material. Interatomic potentials are derived by fitting to the structures of barium aluminates, and used to calculate defect formation energies and thus to predict intrinsic defect disorder in the material. Solution energies for rare earth doping are then calculated, which enable the location of the dopant ions and their solubility limits to be predicted.

Rezende, Marcos V. Dos S.; Valerio, Mário E. G.; Jackson, Robert A.

2011-11-01

30

The mechanism of rare earth incorporation in solution doping process.  

PubMed

The mechanism involved during solution doping process has been systematically investigated by correlating the soot characteristics and solution parameters with the amount of rare earth (RE) incorporated in the core of optical fiber. Experiments show that the amount of RE incorporation may be controlled with better precision by adjusting Al ion concentration in the soaking solution. A model has been developed on the basis of cooperative adsorption mechanism correlating different parameters in the overall process. Theoretical estimation shows good agreement with the experimental results and can be used to predict the extent of RE incorporation for any composition if the soot layer characteristics are known. PMID:18711522

Dhar, Anirban; Pal, Atasi; Paul, Mukul Ch; Ray, P; Maiti, Himadri S; Sen, Ranjan

2008-08-18

31

Synthesis and evaluation of ultra-pure rare-earth-doped glass for laser refrigeration  

NASA Astrophysics Data System (ADS)

Significant progress has been made in synthesizing and characterizing ultra-pure, rare-earth-doped ZIBLAN (ZrF4-InF3- BaF2-LaF3-AlF3-NaF) glass capable of laser refrigeration. Yb3+-doped ZIBLAN glass was produced from fluoride precursors which were individually purified by solvent extraction and subsequently treated with hydrofluoric gas at elevated temperatures to remove oxygen impurities. We have developed two-band differential luminescence thermometry (TBDLT) as a new non-invasive, spectroscopic technique to evaluate the intrinsic quality of Yb3+ doped laser-cooling samples. TBDLT measures changes in the local temperature upon laser excitation via the small changes in the 2F5/2-->2F7/2 fluorescence spectrum. Two commercial band pass filters in combination with a balanced dual InGaAs photodetector are used to select and integrate regions of interest in the fluorescence spectrum with sub-millisecond resolution. The TBDLT technique successfully finds the zero-crossing temperature (ZCT), which is the minimum temperature to which a Yb3+ doped sample can cool, independent of surface heating. ZCT is a useful measure for the presence of impurities and the overall quality of the laser-cooling material. Favorable laser cooling results were obtained for several 1% Yb3+-doped glasses with varying degrees of purity.

Patterson, Wendy M.; Hehlen, Markus P.; Sheik-Bahae, Mansoor; Epstein, Richard I.

2009-02-01

32

Blue photoluminescence in Ti-doped alkaline-earth stannates  

NASA Astrophysics Data System (ADS)

Blue photoluminescence properties of Ti-doped alkaline-earth stannates, A2(Sn1-xTix)O4 (A=Ca, Sr, Ba) (x=0.005 0.15), were examined at room temperature. These stannates showed intense broad emission bands peaking at 445 nm for Ca2SnO4, at 410 nm for Sr2SnO4, and at 425 nm for Ba2SnO4 under UV excitation. Emission intensities were relatively insensitive to Ti concentration and no sharp concentration quenching was observed. Mixing alkaline-earth ions in the crystal structures did not increase the emission intensities in the A2(Sn1-xTix)O4 system. The excitation spectra of these stannates exhibited broad bands just below the fundamental absorption edges, implying that luminescence centers do not consist of the component elements in the host materials. It was suggested that the isolated TiO6 complexes are possible luminescence centers in these materials, as previously proposed in other Ti-doped stannates such as Mg2SnO4 and Y2Sn2O7.

Yamashita, Takahiro; Ueda, Kazushige

2007-04-01

33

Rare-earth doped chalcogenide thin films for optoelectronic applications by laser ablation  

Microsoft Academic Search

Chalcogenide glasses have been extensively studied as host media for rare-earth (RE) doped photonic devices due to potential application as optical amplifiers for optical telecommunication. However, fabrication of RE doped homogeneous thin films of chalcogenide glass systems is a difficult task. Doping high amounts of RE atoms (1 to 2 at%) using conventional preparation methods such as glass quenching or

Prabhat Dwivedi; S. O. Kasap

2005-01-01

34

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

SciTech Connect

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

Adijanto, Lawrence, E-mail: adijanto@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, 220 South 33rd Street 311A Towne Building, University of Pennsylvania Philadelphia, PA 19104-6315 (United States); Balaji Padmanabhan, Venu, E-mail: venub@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, 220 South 33rd Street 311A Towne Building, University of Pennsylvania Philadelphia, PA 19104-6315 (United States); Holmes, Kevin J., E-mail: kholmes@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, 220 South 33rd Street 311A Towne Building, University of Pennsylvania Philadelphia, PA 19104-6315 (United States); Gorte, Raymond J., E-mail: gorte@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, 220 South 33rd Street 311A Towne Building, University of Pennsylvania Philadelphia, PA 19104-6315 (United States); Vohs, John M., E-mail: vohs@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, 220 South 33rd Street 311A Towne Building, University of Pennsylvania Philadelphia, PA 19104-6315 (United States)

2012-06-15

35

Microhardness of flux grown pure doped and mixed rare earth aluminates and orthochromites  

Microsoft Academic Search

The results of microhardness measurements on flux-grown crystals of (i) single (pure) rare earth aluminates RAlO3 (R = Eu, Gd, Dy, Er) and rare earth orthochromites RCrO3 (R = Y, Gd, Yb), (ii) rare earth aluminates doped with neodymium, erbium, ytterbium and holmium, and (iii) mixed rare earth aluminate crystals of the type (La1-x) Pr(x)AlO3 (x=0, 0.25, 0.75 and 1.00)

P. N. Kotru; Ashok K. Razdan; B. M. Wanklyn

1989-01-01

36

Overview of an Intelligent Sensorweb for Integrated Earth Sensing Project  

Microsoft Academic Search

This paper outlines research and development efforts towards an Intelligent Sensorweb for Integrated Earth Sensing (ISIES). After introducing the integrated Earth sensing concept and summarizing some prototype in-situ sensorweb demonstration projects, the paper goes on to describe the key aspects and early results of the ISIES project. The objective is to develop an intelligent sensorweb system that integrates in-situ sensors

P. M. Teillet; A. Chichagov; G. Fedosejevs; R. P. Gauthier; G. Ainsley; M. Maloley; M. Guimond; C. Nadeau; H. Wehn; A. Shankaie; Yang J; M. Cheung; A. Smith; G. Bourgeois; V. C. Tao; S. H. L. Liang; J. Freemantle; M. Salopek

2005-01-01

37

Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration  

Microsoft Academic Search

This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the lasercooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at

Wendy Patterson

2009-01-01

38

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

39

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.

40

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

2013-09-10

41

Raman spectra of soda–lime–silicate glass doped with rare earth  

Microsoft Academic Search

Soda–lime–silicate glasses doped with different rare earth oxides (La2O3, CeO2, Nd2O3, Gd2O3 and Y2O3) of 1mol% content were prepared by the traditional melting–quenching methods. In order to reveal the effects of rare earth elements on the behavior of soda–lime–silicate glass the structures of soda–lime–silicate glasses doped with different rare earth oxides were determined using an INVIA confocal microRaman spectrometer equipped

Mitang Wang; Jinshu Cheng; Mei Li; Feng He

2011-01-01

42

Structure and properties of soda lime silicate glass doped with rare earth  

Microsoft Academic Search

Soda-lime-silicate glasses doped with different rare-earth oxides (La2O3, CeO2, Nd2O3, Gd2O3 and Y2O3) of 1mol% content were prepared with the traditional melting–quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and

Mi-Tang Wang; Jin-Shu Cheng; Mei Li; Feng He

2011-01-01

43

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

PubMed Central

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

2008-01-01

44

Nano-arrays of optically addressable rare-earth-doped semiconductor quantum dots for quantum computing  

NASA Astrophysics Data System (ADS)

Results have been presented on isolating rare earth atoms in small numbers in semiconductor nanoparticles so as to use their organized arrays as hardware for quantum computing. We have tailored atomic states of rare earths, fabricated nanoparticles where these atomic systems are incorporated in small numbers and have patterned arrays of nano-holes on semi-conducting and polymer surfaces to encapsulate these rare earth doped nanoparticles. Results are presented on fabrication, microscopy and spectroscopy of these structures.

Konjhodzic, Aras; Aly, Muhammed; Chhabria, Deepka; Hasan, Zameer U.; Wu, M.; Register, Richard A.

2004-06-01

45

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

Microsoft Academic Search

The integration of data is essential to make transformative progress in understanding the complex processes operating at the Earth's surface and within its interior. While our current ability to collect massive amounts of data, develop structural models, and generate high-resolution dynamics models is well developed, our ability to quantitatively integrate these data and models into holistic interpretations of Earth systems

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

2009-01-01

46

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

47

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

48

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

PubMed

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. PMID:22767269

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

2012-07-06

49

Growth and characterization of rare earths doped triglycine sulfate crystals  

Microsoft Academic Search

Ferroelectric triglycine sulfate (TGS) single crystals have been grown by a temperature-lowering technique from the aqueous solution by doping with samarium sulfate, ytterbium sulfate and terbium sulfate in the ferroelectric phase. The effects of these different dopants on the morphology, growth and various properties such as dielectric, pyroelectric and piezoelectric of doped TGS crystals have been investigated. The decrease in

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

2006-01-01

50

Raman spectra of soda-lime-silicate glass doped with rare earth  

NASA Astrophysics Data System (ADS)

Soda-lime-silicate glasses doped with different rare earth oxides (La 2 O 3 , CeO 2 , Nd 2 O 3 , Gd 2 O 3 and Y 2 O 3 ) of 1 mol% content were prepared by the traditional melting-quenching methods. In order to reveal the effects of rare earth elements on the behavior of soda-lime-silicate glass the structures of soda-lime-silicate glasses doped with different rare earth oxides were determined using an INVIA confocal microRaman spectrometer equipped with a CCD detector, and viscosities of glass melts were measured using a rotating crucible viscometer; the melting temperature of the studied glasses was derived on the basis of the Arrhenius equation. Three expressions of the fraction of non-bridging oxygen (NBO/NBO+BO), average number of non-bridging oxygen (NBO) per tetrahedron (NBO/tetrahedron) and average number of bridging corners per tetrahedron (bridges/tetrahedron) for investigated soda-lime-silicate glasses were given, and the effect of rare earth dopants on the structure of soda-lime-silicate was characterized by the Raman shift, variation of the [SiO 4 ] tetrahedron structural unit Q n ( n =1,2,3,4), fraction of non-bridging oxygen and the average number of bridging corners per tetrahedron. The effect of doping rare earth oxides into glass on the viscosity and melting temperature was interpreted by changes in structure of soda-lime-silicate glasses doped with rare earth oxides.

Wang, Mitang; Cheng, Jinshu; Li, Mei; He, Feng

2011-10-01

51

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

52

Processing and electrical properties of alkaline earth-doped lanthanum gallate  

Microsoft Academic Search

Oxides exhibiting substantial oxygen ion conductivity are utilized in a number of high-temperature applications, including solid oxide fuel cells, oxygen separation membranes, membrane reactors, and oxygen sensors. Alkaline earth-doped lanthanum gallate powders were prepared by glycine\\/nitrate combustion synthesis. Compacts of powders synthesized under fuel-rich conditions were sintered to densities greater than 97% of theoretical. Appropriate doping with Sr or Ba

J. W. Stevenson; T. R. Armstrong; D. E. McCready; L. R. Pederson; W. J. Weber

1997-01-01

53

New high-power rare-earth-doped fiber laser materials and architectures  

Microsoft Academic Search

Kigre is developing new rare-earth-doped glass fiber laser materials specifically for use in multiple clad and multiple core LMA and super mode (guided wave) fiber laser constructs. In this work we describe new end-pump double clad fiber laser designs fabricated from high performance phosphate laser glass compositions. One DC LMA fiber is doped with erbium\\/ytterbium for 1.54mum laser emission. Another

John D. Myers; Ruikun Wu; TaoLue Chen; Michael J. Myers; Christopher R. Hardy; John K. Driver; Ralf Tate

2003-01-01

54

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

55

The integral enstatite chondrite model of the earth  

Microsoft Academic Search

The only primitive meteorites that match satisfactorily both the stable isotope and redox characteristics of the Earth are the Enstatite chondrites. I present an integral Enstatite chondrite model in which the Earth is built from essentially pure EH material, which is justified by the above similarities and by the fact that most elements in these meteorites exist in very refractory

M. Javoy

1995-01-01

56

Sensor Webs: A Geostrategic Technology for Integrated Earth Sensing  

Microsoft Academic Search

This paper provides an overview of sensor webs from the perspective of Earth observation. Definitions of in-situ, proximal, and remote sensing are presented. Sensor webs are also defined and the over-arching concept of integrated Earth sensing is outlined. The paper goes on to describe experiences in the development and deployment of sensor web prototypes in support of vegetation monitoring applications.

Philippe M. Teillet

2010-01-01

57

Rare-earth-doped ? films prepared by plasma-enhanced chemical vapour deposition  

Microsoft Academic Search

Rare-earth-doped thin 0022-3727\\/30\\/13\\/012\\/img2 films were made by plasma-enhanced chemical vapour deposition using a complex containing chelating ligands and tetraethoxysilane. By this means of deposition, the film was successfully doped with terbium or erbium and the luminescence properties were investigated. In the case of 0022-3727\\/30\\/13\\/012\\/img3-doped films, strong luminescence peaks from the 0022-3727\\/30\\/13\\/012\\/img4 level were observed during excitation by a KrF excimer

M. Yoshihara; A. Sekiya; T. Morita; K. Ishii; S. Shimoto; S. Sakai; Y. Ohki

1997-01-01

58

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

Microsoft Academic Search

Aluminophosphate glasses belonging to the oxide system Li2O–BaO–Al2O3–La2O3–P2O5, un-doped and doped with rare-earth metal ions (Ce4+, Nd3+, Sm3+) 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)

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

2006-01-01

59

Analysis of magnetic interactions in rare-earth-doped crystals for quantum manipulation  

Microsoft Academic Search

The influence of magnetic interactions in rare-earth-doped crystals under an external magnetic field has been studied in order to obtain an efficient three-level Lambda system with the hyperfine levels of the rare earth. Nuclear Zeeman effect under the action of an external magnetic field removes the nuclear degeneracy. This interaction does not provide an efficient Lambda system because nuclear-spin flipping

O. Guillot-Noël; Ph. Goldner; E. Antic-Fidancev; J. L. Le Gouët

2005-01-01

60

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

61

Rare-earth-doped GaN: growth, properties, and fabrication of electroluminescent devices  

Microsoft Academic Search

A review is presented of the fabrication, operation, and applications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs emit light due to impact excitation of the rare earth (RE) ions by hot carriers followed by radiative RE relaxation. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The

Andrew J. Steckl; Jason C. Heikenfeld; Dong-Seon Lee; Michael J. Garter; Christopher C. Baker; Yongqiang Wang; Robert Jones

2002-01-01

62

Preparation, characterization and photocatalytic activity of Si-doped and rare earth-doped TiO 2 from mesoporous precursors  

Microsoft Academic Search

Si-doped and rare earth-doped TiO2 with large specific surface area were prepared by the hydrothermal method and sol–gel route, respectively, using C18H37NH2 as template. The samples were characterized by XRD, FT-IR, low-temperature N2 adsorption–desorption measurement, XPS and solid state UV–vis diffuse reflectance spectroscopy. The pore size for Si-doped TiO2 exhibits both mesoporous and microporous distribution, and that for rare earth-doped

Xiaoli Yan; Jing He; David G. Evans; Xue Duan; Yuexiang Zhu

2005-01-01

63

Breaking the low phonon energy barrier for laser cooling in rare-earth doped hosts  

NASA Astrophysics Data System (ADS)

A new approach to cool rare earth doped solids with optical super-radiance (SR) is presented. SR is the coherent, sharply directed spontaneous emission of photons by a system excited with a pulsed laser. We consider an Yb3+ doped ZBLAN sample pumped at the wavelength 1015nm with a rectangular pulsed source with a power of ~700W and duration of 20ns. The intensity of the SR is proportional to the square of the number of excited ions. This unique feature of SR permits an increase in the rate of the cooling process in comparison with the traditional laser cooling of the rare earth doped solids with anti-Stokes spontaneous incoherent radiation (fluorescence). This scheme overcomes the limitation of using only low phonon energy glasses for laser cooling.

Nemova, Galina; Kashyap, Raman

2011-02-01

64

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

NASA Astrophysics Data System (ADS)

Aluminophosphate glasses belonging to the oxide system Li2O BaO Al2O3 La2O3 P2O5, un-doped and doped with rare-earth metal ions (Ce4+, Nd3+, Sm3+) 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

65

Growth and concentration dependencies of rare-earth doped lithium niobate single crystals  

NASA Astrophysics Data System (ADS)

A series of lithium niobate LiNbO3 (LN) single crystals doped by rare-earth elements (Tm, Er, Dy, Tb, Gd, Pr) were grown under the same conditions by the Czochralski technique in a wide range of dopant concentrations. The distribution coefficients of rare-earth elements in the “crystal—melt” system of LN were determined at the beginning of the crystal growth. Their dependence on the dopant concentration in melt ranging from 0.1 to 3.5 wt% was investigated. Concentration dependences of physicochemical, ferroelectric and structural characteristics of doped LN single crystals were studied using X-ray diffraction, thermal analysis and Raman scattering measurements. A mechanism of rare-earth elements incorporation into the crystal lattice of LN was proposed for a wide range of dopant concentrations.

Palatnikov, M. N.; Biryukova, I. V.; Sidorov, N. V.; Denisov, A. V.; Kalinnikov, V. T.; Smith, P. G. R.; Shur, V. Ya.

2006-06-01

66

Processing and electrical properties of alkaline earth-doped lanthanum gallate  

SciTech Connect

Oxides exhibiting substantial oxygen ion conductivity are utilized in a number of high-temperature applications, including solid oxide fuel cells, oxygen separation membranes, membrane reactors, and oxygen sensors. Alkaline earth-doped lanthanum gallate powders were prepared by glycine/nitrate combustion synthesis. Compacts of powders synthesized under fuel-rich conditions were sintered to densities greater than 97% of theoretical. Appropriate doping with Sr or Ba on the A-site of the perovskite structure, and Mg on the B-site, resulted in oxygen ion conductivity higher than that of yttria-stabilized zirconia (YSZ), and high ionic transference numbers. Doping with Ca and Mg resulted in lower conductivity than YSZ. Thermal expansion coefficients of the doped gallates were higher than that of YSZ.

Stevenson, J.W.; Armstrong, T.R.; McCready, D.E.; Pederson, L.R.; Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States). Materials and Chemical Sciences Dept.

1997-10-01

67

Rare-earth doped chalcogenide thin films for optoelectronic applications by laser ablation  

NASA Astrophysics Data System (ADS)

Chalcogenide glasses have been extensively studied as host media for rare-earth (RE) doped photonic devices due to potential application as optical amplifiers for optical telecommunication. However, fabrication of RE doped homogeneous thin films of chalcogenide glass systems is a difficult task. Doping high amounts of RE atoms (1 to 2 at%) using conventional preparation methods such as glass quenching or physical vapor deposition techniques often results in physical or chemical clustering of the RE atoms in the glass matrix also. In this paper, we report the deposition and properties of RE doped chalcogenide films fabricated by pulsed laser deposition (PLD), using 15 ns KrF laser pulses at various laser energy densities and substrate temperatures. We examined the effects of changing the substrate temperature during deposition on the optical constants and photoluminescence. The thermal stability was examined using a temperature modulated differential scaning calorimetry (TMDSC) measurements.

Dwivedi, Prabhat; Kasap, S. O.

2005-03-01

68

Integrated Earth Systems: Confronting Global Change  

NSDL National Science Digital Library

This site is the course syllabus for a geography course taught at Ohio State University. The course is designed to provide a basic understanding of both natural and human caused climate change. Lectures explore the issues surrounding recent climate change and the role of human activities in shaping the physical, chemical and biological characteristics of the environment that sustains life on Earth. Links to the class homepage, tutorials and quizzes from the textbook, and a list of course topics are also included.

Mosley-Thompson, Ellen; University, Ohio S.

69

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

70

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

PubMed

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

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

2013-09-25

71

New high-power rare-earth-doped fiber laser materials and architectures  

NASA Astrophysics Data System (ADS)

Kigre is developing new rare-earth-doped glass fiber laser materials specifically for use in multiple clad and multiple core LMA and super mode (guided wave) fiber laser constructs. In this work we describe new end-pump double clad fiber laser designs fabricated from high performance phosphate laser glass compositions. One DC LMA fiber is doped with erbium/ytterbium for 1.54?m laser emission. Another DC LMA fiber is doped with ytterbium for 1.03?m laser emission. A third DC multiple core "supermode" fiber is doped with neodymium for 1.053?m laser emission. Initial fiber laser performance data is presented. The rebium/ytterbium & ytterbium only doped fibers are end-pumped at 940/975nm with 40-Watt fiber coupled laser diodes. The neodymium-doped fiber is end-pumped with an 808nm 40-Watt fiber coupled laser diodes. Design and performance data for new side-pumped, highly doped phosphate DC LMA fiber laser architectures are presented.

Myers, John D.; Wu, Ruikun; Chen, TaoLue; Myers, Michael J.; Hardy, Christopher R.; Driver, John K.; Tate, Ralf

2003-07-01

72

Lateral earth pressure behind an integral abutment  

Microsoft Academic Search

Integral abutment bridges have gained increasing attention in the past few decades. They provide a cost-effective solution to the high maintenance expenses associated with the joints and bearings found in conventional bridges. This paper describes the observed behaviour of granular soil backfill retained behind an integral abutment subjected to cyclic loading. Significant pressure build-up was observed in the soil behind

Y. A. Khodair

2009-01-01

73

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

SciTech Connect

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

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

2000-06-01

74

Integrating Models and Datasets with Earth System Curator  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

75

An Integrated Geologic Framework for EarthScope's USArray  

NASA Astrophysics Data System (ADS)

The GeoFrame initiative is a new geologic venture that focuses on the construction, stabilization, and modification of the North American continent through time. The initiative's goals can be achieved through systematic integration of geologic knowledge-and particularly geologic time-with the unprecedented Earth imaging to be collected under the USArray program of EarthScope (http://www.earthscope.org/usarray). The GeoFrame initiative encourages a cooperative community approach to collecting and sharing data and will take a coast-to-coast perspective of the continent, focusing not only on the major geologic provinces, but also on the boundaries between these provinces. GeoFrame also offers a tangible, `you can see it and touch it' basis for a national approach to education and outreach in the Earth sciences. The EarthScope project is a massive undertaking to investigate the structure and evolution of the North American continent. Sponsored by the U.S. National Science Foundation (NSF), EarthScope uses modern observational, analytical, and telecommunications technologies to establish fundamental and applied research in the Earth's dynamics, contributing to natural resource exploration and development, the mitigation of geologic hazards and risk, and a greater public understanding of solid Earth systems. One part of this project is USArray, a moving, continent-scale network of seismic stations designed to provide a foundation for the study of the lithosphere and deep Earth.

Tikoff, Basil; van der Pluijm, Ben; Hibbard, Jim; Keller, George Randy; Mogk, David; Selverstone, Jane; Walker, Doug

2006-06-01

76

Radioluminescence of rare-earth doped aluminum oxide.  

PubMed

Al(2)O(3):C is one of the most used radioluminescence materials for fiberoptic dosimetry due mainly to its high efficiency. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, sintered samples of Al(2)O(3):C doped with Tb, Sm, Ce and Tm have been prepared by combustion synthesis and their radioluminescence responses have been evaluated. The influence of the different activators on the radioluminescence spectra has been investigated. PMID:22398324

Santiago, M; de Barros, V S; Khoury, H J; Molina, P; Elihimas, D R

2012-02-18

77

Electronic structure analysis of rare earth ions Ce and Nd doped gallium nitride  

NASA Astrophysics Data System (ADS)

First principle calculations on electronic structure of Rare Earth ions Ce and Nd doped GaN are presented. Band gap narrowing, optical transitions, and hybridization of impurity states with the host are discussed. The dopants introduced 4f states in the band gap of the doped material in such a way that REGa isoelectronic traps facilitate the optical transitions in RE:GaN. The observed formation of intermediate bands and impurity levels in band gap of host material predicted it to be excellent candidate for the future solar cell generation and other optoelectronic devices.

Dar, Amna; Majid, Abdul

2013-09-01

78

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; Lü, Wei; Jia, Yongchao; Lv, Wenzhen; Jiao, Mengmeng; You, Hongpeng

2013-10-15

79

Dependences of Brillouin frequency shift on strain and temperature in optical fibers doped with rare-earth ions  

NASA Astrophysics Data System (ADS)

Brillouin scattering properties in rare-earth-doped fibers, including Nd3+-doped, Tm3+-doped, Sm3+-doped, and Ho3+/Tm3+ co-doped fibers, can potentially be controlled at high speed by pumping, but there has been no report on their detailed investigations. In this study, as the first step toward this goal, the Brillouin gain spectra (BGS) in such rare-earth-doped single-mode fibers are measured, for the first time, at 1.55 ?m without pumping, and the Brillouin frequency shift (BFS) and its dependences on strain and temperature are investigated. Clear BGS was observed for the Nd3+-doped and Tm3+-doped fibers, but BGS was not detected for the Sm3+-doped and Ho3+/Tm3+ co-doped fibers probably because of their extremely high propagation losses at 1.55 ?m and small Brillouin gain coefficients. The BFS of the Nd3+-doped fiber was ~10.82 GHz, and its strain and temperature coefficients were 466 MHz/% and 0.726 MHz/K, respectively. As for the Tm3+-doped fiber, the BFS was ~10.90 GHz, and its strain and temperature coefficients were 433 MHz/% and 0.903 MHz/K, respectively. These measurement results are compared with those of silica fibers.

Mizuno, Yosuke; Hayashi, Neisei; Nakamura, Kentaro

2012-08-01

80

Design and refinement of rare earth doped multicore fiber lasers  

NASA Astrophysics Data System (ADS)

A novel multicore ytterbium doped fiber laser is designed, with the target of maximizing both the effective mode area and the beam quality, by means of a complete home-made computer code. It can be employed to construct high power and Quasi-Gaussian beam lasers. The novel laser configuration exploits a single mode multicore fiber and does not need Talbot cavity or other in-phase mode selection mechanisms. This is an innovative solution, because to the best of our knowledge, for the first time, we have designed a truly single-mode multicore fiber laser. For comparison we have optimized two other laser configurations which are well known in literature, both employing a multimode multicore fiber and a Talbot cavity as a feedback for the in-phase supermode selection. All three multicore fibers, constituted by the same glass, are doped with the same ytterbium ion concentration and pumped with the same input power. Multimodal fiber lasers exhibit lower beam quality, i.e. a higher beam quality factor M2, with respect to the single mode one, even if suitable Talbot cavities are designed, but they are very competitive when a more compact laser cavity is required for the same output power. The novel single mode nineteen core laser exhibits a simulated effective mode area Aeff = 703 ?m2 and a beam quality factor M2 = 1.05, showing better characteristics than the other two lasers.

Prudenzano, F.; Mescia, L.; Di Tommaso, A.; Surico, M.; De Sario, M.

2013-09-01

81

Photoluminescence in rare earth-doped complex hexafluoride phosphors.  

PubMed

In this study, using a simple combustion process and a wet chemical process, fluorides showing intense photoluminescence were prepared and developed as low-cost phosphors. The prepared phosphors were characterized by photoluminescence (PL) techniques. PL emission spectra of the phosphor suggest the presence of Eu(3+) as well as Eu(2+) ions in LiMgBF(6):Eu and Li(2) NaBF(6):Eu lattice sites. This article summarizes the fundamentals and possible applications of optically useful inorganic fluoride with visible photoluminescence of doped Eu(3+) and Eu(2+) ions. Our results on LiMgBF(6):Ce and Li(2) NaBF(6):Ce are also reported. PMID:21739564

Puppalwar, S P; Dhoble, S J; Kumar, Animesh

2011-07-08

82

Rare-earth doped Si-rich ZnO for multiband near-infrared light emitting devices  

NASA Astrophysics Data System (ADS)

Transparent Conductive Oxides (TCOs) are a broad class of organic and inorganic materials exhibiting both optical transparency and electrical conductivity simultaneously. TCOs are utilized as top-con tact passive layers in a number of optoelectronic devices, including flat panel displays and solar cells. Recently, they are also attracting considerable attention as an active platform for a wide range of novel device applications. Zinc oxide (ZnO) is the most promising candidate for optoelectronic integration due to its low cost and Si compatibility. Moreover, it is a biocompatible material and possibly biodegradable. We fabricated rare earth-doped Si-rich ZnO thin films through magnetron sputtering and we investigate their near-infrared emission properties under both optical and electrical injection. Er and Nd efficient (3ms RT lifetime) radiative transitions were simultaneously activated due to energy transfer via the ZnO direct bandgap and its luminescent defect centers. Moreover, by incorporating Si atoms, we demonstrate Si-mediated enhancement of light emission in Er-doped ZnO, and electroluminescence. We fabricated a proof-of-concept 1.55?m-electroluminescent device with record low turn-on voltage (1.5V) in Er-doped Si-rich ZnO at room temperature. These results pave the way to novel Si-compatible light emitters that leverage the optically transparent and electrically conductive ZnO matrix for multiband near-IR telecom and bio-compatible applications.

Pecora, Emanuele Francesco; Murphy, Thomas Ian; Dal Negro, Luca

2013-03-01

83

Mid-infrared (3-5 ?m) emission from rare earth doped KPb2Br5  

NASA Astrophysics Data System (ADS)

Solid-state lasers operating in the mid-infrared (MIR) wavelength region (3-5 ?m) are of significant current interest for laser remote sensing of chemical and biological agents as well as for military countermeasures. The development of MIR solid-state lasers based on oxide and fluoride laser hosts is limited by non-radiative decay through multi-phonon relaxations. Rare earth doped crystals with low maximum phonon energies can exhibit efficient MIR emission at room temperature. In this paper, we present results of the material synthesis and optical properties of rare earth (Pr, Nd, Dy, Er) doped KPb2Br5, which has a maximum phonon energy of only ~140 cm-1.

Hömmerich, U.; Nyein, Ei Ei; Amedzake, P.; Trivedi, S.; Zavada, J. M.

2006-03-01

84

Low temperature laser cooling with a rare-earth doped glass  

NASA Astrophysics Data System (ADS)

A theoretical study of laser cooling at low temperature by anti-Stokes luminescence in a rare-earth doped glass is performed. A model is developed to evaluate the absorption and emission spectra of rare-earth ions in a glass matrix. This model allows the evaluation of the inhomogeneously broadened spectra at any temperature. It takes into account the saturation effects that occur at high excitation. The model is used to evaluate the cooling capability at low temperature of a ytterbium-doped fluorozirconate glass, the latter having been proposed in the literature as a good candidate for the cooling element of a cryocooler. Results are compared with previous estimations, confirming that one could expect a useful cooling efficiency from this material, but with smaller performances than previously estimated. Limitations to the cooling process are discussed. The reabsorption of luminescence is identified as one of the main limitations to the performance of a potential cryocooler.

Lamouche, G.; Lavallard, P.; Suris, R.; Grousson, R.

1998-07-01

85

Raman spectral analysis of TiO2 thin films doped with rare-earth samarium.  

PubMed

TiO(2) thin films doped with rare-earth samarium were prepared on a quartz plate by the sol-gel/spin-coating technique. The samples were annealed at 700 °C to 1100 °C, and the Raman spectra of the samples were obtained. Analyses of Raman spectra show that samarium doping can inhibit the anatase-rutile phase transition. Samarium doping can refine grains of TiO(2) thin films and increase the internal stress, thereby preventing lattice vibration. Nanocrystalline TiO(2) thin films obviously show the phonon confinement effect, i.e., the blueshift of characteristic Raman peak and full width at half-height increase, and the peak shapes asymmetrically broaden with a decrease in the grain sizes of the samples. PMID:22859033

Yang, Chang-Hu; Ma, Zhong-Quan

2012-08-01

86

High-speed optical recording with rare-earth-doped hole-burning materials  

Microsoft Academic Search

We are developing a high density, high speed optical memory, using rare-earth doped hole- burning materials. These materials are theoretically capable of achieving storage densities of 1000 Gigabits\\/cm3 at input\\/output (I\\/O) rates of several gigabits\\/sec. One remarkable attribute of this storage concept is that both the temporal and spatial information encoded on a laser beam can be stored. Because both

Ravinder Kachru; Xiao-An Shen

1996-01-01

87

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 800°C 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

88

Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers  

Microsoft Academic Search

Optical cryocoolers made of luminescent solids are very promising for many applications in the fields of optical telecommunications, aerospace industry, bioimaging, and phototherapy. To the present day, researchers have employed a number of crystal and glass host materials doped with rare-earth ions (Yb3+, Tm3+, and Er3+) to yield anti-Stokes optical refrigeration. In these host materials, the attainable minimum temperature is

Angel J. Garcia-Adeva; Rolindes Balda; Joaquín Fernández

2009-01-01

89

Rare earth doping effect on the elastic moduli of low silica calcium aluminosilicate glasses  

Microsoft Academic Search

Elastic moduli (E, G, K, ?) of calcium aluminosilicate glasses with <10 mol% of SiO2 doped with Er2O3 and Yb2O3, melted in air and under vacuum conditions, have been measured using the pulse echo ultrasonic technique. There was a decrease of the elastic properties, <5%, as rare earth oxide replaces Al2O3 from 0.2 to 1.5 mol% (about 8 wt%). The

J. A. Sampaio; M. L. Baesso; S. Gama; A. A. Coelho; J. A. Eiras; I. A. Santos

2002-01-01

90

Scintillation luminescence of cerium-doped borosilicate glass containing rare-earth oxide  

Microsoft Academic Search

The properties of high rare-earth-containing borosilicate glasses have been investigated to assess the potential for using these materials to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of Ce3+-doped Gd2O3-based glasses. The samples were excited by a high energy X-ray beam and the associated scintillation yield and

Chun Jiang; Qingji Zeng; Fuxi Gan

2000-01-01

91

Investigation of rare earth-doped barium titanate thin films and their optical properties  

Microsoft Academic Search

Rare-earth-doped barium titanate thin films were studied for potential use as an optical amplification medium. Factors determining their luminescence efficiency and emission linewidth were investigated since these parameters govern the optical gain. Metal-organic chemical vapor deposition was used to prepare BaTiO3 films on different oxide substrates using a liquid barium precursor, Ba(hfa)2•PEB. The phase purity, degree of crystallinity, and epitaxy

Andrew R. Teren

2001-01-01

92

Optical properties of rare earth doped barium titanate thin films prepared by metalorganic chemical vapor deposition  

Microsoft Academic Search

The structural and optical properties of rare earth doped barium titanate (BaTiO3) thin films were investigated to assess their potential for optical gain and nonlinear optical applications. Epitaxial films were deposited on MgO and LaAlO3 substrates using low pressure metalorganic chemical vapor deposition. Er, the main dopant ion studied, was incorporated into the films at concentrations as high as 1021\\/

Bruce A. Block

1997-01-01

93

Structural and magnetic property of Mn:ZnO bulk ceramic doped with rare earth (Gd/Sm) atoms  

NASA Astrophysics Data System (ADS)

This paper reports the paramagnetic behavior of Mn doped ZnO co-doped with rare earth (Gd and Sm) atoms. The formation of secondary rare earth oxides (Gd2O3 and Sm2O3) is confirmed from the X-ray diffraction patterns. The rare earth oxides in the system forbids the grain growth and interconnection between the grains. The weak link between the grains suppresses the long range exchange interaction between the Mn ions and hence, reduces the ferromagnetic ordering. Owing to the large mismatch between ionic radii of rare earth and transition metal atoms inside the matrix, the rare earth element cannot contribute to promote ferromagnetic behavior in Mn doped ZnO, irrespective of their high individual magnetic moments.

Das, J.; Mishra, D. K.; Sahu, D. R.; Roul, B. K.

2012-09-01

94

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

2012-05-30

95

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

96

Rare-earth-doped photonic crystals for the development of solid-state optical cryocoolers  

NASA Astrophysics Data System (ADS)

Optical cryocoolers made of luminescent solids are very promising for many applications in the fields of optical telecommunications, aerospace industry, bioimaging, and phototherapy. To the present day, researchers have employed a number of crystal and glass host materials doped with rare-earth ions (Yb3+, Tm3+, and Er3+) to yield anti-Stokes optical refrigeration. In these host materials, the attainable minimum temperature is limited by the average phonon energy of the lattice and the impurity concentration. However, recently Ruan and Kaviany have theoretically demonstrated that the cooling efficiency can be dramatically enhanced when the host material doped with rare-earth ions is ground into a powder made of sub-micron size grains. This is due to two facts: firstly, the phonon spectrum is modified due to finite size of the grains and, secondly, light localization effects increase the photon density, leading to an enhanced absorptivity. In the present work, we propose that using a photonic crystal doped with rare earth ions offers many advantages with regards to getting a larger cooling efficiency at room temperature when compared to standard bulk materials or nano-powders. Indeed, apart to analogous phenomena to the ones predicted in nano-crystalline powders, there is the possibility of directly controlling the spontaneous emission rate of the ions embedded in the structure and, also, the absorption rate in the Stokes side of the absorption band by adequately tuning the density of photonic states, thus obtaining a large improvement in the cooling efficiency.

Garcia-Adeva, Angel J.; Balda, Rolindes; Fernández, Joaquín

2009-02-01

97

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

PubMed

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

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

2010-12-09

98

Optical characterization of some rare earth ions doped bismuth borate glasses and effect of gamma irradiation  

NASA Astrophysics Data System (ADS)

Rare earth doped bismuth borate glasses were prepared by conventional melt annealing method. The density, molar volume, ultraviolet, visible, and infrared spectroscopic and optical energy band gap of these glasses have been measured or calculated and employed to investigate the prepared glassy samples. The refractive index and molar refraction have been calculated using the theory of reflectively of light. The luminescence properties of the glasses were analyzed. The undoped glass shows strong extended UV-near visible absorption bands which are attributed to the collective presence of both trace iron impurities from raw materials and also the sharing of bismuth Bi+3 ions. The rare earth doped samples show the same strong UV-near visible bands as the undoped sample beside extra characteristic bands due to the respective rare earth ions. Results showed that the luminescence intensity changed with different rare earth oxides. The decreasing values of optical band gap and band tail can be understood and related in terms of the structural changes that are taking place in the glass samples. The infrared absorption spectra of the prepared glasses show characteristic absorption bands related to the borate network (BO3, BO4 groups) together with vibrational modes due to Bi-O groups. The IR spectra are slightly affected by gamma irradiation indicating the stability of the structural glassy forming units. The prepared samples reveal varying responses towards the effect of gamma irradiation.

Marzouk, M. A.

2012-07-01

99

Nano and metastable processing of rare earth doped silicate glasses for photonic applications  

NASA Astrophysics Data System (ADS)

Nanotechnology and photonic technology have seen rapid and astounding growth in the last 10 years. Many new properties and applications have been developed in the respective fields. In recent years some nanotechnology has been integrated into the field of photonics. In this study nano and metastable processing of silicate glasses for pholonic applications are examined. Nanopowders of SiO2 were fabricated. These powders were characterized by BET gas adsorption, thermogravimetric analysis, X-Ray Diffraction, and Scanning Electron Microscopy. Optimization of SiO2 nanopowder fabrication parameters proved invaluable since the same parameters were used for multicomponent compositions of Al2O3/SiO2/Er2O 3. Optimization of parameters included O2 flow rate, H 2 flow rates, burner distance, and precursor flow rate. Precursor flow rate, was found to be critical to the fabrication of high quality nanopowders. Multicomponent compositions were investigated for 1.55 mum emission from Er3+. Powders with average particle sizes of 9 nm were synthesized. In a complementary study, compositions of Al2O3/SiO 2/Er2O3 powders were hatched and spray dried for plasma melt quenching. These powders with very high concentrations of Er 2O3 were superheated in a plasma then quickly quenched into a water bath. Various compositions were prepared with different codoping ratios of Al2O3/Er2O3. Lifetime and fluorescence data are reported for emission at 1.55 um. Furthermore, green upconversion was observed with Yb/Er codoping. All compositions of plasma spray powders exhibited low multiexponential decay rates for the 4 I13/2 metastable state. Beat treatments of the powders up to 1400°C crystallized a Er2Si2O7 monoclinic pyrochlore structure. Upon crystallization the crystalline phase exhibited increased lifetimes of 7 ms up from <1 ms. Ordering of Er 3+ atoms is seen as the mechanism for increase in lifetime. This investigation has provided insight into the potential of metastable processing of heavily doped rare earth oxide nanopowders for photonic applications. Rare earth concentrations have been achieved which are 1 to 2 orders of magnitude higher then possible by more conventional synthesis methods. These findings should provide the incentive for follow-up research to further advance and exploit nanotechnology for next generation optical materials and devices.

Finley, Matthew Franklin

2002-01-01

100

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

101

Rare-earth doped GaN and InGaN quantum dots grown by plasma assisted MBE  

NASA Astrophysics Data System (ADS)

We report on the MBE growth of GaN and InGaN quantum dots (QDs) doped with rare earth ions, namely Eu, Tm and Tb exhibiting red, blue and green luminescence, respectively. Intense photoluminescence/cathodoluminescence is observed, resulting from the spatial localization of rare earth ions in dots combined with the confinement properties of the carriers. White light emission has been produced by combining the three rare earths in a multilayer sample of stacked GaN QD planes.

Hori, Y.; Andreev, T.; Biquard, X.; Monroy, E.; Jalabert, D.; Dang, Le Si; Tanaka, M.; Oda, O.; Daudin, B.

2005-05-01

102

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

103

Local precipitation of upconversion nanocrystals in rare-earth-doped oxyfluoride glasses by laser irradiation  

NASA Astrophysics Data System (ADS)

Rare earth-doped oxyfluoride glass of the 50SiO2 -50PbF2 -5ErF3 composition in molar ratio was developed. When the oxyfluoride glass is heat-treated at the first cystallization temperature, the glass gives the glass-ceramic in which rare earth-containing fluorite-type nanocrystals of about 20 nm in diameter uniformly precipitate in the glass matrices. The glass-ceramic is trasnparent to the naked eye like no heat-treated oxyfluoride glass. The glass-ceramic exhibits highly efficient upconversion luminescence under 800 and/or 980 nm laser light excitation. On the other hand, the oxyfluoride glass can be locally changed to glass-ceramic in the forms of dot, line, plane, letter, etc. by thermal energies generated from light absorption of various lasers. In the case of CO2 laser irradiation the formation of such glass-ceramic occurs near the surface of glass. In the case of 800 or 980 nm irradiation by Ti:sapphire laser or laser diodes, on the other hand, the formation of such glass-ceramic occurs near the surface and/or inside of glass. The glass-ceramic parts can be easily read by upconversion luminescence under laser excitation. Therefore, the presently developed rare earth-doped oxyfluoride glass can be utilized as optical devices of the writing and reading memory, which can be utilized as specific devices for security information.

Hashima, Hidekazu; Konishi, Akio; Tanigami, Yoshinori; Shibata, Daisuke; Kawamoto, Yoji

2004-06-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

105

Effects of rare-earth co-doping on the local structure of rare-earth phosphate glasses using high and low energy X-ray diffraction.  

PubMed

Rare-earth co-doping in inorganic materials has a long-held tradition of facilitating highly desirable optoelectronic properties for their application to the laser industry. This study concentrates specifically on rare-earth phosphate glasses, (R2O3)x(R'2O3)y(P2O5)(1-(x+y)), where (R, R') denotes (Ce, Er) or (La, Nd) co-doping and the total rare-earth composition corresponds to a range between metaphosphate, RP3O9, and ultraphosphate, RP5O14. Thereupon, the effects of rare-earth co-doping on the local structure are assessed at the atomic level. Pair-distribution function analysis of high-energy X-ray diffraction data (Q(max) = 28 Å(-1)) is employed to make this assessment. Results reveal a stark structural invariance to rare-earth co-doping which bears testament to the open-framework and rigid nature of these glasses. A range of desirable attributes of these glasses unfold from this finding; in particular, a structural simplicity that will enable facile molecular engineering of rare-earth phosphate glasses with 'dial-up' lasing properties. When considered together with other factors, this finding also demonstrates additional prospects for these co-doped rare-earth phosphate glasses in nuclear waste storage applications. This study also reveals, for the first time, the ability to distinguish between P-O and P[double bond, length as m-dash]O bonding in these rare-earth phosphate glasses from X-ray diffraction data in a fully quantitative manner. Complementary analysis of high-energy X-ray diffraction data on single rare-earth phosphate glasses of similar rare-earth composition to the co-doped materials is also presented in this context. In a technical sense, all high-energy X-ray diffraction data on these glasses are compared with analogous low-energy diffraction data; their salient differences reveal distinct advantages of high-energy X-ray diffraction data for the study of amorphous materials. PMID:23518599

Cramer, Alisha J; Cole, Jacqueline M; FitzGerald, Vicky; Honkimaki, Veijo; Roberts, Mark A; Brennan, Tessa; Martin, Richard A; Saunders, George A; Newport, Robert J

2013-03-21

106

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

107

Scintillation luminescence of cerium-doped borosilicate glass containing rare-earth oxide  

NASA Astrophysics Data System (ADS)

The properties of high rare-earth-containing borosilicate glasses have been investigated to assess the potential for using these materials to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of Ce3+-doped Gd2O3-based glasses. The samples were excited by a high energy X-ray beam and the associated scintillation yield and decay time was measured. The optical transmission of the samples was measured. It was observed that scintillation yield of present scintillation glass is 20% of BGO scintillation yield, decay time is in range of 50 - 80 ns, glass density is 5.50 g/cm3. It was concluded that higher light yield and density make this glass become promising candidate for cerium doped dense glass scintillator.

Jiang, Chun; Zeng, Qingji; Gan, Fuxi

2000-11-01

108

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

109

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

NASA Astrophysics Data System (ADS)

We perform an investigation into the properties of Pr3+:Y2SiO5 whispering-gallery-mode resonators as a first step toward achieving the strong coupling regime of cavity QED with rare-earth-metal-ion-doped crystals. Direct measurement of cavity QED parameters are made using photon echoes, giving good agreement with theoretical predictions. By comparing the ions at the surface of the resonator to those in the center, it is determined that the physical process of making the resonator does not negatively affect the properties of the ions. Coupling between the ions and resonator is analyzed through the observation of optical bistability and normal-mode splitting.

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

2011-06-01

110

Ferromagnetic resonance in GdAl2 crystals doped with anisotropic rare-earth ions  

Microsoft Academic Search

Ferromagnetic resonance measurements of the magnetic anisotropy and resonance linewidth are reported for single-crystal specimens of the cubic Laves-phase intermetallic compound GdAl2 and for RxGd1-xAl2 where R is a heavy rare-earth ion. The doping levels of the samples were: for R=Tb, x=0.0025, 0.01, 0.02, 0.05; for R=Dy, x=0.02; for R=Ho, x=0.02; for R=Er, x=0.01, 0.03. Microwave frequencies close to 9.3,

F. Pelegrini; R. W. Teale; S. Abell; D. St. P. Bunbury

1984-01-01

111

Study of Defects That Trap Excitons in Yttrium Aluminum Garnets Doped With Rare-Earth Elements  

NASA Astrophysics Data System (ADS)

Excitons play a fundamental role in transporting energy in photonic materials. Understanding and controlling excitons dynamics through their interactions with activating impurities and lattice defects is key to improving scintillation and optical properties. Singles crystals of yttrium aluminum garnet (YAG) crystals doped with rare-earths were studied by positron annihilation, thermolunuinescence and optical spectroscopy. Evidence of defect complexes was found in the YAG structure. Positron lifetime measurements were performed to characterize those defects. Effects of dopants on the optical properties and lattice defects were investigated.

Selim, Farida; Varnery, Chris; Collins, Gary; McKay, David; Reda, Sherif

2011-03-01

112

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

113

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

114

Luminescence Characteristics of Rare-Earth Erbium Ion-Doped Nanocrystalline Zinc Oxide  

NASA Astrophysics Data System (ADS)

Er3+-doped ZnO nanocrystalline powders are successfully prepared by the chemical precipitation method, using various doping concentrations of Er3+ at different annealing temperatures from 500°C to 900°C. The characteristic emission peaks of the excitation state 4S3/2 (550 nm), 2H11/2 (520 nm), 4F5/2 (455 nm) ? 4I15/2 transition of Er3+ ions are observed in a wide visible band of the ZnO host. The relationship between the PL intensity of integration of nanocrystalline ZnO:Er3+ and the annealing temperature and doping concentration of Er3+ is given; it is found that the optimal dopant concentration and annealing temperature are 4.0 × 10-3 M and 850°C for the 4S3/2 ? 4I15/2 (550 nm) and 4F5/2 ? 4I15/2 (455 nm) transition of Er3+. Based on these results, the mechanism of the emission spectra of ZnO is analyzed and its defects on the spectral properties are discussed. An energy transfer from excited states of ZnO hosts to doping Er3+ ion centers is revealed by the fact that PL intensity of the peaks of nanocrystalline ZnO:Er3+ changes with the annealing temperature and doping concentration of Er3+, and another from the 4f-4f transition of Er3+.

Guo-Li, Song

115

Rare earth-doped nanocrystalline MgF2: Synthesis, luminescence and thermoluminescence  

NASA Astrophysics Data System (ADS)

The radioluminescence (RL) and thermoluminescence (TL) activation of MgF2 through the incorporation of rare earths is investigated in this work. These materials were obtained by ligand-free solution precipitation and calcination at 500 °C in air, and Ce, Eu and Tb were incorporated at the 1 mol% level. RL results of doped and undoped materials seem to indicate that the incorporation of rare earths creates effective luminescence centers, which is accompanied by an increase in the TL signal intensity in comparison with the undoped material. In particular, RL emission of MgF2:Ce is reported to be centered at 325 nm. The traps associated with the TL signal were found to be unstable under exposure to room light, suggesting potential for applications involving optically stimulated luminescence.

Jacobsohn, L. G.; Roy, A. L.; McPherson, C. L.; Kucera, C. J.; Oliveira, L. C.; Yukihara, E. G.; Ballato, J.

2013-10-01

116

Electrochemical luminescence of n-type ZnO semiconductor electrodes doped with rare earth metals under the anodic polarization  

Microsoft Academic Search

Electrochemical luminescence (ECL) at n-type ZnO semiconductor electrode was measured under anodic polarization. Scanning the potential imposed on the ZnO electrode, emission was suddenly observed around +20V. Using the ZnO electrodes doped with rare earth metal ions as Sm3+, Eu3+, Dy3+, Ho3+ and Er3+, much brighter emission was obtained than the ECL of non-doped ZnO. These emission spectra are ascribed

Toshihito Ohtake; Satoshi Hijii; Noriyuki Sonoyama; Tadayoshi Sakata

2006-01-01

117

Coupled experiment\\/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers  

Microsoft Academic Search

We developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er\\/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB

S. Girard; L. Mescia; M. Vivona; A. Laurent; Y. Ouerdane; C. Marcandella; F. Prudenzano; A. Boukenter; T. Robin; P. Paillet; V. Goiffon; B. Cadier; M. Cannas; R. Boscaino

2011-01-01

118

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

SciTech Connect

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

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

2001-05-01

119

Luminescence of Rare-Earth-Doped Nanoparticles with Aromatic Linker Molecules  

NASA Astrophysics Data System (ADS)

Rare-earth-doped vanadate glasses retain their luminescence when formed as shells around magnetic cores [1]. This property has prompted speculation that composite magneto-photoluminescent (CMPL) structures can be used in biological applications. For example, CMPL nanoparticles can be magnetically tuned to separate cells, proteins and nucleic acids [2]. A crucial step in realizing this goal is to attach organic linkers (between the rare-earth-doped shell and bio-probes), which do not affect the luminescence. We demonstrate with IR spectroscopy that Eu:YVO4 nanoparticles treated with benzoic acid, 3-nitro 4-chloro-benzoic acid and 3,4-dimethoxy benzoic acid all result in the modification of the surface states, replacing the native metal-hydroxyl bond with a longer chain aromatic linker, which can be later functionalized. Photoluminescence spectra under UV-excitation show that the dominant ^5D0 -> ^7F2 transition at ˜620 nm is unaffected by the chemical treatment. The result provides a platform to facilitate the attachment of bio-probes to Eu:YVO4 nanoparticles and related CMPL nanostructures with Fe2O4 cores. [1] N. B. McDowell et al, J. Appl. Phys. 107, 09B327 (2010). [2] T. R. Sathe et al, Anal. Chem. 78, 5627 (2006).

Senty, Tess; Yalamanchi, Mohita; Zhang, Yanwei; Leach, Anya; Seehra, Mohindar; Shi, Xiaodong; Bristow, Alan

2012-02-01

120

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

121

Magneto-Optical Studies of Rare Earth Doped III-V Nitrides  

NASA Astrophysics Data System (ADS)

We investigated the site selective optical and magneto-optical properties of Neodymium doped Gallium and Aluminum Nitride and Erbium doped Gallium Nitride. For our current study, we applied magnetic fields parallel and antiparallel to the C-axis of the crystals and observed the resulting Zeeman splitting both in excitation and emission transitions. On the basis of these measurements, we determined the effective g-factors of all the states involved in the Nd^3+ transitions. For erbium doping, we observed the Zeeman splitting of the ^4I13/2 and ^4I15/2 levels. Due to small crystal field splitting and large Zeeman splitting, the assignment of levels and corresponding g-factors is very complex. In addition, we observed unexpected asymmetries in the emission intensities when we compared the spectra obtained for fields parallel and antiparallel to the growth direction. The degree of this asymmetry depends on the substrate material and is unambiguously related to the strain and resulting internal fields that are induced by lattice mismatch. The asymmetry behavior parallels the ferromagnetic behavior that is induced by the rare earth ions in GaN and hence our observation suggests that magnetization can be controlled by strain.

Mitchell, Brandon; Woodward, Nathaniel; Poplawsky, Jonathan; Dierolf, Volkmar; Jiang, H. X.

2012-02-01

122

Fabrication and characterization of rare-earth metal-chelate-doped plastic film and fiber materials: Eu(3+)-chelate-doped PMMA  

NASA Astrophysics Data System (ADS)

High concentration rare-earth metal ion chelates, Europium 6,6.7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5,-octanedionate, (Eu-FOD) doped PMMA fiber and film were successfully prepared for the first time by casting solution method and gel spinning method. The optical and photoelectric characteristics of Eu(3+)-FOD doped PMMA film and fiber were investigated. Amplified spontaneous emission (ASE) from the Eu-FOD doped PMMA film and fiber was observed, The high- concentration Eu-FOD-doped PMMA fiber and film sample exhibited lasing threshold as low as o. 15 mJ/cm2 when pumped with a 355-nm pulsed laser beam.

Horinouchi, Suguru; Wada, M.; Ishihara, Koki; Eguchi, Masashi; Zhang, Gongjian; Ishikawa, T.; Watanabe, A.; Wang, Lili; Ogata, Naoya

2002-08-01

123

Observational data preparation and availability for Integrated Earth System modeling  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

124

Rare-earth doped GaN and InGaN quantum dots grown by plasma assisted MBE  

Microsoft Academic Search

We report on the MBE growth of GaN and InGaN quantum dots (QDs) doped with rare earth ions, namely Eu, Tm and Tb exhibiting red, blue and green luminescence, respectively. Intense photoluminescence\\/cathodoluminescence is observed, resulting from the spatial localization of rare earth ions in dots combined with the confinement properties of the carriers. White light emission has been produced by

Y. Hori; T. Andreev; X. Biquard; E. Monroy; D. Jalabert; Le Si Dang; M. Tanaka; O. Oda; B. Daudin

2005-01-01

125

The Preparation, Characterization, and their Photocatalytic Activities of Rare-Earth-Doped TiO 2 Nanoparticles  

Microsoft Academic Search

RE\\/TiO2 photocatalysts were prepared by the sol–gel method using rare earth (RE=La3+, Ce3+, Er3+, Pr3+, Gd3+, Nd3+, Sm3+) metal salts and tetra-n-butyl titanate as precursors, and were characterized by XRD, IR, UV–vis diffuse reflection, and transient absorption spectra. Their photocatalytic activities were evaluated using nitrite as a decomposition objective. As a result, suitable content of doping rare earth in TiO2

An-Wu Xu; Yuan Gao; Han-Qin Liu

2002-01-01

126

Low temperature synthesis of anatase rare earth doped titania-silica photocatalyst and its photocatalytic activity under solar-light  

Microsoft Academic Search

A series of rare earth (Sm3+, Nd3+, Ce3+ and Pr3+) doped titania-silica photocatalysts, as a reclaimed solar-light responsive photocatalyst, was prepared by sol–gel method with TEOS and TBT as precursors, by keeping the molar of TEOS:TBT constant at 1:1 and with different rare earth dopant content. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning

Jianjun Zhu; Jimin Xie; Min Chen; Deli Jiang; Dan Wu

2010-01-01

127

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

128

Enhanced Tc in Rare-Earth Doped Ca122 via Mesostructural Defects  

NASA Astrophysics Data System (ADS)

Nonbulk superconductivity with an onset-Tc up to 49 K has been observed in single crystalline rare-earth doped CaFe2As2 [(Ca1-x,REx)122] recently. Such a Tc is more than ˜ 20 K higher than any known compounds that consist of one or more of the Ca, RE, Fe and As elements at ambient or under high pressures. The unusually high onset-Tc has therefore been attributed to interface effect. We have made systematic magnetic, transport, calorimetric and structural studies. They show: a chemically homogeneity of ?x 0.005 over a 1?m; less than 5 % of a bulk superconducting volume fraction; a doping-insensitive onset-Tc in samples with or without the ``collapsed phase'', varying from ˜ 42 K for RE = Nd to 49 K for RE = Pr with a doping sensitive superconducting volume fraction, suggesting that the high onset-Tc cannot be due to chemical doping or the effect of the ``collapsed phase''; an unusually high magnetic anisotropy up to 200, in contrast to the value of 4 from the sample geometric anisotropy, suggesting that the superconducting body has a very high aspect ratio; several steps in the magnetic susceptibilities along both the c- and ab-directions in the field range between 10-3 to 10^+3 Oe, demonstrating the sample consisting of Josephson-Coupled superconducting islands imbedded with nano-scale interfaces; and the presence of superparamagnetic clusters associated with minute As-vacancies, consistent with theoretical calculations. The present studies therefore present the strongest evidence for interface-enhanced Tc to date.

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

2013-03-01

129

Evidence of Interface-Enhanced Tc in Rare-Earth Doped Ca122  

NASA Astrophysics Data System (ADS)

Nonbulk superconductivity with an onset-Tc up to 49 K has been observed in single crystalline rare-earth doped CaFe2As2 [(Ca1-x,REx)122] recently. Such a Tc is more than ˜ 20 K higher than any known compounds that consist of one or more of the Ca, RE, Fe and As elements at ambient or under high pressures. The unusually high onset-Tc has therefore been attributed to interface effect. We have made systematic magnetic, transport, calorimetric and structural studies. They show: a chemically homogeneity of ?x 0.005 over a 1?m; less than 5 % of a bulk superconducting volume fraction; a doping-insensitive onset-Tc in samples with or without the ``collapsed phase'', varying from ˜ 42 K for RE = Nd to 49 K for RE = Pr with a doping sensitive superconducting volume fraction, suggesting that the high onset-Tc cannot be due to chemical doping or the effect of the ``collapsed phase''; an unusually high magnetic anisotropy up to 200, in contrast to the value of 4 from the sample geometric anisotropy, suggesting that the superconducting body has a very high aspect ratio; several steps in the magnetic susceptibilities along both the c- and ab-directions in the field range between 10-3 to 10^+3 Oe, demonstrating the sample consisting of Josephson-Coupled superconducting islands imbedded with nano-scale interfaces; and the presence of superparamagnetic clusters associated with minute As-vacancies, consistent with theoretical calculations. The present studies therefore present the strongest evidence for interface-enhanced Tc to date.

Chu, C. W.; Lv, Bing; Deng, Liangzi; Wei, Fengyan; Xue, Yu-Yi; Gooch, Melissa; Lorenz, Bernd

2013-03-01

130

GEOmon: Towards an integrated system for Earth Observation  

NASA Astrophysics Data System (ADS)

Changes in the atmospheric composition of many chemically and radiatively important gases not only affect the climate, but also have significant impacts on human health, ecosystems and the hy-drological cycle. To understand and predict these long-term changes, high quality integrated ob-servations are required. The EU FP6 project GEOmon is a first step to build a future integrated pan-European Atmospheric Observing System dealing with systematic observations of long-lived greenhouse gases, reactive gases, aerosols, and stratospheric ozone. To achieve this, quality as-sured, harmonized, and representative long-term data sets collected by in-situ and remote sensing instruments (ground based and aircraft) at the European and global level have to be integrated with satellite measurements. As part of the European observation system (GMES) and of IGACO (Integrated Global Atmospheric Chemistry Observations), GEOmon is contributing to the GEOSS (Global Earth Observation System of Systems) aims on air quality and climate change. This paper provides examples of basic investigations within GEOmon activity 2 (Reactive Gases) that are essential for building an integrated observation system such as the analysis of representa-tiveness of in-situ sites, field intercomparisons of ground-based remote sensing profiles, including in-situ data and comparisons of integrated profiles as well as vertically integrated in-situ data, with vertical tropospheric profiles and columns of satellites. In order to determine and understand trends of reactive compounds, harmonized long term data series as well as integrated datasets will be used for the evaluation with selected state-of-the-art chemical transport models used in the framework of GEOmon to simulate the long-term evolution of the atmospheric composition.

Buchmann, B.; Monks, P. S.; Zahn, A.; Wittrock, F.

2008-12-01

131

Effects of Rare-Earth Oxides on Temperature Stability of Acceptor-Doped BaTiO3  

NASA Astrophysics Data System (ADS)

The effects of rare-earth oxides (Yb2O3, Ho2O3, Er2O3) on the temperature stability of acceptor doped BaTiO3 dielectrics were studied. The samples doped with 1 mol % rare-earth oxides exhibited the highest dielectric constants. Substantial reductions in grain size were observed in the specimens with 1 mol % rare-earth oxides (˜0.6 ?m) compared with the nondoped specimens (˜1.5 ?m). As the rare-earth oxide content was increased, the Curie point progressively moved to higher temperatures. The addition of rare-earth oxides improved the temperature dependence of the dielectric constants of the acceptor-doped BaTiO3-rare-earth oxide systems over the whole temperature range studied (-55 to 150°C), and the temperature coefficient of capacitance(TCC) curves satisfied the X8R requirements for >2 mol % Yb2O3 and >3 mol % Er2O3 or Ho2O3.

Song, Young Hoon; Han, Young Ho

2005-08-01

132

Vulnerability of rare-earth-doped fibers for space missions: origins of radiation-induced attenuation  

NASA Astrophysics Data System (ADS)

We characterized the responses of different types of rare-earth doped fibers (Yb, Er and Er/Yb) to various types of radiations like UV, gamma-rays, X-rays and protons. The understanding of the radiation-induced effects in this class of optical fibers is necessary as they are possible candidates for use as part of fiber-based systems like gyroscopes that will have to operate in space environment. For all types of irradiations, the main effect is an increase of the linear absorption of these waveguides due to the generation of point defects in the core and cladding. We characterize the growth and decay kinetics of the radiation-induced attenuation during and after irradiation for various compositions of optical fibers. In this paper, we particularly investigate the relative influence of the rare-earth ions (Er, Yb or Er/Yb) and of the glass matrix dopants (Al, P, ...) on the optical degradation induced by ultraviolet laser exposure at 5 eV. This has been done by using a set of five prototype optical fibers designed by iXFiber SAS to enlighten the role of these parameters. Additional spectroscopic tools like confocal microscopy of luminescence are also used to detect possible changes in the spectroscopy of the rare-earth ions and their consequence on the functionality of the active optical fibers.

Ouerdane, Y.; Girard, S.; Tortech, B.; Robin, T.; Marcandella, C.; Boukenter, A.; Cadier, B.; Meunier, J.-P.; Crochet, P.

2009-05-01

133

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 LaxY1–xPO4: 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 LaxGd1–xPO4: 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, YxGd1–xPO4: 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

134

Postgraduate Education in Earth and Environmental Sciences: an Integrated Concept  

NASA Astrophysics Data System (ADS)

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

Grosfeld, K.; Lohmann, G.; Ladstätter-Weißenmayer, A.; Burrows, J.; Sprengel, C.; Bijma, J.

2009-04-01

135

An Integrated Concept on Earth and Environmental Sciences Postgraduate Education  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

136

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

137

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

138

Effect of rare earth elements doping on the electrical properties of (Ba,Sr)TiO3 thin film capacitors  

Microsoft Academic Search

Barium strontium titanate (BST) thin film capacitors are being intensively investigated for tunable microwave devices, because of their high permittivity, low dielectric loss in the microwave region and field dependent permittivity. This study investigates the effect of rare earth elements doping on the electrical properties of BST thin film capacitors. BST thin films were deposited by an RF magnetron sputtering

Nobuo Kamehara; Kazuaki Kwihara

2008-01-01

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

A highly photoactive bilayer lipid membrane doped with a rare-earth complex  

SciTech Connect

A novel photosensitizer composed of a hemicyanine cation and a rare-earth complex anion (PLnL[sub 4]) was doped into bilayer lipid membranes (BLM) to produce a large photocurrent. The highest photocurrent across the PYbL[sub 4]-BLM may reach to about 50nA under continuous illumination by visible light. It was found that the great enhancement of the photoresponse is due to the promotion of charge by the complex anions. Although there are still some details about the mechanism and membrane structure of PYBL[sub 4]-BLM remaining to be explored, the notable advantages such as being less expensive while also having a high photoresponse and high stability should make the compound a hopeful candidate for solar energy conversion.

Yi-Jin Xiao; Xiao-Xia Gao; Chun-Hui Huang; Ke-Zhi Wang [Peking Univ., Beijing (China)

1994-11-01

141

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

142

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

SciTech Connect

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

McAuslan, D. L.; Korystov, D.; Longdell, J. J. [Jack Dodd Centre for Photonics and Ultra-Cold Atoms, Department of Physics, University of Otago, Dunedin, New Zealand. (New Zealand)

2011-06-15

143

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

144

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

145

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

146

On the optical properties of undoped and rare-earth-doped yttrium aluminium garnet single crystals  

NASA Astrophysics Data System (ADS)

Optical absorption and photoluminescence (PL) measurements were performed on single crystals of undoped Y3Al5O12 (YAG) and a number of rare-earth-doped YAG to study the effect of dopant type and concentration, growth atmosphere, post-growth annealing and UV irradiation on the optical properties of YAG crystals. The presence of hydrogen in the growth atmosphere was found to be essential for enhancing the incorporation of Ce ions in the Ce3+ state in Ce-doped YAG (Ce?:?YAG). Annealing in air was shown to have no effect on the PL emission of Ce?:?YAG crystals. An absorption peak around 256 nm was observed in the undoped YAG and Ce?:?YAG crystals after air anneal at 1200 °C. Optical absorption and annealing experiments support the association of the 256 nm peak with Fe impurities and oxygen ions. UV irradiation modifies the valency of impurities and generates electronic defects leading to an increase in the optical density of YAG crystals. Optimizing the growth and annealing conditions is critical in order to develop Ce?:?YAG single crystals as efficient scintillators.

Varney, C. R.; Mackay, D. T.; Reda, S. M.; Selim, F. A.

2012-01-01

147

Coherency strain enhanced dielectric-temperature property of rare-earth doped BaTiO3  

NASA Astrophysics Data System (ADS)

Core/shell-grained BaTiO3 samples were prepared with addition of rare earth elements. The core/shell interface was semi-coherent, and many misfit dislocations formed in Dy-doped samples. In contrast, a coherent interface and few dislocations were observed in Ho- and Er-doped samples. Dy-doped samples exhibited poor temperature stability, showing a peak with no frequency dispersion. Ho- and Er-doped samples exhibited a broad curve with frequency dispersion. This improved temperature stability is attributed to the coherency strain, which leads to the formation of polar nano-regions in the shell. Coherency at the core/shell interface is critical to improve the temperature stability of core/shell-structured BaTiO3.

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

2013-03-01

148

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 180×10-6 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

149

Effect of transition element doping on crystal structure of rare earth borosilicides REB 44Si 2  

Microsoft Academic Search

On a previous study on samples of doped-YB44Si2, an improvement of thermoelectric properties has been achieved. Regarding the interesting effect of the doping of transition elements on the thermoelectric properties, a single crystal study has been carried out on Zn doped, Rh doped and Ni doped samples to assess how the transition element doping affects the crystal structure. Refinements were

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

2011-01-01

150

Synthesis and evaluation of rare-earth doped glasses and crystals for optical refrigeration  

NASA Astrophysics Data System (ADS)

This research focused on developing and characterizing rare-earth doped, solid-state materials for laser cooling. In particular, the work targeted the optimization of the lasercooling efficiency in Yb3+ and Tm3+ doped fluorides. The first instance of laser-induced cooling in a Tm3+-doped crystal, BaY2F8 was reported. Cooling by 3 degrees Kelvin below ambient temperature was obtained in a single-pass pump geometry at lambda = 1855 nm. Protocols were developed for materials synthesis and purification which can be applied to each component of ZBLANI:Yb 3+/Tm3+ (ZrF4 -- BaF2 -- LaF3 -- AlF3 -- NaF -- InF3: YbF3/TmF3) glass to enable a material with significantly reduced transition-metal impurities. A method for OH- impurity removal and ultra-drying of the metal fluorides was also improved upon. Several characterization tools were used to quantitatively and qualitatively verify purity, including inductively-coupled plasma mass spectrometry (ICP-MS). Here we found a more than 600-fold reduction in transition-metal impurities in a ZrCl2O solution. A non-contact spectroscopic technique for the measurement of laser-induced temperature changes in solids was developed. Two-band differential luminescence thermometry (TBDLT) achieved a sensitivity of ˜7 mK and enabled precise measurement of the zero-crossing temperature and net quantum efficiency. Several Yb3+-doped ZBLANI glasses fabricated from precursors of varying purity and by different processes were analyzed in detail by TBDLT. Laser-induced cooling was observed at room temperature for several of the materials. A net quantum efficiency of 97.39+/-0.01% at 238 K was found for the best ZBLANI:1%Yb 3+ laser-cooling sample produced from purified metal-fluoride precursors, and proved competitive with the best commercially procured material. The TBDLT technique enabled rapid and sensitive benchmarking of laser-cooling materials and provided critical feedback to the development and optimization of high-performance optical cryocooler materials. Also presented is an efficient and numerically stable method to calculate time-dependent, laser-induced temperature distributions in solids, including a detailed description of the computational procedure and its implementation. The model accurately predicted the zero-crossing temperature, the net quantum efficiency, and the functional shape of the transients, based on input parameters such as luminescence spectra, dopant concentration, pump properties, and several well-characterized material properties.

Patterson, Wendy

151

An integrated view of data quality in Earth observation.  

PubMed

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

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

2012-12-10

152

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

153

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

154

Motivational and social cognitive predictors of doping intentions in elite sports: An integrated approach.  

PubMed

Doping use is an important issue in both competitive and non-competitive sports, and poses potentially irreversible health consequences to users. Scholars increasingly call for theory-driven studies on the psychosocial processes underlying doping use that will inform subsequent policy-making and prevention interventions. The aim of the study was to implement an integrative theoretical model to assess the direct and indirect effects of motivational variables, moral orientations, and social cognitions on doping intentions. A randomly selected and representative sample of 750 elite athletes anonymously completed a battery of questionnaires on motivational and moral constructs, and social cognitions related to doping. Hierarchical linear regression analysis and multiple mediation modeling were used. The effects of achievement goals and moral orientations were significantly mediated by attitudinal, normative, and self-efficacy beliefs, in both lifetime ever and never doping users. Moral orientations indirectly predicted the doping intentions of never users, but did not predict ever users' doping intentions. Achievement goals and sportspersonship orientations influence doping intentions indirectly, through the effects of attitudes and self-efficacy beliefs. Sportspersonship (moral) orientations were relevant to doping intentions among athletes with no prior experiences with doping, while achievement goals and situational temptation were relevant to both lifetime never and ever dopers. PMID:23574429

Barkoukis, V; Lazuras, L; Tsorbatzoudis, H; Rodafinos, A

2013-04-10

155

Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping.  

PubMed

NaGdF4 is regarded as an ideal upconversion (UC) host material for lanthanide (Ln(3+)) activators because of its unique crystal structure, high Ln(3+) solubility, low phonon energy and high photochemical stability, and Ln(3+)-doped NaGdF4 UC nanocrystals (NCs) have been widely investigated as bio-imaging and magnetic resonance imaging agents recently. To realize their practical applications, controlling the size and uniformity of the monodisperse Ln(3+)-doped NaGdF4 UC NCs is highly desired. Unlike the routine routes by finely adjusting the multiple experimental parameters, herein we provide a facile and straightforward strategy to modify the size and uniformity of NaGdF4 NCs via alkaline-earth doping for the first time. With the increase of alkaline-earth doping content, the size of NaGdF4 NCs increases gradually, while the size-uniformity is still retained. We attribute this "focusing" of size distribution to the diffusion controlled growth of NaGdF4 NCs induced by alkaline-earth doping. Importantly, adopting the Ca(2+)-doped Yb/Er:NaGdF4 NCs as cores, the complete Ca/Yb/Er:NaGdF4@NaYF4 core-shell particles with excellent size-uniformity can be easily achieved. However, when taking the Yb/Er:NaGdF4 NCs without Ca(2+) doping as cores, they could not be perfectly covered by NaYF4 shells, and the obtained products are non-uniform in size. As a result, the UC emission intensity of the complete core-shell NCs increases by about 30 times in comparison with that of the cores, owing to the effective surface passivation of the Ca(2+)-doped cores and therefore protection of Er(3+) in the cores from the non-radiative decay caused by surface defects, whereas the UC intensity of the incomplete core-shell NCs is enhanced by only 3 times. PMID:24096887

Lei, Lei; Chen, Daqin; Huang, Ping; Xu, Ju; Zhang, Rui; Wang, Yuansheng

2013-10-04

156

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

157

Low-temperature proton spin lattice relaxation maxima of lanthanum hydrides doped with paramagnetic rare earth ions  

NASA Astrophysics Data System (ADS)

The low-temperature proton spin-lattice relaxation is analysed for lanthanum hydrides LaHx intentionally doped with Gd or Ce. These paramagnetic impurities were also characterized by static magnetic susceptibility and electron spin resonance measurements. A quantitative description of the proton relaxation rate maxima, as well as of the electron spin relaxation data, is presented. These analyses indicate that the density of states at the rare earth site disappears only for x \\gtrsim 2.9 .

Leyer, S.; Barnes, R. G.; Buschhaus, C.; Fischer, G.; Pilawa, B.; Pongs, B.; Tinner, A.; Dormann, E.

2004-09-01

158

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

159

Reducing decoherence in optical and spin transitions in rare-earth-metal-ion-doped materials  

NASA Astrophysics Data System (ADS)

In many important situations, the dominant dephasing mechanism in cryogenic rare-earth-metal-ion-doped systems is due to magnetic field fluctuations from spins in the host crystal. Operating at a magnetic field where a transition has a zero first-order Zeeman (ZEFOZ) shift can greatly reduce this dephasing. Here we identify the location of transitions with a zero first-order Zeeman shift for optical transitions in Pr3+:YAG and for spin transitions in Er3+:Y2SiO5. The long coherence times that ZEFOZ can enable would make Pr3+:YAG a strong candidate for achieving the strong-coupling regime of cavity QED, and would be an important step forward in creating long-lived telecommunications wavelength quantum memories in Er3+:Y2SiO5. This work relies mostly on published spin-Hamiltonian parameters, but Raman heterodyne spectroscopy was performed on Pr3+:YAG to measure the parameters for the excited state.

McAuslan, D. L.; Bartholomew, J. G.; Sellars, M. J.; Longdell, J. J.

2012-03-01

160

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 (Pr3+) and small amounts of lithium ions (˜0.1-0.2 wt.%) were produced from the tetraethyl orthosilicate (TEOS), AlCl3·6H2O (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 3P0 ? 3H4 (blue) and 3P0 ? 3F3 (red) transitions of Pr3+ 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

161

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

162

Laser cooling of rare-earth doped solids: the next step  

NASA Astrophysics Data System (ADS)

A quantitative description of optical refrigeration in rare-earth doped solids in the presence of impurities is presented. The model includes the competition of radiative processes with energy migration, energy transfer to transition-metal ions, and multiphonon relaxation. The cooling efficiency is sensitive to the presence of both 3d metal ions with absorption in the near infrared and high-frequency vibrational impurities such as OH. A case study of ZBLAN:Yb3+ identifies Cu2+, Fe2+, Co2+, and OH as the most problematic species and establishes a 1-10 ppm upper limit for each of these impurities for a practical ZBLAN:Yb3+ optical cryocooler operating at 100-150 K to become feasible. The model results form the basis for an advanced strategy for the synthesis of high-purity ZBLAN:Yb3+ that exploits the potential of available purification techniques in an aqueous intermediate step. Such high-performance ZBLAN:Yb3+ is expected to enable optical cryocoolers with ~1% overall efficiency at 120 K and find use in a wide range of applications that require highly reliable, noise-free, and vibration-free cooling of electronic and opto-electronic components.

Hehlen, Markus P.; Epstein, Richard I.; Inoue, Hiroyuki

2006-03-01

163

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

SciTech Connect

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

Neal, John S [ORNL; Boatner, Lynn A [ORNL; Ramey, Joanne Oxendine [ORNL; Wisniewski, D. [Institute of Physics, Nicolaus Copernicus University, Toru?, Poland; Kolopus, James A [ORNL; Cherepy, Nerine [Lawrence Livermore National Laboratory (LLNL); Payne, Stephen A. [Lawrence Livermore National Laboratory (LLNL)

2011-01-01

164

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

165

Proton-exchanged waveguides in rare-earth-doped LiNbO3 and LiTaO3 waveguides  

NASA Astrophysics Data System (ADS)

During the last few years, integrated optical waveguide lasers have been demonstrated in a variety of rare earth doped materials. Different techniques were used to fabricate such devices: ion exchange in neodymium doped glass ion implantation in crystals such as Nd:YAG2 and Nd:LiNbO33, titanium diffusion in Nd:LiNbO34, Er:LiNbO35, and Nd:LiTaO36, and proton exchange in Nd:MgO:LiNbO37 and Nd:LiTaO38. Due to their electro-optic and nonlinear properties, rare earth doped lithium niobate and tantalate are very attractive for realizing mode-locked and Q-switched devices as well as intracavity frequency doubled sources. Following the success we had in realizing such functions in annealed proton exchanged Nd:MgO:LiNbO3 waveguides, we tried to transpose this technique to Nd:LiTaO38 which has the reputation of having a higher optical damage threshold than LiNbO3, and has ben used to produce efficient guided- wave frequency doublers using the periodic domain inversion technique, and Er:LiNbO3 which allows applications in the telecommunication domain. This transposition turns out to be more difficult than expected. In this paper, I will explain these difficulties starting with some information in concerning the proton exchange technique itself. I will then present the results we obtained on the different crystals, to focus the discussion on the reduction of the excited state lifetime induced by the different kinds of proton exchange processes.

de Micheli, Marc P.

1997-04-01

166

Effect of rare-earth doping on the thermoelectric and electrical transport properties of the transition metal pentatelluride hafnium pentatelluride  

NASA Astrophysics Data System (ADS)

The transition metal pentatellurides HfTe5 and ZrTe5 have been observed to possess interesting electrical transport properties. High thermopower and low resistivity values result in high thermoelectric power factors. In addition, they possess anomalous transport behavior. The temperature dependence of the resistivity is semimetallic except for a large resistive peak as a function of temperature at around 75 K for HfTe5 and 145 K for ZrTe5. At a temperature corresponding to this peak, the thermopower crosses zero as it moves from large positive values to large negative values. This behavior has been found to be extremely sensitive to changes in the energetics of the system through influences such as magnetic field, stress, pressure, microwave radiation, and substitutional doping. This behavior has yet to be fully explained. Previous doping studies have shown profound and varied effects on the anomalous transport behavior. In this study we investigate the effect on the electrical resistivity, thermopower, and magnetoresistance of doping HfTe5 with rare-earth elements. We have grown single crystals of nominal Hf0.75RE 0.25Te5 where RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, and Ho. Electrical resistivity and thermopower data from about 10 K to room temperature are presented and discussed in terms of the thermoelectric properties. Doping with rare-earth elements of increasing atomic number leads to a systematic suppression of the anomalous transport behavior. Rare-earth doping also leads to an enhancement of the thermoelectric power factor over that of previously studied pentatellurides and the commonly used thermoelectric material Bi2Te3. For nominal Hf0.75Nd0.25Te5 and Hf0.75 Sm0.25Te5, values more than a factor of 2 larger than that Bi2Te3 are observed. In addition, suppression of the anomalous transport behavior leads to a suppression of the large magnetoresistive effect observed in the parent compounds. Rare-earth doping of HfTe5 has a profound impact on the anomalous electrical transport properties of the parent pentatellurides and produces enhanced thermoelectric properties.

Lowhorn, Nathan Dane

167

First-principles study on defect chemistry and migration of oxide ions in ceria doped with rare-earth cations.  

PubMed

Oxygen transport in rare-earth oxide (RE(2)O(3)) doped CeO(2) with fluorite structure has attracted considerable attention owing to both the range of practical usage (e.g., fuel cells, sensors, etc.) and the fundamental fascination of fast oxide ion transport in crystalline solids. Using density-functional theory, we have calculated the formation energies of point defects and their migration properties in RE(2)O(3) doped CeO(2)(RE = Sc, Y, La, Nd, Sm, Gd, Dy, and Lu). The calculated results show that oxygen vacancies are the dominant defect species obtained by RE(3+) doping. They form associates with the RE(3+) ions, and the corresponding defect association energy is a strong function of the ionic radii of the RE(3+) dopants. The migration of an oxygen vacancy was investigated using the nudged elastic band method. The lowest activation energy for oxygen vacancy hopping is obtained for a straightforward migration path between two adjacent oxygen sites. The migration energy of an oxygen vacancy also strongly depends on the ionic radii of the neighbouring dopant cations. Accordingly, we have identified two factors that affect the oxygen vacancy migration; (1) trapping (or repelling) of an oxygen vacancy at the NN site of the RE(3+) dopant, and (2) reduction (or enlargement) of the migration barrier by RE(3+) doping. These findings provide insight for atomistic level understanding of ionic conductivity in doped ceria and would be beneficial for optimizing ionic conductivity. PMID:19370220

Nakayama, Masanobu; Martin, Manfred

2009-03-11

168

Structural and magnetic properties of rare-earth doped (Sr2-xSmx)FeMoO6 compounds  

NASA Astrophysics Data System (ADS)

Electron doped double perovskite compound (Sr2-xSmx)FeMoO6 (0?x?0.25) has been synthesized by solid-state reaction at high temperature. Crystal structure and magnetic properties of the compounds have been investigated by X-ray powder diffraction (XRD) and magnetic measurements. XRD revealed that all the compounds were of single phase and belonged to a I4/m lattice. The degree of cationic ordering on the B site was decreased pronouncedly by the electron doping. Different from the results of La- and Nd-doped Sr2FeMoO6, Curie temperature (TC) of (Sr2-xSmx)FeMoO6 decreased first with the doping and then increased beyond x=0.15, indicating that steric effect was enhanced as the radius of rare-earth ions decreased. Saturation magnetization (MS) of the compounds decreased with the doping level and anti-site (AS) concentration. Sm moment showed a considerable contribution to MS at low temperature, leading to an abrupt drop of MS between x=0.1 and 0.15.

Zhang, Q.; Liu, G. Y.; Xu, Z. F.; Feng, X. M.; Rao, G. H.

2010-03-01

169

Integrated Earth Observations: Application to Air Quality and Human Health.  

National Technical Information Service (NTIS)

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 nat...

A. Bond G. Foley M. Gant M. Humble S. Tinkle V. Garcia

2007-01-01

170

Electromagnetic wave propagation over an inhomogeneous flat earth - Two-dimensional integral equation formulation  

Microsoft Academic Search

With the aid of a two-dimensional integral equation formulation, the ground wave propagation of electromagnetic waves transmitted by a vertical electric dipole over an inhomogeneous flat earth is investigated. For the configuration in which a ground wave is propagating across an 'island' on a flat earth, the modulus and argument of the attenuation function have been computed. The results for

G. de Jong

1975-01-01

171

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

172

Rare-Earth Doped Wide Bandgap Oxide Semiconductor Materials and Devices  

NASA Astrophysics Data System (ADS)

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

Wellenius, Ian Patrick

173

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

SciTech Connect

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

Le Nguyen, An-Dien

1996-05-01

174

Enhanced laser cooling of rare-earth-ion-doped nanocrystalline powders  

NASA Astrophysics Data System (ADS)

The enhanced laser cooling performance of rare-earth-ion-doped nanocrystalline powders is predicted, compared to the bulk material, using Yb3+:Y2O3 as the model material. This is achieved by enhancing the off-resonance, phonon-assisted absorption, which is proportional to the three factors considered in this paper: the dopant concentration, the pumping field energy, and the excitation coefficient. Using the energy transfer theory for concentration quenching, the optimum concentration corresponding to the maximum cooling power is found to be considerably larger than the currently used value, suggesting noticeable enhancement effects for laser cooling. The pumping field energy is enhanced in random nanopowders compared with bulk crystals under the same irradiation, due to the multiple scattering of photons. Photons are thus localized in the medium and do not propagate through, increasing the photon absorption of the pumping beam (and it is shown that the reabsorption of the fluorescence is negligible). Using molecular dynamics simulations, the phonon density of states (DOS) of the nanopowder is calculated, and found to have broadened modes, and extended small tails at low and high frequencies. The second-order electronic transition rate for the anti-Stokes luminescence is calculated using the Fermi golden rule, which includes the influence of this phonon DOS, and is shown to have enhancement effects on the laser cooling efficiency using nanopowders. It is finally concluded that these three enhancement mechanisms are essentially to increase the population of the three participating carriers (electron, photon, and phonon) in the interacting volume, and this also points out directions for enhancing laser cooling performance in bulk materials.

Ruan, X. L.; Kaviany, M.

2006-04-01

175

Selective-area doping of porous solgel films for integrated optics.  

PubMed

A technique for doping of porous films by surface adsorption of ions from aqueous solution is demonstrated. Fabrication of the films by use of the solgel technique gives a nanometer-scale porosity, which provides high doping levels and homogeneity. Doping through a masking layer patterned by photolithography is thus possible. With Pb as a dopant, lead silicate films with refractive indices of 1.46 to 1.55 were obtained, with submicrometer patterning resolution. Linear control of the refractive index is achieved through variation of the solution pH. Applications of this technique in integrated optics and optical elements are proposed. PMID:18188389

McCarthy, O; Yeatman, E M

1997-12-15

176

Self-induced laser line sweeping and self-pulsing in rare-earth doped fiber lasers  

NASA Astrophysics Data System (ADS)

We report laser line self-sweeping phenomenon in rare-earth doped fiber lasers. The effect of self-sweeping is observed in erbium-doped fiber laser and also in the ytterbium-doped one. The former, having linear layout, is core-pumped by laser diode (LD) at 980 nm. Laser cavity is formed with fiber loop mirror and angle cleaved fiber end. Laser operation is delimited by tunable filter; we observed sweeping regime in 0.5 nm wide interval defined by the filter. Yb-doped allfiber laser has linear layout as well. Laser is cladding-pumped by LD at about 976 nm; cavity is constrained by rightangle cleaved fibers. We observed laser line sweeping having a range of 6 - 8 nm. We characterized both lasers with respect to sweeping properties thoroughly. We present output laser line wavelength and instant output intensity versus time; we show dependence of sweeping range, sweeping rate, and sweeping period on output laser power and pump laser temperature (pump laser wavelength).

Navratil, P.; Vojtíšek, P.; Peterka, P.; Honzátko, P.; Kube?ek, V.

2012-01-01

177

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

2012-09-04

178

Radial integrals for the magnetic form factor of the 5d electrons of rare earth elements.  

PubMed

The radial integrals , where L = 0, 2, 4, for several electronic configurations of the 5d electrons of rare earth elements are calculated using radial wavefunctions from the Hartree-Fock relativistic method in the Cowan program. Gaussian analytical expressions with four exponential terms are fitted to the values for rare earth elements and the fitted coefficients are tabulated. The tables can be used to interpret the form factor measurements for rare earth metals. Using the radial integrals of Ce 4f and 5d electrons, the experimental measurement of the magnetic form factor of CePd(3) is investigated. PMID:22893242

Kobayashi, Kohjiro; Nagao, Tatsuya; Ito, Masahisa

2012-07-26

179

Enhancement of the power factor of the transition metal pentatelluride HfTe5 by rare-earth doping  

NASA Astrophysics Data System (ADS)

The transition metal pentatellurides HfTe5 and ZrTe5 have been observed to possess interesting electrical transport properties with high thermopower and low resistivity values leading to high thermoelectric power factors. We have investigated the effect of doping HfTe5 with rare-earth elements by measuring the power factor data from about 10 K to room temperature on single crystals of Hf1-xRxTe5, where R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, and Ho. Samples that have been doped with Nd (Hf1-xNdxTe5) possess power factors more than a factor of 2 larger than that of the commonly used thermoelectric material Bi2Te3.

Lowhorn, Nathan D.; Tritt, Terry M.; Abbott, Edward E.; Kolis, J. W.

2006-01-01

180

Disordered electronic and magnetic systems - Transition metal (manganese) and rare earth (gadolinium) doped amorphous group IV semiconductors (carbon, silicon, germanium)  

NASA Astrophysics Data System (ADS)

While the physics of electrical doping of semiconductors has been well understood for decades, magnetic doping and the interactions between the carriers and the magnetic moments in semiconductors are still under active investigation for various applications, such as spintronics and quantum computing. Our systematic studies on transition-metal-doped (TM-doped) and rare-earth-doped (RE-doped) amorphous group IV elemental semiconductors provide unique insight into the rich physics of this type of materials. Our model system is the e-beam coevaporated a-GdxSi1-x films. Magnetron cosputtered a-GdxSi 1-x films, despite having very different film morphology at the 10-nm scale from the e-beam coevaporated films, are demonstrated to possess almost the same physical properties. Cosputtered a-GdxC1-x (:Hy) and Gd ion-implanted ta-C (ta-C1-x:Gd x) films are studied for Gd in different a-C matrices with different sp2/sp 3 ratio. All doped a-C films are on the insulating side of the metal-insulator transition. Very similar to a-Gd xSi1-x films, Gd possesses a large magnetic moment in a-C. The moment-moment and moment-carrier interactions lead to a spin-glass ground state and large negative magnetoresistance (MR) below a crossover temperature T' in both a-Gd xC1-x<(:Hy) and ta-C1-x:Gdx films. A small positive MR is found above T'. Transition metal Mn has always been believed to possess a large local moment in Si or Ge. However, e-beam coevaporated a-MnxSi1-x films are found to show a quenched local moment for Mn concentration as low as x=0.005 and up to x=0.175. All films are purely paramagnetic and have very small saturation moments. Unlike Gd, which provides both carriers and local moment, Mn only provides electrical carriers in a-Si. These results suggest an itinerant non-magnetic Mn states in a-Si; the insulating behavior is a result of the strong structural disorder. This quenching of the local Mn moment has not been predicted by any existing theory. Consistent with the small Mn moment, a-MnxSi1- x films show a very small positive MR, in contrast to Gd-doped films.

Zeng, Li

181

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

182

Datacasting: Integration of Earth Science Data and Information using RSS  

NASA Astrophysics Data System (ADS)

Datacasting provides consumers of Earth Science data the ability to extract the files from a data stream that precisely meet a predefined need. For example, “Acquire from a MODIS L2 data stream only the data files that contain information about a wild fire in Southern California”. Our approach to solving this problem has been to take the concept of RSS (Really Simple Syndication) feeds commonly used for delivering regularly changing web content and extending this to represent a stream of data files and deliver regularly changing Earth science data content. In essence, this project is doing for Earth Science what Podcasting has done for audio and video. Where Podcasting extended RSS to revolutionize how users access ongoing audio and video content provided by various media outlets, so too does Datacasting extend RSS to provide users with the ability to download data granules as the data is made available. Moreover, we have taken the concept one step further by creating a solution for filtering on feeds in order to identify precisely the granules of interest based on user-defined criteria. By utilizing customized metadata to seamlessly represent Earth Science metadata, we are providing the ability to view arbitrary scientific metadata within the data feed while maintaining generalized RSS compatibility. By taking this approach with regard to the RSS standard, we are thereby adding the ability to cross-correlate Datacasting and other RSS compliant feeds (e.g., GeoRSS) to create new and useful information.

McCleese, S.; Bingham, A.; Deen, R.; Stough, T.; Chung, N.

2010-12-01

183

Datacasting: Integration of Earth Science Data and Information using RSS  

Microsoft Academic Search

Datacasting provides consumers of Earth Science data the ability to extract the files from a data stream that precisely meet a predefined need. For example, ``Acquire from a MODIS L2 data stream only the data files that contain information about a wild fire in Southern California''. Our approach to solving this problem has been to take the concept of RSS

S. McCleese; A. Bingham; R. Deen; T. Stough; N. Chung

2010-01-01

184

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 (75TeO2-20ZnO-5 Na2O, 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 (Yb2O3 concentrations up to 5 wt%) and an increase in 3F4 lifetime with Yb2O3 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

185

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

Microsoft Academic Search

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

P. Teillet; R. Gauthier; T. Pultz

2002-01-01

186

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

187

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

Microsoft Academic Search

Anatase TiO 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, and

Ji Tianhao; Liu Yang; Zhao Hui; Du Haiyan; Sun Jiayue; Ge Guanglu

2010-01-01

188

Improving visible-light photocatalytic activity for hydrogen evolution over ZnIn 2S 4: A case study of alkaline-earth metal doping  

Microsoft Academic Search

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

Shaohua Shen; Liang Zhao; Xiangjiu Guan; Liejin Guo

189

Red, green, and blue upconversion luminescence of trivalent-rare-earth ion-doped Y2O3 nanocrystals  

NASA Astrophysics Data System (ADS)

Trivalent-rare-earth ion-doped Y2O3 nanocrystals have been synthesized, and their photoluminescence properties have been studied under 980 nm laser diode excitation. The crystallite size estimated by x-ray diffractometry and scanning electron microscopy was about 30-40 nm. In Yb3+ and Tm3+ codoped Y2O3 nanocrystals, the bright blue emissions near 450 and 480 nm have been noticeable due to the 1D2-3F4 and 1G4-3H6 transitions of Tm3+, respectively. The bright green emissions of Er3+ doped Y2O3 nanocrystals appeared near 530 and 550 nm were assigned to the 2H11/2-4I15/2 and 4S3/2-4I15/2 transitions of Er3+, respectively. The ratio of the intensity of green luminescence to that of red luminescence has decreased with an increase of concentration of Yb3+ in Er3+ doped Y2O3 nanocrystals. In sufficient quantities of Yb3+ to Er3+, the bright red emission near 660 nm has been predominant due to the 4F9/2-4I15/2 transition of Er3+. The primary color components are in these red, green, and blue emissions, from which a wide spectrum of colors, including white, would be produced by appropriate mixing them.

Matsuura, Daisuke

2002-12-01

190

Earth Observation and GIS Services Integration Approach in MASS  

NASA Astrophysics Data System (ADS)

This paper describes an environment for the integration of EO and GIS services supporting the provision of EO services and "information products" closer to customer expectations and processes. The paper explains how the adoption of readily available XML-based Web standards and protocols in an open environment can facilitate the integration.

Coene, Y.; Gianfranceschi, S.; Marchetti, P.

191

Integrated Earth Observation System Could Help Reduce Impacts of Natural Hazards  

NASA Astrophysics Data System (ADS)

The development of a framework for an integrated Earth observation system is on a fast track, according to Conrad Lautenbacher, administrator for the U.S. National Oceanic and Atmospheric Administration, because of the impetus provided by a high-level summit this summer, and also because of existing Earth monitoring efforts that have laid much of the groundwork. Lautenbacher made his remarks on 22 October at a workshop on reducing natural disasters through improved Earth observations, held in Washington, D.C. The ministerial-level summit was on 31 July in Washington, D.C. (see Eos, 12 August).

Showstack, Randy

192

Integration of a Modulated Barrier Photodiode with a Doped-Channel Quasi-MISFET.  

National Technical Information Service (NTIS)

An integration scheme for a front-end photo receiver is demonstrated wherein an identical GaAs/InGaAs/AlGaAs heterostructure is used for realizing a modulated barrier photodiode (MBP) and a doped-channel quasi-MISFET. The detectors exhibit optical gains o...

W. Q. Li P. K. Bhattacharya

1989-01-01

193

Cerium-doped mixed-alkali rare-earth double-phosphate scintillators for x- and gamma-ray detection  

NASA Astrophysics Data System (ADS)

Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Cerium-doped K3Lu(PO4)2 and Rb3Lu(PO4)2 scintillators have exhibited light outputs of 32,500 and 28,200 photons/MeV respectively and decay times of 37 and 34 nanoseconds respectively. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K2CsLu(PO4)2 and CsLi2Lu(PO4)2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. In order to better understand and to ultimately optimize the scintillation properties of these scintillators, new members of the rare-earth double-phosphate family have been synthesized by high temperature flux growth. These new samples, represented by the general formula (A,B)3Lu(PO4)2:Ce where A and B are alkali elements, incorporate mixed alkali rather than single alkali components and varying levels of Ce doping. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. In this paper, we identify promising samples and results that clearly demonstrate outstanding light output, up to 270% of BGO, fast decay times, 29-39 nanoseconds, and peak emission wavelengths of ~ 400 nm for many of the samples.

Neal, John S.; Boatner, Lynn A.; Spurrier, Merry; Szupryczynski, Piotr; Melcher, Charles L.

2006-08-01

194

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

195

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

SciTech Connect

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

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

2012-04-10

196

The luminescence properties of the wide bandgap nitrides doped with rare earth ions and gallium nitride doped with conventional isoelectronic impurities  

NASA Astrophysics Data System (ADS)

In this work we study the luminescence properties of GaN, AIN and AlGaN/GaN multiquantum well structure doped with rare earth (RE) ions as well as GaN doped with conventional dopants. The doping method was done through an ion implantation process at room temperature with different ion's doses and implantation energies. The focus was on Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er and Tm ions implanted in GaN epilayers, Eu and Tb ions implanted in crystalline AlN epilayers, Er in situ doped amorphous AlN thin films and AlGaN/GaN multiquantum well structure implanted with Eu ions. It was shown that RE ions embedded in III-nitrides semiconductors followed by post-implantation isochronal thermal annealing at 1100°C in different ambient gases at atmospheric pressure could be activated as efficient luminescence centers. The sharp characteristic emission lines corresponding to RE 3+ intra-4 fn-shell transitions are resolved in spectral range from 350 nm to 1540 nm and observed over the temperature range from 7 K to 330 K. Resulting luminescence was tested by cathodoluminescence (CL), photoluminescence (PL) and luminescence decay kinetics measurements. The fluorescence decay curves of selected transition lines for Pr, Sm, Eu, Tb, Dy, and Er ions implanted in III-nitrides hosts were studied as a function of temperature and analyzed theoretically by applying the Inokuti-Hirayama model. On the basis of recorded spectra, we tabulated emission lines for all investigated RE ions in the GaN epilayers and assigned them to the most probable f-f transitions. In theoretical analyses of experimental results we assume that cation site (Ga, Al) in III-nitride lattice host is the most probable location of implanted RE ions in GaN and AlN and therefore RE ion site symmetry is C3v. For Pr-doped GaN, we have calculated the crystal-field splitting of the multiplet energy levels of Pr3+ (4 f2) using lattice sum models. Furthermore, the model of energy transfers between the host lattice and the RE 4 f n-shell system is presented and discussed in the framework of RE isoelectronic structured trap theory. Moreover, the luminescence properties P, As, and Bi impurities implanted in GaN were investigated by PL and PL excitation spectroscopy. Implanted P, As, and Bi ions in GaN epilayers most probably substitute for N ions and create isoelectronic hole traps in GaN host. On the basis of experimental results and theoretical analysis we have estimated binding energies of exciton bind to P, As, and Bi isoelectronic hole traps. The results indicate that RE doped III-nitrides semiconductors and P, As, and Bi doped GaN epilayer are suitable for visible opt oelectronic devices.

Jadwisienczak, Wojciech M.

197

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

198

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

NASA Astrophysics Data System (ADS)

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 with optics and electronics 'on the shelves' for signal processing and depointing computation, used to control the attitude of satellites in low earth orbits, has been completely developed, through the design of a virtual prototype combined with a breadboard implementation of an IR camera (called MST, and has been developed by EADS-SODERN, in the frame of IASI project). The correlation of the virtual prototyping approach, has allowed to build one complete optical head part of the instrument with efficient and optimized parameters where the performances are consistent with the main mission specifications (pointing accuracy 10 Hz, aperture angle: > 36 degree(s), volume

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

2001-12-01

199

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

200

Station Coordinates, low Degree Harmonics, and Earth Rotation Parameters From an Integrated GPS\\/CHAMP\\/GRACE Processing  

Microsoft Academic Search

Time series of geodetic Earth system parameters as part of a global geodetic reference system have been derived for the year 2004 by means of dynamic satellite orbit adjustment. The procedure applied is the integrated approach where the GPS satellites and the Low Earth Orbiters (LEOs) CHAMP and GRACE are processed simultaneously with common standards. The set of estimated Earth

D. Koenig; R. Koenig; K. Neumayer; M. Rothacher; R. Schmidt; F. Flechtner; U. Meyer

2007-01-01

201

Kidorui genso tenka sekigai hakko device zairyo ni kansuru kenkyu. (Study on the rare earth element doped infrared emission device materials).  

National Technical Information Service (NTIS)

The infrared emission of rare earth element, erbium doped silicon semiconductor occurs at 1.54 (mu)m, close to the minimum loss wavelength region of optical fibers. This semiconductor is expected as a new emission device material. To clarify the mechanism...

1996-01-01

202

Rare earth doped ?-diketone complexes as promising high-density optical recording materials for blue optoelectronics  

Microsoft Academic Search

Some kinds of rare earth ?-diketone complexes with blue-violet light absorption edge were synthesized using the ligands of thenoyltrifluoroacctone (HTTA), 2, 2?-dipyridyl (BIPY) and different metal ions (Gd3+, Sm3+ and La3+). Their contents, structures and optoelectronic parameters were monitored by elemental analysis, MS, IR and UV spectra. The solubility of rare earth ?-diketone complexes in 2, 2, 3, 3-tetrafluoro-1-propanol (TFP)

Dongzhe Ma; Yiqun Wu; Xia Zuo

2005-01-01

203

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

204

Low temperature glassy relaxation in rare earth doped Fe3O4 nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles typically exhibit glassy relaxation at low temperature, which can be affected by doping. Gadolinium and Lanthanum doped Fe3O4 nanoparticles were synthesized using a chemical co-precipitation method. The structural and optical properties of these nanoparticles were characterized by using Transmission Electron Microscope (TEM) and the Raman spectroscopy. The TEM images show the formation of nanoparticles of size ranging between 12-14 nm and Raman spectra are consistent with the formation of Fe3O4. AC magnetic measurements were also conducted on these nanoparticles. From the ac out-of-phase susceptibility (?//) vs temperature (T) graphs, it is observed that the doped nanoparticles show larger amplitude relaxation peaks at low temperature as compared to the undoped particles. These magnetic relaxation features develop roughly between 25K to 35K and show frequency dependence. The increased magnetic relaxation at low temperatures can be attributed to structural defects which may arise due to the doping of lanthanides in Fe3O4 nanoparticles.

Laha, Suvra; Lawes, Gavin

2012-10-01

205

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.

206

Synthesis and optical characterizations of undoped and rare-earth-doped CaF{sub 2} nanoparticles  

SciTech Connect

The synthesis of undoped as well as Yb or Er-doped CaF{sub 2} nanocrystals using a reverse micelle method is reported. X-ray powder diffraction and transmission electron microscopy analysis showed that the products were single phased and rather monodispersed with an average particles size around 20 nm. The emission spectra and fluorescence decay times of both Yb{sup 3+} and Er{sup 3+} rare earths (RE) ions in CaF{sub 2} nanoparticles are presented. The particles size is increased by heating the as-obtained nanoparticles at different temperatures. The effect of annealing on the optical properties of the two RE ions in CaF{sub 2} is also investigated. - Graphical abstract: Transmission Electron Microscopy micrograph of CaF{sub 2} nanoparticles synthesized by a reverse-micelle method.

Bensalah, A. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Ecole Nationale Superieure de Chimie Paris, 11 rue Pierre et Marie Curie, 75321 Paris Cedex 05 (France)]. E-mail: amina-bensalah@enscp.fr; Mortier, M. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Ecole Nationale Superieure de Chimie Paris, 11 rue Pierre et Marie Curie, 75321 Paris Cedex 05 (France); Patriarche, G. [Laboratoire de Photonique et de Nanostructure, UPR20 CNRS, Route de Nozay, 91460 Marcoussis (France); Gredin, P. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Universite Paris 6, 4 place Jussieu tour 54, 75252 Paris Cedex 05 (France); Vivien, D. [Laboratoire de Chimie de la Matiere Condensee de Paris, UMR-CNRS 7574, Ecole Nationale Superieure de Chimie Paris, 11 rue Pierre et Marie Curie, 75321 Paris Cedex 05 (France)

2006-08-15

207

Rare earth oxide-doped titania nanocomposites with enhanced photocatalytic activity towards the degradation of partially hydrolysis polyacrylamide  

NASA Astrophysics Data System (ADS)

Rare-earth oxide-doped titania nanocomposites (RE3+/TiO2, where RE = Eu3+, Pr3+, Gd3+, Nd3+, and Y3+) were prepared by a one-step sol-gel-solvothermal method. The products exhibited anatase phase structure, mesoporosity, and interesting surface compositions with three oxygen species and two titanium species. The products were used as the photocatalysts to degrade a partially hydrolysis polyacrylamide (HPAM) under UV-light irradiation, a very useful polymer in oil recovery. For comparison, Degussa P25 and as-prepared pure TiO2 were also tested under the same conditions. The enhanced photocatalytic activity was obtained on as-prepared Eu3+ (Gd3+, Pr3+)/TiO2 composites, and the reasons were explained. Finally, the degradation pathway of HPAM over the RE3+/TiO2 composite was put forward based on the intermediates produced during the photocatalysis procedure.

Li, Jinhuan; Yang, Xia; Yu, Xiaodan; Xu, Leilei; Kang, Wanli; Yan, Wenhua; Gao, Hongfeng; Liu, Zhonghe; Guo, Yihang

2009-01-01

208

Electromagnetic wave propagation over an inhomogeneous flat earth (two-dimensional integral equation formulation)  

Microsoft Academic Search

With the aid of a two-dimensional integral equation formulation, the ground wave propagation of electromagnetic waves transmitted by a vertical electric dipole over an inhomogeneous flat earth is investigated. For the configuration in which a ground wave is propagating across an \\

G. de Jong

1975-01-01

209

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

210

A Hybrid Integrated Silicon Diode Array for Visible Earth-Horizon Sensing.  

National Technical Information Service (NTIS)

An earth-horizon sensing device which operates principally in the visible portion of the spectrum has been designed as a hybrid integrated circuit. The circuit was fabricated and tested for use in the LES-8/9 communications satellites as part of the syste...

F. J. Bachner R. W. Mountain A. G. Foyt R. A. Cohen W. H. McGonagle

1974-01-01

211

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

212

Room temperature ferromagnetism with large magnetic moment at low field in rare-earth-doped BiFeO3 thin films  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

213

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

NASA Astrophysics Data System (ADS)

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

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

1999-11-01

214

Up-conversion in rare earth-doped silica hollow spheres  

NASA Astrophysics Data System (ADS)

In the present work, Er/Yb co-doped silica hollow spheres are prepared in a two-step process. In a first step, polystyrene-core is silica coated in situ by a modified Stöber sol-gel method and in the second one, the sacrificial polystyrene core is thermally removed. The core-shell and the hollow spheres are characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). PL measurements show up-conversion phenomena upon excitation at 975 nm, through the emission of blue (˜490 nm), green (˜523 nm and ˜536 nm) and red (˜655 nm) light. The up-conversion phenomena are discussed and modelled. The developed model explains the up-conversion phenomena of Er/Yb co-doped silica hollow spheres, with special agreement for high Yb/Er ratio.

Fortes, Luís M.; Li, Yigang; Réfega, Ricardo; Clara Gonçalves, M.

2012-06-01

215

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

216

Optical properties of rare-earth-metal-chelate-doped PMMA and DNA-CTMA films  

NASA Astrophysics Data System (ADS)

We observed optical properties from several kinds of Eu-chelates doped DNA-CTMA and PMMA films. The lifetime in DNA-CTMA was longer than in PMMA, and the quantum yield in DNA-CTMA was also higher than in PMMA. Among them, we calculated each cross section because we compared laser properties of Eu-chelates by interacting DNA-CTMA with PMMA. We will discuss the lasing capability by interacting DNA-CTMA.

Wada, Masahiro; Ishihara, Koki; Kagami, Yoshiharu; Horinouchi, Suguru; Ogata, Naoya

2004-06-01

217

Controllable optical bistability and multistability in a rare-earth-ion-doped optical fiber  

NASA Astrophysics Data System (ADS)

We investigated the optical bistability and multistability in an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF optical fiber inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled via adjusting properly the parameters of the corresponding system. Our scheme may provide some new possibilities for technological applications in optoelectronics and optical-fiber communication.

Wang, Zhiping; Yu, Benli; Zhen, Shenglai; Wu, Xuqiang; Zhu, Jun; Cao, Zhigang

2012-03-01

218

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

219

A magnetic pair-breaking effect in rare earth-doped manganites  

NASA Astrophysics Data System (ADS)

The magnetic properties of La0.60R0.07Di0.33MnO3 ferromagnetic manganites (Di=Sr, Ba) are studied, where La is partly replaced by magnetic rare earths R. It is shown that (i) there is a ferromagnetic coupling between Mn and R spins, (ii) the Curie temperature is lowered compared to the parent La compound and (iii) its depression is correlated with the effective moment of the rare earth ion. This last relation is tentatively explained by a magnetic pair-breaking effect, where fluctuating R moments lower the double-exchange coupling between Mn atoms.

Pierre, J.; Nossov, A.; Vassiliev, V.; Ustinov, V.

1998-12-01

220

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

221

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

222

Cerium-doped mixed-alkali rare-earth double-phosphate scintillators for thermal neutron detection  

NASA Astrophysics Data System (ADS)

Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K2CsLu(PO4)2 and CsLi2Lu(PO4)2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. New members of the rare-earth double-phosphate family have been synthesized by high-temperature flux growth. These new samples, represented by the general formula (A,B)3Lu(PO4)2:Ce where A and B are alkali elements, incorporate lithium as one of the components and varying levels of Ce doping. Characteristics important to gamma-ray and thermal neutron excitation are calculated for three model systems which incorporate total lithium-ion substitution. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. Future work includes (1) synthesis of mixed-alkali scandium and yttrium double-phosphates in which Li ions are substitutional in the structure with varying lithium-ion content up to and including total lithium ion substitution on the alkali ion site and (2) measurements of light output and pulse shape using thermal neutron excitation.

Neal, John S.; Boatner, Lynn A.; Spurrier, Merry; Szupryczynski, Piotr; Melcher, Charles L.

2007-08-01

223

Erbium-doped silica-based waveguide amplifier integrated with a 980\\/1530 nm WDM coupler  

Microsoft Academic Search

A high gain of 27dB is achieved in an erbium-doped silica-based planar waveguide amplifier integrated with a directional coupler which multiplexes the signal and pump light. A low noise figure of 5.0dB is attained with the planar amplifier by using an integrated coupler which is formed of erbium-doped silica-based waveguides.

K. Hattori; T. Kitagawa; M. Oguma; Y. Ohmori; M. Horiguchi

1994-01-01

224

Rare-earth doped transparent glass-ceramics with high cross-sections  

Microsoft Academic Search

Erbium doped oxy-fluoride glass-ceramics (50GeO2,[50?x]PbO,xPbF2) have been prepared by thermal treatments of as-melted glass. The optical absorption and emission cross-sections were measured. The controlled crystallisation of the fluoride compounds by nucleation and growth in the oxide matrix produced crystallites ?10 nm in size and a filling factor of 10?2. The phase separation process was investigated using thermal and structural analysis.

Michel Mortier; Francois Auzel

1999-01-01

225

Luminescence of rare earth-doped Si–ZrO 2 co-sputtered films  

Microsoft Academic Search

Er-doped Si-yttria-stabilized zirconia (YSZ) thin film samples were prepared by rf co-sputtering. Chemical composition of the samples was determined using energy-dispersive spectroscopy (EDS) and the structure of the films by X-ray diffraction (XRD). The samples were annealed to 700°C. Photoluminescence (PL) measurements were performed for the visible and infrared. By exciting with the 488-nm-laser line the Er3+ emissions 2H11\\/2?4I15\\/2, 4S3\\/2?4I15\\/2,

Carlos Rozo; Daniel Jaque; Luis F. Fonseca; José García Solé

2008-01-01

226

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

NASA Astrophysics Data System (ADS)

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; Reis, Signo T.; Brow, Richard K.; Krol, Denise M.

2012-07-01

227

Crystal chemistry and domain structure of rare-earth doped BiFeO 3 ceramics  

Microsoft Academic Search

Bi(1?x)RE\\u000a x\\u000a FeO3 (BREF100x, RE = La, Nd, Sm, Gd) has been investigated with a view to establish a broad overview of their crystal chemistry\\u000a and domain structure. For x ? 0.1, the perovskite phase in all compositions could be indexed according to the rhombohedral, R3c cell of BiFeO3. For Nd and Sm doped compositions with 0.1 x ? 0.2 and x = 0.15, respectively, a new antipolar phase

S. Karimi; I. M. Reaney; Y. Han; J. Pokorny; I. Sterianou

2009-01-01

228

Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship.  

PubMed

Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)?BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis. PMID:21093353

Pisarski, W A; Pisarska, J; M?czka, M; Lisiecki, R; Grobelny, ?; Goryczka, T; Dominiak-Dzik, G; Ryba-Romanowski, W

2010-04-28

229

Simultaneous multidopant investigation of rare-earth-doped optical fibers by an ion microprobe.  

PubMed

The relative distribution of five elements present in the core area of several optical fiber samples has been obtained by utilizing nanoscale-secondary ion mass spectrometry. A strong correlation between the rare-earth (RE) ion and aluminum was observed, consistent with aluminum's improving the solubility of the RE ion. The central dip in distribution was less severe than that observed for germanium, characteristic of the collapse process during fabrication of the fiber preform. PMID:17072389

Sidiroglou, Fotios; Huntington, Shane T; Roberts, Ann; Stern, Richard; Fletcher, Ian R; Baxter, Greg W

2006-11-15

230

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

Microsoft Academic Search

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

Kelly Latrice Nash

2009-01-01

231

a New Combustion Synthesis Technique for Rare Earth-Doped Iii-Nitride Luminescent Powders  

NASA Astrophysics Data System (ADS)

A new low temperature method to produce ((RE)xGa1-x)2O3(1?x?0 and RE=Eu, Yb, Pr and Tm) powders with high purity, high chemical homogeneity and improved crystallinity has been developed. This procedure produces finely divided powders through an exothermic reaction between the precursors. The process starts with aqueous solutions of RE(NO3)3 and Ga(NO3)3 as the precursors and hydrazine as the (non-carbonaceous) fuel. The combustion reaction occurs when heating the precursors between 150 and 200°C in a closed vessel filled with an inert gas (Ar), which yields (RExGa1-x)2O3 directly. The preparation of RE-doped Ga2O3 powders was using a new combustion synthesis technique (Hydrazine / metal nitrate method). The preparation of Eu-doped GaN was using the ammonium hexafluoro-metal method. The powders were crystalline and high-purity as determined by XPS, EDS, SEM and XRD measurements.

Ramos, F. E.; Garcia, R.; Hirata, G. A.; Bosze, E. J.; McKittrick, J.

232

A Hamiltonian theory for an elastic earth: First order analytical integration  

Microsoft Academic Search

In this article an approximate analytical integration is performed of the Hamiltonian corresponding to the rotational motion\\u000a of an Earth whose elastic mantle is deformed by rotation and lunisolar attraction, using Deprit's perturbation method for\\u000a the first order. Besides the usual terms, this Hamiltonian includes the perturbation of the kinetic energy and the elastic\\u000a energy produced with the deformation, as

Juan Getino; José M. Ferrándiz

1991-01-01

233

Integral equation approach to investigate some problems within the Earth-Ionosphere waveguide  

NASA Astrophysics Data System (ADS)

WKB method has been applied to solve some integral equations arising out of wave-particle interaction within the upper atmosphere. Problem of ELF propagation through the Earth-Ionosphere waveguide has been investigated taking into account the inhomogeneities due to asymmetry of the day and night time ionosphere and variations of conductivity of the ionosphere. The results of numerical solutions are graphically presented through appropriate data and compared with previous results.

Sundar De, Syam; Paul, Suman; De, Dipanjan; Chattopadhyay, Subrata

2012-07-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

235

Storage of images in atomic coherences in a rare-earth-ion-doped solid  

NASA Astrophysics Data System (ADS)

We report on storage of images in atomic coherences driven by electromagnetically induced transparency in a doped solid. We demonstrate image storage times up to the regime of milliseconds (i.e., more than two orders of magnitude larger than in gaseous media). Our data also reveal an improvement in the spatial resolution of the retrieved images by a factor of 40. The long storage times become possible by applying additional radio frequency pulse sequences to drive rephasing of the atomic coherences. Moreover, the perturbing effect of atomic diffusion (which significantly limits image storage times in gases) is absent in the solid. In addition, we monitored pronounced oscillations in the intensity of the retrieved image versus the storage time. These oscillations are due to the beating of dark-state polaritons. All of these results demonstrate the superior properties of coherently driven optical data storage in solids.

Heinze, G.; Rudolf, A.; Beil, F.; Halfmann, T.

2010-01-01

236

First-principles study of the magnetic properties of nitrogen-doped alkaline earth metal oxides  

NASA Astrophysics Data System (ADS)

We present a first-principles study of the magnetic properties of N-doped MgO, CaO and SrO, which have been proposed to constitute a new class of dilute magnetic semiconductors (DMSs) with no magnetic elements. In this study, it was found that under a homogeneously distributed condition, Curie temperatures could reach room temperature at sufficient N concentrations in the range of 20-30 at.%; however, an inhomogeneous N distribution in these DMSs is the favored configuration, which indicates that spinodal decomposition leads to a room-temperature blocking temperature at smaller N concentrations than those estimated for room-temperature ferromagnetism in the homogeneous distribution condition.

Seike, Masayoshi; An Dinh, Van; Sato, Kazunori; Katayama Yoshida, Hiroshi

2012-08-01

237

NIR to visible upconversion in rare-earth Ion-doped NaYF4 crystals  

NASA Astrophysics Data System (ADS)

In this paper we investigate the infrared-to-visible upconversion luminescence in bulk crystals and nanocolloid filled photonic crystal fiber with ytterbium and erbium co-doped NaYF4 upconversion phosphor. The phosphor was prepared by using simple co-precipitation synthetic method. The initially prepared phosphor has very weak upconversion fluorescence. The fluorescence significantly increased after the phosphor was annealed at a temperature of 400°C. Nanocolloids of this phosphor were obtained using water and methanol as solvents and they were utilized as laser filling medium in photonic crystal fibers. Under 980nm laser excitation very strong upconversion signals were obtained at 408 nm, 539 nm and 655 nm. Efficiency and decay life time study of the upconverted emissions was conducted to understand the upconversion mechanisms. The reported nanocolloids are good candidates for fluorescent biosensing applications and also as a new laser filling medium in fiber lasers.

Patel, Darayas; Vance, Calvin; King, Newton; Jessup, Malcolm; Green, Lekara; Sarkisov, Sergey

2010-02-01

238

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Enhanced Laser Cooling of Rare-Earth-Ion-Doped Glass Containing Nanometer-Sized Metallic Particles  

NASA Astrophysics Data System (ADS)

The enhanced laser cooling performance of rare-earth-ions-doped glasses containing small particles is predicted. This is achieved by the enhancement of local field around rare earth ions, owing to the surface plasmon resonance of small metallic particles. The role of energy transfer between ions and the particle is theoretical discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption and the fluorescence is predicted. Moreover, taking Yb3+ -doped ZBLAN as example, the cooling power and heat-light converting efficiency are calculated. It is finally concluded that the absorption and the fluorescence are greatly enhanced in these composite materials, the cooling power is increased compared to the bulk material.

Jia, You-Hua; Zhong, Biao; Yin, Jian-Ping

2009-03-01

239

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

Microsoft Academic Search

The Goddard Space Flight Center (GSFC) is one of the largest Earth Science research-based institutions in the nation. Along with the research comes a dedicated group of people who are tasked with developing Earth science research-based education and public outreach materials to reach the broadest possible range of audiences. The GSFC Earth science education community makes use of a wide

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

2008-01-01

240

Enhanced 1.47 ?m emission and lowered upconversion of Tm3+-doped gallate-germanium-bismuth-lead glass by codoping rare earths  

NASA Astrophysics Data System (ADS)

An intense broadband 1.47 ?m emission with a full width at half maximum of 125 nm and a peak emission cross section of 4.056×10-21 cm2 of the Tm3+-doped gallate-germanium-bismuth-lead (GGBP) glass has been obtained upon 808 nm diode-laser excitation. Effects of rare-earth (RE3+=Ho3+, Tb3+, Eu3+, Dy3+) codoping on the spectroscopic properties of the Tm3+-doped GGBP glass have been investigated. It is found that the incorporation of RE3+ into the Tm3+-doped GGBP glass can effectively improve the 1.47 ?m emission and can deduce the upconversion luminescence, which makes the GGBP glass more attractive to use in S-band optical fiber amplifiers.

Shi, D. M.; Zhang, Q. Y.

2008-12-01

241

Dielectric and nonlinear current–voltage characteristics of rare–earth doped CaCu3Ti4O12 ceramics  

Microsoft Academic Search

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.

Laijun Liu; Liang Fang; Yanmin Huang; Yunhua Li; Danping Shi; Shaoying Zheng; Shuangshuang Wu; Changzheng Hu

2011-01-01

242

Simultaneous strain and temperature measurements in composites using extrinsic Fabry–Perot interferometric and intrinsic rare-earth doped fiber sensors  

Microsoft Academic Search

This paper reports on a novel optical fiber-based sensing system for conducting simultaneous strain and temperature measurements. The sensor design involves the use for the first time of an extrinsic Fabry–Perot interferometric (EFPI) strain sensor in conjunction with a rare-earth doped fiber fluorescence decay-time based temperature sensor. The combined sensors were embedded in a carbon fiber reinforced composite system and

T. Liu; G. F. Fernando; Z. Y. Zhang; K. T. V. Grattan

2000-01-01

243

Simultaneous strain and temperature measurements in composites using extrinsic Fabry-Perot interferometric and intrinsic rare-earth-doped fiber sensors  

Microsoft Academic Search

This paper reports on a novel optical fiber-based sensing scheme for conducting simultaneous strain and temperature measurements. The sensor design involved the use of an extrinsic Fabry-Perot interferometric strain sensor and a rare-earth doped fiber fluorescence decay-time based temperature sensor. The combined sensors were embedded in a carbon fiber reinforced composite system and evaluated. The feasibility of using this embedded

Tongyu Liu; Gerard F. Fernando; Zhiyi Zhang; Kenneth T. Grattan

1998-01-01

244

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

245

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

246

RESIF: a French Integrated Antenna for the Observation of Earth Deformation (Invited)  

NASA Astrophysics Data System (ADS)

The densification of the networks and a strong integration of seismic, geodetic and spatial observations will remain a major challenge over the decade to come. In Europe, the EPOS (European Plate Observing System) project will carry this development forward as it is intended to be a major future research infrastructure in Europe which integrates geophysical observations into a single comprehensive solid earth monitoring system. This integrated European structure is made possible only through the strong effort of open data access that has been pushed forward during the last two decades, in particular through the ORFEUS data center and several European projects, such as NERIES. Open data access is in fact the only possible way forward to obtain an integrated geophysical research structure, as the political landscape in Europe remains complex where issues related to civil protection and natural disasters remain within the competence of each nation. RESIF (Réseau Sismologique Français) is built with the intention of being a major French contribution in the development of EPOS. The RESIF infrastructure will be an integrated antenna to observe solid Earth deformation at all time scales. The project therefore includes seismic observations as well as geodetic (GPS, gravimetry) and spatial observations, in partnership between the French CNRS-INSU and all the major national institutes involved in studying and monitoring the earth. Through this project we intend to completely renovate the French permanent and temporary geophysical equipment and the associated data access. In metropolitan France, the present seismic broadband and short period regional seismic networks will be merged and extended to obtain a regular grid of 50 broadband (10Hz-120s) stations and 120 intermediate period (30Hz-40s) stations with higher station density in the seismically most active areas. The already extensive French accelerometric and GPS networks will also integrate RESIF. The total number of permanent earth-based systems in metropolitan France will be approximately 500. The portable seismic, GPS and gravimeter equipment will be strongly increased to obtain a pool of approximately 350 instruments (GPS, intermediate band and broadband seismic). Discussions with the French spatial agency (CNES) will define the priority actions to be taken over the next few years. They are likely to include an improved strategy and data share to increase precision in positioning measurements as well as access to observations of seismic waves and earthquake damage patterns even after minor seismic events. Data from the permanent RESIF antenna will be freely available via standard request tools in real-time or near real-time via a unified French data distribution system and integrated into European and Worldwide data exchange systems. Data from field experiments using the RESIF portable equipment will also be freely available, with a standard distribution delays.

Pedersen, H.

2009-12-01

247

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

248

Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures  

NASA Astrophysics Data System (ADS)

Photonic integrated circuits are a key component of future telecommunication networks, where demands for greater bandwidth, network flexibility, and low energy consumption and cost must all be met. The quest for all-optical components has naturally targeted materials with extremely large nonlinearity, including chalcogenide glasses and semiconductors, such as silicon and AlGaAs (ref. 4). However, issues such as immature fabrication technology for chalcogenide glass and high linear and nonlinear losses for semiconductors motivate the search for other materials. Here we present the first demonstration of nonlinear optics in integrated silica-based glass waveguides using continuous-wave light. We demonstrate four-wave mixing, with low (5 mW) continuous-wave pump power at ? = 1,550 nm, in high-index, doped silica glass ring resonators. The low loss, design flexibility and manufacturability of our device are important attributes for low-cost, high-performance, nonlinear all-optical photonic integrated circuits.

Ferrera, M.; Razzari, L.; Duchesne, D.; Morandotti, R.; Yang, Z.; Liscidini, M.; Sipe, J. E.; Chu, S.; Little, B. E.; Moss, D. J.

2008-12-01

249

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

250

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

NASA Astrophysics Data System (ADS)

An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF4 nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF4 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.

2012-07-01

251

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

252

Effect of particle size and dopant concentration on photophysical properties of Eu3+-doped rare earth oxysulphide phosphor coatings.  

PubMed

Europium-doped rare-earth oxysulphides (red phosphors) are often used as reference luminophore in pyrene-based pressure sensor coatings for aerodynamic applications. Different red phosphor samples were characterized for their particle size, chemical composition, photoluminescent properties and temperature sensitivity. The red phosphor samples were characterized using energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and scanning electron microscopy (SEM) for morphology and particle size measurement. The particle size was in the range of 1.5-5.7 ?m with morphology of hexagonal or spherical shape. It was found that phosphor with higher europium content exhibited higher luminescent emission intensity. The phosphor coatings were prepared by spraying a dispersion of the material in silicone resin. Smooth coatings were obtained by using phosphor samples with smaller particle size. Upon 334 nm excitation, the coatings showed characteristic luminescence 5D0?7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 626 nm (5D0?7F2) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (5D0?7F1). Luminescence decay curves obeyed double exponential behaviour. The phosphor samples showed temperature sensitivity of -0.012 to -0.168%/°C in the temperature range of 25-50 °C. PMID:21215689

Chakradhar, R P S; Basu, Bharathibai J; Lakshmi, R V

2010-12-16

253

Ultraviolet direct printing of rare-earth-doped polymer waveguide amplifiers  

SciTech Connect

Polymer channel waveguide amplifier arrays were fabricated using ultraviolet direct printing methodology. The effects of different weight percentage (wt. %) combinations of rare-earth ions erbium (Er{sup 3+}) and ytterbium (Yb{sup 3+}) on the absorption spectrum, as well as the internal gain, were investigated. With an input signal power of {approx}-18 dBm, the highest internal gain obtained is {approx}16.5 dB at a wavelength of 1533 nm for a 20 mm long multimode channel waveguide codoped with {approx}1 wt. % of Er{sup 3+} and {approx}10 wt. % of Yb{sup 3+} derivatives. The UV direct printing methodology opens a simple platform for the fabrication of dense and compact polymer waveguide laser arrays.

Wong, W.H.; Chan, K.S.; Pun, E.Y.B. [Department of Electronic Engineering and Department of Physics and Material Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Department of Physics and Material Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Department of Electronic Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

2005-07-04

254

White emission phosphors based on Dy3+-doped into anhydrous rare-earth benzenetricarboxylate complexes  

NASA Astrophysics Data System (ADS)

White light emitting rare earth anhydrous complexes RE(TMA):Dy3+ (RE3+ = Y3+ and Lu3+) containing the trimesic acid ligands (TMA) were synthesized and characterized by elemental analysis, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The crystallinity and thermostability of these luminescent materials were determined. Since the first excited triplet state (T1: 24,000 cm-1) of TMA ligand is located at higher energy than the main emitting 4F9/2 level (21,000 cm-1) of the Dy3+ ion, TMA can act as efficient luminescent sensitizer in the intramolecular energy transfer of RE(TMA):Dy3+ material. The near-white emission colour originated from the intraconfigurational transitions of Dy3+ ion 4F9/2?6HJ is discussed.

Silva, Ivan G. N.; Kai, Jiang; Felinto, Maria C. F. C.; Brito, Hermi F.

2013-03-01

255

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

256

Integrated light sources based on self-formed polymer waveguide doped with active medium  

NASA Astrophysics Data System (ADS)

The polymer-based photonic devices have promise as optical components integrated in convenient microchip systems because of ease in the deposition and microfabrication of polymer materials. Furthermore, since the polymers can be easily doped with luminescent materials such as organic dyes, the organic light source devices are also considerable as the integrated optical components. Especially the self-formation method of the fiber type waveguide using the dyedoped photopolymers, called as self-written active (SWA) waveguide technique, brings a simple fabrication scheme of the light sources integrated in the polymer photonic circuit. It has been demonstrated that an in-line optical amplifier and a Fabry-Perot type lasing cavity can be obtained by using the SWA waveguide technique. In this study we have employed this technique to fabricate an incoherent light source with a wideband emission. A serially cascaded SWA waveguide doped with the different organic dyes could be fabricated with a single exposure process. The cascaded SWA waveguide could act as an incoherent light source under UV light irradiation. This device can be expected as a probing light source for the label-free microchip system, which would be available for the biological sensing, environmental measurements, and medical diagnosis.

Sugimoto, S.; Kawaguchi, T.; Yamashita, K.

2012-05-01

257

From the Earth Summit to Rio+20: integration of health and sustainable development.  

PubMed

In 2012, world leaders will meet at the Rio+20 conference to advance sustainable development--20 years after the Earth Summit that resulted in agreement on important principles but insufficient action. Many of the development goals have not been achieved partly because social (including health), economic, and environmental priorities have not been addressed in an integrated manner. Adverse trends have been reported in many key environmental indicators that have worsened since the Earth Summit. Substantial economic growth has occurred in many regions but nevertheless has not benefited many populations of low income and those that have been marginalised, and has resulted in growing inequities. Variable progress in health has been made, and inequities are persistent. Improved health contributes to development and is underpinned by ecosystem stability and equitable economic progress. Implementation of policies that both improve health and promote sustainable development is urgently needed. PMID:22682465

Haines, Andy; Alleyne, George; Kickbusch, Ilona; Dora, Carlos

2012-06-01

258

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

SciTech Connect

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

Ferrer, Sebastian [Dpto. de Matematica Aplicada, Universidad de Murcia, ES-30071 Espinardo, Murcia (Spain); Lara, Martin, E-mail: sferrer@um.e, E-mail: mlara@roa.e [Real Observatorio de la Armada, ES-11110 San Fernando, Cadiz (Spain)

2010-05-15

259

A coupled and workflow integrated modeling system applications for earth system science  

NASA Astrophysics Data System (ADS)

The complexity of earth system models and their applications are getting increase because of the continued development of computational resources, storage systems and distributed high-resolution observation networks. Therefore, the multi component earth system models that are used to develop these applications need to be designed in a new programming approach to make easy interaction among those model components and in between other third party applications. For this purpose, the common interfaces of earth system models can be standardized and also self-describing modeling systems can be built to increase interoperability between models and third party applications such as workflow systems, metadata/data portals, web services and scientific gateways. Fortunately, many efforts are currently underway to create standardized and easy to use multi-component earth system models and their applications such as Earth System Curator and Earth System Framework (ESMF). In this study, it is presented and analyzed a new methodology to combine scientific workflow and modeling framework approach together to create a standardized work environment. The methodology uses the ESMF library to create and self-describing and standardized coupled modeling systems and Kepler scientific workflow application to integrate modeling system to a workflow environment. The proposed methodology is tested using two typical and realistic earth system modeling application. The results of example workflows that are based on the proposed methodology are a part of this study. The first example allows running and analyzing a global circulation model on both a grid computing environment (TeraGrid) and a cluster system with meaningful abstraction of used model and computing environment. The development version of NCAR Community Climate System Model (CCSM4) model is used for this purpose. In this application example, the collection of provenance information has the added benefit of documenting a run in far greater detail than before. This facilitates exploration of runs and leads to possible reproducibility. In second example, a regional coupled climate modeling system (WRF and ROMS) is developed for Mediterranean region and integrated into workflow system to provide better representation of regional climate system. This application has curial importance in downscaling output of the global circulation models over Turkey and near regions and it also can be used to create better representation of regional climate for the future scenarios. As, in the first application example, the workflow application collects provenance information automatically from the coupled earth system modeling system to reproduce, compare and debug the results. The results show that the developed workflow environment is capable of running different earth system models on a different high performance computing resource with a meaningful abstraction. The proposed work environment acts as an abstraction layer and hides the detail of the used infrastructure and earth system model from user and it also collect standardized provenance information about both model and computing resource to represent the work environment as possible as it can.

Utku Turuncoglu, Ufuk; Dalfes, Nuzhet; Murphy, Sylvia; Deluca, Cecelia

2010-05-01

260

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

261

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

262

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

263

Electromagnetic modeling of three-dimensional bodies in layered earths using integral equations  

SciTech Connect

An algorithm based on the method of integral equations has been developed to simulate the electromagnetic response of 3-D bodies in layered earths. The inhomogeneities are replaced mathematically by an equivalent current distribution which is approximated by pulse basis functions. A matrix equation is constructed using the electric dyadic Green's function appropriate to a layered earth and is solved for the vector current in each cell. Subsequently, scattered fields are found by integrating electric and magnetic dyadic Green's functions over the scattering currents. Efficient evaluation of the dyadic Green's functions is a major consideration in reducing computation time. It is found that tabulation/interpolation of the six electric and five magnetic Hankel transforms defining the secondary Green's functions is preferable to any direct Hankel transform calculation using linear filters. A comparison of responses over elongate 3-D bodies with responses over 2-D bodies of identical cross section using plane wave incident fields is the only check available on our solution. Agreement is excellent; however, the length that a 3-D body must have before departures between 2-D transverse electric and corresponding 3-D signatures are insignificant depends strongly on the layering. The 2-D transverse magnetic and corresponding 3-D calculations agree closely regardless of the layered host.

Wannamaker, P.E.; Hohmann, G.W.

1982-01-01

264

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

265

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

266

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

267

Dense sintered conditions and sintering mechanisms for alkaline earth metal (Mg, Ca and Sr)-doped LaCrO 3 perovskites under reducing atmosphere  

Microsoft Academic Search

Dense sintered conditions and sintering mechanisms of alkaline earth metal (AE=Mg, Ca and Sr)-doped LaCrO3 perovskites with stoichiometric compositions under a reducing atmosphere have been investigated. Relative densities ?94% were obtained after firing at 1800 °C for the LaCr0.9Mg0.1O3 and at 1900 °C for the La0.9Ca0.1CrO3 and the La0.9Sr0.1CrO3 in an Ar–CO atmosphere. It was found that during the sintering

Masashi Mori; Tohru Yamamoto; Takayuki Ichikawa; Yasuo Takeda

2002-01-01

268

A new full-wave hybrid differential-integral approach for the investigation of multilayer structures including nonuniformly doped diffusions  

Microsoft Academic Search

A novel hybrid differential-integral approach, based on the transverse wave formulation (TWF) is presented for full-wave investigation of multilayer structures including inhomogeneous layer stacks with arbitrary doping profiles. In combining both the benefits of spatial and spectral resolutions, the TWF offers a natural framework for the implementation of multiresolution and multiscale approaches from physical considerations. The possibility of separating the

Sidina Wane; Damienne Bajon; Henri Baudrand; Patrice Gamand

2005-01-01

269

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

270

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

NASA Astrophysics Data System (ADS)

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

Charlson, R. J.

2006-12-01

271

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

272

Recommendations for Preserving the Integrity of Samples Collected on Mars and Returned to Earth for Analysis  

NASA Astrophysics Data System (ADS)

As part of an integrated approach to planetary exploration, samples will ultimately be returned from Mars to Earth for analysis. This will be the next logical step in our exploration of the red planet as we strive to learn more about its evolution and investigate the possible occurrence of life on Mars. NASA's Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM) has been studying the preservation issues for returning geological samples from Mars. The overriding goal of these studies has been the preservation of pristine Martian signatures in the returned samples, thus maximizing the scientific value of such missions. Preventing contamination/alteration is particularly critical for chemical, biological, and morphological signatures that are indicative of life, either extinct of extant. Such prevention is required for the short term during collection, transport, and re-entry and impact on Earth, as well as for long term curation. In this presentation, we discuss contamination issues within the framework of an Athena-like sampling mission; however, the concepts may be extrapolated to other plausible sampling scenarios. Issues encompassing preservation from the successful collection, to return to Earth, and curation of martian samples are discussed within this framework. We build upon earlier reports, and complement the recent Mars Sample Handling and Requirements Panel (MSHARP) report by concentrating on the samples themselves. Below is a summary of recommendations made by CAPTEM that will maximize the scientific value of any returned Martian samples. These recommendations are made, for the most part, with consideration of the stringent budgetary constraints that will be part of any sample return mission to Mars. The governing principle behind this study is that any procedure or piece of equipment that can impact (contaminate) the Mars samples during collection, transportation, or curation needs to be fully evaluated through analysis and experimentation prior to implementation by a scientific committee, that has expertise in extraterrestrial sample analysis, curation, and preservation.

Neal, C. R.; Jolliff, B. L.; Papike, J. J.; MacPherson, G.

2000-07-01

273

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

274

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

SciTech Connect

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

Berthebaud, D.; Sato, A.; Michiue, Y. [National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Mori, T., E-mail: MORI.Takao@nims.go.jp [National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Nomura, A.; Shishido, T.; Nakajima, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

2011-07-15

275

An Integrated Earth Science, Astronomy, and Physics Course for Elementary Education Majors  

NASA Astrophysics Data System (ADS)

Physical World is a one-semester course designed for elementary education majors, that integrates earth science, astronomy, and physics. The course is part of a four-course set that explores science concepts, processes, and skills, along with the nature of scientific practice, that are included in state and national standards for elementary school science. Geo-science concepts, such as water and seismic waves, are used to illustrate general principles of physics, such as wave transmission, refraction, reflection, and interference. Laboratories are drawn from both introductory physics and earth science courses and have been redesigned to have a strong inquiry component. Pre-assessments were used to evaluate students' prior knowledge of key ideas. The use of pyramid tests measurably enhanced student performance. A major theme of the course is how science is represented (and misrepresented) in the media. Pedagogical challenges encountered in the course are due to various factors, two main ones being lack of previous experience with the natural world among a largely urban student body and the diversity of material that the course covers.

Plotnick, Roy E.; Varelas, Maria; Fan, Qian

2009-03-01

276

A Hamiltonian Theory for an Elastic Earth - First Order Analytical Integration  

NASA Astrophysics Data System (ADS)

In this article an approximate analytical integration is performed of the Hamiltonian corresponding to the rotational motion of an Earth whose elastic mantle is deformed by rotation and lunisolar attraction, using Deprit's perturbation method for the first order. Besides the usual terms, this Hamiltonian includes the perturbation of the kinetic energy and the elastic energy produced with the deformation, as well as their causes, the tidal and the centrifugal potential; these new terms have already been studied for the tidal deformation in previous articles (Getino and Ferrándiz, 1990a, 1990b). The effects of the deformation due to the centrifugal potential are studied in this article, following the same method as that used for the tidal deformation. Numerical tables of the periodic perturbations corresponding to the nutation in obliquity and longitude are obtained. As for the secular effects, a theoretical value of 457 days is obtained for Chandler's period.

Getino, Juan; Ferrándiz, José M.

1991-03-01

277

HOW VIRTUAL GLOBES ARE REVOLUTIONIZING EARTH OBSERVATION DATA ACCESS AND INTEGRATION  

Microsoft Academic Search

The fusion of the World Wide Web and spatial technologies has lead to the development of virtual globes which are increasingly serving as gateways to global geospatial data. Examples include Google Earth (originally Keyhole Earth Viewer), NASA's World Wind, ESRI's ArcGIS Explorer, Microsoft Virtual Earth, GeoFusions' GeoPlayer, Skyline Globe, ossimPlanet, EarthBrowser, and ESRI's ArcGlobe. These systems are revolutionizing earth observation

C. D. Elvidge; B. T. Tuttle

278

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

279

Shape-controlled synthesis of octahedral ?-NaYF 4 and its rare earth doped submicrometer particles in acetic acid  

Microsoft Academic Search

Submicrometer sized pure cubic phase, Eu3+ doped, and Yb3+\\/Er3+ co-doped ?-NaYF4 particles with octahedral morphology have been prepared in acetic acid. The acetate anion plays a critical role in the formation\\u000a of such symmetric octahedral structures through its selective adsorption on the (111) faces of the products. The size of the\\u000a as-prepared octahedra can be tuned by varying the amount

Li Gao; Xin Ge; Zhanli Chai; Guohai Xu; Xin Wang; Cheng Wang

2009-01-01

280

Creation of integrated analytical GIS-system on the Earth Sciences  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

281

Representing human-water interactions in an integrated regional earth system modeling framework  

NASA Astrophysics Data System (ADS)

The hydrologic cycle has been under the influence of human activities, active (modification) or passive (adaptation), since the beginning of civilization. In recent years, the topic of the interactions between human activities and the water cycle in the context of climate change has emerged with critical importance within the hydrologic and climate science communities. However, such interactions have not been sufficiently represented in most hydrologic and land surface models. In this study, we aim to develop and evaluate two critical components relevant to human-water interactions in an integrated regional earth system modeling (iRESM) framework under development. They are (1) an irrigation module to be integrated into the land component of iRESM for managed ecosystems; and (2) a generic water management module to allocate water to different sectors, e.g., irrigation and energy production, which are competing against each other for limited water. We will evaluate these components against in-situ and remotely sensed observations in selected sites and watersheds in the western United States, where irrigation and water management activities are pronounced.

Li, H.; Huang, M.; Wigmosta, M. S.; Ke, Y.; Coleman, A. M.; Leung, L.

2010-12-01

282

Modeling the dynamics of the integrated earth system and the value of global ecosystem services using the GUMBO model  

Microsoft Academic Search

A global unified metamodel of the biosphere (GUMBO) was developed to simulate the integrated earth system and assess the dynamics and values of ecosystem services. It is a ‘metamodel’ in that it represents a synthesis and a simplification of several existing dynamic global models in both the natural and social sciences at an intermediate level of complexity. The current version

Roelof Boumans; Robert Costanza; Joshua Farley; Matthew A. Wilson; Rosimeiry Portela; Jan Rotmans; Ferdinando Villa; Monica Grasso

2002-01-01

283

Integrating Earth System Science Data Into Tribal College and University Curricula  

Microsoft Academic Search

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

P. J. Tilgner; D. J. Perkey

2007-01-01

284

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

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

285

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

286

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

287

A Tunable Er3+-Doped Fiber Laser by Use of an Integrated Optics Mach-Zehnder Interferometer  

Microsoft Academic Search

Wavelength tunability of an Er3+-doped fiber laser is reported by the use of an integrated optics Mach-Zehnder interferometer driven electro-optically. A pump laser threshold of 5 mW and a continuous tunable band from 1530 nm to 1554 nm are achieved with a drive voltage varying between 0 to +7 volts. An evaluation of the design and improvements are given based

N. Azami; A. Saïssy; M. P. de Micheli; G. Monnom; D. B. Ostrowsky; P. Mollier

2001-01-01

288

A Tunable Er3+-Doped Fiber Laser by Use of an Integrated Optics Mach-Zehnder Interferometer  

NASA Astrophysics Data System (ADS)

Wavelength tunability of an Er3+-doped fiber laser is reported by the use of an integrated optics Mach-Zehnder interferometer driven electro-optically. A pump laser threshold of 5 mW and a continuous tunable band from 1530 nm to 1554 nm are achieved with a drive voltage varying between 0 to +7 volts. An evaluation of the design and improvements are given based on the experimental and theoretical analysis.

Azami, N.; Saïssy, A.; de Micheli, M. P.; Monnom, G.; Ostrowsky, D. B.; Mollier, P.

289

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 187°C with a small hump at around 250°C. 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

290

Tuning the two-dimensional carrier density at LaAlO3/SrTiO3 interfaces via rare earth doping  

NASA Astrophysics Data System (ADS)

The transport properties of LaAlO3/SrTiO3 (LAO/STO) heterostructures with rare earth modified RE0.5Sr0.5TiO3 (RE=La, Nd, Sm, Dy) interlayers are studied. Although it was found that the sheet carrier density of the heterostructure follows the trend of the bulk films, purely extrinsic doping effects are excluded based on observed structural distortions as well as detailed resistance versus temperature analysis. Detailed resistance versus temperature analysis revealed a strong interface confinement of the conduction for a single LSTO unit cell between LAO and STO, which tends toward bulk Fermi-liquid behavior as the LSTO thickness is increased.

Schoofs, Frank; Egilmez, Mehmet; Fix, Thomas; MacManus-Driscoll, Judith L.; Blamire, Mark G.

2013-03-01

291

Integrated-optic laser fabricated by field-assisted ion exchange in neodymium-doped soda-lime-silicate glass  

SciTech Connect

A continuous-wave integrated-optic channel waveguide laser operating at 1.057 {mu}m has been fabricated in neodymium-doped soda-lime-silicate laser glass. The device was end-fire pumped with the 0.528-{mu}m line of an argon-ion laser. Threshold for laser action occurs for an absorbed pump power of 31 mW. The slope efficiency for the integrated-optic laser is estimated to be 0.5%. Field-assisted ion exchange in a eutectic melt of CaNO{sub 3} and KNO{sub 3} was used to form the waveguide.

Sanford, N.A.; Malone, K.J.; Larson, D.R. (National Institute of Standards and Technology, Optical Electronic Metrology Group, Mail Stop 724.02, 325 Broadway, Boulder, Colorado 80303 (USA))

1990-04-01

292

LiNbO3 with rare earths: lasers and amplifiers  

NASA Astrophysics Data System (ADS)

Nd:MgO:LiNbO3 combines the laser capabilities of rare-earth doped crystals and the non- linear and electro-optic properties of a well-known material in integrated optics. In this paper the basic characteristics of such a material are reviewed with respect to the goal of fabricating integrated optic lasers and amplifiers.

Lallier, Eric; Pocholle, Jean-Paul; Papuchon, Michel R.; de Micheli, Marc P.; Li, M. J.; He, Q.; Ostrowsky, Daniel B.; Grezes-Besset, Catherine; Pelletier, Emile P.

1991-08-01

293

Emission sensitization and mechanisms of electron-excitation migration in structures based on III-nitrides doped with rare-earth elements (Eu, Er, Sm)  

SciTech Connect

The effect of doping with Eu, Er, and Sm rare-earth ions on the shape of the luminescence spectrum for heterostructures with GaN/In{sub x}Ga{sub 1-x}N (0.1 < x < 0.4) quantum wells and from p-GaN/n-GaN and p-AlGaN/n-GaN junctions is investigated. The results of measurements of the electroluminescence of these structures correlate with the previous data on photoluminescence and Moessbauer spectroscopy. It is shown that it is the GaN 'yellow' (5000-6000 A) band that plays the important role in the excitation of intracenter states in the structures with several GaN/InGaN quantum wells doped with Eu and Sm. In this case, Eu is most likely the sensitizer for Sm. Additional introduction of 3d metal (Fe{sup 57}) in p-GaN/n-GaN:Eu results in the realization of intracenter transitions in Eu{sup 3+}: {sup 5}D{sub 0} {sup {yields} 7}F{sub 1} (6006 A), {sup 5}D{sub 0} {sup {yields} 7}F{sub 2} (6195 A), {sup 5}D{sub 0} {sup {yields} 7}F{sub 3} (6627 A), and {sup 5}D{sub 1} {sup {yields} 7}F{sub 4} (6327 A) due to the occurrence of new, efficient channels of excitation transfer to intracenter states and in the effect of Fe on the local environment of rare-earth ions including due to the f-d hybridization enhancement.

Mezdrogina, M. M., E-mail: margaret.m@mail.ioffe.ru; Danilovsky, E. Yu.; Kuzmin, R. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2010-03-15

294

Preparation and luminescence properties of rare earth Eu3+ doped ZnO-Al2O3-SiO2 glass-ceramics  

NASA Astrophysics Data System (ADS)

Generally, it is very difficult to prepare zinc aluminosilicate glasses because of its high melting temperature. In this work, transparent rare earth Eu3+-doped ZnO-Al2O3-SiO2 glass-ceramics were obtained by sintering the corresponding precursor gels, which were prepared by using tetraethylorthosilicate and inorganic salts as raw materials and by a sol-gel method. X-ray diffraction, infrared spectrometer and fluorescence spectrometer were used to characterize the as-prepared materials. The luminescence properties of Eu3+ in zinc aluminosilicate glass-ceramics were mainly studied. Results showed that ZnAl2O4 nanocrystals were precipitated from ZnO-Al2O3-SiO2 system and dispersed in the SiO2-based glass when the heat-treatment temperature was up to 900oC. A strong emission peak at 614 nm was observed and the peak is assigned to 5Do-->7F2 transition of Eu3+ ions. The luminescence mechanism of Eu 3+ doped ZnO-Al2O3-SiO2 glass-ceramics was analyzed and discussed.

Duan, X. L.; Yuan, D. R.; Liu, Zhiqiang

2007-10-01

295

Effect of Rare-Earth Doping on the Electrical Resistivity and Thermopower of the Transition Metal Pentatelluride HfTe_5  

NASA Astrophysics Data System (ADS)

The transition metal pentatellurides HfTe5 and ZrTe5 exhibit semimetallic resistivity except for a large resistive peak as a function of temperature at around 75 K for HfTe5 and 145 K for ZrTe_5. At a temperature corresponding to this peak, the thermopower crosses zero as it moves from large positive values to large negative values. Previous doping studies have shown profound and varied effects on the anomalous transport. In this study we investigate the effect of doping HfTe5 with rare earth elements. We have grown single crystals of nominal Hf_0.75RE_0.25Te5 where RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho. Electrical resistivity and thermopower data from about 10 K to room temperature will be presented. We report power factors higher than those previously reported in the pentatellurides, as much as a factor of 2 larger than that of Bi_2Te_3.

Lowhorn, Nathan D.; Tritt, Terry M.; Abbott, Edward E.; Kolis, J. W.

2003-11-01

296

Multifunctional role of rare earth doping in optical materials: nonaqueous sol-gel synthesis of stabilized cubic HfO2 luminescent nanoparticles.  

PubMed

In this work a strategy for the control of structure and optical properties of inorganic luminescent oxide-based nanoparticles is presented. The nonaqueous sol-gel route is found to be suitable for the synthesis of hafnia nanoparticles and their doping with rare earths (RE) ions, which gives rise to their luminescence either under UV and X-ray irradiation. Moreover, we have revealed the capability of the technique to achieve the low-temperature stabilization of the cubic phase through the effective incorporation of trivalent RE ions into the crystal lattice. Particular attention has been paid to doping with europium, causing a red luminescence, and with lutetium. Structure and morphology characterization by XRD, TEM/SEM, elemental analysis, and Raman/IR vibrational spectroscopies have confirmed the occurrence of the HfO2 cubic polymorph for dopant concentrations exceeding a threshold value of nominal 5 mol %, for either Lu(3+) or Eu(3+). The optical properties of the nanopowders were investigated by room temperature radio- and photoluminescence experiments. Specific features of Eu(3+) luminescence sensitive to the local crystal field were employed for probing the lattice modifications at the atomic scale. Moreover, we detected an intrinsic blue emission, allowing for a luminescence color switch depending on excitation wavelength in the UV region. We also demonstrate the possibility of changing the emission spectrum by multiple RE doping in minor concentration, while deputing the cubic phase stabilization to a larger concentration of optically inactive Lu(3+) ions. The peculiar properties arising from the solvothermal nonaqueous synthesis here used are described through the comparison with thermally treated powders. PMID:23898781

Lauria, Alessandro; Villa, Irene; Fasoli, Mauro; Niederberger, Markus; Vedda, Anna

2013-08-09

297

An Integrated Alternative Conceptual Framework to Heat Engine Earth, Plate Tectonics, and Elastic Rebound  

Microsoft Academic Search

Physical evidence indicates that a thermally driven Earth, plate tectonics, and elastic rebound theory violate fundamental physical principles, and that Earth is a quantified solid body, the size of which possibly increases with time. Earth's core is considered as a low-temperature, high-energy\\/high- frequency, high-tension material, wherein new elements form, constituting the Excess Mass (EM), which is then added atom-by-atom to

STAVROS T. TASSOS; DAVID J. FORD

2005-01-01

298

Potential Uses of EarthSLOT (an Earth Science, Logistics, and Outreach Terrainbase) for Education and Integration in the International Polar Year  

NASA Astrophysics Data System (ADS)

EarthSLOT is an internet-based, 3D, interactive terrain and data visualization system that may have many potential uses as an education and integration tool for International Polar Year projects. Recently funded by NSF's Office of Polar Programs for use in the Arctic, the global nature of the application lends itself well for use at both poles and everywhere in between. The application allows one to start with a spinning earth and zoom down to surface level. The highest resolution digital elevation models available provide the necessary 3D topographic perspective and a variety of possible high-resolution satellite and aerial imagery layers add surface realism; resolution can be down to the centimeter level for either type of data, and frequently acquired satellite imagery may be updated automatically as it arrives. Superimposed on this can be nearly any form of vector or annotation layers, such as shapefiles, polygons, point data, and 3D models (still and moving), which can be easily imported from existing GIS applications or spreadsheets. External databases can also be queried and the results served seamlessly. The entire application is served over the internet, and any connection with speeds over 300kps allows one to interactively fly with a minimum of performance lag. EarthSLOT stands for Earth Science, Logistics, and Outreach Terrainbase, targeting the user-groups of scientists, logisticians, and the public. Approved scientific users can add their own vector content to the application on their own, such that they can create their own custom applications featuring their data but using our underlying earth model with a minimum of interaction with us. For example, an oceanographer can add ship tracks or buoy locations to the model with links to data, host the link on his or her own web page, and invite collaborators to view the spatial relationship of their data to underlying bathymetry. Logisticians or program managers interested in understanding the spatial relationships between different projects for the purposes of coordinating or facilitating cost sharing of logistics can add layers that show the locations and timing of their projects. Educators or principle investigators interested in outreach can design and implement custom applications to share the motivation, rationale, and results of their work in a large variety of ways. Each of these applications can be freely-shared or password-protected, depending on their nature, on either project home pages or on a central IPY-EarthSLOT site. Our prototype application can be found on-line at www.earthslot.org. We already have substantial Landsat coverage of the Arctic, and in the near future plan to incorporate high resolution mosaics of Greenland and Antarctica. With modest additional funding, we propose that EarthSLOT could be used a central integration tool for projects related to the International Polar Year.

Nolan, M.

2004-12-01

299

Sensing properties of rare earth oxide doped In 2O 3 by a sol–gel method  

Microsoft Academic Search

The powders of pure In2O3 and Eu3+, Gd3+, Ho3+-doped In2O3 with the structure of bixbyite-type were synthesized by a sol–gel method in the citric acid system. The structure and crystal phase of the powders were characterized by using an X-ray diffractometer. The gas sensing characteristics were obtained by measuring the response magnitude as a function of various controlling factors like

Xinshu Niu; Haoxiang Zhong; Xinjun Wang; Kai Jiang

2006-01-01

300

Processing and Properties of Rare Earth Ion-Doped Bismuth Titanate Thin Films by Chemical Solution Deposition method  

Microsoft Academic Search

Ferroelectric (Bi,R)4Ti3O12 [R: rare earth] thin films were synthesized by the chemical solution deposition (CSD) method. Heat treatment above 600°C was required for the fabrication of crystalline (Bi,R)4Ti3O12 thin films of Bi-layered perovskite structure on Pt\\/TiOx\\/SiO2\\/Si substrates. The orientation of the films prepared at 750°C depended upon the kind of substituent rare earth ions. Bi4.12Ti3O12 (BIT) and Bi3.35La0.75Ti3O12 (BLT) thin

Mio Yamada; Naoya Iizawa; Toshiaki Yamaguchi; Wataru Sakamoto; Koichi Kikuta; Toshinobu Yogo; Takashi Hayashi; Shin-ichi Hirano

2003-01-01

301

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

302

Evaluating and improving hydrologic processes in the community land model for integrated earth system modeling  

NASA Astrophysics Data System (ADS)

The community land model (CLM) was primarily designed for coupling with atmospheric models to simulate water, energy, and carbon fluxes between the land surface and atmosphere. In principle, CLM can be run at any resolution, however, validations were mostly conducted at large river basin, continental, or global scales for studies on inter-annual and inter-decadal variability, paleoclimate regimes, and projections of future changes of the global climate system, with limited case studies at flux tower sites and small watersheds. With the emergence of integrated earth system models (iESMs) at global and regional scales, and increasing interests of applying CLM at finer resolutions, it is critical to evaluate and improve the capability of CLM for hydrologic simulations at various scales, so that CLM could be used to represent hydrology, soil, managed and unmanaged ecosystems, and biogeochemical processes across scales, and provide hydrologic information being passed through all the components in a single modeling framework of iESMs. In this presentation, we will report our efforts on the development and validation of CLM hydrologic processes featuring: (1) improved land surface hydrology that incorporates hydrologic processes from the Variable Infiltration Capacity (VIC) land surface model, including the parameterizations of subgrid variability, dynamic surface- and groundwater interactions, and hydraulic redistribution; (2) a semi-distributed extension of CLM (DCLM) for more spatially-explicit hydrologic modeling, which is critical for regional land and water management decisions under climate change mitigation and adaptation scenarios; and (3) applications of CLM at multiple scales ranging from flux towers, small and large watersheds, to continental scales.

Huang, M.; Ke, Y.; Li, H.; Liu, Y.; Wigmosta, M. S.; Coleman, A.; Leung, L.

2011-12-01

303

Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.  

PubMed

In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are suitable for probing, manipulating, sculpting, and sensing at single digit nanoscale. PMID:21534601

Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

2011-05-18

304

Optical and structural investigations on rare earth-doped thin films of phosphate glasses prepared by pulsed laser deposition  

Microsoft Academic Search

Thin films of phosphate glasses were prepared by pulsed laser deposition in oxygen atmosphere on ITO-coated glass and silicon\\u000a substrates respectively, using a Nd:YAG laser (266 nm). The targets were Li2O–Al2O3–P2O5 bulk glasses doped with Pr and Nd. Infrared transmission-, energy dispersive X-ray- and X-ray photoemission spectroscopy\\u000a investigations carried out on targets as well as on the deposited films proved a

C. Vasiliu; G. Epurescu; H. Niciu; O. Dumitrescu; C. Negrila; M. Elisa; M. Filipescu; M. Dinescu; C. E. A. Grigorescu

2009-01-01

305

Crystal fields in Pr3+ doped rare earth gallium garnets, RE3Ga5O12:Pr3+  

Microsoft Academic Search

The optical absorption, site selective excitation and luminescence spectra of the trivalent praseodymium ion in three rare earth gallium garnet matrices, RE3Ga5O12 (REGG; RE=Y, Gd, and Pr) were detected at 4, 77 and 300 K. The 4f2 energy level schemes comprising 56 to 68 crystal field (CF) sublevels were simulated according to a phenomenological model taking into account both the

E. Antic-Fidancev; J. Holsa; J.-C. Krupa; M. Lemaitre-Blaise; P. Porcher

1992-01-01

306

The properties of Sn9Zn lead-free solder alloys doped with trace rare earth elements  

Microsoft Academic Search

The Sn-Zn alloys have been considered as lead-free solders. It is well known that their poor properties of wetting and oxidation\\u000a resistance are the main problems to prevent them from becoming commercially viable solders. In this paper, trace rare earth\\u000a (RE) elements of mainly Ce and La have been used as alloying elements into the Sn-9Zn alloy. The results indicated

C. M. L. Wu; D. Q. Yu; C. M. T. Law; L. Wang

2002-01-01

307

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

308

An Integrated Signal Processing System for the Flat River Earth Strain Observatory of St. Louis University  

Microsoft Academic Search

An extensive observatory for the measurement of long-period and ultra-long-period earth strains is being operated in a mine of the St. Joseph Lead Company at Flat River, Mo. The principal instruments in the observatory, three 100-foot quartz extensometers, provide electrical outputs proportional to earth strain. Each extensometer output consists of a number of components at various levels and frequencies-ultra-long-period secular

Robert Slojkowski

1968-01-01

309

Covaluation: exploring methods for expert and stakeholder valuation in integral earth system governance  

Microsoft Academic Search

Earth system governance can be characterized as multi-actor, multi-level and multi-domain. It is multi- actor because different stakeholders like governments, private actors, and societal actors are involved in the governance process; it is multi-level because different government levels play a role in the governance process through local, regional, national, European, and global governmental institutions. And it is multi-domain, because earth

Nienke van Schie; Mike Duijn; Jurian Edelenbos

310

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

2012-09-11

311

A study of spectroscopic, optical and physical properties of novel fluorophosphate glass materials doped with rare earth ions  

NASA Astrophysics Data System (ADS)

Two sets of Nd2+, Er3+ and Yb3+ doped alkaline-free MgF2-BaF2-Ba(PO3) 2-Al(PO3)3 (MBBA system) and Bi(PO3) 3-Sr(PO3)2-BaF2-MgF 2 (BSBM system) are successfully prepared with the aim of using them as active media. In order to evaluate the potential for the use of laser media, several parameters in physical, optical, and spectroscopic properties should be carefully investigated. For the MBBA system, basic physical and optical properties are carried out. The effects of thermo-mechanical, and mechanical properties on various R.E. doped glasses are reported as a function of types of dopants and their concentration. The density of the current system with R.E. dopants increases because of cationic field strength (CFS) effect. Knoop hardness decreases with the loading time and R.E. concentration because of indentation size effect (ISE) effect. For spectroscopic analysis for Er3+, intensity parameters (Ot) are calculated from least square fitting between measured and calculated oscillator strength. Spontaneous emission probability ( Arad), branching ratio (beta) and predicted radiative lifetime (taurad) have been obtained for certain excited states of the Er3+. Emission cross section for the 4I 13/2 ? 4I15/2 transition was determined by Fuchtbauer-Ladenburg method for the MBBA and BSBM system, respectively. For spectroscopic analysis for Nd3+, Judd-Ofelt analysis is performed for the MBBA and BBBM system doped with Nd2O 3 to evaluate the spontaneous emission probability as well as quality factor and branching ratio. The variation of intensity parameters O 2, O4, and O 6 are analyzed as a function of Nd2O3 concentration. Spectroscopic properties including emission cross section and lifetime are reported as a function of Yb2O3 concentration for MBBA and BBBM system. To our knowledge, the emission cross-section sigma emi, which was found to be ˜0.87, and 1.37 pm2 at the lasing wavelength of 996 nm for the MBBA and BBBM system, is the highest one among fluorophosphate glasses, respectively. The combination of outstanding spectroscopic (high emission cross section and gain coefficient) and optical (low dispersion and small nonlinear refractive index) properties demonstrates that the current Yb3+ activated fluorophosphate glass is an excellent candidate material for fiber and waveguide lasers.

Choi, Ju Hyeon

312

Tri-color upconversion luminescence of Rare earth doped BaTiO3 nanocrystals and lowered color separation.  

PubMed

Upconversion tri-color luminescence of Er(3+)/Tm(3+)/Yb(3+) doped BaTiO3 nanocrystals is observed under the excitation of a 980 nm laser diode. Especially, Er(3+) emission has a considerable contribution to the blue portion of the UC spectra, different from the ever-reported results, in which blue emission originates only from Tm(3+). This realization is beneficial to lower the color separation between blue and green (or red) emissions, in fluorescent labeling. The analysis of excitation power dependence and decay time revealed that blue emission of Er(3+) ion is induced by a dual energy transfer upconversion, while Tm(3+) plays a role of both emitter and activator. PMID:19466159

Liu, Yunxin; Pisarski, Wojciech A; Zeng, Songjun; Xu, Changfu; Yang, Qibin

2009-05-25

313

Ultra-broadband infrared luminescence of Bi-doped thin-films for integrated optics.  

PubMed

Ultra-broadband infrared luminescence has been observed in bismuth (Bi)-doped germanate thin-films prepared by pulsed laser deposition. The films are compatible with various types of substrates, including conventional dielectrics (LaAlO(3), silica) and semiconductors (Si, GaAs). The emission peak position of the films can be finely tuned by changing oxygen partial pressure during the deposition, while the excitation wavelength locates from ultra-violet to near-infrared regions. The physical mechanism behind the observed infrared luminescence of the Bi-doped films, differing from that of the as-made glass, is discussed. PMID:23938725

Xu, Beibei; Hao, Jianhua; Zhou, Shifeng; Qiu, Jianrong

2013-07-29

314

Alkaline earth zinc borate glasses doped with Cu 2+ ions studied by EPR, optical and IR techniques  

Microsoft Academic Search

Copper ions incorporated into alkaline earth zinc borate glasses 10RO+30ZnO+60B2O3 (R=Mg, Ca and Sr) and 10SrO+(30?x)ZnO+60B2O3+xCuO (x=0, 0.1, 0.3, 0.5, and 0.7wt.%) were characterized by electron paramagnetic resonance (EPR), optical absorption and FTIR techniques. The EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The values of spin-Hamiltonian parameters indicate that the Cu2+ ions in

B. Sumalatha; I. Omkaram; T. Rajavardhana Rao; Ch. Linga Raju

2011-01-01

315

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

316

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 Å 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

317

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, Björn; Eichele, Klaus; Meyer, H-Jürgen

2006-04-01

318

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; Giérak, Jacques; Bourhis, Eric

2004-07-01

319

High contrast in vivo bioimaging using multiphoton upconversion in novel rare-earth-doped fluoride upconversion nanoparticles  

NASA Astrophysics Data System (ADS)

Upconversion in rare-earth ions is a sequential multiphoton process that efficiently converts two or more low-energy photons, which are generally near infrared (NIR) light, to produce anti-Stokes emission of a higher energy photon (e.g., NIR, visible, ultraviolet) using continuous-wave (cw) diode laser excitation. Here, we show the engineering of novel, efficient, and biocompatible NIRin-to-NIRout upconversion nanoparticles for biomedical imaging with both excitation and emission being within the "optical transparency window" of tissues. The small animal whole-body imaging with exceptional contrast (signal-to-noise ratio of 310) was shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles. An imaging depth as deep as 3.2-cm was successfully demonstrated using thick animal tissue (pork) under cw laser excitation at 980 nm.

Chen, Guanying; Yang, Chunhui; Prasad, Paras N.

2013-02-01

320

"Space on Earth:" A Learning Community Integrating English, Math, and Science  

ERIC Educational Resources Information Center

|Imagine a mathematics instructor and English instructor sharing an office; scribbled equations litter one desk, snatches of poetry the other. Our learning community, "Space on Earth," grew from conversations in just such an office where we bridged our own disciplinary gap and discovered a shared passion for helping students apply the concepts and…

Fortna, Joanna; Sullivan, Jim

2010-01-01

321

Crystallization, phase transition and optical properties of the rare-earth doped nanophosphors synthesized by chemical deposition.  

SciTech Connect

The structural and electronic properties of Eu{sup 3+}-doped Y{sub 2}O{sub 3} films coated on spherical alumina nanoparticles are studied using transmission electron microscope, x-ray diffraction, and laser spectroscopic techniques. It is observed that the coated films crystallize at temperatures higher than 600{sup o}C and may be completely converted into a cubic Y{sub 2}O{sub 3} nanocrystalline layer at 750{sup o}C. At 900{sup o}C, phase transition occurs between the outer coating layer and the inner core, and different types of crystalline nanophase can be obtained. In the materials that we prepared and studied, all possible crystallographic phases, including two of solid-state laser media, YAlO{sub 3} (YAP), and Y{sub 3}Al{sub 5}O{sub 12} (YAG), may be formed in the pseudo-binary Al{sub 2}O{sub 3}-Y{sub 2}O{sub 3} nanosystem by controlling thermal annealing procedures from 600 to 900{sup o}C, a temperature region far below the conventional solid-state reaction temperature. The spectroscopic properties of Eu{sup 3+} in all the nanophases are characterized in comparison with those of their bulk counterparts.

Chen, X. Y.; Yang, L.; Cook, R. E.; Skanthakumar, S.; Shi, D.; Liu, G. K.; Univ. of Cincinnati

2003-06-01

322

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

323

Design, Development, and Evaluation of an Integrated Mathematics and Science Course to Teach Earth System Science to Preservice Middle School Teachers  

Microsoft Academic Search

Pre-service middle school teachers receive a mixed representation of science during their university education. Science disciplines and mathematics are taught with little attention to integration. Earth system science is seldom presented. Fort Hays State University (FHSU) has addressed this issue through the development of an Integrated Mathematics and Science Course (development partially supported through National Science Foundation's CCLI Program under

P. Adams; J. Heinrichs

2007-01-01

324

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, Poisson’s 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

325

Native American Science Education: A Compelling Opportunity for the Integration of Earth and Space Science  

Microsoft Academic Search

The strong relationships between Earth and sky in the worldviews of Native American people presents a wonderful opportunity for collaborations that can co-create compelling educational opportunities for both Native and non-Native learners. This paper will discuss the relationship among successful science education for Native Americans, standards-based science education, and informal science education. It will address some strategies for combining best

C. A. Morrow; N. Maryboy; D. Begay

2005-01-01

326

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

327

Doping management for high-power fiber lasers: 100 W, few-picosecond pulse generation from an all-fiber-integrated amplifier.  

PubMed

Thermal effects, which limit the average power, can be minimized by using low-doped, longer gain fibers, whereas the presence of nonlinear effects requires use of high-doped, shorter fibers to maximize the peak power. We propose the use of varying doping levels along the gain fiber to circumvent these opposing requirements. By analogy to dispersion management and nonlinearity management, we refer to this scheme as doping management. As a practical first implementation, we report on the development of a fiber laser-amplifier system, the last stage of which has a hybrid gain fiber composed of high-doped and low-doped Yb fibers. The amplifier generates 100 W at 100 MHz with pulse energy of 1 ?J. The seed source is a passively mode-locked fiber oscillator operating in the all-normal-dispersion regime. The amplifier comprises three stages, which are all-fiber-integrated, delivering 13 ps pulses at full power. By optionally placing a grating compressor after the first stage amplifier, chirp of the seed pulses can be controlled, which allows an extra degree of freedom in the interplay between dispersion and self-phase modulation. This way, the laser delivers 4.5 ps pulses with ~200 kW peak power directly from fiber, without using external pulse compression. PMID:22859079

Elahi, P; Y?lmaz, S; Akçaalan, O; Kalayc?o?lu, H; Oktem, B; Senel, C; Ilday, F Ö; Eken, K

2012-08-01

328

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

329

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

330

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 and predictors (withdrawals vs. consumptive demands, as well as natural vs. regulated mean flow) for configuring operating rules. Overall the best performing implementation is with combined priorities rules (flood control storage targets and irrigation release targets) set up 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.

2013-09-01

331

Earth tides  

SciTech Connect

Nineteen papers on gravity, tilt, and strain tides are compiled into this volume. Detailed chapters cover the calculation of the tidal forces and of the Earth's response to them, as well as actual observations of earth tides. Partial Contents: On Earth tides. The tidal forces: Tidal Forces. New Computations of the Tide-Generating Potential. Corrected Tables of Tidal Harmonics. The Theory of Tidal Deformations. Body Tides on an Elliptical, Rotating, Elastic and Oceanless Earth, Deformation of the Earth by Surface Loads. Gravimetric Tidal Loading Computed from Integrated Green's Functions. Tidal Friction in the Solid Earth. Loading Tides Versus Body Tides. Lunar Tidal Acceleration from Earth Satellite Orbit Analysis. Observations: gravity. Tidal Gravity in Britain: Tidal Loading and the Spatial Distribution of the Marine Tide. Tidal Loading along a Profile Europe-East Africa-South Asia-Australia and the Pacific Ocean. Detailed Gravity-Tide Spectrum between One and Four Cycles per Day. Observations: tilt and strain. Cavity and Topographic Effects in Tilt and Strain Measurement. Observations of Local Elastic Effects on Earth Tide Tilts and Strains.

Harrison, J.C.

1984-01-01

332

Native American Science Education: A Compelling Opportunity for the Integration of Earth and Space Science  

NASA Astrophysics Data System (ADS)

The strong relationships between Earth and sky in the worldviews of Native American people presents a wonderful opportunity for collaborations that can co-create compelling educational opportunities for both Native and non-Native learners. This paper will discuss the relationship among successful science education for Native Americans, standards-based science education, and informal science education. It will address some strategies for combining best practice in education with a deep cultural authenticity. Presenting astronomy in a culturally relevant and correct way is not only of value to the Native learner, but it is also of value to the non-Native learner because cultural relevance for Native people demands that science be presented via different learning modalities (e.g. visual, kinesthetic, tactile) and in a way that is more interconnected with other science and non-science disciplines. This kind of multi-modal and interdisciplinary approach is valuable and progressive for Non-native learners as well.

Morrow, C. A.; Maryboy, N.; Begay, D.

2005-05-01

333

Effect of Knowledge Integration Activities on Students' Perception of the Earth's Crust as a Cyclic System.  

ERIC Educational Resources Information Center

|Characterizes students' understanding of the rock cycle system. Examines effects of a knowledge integration activity on their system thinking. Interprets answers to an open-ended test using a systems thinking continuum ranging from a completely static view of the system to an understanding of the system's cyclic nature. Reports meaningful…

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

2003-01-01

334

Electromagnetic scattering of large structures in layered earths using integral equations  

Microsoft Academic Search

An electromagnetic scattering algorithm for large conductivity structures in stratified media has been developed and is based on the method of system iteration and spatial symmetry reduction using volume electric integral equations. The method of system iteration divides a structure into many substructures and solves the resulting matrix equation using a block iterative method. The block submatrices usually need to

Zonghou Xiong; Alan C. Tripp

1995-01-01

335

Orthorhombic superstructures within the rare earth strontium-doped cobaltate perovskites: Ln 1? x Sr x CoO 3? ? ( Ln=Y 3+, Dy 3+–Yb 3+; 0.750? x?0.875)  

Microsoft Academic Search

A combination of electron, synchrotron X-ray and neutron powder diffraction reveals a new orthorhombic structure type within the Sr-doped rare earth perovskite cobaltates Ln1?xSrxCoO3?? (Ln=Y3+, Dy3+, Ho3+, Er3+, Tm3+and Yb3+). Electron diffraction shows a C-centred cell based on a 2?2ap×4ap×4?2ap superstructure of the basic perovskite unit. Not all of these very weak satellite reflections are evident in the synchrotron X-ray

Michael James; Maxim Avdeev; Paris Barnes; Liliana Morales; Kia Wallwork; Ray Withers

2007-01-01

336

Computational Challenges in Integrated Regional Earth System Modeling (iRESM)  

NASA Astrophysics Data System (ADS)

Policy and decision making, in response to climate change, will require both economic and environmental tradeoffs. Decisions about allocating scarce water across competing municipal, agricultural, and ecosystem demands is just one of the challenges ahead, along with decisions regarding competing land use priorities such as biofuels, food, and species habitat. Assessing potential mitigation actions must include processes at a global level and extended time frame. However, adaptation is more relevant on a regional scale and in a shorter time frame, which encourages current research to address mitigation and adaptation separately, even though strategies for mitigation influence our ability for adaptation, and vice versa, none have attempted to fully integrate human and environmental processes at the regional level. The fundamental goal of the iRESM initiative is the critical analyses of the tradeoffs and consequences of decision and policy making on the background of integrated human and environmental systems, combining the different scientific processes, bridging different temporal and geographic scales and resolving the semantic differences between them. Hereby the iRESM Initiative will work in the first instance with the climate, socio-economic, crop and energy modeling communities to develop an initial system. The computational challenges faced by the project go hand in hand with the scientific ones, as the researchers from different domains are starting to bridge the gaps, an adaptive computational framework needs to be established that facilitates the integration and transition across different geographical, time, thematic and semantic divides. With an expectation that more diverse processes and interchanges will be added in the future the framework also needs to be adaptive and flexible, providing the ability to grow with the project needs. We provide an overview of the iRESM initiative from PNNL with the initial architectural framework to evaluate the integration and transformation structures required across the different models within the context of hydrologic supply and demand.

Kleese van Dam, K.; Hibbard, K. A.; Gorton, I.; Liu, Y.

2010-12-01

337

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

338

Integrating the Sun-Earth System (ISES): The 2008-2009 Whole Heliosphere Intervals  

NASA Astrophysics Data System (ADS)

We simulate the Sun-Earth system throughout the extended solar minimum epoch from 2008 to 2009 using coupled geospace, heliosphere and solar numerical models, systematically validating individual model components with databases of observed geospace composition and solar and heliospheric parameters. We isolate and quantify observed changes of 5% to 25% in global ionosphere electron density and 10% to 40% in thermospheric mass density at 250 km associated with fluctuating solar EUV radiation and geomagnetic activity during this nominally "quiet" period. Corresponding modeled changes of responses to both solar EUV radiation and geomagnetic activity are about a factor of two smaller than is observed. We identify, as well, semiannual and annual oscillations that produce geospace variability comparable to solar and geomagnetic influences, and cause distinct differences among the three individual Whole Heliosphere Intervals. From the first Whole Heliosphere Interval (March-April 2008) to the third Whole Heliosphere Interval (June-July 2009) total electron content decreased 37% and mass density at 250 decreased 42% due to these oscillations, which originate partly in the lower atmosphere. Reliable attribution of the geospace base state during the 2008-2009 solar minimum epoch, and geospace comparisons among the Whole Heliosphere Intervals, requires that the semiannual and annual oscillations be properly distinguished from concurrent solar and heliospheric effects.

Drob, Douglas; Lean, Judith; McDonald, Sarah; Huba, Joe; Emmert, John; Wu, Chin-Chun; Wang, Yi-Ming; Krall, Johnathan; Siefring, Carl

2013-04-01

339

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.

340

Structural and optical properties of rare earth-doped (Ba{sub 0.77}Ca{sub 0.23}){sub 1-x}(Sm, Nd, Pr, Yb){sub x}TiO{sub 3}  

SciTech Connect

The structural, dielectric, and vibrational properties of pure and rare earth (RE)-doped Ba{sub 0.77}Ca{sub 0.23}TiO{sub 3} (BCT23; RE = Nd, Sm, Pr, Yb) ceramics obtained via solid-state reaction were investigated. The pure and RE-doped BCT23 ceramics sintered at 1450 deg. C in air for 4 h showed a dense microstructure in all ceramics. The use of RE ions as dopants introduced lattice-parameter changes that manifested in the reduction of the volume of the unit cell. RE-doped BCT23 samples exhibit a more homogenous microstructure due to the absence of a Ti-rich phase in the grain boundaries as demonstrated by scanning electron microscopy imaging. The incorporation of REs led to perturbations of the local symmetry of TiO{sub 6} octahedra and the creation of a new Raman mode. The results of Raman scattering measurements indicated that the Curie temperature of the ferroelectric phase transition depends on the RE ion and ion content, with the Curie temperature shifting toward lower values as the RE content increases, with the exception of Yb{sup 3+} doping, which did not affect the ferroelectric phase transition temperature. The phase transition behavior is explained using the standard soft mode model. Electronic paramagnetic resonance measurements showed the existence of Ti vacancies in the structure of RE-doped BCT23. Defects are created via charge compensation mechanisms due to the incorporation of elements with a different valence state relative to the ions of the pure BCT23 host. It is concluded that the Ti vacancies are responsible for the activation of the Raman mode at 840 cm{sup -1}, which is in agreement with lattice dynamics calculations.

Moraes, A. P. A. [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, 60455-900 Fortaleza-CE (Brazil); Universidade Federal do Mato Grosso, 78060-900, Araguaia-MT (Brazil); Filho, A. G. Souza; Freire, P. T. C.; Filho, J. Mendes [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, 60455-900 Fortaleza-CE (Brazil); M'Peko, J. C.; Hernandes, A. C. [Grupo de Crescimento de Cristais e Materiais Ceramicos, Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, Sao Carlos-SP (Brazil); Antonelli, E. [Universidade Federal de Itajuba (Unifei) - Campus Itabira, Rua Sao Paulo 377, Bairro Amazonas, CEP35900-37 Itabira, MG (Brazil); Blair, Michael W.; Muenchausen, Ross E. [Los Alamos National Laboratory, Materials Science and Technology Division, Los Alamos, New Mexico 87545 (United States); Jacobsohn, Luiz G. [Center for Optical Materials Science and Engineering Technologies - COMSET, and School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Paraguassu, W. [Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem-PA (Brazil)

2011-06-15

341

Research priorities in land use and land-cover change for the Earth system and integrated assessment modelling  

SciTech Connect

This special issue has highlighted recent and innovative methods and results that integrate observations and AQ3 modelling analyses of regional to global aspect of biophysical and biogeochemical interactions of land-cover change with the climate system. Both the Earth System and the Integrated Assessment modeling communities recognize the importance of an accurate representation of land use and land-cover change to understand and quantify the interactions and feedbacks with the climate and socio-economic systems, respectively. To date, cooperation between these communities has been limited. Based on common interests, this work discusses research priorities in representing land use and land-cover change for improved collaboration across modelling, observing and measurement communities. Major research topics in land use and land-cover change are those that help us better understand (1) the interaction of land use and land cover with the climate system (e.g. carbon cycle feedbacks), (2) the provision of goods and ecosystem services by terrestrial (natural and anthropogenic) land-cover types (e.g. food production), (3) land use and management decisions and (4) opportunities and limitations for managing climate change (for both mitigation and adaptation strategies).

Hibbard, Kathleen A.; Janetos, Anthony C.; Van Vuuren, Detlef; Pongratz, Julia; Rose, Steven K.; Betts, Richard; Herold, Martin; Feddema, Johannes J.

2010-11-15

342

Integrated experimental and modeling study of the ionic conductivity of samaria-doped ceria thin films  

SciTech Connect

Oxygen diffusion and ionic conductivity of samaria-doped ceria (SDC) thin films have been studied as a function of composition using experiment and atomistic simulation. SDC thin films were grown on Al2O3 (0001) substrates by oxygen plasma-assisted molecular beam epitaxy (OPA-MBE) technique. The experimental results show a peak in electrical conductivity of SDC at 15 mol% Sm2O3. The oxygen diffusion coefficient obtained from molecular dynamics simulation of the same system shows a peak at about 13 mol% Sm2O3. The activation energy for oxygen diffusion was found to be in the range from 0.8 to 1.0 eV by simulations depending on the Sm2O3 content, which compares well with the range from 0.6 to 0.9 eV given by the experimental work. The simulations also show that oxygen vacancies prefer Sm3+ ions as first neighbors over Ce4+ ions. The present results reveal that the optimum samaria content for ionic conductivity in single crystals of SDC is less than that in polycrystals, which can be related to the preferential segregation of dopant cations to grain boundaries in polycrystals.

Sanghavi, Rahul P.; Devanathan, Ramaswami; Nandasiri, Manjula I.; Kuchibhatla, Satyanarayana V N T; Kovarik, Libor; Thevuthasan, Suntharampillai; Prasad, Shalini

2011-12-12

343

Performance evaluation and life cycle cost analysis of earth to air heat exchanger integrated with adobe building for New Delhi composite climate  

Microsoft Academic Search

This paper aims to develop thermal model of a vault roof building integrated with earth to air heat exchanger (EAHE). The building under consideration is made of brick vault and adobe (or mud) structures. The methodology adopted for developing thermal model of this building with six interconnected rooms is presented in this paper. The energy balance equations were solved simultaneously

Arvind Chel; G. N. Tiwari

2009-01-01

344

Earth materials and earth dynamics  

SciTech Connect

In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

Bennett, K; Shankland, T. [and others

2000-11-01

345

MAPS (My Atlas and Plot Service) for Integrated Earth Observation Data  

NASA Astrophysics Data System (ADS)

DIAS (Data integration and Analysis System) is one of the activities of GEOSS, and also one of Japanese National Key Technology activities. JAMSTEC collaborates with the University of Tokyo, the main contractor of the project. It is a five-year project until March 2011. We at JAMSTEC also have developed a data distribution system toward long-term sustainable services as part of DIAS. We launched the early website at 2007. It provided six integration and analysis datasets in the fields of “Ocean & Fishery Resources”, “Water Cycle” and “Land Ecosystem”. We also investigated users’ needs through an online questionnaire and through interviews regarding the types and quality of required data, data formats, website functions and so on. Accordingly, our new website, MAPS, which is short for My Atlas and Plot Service has been remodeled with four new datasets and new functions to meet users’ needs since the fall in 2010. We have provided online mapping and plotting services with MapServer, and download services with functions of extracting digital data by selected attribute and of converting into another file type. These services provide a powerful visualization and analysis capabilities for the data products. The input items and forms in online questionnaire and Contact-Us page in our website have been refined to collect feedbacks and comments about the new website functions. We are continuously researching the further future needs in order to promote the wider usage of the datasets.

Ichino, M.; Fukuda, K.; Sugiura, N.; Funakoshi, R.

2010-12-01

346

Building Capacity to Integrate NASA Earth Science into Water Resources Management Applications in the Context of a Changing Climate  

NASA Astrophysics Data System (ADS)

The NASA Applied Sciences program provides technical capacity building activities to enable decision-makers to integrate NASA Earth Science into environmental management activities. This includes workshops tailored to end-user needs by working directly with agencies to 1) identify environmental management activities that could benefit from NASA Earth Science and 2) conducting workshops that teach the NASA products and decision-support tools best suited to the identified application area. Building on a successful 3-year effort on air pollution monitoring for environmental applications, the project has expanded into water resources. Climate Change has dramatically increased demand for observational and predictive data in support of decision making activities related to water supply and demand. However, a gap remains between NASA products and applied research and the entities who stand to benefit from their utilization. To fill this gap, the project has developed short courses on 1) impacts of climate change on water resources 2) hands-on exercises on access and interpretation of NASA imagery relevant to water resources management via the use of decision-support web tools and software and 3) case studies on the application of NASA products in the field. The program is currently focused on two areas 1) precipitation products over the central and southern U.S. that help communities and agencies improve flooding forecasts and 2) snow and snow/water equivalent products over the western U.S and Latin America that can provide end-users with improved stream flow prediction in Spring within a framework of decreasing snow availability.

Prados, A. I.; Mehta, A. V.

2011-12-01

347

Expedition Earth and Beyond: Using NASA data resources and integrated educational strategies to promote authentic research in the classroom  

NASA Astrophysics Data System (ADS)

Teachers in today’s classrooms are bound by state required skills, education standards, and high stakes testing. How can they gain skills and confidence to replace units or individual activities with curriculum that incorporates project and inquiry-based learning and promotes authentic research in the classroom? The key to promoting classroom authentic research experiences lies in educator professional development that is structured around teacher needs. The Expedition Earth and Beyond Program is a new geosciences program based at the NASA Johnson Space Center designed to engage, inspire and educate teachers and students in grades 5-14. The program promotes authentic research experiences for classrooms and uses strategies that will help NASA reach its education goals while still allowing educators to teach required standards. Teachers will have access to experts in terrestrial and planetary remote sensing and geoscience; this will enhance their use of content, structure, and relevant experiences to gain the confidence and skills they need to actively engage students in authentic research experiences. Integrated and powerful educational strategies are used to build skills and confidence in teachers. The strategies are as follows: 1) creating Standards-aligned, inquiry-based curricular resources as ready-to-use materials that can be modified by teachers to fit their unique classroom situation; 2) providing ongoing professional development opportunities that focus on active experiences using curricular materials, inquiry-based techniques and expanding content knowledge; 3) connecting science experts to classrooms to deepen content knowledge and provide relevance to classroom activities and real world applications; 4) facilitating students sharing research with their peers and scientists reinforcing their active participation and contributions to research. These components of the Expedition Earth and Beyond Education Program will be enhanced by providing exciting and diverse research opportunities that are inspired by views of Earth from space taken by astronauts on board the International Space Station. The interest and connection to viewing our home planet from space will inevitably spark questions that will drive students to pursue their research investigations, as well as forming a basis for comparisons to the exploration of other planetary bodies in our solar system.

Graff, P. V.; Stefanov, W.; Willis, K.; Runco, S.

2009-12-01

348

Integrated silicon nanowire diodes and the effects of gold doping from the growth catalyst  

Microsoft Academic Search

We report on integrated, silicon single-nanowire diodes. Gold catalyst templates, defined by lithography, controlled the location of nanowires grown with a vapor-liquid-solid mechanism. The nanowire growth, by atmospheric-pressure chemical vapor deposition, used SiCl4 diluted in H2 on (100) n-type silicon substrates. Postgrowth oxidation and wet etching reduced the nanowire diameters and removed unintentional small diameter nanowires. Spin-on glass isolated the

Justin B. Jackson; Divesh Kapoor; Sun-Gon Jun; Mark S. Miller

2007-01-01

349

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance.  

SciTech Connect

Monoclinic potassium rare-earth double tungstates [KRE(WO{sub 4}){sub 2}, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln{sup 3+}) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb{sup 3+}- and Tm{sup 3+}-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

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

2010-01-01

350

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance  

NASA Astrophysics Data System (ADS)

Monoclinic potassium rare-earth double tungstates [KRE(WO4)2, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln3+) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb3+- and Tm3+-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.

Raghothamachar, B.; Carvajal, J. J.; Pujol, M. C.; Mateos, X.; Solé, R.; Aguiló, M.; Díaz, F.; Dudley, M.

2010-06-01

351

Thermal neutron imaging with rare-earth-ion-doped LiCaAlF6 scintillators and a sealed 252Cf source  

NASA Astrophysics Data System (ADS)

Thermal neutron imaging with Ce-doped LiCaAlF6 crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF6 scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF6 single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 50×2 mm2 was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The 252Cf source (<1 MBq) was sealed with 43 mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2 mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF6.

Kawaguchi, Noriaki; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Kamada, Kei; Fukuda, Kentaro; Suyama, Toshihisa; Watanabe, Kenichi; Yamazaki, Atsushi; Chani, Valery; Yoshikawa, Akira

2011-10-01

352

Miscibility of chitosan\\/poly(ethylene oxide) blends and effect of doping alkali and alkali earth metal ions on chitosan\\/PEO interaction  

Microsoft Academic Search

The miscibility of Chitosan (CS) and poly(ethylene oxide) (PEO) in their blends and the effect of K+ and Ca2+ doping on the CS\\/PEO interaction have been investigated in this work. CS and PEO appeared to be miscible and the DSC analysis suggested the Flory–Huggins interaction parameter ?AB to be ?0.21. Doping of K+ and Ca2+ into the CS\\/PEO blend matrix enhanced

Natthida Rakkapao; Yuichi Masubuchi; Hiroshi Watanabe

2011-01-01

353

Flat earth upward continuation  

Microsoft Academic Search

For a thorough understanding of flat earth upward continuation, Poisson's integral equation is transformed from a coordinate system with spherical symmetry to one with planar symmetry. The two separate cases of infinite and finite flat earths are considered. In resulting exact forms a functional factor in the integrands is isolated, a factor which allows the translation of a spherical earth

John V. Shebalin

1979-01-01

354

On purpose in science, conservation and government. The functional integrity of the earth is at issue not biodiversity.  

PubMed

The objectives of conservation have been focused ever more intensively for two decades on the preservation of "biodiversity." Emphasis has been on the losses of species through extinction. The cure has been the establishment of parks and reserves to protect "hot spots," especially in the tropics, where the diversity of species is high. The efforts in preservation have often extended to the development of connecting links among reserves to allow movements among them. The approach has been codified in law in the form of the Endangered Species Act in the United States and the Biodiversity Treaty, both of which address the issue species by species and each of which has obvious weaknesses. Such efforts may be appropriate but they are totally inadequate as the sum of activities in conservation in a world of 6 billion people with exploding technologies for exploiting virtually all of the earth for immediate human benefit. The biosphere is decaying rapidly as a habitat for all life, including people, not because of the extinction of species, but because of the progressive impoverishment of natural communities through human-induced chronic disruption that is now global and ubiquitous. The improverishment leads to progressive environmental dysfunction that is cumulative, but only in its later stages leads to extinction of species. Long before extinction becomes important, genetically distinct, local ecotypes are lost and the natural communities in which they were developed become improverished and dysfunctional. The most conspicuous disruption is that of climate, a global change in the environment of every ecosystem. The most elaborate and carefully interlinked array of natural reserves will succumb as climate is moved out from under them... and biodiversity will suffer the very extinctions the parks were established to avoid. But long before that, the human environment will suffer conspicuous and progressive impoverishment. The objective of conservation is the preservation of the integrity of function of landscapes (and waterbodies). Emphasis falls on forests in the normally naturally forested parts of the earth because forests are so large in area globally and have such a large influence on virtually every aspect of environment. Functional integrity requires structural integrity over 85% or more of the naturally forested zone in most areas. It also requires objective measurement and definition by the scientific community. Suddenly, conservation has become, not the preservation of biodiversity, honorable as that may be, but the preservation of the functional integrity of the human environment. That purpose is the central purpose that we assign to the governments that we establish in democracies to define and defend the public interest. It is past time for the scientific and conservation communities to recognize the urgency of this transition, join in defining competent new objectives for conservation, and to convey to the public the urgency of the need for governmental responsibility in protecting the public interest in a habitable biosphere. PMID:12374052

Woodwell, George M

2002-08-01

355

Design, Development, and Evaluation of an Integrated Mathematics and Science Course to Teach Earth System Science to Preservice Middle School Teachers  

NASA Astrophysics Data System (ADS)

Pre-service middle school teachers receive a mixed representation of science during their university education. Science disciplines and mathematics are taught with little attention to integration. Earth system science is seldom presented. Fort Hays State University (FHSU) has addressed this issue through the development of an Integrated Mathematics and Science Course (development partially supported through National Science Foundation's CCLI Program under DUE#0088818 and DUE#0311042). The course was designed by an interdisciplinary team using a "cycles-of-nature" theme to integrate across earth and space science, physics, chemistry, biology, and mathematics. Several of the themes were earth system science based (e.g. Climate Cycles, Seasonal Cycles, Geophysical Cycles). The course also incorporated statistical analysis of data, estimations, and reading scientific literature. To promote pre-service teachers abilities to do authentic science, six to eight weeks of the fifteen week course were utilized for the preservice teachers to design, conduct, and present a self-designed research project based on the content of the course. Evaluation data from the course indicated that it was successful in a) changing university faculty perceptions of teaching science, b) illustrating novel approaches to preservice teachers, c) improving an understanding of the nature of science in preservice teachers, and d) increasing the preservice teachers understanding of the integrated nature of science.

Adams, P.; Heinrichs, J.

2007-12-01

356

White light luminous properties and energy transfer mechanism of rare earth ions in Ce3+/Tb3+/Sm3+ co-doped glasses  

NASA Astrophysics Data System (ADS)

We report on a kind of Ce3+/Tb3+/Sm3+ co-doped borosilicate glasses which can emit white light luminescence combined with red, green and blue fluorescence. In this manuscript, the energy transfer mechanism between Ce3+ and Tb3+ ions, Ce3+ and Sm3+ ions, and Tb3+ and Sm3+ ions is discussed by analysis of the steady and transient luminescence spectra of the doped ions. Based on the energy transfer mechanism, the near-ideal white light emission from the Ce3+/Tb3+/Sm3+ co-doped glasses with the color coordinate (x=0.335, y=0.337) has been observed under 350-nm excitation. Meanwhile, the calculated parameters such as color rendering index (78-81) and color temperature (4717-5372 K), characterizing luminous properties, show that the glasses can be potential candidates for displays and lighting.

Chen, Qiaoqiao; Dai, Nengli; Liu, Zijun; Chu, Yingbo; Ye, Baoyuan; Li, Haiqing; Peng, Jinggang; Jiang, Zuowen; Li, Jinyan; Wang, Fang; Yang, Luyun

2013-10-01

357

EPOS the European Plate Observing System: a long-term integration plan for research infrastructures on solid Earth sciences at pan-European level  

NASA Astrophysics Data System (ADS)

EPOS (European Plate Observing System) aims to integrate data from permanent national and regional geophysical monitoring networks (seismological, GPS), with the observations from "in-situ" observatories (volcano observatories, in-situ fault zone test sites, etc....) and temporary-monitoring and laboratory experiments through a cyber-infrastructure for data mining and processing, and facilities for data integration, archiving and exchange. By providing an unprecedented high-quality multidisciplinary service to users, EPOS will foster and support research on earthquakes, volcanoes, surface dynamics and tectonics, and will complement similar initiatives in satellite Earth observing systems and ocean sciences. EPOS main aim is to create a coherent Research Infrastructure enabling the next generation of scientists to pursue innovative and challenging solid Earth science research in Europe and in the Mediterranean regions. EPOS has been included in the European roadmap for research infrastructures after positive evaluation by ESFRI (European Strategy Forum on Research Infrastructures) in December 2008. A preparatory phase proposal has been recently submitted to the last EC Call in the Capacities Work Program. Here we present the EPOS concept and the strategic plans for its preparatory phase, focusing on the implementation plan and vision to create an effective service to users. Making observations of solid Earth dynamic processes controlling natural phenomena immediately available and promoting their comparison with experimental observations from cutting-edge laboratory experiments and their interpretation through theoretical analyses and numerical simulations will represent a multidisciplinary platform for discoveries which will foster scientific excellence in solid Earth research.

Cocco, Massimo; van Eclk, Torild; Michelini, Alberto; Epos Team

2010-05-01

358

Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework  

Microsoft Academic Search

We have used the Grid ENabled Integrated Earth system modelling (GENIE) framework to undertake a systematic search for bi-stability\\u000a of the ocean thermohaline circulation (THC) for different surface grids and resolutions of 3-D ocean (GOLDSTEIN) under a 3-D\\u000a dynamical atmosphere model (IGCM). A total of 407,000 years were simulated over a three month period using Grid computing.\\u000a We find bi-stability of

T. M. Lenton; R. Marsh; A. R. Price; D. J. Lunt; Y. Aksenov; J. D. Annan; T. Cooper-Chadwick; S. J. Cox; N. R. Edwards; S. Goswami; J. C. Hargreaves; P. P. Harris; Z. Jiao; V. N. Livina; A. J. Payne; I. C. Rutt; J. G. Shepherd; P. J. Valdes; G. Williams; M. S. Williamson; A. Yool

2007-01-01

359

Effects of rare earth cations doped for La site on the oxide ionic conductivity of LaGaO 3-based perovskite type oxide  

Microsoft Academic Search

For the suppression of hole conduction in the high oxygen partial pressure range, effects of the addition of small amount of rare earth cations were investigated in this study with La0.8Sr0.2Ga0.8Mg0.2O3 ? ?. It was found that the addition of small amount of rare earth cations for La site in LaGaO3 was effective for the suppression of hole conduction under

Tatsumi Ishihara; Hideaki Matsuda; Yusaku Takita

1995-01-01

360

Rare Earth Ion Effects on the Pseudo-Gap in Electron-Doped Superconductors And Possible Nodeless D-Wave Gap  

SciTech Connect

We report angle resolved photoemission (ARPES) studies on electron-doped cuprate superconductor Sm{sub 2-x}Ce{sub x}CuO{sub 4} (x = 0.14 and 0.18). A wide energy range scan shows clear 'waterfall' effect at an energy scale close to 500 meV which is consistent with the value found in Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) but larger than that from hole-doped superconductors. High resolution results from both dopings show pseudo-gap effects that were observed in NCCO. However, the effects are found to be stronger than that observed in optimally doped NCCO. The overall electronic structure is well understood within a simple model in which a {radical}2 x {radical}2 static order is assumed. Both ARPES and optical measurements give the coupling strengths to the Q = ({pi}/2,{pi}/2) (due to the {radical}2 x {radical}2 order) to be about 0.1 eV, compatible with each other. The effect is strong enough to push the band near the nodal region below the Fermi energy, resulting in possible nodeless d-wave superconductivity where zero energy quasi-particle excitation is inhibited.

Park, S.R.; Leem, C.S.; Roh, Y.S.; Choi, K.J.; Kim, J.H.; Kim, B.J.; Koh, H.; Eisaki, H.; Lu, D.H.; Shen, Z.-X.; Armitage, N.P.; Kim, C.

2009-05-21

361

Study of the structure and optical properties of rare-earth-doped aluminate particles prepared by an amorphous citrate sol–gel process  

Microsoft Academic Search

Calcium aluminate, doped with neodymium and europium ions, was prepared by a citrate polymeric precursor sol–gel method. The influence of the synthesis mixture composition and the thermal treatment parameters on the structure, morphology and optical properties of the material were investigated by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, diffuse reflectance, emission and excitation spectroscopy. The amount of organic component

P. N. M. dos Anjos; E. C. Pereira; Y. G. Gobato

2005-01-01

362

Synthesis and characterization of rare-earth doped SrBi{sub 2}Nb{sub 2}O{sub 9} phase in lithium borate based nanocrystallized glasses  

SciTech Connect

Glass composites comprising of un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites are fabricated in the glass system 16.66SrO-16.66[(1-x)Bi{sub 2}O{sub 3}-xSm{sub 2}O{sub 3}]-16.66Nb{sub 2}O{sub 5}-50Li{sub 2}B{sub 4}O{sub 7} (0<=x<=0.5, in mol%) via the melt quenching technique. The glassy nature of the as-quenched samples is established by differential thermal analyses. Transmission electron microscopic studies reveal the presence of about 15 nm sized spherical crystallites of the fluorite-like SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} phase in the samples heat treated at 530 deg. C. The formation of layered perovskite-type un-doped and samarium-doped SrBi{sub 2}Nb{sub 2}O{sub 9} nanocrystallites with an orthorhombic structure through the intermediate fluorite phase is confirmed by X-ray powder diffraction and micro-Raman spectroscopic studies. The influence of samarium doping on the lattice parameters, lattice distortions, and the Raman peak positions of SrBi{sub 2}Nb{sub 2}O{sub 9} perovskite phase is clarified. The dielectric constants of the perovskite SrBi{sub 2}Nb{sub 2}O{sub 9} and SrBi{sub 1.9}Sm{sub 0.1}Nb{sub 2}O{sub 9} nanocrystals are relatively larger than those of the corresponding fluorite-like phase and the precursor glass. - Graphical Abstract: This figure shows the XRD patterns at room temperature for the as-quenched and heat treated samples in Sm{sub 2}O{sub 3}-doped (x=0.1) glass. Based on these results, it is concluded that the formation of samarium-doped perovskite SBN phase takes place via an intermediate fluorite-like phase in the crystallization of this glass.

Harihara Venkataraman, B. [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan); Fujiwara, Takumi [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Komatsu, Takayuki, E-mail: komatsu@mst.nagaokaut.ac.j [Department of Materials Science and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka 940-2188 (Japan)

2009-06-15

363

EarthLabs  

NSDL National Science Digital Library

EarthLabs is a collection of challenging, lab-based high school Earth science curriculum units, each of which integrates text, hands-on activities, interactive visualizations, video, authentic science data, and data visualization and analysis tools. Each unit highlights the interconnectedness and complexities of the Earth system in the context of a specific content area (including Earth system science, climate, weather, atmosphere, cryosphere, environmental science, hurricanes, drought, fisheries, oceans, carbon cycle), and can be integrated into an existing Earth or environmental science course or used as an independent curriculum unit. In addition to the student portal, EarthLabs provides a separate teacher's guide ("EarthLabs for Educators") that provides background and logistical information, pedagogical guidance, and answers to assessments embedded in the student portal.

2012-05-31

364

EarthLabs  

NSDL National Science Digital Library

EarthLabs is a collection of challenging, lab-based high school Earth science curriculum units, each of which integrates text, hands-on activities, interactive visualizations, video, authentic science data, and data visualization and analysis tools. Each unit highlights the interconnectedness and complexities of the Earth system in the context of a specific content area (including Earth system science, climate, weather, atmosphere, cryosphere, environmental science, hurricanes, drought, fisheries, oceans, carbon cycle), and can be integrated into an existing Earth or environmental science course or used as an independent curriculum unit. In addition to the student portal, EarthLabs provides a separate teacher's guide ("EarthLabs for Educators") that provides background and logistical information, pedagogical guidance, and answers to assessments embedded in the student portal.

365

Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO{sub 4}){sub 2} phosphate  

SciTech Connect

Hexagonal KCaGd(PO{sub 4}){sub 2}:RE{sup 3+} (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce{sup 3+}-doped samples, the bands at 207, 256, 275, and 320 nm are assigned to the 4f-5d transitions of Ce{sup 3+} in KCaGd(PO{sub 4}){sub 2}. For Tb{sup 3+}-doped sample, the bands at 203 and 222 nm are related to the 4f-5d spin-allowed transitions. For Eu{sup 3+}-doped sample, the O{sup 2-}-Eu{sup 3+} charge-transfer band (CTB) at 229 nm is observed, and the fine emission spectrum of Eu{sup 3+} indicates that Eu{sup 3+} ions prefer to occupy Gd{sup 3+} or Ca{sup 2+} sites in the host lattice. For Tm{sup 3+}- and Sm{sup 3+}-doped samples, the O{sup 2-}-Tm{sup 3+} and O{sup 2-}-Sm{sup 3+} CTBs are observed to be at 176 and 186 nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb{sup 3+}-doped KCaGd(PO{sub 4}){sub 2} is a potential candidate for 172 nm excited green plasma display phosphors.

Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Science, Beijing 100039 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Heifei 230026 (China)

2007-11-01

366

Large research infrastructure for Earth-Ocean Science: Challenges of multidisciplinary integration across hardware, software, and people networks  

NASA Astrophysics Data System (ADS)

NEPTUNE Canada is operating a regional cabled ocean observatory across the northern Juan de Fuca Plate in the northeastern Pacific. Installation of the first suite of instruments and connectivity equipment was completed in 2009, so this system now provides the continuous power and bandwidth to collect integrated data on physical, chemical, geological, and biological gradients at temporal resolutions relevant to the dynamics of the earth-ocean system. The building of this facility integrates hardware, software, and people networks. Hardware progress to date includes: installation of the 800km powered fiber-optic backbone in the Fall of 2007; development of Nodes and Junction Boxes; acquisition/development and testing of Instruments; development of mobile instrument platforms such as a) a Vertical Profiler and b) a Crawler (University of Bremmen); and integration of over a thousand components into an operating subsea sensor system. Nodes, extension cables, junction boxes, and instruments were installed at 4 out of 5 locations in 2009; the fifth Node is instrumented in September 2010. In parallel, software and hardware systems are acquiring, archiving, and delivering the continuous real-time data through the internet to the world - already many terabytes of data. A web environment (Oceans 2.0) to combine this data access with analysis and visualization, collaborative tools, interoperability, and instrument control is being released. Finally, a network of scientists and technicians are contributing to the process in every phase, and data users already number in the thousands. Initial experiments were planned through a series of workshops and international proposal competitions. At inshore Folger Passage, Barkley Sound, understanding controls on biological productivity help evaluate the effects that marine processes have on fish and marine mammals. Experiments around Barkley Canyon allow quantification of changes in biological and chemical activity associated with nutrient and cross-shelf sediment transport around the shelf/slope break and through the canyon to the deep sea. There and north along the mid-continental slope, instruments on exposed and shallowly buried gas hydrates allow monitoring of changes in their distribution, structure, and venting, particularly related to earthquakes, slope failures and regional plate motions. Circulation obviation retrofit kits (CORKs) at mid-plate ODP 1026-7 monitor real-time changes in crustal temperature and pressure, particularly as they relate to events such as earthquakes, hydrothermal convection or regional plate strain. At Endeavour Ridge, complex interactions among volcanic, tectonic, hydrothermal and biological processes are quantified at the western edge of the Juan de Fuca plate. Across the network, high resolution seismic information elucidates tectonic processes such as earthquakes, and a tsunami system allows determination of open ocean tsunami amplitude, propagation direction, and speed. The infrastructure has further capacity for experiments to expand from this initial suite. Further information and opportunities can be found at http://www.neptunecanada.ca

Best, M.; Barnes, C. R.; Johnson, F.; Pautet, L.; Pirenne, B.; Founding Scientists Of Neptune Canada

2010-12-01

367

Project Earth Science: Astronomy  

NSDL National Science Digital Library

The hands-on, teacher-tested activities in Project Earth Science: Astronomy brings the sometimes daunting concepts of astronomy down to Earth. Background information, supplementary readings, and suggestions for integrating other disciplines provide the teacher with a framework to launch a successful introduction to astronomy. Students will discover Earth's uniqueness by examining it as a part of the whole--one planet within our Solar System. How did the planets form? Are we seeing a star's present or past? Why is Earth's distance from the Sun so important? Project Earth Science: Astronomy will lead you and your students on an exploration that takes you to the stars and back.

Smith, P. S.

2001-01-01

368

Integrated four-channel Mach-Zehnder multi\\/demultiplexer fabricated with phosphorous doped SiO2 waveguides on Si  

Microsoft Academic Search

An analysis and the device performance of an integrated optical 4-channel multi\\/demultiplexer based on Mach-Zehnder interferometers elements are presented. The channel spacing is 77 Å. Single-mode channel waveguides are made from P-doped SiO2 core layers. Waveguide losses as low as 0.05 dB\\/cm and fiber-to-waveguide butt coupling as low as 0.5 dB for ?=1.5 ?m have been obtained. The multiplexer transfers

B. H. Verbeek; C. H. Henry; N. A. Olsson; K. J. Orlowsky; R. F. Kazarinov; B. H. Johnson

1988-01-01

369

Rare-earth ions doping effects on the optical properties of sol–gel fabricated PbTiO3 thin films  

Microsoft Academic Search

Ce, Sm, Dy, Er and Yb doped PbTiO thin films were deposited by sol-gel method on (111)PtyTiySiO ySi substrates. The 3 2 optical properties of the films were characterized by means of ellipsometry using a HeNe-laser source (ls632.8 nm). Real (n) and imaginary (k) parts of the refractive index were obtained applying the Fresnel equation. It is shown that for

S. Iakovlev; C.-H. Solterbeck; M. Es-Souni; V. Zaporojtchenko

2003-01-01

370

Superconductivity and phase diagram in iron-based arsenic-oxides ReFeAsO1?? (Re = rare-earth metal) without fluorine doping  

Microsoft Academic Search

Here we report a new class of superconductors prepared by high-pressure synthesis in the quaternary family ReFeAsO1?? (Re=Sm, Nd, Pr, Ce, La) without fluorine doping. The onset superconducting critical temperature (Tc) in these compounds increases with the reduction of the Re atom size, and the highest Tc obtained so far is 55 K in SmFeAsO1??. For the NdFeAsO1?? compound with

Zhi-An Ren; Guang-Can Che; Xiao-Li Dong; Jie Yang; Wei Lu; Wei Yi; Xiao-Li Shen; Zheng-Cai Li; Li-Ling Sun; Fang Zhou; Zhong-Xian Zhao

2008-01-01

371

Femtosecond laser-induced three-dimensional bright and long-lasting phosphorescence inside calcium aluminosilicate glasses doped with rare earth ions  

Microsoft Academic Search

We report on a novel phenomenon in calcium aluminosilicate glasses doped with Ce3+, Tb3+, and Pr3+. After irradiation by an 800 nm femtosecond pulsed laser, the focused part of the laser in the glasses emits bright and long-lasting phosphorescence able to be clearly seen with the naked eye in the dark even one hour after the removal of the activating

Jianrong Qiu; K. Miura; H. Inouye; Y. Kondo; T. Mitsuyu; K. Hirao

1998-01-01

372

Intense red-emitting multi-rare-earth doped nanoparticles of YVO4 for spectrum conversion towards improved energy harvesting by solar cells  

NASA Astrophysics Data System (ADS)

Yttrium vanadate nano-particles doped with single and multi ions (Sm3+, Eu3+, Bi3+) have been successfully synthesized at room temperature by optimized co-precipitation method. Doped orthovanadate forms monophasic nanocrystals in the 10–50 nm size range. Photoluminescence (PL) excitation shows broad band in the range 250–350 nm due to vanadate absorption and sharp peaks in the range of 390–470 nm due to f–f transitions of Sm3+/Eu3+ and emission in intense red/orange (614, 645, 699 nm). The nanoparticles can efficiently convert UV and blue photons (250–470 nm) to intense red and orange light that can be harnessed by both Si and dye sensitized solar cells for photovoltaic conversion. PL and time-resolved decay suggest that excitation and charge transfer between host, dopant and co-dopants play a profound role in the photophysical processes of multi-ion doped yttrium vanadate nanophosphor. Thin films of such nanophosphor exhibit 80–90% transparency in the visible range. Nanophosphor films convert UV to visible leading to better photon harvesting by solar cells.

Kumar, Vineet; Khan, A. F.; Chawla, Santa

2013-09-01

373

A Potential Hydrogen-Storage Media: C2H4 and C5H5 Molecules Doped with Rare Earth Atoms  

NASA Astrophysics Data System (ADS)

Using first-principles calculations, we predict that a single C2H4 or C5H5 molecule can form a stable complex with two rare earth metals such as La, Eu, and Ho. The La2C2H4 complex then absorbs up to sixteen hydrogen molecules, reaching a gravimetric storage capacity of 9.5wt% by adding a rare-earth metal atom, The results show that Eu-4f electrons have little impact on the hydrogen adsorption. The nature of bonding between Eu and H2 is due to the hybridization of Eu-5d with the H-1s orbital.

Lei, Hong-Wen; Zhang, Hong; Gong, Min; Wu, Wei-Dong

2012-12-01

374

Gene doping.  

PubMed

Gene doping abuses the legitimate approach of gene therapy. While gene therapy aims to correct genetic disorders by introducing a foreign gene to replace an existing faulty one or by manipulating existing gene(s) to achieve a therapeutic benefit, gene doping employs the same concepts to bestow performance advantages on athletes over their competitors. Recent developments in genetic engineering have contributed significantly to the progress of gene therapy research and currently numerous clinical trials are underway. Some athletes and their staff are probably watching this progress closely. Any gene that plays a role in muscle development, oxygen delivery to tissues, neuromuscular coordination, or even pain control is considered a candidate for gene dopers. Unfortunately, detecting gene doping is technically very difficult because the transgenic proteins expressed by the introduced genes are similar to their endogenous counterparts. Researchers today are racing the clock because assuring the continued integrity of sports competition depends on their ability to develop effective detection strategies in preparation for the 2012 Olympics, which may mark the appearance of genetically modified athletes. PMID:20020377

Azzazy, Hassan M E

2010-01-01

375

Earth Institute  

NSDL National Science Digital Library

The mission of the Earth Institute at Columbia University is to help the world achieve sustainability by expanding understanding of the Earth as one integrated system. Through research, education, and the practical application of research to real-world challenges, the Institute addresses nine interconnected global issues: climate and society, water, energy, poverty, ecosystems, public health, food and nutrition, and hazards and urbanization. The Institute's site offers a collection of videotaped events, including the biannual "State of the Planet" conferences, 2002-08, a Distinguished Lecture series, and the Sustainable Development seminar series, as well as e-seminars and e-briefings, information about funding opportunities, and information about educational opportunities at Columbia.

376

Mode-locking of thulium-doped and erbium-doped fiber lasers  

Microsoft Academic Search

This thesis reports work on passive mode-locking of thulium-doped and erbium-doped fiber ring lasers using the technique of polarization additive pulse mode-locking (P-APM). A self-starting, mode-locked Tm+3-doped fiber laser was demonstrated with 360 to 500 fsec pulses tunable from 1.8 to 1.9 mum, the largest tuning range demonstrated from a rare-earth doped fiber. This laser operated in the soliton regime

Lynn Elizabeth Nelson

1997-01-01

377

Synthesis and characterization of polymer composite base on RE3+:Al2O3 nanopowders doped by rare earth metals for application in optoelectronics  

NASA Astrophysics Data System (ADS)

In this work we report the recent results of our investigations on synthesis the PMMA composite base on Al2O3 doped by ytterbium metal. The set of the Al2O3:Yb3+ composite samples was manufactured and examined with respect of their structural, physical and mechanical properties. The investigations have confirmed applicability of developed synthesis method to manufacturing of good structural quality, decent level of agglomeration, good homogeneity and good thermal stability consisting of nanoparticles with average size in the range of several tens of nanometers.

Polis, P.; Jastrzebska, A.; Jureczko, J.; Jusza, A.; Piramidowicz, R.; Anders, K.; Olszyna, A.; Kunicki, A.; Fabianowski, W.

2013-07-01

378

Ambient Large-Scale Template-Mediated Synthesis of High-Aspect Ratio Single-Crystalline, Chemically Doped Rare-Earth Phosphate Nanowires for Bioimaging  

SciTech Connect

A simple and effective template-mediated protocol has been developed for the large-scale, room-temperature preparation of high-aspect-ratio, single-crystalline Tb-doped CePO{sub 4} nanowires, measuring {approx}12 nm in diameter and over 10 {mu}m in length. Moreover, we also isolated sheaf-like bundles of nanostructures. The synthesis mechanism likely involved a crystal splitting step. The resulting nanowires demonstrated an intense redox-sensitive green photoluminescence, which was exploited, in addition to their inherently high biocompatibility and low toxicity, for potential applications in biological imaging and labeling of cells.

Zhang, F.; Wong, S.

2009-12-30

379

Practicing ESD at School: Integration of Formal and Nonformal Education Methods Based on the Earth Charter (Belarusian Experience)  

ERIC Educational Resources Information Center

The Earth Charter represents the philosophy and ethics necessary to create a new period of human civilization. Understanding and adoption of this new vision is the most important mission of education for sustainable development (ESD). This article argues that for successful implementation of ESD principles at school, the school education system…

Savelava, Sofia; Savelau, Dmitry; Cary, Marina Bakhnova

2010-01-01

380

Earth as a System  

NSDL National Science Digital Library

This short video uses animated imagery from satellite remote sensing systems to illustrate that Earth is a complex, evolving body characterized by ceaseless change. Adapted from NASA, this visualization helps explain why understanding Earth as an integrated system of components and processes is essential to science education.

Wgbh/boston

381

Three-dimensional inversion of large-scale EarthScope magnetotelluric data based on the integral equation method: Geoelectrical imaging of the Yellowstone conductive mantle plume  

NASA Astrophysics Data System (ADS)

Interpretation of the EarthScope MT (magnetotelluric) data requires the development of a large-scale inversion method which can address two common problems of 3D MT inversion: computational time and memory requirements. We have developed an efficient method of 3D MT inversion based on an IE (integral equation) formulation of the MT forward modeling problem and a receiver footprint approach, implemented as a massively parallel algorithm. This method is applied to the MT data collected in the western United States as a part of the EarthScope project. As a result, we present one of the first 3D geoelectrical images of the upper mantle beneath Yellowstone revealed by this large-scale 3D inversion of the EarthScope MT data. These images show a highly conductive body associated with the tomographically imaged mantle plume-like layer of hot material rising from the upper mantle toward the Yellowstone volcano. The conductive body identified in these images is west-dipping in a similar way to a P-wave low-velocity body.

Zhdanov, Michael S.; Smith, Robert B.; Gribenko, Alexander; Cuma, Martin; Green, Marie

2011-04-01

382

Use of germanium doped silicon (n-Si?Ge?) for manufacturing radiation hardened devices and integrated circuits  

Microsoft Academic Search

We have investigated the possible application of germanium doped CZ silicon, (n-Si?Ge?) to the manufacture of rad hard bipolar npn transistors, ICs and low power thyristors. The radiation sensitivity of bipolar npn transistors depends on the Ge concentration in the source silicon wafers. The functional failure level of bipolar TTL IC, manufactured using dielectric isolation technology on initial n-Si?Ge? wafers,

S. V. Bytkin

1997-01-01

383

BaY{sub 2}F{sub 8} single crystals doped with rare-earth ions as promising up-conversion media for UV and VUV lasers  

SciTech Connect

BaY{sub 2}F{sub 8} crystals are studied as promising active media for UV and VUV lasers. The up-conversion pumping of rare-earth activators is proposed to solve problems related to the solarisation of the medium and the selection of pump sources. The technology of growing oriented BaY{sub 2}F{sub 8} single crystals is developed and the influence of the crystal orientation on the growth rate and quality of single crystals is determined. (active media)

Pushkar', A A; Uvarova, T V [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Molchanov, V N [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation)

2008-04-30

384

Polar Misunderstandings: Earth's Dynamic Dynamo  

ERIC Educational Resources Information Center

|This article discusses the movement of Earth's north and south poles. The Earth's poles may be a bit more complex and dynamic than what many students and teachers believe. With better understanding, offer them up as a rich landscape for higher-level critical analysis and subject integration. Possible curriculum tie-ins include magnets, Earth

DiSpezio, Michael A.

2011-01-01

385

Mapping of integrated radon emanation for detection of long-distance migration of gases within the earth: Techniques and principles  

Microsoft Academic Search

Integrated measurements of radon concentrations within the ground but close to the surface are being used extensively in search for premonitory signals from earthquakes and in exploration for uranium. We present a description of the different components of the radon signals that may be present and describe methods for separating them. We also show quantitatively what signals the different radon-integrating

Robert L. Fleischer; Antonio Mogro-Campero

1978-01-01

386

Effects of PbF2 doping on structure and spectroscopic properties of Ga2O3-GeO2-Bi2O3-PbO glasses doped with rare earths  

NASA Astrophysics Data System (ADS)

We report an intense room-temperature blue upconversion in Tm3+/Yb+3-codoped Ga2O3-GeO2-Bi2O3-PbO(PbF2) glasses upon excitation with a convenient 980 nm laser diode. Effects of PbF2 doping on the thermal stability, structure, and upconversion properties of Tm3+/Yb3+-codoped gallate-germanium-bismuth-lead glasses have been investigated. We find that the presence of PbF2 provides two potentials: shortening the ultraviolet cutoff band and decreasing the phonon energy of host glasses. The blue-upconversion intensity has a cubelike dependence on incident pump-laser power, indicating a three-photon process. Energy-transfer process and nonradiative phonon-assisted decay could be responsible for the population of the 1G4 emitting level of the Tm3+. The results indicate the potential possibility towards the development of an oxide-based blue-upconversion glass-fiber laser.

Zhang, Q. Y.; Li, T.; Shi, D. M.; Yang, G. F.; Yang, Z. M.; Jiang, Z. H.; Buddhudu, S.

2006-02-01

387

Oxygen vacancy ordering in strontium doped rare earth cobaltate perovskites Ln{sub 1-x}Sr {sub x}CoO{sub 3-{delta}} (Ln = La, Pr and Nd; x > 0.60)  

SciTech Connect

A family of Sr-doped perovskite compounds Ln{sub 1-x}Sr {sub x}CoO{sub 3-{delta}} (Ln = La{sup 3+}, Pr{sup 3+} and Nd{sup 3+}; x > 0.60), were prepared by sol-gel chemistry and reaction at 1100 deg. C under 1 atm of oxygen. This structural family has been shown to be present only for rare earth ions larger than Sm{sup 3+} and an upper limit of Sr{sup 2+} solubility in these phases was found to exist between x = 0.90 and 0.95. X-ray diffraction shows oxygen-deficient, simple cubic (Pm-3m) perovskite crystal structures. The combination of electron and powder neutron diffraction reveals that oxygen vacancy ordering occurs, leading to a tetragonal (P4/mmm) superstructure and a doubling of the basic perovskite unit along the crystallographic c-axis. No additional Ln{sup 3+}/Sr{sup 2+} cation ordering was observed.

James, M. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Building 58, ANSTO, PMB 1, Menai NSW 2234 (Australia)]. E-mail: mja@ansto.gov.au; Tedesco, T. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Building 58, ANSTO, PMB 1, Menai NSW 2234 (Australia); Cassidy, D.J. [Materials and Engineering Sciences, Australian Nuclear Science and Technology Organisation, PMB 1, Menai NSW 2234 (Australia); Withers, R.L. [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)

2005-06-15

388

Phonon Assisted Laser Transitions and Energy Transfer in Rare Earth Laser Crystals.  

National Technical Information Service (NTIS)

An extensive study of energy transfer and phonon interaction in rare earth doped LiYF4 has been conducted. The trivalent rare earth ions Pr, Nd, Dy, Ho, Er, Tm and Yb were used as the optically active ions. Y2Ti2O7, also doped with rare earth ions, was ex...

H. P. Jenssen

1971-01-01

389

The need and potential for building a integrated knowledge-base of the Earth-Human system  

NASA Astrophysics Data System (ADS)

The pursuit of scientific understanding is increasingly based on interdisciplinary research. To understand more deeply the planet and its interactions requires a progressively more holistic approach, exploring knowledge coming from all scientific and engineering disciplines including but not limited to, biology, chemistry, computer sciences, geosciences, material sciences, mathematics, physics, cyberinfrastucture, and social sciences. Nowhere is such an approach more critical than in the study of global climate change in which one of the major challenges is the development of next-generation Earth System Models that include coupled and interactive representations of ecosystems, agricultural working lands and forests, urban environments, biogeochemistry, atmospheric chemistry, ocean and atmospheric currents, the water cycle, land ice, and human activities.

Jacobs, Clifford

2011-03-01

390

Deep and Shallow Solid-Earth Structures Reconstructed with Sequential Integrated Inversion (SII) of Seismic and Gravity Data  

NASA Astrophysics Data System (ADS)

In this paper, the possibility of using simultaneously seismic and gravity data, for the reconstruction of solid-Earth structures, has been investigated through the use of an algorithm which allows joint efficient and reliable optimisation of compressional velocity and mass density parameters. We view the measured data as a realisation of a stochastic process generated by the physical parameters to be sought and we construct a “probability density function” which includes three kinds of information: information derived from gravity measurements; information derived from seismic travel time inversion and information on the physical correlation among density and velocity parameters. We show that combining data has a beneficial effect on the inversion since: it makes the problem more stable and as a consequence, providing that the quality of data is sufficiently high, enables more accurate and reliable reconstruction of the unknown parameters. In this context, we look forward the GOCE mission, which promises high spatial resolution (100 200 km) and accurate (1 2 mGals) gravity data. We show results obtained from data sets calculated for a lateral inhomogeneous earth synthetic model and from seismic and gravity field data analysed: — in the framework of TOMOVES (TOMOgraphy of Mt. VESuvius) experiment, an European project aiming at reconstructing the 3-D image of Mt. Vesuvius volcano and the crust underneath. using high resolution seismic tomography techniques and other geophysical methods; — for a profile inserted in a project aiming at reconstructing the crustal structure between Corsica and the Northern Appennines which crosses the Ligurian Sea and cuts the Ligurian Appennines W of La Spezia, extending up to Parma.

Tondi, Rosaria; de Franco, Roberto; Biella, Giancarlo

2003-07-01

391

The EarthCARE space-borne Doppler 94 GHz radar simulator: correction of multiple scattering, aliasing and NUBF and effects of variable along track integration  

NASA Astrophysics Data System (ADS)

The primary goal of this work is to address several challenges related to spaceborne Doppler radars like future the EarthCARE mission and recent developments of data simulation, correction and processing. The 94 GHz Cloud Profiling Radar onboard the ESA EarthCARE mission will be the first radar in space with Doppler capability allowing mean Doppler velocity measurements. This will enable more accurate characterization of clouds and precipitation (classification, retrieval accuracy, dynamics). It is the only instrument of this kind planned for the immediate post-CloudSat era and represents an irreplaceable asset in regards to climate change studies. Meeting the scientific accuracy requirements of vertical motions of 1 m/s, with a horizontal resolution of 1 km, is very challenging. The five key factors that control the performance of spaceborne radar will be discussed, such as: contribution of multiple scattering (MS), attenuation, velocity folding, non uniform beam filling (NUBF) and effects of along track integration of the signal. The research utilizes an end-to-end simulator for spaceborne Doppler radars. The simulator uses a Monte Carlo module which accounts for MS and produces ideal Doppler spectra as measured by a spaceborne radar flying over 3D highly resolved scenes produced via WRF Model simulations. The estimates of the Doppler moments (reflectivity, mean Doppler velocity and spectrum width) are achieved via the pulse pair technique. The objective method for identification of MS-contaminated range-bins based purely on the reflectivity-derived variables is described, with most important one, cumulative integrated reflectivity, found to be 41 dBZ_int which serves as the threshold value for identification of radar range gates contaminated by MS. This is further demonstrated in a CloudSat case study with the threshold value for CloudSat is found to be 41.9 dBZ_int. The unfolding procedure of Doppler velocities will be presented. Then we will describe the effects of the along track integration and achieved accuracy and biases of Doppler velocity for integration distance of 0.5, 1, 5 and 10 km. This will be complemented by correction of NUBF effect utilizing the along tract reflectivity gradient and velocity bias dependence.

Augustynek, T.; Battaglia, A.; Kollias, P.

2011-12-01

392

Large subsea observatory for earth-ocean science: Challenges of multidisciplinary integration across hardware, software, and people networks  

Microsoft Academic Search

NEPTUNE Canada has installed and is operating a regional cabled ocean observatory from the coast across the northern Juan de Fuca Plate in the northeastern Pacific. Installation of the first suite of instruments and connectivity equipment was completed in 2009, so this system now provides the continuous power and bandwidth to collect integrated data on physical, chemical, geological, and biological

C. R. Barnes; M. M. R. Best; F. R. Johnson; B. Pirenne

2010-01-01

393

Incubational domain characterization in lightly doped ceria  

SciTech Connect

Microstructures of both Gd- and Y-doped ceria with different doping level (i.e., 10 at% and 25 at%) have been comprehensively characterized by means of high resolution transmission electron microscopy and selected area electron diffraction. Coherent nano-sized domains can be widely observed in heavily doped ceria. Nevertheless, it was found that a large amount of dislocations actually exist in lightly doped ceria instead of heavily doped ones. Furthermore, incubational domains can be detected in lightly doped ceria, with dislocations located at the interfaces. The interactions between such linear dislocations and dopant defects have been simulated accordingly. As a consequence, the formation mechanism of incubational domains is rationalized in terms of the interaction between intrinsic dislocations of doped ceria and dopant defects. This study offers the insights into the initial state and related mechanism of the formation of nano-sized domains, which have been widely observed in heavily rare-earth-doped ceria in recent years. - Graphical abstract: Interactions between dislocations and dopants lead to incubational domain formation in lightly doped ceria. Highlights: Black-Right-Pointing-Pointer Microstructures were characterized in both heavily and light Gd-/Y-doped ceria. Black-Right-Pointing-Pointer Dislocations are existed in lightly doped ceria rather than heavily doped one. Black-Right-Pointing-Pointer Interactions between dislocations and dopant defects were simulated. Black-Right-Pointing-Pointer Formation of dislocation associated incubational domain is rationalized.

Li Zhipeng, E-mail: Zhipeng@email.unc.edu [Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599 (United States); Mori, Toshiyuki [Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); John Auchterlonie, Graeme [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, QLD 4072 (Australia); Zou Jin [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, QLD 4072 (Australia); Division of Materials, University of Queensland, St. Lucia, Brisbane, QLD 4072 (Australia); Drennan, John [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, QLD 4072 (Australia)

2012-08-15

394

Earth's spectral reflectivity  

NASA Astrophysics Data System (ADS)

Cyclic spectroscopic observations of the dark and bright sides of the moon (or earthshine and moonshine) have been carried out in the visible spectral region from several astronomical observatories as Earth rotates. The ratio of the earthshine to moonshine has been analyzed to determine the globally-integrated Earth's albedo during the observations. Information concerning to the search of terrestrial planets beyond the solar system can also be obtained from these results.

Montanes, P.

2007-05-01

395

Earth's Seasons  

NSDL National Science Digital Library

A computer animation on the reason for the seasons. Voice-over describes the motion of Earth around the sun to show how the sun's light impacts the tilted Earth at different times of the year, causing seasonal changes.

Rochester Museum And Science Center, Strasenburgh P.

396

Spectral engineering of optical fiber through active nanoparticle doping  

NASA Astrophysics Data System (ADS)

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions. Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of different host materials, varying rare earth doping levels and processing conditions, indicated the ability to influence the spectral behavior of the doped nanoparticle. By using photoluminescence to predict diffusion behavior, the application of a simple one dimensional model for diffusion provided a method for predicting the diffusion coefficient of europium ions in alkaline earth fluorides with order of magnitude accuracy. Modified chemical vapor deposition derived silica preforms were individually solution doped with europium doped alkaline earth fluoride nanoparticles. By using the rare earth doped alkaline earth fluoride nanoparticles as the dopant materials in the core of optical fiber preforms, the resultant optical properties of the glass were significantly influenced by their presence in the core. The incorporation of these rare earth doped alkaline earth fluoride nanoparticles was found to significantly influence the local chemical and structural environment about the rare earth ion, demonstrated homogeneity and uniform distribution of the rare earth dopant and resulted in specifically unique spectral behavior when compared to conventional doping methods. A more detailed structural model of the doped core glass region has been developed based on the spectral behavior of these active fiber preforms. It has been shown that rare earth doping of alkaline earth fluoride nanoparticles provides a material which can be 'tuned' to specific applications through the use of different host materials, processing conditions and doping levels of the rare earth and when used as dopant materials for active optical fibers, provides a means to tailor the optical behavior.

Lindstrom-James, Tiffany

397

A New Northern Eurasia Earth Science Partnership Initiative (NEESPI): Science Plan of Integrated Approach to Regional Climate and Environment Change Studies  

NASA Astrophysics Data System (ADS)

The Northern Eurasia Earth Science Partnership Initiative (NEESPI) is an international large-scale, integrated, regional program of research focusing on the area of Northern Eurasia initiated by NASA and Russian Academy of Sciences. A brief introduction of the NEESPI Science Plan (SP) will be presented. While extensive and diverse, Northern Eurasia has common (and unique) features, the studying of which in a corroborated fashion under the NEESPI umbrella will produce synergetic effects. SP specifically addresses the reasons to look on the region as a "single" piece: transitional economies and land use (the legacy of the former USSR), geographical features (largest landmass in the extratropics mostly isolated from humid air masses), one of the world highest sensitivities to climatic and environmental changes with feedbacks of global concern and extensive and fluent transitional zones between ecosystems. The major NEESPI science question is: How do Northern Eurasia's terrestrial ecosystems dynamics interact with and alter the biosphere, atmosphere, and hydrosphere of the Earth? These dynamics have several facets: Biogeochemical Cycles, Surface Energy and Water Cycles, and Interactions with Human Society, each of which have to be studied in their interactions and complexity. Studying of Ecosystem-Climate Interactions mechanisms and Modeling component became a centerpiece of the SP. These studies can be conducted within a suite of models that are considered as a major instrument to assess our predictive capabilities of environmental changes and ecosystem sustainability in Northern Eurasia to support numerous applications and decision making. The creation of such a suite of models and providing it with an appropriate input data stream emerges as a focus of the Initiative. Remote sensing has an important role in the NEESPI science program, providing up to date and historical, spatially explicit information to inventory and quantify changes in the land surface and in the coastal zone for use in process and modeling studies. Social aspects of the NEESPI SP include the Education and land use components.

Groisman, P. Y.; Bartalev, S. A.

2004-12-01

398

Edible Earth  

NSDL National Science Digital Library

In this activity, learners make a model of the solid Earth's layers that's good enough to eat! Learners use tasty foodstuffs to simulate Earth's inner core, outer core, mantle, and crust. The recipe includes ingredients for one edible Earth, but can be doubled or tripled to accommodate groups of learners. This activity requires adult supervision.

History, American M.

2011-08-20

399

Earth Flow  

NSDL National Science Digital Library

This Flash animation with accompanying audio exhibits the different stages involved in the formation of an earth flow. A step-like scarp forms along with a flowage zone at the toe of the earth flow. The sequence concludes with the stabilization of the earth flow with vegetation. Expect long loading times.

Wiley

400

Earth Calendar  

NSDL National Science Digital Library

This handout lists major events in Earth history with approximate ages (in millions of years before present). The calendar date is determined by setting midnight, January 1, to correspond with the formation of the Earth, and setting the following midnight, December 31, to correspond to the present. Thus, the entire history of the Earth is displayed as a single calendar year.

Barker, Jeffrey

401

Snowball Earth  

NSDL National Science Digital Library

Audio program from the University of Wisconsin's Earthwatch Radio discusses the notion of the entire planet covered with ice. Doug Macdougall is an earth scientist at the University of California-San Diego and author of a new book called "Frozen Earth." He says the planet-wide freeze is known as "Snowball Earth."

402

Planet Earth  

NSDL National Science Digital Library

For those interested in a global view of the weather, Planet Earth is a "real-time 3-D model of the Earth with continuously updating night shadows and clouds." Cloud images are provided by the University of Wisconsin-Madison Space Science and Engineering Center. Planet Earth is shareware with a fee of $29.95.

403

10Gb\\/s high-speed monolithically integrated photoreceiver using InGaAs p-i-n PD and planar doped InAlAs\\/InGaAs HEMTs  

Microsoft Academic Search

A long-wavelength monolithically integrated photoreceiver which is capable of operation at a 10-Gb\\/s NRZ light signal is described. The photoreceiver was fabricated using an Si-planar-doping technique to enhance the uniformity and transconductance of HEMTs and using Be-ion implantation technique. The circuit consists of a p-i-n PD, a transimpedance amplifier, and a buffer stage to provide an output impedance of 50

Y. Akahori; Y. Akatsu; A. Kohzen; J. Yoshida

1992-01-01

404

Design of broadband erbium-doped fiber amplifier using very high-speed integrated circuit hardware description language for next-generation optical network  

NASA Astrophysics Data System (ADS)

We mainly concentrate on the problem of gain broadening and flattening of erbium-doped fiber amplifier (EDFA) using dual forward-pumping configuration in which we use pumping both at 980 and 1480 nm wavelengths. The gain cascading of two EDFAs pumped separately at 980 and 1480 nm combines the advantage of high gain characteristics of 980 nm pumping and broad bandwidth characteristics of 1480 nm pumping. The use of increased number of channels in the present dense wavelength division multiplexing (DWDM) optical network requires a flat gain spectrum across the whole usable bandwidth. The use of very high-speed integrated circuit hardware description language (VHDL-AMS) in lightwave system modeling has been explored. Its application in designing wideband EDFA has not been reported thus far. This work facilitates to design broadband EDFA operating in both the C-band and L-band regions with VHDL-AMS. The amplifier design is made of a dual stage, copumped at 980 and 1480 nm, which delivers an average output power of -16 dBm over the entire 3-dB bandwidth of 80 nm.

Goel, Aditya; Mishra, Ravi Shankar

2011-01-01

405

Dynamic Earth  

NSDL National Science Digital Library

Dynamic Earth consists of four sections and an assessment. Each section explores one aspect of the earth's structure and the movement of its tectonic plates. Simply follow the instructions on the screen to learn about the layers that make up the earth; how the continents arrived at their current locations; the constant movement of the tectonic plates; and the volcanoes, earthquakes, and other events that result from the movements of the plates. Students will view animations, read explanations, and use their mouse to drag and drop the earth's continents in their correct places, highlight features on a map, and cause earth's tectonic plates to move. At various points, students will check their knowledge by taking a quick quiz or playing a game to see how much they have learned about the Dynamic Earth. Students should read section introductions carefully, as they give a basic overview of concepts, and use the Glossary to look up definitions to unfamiliar terms.

Quinn, Ashlinn

2007-01-01

406

Earth Viewer  

NSDL National Science Digital Library

Earth Viewer was written primarily for elementary school students, and shows the daytime and nighttime portions of the Earth for any day of the year. Two views of the Earth are possible: a globe shows the planet as it would appear from space, and a map shows a flat view of the entire surface. The image can be animated or still, and set to any desired latitude and longitude.

Carlisle, Paul

407

Earth Lecture  

NSDL National Science Digital Library

This lecture is about the Earth, the planet which we know the most about, due to our ability to explore its interior as well as exterior. The lecture will compare values and processes on other planets to those on the Earth. It covers topics such as the interior, surface features and observations. It also includes a discussion of the Earth's crust, atmosphere, evolution and magnetic field. There is a quiz at the end of the lecture.

Schombert, Jim

2008-12-15

408

Earth Systems in a Bottle.  

ERIC Educational Resources Information Center

|Introduces an eco-column activity that provides an integrated approach to earth systems science education. Provides a list of the National Science Education Standards addressed in the activity. (YDS)|

Henriques, Laura

2000-01-01

409

Rare-Earth Doped Apatite Laser Materials.  

National Technical Information Service (NTIS)

The report describes the results of the first phase of a program to evaluate the merits of certain members of the mineral family apatite as hosts for the active laser ion holmium. Of the several silicate oxy-apatites (SOAP) studied, preliminary crystal gr...

R. H. Hopkins N. T. Melamed T. Henningsen G. W. Roland

1970-01-01

410

Rare Earth Doped Apatite Laser Materials.  

National Technical Information Service (NTIS)

The report describes the current status of the second and third phases of a program to evaluate certain members of the apatite mineral family as hosts for the active laser ion holmium. A systematic study of the effect of growth parameters in the quality o...

R. H. Hopkins N. T. Melamed T. H. Henningsen G. W. Roland

1970-01-01

411

Earth Day Main > Sierra Club  

NSDL National Science Digital Library

This page from the Sierra Club has links and information dedicated to the celebration of Earth Day. Resources on the site contain information on projects across the country. There are also ideas for integrating eco-friendly projects into your community, and energy saving tips for the home, office and city as a whole. Fact sheets on global warming and other educational materials are also available for integration into your own Earth Day celebration.

2007-04-19

412

Earth Day  

NSDL National Science Digital Library

On April 22, 2005, people around the world will celebrate the 35th anniversary of Earth Day. This Topic in Depth focuses on the past and present of this significant day. From the Wisconsin Historical Society, the first two sites contain historical documents pertaining to Earth Day. The first (1) document features a May 1970 issue of The Gaylord Nelson Newsletter reporting on the first Earth Day. The second (2) document is a speech by Nelson entitled "An Environmental Agenda for the 70's." Housed in the archives of the US Environmental Protection Agency (EPA) website, the next two sites also contain historical documents. The first (3) site contains an article written by Nelson for the EPA Journal in April of 1980, entitled "Earth Day '70: What It Meant." The second (4) site contains an article written by John C. Whitaker (former Interior undersecretary in the Nixon administration) for the EPA Journal in the summer of 1998. The article is entitled "Earth Day Recollections: What It Was Like When the Movement Took Off." The (5) Earth Day Network (first mentioned in the April 4, 2003, Scout Report for Life Sciences) works "to broaden the environmental movement worldwide and to educate and mobilize people, governments, and corporations to take responsibility for a clean and healthy environment." In addition to information sections about Ongoing Programs, Current Campaigns, and News, the Earth Day Network website contains Earth Day 2005 Materials for organizers. From EarthDay.gov, Take Action In Your Classroom (6) offers links to a variety of environmental education resources. The next website, from the U.S. Army Environmental Center, presents (7) Army Earth Day; and links to information about the Army's environmental activities. The final (8) site is an Earth Day-inspired educational website (first reported on in the April 14, 1999 Scout Report for Science & Engineering) from the Wilderness Society. The site offers a collection of environmental education resources for teachers and students. [NL

413

Integrated Q-switched Nd:MgO:LiNbO3 waveguide laser  

NASA Astrophysics Data System (ADS)

The integration of an electrooptic directional coupler permitting the emission of Q-switched pulses is reported for the first time. Despite relatively poor modulator performances, pulses with up to 2.5 W peak power and 1.5 ns width are obtained, due to the low photon cavity lifetime. These are apparently the shortest Q-switched pulses reported to date for rare-earth doped lasers.

Lallier, E.; Pocholle, J. P.; Papuchon, M.; He, Q.; de Micheli, M.; Ostrowsky, D. B.

1992-07-01

414

Synergetic degradation of 2,4-D by integrated photo- and electrochemical catalysis on a Pt doped TiO 2\\/Ti electrode  

Microsoft Academic Search

The photoelectrochemical degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at a Pt doped TiO2\\/Ti electrode was investigated. The electrode was prepared by first oxidizing the surface of a titanium sheet to form TiO2 and then doping platinum in H2PtCl6 solution. The degradation efficiency of 2,4-D in the solution with 51 mg\\/l concentration was, respectively, 16% for electrochemical process and 27% for photochemical

Xie Quan; Shuo Chen; Jing Su; Jingwen Chen; Guohua Chen

2004-01-01

415

Rainbow Earth.  

ERIC Educational Resources Information Center

The environment is a great concern in the 1990s, and everyone needs to work at maintaining our planet. The 1992 Arizona State Library Reading Program, "Rainbow Earth," provides children with many techniques they can use to help the Earth. This reading program guide provides information on the following: goals, objectives, and evaluation; getting…

Arizona State Dept. of Library and Archives, Phoenix.

416

Earth Viewer  

NSDL National Science Digital Library

The representation is an enhanced image and animation of Earth from above that shows daytime and nighttime on 1/2 of the Earth at a time. The representation's viewing angle and date can be manipulated by the viewer, and the representation can be toggled between globe and map views.

Carlisle, Paul

417

Integration of ASTER thermal infrared data and the Google Earth application to examine the relationship between sand transport pathways and dust emission hot-spots  

NASA Astrophysics Data System (ADS)

The identification and characterization of major mineral dust source areas from the Sahara Desert and the composition of these particulates are critical to our understanding of global dust production, models of atmospheric emission and transport, and determination of radiative properties of dust plumes from desert regions. The locations of many of these dust hot-spots have been determined using data such as the Total Ozone Mapping Spectrometer aerosol index (TOMS AI), showing that the largest sources of global dust are located in the Sahara Desert of west and central Africa. Studies using geochemical tracers, surface observations, analysis of meteorological data, and remote sensing have, however, arrived at different and sometimes conflicting delineations of Saharan dust sources. Geomorphic environment is a major control on dust emission source and process. Surface and remote sensing observations of the Bodele Depression, the largest dust source in the Sahara, show that sand saltation on the playa surface and the abrasion of material are the primary processes in generating dust. In order to test the hypothesis that other major natural global dust emission sources are linked to the interaction of sand transport along defined pathways and dust sources, multispectral thermal infrared (TIR) data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) are integrated with the high resolution, mosaicked image data available from the Google Earth application. The geomorphic environment, surface composition and their relative importance as a control on dust emissions are assessed using high resolution data at dust hot-spots that were identified by the TOMS AI at the much lower spatial resolution of one pixel/degree.

Scheidt, S. P.; Lancaster, N.; Ramsey, M.

2007-12-01

418

Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework  

NASA Astrophysics Data System (ADS)

We have used the Grid ENabled Integrated Earth system modelling (GENIE) framework to undertake a systematic search for bi-stability of the ocean thermohaline circulation (THC) for different surface grids and resolutions of 3-D ocean (GOLDSTEIN) under a 3-D dynamical atmosphere model (IGCM). A total of 407,000 years were simulated over a three month period using Grid computing. We find bi-stability of the THC despite significant, quasi-periodic variability in its strength driven by variability in the dynamical atmosphere. The position and width of the hysteresis loop depends on the choice of surface grid (longitude-latitude or equal area), but is less sensitive to changes in ocean resolution. For the same ocean resolution, the region of bi-stability is broader with the IGCM than with a simple energy-moisture balance atmosphere model (EMBM). Feedbacks involving both ocean and atmospheric dynamics are found to promote THC bi-stability. THC switch-off leads to increased import of freshwater at the southern boundary of the Atlantic associated with meridional overturning circulation. This is counteracted by decreased freshwater import associated with gyre and diffusive transports. However, these are localised such that the density gradient between North and South is reduced tending to maintain the THC off state. THC switch-off can also generate net atmospheric freshwater input to the Atlantic that tends to maintain the off state. The ocean feedbacks are present in all resolutions, across most of the bi-stable region, whereas the atmosphere feedback is strongest in the longitude-latitude grid and around the transition where the THC off state is disappearing. Here the net oceanic freshwater import due to the overturning mode weakens, promoting THC switch-on, but the atmosphere counteracts this by increasing net freshwater input. This increases the extent of THC bi-stability in this version of the model.

Lenton, T. M.; Marsh, R.; Price, A. R.; Lunt, D. J.; Aksenov, Y.; Annan, J. D.; Cooper-Chadwick, T.; Cox, S. J.; Edwards, N. R.; Goswami, S.; Hargreaves, J. C.; Harris, P. P.; Jiao, Z.; Livina, V. N.; Payne, A. J.; Rutt, I. C.; Shepherd, J. G.; Valdes, P. J.; Williams, G.; Williamson, M. S.; Yool, A.

2007-11-01

419

Field emission of doped carbon nanotubes  

Microsoft Academic Search

We calculated field-emission currents from nitrogen- and boron-doped single-walled (5,5) carbon nanotubes by integrating time-dependent Schrödinger equations. Nitrogen doping increased the emission current owing to a shift in the energy level of a localized state to the Fermi level, and the creation of coupled states that have characteristics of both localized and extended states. On the other hand, boron doping

Hyo-Shin Ahn; Kwang-Ryeol Lee; Doh-Yeon Kim; Seungwu Han

2006-01-01

420

Song of the Earth  

NSDL National Science Digital Library

This PBS Web site is the online companion to the Nature documentary "Song of the Earth," hosted by David Attenborough. The program explores the elemental purpose of music and offers a fascinating look at the connection between animal sounds and human music. The site includes two detailed lesson plans that integrate science and language arts, designed for grades 9-12. Learning objectives include conducting research on animal behavior, applying scientific methodology, synthesizing information to create presentations, and more. The main Song of the Earth Web site has other features -- such as a list of related links and a photo essay of animal music -- that would make excellent additions to classroom activities.