An X-ray excited wind in Centaurus X-3

NASA Technical Reports Server (NTRS)

Day, C. S. R.; Stevens, Ian R.

1993-01-01

We propose a new interpretation of the behavior of the notable X-ray binary source Centaurus X-3. Based on both theoretical and observational arguments (using EXOSAT data), we suggest that an X-ray excited wind emanating from the O star is present in this system. Further, we suggest that this wind is responsible for the mass transfer in the system rather than Roche-lobe overflow or a normal radiatively driven stellar wind. We show that the ionization conditions in Cen X-3 are too extreme to permit a normal radiatively driven wind to emanate from portions of the stellar surface facing toward the neutron star. In addition, the flux of X-rays from the neutron star is strong enough to drive a thermal wind from the O star with sufficient mass-flux to power the X-ray source. We find that this model can reasonably account for the long duration of the eclipse transitions and other observed features of Cen X-3. If confirmed, this will be the first example of an X-ray excited wind in a massive binary. We also discuss the relationship between the excited wind in Cen X-3 to the situation in eclipsing millisecond pulsars, where an excited wind is also believed to be present.

Discovery of novel solid solution Ca3Si3-x O3+x N4-2x : Eu2+ phosphors: structural evolution and photoluminescence tuning.

PubMed

Wang, Baochen; Liu, Yan-Gai; Huang, Zhaohui; Fang, Minghao; Wu, Xiaowen

2017-12-22

Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca 3 Si 3-x O 3+x N 4-2x : Eu 2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca 3 Si 3-x O 3+x N 4-2x : Eu 2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.

Photoluminescence Properties of Red-Emitting Ca3Sr3-x(PO4)4:xEu3+ Phosphors for White Light-Emitting Diodes.

PubMed

Hakeem, D A; Park, K

2015-07-01

The photoluminescent properties of the Eu(3+)-activated Ca3Sr3(PO4)4 phosphors prepared by a solution combustion method were investigated. The excitation spectra of Ca3Sr3-x(PO4)4:xEu3+ (0.05 ≤ x ≤ 0.6) phosphors under 614 nm wavelength showed a broad band centered at 266 nm along with other peaks at 320, 362, 381, 394, 414, 464, and 534 nm. The emission spectra observed in the range of 450 to 750 nm under excitation at 394 nm were ascribed to the 5D0-7F1-4 transitions of Eu3+ ions. The Ca3Sr3-x(PO4)4:xEu3+ phosphors showed the strongest red emission at 614 nm due to the electric dipole 5DO -->7F2 transition of Eu3+. The strongest emission intensity was obtained for the Eu3+ ions of x = 0.5. The prepared Ca3Sr3-x(PO4)4:xEu3+ can be used as an efficient red phosphor for UV-based white LEDs.

Crystal structures of the new ternary stannides La3Mg4-xSn2+x and LaMg3-xSn2

NASA Astrophysics Data System (ADS)

Solokha, P.; De Negri, S.; Minetti, R.; Proserpio, D. M.; Saccone, A.

2016-01-01

Synthesis and structural characterization of the two new lanthanum-magnesium-stannides La3Mg4-xSn2+x (0.12≤x≤0.40) and LaMg3-xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4-xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6bar2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3-xSn2 phase is the second representative of the trigonal LaMg3-xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3bar1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3-xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La-Mg-Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism.

RXTE Observations of LMC X-1 and LMC X-3

NASA Technical Reports Server (NTRS)

Wilms, J.; Nowak, M. A.; Dove, J. B.; Pottschmidt, K.; Heindl, W. A.; Begelman, M. C.; Staubert, R.

1999-01-01

Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results from long (170 ksec) Rossi X-ray Timing Explorer (RXTE) observations of LMC X-1 and LMC X-3 made in 1996 December. The spectra can be described by a multicolor disk blackbody plus an additional high-energy power-law. Even though the spectra are very soft (Gamma approximately 2.5), RXTE detected a significant signal from LMC X-3 up to energies of 50 keV, the hardest energy at which the object was ever detected. Focusing on LMC X-3 , we present results from the first year of an ongoing monitoring campaign with RXTE which started in 1997 January. We show that the appearance of the object changes considerably over its approximately 200 d long cycle. This variability can either be explained by periodic changes in the mass transfer rate or by a precessing accretion disk analogous to Her X-1.

RXTE Observations of LMC X-1 and LMC X-3

NASA Technical Reports Server (NTRS)

Wilms, J.; Nowak, M. A.; Dove, J. B.; Pottschmidt, K.; Heindl, W. A.; Begelman, M. C.; Staubert, R.

1998-01-01

Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results from long (170 ksec) Rossi X-ray Timing Explorer (RXTE) observations of LMC X-1 and LMC X-3 made in 1996 December. The spectra can be described by a multicolor disk blackbody plus an additional high-energy power-law. Even though the spectra are very soft (Gamma approximately 2.5), RXTE detected a significant signal from LMC X-3 up to energies of 50 keV, the hardest energy at which the object was ever detected. Focusing on LMC X-3, we present results from the first year of an ongoing monitoring campaign with RXTE which started in 1997 January. We show that the appearance of the object changes considerably over its approximately 200d long cycle. This variability can either be explained by periodic changes in the mass transfer rate or by a precessing accretion disk analogous to Her X-1.

Synthesis and characterization of (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upadhyay, Ashutosh; Dwivedi, Saurabh; Pandey, Rishikesh

2016-05-23

We present here the comprehensive x-ray diffraction and polarization-electric field hysteresis studies on (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics with x = 0.52, 0.56 and 0.60. The powder x-ray diffraction data reveals the presence of tetragonal phase for all the compositions. The saturation of hysteresis loop is observed for x ≤ 0.56.

X-ray magnetic circular dichroism in d and f ferromagnetic materials: recent theoretical progress. Part II (Review Article)

NASA Astrophysics Data System (ADS)

Antonov, V. N.; Shpak, A. P.; Yaresko, A. N.

2008-02-01

The present state of theoretical understanding of the x-ray magnetic circular dichroism (XMCD) of 4f and 5f compounds is reviewed. Energy band theory based upon the local spin-density approximation (LSDA) describes the XMCD spectra of transition metal compounds with high accuracy. However, the LSDA does not suffice for lanthanide compounds which have a correlated 4f shell. A satisfactory description of the XMCD spectra could be obtained by using a generalization of the LSDA, in which explicitly f electron Coulomb correlations are taken into account (LSDA +U approach). As examples of this group we consider the compound GdN. We also consider uranium 5f compounds. In those compounds where the 5f electrons are rather delocalized, the LSDA describes the XMCD spectra reasonably well. As an example of this group we consider UFe2. Particular differences occur for uranium compounds in which the 5f electrons are neither delocalized nor localized, but more or less semilocalized. Typical examples are UXAl (X =Co, Rh, and Pt), and UX (X =S, Se, Te). However, the semilocalized 5f's are not inert, but their interaction with conduction electrons plays an important role. We also consider the electronic structure and XMCD spectra of the heavy-fermion compounds UPt3, URu2Si2, UPd2Al3, UNi2Al3, and UBe13, where the degree of the 5f localization is increased in comparison with other uranium compounds. The electronic structure and XMCD spectra of UGe2 which possesses simultaneously ferromagnetism and superconductivity also presented. Recently achieved improvements for describing 5f compounds are discussed.

Disk Disruptions and X-ray Intensity Excursions in Cyg X-2, LMC X-3 and Cyg X-3

NASA Astrophysics Data System (ADS)

Boyd, P. T.; Smale, A. P.

2001-05-01

The RXTE All Sky Monitor soft X-ray light curves of many X-ray binaries show long-term intensity variations (a.k.a "superorbital periodicities") that have been ascribed to precession of a warped, tilted accretion disk around the X-ray source. We have found that the excursion times between X-ray minima in Cyg X-2 can be characterized as a series of integer multiples of the 9.8 binary orbital period, (as opposed to the previously reported stable 77.7 day single periodicity, or a single modulation whose period changes slowly with time). While the data set is too short for a proper statistical analysis, it is clear that the length of any given intensity excursion cannot be used to predict the next (integer) excursion length in the series. In the black hole candidate system LMC X-3, the excursion times are shown to be related to each other by rational fractions. We find that the long term light curve of the unusual galactic X-ray jet source Cyg X-3 can also be described as a series of intensity excursions related to each other by integer multiples of a fundamental underlying clock. In the latter cases, the clock is apparently not related to the known binary periods. A unified physical model, involving both an inclined accretion disk and a fixed-probability disk disruption mechanism is presented, and compared with three-body scattering results. Each time the disk passes through the orbital plane it experiences a fixed probability P that it will disrupt. This model has testable predictions---the distribution of integers should resemble that of an atomic process with a characteristic half life. Further analysis can support or refute the model, and shed light on what system parameters effectively set the value of P.

On the Samarium Substitution Effects in Y3-x Sm x Al5O12 (x = 0.1-3.0)

NASA Astrophysics Data System (ADS)

Skaudzius, Ramunas; Sakirzanovas, Simas; Kareiva, Aivaras

2018-04-01

Yttrium aluminium garnet substituted by samarium Y3-x Sm x Al5O12, (YSmAG, x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 and 3.0) was prepared by an aqueous sol-gel processing using etane-1,2-diol as complexing agent. The end products obtained at 1000°C in air were characterized by x-ray diffraction analysis, infrared spectroscopy (FT-IR) and scanning electron microscopy. It was demonstrated, however, that the total substitution of yttrium by samarium does not proceed in the YSmAG. The single cubic garnet phase was formed only at a low concentration of samarium (x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0). With further substitutional levels, if the amount of samarium was x = 1.5, 2.0, 2.5 and 3, respectively, the formation a of minor amount of side perovskite samarium aluminate SmAlO3 (SmAP) phase was observed. Surprisingly, when yttrium was totally replaced by the samarium (x = 3.0) the main synthesis product was SmAP. The possible formation of Sm3Al5O12 (SmAG) garnet was also investigated for the first time by variation of the temperature in the range of 780-835°C.

Centaurus X-3 - New low- and medium-energy X-ray observations

NASA Technical Reports Server (NTRS)

Long, K.; Agrawal, P. C.; Garmire, G.

1975-01-01

Low- and medium-energy X-ray observations of Cen X-3 during two pointed sounding-rocket experiments are discussed. The lack of low-energy emission from Cen X-3 is consistent with the identification of Krzeminski's star as the optical counterpart of Cen X-3 and normal reddening, in contrast to an earlier measurement by Bleeker et al (1973).

Ferroelastic domain structure and phase transition in single-crystalline [PbZn 1/3Nb 2/3O 3] 1-x[PbTiO 3] x observed via in situ x-ray microbeam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Tao; Du, Zehui; Tamura, Nobumichi

(1-x)Pb(Zn 1/3Nb 2/3)O 3-xPbTiO 3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this study, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25°C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in xmore » = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (T C), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient.« less

Ferroelastic domain structure and phase transition in single-crystalline [PbZn 1/3Nb 2/3O 3] 1-x[PbTiO 3] x observed via in situ x-ray microbeam

DOE PAGES

Li, Tao; Du, Zehui; Tamura, Nobumichi; ...

2017-11-10

(1-x)Pb(Zn 1/3Nb 2/3)O 3-xPbTiO 3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this study, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25°C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in xmore » = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (T C), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient.« less

Window type: 2x3 fixed multipaned steel window flanked by 1x3 ...

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

Window type: 2x3 fixed multipaned steel window flanked by 1x3 multipaned steel casements. Concrete sill and spandrel also illustrated. Building 43, facing east - Harbor Hills Housing Project, 26607 Western Avenue, Lomita, Los Angeles County, CA

Microstructures, optical and photovoltaic properties of CH3NH3PbI3(1‑x)Cl x perovskite films with CuSCN additive

NASA Astrophysics Data System (ADS)

Shirahata, Yasuhiro; Oku, Takeo

2018-05-01

Microstructures, optical and photovoltaic properties of CH3NH3PbI3(1‑x)Cl x perovskite films with copper(I) thiocyanate (CuSCN) additive were investigated. The CuSCN-added CH3NH3PbI3(1‑x)Cl x films were prepared by a hot air blow-assisted spin-coating method. Current density–voltage characteristics of the photovoltaic device using the CuSCN-added CH3NH3PbI3(1‑x)Cl x light-absorbing layer showed increases in short-circuit current density, open-circuit voltage, which resulted in increase in the conversion efficiency. Microstructure analysis showed that the crystal structure of the CuSCN-added CH3NH3PbI3(1‑x)Cl x was a pseudocubic system. From these results, partial substitutions of Pb2+ and anions (I‑ and Cl‑) by Cu ions (Cu+ and Cu2+) and SCN‑, respectively, are considered to occur in the CuSCN-added CH3NH3PbI3(1‑x)Cl x films. Based on the obtained results, reaction mechanisms of the CH3NH3PbI3(1‑x)Cl x films with and without CuSCN additive were discussed.

Window type: paired 3x2 multipaned steel window flanked by 1x3 ...

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

Window type: paired 3x2 multipaned steel window flanked by 1x3 multipaned steel casements, breaking building corner. Broad overhanging eave also illustrated. Second story detail. Building 13, facing east - Harbor Hills Housing Project, 26607 Western Avenue, Lomita, Los Angeles County, CA

Synthesis and crystal structures of new oxyapatites BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, V.D., E-mail: zhvd@ihim.uran.ru; Tyutyunnik, A.P.; Zubkov, V.G.

2012-10-15

New germanate-vanadates with the general formula BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3, have been synthesized by the nitrate-citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa{sub 4}(VO{sub 4}){sub 3}O (space group P6{sub 3}/m (N 176), Z=2, a=9.8327-9.8755(3), and c=7.1203-7.2133(2) ). They may be viewed as continuous series of solid solutions where Ca{sup 2+} and V{sup 5+} cations in the crystal lattice of vanadate BiCa{sub 4}(VO{sub 4}){sub 3}O are replaced by La{sup 3+} and Ge{sup 4+} cations. In the process of substitution, the La{sup 3+} cations occupy mainlymore » the 4f lattice sites of the germanate-vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa{sub 3}(GeO{sub 4}){sub 3} is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO{sub 4} and VO{sub 4} are separated from each other, and the (V/Ge)O{sub 4} tetrahedra exhibit a quasi-independent behavior. - Graphical abstract: Schematic drawing of the BiCa{sub 3}La(VO{sub 4}){sub 2}(GeO{sub 4})O structure in projection on the ac plane. Green-V and Ge, red-Ca(1) and La(1), yellow-Ca(2), La(2) and Bi, dark-blue-O(1)-O(4), blue-O(5). Highlights: Black-Right-Pointing-Pointer The citrate synthesis of germanate-vanadate oxyapatites. Black-Right-Pointing-Pointer The synthesized compounds crystallize in the hexagonal symmetry. Black-Right-Pointing-Pointer A single series of solid solutions BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, (x=0-3). Black-Right-Pointing-Pointer IR an Raman spectra of mixed crystals.« less

Impedance and magnetoelectric characteristics of (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) nano-composites

NASA Astrophysics Data System (ADS)

Nayek, C.; Murugavel, P.; Dinesh Kumar, S.; Subramanian, V.

2015-08-01

We have synthesized the phase-pure (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) magnetoelectric composites without interdiffusion among the existing phases. The magnetic measurements revealed an anomaly at the ferroelectric Curie temperature (393 K) of BaTiO3, and the dielectric data revealed an anomaly at the ferromagnetic transition temperature (360 K) of La0.7Sr0.3MnO3 ascertaining the magnetoelectric coupling in the composite. Impedance analysis indicated dipolar polarization contributions to the dielectric spectrum with two non-Debye-type relaxations. Both the grain and grain boundary contributions were present in the system with dominant grain boundary effect in all the composites. The composites show semiconducting behavior with the barrier hopping-type conducting mechanism. To avoid the free charge carrier and the space charge contributions, the magnetoelectric response was measured at high frequency range. The maximum values of magnetoelectric voltage coefficient measured at 100 kHz were 221 and 219 mV/Oe-cm for x = 0.1 and 0.3 samples, respectively.

Bupivacaine Lozenge Compared with Lidocaine Spray as Topical Pharyngeal Anesthetic before Unsedated Upper Gastrointestinal Endoscopy: A Randomized, Controlled Trial

PubMed Central

Salale, Nesrin; Treldal, Charlotte; Mogensen, Stine; Rasmussen, Mette; Petersen, Janne; Andersen, Ove; Jacobsen, Jette

2014-01-01

Unsedated upper gastrointestinal endoscopy (UGE) can induce patient discomfort, mainly due to a strong gag reflex. The aim was to assess the effect of a bupivacaine lozenge as topical pharyngeal anesthetic compared with standard treatment with a lidocaine spray before UGE. Ninety-nine adult outpatients undergoing unsedated diagnostic UGE were randomized to receive either a bupivacaine lozenge (L-group, n = 51) or lidocaine spray (S-group, n = 42). Primary objective was assessment of patient discomfort including acceptance of the gag reflex during UGE. The L-group assessed the discomfort significantly lower on a visual analog scale compared with the S-group (P = 0.02). There was also a significant difference in the four-point scale assessment of the gag reflex (P = 0.03). It was evaluated as acceptable by 49% in the L-group compared with 31% in the S-group. A bupivacaine lozenge compared with a lidocaine spray proved to be a superior option as topical pharyngeal anesthetic before an UGE. PMID:25374463

Structure and dielectric properties of (Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics

NASA Astrophysics Data System (ADS)

Ghoudi, Hanen; Chkoundali, Souad; Aydi, Abdelhedi; Khirouni, Kamel

2017-11-01

(Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics with compositions x = 0.6, 0.7, 0.8 and 0.9 were synthesized using the solid-state reaction method. These ceramics were examined by X-ray diffraction and dielectric measurements over a broad temperature and frequency ranges. X-ray diffraction patterns revealed a single-perovskite phase crystallized in a cubic structure, for x < 0.8, and in tetragonal, for x ≥ 0.8, with Pm3m and P4mm spaces groups, respectively. Two types of behaviors, classical ferroelectric or relaxor, were observed depending on the x composition. It is noted that temperatures T C (the Curie temperature) or T m (the temperature of maximum permittivity) rise when x increases and the relaxor character grows more significantly when x composition decreases. To analyze the dielectric relaxation degree of relaxor, various models were considered. It was proven that an exponential function could well describe the temperature dependence of the static dielectric constant and relaxation time.

A Computational Study of Chalcogen-containing H2 X…YF and (CH3 )2 X…YF (X=O, S, Se; Y=F, Cl, H) and Pnicogen-containing H3 X'…YF and (CH3 )3 X'…YF (X'=N, P, As) Complexes.

PubMed

McDowell, Sean A C; Buckingham, A David

2018-04-20

A computational study was undertaken for the model complexes H 2 X…YF and (CH 3 ) 2 X…YF (X=O, S, Se; Y=F, Cl, H), and H 3 X'…YF and (CH 3 ) 3 X'…YF (X'=N, P, As), at the MP2/6-311++G(d,p) level of theory. For H 2 X…YF and H 3 X'…YF, noncovalent interactions dominate the binding in order of increasing YF dipole moment, except for H 3 As…F 2 , and possibly H 3 As…ClF. However, for the methyl-substituted complexes (CH 3 ) 2 X…YF and (CH 3 ) 3 X'…YF the binding is especially strong for the complexes containing F 2 , implying significant chemical bonding between the interacting molecules. The relative stability of these complexes can be rationalized by the difference in the electronegativity of the X or X' and Y atoms. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-Ray and UV Orbital Phase Dependence in LMC X-3

NASA Technical Reports Server (NTRS)

Dolan, Joseph F.; Boyd, P. T.; Smale, A. P.

2001-01-01

The black-hole binary LMC X-3 is known to be variable on time scales of days to years. We investigated X-ray and ultraviolet variability in the system as a function of the 1.7 d binary orbit using a 6.4 day observation with the Rossi X-ray Timing Explorer (RXTE) in 1998 December. An abrupt 14 % flux decrease lasting nearly an entire orbit was followed by a return to previous flux levels. This behavior occurred twice at nearly the same binary phase, but is not present in consecutive orbits. When the X-ray flux is at lower intensity, a periodic amplitude modulation of 7 % is evident in data folded modulo the orbital period. The higher intensity data show weaker correlation with phase. This is the first report of X-ray variability at the orbital period of LMC X-3. Archival RXTE observations of LMC X-3 during a high flux state in 1996 December show similar phase dependence. An ultraviolet light curve obtained with the High Speed Photometer (HSP) on the Hubble Space Telescope (HST) shows a phase dependent variability consistent with that observed in the visible, ascribed to the ellipsoidal variation of the visible star. The X-ray spectrum of LMC X-3 is acceptably represented by a phenomenological disk black-body plus a power law. Changes in the spectrum of LMX X-3 during our observations are compatible with earlier observations during which variations in the 2-10 keV flux are closely correlated with the disk geometry spectral model parameter.

Phase transformation in (0.90- x)Pb(Mg 1/3Nb 2/3)O 3- xPbTiO 3-0.10PbZrO 3 piezoelectric ceramic: X-ray diffraction and Raman investigation

NASA Astrophysics Data System (ADS)

Xia, Zhiguo; Li, Qiang

2007-05-01

Piezoelectric ceramics with compositions of (0.90- x)Pb(Mg 1/3Nb 2/3)O 3- xPbTiO 3-0.10PbZrO 3, x=0.28, 0.31, 0.34, 0.37, 0.40 and 0.43, were prepared using the conventional columbite precursor method, and their structural phase transformation and piezoelectric behaviors near the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO 3 content. X-ray diffraction (XRD) results demonstrate that the structure of the ceramics experiences a gradual transition process from rhombohedral phase to tetragonal phase with the increasing of PbTiO 3 content, and that compositions with x=0.34-0.40 lie in the MPB region of this ternary system. A Raman spectra investigation of the ceramic samples testified to the transformation process of rhombohedral phase to tetragonal phase by comparing the relative intensities of tetragonal E(2TO 1) mode and rhombohedral phase R h mode. The structure information was also correlated to the parabola change of the piezoelectric constant; the maximum piezoelectric constants were obtained near the MPB region.

Centaurus X-3. [early x-ray binary star spectroscopy

NASA Technical Reports Server (NTRS)

Hutchings, J. B.; Cowley, A. P.; Crampton, D.; Van Paradus, J.; White, N. E.

1979-01-01

Spectroscopic observations of Krzeminski's star at dispersions 25-60 A/mm are described. The primary is an evolved star of type O6-O8(f) with peculiarities, some of which are attributable to X-ray heating. Broad emission lines at 4640A (N III), 4686 A(He II) and H-alpha show self-absorption and do not originate entirely from the region near the X-ray star. The primary is not highly luminous (bolometric magnitude about -9) and does not show signs of an abnormally strong stellar wind. The X-ray source was 'on' at the time of optical observations. Orbital parameters are presented for the primary, which yield masses of 17 + or - 2 and 1.0 + or - 3 solar masses for the stars. The optical star is undermassive for its luminosity, as are other OB-star X-ray primaries. The rotation is probably synchronized with the orbital motion. The distance to Cen X-3 is estimated to be 10 + or - 1 kpc. Basic data for 12 early-type X-ray primaries are discussed briefly

(Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 solid solutions: phase evolution, microstructure, dielectric properties and impedance analysis

NASA Astrophysics Data System (ADS)

Chen, Xiuli; Li, Xiaoxia; Yan, Xiao; Liu, Gaofeng; Zhou, Huanfu

2018-06-01

Perovskite solid solution ceramics of (Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 (BBSTBV, BBSTBT, 0.02 ≤ x ≤ 0.2) were prepared by the traditional solid state reaction technique. The phase evolution, microstructure and dielectric properties of BBSTBV and BBSTBT ceramics were researched. X-Ray diffraction results illustrated that both BBSTBV and BBSTBT could form a homogenous solid solution which has a similar structure with BaTiO3. The optimized properties of (Ba0.8Bi0.1Sr0.1)(Ti0.8Bi0.1Ti0.1)O3 ceramics with stable ɛ r ( 1769-2293), small Δ ɛ/ ɛ 25 °C values (± 15%) over a broad temperature range from - 58 to 151 °C and low tan δ ≤ 0.03 from - 11 to 131 °C were obtained. In the high-temperature region, the relaxation and conduction process are attributed to the thermal activation and the oxygen vacancies may be the ionic charge carriers in perovskite ferroelectrics.

Global SO(3) x SO(3) x U(1) symmetry of the Hubbard model on bipartite lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmelo, J.M.P., E-mail: carmelo@fisica.uminho.p; Ostlund, Stellan; Sampaio, M.J.

2010-08-15

In this paper the global symmetry of the Hubbard model on a bipartite lattice is found to be larger than SO(4). The model is one of the most studied many-particle quantum problems, yet except in one dimension it has no exact solution, so that there remain many open questions about its properties. Symmetry plays an important role in physics and often can be used to extract useful information on unsolved non-perturbative quantum problems. Specifically, here it is found that for on-site interaction U {ne} 0 the local SU(2) x SU(2) x U(1) gauge symmetry of the Hubbard model on amore » bipartite lattice with N{sub a}{sup D} sites and vanishing transfer integral t = 0 can be lifted to a global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry in the presence of the kinetic-energy hopping term of the Hamiltonian with t > 0. (Examples of a bipartite lattice are the D-dimensional cubic lattices of lattice constant a and edge length L = N{sub a}a for which D = 1, 2, 3,... in the number N{sub a}{sup D} of sites.) The generator of the new found hidden independent charge global U(1) symmetry, which is not related to the ordinary U(1) gauge subgroup of electromagnetism, is one half the rotated-electron number of singly occupied sites operator. Although addition of chemical-potential and magnetic-field operator terms to the model Hamiltonian lowers its symmetry, such terms commute with it. Therefore, its 4{sup N}{sub a}{sup D} energy eigenstates refer to representations of the new found global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry. Consistently, we find that for the Hubbard model on a bipartite lattice the number of independent representations of the group SO(3) x SO(3) x U(1) equals the Hilbert-space dimension 4{sup N}{sub a}{sup D}. It is confirmed elsewhere that the new found symmetry has important physical consequences.« less

Magnetic Structure and Magnetotransport Properties of La0.7Sr0.3Mn1 - x Ni x O3

NASA Astrophysics Data System (ADS)

Troyanchuk, I. O.; Bushinsky, M. V.; Tereshko, N. V.; Sikolenko, V.; Schorr, S.

2018-04-01

La0.7Sr0.3Mn1 - x Ni x O3 (0.12 ≤ x ≤ 0.35) compositions have been studied using neutron diffraction, magnetometry, and measurements of magnetotransport properties. At temperatures of 5-300 K, these compounds were found to have a rhombohedral crystal structure. The substitution of nickel for manganese has been shown to result in a decrease in the Curie temperature from 278 K ( x = 0.12) to 60 K ( x = 0.3); in this case, the spontaneous magnetization of the compositions decreases to zero ( x = 0.33). The magnetoresistive effect for the semimetals with 0.12 ≤ x < 0.18 increases near the Curie temperature, whereas the magnetoresistance of semiconducting compositions with x ≥ 0.2 progressively decreases as the temperature increases. For compositions with x ≥ 0.25, an antiferromagnetic G-type component has been found by neutron diffraction, the Neel temperature of which reaches 260 K (at x = 0.35). The study of the La1- y Sr y Mn0.65Ni0.35O3 ( y ≤ 0.3) system showed that the content of ferromagnetic component decreases with increasing Sr content. It has been inferred that the antiferromagnetism of the compositions with x > 0.25 is due to the strong negative exchange interactions Ni2+-O-Ni2+ and Mn4+-O-Mn4+ and the absence of ionic order. The obtained data have been used to construct the magnetic phase diagram of the La0.7Sr0.3Mn1- x Ni x O3 (0.12 ≤ x ≤ 0.35) system.

Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} (0{<=}x{<=}1): synthesis, structure and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thirumal, M.; Jawahar, I.N.; Surendiran, K.P.

2002-11-20

Oxides belonging to the families Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} were synthesized by the solid state reaction route. Sintering temperatures of 1300 deg. C led to oxides with disordered (cubic) perovskite structure. However, on sintering at 1425 deg. C hexagonally ordered structures were obtained for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} over the entire range (0{<=}x{<=}1) of composition, while for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} the ordered structure exists in a limited range (0{<=}x{<=}0.5). The dielectric constant is close to 30 for the Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} family of oxides while the Mg analoguesmore » have lower dielectric constant of {approx}18 in the range 50 Hz to 500 kHz. At microwave frequencies (5-7 GHz) dielectric constant increases with increase in niobium concentration (22-26) for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9}; for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} it varies between 12 and 14. The 'Zn' compounds have much higher quality factors and lower temperature coefficient of resonant frequency compared to the 'Mg' analogues.« less

Subtype-specific regulation of P2X3 and P2X2/3 receptors by phosphoinositides in peripheral nociceptors

PubMed Central

Mo, Gary; Bernier, Louis-Philippe; Zhao, Qi; Chabot-Doré, Anne-Julie; Ase, Ariel R; Logothetis, Diomedes; Cao, Chang-Qing; Séguéla, Philippe

2009-01-01

Background P2X3 and P2X2/3 purinergic receptor-channels, expressed in primary sensory neurons that mediate nociception, have been implicated in neuropathic and inflammatory pain responses. The phospholipids phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3) are involved in functional modulation of several types of ion channels. We report here evidence that these phospholipids are able to modulate the function of homomeric P2X3 and heteromeric P2X2/3 purinoceptors expressed in dorsal root ganglion (DRG) nociceptors and in heterologous expression systems. Results In dissociated rat DRG neurons, incubation with the PI3K/PI4K inhibitor wortmannin at 35 μM induced a dramatic decrease in the amplitude of ATP- or α,β-meATP-evoked P2X3 currents, while incubation with 100 nM wortmannin (selective PI3K inhibition) produced no significant effect. Intracellular application of PIP2 was able to fully reverse the inhibition of P2X3 currents induced by wortmannin. In Xenopus oocytes and in HEK293 cells expressing recombinant P2X3, 35 μM wortmannin incubation induced a significant decrease in the rate of receptor recovery. Native and recombinant P2X2/3 receptor-mediated currents were inhibited by incubation with wortmannin both at 35 μM and 100 nM. The decrease of P2X2/3 current amplitude induced by wortmannin could be partially reversed by application of PIP2 or PIP3, indicating a sensitivity to both phosphoinositides in DRG neurons and Xenopus oocytes. Using a lipid binding assay, we demonstrate that the C-terminus of the P2X2 subunit binds directly to PIP2, PIP3 and other phosphoinositides. In contrast, no direct binding was detected between the C-terminus of P2X3 subunit and phosphoinositides. Conclusion Our findings indicate a functional regulation of homomeric P2X3 and heteromeric P2X2/3 ATP receptors by phosphoinositides in the plasma membrane of DRG nociceptors, based on subtype-specific mechanisms of direct and indirect

Soft X-ray observations of Centaurus X-3 from Copernicus

NASA Technical Reports Server (NTRS)

Margon, B.; Mason, K. O.; Hawkins, F. J.; Sanford, P. W.

1975-01-01

We have detected soft X-ray emission from Centaurus X-3 in the 0.6-1.9 keV band, using the focusing telescope aboard OAO Copernicus. The flux is compatible with an extrapolation of the harder X-ray spectrum, attenuated by (3-4) times 10 to the 22nd atoms per sq cm of interstellar and/or circumstellar matter. The data are consistent with the distance estimate of 5-10 kpc derived from the spectroscopic modulus of the optical component, and obviate the need to postulate the primary to be an anomalously subluminous hot star. There is currently no compelling evidence that such models must be invoked to explain any of the observed compact X-ray sources.

Relation Between Crystal Structure and Electrochemical Performance of LiNi1/3Zn x Co1/3-xMn1/3O₂ (0.000 ≤ x ≤ 0.133).

PubMed

Wang, Xujun; Wan, Yong; Wang, Ruiqi; Xu, Xiantang; Wang, He; Chang, Mingning; Yuan, Feng; Ge, Xiaohui; Shao, Weiquan; Xu, Sheng

2018-04-01

LiNi1/3ZnxCo1/3-xMn1/3O2 (0.000 ≤ x ≤ 0.133) hollow microspheres are synthesized using MnO2 hollow microspheres both as a self-template and Mn source. These hollow microspheres, ~4 μm in diameter, are composed of approximately 300 nm basic nanoparticles. The XRD patterns of LiNi1/3ZnxCo1/3-xMn1/3O2 were analyzed by the RIETAN-FP program, and the obtained samples have a layered α-NaFeO2 structure. Electrochemical performances of the samples were carried out between 2.5 V and 4.5 V. The behavior of the lattice parameters is consistent with Cycling performance and rate performance change with increase of x. Compared with the others, the sample of x = 0.133 exhibits a relatively superior electrochemical performance. The specific capacity of x = 0.133 was increased by 10.7% than no-doped. In addition, the cyclic voltammograms curves of the second cycle show no significant alteration compared with the first cycle and the electrochemical impedance of zinc doping sample showed smaller transfer resistance than the no-doping sample.

Electronic structure of charge- and spin-controlled Sr(1-(x+y))La(x+y)Ti(1-x)Cr(x)O3.

PubMed

Iwasawa, H; Yamakawa, K; Saitoh, T; Inaba, J; Katsufuji, T; Higashiguchi, M; Shimada, K; Namatame, H; Taniguchi, M

2006-02-17

We present the electronic structure of Sr(1-(x+y))La(x+y)Ti(1-x)Cr(x)O3 investigated by high-resolution photoemission spectroscopy. In the vicinity of the Fermi level, it was found that the electronic structure was composed of a Cr 3d local state with the t(2g)3 configuration and a Ti 3d itinerant state. The energy levels of these Cr and Ti 3d states are well interpreted by the difference of the charge-transfer energy of both ions. The spectral weight of the Cr 3d state is completely proportional to the spin concentration x irrespective of the carrier concentration y, indicating that the spin density can be controlled by x as desired. In contrast, the spectral weight of the Ti 3d state is not proportional to y, depending on the amount of Cr doping.

Polymeric Binders which Reversibly Dissociate at Elevated Temperatures

DTIC Science & Technology

1978-05-01

C0O(CH2)xOC-C- N . ~Nk \\ N . N + H0(CH2)x OH HC. , , tH \\\\ N - N -C. HC-N1-- H H H ~0 ~+ 0CNRNC0 Polymer 14 S. Kasina and J. Nematollahi . "A New and Simple...NUMIIA& i* GOVT ACC9Ir.Q~ N NO. I CIIIIINT’S CATZALOG NUMOIR NWC-TP-591951 OLYUC INDERS WHICH.REVERSIBLY ! Rasear pr.. Ř 7.: , CISS-CIATSEAT ELEV...342M7RA""" El7cadUgee /nary.i TC. Aiea N - 3 F5335431. P ERMFORMING ORGANIZATION NAM E A NlO A OR SS 1 . P O R M CLM l T T S , ~ ~~~Naval Weapons

RXTE Observations of Cygnus X-3

NASA Technical Reports Server (NTRS)

McCollough, M. L.; Robinson, C. R.; Zhang, S. N.; Harmon, B. A.; Paciesas, W. S.; Dieters, S. W.; Hjellming, R. M.; Rupen, M.; Mioduszewski, A. J.; Waltman, E. B.

1997-01-01

In the period between May 1997 and August 1997 a series of pointed RXTE observations were made of Cyg X-3. During this period Cyg X-3 made a transition from a quiescent radio state to a flare state (including a major flare) and then returned to a quiescent radio state. Analyses of the observations are made in the context of concurrent observations in the hard X-ray (CGRO/BATSE), soft X-ray (RXTE/ASM) and the radio (Green Bank Interferometer, Ryle Telescope, and RATAN-600). Preliminary analyses of the observations are presented.

Block 3 X-band receiver-exciter

NASA Technical Reports Server (NTRS)

Johns, C. E.

1987-01-01

The development of an X-band exciter, for use in the X-Band Uplink Subsystem, was completed. The exciter generates the drive signal for the X-band transmitter and also generates coherent test signals for the S- and X-band Block 3 translator and a Doppler reference signal for the Doppler extractor system. In addition to the above, the exciter generates other reference signals that are described. Also presented is an overview of the exciter design and some test data taken on the prototype. A brief discussion of the Block 3 Doppler extractor is presented.

An ab initio study on MgX 3- and CaX 3- superhalogen anions (X=F, Cl, Br)

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Sobczyk, Monika; Dąbkowska, Iwona; Skurski, Piotr

2003-06-01

The vertical electron detachment energies (VDEs) of twenty MX 3- (M=Mg, Ca; X=F, Cl, Br) anions were calculated at the OVGF level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for MgF 3- system (8.793 eV). All negatively charged species possess the VDEs that are larger than 5.9 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the MX 3- species on the ligand-central atom (M-X) distance and on the partial atomic charge localized on Mg or Ca was observed and discussed, as well as the other factors that may influence the electronic stability of such anions.

High-Temperature Thermoelectric Properties of (1 - x) SrTiO3 - ( x) La1/3NbO3 Ceramic Solid Solution

NASA Astrophysics Data System (ADS)

Srivastava, Deepanshu; Azough, F.; Molinari, M.; Parker, S. C.; Freer, R.

2015-06-01

Ceramics based on SrTiO3 are of growing interest as thermoelectric materials because of their high-temperature stability and non-toxicity. Substitution of La and Nb into the perovskite structure provides opportunities to control both the microstructure and properties. Ceramic solid solutions of (1 - x) SrTiO3 - ( x) La1/3NbO3 were prepared by the mixed oxide route, using compositional steps of x = 0.1. Pressed pellets were sintered at temperatures of 1573 K to 1723 K in air. Addition of aliovalent ions (La3+, Nb5+) on the A/B sites (Sr2+, Ti4+) led to A-Site cation deficiency in the stoichiometric compositions and other defect structures which increased carrier concentration. A maximum ZT of 0.004 was obtained for the x = 0.2 stoichiometric sample, although much higher ZT values are possible by sample reduction.

The first search for X-ray polarization in the Centaurus X-3 and Hercules X-1 pulsars

NASA Technical Reports Server (NTRS)

Silver, E. H.; Weisskopf, M. C.; Kestenbaum, H. L.; Long, K. S.; Novick, R.; Wolff, R. S.

1979-01-01

The first search for X-ray polarization in the Cen X-3 and Her X-1 pulsars was performed by the OSO 8 polarimeters in 1975 July and 1975 August, respectively. Three-sigma upper limits to the polarization in Cen X-3 of 13.5% and 19% at 2.6 keV and 5.2 keV, respectively, were obtained when the data were averaged over the pulse and binary periods. The upper limit for Her X-1 at 2.6 keV is 60%. A search for pulse-phase dependent X-ray polarization from both objects was also performed. At the 91% confidence level, emission from Cen X-3 exhibits evidence for X-ray polarization at 2.6 keV that varies with pulse phase. Upper limits to polarization are presented for the leading and trailing edges and peak of the Her X-1 pulse at 2.6 keV.

First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3Cr x Pb1- x I3 mixed perovskites

NASA Astrophysics Data System (ADS)

Huang, H. M.; Zhu, Z. W.; Zhang, C. K.; He, Z. D.; Luo, S. J.

2018-04-01

The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3Cr x Pb1- x I3 ( x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3Cr x Pb1- x I3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 µB per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of <100>, <110> and <111> orientation of organic cation CH3NH3 + on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3 + in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.

Magnetism in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Co{sub x}O{sub 3} (0 ≤ x ≤ 1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Ashutosh, E-mail: ashutosh.pph13@iitp.ac.in; Sharma, Himanshu; Tomy, C. V.

2016-05-23

We study the structural and magnetic properties of La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Co{sub x}O{sub 3} (0 ≤ x ≤ 1). Rietveld refinement of X-ray Diffraction (XRD) pattern suggests phase purity of the polycrystalline samples with R-3c space group. Interplay of Ferromagnetic (FM) and Antiferromagnetic (AFM) interaction upon Co substitution at Mn site in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} is evident from magnetic measurements. There is an optimal cobalt substitution at which the coercive field is maximum.

Monoclinic Sr(1-x)Na(x)SiO(3-0.5x): new superior oxide ion electrolytes.

PubMed

Singh, Preetam; Goodenough, John B

2013-07-10

Oxide ion electrolytes determine the temperature of operation of solid oxide fuel cells, oxygen separation membranes, and oxygen sensors. There is a strong incentive to lower their operating temperatures, in a solid oxide fuel cell, for example, from Top > 800 °C to Top ≈ 500 °C. The use of low-cost Na(+) rather than K(+) as the dopant in monoclinic SrSiO3 (C12/C1) is shown to provide a larger solid solution range (0 < x ≤ 0.45) in Sr1-xNaxSiO3-0.5x and to achieve an oxide ion conductivity σo ≥ 10(-2) S·cm(-1) by 525 °C as a result of lowering the temperature of a smooth transition to full disorder of the mobile oxide ions. The Sr1-xNaxSiO3-0.5x electrolytes are much less hygroscopic than Sr1-xKxSiO3-0.5x and are stable with a nickel composite anode in 5% H2/Ar as well as with cathodes such as La1-xSrxMnO3-δ and Sr0.7Y0.3CoO3-δ in air, which makes them candidate electrolytes for intermediate-temperature solid oxide fuel cells or for other applications of oxide ion electrolytes.

Ba0.06(Na,Bi)0.94Ti1-x(Ni1/3Nb2/3)xO3 ceramics: X-ray diffraction and infrared spectroscopy studies

NASA Astrophysics Data System (ADS)

Mishra, R. K.; Prasad, Ashutosh; Chandra, K. P.; Prasad, K.

2018-05-01

Non-lead ceramic samples of Ba0.06(Na0.5Bi0.5)0.94Ti1-x(Ni1/3Nb2/3)xO3; 0 ≤ x ≤ 1.0 were prepared by standard high temperature ceramic synthesis method. Rietveld refinements of X-ray diffraction data of these ceramics were carried out using FullProf software and determined their crystal symmetry, space group and unit cell dimensions. Rietveld refinement revealed that Ba0.06(Na0.5Bi0.5)0.94TiO3 has a monoclinic structure with space group P4/m while B0.06(Na0.5Bi0.5)0.94(Ni1/3Nb2/3)O3 has tetragonal (pseudo-cubic) structure with space group P4/mmm. Partial replacement of Ti4+ ion by pseudo-cation (Ni1/33 +Nb2/3 5 +) 4 + resulted in the change of unit cell structure from monoclinic to tetragonal. SEM studies were carried out in order to access the quality of the prepared ceramics which showed a change in grain sizes with the increase of (Ni1/33 +Nb2/3 5 +) 4 + content. FTIR spectra confirmed the formation of perovskite type solid solutions.

Thermoelectric properties of LaRh(1-x)Ni(x)O(3).

PubMed

Shibasaki, S; Takahashi, Y; Terasaki, I

2009-03-18

We report measurements and analyses of resistivity, thermopower and thermal conductivity of polycrystalline samples of perovskite LaRh(1-x)Ni(x)O(3). The thermopower is found to be large at 800 K (185 µV K(-1) for x = 0.3), which is ascribed to the high-temperature stability of the low-spin state of Rh(3+)/Rh(4+) ions. This clearly contrasts with the thermopower of the isostructural oxide LaCoO(3), which rapidly decreases above 500 K owing to the spin-state transition. The spin state of the transition-metal ions is one of the most important parameters in oxide thermoelectrics.

Annealing Effect on (FAPbI3)1−x(MAPbBr3)x Perovskite Films in Inverted-Type Perovskite Solar Cells

PubMed Central

Chen, Lung-Chien; Wu, Jia-Ren; Tseng, Zhong-Liang; Chen, Cheng-Chiang; Chang, Sheng Hsiung; Huang, Jun-Kai; Lee, King-Lien; Cheng, Hsin-Ming

2016-01-01

This study determines the effects of annealing treatment on the structure and the optical and electronic behaviors of the mixed (FAPbI3)1−x(MAPbBr3)x perovskite system. The experimental results reveal that (FAPbI3)1−x(MAPbBr3)x (x ~ 0.2) is an effective light-absorbing material for use in inverted planar perovskite solar cells owing to its large absorbance and tunable band gap. Therefore, good band-matching between the (FAPbI3)1−x(MAPbBr3)x and C60 in photovoltaic devices can be controlled by annealing at various temperatures. Accordingly, an inverted mixed perovskite solar cell with a record efficiency of 12.0% under AM1.5G irradiation is realized. PMID:28773874

Evolution of Cygnus X-3 through its Radio and X-ray States

NASA Astrophysics Data System (ADS)

Szostek, A.; Zdziarski, A. A.; McCollough, M. L.

2009-05-01

Based on X-ray spectra and studies of the long-term correlated behavior between radio and soft X-ray, we present a detailed evolution of Cyg X-3 through its radio and X-ray states. We comment on the nature of the hard X-ray tail and possible Simbol X contribution in constraining the models.

Ternary lithium stannides Li xT 3Sn 7-x ( T=Rh, Ir)

NASA Astrophysics Data System (ADS)

Sreeraj, Puravankara; Kurowski, Daniel; Hoffmann, Rolf-Dieter; Wu, Zhiyun; Pöttgen, Rainer

2005-11-01

The ternary stannides Li xRh 3Sn 7-x ( x=0.45, 0.64, 0.80) and Li xIr 3Sn 7-x ( x=0.62 and 0.66) were synthesized from the elements in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. The samples were characterized by X-ray diffraction on powders and single crystals. The stannides adopt the cubic Ir 3Ge 7-type structure (space group Im3¯m, Z=4). In this structure type the tin atoms occupy the Wyckoff positions 12 d and 16 f and form two interpenetrating frameworks consisting of cubes and square antiprisms. The rhodium and iridium atoms center the square antiprisms and are arranged in pairs. With increasing lithium substitution the lattice parameter of Ir 3Sn 7 (936.7) decreases via 932.2 pm ( x=0.62) to 931.2 pm ( x=0.66), while the Ir-Ir distance remains almost the same (290 pm). A similar trend is observed for the rhodium compounds. The lithium atoms substitute Sn on both framework sites. However, the 16 f site shows a substantially larger preference for Li occupation. This is in contrast to the isotypic magnesium based compounds.

Designing new lithium-excess cathode materials from percolation theory: nanohighways in Li(x)Ni(2-4x/3)Sb(x/3)O2.

PubMed

Twu, Nancy; Li, Xin; Urban, Alexander; Balasubramanian, Mahalingam; Lee, Jinhyuk; Liu, Lei; Ceder, Gerbrand

2015-01-14

Increasing lithium content is shown to be a successful strategy for designing new cathode materials. In layered Li(x)Ni(2-4x/3)Sb(x/3)O2 (x = 1.00-1.15), lithium excess improves both discharge capacity and capacity retention at 1C. Structural studies reveal a complex nanostructure pattern of Li-Sb and Ni-Sb ordering where the interface between these domains forms the correct local configuration for good lithium mobility. The <1 nm Li-Sb stripe domains and their interfaces thereby effectively act as nanohighways for lithium diffusion.

New lidocaine lozenge as topical anesthesia compared to lidocaine viscous oral solution before upper gastrointestinal endoscopy

PubMed Central

Mogensen, Stine; Treldal, Charlotte; Feldager, Erik; Pulis, Sylvia; Jacobsen, Jette; Andersen, Ove; Rasmussen, Mette

2012-01-01

Objective To evaluate the effect and acceptance of a new lidocaine lozenge compared with a lidocaine viscous oral solution as a pharyngeal anesthetic before upper gastrointestinal endoscopy (UGE), a diagnostic procedure commonly performed worldwide during which many patients experience severe discomfort mostly because of the gag reflex. Participants The single-blinded, randomized, controlled study involved 110 adult patients undergoing diagnostic UGE at the Department of Gastroenterology, Hvidovre University Hospital, Denmark. Methods The patients were randomized to receive either 100 mg lidocaine as a lozenge or 5 mL lidocaine viscous oral solution 2%. Intravenous midazolam was administered if needed. The effect of a lidocaine lozenge in reducing patient discomfort, including the gag reflex, during UGE compared with a lidocaine oral solution was assessed. Results Questionnaires from the patients showed that the gag reflex was acceptable for 64% in the lozenge group compared with 33% in the oral solution group (P = 0.0072). UGE was evaluated as acceptable by 69% in the lozenge group compared with 39% in the oral solution group (P = 0.0092). The taste was evaluated as good by 78% in the lozenge group (P < 0.0001), and 82% found the lozenge to have good texture (P < 0.0001). Conclusion The lozenge reduced the gag reflex, diminished patients’ discomfort during UGE, and was evaluated as having a good taste and texture. The lozenge improved patients’ acceptance of UGE. PMID:22915898

Synthesis of layered perovskite oxides, ACa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (A = K, Rb, Cs), and characterization of new solid acids, HCa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (O < x [le] 2), exhibiting variable Bronsted acidity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopalakrishnan, J.; Uma, S.; Bhat, V.

1993-01-01

Layered perovskite oxides of the formula ACa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (A = K, Rb, Cs and 0 , x [le] 2) have been prepared. The members adopt the structures of the parent ACa[sub 2]Nb[sub 3]O[sub 10]. Interlayer alkali cations in the niobium-titanium oxide series can be ion-exchanged with Li[sup +], Na[sup +], NG[sub 4][sup +], of H[sup +] to give new derivatives. Intercalation of the protonated derivatives with organic bases reveals that the Bronsted acidity of the solid solution series, HCa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10], depends on the titanium content. While the x = 1 member (HCaLaNb[submore » 2]TiO[sub 10]) is nearly as acidic as the parent HCa[sub 2]Nb[sub 3]O[sub 10], the x = 2 member (HLA[sub 2]NbTi[sub 2]O[sub 10]) is a weak acid hardly intercalating organic bases with pK[sub a] [approximately] 11.3. The variation of acidity is probably due to an ordering of Nb/Ti atoms in the triple octahedral perovskite slabs, [Ca[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10

X-15 ship #3 on lakebed

NASA Technical Reports Server (NTRS)

1962-01-01

The X-15 ship #3 (56-6672) is seen here on the lakebed at the Edwards Air Force Base, Edwards, California. Ship #3 made 65 flights during the program, attaining a top speed of Mach 5.65 and a maximum altitude of 354,200 feet. Only 10 of the 12 X-15 pilots flew Ship #3, and only eight of them earned their astronaut wings during the program. Robert White, Joseph Walker, Robert Rushworth, John 'Jack' McKay, Joseph Engle, William 'Pete' Knight, William Dana, and Michael Adams all earned their astronaut wings in Ship #3. Neil Armstrong and Milton Thompson also flew Ship #3. In fact, Armstrong piloted Ship #3 on its first flight, on 20 December 1961. On 15 November 1967, Ship #3 was launched over Delamar Lake, Nevada with Maj. Michael J. Adams at the controls. The vehicle soon reached a speed of Mach 5.2, and a peak altitude of 266,000 feet. During the climb, an electrical disturbance degraded the aircraft's controllability. Ship #3 began a slow drift in heading, which soon became a spin. Adams radioed that the X-15 'seems squirrelly,' and then said 'I'm in a spin.' Through some combination of pilot technique and basic aerodynamic stability, Adams recovered from the spin, and entered an inverted Mach 4.7 dive. As the X-15 plummeted into the increasingly thicker atmosphere, the Honeywell adaptive flight control system caused the vehicle to begin oscillating. As the pitching motion increased, aerodynamic forces finally broke the aircraft into several major pieces. Adams was killed when the forward fuselage impacted the desert. This was the only fatal accident during the entire X-15 program. The X-15 was a rocket powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was

Mycobacterium tuberculosis PhoY Proteins Promote Persister Formation by Mediating Pst/SenX3-RegX3 Phosphate Sensing.

PubMed

Namugenyi, Sarah B; Aagesen, Alisha M; Elliott, Sarah R; Tischler, Anna D

2017-07-11

The Mycobacterium tuberculosis phosphate-specific transport (Pst) system controls gene expression in response to phosphate availability by inhibiting the activation of the SenX3-RegX3 two-component system under phosphate-rich conditions, but the mechanism of communication between these systems is unknown. In Escherichia coli , inhibition of the two-component system PhoR-PhoB under phosphate-rich conditions requires both the Pst system and PhoU, a putative adaptor protein. E. coli PhoU is also involved in the formation of persisters, a subpopulation of phenotypically antibiotic-tolerant bacteria. M. tuberculosis encodes two PhoU orthologs, PhoY1 and PhoY2. We generated phoY single- and double-deletion mutants and examined the expression of RegX3-regulated genes by quantitative reverse transcription-PCR (qRT-PCR). Gene expression was increased only in the Δ phoY1 Δ phoY2 double mutant and could be restored to the wild-type level by complementation with either phoY1 or phoY2 or by deletion of regX3 These data suggest that the PhoY proteins function redundantly to inhibit SenX3-RegX3 activation. We analyzed the frequencies of antibiotic-tolerant persister variants in the phoY mutants using several antibiotic combinations. Persister frequency was decreased at least 40-fold in the Δ phoY1 Δ phoY2 mutant compared to the frequency in the wild type, and this phenotype was RegX3 dependent. A Δ pstA1 mutant lacking a Pst system transmembrane component exhibited a similar RegX3-dependent decrease in persister frequency. In aerosol-infected mice, the Δ phoY1 Δ phoY2 and Δ pstA1 mutants were more susceptible to treatment with rifampin but not isoniazid. Our data demonstrate that disrupting phosphate sensing mediated by the PhoY proteins and the Pst system enhances the susceptibility of M. tuberculosis to antibiotics both in vitro and during infection. IMPORTANCE Persister variants, subpopulations of bacteria that are phenotypically antibiotic tolerant, contribute to

Facile fabrication of large-grain CH 3NH 3PbI 3-xBr x films for high-efficiency solar cells via CH 3NH 3Br-selective Ostwald ripening

DOE PAGES

Yang, Mengjin; Zhang, Taiyang; Schulz, Philip; ...

2016-08-01

Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH 3NH 3PbI 3-xBr x (MAPbI 3-xBr x) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI 3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI 3-xBr x thin films following an Ostwald ripening process,more » which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I-Br anion exchange reaction, yielding poorer device performance. Lastly, this MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.« less

Structural investigation of (111) oriented (BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices by X-ray diffraction and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Belhadi, J.; Yousfi, S.; Bouyanfif, H.; El Marssi, M.

2018-04-01

(BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices (SLs) with varying x have been grown by pulsed laser deposition on (111) oriented SrTiO3 substrates. In order to obtain good epitaxy and flat samples, a conducting SrRuO3 buffer has been deposited prior to the superlattices to screen the polar mismatch for such (111) SrTiO3 orientation. X-ray diffraction reciprocal space mapping on a different family of planes was collected and evidenced a room temperature structural change at x = 0.5 from a rhombohedral/monoclinic structure for rich BiFeO3 to an orthorhombic symmetry for rich LaFeO3. This symmetry change has been confirmed by Raman spectroscopy and demonstrates the different phase stability compared to similar SLs grown on (100) SrTiO3. The strongly anisotropic strain and oxygen octahedral rotation/tilt system compatibility at the interfaces probably explain the orientation dependence of the phase stability in such superlattices.

HEAO 1 high-energy X-ray observations of Centaurus X-3

NASA Technical Reports Server (NTRS)

Howe, S. K.; Primini, F. A.; Bautz, M. W.; Lang, F. L.; Levine, A. M.; Lewin, W. H. G.

1983-01-01

Pulsations of 4.8 sec were detected up to energies above 38 keV by the present High Energy X-ray and Low Energy Gamma-Ray HEAO 1 satellite experiment observations of Cen X-3, and an analysis of the X-ray spectrum as a function of pulse phase indicates that the spectrum hardens during an interval of about 1.2 sec which lags the pulse peak by about 0.6 sec. The results of correlated observations of pulse period and X-ray intensity include (1) the detection of a high intensity state during which the pulse period is on the average increasing, (2) the measurement of comparable high intensities during episodes of both period increase and decrease, (3) the detection of X-ray pulsations at a much reduced level during a period of low intensity, and (4) the detection of a transition between spin-down, and spin-up episodes that coincides with a rapid decrease in X-ray intensity.

Nano-indentation investigations of (As2Se3)1-x: Snx and (As4S3Se3)1-x: Snx glasses

NASA Astrophysics Data System (ADS)

Harea, D. V.; Harea, E. E.; Iaseniuc, O. V.; Iovu, M. S.

2015-02-01

Experimental results on some physical and optical properties of (As2Se3)1-x:Snx and (As4S3Se3)1-x:Snx (x = 0-10 at %) glasses and amorphous films (d~2.0 μm) are presented. The bulk chalcogenide glasses are studied by X-ray diffraction spectroscopy and nanoindentation methods. It is established that the addition of these amounts of tin (x = 0-10 at %) does not lead to significant changes in the physical properties of the glass, such as values of stress and Young's modulus related to the modification of the density and compactness. It has been found that the addition of these amounts of tin in (As4S3Se3)1-x:Snx does not lead to significant changes in the glass physical properties, such as values of stress and Young's modulus related to the modification of the density and compactness. The study of the photoplastic effect is performed in situ, with illumination of the bulk and thin film samples during indentation as well as their indentation after illumination with a green laser (λ = 532 nm) at a power of P = 50 mV/cm2. The hardness is calculated from load-displacement curves by the Oliver-Pharr method. A sharp increase in hardness is registered if the tin concentration exceeds a value of 34% Sn. The hardness H of (As2Se3)1-x:Snx films varies between 115 and 130 kg/mm2. It is found that the hardness H of amorphous thin films is generally higher than the hardness of bulk samples with the same chemical composition. In this study, we are focused on the mechanical characteristics of high-purity As2Se3: Snx thin films. Keyword: Chalcogenide glasses, hardness,

Photophysical properties of the series fac- and mer-(1-phenylisoquinolinato-N∧C2')(x)(2-phenylpyridinato-N∧C2')(3-x)iridium(III) (x = 1-3).

PubMed

Deaton, Joseph C; Young, Ralph H; Lenhard, Jerome R; Rajeswaran, Manju; Huo, Shouquan

2010-10-18

The photophysical properties of tris-cyclometalated iridium(III) complexes have been probed by chemical and geometric variation through the series fac- and mer-Ir(piq)(x)(ppy)(3-x) (x = 1-3; piq = 1-phenylisoquinolinato-N(∧)C(2'), ppy = 2-phenylpyridinato-N(∧)C(2')). The phosphorescent decays were recorded in solution at 295 K and in polymer films from 2 to 295 K. In the heteroleptic complexes, emission occurs based solely on the piq ligand(s), at least by the nanosecond time scale, as its excited states are the lowest energy. Because fac-Ir(piq)(3) and fac-Ir(ppy)(3) possess practically the same oxidation potential, comparison of photophysical properties through the series fac-Ir(piq)(x)(ppy)(3-x) (x = 1-3) revealed the effects of having one, two, or three emissive piq ligands with no confounding effects from differences in electron withdrawing or donating properties between the spectator ppy ligands and the piq ligands. Effects of placement of piq ligands in different coordination geometries were elucidated by comparisons to the mer series.

Investigating new activators for small-bandgap LaX3 (X = Br, I) scintillators

NASA Astrophysics Data System (ADS)

Rutstrom, Daniel; Collette, Robyn; Stand, Luis; Loyd, Matthew; Wu, Yuntao; Koschan, Merry; Melcher, Charles L.; Zhuravleva, Mariya

2018-02-01

Luminescence and scintillation properties of Bi3+, Sb3+, and Eu2+-doped LaI3 and LaBr3 were explored. Out of the three dopants investigated, Eu2+ was the most promising new activator for small-bandgap LaX3 (X = Br, I) and was further studied in the mixed-halide LaBr3-xIx. Crystals were grown from the melt using the vertical Bridgman method. LaBr3:Eu2+ 0.5% (mol) had the most favorable scintillation properties with a light output of 43,000 ph/MeV and 6% energy resolution at 662 keV. Performance of LaBr3-xIx:Eu2+ worsened for most samples as iodide concentration was increased. Room-temperature scintillation of LaI3:Eu2+ 0.1% and 0.5% was observed and is the first case of room-temperature emission reported for doped LaI3.

Structure cristalline du composé Hg3-xSbx(S+Se)2+xI2-x (x ≃ 0.1)

PubMed Central

Kars, Mohammed; Herrero, Adrian Gómez; Roisnel, Thierry; Rebbah, Allaoua; Otero-Diáz, L. Carlos

2016-01-01

Single crystals of the mercury chalcohalide Hg3-xSbx(S+Se)2+xI2-x (x ≃ 0.1) (mercury anti­mony sulfide selenide iodide), were grown by a chemical transport reaction. The structure contains three independent A (Hg/Sb) atoms; each atom is strongly covalently bonded with two X (Se/S) atoms to form approximately linear X–A–X units. The X–A–X units link to form A 4 X 4 rings, which are combined into infinite crankshaft-type bands running along the [100] direction. Four equatorial E (I/X = Se,S) atoms at relatively long distances complete the distorted octa­hedral coordination of A (Hg/Sb). The crystal under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.814 (6):0.186 (6). The structure is isotypic with Hg3Se2I2 [Beck & Hedderich (2000 ▸). J. Solid State Chem. 151, 73–76], but the current determination reveals a coupled substitution, with partial replacement of Hg+2 by Sb+3, balanced by the equivalent substitution of I−1 by S−2 and Se−2. Bond-valence calculations are consistent with this relative substitution model. PMID:27006793

Identification of the UDP-glucose-4-epimerase required for galactofuranose biosynthesis and galactose metabolism in A. niger.

PubMed

Park, Joohae; Tefsen, Boris; Arentshorst, Mark; Lagendijk, Ellen; van den Hondel, Cees Amjj; van Die, Irma; Ram, Arthur Fj

2014-01-01

Galactofuranose (Gal f )-containing glycoconjugates are important to secure the integrity of the cell wall of filamentous fungi. Mutations that prevent the biosynthesis of Gal f -containing molecules compromise cell wall integrity. In response to cell wall weakening, the cell wall integrity (CWI)-pathway is activated to reinforce the strength of the cell wall. Activation of CWI-pathway in Aspergillus niger is characterized by the specific induction of the agsA gene, which encodes a cell wall α-glucan synthase. In this study, we screened a collection of cell wall mutants with an induced expression of agsA for defects in Gal f biosynthesis using a with anti-Gal f antibody (L10). From this collection of mutants, we previously identified mutants in the UDP-galactopyranose mutase encoding gene ( ugmA ). Here, we have identified six additional UDP-galactopyranose mutase ( ugmA ) mutants and one mutant (named mutant #41) in an additional complementation group that displayed strongly reduced Gal f -levels in the cell wall. By using a whole genome sequencing approach, 21 SNPs in coding regions were identified between mutant #41 and its parental strain which changed the amino acid sequence of the encoded proteins. One of these mutations was in gene An14g03820, which codes for a putative UDP-glucose-4-epimerase (UgeA). The A to G mutation in this gene causes an amino acid change of Asn to Asp at position 191 in the UgeA protein. Targeted deletion of ugeA resulted in an even more severe reduction of Gal f in N-linked glucans, indicating that the UgeA protein in mutant #41 is partially active. The ugeA gene is also required for growth on galactose despite the presence of two UgeA homologs in the A. niger genome. By using a classical mutant screen and whole genome sequencing of a new Gal f -deficient mutant, the UDP-glucose-4-epimerase gene ( ugeA ) has been identified. UgeA is required for the biosynthesis of Gal f as well as for galactose metabolism in Aspergillus niger .

Designing new lithium-excess cathode materials from percolation theory: Nanohighways in Li xNi 2–4x/3Sb x/3O 2

DOE PAGES

Twu, Nancy; Li, Xin; Urban, Alexander; ...

2014-12-17

Increasing lithium content is shown to be a successful strategy for designing new cathode materials. In layered Li xNi 2–4x/3Sb x/3O 2 (x = 1.00–1.15), lithium excess improves both discharge capacity and capacity retention at 1C. Structural studies disclose a complex nanostructure pattern of Li–Sb and Ni–Sb ordering where the interface between these domains forms the correct local configuration for good lithium mobility. The <1 nm Li–Sb stripe domains and their interfaces thereby effectively act as nanohighways for lithium diffusion.

Band Tailing and Deep Defect States in CH 3NH 3Pb(I 1–xBr x) 3 Perovskites As Revealed by Sub-Bandgap Photocurrent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutter-Fella, Carolin M.; Miller, D. Westley; Ngo, Quynh P.

Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. In this paper, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH 3NH 3Pb(I 1–xBr x) 3/TiO 2/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (E u) over the full halide composition space. The Urbach energies are 15–23 meV, lower than those for most semiconductors with similar bandgaps (especially with E g > 1.9 eV). Intentional aging of CH 3NH 3Pb(I 1–xBrmore » x) 3 for up to 2300 h, reveals no change in E u, despite the appearance of the PbI 2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH 3NH 3PbI 3 or mixed CH 3NH 3Pb(I 1–xBr x) 3 compositions, respectively. Finally, the study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH 3NH 3Pb(I 1–xBr x) 3 alloys.« less

Band Tailing and Deep Defect States in CH 3NH 3Pb(I 1–xBr x) 3 Perovskites As Revealed by Sub-Bandgap Photocurrent

DOE PAGES

Sutter-Fella, Carolin M.; Miller, D. Westley; Ngo, Quynh P.; ...

2017-02-15

Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. In this paper, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH 3NH 3Pb(I 1–xBr x) 3/TiO 2/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (E u) over the full halide composition space. The Urbach energies are 15–23 meV, lower than those for most semiconductors with similar bandgaps (especially with E g > 1.9 eV). Intentional aging of CH 3NH 3Pb(I 1–xBrmore » x) 3 for up to 2300 h, reveals no change in E u, despite the appearance of the PbI 2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH 3NH 3PbI 3 or mixed CH 3NH 3Pb(I 1–xBr x) 3 compositions, respectively. Finally, the study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH 3NH 3Pb(I 1–xBr x) 3 alloys.« less

Composition dependence of superconductivity in YBa2(Cu(3-x)Al(x))O(y)

NASA Technical Reports Server (NTRS)

Bansal, N. P.

1993-01-01

Eleven different compositions in the system YBa2(Cu(3-x)Al(x))O(y) (x = 0 to 0.3) have been synthesized and characterized by electrical resistivity measurements, powder X-ray diffraction, and scanning electron microscopy. The superconducting transition temperature T sub c (onset) was almost unaffected by the presence of alumina due to its limited solubility in YBa2Cu3O(7-x). However, T sub c(R = 0) gradually decreased, and the resistive tails became longer with increasing Al2O3 concentration. This was probably due to formation of BaAl2O4 and other impurity phases from chemical decomposition of the superconducting phase by reaction with Al2O3.

Crystal structures of the new ternary stannides La{sub 3}Mg{sub 4−x}Sn{sub 2+x} and LaMg{sub 3−x}Sn{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solokha, P., E-mail: pavlo.solokha@unige.it; De Negri, S.; Minetti, R.

2016-01-15

Synthesis and structural characterization of the two new lanthanum–magnesium–stannides La{sub 3}Mg{sub 4−x}Sn{sub 2+x} (0.12≤x≤0.40) and LaMg{sub 3−x}Sn{sub 2} (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La{sub 3}Mg{sub 4−x}Sn{sub 2+x} phase crystallizes in the hexagonal Zr{sub 3}Cu{sub 4}Si{sub 2} structure type (P6¯2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg{sub 3–x}Sn{sub 2} phase is the second representative of the trigonal LaMg{sub 3−x}Ge{sub 2}more » type, which is a superstructure of the LaLi{sub 3}Sb{sub 2} structure type (P3¯1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg{sub 3−x}Sn{sub 2} off-stoichiometry from the geometrical point of view. Structural relationships between the La–Mg–Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB{sub 2}-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism. - Graphical abstract: Crystal structure of LaMg{sub 3−x}Sn{sub 2} viewed along the (001) direction together with the puckered layer of Mg and Sn atoms hosting Mg2, Mg3 and vacancy □. - Highlights: • Crystal structures of the new La{sub 3}Mg{sub 4−x}Sn{sub 2+x} and LaMg{sub 3−x}Sn{sub 2} phases were determined. • The off-stoichiometry of LaMg{sub 3−x}Sn{sub 2} was discussed from geometrical point of view. • Structural relations between the known La–Mg–Sn phases were established. • The studied

Thermodynamical study of boron doped CeX{sub 3} (X=Pd, Rh)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Ramesh; Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com

2016-05-06

The structural, electronic, thermal, and optical properties of cubic non magnetic CeX{sub 3}(X=Pd, Rh) compounds which crystallize in the Au{sub 3}Cu structure have been studied using the projected augmented wave (PAW) method within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential. In this paper we have calculated the band structure which are interpreted using the density of states. The optical properties such as extinction coefficients clearly illustrate the changes in CeX{sub 3} due to intercalation of boron. Lattice instability is observed in CePd{sub 3}B from the calculated dynamical properties.

Relation of Giant Thermo-EMF, Magnetothermo-EMF, Magnetoresistance, and Magnetization to Magnetic Impurity States in Manganites Nd(1- x)Sr x MnO3 and Sm(1- x)Sr x MnO3

NASA Astrophysics Data System (ADS)

Koroleva, L. I.; Batashev, I. K.; Morozov, A. S.; Balbashov, A. M.; Szymczak, H.; Slawska-Waniew, A.

2018-02-01

Thermo-EMF, magnetothermo-EMF, magnetoresistance, and magnetization of single-crystal samples of Nd(1- x)Sr x MnO3 and Sm(1- x)Sr x MnO3 with 0 ≤ x ≤ 0.3 have been studied experimentally. A sharp increase in the thermo-EMF and giant magnetothermo-EMF and magnetoresistance has been observed near the Curie point T C in compounds with 0.15 ≤ x ≤ 0.3. At the same time, no peculiarities have been found in compositions with x = 0. Since compounds with x > 0 consist of ferromagnetic clusters of the ferron type that reside in an antiferromagnetic A-type matrix, this means that the sharp increase in the thermo-EMF near T C is caused by ferrons. Indeed, the disappearance of ferrons due to a magnetic field or heating above T C leads to an abrupt decrease in the thermo-EMF. Therefore, thermo-EMF in alloyed magnetic semiconductors has been determined by the impurity concentration and the sample volume.

A Multiwavelength Study of Cygnus X-3

NASA Technical Reports Server (NTRS)

McCollough, M. L; Robinson, C. R.; Zhang, S. N.; Paciesas, W. S.; Harmon, B. A.; Hjellming, R. M.; Rupen, M.; Waltman, E. B.; Foster, R. S.; Ghigo, F. D.

1997-01-01

We present a global comparison of long term observations of the hard X-ray (20-100 keV), soft X-ray (1.5-12 keV), infrared (1-2 micron) and radio (2.25, 8.3 and 15 GHz) bands for the unusual X-ray binary Cygnus X-3. Data were obtained in the hard X-ray band from CGRO/BATSE, in the soft X-ray band from Rossi Xray Timing Explorer (RXTE)/ASM, in the radio band from the Green Bank Interferometer and Ryle Telescope and in the infrared band from various ground based observatories. Radio flares, quenched radio states and quiescent radio emission can all be associated with changes in the hard and soft X-ray intensity. The injection of plasma into the radio jet is directly related to changes in the hard and soft X-ray emission. The infrared observations are examined in the context of these findings.

Diffuse phase ferroelectric vs. Polomska transition in (1-x) BiFeO3-(x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) solid solutions

NASA Astrophysics Data System (ADS)

Jha, Pardeep K.; Jha, Priyanka A.; Singh, Vikash; Kumar, Pawan; Asokan, K.; Dwivedi, R. K.

2015-01-01

Investigations on the solid solutions (1-x) BiFeO3 - (x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) in the temperature range 300-750 K show colossal permittivity behavior and the occurrence of diffuse phase ferroelectric transition along with frequency dependent anomaly which disappears at temperature ˜450 K. For x = 0.3, these anomalies have been verified through differential scanning calorimetry and dielectric/impedance/conductivity measurements. The occurrence of peak in pyrocurrent (dPs/dT) vs. T plots also supports phase transition. With the increasing x, transition temperature decreases and diffusivity increases. This anomaly is absent at high frequencies (>100 kHz) in conductivity plots, indicating Polomska like surface phase transition, which is supported by modulus study.

Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Neimet, Yu. Yu.; Kranjčec, M.; Solomon, A. M.; Orliukas, A. F.; Kežionis, A.; Kazakevičius, E.; Šalkus, T.

2014-01-01

Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300-400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.

Pressure dependence of the monoclinic phase in (1–x)Pb(Mg 1/3Nb 2/3)O 3-xPbTiO₃ solid solutions

DOE PAGES

Ahart, Muhtar; Sinogeikin, Stanislav; Shebanova, Olga; ...

2012-12-26

We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1–x)Pb(Mg 1/3Nb 2/3)O 3-xPbTiO₃ (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm⁻¹ starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropicmore » phase boundary region (x=0.33–0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.« less

Compositional dependence of magnetic anisotropy in chemically synthesized Co3- x Fe x O4 (0 ≤ x ≤ 2)

NASA Astrophysics Data System (ADS)

Hayashi, Kensuke; Yamada, Keisuke; Shima, Mutsuhiro

2018-01-01

Magnetic anisotropy of Co3- x Fe x O4 (CFO, 0 ≤ x ≤ 2) thin-film and powder samples prepared by a sol-gel method has been investigated as a function of Fe composition x. Structural analyses by X-ray diffraction show that CFO powder samples exhibit diffraction peaks associated with the spinel structure when x < 2, while CFO thin-film samples with thickness of 130-510 nm yield the peaks when 0 ≤ x ≤ 2. CFO thin-film samples are highly (111)-oriented with the Lotgering factor greater than 0.9 when 0.6 ≤ x ≤ 1.3. The magnetic anisotropy constant K 1 of CFO powder samples estimated from their room-temperature hysteresis loops yields a minimum when x = 0.9. Relatively large in-plane magnetic anisotropy (K eff = 5.7 × 105 erg/cm3) is observed for the CFO thin-film sample when x = 1.3. With increasing x, the magnetic easy axis of the spinel CFO changes from 〈111〉 to 〈100〉 when x = 0.9.

Differential Thermal Analysis of Hg(1-x)Mn(x)Te Alloys in the X=0 to 0.3 Range

NASA Technical Reports Server (NTRS)

Price, M. W.; Scripa, R. N.; Szofran, F. R.; Lehoczky, S. L.; Su, C-H

1998-01-01

Understanding the experimental conditions necessary for the development of radial and axial compositional homogeneity in directionally solidified Hg(0.89)Mn(0.11)Te(MMT) crystals has been difficult due to the lack of segregation coefficient data on the Hg(1-x)Mn(x)Te alloy system in the X = 0 to 0.3 composition range. Determining segregation coefficient data from the available Hg(1-x)Mn(x)Te alloy phase equilibria data is not practical due to discrepancies in the shape of the reported solidus and liquidus curves in the X = 0 to 0.3 range. To resolve these discrepancies and to obtain segregation coefficient data which can be used to understand homogeneity in directionally solidified MMT crystals, the solidus and liquidus temperatures of seven Hg(1-x)Mn(x)Te alloys in the X = 0 to 0.3 range were determined using differential thermal analysis (DTA). The Hg(1-x)Mn(x)Te phase diagram constructed for the X = 0 to 0.3 range of this alloy system from the DTA measurements clarifies the shape of the solidus and liquidus curves in this range. The segregation coefficient for the Hg(1-x)Mn(x)Te system was found to vary from 5 to 4.4 as the solidus composition increased from 0-30 atomic percent MnTe. This information will be useful in the analysis of axial and radial homogeneity of directionally solidified MMT crystals.

Effect of the Sm content on the structure and electrochemical properties of La 1.3 - xSm xCaMg 0.7Ni 9 ( x = 0-0.3) hydrogen storage alloys

NASA Astrophysics Data System (ADS)

Tang, Rui; Wei, Xuedong; Liu, Yongning; Zhu, Changchun; Zhu, Jiewu; Yu, Guang

La 1.3 - xSm xCaMg 0.7Ni 9 (x = 0-0.3) hydrogen storage alloys were prepared by inductive melting and the effect of the Sm content on the structure and electrochemical properties was investigated in the paper. The Sm substitution for La in La 1.3 - xSm xCaMg 0.7Ni 9 (x = 0-0.3) alloys does not change the main phase structure (the rhombohedral PuNi 3-type structure), but leads to a shrinkage of unit cell and a decrease of hydrogen storage capacity. With the increase of the Sm content in the alloys, the maximum discharge capacity of electrode decreases from 400.2 (x = 0) to 346.6 mAh g -1 (x = 0.3), but the high-rate dischargeability and cycling stability is improved. After 100 cycles, the capacity retention rate increases from 75 (x = 0) to 85% (x = 0.3).

Photoelectrical properties of sprayed In2-2xAl2xS3- 3yO3y alloys

NASA Astrophysics Data System (ADS)

Bhira, L.; Belgacem, S.; Bernede, J. C.

2002-11-01

In2-2xAl2xS3-3yO3y alloys have been prepared on Pyrextrademark glass substrates by the spray pyrolysis technique. The shape of the photoconductivity spectrums Iph (hnu) and the variations Iph (f ) and Iph (V) allow us to understand the conduction mechanism and the photocarriers' recombination. For low compositions (xless-than-or-equal0.2), Iph)(V parabolic variation shows that this conduction is limited by the space charge zone in accordance with Child's law (Iph[is proportional to]V2) [N. F. Mott and R. W. Gurney, Electronics Processes in Ionic Crystals (Oxford, New York, 1940), p. 463]. The exploitation of such variation shows that the density of the trap centers increases with the composition. For x[greater-than-or-equal, slanted]0.4, the electrical conduction instead follows Ohm's law. In the same way, the analysis of an extension of Devore's model [Phys. Rev. 102, 86 (1956)] as (Iph)hnu2 versus photon energy hnu shows an increase of the band gap energy Eg according to a parabolic profile. On the other hand, for low compositions (x=0,0.05,0.1,0.2), the conductivity study as a function of the temperature presents a deviation to Arrhenius's law in the intermediate temperature domain ranging from 80 to 330 K. Moreover, in this domain, the study of the activation energy Ea)(T according to Werner's model [Solid State Phenom. 37, 214 (1994)] supposing potential fluctuations at the grain boundaries yields the values of the barrier high phib and the standard deviation sigma][phi. From these results, we see that Eg increased versus x and that the electrical properties are essentially preserved for low aluminum concentration films. This may be due to a minor presence of an Al2O3 phase for such deposits.

Students' "Uses and Gratification Expectancy" Conceptual Framework in Relation to E-Learning Resources

ERIC Educational Resources Information Center

Mondi, Makingu; Woods, Peter; Rafi, Ahmad

2007-01-01

This paper presents the systematic development of a "Uses and Gratification Expectancy" (UGE) conceptual framework which is able to predict students' "Perceived e-Learning Experience." It is argued that students' UGE as regards e-learning resources cannot be implicitly or explicitly explored without first examining underlying communication…

Boron Substituted Na 3 V 2 (P 1 -x B x O 4 ) 3 Cathode Materials with Enhanced Performance for Sodium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Pu; Wang, Xiaofang; Wang, Tianshi

The development of excellent performance of Na-ion batteries remains great challenge owing to the poor stability and sluggish kinetics of cathode materials. Herein, B substituted Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) as stable cathode materials for Na-ion battery is presented. A combined experimental and theoretical investigations on Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) are undertaken to reveal the evolution of crystal and electronic structures and Na storage properties associated with various concentration of B. X-ray diffraction results indicate that the crystal structure of Na 3V 2P 3–xB xO 12 (0more » ≤ x ≤ 1/3) consisted of rhombohedral Na 3V 2(PO 4) 3 with tiny shrinkage of crystal lattice. X-ray absorption spectra and the calculated crystal structures all suggest that the detailed local structural distortion of substituted materials originates from the slight reduction of V–O distances. Na 3V 2P 3-1/6B 1/6O 12 significantly enhances the structural stability and electrochemical performance, giving remarkable enhanced capacity of 100 and 70 mAh g -1 when the C-rate increases to 5 C and 10 C. Spin-polarized density functional theory (DFT) calculation reveals that, as compared with the pristine Na 3V 2(PO 4) 3, the superior electrochemical performance of the substituted materials can be attributed to the emergence of new boundary states near the band gap, lower Na + diffusion energy barriers, and higher structure stability.« less

Structural and Na-ion conduction characteristics of Na 3 PS x Se 4-x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bo, Shou-Hang; Wang, Yan; Ceder, Gerbrand

The recent discovery of the isostructrual cubic Na 3PS 4 and Na 3PSe 4 as fast Na-ion conductors provided a general structural framework for the exploration of new sodium superionic conductors. In this work, we systematically investigated the structures and ionic conduction characteristics of a series of compounds with the general chemical formula of Na 3PS xSe 4-x. Synthesis of Na 3PS 4 under different conditions (e.g., temperature, reaction vessel, mass of the precursors) reveals the reactivity of the precursors with the reaction tubes, producing different polymorphs. X-ray diffraction studies on the solid solution phases Na 3PS xSe 4-x more » identified a tetragonal-to-cubic phase transition with increasing Se concentration. This observation is consistent with the computed stability of the tetragonal and cubic polymorphs, where the energy difference between the two polymorphs becomes very close to zero in Se-rich compositions. Furthermore, ab initio molecular dynamic simulations suggest that the fast Na-ion conduction in Na 3PS xSe 4-x may not be causally related with the symmetry or the composition of these phases. The formation of defects, instead, enables fast Na-ion conduction in this class of materials.« less

Enhanced room temperature multiferroic characteristics in hexagonal LuFe1-xNixO3 (x = 0 - 0.3) nanoparticles

NASA Astrophysics Data System (ADS)

Suresh, Pittala; Vijaya Laxmi, K.; Anil Kumar, P. S.

2018-02-01

Single phase polycrystalline LuFe1-xNixO3 (x = 0 - 0.3) (LFNO) nanoparticles are synthesized using the sol-gel method. X-ray diffraction measurements revealed that the crystal structure of Ni-doped samples is isomorphic to hexagonal LuFeO3 (LFO). The phase pure hexagonal P63cm symmetry exists for 0 ≤ x ≤ 0.3, and the secondary phases appear for x ≥ 0.4. Raman spectra show a shift in the mode frequency corresponding to the changes in Lu-O and Fe-O bond lengths with Ni doping. An enhancement in the magnetization is observed for LFNO throughout the temperature range (400-5 K) compared to LFO. The antiferromagnetic state of LFO becomes ferrimagnetic at low temperatures, and a net magnetization is observed at room temperature with Ni doping. As Ni concentration increases, a systematic increment in the ferroelectric polarization is observed. This enhancement in polarization is believed to be due to the distortion in FeO5 cage, while the improvement in magnetic properties is due to the induced magnetic interactions, caused by the Fe-Ni interactions on the triangular lattice with Ni doping in LuFeO3.

Heteroepitaxial growth of Ba1 - xSrxTiO3/YBa2Cu3O7 - x by plasma-enhanced metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Chern, C. S.; Liang, S.; Shi, Z. Q.; Yoon, S.; Safari, A.; Lu, P.; Kear, B. H.; Goodreau, B. H.; Marks, T. J.; Hou, S. Y.

1994-06-01

Epitaxial Ba1-xSrxTiO3(BST)/YBa2Cu3O7-x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that <100> oriented Ba1-xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7-x layers. The leakage current density through the Ba1-xSrxTiO3 films was about 10-7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1-xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1-xSrxTiO3/YBa2Cu3O7-x heterostructure indicated that conductive oxide materials with close lattice to Ba1-xSrxTiO3 can be good candidates for the bottom electrode.

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

PubMed

Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

2011-11-01

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

Thermodynamic properties of Ba{sub 1-x}La{sub x}CoO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaur, N. K., E-mail: srl-nkgaur@yahoo.co.in; Thakur, Rasna, E-mail: rasnathakur@yahoo.com; Thakur, Rajesh K., E-mail: thakur.rajesh2009@gmail.com

2016-05-06

We have predicted the thermodynamic behavior of Ba{sub 1-x}La{sub x}CoO{sub 3} family at temperature 1K≤T≤300K using the Modified Rigid Ion Model (MRIM). The specific heat of BaCoO{sub 3} with La doping in the perovskite structure at A-site has been reported. Also, the cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ{sub D}), specific heat (C) and Gruneisen parameter (γ) of Ba{sub 1-x}La{sub x}CoO{sub 3} compounds are discussed.

X-15 #3 in flight (USAF Photo)

NASA Technical Reports Server (NTRS)

1960-01-01

This U.S. Air Force photo shows the X-15 ship #3 (56-6672) in flight over the desert in the 1960s. Ship #3 made 65 flights during the program, attaining a top speed of Mach 5.65 and a maximum altitude of 354,200 feet. Only 10 of the 12 X-15 pilots flew Ship #3, and only eight of them earned their astronaut wings during the program. Robert White, Joseph Walker, Robert Rushworth, John 'Jack' McKay, Joseph Engle, William 'Pete' Knight, William Dana, and Michael Adams all earned their astronaut wings in Ship #3. Neil Armstrong and Milton Thompson also flew Ship #3. In fact, Armstrong piloted Ship #3 on its first flight, on 20 December 1961. On 15 November 1967, Ship #3 was launched over Delamar Lake, Nevada with Maj. Michael J. Adams at the controls. The vehicle soon reached a speed of Mach 5.2, and a peak altitude of 266,000 feet. During the climb, an electrical disturbance degraded the aircraft's controllability. Ship #3 began a slow drift in heading, which soon became a spin. Adams radioed that the X-15 'seems squirrelly' and then said 'I'm in a spin.' Through some combination of pilot technique and basic aerodynamic stability, Adams recovered from the spin and entered an inverted Mach 4.7 dive. As the X-15 plummeted into the increasingly thicker atmosphere, the Honeywell adaptive flight control system caused the vehicle to begin oscillating. As the pitching motion increased, aerodynamic forces finally broke the aircraft into several major pieces. Adams was killed when the forward fuselage impacted the desert. This was the only fatal accident during the entire X-15 program. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot

On the growth of CH3NH3PbI3-xClx single crystal and characterization

NASA Astrophysics Data System (ADS)

Su, J.; Wang, W. F.; Lei, Y.; Zhang, L.; Xu, L. H.; Wang, D.; Lu, D.; Bai, Y.

2018-05-01

In this paper, CH3NH3PbI3-xClx crystal was grown by solution cooling method with CH3NH3I and PbCl2 as raw materials. Lead compounds and CH3NH3PbI3-xClx crystal with size about 6 mm × 4 mm × 2 mm were obtained. The chemical reactions with different CH3NH3I/PbCl2 ratios were analyzed. XPS shows the content of chlorine in CH3NH3PbI3-xClx is about 0.91%. PXRD, FT-IR, Raman and absorbance spectra were used to study the structure and optical properties of CH3NH3PbI3-xClx by comparing with CH3NH3PbI3 crystal. The CH3NH3PbI3-xClx crystal grown is of tetragonal structure with the lattice constants a = b = 8.8165 Å, c = 12.7920 Å and the bandgap value of 1.57 eV.

Mo(3)Sb(7-x)Te(x) for Thermoelectric Power Generation

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey; Gascoin, Frank S.; Rasmussen, Julia

2009-01-01

Compounds having compositions of Mo(3)Sb(7-x)Te(x) (where x = 1.5 or 1.6) have been investigated as candidate thermoelectric materials. These compounds are members of a class of semiconductors that includes previously known thermoelectric materials. All of these compounds have complex crystalline and electronic structures. Through selection of chemical compositions and processing conditions, it may be possible to alter the structures to enhance or optimize thermoelectric properties.

Perovskite-Type Oxides. I. Structural, Magnetic, and Morphological Properties of LaMn 1- xCu xO 3 and LaCo 1- xCu xO 3 Solid Solutions with Large Surface Area

NASA Astrophysics Data System (ADS)

Porta, Piero; De Rossi, Sergio; Faticanti, Marco; Minelli, Giuliano; Pettiti, Ida; Lisi, Luciana; Turco, Maria

1999-09-01

Perovskite-type compounds of general formula LaMn1-xCuxO3 and LaCo1-xCuxO3 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by calcining the citrate gel precursors at 823, 923, and 1073 K. The decomposition of the precursors was followed by thermal analysis and the oxides were investigated by means of elemental analysis (atomic absorption and redox titration), X-ray powder diffraction, BET surface area, X-ray absorption (EXAFS and XANES), electron microscopy (SEM and TEM), and magnetic susceptibility. LaMn1-xCuxO3 samples are perovskite-like single phases up to x=0.6. At x=0.8 CuO and La2CuO4 phases are present in addition to perovskite. For x=1.0 the material is formed by CuO and La2CuO4. Mn(IV) was found by redox titration in all Mn-based perovskite samples, its fraction increasing with the increase in copper content. EXAFS and XANES analyses confirmed the presence of Mn(IV). Cation vacancies in equal amounts in the 12-coordinated A and octahedral B sites are suggested in the samples with x=0.0 and x=0.2, while for x=0.6 anionic vacancies are present. Materials with sufficiently high surface area (22-36 m2 g-1 for samples fired at 923 K and 14-22 m2 g-1 for those fired at 1073 K) were obtained. Crystallite sizes in the ranges 390-500 and 590-940 Å for samples calcined at 923 and 1073 K, respectively, were determined from the FWHM of the (102) X-ray diffraction peak. TEM patterns of LaMnO3 showed almost regular hexagonal prismatic crystals with sizes of the same order of magnitude (800 Å) of those drawn from X-ray diffraction, while no evidence of defect clustering was drawn out from TEM and electron diffraction images. For the sample with x=0.6, TEM and electron diffraction patterns revealed perturbation of the structure. Magnetic susceptibility studies show a ferromagnetic behavior that decreases with increase in x. LaCo1-xCuxO3 samples are perovskite-like single phases up to x=0.2. For x=0.4 a small amount of La2CuO4, in addition to perovskite, is detected. For

Thermoelectric properties of Ca(1-x-y)Dy(x)CeyMnO3 for power generation.

PubMed

Park, K; Lee, G W; Jung, J; Kim, S-J; Lim, Y-S; Choi, S-M; Seo, W-S

2011-08-01

The sintered Ca(1-x-y)Dy(x)CeyMnO3 bodies were a single phase with a perovskite structure without any impurity phases. The calculated crystallite sizes of the Ca(1-x-y)Dy(x)CeyMnO3 were in the range of 43.3 to 63.3 nm. The composition significantly affected their microstructural and thermoelectric characteristics. The doped Dy led to both an increase in the electrical conductivity as well as the absolute value of the Seebeck coefficient, resulting in an enhanced power factor. The highest power factor (5.1 x 10(-4) Wm(-1) K(-2)) was obtained for Ca(0.8)Dy(0.2)MnO3 at 800 degrees C. In this study, we systematically discussed the thermoelectric properties of the Ca(1-x-y)Dy(x)CeyMnO3, with respect to the substitution of Dy and/or Ce for Ca.

Direct evidence for double-exchange coupling in Ru- substituted La0.7Pb0.3Mn 1 - x Ru x O3, 0.0 <= x <= 0.4

NASA Astrophysics Data System (ADS)

Sundar Manoharan, S.; Sahu, R. K.; Rao, M. L.; Elefant, D.; Schneider, C. M.

2002-08-01

The La0.7Pb0.3Mn 1 - x Ru x O3 (0.0 <= x <= 0.4) system shows an innate relationship between Mn and Ru ions by a unique double-exchange mediated transport behavior. This is exonerated by the coexistence of Tp and Tc (range 330 K 245 K for 0.0 <= x <= 0.4). For Ru > 30%, the hole carrier mass influences the transport property. X-ray absorption spectra suggest that the Tc-Tp match is due to the transport mediated by the Mn3+/Mn4+ leftrightarrow Ru4+/Ru5+ redox pair and also due to the broad low-spin Ru:4d conduction band. For x > 0.2, T < 0.5Tc obeys a modified variable-range hopping model, where kT0 propto (M/Ms)2, suggesting a random magnetic potential which localizes the charge carriers.

Long-term studies with the Ariel 5 ASM. I - Hercules X-1, Vela X-1, and Centaurus X-3

NASA Technical Reports Server (NTRS)

Holt, S. S.; Kaluzienski, L. J.; Boldt, E. A.; Serlemitsos, P. A.

1979-01-01

Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1, and Cen X-3 accumulated with the Ariel 5 All-Sky Monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the 35 day variation of Her X-1, for which we can refine the period to 34.875 plus or minus 0.030 days. No such longer-term periodicity less than 200 days is observed from Vela X-1. The 26.6 days low-state recurrence period for Cen X-3 is not observed, but a 43.0 day candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

ASCA measurements of the grain-scattered X-ray halos of eclipsing massive X-ray binaries: Vela X-1 and Centaurus X-3

NASA Technical Reports Server (NTRS)

Woo, Jonathan W.; Clark, George W.; Day, Charles S. R.; Nagase, Fumiaki; Takeshima, Toshiaki

1994-01-01

We have measured the decaying dust-scattered X-ray halo of Cen X-3 during its binary eclipse with the ASCA solid-state imaging spectrometer (SIS). The surface brightness profile (SBP) of the image in the low-energy band (0.5-3 keV) lies substantially above the point-spread function (PSF) of the X-ray telescope, while the SBP in the high-energy band (5-10 keV) exhibits no significant deviation. By contrast, the SBPs of Vela X-1 during its eclipse are consistent with the PSF in both the low- and high-energy bands -- strong evidence that a dust halo is indeed present in Cen X-3. Accordingly, we modeled the SBP of Cen X-3 taken from six consecutive time segments under the principal assumptions that the dust is distributed uniformly along a segment of the line of sight, the grains have a power-law size distribution, and the low-energy source flux was the same function of orbital phase before as during our observation. The best-fit set of parameters included a grain density value of 1.3 g/cu cm, substanially less than the density of 'astronomical silicate.' This result supports the idea that interstellar grains are 'fluffy' aggregates of smaller solid particles. We attribute the failure to detect a halo of Vela X-1 during its eclipse phase to extended strong circumsource absorption that probably occurred before the eclipse and allowed the halo to decay away before the observation began.

Magnetic properties of x(Fe2O3).(100-x)[P2O5.Li2O] and x(Fe2O3).(100-x)[P2O5.CaO] glass systems

NASA Astrophysics Data System (ADS)

Andronache, Constantin; Racolta, Dania; Ardelean, Gheorghe

2017-12-01

Magnetic properties of x(Fe2O3).(100-x)[P2O5 .Li2O] and x(Fe2O3).(100-x)[P2O5 .CaO] with 0 < x ≤ 50 mol % were investigated using magnetic susceptibility measurements. The both glass systems were prepared in the same condition. The valence states and the distribution of iron ions in the glass matrix depend on the Fe2O3 content. For the P2O5.CaO glass matrix with x≤35mol%, the data revealed iron ions as isolated or participating in dipole-dipole interaction. For x > 35 mol% an antiferromagnetic coupling is observed. For the P2O5.Li2O glass matrix, the iron ions behave magnetically similarly as in other oxide glasses, but concentration of Fe2O3 over which magnetic superexchange interactions occur is lower. The absolute magnitude of θp values increases when content of Fe2O3 are increased. If the content of the magnetic ions is increased in the glass, the exchange integral increased and as a result the magnitude of the θP increases.

Intricate Li-Sn Disorder in Rare-Earth Metal-Lithium Stannides. Crystal Chemistry of RE3Li4- xSn4+ x (RE = La-Nd, Sm; x < 0.3) and Eu7Li8- xSn10+ x ( x ≈ 2.0).

PubMed

Suen, Nian-Tzu; Guo, Sheng-Ping; Hoos, James; Bobev, Svilen

2018-05-07

Reported are the syntheses, crystal structures, and electronic structures of six rare-earth metal-lithium stannides with the general formulas RE 3 Li 4- x Sn 4+ x (RE = La-Nd, Sm) and Eu 7 Li 8- x Sn 10+ x . These new ternary compounds have been synthesized by high-temperature reactions of the corresponding elements. Their crystal structures have been established using single-crystal X-ray diffraction methods. The RE 3 Li 4- x Sn 4+ x phases crystallize in the orthorhombic body-centered space group Immm (No. 71) with the Zr 3 Cu 4 Si 4 structure type (Pearson code oI22), and the Eu 7 Li 8- x Sn 10+ x phase crystallizes in the orthorhombic base-centered space group Cmmm (No. 65) with the Ce 7 Li 8 Ge 10 structure type (Pearson code oC50). Both structures can be consdered as part of the [RESn 2 ] n [RELi 2 Sn] m homologous series, wherein the structures are intergrowths of imaginary RESn 2 (AlB 2 -like structure type) and RELi 2 Sn (MgAl 2 Cu-like structure type) fragments. Close examination the structures indicates complex occupational Li-Sn disorder, apparently governed by the drive of the structure to achieve an optimal number of valence electrons. This conclusion based on experimental results is supported by detailed electronic structure calculations, carried out using the tight-binding linear muffin-tin orbital method.

Probing structural changes in Ca(1-x)Nd2x/3TiO3 ceramics by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Lowndes, Robert; Deluca, Marco; Azough, Feridoon; Freer, Robert

2013-01-01

Ceramics in the system Ca(1-x)Nd2x/3TiO3, intended for mobile communication applications, exhibit grossly non-linear variations in microwave dielectric properties with composition. There is evidence of a structural transition and the formation of vacancies on the A-site of the perovskite structure. High density, single phase perovskite Ca(1-x)Nd2x/3TiO3 ceramics have been prepared by the mixed oxide route. Raman spectroscopy was used to investigate the structural variations, which impact on dielectric properties. The Raman spectra show that with increasing Nd content, there is a transition from an ordered structure, to a disordered arrangement of cations and vacancies, and back to an ordered arrangement in Ca0.1Nd0.6TiO3. A structural phase transition from orthorhombic Pbnm to monoclinic C2/m coincides with the order-disorder transition at Ca0.1Nd0.6TiO3. Polarized Raman spectroscopy facilitated the assignment of the Raman modes and investigation of the role of importance of domain structures. Large variation in the plane angles was attributed to differences in domain structures. Differences in the angular dependence of the Raman modes with Nd content reflect changes in the preferred orientation of the domains from lamellar twins, to wedge shaped and back to lamellar twins.

The incommensurately modulated(1 - x)Ta 2O 5· xWO 3, 0 ≤ x ≤ 0.267 solid solution

NASA Astrophysics Data System (ADS)

Schmid, Siegbert; Withers, Ray L.; Thompson, John G.

1992-08-01

The phase(1 - x)Ta 2O 5 · WO 3, 0 ≤ x ≤ 0.267 has been studied by X-ray powder diffraction and transmission electron microscopy. It was previously described as an infinite series of anion-deficient, α-UO 3-type "line phases," with compositions resulting from intergrowths of different blocks made up by small numbers of α-UO 3-type cells. More correctly(1 - x)Ta 2O 5· xWO 3, 0 ≤ x ≤ 0.267 is described as an incommensurately modulated structure with a linearly composition-dependent primary modulation wave-vector qprim. = qb*. The underlying orthorhombically distorted α-UO 3-type parent structure has space group symmetry Cmmm ( a ≈ 6.20-6.14, b ≈ 3.66, c ≈ 3.89-3.85Å). Characteristic extinction conditions imply a superspace group symmetry of P : Cmmmm : s, -1,1. The four previously reported crystal structures in the solid solution field are examined by means of apparent valence calculations. Crystal chemical reasons are proposed for the width of the composition range,0 ≤ x ≤ 0.267, observed for the title phase.

Trapping charges at grain boundaries and degradation of CH3NH3Pb(I1-x Br x )3 perovskite solar cells.

PubMed

Nguyen, Bich Phuong; Kim, Gee Yeong; Jo, William; Kim, Byeong Jo; Jung, Hyun Suk

2017-08-04

The electrical properties of CH 3 NH 3 Pb(I 1-x Br x ) 3 (x = 0.13) perovskite materials were investigated under ambient conditions. The local work function and the local current were measured using Kelvin probe force microscopy and conductive atomic force microscopy, respectively. The degradation of the perovskite layers depends on their grain size. As the material degrades, an additional peak in the surface potential appears simultaneously with a sudden increase and subsequent relaxation of the local current. The potential bending at the grain boundaries and the intragrains is the most likely reason for the change of the local current surface of the perovskite layers. The improved understanding of the degradation mechanism garnered from this study helps pave the way toward an improved photo-conversion efficiency in perovskite solar cells.

Trapping charges at grain boundaries and degradation of CH3NH3Pb(I1-x Br x )3 perovskite solar cells

NASA Astrophysics Data System (ADS)

Phuong Nguyen, Bich; Kim, Gee Yeong; Jo, William; Kim, Byeong Jo; Jung, Hyun Suk

2017-08-01

The electrical properties of CH3NH3Pb(I1-x Br x )3 (x = 0.13) perovskite materials were investigated under ambient conditions. The local work function and the local current were measured using Kelvin probe force microscopy and conductive atomic force microscopy, respectively. The degradation of the perovskite layers depends on their grain size. As the material degrades, an additional peak in the surface potential appears simultaneously with a sudden increase and subsequent relaxation of the local current. The potential bending at the grain boundaries and the intragrains is the most likely reason for the change of the local current surface of the perovskite layers. The improved understanding of the degradation mechanism garnered from this study helps pave the way toward an improved photo-conversion efficiency in perovskite solar cells.

Thermoelectric transport properties of Ca3Co4- x Ni x O9+ δ oxide materials

NASA Astrophysics Data System (ADS)

Park, K.; Cha, J. S.; Nam, S. W.; Choi, S.-M.; Seo, W.-S.; Lee, S.; Lim, Y. S.

2016-01-01

Nano-sized Ca3Co4- x Ni x O9+ δ (0 ≤ x ≤ 0.3) thermoelectric powders are synthesized by using the solution combustion method, with aspartic acid as a combustion fuel. The synthesized Ca3Co4- x Ni x O9+ δ nano-sized powders exhibit a spherical-like shape and a smooth surface. Higher Ni content results in a smaller grain size and a higher porosity, resulting in a decrease in the electrical conductivity. However, the Seebeck coefficient of Ni-added Ca3Co4O9 is much higher than that of Ca3Co4O9. The highest power factor (1.4 × 10-4 Wm-1K-2), which is more than nine times larger than that of Ca3Co4O9, is attained for Ca3Co0.38Ni0.2O9+ δ at 800 °C. The addition of a small amount of Ni is highly effective in improving the thermoelectric properties of Ca3Co4O9. We believe that Ca3Co4- x Ni x O9+ δ is a potential p-type thermoelectric material for renewable energy conversion.

Concurrent ionic migration and electronic effects at the memristive TiO x /La1/3Ca2/3MnO3-x interface

NASA Astrophysics Data System (ADS)

Román Acevedo, W.; Ferreyra, C.; Sánchez, M. J.; Acha, C.; Gay, R.; Rubi, D.

2018-03-01

The development of reliable redox-based resistive random-access memory devices requires understanding and disentangling concurrent effects present at memristive interfaces. We report on the fabrication and electrical characterization of TiO x /La1/3Ca2/3MnO3-x microstructured interfaces and on the modeling of their memristive behavior. We show that a careful tuning of the applied external electrical stimuli allows controlling the redox process between both layers, obtaining multilevel non-volatile resistance states. We simulate the oxygen vacancies dynamics at the interface between both oxides, and successfully reproduce the experimental electrical behavior after the inclusion of an electronic effect, related to the presence of an n-p diode at the interface. The formation of the diode is due to the n- and p-character of TiO x and La1/3Ca2/3MnO3-x , respectively. Our analysis indicates that oxygen vacancies migration between both layers is triggered after the diode is polarized either in forward mode or in reverse mode above breakdown. Electrical measurements at different temperatures suggest that the diode can be characterized as Zener-type. The advantages of our junctions for their implementation in RRAM devices are finally discussed.

Superconductivity and charge density wave in ZrTe 3–xSe x

DOE PAGES

Zhu, Xiangde; Ning, Wei; Li, Lijun; ...

2016-06-02

Charge density wave (CDW), the periodic modulation of the electronic charge density, will open a gap on the Fermi surface that commonly leads to decreased or vanishing conductivity. On the other hand superconductivity, a commonly believed competing order, features a Fermi surface gap that results in infinite conductivity. Here we report that superconductivity emerges upon Se doping in CDW conductor ZrTe 3 when the long range CDW order is gradually suppressed. Superconducting critical temperature T c(x) in ZrTe 3–xSe x (0 ≤ x ≤ 0.1) increases up to 4 K plateau for 0.04 ≤ x ≤ 0.07. Further increase inmore » Se content results in diminishing T c and filametary superconductivity. The CDW modes from Raman spectra are observed in x = 0.04 and 0.1 crystals, where signature of ZrTe 3 CDW order in resistivity vanishes. As a result, the electronic-scattering for high T c crystals is dominated by local CDW fluctuations at high temperatures, the resistivity is linear up to highest measured T = 300 K and contributes to substantial in-plane anisotropy.« less

Lithiation-induced zinc clustering of Zn 3, Zn 12, and Zn 18 units in Zintl-like Ca ~30Li 3+xZn 60-x (x=0.44-1.38)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Qisheng

2014-11-14

Zinc clusters are not common for binary intermetallics with relatively low zinc content, but this work shows that zinc clustering can be triggered by lithiation, as exemplified by Ca ~30Li 3+xZn 60-x, P6/mmm, Z = 1, which can be directly converted from CaZn 2. Two end members of the solid solution (x = 0.44 and 1.38) were established and structurally characterized by single-crystal X-ray diffraction analyses: Ca 30Li 3.44(6)Zn59.56(6), a = 15.4651(9) Å, c = 9.3898(3) Å; Ca 30.45(2)Li 4.38(6)Zn 58.62(6), a = 15.524(3) Å, c = 9.413(2) Å. The structures of Ca ~30Li 3+xZn 60-x feature a condensed anionicmore » network of Zn3 triangles, lithium-centered Zn12 icosahedra, and arachno-(Zn,Li)18 tubular clusters that are surrounded respectively by Ca 14, Ca 20, and Ca 30 polyhedra. These polyhedra share faces and form a clathrate-like cationic framework. The specific occupation of lithium in the structure is consistent with theoretical “coloring” analyses. Analysis by the linear muffin-tin orbital (LMTO) method within the atomic sphere approximation reveals that Ca ~30Li 3+xZn 60-x is a metallic, Zintl-like phase with an open-shell electronic structure. The contribution of Ca–Zn polar covalent interactions is about 41%.« less

Did LMC X-3 Undergo a 'Her X-1-like' Anomalous Low State?

NASA Technical Reports Server (NTRS)

Boyd, Patricia t.

2008-01-01

The black hole X-ray binary LMC X-3 has been monitored by the Rossi X-ray Timing Explorer (RXTE) from its launch to the present by the All-Sky Monitor (ASM). This well-sampled light curve is supplemented by frequent pointed observations with the PCA and HEXTE instruments which provide improved sensitivity, time resolution and spectral information. The long-term X-ray luminosity of the system is strongly modulated on timescales of hundreds of days. The mean 2-10 kev X-ray flux varies by a factor of more than 100 during this long-term cycle. This variability has been attributed to the precession of a bright, tilted, and warped accretion disk---the mechanism also invoked to explain the 35-day super-orbital period in the X-ray binary pulsar system Her X-1. The ASM light curve displays a unique episode, starting in December 2003, during which LMC X-3 displayed a very low, nearly constant flux, for about 80 days. This is markedly different from the typical low-flux excursions in LMC X-3, which smoothly evolve toward and then away from a minimum flux on about a 10-day time scale. The character of the long-term variability, as measured by amplitude and characteristic time scale, is not the same after this long low state as it was before. Similar shifts in long-term period and amplitude are seen after the so-called "anomalous low states" in Her X-1, when the 35-day X-ray modulation ceases for an unpredictable length of time. These similar shifts in the long-term amplitude and timescale in the two systems suggests they share a similar mechanism which gives rise to the anomalous low states

Influence of Fe doped on the magnetocaloric behavior of La_{{2}/{3}} Ca_{{1}/{3}} Mn1-x Fe x O3 compounds: a Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Alzate-Cardona, J. D.; Barco-Rios, H.; Restrepo-Parra, E.

2018-02-01

The magnetocaloric behavior of La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 for x  =  0.00, 0.02, 0.03, 0.05, 0.07, 0.08 and 0.10 under the influence of an external magnetic field was simulated and analyzed. Simulations were carried out using the Monte Carlo method and the classical Heisenberg model under the Metropolis algorithm. These mixed valence manganites are characterized by having three types of magnetic ions corresponding to Mn4+≤ft(S=\\frac{3}{2}\\right) , which are bonded with Ca2+ , and Mneg3+ and Mneg\\prime3+ (S=2) , related to La3+ . The Fe ions were randomly included, replacing Mn ions. With this model, the magnetic entropy change, Δ S , in an isothermal process was determined. -Δ Sm showed maximum peaks around the paramagnetic-ferromagnetic transition temperature, which depends on Fe doping. Relative cooling power was computed for different Fe concentrations varying the magnetic applied field. Our model and results show that the Fe doping decreases the magnetocaloric effect in the La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3, making this a bad candidate for magnetic refrigeration. The strong dependence of the magnetocaloric behavior on Fe doping and the external magnetic field in La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 can boost these materials for the future technological applications.

Structural and Na-ion conduction characteristics of Na 3PS xSe 4–x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bo, Shou -Hang; Wang, Yan; Ceder, Gerbrand

The recent discovery of the isostructrual cubic Na 3PS 4 and Na 3PSe 4 as fast Na-ion conductors provided a general structural framework for the exploration of new sodium superionic conductors. In this work, we systematically investigated the structures and ionic conduction characteristics of a series of compounds with the general chemical formula of Na 3PS xSe 4–x. Synthesis of Na 3PS 4 under different conditions (e.g., temperature, reaction vessel, mass of the precursors) reveals the reactivity of the precursors with the reaction tubes, producing different polymorphs. X-ray diffraction studies on the solid solution phases Na 3PS xSe 4–x identifiedmore » a tetragonal-to-cubic phase transition with increasing Se concentration. This observation is consistent with the computed stability of the tetragonal and cubic polymorphs, where the energy difference between the two polymorphs becomes very close to zero in Se-rich compositions. Furthermore, ab initio molecular dynamic simulations suggest that the fast Na-ion conduction in Na 3PS xSe 4–x may not be causally related with the symmetry or the composition of these phases. The formation of defects, instead, enables fast Na-ion conduction in this class of materials.« less

Structural and Na-ion conduction characteristics of Na 3PS xSe 4–x

DOE PAGES

Bo, Shou -Hang; Wang, Yan; Ceder, Gerbrand

2016-05-19

The recent discovery of the isostructrual cubic Na 3PS 4 and Na 3PSe 4 as fast Na-ion conductors provided a general structural framework for the exploration of new sodium superionic conductors. In this work, we systematically investigated the structures and ionic conduction characteristics of a series of compounds with the general chemical formula of Na 3PS xSe 4–x. Synthesis of Na 3PS 4 under different conditions (e.g., temperature, reaction vessel, mass of the precursors) reveals the reactivity of the precursors with the reaction tubes, producing different polymorphs. X-ray diffraction studies on the solid solution phases Na 3PS xSe 4–x identifiedmore » a tetragonal-to-cubic phase transition with increasing Se concentration. This observation is consistent with the computed stability of the tetragonal and cubic polymorphs, where the energy difference between the two polymorphs becomes very close to zero in Se-rich compositions. Furthermore, ab initio molecular dynamic simulations suggest that the fast Na-ion conduction in Na 3PS xSe 4–x may not be causally related with the symmetry or the composition of these phases. The formation of defects, instead, enables fast Na-ion conduction in this class of materials.« less

Cygnus X-3 Returns to an Active State

NASA Astrophysics Data System (ADS)

McCollough, Michael L.; Koljonen, Karri; Gurwell, Mark A.; Trushkin, Sergei; Pooley, Guy G.

2017-08-01

Cygnus X-3 is a well-known microquasar composed of a mass-donating Wolf-Rayet star and a compact object. Recently, Cygnus X-3 has been in a quiescent state for an extended period of time (2011-2016) but returned to an active state on two occasions during 2016/2017 including quenched/hypersoft states, gamma-ray emission, and major radio flares. During these two periods of activity, we undertook multi-wavelength observing campaigns with observations in the radio (RATAN-600, AMI-LA, Metsähovi), submillimeter (SMA, EHT), X-ray (Swift/XRT, MAXI), hard X-ray (Swift/BAT, NuSTAR), and gamma-ray (AGILE, Fermi, VERITAS). At the peak of the major radio flare in April 2017 observations were made with VERITAS (TeV), NuSTAR (hard X-ray), and the Event Horizon Telescope (submillimeter). In this presentation, I will review these observing campaigns and the insights they provide about Cygnus X-3.

Coexistence of two electronic nano-phases on a CH 3NH 3PbI 3–xCl x surface observed in STM measurements

DOE PAGES

Yost, Andrew J.; Pimachev, Artem; Ho, Chun -Chih; ...

2016-10-10

Scanning tunneling microscopy is utilized to investigate the local density of states of a CH 3NH 3PbI 3-xCl x perovskite in cross-sectional geometry. Two electronic phases, 10-20 nm in size, with different electronic properties inside the CH 3NH 3PbI 3-xCl x perovskite layer are observed by the dI/ dV mapping and point spectra. A power law dependence of the dI/dV point spectra is revealed. In addition, the distinct electronic phases are found to have preferential orientations close to the normal direction of the film surface. Density functional theory calculations indicate that the observed electronic phases are associated with local deviationmore » of I/Cl ratio, rather than different orientations of the electric dipole moments in the ferroelectric phases. Furthermore, by comparing the calculated results with experimental data we conclude that phase A (lower contrast in dI/dV mapping at -2.0 V bias) contains a lower I/Cl ratio than that in phase B (higher contrast in dI/dV).« less

Distinct human α(1,3)-fucosyltransferases drive Lewis-X/sialyl Lewis-X assembly in human cells.

PubMed

Mondal, Nandini; Dykstra, Brad; Lee, Jungmin; Ashline, David J; Reinhold, Vernon N; Rossi, Derrick J; Sackstein, Robert

2018-05-11

In humans, six α(1,3)-fucosyltransferases (α(1,3)-FTs: FT3/FT4/FT5/FT6/FT7/FT9) reportedly fucosylate terminal lactosaminyl glycans yielding Lewis-X (Le X ; CD15) and/or sialyl Lewis-X (sLe X ; CD15s), structures that play key functions in cell migration, development, and immunity. Prior studies analyzing α(1,3)-FT specificities utilized either purified and/or recombinant enzymes to modify synthetic substrates under nonphysiological reaction conditions or molecular biology approaches wherein α(1,3)-FTs were expressed in mammalian cell lines, notably excluding investigations using primary human cells. Accordingly, although significant insights into α(1,3)-FT catalytic properties have been obtained, uncertainty persists regarding their human Le X /sLe X biosynthetic range across various glycoconjugates. Here, we undertook a comprehensive evaluation of the lactosaminyl product specificities of intracellularly expressed α(1,3)-FTs using a clinically relevant primary human cell type, mesenchymal stem cells. Cells were transfected with modified mRNA encoding each human α(1,3)-FT, and the resultant α(1,3)-fucosylated lactosaminyl glycoconjugates were analyzed using a combination of flow cytometry and MS. The data show that biosynthesis of sLe X is driven by FTs-3, -5, -6, and -7, with FT6 and FT7 having highest potency. FT4 and FT9 dominantly biosynthesize Le X , and, among all FTs, FT6 holds a unique capacity in creating sLe X and Le X determinants across protein and lipid glycoconjugates. Surprisingly, FT4 does not generate sLe X on glycolipids, and neither FT4, FT6, nor FT9 synthesizes the internally fucosylated sialyllactosamine VIM-2 (CD65s). These results unveil the relevant human lactosaminyl glycans created by human α(1,3)-FTs, providing novel insights on how these isoenzymes stereoselectively shape biosynthesis of vital glycoconjugates, thereby biochemically programming human cell migration and tuning human immunologic and developmental processes. �

Synthesis and crystal structure of the solid solution Co3(SeO3)3-x(PO3OH)x(H2O) involving crystallographic split positions of Se4+ and P5+.

PubMed

Zimmermann, Iwan; Johnsson, Mats

2013-10-21

Three new cobalt selenite hydroxo-phosphates laying in the solid solution Co3(SeO3)3-x(PO3OH)x(H2O), with x = 0.8, x = 1.0, and x = 1.2 are reported. Single crystals were obtained by hydrothermal synthesis and the crystal structure was determined by single crystal X-ray diffraction. The structure can be described as a 3D framework having selenite and hydroxo-phosphate groups protruding into channels in the crystal structure. Se(4+) and P(5+) share a split position in the structure so that either SeO3 groups having a stereochemically active lone pair or tetrahedrally coordinated PO3OH groups are present. The OH-group is thus only present when the split position is occupied by P(5+). The crystal water is coordinated to a cobalt atom and TG and IR measurements show that the water and hydroxyl groups leave the structure at unusually high temperatures (>450 °C). Magnetic susceptibility measurements show antiferromagnetic coupling below 16 K and a magnetic moment of 4.02(3) μB per Co atom was observed.

X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.; Darbro, W. A.; Elsner, R. F.; Williams, A. C.; Kahn, S. M.; Grindlay, J. E.; Naranan, S.; Sutherland, P. G.

1983-01-01

A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.

Tunable White-Light Emission in Single-Cation-Templated Three-Layered 2D Perovskites (CH 3 CH 2 NH 3 ) 4 Pb 3 Br 10–x Cl x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Lingling; Wu, Yilei; Stoumpos, Constantinos C.

Two-dimensional (2D) hybrid halide perovskites come as a family (B) 2(A) n-1PbnX 3n+1 (B and A= cations; X= halide). These perovskites are promising semiconductors for solar cells and optoelectronic applications. Among the fascinating properties of these materials is white-light emission, which has been mostly observed in single-layered 2D lead bromide or chloride systems (n = 1), where the broad emission comes from the transient photoexcited states generated by self-trapped excitons (STEs) from structural distortion. Here we report a multilayered 2D perovskite (n = 3) exhibiting a tunable white-light emission. Ethylammonium (EA+) can stabilize the 2D perovskite structure in EA 4Pbmore » 3Br 10–xCl x (x = 0, 2, 4, 6, 8, 9.5, and 10) with EA + being both the A and B cations in this system. Because of the larger size of EA, these materials show a high distortion level in their inorganic structures, with EA4Pb3Cl10 having a much larger distortion than that of EA 4Pb 3Br 10, which results in broadband white-light emission of EA 4Pb 3Cl 10 in contrast to narrow blue emission of EA4Pb3Br10. The average lifetime of the series decreases gradually from the Cl end to the Br end, indicating that the larger distortion also prolongs the lifetime (more STE states). The band gap of EA 4Pb 3Br 10–xCl x ranges from 3.45 eV (x = 10) to 2.75 eV (x = 0), following Vegard’s law. First-principles density functional theory calculations (DFT) show that both EA 4Pb 3Cl 10 and EA 4Pb 3Br 10 are direct band gap semiconductors. The color rendering index (CRI) of the series improves from 66 (EA 4Pb 3Cl 10) to 83 (EA 4Pb 3Br 0.5Cl 9.5), displaying high tunability and versatility of the title compounds.« less

Magnetic, dielectric properties, and scaling behaviors of Aurivillius compounds Bi6-x/3Fe2Ti3-2x(WCo)xO18 (0 ≤ x ≤ 0.15)

NASA Astrophysics Data System (ADS)

Zuo, X. Z.; Yang, J.; Yuan, B.; Song, D. P.; Tang, X. W.; Zhang, K. J.; Zhu, X. B.; Song, W. H.; Dai, J. M.; Sun, Y. P.

2015-03-01

We investigate the structural, magnetic, dielectric properties, and scaling behaviors of Aurivillius compounds Bi6-x/3Fe2Ti3-2x(WCo)xO18 (0 ≤ x ≤ 0.15). The room-temperature weak ferromagnetism is observed for the W/Co co-doped samples. The results of the dielectric constant ɛr, complex impedance Z ″ , the dc conductivity σdc, and hopping frequency fH manifest that the dielectric relaxation of the x = 0 sample and the doped samples in the dielectric anomaly region (450-750 K) can be ascribed to the trap-controlled ac conduction around the doubly ionized oxygen vacancies and the localized hopping process of oxygen vacancies, respectively. The scaling behaviors reveal that the dynamic process of both electrons in the x = 0 sample and oxygen vacancies in the doped samples is temperature independent. The ferroelectric Curie-temperature Tc decreases slightly from 973 K to 947 K with increasing the doping level of W/Co. In addition, the dielectric loss exhibits a dielectric relaxation above 800 K with the rather large activation energies (1.95 eV ≤ Ea ≤ 2.72 eV).

Magnetic properties of Co 2 2+ Co 1 - x 3+ Fe x 3+ BO5 ( x = 0.10) single crystals with a ludwigite structure

NASA Astrophysics Data System (ADS)

Knyazev, Yu. V.; Kazak, N. V.; Bayukov, O. A.; Platunov, M. S.; Velikanov, D. A.; Bezmaternykh, L. N.; Ivanova, N. B.; Ovchinnikov, S. G.

2017-04-01

The investigation of mixed Co-Fe ludwigite single crystals shows that their magnetic properties are close to the magnetic properties of Fe3BO5 despite the predominance of cobalt ions. The magnetic properties of Co3 - x Fe x BO5 single crystals with x = 0.10 are studied in detail. Magnetometric measurements demonstrate a strong magnetic anisotropy with easy magnetization axis b, and the orbital magnetic moment of cobalt is in a frozen state. The detected temperature dependence of the absorption of Mössbauer spectra allowed us to determine the magnetic ordering temperature, which agrees with the results of magnetization measurements ( T C = 84 K).

On the physical parameters for Centaurus X-3 and Hercules X-1.

NASA Technical Reports Server (NTRS)

Mccluskey, G. E., Jr.; Kondo, Y.

1972-01-01

It is shown how upper and lower limits on the physical parameters of X-ray sources in Centaurus X-3 and Hercules X-1 may be determined from a reasonably simple and straightforward consideration. The basic assumption is that component A (the non-X-ray emitting component) is not a star collapsing toward its Schwartzschild radius (i.e., a black hole). This assumption appears reasonable since component A (the radius of the central occulting star) appears to physically occult component X. If component A is a 'normal' star, both observation and theory indicate that its mass is not greater than about 60 solar masses. The possibility in which component X is either a neutron star or a white dwarf is considered.

Effects of Sb Content (x) on (Bi(1-x)Sb(x))2Te3 Thermoelectric Thin Film Deposited by Effusion Cell Evaporator.

PubMed

Yong, Ho; Na, Sekwon; Gang, Jun-Gu; Jeon, Seong-Jae; Hyun, Seungmin; Lee, Hoo-Jeong

2015-10-01

This paper investigates the effects of the Sb content (x) on (Bi(1-x)Sb(x))2Te3 thermoelectric films with x changing widely from 0 (Sb2Te3) to 1 (Bi2Te3). First, the XRD analysis discloses that with the Sb content (x) increasing, the phase changed gradually from Bi2Te3 to Sb2Te3 as Sb atoms replaced substitutionally Bi atoms. Further microstructure analysis reveals that an extensive grain growth occurred during post-annealing for the samples with high Sb contents. According to the measurement of electrical and thermoelectric properties, the polarity of the charge carrier and Seebeck coefficient switched n-type to p-type in the range of x = 0.45~0.63. For the n-type samples, the power factor is highest when x = 0.18 around 46.01 μW/K(2) whereas Sb2Te3, for the p-type samples, shows the highest value, 62.48 μW/K(2)cm.

Simulation calculations of efficiencies and silicon consumption for CH3NH3PbI3-x-y Br x Cl y /crystalline silicon tandem solar cells

NASA Astrophysics Data System (ADS)

Zhang, Lili; Xie, Ziang; Tian, Fuyang; Qin, Guogang

2017-04-01

Much attention has been paid to two-subcell tandem solar cells (TSCs) with crystalline silicon (c-Si) as the bottom cell (TSC-Si). Previous works have pointed out that the optimal band gap, E g, of the top cell material for a TSC-Si is around 1.75 eV. With a tunable E g and better stability than MAPbI3 (MA  =  CH3NH3), MAPbI3-x-y Br x Cl y is a promising candidate for the top cell material of a TSC-Si. In this work, calculations concerning the E g, refractive index and extinction coefficient of MAPbI3-x-y Br x Cl y are performed using first-principles calculations including the spin-orbit coupling (SOC) effect. MAPbI3-x-y Br x Cl y with five sets of x and y, which have a E g around 1.75 eV, are obtained. On this basis, absorption of the perovskite top cell is calculated applying the Lambert-Beer model (LBM) and the transfer matrix model (TMM), respectively. Considering the Auger recombination in the c-Si bottom cell and radiation coupling between the two subcells, the efficiencies for MAPbI3-x-y Br x Cl y /c-Si TSCs with the five sets of x and y are calculated. Among them, the MAPbI2.375Br0.5Cl0.125/c-Si TSC achieves the highest efficiency of 35.1% with a 440 nm thick top cell and 50 µm thick c-Si when applying the LBM. When applying the TMM, the highest efficiency of 32.5% is predicted with a 580 nm thick MAPbI2.375Br0.5Cl0.125 top cell and 50 µm thick c-Si. Compared with the limiting efficiency of 27.1% for a 190 µm thick c-Si single junction solar cell (SC), the MAPbI2.375Br0.5Cl0.125/c-Si TSC shows a superior performance of high efficiency and low c-Si consumption.

Magnetization reversal properties of Pr{sub 1-x}(Gd/Nd){sub x}MnO{sub 3} (x=0.3, 0.5, 0.7)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswas, Sanjay; Pal, Sudipta, E-mail: sudipta.pal@rediffmail.com; Bose, Esa

2015-06-24

We report measurements of the temperature dependent magnetic properties of single phase orthorhombic perovskites system associated with space group Pbnm compounds Pr{sub 1-x}(Gd/Nd){sub x}MnO{sub 3} (x=0.3, 0.5, 0.7). Magnetic properties radically changes with the doping of Gd or Nd. A magnetization reversal is observed below the Neel temperature (T{sub N}), in DC magnetization measurements (at 50 Oe) in the doped compounds. The reversal of magnetization may be due to the antiparallel coupling between the two magnetic sublattices (|Pr+ Gd/ Nd | and Mn). The hysteresis plot taken at 50K indicates a ferrimagnetic characteristic and existence of spin canting of ionsmore » in the magnetic sublattices.« less

Use of N-acetylcysteine plus simethicone to improve mucosal visibility during upper GI endoscopy: a double-blind, randomized controlled trial.

PubMed

Monrroy, Hugo; Vargas, Jose Ignacio; Glasinovic, Esteban; Candia, Roberto; Azúa, Emilio; Gálvez, Camila; Rojas, Camila; Cabrera, Natalia; Vidaurre, Josefa; Álvarez, Natalia; González, Jessica; Espino, Alberto; González, Robinson; Parra-Blanco, Adolfo

2018-04-01

Upper GI endoscopy (UGE) is essential for the diagnosis of gastrointestinal diseases. Mucus and bubbles may decrease mucosal visibility. The use of mucolytics could improve visualization. Our aim was to determine whether premedication with simethicone or simethicone plus N-acetylcysteine is effective in improving visibility during UGE. This was a randomized, double-blinded, placebo-controlled trial with 2 control groups: no intervention and water 100 mL (W); and 3 intervention groups: simethicone 200 mg (S); S + N-acetylcysteine (NAC) 500 mg (S+NAC500); and S + NAC 1000 mg (S+NAC1000). The solution was ingested 20 minutes before UGE. Gastric visibility was evaluated in 4 segments with a previously described scale. A score of less than 7 points was defined as adequate visibility (AV). Water volume was used to improve visibility, and adverse reactions were evaluated as a secondary outcome. Multiple group comparison was performed using non-parametric one-way analysis of variance (ANOVA). Two hundred thirty patients were included in the study, 68% female, mean age 49 years. The most common indication for UGE was epigastric pain/dyspepsia (33%). AV was more frequent in the S+NAC500 and S+NAC1000 groups (65% and 67%) compared with no intervention (44%, P = .044) and water (41%, P = .022). The gastric total visibility scale (TVS) was significantly better in the S+NAC500 and S+NAC1000 groups compared with water (P = .03 and P = .008). Simethicone was not different from no intervention and water. S+NAC1000 required less water volume to improve visibility. No adverse reactions from the study drugs were observed. Premedication with S+NAC500 and S+NAC1000 improves visibility during UGE. The use of simethicone did not show improvements in gastric visibility. TVS was worse in patients using water alone. (Clinical trial registration number: NCT 01653171.). Copyright © 2018 American Society for Gastrointestinal Endoscopy. All rights reserved.

Structure Evolution and Reactivity of the Sc(2- x)V xO3+δ (0 ≤ x ≤ 2.0) System.

PubMed

Lussier, Joey A; Simon, Fabian J; Whitfield, Pamela S; Singh, Kalpana; Thangadurai, Venkataraman; Bieringer, Mario

2018-05-07

Solid oxide fuel cells (SOFCs) are solid-state electrochemical devices that directly convert chemical energy of fuels into electricity with high efficiency. Because of their fuel flexibility, low emissions, high conversion efficiency, no moving parts, and quiet operation, they are considered as a promising energy conversion technology for low carbon future needs. Solid-state oxide and proton conducting electrolytes play a crucial role in improving the performance and market acceptability of SOFCs. Defect fluorite phases are some of the most promising fast oxide ion conductors for use as electrolytes in SOFCs. We report the synthesis, structure, phase diagram, and high-temperature reactivity of the Sc (2- x) V x O 3+δ (0 ≤ x ≤ 2.00) oxide defect model system. For all Sc (2- x) V x O 3.0 phases with x ≤ 1.08 phase-pure bixbyite-type structures are found, whereas for x ≥ 1.68 phase-pure corundum structures are reported, with a miscibility gap found for 1.08 < x < 1.68. Structural details obtained from the simultaneous Rietveld refinements using powder neutron and X-ray diffraction data are reported for the bixbyite phases, demonstrating a slight V 3+ preference toward the 8b site. In situ X-ray diffraction experiments were used to explore the oxidation of the Sc (2- x) V x O 3.0 phases. In all cases ScVO 4 was found as a final product, accompanied by Sc 2 O 3 for x < 1.0 and V 2 O 5 when x > 1.0; however, the oxidative pathway varied greatly throughout the series. Comments are made on different synthesis strategies, including the effect on crystallinity, reaction times, rate-limiting steps, and reaction pathways. This work provides insight into the mechanisms of solid-state reactions and strategic guidelines for targeted materials synthesis.

Stabilized wide bandgap MAPbBr xI 3-x perovskite by enhanced grain size and improved crystallinity

DOE PAGES

Hu, Miao; Bi, Cheng; Yuan, Yongbo; ...

2015-12-07

In this study, the light instability of CH 3NH 3PbI xBr 3–x has been raised one of the biggest challenges for its application in tandem solar cells. Here we show that an improved crystallinity and grain size of CH 3NH 3PbI xBr 3–x films could stabilize these materials under one sun illumination, improving both the efficiency and stability of the wide-bandgap perovskite solar cells.

Tuning Perpendicular Magnetic Anisotropy by Oxygen Octahedral Rotations in ( La 1 – x Sr x MnO 3 ) / ( SrIrO 3 ) Superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Di; Flint, Charles L.; Balakrishnan, Purnima P.

Here, perpendicular magnetic anisotropy (PMA) plays a critical role in the development of spintronics, thereby demanding new strategies to control PMA. Here we demonstrate a conceptually new type of interface induced PMA that is controlled by oxygen octahedral rotation. In superlattices comprised of La 1–xSr xMnO 3 and SrIrO 3, we find that all superlattices (0 ≤ x ≤ 1) exhibit ferromagnetism despite the fact that La 1–xSr xMnO 3 is antiferromagnetic for x > 0.5. PMA as high as 4 × 10 6 erg/cm 3 is observed by increasing x and attributed to a decrease of oxygen octahedral rotationmore » at interfaces. We also demonstrate that oxygen octahedral deformation cannot explain the trend in PMA. These results reveal a new degree of freedom to control PMA, enabling discovery of emergent magnetic textures and topological phenomena.« less

Tuning Perpendicular Magnetic Anisotropy by Oxygen Octahedral Rotations in ( La 1 – x Sr x MnO 3 ) / ( SrIrO 3 ) Superlattices

DOE PAGES

Yi, Di; Flint, Charles L.; Balakrishnan, Purnima P.; ...

2017-08-14

Here, perpendicular magnetic anisotropy (PMA) plays a critical role in the development of spintronics, thereby demanding new strategies to control PMA. Here we demonstrate a conceptually new type of interface induced PMA that is controlled by oxygen octahedral rotation. In superlattices comprised of La 1–xSr xMnO 3 and SrIrO 3, we find that all superlattices (0 ≤ x ≤ 1) exhibit ferromagnetism despite the fact that La 1–xSr xMnO 3 is antiferromagnetic for x > 0.5. PMA as high as 4 × 10 6 erg/cm 3 is observed by increasing x and attributed to a decrease of oxygen octahedral rotationmore » at interfaces. We also demonstrate that oxygen octahedral deformation cannot explain the trend in PMA. These results reveal a new degree of freedom to control PMA, enabling discovery of emergent magnetic textures and topological phenomena.« less

Origin of giant dielectric permittivity and weak ferromagnetic behavior in (1-x)LaFeO3-xBaTiO3 (0.0 ≤ x ≤ 0.25) solid solutions

NASA Astrophysics Data System (ADS)

Sreenivasu, T.; Tirupathi, P.; Prabahar, K.; Suryanarayana, B.; Chandra Mouli, K.

The solid solutions of (1-x) LaFeO3-xBaTiO3 (0.0≤x≤0.25) have been synthesized successfully by the conventional solid-state reaction method. Room temperature (RT) X-ray diffraction studies reveal the stabilization of orthorhombic phase with Pbnm space group. Complete solubility in the perovskite series was demonstrated up to x=0.25. The dielectric permittivity shows colossal dielectric constant (CDC) at RT. The doping of BaTiO3 in LaFeO3 exhibit pronounced CDC up to a composition x=0.15, further it starts to decrease. The frequency-dependent dielectric loss exhibits polaronic conduction, which can attribute to presence of multiple valence of iron. The relaxation frequency and polaronic conduction mechanism was shifted towards RT as function of x. Moreover, large magnetic moment with weak ferromagnetic behavior is observed in doped LaFeO3 solid solution, which might be the destruction of spin cycloid structure due to insertion of Ti in Fe-O-Fe network of LaFeO3.

Phase development in a U-7 wt.% Mo vs. Al-7 wt.% Ge diffusion couple

NASA Astrophysics Data System (ADS)

Perez, E.; Keiser, D. D.; Sohn, Y. H.

2013-10-01

Fuel development for the Reduced Enrichment for Research and Test Reactors (RERTR) program has demonstrated that U-Mo alloys in contact with Al develop interaction regions with phases that have poor irradiation behavior. The addition of Si to the Al has been considered with positive results. In this study, compositional modification is considered by replacing Si with Ge to determine the effect on the phase development in the system. The microstructural and phase development of a diffusion couple of U-7 wt.% Mo in contact with Al-7 wt.% Ge was examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectroscopy. The interdiffusion zone developed a microstructure that included the cubic-UGe3 phase and amorphous phases. The UGe3 phase was observed with and without Mo and Al solid solution developing a (U,Mo)(Al,Ge)3 phase.

Experimental and numerical study on transverse piezoelectricity of xBiInO3-(1 - x)PbTiO3 films by multilayer cantilevers

NASA Astrophysics Data System (ADS)

Sun, Ke-xue; Zhang, Shu-yi; Shui, Xiu-ji; Wasa, Kiyotaka

2018-02-01

The effective transverse piezoelectric coefficient of the piezoelectric films xBiInO3-(1 - x)PbTiO3 (x = 0,0.10,0.15,0.20) were studied experimentally and numerically by multilayer cantilevers. The xBiInO3-(1 - x)PbTiO3 thin films were deposited on (101)SrRuO3/(100)Pt/(100)MgO substrates and then covered with Pt electrode by RF-magnetron sputtering method. In experiments, the tip vibration amplitudes of the cantilevers for different x of the films were measured, in which the optimized compositions for maximizing the tip vibration can be found. Meanwhile, based on the bending model of multilayer piezoelectric cantilevers, the tip-deflection and transverse piezoelectricity of the cantilevers were simulated by COMSOL software. By comparing the experimental and numerical results, both are in agreement very well, and the mechanism of the optimized transverse piezoelectricity of the cantilevers was proposed finally.

Structural and ferroelectric phase evolution in [KNbO3]1-x[BaNi1/2Nb1/2O3-δ]x (x = 0, 0.1)

NASA Astrophysics Data System (ADS)

Hawley, Christopher; Wu, Liyan; Xiao, Geoffrey; Grinberg, Ilya; Rappe, Andrew; Davies, Peter; Spanier, Jonathan

The phase transition evolution for [KNbO3]1-x[BaNi1/2Nb1/2O3-δ]x (x=0, 0.1) is determined via complementary dielectric constant and Raman scattering measurements. Raman scattering by optical phonons over the range of 100-1000 cm-1 for -190°C < T < 600°C reveals six discernible zone-center optical phonon modes. They are assigned to structural and ferroelectric phases in the solid solution x = 0.1 and compared with those for end member x = 0 and with the results of temperature-dependent dielectric permittivity. Rigorous peak fitting analyses of spectra collected from the solid solution and end member indicate structural and ferroelectric phase transition temperatures that are quite close to those for the KNbO3 end member. Remarkably, despite the inclusion of 5 atomic Work supported by US ARO under W911NF-14-1-0500, NSF 1123696, and DoE BES under DE-FG02-07ER46431. Equipment acquisitions and computational support under DURIP and DoE NERSCC.

A gene stacking approach leads to engineered plants with highly increased galactan levels in Arabidopsis

DOE PAGES

Gondolf, Vibe M.; Stoppel, Rhea; Ebert, Berit; ...

2014-12-10

Background: Engineering of plants with a composition of lignocellulosic biomass that is more suitable for downstream processing is of high interest for next-generation biofuel production. Lignocellulosic biomass contains a high proportion of pentose residues, which are more difficult to convert into fuels than hexoses. Therefore, increasing the hexose/pentose ratio in biomass is one approach for biomass improvement. A genetic engineering approach was used to investigate whether the amount of pectic galactan can be specifically increased in cell walls of Arabidopsis fiber cells, which in turn could provide a potential source of readily fermentable galactose. Results: First it was tested ifmore » overexpression of various plant UDP-glucose 4-epimerases (UGEs) could increase the availability of UDP-galactose and thereby increase the biosynthesis of galactan. Constitutive and tissue-specific expression of a poplar UGE and three Arabidopsis UGEs in Arabidopsis plants could not significantly increase the amount of cell wall bound galactose. We then investigated co-overexpression of AtUGE2 together with the β-1,4-galactan synthase GalS1. Co-overexpression of AtUGE2 and GalS1 led to over 80% increase in cell wall galactose levels in Arabidopsis stems, providing evidence that these proteins work synergistically. Furthermore, AtUGE2 and GalS1 overexpression in combination with overexpression of the NST1 master regulator for secondary cell wall biosynthesis resulted in increased thickness of fiber cell walls in addition to the high cell wall galactose levels. Immunofluorescence microscopy confirmed that the increased galactose was present as β-1,4-galactan in secondary cell walls. Conclusions: This approach clearly indicates that simultaneous overexpression of AtUGE2 and GalS1 increases the cell wall galactose to much higher levels than can be achieved by overexpressing either one of these proteins alone. Moreover, the increased galactan content in fiber cells while

Changes in the Long-Term Intensity Variations in Cygnus X-2 and LMC X-3

NASA Astrophysics Data System (ADS)

Paul, B.; Kitamoto, S.; Makino, F.

2000-01-01

We report the detection of changes in the long-term intensity variations in two X-ray binaries, Cyg X-2 and LMC X-3. In this work, we have used the long-term light curves obtained with the All-Sky Monitors (ASMs) of the Rossi X-Ray Timing Explorer (RXTE), Ginga, Ariel 5, and Vela 5B and the scanning modulation collimator of HEAO 1. It is found that in the light curves of both the sources, obtained with these instruments at various times over the last 30 years, more than one periodic or quasi-periodic component is always present. The multiple prominent peaks in the periodograms have frequencies unrelated to each other. In Cyg X-2, RXTE-ASM data show strong peaks at 40.4 and 68.8 days, and Ginga-ASM data show strong peaks at 53.7 and 61.3 days. Multiple peaks are also observed in LMC X-3. The various strong peaks in the periodograms of LMC X-3 appear at 104, 169, and 216 days (observed with RXTE-ASM) and 105, 214, and 328 days (observed with Ginga-ASM). The present results, when compared with the earlier observations of periodicities in these two systems, demonstrate the absence of any stable long period. The 78 day periodicity detected earlier in Cyg X-2 was probably due to the short time base in the RXTE data that were used, and the periodicity of 198 days in LMC X-3 was due to a relatively short duration of observation with HEAO 1.

Luminescence in microcrystalline green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor

NASA Astrophysics Data System (ADS)

Panse, V. R.; Kokode, N. S.; Shinde, K. N.; Dhoble, S. J.

2018-03-01

Green emitting Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were synthesized via the wet chemical synthesis and the luminescent proprieties were studied when excited at 380 nm and present a dominant and strong green luminescence peak at 543 nm, due to D-F transition. The preparation of Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were confirmed by X-ray diffraction (XRD) results without any secondary or impurity phases. The size and morphology of the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor powders were further examined by scanning electron microscopy (SEM). Photoluminescence (PL) results have shown strongest green emission at 543 nm, which is originated due to 5D4-7F5 transition of Tb3+ ion, for the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor. The addition of concentration Tb3+ was greatly improved the photoluminescence properties of present phosphors. The present study suggests that the Li2Mg1-xZrO4:xTb3+ (0.1 ≤ x ≤ 2.0) phosphor is a strong candidate as a green component for phosphor-converted white light-emitting diodes (LEDs).

Positron annihilation study of Y 1- xPr xBa 2Cu 3O 7

NASA Astrophysics Data System (ADS)

Zhao, Y. G.; Cao, B. S.; Yu, W. Z.; Du, Z. H.; Wang, Y. J.; Luo, C. Y.; Hu, H.; Wang, S.; Yang, J. H.; He, A. S.; Gu, B. L.

1995-02-01

A positron annihilation study of Y 1- xPr xBa 2Cu 3O 7 was performed. The results showed that charge transfer between the CuO 2 planes and 1D CuO chains upon Pr doping, as proposed in the literature, did not occur. Pr doping suppressed the anomaly of positron annihilation lifetime near and below Tc which has been observed in YBa 2Cu 3O 7. The perfection of the 1D CuO chains was reduced by Pr doping and this may be partly responsible for the increase of resistivity with Pr doping, and finally the semiconducting behaviour of DC resistivity in Y 1- xPr xBa 2Cu 3O 7 with x > 0.6.

Tuning Perpendicular Magnetic Anisotropy by Oxygen Octahedral Rotations in ( La 1 - x Sr x MnO 3 ) / ( SrIrO 3 ) Superlattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Di; Flint, Charles L.; Balakrishnan, Purnima P.

Perpendicular magnetic anisotropy (PMA) plays a critical role in the development of spintronics, thereby demanding new strategies to control PMA. Here we demonstrate a conceptually new type of interface induced PMA that is controlled by oxygen octahedral rotation. In superlattices comprised of La1-xSrxMnO3 and SrIrO3, we find that all superlattices (0<=x<=1) exhibit ferromagnetism despite the fact that La1-xSrxMnO3 is antiferromagnetic for x>0.5. PMA as high as 4×10^6 erg/cm^3 is observed by increasing x and attributed to a decrease of oxygen octahedral rotation at interfaces. We also demonstrate that oxygen octahedral deformation cannot explain the trend in PMA. These results revealmore » a new degree of freedom to control PMA, enabling discovery of emergent magnetic textures and topological phenomena.« less

An ab initio study on BeX 3- superhalogen anions (X = F, Cl, Br)

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Skurski, Piotr

2002-06-01

The vertical electron detachment energies (VDE) of 10 BeX 3- (X = F, Cl, Br) anions were calculated at the outer valence Green function (OVGF) level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for BeF 3- system (7.63 eV). All negatively charged species possess the vertical electron detachment energies that are larger than 5.5 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the BeX 3- species on the ligand-central atom (Be-X) distance and on the partial atomic charge localized on Be was observed and discussed, as well as the other factors that may influence the electronic stability of such anions. In addition, the usefulness of the various theoretical treatments for estimating the VDEs of superhalogen anions was tested and analyzed.

On the optical search for Centaurus X-3.

NASA Technical Reports Server (NTRS)

Brucato, R. J.; Kristian, J.; Westphal, J. A.

1972-01-01

Elimination of the optical eclipsing binary LR Cen as a candidate for Cen X-3 on the basis of a real discrepancy of orbital periods. It is believed that the position coincidence of Wray 795 with Cen X-3 is not statistically significant.

Near-thermal reactions of Au(+)(1S,3D) with CH3X (X = F,Cl).

PubMed

Taylor, William S; Matthews, Cullen C; Hicks, Ashley J; Fancher, Kendall G; Chen, Li Chen

2012-01-26

Reactions of Au(+)((1)S) and Au(+)((3)D) with CH(3)F and CH(3)Cl have been carried out in a drift cell in He at a pressure of 3.5 Torr at both room temperature and reduced temperatures in order to explore the influence of the electronic state of the metal on reaction outcomes. State-specific product channels and overall two-body rate constants were identified using electronic state chromatography. These results indicate that Au(+)((1)S) reacts to yield an association product in addition to AuCH(2)(+) in parallel steps with both neutrals. Product distributions for association vs HX elimination were determined to be 79% association/21% HX elimination for X = F and 50% association/50% HX elimination when X = Cl. Reaction of Au(+)((3)D) with CH(3)F also results in HF elimination, which in this case is thought to produce (3)AuCH(2)(+). With CH(3)Cl, Au(+)((3)D) reacts to form AuCH(3)(+) and CH(3)Cl(+) in parallel steps. An additional product channel initiated by Au(+)((3)D) is also observed with both methyl halides, which yields CH(2)X(+) as a higher-order product. Kinetic measurements indicate that the reaction efficiency for both Au(+) states is significantly greater with CH(3)Cl than with CH(3)F. The observed two-body rate constant for depletion of Au(+)((1)S) by CH(3)F represents less than 5% of the limiting rate constant predicted by the average dipole orientation model (ADO) at room temperature and 226 K, whereas CH(3)Cl reacts with Au(+)((1)S) at the ADO limit at both room temperature and 218 K. Rate constants for depletion of Au(+)((3)D) by CH(3)F and CH(3)Cl were measured at 226 and 218 K respectively, and indicate that Au(+)((3)D) is consumed at approximately 2% of the ADO limit by CH(3)F and 69% of the ADO limit by CH(3)Cl. Product formation and overall efficiency for all four reactions are consistent with previous experimental results and available theoretical models.

Evaluation of band alignment of α-Ga2O3/α-(Al x Ga1‑ x )2O3 heterostructures by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Uchida, Takayuki; Jinno, Riena; Takemoto, Shu; Kaneko, Kentaro; Fujita, Shizuo

2018-04-01

The band alignment at an α-Ga2O3/α-(Al x Ga1‑ x )2O3 heterointerface, with different Al compositions (x), grown on a c-plane sapphire substrate was evaluated by X-ray photoelectron spectroscopy. The experimental results show that the heterointerface has the type-I band discontinuity with the valence band offsets of 0.090, 0.12, and 0.14 eV, and the conduction band offsets of 0.34, 0.79, and 1.87 eV, for x values of 0.1, 0.4, and 0.8, respectively. The small band offset for the valence band is attributed to the fact that the valence band of oxides is constituted by the localized O 2p level, which is dominated by the nature of oxygen atoms. The type-I band discontinuity is desirable for a variety of heterostructure devices.

Energy-band alignment of (HfO2)x(Al2O3)1-x gate dielectrics deposited by atomic layer deposition on β-Ga2O3 (-201)

NASA Astrophysics Data System (ADS)

Yuan, Lei; Zhang, Hongpeng; Jia, Renxu; Guo, Lixin; Zhang, Yimen; Zhang, Yuming

2018-03-01

Energy band alignments between series band of Al-rich high-k materials (HfO2)x(Al2O3)1-x and β-Ga2O3 are investigated using X-Ray Photoelectron Spectroscopy (XPS). The results exhibit sufficient conduction band offsets (1.42-1.53 eV) in (HfO2)x(Al2O3)1-x/β-Ga2O3. In addition, it is also obtained that the value of Eg, △Ec, and △Ev for (HfO2)x(Al2O3)1-x/β-Ga2O3 change linearly with x, which can be expressed by 6.98-1.27x, 1.65-0.56x, and 0.48-0.70x, respectively. The higher dielectric constant and higher effective breakdown electric field of (HfO2)x(Al2O3)1-x compared with Al2O3, coupled with sufficient barrier height and lower gate leakage makes it a potential dielectric for high voltage β-Ga2O3 power MOSFET, and also provokes interest in further investigation of HfAlO/β-Ga2O3 interface properties.

Electrical conductivity and thermoelectric power of La1- x Li x CoO3-δ (0 ≤ x ≤ 0.1) oxides

NASA Astrophysics Data System (ADS)

Vecherskii, S. I.; Konopel'ko, M. A.; Batalov, N. N.; Antonov, B. D.; Reznitskikh, O. G.; Yaroslavtseva, T. V.

2016-12-01

The influence of the concentration of lithium ions on the phase composition, the electrical conductivity, and the thermoelectric power of La1- x Li x CoO3-δ (0 ≤ x ≤ 0.1) oxides synthesized by the ceramic method has been investigated. It has been found that the region of the existence of perovskite-type La1- x Li x CoO3-δ solid solutions does not exceed x = 0.05. The doping with lithium leads to an increase in the electrical conductivity of single-phase samples in comparison with that of the LaCoO3 compound. As the temperature increases from 300 to 400 K, the thermoelectric power of the LaCoO3 compound increases from the negative to positive values and then decreases, but remains positive in the temperature range from 400 to 1020 K. The thermoelectric power of the other samples has a positive sign. The results obtained have been discussed based on the models of the electron density of states in LaCoO3 and La1- x Sr x CoO3-δ, proposed in the studies of Señarís-Rodríguez and Goodenough, as well as in the framework of the theory of non-crystalline materials, developed by Mott.

Structural and ferroelectric phase evolution in [KNbO3]1-x[BaNi1/2Nb1/2O3 -δ] x (x =0 ,0.1 )

NASA Astrophysics Data System (ADS)

Hawley, Christopher J.; Wu, Liyan; Xiao, Geoffrey; Grinberg, Ilya; Rappe, Andrew M.; Davies, Peter K.; Spanier, Jonathan E.

2017-08-01

The phase transition evolution for [KNbO3]1-x[BaNi1/2Nb1/2O3 -δ] x(x =0 ,0.1 ) is determined via complementary dielectric permittivity and Raman-scattering measurements. Raman scattering by optical phonons over the range of 100-1000 cm-1 for 83 K x =0.1 and compared with those for end member x =0 and with the results of temperature-dependent dielectric permittivity. Rigorous peak fitting analyses of spectra collected from the solid solution and end member indicate structural and ferroelectric phase transition temperatures that are close to those for the KNbO3 end member despite the inclusion of 5 atomic % of ferroelectrically inactive Ni cations. Density functional theory calculations were performed in the solid solution and end member using both cation displacement and Berry phase-based methods. Differences in the electronic and polar properties between the solid solution and the end member highlights local and nonlocal characteristics, which are discussed in relation to the experimental data.

Crystal Chemistry and Conductivity Studies in the System La 0.5+ x+ yLi 0.5-3 xTi 1-3 yCr 3 yO 3

NASA Astrophysics Data System (ADS)

Martínez-Sarrión, M. L.; Mestres, L.; Morales, M.; Herraiz, M.

2000-12-01

The stoichiometry polymorphism and electrical behavior of solid solutions La0.5+x+yLi0.5-3xTi1-3yCr3yO3 with perovskite-type structure were studied. Data are given in the form of a solid solutions triangle, phase diagrams, XRD patterns for the three polymorphs, A, β, and C, composition dependence of their lattice parameters, and ionic and electronic conductivity plots. Microstructure and composition were studied by SEM/EDS and electron probe microanalysis. These compounds are mixed conductors. Ionic conductivity decreased when the amount of lithium diminished and electronic conductivity increased with chromium content.

The effect of PO 4 doping on the luminescent properties of Sr 3-3zEu 2zV 2-xP xO 8

NASA Astrophysics Data System (ADS)

Cao, S.; Ma, Y. Q.; Yang, K.; Zhu, W. L.; Yin, W. J.; Zheng, G. H.; Wu, M. Z.; Sun, Z. Q.

2010-07-01

The luminescent properties of Sr 3V 2-xP xO 8 (0 ⩽ x ⩽ 2), Eu 3+ doped Sr 2.7Eu 0.2V 2-yP yO 8 (0 ⩽ y ⩽ 2) and Sr 3-3zEu 2zV 0.8P 1.2O 8 (0 < z ⩽ 0.3) have been investigated. For the Sr 3V 2-xP xO 8 (0 ⩽ x ⩽ 2) samples, the VO43- activation and emission intensity reaches the strongest as x = 1.6. For the Sr 2.7Eu 0.2V 2-yP yO 8 (0 ⩽ y ⩽ 2) samples, an appropriate amount of phosphorus doping enhances the Eu 3+ emission with the strongest emission occurring at y = 1.2. For the Sr 3-3zEu 2zV 0.8P 1.2O 8 (0 < z ⩽ 0.3) sample with the phosphorus content fixed at 1.2, it exhibits the most intense emission as Eu 3+ concentration reaches at z = 0.2. Our results indicate that the introduction of the PO43- plays an important role in the photoluminescence properties of the studied samples and the relevant mechanism has been discussed.

Positron lifetime studies of defect structures in Ba(1-x)K(x)BiO3

NASA Astrophysics Data System (ADS)

Obrien, J. C.; Howell, R. H.; Radousky, H. B.; Sterne, P. A.; Hinks, D. G.; Folkerts, T. J.; Shelton, R. N.

1990-12-01

Temperature-dependent positron lifetime experiments have been performed from room temperature to cryogenic temperatures on Ba(1-x)K(x)BiO3, for x = 0.4 and 0.5. From the temperature dependence of the positron lifetime in the normal state, we observe a clear signature of competition between separate defect populations to trap the positron. Theoretical calculations of lifetimes of free or trapped positrons have been performed on Ba(1-x)K(x)BiO3, to help identify these defects. Lifetime measurements separated by long times have been performed and evidence of aging effects in the sample defect populations is seen in these materials.

DFT analysis and FDTD simulation of CH3NH3PbI3-x Cl x mixed halide perovskite solar cells: role of halide mixing and light trapping technique

NASA Astrophysics Data System (ADS)

Saffari, Mohaddeseh; Mohebpour, Mohammad Ali; Rahimpour Soleimani, H.; Bagheri Tagani, Meysam

2017-10-01

Since perovskite solar cells have attracted a great deal of attention over the past few years, the enhancement of their optical absorption and current density are among the basic upcoming challenges. For this reason, first, we have studied the structural and optical properties of organic-inorganic hybrid halide perovskite CH3NH3PbI3 and the compounds doped by chlorine halogen CH3NH3PbI3-x Cl x in the cubic phase by using a density functional theory (DFT). Then, we model a single-junction perovskite solar cell based on a full solution to Maxwell’s equations, using a finite difference time domain (FDTD) technique, which helps us to investigate the light absorption efficiency and optical current density of the cell with CH3NH3PbI3-x Cl x (x  =  0, 1, 2, 3) as the active layer. The results suggest that increasing the amount of chlorine in CH3NH3PbI3-x Cl x compound leads to an increase in the bandgap energy, as well as a decrease in the lattice constants and optical properties, like the refractive index and extinction coefficient of the structure. Also, the results obtained by the simulation express that by taking advantage of the light trapping techniques of SiO2, a remarkable increase of light absorption will be achieved to the magnitude of 83.13%, which is noticeable.

Long-term studies with the Ariel-5 asm. 1: Her X-1, Vela X-1 and Cen X-3. [periodic variations

NASA Technical Reports Server (NTRS)

Holt, S. S.; Kaluzienski, L. J.; Boldt, E. A.; Serlemitsos, P. J.

1978-01-01

Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1 and Cen X-3 accumulated with the Ariel-5 all-sky monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the approximately 35-d variation of Her X-1, for which we can refine the period to 34.875 plus or minus .030-d. No such longer-term periodicity less than 200-d is observed from Vela X-1. The 26.6-d low-state recurrence period for Cen X-3 previously suggested is not observed, but a 43.0-d candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

Structural, Dielectric, and Electrical Properties of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3

NASA Astrophysics Data System (ADS)

Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.

2015-12-01

Polycrystalline samples of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3 (BPFZTO) with x = 0.0, 0.2, 0.3, and 0.4 were prepared by high-temperature solid-state reaction. Preliminary structural analysis of calcined powders of the materials by use of x-ray powder diffraction confirmed formation of single-phase systems with the tetragonal structure. Room-temperature scanning electron micrographs of the samples revealed uniform distribution of grains of low porosity and different dimensions on the surface of the samples. The frequency-temperature dependence of dielectric and electric properties was studied by use of dielectric and complex impedance spectroscopy over a wide range of frequency (1 kHz to 1 MHz) at different temperatures (25-500°C). The dielectric constant of BiFeO3 (BFO) was enhanced by substitution with Pb(Zr0.5Ti0.5)O3 (PZT) whereas the dielectric loss of the BPFZTO compounds decreased with increasing PZT content. A significant contribution of both grains and grain boundaries to the electrical response of the materials was observed. The frequency-dependence of the ac conductivity of BPFZTO followed Jonscher's power law. Negative temperature coefficient of resistance behavior was observed for all the BPFZTO samples. Conductivity by thermally excited charge carriers and oxygen vacancies in the materials was believed to be of the Arrhenius-type.

Structural and thermoelectric properties of n-type Sr1- x Ti x MnO3- δ perovskite system

NASA Astrophysics Data System (ADS)

Kim, C. M.; Seo, J. W.; Choi, S.-M.; Seo, W.-S.; Lee, S.; Lim, Y. S.; Park, K.

2015-03-01

A series of Sr1- x Ti x MnO3- δ (0.05 ≤ x ≤ 0.3) was fabricated by the solid-state reaction method. We studied the structural and thermoelectric properties of Sr1- x Ti x MnO3- δ , with respect to the partial substitution of Ti4+ for Sr2+. The sintered Sr1- x Ti x MnO3- δ crystallized in the hexagonal perovskite-type structure with a space group of P6 3 / mmc. For x ≤ 0.1, the partial substitution of Ti4+ for Sr2+ led to increases in the electrical conductivity and the absolute value of the Seebeck coefficient, thus enhancing the power factor. The highest power factor (2.5 × 10-5 Wm-1K-2) was obtained for Sr0.9Ti0.1MnO3- δ at 800°C. The partial substitution of Ti4+ for Sr2+ in SrMnO3- δ led to a significant improvement in the thermoelectric properties. [Figure not available: see fulltext.

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2009-01-01

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

Pulse periods and the long-term variations of the X-ray pulsars VELA X-1 and Centaurus X-3

NASA Astrophysics Data System (ADS)

Tsunemi, Hiroshi

The paper reports recent determinations of the pulse period for two X-ray pulsars, Vela X-1 and Cen X-3, made in 1987 with the All Sky Monitor (ASM) on board the Ginga satellite. The heliocentric pulse periods are 283.09 + or - 0.01 s and 4.8229 + or - 0.0001 s, respectively. These are the longest and shortest values in their respective observational histories. The random walk model for the Vela X-1 pulsar can explain this result as well as those obtained previously. It is also noted that the pulse-period change for the Cen X-3 system shows a 9-yr periodicity. This is probably due to the activity of the companion star rather than to Doppler-shift variations due to a third body or the precession of the neutron star.

Optical evidence for the spin-state disorder in LaCo1-x Rh x O3

NASA Astrophysics Data System (ADS)

Terasaki, Ichiro; Asai, Shinichiro; Taniguchi, Hiroki; Okazaki, Ryuji; Yasui, Yukio; Ikemoto, Yuka; Moriwaki, Taro

2017-06-01

We have measured the infrared reflectivity of single-crystalline samples of LaCo1-x Rh x O3 (x  =  0, 0.05 and 0.10) from 10 to 300 K from 0.05 to 0.15 eV. We find that the optical phonons of the Co-O stretching mode depend on temperature and the Rh content. Analysis with three Lorentz oscillators reveals that the spin state of Co3+ in LaCo1-x Rh x O3 can be understood in terms of a solid solution of low-spin- and high-spin-state Co3+ ions, and the substituted Rh ion retains some fraction of the high-spin Co3+ ions down to low temperature.

Epitaxial growth and properties of YBa2Cu3O(x)-Pb(Zr(0.6)Ti(0.4))O3-YBa2Cu3O(x) trilayer structure by laser ablation

NASA Astrophysics Data System (ADS)

Boikov, Iu. A.; Esaian, S. K.; Ivanov, Z. G.; Brorsson, G.; Claeson, T.; Lee, J.; Safari, A.

1992-08-01

YBa2Cu3O(x)Pb(Zr(0.6)Ti(0.4))O3-YBa2Cu3O(x) multilayer structure has been grown on SrTiO3 and Al2O3 substrates using laser ablation. The deposition conditions for the growth of trilayers and their properties are studied in this investigation. Scanning electron microscope images and X-ray diffraction analyses indicate that all the constituent films in the trilayer grow epitaxially on SrTiO3 and were highly oriented on Al2O3. Transport measurements on these multilayers show that top YBa2Cu3O(x) films have good superconducting properties.

The Anomalous Low State of LMC X-3

NASA Technical Reports Server (NTRS)

Smale, A. P.; Boyd, P. T.; Markwardt, C. B.

2009-01-01

Archival RXTE ASM and PCA observations of the black hole binary LMC X-3 reveal a dramatic and extended low state lasting from December 8, 2003 until March 18, 2004, unprecedented both in its Low luminosity (Lx(2-10keV)=4.2x 1035 ergs s-1, approximately 4 times fainter than ever before seen from LMC X-3 in its low/hard state, and representing 0.15% of its X-ray luminosity during the high/soft state); and Long duration (approximately equal to 100 days, as compared with 5-20 days for 'normal' low/hard state excursions). During this anomalous low state no significant variability is observed on timescales of days-weeks, and the spectrum is well described by a simple power law with index 1.7 plus or minus 0.2. We examine the variability characteristics of LMC X-3 before and after this event using conventional and topological methods, and show that with the exception of the anomalous low state itself the long-term behavior of the source in topological phase space can be completely described in terms of a well-understood nonlinear dynamics system known as the Duffing oscillator, implying that the accretion disk in LMC X-3 is a driven, dissipative system with two solutions competing for control of its time evolution. This work shows that dynamical information and constraints revealed by topological analysis methods can provide a valuable addition to traditional studies of accretion disk behavior.

Magnetocaloric effect and critical field analysis in Eu substituted La0.7-xEuxSr0.3MnO3 (x = 0.0, 0.1, 0.2, 0.3) manganites

NASA Astrophysics Data System (ADS)

Vadnala, Sudharshan; Asthana, Saket

2018-01-01

In this study, we have investigated magnetic behavior, magnetocaloric effect and critical exponent analysis of La0.7-xEuxSr0.3MnO3 (x = 0.0, 0.1, 0.2, 0.3) manganites synthesized through solid state reaction route. The crystallographic data obtained from refinement of X-ray diffraction patterns reveal that crystal structure changes from rhombohedral (for x = 0.0) to orthorhombic (for x ≥ 0.1). The average ionic radius of A-site is decreased from 1.384 Å (for x = 0.0) to 1.360 Å (for x = 0.3) with Eu3+ substitution which in turn decreases the Mn-O-Mn bond angles. Magnetization measurements are performed in the vicinity of TC to determine magnetocaloric effect (MCE) and critical field behavior. The maximum magnetic entropy change (Δ SMmax) (for μ0ΔH = 6T) increases with the Eu3+ substitution from 3.88 J/kg K (for x = 0.0) to 5.03 J/kg K (for x = 0.3) at the transition temperature. The critical field behaviour of compounds was analysed using various methods such as modified Arrott plots, Kouvel-Fisher method and critical isotherm to determine critical temperature and critical exponents (β, γ and δ). The obtained critical exponents are in good accordance with scaling relation. The temperature dependence of the order parameter n, for different magnetic fields, is studied using the relation ΔSMαHn. The values of n are found to obey the Curie-Weiss law for temperatures above the transition temperature. The rescaled change in entropy data for all compounds collapses into the same universal curve, revealing a second order phase transition.

Composition-property relationships in (Gd3-xLux)(GayAl5-y)O12:Ce (x = 0, 1, 2, 3 and y = 0, 1, 2, 3, 4) multicomponent garnet scintillators

NASA Astrophysics Data System (ADS)

Luo, Jialiang; Wu, Yuntao; Zhang, Guoqing; Zhang, Huaijin; Ren, Guohao

2013-12-01

The (LuxGd3-x)(GayAl5-y)O12:Ce (x = 0, 1, 2, 3 and y = 0, 1, 2, 3, 4) scintillating polycrystalline powders were prepared by high temperature solid state reaction method. A pure cubic phase was confirmed in all samples by X-ray diffraction (XRD). X-ray excited luminescence (XEL), photoluminescence excitation and emission spectra were employed to study the influence of Gd3+-Ga3+ admixture on the luminescent mechanism of Ce3+ as well as the energy transfer from Gd3+ to Ce3+. The band-gap structures with varying Gd3+ and Ga3+ content were constructed to understand the luminescence behaviors. In addition, thermoluminescence spectra (TL) were utilized to identify the moving of conduction band (CB) by monitoring the shift of the corresponding TL peaks. Finally, it was found that incorporation of 40 mol% (y = 2) Ga3+ and 33.3-66.7 mol% (x = 1-2) Gd3+ could secure enough energy-separation between CB and 5d1 of Ce3+ avoiding thermal ionization effect at utmost, and bury the antisite defect traps into CB, and in turn achieving the optimum scintillation efficiency.

Durability of the Li 1+xTi 2–xAl x(PO 4) 3 Solid Electrolyte in Lithium–Sulfur Batteries

DOE PAGES

Wang, Shaofei; Ding, Yu; Zhou, Guangmin; ...

2016-10-31

Adoption of cells with a solid-state electrolyte is a promising solution for eliminating the polysulfide shuttle problem in Li-S batteries. Among the various known lithium-ion conducting solid electrolytes, the sodium superionic conductor (NASICON)-type Li 1+xTi 2-xAl x(PO 4) 3 offers the advantage of good stability under ambient conditions and in contact with air. Accordingly, we present here a comprehensive assessment of the durability of Li 1+xTi 2-xAl x(PO 4) 3 in contact with polysulfide solution and in Li-S cells. Because of its high reduction potential (2.5 V vs Li/Li +), Li 1+xTi 2-xAl x(PO 4) 3 gets lithiated in contactmore » with lithium polysulfide solution and Li 2CO 3 is formed on the particle surface, blocking the interfacial lithium-ion transport between the liquid and solid-state electrolytes. After the lithium insertion into the NASICON framework, the crystal expands in an anisotropic way, weakening the crystal bonds, causing fissures and resultant cracks in the ceramic, corroding the grain boundaries by polysulfide solution, and leaving unfavorable pores. The assembly of pores creates a gateway for polysulfide diffusion from the cathode side to the anode side, causing an abrupt decline in cell performance. Therefore, the solid-state electrolytes need to have good chemical compatibility with both the electrode and electrolyte, long-term stability under harsh chemical environment, and highly stable grain boundaries.« less

Crystal structure and magnetism of the FexNi8-xSi3 materials, 0 ≤ x ≤ 8

NASA Astrophysics Data System (ADS)

Gallus, Simone; Haddouch, Mohammed Ait; Chikovani, Mamuka; Perßon, Jörg; Voigt, Jörg; Friese, Karen; Senyshyn, Anatoliy; Grzechnik, Andrzej

2018-02-01

The crystal structure and magnetic properties of the materials FexNi8-xSi3 with 0 ≤ x ≤ 8 have been investigated to estimate any possible magnetocaloric effect and compare it to that in known magnetocalorics. Two structural ranges could be identified in this system by X-ray and neutron diffraction. The structure of the samples with 0 ≤ x ≤ 4 is related to the trigonal structure of Ni31Si12. Doubled c lattice parameters compared to the one in Ni31Si12 are observed in the samples with x = 2 and x = 3. The average structure of Fe2Ni6Si3 has been determined by X-ray single-crystal diffraction. The compounds with the compositions 5 ≤ x ≤ 8 crystallize in cubic Fe3Si-type structure. Magnetic measurements have shown that the compound Fe3Ni5Si3 displays a phase transition close to room temperature. However, its magnetocaloric effect is much smaller than the one in the promising magnetocaloric materials.

The structural and magnetic investigation of ( x) BiFe0.95Co0.05O3: (1- x) La0.7Ca0.3MnO3 composites

NASA Astrophysics Data System (ADS)

Zhang, Hongguang; Fu, Dexiang; Wang, Yang; Xie, Liang; Li, Yongtao; Chen, Wei

2017-12-01

The structural and magnetic behaviors are studied in the composites ( x) BiFe0.95Co0.05O3: (1- x) La0.7Ca0.3MnO3. An influence on the lattice parameters and magnetic states of BiFe0.95Co0.05O3 (BFCO) to the La0.7Ca0.3MnO3 (LCMO) are investigated. Although the variation of the relative X-ray intensity of LCMO to BFCO with composition ( x) in XRD patterns and the randomly distributed small nanoparticle of LCMO ( 200 nm) mixed in the large nanoparticle of BFCO ( 900 nm) given by SEM images indicate an almost immiscibility of BFCO and LCMO in composites obtained by solid solution method, an obvious change of lattice parameters indicates their mutual influence on lattice structure. A detail magnetic investigation of the composites shows that the Griffiths phase is increased with increase of composition x due to the incorporation of ferromagnetism of BFCO to the paramagnetic phase of LCMO. An approximate magnetic phase diagram for the composites is established, which would be helpful for understanding the magnetic singularity of the composites with colossal magnetoresistance and multiferroics.

The 2010 May Flaring Episode of Cygnus X-3 in Radio, X-Rays, and gamma-Rays

NASA Technical Reports Server (NTRS)

Williams, Peter K. G.; Tomsick, John A.; Bodaghee, Arash; Bower, Geoffrey C.; Pooley, Guy G.; Pottschmidt, Katja; Rodriguez, Jerome; Wilms, Joern; Migliari, Simone; Trushkin, Sergei A.

2011-01-01

In 2009, Cygnus X-3 (Cyg X-3) became the first microquasar to be detected in the GeV gamma-ray regime, via the satellites Fermi and AGILE. The addition of this new band to the observational toolbox holds promise for building a more detailed understanding of the relativistic jets of this and other systems. We present a rich dataset of radio, hard and soft X-ray, and gamma-ray observations of Cyg X-3 made during a flaring episode in 2010 May. We detect a approx.3-d softening and recovery of the X-ray emission, followed almost immediately by a approx.1-Jy radio flare at 15 GHz, followed by a 4.3sigma gamma-ray flare (E > 100 MeV) approx.1.5 d later. The radio sampling is sparse, but we use archival data to argue that it is unlikely the gamma-ray flare was followed by any significant unobserved radio flares. In this case, the sequencing of the observed events is difficult to explain in a model in which the gamma-ray emission is due to inverse Compton scattering of the companion star's radiation field. Our observations suggest that other mechanisms may also be responsible for gamma-ray emission from Cyg X-3.

Evolution of magnetic properties of CaMn1-x Nb x O3 with Nb-doping

NASA Astrophysics Data System (ADS)

Markovich, V.; Fita, I.; Wisniewski, A.; Puzniak, R.; Martin, C.; Mogilyansky, D.; Jung, G.; Gorodetsky, G.

2015-08-01

Magnetic and structural properties of Nb-doped CaMnO3 have been studied and the effect of doping with 0.02  ⩽  x  ⩽  0.1 has been investigated. Substitution of Nb5+ ion for the Mn4+ site of the parent matrix causes one-electron doping with the chemical formula \\text{CaMn}1-2x4+\\text{Mn}x3+\\text{Nb}x5+{{\\text{O}}3} , accompanied by a monotonous increase of the lattice parameters, unit-cell volume, average Mn-O bond distance and a decrease in Mn-O-Mn bond angle, with increasing x. Low temperature magnetic ground state of CaMn1-x Nb x O3 has been found to be dependent on niobium doping level. The ground magnetic state evolves from mostly antiferromagnetic, with a weak ferromagnetic component for x = 0.02-0.08, to charge ordered C-type antiferromagnetic state at x = 0.1. Spontaneous magnetization increases sharply with increasing doping level, approaches a maximal value of 4.1 emu g-1 at T = 10 K for x = 0.08, and then decreases rapidly to reach a very small value of 0.2 emu g-1 for x = 0.1. Anomalous negative magnetization behavior below the magnetic transition temperature has been observed for the compound with x = 0.04 in the field cooled magnetization and remanent dc magnetization measurements. Vertical and horizontal shifts of the hysteresis loop of the field cooled sample have been observed for CaMn0.9Nb0.1O3 as possible signatures of the exchange bias effect. The effect of hydrostatic pressure on dc magnetization for the sample with x  >  0.02 revealed a significant increase of the ferromagnetic phase volume under pressure, linked to progressive suppression of a negative magnetization in x = 0.04 sample.

Structural, magneto-optical properties and cation distribution of SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auwal, I.A.; Güngüneş, H.; Güner, S.

Highlights: • SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites have been prepared by sol-gel autocombustion. • XRD patterns show that SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites exhibit hexagonal structure. • The intrinsic coercivity (H{sub ci}) above 15000 Oe reveals that all samples are magnetically hard materials. - Abstract: SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites were produced via sol-gel auto combustion. XRD patterns show that all the samples are single-phase M-type strontium hexaferrite (SrM). The magnetic hysteresis (σ-H) loops revealed the ferromagnetic nature ofmore » nanoparticles (NPs). The coercive field decreases from 4740 Oe to 2720 Oe with increasing ion content. In particular, SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} NPs with x = 0.0, 0.1, 0.2 have suitable magnetic characteristics (σ{sub s} = 62.03–64.72 emu/g and H{sub c} = 3105–4740 Oe) for magnetic recording. The intrinsic coercivity (H{sub ci}) above 15000 Oe reveals that all samples are magnetically hard materials. Tauc plots were used to specify the direct optical energy band gap (E{sub g}) of NPs. The E{sub g} values are between 1.76 eV and 1.85 eV. {sup 57}Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, relative area and hyperfine magnetic field values on Bi{sup 3+} La{sup 3+} and Y{sup 3+} substitutions have been determined.« less

Magnetically driven negative thermal expansion in antiperovskite Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3)

NASA Astrophysics Data System (ADS)

Guo, X. G.; Lin, J. C.; Tong, P.; Wang, M.; Wu, Y.; Yang, C.; Song, B.; Lin, S.; Song, W. H.; Sun, Y. P.

2015-11-01

Negative thermal expansion (NTE) was investigated for Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3). As x increases, the temperature range where lattice contracts upon heating becomes broad and shifts to lower temperatures. The coefficient of linear thermal expansion beyond -40 ppm/K with a temperature interval of ˜50 K was obtained around room temperature in x = 0.2 and 0.25. Local lattice distortion which was thought to be intimately related to NTE is invisible in the X-ray pair distribution function of x = 0.3. Furthermore, a zero-field-cooling exchange bias was observed as a result of competing ferromagnetic (FM) and antiferromagnetic (AFM) orders. The concomitant FM order serves as an impediment to the growth of the AFM order, and thus broadens the temperature range of NTE. Our result suggests that NTE can be achieved in antiperovskite manganese nitrides by manipulating the magnetic orders without distorting the local structure.

Tuning of magnetism in DyMn1-xFexO3 (x<0.1) system by iron substitution

NASA Astrophysics Data System (ADS)

Mihalik, Matúš; Mihalik, Marián; Zentková, Mária; Uhlířová, Klára; Kratochvílová, Marie; Fitta, Magdalena; Quintero, Pedro A.; Meisel, Mark W.

2018-05-01

The effect of Fe doping on the magnetism of DyMn1-xFexO3 (x<0.1) single crystals is reported. Specifically, TN of the Mn sublattice decreases from 38 K (x = 0) to 33 K (x = 0.1), TS = 17.9 K (x = 0) connected with the transition of Mn-spins into the cycloidal magnetic phase decreases to 15.9 K (x = 0.01) and vanishes for higher x concentrations, while the ordering temperature of the Dy sublattice varies between 5.9 K (x = 0.01) and 4.1 K (x = 0.02). These results indicate the ground state magnetic structure of DyMnO3 can be destabilized, and the multiferroicity is completely suppressed by very low Fe doping. Similar effects were previously observed in the multiferroic TbMn1-xFexO3 system.

Influence of compositional variation on structural, electrical and magnetic characteristics of (Ba1-x Gd) (Ti1-x Fe x ) O3 (0.2 ≤ x ≤ 0.5)

NASA Astrophysics Data System (ADS)

Sahoo, Sushrisangita; Mahapatra, P. K.; Choudhary, R. N. P.; Alagarsamy, Perumal

2018-01-01

The effect of composition variation of (Ba1-x Gd x )(Ti1-x Fe x )O3 (0.2 ≤ x ≤ 0.5) on structural, optical, electrical and multiferroic properties was investigated. The polycrystalline samples were fabricated by a chemico-thermal route. While the compound with composition x ≤ 0.3 has a tetragonal structure akin to BaTiO3, the higher compositions (x > 0.3) crystallize in a mixed phase of the tetragonal and orthorhombic structure. The different polarization mechanisms in the compound were analyzed on the basis of ferroelectric-paraelectric phase transition at 120 °C, magnetic reorientation mediated by Gd3+ ↔ Fe3+ exchange interaction at 200 °C and that induced by antiferromagnetic ordering mediated through the Fe3+ ↔ Fe3+ exchange interactions at 380 °C. Analysis of ac conductivity on the basis of Jonscher’s power law indicates the presence of correlated barrier hopping conduction mechanism in the samples. Among the studied samples, the composition with x = 0.3 exhibiting improved material properties like lower optical band gap and higher optical absorption, high dielectric constant (830 at room temperature and peak value of 3944 at 160 °C and 6478 at 377.5 °C), and the room temperature ME coefficient of 1.53 mV cm-1 Oe-1 have promising technological applications.

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

PubMed

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

Very High Energy Emission from the Binary System Cyg X-3

NASA Astrophysics Data System (ADS)

Sinitsyna, V. G.; Sinitsyna, V. Yu.

2018-03-01

Cyg X-3 is actively studied in the entire range of the electromagnetic spectrum from the radio band to ultrahigh energies. Based on the detection of ultrahigh-energy gamma-ray emission, it has been suggested that Cyg X-3 could be one of the most powerful sources of charged cosmic-ray particles in the Galaxy. We present the results of long-term observations of the Cygnus X-3 region at energies 800 GeV-100 TeV by the SHALON mirror Cherenkov telescope. In 1995 the SHALON observations revealed a new Galactic source of very high energy gamma-ray emission coincident in its coordinates with the microquasar Cyg X-3. To reliably identify the detected source with Cyg X-3, an analysis has been performed and an orbital period of 4.8 h has been found, which is a signature of Cyg X-3. A series of flares in Cyg X-3 at energies >800 GeV and their correlation with the activity in the X-ray and radio bands have been observed. The results obtained in a wide energy range for Cyg X-3, including those during the periods of relativistic jet events, are needed to find the connection and to understand the different components of an accreting binary system.

Comparison of the pharmacokinetics and pharmacodynamics of dapagliflozin in patients with type 1 versus type 2 diabetes mellitus.

PubMed

Tang, W; Leil, T A; Johnsson, E; Boulton, D W; LaCreta, F

2016-03-01

To compare the pharmacokinetics and pharmacodynamics of dapagliflozin in patients with type 1 diabetes mellitus (T1DM) versus type 2 diabetes mellitus (T2DM) in order to explore the potential of dapagliflozin as add-on therapy to insulin in patients with T1DM. Steady-state pharmacokinetics and pharmacodynamics of dapagliflozin (1-100 mg) were evaluated in a meta-analysis of patients with T1DM or T2DM. A model was constructed of the relationship between dapagliflozin systemic exposure and urinary glucose excretion (UGE) in patients with T1DM versus those with T2DM. Data were analysed from 160 patients (T1DM, n = 70; T2DM, n = 90). Dapagliflozin systemic exposure (maximum concentration and area under the curve) increased similarly in a dose-related manner in both patient populations. Dose-dependent increases in 24-h UGE were observed with dapagliflozin in both populations. Unadjusted results showed that with regard to UGE response, dapagliflozin was more potent in patients with T1DM {mean half-maximum effective concentration [EC50 ] = 2.72 ng/ml [95% confidence interval (CI) 1.14, 5.08]} than in patients with T2DM [EC50  = 12.2 ng/ml (95% CI 4.91, 21.1)]. After normalization for baseline fasting plasma glucose, estimated glomerular filtration rate and UGE, however, the UGE potency of dapagliflozin was similar between the two populations [T1DM: mean EC50 , 8.12 ng/ml (95% CI 2.95, 14.6); T2DM: mean EC50 , 7.75 ng/ml (95% CI 1.35, 18.1)]. Dapagliflozin pharmacokinetics and the predicted UGE dose exposure response to dapagliflozin were similar in patients with T1DM and those with T2DM and suggest that the dapagliflozin dosages currently used for the treatment of T2DM may provide benefit as add-on therapy to insulin in patients with T1DM. © 2015 John Wiley & Sons Ltd.

Synthesis, Crystal and Electronic Structures, and Optical Properties of (CH 3NH 3) 2CdX 4 (X = Cl, Br, I)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roccanova, Rachel; Ming, Wenmei; Whiteside, Vincent R.

Here, we report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic–inorganic compounds MA 2CdX 4 (MA = CH 3NH 3; X = Cl, Br, I). MA 2CdI 4 is a new compound, whereas, for MA 2CdCl 4 and MA 2CdBr 4, structural investigations have already been conducted but electronic structures and optical properties are reported here for the first time. Single crystals were grown through slow evaporation of MA 2CdX 4 solutions with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals. Single crystal and variablemore » temperature powder X-ray diffraction measurements suggest that MA 2CdCl 4 forms a 2D layered perovskite structure and has two structural transitions at 283 and 173 K. In contrast, MA 2CdBr 4 and MA 2CdI 4 adopt 0D K 2SO 4-derived crystal structures based on isolated CdX 4 tetrahedra and show no phase transitions down to 20 K. The contrasting crystal structures and chemical compositions in the MA 2CdX 4 family impact their air stabilities, investigated for the first time in this work; MA 2CdCl 4 is air-stable, whereas MA 2CdBr 4 and MA 2CdI 4 partially decompose when left in air. Optical absorption measurements suggest that MA 2CdX 4 have large optical band gaps above 3.9 eV. Room temperature photoluminescence spectra of MA 2CdX 4 yield broad peaks in the 375–955 nm range with full width at half-maximum values up to 208 nm. These PL peaks are tentatively assigned to self-trapped excitons in MA 2CdX 4 following the crystal and electronic structure considerations. The bands around the Fermi level have small dispersions, which is indicative of high charge localization with significant exciton binding energies in MA 2CdX 4. On the basis of our combined experimental and computational results, MA 2CdX 4 and related compounds may be of interest for white-light-emitting phosphors and scintillator applications.« less

Synthesis, Crystal and Electronic Structures, and Optical Properties of (CH 3NH 3) 2CdX 4 (X = Cl, Br, I)

DOE PAGES

Roccanova, Rachel; Ming, Wenmei; Whiteside, Vincent R.; ...

2017-11-02

Here, we report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic–inorganic compounds MA 2CdX 4 (MA = CH 3NH 3; X = Cl, Br, I). MA 2CdI 4 is a new compound, whereas, for MA 2CdCl 4 and MA 2CdBr 4, structural investigations have already been conducted but electronic structures and optical properties are reported here for the first time. Single crystals were grown through slow evaporation of MA 2CdX 4 solutions with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals. Single crystal and variablemore » temperature powder X-ray diffraction measurements suggest that MA 2CdCl 4 forms a 2D layered perovskite structure and has two structural transitions at 283 and 173 K. In contrast, MA 2CdBr 4 and MA 2CdI 4 adopt 0D K 2SO 4-derived crystal structures based on isolated CdX 4 tetrahedra and show no phase transitions down to 20 K. The contrasting crystal structures and chemical compositions in the MA 2CdX 4 family impact their air stabilities, investigated for the first time in this work; MA 2CdCl 4 is air-stable, whereas MA 2CdBr 4 and MA 2CdI 4 partially decompose when left in air. Optical absorption measurements suggest that MA 2CdX 4 have large optical band gaps above 3.9 eV. Room temperature photoluminescence spectra of MA 2CdX 4 yield broad peaks in the 375–955 nm range with full width at half-maximum values up to 208 nm. These PL peaks are tentatively assigned to self-trapped excitons in MA 2CdX 4 following the crystal and electronic structure considerations. The bands around the Fermi level have small dispersions, which is indicative of high charge localization with significant exciton binding energies in MA 2CdX 4. On the basis of our combined experimental and computational results, MA 2CdX 4 and related compounds may be of interest for white-light-emitting phosphors and scintillator applications.« less

X-15 ship #3 on lakebed

NASA Technical Reports Server (NTRS)

1961-01-01

The X-15-3 (56-6672), seen here on the lakebed at Edwards Air Force Base, Edwards, California, was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and movable horizontal stabilizers to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing. Generally, one of two types of X-15 flight profiles was used; a high-altitude flight plan that called for the pilot to maintain a steep rate of climb, or a speed profile that

Enhanced piezoelectricity and high temperature poling effect in (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics via an ethylene glycol route

NASA Astrophysics Data System (ADS)

Tailor, H. N.; Ye, Z.-G.

2010-05-01

A solution chemical method utilizing ethylene glycol as solvent has been developed to prepare the ceramics of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3[(1-x)PMN-xPT] from a precursor powder that can be pressed and fired in one step to produce high quality ceramics with excellent piezoelectric properties. The ceramics reach a relative density of up to 97% of the theoretical value after direct calcinations. This high density is achieved without the need of additional sintering after calcination which is usually required in conventional solid state syntheses to produce ceramics. The ceramics exhibit a unipolar piezoelectric coefficient d33 of 848 pC/N, which is one of the highest values for any unmodified/untextured binary systems reported to date. Since the piezoelectric properties depend on composition and electric field, the effect of poling conditions was investigated. A critical temperature limit has been found, above which poling can dramatically impair the piezoelectric properties due to a field-induced increase in the monoclinic phase component around the morphotropic phase boundary.

Preferred site occupation of 3 d atoms in NixF e4 -xN (x =1 and 3) films revealed by x-ray absorption spectroscopy and magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Takata, Fumiya; Ito, Keita; Takeda, Yukiharu; Saitoh, Yuji; Takanashi, Koki; Kimura, Akio; Suemasu, Takashi

2018-02-01

X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism measurements were performed at the Ni and Fe L2 ,3 absorption edges for N ixF e4 -xN (x =1 and 3) epitaxial films. Spectral line-shape analysis and element-specific magnetic moment evaluations are presented. Shoulders at approximately 2 eV above the Ni L2 ,3 main peaks in the XAS spectrum of N i3FeN were interpreted to originate from hybridization of orbitals between Ni 3 d at face-centered (II) sites and N 2 p at body-centered sites, while such features were missing in NiF e3N film. Similar shoulders were observed at Fe L2 ,3 edges in both films. These results indicate that the orbitals of Ni atoms did not hybridize with those of N atoms in the NiF e3N film. Hence, Ni atoms preferentially occupied corner (I) sites, where the hybridization was weak because of the relatively long distance between Ni at I sites and N atoms. The relatively large magnetic moment deduced from sum-rule analysis of NiF e3N also showed a good agreement with the presence of Ni atoms at I sites.

A Raman scattering study of the structural ordering in Bi1- x La x FeO3 ceramic ferroelectromagnetics

NASA Astrophysics Data System (ADS)

Teplyakova, N. A.; Titov, S. V.; Verbenko, I. A.; Sidorov, N. V.; Reznichenko, L. A.

2015-09-01

Based on Raman spectra, we have studied structural ordering processes in ceramics of ferroelectromagnetics Bi1- x La x FeO3 ( x = 0.075-0.20). It has been found that the structure of Bi1- x La x FeO3 is close to the structure of the crystal BiFeO3. However, lines in Raman spectra of Bi1- x La x FeO3 are considerably broadened compared to lines in the Raman spectrum of the BiFeO3 single crystal, which indicates that the structure of solid solutions is much more disordered. In Raman spectra of Bi1- x La x FeO3, in the range of librational vibrations of octahedra as a whole (50-90 cm-1), several groups of lines are observed in frequency ranges 59-69, 72-77, and 86-92 cm-1 (depending on the composition of solid solution). This confirms X-ray data that examined solid solutions are not single-phase. At a La content x = 0.120, Raman lines in the low-frequency spectral range narrow, which indicates that the ordering of structural units in cationic sublattices somewhat increases. Upon an increase in the content of La in the Bi1- x La x FeO3 structure, no unambiguous dependence of parameters of spectral lines is observed. It is likely that this is explained by the fact that, as the value of x increases, the character of the incorporation of La into the structure of the solid solution changes.

Ferromagnetic behavior in mixed valence europium (Eu2+/Eu3+) oxide EuTi1-xMxO3 (M = Al3+ and Ga3+)

NASA Astrophysics Data System (ADS)

Akahoshi, Daisuke; Horie, Hiroki; Sakai, Shingo; Saito, Toshiaki

2013-10-01

We have investigated the Ti-site substitution effect on the magnetic properties of antiferromagnetic insulator EuTiO3 with a Néel temperature of ˜5 K. Partial substitution of Ti4+ with heterovalent Al3+ or Ga3+ turns the corresponding amount of magnetic Eu2+ into non-magnetic Eu3+. Both EuTi1-xAlxO3 (0.05 ≤ x ≤ 0.10) and EuTi1-xGaxO3 (0.05 ≤ x ≤ 0.10) exhibit ferromagnetic (FM) insulating behavior below ˜4 K. The Eu2+/Eu3+ mixed valence state probably contributes to the emergence of the FM behavior. Fine control of the magneto-electric (ME) phases of EuTi1-xAlxO3 and EuTi1-xGaxO3 would lead to intriguing ME phenomena such as giant ME effect.

Structural and magnetic phase transitions in EuTi 1-xNb xO 3

DOE PAGES

Li, Ling; Morris, James R.; Koehler, Michael R.; ...

2015-07-30

Here, we investigate the structural and magnetic phase transitions in EuTi 1-xNb xO 3 (0≤x≤0.3) with synchrotron powder x-ray diffraction, resonant ultrasound spectroscopy, and magnetization measurements. Upon Nb doping, the Pmmore » $$\\bar{3}$$m ↔ I4/mcm structural transition shifts to higher temperatures and the room temperature lattice parameter increases while the magnitude of the octahedral tilting decreases. In addition, Nb substitution for Ti destabilizes the antiferromagnetic ground state of the parent compound and long-range ferromagnetic order is observed in the samples with x≥0.1. Moreover, the structural transition in pure and doped compounds is marked by a dramatic step-like softening of the elastic moduli near T S, which resembles that of SrTiO 3 and can be adequately modeled using the Landau free energy model employing the same coupling between strain and octahedral tilting order parameter as previously used to model SrTiO 3.« less

Theoretical interpretation of the HEAO-3 observations of Cygnus X-3 under the HEAO-3 Guest Investigator Program

NASA Technical Reports Server (NTRS)

Marscher, Alan P.

1987-01-01

A model of the galactic X-ray source Cygnus X-3 (Cyg X-3) is presented which deviates from previous models by positing that the X-rays originate in a jet rather than a binary system consiting of an ordinary star and a collapsed object. In the new model, the 4.8 hour period of Cyg X-3 is caused by variable absorption which occurs as the jet precesses. The primary role of the accretion disk corona (ADC) in modulating Cyg X-3 radiation is to make the observed intensity of a blob of material in a jet appear dimmer by absorption. The needed derivation of the positional dependence of the density of the ADC is freed of some complications by assuming that only the inner regions of the disk are precessing, with a period shorter than 4.8 hours. This model permits the secondary star to be a supergiant, as indicated by the luminosity of the system. The model is especially helpful in interpreting production of radio outbursts and very high energy gamma rays.

Thermoelectric properties of the ceramic oxide Sr1- x La x TiO3

NASA Astrophysics Data System (ADS)

Mahmud, Iqbal; Yoon, Man-Soon; Kim, Il-Ho; Choi, Moon-Kwan; Ur, Soon-Chul

2016-01-01

The effect of lanthanum on the electric and the thermoelectric properties of the ceramic oxide Sr1- x La x TiO3 (where x = 0.0, 0.04, 0.06, 0.08 and 0.12 mole) have been studied. La-doped SrTiO3 was prepared by using the conventional mixed-oxide reaction method. XRD patterns indicated that almost all the La atoms incorporated into the SrTiO3 crystal provided charge carriers. The lattice parameter increases with increasing La doping content. The relative densities of all the samples varied from 89.6% to 94.8%. The electrical conductivity increased with La doping up to 0.08 moles and then decreased as the content of La was increased above 0.08 moles. The thermal conductivity decreased with increasing La content. The largest absolute value of the Seebeck coefficient, 394 μVK-1 at 973 K, was observed at x = 0.04. The Sr0.92La0.08TiO3 sample showed its maximum electrical conductivity at 773 K and its largest ZT value of 0.20 at 973 K.

Magnetic impurities in conducting oxides. II. (Sr1-xLax)(Ru1-xCox)O3 system

NASA Astrophysics Data System (ADS)

Mamchik, A.; Dmowski, W.; Egami, T.; Chen, I.-Wei

2004-09-01

The perovskite solid solution between ferromagnetic SrRuO3 and antiferromagnetic LaCoO3 is studied and its structural, electronic,and magnetic properties are compared with (Sr1-xLax)(Ru1-xFex)O3 . The lower 3d energy levels of Co3+ cause a local charge transfer from 4dRu4+ , a reaction that has the novel feature of being sensitive to the local atomic structure such as cation order. Despite such a complication, Co , like Fe , spin-polarizes the itinerant electrons in SrRuO3 to form a large local magnetic moment that is switchable at high fields. In the spin glass regime when Anderson localization dominates, a large negative magnetoresistance emerges as a result of spin polarization of mobile electronic carriers that occupy states beyond the mobility edge. A phenomenological model predicting an inverse relation between magnetoresistance and saturation magnetization is proposed to explain the composition dependence of magnetoresistance for both (Sr1-xLax)(Ru1-xCOx)O3 and (Sr1-xLax)(Ru1-xFex)O3 systems.

High-temperature solution growth and characterization of (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 piezo-/ferroelectric single crystals

NASA Astrophysics Data System (ADS)

Paterson, Alisa R.; Zhao, Jinyan; Liu, Zenghui; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

2018-03-01

Complex perovskite PbTiO3-Bi(Me‧Me″)O3 solid solutions represent new materials systems that possess a higher Curie temperature (TC) than the relaxor-PbTiO3 solid solutions, and are useful for potential applications. To this end, novel ferroelectric single crystals of the (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 (PT-BZN) solid solution were successfully grown by the high-temperature solution growth (HTSG) method. Powder X-ray diffraction shows that the symmetry of the grown crystals is tetragonal. The dielectric permittivity and optical domain structures were characterized by dielectric measurements and polarized light microscopy, respectively, as a function of temperature, revealing a first-order ferroelectric-paraelectric phase transition at a TC of 436 ± 2 °C. Based on the TC, the average composition of the crystal platelet was estimated to be 0.58PT-0.42BZN. Piezoresponse force microscopy measurements of the phase and amplitude as a function of voltage reveal the complex polar domain structure and demonstrate the ferroelectric switching behaviour of these materials. These results suggest that the PT-BZN single crystals indeed form a new family of high TC piezo-/ferroelectric materials which are potentially useful for the fabrication of electromechanical transducers for high-temperature applications.

Phase diagram and polarization of stable phases of (Ga1- x In x )2O3

NASA Astrophysics Data System (ADS)

Maccioni, Maria Barbara; Fiorentini, Vincenzo

2016-04-01

The full phase diagram of (Ga1- x In x )2O3 is obtained theoretically. The phases competing for the ground state are monoclinic β (low x), hexagonal (x ˜ 0.5), and bixbyite (large x). Three disconnected mixing regions interlace with two distinct phase-separation regions, and at x ˜ 0.5, the coexistence of hexagonal and β alloys with phase-separated binary components is expected. We also explore the permanent polarization of the phases, but none of them are polar. On the other hand, we find that ɛ-Ga2O3, which was stabilized in recent experiments, is pyroelectric with a large polarization and piezoelectric coupling, and could be used to produce high-density electron gases at interfaces.

Ab initio chemical kinetics for SiH3 reactions with Si(x)H2x+2 (x = 1-4).

PubMed

Raghunath, P; Lin, M C

2010-12-30

Gas-phase kinetics and mechanisms of SiH(3) reactions with SiH(4), Si(2)H(6), Si(3)H(8), and Si(4)H(10), processes of relevance to a-Si thin-film deposition, have been investigated by ab initio molecular orbital and transition-state theory (TST) calculations. Geometric parameters of all the species involved in the title reactions were optimized by density functional theory at the B3LYP and BH&HLYP levels with the 6-311++G(3df,2p) basis set. The potential energy surface of each reaction was refined at the CCSD(T)/6-311++G(3df,2p) level of theory. The results show that the most favorable low energy pathways in the SiH(3) reactions with these silanes occur by H abstraction, leading to the formation of SiH(4) + Si(x)H(2x+1) (silanyl) radicals. For both Si(3)H(8) and n-Si(4)H(10) reactions, the lowest energy barrier channels take place by secondary Si-H abstraction, yielding SiH(4) + s-Si(3)H(7) and SiH(4) + s-Si(4)H(9), respectively. In the i-Si(4)H(10) reaction, tertiary Si-H abstraction has the lowest barrier producing SiH(4) + t-Si(4)H(9). In addition, direct SiH(3)-for-X substitution reactions forming Si(2)H(6) + X (X = H or silanyls) can also occur, but with significantly higher reaction barriers. A comparison of the SiH(3) reactions with the analogous CH(3) reactions with alkanes has been made. The rate constants for low-energy product channels have been calculated for the temperature range 300-2500 K by TST with Eckart tunneling corrections. These results, together with predicted heats of formation of various silanyl radicals and Si(4)H(10) isomers, have been tabulated for modeling of a-Si:H film growth by chemical vapor deposition.

Evidence for a 17-d periodicity from Cyg X-3

NASA Technical Reports Server (NTRS)

Holt, S. S.; Boldt, E. A.; Serlemitsos, P. J.; Kaluzienski, L. J.; Pravdo, S. H.; Peacock, A.; Elvis, M.; Watson, M. G.; Pounds, K. A.

1976-01-01

Data are presented from the Ariel-V All-Sky Monitor which indicate a 17-day periodicity of the X-ray spectra from Cyg X-3 (3U2030+40). The data are consistent with data from the Ariel V Sky Survey Experiment. Assuming that the high intensity state of Cyg X-3 is well fitted by a structureless black body (Serlemitsos et al., 1975), and that the 17-day maxima correspond to increased electron scattering in the source, it is suggested that the 17-day effect is analogous to the 35-day variation in Her X-1. The possible explanation of this phenomenon as a result of the 17-day orbital period of the binary system containing Cyg X-3 is severely constrained by the stability of the well-known 4.8-hour variation.

A Broad-band Spectral and Timing Study of the X-Ray Binary System Centaurus X-3

NASA Technical Reports Server (NTRS)

Audley, Michael Damian

1998-01-01

This dissertation describes a multi-mission investigation of the high mass X-ray binary pulsar Centaurus X-3. Cen X-3 was observed with the Broad Band X-Ray Telescope (BBXRT) in December 1990. This was the first high-resolution solid state X-ray spectrometer to cover the iron K fluorescence region. The Fe K emission feature was resolved into two components for the first time. A broad 6.7 keV feature was found to be a blend of lines from Fe XXI-Fe XXVI with energies ranging from 6.6 to 6.9 keV due to photoionization of the companion's stellar wind. A narrow line at 6.4 keV due to fluorescence of iron in relatively low ionization states was also found. The quasi-periodic oscillations (QPO) at about 40 mHz were used to estimate the surface magnetic field of Cen X-3 as approx. 2.6 x 10(exp 12) G and to predict that there should be a cyclotron scattering resonance absorption feature (CSRF) near 30 keV. In order to further resolve the iron line complex and to investigate the pulse-phase dependence of the iron line intensities, Cen X-3 was observed with the Advanced Satellite for Cosmology and Astrophysics (ASCA). Using ASCA's state-of-the-art non-dispersive X-ray spectrometers the 6.4 keV fluorescent iron line was found to be pulsing while the intensities of the 6.7 and 6.9 keV recombination lines do not vary with pulse phase. This confirms that the 6.4 keV line is due to reflection by relatively neutral matter close to the neutron star while the recombination lines originate in the extended stellar wind. The continuum spectrum was found to be modified by reflection from matter close to the neutron star. Observations with the EXOSAT GSPC were used to search for a CSRF. The EXOSAT spectra were consistent with the presence of a CSRF but an unambiguous detection was not possible because of a lack of sensitivity at energies higher than the cyclotron energy. Cen X-3 was then observed with the Rossi X-Ray Timing Explorer (RXTE) and evidence for a CSRF at 25.1 +/- 0.3 keV was

Dielectric properties and phase transition behaviors in (1-x)PbZrO3-xPb(Mg1/2W1/2)O3 ceramics

NASA Astrophysics Data System (ADS)

Vittayakorn, Naratip; Charoonsuk, Piyanut; Kasiansin, Panisara; Wirunchit, Supamas; Boonchom, Banjong

2009-09-01

The solid solution of lead zirconate [PbZrO3 (PZ)] and lead magnesium tungstate [Pb(Mg1/2W1/2)O3 (PMW)] has been synthesized by the wolframite precursor method. The crystal structure, phase transformations, dielectric and thermal properties of (1-x)PZ-xPMW, where x =0.00-0.10, were investigated. The crystal structure of sintered ceramics was analyzed by x-ray diffraction. Phase-pure perovskite was obtained for all compositions. Furthermore, a change from orthorhombic to rhombohedral symmetry was observed as the mole fraction of increased PMW. As a result, it was found that PbZrO3-Pb(Mg1/2W1/2)O3 undergoes successive transitions from the antiferroelectric phase to the ferroelectric phase to the paraelectric state. The coexistence of orthorhombic and rhombohedral phases in this binary system is located near the composition x =0.1.

Curie-Weiss behavior of Y{sub 1-x}Sr{sub x}MnO{sub 3} (x = 0 and 0.03)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thakur, Rajesh K., E-mail: thakur.rajesh2009@gmail.com; Thakur, Rasna; Gaur, N. K.

2015-06-24

The effect of bivalent cation Sr-doping on magnetic properties in multiferroic YMnO{sub 3} manganites was systemically studied by DC magnetic measurements. Both of the reported samples were prepared by solid-state reaction method with composition Y{sub 1−x}Sr{sub x}MnO{sub 3} (x = 0.00 and 0.03). The X-ray diffraction (XRD) results show that the compounds are synthesized in hexagonal crystal structure with space group P6{sub 3}cm (JCPDS: 25-1079) and slight increase in the lattice parameter is observed with strontium doping. The magnetisation versus temperature curve shows no clear anomaly near the antiferromagnetic transition temperature (T{sub N}), however from the magnetic measurements at 1000Oemore » a slight increase in the magnetisation is clearly witnessed with increasing Stront ium content to the Y-site.« less

Influence of oxygen vacancies on the magnetic and electrical properties of La1-xSrxMnO3-x/2 manganites

NASA Astrophysics Data System (ADS)

Trukhanov, S. V.; Lobanovski, L. S.; Bushinsky, M. V.; Khomchenko, V. A.; Pushkarev, N. V.; Troyanchuk, I. O.; Maignan, A.; Flahaut, D.; Szymczak, H.; Szymczak, R.

2004-11-01

The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} as well as anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} (0le x le 0.30) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the 0 le x le 0.125 are an O'-orthorhombic perovskites whereas in the 0.175 le x le 0.30 - a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses (0.175 < x le 0.30) and temperature of the magnetic moment freezing is 40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} system have been established by the magnetic measurements and compared with those for the stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.

Band alignment of SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) determined by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Feng, Zhaoqing; Feng, Qian; Zhang, Jincheng; Li, Xiang; Li, Fuguo; Huang, Lu; Chen, Hong-Yan; Lu, Hong-Liang; Hao, Yue

2018-03-01

In this work, we report the investigation of the band alignment of SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) utilizing the high resolution X-ray photoelectron spectroscopy (XPS) measurements. The single crystallinity and orientation of β-(AlxGa1-x)2O3 films grown on sapphire by pulsed laser deposition were studied with the high resolution X-ray diffraction. The Ga 2p3/2 and Si 2p core-level spectra as well as valence band spectra were used in the analysis of band alignment. As the mole fraction x of Al increases from 0 to 0.49, the bandgap and conduction band offset values of SiO2/(AlxGa1-x)2O3 increases from 4.9 to 5.6 eV and from 1.5 to 2.1 eV, respectively, while that of valence band offset decreases from 2.2 to 0.9 eV. From the results obtained, the energy band diagram of the studied SiO2/(AlxGa1-x)2O3 (0 ≤ x ≤ 0.49) interfaces is found to be of type I. Energy band lineups of SiO2/(AlxGa1-x)2O3 were thus determined which can be used as for Ga2O3 based power device technology.

Observation of divergent La{sup 3+} ion dilute effect in two series of 3-D fluorescent lanthanide-MOFs-based molecular alloys RE{sub x}La{sub 1−x}–EBTC (RE{sup 3+}=Eu{sup 3+} or Tb{sup 3+}; EBTC{sup 4−}=1,1′-ethynebenzene-3,3′,5,5′-etracarboxylate)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhai, Lu; State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093; Zhang, Wen-Wei, E-mail: wwzhang@nju.edu.cn

The lanthanide metal-organic frameworks (MOFs) [Ln{sub 2}(EBTC){sub 1.5}(CH{sub 3}OH){sub 4}]·6H{sub 2}O are isostructural to each other, where EBTC{sup 4−}=1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate; Ln{sup 3+}=La{sup 3+}, Eu{sup 3+} and Tb{sup 3+}; and the corresponding MOF is abbreviated as Ln–EBTC. MOFs Eu–EBTC and Tb–EBTC emit intense red and green luminescence (visible by bare eyes), respectively. The molecular alloys of Eu{sub x}La{sub 1−x}–EBTC and Tb{sub x}La{sub 1−x}–EBTC have been successfully prepared by mixing Eu{sup 3+}/Tb{sup 3+} and La{sup 3+} salts with the desired molar ratio in the starting material. Two series of Eu{sub x}La{sub 1−x}–EBTC and Tb{sub x}La{sub 1−x}–EBTC molecular alloys are isomorphic to the parentmore » Ln–EBTC MOFs, while exhibit divergent La{sup 3+} ion diluting effect, namely, with increasing the relative amount of La{sup 3+}, the intensity of characteristic emission arising from Tb{sup 3+} ion monotonely increases in Tb{sub x}La{sub 1−x}–EBTC molecular alloys, whereas that of Eu{sup 3+} ion shows non-monotone decrease in Eu{sub x}La{sub 1−x}–EBTC molecular alloys. The possible origin is discussed for such a divergent behavior between Eu{sub x}La{sub 1−x}–EBTC and Tb{sub x}La{sub 1−x}–EBTC molecular alloys. - Graphical abstract: Two series of 3-D fluorescent lanthanide-MOFs-based molecular alloys RE{sub x}La{sub 1−x}–EBTC (RE{sup 3+}=Eu{sup 3+} or Tb{sup 3+}; EBTC{sup 4−}=1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate) have been successfully prepared by mixing Eu{sup 3+}/Tb{sup 3+} and La{sup 3+} salts with the desired molar ratio in the starting material and showed photoluminescence property with divergent La{sup 3+} ion dilute effect. - Highlights: • 3-D molecular alloys of Eu{sub x}La{sub 1−x}–EBTC and Tb{sub x}La{sub 1−x}–EBTC were prepared. • They are isomorphic to the parent Ln–EBTC MOFs. • They show photoluminescence property with divergent

X-ray Photoelectron Spectroscopy study of CaV1-xMoxO3-δ

NASA Astrophysics Data System (ADS)

Belyakov, S. A.; Kuznetsov, M. V.; Shkerin, S. N.

2018-06-01

An investigation was carried out on perovskite-based derivatives of CaV1-xMoxO3-δ using X-ray Photoelectron Spectroscopy (XPS). According to the XRD pattern, the area of homogeneity covers the region from x = 0 to x = 0.6. Wide XPS-peaks of Ca, V, Mo and O are observed, signalling that elements are presented in multiple states. A model for explaining the large chemical shifts of XPS peaks due to different charging effects on different parts of the sample surface is proposed.

Evolution of the mössbauer spectra of ludwigite Co3 - x Fe x O2BO3 with substitution of iron for cobalt

NASA Astrophysics Data System (ADS)

Knyazev, Yu. V.; Ivanova, N. B.; Bayukov, O. A.; Kazak, N. V.; Bezmaternykh, L. N.; Vasiliev, A. D.

2013-06-01

A concentration series of single crystals of iron-cobalt ludwigites Co3 - x Fe x O2BO3 ( x = 0.0125, 0.025, 0.050, 0.10, 1.0) has been synthesized. The structure has been studied using X-ray diffraction and Mössbauer effect. A preferred occupation of nonequivalent crystallographic positions by iron in the ludwigite structure has been revealed. It has been found that the valence of substituting iron ions is three. It has been revealed that the structure of the γ-resonance spectrum of Co2FeO2BO3 is complicated due to a composition disorder in the system.

High temperature transport properties of co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nag, Abanti, E-mail: abanti@nal.res.in; Bose, Rapaka S.C.

Highlights: • The thermoelectric Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu) perovskite are prepared by solid state reaction. • The high temperature transport properties are explored. • The co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} shows non-metal-like temperature dependence of resistivity. • The Seebeck coefficient of Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} exhibits metallic nature. • The puzzling transport phenomenon is originated from oxygen vacancy related defect centres. - Abstract: The co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08) are synthesized by solid-state reaction and the electronic transport propertiesmore » are investigated. Rietveld refinement confirms the formation of single phase orthorhombic structure with gradual increase of cell parameters with doping level. The electronic transport properties such as Seebeck coefficient and electrical resistivity decrease with increasing the dopant concentration for both the co-substituted compositions. All the compositions of Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} show nonmetal-like temperature dependence of resistivity; whereas metal-like temperature dependence of thermopower. This inconsistency is explained by the formation of oxygen vacancy associated defect centres that originates from partial reduction of Mn{sup 4+} to Mn{sup 3+} due to co-substitution. The defect centres act as extrinsic carriers and cause additional contribution to the entropy of the system, leading to increase of Seebeck coefficient as a function of temperature. The transport mechanism of charge carriers is explained in the framework of Mott’s small polaron hopping mechanism.« less

Study on the solid solution of YMn{sub 1-x}Fe{sub x}O{sub 3}: Structural, magnetic and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, S.L.; Green, W.; Lofland, S.E.

The solid solution of YMn{sub 1-x}Fe{sub x}O{sub 3} (x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0) was synthesized from the citrate precursor route. The hexagonal crystal structure related to YMnO{sub 3} was stable for x{<=}0.3. Rietveld refinement was carried out on the composition for x=0.3 and was refined to a major hexagonal phase ({approx}97%) with 3% of orthorhombic Y(Fe/Mn)O{sub 3} phase. The a-axis lattice constant increases and the c-axis lattice constant decreases with x for x{<=}0.2. The increase in the c-axis lattice constant at x=0.3 could be due to the doping of significant amount of d{sup 5} ion (high spin Fe{sup 3+}more » ion) in a trigonal bipyramidal crystal field. The detailed structural, magnetic and dielectric properties are discussed. - Graphical abstract: Temperature dependence of {epsilon} of YMn{sub 1-x}Fe{sub x}O{sub 3} (0.0{<=}x{<=}0.3) at 100 kHz. Inset shows the temperature variation of inverse magnetic susceptibility.« less

V x In (2–x) S 3 Intermediate Band Absorbers Deposited by Atomic Layer Deposition

DOE PAGES

McCarthy, Robert F.; Weimer, Matthew S.; Haasch, Richard T.; ...

2016-03-21

Substitutional alloys of several thin film semiconductors have been proposed as intermediate band (IB) materials for use in next-generation photovoltaics, which aim to utilize a larger fraction of the solar spectrum without sacrificing significant photovoltage. Here, we demonstrate a novel approach to IB material growth, namely atomic layer deposition (ALD), to enable unique control over substitutional-dopant location and density. Two new ALD processes for vanadium sulfide incorporation are introduced, one of which incorporates a vanadium (III) amidinate previously untested for ALD. We synthesize the first thin film V xIn (2-x)S 3 intermediate band semiconductors, using this process, and further demonstratemore » that the V:In ratio, and therefore intraband gap density of states, can be finely tuned according to the ALD dosing schedule. Deposition on a crystalline In 2S 3 underlayer promotes the growth of a tetragonal β-In 2S 3-like phase V xIn (2-x)S 3, which exhibits a distinct sub-band gap absorption peak with onset near 1.1 eV in agreement with computational predictions. But, the V xIn (2-x)S 3 films lack the lower energy transition predicted for a partially filled IB, and photoelectrochemical devices reveal a photocurrent response only from illumination with energy sufficient to span the parent band-gap.« less

Interface energetics and atomic structure of epitaxial La{sub 1−x}Sr{sub x}CoO{sub 3} on Nb:SrTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Overmeere, Quentin, E-mail: quentin.vanovermeere@uclouvain.be, E-mail: john.d.baniecki@jp.fujitsu.com; Baniecki, John D., E-mail: quentin.vanovermeere@uclouvain.be, E-mail: john.d.baniecki@jp.fujitsu.com; Yamazaki, Takashi

2015-06-15

The energetics at oxide semiconductor/La{sub 1−x}Sr{sub x}CoO{sub 3} heterojunctions, including the respective alignment of the valence and conduction bands, govern charge transfer and have to be determined for the design of future La{sub 1−x}Sr{sub x}CoO{sub 3}-based devices. In this letter, the electronic and atomic structures of epitaxial La{sub 1−x}Sr{sub x}CoO{sub 3} on Nb-doped strontium titanate are revealed by scanning transmission electron microscopy, electron energy loss spectroscopy, and in situ x-ray and ultra violet photoelectron spectroscopies. For LaCoO{sub 3}, a valence band (VB) offset of 2.8 ± 0.1 eV is deduced. The large offset is attributed to the orbital contributions of the Co 3dmore » states to the VB maximum of the LaCoO{sub 3} thin films, with no evidence of interface dipole contributions. The sensitivity of the valence band orbital character to spin state ordering and oxygen vacancies is assessed using density functional theory.« less

Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp; Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550; Maeda, Hiroki

Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-freemore » new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.« less

Advanced Data Visualization in Astrophysics: The X3D Pathway

NASA Astrophysics Data System (ADS)

Vogt, Frédéric P. A.; Owen, Chris I.; Verdes-Montenegro, Lourdes; Borthakur, Sanchayeeta

2016-02-01

Most modern astrophysical data sets are multi-dimensional; a characteristic that can nowadays generally be conserved and exploited scientifically during the data reduction/simulation and analysis cascades. However, the same multi-dimensional data sets are systematically cropped, sliced, and/or projected to printable two-dimensional diagrams at the publication stage. In this article, we introduce the concept of the “X3D pathway” as a mean of simplifying and easing the access to data visualization and publication via three-dimensional (3D) diagrams. The X3D pathway exploits the facts that (1) the X3D 3D file format lies at the center of a product tree that includes interactive HTML documents, 3D printing, and high-end animations, and (2) all high-impact-factor and peer-reviewed journals in astrophysics are now published (some exclusively) online. We argue that the X3D standard is an ideal vector for sharing multi-dimensional data sets because it provides direct access to a range of different data visualization techniques, is fully open source, and is a well-defined standard from the International Organization for Standardization. Unlike other earlier propositions to publish multi-dimensional data sets via 3D diagrams, the X3D pathway is not tied to specific software (prone to rapid and unexpected evolution), but instead is compatible with a range of open-source software already in use by our community. The interactive HTML branch of the X3D pathway is also actively supported by leading peer-reviewed journals in the field of astrophysics. Finally, this article provides interested readers with a detailed set of practical astrophysical examples designed to act as a stepping stone toward the implementation of the X3D pathway for any other data set.

Hadron physics through asymptotic SU(3) and the chiral SU(3) x SU(3) algebra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oneda, S.; Matsuda, S.; Perlmutter, A.

From Coral Gables conference on fundamental interactions for theoretical studies; Coral Gables, Florida, USA (22 Jan 1973). See CONF-730124-. The inter- SU(3)-multiplet regularities and clues to a possible level scheme of hadrons are studied in a systematic way. The hypothesis of asymptotic SU(3) is made in the presence of GMO mass splittings with mixing, which allows information to be extracted from the chiral SU(3) x SU(3) charge algebras and from the exotic commutation relations. For the ground states the schemes obtained are compatible with those of the SU(6) x O(3) classification. Sum rules are obtained which recover most of themore » good results of SU(6). (LBS)« less

A Study of Cen X-3 as Seen by INTEGRAL

NASA Astrophysics Data System (ADS)

La Barbera, A.; Baushev, A.; Ferrigno, C.; Piraino, S.; Santangelo, A.; Segreto, A.; Orlandini, M.; Kretschmar, P.; Kreykenbohm, I.; Wilms, J.; Staubert, R.; Coburn, W.; Heindl, W. A.

2004-10-01

We present a preliminary analysis of 14 observa- tions (Science Windows SCW) of the eclipsing High Mass X ray Binary Pulsar Cen X 3 taken during the Galactic Plane Scan (GPS) with INTEGRAL. The source was detected in 4 SCWs by JEM-X for a total exposure time of 8.7 ksec and in 11 SCWs by ISGRI for a total exposure time of 23.8 ksec. The study of the pulse profile is reported. The 10 70 keV spec- trum is also described. The results are compared with those from previous X ray missions. Key words: pulsars, individual: Cen X 3; stars: neu- tron stars; X rays: binaries.

P2X3 and P2X2/3 Receptors Play a Crucial Role in Articular Hyperalgesia Development Through Inflammatory Mechanisms in the Knee Joint Experimental Synovitis.

PubMed

Teixeira, Juliana Maia; Bobinski, Franciane; Parada, Carlos Amílcar; Sluka, Kathleen A; Tambeli, Cláudia Herrera

2017-10-01

Osteoarthritis (OA) is a degenerative and progressive disease characterized by cartilage breakdown and by synovial membrane inflammation, which results in disability, joint swelling, and pain. The purinergic P2X3 and P2X2/3 receptors contribute to development of inflammatory hyperalgesia, participate in arthritis processes in the knee joint, and are expressed in chondrocytes and nociceptive afferent fibers innervating the knee joint. In this study, we hypothesized that P2X3 and P2X2/3 receptors activation by endogenous ATP (adenosine 5'-triphosphate) induces articular hyperalgesia in the knee joint of male and female rats through an indirect sensitization of primary afferent nociceptors dependent on the previous release of pro-inflammatory cytokines and/or on neutrophil migration. We found that the blockade of articular P2X3 and P2X2/3 receptors significantly attenuated carrageenan-induced hyperalgesia in the knee joint of male and estrus female rats in a similar manner. The carrageenan-induced knee joint inflammation increased the expression of P2X3 receptors in chondrocytes of articular cartilage. Further, the blockade of articular P2X3 and P2X2/3 receptors significantly reduced the increased concentration of TNF-α, IL-6, and CINC-1 and the neutrophil migration induced by carrageenan. These findings indicate that P2X3 and P2X2/3 receptors activation by endogenous ATP is essential to hyperalgesia development in the knee joint through an indirect sensitization of primary afferent nociceptors dependent on the previous release of pro-inflammatory cytokines and/or on neutrophil migration.

Luminescence and scintillation characteristics of (GdxY3-x)Al2Ga3O12:Ce (x = 1,2,3) single crystals

NASA Astrophysics Data System (ADS)

Chewpraditkul, Warut; Pattanaboonmee, Nakarin; Sakthong, Ongsa; Chewpraditkul, Weerapong; Szczesniak, Tomasz; Moszynski, Marek; Kamada, Kei; Yoshikawa, Akira; Nikl, Martin

2018-02-01

The luminescence and scintillation characteristics of Czochralski-grown (GdxY3-x)Al2Ga3O12:Ce (x = 1,2,3) single crystals are presented. With increasing Gd content in this garnet host, the 5d2 absorption band was blue-shifted while the 5d1 absorption and 5d1 → 4f emission bands were red-shifted due to an increase in the crystal field splitting of the 5d levels. In addition, the luminescence quenching temperature of the Ce3+emission and activation energy for thermal quenching decreased with increasing Gd content. The Gd3+ → Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. At 662 keV γ - rays, the light yield (LY) of 48,600 ph/MeV and energy resolution of 6.5% was measured for a Gd3Al2Ga3O12:Ce crystal. Scintillation decay measurements were performed using the time-correlated single photon counting technique. Superior time resolution of Gd3Al2Ga3O12:Ce is due to its high LY and fast scintillation response. The total mass attenuation coefficients at 60 and 662 keV γ - rays were also determined.

Structure-property relations in sputter deposited epitaxial (1-x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 thin films

NASA Astrophysics Data System (ADS)

Frederick, Joshua C.

Lead-based ferroelectric materials are of significant technological importance for sensing and actuation due to their high piezoelectric performance (i.e., the ability to convert an electrical signal to mechanical displacement, and vice versa). Traditionally, bulk ceramic or single crystals materials have filled these roles; however, emerging technologies stand to benefit by incorporating thin films to achieve miniaturization while maintaining high efficiency and sensitivity. Currently, chemical systems that have been well characterized in bulk form (e.g. Pb(Mg1/3Nb2/3)O3- xPbTiO3, or PMN-xPT) require further study to optimize both the chemistry and structure for deployment in thin film devices. Furthermore, the effect of internal electric fields is more significant at the length scales of thin films, resulting in self biases that require compensation to reveal their intrinsic dielectric response. To this end, the structure-property relations of epitaxial PMN-xPT films sputter deposited on a variety of substrates were investigated. Attention was paid to how the structure (i.e., strain state, crystal structure, domain configuration, and defects) gave rise to the ferroelectric, dielectric, and piezoelectric response. Three-dimensional visualization of the dielectric response as a simultaneous function of electric field and temperature revealed the true phase transition of the films, which was found to correspond to the strain state and defect concentration. A lead-buffered anneal process was implemented to enhance the ferroelectric and dielectric response of the films without altering their stoichiometry. It was discovered that PMN- xPT films could be domain-engineered to exhibit a mixed domain state through chemistry and substrate choice. Such films exhibited a monoclinic distortion similar to that of the bulk compositions near the morphotropic phase boundary. Finally, it was revealed that the piezoelectric response could be greatly enhanced by declamping the film

Covalency in lanthanides. An X-ray absorption spectroscopy and density functional theory study of LnCl6(x-) (x = 3, 2).

PubMed

Löble, Matthias W; Keith, Jason M; Altman, Alison B; Stieber, S Chantal E; Batista, Enrique R; Boland, Kevin S; Conradson, Steven D; Clark, David L; Lezama Pacheco, Juan; Kozimor, Stosh A; Martin, Richard L; Minasian, Stefan G; Olson, Angela C; Scott, Brian L; Shuh, David K; Tyliszczak, Tolek; Wilkerson, Marianne P; Zehnder, Ralph A

2015-02-25

Covalency in Ln-Cl bonds of Oh-LnCl6(x-) (x = 3 for Ln = Ce(III), Nd(III), Sm(III), Eu(III), Gd(III); x = 2 for Ln = Ce(IV)) anions has been investigated, primarily using Cl K-edge X-ray absorption spectroscopy (XAS) and time-dependent density functional theory (TDDFT); however, Ce L3,2-edge and M5,4-edge XAS were also used to characterize CeCl6(x-) (x = 2, 3). The M5,4-edge XAS spectra were modeled using configuration interaction calculations. The results were evaluated as a function of (1) the lanthanide (Ln) metal identity, which was varied across the series from Ce to Gd, and (2) the Ln oxidation state (when practical, i.e., formally Ce(III) and Ce(IV)). Pronounced mixing between the Cl 3p- and Ln 5d-orbitals (t2g* and eg*) was observed. Experimental results indicated that Ln 5d-orbital mixing decreased when moving across the lanthanide series. In contrast, oxidizing Ce(III) to Ce(IV) had little effect on Cl 3p and Ce 5d-orbital mixing. For LnCl6(3-) (formally Ln(III)), the 4f-orbitals participated only marginally in covalent bonding, which was consistent with historical descriptions. Surprisingly, there was a marked increase in Cl 3p- and Ce(IV) 4f-orbital mixing (t1u* + t2u*) in CeCl6(2-). This unexpected 4f- and 5d-orbital participation in covalent bonding is presented in the context of recent studies on both tetravalent transition metal and actinide hexahalides, MCl6(2-) (M = Ti, Zr, Hf, U).

Synthetic and Spectroscopic Studies on N-(i,j-Disubstituted Phenyl)-4- Substituted Benzenesulphonamides, 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i, j = 2, 3; 2, 4; 2, 5; 2, 6 or 3, 4; and X = CH3 or Cl

NASA Astrophysics Data System (ADS)

Shetty, Mahesha; Gowda, B. Thimme

2005-02-01

Fifty four N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides of the general formula 4-X'C6H4SO2NH(i,j-X2C6H3), where X' = H, CH3, C2H5, F, Cl or Br; i,j = 2,3; 2,4; 2,5; 2,6 or 3, 4; and X = CH3 or Cl, are prepared and characterized and their infrared, 1H and 13C NMR spectra in solution are studied. The N-H stretching vibrations νN-H absorb in the range 3305 - 3205 cm-1, while the asymmetric and symmetric SO2 vibrations vary in the ranges 1377 - 1307 cm-1 and 1184 - 1128 cm-1, respectively. The N-(i,j-disubstituted phenyl)-4-substituted benzenesulphonamides show C-S, S-N and C-N stretching vibrations in the ranges 844 - 800 cm-1, 945 - 891 cm-1 and 1309 - 1170 cm-1, respectively. The compounds do not exhibit particular trends in the variation of these frequencies on substitution either at ortho or meta positions with either a methyl group or Cl. The observed 1H and 13C chemical shifts of are assigned to protons and carbon atoms of the two benzene rings. Incremental shifts of the ring protons and carbon atoms due to -SO2NH(i,j-X2C6H3) groups in C6H5SO2NH(i,j-X2C6H3) and 4-X'C6H4SO2NH- groups in 4-X'C6H4SO2NH(C6H*) are computed and employed to calculate the chemical shifts of the ring protons and carbon atoms in the substituted compounds 4-X'C6H4SO2NH(i,j-X2C6H3). The different methods of calculation lead to almost the same values in most cases and agree well with the observed chemical shifts, indicating the validity of the principle of additivity of the substituent effects with chemical shifts in these compounds.

P2X2 knockout mice and P2X2/P2X3 double knockout mice reveal a role for the P2X2 receptor subunit in mediating multiple sensory effects of ATP

PubMed Central

Cockayne, Debra A; Dunn, Philip M; Zhong, Yu; Rong, Weifang; Hamilton, Sara G; Knight, Gillian E; Ruan, Huai-Zhen; Ma, Bei; Yip, Ping; Nunn, Philip; McMahon, Stephen B; Burnstock, Geoffrey; Ford, Anthony PDW

2005-01-01

Extracellular ATP plays a role in nociceptive signalling and sensory regulation of visceral function through ionotropic receptors variably composed of P2X2 and P2X3 subunits. P2X2 and P2X3 subunits can form homomultimeric P2X2, homomultimeric P2X3, or heteromultimeric P2X2/3 receptors. However, the relative contribution of these receptor subtypes to afferent functions of ATP in vivo is poorly understood. Here we describe null mutant mice lacking the P2X2 receptor subunit (P2X2−/−) and double mutant mice lacking both P2X2 and P2X3 subunits (P2X2/P2X3Dbl−/−), and compare these with previously characterized P2X3−/− mice. In patch-clamp studies, nodose, coeliac and superior cervical ganglia (SCG) neurones from wild-type mice responded to ATP with sustained inward currents, while dorsal root ganglia (DRG) neurones gave predominantly transient currents. Sensory neurones from P2X2−/− mice responded to ATP with only transient inward currents, while sympathetic neurones had barely detectable responses. Neurones from P2X2/P2X3Dbl−/− mice had minimal to no response to ATP. These data indicate that P2X receptors on sensory and sympathetic ganglion neurones involve almost exclusively P2X2 and P2X3 subunits. P2X2−/− and P2X2/P2X3Dbl−/− mice had reduced pain-related behaviours in response to intraplantar injection of formalin. Significantly, P2X3−/−, P2X2−/−, and P2X2/P2X3Dbl−/− mice had reduced urinary bladder reflexes and decreased pelvic afferent nerve activity in response to bladder distension. No deficits in a wide variety of CNS behavioural tests were observed in P2X2−/− mice. Taken together, these data extend our findings for P2X3−/− mice, and reveal an important contribution of heteromeric P2X2/3 receptors to nociceptive responses and mechanosensory transduction within the urinary bladder. PMID:15961431

A giant radio flare from Cygnus X-3 with associated γ-ray emission: The 2011 radio and γ-ray flare of Cyg X-3

DOE PAGES

Corbel, S.; Dubus, G.; Tomsick, J. A.; ...

2012-04-10

With frequent flaring activity of its relativistic jets, Cygnus X-3 (Cyg X-3) is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high-energy γ-ray emission, thanks to detections by Fermi Large Area Telescope (Fermi/LAT) and AGILE. In 2011, we observed Cyg X-3 in order to transit to a soft X-ray state, which is known to be associated with high-energy γ-ray emission. We present the results of a multiwavelength campaign covering a quenched state, when radio emission from Cyg X-3 is at its weakest and the X-ray spectrum is very soft. A giant (~20more » Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E≥ 100 MeV) reveal renewed γ-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the γ-ray emission is not exclusively related to the rare giant radio flares. A three-week period of γ-ray emission is also detected when Cyg X-3 was weakly flaring in radio, right before transition to the radio quenched state. There were no γ-rays observed during the ~1-month long quenched state, when the radio flux is weakest. These results suggest transitions into and out of the ultrasoft X-ray (radio-quenched) state trigger γ-ray emission, implying a connection to the accretion process, and also that the γ-ray activity is related to the level of radio flux (and possibly shock formation), strengthening the connection to the relativistic jets.« less

Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films

NASA Astrophysics Data System (ADS)

Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk

2017-03-01

Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu1 - x Fe x O3 - δ epitaxial thin films ( x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu1 - x Fe x O3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR ( 36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies ( δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr1 - x La x )(Ru1 - x Fe x )O3. These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu1 - x Fe x O3 - δ thin films.

The structure and optical properties of Sr{sub 1−x}Ca{sub x}MoO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopper, H.A.; Macphee, D.E.; Mclaughlin, A.C., E-mail: a.c.mclaughlin@abdn.ac.uk

2016-10-15

The solid solution Sr{sub 1−x}Ca{sub x}MoO{sub 3} (x=0.00, 0.05, 0.10, 0.13, 0.15 and 0.17) has successfully been synthesised and X-ray Powder diffraction has revealed the occurrence of structural phase transitions, from cubic Pm−3m to tetragonal I4/mcm, and then to orthorhombic Imma as the value of x increased. Discontinuities were observed in the cell parameters and bond lengths and angles at the transition from tetragonal to orthorhombic symmetry as a result of the switching of the octahedral rotation axis at the tetragonal to orthorhombic transition. The increased octahedral tilting could also be linked to the decrease in the band gap frommore » 2.20 eV to 2.10 eV as x increased from 0 to 0.17. - Graphical abstract: Table of Contents Figure Caption: Ultraviolet-visible absorbance spectra for Sr{sub 1−x}Ca{sub x}MoO{sub 3} showing a reduction in band gap upon increasing x as a result of increased octahedral tilting. - Highlights: • The solid solution Sr{sub 1−x}Ca{sub x}MoO{sub 3} has been synthesised. • Structural phase transitions are observed. • Discontinuities were observed in the cell parameters and bond lengths and angles. • Upon increasing x from 0 to 0.17 the band gap reduces from 2.20 eV to 2.10 eV.« less

Piezoelectric properties of nonstoichiometric Sr1-xBi2+2x/3Ta2O9 ceramics

NASA Astrophysics Data System (ADS)

Jain, Rajni; Chauhan, Arun Kumar Singh; Gupta, Vinay; Sreenivas, K.

2005-06-01

The effect of poling on the structural, dielectric, and piezoelectric properties has been investigated for sol-gel-derived strontium bismuth tantalate (SBT) [Sr1-xBi2+2x/3Ta2O9] ceramics with x =0.0,0.15,0.30,0.45. The dielectric and ferroelectric properties are found to improve with increase in x up to 0.3. Beyond x >0.3 the properties are found to degrade due to the limited solid solubility and the presence of a mixed phase of bismuth tantalate (BiTaO4) is detected with x =0.45. Poling treatment reduces the dielectric dispersion and dielectric loss in the frequency range (0.1-100kHz). The resonance and antiresonance frequencies increase with increase in x (x=0-0.30), and the corresponding minimum impedance decreases. The measured coupling coefficients (kp) are small (0.0967-0.1) for x =0-0.30, and the electromechanical quality factor (Qm=915) is a maximum for the Sr0.7Bi2.2Ta2O9 composition (x=0.30). The estimated piezoelectric charge coefficient (d31) and piezoelectric voltage coefficient (g31) are 5.2pC/N and 5.8×10-3Vm/N, respectively. The positive values of d31 and g31 and the low dielectric permittivity of SBT yield a high value for the hydrostatic coefficients, despite the low charge coefficient of d33=24pC/N. The maximum values of charge coefficient (dh=34pC/N) and voltage coefficient (gh=39×10-3Vm/N) are obtained for Sr0.7Bi2.2Ta2O9 composition, and the estimated hydrostatic figure of merit (dhgh×10-15=1215m2/N) is high.

Enhanced Photocatalytic Activity in Bi1-x Ba x FeO3 Prepared by a PEG400 Assisted Sol-Gel Method

NASA Astrophysics Data System (ADS)

Zhang, Chenlan; Chen, Jianguo; Jin, Dengren; Cheng, Jinrong

2018-03-01

Ferroelectric Bi1-x Ba x FeO3 nanoparticles for x = 0, 0.01, 0.03, 0.05 and 0.10 were synthesized by a polyethylene glycol 400 (PEG400) assisted sol-gel method. X-ray diffraction reveals that Bi1-x Ba x FeO3 nanoparticles exhibit a distorted rhombohedral structure with the R3c space group, and the diffraction peaks shift upon incorporation of Ba. Transmission electron microscope analysis shows that the particle size of Bi1-x Ba x FeO3 nanoparticles is in the range of 30-60 nm, decreasing with an increase in Ba content. Bi1-x Ba x FeO3 nanoparticles have band gaps in the range of 1.68-2.0 eV, which are capable of responding to visible light irradiation. The rate of the photocatalytic degradation of Bi1-x Ba x FeO3 nanoparticles for x = 0.03 to methyl orange (MO) dye achieves about 81% under visible light irradiation for 3 h, which is higher than that of 66% for pure phase BiFeO3 (BFO). Moreover, the effects of Ba2+ modification on the band gap of BFO crystallites have been investigated and discussed.

Theoretical Study of the B(sup 3) Sigma(sup -, sub u) - X(sup3)Sigma(sub g, sup -) and B"(sup 3)Pi(sub u) - X(sup 3)Sigma(sub g, sup -) Band Systems of S(sub 2)

NASA Technical Reports Server (NTRS)

Pradhan, Atul D.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

Multireference configuration-interaction (MRCI) wavefunctions and potential energy curves have been calculated for the X(sup 3)Sigma(sub g,sup -), B(sup 3)Sigma(sub u, Sup -) and B"(sup 3)Pi((sub u) states of S(sub 2) using correlation consistent Gaussian basis sets. These wavefunctions are utilized to compute the the transition dipole moments of the B(sup 3)Sigma(sub g, sup -) - X(sup 3) Sigma(sub g, sup -) and B"(sup 3)Pi(sub u) - X(sup 3)Sigma(sub g, sup -) systems. Oscillator strengths, transition probabilities, and radiative lifetimes are computed for the X-B system and comparison is made with experimental data.

The dust scattering halo of Cygnus X-3

NASA Astrophysics Data System (ADS)

Corrales, L. R.; Paerels, F.

2015-10-01

Dust grains scatter X-ray light through small angles, producing a diffuse halo image around bright X-ray point sources situated behind a large amount of interstellar material. We present analytic solutions to the integral for the dust scattering intensity, which allow for a Bayesian analysis of the scattering halo around Cygnus X-3. Fitting the optically thin 4-6 keV halo surface brightness profile yields the dust grain size and spatial distribution. We assume a power-law distribution of grain sizes (n ∝ a-p) and fit for p, the grain radius cut-off amax, and dust mass column. We find that a p ≈ 3.5 dust grain size distribution with amax ≈ 0.2 μm fits the halo profile relatively well, whether the dust is distributed uniformly along the line of sight or in clumps. We find that a model consisting of two dust screens, representative of foreground spiral arms, requires the foreground Perseus arm to contain 80 per cent of the total dust mass. The remaining 20 per cent of the dust, which may be associated with the outer spiral arm of the Milky Way, is located within 1 kpc of Cyg X-3. Regardless of which model was used, we found τ_sca ˜ 2 E_keV^{-2}. We examine the energy resolved haloes of Cyg X-3 from 1 to 6 keV and find that there is a sharp drop in scattering halo intensity when E < 2-3 keV, which cannot be explained with multiple scattering effects. We hypothesize that this may be caused by large dust grains or material with unique dielectric properties, causing the scattering cross-section to depart from the Rayleigh-Gans approximation that is used most often in X-ray scattering studies. The foreground Cyg OB2 association, which contains several evolved stars with large extinction values, is a likely culprit for grains of unique size or composition.

Effects of dopant induced defects on structural, multiferroic and optical properties of Bi1-x Pb x FeO3 (0 ≤ x ≤ 0.3) ceramics

NASA Astrophysics Data System (ADS)

Hassnain Jaffari, G.; Aftab, M.; Samad, Abdus; Mumtaz, Fiza; Awan, M. S.; Shah, S. Ismat

2018-01-01

Bi1-x Pb x FeO3 (0 ≤ x ≤ 0.3) has been characterized in detail with an aim to identify role of defect such as dopant, various vacancies, grain boundaries etc, and their effect on structural, optical and multiferroic properties. Structural analysis revealed that Pb substitution transforms the rhombohedral phase of BiFeO3 to the pseudocubic phase for x ≥ 0.15, consistently all vibrational Raman modes associated with the rhombohedral phase are found disappeared. Optical response revealed weakening of the d-d transitions with Pb addition indicating change in the Fe atoms environment consistent with the transition from non-centrosymmetric to the centrosymmetric structure. Transport and dielectric responses are explained in terms of hopping due to the presence of defects like oxygen vacancies and grain boundary conduction. In the high temperature regime, grain boundary conduction led to decrease in resistivity with the presence of a hump that is associated with hopping conduction. Extrinsic contributions in the transport properties correlate well with dielectric response. Magnetic and ferroelectric responses are also presented where role of oxygen vacancies defects has been clearly identified.

Temperature Dependence of the Tunneling Conductance in Ba_1-xK_xBiO_3

NASA Astrophysics Data System (ADS)

Miyakawa, N.; Ozyuzer, L.; Zasadzinski, J. F.

1997-03-01

Tunneling measurements have been made on high-density polycrystalline pellets of Ba_1-xK_xBiO3 using a point contact method. The temperature dependence (up to 30 K) and magnetic field dependence (up to 6T) of the tunneling conductance has been measured. It is found that at temperatures less than 4.2 K the gap region conductance can be fit with a BCS density of states (dos) and thermal smearing only. However, as the temperature is increased a quasiparticle recombination rate, Γ, which increases as T^n (n ~ 3) must be included in the dos to fit the data. The behavior of Γ (T) does not follow the strong-coupling theory of Kaplan et al. (S.B. Kaplan et al. Phys. Rev. B 14), 4854 (1976) We investigate whether this anomalous power law dependence can come out of Eliashberg theory using the electron-phonon spectral function, a^2F(ω) for Ba_1-xK_xBiO_3.

Thermal and electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Erica M.; Poudeu, Pierre F.P., E-mail: ppoudeup@umich.edu

Several compositions of the Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) series were synthesized via solid-state reaction of the elements. The structural stability at various temperatures and the effect of Li:Cu ratio on the thermal conductivity and the electrochemical performance of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells during charge–discharge process were investigated. Differential scanning calorimetry (DSC) measurements showed a sharp endothermic peak at 140 °C for Cu{sub 4−x}Li{sub x}S{sub 2} samples with x=1 and 2, which is ascribed to a structural phase transition. X-ray diffraction (XRD) measurements on various Cu{sub 4−x}Li{sub x}S{sub 2} samples at temperatures below and above 140 °Cmore » indicated a structural phase transition from the room temperature low-symmetry structure to the high temperature cubic structure of Cu{sub 2}S. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples decreases with decreasing Cu:Li ratio and with increasing temperature. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples at room temperature decreases from 1.2 W/m K for Cu:Li=3:1 to 0.7 W/m K for Cu:Li=1:3. Cyclic voltammetry of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells showed that high discharge capacity (165 mA h g{sup −1}) and stable reversible charge–discharge process is observed for Cu:Li=2:2, whereas other Cu:Li ratios lead to low discharge capacity and poor reversibility. The electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells is rationalized by taking into account the competing reactions of Li{sup +} ions with CuS and Cu{sub 2}S during discharge. - Graphical abstract: Tuning Li content in Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells to maintain a Cu/Li ratio equal to unity affords maximum capacity and high stability of the charge–discharge process. - Highlights: • Cu:Li ratio strongly influenced crystal structure and properties of Cu{sub 4-x}Li{sub x}S{sub 2}. • Compositions with x = 1 and

Metal-insulator transition in Nd(1-x)Eu(x)NiO(3) compounds.

PubMed

Escote, M T; Barbeta, V B; Jardim, R F; Campo, J

2006-07-05

Polycrystalline Nd(1-x)Eu(x)NiO(3) (0≤x≤0.5) compounds were synthesized in order to investigate the character of the metal-insulator (MI) phase transition in this series. Samples were prepared through the sol-gel route and subjected to heat treatments at ∼1000 °C under oxygen pressures as high as 80 bar. X-ray diffraction (XRD) and neutron powder diffraction (NPD), electrical resistivity ρ(T), and magnetization M(T) measurements were performed on these compounds. The NPD and XRD results indicated that the samples crystallize in an orthorhombic distorted perovskite structure, space group Pbnm. The analysis of the structural parameters revealed a sudden and small expansion of ∼0.2% of the unit cell volume when electronic localization occurs. This expansion was attributed to a small increase of ∼0.003 Å of the average Ni-O distance and a simultaneous decrease of ∼-0.5° of the Ni-O-Ni superexchange angle. The ρ(T) measurements revealed a MI transition occurring at temperatures ranging from T(MI)∼193 to 336 K for samples with x = 0 and 0.50, respectively. These measurements also show a large thermal hysteresis in NdNiO(3) during heating and cooling processes, suggesting a first-order character of the phase transition at T(MI). The width of this thermal hysteresis was found to decrease appreciably for the sample Nd(0.7)Eu(0.3)NiO(3). The results indicate that cation disorder associated with increasing substitution of Nd by Eu is responsible for changing the first-order character of the transition in NdNiO(3).

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Y. Z.; Wu, M. M.; Peng, J.

2007-05-03

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0) have been investigated by X-ray diffraction and differential thermal analysis. The partial substitution of Er{sup 3+} for Fe{sup 3+} induces pronounced decreases in the phase transition temperature from monoclinic to orthorhombic structure. Rietveld analysis of the XRD data shows that both the monoclinic and orthorhombic Fe{sub 2}(MoO{sub 4}){sub 3}, as well as the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x {le} 0.8) have positive thermal expansion coefficients. However, the linear thermal expansion coefficients of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x = 0.6-2.0)more » decrease with increasing content of Er{sup 3+} and for x {ge} 1.0, compounds Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} show negative thermal expansion properties. Attempts for making zero thermal expansion coefficient materials result in that very low negative thermal expansion coefficient of -0.60 x 10{sup -6} C in Er{sub 1.0}Fe{sub 1.0}(MoO{sub 4}){sub 3} is observed in the temperature range of 180-400 C, and zero thermal expansion is observed in Er{sub 0.8}Fe{sub 1.2}(MoO{sub 4}){sub 3} in the temperature range of 350-450 C. In addition, anisotropic thermal expansions are found for all the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} compounds, with negative thermal expansion coefficients along the a axes.« less

Short-range order in the Ca sub 1-x La sub x F sub 2+x solid solution: 1:0:3 or 1:0:4 clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laval, J.P.; Abaouz, A.; Frit, B.

1989-08-01

The defect structure of the Ca{sub 1-x}La{sub x}F{sub 2+x} solid solution (0 {le} x {le} 0.38) has been examined at room temperature by powder neutron diffraction. Two kinds of (xxx) interstitial anions, whose respective numbers increase linearly with increasing dopant cation concentration, have been found: one labeled F{sup 0} (x {approx} 0.41) is a true interstitial; the other labeled F{sup {prime}{double prime}} (x {approx} 0.31) can be considered a relaxed normal anion. Two 1:0:n defect clusters are compatible, within the experimental errors, with these results: the 1:0:3 (1V{sub F}, OF{prime}, 3F{sup {double prime}}, 2 La{sup 3+}) and the 1:0:4 (1V{submore » F}, OF{prime}, 4F{sup {double prime}}, 3La{sup 3+}) clusters. Charge balance considerations and comparisons with the homologous Ca{sub 1-x}M{sub x}{sup IV}F{sub 2+2x} solid solutions (M{sup IV} = Th, U) allow us to think that the less dense 1:0:3 cluster is present for the whole domain of both kinds of solid solutions.« less

General working principles of CH3NH3PbX3 perovskite solar cells.

PubMed

Gonzalez-Pedro, Victoria; Juarez-Perez, Emilio J; Arsyad, Waode-Sukmawati; Barea, Eva M; Fabregat-Santiago, Francisco; Mora-Sero, Ivan; Bisquert, Juan

2014-02-12

Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin films of CH3NH3PbI(3-x)Clx and CH3NH3PbI3 infiltrated on nanostructured TiO2. The results show nearly identical spectral characteristics indicating a unique photovoltaic operating mechanism that provides long diffusion lengths (1 μm). Carrier conductivity in both devices is closely matched, so that the most significant differences in performance are attributed to recombination rates. These results highlight the central role of the CH3NH3PbX3 semiconductor absorber in carrier collection and provide a new tool for improved optimization of perovskite solar cells. We report for the first time a measurement of the diffusion length in a nanostructured perovskite solar cell.

40 CFR Table 3 to Subpart X of... - Toxic Equivalency Factors

Code of Federal Regulations, 2012 CFR

2012-07-01

... Subpart X of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS... Standards For Hazardous Air Pollutants From Secondary Lead Smelting Pt. 63, Subpt. X, Table 3 Table 3 to Subpart X of Part 63—Toxic Equivalency Factors Dioxin/furan congener Toxic equivalency factor 2,3,7,8...

40 CFR Table 3 to Subpart X of... - Toxic Equivalency Factors

Code of Federal Regulations, 2013 CFR

2013-07-01

... Subpart X of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS... Standards For Hazardous Air Pollutants From Secondary Lead Smelting Pt. 63, Subpt. X, Table 3 Table 3 to Subpart X of Part 63—Toxic Equivalency Factors Dioxin/furan congener Toxic equivalency factor 2,3,7,8...

40 CFR Table 3 to Subpart X of... - Toxic Equivalency Factors

Code of Federal Regulations, 2014 CFR

2014-07-01

... Subpart X of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS... Standards For Hazardous Air Pollutants From Secondary Lead Smelting Pt. 63, Subpt. X, Table 3 Table 3 to Subpart X of Part 63—Toxic Equivalency Factors Dioxin/furan congener Toxicequivalency factor 2,3,7,8...

Identification and SAR of novel diaminopyrimidines. Part 1: The discovery of RO-4, a dual P2X(3)/P2X(2/3) antagonist for the treatment of pain.

PubMed

Carter, David S; Alam, Muzaffar; Cai, Haiying; Dillon, Michael P; Ford, Anthony P D W; Gever, Joel R; Jahangir, Alam; Lin, Clara; Moore, Amy G; Wagner, Paul J; Zhai, Yansheng

2009-03-15

P2X purinoceptors are ligand-gated ion channels whose endogenous ligand is ATP. Both the P2X(3) and P2X(2/3) receptor subtypes have been shown to play an important role in the regulation of sensory function and dual P2X(3)/P2X(2/3) antagonists offer significant potential for the treatment of pain. A high-throughput screen of the Roche compound collection resulted in the identification of a novel series of diaminopyrimidines; subsequent optimization resulted in the discovery of RO-4, a potent, selective and drug-like dual P2X(3)/P2X(2/3) antagonist.

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe 3–xSe x

DOE PAGES

Cui, Shan; He, Lan -Po; Hong, Xiao -Chen; ...

2016-06-09

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe 3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe 3–x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe 3–x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependencemore » of κ 0/T manifests a multigap behavior. Lastly, these results demonstrate multiple nodeless superconducting gaps in ZrTe 3–x Se x, which indicates conventional superconductivity despite of the existence of a CDW QCP.« less

Stable Chloro- and Bromoxenate Cage Anions; [X3(XeO3)3]3- and [X4(XeO3)4]4- (X = Cl or Br).

PubMed

Goettel, James T; Haensch, Veit G; Schrobilgen, Gary J

2017-06-28

The number of isolable compounds which contain different noble-gas-element bonds is limited for xenon and even more so for krypton. Examples of Xe-Cl bonds are rare, and prior to this work, no Xe-Br bonded compound had been isolated in macroscopic quantities. The syntheses, isolation, and characterization of the first compounds to contain Xe-Br bonds and their chlorine analogues are described in the present work. The reactions of XeO 3 with [N(CH 3 ) 4 ]Br and [N(C 2 H 5 ) 4 ]Br have provided two bromoxenate salts, [N(C 2 H 5 ) 4 ] 3 [Br 3 (XeO 3 ) 3 ] and [N(CH 3 ) 4 ] 4 [Br 4 (XeO 3 ) 4 ], in which the cage anions have Xe-Br bond lengths that range from 3.0838(3) to 3.3181(8) Å. The isostructural chloroxenate anions (Xe-Cl bond lengths, 2.9316(2) to 3.101(4) Å) were synthesized by analogy with their bromine analogues. The bromo- and chloroxenate salts are stable in the atmosphere at room temperature and were characterized in the solid state by Raman spectroscopy and low-temperature single-crystal X-ray diffraction, and in the gas phase by quantum-chemical calculations. They are the only known examples of cage anions that contain a noble-gas element. The Xe-Br and Xe-Cl bonds are very weakly covalent and can be viewed as σ-hole interactions, similar to those encountered in halogen bonding. However, the halogen atoms in these cases are valence electron lone pair donors, and the σ* Xe-O orbitals are lone pair acceptors.

3D X-ray ultra-microscopy of bone tissue.

PubMed

Langer, M; Peyrin, F

2016-02-01

We review the current X-ray techniques with 3D imaging capability at the nano-scale: transmission X-ray microscopy, ptychography and in-line phase nano-tomography. We further review the different ultra-structural features that have so far been resolved: the lacuno-canalicular network, collagen orientation, nano-scale mineralization and their use as basis for mechanical simulations. X-ray computed tomography at the micro-metric scale is increasingly considered as the reference technique in imaging of bone micro-structure. The trend has been to push towards increasingly higher resolution. Due to the difficulty of realizing optics in the hard X-ray regime, the magnification has mainly been due to the use of visible light optics and indirect detection of the X-rays, which limits the attainable resolution with respect to the wavelength of the visible light used in detection. Recent developments in X-ray optics and instrumentation have allowed to implement several types of methods that achieve imaging that is limited in resolution by the X-ray wavelength, thus enabling computed tomography at the nano-scale. We review here the X-ray techniques with 3D imaging capability at the nano-scale: transmission X-ray microscopy, ptychography and in-line phase nano-tomography. Further, we review the different ultra-structural features that have so far been resolved and the applications that have been reported: imaging of the lacuno-canalicular network, direct analysis of collagen orientation, analysis of mineralization on the nano-scale and use of 3D images at the nano-scale to drive mechanical simulations. Finally, we discuss the issue of going beyond qualitative description to quantification of ultra-structural features.

Unusual Black Hole Binary LMC X-3: A Transient High-Mass X-Ray Binary That Is Almost Always On?

NASA Technical Reports Server (NTRS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-01-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi- Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with Gamma = 1.41‚+/- 0.65 and a luminosity of 7.97 x 10(exp 33) erg/s (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of approx. 8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of approx. 4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always "on."

Neuropharmacology of Purinergic Receptors in Human Submucous Plexus: Involvement of P2X1, P2X2, P2X3 Channels, P2Y and A3 Metabotropic Receptors in Neurotransmission

PubMed Central

Liñán-Rico, A.; Wunderlich, JE.; Enneking, JT.; Tso, DR.; Grants, I.; Williams, KC.; Otey, A.; Michel, K.; Schemann, M.; Needleman, B.; Harzman, A.; Christofi, FL.

2015-01-01

Rationale The role of purinergic signaling in the human ENS is not well understood. We sought to further characterize the neuropharmacology of purinergic receptors in human ENS and test the hypothesis that endogenous purines are critical regulators of neurotransmission. Experimental Approach LSCM-Fluo-4-(Ca2+)-imaging of postsynaptic Ca2+ transients (PSCaTs) was used as a reporter of neural activity. Synaptic transmission was evoked by fiber tract electrical stimulation in human SMP surgical preparations. Pharmacological analysis of purinergic signaling was done in 1,556 neurons from 234 separate ganglia 107 patients; immunochemical labeling for P2XRs of neurons in ganglia from 19 patients. Real-time MSORT (Di-8-ANEPPS) imaging was used to test effects of adenosine on fast excitatory synaptic potentials (fEPSPs). Results Synaptic transmission is sensitive to pharmacological manipulations that alter accumulation of extracellular purines. Apyrase blocks PSCaTs in a majority of neurons. An ecto-NTPDase-inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP or adenosine deaminase augments PSCaTs. Blockade of reuptake/deamination of eADO inhibits PSCaTs. Adenosine inhibits fEPSPs and PSCaTs (IC50=25μM), sensitive to MRS1220-antagonism (A3AR). A P2Y agonist ADPβS inhibits PSCaTs (IC50=111nM) in neurons without stimulatory ADPβS responses (EC50=960nM). ATP or a P2X1,2,2/3 (α,β-MeATP) agonist evokes fast, slow, biphasic Ca2+ transients or Ca2+ oscillations (EC50=400μM). PSCaTs are sensitive to P2X1 antagonist NF279. Low (20nM) or high (5μM) concentrations of P2X antagonist TNP-ATP block PSCaTs in different neurons; proportions of neurons with P2XR-ir follow the order P2X2>P2X1≫P2X3; P2X1+ P2X2 and P2X3+P2X2 are co-localized. RT-PCR identified mRNA-transcripts for P2X1-7,P2Y1,2,12-14R. Responsive neurons were also identified by HuC/D-ir. Conclusions Purines are critical regulators of neurotransmission in the human enteric nervous system. Purinergic signaling involves

Giant Faraday rotation in Bi(x)Ce(3-x)Fe5O12 epitaxial garnet films.

PubMed

Chandra Sekhar, M; Singh, Mahi R; Basu, Shantanu; Pinnepalli, Sai

2012-04-23

Thin films of Bi(x)Ce(3-x)Fe(5)O(12) with x = 0.7 and 0.8 compositions were prepared by using pulsed laser deposition. We investigated the effects of processing parameters used to fabricate these films by measuring various physical properties such as X-ray diffraction, transmittance, magnetization and Faraday rotation. In this study, we propose a phase diagram which provides a suitable window for the deposition of Bi(x)Ce(3-x)Fe(5)O(12) epitaxial films. We have also observed a giant Faraday rotation of 1-1.10 degree/µm in our optimized films. The measured Faraday rotation value is 1.6 and 50 times larger than that of CeYIG and YIG respectively. A theoretical model has been proposed for Faraday rotation based on density matrix method and an excellent agreement between experiment and theory is found. © 2012 Optical Society of America

Polarized emission from CsPbX3 perovskite quantum dots

NASA Astrophysics Data System (ADS)

Wang, Dan; Wu, Dan; Dong, Di; Chen, Wei; Hao, Junjie; Qin, Jing; Xu, Bing; Wang, Kai; Sun, Xiaowei

2016-06-01

Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption.Compared to organic/inorganic hybrid perovskites, full inorganic perovskite quantum dots (QDs) exhibit higher stability. In this study, full inorganic CsPbX3 (X = Br, I and mixed halide systems Br/I) perovskite QDs have been synthesized and interestingly, these QDs showed highly polarized photoluminescence which is systematically studied for the first time. Furthermore, the polarization of CsPbI3 was as high as 0.36 in hexane and 0.40 as a film. The CsPbX3 perovskite QDs with high polarization properties indicate that they possess great potential for application in new generation displays with wide colour gamut and low power consumption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01915c

Oxygen storage properties of La 1-xSr xFeO 3-δ for chemical-looping reactions–An in-situ neutron and synchrotron X-ray study

DOE PAGES

Taylor, Daniel D.; Schreiber, Nathaniel J.; Levitas, Benjamin D.; ...

2016-05-16

Oxygen storage materials (OSMs) provide lattice oxygen for a number of chemical-looping reactions including natural gas combustion and methane reforming. La 1–xSr xFeO 3-δ has shown promise for use as an OSM in methane reforming reactions due to its high product selectivity, fast oxide diffusion, and cycle stability. Here, we investigate the structural evolution of the series La 1–xSr xFeO 3-δ for x = 0, 1/3, 1/2, 2/3, and 1, using in situ synchrotron X-ray and neutron diffraction, as it is cycled under the conditions of a chemical-looping reactor (methane and oxygen atmospheres). In the compositions x = 1/3, 1/2,more » 2/3, and 1, we discover an envelope , or temperature range, of oxygen storage capacity (OSC), where oxygen can easily and reversibly be inserted and removed from the OSM. Our in situ X-ray and neutron diffraction results reveal that while samples with higher Sr contents had a higher OSC, those same samples suffered from slower reaction kinetics and some, such as the x = 1/2 and x = 2/3 compositions, had local variations in Sr content, which led to inhomogeneous regions with varying reaction rates. Therefore, we highlight the importance of in situ diffraction studies, and we propose that these measurements are required for the thorough evaluation of future candidate OSMs. Furthermore, we recommend La 2/3Sr 1/3FeO 3-δ as the optimal OSM in the series because its structure remains homogeneous throughout the reaction, and its OSC envelope is similar to that of the higher doped materials.« less

Transformation of sintered CsPbBr 3 nanocrystals to cubic CsPbI 3 and gradient CsPbBr xI 3–x through halide exchange

DOE PAGES

Hoffman, Jacob B.; Schleper, A. Lennart; Kamat, Prashant V.

2016-06-20

All-inorganic cesium lead halide (CsPbX 3, X = Br –, I –) perovskites could potentially provide comparable photovoltaic performance with enhanced stability compared to organic–inorganic lead halide species. However, small-bandgap cubic CsPbI3 has been difficult to study due to challenges forming CsPbI 3 in the cubic phase. Here, a low-temperature procedure to form cubic CsPbI 3 has been developed through a halide exchange reaction using films of sintered CsPbBr 3 nanocrystals. The reaction was found to be strongly dependent upon temperature, featuring an Arrhenius relationship. Additionally, film thickness played a significant role in determining internal film structure at intermediate reactionmore » times. Thin films (50 nm) showed only a small distribution of CsPbBr xI 3–x species, while thicker films (350 nm) exhibited much broader distributions. Furthermore, internal film structure was ordered, featuring a compositional gradient within film. Transient absorption spectroscopy showed the influence of halide exchange on the excited state of the material. In thicker films, charge carriers were rapidly transferred to iodide-rich regions near the film surface within the first several picoseconds after excitation. Furthermore, this ultrafast vectorial charge-transfer process illustrates the potential of utilizing compositional gradients to direct charge flow in perovskite-based photovoltaics.« less

High statistics search for ultrahigh energy {gamma}-ray emission from Cygnus X-3 and Hercules X-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borione, A.; Chantell, M.C.; Covault, C.E.

1997-02-01

We have carried out a high statistics (2{times}10{sup 9} events) search for ultrahigh energy {gamma}-ray emission from the x-ray binary sources Cygnus X-3 and Hercules X-1. Using data taken with the CASA-MIA detector over a five year period (1990{endash}1995), we find no evidence for steady emission from either source. The derived 90{percent} C.L. upper limit to the steady integral flux of {gamma} rays from Cygnus X-3 is {Phi}(E{gt}115TeV){lt}6.3{times}10{sup {minus}15} photons cm{sup {minus}2}sec{sup {minus}1}, and from Hercules X-1 it is {Phi}(E{gt}115TeV){lt}8.5{times}10{sup {minus}15} photonscm{sup {minus}2}sec{sup {minus}1}. These limits are more than two orders of magnitude lower than earlier claimed detections and aremore » better than recent experiments operating in the same energy range. We have also searched for transient emission on time periods of one day and 0.5 h and find no evidence for such emission from either source. The typical daily limit on the integral {gamma}-ray flux from Cygnus X-3 or Hercules X-1 is {Phi}{sub daily}(E{gt}115TeV){lt}2.0{times}10{sup {minus}13} photons cm{sup {minus}2}sec{sup {minus}1}. For Cygnus X-3, we see no evidence for emission correlated with the 4.8 h x-ray periodicity or with the occurrence of large radio flares. Unless one postulates that these sources were very active earlier and are now dormant, the limits presented here put into question the earlier results, and highlight the difficulties that possible future experiments will have in detecting {gamma}-ray signals at ultrahigh energies. {copyright} {ital 1997} {ital The American Physical Society}« less

The hypersoft state of Cygnus X-3. A key to jet quenching in X-ray binaries?

NASA Astrophysics Data System (ADS)

Koljonen, K. I. I.; Maccarone, T.; McCollough, M. L.; Gurwell, M.; Trushkin, S. A.; Pooley, G. G.; Piano, G.; Tavani, M.

2018-04-01

Context. Cygnus X-3 is a unique microquasar in the Galaxy hosting a Wolf-Rayet companion orbiting a compact object that most likely is a low-mass black hole. The unique source properties are likely due to the interaction of the compact object with the heavy stellar wind of the companion. Aim. In this paper, we concentrate on a very specific period of time prior to the massive outbursts observed from the source. During this period, Cygnus X-3 is in a so-called hypersoft state, in which the radio and hard X-ray fluxes are found to be at their lowest values (or non-detected), the soft X-ray flux is at its highest values, and sporadic γ-ray emission is observed. We use multiwavelength observations to study the nature of the hypersoft state. Methods: We observed Cygnus X-3 during the hypersoft state with Swift and NuSTAR in X-rays and SMA, AMI-LA, and RATAN-600 in the radio. We also considered X-ray monitoring data from MAXI and γ-ray monitoring data from AGILE and Fermi. Results: We found that the spectra and timing properties of the multiwavelength observations can be explained by a scenario in which the jet production is turned off or highly diminished in the hypersoft state and the missing jet pressure allows the wind to refill the region close to the black hole. The results provide proof of actual jet quenching in soft states of X-ray binaries.

Period changes in Centaurus X-3

NASA Technical Reports Server (NTRS)

Sparks, W. M.

1975-01-01

A number of mechanisms which can change the orbital period are applied to various models of Cen X-3. Only four models which give rise to feasible mechanisms are found. Possible observations which could distinguish between these models are suggested.

Magnetic and magnetocaloric properties of La{sub 0.6}Pr{sub 0.1}Sr{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (0≤x≤0.3) manganites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherif, R., E-mail: cherifrim18@yahoo.fr; Hlil, E.K.; Ellouze, M.

2014-07-01

The La{sub 0.6}Pr{sub 0.1}Sr{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (x=0, 0.1, 0.2 and 0.3) samples have been elaborated by the solid-state reaction method. X-ray powder diffraction shows that all the samples crystallize in a rhombohedric phase with R3{sup ¯}c space group. The variation of magnetization as a function of temperature and applied magnetic field was carried out. The samples for x=0 and 0.1 exhibit a FM–PM transition at the Curie temperature T{sub C}, however, for x=0.2 and 0.3 exhibit an AFM–PM one at the Neel temperature T{sub N}, when the temperature increases. A magneto-caloric effect has been calculated in terms ofmore » isothermal magnetic entropy change. A large magneto-caloric effect has been observed, the maximum entropy change, |ΔS{sub M}{sup max}|, reaches the highest value of 3.28 J/kgK under a magnetic field change of 5 T with an RCP value of 220 J/kg for La{sub 0.6}Pr{sub 0.1}Sr{sub 0.3}MnO{sub 3} composition, which will be an interesting compound for application materials working as magnetic refrigerants near room temperature. - Graphical abstract: Magnetic entropy change versus temperature and applied magnetic field for x=0.1 (a) and RCP versus applied magnetic field for x=0, 0.1 (b). - Highlights: • The La{sub 0.6}Pr{sub 0.1}Sr{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (0≤x≤0.3) polycrystalline samples were prepared by the solid state reaction method. • Crystalline and magnetic structures were investigated using DRX and magnetization measurements. • The magnetocaloric (MC) effect was estimated versus magnetic field and temperatures. • Compounds with x=0, 0.1 exhibit great potential for magnetic refrigeration at room temperature.« less

Unusual Black Hole Binary LMC X-3: A Transient High-mass X-Ray Binary That Is Almost Always On?

NASA Astrophysics Data System (ADS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-11-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi-Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with {{Γ }}=1.41+/- 0.65 and a luminosity of 7.97× {10}33 erg s-1 (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of ˜8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of ˜4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always “on.”

Signature of magnetoelectric coupling of xNiFe2O4 - (1-x)HoMnO3 (x = 0.1 and 0.3) multiferroic nanocomposites

NASA Astrophysics Data System (ADS)

Mandal, S. K.; Debnath, Rajesh; Singh, Swati; Nath, A.; Dey, P.; Nath, T. K.

2017-12-01

The magnetoelectric coupling of xNiFe2O4-(1-x)HoMnO3 (x = 0.1 and 0.3) multiferroics nanocomposites prepared through low temperature chemical pyrophoric reaction process has been investigated at room temperature. The signature of magnetoelectric coefficient of these nanocomposites is mainly due to the magnetostriction and magnetodielectric properties of the materials. These nanocomposites show the ferroelectric behaviour at room temperature. AC electrical properties of nanocomposites have been studied with applied magnetic fields and temperatures. Nyquist plots at different magnetic fields and temperatures have been fitted using parallel combinations of resistance-capacitor circuits. Moreover, we have estimated activation energy of those composites using Arrhenius relation, which indicates that same kinds of charge carrier are responsible for relaxation process in grain boundaries and grain of the sample. Furthermore, from the analysis of ac conductivity data as a function of frequency is attributed to the large polaronic hopping in the conduction process in the system.

Influence of Ce Doping on Structural and Transport Properties of Ca1- x Ce x MnO3 ( x=0.2) Manganite

NASA Astrophysics Data System (ADS)

Varshney, Dinesh; Mansuri, Irfan

2011-01-01

We have investigated structural, electric, magnetic and thermal transport properties of electron doped Ca1- x Ce x MnO3 ( x=0.2) manganites. The Cerium substitution for Ca2+causes electron doping into insulating CaMnO3 without e g electron. At room temperature the polycrystalline Ca0.8Ce0.2MnO3 is in the crystallographic orthorhombic structure, with Pnma space group symmetry from the refinement of x-ray powder diffraction patterns. The electrical resistivity data infers that Ca0.8Ce0.2MnO3 manganite is in the semiconducting phase. A smooth linear behavior of log plot values is obtained and is well fitted with adiabatic small polaron conduction model. Nearest-neighbor hopping of a small polaron leads to a mobility with a thermally activated form. The negative values of thermopower infer electron as carriers in Ca0.8Ce0.2MnO3. From susceptibility measurements the Ce doped CaMnO3 shows a transition from antiferromagnetic (AFM) to paramagnetic (PM) phase.

Polycrystalline (TbXY1-X)2O3 Faraday rotator.

PubMed

Ikesue, Akio; Aung, Yan Lin; Makikawa, Shinji; Yahagi, Akira

2017-11-01

We have succeeded for the first time in synthesizing an optical grade (Tb X Y 1-X ) 2 O 3 (X=0.5-1.0) ceramic Faraday rotator, which greatly exceeds the basic characteristics of the commercial terbium gallium garnet (TGG) (Tb 3 Ga 5 O 12 ) crystal. The Faraday rotation angle increased as the Tb concentration increased, and the Verdet constant increased from 2.1 (82  rad T -1  m -1 at X=0.5) to 3.8 times (154  rad T -1  m -1 at X=1.0) than the TGG single crystal, which is regarded as highest class. Therefore, it is possible to minimize the Faraday rotator length and the magnet in building an optical isolator. It was also confirmed that its optical quality was very comparable to the commercial TGG crystal.

Structural morphology of YBa 2Cu 3O 7- x

NASA Astrophysics Data System (ADS)

Sun, B. N.; Hartman, P.; Woensdregt, C. F.; Schmid, H.

1990-03-01

The structural morphology of YBa 2Cu 3O 7- x (YBCO) has been investigated by application of the periodic bond chain (PBC) theory. For x=1, the F forms were found to be {001}, {011}, {013}, {112} and {114}. Attachment energies have been calculated in broken bond model and in an electrostatic point charge model. For x=1 the theoretical growth habit is tabular to platy {001} with {011} as side faces. For x=0 {010} also becomes an F form. The habit is isometric with large {001} and {011} and small {010} faces. The outermost layer of {001} contains half of the Cu + ( x=1) or Cu 3+ and O 2- ( x=0) ions in an ordered arrangement based on a c(2x2) quadratic lattice. For the outermost layer of (010) ( x=0) an ordering scheme of the copper and oxygen ions is proposed. The occurrence of {010} rather than {011} on grown crystals has to be ascribed to external factors.

Gd3+ spin-lattice relaxation via multi-band conduction electrons in Y(1-x)Gd(x)In3: an electron spin resonance study.

PubMed

Cabrera-Baez, M; Iwamoto, W; Magnavita, E T; Osorio-Guillén, J M; Ribeiro, R A; Avila, M A; Rettori, C

2014-04-30

Interest in the electronic structure of the intermetallic compound YIn3 has been renewed with the recent discovery of superconductivity at T ∼ 1 K, which may be filamentary in nature. In this work we perform electron spin resonance (ESR) experiments on Gd(3+) doped YIn3 (Y1-xGdxIn3; 0.001 ⪅ x ⩽̸ 0.08), showing that the spin-lattice relaxation of the Gd(3+) ions, due to the exchange interaction between the Gd(3+) localized magnetic moment and the conduction electrons (ce), is processed via the presence of s-, p- and d-type ce at the YIn3 Fermi level. These findings are revealed by the Gd(3+) concentration dependence of the Korringa-like relaxation rate d(ΔH)/dT and g-shift (Δg = g - 1.993), that display bottleneck relaxation behavior for the s-electrons and unbottleneck behavior for the p- and d-electrons. The Korringa-like relaxation rates vary from 22(2) Oe/K for x ⪅ 0.001 to 8(2) Oe/K for x = 0.08 and the g-shift values change, respectively, from a positive Δg = +0.047(10) to a negative Δg = -0.008(4). Analysis in terms of a three-band ce model allows the extraction of the corresponding exchange interaction parameters Jfs, Jfp and Jfd.

3rd International Conference on X-ray Technique

NASA Astrophysics Data System (ADS)

Potrakhov, N. N.; Gryaznov, A. Yu; Lisenkov, A. A.; Kostrin, D. K.

2017-02-01

In this preface a brief history, modern aspects and future tendencies in development of the X-ray technique as seen from the 3rd International Conference on X-ray Technique that was held on 24-25 November 2016 in Saint Petersburg, Russia are described On 24-25 November 2016 in Saint Petersburg on the basis of Saint Petersburg State Electrotechnical University “LETI” n. a. V. I. Ulyanov (Lenin) was held the 3rd International Conference on X-ray Technique. The tradition to hold a similar conference in our country was laid in Soviet times. The last of them, the All-Union Conference on the Prospects of X-ray Tubes and Equipment was organized and held more than a quarter century ago - on 21-23 November 1999, at the initiative and under the leadership of the chief engineer of the Leningrad association of electronic industry “Svetlana” Borovsky Alexander Ivanovich and the chief of special design bureau of X-ray devices of “Svetlana” Shchukin Gennady Anatolievich. The most active part in the organization and work of the conference played members of the department of X-ray and electron beam instruments of Leningrad Electrotechnical Institute “LETI” (the former name of Saint Petersburg State Electrotechnical University “LETI”), represented by head of the department professor Ivanov Stanislav Alekseevich.

Spontaneous firing and evoked responses of spinal nociceptive neurons are attenuated by blockade of P2X3 and P2X2/3 receptors in inflamed rats.

PubMed

Xu, Jun; Chu, Katharine L; Brederson, Jill-Desiree; Jarvis, Michael F; McGaraughty, Steve

2012-08-01

P2X3 and P2X2/3 receptors are selectively expressed on primary afferent nociceptors and have been implicated in modulating nociception in different models of pathological pain, including inflammatory pain. In an effort to delineate further the role of P2X3 receptors (homomeric and heteromeric) in the modulation of nociceptive transmission after a chronic inflammation injury, A-317491, a potent and selective P2X3-P2X2/3 antagonist, was administered to CFA-inflamed rats in order to examine its effects on responses of spinal dorsal horn neurons to mechanical and thermal stimulation. Systemic injection of A-317491 (30 μmol/kg, i.v.) reduced the responses of wide-dynamic-range (WDR) and nociceptive specific (NS) neurons to both high-intensity mechanical (pinch) and heat (49°C) stimulation. A-317491 also decreased low-intensity (10 g von Frey hair) mechanically evoked activity of WDR neurons but did not alter WDR neuronal responses to cold stimulation (5°C). Spontaneous firing of WDR neurons in CFA-inflamed rats was also significantly attenuated by A-317491 injection. By using immunohistochemistry, P2X3 receptors were demonstrated to be enhanced in lamina II of the spinal dorsal horn after inflammation. In summary, blockade of P2X3 and P2X2/3 receptors dampens mechanical- and heat-related signaling, as well as nonevoked activity of key classes of spinal nociceptive neurons in inflamed animals. These data suggest that P2X3 and/or P2X2/3 receptors have a broad contribution to somatosensory/nociceptive transmission in rats with a chronic inflammatory injury and are consistent with previous behavioral data demonstrating antiallodynic and antihyperalgesic effects of receptor antagonists. Copyright © 2012 Wiley Periodicals, Inc.

Efficient and selective heavy metal sequestration from water by using layered sulfide K 2x Sn 4-x S 8-x (x = 0.65–1; KTS-3)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarma, Debajit; Islam, Saiful M.; Subrahmanyam, K. S.

Heavy metal ions (Cd 2+, Hg 2+, As 3+ and Pb 2+) are an important contributor to the contamination of groundwater and other water bodies in and around industrial areas. Herein, we demonstrate the rapid and efficient capacity of a layered metal sulfide material, K2xSn4-xS8-x (x = 0.65-1, KTS-3) for heavy metal ion removal from water. The effect of concentration, pH, kinetics, and competitive ions such as Na +/Ca 2+ on the heavy metal ion removal capacity of KTS-3 was systematically investigated. X-ray photoelectron spectroscopy (XPS), elemental analyses, and powder X-ray diffraction studies revealed that the heavy metal ion-exchange ofmore » KTS-3 is complete (quantitative replacement of all potassium ions) and topotactic. The heavy metal ion-exchange by using KTS-3 follows the Langmuir-Freundlich model with high exchange capacities, q(m) 205(17) mg g -1 for Cd 2+, 372(21) mg g -1 for Hg 2+ and 391(89) mg g -1 for Pb 2+. KTS-3 retains excellent heavy metal ion-exchange capacity even in very high concentration (1 M) of competing ions (Na +/Ca 2+) and also over a broad pH range (2-12). KTS-3 also exhibits very good ion-exchange capacity for precious Ag + and toxic As 3+ ions. The kinetics of heavy metal ion adsorption by KTS-3 are rapid (absorbs all ions within a few minutes). These properties and the environmentally friendly character of KTS-3 make it a promising candidate for sequestration of heavy metal ions from water.« less

Effects of Ga substitution in Ce:Tb3Ga x Al5- x O12 single crystals for scintillator applications

NASA Astrophysics Data System (ADS)

Nakauchi, Daisuke; Okada, Go; Kawano, Naoki; Kawaguchi, Noriaki; Yanagida, Takayuki

2018-02-01

Bulk single crystals of Ce-doped Tb3Ga x Al5- x O12 (x = 0-4) were successfully synthesized by the floating zone method. The samples exhibit photoluminescence and scintillation with an intense broad emission due to the 5d-4f transitions of Ce3+ peaking around 550 nm as well as a few sharp peaks due to the 4f-4f transitions of Tb3+. Pulse height spectrum measurements under 137Cs γ-ray irradiation demonstrated a clear photoabsorption peak, in which the scintillation light yields were estimated to be 57,000 (x = 0), 28,000 (x = 1), 19,000 (x = 2), and 10,000 (x = 3) photons/MeV. Afterglow level can be suppressed with an appropriate addition of Ga, in which the optimum concertation is x = 2 leading an afterglow level of 23 ppm.

E2 and SN2 Reactions of X(-) + CH3CH2X (X = F, Cl); an ab Initio and DFT Benchmark Study.

PubMed

Bento, A Patrícia; Solà, Miquel; Bickelhaupt, F Matthias

2008-06-01

We have computed consistent benchmark potential energy surfaces (PESs) for the anti-E2, syn-E2, and SN2 pathways of X(-) + CH3CH2X with X = F and Cl. This benchmark has been used to evaluate the performance of 31 popular density functionals, covering local-density approximation, generalized gradient approximation (GGA), meta-GGA, and hybrid density-functional theory (DFT). The ab initio benchmark has been obtained by exploring the PESs using a hierarchical series of ab initio methods [up to CCSD(T)] in combination with a hierarchical series of Gaussian-type basis sets (up to aug-cc-pVQZ). Our best CCSD(T) estimates show that the overall barriers for the various pathways increase in the order anti-E2 (X = F) < SN2 (X = F) < SN2 (X = Cl) ∼ syn-E2 (X = F) < anti-E2 (X = Cl) < syn-E2 (X = Cl). Thus, anti-E2 dominates for F(-) + CH3CH2F, and SN2 dominates for Cl(-) + CH3CH2Cl, while syn-E2 is in all cases the least favorable pathway. Best overall agreement with our ab initio benchmark is obtained by representatives from each of the three categories of functionals, GGA, meta-GGA, and hybrid DFT, with mean absolute errors in, for example, central barriers of 4.3 (OPBE), 2.2 (M06-L), and 2.0 kcal/mol (M06), respectively. Importantly, the hybrid functional BHandH and the meta-GGA M06-L yield incorrect trends and qualitative features of the PESs (in particular, an erroneous preference for SN2 over the anti-E2 in the case of F(-) + CH3CH2F) even though they are among the best functionals as measured by their small mean absolute errors of 3.3 and 2.2 kcal/mol in reaction barriers. OLYP and B3LYP have somewhat higher mean absolute errors in central barriers (5.6 and 4.8 kcal/mol, respectively), but the error distribution is somewhat more uniform, and as a consequence, the correct trends are reproduced.

Luminescent properties of Cr-doped (GdX, Y1-X)3Al5O12 infra-red scintillator crystals

NASA Astrophysics Data System (ADS)

Suzuki, Akira; Kurosawa, Shunsuke; Yamaji, Akihiro; Shoji, Yasuhiro; Pejchal, Jan; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira

2014-10-01

Cr-doped (GdX Y1-X)3Al5O12 (X = 0, 0.25, 0.50) crystals prepared by the micro-pulling down method were investigated to develop a infra-red scintillator for implantable patient dosimeter in radiation therapy. In order to evaluate their optical and scintillation performance, the following properties were measured: (i) transmittance between ultra-violet and near-infra red region, (ii) photoluminescence spectra under Xe-lamp excitation, and (iii) X-ray excited radio-luminescence spectra. Cr:Y3Al5O12 and Cr:(Gd0.25 Y0.75)3Al5O12 crystals showed increased transmittance of 80%, while Cr:(Gd0.50 Y0.50)3Al5O12 had a lower transmittance of 40% due to its polycrystalline structure. In addition, all the Cr:(GdX Y1-X)3Al5O12 crystals showed sharp scintillation luminescence peaks ascribed to Cr3+ d-d transitions. Therefore, these results suggested that Cr:Y3Al5O12 and Cr:(Gd0.25 Y0.75)3Al5O12 crystals can be candidate materials for the dosimeter use.

(Ba1-x Bi x )(Ti1-x Ni0.5x Sn0.5x )O3 Solid Solution: Phase Evolution, Microstructure, Dielectric Properties, and Impedance Analysis

NASA Astrophysics Data System (ADS)

Chen, Xiuli; Li, Xiaoxia; Yan, Xiao; Liu, Gaofeng; Zhou, Huanfu

2018-02-01

(Ba1-x Bi x )(Ti1-x Ni0.5x Sn0.5x )O3 (BBTNS, 0.02 ≤ x ≤ 0.1) samples have been synthesized by traditional solid-state reaction technique and their structural transformation and dielectric properties investigated. X-ray diffraction (XRD) analysis revealed that BBTNS could form a homogeneous solid solution, and the transformation from tetragonal to pseudocubic phase occurred at 0.04 ≤ &!nbsp;x ≤ 0.06. Optimized properties with stable ɛ r (˜ 1829 to 1838), small Δɛ/ɛ 25°C values (± 15%) over a broad temperature range from -60°C to 140°C, and low tan Δ (≤ 0.02) from 4°C to 194°C were obtained at x = 0.1. The relaxation and conduction process in the high-temperature region are attributed to thermal activation, and oxygen vacancies may be the ionic charge carriers in perovskite ferroelectrics.

Solid solubility, phase transitions, thermal expansion, and compressibility in Sc{sub 1−x}Al{sub x}F{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morelock, Cody R.; Gallington, Leighanne C.; Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu

2015-02-15

With the goal of thermal expansion control, the synthesis and properties of Sc{sub 1−x}Al{sub x}F{sub 3} were investigated. The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. Solid solutions (x≤0.50) were characterized by synchrotron powder diffraction at ambient pressure between 100 and 900 K and at pressures <0.414 GPa while heating from 298 to 523 K. A phase transition from cubic to rhombohedral is observed. The transition temperature increases smoothly with Al{sup 3+} content, approaching 500 K at the solid solubility limit, and also upon compression at fixed Al{sup 3+} content. The slope of themore » pressure–temperature phase boundary is ∼0.5 K MPa{sup −1}, which is steep relative to that for most symmetry-lowering phase transitions in perovskites. The volume coefficient of thermal expansion (CTE) for the rhombohedral phase is strongly positive, but the cubic-phase CTE varies from negative (x<0.15) to near-zero (x=0.15) to positive (x>0.20) between ∼600 and 800 K. The cubic solid solutions elastically stiffen on heating, while Al{sup 3+} substitution causes softening at a given temperature. - Graphical abstract: The cubic-phase coefficient of thermal expansion for Sc{sub 1−x}Al{sub x}F{sub 3}(solubility limit ∼50% at ∼1340 K) becomes more positive with increased Al{sup 3+} substitution, but the average isothermal bulk modulus decreases (elastic softening). - Highlights: • The solubility limit of AlF{sub 3} in ScF{sub 3} at ∼1340 K is ∼50%. • The phase transition temperature of Sc{sub 1−x}Al{sub x}F{sub 3} increases smoothly with x. • The cubic-phase volume CTE varies from negative to positive with increasing x. • The cubic solid solutions elastically stiffen on heating. • Al{sup 3+} substitution causes softening at a given temperature.« less

Crystal structure characteristics, dielectric loss, and vibrational spectra of Zn-rich non-stoichiometric Ba[(Zn1/3Nb2/3)1-x Zn x ]O3 ceramics

NASA Astrophysics Data System (ADS)

Li, Jianzhu; Xing, Chao; Qiao, Hengyang; Chen, Huiling; Yang, Jun; Dong, Helei; Shi, Feng

2017-07-01

Zn-Rich non-stoichiometric Ba(Zn1/3Nb2/3)1-x Zn x O3 (BZNZ) (x  =  0.01, 0.02, 0.03, 0.04) ceramics were prepared by the solid-state reaction method at 1500 °C for 2 h. The crystal structures and morphologies were analyzed by x-ray diffraction (XRD) and scanning electron microscopy. The vibration modes were obtained by Raman scattering spectroscopy and Fourier transform far-infrared (FTIR) reflectance spectroscopy. Rietveld refinement was performed for the XRD data. The relationship between crystal structures, dielectric properties, and phonon modes was analyzed in detail. XRD results show that the main phase is Ba(Zn1/3Nb2/3)O3. The Raman results displayed that the ordering structure of BZNZ transformed from 1:2 to 1:1 when x changed from 0.02 to 0.04, and the dielectric losses have a positive correlation with the full width at half maximum values of the A 1g(O) and E g(O) modes. The FTIR spectra were analyzed by the Kramers-Krönig method to obtain the real parts (ɛ‧) and the imaginary parts (ɛ″) of the dielectric constant. When x  =  0.02, the sample possesses uniform grains with clear boundaries and the lowest dielectric loss value (tanδ  =  5.5  ×  10‒4) due to the largest packing fraction.

Preparation, electronic structure, and chemical bonding of lead-free (1 - x)(K0.5Bi0.5)TiO3- xBaTiO3 solid solution

NASA Astrophysics Data System (ADS)

Sasikumar, S.; Saravanan, R.; Saravanakumar, S.; Robert, M. Charles

2018-01-01

Polycrystalline lead-free (1 - x)(K0.5Bi0.5)TiO3- xBaTiO3, ((1 - x)KBT- xBT) ( x = 0.00, 0.08, 0.12) ceramics were synthesized via solid-state reaction method. The powder X-ray diffraction (PXRD) and structural refinement results confirm that a single-phase tetragonal structure with space group P4mm. Charge density distribution inside the unit cell of (1 - x)KBT- xBT was investigated by the maximum entropy method. Charge density analysis reveals the reduction in ionic nature along K/Bi-O bond and enhancement of covalent nature along Ti-O bond with the addition of BaTiO3. The charge density distribution studies done using maximum entropy method for (1 - x)KBT- xBT have not been done so far. The surface morphology study was done using scanning electron microscopy (SEM). Energy dispersive X-rays spectra (EDS) were used to investigate the elemental compositions present in the system. The dielectric constant and loss tangent were studied as a function of frequency. The dielectric constant and loss were decreased with increase of frequency. Room temperature dielectric constant ( ɛ) and loss (tan δ) were measured for x = 0.00 about 511 and 0.51, respectively, at a frequency of 10 kHz.

Development of a 3-D X-ray system

NASA Astrophysics Data System (ADS)

Evans, James Paul Owain

The interpretation of standard two-dimensional x-ray images by humans is often very difficult. This is due to the lack of visual cues to depth in an image which has been produced by transmitted radiation. The solution put forward in this research is to introduce binocular parallax, a powerful physiological depth cue, into the resultant shadowgraph x-ray image. This has been achieved by developing a binocular stereoscopic x-ray imaging technique, which can be used for both visual inspection by human observers and also for the extraction of three-dimensional co-ordinate information. The technique is implemented in the design and development of two experimental x-ray systems and also the development of measurement algorithms. The first experimental machine is based on standard linear x-ray detector arrays and was designed as an optimum configuration for visual inspection by human observers. However, it was felt that a combination of the 3-D visual inspection capability together with a measurement facility would enhance the usefulness of the technique. Therefore, both a theoretical and an empirical analysis of the co-ordinate measurement capability of the machine has been carried out. The measurement is based on close-range photogrammetric techniques. The accuracy of the measurement has been found to be of the order of 4mm in x, 3mm in y and 6mm in z. A second experimental machine was developed and based on the same technique as that used for the first machine. However, a major departure has been the introduction of a dual energy linear x-ray detector array which will allow, in general, the discrimination between organic and inorganic substances. The second design is a compromise between ease of visual inspection for human observers and optimum three-dimensional co-ordinate measurement capability. The system is part of an on going research programme into the possibility of introducing psychological depth cues into the resultant x-ray images. The research presented in

High-rate deposition of LiNb 1- xTa xO 3 films by thermal plasma spray CVD

NASA Astrophysics Data System (ADS)

Majima, T.; Yamamoto, H.; Kulinich, S. A.; Terashima, K.

2000-12-01

LiNb 1- xTa xO 3 films were prepared by a thermal plasma spray CVD method using liquid source materials. Preferentially (0 0 1)-oriented LiNb 1- xTa xO 3 films with satisfactory in-plane and out-of-plane alignment were fabricated on sapphire (0 0 1) substrates. The full-width at half-maximum (FWHM) of the (0 0 6) rocking curve could achieve 0.12°, which was comparable with those of LiNbO 3 and LiTaO 3 films prepared by other conventional vapor-phase deposition methods. The deposition rate was up to 0.07 μm/min, which was 5-40 times faster than those for most other conventional vapor-phase deposition methods. From inductively coupled plasma atomic emission spectroscopy analysis, x values of these films were estimated to be 0.36-0.49.

Support for joint infrared and Copernicus X-Ray observations of Cygnus X-3

NASA Technical Reports Server (NTRS)

1979-01-01

Simultaneous X-ray and infrared measurements were carried out of the flares from Cygnus X-3 from the Copernicus spacecraft observatory. The detectors, InSb, were arranged so that 1.65 and 2.2 micrometer broadbend photometry was performed through a common diaphragm. The measurements were used to determine the energy distribution during a flare and thus learn about the infrared spectrum and its changes during the flare.

Optically stimulated luminescence in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass

NASA Astrophysics Data System (ADS)

Nanto, H.; Nakagawa, R.; Takei, Y.; Hirasawa, K.; Miyamoto, Y.; Masai, H.; Kurobori, T.; Yanagida, T.; Fujimoto, Y.

2015-06-01

An intense optically stimulated luminescence (OSL) was observed, for the first time, in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass. It was found that the peak wavelength of OSL emission spectrum and its stimulation spectrum is about 400 nm and 600 nm, respectively. The OSL intensity is depended on the SnO contents (x=0.05-1.5) and the most intense OSL was observed in 1.0 mol% SnO doped glass. It was found that the OSL intensity is increased with increasing x-ray absorbed dose. Fairly good fading characteristics were observed in the x-ray irradiated glass, showing that this glass is useful as a candidate for OSL sensor materials for ionizing radiation monitoring.

Theoretical Study of the Jahn-Teller effect in CH3CN+ (X2E) and CD3CN+ (X2E): multimode spin-vibronic energy level calculations.

PubMed

Zhang, Shiyang; Mo, Yuxiang

2009-10-15

The spin-vibronic energy levels for CH(3)CN(+)(X(2)E) and CD(3)CN(+)(X(2)E) have been calculated using a diabatic model including multimode vibronic couplings and spin-orbit interaction without adjusting any parameter. The diabatic potential energy surfaces are represented by the Taylor expansions including linear, quadratic and bilinear vibronic coupling terms. The normal coordinates used in the Taylor expansion were expressed by the mass-weighted Cartesian coordinates. The adiabatic potential energy surfaces for CH(3)CN(+) and CD(3)CN(+) were calculated at the level of CASPT2/cc-pvtz, and the spin-orbit coupling constant was calculated at the level of MRCI/CAS/cc-pvtz. The spin-orbit energy splittings for the ground vibrational states of CH(3)CN(+)(X(2)E) and CD(3)CN(+)(X(2)E) are 20 and 16 cm(-1), respectively, which are resulted from the quenching of the spin-orbit coupling strength of 51 cm(-1). The calculated spin-vibronic levels are in good agreement with the experimental data. The calculation results show that the Jahn-Teller effects in CH(3)CN(+)(X(2)E) and CD(3)CN(+)(X(2)E) are essential to understand their spin-vibronic energy structure.

Critical current density in (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x melt-textured composites

NASA Astrophysics Data System (ADS)

Opata, Yuri Aparecido; Monteiro, João Frederico Haas Leandro; Jurelo, Alcione Roberto; Siqueira, Ezequiel Costa

2018-06-01

Melt textured (YBa2Cu3O7-δ)1-x-(PrBa2Cu3O7-δ)x composites (x = 0.00 and x = 0.05) were grown using the top seeding method. The effect of the PrBa2Cu3O7-δ phase on the growth process and the modification of the microstructure as well as on the physical properties was analyzed. X-ray analyses indicated that both pure and Pr-doped samples present an orthorhombic superconducting phase. From resistivity measurements for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, the Tcab did not change and was around 90.5 K. However, from magnetic measurements, the superconductivity was observed in critical temperatures TC = 92.9 K and 92.4 K for YBa2Cu3O7-δ and (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 samples, respectively. The YBa2Cu3O7-δ sample showed higher critical current densities than those shown by the (YBa2Cu3O7-δ)0.95-(PrBa2Cu3O7-δ)0.05 sample, with values of JC = 5.85 × 105 A/cm2 and 4.72 × 105 A/cm2, respectively. This paper also discusses the importance of Pr substitution on nano- and micro-meter scales to enhance JC(H).

Dy3TaO7, A stoichiometric spin glass and the effect of disorder via chemical substitution in the Dy3-xYxTaO7 (0 ≤ x ≤ 3) solid solution

NASA Astrophysics Data System (ADS)

Gómez-García, J. Francisco; Bucio, Lauro; Tavizon, Gustavo

2018-01-01

In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) studies of the Dy3-xYxTaO7 solid solution. The structural characterization of samples was performed by Rietveld refinements of the X-ray diffraction data. All compounds crystallized in a weberite-related structure in the orthorhombic C2221 space group (No. 20); the variations of the lattice parameters obey the Vegard´s law in the whole range of composition. DC magnetic measurements of the Dy3-xYxTaO7 system showed a Curie-Weiss paramagnetic behaviour, with antiferromagnetic interactions at T>150 K. Below 3 K a spin glass behaviour in the 0 ≤ x ≤ 1 range of the solid solution was observed. The stoichiometric Dy3TaO7 compound showed spin glass behaviour although there is no evidence of structural disorder. For some Y3+ doped compounds (x = 0.33, 0.66 and 1.0), chemical disorder reduced the freezing temperature (Tg) values with a ×1/3 dependence. Cole-Cole analysis of the AC magnetic field response showed similar phenomenological parameters for the stoichiometric (x = 0) and the Y3+ doped compounds with spin glassiness, suggesting an analogous mechanism for these compounds. For the Dy3-xYxTaO7 system, in which the spin glass behaviour seems to exhibit a critical concentration, a magnetic phase diagram is proposed.

Double valley Dirac fermions for 3D and 2D Hg1-x Cd x Te with strong asymmetry

NASA Astrophysics Data System (ADS)

Marchewka, M.

2017-04-01

In this paper the possibility to bring about the double-valley Dirac fermions in some quantum structures is predicted. These quantum structures are: strained 3D Hg1-x Cd x Te topological insulator (TI) with strong interface inversion asymmetry and the asymmetric Hg1-x Cd x Te double quantum wells (DQW). The numerical analysis of the dispersion relation for 3D TI Hg1-x Cd x Te for the proper Cd (x)-content of the Hg1-x Cd x Te compound clearly shows that the inversion symmetry breaking together with the unaxial tensile strain causes the splitting of each of the Dirac nodes (two belonging to two interfaces) into two in the proximity of the Γ-point. Similar effects can be obtained for asymmetric Hg1-x Cd x Te DQW with the proper content of Cd and proper width of the quantum wells. The aim of this work is to explore the inversion symmetry breaking in 3D TI and 2D DQW mixed HgCdTe systems. It is shown that this symmetry breaking leads to the dependence of carriers energy on quasi-momentum similar to that of Weyl fermions.

Thermal behaviour of GdCo1-xMnxO3 cobaltates

NASA Astrophysics Data System (ADS)

Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.

2018-05-01

With the objective of exploring the unknown thermodynamic behavior of GdCo1-xMnxO3 family, we present here an investigation of the temperature-dependent (10K≤T≤1000K) thermodynamic properties of GdCo1-xMnxO3 (x=0.1 to 0.8). The specific heat of GdCoO3 with Mn doping in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM). The cohesive energy, specific heat (C), volume thermal expansion (α) and Gruneisen parameter (γ) of GdCo1-xMnxO3 compounds are also discussed.

Study of ultra-high energy emission from Cygnus X-3 and Hercules X-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dingus, B.L.

1988-11-01

The CYGNUS experiment, consisting of an extensive air shower detector and a muon detector, was built at Los Alamos, New Mexico (latitude 36 N, longitude 107W, altitude 2310 meters), to search for point sources of ultra-high energy (>10/sup 14/ eV) particles. These particles must be long-lived neutral particles because of the long source distances and the presence of the intragalactic magnetic field. Gamma rays are the most likely candidates because of the short neutron lifetime and the small neutrino cross section. Therefore, the muon content of the source showers is examined to determine if these events are muon poor asmore » is expected for gamma-initiated showers. The data set from April 1986 to July 1987 is searched for continual emission from Cygnus X-3 and Hercules X-1, and an upper bound to flux is determined for both sources. The flux limit for Cygnus X-3, 2.0 /times/ 10/sup /minus/13/ cm/sup /minus/2/ sec/sup /minus/1/ above 50 TeV, is lower than previous ultra-high energy observations. Hercules X-1 has never been observed continually at ultra-high energies. Cygnus X-3 is observed for a shorter interval of time, beginning on 17 April 1986 and ending 1 June 1986. There is one chance in 300 that the observation is due to a random fluctuation. The signal is correlated with the 4.8 hour orbital period, and the muon content of the showers in the signal is inconsistent with the conventional prediction of gamma- initiated showers. An episodic signal is also reported for Hercules X-1, and it consists of two bursts of less than one hour duration on 24 July 1986. The probability is one chance in 12,000 that this observation is not associated with Hercules X-1. The signal is pulsed at frequency near, but significantly different from, the x-ray pulsar frequency. The muon content of the signal showers is also anomalous, assuming the showers are initiated by gamma rays. 62 refs., 60 figs.« less

CaMn(1-x)Nb(x)O3 (x < or = 0.08) perovskite-type phases as promising new high-temperature n-type thermoelectric materials.

PubMed

Bocher, L; Aguirre, M H; Logvinovich, D; Shkabko, A; Robert, R; Trottmann, M; Weidenkaff, A

2008-09-15

Perovskite-type CaMn(1-x)Nb(x)O(3+/-delta) (x = 0.02, 0.05, and 0.08) compounds were synthesized by applying both a "chimie douce" (SC) synthesis and a classical solid state reaction (SSR) method. The crystallographic parameters of the resulting phases were determined from X-ray, electron, and neutron diffraction data. The manganese oxidations states (Mn(4+)/Mn(3+)) were investigated by X-ray photoemission spectroscopy. The orthorhombic CaMn(1-x)Nb(x)O(3+/-delta) (x = 0.02, 0.05, and 0.08) phases were studied in terms of their high-temperature thermoelectric properties (Seebeck coefficient, electrical resistivity, and thermal conductivity). Differences in electrical transport and thermal properties can be correlated with different microstructures obtained by the two synthesis methods. In the high-temperature range, the electron-doped manganate phases exhibit large absolute Seebeck coefficient and low electrical resistivity values, resulting in a high power factor, PF (e.g., for x = 0.05, S(1000K) = -180 microV K(-1), rho(1000K) = 16.8 mohms cm, and PF > 1.90 x 10(-4) W m(-1) K(-2) for 450 K < T < 1070 K). Furthermore, lower thermal conductivity values are achieved for the SC-derived phases (kappa < 1 W m(-1) K(-1)) compared to the SSR compounds. High power factors combined with low thermal conductivity (leading to ZT values > 0.3) make these phases the best perovskitic candidates as n-type polycrystalline thermoelectric materials operating in air at high temperatures.

Mixed nickel-gallium tellurides Ni{sub 3−x}GaTe{sub 2} as a matrix for incorporating magnetic cations: A Ni{sub 3−x}Fe{sub x}GaTe{sub 2} series

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuznetsov, Alexey N., E-mail: alexei@inorg.chem.msu.ru; N.S. Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninsky pr. 31, GSP-1, 119991 Moscow; Stroganova, Ekaterina A.

Using a high-temperature ampoule technique, a series of mixed nickel-iron-gallium metal-rich tellurides with layered structures, Ni{sub 3-x}Fe{sub x}GaTe{sub 2}, were prepared and characterized based on X-ray powder diffraction, energy-dispersive spectroscopy, and {sup 57}Fe Mössbauer spectroscopy data. These compounds may be regarded as a result of partial substitution of nickel by iron in the recently reported ternary Ni{sub 3-x}GaTe{sub 2} series, which are based on NiAs/Ni{sub 2}In type of structure. The compositional boundary for the substitution was found to be at x~1. According to the Mössbauer spectroscopy data, the substitution is not statistical, and iron atoms with the increase in xmore » tend to preferentially occupy those nickel positions that are partially vacant in the initial ternary compound. Magnetic measurements data for the Ni{sub 3-x}Fe{sub x}GaTe{sub 2} series show dramatic change in behavior from temperature-independent paramagnetic properties of the initial matrix to a low-temperature (~75 K) ferromagnetic ordering in the Ni{sub 2}FeGaTe{sub 2}. - Graphical abstract: Ordered substitution of nickel by iron in the Ni{sub 3−x}GaTe{sub 2} series leading to ferromagnetic ordering. - Highlights: • A series of Ni{sub 3−x}Fe{sub x}GaTe{sub 2} compounds were synthesized. • They adopt the NiAs/Ni{sub 2}In type of structure with ordered iron distribution. • The distribution of iron was studied using {sup 57}Fe Mössbauer spectroscopy. • An increase in iron content leads to the strong ferromagnetic coupling.« less

Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.

2016-03-23

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1-xSr xCoO 3-δ. We attempt tomore » rationalize the high activities of La 1-xSr xCoO 3-δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

DOE PAGES

Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.; ...

2016-03-23

Here, perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1–xSr xCoO 3–δ. We attemptmore » to rationalize the high activities of La 1–xSr xCoO 3–δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

Structural transformations in (1 -x ) Na0.5Bi0.5TiO3-x BaTiO3 single crystals studied by Raman spectroscopy

NASA Astrophysics Data System (ADS)

de la Flor, G.; Malcherek, T.; Gorfman, S.; Mihailova, B.

2017-12-01

Hard-mode Raman spectroscopy was applied to analyze the temperature-induced transformation processes in perovskite-type (ABO3) single crystals of (1 -x ) Na0.5Bi0.5TiO3-x BaTiO3 (NBT-x BT ) in a wide temperature range between 100 and 1010 K and a composition range of x =0 -0.074 across the morphotropic phase boundary (MPB). The results show abundant uncoupled ferroic structural distortions even at 1010 K and coexistence of two types of mesoscopic-scale ferroic order at lower temperatures. Octahedral BO6 tilting is typical of pure NBT, while the incorporation of A-site Ba2 + suppresses the tilting and promotes the off centering of BO6 octahedra. The temperature evolution of the phonon modes clearly reveals the two macroscopically observed critical temperatures Tm and Td as well as, in the case of x ≠0 , two characteristic temperatures T' and T'' preceding the Tm and Td, respectively, which are attributed to mesoscopic-scale antiferroelectric and ferroelectric coupling processes within the A-site-cation subsystem. At x <xMPB the two sublattices, off-centered A-site cations and off-centered B-site cations, remain incoherent in the entire temperature range. Only when the amount of Ba reaches xMPB the two subsystems couple dynamically, which can explain the enhancement of properties at the MPB. The overall ferroic distortion, however, has a minimum at the MPB, probably because at xMPB the ferroelectric coupling between B-site Ti4 + cations is reduced to a greater extent than the enhancement of ferroelectric coupling between A-site Bi3 + cations.

Combinatorial studies of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 thin-film chips

NASA Astrophysics Data System (ADS)

Cheng, Hong-Wei; Zhang, Xue-Jin; Zhang, Shan-Tao; Feng, Yan; Chen, Yan-Feng; Liu, Zhi-Guo; Cheng, Guang-Xi

2004-09-01

Applying a combinatorial methodology, (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-BT) thin-film chips were fabricated on (001)-LaAlO3 substrates by pulsed laser deposition with a few quaternary masks. A series of NBT-BT library with the composition of BT ranged from 0 to 44% was obtained with uniform composition and well crystallinity. The relation between the concentration of NBT-BT and their structural and dielectric properties were investigated by x-ray diffraction (XRD), evanescent microwave probe, atomic force microscopy, and Raman spectroscopy. An obvious morphotropic phase boundary (MPB) was established to be about 9% BT by XRD, Raman frequency shift, and dielectric anomaly, different from the well-known MPB of the materials. The result shows the high efficiency of combinatorial method in searching new relaxor ferroelectrics.

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe3-x Se x

NASA Astrophysics Data System (ADS)

Shan, Cui; Lan-Po, He; Xiao-Chen, Hong; Xiang-De, Zhu; Cedomir, Petrovic; Shi-Yan, Li

2016-07-01

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe3-x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe3-x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ 0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe3-x Se x , which indicates conventional superconductivity despite of the existence of a CDW QCP. Project supported by the National Basic Research Program of China (Grant Nos. 2012CB821402 and 2015CB921401), the National Natural Science Foundation of China (Grant Nos. 91421101, 11422429, and 11204312), the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, China, and STCSM of China (Grant No. 15XD1500200). Work at Brookhaven National Laboratory was supported by the US DOE under Contract No. DESC00112704.

X-15 #3 with test pilot Bill Dana

NASA Technical Reports Server (NTRS)

1967-01-01

NASA research pilot Bill Dana is seen here next to the X-15 #3 (56-6672) rocket-powered aircraft after a flight. William H. Dana is Chief Engineer at NASA's Dryden Flight Research Center, Edwards, California. Formerly an aerospace research pilot at Dryden, Dana flew the F-15 HIDEC research aircraft and the Advanced Fighter Technology Integration/F-16 aircraft. Dana flew the famed X-15 research airplane 16 times, reaching a top speed of 3,897 miles per hour and a peak altitude of 306,900 feet (over 58 miles high). The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation built three X-15 aircraft for the program. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and movable horizontal stabilizers to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a

Physical parameters of the Centaurus X-3 system

NASA Technical Reports Server (NTRS)

Osmer, P. S.; Whelan, J. A. J.; Hiltner, W. A.

1975-01-01

Photographic spectra of Cen X-3 show that the primary star has a spectral type near O6.5 with weak, variable emission at 4640 and 4686 A. No orbital motion of the emission or absorption lines is detected; for the latter the upper limit is about plus or minus 50 km/sec. Analysis of the available data indicates that the primary is a factor of 2-3 less massive than expected from normal evolutionary models while the X-ray source has a mass near 1.5 times the solar mass.

ZnO-Assisted Growth of CH3NH3PbI3- xCl x Film and Efficient Planar Perovskite Solar Cells with a TiO2/ZnO/C60 Electron Transport Trilayer.

PubMed

Xu, Jia; Fang, Mingde; Chen, Jing; Zhang, Bing; Yao, Jianxi; Dai, Songyuan

2018-06-06

Appropriate electron transport layers (ETL) are essential in perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Herein, a TiO 2 /ZnO/C 60 trilayer fabricated on a transparent fluorine-doped tin oxide (FTO) glass substrate is used as a compound ETL in planar PSCs. The trilayer shows positive effects on both perovskite synthesis and device performance. The ZnO layer assists growth of CH 3 NH 3 PbI 3- x Cl x ( x ≈ 0) annealed at a lower temperature and with a shorter time, which is due to a more rapid and easier decomposition of the intermediate CH 3 NH 3 PbCl 3 phase in the growth of CH 3 NH 3 PbI 3- x Cl x . All three materials in the trilayer are important for obtaining PSCs with a high PCE. ZnO is critical for enhancing the open circuit voltage by ensuring proper energy alignment with the TiO 2 and C 60 layers. C 60 enhances carrier extraction from the CH 3 NH 3 PbI 3- x Cl x layer. TiO 2 eliminates charge recombination at the FTO surface and ensures efficient electron collection. The best-performing PSC based on the TiO 2 /ZnO/C 60 electron transport trilayer features a PCE of 18.63% with a fill factor of 79.12%. These findings help develop an understanding of the effects of ZnO-containing ETLs on perovskite film synthesis and show promise for the future development of high-performance PSCs with compound ETLs.

Electronic, elastic and optical properties of divalent (R+2X) and trivalent (R+3X) rare earth monochalcogenides

NASA Astrophysics Data System (ADS)

Kumar, V.; Chandra, S.; Singh, J. K.

2017-08-01

Based on plasma oscillations theory of solids, simple relations have been proposed for the calculation of bond length, specific gravity, homopolar energy gap, heteropolar energy gap, average energy gap, crystal ionicity, bulk modulus, electronic polarizability and dielectric constant of rare earth divalent R+2X and trivalent R+3X monochalcogenides. The specific gravity of nine R+2X, twenty R+3X, and bulk modulus of twenty R+3X monochalcogenides have been calculated for the first time. The calculated values of all parameters are compared with the available experimental and the reported values. A fairly good agreement has been obtained between them. The average percentage deviation of two parameters: bulk modulus and electronic polarizability for which experimental data are known, have also been calculated and found to be better than the earlier correlations.