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Sample records for 2cusub 3osub 7-delta

  1. Properties of epitaxial YBa sub 2 Cu sub 3 O sub 7-. delta. -based superconducting superlattices

    SciTech Connect

    Norton, D.P.; Lowndes, D.H.; Zheng, Z.Y.; Feenstra, R. ); Zhu, Shen . Dept. of Physics and Astronomy)

    1991-09-01

    Epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting superlattices have been fabricated using pulsed laser deposition in which c-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as one unit cell thick are separated by relatively thick PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} based barrier layers. The superlattice {Tc} (R=0) decreases rapidly with increasing barrier layer thickness, but then saturates at a finite {Tc} for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers as thin as a single c-axis unit cell. The superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}-based superlattices are shown to depend strongly on the electronic properties of the barrier layers. The resistive transition width decreases significantly as the hole carrier density in the barrier layers is increased. However, {Tc} (onset) does not change, contrary to predictions of hole filling models. Theoretical analyses suggest that the broadening of the resistive transition for the thinnest YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers is most likely due to a crossover to 2D resistive behavior involving thermally-generated vortices. Scanning tunneling microscopy reveals that epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films grow unit cell-by-unit cell, by a terraced-island growth mode. This terraced microstructure explains the steps found in ultrathin YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers in these superlattices. These steps may act as superconducting weak links, providing support for 2D Josephson-coupled-array models of superconducting superlattices. 34 refs., 5 figs.

  2. Penetration Depth Studies in Nickel and Zinc Doped Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Ulm, Eric R.

    1995-01-01

    Many recent experiments have supported the hypothesis of d-wave superconductivity in the high-T_ {c} superconductors. Measurements of lambda(T), the magnetic field penetration depth, have given some of the best evidence for d-wave superconductivity in YBa_2Cu _3O_{7-delta} . This thesis reports measurements of lambda(T) in pure, Ni and Zn-doped YBa _2Cu_3O_ {7-delta} films by measuring the change in the mutual inductance of two coils on opposite sides of the films. The low-temperature linear dependence of lambda(T) at low temperatures in YBa_2Cu_3O _{7-delta} and rapid increase in lambda(0) with doping support the hypothesis of d-wave superconductivity and are inconsistent with the predictions of s-wave models. Alternative explanations for the linear lambda(T) have been proposed in terms of fluctuations in the phase of the order parameter. These fluctuations should be more pronounced in films with large values of lambda (0). We find that the linear term actually disappears in films with large lambda(0), showing that phase fluctuations are not responsible for the linear behavior observed in YBa_2Cu _3O_{7-delta} .

  3. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using X-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  4. Near-edge study of gold-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1991-01-01

    The valence of Cu and Au in YBa2Au0.3Cu2.7O7-delta was investigated using x-ray absorption near edge structure (XANES). X-ray and neutron diffraction studies indicate that Au goes on the Cu(1) site and Cu K-edge XANES shows that this has little effect on the oxidation state of the remaining copper. The Au L3 edge develops a white line feature whose position lies between that of trivalent gold oxide and monovalent potassium gold cyanide, and whose height relative to the edge step is smaller than in the two reference compounds. The appearance of the Au L3 edge suggests that fewer Au 3d states are involved in forming the Au-O bond in YBa2Au0.3Cu2.7O7-delta than in trivalent gold oxide.

  5. Normal State Transport in Superconducting Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) and Semiconducting Praseodymium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Browning, Valerie Michelle

    1995-01-01

    The discovery, in 1986, of materials with superconducting transition temperatures well above 77 K has generated a renewed interest in potential applications for superconductors. Unfortunately, the widespread use of high temperature superconductors (HTS) has not been realized due to their poor performance in terms of electrical and physical properties. Although the mechanism of high temperature superconductivity remains a mystery, it is hoped that an understanding of the HTS will result in the ability to engineer better quality materials. The normal state of the HTS exhibits several features which are considered unusual. Among these features are a linear temperature dependence of the resistivity and a temperature dependent Hall effect. It is believed that knowledge of the normal state transport properties of the HTS is crucial to understanding superconductivity in these materials. In an effort to better understand the normal state of the these materials, the transport properties of single crystal samples of two members of the superconducting RBa_2Cu_3O _{7-delta} ("123") family were studied (R = yttrium and many of the rare earth elements). Resistivity, Hall effect, and magnetoresistance measurements were performed on a detwinned single crystal sample of YBa_2Cu_3 _{7-delta} (Y 123). Measurements were repeated after various oxygen anneals to study the effects of oxygen inhomogeneities on the sample's transport properties. These results indicate that oxygen inhomogeneities strongly influence the transport properties of this system. A model is presented which takes into account oxygen defects in calculating the resistivity and Hall coefficient. Of the rare earth elements that will form the 123 structure, only PrBa_2Cu _3O_{7-delta} (Pr 123) does not superconduct. Pr 123 exhibits a non-metallic temperature dependent resistivity as opposed to the metallic resistivity exhibited by the superconducting 123 family members. Magnetotransport and magnetization measurements

  6. Flux Pinning Phenomena in Electron Irradiated Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Single Crystals

    NASA Astrophysics Data System (ADS)

    Giapintzakis, John Konstantinos

    1992-01-01

    It has been shown that 1 MeV electron irradiation to a typical dose Phi~ 1times 10^{19} cm^{ -2} results in an enhancement of the critical current density in twinned and untwinned YBa_2 Cu_3O_{7 -delta} single crystals. Values up to two times the preirradiation J_{c} at 10 K and 1 T are observed. The J _{c} enhancement is accompanied by a dramatic increase of the irreversibility field. A threshold incident electron energy (E_{ t}~ 0.5 MeV) is found above which flux pinning enhancement is observed. The data indicated that the electron radiation-induced defects are effective pinning centers only for the orientation H parallel c-axis. In-situ TEM studies in the HVEM suggest that the pinning centers must be smaller than 20 A. A comparison of the electron irradiation results with those of proton irradiation experiments indicate a lower magnitude of enhancement of J_{c} at 10 K and 2 T for the electron case. The probable explanation is the difference in the energy spectra of the PKAs produced by the two types of irradiation. GdBa_2Cu_3O_{7-delta } and EuBa_2Cu_3O _{7-delta} single crystals irradiated with 0.6 MeV electrons displayed similar flux pinning enhancements as YBa_2Cu _3O_{7-delta} crystals, indicating that Y displacements are not primary flux pinners. The evidence from annealing studies suggests that the primary pinning center produced by the electron irradiation is not associated with the oxygen in the Cu-O chains. Instead, a consistent interpretation of the data suggests that the primary pinning defect is most likely based on the displacement of a copper atom from the CuO_2 plane. In order to account for the complete enhancement of J_{c} other pinning mechanisms aside from point defects, such as small point defect clusters, should be considered.

  7. Macroscopic Magnetic Properties of Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Matthews, David Neil

    The work described in this thesis on the macroscopic properties of rm YBa_2Cu_3O _{7-delta} constitutes a selected programme which attempts to understand the magnetic behaviour of the new high temperature superconductors. Despite the discovery of the Bi and Tl compounds during the course of this work, the studies described in this thesis have been restricted almost entirely to YBa_2Cu_3O_{7-delta }. Both the Bi and Tl materials are difficult to prepare reproducibly and it was decided as a matter of policy, that more meaningful information could be obtained by studying only one material in depth rather than spreading the research effort over a range of compounds. One of the biggest problems with high temperature superconductors is their low current carrying capacity. At the commencement of this work no group had achieved critical current densities in excess of 500 A/cm^2 and it soon became recognised that grain alignment was required to increase J_{c}. A method is described in this thesis by which the surface of YBa_2Cu_3O _{7-delta} can be aligned by uniaxial pressure and subsequent sintering. This results in a material with a very high degree of c-axis orientation. The transport and magnetic properties of this material were measured and compared to standard polycrystalline material and single crystal. Results are discussed in terms of a critical state model which was successful in describing many of the experimental observations. As in conventional superconductors, thermally activated flux motion is a key mechanism in these new materials and a method was developed by which the pinning potential U_{o} can be measured using the time decay of a trapped intragranular field in the presence of a transport current. A detailed investigation of the magnetoresistive properties of rm YBa_2Cu_3O _{7-delta} was made from which a method was devised to estimate the average lower critical field of the grains (H_{clg}). As a comparison similar measurements were performed on some

  8. Synthesis and structural chemistry of Au(III)-substituted Ba2YCu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Banerjea, A.; Hambourger, P. D.

    1988-01-01

    Gold-substituted superconductors, Ba2Y(Au(x)Cu(1-x))3O(7-delta) (x = 0-0.1) were synthesized. For x = 0.1, there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. Substituted gold is found to be trivalent by XPS. Replacing Cu(1) in the copper oxide chain with a slight reordering of oxygen is consistent with c axis expansion. The formal charge of the site remains trivalent; remaining Cu in the chains may be reduced resulting in an oxygen stoichiometry is less than or equal to 7. A small effect on T(sub c)(89 K for x = 0.10) is observed upon gold substitution.

  9. XANES and EXAFS study of Au-substituted YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Ruckman, Mark W.; Hepp, Aloysius F.

    1990-01-01

    The near-edge structure (XANES) of the Au L3 and Cu K edges of YBa2Au(0.3)Cu(2.7)O(7-delta) was studied. X ray diffraction suggests that Au goes on the Cu(1) site and XANES shows that this has little effect on the oxidation state of the remaining copper. The gold L3 edge develops a white line feature whose position lies between that of trivalent gold oxide (Au2O3) and monovalent potassium gold cyanide (KAu(CN)2) and whose intensity relative to the edge step is smaller than in the two reference compounds. The L3 EXAFS for Au in the superconductor resembles that of Au2O3. However, differences in the envelope of the Fourier filtered component for the first shell suggest that the local structure of the Au in the superconductor is not equivalent to Au2O3.

  10. Physical Properties of Oxygen Deficient YTTRIUM(1) BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Superconductors.

    NASA Astrophysics Data System (ADS)

    Sun, He Bi.

    The physical properties of oxygen deficient polycrystalline rm YBa_2Cu_3O_{7 -delta} superconducting materials have been systematically investigated. These properties include magnetic susceptibility, electrical transport, thermoelectric power and infrared reflectivity. A great deal of this study has concentrated on the magnetic and transport properties of these materials when they are in the mixed state. The polycrystalline specimens used in this work were prepared through a solid state reaction. The oxygen content of the specimens was controlled using several annealing methods and the oxygen deficiency delta was determined by X-ray diffraction, gas evolution, iodometric titration and neutron diffraction techniques. A new method has been developed for the investigation of magnetic relaxation in these materials using the conventional a.c. susceptibility technique after modification. This thesis represents the first detailed and systematic study of the thermal activation energy for high Tc superconductors using many different methods, including a.c. susceptibility, magnetic relaxation, electric resistivity and thermoelectric power. All the results obtained, including their numerical values and field dependence are consistent with and comparable to previously reported data. A modified critical state model has been successfully used to interpret the magnetic field dependence of the isothermal a.c. susceptibility data, including field dependent a.c. losses and the chi^' -chi^{'' } interrelationship. This study highlights the strong influence that delta exerts on the superconducting and normal state properties of polycrystalline rm YBa_2Cu_3O_{7-delta } material. In particular, for transport properties, delta affects the carrier doping in the CuO_2 planes, which determines the carrier concentration. Therefore increasing delta reduces the superconducting transition temperature. For the magnetic property, delta has a negative influence on the pinning energy in

  11. Flux Creep Studies in YTTRIUM(1) BARIUM(2) COPPER(3) OXIDE(7-DELTA) Superconductors

    NASA Astrophysics Data System (ADS)

    Sun, Yang Ren

    Magnetic relaxation studies were performed on a proton irradiated high J_{c} YBa_2Cu _3O_{7-delta} single crystal and a melt-texture-growth YBa _2Cu_3O_ {7-delta} sample. Significant deviation from the logarithmic time decay predicted by conventional Anderson-Kim theory was observed for a wide range of temperature and magnetic field. The flux creep data, with durations up to 3.5 times 10^5 s, could be analyzed using several recent models with comparable accuracies. The difficulty in distinguishing between these models is due to the fact that the time window of observations, which usually covers ~2 or 3 decades, is too short for magnetic relaxation studies. To complement these studies in the direct time domain, the effects of field-sweep rate K = partial H/partialt on magnetization hysteresis loops M(H) and on flux-creep M(t) were investigated both theoretically and experimentally. We find the basic relation between M and K is, to first order, the following: M = const - (dM/dln(t)) ln(K) - (Kt_{ eff}/10), where dM/dln(t) = ac/30 is the flux-creep rate in a cylindrical sample of radius a, and t_{eff} is an effective attempt time for vortex hopping. The largest possible M, which corresponds to the critical current density J_{c0} in the absence of thermal activation, develops when at high sweep rate K >= K_{ max} = ac/ ((1 + aalpha )t_{eff}) with alpha = partial J/partialH. Such studies provided a way to measure t_{eff}, whose magnitude has been rather controversial; furthermore, the analysis revealed the time origin of flux creep, t* = ac/K(1 + aalpha), which is essential in studying the initial stages of relaxation. The model agrees well with experiments yielding t_ {eff}~0.2 s for the melt -textured-growth sample. By combining conventional flux creep experiments with measurements of magnetization versus magnetic field sweep rate, we are able to detect the decay of magnetization in both its middle and very early stages, thereby expanding the observational time window

  12. Structural chemistry of Au(III)-substituted Ba2YCu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.

    1988-01-01

    A series of gold-substituted perovskite superconductors Ba2Y(Cu/1-x/Aux)3O(7-delta)(x = 0-0.1) was synthesized. For x = 0.1, there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A), but a 0.06 A c-axis expansion to 11.75 A was observed. Substituted gold was found to be trivalent by X-ray photoelectron spectroscopy. Replacing Cu(1) in the copper oxide chain with a slight reordering of oxygen is consistent with c-axis expansion. The formal charge of the site remains trivalent, while remaining Cu in the chains is reduced to Cu(I), resulting in an oxygen stoichiometry of less than 7. Finally, no large effect on Tc is observed (Tc = 89 K for x = 0.10), in contrast to the effect of a number of other metal ion dopants. These results are discussed relative to the chemistry of Au(III) and to the use of the metal in structures containing gold and ceramic superconductors.

  13. Experimental Studies on Penetration Depth in Yttrium BARIUM(2)COPPER(3)OXIDE(7-DELTA) Superconductors

    NASA Astrophysics Data System (ADS)

    Lee, Juyoung

    There is growing evidence for a d-wave order parameter in high-T_{c} superconductors, which is of a great concern these days. The magnetic penetration depth lambda(T) of d-wave superconductors is predicted to be very sensitive to impurity effects: a rapid increase of lambda(0) and a decrease in the curvature of deltalambda(T) at low T should occur in disordered d-wave superconductors. Therefore, measurements of lambda(T) in deliberately disordered samples can lead to crucial information on the existence of a d-wave order parameter. We performed detailed penetration depth measurements on rm YBa _2Cu_3O_{7-delta} thin films by a two-coil method. Systematic oxygen depletion of the thin films is also made. lambda^2(0)/ lambda^2(T/T_{c}) vs T/T_{c} is the same for all films, even when oxygen is depleted. Also T _{c} vs 1/lambda^2(0) , reproduces the muSR results of Uemura et al. on bulk sample. This strongly suggests that the measured 1/lambda^2(T) is the property of superconducting grains, not the effect of "damaged" material like grain boundaries. There is extremely good agreement of lambda(T/T_{c}) between the thin films and Hardy's single crystal data above a crossover temperature of 25K, and also a deviation below the crossover temperature. The deviation at low T is quantified by two low T parameters: the increase of lambda(0) and the decrease in the curvature of lambda(T) at low T. Our result is consistent with the d -wave model analyzed by Hirschfeld et al., thus supporting a d-wave energy gap in high-T_{c} superconductors. This research has been supported by DOE Grant No. DE-FG02-90ER45427 through Midwest Superconductivity Consortium.

  14. Millimeter wave surface resistance of RBa2Cu3O(7-delta) (R=Y,Eu,Dy,Sm,Er) superconductors

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Eck, T. G.; Bhasin, K. B.; Warner, J. D.; Jenkins, K. A.

    1990-01-01

    The measurements are reported of the millimeter wave surface resistance R(sub s) at 58.6 GHz of bulk samples of RBa2Cu3O(7-delta) (R = Y,Eu,Dy,Sm,Er) and of YBa2Cu3O(7-delta) superconducting films, in the temperature range from 20 to 300 K. The bulk samples were prepared by cold pressing the powders of RBa2Cu3O(7-delta) into one in. disks. The powders were prepared by several sinterings in one atmosphere of oxygen at 925 C, with grindings between sinterings, to obtain the superconducting phase. The thin films were deposited on SrTiO3 and LaGaO3 substrates by pulsed laser ablation. Each sample was measured by replacing the end wall of a gold-plated Te sub 013 circular mode copper cavity with the sample and determining the cavity quality factor . From the difference in the Q-factor of the cavity, with and without the sample, the R(sub s) of the sample was determined.

  15. IL-7 splicing variant IL-7{delta}5 induces human breast cancer cell proliferation via activation of PI3K/Akt pathway

    SciTech Connect

    Pan, Deshun; Liu, Bing; Jin, Xiaobao; Zhu, Jiayong

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer This study confirms the role of IL-7{delta}5 in breast cancer cell proliferation. Black-Right-Pointing-Pointer IL-7{delta}5 promotes breast cancer cell proliferation and cell cycle progression. Black-Right-Pointing-Pointer IL-7{delta}5 promotes cell proliferation via activation of PI3K/Akt pathway. -- Abstract: Various tumor cells express interleukin 7 (IL-7) and IL-7 variants. IL-7 has been confirmed to stimulate solid tumor cell proliferation. However, the effect of IL-7 variants on tumor cell proliferation remains unclear. In this study, we evaluated the role of IL-7{delta}5 (an IL-7 variant lacking exon 5) on proliferation and cell cycle progression of human MDA-MB-231 and MCF-7 breast cancer cells. The results showed that IL-7{delta}5 promoted cell proliferation and cell cycle progression from G1 phase to G2/M phase, associated with upregulation of cyclin D1 expression and the downregulation of p27{sup kip1} expression. Mechanistically, we found that IL-7{delta}5 induced the activation of Akt. Inhibition of PI3K/Akt pathway by LY294002 reversed the proliferation and cell cycle progression of MDA-MB-231 and MCF-7 cells induced by IL-7{delta}5. In conclusion, our findings demonstrate that IL-7{delta}5 variant induces human breast cancer cell proliferation and cell cycle progression via activation of PI3K/Akt pathway. Thus, IL-7{delta}5 may be a potential target for human breast cancer therapeutics intervention.

  16. Studies of Pure and Iron Doped Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Siddique, Rezaul K.

    YBa_2(Cu_ {1-x}Fe_{ x})O_{7-delta } (YBCO) compounds for x = 0.0, 0.01, 0.02, 0.05, 0.15, and 0.25 were studied. Samples include fully oxygenated virgin, and oxygen deficient samples, and the oxygen deficient samples after reoxygenation. X-ray diffraction, oxygen content, and magnetization measurements were used for obtaining information respectively on crystal structure, oxygen stoichiometry, and superconducting (SC) critical temperature (T_{c}). By isothermal vacuum annealing (VA) pure (x = 0) YBCO superconducting samples in the temperature range 300-800C, some important results such as: (1) the steplike increase of c axis length, and (2) the familiar plateaus in T_{c} with oxygen stoichiometry were reproduced. For x = 0.02-0.05, the symmetry of crystal changed from orthorhombic to tetragonal, and for x = 0.25, sample became non SC. We find evidence that the Fe-O bonds in YBCO are stronger than the Cu-O bonds. Mossbauer studies of Fe doped virgin samples; by VA these virgin samples at 800C; and reoxygenating these oxygen desorbed samples at 410C were used for identifying Fe sites, and for determining oxygen coordination of Fe. Only three quadrupole doublets each corresponding to an Fe site were sufficient to fit room temperature (RT) Mossbauer spectra of virgin samples for x <= 0.15, while for x = 0.25, two additional magnetic sextets had to be added. The subspectra are explained in terms of square planar, pseudotetrahedral, and octahedral oxygen environment around Fe atoms in the crystal. Due to vacuum annealing samples at T_{a } >= 400C, new Fe sites appeared in all RT spectra, and depending on the value of x, and the annealing temperature, T_{a}, one or two magnetic sites evolved. From the Mossbauer spectra of virgin (x = 0.25 only), and oxygen deficient samples as a function of temperature we determined the magnetic ordering temperature, T_{ N}. The values of T_ {N} are 394K for the 25% virgin, and from 419-472K for the 2-25% samples vacuum annealed at 800C

  17. Boson localization and universality in YBa2Cu(3-x)M(x)O(7-delta)

    NASA Technical Reports Server (NTRS)

    Kallio, A.; Apaja, V.; Poykko, S.

    1995-01-01

    We consider a two component mixture of charged fermions on neutralizing background with all sign combinations and arbitrarily small mass ratios. In the two impurity limit for the heavier component we show that the pair forms a bound state for all charge combinations. In the lowest order approximation we derive a closed form expression Veff(r) for the binding potential which has short-range repulsion followed by attraction. In the classical limit, when the mass of embedded particles is large m2 much greater than m, we can calculate from Veff(r) also the cohesive energy E and the bond length R of a metallic crystal such as lithium. The lowest order result is R = 3.1 A, E = -0.9 eV, not entirely different from the experimental result for lithium metal. The same interaction for two holes on a parabolic band with m2 greater than m gives the quantum mechanical bound state which one may interpret as a boson or local pair in the case of high-Te and heavy fermion superconductors. We also show that for compounds of the type YBa2Cu(3 - x)M(x)O(7 - delta) one can understand most of the experimental results for the superconducting and normal states with a single temperature dependent boson breaking function f(T) for each impurity content x governing the decay of bosons into pairing fermions. In the normal state f(T) turns out to be a linear, universal function, independent of the impurity content I and the oxygen content delta. We predict with universality a depression in Tc(x) with slight down bending in agreement with experiment. As a natural consequence of the model the bosons become localized slightly above Tc due to the Wigner crystallization, enhanced with lattice local field minima. The holes remain delocalized with a linearly increasing concentration in the normal state, thus explaining the rising Hall density. The boson localization temperature T(sub BL) shows up as a minimum in the Hall density R(sub ab)(exp -1). We also give explanation for very recently observed

  18. Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

    NASA Technical Reports Server (NTRS)

    Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

    1991-01-01

    Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

  19. Proximity effect in gold-coated YBa(2)Cu(3)O(7-delta) films studied by scanning tunneling spectroscopy.

    PubMed

    Sharoni, Amos; Asulin, Itay; Koren, Gad; Millo, Oded

    2004-01-09

    Scanning tunneling spectroscopy on gold layers overcoating c-axis YBa(2)Cu(3)O(7-delta) (YBCO) films reveals proximity-induced gap structures. The gap size reduces exponentially with the distance from a-axis facets, indicating that the proximity effect is primarily due to the (100) YBCO facets. The penetration depth of superconductivity into the gold is approximately 30 nm, in good agreement with estimations for the dirty limit. The extrapolated gap at the interface is approximately 15 meV, similar to the value of an s-wave component of the order parameter measured at the YBCO surface in recent point-contact experiments.

  20. Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

    NASA Astrophysics Data System (ADS)

    Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

    1991-12-01

    Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

  1. Interplay between static and dynamic properties of semifluxons in YBa2Cu3O(7-delta) 0-pi Josephson junctions.

    PubMed

    Cedergren, K; Kirtley, J R; Bauch, T; Rotoli, G; Troeman, A; Hilgenkamp, H; Tafuri, F; Lombardi, F

    2010-04-30

    We have investigated the static and dynamic properties of long YBa2Cu3O(7-delta) 0-pi Josephson junctions and compared them with those of conventional 0 junctions. Scanning SQUID microscope imaging has revealed the presence of a semifluxon at the phase discontinuity point in 0-pi Josephson junctions. Zero field steps have been detected in the current-voltage characteristics of all junctions. Comparison with simulation allows us to attribute these steps to fluxons traveling in the junction for conventional 0 junctions and to fluxon-semifluxon interactions in the case of 0-pi Josephson junctions.

  2. Synthesis and Superconductivity of the YTTRIUM(1-X) Praseodymium(x) BARIUM(2) COPPER(3) OXYGEN(7-DELTA) System

    NASA Astrophysics Data System (ADS)

    Paulius, Lisa Maria

    1993-01-01

    We report techniques for growing single crystals of Y_{1-x}Pr_ {x}Ba_2Cu_3O_{7-delta } in both Al_2O_3 and ZrO_2 crucibles. We characterize the crystals with measurements of the dc magnetic susceptibility, electrical resistivity, and electron micro -probe analysis. The effects of contamination from the crucible material are discussed. A direct method for determining the field H_{fcs} at which a superconductor enters the fully critical state (i.e., the field at which flux first penetrates throughout the entire sample) is introduced. In addition, a formula for calculating the critical current density J_{c } from the value of H_ {fcs} (J_{cH}) is given. The behavior of J_{cH }(x) is compared to the variation of the pinning energy U in the Y_{1-x}Pr _{x}Ba_2Cu_3O_{7 -delta} system. These results are compared to the values of J_{c}(x) deduced from the magnetic hysteresis measurements. The results of magnetic measurements on two sets of samples of Y_{1-x}Pr _{x}Ba_2Cu_3O_{7 -delta} are presented. One set of samples was prepared using a sol-gel process, the other was prepared using a solid state reaction technique. Both U at 27 K and J_{c} at 10 K exhibit maxima at x ~ 0.1 -0.2 with values that are about twice the corresponding values at x = 0. The enhancement of U may be due to a local suppression of the superconducting order parameter in the vicinity of the Pr ions due to magnetic pairbreaking. The dependence of the superconducting transition temperature T_{c} on pressure in Y_{1-x}Pr _{x}Ba_2Cu_3O_{7 -delta} is measured and analyzed in terms of a phenomenological model. We show that the crossover that occurs with increasing x near x ~ 0.2 in the pressure dependence of T_ {c} from positive to large negative values can be accounted for by this model. Finally, the pressure dependence of the metal -insulator transition in the RNiO_3 system (R = Nd, Pr, and rm Nd_{0.7 }La_{0.3}) is investigated. The transition temperature decreases under pressure with a common rate of

  3. Millimeter-wave surface resistance of laser-ablated YBa2Cu3O(7-delta) superconducting films

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Warner, J. D.

    1990-01-01

    The millimeter-wave surface resistance of YBa2Cu3O(7-delta) superconducting films was measured in a gold-plated copper host cavity at 58.6 GHz between 25 and 300 K. High-quality laser-ablated films of 1.2-micron thickness were deposited on SrTiO3 and LaGaO3 substrates. Their transition temperatures were 90.0 and 88.9 K, with a surface resistance at 70 K of 82 and 116 milliohms, respectively. These values are better than the values for the gold-plated cavity at the same temperature and frequency.

  4. Transverse conductivity in Y_{1-y}Pr_{y}Ba_{2}Cu_{3}O_{7-\\delta } single crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya; Dobrovolskiy, O. V.; Nazyrov, Z. F.; Goulatis, I. L.

    2014-04-01

    The out-of-plane resistivity of high-quality Y_{1-y}Pr_{y}Ba_{2}Cu_{3}O_{7-\\delta } single crystals was measured and analyzed within the range {{T}_{{\\rm{c}}}}-300 K. The temperature dependence of the resistivity \\rho \\left( T \\right) can be described well by a model that takes into account scattering of electrons by phonons and defects, in conjunction with a transition to the ‘semiconductor’-type behavior with increasing praseodymium concentration. The effect of fluctuations is described well by the 3D Aslamazov-Larkin model. The electron-phonon interaction in the Y_{1-y}PryBa_{2}Cu_{3}O_{7-\\delta } is strong, but it is weakened with increasing praseodymium concentration. A parabolic correlation between the critical temperature {{T}_{{\\rm{c}}}} and the parameter characterizing the volume fraction of the ‘semiconductor’ phase was observed. The quantified scattering and fluctuation parameters in the investigated interval of praseodymium concentrations (y<0.35) are reported.

  5. Far-Infrared Absorptivity of the Superconducting State of Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Crystals

    NASA Astrophysics Data System (ADS)

    Pham, Thi

    1992-01-01

    Measurements and analysis of the absorptivity A(omega) are reported, for a series of YBa_2Cu_3O _{7-delta} crystals at the fixed temperature of 2K and in the frequency range from 80 to 650 cm^{-1} (10 and 80 meV). The focus is on twin-free crystals where the crystallographic axes are uniformly aligned throughout the sample. The measured absorptivity is finite in the vicinity of 3.5 k_{B}T _{c} (230 cm ^{-1}) and anisotropic. For radiation polarized along the crystallographic a-axis of the twin -free YBa_2Cu_3O _{7-delta} crystals the absorptivity is ~0.5% with structures it begins an approximately linear rise near 310 cm^{-1}.. From A(omega) and published reflectivity data the real part of the conductivity sigma_1(omega) is obtained by a Kramers-Kronig analysis. The lineshape of a phonon at 350 cm^{-1} is asymmetric indicating a Fano effect. Three features at high frequencies 400-550 cm^{-1} are consistent with phonons shifted upward by ~315 cm^{-1}. These observations are consistent with an order parameter gap 2Delta being near 315 cm^{-1}. Below 2Delta^ectral features appear to be phonon-related but have large oscillator strengths compared to the corresponding infrared-active phonons above T_{c}. The implications of the experimental observations are discussed.

  6. Laser ablation synthesis and properties of epitaxial YBa sub 2 Cu sub 3 O sub 7-. delta. /PrBa sub 2 Cu sub 3 O sub 7-. delta. superconducting superlattices

    SciTech Connect

    Lowndes, D.H.; Norton, D.P.; Zheng, X.Y. ); Zhu, Shen . Dept. of Physics and Astronomy)

    1991-09-01

    Pulsed laser ablation has been used to fabricate epitaxial superlattices in which c-axis-perpendicular YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) layers as thin as a single unit cell are separated by semiconducting PrBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (PBCO) layers. The superlattice {Tc} (R=0) decreases rapidly with increasing PBCO thickness, but then saturates at {Tc}{approximately}19 K, 54 K, 71 K, or 80 K, for structures containing isolated, 1-,2-,3-, or 4-cell-thick YBCO layers, respectively. Recent theoretical analyses suggest that the decrease of {Tc} and broadening of the resistive transition for the thinnest YBCO layers is most likely due either to a crossover from 3D to 2D resistive behavior, or to hole-filling in the YBCO layers caused by electron transfer from the PBCO. We find that the resistance in the superconducting transition region scales with temperature as expected for dissipation by characteristically 2D (vortex) excitations. Departures from the universal'' resistance behavior expected for a 2D Ginzburg-Landau Coulomb gas, as the YBCO thickness is increased or the PBCO thickness is decreased, can be attributed to the onset of phase coupling between the YBCO layers. Thus, the experiments show that YBCO's effective anisotropy can be greatly increased by separating very thin YBCO layers by thicker PBCO layers in superlattice structures. As a results, characteristic 2D dissipation can be observed over a greatly expanded temperature range, relative to both thicker-film and single-crystal YBCO specimens. Experiments also were carried out using two additional isostructural sets of superlattices in which the PBCO layers were replaced by more conductive Y- or Ca-doped PBCO layers, in order to alter any electron transfer from PBCO to YBCO.

  7. Fabrication and Properties of Bulk and Thick Film YTTRIUM(1) BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Superconductors

    NASA Astrophysics Data System (ADS)

    Bailey, Andrew

    Many of the applications envisaged for the new high critical temperature cuprate superconductors require the ability to produce high quality material in layers of 1-100mum thickness which can be used as prepared, or after patterning into discrete forms. Among the possible applications in the foreseeable future are EMI/EMC shielding, pcb interconnects, inductances, stripline, mixers and resonators. Consequently it is important to establish methods of 'thick film' manufacture which provide the versatility necessary for the wide range of uses. During the course of this research, a variety of processing methods have been studied in an attempt to optimize the important film parameters of density, adhesion, strength and good stable superconducting characteristics. Details will be given of substrate-layer interaction for the various substrates that were studied, which included alumina, sapphire, single crystal (100)MgO and yttria stabilised zirconia together with a number of methods of substrate passivation. To date, the most successful substrate for Y_1Ba_2Cu_3O_{7-delta } thick film production has been yttria stabilised zirconia. This thesis will discuss the results of investigations, using yttria stabilised zirconia substrates, which have identified satisfactory means of obtaining superconducting layers with T_{c} = 91.5K and J_{c~ }3000 Acm^{-2} in zero applied magnetic field. At the time of writing, this value of critical current density remains the highest reported value for Y_1Ba_2Cu _3O_{7-delta} thick films. These high quality thick films were then used in a study of conduction mechanisms and the results are interpreted in terms of flux pinning and thermodynamic fluctuation theory. These results highlighted the complex nature of the conduction process in these new ceramics, which is dominated by the weak-link intergranular contacts. Finally, details are given of Josephson characteristics that were observed in variable thickness microbridges patterned into the

  8. Magnetic penetration depth of YBa2Cu3O(7-delta) thin films determined by the power transmission method

    NASA Technical Reports Server (NTRS)

    Heinen, Vernon O.; Miranda, Felix A.; Bhasin, Kul B.

    1992-01-01

    A power transmission measurement technique was used to determine the magnetic penetration depth (lambda) of YBa2Cu3O(7-delta) superconducting thin films on LaAlO3 within the 26.5 to 40.0 GHz frequency range, and at temperatures from 20 to 300 K. Values of lambda ranging from 1100 to 2500 A were obtained at low temperatures. The anisotropy of lambda was determined from measurements of c-axis and a-axis oriented films. An estimate of the intrinsic value of lambda of 90 +/- 30 nm was obtained from the dependence of lambda on film thickness. The advantage of this technique is that it allows lambda to be determined nondestructively.

  9. Magnetic hysteresis of p(+) and He-3(2+) irradiated melt-textured YBa2Cu3O(7-delta)

    NASA Technical Reports Server (NTRS)

    Song, S. N.; Liu, J.; Chen, I. G.; Weinstein, Roy

    1992-01-01

    We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O(7-delta) samples before and after p(+) and He-3(2+) irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper He-3(2+) fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence. After the irradiation, the best fit has been achieved by using an exponential form. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.

  10. The role of interfacial defects in enhancing the critical current density of YBa2Cu3O7-delta coatings

    SciTech Connect

    Foltyn, Stephen R; Wang, Haiyan; Civale, Leonardo; Maiorov, Boris A; Jia, Quanxi

    2009-01-01

    The critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}0{sub 7-{delta}} (YBCO) films can approach 10 MA/cm{sup 2} at 77 K in self field , but only for very thin films. We have shown previously that strong thickness dependence results if J{sub c} is enhanced near the film-substrate interface. In the present work we investigate interfacial enhancement using laser-deposited YBCO films on NdGaO{sub 3} substrates, and find that we can adjust deposition conditions to switch the enhancement on and off. Interestingly, we find that the 'on' state is accompanied by interfacial misfit dislocations, establishing an unambiguous correlation between enhanced J{sub c} and dislocations at the film-substrate interface.

  11. Large-area YBa2Cu3O(7-delta) thin films on sapphire for microwave applications

    NASA Technical Reports Server (NTRS)

    Cole, B. F.; Liang, G.-C.; Newman, N.; Char, K.; Zaharchuk, G.; Martens, J. S.

    1992-01-01

    We have deposited YBa2Cu3O(7-delta) (YBCO) films with low microwave surface resistance (Rs) on 5-cm-diam, oxide-buffered sapphire substrates by planar magnetron sputtering. MgO buffer layers are used on M-plane (1 0 -1 0) sapphire, and R-plane (1 -1 0 2) sapphire is buffered by CeO2. Rs values of 450-620 microhms at 77 K and 10 GHz were measured across an entire 5-cm diam YBCO film on M-plane sapphire. For YBCO on R-plane sapphire, Rs values at 77 K and 10 GHz were 950 microohms for a 5-cm-diam wafer and 700 microohms for 1 x 1 sq cm samples.

  12. Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

    NASA Technical Reports Server (NTRS)

    To, H. Y.; Valco, G. J.; Bhasin, K. B.

    1993-01-01

    YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

  13. Penetration depth lambda(T) of YBa2Cu3O(7-delta) films determined from the kinetic inductance

    NASA Astrophysics Data System (ADS)

    Lee, Juyoung; Lemberger, Thomas R.

    1993-05-01

    We examine the temperature dependence of the magnetic penetration depth lambda(T) of YBa2Cu3O(7-delta), determined from the kinetic inductance of a film patterned into a long meander line. This technique has sufficient sensitivity to study lambda(T) to lower temperatures than have been examined previously. A numerical model which includes both the magnetic and kinetic inductances of the samples extracts lambda(T) from the measured voltage. In reasonable agreement with other measurements, lambda(0) about 2100 A is deduced from fitting lambda(0)-squared/lambda(T)-squared to the function 1 - (T/Tc)-squared for T/Tc greater than 0.4. We find lambda(T)/lambda(0) - 1 is proportional to (T/Tc)-squared for T/Tc between 0.06 and 0.4.

  14. Irreversibility Line, Hall Effect, and Longitudinal Resistivity Measurements on Cobalt-Doped Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Neiman, Regina Lynn

    1995-01-01

    We have developed a procedure for growing high -quality single crystals of YBa_2(Cu _{1-x}Co _{x})_3O _{7-delta}. By high-pressure oxygen annealing, we produced single crystals having transition temperatures, T_{c}, comparable with those of polycrystalline samples of the same cobalt concentration. We have investigated the effect of cobalt on T _{c} and the DC irreversibility line. As seen previously, we found that the dependence of T_{c} on the concentration of cobalt changes at the orthorhombic -to-tetragonal phase transition. We also found that the DC irreversibility line changes functional form at approximately 2.5% to 3% cobalt substitution, where the orthorhombic -to-tetragonal phase transition occurs. We have measured the in-plane Hall effect and the in-plane resistivity of cobalt-doped YBa_2 Cu_3O_{7 -delta} single-crystal samples. The sign-reversal in the Hall effect below T_ {c} disappears at approximately the orthorhombic-to-tetragonal phase transition. The resistivities were converted into conductivities to investigate the field dependence of the Hall effect. The Hall conductivity, sigma_{xy}, is the sum of two terms, C_1/H and C_2H, where C_1 and C_2 are field-independent but temperature-dependent. The temperature dependences of C_1 and C_2 were qualitatively unaffected by cobalt-doping. From our measurements, it appears that the orthorhombic -to-tetragonal phase transition is important in the behavior of cobalt-doped Y?BCO samples. In order to explain the effect of cobalt on YBCO, it seems that more emphasis should be put on understanding what happens when the sample changes phase from orthorhombic to tetragonal.

  15. Electrical Transport Properties of Epitaxial and Granular Oriented Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Thin Films

    NASA Astrophysics Data System (ADS)

    Jones, Edwin Clay

    1992-01-01

    Strong correlations between the Hall coefficient R_{H}, the transition temperature T_{c}, and the critical current density J_{c} were established in a series of epitaxial YBa_2Cu_3O_ {7-delta} thin films as a function of oxygen deficiency delta. Steady increases in R_{H} with delta suggests that dexoygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T_ {c}. In contrast, two well known plateaus occurring at 90K and 60K were observed in T _{c} vs. delta . Others have ascribed these plateaus to either electronic phenomena or oxygen clustering. We find that in the 90K plateau, the critical current density J _{c}(delta ,H = 0) decreased with delta and extrapolates toward zero at the edge of the plateau, while the relative field dependence of J_ {c}(delta,H) is independent of delta. Furthermore, a fluctuation analysis of the resistive transitions indicates a constant upper critical field B_{ c2}(0) = 110T across this plateau. These observations suggest that the oxygen clustering/percolation scenario occurs on the 90K plateau. Moreover, computer simulations showed this oxygen clustering/percolation picture to be a plausible explanation for the occasional observation of a sign reversal of R _{H} near T _{c}. For large oxygen deficiencies (delta > 0.5) and for the granular oriented YBa_2Cu_3O _{7-delta} thin films, rapid decreases in J_{c} with applied field were observed which is reminiscent of the conventional granular alloys. In addition, the self -field critical current densities J_{c} behaved as SNS weak link systems in a Josephson mixed state. In sum, due to the short coherence length xi in these materials, many properties formerly believed to be "intrinsic" in nature are apparently "extrinsic" in nature.

  16. Elucidation of the mechanism in fluorine-free prepared YBa2Cu3O(7-delta) coatings.

    PubMed

    Vermeir, Pieter; Cardinael, Iwein; Schaubroeck, Joseph; Verbeken, Kim; Bäcker, Michael; Lommens, Petra; Knaepen, Werner; D'haen, Jan; De Buysser, Klaartje; Van Driessche, Isabel

    2010-05-17

    In this work, the reaction mechanism used in the preparation of fluorine-free superconducting YBa(2)Cu(3)O(7-delta) (YBCO) was investigated. To determine which precursor interactions are dominant, a comprehensive thermal analysis (thermogravimetric analysis-differential thermal analysis) study was performed. The results suggest that a three step reaction mechanism, with a predominant role for BaCO(3), is responsible for the conversion of the initial state to the superconducting phase. In the presence of CuO, the decarboxylation of BaCO(3) is kinetically favored with the formation of BaCuO(2) as a result. BaCuO(2) reacts with the remaining CuO to form a liquid which ultimately reacts with Y(2)O(3) in a last step to form YBCO. High temperature X-ray diffraction experiments confirm that these results are applicable for thin film synthesis prepared from an aqueous fluorine-free sol-gel precursor.

  17. Studies of iron impurities in YxPr1-xBa2Cu3O7-delta

    NASA Technical Reports Server (NTRS)

    Swartzendruber, L. J.; Bennett, L. H.; Ritter, J.; Rubinstein, M.; Harford, M. Z.

    1990-01-01

    Pr is the only rare earth which, when substituted for Y in YBa2Cu3O7, significantly alters the superconducting transition temperature T(sub c) without changing the crystal structure. For YxPr1-xBa2Cu3O7-delta with delta approx. equal to 0, T(sub c) is reduced rapidly as x is increased, reaching zero for x about 0.5. For x above 0.5 the compound is antiferromagnetic with a Neel temperature that increases with increasing x, rising to above room temperature for x near 1. A similar behavior is observed when the oxygen deficit delta is increased from zero to 1 with x=0. For the case of Pr substitution, the drop in T(sub c) is believed due to magnetic interactions. For the case of varying delta with x=0, the drop can be attributed to a combination of magnetic interactions, band filling, and changes in crystal structure. To study these effects, the Mossbauer effect of 57 Fe atoms substituted for the Cu atoms has been observed as a function of delta, x, and temperature. The observed spectra are all well described by a two quadrupole-split pairs, a central singlet, and a six-line magnetic hyperfine field pattern. For several Pr compositions both delta and temperature were varied, and the results support the hypothesis that a magnetic interaction exists between the Fe in the Cu lattice and the substitutional Pr atoms.

  18. Ni{sub 7-{delta}}SnTe{sub 2}: Modulated crystal structure refinement, electronic structure and anisotropy of electroconductivity

    SciTech Connect

    Isaeva, A.A.; Baranov, A.I.; Doert, Th.; Popovkin, B.A. Kulbachinskii, V.A.; Gurin, P.V.; Kytin, V.G.; Shtanov, V.I.

    2007-01-15

    Single crystals of Ni{sub 7-{delta}}SnTe{sub 2} were grown during re-crystallization of the presynthesized powder in a two zone furnace. The modulated structure was solved and refined in the (3+2)-dimensional superspace group I4/mmm(0-{alpha}0, {alpha}00)0.ss.mm with lattice parameters a=3.759(1) and c=19.410(2)A (measured at 153K) and Z=2. Satellite reflections observed in the diffraction images can be assigned to the incommensurate modulation vectors q{sub 1}=da* and q{sub 2}=db* with d=0.410(1). The composition resulting from X-ray structure refinement is Ni{sub 5.81}SnTe{sub 2}. The structure model has been also developed in the orthorhombic (3+1)-dimensional superspace group Immm({alpha}00)00s assuming twinning according to [110], giving thus the composition Ni{sub 5.79}SnTe{sub 2}. The origin of the modulation can be attributed to a variation of the occupancy of the Ni(3) site in Ni/Te slabs of the structure. Band structure calculations on a commensurate approximant and single crystal electrical resistivity measurements reveal anisotropic metallic conductivity for this compound.

  19. A Investigation of Electrodynamic Properties of High Transition Temperature Superconducting Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Single Crystals.

    NASA Astrophysics Data System (ADS)

    Ling, Dah-Chin

    1995-01-01

    field can be detected at modulation frequency by a lock-in amplifier. We have observed periodic voltage oscillations as a function of the applied dc magnetic field parallel the ab-planes of a rm YBa_2Cu _3O_{7-delta} single crystal with a dc bias current along the c-axis. The modulated voltage versus magnetic field patterns are similar to the magnetic-field interference patterns associated with a Josephson junction or a dc SQUID, strongly suggesting that Josephson junctions may occur naturally in rm YBa_2Cu_3O_{7-delta} single crystals. The observed field periods indicate that the Josephson junctions are probably at the stacking faults along the c-axis within a single crystal sample or in a large unit cell of superlattice structures, such as rm Y_2Ba_4Cu_7O_ {15-delta}.

  20. Demonstration of Y1Ba2Cu3O(7-delta) and complementary metal-oxide-semiconductor device fabrication on the same sapphire substrate

    NASA Technical Reports Server (NTRS)

    Burns, M. J.; De La Houssaye, P. R.; Russell, S. D.; Garcia, G. A.; Clayton, S. R.; Ruby, W. S.; Lee, L. P.

    1993-01-01

    We report the first fabrication of active semiconductor and high-temperature superconducting devices on the same substrate. Test structures of complementary MOS transistors were fabricated on the same sapphire substrate as test structures of Y1Ba2Cu3O(7-delta) flux-flow transistors, and separately, Y1Ba2Cu3O(7-delta) superconducting quantum interference devices utilizing both biepitaxial and step-edge Josephson junctions. Both semiconductor and superconductor devices were operated at 77 K. The cofabrication of devices using these disparate yet complementary electronic technologies on the same substrate opens the door for the fabrication of true semiconductive/superconductive hybrid integrated circuits capable of exploiting the best features of each of these technologies.

  1. Studies of microstructure/critical current density relationships for grain boundaries in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} bicrystals

    SciTech Connect

    Babcock, S.E.; Cai, Xue-Yu; Larbalestier, D.C.; Shin, D.H.; Zhang, Na; Gao, Yufei; Merkle, K.L.; Kaiser, D.L.; Zhang, Hong

    1992-11-01

    Results of coupled electromagnetic and microstructural studies of bicrystalline YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} specimens are described from a microstructural perspective. High-spatial-resolution transmission electron microscopy techniques (imaging and energy dispersive x-ray microanalysis) are used to probe the structure and composition of the grain boundaries. All of the boundaries studied possess microstructural features that are consistent with their specific electromagnetic character.

  2. Infrared Optical Studies of Yttrium BARIUM(2) (COPPER(1-X)M(X))(3) OXYGEN(7-DELTA) (m = Zinc, Nickel) High Transition Temperature Superconductors.

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Tae

    The infrared reflectances R(nu,T) are presented of rm YBa_2(Cu _{1-x}M_{x})_3O _{7-delta} films (M = Zn, Ni) for frequencies 50 cm^{-1 } < nu < 1000 cm^{-1} and temperatures T = 10K, 100K and 300K. The "best fit" conductivities, sigma_1(nu,10K), for both Zn and Ni-doped films show no clear evidence of superconductivity, i.e., the superconducting density of states is very gapless. This degree of gaplessness is consistent with the large penetration depths measured in the same films. It agrees with estimates based on the measured carrier scattering rate 1/tau(10K) and theories of d-wave superconductors. The carrier scattering rate 1/tau(T) increases with dopant concentration x and with T; it does not change rapidly just below T_{C} as in pure rm YBa_2Cu_3O_ {7-delta}. The plasma frequency omega_{P} = 8500cm^ {-1} +/- 500cm^{-1}, independent of dopant concentration and T, agrees with values obtained in pure rm YBa_2Cu _3O_{7-delta} films.

  3. Epitaxial yttria-stabilized zirconia on (1 -1 0 2) sapphire for YBa2Cu3O(7-delta) thin films

    NASA Technical Reports Server (NTRS)

    Wu, X. D.; Muenchausen, R. E.; Nogar, N. S.; Pique, A.; Edwards, R.

    1991-01-01

    Epitaxial yttria-stabilized zirconia (YSZ) films were deposited on (1 -1 0 2) sapphire by pulsed laser deposition. The films are formed in a cubic phase with the a axis normal to the substrate surface. Ion beam channeling measurements show that the YSZ films are highly crystalline with a channeling minimum yield of 8 percent. The epitaxial relationship between the film and substrate is further confirmed by a cross-section TEM study. Epitaxial YBa2Cu3O(7-delta) thin films deposited on YSZ/sapphire have Tc and Jc of up to 89 K and 10 to the 6th A/sq cm at 77 K, respectively.

  4. High Temperature Superconductivity in Praseodymium Doped (0%, 2%, 4%) in Melt-Textured Y(1-x)Pr(x)Ba2Cu3O(7-delta) Systems

    NASA Technical Reports Server (NTRS)

    James, Claudell

    1995-01-01

    A study of the magnetic and structural properties of the alloy Y(1-x)Pr(x)Ba2Cu3O(7-delta) of 0%, 2%, and 4% doping of praseodymium is presented. The resulting oxides of the alloy series are a high-temperature superconductor Y-Ba-Cu-O, which has an orthorhombic superconducting crystal-lattice. Magnetic relaxation studies have been performed on the Y-Pr-Ba-CuO bulk samples for field orientation parallel to the c-axis, using a vibrating sample magnetometer. Relaxation was measured at several temperatures to obtain the irreversible magnetization curves used for the Bean model. Magnetization current densities were derived from the relaxation data. Field and temperature dependence of the logarithmic flux-creep relaxation was measured in critical state. The data indicates that the effective activation energy U(eff) increases with increasing T between 77 K and 86 K. Also, the data shows that U(eff)(T) and superconducting transition temperature, Tc, decreased as the lattice parameters increased with increasing Pr ion concentration, x, for the corresponding Y(1-x)Pr(x)Ba(x)Cu3O(7-delta) oxides. One contribution to Tc decrease in this sampling is suspected to be due to the larger ionic radius of the Pr(3+) ion. The upper critical field (H(sub c2)) was measured in the presence of magnetic field parallel to the c axis. A linear temperature dependence with H(sub c2) was obtained.

  5. T (sub c)-delta relations in YBa2Cu3O(7-delta) thin films: Effects of oxygen pressure during growth

    NASA Astrophysics Data System (ADS)

    Feenstra, R.; Norton, D. P.; Budai, J. D.; Christen, D. K.; Lowndes, D. H.; Matijasevic, V. C.; Eom, C. B.; Geballe, T. H.; Hellman, E. S.; Hartford, E. H.

    1992-04-01

    The (Tc) dependence on oxygen content was measured for YBa2Cu3O(7-delta) films grown with a variety of techniques (solid phase epitaxy, laser ablation, off-axis sputtering, co-evaporation) at oxygen pressures p(O2) ranging from 1.0 atm to 0.1 mTorr. Dissimilar dependences resulted for each film type, with (Tc) either increasing or decreasing for small increments in delta from maximum oxygen occupancy. Varying systematically with p(O2) during growth, the deviations are attributed to competing effects from hole-doping lattice defects (most likely on the Y-site) on the carrier density of the CuO2 planes and basal plane oxygen capacity, respectively, giving rise to overdoping or underdoping after low temperature oxidation in 1.0 atm of oxygen.

  6. Microwave properties of YBa2Cu3O(7-delta) high-transition-temperature superconducting thin films measured by the power transmission method

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.

    1991-01-01

    The microwave response of YBa2Cu3O(7-delta) superconducting thin films deposited on LaAlO3, MgO, YSZ, and LaGaO3 substrates are studied. It is found that the microwave transmission properties are very weakly dependent on temperature in the normal state but change drastically upon transition to the superconducting state. In particular, the transmission decreases and there is a negative phase shift with respect to the phase at room temperature when the sample is cooled through its transition temperature. The magnetic penetration depth for all the films was determined from the surface reactance of the films. The microwave complex conductivity is determined in both the normal and the superconducting state. It is observed that both sigma1 and sigma2 increase in transition to the superconducting state. The surface resistivity is calculated for all the films.

  7. Very Large Scale Integration of Nano-Patterned YBa2Cu3O7-delta Josephson Junctions in a Two-Dimensional Array

    SciTech Connect

    Cybart, Shane A; Anton, Steven; Wu, Stephen; Clarke, John; Dynes, Robert

    2009-09-01

    Very large scale integration of Josephson junctions in a two-dimensional series-parallel array has been achieved by ion irradiating a YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film through slits in a nano-fabricated mask created with electron beam lithography and reactive ion etching. The mask consisted of 15,820 high-aspect ratio (20:1), 35-nm wide slits that restricted the irradiation in the film below to form Josephson junctions. Characterizing each parallel segment k, containing 28 junctions, with a single critical current I{sub ck} we found a standard deviation in I{sub ck} of about 16%.

  8. Dependence of the critical temperature of laser-ablated YBa2Cu3O(7-delta) thin films on LaAlO3 substrate growth technique

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Bhasin, Kul B.; Miranda, Felix A.

    1991-01-01

    Samples of LaAlO3 made by flame fusion and Czochralski method were subjected to the same temperature conditions that they have to undergo during the laser ablation deposition of YBa2Cu3O(7 - delta) thin films. After oxygen annealing at 750 C, the LaAlO3 substrate made by two methods experienced surface roughening. The degree of roughening on the substrate made by Czochralski method was three times greater than that on the substrate made by flame fusion. This excessive surface roughening may be the origin of the experimentally observed lowering of the critical temperature of a film deposited by laser ablation on a LaAlO3 substrate made by Czochralski method with respect to its counterpart deposited on LaAlO3 substrates made by flame fusion.

  9. Doping directed at the oxygen sites in Y1Ba2Cu3O(7-delta) - The effect of sulfur, fluorine, and chlorine

    NASA Technical Reports Server (NTRS)

    Bansal, N. P.; Boyne, D.; Farrell, D. E.

    1988-01-01

    The effect of three dopants directed at the oxygen sites in Y1Ba2Cu3O(7-delta) have been investigated: sulfur, fluorine, and chlorine. Single-phase material has been obtained up to a (nominal) replacement of about 1 percent of the oxygen. Although the lattice parameters are unchanged, all dopants raise Tc (very slightly), sharpen the resistive transition, reduce the normal state resistivity, and very substantially increase the (magnetically determined) fraction of the material that is superconducting. All of these results differ qualitatively from those obtained with dopants directed at other locations in the 123 structure, and it is suggested that small additions of sulfur, fluorine, or chlorine may help to stabilize the ideal 123 stoichiometry.

  10. Magnetization Studies of the Effects of Oxygen Deficiency Delta on the Superconductive Properties of Aligned Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Materials

    NASA Astrophysics Data System (ADS)

    Ossandon, Jorge G.

    Magnetically aligned samples of sintered YBa _2Cu_3O_ {7-delta} were used to test the effects of oxygen-deficiency delta (with 0<=qdelta<=q 0.2) on the superconductive magnetization M, critical current density J_{c}, irreversibility field B_{irr }, upper critical field H_{ rm c2}, coherence length xi , condensation energy F_{c}, London penetration depth lambda and related properties as functions of temperature T and applied magnetic field H | c. In selected cases, studies were also made with H | ab. The open porosity and granularity of the material allowed rapid and homogeneous oxygenation. The oxygen content was monitored in situ by Thermo-Gravimetric Analysis. We found no significant enhancement of intragrain J_{c} with chain -site O-defects. With few exceptions, maximum J _{c} occurred at full oxygenation. This implies that chain-site O-defects are not strong or effective pinning centers over most of the field-temperature regime investigated. Except for T _{c}, which was practically independent of delta within the interval 0<=qdelta<=q 0.11 (so called "T_{c} -plateau"), most properties such as J_{ c}, F_{c}, H_{c2} , B_{irr}(T), lambda and xi were strongly and continuously influenced by the oxygen deficiency. The observed abnormal magnetization ("fishtail" or "bowtie" effect) with H | c was weak at low T but became more pronounced as T and delta increased. No abnormal magnetization was detected with H | ab. As oxygen was removed, B_{irr }(T) and H_{c2}(T) separated and both lines shifted to lower T and lower H. Moreover, B_{irr} was strongly correlated with J _{c} at low temperature. Determination of the thermodynamic critical field H_{ c} yielded condensation energies F _{c}(delta) that suffered a strong reduction with increasing delta. As predicted by a simple, single-site pinning model, a good correlation was found between J _{c}(delta) and the product F_{c}xi _{ab} (where xi_{ab} is the coherence length in the a-b plane). This correlation was corroborated by

  11. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1991-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

  12. Characterizing transport current defects in 1-cm-wide YBa[sub 2]Cu[sub 3]O[sub 7-delta] coated conductors.

    SciTech Connect

    Brown, G. W.; Hawley, M. E.; Peterson, E. J.; Coulter, J. Y.; Dowden, P. C.; Arendt, P. N.; Foltyn, S. R.; Mueller, F. M.

    2001-01-01

    We have used a low temperature magnetic imaging system to determine current pathways in 5 cm long 'good' and 'bad' regions of a 1-cm-wide YBa2Cu3O7-{delta} coated conductor. The good and bad regions were identified with 4 point probe measurements taken at 1 cm intervals along the tape length. The current density map from the good region showed the expected edge peaked structure, similar to that seen in previous work on high quality test samples grown on single crystal substrates. The structure was also consistent with theoretical understanding of thin film superconductors where demagnetizing effects are strong. The maps from the bad region showed that the current was primarily confined to the right half of the sample. The left half carried only a small current that reached saturation quickly. Effectively halving the sample width quantitatively explains the critical current measured in that section. Spatially resolved xray analysis with 1 mm resolution was used to further characterize the bad section and suggested an abnormally large amount of a-axis YBCO present. This may be the result of non-uniform heating leading to a low deposition temperature in that area.

  13. Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

    1990-01-01

    A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies.

  14. Microwave conductivity of laser ablated YBa2Cu3O(7-delta) superconducting films and its relation to microstrip transmission line performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.; Miranda, F. A.; Gordon, W. L.

    1991-01-01

    The discovery of high temperature superconductor oxides has raised the possibility of a new class of millimeter and microwave devices operating at temperatures considerably higher than liquid helium temperatures. Therefore, materials properties such as conductivity, current density, and sheet resistance as a function of temperature and frequency, possible anisotropies, moisture absorption, thermal expansion, and others, have to be well characterized and understood. The millimeter wave response of laser ablated YBa2Cu3O(7-delta)/LaAlO3 thin films was studied as a function of temperature and frequency. In particular, the evaluation of their microwave conductivity was emphasized, since knowledge of this parameter provides a basis for the derivation of other relevant properties of these superconducting oxides, and for using them in the fabrication of actual passive circuits. The microwave conductivity for these films was measured at frequencies from 26.5 to 40.0 GHz, in the temperature range from 20 to 300 K. The values of the conductivity are obtained from the millimeter wave power transmitted through the films, using a two fluid model.

  15. The Case for and against a D-Wave Pairing State in the High Temperature Superconductor Lutetium BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Buan, John Stuart

    1995-01-01

    The nature of the pairing state of the high-temperature superconductor, LuBa_2Cu _3O_{7-delta} , has been investigated. The work was performed on a high-quality single crystal of the material obtained from the University of California, Davis. The study involved two phases, characterization of the crystal quality, which includes x-ray diffraction measurements, specific heat measurements near T_{rm c} and low-field magnetization measurements, and pairing state experiments, including measurements of the low temperature specific heat, the anisotropic specific heat near T _{rm c} and the anisotropic transverse magnetization. The anisotropic specific heat near the transition is defined as follows:{{int limits_sp{rm T_1}{ rm T_2}}rm dT[ C _{p}(H_{b} = 6T)-C_ {p}(H_{a} = 6T)]/T over{intlimits_sp{rm T_1}{rm T_2}}rm dT[ C_{p}(H = 0T)-C_ {p}(H_{a} = 6T)]/T }with subscripts 'a' and 'b' referring to the respective crystallographic axes. The data were taken using a well-established ac calorimetric technique. The results indicate a role for the CuO chains in the superconductivity present in the 123 system. The implications of this fact for the pairing state theories are discussed. The anisotropic transverse magnetic magnetization was also measured. Using a commercial DC SQUID susceptometer and a custom made sample rotation stage, the magnetization was measured at an angle perpendicular to the magnetic field vector, as a function of angle in the basal plane, with the field applied in the a-b plane of the crystal. The results of this experiment when performed on a "d"-wave superconductor have been predicted. The results of this work are examined in the context of the earlier theoretical work.

  16. Ion-Assisted Laser Deposition of Intermediate Layers for Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Thin Film Growth on Polycrystalline and Amorphous Substrates.

    NASA Astrophysics Data System (ADS)

    Reade, Ronald Paul

    The growth of YB_2Cu _3O_{7-delta} (YBCO) high-temperature superconductor thin films has largely been limited to deposition on single-crystal substrates to date. In order to expand the range of potential applications, growth on polycrystalline and amorphous substrates is desirable. In particular, the deposition of YBCO thin films with high critical current densities on polycrystalline metal alloys would allow the manufacture of superconducting tapes. However, it is shown that it is not possible to grow YBCO thin films directly on this type of substrate due to chemical and structural incompatibility. This work investigates the use of a yttria-stabilized zirconia (YSZ) intermediate layer to address this problem. An ion-assisted pulsed-laser deposition process is developed to provide control of orientation during the growth of the YSZ layers. The important properties of YBCO and YSZ are summarized and the status of research on thin film growth of these materials is reviewed. An overview of the pulsed-laser deposition (PLD) technique is presented. The use of ion -assisted deposition techniques to control thin film properties is discussed. Using an ion-assisted PLD process, the growth of (001) YSZ layers with controlled alignment of the in -plane crystal axes is achieved on polycrystalline metal and other polycrystalline and amorphous substrates. Studies of the important process parameters are presented. These layers are demonstrated to be appropriate for the subsequent deposition of c-axis YBCO thin films with alignment of the in-plane axes. A critical temperature of 92K and critical current densities (at 77K) of 6times 10^5 and 5times 10^4 A/cm ^2 without and with a 0.4T magnetic field, have been achieved. These critical current densities are higher than those demonstrated for competing technologies. The applicability of the developed technology is discussed. The control of film orientation using the ion-assisted PLD process is compared to the existing theory and

  17. Electronic structure of the quenched superconductivity materials Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-delta/

    SciTech Connect

    Kang, J.S.; Allen, J.W.; Shen, Z.X.; Ellis, W.P.; Yeh, J.J.; Lee, B.W.; Maple, M.B.; Spicer, W.E.; Lindau, I.

    1988-01-01

    The superconductivity of the Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-delta/ system is quenched as x increases. It has been speculated that Pr has valence 4+, resulting in extra charge in the Cu-O planes, and causing T/sub c/-quenching. To study the Pr electronic state, we have measured valence band resonant photoemission of the Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7- delta/ system for x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0. We find that the Pr valence is close to 3+ for all x and that the extracted Pr 4f spectral weight has a complex lineshape, implying extensive Pr 4f/O 2p hybridization which probably causes the T/sub c/-quenching by disrupting the electronic or magnetic structure of the x = 0 material, perhaps via a Pr-Cu superexchange interaction. 36 refs., 4 figs.

  18. Superconductivity of the Pr-substituted (Nd/sub 1-x/Pr/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7-/delta// system

    SciTech Connect

    Ku, H.C.; Chen, C.C.; Hsu, S.W.

    1988-12-01

    Electrical, magnetic and crystallographic measurements have been carried out for the pseudoquaternary (Nd/sub 1-x/Pr/sub x/)Ba/sub 2/Cu/sub 3/O/sub 7-/delta// system. Orthorhombic phase persists from chi = 0.0 up to chi = 0.7 and transforms into the tetragonal structure only for chi /ge/ 0.8. Superconducting transition temperature T/sub c/ decreases linearly from 92 K for chi = 0.0 to below 10 K for chi = 0.3 and extrapolated to 0 K around chi = 0.35. Magnetic susceptibility indicates that the valence of the Pr ion is close to 4+. Pr/sup 4+/ is a very powerful oxidizing agent and may distort or move oxygen away from the Cu-O chain and/or the /CuO/sub 2/ planes and seriously suppress superconductivity.

  19. Hybridization and Electron Doping in the Highly - Electronic Materials YTTRIUM(1-X) Uranium(x) PALLADIUM(3) and YTTRIUM(1-X) Praseodymium(x) BARIUM(2) COPPER(3) OXYGEN(7-DELTA)

    NASA Astrophysics Data System (ADS)

    Seaman, Christopher Lawrence

    Measurements of electrical resistivity rho(T), magnetic susceptibility chi (T), and specific heat C(T) for the system Y_{1-x}U_{x}Pd _3 are presented. The data are consistent with nearly localized tetravalent U ions leading to "Fermi -level tuning" and competition between single ion Kondo (0 < x <= 0.2) and cooperative spin glass-like (0.3 <= x <= 0.5) behavior. The Kondo behavior is unusual and well described by the two-channel quadrupolar Kondo effect which exhibits non-Fermi liquid behavior. At low temperatures T<< T_{K }, where T_{K } is the Kondo temperature, the electrical resistivity varies nearly linearly with temperature rho(T)/rho(0)~1-T/(aT_ {K}), and the electronic specific heat diverges logarithmically Delta C/T ~{-(1}/T_{K})lnT with a finite residual T = 0 entropy S(0) ~ (R/2)ln2. This appears to be the first example of the quadrupolar Kondo effect and two-channel behavior in a dilute alloy with concomitant non-Fermi liquid behavior. The magnetic penetration depth of the high-T _{c} superconducting system Y_{1-x}Pr_{x }Ba_2Cu_3O_{6.97} has been measured for 0.05 <= x <= 0.4 using the technique of transverse -field muon-spin relaxation. The temperature dependence is similar to that of the related compounds rm YBa_2Cu_3O_{7-delta} with varying oxygen content. The zero-temperature relaxation rate sigma(0) and T _{c} both decrease monotonically with x, in a manner similar to that of YBa_2Cu_3O_{7-delta} with increasing delta. This observation is consistent with the interpretation that T_{c} is largely suppressed by means of the annihilation of holes in the conducting CuO_2 planes by the Pr ions. A simple explanation is that Pr is nearly tetravalent in this system. The influence of magnetic pair breaking, finite mean free path, and correlation with results for other high-T_{c} superconductors are discussed. Resistive superconducting transitions have been measured for single crystals of Y_ {1-x}Pr_{x}Ba_2Cu_3O _{7-delta} in applied magnetic fields as high

  20. Ion-assisted laser deposition of intermediate layers for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film growth on polycrystalline and amorphous substrates

    SciTech Connect

    Reade, R.P.

    1993-11-01

    The growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) high-temperature superconductor thin films has largely been limited to deposition on single-crystal substrates to date. In order to expand the range of potential applications, growth on polycrystalline and amorphous substrates is desirable. In particular, the deposition of YBCO thin films with high critical current densities on polycrystalline metal alloys would allow the manufacture of superconducting tapes. However, it is shown that it is not possible to grow YBCO thin films directly on this type of substrate due to chemical and structural incompatibility. This work investigates the use of a yttria-stabilized zirconia (YSZ) intermediate layer to address this problem. An ion-assisted pulsed-laser deposition process is developed to provide control of orientation during the growth of the YSZ layers. The important properties of YBCO and YSZ are summarized and the status of research on thin film growth of these materials is reviewed. An overview of the pulsed-laser deposition (PLD) technique is presented. The use of ion-assisted deposition techniques to control thin film properties is discussed.

  1. Formation of Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or < x < or = 0.7) Superconductors from an Undercooled Melt Via Aero-Acoustic Levitation

    NASA Technical Reports Server (NTRS)

    Gustafson, D. E.; Hofmeister, W. H.; Bayuzick, R. J.

    2001-01-01

    Melt processing of RE123 superconductors has gained importance in recent years. While the first high temperature superconductors (HTSCs) were made using traditional ceramic press and sinter technology, recent fabrication efforts have employed alternate processing techniques including laser ablation and ion beam assisted deposition for thin film fabrication of tapes and wires and melt growth for bulk materials. To optimize these techniques and identify other potential processing strategies, phase relation studies on HTSCs have been conducted on a wide variety of superconducting compounds using numerous processing strategies. This data has enhanced the understanding of these complex systems and allowed more accurate modeling of phase interactions. All of this research has proved useful in identifying processing capabilities for HTSCs but has failed to achieve a breakthrough for wide spread application of these materials. This study examines the role of full to partial substitution of Nd in the Y123 structure under rapid solidification conditions. Aero-acoustic levitation (AAL) was used to levitate and undercool RE123 in pure oxygen binary alloys with RE = Nd an Y along a range of compositions corresponding to Y(x)Nd(1-x) Ba2Cu3O(7-delta) (0 = or < x < or = 0.7) which were melted by a CO2 laser. Higher Y content spheres could not be melted in the AAL and were excluded from this report. Solidification structures were examined using scanning electron microscopy, electron dispersive spectroscopy, and powder x-ray diffraction to characterize microstructures and identify phases.

  2. Several Microstrip-Based Conductor/Thin Film Ferroelectric Phase Shifter Designs Using (YBa2Cu3O(7 - Delta), Au)/SrTiO3/LaAlO3 Structures

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Romanofsky, R. R.; Miranda, F. A.

    1998-01-01

    We have designed, fabricated, and tested several novel microstrip-base YBa2Cu3O7-delta/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3ALO3 (Au/STO/LAO) phase shifters. The first design consists of eight coupled microstrip phase shifters (CMPS) in series. This design using YBCO achieved a relative insertion phase shift (Delta f) of 484 degrees with a figure of merit of 80 degrees/dB at Vdc = 375 V, 16 GHz, and 40 K. A Delta f of 290 degrees was observed while maintaining the insertion loss below 4.5 dB. At 77 K, a Delta of 420 degrees was obtained for this phase shifter at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. A second compact design, consisting of an Au meander line and a CMPS section was also tested. Of the two samples tested, the best showed a figure of merit of 43 degrees/dB with Delta f = 290 degrees and 6.8 dB loss, at 40 K, 10 GHz and 400 V. Experimental and modeling results on these circuits will be discussed in the context of potential applications.

  3. Synthesis, crystal chemistry and physical properties of the Ruddlesden-Popper phases Sr{sub 3}Fe{sub 2-x}Ni{sub x}O{sub 7-{delta}} (0=

    SciTech Connect

    Mogni, Liliana; Prado, Fernando . E-mail: fprado@cab.cnea.gov.ar; Ascolani, Hugo; Abbate, Miguel; Moreno, Mario S.; Manthiram, Arumugam; Caneiro, Alberto

    2005-05-15

    The crystal chemistry, electronic structure, and electrical and magnetic properties of the novel perovskite-related nickel oxides Sr{sub 3}Fe{sub 2-x}Ni{sub x}O{sub 7-{delta}} with 0==0.3. The electrical resistivity decreases with increasing Ni content as the p-p band gap tend to close due to the reduction of the T{sub {sigma}} value. Negative magnetoresistance ({approx}-24% for x=0.6 and -7% for x=1.0 at 20K and 9T) was observed for the Ni containing samples.

  4. Raman Studies of Yttrium BARIUM(2) (COPPER(1-X) NICKEL(X)(3) OXYGEN(7-DELTA) and (yttrium BARIUM(2) COPPER(3) OXYGEN(7))(M)(PRASEODYMIUM BARIUM(2) COPPER(3) OXYGEN(7))(N) Superlattices

    NASA Astrophysics Data System (ADS)

    Ham, Kyungmin

    Raman measurements on YBa_2(Cu _{1-x}Ni_{x})O_ {7-delta} and (YBa _2Cu_3O_7)_{m}(PrBa _2Cu_3O_7)_{n} superlattices have been performed. The unusual softening of the B_{1g} -like phonon of YBa_2Cu_3O _7 is studied as a function of T _{c} by substituting up to 6 atomic percent nickel for Cu. The abrupt onset and small temperature range over which the softening occurs in undoped YBa_2Cu_3O_7 are modified upon doping with the softening occurring well above T_{c} and continuing smoothly to 10K when T_{ c} is reduced to 71K. The phonon linewidth in the doped films shows no anomalies, regardless of Ni concentration. In contrast, the self-energies of the A_{g} modes associated with the plane copper (Cu(2)) and apical oxygen (O4) atoms reveal normal thermal behavior for all films. We conclude that an additional mechanism, besides strong coupling of phonons to superconducting electrons, contributes to the B_{1g} phonon anomalies in the Ni-doped samples. The Raman spectra from artificial structures of c- and a-axis oriented superlattices (YBa _2Cu_3O_7)_{m}(PrBa _2Cu_3O_7)_{n} with 1 < m, n < 15 are, in general, similar to those obtained from samples of the individual constituents. The observed Raman active vibrations of the superlattice are readily identified through comparison with spectra from the bulk components. The dependence of the phonon frequencies on m and n shows a significant softening of the vibration associated with the apical oxygen atom (O(4)) in PrBa_2Cu_3O _7 with reductions in the Pr-layer thickness (d_{Pr}). The modifications to the self energy of this phonon for both superlattice orientations only occur when d_{Pr} < 25A and therefore establish the primary importance of the Pr-layer thickness in affecting the observed softening. These phonon renormalizations are consistent with charge redistribution in the immediate vicinity (~10A) of the interface arising from the unequal Fermi energies associated with the alternating layers. The degree of inter

  5. High-pressure behavior and equations of state of the cobaltates YBaCo{sub 4}O{sub 7}, YBaCo{sub 4}O{sub 7+{delta}}, YBaCoZn{sub 3}O{sub 7} and BaCoO{sub 3-x}

    SciTech Connect

    Juarez-Arellano, Erick A.; Avdeev, Maxim; Yakovlev, Sergey; Lopez-de-la-Torre, Laura; Bayarjargal, Lkhamsuren; Winkler, Bjoern; Friedrich, Alexandra; Kharton, Vladislav V.

    2012-12-15

    The compressibilities of the cobaltates YBaCo{sub 4}O{sub 7}, YBaCo{sub 4}O{sub 7+{delta}}, YBaCoZn{sub 3}O{sub 7} and BaCoO{sub 3-x} were investigated by in situ powder X-ray diffraction experiments up to 30 GPa using diamond anvil cells. Pressure-induced phase transitions and amorphization were observed in all the samples. The onset of the pressure-induced phase transition and the onset of the amorphization were observed at {approx}11.7 and 12.2 GPa (YBaCo{sub 4}O{sub 7}), at {approx}14.2 and 16.1 GPa (YBaCo{sub 4}O{sub 7+{delta}}), and at {approx}16.7 and 18.7 GPa (YBaCoZn{sub 3}O{sub 7}), respectively. An attempt to laser anneal at high-pressure failed as it led to a decomposition of the YBaCo{sub 4}O{sub 7} phase into a mixture of phases. Fits of second- and third-order Birch-Murnaghan equations-of-state to the p-V data result in B{sub 0}=109(3) GPa for YBaCo{sub 4}O{sub 7}; B{sub 0}=186(4) GPa and B Prime =1.5 for YBaCo{sub 4}O{sub 7+{delta}}; and B{sub 0}=117(1) GPa for YBaCoZn{sub 3}O{sub 7}. The high-pressure behavior of the studied compounds was compared with isostructural compounds and it is shown that the oxygen-content has a very large effect on the high-pressure behavior of this class of materials. Highlights: Black-Right-Pointing-Pointer Compressibilities were investigated by in situ DAC powder X-ray diffraction experiments. Black-Right-Pointing-Pointer Pressure-induced phase transitions were observed in all the samples. Black-Right-Pointing-Pointer High-pressure phases were very sensitive to small amounts of stresses and strains. Black-Right-Pointing-Pointer Due to the metastability of the compounds, laser annealing leads to decomposition. Black-Right-Pointing-Pointer Oxygen-content has a very large effect on the high pressure behavior in these materials.

  6. Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, and Nd): Three new Pt-containing [A{sub 2}{sup '}O{sub 1+{delta}}] [A{sub n}B{sub n-1}O{sub 3n}]-type hexagonal perovskites

    SciTech Connect

    Ebbinghaus, Stefan G. Erztoument, Chasanoglou; Marozau, Ivan

    2007-12-15

    Polycrystalline samples of Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, Nd) were prepared by conventional solid state synthesis. The three compounds are new examples for n=2 members of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family of hexagonal perovskites containing platinum as the B-type cation. XRD Rietveld refinements show the platinates to crystallize in space group R3-bar and, in the case of Pr and Nd, revealed a complete ordering of Ln/Sr on the two distinct A-type positions, while for La a partial disorder was observed. By XANES investigations at the Pt-L{sub III} threshold the oxidation state +4 for platinum was found. Thermogravimetry revealed a small oxygen excess for Ln=La and Pr ({delta}=0.13 and 0.07), pointing to the presence of peroxide ions as already observed for isostructural Ru- and Ir-based compounds. UV-Vis measurements were done for the yellow lanthanum and the green neodymium compound. They revealed two optical band gaps of 2.52 and 3.05 eV, respectively. Magnetic measurements showed La{sub 2}Sr{sub 2}PtO{sub 7+{delta}} to be diamagnetic as expected for Pt{sup 4+} with low-spin (t{sub 2g}{sup 6}) configuration. For Ln=Pr and Nd the observed strong paramagnetism can be explained solely by the magnetic moments of the rare earths. - Graphical abstract: Hexagonal perovskites of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family have so far only been known for the transition metals Mn, Nb, Ru, and Ir. In this paper, three new n=2 examples containing platinum as B-type cation are presented. The structure and physical properties of the three title compounds were investigated by XRD Rietveld refinements, thermogravimetry, X-ray absorption spectroscopy, magnetic measurements and optical spectroscopy.

  7. Contrasting Effects of Ca{sup 2+} and Ho{sup 3+} Substitutions on Superconductivity and Excess conductivity of (Ho{sub 1-x}Ca{sub x})(Ba{sub 2-y}Ho{sub y})Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Maulud, M. F.; Hamidi, Z. S.; Yusof, A. A.; Yusof, M. I. M.; Yahya, A. K.

    2010-07-07

    Effects of Ho{sup 3+} and Ca{sup 2+} substitutions in (Ho{sub 1-x}Ca{sub x})(Ba{sub 2-y}Ho{sub y})Cu{sub 3}O{sub 7-{delta}}ceramics on normal and superconducting state behaviour were investigated. Electrical resistivity measurements showed increasing Ho{sup 3+} substitution at Ba{sup 2+} site (x = 0, 0.4, y = 0-0.4) caused normal state resistivity to change from metal-like to semimetal/semiconductor-like behaviour and suppressed T{sub c} from 89 K (y = 0) to 72 K (y = 0.4) while substitution of Ca{sup 2+} for Ho{sup 3+}((x = 0.2) 0.4, (y 0.4)) revives metallic behaviour of the normal state with increasing x. Excess conductivity analysis based on Asmalazov-Larkin theory showed 2D to 3D transition for all superconducting samples but with contrasting effects of the substitutions on AL{sub 2D} and AL{sub 3D} constants. The resistivity and excess conductivity results indicate effective hole filling Ho{sup 3+} and hole doping by by Ca{sup 2+} substitutions.

  8. Nanoparticulate Flux Pinning Centers for YBa2Cu3O7-delta Films (Postprint)

    DTIC Science & Technology

    2012-02-01

    compares recent efforts by the U.S. Air Force Research Laboratory to incorporate insulating nanoparticles into the YBCO superconducting thin films...to incorporate insulating nanoparticles into the YBCO superconducting thin films by pulsed laser deposition. Index Terms—Flux pinning, high-temperature...superconductors (HTS), rare earth doping, YBCO . I. INTRODUCTION THE pinning properties of ( YBCO ) makethis superconductor desirable for use in

  9. Anomalous noise in the pseudogap regime of YBa2Cu3O(7-delta).

    PubMed

    Caplan, D S; Orlyanchik, V; Weissman, M B; Van Harlingen, D J; Fradkin, E H; Hinton, M J; Lemberger, T R

    2010-04-30

    An unusual noise component is found near and below about 250 K in the normal state of underdoped YBCO and Ca-YBCO films. This noise regime, unlike the more typical noise above 250 K, has features expected for a symmetry-breaking collective electronic state. These include large individual fluctuators, a magnetic sensitivity, and aging effects. A possible interpretation in terms of fluctuating charge nematic order is presented.

  10. Diffusion synthesis of textured YBa2Cu3O(7-delta) ceramic

    NASA Astrophysics Data System (ADS)

    Kalanda, N. A.; Shambalev, V. N.; Pan'kov, V. V.

    1991-07-01

    A method is described whereby a textured high-temperature superconductor ceramic of the system Y-Ba-Cu-O is synthesized by the diffusion method using various mixtures of Y-Ba-Cu-O and Ba-Cu-O systems. The basal plane of the perovskite structure is shown to be formed in the direction of the diffusion flow. Critical current densities in excess of 1000 A/sq cm at 77 K have been demonstrated for the best specimens.

  11. Dynamic Field and Current Distributions in Multifilamentary YBa2Cu3O7-delta Thin Films with Magnetic Coupling (POSTPRINT)

    DTIC Science & Technology

    2010-03-01

    SUBJECT TERMS superconductivity, critical current density, magnetic field, YBa2Cu3O7-z or YBCO , time-resolved magneto-optical imaging, multifilament...field distributions in YBa2Cu3O7− YBCO thin films. We present finite-element model FEM simulations that allow a direct comparison of the...both a test of the model itself as well as new informa- tion on the complex behavior of YBCO thin films observed previously.7 We find for filamentary

  12. Chemical solution approaches to YBa2Cu3O7_delta-Au nanocomposite superconducting thin films.

    PubMed

    Martínez-Julián, F; Ricart, S; Pomar, A; Col, M; Abellán, P; Sandiumenge, F; Casanove, M J; Obradors, X; Puig, T; Pastoriza-Santos, I; Liz-Marzán, L M

    2011-04-01

    We explore the feasibility of preparing YBa2CU3O7-Au (YBCO-Au) nanocomposite thin films by chemical solution deposition (CSD). Two approaches were used: (i) A standard in-situ methodology where Au metallorganic salts are added into the precursor solution of YBCO trifluoroacetate (TFA) salts and (ii) a novel approach where stable colloidal solutions of preformed gold nanoparticles (5-15 nm) were homogeneously mixed with TFA-YBCO solutions. A detailed analysis of the microstructure of the films showed that in both cases, there is a strong tendency of gold nanoparticles to migrate to the film surface. However the kinetics of this migration evidences important differences and in the case of preformed nanoparticles their size remains unchanged (a few nanometers) whereas for the in-situ nanocomposites gold ripening leads to large particles (hundreds of nanometers). The grown YBCO-Au films showed good superconducting characteristics (J(c) 2 MA/cm2 at 77 K) but the absence of Au inclusions inside the YBCO matrix explains the fact that no enhancement of vortex pinning was observed.

  13. Growth and properties of ultrathin YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} layers

    SciTech Connect

    Norton, D.P.; Lowndes, D.H.

    1992-09-01

    We report on the superconducting properties of ultrathin c-axis-oriented YBa{sub 2}CU{sub 3}0{sub 7-8} (YBCO) layers grown by pulsed-laser deposition. For single YBCO layers embedded in a PrBa{sub 2}Cu{sub 3}O{sub 7-8} matrix, with a YBCO layer thickness as small as one unit cell, there is evidence of a superconducting transition. We also find that the superconducting properties of ultrathin YBCO layers can be significantly enhanced by use of more conductive buffer and cap layers. In particular, Pr{sub 0.5}Ca{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-8}/YBCO/Pr{sub 0.5}Ca{sub 0.5}Ba{sub 2}Cu{sub 3}O{sub 7-8} ultrathin structures have transport properties superior to PrBa{sub 2}Cu{sub 3}O{sub 7-8}/YBCO/PrBa{sub 2}Cu{sub 3}O{sub 7-8} including an increase in {Tc} and a narrower superconducting transition.

  14. The Effect of Strain on Grains and Grain Boundaries in YBa2Cu3O7-Delta Coated Conductors (Postprint)

    DTIC Science & Technology

    2009-12-09

    sample had a 2.5◦ GB isolated with the FIB and one had a 4◦ GB. The 200 nm thick YBCO thin films were deposited by pulsed-laser deposition on 4 mm × 12...transport current critical current density (Jc) of YBa2Cu3O7−δ ( YBCO ) coated conductors that are produced with metal–organic deposition (MOD) was...boundaries from the two kinds of YBCO samples can be expressed by the same function, however with a greater effective tensile strain at the grain

  15. Effects of High Energy Electron Irradiation on a Yttrium Barium(2) Copper(3) Oxygen(7-delta) High Temperature Superconductor

    DTIC Science & Technology

    1991-09-01

    must be overcome however,is the relatively low current densities measured in bulk superconducting samples. Towards this goal, it is theorized that by...superconductor to its normal state. The value of that current which produces vortices sufficiently large enough to destroy the superconducting state is...Texas Center for Superconductivity at the University of Houston Houston, Texas 77204-5932 Defect Size Dependence of Critical Current Density

  16. Y1Ba2Cu3O(7-delta) thin film dc SQUIDs (superconducting quantum interference device)

    NASA Astrophysics Data System (ADS)

    Racah, Daniel

    1991-03-01

    Direct current superconducting quantum interferometers (SQUIDs) based on HTSC thin films have been measured and characterized. The thin films used were of different quality: (1) Granular films on Sapphire substrates, prepared either by e-gun evaporation, by laser ablation or by MOCVD (metal oxide chemical vapor deposition), (2) Epitaxial films on MgO substrates. Modulations of the voltage on the SQUIDs as a function of the applied flux have been observed in a wide range of temperatures. The nature of the modulation was found to be strongly dependent on the morphology of the film and on its critical current. The SQUIDs based on granular films were relatively noisy, hysteretic and with a complicated V-phi shape. Those devices based on low quality (lowIc) granular films could be measured only at low temperatures (much lower than 77 K). While those of higher quality (granular films with high Ic) could be measured near to the superconductive transition. The SQUID based on high quality epitaxial film was measured near Tc and showed an anomalous, time dependent behavior.

  17. Minute Doping with Deleterious Rare Earths in YBa2Cu3O7-delta Films for Flux Pinning Enhancements (Postprint)

    DTIC Science & Technology

    2012-02-01

    Journal article published Applied Physics Letters, Vol. 89 , 2006. © 2006 American Institute of Physics. The U.S. Government is joint author of this...NUMBER (Include Area Code) N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39-18 APPLIED PHYSICS LETTERS 89 , 012503 2006...in quantities that other REs enhance performance, aElectronic mail: paul.barnes@wpafb.af.mil 0003-6951/2006/ 89 1/012503/3/$23.00 89 , 01250

  18. Flux Pinning in YBa2Cu3O7-delta Thin Film Samples Linked to Stacking Fault Density (Postprint)

    DTIC Science & Technology

    2008-10-01

    Yoon, H. Wang, T.J. Haugan, F.J. Baca, N.A. Pierce, and P.N. Barnes Power Generation Branch Power Division OCTOBER 2008...ADDRESS(ES) 8. PERFORMING ORGANIZATION Texas A&M University Power Generation Branch (AFRL/RZPG) Power Division Air Force Research Laboratory

  19. Anisotropy of the Transport Properties in Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) (110) Thin Films

    NASA Astrophysics Data System (ADS)

    Wu, Judy Zhihong

    The anisotropy of the transport properties was studied systematically on high-quality epitaxial YBCO (110) thin-films obtained by both dc magnetron-sputtering and pulsed laser-ablation on single crystal (110) SrTiO _3 substrates. These films have in-plane alignment of the c-axis of YBCO, which is essential to the transport study of the anisotropy between the ab-plane and the c-axis. Along the c-axis, rho shows a semiconductor-like upturn as T decreases and a metallic T-linear behavior along the Cu-O plane. This confirms the correlation between the semiconductor-like rho along the c-axis and slight oxygen -deficiency in YBCO. As point-defects are introduced into the thin-film by the 200 keV proton-irradiation, the rho-anisotropy dramatically changes. Along the Cu-O planes, these defects contribute only a residual rho as in normal metals. Along the c-axis, rho is significantly reduced. A "phase transition" from semiconductor-like to metal-like is completed at a low proton dose of 6times10 ^{14} ions/cm^2 , where little effect is observed on T_ {c} and rho_{ab }. This suggests that the unusual normal-state transport properties are irrelevant to the mechanism of HTS. In the superconducting state, the J_ {c,trans} has been measured as functions of T, H, and the direction of H. The T-dependence along the Cu-O plane fits the vortex-glass model while along the c-axis, it fits the Josephson tunnel-junction model. This observation implies that the extrinsic weak-link effect determines J_{c,trans} along the Cu-O plane while the intrinsic tunnelling of the charge carriers limits J_{c,trans } along the c-axis. Similar measurements have also been conducted on YBCO a-, c-, and (113)-oriented thin films. Intrinsic pinning is the strongest pinning effect in YBCO despite the orientation of the film. J _{c}-anisotropy in different field directions is due to the anisotropy of the pinning-effect. The surface pinning-effect is observed (for the first time) on YBCO. It becomes visible only at high T's, which is explained as the result of extremely short xi of YBCO.

  20. Enhancement of Electrical Properties by Tailoring Nanoparticles in Holmium-doped YBa2Cu3O7-Delta Superconductors

    DTIC Science & Technology

    2008-01-01

    Nanoparticles in Holmium -doped YBa2Cu3O7-d Superconductors 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER...by ANSI Std Z39-18 2008 NRL REVIEW 185 NANOSCIENCE TECHNOLOGY Enhancement of Electrical Properties by Tailoring Nanoparticles in Holmium -doped...nanoparticles in the size range of 10 to 100 nm in an HTS coating of composition YBa2Cu3O7 (YBCO) doped with holmium (Ho:Y ratio 1:1). This particular

  1. Investigation of transverse Peltier effect on top-seeded melt textureYBa2Cu3O7 - delta

    NASA Astrophysics Data System (ADS)

    He, Z. H.; Ma, Z. G.; Li, Q. Y.; Luo, Y. Y.; Zhang, J. X.; Meng, R. L.; Chu, C. W.

    1996-12-01

    The transverse Peltier effect is investigated on the top-seeded melt texture superconductor YBa2Cu3O7-δ (YBCO). By restricting the heat absorbing or evolving on one of the sample's surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the ab plane and the c axis, |Sab-Sc|, is about 35 μV/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C 235-240, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off-diagonal thermoelectric effect is responsible for the anomalously high laser-induced transient transverse voltage on the oriented YBCO superconducting thin films.

  2. Prime Contract Awards Alphabetically by Contractor, by State or Country, and Place. Part 7 (Delta Engineering Services - Electronic Design Engr)

    DTIC Science & Technology

    1990-01-01

    Coe) r1-0 0 u£H a 0 a Ie MOD a 0.00 tooo Clip qwei10 0-0 M ci 0 if U t 000 v (𔃾.4 M’ .4 In 0 M0 .4.410 I’A 40 cl 0 CIA- CN -0 0 ince 3 0 OD o0 O CS...40040 VOco aon vn60 04-4.4-4.4 0444444 0-4N00000000.4 00o vr0.44.4 0* S 4 moo0 44.4.4.4.4 04-.4.4.4.4.4.4 0- 1-.4-44.401000 040 0O44-44 III so W>-00000...00. 0N~-O O- C-f Clb. CO-a cj~ I C, .M MC C,0-an a.) -4 Clip -l V) MC o ini n n S (f 3W I (flm>fo a - 0-4 . 0.4 0f 0 0.4 0N~4 0-4 0-4 0-4 04-4 - le -4

  3. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  4. Tuning Porosity of YBa2Cu3O7-delta Vicinal Films by Insertion of Y2BaCuO5 Nanoparticles (Postprint)

    DTIC Science & Technology

    2012-02-01

    microstructure on Jc. By growing YBa2Cu3O7−δ YBCO films at a small vicinal angle, we have recently obtained a highly porous structure in these films...accompanied with a significantly enhanced Jc. This result raises a challenging question on whether the porosity can be tailored in YBCO films to allow a...higher Jc. In this study, we have explored the insertion of Y2BaCuO5 (211) nanoparticles in vicinal YBCO thick films to alter the strain at the

  5. Effect of Structural Relaxation on the Metal-Insulator Transition in Heavily Underdoped YBa $_2 2 Cu _3 3 O _{7-delta }$ 7 - δ Single Crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Dobrovolskiy, O. V.; Nazyrov, Z. F.; Kotvitskaya, K. A.; Chroneos, A.

    2015-08-01

    We report the results of a study of the effect of structural relaxation on the basal-plane conductivity of heavily underdoped high- YBaCuO single crystals. An increase of the oxygen deficiency in YBaCuO has been found to strengthen localization effects and to lead to the realization of a transition of the metal-insulator type, which always precedes the superconducting transition. In addition, a 5-day room-temperature annealing of the samples has been revealed to result in a notable shift of the metal-insulator transition point toward higher temperatures.

  6. Analysis of Thermodynamic and Transport Properties of La(2-x)M(x) CuO4 and YBa2CuO(7 - delta) Superconductors (Preprint)

    DTIC Science & Technology

    1988-06-01

    the qualitative agreement of the GL thoery with experiment deserves mention. As is done in the GL-theory for a single even-parity order parameter, we...21. ABSTRACT SECURITY CLASSIFICATION EUNCLASSIFIEDIUNLIMITED 19 SAME AS RPT 0] DTIC USERS Unclassified 22a. NAME OF RESPONSIBLE INDIVIDUAL 22b...us to believe, as has been suggested on the basis of high-resolution X-ray scattering experiments , [21] that s- and d-wave coupling may exist in the

  7. Effect of a Compressive Uniaxial Strain on the Critical Current Density of Grain Boundaries in Superconducting YBa2Cu3O7-delta Films (POSTPRINT)

    DTIC Science & Technology

    2010-03-01

    composition by doping the grains [10] or the grain boundaries [11]. One of the most striking results is obtained by use of calcium doping in YBa2Cu3O7 (YBCO... Doping affects both the charge carrier concentra- tion and the strain fields at grain boundaries, which makes it hard to determine to what extent the...laser depo- sition onto single-crystal and bicrystalline SrTiO3 (STO) substrates. The bicrystalline substrates had symmetric [001]-tilt grain boundaries

  8. Electromagnetic Characterization of YBa2Cu3O7-Delta Thin Films with Calcium Doping for Bi-Crystal Grain Boundary Conductivity Enhancement (Postprint)

    DTIC Science & Technology

    2008-02-08

    boundary of a vicinal and donor- doped 5 SrTiO3 bi-crystal results in a depletion zone ∼200 nm wide, with the interface potential at the middle of the...AFRL-RZ-WP-TP-2012-0146 ELECTROMAGNETIC CHARACTERIZATION OF YBa2Cu3O7−δ THIN FILMS WITH CALCIUM DOPING FOR BI-CRYSTAL GRAIN BOUNDARY...WITH CALCIUM DOPING FOR BI-CRYSTAL GRAIN BOUNDARY CONDUCTIVITY ENHANCEMENT (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c

  9. Time Resolved Magneto-Optical Imaging in High Frequency AC Currents of YBa2Cu3O7-delta Thin Films (Postprint)

    DTIC Science & Technology

    2012-02-01

    resolved imaging, we use a Q-switched Nd:YLF diode-pumped solid-state laser which provides 100 -nsec short pulses at 527- nm wavelength. The pulse...dimensions of 10 mm × 5 mm [12]. The YBCO films are about 250- nm thick. The samples exhibit a critical transition temperature (Tc) of ~91 K, as determined by...of the magnetic flux density distribution in YBa2Cu3O7-δ ( YBCO ) thin film samples is studied in small steps of the phase of the applied AC current

  10. Effects of Nanoscale Defects on Critical Current Density of (Y1-xEux)Ba2Cu3O7-delta Thin Films (Postprint)

    DTIC Science & Technology

    2010-02-01

    the high density of pores observed in the unsubstituted YBCO films in this study, ranging from 100 to 200 nm in size, with a number density of 2...spacing of the observed threading dislocations was 40 1012 m2 and 100 nm , respectively. The matching field for this density is well below 1 T...shows the double oxide layers. Normally strong white fringes of Cu–O planes between the Ba–O planes are observed at 1.2 nm spacing for YBCO [19]. Such

  11. Time-Resolved Magneto-Optical Imaging of Y1Ba2Cu3O7-delta Thin Films in High-Frequency AC Current Regime (Postprint)

    DTIC Science & Technology

    2012-02-01

    pumped solid-state laser which provides 100 ns short pulses at 527 nm wavelength. The pulse repetition frequency (PRF) of the laser can be varied...substrate with typical dimensions of 10 mm × 5 mm [14]. The YBCO films are about 250 nm thick. The samples exhibit a critical transition temperature (Tc) of...evolution of the magnetic flux density distribution in YBa2Cu3O7−δ ( YBCO ) thin film samples is studied as a function of the phase of the applied AC current

  12. Metallic Normal State of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}

    SciTech Connect

    Kunchur, Milind N.; Ivlev, B. I.; Christen, D. K.; Phillips, J. M.

    2000-05-29

    Flux flow was studied over an entire temperature range down to T{approx}2% of T{sub c} by using intense pulsed current densities to overcome flux-vortex pinning. The resistivity at high vortex velocities is proportional to B and roughly follows {rho}{approx}{rho}{sub n}B/H{sub c2} , with a prefactor of order unity. Contrary to some speculation, {rho}{sub n} saturates to a finite residual value as T{yields}0 , indicating a metallic ({rho}{yields}finite ) rather than insulating ({rho}{yields}{infinity}) normal state, and the vortex dissipation continues to be conventional as T{yields}0 . (c) 2000 The American Physical Society.

  13. Effect of a Compressive Uniaxial Strain on the Critical Current Density of Grain Boundaries in Superconducting YBa2Cu3O7-delta Films

    DTIC Science & Technology

    2009-07-09

    the chemical composition by doping the grains [10] or the grain boundaries [11]. One of the most striking results is obtained by use of calcium doping ...increase in Jc;GB [12–14]. Doping affects both the charge carrier concentra- tion and the strain fields at grain boundaries, which makes it hard to...deposited by pulsed-laser depo- sition onto single-crystal and bicrystalline SrTiO3 (STO) substrates. The bicrystalline substrates had symmetric [001

  14. Optimization of Minute Doping of Y1-xRExBa2Cu3O7-delta Thin Films with RE = Tb and Nd (Postprint)

    DTIC Science & Technology

    2010-01-01

    currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3 . DATES COVERED...Nd J.N. Reichart 1,2 , E.L. Thomas 3 , T.J. Haugan 2 , X. Song 4 , B. M. Ruter-Schoppman 2 , P.N. Barnes 2 1 Wright State University, Dayton...Ohio 45435, USA 2 Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433-7919, USA 3 University of Dayton Research Institute, Dayton, Ohio

  15. Flux Pinning and Properties of Solid-Solution (Y,Nd)1+xBa2-xCu3O7-delta Superconductors (Preprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0095 FLUX PINNING AND PROPERTIES OF SOLID - SOLUTION (Y,Nd)1+xBa2-xCu3O7-δ SUPERCONDUCTORS (PREPRINT) Timothy J. Haugan...2001 – 01 April 2003 4. TITLE AND SUBTITLE FLUX PINNING AND PROPERTIES OF SOLID - SOLUTION (Y,Nd)1+xBa2-xCu3O7-δ SUPERCONDUCTORS (PREPRINT) 5a...FLUX PINNING and PROPERTIES OF SOLID - SOLUTION (Y,Nd)1+xBa2-xCu3O7- SUPERCONDUCTORS T. J. Haugan, M. E. Fowler, J. C. Tolliver, P. N. Barnes

  16. Electrical and Magnetic Properties of the Percolative Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) - YTTRIUM(2) Barium Copper OXYGEN(5) Systems

    NASA Astrophysics Data System (ADS)

    Sedghi Gamchi, Hassan

    1995-01-01

    The electrical and magnetic behaviour of the mixed two phase, percolative system, YBCO(123)-YBCO(211) has been investigated. The normal-state resistivity of this system is best represented by a variable range hopping (VRH) model in which the electronic states of the system are localized. From this model the localization length, alpha^{-1} and the activation energies involved in the hopping process have been determined. The form of the superconducting resistive transition is shown to depend strongly on the intergranular weak-link structure. The resistivity tails have been interpreted in terms of the phase slip and thermally activated flux creep models with the magnetic field dependence of the activation energies found to follow an inverse power-law relationship. A detailed investigation of the ac magnetic susceptibility of this system has shown that the flux pinning energies were found to decrease rapidly as the Y_ {211} concentration increased. These measurements support the view that the observed pinning is associated with the intergranular weak-link system rather than with the intrinsic crystalline material. Changes in the H-T phase diagram have been established as a function of composition and it is found that the irreversibility line (IL) is consistent with H^{rm q}~ (1-t), while the IL moves to lower temperatures and magnetic fields as the intergranular pinning strengths are decreased. DC field dependent ac susceptibility results have been adequately described by a critical state model in which the critical current density is given by alpha(T)/(H_{rm o} + H_{{dc }})^{rm n}. The functional relationship of the material dependent parameter alpha(T) has been determined. The hysteresis behaviour of chi_{ {ac}} H_ {{dc}} in a cycled dc magnetic field have been measured and the average lower critical field, H_{{clg }} for the superconducting grains has been established and its temperature dependence determined. The internal relationship between the susceptibility components chi^{'} _{{ac}} and chi^{''} _{{ac}} have been investigated theoretically and experimentally. A significant difference exists between the observed and predicted results which has been discussed.

  17. Flux pinning enhancement in melt processed YBa2Cu3O7 - delta through rare-earth ion (Nd, La) substitutions

    NASA Astrophysics Data System (ADS)

    Varanasi, Chakrapani; McGinn, Paul J.; Blackstead, Howard A.; Pulling, David B.

    1995-08-01

    Stoichiometric YBa2Cu3O7-δ (Y123) samples doped with excess Nd2O3 and La2O3 additions were melt processed in air. Because decomposition and reformation of 123 occurs during melt processing, lighter rare-earth ion substitution in 123 takes place. As the lighter rare-earth ion sizes (Nd, La) are comparable to that of Ba2+, in addition to Y ion site substitution, partial substitution into the Ba2+ sites is also anticipated. The Tc and magnetic properties of lighter rare-earth oxide doped samples were analyzed and compared with undoped Y123 to investigate the flux pinning enhancement due to these substitutions. The lighter rare-earth oxide doped, melt processed 123 shows significant improvement in magnetization compared to undoped samples, which is likely due to point defects created by partial substitutions of the lighter rare-earth ions.

  18. Very Large Scale Integration of Nano-Patterned YBa2Cu3O7-delta Josephson Junctions in a Two-Dimensional Array

    DTIC Science & Technology

    2010-03-26

    Array Shane A. Cybart,∗,†,‡ Steven M. Anton,†,‡ Stephen M. Wu,†,‡ John Clarke,†,‡ and Robert C. Dynes†,‡ Department of Physics, University of California...bias currents in the opposite direction, the asymmetry had the opposite sign, consistent with our interpretation. We analyzed our data using the Bardeen ...B 2000, 63, 024511. (42) Bardeen , J.; Stephen, M. J. Phys. Rev 1965, 140, A1197. (43) Welty, R. P.; Martinis, J. M. IEEE Trans. Magn. 1991, 27, 2924

  19. Low-temperature solid-state reaction of in situ growth of YBa2Cu3O7 - delta thin films by resistive evaporation

    NASA Astrophysics Data System (ADS)

    Azoulay, Jacob

    1992-12-01

    Thin films of Y-Ba-Cu-O were in situ prepared with the use of a simple conventional inexpensive vacuum system. No thickness monitor or control system is required. A pulverized mixture of Y, BaF2, and Cu constituents weighed in the atomic proportion was evaporated from resistively heated source onto a MgO substrate. The substrates temperature was then raised to 700 °C after evaporation. Oxygen was injected through a nozzle placed near the substrate surface, thus raising the pressure to about 8 Pa (60 mTorr). The film was kept at this stage for about 15 min, after which it was gradually cooled to room temperature and the pressure raised to atmospheric pressure. The obtained films with no further heat treatment were found to be superconductors with zero resistance at 85 K detected by four-probe dc measurements.

  20. Microwave Conductivity of Laser Ablated YBa2Cu3O7-delta Superconducting Films and Its Relation to Microstrip Transmission Line Performance

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Warner, J. D.; Chorey, C. M.; Ebihara, B. T.; Romanofsky, R. R.; Heinen, V. O.

    1990-01-01

    We report on the values of the microwave conductivity in the normal (sigma(subN)) and superconducting (sigma*=sigma(sub1)-j sigma(sub2)) states of two laser ablated YBa2CU3O7(sigma) thin films at 35 GHz, in the temperature range from 20 to 300 K. The films 0.7 and 0.4 micrometers) were deposited on LaA10(sub3) by laser ablation. The conductivity was obtained from the microwave power transmitted through the films and assuming a two-fluid model. Values of sigma(subN) approximately 2.3 X 10(exp5) S/m at room temperature for both films, and of sigma(sub1) approximately 6.3 X 10(exp5) and 4.6 X 10(exp5) S/m at temperatures around 80 K were obtained for the 0.7 and 0.4 micrometer films respectively. For sigma(sub2) values of 4.9 X 10(exp6) and 5.4 X 10(exp6) S/m were obtained for the 0.7 and 0.4 micrometer films at 80 K. The expected conductor losses and Q-factor of a superconducting ring resonator were calculated using these conductivity values. The theoretical values were then compared with the experimental results obtained for a resonator fabricated from one of these films.

  1. Superconducting Properties of (Mx/YBa2Cu3O7-delta y)N Multilayer Films with Variable Layer Thickness x (Postprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0132 SUPERCONDUCTING PROPERTIES OF (Mx/YBa2Cu3O7-δy)N MULTILAYER FILMS WITH VARIABLE LAYER THICKNESS x (POSTPRINT...April 2007 4. TITLE AND SUBTITLE SUPERCONDUCTING PROPERTIES OF (Mx/YBa2Cu3O7-δy)N MULTILAYER FILMS WITH VARIABLE LAYER THICKNESS x (POSTPRINT) 5a...effort was completed in 2007. Paper has color content. 14. ABSTRACT The superconducting properties of (Mx /YBa2Cu3O7-dy)N multilayer films were

  2. Effect of Ca doping on microstructural and superconducting properties of DyBa2Cu3O7-delta/Caz (0 leq z leq 0.2) ceramics

    NASA Astrophysics Data System (ADS)

    Y Laval, J.; Orlova, T. S.

    2003-10-01

    Using bright-field and energy selective x-ray analysis techniques in transmission electron microscopy, we have studied the effect of Ca doping on the microstructural and superconducting properties in DyBa2Cu3Oy/Caz (z = 0, 0.05, 0.1 and 0.2) ceramics, i.e. for the case when Ca was added in excess to the stoichiometric 123 composition. It was found that in this case approximately half of the added Ca amount entered the 123-lattice. Thus, in the composition with nominal z = 0.1 (0.77 at%) average Ca concentration in the grains was about 0.4 at%. On the basis of measured atomic concentrations and 123 stoichiometry of grains, it was concluded that Ca predominantly substituted Dy in the bulk for all levels of doping (0 leq z leq 0.2), although for z = 0.2 the rate of substitution for Ba also became pronounced. This substitution of Dy3+ by Ca2+ seems to explain the observed decrease in Tc from 92 K in an undoped sample to 74 77 K for compositions with z = 0.1 0.2. Ca segregated in grain boundaries (GBs). The concentration of Ca in most 'clean' (secondary-phase-free) GBs was 1.5 3.5 times higher than in the adjacent grains. Ca segregated in a narrow region (d leq 5 nm) around the GB. In the majority of GBs, Ca substitution for Dy was favoured, although with increasing the doping level from z = 0.1 to z = 0.2 the rate of the substitution for Ba increased. This substitution for Dy most probably explains the obtained dramatic increase of Jc at T leq 0.8 Tc in the Ca-doped samples. Ca segregation in GBs is the most probable reason for the superconductor normal-metal superconductor (SNS) behaviour of the GB network in Ca-doped samples. Ca doping led to a higher proportion of clean GBs, in the sample with z = 0.1, that could be responsible for a slower decrease of Jc with magnetic field in this sample.

  3. Effect of Ca doping on microstructural and superconducting properties of DyBa2Cu3O7-delta/Caz (0 leq z leq 0.2) ceramics

    NASA Astrophysics Data System (ADS)

    Laval, J. Y.; Orlova, T. S.

    2003-10-01

    Using bright-field and energy selective x-ray analysis techniques in transmission electron microscopy, we have studied the effect of Ca doping on the microstructural and superconducting properties in DyBa2Cu3Oy/Caz (z = 0, 0.05, 0.1 and 0.2) ceramics, i.e. for the case when Ca was added in excess to the stoichiometric 123 composition. It was found that in this case approximately half of the added Ca amount entered the 123-lattice. Thus, in the composition with nominal z = 0.1 (0.77 at%) average Ca concentration in the grains was about 0.4 at%. On the basis of measured atomic concentrations and 123 stoichiometry of grains, it was concluded that Ca predominantly substituted Dy in the bulk for all levels of doping (0 leq z leq 0.2), although for z = 0.2 the rate of substitution for Ba also became pronounced. This substitution of Dy3+ by Ca2+ seems to explain the observed decrease in Tc from 92 K in an undoped sample to 74-77 K for compositions with z = 0.1-0.2. Ca segregated in grain boundaries (GBs). The concentration of Ca in most 'clean' (secondary-phase-free) GBs was 1.5-3.5 times higher than in the adjacent grains. Ca segregated in a narrow region (d leq 5 nm) around the GB. In the majority of GBs, Ca substitution for Dy was favoured, although with increasing the doping level from z = 0.1 to z = 0.2 the rate of the substitution for Ba increased. This substitution for Dy most probably explains the obtained dramatic increase of Jc at T leq 0.8 Tc in the Ca-doped samples. Ca segregation in GBs is the most probable reason for the superconductor-normal-metal-superconductor (SNS) behaviour of the GB network in Ca-doped samples. Ca doping led to a higher proportion of clean GBs, in the sample with z = 0.1, that could be responsible for a slower decrease of Jc with magnetic field in this sample.

  4. Flux Pinning and Properties of Solid-Solution (Y,Nd)1+XBa2-x Cu3O7-delta Superconductors Processed in Air and Partial Oxygen Atmospheres (Preprint)

    DTIC Science & Technology

    2004-04-01

    AFRL-PR-WP-TP-2006-204 FLUX PINNING AND PROPERTIES OF SOLID - SOLUTION (Y,Nd)1+XBa2-xCu3O7-δ SUPERCONDUCTORS PROCESSED IN AIR AND PARTIAL...SUBTITLE FLUX PINNING AND PROPERTIES OF SOLID - SOLUTION (Y,Nd)i+),(Ba,_„ Cu3 07_5 SUPERCONDUCTORS PROCESSED IN AIR AND PARTIAL OXYGEN ATMOSPHERES (PREPRINT

  5. Application of energy-dispersive X-ray elemental mapping to probe the homogeneity of sol-gel derived YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and related phases

    SciTech Connect

    Houk, C.S.; Burgoine, G.A.; Page, C.J.

    1995-04-01

    The authors describe results obtained using energy dispersive X-ray (EDX) elemental mapping to probe the homogeneity of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. Sol-gel synthesis and conventional solid-state synthesis of the ceramic with firing to 950{degrees}C and sol-gel synthesis with firing at 700{degrees}C are the synthetic routes considered. It was found that the low temperature sol-gel method yields high-quality YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} provided the firing stage is of sufficient duration.

  6. Rapid doubling of the critical current of Yba{sub 2}Cu{sub 3}O{sub 7-{delta}} coated conductor for viable high-speed industrial processing.

    SciTech Connect

    Leroux, M.; Kihlstrom, K. J.; Holleis, S.; Rupich, M. W.; Sathyamurthy, S.; Fleshler, S.; Sheng, H. P.; Miller, D. J.; Eley, S.; Civale, L.; Kayani, A.; Niraula, P. M.; Welp, U.; Kwok, W. -K.

    2015-11-09

    We demonstrate that 3.5-MeV oxygen irradiation can markedly enhance the in-field critical current of commercial 2nd generation superconducting tapes with an exposure time of just one second per 0.8 cm2. The speed demonstrated here is now at the level required for an industrial reel-to-reel post-processing. The irradiation is made on production line samples through the protective silver coating and does not require any modification of the growth process. From TEM imaging, we identify small clusters as the main source of increased vortex pinning.

  7. Magnetization and flux pinning in high-Tc cuprates: Irradiated and oxygen deficient materials

    NASA Astrophysics Data System (ADS)

    Thompson, J. R.; Sun, Yang Ren; Ossandon, J. G.; Christen, D. K.; Kerchner, H. R.; Sales, B. C.; Chakoumakos, B. C.; Civale, L.; Marwick, A. C.; Holtzberg, F.

    1992-11-01

    Recent studies of the intragrain current density J and vortex pinning in high Tc superconductors are surveyed. Materials include Y1Ba2Cu3O(7-delta) and Bi2Sr2Ca1Cu2O8 single crystals and aligned polycrystals. To probe the flux pinning, the strength, number, and morphology of defects were modified. Varying the oxygen content (7-delta) in YBa2Cu3O(7-delta) or irradiating the materials with ions, having either light or heavy masses, gives systematic changes in the character of the all-important defects.

  8. Non-Equilibrium Superconductivity and Quasiparticle Dynamics in YBaCuO

    SciTech Connect

    Siders, J.L.W.; Jacobs, R.N.; Siders, C.W.; Trugman, S.A.; Taylor, A.J.

    1999-05-21

    The authors use optical pump, coherent terahertz probe spectroscopy to transiently excite nonequilibrium populations of quasiparticles in YBa{sub 2}Cu{sub 3}O{sub 7.{delta}} and monitor, with picosecond resolution, the superfluid and quasiparticle dynamics.

  9. Seed crystals with improved properties for melt processing superconductors for practical applications

    DOEpatents

    Veal, Boyd W.; Paulikas, Arvydas; Balachandran, Uthamalingam; Zhong, Wei

    1997-01-01

    A method of fabricating bulk superconducting material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta. comprising heating compressed powder oxides and/or carbonates of R and Ba and Cu present in mole ratios to form RBa.sub.2 Cu.sub.3 O.sub.7-.delta. in physical contact with an oxide single crystal seed to a temperature sufficient to form a liquid phase in the RBa.sub.2 Cu.sub.3 O.sub.7-.delta. while maintaining the single crystal seed solid to grow the superconducting material and thereafter cooling to provide a material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta.. R is a rare earth or Y or La and the single crystal seed has a lattice mismatch with RBa.sub.2 Cu.sub.3 O.sub.7-.delta. of less than about 2% at the growth temperature. The starting material may be such that the final product contains a minor amount of R.sub.2 BaCuO.sub.5.

  10. Superconductivity and magnetism in rapidly solidified perovskites

    SciTech Connect

    O'Handley, R.C.; Kalonji, G.

    1991-01-01

    The report is divided into six parts, reflecting major thrusts of our work since 1987. The six areas are: molecular orbital theory of high {Tc} superconductivity; rapid solidification processing of oxide superconductors; time dependent magnetic and superconducting properties of these inhomogeneous materials; excess Gd in Gd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} perovskites; rapid solidification and directional annealing to achieve high Jc; and Mossbauer studies of T = Fe, Co and Ni site selection in YBa{sub 2}(CuT){sub 3}O{sub 7-{delta}} and GdBa{sub 2}(CuT){sub 3}O{sub 7-{delta}}.

  11. Superconductivity and magnetism in rapidly solidified perovskites. Final report, September 1, 1988--August 31, 1991

    SciTech Connect

    O`Handley, R.C.; Kalonji, G.

    1991-12-31

    The report is divided into six parts, reflecting major thrusts of our work since 1987. The six areas are: molecular orbital theory of high {Tc} superconductivity; rapid solidification processing of oxide superconductors; time dependent magnetic and superconducting properties of these inhomogeneous materials; excess Gd in Gd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} perovskites; rapid solidification and directional annealing to achieve high Jc; and Mossbauer studies of T = Fe, Co and Ni site selection in YBa{sub 2}(CuT){sub 3}O{sub 7-{delta}} and GdBa{sub 2}(CuT){sub 3}O{sub 7-{delta}}.

  12. Insert Coil Test for HEP High Field Magnets Using YBCO Coated Conductor Tapes

    SciTech Connect

    Lombardo, V.; Barzi, E.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2011-06-15

    The final beam cooling stages of a Muon Collider may require DC solenoid magnets with magnetic fields of 30-50 T. In this paper we present progress in insert coil development using commercially available YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} Coated Conductor. Technological aspects covered in the development, including coil geometry, insulation, manufacturing process and testing are summarized and discussed. Test results of double pancake coils operated in liquid nitrogen and liquid helium are presented and compared with the performance of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} tape short samples.

  13. Analysis of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; Gaidis, M. C.

    1996-01-01

    The prospects of a YBa2Cu3O7(delta)(YBCO) hot-electron bolometer (HEB) mixer for a THz heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate.

  14. Cuprate-titanate superconductor and method for making

    DOEpatents

    Toreki, R.; Poeppelmeier, K.; Dabrowski, B.

    1995-05-23

    A new copper oxide superconductor of the formula Ln{sub 1{minus}x}M{sub x}Sr{sub 2}Cu{sub 3{minus}y}Ti{sub y}O{sub 7+{delta}} is disclosed, and exhibits a {Tc} of 60 K with deviations from linear metallic behavior as high as 130 K. 2 Figs.

  15. Cuprate-titanate superconductor and method for making

    DOEpatents

    Toreki, Robert; Poeppelmeier, Kenneth; Dabrowski, Bogdan

    1995-01-01

    A new copper oxide superconductor of the formula Ln.sub.1-x M.sub.x Sr.sub.2 Cu.sub.3-y Ti.sub.y O.sub.7+.delta. is disclosed, and exhibits a Tc of 60.degree. K. with deviations from linear metallic behavior as high as 130.degree. K.

  16. Virial coefficients of neon, argon, and krypton at temperatures up to 3000/sup 0/K

    SciTech Connect

    Sevast'yanov, R.M.; Chernyavskaya, R.A.

    1987-12-01

    The second and third virial coefficients are calculated for a (12-7, delta) pair model potential. With their help the fourth virial coefficient is determined from the experimental pressure, density, and temperature data from the Amsterdam laboratory. The limits of applicability of the equation of state obtained are indicated.

  17. Phenotype of HIV-1 lacking a functional nuclear localization signal in matrix protein of gag and Vpr is comparable to wild-type HIV-1 in primary macrophages.

    PubMed

    Kootstra, N A; Schuitemaker, H

    1999-01-20

    Human immunodeficiency virus type 1 (HIV-1) is considered to infect nondividing cells because nuclear localization signals (NLS) in matrix (MA, p17(Gag)) and Vpr allow active nuclear transport of the preintegration complex. Previous studies demonstrated that HIV-1 reverse transcription is successful only in cells with proliferative potential, thus restricting HIV-1 replication to cycling cells. To sort out this apparent discrepancy we compared the phenotype of a chimeric HIV-1 variant lacking a functional Vpr and MA-NLS (R7. deltaVpr.deltaNLS), and previously described to lack replicative capacity in macrophages and growth-arrested cells, with a chimera lacking a functional Vpr (R7.deltaVpr). Both variants replicated efficiently in primary macrophages, with only minimal differences in the kinetics of reverse transcription, integration, or p24 production. In agreement with our previous observation, elongation of reverse transcription was restricted to the proliferating subpopulation of macrophages. Replication of R7.deltaVpr and R7.deltaVpr.deltaNLS could also be demonstrated in aphidicolin-treated macrophages, indicating efficient nuclear transport in G1/S phase-arrested cells. In conclusion, our results confirm the dependency of the process of HIV-1 reverse transcriptase on cell proliferation in primary macrophages and exclude an important role of MA-NLS and Vpr in macrophage infection.

  18. Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

    NASA Technical Reports Server (NTRS)

    Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

    1995-01-01

    Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

  19. The surface coordination chemistry of cuprate high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Xu, Feng

    The goals of the research described in this dissertation were: (1) to explore the surface coordination chemistry of cuprate high-temperature superconductors (HTSCs); (2) to develop chemical methodology for directly tailoring the surface and interfacial properties of cuprate HTSCs. This thesis documents the first survey of the surface coordination chemistry of a cuprate HTSC, YBa2Cu3O7-delta. Functional groups that can chemically bind to YBa2Cu3O 7-delta have been determined using cyclic voltammetry in conjunction with a series of redox-active ferrocenyl containing adsorbate molecules. Primary alkylamines have emerged as the optimum adsorbates for HTSCs, forming stable and robust monolayer films with no apparent damage to the bulk properties of the underlying superconductors. The interactions between alkylamine adsorbates and YBa2Cu3O7-delta have been shown to involve Cu(II)-NR3 coordination chemistry. The influence of organic monolayers on the properties of YBa2Cu3O 7-delta has been examined using cyclic voltammetry, X-ray powder diffraction, atomic force microscopy, and resistivity vs. temperature measurements. The presence of H2O in the soaking solution adversely affects the adsorption process due to a competing corrosion reaction. However, stable monolayers form on HTSC substrates under rigorously dry conditions. Significantly, monolayer modified HTSCs are substantially more stable to corrosion environmental reagents. The formation kinetics of redox-active alkylamine monolayers on ceramic YBa2Cu3O7-delta are proposed to involve two major processes: a fast adsorption process and a relatively slow pore diffusion process. Surface-solution adsorbate exchange is very dynamic and reversible, which appears to occur via an associative pathway. Monolayers on c-axis-oriented thin films have been shown to be more densely-packed and stable than those on ceramic substrates. Notably, the surface alkylamine "ligands" display traits of Cu(II)-based coordination chemistry

  20. Integration of metabolic modeling and phenotypic data in evaluation and improvement of ethanol production using respiration-deficient mutants of Saccharomyces cerevisiae.

    PubMed

    Dikicioglu, Duygu; Pir, Pinar; Onsan, Z Ilsen; Ulgen, Kutlu O; Kirdar, Betul; Oliver, Stephen G

    2008-09-01

    Flux balance analysis and phenotypic data were used to provide clues to the relationships between the activities of gene products and the phenotypes resulting from the deletion of genes involved in respiratory function in Saccharomyces cerevisiae. The effect of partial or complete respiratory deficiency on the ethanol production and growth characteristics of hap4Delta/hap4Delta, mig1Delta/mig1Delta, qdr3Delta/qdr3Delta, pdr3Delta/pdr3Delta, qcr7Delta/qcr7Delta, cyt1Delta/cyt1Delta, and rip1Delta/rip1Delta mutants grown in microaerated chemostats was investigated. The study provided additional evidence for the importance of the selection of a physiologically relevant objective function, and it may improve quantitative predictions of exchange fluxes, as well as qualitative estimations of changes in intracellular fluxes. Ethanol production was successfully predicted by flux balance analysis in the case of the qdr3Delta/qdr3Delta mutant, with maximization of ethanol production as the objective function, suggesting an additional role for Qdr3p in respiration. The absence of similar changes in estimated intracellular fluxes in the qcr7Delta/qcr7Delta mutant compared to the rip1Delta/rip1Delta and cyt1Delta/cyt1Delta mutants indicated that the effect of the deletion of this subunit of complex III was somehow compensated for. Analysis of predicted flux distributions indicated self-organization of intracellular fluxes to avoid NAD(+)/NADH imbalance in rip1Delta/rip1Delta and cyt1Delta/cyt1Delta mutants, but not the qcr7Delta/qcr7Delta mutant. The flux through the glycerol efflux channel, Fps1p, was estimated to be zero in all strains under the investigated conditions. This indicates that previous strategies for improving ethanol production, such as the overexpression of the glutamate synthase gene GLT1 in a GDH1 deletion background or deletion of the glycerol efflux channel gene FPS1 and overexpression of GLT1, are unnecessary in a respiration-deficient background.

  1. Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul B. (Editor); Heinen, Vernon O. (Editor)

    1990-01-01

    Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.

  2. Melting of the Abrikosov flux lattice in anisotropic superconductors

    NASA Technical Reports Server (NTRS)

    Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

    1992-01-01

    It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

  3. Experimental evidence for flux-lattice melting. [in high-Tc superconductors

    NASA Technical Reports Server (NTRS)

    Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.

    1991-01-01

    A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.

  4. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-01-01

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  5. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-02-02

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  6. Superconducting submillimeter and millimeter wave detectors

    SciTech Connect

    Nahum, M.

    1992-10-20

    The series of projects described in this dissertation was stimulated by the discovery of high temperature superconductivity. Our goal was to develop useful applications which would be competitive with the current state of technology. The high-[Tc] microbolometer was developed into the most sensitive direct detector of millimeter waves, when operated at liquid nitrogen temperatures. The thermal boundary resistance of thin YBa[sub 2]Cu[sub 3]0[sub 7-[delta

  7. Thin film seeds for melt processing textured superconductors for practical applications

    DOEpatents

    Veal, Boyd W.; Paulikas, Arvydas; Balachandran, Uthamalingam; Zhong, Wei

    1999-01-01

    A method of fabricating bulk superconducting material such as RBa.sub.2 Cu.sub.3 O.sub.7-.delta. where R is La or Y comprising depositing a thin epitaxially oriented film of Nd or Sm (123) on an oxide substrate. The powder oxides of RBa.sub.2 Cu.sub.3 O.sub.7-.delta. or oxides and/or carbonates of R and Ba and Cu present in mole ratios to form RBa.sub.2 Cu.sub.3 O.sub.7-.delta., where R is Y or La are heated, in physical contact with the thin film of Nd or Sm (123) on the oxide substrate to a temperature sufficient to form a liquid phase in the oxide or carbonate mixture while maintaining the thin film solid to grow a large single domain 123 superconducting material. Then the material is cooled. The thin film is between 200 .ANG. and 2000 .ANG.. A construction prepared by the method is also disclosed.

  8. Mcp7, a meiosis-specific coiled-coil protein of fission yeast, associates with Meu13 and is required for meiotic recombination.

    PubMed

    Saito, Takamune T; Tougan, Takahiro; Kasama, Takashi; Okuzaki, Daisuke; Nojima, Hiroshi

    2004-01-01

    We previously showed that Meu13 of Schizosaccharomyces pombe functions in homologous pairing and recombination at meiosis I. Here we show that a meiosis-specific gene encodes a coiled-coil protein that complexes with Meu13 during meiosis in vivo. This gene denoted as mcp7+ (after meiotic coiled-coil protein) is an ortholog of Mnd1 of Saccharomyces cerevisiae. Mcp7 proteins are detected on meiotic chromatin. The phenotypes of mcp7Delta cells are similar to those of meu13Delta cells as they show reduced recombination rates and spore viability and produce spores with abnormal morphology. However, a delay in initiation of meiosis I chromosome segregation of mcp7Delta cells is not so conspicuous as meu13Delta cells, and no meiotic delay is observed in mcp7Deltameu13Delta cells. Mcp7 and Meu13 proteins depend on each other differently; Mcp7 becomes more stable in meu13Delta cells, whereas Meu13 becomes less stable in mcp7Delta cells. Genetic analysis shows that Mcp7 acts in the downstream of Dmc1, homologs of Escherichia coli RecA protein, for both recombination and subsequent sporulation. Taken together, we conclude that Mcp7 associates with Meu13 and together they play a key role in meiotic recombination.

  9. Transcriptomic analysis of Saccharomyces cerevisiae physiology in the context of galactose assimilation perturbations.

    PubMed

    Syriopoulos, C; Panayotarou, A; Lai, K; Klapa, Maria I

    2008-09-01

    Despite being extensively studied in various organisms due to scientific, industrial and medical interest, the galactose assimilation function and regulation, and especially its interaction with other parts of cellular physiology, have not been fully elucidated yet. The post-genomic era holistic techniques ("omics") could assist towards this goal. In this paper, we holistically analyzed full-genome Saccharomyces cerevisiae transcriptional profiling data concerning its glucose- and galactose-grown wild-type (WT) physiology and its glucose-grown gal7-deficient (GAL7Delta) physiology, as these were obtained in the experiment described in Lai and Elsas (Biochem. Biophys. Res. Commun. 2000, 271, 392-400). The gal7 gene encodes for the second enzyme of the galactose assimilation, Leloir, pathway, and its deficiency in humans causes a potentially lethal disease, named "classic galactosemia". Analysis of the galactose-grown compared to the glucose-grown WT physiology indicated a significant increase in the transcriptional expression of the ribosomal machinery and decrease in the transcriptional activity of the fatty acids' beta-oxidation at the peroxisomes. Comparison of GAL7Delta to WT physiology in glucose indicated a significant transcriptional increase in the mitochondrial activity and the rate of catabolism of disaccharides, including sucrose, mannose and trehalose, towards amplified biosynthesis of the main cell wall components. Comparison with other physiological conditions indicated strong correlation between the glucose-grown GAL7Delta transcriptional physiology and the WT growth under glucose derepression conditions. Finally, the acquired results and the large number of still unknown genes that were related to the galactose assimilation regulation indicated the need for further, specifically designed, perturbations and integrated analyses of multiple levels of cellular function.

  10. Microwave response of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Miranda, Felix Antonio

    1991-01-01

    We have studied the microwave response of YBa2Cu3O(7 - delta), Bi-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O high transition temperature superconducting (HTS) thin films by performing power transmission measurements. These measurements were carried out in the temperature range of 300 K to 20 K and at frequencies within the range of 30 to 40 GHz. Through these measurements we have determined the magnetic penetration depth (lambda), the complex conductivity (sigma(sup *) = sigma(sub 1) - j sigma(sub 2)) and the surface resistance (R(sub s)). An estimate of the intrinsic penetration depth (lambda approx. 121 nm) for the YBa2Cu3O(7 - delta) HTS has been obtained from the film thickness dependence of lambda. This value compares favorably with the best values reported so far (approx. 140 nm) in single crystals and high quality c-axis oriented thin films. Furthermore, it was observed that our technique is sensitive to the intrinsic anisotropy of lambda in this superconductor. Values of lambda are also reported for Bi-based and Tl-based thin films. We observed that for the three types of superconductors, both sigma(sub 1) and sigma(sub 2) increased when cooling the films below their transition temperature. The measured R(sub s) are in good agreement with other R(sub S) values obtained using resonant activity techniques if we assume a quadratic frequency dependence. Our analysis shows that, of the three types of HTS films studied, the YBa2Cu3O(7 - delta) thin film, deposited by laser ablation and off-axis magnetron sputtering are the most promising for microwave applications.

  11. LETTER TO THE EDITOR: The oxygen-isotope effect on the in-plane penetration depth in underdoped Y1-x Prx Ba2 Cu3 O7-δ as revealed by muon-spin rotation

    NASA Astrophysics Data System (ADS)

    Khasanov, R.; Shengelaya, A.; Conder, K.; Morenzoni, E.; Savic, I. M.; Keller, H.

    2003-01-01

    The oxygen-isotope (16O/18O) effect (OIE) on the in-plane penetration depth lambdaab (0) in underdoped Y1-x Prx Ba2 Cu3 O7-delta was studied by means of muon-spin rotation. A pronounced OIE on lambdaab-2 (0) was observed with a relative isotope shift of Deltalambdaab-2 /lambda ab-2 = -5(2)% for x = 0.3 and -9(2)% for x = 0.4. The OIE exponents of Tc and of lambdaab-2 (0) exhibit a relation that appears to be generic for cuprate superconductors.

  12. Thermal conversions of the yttrium-barium-copper salt of carboxylated cellulose and the synthesis of yttrium barium cuprate from it

    SciTech Connect

    Kaputskii, F.N.; Bashmakov, I.A.; Novikov, V.P.

    1994-09-20

    Thermal solid-phase conversions of the yttrium-barium-copper salt of tricarboxycellulose (TCC) with a 1-2-3 cation stoichiometry, respectively, have been considered. Yttrium barium cuprate is the end product of the thermal treatment of the triple salt. According to the data of X-ray analysis the onset of 1-2-3 phase formation is noticeable at 750-800{degrees}C. The temperature 875{degrees}C (with a duration of heating of 12 h) is sufficient for practically complete conversion of the Y-Ba-Cu salt of TCC into YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}.

  13. Dynamic spin correlations in 'stuffed' spin ice Ho(2+x)Ti(2-x)O(7-d)

    SciTech Connect

    Ehlers, Georg

    2008-02-01

    The magnetic correlations in 'stuffed' spin ice Ho{sub 2+x}Ti{sub 2-x}O{sub 7-{delta}} have been characterized using quasielastic neutron scattering. At temperatures above 1K , these correlations are short ranged in nature and dynamic on a picosecond to nanosecond time scale. As for the case of pure spin ice Ho{sub 2+x}Ti{sub 2-x}O{sub 7}, one can identify, above the freezing temperature, a quantum relaxation regime which is enhanced as it persists to even higher temperatures, T{approx}30-40K , than in the parent compound.

  14. Inhomogeneity Induced Coupling in YBCO/BaTiO{sub 3} Composites

    SciTech Connect

    Mohanta, A.; Behera, D.

    2008-10-23

    Ferroelectric and high temperature superconducting materials are two promising materials for future electronic devices. The superconducting properties and the related microstructures of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} with BaTiO{sub 3} addition, prepared by partial melt processing, were investigated with temperature-resistivity, X-ray diffraction and SEM-EDX analysis. For lower concentration of BaTiO{sub 3} it shows a fractal behaviour approaching the exponent of three-dimensional percolation model. The transport properties studied by four-probe arrangement show a different behaviour depending on the wt.% of ferroelectric to superconductor.

  15. DELTA: An Expert System for Diesel Electric Locomotive Repair

    DTIC Science & Technology

    1984-06-01

    for Representing Procedural Knowledge. AD-P003 924 Failure Detection Processes by Pattern Recognition and Expert Systems. AD-P003 925’ GUIDON . AD-P003...3ENT, PART NOTICE (CON’T) AD#: TITLE: AD-P003 934 Artificial Intelligence Contributibnsto, Training and Maintenance. AD-P003 935 NAVATIR1 s (Naval Air...P003 947 On the Requirements of Expert Systens-for Fault Isolation. IAcce~Sslm For NTIS GRA&T DTIC TAB ’’A e;e~ s rind sale... ;’-,:i~’. . [ A7 7: DELTA

  16. Slip-Cast Superconductive Parts

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Buckley, John D.; Vasquez, Peter; Buck, Gregory M.; Hicks, Lana P.; Hooker, Matthew W.; Taylor, Theodore D.

    1993-01-01

    Complex shapes fabricated without machining. Nonaqueous slip-casting technique used to form complexly shaped parts from high-temperature superconductive materials like YBa(2)Cu(3)O(7-delta). Such parts useful in motors, vibration dampers, and bearings. In process, organic solvent used as liquid medium. Ceramic molds made by lost-wax process used instead of plaster-of-paris molds, used in aqueous slip-casting but impervious to organic solvents and cannot drain away liquid medium. Organic-solvent-based castings do not stick to ceramic molds as they do to plaster molds.

  17. Spatially Resolved Observation of Static Magnetic Flux States in YBa2Cu3O7-dgr Grain Boundary Josephson Junctions.

    PubMed

    Fischer, G M; Mayer, B; Gross, R; Nissel, T; Husemann, K D; Huebener, R P; Freltoft, T; Shen, Y; Vase, P

    1994-02-25

    With low-temperature scanning electron microscopy, the magnetic flux states in high critical temperature Josephson junctions have been imaged. The experiments were performed with YBa(2)Cu(3)O(7-delta) thin-film grain boundary Josephson junctions fabricated on [001] tilt SrTiO(3) bicrystals. For applied magnetic fields parallel to the grain boundary plane, which correspond to local maxima of the magnetic field dependence of the critical current, the images clearly show the corresponding magnetic flux states in the grain boundary junction. The spatial modulation of the Josephson current density by the external magnetic field is imaged directly with a spatial resolution of about 1 micrometer.

  18. Microwave properties of high transition temperature superconducting thin films

    NASA Technical Reports Server (NTRS)

    Gordon, W. L.

    1991-01-01

    Extensive studies of the interaction of microwaves with YBa2Cu3O(7-delta), Bi-based, and Tl-based superconducting thin films deposited in several microwave substrates were performed. The data were obtained by measuring the microwave power transmitted through the film in the normal and the superconducting state and by resonant cavity techniques. The main motives were to qualify and understand the physical parameters such as the magnetic penetration depth, the complex conductivity, and the surface impedance, of high temperature superconducting (HTS) materials at microwave frequencies. Based on these parameters, the suitability of these HTS thin films is discussed for microwave applications.

  19. Development and evaluation of superconducting circuit elements

    NASA Technical Reports Server (NTRS)

    Haertling, Gene H.; Lee, Burtrand; Hsi, Dennis; Modi, Vibhakar; Marone, Matt

    1990-01-01

    An approach to the application of high Tc ceramic superconductors to practical circuit elements was developed and demonstrated. This method, known as the rigid-conductor process (RCP), involves the combination of a pre-formed, sintered, and tested superconductor material with an appropriate, rigid substrate via an epoxy adhesive which also serves to encapsulate the element from the ambient environment. Emphasis was on the practical means to achieve functional, reliable, and reproducible components. Although all of the work described in this report involved a YBa2Cu3Osub(7-x) high Tc superconductor material, the techniques developed and conclusions reached are equally applicable to other high Tc materials.

  20. The RSC chromatin remodeling complex bears an essential fungal-specific protein module with broad functional roles.

    PubMed

    Wilson, Boris; Erdjument-Bromage, Hediye; Tempst, Paul; Cairns, Bradley R

    2006-02-01

    RSC is an essential and abundant ATP-dependent chromatin remodeling complex from Saccharomyces cerevisiae. Here we show that the RSC components Rsc7/Npl6 and Rsc14/Ldb7 interact physically and/or functionally with Rsc3, Rsc30, and Htl1 to form a module important for a broad range of RSC functions. A strain lacking Rsc7 fails to properly assemble RSC, which confers sensitivity to temperature and to agents that cause DNA damage, microtubule depolymerization, or cell wall stress (likely via transcriptional misregulation). Cells lacking Rsc14 display sensitivity to cell wall stress and are deficient in the assembly of Rsc3 and Rsc30. Interestingly, certain rsc7delta and rsc14delta phenotypes are suppressed by an increased dosage of Rsc3, an essential RSC member with roles in cell wall integrity and spindle checkpoint pathways. Thus, Rsc7 and Rsc14 have different roles in the module as well as sharing physical and functional connections to Rsc3. Using a genetic array of nonessential null mutations (SGA) we identified mutations that are sick/lethal in combination with the rsc7delta mutation, which revealed connections to a surprisingly large number of chromatin remodeling complexes and cellular processes. Taken together, we define a protein module on the RSC complex with links to a broad spectrum of cellular functions.

  1. Cdc7-dependent phosphorylation of Mer2 facilitates initiation of yeast meiotic recombination.

    PubMed

    Sasanuma, Hiroyuki; Hirota, Kouji; Fukuda, Tomoyuki; Kakusho, Naoko; Kugou, Kazuto; Kawasaki, Yasuo; Shibata, Takehiko; Masai, Hisao; Ohta, Kunihiro

    2008-02-01

    Meiosis ensures genetic diversification of gametes and sexual reproduction. For successful meiosis, multiple events such as DNA replication, recombination, and chromosome segregation must occur coordinately in a strict regulated order. We investigated the meiotic roles of Cdc7 kinase in the initiation of meiotic recombination, namely, DNA double-strand breaks (DSBs) mediated by Spo11 and other coactivating proteins. Genetic analysis using bob1-1 cdc7Delta reveals that Cdc7 is essential for meiotic DSBs and meiosis I progression. We also demonstrate that the N-terminal region of Mer2, a Spo11 ancillary protein required for DSB formation and phosphorylated by cyclin-dependent kinase (CDK), contains two types of Cdc7-dependent phosphorylation sites near the CDK site (Ser30): One (Ser29) is essential for meiotic DSB formation, and the others exhibit a cumulative effect to facilitate DSB formation. Importantly, mutations on these sites confer severe defects in DSB formation even when the CDK phosphorylation is present at Ser30. Diploids of cdc7Delta display defects in the chromatin binding of not only Spo11 but also Rec114 and Mei4, other meiotic coactivators that may assist Spo11 binding to DSB hot spots. We thus propose that Cdc7, in concert with CDK, regulates Spo11 loading to DSB sites via Mer2 phosphorylation.

  2. Fabrication of high critical current density superconducting tapes by epitaxial deposition of YBCO thick films on biaxially textured metal substrates

    SciTech Connect

    Goyal, A.; Norton, D.P.; Paranthaman, M.

    1996-12-31

    High critical current density YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes were fabricated by epitaxial deposition on rolling- assisted-biaxially-textured-substrates (RABiTS). The RABiTS technique uses well established, industrially scaleable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers to yield chemically and structurally compatible surfaces. Epitaxial YBCO films grown on such substrates have critical current densities approaching 10{sup 6} A/cm{sup 2} at 77K in zero field and have field dependences similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for fabricating long lengths of high J{sub c} wire capable of carrying high currents in high magnetic fields and at elevated temperatures.

  3. Miniaturized high-temperature superconductor microstrip patch antenna

    NASA Astrophysics Data System (ADS)

    Chaloupka, Heinz; Piel, Helmut; Pischke, Arndt; Klein, Norbert; Peiniger, Michael; Splitt, Georg

    1991-09-01

    Experimental as well as computational results are presented for 2.4 GHz microstrip antennas which are miniaturized (total length, 6 mm) by both a new, stepped impedance patch shape and a relatively high substrate permittivity. The antennas investigated were fabricated from YBa2Cu3O(7-delta) thin films epitaxially grown on single-crystalline LaAlO3 substrates by pulsed excimer laser ablation or by high-pressure oxygen DC sputtering and, for comparison, from copper on the same substrate material. It is shown that the radiation efficiency of this antenna structure is only about 1 percent to 6 percent for copper at 77 K but is increased to values between 35 percent and 65 percent for HTS films. From experimental investigations of the power dependence of the antenna gain at 77 K, nonlinearities, especially a sharp drop at a current density of about 2 x 10 to the 6th A/sq cm, were observed.

  4. Superconducting miniaturized planar antennas

    NASA Astrophysics Data System (ADS)

    Pischke, A.; Chaloupka, H.; Klein, N.; Splitt, G.

    This contribution reports on experimental as well as theoretical investigations of superconducting 2.4 GHz microstrip antenna. Due to both a new stepped-impedance patch shape and a high permittivity substrate (LaAlO3) the size was reduced to an area of only 6x6 mm. The measured radiation efficiency of antennas fabricated from YBa2Cu3O(7-delta) is at 77 K in the order of 45 and 65 percent for a substrate height of 0.5 mm and 1 mm respectively. In contrast, a copper antenna yields an efficiency of 3 and 6 percent only. Deviations from a linear transmission behavior of the superconducting antenna can be observed at a current density of 500,000 A/sq cm. An increase in frequency bandwidth from 4 MHz to over 9 MHz results from replacing the single-patch structure by a double-patch structure (stacked patches).

  5. Fabrication and Characterization of Ultrathin PBCO/YBCO/PBCO Constrictions for Hot Electron Bolometer THz Mixing Application

    NASA Astrophysics Data System (ADS)

    Peroz, Christophe; Degardin, Annick F.; Villegier, Jean-Claude; Kreisler, Alain J.

    2007-06-01

    Superconducting Hot Electron Bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the terahertz range because of their ultrawide bandwidth, high conversion gain, and low intrinsic noise level, even at 77 K. A technological process to realize HEBs based on high-Tc YBa2Cu3O7-delta (YBCO) materials is described. Ultra-thin 12 to 40 nm layers were sputtered on MgO (100) substrates, sub-micrometer constrictions (0.5 mum times 0.5 mum) were etched on these and log-periodic gold antennas were then integrated. Good superconducting properties were measured after the whole process. Electrical transport characteristics of the device are discussed, aging effects are considered and regular bolometric THz response results are given.

  6. Magnetic studies of current conduction and flux pinning in high-T(sub c) cuprates: Virgin, irradiated, and oxygen deficient materials

    NASA Astrophysics Data System (ADS)

    Thompson, J. R.; Sun, Yang Ren; Ossandon, J. G.; Christen, D. K.; Kerchner, H. R.; Sles, B. C.; Chakoumakos, B. C.; Civale, L.; Marwick, A. D.; Holtzberg, F.

    1992-09-01

    To increase the current density and pinning of magnetic flux in high temperature superconductors, defects with point-like and line-like geometries were created in controlled numbers using ion irradiation methods. Single crystals of Y1Ba2Cu3O7 and Bi2Sr2Ca1Cu2O8 superconductors were studied using dc magnetic methods. These studies showed greatly increased irreversibility in the vortex state magnetization and enhanced intragrain current density J(sub c) following irradiation. Linear defects, created by irradiation with energetic heavy ions, are particularly effective in pinning vortices at higher temperatures and magnetic fields. Further investigations of 'flux creep' (the time dependence of magnetization) are well described by recent vortex glass and collective pinning theories. Complementary investigations have delineated the role of oxygen deficiency (delta) on pinning in aligned Y1Ba2Cu3O(7-delta) materials.

  7. Miniaturized High-Temperature Superconducting/Dielectric Multilayer Filters for Satellite Communications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    1997-01-01

    Most communication satellites contain well over a hundred filters in their payload. Current technology in typical satellite multiplexers use dual-mode cavity or dielectric resonator filters that are large (approx. 25 to 125 cu in) and heavy (up to 600 g). As the complexity of future advanced electronic systems for satellite communications increases, even more filters will be needed, requiring filter miniaturization without performance degradation. Such improvements in filter technology will enhance satellite performance. To reduce the size, weight, and cost of the multiplexers without compromising performance, the NASA Lewis Research Center is collaborating with industry to develop a new class of dual-mode multilayer filters consisting of YBa2Cu3O7-delta high-temperature superconducting (HTS) thin films on LaAlO3 substrates.

  8. Application of ceramic superconductors in high speed turbines

    NASA Technical Reports Server (NTRS)

    Mcmichael, C. K.; Lamb, M. A.; Lin, M. W.; Ma, K. B.; Chu, W. K.

    1992-01-01

    A turbine system was modified to adapt melt textured YBa2Cu3O(7-delta) (YBCO) with high energy permanent magnets to form a hybrid superconducting magnetic bearing (HSMB). The HSMB/turbine prototype has achieved a static axial thrust capacity exceeding 41 N/sq cm (60 psi) and a radial magnetic stiffness of 7 N/mm in a field cooled state at 77 K. A comparison was made between different configurations of magnets and superconductor for radial stability, axial instability, and force hystereses. This systematic study lead to a greater understanding of the interactions between YBCO and high energy permanent magnets to define design parameters for high rotational devices using the HSMB design.

  9. Hybrid Superconducting Magnetic Bearing (HSMB) for high load devices

    NASA Technical Reports Server (NTRS)

    Mcmichael, C. K.; Ma, K. B.; Lamb, M. A.; Lin, M. W.; Chow, L.; Meng, R. L.; Hor, P. H.; Chu, W. K.

    1992-01-01

    Lifting capacities greater than 41 N/cm(exp 2) (60 psi) at 77 K have been achieved with a new type of levitation (hybrid) using a combination of permanent magnets and high quality melt-mixtured YBa2Cu3O(7-delta) (YBCO). The key concept of the hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets for high levitation or suspension forces in conjunction with a superconductor's flux pinning characteristics to counteract the inherent instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust bearing configuration

  10. Hybrid Superconducting Magnetic Bearing (HSMB) for high load devices

    NASA Astrophysics Data System (ADS)

    McMichael, C. K.; Ma, K. B.; Lamb, M. A.; Lin, M. W.; Chow, L.; Meng, R. L.; Hor, P. H.; Chu, W. K.

    1992-05-01

    Lifting capacities greater than 41 N/cm(exp 2) (60 psi) at 77 K have been achieved with a new type of levitation (hybrid) using a combination of permanent magnets and high quality melt-mixtured YBa2Cu3O(7-delta) (YBCO). The key concept of the hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets for high levitation or suspension forces in conjunction with a superconductor's flux pinning characteristics to counteract the inherent instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust bearing configuration

  11. Practical adaptation in bulk superconducting magnetic bearing applications

    NASA Astrophysics Data System (ADS)

    McMichael, C. K.; Ma, K. B.; Lamb, M. A.; Lin, M. W.; Chow, L.; Meng, R. L.; Hor, P. H.; Chu, W. K.

    1992-04-01

    Lifting capacities greater than 41 N/sq cm (60 psi) at 77 K have been achieved using a combination of permanent magnets and high quality melt-textured YBa2Cu3O(7-delta) (YBCO). The key concept of this hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets to support high loads in conjunction with flux pinning in a type II superconductor to counteract instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust and journal bearing configurations on a bearing prototype.

  12. Buffer layers for high-Tc thin films on sapphire

    NASA Technical Reports Server (NTRS)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  13. High-quality planar high-T{sub c} Josephson junctions

    SciTech Connect

    Bergeal, N.; Grison, X.; Lesueur, J.; Faini, G.; Aprili, M.; Contour, J.P.

    2005-09-05

    Reproducible high-T{sub c} Josephson junctions have been made in a rather simple two-step process using ion irradiation. A microbridge (1 to 5 {mu}m wide) is firstly designed by ion irradiating a c-axis-oriented YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film through a gold mask such as the nonprotected part becomes insulating. A lower T{sub c} part is then defined within the bridge by irradiating with a much lower fluence through a narrow slit (20 nm) opened in a standard electronic photoresist. These planar junctions, whose settings can be finely tuned, exhibit reproducible and nearly ideal Josephson characteristics. This process can be used to produce complex Josephson circuits.

  14. Analysis and Optimization of Thin Film Ferroelectric Phase Shifters

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.; VanKeuls, Fred W.; Warner, Joseph D.; Mueller, Carl H.; Alterovitz, Samuel A.; Miranda, Felix A.; Qureshi, A. Haq; Romanofsky, Robert R. (Technical Monitor)

    2000-01-01

    Microwave phase shifters have been fabricated from (YBa2Cu3O(7-delta) or Au)/SrTiO3 and Au/Ba(x)Sr(1-x)TiO3 films on LaAlO3 and MgO substrates. These coupled microstrip devices rival the performance of their semiconductor counter-parts parts at Ku- and K-band frequencies. Typical insertion loss for room temperature ferroelectric phase shifters at K-band is approximately equal 5 dB. An experimental and theoretical investigation of these novel devices explains the role of the ferroelectric film in overall device performance. A roadmap to the development of a 3 dB insertion loss phase shifter that would enable a new type of phased array antenna is discussed.

  15. Spin dynamics and implications for superconductivity: Some problems with the d-wave scenario

    SciTech Connect

    Levin, K.; Zha, Y.; Radtke, R.J.; Si, Q.; Norman, M.R.; Schuttler, H.B.

    1993-09-01

    We review the spin dynamics of the normal state of the cuprates with special emphasis on neutron data in both the YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4} systems. When realistic models of the Fermi surface shapes are incorporated, along with a moderate degree of spin fluctuations, we find good semi-quantiative agreement with experiment for both cuprates. Building on the success of this Fermi-liquid-based scheme, we explore the implications for d-wave pairing from a number of vantage points. We conclude that our present experimental and theoretical understanding is inadequate to confirm or refute the d-wave scenario.

  16. Superconducting Microwave Electronics at Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Bhasin, Kul B.; Leonard, Regis F.

    1991-01-01

    Over the last three years, NASA Lewis Research Center has investigated the application of newly discovered high temperature superconductors to microwave electronics. Using thin films of YBa2Cu3O7-delta and Tl2Ca2Ba2Cu3Ox deposited on a variety of substrates, including strontium titanate, lanthanum gallate, lanthanum aluminate and magnesium oxide, a number of microwave circuits have been fabricated and evaluated. These include a cavity resonator at 60 GHz, microstrip resonators at 35 GHz, a superconducting antenna array at 35 GHz, a dielectric resonator at 9 GHz, and a microstrip filter at 5 GHz. Performance of some of these circuits as well as suggestions for other applications are reported.

  17. Pyrochlore catalysts for hydrocarbon fuel reforming

    DOEpatents

    Berry, David A.; Shekhawat, Dushyant; Haynes, Daniel; Smith, Mark; Spivey, James J.

    2012-08-14

    A method of catalytically reforming a reactant gas mixture using a pyrochlore catalyst material comprised of one or more pyrochlores having the composition A2B2-y-zB'yB"zO7-.DELTA., where y>0 and z.gtoreq.0. Distribution of catalytically active metals throughout the structure at the B site creates an active and well dispersed metal locked into place in the crystal structure. This greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Further, oxygen mobility may also be enhanced by elemental exchange of promoters at sites in the pyrochlore. The pyrochlore catalyst material may be utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H2+CO) for fuel cells, among other uses.

  18. Pyrochlore-type catalysts for the reforming of hydrocarbon fuels

    DOEpatents

    Berry, David A [Morgantown, WV; Shekhawat, Dushyant [Morgantown, WV; Haynes, Daniel [Morgantown, WV; Smith, Mark [Morgantown, WV; Spivey, James J [Baton Rouge, LA

    2012-03-13

    A method of catalytically reforming a reactant gas mixture using a pyrochlore catalyst material comprised of one or more pyrochlores having the composition A.sub.2-w-xA'.sub.wA''.sub.xB.sub.2-y-zB'.sub.yB''.sub.zO.sub.7-.DELTA.. Distribution of catalytically active metals throughout the structure at the B site creates an active and well dispersed metal locked into place in the crystal structure. This greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Further, oxygen mobility may also be enhanced by elemental exchange of promoters at sites in the pyrochlore. The pyrochlore catalyst material may be utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H.sub.2+CO) for fuel cells, among other uses.

  19. Coplanar waveguide microwave filter of YBa2Cu3O7

    NASA Technical Reports Server (NTRS)

    Chew, Wilbert; Riley, A. L.; Rascoe, Daniel L.; Hunt, Brian D.; Foote, Marc C.; Cooley, Thomas W.; Bajuk, Louis J.

    1991-01-01

    Thin film low-pass microwave filters have been made with laser-ablated YBa2Cu3O(7-delta) (YBCO) deposited on LaAlO3 substrates, using a coplanar waveguide structure. The coplanar waveguide sections had dimensions suited for integrated circuits. Measured losses in liquid nitrogen were superior to the loss in a similar thin-film copper filter throughout the 0 to 9.5 GHz pass-band. A simple transmission-line model is adequate for filter design using YBCO films with repeatable characteristics. The measured filters demonstrate the performance of fully patterned YBCO after sealing in space-qualifiable hermetic packages. Five packaged filters of this design were delivered to the Naval Research Laboratory as candidates for space flight in the High Temperature Superconductivity Space Experiment.

  20. Correlation Between Grain and Grain-Boundary Critical Current Densities in ex situ Coated Conductors with Variable YBa2Cu3O7- δ Layer Thickness

    SciTech Connect

    Palau, A.; Puig, T.; Obradors, X.; Feenstra, Roeland; Gapud, Albert Agcaoili

    2006-01-01

    The dependence of the percolative critical current density at low magnetic fields on YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) layer thickness is studied by comparing grain, J{sub c}{sup G}, and grain-boundary, J{sub c}{sup GB}, critical current densities for a series of ex situ processed YBCO films on a RABiTS template. Both critical current densities decrease as a function of thickness and the values of J{sub c}{sup G} and J{sub c}{sup GB} show a clear correlation which suggests the existence of an interaction between Abrikosov-Josephson vortices on the grain boundaries and Abrikosov vortices in the bulk of the grains. This opens the possibility to improve J{sub c}{sup GB} by optimizing the pinning capabilities of the grains.

  1. Fast neutron irradiation effects on magnetization relaxation in YBCO single crystals

    SciTech Connect

    Lensink, J.G.; Griessen, R. . Faculty of Physics and Astronomy); Wiesinger, H.P.; Sauerzopf, F.M.; Weber, H.W. ); Crabtree, G.W. )

    1991-07-01

    A high-quality YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystal has been investigated by torque magnetometry prior to and following fast neutron irradiation to a fluence of 2{times}10{sup 21} m{sup {minus}2} (E > 0.1 MeV). In addition to large enhancements of the critical current densities, which have been observed in similar form previously by Sauerzopf et al, we find a dramatic change in the relaxation behavior following irradiation. At low temperatures ({le} 50 k) the relaxation rates are lowered by factors up to 4 in the irradiated state in a magnetic field of 1.5 T. At higher temperatures, on the other hand, they are enhanced compared to the unirradiated state. Both before and after irradiation, the magnetization relaxation follows a logarithmic time dependence, which we ascribe to thermally activated flux motion.

  2. Coplanar waveguide microwave filter of YBa2Cu3O7

    NASA Astrophysics Data System (ADS)

    Chew, Wilbert; Riley, A. L.; Rascoe, Daniel L.; Hunt, Brian D.; Foote, Marc C.; Cooley, Thomas W.; Bajuk, Louis J.

    1991-07-01

    Thin film low-pass microwave filters have been made with laser-ablated YBa2Cu3O(7-delta) (YBCO) deposited on LaAlO3 substrates, using a coplanar waveguide structure. The coplanar waveguide sections had dimensions suited for integrated circuits. Measured losses in liquid nitrogen were superior to the loss in a similar thin-film copper filter throughout the 0 to 9.5 GHz pass-band. A simple transmission-line model is adequate for filter design using YBCO films with repeatable characteristics. The measured filters demonstrate the performance of fully patterned YBCO after sealing in space-qualifiable hermetic packages. Five packaged filters of this design were delivered to the Naval Research Laboratory as candidates for space flight in the High Temperature Superconductivity Space Experiment.

  3. Comparison between the magnetic and transport critical current densities in high critical current density melt-textured yttrium barium copper-oxide

    NASA Technical Reports Server (NTRS)

    Gao, L.; Meng, R. L.; Xue, Y. Y.; Hor, P. H.; Chu, C. W.

    1991-01-01

    Using a recently developed pulsed critical current density (Jc) measuring system, the Jc of the high-Jc melt-textured YBa2Cu3O(7-delta) (Y123) bulk samples has been determined. I-V curves with a voltage resolution of 0.5 microV were obtained, and transport Jc's along the a-b plane as high as 7.2 x 10 to the 4th A/sq cm were extracted. These results are comparable to the values obtained magnetically. On the other hand, transport Jc along the c axis were found to be two orders of magnitude smaller, even though the magnetic Jc along the c axis is only about five times smaller than Jc along the a-b plane. It is suggested that for the high-temperature superconducting materials which are highly anisotropic, caution should be taken when using the nontransport magnetic methods to determine Jc.

  4. Engineering of a novel Saccharomyces cerevisiae wine strain with a respiratory phenotype at high external glucose concentrations.

    PubMed

    Henricsson, C; de Jesus Ferreira, M C; Hedfalk, K; Elbing, K; Larsson, C; Bill, R M; Norbeck, J; Hohmann, S; Gustafsson, L

    2005-10-01

    The recently described respiratory strain Saccharomyces cerevisiae KOY.TM6*P is, to our knowledge, the only reported strain of S. cerevisiae which completely redirects the flux of glucose from ethanol fermentation to respiration, even at high external glucose concentrations (27). In the KOY.TM6*P strain, portions of the genes encoding the predominant hexose transporter proteins, Hxt1 and Hxt7, were fused within the regions encoding transmembrane (TM) domain 6. The resulting chimeric gene, TM6*, encoded a chimera composed of the amino-terminal half of Hxt1 and the carboxy-terminal half of Hxt7. It was subsequently integrated into the genome of an hxt null strain. In this study, we have demonstrated the transferability of this respiratory phenotype to the V5 hxt1-7Delta strain, a derivative of a strain used in enology. We also show by using this mutant that it is not necessary to transform a complete hxt null strain with the TM6* construct to obtain a non-ethanol-producing phenotype. The resulting V5.TM6*P strain, obtained by transformation of the V5 hxt1-7Delta strain with the TM6* chimeric gene, produced only minor amounts of ethanol when cultured on external glucose concentrations as high as 5%. Despite the fact that glucose flux was reduced to 30% in the V5.TM6*P strain compared with that of its parental strain, the V5.TM6*P strain produced biomass at a specific rate as high as 85% that of the V5 wild-type strain. Even more relevant for the potential use of such a strain for the production of heterologous proteins and also of low-alcohol beverages is the observation that the biomass yield increased 50% with the mutant compared to its parental strain.

  5. The Electronic Structure of Metallic and Bimetallic Clusters of IRON-57 with Chromium, TIN-119 and Platinum.

    NASA Astrophysics Data System (ADS)

    Nagarathna, H. M.

    Rare gas matrix isolation techniques have been used in conjunction with Mossbauer spectroscopy to study the bimetallic clusters of ('57)Fe with Cr, ('119)Sn and Pt. Various molecules have been identified by concentration and temperature dependence studies and also with the aid of Monte Carlo calculations. The iron-tin system is studied using both ('57)Fe and ('119)Sn Mossbauer isotopes. The Mossbauer parameters of FeCr, FeSn and FePt heteronuclear diatomic molecules and Sn(,2) homonuclear diatomic molecules isolated in argon at 4.2 K are obtained very accurately and used to determine their electronic ground states. In addition to diatomic molecules, the larger clusters have also been characterized using Mossbauer spectroscopy and their relevance to bulk alloys is discussed. SCF-X(alpha)-SW molecular orbital calculations are performed on Fe(,2), FeCr, Sn(,2), FeSn and FePt diatomic molecules to determine their electronic ground states by looking at the calculations which agreed with the measured Mossbauer hyperfine parameters. The most probable electronic ground state for Fe(,2) is determined to be a ('7)(SIGMA)(,g) and for FeCr a ('7)(SIGMA) or ('7)(DELTA) indicating a ferromagnetic coupling between the atoms. The calculations indicated a need for a smaller value of the quadrupole moment of the ('57)Fe nucleus. For Sn(,2) a ('3)(SIGMA)(,g) is the most probable ground state and for FeSn a ('7)(DELTA). The calculations showed a ('5)(SIGMA) state as the most probable electronic ground state for FePt. The X(alpha)-SW calculations are found to be very useful in understanding the nature of chemical bonding between the atoms in the above molecules. Antimony metal clusters are also studied using ('121)Sb Mossbauer spectroscopy and extended Huckel molecular orbital calculations. A good correlation is observed between the experimental and calculated data.

  6. Electronic properties of superconductors studied using photo induced activation of microwave absorption (PIAMA)

    SciTech Connect

    Feenstra, B.J.; Schooveld, W.A.; Bos, C.

    1995-12-31

    Electronic properties of superconductors are contemporarily being studied using many different experimental techniques, among which infrared spectrometry, photoelectron spectroscopy and microwave cavity techniques play an important role. The data analysis, however, is complicated by the fact that in these materials the phonon-frequency range overlaps with the one in which the energy gap is expected. This problem can be circumvented by making use of two different sources, one to induce the excitations (the Free Electron Laser in Nieuwegein, The Netherlands, FELIX), and one to study the behavior of these excitations (i.e. quasiparticles). In our case the latter source is monochromatic microwave radiation, transmitted through a thin superconducting film. We measured both a conventional superconductor (NbN, T{sub c} = 17 K) and a high T{sub c} superconductor (SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, T{sub c} = 92 K). For NbN we observed a positive change in transmission, followed by a relaxation to a transmission smaller than the original value, after which the starting situation was restored within {approximately} 100 {mu}s. In case of SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, the changes persisted above T{sub c}. At very low temperatures we observed slow oscillations ({approximately} 4kHz) in the induced signal, which were absent in NbN. The long time scales can possibly be explained by the so-called bottleneck, i.e. quasiparticles excited with a lot of excess energy lose part of their energy by exciting other quasiparticles. In this case the quasiparticle lifetime is enhanced considerably. The oscillations point towards an intrinsic difference of the low energy excitations, i.e. the symmetry of the pairing.

  7. Bni5p, a septin-interacting protein, is required for normal septin function and cytokinesis in Saccharomyces cerevisiae.

    PubMed

    Lee, Philip R; Song, Sukgil; Ro, Hyeon-Su; Park, Chong J; Lippincott, John; Li, Rong; Pringle, John R; De Virgilio, Claudio; Longtine, Mark S; Lee, Kyung S

    2002-10-01

    In the budding yeast Saccharomyces cerevisiae, the Cdc3p, Cdc10p, Cdc11p, Cdc12p, and Sep7p/Shs1p septins assemble early in the cell cycle in a ring that marks the future cytokinetic site. The septins appear to be major structural components of a set of filaments at the mother-bud neck and function as a scaffold for recruiting proteins involved in cytokinesis and other processes. We isolated a novel gene, BNI5, as a dosage suppressor of the cdc12-6 growth defect. Overexpression of BNI5 also suppressed the growth defects of cdc10-1, cdc11-6, and sep7Delta strains. Loss of BNI5 resulted in a cytokinesis defect, as evidenced by the formation of connected cells with shared cytoplasms, and deletion of BNI5 in a cdc3-6, cdc10-1, cdc11-6, cdc12-6, or sep7Delta mutant strain resulted in enhanced defects in septin localization and cytokinesis. Bni5p localizes to the mother-bud neck in a septin-dependent manner shortly after bud emergence and disappears from the neck approximately 2 to 3 min before spindle disassembly. Two-hybrid, in vitro binding, and protein-localization studies suggest that Bni5p interacts with the N-terminal domain of Cdc11p, which also appears to be sufficient for the localization of Cdc11p, its interaction with other septins, and other critical aspects of its function. Our data suggest that the Bni5p-septin interaction is important for septin ring stability and function, which is in turn critical for normal cytokinesis.

  8. Etude des phenomenes dynamiques ultrarapides et des caracteristiques impulsionnelles d'emission terahertz du supraconducteur YBCO

    NASA Astrophysics Data System (ADS)

    Savard, Stephane

    Les premieres etudes d'antennes a base de supraconducteurs a haute temperature critique emettant une impulsion electromagnetique dont le contenu en frequence se situe dans le domaine terahertz remontent a 1996. Une antenne supraconductrice est formee d'un micro-pont d'une couche mince supraconductrice sur lequel un courant continu est applique. Un faisceau laser dans le visible est focalise sur le micro-pont et place le supraconducteur dans un etat hors-equilibre ou des paires sont brisees. Grace a la relaxation des quasiparticules en surplus et eventuellement de la reformation des paires supraconductrices, nous pouvons etudier la nature de la supraconductivite. L'analyse de la cinetique temporelle du champ electromagnetique emis par une telle antenne terahertz supraconductrice s'est averee utile pour decrire qualitativement les caracteristiques de celle-ci en fonction des parametres d'operation tels que le courant applique, la temperature et la puissance d'excitation. La comprehension de l'etat hors-equilibre est la cle pour comprendre le fonctionnement des antennes terahertz supraconductrices a haute temperature critique. Dans le but de comprendre ultimement cet etat hors-equilibre, nous avions besoin d'une methode et d'un modele pour extraire de facon plus systematique les proprietes intrinseques du materiau qui compose l'antenne terahertz a partir des caracteristiques d'emission de celle-ci. Nous avons developpe une procedure pour calibrer le spectrometre dans le domaine temporel en utilisant des antennes terahertz de GaAs bombarde aux protons H+ comme emetteur et detecteur. Une fois le montage calibre, nous y avons insere une antenne emettrice dipolaire de YBa 2Cu3O7-delta . Un modele avec des fonctions exponentielles de montee et de descente du signal est utilise pour lisser le spectre du champ electromagnetique de l'antenne de YBa 2Cu3O7-delta, ce qui nous permet d'extraire les proprietes intrinseques de ce dernier. Pour confirmer la validite du modele

  9. Characterization of Hybrid Ferroelectric/HTS Thin Films for Tunable Microwave Components

    NASA Technical Reports Server (NTRS)

    Winters, M. D.; Mueller, C. H.; Bhasin, K. B.; Miranda, F. A.

    1996-01-01

    Since the discovery of High-Temperature-Superconductors (HTS) in 1986, a diversity of HTS-based microwave components has been demonstrated. Because of their low conductor losses, HTS-based components are very attractive for integration into microwave circuits for space communication systems. Recent advancements have made deposition of ferroelectric thin films onto HTS thin films possible. Due to the sensitivity of the ferroelectric's dielectric constant (epsilon(sub r)) to an externally applied electric field (E), ferroelectric/superconducting structures could be used in the fabrication of low loss, tunable microwave components. In this paper, we report on our study of Ba(0.5)Sr(0.5)TiO3/YBa2Cu3O(7-delta) and Ba(0.08)Sr(0.92)TiO3/YBa2Cu3O(7-delta) ferroelectric/superconducting thin films on lanthanum aluminate (LaAlO3) substrates. For the (Ba:Sr, 0.50:0.50) epitaxial sample, a epsilon(sub r) of 425 and a loss tangent (tan delta) of 0.040 were measured at 298 K, 1.0 MHz, and zero applied E. For the same sample, a epsilon(sub r) of 360 and tan delta of 0.036 were obtained at 77 K, 1.0 MHz, and zero applied E. Variations in epsilon(sub r) from 180 to 360 were observed over an applied E range of 0V/cm less than or equal to E less than or equal to 5.62 x 10(exp 4) V/cm with little change in tan delta. However, the range of epsilon(sub r) variation for the polycrystalline (Ba:Sr, 0.08:0.92) sample over 0V/cm less than or equal to E less than or equal to 4.00 x 10(exp 4) V/cm was only 3.6 percent while tan delta increased markedly. These results indicate that a lack of epitaxy between the ferroelectric and superconducting layers decreases tuning and increases microwave losses.

  10. Solution-based deposition of ultrathin metal oxide films on metal and superconductor surfaces

    NASA Astrophysics Data System (ADS)

    Westwood, Glenn

    Solution chemical methods were used to deposit ultrathin metal oxide films on metal and superconductor surfaces. Platinum-molybdenum oxide films were deposited by spontaneous adsorption and electrodeposition of hexamolybdoplatinate, PtMO6O248-. Spectroscopic characterization by 17O and 195Pt NMR showed that the PtMo6O248- anion is stable in aqueous solution below pH 4. The interaction of this solution stable anion with Au and Ag was characterized by in situ scanning tunneling microscopy, x-ray photoelectron spectroscopy, and cyclic voltammetry. The anion was partially reduced upon adsorption on Ag, but spontaneously adsorbed on Au to form an amorphous surface phase. The electrodeposition of hexamolybdoplatinate on Au electrodes resulted in an electrode surface that was different from the spontaneously adsorbed species, in terms of composition, voltammetry, and reactivity. Cyclic voltammetry was also used to compare the reactivity of these materials for the electrooxidation of methanol. Ultrathin zirconia films were deposited on YBa2Cu3O 7-delta by alternating exposures to tetra n-propyl zirconate, Zr4(OPrn)16, and H2O in n-propanol. Physical and chemical characterization of these films was done by x-ray photoelectron spectroscopy, atomic force microscopy, and cross-section transmission electron microscopy. The zirconia films were determined to be ultrathin (<10 nm) and highly conformal to the surface of YBa2Cu3O7-delta. Metal-insulator-superconductor tunnel junctions fabricated in this fashion were characterized by current-voltage and conductivity-voltage measurements. Solution deposition from Zr4(OPrn) 16 was also used to deposit ultrathin zirconia films on gold, silver, and aluminum surfaces. X-ray photoelectron spectroscopy and atomic force microscopy were used to compare the physical properties of these films. Electrical measurements showed that zirconia films on Ag and Au are not insulating, but aluminum-zirconia-aluminum capacitors fabricated by this method

  11. Thin Film Multilayer Conductor/Ferroelectric Tunable Microwave Components for Communication Applications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Romanofsky, Robert R.; VanKeuls, Frederick W.; Mueller, Carl H.; Treece, Randolph E.; Rivkin, Tania V.

    1997-01-01

    High Temperature Superconductor/Ferroelectric (HTS/FE ) thin film multilayered structures deposited onto dielectric substrates are currently being investigated for use in low loss, tunable microwave components for satellite and ground based communications. The main goal for this technology is to achieve maximum tunability while keeping the microwave losses as low as possible, so as to avoid performance degradation when replacing conventional technology (e.g., filters and oscillators) with HTS/FE components. Therefore, for HTS/FE components to be successfully integrated into current working systems, full optimization of the material and electrical properties of the ferroelectric films, without degrading those of the HTS film; is required. Hence, aspects such as the appropriate type of ferroelectric and optimization of the deposition conditions (e.g., deposition temperature) should be carefully considered. The tunability range as well as the microwave losses of the desired varactor (i.e., tunable component) are also dependent on the geometry chosen (e.g., parallel plate capacitor, interdigital capacitor, coplanar waveguide, etc.). In addition, the performance of the circuit is dependent on the location of the varactor in the circuit and the biasing circuitry. In this paper, we will present our results on the study of the SrTiO3/YBa2Cu3O(7-delta)/LaAl03 (STO/YBCO/LAO) and the Ba(x)Sr(1-x)TiO3/YBa2Cu3O(7-delta)/LaAl03(BSTO/YBCO/ILAO) HTS/FE multilayered structures. We have observed that the amount of variation of the dielectric constant upon the application of a dc electric field is closely related to the microstructure of the film. The largest tuning of the STO/YBCO/LAO structure corresponded to single-phased, epitaxial STO films deposited at 800 C and with a thickness of 500 nm. Higher temperatures resulted in interfacial degradation and poor film quality, while lower deposition temperatures resulted in films with lower dielectric constants, lower tunabilities, and

  12. Partial solubility parameters of lactose, mannitol and saccharose using the modified extended Hansen method and evaporation light scattering detection.

    PubMed

    Peña, M A; Daali, Y; Barra, J; Bustamante, P

    2000-02-01

    The modified extended Hansen method was tested for the first time to determine partial solubility parameters of non-polymeric pharmaceutical excipients. The method was formerly tested with drug molecules, and is based upon a regression analysis of the logarithm of the mole fraction solubility of the solute against the partial solubility parameters of a series of solvents of different chemical classes. Two monosaccharides and one disaccharide (lactose monohydrate, saccharose and mannitol) were chosen. The solubility of these compounds was determined in a series of solvents ranging from nonpolar to polar and covering a wide range of the solubility parameter scale. Sugars do not absorb at the UV-vis region, and the saturated solutions were assayed with a recent chromatographic technique coupled to an evaporative light scattering detector. This technique was suitable to determine the concentration dissolved in most solvents. The modified extended Hansen method provided better results than the original approach. The best model was the four parameter equation, which includes the dispersion delta d, dipolar delta p, acidic delta a and basic delta b partial solubility parameters. The partial solubility parameters obtained, expressed as MPa1/2, were delta d = 17.6, delta p = 28.7, delta h = 19, delta a = 14.5, delta b = 12.4, delta T = 32.8 for lactose, delta d = 16.2, delta p = 24.5, delta h = 14.6, delta a = 8.7, delta b = 12.2, delta T = 32.8 for mannitol and delta d = 17.1, delta p = 18.5, delta h = 13, delta a = 11.3, delta b = 7.6, delta T = 28.4 for saccharose. The high total solubility parameters delta T obtained agree with the polar nature of the sugars. The dispersion parameters delta d are quite similar for the three sugars indicating that the polar delta p and hydrogen bonding parameters (delta h, delta a, delta b) are responsible for the variation in the total solubility parameters delta T obtained, as also found for drugs. The results suggest that the method

  13. Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi(0) Production in Polarized p plus p Collisions at s = 200 GeV

    SciTech Connect

    Adare, A.; Awes, Terry C; Cianciolo, Vince; Enokizono, Akitomo; Read Jr, Kenneth F; Silvermyr, David O; Sorensen, Soren P; Stankus, Paul W; Young, Glenn R; PHENIX, Collaboration

    2009-01-01

    The double helicity asymmetry in neutral pion production for p{sub T} = 1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, {Delta}G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of {mu}{sup 2} = 4 GeV{sup 2} a next to leading order QCD analysis gives {Delta}G{sup [0.02,0.3]} = 0.2, with a constraint of -0.7 < {Delta}G{sup [0.02,0.3]} < 0.5 at {Delta}{chi}{sup 2} = 9 (-3{sigma}) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the {Delta}G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

  14. High-sensitive scanning laser magneto-optical imaging system.

    PubMed

    Murakami, Hironaru; Tonouchi, Masayoshi

    2010-01-01

    A high-sensitive scanning laser magneto-optical (MO) imaging system has been developed. The system is mainly composed of a laser source, galvano meters, and a high-sensitive differential optical-detector. Preliminary evaluation of system performance by using a Faraday indicator with a Faraday rotation coefficient of 3.47 x 10(-5) rad/microm Oe shows a magnetic sensitivity of about 5 microT, without any need for accumulation or averaging processing. Using the developed MO system we have succeeded in the fast and quantitative imaging of a rotationally symmetric magnetic field distribution around an YBa(2)Cu(3)O(7-delta) (YBCO) strip line applied with dc-biased current, and also succeeded in the detection of quantized fine signals corresponding to magnetic flux quantum generation in a superconducting loop of an YBCO Josephson vortex flow transistor. Thus, the developed system enables us not only to do fast imaging and local signal detection but also to directly evaluate both the strength and direction of a magnetic signal.

  15. A K-band Frequency Agile Microstrip Bandpass Filter using a Thin Film HTS/Ferroelectric/dielectric Multilayer Configuration

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred; Miranda, Felix A.

    1998-01-01

    We report on YBa2Cu3O(7-delta) (YBCO) thin film/SrTiO3 (STO) thin film K-band tunable bandpass filters on LaAlO3 (LAO) dielectric substrates. The 2 pole filter has a center frequency of 19 GHz and a 4% bandwidth. Tunability is achieved through the non-linear dc electric field dependence of the relative dielectric constant of STO(epsilon(sub rSTO). A large tunability ((Delta)f/f(sub 0) = (f(sub Vmax) - f(sub 0)/f(sub 0), where f(sub 0) is the center frequency of the filter at no bias and f(sub Vmax) is the center frequency of the filter at the maximum applied bias) of greater than 10% was obtained in YBCO/STO/LAO microstrip bandpass filters operating below 77 K. A center frequency shift of 2.3 GHz (i.e., a tunability factor of approximately 15%) was obtained at a 400 V bipolar dc bias, and 30 K, with minimal degradation in the insertion loss of the filter. This paper addresses design, fabrication and testing of tunable filters based on STO ferroelectric thin films. The performance of the YBCO/STO/LAO filters is compared to that of gold/STO/LAO counterparts.

  16. Tetragonal YBaFe{sub 4}O{sub 7.0}: a stoichiometric polymorph of the '114' ferrite family

    SciTech Connect

    Duffort, V.; Caignaert, V.; Pralong, V.; Barrier, N.; Raveau, B.; Avdeev, M.; Zheng, H.; Mitchell, J. F.

    2012-03-01

    The exploration of the phase diagram of the ferrite YBaFe{sub 4}O{sub 7+{delta}} versus the oxygen content {delta} and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4{sup -}3m), which is observed up to 600 C and for 0 < {delta} {le} 0.65, a stoichiometric tetragonal form ({delta} = 0) is isolated below 300 C that is stable only in the absence of oxidizing atmosphere. The resolution of the structure of this new YBaFe{sub 4}O{sub 7.0} form, from combined neutron and synchrotron data, in the space group I4{sup -}, shows significant displacements of the atoms with respect to the cubic form, especially concerning the oxygen atoms surrounding the barium cations. The decrease of several Ba-O distances around the underbonded barium cations is explained by the existence of hybridized Ba{sup (2-{delta})+}-O{sup 2-}-Fe{sup (2+{delta})+} bonds, in agreement with Moessbauer spectroscopy. The role of coulombic repulsions in the [Fe{sub 4}O] and [Fe{sub 4}] tetrahedra of the [Fe{sub 4}]{infinity} sublattice on the structural transition is also discussed.

  17. Late-Glacial to Late-holocene Shifts in Global Precipitation Delta(sup 18)O

    NASA Technical Reports Server (NTRS)

    Jasechko, S.; Lechler, A.; Pausata, F.S.R.; Fawcett, P.J.; Gleeson, T.; Cendon, D.I.; Galewsky, J.; LeGrande, A. N.; Risi, C.; Sharp, Z. D.; Welker, J. M.; Werner, M.; Yoshimura, K.

    2015-01-01

    Reconstructions of Quaternary climate are often based on the isotopic content of paleo-precipitation preserved in proxy records. While many paleo-precipitation isotope records are available, few studies have synthesized these dispersed records to explore spatial patterns of late-glacial precipitation delta(sup 18)O. Here we present a synthesis of 86 globally distributed groundwater (n 59), cave calcite (n 15) and ice core (n 12) isotope records spanning the late-glacial (defined as 50,000 to 20,000 years ago) to the late-Holocene (within the past 5000 years). We show that precipitation delta(sup 18)O changes from the late-glacial to the late-Holocene range from -7.1% (delta(sup 18)O(late-Holocene) > delta(sup 18)O(late-glacial) to +1.7% (delta(sup 18)O(late-glacial) > delta(sup 18)O(late-Holocene), with the majority (77) of records having lower late-glacial delta(sup 18)O than late-Holocene delta(sup 18)O values. High-magnitude, negative precipitation delta(sup 18)O shifts are common at high latitudes, high altitudes and continental interiors.

  18. JPRS report: Science and technology. Central Eurasia: Physics and mathematics

    NASA Astrophysics Data System (ADS)

    1993-12-01

    Translations in the area of science and technology are presented, and the topics covered include the following: (1) spectrophotometric unit to measure absorption of IR, visible, and UV laser radiation by molecular gases; (2) transparency of the surface atmosphere to the radiation of a pulsed CO2 laser; (3) laser beam propagation along vertical and slanted extended paths through a turbulent atmosphere; (4) change in the index of refraction in the active zone of powerful laser radiation; (5) dependence of superconducting transition temperature in high temperature superconductor YBa2Cu3O(7-delta) on electron structure parameters of CuO2 layers; (6) distribution of normal and plane components of magnetic induction in thin HTSC films; (7) distribution of superconducting currents during remagnetization of thin YBCuO film in normal field; (8) study of surface currents in HTSC monocrystals and thin films; (9) volt-ampere characteristics of ceramic superconductors Bi2Sr2Ca2Cu3O(8+delta); (9) microstructure formation of high-temperature superconducting films using laser holography; (10) superconducting induction switch controlled by pulsed magnetic field; and (11) possibility of using high-power microwaves in technology.

  19. The mechanism of high-T(sub c) superconductivity due to bound hole mediators: Relationship to ferroelectricity

    NASA Technical Reports Server (NTRS)

    Vezzoli, G. C.; Stanley, William

    1990-01-01

    The mediation by bound holes creating Cooper pairing in high T(sub c) superconductors has its origin in charge transfer excitations on the multivalence cation (virtual excitions) and in bound excitions or polarizations associated with the oxygen 2p electrons. These phenomena are produced and/or enhanced by a high internal electric field which is itself created by virtue of the unique crystal structures and polyhedral building blocks of high T(sub c) materials. The polarizations which can create oxygen holes (in addition to excitions) may be due to simply the internal electric field or to polaronic and electron-deficient bond behavior. This gives rise to two energy-dependent oxygen bands near the Fermi level. The magnitude and direction of the internal electric fields were calculated for Y1Ba2Cu3O(7-delta) (1-2-3) and show strong z-direction fields at the Cu(2), O2, and O3 sites and an even stronger -z direction field at the O4 site. The field calculations also show why electrical conductivity in the 1-2-3 material is essentially in the base plane of the CuO5 pyramid (the CuO2 plane).

  20. Role of prostaglandins in marihuana-induced bronchodilation.

    PubMed

    Laviolette, M; Bélanger, J

    1986-01-01

    In vitro evidence suggests that physiological effects of marihuana may be mediated by prostaglandins via the stimulation of phospholipase A2. To verify if marihuana could act by this route in vivo, we tested the effects of acetylsalicylic and mefenamic acids, inhibitors of cyclooxygenase, on marihuana-induced bronchodilation and tachycardia. In 11 healthy volunteers, marihuana smoking (7 mg/kg, 1.7% delta 9-tetrahydrocannabinol) produced a significant increase in specific airway conductance (from 0.262 +/- 0.033 to 0.360 +/- 0.050 s-1 X cm H2O-1, mean +/- SE, p less than 0.01), forced expiratory volume in 1 s (4.02 +/- 0.22-4.27 +/- 0.25 liter, p less than 0.05) and heart rate (73.2 +/- 2.0-108.5 +/- 5.2 beats/min, p less than 0.001). In a second session, acetylsalicylic or mefenamic acid was taken for 30 h before marihuana smoking. No inhibition of marihuana-induced increase of specific airway conductance, forced expiratory volume in 1 s and heart rate was found. These findings suggest that the bronchodilation and the tachycardia induced by marihuana smoking in humans are not mediated by prostaglandins.

  1. The origin of persistent spin dynamics and residual entropy in the stuffed spin ice Ho2.3Ti1.7O7-?

    SciTech Connect

    Ehlers, Georg

    2007-01-01

    The so-called 'spin ices' form when exchange interactions, crystal fields, and dipolar interactions are in a delicate balance. This gives rise to a ground state which has a considerable amount of residual spin entropy, much like the proton entropy in water ice through the freezing transition. Recently, 'stuffed' spin ices have provided a means to probe how delicate a balance is needed to stabilize the disordered ground state. Surprisingly, it is found that an increase of the density of spins results in very little change in the residual entropy, which leads to the interesting idea that residual entropy states might be more common than once believed for magnetism. In this communication, we detail the crystal growth of stuffed spin ice Ho{sub 2.3}Ti{sub 1.7}O{sub 7-{delta}}, and we complete neutron scattering experiments to observe how the spins order at low temperatures. It is found that even with this large perturbation, the system still has some key signatures of the spin ice state, but the spin dynamics is significantly altered. With this new data, an explanation emerges for the zero-point entropy in the stuffed spin ices.

  2. Space qualified hybrid superconductor/semiconductor planar oscillator circuit

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Chorey, C. M.; Romanofsky, R. R.; Bhasin, K. B.

    1995-01-01

    We report on the space qualification of a hybrid superconductor/semiconductor planar local oscillator (LO) at 8.4 GHz. This oscillator was designed, fabricated, and tested as a component for the High Temperature Superconductivity Space Experiment 2 (HTSSE-2). The LO consisted of a GaAs MESFET and microstrip circuitry patterned onto a YBa2Cu3O(7-delta) high temperature superconducting (HTS) thin film on a 1.0 x 1.0 sq cm lanthanum aluminate (LaAlO3) substrate. At 77 K, this oscillator achieved power output levels up to 10 dBm into a 50 Ohm load. When incorporated into a full cryogenic receiver, the LO provided output powers within 0.0-3.0 dBm with less than 50 mW of dc power dissipation. Space qualification data on the sensitivity of the HTS films to the processing steps involved in the fabrication of HTS-based components are presented. Data on ohmic contacts, strength of wire bonds made to such contacts, and aging effects as well as vibration test results are discussed.

  3. Irreversible properties of YBCO thick films deposited by liquid phase epitaxy on single crystalline substrates

    NASA Astrophysics Data System (ADS)

    Vostner, A.; Tönies, S.; Weber, H. W.; Cheng, Y. S.; Kurumovic, A.; Evetts, J. E.; Mennema, S. H.; Zandbergen, H. W.

    2003-10-01

    We report on the field and temperature dependence of the critical transport current density Jc, the angular dependence of the transport current at various external magnetic fields and the irreversibility fields in YBa2Cu3O7-delta (Y-123) thick films prepared by liquid phase epitaxy (LPE). A comparison of the irreversible properties between specimens produced with and without silver additions to the melt is also presented. Transmission electron microscopy (TEM) was employed to obtain information on the correlation between the transport properties and the microstructure. The samples were deposited either directly on NdGaO3 (NGO) or on seeded (100) MgO substrates, where a 200 nm thin YBCO film deposited by pulsed laser deposition (PLD) acts as seed layer for the LPE process. The final thickness of the Y-123 layer is of the order of 1 µm for the NGO and between 2 and 10 µm for the MgO samples. The critical current densities reach 3 × 109 A m-2 at zero field and 77 K in the best case.

  4. Particle Engulfment and Pushing Micro-Gravity Experiments and Mathematical Modeling

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Catalina, A. V.; Juretzko, F.; Mukherjee, S.; Sen, S.

    2000-01-01

    The phenomenon of interaction of particles with solid-liquid interfaces that results in particle engulfment or pushing (PEP) has been Studied since mid 1960's. While the original interest stemmed from geology applications (frost heaving in soil), it was recognized early that understanding particle behavior at solidifying interfaces mi ht yield 9 practical benefits in other fields. In metallurgical applications the issue is the location of particles with respect to grain boundaries at the end of solidification. Considerable amount of experimental and theoretical research was lately focused on applications to metal matrix composites produced by casting; or spray forming techniques. Another application of PEP is in the growing of Y1Ba2CU3O7-delta(123) superconductor crystals from an undercooled liquid. The oxide melt contains Y2Ba1CU1O5 (211) precipitates, which act as flux pinning sites. The paper presents results of PEP micro-gravity research performed by the authors on two shuttle missions using metallic and polymeric materials. In addition. a discussion on the theoretical aspects of the physics of PEP is offered. Analytical and numerical models for planar solidification interfaces developed by the authors are used to explain the experimental results. Shortcomings of steady-state models are emphasized. A numerical model that includes the effect of the solutal field and of natural convection is introduced. A discussion of phenomena associated with dendritic solidification based on experimental observations is also offered. A mechanism of engulfment is proposed.

  5. Progress in Nanoengineered Microstructures for Tunable High-Current, High-Temperature Superconducting Wires

    SciTech Connect

    Holesinger, T. G.; Civale, L.; Maiorov, B.; Feldmann, D. M.; Coulter, Yates; Miller, D. J.; Maroni, Victor A.; Chen, Zhijun; Larbalestier, D. C.; Feenstra, Roeland; Li, Xiaoping; Huang, Y.; Kodenkandath, Thomas; Zhang, W.; Rupich, Marty; Malozemoff, Alex

    2008-01-01

    High critical current densities (J{sub c}) in thick films of the Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO, {Tc}{approx}92 K) superconductor directly depend upon the types of nanoscale defects and their densities within the films. A major challenge for developing a viable wire technology is to introduce nanoscale defect structures into the YBCO grains of the thick film suitable for flux pinning and the tailoring of the superconducting properties to specific, application-dependent, temperature and magnetic field conditions. Concurrently, the YBCO film needs to be integrated into a macroscopically defect-free conductor in which the grain-to-grain connectivity maintains levels of inter-grain J{sub c} that are comparable to the intra-grain J{sub c}. That is, high critical current (I{sub c}) YBCO coated conductors must contain engineered in homogeneities on the nanoscale, while being homogeneous on the macroscale. An analysis is presented of the advances in high-performance YBCO coated-conductors using chemical solution deposition (CSD) based on metal trifluoroacetates and the subsequent processing to nano-engineer the microstructure for tunable superconducting wires. Multi-scale structural, chemical, and electrical investigations of the CSD film processes, thick film development, key microstructural features, and wire properties are presented. Prospects for further development of much higher I{sub c} wires for large-scale, commercial application are discussed within the context of these recent advances.

  6. Hysteresis and relaxation in TlBa2Ca2Cu3Oy superconducting polycrystals

    NASA Astrophysics Data System (ADS)

    Batista-Leyva, A. J.; Cobas, R.; Orlando, M. T. D.; Altshuler, E.

    2003-08-01

    We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa2Ca2Cu3Oy (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa2Cu3O7-delta (YBCO), (Hg, Re)Ba2Ca2Cu3O8+delta (HBCCO) and (Bi, Pb)2Sr2Ca2Cu3O10-delta (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model.

  7. Point contact spectroscopy in oriented La[sub 2-x]Sr[sub x]CuO[sub 4] superconductors; energy gap and Fermi velocity

    SciTech Connect

    Hass, N. ); Deutscher, G. ); Revcolevschi, A.; Dhalenne, G. )

    1994-08-01

    Point contact measurements in oriented La[sub 2-x]Sr[sub x]CuO[sub 4] samples were performed using metal tips. The current-voltage curves measured along the CuO plane direction (ab) are characteristic of the Andreev reflection phenomenon. The superconducting energy gap in the ab plane is determined, [Delta][sub ab] = 6 [+-] 1 meV, with a possibility for the existence of a lower subgap in the plane. A lower limit for the Fermi velocity in the CuO planes is also set by the measurements; V[sub F] [ge] 6 [times] 10[sup 7] cm/sec, which is significantly higher than the average velocity obtained by band calculations. The results are discussed in the context of different models for superconductivity in the layered oxides. In particular, the authors raise the possibility of an anisotropic gap parameter which may indicate a nonstandard s-wave pairing in La[sub 2-x]Sr[sub x]CuO[sub 4]. A comparison with previous results obtained on YBa[sub 2]Cu[sub 3]O[sub 7-[delta

  8. Observations of YBCO superconductors under a low-temperature scanning electron microscope

    SciTech Connect

    Vyas, A.; Lam, C. C.; Li, S. H.; Lam, H. S.; Fung, P. C. W.

    1999-09-01

    Microscopic analyses have been performed on YBCO superconductors with Ca-doping and Gd-doping as a function of temperature by employing a low-temperature scanning electron microscope (LTSEM). On lowering temperature of the sample from 300 K to 90 K, the brightness of the SEM image changes due to the change in resistance of the sample. For the underdoped cuprates Y{sub 1-x}Ca{sub x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}}, with x=0.2, the pseudo gap in the normal state is opened at a temperature T* which far below the critical temperature T{sub c} of the superconductor. The opening of the pseudo gap has directly been observed under LTSEM (temperature fluctuating in the range of {+-}5 K). At temperature T* the formation of quasi-particles takes place, thus a sudden brightness change in the SEM image is observed. The results of these measurements are compared with the four-point probe measurements. It is proved that the data of these two measurements are quite in agreement with each other.

  9. Hyperosmotic stress induces metacaspase- and mitochondria-dependent apoptosis in Saccharomyces cerevisiae.

    PubMed

    Silva, Rui D; Sotoca, Roberto; Johansson, Björn; Ludovico, Paula; Sansonetty, Filipe; Silva, Manuel T; Peinado, José M; Côrte-Real, Manuela

    2005-11-01

    During the last years, several reports described an apoptosis-like programmed cell death process in yeast in response to different environmental aggressions. Here, evidence is presented that hyperosmotic stress caused by high glucose or sorbitol concentrations in culture medium induces in Saccharomyces cerevisiae a cell death process accompanied by morphological and biochemical indicators of apoptotic programmed cell death, namely chromatin condensation along the nuclear envelope, mitochondrial swelling and reduction of cristae number, production of reactive oxygen species and DNA strand breaks, with maintenance of plasma membrane integrity. Disruption of AIF1 had no effect on cell survival, but lack of Yca1p drastically reduced metacaspase activation and decreased cell death indicating that this death process was associated to activation of this protease. Supporting the involvement of mitochondria and cytochrome c in caspase activation, the mutant strains cyc1Deltacyc7Delta and cyc3Delta, both lacking mature cytochrome c, displayed a decrease in caspase activation associated to increased cell survival when exposed to hyperosmotic stress. These findings indicate that hyperosmotic stress triggers S. cerevisiae into an apoptosis-like programmed cell death that is mediated by a caspase-dependent mitochondrial pathway partially dependent on cytochrome c.

  10. CDC7/DBF4 functions in the translesion synthesis branch of the RAD6 epistasis group in Saccharomyces cerevisiae.

    PubMed Central

    Pessoa-Brandão, Luis; Sclafani, Robert A

    2004-01-01

    CDC7 and DBF4 encode the essential Cdc7-Dbf4 protein kinase required for DNA replication in eukaryotes from yeast to human. Cdc7-Dbf4 is also required for DNA damage-induced mutagenesis, one of several postreplicational DNA damage tolerance mechanisms mediated by the RAD6 epistasis group. Several genes have been determined to function in separate branches within this group, including RAD5, REV3/REV7 (Pol zeta), RAD30 (Pol eta), and POL30 (PCNA). An extensive genetic analysis of the interactions between CDC7 and REV3, RAD30, RAD5, or POL30 in response to DNA damage was done to determine its role in the RAD6 pathway. CDC7, RAD5, POL30, and RAD30 were found to constitute four separate branches of the RAD6 epistasis group in response to UV and MMS exposure. CDC7 is also shown to function separately from REV3 in response to MMS. However, they belong in the same pathway in response to UV. We propose that the Cdc7-Dbf4 kinase associates with components of the translesion synthesis pathway and that this interaction is dependent upon the type of DNA damage. Finally, activation of the DNA damage checkpoint and the resulting cell cycle delay is intact in cdc7Delta mcm5-bob1 cells, suggesting a direct role for CDC7 in DNA repair/damage tolerance. PMID:15342501

  11. Experimental Investigation of High Temperature Superconducting Imaging Surface Magnetometry

    SciTech Connect

    Espy, M.A.; Matlachov, A.N.; Kraus, R.H., Jr.

    1999-06-21

    The behavior of high temperature superconducting quantum interference devices (SQUIDs) in the presence of high temperature superconducting surfaces has been investigated. When current sources are placed close to a superconducting imaging surface (SIS) an image current is produced due to the Meissner effect. When a SQUID magnetometer is placed near such a surface it will perform in a gradiometric fashion provided the SQUID and source distances to the SIS are much less than the size of the SIS. We present the first ever experimental verification of this effect for a high temperature SIS. Results are presented for two SQUID-SIS configurations, using a 100 mm diameter YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} disc as the SIS. These results indicate that when the current source and sensor coil (SQUID) are close to the SIS, the behavior is that of a first-order gradiometer. The results are compared to analytic solutions as well as the theoretical predictions of a finite element model.

  12. High T{sub c} superconducting asymmetric gradiometer for biomagnetic applications

    SciTech Connect

    Kouznetsov, K. A.; Borgmann, J.; Clarke, John

    2000-07-01

    We describe a high transition temperature superconducting, first-order gradiometer intended for biomagnetic measurements in an unshielded environment. The gradiometer involves a single-layer, planar flux transformer with two loops of unequal size, the smaller of which is inductively coupled to the pickup loop of a directly coupled magnetometer. In this configuration, the presence of the flux transformer reduces the sensitivity of the magnetometer by only about 5%. The flux transformer is patterned in a thin film of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} deposited on a 100 mm diam wafer, and has a baseline of 48 mm. The flux transformer and magnetometer substrates are permanently bonded together in a flipchip arrangement. The common mode rejection of uniform magnetic field fluctuations in any direction is better than 1 part per 100. The outputs of two such gradiometers are subtracted to form a second-order gradiometer, which rejects first-order gradient fluctuations to about 1 part in 100. With the aid of three orthogonally mounted magnetometers, one can reduce the response of the gradiometers to uniform field fluctuations to below 100 ppm. This system is used to detect magnetic signals from the human heart in an unshielded environment. (c) 2000 American Institute of Physics.

  13. Fixed-frequency and Frequency-agile (au, HTS) Microstrip Bandstop Filters for L-band Applications

    NASA Technical Reports Server (NTRS)

    Saenz, Eileen M.; Subramanyam, Guru; VanKeuls, Fred W.; Chen, Chonglin; Miranda, Felix A.

    2001-01-01

    In this work, we report on the performance of a highly selective, compact 1.83 x 2.08 cm(exp 2) (approx. 0.72 x 0.82 in(exp 2) microstrip line bandstop filter of YBa2CU3O(7-delta) (YBCO) on LaAlO3 (LAO) substrate. The filter is designed for a center frequency of 1.623 GHz for a bandwidth at 3 dB from reference baseline of less than 5.15 MHz, and a bandstop rejection of 30 dB or better. The design and optimization of the filter was performed using Zeland's IE3D circuit simulator. The optimized design was used to fabricate gold (Au) and High-Temperature Superconductor (HTS) versions of the filter. We have also studied an electronically tunable version of the same filter. Tunability of the bandstop characteristics is achieved by the integration of a thin film conductor (Au or HTS) and the nonlinear dielectric ferroelectric SrTiO3 in a conductor/ferroelectric/dielectric modified microstrip configuration. The performance of these filters and comparison with the simulated data will be presented.

  14. Superconducting current in hybrid structures with an antiferromagnetic interlayer

    SciTech Connect

    Zaitsev, A. V. Ovsyannikov, G. A.; Constantinian, K. Y. Kislinskii, Yu. V.; Shadrin, A. V.; Borisenko, I. V.; Komissinskiy, P. V.

    2010-02-15

    It is shown experimentally that the superconducting current density in Nb/Au/Ca{sub 1-x}Sr{sub x}CuO{sub 2}/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} hybrid superconducting heterostructures with a Ca{sub 1-x}Sr{sub x}CuO{sub 2} anti-ferromagnetic (AF) cuprate interlayer is anomalously high for interlayer thicknesses d{sub M} = 10-50 nm and the characteristic damping length for superconducting correlations is on the order of 10 nm. The experimental results are explained on the basis of theoretical analysis of a junction of two superconductors (S' and S) connected by a magnetic multilayer with the AF ordering of magnetization in the layers. It is shown that with such a magnetization ordering, anomalous proximity effect determined by the singlet component of the condensate wavefunction may take place. As a result, the critical currents in S'/I/AF/S and S'/I/N/S structures (I denotes an insulator, and N, the normal metal) may coincide in order of magnitude even when the thickness of the AF interlayer considerably exceeds the decay length of the condensate wavefunction in ferromagnetic layers.

  15. Search for Cosmic-Ray-Induced Gamma-Ray Emission in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bloom, E. D.; Bonamente, E.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cavazzuti, E.; Chaves, R. C. G.; Kuss, M.; Pesce-Rollins, M.; Sgro, C.; Spandre, G.; Tinivella, M.

    2014-01-01

    Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into gamma rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended gamma-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7 delta, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R(sub 200), to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the gamma-ray flux from individual clusters in our sample.

  16. Measurements on Subscale Y-Ba-Cu-O Racetrack Coils at 77 K and Self-Field

    SciTech Connect

    Wang, X.; Caspi, S.; Cheng, D. W.; Dietderich, D. R.; Felice, H.; Ferracin, P.; Godeke, A.; Joseph, J. M.; Lizarazo, J.; Prestemon, S. O.; Sabbi, G.

    2009-10-19

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes carry significant amount of current at fields beyond the limit of Nb-based conductors. This makes the YBCO tapes a possible conductor candidate for insert magnets to increase the bore field of Nb{sub 3}Sn high-field dipoles. As an initial step of the YBCO insert technology development, two subscale racetrack coils were wound using Kapton-insulated commercial YBCO tapes. Both coils had two layers; one had 3 turns in each layer and the other 10 turns. The coils were supported by G10 side rails and waxed strips and not impregnated. The critical current of the coils was measured at 77 K and self-field. A 2D model considering the magnetic-field dependence of the critical current was used to estimate the expected critical current. The measured results show that both coils reached 80%-95% of the expected values, indicating the feasibility of the design concept and fabrication process.

  17. Modified two-fluid model of conductivity for superconducting surface resistance calculation. Master's thesis

    SciTech Connect

    Linden, D.S.

    1993-05-01

    The traditional two-fluid model of superconducting conductivity was modified to make it accurate, while remaining fast, for designing and simulating microwave devices. The modification reflects the BCS coherence effects in the conductivity of a superconductor, and is incorporated through the ratio of normal to superconducting electrons. This modified ratio is a simple analytical expression which depends on frequency, temperature and material parameters. This modified two-fluid model allows accurate and rapid calculation of the microwave surface impedance of a superconductor in the clean and dirty limits and in the weak- and strong-coupled regimes. The model compares well with surface resistance data for Nb and provides insight into Nb3Sn and Y1Ba2Cu3O(7-delta). Numerical calculations with the modified two-fluid model are an order of magnitude faster than the quasi-classical program by Zimmermann (1), and two to five orders of magnitude faster than Halbritter's BCS program (2) for surface resistance.

  18. Progress in Wind-and-React Bi-2212 Accelerator Magnet Technology

    SciTech Connect

    Godeke, A.; Cheng, D.; Dietderich, D.R.; Hannaford, C.R.; Prestemon, S.O.; Sabbi, G.; Wang, X.; Hikichi, Y.; Nishioka, J.; Hasegawa, T.

    2009-08-16

    We report on our progress in the development of the technology for the application of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x}(Bi-2212) in Wind-and-React accelerator magnets. A series of superconducting subscale coils has been manufactured at LBNL and reacted at the wire manufacturer SWCC. Selected coils are impregnated and tested in self-field, even though the coils exhibited leakage during the partial melt heat treatment. Other coils have been disassembled after reaction and submitted to critical current (Ic) tests on individual cable sections. We report on the results of the current carrying capacity of the coils. Voltage-current (VI) transitions were reproducibly measured up to a quench currents around 1400 A, which is 25% of the expected performance. The results indicate that the coils are limited by the inner windings. We further compare possibilities to use Bi-2212 and Nb{sub 3}Sn tilted solenoid, and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) racetrack inserts to increase the magnetic field in HD2, a 36 mm bore Nb{sub 3}Sn dipole magnet which recently achieved a bore magnetic field of 13.8 T. The application of Bi-2212 and/or YBCO in accelerator type magnets, if successful, will open the road to higher magnetic fields, far surpassing the limitations of Nb{sub 3}Sn magnet technology.

  19. Magneto-torque measurements on single crystal yttrium barium copper oxide and flux jump avalanches

    NASA Astrophysics Data System (ADS)

    Hope, Andrew P.

    The phase diagram of the high temperature superconductors has been of much interest since their discovery, especially within the vortex state. The high temperature superconductors have a layered nature to their crystalline structure, which leads to a magnetic field angular dependence of the vortex state. Included in this angular dependence is a torque which tends to align layers parallel to the applied field. A staircase pattern to the vorticles can also occur when the applied magnetic field is aligned within a certain angular regime, which is nearly parallel to the layers. The staircase pattern forms from altering "Abrikosov" vortices, aligned orthogonal to the crystalline layers; and "Josephson" vortices, aligned parallel to the crystalline layers. A series of avalanche-like jumps are observed in torque measurements within the vortex state of single crystals of the high temperature superconductor YBasb2Cusb3Osb{7-delta}. Emerging as a saw-tooth pattern in torque versus field orientation in a restricted angular regime, these jumps are discontinuous on our most resolute angular scale. While reminiscent of the classical flux jump instability, the present jumps are instead proposed to arise from a collaboration between twin boundary pinning and the staircase vortex structure.

  20. Enhancement of Flux Pinning and Critical Currents in YBa2Cu3O7-δ Films by Nano-Scale Iridium Pretreatment of Substrate Surfaces

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Gapud, Albert Agcaoili; Kang, Sukill; Christen, Hans M; Leonard, Keith J; Martin, Patrick M; Thompson, James R; Christen, David K; Meng, R.; Rusakova, I.; Chu, C. W.; Johansen, T. H.

    2005-01-01

    We have acquired positive results in a controlled study to investigate the effects of substrate surface modification on the growth-induced flux-pinning nanostructures in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films. Nanoscale iridium (Ir) particles were applied to single-crystal SrTiO{sub 3} substrate surfaces using dc-magnetron sputtering. Superconducting properties of YBCO films grown on the Ir-modified substrates, measured by transport and magneto-optical imaging, have shown substantial improvement in the critical current densities (J{sub c}) at 77 K over those on untreated, control substrates. Results also show a nearly uniform enhancement of J{sub c} over all orientations of magnetic field. Present results are found to be consistent with cross-sectional transmission electron microscopy investigations. Ultimately, the objective of this approach is to produce enhancements in the properties of coated conductors by a simple pretreatment of the substrate surface.

  1. Anisotropic Nonmonotonic Behavior of the Superconducting Critical Current in Thin YBa2Cu3O7-δ Films on Vicinal SrTiO3 Surfaces

    SciTech Connect

    Cantoni, Claudia; Verebelyi, Darren; Specht, Eliot D; Budai, John D; Christen, David K

    2005-01-01

    The critical current density of epitaxial YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films grown on vicinal SrTiO{sub 3} substrates was investigated by electrical transport measurements along and across the steps of the SrTiO{sub 3} surface for a range of temperatures of 10 to 85 K and in applied magnetic fields varying from 0 to 14 T. For vicinal angles of 4{sup o} and 8{sup o}, we found evidence of enhanced pinning in the longitudinal direction at low magnetic fields for a wide region of temperatures and attribute this phenomenon to antiphase boundaries in the YBCO film. The transverse J{sub c} data showed a peak in the J{sub c}(H) curve at low magnetic fields, which was explained on the basis of magnetic interaction between Abrikosov and Abrikosov-Josephson vortices. The in-plane J{sub c} anisotropy observed for vicinal angles of 0.4{sup o} was reversed with respect to the 8{sup o} and 4{sup o} samples. This phenomenon was interpreted on the basis of strain induced in the YBCO film by the stepped substrate's surface.

  2. Normal Liver Tissue Density Dose Response in Patients Treated With Stereotactic Body Radiation Therapy for Liver Metastases

    SciTech Connect

    Howells, Christopher C.; Stinauer, Michelle A.; Diot, Quentin; Westerly, David C.; Schefter, Tracey E.; Kavanagh, Brian D.; Miften, Moyed

    2012-11-01

    Purpose: To evaluate the temporal dose response of normal liver tissue for patients with liver metastases treated with stereotactic body radiation therapy (SBRT). Methods and Materials: Ninety-nine noncontrast follow-up computed tomography (CT) scans of 34 patients who received SBRT between 2004 and 2011 were retrospectively analyzed at a median of 8 months post-SBRT (range, 0.7-36 months). SBRT-induced normal liver tissue density changes in follow-up CT scans were evaluated at 2, 6, 10, 15, and 27 months. The dose distributions from planning CTs were mapped to follow-up CTs to relate the mean Hounsfield unit change ({Delta}HU) to dose received over the range 0-55 Gy in 3-5 fractions. An absolute density change of 7 HU was considered a significant radiographic change in normal liver tissue. Results: Increasing radiation dose was linearly correlated with lower post-SBRT liver tissue density (slope, -0.65 {Delta}HU/5 Gy). The threshold for significant change (-7 {Delta}HU) was observed in the range of 30-35 Gy. This effect did not vary significantly over the time intervals evaluated. Conclusions: SBRT induces a dose-dependent and relatively time-independent hypodense radiation reaction within normal liver tissue that is characterized by a decrease of >7 HU in liver density for doses >30-35 Gy.

  3. Shape dependence of the sawtooth instability and neoclassical tearing modes in ECH heated TCV plasmas

    NASA Astrophysics Data System (ADS)

    Reimerdes, H.; Goodman, T. P.; Pochelon, A.; Sauter, O.; Henderson, M. A.; Martynov, An.

    2000-10-01

    The TCV tokamak (R=0.88m, a=0.25m, B=1.43T) was designed to produce a large variety of plasma shapes (kappa<2.7, -0.7< delta<1.0 already achieved). Together with a flexible electron cyclotron heating (ECH) system, with a total of 2.7MW of heating power, TCV is particularly suited for the analysis of MHD instabilities. The sawtooth instability is observed to depend strongly on the shape of the poloidal plasma cross section. Systematic scans of elongation (kappa), and triangularity, (delta), show particularly small and brief sawteeth at low delta and at high kappa. The amplification of this shaping effect by central ECH, which increases or decreases the sawtooth period depending on the plasma shape, is linked to the role of ideal or resistive MHD in triggering the sawtooth crash. The experimental central pressure is consistent with numerical and analytical predictions for the ideal internal kink stability. Neoclassical tearing modes have been identified in ECH heated low density discharges. The island has an m/n=2/1 structure and the evolution of its width is well described by the modified Rutherford equation. High local pressure gradients are deemed responsible for the destabilization of the neoclassical mode, which could be avoided by a broadening of the power deposition profile. In TCV, the seed island is usually provided by a conventional tearing mode requiring the reconciliation of conventional and neoclassical tearing for an accurate description.

  4. Glass precursor approach to high-temperature superconductors

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1992-01-01

    The available studies on the synthesis of high T sub c superconductors (HTS) via the glass precursor approach were reviewed. Melts of the Bi-Sr-Ca-Cu-O system as well as those doped with oxides of some other elements (Pb, Al, V, Te, Nb, etc.) could be quenched into glasses which, on further heat treatments under appropriate conditions, crystallized into the superconducting phase(s). The nature of the HTS phase(s) formed depends on the annealing temperature, time, atmosphere, and the cooling rate and also on the glass composition. Long term annealing was needed to obtain a large fraction of the 110 K phase. The high T sub c phase did not crystallize out directly from the glass matrix, but was preceded by the precipitation of other phases. The 110 K HTS was produced at high temperatures by reaction between the phases formed at lower temperatures resulting in multiphase material. The presence of a glass former such as B2O3 was necessary for the Y-Ba-Cu-O melt to form a glass on fast cooling. A discontinuous YBa2Cu3O(7-delta) HTS phase crystallized out on heat treatment of this glass. Attempts to prepare Tl-Ba-Ca-Cu-O system in the glassy state were not successful.

  5. Implication of fetal SMN2 expression in type I SMA pathogenesis: protection or pathological gain of function?

    PubMed

    Soler-Botija, Carolina; Cuscó, Ivón; Caselles, Lídia; López, Eva; Baiget, Montserrat; Tizzano, Eduardo F

    2005-03-01

    Spinal muscular atrophy (SMA) is caused by mutations in the survival motor neuron gene 1 (SMN1). The SMN2 gene, which is the highly homologous SMN1 copy that is present in all the patients, is unable to prevent the disease. Most of the SMN1 transcript is full-length, whereas a substantial proportion of the SMN2 transcript lacks exon 7 (delta7). We characterized the developmental expression of SMN2 by comparing control and SMA fetuses. The control spinal cord revealed the highest amount of FL SMN, most of which was of SMN1 origin. When analyzing the SMA spinal cord transcripts, we detected a considerable reduction in the FL/delta7 ratios due to a decrease in the FL and an increase in delta7 isoform. After immunoblot and immunohistochemistry analyses, we found that the amount of SMN2 protein in the SMA spinal cord and muscle was lower than in the controls. However, the results of the expression of SMN2 in intestine, lung, adrenal gland, kidney, and eye, which are unaffected by the disease, were the same in controls and SMA samples. In these tissues, SMN2 may compensate for the absence of SMN1, whereas in SMA motor neurons, a cell-specific dysregulation of the SMN2 expression could favor the onset of the acute form of the disease.

  6. Sti1 and Cdc37 can stabilize Hsp90 in chaperone complexes with a protein kinase.

    PubMed

    Lee, Paul; Shabbir, Arsalan; Cardozo, Christopher; Caplan, Avrom J

    2004-04-01

    Hsp90 functions in association with several cochaperones for folding of protein kinases and transcription factors, although the relative contribution of each to the overall reaction is unknown. We assayed the role of nine different cochaperones in the activation of Ste11, a Saccharomyces cerevisiae mitogen-activated protein kinase kinase kinase. Studies on signaling via this protein kinase pathway was measured by alpha-factor-stimulated induction of FIG1 or lacZ, and repression of HHF1. Several cochaperone mutants tested had reduced FIG1 induction or HHF1 repression, although to differing extents. The greatest defects were in cpr7Delta, sse1Delta, and ydj1Delta mutants. Assays of Ste11 kinase activity revealed a pattern of defects in the cochaperone mutant strains that were similar to the gene expression studies. Overexpression of CDC37, a chaperone required for protein kinase folding, suppressed defects the sti1Delta mutant back to wild-type levels. CDC37 overexpression also restored stable Hsp90 binding to the Ste11 protein kinase domain in the sti1Delta mutant strain. These data suggest that Cdc37 and Sti1 have functional overlap in stabilizing Hsp90:client complexes. Finally, we show that Cns1 functions in MAP kinase signaling in association with Cpr7.

  7. Motivational effects of smoked marijuana: behavioral contingencies and low-probability activities.

    PubMed Central

    Foltin, R W; Fischman, M W; Brady, J V; Bernstein, D J; Capriotti, R M; Nellis, M J; Kelly, T H

    1990-01-01

    Six adult male research volunteers, in two groups of 3 subjects each, lived in a residential laboratory for 15 days. All contact with the experimenters was through a networked computer system, and subjects' behavior was monitored continuously and recorded. During the first part of each day, they were allowed to socialize. Two cigarettes containing active marijuana (2.7% delta 9-THC) or placebo were smoked during the private work period and the period of access to social activities. Three-day contingency conditions requiring subjects to engage in a low-probability work activity (instrumental activity) in order to earn time that could be spent engaging in a high-probability work activity (contingent activity) were programmed during periods of placebo and active-marijuana smoking. During placebo administration, the contingency requirement reliably increased the amount of time that subjects spent engaged in the low-probability instrumental activity and decreased the time spent engaged in the high-probability activity. During active-marijuana administration, however, the increases in instrumental activity were consistently larger than observed under placebo conditions. The decreases in contingent activity were similar to those seen under placebo conditions. Smoking active marijuana was thus observed to produce increments in instrumental activity under motivational conditions involving contingencies for "work activities." PMID:2299291

  8. Trans-18:1 isomers in rat milk fat as effective biomarkers for the determination of individual isomeric trans-18:1 acids in the dams' diet.

    PubMed

    Wolff, Robert L

    2003-11-01

    Female rats were fed a diet containing by weight 10% partially hydrogenated sunflower oil, 2% sunflower oil, and 1% rapeseed oil during gestation and lactation. The trans-18:1 isomer profile of the fat supplement was (in % of total trans 18:1 acids in the fat supplement): delta4, 0.5; delta5, 1.0; delta6-delta8, 18.0; delta9 (elaidic), 13.5; delta10, 22.2; delta11 (vaccenic), 16.0; delta12, 11.3; delta13-delta14, 12.8; delta15, 2.5; and delta16, 2.2 (total trans 18:1 acids in the fat supplement: 40.6%). The cis 18:1 isomer profile was (in % of total cis-18:1 isomers): delta6-delta8, 2.1; delta9 (oleic), 70.9; delta10, 6.1; delta11, 8.3; delta12, 4.0; delta13, 2.8; delta14, 4.6, and delta15, 1.2 (total cis-18:1 acids in the fat supplement: 32.6%). Suckling rats from four litters were sacrificed at day 17 or 18 after birth, and their stomach content (milk) was analyzed. The trans-18:1 isomer profile of milk was (relative proportions, in % of total): delta4, 0.3; delta5, 1.1; delta6-delta8, 16.8; delta9, 15.3; delta10, 22.0; delta11, 16.7; delta12, 11.8; delta13-14, 11.8; delta15, 2.5, and delta16, 1.9 (total trans 18:1 acids in milk: %). That of cis-18:1 isomers was (proportions in % relative to total cis-18:1 isomers): delta6-delta8, 4.7; delta9, 72.5; delta10, 4.0; delta11, 8.0; delta12, 7.1; delta13, 1.9; delta14, 1.0, and delta15, 0.7 (total cis-18:1 acids in milk: %). These results demonstrate that all isomeric acids, independent of the geometry and the position of the ethylenic bond, are incorporated into milk lipids. With regard to trans-18:1 isomers, the distribution profile in milk is identical to that in the dams' diet, i.e., there is no discrimination against any positional isomer between their ingestion and their deposition into milk lipids. As a consequence, this study indicates that the trans-18:1 isomer profile of milk reflects that in the dams' diet and supports our earlier hypothesis that the profile of trans-18:1 isomers in milk can be used to

  9. YBCO High-Temperature Superconducting Filters on M-Plane Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Sabataitis, J. C.; Mueller, C. H.; Miranda, F. A.; Warner, J.; Bhasin, K. B.

    1996-01-01

    Since the discovery of High Temperature Superconductors (HTS) in 1986, microwave circuits have been demonstrated using HTS films on various substrates. These HTS-based circuits have proven to operate with less power loss than their metallic film counterparts at 77 K. This translates into smaller and lighter microwave circuits for space communication systems such as multiplexer filter banks. High quality HTS films have conventionally been deposited on lanthanum aluminate (LaAlO3) substrates. However, LaAlO3 has a relative dielectric constant (epsilon(sub r)) of 24. With a epsilon(sub r) approx. 9.4-11.6, sapphire (Al2O3) would be a preferable substrate for the fabrication of HTS-based components since the lower dielectric constant would permit wider microstrip lines to be used in filter design, since the lower dielectric constant would permit wider microstrip lines to be used for a given characteristic impedance (Z(sub 0)), thus lowering the insertion losses and increasing the power handling capabilities of the devices. We report on the fabrication and characterization of YBa2Cu3O(7-delta) (YBCO) on M-plane sapphire bandpass filters at 4.0 GHz. For a YBCO 'hairpin' filter, a minimum insertion loss of 0.5 dB was measured at 77 K as compared with 1.4 dB for its gold counterpart. In an 'edge-coupled' configuration, the insertion loss went down from 0.9 dB for the gold film to 0.8 dB for the YBCO film at the same temperature.

  10. Regioselective Porphyrin Bridge Cleavage Controlled by Electronic Effects. Coupled Oxidation of 3-Demethyl-3-(trifluoromethyl)mesohemin IX and Identification of Its Four Biliverdin Derivatives.

    PubMed

    Crusats, Joaquim; Suzuki, Akihiro; Mizutani, Tadashi; Ogoshi, Hisanobu

    1998-02-06

    This report describes the nonenzymatic oxidative cleavage of the title porphyrin (2) performed with oxygen and ascorbic acid in aqueous pyridine at 37 degrees C (coupled oxidation), via hydrolysis of the corresponding verdoheme intermediates, followed by esterification of the resulting free acid mesobiliverdin analogues to their dimethyl esters 4 (alpha isomer), 5 (beta isomer), 6 (gamma isomer), and 7 (delta isomer). The four biliverdin derivatives were purified by HPLC, and their structures were confirmed by FAB MS and also by UV-vis and (1)H NMR spectroscopies. The purity of each compound was checked by (19)F NMR, and the four regioisomers were assigned through their 2D-NMR ROESY spectra and confirmed by UV-vis spectroscopy. The ratio of regioisomers was determined by (19)F NMR spectroscopy before any purification of single compounds was attempted: alpha:beta:gamma:delta 11:6:26:57 (%). This unusually high regioselectivity was attributed to the electron-withdrawing effect of the CF(3) group on the electronic structure of porphyrin as shown considering the ab initio calculations of an iron(II) beta-substituted (trifluoromethyl)porphyrin used as a model compound. In porphyrin 2, the oxidation clearly takes place at the electron richest meso positions, the order of reactivity strictly following that of electron density, pointing out that the regiospecificity of the bridge cleavage can be effectively controlled by the electronic effects of some strategic substituents in the chromophore. The relevance of all these results in the study of the mechanism of the reactions involved in the natural catabolism of heme, catalyzed by heme oxygenase, is discussed. The advantages of 2 derived from this work, which make it a suitable model compound for the enzymatic reaction, are also discussed.

  11. Experimental transport studies of yttrium barium copper oxide and lambda-DNA

    NASA Astrophysics Data System (ADS)

    Zhang, Yuexing

    This dissertation consists of two parts. In Part I, we focus on the quasi-particle transport properties in the high temperature superconductor YBa2Cu3O7-delta (YBCO), probed by the thermal Hall conductivity (kappa xy). The thermal Hall conductivity selectively reflects the transport behaviors of the charge carriers. By measuring kappaxy in the normal state YBCO, we established a new method to determine the Wiedemann-Franz (WF) ratio in cuprates. We determined the Hall-channel WF ratio kappa xy/sigmaxyT in Cu and YBCO. In the latter, we uncovered a T-linear dependence and suppression of the Hallchannel WF ratio. The suppression of the Hall-channel WF ratio in systems with predominant electron-electron scattering will be discussed. Thermal transport behaviors of the quasi-particles in the mixed state were studied by measuring kappaxx and kappa xy in a high-purity YBCO crystal. From the field-dependence of the thermal conductivity kappaxx, we separated the quasi particle contribution (kappae) from the phonon background. In the Hall channel, we observed that the (weak-field) kappa xy increased 103-fold between T c (90 K) and 30 K, implying a 100-fold enhancement of the quasi-particle lifetime. We found that kappaxy exhibited a specific scaling behavior below ˜30 K. The implication of the scaling behavior will be discussed. In Part II, we describe an experiment on determining the electrical conductivity of the bacteriophage lambda-DNA, an issue currently under intense debate. We covalently bonded the DNA to Au electrodes by incorporating thiol modified dTTP into the 'sticky' ends of the lambda-DNA. Two-probe measurements on such molecules provided a lower bound for the resistivity rho > 10 6 mum at bias potentials up to 20 V, in conflict with recent claims of moderate to high conductivity. We stress the importance of eliminating salt residues in these measurements.

  12. Lunar Limb Observatory: an Incremental Plan for the Utilization, Exploration, and Settlement of the Moon

    NASA Astrophysics Data System (ADS)

    Lowman, Paul. D., Jr.

    1996-10-01

    This paper proposes a comprehensive incremental program, Lunar Limb Observatory (LLO), for a return to the Moon, beginning with robotic missions and ending with a permanent lunar settlement. Several recent technological developments make such a program both affordable and scientifically valuable: robotic telescopes, the Internet, light-weight telescopes, shared- autonomy/predictive graphics telerobotic devices, and optical interferometry systems. Reasons for focussing new NASA programs on the Moon include public interest, Moon-based astronomy, renewed lunar exploration, lunar resources (especially helium-3), technological stimulus, accessibility of the Moon (compared to any planet), and dispersal of the human species to counter predictable natural catastrophes, asteroidal or cometary impacts in particular. The proposed Lunar Limb Observatory would be located in the crater Riccioli, with auxiliary robotic telescopes in M. Smythii and at the North and South Poles. The first phase of the program, after site certification, would be a series of 5 Delta-launched telerobotic missions to Riccioli (or Grimaldi if Riccioli proves unsuitable), emplacing robotic telescopes and carrying out surface exploration. The next phase would be 7 Delta-launched telerobotic missions to M. Smythii (2 missions), the South Pole (3 missions), and the North Pole (2 missions), emplacing robotic telescopes to provide continuous all-sky coverage. Lunar base establishment would begin with two unmanned Shuttle/Fitan-Centaur missions to Riccioli, for shelter emplacement, followed by the first manned return, also using the Shuttle/Fitan-Centaur mode. The main LLO at Riccioli would then be permanently or periodically inhabited, for surface exploration, telerobotic rover and telescope operation and maintenance, and support of Earth-based student projects. The LLO would evolve into a permanent human settlement, serving, among other functions, as a test area and staging base for the exploration

  13. Sequentially evaporated thin Y-Ba-Co-O superconducting films on microwave substrates

    NASA Technical Reports Server (NTRS)

    Valco, G. J.; Rohrer, N. J.; Warner, J. D.; Bhasin, K. B.

    1989-01-01

    The development of high T sub c superconducting thin films on various microwave substrates is of major interest in space electronic systems. Thin films of YBa2Cu3O(7-Delta) were formed on SrTiO3, MgO, ZrO2 coated Al2O3, and LaAlO3 substrates by multi-layer sequential evaporation and subsequent annealing in oxygen. The technique allows controlled deposition of Cu, BaF2 and Y layers, as well as the ZrO buffer layers, to achieve reproducibility for microwave circuit fabrication. The three layer structure of Cu/BaF2/Y is repeated a minimum of four times. The films were annealed in an ambient of oxygen bubbled through water at temperatures between 850 C and 900 C followed by slow cooling (-2 C/minute) to 450 C, a low temperature anneal, and slow cooling to room temperature. Annealing times ranged from 15 minutes to 5 hrs. at high temperature and 0 to 6 hr. at 450 C. Silver contacts for four probe electrical measurements were formed by evaporation followed with an anneal at 500 C. The films were characterized by resistance-temperature measurements, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. Critical transition temperatures ranged from 30 K to 87 K as a function of the substrate, composition of the film, thicknesses of the layers, and annealing conditions. Microwave ring resonator circuits were also patterned on these MgO and LaAlO3 substrates.

  14. Epidermal growth factor receptor in glioma: signal transduction, neuropathology, imaging, and radioresistance.

    PubMed

    Hatanpaa, Kimmo J; Burma, Sandeep; Zhao, Dawen; Habib, Amyn A

    2010-09-01

    Aberrant epidermal growth factor receptor (EGFR) signaling is common in cancer. Increased expression of wild type and mutant EGFR is a widespread feature of diverse types of cancer. EGFR signaling in cancer has been the focus of intense investigation for decades primarily for two reasons. First, aberrant EGFR signaling is likely to play an important role in the pathogenesis of cancer, and therefore, the mechanisms of EGFR-mediated oncogenic signaling are of interest. Second, the EGFR signaling system is an attractive target for therapeutic intervention. EGFR gene amplification and overexpression are a particularly striking feature of glioblastoma (GBM), observed in approximately 40% of tumors. GBM is the most common primary malignant tumor of the central nervous system in adults. In approximately 50% of tumors with EGFR amplification, a specific EGFR mutant (EGFRvIII, also known as EGFR type III, de2-7, Delta EGFR) can be detected. This mutant is highly oncogenic and is generated from a deletion of exons 2 to 7 of the EGFR gene, which results in an in-frame deletion of 267 amino acids from the extracellular domain of the receptor. EGFRvIII is unable to bind ligand, and it signals constitutively. Although EGFRvIII has the same signaling domain as the wild type receptor, it seems to generate a distinct set of downstream signals that may contribute to an increased tumorigenicity. In this review, we discuss recent progress in key aspects of EGFR signaling in GBM, focusing on neuropathology, signal transduction, imaging of the EGFR, and the role of the EGFR in mediating resistance to radiation therapy in GBM.

  15. X-ray Structure Refinements and Strain Analysis of Substituted Cubic Lead Pyrochlores Pb

    SciTech Connect

    Nalini, G.; Somashekar, R.; Guru Row T. N.

    2001-01-01

    The phase diagrams in the PbO-Nb{sub 2}O{sub 5} system and the PbO-Ta{sub 2}O{sub 5} system depict pyrochlore structure at certain molar ratios. Compositions Pb{sub 2}Nb{sub 1.51}Pb{sub 0.49}O{sub 6.30} (1), Pb{sub 2}Ta{sub 1.4}Pb{sub 0.6}O{sub 6.21} (2), and Pb{sub 2}Ta{sub 1.25}Pb{sub 0.75}O{sub 6.57} (3) belonging to this family, are refined in the cubic space group Fd{ovr 3}m (Z=8; lattice parameter a=10.762(1), 10.744(1), 10.757(5) {angstrom}, respectively) using the Rietveld refinement approach. The analyses suggest that the B-site is partially occupied by Pb leading to the general formula Pb{sub 2}(M{sub 2-y}Pb{sub y})O{sub 7-{delta}}(0.0 < y < 0.8; M=Nb or Ta). There is an overall broadening observed in the X-ray peak widths in 1, 2, and 3 compared to the Pb-deficient parent phases. It is observed that the X-ray peak widths of 2 is broad, while 3 displays narrow peak widths. It is found via strain analysis that the line broadening observed correlates with the strain in the lattice.

  16. Characterization of a high-temperature superconducting conductor on round core cables in magnetic fields up to 20 T

    SciTech Connect

    van der Laan, D. C.; Noyes, P. D.; Miller, G. E.; Weijers, H. W.; Willering, G. P.

    2013-02-13

    The next generation of high-ï¬eld magnets that will operate at magnetic ï¬elds substantially above 20 T, or at temperatures substantially above 4.2 K, requires high-temperature superconductors (HTS). Conductor on round core (CORC) cables, in which RE-Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (RE = rare earth) (REBCO) coated conductors are wound in a helical fashion on a flexible core, are a practical and versatile HTS cable option for low-inductance, high-field magnets. We performed the first tests of CORC magnet cables in liquid helium in magnetic fields of up to 20 T. A record critical current I{sub c} of 5021 A was measured at 4.2 K and 19 T. In a cable with an outer diameter of 7.5 mm, this value corresponds to an engineering current density J{sub e} of 114 A mm{sup -2} , the highest J{sub e} ever reported for a superconducting cable at such high magnetic fields. Additionally, the first magnet wound from an HTS cable was constructed from a 6 m-long CORC cable. The 12-turn, double-layer magnet had an inner diameter of 9 cm and was tested in a magnetic field of 20 T, at which it had an I{sub c} of 1966 A. The cables were quenched repetitively without degradation during the measurements, demonstrating the feasibility of HTS CORC cables for use in high-field magnet applications.

  17. Congenital insensitivity to pain: novel SCN9A missense and in-frame deletion mutations.

    PubMed

    Cox, James J; Sheynin, Jony; Shorer, Zamir; Reimann, Frank; Nicholas, Adeline K; Zubovic, Lorena; Baralle, Marco; Wraige, Elizabeth; Manor, Esther; Levy, Jacov; Woods, C Geoffery; Parvari, Ruti

    2010-09-01

    SCN9Aencodes the voltage-gated sodium channel Na(v)1.7, a protein highly expressed in pain-sensing neurons. Mutations in SCN9A cause three human pain disorders: bi-allelic loss of function mutations result in Channelopathy-associated Insensitivity to Pain (CIP), whereas activating mutations cause severe episodic pain in Paroxysmal Extreme Pain Disorder (PEPD) and Primary Erythermalgia (PE). To date, all mutations in SCN9A that cause a complete inability to experience pain are protein truncating and presumably lead to no protein being produced. Here, we describe the identification and functional characterization of two novel non-truncating mutations in families with CIP: a homozygously-inherited missense mutation found in a consanguineous Israeli Bedouin family (Na(v)1.7-R896Q) and a five amino acid in-frame deletion found in a sporadic compound heterozygote (Na(v)1.7-DeltaR1370-L1374). Both of these mutations map to the pore region of the Na(v)1.7 sodium channel. Using transient transfection of PC12 cells we found a significant reduction in membrane localization of the mutant protein compared to the wild type. Furthermore, voltage clamp experiments of mutant-transfected HEK293 cells show a complete loss of function of the sodium channel, consistent with the absence of pain phenotype. In summary, this study has identified critical amino acids needed for the normal subcellular localization and function of Na(v)1.7.

  18. Particle Engulfment and Pushing By Solidifying Interfaces

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Mukherjee, Sundeep; Juretzko, Frank Robert; Catalina, A.drian V.; Sen, Subhayu; Curreri, P. A.

    2001-01-01

    The phenomenon of interaction of particles with solid-liquid interfaces (SLI) has been studied since the mid 1960's. While the original interest stemmed from geology applications (frost heaving in soil), researchers soon realized that fundamental understanding of particles behavior at solidifying interfaces might yield practical benefits in other fields, including metallurgy. In materials engineering the main issue is the location of particles with respect to grain boundaries at the end of solidification. Considerable experimental and theoretical research was lately focused on applications to metal matrix composites produced by casting or spray forming techniques, and on inclusion management in steel. Another application of particle SLI interaction is in the growing of Y1Ba2Cu3O(7-delta) (123) superconductor crystals from an undercooled liquid. The oxide melt contains Y2Ba1Cu1O5 (211) precipitates, which act as flux pinning sites. The experimental evidence on transparent organic materials, as well as the recent in situ observations on steel demonstrates that there exist a critical velocity of the planar SLI below which particles are pushed ahead of the interface, and above which particles are engulfment. The engulfment of a SiC particle in succinonitrile is exemplified. However, in most commercial alloys dendritic interfaces must be considered. Indeed, most data available on metallic alloys are on dendritic structures. The term engulfment is used to describe incorporation of a particle by a planar or cellular interface as a result of local interface perturbation, as opposed to entrapment that implies particle incorporation at cells or dendrites boundaries. During entrapment the particles are pushed in the intercellular or interdendritic regions and then captured when local solidification occurs. The physics of these two phenomena is fundamentally different.

  19. ADAPTIVE OPTICS IMAGES. II. 12 KEPLER OBJECTS OF INTEREST AND 15 CONFIRMED TRANSITING PLANETS

    SciTech Connect

    Adams, E. R.; Dupree, A. K.; Kulesa, C.; McCarthy, D.

    2013-07-01

    All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or producing a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are an effective way of resolving most blends. Here we present visual companions and detection limits for 12 Kepler planet candidate host stars, of which 4 have companions within 4''. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.''1, while KOI 174 has a companion at 0.''5. In addition, observations were made of 15 transiting planets that were previously discovered by other surveys. The only companion found within 1'' of a known planet is the previously identified companion to WASP-2b. An additional four systems have companions between 1'' and 4'': HAT-P-30b (3.''7, {Delta}Ks = 2.9), HAT-P-32b (2.''9, {Delta}Ks = 3.4), TrES-1b (2.''3, {Delta}Ks = 7.7), and WASP-P-33b (1.''9, {Delta}Ks = 5.5), some of which have not been reported previously. Depending on the spatial resolution of the transit photometry for these systems, these companion stars may require a reassessment of the planetary parameters derived from transit light curves. For all systems observed, we report the limiting magnitudes beyond which additional fainter objects located 0.''1-4'' from the target may still exist.

  20. Microgravity Processing of Oxide Superconductors

    NASA Technical Reports Server (NTRS)

    Olive, James R.; Hofmeister, William H.; Bayuzick, Robert J.; Vlasse, Marcus

    1999-01-01

    Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

  1. Critical Currents of Ex-Situ YBa2Cu3O7-δ Thin Films on Rolling Assisted Biaxially Textured Substrates: Thickness, Field, and Temperature Dependencies

    SciTech Connect

    Ijaduola, Anota O; Thompson, James R; Feenstra, Roeland; Christen, David K; Gapud, Albert Agcaoili; Song, X.

    2006-01-01

    The critical current density J{sub c} flowing in thin YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films of various thicknesses d has been studied magnetometrically, both as a function of applied field H and temperature T, with a central objective to determine the dominant source of vortex pinning in these materials. The films, grown by a BaF{sub 2} ex situ process and deposited on buffered rolling assisted biaxially textured substrates ('RABiTS') substrates of Ni-5% W, have thicknesses d ranging from 28 nm to 1.5 {micro}m. Isothermal magnetization loops M(H;T) and remanent magnetization M{sub rem}(T) in H=0 were measured with H{parallel}c-axis (i.e., normal to film plane). The resulting J{sub c}(d) values (obtained from a modified critical state model) increase with thickness d, peak near d-120 nm, and thereafter decrease as the films get thicker. For a wide range of temperatures and intermediate fields, we find J{sub c} {infinity} H{sup -{alpha}} with {alpha}-(0.56-0.69) for all materials. This feature can be attributed to pinning by large random defects, which theoretically has power-law exponent {alpha} = 5/8. Calculated values for the size and density of defects are comparable with those observed by TEM in the films. As a function of temperature, we find J{sub c}(T,sf)-[1-(T/T{sub c}){sup 2}]{sup n} with n-1.2-1.4. This points to '{delta}T{sub c} pinning' (pinning that suppresses T{sub c} locally) in these YBCO materials.

  2. Lunar Limb Observatory: An Incremental Plan for the Utilization, Exploration, and Settlement of the Moon

    NASA Technical Reports Server (NTRS)

    Lowman, Paul. D., Jr.

    1996-01-01

    This paper proposes a comprehensive incremental program, Lunar Limb Observatory (LLO), for a return to the Moon, beginning with robotic missions and ending with a permanent lunar settlement. Several recent technological developments make such a program both affordable and scientifically valuable: robotic telescopes, the Internet, light-weight telescopes, shared- autonomy/predictive graphics telerobotic devices, and optical interferometry systems. Reasons for focussing new NASA programs on the Moon include public interest, Moon-based astronomy, renewed lunar exploration, lunar resources (especially helium-3), technological stimulus, accessibility of the Moon (compared to any planet), and dispersal of the human species to counter predictable natural catastrophes, asteroidal or cometary impacts in particular. The proposed Lunar Limb Observatory would be located in the crater Riccioli, with auxiliary robotic telescopes in M. Smythii and at the North and South Poles. The first phase of the program, after site certification, would be a series of 5 Delta-launched telerobotic missions to Riccioli (or Grimaldi if Riccioli proves unsuitable), emplacing robotic telescopes and carrying out surface exploration. The next phase would be 7 Delta-launched telerobotic missions to M. Smythii (2 missions), the South Pole (3 missions), and the North Pole (2 missions), emplacing robotic telescopes to provide continuous all-sky coverage. Lunar base establishment would begin with two unmanned Shuttle/Fitan-Centaur missions to Riccioli, for shelter emplacement, followed by the first manned return, also using the Shuttle/Fitan-Centaur mode. The main LLO at Riccioli would then be permanently or periodically inhabited, for surface exploration, telerobotic rover and telescope operation and maintenance, and support of Earth-based student projects. The LLO would evolve into a permanent human settlement, serving, among other functions, as a test area and staging base for the exploration

  3. Overview of Results from the National Spherical Torus Experiment (NSTX)

    SciTech Connect

    Gates, D; Ahn, J; Allain, J; Andre, R; Bastasz, R; Bell, M; Bell, R; Belova, E; Berkery, J; Betti, R; Bialek, J; Biewer, T; Bigelow, T; Bitter, M; Boedo, J; Bonoli, P; Bozzer, A; Brennan, D; Breslau, J; Brower, D; Bush, C; Canik, J; Caravelli, G; Carter, M; Caughman, J; Chang, C; Choe, W; Crocker, N; Darrow, D; Delgado-Aparicio, L; Diem, S; D'Ippolito, D; Domier, C; Dorland, W; Efthimion, P; Ejiri, A; Ershov, N; Evans, T; Feibush, E; Fenstermacher, M; Ferron, J; Finkenthal, M; Foley, J; Frazin, R; Fredrickson, E; Fu, G; Funaba, H; Gerhardt, S; Glasser, A; Gorelenkov, N; Grisham, L; Hahm, T; Harvey, R; Hassanein, A; Heidbrink, W; Hill, K; Hillesheim, J; Hillis, D; Hirooka, Y; Hosea, J; Hu, B; Humphreys, D; Idehara, T; Indireshkumar, K; Ishida, A; Jaeger, F; Jarboe, T; Jardin, S; Jaworski, M; Ji, H; Jung, H; Kaita, R; Kallman, J; Katsuro-Hopkins, O; Kawahata, K; Kawamori, E; Kaye, S; Kessel, C; Kim, J; Kimura, H; Kolemen, E; Krasheninnikov, S; Krstic, P; Ku, S; Kubota, S; Kugel, H; La Haye, R; Lao, L; LeBlanc, B; Lee, W; Lee, K; Leuer, J; Levinton, F; Liang, Y; Liu, D; Luhmann, N; Maingi, R; Majeski, R; Manickam, J; Mansfield, D; Maqueda, R; Mazzucato, E; McCune, D; McGeehan, B; McKee, G; Medley, S; Menard, J; Menon, M; Meyer, H; Mikkelsen, D; Miloshevsky, G; Mitarai, O; Mueller, D; Mueller, S; Munsat, T; Myra, J; Nagayama, Y; Nelson, B; Nguyen, X; Nishino, N; Nishiura, M; Nygren, R; Ono, M; Osborne, T; Pacella, D; Park, H; Park, J; Paul, S; Peebles, W; Penaflor, B; Peng, M; Phillips, C; Pigarov, A; Podesta, M; Preinhaelter, J; Ram, A; Raman, R; Rasmussen, D; Redd, A; Reimerdes, H; Rewoldt, G; Ross, P; Rowley, C; Ruskov, E; Russell, D; Ruzic, D; Ryan, P; Sabbagh, S; Schaffer, M; Schuster, E; Scott, S; Shaing, K; Sharpe, P; Shevchenko, V; Shinohara, K; Sizyuk, V; Skinner, C; Smirnov, A; Smith, D; Smith, S; Snyder, P; Soloman, W; Sontag, A; Soukhanovskii, V; Stoltzfus-Dueck, T; Stotler, D; Strait, T; Stratton, B; Stutman, D; Takahashi, R; Takase, Y; Tamura, N; Tang, X; Taylor, G; Taylor, C; Ticos, C; Tritz, K; Tsarouhas, D; Turrnbull, A; Tynan, G; Ulrickson, M; Umansky, M; Urban, J; Utergberg, E; Walker, M; Wampler, W; Wang, J; Wang, W; Weland, A

    2009-01-05

    The mission of NSTX is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high {beta} operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale-length. Results from n = 3 braking studies confirm the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of High Harmonic Fast-Waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance l{sub i} {approx} 0.4 with strong shaping ({kappa} {approx} 2.7, {delta} {approx} 0.8) with {beta}{sub N} approaching the with-wall beta limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f{sub NI} {approx} 71%. Instabilities driven by super-Alfvenic ions are an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvenic. Linear TAE thresholds and appreciable fast-ion loss during multi-mode bursts are measured and these results are compared to theory. RWM/RFA feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with {beta} above the no-wall limit. The impact of n > 1 error fields on stability is a important result for ITER. Other highlights are

  4. Synthesis, crystal structure, dielectric properties, and potential use of nanocrystalline complex perovskite ceramic oxide Ba{sub 2}ErZrO{sub 5.5}

    SciTech Connect

    Jose, R. John, Asha M.; Thomas, J.K.; James, J.; Koshy, J.; Divakar, R.; Mohandas, E.

    2007-12-04

    A new member belongs to Ba{sub 2}REZrO{sub 5.5} (RE = Rare-Earth) perovskites, viz. Ba{sub 2}ErZrO{sub 5.5}, is synthesized as nanocrystals using a combustion process. Unlike the other Ba{sub 2}REZrO{sub 5.5} perovskites, which are cubic, Ba{sub 2}ErZrO{sub 5.5} crystallizes in tetragonal structure having space group P4/mnc (no. 128). Phase purity and ultrafine morphology of Ba{sub 2}ErZrO{sub 5.5} powders were examined using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transform of infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area measurements, and transmission electron microscopy (TEM). Nanocrystals of Ba{sub 2}ErZrO{sub 5.5} was sintered at {approx}1500 deg. C for 4 h; whereas coarse-grained powders synthesized through solid state reaction could not be sintered even at 1700 deg. C for prolonged duration. XRD pattern of Ba{sub 2}ErZrO{sub 5.5} was refined for atomic coordinates, lattice parameters, occupancies, and thermal factors using Rietveld analysis of XRD. Dielectric constant ({epsilon}') of Ba{sub 2}ErZrO{sub 5.5} at 10 MHz is 21.62 {+-} 2 and dielectric loss (tan {delta}) is 5 x 10{sup -3} at room temperature. Similar to the other Ba{sub 2}REZrO{sub 5.5} perovskites, Ba{sub 2}ErZrO{sub 5.5} is also showed chemically stability with YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and Bi{sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} (Bi-2212) superconductors. Ba{sub 2}ErZrO{sub 5.5} can possibly be used as a substrate for high temperature superconductor (HTS) films, or be used as an insulator in the active superconductor-insulator-superconductor (SIS) structures.

  5. d-orbital effects on stereochemical non-rigidity: twisted Ti(IV) intramolecular dynamics.

    PubMed

    Davis, Anna V; Firman, Timothy K; Hay, Benjamin P; Raymond, Kenneth N

    2006-07-26

    The isomerization dynamics of tris-catecholate complexes have been investigated by variable-temperature NMR methods, demonstrating that the intramolecular racemization of Delta and Lambda enantiomers of d0 Ti(IV) is facile and faster than that of d10 Ga(III) and Ge(IV) analogues. Activation parameters for the racemization of K2[Ti2(3)] (H(2)2 = 2,3-dihydroxy-N,N'-diisopropylterephthalamide) were determined from line shape analysis of 1H NMR spectra [methanol-d4: deltaH++ = 47(1) kJ/mol; deltaS++ = -34(4) J/mol K; deltaG++(298) = 57(3) kJ/mol; DMF-d7: deltaH++ = 55(1) kJ/mol; deltaS++ = -16(4) J/mol K; deltaG++(298) = 59(3) kJ/mol; D2O (pD* = 8.6, 20% MeOD): deltaH++ = 48(3) kJ/mol; deltaS++ = -28(10) J/mol K; deltaG++(298) = 56(3) kJ/mol]. The study of K2[Ti4(3)] (H(2)4 = 2,3-dihydroxy-N-tert-butyl-N'-benzylterephthalamide) reveals two distinct isomerization processes: faster racemization of mer-[Ti4(3)]2- by way of a Bailar twist mechanism (D3h transition state) [T(c) approximately 242 K, methanol-d4], and a slower merright harpoon over left harpoonfac [Ti4(3)]2- isomerization by way of a Rây-Dutt mechanism (C2v transition state) [T(c) approximately 281 K, methanol-d4]. The solution behavior of the Ti(IV) complexes mirrors that reported previously for analogous Ga(III) complexes, while that of analogous Ge(IV) complexes was too inert to be detected by 1H NMR up to 400 K. These experimental findings are augmented by DFT calculations of the ML3 ground states and Bailar and Rây-Dutt transition states, which correctly predict the relative kinetic barriers of complexes of the three metal ions, in addition to faithfully reproducing the ground-state structures. Orbital calculations support the conclusion that participation of the Ti(IV) d orbitals in ligand bonding contributes to the greater stabilization of the prismatic Ti(IV) transition states.

  6. Gender-dependent expression of alpha and beta estrogen receptors in human nontumor and tumor lung tissue.

    PubMed

    Fasco, Michael J; Hurteau, Gregory J; Spivack, Simon D

    2002-02-25

    Estrogen receptor (ER) expression in human lung has been understudied, particularly in light of its potential biological importance in the female lung cancer epidemic. Reverse transcription-polymerase chain reaction was used to probe mRNA expression of wild-type ERalpha and ERbeta and their splice variants in human bronchogenic tumor and adjacent nontumor specimens. In tumor tissue from 13 women and 13 men, ERalpha was expressed in 85% of women versus 15% in men [P=0.001]. ERbeta was expressed equally in tumors from women versus men [92% vs. 69%, P=ns]. Both ERalpha and beta forms were expressed simultaneously in the lung tumors of 77% of women versus 15% of men [P=0.005]. Among adjacent nontumor lung specimens, 31% of the women expressed ERalpha mRNA versus 0% of men [P=0.101], and 39% of women expressed ERbeta mRNA versus 31% of men [P=ns]; only one woman and no men expressed both ERalpha and beta in nontumor tissue. Females expressed ERalpha [P=0.017], ERbeta [P=0.013], and ERalpha+beta [P=0.002] more frequently in tumor versus nontumor tissue, whereas in males expression of ERalpha, beta and both alpha+beta was not clearly different for tumor versus nontumor tissue. In specimens expressing ERalpha mRNA, the transcript lacking exon 7 (delta7) was the major splice variant with varying contributions from the transcripts delta4, delta3+4, delta5 and others unidentified. Alternative splicing of ERbeta mRNA was observed, but not to as great an extent as for ERalpha mRNA. ERalpha promoter usage in tumors varied among individuals. When the ER receptors were co-expressed in tumors, ERalpha was quantitatively more abundant in the majority of cases than ERbeta. Within this small group of 26 patients, no correlation was found between age, smoking history, plasma nicotine, cotinine, estradiol concentrations or histopathologic type with tumor or nontumor estrogen receptor status of any type. However, several positive correlations imply that: (1) ERalpha expression occurs

  7. Efficacy and safety of 10% and 16% carbamide peroxide tooth-whitening gels: a randomized clinical trial.

    PubMed

    Meireles, Sônia Saeger; Heckmann, Sani Silva; Leida, Fedinan Luis; dos Santos, Iná da Silva; Della Bona, Alvaro; Demarco, Flávio Fernando

    2008-01-01

    This double-blind randomized clinical trial evaluated the efficacy and safety of two carbamide peroxide concentrations used in at-home vital bleaching. Ninety-two volunteers with a shade mean of C1 or darker for the six maxillary anterior teeth were randomized into two balanced groups (n=46) according to bleaching agent concentration: 10% (CP10) or 16% (CP16) carbamide peroxide. The patients were instructed to use the whitening agent in a tray for two hours once a day for three weeks. Shade evaluations were done with a value-oriented shade guide and a spectrophotometer at baseline and one week post-bleaching (four-week evaluation). Tooth sensitivity was measured daily using a scale ranging from 0 (no sensitivity) to 4 (severe sensitivity). At the end of the study, the volunteers filled out a questionnaire with seven questions aimed to give their opinion about the adopted treatment regimen. Both carbamide peroxide concentrations resulted in significantly lighter teeth at the four-week evaluation compared to the baseline for all color parameters (p < 0.0001) and shade median (p < 0.001). There was no significant difference between the two groups in terms of shade change difference with either the spectrophotometer (p = 0.1) or the shade guide (p = 0.7). Also, no statistically significant difference was found in relation to deltaL* (p = 0.7), delta a* and deltaE* (p = 0.5). A significant reduction in yellowness (delta b*) was observed for CP16 compared to CP10 (p = 0.05) in crude analysis, which disappeared after controlling for b* parameter at baseline. The group treated with CP16 experienced more tooth sensitivity during the first (p = 0.02) and third (p = 0.01) weeks of treatment compared to the CP10 group. However, no major difference was observed (p = 0.09) when the degree of tooth sensitivity between groups was compared. Both 10% and 16% carbamide peroxide concentrations were equally effective and safe for a three-week at-home tooth-bleaching treatment.

  8. Multiple origins of Canadian Cordilleran gold deposits: geochemical characteristics

    SciTech Connect

    Murowchick, J.B.; Nesbitt, B.E.; Muehlenbachs, K.

    1985-01-01

    Two types of lode Au mineralization (Mother Lode and Epithermal) can be recognized in the Canadian Cordillera by geochemical characteristics. The Coquihalla Au belt, a typical ML district, has steeply-dipping Q-cc-ab-Au veins. Host rocks are greywackes, slates and greenstones in fault contact with a serpentinite body. Isotopic analyses: Q-cc and antigorite-mt paris gives temperatures around 250/sup 0/C. delta/sup 18/O/sub SMOW/ are exceptionally high: vein Q = 16 to 18 per thousand, antigorite = 7.4 to 9.5 per thousand, and cc = 14 to 18 per thousand with delta/sup 13/C/sub PDB/ =-2.9 to -6.9 per thousand. deltaD are low: -111 to -142 for the serpentines and -84 to -100 for fluid inclusion waters extracted by crushing vein Q. These fluids have low salinity and contain CO/sub 2/. The delta/sup 18/O for the ore fluid is about 8 per thousand and was also the serpentinizing fluid. The deltaD suggest that the fluid was dominantly meteoric, but evolved by reaction with the metasediments during deep circulation. The typical ML assemblage is Q-cc-ab with aspy, py, po, Au, +/-AU tellurides +/- scheelite; Au/Ag = 4 to 7 in this belt. Other ML deposits in BC show similar isotopic and mineralogic traits. Epithermal deposits in the Canadian Cordillera are comparable to well-studied US examples: their fluids were shallow-circulated meteoric waters (delta/sup 18/O=-14 to -7), delta/sup 18/O=-5 to +2, T=200-300/sup 0/C, Au/Ag<1, and have Q, chalcedony, cc, hematite, adularia, barite, py, cpy, Ag/sub 2/S, Au, electrum and anomalous Hg, As, and Tl contents. The association of Hg and Sb occurrences near many B.C. ML deposits suggests that these may be the epithermal expression of deeper ML mineralization.

  9. Manufacturing of intermediate-temperature solid oxide fuel cells using novel cathode compositions

    NASA Astrophysics Data System (ADS)

    Torres Garibay, Claudia Isela

    The development of intermediate temperatures solid oxide fuel cells (IT-SOFC) with YSZ electrolytes imposes a double requirement in their manufacturing. First, the electrolyte has to be kept as thin as possible to minimize ohmic polarization losses. Second, the cathode compositions used must exhibit an adequate catalytic activity at the operating temperature (600--800°C). Current methods to manufacture thin YSZ electrolytes require complex processes, and sometimes costly equipment. Cathode compositions traditionally used for high temperature solid oxide fuel cells, such as (La,Sr)MnO3 do not exhibit good catalytic properties at intermediate temperatures. These challenges present areas of opportunity in the development of original manufacturing techniques and new cathode compositions. This study presents a low-cost fabrication procedure for IT-SOFC using tape casting, co-firing and screen printing. The electrochemical performance of the cells is evaluated using a known cathode composition for IT-SOFC, such as La0.6Sr0.4CoO 3-delta (LSC), novel perovskite oxides, such as Nd0.6Sr 0.4CoO3-delta (NSC), and perovskite-related intergrowth oxides compositions, like Sr0.7La0.3Fe1.4Co 0.6O7-delta (SLFCO7) and LaSr3Fe1.5Co 1.5O10-delta (LSFCO10). The impact of conductivity is studied by substituting Fe for Co in the case of the perovskite oxides, with compositions such as La0.6Sr0.4Co0.5Fe0.5O 3-delta (LSCF), and Nd0.6Sr0.4Co0.5Fe 0.5O3-delta (NSCF) and by infiltration of NSCF with silver. The effect of the cathode sintering temperature is studied using LSC and LSCF cathodes. It is found that there is generally a correlation between cell performance and conductivity. However, the microstructure of the cathode is also important in determining cell performance by tailoring the cathode sintering temperature. IT-SOFC with SLFCO7 cathodes show a performance comparable to cells with LSFC cathode. In the case of LSFCO10, the performance loss associated with its lower conductivity

  10. Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves

    SciTech Connect

    Hicken, Malcolm; Wood-Vasey, W.Michael; Blondin, Stephane; Challis, Peter; Jha, Saurabh; Kelly, Patrick L.; Rest, Armin; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2012-04-06

    We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013{sub -0.068}{sup +0.066} (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (R{sub V} = 3.1), and MLCS2k2 (R{sub V} = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < {Delta} < 1.2. MLCS2k2 with R{sub V} = 3.1 overestimates host-galaxy extinction while R{sub V} {approx} 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2{sigma}, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.

  11. Nonlinear systems for frequency conversion from IR to RF

    NASA Astrophysics Data System (ADS)

    Dolasinski, Brian D.

    spectrum using an infrared camera that runs at a rate of 35 frames per second. We have demonstrated the ability to image 2 THz to 26 THz both in static and in real time conditions. We will present images of carbon fibers illuminated at different THz frequencies. Lastly, microwave generation was demonstrated by ultrafast photo-excitation experiments to induce non-equilibrium quasi-particle relaxation. Using a laser with a pulse energy of 1 mJ and a pulse duration greater than 120 fs (808 nm wavelength) incident on a charged, superconducting YBa2Cu 2O7-delta (YBCO) thin film ring, the photo-response was measured with a series of microwave antennas. From the observed nanosecond response time of the transient pulse, we extracted the frequency spectrum in the GHz regime that was dependent on the incident beam diameter, pulse duration, power, and the physical structure of the YBCO thin film.

  12. Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes

    NASA Astrophysics Data System (ADS)

    Nguyen, Doan Ngoc

    the numerical calculations. The numerical calculations are also capable of investigating eddy current loss in the stabilizer and ferromagnetic loss in the substrate of YBa2Cu3O 7-delta (YBCO) coated conductor. AC loss characteristics and electrodynamics in several (Bi,Pb)2 Sr2Ca2Cu3Ox (Bi-2223) and YBCO tapes were studied experimentally and numerically. It was found that AC loss behavior Ax in HTS tapes is strongly affected by the sample parameters such as cross-section, structure, dimensions, critical current distribution as well as by operation parameters including temperature, frequency, the phase difference between transport current and magnetic field, the orientation of magnetic field. The Ni-5%W substrate in YBCO conductors generates some ferromagnetic loss but this loss component is significantly reduced by a small parallel DC magnetic field. At a given AC magnetic field B0, there is a temperature Tmax at which the magnetization loss is maximum. The design of HTS devices needs to be optimized to avoid operating at that temperature. In general, the total AC loss in HTS tapes is still high for many power device applications, especially for those that present a rather high AC applied magnetic field. The development of low loss conductors is therefore crucial for HTS large-scale applications.

  13. Aspects of the strontium oxide-copper oxide-titanium dioxide ternary system related to the deposition of strontium titanate and copper doped strontium titanate thin film buffer layers

    NASA Astrophysics Data System (ADS)

    Ayala, Alicia

    YBa2Cu3O7-delta (YBCO) coated conductors are promising materials for large-scale superconductivity applications. One version of a YBCO coated conductor is based on ion beam assisted deposition (IBAD) of magnesium oxide (MgO) onto polycrystalline metal substrates. SrTiO3 (STO) is often deposited by physical vapor deposition (PVD) methods as a buffer layer between the YBCO and IBAD MgO due to its chemical stability and lattice mismatch of only ˜1.5% with YBCO. In this work, some aspects of the stability of STO with respect to copper (Cu) and chemical solution deposition of STO on IBAD MgO templates were examined. Solubility limits of Cu in STO were established by processing Cu-doped STO powders by conventional bulk preparation techniques. The maximum solubility of Cu in STO was ˜1% as determined by transmission electron microscopy (TEM) and Rietveld refinements of x-ray diffraction (XRD) data. XRD analysis, performed in collaboration with NIST, on powder compositions on the STO/SrCuO 2 tie line did not identify any ternary phases. SrCu0.10Ti0.90Oy buffer layers were prepared by pulsed laser deposition (PLD) and CSD on IBAD MgO flexible metallic textured tapes. TEM analysis of a ˜100 nm thick SrCu0.10Ti 0.90Oy buffer layer deposited by PLD showed a smooth Cu-doped STO/MgO interface. A ˜600 nm thick YBCO film, deposited onto the SrCu 0.10Ti0.90Oy buffer by PLD, exhibited a T c of 87 K and critical current density (Jc) of ˜1 MA/cm 2. STO and Cu-doped STO thin films by CSD were ˜30 nm thick. The in plane alignment (FWHM) after deposition of the STO improved by ˜1° while it degraded by ˜2° with the SrCu0.05TiOy buffer. YBCO was deposited by PLD on the STO and SrCu0.05TiO y buffers. The in plane alignment (FWHM) of the YBCO with the STO buffer layer slightly improved while that of the YBCO with the SrCu0.05TiO y buffer layer remained constant. A goal of the CSD approach to fabrication of coated conductors is process simplicity. In this study, single layer

  14. A Magnetic Bumper-Tether System Using ZFC Y123

    NASA Technical Reports Server (NTRS)

    Weinstein, Roy; Parks, Drew; Sawh, Ravi-Persad; Obot, Victor; Liu, Jianxiong; Arndt, G. D.

    1996-01-01

    We consider the use of magnetic forces in a bumper system, to soften docking procedures. We investigate a system which exhibits no magnetic field except during the docking process, which, if desired, can automatically tether two craft together, and which provides lateral stability during docking. A system composed of zero field cooled Y(1.7)Ba2Cu3O(7-delta) (Y123) tiles and electromagnets is proposed. The Y123 high temperature superconductor (HTS) is mounted on one craft, and the electromagnet on the other. Results of small prototype laboratory experiments are reported. The electromagnet has, for convenience, been replaced by a permanent SmCo ferromagnet in these measurements. When the two craft approach, a mirror image of the ferromagnet is induced in the Y123, and a repulsive bumper force, F(sub B), results. F(sub B) is velocity dependent, and increases with v. For presently available HTS materials, bumper pressure of approx. 3.7 N/cm(exp 2) is achieved using SmCo. This extrapolates to approx. 18 N/cm(exp 2) for an electromagnet, or a force of up to 20 tons for a 1 m(exp 2) system. After reaching a minimum distance of approach, the two colliding craft begin to separate. However, the consequent change of SmCo magnetic field at the Y123 results in a reversal of current in the Y123 so that the Y123 is attractive to the SmCo. The attractive (tether) force, F(sub T), is a function of R = B(sub Fe)/B(sub t, max), where B(sub Fe) is the field at the surface of the ferromagnet, and B(sub t, max) is the maximum trapped field of the Y123, i.e., the trapped field in the so-called critical state. For R greater than or equal to 2, F(sub T) saturates at a value comparable to F(sub B). For a range of initial approach velocities the two craft are tethered following the bumper sequence. Most of the kinetic energy of the collision is first converted to magnetic field energy in the Y123, and then into heat via the creep mechanism. About 15% of the work done against magnetic forces

  15. Use of Physio-Hydrological Units for SMOS Validation at the Valencia Anchor Station Study Area

    NASA Astrophysics Data System (ADS)

    Millán-Scheiding, C.; Antolín, C.; Marco, J.; Soriano, M. P.; Torre, E.; Requena, F.; Carbó, E.; Cano, A.; Lopez-Baeza, E.

    2009-04-01

    The SMOS space mission will soil moisture over the continents and ocean surface salinity with the sufficient resolution to be used in global climate change studies. With the aim of validating SMOS land data and products at the Valencia Anchor Station site (VAS) in a Mediterranean Ecosystem area of Spain, we have designed a sample methodology using a subdivision of the landscape in environmental units related to the spatial variability of soil moisture (Millán-Scheiding, 2006; Lopez-Baeza, et al. 2008). These physio-hydrological units are heterogeneously structured entities which present a certain degree of internal uniformity of hydrological parameters. The units are delimited by integrating areas with the same physio-morphology, soil type, vegetation, geology and topography (Flugel, et al 2003; Millán-Scheiding et al, 2007). Each of these units presented over the same pedological characteristics, vegetation cover, and landscape position should have a certain degree of internal uniformity in its hydrological parameters and therefore similar soil moisture (SM). The main assumption for each unit is that the dynamical variation of the hydrological parameters within one unit should be minimum compared to the dynamics of another unit. This methodology will hopefully provide an effective sampling design consisting of a reduced number of measuring points, sparsely distributed over the area, or alternatively, using SM validation networks where each sampling point is located where it is representative of the mean soil moisture of a complete unit area. The Experimental Plan for the SMOS Validation Rehearsal Campaign at the VAS area of April-May 2008 used this environmental subdivision in the selection and sampling of over 21.000 soil moisture points in a control area of 10 x 10 km2. The ground measurements were carried out during 4 nights corresponding to a drying out period of the soil. The sampling consisted of 700 plots with 4 volumetric SM cylinders and 7 Delta-T Theta

  16. Thermodynamics of the magnetic-field-induced "normal" state in an underdoped high Tc superconductor

    NASA Astrophysics Data System (ADS)

    Riggs, Scott Chandler

    High magnetic fields are used to kill superconductivity and probe what happens to system when it cannot reach the ideal ground state, i.e. what is the normal-state ground state? Early work in High-Tc, where the application of magnetic field destroyed the zero resistance state and recovered a resistivity value that connected continuously with the zero field curve, lead people to believe this magnetic-field-induced-state had fully driven the system normal, revealing the true underlying ground state, without any vestige of superconductivity. Many experiments done in this region of phase space have results interpreted as coming from the low energy ground state excitations. With the emergence of ultra-clean crystals in a unique family of hole doped high-Tc superconductors, YBa2Cu3O 7-delta, YBCO, a new and highly unexpected phenomena of quantum oscillations were discovered, and they followed the standard Liftshitz-Kosevich (LK) theory for a normal metal. The results suddenly made the problem of high-T c appear to be analogous to superconductivity in the organics, which is brought about by a wave-vector nesting and Fermi surface reconstruction. The only problem, it appeared, that needed to be reconciled was with Angle Resolved Photo-Emission Spectroscopy (ARPES) and Scanning Tunneling Microscopy (STM) data that claimed to see no such Fermi surface, instead only "arcs", a set of disconnected segments in the Brillouin zone which quasiparticle peaks are observed at the Fermi energy, which in a mean field description does not allow for a continuous Fermi surface contour. These two discrepancies led to the "arc vs pocket" debate, which is still unresolved. The other kink in the quantum oscillation armor is that, to this date, quantum oscillations in the hole-doped cuprates have only been seen in YBCO, the only cuprate structure to have CuO chains, which conduct and are located in between two CuO2 superconducting planes in the unit cell. In an attempt to reconcile the "arc vs