Magnetic And Superconducting Properties Of Ru Sr2 Gd1.5 Ce0.5 Cu2 O10-δ Samples: Dependence On The Oxygen Content And Aging Effects

The magnetic and superconducting properties of Ru Sr2 Gd1.5 Ce0.5 Cu2 O10-δ polycrystalline samples with different oxygen-doping levels are presented. A strong suppression of the superconducting temperature (Tc), as well as a reduction in the superconducting fraction, occurs as the oxygen content is reduced by annealing the samples in oxygen-deprived atmospheres. Drastic changes in the electrical resistivity are observed above Tc, possibly associated with oxygen removal, mainly from grain boundaries. However, the magnetic ordering is relatively less affected by the changes in oxygen content of the samples. The spin-glass transition is enhanced and shifted to higher temperatures with the reduction in oxygen content. This could be correlated with an increase in the spin disorder and frustration for the oxygen-depleted samples. Also, the same oxygen-vacancy-induced disorder could explain the reduction in the fraction of the sample showing antiferromagnetic order. We also report significant changes in the measured properties of the samples as a function of time. © 2005 The American Physical Society.7113Felner, I., Asaf, U., Levi, Y., Millo, O., (1997) Phys. Rev. B, 55, p. 3374. , PRBMDO 0163-1829 10.1103/PhysRevB.55.R3374Bernhard, C., Tallon, J.L., Niedermayer, Ch., Blasius, Th., Golnik, A., Brücher, E., Kremer, R.K., Ansaldo, E.J., (1999) Phys. Rev. B, 59, p. 14099. , PRBMDO. 0163-1829. 10.1103/PhysRevB.59.14099Awana, V.P.S., Karppinen, M., Yamauchi, H., (2003) Studies of High Tc Superconductors, 46, p. 77. , edited by A. V. Narlikar (Nova Science Publishers, New YorkMatvejeff, M., Awana, V.P.S., Jang, L.-Y., Liu, R.S., Yamauchi, H., Karppinen, M., (2003) Physica C, 392-396, p. 87. , PHYCE6 0921-4534Cardoso, C.A., Araujo-Moreira, F.M., Awana, V.P.S., Kishan, H., Takayama-Muromachi, E., De Lima, O.F., (2004) Physica C, 405, p. 212. , PHYCE6 0921-4534Cardoso, C.A., Araujo-Moreira, F.M., Awana, V.P.S., Takayama-Muromachi, E., De Lima, O.F., Yamauchi, H., Karppinen, M., (2003) Phys. Rev. B, 67, p. 020407. , PRBMDO 0163-1829 10.1103/PhysRevB.67.020407Shi, L., Li, G., Fan, X.J., Feng, S.J., Li, X.-G., (2003) Physica C, 399, p. 69. , PHYCE6 0921-4534Felner, I., Asaf, U., Ritter, F., Klamut, P.W., Dabrowski, B., (2001) Physica C, 364-365, p. 368. , PHYCE6 0921-4534Felner, I., Asaf, U., Galstyan, E., (2002) Phys. Rev. B, 66, p. 024503. , PRBMDO 0163-1829 10.1103/PhysRevB.66.024503Felner, I., Asaf, U., Levi, Y., Millo, O., (2000) Physica C, 334, p. 141. , PHYCE6 0921-4534 10.1016/S0921-4534(00)00250-1Awana, V.P.S., Ansari, M.A., Gupta, A., Saxena, R.B., Kishan, H., Buddhikot, D., Malik, S.K., (2004) Phys. Rev. B, 70, p. 104520. , PRBMDO 0163-1829 10.1103/PhysRevB.70.104520Yoshizawa, H., Mitsuda, S., Aruga, H., Ito, A., (1987) Phys. Rev. Lett., 59, p. 2364. , PRLTAO 0031-9007 10.1103/PhysRevLett.59.2364Binder, K., Young, A.P., (1986) Rev. Mod. Phys., 58, p. 801. , RMPHAT 0034-6861 10.1103/RevModPhys.58.801Mydosh, J.A., (1993) Spin Glasses An Experimental Introduction, , Taylor & Francis, LondonFelner, I., Galstyan, E., Herber, R.H., Nowik, I., (2004) Phys. Rev. B, 70, p. 094504. , PRBMDO 0163-1829 10.1103/PhysRevB.70.094504Shengelaya, A., Khasanov, R., Eschenko, D.G., Felner, I., Asaf, U., Savić, I.M., Keller, H., Müller, K.A., (2004) Phys. Rev. B, 69, p. 024517. , PRBMDO. 0163-1829. 10.1103/PhysRevB.69.024517Xue, Y.Y., Cao, D.H., Lorenz, B., Chu, C.W., (2002) Phys. Rev. B, 65, p. 020511. , PRBMDO 0163-1829 10.1103/PhysRevB.65.02051

Structural And Magnetic Study Of Labacocu O5+δ

The structure and magnetic properties of the compound LaBaCuCo O5+δ have been studied for the non-stoichiometric oxygen concentration δ≈0.6. The structure is pseudo-cubic with a tripled perovskite unit cell. The crystal structure was determined by a combined Rietveld fit to neutron and synchrotron x-ray powder diffraction data in the orthorhombic Pmmm space group, with cell parameters a=3.9223 (3) Å, b=3.9360 (3) Å, c=11.7073 (8) Å, and V=180.74 (2) Å3 (room temperature). Antiferromagnetic ordering of Cu and Co magnetic moments is observed below 205 (4) K. The magnetic structure with cell aM =2a, bM =2b, and cM =2c, could be described with the Shubnikov space group Fmm m′. The magnetic moments of both equivalent Cu/Co sites were determined at 50 and 170 K to be 0.83 (3) μB and 0.58 (3) μB, respectively, consistent with one unpaired electron per atom. The fit of the intensities to a simple mean field magnetic model appeared to be insufficient to account for the variation of moments at temperatures close to TN while a three dimensional Heisenberg model could improve the fit. Susceptibility measurements between 4 and 350 K also show irreversibility below 150 K. The local environments of Cu and Co were studied by extended x-ray absorption fine structure spectroscopy at both absorption edges. Cu atoms adopt an elongated octahedral or square-based pyramidal oxygen environment which suggests mainly the presence of Cu(II) in the structure. Co adopts different local environments, depending on the electronic and spin states. © 2005 The American Physical Society.7114Er-Rakho, L., Michel, C., Lacorre, P., Raveau, B., (1988) J. Solid State Chem., 73, p. 531. , JSSCBI 0022-4596 10.1016/0022-4596(88)90141-7Meyer, C., Hartmann-Boutron, F., Gros, Y., Strobel, P., (1990) Solid State Commun., 76, p. 163. , SSCOA4 0038-1098 10.1016/0038-1098(90)90535-JAtanassova, Y.K., Popov, V.N., Bogachev, G.G., Iliev, M.N., Mitros, C., Psycharis, V., Pissas, M., (1993) Phys. Rev. B, 47, p. 15201. , PRBMDO 0163-1829 10.1103/PhysRevB.47.15201Mombrú, A.W., Christides, C., Lappas, A., Prassides, K., Pissas, M., Mitros, C., Niarchos, D., (1994) Inorg. Chem., 33, p. 1255. , INOCAJ. 0020-1669Caignaert, V., Mirebeau, I., Bouree, F., Nguyen, N., Ducouret, A., Greneche, J.M., Raveau, B., (1995) J. Solid State Chem., 114, p. 24. , JSSCBI 0022-4596 10.1006/jssc.1995.1004Mombrú, A.W., Prassides, K., Christides, C., Erwin, R., Pissas, M., Niarchos, C., Mitros, D., (1998) J. Phys.: Condens. Matter, 10, p. 1247. , JCOMEL. 0953-8984. 10.1088/0953-8984/10/6/008Ruiz-Aragón, M., Amador, U., Morán, E., Andersen, N.H., (1994) Physica C, 235-240, p. 1609. , PHYCE6. 0921-4534Pissas, M., Mitros, C., Kallias, G., Psycharis, V., Niarchos, D., Simopoulos, A., Kostikas, A., Prassides, K., (1991) Physica C, 185, p. 553. , PHYCE6 0921-4534Pissas, M., Mitros, C., Kallias, G., Psycharis, V., Simopoulos, A., Kostikas, A., Niarchos, D., (1992) Physica C, 192, p. 35. , PHYCE6 0921-4534 10.1016/0921-4534(92)90740-4Er-Rakho, L., Michel, C., Studer, F., Raveau, B., (1977) J. Phys. Chem. Solids, 48, p. 377. , JPCSAW 0022-3697Pardo, H., Ortiz, W.A., Araújo-Moreira, F.M., Suescun, L., Toby, B., Quagliata, E., Negreira, C.A., Mombrú, A.W., (1999) Physica C, 313, p. 105. , PHYCE6. 0921-4534. 10.1016/S0921-4534(98)00668-6Mombrú, A.W., Pardo, H., Suescun, L., Toby, B.H., Ortiz, W.A., Negreira, C.A., Araújo-Moreira, F.M., (2001) Physica C, 356, p. 149. , PHYCE6. 0921-4534Mombrú, A.W., Goeta, A.E., Pardo, H., Lisboa-Filho, P.N., Suescun, L., Mariezcurrena, R.A., Ventura, O.N., Araújo-Moreira, F.M., (2002) J. Solid State Chem., 166, p. 251. , JSSCBI. 0022-4596Guskos, N., Likodimos, V., Kuriata, J., Metz, H., Windsch, W., Wabia, M., Mitros, C., Niarchos, D., (1994) Phys. Status Solidi B, 181, p. 69. , PSSBBD 0370-1972Ruiz-Aragón, M.J., Morán, E., Amador, U., Martínez, J.L., Andersen, N.H., Ehrenberg, H., (1998) Phys. Rev. B, 58, p. 6291. , PRBMDO. 0163-1829. 10.1103/PhysRevB.58.6291Pissas, M., Kallias, G., Psycharis, V., Gamari-Seale, H., Niarchos, D., Simopoulos, A., Sonntag, R., (1997) Phys. Rev. B, 55, p. 397. , PRBMDO 0163-1829 10.1103/PhysRevB.55.397Potze, R.H., Sawatzky, G.A., Abbate, M., (1995) Phys. Rev. B, 51, p. 11501. , PRBMDO 0163-1829 10.1103/PhysRevB.51.11501Takahashi, H., Munakata, F., Yamanaka, M., (1998) Phys. Rev. B, 57, p. 15211. , PRBMDO 0163-1829 10.1103/PhysRevB.57.15211Chappel, E., Holzapfel, M., Chouteau, G., Ott, A., (2000) J. Solid State Chem., 154, p. 451. , JSSCBI 0022-4596Krimmel, A., Reehuis, M., Paraskevopoulos, M., Hemberger, J., Loidl, A., (2001) Phys. Rev. B, 64, p. 224404. , PRBMDO 0163-1829 10.1103/PhysRevB.64.224404Brinks, H.W., Fjellvåg, H., Kjekshus, A., Hauback, B.C., (1999) J. Solid State Chem., 147, p. 467. , JSSCBI. 0022-4596Pouchard, M., Villesuzanne, A., Doumerc, J.P., (2001) J. Solid State Chem., 162, p. 282. , JSSCBI 0022-4596 10.1006/jssc.2001.9294Paraskevopoulos, M., Hemberger, J., Krimmel, A., Loidl, A., (2001) Phys. Rev. B, 63, p. 224416. , PRBMDO 0163-1829 10.1103/PhysRevB.63.224416Nakatsugawa, H., Iguchi, E., (2001) J. Solid State Chem., 159, p. 215. , JSSCBI 0022-4596Hansteen, O.H., Fjellvåg, H., Hauback, B.C., (1998) J. Solid State Chem., 141, p. 411. , JSSCBI. 0022-4596Fauth, F., Suard, E., Caignaert, V., (2001) Phys. Rev. B, 65, p. 060401. , PRBMDO 0163-1829 10.1103/PhysRevB.65.060401Huang, Q.Z., Karen, V.L., Santoro, A., Kjekshus, A., Lindén, J., Pietari, T., Karen, P., (2003) J. Solid State Chem., 172, p. 73. , JSSCBI. 0022-4596Barbey, L., Nguyen, N., Caignaert, V., Hervieu, M., Raveau, B., (1992) Mater. Res. Bull., 27, p. 295. , MRBUAC 0025-5408 10.1016/0025-5408(92)90058-8Zaliznyak, I.A., Tranquada, J.M., Erwin, R., Moritomo, Y., (2001) Phys. Rev. B, 64, p. 195117. , PRBMDO 0163-1829 10.1103/PhysRevB.64.195117Wu, J., Leighton, C., (2003) Phys. Rev. B, 67, p. 174408. , PRBMDO 0163-1829 10.1103/PhysRevB.67.174408Ibarra, M.R., Mahendiran, R., Marquina, C., García-Landa, B., Blasco, J., (1998) Phys. Rev. B, 57, p. 3217. , PRBMDO. 0163-1829. 10.1103/PhysRevB.57.R3217Huang, Q., Karen, P., Karen, V.L., Kjekshus, A., Lynn, J.W., Mighell, A.D., Natali Sora, I., Santoro, A., (1994) J. Solid State Chem., 108, p. 80. , JSSCBI 0022-4596 10.1006/jssc.1994.1012http://www.ncnr.nist.gov/Larson, A.C., Von Dreele, R.B., (1987), LA-UR-86-748Toby, B.H., (2001) J. Appl. Crystallogr., 34, p. 210. , JACGAR 0021-8898 10.1107/S0021889801002242Von Dreele, R.B., (1994)Newville, M., Ravel, B., (2001)Torardi, C.C., McCarron III, E.M., Subramanian, M.A., Sleight, A.W., Cox, D.E., (1987) Mater. Res. Bull., 22, p. 1563. , MRBUAC 0025-5408Demazeau, G., Parent, C., Pouchard, M., Hagenmueller, P., (1972) Mater. Res. Bull., 7, p. 913. , MRBUAC 0025-5408David, W.I.F., Harrison, W.T.A., Ibberson, R.M., Weller, M.T., Grasmeder, J.R., Lanchester, P.C., (1987) Nature (London), 328, p. 328. , NATUAS 0028-0836Izumi, F., Asano, H., Ishigaki, T., Takayama-Muromachi, E., Matsui, Y., Uchida, Y., (1987) Jpn. J. Appl. Phys., Part 2, 26, p. 1153. , JAPLD8 0021-4922Izumi, F., Takayama-Muromachi, E., Kobayashi, M., Uchida, Y., Asano, H., Ishigaki, T., Watanabe, N., (1988) Jpn. J. Appl. Phys., Part 2, 27, p. 824. , JAPLD8 0021-4922Domenges, B., Hervieu, M., Michel, C., Maignan, A., Raveau, B., (1988) Phys. Status Solidi a, 107, p. 73. , PSSABA 0031-8965Ruiz-González, L., Boulahya, K., Parras, M., Alonso, J., González-Calbet, J.M., (2002) Chem.-Eur. J., 8 (24), p. 5694. , CEUJED. 0947-6539Shubnikov, A.V., Belov, N.V., (1964) Colored Symmetry, , Pergamon Press, Oxfor

Critical analysis of autoregressive and fast Fourier transform markers of cardiovascular variability in rats and humans

The autonomic nervous system plays an important role in physiological and pathological conditions, and has been extensively evaluated by parametric and non-parametric spectral analysis. To compare the results obtained with fast Fourier transform (FFT) and the autoregressive (AR) method, we performed a comprehensive comparative study using data from humans and rats during pharmacological blockade (in rats), a postural test (in humans), and in the hypertensive state (in both humans and rats). Although postural hypotension in humans induced an increase in normalized low-frequency (LFnu) of systolic blood pressure, the increase in the ratio was detected only by AR. In rats, AR and FFT analysis did not agree for LFnu and high frequency (HFnu) under basal conditions and after vagal blockade. The increase in the LF/HF ratio of the pulse interval, induced by methylatropine, was detected only by FFT. In hypertensive patients, changes in LF and HF for systolic blood pressure were observed only by AR; FFT was able to detect the reduction in both blood pressure variance and total power. In hypertensive rats, AR presented different values of variance and total power for systolic blood pressure. Moreover, AR and FFT presented discordant results for LF, LFnu, HF, LF/HF ratio, and total power for pulse interval. We provide evidence for disagreement in 23% of the indices of blood pressure and heart rate variability in humans and 67% discordance in rats when these variables are evaluated by AR and FFT under physiological and pathological conditions. The overall disagreement between AR and FFT in this study was 43%.FINEPFAPESPZerbini Foundatio

The spinorial geometry of supersymmetric heterotic string backgrounds

We determine the geometry of supersymmetric heterotic string backgrounds for which all parallel spinors with respect to the connection $\hat\nabla$ with torsion $H$, the NS$\otimes$NS three-form field strength, are Killing. We find that there are two classes of such backgrounds, the null and the timelike. The Killing spinors of the null backgrounds have stability subgroups K\ltimes\bR^8 in $Spin(9,1)$, for $K=Spin(7)$, SU(4), $Sp(2)$, $SU(2)\times SU(2)$ and $\{1\}$, and the Killing spinors of the timelike backgrounds have stability subgroups $G_2$, SU(3), SU(2) and $\{1\}$. The former admit a single null $\hat\nabla$-parallel vector field while the latter admit a timelike and two, three, five and nine spacelike $\hat\nabla$-parallel vector fields, respectively. The spacetime of the null backgrounds is a Lorentzian two-parameter family of Riemannian manifolds $B$ with skew-symmetric torsion. If the rotation of the null vector field vanishes, the holonomy of the connection with torsion of $B$ is contained in $K$. The spacetime of time-like backgrounds is a principal bundle $P$ with fibre a Lorentzian Lie group and base space a suitable Riemannian manifold with skew-symmetric torsion. The principal bundle is equipped with a connection $\lambda$ which determines the non-horizontal part of the spacetime metric and of $H$. The curvature of $\lambda$ takes values in an appropriate Lie algebra constructed from that of $K$. In addition $dH$ has only horizontal components and contains the Pontrjagin class of $P$. We have computed in all cases the Killing spinor bilinears, expressed the fluxes in terms of the geometry and determine the field equations that are implied by the Killing spinor equations.Comment: 73pp. v2: minor change

A feasibility cachaca type recognition using computer vision and pattern recognition

Brazilian rum (also known as cachaça) is the third most commonly consumed distilled alcoholic drink in the world, with approximately 2.5 billion liters produced each year. It is a traditional drink with refined features and a delicate aroma that is produced mainly in Brazil but consumed in many countries. It can be aged in various types of wood for 1-3 years, which adds aroma and a distinctive flavor with different characteristics that affect the price. A research challenge is to develop a cheap automatic recognition system that inspects the finished product for the wood type and the aging time of its production. Some classical methods use chemical analysis, but this approach requires relatively expensive laboratory equipment. By contrast, the system proposed in this paper captures image signals from samples and uses an intelligent classification technique to recognize the wood type and the aging time. The classification system uses an ensemble of classifiers obtained from different wavelet decompositions. Each classifier is obtained with different wavelet transform settings. We compared the proposed approach with classical methods based on chemical features. We analyzed 105 samples that had been aged for 3 years and we showed that the proposed solution could automatically recognize wood types and the aging time with an accuracy up to 100.00% and 85.71% respectively, and our method is also cheaper.info:eu-repo/semantics/publishedVersio

Antioxidant capacity and toxicological evaluation of pterospartum tridentatum flower extracts

Pterospartum tridentatum Willk. (prickled broom) is an autochthonous plant, common in Portuguese territory. The yellow flowers are used in traditional medicine, as a potential cure for all body illnesses, mainly for throat irritation treatment or for diabetes, hypertension and hypercholesterolemia therapy.Despite its traditional use, no toxicological assessment has been performed as we know. A high antioxidant activity of P. tridentatum flower water extract was acessed in good agreement with its ESI-MS spectrum that revealed the presence of several flavonoids, as luteolin-O-(O-acetyl)-glucuronide, luteolin-O- glucuronide or isorhamnetin-O-hexoside. Mitocondrial respiratory rates (state 4, state 3 and FCCP-stimulated respiration) and respiratory indexes (respiratory control and P/O ratios) showed no consistent decrease of respiratory and phosphorylative efficiencies for the concentrations tested (up to 500 μg.mL-1). Cytotoxicity evaluation, using MTT assay, was reliable with the previous results. In conclusion, for the concentration range commonly used P. tridentatum flowers usage can be regarded as harmless and trustworthy

Elastic properties of polycrystalline YBa_2Cu_3O_7: Evidence for granularity induced martensitic behavior

In this work we present the study of the elastic properties of polycrystalline samples of superconducting YBa_2Cu_3O_7 prepared by the sol-gel method. The quality of all samples was checked by x-ray diffraction and scanning electronic microscopy while their physical properties were verified by transport and magnetic measurements. The elastic study was performed using the standard pulse-echo technique through measuring the phase velocity and the attenuation of ultrasonic waves (in the range of a few MHz) as a function of temperature. We have focused this study on the low temperatures interval (T < 200K). The obtained results show a strong hysteretic behavior in the ultrasonic attenuation (in addition to usually observed hysteretic behavior for the velocity) which strongly supports the existence of a martensitic-like phase above the superconducting critical temperature T_C. We argue that this peculiar behavior can be attributed to the granularity present in the samples.Comment: Physica C (in press