Superconducting Volume Fraction in Overdoped Regime of La_2-x_Sr_x_CuO_4_: Implication for Phase Separation from Magnetic-Susceptibility Measurement

We have grown a single crystal of La_2-x_Sr_x_CuO_4_ in which the Sr concentration, x, continuously changes from 0.24 to 0.29 in the overdoped regime and obtained many pieces of single crystals with different x values by slicing the single crystal. From detailed measurements of the magnetic susceptibility, chi, of each piece, it has been found that the absolute value of chi at the measured lowest temperature 2 K, |chi_2K_|, on field cooling rapidly decreases with increasing x as well as the superconducting (SC) transition temperature. As the value of |chi_2K_| is regarded as corresponding to the SC volume fraction in a sample, it has been concluded that a phase separation into SC and normal-state regions occurs in a sample of La_2-x_Sr_x_CuO_4_ in the overdoped regime.Comment: 4 pages, 3 figures, ver. 2 has been accepted in J. Phys. Soc. Jp

In-situ epitaxial growth of superconducting La-based bilayer cuprate thin films

We investigate the epitaxial growth of bilayer cuprate La2CaCu2O6+\delta using pure ozone as an oxidant, and find that even the crystal with parent composition without cation substitution can show metallic behavior with the aid of epitaxial strain effect. The hole concentration is controlled simply by excess-oxygen doping, and the films grown under the optimum conditions exhibit superconductivity below 30 K. This is the first result on the superconductivity of bilayer La2CaCu2O6+\delta induced purely by the excess oxygen.Comment: 5 pages, 3 figures, To appear in Phys. Rev. B, Rapid Communication

Evidence for Magnetic Pseudoscaling in Overdoped La(2-x)Sr(x)CuO(4)

We report the results of electronic Raman scattering experiments on an overdoped La(1.78)Sr(0.22)CuO(4) single crystal as a function of temperature. The scattering rate Gamma(w->0,T) has been determined from the normal state B(1g) spectra in the range 50 K < T < 300 K. Gamma(T) decreases linearly from 300 K to about 175 K and then undergoes a reduction with respect to the expected mean-field behavior. This trend suggests a crossover to pseudoscaling regime at about T(cr)=160 K. The results are in good agreement with the prediction of the nearly antiferromagnetic Fermi liquid model. There is no evidence of a pseudogap in the spectra obtained from this overdoped sample.Comment: RevTex, 4 pages with 3 PS figures included, replaced with minor changes in the text and reference

Doping Dependence of the Pseudogap in La(2-x)Sr(x)CuO(4)

We report the results of Raman scattering experiments on single crystals of La(2-x)Sr(x)CuO(4) that span the range from underdoped (x = 0.10) to overdoped (x =0.22). The spectra are consistent with the existence of a strong anisotropic quasiparticle interaction that results in a normal state depletion of spectral weight from regions of the Fermi surface located near the zone axes. The strength of the interaction decreases rapidly with increasing hole concentration and the spectral evidence for the pseudogap vanishes when the optimum doping level is reached. The results suggest that the pseudogap and superconducting gap arise from different mechanisms.Comment: 7 pages, 6 eps figures, added new sections, figures, reference

Targeting survivin and p53 in pediatric acute lymphoblastic leukemia

Despite advances in treatment and outcomes for patients with pediatric acute lymphoblastic leukemia (ALL), there continue to be subsets of patients who are refractory to standard chemotherapy and hematopoietic stem cell transplant. Therefore, novel gene targets for therapy are needed to further advance treatment for this disease. RNA interference technology has identified survivin as a potential therapeutic target. Survivin, a member of the inhibitor of apoptosis (IAP) proteins and chromosome passenger complex, is expressed in hematologic malignancies and overexpressed in relapsed pediatric ALL. Our studies show that survivin is uniformly expressed at high levels in multiple pediatric ALL cell lines. Furthermore, silencing of survivin expression in pediatric ALL cell lines as well as primary leukemic blasts reduces viability of these cells. This includes cell lines derived from patients with relapsed disease featuring cytogenetic anomalies such as t(12;21), Philadelphia chromosome t(9;22), t(1;19) as well as a cell line carrying t(17;19) from a patient with de novo ALL. Furthermore, inhibition of survivin increases p53-dependent apoptosis that can be rescued by inhibition of p53. Finally, a screen of randomly selected primary patient samples confirms that survivin-specific small interfering RNA and survivin-targeted drug, YM155, effectively reduce viability of leukemic blasts

Preparation of covellite and digenite thin films by an intermittent spray pyrolysis deposition method

Intermittent spray pyrolysis of 0.01-0.20 M aqueous solutions of CuCl (dissolved in the presence of 3-fold molar amount of thiourea) onto a heated alkali-free glass substrate in air already at 225-275 degreesC resulted in various thin films of CuS (covellite) and/or Cu(1.8)s (Cu9S5, digenite). A combination of low pyrolysis temperatures (225-250 degreesC) and low solution concentrations (0.01-0.02 M) has resulted in the formation of thin solid CuS films. At a pyrolysis temperature of 275 degreesC Cu1.8S films have been obtained. The higher concentration range (0.05-0.20 M) has been found favorable for simultaneous formation of Cu1.8S and CuS. In the two-phase layers the crystal growth of CuS has seemed to be limited, whilst the growth of Cu1.8S has been preferentially favored especially on its (0 0 15) lattice plane. (C) 2001 Elsevier Science Ltd. All rights reserved

Fluorine doped tin oxide film with high haze and transmittance prepared for dye-sensitized solar cells

autho

Preparation of SnO2 transparent conducting films for dye-sensitized solar cells by SPD technique

Tin oxide, SnO2, transparent conducting oxide (TCO) films for dye-sensitized solar cells (DSSCs) was investigated. We found that an electrical conductivity is not the only parameter that governs conversion efficiency of DSSC. The conversion efficiency was strongly influenced by haze ratio that is easily tuned by controlling the surface morphology of TCO layer by spray pyrolysis deposition (SPD) technique. The conversion efficiency was enhanced as high as 7.6%, attributing to an effective incident light harvest of a working electrode in the consequence of the confinement of the incident light within the cell