Evolution of nanocrystalline BaBi2Nb2O9 in Li2B4O7 BaO-Bi(2)O3-Nb2O5 glass system

Transparent glasses and glass nano crystal composites (GNCs) of various compositions in the system (100 - x)Li2B4O7-x (BaO-Bi2O3-Nb2O5) (where x = 10, 20, and 30 in molar ratio) were fabricated via splat-quenching technique. The glassy nature of the as quenched samples was established by differential thermal analyses. X-ray powder diffraction and transmission electron microscopic (TEM) studies confirmed the formation of layered perovskite BBN via a fluorite like phase. TEM studies revealed the presence of 10 nm sized spherical crystallites of fluorite like BaBi2Nb2O9 phase in the glassy matrix of Li2B4O7 (LBO). The influence of composition on the dielectric and the optical properties (transmission, optical band gap) of these samples has been investigated. (c) 2007 Elsevier B.V. All rights reserved.

Data integration from two microarray platforms identifies bi-allelic genetic inactivation of RIC8A in a breast cancer cell line

Background: Using array comparative genomic hybridization (aCGH), a large number of deleted genomic regions have been identified in human cancers. However, subsequent efforts to identify target genes selected for inactivation in these regions have often been challenging. Methods: We integrated here genome-wide copy number data with gene expression data and non-sense mediated mRNA decay rates in breast cancer cell lines to prioritize gene candidates that are likely to be tumour suppressor genes inactivated by bi-allelic genetic events. The candidates were sequenced to identify potential mutations. Results: This integrated genomic approach led to the identification of RIC8A at 11p15 as a putative candidate target gene for the genomic deletion in the ZR-75-1 breast cancer cell line. We identified a truncating mutation in this cell line, leading to loss of expression and rapid decay of the transcript. We screened 127 breast cancers for RIC8A mutations, but did not find any pathogenic mutations. No promoter hypermethylation in these tumours was detected either. However, analysis of gene expression data from breast tumours identified a small group of aggressive tumours that displayed low levels of RIC8A transcripts. qRT-PCR analysis of 38 breast tumours showed a strong association between low RIC8A expression and the presence of TP53 mutations (P = 0.006). Conclusion: We demonstrate a data integration strategy leading to the identification of RIC8A as a gene undergoing a classical double-hit genetic inactivation in a breast cancer cell line, as well as in vivo evidence of loss of RIC8A expression in a subgroup of aggressive TP53 mutant breast cancers.

Behaviour of Bi-adhesive Joints

The use of relatively low modulus adhesive at the ends of overlap in a bi-adhesive bondline of a bonded joint can reduce the stress concentration significantly and, therefore, potentially lead to higher strength of the joint. This study presents the two-dimensional and three-dimensional nonlinear (geometric and material) finite element analyses of adhesively bonded single lap joints having modulus-graded bondline under monotonic loading conditions. The adhesives were modelled as an elasto-plastic multi-linear material, while the substrates were regarded as both linear elastic and bi-linear elasto-plastic material. The computational simulations have been performed to investigate the bondline behaviour by studying the stress and strain distributions both at the mid-plane as well as at the interface of the bondline. It has been observed that the static strength is higher for joints with bi-adhesive bondlines compared to those with single adhesives in bondline. Higher joint strength has also been observed for optimum bi-adhesive bondline ratio through parametric studies. Effects of load level, and bondline thickness on stress distribution in the bi-adhesive bondline have also been studied. 3D analysis results reveal the existence of complex multi-axial stress/strain state at the ends of the overlap in the bondline which cannot be observed in 2D plane strain analysis. About 1/3rd of the width of the joint from the free edge in the width direction has 3D stress state, especially in the compliant adhesive of the bondline. Magnitudes of longitudinal and lateral stress/strain components are comparable to peel stress/strain components. It has also been analytically shown that the in-plane global stiffness of the joint remains unaffected by modulus gradation of the bondline adhesive. (C) Koninklijke Brill NV, Leiden, 2010.

Dielectric properties of glasses prepared by quenching melts of superconducting Bi‐Ca‐Sr‐Cu‐O cuprates

Glasses obtained from quenching melts of superconducting bismuth cuprates of the formula Bi2(Ca,Sr)n+1CunO2n+4 with n=1 and 3 exhibit novel dielectric properties. They possess relatively high dielectric constants as well as high electrical conductivity. The novel dielectric properties of these cuprate glasses are likely to be of electronic origin. They exhibit a weak microwave absorption due to the presence of microcrystallites.

Neutron diffraction evidence for oxygen dimers in Bi-Ca-Sr-Cu-O superconductors

A comparative neutron diffraction study of Bi2CaSr2Cu2O8+δ, Bi2Ca2SrCu2O8+δ and Bi2Ca1.5Y0.5SrCu2O8+δ has not only shown the presence of considerable oxygen excess in the Bi layers, but also evidence for oxygen pairing giving rise to O1−2 or O2−2 type species, probably the latter. The proportion of the paired species increases when Y partly replaces Ca. Furthermore, the Tc decreases with an increase in paired species.

A possible mechanism for high-temperature superconductivity: Application to Bi and Tl compounds

We applied our previous theory of high temperature superconductivity to Bi and Tl compounds in this paper. The theory involves the role of electron pairs in the spin singlet of species Xequal-or-greater, slanted (Bi3+ (6S2), Tl(6S2) etc.) and their virtual excited state X0 (Bi5+ (6s0), Tl3+ (6s0), etc.) in the pairing interaction of quasiholes. Bi and Tl species provide additional channels of kind (Xequal-or-greater, slanted left angle bracket X0) owing to the charge fluctuations. We treated the two states of these species like a two-level Bose system. We used the pseudospin formalism to calculate the expression for the critical temperature in this paper. We also calculated numerically the value of Tc for Bi and Tl compounds and found a good agreement between theory and experiment.

Crystal chemistry of a new solid solution in the BaO-Bi2O3-Nb2O5 system: Ba-5x/2-Bi(1-x)5/3Nb5O15

A solid solution of the type Ba5x/2Bi(1-x)5/3Nb5O15 has been identified in the BaO-Bi2O3-Nb2O5 system for the first time. The limits of the solid solution are within the range 0.52 <= x <= 0.80. The compositions x = 0.52, 0.60, 0.72, 0.77, 0.78, and 0.80 were synthesized by the solid-state technique from the starting materials in stoichiometric quantities. The powder X-ray patterns of all the phases in the domain indicate a structural similarity to tetragonal tungsten bronzes (TTBs). The compositions below x = 0.52 and those above x = 0.80 exhibit barium niobate and bismuth niobate impurities, respectively. Single crystals of the composition x = 0.77 were obtained by the melt cooling technique. The crystal structure of Ba3.85/2Bi1.15/3Nb5O15 (x = 0.77) was solved in the tetragonal space group P4bm (No. 100) with a = 12.4938 (14) angstrom, c = 3.9519 (2) A, V = 616.87 (10) angstrom(3), and Z = 2 and was refined to an R index of 0.034. Dielectric measurements on all the phases indicate a typical relaxor behavior with a broad phase transition at T-m approximate to 300 K.

A computer study of the miscibility limits of Sb-Te-Bi

The quaternary system Sb1bTe1bBi1bSe with small amounts of suitable dopants is of interest for the manufacture of thermoelectric modules which exhibit the Peltier and Seebeck effects. This property could be useful in the production of energy from the thermoelectric effect. Other substances are bismuth telluride (Bi2Te3) and Sb1bTe1bBi and compounds such as ZnIn2Se4. In the present paper the application of computer programs such as MIGAP of Kaufman is used to indicate the stability of the ternary limits of Sb1bTe1bBi within the temperature ranges of interest, namely 273 K to 300 K.

High-temperature superconductivity in bismuth-copper oxides of the type BimMnCupOx (M=Mg, Ca, Sr, Ba, Bi)

Several oxides of the Bi m M n Cu p O x family (m=2, 3;n=2, 3, 4;p=1, 2, 3 and M=alkaline earth or Bi), possessing structures similar to the Aurivillius family of oxides, show highT c superconductivity.

Indications of superconductivity in the 200–300K range in the Bi-Ca-Sr-Cu-O system

Some of the Bi-Ca-Sr-Cu-O compositions show indications of onset of superconductivity in the 200–300 K region, possibly due to the intergrowth of different layered sequences.

Crystal Chemistry of the Noncentrosymmetric Eulytites: A(3)Bi(XO4)(3) (X = V, A = Pb; X = P, A = Ca, Cd, Sr, Pb)

Eulytite compounds, A(3)Bi(XO4)(3) (X = P, A = Ca, Cd, Sr, Pb), belong to the noncentrosymmetric space group l (4) over bar 3d (No. 220) as determined by single-crystal X-ray diffraction studies. The crystals were grown from the melt-cool technique with considerable difficulty as the compounds melt incongruently at their melting temperature, except for the compound Pb3Bi(PO4)(3). The unit cell parameter a is 9.984(5), 9.8611(3), 10.2035(3), and 10.3722(2) angstrom for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), Sr3Bi(PO4)(3), and Pb3Bi(PO4)(3) respectively, and there are four formula units in the unit cell. The structure of Pb3Bi(VO4)(3), a unique eulytite with vanadium substitution, is compared with all these phosphorus substituted eulytites. The A(2+) and Bi3+ cations occupy the special position (16c) while the O anions occupy the general Wyckoff position (48e) in the crystal structure. Only one O position has been identified for Pb3Bi(PO4)(3) and Pb3Bi(VO4)(3), whereas two O atom sites were identified for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), and Sr3Bi(PO4)(3). The UV-vis diffuse reflectance spectra indicate large band gaps for all the phosphate eulytites while a lower band gap is observed for the vanadate eulytite. The feasibility of the use of these compounds in optoelectronic devices has been tested by measuring the second-harmonic generation (SHG) values which have been found to be of a magnitude equivalent to the commercially used KDP (KH2PO4).

Superconductivity in Ba(Pb,Bi,Sb)O3, Ba(Pb,Bi,Te)O3 and (Ba,La) (Pb,Bi,Tl)O3 systems

It is possible to substitute Bi in the superconducting BaPb0.75Bi0.25O3 by Sb or Te without destroying the superconductivity. With Sb, a continuous series of solid solutions BaPb0.75Bi0.25?ySbyO3 (0 less-than-or-equals, slant y less-than-or-equals, slant 0.25) exists, while with Te, perovskite BaPb0.75Bi0.25?yTeyO3 exists only upto y = 0.15. With increasing substitution by Sb or Te, Tc decreases continously in both the systems. Superconductivity with a maximum Tc of 8K is found in Ba0.9La0.1Pb0.9?yBiyTl0.1O3 for y = 0.25.

Probing disorder in cubic pyrochlore Bi-1 Zn-5(1) Nb-0(1) O-5(7) (BZN) thin films

The dielectric response of pulsed laser ablated Bi-1 Zn-5(1) Nb-0(1) O-5(7) (BZN) thin films are investigated within the temperature range of 300-660 K and frequency range of 100 Hz-100 kHz Thin film exhibited a strong dielectric relaxation behavior A sharp rise in dielectric constant of BZN thin film at high temperatures is related to disorder in canon and anion lattices Observed dielectric relaxation implies a redistribution of charges within the unit cell This phenomenon suggests that the large change in dielectric constant is due to a dynamical rise of dipolar fluctuations in the unit cell XPS spectra of BZN (A(2)B(2)O(6)O') cubic pyrochlore confirm that the relaxation corresponds to the ionic hopping among the A and O' positions of several local potential minima Barrier height for hopping is distributed between 0 and 0 94 eV The O is spectrum confirms presence of two types of oxygen in BZN thin film The disorder in charge neutralized thin film is correlated with XPS spectra (C) 2010 Elsevier Ltd All rights reserved