1,042 research outputs found

    Evidence for a vortex-glass transition in superconducting Ba(Fe0.9_{0.9}Co0.1_{0.1})2_{2}As2_{2}

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    Measurements of magneto-resistivity and magnetic susceptibility were performed on single crystals of superconducting Ba(Fe0.9_{0.9}Co0.1_{0.1})2_{2}As2_{2} close to the conditions of optimal doping. The high quality of the investigated samples allows us to reveal a dynamic scaling behaviour associated with a vortex-glass phase transition in the limit of weak degree of quenched disorder. Accordingly, the dissipative component of the ac susceptibility is well reproduced within the framework of Havriliak-Negami relaxation, assuming a critical power-law divergence for the characteristic correlation time τ\tau of the vortex dynamics. Remarkably, the random disorder introduced by the Fe1−x_{1-x}Cox_{x} chemical substitution is found to act on the vortices as a much weaker quenched disorder than previously reported for cuprate superconductors such as, e.g., Y1−x_{1-x}Prx_{x}Ba2_{2}Cu3_{3}O7−δ_{7-\delta}.Comment: 10 pages, 8 figure

    Tamoxifen, aminoglutethimide and danazol: effect of therapy on hormones in post-menopausal patients with breast cancer.

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    Gonadotrophins, oestradiol, androstenedione, testosterone and dehydroepiandrosterone sulphate (DHAS) were measured sequentially in 72 patients with advanced breast cancer receiving endocrine therapy of various types. Tamoxifen significantly reduced gonadotrophins but did not effect other hormones. Danazol also reduced gonadotrophins. Aminoglutethimide (AGT) reduced oestradiol and DHAS but had not effect on gonadotrophins. The effects of administering tamoxifen, AGT and danazol together (TAD) together were therefore examined. This combination reduced gonadotrophins, oestradiol and DHAS, but no further than tamoxifen and AGT alone. The degree and duration of hormone suppression were similar in both responders and non-responders to tamoxifen, AGT or TAD, though patients responding to AGT showed more complete suppression at the end of the course of treatment, perhaps because they were treated longer. On relapse, adequate gonadotrophin and steroid suppression was demonstrated in patients receiving tamoxifen and AGT respectively. We conclude that (a) response to endocrine therapy is unlikely to be related to the degree of endocrine suppression produced by the therapy; (b) combination endocrine therapy does not further reduce serum-hormone concentrations and (c) relapse is unlikely to be due to escape from the hormone-inhibitory effects of endocrine agents

    c-erbB-2 expression in benign and malignant breast disease.

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    An antibody, 21N, raised against a synthetic peptide from the predicted sequence of the c-erbB-2 protein has been used immunocytochemically in a retrospective study of formalin fixed paraffin embedded breast biopsies. Fourteen out of 103 infiltrating ductal carcinomas exhibited positive membrane staining. Fifty-four of these tumours had lymph node involvement of which nine contained stained cells. These were all cases where the primary tumour was positive. In this series there was no correlation between c-erbB-2 overexpression and lymph node status. In five of the positive cases studied there was an associated in situ component which was also positively stained. Ten out of 24 pure intraduct carcinomas showed membrane staining, but none of the 149 benign conditions studied, which included 22 radial scars and 13 cases of atypical ductal proliferation, demonstrated the pattern of staining associated with overexpression. It is concluded that the c-erbB-2 protein is overexpressed in a minority (approximately 14%) of infiltrating ductal carcinomas and only in cells that are cytologically malignant. Overexpression of c-erbB-2 is considered in relation to pathogenesis

    Viscoelasticity near the gel-point: a molecular dynamics study

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    We report on extensive molecular dynamics simulations on systems of soft spheres of functionality f, i.e. particles that are capable of bonding irreversibly with a maximum of f other particles. These bonds are randomly distributed throughout the system and imposed with probability p. At a critical concentration of bonds, p_c approximately equal to 0.2488 for f=6, a gel is formed and the shear viscosity \eta diverges according to \eta ~ (p_c-p)^{-s}. We find s is approximately 0.7 in agreement with some experiments and with a recent theoretical prediction based on Rouse dynamics of phantom chains. The diffusion constant decreases as the gel point is approached but does not display a well-defined power law.Comment: 4 pages, 4 figure

    He II λ\lambda4686 emission from the massive binary system in η\eta Car: constraints to the orbital elements and the nature of the periodic minima

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    {\eta} Carinae is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II λ4686\lambda 4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He II λ4686\lambda 4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of EW(He II λ4686\lambda 4686), the line radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW(He II λ4686\lambda 4686) variations, combined with other measurements, yield an orbital period 2022.7±0.32022.7\pm0.3 d. The observed variability of the EW(He II λ4686\lambda 4686) was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary's atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135∘135^\circ-153∘153^\circ, and the longitude of periastron to 234∘234^\circ-252∘252^\circ. It also suggests that periastron passage occurred on T0=2456874.4±1.3T_0 = 2456874.4\pm1.3 d. Our model also reproduced EW(He II λ4686\lambda 4686) variations from a polar view of the primary star as determined from the observed He II λ4686\lambda 4686 emission scattered off the Homunculus nebula.Comment: The article contains 23 pages and 17 figures. It has been accepted for publication in Ap
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