Microwave properties of DyBa_2Cu_3O_(7-x) monodomains and related compounds in magnetic fields

We present a microwave characterization of a DyBa$_{2}$Cu$_{3}$O$_{7-x}$ single domain, grown by the top-seeded melt-textured technique. We report the (a,b) plane field-induced surface resistance, $\Delta R_s(H)$, at 48.3 GHz, measured by means of a cylindrical metal cavity in the end-wall-replacement configuration. Changes in the cavity quality factor Q against the applied magnetic field yield $\Delta R_s(H)$ at fixed temperatures. The temperature range [70 K ; T_c] was explored. The magnetic field $\mu_0 H <$ 0.8 T was applied along the c axis. The field dependence of $\Delta R_s(H)$ does not exhibit the steep, step-like increase at low fields typical of weak-links. This result indicates the single-domain character of the sample under investigation. $\Delta R_s(H)$ exhibits a nearly square-root dependence on H, as expected for fluxon motion. From the analysis of the data in terms of motion of Abrikosov vortices we estimate the temperature dependences of the London penetration depth $\lambda$ and the vortex viscosity $\eta$, and their zero-temperature values $\lambda(0)=$165 nm and $\eta(0)=$ 3 10$^{-7}$ Nsm$^{-2}$, which are found in excellent agreement with reported data in YBa$_{2}$Cu$_{3}$O$_{7-x}$ single crystals. Comparison of microwave properties with those of related samples indicate the need for reporting data as a function of T/T_c in order to obtain universal laws.Comment: 6 pages, 4 figures, LaTeX, submitted to Journal of Applied Physic

Strongly Enhanced Current Densities in Superconducting Coated Conductors of YBa2Cu3O7-x + BaZrO3

There are numerous potential applications for superconducting tapes, based on YBa2Cu3O7-x (YBCO) films coated onto metallic substrates. A long established goal of more than 15 years has been to understand the magnetic flux pinning mechanisms which allow films to maintain high current densities out to high magnetic fields. In fact, films carry 1-2 orders of magnitude higher current densities than any other form of the material. For this reason, the idea of further improving pinning has received little attention. Now that commercialisation of conductors is much closer, for both better performance and lower fabrication costs, an important goal is to achieve enhanced pinning in a practical way. In this work, we demonstrate a simple and industrially scaleable route which yields a 1.5 to 5-fold improvement in the in-field current densities of already-high-quality conductors

Glutathione S-transferase M1-null genotype as risk factor for SOS in oxaliplatin-treated patients with metastatic colorectal cancer

Background: Oxaliplatin is used as a neo-adjuvant therapy in hepatic colorectal carcinoma metastasis. This treatment has significant side effects, as oxaliplatin is toxic to the sinusoidal endothelial cells and can induce sinusoidal obstruction syndrome (SOS), which is related to decreased overall survival. Glutathione has an important role in the defence system, catalysed by glutathione S-transferase (GST), including two non-enzyme producing polymorphisms (GSTM1-null and GSTT1-null). We hypothesise that patients with a non-enzyme producing polymorphism have a higher risk of developing toxic injury owing to oxaliplatin. Methods: In the nontumour-bearing liver, the presence of SOS was studied histopathologically. The genotype was determined by a semi-nested PCR. Results: Thirty-two of the 55 (58%) patients showed SOS lesions, consisting of 27% mild, 22% moderate and 9% severe lesions. The GSTM1-null genotype was present in 25 of the 55 (46%). Multivariate analysis showed that the GSTM1-null genotype significantly correlated with the presence of (moderate-severe) SOS (P=0.026). Conclusion: The GSTM1-null genotype is an independent risk factor for SOS. This finding allows us, in association with other risk factors, to conceive a potential risk profile predicting whether the patient is at risk of developing SOS, before starting oxaliplatin, and subsequently might result in adjustment of treatment

Modulated misfit structure of the thermoelectric [Bi0.84CaO 2]2[CoO2]1.69 cobalt oxide

The structure of the thermoelectric lamellar misfit cobalt oxide [Bi 0.84CaO2]2[CoO2]1.69 has been refined using single crystal X-ray diffraction data. Using the four dimensional superspace formalism for aperiodic structures, the superspace group is confirmed P2/m(0δ1/2) (a1 = 4.9069(4), b1 = 4.7135(7), b2 = 2.8256(4), c1 = 14.668(5) Å, β1 = 93.32(1)°). The modulated displacements and site occupancies have been refined and are both compatible with the misfit character of the structure, and with a longitudinal modulation of the Bi-O layers of the structure. This modulation is similar to the corresponding one in the related Sr phase [Bi0.87SrO2]2[CoO2]1.82, but now oriented in the orthogonal direction. Because its incommensurate wavelength is locked with the aperiodicity of the misfit structure, it is possible to distinguish between the modulation parameters induced by the accommodation of both subsystems and those related to the longitudinal modulation of the Bi-O layers. In this original structure, two independent aperiodic phenomena coexist in an single crystallographic direction. A particular attention has been paid to the structural configuration of the CoO2 layer, in relation with other similar phases. The thermoelectric properties are probably directly related to the specific distortion of the compressed layer, but the different measured values for the Seebeck coefficient cannot be related to a significant modification of the CoO6 octahedra. © 2008 American Chemical Society

3D laser shock peening as a way to improve geometrical accuracy in selective laser melting

One of the major drawbacks of selective laser melting (SLM) is the accumulation of tensile residual stresses (TRS) in the surface and subsurface zones of produced parts which can lead to cracking, delamination, geometrical distortions, and a decrease in fatigue life. 3D laser shock peening (3D LSP) is a novel hybrid method which introduces a repetitive LSP treatment during the manufacturing phase of the SLM process. In this paper, the ability of 3D LSP to convert TRS into beneficial compressive residual stresses and their subsequent effect on the geometrical accuracy of produced parts were investigated. Samples made of Ti6Al4V were manufactured with the 3D LSP process and treated with different processing parameters. Cuboidal samples were used for residual stress measurements, and the evolution of residual stresses was evaluated. Geometrical distortions were measured on bridge-like samples, and the influence on the final sample geometry was quantified. A significant improvement in geometrical accuracy resulting from reduced distortions was observed in all selected 3D LSP processing conditions