Aluminium substitution induced superstructures in Mg1-xAlxB2 (x = 0.0 to 0.50): An X-ray diffraction study

The physical property characterization of Al doped Mg1-xAlxB2 system with x = 0.0 to 0.50 is reported. The results related to phase formation, structural transition, resistivity R(T) and magnetization M(T) measurements are discussed in detail. It is shown that the addition of electrons to MgB2 through Al results in loss of superconductivity. Also seen is a structural transition associated with the collapse of boron layers reflected by the continuous decrease in the c parameter. The main emphasis in this paper is on slow scan X-ray diffraction (XRD) results, which confirm the existence of a superstructure along the c-direction for the x = 0.50 sample. The appearance of some additional peaks, viz. [103], [004], [104] and [112], results in doubling of the lattice parameter along the c-axis. This possibly indicates the alternative ordering of Al and Mg in MgAlB4 separated by hexagonal boron layers but still maintaining the same hexagonal AlB2 type structure.Comment: 17 Pages Text + Figs. To appear in Physica

On the melt processed YBa2Cu3O7 12x physico-chemical characterization

We determined the proper conditions to obtain superconducting samples by melting. Two preparation methods were investigated: arc melting of YBa2Cu3O7 prereacted powders at about 1900\ub0C and partial melting at T = 1080\ub0C, just 50\ub0C above the peritectic decomposition of YBa2Cu3O7. The latter one revealed itself a one-step technique to obtain high Tc superconductors by melting. Micrographic, structural, electric and magnetic characterizations of these materials are reported and compared with the corresponding properties of the more traditional sintered samples: the best results were obtained for the partially melted samples annealed in flowing oxygen at suitable temperature

Hepatocellular carcinoma in thalassaemia : an update of the Italian registry

Summary: The risk of developing hepatocellular carcinoma (HCC) in patients with thalassaemia is increased by transfusion-transmitted infections and haemosiderosis. All Italian Thalassaemia Centres use an ad hoc form to report all diagnoses of HCC to the Italian Registry. Since our last report, in 2002, up to December 2012, 62 new cases were identified, 52% of whom were affected by thalassaemia major (TM) and 45% by thalassaemia intermedia (TI). Two had sickle-thalassaemia (ST). The incidence of the tumour is increasing, possibly because of the longer survival of patients and consequent longer exposure to the noxious effects of the hepatotropic viruses and iron. Three patients were hepatitis B surface antigen-positive, 36 patients showed evidence of past infection with hepatitis B virus (HBV). Fifty-four patients had antibodies against hepatitis C virus (HCV), 43 of whom were HCV RNA positive. Only 4 had no evidence of exposure either to HCV or HBV. The mean liver iron concentration was 8 mg/g dry weight. Therapy included chemoembolization, thermoablation with radiofrequency and surgical excision. Three patients underwent liver transplant, 21 received palliative therapy. As of December 2012, 41 patients had died. The average survival time from HCC detection to death was 11\ub75 months (1\ub74-107\ub72 months). Ultrasonography is recommended every 6 months to enable early diagnosis of HCC, which is crucial to decrease mortality