Investigation of the structural, electrical, and dielectric properties of La0.5Sm0.2Sr0.3Mn1-x Cr x O3 for electrical application.

In the present research, polycrystalline samples of La0.5Sm0.2Sr0.3Mn1-x Cr x O3 are prepared using the self-combustion method. Then, we have studied their crystalline structure, and dielectric and electrical properties. The X-ray diffraction study shows that all the samples exhibit a single phase with orthorhombic structure (space group Pnma). The studied samples were also characterized by complex impedance spectroscopy in a wide range of temperatures and frequency. AC conductivity analyses are used to study the transport property of the investigated samples. These analyses indicate that the conduction mechanism is strongly dependent on temperature and frequency. It is also found that the conductivity decreases with Cr concentration. Complex impedance analysis confirms the contributions of grain and grain boundaries in the conduction mechanism. Finally, the impedance spectra, characterized by the appearance of semicircle arcs at different temperatures, were well modeled in terms of equivalent electrical circuits to explain the impedance results.

[Uncommon evolution of aneurysm of the ascending aorta in Marfan syndrome. A case report (author's transl)]. / Evoluzione insolita di aneurisma dell'aorta ascendente nella sindrome di Marfan. A proposito di un caso.

The Authors report a case of aneurysm of the ascending aorta in Marfan syndrome, with fatal outcome (2 months after the onset of the symptoms), caused neither by dissection nor by rupture of the aorta, but by serious myocardial involvement due to anoxic damage and acute volume overload of left ventricle. The Authors describe the possible mechanisms of this evolution and point out the usefulness of the identification of this uncommon evolution for a useful and opportune surgical therapy.

[Mitral insufficiency associated with interatrial defect (ostium secundum). Problems of diagnosis and surgical treatment]. / L'insufficienza mitralica associata a difetto interatriale (ostium secundum). Problemi di diagnosi e di terpaia chirurgica.

Of the 255 patients under observation of the AA. with ostium secundum interatrial defect who underwent surgery, 23 (9%) presented an associated mitral regurgitation. All patients had a hemodynamic test and a complete contrahistography, 8 patients polygraphic and 5 patients echocardiographic examinations. The clinical data alone, ecgraphic and Rx, supplied sufficient indications for a correct diagnosis in 87% of the cases. 22 patients underwent surgery: the septal defect was corrected in all patients, mitral regurgitation only in 9; in 5 by valve substitution, in 4 through conservative techniques. Only one patient died of cerebral coma. A report is made on the data relative to the clinical history, Rx, ecgraphic and hemodynamic examinations of the 23 patients under observation, the various anatomosurgical aspects of the valvular alterations, and the criteria adopted for the surgical correction of the mitral regurgitation.