Magnetic and magnetocaloric properties of La0.55Bi0.05Sr0.4CoO3 and their implementation in critical behaviour study and spontaneous magnetization estimation.

In this work, we present the results of the magnetic, critical, and magnetocaloric properties of the rhombohedral-structured La0.55Bi0.05Sr0.4CoO3 cobaltite. Based on the modified Arrott plot, Kouvel-Fisher, and critical isotherm analyses, we obtained the values of critical exponents (ß, γ, and δ) as well as Curie temperature (T C) for the investigated compound. These components were consistent with their corresponding values and they were validated by the Widom scaling law and scaling theory. The obtained critical exponents were close to the theoretical prediction of the mean-field model values, revealing the characteristic of long-range ferromagnetic interactions. The magnetic entropy, heat capacity, and local exponent n(T, µ 0 H) of the La0.55Bi0.05Sr0.4CoO3 compound collapsed to a single universal curve, confirming its universal behaviour. The estimated spontaneous magnetization value extracted through the analysis of the magnetic entropy change was consistent with that deduced through the classical extrapolation of the Arrott curves. Thus, the magnetic entropy change is a valid and useful approach to estimate the spontaneous magnetization of La0.55Bi0.05Sr0.4CoO3.

[Valgus osteotomy in the treatment of pseudoarthrosis of the femoral neck: 41 cases]. / Ostéotomie de valgisation dans les pseudarthroses du col du fémur: à propos de 41 cas.

PURPOSE OF THE STUDY: Treating hip trauma victims who develop nonunion of the femoral neck remains a challenge in orthopedic surgery. We studied the clinical and radiological outcome after Pauwels osteotomy for valgisation. MATERIAL AND METHODS: This retrospective series included 41 patients (25 men and 16 women), mean age 44.5 years. Initial treatment was surgical in 21 cases and had been insufficient in 91%. Nonunion (subcapital in 53%, transcervical in 40% and basicervical in 7%) had persisted for 16 months. A tight nonunion was present in 65.9% of the cases and the femoral head appeared normal in 70%. Femoral osteotomy was performed for simple valgisation in 78% of the cases with a mean 31.5 degrees correction (range 15 degrees to 50 degrees ). A nail or screwed plate was used for fixation. Results were analyzed at a mean 76 months post-surgery. RESULTS: Bone healing was achieved in 98% of the cases. The only failure was related to inappropriate surgical technique. Necrosis was observed in 16 cases. The functional outcome was very good or good in 82% of the patients. CONCLUSION: Osteotomy for valgisation remains a very good salvage procedure for nonunion of the femoral neck following hip trauma. It can be used for elderly subjects even in the presence of early stage or partial necrosis.

[Consequences of tibiotalar arthrodesis on the foot. A retrospective study of 36 cases with 8.5 years of followup]. / Etude du retentissement de l'arthrodèse tibio-talienne sur le pied. A propos de 36 cas revus avec un recul moyen de 8 ans et demi.

The authors report the results of a retrospective study of 36 cases of tibiotalar arthrodesis performed in 22 men and 14 women with an average age of 32 years. All patients were reviewed with an average of 8.5 years follow-up. The predominating etiologies were ankle osteoarthritis (15 cases) and neurologic deformities of the foot (13 cases). Arthrodesis was performed using the Meary technique in 60% of cases, using the Charnley technique in 20% and the Crawford-Adams technique or with clamps in the other cases. Fusion was obtained in 97% of cases. Long-term results were assessed using Duquennoy et al.'s scoring system. They were very good or good in 58% of cases, fair in 31% and poor in 11%. The study of distal repercussions of tibiotalar arthrodesis shows progressive deterioration of the subtalar joint in 70% of cases and appearance or increase of degenerative changes in 75% of cases. The final results of the procedure depend on this deterioration; the latter is related with the arthrodesis position. Midtalar joint is a compensation joint showing hypermobility in 40% of cases. Degenerative changes were limited and asymptomatic in 80% of cases. Based on the findings in this study and on the literature, we conclude that the foot should be fixed at 90 degrees or with less than 5 degrees of equinus, with 5 degrees of valgus and 10 to 15 degrees of external rotation.