RESUMO
Magnetic refrigeration technology can achieve higher energy efficiency based on the magnetocaloric effect (MCE). However, the practical application of MCE materials is hindered by their poor mechanical properties, making them challenging to process into devices. Conventional strengthening strategies usually lead to a trade-off with refrigeration capacity reduction. Here, a novel design is presented to overcome this dilemma by forming dual-phase alloys through in situ precipitation of a tough magnetic refrigeration phase within an intermetallic compound with excellent MCE. In the alloy 87.5Gd-12.5Co, incorporating the interconnected tough phase Gd contributes to enhanced strength (≈505 MPa) with good ductility (≈9.2%). The strengthening phase Gd simultaneously exhibits excellent MCE, enabling the alloy to achieve a peak refrigeration capacity of 720 J kg-1. Moreover, the alloy shows low thermal expansion induced by the synergistic effect of the two phases. It is beneficial for maintaining structural stability during heat exchange in magnetic refrigeration. The coupling interaction between the two magnetic phases can broaden the refrigeration temperature range and reduce hysteresis. This study guides the development of new high-performance materials with an excellent combination of mechanical and magnetic refrigeration properties as needed for gas liquefaction and refrigerators.
RESUMO
STUDY OBJECTIVES: A new tip for the electroablation of pneumocysts was examined clinically as a second-line method for stapled resection of pneumocysts during video-assisted thoracoscopic surgery (VATS). DESIGN: A trial to assess feasibility. SETTINGS: National referral hospitals. PATIENTS: One hundred seven patients were studied, of whom 99 patients were eligible for the study (85 men and 14 women; age range, 15 to 69 years; median age, 23 years), who had undergone VATS for primary spontaneous pneumothorax between July 1996 and June 1998. Apical pneumocysts were resected employing staplers, and residual pneumocysts, if present, were electroablated employing a new tip for the electrosurgery unit (ball shape, 8 mm in diameter, and made of stainless steel). MEASUREMENTS AND RESULTS: Thirty-three patients (33%) underwent electroablation only for small (< 2 cm in diameter) pneumocysts (group S), and 11 patients (11%) underwent electroablation for large (>/= 2 cm in diameter) pneumocysts (group L). The remaining 55 patients (56%) did not undergo electroablation because there were no residual pneumocysts (group N). There were no complications during surgery. The duration of the operation was significantly shorter (about 20 min on average) for group N, but there was no significant difference in the amount of blood loss, the number of applied staples, the duration of drainage, and the duration of hospital stay. Group S achieved a 100% relapse-free rate (33 of 33 patients), group L achieved a 64% relapse-free rate (7 of 11 patients), and group N achieved an 89% relapse-free rate (49 of 55 patients) [group S vs group N, p = 0.08; group L vs group N, p = 0.001; and group S vs group L, p = 0.002]. CONCLUSION: Electroablation with the M-tip is feasible as a second-line method for the treatment of small pneumocysts following the stapling technique during VATS.
