RESUMEN
Our recently developed trajectory surface hopping method uses numerical time derivatives of adiabatic potential gradients to estimate the nonadiabatic transition probability and the hopping direction. To demonstrate the practicality of the novel method, we applied it to the intermolecular photodissociation of a carbon dioxide dimer cation (CO2)2 +. Our simulations reproduced the measured velocity distribution of CO2 + fragments consisting of two (fast and slow) components and revealed that nonadiabatic transitions occur promptly toward the electronic ground state regardless of the fragment velocity. The structure of (CO2)2 + at optical excitation governs the fate of subsequent nonadiabatic dynamics leading to a fast or slow dissociation. Our method gave similar results to the fewest switches algorithm at lower computational expense. Our fast and robust surface hopping method is promising for the investigation of nonadiabatic dynamics in large and complex systems.
RESUMEN
BACKGROUND: Studies have shown that use of cement is a risk factor for fat embolism in elderly patients with femoral neck fracture. We investigated the usefulness of the cementless femoral head replacement technique. METHODS: A retrospective study of 58 patients who had undergone this technique between January 1995 and May 2001 was conducted. Perioperative complications, hospital length of stay, activities of daily living, and postoperative mortality were studied. RESULTS: Of 58 patients, 42 (72.4%) were fe- males, and the mean age was 75.4 years. Twenty patients (69.0%) were classified as ASA class 2, and 50 patients (86.2%) had preoperative medical complications. Cardiovascular complications were the most prevalent, and 6 patients (10.3%) had serious perioperative complications, and postoperative death was noted in 1 patient within one month (1.7%), and 4 patients (6.9%) within one year. Average length of hospital stay was 64.2 days and activities of daily living were the same level as before the fracture. CONCLUSIONS: Early rehabilitation was possible and hospital length of stay and activities of daily living were not inferior to the other treatments. We believe that cementless femoral head replacement technique was useful for elderly patients.