ABSTRACT
We consider the extended Hubbard model and introduce a corresponding Heisenberg-like problem written in terms of spin operators. The derived formalism is reminiscent of Anderson's idea of the effective exchange interaction and takes into account nonlocal correlation effects. The results for the exchange interaction and spin susceptibility in the magnetic phase are expressed in terms of single-particle quantities. This fact not only can be used for realistic calculations of multiband systems but also allows us to reconsider a general description of many-body effects in the most interesting physical regimes, where the physical properties of the system are dominated by collective (bosonic) fluctuations. In the strongly spin-polarized limit, when the local magnetic moment is well defined, the exchange interaction reduces to a standard expression of the density functional theory that has been successfully used in practical calculations of magnetic properties of real materials.
ABSTRACT
Atherosclerosis of femoropopliteal arteries is an important cause of morbidity and mortality. Percutaneous transluminal angioplasty (PTA) has only limited success in treating these arteries, mainly because of the high rate of recurrent stenosis. Cryoplasty has been proposed as a technique which might improve treatment outcome. This study reports our single-center experience with cryoplasty. Thirty-two claudicants, 33 arteries, in whom conservative therapy failed, were consecutively included. Duplex ultrasound (US), angiography, and ankle-brachial index (ABI) measurement were performed before the procedure; ABI and duplex US, 2 weeks and 3, 6, and 12 months after the procedure. Patients' symptoms were categorized according to the Rutherford classification. Lesions were classified as TASC A, B, or C according to angiographic appearance. Differences in ABI before and after the procedure were defined as significant at p < 0.05 by paired t-test. Patency was evaluated using duplex US by determining the peak systolic velocity ratio. Sixteen TASC A lesions, 13 TASC B lesions, and 4 TASC C lesions were included. ABI improved significantly for TASC A lesions 2 weeks and 3 months postprocedure. Patency after 2 weeks, 6 months, and 12 months was 93%, 67%, and 64% for TASC A lesions, 83%, 31%, and 31% for TASC B lesions, and 100%, 50%, and 33% for TASC C lesions, respectively. In conclusion, cryoplasty has good immediate success rates and patency rates similar to the results of conventional PTA in the literature.
