ABSTRACT
Vanadium(iv) complexes have recently shown record quantum spin coherence times that in several circumstances are limited by spin-lattice relaxation. The role of the environment and vibronic properties in the low temperature dynamics is here investigated by a comparative study of the magnetization dynamics as a function of crystallite size and the steric hindrance of the ß-diketonate ligands in VO(acac)2 (1), VO(dpm)2 (2) and VO(dbm)2 (3) evaporable complexes (acac- = acetylacetonate, dpm- = dipivaloylmethanate, and dbm- = dibenzoylmethanate). A pronounced crystallite size dependence of the relaxation time is observed at unusually high temperatures (up to 40 K), which is associated with a giant spin-phonon bottleneck effect. We model this behaviour by an ad hoc force field approach derived from density functional theory calculations, which evidences a correlation of the intensity of the phenomenon with ligand dimensions and the unit cell size.
ABSTRACT
OBJECTIVE: Critical limb ischemia (CLI) patients have poor long-term prognosis. We showed that iloprost improves outcomes (major amputation and survival) up a 5-year follow-up, but it is not known if in this length of time the survival curves, of clinical responders and non-responders, differ. PATIENTS AND METHODS: A retrospective study enrolling 102 consecutive patients between 2004-2008, with clinical and instrumental (ultrasound, angiography, transcutaneous tensiometry of oxygen TcpO2 and carbon dioxide TcpCO2 in the affected and contralateral limbs) diagnosis of critical ischemia. All patients received the best medical therapy. Iloprost was administered (0.5-2 ng/kg/min 6 hours/day for 2-4 weeks) in all patients initially considered unsuitable for revascularization, repeating it regularly in time every six-twelve months in the case of positive response. The minimum expected follow-up was 4 years. RESULTS: 71.5% of patients were treated with iloprost and the responder rate was 71.2%. Most of the patients were regularly retreated with repeated cycles. Initial median supine TcpCO2 in symptomatic limb was higher in untreated patients than those treated (58 vs. 49 mmHg; p < 0.05) and in non-responders compared to responders (60 vs. 49 mmHg; p < 0.05). TcpCO2 directly and significantly correlated with the highest risk of mortality and seems to represent a new accurate prognostic criterion of unfavourable short and long-term response to prostanoid. In iloprost group, major amputations were significantly reduced. Revascularization was significantly higher in non-responders (57.1% vs. 11.5%; p < 0.05). There was a significantly higher prevalence of subsequent myocardial infarction in the non-iloprost group (27.6% vs. 9.6%; p < 0.05). The survival rate of non-responders was higher than untreated up until the second year (76.2% vs. 62%; p < 0.05). At 4 years we found higher survival in patients treated with iloprost (64.3% vs. 41% in untreated; p < 0.05) and in responders (75% vs. 38.1% in non-responders; p < 0.05). CONCLUSIONS: Our results confirm the favourable role of iloprost on the long-term outcome in patients with CLI. In particular, the maximum benefit is obtained in responder patients treated with multiple cycles of infusion.
