ABSTRACT
We determine the magnetic-field dependence of the pseudogap closing temperature T* within a precursor superconductivity scenario. Detailed calculations with an anisotropic lattice model with d-wave superconductivity account for a recently determined experimental relation in BSCCO between the pseudogap closing field and the pseudogap temperature at zero field, as well as for the weak initial dependence of T* at low fields. Our results indicate that the available experimental data are fully compatible with a superconducting origin of the pseudogap in cuprate superconductors.
ABSTRACT
The canonical partition function of a system of rotators (classical X-Y spins) on a lattice, coupled by terms decaying as the inverse of their distance to the power alpha, is analytically computed. It is also shown how to compute a rescaling function that allows us to reduce the model, for any d-dimensional lattice and for any alpha
ABSTRACT
The tripeptide ZAMI-420 has been shown by Gervasi et al. (4) to be able to prevent experimentally-induced gastric damage, possibly by interfering with the synthesis and the action of thromboxane A2 (TXA2), a potent vasoconstrictor and platelet aggregator. Further studies on a canine stomach wedge preparation, supplied with a fixed flow of 10 ml/min-1 of arterial blood from the same dog have been designed to investigate this hypothesis. Bolus injection of arachidonic acid (AA) through a 30-sec incubation coil that allows the production of TXA2 resulted in a dose-related increase in resistance to flow in the stomach wedge vasculature and blanching of the gastric mucosa. This was progressively inhibited by ZAMI-420 perfused through the delay coil. Similar results were obtained with 1-benzylimidazole (BI). ZAMI-420, but not BI, produced a partial inhibition of TXA2-induced vasoconstriction when infused close to the stomach. Investigations of the antagonistic action of ZAMI-420 on the pharmacological effect of the formed TXA2 were carried out using strips of celiac and mesenteric artery from rabbits and gastric artery from dogs. Preincubation of these vascular preparations with ZAMI-420 led to progressive inhibition of the contraction induced either by the stable endoperoxide U-46619 or by CaCl2. Whittle et al. (3) reported that TXA2 may be involved in the pathogenesis of ulcerative disorders of the stomach; if so, both the inhibition of the synthesis and the antagonism of TXA2-induced effects could be of value in the prevention of experimentally-induced gastric disorders.
