Superconductivity in a Mesoscopic Double Square Loop: Effect of Imperfections

We have generalized the network approach to include the effects of short-range imperfections in order to analyze recent experiments on mesoscopic superconducting double loops. The presence of weakly scattering imperfections causes gaps in the phase boundary $B(T)$ or $\Phi(T)$ for certain intervals of $T$, which depend on the magnetic flux penetrating each loop. This is accompanied by a critical temperature $T_c(\Phi)$, showing a smooth transition between symmetric and antisymmetric states. When the scattering strength of imperfections increases beyond a certain limit, gaps in the phase boundary $T_c(B)$ or $T_c(\Phi)$ appear for values of magnetic flux lying in intervals around half-integer $\Phi_0=hc/2e$. The critical temperature corresponding to these values of magnetic flux is determined mainly by imperfections in the central branch. The calculated phase boundary is in good agreement with experiment.Comment: 9 pages, 6 figure

Three-body non-additive forces between spin-polarized alkali atoms

Three-body non-additive forces in systems of three spin-polarized alkali atoms (Li, Na, K, Rb and Cs) are investigated using high-level ab initio calculations. The non-additive forces are found to be large, especially near the equilateral equilibrium geometries. For Li, they increase the three-atom potential well depth by a factor of 4 and reduce the equilibrium interatomic distance by 0.9 A. The non-additive forces originate principally from chemical bonding arising from sp mixing effects.Comment: 4 pages, 3 figures (in 5 files

Levels of maternal plasma corticotropin-releasing factor and urocortin during labor

OBJECTIVE: Corticotropin-releasing factor (CRF) is produced by the placenta and intrauterine tissues and secreted in increasing amounts from early to term pregnancy. In the presence of labor, a more incisive increase in CRF levels has been described, and women with preterm labor or those destined to have premature delivery have higher midpregnancy CRF levels than those who deliver at term. Urocortin is a 40-amino acid peptide belonging to the CRF family, expressed by human trophoblast and fetal membranes, which has the same biologic effects as CRF. Acting on the same CRF receptors, urocortin stimulates myometrial contractility and ACTH and prostaglandin release from cultured human placental cells. Because no data exist about urocortin levels in the maternal circulation at parturition, we investigated whether maternal plasma urocortin and CRF levels change according to cervical dilatation in healthy pregnant women at term labor. METHODS: In a cross-sectional study of labor, a single maternal blood sample was collected from healthy pregnant women at term (n 40); in a second longitudinal study, plasma samples were collected longitudinally in a subset of patients (n 8) throughout labor, according to a Bishop score evaluation. RESULTS: Both maternal plasma CRF and urocortin levels were higher in labor than those previously reported during pregnancy, but they did not change significantly during the different stages of labor when evaluated longitudinally. Some patients showed a trend toward increasing levels, whereas others had variable concentrations. CONCLUSION: Neither CRF nor urocortin levels changed during the progression of spontaneous labor

The biodiscovery potential of marine bacteria: an investigation of phylogeny and function

A collection of marine bacteria isolated from a temperate coastal zone has been screened in a programme of biodiscovery. A total of 34 enzymes with biotechnological potential were screened in 374 isolates of marine bacteria. Only two enzymes were found in all isolates while the majority of enzyme activities were present in a smaller proportion of the isolates. A cluster analysis demonstrated no significant correlation between taxonomy and enzyme function. However, there was evidence of co-occurrence of some enzyme activity in the same isolate. In this study marine Proteobacteria had a higher complement of enzymes with biodiscovery potential than Actinobacteria; this contrasts with the terrestrial environment where the Actinobacteria phylum is a proven source of enzymes with important industrial applications. In addition, a number of novel enzyme functions were more abundant in this marine culture collection than would be expected on the basis of knowledge from terrestrial bacteria. There is a strong case for future investigation of marine bacteria as a source for biodiscovery