Stability of superfluid Fermi gases in optical lattices

Critical velocities of superfluid Fermi gases in optical lattices are theoretically investigated across the BCS-BEC crossover. We calculate the excitation spectra in the presence of a superfluid flow in one- and two-dimensional optical lattices. It is found that the spectrum of low-lying Anderson-Bogoliubov (AB) mode exhibits a roton-like structure in the short-wavelength region due to the strong charge density wave fluctuations, and with increasing the superfluid velocity one of the roton-like minima reaches zero before the single-particle spectrum does. This means that superfluid Fermi gases in optical lattices are destabilized due to spontaneous emission of the roton-like AB mode instead of due to Cooper pair breaking.Comment: 4 pages, 4 figures, conference proceeding for ISQM-TOKYO'0

Stability of condensate in superconductors

According to the BCS theory the superconducting condensate develops in a single quantum mode and no Cooper pairs out of the condensate are assumed. Here we discuss a mechanism by which the successful mode inhibits condensation in neighboring modes and suppresses a creation of noncondensed Cooper pairs. It is shown that condensed and noncondensed Cooper pairs are separated by an energy gap which is smaller than the superconducting gap but large enough to prevent nucleation in all other modes and to eliminate effects of noncondensed Cooper pairs on properties of superconductors. Our result thus justifies basic assumptions of the BCS theory and confirms that the BCS condensate is stable with respect to two-particle excitations

Uekama K. Contribution of P-glycoprotein to the enhancing effects of dimethyl-beta-cyclodextrin on oral bioavailability of tacrolimus

ABSTRACT We recently reported that of all hydrophilic cyclodextrin (CyD) derivatives examined, 2,6-di-O-methyl-␤-cyclodextrin (DM-␤-CyD) most significantly increased the aqueous solubility and the dissolution rate, resulting in the improvement of oral bioavailability of the immunosuppressive drug tacrolimus in rats. In the present study, we showed that DM-␤-CyD increased the dissolution rate and oral bioavailability of tacrolimus in rats with increases in the molar ratio of the complexes (DM-␤-CyD: tacrolimus). However, nonlinear pharmacokinetic behavior of tacrolimus after oral administration in rats was observed. Thus, an additional mechanism of the solubilizing effect of DM-␤-CyD on oral bioavailability of tacrolimus was postulated. To gain insight into this additional mechanism of action of DM-␤-CyD, its effects on the efflux of tacrolimus and rhodamine 123, a P-glycoprotein (P-gp) substrate, were examined using both Caco-2 and vinblastine-resistant Caco-2 (Caco-2R) cell monolayers. Pretreatment of the apical membranes of the monolayers with DM-␤-CyD decreased the efflux of tacrolimus and rhodamine 123 without an associated cytotoxicity. DM-␤-CyD decreased the P-gp level in the apical membranes of both Caco-2 and Caco-2R cell monolayers, probably by allowing release of P-gp from the apical membrane into the transport buffer. DM-␤-CyD, however, did not decrease the MDR1 gene expression in Caco-2 or Caco-2R cells. These results suggested that the enhancing effect of DM-␤-CyD on the oral bioavailability of tacrolimus is due not only to its solubilizing effect but also, at least in part, to its inhibitory effect on the P-gp-mediated efflux of tacrolimus from intestinal epithelial cells

Cholesterol but not association with detergent resistant membranes is necessary for the transport function of MRP2/ABCC2

AbstractMRP2(/ABCC2) excretes amphiphilic organic anions into bile, and associates with detergent-resistant bile canalicular membrane domains (DRM). Here, we have evaluated sensitivities of MRP2 transport function and DRM association by titrating the cellular cholesterol content. We demonstrate that the role of cholesterol in the partitioning of MRP2 to DRM can be separated from the role of cholesterol in the function of MRP2, such that (i) cholesterol is not necessary for the polarized distribution of MRP2 at the canalicular membrane, (ii) partitioning into DRM is not required for MRP2 function, yet (iii) the presence of cholesterol is necessary for transport activity

Comprehensive molecular diagnosis of Epstein–Barr virus-associated lymphoproliferative diseases using next-generation sequencing

International audienceEpstein-Barr virus (EBV) is associated with several life-threatening diseases, such as lymphoproliferative disease (LPD), particularly in immunocompromised hosts. Some categories of primary immunodeficiency diseases (PIDs) including X-linked lymphoproliferative syndrome (XLP), are characterized by susceptibility and vulnerability to EBV infection. The number of genetically defined PIDs is rapidly increasing, and clinical genetic testing plays an important role in establishing a definitive diagnosis. Whole-exome sequencing is performed for diagnosing rare genetic diseases, but is both expensive and time-consuming. Low-cost, high-throughput gene analysis systems are thus necessary. We developed a comprehensive molecular diagnostic method using a two-step tailed polymerase chain reaction (PCR) and a next-generation sequencing (NGS) platform to detect mutations in 23 candidate genes responsible for XLP or XLP-like diseases. Samples from 19 patients suspected of having EBV-associated LPD were used in this comprehensive molecular diagnosis. Causative gene mutations (involving PRF1 and SH2D1A) were detected in two of the 19 patients studied. This comprehensive diagnosis method effectively detected mutations in all coding exons of 23 genes with sufficient read numbers for each amplicon. This comprehensive molecular diagnostic method using PCR and NGS provides a rapid, accurate, low-cost diagnosis for patients with XLP or XLP-like diseases