211 research outputs found
The quasi-particle gap in a disordered boson Hubbard model in two dimensions
We investigate the behavior of the quasi-particle energy gap near quantum
phase transitions in a two-dimensional disordered boson Hubbard model at a
commensurate filling. Via Monte Carlo simulations of ensembles with fixed
numbers of particles, we observe the behavior of the gap as a function of the
tuning parameter for various strength of diagonal disorder. For weak disorder,
we find that gapped Mott insulating phase is sustained up to the transition
point and disappears only in a superfluid, strongly supporting a direct
Mott-insulator-to-superfluid transition. Bose glass behavior, insulating with
vanishing gap, appears only when the strength of disorder is bigger than a
critical value
Superfluid-insulator transitions of two-species Bosons in an optical lattice
We consider a realization of the two-species bosonic Hubbard model with
variable interspecies interaction and hopping strength. We analyze the
superfluid-insulator (SI) transition for the relevant parameter regimes and
compute the ground state phase diagram for odd filling at commensurate
densities. We find that in contrast to the even commensurate filling case, the
superfluid-insulator transition occurs with (a) simultaneous onset of
superfluidity of both species or (b) coexistence of Mott insulating state of
one species and superfluidity of the other or, in the case of unit filling, (c)
complete depopulation of one species. The superfluid-insulator transition can
be first order in a large region of the phase diagram. We develop a variational
mean-field method which takes into account the effect of second order quantum
fluctuations on the superfluid-insulator transition and corroborate the
mean-field phase diagram using a quantum Monte Carlo study.Comment: 12 pages, 11 figure
Implications of MicroRNAs in the Vascular Homeostasis and Remodeling
Vascular remodeling or arterial remodeling is a process of adaptive alteration of vascular wall architecture and leads to the endothelial cell (EC) dysfunction and synthetic or contractile phenotypic change of VSMCs, and the infiltration of monocytes and Macrophages that promotes vascular diseases including atherosclerosis. Recent findings have demonstrated that microRNAs (miRNAs) are involved in regulating gene expression at posttranscriptional level and disease pathogenesis. A change of miRNA expression profiles plays key roles in the gene expressions and the regulation of cellular functions. In this chapter, we summarize the vascular remodeling-related miRNAs and their functions in vascular biology
- โฆ