Phase diagrams of period-4 spin chains consisting of three kinds of spins

We study a period-4 antiferromagnetic mixed quantum spin chain consisting of three kinds of spins. When the ground state is singlet, the spin magnitudes in a unit cell are arrayed as (s-t, s, s+t, s) with integer or half-odd integer s and t (0 <= t < s). The spin Hamiltonian is mapped onto a nonlinear sigma model (NLSM) in a previously developed method. The resultant NLSM includes only two independent parameters originating from four exchange constants for fixed s and t. The topological angle in the NLSM determines the gapless phase boundaries between disordered phases in the parameter space. The phase diagrams for various s and t shows rich structures. We systematically explain the phases in the singlet-cluster-solid picture.Comment: 8 pages (16 figures included

Continuous quantum measurement of a Bose-Einstein condensate: a stochastic Gross-Pitaevskii equation

We analyze the dynamics of a Bose-Einstein condensate undergoing a continuous dispersive imaging by using a Lindblad operator formalism. Continuous strong measurements drive the condensate out of the coherent state description assumed within the Gross-Pitaevskii mean-field approach. Continuous weak measurements allow instead to replace, for timescales short enough, the exact problem with its mean-field approximation through a stochastic analogue of the Gross-Pitaevskii equation. The latter is used to show the unwinding of a dark soliton undergoing a continuous imaging.Comment: 13 pages, 10 figure

Computational aeroelasticity framework for analyzing flapping wing micro air vehicles

Published versio

Projected SO(5) Hamiltonian for Cuprates and Its Applications

The projected SO(5) (pSO(5)) Hamiltonian incorporates the quantum spin and superconducting fluctuations of underdoped cuprates in terms of four bosons moving on a coarse grained lattice. A simple mean field approximation can explain some key feautures of the experimental phase diagram: (i) The Mott transition between antiferromagnet and superconductor, (ii) The increase of T_c and superfluid stiffness with hole concentration x and (iii) The increase of antiferromagnetic resonance energy as sqrt{x-x_c} in the superconducting phase. We apply this theory to explain the ``two gaps'' problem found in underdoped cuprate Superconductor-Normal- Superconductor junctions. In particular we explain the sharp subgap Andreev peaks of the differential resistance, as signatures of the antiferromagnetic resonance (the magnon mass gap). A critical test of this theory is proposed. The tunneling charge, as measured by shot noise, should change by increments of Delta Q= 2e at the Andreev peaks, rather than by Delta Q=e as in conventional superconductors.Comment: 3 EPS figure

Effects of Reynolds Number and Flapping Kinematics on Hovering Aerodynamics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76695/1/AIAA-2007-129-236.pd

Interesting magnetic properties of Fe1−x_{1-x}Cox_xSi alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed.Comment: 11 pages and 3 figure

Effect of Pivot Point on Aerodynamic Force and Vortical Structure of Pitching Flat Plate Wings

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106512/1/AIAA2013-792.pd

Three-Dimensional Adaptive Grid Computation with Conservative, Marker-Based Tracking for Interfacial Fluid Dynamics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76614/1/AIAA-2006-1523-676.pd

Influence of Effective Angle of Attack Oscillation Amplitude on Force Generation by Pitching-Plunging Flat Plates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97081/1/AIAA2012-2665.pd

Shear stress regulation of miR-93 and miR-484 maturation through nucleolin.

Pulsatile shear (PS) and oscillatory shear (OS) elicit distinct mechanotransduction signals that maintain endothelial homeostasis or induce endothelial dysfunction, respectively. A subset of microRNAs (miRs) in vascular endothelial cells (ECs) are differentially regulated by PS and OS, but the regulation of the miR processing and its implications in EC biology by shear stress are poorly understood. From a systematic in silico analysis for RNA binding proteins that regulate miR processing, we found that nucleolin (NCL) is a major regulator of miR processing in response to OS and essential for the maturation of miR-93 and miR-484 that target mRNAs encoding Krüppel-like factor 2 (KLF2) and endothelial nitric oxide synthase (eNOS). Additionally, anti-miR-93 and anti-miR-484 restore KLF2 and eNOS expression and NO bioavailability in ECs under OS. Analysis of posttranslational modifications of NCL identified that serine 328 (S328) phosphorylation by AMP-activated protein kinase (AMPK) was a major PS-activated event. AMPK phosphorylation of NCL sequesters it in the nucleus, thereby inhibiting miR-93 and miR-484 processing and their subsequent targeting of KLF2 and eNOS mRNA. Elevated levels of miR-93 and miR-484 were found in sera collected from individuals afflicted with coronary artery disease in two cohorts. These findings provide translational relevance of the AMPK-NCL-miR-93/miR-484 axis in miRNA processing in EC health and coronary artery disease