On the phase transition of light in cavity QED lattices

Systems of strongly interacting atoms and photons, that can be realized wiring up individual cavity QED systems into lattices, are perceived as a new platform for quantum simulation. While sharing important properties with other systems of interacting quantum particles here we argue that the nature of light-matter interaction gives rise to unique features with no analogs in condensed matter or atomic physics setups. By discussing the physics of a lattice model of delocalized photons coupled locally with two-level systems through the elementary light-matter interaction described by the Rabi model, we argue that the inclusion of counter rotating terms, so far neglected, is crucial to stabilize finite-density quantum phases of correlated photons out of the vacuum, with no need for an artificially engineered chemical potential. We show that the competition between photon delocalization and Rabi non-linearity drives the system across a novel $Z_2$ parity symmetry-breaking quantum criticality between two gapped phases which shares similarities with the Dicke transition of quantum optics and the Ising critical point of quantum magnetism. We discuss the phase diagram as well as the low-energy excitation spectrum and present analytic estimates for critical quantities.Comment: 5+3 pages, published versio

Protein folding rates correlate with heterogeneity of folding mechanism

By observing trends in the folding kinetics of experimental 2-state proteins at their transition midpoints, and by observing trends in the barrier heights of numerous simulations of coarse grained, C-alpha model, Go proteins, we show that folding rates correlate with the degree of heterogeneity in the formation of native contacts. Statistically significant correlations are observed between folding rates and measures of heterogeneity inherent in the native topology, as well as between rates and the variance in the distribution of either experimentally measured or simulated phi-values.Comment: 11 pages, 3 figures, 1 tabl

Excitations of optically driven atomic condensate in a cavity: theory of photodetection measurements

Recent experiments have demonstrated an open system realization of the Dicke quantum phase transition in the motional degrees of freedom of an optically driven Bose-Einstein condensate in a cavity. Relevant collective excitations of this light-matter system are polaritonic in nature, allowing access to the quantum critical behavior of the Dicke model through light leaking out of the cavity. This opens the path to using photodetection based quantum optical techniques to study the dynamics and excitations of this elementary quantum critical system. We first discuss the photon flux observed at the cavity face and find that it displays a different scaling law near criticality than that obtained from the mean field theory for the equivalent closed system. Next, we study the second order correlation measurements of photons leaking out of the cavity. Finally, we discuss a modulation technique that directly captures the softening of polaritonic excitations. Our analysis takes into account the effect of the finite size of the system which may result in an effective symmetry breaking term.Comment: 18 pages, 5 figure

Численная модель системы вывода электронного пучка медицинского ускорителя

A novel incremental ring rolling process is proposed, in which a narrow mandrel is moved both radially and axially. The process has potential to allow flexible near-net-shape forming of both hot and cold rings, and has been assessed by experiments on commercial cold ring rolling machines, a physical simulation using wax rings, and two finite element models. The results suggest that the process is technically feasible although the cycle time increases with the degree of flexibility and the stability of deformation depends on careful design of the tool path

Analytical approach for entropy generation and heat transfer in CNT-nanofluid dynamics through a ciliated porous medium

The transportation of biological and industrial nanofluids by natural propulsion like cilia movement and self-generated contraction-relaxation of flexible walls has significant applications in numerous emerging technologies. Inspired by multi-disciplinary progress and innovation in this direction, a thermo-fluid mechanical model is proposed to study the entropy generation and convective heat transfer of nanofluids fabricated by the dispersion of single-wall carbon nanotubes (SWCNT) nanoparticles in water as the base fluid. The regime studied comprises heat transfer and steady, viscous, incompressible flow, induced by metachronal wave propulsion due to beating cilia, through a cylindrical tube containing a sparse (i.e. high permeability) homogenous porous medium. The flow is of the creeping type and is restricted under the low Reynolds number and long wavelength approximations. Slip effects at the wall are incorporated and the generalized Darcy drag-force model is utilized to mimic porous media effects. Cilia boundary conditions for velocity components are employed to determine analytical solutions to the resulting non-dimensionalized boundary value problem. The influence of pertinent physical parameters on temperature, axial velocity, pressure rise and pressure gradient, entropy generation function, Bejan number and stream-line distributions are computed numerically. A comparative study between SWCNT nanofluids and pure water is also computed. The computations demonstrate that axial flow is accelerated with increasing slip parameter and Darcy number and is greater for SWCNT- nanofluids than for pure water. Furthermore the size of the bolus for SWCNT-nanofluids is larger than that of the pure water. The study is applicable in designing and fabricating nanoscale and microfluidics devices, artificial cilia and biomimetic micro-pump

Multi-ancestry genome-wide association meta-analysis of Parkinson?s disease

Although over 90 independent risk variants have been identified for Parkinson’s disease using genome-wide association studies, most studies have been performed in just one population at a time. Here we performed a large-scale multi-ancestry meta-analysis of Parkinson’s disease with 49,049 cases, 18,785 proxy cases and 2,458,063 controls including individuals of European, East Asian, Latin American and African ancestry. In a meta-analysis, we identified 78 independent genome-wide significant loci, including 12 potentially novel loci (MTF2, PIK3CA, ADD1, SYBU, IRS2, USP8, PIGL, FASN, MYLK2, USP25, EP300 and PPP6R2) and fine-mapped 6 putative causal variants at 6 known PD loci. By combining our results with publicly available eQTL data, we identified 25 putative risk genes in these novel loci whose expression is associated with PD risk. This work lays the groundwork for future efforts aimed at identifying PD loci in non-European populations

Characterization of Water Distribution in Xanthan-Curdlan Hydrogel Complex Using Magnetic Resonance Imaging, Nuclear Magnetic Resonance Relaxometry, Rheology, and Scanning Electron Microscopy

Xanthan-curdlan hydrogel complex (XCHC) has been shown capable of retaining moisture up to 5 freeze-thaw cycles (FTCs); however, moisture distribution in the complex in relation to the hydrogel composition and structure remains uncharacterized. In the present study, magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) relaxometry, rheology, and scanning electron microscopy (SEM) were used to examine the effect of water distribution and interaction with 2.0% aqueous solutions of xanthan, curdlan, and XCHC consisting of equal amounts of both polysaccharides. A gel structure with an indication of syneresis was clearly seen in the MR image of curdlan alone, whereas the distribution of protons throughout xanthan and XCHC samples remained homogeneous and showed no detectable syneresis. The three-dimensional network, indicated by frequency sweeps, of curdlan was responsible for curdlan's gel structure. The frequency sweep and slope of the storage modulus (G') of XCHC was significantly closer to curdlan with higher elasticity and less dependency upon angular frequency than xanthan alone. The reduction in XCHC dynamic moduli (G' and G '') compared to curdlan could be attributed to the formation of wavy layers instead of a fully cured three-dimensional structure. Addition of xanthan to curdlan restricted XCHC spin-spin relaxation time (T-2) to intermediate and slower exchange regimes, namely approximately 110 and 342 ms, respectively, promoting the polymer's interaction with water while inhibiting interpolymer interactions found in curdlan. A 3rd proton pool with the slowest T-2 seen in curdlan was not found in XCHC, correlating to the absence of syneresis