Persistence Exponents and Scaling In Two Dimensional XY model and A Nematic Model

The persistence exponents associated with the T=0 quenching dynamics of the two dimensional XY model and a two dimensional uniaxial spin nematic model have been evaluated using a numerical simulation. The site persistence or the probability that the sign of a local spin component does not change starting from initial time t=0 up to certain time t, is found to decay as L(t)^-theta, (L(t) is the linear domain length scale), with theta =0.305 for the two dimensional XY model and 0.199 for the two dimensional uniaxial spin nematic model. We have also investigated the scaling (at the late time of phase ordering) associated with the correlated persistent sites in both models. The persistence correlation length was found to grow in same way as L(t).Comment: 8 figures, only three new references are included in this version. (ref. 18 and ref. 32

Topological transition in a two-dimensional model of liquid crystal

Simulations of nematic-isotropic transition of liquid crystals in two dimensions are performed using an O(2) vector model characterised by non linear nearest neighbour spin interaction governed by the fourth Legendre polynomial $P\_4$. The system is studied through standard Finite-Size Scaling and conformal rescaling of density profiles of correlation functions. A topological transition between a paramagnetic phase at high temperature and a critical phase at low temperature is observed. The low temperature limit is discussed in the spin wave approximation and confirms the numerical results

Role of disclinations in determining the morphology of deformable fluid interfaces

We study the equilibrium shapes of vesicles, with an in-plane nematic order, using a Monte-Carlo scheme and show that highly curved shapes, like tubes and discs, with a striking similarity to the structures engendered by certain curvature sensing peripheral membrane proteins, can be spontaneously generated by anisotropic directional curvature with nematic disclinations playing and important role. We show that the coupling between nematic order and local curvature could lead to like defects moving towards each other and unlike defects moving away, in turn leading to tube formation. Thermally induced defect pair production lead to branched tubular structures. It is also shown that helical arrangement of the membrane tubes, with nematic field spiraling around it, is a dominant soft mode of the system.Comment: 6 Figures; Soft Matter, Advance Article 201

Correlations in the Sine-Gordon Model with Finite Soliton Density

We study the sine-Gordon (SG) model at finite densities of the topological charge and small SG interaction constant, related to the one-dimensional Hubbard model near half-filling. Using the modified WKB approach, we find that the spectrum of the Gaussian fluctuations around the classical solution reproduces the results of the Bethe ansatz studies. The modification of the collective coordinate method allows us to write down the action, free from infra-red divergencies. The behaviour of the density-type correlation functions is non-trivial and we demonstrate the existence of leading and sub-leading asymptotes. A consistent definition of the charge-raising operator is discussed. The superconducting-type correlations are shown to decrease slowly at small soliton densities, while the spectral weight of right (left) moving fermions is spread over neighboring "4k_F" harmonics.Comment: 12 pages, 3 eps figures, REVTEX; a discussion of fermions is adde

Provable first-order transitions for liquid crystal and lattice gauge models with continuous symmetries

We consider various sufficiently nonlinear sigma models for nematic liquid crystal ordering of RP^{N-1} type and of lattice gauge type with continous symmetries. We rigorously show that they exhibit a first-order transition in the temperature. The result holds in dimension 2 or more for the RP^{N-1} models and in dimension 3 or more for the lattice gauge models. In the two-dimensional case our results clarify and solve a recent controversy about the possibility of such transitions. For lattice gauge models our methods provide the first proof of a first-order transition in a model with a continuous gauge symmetry

Efficacy of ruxolitinib cream in vitiligo by patient characteristics and affected body areas: Descriptive subgroup analyses from a phase 2, randomized, double-blind trial

To the Editor: Vitiligo is a chronic autoimmune disease resulting in patches of depigmented skin and reduced quality of life. In a randomized, dose-ranging phase 2 study (NCT03099304) in 157 adult patients, the Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib cream produced substantial repigmentation of facial and total body vitiligo lesions after 24 weeks, with continued improvement through week 52, and was well tolerated.3 Here, we present treatment response subanalyses from the phase 2 trial

Incommensurate ground state of double-layer quantum Hall systems

Double-layer quantum Hall systems possess interlayer phase coherence at sufficiently small layer separations, even without interlayer tunneling. When interlayer tunneling is present, application of a sufficiently strong in-plane magnetic field $B_\parallel > B_c$ drives a commensurate-incommensurate (CI) transition to an incommensurate soliton-lattice (SL) state. We calculate the Hartree-Fock ground-state energy of the SL state for all values of $B_\parallel$ within a gradient approximation, and use it to obtain the anisotropic SL stiffness, the Kosterlitz-Thouless melting temperature for the SL, and the SL magnetization. The in-plane differential magnetic susceptibility diverges as $(B_\parallel - B_c)^{-1}$ when the CI transition is approached from the SL state.Comment: 12 pages, 7 figures, to be published in Physical Review

Persistent mucosal damage and risk of epilepsy in people with celiac disease

BACKGROUND: Celiac disease (CD) is associated with an increased risk of developing epilepsy, a risk that persists after CD diagnosis. A significant proportion of CD patients have persistent villous atrophy (VA) on follow-up biopsy. This study's objective was to determine whether persistent VA on follow-up biopsy affects long-term epilepsy risk and epilepsy-related hospital emergency admissions. METHODS: Nationwide Cohort Study. We identified all people in Sweden with histological evidence of CD who underwent a follow-up small intestinal biopsy (1969-2008). We compared those with persistent VA to those who showed histological improvement, assessing the development of epilepsy and related emergency hospital admissions (defined according to relevant ICD codes in the Swedish Patient Register). Cox regression analysis was used to assess outcome measures. RESULTS: Of 7590 people with CD who had a follow-up biopsy, VA was present in 43%. The presence of persistent VA was significantly associated with a reduced risk of developing newly-diagnosed epilepsy (hazard ratio [HR] 0.61; 95% confidence interval [CI] 0.38-0.98). On stratified analysis this effect was primarily amongst males (HR 0.35; 95 CI 0.15-0.80). Among the 58 CD patients with a prior diagnosis of epilepsy, those with persistent VA were less likely to visit an emergency department with epilepsy (HR 0.37; 95%CI 0.09-1.09). CONCLUSIONS: In a population-based study of CD individuals, persisting VA on follow up biopsy was associated with reduced future risk of developing epilepsy but did not influence emergency epilepsy-related hospital admissions. Mechanisms as to why persistent VA confers this benefit requires further exploration