395 research outputs found
External and intrinsic anchoring in nematic liquid crystals: A Monte Carlo study
We present a Monte Carlo study of external surface anchoring in nematic cells
with partially disordered solid substrates, as well as of intrinsic anchoring
at free nematic interfaces. The simulations are based on the simple hexagonal
lattice model with a spatially anisotropic intermolecular potential. We
estimate the corresponding extrapolation length by imposing an elastic
deformation in a hybrid cell-like nematic sample. Our estimates for
increase with increasing surface disorder and are essentially
temperature--independent. Experimental values of are approached only when
both the coupling of nematic molecules with the substrate and the anisotropy of
nematic--nematic interactions are weak.Comment: Revisions primarily in section I
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
Cluster Monte Carlo Simulations of the Nematic--Isotropic Transition
We report the results of simulations of the Lebwohl-Lasher model of the
nematic-isotropic transition using a new cluster Monte Carlo algorithm. The
algorithm is a modification of the Wolff algorithm for spin systems, and
greatly reduces critical slowing down. We calculate the free energy in the
neighborhood of the transition for systems up to linear size 70. We find a
double well structure with a barrier that grows with increasing system size,
obeying finite size scaling for systems of size greater than 35. We thus obtain
an estimate of the value of the transition temperature in the thermodynamic
limit.Comment: 4 figure
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
PSS44 USTEKINUMAB IMPROVES WORK PRODUCTIVITY AND DECREASES WORKDAYS MISSED DUE TO PSORIASIS IN PATIENTS WITH MODERATE TO SEVERE PSORIASIS
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
. 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
Everolimus plus exemestane in postmenopausal patients with HR(+) breast cancer: BOLERO-2 final progression-free survival analysis.
IntroductionEffective treatments for hormone-receptor-positive (HR(+)) breast cancer (BC) following relapse/progression on nonsteroidal aromatase inhibitor (NSAI) therapy are needed. Initial Breast Cancer Trials of OraL EveROlimus-2 (BOLERO-2) trial data demonstrated that everolimus and exemestane significantly prolonged progression-free survival (PFS) versus placebo plus exemestane alone in this patient population.MethodsBOLERO-2 is a phase 3, double-blind, randomized, international trial comparing everolimus (10 mg/day) plus exemestane (25 mg/day) versus placebo plus exemestane in postmenopausal women with HR(+) advanced BC with recurrence/progression during or after NSAIs. The primary endpoint was PFS by local investigator review, and was confirmed by independent central radiology review. Overall survival, response rate, and clinical benefit rate were secondary endpoints.ResultsFinal study results with median 18-month follow-up show that median PFS remained significantly longer with everolimus plus exemestane versus placebo plus exemestane [investigator review: 7.8 versus 3.2 months, respectively; hazard ratio = 0.45 (95% confidence interval 0.38-0.54); log-rank P < 0.0001; central review: 11.0 versus 4.1 months, respectively; hazard ratio = 0.38 (95% confidence interval 0.31-0.48); log-rank P < 0.0001] in the overall population and in all prospectively defined subgroups, including patients with visceral metastases, [corrected] and irrespective of age. The incidence and severity of adverse events were consistent with those reported at the interim analysis and in other everolimus trials.ConclusionThe addition of everolimus to exemestane markedly prolonged PFS in patients with HR(+) advanced BC with disease recurrence/progression following prior NSAIs. These results further support the use of everolimus plus exemestane in this patient population. ClinicalTrials.gov #NCT00863655
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
Defect structures and torque on an elongated colloidal particle immersed in a liquid crystal host
Combining molecular dynamics and Monte Carlo simulation we study defect
structures around an elongated colloidal particle embedded in a nematic liquid
crystal host. By studying nematic ordering near the particle and the
disclination core region we are able to examine the defect core structure and
the difference between two simulation techniques. In addition, we also study
the torque on a particle tilted with respect to the director, and modification
of this torque when the particle is close to the cell wall
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