39 research outputs found
Wang-Landau sampling in three-dimensional polymers
Monte Carlo simulations using Wang-Landau sampling are performed to study
three-dimensional chains of homopolymers on a lattice. We confirm the accuracy
of the method by calculating the thermodynamic properties of this system. Our
results are in good agreement with those obtained using Metropolis importance
sampling. This algorithm enables one to accurately simulate the usually hardly
accessible low-temperature regions since it determines the density of states in
a single simulation.Comment: 5 pages, 9 figures arch-ive/Brazilian Journal of Physic
Short-time behavior of a classical ferromagnet with double-exchange interaction
We investigate the critical dynamics of a classical ferromagnet on the simple
cubic lattice with double-exchange interaction. Estimates for the dynamic
critical exponents and are obtained using short-time Monte Carlo
simulations. We also estimate the static critical exponents and
studying the behavior of the samples at an early time. Our results are in good
agreement with available estimates and support the assertion that this model
and the classical Heisenberg model belong to the same universality class
What Is the Real Impact of Estrogen Receptor Status on the Prognosis and Treatment of HER2-Positive Early Breast Cancer?
HER2+ early breast cancer is a heterogeneous disease, comprising all the intrinsic breast cancer subtypes. The only biomarker available nowadays for anti-HER2 treatment selection is HER2 status itself, but estrogen receptor (ER) status is emerging as a robust predictive marker within HER2+ disease. In this Perspective, we discuss the biological and clinical differences between patients with HER2+/ER-positive (ER+) disease versus those with HER2+/ ER-negative (ER-neg) tumors, namely, short-term and long-term (>5 years after diagnosis) prognosis, response to neoadjuvant treatment and benefit from adjuvant anti-HER2–targeted therapies. We also address other possible biomarkers to be used for patient selection in future clinical trials, such as gene signatures, PAM50 subtypes, tumor-infiltrating lymphocytes, PIK3CA mutations, and changes in Ki67 score during treatment and discuss their limitations. Finally, we suggest new clinical trial designs that can have an impact on clinical practice, aiming to test treatment deescalation separately for patients with HER2+/ER+ and HER2+/ER-neg tumors. We also propose an integrated classification of HER2+ disease, comprising DNA, RNA, protein expression, and microenvironment characteristics, in order to identify those tumors that are truly “HER2-addicted” and may benefit the most from anti-HER2 treatment
Quasicondensate and superfluid fraction in the 2D charged-boson gas at finite temperature
The Bogoliubov - de Gennes equations are solved for the Coulomb Bose gas
describing a fluid of charged bosons at finite temperature. The approach is
applicable in the weak coupling regime and the extent of its quantitative
usefulness is tested in the three-dimensional fluid, for which diffusion Monte
Carlo data are available on the condensate fraction at zero temperature. The
one-body density matrix is then evaluated by the same approach for the
two-dimensional fluid with e^2/r interactions, to demonstrate the presence of a
quasi-condensate from its power-law decay with increasing distance and to
evaluate the superfluid fraction as a function of temperature at weak coupling.Comment: 9 pages, 2 figure
Critical exponents and equation of state of the three-dimensional Heisenberg universality class
We improve the theoretical estimates of the critical exponents for the
three-dimensional Heisenberg universality class. We find gamma=1.3960(9),
nu=0.7112(5), eta=0.0375(5), alpha=-0.1336(15), beta=0.3689(3), and
delta=4.783(3). We consider an improved lattice phi^4 Hamiltonian with
suppressed leading scaling corrections. Our results are obtained by combining
Monte Carlo simulations based on finite-size scaling methods and
high-temperature expansions. The critical exponents are computed from
high-temperature expansions specialized to the phi^4 improved model. By the
same technique we determine the coefficients of the small-magnetization
expansion of the equation of state. This expansion is extended analytically by
means of approximate parametric representations, obtaining the equation of
state in the whole critical region. We also determine a number of universal
amplitude ratios.Comment: 40 pages, final version. In publication in Phys. Rev.
The Ising model with a periodic spin-lattice coupling on the triangular lattice
In this work, we study and evaluate the impact of a periodic spin-lattice
coupling in an Ising-like system on a 2D triangular lattice. Our proposed
simple Hamiltonian considers this additional interaction as an effect of
preferential phonon propagation direction augmented by the symmetry of the
underline lattice. The simplified analytical description of this new model
brought us consistent information about its ground state and thermal behavior,
and allowed us to highlight a singularity where the model behaves as several
decoupled one-dimensional Ising systems. A thorough analysis was obtained via
numerical simulations using the Wang-Landau Monte Carlo method that estimates
the density of states g(E) to explore the phase diagram and other thermodynamic
properties of interest. Also, we used the finite size scaling technique to
characterize the critical exponents and the nature of the phase transitions
that, despite the strong influence of the spin-lattice coupling, turned out to
be within the same universality class as the original 2D Ising model