370 research outputs found
Entropic sampling dynamics of the globally-coupled kinetic Ising model
The entropic sampling dynamics based on the reversible information transfer
to and from the environment is applied to the globally coupled Ising model in
the presence of an oscillating magnetic field. When the driving frequency is
low enough, coherence between the magnetization and the external magnetic field
is observed; such behavior tends to weaken with the system size. The time-scale
matching between the intrinsic time scale, defined in the absence of the
external magnetic field, and the extrinsic time scale, given by the inverse of
the driving frequency, is used to explain the observed coherence behavior.Comment: 8 page
Electronic and Magnetic Properties of Electron-doped Superconductor, Sm_{1.85}Ce_{0.15}CuO_{4-delta}
Temperature-dependent magnetization (M(T)) and specific heat (C_p(T))
measurements were carried out on single crystal Sm_{1.85}Ce_{0.15}CuO_{4-delta}
(T_c = 16.5 K). The magnetic anisotropy in the static susceptibility, chi
{equiv} M/H, is apparent not only in its magnitude but also in its temperature
dependence, with chi_{perp} for H{perp}c larger than chi_{parallel} for
H{parallel}c. For both field orientations, chi does not follow the Curie-Weiss
behavior due to the small energy gap of the J = 7/2 multiplet above the J = 5/2
ground-state multiplet. However, with increasing temperature, chi_{parallel}(T)
exhibits a broad minimum near 100 K and then a slow increase while
chi_{perp}(T) shows a monotonic decrease. A sharp peak in C_p(T) at 4.7 K
manifests an antiferromagnetic ordering. The electronic contribution, gamma, to
C_p(T) is estimated to be gamma = 103.2 (7) mJ/moleSmK^2. The entropy
associated with the magnetic ordering is much smaller than Rln2, where R is the
gas constant, which is usually expected for the doublet ground state of
Sm^{+3}. The unusual magnetic and electronic properties evident in M(T) and
C_p(T) are probably due to a strong anisotropic interaction between conduction
electrons and localized electrons at Sm^{+3} sites.Comment: 5 pages, 5 encapsulated postscript figures, late
Direct Evidence of the Discontinuous Character of the Kosterlitz-Thouless Jump
It is numerically shown that the discontinuous character of the helicity
modulus of the two-dimensional XY model at the Kosterlitz-Thouless (KT)
transition can be directly related to a higher order derivative of the free
energy without presuming any {\it a priori} knowledge of the nature of the
transition. It is also suggested that this higher order derivative is of
intrinsic interest in that it gives an additional characteristics of the KT
transition which might be associated with a universal number akin to the
universal value of the helicity modulus at the critical temperature.Comment: 4 pages, to appear in PR
Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics
The dynamic critical exponent is determined from numerical simulations
for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models
with relaxational dynamics. It is suggested that the dynamics is characterized
by two distinct dynamic critical indices and related to the
divergence of the relaxation time by and
, where is the correlation length and the
wavevector. The values determined are and for the
3D LCG and and for the 3D XY model. It is argued
that the nonlinear exponent relates to , whereas the usual
Hohenberg-Halperin classification relates to . Possible implications for the
interpretation of experiments are pointed out. Comparisons with other existing
results are discussed.Comment: to appear in PR
Scaling determination of the nonlinear I-V characteristics for 2D superconducting networks
It is shown from computer simulations that the current-voltage (-)
characteristics for the two-dimensional XY model with resistively-shunted
Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size
scaling form from which the nonlinear - exponent can be determined to
good precision. This determination supports the conclusion , where
is the dynamic critical exponent. The results are discussed in the light of the
contrary conclusion reached by Tang and Chen [Phys. Rev. B {\bf 67}, 024508
(2003)] and the possibility of a breakdown of scaling suggested by Bormann
[Phys. Rev. Lett. {\bf 78}, 4324 (1997)].Comment: 6 pages, to appear in PR
Fractal Profit Landscape of the Stock Market
We investigate the structure of the profit landscape obtained from the most
basic, fluctuation based, trading strategy applied for the daily stock price
data. The strategy is parameterized by only two variables, p and q. Stocks are
sold and bought if the log return is bigger than p and less than -q,
respectively. Repetition of this simple strategy for a long time gives the
profit defined in the underlying two-dimensional parameter space of p and q. It
is revealed that the local maxima in the profit landscape are spread in the
form of a fractal structure. The fractal structure implies that successful
strategies are not localized to any region of the profit landscape and are
neither spaced evenly throughout the profit landscape, which makes the
optimization notoriously hard and hypersensitive for partial or limited
information. The concrete implication of this property is demonstrated by
showing that optimization of one stock for future values or other stocks
renders worse profit than a strategy that ignores fluctuations, i.e., a
long-term buy-and-hold strategy.Comment: 12 pages, 4 figure
Finite-temperature resistive transition in the two-dimensional XY gauge glass model
We investigate numerically the resistive transition in the two-dimensional XY
gauge glass model. The resistively-shunted junction dynamics subject to the
fluctuating twist boundary condition is used and the linear resistances in the
absence of an external current at various system sizes are computed. Through
the use of the standard finite-size scaling method, the finite temperature
resistive transition is found at (in units of the Josephson
coupling strength) with dynamic critical exponent and the static
exponent , in contrast to widely believed expectation of the
zero-temperature transition. Comparisons with existing experiments and
simulations are also made.Comment: 5 pages in two columns, 4 eps figures included, to appear in PR
Reducing combinatorial uncertainties: A new technique based on MT2 variables
We propose a new method to resolve combinatorial ambiguities in hadron
collider events involving two invisible particles in the final state. This
method is based on the kinematic variable MT2 and on the MT2-assisted-on-shell
reconstruction of invisible momenta, that are reformulated as `test' variables
Ti of the correct combination against the incorrect ones. We show how the
efficiency of the single Ti in providing the correct answer can be
systematically improved by combining the different Ti and/or by introducing
cuts on suitable, combination-insensitive kinematic variables. We illustrate
our whole approach in the specific example of top anti-top production, followed
by a leptonic decay of the W on both sides. However, by construction, our
method is also directly applicable to many topologies of interest for new
physics, in particular events producing a pair of undetected particles, that
are potential dark-matter candidates. We finally emphasize that our method is
apt to several generalizations, that we outline in the last sections of the
paper.Comment: 1+23 pages, 8 figures. Main changes in v3: (1) discussion at the end
of sec. 2 improved; (2) added sec. 4.2 about the method's dependence on mass
information. Matches journal versio
Immune evasion in cancer: mechanistic basis and therapeutic strategies
Cancer immune evasion is a major stumbling block in designing effective anticancer therapeutic strategies. Although considerable progress has been made in understanding how cancers evade destructive immunity, measures to counteract tumor escape have not kept pace. There are a number of factors that contribute to tumor persistence despite having a normal host immune system. Immune editing is one of the key aspects why tumors evade surveillance causing the tumors to lie dormant in patients for years through “equilibrium” and “senescence” before re- emerging. In addition, tumors exploit several immunological processes such as targeting the regulatory T cell function or their secretions, antigen presentation, modifying the production of immune suppressive mediators, tolerance and immune deviation. Besides these, tumor heterogeneity and metastasis also play a critical role in tumor growth. A number of potential targets like promoting Th1, NK cell, γδ T cell responses, inhibiting Treg functionality, induction of IL-12, use of drugs including phytochemicals have been designed to counter tumor progression with much success. Some natural agents and phytochemicals merit further study. For example, use of certain key polysaccharide components from mushrooms and plants have shown possess therapeutic impact on tumor-imposed genetic instability, anti-growth signaling, replicative immortality, deregulated metabolism etc. In this review, we will discuss the advances made towards understanding the basis of cancer immune evasion and summarize the efficacy of various therapeutic measures and targets that have been developed or are being investigated to enhance tumor rejection
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