1,258 research outputs found
The reaction at low energies in a chiral quark model
A chiral quark-model approach is extended to the study of the
scattering at low energies. The process of at
MeV/c (i.e. the center mass energy GeV) is
investigated. This approach is successful in describing the differential cross
sections and total cross section with the roles of the low-lying
resonances in shells clarified. The dominates the
reactions over the energy region considered here. Around MeV/c,
the is responsible for a strong resonant peak in the
cross section. The has obvious contributions around
MeV/c, while the contribution of is less
important in this energy region. The non-resonant background contributions,
i.e. -channel and -channel, also play important roles in the explanation
of the angular distributions due to amplitude interferences.Comment: 18 pages and 7 figure
Gene Expression Based Leukemia Sub-Classification Using Committee Neural Networks
Analysis of gene expression data provides an objective and efficient technique for sub-classification of leukemia. The purpose of the present study was to design a committee neural networks based classification systems to subcategorize leukemia gene expression data. In the study, a binary classification system was considered to differentiate acute lymphoblastic leukemia from acute myeloid leukemia. A ternary classification system which classifies leukemia expression data into three subclasses including B-cell acute lymphoblastic leukemia, T-cell acute lymphoblastic leukemia and acute myeloid leukemia was also developed. In each classification system gene expression profiles of leukemia patients were first subjected to a sequence of simple preprocessing steps. This resulted in filtering out approximately 95 percent of the non-informative genes. The remaining 5 percent of the informative genes were used to train a set of artificial neural networks with different parameters and architectures. The networks that gave the best results during initial testing were recruited into a committee. The committee decision was by majority voting. The committee neural network system was later evaluated using data not used in training. The binary classification system classified microarray gene expression profiles into two categories with 100 percent accuracy and the ternary system correctly predicted the three subclasses of leukemia in over 97 percent of the cases
Networking Effects on Cooperation in Evolutionary Snowdrift Game
The effects of networking on the extent of cooperation emerging in a
competitive setting are studied. The evolutionary snowdrift game, which
represents a realistic alternative to the well-known Prisoner's Dilemma, is
studied in the Watts-Strogatz network that spans the regular, small-world, and
random networks through random re-wiring. Over a wide range of payoffs, a
re-wired network is found to suppress cooperation when compared with a
well-mixed or fully connected system. Two extinction payoffs, that characterize
the emergence of a homogeneous steady state, are identified. It is found that,
unlike in the Prisoner's Dilemma, the standard deviation of the degree
distribution is the dominant network property that governs the extinction
payoffs.Comment: Changed conten
Pure multiplicative stochastic resonance of anti-tumor model with seasonal modulability
The effects of pure multiplicative noise on stochastic resonance in an
anti-tumor system modulated by a seasonal external field are investigated by
using theoretical analyses of the generalized potential and numerical
simulations. For optimally selected values of the multiplicative noise
intensity quasi-symmetry of two potential minima and stochastic resonance are
observed. Theoretical results and numerical simulations are in good
quantitative agreement.Comment: 5 pages, 5 figure
Spatiotemporal Fluctuation Induced Transition in a Tumor Model with Immune Surveillance
We report on a simple model of spatial extend anti-tumor system with a
fluctuation in growth rate, which can undergo a nonequilibrium phase
transition. Three states as excited, sub-excited and non-excited states of a
tumor are defined to describe its growth. The multiplicative noise is found to
be double-face: The positive effect on a non-excited tumor and the negative
effect on an excited tumor.Comment: 8pages,5figure
Effects of Contrarians in the Minority Game
We study the effects of the presence of contrarians in an agent-based model
of competing populations. Contrarians are common in societies. These
contrarians are agents who deliberately prefer to hold an opinion that is
contrary to the prevailing idea of the commons or normal agents. Contrarians
are introduced within the context of the Minority Game (MG), which is a binary
model for an evolving and adaptive population of agents competing for a limited
resource. Results of numerical simulations reveal that the average success rate
among the agents depends non-monotonically on the fraction of
contrarians. For small , the contrarians systematically outperform the
normal agents by avoiding the crowd effect and enhance the overall success
rate. For high , the anti-persistent nature of the MG is disturbed and
the few normal agents outperform the contrarians. Qualitative discussion and
analytic results for the small and high regimes are also
presented, and the crossover behavior between the two regimes is discussed.Comment: revtex, 11 pages, 4 figure
A Tracker Solution for a Holographic Dark Energy Model
We investigate a kind of holographic dark energy model with the future event
horizon the IR cutoff and the equation of state -1. In this model, the
constraint on the equation of state automatically specifies an interaction
between matter and dark energy. With this interaction included, an accelerating
expansion is obtained as well as the transition from deceleration to
acceleration. It is found that there exists a stable tracker solution for the
numerical parameter , and smaller than one will not lead to a physical
solution. This model provides another possible phenomenological framework to
alleviate the cosmological coincidence problem in the context of holographic
dark energy. Some properties of the evolution which are relevant to
cosmological parameters are also discussed.Comment: 10 pages, 3 figures; accepted for publication in Int.J.Mod.Phys.
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