495 research outputs found
Econophysics studies in Estonia
A short review of the econophysics research done in Estonia, devoted to the
15th anniversary of the term "econophysics".Comment: Submitted to the special issue on "Econophysics" of the journal
Science & Culture (http://www.scienceandculture-isna.org/journal.htm), a
publication of the Indian Science News Association, established in 193
Dimer diffusion in a washboard potential
The transport of a dimer, consisting of two Brownian particles bounded by a
harmonic potential, moving on a periodic substrate is investigated both
numerically and analytically. The mobility and diffusion of the dimer center of
mass present distinct properties when compared with those of a monomer under
the same transport conditions. Both the average current and the diffusion
coefficient are found to be complicated non-monotonic functions of the driving
force. The influence of dimer equilibrium length, coupling strength and damping
constant on the dimer transport properties are also examined in detail.Comment: Final revised version. 7 pages, 6 figure
Gamma-distribution and wealth inequality
We discuss the equivalence between kinetic wealth-exchange models, in which
agents exchange wealth during trades, and mechanical models of particles,
exchanging energy during collisions. The universality of the underlying
dynamics is shown both through a variational approach based on the minimization
of the Boltzmann entropy and a complementary microscopic analysis of the
collision dynamics of molecules in a gas. In various relevant cases the
equilibrium distribution is the same for all these models, namely a
gamma-distribution with suitably defined temperature and number of dimensions.
This in turn allows one to quantify the inequalities observed in the wealth
distributions and suggests that their origin should be traced back to very
general underlying mechanisms: for instance, it follows that the smaller the
fraction of the relevant quantity (e.g. wealth or energy) that agents can
exchange during an interaction, the closer the corresponding equilibrium
distribution is to a fair distribution.Comment: Presented to the International Workshop and Conference on:
Statistical Physics Approaches to Multi-disciplinary Problems, January 07-13,
2008, IIT Guwahati, Indi
Basic kinetic wealth-exchange models: common features and open problems
We review the basic kinetic wealth-exchange models of Angle [J. Angle, Social
Forces 65 (1986) 293; J. Math. Sociol. 26 (2002) 217], Bennati [E. Bennati,
Rivista Internazionale di Scienze Economiche e Commerciali 35 (1988) 735],
Chakraborti and Chakrabarti [A. Chakraborti, B. K. Chakrabarti, Eur. Phys. J. B
17 (2000) 167], and of Dragulescu and Yakovenko [A. Dragulescu, V. M.
Yakovenko, Eur. Phys. J. B 17 (2000) 723]. Analytical fitting forms for the
equilibrium wealth distributions are proposed. The influence of heterogeneity
is investigated, the appearance of the fat tail in the wealth distribution and
the relaxation to equilibrium are discussed. A unified reformulation of the
models considered is suggested.Comment: Updated version; 9 pages, 5 figures, 2 table
Fractional Fokker-Planck dynamics: Numerical algorithm and simulations
Anomalous transport in a tilted periodic potential is investigated
numerically within the framework of the fractional Fokker-Planck dynamics via
the underlying CTRW. An efficient numerical algorithm is developed which is
applicable for an arbitrary potential. This algorithm is then applied to
investigate the fractional current and the corresponding nonlinear mobility in
different washboard potentials. Normal and fractional diffusion are compared
through their time evolution of the probability density in state space.
Moreover, we discuss the stationary probability density of the fractional
current values.Comment: 10 pages, 9 figure
Fractional diffusion in periodic potentials
Fractional, anomalous diffusion in space-periodic potentials is investigated.
The analytical solution for the effective, fractional diffusion coefficient in
an arbitrary periodic potential is obtained in closed form in terms of two
quadratures. This theoretical result is corroborated by numerical simulations
for different shapes of the periodic potential. Normal and fractional spreading
processes are contrasted via their time evolution of the corresponding
probability densities in state space. While there are distinct differences
occurring at small evolution times, a re-scaling of time yields a mutual
matching between the long-time behaviors of normal and fractional diffusion
Predicting language diversity with complex network
Evolution and propagation of the world's languages is a complex phenomenon,
driven, to a large extent, by social interactions. Multilingual society can be
seen as a system of interacting agents, where the interaction leads to a
modification of the language spoken by the individuals. Two people can reach
the state of full linguistic compatibility due to the positive interactions,
like transfer of loanwords. But, on the other hand, if they speak entirely
different languages, they will separate from each other. These simple
observations make the network science the most suitable framework to describe
and analyze dynamics of language change. Although many mechanisms have been
explained, we lack a qualitative description of the scaling behavior for
different sizes of a population. Here we address the issue of the language
diversity in societies of different sizes, and we show that local interactions
are crucial to capture characteristics of the empirical data. We propose a
model of social interactions, extending the idea from, that explains the growth
of the language diversity with the size of a population of country or society.
We argue that high clustering and network disintegration are the most important
characteristics of models properly describing empirical data. Furthermore, we
cancel the contradiction between previous models and the Solomon Islands case.
Our results demonstrate the importance of the topology of the network, and the
rewiring mechanism in the process of language change
A ligand-based system for receptor-specific delivery of proteins
Gene delivery using vector or viral-based methods is often limited by technical and safety barriers. A promising alternative that circumvents these shortcomings is the direct delivery of proteins into cells. Here we introduce a non-viral, ligand-mediated protein delivery system capable of selectively targeting primary skin cells in-vivo. Using orthologous self-labelling tags and chemical cross-linkers, we conjugate large proteins to ligands that bind their natural receptors on the surface of keratinocytes. Targeted CRE-mediated recombination was achieved by delivery of ligand cross-linked CRE protein to the skin of transgenic reporter mice, but was absent in mice lacking the ligand\u2019s cell surface receptor. We further show that ligands mediate the intracellular delivery of Cas9 allowing for CRISPR-mediated gene editing in the skin more efficiently than adeno-associated viral gene delivery. Thus, a ligand-based system enables the effective and receptor-specific delivery of large proteins and may be applied to the treatment of skin-related genetic diseases
Quality Specifications for the Determination of Copper, Zinc, and Selenium in Human Serum or Plasma: Evaluation of an Approach Based on Biological and Analytical Variation
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