81,351 research outputs found
Controversies concerning thymus-derived regulatory T cells: fundamental issues and a new perspective
Thymus-derived regulatory T cells (Tregs) are considered to be a distinct T-cell lineage that is genetically programmed and specialised for immunosuppression. This perspective is based on the key evidence that CD25(+) Tregs emigrate to neonatal spleen a few days later than other T cells and that thymectomy of 3-day-old mice depletes Tregs only, causing autoimmune diseases. Although widely believed, the evidence has never been reproduced as originally reported, and some studies indicate that Tregs exist in neonates. Thus we examine the consequences of the controversial evidence, revisit the fundamental issues of Tregs and thereby reveal the overlooked relationship of T-cell activation and Foxp3-mediated control of the T-cell system. Here we provide a new model of Tregs and Foxp3, a feedback control perspective, which views Tregs as a component of the system that controls T-cell activation, rather than as a distinct genetically programmed lineage. This perspective provides new insights into the roles of self-reactivity, T cell–antigen-presenting cell interaction and T-cell activation in Foxp3-mediated immune regulation
Dynamic Tax Competition under Asymmetric Productivity of Public Capital
We here expand the static tax competition models in symmetric small regions, which were indicated by Zodrow and Mieszkowski (1986) and Wilson (1986), to a dynamic tax competition model in large regions, taking consideration of the regional asymmetry of productivity of public capital and the existence of capital accumulation. The aim of this paper is to verify how the taxation policy affects asymmetric equilibrium based on a simulation analysis using an overlapping generations model in two regions. It is assumed that the public capital as a public input is formed on the basis of the capital tax of local governments and the lump-sum tax of the central government. As demonstrated in related literature, the optimal capital tax rate should become zero when the lump-sum tax is imposed only on older generations, however, the optimal tax rate may become positive when it is imposed proportionally on younger and older generations. In the asymmetric equilibrium, several cooperative solutions can possibly exist which can achieve a higher welfare standard than the actualized cooperative solution either in Region1 or 2
Three-dimensional eddy current analysis by the boundary element method using vector potential
A boundary-element method using a magnetic vector potential for eddy-current analysis is described. For three-dimensional (3-D) problems, the tangential and normal components of the vector potential, tangential components of the magnetic flux density, and an electric scalar potential on conductor surfaces are chosen as unknown variables. When the approximation is introduced so that the conductivity of the conductor is very large in comparison with the conductivity of air, the number of unknowns can be reduced; also, for axisymmetric models the scalar potential can be eliminated from the unknown variables. The formulation of the boundary-element method using the vector potential, and computation results by the proposed method, are presented </p
Transport through a single Anderson impurity coupled to one normal and two superconducting leads
We study the interplay between the Kondo and Andreev-Josephson effects in a
quantum dot coupled to one normal and two superconducting (SC) leads. In the
large gap limit, the low-energy states of this system can be described exactly
by a local Fermi liquid for the interacting Bogoliubov particles. The phase
shift and the renormalized parameters for the Bogoliubov particles vary
depending on the Josephson phase between the two SC leads. We explore the
precise features of a crossover that occurs between the Kondo singlet and local
Cooper-pairing states as the Josephson phase varies, using the numerical
renormalization group approach.Comment: 4 pages, 4 figures, contribution to SCES 201
Dynamics of two-photon paired superradiance
We develop for dipole-forbidden transition a dynamical theory of two-photon
paired superradiance, or PSR for short. This is a cooperative process
characterized by two photons back to back emitted with equal energies. By
irradiation of trigger laser from two target ends, with its frequency tuned at
the half energy between two levels, a macroscopically coherent state of medium
and fields dynamically emerges as time evolves and large signal of amplified
output occurs with a time delay. The basic semi-classical equations in 1+1
spacetime dimensions are derived for the field plus medium system to describe
the spacetime evolution of the entire system, and numerically solved to
demonstrate existence of both explosive and weak PSR phenomena in the presence
of relaxation terms. The explosive PSR event terminates accompanying a sudden
release of most energy stored in the target. Our numerical simulations are
performed using a vibrational transition of
para-H molecule, and taking many different excited atom number densities
and different initial coherences between the metastable and the ground states.
In an example of number density close to cm and of high
initial coherence, the explosive event terminates at several nano seconds after
the trigger irradiation, when the phase relaxation time of ns is
taken. After PSR events the system is expected to follow a steady state
solution which is obtained by analytic means, and is made of many objects of
field condensates endowed with a topological stability.Comment: 31 pages, 15 figures. Revised for publication. Title slightly
changed, detailed explanation added, minor typos corrected. All equations and
figures unchange
Basic oscillation measurables in the neutrino pair beam
It is shown that the vector current contribution of neutrino interaction with
electrons in ion gives rise to oscillating component, which is absent for the
axial-vector contribution, when a single neutrino is detected in the recently
proposed neutrino pair beam. CP violation measurements are thus possible with
high precision along with determination of mass hierarchical patterns.Comment: 10 pages, 9 figure
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