7 research outputs found
Statistics of leaders and lead changes in growing networks
We investigate various aspects of the statistics of leaders in growing
network models defined by stochastic attachment rules. The leader is the node
with highest degree at a given time (or the node which reached that degree
first if there are co-leaders). This comprehensive study includes the full
distribution of the degree of the leader, its identity, the number of
co-leaders, as well as several observables characterizing the whole history of
lead changes: number of lead changes, number of distinct leaders, lead
persistence probability. We successively consider the following network models:
uniform attachment, linear attachment (the Barabasi-Albert model), and
generalized preferential attachment with initial attractiveness.Comment: 28 pages, 14 figures, 1 tabl
Absence of logarithmic scaling in the ageing behaviour of the 4D spherical model
The non-equilibrium dynamics of the kinetic spherical model, quenched to
T<=T_c, with a non-conserved order-parameter is studied at its upper critical
dimension d=d*=4. In the scaling limit where both the waiting time s and the
observation time t are large and the ratio y=t/s>1 is fixed, the scaling
functions of the two-time autocorrelation and autoresponse functions do not
contain any logarithmic correction factors and the typical size of correlated
domains scales for large times as L(t) ~ t^0.5 .Comment: Latex2e, 12 pages, 2 figures included, (final form
Finite-time fluctuations in the degree statistics of growing networks
This paper presents a comprehensive analysis of the degree statistics in
models for growing networks where new nodes enter one at a time and attach to
one earlier node according to a stochastic rule. The models with uniform
attachment, linear attachment (the Barab\'asi-Albert model), and generalized
preferential attachment with initial attractiveness are successively
considered. The main emphasis is on finite-size (i.e., finite-time) effects,
which are shown to exhibit different behaviors in three regimes of the
size-degree plane: stationary, finite-size scaling, large deviations.Comment: 33 pages, 7 figures, 1 tabl
In vivo and ex vivo percutaneous absorption of [14C]-bisphenol A in rats: a possible extrapolation to human absorption?
Bisphenol A (BPA) is a monomer used mainly in the synthesis of polycarbonates and epoxy resins. Percutaneous absorption is the second source of exposure, after inhalation, in the work environment. However, studies on this route of absorption are lacking or incomplete. In this study, percutaneous BPA absorption was measured in vivo and ex vivo in the rat, and ex vivo in humans. An approximately 12-fold difference in permeability between rat skin and human skin was found, with permeability being higher in the rat. In addition, inter- and intra-individual variability of up to tenfold was observed in humans. No accumulation of BPA in the skin was found during exposure. The skin clearance rate following exposure was estimated at 0.4 μg/cm²/h. Ex vivo and in vivo percutaneous absorption fluxes of BPA in the rat were in the same range (about 2.0 μg/cm²/h), suggesting that extrapolation to the in vivo situation in humans may be possible. The European tolerable daily intake (TDI) of BPA is 50 μg/kg body weight. However, many research projects have highlighted the significant effects of BPA in rodents at doses lower than 10 μg/kg/day. A 1-h occupational exposure over 2,000 cm² (forearms and hands) may lead to a BPA absorption of 4 μg/kg/day. This is 8% of the European TDI and is very close to the value at which effects have been observed in animals. This absorption must therefore be taken into account when evaluating risks of BPA exposure, at least until more relevant results on the toxicity of BPA in humans are available
Feasibility study of a decelerating radio frequency quadrupole system for the antiproton decelerator AD
This feasibility study reports on a decelerating Radio-Frequency Quadrupole (RFQ) system for post-deceleration of the 100 MeV/c antiproton beam of the AD machine. The corresponding kinetic energy of 5.314 MeV is reduced to values which can be chosen between 10 to 100 keV with minimal blow-up of the normalised beam emittances. This wide range of output energy is required for the second phase of the ASACUSA experiment; it is achieved by electrostatic means. The study gives details of the overall performance of the system, the proposed implementation of the RFQ, the associated rf equipment, the beam lines, the diagnostics as well as estimations for the cost and the manpower requirements of the project