The Effect of absorbing sites on the one-dimensional cellular automaton traffic flow with open boundaries

The effect of the absorbing sites with an absorbing rate β0 , in both one absorbing site (one way out) and two absorbing sites (two ways out) in a road, on the traffic flow phase transition is investigated using numerical simulations in the one-dimensional cellular automaton traffic flow model with open boundaries using parallel dynamics. It is found that the behavior of density and current depends strongly on the value of β0 , the position of the way(s) out from the entering and the distance between the ways out. Indeed, in the case of one way out, there exist a critical position of the way out ic1 below which the current is constant for β0 β0c2 When the way out is located at a position greater than i c2 , the current increases with β0 for β0 β0c2 . In the later case the density undergoes two successive first order transitions; from high density to maximal current phase at β0 =β0c1 and from intermediate density to the low one at β0 =β0c2 . In the case of two ways out located respectively at the positions i1 and i2, the two successive transitions occur only when the distance i2 - i1 seating the two ways is smaller than a critical distance dc , otherwise the traffic flow increases with β0, passes through a maximum at β0 =βmax and decreases for any value of β0 greater than βmax. The values of β0c1, β0c2, ic1, ic2 and dc depend on the injecting rate α, the extracting rate β and the position(s) of the way(s) out in the road. Moreover ic1 and ic2 , depend on the size of the system. Phase diagrams in the (α, β0 ), ( β, β0 ) and (i1 ,β0 ) planes are established. It is found that the transitions between Free traffic, Congested traffic and maximal current phase are first order.The effect of the absorbing sites with an absorbing rate β0 , in both one absorbing site (one way out) and two absorbing sites (two ways out) in a road, on the traffic flow phase transition is investigated using numerical simulations in the one-dimensional cellular automaton traffic flow model with open boundaries using parallel dynamics. It is found that the behavior of density and current depends strongly on the value of β0 , the position of the way(s) out from the entering and the distance between the ways out. Indeed, in the case of one way out, there exist a critical position of the way out ic1 below which the current is constant for β0 β0c2 When the way out is located at a position greater than i c2 , the current increases with β0 for β0 β0c2 . In the later case the density undergoes two successive first order transitions; from high density to maximal current phase at β0 =β0c1 and from intermediate density to the low one at β0 =β0c2 . In the case of two ways out located respectively at the positions i1 and i2, the two successive transitions occur only when the distance i2 - i1 seating the two ways is smaller than a critical distance dc , otherwise the traffic flow increases with β0, passes through a maximum at β0 =βmax and decreases for any value of β0 greater than βmax. The values of β0c1, β0c2, ic1, ic2 and dc depend on the injecting rate α, the extracting rate β and the position(s) of the way(s) out in the road. Moreover ic1 and ic2 , depend on the size of the system. Phase diagrams in the (α, β0 ), ( β, β0 ) and (i1 ,β0 ) planes are established. It is found that the transitions between Free traffic, Congested traffic and maximal current phase are first order

Vesicle dynamics in confined steady and harmonically modulated Poiseuille flows

We present a numerical study of the time-dependent motion of a two-dimensional vesicle in a channel under an imposed flow. In a Poiseuille flow the shape of the vesicle depends on the flow strength, the mechanical properties of the membrane, and the width of the channel as reported in the past. This study is focused on the centered snaking (CSn) shape, where the vesicle shows an oscillatory motion like a swimmer flagella even though the flow is stationary. We quantify this behavior by the amplitude and frequency of the oscillations of the vesicle's center of mass. We observe regions in parameter space, where the CSn coexists with the parachute or the unconfined slipper. The influence of an amplitude modulation of the imposed flow on the dynamics and shape of the snaking vesicle is also investigated. For large modulation amplitudes transitions to static shapes are observed. A smaller modulation amplitude induces a modulation in amplitude and frequency of the center of mass of the snaking vesicle. In a certain parameter range we find that the center of mass oscillates with a constant envelope indicating the presence of at least two stable states.Comment: 10 pages, 7 figure

BB84 with Both Several Cloning and Intercept-resend Attacks

The goal of the protocol QKD BB84 is to allow a transmitter and a receiver which uses a quantum channel to exchange their keys and to detect the presence of eavesdropping attacks. In the present research, we investigate the effect of several eavesdroppers with both intercept-resend and cloning attacks. We will propose the different possible cases of the positioning of the eavesdroppers and their strategies of attacks; also we will calculate the mutual information for each case. The explicit expressions of the mutual information and quantum error clearly show that the security of the exchanged information depends on the numbers of the eavesdroppers and their attacks parameters on the quantum channel

Erythrocyte-erythrocyte aggregation dynamics under shear flow

Red blood cells (RBCs) -- erythrocytes -- suspended in plasma tend to aggregate and form rouleaux. During aggregation the first stage consists in the formation of RBC doublets [Blood cells, molecules, and diseases 25, 339 (1999)]. While aggregates are normally dissociated by moderate flow stresses, under some pathological conditions the aggregation becomes irreversible, which leads to high blood viscosity and vessel occlusion. We perform here two-dimensional simulations to study the doublet dynamics under shear flow in different conditions and its impact on rheology. We sum up our results on the dynamics of doublet in a rich phase diagram in the parameter space (flow strength, adhesion energy) showing four different types of doublet configurations and dynamics. We find that membrane tank-treading plays an important role in doublet disaggregation, in agreement with experiments on RBCs. A remarkable feature found here is that when a single cell performs tumbling (by increasing vesicle internal viscosity) the doublet formed due to adhesion (even very weak) remains stable even under a very strong shear rate. It is seen in this regime that an increase of shear rate induces an adaptation of the doublet conformation allowing the aggregate to resist cell-cell detachment. We show that the normalized effective viscosity of doublet suspension increases significantly with the adhesion energy, a fact which should affect blood perfusion in microcirculation.Comment: 14page

Predicting optimal hematocrit in silico

Optimal hematocrit $H_o$ maximizes oxygen transport. In healthy humans, the average hematocrit $H$ is in the range of 40-45$\%$, but it can significantly change in blood pathologies such as severe anemia (low $H$) and polycythemia (high $H$). Whether the hematocrit level in humans corresponds to the optimal one is a long standing physiological question. Here, using numerical simulations with the Lattice Boltzmann method and two mechanical models of the red blood cell (RBC) we predict the optimal hematocrit, and explore how altering the mechanical properties of RBCs affects $H_o$. We develop a simplified analytical theory that accounts for results obtained from numerical simulations and provides insight into the physical mechanisms determining $H_o$. Our numerical and analytical models can easily be modified to incorporate a wide range of mechanical properties of RBCs as well as other soft particles thereby providing means for the rational design of blood substitutes. Our work lays the foundations for systematic theoretical study of the optimal hematocrit and its link with pathological RBCs associated with various diseases (e.g. sickle cell anemia, diabetes mellitus, malaria, elliptocytosis)