On the rotation of ONC stars in the Tsallis formalism context

The theoretical distribution function of the projected rotational velocity is derived in the context of the Tsallis formalism. The distribution is used to estimate the average for a stellar sample from the Orion Nebula Cloud (ONC), producing an excellent result when compared with observational data. In addition, the value of the parameter q obtained from the distribution of observed rotations reinforces the idea that there is a relation between this parameter and the age of the cluster.Comment: 6 pages, 2 figure

The use of violence ini llegal markets: evidence from mahogany trade in the Brazilian Amazon

Agents operating in illegal markets cannot resort to the justice system to guarantee property rights, to enforce contracts, or to seek protection from competitors’ improper behaviors. In these contexts, violence is used to enforce previous agreements and to fight for market share. This relationship plays a major role in the debate on the pernicious effects of the illegality of drug trade. This paper explores a singular episode of transition of a market from legal to illegal to provide a first piece of evidence on the causal effect of illegality on systemic violence. Brazil has historically been the main world producer of big leaf mahogany (a tropical wood). Starting in the 1990s, policies restricting extraction and trade of mahogany, culminating with prohibition, were implemented. First, we present evidence that large scale mahogany trade persisted after prohibition, through misclassification of mahogany exports as “other tropical timber species.” Second, we document relative increases in violence after prohibition in areas with: (i) higher share of mahogany exports before prohibition; (ii) higher suspected illegal mahogany activity after prohibition; and (iii) natural occurrence of mahogany. We believe this is one of the first documented experiences of increase in violence following the transition of a market from legal to illegal.illegal markets, violence, homicide, mahogany, Brazil Jel Codes: K42, O13, O17, Q58

The Use of Violence in Illegal Markets: Evidence from Mahogany Trade in the Brazilian Amazon

Agents operating in illegal markets cannot resort to the justice system to guarantee property rights, to enforce contracts, or to seek protection from competitors' improper behaviors. In these contexts, violence is used to enforce previous agreements and to fight for market share. This relationship plays a major role in the debate on the pernicious effects of the illegality of drug trade. This paper explores a singular episode of transition of a market from legal to illegal to provide a first piece of evidence on the causal effect of illegality on systemic violence. Brazil has historically been the main world producer of big leaf mahogany (a tropical wood). Starting in the 1990s, policies restricting extraction and trade of mahogany, culminating with prohibition, were implemented. First, we present evidence that large scale mahogany trade persisted after prohibition, through misclassification of mahogany exports as "other tropical timber species." Second, we document relative increases in violence after prohibition in areas with: (i) higher share of mahogany exports before prohibition; (ii) higher suspected illegal mahogany activity after prohibition; and (iii) natural occurrence of mahogany. We believe this is one of the first documented experiences of increase in violence following the transition of a market from legal to illegal.illegal markets, violence, homicide, mahogany, Brazil

Strong evidences for a nonextensive behavior of the rotation period in Open Clusters

Time-dependent nonextensivity in a stellar astrophysical scenario combines nonextensive entropic indices $q_{K}$ derived from the modified Kawaler's parametrization, and $q$, obtained from rotational velocity distribution. These $q$'s are related through a heuristic single relation given by $q\approx q_{0}(1-\Delta t/q_{K})$, where $t$ is the cluster age. In a nonextensive scenario, these indices are quantities that measure the degree of nonextensivity present in the system. Recent studies reveal that the index $q$ is correlated to the formation rate of high-energy tails present in the distribution of rotation velocity. On the other hand, the index $q_{K}$ is determined by the stellar rotation-age relationship. This depends on the magnetic field configuration through the expression $q_{K}=1+4aN/3$, where $a$ and $N$ denote the saturation level of the star magnetic field and its topology, respectively. In the present study, we show that the connection $q-q_{K}$ is also consistent with 548 rotation period data for single main-sequence stars in 11 Open Clusters aged less than 1 Gyr. The value of $q_{K}\sim$ 2.5 from our unsaturated model shows that the mean magnetic field topology of these stars is slightly more complex than a purely radial field. Our results also suggest that stellar rotational braking behavior affects the degree of anti-correlation between $q$ and cluster age $t$. Finally, we suggest that stellar magnetic braking can be scaled by the entropic index $q$.Comment: 6 pages and 2 figures, accepted to EPL on October 17, 201

An extended formalism for preferential attachment in heterogeneous complex networks

In this paper we present a framework for the extension of the preferential attachment (PA) model to heterogeneous complex networks. We define a class of heterogeneous PA models, where node properties are described by fixed states in an arbitrary metric space, and introduce an affinity function that biases the attachment probabilities of links. We perform an analytical study of the stationary degree distributions in heterogeneous PA networks. We show that their degree densities exhibit a richer scaling behavior than their homogeneous counterparts, and that the power law scaling in the degree distribution is robust in presence of heterogeneity

Preferential attachment growth model and nonextensive statistical mechanics

We introduce a two-dimensional growth model where every new site is located, at a distance $r$ from the barycenter of the pre-existing graph, according to the probability law $1/r^{2+\alpha_G} (\alpha_G \ge 0)$, and is attached to (only) one pre-existing site with a probability $\propto k_i/r^{\alpha_A}_i (\alpha_A \ge 0$; $k_i$ is the number of links of the $i^{th}$ site of the pre-existing graph, and $r_i$ its distance to the new site). Then we numerically determine that the probability distribution for a site to have $k$ links is asymptotically given, for all values of $\alpha_G$, by $P(k) \propto e_q^{-k/\kappa}$, where $e_q^x \equiv [1+(1-q)x]^{1/(1-q)}$ is the function naturally emerging within nonextensive statistical mechanics. The entropic index is numerically given (at least for $\alpha_A$ not too large) by $q = 1+(1/3) e^{-0.526 \alpha_A}$, and the characteristic number of links by $\kappa \simeq 0.1+0.08 \alpha_A$. The $\alpha_A=0$ particular case belongs to the same universality class to which the Barabasi-Albert model belongs. In addition to this, we have numerically studied the rate at which the average number of links $$ increases with the scaled time $t/i$; asymptotically, $\propto (t/i)^\beta$, the exponent being close to $\beta={1/2}(1-\alpha_A)$ for $0 \le \alpha_A \le 1$, and zero otherwise. The present results reinforce the conjecture that the microscopic dynamics of nonextensive systems typically build (for instance, in Gibbs $\Gamma$-space for Hamiltonian systems) a scale-free network.Comment: 5 pages including 5 figures (the original colored figures 1 and 5a can be asked directly to the authors

The mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed

The electrosynthesis of the composite with of the overoxidized polypyrrole with cobalt oxy-hydroxide in strongly acidic media has been described mathematically, using linear stability theory and bifurcation analysis. The steadystates stability conditions and oscillatory and monotonic instability requirements have been described too. The system´s behavior was compared with behavior of other systems with overoxidation, electropolymerization of heterocyclic compounds and electrosynthesis of the cobalt oxy-hydroxides