[en] The aim of this paper is to show the experiences in controlling occupational exposure production of radiopharmaceuticals in the Isotope Center (CENTIS) of the Republic of Cuba. data corresponding period 1996-2014 to 896 records are processed. The percentage distributions of the annual effective dose (E), the equivalent dose in the hands (Hp (0.07)) and the equivalent dose in crystalline (Hp (3)), are presented. The annual performance of the average values ​​of these dose quantities is plotted. The results of the internal dosimetry are processed. Annual activities manipulated radioisotopes greater contribution and its relation to the distribution of the collective dose directly linked S of staff, they are evaluated. The ALARA principle is implemented and maintained, based on qualitative and quantitative analysis, as appropriate. The (63-98)% of workers are monitored to E and the (80-100)% for Hp (0.07) and Hp (3), receives less than 10% of annual exposure limits. Groups of workers Radiopharmacy and Inspection and Testing are the greatest contribution to the collective dose, whose S to E equal to or greater than 2 mSv is the (9-62)% of total annual S. The maximum value of S is 98.3 mSv recorded man-1 and this occurs in 2011, however the highest value of 99Mo activity is handled in 2012 and a later year for 131I. They are identified as the most effective means for optimizing radiation safety the use of electronic dosimeters, internal shields process in hot cells and glove boxes and shields for collection of radioactive waste. a reduction in personnel exposure between (10-27)% is obtained. It is shown that exposure of workers in the production of radiopharmaceuticals in Cuba is acceptably low. (author)

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[en] The presence of the aging phenomenon in the homogeneous cooling state (HCS) of a granular fluid composed of inelastic hard spheres or disks is investigated. As a consequence of the scaling property of the N-particle distribution function, it is obtained that the decay of the normalized two-time correlation functions slows down as the time elapsed since the beginning of the measurement increases. This result is confirmed by molecular dynamics simulations for the particular case of the total energy of the system. The agreement is also quantitative in the low density limit, for which an explicit analytical form of the time correlation function has been derived. Moreover, the reported results provide support for the existence of the HCS as a solution of the N-particle Liouville equation

[en] It is shown that the hydrodynamic modes of a dilute granular gas of inelastic hard spheres can be identified, and calculated in the long wavelength limit. Assuming they dominate at long times, formal expressions for the Navier-Stokes transport coefficients are derived. They can be expressed in a form that generalizes the Green-Kubo relations for molecular systems, and it is shown that they can also be evaluated by means of N-particle simulation methods. The form of the hydrodynamic modes to zeroth order in the gradients is used to detect the presence of inherent velocity correlations in the homogeneous cooling state, even in the low density limit. They manifest themselves in the fluctuations of the total energy of the system. The theoretical predictions are shown to be in agreement with molecular dynamics simulations. Relevant related questions deserving further attention are pointed out

[en] A simple model of a vibrated granular monolayer is studied. It consists of inelastic hard spheres confined between two parallel hard plates separated at a distance smaller than twice the diameter of the particles. Both walls are elastic and one of them is vibrating in a sawtooth way. For low densities, a kinetic equation is proposed, from which closed evolution equations for the horizontal and vertical temperatures are derived, assuming spatial homogeneity and that the system is very thin. An excellent agreement between the theoretical predictions and molecular dynamics simulation results is obtained, both for the stationary values and for the dynamics of the temperatures. (paper: classical statistical mechanics, equilibrium and non-equilibrium)

[en] Using kinetic theory we analyse the fluctuations of the total internal energy of a granular gas under stationary uniform shear flow, and find that they are coupled to fluctuations in the different components of the total pressure tensor. Explicit expressions for all the possible one- and two-time cross and auto correlations of the fluctuations are obtained for the two dimensional case. For the range of inelasticity considered, good agreement is found between the theoretical predictions and Molecular Dynamics simulations. (paper)

[en] The local balance equations for the density, momentum, and energy of a dilute gas of elastic or inelastic hard spheres, strongly confined between two parallel hard plates are obtained. The starting point is a Boltzmann-like kinetic equation, recently derived for this system. As a consequence of the confinement, the pressure tensor and the heat flux contain, in addition to the terms associated to the motion of the particles, collisional transfer contributions, similar to those that appear beyond the dilute limit. The complexity of these terms, and of the kinetic equation itself, compromise the potential of the equation to describe the rich phenomenology observed in this kind of systems. For this reason, a simpler model equation based on the Boltzmann equation is proposed. The model is formulated to keep the main properties of the underlying equation, and it is expected to provide relevant information in more general states than the original equation. As an illustration, the solution describing a macroscopic state with uniform temperature, but a density gradient perpendicular to the plates is considered. This is the equilibrium state for an elastic system, and the inhomogeneous cooling state for the case of inelastic hard spheres. The results are in good agreement with previous results obtained directly from the Boltzmann equation. (statphys 27)

[en] A kinetic equation for a system of elastic hard spheres or disks confined by a hard wall of arbitrary shape is derived. It is a generalization of the modified Enskog equation in which the effects of the confinement are taken into account and it is supposed to be valid up to moderate densities. From the equation, balance equations for the hydrodynamic fields are derived, identifying the collisional transfer contributions to the pressure tensor and heat flux. A Lyapunov functional, $\mathcal{H}[f]$, is identified. For any solution of the kinetic equation, $\mathcal{H}$ decays monotonically in time until the system reaches the inhomogeneous equilibrium distribution, that is a Maxwellian distribution with a density field consistent with equilibrium statistical mechanics.