On the exposure to mobile phone radiation in trains

This report presents theoretical estimates of the Power Density levels which may be reached inside trains. Two possible sources of high levels of radiation are discussed. The first one arises since the walls of the wagons are metallic and therefore bounce back almost all radiation impinging on them. The second is due to the simultaneous emission of a seemingly large number of nearby telephones. The theoretical study presented here shows that Power Densities stay at values below reference levels always.Comment: 9 pages, 1 figur

Interplay between the magnetic anisotropy contributions of Cobalt nanowires

We report on the magnetic properties and the crystallographic structure of the cobalt nanowire arrays as a function of their nanoscale dimensions. X-ray diffraction measurements show the appearance of an in-plane HCP-Co phase for nanowires with 50 nm diameter, suggesting a partial reorientation of the magnetocrystalline anisotropy axis along the membrane plane with increasing pore diameter. No significant changes in the magnetic behavior of the nanowire system are observed with decreasing temperature, indicating that the effective magnetoelastic anisotropy does not play a dominant role in the remagnetization processes of individual nanowires. An enhancement of the total magnetic anisotropy is found at room temperature with a decreasing nanowire diameter-to-length ratio (d/L), a result that is quantitatively analyzed on the basis of a simplified shape anisotropy model.Comment: 8 pages, 4 figure

Desorption Dynamics of Heavy Alkali Metal Atoms (Rb, Cs) off the Surface of Helium Nanodroplets

We present a combined ion imaging and density functional theory study of the dynamics of the desorption process of rubidium and cesium atoms off the surface of helium nanodroplets upon excitation of the perturbed $6s$ and $7s$ states, respectively. Both experimental and theoretical results are well represented by the pseudodiatomic model for effective masses of the helium droplet in the desorption reaction of m_eff/m_He~10 (Rb) and 13 (Cs). Deviations from this model are found for Rb excited to the 6p state. Photoelectron spectra indicate that the dopant-droplet interaction induces relaxation into low-lying electronic states of the desorbed atoms in the course of the ejection process.Comment: in press, J. Phys. Chem. A (2014

Ca impurity in small mixed 4^4He-3^3He clusters

The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the $^4$He-$^3$He interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for $^4$He clusters, and to become fully solvated for $^3$He clusters. We have calculated the absorption spectrum of Ca around the $4s4p \leftarrow 4s^2$ transition and have found that it is blue-shifted from that of the free-atom transition by an amount that depends on the size and composition of the cluster.Comment: 24 pages, 11 figures. Accepted on Journal of Chemical Physic

The thermodynamics of urban population flows

Orderliness, reflected via mathematical laws, is encountered in different frameworks involving social groups. Here we show that a thermodynamics can be constructed that macroscopically describes urban population flows. Microscopic dynamic equations and simulations with random walkers underlie the macroscopic approach. Our results might be regarded, via suitable analogies, as a step towards building an explicit social thermodynamics

Paired and semipaired domination in triangulations

A dominating set of a graph $G$ is a subset $D$ of vertices such that every vertex not in $D$ is adjacent to at least one vertex in $D$. A dominating set $D$ is paired if the subgraph induced by its vertices has a perfect matching, and semipaired if every vertex in $D$ is paired with exactly one other vertex in $D$ that is within distance 2 from it. The paired domination number, denoted by $\gamma_{pr}(G)$, is the minimum cardinality of a paired dominating set of $G$, and the semipaired domination number, denoted by $\gamma_{pr2}(G)$, is the minimum cardinality of a semipaired dominating set of $G$. A near-triangulation is a biconnected planar graph that admits a plane embedding such that all of its faces are triangles except possibly the outer face. We show in this paper that $\gamma_{pr}(G) \le 2 \lfloor \frac{n}{4} \rfloor$ for any near-triangulation $G$ of order $n\ge 4$, and that with some exceptions, $\gamma_{pr2}(G) \le \lfloor \frac{2n}{5} \rfloor$ for any near-triangulation $G$ of order $n\ge 5$

Introducción de una etapa ácida en la secuencia TCF

El oxígeno y el peróxido no son capaces de eliminar los ácidos hexenurónicos (HexA) en gran extensión, por lo que las pastas TCF de mercado blanqueadas con la secuencia Q-POP, tienen alta reversión. La introducción de una etapa ácida A-Q-POP en la secuencia actual, mediante la adición de ácido fórmico y ácido sulfúrico para conseguir un pH final 3,0-3,5, elimina los HexA significativamente. En este trabajo la etapa ácida se llevó a cabo a temperaturas elevadas 110-115ºC. Los mejores resultados se obtuvieron a 115ºC y una hora de tiempo de retención. En estas condiciones se consigue un índice kappa final de 2,0, un nivel de HexA de 6,0 mEq/kg y una reversión de blancura de solo el 9,4 % tras envejecimiento en cámara climática a 80ºC y 65%HR durante 48 h. Las pastas obtenidas tienen menor índice de tracción pero mejor desgote, permeabilidad al aire y opacidad.____________________________________To a large extent, oxygen and peroxide stages are unable to remove hexenuronic acids (HexA), so that bleached TCF market pulps, using a Q-POP sequence, have high reversion. The introduction of an acid stage by adding formic acid and sulphuric acid at a pH of 3,0 – 3,5 improves selectivity and removes a significant amount of HexA. Optimum conditions were seen to be 115ºC and a retention time of 1 hour. Such conditions were able to produce a final Kappa number of 2,0, a HexA level of 6,0 mEq/kg, and a reversion in controlled-climate chamber of only 9,4%. The pulp thus produced had lower tensile strength, but also greater dewatering, air permeability and opacity

Proximity effect-assisted absorption of spin currents in superconductors

The injection of pure spin current into superconductors by the dynamics of a ferromagnetic contact is studied theoretically. Taking into account suppression of the order parameter at the interfaces (inverse proximity effect) and the energy-dependence of spin-flip scattering, we determine the temperature-dependent ferromagnetic resonance linewidth broadening. Our results agree with recent experiments in Nb|permalloy bilayers [C. Bell et al., arXiv:cond-mat/0702461].Comment: 4 page

Semiempirical Study of Geometries and Valence Isomerization of Pyrene-4,5-oxide and Pyrene-2,3-oxide, Their Oxepines and Related Compounds

A conformational Study of the energies and geometries of the stable compounds obtained from pyrene via enzymatic treatment with oxygen has been carried out using two semiempirical quantum mechanical methods: AM1 and MNDO. The energies of the two possible isomers are strongly dependent upon the spatial position of the oxygen of the pyrene molecule. The valence isomerization of pyrene-4,5-oxide and pyrene-2,3-oxide and their oxepine is discused and related to AM1 and MNDO calculations