[en] Thin films of SiO deposited on Si substrates by thermal evaporation have been characterised by the analysis of infrared absorption bands and optical constants determination. The structure of the films has been studied in terms of the RBM (Random Bonding Model) and a deviation from the pure RBM structure has been found in the relative concentration of the different tetrahedra Si-O_y-Si_4-y (y=1-4) and in the presence of an additional contribution of Si-O₄ tetrahedra confirmed by the optical properties. Comparative study of films deposited under different conditions and with different thickness suggests that the local arrangement of Si and O atoms, the oxygen content of the films and morphological changes in the films must be considered to account for all the effects observed

[en] The mean field in a globally coupled system of chaotic logistic maps does not obey the standard rules of statistics, even for systems of very large sizes. This indicates the existence of intrinsic instabilities in its evolution. Here these instabilities are related to the very non-smooth behavior of mean values in a single logistic map, as a function of its parameter. Problems of this kind do not affect a similar system of coupled tent maps, where good statistical behavior has been found. We also explore the transition between these two regimes. (author). 15 refs, 9 figs

[en] We show that an ensemble of logistic maps, with parameters distributed in some range inside a chaotic region, cannot be statistical. This is so because any parameter range for this map includes periodic windows. The effects of this periodicity in the averages of the system can be estimated, and are also apparent in the power spectra of average values. As a counterexample, we show that the behaviour for tent maps, where chaotic regions do not include periodic windows, is statistical. (author). 9 refs, 2 figs, 1 tab

[en] A study on plasma synthesis of polyethylene oxide (Peo) using ethanol and ethylene glycol as precursors to obtain potentially biodegradable polyethylenes is presented. The surface of the Peo obtained from ethanol is smooth with some rough parts and others with particles with an average diameter of 3.96 μm. The thicknesses of the Peo films were from 7 to 46 μm, which indicates that the greater the power of synthesis, the greater the film thickness, with an increase rate of 0.38 μm/W. For the Peo obtained with ethylene glycol, the thickness ranges from 5.9 μm to 49.7 μm with a growth rate of 0.46 μm/W. The structural analysis by infrared spectroscopy for both materials shows the CH and OH functional groups characteristic of ethanol and ethylene glycol, and C=O product of dehydrogenation probably from the synthesis, the vibration of the group ≈C≈ that has been found in the plasma polymerization it only appears in the first material. The films synthesized with both precursors have a slight hydrophilic tendency because the contact angles with water, Krebs-Ringer solution and Pbs solution oscillate between 90 ° and 57 °. The second material being the best affinity to be in contact with the three solvents.The electromagnetic absorption was studied by means of UV-Vis spectroscopy, as a result of which the Peo and the Peg show electromagnetic sensitivity in the two regions, for the first material with greater intensity in the visible region, which could indicate its possible degradation before the sunlight and for the second polymer the greatest intensity is in the ultraviolet region with decrease in the visible which represents the same case as the Peo from ethanol.The study of electrical conductivity indicates that both materials have insulating behavior with 3 orders of magnitude ranging from 10^-8 to 10^-10 S/m. However, measuring their electronic activation energy these materials have organic semiconductor behavior because they are within the limits of these from 0.01 eV to 2.5 eV. The above was studied to see the behavior of the material for its possible application in biomaterials because the body generates electrical impulses that in turn would interact with the polymer. (author)

[en] We examine under what circumstances the INTEGRAL/SPI 511 keV signal can originate from decays of MeV-scale composite states produced by: (A) thermonuclear (type Ia) or (B) core collapse supernovae (SNe). The requisite dynamical properties that would account for the observed data are quite distinct, for cases (A) and (B). We determine these requirements in simple hidden valley models, where the escape fraction problem is naturally addressed, due to the long lifetime of the new composite states. A novel feature of scenario (A) is that the dynamics of type Ia SNe, standard candles for cosmological measurements, might be affected by our mechanism. In case (A), the mass of the state mediating between the hidden sector and the SM e⁺e^- could be a few hundred GeV and within the reach of a 500GeV e⁺e^- linear collider. We also note that kinetic mixing of the photon with a light vector state may provide an interesting alternate mediation mechanism in this case. Scenarios based on case (B) are challenged by the need for a mechanism to transport some of the produced positrons toward the Galactic bulge, due to the inferred distribution of core collapse sources. The mass of the mediator in case (B) is typically hundreds of TeV, leading to long-lived particles that could, under certain circumstances, include a viable dark matter candidate. The appearance of long-lived particles in typical models leads to cosmological constraints and we address how a consistent cosmic history may be achieved.

[en] Xylenes and trimethylbenzenes were isomerized in the gaseous phase using as protonating agents D₃⁺ and HeT⁺ ion, obtained by γ radiolysis of D₂, and by T₂β decay, respectively. Experiments with HeT⁺ ions confirmed that methylbenzenes undergo isomerization by intramolecular 1,2-methyl shifts. A protodemethylation reaction was also observed and was ascribed to the relatively high energy of the reactant. The use of the less energetic D₃⁺ ions shows that the gas phase isomerization results are qualitatively in agreement with solution isomerization data. p-Xylene and o-xylene isomerize faster than m-xylene; m-xylene rearranges faster to p-xylene than to o-xylene. Mesitylene does not undergo isomerization, while hemimellitene isomerizes to pseudocumene which, more slowly, rearranges to give mesitylene. A reaction scheme is suggested and its kinetics studied

[en] In situ stress is one of the main factors to be taken into account in the design of tunnels, as it can cause inadmissible stresses and strains leading to high deviations in the budgets. For that reason, the stress state is directly introduced into the numerical models used for the design of tunnels. In Spain, although several tunnels have been carried out with an important overburden in tectonically relevant zones, a quantitative determination of the stresses has not been usually included in civil work projects. Therefore, it is considered necessary to implement a routine procedure of study of civil work projects involving tunnels excavated in rock, and a new detailed methodology is proposed. The challenge is that project managers, who face works in which stresses may play a determinant role, may have a practical reference enabling them to optimize available resources and to include the real stress information in the design of underground works. (Author)

[en] The very surprising broad peaks seen in the power spectra of the mean field in a globally coupled map system, indicating subtle coherences between the elements even in the ''turbulent'' phase, are investigated in detail with respect to number of elements coupled, nonlinearity and global coupling strength. We find that the peaks are determined by two distinct components: effective renormalization of the nonlinearity parameter in the local mapping and the strength of the mean field iteration term. We also demonstrate the influence of background noise on the peaks - which is quite counterintuitive, as the peaks become sharper with increase in strength of noise, up to a certain critical noise strength. (author). 11 refs, 10 figs

[en] The time interval sequences and the spatio-temporal patterns of the firings of a coupled neuronal network are investigated in this paper. For a single neuron stimulated by an external stimulus I, the time interval sequences show a low frequency firing of bursts of spikes, and reversed period-doubling cascade to a high frequency repetitive firing state as the stimulus I is increased. For two neurons coupled to each other through the firing of the spikes, the complexity of the time interval sequences becomes simple as the coupling strength increases. A network with large numbers of neurons shows a complex spatio-temporal pattern structure. As the coupling strength increases, the numbers of phase locked neurons increase and the time interval diagram shows temporal chaos and a bifurcation in the space. The dynamical behaviour is also verified by the Lyapunov exponent. (author). 17 refs, 6 figs

[en] We study a realistic coupled map system, modelling a p - i - n diode structure. As we vary the parameter corresponding to the (scaled) external potential in the model, the dynamics goes through a flip bifurcation and then a Hopf bifurcation, and as the parameter is increased further, we find evidence of a sequence of mode locked windows embedded in the quasiperiodic motion, with periodic attractors whose winding numbers p = p/q, are given by a Farey series. The interesting thing about this Farey sequence is that it is generated between two parent attractors with p = 2/7 and 2/8, where 2/8 implies two distinct coexisting attractors with p = 1/4, and the correct series is obtained only when we use parent winding number 2/8 and not 1/4. So unlike a regular Farey tree, p and q need not be relatively prime here, p = 2 x p/2 x q is permissible, where such attractors are actually comprised of two coexisting attractors with p = p/q. We also checked that the positions and widths of these windows exhibit well defined power law scaling. When the potential is increased further, the Farey windows still provide a ''skeleton'' for the dynamics, and within each window there is a host of other interesting dynamical features, including multiple forward and reverse Feigenbaum trees. (author). 15 refs, 7 figs