Interaction of moving breathers with an impurity

We analyze the influence of an impurity in the evolution of moving discrete breathers in a Klein--Gordon chain with non-weak nonlinearity. Three different behaviours can be observed when moving breathers interact with the impurity: they pass through the impurity continuing their direction of movement; they are reflected by the impurity; they are trapped by the impurity, giving rise to chaotic breathers. Resonance with a breather centred at the impurity site is conjectured to be a necessary condition for the appearance of the trapping phenomenon.Comment: 4 pages, 2 figures, Proceedings of the Third Conference, San Lorenzo De El Escorial, Spain 17-21 June 200

Goodness of fit in optimizing consumer's model

We provide two new indices of efficiency for determining the degree of coherence in an agent's consumption decisions. We analyze to which extent they improve the efficiency displayed by Varian's (Journal of Econometrics, 1990) index. We report on the results of a Montecarlo experiment that confirms that strict improvements of Varian's vector-index appear on a regular basis.Consumer behavior; GARP; revealed preference; goodness of fit

Impulse-induced localized nonlinear modes in an electrical lattice

Intrinsic localized modes, also called discrete breathers, can exist under certain conditions in one-dimensional nonlinear electrical lattices driven by external harmonic excitations. In this work, we have studied experimentally the efectiveness of generic periodic excitations of variable waveform at generating discrete breathers in such lattices. We have found that this generation phenomenon is optimally controlled by the impulse transmitted by the external excitation (time integral over two consecutive zerosComment: 5 pages, 8 figure

Charge transport in poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers

We investigate the charge transport in synthetic DNA polymers built up from single types of base pairs. In the context of a polaron-like model, for which an electronic tight-binding system and bond vibrations of the double helix are coupled, we present estimates for the electron-vibration coupling strengths utilizing a quantum-chemical procedure. Subsequent studies concerning the mobility of polaron solutions, representing the state of a localized charge in unison with its associated helix deformation, show that the system for poly(dG)-poly(dC) and poly(dA)-poly(dT) DNA polymers, respectively possess quantitatively distinct transport properties. While the former supports unidirectionally moving electron breathers attributed to highly efficient long-range conductivity the breather mobility in the latter case is comparatively restrained inhibiting charge transport. Our results are in agreement with recent experimental results demonstrating that poly(dG)-poly(dC) DNA molecules acts as a semiconducting nanowire and exhibits better conductance than poly(dA)-poly(dT) ones.Comment: 11 pages, 5 figure

The relationship between Mathematical Utility Theory and the Integrability Problem: some arguments in favour

The resort to utility-theoretical issues will permit us to propose a constructive procedure for deriving a homogeneous of degree one, continuous function that gives raise to a primitive demand function under suitably mild conditions. This constitutes the first elementary proof of a necessary and sufficient condition for an integrability problem to have a solution by continuous (subjective utility) functions. Such achievement reinforces the relevance of a technique that was succesfully formalized in Alcantud and Rodríguez-Palmero (2001). The analysis of these two works exposes deep relationships between two apparently separate fields: mathematical utility theory and the revealed preference approach to the integrability problem.Strong Axiom of Homothetic Revelation; revealed preference; continuous homogeneous of degree one utility; integrability of demand.

Nonlinear localized modes in two-dimensional electrical lattices

We report the observation of spontaneous localization of energy in two spatial dimensions in the context of nonlinear electrical lattices. Both stationary and traveling self-localized modes were generated experimentally and theoretically in a family of two-dimensional square, as well as hon- eycomb lattices composed of 6x6 elements. Specifically, we find regions in driver voltage and frequency where stationary discrete breathers, also known as intrinsic localized modes (ILM), exist and are stable due to the interplay of damping and spatially homogeneous driving. By introduc- ing additional capacitors into the unit cell, these lattices can controllably induce traveling discrete breathers. When more than one such ILMs are experimentally generated in the lattice, the interplay of nonlinearity, discreteness and wave interactions generate a complex dynamics wherein the ILMs attempt to maintain a minimum distance between one another. Numerical simulations show good agreement with experimental results, and confirm that these phenomena qualitatively carry over to larger lattice sizes.Comment: 5 pages, 6 figure

Lightning Safety: How Is It Conducted at NIAAA Member High Schools?

The purposes of this study were to explore the current scenario of interscholastic athletics in regards to the existence and enforcement of lightning safety policies applied to athletic outdoor activities, and to identify the common practices related to lightning safety currently utilized. The results showed that 87.2% of the respondents (N=804) have lightning safety policies. However, only 90.3% of the respondents who have lightning safety policies actually enforce them. It seems that during practices coaches are most commonly responsible for making the decision to stop/resume activity, and that during games athletic directors are most commonly making the call. However, almost one third of the respondents (N=804) do not have a clear designation as to who makes the decision. A less than desirable percentage of respondents reported frequent use of a lightning detection system, availability of shelters for spectators, and posted lightning policy in facilities. Only 7.8% of the respondents indicated that all athletic coaches and staff receive lightning safety training. The results also showed that more experienced administrators were more likely to have and enforce lightning safety policies, and employ lightning safety best practices. This study provides high school athletic administrators and principals with relevant information that can be used to support their decision to adopt and enforce lightning safety policies for interscholastic athletic activities