Unidimensional model of the ad-atom diffusion on a substrate submitted to a standing acoustic wave II. Solutions of the ad-atom motion equation

The ad-atom dynamic equation, a Langevin type equation is analyzed and solved using some non-linear analytical and numerical tools. We noticeably show that the effect of the surface acoustic wave is to induce an effective potential that governs the diffusion of the ad-atom: the minima of this effective potential correspond to the preferential sites in which the ad-atom spends more time. The strength of this effective potential is compared to the destructuring role of the thermal diffusion and to the crystalline potential induced by the substrate

Market oriented cognitive subcultures in a multiple stakeholder environment

The importance of an organisation wide market oriented culture revolves around the performance implications of a focus on customers. However, in contemporary multiple stakeholder environments different notions of ‘the customer’ can exist adding complexity and introducing the possibility of different market oriented subcultures. An analysis of managers’ cognitive maps within a single case study highlight different beliefs and values associated with two alternative market oriented subcultures externally driven by a focus on two different customer groups. The lack of management consensus was further emphasised by two other alternative internally driven subcultures within the same firm. The implications are briefly discussed

Public access to land in Scots law : two cases on the continuing place for public rights of way

Reviews two Scottish cases on the existence of rights of way under Scots law, including vehicular rights over private land adjacent to a harbour and used by fishermen to store equipment and launch boats

Relaxation kinetics in two-dimensional structures

We have studied the approach to equilibrium of islands and pores in two dimensions. The two-regime scenario observed when islands evolve according to a set of particular rules, namely relaxation by steps at low temperature and smooth at high temperature, is generalized to a wide class of kinetic models and the two kinds of structures. Scaling laws for equilibration times are analytically derived and confirmed by kinetic Monte Carlo simulations.Comment: 6 pages, 7 figures, 1 tabl

Low temperature shape relaxation of 2-d islands by edge diffusion

We present a precise microscopic description of the limiting step for low temperature shape relaxation of two dimensional islands in which activated diffusion of particles along the boundary is the only mechanism of transport allowed. In particular, we are able to explain why the system is driven irreversibly towards equilibrium. Based on this description, we present a scheme for calculating the duration of the limiting step at each stage of the relaxation process. Finally, we calculate numerically the total relaxation time as predicted by our results and compare it with simulations of the relaxation process.Comment: 11 pages, 5 figures, to appear in Phys. Rev.

Cognitive shifts within leader and follower teams:Where consensus develops in mental models during an organizational crisis

This empirical study investigates cognitive shifts in both leader and follower teams when developing consensus or agreement in how to resolve a slowly emerging organizational crisis over time. The cognitive maps of leaders and followers are analyzed in team settings to explain where consensus is formed. The findings indicate that consensus, or the agreement on the causal beliefs held to be critical to organizational adaptation and success, builds over time within both leader and follower teams. However, when comparing the development of consensus longitudinally, the findings confirm that the mental models of leadership teams converge towards follower teams, and not the other way around, during the crisis. The study provides new insights into the importance of the causal beliefs of follower teams when developing a vision to coordinate action to resolve a crisis

Unidimensional model of the ad-atom diffusion on a substrate submitted to a standing acoustic wave I. Derivation of the ad-atom motion equation

The effect of a standing acoustic wave on the diffusion of an ad-atom on a crystalline surface is theoretically studied. We used an unidimensional space model to study the ad-atom+substrate system. The dynamic equation of the ad-atom, a Generalized Langevin equation, is analytically derived from the full Hamiltonian of the ad-atom+substrate system submitted to the acoustic wave. A detailed analysis of each term of this equation, as well as of their properties, is presented. Special attention is devoted to the expression of the effective force induced by the wave on the ad-atom. It has essentially the same spatial and time dependences as its parent standing acoustic wave

The contamination of the surface of Vesta by impacts and the delivery of the dark material

The Dawn spacecraft observed the presence of dark material, which in turn proved to be associated with OH and H-rich material, on the surface of Vesta. The source of this dark material has been identified with the low albedo asteroids, but it is still a matter of debate whether the delivery of the dark material is associated with a few large impact events, to micrometeorites or to the continuous, secular flux of impactors on Vesta. The continuous flux scenario predicts that a significant fraction of the exogenous material accreted by Vesta should be due to non-dark impactors likely analogous to ordinary chondrites, which instead represent only a minor contaminant in the HED meteorites. We explored the continuous flux scenario and its implications for the composition of the vestan regolith, taking advantage of the data from the Dawn mission and the HED meteorites. We used our model to show that the stochastic events scenario and the micrometeoritic flux scenario are natural consequences of the continuous flux scenario. We then used the model to estimate the amounts of dark and hydroxylate materials delivered on Vesta since the LHB and we showed how our results match well with the values estimated by the Dawn mission. We used our model to assess the amount of Fe and siderophile elements that the continuous flux of impactors would mix in the vestan regolith: concerning the siderophile elements, we focused our attention on the role of Ni. The results are in agreement with the data available on the Fe and Ni content of the HED meteorites and can be used as a reference frame in future studies of the data from the Dawn mission and of the HED meteorites. Our model cannot yet provide an answer to the fate of the missing non-carbonaceous contaminants, but we discuss possible reasons for this discrepancy.Comment: 31 pages, 7 figures, 4 tables. Accepted for publication on the journal ICARUS, "Dark and Bright Materials on Vesta" special issu