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Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.

A two agents non-cooperative model is applied in the context of tourism. It is shown that a sharing of resources between the public and private sector gives an optimal solution which is stable in the sense that for both agents the deviation from the optimal solution is not convenient. The optimal solution corresponds to the social optimum.

Congestion is an important management problem at mass tourist sites. This essay focuses on the social carrying capacity (SCC) of a tourist site as indicator of residents' and visitors' perception of crowding, intended as the maximum number of visitors (MNV) tolerated. In case of conflict between the residents' MNV tolerated and the visitors' MNV tolerated, the policy-maker has to mediate. We consider the case in which the residents' SCC is lower than the visitors' SCC, and the site SCC is the result of a compromise between these two aspects of the SCC. This can be measured by making reference to two criteria of choice: the utility maximisation criterion and the voting rule. The use of one method rather than the other depends on the data available about the individual preferences on crowding. Assuming that individual preferences are known, a maximisation model for the computation of the site SCC is conceived. It represents the case in which the residents' SCC is the limiting factor. The site SCC is intended as the number of visitors which maximises the social welfare function. Because a local policy-maker maximises the welfare of residents, in this model visitors are represented by those residents whose welfare wholly depends on the tourism sector, while the social costs due to crowding are borne by those residents who are partially or totally independent from tourism. Nevertheless, in practice, the individual preferences about crowding are not always known. In this case, the MNV tolerated can be computed by applying the majority voting rule. It is shown that, under certain conditions, the optimum number of visitors, obtained through a maximisation model, is equal to the MNV tolerated by the majority of voters.

Modelling water ecosystem dynamics requires a thorough knowledge of the chemico-physical parameters in the constitutive equations of the chosen model. These processes are mathematically described by ordinary, in general non-linear, differential equations whose solution depends strongly on the parameter values. We used the adjoint equation method, minimizing the square deviation between states and observations with the conjugate gradient method, in order to estimate the parameters of a logistic growth model on the basis of macroalgae data collected in the Gulf of Trieste. An extension of the method to a more complete trophic model is also discussed.

Congestion is an important management problem at mass tourist sites. This essay focuses on the social carrying capacity (SCC) of a tourist site as indicator of residents and visitors perception of crowding, intended as the maximum number of visitors (MNV) tolerated. In case of conflict between the residents MNV tolerated and the visitors MNV tolerated, the policy-maker has to mediate. We consider the case in which the residents SCC is lower than the visitors SCC, and the site SCC is the result of a compromise between these two aspects of the SCC. This can be measured by making reference to two criteria of choice: the utility maximisation criterion and the voting rule. The use of one method rather than the other depends on the data available about the individual preferences on crowding. Assuming that individual preferences are known, a maximisation model for the computation of the site SCC is conceived. It represents the case in which the residents SCC is the limiting factor. The site SCC is intended as the number of visitors which maximises the social welfare function. Because a local policy-maker maximises the welfare of residents, in this model visitors are represented by those residents whose welfare wholly depends on the tourism sector, while the social costs due to crowding are borne by those residents who are partially or totally independent from tourism. Nevertheless, in practice, the individual preferences about crowding are not always known. In this case, the MNV tolerated can be computed by applying the majority voting rule. It is shown that, under certain conditions, the optimum number of visitors, obtained through a maximisation model, is equal to the MNV tolerated by the majority of voters.

This essay focuses on social carrying capacity (SCC) as an indicator of tourism sustainable development, and establishes a practical definition of SCC based on the majority rule. In order to understand the main difficulties encountered in measuring SCC from the point of view of beach visitors and residents, data about the well developed tourist resort of Marina di Ravenna (Italy) on the North- Western Adriatic coast were used. We also highlight that, when crowded situations are very frequent and these two aspects of the SCC are in conflict, coastal policy-making should result in a compromise between the need to preserve residents’ life style and to increase the economic benefits of the beach rec

Mobile applications hold promise to foster sustainable mobility behavior, but evaluations of their effectiveness are subject to a number of empirical challenges. We conduct a randomized controlled trial with three distinctive features: unobtrusive tracking of the control group, limited sample attrition, and a representative sample. In our study, 410 participants track their mobility behavior over a 5 week period. After 1 week, the treatment group engages with the user interface of the “Swiss Climate Challenge App”. The user interface combines information on individual CO 2 emissions with gamification features. We find a treatment effect that implies a 9.8 % reduction in emissions caused by access to the mobile application. While we lack the statistical power to exclude a zero average effect, we find statistically significant emission reductions in the second half of the intervention period, among subjects in medium population density areas, and among men. Our findings suggest that mobile applications could generate considerable net benefits, but larger studies will be needed for validation.