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Anticipating and understanding fluctuations in the agri-food market is very important in order to implement policies that can assure fair prices and food availability. In this paper, we contribute to the understanding of this market by exploring its efficiency and whether the local Hurst exponent can help to anticipate its trend or not. We have analyzed the time series of the price for different agri-commodities and classified each day into persistent, anti-persistent, or white-noise. Next, we have studied the probability and speed to mean reversion for several rolling windows. We found that in general mean reversion is more probable and occurs faster during anti-persistent periods. In contrast, for most of the rolling windows we could not find a significant effect of persistence in mean reversion. Hence, we conclude that the Hurst exponent can help to anticipate the future trend and range of the expected prices in this market.

In this paper, we study the phenomena of collapse and anomalous diffusion in shared mobility systems. In particular, we focus on a fleet of vehicles moving through a stations network and analyse the effect of self-journeys in system stability, using a mathematical simplex under stochastic flows. With a birth-death process approach, we find analytical upper bounds for random walk and we monitor how the system collapses by super diffusing under different randomization conditions. Using the multi-scale entropy metric, we show that real data from a bike-sharing fleet in the city of Salamanca (Spain) present a complex behaviour with more of a 1/f signal than a disorganized system with a white noise signal.

A so-called COVID-19 passport or Immunity passport (IP) has been proposed to facilitate the mobility of individuals while the SARS-CoV-2 pandemic persists. A COVID-19 passport can play a key role in the control of the pandemic, specifically in areas with a high density of population, and the help of smart city technology could be very useful to successfully implement IPs. This research studies the impact of ethical judgments on user attitudes toward using vaccine passports based on a Multidimensional Ethics Scale (MES) that contains five ethical constructs: moral equity, relativism, egoism, utilitarianism, and contractualism. Regression analysis shows that MES satisfactorily explains attitude (R 2 = 87.82%, p < 0.001) and that a positive evaluation in moral equity, egoism and utilitarianism is significant ( p < 0.001). The objective of the passport (variable leisure) shows a significant negative moderating effect on moral equity (coefficient = -0.147, p = 0.0302) and a positive one on relativism (coefficient = 0.158, p = 0.0287). Adjustment by means of fsQCA shows that five ethical constructs satisfactorily explain both favorable and unfavorable attitudes toward IPs. Solutions explaining acceptance attain an overall consistency (cons) = 0.871 and coverage (cov) = 0.980. In the case of resistance, we found that cons = 0.979 and cov = 0.775. However, that influence is asymmetrical. To have a positive attitude toward the passport, it is a sufficient condition to attain a positive evaluation on a single ethical factor. On the other hand, when explaining resistance, and with the exception of the recipe ~utilitarianism (cons = 0.911 and cov = 0.859), explanatory prime implications require the interaction of at least two variables. Likewise, the context in which the passport is required is significant to explain rejection.