Influence of the geometry on a field-road model : the case of a conical field

Field-road models are reaction-diffusion systems which have been recently introduced to account for the effect of a road on propagation phenomena arising in epidemiology and ecology. Such systems consist in coupling a classical Fisher-KPP equation to a line with fast diffusion accounting for a road. A series of works investigate the spreading properties of such systems when the road is a straight line and the field a half-plane. Here, we take interest in the case where the field is a cone. Our main result is that the spreading speed is not influenced by the angle of the cone

The Bose polaron problem: effect of mass imbalance on binding energy

By means of Quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T = 0. The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to $^{40}$K impurities in a gas of $^{87}$Rb atoms we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.Comment: 5 pages, 3 figure

Reunion overseas: introduced wild boars and cultivated orange trees interact in the Brazilian Atlantic forest

Little is known concerning novel interactions between species that typically interact in their native range but, as a consequence of human activity, are also interacting out of their original distribution under new ecological conditions. Objective: We investigate the interaction between the orange tree and wild boar, both of which share Asian origins and have been introduced to the Americas (i.e. the overseas). Methods: Specifically, we assessed whether i) wild boars consume orange (Citrus sinensis) fruits and seeds in orchards adjacent to a remnant of the Atlantic Forest of Brazil, ii) the orange seeds are viable after passing through boar’s digestive tract and iii) whether the orange tree may naturalise in the forest remnant assisted by wild boars. Results: Our camera surveys indicated that wild boar was by far the most frequent consumer of orange fruits (40.5 % of camera trap-days). A considerable proportion of sown orange seeds extracted from fresh boar feces emerged seedlings (27.8 %, N = 386) under controlled greenhouse conditions. Further, 37.6 % of sown seeds (N = 500) in the forest remnant emerged seedlings in July 2015; however, after ~4 years (March 2019) only 9 seedlings survived (i.e. 4.8 %, N = 188). Finally, 52 sweet orange seedlings were found during surveys within the forest remnant which is intensively used by wild boars. This study indicates a high potential of boars to act as effective seed dispersers of the sweet orange. However, harsh competition with native vegetation and the incidence of lethal diseases, which quickly kill sweet orange trees under non-agricultural conditions, could seriously limit orange tree establishment in the forest. Conclusions: Our results have important implications not only because the wild boar could be a vector of potential invasive species, but also because they disperse seeds of some native species (e.g. the queen palm, Syagrus romanzofiana) in defaunated forests, where large native seed dispersers are missing; thus, wild boars could exert critical ecological functions lost due to human activityinfo:eu-repo/semantics/publishedVersio

Adjusting the Labor Supply to Mitigate Violent Shocks: Evidence from Rural Colombia

This paper studies the use of labor markets to mitigate the impact of violent shocks on households in rural areas in Colombia. It examines changes in the labor supply from on-farm to off-farm labor as a means of coping with the violent shock and the ensuing redistribution of time within households. It identifies the heterogeneous response by gender. Because the incidence of violent shocks is not exogenous, the analysis uses instrumental variables that capture several dimensions of the cost of exercising terror. As a response to the violent shocks, households decrease the time spent on on-farm work and increase their supply of labor to off-farm activities (non-agricultural ones). Men carry the bulk of the adjustment in the use of time inasmuch as they supply the most hours to off-farm non-agricultural work and formal labor markets. Labor markets do not fully absorb the additional labor supply. Women in particular are unable to find jobs in formal labor markets and men have increased time dedicated to leisure and household chores. Additional off-farm supply does not fully cover the decrease in consumption. The results suggest that in rural Colombia, labor markets are a limited alternative for coping with violent shocks. Thus, policies in conflict-affected countries should go beyond short-term relief and aim at preventing labor markets from collapsing and at supporting the recovery of agricultural production.Conflict, labor markets, developing economies, instrumental variables

Fifteen years follow-up of photorefractive keratectomy up to 10 D of myopia: outcomes and analysis of the refractive regression

PURPOSE: To evaluate outcomes of photorefractive keratectomy up to -10.00 D of myopia and -4.50 of astigmatism and to develop a predictive model for the refractive changes in the long term. SETTING: Vissum Corporation and Miguel Hernandez University (Alicante, Spain). DESIGN: Retrospective-prospective observational series of cases. METHODS: This study included 33 eyes of 33 patients aged 46.79±7.04 years (range 40-57) operated with the VISX 20/20 excimer laser with optical zones of 6 mm. No mitomycin C was used in any of these cases. The minimum follow-up was 15 years. The main outcome measures were: uncorrected and corrected distance visual acuity, manifest refraction and corneal topography. Linear regression models were developed from the observed refractive changes over time. RESULTS: Safety and efficacy indexes at 15 years were 1.18 and 0.83, respectively. No statistically significant differences were detected for any keratometric variable during the follow-up (p≥0.103). 15 years after the surgery 54.55% of the eyes were within ±1.00 D of spherical equivalent and 84.85% within ±2.00 D. The uncorrected distance visual acuity at 15 years was 20/25 or better in 60.6% of the eyes and 20/40 or better in 72.73% of the eyes. The correlation between the attempted and the achieved refractions was r=0.948 (p<0.001) at 1 year, and r=0.821 (p<0.001) at 15 years. No corneal ectasia was detected in any case during the follow-up. CONCLUSIONS: Photorefractive keratectomy is a safe refractive procedure in the long term within the range of myopia currently considered suitable for its use, although its efficacy decreases with time, especially, in high myopia. The model developed predicts a myopic regression of 2.00 D at 15 years for an ablation depth of 130 µm