Dynamic saddle-node bifurcation in a class of slow and fast predator-prey models

25 pagesWe study the stability loss delay phenomenon in the dynamic saddle-node bifurcation in a class of three-dimensional prey and predator systems. The dynamics of the predator is assumed to be slow comparatively to the dynamics of the preys. As an application, a well-known model considered by Clark will be discussed

Assessment of dairy cows comfort in Algerian farms by the Welfare Quality® Protocol

The objective of this study was to determine the frequency and degree of discomfort in dairy cows and the risk factors associated by taking into account six animal welfare indicators included in the Welfare Quality® Protocol (WQ®): lying time, lying outside lying area, collision and cleanliness assessed on three body areas: udder, hindquarters and hind limbs. These indicators were carried out on 1,200 dairy cows belonging to 100 dairy farms in the province of Algiers, which 53% were kept in permanent tie stalls and 47% in partial tie stalls. Observation results showed a low average overall score of comfort (40.8 ± 10.62). This was mainly related to a long lying time (5.9s ± 0.89) of which 41.0% of the farms surveyed exceeded the alert threshold (>6.3s) and 39.0% the alarm threshold (>5.2s), a very high degree of dirtiness in udder (62.6%±21.9), hind quarters (60.6%±21.5) and hind limbs (60.6±21.4). As a result, the majority of farms exceeded the alert thresholds: 100.0% (udder), 86.0% (hindquarters) and 63.0% (hind limbs). Highly significant correlations were observed between the different aspects of comfort assessed (p < 0.0001). To reconcile dairy cows’ welfare and productivity, it is essential to improve their comfort

A method for the reconstruction of unknown non-monotonic growth functions in the chemostat

We propose an adaptive control law that allows one to identify unstable steady states of the open-loop system in the single-species chemostat model without the knowledge of the growth function. We then show how one can use this control law to trace out (reconstruct) the whole graph of the growth function. The process of tracing out the graph can be performed either continuously or step-wise. We present and compare both approaches. Even in the case of two species in competition, which is not directly accessible with our approach due to lack of controllability, feedback control improves identifiability of the non-dominant growth rate.Comment: expansion of ideas from proceedings paper (17 pages, 8 figures), proceedings paper is version v

Renewed and emerging concerns over the production and emission of ozone-depleting substances

Stratospheric ozone depletion, first observed in the 1980s, has been caused by the increased production and use of substances such as chlorofluorocarbons (CFCs), halons and other chlorine-containing and bromine-containing compounds, collectively termed ozone-depleting substances (ODSs). Following controls on the production of major, long-lived ODSs by the Montreal Protocol, the ozone layer is now showing initial signs of recovery and is anticipated to return to pre-depletion levels in the mid-to-late twenty-first century, likely 2050–2060. These return dates assume widespread compliance with the Montreal Protocol and, thereby, continued reductions in ODS emissions. However, recent observations reveal increasing emissions of some controlled (for example, CFC-11, as in eastern China) and uncontrolled substances (for example, very short-lived substances (VSLSs)). Indeed, the emissions of a number of uncontrolled VSLSs are adding significant amounts of ozone-depleting chlorine to the atmosphere. In this Review, we discuss recent emissions of both long-lived ODSs and halogenated VSLSs, and how these might lead to a delay in ozone recovery. Continued improvements in observational tools and modelling approaches are needed to assess these emerging challenges to a timely recovery of the ozone layer

Dynamic transcritical bifurcations in a class of slow-fast predator-prey models

aeres : ACLInternational audienceWe study the stability loss delay phenomenon in a dynamic transcritical bifurcation in a class of three-dimensional prey and predator systems. The dynamics of the predator is assumed to be slow comparatively to the dynamics of the prey. As an application, a well-known model considered by Clark will be discussed