SIRS epidemics with individual heterogeneity of immunity waning.

In the current paper we analyse an extended SIRS epidemic model in which immunity at the individual level wanes gradually at exponential rate, but where the waning rate may differ between individuals, for instance as an effect of differences in immune systems. The model also includes vaccination schemes aimed to reach and maintain herd immunity. We consider both the informed situation where the individual waning parameters are known, thus allowing selection of vaccinees being based on both time since last vaccination as well as on the individual waning rate, and the more likely uninformed situation where individual waning parameters are unobserved, thus only allowing vaccination schemes to depend on time since last vaccination.

Extending susceptible-infectious-recovered-susceptible epidemics to allow for gradual waning of immunity.

Susceptible-infectious-recovered-susceptible (SIRS) epidemic models assume that individual immunity wanes in one leap, from complete immunity to complete susceptibility. For many diseases immunity on the contrary wanes gradually, something that has become even more evident during COVID-19 pandemic where also recently infected have a reinfection risk, and booster vaccines are given to increase immunity. Here, a novel mathematical model is presented allowing for the gradual decay of immunity following linear or exponential waning functions.

Dynamics of a stochastic coronavirus (COVID-19) epidemic model with Markovian switching.

In this paper, we analyze a stochastic coronavirus (COVID-19) epidemic model which is perturbed by both white noise and telegraph noise incorporating general incidence rate. Firstly, we investigate the existence and uniqueness of a global positive solution. Then, we establish the stochastic threshold for the extinction and the persistence of the disease.

Efficiency of Urea Solutions in Enhanced Oil Recovery.

We examine the applicability of urea solutions as a novel cost-effective chemical for enhanced oil recovery processes. Two sandpack flooding experiments were conducted using 5 and 10 wt % urea solutions. Another flooding experiment was also carried out using the same sandpack with fresh water and used as a reference.

The encapsulation of the gemcitabine anticancer drug into grapheme nest: a theoretical study.

The efficient transport of a drug molecule until its target cell constitutes a significant challenge for delivery processes. To achieve such objectives, solid nanocapsules that protect the immune system during the transport should be developed and controlled at the nanoscale level. From this point of view, nanostructures based on graphene sheets could present some promising properties due to their ultimate size and dimension.