Mathematical Modelling with Multidisciplinary Applications (M3A)
http://hdl.handle.net/20.500.11824/13
Wed, 03 May 2023 12:16:57 GMT2023-05-03T12:16:57ZOptimal vaccine allocation for the control of sexually transmitted infections
http://hdl.handle.net/20.500.11824/1587
Optimal vaccine allocation for the control of sexually transmitted infections
Saldaña, F.; Steindorf, V.; Srivastav, A.K.; Stollenwerk, N.; Aguiar, M.
The burden of sexually transmitted infections (STIs) poses a challenge due to its
large negative impact on sexual and reproductive health worldwide. Besides simple
prevention measures and available treatment efforts, prophylactic vaccination is a
powerful tool for controlling some viral STIs and their associated diseases. Here, we
investigate how prophylactic vaccines are best distributed to prevent and control STIs.
We consider sex-specific differences in susceptibility to infection, as well as disease
severity outcomes. Different vaccination strategies are compared assuming distinct
budget constraints that mimic a scarce vaccine stockpile. Vaccination strategies are
obtained as solutions to an optimal control problem subject to a two-sex Kermack–
McKendrick-type model, where the control variables are the daily vaccination rates
for females and males. One important aspect of our approach relies on conceptualizing
a limited but specific vaccine stockpile via an isoperimetric constraint. We solve the
optimal control problem via Pontryagin’sMaximum Principle and obtain a numerical
approximation for the solution using a modified version of the forward–backward
sweep method that handles the isoperimetric budget constraint in our formulation. The
results suggest that for a limited vaccine supply (20%–30%vaccination coverage), onesex
vaccination, prioritizing females, appears to be more beneficial than the inclusion
of both sexes into the vaccination program.Whereas, if the vaccine supply is relatively
large (enough to reach at least 40% coverage), vaccinating both sexes, with a slightly
higher rate for females, is optimal and provides an effective and faster approach to
reducing the prevalence of the infection.
Sat, 15 Apr 2023 00:00:00 GMThttp://hdl.handle.net/20.500.11824/15872023-04-15T00:00:00ZPartition Constant of Binary Mixtures for the Equilibrium between a Bulk and a Confined Phase
http://hdl.handle.net/20.500.11824/1585
Partition Constant of Binary Mixtures for the Equilibrium between a Bulk and a Confined Phase
Cortés, H.E.; Scherlis, D. A.; Factorovich, M. H.
It is well-known that the thermodynamic, kinetic and structural properties of fluids, and in particular of water and its solutions, can be drastically affected in nanospaces. A possible consequence of nanoscale confinement of a solution is the partial segregation of its components. Thereby, confinement in nanoporous materials (NPM) has been proposed as a means for the separation of mixtures. In fact, separation science can take great advantage of NPM due to the tunability of their properties as a function of nanostructure, morphology, pore size, and surface chemistry. Alcohol-water mixtures are in this context among the most relevant systems. However, a quantitative thermodynamic description allowing for the prediction of the segregation capabilities as a function of the material-solution characteristics is missing. In the present study we attempt to fill this vacancy, by contributing a thermodynamic treatment for the calculation of the partition coefficient in confinement. Combining the multilayer adsorption model for binary mixtures with the Young equation, we conclude that the liquid-vapor surface tension and the contact angle of the pure substances can be used to predict the separation ability of a particular material for a given mixture to a semiquantitative extent. Moreover, we develop a Kelvin-type equation that relates the partition coefficient to the radius of the pore, the contact angle, and the liquid-vapor surface tensions of the constituents. To assess the validity of our thermodynamic formulation, coarse grained molecular dynamics simulations were performed on models of alcohol-water mixtures confined in cylindrical pores. To this end, a coarse-grained amphiphilic molecule was parametrized to be used in conjunction with the mW potential for water. This amphiphilic model reproduces some of the properties of methanol such as enthalpy of vaporization and liquid-vapor surface tension, and the minimum of the excess enthalpy for the aqueous solution. The partition coefficient turns out to be highly dependent on the molar fraction, on the interaction between the components and the confining matrix, and on the radius of the pore. A remarkable agreement between the theory and the simulations is found for pores of radius larger than 15 Å.
Thu, 15 Sep 2022 00:00:00 GMThttp://hdl.handle.net/20.500.11824/15852022-09-15T00:00:00ZModeling the transmission dynamics and vaccination strategies for human papillomavirus infection: An optimal control approach
http://hdl.handle.net/20.500.11824/1584
Modeling the transmission dynamics and vaccination strategies for human papillomavirus infection: An optimal control approach
Saldaña, F.; Camacho-Gutiérrez, J. A.; Villavicencio-Pulido, G.; Velasco-Hernández, J. X.
Human papillomavirus (HPV) vaccines have been introduced in several countries and have shown positive results in reducing HPV infection and related diseases. Nevertheless, immunization programs remain sub-optimal and more effort is needed to design efficient vaccination deployment. We formulate a two-sex deterministic mathematical model that incorporates the most important epidemiological features of HPV infection and associated cancers. To assess the population-level impact of HPV immunization programs, the model incorporates school-based vaccine delivery for juveniles and catch-up vaccination for adults. The dynamics of the model are rigorously analyzed using the next-generation operator, the center manifold theorem, and normal forms theory. We formulate an optimal control problem to determine the best deployment strategy for HPV vaccination for several plausible scenarios. We establish the existence of solutions of the optimal control problem, and use Pontryagin’s Maximum Principle to characterize the necessary conditions for optimal control solutions. The findings suggest that if girls-only programs are complemented with catch-up vaccination for adult females, such program has the potential to achieve HPV-associated cancers eradication even if boys and males do not receive the vaccine. We also find that the optimal vaccine deployment, in terms of minimizing HPV associated diseases and the cost of vaccination, is to allocate as much vaccines as possible at the initial phase of the epidemic and once a high vaccination coverage is reached then gradually decrease vaccination rates.
Thu, 01 Dec 2022 00:00:00 GMThttp://hdl.handle.net/20.500.11824/15842022-12-01T00:00:00ZInteraction Mechanism Between the HSV-1 Glycoprotein B and the Antimicrobial Peptide Amyloid-β
http://hdl.handle.net/20.500.11824/1570
Interaction Mechanism Between the HSV-1 Glycoprotein B and the Antimicrobial Peptide Amyloid-β
Bourgade, K.; Frost, E.; Dupuis, G.; Witkowski, J.M.; Laurent, B.; Calmettes, C.; Ramassamy, C.; Desroches, M.; Rodrigues, S.; Fülöp, T.
Background: Unravelling the mystery of Alzheimer's disease (AD) requires urgent resolution given the worldwide increase of the aging population. There is a growing concern that the current leading AD hypothesis, the amyloid cascade hypothesis, does not stand up to validation with respect to emerging new data. Indeed, several paradoxes are being discussed in the literature, for instance, both the deposition of the amyloid-β peptide (Aβ) and the intracellular neurofibrillary tangles could occur within the brain without any cognitive pathology. Thus, these paradoxes suggest that something more fundamental is at play in the onset of the disease and other key and related pathomechanisms must be investigated. Objective: The present study follows our previous investigations on the infectious hypothesis, which posits that some pathogens are linked to late onset AD. Our studies also build upon the finding that Aβ is a powerful antimicrobial agent, produced by neurons in response to viral infection, capable of inhibiting pathogens as observed in in vitro experiments. Herein, we ask what are the molecular mechanisms in play when Aβ neutralizes infectious pathogens? Methods: To answer this question, we probed at nanoscale lengths with FRET (Förster Resonance Energy Transfer), the interaction between Aβ peptides and glycoprotein B (responsible of virus-cell binding) within the HSV-1 virion Results: The experiments show an energy transfer between Aβ peptides and glycoprotein B when membrane is intact. No energy transfer occurs after membrane disruption or treatment with blocking antibody. Conclusion: We concluded that Aβ insert into viral membrane, close to glycoprotein B, and participate in virus neutralization.
Mon, 19 Sep 2022 00:00:00 GMThttp://hdl.handle.net/20.500.11824/15702022-09-19T00:00:00Z