Mathematical, Computational and Experimental Neurosciencehttp://hdl.handle.net/20.500.11824/6722022-10-03T20:35:34Z2022-10-03T20:35:34ZFock-space approach to stochastic susceptible-infected-recovered modelsBarros de Souza, D.Araújo, H.Duarte-Fillho, G.Gaffney, E.Nóbrega Santos, F.Raposo, E.http://hdl.handle.net/20.500.11824/15002022-08-04T22:19:31Z2022-07-25T00:00:00ZFock-space approach to stochastic susceptible-infected-recovered models
Barros de Souza, D.; Araújo, H.; Duarte-Fillho, G.; Gaffney, E.; Nóbrega Santos, F.; Raposo, E.
We investigate the stochastic susceptible-infected-recovered (SIR) model of infectious disease dynamics in the Fock-space approach. In contrast to conventional SIR models based on ordinary differential equations for the subpopulation sizes of S, I, and R individuals, the stochastic SIR model is driven by a master equation governing the transition probabilities among the system’s states defined by SIR occupation numbers. In the Fock-space approach the master equation is recast in the form of a real-valued Schrödinger-type equation with a second quantization Hamiltonian-like operator describing the infection and recovery processes. We find exact analytic expressions for the Hamiltonian eigenvalues for any population size N. We present small- and large-N results for the average numbers of SIR individuals and basic reproduction number. For small N we also obtain the probability distributions of SIR states, epidemic sizes and durations, which cannot be found from deterministic SIR models. Our Fock-space approach to stochastic SIR models introduces a powerful set of tools to calculate central quantities of epidemic processes, especially for relatively small populations where statistical fluctuations not captured by conventional deterministic SIR models play a crucial role.We investigate the stochastic susceptible-infected-recovered (SIR) model of infectious disease dynamics in the Fock-space approach. In contrast to conventional SIR models based on ordinary differential equations for the subpopulation sizes of S, I, and R individuals, the stochastic SIR model is driven by a master equation governing the transition probabilities among the system’s states defined by SIR occupation numbers. In the Fock-space approach the master equation is recast in the form of a real-valued Schrödinger-type equation with a second quantization Hamiltonian-like operator describing the infection and recovery processes. We find exact analytic expressions for the Hamiltonian eigenvalues for any population size N. We present small- and large-N results for the average numbers of SIR individuals and basic reproduction number. For small N we also obtain the probability distributions of SIR states, epidemic sizes and durations, which cannot be found from deterministic SIR models. Our Fock-space approach to stochastic SIR models introduces a powerful set of tools to calculate central quantities of epidemic processes, especially for relatively small populations where statistical fluctuations not captured by conventional deterministic SIR models play a crucial role.
2022-07-25T00:00:00ZA phenomenological model for interfacial water near hydrophilic polymersEarls, A.Calderer, M.-C.Desroches, M.Zarnescu, A.Rodrigues, S.http://hdl.handle.net/20.500.11824/14932022-07-08T22:20:17Z2022-06-30T00:00:00ZA phenomenological model for interfacial water near hydrophilic polymers
Earls, A.; Calderer, M.-C.; Desroches, M.; Zarnescu, A.; Rodrigues, S.
We propose a minimalist phenomenological model for the ‘interfacial water’ phenomenon that
occurs near hydrophilic polymeric surfaces. We achieve this by combining a Ginzburg–Landau
approach with Maxwell’s equations which leads us to a well-posed model providing a
macroscopic interpretation of experimental observations. From the derived governing equations,
we estimate the unknown parameters using experimental measurements from the literature. The
resulting profiles of the polarization and electric potential show exponential decay near the
surface, in qualitative agreement with experiments. Furthermore, the model’s quantitative
prediction of the electric potential at the hydrophilic surface is in excellent agreement with
experiments. The proposed model is a first step towards a more complete parsimonious
macroscopic model that will, for example, help to elucidate the effects of interfacial water on
cells (e.g. neuronal excitability), the effects of infrared neural stimulation or the effects of drugs
mediated by interfacial water.
2022-06-30T00:00:00ZImmunosenescence and Altered Vaccine Efficiency in Older Subjects: A Myth Difficult to ChangeFülöp, T.Larbi, A.Pawelec, G.Cohen, A.Provost, G.Khalil, A.Lacombe, G.Rodrigues, S.Desroches, M.Hirokawa, K.Franceschi, C.Witkowski, J.M.http://hdl.handle.net/20.500.11824/14922022-07-08T22:20:15Z2022-04-01T00:00:00ZImmunosenescence and Altered Vaccine Efficiency in Older Subjects: A Myth Difficult to Change
Fülöp, T.; Larbi, A.; Pawelec, G.; Cohen, A.; Provost, G.; Khalil, A.; Lacombe, G.; Rodrigues, S.; Desroches, M.; Hirokawa, K.; Franceschi, C.; Witkowski, J.M.
Organismal ageing is associated with many physiological changes, including differences in the immune system of most animals. These differences are often considered to be a key cause of age-associated diseases as well as decreased vaccine responses in humans. The most often cited vaccine failure is seasonal influenza, but, while it is usually the case that the efficiency of this vaccine is lower in older than younger adults, this is not always true, and the reasons for the differential responses are manifold. Undoubtedly, changes in the innate and adaptive immune response with ageing are associated with failure to respond to the influenza vaccine, but the cause is unclear. Moreover, recent advances in vaccine formulations and adjuvants, as well as in our understanding of immune changes with ageing, have contributed to the development of vaccines, such as those against herpes zoster and SARS-CoV-2, that can protect against serious disease in older adults just as well as in younger people. In the present article, we discuss the reasons why it is a myth that vaccines inevitably protect less well in older individuals, and that vaccines represent one of the most powerful means to protect the health and ensure the quality of life of older adults.
2022-04-01T00:00:00ZHyperactivation of monocytes and macrophages in MCI patients contributes to the progression of Alzheimer's diseaseMunawara, U.Catanzaro, M.Xu, W.Tan, C.Hirokawa, K.Bosco, N.Dumoulin, D.Khalil, A.Larbi, A.Lévesque, S.Ramassamy, C.Barron, A.Cunnane, S.Beauregard, P.Bellenger, J.P.Rodrigues, S.Desroches, M.Witkowski, J.M.Laurent, B.Frost, E.Fülöp, T.http://hdl.handle.net/20.500.11824/14372022-02-28T23:19:42Z2021-12-01T00:00:00ZHyperactivation of monocytes and macrophages in MCI patients contributes to the progression of Alzheimer's disease
Munawara, U.; Catanzaro, M.; Xu, W.; Tan, C.; Hirokawa, K.; Bosco, N.; Dumoulin, D.; Khalil, A.; Larbi, A.; Lévesque, S.; Ramassamy, C.; Barron, A.; Cunnane, S.; Beauregard, P.; Bellenger, J.P.; Rodrigues, S.; Desroches, M.; Witkowski, J.M.; Laurent, B.; Frost, E.; Fülöp, T.
Background: Alzheimer’s disease (AD) is the most common neurodegenerative disease ultimately manifesting as clinical dementia. Despite considerable effort and ample experimental data, the role of neuroinflammation related to systemic inflammation is still unsettled. While the implication of microglia is well recognized, the exact contribution of peripheral monocytes/macrophages is still largely unknown, especially concerning their role in the various stages of AD. Objectives: AD develops over decades and its clinical manifestation is preceded by subjective memory complaints (SMC) and mild cognitive impairment (MCI); thus, the question arises how the peripheral innate immune response changes with the progression of the disease. Therefore, to further investigate the roles of monocytes/macrophages in the progression of AD we assessed their phenotypes and functions in patients at SMC, MCI and AD stages and compared them with cognitively healthy controls. We also conceptualised an idealised mathematical model to explain the functionality of monocytes/macrophages along the progression of the disease. Results: We show that there are distinct phenotypic and functional changes in monocyte and macrophage populations as the disease progresses. Higher free radical production upon stimulation could already be observed for the monocytes of SMC patients. The most striking results show that activation of peripheral monocytes (hyperactivation) is the strongest in the MCI group, at the prodromal stage of the disease. Monocytes exhibit significantly increased chemotaxis, free radical production, and cytokine production in response to TLR2 and TLR4 stimulation. Conclusion: Our data suggest that the peripheral innate immune system is activated during the progression from SMC through MCI to AD, with the highest levels of activation being in MCI subjects and the lowest in AD patients. Some of these parameters may be used as biomarkers, but more holistic immune studies are needed to find the best period of the disease for clinical intervention.
2021-12-01T00:00:00Z