| Lunes 17/04 | Martes 18/04 |
| 11:00-11:40 |
A. Ventura |
|
|
| 11:50-12:30 |
Ignacio Sánchez - Teresa Krick |
|
|
| 12:45-13:45 |
Agasajo de apertura |
|
|
| 14:00-14:40 |
M. Pérez Millán |
13:30-14:10 |
R. Balderrama |
| 14:50-15:30 |
A. Shiu |
14:20-15:00 |
P. Amster |
| |
|
15:10-15:50 |
G. Robledo |
Lunes 17/04:
(11 - 11:40) Alejandra Ventura: Pulsatile inputs in cell signaling: frequency selectivity
Cellular processes are frequently regulated by signals whose activity changes over time, often in a pulsatile manner, in the form of either periodic oscillations or stochastic pulses. Pulsatile signals are characterized by the amplitude and duration of the pulses, and by the time between consecutive pulses. Changes in these properties can potentially lead to different cellular responses. In this work we study which properties determine the existence of an optimal activating signal for a signaling target. Particularly, we focus on the frequency of the activating signal, for doing so we consider dose-conserved pulsatile inputs,meaning that the amplitude of the pulses is varied along with frequency to conserve input dose. When a pulsatile signal stimulates a (simple) signaling component, an initial, transient response is induced, later a stationary periodic behavior is achieved. This last phase is obtained when the stimulation lasts for a long time compared with the timescale of the signaling component. Several articles in the literature have looked for motifs and conditions leading to frequency preference. However, all of them focus on the stationary response. In this work we focus on what we call transient frequency preference (TFP), meaning with this that there is a maximum in the frequency-response curve when the response is measured in a time window within the transient phase.
(11:50 - 12:30) Ignacio Sánchez - Teresa Krick: Mathematical estimates for a case of biomolecular diversity
Linear motifs are short protein subsequences that mediate protein interactions. Hundreds of motif classes including thousands of motif instances are known. Here, we estimate by mathematical tools how many motif classes may remain undiscovered.
(12:45 - 13:45) Agasajo de apertura
(14 - 14:40) Mercedes Pérez Millán : Multistationarity questions in reduced vs extended biochemical reaction networks
We study multistationarity questions in biochemical reaction networks under mass-action kinetics under reduction or extension by intermediate complexes. We simplify and extend previous results by PM-Dickenstein-Shiu-Conradi (2012), Feliu-Wiuf (2013), Dickenstein-PM-Shiu-Tang (2019) and Sadeghimanesh-Feliu (2019), and we present a computer implementation. We also study phosphorylation networks with any number of phosphorylation sites in case the kinase acts distributively and the phosphatase acts in a mixed fashion, both distributively and processively. This is joint work with Alicia Dickenstein, Magalí Giaroli, and Rick Rischter.
(14:50 - 15:30) Anne Shiu: Absolute concentration robustness and multistationarity in biochemical reaction systems
A biochemical reaction system exhibits absolute concentration robustness (ACR) in some species if the positive steady-state value of that species does not depend on initial conditions. We present results characterizing ACR for small networks, specifically, those with only a few species or reactions - or with low-dimensional stoichiometric subspace. We also investigate the relationship between ACR and multistationarity (that is, the capacity to admit multiple positive steady states, which underlies biochemical switches). In particular, we consider a stochastic block framework for generating random networks, and prove edge-probability thresholds at which - with high probability - multistationarity appears and ACR becomes rare. We also show that the small window in which both properties occur only appears in networks with many species. Taken together, our results confirm that, in random reversible networks, ACR and multistationarity together, or even ACR on its own, is highly atypical.
Martes 18/04:
(13:30 - 14:10) Rocío Balderrama: Optimal control for a SIR epidemic model with limited quarantine
Social distance and total lock-downs are interventions that have been used to mitigate the spread of the COVID-19 virus. However, these measures could be harmful to societies in terms of social and economic costs. Using optimal control tools and numerical computations we investigate the optimal strategies that minimize the impact of an epidemic, by studying the conditions for an optimal control of a Susceptible-Infected-Recovered model.
(14:20 - 15:00) Pablo Amster: A bifurcation result for the periodic solutions of a non-autonomous delayed chemostat model
In this talk, we shall present a model describing the dynamics
between nutrient and microbial biomass inside a chemostat having a
periodic input of the limiting nutrient. We assume the existence of a
time delay between the absorption of the nutrient by the biomass cells
and its effects on the cell growth. The consumption of the nutrient is
modeled by an increasing function depending on a parameter. We shall
prove the existence of a branch of nontrivial periodic solutions that
arises when the parameter crosses a threshold value.
(15:10 - 15:50) Gonzalo Robledo: Sensitivity analysis of time varying ecological communities
We consider an ecological network of N species described by a
system of non autonomous ordinary differential equations in which the
(i,j) coefficient of the community matrix allows to describe the direct
effect of the i-th species into the j-th one. Now, in order to estimate
the total (direct and indirect) effects, we carry out a sensitivity
analysis with respect to press type perturbations. Firstly, we will
revisit the classical results obtained for the the autonomous case,
which have been stated in terms of the equilibria. Secondly, we provide
some useful ways for generalize these sensitivity methods to the non
autonomous framework: the main idea is to work with globally bounded
solutions (GBS) instead of equilibria, and to assume that the
linearization around the GBS satisfies the property of exponential
dichotomy. Finally, we present some examples of Lotka-Volterra systems
with periodic and almost periodic coefficients.