Mariano López de Haro

Recent results for the structural properties of binary fluid mixtures of additive hard spheres

In this talk I will present an overview of recent work on the structural properties of binary hard-sphere mixtures. This is based on the use of analytical methods that will be briefly described. The focus will be on both the asymptotic behavior and structural crossovers observed for the total correlation functions and on new findings about the character of the diverse direct correlation functions

Cecilia Noguez

Optical response of plasmonic arrays and radiative heat transfer at the nanoscale

I provide an overview of recent results in studying optical properties of metal nanostructures, emphasizing the relationship between shape, size, environment, and the plasmonic response of individual metal nanoparticles and their arrays. A spectral representation formalism is developed to study the optical response of nanoparticles, which allows us to analyze their response in terms of the interacting surface plasmons excited at the interfaces by separating the contributions of the geometry from those of the dielectric properties. Neither numerical nor other analytical methods can do this separation. These insights into the physical origin of the optical response are very useful for designing systems with desired properties and potential applications. Here, we discuss recent results of the spectral representation for nested nanoparticles, vertical-stacked plasmonic lattices, and the near-field energy transfer between two nanoparticles by considering the coupling between all the thermal electric fields.

Ehécatl del Río

Real-time optimization of uncertain stochastic systems

In this context, real-time optimization is the optimization of stochastic systems by making use of a model, under the assumption that this model is not perfect (system-model mismatch), but with the possibility of sampling the system (assuming this action is expensive). This is a common paradigm in many systems of interest, from aircrafts to chemical reactors, to robotics, to many other systems. This talk will present a new class of real-time optimization algorithms that integrate elements from mathematical optimization (derivative-free optimization) and machine learning (multi-fidelity Gaussian processes) into a Bayesian optimization framework. We will analyze the benefits and shortcoming of the approach in the context of systems which must be optimized while also operated withing some safe conditions, such as chemical reactors and mechanical systems.

David Reguera

How well do we understand nucleation phenomena?

Matter appears in nature in different aggregation states called phases. How atoms and molecules of which matter is made manage to shift between these different states is one of the most fascinating processes in physics. These phase transitions are commonly controlled and triggered by a non-equilibrium physical mechanism, called nucleation, that describes the formation of the first seeds of the new phase. Nucleation is behind many phenomena of utmost scientific and technological interest, ranging from nuclear systems and biological assembly to galaxy formation. However, due to its rare and non-equilibrium nature, it is still one of the few classical problems that remains incompletely understood. In fact, deviations between theoretical predictions and experiments can reach several orders of magnitude even in the simplest case of condensation. In this talk, I will summarize our recent efforts to test the validity and accuracy of classical nucleation theory using computer simulations, and discuss how far theory is from providing a quantitative understanding of one of the most crucial processes in atmospheric and condensed matter science.

Jasna Brujic

Colloidal foldamers in 2d

The goal of self-assembly is to program particle interactions such that they aggregate into a unique architecture with a specific function. In biology, linear sequences of amino acids have evolved to spontaneously fold into well-defined protein geometries. In a system of much reduced complexity, we show an analogous design strategy that successfully folds colloidomers, i.e. polymers made of micron-sized droplets, into desired folds. These supra-colloidal building blocks pave the path towards programmable macroscopic architectures, such as aperiodic crystals or colloidal micelles.

Rosa María Velasco

The shock-wave structure in dilute gases

In this talk we will present some aspects of the shock-wave structure produced in dilute gases. The Linear Irreversible Thermodynamics model (LIT) is discussed and applied to study the density and temperature profiles. The usual Navier-Stokes-Fourier (NSF) equations and the Holian conjecture performance are considered for comparison. The LIT model and the Holian conjecture share the lack of isotropy caused by the propagation direction in a plane shock wave. The results will be compared within themselves and the existing experimental data for He at M = 1.59.

Victor Romero Rochin

Thermodynamic derivation of the scaling hypothesis in the vicinity of the critical point

The scaling hypothesis, introduced by Widom in 1965 and valid in the neighborhood of the critical point, became a milestone in our understanding of the universal properties of critical phenomena. It led to the development of the renormalization group, one of the most important and transcendental theoretical tools of the last decades. In this talk we will show that the scaling hypothesis is not a "hypothesis" but, rather, that it follows rigorously from the laws of thermodynamics when applied to first order phase transitions that end at a critical point, such as in the paramagnetic-ferromagnetic or the liquid-vapor phase transitions. To be specific we show that the free energies, in the vicinity of the critical point, must have the hypothesized scaling form predicted by Widom. We also discuss further challenges in critical phenomena on which thermodynamics alone should give us deeper insight and information.

Pavel Castro Villareal

Low-dimensional colloidal particle systems

Through different theoretical settings, numerical schemes and experiments it is reported the stochastic dynamics of a tagged Brownian particle within an interacting paramagnetic colloidal particle system. This dynamics is studied in low-dimensional confinement spaces without hydrodynamic effects. In particular, on a straight channel case, our findings show consistency between the regime parameters considered in the theory and the typical behavior of the single-file diffusion before a sufficiently long time and below a certain temperature near the crystallization state. Furthermore, for the circular channel case, the confining geometry induces new time scales, namely, the systems display four temporal regimes in the following order: one-dimensional free diffusion, single file subdiffusion, free-cluster rotational diffusion, and the expected saturation due to the compactness of the space. Our generic approach can be used to predict the long-time dynamics of many other confined physical systems. Finally, an attempt to extend our theoretical tools to the active particle systems is shown through a few preliminary results.

Rosana Collepardo Guevara

Multiscale modelling of DNA packaging inside cells

The three-dimensional organisation of the DNA is one of the great marvels of physical biology. By winding around a special class of proteins, the metre-long DNA manages to compress enormously to fit inside tiny (6 μm) nuclei, avoid entanglement and, moreover, maintain exquisite control over the accessibility of the information it carries. The structure of this remarkable complex of DNA and proteins, known as chromatin, determines how easily the DNA can be accessed and, thus, it is intimately linked to gene expression regulation. In this talk, I will present our multiscale modelling techniques designed to investigate the structure of chromatin in conditions that mimic those inside cells (Farr et al, Nature Communications, 2021). I will discuss why nucleosomes, the building blocks of chromatin, should be viewed as highly plastic particles that foster multivalent interactions and promote chromatin’s liquid-like properties.

Laura Domínguez

The genesis of Alzheimer's disease, and the influence of the environment on the production of amyloid-β peptides

In this talk I will present our most resent research about the genesis of Alzheimer's disease through the production of amyloid-β peptides by γ-secretase.

γ-secretase (GS) is a multi-subunit membrane-embedded aspartyl protease that cleaves more than 80 integral membrane proteins, including the amyloid precursor protein (APP) to produce the amyloid-β (Aβ) peptides. According to the amyloidogenic hypothesis, oligomerization, accumulation and aggregation of the 42-amino acid length Aβ isoform in the brain is the primary influence driving the development and progression of Alzheimer's disease (AD).

Based on recent experimental structural studies and using multiscale computational modeling approaches together with pH replica exchange molecular dynamics, we analyzed the influence of the environment on the GS conformational changes. From our simulations, we are able to provide a plausible explanation for the activation and inhibition of GS by changes in the pH and the presence of a variety of charged lipids, as observed in previous experimental studies. We finally suggest how cholesterol-rich multicomponent lipid bilayers may also regulate the enzyme activity.

Ana Laura Benavides

Statistical mechanics approach to determine the Widom line of some real substances

Whenever we think of the supercritical region we expect to find matter in a single “supercritical fluid” phase. Nowadays, there is experimental and theoretical evidence that under supercritical conditions, a system can be found in different (thermodynamic, structural, or dynamic) domains. Nevertheless, there is still no consensus on the characterization of these domains and their borders (Widom line, Frenkel line, melting line). There is also no consensus on the gas-like and liquid-like border, whether they are separated by a line (Widom line) or by a transition region (delta Widom). Additionally, concerning this Widom line, there are also different definitions considered in the literature. This work represents an effort to better understand and characterize the region "close enough" to the critical point assuming that the gas-like and liquid-like regimens are separated by a line as a continuation of a vapor-liquid saturation curve in the pressure-temperature plane. We selected the definition of the Widom line as the locus of points of the maximum correlation length and used it to determine it for some discrete potentials. This theoretical study helped us to propose a criterion based on critical phenomena that contains implicitly the coincidence of the locus of maxima of several response functions using only the locus of two of them. The criterion also provides a quantitative determination of the Widom line endpoint coordinates and was used in the determination of the Widom line of some real substances, including water.