Directed assembly of advanced materials in soft condensed matter provides a fascinating tool for producing a new generation of technological applications that combine several properties and may respond to external conditions. In particular, ordered fluids offer the potential for many innovative applications based on the directed assembly of particles because of their unique properties. In this talk, I will present an overview of the methods we have used to engineer topological defects within liquid crystals and at their interfaces. Then, I will explain how liquid crystal defects can be used to develop new mechanisms for the assembly of colloidal particles. Finally, I will discuss how these assemblies will offer essential insights for novel applications in different technological fields.

$T^3$ in Grande Ourse*

Rupert will entertain us with possible explanations of the
${\mathbf b \mathbf \to \mathbf s}$ anomalies at one-loop:
Indications of lepton flavour universality violation in ${\mathbf b
\mathbf \to \mathbf s}$ transitions at LHCb present one of the
most statistically significant departures from the SM in recent years. I will summarise these observations and review the EFT techniques used to describe them. I will motivate and discuss explanations involving effects induced by new physics at loop level and assess the viability of such solutions given the various important constraints.
This will initially be in an EFT context, before moving to specific simplified models. Finally, I will turn to complementary tests of this new physics.

*tea/coffee/biscuits break around 4pm

Colloidal suspensions are ubiquitous in our daily life. Micrometric particles dispersed in a solvent are indeed present in common liquids such as paints, inks or even food products. We will discuss the properties of those colloidal suspensions from their liquid phase to solid deposits after drying.
First, colloidal suspensions exhibit a wide range of rheological behaviors from shear-thinning to yield stress fluids. We will focus on the shear-thickening transition when dense suspensions experience a dramatic increase in viscosity above a critical shear-stress. By changing the physico-chemistry of the particles, we can tune this rheological transition and thus understand the interactions involved in this behavior.
Increasing concentration can also be noticed during drying when solvent evaporates: particles finally form a solid deposit. After drying, a drop of a colloidal suspension leads to a variety of patterns from coffee-stain to more homogeneous coatings in paintings. We will discuss the effect of the initial concentration of particles on the drying pattern and on the subsequent mechanical instabilities.
Finally, after the whole drying of the colloidal suspension, coatings are achieved. Depending of the nature of the particles, we can tune the wettability of the substrate up to superhydrophobic solid. We will briefly discuss how such a water-repellent substrate can allow levitation of liquids.

Glasses are generally regarded as highly disordered and the idea of “controlling” molecular packing in glasses is reasonably met with skepticism. However, as glasses are non-equilibrium materials, a vast array of amorphous structures are possible in principle. Physical vapor deposition (PVD) allows a surprising amount of control over molecular packing in glasses and can be used to test the limits of amorphous packing in two ways. PVD can prepare glasses that approach the limits of the most dense and lowest energy amorphous packings that are possible. The activation barriers for rearrangements in these materials are very high, giving rise to high thermal and chemical stability. In addition, PVD allows control over anisotropic packing in glasses. For rod-shaped molecules, for example, glasses can be prepared in which the molecules have a substantial tendency to stand-up or lie-down relative to the substrate. As these materials have applications in organic electronics, an important question is: How much anisotropic order can be added to a glass without destroying key technological advantages such as macroscopic homogeneity? The high density and anisotropic packing of PVD glasses can be explained by a mechanism that is “anti-epitaxial” as structure is templated by the top surface rather than by the underlying substrate.

Recent data on b->c ℓ nu and b→sℓℓ transitions exhibit an interesting pattern of deviations from Standard Model expectations, hinting at the violation of lepton flavour universality. I will recall the current situation for the various observables of interest. I will discuss the theoretical approaches used to determine the Standard Model predictions for these observables and some of their shortcomings, before explaining how the observed deviations can be analysed in a model-independent framework. I will then briefly discuss some of the simplified New Physics models used to explain the deviations observed.

Understanding the fundamental nature of the glass transition and amorphous solids is at the core of a large research effort. The theoretical description of glassy solids remains mainly phenomenological. This work explores the hypothesis that a new amorphous phase of matter naturally explains their physical properties. We analyze the thermodynamics of glasses in the limit of large dimensions. This exact mean-field theory predicts two glassy phases, `simple' and `marginally stable', separated by a Gardner transition. We find that glasses are marginally stable in a wide range of physical conditions, covering regimes relevant to describe granular matter, foams, emulsions, hard and soft colloids, and molecular glasses. We confront our theoretical predictions to three-dimensional numerical simulations. We develop an efficient numerical scheme which creates well-relaxed glasses. Colloidal and granular glasses are found to be marginally stable: they evolve in a hierarchical landscape, and present delocalized low-lying excitations. Temperature cycles in this regime give rise to rejuvenation and memory effects, previously observed in spin glasses. In contrast, the behavior of molecular glasses is governed by localized two level systems, whose low-temperature quantum tunneling properties are analyzed. We investigate the role of the configurational entropy in the glassy dynamical slowdown accompanying glass formation. We measure the configurational entropy in extremely supercooled liquids, and assess thermodynamic theories of the glass transition.

Complete understanding of cell mechanics requires probing also the mechanical properties of individual proteins, filaments, and molecular complexes, since these provide structural stability and mechanical flexibility to the living cell. Moreover, the dynamical response of biological systems at the nano- and microscales span over several orders of magnitude in time. Thus, access to a wide range of length and time scales is required to decipher the molecular determinants of cell mechanics. High-speed atomic force microscopy (HS-AFM) is a unique technology allowing subsecond, nanometric imaging[1]. We have adapted HS-AFM to perform high-speed force spectroscopy (HS-FS) probing protein unfolding and receptor/ligand unbinding up to the velocity of molecular dynamics simulations[2–5]. This combination provides atomistic understanding of biomolecular processes based on experimental results. Our recent results revealed heterogeneous and rate dependent unfolding and unbinding pathways on different biomolecules. We have also developed high-frequency microrheology (HFMR) to probe the mechanics of cells at high frequencies, up to 100 kHz[6]. We report the viscoelastic response of different cell types and upon cytoskeletal drug treatments. At a few microsecond timescales, cells exhibit rich viscoelastic responses that depend on the state of the cytoskeleton and on the cell type. Mechanical measurements over the widest dynamic range provide mechanistic understanding of molecular and cellular mechanics allowing direct evaluation of theoretical predictions.

References
[1] T. Ando, N. Kodera, E. Takai, D. Maruyama, K. Saito, A. Toda, A high-speed atomic force microscope for studying biological macromolecules, Proceedings of the National Academy of Sciences. 98 (2001) 12468–12472. doi:10.1073/pnas.211400898.
[2] F. Rico, L. Gonzalez, I. Casuso, M. Puig-Vidal, S. Scheuring, High-Speed Force Spectroscopy Unfolds Titin at the Velocity of Molecular Dynamics Simulations, Science. 342 (2013) 741–743.
[3] F. Sumbul, A. Marchesi, H. Takahashi, S. Scheuring, F. Rico, High-Speed Force Spectroscopy for Single Protein Unfolding, in: Y.L. Lyubchenko (Ed.), Nanoscale Imaging: Methods and Protocols, Springer New York, New York, NY, 2018: pp. 243–264.
[4] H. Takahashi, F. Rico, C. Chipot, S. Scheuring, α-Helix Unwinding as Force Buffer in Spectrins, ACS Nano. 12 (2018) 2719–2727.
[5] F. Rico, A. Russek, L. González, H. Grubmüller, S. Scheuring, Heterogeneous and rate-dependent streptavidin–biotin unbinding revealed by high-speed force spectroscopy and atomistic simulations, PNAS. 116 (2019) 6594–6601.
[6] A. Rigato, A. Miyagi, S. Scheuring, F. Rico, High-frequency microrheology reveals cytoskeleton dynamics in living cells, Nat Phys. 13 (2017) 771–775.

The Twistable Wormlike chain (TWLC) is considered a standard model of DNA mechanics. Although this model captures some of the essential features observed in single molecule experiments, it is incomplete as it neglects an important interaction term which couples twist and bending degrees of freedom. Such twist-bend coupling follows from simple symmetry arguments
about the structure of the double helix. In this talk we will review some recent results showing how twist-bend coupling influences the structure and fluctuations of DNA. Our analysis is extended to the high deformation regime which is governed by interactions that go beyond linear elasticity, which will be briefly discussed.

When liquids are cooled fast enough to avoid crystallization, they undergo what is known as a glass transition : their viscosity increases by several orders of magnitude until they become rigid. Although at the molecular scale these materials remain amorphous and display no long-range order, experimental and computational studies of several glassy materials do indicate the presence of subtle forms of local order. My work is focused on answering the following question: are amorphous materials as amorphous as they look? I will present a method based on information theory, called community detection, whose purpose is to bring out structural diversity in amorphous materials. I will show that this method is able to highlight structural heterogeneities in three different model glass-formers. Finally, I will discuss the correlation of these structural heterogeneities with the particles' mobility.