Abstract:
We study the behaviour of a semi-dilute solution of polymers in micro channels, where a main flow of continuous flow rate cross a perpendicular oscillatory flow. We found that at high oscillatory flow rates the flow in the main channel exhibits turbulence. We show that this behaviour depends on both main and oscillatory flow rate. The effect off both shear thinning and elasticity on the nature of the flow are also investigated by comparing our results to numerical simulations of purely shear-thinning fluid.


Abstract (fr) :
Nous avons étudié la réponse de l’écoulement laminaire d’une solution semi-dilué de polymères à une perturbation sinusoïdale dans des micro-canaux. Dans notre montage deux écoulements, un écoulement principal constant et un écoulement sinusoïdal se croisent. Lorsque l’amplitude des oscillations devient suffisamment grande, l’écoulement principal perd sont caractère laminaire et devient turbulent. Notre investigation a montré que cette transition est dépendante du débit des deux écoulements. Nous avons aussi étudié l’effet des caractères rhéofluidifiants et élastiques de notre fluide en comparant nos résultats expérimentaux à des simulations numériques réalisées sur des modèles purement rhéofluidifiants.

Quantum cryptography is the most mature quantum information technology and there exist several companies selling quantum cryptography products. In recent years, several attacks have hacked quantum cryptography implementations. These attacks have proven that implementations of quantum cryptography are subtler than expected and that any mismatch between theory and experiment may open important security loopholes. To close this gap, we introduce the device-independent approach to quantum information theory in which devices are just seen as quantum black boxes processing classical information. This level of abstraction makes the protocols defined in this scenario insensitive to the recent hacking attacks.

We then discuss the device-independent scenario from a more fundamental point of view and introduce the set of almost quantum correlations. We prove that this set (i) is supra-quantum, as it predicts correlations that are impossible in the quantum formalism but (ii) is operationally equivalent to the quantum set for many information tasks. These results then demonstrate that it is possible to modify the structure of quantum correlations without running into any strong operational contradiction with quantum predictions. Intriguingly, the set of almost quantum correlations can also be derived within the history approach introduced in the context of quantum gravity.

The mitotic spindle is a microtubule (MT) based structure that sets the position of cell division. Its positioning is crucial for proper cell division and is highly regulated by hundreds of MT associated proteins and molecular motors. One of them is dynein, minus end directed motor protein that can be recruited at the membrane and pull on astral microtubules to position the spindle. In vivo, it is often difficult to assess the specific function of microtubules or its associated proteins in spindle formation and positioning.
Here, we reconstitute in vitro the interaction of two asters inside 3D water in oil emulsion droplets. We study the positioning of two centrosomes from which microtubules are nucleated, that exert pushing and/or dynein mediated pulling forces when reaching the cortex.
We show that very simple systems, involving only microtubule dynamics, confinement, pushing and pulling forces can lead to self-organized patterns that are biologically relevant. In particular, we reproduce a 'mitotic spindle' like organization with just these components.

At the LHC, New Physics could be better parametrised with form factors than with contact interactions, if the New Physics scale is similar to the LHC energy. As a toy example, I consider the process pp -> l+l- , fit the high-energy tail to a function, and show that the resulting limits can be analytically translated to a wide variety of models (no event simulation required).