Transport efficiency of metachronal waves in 3d cilia arrays immersed in a two-phase flow

The present work reports the formation and the characterization of antipleptic and symplectic metachronal waves in 3D cilia arrays immersed in a two-fluid environment, with a viscosity ratio of 20. A coupled lattice-Boltzmann-Immersed-Boundary solver is used. The periciliary layer is confined between the epithelial surface and the mucus. Its thickness is chosen such that the tips of the cilia can penetrate the mucus. A purely hydrodynamical feedback of the fluid is taken into account and a coupling parameter $\alpha$ is introduced allowing the tuning of both the direction of the wave propagation, and the strength of the fluid feedback. A comparative study of both antipleptic and symplectic waves, mapping a cilia inter-spacing ranging from 1.67 up to 5 cilia length, is performed by imposing the metachrony. Antipleptic waves are found to systematically outperform sympletic waves. They are shown to be more efficient for transporting and mixing the fluids, while spending less energy than symplectic, random, or synchronized motions

Financement dynamique des intermédiaires financiers : l’effet de la volatilité du taux de crédit sur les dépôts de base

L’étude examine les effets à court et long terme de la volatilité du taux de crédit sur les moyens de financement d’un intermédiaire financier qui est caractérisé par la neutralité au risque et des rendements constants à l’échelle dans sa technologie de transformation d’actifs. Étant donné l’existence de coûts d’ajustement convexes, nous démontrons que le flux courant de dépôts nouveaux est une fonction croissante du prix d’ordre des dépôts existants. Nous prouvons aussi qu’un accroissement de la volatilité du taux de crédit augmente le flux courant de dépôts nouveaux. De plus, si le taux de crédit ne présente pas de corrélation chronologique, cette volatilité accrue fait monter le niveau anticipé d’équilibre à long terme des dépôts de base. Ces résultats se vérifient également dans la plupart des cas où le taux est corrélé chronologiquement. Les fluctuations du taux de crédit étant corrélées, le modèle d’optimisation peut même entraîner une situation particulière, la désintermédiation à long terme des dépôts de base. C’est le cas si le coût marginal d’ajustement est plus convexe que la fonction d’intermédiation : ceci ne se réalise (de façon non ambiguë) que s’il y a forte persistance temporelle des fluctuations du taux de crédit, que si le facteur d’actualisation est faible et que si le taux d’attrition des dépôts existants est élevé.This paper looks at the near-term and equilibrium effects of loan-rate volatility on the optimal liability-funding policies of a risk-neutral intermediary that exhibits constant returns to scale in its asset transformation technology. It is shown, first, that given convex adjustment costs, the flow of current new savings is an increasing function of the shadow price of existing deposits. It is shown, next, that increased credit-rate volatility raises this current flow of new savings; and rate volatility also affects positively the expected long-run holding of core deposits, if the loan rate is serially uncorrelated. These results hold true for most cases of serial correlation as well. Finally, it is shown that when credit rate fluctuations show temporal persistence, the model will lead explicitly to long-run disintermediation under the following restrictive conditions: the adjustment cost technology is more convex than the intermediation technology, where more convex hinges on serial correlation in rates, the discount factor and the attrition rate of core deposits

Une analyse économétrique de la demande et de l’offre de dépôts des sociétés de crédit populaire : le cas des Caisses populaires

The aim of the study is to explain Quebec major credit union's deposit market by way of integrating its public demand function with the institution's rate-setting operation. The demand for Caisses' deposits is specified as a dynamic stock adjustment model. On the other hand, the intermediary's rate-setting reduced form is derived from a risk-return portfolio balance model in which the managers maximize the expected utility of reserves. The two models are integrated by means of a liability composite rate.Econometric estimates of the integrated model provide us with interesting policy insights. For instance, the Quebecois public views chartered banks' deposits as a weak substitute for Caisses' deposits; it is also more responsive to nonrate arguments, such as loan eligibility or the institution's ethnic appeal. On the supply side, competitive liability rates are more important than returns on assets when the Caisses set its deposit rate. Finally, the impact growth imbalance between loans and deposits is well captured by a flow variable, without infringing on the steady determination based on rates

Une analyse économétrique du comportement d’intermédiation financière des sociétés de crédit populaire : le cas des caisses populaires

Considering the Caisses populaires as a financial system, we propose an econometric model of its consolidated balance sheet built around the following four major blocks. The first one presents a dynamic sub-model of the Caisses' asset portfolio, which emphasizes their intermediation among assets on the basis of the latter interest rates. In a second block, these rates are endogenized with respect to the key variables of both the real and monetary sectors of the economy. On the liability side, the Caisses' deposit market is dealt with in a third block, namely a demand for deposits or flow equation and a supply of deposits or rate setting operation. Finally, adjustment equations for the balance sheet items not already considered, are grouped in a fourth block. The overall model is dynamized through the deposit equation.From the model's econometric estimation, we arrive at the following conclusions about financial management and liquidity policies. On the asset side of the balance sheet, the Caisses aim mainly at satisfying their members' needs for mortgages and, to a lesser but growing degree, for consumer loans. Next, for the funds remaining after satisfying internal needs, the institution proceeds to some sort of secondary, medium-term intermediation, then preferring quasi-liquid and higher yielding bonds to reserves. On the liability side, the Caisses seem to set their rate on deposits on the basis of the one for chartered banks (price leadership) as well as on the basis of the most representative asset rates, i.e. the ones on consumer and mortgage loans. Finally, the public demand for the Caisses' deposits, is more a function of the borrowing privileges offered to the members than of the intrinsic competitive rate paid on them

La programmation déterministe du budget de capital : un modèle financier

The financial model presented in the article attempts to further integrate capital budgeting into the firm's overall financial planning policy. Although it is an extension and generalization of Bernhard and Weingartner's previous models, it differs from these works by some basic assumptions related to both the objective function and constraint set.

Buckling Cascade of Thin Plates: Forms, Constraints and Similarity

We experimentally study compression of thin plates in rectangular boxes with variable height. A cascade of buckling is generated. It gives rise to a self-similar evolution of elastic reaction of plates with box height which surprisingly exhibits repetitive vanishing and negative stiffness. These features are understood from properties of Euler's equation for elastica

Influence of shear stress applied during flow stoppage and rest period on the mechanical properties of thixotropic suspensions

We study the solid mechanical properties of several thixotropic suspensions as a function of the shear stress history applied during their flow stoppage and their aging in their solid state. We show that their elastic modulus and yield stress depend strongly on the shear stress applied during their solid-liquid transition (i.e., during flow stoppage) while applying the same stress only before or only after this transition may induce only second-order effects: there is negligible dependence of the mechanical properties on the preshear history and on the shear stress applied at rest. We also found that the suspensions age with a structuration rate that hardly depends on the stress history. We propose a physical sketch based on the freezing of a microstructure whose anisotropy depends on the stress applied during the liquid-solid transition to explain why the mechanical properties depend strongly on this stress. This sketch points out the role of the internal forces in the colloidal suspensions' behavior. We finally discuss briefly the macroscopic consequences of this phenomenon and show the importance of using a controlled-stress rheometer

Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids

We study both experimentally and theoretically the rheological behavior of isotropic bidisperse suspensions of noncolloidal particles in yield stress fluids. We focus on materials in which noncolloidal particles interact with the suspending fluid only through hydrodynamical interactions. We observe that both the elastic modulus and yield stress of bidisperse suspensions are lower than those of monodisperse suspensions of same solid volume fraction. Moreover, we show that the dimensionless yield stress of such suspensions is linked to their dimensionless elastic modulus and to their solid volume fraction through the simple equation of Chateau et al.[J. rheol. 52, 489-506 (2008)]. We also show that the effect of the particle size heterogeneity can be described by means of a packing model developed to estimate random loose packing of assemblies of dry particles. All these observations finally allow us to propose simple closed form estimates for both the elastic modulus and the yield stress of bidisperse suspensions: while the elastic modulus is a function of the reduced volume fraction $\phi/\phi_m$ only, where $\phi_m$ is the estimated random loose packing, the yield stress is a function of both the volume fraction $\phi$ and the reduced volume fraction