Magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine molecules (M ≡\equiv Fe, Co)

We report on a theoretical study of magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine (M-Pc) molecules where M is a metal atom: Fe-Pc on a Cu(110)(2$\times$1)-O surface and Co-Pc layers on Pb(111) islands. The magnetic transitions correspond to the change of orientation of the spin angular momentum of the metal ion with respect to the surroundings and possibly an applied magnetic field. The adsorbed Fe-Pc system is studied with a Density Functional Theory (DFT) transport approach showing that i) the magnetic structure of the Fe atom in the adsorbed Fe-Pc is quite different from that of the free Fe atom or of other adsorbed Fe systems and ii) that injection of electrons (holes) into the Fe atom in the adsorbed Fe-Pc molecule dominantly involves the Fe $3d_{z^2}$ orbital. These results fully specify the magnetic structure of the system and the process responsible for magnetic transitions. The dynamics of the magnetic transitions induced by tunnelling electrons is treated in a strong-coupling approach. The Fe-Pc treatment is extended to the Co-Pc case. The present calculations accurately reproduce the strength of the magnetic transitions as observed by magnetic IETS (Inelastic Electron Tunnelling Spectroscopy) experiments; in particular, the dominance of the inelastic current in the conduction of the adsorbed M-Pc molecule is accounted for

A microscopic approach to nonlinear Reaction-Diffusion: the case of morphogen gradient formation

We develop a microscopic theory for reaction-difusion (R-D) processes based on a generalization of Einstein's master equation with a reactive term and we show how the mean field formulation leads to a generalized R-D equation with non-classical solutions. For the $n$-th order annihilation reaction $A+A+A+...+A\rightarrow 0$, we obtain a nonlinear reaction-diffusion equation for which we discuss scaling and non-scaling formulations. We find steady states with either solutions exhibiting long range power law behavior (for $n>\alpha$) showing the relative dominance of sub-diffusion over reaction effects in constrained systems, or conversely solutions (for $n<\alpha<n+1$) with finite support of the concentration distribution describing situations where diffusion is slow and extinction is fast. Theoretical results are compared with experimental data for morphogen gradient formation.Comment: Article, 10 pages, 5 figure

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

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 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

Appropriate Design of Parallel Manipulators

International audienceAlthough parallel structures have found a niche market in many applications such as machine tools, telescope positioning or food packaging, they are not as successful as expected. The main reason of this relative lack of success is that the study and hardware of parallel structures have clearly not reached the same level of completeness than the one of serial structures. Among the main issues that have to be addressed, the design problem is crucial. Indeed, the performances that can be expected from a parallel robot are heavily dependent upon the choice of the mechanical structure and even more from its dimensioning. In this chapter, we show that classical design methodologies are not appropriate for such closed-loop mechanism and examine what alternatives are possible

Propagation and organization in lattice random media

We show that a signal can propagate in a particular direction through a model random medium regardless of the precise state of the medium. As a prototype, we consider a point particle moving on a one-dimensional lattice whose sites are occupied by scatterers with the following properties: (i) the state of each site is defined by its spin (up or down); (ii) the particle arriving at a site is scattered forward (backward) if the spin is up (down); (iii) the state of the site is modified by the passage of the particle, i.e. the spin of the site where a scattering has taken place, flips ($\uparrow \Leftrightarrow \downarrow$). We consider one dimensional and triangular lattices, for which we give a microscopic description of the dynamics, prove the propagation of a particle through the scatterers, and compute analytically its statistical properties. In particular we prove that, in one dimension, the average propagation velocity is $= 1/(3-2q)$, with $q$ the probability that a site has a spin $\uparrow$, and, in the triangular lattice, the average propagation velocity is independent of the scatterers distribution: $= 1/8$. In both cases, the origin of the propagation is a blocking mechanism, restricting the motion of the particle in the direction opposite to the ultimate propagation direction, and there is a specific re-organization of the spins after the passage of the particle. A detailed mathematical analysis of this phenomenon is, to the best of our knowledge, presented here for the first time.Comment: 30 pages, 15 separate figures (in PostScript); submitted to J. Stat. Phy

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.