Vortices in superconductors with a columnar defect: finite size effects

In the present work we investigate the behavior of a vortex in a long superconducting cylinder near to a columnar defect at the center. The derivations of the local magnetic field distribution and the Gibbs free energy will be carried out for a cylinder and a cavity of arbitrary sizes. From the general expressions, it considered two particular limits: one in which the radius of the cavity is very small but the radius of the superconducting cylinder is kept finite; and one in which the radius of the superconducting cylinder is taken very large (infinite) but the radius of the cavity is kept finite. In both cases the maximum number of vortices which are allowed in the cavity is determined. In addition, the surface barrier field for flux entrance into the cavity is calculated.Comment: 13 pages, 1 figur

A Simple Inner-Stopper Guarded Trephine for Creation of Uniform Keratectomy Wounds in Rodents

Purpose: Creating controllable, reproducible keratectomy wounds in rodent corneas can be a challenge due to their small size, thickness, and the lack of usual tools available for human eyes such as a vacuum trephine. The purpose of this work is to provide a consistent, reproducible corneal stromal defect in rats using a simple, economical, and customized inner-stopper guarded trephine. Methods: The inner-stopper guarded trephine is used to induce a circular wound in rat corneas. After trephination, the corneal flap can be removed by manual dissection using a blunt spatula. We used optical coherence topography (OCT) to measure the defect wound depth induced in ex vivo rat eyes. Results: Despite a minor learning curve, this simple device enables depth control, reduces variability of manual keratectomy wound depth in rats, and decreases the risk for corneal perforation during keratectomy. Corneal defect creation was highly reproducible across different researchers and was independent of their surgical training. Conclusion: This inner-stopper guarded trephine can be utilized and applied to preclinical testing of a wide range of corneal wound healing therapies, including but not limited to biotherapeutics, corneal prosthetics, and regenerative technologies

Quelle stratégie appliquée pour corriger le déficit budgétaire en Tunisie ? Le modèle à effet seuil

Macroeconomic policies in Tunisia are characterized by a set of deficiencies. They illustrate their weakness in achieving an economic balance following the 2011 revolution and the covid-19 health problem. Indeed, the economy announces financial insufficiencies compared to several countries, such as Morocco. Fiscal policy is being called into question to create the conditions for stable and efficient economic growth. Indeed, fiscal and monetary policy constantly monitors aggregate demand. The latter makes it possible to increase the general level of prices and also a weak aggregate demand makes it possible to reflect an economic recession. We must act on aggregate demand in order to achieve stable economic growth. Fiscal policy acts between government spending and resources. And, monetary policy controls the supply of money by choosing a suitable interest rate that it encourages investors to invest within the country. The objective of this work is to present the conditions for a remarkable increase in public spending in Tunisia. The objectives of fiscal policy are to identify the causes in order to achieve a good balance and to draw inspiration from theoretical and empirical work for a change of state and to have economic mutations. Indeed, recent econometric methods in non-linear time series can be implemented to explain this economic phenomenon: the threshold effect model. The latter is represented by different linear dynamics depending about the country.     JEL Classification: H62, C51. Article type: Empirical research.Les politiques macroéconomiques en Tunisie se caractérisent par un ensemble de déficiences. Elles illustrent leur faiblesse à réaliser un équilibre économique à la suite de la révolution 2011 et le problème sanitaire covid-19. En effet, l’économie annonce des insuffisantes financières comparativement à plusieurs pays, comme le Maroc. La politique budgétaire est remise en question pour créer les conditions d’une croissance économique stable et performante. En effet, la politique budgétaire et monétaire fait surveiller en permanence la demande globale. Cette dernière permet d’augmenter le niveau général des prix et aussi une demande globale faible permet de traduire une récession économique. Il faut bien agir sur la demande globale pour bien atteindre une croissance économique stable. La politique budgétaire agit entre les dépenses et les ressources de l’État. Et, la politique monétaire contrôle l’offre de monnaie par le choix d’un taux d’intérêt convenable qu’il permet d’encourager les investisseurs d’investir à l’intérieur du pays. L’objectif de ce travail est de présenter les conditions d’une augmentation remarquable des dépenses publiques en Tunisie. Les objectifs de la politique budgétaire est d’identifier les causes pour bien atteindre l’équilibre et de s’inspirer des travaux théoriques et empiriques pour un changement de l’Etat et avoir les mutations économiques. En effet, des méthodes économétriques récentes en séries temporelles non-linéaires peuvent être mises en œuvre pour expliquer ce phénomène économique : le modèle à effet seuil. Ce dernier est représenté par des dynamiques linéaires différentes selon la situation du pays.     Classification JEL : H62, C51. Type de l’article : Recherche appliquée

Financial stability and economic performance in Europe

This paper aims at establishing the link between economic performance and financial stability in the European Union. We use the seminal framework of Beck and Levine (2004) – both in terms of variables and econometric method – to estimate this causal relationship, independently from but controlling for the level of financial depth. Using a panel GMM with instrumental variables, our contribution involves testing how different measures of financial instability (an institutional index, microeconomic indicators, and our own statistical index derived from a principal component analysis) affect economic performance (or components of aggregate dynamics like consumption, investment and disposable income). We find that financial instability has a negative effect on economic growth

Una tipologia poètica de Carles Riba als Escolis

Segons M. H. Abrams, qualsevol teoria de l'art o de la literatura ha de ser construïda a partir de quatre elements bàsics: l'autor, l'obra, el públic i l'univers. Les nocions dels tres primers elements són prou clares; però, què cal entendre per «univers»? Per a Abrams, l'univers constituiria el tema de l'obra, allò de què tracta

Comparación de estimaciones lineales en modelos de equilibrio dinámico estocástico con sector bancario

Los modelos DSGE con estructuras amplias y complejas son de popular uso en la actualidad para estudiar los efectos que diferentes agentes y variables tienen sobre la economía real. Así pues, en el presente artículo, no sólo se hace una revisión de la literatura relacionada, sino que se plantea un modelo de esta naturaleza con tres sectores hogares, firmas e industria bancaria el cual es usado, fundamentalmente, para comparar dos métodos lineales de estimación. El ejercicio no sólo deja un modelo útil para el análisis sino que evidencia el ajuste y versatilidad que tienen los métodos lineales de estimación para modelos DSGE en los cuales se incluyan más agentes o estructuras

Perspectives économiques 2016-2018

Ce numéro de la Revue de l'OFCE consacré aux prévisions économiques pour les années 2016-2018 est composé de plusieurs articles qui peuvent être lus indépendamment