On permanent and breaking waves in hyperelastic rods and rings

We prove that the only global strong solution of the periodic rod equation vanishing in at least one point $(t_0,x_0)$ is the identically zero solution. Such conclusion holds provided the physical parameter $\gamma$ of the model (related to the finger deformation tensor) is outside some neighborhood of the origin and applies in particular for the Camassa--Holm equation, corresponding to $\gamma=1$. We also establish the analogue of this unique continuation result in the case of non-periodic solutions defined on the whole real line with vanishing boundary conditions at infinity. Our analysis relies on the application of new local-in-space blowup criteria and involves the computation of several best constants in convolution estimates and weighted Poincar\'e inequalities.Comment: Corrected proofs. To appear on J. Funct. Ana

Blowup issues for a class of nonlinear dispersive wave equations

In this paper we consider the nonlinear dispersive wave equation on the real line, $u_t-u_{txx}+[f(u)]_x-[f(u)]_{xxx}+\bigl[g(u)+\frac{f''(u)}{2}u_x^2\bigr]_x=0$, that for appropriate choices of the functions $f$ and $g$ includes well known models, such as Dai's equation for the study of vibrations inside elastic rods or the Camassa--Holm equation modelling water wave propagation in shallow water. We establish a local-in-space blowup criterion (i.e., a criterion involving only the properties of the data $u_0$ in a neighbourhood of a single point) simplifying and extending earlier blowup criteria for this equation. Our arguments apply both to the finite and infinite energy case, yielding the finite time blowup of strong solutions with possibly different behavior as $x\to+\infty$ and $x\to-\infty$

Sigma Model Corrections to the Confining Background

Sigma model ($\alpha^{\prime}$) corrections to the confining string background are obtained. The main result is that the Poincar\'e invariant ansatz is maintained. Physical conditions for the dissapearance of the naked singularity are discussed.Comment: LaTeX,12 page

Indigenous female entrepeneurship: a qualitative studies in the context of Bolivia

Indigenous entrepreneurship and the gender approach to entrepreneurship are areas that have grown in interest in the entrepreneurship literature in recent years. This paper combines both research streams with the aim of analysing the social and individual factors affecting indigenous quechua female entrepreneurs of Bolivia. Based on the analysis of qualitative data from forty-two face-to-face interviews to indigenous entreprenerurs (female and male), the specific characteristics of these entrepreneurs, the barriers and the facilitators of entrepreneurial activities by women, as well as the role of social capital were extracted. The existence of a sexist and patriarchal culture has been found. However, regarding production, family becomes the production unit; the woman and the man have specific and complementary roles. In addition, there is growing individualism that results in a loss of indigenous values

Automatic code generation for ATLAS communications drivers

ATLAS is a software development platform created in our Department. Among other benefits, it provides support to easily distribute applications over a network. In these applications, communications issues among the different processes should be faced. Pursuing to isolate application developers from the intricacies of these issues, communication drivers are automatically generated from an interface declaration of each process. This automatic code generation --not unlike the generation of stubs in CORBA from the IDL specification-- is the main topic of this report.Postprint (published version

Las comunidades de liderazgo de centros educativos

El artículo presenta los derroteros más novedosos y actuales desde los que se está abordando el tema del liderazgo institucional en estos momentos. La propuesta de la construcción de comunidades de líderes debe integrarse en el vasto panorama del trabajo colaborativo que se expande y distribuye a todos los niveles con auténtica virulencia. La idea central de la comunidad de liderazgo es el encuentro de un conjunto de líderes -normalmente directivos- de varios centros de formación que trabajan en colaboración para mejorar la calidad, expresada sobre todo en los resultados de aprendizaje de los alum­nos, de todos los colegios de una zona y con la mirada puesta en el horizonte, como fondo, de una auténtica reforma educativa a nivel de todo el sistema escolar.Aquest article presenta els camins més nous i actuals des dels quals s'està tractant el tema del lideratge institucional en aquests moments. La proposta de la construcció de comuni­tats de líders s'ha d'integrar en el vast panorama del treball col·laboratiu que s'expandeix i es distribueix a tots els nivells amb autèntica virulència. La idea central de la comunitat de lideratge és la trobada d'un conjunt de líders -normalment directius- de diversos centres de formació que treballen en col·laboració per millorar la qualitat, expressada sobretot en els resultats d'aprenentatge dels alumnes, de tots els col·legis d'una zona i amb la mirada posada en l'horitzó, com a fons, d'una autèntica reforma educativa de tot el sistema escolar.This paper shows the most innovative and current courses from where at present the topic of institutional leadership is being tackled. The suggestion for cultivating communities of leaders should be included in the vast collaborative working scene that is expanded and divided into all levels with real virulence. The main idea of the Community Leadership is about leaders - usually managers - from different training centers enabling them to improve quality, but above all this quality should be reflected in the student learning outcomes, from each and every one of schools from a region, and setting our sights on the future, an educational reform which involves all level of the education system

Measuring the importance of oil-related revenues in total fiscal income for Mexico

Revenues from oil exports are an important part of government budgets in Mexico. A time-series analysis is conducted using monthly data from 1990 to 2005 examining three different specifications to determine how international oil price fluctuations and government income generated from oil exports influence fiscal policy in Mexico. The behavior of government spending and taxation is consistent with the spend-tax hypothesis. The results show that there is an inverse relationship between oil-related revenues and tax revenue from non-oil sources. Fiscal policy reform is urgently needed in order to improve tax collection as oil reserves in Mexico become more and more deplete