The multi-fractal structure of contrast changes in natural images: from sharp edges to textures

We present a formalism that leads very naturally to a hierarchical description of the different contrast structures in images, providing precise definitions of sharp edges and other texture components. Within this formalism, we achieve a decomposition of pixels of the image in sets, the fractal components of the image, such that each set only contains points characterized by a fixed stregth of the singularity of the contrast gradient in its neighborhood. A crucial role in this description of images is played by the behavior of contrast differences under changes in scale. Contrary to naive scaling ideas where the image is thought to have uniform transformation properties \cite{Fie87}, each of these fractal components has its own transformation law and scaling exponents. A conjecture on their biological relevance is also given.Comment: 41 pages, 8 figures, LaTe

Multifractal wavelet filter of natural images

Natural images are characterized by the multiscaling properties of their contrast gradient, in addition to their power spectrum. In this work we show that those properties uniquely define an {\em intrinsic wavelet} and present a suitable technique to obtain it from an ensemble of images. Once this wavelet is known, images can be represented as expansions in the associated wavelet basis. The resulting code has the remarkable properties that it separates independent features at different resolution level, reducing the redundancy, and remains essentially unchanged under changes in the power spectrum. The possible generalization of this representation to other systems is discussed.Comment: 4 pages, 4 figures, RevTe

DEMAND FOR CHILD CARE AND FEMALE EMPLOYMENT IN COLOMBIA

Due to the increase in labor force attachment of mothers of young children in the last decade, child care policies have a renewed importance. This paper uses Colombian data to perform a characterization of the child care market, generating stylized facts to inform the debate. The main trends are: highly informal market, high participation and employment rates of mothers of young children, relatively little unmet need" for child care services and the poor facing constraints to access the market for child care, both in quantity and price. This study analyzes how Colombian families make their child care decisions, simultaneously choosing whether the mother works, whether to pay for care and what mode to use. The estimations performed suggest that there is a strong positive effect of child care choice on the mother´s working decision, and that this effect is much higher for low-income families. As children grow the availability of formal care modes becomes determinant to enable the mother´s labor force attachment."Child care

A Proposal to Improve Our Understanding of Entrepreneurship Using the Panel Study of Income Dynamics

This paper aims to evidence how relatively marginal changes in the Panel Study of Income Dynamics survey, particularly on the measurement of returns to entrepreneurship - both financial and human capital - can yield sizeable benefits for research and policy on entrepreneurship. Accurate measurement of returns to all the resources invested in entrepreneurial endeavors is not only essential to understand the motivations and barriers to start a business, but can ultimately provide the basis to improve the effectiveness of programs and policies to foster entrepreneurial activity in the economy.In fact, recent studies question the importance of pecuniary benefits in the decision to become an entrepreneur. However, these are based on measures of total earnings and sample aggregate returns. Thus, adequate individual data on business income and its components has an enormous value for both research and policy design altogether.entrepreneurship, returns to entrepreneurship, survey, PSID

Business Ownership and Self-Employment in Developing Economies: The Colombian Case

We characterize entrepreneurship in developing economies through a case study for Colombia. We document self-employment and business ownership since the 1980s; while the relative size of these groups within the labor force is stable across time, they differ significantly in important observable dimensions such as education and business sector. We then study the motivations to become an entrepreneur. First, we analyze the transition into and out of potential forms of entrepreneurship by measuring the flows across occupations, and study the determinants of entry and exit into and out of self-employment and business ownership; there is surprisingly little transition between self-employment and business ownership. Second, we focus on the financial motivations by measuring the differences in earnings of self-employment and businessownership relative to salaried work, at the mean and along the distribution. There is a substantial earnings premium to become a business owner, but it is not financially attractive to become self-employed. The results of this paper suggest that while business ownership is what the literature associates with entrepreneurship, self-employment is basically a subsistence activity.Entrepreneurship, self-employment, business ownership, transition prob-ability, earnings premium

Midiendo la integralidad y equidad de género en la atención de usuarios/as de sustancias : un estudio de caso en la provincia de Buenos Aires

El presente trabajo se enmarca en la tesis de doctorado sobre la evaluación desde una perspectiva de género y de derechos de las políticas públicas en materia de drogas. En este caso centraré mi exposición en la propuesta de criterios necesarios para medir la integralidad y equidad de género en la atención de usuarios/as de sustancias en un Hospital Público especializado en el abordaje de los consumos problemáticos de sustancias, de la Provincia de Buenos Aires. Para este análisis se tienen en cuenta la presencia en las prácticas y representaciones de los/as profesionales de la salud de criterios de integralidad, promoción de ciudadanía, autonomía y equidad género en la atención. De acuerdo a la investigación se identificaron distintas barreras de accesibilidad y permanencia en los tratamientos que pueden ser clasificadas en tres grupos (Rossi et al., 2009; Parga, 2012): aquellas vinculadas a factores relativos a elementos organizacionales/institucionales; las asociadas con componentes existentes en la relación equipo de salud-paciente y aquellos relacionados con factores relativos a los/as mismos/as usuarios/as. Asimismo, pudimos observar que el hecho de que el servicio no tuviera una lectura del proceso de salud/enfermedad/atención con perspectiva de género, se tradujo en inequidades en salud.Fil: Parga, Jimena. Universidad Nacional de La Plat

The effect of hydrogen sulphide on ammonium bisulphite when used as an oxygen scavenger in aqueous solutions

Peer reviewedPostprin

La universidad no será una obra salesiana si la pedagogía salesiana no se transforma en docencia universitaria

Hace 19 años exactamente fui invitado por el P. Juan Bottasso a participar como observador en una reunión de las autoridades salesianas del Ecuador, que tenía lugar en San Patricio (Quito), y donde se discutía sobre la pertinencia o no de crear una universidad. Quienes estaban a favor, argumentaban en razón de: a) una demanda creciente de jóvenes de sectores medios y modestos por una educación superior, que les garantizara una profesionalización y formación académica; b) que la educación universitaria se había convertido en una necesidad cada vez más generalizada en todo el mundo, precisamente cuando ya la educa- ción media se encontraba relativamente satisfecha

¿QUÉ COOPERACIÓN INTERNACIONAL PARA QUÉ DESARROLLO? UN PARADIGMA NEOCOLONIAL

El nuevo orden económico global además de transformar las posibilidades de desarrollo en una cuestionable e incierta “lucha contra la pobreza” en los países subdesarrollados, se ha servido de la ayuda y cooperación internacional para estos países del Tercer Mundo, con la finalidad de consolidar el modelo de acumulación capitalista. Esto no sólo ha repercutido en la inutilidad, ineficacia y defectuosa implementación de muchos proyectos de desarrollo y de programas sociales, sino que también ha contribuido al crecimiento de las desigualdades en dichos países.The new global economic order, in addition to changing the possibilities of development in underdeveloped countries in their “fight against poverty” has used international aide and cooperation for these Third World countries to consolidate the model of capitalist accumulation. This has not only produced useless, inefficient and defective implementation of development projects and socials programs, but has also contributed to a progressive inequity in those countries