2,660 research outputs found
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
Tackling the development of hormone therapy resistance in breast cancer through mathematical modelling
Patients suffering from estrogen-driven breast cancer frequently develop hardly predictable resistance to hormone therapy, which significantly complicates treatment. Current approaches for tackling this problem include cell models and clinical studies, both supported by sequencing technologies like RNA-seq, and offering different strengths and limitations. This dissertation addresses the challenge of predicting resistance to hormone therapy in breast cancer by merging advances in bioinformatics and Bayesian statistics, and applying them to two types of data – RNA-seq data and clinical data. First, we explore the statistical analysis of clinical data through Bayesian inference combined with enhanced Markov Chain Monte Carlo techniques, and introduce a novel algorithm for adaptive integration in prospective Modified Hamiltonian Monte Carlo (MHMC) methods. We demonstrate its positive effect on performance of MHMC in biomedical applications using clinical data of breast cancer patients. Next, we propose and implement an RNA-seq pipeline within our interactive web-app for the analysis of resistant breast cancer cell lines sequenced at CIC bioGUNE. Finally, we propose an original approach based on a Bayesian logistics regression model coupled with a simulated annealing-like algorithm for a combined analysis of RNA-seq and clinical data, and apply it to ad hoc data to obtain and validate in-silico and in-vitro a novel 6-gene signature for stratifying patient response to hormone therapy
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
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