Online Active Linear Regression via Thresholding

We consider the problem of online active learning to collect data for regression modeling. Specifically, we consider a decision maker with a limited experimentation budget who must efficiently learn an underlying linear population model. Our main contribution is a novel threshold-based algorithm for selection of most informative observations; we characterize its performance and fundamental lower bounds. We extend the algorithm and its guarantees to sparse linear regression in high-dimensional settings. Simulations suggest the algorithm is remarkably robust: it provides significant benefits over passive random sampling in real-world datasets that exhibit high nonlinearity and high dimensionality --- significantly reducing both the mean and variance of the squared error.Comment: Published in AAAI 201

Active Learning for Accurate Estimation of Linear Models

We explore the sequential decision making problem where the goal is to estimate uniformly well a number of linear models, given a shared budget of random contexts independently sampled from a known distribution. The decision maker must query one of the linear models for each incoming context, and receives an observation corrupted by noise levels that are unknown, and depend on the model instance. We present Trace-UCB, an adaptive allocation algorithm that learns the noise levels while balancing contexts accordingly across the different linear functions, and derive guarantees for simple regret in both expectation and high-probability. Finally, we extend the algorithm and its guarantees to high dimensional settings, where the number of linear models times the dimension of the contextual space is higher than the total budget of samples. Simulations with real data suggest that Trace-UCB is remarkably robust, outperforming a number of baselines even when its assumptions are violated.Comment: 37 pages, 8 figures, International Conference on Machine Learning, ICML 201

Learning multifractal structure in large networks

Generating random graphs to model networks has a rich history. In this paper, we analyze and improve upon the multifractal network generator (MFNG) introduced by Palla et al. We provide a new result on the probability of subgraphs existing in graphs generated with MFNG. From this result it follows that we can quickly compute moments of an important set of graph properties, such as the expected number of edges, stars, and cliques. Specifically, we show how to compute these moments in time complexity independent of the size of the graph and the number of recursive levels in the generative model. We leverage this theory to a new method of moments algorithm for fitting large networks to MFNG. Empirically, this new approach effectively simulates properties of several social and information networks. In terms of matching subgraph counts, our method outperforms similar algorithms used with the Stochastic Kronecker Graph model. Furthermore, we present a fast approximation algorithm to generate graph instances following the multi- fractal structure. The approximation scheme is an improvement over previous methods, which ran in time complexity quadratic in the number of vertices. Combined, our method of moments and fast sampling scheme provide the first scalable framework for effectively modeling large networks with MFNG

Calidad en la Formación Inicial Docente: los déficits de las competencias pedagógicas y disciplinares en Chile

Los procesos de Formación Docente tienen un rol clave en el mejoramiento de los sistemas educativos. Medir la calidad de la formación recibida por los nuevos profesores adquiere gran relevancia. Este artículo busca analizar estadísticamente los niveles de logro alcanzados por 3.219 profesores noveles en la Prueba Inicia 2011. Por medio de una batería de ítems esta prueba evalúa conocimientos disciplinares y pedagógicos de los profesores recién egresados del Sistema de Educación Superior chileno. Los resultados señalan que el 60% carecería de las competencias básicas para ejercer, registrando escaso dominio disciplinar, manejo pedagógico, en especial en Ciencias y Matemática. Los egresados de Institutos Profesionales obtienen los peores resultados, así como las instituciones no selectivas. Presentan una mayor calidad en la formación de los profesores cuando las instituciones implementan sistemas de selección o reclutamiento más estricto, así como las que tienen mejores índices en los sistemas de acreditación. Teacher Education processes have a key role in improving education systems, that is why measuring the quality of the training received by new teachers is more relevant. This article a study which analyzes descriptive and inferential levels achieved for the Test Inicia 2011. Through a battery of items this test assesses disciplinary and pedagogical knowledge of teachers recently graduated from the Chilean higher education system. The results indicate that 60% lack of basic skills for teaching practice, showing little knowledge of the discipline and educational management, especially in science and math. Graduates of Professional Institutes and nonselective institutions obtained the worst results. The institutions that implement stricter selection systems and they have better levels of accreditation, have a higher quality of initial teacher training

Probiotic Bacteria as an Healthy Alternative for Fish Aquaculture

One of the problems of the aquaculture industry is the presence of pathogenic microorganisms whose proliferation is enhanced when the healthy quality of the culture systems do not meet comply with physical-chemical-biological parameters. In order to improve these problems, less aggressive alternatives to the environment have been sought. This is why probiotic bacteria are proposed as an alternative to the same systems where they will be applied, since they generate greater interest in not presenting a threat to the ecosystem, favor survival, improve the immune system of organisms and have antibacterial properties against pathogenic bacteria. This chapter reviews current research related to the search for marine probiotics for application in the aquaculture industry. Additionally, we deliver results from our work related to the research and application of probiotics. The reported studies demonstrate the positive effects of marine bacteria for their aquaculture application. The evidences found in our work allow us to conclude that larval survival is favored by the application of probiotics in the use of vectors such as rotifers, artemia and biofilms. However, depending on the species of interest, it is necessary to study the market for the biotechnological application of probiotics, to evaluate the feasibility of its production on a larger scale and its commercial feasibility

Consolidando la Política de Inversiones Por Medio De La Cláusula de Nación más Favorecida en los Tratados Internacionales de Inversión

Resumen La cláusula de nación más favorecida ha recibido mucha atención en el régimen internacional de inversiones en los últimos años. Las discusiones han girado respecto a si dicha disposición permite atraer condiciones más favorables relativas a la solución de controversias. Este trabajo se aleja de dicha discusión y analiza otro problema que ha contado con menos atención. Se refiere, particularmente, a la posibilidad de que por medio de dicha cláusula se atraigan condiciones sustantivas más favorables contenidas en tratados celebrados previamente. Esa posibilidad es de interés, pues la misma podría hacer difícil la modificación de la política de atracción de inversiones de los Estados que ha sido plasmada en sus tratados de inversión. Si se considera que eventuales giros en la estrategia de desarrollo son deseables, la cláusula constituye un obstáculo que debería ser analizado con detención. Palabras Clave: Cláusula de nación más favorecida, inversión extranjera, política de desarrollo, tratados bilaterales de inversión, multilateralismo. Abstract Consolidating the Investment Policy through the most favored Nation Clause in International Investment Agreements The most favored nation clause has attracted much attention in the international investment regime in the past years. The debate has been centered on whether such regulation allows the attraction of more favorable conditions regarding the resolution of controversies. This paper moves away from this debate to analyze another problem that has gained much less attention: the possibility that, through the mentioned clause, more favorable conditions are attracted and included in previously signed treaties. This possibility is of great interest since it could hinder the modification of the investment attraction policies of the States as expressed in their investment treaties. If eventual shifts in the development strategy are desirable, the clause constitutes an obstacle that should be thoroughly examined. Keywords: Most favored nation treatment, foreign investment, development policy, bilateral investment treaties, multilateralism