Recommender Systems by means of Information Retrieval

In this paper we present a method for reformulating the Recommender Systems problem in an Information Retrieval one. In our tests we have a dataset of users who give ratings for some movies; we hide some values from the dataset, and we try to predict them again using its remaining portion (the so-called "leave-n-out approach"). In order to use an Information Retrieval algorithm, we reformulate this Recommender Systems problem in this way: a user corresponds to a document, a movie corresponds to a term, the active user (whose rating we want to predict) plays the role of the query, and the ratings are used as weigths, in place of the weighting schema of the original IR algorithm. The output is the ranking list of the documents ("users") relevant for the query ("active user"). We use the ratings of these users, weighted according to the rank, to predict the rating of the active user. We carry out the comparison by means of a typical metric, namely the accuracy of the predictions returned by the algorithm, and we compare this to the real ratings from users. In our first tests, we use two different Information Retrieval algorithms: LSPR, a recently proposed model based on Discrete Fourier Transform, and a simple vector space model

EL ROL DE LA REGULACIÓN TRANSCRIPCIONAL EN LA EFICIENCIA DE LA SIMBIOSIS FIJADORA DE NITRÓGENO

El nitrógeno es un macronutriente esencial para todos los seres vivos. A pesar de su abundancia en la atmósfera, sólo un limitado número de microorganismos es capaz de asimilarlo el nitrógeno de manera directa. En los sistemas agrícolas, el nitrógeno es provisto en la forma de fertilizantes químicos. Sin embargo, la utilización indiscriminada de fertilizantes trae aparejado graves problemas ambientales y socio- económicos. La fijación biológica de nitrógeno (FBN) constituye una alternativa promisoria, debido a su bajo costo de implementación y la sustentabilidad del proceso. Las leguminosas de grano, utilizadas para el consumo humano y de ganado, incluyen las especies de mayor interés comercial, tanto a nivel global como local. El poroto es la leguminosa de grano más importante para el consumo humano. En los últimos años en nuestro grupo de investigación hemos avanzado en el estudio de los genes de poroto (Phaseolus vulgaris) vinculados a la nodulación. Estos estudios han permitido identificar nuevos genes vinculados a la simbiosis. En particular, nos hemos enfocado en la caracterización de los mecanismos moleculares de la planta que le permiten discriminar y seleccionar aquellas cepas de Rhizobium etli más eficientes en la nodulación, y consecuentemente en la producción de formas de nitrógeno asimilables para la planta. Estudios transcriptómicos nos han permitido identificar transcriptos que se acumulan diferencialmente en respuesta a cepas de rizobio que son seleccionados por la planta y que presentan una mayor eficiencia simbiótica (Dalla Via et al., 2015). A partir de esta información se identificaron RNAs no codificantes pequeños (miRNAs y siRNAs), RNAs no codificantes largos (lncRNAs) y mRNAs que codifican proteínas que participan del silenciamiento transcripcional. Teniendo en cuenta que estudios previos en nuestro laboratorio llevaron a la identificación y caracterización de factores de transcripción y de RNAs no codificantes (ncRNAs) asociados a la nodulación eficiente en poroto, el objetivo general de este trabajo es profundizar la caracterización de la regulación y función de los genes NF-Y y SIN1 y explorar la red transcripcional controlada por los productos de dichos genes. Por otro lado, se pretende además explorar la función de un grupo de proteínas involucradas en los mecanismos de acción de ncRNAs, en el proceso de selección de los partners simbióticos, infección bacteriana y organogénesis de nódulos fijadores de nitrógeno en P. vulgaris. Los objetivos particulares son: 1-Estudiar de la función de los genes Phvul.003G281400 y Phvul.004G006200 en el contexto de la nodulación eficiente. 2-Caracterizar la función del gen PvCYCP que codifica la ciclina de tipo P. 3-Identificar los genes controlados, directa o indirectamente, por los factores de transcripción NF-Y y SIN1 en respuesta a la simbiosis.   &nbsp

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The high-frequency upgrade of the Sardinia Radio Telescope

We present the status of the Sardinia Radio Telescope (SRT) and its forthcoming update planned in the next few years. The post-process scenario of the upgraded infrastructure will allow the national and international scientific community to use the SRT for the study of the Universe at high radio frequencies (up to 116 GHz), both in single dish and in interferometric mode. A telescope like SRT, operating at high frequencies, represents a unique resource for the scientific community. The telescope will be ideal for mapping quickly and with relatively high angular resolution extended radio emissions characterized by low surface brightness. It will also be essential for spectroscopic and polarimetric studies of both Galactic and extragalactic radio sources. With the use of the interferometric technique, SRT and the other Italian antennas (Medicina and Noto) will operate within the national and international radiotelescope network, allowing astronomers to obtain images of radio sources at very high angular resolution

Status of the High-Frequency Upgrade of the Sardinia Radio Telescope

The Sardinia Radio Telescope is going through a major upgrade aimed at observing the universe at up to 116 GHz. A budget of 18.700.000 E has been awarded to the Italian National Institute of Astrophysics to acquire new state-of-the-art receivers, back-end, and high-performance computing, to develop a sophisticated metrology system and to upgrade the infrastructure and laboratories. This contribution draws the status of the whole project at eight months from the end of the funding scheme planned for August 2022