An analysis of word embedding spaces and regularities

Word embeddings are widely use in several applications due to their ability to capture semantic relationships between words as relations between vectors in high dimensional spaces. One of the main problems to obtain the information is to deal with the phenomena known as the Curse of Dimensionality, the fact that some intuitive results for well known distances are not valid in high dimensional contexts. In this thesis we explore the problem to distinguish between synonyms or antonyms pairs of words and non-related pairs of words attending just to the distance between the words of the pair. We considerer several norms and explore the problem in the two principal kinds of embeddings, GloVe and Word2Vec

Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behavior rules out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow; perhaps related to turbulence in the accretion disk; coupled with hydrodynamic instabilities, leads to the non-ballistic dynamics that cause the observed non-periodic changes in the direction of the inner jet.Comment: Accepted for Publication in The Astrophysical Journal. 11 pages, 6 figures, 4 tables. High resolution images on figure 1 and complete tables 1 and 2 may be provided on reques

3C 286: a bright, compact, stable, and highly polarized calibrator for millimeter-wavelength observations

(Context.) A number of millimeter and submillimeter facilities with linear polarization observing capabilities have started operating during last years. These facilities, as well as other previous millimeter telescopes and interferometers, require bright and stable linear polarization calibrators to calibrate new instruments and to monitor their instrumental polarization. The current limited number of adequate calibrators implies difficulties in the acquisition of these calibration observations. (Aims.) Looking for additional linear polarization calibrators in the millimeter spectral range, in mid-2006 we started monitoring 3C 286, a standard and highly stable polarization calibrator for radio observations. (Methods.) Here we present the 3 and 1 mm monitoring observations obtained between September 2006 and January 2012 with the XPOL polarimeter on the IRAM 30 m Millimeter Telescope. (Results.) Our observations show that 3C 286 is a bright source of constant total flux with 3 mm flux density S_3mm = (0.91 \pm 0.02) Jy. The 3mm linear polarization degree (p_3mm =[13.5\pm0.3]%) and polarization angle (chi_3mm =[37.3\pm0.8]deg.,expressed in the equatorial coordinate system) are also constant during the time span of our observations. Although with poorer time sampling and signal-to-noise ratio, our 1 mm observations of 3C 286 are also reproduced by a constant source of 1 mm flux density (S_1mm = [0.30 \pm 0.03] Jy), polarization fraction (p_1mm = [14.4 \pm 1.8] %), and polarization angle (chi_1mm = [33.1 \pm 5.7]deg.). (Conclusions.) This, together with the previously known compact structure of 3C 286 -extended by ~3.5" in the sky- allow us to propose 3C 286 as a new calibrator for both single dish and interferometric polarization observations at 3 mm, and possibly at shorter wavelengths.Comment: Accepted for publication in A&A. 7 pages, 4 figures, 8 tables. Updated data sets with regard to previous version. New discussion about multi frequency properties of the source. Section 3.3, Figures 3 and 4, and Tables 7 and 8 are ne

Shape basis interpretation for monocular deformable 3D reconstruction

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, we propose a novel interpretable shape model to encode object non-rigidity. We first use the initial frames of a monocular video to recover a rest shape, used later to compute a dissimilarity measure based on a distance matrix measurement. Spectral analysis is then applied to this matrix to obtain a reduced shape basis, that in contrast to existing approaches, can be physically interpreted. In turn, these pre-computed shape bases are used to linearly span the deformation of a wide variety of objects. We introduce the low-rank basis into a sequential approach to recover both camera motion and non-rigid shape from the monocular video, by simply optimizing the weights of the linear combination using bundle adjustment. Since the number of parameters to optimize per frame is relatively small, specially when physical priors are considered, our approach is fast and can potentially run in real time. Validation is done in a wide variety of real-world objects, undergoing both inextensible and extensible deformations. Our approach achieves remarkable robustness to artifacts such as noisy and missing measurements and shows an improved performance to competing methods.Peer ReviewedPostprint (author's final draft

Status and management of the sea cucumber fishery of La Grande Terre, New Caledonia

From October 2006 to May 2008, The WorldFish Center coordinated a ZoNéCo project to provide support to the Southern and Northern Provinces for decisions about how best to manage the sea cucumber fishery around La Grande Terre. We collected data during underwater population surveys, questionnaire-based interviews with fishers and processors, and landing catch surveys. A core aim was to furnish the Provinces with ‘ballpark’ estimates of the abundance and density of commercially important sea cucumbers on 50 lagoon and barrier reefs. Analysis and synthesis of the ecological and sociological data provide the basis for informed recommendations for fisheries management. Counts of trochus and giant clams on the reefs allow us to also describe the general status of those resources. We propose 13 recommendations for management actions and fishery regulations and advocate an adaptive management approach. This multidisciplinary study should serve as a useful template for assessing other fisheries, and we provide a series of generic ‘lessons learnt’ to aid future programmes. (PDF has 140 pages.

Chemical and hydrodynamic alignment of an enzyme

Motivated by the implications of the complex and dynamic modular geometry of an enzyme on its motion, we investigate the effect of combining long-range internal and external hydrodynamic interactions due to thermal fluctuations with short-range surface interactions. An asymmetric dumbbell consisting of two unequal subunits, in a nonuniform suspension of a solute with which it interacts via hydrodynamic interactions as well as non-contact surface interactions, is shown to have two alignment mechanisms due to the two types of interactions. In addition to alignment, the chemical gradient results in a drift velocity that is modified by hydrodynamic interactions between the constituents of the enzyme.Comment: 7+4 pages, 3 figure

Students’ birth date and academic progression

Education laws which impose starting cut-off dates for students to begin compulsory education may be negative for those students who are born just before these cut-offs; this is because these students will be among the youngest in their classroom, while those born just after (the oldest students) will see their academic achievement increased. The current research works on this subject employing census and longitudinal data for the most populated region of Spain (Andalusia), making use of a regression discontinuity methodology. We find that the youngest students in the classroom (due to this school entry cut-off) present lower academic achievement compared to the oldest students, being this effect reduced while students progress in their education. This motivates policy interventions aimed at giving the option to parents to choose whether or not to delay their children’s access to school when the latter are too young.Campus de Excelencia Internacional Andalucía Tech. The data used in this research has been provided by Agencia Andaluza de Evaluación Educativa, Consejería de Educación, Junta de Andalucía. This work has been partly supported by the Ministerio de Economía, Industria y Competitividad under Research Project ECO2017-88883-R; by the Andalusian Regional Ministry of Innovation, Science and Enterprises (PAI group SEJ-532) and the postdoctoral contract from the Plan Propio signed by the Universidad de Málaga

The teaching crisis in less developed countries

There is a huge concern on the influence of teachers on students’ cognitive learning. However, little is known about the causal impact of teachers’ knowledge on students’ performance. In addition, this effect is likely to change depending on the group of countries and regions under analysis. In the current research, we propose to study this subject for sixth grade teachers and, concretely, for less developed regions. To achieve this aim, we have employed the heterogeneity within-student between-subjects of teachers’ subject knowledge on students’ academic achievement. We have found that, for the countries under analysis, teachers’ subject knowledge does not have a significant influence on students’ academic achievement; many robustness checks have supported this result. This could be indicating that, in these countries, teachers do not have enough knowledge to teach students, what brings some policy implications.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Are early writers and readers more successful than their counterparts?

There exists an increasing number of scientific contributions focused on the influence of the attendance to early childhood and/or preprimary education on the future academic track of the students, which employ the quarter of birth of the student as a proxy for infants’ maturity. The present work goes a step further by employing information on the precise time when children begin to exhibit the basic competences (reading and writing), controlling by the effect of the quarter of birth, for andalusian students aged 10-11 and 14-15. This study uses descriptive analysis as starting point to specify multivariate estimates for the age at which the student began to read and write, together with students’ quarter of birth. Moreover, the effect of these variables on the likelihood of repeating a course has also been analyzed. Results show that the quarter of birth and the age when the student began to read and write affect students’ early academic achievement –primary education– and the likelihood of repeating, but this effect is weakened once non-repeaters reach age 14-15. In addition, students from households where parents have a low level of education present a late start in beginning to read and write and, thus, lower achievement than their older counterparts. This highlights the need to increase the investments in public early education for students living in this kind of families –by increasing the supply of public early education places and scholarships–, so they can develop these competences as soon as possible. This kind of interventions could have a relevant role in fostering higher social mobility.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech; Andalusian Regional Ministry of Innovation, Science and Employment [PAI group SEJ-532 and Excellence Project SEJ-2727]; the Research Plan of the University of Malaga (Capacity Building Programme I+D+i of Universities 2014-2015) and by the Ministry of Economy and Competitiveness of Spain [Research Project ECO2014-56397-P]