Marginal AMP Chain Graphs

We present a new family of models that is based on graphs that may have undirected, directed and bidirected edges. We name these new models marginal AMP (MAMP) chain graphs because each of them is Markov equivalent to some AMP chain graph under marginalization of some of its nodes. However, MAMP chain graphs do not only subsume AMP chain graphs but also multivariate regression chain graphs. We describe global and pairwise Markov properties for MAMP chain graphs and prove their equivalence for compositional graphoids. We also characterize when two MAMP chain graphs are Markov equivalent. For Gaussian probability distributions, we also show that every MAMP chain graph is Markov equivalent to some directed and acyclic graph with deterministic nodes under marginalization and conditioning on some of its nodes. This is important because it implies that the independence model represented by a MAMP chain graph can be accounted for by some data generating process that is partially observed and has selection bias. Finally, we modify MAMP chain graphs so that they are closed under marginalization for Gaussian probability distributions. This is a desirable feature because it guarantees parsimonious models under marginalization.Comment: Changes from v1 to v2: Discussion section got extended. Changes from v2 to v3: New Sections 3 and 5. Changes from v3 to v4: Example 4 added to discussion section. Changes from v4 to v5: None. Changes from v5 to v6: Some minor and major errors have been corrected. The latter include the definitions of descending route and pairwise separation base, and the proofs of Theorems 5 and

Design and early development of a UAV terminal and a ground station for laser communications

A free-space laser communication system has been designed and partially developed as an alternative to standard RF links from UAV to ground stations. This project belongs to the SINTONIA program (acronym in Spanish for low environmental-impact unmanned systems), led by BR&TE (Boeing Research and Technology Europe) with the purpose of boosting Spanish UAV technology. A MEMS-based modulating retroreflector has been proposed as a communication terminal onboard the UAV, allowing both the laser transmitter and the acquisition, tracking and pointing subsystems to be eliminated. This results in an important reduction of power, size and weight, moving the burden to the ground station. In the ground station, the ATP subsystem is based on a GPS-aided two-axis gimbal for tracking and coarse pointing, and a fast steering mirror for fine pointing. A beacon-based system has been designed, taking advantage of the retroreflector optical principle, in order to determine the position of the UAV in real-time. The system manages the laser power in an optimal way, based on a distance-dependent beam-divergence control and by creating two different optical paths within the same physical path using different states of polarization.Comment: 9 pages, 12 figures. Appears in Proceedings of the SPIE Security+Defence (Prague, Czech Republic, 2011

Metal-Poor Stars Observed with the Magellan Telescope. III. New Extremely and Ultra Metal-Poor Stars from SDSS/SEGUE and Insights on the Formation of Ultra Metal-Poor Stars

We report the discovery of one extremely metal-poor (EMP; [Fe/H]<-3) and one ultra metal-poor (UMP; [Fe/H]<-4) star selected from the SDSS/SEGUE survey. These stars were identified as EMP candidates based on their medium-resolution (R~2,000) spectra, and were followed-up with high-resolution (R~35,000) spectroscopy with the Magellan-Clay Telescope. Their derived chemical abundances exhibit good agreement with those of stars with similar metallicities. We also provide new insights on the formation of the UMP stars, based on comparison with a new set of theoretical models of supernovae nucleosynthesis. The models were matched with 20 UMP stars found in the literature, together with one of the program stars (SDSS J1204+1201), with [Fe/H]=-4.34. From fitting their abundances, we find that the supernovae progenitors, for stars where carbon and nitrogen are measured, had masses ranging from 20.5 M_sun to 28 M_sun and explosion energies from 0.3 to 0.9x10^51 erg. These results are highly sensitive to the carbon and nitrogen abundance determinations, which is one of the main drivers for future high-resolution follow-up of UMP candidates. In addition, we are able to reproduce the different CNO abundance patterns found in UMP stars with a single progenitor type, by varying its mass and explosion energy.Comment: 15 pages, 12 figures; accepted for publication in Ap

Capacity pricing schemes to implement open-access rail in Tanzania

We analyze alternative capacity pricing schemes (access charges) to implement an open-access railway system in Tanzania. We show that the implementation of variable access charges widely used in the railway industry may result in levels of traffic lower than the traffic operated by an integrated railway company. We propose the use of fixed access charges to avoid this problem and discuss the main advantages and disadvantages to implement them in the context of multiple freight train services in Tanzania

Association between chronic irritability and depressive symptoms in children and adolescents.

Association between chronic irritability and depressive symptoms in children and adolescents. Busto-Garrido, M.; Gutierrez-Castillo, D; Navas- Gonzalez, JR; Gutierrez-Bedmar, M; Gutierrez-Casares, JR; Martin-Lunar, MT; Rodríguez-Rosado, A; Pena-Andreu, JM. European Psychiatry 415(2017) 5221.Chronic irritability is the most frequently reported symptom in child and adolescent depression. The association of both has been linked with high rates of chronicity, comorbility and impairment. Objectives To study the association between chronic irritability and depressive symptoms in children and adolescents. Methods We have studied 857 participants recruited from the only Child and Adolescent Mental Health Clinic in a catchment area of 122968 people under 18 (2004-2010). A sample of 677 participants (57 controls and 620 patients) was included to carry out a cross-sectional study. Chronic irritability was measured by a Visual Analog Scale (VAS irritability) -scored from 0 to 10-, and depressive symptoms by the Children's Depression Inventory (CDI). The participants were categorized into controls and patients, and according to their chronic irritability (≤4 [I],5 [II] and ≥6 [III]). The mean of CDI score was calculated for each of the groups, adjusted by sex and age, and analyzed by ANCOVA. Results The following means were obtained from the controls: 13,71 (group I), 9,82 (group II) and 17,45 (group III). Regarding to the patients: 13,92 (group I), 11,54 (group II) and 15,64 (group III). A quadratic association (p <0,0015) was found between VAS irritability score and CDI score. Conclussions There is not a lineal association between chronic irritability and depressive symptoms in children and adolescent. High rates of depressive symptoms were associated both with high and low rates of irritability. Several questions remain unexplained about the status of irritability in psychiatry as Stringaris group has been pointed out. Disclosure statement I have no potential conflict of interest to discloseUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech