Multi-GPU maximum entropy image synthesis for radio astronomy

The maximum entropy method (MEM) is a well known deconvolution technique in radio-interferometry. This method solves a non-linear optimization problem with an entropy regularization term. Other heuristics such as CLEAN are faster but highly user dependent. Nevertheless, MEM has the following advantages: it is unsupervised, it has a statistical basis, it has a better resolution and better image quality under certain conditions. This work presents a high performance GPU version of non-gridding MEM, which is tested using real and simulated data. We propose a single-GPU and a multi-GPU implementation for single and multi-spectral data, respectively. We also make use of the Peer-to-Peer and Unified Virtual Addressing features of newer GPUs which allows to exploit transparently and efficiently multiple GPUs. Several ALMA data sets are used to demonstrate the effectiveness in imaging and to evaluate GPU performance. The results show that a speedup from 1000 to 5000 times faster than a sequential version can be achieved, depending on data and image size. This allows to reconstruct the HD142527 CO(6-5) short baseline data set in 2.1 minutes, instead of 2.5 days that takes a sequential version on CPU.Comment: 11 pages, 13 figure

On the algebraic structure of rotationally invariant two-dimensional Hamiltonians on the noncommutative phase space

We study two-dimensional Hamiltonians in phase space with noncommutativity both in coordinates and momenta. We consider the generator of rotations on the noncommutative plane and the Lie algebra generated by Hermitian rotationally invariant quadratic forms of noncommutative dynamical variables. We show that two quantum phases are possible, characterized by the Lie algebras $sl(2,\mathbb{R})$ or $su(2)$ according to the relation between the noncommutativity parameters, with the rotation generator related with the Casimir operator. From this algebraic perspective, we analyze the spectrum of some simple models with nonrelativistic rotationally invariant Hamiltonians in this noncommutative phase space, as the isotropic harmonic oscillator, the Landau problem and the cylindrical well potential. PACS: 03.65.-w; 03.65.Fd MSC: 81R05; 20C35; 22E70Comment: 49 pages. No figures. Version to appear in JP

A hypothetical learning trajectory for trigonometric equations with infinite solutions

This work has been carried out within the framework of Ph.D. Program in Education of the Autonomous University of Barcelona has been financed in part by the project PID2019-104964GB-100. Also, this has received the support of the project Fondecyt N°11190284

Detección de anticuerpos séricos contra Toxoplasma gondii (Nicolle y Manceaux, 1909) en llamas (Lama glama Linneaus, 1758) y alpacas (Lama pacos Linneaus, 1758 ) de Chile.

Sera samples from 113 Ilamas (Lama glama) and 127 alpacas (Lama pacos) from the IX and V Regions, respectively, of Chile were tested for Toxoplasma gondii antibodies. The modified agglutination test (MAT) was used in both species and titers 1:25 were considered diagnostically significant based in previously published data. Sera from 49 lamas (43.3%) and 15 alpacas (11.8%) were positive to T. gondii. Percentaje seropositivity in serum dilutions of 1:25, 1:50, 1:500 and 1:5000 was 17.6%; 7.9%; 14.1% and 3.5% in lamas and 0%; 2.3%; 0.7% and 8.6% in alpacas, respectively. The rather low prevalence in alpacas may be associated with geographical conditions, management practices or contacts with cats rather than different species susceptibility. As expected, older animals showed higher reactivity of T. gondii than young animals.Se obtuvieron 113 sueros de llamas y 127 de alpacas de criaderos ubicados en la IX y V Regiones del país respectivamente para determinar la presencia de infección de T. gondii. Para el análisis de los sueros se utilizó el "test" modificado de aglutinación (MAT) a diluciones 1:25; 1:50, 1:500; 1:5000. Del total de 113 sueros de llamas estudiados 49 (43,3%) de ellas presentaron anticuerpos contra T. gondii, mientras que en las alpacas 15 de las 127 (11,8%) fueron positivas. El número de animales positivos en las diluciones 1/25; 1/50; 1/500; 1/5000 fue de 20 (17,6%); 9 (7,9%); 16 (10,6%); 4 (3,5%) en las llamas, respectivamente. En las alpacas los valores fueron de 0 (0%); 3 (2,3%); 1 (0,7%); 11 (8,6%), respectivamente. Aunque no existen antecedentes clínicos de la infección en los establecimientos estudiados, su potencial implicancia en este tipo de patología debería ser considerada a base de los resultados del presente trabajo que demuestra que llamas y alpacas del centro-sur de Chile son reaccionantes a la infección por T. gondii

The Influence of Abiotic Factors on an Invasive Pest of Pulse Crops, Sitona lineatus

Pea leaf weevil, Sitona lineatus (L.), native to Europe and North Africa, has been introduced into many other countries around the world, including the USA and Canada. Adults are oligophagous pests on leguminaceous plants. Sitona lineatus was first recorded in Canada in 1997, near Lethbridge, Alberta. Since then, it has spread north in Alberta and west into Saskatchewan in 2007. Bioclimatic simulation models were used to predict the distribution and extent of establishment of S. lineatus in Canada based on its current geographic range, phenology, relative abundance, and empirical data. The study identified areas in Canada that are at risk for future establishment of S. lineatus and developed a better understanding of climate effects. Climate change projections (General Circulation Models) were then imposed on the bioclimatic model of S. lineatus. Bioclimatic model output varied for each of the three General Circulation Models. In terms of suitability for pest establishment (Ecoclimatic Index), the NCAR273 CCSM climate data resulted in the most significant shift northward

New distance measures for classifying X-ray astronomy data into stellar classes

The classification of the X-ray sources into classes (such as extragalactic sources, background stars, ...) is an essential task in astronomy. Typically, one of the classes corresponds to extragalactic radiation, whose photon emission behaviour is well characterized by a homogeneous Poisson process. We propose to use normalized versions of the Wasserstein and Zolotarev distances to quantify the deviation of the distribution of photon interarrival times from the exponential class. Our main motivation is the analysis of a massive dataset from X-ray astronomy obtained by the Chandra Orion Ultradeep Project (COUP). This project yielded a large catalog of 1616 X-ray cosmic sources in the Orion Nebula region, with their series of photon arrival times and associated energies. We consider the plug-in estimators of these metrics, determine their asymptotic distributions, and illustrate their finite-sample performance with a Monte Carlo study. We estimate these metrics for each COUP source from three different classes. We conclude that our proposal provides a striking amount of information on the nature of the photon emitting sources. Further, these variables have the ability to identify X-ray sources wrongly catalogued before. As an appealing conclusion, we show that some sources, previously classified as extragalactic emissions, have a much higher probability of being young stars in Orion Nebula.Comment: 29 page

Comparative pan-genome analysis of Piscirickettsia salmonis reveals genomic divergences within genogroups

Indexación: Scopus.Piscirickettsia salmonis is the etiological agent of salmonid rickettsial septicemia, a disease that seriously affects the salmonid industry. Despite efforts to genomically characterize P. salmonis, functional information on the life cycle, pathogenesis mechanisms, diagnosis, treatment, and control of this fish pathogen remain lacking. To address this knowledge gap, the present study conducted an in silico pan-genome analysis of 19 P. salmonis strains from distinct geographic locations and genogroups. Results revealed an expected open pan-genome of 3,463 genes and a core-genome of 1,732 genes. Two marked genogroups were identified, as confirmed by phylogenetic and phylogenomic relationships to the LF-89 and EM-90 reference strains, as well as by assessments of genomic structures. Different structural configurations were found for the six identified copies of the ribosomal operon in the P. salmonis genome, indicating translocation throughout the genetic material. Chromosomal divergences in genomic localization and quantity of genetic cassettes were also found for the Dot/Icm type IVB secretion system. To determine divergences between core-genomes, additional pan-genome descriptions were compiled for the so-termed LF and EM genogroups. Open pan-genomes composed of 2,924 and 2,778 genes and core-genomes composed of 2,170 and 2,228 genes were respectively found for the LF and EM genogroups. The core-genomes were functionally annotated using the Gene Ontology, KEGG, and Virulence Factor databases, revealing the presence of several shared groups of genes related to basic function of intracellular survival and bacterial pathogenesis. Additionally, the specific pan-genomes for the LF and EM genogroups were defined, resulting in the identification of 148 and 273 exclusive proteins, respectively. Notably, specific virulence factors linked to adherence, colonization, invasion factors, and endotoxins were established. The obtained data suggest that these genes could be directly associated with inter-genogroup differences in pathogenesis and host-pathogen interactions, information that could be useful in designing novel strategies for diagnosing and controlling P. salmonis infection. © 2017 Nourdin-Galindo, Sánchez, Molina, Espinoza-Rojas, Oliver, Ruiz, Vargas-Chacoff, Cárcamo, Figueroa, Mancilla, Maracaja-Coutinho and Yañez.https://www.frontiersin.org/articles/10.3389/fcimb.2017.00459/ful

Abundance of Lygus spp. (Heteroptera:Miridae) in canola adjacent to forage and seed alfalfa

Our objectives were to document the abundance of lygus bugs (Miridae) in canola after the cutting of adjacent alfalfa hay fields and to document their seasonal activity in canola plots grown in close proximity to alfalfa seed. Cutting alfalfa did not increase abundance of lygus bugs in nearby canola in sites near Barrhead, Alberta (1998-1999), in the Peace River area of British Columbia (2000) or near Carman, Manitoba (2001). In Saskatoon, from 1993-1995, lygus bug numbers remained at low levels in seed alfalfa and canola and there was no indication that the pest species (L. lineolaris) in canola moved in significant numbers from the adjacent alfalfa seed field. We conclude that alfalfa forage harvesting generally does not result in massive movement of lygus bugs to nearby canola

Phenomenological aspects of the fermion and scalar sectors of a S4S_4 flavored 3-3-1 model

We propose a viable and predictive model based on the $SU(3)_C \times SU(3)_L \times U(1)_X$ gauge symmetry, supplemented by the global $U(1)_{Lg}$ symmetry, the $S_4$ family symmetry and several auxiliary cyclic symmetries, which successfully reproduces the observed SM fermion mass and mixing pattern. The SM charged fermion mass and quark mixing hierarchy is caused by the spontaneous breaking of the discrete symmetries, whereas the tiny active neutrino masses are generated through an inverse seesaw mechanism mediated by right-handed Majorana neutrinos. The model is consistent with the SM fermion masses and mixings and successfully accommodates the current Higgs diphoton decay rate constraints as well as the constraints arising from oblique $S$, $T$ and $U$ parameters and meson oscillations.Comment: 23 pages, 7 figure