University of Los Andes

About: University of Los Andes is a education organization based out in Bogotá, Colombia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 17616 authors who have published 25555 publications receiving 413463 citations.

Contemporary cryptic sexuality in Trypanosoma cruzi

Abstract: Clonal propagation is considered to be the predominant mode of reproduction among many parasitic protozoa. However, this assumption may overlook unorthodox, infrequent or cryptic sexuality. Trypanosoma cruzi, which causes Chagas disease, is known to undergo non-Mendelian genetic exchange in the laboratory. In the field, evidence of extant genetic exchange is limited. In this study, we undertook intensive sampling of T. cruzi Discrete Typing Unit I in endemic eastern Colombia. Using Fluorescence-activated cell sorting, we generated 269 biological clones from 67 strains. Each clone was genotyped across 24 microsatellite loci. Subsequently, 100 representative clones were typed using 10 mitochondrial sequence targets (3.76 Kbp total). Clonal diversity among humans, reservoir hosts and vectors suggested complex patterns of superinfection and/or coinfection in oral and vector-borne Chagas disease cases. Clonal diversity between mother and foetus in a congenital case demonstrates that domestic TcI genotypes are infective in utero. Importantly, gross incongruence between nuclear and mitochondrial markers is strong evidence for widespread genetic exchange throughout the data set. Furthermore, a confirmed mosaic maxicircle sequence suggests intermolecular recombination between individuals as a further mechanism of genetic reassortment. Finally, robust dating based on mitochondrial DNA indicates that the emergence of a widespread domestic TcI clade that we now name TcI(DOM) (formerly TcIa/VEN(Dom)) occurred 23 000 ± 12 000 years ago and was followed by population expansion, broadly corresponding with the earliest human migration into the Americas.

Radiated seismic energy from coda measurements and no scaling in apparent stress with seismic moment

Abstract: [1] The seismic coda consists of scattered waves that leave the earthquake source in a variety of directions. The averaging of source radiation that results leads to stable ground motion spectra that we use as the basis for a robust measurement of radiated wave energy. We apply an empirical Green's function (EGF) method to the seismic coda in order to investigate scaling of the radiated seismic energy. We correct for path effects in the spectra of earthquakes by using a stack of closely located, small earthquakes as an EGF. We apply this approach to four earthquake sequences in western North America that span a magnitude range from Mw 3.0–Mw 7.1. Our estimates of scaled energy are consistent with independent measurements, where available. We find no dependence in individual seismic energy estimates on source-station distance, which validates the EGF approximation. We find that a constant scaled energy of 3.5 × 10−5 provides a reasonable fit to the data, with no dependence of the scaled energy on seismic moment.

Search for electroweak production of charginos and neutralinos using leptonic final states in pp collisions at sqrt(s) = 7 TeV

Abstract: The 2011 dataset of the CMS experiment, consisting of an integrated luminosity of 4.98 inverse femtobarns of pp collisions at sqrt(s) = 7 TeV, enables expanded searches for direct electroweak pair production of charginos and neutralinos in supersymmetric models as well as their analogs in other models of new physics. Searches sensitive to such processes, with decays to final states that contain two or more leptons, are presented. Final states with three leptons, with a same-sign lepton pair, and with an opposite-sign lepton pair in conjunction with two jets, are examined. No excesses above the standard model expectations are observed. The results are used in conjunction with previous results on four-lepton final states to exclude a range of chargino and neutralino masses from approximately 200 to 500 GeV in the context of models that assume large branching fractions of charginos and neutralinos to leptons and vector bosons.

Fermionic modular categories and the 16-fold way

Abstract: We study spin and super-modular categories systematically as inspired by fermionic topological phases of matter, which are always fermion parity enriched and modelled by spin topological quantum field theories at low energy. We formulate a 16-fold way conjecture for the minimal modular extensions of super-modular categories to spin modular categories, which is a categorical formulation of gauging the fermion parity. We investigate general properties of super-modular categories such as fermions in twisted Drinfeld doubles, Verlinde formulas for naive quotients, and explicit extensions of PSU(2)4m+2 with an eye towards a classification of the low-rank cases.

Charged particle transverse momentum spectra in pp collisions at s√=0.9 and 7 TeV

Abstract: The charged particle transverse momentum (pT) spectra are presented for pp collisions at sqrt(s)=0.9 and 7 TeV. The data samples were collected with the CMS detector at the LHC and correspond to integrated luminosities of 231 inverse microbarns and 2.96 inverse picobarns, respectively. Calorimeter-based high-transverse-energy triggers are employed to enhance the statistical reach of the high-pT measurements. The results are compared with both leading-order QCD and with an empirical scaling of measurements at different collision energies using the scaling variable xT = 2 pT/sqrt(s) over the pT range up to 200 GeV/c. Using a combination of xT scaling and direct interpolation at fixed pT, a reference transverse momentum spectrum at sqrt(s)=2.76 TeV is constructed, which can be used for studying high-pT particle suppression in the dense QCD medium produced in heavy-ion collisions at that centre-of-mass energy.