Método alternativo para la determinación del coeficiente de Manning en canales.

"El objeto de esta investigación es evaluar los coeficientes de rugosidad de Manning de revestimientos flexibles en canales de aprovechamientos hidráulicos. La utilización de nuevos materiales en estas aplicaciones, conlleva la necesidad de estudiar sus características y entre ellas es de particular interés obtener los valores del coeficiente de rugosidad más extensamente empleado en la práctica: el coeficiente de Manning. Para el efecto, se requiere realizar ensayos en canales de laboratorio, así como ensayos de campo, en tramos de canales reales revestidos con estos materiales. En este artículo se analiza la viabilidad de los ensayos de laboratorio, como caracterización de los materiales para uso en canales reales, con lo cual se enfatiza en los aspectos teóricos y metodológicos de la rugosidad en un canal rectangular construido en madera. Como conclusión del trabajo, se puede afirmar que los valores del coeficiente de Manning, obtenidos para los 2 ensayos evaluados en un mismo canal de madera construido en el laboratorio, difieren en un 17 por ciento, lo que pone de manifiesto la necesidad de cuantificar con un mejor criterio el valor de la rugosidad absoluta ""n""

Faixas normais de nutrientes em cana-de-açúcar pelos métodos ChM, DRIS e CND e nível crítico pela distribuição normal reduzida

Existem diversos métodos para a interpretação da diagnose foliar; o nível crítico ou as faixas de suficiência descritas na literatura são os mais utilizados. Porém, o uso de métodos de determinação de faixas normais de nutrientes que contemplam regiões específicas (localidades) aumenta a eficiência da interpretação. O objetivo deste trabalho foi determinar as faixas normais de nutrientes para a cultura da cana-de-açúcar, mediante a utilização dos métodos Chance Matemática (ChM), Sistema Integrado de Diagnose e Recomendação (DRIS) e Diagnose da Composição Nutricional (CND), além do Nível Crítico determinado pelo método de distribuição normal reduzida. O trabalho foi realizado tomando-se como base dados relativos a teores de nutrientes em amostras foliares e de produtividade de lavouras comerciais de cana-de-açúcar, localizadas no município de Campos de Goytacazes, RJ. Com o método da ChM, foram obtidas faixas de suficiência semelhantes aos métodos DRIS e CND, para N, Ca, S e Mn, enquanto para P, K, Mg, Cu e Zn os valores obtidos pela ChM foram superiores. A utilização dos métodos ChM, DRIS e CND, em lavouras comerciais de cana-de-açúcar em geral, possibilitou a obtenção de menor amplitude da faixa normal dos nutrientes, em comparação com os valores alcançados pelos métodos nível crítico e faixa de suficiência

Demonstration of a novel technique to measure two-photon exchange effects in elastic e±pe^\pm p scattering

The discrepancy between proton electromagnetic form factors extracted using unpolarized and polarized scattering data is believed to be a consequence of two-photon exchange (TPE) effects. However, the calculations of TPE corrections have significant model dependence, and there is limited direct experimental evidence for such corrections. We present the results of a new experimental technique for making direct $e^\pm p$ comparisons, which has the potential to make precise measurements over a broad range in $Q^2$ and scattering angles. We use the Jefferson Lab electron beam and the Hall B photon tagger to generate a clean but untagged photon beam. The photon beam impinges on a converter foil to generate a mixed beam of electrons, positrons, and photons. A chicane is used to separate and recombine the electron and positron beams while the photon beam is stopped by a photon blocker. This provides a combined electron and positron beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen target. The large acceptance CLAS detector is used to identify and reconstruct elastic scattering events, determining both the initial lepton energy and the sign of the scattered lepton. The data were collected in two days with a primary electron beam energy of only 3.3 GeV, limiting the data from this run to smaller values of $Q^2$ and scattering angle. Nonetheless, this measurement yields a data sample for $e^\pm p$ with statistics comparable to those of the best previous measurements. We have shown that we can cleanly identify elastic scattering events and correct for the difference in acceptance for electron and positron scattering. The final ratio of positron to electron scattering: $R=1.027\pm0.005\pm0.05$ for $=0.206$ GeV$^2$ and $0.830\leq \epsilon\leq 0.943$

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Seasonal drought limits tree species across the Neotropics

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water-stress on the physiological processes of most tree species. This process implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions it predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry-tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the Western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance’ hypothesis has broad applicability in the world's most species-rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region

SUPLEMENTO DEL XV CONGRESO INTERNACIONAL DE ACTIVIDAD FÍSICA Y DEPORTE. 17,18 y 19 DE OCTUBRE DEL 2018. ENSENADA, BAJA CALIFORNIA, MÉXICO

Compendio, en formato artículo, de los mejores trabajos presentados en el XV CONGRESO INTERNACIONAL DE ACTIVIDAD FÍSICA Y DEPORTE celebrado los días  17,18 y 19 de octubre del 2018 en la Universidad Autónoma de Baja California en la ciudad de Ensenada, Baja California, México:La nutrición en la actividad física y deportiva: alimentos funcionales con nanotecnología, aplicaciones potenciales. González González, K.Y.; Huerta Plaza, B.A.; Amaya Parra, G. (118-130)Perfil antropométrico, físico y hábitos alimentarios en escolares indígenas de Tijuana México. Avendaño Cano, D.L.; Gómez Miranda, L.M.; Aburto Corona, J.A. (131-142)Relación entre el clima de aprendizaje en Educación Física y la percepción de los estudiantes en las competencias del profesorado. Baños, R; Ortiz-Camacho, M.M.; Baena-Extremera, A.; Granero-Gallegos, A.; Machado-Parra, J.P.; Rentería, I.; Acosta, I.; Ramírez, L. (143-153)Valoración de capacidades físicas, composición corporal y consumo de vitaminas en una competencia de Crossfit. Cervantes-Hernández, N.; Hernández Nájera, N.; Carrasco Legleu, C.E.; Candia Lujan, R.; Enríquez Del Castillo, L.A. (154-164)Relación de la actividad física, características antropométricas y VO2máx en jóvenes universitarios: características por género. Enríquez-del Castillo, L.A.; Cervantes-Hernández, N.; Carrasco-Legleu, C.E.; Candia Luján, R. (165-174)Entrenamiento vibratorio de cuerpo completo y sus efectos sobre la composición corporal en jóvenes universitarios. Flores-Chico, B.; Bañuelos-Teres, L.E.; Buendía Lozada, E.R.P. (175-183)Actualización curricular, plan 2016 de la Licenciatura en Cultura Física de la BUAP. Flores-Chico, B.; Flores-Flores, A.; López de La Rosa, LE.; Aguilar-Enríquez, R.I.; Caballero Gómez, JM; Villanueva-Huerta, JA. (184-192)Evaluación psicológica y de la musculatura isquiosural de basquetbolistas universitarias en distintas etapas deportivas. Moranchel-Charros, R.; Martínez-Velázquez, E.S. (193-203)Efecto del ejercicio físico sobre la fuerza, resistencia y riesgo de caída en mujeres adultas. Ortiz Ortiz, M; Espinoza Gutiérrez, R; Gómez Miranda, LM.; Guzmán Gutiérrez, EC.; Calleja Núñez, JJ. (204-212)Desigualdad vs igualdad numérica y su efecto en la técnica de jugadores de fútbol infantil. Vega-Orozco, SI; Gavotto Nogales, OI; Bernal Reyes, F; Horta Gim, MA; Sarabia Sainz, HM. (213-224

Measurement of the View the tt production cross-section using eμ events with b-tagged jets in pp collisions at √s = 13 TeV with the ATLAS detector

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron–muon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously σtt¯ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: σtt¯ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented