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Search Results: 1 - 10 of 32439 matches for " Antonio Tejeda "
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Uncertainty principle for experimental measurements: Fast versus slow probes
Philipp Hansmann,Thomas Ayral,Antonio Tejeda,Silke Biermann
Physics , 2015,
Abstract: The result of a physical measurement depends on the timescale of the experimental probe. In solid-state systems, this simple quantum mechanical principle has far-reaching consequences: the interplay of several degrees of freedom close to charge, spin or orbital instabilities combined with the disparity of the time scales associated to their fluctuations can lead to seemingly contradictory experimental findings. A particularly striking example is provided by systems of adatoms adsorbed on semiconductor surfaces where different experiments -- angle-resolved photoemission, scanning tunneling microscopy and core-level spectroscopy -- suggest different ordering phenomena. Using most recent first principles many-body techniques, we resolve this puzzle by invoking the time scales of fluctuations when approaching the different instabilities. These findings suggest a re-interpretation of ordering phenomena and their fluctuations in a wide class of solid-state systems ranging from organic materials to high-temperature superconducting cuprates.
Efecto del enriquecimiento ambiental sobre la conducta, parámetros de producción y respuesta inmune en pollos de engorda
Alberto Tejeda Perea,Francisco Galindo Maldonado,José Antonio Quintana López
Veterinaria México , 2002,
Abstract: Los objetivos del presente estudio fueron evaluar el efecto del enriquecimiento ambiental sobre conductas individuales y sociales, parámetros de producción y respuesta inmune en 220 pollos de engorda. Se instrumentaron cinco tratamientos: Testigo, juguetes y alfalfa, caja con arena, uso de perchas y una combinación. La conducta fue relacionada con las variables de producción: Peso vivo final, conversión alimentaria y respuesta inmune a la vacunación contra la enfermedad de Newcastle. No se encontraron diferencias conductuales entre las frecuencias de utilización de los factores de enriquecimiento entre los tratamientos con un solo elemento y el que los combinaba, pero se observaron diferencias cuando se utilizaron con respecto al testigo. La conducta de picoteo a la cabeza fue significativamente menor en el tratamiento donde se encontraba la caja de arena (P < 0.05) y la mayor frecuencia se encontró en el tratamiento con perchas y el tratamiento que los combinaba (P < 0.05). No se encontraron diferencias entre tratamientos en las variables de producción consideradas. La respuesta inmune fue buena y tampoco se encontraron diferencias entre tratamientos. Son necesarios más estudios que aborden la problemática entre enriquecimiento ambiental y epidemiología, en condiciones comerciales.
Dise?o patrimonial chileno
Tejeda,Guillermo;
ARQ (Santiago) , 2001, DOI: 10.4067/S0717-69962001004900016
Abstract: in a country like chile, which fights in defense of its fragile memory, guillermo tejeda gives an impulse to the preservation and investigation of the national graphic patrimony. with the current take off of the graphic design in chile, tejeda proposes the necessity to appreciate the legacy of mauricio amster, of the national library or of a publishing house like quimantú, among others
Dise o patrimonial chileno
Guillermo Tejeda
ARQ , 2001,
Abstract: En un país como el nuestro, que lucha en defensa de su frágil memoria, Guillermo Tejeda da un impulso a la preservación e investigación del patrimonio gráfico nacional. Con el actual desarrollo del dise o gráfico en Chile, Tejeda propone la necesidad de apreciar el legado de un Mauricio Amster, de una Biblioteca Nacional o de una Editorial Quimantú In a country like Chile, which fights in defense of its fragile memory, Guillermo Tejeda gives an impulse to the preservation and investigation of the national graphic patrimony. With the current take off of the graphic design in Chile, Tejeda proposes the necessity to appreciate the legacy of Mauricio Amster, of the National Library or of a publishing house like Quimantú, among others
Can we admit the way in which $\sin(x)$ is typically defined?
Ignacio Tejeda
Mathematics , 2015,
Abstract: I review some facts which the usual sen(x) and cos(x) definitions are based on. The purpose of this paper is to show that this facts can be proved if we assume some basic ideas of elementary geometry.
Glass-(nAg, nCu) Biocide Coatings on Ceramic Oxide Substrates
Leticia Esteban-Tejeda, Francisco Malpartida, Luis Antonio Díaz, Ramón Torrecillas, Fernando Rojo, José Serafín Moya
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033135
Abstract: The present work was focused on obtaining biocide coatings constituted by a glassy soda-lime matrix containing silver or copper nanoparticles on ceramic (alumina and zirconia based) substrates. Both glassy coatings showed a high biocide activity against Gram?, Gram+ bacteria and yeast, reducing cell numbers more than three logarithms. Silver nanoparticles had a significantly higher biocide activity than copper nanoparticles, since the lixiviation levels required to reduce cell numbers more than 3 logarithms was of almost 1–2 μg/cm2 in the case of silver nanoparticles, and 10–15 μg/cm2 for the copper nanoparticles.
Three and two-hadron correlations in \sqrt{s_{NN}}=200 GeV proton-proton and nucleus-nucleus collisions
Alejandro Ayala,Jamal Jalilian-Marian,J. Magnin,Antonio Ortiz,G. Paic,Maria Elena Tejeda-Yeomans
Physics , 2009, DOI: 10.1103/PhysRevLett.104.042301
Abstract: We compare the azimuthal correlations arising from three and two hadron production in high energy proton-proton and nucleus-nucleus collisions at \sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three and two-to-two parton-processes in perturbative QCD. We first compute the two and three hadron production cross sections in mid-rapidity proton-proton collisions. Then we consider Au + Au collisions including parton energy loss using the modified fragmentation function approach. By examining the geometrical paths the hard partons follow through the medium, we show that the two away-side partons produced in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Therefore there is a large probability that in the former processes one of the particles escapes while the other gets absorbed. This effect leads to an enhancement in the azimuthal correlations of the two-to-three with respect to the two-to-two parton-processes when comparing to the same processes in proton-proton collisions since in average the particle with the shortest path length looses less energy with respect to the away side particle in two-to-two processes. We argue that this phenomenon may be responsible for the shape of the away-side in azimuthal correlations observed in mid-rapidity Au + Au collisions at RHIC.
Three-hadron angular correlations from pQCD at RHIC and LHC
Alejandro Ayala,Jamal Jalilian-Marian,Antonio Ortiz,Guy Paic,J. Magnin,Maria Elena Tejeda-Yeomans
Physics , 2011, DOI: 10.1103/PhysRevC.84.024915
Abstract: We study three-hadron azimuthal angular correlations in high energy proton-proton and central nucleus-nucleus collisions at RHIC and LHC at mid-rapidity. We use the LO parton matrix elements for 2 \rightarrow 3 processes and include the effect of parton energy loss in the Quark-Gluon Plasma using the modified fragmentation function approach. For the case when the produced hadrons have either same or not too different momenta, we observe two away side peaks at 2pi/3 and 4pi/3. We consider the dependence of the angular correlations on energy loss parameters that have been used in studies of single inclusive hadron production at RHIC. Our results on the angular dependence of the cross section agree well with preliminary data by the PHENIX collaboration. We comment on the possible contribution of 2 \rightarrow 3 processes to di-hadron angular correlations and how a comparison of the two processes may help characterize the plasma further.
The broad away side of azimuthal correlations: 3 vs 2 final state particles in high energy nuclear collisions
Alejandro Ayala,Jamal Jalilian-Marian,J. Magnin,Antonio Ortiz,G. Paic,Maria Elena Tejeda-Yeomans
Physics , 2011, DOI: 10.1063/1.3579435
Abstract: In high energy heavy ion collisions at RHIC there are important aspects of the medium induced dynamics, that are still not well understood. In particular, there is a broadening and even a double hump structure of the away-side peak appearing in azimuthal correlation studies in Au+Au collisions which is absent in p+p collisions at the same energies. These features are already present but suppressed in p+p collisions: 2 to 3 parton processes produce such structures but are suppressed with respect to 2 to 2 processes. We argue that in A+A collisions the different geometry for the trajectories of 3 as opposed to 2 particles in the final state, together with the medium induced energy loss effects on the different cross sections, create a scenario that enhances processes with 3 particles in the final state, which gives on average this double hump structure.
Wide-Gap Semiconducting Graphene from Nitrogen-Seeded SiC
Feng Wang,Gang Liu,Sara Rothwell,Meredith Nevius,Antonio Tejeda,Amina Taleb-Ibrahimi,Leonard Feldman,Philip Cohen,Edward Conrad
Physics , 2013, DOI: 10.1021/nl402544n
Abstract: All carbon electronics based on graphene has been an elusive goal. For more than a decade, the inability to produce significant band-gaps in this material has prevented the development of semiconducting graphene. While chemical functionalization was thought to be a route to semiconducting graphene, disorder in the chemical adsorbates, leading to low mobilities, have proved to be a hurdle in its production. We demonstrate a new approach to produce semiconducting graphene that uses a small concentration of covalently bonded surface nitrogen, not as a means to functionalize graphene, but instead as a way to constrain and bend graphene. We demonstrate that a submonolayer concentration of nitrogen on SiC is sufficient to pin epitaxial graphene to the SiC interface as it grows, causing the graphene to buckle. The resulting 3-dimensional modulation of the graphene opens a band-gap greater than 0.7eV in the otherwise continuous metallic graphene sheet.
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