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Search Results: 1 - 10 of 3249 matches for " Arturo Lezama "
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Theoretical study of dark resonances in micro-metric thin cells
Horacio Failache,Lorenzo Lenci,Arturo Lezama,Daniel Bloch,Martial Ducloy
Physics , 2007, DOI: 10.1103/PhysRevA.76.053826
Abstract: We investigate theoretically dark resonance spectroscopy for a dilute atomic vapor confined in a thin (micro-metric) cell. We identify the physical parameters characterizing the spectra and study their influence. We focus on a Hanle-type situation, with an optical irradiation under normal incidence and resonant with the atomic transition. The dark resonance spectrum is predicted to combine broad wings with a sharp maximum at line-center, that can be singled out when detecting a derivative of the dark resonance spectrum. This narrow signal derivative, shown to broaden only sub-linearly with the cell length, is a signature of the contribution of atoms slow enough to fly between the cell windows in a time as long as the characteristic ground state optical pumping time. We suggest that this dark resonance spectroscopy in micro-metric thin cells could be a suitable tool for probing the effective velocity distribution in the thin cell arising from the atomic desorption processes, and notably to identify the limiting factors affecting desorption under a grazing incidence.
Vacuum squeezing via polarization self-rotation and excess noise in hot Rb vapors
Eugeniy E. Mikhailov,Arturo Lezama,Thomas W. Noel,Irina Novikova
Physics , 2009, DOI: 10.1080/09500340903159503
Abstract: We present experimental and theoretical analysis of quantum fluctuation in a vacuum field in the presence of orthogonal linearly polarized pump field propagating through a Rb vapor cell. Previously reported theoretical and experimental studies provided somewhat contradictory conclusions regarding the possibility to observe the "squeezed vacuum" -- the reduction of vacuum fluctuations below standard quantum limit -- in this system. Here, using the D1 transitions of Rb in a cell without buffer as as an example, we demonstrate that vacuum squeezing is corrupted by incoherent processes (such as spontaneous emission, elastic scattering, etc.), and its observation is only possible in a specific small region of the experimental parameter space. Numerical simulations, in good agreement with the experiment, demonstrate that the two excited state hyperfine levels play a crucial role in the squeezing and excess noise production. The significant influence of far-detuned atoms on the field fluctuations at low noise frequencies imposes the explicit consideration of the full velocity distribution of the atomic vapor.
VALORES Y FACTORES SOCIODEMOGRáFICOS EN ESTUDIANTES UNIVERSITARIOS: UN ESTUDIO COMPARATIVO
ANGELUCCI,LUISA; DA SILVA,JOSé; JUáREZ,JOSé; SERRANO,ARTURO; LEZAMA,JOSé; MORENO,AGUSTíN;
Acta Colombiana de Psicología , 2009,
Abstract: the purpose of this study was to compare the values of university students as a function of socio-demographic variables such as: gender, kind of school (religious vs. non-religious; private vs. public), religion (catholic - non catholic) and age. a self-administered scale of 55 values was designed for this research and it was used with a sample of 3.384 students selected intentionally. the values scale showed five dimensions: cosmopolitan, social, instrumental, moral and conservative. results indicated that women presented a higher appreciation of moral, social and conservative values, whereas men valued more the cosmopolitan values. the students that attended religious schools valued more the conservative dimension. the socio demographic variable of major influence in the axiological preferences was gender and the value dimension differentiated by most socio-demographic factors was the conservative.
Jerarquía de valores en estudiantes universitarios
Angelucci,Luisa; Juárez,José F; Dakduk,Silvana; Lezama,José; Moreno,Agustín; Serrano,Arturo;
Argos , 2008,
Abstract: the purpose of this work is to characterize the student population of the universidad católica andrés bello, caracas, regarding their value hierarchy. a 55-aspect instrument which qualified according to the importance given to them was used. a 3,384-student sample, with an average age of 21, and quotas by careers and promotion year was selected. the results indicated that the most important values are family, happiness, health and honesty, whereas the least important values are appearance, ambition, rebelliousness, cowardice and laziness. as a conclusion, this research offers a current hierarchy of values in this sample of university youngsters that is in accordance with that found in previous researches, where classical values are considered as the most important.
Polarization Self-rotation in Ultracold Atomic Rb
Travis Horrom,Salim Balik,Arturo Lezama,Mark D. Havey,Eugeniy E. Mikhailov
Physics , 2011, DOI: 10.1103/PhysRevA.83.053850
Abstract: We report on a combined experimental and theoretical study of polarization self-rotation in an ultracold atomic sample. In the experiments, a probe laser is tuned in the spectral vicinity of the D1 line to observe polarization self-rotation in a sample of ultracold Rb prepared in a magneto-optical trap. Systematic measurements of the rotation angle of the light-polarization ellipse as a function of laser intensity, initial ellipticity and detuning are made. The observations, in good agreement with theoretical simulations, are indicative of the presence of a residual static magnetic field, resulting in measured asymmetries in the rotation angle for right and left ellipticities. In this paper we present our detailed experimental results and analysis of the combined influences of polarization self-rotation and the Faraday effect.
Quadrature noise in light propagating through a cold 87Rb atomic gas
Travis Horrom,Arturo Lezama,Salim Balik,Mark D. Havey,Eugeniy E. Mikhailov
Physics , 2011, DOI: 10.1080/09500340.2011.594181
Abstract: We report on the study of the noise properties of laser light propagating through a cold 87Rb atomic sample held in a magneto-optical trap. The laser is tuned around the Fg = 2 \rightarrow Fe = 1, 2 D1 transitions of 87Rb. We observe quadrature-dependent noise in the light signal, an indication that it may be possible to produce squeezed states of light. We measure the minimum and maximum phase-dependent noise as a function of detuning and compare these results to theoretical predictions to explore the best conditions for light squeezing using cold atomic Rb.
Percepción y actitud de productores ca?eros sobre la composta de cachaza y vinaza
Quiroz Guerrero, Ismael;Pérez Vázquez, Arturo;Landeros Sánchez, Cesáreo;Morales Ramos, Victorino;Zetina Lezama, Rigoberto;
Tropical and subtropical agroecosystems , 2011,
Abstract: the aim of this study was to identify the sugar cane farmers' perception and attitude regarding the use of filter cake compost and vinasse in the cultivation of sugar cane. twenty four farmers that applied compost, fifty farmers that used vinasse, and others fifty farmers who did not use any of the two products were interviewed. the statistical analyses included multidimensional analysis, factor and frequency analysis, and averages, which were carried out using statistica 7.0. the results indicate that the 65 % of sugar cane producers who applied compost have a negative perception and attitude of 2.9 (negative). also, 68 % who applied vinasse, presented a negative perception and an attitude of 2.4 (negative). producers who did not apply these two products, the 70 % had a positive perception of compost and negative perception towards the vinasse (63 %). besides, the attitude was 3.5 (positive), and 2.1 (negative) to the use of compost and vinasse, respectively. it can be concluded that the negative perception and attitude towards the use of compost and vinasse is due to the inadequate management made by the factory.
Presentación sistémica de Aspergillus spp con semiología neurológica en un Pastor Alemán: informe de un caso clínico
Hernández Tapia, Ana Laura;Santoscoy Mejía, Eduardo Carlos;Ramírez Lezama, José;Cervantes Olivares, Roberto A.;Quiroz Mercado, Joaquín Arturo;
Veterinaria México , 2010,
Abstract: infections of the central nervous system are uncommon in dogs. pathogenic fungi such as aspergillus, cryptococcus spp, blastomyces dermatitidis and coccidioides immitis have been reported. an aspergillus infection is mainly a respiratory event and very seldom it may become disseminated, the german shepherd seems to be the more prone to this type of aspergillosis specially if an immunological deficiency is present. a 1.5 year old female german shepherd from cancun, quintana roo, state, in the southeast of mexico was presented to the small animal hospital, she showed tetraparesis, hiporeflex and deep retarded sensitivity in all four members, loss of sensitivity in the left side of the face, absence of pupil reflex and menace reflex as well as absence of muscular tone of the vulva and anal sphincter. the third day after presentation, she died. at necropsy polyencephalomalace, mielitis and diffuse leucomielitis piogranomalotosus were found. in the cytology of lymph node and other tissues aspergilli like hiphae were observed, this was confirmed by using the highly specific double diffusion test. then, a pcr test was carried out with tissue fixed in 10% formaldehyde, but it failed probably due to destruction of the dna.
Clasificación florística de los bosques y arbustales de las sierras del Uruguay
Gautreau,Pierre; Lezama,Felipe;
Ecolog?-a austral , 2009,
Abstract: the woodland ecosystems of uruguay have been only described physiognomically, and the controls of their heterogeneity are still poorly understood. the aim of this paper is to describe the variations in species composition of the woody vegetation of the eastern and northeastern hills of uruguay. in three selected areas under extensive cattle grazing, 122 vegetation samples were collected. we identified five main vegetation units: myrceugenia euosma and baccharis dracunculifolia shrublands, syagrus romanzoffiana woods, myrsine coriacea woods and eugenia uniflora woods. correspondence analysis was carried out to describe floristic gradients. the first axis showed a physiognomic gradient from shrub to wood formations, partly determined by water availability linked to soil depth, a factor related to geomorphology, while the second axis revealed differences among communities related to geology. it is the first floristic classification of the woody vegetation in uruguay, and it proves that, despite the great structural uniformity, the woody vegetation of these hills is floristically heterogenous. little importance has been given to the geological and edaphic factors responsible for the woods variation in the past, and no descriptions of the shrublands existed. the classification proposed constitutes an alternative to the physiognomic typology used in uruguay to describe woody vegetation. it shows the limitations of this typology, offers new categories that allow for comparisons with southern brazil communities, and provides useful information for designing regional conservation strategies.
La construcción gubernamental de la contaminación ambiental: la política del aire para la Ciudad de México, 1979-1996.(Parte B)
José Luis Lezama
Economía, sociedad y territorio , 1997,
Abstract:
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