8,038 research outputs found
Kinetic Monte Carlo simulation of the nitridation of the GaAs (100) surfaces
We present, in this work, our preliminary results of a systematic theoretical
study of the adsorption of N over As-terminated GaAs (100) (21)
surfaces. We analyzed the changes in the bond-lenghts, bond-angles and the
energetics involved before and after deposition. Our results show that the
N-atoms will prefer the unoccupied sites of the surface, close to the As dimer.
The presence of the N pushes the As dimer out of the surface, leading to the
anion exchange between the N and As atoms. Based on our results, we discussed
about the kinetics of the N islands formation during epitaxial growth of the
III-Nitrides.Comment: 4 pages, 7 figures, accepted for publication in Braz. J. Phys.,
special number, Proceedings of BWSP-12, 12th Brazilian Workshop on
Semiconductor Physic
Ab initio calculation of the dynamical properties of PPP and PPV
In this work, we have calculated the vibrational modes and frequencies of the
crystalline PPP (in both the Pbam and Pnnm symmetries) and PPV (in the P21/c
symmetry). Our results are in good agreement with the available experimental
data. Also, we have calculated the temperature dependence of their specific
heats at constant volume, and of their vibrational entropies. Based on our
results, at high temperatures, the PPP is more stable in the Pnnm structure
than in the Pbam one.Comment: 5 pages, 7 figures, accepted for publication in Braz. J. Phys.,
special number, Proceedings of BWSP-12, 12th Brazilian Workshop on
Semiconductor Physic
Observation of the dielectric-waveguide mode of light propagation in p-n junctions
Theoretical considerations of the propagation of electromagnetic energy near a p-n junction (1) show that the “sandwich” formed by having a depletion layer bounded by the p and n regions can act as a dielectric waveguide. (1,2
Specific heat amplitude ratios for anisotropic Lifshitz critical behaviors
We determine the specific heat amplitude ratio near a -axial Lifshitz
point and show its universal character. Using a recent renormalization group
picture along with new field-theoretical -expansion techniques,
we established this amplitude ratio at one-loop order. We estimate the
numerical value of this amplitude ratio for and . The result is in
very good agreement with its experimental measurement on the magnetic material
. It is shown that in the limit it trivially reduces to the
Ising-like amplitude ratio.Comment: 8 pages, RevTex, accepted as a Brief Report in Physical Review
Influence of duration of exposure to field conditions on viability of fecal samples for NIRS analysis.
Abstract: This experiment was conducted to address the issue of spectral integrity of pelleted feces exposed to environmental conditions at different times of the year in near infrared reflectance spectroscopy analysis, using goats as the representative herbivore. Both dietary crude protein and digestible organic matter were predicted. Results indicated that fecal samples collected with up to 7 days of exposure provided similar estimates of diet crude protein and digestible organic matter from samples collected immediately after defecation. Goat feces response to environmental conditions provided useful information as to how collection of many wild herbivores' fecal material could be efficiently sampled for future near infrared reflectance spectroscopy analyses
Potencial agrĂcola do solo para o cultivo da cebola.
No Nordeste, o cultivo da cebola é realizado durante o ano todo, com concentração de plantio nos meses de janeiro a março e colheitas de maio a julho (120 dias), para atender à demanda dos mercados consumidores das regiões Sul e Sudeste
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