11 research outputs found
Some Obreshkov measures of dependence and their use
No full textThe dependence in the world of the uncertainty is a complex concept. The textbooks do avoid any discussions in this regard. However, dependence exists and can be measured. We use the concept of dependence proposed about 50 years ago by the famous Bulgarian mathematician N. Obreshkov and discuss the ways of its interpretation establish some additional interesting properties, and point out areas of applications. Then we apply it to some examples to illustrate how suitable this approach is in the studies of local dependence between non-numeric and numeric random variables
Nonresonant formation of H− near unreconstructed Si(100) surfaces
No full textWe calculate ab initio the fraction of outgoing negative hydrogen ions that are normally incident on an unreconstructed Si(100) surface with kinetic energies between 50 and 150eV. The ground-state electronic structure of the surface is derived from a self-consistent screened Thomas–Fermi–von Weizsäcker pseudopotential including Wang-Teter shell structure corrections. Orbitals and energies of the electronic states in this potential are obtained by solving Kohn-Sham equations. The dynamics of the transfer of a single electron during the ion-surface collision is represented within the Newns-Anderson model, including image-charge interactions and electron translation factor. We show that the outgoing H− fraction evolves at large distances from the surface due to nonresonant transitions from the valence band levels of the substrate into the affinity level of H−. In particular, we show that electron capture from dangling-bond surface-state resonances determines the final negative-ion fraction. We find good qualitative agreement with the experimental results of Maazouz et al. [Surf. Sci. 398, 49 (1998)] for the scattering of hydrogen atoms and ions on silicon surfaces, even though our calculations do not include the effects of reconstruction and projectile motion parallel to the surface
Neutralization of H− near vicinal metal surfaces
No full textWe calculate the neutralization probability of H− ions due to charge transfer in collisions with metal vicinal surfaces. We apply a statistical Thomas-Fermi model with gradient correction to the kinetic energy and a local density approximation for the exchange-correlation energy to compute the ground-state electronic structure of the surface. In comparison with calculations for flat surfaces, we find work-function changes, induced by the vicinal superstructure, in good agreement with published experimental and theoretical data. We evaluate the shift and width of the H− affinity level resonance for fixed positions of the ion near the surface. For incident anions with a kinetic energy of 1keV, the calculated ion-neutralization probabilities depend sensitively on the impact direction, point of closest approach of the trajectory, and the surface morphology. We find that the ion survival is more likely if the H− ions approach the step from above, as compared to ions that approach a step from below under otherwise identical scattering conditions. In particular, the electron loss after reflection at a terrace of a monoatomically stepped Al surface is predicted to be resonantly enhanced if the ion approaches a step from below
Blueshift of high-order harmonic generation in crystalline silicon subjected to intense femtosecond near-infrared laser pulse
No full textWe present the generation of high order harmonics in crystalline silicon subjected to intense near-infrared 30fs laser pulse. The harmonic spectrum extends from the near infrared to the extreme ultraviolet spectral region. Depending on the pulsed laser intensity, we distinguish two regimes of harmonic generation: (i) perturbative regime: electron-hole pairs born during each half-cycle of the laser pulse via multiphoton and tunnel transitions are accelerated in the laser electric field and gain kinetic energy; the electron-hole pairs then recombine in the ground state by emitting a single high-energy photon. The resultant high harmonic spectrum consists of sharp peaks at odd harmonic orders. (ii) non-perturbative regime: the intensity of the harmonics increases, their spectral width broadens and the position of harmonics shifts to shorter wavelengths. The blueshift of high harmonics in silicon are independent on the harmonic order which may be helpful in the design of continuously tunable XUV sources
Hydrogen-anion formation near a (2×1)-reconstructed Si(100) surface: substrate-electronic-structure and trajectory dependence
No full textWe calculated the yield of outgoing hydrogen negative ions after the reflection of 1-keV neutral hydrogen atoms from a (2×1)-reconstructed Si(100) surface. We find that the charge-transfer dynamics at the reconstructed surface is dependent on both the surface-electronic structure and orientation of the projectile trajectory relative to the crystal azimuthal directions. Our results are in good quantitative agreement with the measured Hˉ fractions of Maazouz and Esaulov [Surf. Sci. 398 49 (1998)] for scattering trajectories that are aligned perpendicularly to rows of silicon dimers
H− formation in collisions of hydrogen atoms with Al(100) surfaces
No full textWe theoretically investigate the electron transfer dynamics during the reflection of hydrogen atoms on an Al(100) surface for a wide range of collision energies below 6 keV. We find a nonmonotonic variation of the hydrogen-negative-ion fractions as functions of the projectile impact velocity due to nonadiabatic electron transfer. Our calculated anion fractions for projectiles scattered along high Miller-index crystal-surface directions are in good quantitative agreement with measured H− fractions for a wide range of exit velocities
БОЛЕСТТА AMOR HEREOS В СРЕДНОВЕКОВНИЯ РОМАН HISTORIA DE JACOBO XALABÍN
No full textThe History of Jacobo Xalabín (La historia de Jacobo Xalabín) is a medieval anonymous novel written in the Catalan language. According to the latest research, it dates between 1492 and 1536. The narrator takes us to the court of Sultan Murad I in 1387. Sultan Yakub's first-born son rejects the love of his stepmother Isa Celebina, as a result of which she falls ill. Advised by the only doctor who discovered the cause of her illness – the Jew Kir Moshe, in order to cure her, they planned the death of Yakub Celebi. Although the inclusion of Isa Chelebina's illness in the narrative is only one of its elements, accurate conclusions can be drawn from the narrative about the level of modern medical practice at that time in the examination of patients, the treatment of identified diseases and the imposition of certain stereotypes regarding the qualifications of doctors in different countries. Added to them is the clearly expressed personal attitude of the author towards certain ethnic and religious types – the Christian wife of the ruler Isa Celebina, and the doctor from Constantinople, the Jew Kir Moshe
