Direct biexciton generation in Si nanocrystal by a single photon.

It has been shown theoretically that a strong quantum confinement regime in Si nanocrystals promotes highly efficient simultaneous excitation of two electron-hole pairs (biexciton) by a single photon. The rate (inverse lifetime) of biexciton generation has been calculated analytically as a function of the nanocrystal radius. The size-dependence of the rate in Si nanocrystal turns out to be sharp enough-in fact, it is inversely proportional to the sixth power of the radius.

Extreme ultraviolet Fourier-transform spectroscopy with high order harmonics.

We demonstrate a new scheme for extreme ultraviolet (xuv) Fourier-transform spectroscopy based on the generation of two phase-locked high-harmonic beams. It allows us to measure for the first time interferograms at wavelengths as short as 90 nm, and open the perspective of performing high-resolution Fourier-transform absorption spectroscopy in the xuv. Our measurements also demonstrate that a precise control of the relative phase of harmonic pulses can be obtained with an accuracy on an attosecond time scale, of importance for future xuv pump-xuv probe attosecond spectroscopy.

Nonlinear excitation of the Mie resonance in a laser-irradiated cluster.

The nonlinear collective electron dynamics inside a large heated cluster irradiated by a strong linearly polarized short laser pulse are considered in the approximation of an incompressible medium. When the incident radiation frequency is near three-photon resonance with the Mie frequency, the field inside the cluster exhibits a third harmonic with an amplitude comparable with that of the fundamental. In the same parameter range, due to shielding, the field inside the cluster at the fundamental frequency is strongly reduced with respect to the incident field.

[Relaxant effects of oligopeptides isolated from the tracheal mucosa and pulmonary parenchyma on the smooth muscle of isolated rat trachea].

Relaxant effect of oligopeptides extracted from tracheal mucosa (PTM), lung parenchyma (PLP), aortal wall (PAW) and thymic gland (PTG) was investigated using acetylcholine-induced constriction of tracheal strips. Time of 50 percent relaxation of constricted strips treated with saline, atropine or peptides was measured. Both PTM and PLP in concentrations 10(-6)-10(-3) g/ml accelerated relaxation in dose-dependent manner, however this effect was less prominent compared with atropine.

[Treatment of epilepsy in children with regard to the functional asymmetry of cerebral hemispheres].

Altogether 40 children suffering from epilepsy with a focus of epileptic activity in the right hemisphere were treated. Analysis is made of the dependence of the efficacy of benzonal and finlepsin on the individual characteristics of functional asymmetry of the brain hemispheres. Benzonal turned out effective in the treatment of the right-handed with the dominant by speech left hemisphere.