Femtosecond response of polyatomic molecules to ultra-intense hard X-rays.

X-ray free-electron lasers enable the investigation of the structure and dynamics of diverse systems, including atoms, molecules, nanocrystals and single bioparticles, under extreme conditions. Many imaging applications that target biological systems and complex materials use hard X-ray pulses with extremely high peak intensities (exceeding 1020 watts per square centimetre). However, fundamental investigations have focused mainly on the individual response of atoms and small molecules using soft X-rays with much lower intensities. Studies with intense X-ray pulses have shown that irradiated atoms reach a very high degree of ionization, owing to multiphoton absorption, which in a heteronuclear molecular system occurs predominantly locally on a heavy atom (provided that the absorption cross-section of the heavy atom is considerably larger than those of its neighbours) and is followed by efficient redistribution of the induced charge. In serial femtosecond crystallography of biological objects-an application of X-ray free-electron lasers that greatly enhances our ability to determine protein structure-the ionization of heavy atoms increases the local radiation damage that is seen in the diffraction patterns of these objects and has been suggested as a way of phasing the diffraction data. On the basis of experiments using either soft or less-intense hard X-rays, it is thought that the induced charge and associated radiation damage of atoms in polyatomic molecules can be inferred from the charge that is induced in an isolated atom under otherwise comparable irradiation conditions. Here we show that the femtosecond response of small polyatomic molecules that contain one heavy atom to ultra-intense (with intensities approaching 1020 watts per square centimetre), hard (with photon energies of 8.3 kiloelectronvolts) X-ray pulses is qualitatively different: our experimental and modelling results establish that, under these conditions, the ionization of a molecule is considerably enhanced compared to that of an individual heavy atom with the same absorption cross-section. This enhancement is driven by ultrafast charge transfer within the molecule, which refills the core holes that are created in the heavy atom, providing further targets for inner-shell ionization and resulting in the emission of more than 50 electrons during the X-ray pulse. Our results demonstrate that efficient modelling of X-ray-driven processes in complex systems at ultrahigh intensities is feasible.

Using lossy mode resonance for in situ measurement of the refractive index of a layer deposited on an optical fiber lateral surface.

We demonstrate an approach that allows for measurement of the real part of the refractive index (RI) and the thickness of the coating deposited on the cylindrical surface of a thinned optical fiber using a tin dioxide (SnO2) film as an example. While the layer is being synthesized, lossy mode resonances (LMRs) are observed in the transmission spectra of the fiber light guide at any particular wavelength at regular intervals. It is shown that there are at least two functions by which the RI of a film can be calculated from the obtained spectra.

[Psychological defense mechanism of elderly people having mild cognitive impairments.]

The article presents the results of psychological defense mechanism research of elderly persons group having mild cognitive impairments (51 persons). The leading defense mechanisms in this group were «reactive entity¼ and «denial¼. Reliable correlation between capacity of short-term memory, the MMSE test and «substitution¼, attention rate and «regression¼, leading psychological defense and indicators of anxiety, fear, depression and aggression of the studied group are found. The found correlation between defense tension and psychological parameters disclose features of intra personal adaptation of elderly persons having mild cognitive impairments. The received results can be used for psychological diagnostics and correction of emotional, personal and cognitive disorders of the elderly people.

[Preparation of cell walls of group A Streptococcus. Methods of disintegration, isolation and control]. / Poluchenie kletochnykh stenok streptokokka gruppy A. Metody dezintegratsii, vydeleniia i kontrolia

A method for disintegration of cells of group A streptococcus on the Edebeau extrusion press was developed. The level of disintegration was controlled by cell count in stained preparations, Coultier electronic counter and electron microscope. The streptococcus cell disintegration in the Edebeau extrusion press at a temperature of --40 degrees, a pressure of 3200 kg/cm2 and two cycles of the process was completed by 96-98%.