Diamond-based HBAR as a high-pressure sensor.

Features of an application of a High-overtone Bulk Acoustic Resonator (HBAR) as a high-pressure sensor have been considered. In this way, the second version of an integrated measurement system combining a Diamond Anvil Cell (DAC) and an HBAR operating in the microwave frequency band from 1.3 to 3.7 GHz was developed. A specific configuration of HBAR based on a piezoelectric layered structure as "Al/ASN/Mo/(100) diamond" was proposed. Two independent methods of pressure control were used to calibrate the embedded HBAR as a pressure sensor: a stress-induced shift of the diamond Raman line and the shift of the R1 luminescence line of Cr3+ in the ruby matrix. A stable correlation between the frequency shifts of the acoustic overtones in the HBAR, the shift of the diamond Raman line and the shift of the R1 line with a change in pressure applied to the W-gasket with embedded ruby particles was established in the range of 0 … 30 GPa. The sensitivity of an investigated sensor to the pressure variation was found to be equal 1ΔPΔff=4.8∙10-4GPa-1. The maximal value of 30 GPa obtained in a given work can be easily increased after a minor reconfiguration of the DAC. Considering the range of 0 - 5 GPa a proposed built-in DAC acoustoelectronic sensor has the better performance and sensitivity compared with known methods of a pressure measurement.

[Biological aspects of treatment resistance in psychiatry and pharmacodynamic approaches to its management]. / Biologicheskie predposylki formirovaniya lekarstvennoi rezistentnosti v psikhiatrii i farmakodinamicheskie podkhody k ee preodoleniyu.

Treatment resistance is a persistent neurochemical condition characterized by the presence of «hybrid¼ metabolism, which combines both pathological and drug-dependent metabolisms. The difficulties in management and prevention of treatment resistance are associated with a lack of understanding of neurochemical aspects of the development of higher mental functions. The authors suggest that the basic types of species-preserving behavior are associated with the activity of monoaminergic systems while the modulation of their activity is predetermined by local neuronal networks in the rostral parts of the brain, where a variety of co-transmitters play an important role. It is emphasized that the mechanisms of the development of resistance after previous treatment with agonists (antidepressants, anxiolytics) or antagonists (antipsychotics) are different. Depending on drug actions on synaptic transmission, methodological aspects of treatment resistance management by means of «polar therapy¼, «sensitization¼ and combination strategies are considered.

Toward the Ultra-incompressible Carbon Materials. Computational Simulation and Experimental Observation.

The common opinion that diamond is the stiffest material is disproved by a number of experimental studies where the fabrication of carbon materials based on polymerized fullerenes with outstanding mechanical stiffness was reported. Here we investigated the nature of this unusual effect. We present a model constituted of compressed polymerized fullerite clusters implemented in a diamond matrix with bulk modulus B0 much higher than that of diamond. The calculated B0 value depends on the sizes of both fullerite grain and diamond environment and shows close correspondence with measured data. Additionally, we provide results of experimental study of atomic structure and mechanical properties of ultrahard carbon material supported the presented model.

Polymerization of nitrogen in sodium azide.

The high-pressure behavior of nitrogen in NaN(3) was studied to 160 GPa at 120-3300 K using Raman spectroscopy, electrical conductivity, laser heating, and shear deformation methods. Nitrogen in sodium azide is in a molecularlike form; azide ions N(3-) are straight chains of three atoms linked with covalent bonds and weakly interact with each other. By application of high pressures we strongly increased interaction between ions. We found that at pressures above 19 GPa a new phase appeared, indicating a strong coupling between the azide ions. Another transformation occurs at about 50 GPa, accompanied by the appearance of new Raman peaks and a darkening of the sample. With increasing pressure, the sample becomes completely opaque above 120 GPa, and the azide molecular vibron disappears, evidencing completion of the transformation to a nonmolecular nitrogen state with amorphouslike structure which crystallizes after laser heating up to 3300 K. Laser heating and the application of shear stress accelerates the transformation and causes the transformations to occur at lower pressures. These changes can be interpreted in terms of a transformation of the azide ions to larger nitrogen clusters and then polymeric nitrogen net. The polymeric forms can be preserved on decompression in the diamond anvil cell but transform back to the starting azide and other new phases under ambient conditions.