After fixing the DNA molecule in the form of a double helix on the surface of a thickness shear mode resonator (QCM), mechanical oscillations at increasing amplitude cause detorsion of the helix. The force necessary for detorsion can be determined from the voltage applied to the QCM at the rupture moment. The high sensitivity of this method is due to the fact that measurements are carried out in the frequency region around the QCM resonance, where any (even very weak) distortions of the consistent oscillating system cause noticeable distortions of the amplitude-frequency dependence, and these distortions are used to fix the rupture moment. The measured rupture forces were within 30-40 pN, and the sensitivity was 10(8) molecules. It was demonstrated that the proposed procedure allows one to determine the factors that affect the stability of the DNA double helix. This procedure can be the basis for the development of a new method of rapid DNA analysis. Experiments performed with model DNA showed that it is possible to reveal complementarity between two DNA samples.

It is shown that an increase in the amplitude of QCM shear oscillations during frequency scanning around the resonance frequency is accompanied (at a definite voltage) by distortions in the amplitude-frequency dependence for QCM. We demonstrated that these distortions are connected to the rupture of macromolecules from the QCM surface. It is shown that the identification of the rupture of particles and macromolecules from the QCM surface can be carried out by relying on the analysis of these distortions of the amplitude-frequency dependence. The distortions were distinguished as a signal. The number of broken bonds can be estimated from the value of this distortion signal, and the threshold voltage applied to the system can be used to estimate the rupture force to high accuracy. Using the proposed method, we estimated the strength of a physical bond, which was 3 pN. This procedure can be useful for studying biological objects and represents an advanced step in the development of the REVS (rupture event scanning) technique.

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The main idea of the investigation was to define testing parameters with the lowest influence of internal and external diffusion on catalytic activity in hydrodesulfurization of dibenzothiophene. Traditional experimental methods were used to determine the conditions for the influence of internal and external diffusion. Simultaneous change of a linear feedstock rate and a catalyst loading at constant weight hour space velocity were used to determine the process temperature (240–260 °C) at which the impact of external diffusion is minimal. Catalytic tests, including the variation of the catalyst fraction size, were carried out to define the conditions with the lowest influence of internal diffusion. It was found that when the catalyst with the fraction size of 0.1–0.25 mm was used, the fluctuation of sulfur conversion was the smallest. Besides, to validate experimental results, the calculations were performed with mass balance equations and expressions used for HDS modeling. The resulting data and catalytic experiments demonstrated that the lowest influence of internal and external diffusion is achieved at a temperature process less than 260 °C and a catalyst fraction of 0.1–0.25 mm.

We describe the new procedure developed to determine the functional groups on the surface of nanoparticles formed in photonucleation of furfural, one of the aldehydes generated during forest fire events. The procedure is based on the detection of nanoparticle rupture from chemically modified surface of the quartz crystal microbalance oscillating in the thickness shear mode under voltage sweep. The rupture force is determined from the voltage at which the rupture occurs. It depends on particle mass and on the affinity of the surface functional groups of the particle to the groups that are present on the modified QCM surface. It was demonstrated with the amine modification of the surface that the nanoparticles formed in furfural photonucleation contain carbonyl and carboxyl groups. The applicability of the method for the investigation of functional groups on the surface of the nanoparticles of atmospheric aerosol is demonstrated.