The mechanism of lesion formation by focused ultrasound ablation catheter for treatment of atrial fibrillation

Acoustical Physics - The application of therapeutic ultrasound for the treatment of atrial fibrillation (AF) is investigated. The results of theoretical and experimental investigation of ultrasound...     

Corpuscular Diagnosis of the Plasma of Penning Ion Sources

The results of the studies of the energy distribution and atomic-molecular composition of the ions emitted from two Penning ion sources are presented. The transitions between different discharge modes, when the operating pressure and voltage on the anode are changed, are investigated. The energy spectra and mass-charge spectra are measured and the dependences of the fraction of atomic ions on the discharge parameters are determined.     

Characterization of cylindrical ultrasonic transducers using acoustic holography

We present the results of studying the vibrational velocity distribution over the surface of cylindrical ultrasound transducers by acoustic holography. We describe two approaches for acoustic holography: the spatial spectrum method and the Rayleigh integral method. In the case of cylindrical sources the spectral method has a specific feature in comparison to the case of quasi-plane sources: small-scale spectrum components having the form of evanescent (nonpropagating) waves near the source, turn into propagating waves at a certain distance from the source. The use of such a mixed type of waves makes it possible to increase the holographic resolution. To conduct holography of cylindrical sources by the Rayleigh integral method, a modification consisting in the superimposing of boundaries on the integration region is proposed. We present the results of numerical simulation and physical experiments on holography of small cylindrical piezoelectric transducers. We demonstrate that the proposed methods of holography make it possible to recover the vibration structure of source surfaces up to order of the wavelength scales.     

Thin films of palladium oxide for gas sensors

Thin films of PdO obtained by thermal oxidation of Pd films in air in the temperature range of 240–800°C were characterized using fast electron diffraction, transmission electron microscopy, and optical spectroscopy. The PdO films were found to be non-stoichiometric. With increasing oxidation temperature, the deviation of the PdO film composition from the stoichiometric component ratio becomes less pronounced. The resistivity response of PdO films to the presence of ozone in air was studied for the first time and good prospects for using this material for gas sensors are demonstrated.     

Grafting Poly(3‐hexylthiophene) from Silicon Nanocrystal Surfaces: Synthesis and Properties of a Functional Hybrid Material with Direct Interfacial Contact

Hybrid functional materials (HFMs) comprised of semiconductor nanoparticles and conjugated polymers offer the potential of synergetic photophysical properties. We have developed HFMs based upon silicon nanocrystals (SiNCs) and the conductive polymer poly(3‐hexylthiophene) (SiNC@P3HT) by applying surface‐initiated Kumada catalyst transfer polycondensation (SI‐KCTP). One unique characteristic of the developed SiNC@P3HT is the formation of a direct covalent bonding between SiNCs and P3HT. The presented method for obtaining direct interfacial attachment, which is not accessible using other methods, may allow for the development of materials with efficient electronic communication at the donor–acceptor interfaces. Systematic characterization provides evidence of a core–shell structure, enhanced interfacial electron and/or energy transfer between the P3HT and SiNC components, as well as formation of a type‐II heterostructure.     

On global continuability of solutions of infinite-dimensional ordinary differential equations

We prove necessary and sufficient conditions for global in time existence of solutions of ordinary differential equations on infinite dimensional Banach spaces and manifolds under some natural additional hypotheses, in particular, for equations with right-hand sides, given on everywhere dense subsets of phase spaces.     

Expression of CAS9 Nuclease of the CRISPR/Cas Genome Editing System in the Filamentous Fungus Penicillium verruculosum

Moscow University Chemistry Bulletin - The cas9 gene of the Streptococcus pyogenes bacterium, which encodes Cas9 nuclease of the class 2 CRISPR/Cas system, is expressed in the filamentous fungus...     

Nonvariational time-dependent multiconfiguration self-consistent field equations for electronic dynamics in laser-driven molecules

A time-dependent multiconfiguration self-consistent field (TDMCSCF) scheme is developed to describe the time-resolved electron dynamics of a laser-driven many-electron atomic or molecular system, starting directly from the time-dependent Schrodinger equation for the system. This nonvariational formulation aims at the full exploitations of concepts, tools, and facilities of existing, well-developed quantum chemical MCSCF codes. The theory uses, in particular, a unitary representation of time-dependent configuration mixings and orbital transformations. Within a short-time, or adiabatic approximation, the TDMCSCF scheme amounts to a second-order split-operator algorithm involving generically the two noncommuting one-electron and two-electron parts of the time-dependent electronic Hamiltonian. We implement the scheme to calculate the laser-induced dynamics of the two-electron H2 molecule described within a minimal basis, and show how electron correlation is affected by the interaction of the molecule with a strong laser field.     

Effects of single amino acid substitution on the dissociation of multiply charged multiprotein complexes in the gas phase

The effects of amino acid substitutions on the product ion charge distributions for protonated and deprotonated homogeneous and heterogeneous multiprotein complexes in the gas phase are studied using Fourier-transform mass spectrometry and the blackbody infrared radiative dissociation technique. Notably, it is shown that a single amino acid substitution in the leaving subunit can cause a small but measurable change in product ion charge distribution. Evidence that the degree of charge enrichment of the leaving subunit is influenced by the number of strongly basic or acidic residues within the subunit for the protonated and deprotonated complexes, respectively, is reported.