Diazatriphenylenes and their thiophene analogues: Synthesis and applications

This review highlights the recent advances in the field of the synthesis of diazatriphenylenes and their structural analogues, such as phenanthrenes, fused with the thiophene ring, and naphthalenes, condensed with two thiophene rings. Also applications of these compounds are considered. © ARKAT USA, Inc.The research was financially supported by the Russian Science Foundation (Project No. 16-13-10435) and the Russian Foundation for Basic Research (research project №. 17-03-00011-А)

Synthesis of Heteroannulated Indolopyrazines through Domino N-H Palladium-Catalyzed/Metal-Free Oxidative C-H Bond Activation

A convenient approach to [1,2,5]oxadiazolo[3′,4′:5,6]pyrazino[2,3-b]indoles and their heteroannulated analogues bearing various aryl substituents in the backbone has been developed. This synthetic protocol is based on Pd-catalyzed Buchwald-Hartwig and subsequent annulation by intramolecular oxidative cyclodehydrogenation. The photophysical properties for new polycycles have been measured. © 2020 American Chemical Society.Russian Foundation for Basic Research, RFBR: 18-29-23045, 18-33-00103-mol_aThis work was supported by the Russian Foundation for Basic Research (research project no. 18-29-23045 mk). Y.A.K. would like to acknowledge the financial support for the part of the synthetic section from the Russian Foundation for Basic Research (research project no. 18-33-00103-mol_a)

APPLICATION OF AZAHETEROCYCLIC PUSH-PULL SYSTEMS AS FLUORESCENT SENSORS AND SENSITIZERS FOR SOLAR CELLS

This work was supported by the Russian Science Foundation (Project No. 18-13-00409)

Azaheterocyclic push-pull chromophores: synthesis, photophysical properties and applications as fluorescent sensors

The recently obtained data on functionalization of pyrimidine [1–9] and pyrazine [10–12] derivatives by Suzuki or transition metal-free cross-coupling reactions will be presented. Due to the significant π-deficient character of azaheterocyclic moiety, they can be used as electron-withdrawing group in push-pull structures in which intramolecular charge transfer process occurs (figure). The photophysical properties for such fluorophores have been investigated using absorption and emission spectral analyses, both in solution and in solid-state. Some dyes exhibit strong emission solvatochromism (up to 200 nm) and possess high quantum yields, depending on their molecular structure and solvent polarity. Meanwhile, fluorescence studies have shown that emission of this fluorophores is sensitive towards various nitroaromatic compounds, either in solutions or in a vapor phase. Thus, these compounds can be regarded as promising multifunctional chemosensors.This work was supported by the Russian Foundation for Basic Research (Research Project № 18-29-23045 мк)

Quasi free-standing one-dimensional nanocrystals of PbTe grown in 1.4 nm SWNTs

Here, we show successful filling of 1.4 nm single-walled carbon nanotubes (SWNT) with PbTe nanocrystals. The structure of one-dimensional PbTe in SWNT was determined using high-resolution transmission electron microscopy (HRTEM). The electronic structure of composites was studied by optical absorbance and Raman spectroscopies indicating no noticeable interaction of encapsulated PbTe with SWNT wall. Experimental data are supported by ab-initio calculations, showing non-zero density of states at the Fermi level of PbTe@SWNT(10,10) provided by both SWNT and PbTe states and thus metallic conductivity of the composite

Acute ischemic stroke lesion segmentation in non-contrast CT images using 3D convolutional neural networks

In this paper, an automatic algorithm aimed at volumetric segmentation of acute ischemic stroke lesion in non-contrast computed tomography brain 3D images is proposed. Our deep-learning approach is based on the popular 3D U-Net convolutional neural network architecture, which was modified by adding the squeeze-and-excitation blocks and residual connections. Robust pre-processing methods were implemented to improve the segmentation accuracy. Moreover, a specific patches sampling strategy was used to address the large size of medical images, to smooth out the effect of the class imbalance problem and to stabilize neural network training. All experiments were performed using five-fold cross-validation on the dataset containing non-contrast computed tomography volumetric brain scans of 81 patients diagnosed with acute ischemic stroke. Two radiology experts manually segmented images independently and then verified the labeling results for inconsistencies. The quantitative results of the proposed algorithm and obtained segmentation were measured by the Dice similarity coefficient, sensitivity, specificity and precision metrics. Our proposed model achieves an average Dice of $0.628\pm0.033$, sensitivity of $0.699\pm0.039$, specificity of $0.9965\pm0.0016$ and precision of $0.619\pm0.036$, showing promising segmentation results.Comment: 18 pages, 4 figures, 2 table