Silicon-Based Avalanche Photodiodes: Advancements and Applications in Medical Imaging.

Avalanche photodiodes have emerged as a promising technology with significant potential for various medical applications. This article presents an overview of the advancements and applications of avalanche photodiodes in the field of medical imaging. Avalanche photodiodes offer distinct advantages over traditional photodetectors, including a higher responsivity, faster response times, and superior signal-to-noise ratios.

Single-Element 2D Materials beyond Graphene: Methods of Epitaxial Synthesis.

Today, two-dimensional materials are one of the key research topics for scientists around the world. Interest in 2D materials is not surprising because, thanks to their remarkable mechanical, thermal, electrical, magnetic, and optical properties, they promise to revolutionize electronics. The unique properties of graphene-like 2D materials give them the potential to create completely new types of devices for functional electronics, nanophotonics, and quantum technologies.

Interaction specificity of benzimidazol group compounds with AT-containing polynucleotides.

The interaction between polynucleotides: poly(dA)-poly(dT), poly(dA-dT), poly(am2dA-dT), and the AT-specific compounds of benzimidazol group has been studied. It is been shown that these compounds bind to poly(dA)-poly(dT) and poly(dA-dT) at low and high salt concentration in solution. Poly(am2dA-dT) interacts with AT-specific compounds only at low salt, where this polynucleotide is in a B-form, but not at high salt, when the polynucleotide converts to another conformation.

A study of interactions of platinum (II) compounds with DNA by means of CD spectra of solutions and liquid crystalline microphases of DNA.

The optical properties of the DNA complexes with divalent platinum compounds of the cis-diamine type differing both in the nature of anionic and neutral ligands and in the spatial arrangement about the platinum atom were studied. The platinum compounds cis-[Pt(NH3)2Cl2], [Pt(en)Cl2], [Pt(tetrameen)Cl2], cis-[Pt(NH3)2NO2Cl], and cis-[PtNH3(Bz)Cl2] at small values of r (r is the molar ratio of a platinum compound to DNA nucleotides in the reaction mixture) were found to induce an increase in the amplitude of the positive band in the circular dichroic (CD) spectrum of linear DNA. All the compounds listed except cis-[Pt(NH3)2NO2Cl] caused a sharp decrease of the amplitude of the negative band in the CD spectrum of a liquid crystalline microphase of DNA formed in solution in the presence of poly(ethylene glycol).

["External chromophores" and intensive bands in circular dichroism spectra of liquid-crystalline microphases of nucleic acids].

From the analysis of CD-spectra of liquid crystalline microphases formed from DNA molecules in complexes with "external chromophores" requirements are formulated for the compounds to be used in revealing peculiarities of spatial structure of nucleic acids liquid crystalline microphases. These requirements satisfied it is possible to record the CD-spectra having intensive bands in the regions of chromophores absorption. These bands prove the helical pattern of the spatial structure of nucleic acid liquid crystalline microphase.

[Optical properties of DNA complexes with antitumor compounds of bivalent platinum].

The optical properties of the DNA complexes with the compounds of bivalent platinum were studied. The compounds differed by the nature of the anionic and neutral ligands and their spatial arrangement about the platinum atom. It was shown that the same as cis-[Pt (NH3)2Cl2] the platinum compounds with the biological activity, i.

[Effect of biologically active compounds of divalent platinum on the properties of the liquid crystal "microphase" of DNA].

The optical properties of the "microphases" modeling the state of the DNA molecule in the cell and formed of both the low molecular DNA and the DNA complexes with cis- and trans-isomers of dichlorodiamine platininum (II) were studied. It was shown that the intensive band characteristic of the circular dichroism spectrum of the initial DNA "microphase" was decreasing with binding of DNA to cis-Pt (II) or trans-Pt (II). The effect of cis-Pt (II) on the "microphase" optical properties was more significant than that of trans-Pt (II).

Liquid crystalline microphases of DNA molecules complexed with compounds of platinum(II).

The formation of liquid crystalline microphases (0.3 M NaClO4, and 120 and 170 mg PEG/ml) from low-Mr DNA (salmon sperm) complexed with cis and trans dichlorodiamine-platinum(II) was investigated. It was shown that the amplitude of the negative band in the CD spectrum, characteristic of a liquid crystalline microphase of DNA, decreased upon complexing with platinum compounds.

A compact from of methylated DNA is solutions containing poly (ethylene glycol).

Some peculiarities of compactization of double-stranded DNA molecules containing methylated nitrogen bases have been studied in water-salt solutions of PEG. It is shown that the methylation of N7-atoms of guanyl residues in original DNA molecules does not prevent the formation of DNA compact particles, but results in a decrease of the amplitude of the negative band in the CD spectrum of compact particles. The influence of N7-guanine methylation on the shape of the CD spectrum being the greater, the lower is the concentration of PEG.

[Compact form of DNA in solution. X. Peculiarities of circular dichroism spectra of DNA compact particles forming polyethylene glycol-containing water-salt solutions].

The experimental data indicating that the amplitude of the negative band in CD spectra of DNA compact particles forming in PEG-containing water-salt solutions intensifies with the decrease of DNA molecular weight are presented. This effect is not explained by the light scattering on the compact particles. The presence of the negative band in CD spectrum of DNA compact particles is interpreted as result of formation of dichrographic-active "microcrystalline" region ("domains") (if DNA compact particles are formed from double-stranded molecules with unaltered secondary structure); it is also supposed that the number of these regions in the particle and their dichrographic activity doesn't depend on the particles size.

[DNA compact form. 8. X-ray diffraction study of DNA compact particles, formed in solutions containing polyethylene glycol].

A comparative X-ray study of DNA compact particles, formed in PEG-containing solution from native DNA and from DNA molecules with altered secondary structure was carried out. Low-angle reflections, present in X-ray patterns of compact particles (in powder form) from native DNA, correspond to spacings of 84, 42 and 35 A, while wide-angle reflections correspond to spacings of 12.8; 8.

[DNA compact form in solution. VII. Transforming activity of precompact forms of DNA].

Data on transforming activity of DNA in water-salt (0.3 M NaCl) solutions containing polyethylene glycol (PEG) are presented. Bacillus subtilis deficient mutant lys 42 and prototrophic strain SHgw were used as recipient and donor, respectively, for transformation experiments.

A comparative X-ray diffraction and circular dichroism study of DNA compact particles formed in water-salt solutions, containing poly(ethylene glycol).

Comparative CD and X-ray diffraction studies of DNA compact particules which were obtained in PEG-containing water-salt solutions, have been carried out. Compact particles, formed from native DNA, produce a psi CD spectrum (characterized by a negative band at lambda-270 nm) and a small-angle X-ray diffraction pattern, which shows two reflections: I at 34-40 A and II at 80-90 A (together with its second-order reflection). Compact particules, formed from DNA molecules with partially disordered secondary structure, do not produce the psi CD spectrum and the reflection I, while the reflection II remains unchanged.

[DNA compact form. VI. Changes of DNA secondary structure under conditions preceding its compaction in a solution].

Optical and thermochemical properties of E. coli DNA molecules are compared in solutions containing poly(ethyleneglycol) (PEG) in concentrations at which compactization is not yet observed. It is shown that under conditions preceding DNA compactization (CPEG less than 60 mg/ml) changes in CD spectra occur which suggest that the secondary structure of some DNA fragments is altered.

[The compact form of DNA in solution. V. The heat effect preceding compactization of double-chained DNA in PEG containing water-salt solutions].

DNA-dependent heat effects accompanying mixing of water-salt (0.3 M NaCl) solutions of PEG and DNA within the range of PEG 10-50 mg/ml at 25 degrees C were determined by the method of difference microcalorimetry. It was found that, unlike optical and hydrodynamical methods, microcalorimetry makes it possible to detect some changes of the DNA-PEG system preceding formation of compact particles of DNA.

[The compact form of DNA in solution. IV. The effect of secondary structure defectiveness on the arrangement of double-chained DNA molecules into compact particles].

Influence of pH on absorbance and CD-spectra of DNA in PEG-containing water-salt solutions has been studied. The changes in the spectra appeared due to disturbance of the DNA secondary structure upon acidification of the medium proir to or after DNA compactization. If acidification preceeds DNA compactization an intense negative band in the CD spectrum inherent to the compact particles is observed at pH values 7-4.