The diversity of carbon materials has allowed them to be used for fundamental and applied research to date. The newest modifications of carbon, such as nanodiamonds, graphene, fullerenes, and ...nanotubes, are of particular interest owing to their outstanding physical and chemical properties, as well as to prospects of their practical application in various fields of industry, from medicine to nanoelectronics. At the same time, one-dimensional forms of carbon, predicted in the 1960s, were underestimated because of imperfection of experimental tools 1–3.
•Nanometer silica films were synthesized by different methods and processed in hydrogen plasma.•Low-temperature luminescence excited by synchrotron radiation in VUV region was studied.•The conversion ...of hydrogen passivated emission centers was observed.•The luminescence of quantum dots was manifested in the emission spectra.
Optically active defects in modified silicon oxide films on a silicon substrate have been studied by low-temperature photoluminescence (PL) spectroscopy using excitation by synchrotron radiation in the vacuum ultraviolet region. Films of dry thermal silicon oxide obtained by treatment of stoichiometric SiO2 in hydrogen plasma, films of wet thermal silicon oxide, and films with low dielectric constant (so called "low-k" dielectrics) have been studied. Investigations of various type SiO2 films detect the PL centers, which can be conditionally divided into two groups. The first group includes intrinsic point defects, the different variants of oxygen-deficient centers (ODCs). The second group contains centers like the spatially confined excitons in silicon quantum dots (SiQDs). It is shown that SiQDs differ in spectral characteristics, are formed in different ways, due to the transformation and clustering of point defects such as E'-centers, ODC(I) and ODC(II). In this case, the size and spectral properties of quantum dots depend on the mechanism of their formation. Schemes for the conversion of these defects are proposed.
It was found that for wet films and nonstoichiometric SiOx films treated in hydrogen plasma, "metastable" centers ODC(I) and ODC(II) arise only under the action of synchrotron radiation in the region of interband or exciton absorption and then they decay because of radiative relaxation. The absence of stable ODC centers in these films is due to their clustering and the formation of SiQDs. In "low-k" mesoporous films, on the contrary, silicon quantum dots SiQDs are not formed, but ODC(I) and ODC(II) centers are clearly manifested. A scheme of electronic transitions upon indirect excitation of silicon quantum dots through exciton states of the SiO2 matrix is considered. The presented results demonstrate the possibility of controlling the optical properties of silicon thin-film structures by creating in them both oxygen-deficient point defects and quantum dots of various sizes.
Telomeres are special DNA-protein structures that are located at the ends of linear eukaryotic chromosomes. The telomere length determines the proliferation potential of cells. Telomerase is a key ...component of the telomere length maintenance system. While telomerase is inactive in the majority of somatic cells, its activity determines the clonogenic potential of stem cells as a resource for tissue and organism regeneration. Reactivation of telomerase occurs during the process of immortalization in the majority of cancer cells. Telomerase is a ribonucleoprotein that contains telomerase reverse transcriptase and telomerase RNA components. The RNA processing mechanism of telomerase involves exosome trimming or degradation of the primary precursor. Recent data provide evidence that the competition between the processing and decay of telomerase RNA may regulate the amount of RNA at the physiological level. We show that termination of human telomerase RNA transcription is dependent on its promoter, which engages with the multisubunit complex Integrator to interact with RNA polymerase II and terminate transcription of the human telomerase RNA gene followed by further processing.
The influence of the quality of welding thin steel sheets on the physical and mechanical properties of electric steel has been studied using Lamb waves. It is shown that Lamb waves excited in the ...zero symmetric mode are an effective source of information about the state of the material both in the welded joint of the plates and in the zone of base metal not affected by thermal influences. Markers of the quality of welded joints are determined. It is established that the most informative parameters are the phase velocity of a Lamb wave and its amplitude. Based on velocity measurements, macroscopic anisotropy of the acoustic properties of the material is found. It is assumed that the origin of this anisotropy is due to residual stresses arising in the technological process of processing steel sheets. The results obtained are of interest for specialized quality control of butt joints in thin steel sheets.
Over the past 20 years, programs to replace medium and high voltage oil-filled circuit breakers with modern sulfur hexafluoride (SF6) (medium and high voltage) and vacuum (medium voltage) circuit ...breakers have been implemented at the Mosenergo power plants. The SF6 and vacuum switching equipment has undeniable advantages over the oil-filled equipment. It is characterized by a much greater switching resource and higher reliability, while the absence of oil has a positive effect on the environmental situation. But most importantly, SF6 and vacuum circuit breakers clear faults much faster. However, in recent years, there have been some accidents at the Mosenergo M. Ya. Ufaev TÉTs-11 and TÉTs-12 cogeneration plants, associated with the breakdown of SF6 circuit breakers when clearing fault currents, the values of which were much lower than the switching capacities of the circuit breakers. In the course of the study, it was established that the breakdown of SF6 switching devices occurred due to a re-ignition of the arc inside the circuit breaker chamber during clearing, which, in turn, may result from a small distance between the terminals of the tripping elements inside the SF6 circuit breaker, as well as its fast response. An answer was received to a number of important questions, in particular, about the effect of the transient recovery voltage (TRV) on various types of circuit breakers, and why only the SF
6
circuit breakers were damaged. It was found that under the normal operating conditions, additional RC circuits had to be installed at the Mosenergo TÉTs-11, TÉTs-12, and TÉTs-16 cogeneration plants to suppress the TRV effect. While conducting the study, it became clear that the installation of the medium voltage circuit breakers requires additional testing of the circuit breakers themselves to ensure their ability to handle the TRV values generated at the installation site. Accordingly, it is necessary to analyze the parameters of the adjacent network and the switchgear itself in terms of the occurrence of possible resonant processes and the possibility of switching such processes using commercial circuit breakers.
BH3 mimetics represent a promising tool in cancer treatment. Recently, the drugs targeting the Mcl-1 protein progressed into clinical trials, and numerous studies are focused on the investigation of ...their activity in various preclinical models. We investigated two BH3 mimetics to Mcl-1, A1210477 and S63845, and found their different efficacies in on-target doses, despite the fact that both agents interacted with the target. Thus, S63845 induced apoptosis more effectively through a Bak-dependent mechanism. There was an increase in the level of Bcl-xL protein in cells with acquired resistance to Mcl-1 inhibition. Cell lines sensitive to S63845 demonstrated low expression of Bcl-xL. Tumor tissues from patients with lung adenocarcinoma were characterized by decreased Bcl-xL and increased Bak levels of both mRNA and proteins. Concomitant inhibition of Bcl-xL and Mcl-1 demonstrated dramatic cytotoxicity in six of seven studied cell lines. We proposed that co-targeting Bcl-xL and Mcl-1 might lead to a release of Bak, which cannot be neutralized by other anti-apoptotic proteins. Surprisingly, in Bak-knockout cells, inhibition of Mcl-1 and Bcl-xL still resulted in pronounced cell death, arguing against a sole role of Bak in the studied phenomenon. We demonstrate that Bak and Bcl-xL are co-factors for, respectively, sensitivity and resistance to Mcl-1 inhibition.
A producer strain of
Komagataella phaffii
of recombinant beluga whale (
Delphinapterus leucas
) chymosin with a productivity of 80 mg/L was obtained, and the physico-chemical properties of the enzyme ...were studied for possible use in the food industry. The specific activity of the recombinant beluga chymosin was 55 IMCU/mg, which is significantly lower than that of recombinant bovine chymosin. The beluga whale chymosin has a high nonspecific proteolytic activity, which impaired its properties and ruled out its used in the food industry. Apparently, the amino acid substitutions K221M and K294Q are critically important and lead to a lower binding of casein micelles to the recombinant chymosin of the beluga whale.
The upconversion luminescence (UCL) of nanocrystalline gadolinium oxide (Gd
2
O
3
) doped with Er
3+
and Yb
3+
ions has been studied in the temperature range of 90–400 K. The nanocrystals were ...synthesized by chemical vapor deposition and possessed a cubic crystalline structure with an average particle size within 48–57 nm. It is established that the USL intensity in the red (
4
F
9/2
→
4
I
15/2
transition in Er3+ ion) and green (
4
S
3/2
→
4
I
15/2
transition) spectral regions depends on the sample temperature and concentration of dopant ions, as well as on the additional structural defects (anion vacancies) created in the crystal lattice by the introduction of Zn
2+
ions or irradiation with high-energy (10 MeV) electrons. The luminescence efficiency and spectrum of the upconversion phosphor are determined by energy transfer processes.
The conversion of the energy absorbed by cubic Gd
2
O
3
nanocrystals doped with Er
3+
and codoped with Yb
3+
and Zn
2+
ions in a temperature range of 95–425 K is studied at various concentrations of ...dopants. The photoluminescence spectra confirm the ability of excitation energy transfer from the Gd
3+
ions or the matrix towards the Er
3+
ions. The population of upper excited states in the Er
3+
ions depends on the way of excitation, which cause the alterations in the probability of multiphonon relaxation from the excited states to the radiative levels. The kinetics of photoluminescence decay exhibit the possible energy transfer from anionic defects created by extra doping with Zn
2+
ions. The temperature dependences of the upconversion luminescence yield for emission lines of 560 and 660 nm are found to be different.
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