Design of a High-Q Diamond-Loaded Cavity for a Third-Harmonic Subterahertz Gyrotron Driven by a Low-Power Electron Beam

A continuous-wave (CW) high-harmonic gyrotron driven by a low-power electron beam is a compact radiation source demanded by terahertz applications. Its physical feasibility, however, is hampered by ohmic losses and mode competition in the gyrotron cavity. An ultralow-loss diamond loading of the cavity can give a clue to this problem. This article is concerned with theoretical aspects of mode selection and design for a gyrotron cavity loaded with coaxial rod made of chemical vapor deposition (CVD) diamond. As an example, the design of a high-Q diamond-loaded cavity for a third-harmonic 658-GHz gyrotron powered by a 0.1-A, 15-kV electron beam is presented. It is shown that the designed cavity enables the gyrotron to produce up to 116-W output power in a single oscillating mode

Difficulties of succession pipeline in large industrial enterprises of Nizhny Tagil in studies of tendencies of competitiveness of higher technical education

There have been significant changes in the higher education system in Russia recently. The possibility to apply for post-secondary education to several universities according to the results of the Unified State Examination (USE) and the transition to the two-level structure of higher education have significantly changed the landscape of competitiveness not only between individual universities, but also between large cities, which have become centers of mass attraction of applicants and young specialists. The number of students studying federally funded has been decreasing over the years. As a result, regional universities suffer a shortage of applicants, while local industrial enterprises suffer a shortage of young qualified personnel. The described problems are fully demonstrated in the system of higher education and training of young engineering personnel for large industrial enterprises in Nizhny Tagil. The article reviews the results of the study on the motivational field of academic migration of young people from the Nizhny Tagil city, conducted in February-March 2020. © Published under licence by IOP Publishing Ltd

To the issue of transformation of 'old industrial area' geobrand through example of Sverdlovsk Region

The authors of the article present the results of theoretical and methodological review of term 'old industrial area', in the result of which its features and identical problems of functioning were identified. Similarity of such regions is demonstrated in correlation of economic downfall with level of social strain; difficulty of industrial fields transformation; disinclination to accessibility of innovations; imperfection of financial institutions and problems of industrial heritage valorization. Transformation of 'old industrial area' is considered through example of Sverdlovsk Region. The authors defined several directions of its implementation and explained geotransformation of the considered region from a historically developed image of a 'state stronghold' to the image of developing region with modern capital acquiring features of international metropolitan city. The article describes formation of new dynamically developing image of 'capital area' for Sverdlovsk Region having innovative path of evolution in terms of ability to engage young people both from different parts of Russia and various countries. Taking into account a number of facts it is also the evidence that intensification of trend of migration to the capital of Sverdlovsk Region for educational reasons is directly related to its image of a big city. © Published under licence by IOP Publishing Ltd

Inelastic scattering of photoelectrons from He nanodroplets

We present a detailed study of inelastic energy-loss collisions of photoelectrons emitted from He nanodroplets by tunable extreme ultraviolet (XUV) radiation. Using coincidence imaging detection of electrons and ions, we probe the lowest He droplet excited states up to the electron impact ionization threshold. We find significant signal contributions from photoelectrons emitted from free He atoms accompanying the He nanodroplet beam. Furthermore, signal contributions from photoionization and electron impact excitation/ionization occurring in pairs of nearest-neighbor atoms in the He droplets are detected. This work highlights the importance of inelastic electron scattering in the interaction of nanoparticles with XUV radiation

Algorithm for management of patients with X-ray endovascular artery embolization of the prostate for its benign hyperplasia

X-ray endovascular prostatic artery embolization (XEPAE) is a comparatively new alternative treatment for benign prostatic hyperplasia (BPH), which has shown good results in Russia and foreign countries. The dissimilarity from other treatments for this nosology is the use of superselective artery ischemia of the prostate, which leads to a decrease in its sizes and a progressive reduction in lower urinary tract symptoms. Twelve patients aged 59–71 years (mean age, 66 years) with BPH have been operated on since 2014. The mean follow-up period was 8.4 months (3–17 months). The patients were divided into 3 groups in accordance with prostate volume: 1) 60–100 cm3 (n = 3); 2) 100–200 сm3 (n = 5); 3) ≥ 200 см3 (n = 4). The mean prostatic specific antigen level was 5.1 ± 2.7 ng/ml (2.7–6.3 ng/ml). Due to the increased pro static specific antigen level up to 4 ng/ml, 6 patients underwent transrectal and/or targeted biopsy of the prostate, which failed to reveal the morphological signs of its malignant process. The examination algorithm included all necessary laboratory and clinical examinations, as those during surgery for BPH, as well as multislice spiral computed tomography and/or magnetic resonance imaging, angiography of small pelvic vessels and organs.  Postoperative patient monitoring revealed that the total International Prognostic Scoring System scores decreased by 41.3 and 61.4 % at 3- and 6-month follow-ups, respectively; then these values were insignificant. The prostate volume substantially decreased at 3 months; but at 6 months it was 47 % of the baseline one. The urine flow rate rose from 6.7 to 15.9 ml/sec. The quality of life index became summarily quite satisfactory at 6-month follow-up and amounted to 3.3 ± 1.3. Thus, it may be stated that XEPAE is a safe and highly effective treatment for BPH if its medical treatment is ineffective. This surgical treatment performed for 3–6 months substantially decreases the prostate, normalizes urination, and restores quality of life. Patients with severe comorbidity and a high operative-anesthetic risk should be a promising area in the use of this technique. Patients with cystostome and preserved bladder capacity and those with acute urinary retention in the presence of BPH will serve as important additional areas in the application of XEPAE

Real-time dynamics of the formation of hydrated electrons upon irradiation of water clusters with extreme ultraviolet light

Free electrons in a polar liquid can form a bound state via interaction with the molecular environment. This so-called hydrated electron state in water is of fundamental importance e.g.~in cellular biology or radiation chemistry. Hydrated electrons are highly reactive radicals that can either directly interact with DNA or enzymes, or form highly excited hydrogen (H∗) after being captured by protons. Here, we investigate the formation of the hydrated electron in real-time employing XUV femtosecond pulses from a free electron laser, in this way observing the initial steps of the hydration process. Using time-resolved photoelectron spectroscopy we find formation timescales in the low picosecond range and resolve the prominent dynamics of forming excited hydrogen states

Penning Spectroscopy and Structure of Acetylene Oligomers in He Nanodroplets

Embedded atoms or molecules in a photoexcited He nanodroplet are well-known to be ionized through inter-atomic relaxation in a Penning process. In this work, we investigate the Penning ionization of acetylene oligomers occurring from the photoexcitation bands of He nanodroplets. In close analogy to conventional Penning electron spectroscopy by thermal atomic collisions, the n = 2 photoexcitation band plays the role of the metastable atomic $1s2s$ $^{3,1}S$ He$^\ast$. This facilitates electron spectroscopy of acetylene aggregates in the sub-kelvin He environment, providing the following insight into their structure: The molecules in the dopant cluster are loosely bound van der Waals complexes rather than forming covalent compounds. In addition, this work reveals a Penning process stemming from the n = 4 band where charge-transfer from autoionized He in the droplets is known to be the dominant relaxation channel. This allows for excited states of the remnant dopant oligomer Penning-ions to be studied. Hence, we demonstrate Penning ionization electron spectroscopy of doped droplets as an effective technique for investigating dopant oligomers which are easily formed by attachment to the host cluster.Comment: 22 pages, 1 png figure, 4 postscript figure

Large-scale template-based structural modeling of T-cell receptors with known antigen specificity reveals complementarity features

IntroductionT-cell receptor (TCR) recognition of foreign peptides presented by the major histocompatibility complex (MHC) initiates the adaptive immune response against pathogens. While a large number of TCR sequences specific to different antigenic peptides are known to date, the structural data describing the conformation and contacting residues for TCR-peptide-MHC complexes is relatively limited. In the present study we aim to extend and analyze the set of available structures by performing highly accurate template-based modeling of these complexes using TCR sequences with known specificity. MethodsIdentification of CDR3 sequences and their further clustering, based on available spatial structures, V- and J-genes of corresponding T-cell receptors, and epitopes, was performed using the VDJdb database. Modeling of the selected CDR3 loops was conducted using a stepwise introduction of single amino acid substitutions to the template PDB structures, followed by optimization of the TCR-peptide-MHC contacting interface using the Rosetta package applications. Statistical analysis and recursive feature elimination procedures were carried out on computed energy values and properties of contacting amino acid residues between CDR3 loops and peptides, using R.ResultsUsing the set of 29 complex templates (including a template with SARS-CoV-2 antigen) and 732 specificity records, we built a database of 1585 model structures carrying substitutions in either TCRα or TCRβ chains with some models representing the result of different mutation pathways for the same final structure. This database allowed us to analyze features of amino acid contacts in TCR - peptide interfaces that govern antigen recognition preferences and interpret these interactions in terms of physicochemical properties of interacting residues.ConclusionOur results provide a methodology for creating high-quality TCR-peptide-MHC models for antigens of interest that can be utilized to predict TCR specificity

Delocalized nonlinear vibrational modes in graphene: second harmonic generation and negative pressure

With the help of molecular dynamics simulations, delocalized nonlinear vibrational modes (DNVM) in graphene are analyzed. Such modes are dictated by the lattice symmetry, they are exact solutions to the atomic equations of motion, regardless the employed interatomic potential and for any mode amplitude (though for large amplitudes they are typically unstable). In this study, only one‐ and two‐component DNVM are analyzed, they are reducible to the dynamical systems with one and two degrees of freedom, respectively. There exist 4 one‐component and 12 two‐component DNVM with in‐plane atomic displacements. Any two‐component mode includes one of the one‐component modes. If the amplitudes of the modes constituting a two‐component mode are properly chosen, periodic in time vibrations are observed for the two degrees of freedom at frequencies ω and 2ω, that is, second harmonic generation takes place. For particular DNVM, the higher harmonic can have frequency nearly two times larger than the maximal frequency of the phonon spectrum of graphene. Excitation of some of DNVM results in the appearance of negative in‐plane pressure in graphene. This counterintuitive result is explained by the rotational motion of carbon hexagons. Our results contribute to the understanding of nonlinear dynamics of the graphene lattice

SYNTHESIS OF N,S-CONTAINING COMPOUNDS USING (ISO)THIOCYANIC ACID SURROGATES

This work was supported by the Russian Science Foundation, project # 21-73-10212