Operator method in solving non-linear equations of the Hartree-Fock type

The operator method is used to construct the solutions of the problem of the polaron in the strong coupling limit and of the helium atom on the basis of the Hartree-Fock equation. $E_0=-0.1085128052\alpha^2$ is obtained for the polaron ground-state energy. Energies for 2s- and 3s-states are also calculated. The other excited states are briefly discussed.Comment: 7 page

Hiatal hernia surgery: laparoscopic versus robotic approach?

Aim. Evaluate the advantages and disadvantages of laparoscopic and robot-assisted anti-reflux operations.General findings. Reflux esophagitis in the association with hiatal hernia on the third place in the structure of gastroenterological diseases. The development of minimally invasive surgical technologies has led to an increase in the number of laparoscopic and robot-assisted anti-reflux operations. The literature review includes 12 studies, the results of which were published from 2002 to 2020, with a total number of patients 1633. In most of them, when comparing laparoscopic and robot-assisted anti-reflux operations, the advantages of one or another technique were not revealed. In some studies, the high cost and duration of the operation were noted when using the da Vinci robotic surgical complex. Other studies have reported possible improvements in the treatment outcomes of patients with large or recurrent hiatal hernias due to the high precision of movement and improved visualization characteristic of therobot-assisted surgeries.Conclusion. It is necessary to conduct more researches on this problem to develop indications for the choice of a particular surgical approach, as well as to create a single transparent algorithm for the surgical treatment of patients with reflux esophagitis and hiatal hernia

X-ray sources of nanosecond pulses based on semiconductor opening switch for CT

This study describes the development of prototype CT scanners with 2 different pulsed X-ray sources. X-ray sources used in this work have a semiconductor opening switch. It is used to generate high voltage pulses and provides pulse repetition frequency up to 5 kHz. The work uses two pulsed X-ray sources, which have different peak voltages and pulse energies. Tomographic sections and 3D images for test objects are obtained, the advantages of pulsed X-ray sources compared to continuous sources are discussed. © 2020 American Institute of Physics Inc.. All rights reserved.he research is supported by the Russian Science Foundation (RSF), grant № 18-79-00020

THE TREATMENT OF INFECTIOUS COMPLICATIONS AFTER HIP REPLACEMENTV

Purpose of the study – to estimate the effectiveness of periprosthetic infection of the hip using different modifications of spacers. Material and methods. The authors analyzed treatment outcomes of 168 patients with clinical and laboratory signs of infection after hip replacement. Patients were divided into two groups: 87 patients (control group) underwent a standard two-stage revision hip joint arthroplasty with a spacer; 81 patients (test group) underwent preoperative examination procedure suggested by authors that was the basis for future selection of surgical technique using various spacers and customized follow up treatment. Results. The authors observed in test group a marked reduction of microbial contamination of periprosthetic tissue: 1 month after spacer implantation the test group features four times less pathogens as compared to control group. Need for re-revision was decreased by 1.8 times, twofold decrease in need for spacer revision after secondary examination, 1,4 less duration of hospital stay and 1,8 less disability duration was observed as compared to outcomes in control group after standard treatment approach. Functional outcomes of patients in test group in 6 months after secondary examination in regard of infectious complication after hip replacement were characterized by better Harris Hip scores as compared to control group. 6-12 months after revision the patients of test group were 1.3 times less reporting limitations of functional activity, twice less using support means and 2.2 times less needed pain medication. Conclusion. Complex treatment that includes preoperative examination, evaluation of bone defect volume, algorithm of choosing the antibiotic spacer type and its implantation technique as well as customized postoperative follow up treatment was proved to be efficient and results in stable eradication of chronic suppurative inflammation

Neutral and non-neutral collisionless plasma equilibria for twisted flux tubes: the Gold-Hoyle model in a background field

We calculate exact one-dimensional collisionless plasma equilibria for a continuum of flux tube models, for which the total magnetic field is made up of the “force-free” Gold-Hoyle magnetic flux tube embedded in a uniform and anti-parallel background magnetic field. For a sufficiently weak background magnetic field, the axial component of the total magnetic field reverses at some finite radius. The presence of the background magnetic field means that the total system is not exactly force-free, but by reducing its magnitude, the departure from force-free can be made as small as desired. The distribution function for each species is a function of the three constants of motion; namely, the Hamiltonian and the canonical momenta in the axial and azimuthal directions. Poisson's equation and Ampère's law are solved exactly, and the solution allows either electrically neutral or non-neutral configurations, depending on the values of the bulk ion and electron flows. These equilibria have possible applications in various solar, space, and astrophysical contexts, as well as in the laboratory

Target mass number dependence of subthreshold antiproton production in proton-, deuteron- and alpha-particle-induced reactions

Data from KEK on subthreshold \bar{\mrm{p}} as well as on $\pi^\pm$ and \mrm{K}^\pm production in proton-, deuteron- and $\alpha$-induced reactions at energies between 2.0 and 12.0 A GeV for C, Cu and Pb targets are described within a unified approach. We use a model which considers a nuclear reaction as an incoherent sum over collisions of varying numbers of projectile and target nucleons. It samples complete events and thus allows for the simultaneous consideration of all final particles including the decay products of the nuclear residues. The enormous enhancement of the \bar{\mrm{p}} cross section, as well as the moderate increase of meson production in deuteron and $\alpha$ induced compared to proton-induced reactions, is well reproduced for all target nuclei. In our approach, the observed enhancement near the production threshold is mainly due to the contributions from the interactions of few-nucleon clusters by simultaneously considering fragmentation processes of the nuclear residues. The ability of the model to reproduce the target mass dependence may be considered as a further proof of the validity of the cluster concept.Comment: 9 pages, 4 figure

Oxidation Of Adenosine And Inosine: The Chemistry Of 8-oxo-7,8-dihydropurines, Purine Iminoquinones, And Purine Quinones As Observed By Ultrafast Spectroscopy

Oxidative damage to purine nucleic acid bases proceeds through quinoidal intermediates derived from their corresponding 8-oxo-7,8-dihydropurine bases. Oxidation studies of 8-oxo-7,8-dihyroadenosine and 8-oxo-7,8-dihydroinosine indicate that these quinoidal species can produce stable cross links with a wide variety of nucleophiles in the 2-positions of the purines. An azide precursor for the adenosine iminoquinone has been synthesized and applied in ultrafast transient absorption spectroscopic studies. Thus, the adenosine iminoquinone can be observed directly, and its susceptibility to nudeophilic attack with various nucleophiles as well as the stability of the resulting cross linked species have been evaluated Finally, these observations indicate that this azide might be a very useful photoaffurity labeling agent, because the reactive intermediate, adenosine iminoquinone, is such a good mimic for the universal purine base adenosine

Production of the 1S0 diproton in the pp -> pp pi0 reaction at 0.8 GeV

The pp -> pp pi0 differential cross section has been measured with the ANKE spectrometer at COSY-Juelich for pion cms angles between 0 and 15.4 degrees at a proton beam energy of 0.8 GeV. The selection of diproton pairs with an excitation energy E_{pp} < 3 MeV ensures that the final pp system is dominantly in the spin-singlet 1S0 state. The kinematics are therefore very similar to those of pp -> d pi+ but with different spin and isospin transitions. The results will thus provide a crucial extra test of pion production models in nucleon-nucleon collisions. The cross sections, which are over two orders of magnitude smaller than those of pp -> d pi+, show a forward dip, even stronger than that seen at lower energies. This behaviour is well reproduced in a theoretical model that includes P-wave Delta-N states.Comment: 10 pages, 5 eps figures, prepared using elsart.cl

Analysis of hadron production in nucleus-nucleus interactions up to and out of kinematical limit of free NN-collisions in the frame of FRITIOF model

In the framework of the modified FRITIOF model, the inclusive spectra of the cumulative $\pi ^0$-, $\pi ^-$-mesons and protons produced in the nucleus-nucleus interactions at 4.5 GeV/c/nucleon and 4.2 GeV/c/nucleon are calculated. It is shown that the model reproduces qualitatively, and in some cases quantitatively the main experimental regularities of $\pi$-mesons production, and "soft" part of the proton spectra. According to the model the production of the cumulative particles is connected with the mechanism of the "soft" nucleon-nucleon interaction.Comment: 12 pages, 11 figure