Computer simulation of high current vacuum arc with developed anode spot

A self-consistent simulation of anode heating by 4.5 kA vacuum arc during the half-wave of 50 Hz current with 1 m/s contact opening was carried out. The calculations were done in the framework of hybrid high current vacuum arc model, which treats ions and atoms as macroparticles with the help of particle-in-cell methods, but electron subsystem is treated as massless fluid with quasineutrality assumed. The occurrence of an anode plasma plume (similar to that found in experiments) was obtained as a result of modeling. It is shown that the energy flux of line radiation from the interelectrode plasma to the anode is a critical reason of the appearance and maintenance of the anode plume. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBRRussian Academy of Sciences, RAS: 1118-2-2-16This work was supported in part by RFBR (grants nos: 17-02-00346, 18-08-00547, 19-08-00783, 19-58-53006), by RAS Program (project no. 11) and UB RAS Program (project no. 18-2-2-16)

Modeling of plasma jet of vacuum arc with copper-chromium cathode under action of strong axial magnetic field

This paper deals with the computer simulation of a vacuum arc with composite cathode under action of external axial magnetic using hybrid model. The described hybrid model treats the electrons as a massless fluid and ions as macroparticles. It is shown that the average charge state of ions in a jet of a vacuum arc increases with increasing magnetic field. The calculation results are consistent with experimental data. © 2019 IOP Publishing Ltd. All rights reserved.Russian Science Foundation, RSF: 18-19-00069This work was supported by Russian Science Foundation (project No. 18-19-00069)

On Hybrid Type of Cathode Attachment in High Current Vacuum Arcs

This paper discusses the issues of a possible change of the type of cathode attachment of high-current vacuum arcs (HCVA) with an average cathode current density of more than 105 A/cm2. This type of HCVA is used as pumping plasma gun in experiments with plasma puff z-pinches. These experiments showed that the measured linear mass of the HCVA plasma jet is much higher (by a factor of 10 or more) than the expected mass, which can be obtained from the assumption that cathode attachment occurs only through a multitude of cathode spots emitting supersonic plasma jets. It is shown that in HCVA of the type under consideration, at some time instant there are two types of cathode attachments - cathode spots and thermionic erosion attachment (TEA). It can be said that HCVA of this type have a hybrid cathodic attachment. Unlike cathode spots, TEA produces a subsonic plasma flow, which contributes to an increase in the linear mass of the HCVA plasma jet. © 2021 Institute of Physics Publishing. All rights reserved

LONG-TERM PROGNOSIS IN PATIENTS WITH A LOCAL BREAST CANCER RELAPSE AFTER ORGAN-SAVING TREATMENT

The paper presents the results of a follow-up of 861 patients who have undergone organ-saving treatment (OST) for early breast can- cer. The relapse rate was 7.3% (63/861). The main task was to study an association of survival rates with the predictors characteriz- ing a local relapse. Five-year overall survival after the start of treatment for a local relapse was 65.7% (standard error 8.3). A Cox multivariance regression analysis led to the conclusion that the local relapse is a statistically significant factor of worsening survival without distant metastases when it develops within 3 years after primary OST

On possible reasons of positive near-anode voltage drop in high-current vacuum arc

In this paper we consider some reasons for the occurrence of a positive near-anode potential drop during current constriction in high-current vacuum arc. It is shown that if the radius of constriction is much larger than the electron mean free path, then a positive voltage drop in the near-anode plasma sheath does not occur, but an additional drop may occur in the near-anode plasma layer due to the anomalous resistance. If the current constriction radius is much less than the electron mean free path, then a positive voltage drop in the sheath arises under the usual condition, and the kinetic instabilities in the near-anode plasma do not develop. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: 17-02-00346, 18-08-00547Russian Academy of Sciences, RASNational Natural Science Foundation of China, NSFC: 5191153011318-2-2-16This work was supported in part by RFBR(grant Nos. 17-02-00346, 18-08-00547, 19-08-00783, 19-58-53006), by RAS Program (project No. 11) and UB RAS Program (project No. 18-2-2-16), as well as by National Natural Science Foundation of China (project No. 51911530113)

Study of the ion plasma flow generated by a high-current vacuum arc

The vacuum arc discharge is intensively explored for a long time. It acts as a source of multiply charged plasma. The results of the special type plasma gun (5-10 kA, 12 μs) ion flow study with high temporal resolution and the electrode erosion dependences on the amplitude of the current pulse are presented in the research. The ion flow intensity had good reproducibility from series to series, while the values of total mass erosion differ significantly for different series of experiments under the same conditions. The ion erosion was measured to be significantly higher than that for arc sources with currents up to 1 kA. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: 17-02-00346, 18-08-00547Russian Academy of Sciences, RAS18-2-2-16This work was supported in part by RFBR (grant Nos. 17-02-00346, 18-08-00547, 19-08-00783, 19-58-53006), by RAS Program (project No. 11) and UB RAS Program (project No. 18-2-2-16)

Comparative analysis of parasternal lymph collector exposures in the organ-sparing treatment of patients with operable breast cancer

The paper presents the results of a follow-up of 593 patients with the internal and central localization of clinical stages I-IIb breast cancer whose treatment comprises parasternal treatment techniques: teleradiotherapy (TRT), intratissue radiotherapy (ITRT), and video-assisted thoracoscopic parasternal lymphadenectomy (VAPL). A control group included 846 patients with the external localiza- tion of a tumor. There was a statistically significant increase in 5-year overall (98.2%) and relapse-free (96.2%) survival rates in Stage I in the VAPL versus TRT and ITRT groups (overall survival, 92.5 and 89.7%; relapse-free survival, 80.8 and 73.4%, respectively) (p < 0.05). There was no difference in survival rates between the study and control groups. It is concluded that VAPL permits the objective staging of the disease and any therapeutic exposure of the parasternal area made survival rates similar in the study and control groups

Comparative analysis of the long-term results of treatment in patients with Stages I-IIa breast cancer in relation to major prognostic factors

The analysis of the long-term results of treatment in patients with Stages I-IIa breast cancer in relation to major prognostic factors re- vealed poor morphological factors that greatly influenced the lifespan of female patients, such as tumor invasion along the neural fibers, tumor necrosis, cancer emboli in the lymph gaps and vessels, vascular tumor invasion