Application of a hybrid model for the numerical study of the generation of runaway electrons and the formation of high-pressure gas discharge

The paper analyses the details of the application of the hybrid model for calculation of the formation of high-pressure gas discharge in conditions where the transition of electrons into runaway mode is possible. In hybrid model, PIC MC method is used only for calculation of runaway electrons, and the standard hydrodynamic approach is used for calculation of plasma electrons. Using such model can significantly reduce computing resources. The results of calculation of kinetics of electrons emitted from a micro-spike on the cathode during the formation of the cathode layer of nanosecond and sub-nanosecond high-pressure gas discharge are presented. The conditions of transition of electrons into runaway mode at this stage and their influence on the further formation of the gas discharge are analyzed. © 2018 Institute of Physics Publishing. All rights reserved.The work was supported by RFBR, Grant 16-08-00894

Diagnosis and classification of Mirizzi syndrome

Objective. To determine the factors, predisposing to development of Mirizzi syndrome; to improve diagnosis and classification of it, taking into account of these factors and possibilities to apply a definite kind of endoscopic or operative treatment. Materials and methods. Retrospective analysis was done for results of treatment of 21 patients with Mirizzi syndrome: Type I in accordance to classification of McSherry (1982) was present in 7 patients, while a Type II - in 14. Results. There was established, that atypia (the variant anatomy) of the ductus cysticus localization predisposes for contact between hepaticocholedochus and a gallbladder of with ductus cysticus, leading to development of Mirizzi syndrome Types I and II. Squeezing (Type I) or fistula (Type II) are observed on any level of hepaticocholedochus. In syndrome of Mirizzi Type II the duct distal to fistula may be not dilated (Subtype IIA) or dilated (Subtype IIB). Conclusion. Atypia (the variant anatomy) of the ductus cysticus duct constitute a factor, promoting development of Mirizzi syndrome. While diagnostic process for Mirizzi syndrome it is necessary to take into account a localization of squeezing of hepaticocholedochus or of fistula, presence of atypia of the ductus cysticus and its stump localization, character of the gallbladder inflammation, quantity and size of calculi. Proposition to include the Types IIA and IIB II in Mirizzi syndrome, depending on the dilation degree present in hepaticocholedochus distally, to the fistula, constitutes a substantiated principle, because it takes into account a possibility to perform endoscopic lithoextraction and to impact the choice of the surgical treatment method

Diagnostic system of determination of an acute cholangitis

Objecive. To elaborate a diagnostic system, permitting to confirm or exclude the diagnosis of an acute cholangitis in patients, suffering biliary ducts obstruction. Materials and methods. The wok is based on analysis of clinical, laboratory and instrumental indices in 174 patients, suffering the biliary ducts obstruction (in 18 - with an acute cholangitis). Results. The diagnostic system was constructed, taking into account informativity of such indices, as ratio of the segmented and stab neutrophils quantity, quantity of stab neutrophils, bilirubin, a gallbladder wall thickness, quantity of monocytes, leukocytes, the Charcot’s triad presence, the body temperature, level of amylase, the duodenal papilla magna size, quantity of lymphocytes, presence of excluded gallbladder, presence of cholecystectomy in anamnesis, the immobile calculus of duodenal papilla magna, tumor, the eosinophils quantity, as well as the presence of any choledocholithiasis and age. Conclusion. The elaborated diagnostic scheme for determination of an acute cholangitis in patients, suffering biliary ducts obstruction, owes high security (≥ 95%), because the part of failed diagnosis did not exceeded 5% and have constituted 2.8%

Endoscopic and surgical treatment of the Mirizzi syndrome

Academia Medicală de Studii Postuniversitare, Harkov, Ucraina, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Sindromul Mirizzi se caracterizează prin compresia căii biliare de către colecist sau formarea unei fistule între acestea, care corespunde tipului Mirizzi I şi II (McSherry, 1984). Diagnosticul se confirmă prin ERCP. Corecţia chirurgicală este complexă şi adesea în cazurile de Mirizzi II este necesară aplicarea hepaticojejunostomiei. Scop: Evaluarea oportunităţilor tratamentului endoscopic şi chirurgical al sindromului Mirizzi pentru păstrarea pasajului bilei spre duoden. Material şi metode: Dintre 2144 pacienţi cu litiază biliară, obstrucţia căilor biliare a fost evidențiată la 328 (15,3%). Sindromul Mirizzi a fost diagnosticat în 21 (6,4%) cazuri: de tip I – la 6 (28,6%) pacienţi, de tip II – la 15 (71,4%). Rezultate: În două cazuri de Mirizzi I iniţial a fost practicat drenajul biliar transnazal, într-un caz – stentarea ductului biliar comun. Colecistectomia laparoscopică s-a efectuat la 5 pacienţi şi deschisă – la unul. La 2 din 15 (13,3%) pacienţi cu Mirizzi II s-a reuşit litotripsia, la un bolnav a fost realizată stentarea biliară. Pentru a reduce icterul în 12 cazuri a fost aplicat drenajul biliar transnazal. Ulterior, 9 pacienţi au suportat colecistectomie cu plastia defectului ductului biliar comun, la 2 bolnavi s-a efectuat colecistectomie laparoscopică cu extragerea calculilor biliari, şi într-un caz s-a practicat hepaticojejunostomia. Astfel, la 14 din 15 (93,3%) bolnavi cu Mirizzi II pasajul biliar fiziologic a fost restabilit cu succes. Mortalitatea postoperatorie a constituit 0, morbiditatea – 19% (4 pacienţi). Concluzie: Aplicarea tratamentului endoscopic şi chirurgical la pacienţii cu Mirizzi II a permis restabilirea pasajul biliar fiziologic în 93% din cazurile noastre.Introduction: The Mirizzi syndrome is characterized by compression of bile duct by gallbladder or fistula formation between them, that corresponds to the Mirizzi type I and type II (McSherry, 1984). The diagnosis confirms by ERCP. Surgical correction is complex and often needs hepaticojejunostomy in cases of Mirizzi II. Aim: Evaluate opportunities of the endoscopic and surgical treatment of Mirizzi syndrome in the preservation of bile passage to the duodenum. Material and methods: Among 2144 patients with cholelithiasis, biliary tract obstruction occurred in 328 (15.3%). Mirizzi syndrome was diagnosed in 21 (6.4%): type I – in 6 (28.6%) patients, type II – in 15 (71.4%). Results: In two cases of Mirizzi I initially transnasal biliary drainage was performed and in one – the common bile duct stenting. In 5 patients laparoscopic and in one open cholecystectomy was performed. In 2 of 15 (13.3%) patients with Mirizzi II lithotr ipsy was successful; in one bile duct stenting was performed. To reduce jaundice in 12 cases transnasal biliary drainage was introduced. Thereafter, 9 patients underwent cholecystectomy with the common bile duct defect plasty, 2 patients underwent laparoscopic cholecystolitotomy with bile duct stones extraction, and in one case hepaticojejunostomy was formed. Thus, in 14 of 15 (93.3%) of Mirizzi II physiological bile passage was successfully restored. Postoperative mortality was 0, morbidity was 19% (4 patients). Conclusion: The use of endoscopic and surgical treatment in cases of Mirizzi II allowed restoring the physiological bile passage in 93% of cases

Effect of the metal-support interaction in Ag/CeO2 catalysts on their activity in ethanol oxidation

The interaction of silver with the surface of CeO2 in the Ag/CeO2 catalysts prepared by coprecipitation and impregnation techniques was studied by temperature-programmed reduction, X-ray diffraction, and high-resolution transmission electron microscopy. It was shown that coprecipitation technique led to formation of strong silver–support interaction and the epitaxy of silver particles (d111 = 2.35 Å) on the surface of CeO2 (d111 = 3.1 Å). This provided incresed catalytic activity in the oxidative dehydrogenation of ethanol at relatively low temperatures (a 15% conversion of ethanol with 100% selectivity for the formation of acetaldehyde was reached at 85°C). Above 130°C, the deep oxidation of ethanol to CO2 becomes the predominant direction of a catalytic reaction, and the Ag/CеО2 catalyst obtained by impregnation technique was most active in this region as a consequence of the weaker metal–support interaction

Features of the Electron Avalanche Formation Process in a Strongly Inhomogeneous Electric Field under High Overvoltages

The simulation of the electron avalanche formation process in subnanosecond discharges of high pressure was carried out by means of the Monte-Carlo approach. The discharge gap under consideration was of the configuration “the finger-shaped cathode – the hemispherical anode”. The presence of a conic-shaped microprotrusion on a cathode surface was assumed. Such the electrode configuration provided the strongly inhomogeneous distribution of an electric field. A gas simulated was nitrogen at a pressure of 6 atm. An average electric field strength across the discharge gap was varied from 200 kV/cm up to 400 kV/cm. Microprotrusion height was varied from 0 um up to 30 um. The critical size and formation time of an electron avalanche were determined under various conditions simulated. The threshold electric field strength for electrons to transit into the continuous accelerating regime was calculated for various heights of the microprotrusion. The applicability of the non-self-consistent Monte-Carlo technique for the investigation of the runaway electron kinetics and the correct simulation of the runaway electron beam transport across the discharge gap was shown. © 2021 Institute of Physics Publishing. All rights reserved.This work was supported in part by the Russian Foundation for Basic Research under Project 20-38-90147 and Project 20-08-00172

Mathematical Model of the Shell with the Infill for Retaining Structures

A description of finite element model and analysis of a shell with an infill is performed. A large diameter thin cylindrical shell structure with the edge leaning against compressible foundation soil is analyzed. Different materials are considered individually for the models of each structure shell and infill component (metal or reinforced concrete shell, and granular or elastic infill in a shell and foundation soil loaded by the structure). Contact conditions between 1) the infill and the shell’s inner surface and 2) between the foundation material and the shell edge are analyzed. An example of calculating strain conditions in the shell according to the proposed finite element model and tasks of its development process and specification are provided in this paper