Mathematical retroreflectors

Retroreflectors are optical devices that reverse the direction of incident beams of light. Here we present a collection of billiard type retroreflectors consisting of four objects; three of them are asymptotically perfect retroreflectors, and the fourth one is a retroreflector which is very close to perfect. Three objects of the collection have recently been discovered and published or submitted for publication. The fourth object - notched angle - is a new one; a proof of its retroreflectivity is given.Comment: 32 pages, 19 figure

High frequency limit of the Transport Cross Section and boundedness of the Total Cross Section in scattering by an obstacle with impedance boundary conditions

The scalar scattering of the plane wave by a strictly convex obstacle with impedance boundary conditions is considered. The uniform boundedness of the Total Cross Section for all values of frequencies is proved. The high frequency limit of the Transport Cross Section is founded and presented as a classical functional of the variational theory

Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT

This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. Since 1998, digital receivers performing on-the-fly dynamic spectrum calculations or waveform data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio telescope. Here we detail these receivers developed for operation in the strong interference environment that prevails in the decameter wavelength range. Data collected with these receivers allowed us to discover numerous radio astronomical objects and phenomena at low frequencies, a summary of which is also presented.Comment: 24 pages, 15 figure

Echinococcal Cyst Blockade — the Rare Cause of Acute Pancreatitis and Obstructive Jaundice

Aim: demonstrate an algorithm for the diagnosis and treatment of acute pancreatitis and obstructive jaundice caused by obstruction of the terminal part of the common bile duct by daughter echinococcal cyst.Key points. The article presents a clinical case of acute echinococcal obstruction of the terminal part of the common bile duct in a patient with a complicated course of liver echinococcosis. A 33-year-old man was hospitalized with epigastrium and right hypochondrium pains and jaundice. In 2019 the patient underwent the removal of a cyst in the 7th liver segment and cholecystectomy for liver and gallbladder echinococcal lesions. Laboratory research revealed leukocytosis, hyperbilirubinemia and an increase in the transaminases level. Transabdominal ultrasound showed signs of dilatation throughout bile ducts. Duodenoscopy revealed a fixed yellowish-white oval formation with transluent capsule, completely blocking bile and pancreatic juice outflow at the major duodenal papilla. After non-annulation endoscopic papillotomy, migration of the substrate (echinococcal cyst) into the duodenum was noted, active flow of bile and pancreatic secretions was restored. Oral transpapillary cholangioscopy was performed for a detailed bile ducts examination. It revealed no echinococcal cysts, residual parasitic structures or biliary tree lesions. The treatment was completed with pancreatic stenting. After complex treatment in the intensive care and surgery unit with complete condition stabilization, the patient was discharged with recommendations for further treatment in a specialized clinic.Conclusion. Migration of a daughter cyst from the echinococcal liver focus can cause acute blockade of the terminal part of the common bile duct and acute obstructive pancreatitis. The combination of clinical, radiological and endoscopic methods allows to diagnose and eliminate this rare complication of liver echinococcosis with subsequent successful treatment

ELECTROCHEMICAL CHARACTERISTICS OF BIMETALLIC IMPLANT FOR OSTEOSYNTHESIS

The article presents experimental results of electrochemical characteristics of bimetallic implants in experiment

МЕТОДИЧЕСКИЕ АСПЕКТЫ ПРОВЕДЕНИЯ ФОТОДИНАМИЧЕСКОЙ ТЕРАПИИ СОЛИДНОЙ КАРЦИНОМЫ ЭРЛИХА У МЫШЕЙ ЛИНИИ BALB/C С РАЗЛИЧНОЙ ЛОКАЛИЗАЦИЕЙ ОПУХОЛИ

Background. Photodynamic Therapy is one of the treatment methods used in modern oncology. Evaluation of the efficacy in vivo of photosensitizers on tumor models is generally accepted, but the photodynamic  therapy technique in mice is not without drawbacks.The purpose of the study was evaluation of the efficacy of photodynamic therapy in mice with Ehrlich tumor model after subcutaneous and intracutaneous injection of tumor cells.Material and Methods. The study was conducted on BAL B/C mice of both sexes. Fotoditazin® and Radachlorin® were used as photosensitizers. For photoactivation, the Alod laser apparatus with a wavelength of 662 nm was used.Results. A comparison of photodynamic therapy with subcutaneous and intracutaneous localization of Ehrlich tumor was performed. It was shown that depending on the location and depth of inoculation of Ehrlich tumor, the pharmacokinetics (both the fluorescence intensity over time and the contrast ratio of the tumor/surrounding tissue) and pharmacodynamics (tumor growth inhibition, survival) of photosensitizers are significantly different. Higher contrast of the tumor/surrounding tissue is observed with intracutaneous localization of the tumor.Conclusion. A model with intracutaneous localization of Ehrlich tumor can be recommended for a primary assessment of efficacy; it allows the use of fewer animals in the experiment. When planning experiments to study photosensitizers and evaluating their results, the advantages and disadvantages of different methods for modeling tumors in mice should be taken into account.Введение. Фотодинамическая терапия – один из методов лечения, применяемых в  современной онкологии. Оценка эффективности фотосенсибилизаторов in vivo на  моделях опухолей является общепринятой, однако методика проведения  фотодинамической терапии у мышей не лишена недостатков. Цель исследования – оценить эффективность фотодинамической терапии у мышей на модели опухоли Эрлиха при подкожной и внутрикожной инъекции опухолевых клеток. Материал и методы. Исследование проведено на мышах BalB/c обоего пола. В качестве фотосенсибилизаторов использовали препараты Фотодитазин и Радахлорин.  Для фотоактивации применяли лазерный аппарат Алод с длиной волны 662 нм. Результаты. Проведено сравнение фотодинамической терапии при подкожной и внутрикожной локализации опухоли Эрлиха. Показано, что в зависимости от  локализации и глубины инъекции опухоли Эрлиха в значительной степени различаются фармакокинетика (как интенсивность флуоресценции во времени, так и контрастность по отношению опухоль/окружающие ткани) и фармакодинамика (торможение роста  опухоли, выживаемость животных) фотосенсибилизаторов. Большая контрастность опухоль/окружающие ткани наблюдается при внутрикожной локализации опухоли. Заключение. Модель с внутрикожной локализацией опухоли Эрлиха может быть рекомендована для первичной оценки эффективности и позволяет использовать меньшее число животных в эксперименте. При планировании экспериментов по изучению фотосенсибилизаторов и оценке их результатов должны учитываться преимущества и недостатки разных способов моделирования опухоли у мышей. 

Know Your Heart: Rationale, design and conduct of a cross-sectional study of cardiovascular structure, function and risk factors in 4500 men and women aged 35-69 years from two Russian cities, 2015-18 [version 2; referees: 3 approved]

Russia has one of the highest rates of cardiovascular disease in the world. The International Project on Cardiovascular Disease in Russia (IPCDR) was set up to understand the reasons for this. A substantial component of this study was the Know Your Heart Study devoted to characterising the nature and causes of cardiovascular disease in Russia by conducting large cross-sectional surveys in two Russian cities Novosibirsk and Arkhangelsk. The study population was 4542 men and women aged 35-69 years recruited from the general population. Fieldwork took place between 2015-18. There were two study components: 1) a baseline interview to collect information on socio-demographic characteristics and cardiovascular risk factors, usually conducted at home, and 2) a comprehensive health check at a primary care clinic which included detailed examination of the cardiovascular system. In this paper we describe in detail the rationale for, design and conduct of these studies

Recombinant Vesicular Stomatitis Virus Vaccine Vectors Expressing Filovirus Glycoproteins Lack Neurovirulence in Nonhuman Primates

The filoviruses, Marburg virus and Ebola virus, cause severe hemorrhagic fever with high mortality in humans and nonhuman primates. Among the most promising filovirus vaccines under development is a system based on recombinant vesicular stomatitis virus (rVSV) that expresses an individual filovirus glycoprotein (GP) in place of the VSV glycoprotein (G). The main concern with all replication-competent vaccines, including the rVSV filovirus GP vectors, is their safety. To address this concern, we performed a neurovirulence study using 21 cynomolgus macaques where the vaccines were administered intrathalamically. Seven animals received a rVSV vector expressing the Zaire ebolavirus (ZEBOV) GP; seven animals received a rVSV vector expressing the Lake Victoria marburgvirus (MARV) GP; three animals received rVSV-wild type (wt) vector, and four animals received vehicle control. Two of three animals given rVSV-wt showed severe neurological symptoms whereas animals receiving vehicle control, rVSV-ZEBOV-GP, or rVSV-MARV-GP did not develop these symptoms. Histological analysis revealed major lesions in neural tissues of all three rVSV-wt animals; however, no significant lesions were observed in any animals from the filovirus vaccine or vehicle control groups. These data strongly suggest that rVSV filovirus GP vaccine vectors lack the neurovirulence properties associated with the rVSV-wt parent vector and support their further development as a vaccine platform for human use