Terahertz Generation and Detection by Plasma Waves in Nanometer Gate High Electron Mobility Transistors

The high electron mobility transistors can act as a resonator cavity for the plasma waves that can reach THz frequencies for a nanometer size devices. As was predicted by Dyakonov and Shur in 1993, the steady state of the current flow in a gated 2D electron gas can become unstable leading to the emission of an electromagnetic radiation at the plasma wave frequencies. The theory predicted also that the plasma waves can be used for resonant detection of THz electromagnetic radiation. In the present paper we review our recent experiments on THz emission and detection performed on high electron mobility transistors based on different semiconductor structures: InGaAs/GaAlAs, GaAs/GaAlAs, and Si

FIRST TRIES OF USING INNOVATIONAL CAPSO VISION CAPSULE ENDOSCOPY SYSTEM IN TREATING CHILDREN

Vide-capsule  endoscopy has been used successfully in treating children to assess the condition of the small intestine in spots that are not available to conventional endoscopy. The article presents the innovative technical characteristics of the new system for videocapsule endoscopy  — Capso Vision Capsule Endoscopy  System: panoramic view, provided  by the side optics, and data storage in the video processor  of the capsule itself. The article presents  the results of the diagnostic system in treatment of 5 children with a description  of the detected pathological changes. Both the positive aspects and disadvantages  of Capso Vision Capsule Endoscopy System in treatment of children are discussed

Field Effect Transistors for Terahertz Detection: Physics and First Imaging Applications

Resonant frequencies of the two-dimensional plasma in FETs increase with the reduction of the channel dimensions and can reach the THz range for sub-micron gate lengths. Nonlinear properties of the electron plasma in the transistor channel can be used for the detection and mixing of THz frequencies. At cryogenic temperatures resonant and gate voltage tunable detection related to plasma waves resonances, is observed. At room temperature, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector. We present the main theoretical and experimental results on THz detection by FETs in the context of their possible application for THz imaging.Comment: 22 pages, 12 figures, review pape

Helicity sensitive terahertz radiation detection by field effect transistors

Terahertz light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse is by several orders of magnitude higher than any earlier reported one. Also linear polarization sensitive photoresponse was registered by the same transistors. The results provide the basis for a new sensitive, all-electric, room-temperature and fast (better than 1 ns) characterisation of all polarization parameters (Stokes parameters) of terahertz radiation. It paves the way towards terahertz ellipsometry and polarization sensitive imaging based on plasma effects in field-effect-transistors.Comment: 7 pages, 4 figure

The role of nelarabine in the treatment of T-cell acute lymphoblastic leukemia: literature review and own experience

Aim. The analysis of experience of nelarabine use in refractory/relapsed T-cell acute lymphoblastic leukemia (T-ALL) depending on the immunophenotype and the line of therapy. Materials and methods. All the patients with relapsed or refractory T-ALL aged from 0 to 18 years who received treatment with nelarabine as a part of the therapeutic element R6 were included in the study. For all patients a detailed immunological analysis of leukemia cells with discrimination of immunological variants TI, TII, TIII or TIV was performed. Patients administered with nelarabine as a first therapeutic element were referred to the first-line therapy group, other patients were referred to the second-line therapy group. Nelarabine was administered as intravenous infusion at a dose of 650 mg/m2, on days 1-5. Allogeneic hematopoietic stem cells transplantation (allo-HSCT) was considered for all patients. Results. From 2009 to 2017, 54 patients with refractory/relapsed T-ALL were treated with nelarabine. Five-year event-free survival (EFS) and overall survival (OS) was 28% for all patients, cumulative risk of relapse (CIR) was 27%. EFS was significantly higher in nelarabine first-line therapy group in comparison with second-line therapy group (34±8% vs 8±8%, p=0,05). In patients after allo-HSCT EFS, OS and CIR were 51±10%, 50±10% and 39,1±9,5% accordingly. The best results were achieved in patients with TI immunophenotype. No toxicity-related mortality as well as severe neurologic complications or discontinuation of therapy associated with use of nelarabine were reported. Conclusion. The use of nelarabine is an effective strategy for the treatment of relapsed and refractory T-ALL. The best treatment outcomes were obtained in patients with TI immunophenotype and in the first-line therapy group. Optimal dosage regimens can be established during controlled clinical trials

ОСТРАЯ КИШЕЧНАЯ ИНФЕКЦИЯ КАК МАСКА ОСТРОГО АППЕНДИЦИТА У ДЕТЕЙ

The issue of differential diagnosis of acute appendicitis and acute intestinal infections in contemporary medicine remains relevant for clinical practice of surgeons and pediatricians. Late diagnosis of appendicitis results in development of complicated forms of vermiform appendix inflammation. This prolongs operative intervention, duration of antibacterial therapy and duration of a child’s inpatient stay. The article presents clinical observation of three children treated for perforated appendix and generalized purulent peritonitis. The described cases demonstrate the need in multidisciplinary approach and complex diagnosis of patients with such complaints as abdominal pain, fever and diarrhea.Проблема дифференциальной диагностики острого аппендицита и острых кишечных инфекций в современной медицине остается актуальной проблемой в клинической практике врача-хирурга и педиатра. Недиагностированный вовремя аппендицит приводит к развитию осложненных форм воспаления червеобразного отростка, что пролонгирует оперативное вмешательство и сроки антибактериальной терапии, увеличивая длительность пребывания ребенка в стационаре. В статье представлено клиническое наблюдение трех детей, находившихся на лечении по поводу перфоративного аппендицита, разлитого гнойного перитонита. Описанные случаи демонстрируют необходимость мультидисциплинарного подхода и комплексной диагностики пациентов с такими жалобами, как боль в животе, лихорадка и диарея