Анализ параметров активной фазированной антенной решетки радиотелескопа ГУРТ

Представлены методика расчета и результаты численного анализа параметров активной фазированной антенной решетки (АФАР) Гигантского украинского радиотелескопа (ГУРТ) декаметрового и метрового диапазонов волн, который сооружается в настоящее время вблизи г. Харькова на территории Радиоастрономической обсерватории им. С. Я. Брауде Радиоастрономического института Национальной академии наук Украины. Методика базируется на матричной теории антенных решеток, сочетающей в себе электродинамический подход к анализу решетки излучателей с методами теории многополюсников СВЧ для описания фидерной схемы АФАР. Приведены и проанализированы результаты численного расчета эффективной площади АФАР и коэффициента передачи, который в случае пассивной ФАР ассоциируется с КПД, в широком секторе сканирования луча в диапазоне частот 10- 80 МГц.Надаються методика розрахунку та результати числового аналізу параметрів активної фазованої антенної решітки (АФАР) Гігантського українського радіотелескопу (ГУРТ) декаметрового та метрового діапазонів хвиль, що наразі споруджується поблизу м. Харкова на території Радіоастрономічної обсерваторії ім. С. Я. Брауде Радіоастрономічного інституту Національної академії наук України. Методика базується на матричній теорії антенних решіток, що поєднує електродинамічний підхід до аналізу решітки випромінювачів з методами теорії багатополюсників НВЧ для опису фідерної схеми АФАР. Наведені та проаналізовані результати числового розрахунку ефективної площі АФАР та коефіцієнту передачі, що в разі пасивної ФАР асоціюється з ККД, у широкому секторі сканування променя в діапазоні частот 10 - 80 МГц.The calculation technique results of numerical analysis of parameters of active phased antenna array (APAA) of the Giant Ukrainian Radio Telescope (GURT) of decameter and meter wavelengths which is being built now nearby Kharkiv at the area of S. Ya. Braude Radio Astronomy Observatory of the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine are presented. The technique is based on the matrix theory of antenna arrays which combines an electromagnetic approach to analysis of radiators array with the methods of microwave multiport theory for the APAA feed network description. The results of numerical calculation of the APAA effective area and its gain, which in case of passive array is associated with its efficiency, are given and analyzed for a wide scan range within 10 to 80 MHz

Microfluidic droplet platform for ultrahigh-throughput single-cell screening of biodiversity

© 2017, National Academy of Sciences. All rights reserved.Ultrahigh-throughput screening (uHTS) techniques can identify unique functionality from millions of variants. To mimic the natural selection mechanisms that occur by compartmentalization in vivo, we developed a technique based on single-cell encapsulation in droplets of a monodisperse microfluidic double water-in-oil-in-water emulsion (MDE). Biocompatible MDE enables in-droplet cultivation of different living species. The combination of droplet-generating machinery with FACS followed by next-generation sequencing and liquid chromatography-mass spectrometry analysis of the secretomes of encapsulated organisms yielded detailed genotype/phenotype descriptions. This platform was probed with uHTS for biocatalysts anchored to yeast with enrichment close to the theoretically calculated limit and cell-to-cell interactions. MDE-FACS allowed the identification of human butyrylcholinesterase mutants that undergo self-reactivation after inhibition by the organophosphorus agent paraoxon. The versatility of the platform allowed the identification of bacteria, including slow-growing oral microbiota species that suppress the growth of a common pathogen, Staphylococcus aureus, and predicted which genera were associated with inhibitory activity

Monitoring of breast cancer progression via aptamer-based detection of circulating tumor cells in clinical blood samples

Introduction: Breast cancer (BC) diagnostics lack noninvasive methods and procedures for screening and monitoring disease dynamics. Admitted CellSearch® is used for fluid biopsy and capture of circulating tumor cells of only epithelial origin. Here we describe an RNA aptamer (MDA231) for detecting BC cells in clinical samples, including blood. The MDA231 aptamer was originally selected against triple-negative breast cancer cell line MDA-MB-231 using cell-SELEX.Methods: The aptamer structure in solution was predicted using mFold program and molecular dynamic simulations. The affinity and specificity of the evolved aptamers were evaluated by flow cytometry and laser scanning microscopy on clinical tissues from breast cancer patients. CTCs were isolated form the patients’ blood using the developed method of aptamer-based magnetic separation. Breast cancer origin of CTCs was confirmed by cytological, RT-qPCR and Immunocytochemical analyses.Results: MDA231 can specifically recognize breast cancer cells in surgically resected tissues from patients with different molecular subtypes: triple-negative, Luminal A, and Luminal B, but not in benign tumors, lung cancer, glial tumor and healthy epithelial from lungs and breast. This RNA aptamer can identify cancer cells in complex cellular environments, including tumor biopsies (e.g., tumor tissues vs. margins) and clinical blood samples (e.g., circulating tumor cells). Breast cancer origin of the aptamer-based magnetically separated CTCs has been proved by immunocytochemistry and mammaglobin mRNA expression.Discussion: We suggest a simple, minimally-invasive breast cancer diagnostic method based on non-epithelial MDA231 aptamer-specific magnetic isolation of circulating tumor cells. Isolated cells are intact and can be utilized for molecular diagnostics purposes

Negative Pressure Provides Simple and Stable Droplet Generation in a Flow-Focusing Microfluidic Device

Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually T-junction and flow-focusing microfluidic devices connected to syringe pumps or pressure controllers are used. Here, we investigated droplet-generation regimes in a flow-focusing microfluidic device induced by the negative pressure in the outlet reservoir, generated by a low-cost mini diaphragm vacuum pump. During the study, we compared two ways of adjusting the negative pressure using a compact electro-pneumatic regulator and a manual airflow control valve. The results showed that both types of regulators are suitable for the stable generation of monodisperse droplets for at least 4 h, with variations in diameter less than 1 µm. Droplet diameters at high levels of negative pressure were mainly determined by the hydrodynamic resistances of the inlet microchannels, although the absolute pressure value defined the generation frequency; however, the electro-pneumatic regulator is preferable and convenient for the accurate control of the pressure by an external electric signal, providing more stable pressure, and a wide range of droplet diameters and generation frequencies. The method of droplet generation suggested here is a simple, stable, reliable, and portable way of high-throughput production of relatively large volumes of monodisperse emulsions for biomedical applications

Methods for studying two-phase flows in porous media: Numerical simulation and experiments on microfluidics chips

Copyright 2020, Society of Petroleum Engineers. In this paper, experimental and computational approaches are used to study multiphase flows. In the firstmethod, filtration experiments are carried out using microfluidics technology. Microfluidic chips weremade from polydimethylsiloxane using soft lithography. To give the desired surface properties, the innerwalls of the channels were treated with a hydrophobic or hydrophilic coating. Injection of liquids wascarried out using a syringe pump at a constant flow rate. To measure the pressure difference at the inletand outlet of the microchip, we used the method of measuring changes in gas volume. For numericalmodeling, the most modern model of the Boltzmann lattice equations, adapted for two-phase flows ofincompressible immiscible liquids, is used. The effects that occur at the phase boundary are described usingthe color field gradient model. Experimental studies have shown the possibility of studying the processesof liquid displacement from the microchannel system in a microfluidic chip simulating a porous medium.The dynamics of the displacement of liquids (water and oil) from a system of microchannels with differenthydrodynamic drag cardinally depends on the angle of wettability of its walls. In the case of microchannelswith hydrophilic walls, a complete displacement of oil by water occurs almost simultaneously from bothchannels. When water is displaced by oil from channels with a hydrophilic and hydrophobic coating, it isrequired to create an increased flow rate of the displacing liquid through microchannels. In this case, at thejunction of the microchannels, before leaving the chip, emulsion droplets of "water in oil" will form. Inthe case of oil displacement by water from microchannels with a hydrophobic coating, complete removalof oil from the channel with high resistance did not occur. This is due to the fact that the viscosity of theoil is 30 times higher than the viscosity of water. The paper shows a successful comparison of the resultsof numerical modeling and experimental research in a two-phase flow in a pore doublet. Demonstratedexamples of the developed program code are shown: the formation of emulsions at high flow rates, themotion of a drop under the influence of mass force; flow in digital microtomographic image; displacementof viscous oil from the pore medium

Dissolution and mixing of flavin mononucleotide in microfluidic chips for bioassay

Dissolution and mixing of flavin mononucleotide (FMN), which activates a luminescent reaction, were considered in various designs of microfluidic chip for pollution analysis of liquid samples. The aim was to determine the velocity mode of fluid flow ensured the uniform distribution of the FMN in the reaction chamber. Simulation of concentration distribution of FMN in various designs of microfluidic chips was conducted. It was shown that the passive mixing techniques based on the constant flow rate didn’t provide mixing of FMN in acceptable time (3 seconds). The most efficient mixing was achieved using variable flow rate with a gradually increasing frequency of oscillation