83 research outputs found
9.4 T Double-Tuned 13C/1H Human Head Array Using a Combination of Surface Loops and Dipole Antennas
No full textDipole antennas have been successfully utilized at ultra-high fields (UHF, >7 T) for human body and head imaging. Combining X-nuclei surface loops and 1H dipoles can substantially simplify the design of a double-tuned UHF human head coil. In this work, we developed and constructed a novel 13C/1H human head 9.4 T array coil consisting of eight 13C surface loops and eight 1H folded-end dipoles surrounding the head. We showed that coupling between loops and dipoles can be minimized by placing four 1H traps into each 13C loop. The new coil demonstrated an improved 1H longitudinal coverage and reasonable Tx efficiency
ЗАСТОСУВАННЯ СЛОВНИКОВИХ ОН-ЛАЙН ТРЕНАЖЕРІВ ДЛЯ ФОРМУВАННЯ ІНШОМОВНОЇ ЛЕКСИЧНОЇ КОМПЕТЕНЦІЇ МАЙБУТНЬОГО ПЕДАГОГА
Get PDFThe article considers modern approaches and innovative means of development of the foreign language communicative competence of future teachers. The author emphasizes and substantiates the necessity of widespread usage of digital technologies in the process of modern students` foreign language training as a component of professional pedagogical competence. The usage of on-line resources contributes not only to the acquisition of a foreign language, at the same time it is also an example, according to the methodological point of view, and can be used in further pedagogical activities in foreign language classes in pre-school establishments and in foreign language lessons in the New Ukrainian School.After graduating the university modern bachelors will work with the children – representatives of Generation Z, so the ability to use digital means of teaching a foreign language is a demand of time, because modern children, born in the digital would, must be taught by digital means. This is their natural environment.World leading countries understand the necessity of preparing teachers with a high level of a formed digital competence. So, the task of the XXI century modern university, which trains future educators for professional activity, is to form their readiness to teach in the New Ukrainian School by such means that follow the demands of time and will allow to form the XXI Century Competences.The article states that mastering the foreign language lexical material and deepening the level of lexical skills and abilities formation of students-bachelors of the specialty 013 Primary education, 012 Preschool education have a great general and practical significance, because the word is the main component of foreign language communicative competence, and the dictionary on-line simulators, which the author uses in the discipline "Foreign Language and Teaching Methodology (the German language)", allow to intensify the learning process both in the classroom and during the students’ self-work.У статті розглянуто сучасні підходи та інноваційні засоби розвитку іншомовної комунікативної компетенції майбутніх педагогів. Автор підкреслює необхідність широкого використання цифрових технологій в процесі іншомовної підготовки сучасних студентів як складника професійної педагогічної компетентності, оскільки застосування он-лайн ресурсів сприяє не тільки оволодінню іноземної мови, а й одночасно є прикладом з методичної точки зору і може застосовуватися у подальшій педагогічній діяльності на заняттях з іноземної мови у закладах дошкільної освіти та на уроках з іноземної мови в Новій український школі. Для практичного застосування запропоновані словникові он-лайн тренажери, які автор використовує на заняттях з дисципліни «Іноземна мова з методикою навчання (німецька мова)» в процесі підготовки бакалаврів спеціальностей 013 «Початкова освіта», 012 «Дошкільна освіта»
Folded‐end dipole transceiver array for human whole‐brain imaging at 7 T
No full textThe advancement of clinical applications of ultrahigh field (UHF) MRI depends heavily on advances in technology, including the development of new radiofrequency (RF) coil designs. Currently, the number of commercially available 7 T head RF coils is rather limited, implying a need to develop novel RF head coil designs that offer superior transmit and receive performance. RF coils to be used for clinical applications must be robust and reliable. In particular, for transmit arrays, if a transmit channel fails the local specific absorption rate may increase, significantly increasing local tissue heating. Recently, dipole antennas have been proposed and used to design UHF head transmit and receive arrays. The dipole provides a unique simplicity while offering comparable transmit efficiency and signal-to-noise ratio with the conventional loop design. Recently, we developed a novel array design in our laboratory using a folded-end dipole antenna. In this work, we developed, constructed and evaluated an eight-element transceiver bent folded-end dipole array for human head imaging at 7 T. Driven in the quadrature circularly polarized mode, the array demonstrated more than 20% higher transmit efficiency and significantly better whole-brain coverage than that provided by a widely used commercial array. In addition, we evaluated passive dipole antennas for decoupling the proposed array. We demonstrated that in contrast to the common unfolded dipole array, the passive dipoles moved away from the sample not only minimize coupling between the adjacent folded-end active dipoles but also produce practically no destructive interference with the quadrature mode of the array
Decoupling of Folded Dipole Antenna Elements of a Human Head Array at 9.4T
No full textDipole antennas have been successfully utilized at ultra-high fields (UHF, >7 T) as elements of human body arrays. Usage of dipoles for UHF human head arrays is still under development. In this case, dipoles must be made much shorter, and placed at a relatively large distance to the head. As a result, dipoles are not well loaded and are often purely decoupled. In this work, we developed a novel method of decoupling of adjacent dipole antennas, and used this technique while constructing a novel 9.4 T human head TxRx dipole array coil. The array demonstrates good decoupling and full-brain coverage
Decoupling of folded‐end dipole antenna elements of a 9.4 T human head array using an RF shield
No full textDipole antennas have recently been introduced to the field of MRI and successfully used, mostly as elements of ultra-high field (UHF, ≥ 7 T) human body arrays. Usage of dipole antennas for UHF human head transmit (Tx) arrays is still under development. Due to the substantially smaller size of the sample, dipoles must be made significantly shorter than in the body array. Additionally, head Tx arrays are commonly placed on the surface of rigid helmets made sufficiently large to accommodate tight-fit receive arrays. As a result, dipoles are not well loaded and are often poorly decoupled, which compromises Tx efficiency. Commonly, adjacent array elements are decoupled by circuits electrically connected to them. Placement of such circuits between distantly located dipoles is difficult. Alternatively, decoupling is provided by placing passive antennas between adjacent dipole elements. This method only works when these additional components are sufficiently small (compared with the size of active dipoles). Otherwise, RF fields produced by passive elements interfere destructively with the RF field of the array itself, and previously reported designs have used passive dipoles of about the size of array dipoles. In this work, we developed a novel method of decoupling for adjacent dipole antennas, and used this technique while constructing a 9.4 T human head eight-element transceiver array. Decoupling is provided without any additional circuits by simply folding the dipoles and using an RF shield located close to the folded portion of the dipoles. The array reported in this work demonstrates good decoupling and whole-brain coverage
Nomenclatural notes on saline vegetation of Ukraine, southern Russia and Kazakhstan
No full textIn this syntaxonomic nomenclature note we introduce the Plantagini salsae-Artemision santonici (Artemisia santonicae-Limonietalia gmelinii, Festuco-Puccinellietea), a new name for the syntaxon carrying an illegitimate name 'Artemis ionsantonici Shelyag-Sosonko & Solomakha 1987'. This vegetation comprises Artemisia santonicum dominated salt-steppevegetation on solonetz-like soils of slightly elevated habitats of alluvial plains and of the slopes of shallow depressions inthe steppe zone of Ukraine and forest-steppe and steppe zones of Russia. We also suggest a nomenclatural adjustment(nomen inversum) for the 'Artemisio pauciflorae-Camphorosmion monspeliacae' (Artemisietalia pauciflorae, FestucoPuccinellietea).The steppe vegetation classified within this latter syntaxon occurs in southern Russia and northern Kazakhstan
Influence of new snow on growth and melting of sea ice
Get PDFNumerical experiments were carried out using the thermodynamic model with the aim to optimize choice of parameterization of the density of fresh snow, its albedo, and thermal conductivity coefficient in order to reproduce the seasonal evolution of ice thickness in the North-Eastern part of the Sea of Azov. The simulation results were compared with each other as well as with the observations obtained at the costal station of the Southern Scientific Center of the Russian Academy of Sciences in the Taganrog Bay. It is shown that small differences in the schemes of parameterization of physical and thermal properties of snow and ice cover may result in significant scatter in the simulation results. To assess the quality of the forecasting of the seasonal course of the ice thickness, the standard deviation of the calculated ice thickness from the average value for the period of measuring ice thickness, the standard deviation, the correlation coefficient, and the verification of the forecast were determined. Based on the analysis of these parameters, the optimal configuration of the snow layer parameters is proposed, which allows adequate reproducing of the seasonal thermal dynamics of the sea ice thickness. For the conditions of winter 2010/2011 the most close values of calculated ice thickness to results of the measurements in the North-Eastern part of the Taganrog Bay were obtained by determining the dependence of the density of fresh snow on the temperature in the near-surface layer of the atmosphere by the algorithm CLASS, albedo of the snow surface - by the scheme EHAM5, and the coefficient of thermal conductivity of snow – by the formulas of N.I. Osokin or M. Janson
A self-matched leaky-wave antenna for ultrahigh-field magnetic resonance imaging with low specific absorption rate
Get PDFThe technology of magnetic resonance imaging is developing towards higher magnetic fields to improve resolution and contrast. However, whole-body imaging at 7 T or even higher flux densities remains challenging due to wave interference, tissue inhomogeneities, and high RF power deposition. Nowadays, proper RF excitation of a human body in prostate and cardiac MRI is only possible to achieve by using phased arrays of antennas attached to the body (so-called surface coils). Due to safety concerns, the design of such coils aims at minimization of the local specific absorption rate (SAR), keeping the highest possible RF signal in the region of interest. Most previously demonstrated approaches were based on resonant structures such as e.g. dipoles, capacitively-loaded loops, TEM-line sections. In this study, we show that there is a better compromise between the transmit signal B1+ and the local SAR using non-resonant surface coils generating a low electric field in the proximity of their conductors. With this aim, we propose and experimentally demonstrate a leaky-wave antenna implemented as a periodically-slotted microstrip transmission line. Due to its non-resonant radiation, it induces only slightly over half the peak local SAR compared to a state-of-the-art dipole antenna but has the same transmit efficiency in prostate imaging at 7 T. Unlike other antennas for MRI, the leaky-wave antenna does not require to be tuned and matched when placed on a body, which makes it easy-to-use in prostate imaging at 7 T MRI
Double-Row 16-element Folded-End Dipole Transceiver Array for Human Whole Brain Imaging at 9.4 T
No full textHomogeneity and coverage of transmit (Tx) RF coils at ultra-high field (UHF,>7 T) can be improved by 3D RF shimming. This, however, requires using multi-row Tx-arrays. Dipole antennas provide unique simplicity and robustness while offering comparable Tx-efficiency and SNR to conventional loop designs. Single-row UHF dipole Tx-arrays for human head imaging have been previously described. Recently, we developed a novel type of dipole elements, a folded-end dipole, which improved the longitudinal coverage and specific absorption rate (SAR) efficiency. In this work, we developed, constructed, and evaluated a 16-element double-row transceiver folded-end dipole array for human whole-brain imaging at 9.4 T
Quadrature transceive wireless coil: Design concept and application for bilateral breast MRI at 1.5 T
No full textPurpose: Development of a novel quadrature inductively driven transceive wireless coil for breast MRI at 1.5 T.Methods: A quadrature wireless coil (HHMM-coil) design has been developed as a combination of two linearly polarized coils: a pair of 'metasolenoid' coils (MM-coil) and a pair of Helmholtz-type coils (HH-coil). The MM-coil consisted of an array of split-loop resonators. The HH-coil design included two electrically connected flat spirals. All the wireless coils were coupled to a whole-body birdcage coil. The HHMM-coil was studied and compared to the linear coils in terms of transmit and SAR efficiencies via numerical simulations. A prototype of HHMM-coil was built and tested on a 1.5 T scanner in a phantom and healthy volunteer. We also proposed an extended design of the HHMM-coil and compared its performance to a dedicated breast array.Results: Numerical simulations of the HHMM-coil with a female voxel model have shown more than a 2.5-fold increase in transmit efficiency and a 1.7-fold enhancement of SAR efficiency compared to the linearly polarized coils. Phantom and in vivo imaging showed good agreement with the numerical simulations. Moreover, the HHMM-coil provided good image quality, visualizing all areas of interest similar to a multichannel breast array with a 32% reduction in signal-to-noise ratio.Conclusion: The proposed quadrature HHMM-coil allows the B+1-field to be significantly better focused in the region-of-interest compared to the linearly polarized coils. Thus, the HHMM-coil provides high-quality breast imaging on a 1.5 T scanner using a whole-body birdcage coil for transmit and receive
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