On the influence of acoustic waves on coherent bremsstrahlung in crystals

We investigate the coherent bremsstrahlung by relativistic electrons in a single crystal excited by hypersonic vibrations. The formula for the corresponding differential cross-section is derived in the case of a sinusoidal wave. The conditions are specified under which the influence of the hypersound is essential. The case is considered in detail when the electron enters into the crystal at small angles with respect to a crystallographic axis. It is shown that in dependence of the parameters, the presence of hypersonic waves can either enhance or reduce the bremsstrahlung cross-section.Comment: 11 pages, 6 EPS figures, LaTe

Coherent radiation of an ultra-relativistic charged particle channeled in a periodically bent crystal

We suggest a new type of the undulator radiation which is generated by an ultra-relativistic particle channeled along a periodically bent crystallographic plane or axis. The electromagnetic radiation arises mainly due to the bending of the particle's trajectory, which follows the shape of the channel. The parameters of this undulator, which totally define the spectrum and the angular distribution of the radiation (both spontaneous and stimulated), depend on the type of the crystal and the crystallographic plane (axis), on the type of a projectile and its energy, and on the shape of the bent channel, and, thus, can be varied significantly by varying these characteristics. As an example, we consider the acoustically induced radiation (AIR) which is generated by ultra-relativistic particles channeled in a crystal which is bent by a transverse acoustic wave. The AIR mechanism allows to make the undulator with the main parameters varying in wide ranges, which are inaccessible in the undulators based on the motion of particles in the periodic magnetic fields and also in the field of the laser radiation. The intensity of AIR can be easily made larger than the intensity of the radiation in a linear crystal and can be varied in a wide range by varying the frequency and the amplitude of the acoustic wave in the crystal. A possibility to generate stimulated emission of high-energy photons (in keV - MeV region) is also discussed.Comment: published in J. Phys. G: Nucl. Part. Phys. 24 (1998) L45-L53, http://www.iop.or

The influence of the dechanneling process on the photon emission by an ultra-relativistc positron channeling in a periodically bent crystal

We investigate, both analytically and numerically, the influence of the dechanneling process on the parameters of undulator radiation generated by ultra-relativistic positron channelling along a crystal plane, which is periodically bent. The bending might be due either to the propagation of a transverse acoustic wave through the crystal, or due to the static strain as it occurs in superlattices. In either case the periodically bent crystal serves as an undulator which allows to generate X-ray and gamma-radiation. We propose the scheme for accurate quantitative treatment of the radiation in presence of the dechanneling. The scheme includes (i) the analytic expression for spectral-angular distribution which contains, as a parameter, the dechanneling length, (ii) the simulation procedure of the dechanneling process of a positron in periodically bent crystals. Using these we calculate the dechanneling lengths of 5 GeV positrons channeling in Si, Ge and W crystals, and the spectral-angular and spectral distributions of the undulator over broad ranges of the photons. The calculations are performed for various parameters of the channel bending.Comment: published in J. Phys. G: Nucl. Part. Phys. 27 (2001) 95-125, http://www.iop.or

Сравнительный анализ эхокардиографических показателей времени ускорения и соотношения времени ускорения к общему времени выброса левого желудочка с показателями катетеризации в оценке тяжести аортального стеноза у пациентов с Normal flow High Gradient

Purpose. 1. To compare the ultrasound indices of time in comparison (AT), cardiac catheterization evaluating severity (AT/ET) with the indices of direct cardiac catheterization and assess the prognostic ability in the assessment of severity of AS in patients with Normal flow High Gradient 2. To determine the threshold values for the indicators of AT and AT/ET in predicting severe AS.Materials and methods. This is prospective single center study. We evaluated results of treatment of 75 patients with mean age 72 ± 6 years that were planned for aortic valve replacement due to aortic stenosis. Inclusion criteria: isolated aortic valve stenosis with ultrasound characteristics of severe AS. Before transcatheter aortic valve implantation, all patients underwent cardiac catheterization with the measurement of parameters necessary to assess the severity of AS.Results. Linear regression analysis showed a statistically significant correlation between AT and AT/ET (p < 0.05). The ROC-analysis has showed the highest predictive ability in assessing the severity of aortic stenosis for the AT / ET index (AUC – 87%, p < 0.001), slightly lower predictive power for the AT parameter (AUC – 80%, p < 0.001). The sensitivity and specificity of the AT / ET indicator in determining severe AS was 84% and 79%, respectively. For the AT indicator, the sensitivity was 82% and the specificity was 46%. The threshold values for AT and AT / ET were 105 ms and 0.35, respectively.Conclusions. 1. AT and AT / ET have a strong correlation with catheterization data and a high predictive ability of severe aortic stenosis in patients with Normal Flow High Gradient patients. 2. Threshold values for AT and AT /ET, that predict a high probability of AS, were 105ms and 0.35ms respectively. The study showed, echocardiographic indicators AT and AT ET have a strong correlation with catheterization data and a high predictive ability of severe aortic stenosis in patients with Normal Flow High Gradient patients. Threshold values for AT and AT ET, that predict a high probability of AS, were 105 ms and 0.35 ms respectively.Цель исследования: 1. Сравнить эхокардиографические показатели времени ускорения (АТ), соотношения времени ускорения к общему времени выброса левого желудочка (AT/ET) и общего времени выброса левого желудочка (ЕТ) с данными прямой катетеризации сердца и оценить предсказательную способность тяжелого аортального стеноза (АС) у пациентов с сохраненным ударным объемом ЛЖ и высокими трансаортальными градиентами. 2. Определить пороговые значения для показателей АТ и АТ/ЕТ в диагностике тяжелого АС.Материал и методы. Проспективно собраны данные 75 пациентов, средний возраст 72 ± 6 лет, которым планировалась транскатетерная имплантация аортального клапана (АК). Критерии включения: изолированный стеноз АК с эхокардиографическими характеристиками, соответствующими тяжелому стенозу с сохраненным ударным объемом ЛЖ и высокими трансаортальными градиентами. Всем исследуемым перед транскатетерной имплантацией АК проводили катетеризацию сердца с измерением показателей, необходимых для оценки тяжести АС.Результаты. Анализ линейной регрессии продемонстрировал статистически значимую корреляционную связь между показателями АT и AT/ET, р < 0,05. Кривая ROC-анализа продемонстрировала наибольшую диагностическую способность в оценке тяжести АС для показателя AT/ET, значение площади под кривой AUC 87 (р < 0,001), несколько меньшую диагностическую способность для показателя АТ, значение под кривой АUC 0,8 (р < 0,001). Чувствительность и специфичность показателя AT/ET в определении тяжелого АС составили 84 и 79% соответственно, для показателя АТ чувствительность – 82% и специфичность – 46%. Были выявлены пороговые значения для показателя АТ и АТ/ЕТ в определении тяжелого стеноза АК – 105 и 0,35 мс соответственно.Выводы. 1. Эхокардиографические показатели АТ и АТ/ЕТ обладают сильной корреляционной связью с данными катетеризации и высокой предсказательной способностью тяжелого АС у пациентов с сохраненным ударным объемом ЛЖ и высокими трансаортальными градиентами. 2. Пороговые значения показателей АТ 105 мс и АТ/ЕТ 0,35 мс могут с высокой долей вероятности диагностировать тяжелый АС

Сравнение эхокардиографического и катетерного методов в диагностике тяжелого стеноза аортального клапана

Purpose. 1. Assess the consistency of echocardiographic measurements with catheterization data in severe aortic stenosis.Assess if inter-method consistency improves after adjusting scores for the pressure recovery factor.To identify factors affecting the consistency of echocardiography and catheterization data.Materials and methods. Prospectively, 70 patients (mean age 72 ± 6 years, 38 females) have been included. All patient underwentcardiac catheterization with single-meter echoscanning of the parameters necessary to assess the severity of aortic valve stenosis before transcatheter aortic valve implantation. Inclusion criteria were isolated aortic stenosis (EOA <1 cm2, Gmax ≥64 mm Hg, Gmean ≥40 mm Hg. Exclusion criteria were LV stroke volume index <35 ml/m2 and a reduced EF <50%, concomitant nontrivial regurgitation of the aortic and mitral valves.Result. The linear regression method showed a weak correlation between the Gmax (Doppler) and Pmean indices, r = 0.48, p = 0.001. Revealed high values of the average difference between the two methods in comparison with the Blent–Altman (SR 19 ± 17 mm Hg.) and low intraclasscorrelation values (ICC = 0.34). After adjusting the Gmax (Doppler) indices for the pressure recovery factor, the correlation between the methods r = 0.84, p ≤ 0.001, significantly improved. There was a decrease in the mean indices, the difference between the two HR methods was (3.15 ± 12 mm Hg.) with highly significant intraclasscorrelation values (ICC = 0.89). Similarly, a low correlation with high values of the average difference was observed when comparing EOA (Doppler) and EOA (catheterization) r = 0.55, p = 0.01, SR 0.21 ± 0.15 cm2, ICC = 0.53. With an improvement in the correlation between the methods after adjustment for the pressure recovery coefficient, r = 0.9, p ≤ 0.001, CP = 0.04 ± 0.08 cm2, ICC = 0.92. Comparison of Gmean (Doppler) indices with catheter Pmean has showed a high correlation between the methods, r = 0.7, p ≤ 0.001, there were relatively low indices of the average difference between the two methods of HR = 7.2 ± 22 mm Hg and a significant intraclass correlation (ICC = 0.72). The method of analysis of multiple regression revealed that the diameter of the sinotubular ridge was a significant factor affecting the correlation between echocardiography and catheterization data, OR 1.2 (CI 0.09; 2.9).ConclusionsThe maximum Doppler gradient (Gmax) and the effective orifice area (EOA) have low consistency and weak correlation with catheterization data, in contrast to the average Doppler gradient (Gmean) which have a high consistency with catheterization data.After correcting for pressure recovery factor, there is a significant improvement in the consistency between Gmax and EOA with catheterization data.The diameter of the sinotobular junction is a significant factor influencing the consistency of echocardiography and catheterization data, which must be taken into account when assessing the severity of aortic stenosis.Цель исследования. 1. Оценить согласованность измерений, проведенных методом эхокардиографии, с данными катетеризации при  тяжелом стенозе аорты.Оценить, улучшается ли согласованность между методами после коррекции показателей на коэффициент восстановления давления.Выявить факторы, влияющие на согласованность данных эхокардиографии и катетеризации.Материал и методы. Проспективно были собраны данные 70 пациентов (из них 38 женщин), средний возраст 72 ± 6 лет, которым перед транскатетерной имплантацией аортального клапана (апикальным доступом) проводили катетеризацию сердца с одномоментным эхосканированием показателей, необходимых для оценки тяжести стеноза аортального клапана.Критерии включения в исследование: изолированный стеноз аортального клапана с эхокардиографическими характеристиками, соответствующими тяжелому стенозу: эффективная площадь отверстия аортального клапана (ЕOA) <1 cм2, максимальный градиент на аортальном клапане (Gmax) ≥64 мм рт.ст., средний градиент на аортальном клапане (Gmean) ≥40 мм рт.ст.Критерии исключения: пациенты с индексируемым ударным объемом ЛЖ к площади поверхности тела <35 мл/м2, сниженной фракцией выброса <50%, пациенты с сочетанной нетривиальной регургитацией на аортальном и митральном клапанах и пациенты с сочетанным значимым стенозом митрального клапана, ускоренным кровотоком в выносящем тракте левого желудочка (выше 1,1 м/c) и постоянной  формой фибрилляции предсердий.Результаты. Метод линейной регрессии продемонстрировал слабую корреляционную связь между показателями Gmax (допплер) и Pmean, r = 0,48, р = 0,001. Отмечались высокие значения средней разницы (СР) между двумя методами при сравнении Бленда–Альтмана (СР = 19 ± 17 мм рт.ст.) и низкие значения внутриклассовой корреляции (ICC = 0,34). После корректировки показателей Gmax (допплер) на коэффициент восстановления давления значительно улучшилась корреляционная связь между методами, r = 0,84, р ≤ 0,001, отмечалось снижение показателей средней разницы между двумя методами (СР = 3,15 ± 12 мм рт.ст.) с высокодостоверными значениями внутриклассовой корреляции (ICC = 0,89).Аналогично низкая корреляционная связь с высокими значениями средней разницы наблюдалась и при сравнении ЕОА (допплер) и ЕОА (катетеризация), r = 0,55, р = 0,01, СР = 0,21 ± 0,15 см2, ICC = 0,53, с улучшением согласованности между методами после корректировки на коэффициент восстановления давления, r = 0,9, р ≤ 0,001, СР = 0,04 ± 0,08 см2, ICC = 0,92.Сравнение показателей Gmean (допплер) c катетерным Pmean продемонстрировало высокую корреляционную связь между методами, г = 0,7, р ≤ 0,001, отмечались относительно низкие показатели средней разницы между двумя методами (СР = 7,2 ± 22 мм рт.ст) и значимая внутриклассовая корреляция (ICC = 0,72).Методом анализа множественной регрессии выявлено, что диаметр синотобулярного соединения является значимым фактором, оказывающим влияние на согласованость данных эхокардиографии и катетеризации OR 1,2 (95%ДИ 0,09; 2,9).ВыводыПоказатели максимального допплеровского градиента (Gmax) и площадь эффективного отверстия (EOA) имеют низкую согласованностью и слабую корреляционную связь с данными катетеризации, в отличие от показателей среднего допплеровского градиента (Gmean), которые имеют высокую согласован ность с данными катетеризации.После коррекции на коэффициент восстановления давления значительно улучшается согласованность между показателями Gmax и EOA с данными катетеризации.Диаметр синотобулярного соединения является значимым фактором, влияющим на согласованность данных эхокардиографии и катетеризации, который необходимо учитывать при оценке тяжести стеноза аорты.

Comparisons between Tethyan Anorthosite-bearing Ophiolites and Archean Anorthosite-bearing Layered Intrusions: Implications for Archean Geodynamic Processes

Elucidating the petrogenesis and geodynamic setting(s) of anorthosites in Archean layered intrusions and Tethyan ophiolites has significant implications for crustal evolution and growth throughout Earth history. Archean anorthosite-bearing layered intrusions occur on every continent. Tethyan ophiolites occur in Europe, Africa, and Asia. In this contribution, the field, petrographic, petrological, and geochemical characteristics of 100 Tethyan anorthosite-bearing ophiolites and 155 Archean anorthosite-bearing layered intrusions are compared. Tethyan anorthosite-bearing ophiolites range from Devonian to Paleocene in age, are variably composite, contain anorthosites with highly calcic (An44-100) plagioclase and magmatic amphibole. These ophiolites formed predominantly at convergent plate margins, with some forming in mid-ocean ridge, continental rift, and mantle plume settings. The predominantly convergent plate margin tectonic setting of Tethyan anorthosite-bearing ophiolites is indicated by negative Nb and Ti anomalies and magmatic amphibole. Archean anorthosite-bearing layered intrusions are Eoarchean to Neoarchean in age, have megacrystic anorthosites with highly calcic (An20-100) plagioclase and magmatic amphibole and are interlayered with gabbros and leucogabbros and intrude pillow basalts. These Archean layered intrusions are interpreted to have predominantly formed at convergent plate margins, with the remainder forming in mantle plume, continental rift, oceanic plateau, post-orogenic, anorogenic, mid-ocean ridge, and passive continental margin settings. These layered intrusions predominantly crystallized from hydrous Ca- and Al-rich tholeiitic magmas. The field, petrographic and geochemical similarities between Archean and Tethyan anorthosites indicate that they were produced by similar geodynamic processes mainly in suprasubduction zone settings. We suggest that Archean anorthosite-bearing layered intrusions and spatially associated greenstone belts represent dismembered subduction-related Archean ophiolites

Model for screening of resonant magnetic perturbations by plasma in a realistic tokamak geometry and its impact on divertor strike points

This work addresses the question of the relation between strike-point splitting and magnetic stochasticity at the edge of a poloidally diverted tokamak in the presence of externally imposed magnetic perturbations. More specifically, ad-hoc helical current sheets are introduced in order to mimic a hypothetical screening of the external resonant magnetic perturbations by the plasma. These current sheets, which suppress magnetic islands, are found to reduce the amount of splitting expected at the target, which suggests that screening effects should be observable experimentally. Multiple screening current sheets reinforce each other, i.e. less current relative to the case of only one current sheet is required to screen the perturbation.Comment: Accepted in the Proceedings of the 19th International Conference on Plasma Surface Interactions, to be published in Journal of Nuclear Materials. Version 2: minor formatting and text improvements, more results mentioned in the conclusion and abstrac

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET

Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate