Ionospheric effects during first 2 hours after the Chelyabinsk meteorite impact

This paper presents the analysis of ionospheric effects in the region close to the Chelyabinsk meteorite explosion at 03:20UT 2013 February 15 from the Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) EKB radar data, and from the Institute of Geophysics of Ural Branch of Russian Academy of Sciences (IG UB RAS) PARUS ionosonde data. Both instruments are located within the IG UB RAS Arti Observatory approximately 200 km northward from the estimated explosion site. According to the data obtained, the ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. However, it obviously did not lead to a variation in the ionosphere mean parameters in the region above the disturbance center during the first 2 hours. Essential effects, however, were observed at more than 100-200 km from the explosion site and farther up to 1500 km.Comment: 30 pages, 15 figures, submitted to JAST

Superhyperfine interactions in Ce3+ doped LiYF4 crystal: ENDOR measurements

The first observation of the resolved Mims electron-nuclear double resonance (ENDOR) spectra from the nearby and remote nuclei of 19F and 7Li nuclei on impurity Ce3+ ions in LiYF4 crystal is reported. It shows that LiYF4:Ce3+ system can be exploited as a convenient matrix for performing spin manipulations and adjusting quantum computation protocols while ENDOR technique could be used for the investigation of electron-nuclear interaction with all the nuclei of the system and exploited for the electron-nuclear spin manipulations.Comment: 4 pages, 2 figures, 1 Table. Reported on Theor-2017 (Kazan, Russia) Conferenc

Relevant Aspects of Standardisation of Plant Raw Materials and Herbal Medicinal Products Containing Phenolic Compounds

Currently experts are actively working on Russian specifications for herbal drugs, herbal drug preparations, and herbal medicinal products, and specifically on analytical procedures to evaluate the quality of these medicines. The aim of this study was to provide a scientific basis for improving the procedures of qualitative and quantitative analysis of herbal drugs, herbal drug preparations and herbal medicinal products containing phenolic compounds. It was shown that the chemical nature, physicochemical and spectral characteristics of biologically active compounds should be considered a basis for the development of new methodological approaches to standardisation of plant raw materials and herbal medicines. The study used an example of herbal drugs and herbal medicinal products containing flavonoids, phenylpropanoids, and anthracene derivatives to justify the feasibility of standardisation using TLC, HPLC, spectrophotometry, as well as indicative reference standards as criteria of identity and quality. The study substantiated the necessity of a state system for development and registration of reference standards for pharmacopoeial analyses

The 1867 Virgin Island Tsunami

International audienceThe 1867 Virgin Island Tsunami reached large magnitude on the coasts of the Caribbean Islands. A maximum tsunami height of 10 m was reported for two coastal locations (Deshaies and Sainte-Rose) in Guadeloupe. Modelling of the 1867 tsunami is performed in the framework of the nonlinear shallow-water theory. The directivity of the tsunami wave source in the Caribbean Sea according to the assumed initial waveform is investigated. The tsunami records at the several coastal regions in the Lesser Antilles, Virgin Islands, Puerto Rico and South America are simulated. The comparison between the computed and observed data is in reasonable agreement

On the nonlinear NMR and magnon BEC in antiferromagnetic materials with coupled electron-nuclear spin precession

We present a new study of nonlinear NMR and Bose-Einstein Condensation (BEC) of nuclear spin waves in antiferromagnetic MnCO3 with coupled electron and nuclear spins. In particular, we show that the observed behaviour of NMR signals strongly contradicts the conventional description of paramagnetic ensembles of noninteracting spins based on the phenomenological Bloch equations. We present a new theoretical description of the coupled electron-nuclear spin precession, which takes into account an indirect relaxation of nuclear spins via the electron subsystem. We show that the magnitude of the nuclear magnetization is conserved for arbitrary large excitation powers, which is drastically different from the conventional heating scenario derived from the Bloch equations. This provides strong evidence that the coherent precession of macroscopic nuclear magnetization observed experimentally can be identified with BEC of nuclear spin waves with k=0.Comment: 12 pages, 8 figure

Новые подходы к стандартизации травы монарды дудчатой

Objectives. The Monarda fistulosa herb of the Lamiaceae family is particularly interesting among essential oils from medicinal plants that have a wide spectrum of pharmacological activities. However, information regarding some of its flavonoids, which are found in the essential oil, is controversial. Inaccuracies in identification of the chemical composition of the herb have led to several different standardization approaches, which are cumbersome. To establish a uniform classification, here, we present confirmation for new approaches for the standardization of the Monarda fistulosa herb. Methods. Silica gel column chromatography was used to extract the flavonoids. Identification was based on ultraviolet spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, and acidic hydrolysis. The quality of the proposed quantitation methodology for total flavonoids was assessed by differential spectrophotometry at 394 nm, in isorhoifolin equivalent.Results. We have verified new approaches for the standardization of the Monarda fistulosa herb. The approaches can determine the authenticity of the herb by detecting monoterpene phenols and flavonoids that have diagnostic value. We also developed a technique for quantitation of the total flavonoids. Conclusions. We investigated the possibility of establishing the authenticity of the Monarda fistulosa herb based on the diagnostically significant flavonoids, isorhoifolin and linarin.Цели. Среди эфиромасличных лекарственных растений, обладающих широким спектром фармакологической активности, особый интерес представляет трава монарды дудчатой (Monarda fistulosa) семейства Яснотковых. Однако информация о некоторых флавоноидах, содержащихся в ней наряду с эфирным маслом, носит противоречивый характер. Неточности, выявленные в отношении химического состава травы, становятся причиной появления различных подходов к стандартизации, что создает трудности. Для обеспечения единообразия классификации в данной работе представлено обоснование новых, ранее не применявшихся подходов к стандартизации травы монарды дудчатой. Методы. Для экстракции флавоноидов использовали колоночную хроматографию на силикагеле. Идентификацию осуществляли на основании данных ультрафиолетовой спектроскопии, спектроскопии ядерного магнитного резонанса и масс-спектрометрии, а также результатов кислотного гидролиза. Оценку качества предложенной методики количественного определения суммы флавоноидов проводили методом дифференциальной спектрофотометрии при 394 нм в пересчете на изороифолин. Результаты. Обоснованы подходы к стандартизации травы монарды дудчатой, заключающиеся в определении ее подлинности путем обнаружения монотерпеновых фенолов и флавоноидов, имеющих диагностическое значение. Разработана методика количественного определения суммы флавоноидов.Выводы. Изучена возможность определения подлинности травы монарды дудчатой, исходя из диагностически значимых флавоноидов – изороифолина и линарина

Strongly nonlinear steepening of long interfacial waves

International audienceThe transformation of nonlinear long internal waves in a two-layer fluid is studied in the Boussinesq and rigid-lid approximation. Explicit analytic formulation of the evolution equation in terms of the Riemann invariants allows us to obtain analytical results characterizing strongly nonlinear wave steepening, including the spectral evolution. Effects manifesting the action of high nonlinear corrections of the model are highlighted. It is shown, in particular, that the breaking points on the wave profile may shift from the zero-crossing level. The wave steepening happens in a different way if the density jump is placed near the middle of the water bulk: then the wave deformation is almost symmetrical and two phases appear where the wave breaks

Nonlinear mechanism of tsunami wave generation by atmospheric disturbances

International audienceThe problem of tsunami wave generation by variable meteo-conditions is discussed. The simplified linear and nonlinear shallow water models are derived, and their analytical solutions for a basin of constant depth are discussed. The shallow-water model describes well the properties of the generated tsunami waves for all regimes, except the resonance case. The nonlinear-dispersive model based on the forced Korteweg-de Vries equation is developed to describe the resonant mechanism of the tsunami wave generation by the atmospheric disturbances moving with near-critical speed (long wave speed). Some analytical solutions of the nonlinear dispersive model are obtained. They illustrate the different regimes of soliton generation and the focusing of frequency modulated wave packets

Probing the Yb3+^{3+} spin relaxation in Y0.98_{0.98}Yb0.02_{0.02}Ba2_{2}Cu3_{3}Ox_{x} by Electron Paramagnetic Resonance

The relaxation of Yb$^{3+}$ in YBa$_{2}$Cu$_{3}$O$_{x}$ ($6<x<7$) was studied using Electron Paramagnetic Resonance (EPR). It was found that both electronic and phononic processes contribute to the Yb$^{3+}$ relaxation. The phononic part of the relaxation has an exponential temperature dependence, which can be explained by a Raman process via the coupling to high-energy ($\sim$500 K) optical phonons or an Orbach-like process via the excited vibronic levels of the Cu$^{2+}$ ions (localized Slonczewski-modes). In a sample with a maximum oxygen doping $x$=6.98, the electronic part of the relaxation follows a Korringa law in the normal state and strongly decreases below $T_{c}$. Comparison of the samples with and without Zn doping proved that the superconducting gap opening is responsible for the sharp decrease of Yb$^{3+}$ relaxation in YBa$_{2}$Cu$_{3}$O$_{6.98}$. It was shown that the electronic part of the Yb$^{3+}$ relaxation in the superconducting state follows the same temperature dependence as $^{63}$Cu and $^{17}$O nuclear relaxations despite the huge difference between the corresponding electronic and nuclear relaxation rates.Comment: 8 pages, 6 figure