SEARCH FOR AEROSOL MICROPARTICLES IN DATED LAYERS OF BOTTOM SEDIMENTS USING SYNCHROTRON RADIATION

The SR-micro-XRF method was used to search for microparticles of extraterrestrial matter in the bottom sediments of Lake Zapovednoye, located 60 km from the epicentre of the explosion of the Tunguska cosmic body (TCB) in 1908. The material of bottom sediments dating back to 1908–1910 was studied. The samples for the study were prepared in the form of a powder applied to a conductive adhesive tape, which made it possible to combine the data of optical observations, electron microscopy, and micro-XRF scanning. The experiments were carried out at the Large-Scale Research Facilities "Kurchatov Centre for Synchrotron Research" using a confocal X-ray microscope developed at the Budker Institute of Nuclear Physics SB RAS. The data obtained indicate the presence of microparticles with an increased Ni/Fe ratio, possibly of extraterrestrial origin

VARIATIONS IN SOLAR ACTIVITY AND CHANGES IN THE LEVEL OF KHAKASSIA SALT LAKES IN THE LAST MILLENNIUM

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Monogenetic near-island seamounts in the Galapagos Archipelago

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(12), (2020): e2020GC008914, https://doi.org/10.1029/2020GC008914.Rarely have small seamounts on the flanks of hotspot derived ocean‐island volcanoes been the targets of sampling, due to sparse high‐resolution mapping near ocean islands. In the Galápagos Archipelago, for instance, sampling has primarily targeted the subaerial volcanic edifices, with only a few studies focusing on large‐volume submarine features. Sampling restricted to these large volcanic features may present a selection bias, potentially resulting in a skewed view of magmatic and source processes because mature magmatic systems support mixing and volcanic accretion that overprints early magmatic stages. We demonstrate how finer‐scale sampling of satellite seamounts surrounding the volcanic islands in the Galápagos can be used to lessen this bias and thus, better constrain the evolution of these volcanoes. Seamounts were targeted in the vicinity of Floreana and Fernandina Islands, and between Santiago and Santa Cruz. In all regions, individual seamounts are typically monogenetic, but each seamount field requires multigenerational magmatic episodes to account for their geochemical variability. This study demonstrates that in the southern and eastern regions the seamounts are characterized by greater geochemical variability than the islands they surround but all three regions have (Sr‐Nd‐He) isotopic signatures that resemble neighboring islands. Variations in seamount chemistry from alkalic to tholeiitic near Fernandina support the concept that islands along the center of the hotspot track undergo greater mean depths of melting, as predicted by plume theory. Patterns of geochemical and isotopic enrichment of seamounts within each region support fine‐scale mantle heterogeneities in the mantle plume sourcing the Galápagos hotspot.This work was carried out with funding from National Science Foundation Division of Ocean Sciences (OCE‐1634952 to V. D. Wanless, OCE‐1634685 to S. A. Soule). The authors have no competing interests to declare. We thank Sally Gibson and three anonymous reviewers for providing detailed and critical feedback on this manuscript.2021-05-0

Transit Timing Observations from Kepler. VIII Catalog of Transit Timing Measurements of the First Twelve Quarters

Following Ford et al. (2011, 2012) and Steffen et al. (2012) we derived the transit timing of 1960 Kepler KOIs using the pre-search data conditioning (PDC) light curves of the first twelve quarters of the Kepler data. For 721 KOIs with large enough SNRs, we obtained also the duration and depth of each transit. The results are presented as a catalog for the community to use. We derived a few statistics of our results that could be used to indicate significant variations. Including systems found by previous works, we have found 130 KOIs that showed highly significant TTVs, and 13 that had short-period TTV modulations with small amplitudes. We consider two effects that could cause apparent periodic TTV - the finite sampling of the observations and the interference with the stellar activity, stellar spots in particular. We briefly discuss some statistical aspects of our detected TTVs. We show that the TTV period is correlated with the orbital period of the planet and with the TTV amplitude.Comment: Accepted for publication to ApJ. 57 pages, 23 Figures. Machine readable catalogs are available at ftp://wise-ftp.tau.ac.il/pub/tauttv/TT

On the Supposed Presence of Miocene Tayassuidae and Dromomerycinae (Mammalia, Cetartiodactyla) in South America

The earliest record of North American mammals in South America is significant for constraining the timing of intercontinental faunal interchange. At present, the oldest securely dated remains of a North American terrestrial mammal in South America pertain to a late Miocene procyonid; a few other North American mammal groups are present in late Miocene and early Pliocene outcrops in South America, but most are not recorded until the late Pliocene or Pleistocene, after the complete emergence of the Panamanian Isthmus. This long-established pattern has recently been called into question by reports of a proboscidean, two tayassuids, and a dromomerycine cervoid in supposed late Miocene deposits of Peruvian Amazon. In this contribution, we analyze the taxonomic identities and stratigraphic provenances of the tayassuid and dromomerycine fossils in detail. We conclude that these specimens are not distinguishable from modern tayassuids (Tayassu pecari and Dicotyles tajacu) and cervids, and that previous taxonomic identifications are based on misinterpretation of characters or inadequate specimens. In addition, there is insufficient evidence to support a late Miocene age for these terrestrial cetartiodactyl fossils; the stratigraphic provenance of the specimens is highly dubious, and the fossils are likely Quaternary in age.Fil: Gasparini, Germán Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; ArgentinaFil: Parisi Dutrá, Rodrigo. Universidade Federal de Minas Gerais; BrasilFil: Perini, Fernando A.. Universidade Federal de Minas Gerais; BrasilFil: Croft, Darin. Case Western Reserve University; Estados UnidosFil: Cozzuol, Mario Alberto. Universidade Federal de Minas Gerais; BrasilFil: Missagia, Rafaela V.. Universidade Federal de Minas Gerais; BrasilFil: Lucas, Spencer G.. New Mexico Museum Of Natural History And Science; Estados Unido

Local and global Fokker-Planck neoclassical calculations showing flow and bootstrap current modification in a pedestal

In transport barriers, particularly H-mode edge pedestals, radial scale lengths can become comparable to the ion orbit width, causing neoclassical physics to become radially nonlocal. In this work, the resulting changes to neoclassical flow and current are examined both analytically and numerically. Steep density gradients are considered, with scale lengths comparable to the poloidal ion gyroradius, together with strong radial electric fields sufficient to electrostatically confine the ions. Attention is restricted to relatively weak ion temperature gradients (but permitting arbitrary electron temperature gradients), since in this limit a delta-f (small departures from a Maxwellian distribution) rather than full-f approach is justified. This assumption is in fact consistent with measured inter-ELM H-Mode edge pedestal density and ion temperature profiles in many present experiments, and is expected to be increasingly valid in future lower collisionality experiments. In the numerical analysis, the distribution function and Rosenbluth potentials are solved for simultaneously, allowing use of the exact field term in the linearized Fokker-Planck collision operator. In the pedestal, the parallel and poloidal flows are found to deviate strongly from the best available conventional neoclassical prediction, with large poloidal variation of a different form than in the local theory. These predicted effects may be observable experimentally. In the local limit, the Sauter bootstrap current formulae appear accurate at low collisionality, but they can overestimate the bootstrap current near the plateau regime. In the pedestal ordering, ion contributions to the bootstrap and Pfirsch-Schluter currents are also modified

ПОИСК АЭРОЗОЛЬНЫХ МИКРОЧАСТИЦ В ДАТИРОВАННЫХ СЛОЯХ ДОННЫХ ОТЛОЖЕНИЙ С ИСПОЛЬЗОВАНИЕМ СИНХРОТРОННОГО ИЗЛУЧЕНИЯ

The SR-micro-XRF method was used to search for microparticles of extraterrestrial matter in the bottom sediments of Lake Zapovednoye, located 60 km from the epicentre of the explosion of the Tunguska cosmic body (TCB) in 1908. The material of bottom sediments dating back to 1908–1910 was studied. The samples for the study were prepared in the form of a powder applied to a conductive adhesive tape, which made it possible to combine the data of optical observations, electron microscopy, and micro-XRF scanning. The experiments were carried out at the Large-Scale Research Facilities "Kurchatov Centre for Synchrotron Research" using a confocal X-ray microscope developed at the Budker Institute of Nuclear Physics SB RAS. The data obtained indicate the presence of microparticles with an increased Ni/Fe ratio, possibly of extraterrestrial origin.Методом микро-РФА-СИ проведен поиск микрочастиц внеземного вещества в донных осадках озера Заповедного, расположенного в 60 км от эпицентра взрыва Тунгусского космического тела (ТКТ) в 1908 г. Исследован материал донных отложений, датируемый 1908–1910 гг. Образцы для исследования были приготовлены в виде порошка, нанесенного на токопроводящую клейкую ленту, что позволило совместить данные оптических наблюдений, электронной микроскопии и микро-РФА сканирования. Эксперименты проводились с использованием УНУ «Курчатовский центр синхротронного излучения КИСИ» с использованием конфокального рентгеновского микроскопа, разработанного в ИЯФ СО РАН. Полученные данные свидетельствуют о наличии микрочастиц с повышенным отношением Ni/Fe, возможно имеющих внеземное происхождение. Используемые методики микро-РФА-СИ позволяют проводить поиск и изучение частиц с микрометровым пространственным разрешением в матрицах различного состава на основе данных о распределении породообразующих и следовых элементов

Annual Sedimentary Record From Lake Donguz-Orun (Central Caucasus) Constrained by High Resolution SR-XRF Analysis and Its Potential for Climate Reconstructions

Bottom sediments of the proglacial Lake Donguz-Orun situated at ∼2500 m a.s.l. in the Elbrus Region (Central Caucasus) reveal regular laminae, characteristic of proglacial varved lakes. This is the first laminated sediment sequence recorded in the region. However, visual counting of the layers was restricted due to partial indistinctness of the lamination. In order to confirm the annual sedimentary cyclicity and proceed with annually resolved data, in addition to the visual identification we used high-resolution geochemical markers. The upper 160 mm of the sediment core were scanned at 200 μm intervals using synchrotron radiation X-ray fluorescence analysis (SR-XRF). Additional ultrahigh resolution scanning at 30 μm increments was employed for the upper 20 mm of the core. The Rb/Sr and Zr/Rb ratios are interpreted to record annual changes in grain-size. Based on this geochemical assessment, we identified 88 annual layers covering the interval between 1922 and 2010, while visually we have been able to identify between 70 and 100 layers. The correctness of the geochemical results is confirmed by mean accumulation rates assessed by 137Cs and 210Pb dating. Cross-correlation between the ring width of local pine chronology and the layer thickness, identified as a distance between the annual Rb/Sr peaks, allowed for the accurate dating of the uppermost preserved year of the sediment sequence (AD 2010). Annually averaged elemental data were then compared with regional meteorological observations, glacier mass balance and tree-ring chronologies. The comparison revealed notable conformities: content of bromine is positively correlated with annual temperatures (r = 0.41, p < 0.01), content of terrigenous elements (major elements with the origin in watershed rocks) is positively correlated (up to r = 0.44, p < 0.01) with annual precipitation. A high statistically significant negative relationship is observed between the concentrations of terrigenous elements and tree-ring width of local pine chronology (up to r = -0.56, p < 0.01). Taken together, these data point to a common composite climatic signal in the two independent records (lake sediments and tree rings) and confirm that the laminae represent annual layers (i.e., varves). These findings open opportunities for high-resolution multiproxy climate reconstructions 300–350 years long using the longer sediment core and tree-ring records

Архив климатических изменений и сейсмических событий в ледниковых глинах озера Кучерлинского (Алтай)

Core samples taken from the bottom sediments of the glacial Lake Kucherla (Gorny Altai, Russia) clearly show annual layers represented by glacial clays. In our study, age-depth modeling is based the varve chronology and Cs-137, Pb-210 and C-14 isotope data. Our model is a highly accurate and reliable demonstration of the annual sedimentation history within the past 1400 years. The time series of geochemical indicators of climate change were obtained by synchrotron radiation micro X-ray fluorescence (SR-μXRF) core scanning. Instrumental meteorological observations from 1940 to 2016 were used to construct transfer functions for the average annual temperatures and atmospheric precipitation amounts. A geochemical trace of a catastrophic seismic event, the Mongolian earthquake of 1761, was found in the cross-section of the bottom sediments.В керне донных осадков ледникового озера Кучерлинского (Алтай) видна годовая слоистость (ленточные глины). На основе данных варвохронологии (подсчет слоев) и изотопных исследований (Cs-137, Pb-210, C-14) была построена точная возрастная модель (глубина керна – возраст осадка) на 1400 лет назад. Методом сканирующего микрорентгенофлуоресцентного анализа с использованием синхротронного излучения получены временные ряды геохимических индикаторов климатических изменений. Для временного интервала 1940–2016 гг. на основе инструментальных метеонаблюдений построены трансферные функции для среднегодовых значений температуры и количества атмосферных выпадений. В разрезе донных осадков найден геохимический след катастрофического сейсмического события – Монгольского землетрясения 1761 г

A First Comparison of Kepler Planet Candidates in Single and Multiple Systems

In this letter we present an overview of the rich population of systems with multiple candidate transiting planets found in the first four months of Kepler data. The census of multiples includes 115 targets that show 2 candidate planets, 45 with 3, 8 with 4, and 1 each with 5 and 6, for a total of 170 systems with 408 candidates. When compared to the 827 systems with only one candidate, the multiples account for 17 percent of the total number of systems, and a third of all the planet candidates. We compare the characteristics of candidates found in multiples with those found in singles. False positives due to eclipsing binaries are much less common for the multiples, as expected. Singles and multiples are both dominated by planets smaller than Neptune; 69 +2/-3 percent for singles and 86 +2/-5 percent for multiples. This result, that systems with multiple transiting planets are less likely to include a transiting giant planet, suggests that close-in giant planets tend to disrupt the orbital inclinations of small planets in flat systems, or maybe even to prevent the formation of such systems in the first place.Comment: 13 pages, 13 figures, submitted to ApJ Letter