Metastable Olivine within Oceanic Lithosphere in the Uppermost Lower Mantle Beneath the Eastern United States

Approximately two-thirds of Earth\u27s outermost shell is composed of oceanic plates that form at spreading ridges and recycle back to Earth\u27s interior in subduction zones. A series of physical and chemical changes occur in the subducting lithospheric slab as the temperature and pressure increase with depth. In particular, olivine, the most abundant mineral in the upper mantle, progressively transforms to its high-pressure polymorphs near the mantle transition zone, which is bounded by the 410 km and 660 km discontinuities. However, whether olivine still exists in the core of slabs once they penetrate the 660 km discontinuity remains debated. Based on SKS and SKKS shear-wave differential splitting times, we report new evidence that reveals the presence of metastable olivine in the uppermost lower mantle within the ancient Farallon plate beneath the eastern United States. We estimate that the low-density olivine layer in the subducted Farallon slab may compensate the high density of the rest of the slab associated with the low temperature, leading to neutral buoyancy and preventing further sinking of the slab into the deeper part of the lower mantle

SEISMIC STRUCTURE OF THE EUROPEAN CRUST AND UPPER MANTLE BASED ON ADJOINT TOMOGRAPHY

We use adjoint tomography to estimate three-dimensional variations in seismic parameters within the crust and upper mantle beneath Europe and the North Atlantic Ocean. Spectral-element and adjoint methods are used to numerically calculate synthetic seismograms and sensitivity kernels in three-dimensional Earth models. Combined with gradient- based optimization algorithms, e.g., preconditioned conjugate-gradient and L-BFGS methods, we iteratively update seismic models of Earth's interior. A three-stage inversion strategy is designed to estimate variations in elastic wavespeeds, anelastic attenuation and radial & azimuthal anisotropy. In stage one, frequency-dependent phase differences between observed and simulated seismograms are used to determine a new radially anisotropic wavespeed model for the European crust and upper mantle, namely EU30. Long-wavelength structures in EU30 compare favorably with previous body- and surface-wave tomographic models. Some hitherto unidentified features naturally emerge from the smooth starting model. In stage two, frequency-dependent amplitude differences combined with remaining phase anomalies are used to simultaneously constrain elastic and anelastic structures. A new anelastic model, named EU50, is constructed in this stage. We observe several notable features, such as enhanced attenuation within the mantle transition zone beneath the North Atlantic Ocean. In the first two stages, long-period surface waves and short-period body waves in three-component seismograms are combined to simultaneously constrain shallow and deep structures. In stage three, frequency-dependent phase and amplitude anomalies of three-component surface waves are used to construct a radially and azimuthally anisotropic model EU60. We find that the direction of the fast axis is closely tied to the tectonic evolution in this region, such as extension along the North Atlantic Ridge, trench retreat in the Mediterranean, and counterclockwise rotation of the Anatolian Plate. Radial peak-to- peak anisotropic strength profiles identify distinct brittle-ductile transitions in lithospheric strength beneath oceans and continents, in agreement with observations in mineral physics experiments

Real-time positioning of a specific object in the big data environment

Abstract Real-time positioning of a specific object in the big data environment can improve the monitoring and management capacity for network data. For the real-time positioning of the specific object, it is necessary to quickly search the network data representing a specific object and match its pattern strings and compare the corresponding Internet protocol (IP) address of the matched network data with the IP address library in real time, so as to determine the position of the specific object. When a traditional method is used for pattern string matching, it will occupy a lot of memories and network resources, thereby reducing the positioning effect of the specific object in the big data environment. A positioning method for a specific object of high performance and multi-pattern matching based on three indexes in the big data network environment is proposed in this paper. Firstly, the initialization of Modified Wu-Manber (MWM) algorithm was carried out, and the algorithm was used to match the network data continuously. Secondly, the three indexes were used to improve the MWM algorithm, and the real-time and fast positioning of a specific object in the big data environment was completed by the Third Index Modified Wu-Manber (TMWM). The experimental results show that compared with the traditional method, the proposed algorithm reduces the pattern string matching scope of network data representing the specific object, improves the search speed of the specific object, and locates the specific object in the big data environment in an effective and rapid manner

Additional file 2: of Real-time positioning of a specific object in the big data environment

Test samples from the SOGOU Chinese Thesaurus that contains 250 thousand phrases. (TXT 1956 kb

Additional file 3: of Real-time positioning of a specific object in the big data environment

Test samples from the SOGOU Chinese Thesaurus that contains 300 thousand phrases. (TXT 2350 kb

Radial anisotropy of the North American upper mantle based on adjoint tomography with USArray

International audienc

Gastric calcifying fibrous tumor: A case of suspected immunoglobulin G4-related gastric disease

Gastrointestinal lesions resulting from immunoglobulin G4-related disease are classified into two types: One is a gastrointestinal lesion showing marked thickening of the wall, and the other is an IgG4-related pseudotumor. We report the case of a woman with gastric calcifying fibrous tumor undergoing endoscopic resection that contained 62 IgG4+ plasma cells per high-power field and an IgG4-to-IgG ratio of 41% in lesional plasma cells, which shared clinical and histopathological features associated with gastric IgG4-related pseudotumor. So, we postulate that calcifying fibrous tumor as part of the spectrum of IgG4-related disease might be the unifying concept with IgG4-related pseudotumor. Meanwhile, the patient had coexistent autoimmune diseases, including autoimmune atrophic gastritis, Hashimoto's thyroiditis, and possible primary biliary cirrhosis. The clinical follow-up evaluation was uneventful

The Effects of the Addition of Ti3SiC2 on the Microstructure and Properties of Laser Cladding Composite Coatings

This study explored the effects of Ti3SiC2 on the microstructure and properties of laser cladding coatings using X-ray diffractometer, scanning electron microscope, electrochemical workstation, and UMT-2 wear tester analyses. It was found that with the addition of Ti3SiC2, the reinforcing phases in the composite coating were TiC, Ti(B,C)2, honeycomb-like (Cr, Fe)23C6, and a novel composite ceramic with an “eyeball” structure, which had an inside core of Al2O3 and TiC outer surrounding structure. The microhardness, wear, and corrosion resistance of the composite coating were about 1.35, 2, and 4.3 times those of the original coating, respectively. The main wear mechanisms of the original coating were severe fatigue spalling and microcutting, while the main mechanisms of the composite coating were slight microcutting and the formation of the transferred film