Seismic velocities in Southern Tibet lower crust: a receiver function approach for eclogite detection

Beneath the Tibet plateau, the deficit of crustal thickening with respect to what is expected from the plate tectonic constraints is thought to be absorbed either by lateral extrusion or by vertical rock-mass transfer. To nourish the unsettled debate of the relative importance of these two processes, we propose a new approach, based on the S-to-P and the P-to-S wave conversions, enabling the precise determination of the seismic velocities. The weighted amplitudes of the direct conversion and of reverberations are stacked at their predicted arrival times for various values of layer thickness and v(P)/v(S) ratio separately for two sets of P- and S-receiver functions. For each set of receiver functions, coherent stack gives the v(P)/v(S) ratio and thickness for the considered layer (the grid search stacking method). The values of v(P)/v(S) ratio and layer thickness are functions of the velocity used for stacking the set of receiver functions, but using the P- and S-receiver functions allows us to solve this indetermination and to find the effective parameters of the layer: velocity v(S), v(P)/v(S) ratio and thickness. We use a bootstrap resampling of the receiver function data sets to estimate the parameters uncertainties. For the Southern Lhasa Block, the migrated sections of both P- and S-receiver functions (Hi-CLIMB experiment data) show a layer in the lower crust that may be related to the lower Indian crust underplated beneath Tibet. With the grid search stacking method, high shear wave velocities (v(S) similar to 4.73 km s(-1)) and low v(P)/v(S) ratios (similar to 1.69) are detected in this layer. Such values are typical for high-grade eclogites, and the low v(P)/v(S) ratio precludes the confusion with mafic granulites. There is no evidence for partial eclogitization near and south of the Yarlung-Tsangpo Suture, and the about 19 km thick eclogitic layer extends northwards only to about the middle of the Lhasa terrane

Geographical distribution and spatio-temporal changes in the occurrence of invasive plant species in Slovak Republic

Biological systems are subject to a dramatic increase in invading species in the 21st century due to increasing globalization around the world. In the near future, these species will cause more extensive ecological as well as socio-economic damage. Biotic invasions will result not only in a reduction of the original biodiversity, but also total loss, particularly degradation of natural habitats – especially Natura 2000 habitats. This study aims to understand the processes of spread of invasive plant species, their way of life, adaptation to environmental changes and displacement of native species. Without the local level, it is not possible to understand these processes on the regional and continental dimensions and thus implement scientific facts and findings into the prediction of the development of global biosystems. The research was conducted during the vegetation period in the years 2017–2021 in the studied areas of non-forest and forest habitats in the central part of Slovakia. We recorded 242 localities in the area with the occurrence of invasive plant species in an area of 3.057 km2 out of the total mapped area of 169.024 km2. We recorded the highest number of localities and the most expansive distribution for the species Stenactis annua, Robinia pseudoacacia, Solidago canadensis, Impatiens glandulifera and Fallopia japonica

High-Pressure Study of h.c.p.

Depending on the loading procedure of diamond anvil cells, argon under pressure either crystallizes in f.c.c. or h.c.p. configurations. The elastic properties of the h.c.p. crystals are comparable to those with the f.c.c. structure

The 2015 Gorkha earthquake: A large event illuminating the Main Himalayan Thrust fault

International audienceThe 2015 Gorkha earthquake sequence provides an outstanding opportunity to better characterize the geometry of the Main Himalayan Thrust (MHT). To overcome limitations due to unaccounted lateral heterogeneities, we perform Centroid Moment Tensor inversions in a 3-D Earth model for the main shock and largest aftershocks. In parallel, we recompute S-toP and P-to-S receiver functions from the Hi-CLIMB data set. Inverted centroid locations fall within a low-velocity zone at 10–15 km depth and corresponding to the subhorizontal portion of the MHT that ruptured during the Gorkha earthquake. North of the main shock hypocenter, receiver functions indicate a north dipping feature that likely corresponds to the midcrustal ramp connecting the flat portion to the deep part of the MHT. Our analysis of the main shock indicates that long-period energy emanated updip of high-frequency radiation sources previously inferred. This frequency-dependent rupture process might be explained by different factors such as fault geometry and the presence of fluids

Thermal and tectonic consequences of India underthrusting Tibet

The Tibetan Plateau is the largest orogenic system on Earth, and has been influential in our understanding of how the continental lithosphere deforms. Beneath the plateau are some of the deepest ( ~ 100 ) earthquakes observed within the continental lithosphere, which have been pivotal in ongoing debates about the rheology and behaviour of the continents. We present new observations of earthquake depths from the region, and use thermal models to suggest that all of them occur in material at temperatures of ≲600 °C. Thermal modelling, combined with experimentally derived flow laws, suggests that if the Indian lower crust is anhydrous it will remain strong beneath the entire southern half of the Tibetan plateau, as is also suggested by dynamic models. In northwest Tibet, the strong underthrust Indian lower crust abuts the rigid Tarim Basin, and may be responsible for both the clockwise rotation of Tarim relative to stable Eurasia and the gradient of shortening along the Tien Shan

Distribution of immune cells in head and neck cancer: CD8+ T-cells and CD20+ B-cells in metastatic lymph nodes are associated with favourable outcome in patients with oro- and hypopharyngeal carcinoma

<p>Abstract</p> <p>Background</p> <p>Tumour infiltrating lymphocytes (TIL) are generally considered to represent a host immune response directed against tumour antigens. TIL are also increasingly recognised as possible prognostic parameters. However, the effects observed are variable indicating that results cannot be extrapolated from type of tumour to another. Moreover, it has been suggested that primary solid tumours may be ignored by the immune system and that a meaningful immune response is only mounted in regional lymph nodes.</p> <p>Methods</p> <p>We have examined the local distribution of immune cells in tumour-related compartments in head and neck squamous cell carcinomas (HNSCC). In a second step, the prognostic impact of these cells on disease-free survival (DFS) was analysed. A total of 198 tissue cores from 33 patients were evaluated using tissue mircroarray technique and immunohistochemistry. Tumour-infiltrating immune cells were identified using antibodies specific for CD3, CD8, GranzymeB, FoxP3, CD20 and CD68 and quantified using an image analysis system.</p> <p>Results</p> <p>We demonstrate a relative expansion of FoxP3⁺regulatory T-cells (Treg) and of cytotoxic T-cells among tumour infitrating T-cells. We also show that intratumoural CD20⁺B-cells are significantly more frequent in metastatic deposits than in primary tumours. Furthermore, we observed a reduced number of peritumoural CD8⁺T-cells in metastatic lymph nodes as compared to univolved regional nodes suggesting a local down-modulation of cellular immunity. All other immune cells did not show significant alterations in distribution. We did not observe an association of tumour infiltrating immune cells at the primary site with outcome. However, increased numbers of intraepithelial CD8⁺TIL in metastatic tumours as well as large numbers of peritumoural B-cells in lymph node metastases were associated with favourable outcome. Unexpectedly, no effect on patient outcome was observed for Treg in any compartment.</p> <p>Conclusion</p> <p>Our results suggest that alterations in lymphocyte distribution in regional lymph nodes rather than at the primary tumour site may be relevant for patient prognosis. Moreover, we demonstrate that in addition to cellular immunity humoral immune responses may be clinically relevant in anti-tumour immunity.</p

A systematic review of the clinical effectiveness of 64-slice or higher computed tomography angiography as an alternative to invasive coronary angiography in the investigation of suspected coronary artery disease

<p>Abstract</p> <p>Background</p> <p>This systematic review summarized recent evidence pertaining to the clinical effectiveness of 64-slice or higher computed tomography angiography (CTA) in patients with suspected coronary artery disease (CAD). If CTA proves to be a successful diagnostic performance measure, it could prevent the use of invasive diagnostic procedures in some patients. This would provide multiple health and cost benefits, particularly for under resourced areas where invasive coronary angiography is not always available.</p> <p>Methods</p> <p>A systematic method of literature searching and selection was employed with searches limited to December 2006 to March 2009. Included studies were quality assessed using National Health and Medical Research Council (NHMRC) diagnostic levels of evidence and a modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Individual and pooled diagnostic performance measures were calculated using standard meta-analytic techniques at the patient, vessel and segment level. A positive result was defined as greater than or equal to 50% stenosis.</p> <p>Results</p> <p>Twenty-eight studies were included in the systematic review examining 3,674 patients. The primary meta-analysis at the patient-level indicated a sensitivity of 98.2% and specificity of 81.6%. The median (range) positive predictive value (PPV) was 90.5% (76%-100%) and negative predictive value (NPV) 99.0% (83%-100%). In all vessels, the pooled sensitivity was 94.9%, specificity 89.5%, and median (range) PPV 75.0% (53%-95%) and NPV 99.0% (93%-100%). At the individual artery level, overall diagnostic accuracy appeared to be slightly higher in the left main coronary artery and slightly lower in the left anterior descending and circumflex artery. In all segments, the sensitivity was 91.3%, specificity 94.0% and median (range) PPV 69.0% (44%-86%) and NPV 99.0% (98%-100%).</p> <p>Conclusions</p> <p>The high sensitivity indicates that CTA can effectively identify the majority of patients with significant coronary artery stenosis. The high NPV at the patient, vessel and segment level establishes CTA as an effective non-invasive alternative to invasive coronary angiography (ICA) for the exclusion of stenosis.</p

Spatial variation in exhumation rates across Ladakh and the Karakoram: New apatite fission track data from the Eastern Karakoram, NW India

Characterization of low-temperature cooling histories and associated exhumation rates is critical for deciphering the recent evolution of orogenic regions. However, these may vary significantly over relatively short distances within orogens. It is pertinent therefore to constrain cooling histories and hence exhumation rates across major tectonic boundaries. We report the first apatite fission track ages from the Karakoram Fault Zone in the Eastern Karakoram range, which forms part of the western margin of the Tibetan Plateau. Ten samples, from elevations of 3477–4875m, have apatite fission track dates from 3.3 ± 0.3 Ma to 7.4± 1.1Ma. The ages correspond to modeled average erosional exhumation rates of 0.67+ 0.27-0.18mm/yr across the Eastern Karakoram. The results are consistent with a trend northward from the Indus suture zone, across the Ladakh terrane and into the Karakoram, in which tectonic uplift associated with crustal thickening increases toward the north, raising elevation and promoting glaciation and generation of extreme relief. As a result, erosion and exhumation rates increase south to north. Present-day precipitation on the other hand varies little within the study area and on a larger scale decreases southwest to northeast across this portion of the orogen. The Eastern Karakoram results highlight the diverse patterns of exhumation driven by regional variations in tectonic response to collision along the western margin of Tibet