The westward drift of the lithosphere. A tidal ratchet?

Is the westerly rotation of the lithosphere an ephemeral accidental recent phenomenon or is it a stable process of Earth’s geodynamics? The reason why the tidal drag has been questioned as the mechanism determining the lithospheric shift relative to the underlying mantle is the apparent too high viscosity of the asthenosphere. However, plate boundaries asymmetries are a robust indication of the ‘westerly’ decoupling of the entire Earth’s outer lithospheric shell and new studies support lower viscosities in the low-velocity layer (LVZ) atop the asthenosphere. Since the solid Earth tide oscillation is longer in one side relative to the other due to the contemporaneous Moon’s revolution, we demonstrate that a non-linear rheological behavior is expected in the lithosphere mantle interplay. This may provide a sort of ratchet favoring lowering of the LVZ viscosity under shear, allowing decoupling in the LVZ and triggering the westerly motion of the lithosphere relative to the mantle

Asymmetric Atlantic continental margins

We analyze the gross crustal structure of the Atlantic Ocean passive continental margins from north to the south, comparing eleven sections of the conjugate margins. As a general result, the western margins show a sharper continental-ocean transition with respect to the eastern margins that rather show a wider stretched and thinner margin. The Moho is in average about 5.7°±1° dipping toward the interior of the continent on the western side, whereas it is about 2.7°±1° in the eastern margins. Moreover, the stretched continental crust is on average 244 km wide on the western side, whereas it is up to about 439 km on the eastern side of the Atlantic. This systematic asymmetry reflects the early stages of the diachronous Mesozoic to Cenozoic continental rifting, which is inferred as the result of a polarized westward motion of both western and eastern plates, being Greenland, Northern and Southern Americas plates moving westward faster with respect to Scandinavia, Europe and Africa, relative to the underlying mantle

Hydraulic stream network conditioning by a tectonically induced, giant, deep-seated landslide along the front of the Apennine chain (south Italy)

Abstract. The tectonic stresses that produced the uplift of Apennine chain ridge in southern Italy generated advanced buried thrusts of allochthonous deposits that induced deformations of foredeep deposits. This thrust may cause giant, deep-seated landslides at the front of the chain. Starting from a specific case history in low Biferno Valley, this work presents how giant, deep-seated landslides along the front of the chain may be generated by the thrust of allochthonous nappe of the chain. In addition, the influence that these huge phenomena may have on landslide and flood susceptibility and on natural hazards of the involved area is analysed. The work presents an interpretation of local morphology and stream network paths of low Biferno Valley as a consequence of a giant, deep-seated landslide affecting the right side of the valley. The proposed interpretation is supported by numerical geomorphological analyses of the area at stake. It is shown how both the morphologies of the catchments of the river Biferno and its tributary Cigno and stream paths are strongly conditioned by this large, deep-seated landslide. This landslide deviates the stream paths affecting both the flooding susceptibility of low Biferno Valley and landslide susceptibility on the left side of Biferno Valley

Enzymatic Inactivation of Oxysterols in Breast Tumor Cells Constraints Metastasis Formation by Reprogramming the Metastatic Lung Microenvironment

Recent evidence indicates that immune cells contribute to the formation of tumor metastases by regulating the pre-metastatic niche. Whether tumor-derived factors involved in primary tumor formation play a role in metastasis formation is poorly characterized. Oxysterols act as endogenous regulators of lipid metabolism through the interaction with the nuclear Liver X Receptors-(LXR)alpha and LXR beta. In the context of tumor development, they establish a pro-tumor environment by dampening antitumor immune responses, and by recruiting pro-angiogenic and immunosuppressive neutrophils. However, the ability of LXR/oxysterol axis to promote tumor invasion and metastasis by exploiting immune cells, is still up to debate. In this study we provide evidence that oxysterols participate in the primary growth of orthotopically implanted 4T1 breast tumors by establishing a tumor-promoting microenvironment. Furthermore, we show that oxysterols are involved in the metastatic spread of 4T1 breast tumors, since their enzymatic inactivation mediated by the sulfotransferase 2B1b, reduces the number of metastatic cells in the lungs of tumor-bearing mice. Finally, we provide evidence that oxysterols support the metastatic cascade by modifying the lung metastatic niche, particularly allowing the recruitment of tumor-promoting neutrophils. These results identify a possible new metastatic pathway to target in order to prevent metastasis formation in breast cancer patients

The 2013–2018 matese and beneventano seismic sequences (Central–Southern apennines). New constraints on the hypocentral depth determination

The Matese and Beneventano areas coincide with the transition from the central to the southern Apennines and are characterized by both SW-and NE-dipping normal faulting seismogenic structures, responsible for the large historical earthquakes. We studied the Matese and Beneventano seismicity by means of high-precision locations of earthquakes spanning from 29 December 2013 to 4 September 2018. Events were located by using all of the available data from temporary and permanent stations in the area and a 1D computed velocity model, inverting the dataset with the Velest code. For events M > 2.8 we used P-and S-waves arrival times of the strong motion stations located in the study area. A constant value of 1.83 for Vp/Vs was computed with a modified Wadati method. The dataset consists of 2378 earthquakes, 18,715 P-and 12,295 S-wave arrival times. We computed 55 new fault plane solutions. The mechanisms show predominantly normal fault movements, with T-axis trends oriented NE–SW. Only relatively small E–W trending clusters in the eastern peripheral zones of the Apenninic belt show right-lateral strike-slip kinematics similar to that observed in the Potenza (1990–1991) and Molise (2002 and 2018) sequences. These belong to transfer zones associated with differential slab retreat of the Adriatic plate subduction beneath the Apennines. The Matese sequence (December 2013–February 2014; main shock Mw 5.0) is the most relevant part of our dataset. Hypocentral depths along the axis of the Apenninic belt are in agreement with previous seismological studies that place most of the earthquakes in the brittle upper crust. We confirm a general deepening of seismicity moving from west to the east along the Apennines. Seismicity depth is controlled by heat-flow, which is lower in the eastern side, thus causing a deeper brittle–ductile transition

Fault on-off versus coseismic fluids reaction

AbstractThe fault activation (fault on) interrupts the enduring fault locking (fault off) and marks the end of a seismic cycle in which the brittle-ductile transition (BDT) acts as a sort of switch. We suggest that the fluid flow rates differ during the different periods of the seismic cycle (interseismic, pre-seismic, coseismic and post-seismic) and in particular as a function of the tectonic style. Regional examples indicate that tectonic-related fluids anomalies depend on the stage of the tectonic cycle and the tectonic style. Although it is difficult to model an increasing permeability with depth and several BDT transitions plus independent acquicludes may occur in the crust, we devised the simplest numerical model of a fault constantly shearing in the ductile deeper crust while being locked in the brittle shallow layer, with variable homogeneous permeabilities. The results indicate different behaviors in the three main tectonic settings. In tensional tectonics, a stretched band antithetic to the normal fault forms above the BDT during the interseismic period. Fractures close and fluids are expelled during the coseismic stage. The mechanism reverses in compressional tectonics. During the interseismic stage, an over-compressed band forms above the BDT. The band dilates while rebounding in the coseismic stage and attracts fluids locally. At the tip lines along strike-slip faults, two couples of subvertical bands show different behavior, one in dilation/compression and one in compression/dilation. This deformation pattern inverts during the coseismic stage. Sometimes a pre-seismic stage in which fluids start moving may be observed and could potentially become a precursor

Strain rate relaxation of normal and thrust faults in Italy

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Hydraulic stream network conditioning by a tectonically induced, giant, deep-seated landslide along the front of the Apennine chain (south Italy)

The tectonic stresses that produced the uplift of Apennine chain ridge in southern Italy generated advanced buried thrusts of allochthonous deposits that induced deformations of foredeep deposits. This thrust may cause giant, deep-seated landslides at the front of the chain. Starting from a specific case history in low Biferno Valley, this work presents how giant, deep-seated landslides along the front of the chain may be generated by the thrust of allochthonous nappe of the chain. In addition, the influence that these huge phenomena may have on landslide and flood susceptibility and on natural hazards of the involved area is analysed. The work presents an interpretation of local morphology and stream network paths of low Biferno Valley as a consequence of a giant, deep-seated landslide affecting the right side of the valley. The proposed interpretation is supported by numerical geomorphological analyses of the area at stake. It is shown how both the morphologies of the catchments of the river Biferno and its tributary Cigno and stream paths are strongly conditioned by this large, deep-seated landslide. This landslide deviates the stream paths affecting both the flooding susceptibility of low Biferno Valley and landslide susceptibility on the left side of Biferno Valley

Extrafoveal Müller cells detection in vivo in the human retina: a pilot study based on optical coherence tomography

Müller cells (MC) represent a key element for the metabolic and functional regulation of the vertebrate retina. The aim of the present study was to test the feasibility of a new method for the in-vivo detection and quantification of extrafoveal MC in human retina. We developed a new approach to isolate and analyse extrafoveal MC in vivo, starting from structural optical coherence tomography data. Our pilot investigation was based on the optical properties of MC, which are known to not interfere with the light reaching the outer retinal structures. We reconstructed MC in the macular region of 18 healthy subjects and the quantitative analyses revealed ~42,000/9 mm2 cells detected. Furthermore, we included 2 patients affected by peripheral intraocular melanoma, with macular sparing, needing surgical enucleation. We used these two eyes to perform a qualitative comparison between our reconstructions and histological findings. Our study represents the first pilot investigation dedicated on the non-invasive isolation and quantification of MC, in-vivo, in human retina. Although we are aware that our study has several limitations, first of all related with the proper detection of foveal MC, because of the peculiar z-shape morphology, this approach may open new opportunities for the non-invasive in vivo analysis of MC, providing also potential useful perspectives in retinal diseases