Shear Patterns Research Articles

An In Vitro Model to Study Endothelialization of Cardiac Graft Tissues Under Flow.

Pulmonary valve replacement is performed with excellent resultant hemodynamics in patients that have underlying congenital or acquired heart valve defects. Despite recent advancements in right ventricular outflow tract reconstruction, an increased risk of developing infective endocarditis remains, which has a more common occurrence for conduits of bovine jugular vein (BJV) origin compared with cryopreserved homografts. The reason for this is unclear although it is hypothesized to be associated with an aberrant phenotypic state of cells that reendothelialize the graft tissue postimplantation. The aim of this study was to develop an in vitro model that enables the analysis of endothelial cell (EC) attachment to cardiac graft tissues under flow. In the experiments, EC attachment was optimized on bovine pericardium (BP) patch using human umbilical vein ECs. Different biological coatings, namely gelatin, fibronectin, plasma, or a combination of fibronectin and plasma were tested. After cell adaptation, graft tissues were exposed to laminar flow in a parallel-plate flow chamber. Cell retention to the tissue was analyzed after nuclear staining with YO-PRO-1 and a membranous localization of VE-cadherin. Experiments showed that combined coating with fibronectin and blood plasma together with a two-phased shear pattern resulted in a relevant cell monolayer on BP patch and cryopreserved homograft. For BJV tissue, no adherent cells under both static and shear conditions were initially observed. In conclusion, having established the new flow chamber system we could obtain EC layers on the surface of BP patch and cryopreserved pulmonary homograft tissues. The presented in vitro system can serve as a competent model to study cell phenotypes on cardiac grafts in the close-to-physiologic environment. Moreover, this approach allows broad applications and enables further development by testing more complex conditions.

The formation of the cross shear bands and its influence on dynamic recrystallization and mechanical properties under Turned-Reverse Rolling

Two rolling routes, traditional forward rolling (FR) and turned-reverse rolling (TRR, with tilting angle of 180° along transverse direction (TD)) were performed on AZ31B magnesium (Mg) alloy sheets. Different morphologies of shear bands and its influence on the dynamic recrystallization (DRX) and mechanical properties were investigated. The shear bands (SBs) in the FR and TRR samples show variant morphologies due to the different shear patterns. Especially, the cross shear stress results in a higher number fraction of discontinuous DRXed (DDRXed) grains with random orientation in the TRR sample, contributing to the weakening of {0001} basal texture, while continuous DRX (CDRX) dominates in the FR route, where most of DRXed grains inherit the parent orientation. Furthermore, the TRR sample shows a larger total elongation value (>35 %) than that of the FR sample without sacrificing the strength (∼275 MPa), which can be attributed to not only a more homogeneous strain in the cross SBs (CSRs) but also the activation of non-base slip in the DDRXed grains.

Impact of tibetan plateau snow cover on tropical cyclogenesis via the Madden–Julian oscillation during the following boreal summer

This study investigates the role of the interannual variation of boreal winter (December–February) snow cover over the Tibetan Plateau (TPSC) in modulating the relationship between the Madden Julian Oscillation (MJO) and tropical cyclogenesis over the western North Pacific (WNP) during the following boreal summer (June–October). During the boreal summer following a high snow cover anomaly (SCA), MJO-associated convection tends to be confined to the west of 140 °E, coinciding with more frequent tropical cyclone (TC) activity in this region. By contrast, there tends to be stronger MJO-associated convection extending farther east during years following low SCA. The MJO-associated convection extends to ~ 160 °E over the WNP basin with a peak around 140 °E. Thus, more TCs form farther east in the WNP in these years. We use composite analyses of large-scale environmental factors to demonstrate that low-level relative vorticity is one of the most important factors in controlling TCs in response to the change of MJO-associated convection between years with high SCA and low SCA. Meanwhile, eddy kinetic energy variations associated with the MJO are consistent with changes in tropical cyclogenesis over the WNP basin between years with high and low SCA. The Asian summer monsoon plays an important role in linking prior winter TPSC to MJO activity in the following summer. During high-SCA years, increased snow cover results in positive soil moisture anomalies and cooling over the Tibetan Plateau, thus weakening the following summer Asian monsoon and weakening associated water vapor advection, while the opposite chain of events occurs in low-SCA years. These changes in high-SCA years are favorable for MJO propagation and are unfavorable for MJO propagation in low-SCA years. Meanwhile, the interannual variation of SCA exerts a significant impact on the upper-tropospheric circulation and thus changes in vertical wind shear. During high-SCA years, there are anomalous upper-level easterlies in the Indian Ocean and upper-level westerlies in the Pacific Ocean, which result in anomalous easterly wind shear in the Indian Ocean and anomalous westerly shear in the Pacific Ocean. The opposite shear pattern arises in low-SCA years. In addition to changes in wind shear, the background vertical motion associated with changes in TPSC may also be partly responsible for changes in MJO activity.

Inorganic nitrate supplementation attenuates conduit artery retrograde and oscillatory shear in older adults.

Aging causes deleterious changes in resting conduit artery shear patterns and reduced blood flow during exercise partially attributable to reduced nitric oxide (NO). Inorganic nitrate increases circulating NO bioavailability and may, therefore, improve age-associated changes in shear rate as well as exercise hyperemia. Ten older adults (age: 67 ± 3 yr) consumed 4.03 mmol nitrate and 0.29 mmol nitrite (active) or devoid of both (placebo) daily for 4 wk in a randomized, double-blinded, crossover fashion. Brachial artery diameter (D) and blood velocity (Vmean) were measured via Doppler ultrasound at rest for the characterization of shear profile as well as during two handgrip exercise trials (4 and 8 kg) for calculation of forearm blood flow (Vmean × cross-sectional area, FBF) and conductance [FBF/mean arterial pressure, forearm vascular conductance (FVC)]. Plasma [nitrate] and [nitrite] increased following active (P < 0.05 for both) but not placebo (P = 0.68 and 0.40, respectively) supplementation. Neither mean nor antegrade shear rate changed following either supplement (beverage-by-time P = 0.14 and 0.21, respectively). Retrograde (-13.4 ± 7.0 to -9.7 ± 6.8·s-1) and oscillatory (0.20 ± 0.08 to 0.15 ± 0.09 A.U., P < 0.05 for both) shear decreased following active, but not placebo (P = 0.81 and 0.70, respectively), supplementation. The FBF response (Δ from rest) to neither 4-kg nor 8-kg trials changed following either supplement (beverage-by-time P = 0.53 and 0.11, respectively). Similarly, no changes were observed in FVC responses to 4-kg or 8-kg trials (beverage-by-time P = 0.23 and 0.07, respectively). These data indicate that inorganic nitrate supplementation improves conduit artery shear profiles, but not exercise hyperemia, in older adults.NEW & NOTEWORTHY We report for the first time, to our knowledge, that 4 wk of inorganic nitrate supplementation attenuates retrograde and oscillatory shear in the brachial artery of older adults. However, this was not associated with greater hyperemic or vasodilatory responses to exercise. In sum, these data highlight favorable changes in shear patterns with aging, which may reduce the risk of atherosclerotic cardiovascular disease.

Formation conditions and evolution of fractures in multiple tight rocks: Implications for unconventional reservoir exploitation

Physical simulation experiments of rock fracturing can effectively simulate the extension of artificial fractures within different lithology and interbedded rocks. Previous studies have focused on the conditions of artificial fracture initiation and propagation, while few studies have been conducted on the evolution and influencing factors of fractures in reservoir rocks. In this study, fracture evolution simulation was performed using a self-developed physical fracturing simulation device and a real-time acoustic emission fracture monitoring system. Results show the presence of four main fracture patterns within the selected lithologies and their combinations, including simple shear, simple, network, and X-shear fracture patterns. The variation trend of the principal stress difference and fracture pressure, as well as the values of the network, X-shear, simple, and simple shear fracture patterns all increased successively. The values of the network and X-shear fracture patterns were smallest, while the fracture pressure and principal stress difference were less than 65 and 40 MPa, respectively. Furthermore, the trends of the brittle mineral content and brittleness index were opposite.The interlaminar modulus difference mainly controls the cracks extending at the interface of the interlayer, and is conducive to the extension of cracks at values less than 3 GPa. Furthermore, the tendency of network, X-shear, simple, and simple shear fracture patterns to gradually simplify implies that the fracturing treatment effect and fracturing performance may have sequentially deteriorated. This study may provide a reference for the determination of reservoir fracturing ability and fracturing reconstruction design in unconventional reservoir development.

ВПЛИВ ПІДРОБКИ ГІРСЬКОГО МАСИВУ НА СТАН ГІРНИЧИХ ВИРОБОК

Purpose. Research of influence of shifts of rocks on a condition of mine workings at their undermining by longwalls. Methods. The study used a computer simulation method. The simulation was performed by simulating the process of rock shift. The initial coordinates of the points of the rock mass turned into the final ones. This allowed to build sections of the rock mass after undermining, which characterized its deformed state, as well as graphs of displacements and deformations in the mine workings. Results. The performed simulation showed that during the movement of the longwall, the mine working (drift), which is undermined, consistently falls into the zone of horizontal deformations of tension, compression and complete displacements. After stopping the longwall, part of the mine working near the boundaries of the displacement area will be constantly in the zones of stretching and compression. It is established that at a distance of 40 m in front of the moving face, the mine working is in the least favorable conditions with maximum vertical compression deformations. Under the given conditions the drift for the most part after completion of clearing works is in a zone of full subsidence. This zone is characterized by the maximum possible subsidence and the absence of deformations. The performed researchers showed that the conditions of undermining of the southern field haulage drift of seam l7 proved to be quite favorable. Shifts and deformations did not cause a significant deterioration in the state of mine working, except for the increase of slopes on the edge sections of the subsidence trough, which makes it difficult to carry out electric locomotive rolling. For any other purpose, after minor repairs, the mine working may continue to operate. Scientific novelty. The study of the process of shear by computer simulation allowed to establish the patterns of shear and deformation during undermining of the mine working. This is the first time for the conditions of the Ukrainian Donbass. Practical significance. The obtained results can be used to predict the condition of mine workings that are undermined during the cleaning works in similar conditions. Key words: undermining overlying mine workings, shifts, deformations, zone of full subsidence, subsidence trough.

Hourly staircase sprinting exercise "snacks" improve femoral artery shear patterns but not flow-mediated dilation or cerebrovascular regulation: a pilot study.

Healthy males (n = 10; age: 24 ± 4 years; body mass index: 24 ± 2 kg·m-2) completed 2 randomized conditions separated by ≥48 h involving 6-8.5 h of sitting with ("stair snacks") and without (sedentary) hourly staircase sprint interval exercise (∼14-20 s each). Resting blood flow and shear rates were measured in the femoral artery, internal carotid artery, and vertebral artery (Duplex ultrasound). Flow-mediated dilation (FMD) was quantified as an index of peripheral endothelial function in the femoral artery. Neurovascular coupling (NVC; regional blood flow response to local increases in cerebral metabolism) was assessed in the posterior cerebral artery (transcranial Doppler ultrasound). Femoral artery hemodynamics were higher following the active trial with no change in the sedentary trial, including blood flow (+32 ± 23% vs. -10 ± 28%; P = 0.015 and P = 0.253, respectively), vascular conductance (+32 ± 27% vs. -15 ± 26%; P = 0.012 and P = 0.098, respectively), and mean shear rate (+17 ± 8% vs. -8 ± 28%; P = 0.004 and P = 0.310, respectively). The change in FMD was not different within or between conditions (P = 0.184). Global cerebral blood flow (CBF), conductance, shear patterns, and NVC were not different within or between conditions (all P > 0.05). Overall, exercise "stair snacks" improve femoral artery blood flow and shear patterns but not peripheral (e.g., FMD) or cerebral (e.g., CBF and NVC) vascular function following prolonged sitting. The study was registered at ClinicalTrials.gov (NCT03374436). Novelty: Breaking up 8.5 h of sitting with hourly staircase sprinting exercise "snacks" improves resting femoral artery shear patterns but not FMD. Cerebral blood flow and neurovascular coupling were unaltered following 6 h of sitting with and without hourly exercise breaks.

J2-deformation-type soil model coupled with state-dependent dilatancy and fabric evolution: multiaxial formulation and FEM implementation

In this paper, an original J2-deformation type model coupled with state-dependent dilatancy is further extended to a multiaxial stress space. Compared with most existing models, the proposed model only requires ten parameters, which can be easily calibrated, and does not involve any abstruse concepts in elastoplasticity theory. The model is then implemented into ABAQUS through a user-defined subroutine (UMAT), and the capability of the extended model in capturing the mechanical behavior of sand is demonstrated by element tests, including conventional triaxial tests and true triaxial tests. To demonstrate the robustness of the model, two typical boundary value problems are illustrated, i.e., the biaxial compression test and the strip footing test. The model is further incorporated with anisotropic critical state theory to simulate anisotropic soil behavior. The biaxial compression test with smooth and rough boundaries is simulated with the anisotropic model. The results confirm the impact of fabric anisotropy and boundary constraints on the shear strain distributions and patterns of shear bands. The simulation results show the capability of the proposed model, which can be applied in practical analyses and geotechnical engineering designs.

The Compressive Behavior of Porous TC4 Alloy Scaffolds Manufactured by Selective Laser Melting

Porous TC4 alloy scaffolds with curved struts were fabricated by selective laser melting (SLM), and the compression deformation behavior of the TC4 alloy scaffolds was studied. When the porous scaffold is compressed along the direction of the building, the stress of the porous scaffold first increases sharply with the increase in the strain, then decreases rapidly and finally shows a stepped increasing trend. Combined with the finite element method and uniaxial compression experiments, the shear position of porous scaffold takes precedence over other parts, and the fracture mainly occurs on the strut near the joint of the porous scaffold. The fracture surface analysis shows that the joint is a ductile fracture, and there is a shallow “dimple” pattern of shear or tear type on the fracture surface, while the fracture morphology of the strut near the joint of porous TC4 alloy scaffold is relatively smooth, which is a typical brittle fracture. The mixed fracture mode is caused by the more concentrated stress at the strut than the joint and the hexagonal close-packed (hcp) fine martensite α′ formed by the SLM.

Identifying Subseasonal Variability Relevant to Atlantic Tropical Cyclone Activity

AbstractThe primary atmospheric oscillations and variables associated with subseasonal Atlantic tropical cyclone (TC) activity are identified, based on 37 years of reanalysis data. TC activity, represented by accumulated cyclone energy (ACE), is computed for combined phases of the Madden–Julian oscillation (MJO) and El Niño–Southern Oscillation (ENSO). The MJO influence on TC activity becomes greater when the ENSO state is cooler. There is also a shift in the favorable MJO phase for TC activity with ENSO state. For strong La Niñas, MJO phases 4 and 5 (enhanced convection over the Maritime Continent) are most likely to have above-average ACE. To investigate other potential factors that influence subseasonal TC activity, two novel methods are developed: ACE by year (ABY) and seasonal and climatology removed (SNCR). Both methods isolate subseasonal signals of environmental conditions in association with a variable of interest. Vorticity, sea surface temperature, relative humidity, and genesis potential all show little signal in association with subseasonal Atlantic TC activity. The most important identifier of enhanced TC activity is negative vertical wind shear anomalies in the main development region of the Atlantic basin, and positive shear anomalies in the subtropical Atlantic. The shear pattern associated with a favorable MJO for TCs is similar to but distinct from the shear pattern associated with enhanced subseasonal TC activity. These findings demonstrate a nonlinear MJO–ENSO interaction and a pattern of wind shear anomalies that is linked to subseasonal TC activity.

Influence of sprint exercise on aortic pulse wave velocity and femoral artery shear patterns

Aortic stiffness may affect shear patterns in the peripheral vasculature.This study examined if sprint exercise, which typically increases aortic stiffness is associated with increased peripheral retrograde blood flow and impaired microvascular function. Twenty participants (10 women; age: 27 ± 5years) underwent arterial stiffness, shear rate, and microvascular function assessment at three time points: baseline; following time control; ~ 2min post a 30-s cycle ergometer sprint against 7.0% body mass. Aortic stiffness was assessed using carotid-femoral pulse wave velocity (cfPWV). Superficial femoral artery (SFA) diameter and blood velocity were assessed using Doppler-ultrasound and were used to calculate shear rates and resistance index (RI). SFA wave reflections were obtained via wave intensity analysis. Vastus medialis microvascular function was measured as tissue saturation index reactivity pre-post exercise via near-infrared spectroscopy. cfPWV increased by + 0.8 ± 0.7m·s-1 following exercise (p < 0.001). Retrograde shear was reduced following exercise compared with time control (-4.9 ± 3.8s-1; p < 0.001), while tissue saturation index was increased post-exercise from baseline (+ 2.3 ± 4.6%; p = 0.04). Reductions in SFA wave reflections (-1.70 ± 1.96aU) and RI (-0.17 ± 0.13aU) were also noted following exercise (p < 0.001). These data suggest sprint exercise-mediated changes in peripheral shear patterns and microvascular function in the exercised vasculature occur independent from increases in aortic stiffness. Exercise-induced reductions in SFA retrograde shear may be related to decreased wave reflections and peripheral vascular resistance.

Deformation styles related to intraplate strike-slip fault systems of the Saharan-Tunisian Southern Atlas (North Africa): New kinematic models

The complex geometry and tectonic evolution of the Saharan-Tunisian Southern Atlas strike-slip fault systems, North Africa, have not been investigated comprehensively to date. This paper proposes new conceptual models to better understand the structural styles along these intraplate fault zones. We use a multidisciplinary approach including field observations, geological mapping, stress analysis and seismic data to investigate the development and interaction of major strike-slip fault segments. The regional fault system is dominated by the E-W trending Biskra, Alima, Orbata, Bouhedma and Chotts basement faults that constitute the Principal Displacement Zones (PDZs).Our analyses and interpretations reveal that each PDZ has a typical dextral strike-slip architecture comprising multi-scale fault segments that are linked through dilational and contractional stepovers/bends. During Mesozoic times, under NE-SW Shmin, the transtensional fault segments of Biskra and Alima formed the boundaries of the Khanguet Sidi Neji-Gafsa (KSG) Basin, which developed as a Z-shaped dextral releasing stepover. During the Cenozoic, the KSG Basin was inverted, under NW-SE SHmax, in response to the Africa-Eurasia convergence. This inversion occurred mainly along basin sidewalls by reactivation of the pre-existing normal-oblique faults as right-lateral transpressional shears. Further east, the E-W dextral strike-slip faults of Orbata and Bouhedma connected via a NE-SW restraining stepover.Finally, all E-W dextral strike-slip fault segments are associated with ENE right-stepping en echelon folds and Riedel shear patterns of different scales, in response to basement wrenching. Currently, most fault zones are still active with deep strike-slip earthquakes.

The Role of Tricellular Junctions in the Transport of Macromolecules Across Endothelium

PurposeTransport of water and solutes across vascular endothelium is important in normal physiology and critical in the development of various diseases, including atherosclerosis. However, there is debate about the routes for such transport. We recently showed that an albumin-sized tracer crossed endothelium at bicellular and tricellular junctions, a tracer having the size of high density lipoprotein crossed only through tricellular junctions, and a tracer with the size of low density lipoprotein was unable to cross by either route and instead traversed the cells themselves. Here we review previous work on the structure and function of tricellular junctions. We then describe a study in which we assessed the role of such junctions in the transport of an albumin-sized tracer.MethodsWe examined normal endothelial monolayers, the effect of agonists that modify their permeability, and the influence of different patterns of shear stress.ResultsUnder normal conditions, approximately 85% of transendothelial transport occurred through tricellular junctions. This fraction was unchanged when permeability was reduced by sphingosine-1-phosphate or increased by thrombin, and also did not differ between endothelium exposed to multidirectional as opposed to uniaxial shear stress despite a > 50% difference in permeability.ConclusionThese data show that tricellular junctions dominate normal transport of this tracer and largely determine influences of agonists and shear. The effects were attributable to changes in both the number and conductivity of the junctions. Further investigation of these structures will lead to increased understanding of endothelial barrier function and may suggest new therapeutic strategies in disease.

Mechanomics analysis of hESCs under combined mechanical shear, stretch, and compression.

Human embryonic stem cells (hESCs) can differentiate to three germ layers within biochemical and biomechanical niches. The complicated mechanical environments in vivo could have diverse effects on the fate decision and biological functions of hESCs. To globally screen mechanosensitive molecules, three typical types of mechanical stimuli, i.e., tensile stretch, shear flow, and mechanical compression, were applied in respective parameter sets of loading pattern, amplitude, frequency, and/or duration, and then, iTRAQ proteomics test was used for identifying and quantifying differentially expressed proteins in hESCs. Bioinformatics analysis identified 37, 41, and 23 proteins under stretch pattern, frequency, and duration, 13, 18, and 41 proteins under shear pattern, amplitude, and duration, and 4, 0, and 183 proteins under compression amplitude, frequency, and duration, respectively, where distinct parameters yielded the differentially weighted preferences under each stimulus. Ten mechanosensitive proteins were commonly shared between two of three mechanical stimuli, together with numerous proteins identified under single stimulus. More importantly, functional GSEA and WGCNA analyses elaborated the variations of the screened proteins with loading parameters. Common functions in protein synthesis and modification were identified among three stimuli, and specific functions were observed in skin development under stretch alone. In conclusion, mechanomics analysis is indispensable to map actual mechanosensitive proteins under physiologically mimicking mechanical environment, and sheds light on understanding the core hub proteins in mechanobiology.

Crystallographic and Geometric Factors in the Shear Development in &lt;001&gt; FCC Single Crystals: Molecular Dynamics Simulation and Experimental Study

An approach to the study of the mechanisms of shear deformation in the bulk of face centered cubic (FCC) single crystals based on molecular dynamics simulation is proposed. Similar shear patterns obtained experimentally, and in simulations, allow consideration of the effect of crystallographic and geometric factors on deformation mechanisms. Deformation of &lt;001&gt; single-crystal samples in the form of tetragonal prisms with {110} and {100} lateral faces and different height-to-width ratios was studied. The simulation showed that the sample vertices are the preferential sites for shear initiation. It was found that the formation of deformation domains and interaction of shear planes are caused by the geometry of shear planes in the bulk of the single crystal, i.e., by their location in relation to basic stress concentrators and by their orientations relative to the lateral faces. The deformation patterns obtained in the simulations were in good agreement with those observed in the experiments. The fractions of sliding dislocations and dislocation barriers were determined for different materials, taking into account the crystallographic and geometric factors.

Alterations in resting cerebrovascular regulation do not affect reactivity to hypoxia, hyperoxia or neurovascular coupling following a SCUBA dive.

What is the central question of this study? What are the characteristics of cerebral blood flow (CBF) regulation following a single SCUBA dive to a depth of 18m sea water with a 47min bottom time. What is the main finding and its importance? Acute alterations in CBF regulation at rest, including extra-cranial vasodilatation, reductions in shear patterns and elevations in intra-cranial blood velocity were observed at rest following a single SCUBA dive. These subtle changes in CBF regulation did not translate into any functional changes in cerebrovascular reactivity to hypoxia or hyperoxia, or neurovascular coupling following a single SCUBA dive. Reductions in vascular function during a SCUBA dive - due to hyperoxia-induced oxidative stress, arterial and venous gas emboli and altered endothelial integrity - may also extend to the cerebrovasculature following return to the surface. This study aimed to characterize cerebral blood flow (CBF) regulation following a single SCUBA dive to a depth of 18m sea water with a 47min bottom time. Prior to and following the dive, participants (n=11) completed (1) resting CBF in the internal carotid (ICA) and vertebral (VA) arteries (duplex ultrasound) and intra-cranial blood velocity (v) of the middle and posterior cerebral arteries (MCAv and PCAv, respectively) (transcranial Doppler ultrasound); (2) cerebrovascular reactivity to acute poikilocapnic hypoxia (i.e. , 0.10) and hyperoxia (i.e. , 1.0); and (3) neurovascular coupling (NVC; regional CBF response to local increases in cerebral metabolism). Global CBF, cerebrovascular reactivity to hypoxia and hyperoxia, and NVC were unaltered following a SCUBA dive (all P>0.05); however, there were subtle changes in other cerebrovascular metrics post-dive, including reductions in ICA (-13±8%, P=0.003) and VA (-11±14%, P=0.021) shear rate, lower ICAv (-10±9%, P=0.008) and VAv (-9±14%, P=0.028), increases in ICA diameter (+4±5%, P=0.017) and elevations in PCAv (+10±19%, P=0.047). Although we observed subtle alterations in CBF regulation at rest, these changes did not translate into any functional changes in cerebrovascular reactivity to hypoxia or hyperoxia, or NVC. Whether prolonged exposure to hyperoxia and hyperbaria during longer, deeper, colder and/or repetitive SCUBA dives would provoke changes to the cerebrovasculature requires further investigation.

Surface deformation and tectonic background of the 2019 Ms 6.0 Changning earthquake, Sichuan basin, SW China

The June 17, 2019 Ms 6.0 Changning earthquake at a depth of 3–5 km struck the Changning anticline fold system. No active faults have been observed in the region. Some studies have attributed the earthquake to the regional shale gas exploitation. Following the earthquake, we conducted a field survey to investigate co-seismic surface deformation in the area, and observed many surface fractures and uplifted areas. Our work indicated that the deformation followed a Riedel shear pattern. The fractures and uplifted areas represent T-fractures and S-extrusions, respectively. The observed Riedel shear pattern is indicative of left-lateral strike-slip motion. To ascertain the relationship between the Riedel shear pattern and regional tectonics, we investigated the trends in layer striations and fault scratches. The results indicated that there were two stages in the evolution of the anticline. In the first stage, the principal compressive stress that dominated the original formation of the anticline trended NE-SW. In the second stage, the regional principal compressive stress shifted to the current E-W trend, generating oblique motion that included reverse and left-lateral components. We propose that the tectonic stress field in this region had a strong bearing on the focal mechanism of the mainshock and the co-seismic surface deformation. Both the eastward expansion of the Xianshuihe area and southeastward expansion of the Longmen Shan have affected the current Changning anticline fold system.

Shapley supercluster survey: mapping the dark matter distribution

ABSTRACT We present a 23 deg2 weak gravitational lensing survey of the Shapley supercluster core and its surroundings using gri VST images as part of the Shapley Supercluster Survey (ShaSS). This study reveals the overall matter distribution over a region containing 11 clusters at z ∼ 0.048 that are all interconnected, as well as several ongoing cluster–cluster interactions. Galaxy shapes have been measured by using the Kaiser–Squires–Broadhurst method for the g- and r-band images and background galaxies were selected via the gri colour–colour diagram. This technique has allowed us to detect all of the clusters, either in the g- or r-band images, although at different σ levels, indicating that the underlying dark matter distribution is tightly correlated with the number density of the member galaxies. The deeper r-band images have traced the five interacting clusters in the supercluster core as a single coherent structure, confirmed the presence of a filament extending North from the core, and have revealed a background cluster at z ∼ 0.17. We have measured the masses of the four richest clusters (A3556, A3558, A3560, and A3562) in the two-dimensional shear pattern, assuming a spherical Navarro–Frenk–White profile and obtaining a total mass of $\mathcal {M}_{\rm ShaSS,WL}{=}1.56^{+0.81}_{-0.55}{\times }10^{15\, }{\rm M}_{\odot }$, which is consistent with dynamical and X-ray studies. Our analysis provides further evidence of the ongoing dynamical evolution in the ShaSS region.

Multiyear Hybrid Prediction of Atlantic Tropical Cyclone Activity and the Predictability Sources

AbstractA hybrid statistical–dynamical model is developed to predict multiyear variability of Atlantic tropical cyclone (TC) activity. A Poisson model takes sea surface temperature (SST) averaged over the Atlantic main development region (MDR) and the Atlantic subpolar gyre region (SPG) from the initialized CESM prediction as predictors, and skillfully predicts the basinwide TC frequency, accumulated cyclone energy (ACE), landfalling TC frequency, and hurricane and major hurricane days. Further analysis shows that the SPG SST is a more important source of predictability than the MDR SST for multiyear Atlantic TC activity. The comparison between the uninitialized and initialized CESM predictions suggests that the SPG SST is better predicted by the initialized CESM owing to the better prediction of Atlantic meridional overturning circulation, which contributes to the overall more skillful TC predictions. On the other hand, the skillful prediction of the basinwide TC frequency by the uninitialized CESM suggests the role of external forcing in the variability of Atlantic TC activity. The dependence of the hybrid prediction skills on the dynamic model ensemble size is also explored, and an ensemble size of ~20 is suggested as optimal. Further analysis shows that the SPG SST is associated with the variability of vertical wind shear and precipitable water over the tropical Atlantic even when the influence of the MDR SST is controlled. The spatial patterns of vertical wind shear and precipitable water suggest a strong modulation of ACE and hurricane frequency but a relatively weak influence on the basinwide TC frequency. The physical mechanisms between the SPG SST and Atlantic TC activity are discussed.

LATE NEOGENE DEFORMATION OF ROCK SUCCESSIONS AT RENAH GAJAH MATI I REGION, SELUMA REGENCY IN BENGKULU

Lack of work focusing on deformation mechanism has been undertaken in the Late Tertiary sequence during Late Neogene time at the Renah Gajah Mati I region in Bengkulu basin. The present study was aimed at reconstructing tectonic deformation occurring within the basin during the Late Neogene, employing balancing and restoring techniques, kinematic and dynamic analyses. The Late Neogene deformation was mainly controlled by compression, which has resulted in folding and thrusting. Hence, the rock sections underwent shortening that varied from 1.42-1.83 km or 0.75%-0.78% with the estimated rate of deformation 0.12-0.15 mm/year. Two types of tectonic structures developed within the region, fault propagation folds and trishear faults. The brittle deformation extended sequentially in the direction of tectonic transport, resulting in a series of faults. The generated faults constitute imbricate fans with a relatively closely-spaced thrust system. The array of thrusts is apparently associated with folds that strike NW-SE, implying the geometry of fault-linked folding. The hanging wall anticlines are generally asymmetric overturned folds, indicating a shallow ramping fault with a high shear pattern. In regional context, the general strike of structures within the study area appears relatively parallel to the NW-SE trending Barisan orogen. This feature suggests that tectonic transport responsible for structuring was likely at the NE- SW direction.