Extensional Deformation Research Articles

Linked Flaps of the Thoracodorsal Vascular Tree for Correcting Extensive Post-Burn Deformities and Achieving Optimal Reconstruction Outcomes.

Autologous skin grafting has been the popular method for reconstructing post-burn defects. However, this technique has limitations such as high contracture rates and inadequate volume coverage. This report aims to propose the principles and advantages of utilizing microsurgically linked perforator flaps for the reconstruction of extensive burn defects and associated post-burn scar contracture in the lower and upper extremities and trunk. Patients who underwent free tissue transfer for primary and secondary burn wound reconstruction at a single institution between 2016 and 2023 were included in the study. Patients received thoracodorsal vascular tree-linked flaps for the correction of post-burn deformities. Postoperative results were evaluated, including flap survival, complications, and the DASH self-report questionnaire for upper extremity reconstruction. Among the 20 patients, 12 required primary reconstruction, while 8 underwent secondary reconstruction using anastomotic chimeric free tissue transfer. The majority of burn injuries resulted from thermal contact (n = 8), followed by flames (n = 5), scalds (n = 4), electrical contact (n = 2), and friction (n = 1). The most frequently utilized combinations were the thoracodorsal artery perforator (TDAp) and anterolateral thigh (ALT) flap (11 cases). Additionally, four cases involved the pedicled TDAp flap in conjunction with the deep inferior epigastric artery perforator (DIEP) flap. The average DASH score for upper extremity burn patients was 10.58. Three-dimensional tissue coverage achieved through the linkage of two or even three independent free flaps is increasingly utilized in post-burn reconstruction. This approach offers multiple advantages and represents a viable option for burn reconstruction.

Sourcing of the Oligocene to Pliocene sediments of the Ningnan Basin: Evidence for Tibetan Plateau growth and local faulting unravelled by detrital apatite fission‐track and U–Pb double dating

AbstractThe Cenozoic topographic growth of the Tibetan Plateau is a pulsed, polyphase process that still requires more constraints. The Cenozoic sedimentary record of the Ningnan Basin, a continental basin located adjacent to the northeastern margin of the Tibetan Plateau, is a key archive for recording the surface evolution of the Tibetan Plateau. This work reports new provenance data (apatite fission‐track, apatite U–Pb dating, and trace element analysis on the same individual grains) from the Oligocene–Pliocene sedimentary sequence that filled the Ningnan Basin. The data set shows variations in provenance patterns through the Miocene which are related to the tectonic evolution of the northeastern margin of the Tibetan Plateau. In contrast to a primary provenance from the Western Ordos Block (WOB) during the Oligocene, the Miocene sediments were mostly derived from the recycling of Mesozoic successions that occur along the northwestern Haiyuan Fault, documenting it was active in the last ca. 15 Myr. These sediments, in turn, were derived from different orogenic blocks but mainly from different segments of the Qilian Mountains. We show that the Late Miocene–Pliocene sediments were primarily derived from transpressional uplift along the Haiyuan Fault, which affected regions such as the Liupan Mountains. Progressive northeastward migration of tectonic stress since the Middle Miocene has induced extensive regional deformation in the northeastern Tibetan Plateau, particularly along the Haiyuan Fault. The provenance record of the neighbouring Cenozoic basins is a key archive for deciphering this tectonic evolution.

Geological and Geomorphological Characterization of the Anthropogenic Landslide of Pie de la Cuesta in the Vitor Valley, Arequipa, Peru

This study presents the geological and geomorphological characterization of the Pie de la Cuesta landslide, a large (>60 ha) slow-moving (up 4.5 m/month) landslide in Southern Peru. The landslide has been active since 1975 and underwent a significant re-activation in 2016; the mass movement has caused the loss of property and agricultural land and it is currently moving, causing further damage to property and land. We use a combination of historical aerial photographs, satellite images and field work to characterize the landslide’s geology and geomorphology. The landslide is affecting the slope of the Vitor Valley, constituted by a coarsening upward sedimentary sequence transitioning from layers of mudstone and gypsum at the base, to sandstone and conglomerate at the top with a significant ignimbrite layer interbedded within conglomerates near the top of the sequence. The landslide is triggered by an irrigation system that provides up to 10 L/s of water infiltrating the landslide mass. This water forms two groundwater levels at lithological transitions between conglomerates and mudstones, defining the main failure planes. The landslide is characterized by three main structural domains defined by extension, translation and compression deformation regimes. The extensional zone, near the top of the slope, is defined by a main horst–graben structure that transitions into the translation zone defined by toppling and disaggregating blocks that eventually become earth flows that characterize the compressional zone at the front of the landslides, defined by thrusting structures covering the agricultural land at the valley floor. The deformation rates range from 8 cm/month at the top of the slope to 4.5 m/month within the earth flows. As of May 2023, 22.7 ha of potential agricultural land has been buried.

Investigation on the failure mechanism of friction-based self-centering timber beam-column joint considering bolt bearing effect: Experimental study and theoretical analyses

For friction-based self-centering timber structures, the bearing between friction bolts and the edge of holes is inevitable, due to machining inaccuracies and significant deformations at the beam-column joints. However, this issue has yet to be addressed in existing research. A limit state investigation was conducted on these friction-based self-centering timber beam-column joints under extensive deformation to analyze the failure mechanism and the loss of pretension force throughout the loading process. The influence of bolt bearing behavior on the residual deformation, loading capacity, energy dissipation capacity, and stiffness of the joint was studied. Finally, a theoretical prediction model considering single bolt and multi bolts bearing was proposed incorporating theoretical analysis and experimental results. The results indicate that the damage of the joint is concentrated on the compression deformation at the edge of bolt holes in friction pads and timber beams. The joint ultimately fails due to the end face of the column being crushed by the anchor used to fix post-tensioned (PT) strands. The joint exhibits good hysteresis characteristics within a 4 % drift and still demonstrates good recoverability within a 6 % drift. The loss rate of pretension force is below 15 % when the drift is lower than 4 %, but it increases significantly after the drift exceeds 5 %. When the drift is less than 4 %, the joints primarily exhibit single bolt bearing mode, resulting in only a slight increase in stiffness for the joints. When the drift exceeds 8 %, the joints primarily exhibit a multi bolt bearing mode, resulting in a maximum increase of approximately 64.5 % in joint stiffness. The theoretical bolt bearing model derived can better predict the position of bolts bearing the edge of holes and the damage state of friction-based self-centering timber beam-column joints.

Tectonostratigraphic models of an extensional back-arc basin: inferences for the evolution of the Pannonian Basin system

The subsidence history and sedimentary architecture of extensional basins are controlled by the interplay between tectonics, mantle dynamics, and climatic variations. Observations from outcrop to regional seismic scales coupled with numerical modelling techniques, including basin-scale stratigraphic, crustal-scale tectonic and mantle-scale subduction models contribute to quantify basin evolution. Here, we review and discuss both tectonic and stratigraphic applications of such models and compare them with observations from the Pannonian Basin system of Central Europe. We show that diachronous localization of back-arc extension, crustal thinning, asthenospheric upwelling and subsequent thermal relaxation are superimposed on an overall slow plate convergence. These processes result in contrasting subsidence and uplift patterns and a variable heat flow evolution in different parts of the basin system. The crustal stress-field of the subbasins does not always reflect their contrasting vertical motions. Extensional deformation generally migrates from the basin margins towards the basin centre. Structural inversion is localized along hot and weak inherited zones from the Middle Miocene to Present. Tectonic subsidence focuses sedimentation along deep depocenters, sourced by exhumed footwalls and from the neighbouring orogens. The overall post-rift sediment progradation are influenced by inherited bathymetries from the preceding syn-rift stage and by enhanced differential vertical motions.

Three-Dimensional Site Response Analysis of Clay Soil Considering the Effects of Soil Behavior and Type

To understand changes in bedrock motion at the ground surface, frequency effects, and spatial distribution within the soil, it is important to look at how a site responds to earthquakes. This is important for soil–structure interaction in structural and geotechnical earthquake engineering. This study deals with the effect of classifying clays according to shear wave velocity (stiff/medium/soft) and nonlinearity in behavior (linear/nonlinear) on the analysis of the site response. A 3D soil model with a combination of free fields and quiet boundaries and advanced constitutive models for soil to obtain accurate results was used to conduct this study. A strong TABAS earthquake was used to excite the compliant base of the model after converting the velocity record of TABAS to an equivalent surface traction force using a horizontal force–time history proportional to the velocity–time history. This study reveals that the site response analysis is affected by the type of clay soil and the soil material behavior, with soft clay soil causing higher PGV and PGV values in the linear case and lower values in the nonlinear case due to soil yielding, which causes soil response attenuation. This results in extremely conservative and expensive building designs when linear soil behavior is adopted. On the other hand, the applied earthquake exhibits greater attenuation at longer frequencies and greater amplification at mid and short frequencies. However, at frequencies near the applied earthquake frequency, neither attenuation nor amplification occurs. Furthermore, nonlinear soil behavior is crucial for soil evaluation and foundation design due to higher octahedral shear strain and settlement values, especially in softer soils, resulting from extensive plastic deformation.

Contemporary crustal strain rates derived from GPS measurements in southwestern China

Surface strain rates in southwestern China can provide constraints on tectonic evolution of the Tibetan Plateau. Unfortunately, different strain rate fields were obtained from different authors although almost the same GPS data were exploited. Based on updated GPS data, in this paper, we calculate the strain rates in southwestern China using the method proposed by Zhu et al. (2005, 2006). The results confirm that the strain rates in the Sichuan Basin and the South China Block are very small, and the high values are largely concentrated along the Xianshuihe-Anninghe-Xiaojiang fault system and the Sagaing Fault. Furthermore, the highest principal strain rates are located around the eastern Himalayan syntaxis (EHS), with compressive orientations perpendicular to the strike of the Main Thrust Belt. The basic characteristic of the strain rate distribution is in accordance with the tectonic structures from the geological and geophysical investigations. In particular, the two calculated extensive deformation regions basically match the locations of normal-faulting earthquakes in the Sichuan-Yunnan Rhombic Block (SYRB), with one in N-S extension trending in the northern SYRB, and the other nearly E-W orientation in the southern SYRB. We suggest that the extensive deformation and the normal faulting earthquakes in southwestern China is mainly controlled by the lower crustal channel flow with a bend direction, rather than by gravitational spreading alone, as previous authors proposed.

Constitutive modelling for understanding stress-stretch behaviour of Lennard-Jones non-crystalline molecular Solid

Abstract Non-crystalline molecular solid materials have many scientific and engineering applications. This study develops a constitutive equation for understanding stress-stretch behaviour of non-crystalline molecular solid using Lennard-Jones (LJ) intermolecular interaction. The strain energy derived from Lennard-Jones interactions between molecules. Based on the excluded volume (spherical volume occupied by the molecules maintaining centre to centre distance with a reference molecule) and density of the molecules, strain energy density is developed. In order to relate the molecular approach with continuum approximation, the excluded volume and density are expressed as a function of strain invariants of right Cauchy-Green deformation tensor. Finally, the constitutive equation in the form of Cauchy stress tensor is developed using the present strain energy density function. The present constitutive model is used to study finite deformations of the molecular solid like uniaxial extension. We compare our theoretical results with the experimental data of flexible polyurethane foams and obtain very good agreements. The current constitutive model can predict the deformation of micro/nano engineering system components.

Effective extensional-torsional elasticity and dynamics of helical filaments under distributed loads

We study slender, helical elastic rods subject to distributed forces and moments. Focussing on the case when the helix axis remains straight, we employ the method of multiple scales to systematically derive an ‘equivalent-rod’ theory from the Kirchhoff rod equations: the helical filament is described as a naturally-straight rod (aligned with the helix axis) for which the extensional and torsional deformations are coupled. Importantly, our analysis is asymptotically exact in the limit of a ‘highly-coiled’ filament (i.e., when the helical wavelength is much smaller than the characteristic lengthscale over which the filament bends due to external loading) and is able to account for large, unsteady displacements. In addition, our analysis yields explicit conditions on the external loading that must be satisfied for a straight helix axis. In the small-deformation limit, we exactly recover the coupled wave equations used to describe the free vibrations of helical coil springs, thereby justifying previous equivalent-rod approximations in which linearised stiffness coefficients are assumed to apply locally and dynamically. We then illustrate our theory with two loading scenarios: (I) a heavy helical rod deforming under its own weight; and (II) the dynamics of axial rotation (twirling) in viscous fluid, which may be considered as a simple model for a bacteria flagellar filament. In both scenarios, we demonstrate excellent agreement with solutions of the full Kirchhoff rod equations, even beyond the formal limit of validity of the ‘highly-coiled’ assumption. More broadly, our analysis provides a framework to develop reduced models of helical rods in a wide variety of physical and biological settings, and yields analytical insight into their elastic instabilities. In particular, our analysis indicates that tensile instabilities are a generic phenomenon when helical rods are subject to a combination of distributed forces and moments.

A Novel Mechanism to Accelerate Stress Relaxation of Toughened Blends: Stress-Induced Core-Shell Morphological Reconstruction and Its Application in Thermoforming and Dimensional Stabilization

Improving thermoforming efficiency and dimensional stability in thermoplastic products is a common challenge. This study investigates toughened polyamide 612 (PA612) blends made by adding maleic anhydride-functionalized SEBS (mSEBS) elastomers, along with high-density polyethylene (HDPE), polyphenylene Oxide (PPO), and polyphenylene Sulfide (PPS). Analyses showed that mSEBS forms a core-shell structure with HDPE or PPO and a sea-island structure with PPS in the PA612 matrix. The study uniquely examines how these structures affect stress relaxation. The results, modeled by a steady-state creep model, revealed that the core-shell structures reduced the characteristic relaxation time (λ) by over three orders of magnitude compared to PA612/mSEBS blends. Additionally, PA612/mSEBS/HDPE blends were more temperature-sensitive, reducing λ by six orders of magnitude compared to PA612/mSEBS/PPO blends. Further analysis showed that stress-induced core-shell morphological reconstruction (SCMR) significantly improved stress relaxation by promoting extensive plastic deformation and energy dissipation. These toughened PA612 blends exhibited excellent thermoforming efficiency and dimensional stability. A 3D finite element model confirmed SCMR as an effective strategy for stress relaxation, providing valuable insights for designing toughened blends with superior processing efficiency and stability.

Silver nanoparticles bridging liquid metal for wearable electromagnetic interference fabric

Stretchable conductive fibers are essential for the advancement of wearable electronic textiles. However, a significant challenge arises as their conductivity sharply decreases when stretched due to disruptions in electronic transport. Coating fibers with soft liquid metal (LM) has emerged as a promising solution. Despite this, there remains an urgent need to develop methods that enhance LM adhesion to substrates while facilitating efficient electron transport pathways. This study demonstrates a novel Ag-LM conductive network strategy for fabricating a thermoplastic polyurethane/polydopamine/silver-LM (TPU/PDA/Ag-LM) fiber membrane. This membrane exhibits outstanding stretchable electromagnetic interference (EMI) shielding performance and is produced through straightforward electrospinning, electroless depositing, and LM coating and activation. The TPU/PDA/Ag fiber membrane is initially prepared via polydopamine-assisted deposition of silver nanoparticles (AgNPs) on electrospun TPU fibers. The presence of AgNPs on the surface of TPU/PDA fibers enhances LM adhesion to the substrate and bridges adjacent LM to establish efficient conductive paths. This interaction benefits from the reactive alloying between AgNPs and LM, where the LM infiltrates the gaps among AgNPs, forming a distinctive LM-Ag alloy layer that uniformly coats the surface of TPU fibers. As anticipated, the unique three-dimensional (3D) interconnected LM-Ag conductive network remains intact during stretching, ensuring strain-invariant conductivity. The fabricated TPU/PDA/Ag-LM fiber membrane demonstrates exceptional EMI shielding effectiveness (SE) of 77.4 dB within the frequency range of 8.2–12.8 GHz and maintains an excellent EMI SE of 37.2 dB under extensive tensile deformation of 300%. Furthermore, the TPU/PDA/Ag-LM fiber membrane shows remarkable mechanical properties and stable Joule heating performance even under significant stretching.

Technological and Mechanical Studies on Additively Manufactured Cellular Structures Made of the Ultrafuse 316L Composite Filament

Regular cellular materials produced using additive manufacturing (AM) techniques represent a significant development trend in modern engineering materials. Depending on the applied elementary unit cell of topology, it is possible to define the course of the structure deformation process in order to obtain the highest possible energy absorption effectiveness. This feature makes regular cellular structural materials particularly attractive for a number of industrial branches. This paper presents the results of technological trials and the results of experimental studies on the mechanical properties of regular cellular structures made using 3D printing technology under compression test loading conditions. The material used for their production was the Ultrafuse 316L filament and the fused filament fabrication (FFF) technique. The proposed material is a polymer-metal composite with a manufacturing process similar to metal injection moulding (MIM). The adopted research methodology included a feasibility study aimed at achieving material homogeneity and compression tests of the developed and manufactured regular cellular structures under quasi-static loading conditions. Several structural topologies were analysed. Experimental results indicated that regular cellular structures made from 316L steel exhibit high mechanical strength and extensive plastic deformation capabilities. The utilized in this work manufacturing technology used combines the advantages of 3D printing process with the potential of powder metallurgy. The proposed technique of structure manufacturing process is much cheaper than other based on melting metallic powders.

Influence of hydrogen on deformation and embrittlement mechanisms in a high Mn austenitic steel: In-Situ neutron diffraction and diffraction line profile analysis

Austenitic steels have relatively high resistance to hydrogen embrittlement and play a critical role in hydrogen service applications. In particular, high Mn austenitic steels are considered economically viable alloy alternatives for these applications. The current study employed in-situ and ex-situ neutron diffraction techniques combined with diffraction line profile analysis (DLPA) to investigate the influence of hydrogen on deformation and embrittlement mechanisms in a high Mn (approximately 30 wt pct) austenitic steel. Investigation using both neutron diffraction and electron backscatter diffraction revealed the presence of extensive deformation twins and stacking faults within the steel microstructure after tensile deformation in the non-charged condition. These microstructural features suggest planar deformation behavior, which is expected from the relatively low stacking fault energy (SFE) of the alloy (approximately 29 mJ/m2). Hydrogen pre-charging resulted in apparent increases in both dislocations and stacking faults, contributing to macroscopic hardening and embrittlement mechanisms. Overall, numerical parameters obtained through neutron DLPA were used to elucidate the underlying mechanisms associated with hydrogen effects on the mechanical behavior, i.e. macroscopic strengthening, strain hardening rate, and embrittlement.

Predictive model for the instability of flexible formwork concrete wall in secondary mining of non-pillar coal mining

The secondary mining movement in non-pillar coal extraction causes significant overrun damage to flexible formwork concrete walls, leading to extensive deformation of roadway roof and bottom plates. This adversely affects working face efficiency and safety. The engineering context focuses on the non-pillar gob-side retaining walls in the 1315 working face of Zhaozhuang Coal Mine and the 23107 working face of Xiegou Coal Mine. Through on-site investigation, numerical simulation, theoretical analysis, and testing, we explore the stress migration law and destabilizing mechanism of the flexible formwork concrete wall influenced by the secondary mining movement of the coal-free pillar along the hollow wall. The research results showed that: (1) During the mining back process, the concrete wall formed with flexible formwork may experience stress concentration, leading to excessive damage and compromising mining safety. (2) Developing a predictive stress model for the concrete wall with flexible formwork is essential. If the stress surpasses the ultimate compressive strength during mining back, reinforcement becomes necessary.3) The length of damage overrun in the flexible formwork concrete wall exhibits two distinct stages as the distance back to mining increases. The first stage shows nearly linear growth, while the second stage indicates a decreasing growth rate, ultimately stabilizing. The application of Z6 concrete reinforcing agent effectively strengthens the flexible formwork concrete wall.

Influence of Polymer Concentration on the Viscous and (Linear and Non-Linear) Viscoelastic Properties of Hydrolyzed Polyacrylamide Systems in Bulk Shear Field and Porous Media.

Enhanced oil recovery (EOR) methods are generally employed in depleted reservoirs to increase the recovery factor beyond that of water flooding. Polymer flooding is one of the major EOR methods. EOR polymer solutions (especially the synthetic ones characterized by flexible chains) that flow through porous media are not only subjected to shearing forces but also extensional deformation, and therefore, they exhibit not only Newtonian and shear thinning behavior but also shear thickening behavior at a certain porous media shear rate/velocity. Shear rheometry has been widely used to characterize the rheological properties of EOR polymer systems. This paper aims to investigate the effect of the polymers' concentrations, ranging from 25 ppm to 2500 ppm, on the viscous, linear, and non-linear viscoelastic properties of hydrolyzed polyacrylamide (HPAM) in shear field and porous media. The results observed indicate that viscous properties such as Newtonian viscosity increase monotonically with the increase in concentration in both fields. However, linear viscoelastic properties, such as shear characteristic time, were absent for concentrations not critical in both shear rheometry and porous media. Beyond the critical association concentration (CAC), the modified shear thinning index decreases in terms of concentration in both fields, signifying their intensified thinning. At those concentrations higher than CAC, the viscoelastic onset rate remains constant in both fields. In both fields, the shear thickening index, a strict non-linear viscoelastic property, initially increases with concentration and then decreases with concentration, signifying that the polymer chains do not stretch significantly at higher concentrations. Also, another general observation is that the rheological properties of the polymer solutions in both porous media and shear rheometry only follow a similar trend if the concentration is higher than the CAC. At concentrations less than the CAC, the shear and porous media onset rates follow different trends, possibly due to the higher inertial effect in the rheometer.

A Mid‐Crustal Channel of Positive Radial Anisotropy Beneath the Eastern South China Block From F‐J Multimodal Ambient Noise Tomography

AbstractWe investigated the crustal radial anisotropy in the eastern South China Block (ESCB) with the F‐J multimodal ambient noise tomography. Well corresponding to widespread mid‐crustal low‐velocity zones in the model, a pronounced mid‐crustal channel of positive radial anisotropy is revealed. In the Cathaysia Block, it may origin from sub‐horizontally aligned quartz induced by extension and correspond to the phase transition of to quartz. In other areas, while, it may be relevant to other well‐aligned minerals. This positive mid‐crustal radial anisotropy channel not only provides the solid evidence for dominative extensional deformation since late Mesozoic, but also may indicate an important detachment surface, contributing much to the early Mesozoic magmatism in the ESCB.

Geodynamic modeling on continental collision in Qilian orogenic belt

The Qilian orogenic belt (QOB) located in the northeast margin of the Tibetan Plateau is featured by remarkable crustal thrusting and shortening, providing a key natural example to understand the lithospheric deformation of the Tibetan Plateau. Two types of continental collision are observed in the QOB: lithosphere subduction beneath Southern Qilian and crust underthrusting of Alxa terrain along the North Border Thrust (NBT). Deep seismic reflection profiles reveal complex stress field evolution, including compressional deformation in the lower crust, extensional deformation in the upper crust, and detachment deformation in the middle crust. In this study, we use 2D numerical modeling to investigate the dynamics of these two different collision types and the evolution of Qilian uplift. Model results suggest three patterns of continental collision, i.e., crust underthrusting follows lithosphere subduction, lithosphere subduction and the failed underthrusting/subduction. The key factors that may influence model evolution, including crustal rheology, convergence direction and rate, are systematically investigated. Our model results are further compared to observations, suggesting that lower convergence rate and crust underthrusting along NBT likely control the uplift and crust stress stratification of the QOB.

Experimental investigation of Lord Kelvin’s isentropic thermoelastic cooling and heating expression for tensile bars in two engineering alloys

ABSTRACT Solids change temperature when rapidly and elastically stressed. The effect proposed by W. Thomson, who was ennobled as Lord Kelvin, is adiabatic thermoelastic cooling or heating depending on the sign of the stress. A highly sensitive radiometrically calibrated, cooled infrared camera was employed to measure temperatures both decreasing and increasing. Temperature measurements made from the reversible, elastic part of the stress–strain curve during rapid uniaxial tensile loading and unloading were investigated. The quasi-isentropic cooling temperature from the stress loading curve is recovered by heating after the specimen fractures when the load is released. These measurements establish for the first-time isentropic temperature recovery. The materials tested are an AISI 4340 steel and an aluminium 2024 alloy. Measurements of the stress cooling are − 0.65 ± 0.05 K/GPa for steel and − 1.8 ± 0.3 K/GPa for aluminium alloy. The thermoelastic heating is − 1.2 ± 0.3 K/GPa for steel and − 1.8 ± 0.2 K/GPa for aluminium. These values are compared to Thomson’s theoretical thermoelastic prediction; comparisons are also made to equations of state tables. The experimental values are below theoretical predictions. The quasi-isentropic, elastic part of the temperature change is fully recovered after extensive plastic deformation by the fracture stress release wave.

Long-term stability of sediment routing on an active continental margin: Insights from detrital zircon U-Pb ages and measured stratigraphy of Carboniferous to Miocene strata, Sierra de Narváez, NW Argentina

The complex Phanerozoic tectonic evolution of the western margin of South America, including extensional, neutral, and contractional deformation regimes, provides an opportunity to test how sedimentary systems were affected by variable tectonics on a long-lived active margin. Here, we report new geologic mapping, measured stratigraphic sections, paleocurrent measurements, and detrital zircon U-Pb ages from the Fiambalá area, NW Argentina, that together constrain the evolution of sediment routing and basin systems of the northern Sierras Pampeanas during Carboniferous to Miocene time. Carboniferous to Triassic strata of the Paganzo Group include fluvial, lacustrine, and eolian intervals deposited in an extensional setting with SSW-directed paleocurrent orientations. The Mesozoic El Pedernal Formation consists of a lower, basalt interval and an upper, conglomerate and sandstone interval, which has a new detrital zircon maximum depositional age of ca. 88 Ma. Observed strata of the Miocene Tambería Formation include fluvial to eolian sandstones of the lower member of the formation and alluvial conglomerates of the middle member. Whereas lower member Tambería fluvial strata have SSW-oriented paleocurrents, middle member conglomerates indicate broadly E-directed paleoflow.Detrital zircon age distributions of the Paganzo Group, El Pedernal Formation, and Tambería Formation are remarkably consistent, with dominant age peaks ca. 1.3–0.9 Ga and ca. 660-450 Ma. The ages and relative magnitudes of these peaks are consistent with derivation from igneous sources associated with Choiyoi magmatism (330-215 Ma), the Famatinian (490-450 Ma) and Pampean (540-510 Ma) orogens, basement of the MARA block (ca. 1.3–0.9 Ga), and recycling of Neoproterozoic to Cambrian sedimentary successions derived from central Gondwana (ca. 1.3–0.9 Ga, 650-590 Ma, 540-510 Ma).The consistent paleocurrent orientations and detrital zircon U-Pb ages of the Carboniferous Paganzo Group to the Miocene lower member of the Tambería Formation suggest that a S-directed axial drainage network with a consistent sediment source area persisted in the region for ∼300 Myr. This axial drainage network was succeeded by an E-directed transverse drainage network initiated between 15 Ma and 8 Ma due to growth of the Andean thrust wedge, coeval with tectonic compartmentalization and drainage modification of nearby foreland depocenters. These findings highlight the potential for long-term persistence of drainage networks on continental margins under changing tectonic regimes.

Fabrication of dual dynamic crosslinking polyurethane networks towards self-healing, resist fatigue, and highly stretchable ionic skins

The limited anti-fatigue performance of self-healing polyurethane elastomers under high-strain conditions restricts their application in high-performance ionic skins. Herein, a polyurethane network (PU-DDN) synergistically reversibly crosslinked by dynamic thiourethane bonds and hydrogen bonds was synthesized successfully. This dual reversibly crosslinking strategy not only endowed the polyurethane network with an excellent fatigue resistance (showing a residual strain of only 63 % after 10 uninterrupted cyclic tensile tests at 400 % strains), but also imparted it with a high strength (6.12 MPa) and stretchability (611.42 %). Owing to the thermo-reversibility of dual dynamic networks, the damaged PU-DDN heated at 100 °C for 3h could fully restore its initial mechanical properties. Subsequently, transparent stretchable ionic skins were fabricated by mixing the PU-DDN with ionic liquids. A resulting highly-sensitive ionic skin (GF1 = 1.25, GF2 = 2.01) named PU-DDN/IL20 demonstrated exceptional durability, which could produce repeatable electrical signals even after 2000 cycles of stretching to an extensive deformation of 400 %. Meanwhile, it can also monitor human motions, showcasing its promising potential in the realm of intelligent wearable applications.