Reverse Regime Research Articles

Magnetization dynamics in single and trilayer nanowires

We have studied the magnetization dynamics of single Py(t) (t= 20 nm, 50 nm) and trilayer [Py(50)/Pd(tPd)/Py(20)] nanowire arrays fabricated over large areas using deep ultraviolet lithography technique. The dynamic properties are sensitive to the field orientation and magnetic film thicknesses. A single resonant mode corresponding to the excitations at the bulk part of the wire is detected in all the single-layer nanowire arrays. Furthermore, the spacer layer thickness influenced the dynamic properties in trilayer samples due to the different coupling mechanisms. A single resonant mode is observed intPd= 2 nm trilayer nanowires with a sharp frequency jump from 13 GHz to 15 GHz across the reversal regime. This indicates the exchange coupling and the coherence in magnetization precession in the ferromagnetic layers. On the other hand, wires with 10 nm-spacer display two well-resolved modes separated by ∼3 GHz with a gradual change in frequency across the reversal regime from-26mT to-46mT, indicating the presence of long-range dipolar interactions instead of exchange coupling. The spacer layer of the proposed spin-valve-type structure can be tailored for desired microwave splitters or combiners.

Non-Stationary Effects of Current-Load on Electrochemical Behavior of La0.8Sr0.2MnO3- δ in Solid Oxide Electrolysis Cell

High-temperature solid oxide water electrolysis is a highly efficient and carbon-free technology employed for energy conversion, offering numerous advantages over traditional low-temperature water electrolysis methods. These benefits include fast electrode kinetics without the need for Pt group metals and the potential to operate in reversible regimes (fuel cell/steam electrolysis), attributed to the elevated operating temperature (i.e., 600-800 °C). However, the high operating temperature imposes stringent material requirements.While recent attention has been directed towards developing and characterizing new materials for both electrodes and electrolytes, a comprehensive understanding of the underlying reaction mechanisms remains incomplete, hindering the further advancement of the solid oxide cells.Despite the emergence of more advanced materials in recent years, the lanthanum-strontium-manganite La1-xSrxMnO3-δ (LSM) remains to be widely used for an oxygen electrode construction. This preference is due to its cost-effectiveness, high electrical conductivity, thermal and chemical stability, and compatibility with various solid electrolytes. Although LSM has been known for several decades, the reaction mechanism occurring on this oxygen electrode in a broad range of electrode potentials is inadequately described, with discrepancies arising among different authors. These inconsistencies are often linked to the evolving understanding of the non-stationary properties of the LSM lattice – the inner defect chemistry of LSM.Contemporary studies increasingly adopt the concept of ionic conductivity of LSM enabled by cathodic polarization to describe the oxygen reduction reaction. This shift from exclusive electron to ionic-electron conductivity enhances the performance of the LSM electrode, potentially causing discrepancies in the literature as experimental data may not align with theoretical descriptions. Conversely, for the oxygen evolution reaction during anodic polarization, a reversed reaction mechanism is considered without accounting for ionic conductivity of LSM under either stationary or non-stationary conditions. This approach may oversimplify the defect chemistry of LSM, particularly during transitions between operational regimes (i.e., fuel cell and electrolyser regimes). However, such changes are difficult to describe only by experimental approach. Here a combination with mathematical modelling seems to be promising approach allowing to gain deeper understanding.The primary objective of this study is to further investigate the impact of LSM defect chemistry on electrode performance, proposing a reaction scheme during both operating regimes and, crucially, during transitions between them.To address this goal, a series of experiments were conducted under both current-less and current-load conditions using laboratory button single cells. Various gas compositions and operating temperatures were used to determine whether LSM becomes a mixed ionic-electron conductor. Potentiostatic or potentiodynamic methods were used to clarify how this altered property influences individual operating regimes. The results indicate that cathodic polarization leads to a partial reduction of Mn4+ to Mn2+ in the crystalline lattice of LSM, creating oxygen vacancies through which oxide ions can be transported. Additionally, these lattice changes, though temporary, impact the oxygen evolution reaction region under certain conditions. A mathematical model incorporating parallel reaction pathways for both operating regimes supports these experimental results, predicting a cathodic potential at which ionic conductivity becomes viable and identifying conditions where partial reduction of Mn ions is no longer possible.This work contributes to understanding solid oxide cells, providing a solid foundation for more complex mathematical modeling of electrolysis cells. It underscores the necessity to fully comprehend the electrochemical behavior of electrode materials for the continued development of this technology.This work was supported by the Technology Agency of the Czech Republic under project no. TK04030143 (Advanced reversible system for hydrogen production on base of the high temperature solid oxide cell).

Water Transport Management in a Bipolar Membrane for CO2 Electrolysis Application

Bipolar membranes (BPMs) offer significant potential for electrochemical technologies, especially in CO2 electrolysis. Their unique ability to create pH gradients provides optimum chemical microenvironments at the cathode and anode for efficient, cheap and sustainable CO2 electrolysis. However, state-of-the-art BPMs are limited in their performance due to phenomena such as membrane degradation and membrane dehydration leading to low ionic conductivity, and hence their complete potential for various electrochemical technologies is yet to be realized. Previous studies have identified water transport as one of the main factors limiting the performance of BPM. A multi-physics model of BPM can serve as a useful tool to gain a comprehensive understanding of different performance limiting factors and thereafter propose solutions to overcome these limitations. The goal of the present study is to provide model based design guidelines for a BPM that facilitates efficient water transport, making it a suitable candidate for integration into a zero-gap CO2 reduction electrolyzer operating at industrial-grade performance levels.We have built a 1-D continuum model of a BPM kept in an aqueous (bi)carbonate electrolyte solution, incorporating physical phenomena such as water-dependent transport of ions and neutral species, field-enhanced homogeneous reactions (water-dissociation and acid-base reactions) along with CO2 phase transfer reaction at the BPM-aqueous electrolyte interfaces. The continuum model employs Poisson-Nernst-Planck equations to resolve local chemical species concentration. The effect of the electric field on the equilibrium dissociation constants of various charge-generating homogenous reactions is incorporated. This becomes important especially at interfaces within the domain where a sharp increase in electric field is observed. Unlike previous modeling studies, we also incorporate mass-conservation equation for water transport to resolve local water concentration inside the BPM. Local water concentration influences the transport of species in the BPM through their water-dependent activity and diffusivity. The electric potential distribution is resolved by incorporating water-dependent local permittivity of the BPM.Our model investigates both the reverse and forward bias operational modes of the BPM. In alignment with the experimental observation, in the reverse bias regime, the model identifies a distinct initial phase where current density is limited, with the majority of the current carried by protons and hydroxide ions at low overpotentials. As the potential increases, there's a rapid increase in current density, indicating a breakdown regime caused by an electric field-enhanced water dissociation reaction at the BPM interface. At even higher potentials, the polarization curve enters a third phase where the current density saturates characterized by water transport limitation. This aspect of the BPM polarization curve is uniquely captured by our model. Conversely, in the forward bias mode, as expected we do not observe any limitations due to mass transport, since water is generated at the bipolar junction. Here, the model forecasts a saturation of CO2 in the electrolyte, leading to gas bubbles forming at the BPM interface. To address the issue of water transport limitation, we conduct various parametric studies focusing on different membrane characteristics, such as individual layer thicknesses and their ion exchange capacities. The outcomes of these analyses provide crucial guidelines for optimizing these parameters and enhancing water management in BPM-based systems.

Voltage-controlled nonlinear optical properties in gold nanofilms via electrothermal effect

Dynamic control of the optical properties of gold nanostructures is crucial for advancing photonics technologies spanning optical signal processing, on-chip light sources and optical computing. Despite recent advances in tunable plasmons in gold nanostructures, most studies are limited to the linear or static regime, leaving the dynamic manipulation of nonlinear optical properties unexplored. This study demonstrates the voltage-controlled Kerr nonlinear optical response of gold nanofilms via the electrothermal effect. By applying relatively low voltages (~10 V), the nonlinear absorption coefficient and refractive index are reduced by 40.4% and 33.1%, respectively, due to the increased damping coefficient of gold nanofilm. Furthermore, a voltage-controlled all-fiber gold nanofilm saturable absorber is fabricated and used in mode-locked fiber lasers, enabling reversible wavelength-tuning and operation regimes switching (e.g., mode-locking—Q-switched mode-locking). These findings advance the understanding of electrically controlled nonlinear optical responses in gold nanofilms and offer a flexible approach for controlling fiber laser operations.

Parametrical design and optimization of a reverse circulation drill bit for dust control

The reverse circulation down-the-hole air hammer drilling (RC-DTH) method is renowned for its efficiency in hard rock formations and exceptional dust control performance. It presents opportunities for cost-saving, efficiency improvement, energy conservation, and environmental protection. Reverse circulation drill bits are critical components of this method. This study focused on the air reverse circulation regime, investigating various geometric parameters of the RC drill bits through computational and experimental methods to enhance its dust control performance. Results indicate that increasing the layers of suction nozzles, enlarging the diameters of the suction and mixing nozzles, and optimizing the input airflow rate can effectively channel airflow toward the central passage of the drill tool. Consequently, this optimization significantly improves the dust control performance of the RC drill bits. Conversely, increases in the flushing nozzle diameter and alterations in the suction nozzle location have detrimental effects on the dust control capability of the RC drill bits. Field tests were conducted at the Yuan Jiacun iron mine, affiliated with Taiyuan Iron and Steel (Group) CO., LTD. The field tests demonstrate that the optimized RC drill bit exhibits excellent dust performance.

Phase-field damage simulation of subloop loading in TiNi SMA

In practical applications, TiNi shape memory alloys (SMAs) exhibit behavior that can pose a challenge with current constitutive models and their implementations in finite element method (FEM) software. TiNi SMA devices typically operate in the forward or reverse martensitic transformation regime, which is known as subloop loading. During such cyclic loading–unloading, the hysteresis stress–strain loop changes because of material damage, which can be considered the fatigue of TiNi SMAs. During both the loading and unloading processes, the stress plateau decreases. At the same time, the accumulated (residual) martensitic transformation strain increases. In this study, the experimental investigation results and observations of the aforementioned phenomena are presented. Next, the phase-field damage model is employed, along with a modified Lagoudas constitutive model, to simulate the change in stress–strain hysteresis. Furthermore, a fatigue function is used to simulate the accumulation of martensitic transformation strain. The experimental stress–strain response is compared with the simulation results, and good quantitative and qualitative agreement is obtained. The damage and martensitic volume fraction with respect to strain are discussed for full-loop and subloop loading. The observations and conclusions, as well as open questions, are presented. Possible directions for future research are provided.

Planarization of p-GaN surfaces on MOCVD grown V-defect engineered GaN-based LEDs

The large polarization barriers between the quantum wells and quantum barriers in long-wavelength GaN-based light-emitting diodes (LEDs) inhibit their performance by requiring excess driving voltages to reach standard operating current densities. Lateral injection of carriers directly into quantum wells is required to circumvent this issue. V-defects are naturally occurring inverted hexagonal defects with semipolar 101¯1-plane sidewalls generated on surface depressions from threading dislocations. LEDs engineered to intentionally generate V-defects below the active region of the LED can achieve lateral carrier injection through the V-defect sidewalls and have already been able to demonstrate world record wall-plug efficiencies for LEDs in the green-red wavelengths. V-defects can be enlarged during kinetically limited growth where the growth rate of the c-plane GaN is faster than that of their sidewalls, leaving them unfilled. We report on the metal organic chemical vapor deposition growth conditions required to fill in V-defects with p-GaN during epitaxial growth of the LED post the active region. Circular transmission length measurements of Pd/Au contacts processed on p-GaN surfaces with various amounts of unfilled V-defects showed no significant difference in their sheet resistance and specific contact resistance. J–V measurements of LEDs grown with varying unfilled V-defect densities showed no significant difference in the forward bias regime. However, in the reverse bias regime, catastrophic breakdown occurred at markedly lower voltages for samples with larger unfilled V-defect densities. This suggests that unfilled V-defects may act as hotspots for device failure, and planarizing LED surfaces may help prevent early degradation of LED devices.

Coarse-Grained Simulations on Polyethylene Crystal Network Formation and Microstructure Analysis.

Understanding and characterizing semi-crystalline models with crystalline and amorphous segments is crucial for industrial applications. A coarse-grained molecular dynamics (CGMD) simulations study probed the crystal network formation in high-density polyethylene (HDPE) from melt, and shed light on tensile properties for microstructure analysis. Modified Paul-Yoon-Smith (PYS/R) forcefield parameters are used to compute the interatomic forces among the PE chains. The isothermal crystallization at 300 K and 1 atm predicts the multi-nucleus crystal growth; moreover, the lamellar crystal stems and amorphous region are alternatively oriented. A one-dimensional density distribution along the alternative lamellar stems further confirms the ordering of the lamellar-stack orientation. Using this plastic model preparation approach, the semi-crystalline model density (ρcr) of ca. 0.913 g·cm-3 and amorphous model density (ρam) of ca. 0.856 g·cm-3 are obtained. Furthermore, the ratio of ρcr/ρam ≈ 1.06 is in good agreement with computational (≈1.096) and experimental (≈1.14) data, ensuring the reliability of the simulations. The degree of crystallinity (χc) of the model is ca. 52% at 300 K. Nevertheless, there is a gradual increase in crystallinity over the specified time, indicating the alignment of the lamellar stems during crystallization. The characteristic stress-strain curve mimicking tensile tests along the z-axis orientation exhibits a reversible sharp elastic regime, tensile strength at yield ca. 100 MPa, and a non-reversible tensile strength at break of 350%. The cavitation mechanism embraces the alignment of lamellar stems along the deformation axis. The study highlights an explanatory model of crystal network formation for the PE model using a PYS/R forcefield, and it produces a microstructure with ordered lamellar and amorphous segments with robust mechanical properties, which aids in predicting the microstructure-mechanical property relationships in plastics under applied forces.

Reversible, irreversible, and mixed regimes for periodically driven disks in random obstacle arrays.

We examine an assembly of repulsive disks interacting with a random obstacle array under a periodic drive and find a transition from reversible to irreversible dynamics as a function of drive amplitude or disk density. At low densities and drives, the system rapidly forms a reversible state where the disks return to their exact positions at the end of each cycle. In contrast, at high amplitudes or high densities, the system enters an irreversible state where the disks exhibit normal diffusion. Between these two regimes, there can be an intermediate irreversible state where most of the system is reversible, but localized irreversible regions are present that are prevented from spreading through the system due to a screening effect from the obstacles. We also find states that we term "combinatorial reversible states" in which the disks return to their original positions after multiple driving cycles. In these states, individual disks exchange positions but form the same configurations during the subcycles of the larger reversible cycle.

Control of Reverse Flow over Cantilevered Swept Blades Using Passive Camber Morphing

High-speed rotorcraft experience a region of reversed flow over the retreating blade at high advance ratios. This reverse flow region results in multiple unfavorable effects, including negative lift, increased drag, and a large pitching moment impulse. The effect of the sweep angle on a rotor blade in reverse flow was explored, and it was demonstrated that the introduction of a trailing edge reflex camber could mitigate the adverse effects seen in this regime. A cantilevered, finite-span NACA 63-218 blade was examined at a Reynolds number Rec=2.38×105 both with and without a 10° trailing edge reflex camber. Three blades were tested: one with 20° forward sweep, one with 20° backward sweep, and one with no sweep. The experiments consisted of load measurements across a range of angles of attack, as well as volumetric flowfield measurements using stereoscopic particle image velocimetry on the two swept models at 10° angle of attack in reverse flow. The flowfields exhibited a highly three-dimensional separation bubble that existed on the blades in both backward and forward sweep conditions. Cambering of the trailing edge led to almost complete flow attachment on the backward swept model and a significant reduction in separation over the forward swept model. Cambering also led to a large reduction in drag in the entire reverse flow regime in both swept and unswept conditions. A large reduction in pitching moment and a smaller reduction in negative lift were also observed at moderate angles of attack.

In situ tracking the phase change in metastable copper oxide thin film via thermal oxidation

Phase change (PC) materials, such as metal oxides, possess high fundamental and applied importance for modern memory, sensor, and photonic devices. However, revealing the kinetics and mechanisms of PC and achieving the reversible and irreversible PC regimes are still a challenge. Here, we report on 200 nm films of metastable Cu4O3 obtained by magnetron sputtering. In situ structural and optical analyses during air annealing revealed the thermal induced PC from Cu4O3 to CuO. Combination of x-ray diffraction and optical transmittance with heating up to 450 °C allowed us to explore the PC rate and then to correlate it with classical nucleation and crystal growth mechanism. We have also revealed two regimes of PC, possessing reversible 12% (1.42–1.25 eV) and irreversible 220% (1.25–2.75 eV) direct bandgap tuning by temperature. The results, thereby, pave the way for controllable transformation of copper oxide thin films to achieve the desired microstructure and its functionality.

Temperature and field dependencies of current leakage mechanisms in IrOx contacts on InAlN/GaN heterostructures

This Letter reports on the mechanisms of reverse leakage current transport in InAlN/GaN heterostructure Schottky diodes with intentionally oxidized iridium oxide (IrOx) contacts across a wide temperature range. Current–voltage characteristics were experimentally measured from 25 to 500 °C (≈ 300 to 773 K). Three distinct regions in the reverse bias regime of operation and their corresponding dominant current transport mechanisms are identified. A trap-assisted tunneling mechanism is observed at low reverse bias, and trap energy levels are between 1.12 and 1.99 eV. At medium reverse bias, Poole–Frenkel emission is decomposed into low-field, mid-field, and high-field regions and the related trap activation energies vary from 0.38 to 2.04 eV. At high reverse bias, the Fowler–Nordheim model is applied and the effective barrier height to tunneling is 0.78 eV. The model of the reverse leakage current constructed using the parameters associated with these transport mechanisms closely aligns with the experimental data and supports the advancement of high-temperature electronics based on IrOx -gated InAlN/GaN heterostructure technology.

Carbon source priority and availability limit bidirectional electron transfer in freshwater mixed culture electrochemically active bacterial biofilms

This study investigated, if a mixed electroactive bacterial (EAB) culture cultivated heterotrophically at a positive applied potential could be adapted from oxidative to reductive or bidirectional extracellular electron transfer (EET). To this end, a periodic potential reversal regime between − 0.5 and 0.2 V vs. Ag/AgCl was applied. This yielded biofilm detachment and mediated electroautotrophic EET in combination with carbonate, i.e., dissolved CO2, as the sole carbon source, whereby the emerged mixed culture (S1) contained previously unknown EAB. Using acetate (S2) as well as a mixture of acetate and carbonate (S3) as the main carbon sources yielded primarily alternating electrogenic organoheterotropic metabolism with the higher maximum oxidation current densities recorded for mixed carbon media, exceeding on average 1 mA cm−2. More frequent periodic polarization reversal resulted in the increase of maximum oxidative current densities by about 50% for S2-BES and 80% for S3-BES, in comparison to half-batch polarization. The EAB mixed cultures developed accordingly, with S1 represented by mostly aerobes (84.8%) and being very different in composition to S2 and S3, dominated by anaerobes (96.9 and 96.5%, respectively). S2 and S3 biofilms remained attached to the electrodes. There was only minor evidence of fully reversible bidirectional EET. In conclusion the three triplicates fed with organic and/or inorganic carbon sources demonstrated two forms of diauxie: Firstly, S1-BES showed a preference for the electrode as the electron donor via mediated EET. Secondly, S2-BES and S3-BES showed a preference for acetate as electron donor and c-source, as long as this was available, switching to CO2 reduction, when acetate was depleted.Graphical

Internal stress development within wood during drying: A master curve concept and its application on drying stress evaluation

The generation of internal stress (IS) in flat-sawn and quarter-sawn rubberwood boards during drying has been investigated using an online restoring force (RF) technique, which restrained a half-split rectangular wood specimen. Particular attention was given to the longest IS reversal regime. The IS development proceeds faster in the flat-sawn specimens than that in the quarter-sawn specimens while the maximum IS magnitudes in both specimens are rather similar. By normalizing the IS reversal period, a master IS profile, the derivative of the measured RF to the IS reversal time ratio versus the IS reversal time ratio, is proposed. This master curve, exhibiting some degree of independence from wood orientation and drying temperature, shows variations correlated with the free water content in the wet zone and the dry/wet zone fractions. The process of IS reversal, unaffected by temporary unrestraint, advances as the dry zone expands inwards and ends when the wet zone disappears. Assuming mechanical equilibrium between the dry and wet zones, the IS in both zones can be estimated from the RF data. The maximum tensile IS in the dry zone, indicating a risk of surface checks, evolves at slightly lower magnitudes at higher drying temperatures and is lower in the quarter-sawn specimens. The IS relaxation in the dry zone, still largely taking place in the absence of the applied RF, highlights the main contribution of the dry/wet zone fractions, continuing to proceed without restraining, to the IS development. These findings, emphasizing the significance of dry and wet zones, should pave the way for a better understanding of the IS development within wood during drying.

1D Geomechanical Model For Wellbore Stability in Z Field, Y Well Sanga Sanga Working Area, Kutai Basin

This research is about 1D geomechanical model for wellbore stability in Z Field, Y Well Sanga Sanga Working Area, Kutai Basin where wells have been drilled. The Purpose of this Research is to analyze the stability of the well starting from knowing the stress regime that occurs, predicting the occurrence of wellbore failure, and determining safe mud weight window for next drilling. The method use in this Research is a numerical modelling method using log data and drilling data that has been obtained and then managed using Techlog Software. The result of this Research show the magnitude of mechanical properties of the rock that have been obtained, then in general the stress regime that occurs in the Z Field formation is the normal regime even though the strike slip and reverse regime are inserted at a certain depth, then based on the prediction results of failure in this well is wide breakout, which in general occurs in lithology with sandstone, finaly safe mud weight window can be estimated properly, so that it can be used for further well drilling. This research is about 1D geomechanical model for wellbore stability in Z Field, Y Well Sanga Sanga Working Area, Kutai Basin where wells have been drilled. The Purpose of this Research is to analyze the stability of the well starting from knowing the value of the mechanical properties of the formation, the stress regime that occurs, predicting the occurrence of wellbore failure, and determining safe mud weight window for next drilling. The method use in this Research is a numerical modelling method using log data and drilling data that has been obtained and then managed using Techlog Software. The result of this Research show the magnitude of mechanical properties of the rock that have been obtained, then in general the stress regime that occurs in the Z Field formation is the normal regime even though the strike slip and reverse regime are inserted at a certain depth, then based on the prediction results of failure in this well is wide breakout, which in general occurs in lithology with sandstone, finaly safe mud weight window can be estimated properly, so that it can be used for further well drilling.

The electrodiffusional theory for the wall shear stress measurement by two-strip probe

This article deals with the derivation of the fundamental theory describing the mass transport on the active surface of a two-strip mass transfer probe for an arbitrary direction of fluid flow. The existence of such a general theory is a critical point for the application of the electrodiffusion method using a two-strip probe. Considering the different possible sizes of the probe segments, the analytical formulas for the average mass transfer coefficients are derived and presented in dimensionless forms for both segments. The correctness of the derived analytical expressions is verified by numerical solution of the convection-diffusion transport equation. A methodology for possible experimental data treatment is also proposed. It is based on the evaluation of two current signals collected from the segments of a two-strip probe. From the derived equations, it is possible to determine the magnitude and direction of the wall shear rate vector for both frontal and reverse flow regimes. From the analysis of the current ratio predictions for different probe geometries, an optimal probe configuration is found with respect to the sensitivity of the flow direction measurement.

Rock Strength and In Situ Stress Analysis for Wellbore Instability, Fault Stress Regime Prediction, 3D Structural and Geomechanical Modelling in H-field Offshore of Rio Del Rey Basin, Southwest Region, Cameroon

The study involved the determination of strength parameters and in situ stresses in two wells pseudo-named H005 and H008 in a hydrocarbon field located offshore of Rio Del Rey basin. The work was aimed at revealing the stability of formation rocks and fault stress regimes associated with the study wells. The parameters determined employed only empirical correlations and tools since core samples were not available for laboratory experiments. The unconfined compressive strength for the two wells was relatively low varying from 1500 to 3300 psi in well H005 and from 1000 to 4000 psi in well H008. The friction angle varies from 21.0° to 23.0° in well H005 and from 21.0° to 27.0° in well H008. The results of the in situ stress analysis in well H005 indicate a reverse fault stress regime where maximum horizontal stress (SH) is greater than the minimum horizontal stress (Sh), which is in turn greater than the vertical stress (SV) in the shallow part of the well (1028.5–1249 m), while a normal fault stress regime where the vertical stress is greater than the two horizontal stresses was interpreted at a depth from 1250 to 1390 m. Unlike well H005, the entire depth of well H008 under interpretation revealed a normal fault stress regime. The outcome of the 3D geomechanical model closely agrees with the 1D model. It was concluded that the formation rocks are weak, and the wells are dominated by normal fault stress regimes.

Review of tectonic inversion of sedimentary basins in NE and N Brazil: Analysis of mechanisms, timing and effects on structures and relief

Most intraplate areas worldwide are under compression characterized by thrust and strike-slip deformations. The sources of the stresses in these regions are a combination of far-field (regional) stresses (e.g., ridge push, slab pull, lithospheric drag) and near-field (local) stresses (e.g., topography, lateral and vertical anisotropy of strength or elastic properties, erosion, flexural bending, overloading, buoyancy of low-density regions). These intraplate regions are sites favorable for the tectonic inversion of sedimentary basins. Here, we review the tectonic inversions of the sedimentary basins in NE and N Brazil, which comprise a significant part of the South American intraplate (the South American Platform). These regions have been under compression since the Late Cretaceous. Reports of post-rift basin inversions derived from seismic profiles, fault-slip data, and topography have been described in the Sergipe-Alagoas, Paraíba, Potiguar, Ceará, Rio do Peixe, Araripe (NE Brazil), and Solimões (N Brazil) basins. Reports of inversions in the rift phase have also been described in the Araripe Basin. The present-day stress field indicates that inversions in NE Brazil can mainly be characterized as strike-slip and thrust fault regimes, whereas in N Brazil, inversions have occurred under reverse stress regimes. The most frequent inversion structures are reactivated faults, folds, and dome structures affecting the topography and the consequent uplift of rift and post-rift sedimentary units. Inversions have led to the reactivation of continental-scale structures, such as the strike-slip dextral shearing of the Transbrasiliano lineament, which affected rift and post-rift units in the Equatorial Margin of Brazil. The small crustal thickness of these areas favors inversion, as indicated by the most recent Moho depth map of South America. The interplay between far-field and near-field stresses explains the stress pattern in NE and N Brazil, where inversions have been observed.

Regulating the Flow-Driven Translocation of Macromolecules through Nanochannels by Interfacial Physical Adsorption

By using a model system composed of an anodic aluminum oxide nanopore (AAO), poly(benzyl acrylate) (PBAN) adsorbent, and polystyrene (PSN) probe, where N represents the degree of polymerization, this work has explored how the physical adsorption of PBA onto the surface of the AAO nanopore (rp ≈ 10 nm) influences the flow-driven translocation of PS in toluene. In the low flow rate range (Q = 0.02 mL/h), the translocation of PS chains is purely diffusive, and the partially reversible adsorption behavior of PBAN is observed only when N < ∼360, showing a strong chain length dependence. In the partially reversible regime, the interfacial thickness (δ) of the adsorption layer is estimated to be from ∼1.5 to ∼2.9 nm depending on the chain length. In the mixed solutions, when N increases from 0 to 75 and 150 for PBAN, the cut-off size (COS) of the membrane for broadly distributed PSB-285K (Mw/Mn ≈ 2.48) is estimated to decrease from ∼10.0 to ∼8.0 and ∼6.0 nm, respectively; in addition, the introduction of PBA360 can promote the separation of narrowly distributed PS655 and PS1200 by regulating re, whereas in the high flow rate range (Q > 0.02 mL/h), the translocation for PS long chains is based on the mechanism of molecular deformation, and the flow rate-dependent translocation shows a strong dependence on the chain length of PBAN. Namely, in mixed solutions, when N increases from 150 to 360, the critical flow rate (Qc) is found to slightly increase from ∼0.30 to ∼0.45 mL/h for PS1500 translocation; in addition, the cut-off performance of PSB-285K displays dependence both on flow rate and PBAN chain length. Our result has demonstrated a novel strategy to regulate the cut-off performance during the translocation of (bio)macromolecules through nanopores via partially reversible interfacial physical adsorption.

The dual role of hydrogen in grain boundary mobility

The effect of solute hydrogen on shear-coupled grain boundary (GB) migration is investigated with the dislocation-array type Σ25(430)[001] GB and a dual role of hydrogen on GB mobility is unraveled. In the low temperature and high loading rate regime, where hydrogen diffusion is substantially slower than GB motion, GB breaks away from the hydrogen atmosphere and transforms into a new stable phase with highly enhanced mobility. In the reverse regime, hydrogen atoms move along with GB, exerting a drag force on GB and decreasing its mobility. These findings provide rationale for the coexistence of hydrogen hardening and softening observed experimentally in polycrystalline materials.