Anisotropy Of Susceptibility Research Articles

ON THE QUESTION OF HYDRODYNAMIC INSTABILITY OF NEMATICS IN A MAGNETIC FIELD. III: ACCOUNTING FOR THE INERTIAL TERM IN THE EQUATION OF MOTION IN THE MODEL OF MAGNETOHYDRODYNAMIC DOMAIN FOR SPLAY DISTORTION

A magnetohydrodynamic domain model describing the motion of a nematic liquid with positive anisotropy of diamagnetic susceptibility in the splay distortion geometry is considered. The inertial term is taken into account in the equation of motion of a nematic model. This approach makes it possible to introduce dimensionless parameters into the model: ratios of Eriksen numbers to Reynolds numbers. The introduction of such parameters allows one to experimentally assess the relative role of elastic and viscous forces in nematics of different nature.

DeepSTI: Towards tensor reconstruction using fewer orientations in susceptibility tensor imaging.

Susceptibility tensor imaging (STI) is an emerging magnetic resonance imaging technique that characterizes the anisotropic tissue magnetic susceptibility with a second-order tensor model. STI has the potential to provide information for both the reconstruction of white matter fiber pathways and detection of myelin changes in the brain at mm resolution or less, which would be of great value for understanding brain structure and function in healthy and diseased brain. However, the application of STI in vivo has been hindered by its cumbersome and time-consuming acquisition requirement of measuring susceptibility induced MR phase changes at multiple head orientations. Usually, sampling at more than six orientations is required to obtain sufficient information for the ill-posed STI dipole inversion. This complexity is enhanced by the limitation in head rotation angles due to physical constraints of the head coil. As a result, STI has not yet been widely applied in human studies in vivo. In this work, we tackle these issues by proposing an image reconstruction algorithm for STI that leverages data-driven priors. Our method, called DeepSTI, learns the data prior implicitly via a deep neural network that approximates the proximal operator of a regularizer function for STI. The dipole inversion problem is then solved iteratively using the learned proximal network. Experimental results using both simulation and in vivo human data demonstrate great improvement over state-of-the-art algorithms in terms of the reconstructed tensor image, principal eigenvector maps and tractography results, while allowing for tensor reconstruction with MR phase measured at much less than six different orientations. Notably, promising reconstruction results are achieved by our method from only one orientation in human in vivo, and we demonstrate a potential application of this technique for estimating lesion susceptibility anisotropy in patients with multiple sclerosis.

Are Actinyl Cations Good Probes for Structure Determination in Solution by NMR?

We report on NMR spectroscopy, CAS-based method calculations, and X-ray diffraction of AnV and AnVI complexes with a neutral and slightly flexible TEDGA ligand. After checking that pNMR shifts mainly arise from pseudocontact interactions, we analyze pNMR shifts considering the axial and rhombic anisotropy of the actinyl magnetic susceptibilities. The results are compared to those of a previous study performed on [AnVIO2]2+ complexes with dipicolinic acid. It is shown that 5f2 cations (PuVI and NpV) make very good candidates for determining the structure of actinyl complexes in solution by 1H NMR spectroscopy as shown by the invariance of the magnetic properties to the equatorial ligands, as opposed to the NpVI complexes with a 5f1 configuration.

Structural Evolution of Paramagnetic Lanthanide Compounds in Solution Compared to Time- and Ensemble-Average Structures.

Anisotropy in the magnetic susceptibility strongly influences the paramagnetic shifts seen in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) experiments. A previous study on a series of C3-symmetric prototype MRI contrast agents showed that their magnetic anisotropy was highly sensitive to changes in molecular geometry and concluded that changes in the average angle between the lanthanide-oxygen (Ln-O) bonds and the molecular C3 axis due to solvent interactions had a significant impact on the magnetic anisotropy and, consequently, the paramagnetic shift. However, this study, like many others, was predicated on an idealized C3-symmetric structural model, which may not be representative of the dynamic structure in solution at the single-molecule level. Here, we address this by using ab initio molecular dynamics simulations to simulate how the molecular geometry, in particular the angles between the Ln-O bonds and the pseudo-C3 axis, evolves over time in the solution, mimicking typical experimental conditions. We observe large-amplitude oscillations in the O-Ln-C̃3 angles, and complete active space self-consistent field spin-orbit calculations show that this leads to similarly large oscillations in the pseudocontact (dipolar) paramagnetic NMR shifts. The time-averaged shifts show good agreement with experimental measurements, while the large fluctuations suggest that an idealized structure provides an incomplete description of the solution dynamics. Our observations have significant implications for modeling the electronic and nuclear relaxation times in this and other systems where the magnetic susceptibility is exquisitely sensitive to the molecular structure.

Quantum paramagnetism in a non-Kramers rare-earth oxide: Monoclinic Pr2Ti2O7

Little is so far known about the magnetism of the ${A}_{2}{B}_{2}{\mathrm{O}}_{7}$ monoclinic layered perovskites that replace the spin-ice supporting pyrochlore structure for ${r}_{A}/{r}_{B}>1.78$. We show that high quality monoclinic ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ single crystals with a three-dimensional network of non-Kramers ${\mathrm{Pr}}^{3+}$ ions that interact through edge-sharing superexchange interactions, form a singlet ground-state quantum paramagnet that does not undergo any magnetic phase transitions down to, at least, 1.8 K. The chemical phase stability, structure, and magnetic properties of the layered perovskite ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ were investigated using x-ray diffraction, transmission electron microscopy, and magnetization measurements. Synthesis of polycrystalline samples with the nominal compositions of ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2+x}{\mathrm{O}}_{7}$ ($\ensuremath{-}0.16\ensuremath{\le}x\ensuremath{\le}0.16$) showed that deviations from the ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ stoichiometry lead to secondary phases of related structures including the perovskite phase ${\mathrm{Pr}}_{2/3}{\mathrm{TiO}}_{3}$ and the orthorhombic phases ${\mathrm{Pr}}_{4}{\mathrm{Ti}}_{9}{\mathrm{O}}_{24}$ and ${\mathrm{Pr}}_{2}{\mathrm{TiO}}_{5}$. No indications of site disordering (stuffing and antistuffing) or vacancy defects were observed in the ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ majority phase. A procedure for growth of high-structural-quality stoichiometric single crystals of ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ by the traveling solvent floating zone method is reported. Thermomagnetic measurements of single-crystalline ${\mathrm{Pr}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ reveal an isolated singlet ground state that we associate with the low-symmetry crystal electric-field environments that split the ($2J+1=9$)-fold degenerate spin-orbital multiplets of the four differently coordinated ${\mathrm{Pr}}^{3+}$ ions into 36 isolated singlets resulting in an anisotropic temperature-independent van Vleck susceptibility at low $T$. A small isotropic Curie term is associated with 0.96(2)% noninteracting ${\mathrm{Pr}}^{4+}$ impurities.

Structure of the normal state and origin of the Schottky anomaly in the correlated heavy-fermion superconductor UTe2

The recently discovered $\mathrm{U}{\mathrm{Te}}_{2}$ superconductor is regarded as a heavy-fermion mixed-valence system with very peculiar properties within the normal and superconducting (SC) states. It shows no signs of magnetic order, but has a strong anisotropy of magnetic susceptibility and SC critical field. In addition to a heavy-fermion-like behavior in the normal state, it exhibits a distinctive Schottky-type anomaly at $\ensuremath{\sim}12$ K and a characteristic excitations gap $\ensuremath{\sim}35\ensuremath{-}40$ K. Here, we show, by virtue of dynamical mean-field theory calculations with a quasiatomic treatment of electron correlations, that ab initio-derived crystal-field splitting of the $5{f}^{2}$ ionic configuration yields agreement with these experimental observations. A close analogy of the normal paramagnetic state of $\mathrm{U}{\mathrm{Te}}_{2}$ to that of $\mathrm{U}{\mathrm{Ru}}_{2}{\mathrm{Si}}_{2}$ in the Kondo arrest scenario is revealed. We consider the impact of anisotropic superexchange interactions within the U-U structural dimer on magnetization and development of strong orbital and magnetic moment fluctuations in $\mathrm{U}{\mathrm{Te}}_{2}$.

High angular resolution susceptibility imaging and estimation of fiber orientation distribution functions in primate brain

Uncovering brain-tissue microstructure including axonal characteristics is a major neuroimaging research focus. Within this scope, anisotropic properties of magnetic susceptibility in white matter have been successfully employed to estimate primary axonal trajectories using mono-tensorial models. However, anisotropic susceptibility has not yet been considered for modeling more complex fiber structures within a voxel, such as intersecting bundles, or an estimation of orientation distribution functions (ODFs). This information is routinely obtained by high angular resolution diffusion imaging (HARDI) techniques. In applications to fixed tissue, however, diffusion-weighted imaging suffers from an inherently low signal-to-noise ratio and limited spatial resolution, leading to high demands on the performance of the gradient system in order to mitigate these limitations. In the current work, high angular resolution susceptibility imaging (HARSI) is proposed as a novel, phase-based methodology to estimate ODFs. A multiple gradient-echo dataset was acquired in an entire fixed chimpanzee brain at 61 orientations by reorienting the specimen in the magnetic field. The constant solid angle method was adapted for estimating phase-based ODFs. HARDI data were also acquired for comparison. HARSI yielded information on whole-brain fiber architecture, including identification of peaks of multiple bundles that resembled features of the HARDI results. Distinct differences between both methods suggest that susceptibility properties may offer complementary microstructural information. These proof-of-concept results indicate a potential to study the axonal organization in post-mortem primate and human brain at high resolution.

Dyke or pipe? Contributions of magnetic fabrics to the reconstruction of the geometry of an eroded subvolcanic body (Cadí basin, Pyrenees)

The reconstruction of the geometry of igneous bodies in inverted basins is often a difficult task, because most of their volume can be either below or above the topographic surface. Indirect methods, such as the determination of their internal fabric can give clues to constrain geometrical reconstructions. The Sant Salvador intrusion, located in the Late Carboniferous-Permian Cadí basin (Central-Eastern Pyrenees), is a good example for testing the application of magnetic fabrics to shallow igneous bodies because of (i) its characteristics in terms of crystal composition/orientation, showing a homogeneous petrofabric controlled by plagioclase crystals 0.4 mm in size, (ii) its good, though partial, preservation, (iii) its position in the stratigraphical succession, between volcaniclastic sediments and unconformably overlying red beds, and (iv) the many unknown factors related to the intrusion, including the geometry of the body and its depth and the amount of erosion after intrusion. Furthermore, the Sant Salvador intrusion provides opportunity for checking the correspondence between the petrofabric and the magnetic fabrics when the magnetic carriers of susceptibility (with an average value of 5217·10−6 SI) are mainly ferromagnetic. In this case the main magnetic carriers are magnetite and also hematite, the latter resulting from oxidation processes at the paleosurface. The results of Anisotropy of Magnetic Susceptibility show a bimodality in the K1 disposition after bedding restitution: vertical in the deeper areas of the intrusion and subhorizontal, E-W, in the uppermost stratigraphic positions with an intermediate necking zone in which transition from vertical to horizontal flow is interpreted to occur. Bands deflecting the mineral foliation at the micro scale have also a tectonic or thermal origin but do not seem to interfere with the magnetic ellipsoid axes. Columnar jointing is interpreted to be parallel to the long axis of the intrusion (and therefore to magma flow, and perpendicular to the paleosurface. All these features indicate that the Sant Salvador intrusion can be interpreted as a subvertical pipe feeding a sill that was eroded before the sedimentation of the overlying red beds.

Anisotropy of magnetic susceptibility of the Late Cretaceous–Eocene sediments in the southeastern Fenwei Graben and its tectono-sedimentary significance

Anisotropy of magnetic susceptibility of the Late Cretaceous–Eocene sediments in the southeastern Fenwei Graben and its tectono-sedimentary significance

Differences in the Optical Response of MSU and CPP Crystals During Magnetic Orientation: Possibility of Diagnosing Gout and Pseudogout.

Pseudogout is crystalline arthritis. It has a similar clinical picture to that of gout, and it is difficult to distinguish the two diseases using conventional analysis methods. However, it is important to identify the different crystals responsible for these two cases because the treatment strategies are different. In a previous study, we reported magnetic orientation of monosodium urate (MSU) crystals, which are the causative agent of gout, at the permanent magnet level. In this study, we investigated the effect of an applied magnetic field on calcium pyrophosphate (CPP) crystals, which are the causative agent of pseudogout, and the difference in the magnetic responses of CPP and MSU crystals. We found that the CPP crystals were oriented in a magnetic field on milli-Tesla order because of the anisotropy of the diamagnetic susceptibility. In addition, the CPP crystals exhibited different anisotropic magnetic properties from those of MSU crystals, which led to a characteristic difference between the orientations of the two crystals. That is, we found that the causative agents of gout and pseudogout responded differently to a magnetic field. This report suggests that the discrimination between CPP and MSU by optical measurements is possible by application of magnetic fields appropriately. © 2023 Bioelectromagnetics Society.

Fabric characteristics of in situ sand with/without liquefaction verified by anisotropy of magnetic susceptibility

It is well known that fabric of sand may significantly affect mechanical behaviors and liquefaction resistance of sand. Various optical techniques are currently utilized to visualize the fabric, especially the distribution of the long axis of soil particles. However, none of these methods provides an ideal solution in laboratory tests and in situ observation. In this study, anisotropy of magnetic susceptibility (AMS) was first proposed as a convenient and efficient way to evaluate the liquefaction of clean sand. At first, investigations with scanning electron microscopy (SEM) and AMS were simultaneously conducted on two groups of soil specimens with different initial fabrics to verify the feasibility of the AMS technique. Then, 80 in situ samples were collected to analyze the feature of liquefied and non-liquefied sand layers through AMS tests. It is clearly known from the test results that the natural sedimentary fabric was destroyed during liquefaction and the fabric anisotropy was greatly changed after liquefaction. The feasibility of evaluating soil fabric using the AMS survey was verified by the laboratory tests. Furthermore, the applicability of AMS in detecting liquefied layer in situ was confirmed for the first time. • Anisotropy of magnetic susceptibility (AMS) was proposed to evaluate liquefaction. • Feasibility of AMS was verified by comparing with an optical method in laboratory. • AMS was used on in-situ samples to detect the anisotropic fabric for the first time.

Unusual coercivity and zero-field stabilization of fully saturated magnetization in single crystals of LaCrGe3

${\mathrm{LaCrGe}}_{3}$ is an itinerant, metallic ferromagnet with a Curie temperature $({T}_{C})$ of $\ensuremath{\sim}$86 K. Whereas ${\mathrm{LaCrGe}}_{3}$ has been studied extensively as a function of pressure as an example of avoided ferromagnetic quantum criticality, questions about its ambient pressure-ordered state remain: specifically, whether there is a change in the nature of the ferromagnetically ordered state below ${T}_{C}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}$ 86 K. We present anisotropic $M(H)$ isotherms, coupled with anisotropic AC susceptibility data, and demonstrate that ${\mathrm{LaCrGe}}_{3}$ has a remarkable, low temperature coercivity associated with exceptionally sharp, complete magnetization reversals to and from fully polarized states. This coercivity is temperature dependent; it drops to zero in the 40--55 K region and reappears in the 70--85 K regions. At low temperatures ${\mathrm{LaCrGe}}_{3}$ has magnetization loops and behavior that has been previously associated with micromagnetic/nanocrystalline materials, not bulk macroscopic samples.

Magnetism and Transport Properties of EuCdBi2 with Bi Square Net

We report a possible coexistence of nontrivial topology and antiferromagnetism in the newly discovered compounds EuCdBi2, with magnetic Eu layer locating above and below Bi square net. The X-ray diffraction on single crystals and powder indicats that this 112-type material crystalizes in space group of I4/mmm, the same as SrMnBi2 and EuMnBi2. Our combined measurements of magnetization, electrical transport and specific heat consistently reveal antiferromagnetic (AFM) transition of Eu2+ moments at TN = 20 K. The Eu moments are not saturated under a field of 7 T at 1.8 K. The anisotropic susceptibility suggests the Eu moments lie in the ab plane, and a metamagnetic (MM) transition is observed near 1 T below TN. Large positive magnetoresistance (MR) present for both H ‖ ab and H ‖ c, which are considered to contain part contributions from Dirac bands. Hall measurements show the electron-hole compensation effect is prominent above 100 K, with a crossover of Hall resistance from negative to positive values at ∼150 K. The fitted mobility of electrons is as high as 3250 cm2 V−1 S−1 at 1.8 K. Interestingly, the rapid increase of carrier density and suppression of mobility appear at around TN, indicating non-negligible interaction between Eu moments and electron/hole bands. EuCdBi2 may provide a new platform to investigate the interplay of topological bands and antiferromagnetic order.

Iron accumulation and axonal damage of cerebellum in idiopathic cervical dystonia.

Postmortem brain study indicated that cerebellar Purkinje cell (PC) loss might be a pathological finding in patients with inherited and idiopathic cervical dystonia (ICD). The analysis of conventional magnetic resonance imaging brain scans failed to yield support for this finding. Previous studies have identified that iron overload can be the consequence of neuron death. The objectives of this study were to investigate iron distribution and demonstrate changes in axons in the cerebellum, providing evidence for PC loss in patients with ICD. Twenty-eight patients with ICD (20 females) and 28 age- and sex-matched healthy controls were recruited. A spatially unbiased infratentorial template was applied to perform cerebellum optimized quantitative susceptibility mapping and diffusion tensor analysis based on magnetic resonance imaging. Voxel-wise analysis was performed to assess cerebellar tissue magnetic susceptibility and fractional anisotropy (FA) alterations, and the clinical relevance of these findings was investigated in the patients with ICD. Increased susceptibility values revealed by quantitative susceptibility mapping in the right lobule CrusI, CrusII, VIIb, VIIIa, VIIIb and IX were found in the patients with ICD. A reduced FA value was found across almost all the cerebellum; an FA value of the significant clusters within the right lobule VIIIa significantly correlated with the motor severity of patients with ICD (r=-0.575, p=0.002). Our study provided evidence for cerebellar iron overload and axonal damage in patients with ICD, which may indicate PC loss and related axonal changes. These results provide evidence for the neuropathological findings in patients with ICD and further highlight the cerebellar involvement in the pathophysiology of dystonia.

Toward Better Understanding of the Ferrofluid Impregnation Process and Potential Artefacts—A Prerequisite for Reliable Interpretation of Magnetic Pore Fabrics

AbstractMagnetic pore fabrics (MPFs) serve as efficient proxy for pore alignment and preferential flow directions. Anisotropy of magnetic susceptibility of impregnated samples reflects the shape and arrangement of ferrofluid‐filled pores. Reliable interpretation requires that the entire connected pore space is reached by ferrofluid. This study investigates impregnation efficiencies of various methods (standard vacuum, pressure injection, magnetic flowthrough, and resin impregnation) and ferrofluids (water‐based versus oil‐based) on sandstone and calcarenite with different wettabilities. Mass‐based and susceptibility‐based impregnation efficiencies further evaluate the influence of impregnation time and flow rate. Because directional impregnation may introduce artificial fabrics, mutually perpendicular cores were measured, and subsamples served to capture spatial variability. Impregnation efficiencies vary between <1% and >100%, with resin impregnation and pressure injection using oil‐based ferrofluids being least efficient. Oil‐based ferrofluid generally leads to lower susceptibility‐based compared to mass‐based impregnation efficiencies, suggesting particle filtering. Water‐based ferrofluids show larger ranges of susceptibility‐based compared to mass‐based impregnation efficiencies. In particular, impregnation efficiencies >100% exclusively occur for susceptibility‐based impregnation efficiencies of water‐based ferrofluid, using either standard vacuum or pressure injection methods. MPFs after magnetic flowthrough impregnation reflect the impregnation direction rather than pore fabric. A major challenge is to apply enough force to reach sufficiently high impregnation efficiencies without creating MPFs that do not represent pore fabrics. While we cannot define a best practice for ferrofluid impregnation yet, this study improves our understanding of the impregnation process, and provides experimental procedures to identify artifacts.

Age and Depositional Environment of Whale-Bearing Sedimentary Succession from the Lower Pliocene of Tuscany (Italy): Insights from Palaeomagnetism, Calcareous Microfossils and Facies Analyses

A c. 31 m thick section straddling the fossil find of an Early Pliocene baleen whale (“Brunella”, hereafter), made in 2007 in the sedimentary fill of the Middle Ombrone Basin of Tuscany, is investigated for depositional age and environment combining palaeomagnetic, micropalaeontological (Foraminifera and calcareous nannofossils) and sedimentary facies analyses. Resting unconformably onto Late Miocene continental deposits, the Early Pliocene marine deposits include, from bottom to top, a coarse-grained wave-winnowing lag, the few metres-thick fossiliferous sandstone bedset from which Brunella was unearthed, and several metres of clays. The stratigraphic organisation of these deposits indicate deposition in a deepening upward inner shelf environment. Successful isolation of characteristic remanent magnetisation and calcareous nannofossil content indicate the investigated marine section was deposited during the interval of polarity Chron C3n.2n corresponding to the basal part of the Mediterranean nannofossil zone MNN13 (between Helicosphaera sellii Base common and the Amaurolithus primus Top) and allow estimating the depositional age of Brunella to c. 4.6 Ma. Sedimentary facies, benthic Foraminifera association and anisotropy of magnetic susceptibility characterising the deposits that embedded Brunella suggest deposition above the fair-weather base level.

Strain Localization: Analog Modeling and Anisotropy of Magnetic Susceptibility

AbstractThe majority of the strain in Earth crust and upper mantle is localized to the high strain zones developed at ductile‐to‐brittle condition at kilometer‐to‐micrometer scale. Therefore, they represent the key to understanding the deformation evolution of the lithosphere. The finite strain pattern recorded within these zones has been therefore a subject of research in geology. The methods studying rock magnetism such as the anisotropy of magnetic susceptibility (AMS) are frequently used techniques to characterize and quantify deformation and flow record in rocks. Numerous sedimentary, subsolidus and submagmatic deformation zones exhibit typical evolution of the AMS ellipsoid across the strain gradient suggesting indirect not straightforward correlation between AMS and strain ellipsoids. To document spatiotemporal and internal fabric evolution during strain localization, pure shear, simple shear, and shear zone (SZ) analog experiments were performed using shear‐thinning thixotropic material of plaster of Paris. The experimental results closely resemble the record from natural SZs in sedimentary rock systems but also in subsolidus SZs and submagmatic mushy systems. The magnetic fabric evolution across deformation zones is interpreted to be associated with the intersection and transposition of preexisting primary fabric with shear fabrics and evolution of synkinematic subfabrics. Their development is attributed to localization of deformation at microscale due to the self‐organized slip of anisometric particles forming microshear planes reflecting the symmetry of deformation. The experimental results when confronted with the natural examples implies that the localization and partitioning of deformation is one of the most important factors for the interpretation of AMS in deformation zones.

Highly effective electromagnetic interference shielding composites with solvent-dispersed uniformly aligned graphene nanosheets enabled by strong intrinsic diamagnetism under magnetic field

Graphene nanosheets (GNS) have been regarded as one of the best fillers in polymers for electromagnetic interference (EMI) shielding composites, but it remains a challenge to prepare well-dispersed and highly aligned GNS for optimal EMI shielding despite many recently developed methods. Here we demonstrate a new technology that not only enables uniform alignment of GNS in polymer composites in any direction but also allows us to systematically tune the composites for optimal EMI performance. The technique makes use of graphene's strong intrinsic and anisotropic diamagnetic susceptibility. Unlike paramagnetism and ferromagnetism, diamagnetism allows us to fully control the orientation of GNS by a rotating magnetic field without causing any aggregation or introducing unwanted magnetic particles due to the repulsive force between GNS. This process for GNS composites further enables us to systematically modify GNS concentration and polymer matrix besides GNS orientations. A record-high shielding effectiveness (SE) of 95 dB is achieved with industrially mass-produced multilayer GNS aligned parallel to the surface of a mixed polyvinylidene fluoride-epoxy composite, and a 50% higher SE is further achieved with few-layer GNS. This technique is scalable, thus opening the practical applications of graphene in EMI shielding.

Hydrodynamic variations and human activities have influenced sediment fluxes in the pearl river delta since the late holocene

Climate change and human activity can both exert a role in the river discharge and sediment load in river deltas when the sea level remains relatively stable. The Pearl River Delta constitutes the metropolitan region of the Guangdong–Hong Kong–Macau Greater Bay Area, and its evolution in the past and future impacts the sustainable development of this region. In this manuscript, a core situated in the northern South China Sea, adjacent to Qiao Island of Zhuhai city in the Pearl River Delta, was selected to investigate the hydrodynamic variation influenced by tropical processes and the sediment flux imposed by human activities. Using paleosecular variations (PSVs) in geomagnetic field correlations constrained by seven radiocarbon ages, an ∼2.5 kyr chronology was provided for core sediments ∼2.8 m in length. The magnetic fabric results suggest that deposition was influenced by the two types of hydrodynamic-weak energy modulated by El Niño–Southern Oscillation (ENSO) activity and higher energy regulated by high-frequency tropical storms. The cyclic variations in the degree of anisotropy of magnetic susceptibility (P) indicate two periodic changes at approximately 300 and 100 years, which were forced by ENSO activity, while the ratio of lineation with foliation (q value) implies a higher energy flow period of 1.3–1.9 kyr, arising from strong tropical storms. Moreover, the high saturation remanence (SIRM) introduces more sediment flux, which is impacted by growing human activity during the period of 1.0–1.6 kyr.

An experimental baseline for ice-till strain indicators

Subglacial till can deform when overriding ice exerts shear traction at the ice–till interface. This deformation leaves a strain signature in the till, aligning grains in the direction of ice flow and producing a range of diagnostic microstructures. Constraining the conditions that produce these kinematic indicators is key to interpreting the myriad of features found in basal till deposits. Here, we used a cryogenic ring shear device with transparent sample chamber walls to slip a ring of temperate ice over a till bed from which we examined the strain signature in the till. We used cameras mounted to the side of the ring shear and bead strings inserted in the till to estimate the strain distribution within the till layer. Following the completion of the experiment, we extracted and analyzed anisotropy of magnetic susceptibility (AMS) samples and created thin sections of the till bed for microstructure analysis. We then compared the AMS and microstructures with the observed strain history to examine the relationship between kinematic indicators and strain in a setting where shear traction is supplied by ice. We found that AMS fabrics show a high degree of clustering in regions of high strain near the ice–till interface. In the uppermost zone of till, k1 eigenvector azimuths are generally aligned with ice flow, and S1 eigenvalues are high. However, S1 eigenvalues and the alignment of the k1 eigenvector with ice flow decrease nonlinearly with distance from the ice–till interface. There is a high occurrence of microshears in the zone of increased deformation.