Local Field Research Articles

Modulating the Selective Enrichment and Depletion of Ions Using Electrorheological Fluids in Variable-Area Microchannels.

Electrorheological fluids are suspensions that are characterized by a strong functional dependence of their constitutive behavior on the local electric field. While such fluids are known to be promising in different applications of microfluidics including electrokinetic flows, their capabilities of controlling ion transport and preferential solute segregation in confined fluidic systems remain to be explored. In this work, we bring out the unique role of electrorheological fluids in orchestrating the selective enrichment and depletion of charged species in variable area microfluidic channels. Our reported phenomenon is fundamentally distinctive from other types of nonlinear electrokinetic effects previously reported, in a sense that here the dependence of the flow rheology on the electric field turns out to be the central mechanism toward orchestrating the observed nonlinear ion transport. Our results indicate exclusive features of the resulting ion concentration polarization, such as more pronounced ion concentration polarization, controlled largely by the influence of the variations in the channel cross section on the driving electrokinetic forces and the resistive viscous interactions. The underlying physical mechanism is captured aptly by a simple one-dimensional area-averaged model, and validated by full-scale three-dimensional simulations. Our illustrative case study for a converging-diverging microchannel with cross-sectionally uniform solute concentrations reveals that electrorheological effect with greater contrast between the deep and shallow region depths, greater solute concentration, and larger applied axial electric field, all acting in tandem, magnifies the solute enrichment and depletion in the respective segregation zones, bearing significant implications in analytical chemistry, bioanalysis, and beyond.

Varying Projection Quality of Good Local Electric Field Gradients of Monochlorobenzaldehydes.

Rotational spectroscopy is an excellent tool for structure determination, which can provide additional insights into local electronic structure by investigating the hyperfine pattern due to nuclear quadrupole coupling. Jet-cooled molecules are good experimental benchmark targets for electronic structure calculations, as they are free of environmental effects. We report the rotational spectra of 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, and 4-chlorobenzaldehyde, including a complete experimental description of the nuclear quadrupole coupling constants, which were previously not experimentally determined. We identified two conformers for 3-chlorobenzaldehyde and one conformer each for 2-chlorobenzaldehyde and 4-chlorobenzaldehyde. Rigorous structure fitting of 4-chlorobenzaldehyde was performed to determine bond lengths for r0, rs, rese, and rm(1) structures. Comparing experimental nuclear quadrupole coupling constants to computational results showed agreement in the nuclear axis system, but the accuracy of the projection into the principal axis system decreases in near-oblate 2-chlorobenzaldehyde. The experimental angle Θaz = 19.16° between the principal a-axis and nuclear z-axis is larger than predicted by multiple computational methods by ≥4°. It is attributed to the high sensitivity of 2-chlorobenzaldehyde to low-energy vibrational contributions.

Electrospun Ba(Ti0.80 Zr0.20)O3-0.5(Ba0.70Ca0.30)TiO3-CoFe2O4 multiferroic hybrid nanofiber for the localized piezocatalytic degradation of organic pollutants

Multiferroic Ba(Ti[Formula: see text]Zr[Formula: see text])O3-0.5(Ba[Formula: see text]Ca[Formula: see text])TiO3 (BCTZ)@CoFe2O4 (CFO) hybrid nanofibers (NFs) were fabricated by a sol–gel electrospinning. The perovskite structure of ferroelectric BCTZ and the spinel structure of ferromagnetic CFO coexist and are homogeneously distributed, and their interface along the perovskite [110] zone axis was directly observed. The indirect magnetoelectric (ME) coupling effect was observed from the magnetization versus temperature (M–T) curves, demonstrating a distinct singularity on the dM/dT curve near the ferroelectric Curie temperature ([Formula: see text][Formula: see text]) of 387 K. The piezocatalytic rate of BCTZ@CFO multiferroic hybrid NF (2.6 × 10[Formula: see text]min[Formula: see text]) is higher than NP (1.9 × 10[Formula: see text]min[Formula: see text]) because the piezoelectricity of the one-dimensional (1D) multiferroic NF is higher than that of NPs, beneficial for the mechanical vibration-induced localized built-in electric fields for piezocatalysis under ultrasound.

Nutrient use and methane emissions in growing beef fed different protein sources and a pasture-based diet.

This study investigated the effects of different protein sources on feed intake, nutrient, and energy utilization, growth performance, and enteric methane (CH4) emissions in growing beef cattle, also evaluated against a pasture-based diet. Thirty-two Holstein × Angus growing beef were allocated to four dietary treatments: a total mixed ration (TMR) including solvent-extracted soybean meal as the main protein source (SB; n = 8), TMR with local brewers' spent grains (BSG; n = 8), TMR with local field beans (BNS; n = 8), and a diet consisting solely of fresh-cut Italian ryegrass (GRA; n = 8). Every four weeks, animals were moved to digestibility stalls within respiration chambers to measure nutrient intakes, energy and nitrogen (N) utilization, and enteric CH4 emissions. Feed intake (Calan gates), nutrient intakes, and CH4 emissions (GreenFeed) were also measured when animals were group-housed. In respiratory chambers, enteric CH4 yield per kg of dry matter intake (DMI), per kg of organic matter intake (OMI), and per kg body weight were lower (P < 0.05) for GRA. Feces and urine energy outputs were higher (P = 0.007 and P < 0.001, respectively) for GRA steers than concentrate-fed steers. Urinary nitrogen output (UNO, P = 0.026), manure (feces+urine) nitrogen output (MNO, P = 0.034), UNO/nitrogen intake (P = 0.002), and MNO/nitrogen intake (P = 0.006) were higher for GRA. During group-housing periods, CH4 emissions, measured by GreenFeed, were similar to those measured in chambers. Similar CH4 yield between treatments, expressed per kg digestible DMI and digestible OMI, may indicate that the lower diet digestibility was likely the reason for the reduced enteric CH4 emissions in pasture-based diets. The higher energy output and nitrogen losses, and the reduced nitrogen utilization for steers fed the fresh-cut ryegrass diet indicate less efficient energy and nitrogen utilization, which can be considered environmentally undesirable. The lower growth rates in the pasture-based system should also be accounted for when this is adopted for reducing production costs.

Supramolecularly Built Local Electric Field Microenvironment around Cobalt Phthalocyanine in Covalent Organic Frameworks for Enhanced Photocatalysis.

The local electric field (LEF) plays an important role in the catalytic process; however, the precise construction and manipulation of the electric field microenvironment around the active site remains a significant challenge. Here, we have developed a supramolecular strategy for the implementation of a LEF by introducing the host macrocycle 18-crown-6 (18C6) into a cobalt phthalocyanine (CoPc)-containing covalent organic framework (COF). Utilizing the supramolecular interaction between 18C6 and potassium ion (K+), a locally enhanced K+ concentration around CoPc can be built to generate a LEF microenvironment around the catalytically active Co site. The COF with this supramolecularly built LEF realizes an activity of up to 7.79 mmol mmolCo-1 h-1 in the photocatalytic CO2 reduction reaction (CO2RR), which is a 180% improvement compared to its counterpart without 18C6 units. The effect of LEF can be subtly controlled by fully harnessing the K+@18C6 interaction by changing the potassium salts with different counterions. In situ spectroscopy and density functional theory calculations show that the complexation of K+ by 18C6 creates a positive electric field that stabilizes the critical intermediate *COOH involved in CO2RR, which can be tuned by the halide ion-mediated K+@18C6 interaction and hydrogen-bonding interaction, consequently leading to improved catalytic performance to varying degrees.

Effect of collapse-type lateral pressure induced by irrigation on loess landslides

Loess collapse-type lateral pressure may have a landslide-promoting effect in loess slope areas. A study on the variability of loess collapse-type lateral pressure in the Heifangtai area and its sliding mechanism has been analysed. Collapse tests and numerical simulations were conducted according to local safety field theory. The results indicate that the Heifangtai loess is self-weighted collapsible loess. As the depth or moisture content increases, the lateral pressure gradually increases, and correspondingly the deformation becomes greater. In a saturated state, the maximum lateral pressure reaches 123 kPa, and the lateral pressure coefficient increases up to 1.4 times. As the water content increases from 4% to 20%, the total slope displacement is predominantly horizontal, increasing from 12 to 140 mm, the lateral pressure coefficient gradually increases and the increase range gradually expands; the failure area becomes gradually wider until the slope toe is penetrated. Collapse action leads to tensile stresses in the upper part of the slope, making it prone to collapse-type crack formation, resulting in dominant channels of surface water infiltration and forming landslide scarps. Furthermore, collapse action also enables the formation of compressive stresses in the lower part of the slope, resulting in outward extrusion of deep soil, increased sliding force and landslide formation.

High‐voltage electron microscopy analyses for crack‐tip dislocations and their shielding effect on fracture toughness in MgO and Si crystals

AbstractIn this study, characteristics of dislocation structures around a crack‐tip in both crystals of MgO and Si were investigated using high‐voltage electron microscopy (HVEM). The interaction between a crack and dislocations was analyzed to discuss the effect of crack‐tip plasticity on fracture toughness. The present paper first demonstrates a dislocation configuration around a crack‐tip in a MgO thin crystal, where the plastic zone called 45°‐shear type is dominant under the plane stress condition. Then, the slip systems necessary for brittle‐to‐ductile transition in ionic crystals with the rock‐salt structure are discussed based on the temperature dependence of stress‐strain relationships and the aspect of crack front observed in NaCl crystals. Second, crack‐tip dislocations near the surface of bulk Si crystals are exhibited based on the 3D analyses using HVEM tomography. We focus on a newfound plastic zone being perpendicular to the crack plane, which is different from either 45°‐shear type or the hinge type generally well‐known. The dislocation loops observed in this plastic zone fundamentally have a crack‐tip shielding effect to increase fracture toughness. Still, in addition, they contribute to activating crack‐tip dislocations by their localized antishielding field. These analyses reveal a fundamental toughening mechanism for crystalline materials.

Theta and beta power in the subthalamic nucleus respond to conflict across subregion and hemisphere

Abstract The subthalamic nucleus is thought to play a crucial role in controlling impulsive actions. Networked among the basal ganglia and receiving input from several cortical areas, the subthalamic nucleus is well-positioned to influence action selection when faced with competing and conflicting action outcomes. The purpose of this study was to test the dissociable roles of the dorsal and ventral aspects of the subthalamic nucleus during action conflict in patients with Parkinson’s disease undergoing intraoperative neurophysiological recording and to explore a potential mechanism for this inhibitory control. We hypothesized that modulations of neurophysiological activity during action conflict would be more pronounced in the dorsal subthalamic nucleus compared to the ventral subthalamic nucleus, due to the dissociation of cortical afferents to subthalamic nucleus subregions and previous findings of deep brain stimulation targeting subthalamic nucleus subregions in Parkinson’s disease. We recorded neurophysiological activity while ten participants with Parkinson’s disease performed the Simon task during deep brain stimulation surgery. Response-locked local field potentials in the theta and beta band (associated with conflict control and movement inhibition, respectively) were analyzed across subthalamic nucleus subregions and hemispheres relative to the motor response (ipsilateral/contralateral). In the presence of action conflict, the dorsal subthalamic nucleus, connected to cortical motor regions, exhibited larger theta power relative to the ventral subthalamic nucleus subregion which is linked to the limbic circuits (P&amp;lt;0.05). This evidence supports independent subregion function in conflict control. However, both subregions had relatively increased beta power for conflict trials compared to non-conflict in the hemisphere ipsilateral to the motor response. The conflict related beta modulation was not present in the contralateral hemisphere. This indicates the importance of the ipsilateral hemisphere in the inhibition of incorrect action impulses. Additionally, higher inter-trial beta power in the ventral subregion correlated with reduced accuracy on conflict trials, which we propose could serve as a biomarker for impaired task performance. The results of the study support the existence of a functional dissociation within subthalamic nucleus subregions, emphasizing the role of the dorsal subthalamic nucleus in modulating action conflict.

ADMNet: adaptive deformable convolution large model combining multi-level progressive fusion for Building Change Detection

ABSTRACT Building Change Detection (BCD) based on high-resolution Remote Sensing Images (RSI) simplifies urban surface monitoring. Nevertheless, the mainstream detection methods utilizing traditional convolution and attention mechanisms are often prone to errors due to the loss of edge detail information and underutilization of global context information. To address these issues, this paper presents a large model, namely ADMNet, which is built on adaptive deformable convolution and is designed to handles various types of building change information. First, we propose a Siamese neural network based on adaptive deformable convolution (ADC) modules. The ADC module incorporates spatial offset parameters into convolutional kernel sampling and mapping weights to capture irregularly varying edge features for local adaptive receptive fields. Second, we utilize a large model semantically driven to enhance model context awareness and construct long-range feature dependencies from multi-scale edge information, which are then integrated with locally adaptive edge structure features to achieve accurate edge localization. Furthermore, we design a Multi-Level Progressive Feature Fusion (MLPFF) module that enhances feature characterization capabilities to ensure internal integrity and improves model detection performance by integrating a priori knowledge from large-model transfer learning. To evaluate the effectiveness and generalizability of ADMNet, we conduct comparative experiments with current mainstream methods on two building datasets, LEVIR-CD and WHU-CD, and a land cover dataset, SYSU-CD. The results show that ADMNet outperforms all comparative methods. The source code is available at https://github.com/spaceYu180/ADMNet.

Synthesis and Characterization of PVC/(Co3O4/CNT)@Au Semiconductor Nanocomposite for Enhanced Medium-Voltage Cable Insulation

Abstract This study presents the synthesis, characterization, and application of a novel PVC/(Co3O4/CNT)@Au nanocomposite for enhanced medium-voltage cable insulation. The nanocomposite was developed by incorporating Co3O4 octahedron nanoparticles, carbon nanotubes (CNTs), and gold nanoparticles (Au) into a polyvinyl chloride matrix. Compared to standard PVC insulation, the nanocomposite exhibited a 3% improvement in relative permittivity (increased from 2.34 to 2.41) and significantly enhanced field uniformity, as evidenced by simulation studies. Fourier-transform infrared spectroscopy, X-ray diffraction, and electron microscopy confirmed the successful integration of nanofillers and highlighted their contributions to the composite’s properties. Optical characterization revealed a direct bandgap of 4.60 eV and an Urbach energy of 0.3674 eV, indicating a wide-bandgap semiconductor with moderate structural disorder. AC conductivity measurements demonstrated frequency-dependent behavior, while dielectric constant and loss analyses suggested the material’s potential for energy storage and insulation applications. The choice of Co3O4 and CNTs was guided by their synergistic impact on charge trapping, field grading, and thermal management, while Au nanoparticles enhanced charge transfer and local electric field distribution. These findings demonstrate the nanocomposite’s promise in addressing the limitations of traditional PVC insulation, offering improved dielectric performance, reliability, and durability for power transmission and distribution systems.&amp;#xD;

Advances, Challenges, and Opportunities in Plasmonic Nanogap-Enhanced Raman Scattering with Nanoparticles.

Surface-enhanced Raman scattering has been widely used for molecular/material characterization and chemical and biological sensing and imaging applications. In particular, plasmonic nanogap-enhanced Raman scattering (NERS) is based on the highly localized electric field formed within the nanogap between closely spaced metallic surfaces to more strongly amplify Raman signals than the cases with molecules on metal surfaces. Nanoparticle-based NERS offers extraordinarily strong Raman signals and a plethora of opportunities in sensing, imaging and many different types of biomedical applications. Despite its potential, several challenges still remain for NERS to be widely useful in real-world applications. This Perspective introduces various plasmonic nanogap configurations with nanoparticles, discusses key advances and critical challenges while addressing possible misunderstandings in this field, and provides future directions for NERS to generate stronger, more uniform, and stable signals over a large number of structures for practical applications.

The Gaussian-Linear Hidden Markov model: a Python package

Abstract We propose the Gaussian-Linear Hidden Markov model (GLHMM), a generalisation of different types of HMMs commonly used in neuroscience. In short, the GLHMM is a general framework where linear regression is used to flexibly parameterise the Gaussian state distribution, thereby accommodating a wide range of uses —including unsupervised, encoding and decoding models. GLHMM is available as a Python toolbox with an emphasis on statistical testing and out-of-sample prediction —i.e. aimed at finding and characterising brain-behaviour associations. The toolbox uses a stochastic variational inference approach, enabling it to handle large data sets at reasonable computational time. The GLHMM can work with various types of data, including animal recordings or non-brain data, and is suitable for a broad range of experimental paradigms. For demonstration, we show examples with fMRI, local field potential, electrocorticography, magnetoencephalography and pupillometry.

Strategies for Real-time Adjustment of Stimulation Patterns in Closed-loop Deep Brain Stimulation for Parkinsons Disease: A Comprehensive Review

Parkinsons disease (PD) is a prevalent neurodegenerative disorder that poses significant healthcare challenges worldwide. Deep brain stimulation (DBS) has proven effective for managing PD, particularly for patients with inadequate medication response. However, traditional high-frequency DBS systems lack the capability to adjust stimulation patterns in real time based on patient responses. In contrast, closed-loop DBS systems, which adjust stimulation based on recorded biomarkers, present a promising alternative that allows more flexible, on-demand electrical pulses delivery, offering possibility of achieving better therapeutic outcomes with less invasive stimulus. This review article explored various strategies for real-time adjustment of stimulation parameters in closed-loop DBS primarily based on electrophysiological biomarkers, particularly local field potentials (LFPs). We categorize these strategies into four categories: simple on-demand methods, control methods in systems theory, optimization or machine learning algorithms, and desynchronization approaches. By synthesizing existing literature, we provide a comprehensive overview of these strategies, highlighting contributions from multiple disciplines and the prospect of optimizing treatment for Parkinsons disease using closed-loop approach.

Reconstruction of Local Three-dimensional Temperature Field of Tumor Cells with Low-toxic Nanoscale Quantum-dot Thermometer and Cepstrum Spatial Localization Algorithm.

The optimal method for three-dimensional thermal imaging within cells involves collecting intracellular temperature responses while simultaneously obtaining corresponding 3D positional information. Current temperature measurement techniques based on the photothermal properties of quantum dots face several limitations, including high cytotoxicity and low fluorescence quantum yields. These issues affect the normal metabolic processes of tumor cells. This study synthesizes a low-toxicity cell membrane-targeted quantum dot temperature sensor by optimizing the synthesis method of CdTe/CdS/ZnS core-shell structured quantum dots. Compared to CdTe-targeted quantum dot temperature sensors, the cytotoxicity of CdTe/CdS/ZnS-targeted quantum dot temperature sensors is reduced by 40.79%. Additionally, a novel cepstrum-based spatial localization algorithm is proposed to achieve rapidly compute the three-dimensional positions of densely distributed quantum dot temperature sensors. Ultimately, both targeted and non-targeted CdTe/CdS/ZnS quantum dot temperature sensors were used simultaneously to label the internal and external regions of human osteosarcoma cells to obtain temperature data at these labeling positions. By combining this with the cepstrum-based spatial localization algorithm, the spatial coordinates of the quantum dot temperature sensors were obtained. Three-dimensional temperature field reconstruction of three local regions was achieved within a 12 μm axial range in living cells. The method described in this paper can be widely applied to the quantitative study of intracellular thermal responses.

The Optical Extinction Law Depends on Magnetic Field Orientation: The RV–ψ Relation

Abstract For aspherical interstellar dust grains aligned with their short axes preferentially parallel to the local magnetic field, the amount of extinction per grain is larger when the magnetic field is along the line of sight and smaller when in the plane of the sky. To the extent that optical extinction arises from both aligned and unaligned grain populations with different extinction properties, changes in the magnetic field orientation induce changes in its wavelength dependence, parameterized by R V ≡ A V /E(B − V). We demonstrate that the measured total and polarized extinction curves of the diffuse Galactic interstellar medium imply R V varies from 3.21 when the magnetic field is along the line of sight (ψ = 0) to R V = 3.05 when in the plane of the sky (ψ = 90°). This effect could therefore account for much of the large-scale R V variation observed across the sky (σ(R V ) ≃ 0.2), particularly at high Galactic latitudes.

Dorsal hippocampus represents locations to avoid as well as locations to approach during approach-avoidance conflict.

Worrying about perceived threats is a hallmark of multiple psychological disorders including anxiety. This concern about future events is particularly important when an individual is faced with an approach-avoidance conflict. Potential goals to approach are known to be represented in the dorsal hippocampus during theta cycles. Similarly, important information that is distant from the animal's position is represented during hippocampal high-synchrony events (HSEs), which coincide with sharp-wave ripples (SWRs). It is likely that potential future threats may be similarly represented. We examined how threats and rewards were represented within the hippocampus during approach-avoidance conflicts in rats faced with a predator-like robot guarding a food reward. We found decoding of the pseudo-predator's location during HSEs when hesitating in the nest and during theta prior to retreating as the rats approached the pseudo-predator. After the first attack, we observed new place fields appearing at the location of the robot (not the location the rat was when attacked). The anxiolytic diazepam reduced anxiety-like behavior and altered hippocampal local field potentials (LFPs), including reducing SWRs, suggesting that one potential mechanism of diazepam's actions may be through altered representations of imagined threat. These results suggest that hippocampal representation of potential threats could be an important mechanism that underlies worry and a potential target for anxiolytics.

Resonant enhancement and confinement of microwave field in coupled conductive rod systems

Abstract We investigated the resonant interaction of incident microwaves with a finite linear array of equidistantly arranged conductive rods of finite height. When strong coupling is established between adjacent rods, which act as open resonators for radial waves, a series of resonances emerges, corresponding to the number of rods in the array. Each resonance exhibits distinct charge oscillation amplitudes and phases along the rods, leading to varying radiative losses. Notably, in a system of two resonantly interacting rods, antiphase charge oscillations result in a nearly 30-fold increase in localized field intensity and a quality factor of approximately 400. This study demonstrates the feasibility of creating high-quality open resonators with sub-wavelength confinement, offering the potential for microwave-to-optical conversion and enabling control over quantum processes in materials, thereby broadening their application scope.

Fast electrons produced by lower hybrid wave and effects on plasma–wall interactions

Abstract Lower hybrid wave (LHW) current drive plays a crucial role in sustaining steady-state (SS) discharges on the Experimental Advanced Superconducting Tokamak (EAST). Hotspots frequently form on the wave antenna and guard limiters during SS operations. Although both experimental and theoretical studies suggest that fast electrons could be responsible for these hotspots, the underlying mechanisms of fast electron generation under typical EAST operational parameters and their impact on the hotspots remain unresolved. In this work, particle-in-cell simulations are used to investigate the interactions between LHWs and electrons in front of the antenna, taking into account the realistic incident power spectra and localized field effects. The results show that, due to resonance overlap, fast electrons are produced through resonant interactions between electrons and LHW components with a high parallel refractive index (N ∥). The velocity distribution function in velocity space is found to significantly depend on plasma parameters near the antenna, such as q 95, electron temperature, and input power. These fast electrons notably enhance the sheath potential on the guard limiters and increase the heat flux to the wall.

Weil representations of twisted loop groups of type A n (2)

Abstract We construct Weil representations of twisted loop groups of type A n ( 2 ) {A_{n}^{(2)}} over local fields. We prove that the associated cover of the twisted loop group is the two fold metaplectic cover of the affine Kac–Moody group of type A n ( 2 ) {A_{n}^{(2)}} given by Patnaik and Puskas.

3D-Porous Electrocatalyst with Tip-Enhanced Electric Field Effect Enables High-Performance Proton Exchange Membrane Water Electrolyzer.

Hydrogen evolution reaction (HER), as one of the most advanced methods for the green production of hydrogen, is greatly impeded by inefficient mass transfer. Here we present an efficiently reactant enriched and mass traffic system by integrating high-curvature Pt nanocones with 3D porous TiAl framework to enhance mass transfer rate. Theoretical simulations, in situ Raman spectroscopy and potential-dependent Fourier transform infrared spectroscopy results disclose that the strong local electric field induced by high-curvature Pt can greatly promote the H3O+ supply rate during HER, resulting in ∼1.6 times higher H3O+ concentration around the Pt nanocone than that in electrolyte. X-ray computed tomography and molecular dynamic simulation demonstrate the diffusion coefficient of H3O+ in 3D TiAl framework surpasses that in commercial carbon support by more than 16.7 times. Consequently, Pt/TiAl-nanocone exhibits a high mass activity of 17.2 mA cm-2 Pt at an overpotential of 100 mV with an ultrahigh TOF value of 42.9 atom-1 s-1. In a proton exchange membrane water electrolyzer, the Pt/TiAl-nanocone cathode achieves an industrial-scale current density of 1.0 A cm-2 with a cell voltage of 1.88 V at 60 °C and can operate stably for at least 800 h with a sluggish voltage decay rate of 137 µV h-1.