Direct Diffusion Research Articles

Study on the Effect of Cracking Parameters on the Migration Characteristics of Chloride Ions in Cracked Concrete

In engineering, concrete often develops cracks due to various reasons, which accelerate the erosion rate of chloride ions in concrete and consequently expedite the degradation of the mechanical properties of concrete structures. This study simplifies the four-phase model into a two-phase model using homogenization methods. Based on this, numerical simulations are employed to investigate the influences of dimensionless structural parameters and material parameters of cracks on the equivalent diffusion coefficient of cracked concrete, and a theoretical model for the equivalent diffusion coefficient of cracked concrete is established according to Fick’s diffusion law. The research findings indicate that when cracks are positioned in the middle of the boundary through which chloride ions enter and exit the concrete, and the direction of the cracks is parallel to the diffusion direction of chloride ions; this scenario is the most detrimental to the durability of concrete. For n cracks (n ≥ 2), when they are parallel to the x-axis and symmetrical about the x-axis, and the spacing between cracks equals 1/n times the width of the concrete, this scenario is the most detrimental to the durability of concrete containing multiple cracks. Whether for a single crack or multiple cracks, when they are in the most unfavorable condition, the “parallel-then-series” theoretical model can accurately predict the equivalent diffusion coefficient of cracked concrete.

Mechanisms of rapid magnetocaloric enhancement of La–Fe–Co–Si alloy by high-temperature hot compression with large deformation

In this study, the microstructure, phase composition, magnetic transition, and magnetocaloric effect of the LaFe10.6Co0.9Si1.5 alloy hot compressed at high temperatures over 1173 K with a strain rate 0.005 s−1 and reduction ratio 50%–70 % are studied. No La(Fe, Si, Co)13 phase is formed until the hot-compression temperature is elevated to 1273 K and the reduction ratio is increased to 70 %. As a result, 86.8 ± 2 wt% 1:13 phases are rapidly obtained in the LaFe10.6Co0.9Si1.5 ingot. The whole process can be completed within only 10 min and no post-annealing process is needed. This fast formation of the La(Fe, Si, Co)13 phases is possibly induced by the directional atomic diffusion, accelerated atomic diffusion, and the stability of the La(Fe, Si, Co)13 phase and structural relaxation caused by the sufficiently restored elastic energy during the hot compression. The LaFe10.6Co0.9Si1.5 ingot hot compressed at 1273 K with a reduction ratio 70 % at a strain rate 0.005/s exhibits a second-order phase transition and negligible magnetic hysteresis. A large magnetic entropy change of 4.4 J/kg.K and a wide working temperature range of 57 K under 2 T are acquired near room temperature. This study proposes a new efficient hot compression route for processing the La–Fe–Co–Si alloy and enhancing the magnetocaloric effect.

Assessment of Gravity Waves From Tropopause to Thermosphere and Ionosphere in High‐Resolution WACCM‐X Simulations

AbstractA new version of NCAR Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension (WACCM‐X) has been developed. The main feature of this version is the species‐dependent spectral element (SE) dynamical core solved on a cubed sphere grid, eliminating the polar singularity and enabling simulations at high‐resolutions. Molecular viscosity and diffusion in the horizontal direction are also included. The Conservative Semi‐Lagrangian Multi‐Tracer Transport Scheme (CSLAM) is employed for the species transport. An efficient regridding scheme based on the Earth System Modeling Framework is used to map fields between the physics mesh and geomagnetic grid. Simulations have been performed at coarse (∼200 km and 0.25 scale height) and high (∼25 km and 0.1 scale height) resolutions. Spatial distribution of the resolved gravity waves from the high‐resolution simulations compares well with available observations in the middle and upper atmosphere. Analysis of the scale dependence of the gravity wave energy density and momentum flux shows that, while larger scale waves are dominant energetically at most latitudes, smaller scale waves contribute significantly to the total momentum flux, especially at mid‐high latitudes. The waves in the thermosphere are shown to be strongly modulated by the large‐scale wind through Doppler shift and molecular damping, and they cause large neutral atmosphere and plasma perturbations.

Research on internal flow characteristics of the planar conical tube for valveless piezoelectric micropump

Abstract As the most commonly used driving and executing components in microfluidic systems, valveless piezoelectric micropumps have broad application prospects in numerous fields. The steady and unsteady characteristics of planar conical tubes for valveless piezoelectric micropumps were simulated using CFX software at different pressure amplitudes and driving frequencies. The aim was to obtain the factors affecting the flow performance of the valveless piezoelectric micropump. The results show that the numbers of Remax in both diffusion and contraction directions of the planar conical tube increase with increasing pressure. When the number of Wo is lower, the number of Remax under a steady state is approximately equal to that under an unsteady state, and the maximum relative deviation is only 0.25%. The greater the Wo number, the smaller the velocity on the minimum flow section, and the more significant the velocity change. The rectification efficiency η of the valveless piezoelectric micropump and the efficiency λ of the planar conical tube both increase with increasing pressure under steady conditions, and the maximum values can be reached at 11.2% and 1.56, respectively.

A retrospective case-control study on the effectiveness of preoperative diffusion tensor imaging for mitigating nerve injury in extreme lateral interbody fusion surgery

Extreme Lateral Interbody Fusion (XLIF) has been established as an effective treatment for degenerative disorders of the lumbar spine. Nevertheless, there is a potential risk of lumbar plexus damage associated with XLIF, especially during surgeries at the L4-5 segment. Diffusion Tensor Imaging (DTI) evaluates the directional diffusion of water molecules in tissue, providing a more intricate depiction of internal tissue microstructure compared to conventional MRI techniques. The capability of DTI sequences to elucidate the 3-dimensional interplay between lumbar nerve pathways and adjacent musculoskeletal structures, potentially reducing the incidence of nerve injury complications related to XLIF, remains to be established. This study evaluates the effectiveness of preoperative Diffusion Tensor Imaging (DTI) in reducing neurological complications after Extreme Lateral Interbody Fusion (XLIF) surgeries at the L4-5 level, focusing on the interaction between lumbar nerves and the psoas major muscle. Retrospective case-control study. The study included 128 patients undergoing XLIF surgery for degenerative disorders at the L4-5 segment: 68 in the traditional group and 62 in the DTI group. The study assessed Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores, along with complication rates. It also documented psoas major muscle morphology and its correlation with nerve pathways. A retrospective analysis of 128 patients undergoing XLIF surgery for degenerative disorders at the L4-5 segment between February 2020 and August 2022 was conducted. The cohort was divided into a traditional group (68 patients) receiving presurgery MRI scans to identify surgical entry points at the intervertebral space midpoint (Zones II-III junction) and a DTI group (62 patients) who additionally underwent preoperative DTI to customize entry points. The study evaluated VAS and ODI scores, complication rates, psoas major muscle morphology, and its interaction with nerve pathways. The traditional group uniformly chose the Zone II-III junction for entry. In contrast, the DTI group's entry points varied. Postoperative follow-up revealed significant improvements in VAS and ODI scores in both groups. However, the DTI group experienced fewer immediate postoperative complications such as thigh pain, numbness, and motor disturbances. The study also noted a ventral shift in nerve positioning in patients with elevated psoas muscles. Preoperative DTI effectively maps the relationship between the psoas major muscle and lumbar nerves. Tailoring surgical entry points based on DTI results significantly reduces the risk of nerve damage in XLIF surgeries. The study underscores the importance of recognizing variability in lumbar nerve pathways due to differing psoas muscle morphologies, highlighting a higher risk of nerve injury in patients with elevated psoas muscles during XLIF procedures.

Prenatal and childhood air pollution exposure, cellular immune biomarkers, and brain connectivity in early adolescents

IntroductionAmbient air pollution is a neurotoxicant with hypothesized immune-related mechanisms. Adolescent brain structural and functional connectivity may be especially vulnerable to ambient pollution due to the refinement of large-scale brain networks during this period, which vary by sex and have important implications for cognitive, behavioral, and emotional functioning. In the current study we explored associations between air pollutants, immune markers, and structural and functional connectivity in early adolescence by leveraging cross-sectional sex-stratified data from the Adolescent Brain Cognitive Development℠ Study®. MethodsPollutant concentrations of fine particulate matter, nitrogen dioxide, and ozone were assigned to each child's primary residential address during the prenatal period and childhood (9-10 years-old) using an ensemble-based modeling approach. Data collected at 11-13 years-old included resting-state functional connectivity of the default mode, frontoparietal, and salience networks and limbic regions of interest, intracellular directional and isotropic diffusion of available white matter tracts, and markers of cellular immune activation. Using partial least squares correlation, a multivariate data-driven method that identifies important variables within latent dimensions, we investigated associations between 1) pollutants and structural and functional connectivity, 2) pollutants and immune markers, and 3) immune markers and structural and functional connectivity, in each sex separately. ResultsAir pollution exposure was related to white matter intracellular directional and isotropic diffusion at ages 11–13 years, but the direction of associations varied by sex. There were no associations between pollutants and resting-state functional connectivity at ages 11–13 years. Childhood exposure to nitrogen dioxide was negatively correlated with white blood cell count in males. Immune biomarkers were positively correlated with white matter intracellular directional diffusion in females and both white matter intracellular directional and isotropic diffusion in males. Lastly, there was a reliable negative correlation between lymphocyte-to-monocyte ratio and default mode network resting-state functional connectivity in females, as well as a compromised immune marker profile associated with lower resting-state functional connectivity between the salience network and the left hippocampus in males. In post-hoc exploratory analyses, we found that the PLSC-identified white matter tracts and resting-state networks related to processing speed and cognitive control performance from the NIH Toolbox. ConclusionsWe identified novel links between childhood nitrogen dioxide and cellular immune activation in males, and brain network connectivity and immune markers in both sexes. Future research should explore the potentially mediating role of immune activity in how pollutants affect neurological outcomes as well as the potential consequences of immune-related patterns of brain connectivity in service of improved brain health for all.

Spatial diffusion of potentially toxic elements in soils around non-ferrous metal mines

This study focuses on the diffusion patterns of principal ore-forming elements (Pb and Zn) and associated elements (Cd, Cu, Cr, and As) in lead-zinc ore. Sampling points in upwind and downwind directions of lead-zinc ore areas at various densities (1 N/km2 – 4 N/km2) were categorized. This study analyzed the statistical relationship between the content of PTEs in the soil around lead-zinc ore and the source strength and dominant wind direction, constructed one-dimensional and two-dimensional diffusion model, and simulated the EER scope caused by PTEs. The findings indicate that: (1) concerning source strength, the content of PTEs in soils of high-density ore aggregation areas is significantly higher than in low-density ore aggregation areas. However, the impact of source strength decreases with decreasing ore grade, with a difference in Pb content of 1.71 times among principal ore-forming elements and almost consistent Cd content among associated elements. (2) Regarding the transport pathways, for most PTEs, the inverse proportion coefficients downwind are higher than upwind, approximately 1.18–3.63 times, indicating greater migration distances of PTEs downwind due to atmospheric dispersion. (3) By establishing a two-dimensional risk diffusion model, the study simulates the maximum radius of risk diffusion (r = 5.7 km), the 50% probability radius (r = 3.1 km), and the minimum radius (r = 0.8 km) based on the maximum, median, and minimum values statistically obtained from the EER. This study provides a scientific basis for implementing preventive measures for PTEs accumulation in soil within different pollution ranges. Different risk prevention and control measures should be adopted for PTEs accumulation in soil within the three ranges after cutting off pollution sources. Subsequent research should further investigate the impact and contribution of atmospheric transmission and surface runoff on the diffusion of PTEs in areas with high risk near lead-zinc ore.

Removal of Pb pollution using alginate-coupled magnetic sludge biochar: Solidification and stabilization behavior and electron promotion mechanisms

Environmental and human health problems caused by Pb pollution have attracted much attention, and solidification and stabilization are effective means for its remediation. Improving the ability of biochar to remediate heavy metals through modification is the focus of current biochar research. This study used calcium-alginate gel (GB) and Fe3+ (magnetic) to encapsulate and improve sludge biochar (SB), and explored the adsorption behavior and passivation mechanism of Pb2+ on it from outside to inside. The magnetic-biochar (MB) in magnetic-biochar-gel microspheres (MBGB) showed a homogeneous dispersion and part of the Fe ion was detached from the MB into the three-dimensional pores of the gel. The results of kinetic, isothermal and pH adsorption experiments showed that the MBGB has 108.4 % and 200 % higher Pb2+ adsorption capacity and rate than SB and can be applied to pH 3–9. The adsorption of Pb2+ by MBGB is a multilayer adsorption with both physical and chemical mechanisms. Mineralogical and electrochemical results demonstrate that the cross-linking of the gel with magnetic-biochar (MB) can provide a directional diffusion channel for Pb2+ from the outside to the inside. The electron transfer rate of MBGB was significantly higher than that of SB (222.2 %) after the reaction. The dissolved cations and electrons on the MB guide Pb2+ from the MBGB surface to the internal MB quickly via accelerating the electron transfer and migration rate between Pb2+ and MB. Subsequently, the abundance of PO43− on the MB ensures stable mineral precipitation (Pyromorphite). Moreover, four-step extraction analysis confirmed that most of Pb2+ in MBGB was stable (36.2 % acid-soluble and 47.6 % non-bioavailable). Meanwhile, the Pb adsorption efficiency of MBGB was still >93.0 % after three cycles of adsorption-desorption. Excellent reuse performance and stability guarantee the environmental security of MBGB. The results of the study provide theoretical support for the efficient treatment of Pb2+ polluted water assisted by gel materials.

A CFD study on radionuclides diffusion and dose assessment in Daya Bay nuclear power plant

Computational fluid dynamics (CFD) is used to simulate the short-range dispersion of radionuclides in a real nuclear power plant site. Firstly, the results of the validation case showed that the wind speed and concentration distribution were consistent with the measured data. Then, the potential consequences of radionuclide diffusion within the Daya Bay Nuclear Power Plant (DBNPP) were evaluated. Based on the wind direction and speed data from DBNNP over a 30-year period, the prevailing wind is northeasterly and southwesterly. The simulation results show that northeasterly and southwesterly winds dominate the diffusion direction of radionuclides, which mainly accumulate near nuclear reactor containment vessels. However, radionuclides cover most areas of DBNPP under a tailwind condition, causing severe contamination. Finally, it is necessary to pay attention to the accumulation of I-131 and Cs-137, and corresponding actions should be taken for regions of different radiation doses.

The Impact of Surface Roughness on Conformal Cooling Channels for Injection Molding.

Injection molding technology is widely utilized across various industries for its ability to fabricate complex-shaped components with exceptional dimensional accuracy. However, challenges related to injection quality often arise, necessitating innovative approaches for improvement. This study investigates the influence of surface roughness on the efficiency of conformal cooling channels produced using additive manufacturing technologies, specifically Direct Metal Laser Sintering (DMLS) and Atomic Diffusion Additive Manufacturing (ADAM). Through a combination of experimental measurements, including surface roughness analysis, scanning electron microscopy, and cooling system flow analysis, this study elucidates the impact of surface roughness on coolant flow dynamics and pressure distribution within the cooling channels. The results reveal significant differences in surface roughness between DMLS and ADAM technologies, with corresponding effects on coolant flow behavior. Following that fact, this study shows that when cooling channels' surface roughness is lowered up to 90%, the reduction in coolant media pressure is lowered by 0.033 MPa. Regression models are developed to quantitatively describe the relationship between surface roughness and key parameters, such as coolant pressure, Reynolds number, and flow velocity. Practical implications for the optimization of injection molding cooling systems are discussed, highlighting the importance of informed decision making in technology selection and post-processing techniques. Overall, this research contributes to a deeper understanding of the role of surface roughness in injection molding processes and provides valuable insights for enhancing cooling system efficiency and product quality.

FlexDTI: flexible diffusion gradient encoding scheme-based highly efficient diffusion tensor imaging using deep learning

Objective. Most deep neural network-based diffusion tensor imaging methods require the diffusion gradients’ number and directions in the data to be reconstructed to match those in the training data. This work aims to develop and evaluate a novel dynamic-convolution-based method called FlexDTI for highly efficient diffusion tensor reconstruction with flexible diffusion encoding gradient scheme. Approach. FlexDTI was developed to achieve high-quality DTI parametric mapping with flexible number and directions of diffusion encoding gradients. The method used dynamic convolution kernels to embed diffusion gradient direction information into feature maps of the corresponding diffusion signal. Furthermore, it realized the generalization of a flexible number of diffusion gradient directions by setting the maximum number of input channels of the network. The network was trained and tested using datasets from the Human Connectome Project and local hospitals. Results from FlexDTI and other advanced tensor parameter estimation methods were compared. Main results. Compared to other methods, FlexDTI successfully achieves high-quality diffusion tensor-derived parameters even if the number and directions of diffusion encoding gradients change. It reduces normalized root mean squared error by about 50% on fractional anisotropy and 15% on mean diffusivity, compared with the state-of-the-art deep learning method with flexible diffusion encoding gradient scheme. Significance. FlexDTI can well learn diffusion gradient direction information to achieve generalized DTI reconstruction with flexible diffusion gradient scheme. Both flexibility and reconstruction quality can be taken into account in this network.

Leptomeningeal carcinomatosis, an emerging disease in internal medicine departments with a generally poor prognosis: two case reports

As a result of improved diagnostic methods and higher cancer patient survival rates, leptomeningeal carcinomatosis is being found in internal medicine departments more frequently. Melanoma, lung cancer, and breast adenocarcinoma are the three cancers that are most commonly associated. When the main tumor diffuses through the bloodstream, cerebrospinal fluid, or direct diffusion and causes multiple focal neurological symptoms, it is known as leptomeningeal involvement; the prognosis is usually not good. Despite multimodal treatment, leptomeningeal carcinomatosis is an advanced form of cancer that frequently results in rapid death. Treatment is typically palliative and consists primarily of intrathecal or systemic radiation and/or chemotherapy. New experimental therapies and immunotherapy are promising means of lowering morbidity and mortality. Clinical cases of leptomeningeal carcinomatosis are reported; both cases were identified at the Ospedale dei Castelli’s Department of Internal Medicine and resulted from primary breast pathology.

Low-temperature direct diffusion bonding of Zr702 alloys via electric current assistance

Integrated zirconium (Zr) alloy fuel claddings require low-temperature and high-efficiency joining technologies for nuclear applications. However, conventional direct-joining technologies make it challenging to satisfy critical requirements at relatively low temperatures in a short time. As a promising alternative, the electric-current-assisted joining (ECAJ) method was studied to reduce the joining temperature and time required for the direct joining process. ECAJ was performed on a spark plasma sintering apparatus, with the specimens assembled with and without graphite dies in the two models. The microstructural evolution and mechanical properties of Zr/Zr joints were investigated at 600 − 900 °C for 1 s to 30 min under a pressure of 30 MPa using different configurations with or without a graphite die. While the joint quality varied with the joining conditions, no significant phase transformation, abnormal grain growth, or preferential orientation was observed at the interface. The maximum shear strength of 404 ± 78 MPa and hardness of 370.9 ± 49.8 HV were achieved at 600 °C for 10 min using a die-less configuration. The joining mechanism was discussed in terms of the potential thermal and electric effects inside the specimen, with the low-temperature joining mechanism attributed to the combined effect of transient overheating and electric-field-accelerated element self-diffusion at the interface, with the latter playing a leading role.

Dual-type confinement strategy: Improving the stability of organic composite cathodes for Lithium-ion batteries with longer lifespan

Inclusive reports on organic cathodes are the key evidence of their superior performance for Lithium-ion batteries. However, it is still promising to simultaneously achieve a higher practical specific capacity and longer cycling life, owing to the crucial concern of the dissolution of active molecules in organic electrolytes. The introduction of porous carbon confinement and coating which can impart discharge capacity and cycling stability, is highly beneficial. Herein, we designed and prepared a novel composite cathode (designated as HKUST-1-C@DHAQ@TiO2) with small molecules (DHAQ) in porous carbon skeleton (HKUST-1-C) as core and TiO2 as shell. The unique dual-type confinement strategy offers short Li+/e- diffusion directions for redox reactions and superior structural stability during cycling without dissolution or decomposition of the components, resulting in excellent electrochemical performance. The HKUST-1-C@DHAQ@TiO2 cathode delivers significant specific capacity (209 mAh g−1, 0.1 A g−1), markable Coulombic efficiency (nearly 100 %), notable cycling stability (86 % retention for provided 200 cycles) and excellent rate capacity (138 mAh g−1 at 1.0 A g−1). The presented findings offer the deep understanding of redox reactions and organic cathode evolution mechanisms for the progress of smarter energy storage batteries.

Anisotropic grain boundary diffusion process in textured sintered and hot-deformed Nd-Fe-B magnets

A systematic study of the dependence of the Grain Boundary Diffusion Process (GBDP) on texture using Dy and Dy-Nd-Cu in microcrystalline sintered and nanocrystalline hot deformed Nd-Fe-B magnets was performed. Diffusion parallel or perpendicular to the texture direction, the nominal c-axes orientation in the polycrystals, was investigated. By measuring thin slices from the respective samples, coercivity as a function of (i) magnet thickness and (ii) diffusion depth was obtained showing that GBDP efficiency depends on the diffusion direction, diffusion source as well as the grain morphology originating from the magnet production route. In nanocrystalline hot deformed magnets perpendicular diffusion is superior due to the platelet-like shape of the grains. Microcrystalline sintered magnets consist of equiaxed grains hence the main effects originate in anisotropic lattice diffusion and pole surface hardening. The magnetic properties are correlated with a comprehensive analysis of microstructure, chemistry and magnetization reversal.

Endophthalmitis therapy revolution: Proof of concept based on in vivo evaluation of maleic acid modified chitosan

The aim was to develop chitosan-maleic acid (CS-MA) based ocular inserts with enhanced mucoadhesiveness for prevention of endophthalmitis caused by Escherichia coli. Therefore, chitosan (CS) and maleic acid (MA) were conjugated via formation of amide bond. Characterization via proton nuclear magnetic resonance and infrared spectroscopy was carried out and attached maleic acid groups were quantified by free amino groups assay. Biocompatibility of the conjugate was assessed following resazurin assay on fibroblasts, membrane damage on human erythrocytes and Hen's Egg-Chorioallantoic membrane tests. Inserts were pressed and characterized in terms of swelling behavior, pH, hardness, in vitro drug release and disintegration. To test mucoadhesive properties of CS-MA inserts, rheometer, rotating cylinder, inclined plane, and texture analyzer were the instruments utilized. Furthermore, antibacterial efficacy of the conjugate was established by direct agar diffusion method and in vivo Draize test was carried out to determine tolerability of the inserts. Results exhibited successful synthesis of the biomaterial, maintaining the great biocompatibility of native chitosan even though a 68.81 % of modification was achieved. Additionally, mucoadhesive studies showed improved properties of CS-MA compared to native polymer, with 2.42-fold, 4-fold, 3.42-fold and 4.05-fold increase in dynamic viscosity, retention time, overall attachment work and peak force of detachment, respectively. Finally, antibacterial activity was enhanced in 1.77-fold and in vivo experiments showed no irritation and good tolerability of CS-MA inserts. In conclusion, CS-MA ocular inserts effectively developed exhibiting promising features capable of revolutionizing the endophthalmitis therapy field.

Two-dimensional lead halide perovskite lateral homojunctions enabled by phase pinning

Two-dimensional organic-inorganic hybrid halide perovskites possess diverse structural polymorphs with versatile physical properties, which can be controlled by order-disorder transition of the spacer cation, making them attractive for constructing semiconductor homojunctions. Here, we demonstrate a space-cation-dopant-induced phase stabilization approach to creating a lateral homojunction composed of ordered and disordered phases within a two-dimensional perovskite. By doping a small quantity of pentylammonium into (butylammonium)2PbI4 or vice versa, we effectively suppress the ordering transition of the spacer cation and the associated out-of-plane octahedral tilting in the inorganic framework, resulting in phase pining of the disordered phase when decreasing temperature or increasing pressure. This enables epitaxial growth of a two-dimensional perovskite homojunction with tunable optical properties under temperature and pressure stimuli, as well as directional exciton diffusion across the interface. Our results demonstrate a previously unexplored strategy for constructing two-dimensional perovskite heterostructures by thermodynamic tuning and spacer cation doping.

Multiple techniques to evaluate the relationship between carotid artery plaque and acute stroke.

To evaluate the important characteristics of the plaque vulnerability using multimodal ultrasound imaging methods (2D, contrast-enhanced ultrasound, and elastography), and to explore the relationship between plaque and acute stroke. A total of 244 patients with carotid plaque were enrolled, including 104 patients with acute stroke ipsilateral to the plaque as the case group and 140 patients as the control group. All patients underwent conventional carotid ultrasound, contrast-enhanced ultrasound (CEUS) and elastography (SWE). The results of each examination were compared and analyzed, and the relationship between the results and the occurrence of stroke was discussed. In the acute stroke group, the men, with a history of alcohol consumption the direction of contrast media diffusion was higher than that in the control group, but the plaque gray value (GSM), maximum, average and minimum Young's elastic modulus imaging values (YM) were slightly lower than those in the control group (P < 0.05). Logistic regression analysis showed that waist to body ratio (WHtR), GSM, YM, neovascularization density and contrast diffusion direction were independent risk factors for predicting acute ischemic stroke. The influence degree of each factor from strong to weak was waist to body ratio, neovascularity density, GSM and YM, respectively. The area under the curve (AUC) for the diagnosis of acute ischemic stroke by regression model was 0.746. The combination of multiple ultrasound techniques to evaluate the vulnerability of carotid plaque and predict the occurrence of acute stroke provides valuable information for clinical decision making.

Floating-Point Approximation Enabling Cost-Effective and High-Precision Digital Implementation of FitzHugh-Nagumo Neural Networks.

The study of neuron interactions and hardware implementations are crucial research directions in neuroscience, particularly in developing large-scale biological neural networks. The FitzHugh-Nagumo (FHN) model is a popular neuron model with highly biological plausibility, but its complexity makes it difficult to apply at scale. This paper presents a cost-saving and improved precision approximation algorithm for the digital implementation of the FHN model. By converting the computational data into floating-point numbers, the original multiplication calculations are replaced by adding the floating-point exponent part and fitting the mantissa part with piecewise linear. In the hardware implementation, shifters and adders are used, greatly reducing resource overhead. Implementing FHN neurons by this approximation calculations on FPGA reduces the normalized root mean square error (RMSE) to 3.5% of the state-of-the-art (SOTA) while maintaining a performance overhead ratio improvement of 1.09 times. Compared to implementations based on approximate multipliers, the proposed method achieves a 20% reduction in error at the cost of a 2.8% increase in overhead.This model gained additional biological properties compared to LIF while reducing the deployment scale by only 9%. Furthermore, the hardware implementation of nine coupled circular networks with eight nodes and directional diffusion was carried out to demonstrate the algorithm's effectiveness on neural networks. The error decreased to 60% compared to the single neuron of the SOTA. This hardware-friendly algorithm allows for the low-cost implementation of high-precision hardware simulation, providing a novel perspective for studying large-scale, biologically plausible neural networks.

High-fidelity intravoxel incoherent motion parameter mapping using locally low-rank and subspace modeling

PurposeIntravoxel incoherent motion (IVIM) is a quantitative magnetic resonance imaging (MRI) method used to quantify perfusion properties of tissue non-invasively without contrast. However, clinical applications are limited by unreliable parameter estimates, particularly for the perfusion fraction (f) and pseudodiffusion coefficient (D*). This study aims to develop a high-fidelity reconstruction for reliable estimation of IVIM parameters. The proposed method is versatile and amenable to various acquisition schemes and fitting methods. MethodsTo address current challenges with IVIM, we adapted several advanced reconstruction techniques. We used a low-rank approximation of IVIM images and temporal subspace modeling to constrain the magnetization dynamics of the bi-exponential diffusion signal decay. In addition, motion-induced phase variations were corrected between diffusion directions and b-values, facilitating the use of high SNR real-valued diffusion data. The proposed method was evaluated in simulations and in vivo brain acquisitions in six healthy subjects and six individuals with a history of SARS-CoV-2 infection and compared with the conventionally reconstructed magnitude data. Following reconstruction, IVIM parameters were estimated voxel-wise. ResultsOur proposed method reduced noise contamination in simulations, resulting in a 60%, 58.9%, and 83.9% reduction in the NRMSE for D, f, and D*, respectively, compared to the conventional reconstruction. In vivo, anisotropic properties of D, f, and D* were preserved with the proposed method, highlighting microvascular differences in gray matter between individuals with a history of COVID-19 and those without (p = 0.0210), which wasn't observed with the conventional reconstruction. ConclusionThe proposed method yielded a more reliable estimation of IVIM parameters with less noise than the conventional reconstruction. Further, the proposed method preserved anisotropic properties of IVIM parameter estimates and demonstrated differences in microvascular perfusion in COVID-affected subjects, which weren't observed with conventional reconstruction methods.