Axial Gradient Research Articles

Comprehensive characterization of natural polysaccharide-based hydrogels with gradient structure in concentration and stiffness

Gradient hydrogels are functionally graded biomaterials that over the last decades have garnered significant attention as valuable materials for tissue repair and regeneration. This study elucidates key factors crucially determining the character or pattern of a buoyancy-driven gradient in agarose hydrogels and also provides fundamental information regarding the complex interpretation of the formed gradient hydrogels obtained by the different characterization techniques, including rheology, UV-Vis spectroscopy, FCS, AFM, SEM. The employed techniques were successfully optimized to enhance the understanding of the gradient properties of these hydrogels. Demonstrated results showed that the agarose concentration gradient could be successfully controlled and tailored, which offers a valuable contribution to the design of gradient hydrogel. Moreover, a novel method for determining the average agarose concentration along the gradient axis is presented, improving the precision of gradient characterization. The integration of these approaches significantly enhances the comprehension of the internal structure and properties of gradient materials, contributing to advancements in their understanding and application.

Streaming electric field, electroviscous effect, and electrokinetic liquid flows in the induced pressure-driven transport of active liquids in narrow capillaries.

In this paper, we develop a theory for studying the electrokinetic effects in a charged nanocapillary filled with active liquid. The active particles present within the active liquid are self-driven, demonstrate vortex defects, and enforce a circumferentially arranged polarization field. Under such circumstances, there is the development of an induced pressure-gradient-driven transport dictated (similar to diffusioosmotic transport) by the presence of an axial gradient in the activity (or the concentration of the active particles). This pressure-driven transport has a profile different from the standard Hagen-Poiseuille flow in a nanocapillary. Also, this induced pressure-driven flow drives electrokinetic effects, which are characterized by the generation of a streaming electric field, associated electroosmotic (EOS) transport opposing pressure-driven flow, and electroviscous effect. We quantify these effects as functions of dimensionless parameters that vary inversely as the strength of the activity-induced pressure-driven flow and salt concentrations. Overall, we anticipate that this paper will draw immense attention toward a new type of activity-induced pressure-driven flow and associated electrokinetic phenomena in charged nanoconfinements.

Deep learning model for automated diagnosis of degenerative cervical spondylosis and altered spinal cord signal on MRI

BACKGROUND CONTEXTA deep learning (DL) model for degenerative cervical spondylosis on MRI could enhance reporting consistency and efficiency, addressing a significant global health issue. PURPOSECreate a DL model to detect and classify cervical cord signal abnormalities, spinal canal and neural foraminal stenosis. STUDY DESIGN/SETTINGRetrospective study conducted from January 2013 to July 2021, excluding cases with instrumentation. PATIENT SAMPLEOverall, 504 MRI cervical spines were analyzed (504 patients, mean=58 years±13.7[SD]; 202 women) with 454 for training (90%) and 50 (10%) for internal testing. In addition, 100 MRI cervical spines were available for external testing (100 patients, mean=60 years±13.0[SD];26 women). OUTCOME MEASURESAutomated detection and classification of spinal canal stenosis, neural foraminal stenosis, and cord signal abnormality using the DL model. Recall(%), inter-rater agreement (Gwet's kappa), sensitivity, and specificity were calculated. METHODSUtilizing axial T2-weighted gradient echo and sagittal T2-weighted images, a transformer-based DL model was trained on data labeled by an experienced musculoskeletal radiologist (12 years of experience). Internal testing involved data labeled in consensus by two musculoskeletal radiologists (reference standard, both with 12-years-experience), two subspecialist radiologists, and two in-training radiologists. External testing was performed. RESULTSThe DL model exhibited substantial agreement surpassing all readers in all classes for spinal canal (κ=0.78, p<0.001 vs. κ range=0.57-0.70 for readers) and neural foraminal stenosis (κ=0.80, p<0.001 vs. κ range=0.63-0.69 for readers) classification. The DL model's recall for cord signal abnormality (92.3%) was similar to all readers (range: 92.3-100.0%). Nearly perfect agreement was demonstrated for binary classification (normal/mild vs. moderate/severe) (κ=0.95, p<0.001 for spinal canal; κ=0.90, p<0.001 for neural foramina). External testing showed substantial agreement using all classes (κ=0.76, p<0.001 for spinal canal; κ=0.66, p<0.001 for neural foramina) and high recall for cord signal abnormality (91.9%). The DL model demonstrated high sensitivities (range:83.7%–92.4%) and specificities (range:87.8%–98.3%) on both internal and external datasets for spinal canal and neural foramina classification. CONCLUSIONSOur DL model for degenerative cervical spondylosis on MRI showed good performance, demonstrating substantial agreement with the reference standard. This tool could assist radiologists in improving the efficiency and consistency of MRI cervical spondylosis assessments in clinical practice.

Evaluation of the Contrast Enhancement Performance of Gadopiclenol for Magnetic Resonance Angiography in Healthy Rabbits and Pigs.

Unexpected accumulations of gadolinium in various organs were reported after the administration of gadolinium-based contrast agents, making desirable to reduce the dose while maintaining equivalent diagnostic performance. The aim of this study was to evaluate the contrast enhancement performance of high relaxivity gadopiclenol compared with gadoterate meglumine in abdominal contrast-enhanced magnetic resonance angiography (CE-MRA). In a first study in healthy rabbits, axial 3D gradient echo sequences were applied at 4.7 T to study arterial enhancement as a function of gadopiclenol dose (0.025, 0.05, 0.075, and 0.1 mmol Gd/kg) or gadoterate meglumine at 0.1 mmol Gd/kg (n = 5-6/group). The increase in signal-to-noise ratio (ΔSNR) in the aorta at the first pass was measured and compared. In a second, crossover study in 6 healthy pigs, abdominal CE-MRA sequences were acquired at 3 T with gadopiclenol at 0.05 mmol Gd/kg or gadoterate meglumine at 0.1 mmol Gd/kg at a 1-week interval. Quantitatively on the maximum intensity projection (MIP) images, the mean MIP SNR within the aorta of both groups was compared. Qualitatively, a blinded comparison of the angiograms was performed by an experienced radiologist to determine the preferred contrast agent. In the rabbit, ∆SNR is linearly correlated with the gadopiclenol dose ( P = 0.0010). Compared with gadoterate meglumine 0.1 mmol Gd/kg, an increase in the ∆SNR is observed after 0.05, 0.075, and 0.1 mmol Gd/kg of gadopiclenol (+63% P = 0.0731, +78% P = 0.0081, and +72% P = 0.0773, respectively), whereas at 0.025 mmol Gd/kg, ∆SNR is in the same range as with gadoterate meglumine 0.1 mmol Gd/kg (+15% P > 0.9999). In pigs, contrast enhancement after gadopiclenol at 0.05 mmol/kg is +22% superior to MIP SNR after gadoterate meglumine at 0.1 mmol Gd/kg ( P = 0.3095). Qualitatively, a preference was shown for gadopiclenol images (3/6) over the gadoterate meglumine examinations (1/6), with no preference being shown for the remainder (2/6). First-pass CE-MRA is feasible with gadopiclenol at 0.05 mmol Gd/kg with at least the same arterial signal enhancement and image quality as gadoterate meglumine at 0.1 mmol Gd/kg.

Dual beam optical coherence tomography angiography for decoupling axial velocity gradient

Axial velocity gradient (AVG) in the optical coherence tomography angiography (OCTA) signal affects measurement accuracy when the flow is not perpendicular to the scanning beam. We developed a dual beam OCTA method to decouple the contribution of AVG from the decorrelation signal. Decoupling is first verified by phantom experiments which reduces measurement uncertainty from 1.5 to 0.7% (standard deviation). We also tested the method in human skin in vivo and the results indicate that the contribution of AVG to decorrelation signal is reduced.

Assessing Axillary Lymph Node Burden and Prognosis in cT1-T2 Stage Breast Cancer Using Machine Learning Methods: A Retrospective Dual-Institutional MRI Study.

Pathological axillary lymph node (pALN) burden is an important factor for treatment decision-making in clinical T1-T2 (cT1-T2) stage breast cancer. Preoperative assessment of the pALN burden and prognosis aids in the individualized selection of therapeutic approaches. To develop and validate a machine learning (ML) model based on clinicopathological and MRI characteristics for assessing pALN burden and survival in patients with cT1-T2 stage breast cancer. Retrospective. A total of 506 females (range: 24-83 years) with cT1-T2 stage breast cancer from two institutions, forming the training (N = 340), internal validation (N = 85), and external validation cohorts (N = 81), respectively. This study used 1.5-T, axial fat-suppressed T2-weighted turbo spin-echo sequence and axial three-dimensional dynamic contrast-enhanced fat-suppressed T1-weighted gradient echo sequence. Four ML methods (eXtreme Gradient Boosting [XGBoost], Support Vector Machine, k-Nearest Neighbor, Classification and Regression Tree) were employed to develop models based on clinicopathological and MRI characteristics. The performance of these models was evaluated by their discriminative ability. The best-performing model was further analyzed to establish interpretability and used to calculate the pALN score. The relationships between the pALN score and disease-free survival (DFS) were examined. Chi-squared test, Fisher's exact test, univariable logistic regression, area under the curve (AUC), Delong test, net reclassification improvement, integrated discrimination improvement, Hosmer-Lemeshow test, log-rank, Cox regression analyses, and intraclass correlation coefficient were performed. A P-value <0.05 was considered statistically significant. The XGB II model, developed based on the XGBoost algorithm, outperformed the other models with AUCs of 0.805, 0.803, and 0.818 in the three cohorts. The Shapley additive explanation plot indicated that the top variable in the XGB II model was the Node Reporting and Data System score. In multivariable Cox regression analysis, the pALN score was significantly associated with DFS (hazard ratio: 4.013, 95% confidence interval: 1.059-15.207). The XGB II model may allow to evaluate pALN burden and could provide prognostic information in cT1-T2 stage breast cancer patients. 3 TECHNICAL EFFICACY: Stage 2.

Investigation on the Influence of Thermal Inertia on the Dynamic Characteristics of a Gas Turbine

In mini-grids and marine-isolated grids, power generation gas turbines are subjected to rapid start-up, shutdown, and acceleration/deceleration. This sudden load change can pose a significant impact on the power grid, severely affecting the operational characteristics of gas turbines. To understand the dynamic characteristics of the gas turbine in the transitional processes, this testing takes twin-shaft medium-sized power generation gas turbines as the test object, and goes through the process of startup, acceleration, deceleration, acceleration, shutdown in one hour, and repeats this process 40 times continuously. With fuel flow as the control parameter and power turbine outlet temperature and high-pressure turbine speed as the controlled parameters, the parameter response rate of the gas turbine under various transition processes is analyzed and the effect of thermal inertia on the gas turbine mass temperature as well as speed is studied. Research findings: During the transition processes, the gas temperature exhibited an axial gradient distribution in the channel. In both the acceleration and deceleration processes, the working fluid temperature gradually decreased along the flow direction. And thermal inertia posed different extents of impact on the dynamic characteristics of the gas turbine under different transitional processes. In the same transition process, the impacts of thermal inertia on the response speeds of temperature and rotational speed varied. The results of this study help to more accurately predict the operating state of the gas turbine during the transition process and lay the foundation for the dynamic simulation model of the non-adiabatic gas turbine.

Stabilization of magneto-Rayleigh-Taylor instability with non-uniform density and magnetic field profiles in Cartesian Geometry

Managing the Rayleigh–Taylor instability growth rate is one of the main challenges in inertial fusion. Among the proposed methods to tackle this issue, the application of a pre-embedded axial magnetic field and plasma density gradient of layers can be mentioned. Recent experimental evidence in Z-pinch devices shows that it is possible to suppress the growth rate of the Rayleigh-Taylor instability by applying a power law density gradient profile with exponent 2. In this work, in the framework of Cartesian coordinates, for a confined plasma between two fixed planes, the dispersion relation of a magnetized plasma has been obtained using linearization of the ideal MHD equations. Here, plasma with a power-law density profile of ∝r3 and magnetic field with the exponential profile is used. It is shown that for the relative strength of the magnetic field with a value of, ωf*=0.4 and more, the growth rate of instability appears only in a limited range of the range of reduced wave numbers, k*. By increasing this ratio, stability conditions are much improved. On the other hand, recent experimental studies show that self-generated plasma rotation is produced in an imploding Z-pinch device with an initial axial magnetic field. In the second part, the effect of plasma rotation on plasma stability conditions is investigated. Again, a new dispersion relation of the rotating magnetized plasma was derived. It is shown that in the non-magnetized case, a large relative angular velocity, Ω, is necessary to suppress the instability. However, for relative magnetic field strength, ωf*=0.4 and more, stable conditions can be achieved with a relatively lower angular velocity of about 5.

Simulation and experimental study of thermoelectric generators with an axial gradient metal foam heat exchanger

The utilization of metal foam for heat transfer augmentation is regarded as a highly efficient technique, albeit associated with significant pressure losses. To enhance the feasibility of employing metal foam in thermoelectric generators and mitigate the high-pressure drop, we propose an enhancement strategy involving the partial axial filling of gradient metal foam. Both analytical modeling and experimental investigation were employed to evaluate the effects of porosity, pore density, and gradient structure at various filling rates on the overall performance of thermoelectric generators. The results show that arranging metal foam with increasingly high frame density in the direction of fluid flow, rather than adopting increasingly sparse or constant structures, leads to improved voltage uniformity and reduced pressure drop. A positive gradient configuration with a pore density distribution of 5-10-20 PPI yielded the highest net power at 118.3 W, which is 12.5 % higher than that of metal foam with constant 20 PPI. Ultimately, empirical verification substantiates the comprehensive performance advantages of positive gradient configuration. For filling rates of 30 %, 60 %, and 100 %, pressure drop is reduced by 35.9 %, 33.4 %, and 29.2 %, respectively, in comparison to constant 20 PPI metal foam, despite a modest reduction in output power, which remains less than 3 %.

Acoustic noise reduction in the NexGen 7 T scanner.

Driven by the Lorentz force, acoustic noise may arguably be the next physiological challenge associated with ultra-high field MRI scanners and powerful gradient coils. This work consisted of isolating and mitigating the main sound pathway in the NexGen 7 T scanner equipped with the investigational Impulse head gradient coil. Sound pressure level (SPL) measurements were performed with and without the RF coil to assess its acoustic impact. Vibration measurements were carried out on the gradient coil, the RF coil, and on the patient table to distinguish the different vibration mechanisms and pathways. Vibrations of the RF coil were modified by either making contact with the patient bore liner with padding material or by changing directly the RF shield with phosphor bronze mesh material. SPL and vibration measurements demonstrated that eddy-currents induced in the RF shield were the primary cause of acoustic noise. Replacing the conventional solid copper shield with phosphor bronze mesh material altered the vibrations of the RF shield and decreased SPL by 6 to 8 dB at the highest frequencies in EPI, depending on the gradient axis, while boosting the transmit B1 + field by 15%. Padding led to slightly less sound reduction on the X and Z gradient axes, but with minimal impact for the Y axis. This study demonstrates the potential importance of eddy-current induced vibrations in the RF coil in terms of acoustic noise and opens new horizons for mitigation measures.

The combustion characteristics and stable limit of a novel combustor with gradient porous media for hydrogen-enriched natural gas

Injecting hydrogen into natural gas pipelines for delivery to end users is currently considered as one of the potential solutions to the challenges of hydrogen transportation and utilization. However, the blending of hydrogen accelerates the flame propagation speed of the mixture, leading to flame instability and other issues. In this paper, a gradient porous structural burner was proposed, then the effects of pore size gradient and porosity gradient on the combustion characteristics and stability limits of hydrogen-enriched natural gas flames were investigated numerically. This paper proposed a spatial gradient-based porous structure, and the results showed that the axial gradient porous structure with increasing pore size enhances the maximum temperature by approximately 26 %. The radial gradient structures with decreasing porosity and increasing pore size increased the maximum temperature by approximately 25.8 % and 24.8 %, respectively, and improved flame uniformity. Compared to the conventional two-stage uniform structure, the axial pore size increment structure improved the stability limit by approximately 117 %, while the radial pore size increment structure increased the stability limit by 47 %. The results provide reference for the design and optimization of new porous media burner structures that are applicable under wide power ranges and hydrogen blending conditions.

Effect of Additive Manufactured Gyroid Porous Structure of Hybrid Gradients on Mechanical and Failure Properties

In bone tissue engineering, good structural and forming qualities are prerequisites for the long-term implantation of scaffolds. To mitigate the stress-shielding effect between porous bone scaffolds and the human skeleton, this study proposes a method for designing non-linear gradient gyroid porous structures with radial-axial hybrid gradients that are precisely controlled by multivariate polynomial functions to simulate human bone characteristics. The influence of the volumetric energy density on the forming quality of the porous structures was evaluated by characterizing the internal strut morphology and measuring the strut width and porosity. Finite element analysis combined with experimental observations revealed that during compression, the thin struts at the top and bottom of the hybrid-gradient porous structure deformed first, and the compressive stress and shear stress were gradually transferred from the thin struts at the upper and lower ends of the structure to the thicker struts in the middle. Compared with the axial gradient, the edge struts of the hybrid-gradient porous structures can withstand higher shear and compressive stresses. Furthermore, owing to the variation in the radial gradient, compared to structures with 20 % axial porosity variation, the hybrid-gradient porous structure with 40 % radial porosity variation and 20 % axial porosity variation exhibited an 18.10 % increase in elastic modulus and a 4.29 % increase in yield strength. Additionally, its effective energy absorption was 20.39 % higher than that of the homogeneous structures. Compared to radial-gradient porous structures, the hybrid-gradient porous structure showed a lower sensitivity of the elastic modulus and yield strength to the volumetric energy density.

Bi-planar magnetic stabilisation coils for an inertial sensor based on atom interferometry

Inertial sensors that measure the acceleration of ultracold atoms promise unrivalled accuracy compared to classical equivalents. However, atomic systems are sensitive to various perturbations, including magnetic fields, which can introduce measurement inaccuracies. To address this challenge, we have designed, manufactured, and validated a magnetic field stabilisation system for a quantum sensor based on atom interferometry. We solve for the magnetic field generated by surface currents in-between a pair of bi-rectangular coils and approximate the surface current using discrete wires. The wires are wound by-hand onto machined panels which are retrofitted onto the existing mounting structure of the sensor without interfering with any experimental components. Along the central 60mm of the y-axis, which aligns with the trajectory of the atoms during interferometry, the coils are measured to generate an independent uniform axial magnetic field with a strength of Bz=22.81±0.01μT/A [mean±2σstd. error] and an independent linear axial field gradient of strength dBz/dy=10.6±0.1μT/Am. The uniform Bz field is measured to deviate by a maximum value of 1.3% in the same region, which is a factor of three times more uniform than the previously-used on-sensor rectangular Bz compensation set.

Enhanced strength–ductility synergy in Ti55531 titanium alloys through gradient microstructural design strategy

The strength-ductility trade-off dilemma still exists for titanium alloys, which is a challenging and pressing issue within the realm of microstructure design and property control. In the present work, a typical axial gradient microstructure was prepared in Ti55531 titanium alloy through a composite strengthening process involving rapid electropulsing treatment (EPT) combined with step-quench treatment (SQT). The results show that a significant improvement of 450 MPa (54 %) and 6.3 % (100 %) for the strength and ductility are obtained respectively for gradient microstructure by EPT + SQT (GMES) compared to that gradient microstructure prepared by EPT (GME) only. This indicates that the enhanced strength-ductility synergy observed in GMES is attributed to the characteristic Twinning induced Plasticity (TWIP) mechanism employed in this novel design of gradient microstructure. Furthermore, a detailed analysis and discussion are provided on the physical deformation mechanism and crack initiation behaviour of the gradient microstructure, providing valuable insights for the design of high-strength, high-ductility metals such as beta titanium alloys, advanced steels, and multi-phase alloys.

Functional connectome through the human life span.

The lifespan growth of the functional connectome remains unknown. Here, we assemble task-free functional and structural magnetic resonance imaging data from 33,250 individuals aged 32 postmenstrual weeks to 80 years from 132 global sites. We report critical inflection points in the nonlinear growth curves of the global mean and variance of the connectome, peaking in the late fourth and late third decades of life, respectively. After constructing a fine-grained, lifespan-wide suite of system-level brain atlases, we show distinct maturation timelines for functional segregation within different systems. Lifespan growth of regional connectivity is organized along a primary-to-association cortical axis. These connectome-based normative models reveal substantial individual heterogeneities in functional brain networks in patients with autism spectrum disorder, major depressive disorder, and Alzheimer's disease. These findings elucidate the lifespan evolution of the functional connectome and can serve as a normative reference for quantifying individual variation in development, aging, and neuropsychiatric disorders.

Prognostic Value of MRI Assessment of Residual Peritumoral Edema in Breast Cancer Treated With Neoadjuvant Chemotherapy.

Peritumoral edema (PE) identified on T2-weighted breast MRI is a factor for poor prognosis in breast cancer. To assess the prognostic value of residual PE (rPE) in patients with PE positive breast cancer prior to neoadjuvant chemotherapy (NACT) who subsequently underwent curative surgery. Retrospective. In total, 128 patients with nonmetastatic invasive breast cancer who underwent breast MRI before and after NACT. Axial precontrast 2D fast spin echo T2W fat-suppressed sequence. Axial dynamic 3D gradient echo T1W fat-suppressed sequence. PE was diagnosed when a signal intensity as high as water was detected surrounding the tumor on a T2-weighted breast MRI. PE was qualitatively evaluated by three readers with more than 20 years of experience in interpreting breast field imaging findings. Residual cancer burden (RCB) were assessed post-NACT. Recurrence-free survival (RFS) and overall survival (OS) were evaluated as the endpoints of this study. Chi-square test; Kaplan-Meier method, log-rank test, and Cox proportional hazard model. A P-value <0.05 was considered statistically significant. Pre-PE was observed in 64 out of 128 patients. Of these, rPE was observed in 21. In the log-rank test, breast cancer with rPE had significantly worse RFS and OS than that without rPE. Cox proportional hazard analysis identified rPE as a significant prognostic factor for recurrence (hazard ratio, 11.6; 95% confidence interval [CI], 3.05-43.8) and death (hazard ratio, 17.8; 95% CI, 3.30-96.3). Breast cancer with rPE had significant worse RFS and OS than that without rPE in RCB class II, and significant worse OS in pathological complete response, class I and class II in the log-rank test. rPE on a T2-weighted breast MRI was a significant factor for breast cancer recurrence and death in patients with pre-PE-positive breast cancer treated with NACT. Stage 2.

Customized 3D‐printed heterogeneous porous titanium scaffolds for bone tissue engineering

AbstractBone defect is a common clinical disease. Due to the uncertainty of trauma or infection areas, customized size features are often required for bone substitutes. By inspiration of the natural bone structure, this study designs porous scaffolds with a biomimetic design perspective by using different inner and outer pore units. The outer pore units adopt body‐centered cubic (BCC) structure to simulate the weight‐bearing function of human cortical bone, while inner pore units using I‐Wrapped Package structure, a kind of three periods minimum surface, to obtain a good permeability and simulates the inner layer of cancellous bone. To further regulate the overall modulus of the scaffold within the range of natural bone modulus in the human body, the scaffold was designed to axial gradient structure. Compression experiments were conducted, and the results indicated that when the volume fraction linearly increased from 20% to 50%, the Young's modulus was close to the cortical bone modulus in the human body. In vitro cell experiments further proved that osteoblasts have good cellular activity and spreading morphology on the surface of this scaffold. The customized 3D‐printed heterogeneous porous titanium scaffold has great application potential in bone tissue engineering.

Functional gradients reveal cortical hierarchy changes in multiple sclerosis

AbstractFunctional gradient (FG) analysis represents an increasingly popular methodological perspective for investigating brain hierarchical organization but whether and how network hierarchy changes concomitant with functional connectivity alterations in multiple sclerosis (MS) has remained elusive. Here, we analyzed FG components to uncover possible alterations in cortical hierarchy using resting‐state functional MRI (rs‐fMRI) data acquired in 122 MS patients and 97 healthy control (HC) subjects. Cortical hierarchy was assessed by deriving regional FG scores from rs‐fMRI connectivity matrices using a functional parcellation of the cerebral cortex. The FG analysis identified a primary (visual‐to‐sensorimotor) and a secondary (sensory‐to‐transmodal) component. Results showed a significant alteration in cortical hierarchy as indexed by regional changes in FG scores in MS patients within the sensorimotor network and a compression (i.e., a reduced standard deviation across all cortical parcels) of the sensory‐transmodal gradient axis, suggesting disrupted segregation between sensory and cognitive processing. Moreover, FG scores within limbic and default mode networks were significantly correlated (, p &lt; .005 after Bonferroni correction for both) with the symbol digit modality test (SDMT) score, a measure of information processing speed commonly used in MS neuropsychological assessments. Finally, leveraging supervised machine learning, we tested the predictive value of network‐level FG features, highlighting the prominent role of the FG scores within the default mode network in the accurate prediction of SDMT scores in MS patients (average mean absolute error of 1.22 ± 0.07 points on a hold‐out set of 24 patients). Our work provides a comprehensive evaluation of FG alterations in MS, shedding light on the hierarchical organization of the MS brain and suggesting that FG connectivity analysis can be regarded as a valuable approach in rs‐fMRI studies across different MS populations.

Symmetric/Asymmetric Vibrational Characteristics of Bi-Directional Functionally Graded Annular Microplates

In this study, a free vibration model of bi-directional functionally graded (BD-FG) annular microplates is established based on the modified couple stress theory (MCST) and the first-order shear deformation theory (FSDT), and the corresponding governing equations are derived from Hamilton’s principle. The annular microplates are assumed to be composed of metal and ceramic materials, and the equivalent material properties are a combination of power-law function and exponential ones. The generalized differential quadrature method (GDQM) is used to obtain the vibration frequencies and mode displacements for the C–C, S–C, C–S, and S–S (S: simply supported; C: clamped) annular microplates. The convergence and validity of the proposed model are verified through selective numerical examples. Further, the effects of gradient index, material length scale parameter, boundary conditions, and geometrical dimensions on the symmetric/asymmetric vibration frequencies of the annular microplate are explored. The modal assurance criterion is applied to estimate the influence of the radial gradient index and material length scale parameter on different-order mode displacements of the annular microplate. The results show that: (1) the vibration frequencies of the annular microplate are sensitive to changes in the geometry and boundary conditions; (2) compared with the axial gradient index, the radial gradient index not only affects the vibration frequencies of the annular microplate, but also impacts the distribution of the highest and lowest points of the vibration mode displacements as well as the vibration mode nodal lines; (3) as the material length scale parameter increases, the vibration frequencies are significantly increased, and the higher-order vibration modes of the annular microplate also change.

Gradient matters via filament diameter-adjustable 3D printing

Gradient matters with hierarchical structures endow the natural world with excellent integrity and diversity. Currently, direct ink writing 3D printing is attracting tremendous interest, and has been used to explore the fabrication of 1D and 2D hierarchical structures by adjusting the diameter, spacing, and angle between filaments. However, it is difficult to generate complex 3D gradient matters owing to the inherent limitations of existing methods in terms of available gradient dimension, gradient resolution, and shape fidelity. Here, we report a filament diameter-adjustable 3D printing strategy that enables conventional extrusion 3D printers to produce 1D, 2D, and 3D gradient matters with tunable heterogeneous structures by continuously varying the volume of deposited ink on the printing trajectory. In detail, we develop diameter-programmable filaments by customizing the printing velocity and height. To achieve high shape fidelity, we specially add supporting layers at needed locations. Finally, we showcase multi-disciplinary applications of our strategy in creating horizontal, radial, and axial gradient structures, letter-embedded structures, metastructures, tissue-mimicking scaffolds, flexible electronics, and time-driven devices. By showing the potential of this strategy, we anticipate that it could be easily extended to a variety of filament-based additive manufacturing technologies and facilitate the development of functionally graded structures.