162 research outputs found
The Effect of High Tibial Osteotomy Correction Angle on Cartilage and Meniscus Loading Using Finite Element Analysis
Medial opening wedge high tibial osteotomy (MOWHTO) is a popular clinical method for curing the osteoarthritis (OA) caused by varus deformity. However, the ideal alignment to maximize osteotomy successful rate and post-operative knee function remains controversial to date. Moreover, the between-patient variability of knee joint biomechanics, particularly during functional tasks, signifies critical importance of conducting patient-specific planning. For this reason, this study introduces a subject-specific modeling procedure to determine the biomechanical effects of simulated different alignments of MOWHTO on tibiofemoral cartilage stress distribution. A 3D finite element (FE) knee model was developed from MRI images of a healthy living subject and used to simulate different alignments following MOWHTO (i.e. 0.2°, 2.7°, 3.9° and 6.6° valgus). Loading and boundary conditions were assigned based on the subject-specific kinematic and kinetic data recorded during gait tests. The compressive and shear stress distributions in the femoral cartilage and tibia cartilage were quantified. It was found that when the loading axis shifted laterally, the peak stresses in the medial compartment decreased, but increased in the lateral compartment. The findings suggest that equal loading between two compartments can be successfully achieved by performing MOWHTO with a HKA angle around 3.9 to 6.6° valgus. More importantly, this patient-specific non-invasive analysis of stress distribution that provided a quantitative insight to evaluate the mechanical responses of the soft tissue within knee joint as a result of adjusting the loading axis, may be used as a preoperative assessment tool to predict the consequential mechanical loading information for surgeon to decide the patient specific optimal angle
Asymptotic-Preserving Neural Networks for Multiscale Kinetic Equations
In this paper, we present two novel Asymptotic-Preserving Neural Networks
(APNNs) for tackling multiscale time-dependent kinetic problems, encompassing
the linear transport equation and Bhatnagar-Gross-Krook (BGK) equation with
diffusive scaling. Our primary objective is to devise efficient and accurate
APNN approaches for resolving multiscale kinetic equations. We have established
a neural network based on even-odd decomposition and concluded that enforcing
the initial condition for the linear transport equation with inflow boundary
conditions is crucial. This APNN method based on even-odd parity relaxes the
stringent conservation prerequisites while concurrently introducing an
auxiliary deep neural network. Additionally, we have incorporated the
conservation laws of mass, momentum, and energy for the Boltzmann-BGK equation
into the APNN framework by enforcing exact boundary conditions. This is our
second contribution. The most notable finding of this study is that
approximating the zeroth, first and second moments of the particle density
distribution is simpler than the distribution itself. Furthermore, a compelling
phenomenon in the training process is that the convergence of density is
swifter than that of momentum and energy. Finally, we investigate several
benchmark problems to demonstrate the efficacy of our proposed APNN methods
Effects of Different Dietary Lipid Sources on Spawning Performance, Egg and Larval Quality, and Egg Fatty Acid Composition in Tongue Sole Cynoglossus semilaevis
A 60-day feeding experiment was conducted to investigate the effects of dietary lipid sources on reproduction of Cynoglossus semilaevis. Experimental diets were formulated with similar proximate compositions but different lipid sources (6.5%): fish oil (FO), soybean oil (SO) and olive oil (OO). The results showed that the relative fecundity in group FO and OO was significantly higher than that in group SO. Group OO showed a significantly higher buoyant egg rate than group FO and SO. The hatching rate and larval survival rate at 7 days post hatching were the highest in group FO, followed by group OO, and group SO recorded the lowest values. Group FO showed significantly higher egg diameter and larval survival activity index (SAI) and significantly lower larval deformity rate compared to group SO and OO. Fatty acid compositions of eggs reflected closely those of the diets. These results showed that the olive oil supplement in diets for tongue sole positively influenced the broodstock fecundity and buoyant egg rate though fish oil resulted in the highest hatching rate and best larval quality among the tested oils. The dietary soybean oil supplement reduced the spawning performance, and egg and larval quality
Asymptotic-Preserving Convolutional DeepONets Capture the Diffusive Behavior of the Multiscale Linear Transport Equations
In this paper, we introduce two types of novel Asymptotic-Preserving
Convolutional Deep Operator Networks (APCONs) designed to address the
multiscale time-dependent linear transport problem. We observe that the vanilla
physics-informed DeepONets with modified MLP may exhibit instability in
maintaining the desired limiting macroscopic behavior. Therefore, this
necessitates the utilization of an asymptotic-preserving loss function. Drawing
inspiration from the heat kernel in the diffusion equation, we propose a new
architecture called Convolutional Deep Operator Networks, which employ multiple
local convolution operations instead of a global heat kernel, along with
pooling and activation operations in each filter layer. Our APCON methods
possess a parameter count that is independent of the grid size and are capable
of capturing the diffusive behavior of the linear transport problem. Finally,
we validate the effectiveness of our methods through several numerical
examples
Iterative PnP and its application in 3D-2D vascular image registration for robot navigation
This paper reports on a new real-time robot-centered 3D-2D vascular image
alignment algorithm, which is robust to outliers and can align nonrigid shapes.
Few works have managed to achieve both real-time and accurate performance for
vascular intervention robots. This work bridges high-accuracy 3D-2D
registration techniques and computational efficiency requirements in
intervention robot applications. We categorize centerline-based vascular 3D-2D
image registration problems as an iterative Perspective-n-Point (PnP) problem
and propose to use the Levenberg-Marquardt solver on the Lie manifold. Then,
the recently developed Reproducing Kernel Hilbert Space (RKHS) algorithm is
introduced to overcome the ``big-to-small'' problem in typical robotic
scenarios. Finally, an iterative reweighted least squares is applied to solve
RKHS-based formulation efficiently. Experiments indicate that the proposed
algorithm processes registration over 50 Hz (rigid) and 20 Hz (nonrigid) and
obtains competing registration accuracy similar to other works. Results
indicate that our Iterative PnP is suitable for future vascular intervention
robot applications.Comment: Submitted to ICRA 202
Optical flow-based vascular respiratory motion compensation
This paper develops a new vascular respiratory motion compensation algorithm,
Motion-Related Compensation (MRC), to conduct vascular respiratory motion
compensation by extrapolating the correlation between invisible vascular and
visible non-vascular. Robot-assisted vascular intervention can significantly
reduce the radiation exposure of surgeons. In robot-assisted image-guided
intervention, blood vessels are constantly moving/deforming due to respiration,
and they are invisible in the X-ray images unless contrast agents are injected.
The vascular respiratory motion compensation technique predicts 2D vascular
roadmaps in live X-ray images. When blood vessels are visible after contrast
agents injection, vascular respiratory motion compensation is conducted based
on the sparse Lucas-Kanade feature tracker. An MRC model is trained to learn
the correlation between vascular and non-vascular motions. During the
intervention, the invisible blood vessels are predicted with visible tissues
and the trained MRC model. Moreover, a Gaussian-based outlier filter is adopted
for refinement. Experiments on in-vivo data sets show that the proposed method
can yield vascular respiratory motion compensation in 0.032 sec, with an
average error 1.086 mm. Our real-time and accurate vascular respiratory motion
compensation approach contributes to modern vascular intervention and surgical
robots.Comment: This manuscript has been accepted by IEEE Robotics and Automation
Letter
Strain Induced One-Dimensional Landau-Level Quantization in Corrugated Graphene
Theoretical research has predicted that ripples of graphene generates
effective gauge field on its low energy electronic structure and could lead to
zero-energy flat bands, which are the analog of Landau levels in real magnetic
fields. Here we demonstrate, using a combination of scanning tunneling
microscopy and tight-binding approximation, that the zero-energy Landau levels
with vanishing Fermi velocities will form when the effective pseudomagnetic
flux per ripple is larger than the flux quantum. Our analysis indicates that
the effective gauge field of the ripples results in zero-energy flat bands in
one direction but not in another. The Fermi velocities in the perpendicular
direction of the ripples are not renormalized at all. The condition to generate
the ripples is also discussed according to classical thin-film elasticity
theory.Comment: 4 figures, Phys. Rev.
Quasi-Synchronous Random Access for Massive MIMO-Based LEO Satellite Constellations
Low earth orbit (LEO) satellite constellation-enabled communication networks
are expected to be an important part of many Internet of Things (IoT)
deployments due to their unique advantage of providing seamless global
coverage. In this paper, we investigate the random access problem in massive
multiple-input multiple-output-based LEO satellite systems, where the
multi-satellite cooperative processing mechanism is considered. Specifically,
at edge satellite nodes, we conceive a training sequence padded multi-carrier
system to overcome the issue of imperfect synchronization, where the training
sequence is utilized to detect the devices' activity and estimate their
channels. Considering the inherent sparsity of terrestrial-satellite links and
the sporadic traffic feature of IoT terminals, we utilize the orthogonal
approximate message passing-multiple measurement vector algorithm to estimate
the delay coefficients and user terminal activity. To further utilize the
structure of the receive array, a two-dimensional estimation of signal
parameters via rotational invariance technique is performed for enhancing
channel estimation. Finally, at the central server node, we propose a majority
voting scheme to enhance activity detection by aggregating backhaul information
from multiple satellites. Moreover, multi-satellite cooperative linear data
detection and multi-satellite cooperative Bayesian dequantization data
detection are proposed to cope with perfect and quantized backhaul,
respectively. Simulation results verify the effectiveness of our proposed
schemes in terms of channel estimation, activity detection, and data detection
for quasi-synchronous random access in satellite systems.Comment: 38 pages, 16 figures. This paper has been accepted by IEEE JSAC SI on
3GPP Technologies: 5G-Advanced and Beyond. Copyright may be transferred
without notice, after which this version may no longer be accessibl
Multiomics Point of Departure (moPOD) Modeling Supports an Adverse Outcome Pathway Network for Ionizing Radiation
While adverse biological effects of acute high-dose ionizing radiation have been extensively investigated, knowledge on chronic low-dose effects is scarce. The aims of the present study were to identify hazards of low-dose ionizing radiation to Daphnia magna using multiomics dose–response modeling and to demonstrate the use of omics data to support an adverse outcome pathway (AOP) network development for ionizing radiation. Neonatal D. magna were exposed to γ radiation for 8 days. Transcriptomic analysis was performed after 4 and 8 days of exposure, whereas metabolomics and confirmative bioassays to support the omics analyses were conducted after 8 days of exposure. Benchmark doses (BMDs, 10% benchmark response) as points of departure (PODs) were estimated for both dose-responsive genes/metabolites and the enriched KEGG pathways. Relevant pathways derived using the BMD modeling and additional functional end points measured by the bioassays were overlaid with a previously published AOP network. The results showed that several molecular pathways were highly relevant to the known modes of action of γ radiation, including oxidative stress, DNA damage, mitochondrial dysfunction, protein degradation, and apoptosis. The functional assays showed increased oxidative stress and decreased mitochondrial membrane potential and ATP pool. Ranking of PODs at the pathway and functional levels showed that oxidative damage related functions had relatively low PODs, followed by DNA damage, energy metabolism, and apoptosis. These were supportive of causal events in the proposed AOP network. This approach yielded promising results and can potentially provide additional empirical evidence to support further AOP development for ionizing radiation.publishedVersio
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