87 research outputs found
Heave Motion Measurement by Adaptive Filter Based on Longuet-Higgins Wave Model
A method is proposed to obtain heave motion information based on the Longuet-Higgins wave model. The Longuet-Higgins wave model which is closer to the sea wave is introduced. Based on it, random process of the noise is analyzed and the highpass filter is designed to reduce errors. Then it is the key point in this article that an adaptive algorithm is put forward because of the complexity of the waves. The algorithm adjusts the cutoff frequency to reduce the amplitude attenuation of the filter by analyzing the wave. For the same reason the comprehensive parameter of the phase compensation can be also obtained by the algorithm. Simulation measurement results show that under the rough sea situation the maximum value of absolute error is 0.4942 m according to the normal method, the method is 0.1170 m, and the average error ratio of the rough sea test reduces to 3.89% from 12.54%, which demonstrates that the adaptive filter is more effective in measuring heave movement. A variety of simulation cases show that the adaptive filter can also improve the precision of the heave motion under different sea situations
The effect of Cu content on corrosion, wear and tribocorrosion resistance of Ti-Mo-Cu alloy for load-bearing bone implants
In this study, the effects of Cu content on wear, corrosion, and tribocorrosion resistance of Ti-10Mo-xCu alloy were investigated. Results revealed that hardness of Ti-10Mo-xCu alloy increased from 355.1 ± 15.2 HV to 390.8 ± 17.6 HV by increasing Cu content from 0 % to 5 %, much higher than CP Ti (106.6 ± 15.1 HV) and comparable to Ti64 (389.7 ± 13.9 HV). With a higher Cu content, wear and tribocorrosion resistance of Ti-10Mo-xCu alloys were enhanced, and corrosion resistance showed an initial increase with a subsequent decrease. Wear mechanisms under pure mechanical wear and tribocorrosion conditions of Ti-10Mo-xCu alloys were a combination of delamination, abrasion and adhesion wear
Design and performance evaluation of additively manufactured composite lattice structures of commercially pure Ti (CP-Ti)
Ti alloys with lattice structures are garnering more and more attention in the field of bone repair or regeneration
due to their superior structural, mechanical, and biological properties. In this study, six types of composite lattice
structures with different strut radius that consist of simple cubic (structure A), body-centered cubic (structure B),
and edge-centered cubic (structure C) unit cells are designed. The designed structures are firstly simulated and
analysed by the finite element (FE) method. Commercially pure Ti (CP–Ti) lattice structures with optimized unit
cells and strut radius are then fabricated by selective laser melting (SLM), and the dimensions, microtopography,
and mechanical properties are characterised. The results show that among the six types of composite lattice
structures, combined BA, CA, and CB structures exhibit smaller maximum von-Mises stress, indicating that these
structures have higher strength. Based on the fitting curves of stress/specific surface area versus strut radius, the
optimized strut radius of BA, CA, and CB structures is 0.28, 0.23, and 0.30 mm respectively. Their corresponding
compressive yield strength and compressive modulus are 42.28, 30.11, and 176.96 MPa, and 4.13, 2.16, and
7.84 GPa, respectively. The CP-Ti with CB unit structure presents a similar strength and compressive modulus to
the cortical bone, which makes it a potential candidate for subchondral bone restorations
Fast-MC-PET: A Novel Deep Learning-aided Motion Correction and Reconstruction Framework for Accelerated PET
Patient motion during PET is inevitable. Its long acquisition time not only
increases the motion and the associated artifacts but also the patient's
discomfort, thus PET acceleration is desirable. However, accelerating PET
acquisition will result in reconstructed images with low SNR, and the image
quality will still be degraded by motion-induced artifacts. Most of the
previous PET motion correction methods are motion type specific that require
motion modeling, thus may fail when multiple types of motion present together.
Also, those methods are customized for standard long acquisition and could not
be directly applied to accelerated PET. To this end, modeling-free universal
motion correction reconstruction for accelerated PET is still highly
under-explored. In this work, we propose a novel deep learning-aided motion
correction and reconstruction framework for accelerated PET, called
Fast-MC-PET. Our framework consists of a universal motion correction (UMC) and
a short-to-long acquisition reconstruction (SL-Reon) module. The UMC enables
modeling-free motion correction by estimating quasi-continuous motion from
ultra-short frame reconstructions and using this information for
motion-compensated reconstruction. Then, the SL-Recon converts the accelerated
UMC image with low counts to a high-quality image with high counts for our
final reconstruction output. Our experimental results on human studies show
that our Fast-MC-PET can enable 7-fold acceleration and use only 2 minutes
acquisition to generate high-quality reconstruction images that
outperform/match previous motion correction reconstruction methods using
standard 15 minutes long acquisition data.Comment: Accepted at Information Processing in Medical Imaging (IPMI 2023
Genetic and Clinical Profiles of Disseminated Bacillus Calmette-Guérin Disease and Chronic Granulomatous Disease in China
Background: Disseminated Bacillus Calmette-Guérin disease (D-BCG) in children with chronic granulomatous disease (CGD) can be fatal, while its clinical characteristics remain unclear because both diseases are extremely rare. The patients with CGD receive BCG vaccination, because BCG vaccination is usually performed within 24 h after delivery in China.Methods: We prospectively followed-up Chinese patients with CGD who developed D-BCG to characterize their clinical and genetic characteristics. The diagnoses were based on the patients' clinical, genetic, and microbiological characteristics.Results: Between September 2009 and September 2016, we identified 23 patients with CGD who developed D-BCG. Their overall 10-year survival rate was 34%. We created a simple dissemination score to evaluate the number of infected organ systems and the survival probabilities after 8 years were 62 and 17% among patients with simple dissemination scores of ≤3 and >3, respectively (p = 0.0424). Survival was not significantly associated with the CGD stimulation index or interferon-γ treatment. Eight patients underwent umbilical cord blood transplantation and 5 of them were successfully treated. The genetic analyses found mutations in CYBB (19 patients), CYBA (1 patient), NCF1 (1 patient), and NCF2 (1 patient). We identified 6 novel highly likely pathogenic mutations, including 4 mutations in CYBB and 2 mutations in NCF1.Conclusions: D-BCG is a deadly complication of CGD. The extent of BCG spreading is strongly associated with clinical outcomes, and hematopoietic stem cell transplantation may be a therapeutic option for this condition
The Optimization of Ti Gradient Porous Structure Involves the Finite Element Simulation Analysis
Titanium (Ti) and its alloys are attracting special attention in the field of dentistry and orthopedic bioengineering because of their mechanical adaptability and biological compatibility with the natural bone. The dental implant is subjected to masticatory forces in the oral environment and transfers these forces to the surrounding bone tissue. Therefore, by simulating the mechanical behavior of implants and surrounding bone tissue we can assess the effects of implants on bone growth quite accurately. In this study, dental implants with different gradient pore structures that consisted of simple cubic (structure a), body centered cubic (structure b) and side centered cubic (structure c) were designed, respectively. The strength of the designed gradient porous implant in the oral environment was simulated by three-dimensional finite element simulation technique to assess the mechanical adaptation by the stress-strain distribution within the surrounding bone tissue and by examining the fretting of the implant-bone interface. The results show that the maximum equivalent stress and strain in the surrounding bone tissue increase with the increase of porosity. The stress distribution of the gradient implant with a smaller difference between outer and inner pore structure is more uniform. So, a-b type porous implant exhibited less stress concentration. For a-b structure, when the porosity is between 40 and 47%, the stress and strain of bone tissue are in the range of normal growth. When subject to lingual and buccal stresses, an implant with higher porosity can achieve more uniform stress distribution in the surrounding cancellous bone than that of low porosity implant. Based on the simulated results, to achieve an improved mechanical fixation of the implant, the optimum gradient porous structure parameters should be: average porosity 46% with an inner porosity of 13% (b structure) and outer porosity of 59% (a structure), and outer pore sized 500 μm. With this optimized structure, the bone can achieve optimal ingrowth into the gradient porous structure, thus provide stable mechanical fixation of the implant. The maximum equivalent stress achieved 99 MPa, which is far below the simulation yield strength of 299 MPa
SHP-2 Promotes the Maturation of Oligodendrocyte Precursor Cells Through Akt and ERK1/2 Signaling In Vitro
Background: Oligodendrocyte precursor cells (OPCs) differentiate into oligodendrocytes (OLs), which are responsible for myelination. Myelin is essential for saltatory nerve conduction in the vertebrate nervous system. However, the molecular mechanisms of maturation and myelination by oligodendrocytes remain elusive. Methods and Findings: In the present study, we showed that maturation of oligodendrocytes was attenuated by sodium orthovanadate (a comprehensive inhibitor of tyrosine phosphatases) and PTPi IV (a specific inhibitor of SHP-2). It is also found that SHP-2 was persistently expressed during maturation process of OPCs. Down-regulation of endogenous SHP-2 led to impairment of oligodendrocytes maturation and this effect was triiodo-L-thyronine (T3) dependent. Furthermore, overexpression of SHP-2 was shown to promote maturation of oligodendrocytes. Finally, it has been identified that SHP-2 was involved in activation of Akt and extracellular-regulated kinases 1 and 2 (ERK1/2) induced by T3 in oligodendrocytes
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