A variety of precise experiments have been carried out to establish the character of the superconducting state in Sr2RuO4. Many of these appear to imply contradictory conclusions concerning the ...symmetries of this state. Here we propose that these results can be reconciled if we assume that there is a near-degeneracy between a dx2−y2 (B1g in group theory nomenclature) and a gxy(x2−y2) (A2g) superconducting state. From a weak-coupling perspective, such an accidental degeneracy can occur at a point at which a balance between the on-site and nearest-neighbor repulsions triggers a d-wave to g-wave transition.
Nucleation plays a critical role in many physical and biological phenomena that range from crystallization, melting and evaporation to the formation of clouds and the initiation of neurodegenerative ...diseases
. However, nucleation is a challenging process to study experimentally, especially in its early stages, when several atoms or molecules start to form a new phase from a parent phase. A number of experimental and computational methods have been used to investigate nucleation processes
, but experimental determination of the three-dimensional atomic structure and the dynamics of early-stage nuclei has been unachievable. Here we use atomic electron tomography to study early-stage nucleation in four dimensions (that is, including time) at atomic resolution. Using FePt nanoparticles as a model system, we find that early-stage nuclei are irregularly shaped, each has a core of one to a few atoms with the maximum order parameter, and the order parameter gradient points from the core to the boundary of the nucleus. We capture the structure and dynamics of the same nuclei undergoing growth, fluctuation, dissolution, merging and/or division, which are regulated by the order parameter distribution and its gradient. These experimental observations are corroborated by molecular dynamics simulations of heterogeneous and homogeneous nucleation in liquid-solid phase transitions of Pt. Our experimental and molecular dynamics results indicate that a theory beyond classical nucleation theory
is needed to describe early-stage nucleation at the atomic scale. We anticipate that the reported approach will open the door to the study of many fundamental problems in materials science, nanoscience, condensed matter physics and chemistry, such as phase transition, atomic diffusion, grain boundary dynamics, interface motion, defect dynamics and surface reconstruction with four-dimensional atomic resolution.
Currently, clinically available orthopedic implants are extremely biocompatible but they lack specific biological characteristics that allow for further interaction with surrounding tissues. The ...extracellular matrix (ECM)-coated scaffolds have received considerable interest for bone regeneration due to their ability in upregulating regenerative cellular behaviors. This study delves into the designing and fabrication of three-dimensional (3D)-printed scaffolds that were made out of calcium silicate (CS), polycaprolactone (PCL), and decellularized ECM (dECM) from MG63 cells, generating a promising bone tissue engineering strategy that revolves around the concept of enhancing osteogenesis by creating an osteoinductive microenvironment with osteogenesis-promoting dECM. We cultured MG63 on scaffolds to obtain a dECM-coated CS/PCL scaffold and further studied the biological performance of the dECM hybrid scaffolds. The results indicated that the dECM-coated CS/PCL scaffolds exhibited excellent biocompatibility and effectively enhanced cellular adhesion, proliferation, and differentiation of human Wharton's Jelly mesenchymal stem cells by increasing the expression of osteogenic-related genes. They also presented anti-inflammatory characteristics by showing a decrease in the expression of tumor necrosis factor-alpha (TNF-α) and interleukin-1 (IL-1). Histological analysis of in vivo experiments presented excellent bone regenerative capabilities of the dECM-coated scaffold. Overall, our work presented a promising technique for producing bioscaffolds that can augment bone tissue regeneration in numerous aspects.
Calcium silicate (CS) cements have excellent bioactivity and can induce the bone-like apatite formation. They are good biomaterials for bone tissue engineering and bone regenerative medicine. ...However, they have degradability and the dissolved CS can cause the inflammatory response at the early post-implantation stage. The purpose of this study was to design and prepare the curcumin-loaded mesoporous CS (MesoCS/curcumin) cements as a strategy to reduce the inflammatory reaction after implantation.
The MesoCS/curcumin cements were designed and prepared. The characteristics of MesoCS/curcumin specimens were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their physical properties, biocompatibility, and anti-inflammatory ability were also evaluated.
The MesoCS/curcumin cements displayed excellent biocompatibility and physical properties. Their crystalline characterizations were very similar with MesoCS cements. After soaking in simulated body fluid, the bone-like apatite layer of the MesoCS/curcumin cements could be formed. In addition, it could inhibit the expression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) after inflammation reaction induced by lipopolysaccharides and had good anti-inflammatory ability.
Adding curcumin in MesoCS cements can reduce the inflammatory reaction, but does not affect the original biological activity and properties of MesoCS cements. It can provide a good strategy to inhibit the inflammatory reaction after implantation for bone tissue engineering and bone regenerative medicine.
Various surgical techniques exist to repair or reconstruct complete scapholunate (SL) interosseous ligament tears, including capsulodesis, static or dynamic tenodesis, ligament reconstruction with ...tendon graft, bone-retinaculum-bone reconstruction, and the reduction and association of the scaphoid and lunate (RASL) procedure. The choice of surgical technique depends on arthroscopic assessment using the Geissler classification and European Wrist Arthroscopy Society staging of SL injury. This article describes arthroscopy-assisted extracapsular SL reconstruction using free tendon graft and internal brace augmentation for the treatment of unrepairable complete SL interosseous ligament tears.
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3D printing has been popularly used in the bone tissue engineering, as many of the biomaterials for this field of study can be prepared for and produced from this additive manufacturing technique. In ...this study, we strategized a solvent-free processing to fabricate the polydopamine-modified calcium silicate (PDACS)/poly-caprolactone (PCL) scaffold with Wharton's jelly mesenchymal stem cells (WJMSCs) incorporated with human umbilical vein endothelial cells (HUVEC)-laden hydrogel. The PDACS/PCL/hydrogel 3D scaffold yielded a Young's modulus of the 3D scaffolds as high as 75 MPa. In addition, the vascular morphogenesis and cellular behaviors regulated by our hybrid scaffolds were also intricately evaluated. Furthermore, the HUVEC in the bioink exhibited higher levels of angiogenic biomarkers and showed potential for the formation of complex vascular networks. Higher levels of bone formation proteins were also observed in our composites. Such a hybrid of synthetic materials with cell constituents not only enhances osteogenesis but also stimulates vessel network development in angiogenesis, presenting the fact that 3D printing can be further applied in improving bone tissue regeneration in numerous aspects. We believe that this method may serve as a useful and effective approach for the regeneration of defective complex hard tissues in deep bone structures.
•Bioscaffold contained the polydopamine-coated calcium silicate (PDACS)/poly-caprolactone with stem cells incorporated with bioink.•HUVECs in the bioink exhibited higher levels of angiogenic biomarkers and showed potential for the formation of complex vascular networks.•Higher levels of bone formation proteins were also observed in our fabricated composite scaffolds.•This cell-laden hydrogel/ mussel-inspired PDACS hierarchical 3D porous scaffold shows great potential for future orthopaedic applications.
Current machine learning models for pneumonia detection perform poorly compared to those for other diseases. I aim to use a novel approach to build a model that can improve on performance and be ...applicable to other diseases.
My approach uses multi-tier neural networks instead of using single convolutional neural networks (CNNs) like what other researchers have done. My multi-tier model consists of three tier-1 Neural Networks (NNs) and one tier-2 NN. For the tier-1 NN, I use 3 selected ImageNet-trained CNNs (ResNet152V2, DenseNet201, and NASNet Hub) as the starting bases, and train each of them via transfer learning. Then, a tier-2 NN is employed to combine the prediction results from the well-trained tier-1 NNs. The tier-2 NN model is trained with the same dataset. It produces the final predictions with substantially improved performance. The dataset used for my model is pre-processed by me, and based on a public chest X-ray dataset from the NIHCC.
My model achieved an AUC score of 76.5%, which is better than each of the tier-1 NNs alone and better than most existing models created by others.
My multi-tier approach accurately detects pneumonia from chest X-rays. It’s practical and it employs incremental learning, meaning it can be continuously improved over time. In the future, I could extend my model from binary classification to multiclass classification, apply it for lung cancer, or even other diseases.
The present study provides a solvent-free processing method for establishing the ideal porous 3-dimension (3D) scaffold filled with different ratios of calcium silicate-based (CS) powder and ...polycaprolactone (PCL) for 3D bone substitute application. Characterization of hybrid scaffolds developed underwent assessments for physicochemical properties and biodegradation. Adhesion and growth of human Wharton’s Jelly mesenchymal stem cells (WJMSCs) on the CS/PCL blended scaffold were investigated
in vitro
. Cell attachment and morphology were examined by scanning electron microscope (SEM) and confocal microscope observations. Colorimetric assay was tested for assessing cell metabolic activity. In addition, RT-qPCR was also performed for the osteogenic-related and angiogenesis-related gene expression. As a result, the hydrophilicity of the scaffolds was further significantly improved after we additive CS into PCL, as well as the compressive strength up to 5.8 MPa. SEM showed that a great amount of precipitated bone-like apatite formed on the scaffold surface after immersed in the simulated body fluid. The 3D-printed scaffolds were found to enhance cell adhesion, proliferation and differentiation. Additionally, results of osteogenesis and angiogenesis proteins were expressed obviously greater in the response of WJMSCs. These results indicate the CS/PCL composite exhibited a favorable bioactivity and osteoconductive properties that could be served as a promising biomaterial for bone tissue engineering scaffolds.
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