Kinetics of Martensite/Austenite Decomposition during Tempering of Ultrafine Nano-Bainitic Steels.

In this study, the decomposition of a martensite/austenite (M/A) microconstituent in bainitic steels was analyzed using differential scanning calorimetry (DSC) data in conjunction with Kissinger's and Johnson-Mehl-Avrami-Kolmogorov (JMAK)'s formulas. In bainitic steel subjected to austempering heat treatment, the presence of an M/A microstructure adversely affects the mechanical properties. According to the kinetic equations derived, it is observed that after tempering the sample at 600 °C for 4000 s, the generation of each phase reaches its maximum. The SEM images taken before and after tempering reveal extensive decomposition of the M/A constituent in the microstructure. The proportion of the M/A microstructure decreased significantly from about 10% before tempering to less than 1% after. Additionally, the content of residual austenite also reduced nearly to zero. These observations are consistent with the predictions of the kinetic equations.

WDFF-Net: Weighted Dual-Branch Feature Fusion Network for Polyp Segmentation With Object-Aware Attention Mechanism.

Colon polyps in colonoscopy images exhibit significant differences in color, size, shape, appearance, and location, posing significant challenges to accurate polyp segmentation. In this paper, a Weighted Dual-branch Feature Fusion Network is proposed for Polyp Segmentation, named WDFF-Net, which adopts HarDNet68 as the backbone network. First, a dual-branch feature fusion network architecture is constructed, which includes a shared feature extractor and two feature fusion branches, i.e. Progressive Feature Fusion (PFF) branch and Scale-aware Feature Fusion (SFF) branch. The branches fuse the deep features of multiple layers for different purposes and with different fusion ways. The PFF branch is to address the under-segmentation or over-segmentation problems of flat polyps with low-edge contrast by iteratively fusing the features from low, medium, and high layers. The SFF branch is to tackle the the problem of drastic variations in polyp size and shape, especially the missed segmentation problem for small polyps. These two branches are complementary and play different roles, in improving segmentation accuracy. Second, an Object-aware Attention Mechanism (OAM) is proposed to enhance the features of the target regions and suppress those of the background regions, to interfere with the segmentation performance. Third, a weighted dual-branch the segmentation loss function is specifically designed, which dynamically assigns the weight factors of the loss functions for two branches to optimize their collaborative training. Experimental results on five public colon polyp datasets demonstrate that, the proposed WDFF-Net can achieve a superior segmentation performance with lower model complexity and faster inference speed, while maintaining good generalization ability.

TP-Net: Two-Path Network for Retinal Vessel Segmentation.

Refined and automatic retinal vessel segmentation is crucial for computer-aided early diagnosis of retinopathy. However, existing methods often suffer from mis-segmentation when dealing with thin and low-contrast vessels. In this paper, a two-path retinal vessel segmentation network is proposed, namely TP-Net, which consists of three core parts, i.e. main-path, sub-path, and multi-scale feature aggregation module (MFAM). Main-path is to detect the trunk area of the retinal vessels, and the sub-path to effectively capture edge information of the retinal vessels. The prediction results of the two paths are combined by MFAM, obtaining refined segmentation of retinal vessels. In the main-path, a three-layer lightweight backbone network is elaborately designed according to the characteristics of retinal vessels, and then a global feature selection mechanism (GFSM) is proposed, which can autonomously select features that are more important for the segmentation task from the features at different layers of the network, thereby, enhancing the segmentation capability for low-contrast vessels. In the sub-path, an edge feature extraction method and an edge loss function are proposed, which can enhance the ability of the network to capture edge information and reduce the mis-segmentation of thin vessels. Finally, MFAM is proposed to fuse the prediction results of main-path and sub-path, which can remove background noises while preserving edge details, and thus, obtaining refined segmentation of retinal vessels. The proposed TP-Net has been evaluated on three public retinal vessel datasets, namely DRIVE, STARE, and CHASE DB1. The experimental results show that the TP-Net achieved a superior performance and generalization ability with fewer model parameters compared with the state-of-the-art methods.

Effect of Various Fly Ash and Ground Granulated Blast Furnace Slag Content on Concrete Properties: Experiments and Modelling.

Concrete is known as the most globally used construction material, but it releases a huge amount of greenhouse gases due to cement production. Recently, Supplementary Cementitious Materials (SCMs) such as fly ash and Ground Granulated Blast Furnace Slag (GGBFS) have been widely used in concrete to reduce the cement content. However, SCMs can alter the mechanical properties and time-dependent behaviors of concrete and the early age mechanical properties of concrete significantly affect the concrete cracking in the engineering field. Therefore, evaluation of the development of the mechanical properties of SCMs-based concrete is vital. In this paper, the time development of mechanical properties of concrete mixes with various fly ash and GGBFS was experimentally investigated. Four different cement replacement levels including 0%, 20%, 30%, and 40% by fly ash and GGBFS as well as ternary binders were considered. Compressive strength, splitting tensile strength, flexural strength, and elastic modulus of concrete were measured until 28 days. Three additional concrete mixes with ternary binders were also cast to investigate the early-age autogenous shrinkage development until 28 days. In addition, prediction models in existing standards were used and compared to experimental results. The comparison results showed that the prediction models overestimated the compressive strength but underestimated the splitting tensile strength development and autogenous shrinkage. As a result, a model capturing the effect of fly ash and GGBFS on the development of compressive and splitting tensile strength is proposed to improve the prediction accuracy for current standards and empirical models.

Combined contralateral C7 to C7 and L5 to S1 cross nerve transfer for treating limb hemiplegia after stroke.

BACKGROUND: Contralateral C7 to C7 cross nerve transfer has been proved to be safe and effective for patients with spastic arm paralysis due to stroke and traumatic brain injury. For the lower limb, contralateral L5 to S1 cross nerve transfer serves as a novel surgical approach. In many cases, patients with hemiplegia have both upper and lower limb dysfunction and hope to restore all limb functions within one operation. To cope with this demand, we performed combined contralateral C7 to C7 and L5 to S1 cross nerve transfer in two cases successfully. CASE DESCRIPTION: Two patients were enrolled in this study. The first patient is a 36-year-old woman who had spasticity and hemiplegia in both upper and lower limbs on the left side after a right cerebral hemorrhage 14 years prior. The second patient is a 64-year-old man who suffered from permanent muscle weakness in his right limbs, especially the leg, after a left cerebral hemorrhage 7 years prior. Both patients underwent the combined nerve transfer to improve upper and lower limb motor functions simultaneously. During the 10-month follow-up after surgery, the limb functions of both patients improved significantly. CONCLUSIONS: This study demonstrates the safety and benefits of combined contralateral C7 to C7 and L5 to S1 cross nerve transfer for hemiplegic patients after stroke. This novel combined surgical approach could provide an optimal choice for patients suffering from both upper and lower limb dysfunction, to reduce hospital stay while reducing financial burden.

Hydroxytyrosol contributes to cell proliferation and inhibits apoptosis in pulsed electromagnetic fields treated human umbilical vein endothelial cells in vitro.

A variety of pulsed electromagnetic fields (PEMFs) have been experimentally and clinically used in an effort to promote wound healing, although the mechanisms involved remain unknown. The aim of the present study was to investigate the action of a novel protocol of co­treatment with PEMFs and hydroxytyrosol (HTY) on the proliferation and differentiation potential of human umbilical vein endothelial cells (HUVECs). The HUVECs were assigned randomly into three groups: Control, PEMF­treated and PEMF + HT­treated. The intensity of the electromagnetic field used in this protocol was 2.25 mT, the frequency of the bursts was 50 Hz and the application time was 15 min. A Cell Counting kit­8 (CCK­8) assay was used to assess cell proliferation, and cell apoptosis was analyzed by TUNEL apoptosis assay kit and calcein­acetoxymethyl/propidium iodide dual­staining assay. In addition, protein and mRNA expression levels of protein kinase B (Akt), mechanistic target of rapamycin (mTOR), transforming growth factor (TGF)­ß1 and p53 were determined by western blotting and reverse transcription­quantitative polymerase chain reaction assays, respectively. The CCK­8 assay demonstrated that HTY contributed to HUVEC proliferation mediated by PEMFs in a time­dependent manner. The Transwell assay and scratch wound results demonstrated that co­treatment of HTY and PEMFs could increase HUVEC migration. Furthermore, the levels of apoptotic cells were reversed by pre­incubation with HTY in the PEMF treatment group, while PEMF treatment alone had no such effect. The proteins and mRNA expression levels of Akt, mTOR, TGF­ß1 were elevated in co­treatment of HTY and PEMFs, whereas there was no effect on levels of p53. Therefore, the results indicated that combined exposure of HUVECs to PEMFs and HTY exerted protective effects in HUVECs by promoting cell proliferation and inhibiting apoptosis. In conclusion, to the best of our knowledge, the present study was the first to demonstrate the beneficial roles of HTY and PEMF combined treatment in HUVECs, which may represent an effective treatment for wound healing.

Preparation and evaluation of an Arg-Gly-Asp-modified chitosan/hydroxyapatite scaffold for application in bone tissue engineering.

Bone tissue engineering has become a promising method for the repair of bone defects, and the production of a scaffold with high cell affinity and osseointegrative properties is crucial for successful bone substitute. Chitosan (CS)/hydroxyapatite (HA) composite was prepared by in situ compositing combined with lyophilization, and further modified by arginine­glycine­aspartic acid (RGD) via physical adsorption. In order to evaluate the cell adhesion rate, viability, morphology, and alkaline phosphatase (ALP) activity, the RGD­CS/HA scaffold was seeded with bone marrow stromal cells (BMSCs). The osseointegrative properties of the RGD­CS/HA scaffold were evaluated by in vivo heterotopic ossification and in vivo bone defect repair. After 4 h culture with the RGD­CS/HA scaffold, the adhesion rate of the BMSCs was 80.7%. After 3 days, BMSCs were fusiform in shape and evenly distributed on the RGD­CS/HA scaffold. Formation of extracellular matrix and numerous cell­cell interactions were observed after 48 h of culture, with an ALP content of 0.006 ± 0.0008 U/l/ng. Furthermore, the osseointegrative ability and biomechanical properties of the RGD­CS/HA scaffold were comparable to that of normal bone tissue. The biocompatibility, cytocompatibility, histocompatibility and osseointegrative properties of the RGD­CS/HA scaffold support its use in bone tissue engineering applications.

Effect of long-term pulsed electromagnetic field exposure on hepatic and immunologic functions of rats.

BACKGROUND: In this report, the effects of long-term pulsed electromagnetic field (PEMF) exposure on hepatic and immunologic functions were examined. METHODS: Male rats were randomly divided into four groups: a control group and three experimental groups exposed to a 50-Hz PEMF at 5, 10, or 20 mT for 10 weeks. RESULTS: Compared with the control group, activities of serum alanine aminotransferase and aspartate aminotransferase and concentrations of serum, liver, and spleen Metabolism of lipid peroxidation (MDA) in the 10- and 20-mT PEMF groups were significantly increased. The activities of Glutathione peroxidase (GSH-Px) and Superoxide Dismutase (SOD) in the serum, liver, and spleen and concentrations of serum immunoglobulins were significantly decreased. CONCLUSION: These results demonstrate that long-term exposure to PEMF can lead to oxidative damage of the liver and spleen.

Improving bone marrow stromal cell attachment on chitosan/hydroxyapatite scaffolds by an immobilized RGD peptide.

Ample cell adhesion to scaffolds is essential for effective bone tissue engineering. Chitosan/hydroxyapatite (CS/HA) scaffolds with channel-shaped and spherically shaped pore morphologies were prepared via in situ compositing hybridization in combination with lyophilization. The sizes of channel-shaped and spherically shaped pores of the CS/HA scaffolds were 150-650 µm and 3-15 µm, respectively. The RGD peptide (Arg-Gly-Asp) was bound to the surface of CS/HA scaffolds via physical adsorption. More than 63% of RGD present in a PBS solution spontaneously adsorbed onto CS/HA scaffolds. High numbers of viable bone marrow stromal cells (BMSCs) were observed by confocal and fluorescence microscopy for cells cultured on CS/HA scaffolds with and without RGD for 3 days. BMSCs on CS/HA scaffolds with RGD (RGD-CS/HA) were incubated for 4 h under standard culture conditions, and the degree of cell adhesion was calculated. Cell adhesion to RGD-CS/HA scaffolds with different RGD concentrations was 71.6% and 80.7%, respectively. This was 30.9% and 47.5% higher than adhesion to the CS/HA scaffold without RGD, respectively. BMSCs cultured on the scaffolds for 14 days with osteogenic supplements expressed 103% higher alkaline phosphatase on the RGD-CS/HA scaffold (0.001 97 ± 0.000 31 U/L/ng), than on the unmodified scaffold (0.000 97 ± 0.000 25 U/L/ng) (p < 0.01), indicating that a RGD peptide significantly promotes osteogenic differentiation of BMSCs on CS/HA scaffolds. The results of this study indicate that RGD-CS/HA scaffolds promote initial cell adhesion, spread and differentiation toward an osteogenic phenotype.

Melatonin alleviates behavioral deficits associated with apoptosis and cholinergic system dysfunction in the APP 695 transgenic mouse model of Alzheimer's disease.

Melatonin is an endogenous antioxidant and free radical scavenger. A transgenic (Tg) mouse model for Alzheimer's disease mimics the accumulation of senile plaques, neuronal apoptosis and memory impairment. Previous studies indicated that melatonin reduced beta-amyloid (Abeta)-induced neurotoxicity. In this study, after giving melatonin at 10 mg/kg to APP 695 transgenic (APP 695 Tg) mice for 4 months, we evaluated the long-term influence of melatonin on behavior, biochemical and neuropathologic changes in APP 695 Tg mice. Step-down and step-through passive avoidance tests suggested that 8-month-old APP 695 Tg mice showed decreases in step-down latency and step-through latency and increases in count of error throughout the entire learning trial and memory session, which suggested learning and memory impairment. However, melatonin alleviated learning and memory deficits. Additionally, choline acetyltransferase (ChAT) activity also decreased in the frontal cortex and hippocampus of APP 695 Tg mice compared with non-Tg littermates. Melatonin supplementation increased ChAT activity in the frontal cortex and hippocampus. DNA fragmentation was present in the frontal cortex of the APP 695 Tg mice; melatonin reduced the number of apoptotic neurons. Congo Red staining and Bielschowsky silver impregnation both showed the apparent extracellular Abeta deposition in frontal cortex of APP 695 Tg mice. However, melatonin decreased the Abeta deposits. Our results indicate that neuroprotection by melatonin is partly related to modulation of apoptosis and protection of the cholinergic system. Early rational melatonin interventions may be one of the most promising strategies in the development of approaches to retard or prevent Abeta-mediated disease progression.