Tech Science Press
Not a member yet
3972 research outputs found
Sort by
Integration of Biochemical and Biomechanical Signals Regulating Endothelial Barrier Function
Get PDFEndothelial barrier function is critical for tissue homeostasis throughout the body. Disruption of the endothelial monolayer leads to edema, vascular diseases and even cancer metastasis among other pathological conditions. Breakdown of the endothelial barrier integrity triggered by cytokines (e.g.IL-8,IL-1β) and growth factors (e.g.VEGF) is well documented. However, endothelial cells are subject to major biomechanical forces that affect their behavior. Due to their unique location at the interface between circulating blood and surrounding tissues, endothelial cells experience shear stress, strain and contraction forces. More than three decades ago, it was already appreciated that shear flow caused endothelial cells alignment in the direction of the flow. After that observation, it took around 20 years to begin to uncover some of the mechanisms used by the cells for mechanotransduction. In this review, we describe mechanosensors on the endothelium identified to date and the associated signaling pathways that integrate biochemical and biomechanical inputs into biological responses and how they modulate the integrity of the endothelial barrier
Transforming Growth Factor-β<sub>1</sub> Remodels the Cytoskeleton Organization of Mature Dendritic Cells <i>via</i> Smad2/3 Signaling Pathway
No full textDendritic cells (DCs) are the most potent professional antigen presenting cells as now known, which play critical roles in the initiation, programming and regulation of the immune response. Transforming growth factor-β1 (TGF-β1), one of the major suppressive cytokines in tumor microenvironment, can deteriorate the biomechanical characteristics and motility of mature dendritic cells (mDCs)，but the underlying molecular mechanisms are not well defined. In this study, the effects of TGF-β1 on the motilities and T cell priming capabilities of mDCs as well as the molecular regulatory mechanisms were investigated. The results showed that the cytoskeleton (F-actin) organizations of mDCs were abnormally remodeled by TGF-β1. Simultaneously, the migration and immune priming capabilities of mDCs were impaired by TGF-β1 via Smad2/3 signaling pathway. It’s significant for further understanding the interaction of DCs and TGF-β1 in tumor host, as well as the immune escape mechanism of cancer, which may be important for enhancing the clinical efficiency of DCs-based immunotherapy against cancer
Study on the Contact Stress Concentration and the Hyperplasia of the Canine Trachea Granulation Tissue after Stenting
Get PDFTracheal stenosis is a common respiratory disease and is usually treated by stent implantation. However, the implanted stent often causes excessive hyperplasia of trachea granulation tissue, leading to the restenosis. Although surgical removal or chemical suppression can be used to alleviate the restenosis, the efficacy is limited. Thus, restenosis remains a thorny complication. We investigated this issue from the perspective of the “tress-growth”relationship. Firstly, the lower airway of 5 experimental dogs were CT-scanned to reconstruct the 3D numerical models; secondly, the implantations of the Nitinol alloy stents were numerically simulated; thirdly, 45 days after the stenting, the dogs were evaluated for the hyperplasia of the trachea granulation tissue by CT imaging, bronchoscopy and histological sectioning; finally, the correlation analysis was performed between the contact stress and the hyperplasic thickness of the granulation tissue. Results show that the hyperplasia of the trachea granulation tissue and the local contact stress are positively correlated (R=0.82) and the high local dilation stress can promote the hyperplasia of the trachea granulation tissue, probably through the recombination of basic fibroblast growth factor or the dysfunction of plasminogen activator inhibitor-1. Therefore, contact stress concentration should be prevented in the future design of the tracheal stent
An Effective Approach of Secured Medical Image Transmission Using Encryption Method
Get PDFVarious chaos-based image encryption schemes have been proposed in last few years. The proposed image encryption method uses chaotic map. The encryption is done by using 256 bit long external secret key. The initial condition for the chaotic mapping is evaluated by the use of external secret key along with the mapping function. Besides that, the proposed method is made more robust by applying multiple operations to the pixels of the image depending on the outcome of the calculation of the logistic map. Moreover, block shuffling of the image and modifying the secret key after encryption of each row is also done to add chaos to the proposed method
Intravascular Optical Coherence Tomography Image Segmentation Based on Support Vector Machine Algorithm
Get PDFIntravascular optical coherence tomography (IVOCT) is becoming more and more popular in clinical diagnosis of coronary atherosclerotic. However, reading IVOCT images is of large amount of work. This article describes a method based on image feature extraction and support vector machine (SVM) to achieve semi-automatic segmentation of IVOCT images. The image features utilized in this work including light attenuation coefficients and image textures based on gray level co-occurrence matrix. Different sets of hyper-parameters and image features were tested. This method achieved an accuracy of 83% on the test images. Single class accuracy of 89% for fibrous, 79.3% for calcification and 86.5% lipid tissue. The results show that this method can be a considerable way for semi-automatic segmentation of atherosclerotic plaque components in clinical IVOCT images
Efficiently and Conveniently Heparin/ PEG-PCL Core-Shell Microcarriers Fabrication and Optimization via Coaxial-Electrospraying
Get PDFHeparin/ PEG-PCL core-shell microcarriers were fabricated in one-step via coaxial-electrospraying technology. Optimization of the coaxial-electrospraying processing is by controlling the PEG-PCL concentration, applied voltage, receiving distance, and feed rate. The influence of the electrospray parameters on microsphere morphology was studied by optical microscopy and scanning electron microscopy. The functional groups and components of the electrosprayed microspheres were characterized by Fourier transform infrared spectroscopy (FTIR). Transmission electron microscope (TEM) observation proved the core-shell structure of heparin-loaded PEG-PCL microspheres. Drug loading and releasing study demonstrated that PEG-PCL concentration could control the encapsulation efficiency and releasing activity of the heparin in the microspheres. The hemocompatibility assays indicated that the anticoagulant property of PCL membranes improved markedly, when the surface modified with heparin-loaded PEG-PCL microspheres
Stress-Based Plaque Vulnerability Index and Assessment for Carotid Atherosclerotic Plaques Using Patient-Specific Vessel Material Properties
Get PDFCardiovascular diseases are closely linked to atherosclerotic plaque development and rupture. Assessment of plaque vulnerability is of fundamental significance to cardiovascular research and disease diagnosis, prevention, treatment and management. Magnetic resonance image (MRI) data of carotid atherosclerotic plaques from 8 patients (5 male, 3 female; age: 62-83, mean=71) were acquired at the University of Washington (UW), Seattle by the Vascular Imaging Laboratory (VIL) with written informed consent obtained. Patient-specific vessel material properties were quantified using Cine MRI data for modeling use. 3D thin-layer models were used to obtain plaque stress and strain for plaque assessment. A stress-based plaque vulnerability index (SPVI) was proposed to combine mechanical analysis, plaque morphology and composition for more complete carotid plaque vulnerability assessment. The five intervals (unit: kPa) [0, 46.8), [46.8, 80), [80, 92), [92, 103), and [103, +∞) from in vivo material models were used for SPVI values of 0, 1, 2, 3 and 4, respectively. The optimized agreement rate was 85.19%. The use of patient-specific material properties in plaque models could potentially improve the accuracy of model stress/strain calculations. SPVI has the potential to improve the current image-based screening and plaque vulnerability assessment schemes
Effect of Hybridization on the Mechanical Properties of Pineapple Leaf Fiber/Kenaf Phenolic Hybrid Composites
Get PDFIn this study, pineapple leaf fiber (PALF), kenaf fiber (KF) and PALF/KF/phenolic (PF) composites were fabricated and their mechanical properties were investigated. The mechanical properties (tensile, flexural and impact) of the PALF/KF/PF hybrid composites were investigated and compared with PALF/KF composites. The 3P7K exhibited enhanced tensile strength (46.96 MPa) and modulus (6.84 GPa), flexural strength (84.21 MPa) and modulus (5.81 GPa), and impact strength (5.39 kJ/m2) when compared with the PALF/PF and KF/PF composites. Scanning electron microscopy (SEM) was used to observe the fracture surfaces of the tensile testing samples. The microstructure of the 7P3K hybrid composite showed good interfacial bonding and the addition of KF improved the interfacial strength. It has been concluded that the 3P7K ratio allowed obtaining materials with better mechanical properties (tensile, flexural and impact strengths) than PALF/PF and KF/PF composites. The results obtained in this study will be used for further comparative study of untreated hybrid composites with treated hybrid composites
The Role of Bamboo Nanoparticles in Kenaf Fiber Reinforced Unsaturated Polyester Composites
Get PDFIn this study, bamboo nanoparticles in concentration ranges from 0–5% were incorporated along with woven/nonwoven kenaf fiber mat into unsaturated polyester and the developed composites were further characterized. Bamboo chips were subjected to ball milling process for the synthesis of nanoparticles with a particle size of 52.92 nm. The effect that the incorporation of nanoparticles had on various properties of reinforced composites was further observed. Due to the high surface area of nanoparticles, incorporation of 3% of nanofillers contributed towards strong bonding and better wettability with matrix, thus resulting in excellent mechanical properties and thermal characteristics in reinforced unsaturated polyester composites. Furthermore, mechanical characteristics of reinforced composites were deteriorated by the addition of a higher percentage of nanoparticles (>3%) due to agglomeration, as confirmed by scanning electron microscopy. Moreover, ordered structural arrangement of woven kenaf textile fiber showed enhancement in interfacial adhesion and promoted superior mechanical strength in reinforced composites as compared with nonwoven composites
Shear Strength and Morphological Study of Polyurethane-OMMT Clay Nanocomposite Adhesive Derived from Vegetable Oil-Based Constituents
Get PDFIn the current work, we have synthesized vegetable oil-based polyurethane-OMMT clay nanocomposite (PUNC) adhesive with the incorporation of different wt% of organically modified nanoclay (1 to 5 wt%) into the biobased polyurethane (PU) matrix through in-situ polymerization process via ultrasonication method. At the initial stage, PU adhesive was prepared using polyol and partially biobased aliphatic isocyanate, wherein polyol was derived from the transesterified castor oil using ethylene glycol. The formation of PU and PUNC adhesive was confirmed using Fourier transform infrared (FTIR) spectroscopy analysis. The tensile strength of PU with different wt% of nanoclay was determined and the analysis showed that the loading of 3 wt% of nanoclay within the PU matrix showed better performance as compared to the others. Furthermore, shear strength of PU and PUNC (3 wt% nanoclay) adhesives were determined using lap shear test, in which PUNC adhesive showed higher adhesive strength at 70 °C. Subsequently, the dispersibility of OMMT nanoclay within the PU matrix along with exfoliation and amorphous structure was confirmed through wide angle X-ray diffractometer (WAXD) and transmission electron microscopy (TEM) analysis. The phase separation structure was analyzed using dynamic mechanical analysis (DMA). The analysis revealed that with the addition of organically modified nanoclay in the PU matrix, the glass transition temperature (Tg) of the damping curve was shifted towards higher temperature