Stretching Micro Metal Particles into Uniformly Dispersed and Sized Nanoparticles in Polymer.

There is a longstanding challenge to disperse metal nanoparticles uniformly in bulk polymers for widespread applications. Conventional scale-down techniques often are only able to shrink larger elements (such as microparticles and microfibers) into micro/nano-elements (i.e. nanoparticles and nanofibers) without much altering their relative spatial and size distributions. Here we show an unusual phenomenon that tin (Sn) microparticles with both poor size distribution and spatial dispersion were stretched into uniformly dispersed and sized Sn nanoparticles in polyethersulfone (PES) through a stack and draw technique in thermal drawing. It is believed that the capillary instability plays a crucial role during thermal drawing. This novel, inexpensive, and scalable method overcomes the longstanding challenge to produce bulk polymer-metal nanocomposites (PMNCs) with a uniform dispersion of metallic nano-elements

Influence of porosity on osteogenesis, bone growth and osteointegration in trabecular tantalum scaffolds fabricated by additive manufacturing

Porous tantalum implants are a class of materials commonly used in clinical practice to repair bone defects. However, the cumbersome and problematic preparation procedure have limited their widespread application. Additive manufacturing has revolutionized the design and process of orthopedic implants, but the pore architecture feature of porous tantalum scaffolds prepared from additive materials for optimal osseointegration are unclear, particularly the influence of porosity. We prepared trabecular bone-mimicking tantalum scaffolds with three different porosities (60%, 70% and 80%) using the laser powder bed fusing technique to examine and compare the effects of adhesion, proliferation and osteogenic differentiation capacity of rat mesenchymal stem cells on the scaffolds in vitro. The in vivo bone ingrowth and osseointegration effects of each scaffold were analyzed in a rat femoral bone defect model. Three porous tantalum scaffolds were successfully prepared and characterized. In vitro studies showed that scaffolds with 70% and 80% porosity had a better ability to osteogenic proliferation and differentiation than scaffolds with 60% porosity. In vivo studies further confirmed that tantalum scaffolds with the 70% and 80% porosity had a better ability for bone ingrowh than the scaffold with 60% porosity. As for osseointegration, more bone was bound to the material in the scaffold with 70% porosity, suggesting that the 3D printed trabecular tantalum scaffold with 70% porosity could be the optimal choice for subsequent implant design, which we will further confirm in a large animal preclinical model for better clinical use

Bridge structure deformation prediction based on GNSS data using Kalman-ARIMA-GARCH model

Bridges are an essential part of the ground transportation system. Health monitoring is fundamentally important for the safety and service life of bridges. A large amount of structural information is obtained from various sensors using sensing technology, and the data processing has become a challenging issue. To improve the prediction accuracy of bridge structure deformation based on data mining and to accurately evaluate the time-varying characteristics of bridge structure performance evolution, this paper proposes a new method for bridge structure deformation prediction, which integrates the Kalman filter, autoregressive integrated moving average model (ARIMA), and generalized autoregressive conditional heteroskedasticity (GARCH). Firstly, the raw deformation data is directly pre-processed using the Kalman filter to reduce the noise. After that, the linear recursive ARIMA model is established to analyze and predict the structure deformation. Finally, the nonlinear recursive GARCH model is introduced to further improve the accuracy of the prediction. Simulation results based on measured sensor data from the Global Navigation Satellite System (GNSS) deformation monitoring system demonstrated that: (1) the Kalman filter is capable of denoising the bridge deformation monitoring data; (2) the prediction accuracy of the proposed Kalman-ARIMA-GARCH model is satisfactory, where the mean absolute error increases only from 3.402 mm to 5.847 mm with the increment of the prediction step; and (3) in comparision to the Kalman-ARIMA model, the Kalman-ARIMA-GARCH model results in superior prediction accuracy as it includes partial nonlinear characteristics (heteroscedasticity); the mean absolute error of five-step prediction using the proposed model is improved by 10.12%. This paper provides a new way for structural behavior prediction based on data processing, which can lay a foundation for the early warning of bridge health monitoring system based on sensor data using sensing technolog

Venous thromboembolism after oral and maxillofacial oncologic surgery : report and analysis of 14 cases in Chinese population

Venous thromboembolism (VTE) including deep vein thrombosis (DVT) and pulmonary embolism (PE) is a leading cause of death in cancer patients. The aim of this study was to explore the potential risk factor of VTE in oral and maxillofacial oncological surgery. The data of patients who received operation in our institution were gathered in this retrospective study. A diagnosis of VTE was screened and confirmed by computer tomography angiography (CTA) of pulmonary artery or ultrasonography examination of lower extremity. Medical history and all perioperative details were analyzed. 14 patients were diagnosed as VTE, including 6 cases of PE, 7 cases of DVT, 1case of DVT and PE. The mean age of these patients was 62.07 years. Reconstruction was performed in 12 patients of these cases, most of which were diagnosed as malignance. Mean length of surgery was 8.74 hours, and lower extremity deep venous cannula (DVC) was performed in all these patients. We analyzed several characters of oral and maxillofacial surgery and suggested pay attention to lower extremity DVC which had a high correlation with DVT according to our data

Research on Distribution of Flow Field and Simulation of Working Pulsation Based on Rotating-Sleeve Distributing-Flow System

To solve problems of leakage, vibration, and noise caused by disorders of flow field distribution and working pulsation in the rotating-sleeve distributing-flow system, governing equations of plunger and rotating sleeve and computational fluid dynamics (CFD) model are developed through sliding mesh and dynamic mesh technology to simulate flow field and working pulsation. Simulation results show that the following issues exist: obviously periodic fluctuation and sharp corner in flow pulsation, backward flow when fluid is transformed between discharge and suction, and serious turbulence and large loss in kinetic energy around the damping groove in transitional movements. Pressure in the pump chamber rapidly rises to 2.2 MPa involving over 10% more than nominal pressure when the plunger is at the Top Dead Center (TDC) considering changes about damping groove’s position and flow area in two transitional movements. Shortly pressure overshoot gradually decreases to a normal condition with increasing flow area. Similarly, pressure in the pump chamber instantaneously drops to a saturated vapor pressure −98.9 KPa when the plunger is at the Bottom Dead Center (BDC). With increasing flow area the overshoot gradually increases to the normal condition. This research provides foundations for investigating flow field characteristic and structure optimization of rotating-sleeve distributing-flow system

3D Bioprinting for Tissue and Organ Fabrication

The field of regenerative medicine has progressed tremendously over the past few decades in its ability to fabricate functional tissue substitutes. Conventional approaches based on scaffolding and microengineering are limited in their capacity of producing tissue constructs with precise biomimetic properties. Three-dimensional (3D) bioprinting technology, on the other hand, promises to bridge the divergence between artificially engineered tissue constructs and native tissues. In a sense, 3D bioprinting offers unprecedented versatility to co-deliver cells and biomaterials with precise control over their compositions, spatial distributions, and architectural accuracy, therefore achieving detailed or even personalized recapitulation of the fine shape, structure, and architecture of target tissues and organs. Here we briefly describe recent progresses of 3D bioprinting technology and associated bioinks suitable for the printing process. We then focus on the applications of this technology in fabrication of biomimetic constructs of several representative tissues and organs, including blood vessel, heart, liver, and cartilage. We finally conclude with future challenges in 3D bioprinting as well as potential solutions for further development.United States. Office of Naval Research. Young Investigator ProgramNational Institutes of Health (U.S.) (Grants EB012597, AR057837, DE021468, HL099073 and R56AI105024)Presidential Early Career Award for Scientists and Engineer