Preparation and Characterization of Electrospun Polylactic Acid (PLA) Fiber Loaded with Birch Bark Triterpene Extract for Wound Dressing

Drug-loaded electrospun fibers have attracted increasing attention as a promising wound dressing material due to their capability of preventing from infections and inflammation and maintaining an appropriate environment for wound healing. In this study, polylactic acid (PLA), which is widely used in wound management, was chosen as electrospinnable polymer. A triterpene extract (TE) from the outer bark of birch known for its anti-inflammatory, antiviral, antibacterial, and wound healing effects was chosen to produce TE-loaded PLA electrospun fibers for wound dressing. A binary solvent system of dichloromethane (DCM) and dimethyl sulfoxide (DMSO) was employed, and the ratio of the solvents was optimized for preparing smooth and uniform fibers. The morphology of TE-loaded PLA electrospun fibers was investigated by scanning electron microscopy (SEM). The entrapment of TE in PLA fibers was confirmed by confocal laser scanning microscopy (CLSM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to analyze the solid state of TE in PLA fibers. The release behavior of TE was assayed by a shaking flask method for a period of 96 h. The results revealed that TE-loaded electrospun PLA microfibers could be reliably prepared and are promising future candidates in wound therapy

Analysis on the Trend and Factors of Total Factor Productivity of Agricultural Export Enterprises in China

There is an “export productivity paradox” in Chinese enterprises, which has been confirmed in agricultural enterprises. This paper attempts to explain this phenomenon from the perspective of the components of TFP. This paper uses the SFA-Malmquist method to decompose and compare the TFP of China’s agricultural export enterprises based on the data of the state-level leading agricultural enterprises from 2016 to 2017. The conclusions are as follows: firstly, China’s agricultural TFP shows a negative growth trend, and the growth rate of TFP of agricultural export enterprises is less than that of agricultural non-exported enterprises; secondly, the growth rate of TFP of grain and animal husbandry export enterprises is less than that of non-export enterprises; the growth rate of TFP of private agricultural export enterprises is lower than that of non-export enterprises of the same type; the growth rate of TFP of export enterprises in eastern and western regions is lower than that of non-export enterprises; and thirdly, technical progress is an important reason for the change of TFP of China’s agricultural enterprises. However, compared with agricultural non-exported enterprises, improving the technical efficiency of enterprises can more promote the TFP of agricultural export enterprises

Effect of Liquid Natural Rubber on Properties of Natural Rubber/Silica Composite Prepared by Wet Compounding

Natural rubber/silica composites (NR/SiO2) was prepared by wet compounding technology with liquid natural rubber(LNR) as compatibilizer. Curing characteristics, processing properties, filler dispersion and mechanical properties were investigated.The results showe that the optimum cure time is decreased 4.16 min, the processing properties of the composites were improved with the incorporation of LNR; better silica dispersion in NR in presence of LNR; the when silica is 60 phr, tensile strength and tear strength of the vulcanizates were increase 25.73% and 66.59%respectively; as far as the dynamic mechanical properties are concerned, the W(NR/SiO2) composites with LNR owned a combination of high wet skid resistance and low rolling resistance. It is revealed that LNR has better compatibility, which is attributed to LNR reaction with both NR and SiO2 to form compatibilizing interface

Ontology-based interoperation model of collaborative product development

The reuse of existing systems is an important objective of HLA (High Level Architecture)-based collaborative product development systems. However, in order to reuse an existing system, its interoperation interface has to be modified to comply with the objective and interaction representations defined in a corresponding FOM (Federation Object Model). Such modifications imply added time and effort, which diminishes the efficiency of system reuse in collaborative product development. This paper presents a heavy-weighted ontology-based construction method for interoperation models to support the reuse of subsystems in various collaborative contexts. In this method ontologies are used to specify the semantics of object classes and interaction classes in subsystems in a formal and computer readable fashion. In doing so, a FCA (Formal Concept Analysis) -like construction method is introduced to establish the original interoperation ontology from scratch. An automatic transforming method from a SOM (Simulation Object Model) into interoperation ontology is also described to make it easy for existing HLA-based systems to adopt this approach. Then a consistency verification method is introduced to guarantee the consistency of the interoperation ontologies. A case study is used to demonstrate the feasibility of the proposed method. As a human- friendly modeling method, compared with existing interoperation modeling methods, the proposed method is more flexible, efficient and reliable.Peer reviewed: YesNRC publication: Ye

Monitoring Setting and Hardening of Concrete By Active Acoustic Method: Effects of Water-to-Cement Ratio and Pozzolanic Materials

An active acoustic method is used to monitor the setting and hardening of early age concrete, by recording and analyzing the wave velocity and attenuation coefficient. The effects of water-to-cement ratio and pozzolanic materials (fly ash and silica fume) are examined. The central frequency of the acoustic excitation is 6 kHz, which is much lower than that of ultrasound and can enhance the signal-to-noise ratio when applied to very early age concrete. It was found that the wave velocity measurement can reveal clearly three stages in the hydration process of early age concrete, and an aluminate hydrates phase transition period can be defined based on the attenuation coefficient measurement. Lower water-to-cement ratio and the incorporation of more silica fume facilitate a faster development of both wave velocity and attenuation coefficient, and achieve higher one-day wave velocity values, showing their accelerating effects. The incorporation of fly ash postpones the development of both wave velocity and attenuation coefficient, and achieves lower one-day wave velocity values, showing its retardation effect. The attenuation coefficients of all concretes tend to converge to the same value, i.e. 4 Np/m

Ontology fusion in HLA-based collaborative engineering environments

In high-level-architecture (HLA)-based distributed heterogeneous collaborative engineering environments (CEEs), the construction of federation object model files is time consuming. This paper presents an ontology fusion approach aiming at establishing a common understanding in such collaborative environments. The proposed approach has three steps: ontology mapping, ontology alignment, and ontology merging. Ontology mapping employs a top-down approach to explore all bridge relations between two terms from different ontologies based on bridge axioms and deduction rules. Ontology alignment adopts a bottom-up approach to discover implicit bridge relations between two terms from different domain ontologies based on equivalent inference. Ontology merging generates a new collaboration ontology from discovered equivalent bridge relations. It adopts an axiom-based ontology fusion strategy and takes heavy-weighted ontologies into consideration. It can find all the explicit and derived interontology relations. In a typical CEE, the proposed approach has a great potential to improve the efficiency of preparation for HLA-based collaborative engineering processes, reduce the work load for adaptive adjustment of existing platforms, and enhance the reusability and flexibility of CEEs. A case study has been conducted to validate the feasibility of the proposed approach.Peer reviewed: YesNRC publication: Ye