Effect of the Antimicrobial Peptide D-Nal-Pac-525 on the Growth of Streptococcus mutans and Its Biofilm Formation

( Huajun Li ),( Jya Wei Cheng ),( Hui Yuan Yu ),( Yi Xin ),( Li Tang ),( Yufang Ma ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.8

Streptococcus mutans is the primary etiological agent of dental caries. The antimicrobial peptide D-Nal-Pac-525 was designed by replacing the tryptophans of the Trp-rich peptide Pac-525 with D-β-naphthyalanines. To assess the effect of D-Nal-Pac-525 on cariogenic bacteria, the activity of D-Nal-Pac-525 on the growth of S. mutans and its biofilm formation were examined. D-Nal- Pac-525 showed robust antimicrobial activity against S. mutans (minimum inhibitory concentration of 4 μg/ml). Using scanning electron microscopy and transmission electron microscopy, it was shown that D-Nal-Pac-525 caused morphological changes and damaged the cell membrane of S. mutans. D-Nal-Pac-525 inhibited biofilm formation of S. mutans at 2 μg/ml. The results of this study suggest that D-Nal-Pac-525 has great potential for clinical application as a dental caries-preventing agent.

Cutting fluid corrosion inhibitors from inorganic to organic: Progress and applications

Haogang Li,Yanbin Zhang,Changhe Li,Zongming Zhou,Xiaolin Nie,Yun Chen,Huajun Cao,Bo Liu,Naiqing Zhang,Zafar Said,Sujan Debnath,Muhammad Jamil,Hafiz Muhammad Ali,Shubham Sharma 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.5

Water-based cutting fluid has a broad application area and a hundred year history, but its poor corrosioninhibition and anti-rust ability limit its further promotion. Adding corrosion inhibitors can effectively solve the aboveproblems. However, no review papers are available on cutting fluid corrosion inhibitors, and their mechanism, suitability,and performance influencing factors have not been revealed. This article discusses cutting fluid corrosion inhibitorsto fill the gaps in theoretical research and industrial applications. Inorganic matters are initially used in corrosion inhibitiondue to their strong oxidizing properties. Therefore, the film formation mechanism of inorganic corrosion inhibitoroxide and precipitation film is first analyzed, and the applications in corrosive medium are summarized. Given thatinorganic corrosion inhibitors are not environmentally friendly and expensive, organic corrosion inhibitors are currentlyused as replacement. Thus, the film formation mechanism of different organic corrosion inhibitors adsorptionfilm is analyzed, and their suitability with metals is determined. The influence of molecular structure and temperatureon their corrosion inhibition effect is also studied, and the performance of inorganic and organic corrosion inhibitors iscompared. However, single organic corrosion inhibitors are greatly affected by metal surface state, temperature, andimmersion time. Therefore, the synergistic film formation after the compounding of organic and inorganic corrosioninhibitors is analyzed. In addition, the influence rate of concentration, molecular structure, and temperature on corrosioninhibition performance is revealed, and a matching database of corrosion inhibitor type and metal type in cuttingis established. Finally, in view of the limitations of cutting fluid corrosion inhibitors, the establishment of a moleculardynamics model of corrosion inhibitor failure and accelerates corrosion and the development of general-purpose greenadditives based on the molecular design and physical and chemical analysis of the suitability of corrosion inhibitor andbase liquid are prospected.

Energy Dissipation Characteristics Modelling for Hot Extrusion Forming of Aluminum-Alloy Components

Hongcheng Li,Yuanjie Wu,Huajun Cao,Feng Lu,Congbo Li 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.6

The hot extrusion forming process is widely used to process aluminum-alloy components in both the automobile and aircraft manufacturing industries. Since it involves pushing the material through the die at increased temperature, it is very energy-intensive despite requiring less blank material allowance. During hot extrusion forming, the multi-stage dynamic conversion of electricity, mechanical energy, and hydraulic energy to heat results in high energy dissipation. In order to improve the power and energy conversion efficiency of hot extrusion forming process, it is necessary to identify the energy dissipation characteristics. The transfer and conversion paths of the electrical, mechanical, and hydraulic energy from the motor to the hydraulic cylinder were firstly depicted based on the motion cycle of the extruder. A bond graph-based energy dissipation model was then proposed for dynamically identifying the energy-saving potentials. The energy dissipation model integrated the power bond graph sub-model of energy conversion elements such as motor, pump, hydraulic valve group, and hydraulic cylinder. These power bond graph sub-models were separately developed to find the energy dissipation state equations of energy conversion elements. An experiment was carried out using data obtained from the energy management system to validate the bond graph-based energy dissipation model. The results have shown that the power and energy conversion efficiency of hot extrusion forming is primarily controlled by the parameters such as extrusion velocity and extrusion force. Both the higher extrusion velocity and lower extrusion force will reduce the power and energy conversion efficiency. An optimal combination of extrusion velocity and pressure can achieve the lowest energy consumption per unit product.

Quasi-Two-Dimensional Metal Oxide Semiconductors Based Ultrasensitive Potentiometric Biosensors

Chen, Huajun,Rim, You Seung,Wang, Isaac Caleb,Li, Chao,Zhu, Bowen,Sun, Mo,Goorsky, Mark S.,He, Ximin,Yang, Yang American Chemical Society 2017 ACS NANO Vol.11 No.5

<P>Ultrasensitive field-effect transistor-based biosensors using quasi two -dimensional metal oxide semiconductors were demonstrated. Quasi-two-dimensional low-dimensional metal oxide semiconductors were highly sensitive to electrical perturbations at the semiconductor bio interface and showed competitive sensitivity compared with other nanomaterial-based biosensors. Also, the solution process made our platform simple and highly reproducible, which was favorable compared with other nanobioelectronics. A quasi-two-dimensional In2O3-based pH sensor showed a small detection limit of 0.0005 pH and detected the glucose concentration at femtomolar levels. Detailed electrical characterization unveiled how the device's parameters affect the biosensor sensitivity, and lowest detectable charge was extrapolated, which was consistent with the experimental data.</P>

Lossless Compression for Hyperspectral Images based on Adaptive Band Selection and Adaptive Predictor Selection

( Fuquan Zhu ),( Huajun Wang ),( Liping Yang ),( Changguo Li ),( Sen Wang ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.8

With the wide application of hyperspectral images, it becomes more and more important to compress hyperspectral images. Conventional recursive least squares (CRLS) algorithm has great potentiality in lossless compression for hyperspectral images. The prediction accuracy of CRLS is closely related to the correlations between the reference bands and the current band, and the similarity between pixels in prediction context. According to this characteristic, we present an improved CRLS with adaptive band selection and adaptive predictor selection (CRLS-ABS-APS). Firstly, a spectral vector correlation coefficient-based k-means clustering algorithm is employed to generate clustering map. Afterwards, an adaptive band selection strategy based on inter-spectral correlation coefficient is adopted to select the reference bands for each band. Then, an adaptive predictor selection strategy based on clustering map is adopted to select the optimal CRLS predictor for each pixel. In addition, a double snake scan mode is used to further improve the similarity of prediction context, and a recursive average estimation method is used to accelerate the local average calculation. Finally, the prediction residuals are entropy encoded by arithmetic encoder. Experiments on the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) 2006 data set show that the CRLS-ABS-APS achieves average bit rates of 3.28 bpp, 5.55 bpp and 2.39 bpp on the three subsets, respectively. The results indicate that the CRLS-ABS-APS effectively improves the compression effect with lower computation complexity, and outperforms to the current state-of-the-art methods.

Iron interferes with quorum sensing-mediated cooperation in Pseudomonas aeruginosa by affecting the expression of ppyR and mexT, in addition to rhlR

Sun Feng,Li Na,Wang Lijia,Feng Huajun,Shen Dongsheng,Wang Meizhen 한국미생물학회 2020 The journal of microbiology Vol.58 No.11

The stabilization of quorum sensing (QS) is vital for bacterial survival in various environments. Although the mechanisms of QS stabilization in certain conditions have been well studied, the impact of environmental factors has received much less attention. In this study, we show that the supplementation of 25 μM iron in competition experiments and 50 μM in evolution experiments to casein growth cultures significantly increased the possibility of population collapse by affecting elastase production. However, the expression of lasI and lasR remained constant regardless of iron concentration and hence this effect was not through interference with the LasIR circuit, which mainly regulates the secretion of elastase in Pseudomonas aeruginosa. However, the expression of rhlR was significantly inhibited by iron treatment, which could affect the production of elastase. Further, based on both reverse transcription quantitative polymerase chain reaction and gene knock-out assays, we show that iron inhibits the transcription of ppyR and enhances the expression of mexT, both of which decrease elastase production and correspondingly interfere with QS stabilization. Our findings show that environmental factors can affect the genes of QS circuits, interfering with QS stabilization. These findings are not only beneficial in understanding the mechanistic effect of iron on QS stabilization, but also demonstrate the complexity of QS stabilization by linking non-QS-related genes with QS traits.

Exergy-based Energy Efficiency Evaluation Model for Machine Tools Considering Thermal Stability

Ben-jie Li,Huajun Cao,Bernard Hon,Lei Liu,Xi Gao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.2

Machine tools, as the extensively used basic equipment of manufacturing industry, are characterized by intensive and inefficient energy consumption. With the launch and implementation of ISO 14955-1, energy efficiency has become an important criterion for machine tool evaluation. However, most ongoing research on energy efficiency evaluation of machine tools emphasizes on workpiece material removal energy efficiency and rarely considers energy consumption needed to ensure machining accuracy and accuracy consistency, especially energy consumption for thermal stability control of machine tools. In light of this, an exergy analysis based approach is presented to assess the comprehensive energy efficiency of machine tools, including energy consumption for material removal and thermal stability control. The key performance indexes of exergy efficiency, exergy destruction, and specific exergy consumption are analyzed. The feasibility of the proposed approach was demonstrated by a case study, in which the comprehensive energy efficiency of a machine tool was found to be 21.57% instead of 14.38% of material removal energy efficiency. The proposed method is more effective to evaluate the comprehensive energy efficiency, to support designers to design high-efficient machine tool and users to operate machine tool for green and precision machining.

An adaptive parameter optimization model and system for sustainable gear dry hobbing in batch production

Ying Zhang,Huajun Cao,Peng Chen,Li-Bin Zhu,Xiao Yang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6

Gear hobbing technology is one of the most widely used forming processes of gear teeth. And the development of dry hobbing technologyprovides a solution for realizing productive, economical, and ecological gear production. Since there is no cutting oil for coolingand lubrication in dry hobbing process, the hob tool life, thermal deformation errors of machine tool, and quality of workpiece are sensitiveto the cutting parameters, especially the cutting speed and tip chip thickness. Considering this situation, a dry hobbing parametersoptimization model with the hobbing efficiency as our objective, and the hobbing cost per piece, gear quality, tact time as constraints wasestablished, in which the cutting speed and tip chip thickness were considered as optimal variables and the material of workpiece, coatingof hob, and feed rate were considered comprehensively. An iterative test method is proposed to solve this model. And for the applicationin automated production line, an online adaptive application system was also developed based on SINUMERIK 840D NC system. Theparameters of five different kinds of material gear were optimized by applying this model and system, and the result showed the modeland the system were practical.

The inhibitory effect of gut microbiota and its metabolites on colorectal cancer

Chen Chao,Huajun Li 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.11

Colorectal cancer (CRC) is regarded as one of the most common and deadly forms of cancer. Gut microbiota is vital to retain and promote several functions of intestinal. Although previous researches have shown that some gut microbiota have the abilities to inhibit tumorigenesis and prevent cancer from progressing, they have not yet clearly identified associative mechanisms. This review not only concentrates on the antitumor effects of metabolites produced by gut microbiota, for example, SCFA, ferrichrome, urolithins, equol and conjugated linoleic acids, but also the molecules which constituted the bacterial cell wall have the antitumor effect in the host, including lipopolysaccharide, lipoteichoic acid, β-glucans and peptidoglycan. The aim of our review is to develop a possible therapeutic method, which use the products of gut microbiota metabolism or gut microbiota constituents to help treat or prevent colorectal cancer.

An Analytical Model of Chip Heat-Carrying Capacity for High-Speed Dry Hobbing Based on 3D Chip Geometry

Xiao Yang,Huajun Cao,Yong-peng Chen,Li-Bin Zhu,Ben-jie Li 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.2

High-speed dry hobbing is the dominating green technique for gear hobbing owing to its high productivity and environmental friendliness. However, a large amount of cutting heat is generated during the machining process due to the absence of metalworking fluids and the adoption of high cutting speed. A better understanding of chip heat-carrying capacity for high-speed dry hobbing is quite necessary when aiming to reduce the influence of cutting heat on machining precision. In this paper, an analytical model is established to quantitatively determine the chip heat-carrying capacity of high-speed dry hobbing. According to the progressive heat transfer characteristic of high-speed dry hobbing, cutting heat generation and transmission are analyzed. 3D chip geometry is numerically calculated by modeling the complex hob geometry and the interrelated kinematic relations of high-speed dry hobbing. Based on the 3D chip geometry and the specific cutting energy, chip heat-carrying capacity model is developed considering three heat sources. In this model, chip heat partition is experimentally determined by calorimetric method. With the help of the developed model, chip heat-carrying quantity and chip heat-carrying efficiency are discussed by investigating their influence factors (hob rotation speed, axial feed, feed method, chip removal time and hob geometry).