The surge of resistant food pathogens is a major threat worldwide. Previous research conducted on phytochemicals has shown their antibacterial activity against pathogenic bacteria. The design of antimicrobial agents to curb pathogenic disease remains a challenge demanding critical attention. Flavonoids such as apigenin and quercetin were evaluated against Gram-positive and Gram-negative bacteria. The results indicated that the antibacterial activity of each flavonoid occurred at a different minimum inhibitory concentration. However, the antimicrobial activity results of the modified flavonoids were also reported, and it was observed that the Gram-positive bacteria were more susceptible in comparison to the Gram-negative bacteria. The cell wall structure of the Gram-positive and Gram-negative bacteria could be the main reason for the bacteria susceptibility. Modified flavonoids could be used as a suitable alternative antimicrobial agent for the treatment of infectious diseases. Our results indicated 100% inhibition of Listeria monocytogenes, Pseudomonas aeruginosa, and Aeromonas hydrophila with modified flavonoids.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.9b00077

Antimicrobial Activity of a New Class of Phosphorylated and Modified Flavonoids.

The present work aims at studying the thermal and dielectric properties of addition-cure liquid silicone rubber (ALSR) matrix composites using boron nitride (BN) and aluminum nitride (AlN) as a hybrid thermal conductive filler. Composite samples with different filler contents were fabricated, and the density, thermal conductivity, thermal stability, dielectric properties, and volume resistivity of the samples were measured. According to the experimental results, the density, thermal conductivity, dielectric constant and dielectric loss tangent values all increased with the increasing addition of filler. When the weight fraction of hBN filler was 50 wt%, the thermal conductivity of composites was 0.554 W (m−1 K−1), which is 3.4 times higher than that of pure ALSR. The corresponding relative permittivity and dielectric loss were 3.98 and 0.0085 at 1 MHz, respectively. Furthermore, TGA results revealed that the AlN/BN hybrid filler could also improve the thermal stability of ALSR. The volume resistivity of ALSR composites was higher than that of pure ALSR. The addition of fillers improved the thermal properties of ALSR and had little effect on its insulation properties. This characteristic makes ALSR composites attractive in the field of insulating materials.

/pdf/research-on-the-thermal-conductivity-and-dielectric-359wy5t991.pdf

Research on the thermal conductivity and dielectric properties of AlN and BN co-filled addition-cure liquid silicone rubber composites

Pozzolanic activity and hydration properties of feldspar after mechanical activation

For the first time, it was experimented with high voltage electrostatic field (HVEF) for the optimization of the bonding process of urea formaldehyde (UF) resin to wood. Varying HVEF treatment times (0–8 min) and intensities (5–20 kV) were applied. Wood surface characteristics, polymerization extent of UF, and bonding interphase of UF to wood were examined by electron spin resonance (ESR) spectroscopy, dynamic contact angle goniometers, Fourier transform infrared spectroscopy (FTIR), X-ray densitometer, fluorescence microscope and bonding strength measurement. The results indicated that HVEF treatments applied to wood veneer induced a decrease in contact angles and an increase in the free radicals of wood, and surface energy varied with treatment times and intensities. These varieties were because triggered free electrons, broken chemical bonds and new ions appeared on the wood surface with HVEF treatment. An aggregated performance was obviously obtained in micrographs and vertical density profiles (VPDs). It was explained that resin penetration into wood structure was significantly shallow, and resin concentration and density at bonding interphase were more enhanced than the control. This is due to the increment of surface energy and lower contact angles providing more chances for possible reactions of wood surface with the UF resin. Resin penetration depth and density varied with different treatment times and intensities. Increased cross-linking extent of UF was obtained under varied conditions of HVEF treatment. The bonding strength was measured as a function of treatment times and intensities respectively; it increased by 85% and the wood failure ratio significantly increased by 70% under HVEF treatment (20 kV, 8 min) due to the aggregation performance and more cross-linked UF resin. It was manifested that both treatment time and intensity play a significant role in HVEF treatment, and HVEF treatment has a significant influence on the characteristics of the wood surface and the bonding properties of wood composites.

Influence of high voltage electrostatic field (HVEF) on bonding characteristics of Masson (Pinus massoniana Lamb.) veneer composites

Weight reduction is very important to aircraft. Laser welding technology is beneficial to reduce the weight of aircraft structure. However, due to the unclear laser welding properties of Al-Li alloy, the research on laser welding of Al-Li alloy is necessary. In current study, the temperature field, stress field and deformation of laser welding are simulated. The optimal welding parameters are obtained by simulation, which are used to weld the real Al-Li alloy sheet. Besides, the microstructure and mechanical property of welded joints are analyzed. It is found that the simulated optimal welding parameters are suitable for welding real Al-Li alloy sheet. And the simulation results are consistent with the experimental results.

Numerical simulation optimization for laser welding parameter of 5A90 Al-Li alloy and its experiment verification

Moso bamboo (Phyllostachys pubescens) linear-vibration welded joints with three different combinations between the inner and outer surfaces were studied in this paper. The tensile-shear strength, the microstructures and welded layer thickness observed by SEM and the density profiles measured by X-ray densitometer of the welded samples have been considered and compared. The maximum average tensile-shear strength of outer-outer, inner-inner and outer-inner welded joints were 5.91, 7.15 and 6.24 MPa, respectively. And only the inner-inner welded joints have the bamboo failure after the shear test. The welded joint is composed of a lot of bamboo fibers entangled in the molten and flown intercellular materials which decide the final mechanical performance of the welded joints. The thickness of the outer-outer welded layer is the smallest and the inner-inner welded layer is the highest. However, the maximum density reached in the inner-inner welded joint is smaller than in the outer-outer welded joint o...

The study of linear vibrational welding of moso bamboo

Mechanical welding technology has been widely employed in the making of bonding joints with wood. Moso bamboo, a lignocellulosic biomaterial, can also be bonded using mechanical welding technology. The surface response methodology was used to define welding parameters yielding optimal joint strength. In the range of this experiment, it was found that the vibration amplitude and the welding pressure both had a significant influence on the performance of the joint, while the welding time did not. The quadratic model was able to significantly fit the actual results and could be used to determine and optimize the bonding strength.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_09_2_2500_Zhang_Optimization_Tensile_Shear_Strength/2667

Optimization of Tensile Shear Strength of Linear Mechanically Welded Outer-to-Inner Flattened Moso Bamboo (Phyllostachys pubescens)

An assessment of volatile organic compounds pollutant emissions from wood materials: A review.

Wood dust is the major wastes from timber and wood-based panel processing, including wood sawing, sanding, chipping, flaking, etc., which easily causes fire and explosions. The fine wood dust had risks of inhaling the dust air, causing problems to the respiratory system of workers, as well as the explosive risk of the wood dust-air mixture. Wood dust explosions occur worldwide, which have caused massive damages to equipment, buildings, and environments, killed people, and threatened human health. This study was aimed at exploring the causes, affecting factors, mechanisms, models of wood dust explosions, and their environmental/health impacts through reviewing and analyzing the collected data in order to minimize wood dust explosion risks by improving of safety procedures in the wood processing industry. To better understood and prevent wood dust explosion cases in the future, this review collected the explosion reports and analyzed the accident information through the following aspects: 1) Summarization of published review articles regarding wood dust explosions in Introduction, 2) Scrutinization of wood dust explosion cases and design of testing device, 3) Exploration of effects of wood dust properties and surrounding conditions on explosion and their mechanisms, 4) Investigation of methods for reducing wood dust explosion risks, 5) Modeling and simulation of wood dust explosions, 6) Examination of environmental and health impacts of wood dust explosions. Finally, the findings in this review were summarized in Conclusions. By collecting dust explosion reports, reviewing literature, and analyzing the collected data, wood dust explosions can be better understood. The results of this study can be useful for the design of equipment and dust absorption systems, as well as further suggestion of safety improvement procedures to minimize or eliminate risks of wood dust-related fire and explosion in the wood processing industry and mitigate its impacts on environments and health. 

Xihe Zhou

Papers

The study of linear vibrational welding of moso bamboo

Optimization of Tensile Shear Strength of Linear Mechanically Welded Outer-to-Inner Flattened Moso Bamboo (Phyllostachys pubescens)

An assessment of volatile organic compounds pollutant emissions from wood materials: A review.

Combustible wood dust explosions and impacts on environments and health - A review.

Environmental and human health impacts of volatile organic compounds: A perspective review.