为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,...为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,并借助冷冻干燥技术,成功制备出具备多孔结构的复合气凝胶纤维。通过调节银纳米粒子的负载量,深入研究其对材料电磁屏蔽性能等方面的影响。研究结果显示,该复合材料在X波段(8.2~12.4 GHz)的电磁干扰(EMI)屏蔽效能值达到33 dB,且EMI SE A占总EMI值的60%,说明其以吸收屏蔽为主导,这基于气凝胶纤维的高比表面积和银纳米粒子的导电性对电磁波的吸收。展开更多
Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nano...Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.展开更多
Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptio...Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.展开更多
To enhance the productivity of Carya illinoinensis cv.‘Shaoxing’and mitigate the loss of flowers and fruits,the effects of different concentrations of Piperonyl Butoxide(PBO)wettable powder(2,5,and 10 g·L^(-1))...To enhance the productivity of Carya illinoinensis cv.‘Shaoxing’and mitigate the loss of flowers and fruits,the effects of different concentrations of Piperonyl Butoxide(PBO)wettable powder(2,5,and 10 g·L^(-1))and Paclobutrazol(PP_(333))(150,300,and 450 mg·L^(-1),based on active ingredients)on 6-year-old‘Shaoxing’plants were investigated with water sprayed as the control.The results showed that:(1)Treatment with 10 g·L^(-1)PBO and 450 mg·L^(-1)PP_(333)significantly inhibited the excessive growth of‘Shaoxing’branches.Also,10 g·L^(-1)PBO exhibited the best diameter increment effect on fruiting branches,and 150 mg·L^(-1)PP_(333) exhibited the best diameter increment effect on vegetative branches.(2)The content of soluble sugar and soluble protein in leaves treated reached the highest level after treatment with 450 mg·L^(-1)PP_(333),while the content of starch sugar in leaves reached the highest level after treatment with 300 mg·L^(-1)PP_(333).The application of PBO and PP_(333)mitigated the decline in N,P,K,and other nutrient levels observed in the leaves of‘Shaoxing’.As the PBO and PP_(333) concentrations increased,the nutrient elements in the leaves first increased and then decreased.Among them,300 mg·L^(-1)PP_(333)treatment exhibited the best effect on increasing the content of N,P,and K in the leaves at the late stage of fruit development.(3)In terms of fruit setting rate and nutritional quality of‘Shaoxing’fruit,5 g·L^(-1)PBO treatment showed the most promising effect on improving fruit setting rate,150 mg·L^(-1)PP_(333)exhibited the best effect on improving reducing sugar and decreasing tannin content in the kernel,10 g·L^(-1)PBO had the best effect on improving the crude fat content,and 2 g·L^(-1)PBO had the best effect on improving the cellulose content in the kernel.(4)Principal component analysis showed that 450 mg·L^(-1)PP_(333)treatment had the most comprehensive regulatory effect on the growth and development of current-year branches,leaves,and fruits of‘Shaoxing’.This study provided a theoretical basis and data reference for the growth and development of C.illinoinensis cv.‘Shaoxing’fruits from the perspective of the application of plant growth regulators.展开更多
The efficacy of insecticide-treated nets (ITNs) is increasingly compromised by the prevalence of malaria vectors resistant to pyrethroids. In response to this issue, a new generation of ITNs has been developed that in...The efficacy of insecticide-treated nets (ITNs) is increasingly compromised by the prevalence of malaria vectors resistant to pyrethroids. In response to this issue, a new generation of ITNs has been developed that incorporate synergistic components, such as piperonyl butoxide (PBO). The purpose of this study is to provide entomological evidence for the efficacy of a PBO-based ITN brand at the village level, serving as a basis for decision-making before large-scale net deployment. During the high malaria transmission period, ITNs were distributed in each group and vector sampling was conducted biweekly in selected households. Bionomic data were collected to assess the resistance of wild An. gambiae populations to various chemical insecticides. There was a significant disparity in total An. gambiae sl. collected between the ITN arms, the intervention arm (ITN arms), and the control arm (P = 0.003). An. coluzzi was identified as the predominant species in the study area, as confirmed by PCR analysis. Analysis of the blood-feeding inhibition rate revealed that 100% permethrin + PBO ITN exhibited significantly greater inhibition than 66.81% permethrin only ITN. According to the log-time probit regression analysis, permethrin exhibited a knockdown time of 256 min without synergists, while it decreased to 139 min (P = 0.001) when pre-exposed to PBO. The evidence from this trial supports the use of PBO ITNs over standard ITNs for pyrethroids to combat pyrethroid resistance and improve protection against malaria for both individuals and communities, particularly in areas with high pyrethroid resistance.展开更多
文摘为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,并借助冷冻干燥技术,成功制备出具备多孔结构的复合气凝胶纤维。通过调节银纳米粒子的负载量,深入研究其对材料电磁屏蔽性能等方面的影响。研究结果显示,该复合材料在X波段(8.2~12.4 GHz)的电磁干扰(EMI)屏蔽效能值达到33 dB,且EMI SE A占总EMI值的60%,说明其以吸收屏蔽为主导,这基于气凝胶纤维的高比表面积和银纳米粒子的导电性对电磁波的吸收。
基金the National Natural Science Foundation of China(52203100)Shaanxi Province Key Research and Development Plan Project(2024GX-YBXM-386)+3 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2682)Undergraduate Innovation&Business Program of Northwestern Polytechnical University(S202310699322)the Analytical&Testing Center of Northwestern Polytechnical University for SEM tests performed in this work.
文摘Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.
基金supported by the National Natural Science Foundation of China(No.U21A2094)CASHIPS Director’s Fund(Nos.YZJJZX202015,YZJJ202304-CX,YZJJ2023QN36)+1 种基金Anhui Province Postdoctoral Researcher Research Project(No.E24F0D27)Central Government Guiding Local Government Science and Technology Development Special Fund Project(No.2022ZB09002).
文摘Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.
基金funded by the Guangxi Innovation-Driven Development Project(Grant Number AA17204058).
文摘To enhance the productivity of Carya illinoinensis cv.‘Shaoxing’and mitigate the loss of flowers and fruits,the effects of different concentrations of Piperonyl Butoxide(PBO)wettable powder(2,5,and 10 g·L^(-1))and Paclobutrazol(PP_(333))(150,300,and 450 mg·L^(-1),based on active ingredients)on 6-year-old‘Shaoxing’plants were investigated with water sprayed as the control.The results showed that:(1)Treatment with 10 g·L^(-1)PBO and 450 mg·L^(-1)PP_(333)significantly inhibited the excessive growth of‘Shaoxing’branches.Also,10 g·L^(-1)PBO exhibited the best diameter increment effect on fruiting branches,and 150 mg·L^(-1)PP_(333) exhibited the best diameter increment effect on vegetative branches.(2)The content of soluble sugar and soluble protein in leaves treated reached the highest level after treatment with 450 mg·L^(-1)PP_(333),while the content of starch sugar in leaves reached the highest level after treatment with 300 mg·L^(-1)PP_(333).The application of PBO and PP_(333)mitigated the decline in N,P,K,and other nutrient levels observed in the leaves of‘Shaoxing’.As the PBO and PP_(333) concentrations increased,the nutrient elements in the leaves first increased and then decreased.Among them,300 mg·L^(-1)PP_(333)treatment exhibited the best effect on increasing the content of N,P,and K in the leaves at the late stage of fruit development.(3)In terms of fruit setting rate and nutritional quality of‘Shaoxing’fruit,5 g·L^(-1)PBO treatment showed the most promising effect on improving fruit setting rate,150 mg·L^(-1)PP_(333)exhibited the best effect on improving reducing sugar and decreasing tannin content in the kernel,10 g·L^(-1)PBO had the best effect on improving the crude fat content,and 2 g·L^(-1)PBO had the best effect on improving the cellulose content in the kernel.(4)Principal component analysis showed that 450 mg·L^(-1)PP_(333)treatment had the most comprehensive regulatory effect on the growth and development of current-year branches,leaves,and fruits of‘Shaoxing’.This study provided a theoretical basis and data reference for the growth and development of C.illinoinensis cv.‘Shaoxing’fruits from the perspective of the application of plant growth regulators.
文摘The efficacy of insecticide-treated nets (ITNs) is increasingly compromised by the prevalence of malaria vectors resistant to pyrethroids. In response to this issue, a new generation of ITNs has been developed that incorporate synergistic components, such as piperonyl butoxide (PBO). The purpose of this study is to provide entomological evidence for the efficacy of a PBO-based ITN brand at the village level, serving as a basis for decision-making before large-scale net deployment. During the high malaria transmission period, ITNs were distributed in each group and vector sampling was conducted biweekly in selected households. Bionomic data were collected to assess the resistance of wild An. gambiae populations to various chemical insecticides. There was a significant disparity in total An. gambiae sl. collected between the ITN arms, the intervention arm (ITN arms), and the control arm (P = 0.003). An. coluzzi was identified as the predominant species in the study area, as confirmed by PCR analysis. Analysis of the blood-feeding inhibition rate revealed that 100% permethrin + PBO ITN exhibited significantly greater inhibition than 66.81% permethrin only ITN. According to the log-time probit regression analysis, permethrin exhibited a knockdown time of 256 min without synergists, while it decreased to 139 min (P = 0.001) when pre-exposed to PBO. The evidence from this trial supports the use of PBO ITNs over standard ITNs for pyrethroids to combat pyrethroid resistance and improve protection against malaria for both individuals and communities, particularly in areas with high pyrethroid resistance.
