For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refi...For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition.The strategy,namely UVlight and IR-laser hybrid chemical modification(UVIR-CM)strategy,includes two steps,an ultraviolet light(UV-light)catalytic advanced oxidation and an infrared laser(IR-laser)assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon.The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation,crosssection transmission electron microscopy(TEM)observation,Raman spectroscopy analysis and nanoindentation test.Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’IR-laser scanned area.And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium.But for the UVIR-CM strategy,a uniform and amorphous silicate layer is detected in a certain boundary.The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step.Attributing to synergism of photochemical,photothermal and kinetic effects induced by IR-laser,the modified layer displays layered structure with about 600 nm thickness,(2.7±0.60)GPa nanohardness,and(93.7±22.9)GPa indentation modulus.And the layered structure is amorphous layer,nanocrystal and micro-twins layer from the surface to the interior of sample.Consequently,it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area.Meanwhile,its original excellent mechanical properties also are maintained under a certain depth.The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.展开更多
Input ground motions have significant impacts on the uncertainty of structural responses in time-history analysis.In this study,records were selected and scaled for the evaluation of mean structural responses accordin...Input ground motions have significant impacts on the uncertainty of structural responses in time-history analysis.In this study,records were selected and scaled for the evaluation of mean structural responses according to the target spectrum.The Newmark-Hall spectrum is closely related to seismic response of short,medium and long-period structures,so it was taken as the target spectrum here.The nonlinear time-history analyses of 9-story and 20-story steel moment-resisting frame structures were carried out as examples.They represent medium and long-period buildings,respectively.Three target spectra with risk of 50%,10%and 2%probabilities for exceedance in 50 years were calculated by the average Newmark-Hall spectrum method for three ground motion sets developed in the SAC Steel Project.The predicted structural mean responses of these Newmark-Hall spectra were compared with those calculated by the average spectral acceleration method for the same record set.It is found that both methods have similar accuracy for estimating the structural mean response.However,the method proposed herein is more effective in reducing the variability of the structural responses.Also,the proposed method is more advantageous for the time-history analysis of long-period structures or structures with more severe nonlinear responses under strong seismic excitations.展开更多
Hydrothermal fabrication of selectively doped（Ag＋＋ Pd3＋） advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions（autogeneous; 150°C）.Gluconic acid has been used as a surfa...Hydrothermal fabrication of selectively doped（Ag＋＋ Pd3＋） advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions（autogeneous; 150°C）.Gluconic acid has been used as a surface modifier to effectively control the particle size and morphology of these ZnO nanoparticles. The experimental parameters were tuned to achieve optimum conditions for the synthesis of selectively doped ZnO nanomaterials with an experimental duration of 4 hr. These selectively doped ZnO nanoparticles were characterized using powder X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, UV–Vis spectroscopy and scanning electron microscopy（SEM）. The solar driven photocatalytic studies have been carried out for organic dyes, i.e., Procion MX-5B dye,Cibacron Brilliant Yellow dye, Indigo Carmine dye, separately and all three mixed, by using gluconic acid modified selectively doped advanced ZnO nanomaterial. The influence of catalyst, its concentration and initial dye concentration resulted in the photocatalytic efficiency of 89% under daylight.展开更多
Cable-like Au@SiO2 Janus composite nanorods with PS and PEG grafting on both ends respectively are fabricated by skiving in combination of a post favorable modification. The cable-like Au@SiO2 composite nanofibers are...Cable-like Au@SiO2 Janus composite nanorods with PS and PEG grafting on both ends respectively are fabricated by skiving in combination of a post favorable modification. The cable-like Au@SiO2 composite nanofibers are synthesized in the channel of porous anodic aluminium oxide （AAO） membrane. After skiving, the corresponding composite nanorods are obtained. Following, PEG-SH and PS-SH are conjugated onto the two ends of the nanorods by a selective partial modification, respectively. Length and diameter of the Au@SiO2 Janus composite nanorods can be tuned controllably. It can be extended to fabricate a variety of different Janus nanorods with different compositions and microstructures.展开更多
Pd-based egg-shell nano-catalysts were prepared using porous hollow silica nanoparticles （PHSNs） as support, and the as-prepared catalysts were modified with TiO2 to promote their selectivity for hydro-genation of a...Pd-based egg-shell nano-catalysts were prepared using porous hollow silica nanoparticles （PHSNs） as support, and the as-prepared catalysts were modified with TiO2 to promote their selectivity for hydro-genation of acetylene. Pd nanoparticles were loaded evenly on PHSNs and TiO2 was loaded on the active Pd particles. The effects of reduction time and temperature and the amount of TiO2 added on catalytic per-formances were investigated by using a fixed-bed micro-reactor. It was found that the catalysts showed better performance when reduced at 300 ℃ than at 500℃, and if reduced for 1 h than 3 h. When the amount of Ti added was 6 times that of Pd, the catalyst showed the highest ethylene selectivity.展开更多
Aims Identifying the potential role of vegetation context(defined as the density,species identity/diversity and height of co-occurring plants)in modifying selection on floral traits is a critical step for clarifying a...Aims Identifying the potential role of vegetation context(defined as the density,species identity/diversity and height of co-occurring plants)in modifying selection on floral traits is a critical step for clarifying and predicting the floral evolutionary trajectory in complex co-flowering species competition environments.It is also helpful to understand the variation in pollinator-mediated selection.Methods We experimentally reduced vegetation height around individual plants of Spiranthes sinensis(a bumblebee-pollinated perennial orchid herb)and estimated how vegetation context modified selection on four floral traits(flowering start,plant height,corolla size and number of flowers)through female function and pollen removal over two continuous years.We randomly selected independent plants in each year.Important Findings We demonstrated that vegetation context modified selection for earlier flowering start and shorter plant height of S.sinensis.The strength of selection differed between years.In addition,selection was stronger through female function than through pollen removal.Our findings indicate the potential role of vegetation context in shaping the differentiation and diversification of flowers in angiosperms.展开更多
Aggregation represents a significant challenge for the long-term formulation stability of insulin therapeutics.The supramolecular PEGylation of insulin with conjugates of cucurbit[7]uril and polyethylene glycol(CB[7]-...Aggregation represents a significant challenge for the long-term formulation stability of insulin therapeutics.The supramolecular PEGylation of insulin with conjugates of cucurbit[7]uril and polyethylene glycol(CB[7]-PEG)has been shown to stabilize insulin formulations by reducing aggregation propensity.Yet prolonged in vivo duration of action,arising from sustained complex formation in the subcutaneous depot,limits the application scope for meal-time insulin uses and could increase hypoglycemic risk several hours after a meal.Supramolecular affinity of CB[7]in binding the B1-Phe residue on insulin is central to supramolecular PEGylation using this approach.Accordingly,here we synthesized N-terminal acid-modified insulin analogs to reduce CB[7]interaction affinity at physiological pH and reduce the duration of action by decreasing the subcutaneous depot effect of the formulation.These insulin analogs show weak to no interaction with CB[7]-PEG at physiological pH but demonstrate high formulation stability at reduced pH.Accordingly,N-terminal modified analogs have in vitro and in vivo bioactivity comparable to native insulin.Furthermore,in a rat model of diabetes,the acid-modified insulin formulated with CB[7]-PEG offers a reduced duration of action compared to native insulin formulated with CB[7]-PEG.This work extends the application of supramolecular PEGylation of insulin to achieve enhanced stability while reducing the risks arising from a subcutaneous depot effect prolonging in vivo duration of action.展开更多
基金supported by the National Natural Science Foundation of China(52075161,51875192).
文摘For high performance manufacturing of micro parts and features,a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition.The strategy,namely UVlight and IR-laser hybrid chemical modification(UVIR-CM)strategy,includes two steps,an ultraviolet light(UV-light)catalytic advanced oxidation and an infrared laser(IR-laser)assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon.The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation,crosssection transmission electron microscopy(TEM)observation,Raman spectroscopy analysis and nanoindentation test.Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’IR-laser scanned area.And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium.But for the UVIR-CM strategy,a uniform and amorphous silicate layer is detected in a certain boundary.The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step.Attributing to synergism of photochemical,photothermal and kinetic effects induced by IR-laser,the modified layer displays layered structure with about 600 nm thickness,(2.7±0.60)GPa nanohardness,and(93.7±22.9)GPa indentation modulus.And the layered structure is amorphous layer,nanocrystal and micro-twins layer from the surface to the interior of sample.Consequently,it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area.Meanwhile,its original excellent mechanical properties also are maintained under a certain depth.The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.
基金National Natural Science Foundation of Hebei Province under Grant No.E2020202038the National Natural Science Foundation of China under Grant No.51778206。
文摘Input ground motions have significant impacts on the uncertainty of structural responses in time-history analysis.In this study,records were selected and scaled for the evaluation of mean structural responses according to the target spectrum.The Newmark-Hall spectrum is closely related to seismic response of short,medium and long-period structures,so it was taken as the target spectrum here.The nonlinear time-history analyses of 9-story and 20-story steel moment-resisting frame structures were carried out as examples.They represent medium and long-period buildings,respectively.Three target spectra with risk of 50%,10%and 2%probabilities for exceedance in 50 years were calculated by the average Newmark-Hall spectrum method for three ground motion sets developed in the SAC Steel Project.The predicted structural mean responses of these Newmark-Hall spectra were compared with those calculated by the average spectral acceleration method for the same record set.It is found that both methods have similar accuracy for estimating the structural mean response.However,the method proposed herein is more effective in reducing the variability of the structural responses.Also,the proposed method is more advantageous for the time-history analysis of long-period structures or structures with more severe nonlinear responses under strong seismic excitations.
基金supported by University Grant Commission under University with Potential for excellence Programme (UPE), University of Mysore
文摘Hydrothermal fabrication of selectively doped（Ag＋＋ Pd3＋） advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions（autogeneous; 150°C）.Gluconic acid has been used as a surface modifier to effectively control the particle size and morphology of these ZnO nanoparticles. The experimental parameters were tuned to achieve optimum conditions for the synthesis of selectively doped ZnO nanomaterials with an experimental duration of 4 hr. These selectively doped ZnO nanoparticles were characterized using powder X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, UV–Vis spectroscopy and scanning electron microscopy（SEM）. The solar driven photocatalytic studies have been carried out for organic dyes, i.e., Procion MX-5B dye,Cibacron Brilliant Yellow dye, Indigo Carmine dye, separately and all three mixed, by using gluconic acid modified selectively doped advanced ZnO nanomaterial. The influence of catalyst, its concentration and initial dye concentration resulted in the photocatalytic efficiency of 89% under daylight.
基金supported by the National Natural Science Foundation of China(Nos. 51233007 and 51622308)
文摘Cable-like Au@SiO2 Janus composite nanorods with PS and PEG grafting on both ends respectively are fabricated by skiving in combination of a post favorable modification. The cable-like Au@SiO2 composite nanofibers are synthesized in the channel of porous anodic aluminium oxide （AAO） membrane. After skiving, the corresponding composite nanorods are obtained. Following, PEG-SH and PS-SH are conjugated onto the two ends of the nanorods by a selective partial modification, respectively. Length and diameter of the Au@SiO2 Janus composite nanorods can be tuned controllably. It can be extended to fabricate a variety of different Janus nanorods with different compositions and microstructures.
基金the financial support provided by National Natural Science Foundation of China (Nos.20821004 and 50642042)the Key Research Program of Ministry ofEducation of China (No. 108009)+1 种基金CNPC Innovation Foundation (No.06-04D-01-01-02)the Chinese Universities Scientific Fund
文摘Pd-based egg-shell nano-catalysts were prepared using porous hollow silica nanoparticles （PHSNs） as support, and the as-prepared catalysts were modified with TiO2 to promote their selectivity for hydro-genation of acetylene. Pd nanoparticles were loaded evenly on PHSNs and TiO2 was loaded on the active Pd particles. The effects of reduction time and temperature and the amount of TiO2 added on catalytic per-formances were investigated by using a fixed-bed micro-reactor. It was found that the catalysts showed better performance when reduced at 300 ℃ than at 500℃, and if reduced for 1 h than 3 h. When the amount of Ti added was 6 times that of Pd, the catalyst showed the highest ethylene selectivity.
基金This research was supported by the Funds of the Science and Technology Department of Sichuan Province(2019YJ0393,2020YFSO309)Joint Funds of the National Natural Science Foundation of China and Yunnan Provincial Government(U1602263).
文摘Aims Identifying the potential role of vegetation context(defined as the density,species identity/diversity and height of co-occurring plants)in modifying selection on floral traits is a critical step for clarifying and predicting the floral evolutionary trajectory in complex co-flowering species competition environments.It is also helpful to understand the variation in pollinator-mediated selection.Methods We experimentally reduced vegetation height around individual plants of Spiranthes sinensis(a bumblebee-pollinated perennial orchid herb)and estimated how vegetation context modified selection on four floral traits(flowering start,plant height,corolla size and number of flowers)through female function and pollen removal over two continuous years.We randomly selected independent plants in each year.Important Findings We demonstrated that vegetation context modified selection for earlier flowering start and shorter plant height of S.sinensis.The strength of selection differed between years.In addition,selection was stronger through female function than through pollen removal.Our findings indicate the potential role of vegetation context in shaping the differentiation and diversification of flowers in angiosperms.
基金NIDDK(DK120430,DK121336,USA)to Danny Hung-Chieh ChouJDRF(5-CDA-2020-947-A-N,USA)to Matthew J.Webber。
文摘Aggregation represents a significant challenge for the long-term formulation stability of insulin therapeutics.The supramolecular PEGylation of insulin with conjugates of cucurbit[7]uril and polyethylene glycol(CB[7]-PEG)has been shown to stabilize insulin formulations by reducing aggregation propensity.Yet prolonged in vivo duration of action,arising from sustained complex formation in the subcutaneous depot,limits the application scope for meal-time insulin uses and could increase hypoglycemic risk several hours after a meal.Supramolecular affinity of CB[7]in binding the B1-Phe residue on insulin is central to supramolecular PEGylation using this approach.Accordingly,here we synthesized N-terminal acid-modified insulin analogs to reduce CB[7]interaction affinity at physiological pH and reduce the duration of action by decreasing the subcutaneous depot effect of the formulation.These insulin analogs show weak to no interaction with CB[7]-PEG at physiological pH but demonstrate high formulation stability at reduced pH.Accordingly,N-terminal modified analogs have in vitro and in vivo bioactivity comparable to native insulin.Furthermore,in a rat model of diabetes,the acid-modified insulin formulated with CB[7]-PEG offers a reduced duration of action compared to native insulin formulated with CB[7]-PEG.This work extends the application of supramolecular PEGylation of insulin to achieve enhanced stability while reducing the risks arising from a subcutaneous depot effect prolonging in vivo duration of action.
