Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of flor...Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored.We investigated floral trait variation,pollination,and nectar robbing among individual plants in a population of the bumble bee-pollinated plant,Caryopteris divaricata,from which flowers are also robbed by bumble bees with varying intensity across individuals.We measured the variation in corolla tube length,nectar volume and sugar concentration among individual plants,and evaluated whether the variation were recognized by pollinators and robbers.We investigated the in-fluence of nectar robbing on legitimate visitation and seed production per fruit.We found that the primary nectar robber(Bombus nobilis)preferred to forage on plants with long-tubed flowers,which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes.Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors(mainly B.picipes)and higher seed production.Nectar robbing signifi-cantly reduced seed production because it decreased pollinator visits.However,neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded.This finding suggests that floral trait variation might not be driven by pollinators.Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.展开更多
Biodiversity loss during the Anthropocene is a serious ecological challenge.Pollinators are important vectors that provide multiple essential ecosystem services but are declining rapidly in this changing world.However...Biodiversity loss during the Anthropocene is a serious ecological challenge.Pollinators are important vectors that provide multiple essential ecosystem services but are declining rapidly in this changing world.However,several studies have argued that a high abundance of managed bee pollinators,such as honeybees(Apis mellifera),may be sufficient to provide pollination services for crop productivity,and sociological studies indicate that the majority of farmers worldwide do not recognize the contribution of wild pollinator diversity to agricultural yield.Here,we review the importance of pollinator diversity in natural and agricultural ecosystems that may be thwarted by the increase in abundance of managed pollinators such as honeybees.We also emphasize the additional roles diverse pollinator communities play in environmental safety,culture,and aesthetics.Research indicates that in natural ecosystems,pollinator diversity enhances pollination during environmental and climatic perturbations,thus alleviating pollen limitation.In agricultural ecosystems,pollinator diversity increases the quality and quantity of crop yield.Furthermore,studies indicate that many pollinator groups are useful in monitoring environmental pollution,aid in pest and disease control,and provide cultural and aesthetic value.During the uncertainties that may accompany rapid environmental changes in the Anthropocene,the conservation of pollinator diversity must expand beyond bee conservation.Similarly,the value of pollinator diversity maintenance extends beyond the provision of pollination services.Accordingly,conservation of pollinator diversity requires an interdisciplinary approach with contributions from environmentalists,taxonomists,and social scientists,including artists,who can shape opinions and behavior.展开更多
Cerebral perfusion computed tomography(PCT)is an important imaging modality for evaluating cerebrovascular diseases and stroke symptoms.With widespread public concern about the potential cancer risks and health hazard...Cerebral perfusion computed tomography(PCT)is an important imaging modality for evaluating cerebrovascular diseases and stroke symptoms.With widespread public concern about the potential cancer risks and health hazards associated with cumulative radiation exposure in PCT imaging,considerable research has been conducted to reduce the radiation dose in X-ray-based brain perfusion imaging.Reducing the dose of X-rays causes severe noise and artifacts in PCT images.To solve this problem,we propose a deep learning method called NCS-Unet.The exceptional characteristics of non-subsampled contourlet transform(NSCT)and the Sobel filter are introduced into NCS-Unet.NSCT decomposes the convolved features into high-and low-frequency components.The decomposed high-frequency component retains image edges,contrast imaging traces,and noise,whereas the low-frequency component retains the main image information.The Sobel filter extracts the contours of the original image and the imaging traces caused by the contrast agent decay.The extracted information is added to NCS-Unet to improve its performance in noise reduction and artifact removal.Qualitative and quantitative analyses demonstrated that the proposed NCS-Unet can improve the quality of low-dose cone-beam CT perfusion reconstruction images and the accuracy of perfusion parameter calculations.展开更多
Graphene is an ideal reinforcing phase for a high-performance composite filler,which is of great theoretical and practical significance for improving the wettability and reliability of the filler.However,the poor adso...Graphene is an ideal reinforcing phase for a high-performance composite filler,which is of great theoretical and practical significance for improving the wettability and reliability of the filler.However,the poor adsorption characteristics between graphene and the silver base filler significantly affect the application of graphene filler in the brazing field.It is a great challenge to improve the adsorption characteristics between a graphene and silver base filler.To solve this issue,the adsorption characteristic between graphene and silver was studied with first principle calculation.The effects of Ga,Mo,and W on the adsorption properties of graphene were explored.There are three possible adsorbed sites,the hollow site(H),the bridge site(B),and the top site(T).Based on this research,the top site is the most preferentially adsorbed site for Ag atoms,and there is a strong interaction between graphene and Ag atoms.Metal element doping enhances local hybridization between C or metal atoms and Ag.Furthermore,compared with other doped structures(Ga and Mo),W atom doping is the most stable adsorption structure and can also improve effective adsorption characteristic performance between graphene and Ag.展开更多
基金The research was supported by the National Natural Science Foundation of China(No.31970253 and 32270243)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB31010000)+1 种基金AL was also supported by a Ramon y Cajal contract(RYC-2015-19034)from the Spanish Ministry of Science,Innovation and Universities,the Spanish State Research Agency,European Social Funds(ESF invests in your future)and the University of the Balearic Islands,and by the project PRPPID2020-117863RB-I00financed by the Spanish Ministry of Science and Innovation and the Spanish Research Agency(MCIN/AEI/10.13039/501100011033).
文摘Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored.We investigated floral trait variation,pollination,and nectar robbing among individual plants in a population of the bumble bee-pollinated plant,Caryopteris divaricata,from which flowers are also robbed by bumble bees with varying intensity across individuals.We measured the variation in corolla tube length,nectar volume and sugar concentration among individual plants,and evaluated whether the variation were recognized by pollinators and robbers.We investigated the in-fluence of nectar robbing on legitimate visitation and seed production per fruit.We found that the primary nectar robber(Bombus nobilis)preferred to forage on plants with long-tubed flowers,which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes.Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors(mainly B.picipes)and higher seed production.Nectar robbing signifi-cantly reduced seed production because it decreased pollinator visits.However,neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded.This finding suggests that floral trait variation might not be driven by pollinators.Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.
基金supported by the National Natural Science Foundation of China(Grant No.31970253,31770255 and 32100188)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB31010000).
文摘Biodiversity loss during the Anthropocene is a serious ecological challenge.Pollinators are important vectors that provide multiple essential ecosystem services but are declining rapidly in this changing world.However,several studies have argued that a high abundance of managed bee pollinators,such as honeybees(Apis mellifera),may be sufficient to provide pollination services for crop productivity,and sociological studies indicate that the majority of farmers worldwide do not recognize the contribution of wild pollinator diversity to agricultural yield.Here,we review the importance of pollinator diversity in natural and agricultural ecosystems that may be thwarted by the increase in abundance of managed pollinators such as honeybees.We also emphasize the additional roles diverse pollinator communities play in environmental safety,culture,and aesthetics.Research indicates that in natural ecosystems,pollinator diversity enhances pollination during environmental and climatic perturbations,thus alleviating pollen limitation.In agricultural ecosystems,pollinator diversity increases the quality and quantity of crop yield.Furthermore,studies indicate that many pollinator groups are useful in monitoring environmental pollution,aid in pest and disease control,and provide cultural and aesthetic value.During the uncertainties that may accompany rapid environmental changes in the Anthropocene,the conservation of pollinator diversity must expand beyond bee conservation.Similarly,the value of pollinator diversity maintenance extends beyond the provision of pollination services.Accordingly,conservation of pollinator diversity requires an interdisciplinary approach with contributions from environmentalists,taxonomists,and social scientists,including artists,who can shape opinions and behavior.
基金supported in part by Science and Technology Program of Guangdong (No. 2018B030333001)the State’s Key Project of Research and Development Plan (Nos. 2017YFC0109202,2017YFA0104302 and 2017YFC0107900)the National Natural Science Foundation (Nos. 81530060 and 61871117)
文摘Cerebral perfusion computed tomography(PCT)is an important imaging modality for evaluating cerebrovascular diseases and stroke symptoms.With widespread public concern about the potential cancer risks and health hazards associated with cumulative radiation exposure in PCT imaging,considerable research has been conducted to reduce the radiation dose in X-ray-based brain perfusion imaging.Reducing the dose of X-rays causes severe noise and artifacts in PCT images.To solve this problem,we propose a deep learning method called NCS-Unet.The exceptional characteristics of non-subsampled contourlet transform(NSCT)and the Sobel filter are introduced into NCS-Unet.NSCT decomposes the convolved features into high-and low-frequency components.The decomposed high-frequency component retains image edges,contrast imaging traces,and noise,whereas the low-frequency component retains the main image information.The Sobel filter extracts the contours of the original image and the imaging traces caused by the contrast agent decay.The extracted information is added to NCS-Unet to improve its performance in noise reduction and artifact removal.Qualitative and quantitative analyses demonstrated that the proposed NCS-Unet can improve the quality of low-dose cone-beam CT perfusion reconstruction images and the accuracy of perfusion parameter calculations.
基金the Extracurricular Open Experiment of Southwest Petroleum University(No.KSZ18513)the State Key Program of National Natural Science Foundation of China(No.51474181).
文摘Graphene is an ideal reinforcing phase for a high-performance composite filler,which is of great theoretical and practical significance for improving the wettability and reliability of the filler.However,the poor adsorption characteristics between graphene and the silver base filler significantly affect the application of graphene filler in the brazing field.It is a great challenge to improve the adsorption characteristics between a graphene and silver base filler.To solve this issue,the adsorption characteristic between graphene and silver was studied with first principle calculation.The effects of Ga,Mo,and W on the adsorption properties of graphene were explored.There are three possible adsorbed sites,the hollow site(H),the bridge site(B),and the top site(T).Based on this research,the top site is the most preferentially adsorbed site for Ag atoms,and there is a strong interaction between graphene and Ag atoms.Metal element doping enhances local hybridization between C or metal atoms and Ag.Furthermore,compared with other doped structures(Ga and Mo),W atom doping is the most stable adsorption structure and can also improve effective adsorption characteristic performance between graphene and Ag.