Understanding genome-wide diversity,inbreeding,and the burden of accumulated deleterious mutations in small and isolated populations is essential for predicting and enhancing population persistence and resilience.Howe...Understanding genome-wide diversity,inbreeding,and the burden of accumulated deleterious mutations in small and isolated populations is essential for predicting and enhancing population persistence and resilience.However,these effects are rarely studied in limestone karst plants.Here,we re-sequenced the nuclear genomes of 62 individuals of the Begonia masoniana complex(B.liuyanii,B.longgangensis,B.masoniana and B.variegata)and investigated genomic divergence and genetic load for these four species.Our analyses revealed four distinct clusters corresponding to each species within the complex.Notably,there was only limited admixture between B.liuyanii and B.longgangensis occurring in overlapping geographic regions.All species experienced historical bottlenecks during the Pleistocene,which were likely caused by glacial climate fluctuations.We detected an asymmetric historical gene flow between group pairs within this timeframe,highlighting a distinctive pattern of interspecific divergence attributable to karst geographic isolation.We found that isolated populations of B.masoniana have limited gene flow,the smallest recent population size,the highest inbreeding coefficients,and the greatest accumulation of recessive deleterious mutations.These findings underscore the urgency to prioritize conservation efforts for these isolated population.This study is among the first to disentangle the genetic differentiation and specific demographic history of karst Begonia plants at the whole-genome level,shedding light on the potential risks associated with the accumulation of deleterious mutations over generations of inbreeding.Moreover,our findings may facilitate conservation planning by providing critical baseline genetic data and a better understanding of the historical events that have shaped current population structure of rare and endangered karst plants.展开更多
AIM: To investigate the roles of nuclear factor(NF)-κB and angiotensin Ⅱ receptor type 1(AT1R) in the pathogenesis of non-alcoholic fatty liver disease(NAFLD).METHODS: Forty-two healthy adult male SpragueDawley rats...AIM: To investigate the roles of nuclear factor(NF)-κB and angiotensin Ⅱ receptor type 1(AT1R) in the pathogenesis of non-alcoholic fatty liver disease(NAFLD).METHODS: Forty-two healthy adult male SpragueDawley rats were randomly divided into three groups:the control group(normal diet), the model group,and the intervention group(10 wk of a high-fat diet feeding, followed by an intraperitoneal injection of PDTC); 6 rats in each group were sacrificed at 6, 10,and 14 wk. After sacrifice, liver tissue was taken,paraffin sections of liver tissue specimens were prepared, hematoxylin and eosin(HE) staining was performed, and pathological changes in liver tissue(i.e., liver fibrosis) were observed by light microscopy.NF-κB expression in liver tissue was detected by immunohistochemistry, and the expression of AT1 R in the liver tissue was detected by reverse transcriptionpolymerase chain reaction(RT-PCR). The data are expressed as mean ± SD. A two-sample t test was used to compare the control group and the model group at different time points, paired t tests were used to compare the differences between the intervention group and the model group, and analysis of variance was used to compare the model group with the control group. Homogeneity of variance was analyzed with single factor analysis of variance. H variance analysis was used to compare the variance. P < 0.05 wasconsidered statistically significant.RESULTS: The NAFLD model was successful after 6wk and 10 wk. Liver fibrosis was found in four rats in the model group, but in only one rat in the intervention group at 14 wk. Liver steatosis, inflammation, and fibrosis were gradually increased throughout the model. In the intervention group, the body mass,rat liver index, serum lipid, and transaminase levels were not increased compared to the model group.In the model group, the degree of liver steatosis was increased at 6, 10, and 14 wk, and was significantly higher than in the control group(P < 0.01). In the model group, different degrees of liver cell necrosis were visible and small leaves, punctated inflammation,focal necrosis, and obvious ballooning degeneration were observed. Partial necrosis and confluent necrosis were observed. In the model group, liver inflammatory activity scores at 6, 10, and 14 wk were higher than in the control group(P < 0.01). Active inflammation in liver tissue in the intervention group was lower than in the model group(P < 0.05). HE staining showed liver fibrosis only at 14 wk in 4/6 rats in the model group and in 1/6 rats in the intervention group. NF-κB positive cells were stained yellow or ensemble yellow,and NF-κB was localized in the cytoplasm and/or nucleus. The model group showed NF-κB activation at6, 10, and 14 wk in liver cells; at the same time points,there were statistically significant differences in the control group(P < 0.01). Over time, NF-κB expression increased; this was statistically lower(P < 0.05) at14 weeks in the intervention group compared to the model group, but significantly increased(P < 0.05)compared with the control group; RT-PCR showed that AT1 R mRNA expression increased gradually in the model group; at 14 wk, the expression was significantly different compared with expression at 10 weeks as well as at 6 weeks(P < 0.05). In the model group, AT1 R mRNA expression was significantly higher than at the same time point in the control group(P <0.01).CONCLUSION: With increasing severity of NAFLD,NF-κB activity is enhanced, and the inhibition of NF-κB activity may reduce AT1 R mRNA expression in NAFLD.展开更多
By using a simplified Coulomb explosion model, the laser-driven Coulomb explosion processes of three deuterated alkane clusters, i.e., deuterated methane（CD4）N, ethane（C2D6）N and propane（C3D8）N clusters are simu...By using a simplified Coulomb explosion model, the laser-driven Coulomb explosion processes of three deuterated alkane clusters, i.e., deuterated methane（CD4）N, ethane（C2D6）N and propane（C3D8）N clusters are simulated numerically.The overrun phenomenon that the deuterons overtake the carbon ions inside the expanding clusters, as well as the dependence of the energetic deuterons and fusion neutron yield on cluster size, is discussed in detail. Researches show that the average kinetic energy of deuterons and neutron yield generated in the Coulomb explosion of（C2D6）N cluster are higher than those of（CD4）N cluster with the same size, in qualitative agreement with the reported conclusions from the experiments of（C2 H6）N and（CH4）N clusters. It is indicated that（C2D6）N clusters are superior to（CD4）N clusters as a target for the laser-induced nuclear fusion reaction to achieve a higher neutron yield. In addition, by comparing the relevant data of（C3D8）N cluster with those of（C2D6）N cluster with the same size, it is theoretically concluded that（C3D8）N clusters with a larger competitive parameter might be a potential candidate for improving neutron generation. This will provide a theoretical basis for target selection in developing experimental schemes on laser-driven nuclear fusion in the future.展开更多
To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn an...To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn and Al contents in the steel and the reaction time on the interfacial reaction were investigated.It was observed that the erosion of the MgO refractory is caused by the reaction of Al and Mn in the steel with MgO in the refractory,which would lead to the formation of(Mn,Mg)O·Al_(2)O_(3) spinel and(Mn,Mg)O solid solution.The formation mechanism of the spinel and solid solution is as follows.The Al in the steel firstly reacts with MgO in the refractory to generate MgO·Al_(2)O_(3) spinel,and then,the spinel reacts with Mn in the steel to form(Mn,Mg)O·Al_(2)O_(3) spinel.Finally,the MnO in the spinel reacts with the MgO in the inner refractory to form(Mn,Mg)O solid solution.In addition,only(Mn,Mg)O·Al_(2)O_(3) spinel is present in the interfacial reaction layer of the refractory when the Al content in the steel is sufficient.展开更多
物种是生物多样性的基本单元,生殖隔离被认为是物种形成的关键;然而物种并不是静止的而是处于不断的分化演变之中,已经稳定成型但尚未到达分化后期的物种可能存在不完全的生殖隔离。对于物种的认识不能单从某一侧面或局部特征来界定,而...物种是生物多样性的基本单元,生殖隔离被认为是物种形成的关键;然而物种并不是静止的而是处于不断的分化演变之中,已经稳定成型但尚未到达分化后期的物种可能存在不完全的生殖隔离。对于物种的认识不能单从某一侧面或局部特征来界定,而应通过"整合物种概念"来确定物种地位。Flora of China记载了中国产白桫椤属(Sphaeropteris)2种,即白桫椤(S.brunoniana)和笔筒树(S.lepifera),并认为原产中国海南的海南白桫椤(S.hainanensis)和白桫椤为同一物种而将其并入白桫椤;但海南白桫椤在形态上已出现了分化。为探讨白桫椤及其近缘物种的亲缘关系和物种多样性分化的情况,本文采集到9个居群共21个样本,通过GBS简化基因组测序技术获得单核苷酸变异位点(SNP),进行系统发育树的构建和主成分及遗传结构的分析,并结合叶片数量性状的统计分析和孢子形态的观察测量。结果表明,海南白桫椤不仅与云南产白桫椤的基因型不同,且在叶片特征和孢子纹饰上有明显差异;但两个居群的生殖隔离较弱,在广西沿海地区形成杂交产物,其叶片特征为亲本的中间类型。因此,我们认为海南白桫椤是由于地理隔离而形成的一个处在分化路上的物种,建议恢复其物种地位;广西产白桫椤为自然杂交群体,应另处理为独立的自然杂交分类群--广西白桫椤(S. brunoniana×hainanensis)。展开更多
Spontaneous hybridization in ex situ facilities can undermine the genetic integrity of ex situ collections and potentially contaminate open-pollinated seeds or seedlings destined for the reintroduction of endangered p...Spontaneous hybridization in ex situ facilities can undermine the genetic integrity of ex situ collections and potentially contaminate open-pollinated seeds or seedlings destined for the reintroduction of endangered plant species into the wild. In the present study, the potential risk of hybridization between two endangered Chinese endemic species, namely Sinojackia xylocarpa Hu and S. rehderiana Hu, which are naturally allopatric species but were conserved ex situ in Wuhan Botanical Garden （WBG）, Wuhan, China, were investigated over three consecutive years from 2003 to 2005. The entire overlapping flowering period of the two species was 14-20 d and the two species shared the same pollinator insects during the entire flowering season in WBG. The floral isolation between the two species was not an issue in the ex sltu collection at WBG. The results suggest an opportunity for pollen transfer between species and a potential risk of genetic Introgression and loss of genetic identity of open-pollinated seeds produced in the ex sltu Collection of these two endangered species. An artificial reciprocal cross between S xylocarpa and S. rehderlana confirmed that the two congener species could readily set seeds, indicating no post-pollination barriers to hybridization and the importance of spatial isolation as a barrier to inter-specific crossing. Therefore, to manage these crossable species with overlapping flowering times and shared pollination vectors in ex situ facilities, spatial isolation should be carefully considered to minimize the possibility of spontaneous hybridization.展开更多
Metasurfaces have enabled the realization of several optical functionalities over an ultrathin platform,fostering the exciting field of flat optics.Traditional metasurfaces are achieved by arranging a layout of static...Metasurfaces have enabled the realization of several optical functionalities over an ultrathin platform,fostering the exciting field of flat optics.Traditional metasurfaces are achieved by arranging a layout of static meta-atoms to imprint a desired operation on the impinging wavefront,but their functionality cannot be altered.Reconfigurability and programmability of metasurfaces are the next important step to broaden their impact,adding customized on-demand functionality in which each meta-atom can be individually reprogrammed.We demonstrate a mechanical metasurface platform with controllable rotation at the meta-atom level,which can implement continuous Pancharatnam–Berry phase control of circularly polarized microwaves.As the proof-of-concept experiments,we demonstrate metalensing,focused vortex beam generation,and holographic imaging in the same metasurface template,exhibiting versatility and superior performance.Such dynamic control of electromagnetic waves using a single,low-cost metasurface paves an avenue towards practical applications,driving the field of reprogrammable intelligent metasurfaces for a variety of applications.展开更多
The silicone rubber composites present remarkable mechanical properties due to the double network structure constructed with molecular network of matrix and filler network of silica.Nevertheless,the filler network str...The silicone rubber composites present remarkable mechanical properties due to the double network structure constructed with molecular network of matrix and filler network of silica.Nevertheless,the filler network structure and corresponding reinforcement mechanism are still under debate and need to be further probed with the aid of applicative advanced analysis techniques.Herein,small-angle neutron scattering(SANS)and synchrotron radiation X-ray nano-computed tomography(Nano-CT)techniques are employed to explore the evolution of filler networks of fumed,precipitated and sol-gel silica,respectively.Our studying results reveal the formation of filler network constructed by the interconnecting of branched silica aggregates.And the silica with highly associated structure,pertaining to amorphous morphology,small size,and large surface area,presents short distance and effective molecular chain bridge between aggregates,thus forming strong and steady filler networks.This work would provide deep-seated revisiting of filler networks and corresponding reinforcement mechanism and offer guidance for optimizing the mechanical properties of silicone rubber.展开更多
We show that inhomogeneous waveguides of slowly varied parity-time(PT) symmetry support localized optical resonances.The resonance is closely related to the formation of exceptional points separating exact and broken ...We show that inhomogeneous waveguides of slowly varied parity-time(PT) symmetry support localized optical resonances.The resonance is closely related to the formation of exceptional points separating exact and broken PT phases.Salient features of this kind of non-Hermitian resonance, including the formation of half-vortex flux and the discrete nature,are discussed.This investigation highlights the unprecedented uniqueness of field dynamics in non-Hermitian systems with many potential adaptive applications.展开更多
This study proposes an approach to generate high-order exceptional points (EPs) in non-Herniitian systems.A system comprising a homogenous waveguide is considered wlierein the imaginary part of the refractive index is...This study proposes an approach to generate high-order exceptional points (EPs) in non-Herniitian systems.A system comprising a homogenous waveguide is considered wlierein the imaginary part of the refractive index is modulated using a one-dimensional Moire profile.This gain-loss niodulation couples different lossless waveguide modes,and these hybrid modes can be modeled using a non-Hcnnitian matrix with complex off-diagonal elements.Results indicate that third-order EPs can be produced by the coalescence of two sccond-ordcr EPs.Then,the necessary rcquiiGmcnts arc analyzed using couplcd-wavc ccjuations and the physical effects of the singularities are discussed.展开更多
Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only speci...Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus （Sapindaceae）, is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages （young and old）. Spatial distribution of males and females was further studied in six large populations occurring in different habitats （fragmented and continuous）. The study revealed a slight trend of male- biased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations （13 out of 15） did not display statistically significant deviation from equality. All of the four significantly male-biased populations in the young class shifted to equality or even female-biased, The Ripley＇s K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male-biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.展开更多
Monolayer(1L)transition metal dichalcogenides(TMDCs)have been attracting tremendous interest in recent years as promising candidate materials in atomic-scale optoelectronic devices due to their direct band gaps(1.5-2....Monolayer(1L)transition metal dichalcogenides(TMDCs)have been attracting tremendous interest in recent years as promising candidate materials in atomic-scale optoelectronic devices due to their direct band gaps(1.5-2.2 eV)and strong light-matter interactions.Unfortunately,their practical applications are limited by low visible light absorption stemming from atomic thickness and negligible infrared response.Here,we report the triangular Sb_(2)O_(3) microresonators in wide thickness and lateral size distributions grown on 1L TMDCs and their created significant broadband enhancement of light adsorption and photoresponse in 1L WSe_(2) crystal via coexisting Fabry-Perot and whispering gallery type resonances.As an example of demonstration,1L WSe_(2) crystal coupled to Sb_(2)O_(3) microresonators with widely distributed sizes exhibits the enhanced visible light absorption by up to 5 folds and the simultaneously extended near infrared(NIR)one of more than 50%.For application of 1L WSe_(2) in photodetection,incorporation of Sb2O3 microresonators leads to significantly enhanced visible light responsivity by~10^(4) order and expanded NIR one of more than 400 mA·W^(-1).Similar results have been observed in the other 1L W(Mo)dichalcogenides coupled to Sb2O3 microresonators.This work provides a new route for development of the high-performance monolayer TMDCs-based optoelectronic devices.展开更多
Understanding the mode’s origin in planar metamaterials is fundamental for related applications in nanophotonics and plasmonics.For complex planar metamaterials,conventional analysis that directly obtains the final c...Understanding the mode’s origin in planar metamaterials is fundamental for related applications in nanophotonics and plasmonics.For complex planar metamaterials,conventional analysis that directly obtains the final charge/current distribution of a mode is usually difficult in helping to understand the mode’s origin.In this paper,we propose a mode evolution method(MEM)with a core analysis tool,i.e.,plasmonic evolution maps(PEMs),to describe the mode evolution in several complementary planar metamaterials with designed plasmonic atoms/molecules.The PEMs could not only clearly explain a mode’s origin,but also reveal the role of a structure’s symmetry in the mode formation process.The MEM with PEMs can work as a simple,efficient,and universal approach for the mode analysis in different kinds of planar metamaterials.展开更多
基金supported by Key-Area Research and Development Program of Guangdong Province(Grant No.2022B1111230001)National Natural Science Foundation of China(31860048).
文摘Understanding genome-wide diversity,inbreeding,and the burden of accumulated deleterious mutations in small and isolated populations is essential for predicting and enhancing population persistence and resilience.However,these effects are rarely studied in limestone karst plants.Here,we re-sequenced the nuclear genomes of 62 individuals of the Begonia masoniana complex(B.liuyanii,B.longgangensis,B.masoniana and B.variegata)and investigated genomic divergence and genetic load for these four species.Our analyses revealed four distinct clusters corresponding to each species within the complex.Notably,there was only limited admixture between B.liuyanii and B.longgangensis occurring in overlapping geographic regions.All species experienced historical bottlenecks during the Pleistocene,which were likely caused by glacial climate fluctuations.We detected an asymmetric historical gene flow between group pairs within this timeframe,highlighting a distinctive pattern of interspecific divergence attributable to karst geographic isolation.We found that isolated populations of B.masoniana have limited gene flow,the smallest recent population size,the highest inbreeding coefficients,and the greatest accumulation of recessive deleterious mutations.These findings underscore the urgency to prioritize conservation efforts for these isolated population.This study is among the first to disentangle the genetic differentiation and specific demographic history of karst Begonia plants at the whole-genome level,shedding light on the potential risks associated with the accumulation of deleterious mutations over generations of inbreeding.Moreover,our findings may facilitate conservation planning by providing critical baseline genetic data and a better understanding of the historical events that have shaped current population structure of rare and endangered karst plants.
基金Supported by grants from the Science and Technology Department of Sichuan Province,No.2011SZ0094
文摘AIM: To investigate the roles of nuclear factor(NF)-κB and angiotensin Ⅱ receptor type 1(AT1R) in the pathogenesis of non-alcoholic fatty liver disease(NAFLD).METHODS: Forty-two healthy adult male SpragueDawley rats were randomly divided into three groups:the control group(normal diet), the model group,and the intervention group(10 wk of a high-fat diet feeding, followed by an intraperitoneal injection of PDTC); 6 rats in each group were sacrificed at 6, 10,and 14 wk. After sacrifice, liver tissue was taken,paraffin sections of liver tissue specimens were prepared, hematoxylin and eosin(HE) staining was performed, and pathological changes in liver tissue(i.e., liver fibrosis) were observed by light microscopy.NF-κB expression in liver tissue was detected by immunohistochemistry, and the expression of AT1 R in the liver tissue was detected by reverse transcriptionpolymerase chain reaction(RT-PCR). The data are expressed as mean ± SD. A two-sample t test was used to compare the control group and the model group at different time points, paired t tests were used to compare the differences between the intervention group and the model group, and analysis of variance was used to compare the model group with the control group. Homogeneity of variance was analyzed with single factor analysis of variance. H variance analysis was used to compare the variance. P < 0.05 wasconsidered statistically significant.RESULTS: The NAFLD model was successful after 6wk and 10 wk. Liver fibrosis was found in four rats in the model group, but in only one rat in the intervention group at 14 wk. Liver steatosis, inflammation, and fibrosis were gradually increased throughout the model. In the intervention group, the body mass,rat liver index, serum lipid, and transaminase levels were not increased compared to the model group.In the model group, the degree of liver steatosis was increased at 6, 10, and 14 wk, and was significantly higher than in the control group(P < 0.01). In the model group, different degrees of liver cell necrosis were visible and small leaves, punctated inflammation,focal necrosis, and obvious ballooning degeneration were observed. Partial necrosis and confluent necrosis were observed. In the model group, liver inflammatory activity scores at 6, 10, and 14 wk were higher than in the control group(P < 0.01). Active inflammation in liver tissue in the intervention group was lower than in the model group(P < 0.05). HE staining showed liver fibrosis only at 14 wk in 4/6 rats in the model group and in 1/6 rats in the intervention group. NF-κB positive cells were stained yellow or ensemble yellow,and NF-κB was localized in the cytoplasm and/or nucleus. The model group showed NF-κB activation at6, 10, and 14 wk in liver cells; at the same time points,there were statistically significant differences in the control group(P < 0.01). Over time, NF-κB expression increased; this was statistically lower(P < 0.05) at14 weeks in the intervention group compared to the model group, but significantly increased(P < 0.05)compared with the control group; RT-PCR showed that AT1 R mRNA expression increased gradually in the model group; at 14 wk, the expression was significantly different compared with expression at 10 weeks as well as at 6 weeks(P < 0.05). In the model group, AT1 R mRNA expression was significantly higher than at the same time point in the control group(P <0.01).CONCLUSION: With increasing severity of NAFLD,NF-κB activity is enhanced, and the inhibition of NF-κB activity may reduce AT1 R mRNA expression in NAFLD.
基金supported by the National Natural Science Foundation of China(Grant No.11005080)
文摘By using a simplified Coulomb explosion model, the laser-driven Coulomb explosion processes of three deuterated alkane clusters, i.e., deuterated methane（CD4）N, ethane（C2D6）N and propane（C3D8）N clusters are simulated numerically.The overrun phenomenon that the deuterons overtake the carbon ions inside the expanding clusters, as well as the dependence of the energetic deuterons and fusion neutron yield on cluster size, is discussed in detail. Researches show that the average kinetic energy of deuterons and neutron yield generated in the Coulomb explosion of（C2D6）N cluster are higher than those of（CD4）N cluster with the same size, in qualitative agreement with the reported conclusions from the experiments of（C2 H6）N and（CH4）N clusters. It is indicated that（C2D6）N clusters are superior to（CD4）N clusters as a target for the laser-induced nuclear fusion reaction to achieve a higher neutron yield. In addition, by comparing the relevant data of（C3D8）N cluster with those of（C2D6）N cluster with the same size, it is theoretically concluded that（C3D8）N clusters with a larger competitive parameter might be a potential candidate for improving neutron generation. This will provide a theoretical basis for target selection in developing experimental schemes on laser-driven nuclear fusion in the future.
基金the support of the National Natural Science Foundation of China(Grant Nos.52274337 and 52174317)。
文摘To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn and Al contents in the steel and the reaction time on the interfacial reaction were investigated.It was observed that the erosion of the MgO refractory is caused by the reaction of Al and Mn in the steel with MgO in the refractory,which would lead to the formation of(Mn,Mg)O·Al_(2)O_(3) spinel and(Mn,Mg)O solid solution.The formation mechanism of the spinel and solid solution is as follows.The Al in the steel firstly reacts with MgO in the refractory to generate MgO·Al_(2)O_(3) spinel,and then,the spinel reacts with Mn in the steel to form(Mn,Mg)O·Al_(2)O_(3) spinel.Finally,the MnO in the spinel reacts with the MgO in the inner refractory to form(Mn,Mg)O solid solution.In addition,only(Mn,Mg)O·Al_(2)O_(3) spinel is present in the interfacial reaction layer of the refractory when the Al content in the steel is sufficient.
文摘物种是生物多样性的基本单元,生殖隔离被认为是物种形成的关键;然而物种并不是静止的而是处于不断的分化演变之中,已经稳定成型但尚未到达分化后期的物种可能存在不完全的生殖隔离。对于物种的认识不能单从某一侧面或局部特征来界定,而应通过"整合物种概念"来确定物种地位。Flora of China记载了中国产白桫椤属(Sphaeropteris)2种,即白桫椤(S.brunoniana)和笔筒树(S.lepifera),并认为原产中国海南的海南白桫椤(S.hainanensis)和白桫椤为同一物种而将其并入白桫椤;但海南白桫椤在形态上已出现了分化。为探讨白桫椤及其近缘物种的亲缘关系和物种多样性分化的情况,本文采集到9个居群共21个样本,通过GBS简化基因组测序技术获得单核苷酸变异位点(SNP),进行系统发育树的构建和主成分及遗传结构的分析,并结合叶片数量性状的统计分析和孢子形态的观察测量。结果表明,海南白桫椤不仅与云南产白桫椤的基因型不同,且在叶片特征和孢子纹饰上有明显差异;但两个居群的生殖隔离较弱,在广西沿海地区形成杂交产物,其叶片特征为亲本的中间类型。因此,我们认为海南白桫椤是由于地理隔离而形成的一个处在分化路上的物种,建议恢复其物种地位;广西产白桫椤为自然杂交群体,应另处理为独立的自然杂交分类群--广西白桫椤(S. brunoniana×hainanensis)。
基金Supported by the National Natural Science Foundation of China （30370153）, and the Key Project of the Knowledge Innovation of the Chinese Academy of Sciences （KSCX2-SW-104）.
文摘Spontaneous hybridization in ex situ facilities can undermine the genetic integrity of ex situ collections and potentially contaminate open-pollinated seeds or seedlings destined for the reintroduction of endangered plant species into the wild. In the present study, the potential risk of hybridization between two endangered Chinese endemic species, namely Sinojackia xylocarpa Hu and S. rehderiana Hu, which are naturally allopatric species but were conserved ex situ in Wuhan Botanical Garden （WBG）, Wuhan, China, were investigated over three consecutive years from 2003 to 2005. The entire overlapping flowering period of the two species was 14-20 d and the two species shared the same pollinator insects during the entire flowering season in WBG. The floral isolation between the two species was not an issue in the ex sltu collection at WBG. The results suggest an opportunity for pollen transfer between species and a potential risk of genetic Introgression and loss of genetic identity of open-pollinated seeds produced in the ex sltu Collection of these two endangered species. An artificial reciprocal cross between S xylocarpa and S. rehderlana confirmed that the two congener species could readily set seeds, indicating no post-pollination barriers to hybridization and the importance of spatial isolation as a barrier to inter-specific crossing. Therefore, to manage these crossable species with overlapping flowering times and shared pollination vectors in ex situ facilities, spatial isolation should be carefully considered to minimize the possibility of spontaneous hybridization.
基金supported by the National Natural Science Foundation of China (Grant Nos. 62005193, 61805129, 62075158, and 11874245)Key Research and Development Program of Shanxi Province (Grant No. 201903D121026)+1 种基金Tianjin Municipal Fund for Distinguished Young Scholars (Grant No. 18JCJQJC45600)partially supported by the Air Force Office of Scientific Research and the Simons Foundation
文摘Metasurfaces have enabled the realization of several optical functionalities over an ultrathin platform,fostering the exciting field of flat optics.Traditional metasurfaces are achieved by arranging a layout of static meta-atoms to imprint a desired operation on the impinging wavefront,but their functionality cannot be altered.Reconfigurability and programmability of metasurfaces are the next important step to broaden their impact,adding customized on-demand functionality in which each meta-atom can be individually reprogrammed.We demonstrate a mechanical metasurface platform with controllable rotation at the meta-atom level,which can implement continuous Pancharatnam–Berry phase control of circularly polarized microwaves.As the proof-of-concept experiments,we demonstrate metalensing,focused vortex beam generation,and holographic imaging in the same metasurface template,exhibiting versatility and superior performance.Such dynamic control of electromagnetic waves using a single,low-cost metasurface paves an avenue towards practical applications,driving the field of reprogrammable intelligent metasurfaces for a variety of applications.
基金the National Natural Science Foundation of China(Nos.11605171 and 21973076)Sichuan Science and Technology Program(No.2018GZ0155)+2 种基金Ph.D program Foundation of SWUST(No.18ZX7112)Longshan Program for Talents(SWUST,No.I8 LZXT11)the Project of State Key Laboratory of Environment-Friendly Energy Materials(SWUST,No.19FKSY16).
文摘The silicone rubber composites present remarkable mechanical properties due to the double network structure constructed with molecular network of matrix and filler network of silica.Nevertheless,the filler network structure and corresponding reinforcement mechanism are still under debate and need to be further probed with the aid of applicative advanced analysis techniques.Herein,small-angle neutron scattering(SANS)and synchrotron radiation X-ray nano-computed tomography(Nano-CT)techniques are employed to explore the evolution of filler networks of fumed,precipitated and sol-gel silica,respectively.Our studying results reveal the formation of filler network constructed by the interconnecting of branched silica aggregates.And the silica with highly associated structure,pertaining to amorphous morphology,small size,and large surface area,presents short distance and effective molecular chain bridge between aggregates,thus forming strong and steady filler networks.This work would provide deep-seated revisiting of filler networks and corresponding reinforcement mechanism and offer guidance for optimizing the mechanical properties of silicone rubber.
基金supported by the National Natural Science Foundation of China (NSFC)(No.11874228)。
文摘We show that inhomogeneous waveguides of slowly varied parity-time(PT) symmetry support localized optical resonances.The resonance is closely related to the formation of exceptional points separating exact and broken PT phases.Salient features of this kind of non-Hermitian resonance, including the formation of half-vortex flux and the discrete nature,are discussed.This investigation highlights the unprecedented uniqueness of field dynamics in non-Hermitian systems with many potential adaptive applications.
基金Y. R. Z., Z. Z. Z., and J. Q. Y. contributed equally to this study. The authors acknowledge support from the National Natural Science Foundation of China (NSFC) under Grant Nos. 11574162, 11674244, and 11874228.
文摘This study proposes an approach to generate high-order exceptional points (EPs) in non-Herniitian systems.A system comprising a homogenous waveguide is considered wlierein the imaginary part of the refractive index is modulated using a one-dimensional Moire profile.This gain-loss niodulation couples different lossless waveguide modes,and these hybrid modes can be modeled using a non-Hcnnitian matrix with complex off-diagonal elements.Results indicate that third-order EPs can be produced by the coalescence of two sccond-ordcr EPs.Then,the necessary rcquiiGmcnts arc analyzed using couplcd-wavc ccjuations and the physical effects of the singularities are discussed.
基金the National Natural Science Foundation of China (30470185)KIP Pilot Project of the Chinese Academy of Sciences (KSCX2-YW-N-061)
文摘Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus （Sapindaceae）, is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages （young and old）. Spatial distribution of males and females was further studied in six large populations occurring in different habitats （fragmented and continuous）. The study revealed a slight trend of male- biased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations （13 out of 15） did not display statistically significant deviation from equality. All of the four significantly male-biased populations in the young class shifted to equality or even female-biased, The Ripley＇s K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male-biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.
基金This work is supported by the National Natural Science Foundation of China(Nos.51732010,5197228051801175),and Natural Science Foundation of Hebei Province(No.E2019203233).
文摘Monolayer(1L)transition metal dichalcogenides(TMDCs)have been attracting tremendous interest in recent years as promising candidate materials in atomic-scale optoelectronic devices due to their direct band gaps(1.5-2.2 eV)and strong light-matter interactions.Unfortunately,their practical applications are limited by low visible light absorption stemming from atomic thickness and negligible infrared response.Here,we report the triangular Sb_(2)O_(3) microresonators in wide thickness and lateral size distributions grown on 1L TMDCs and their created significant broadband enhancement of light adsorption and photoresponse in 1L WSe_(2) crystal via coexisting Fabry-Perot and whispering gallery type resonances.As an example of demonstration,1L WSe_(2) crystal coupled to Sb_(2)O_(3) microresonators with widely distributed sizes exhibits the enhanced visible light absorption by up to 5 folds and the simultaneously extended near infrared(NIR)one of more than 50%.For application of 1L WSe_(2) in photodetection,incorporation of Sb2O3 microresonators leads to significantly enhanced visible light responsivity by~10^(4) order and expanded NIR one of more than 400 mA·W^(-1).Similar results have been observed in the other 1L W(Mo)dichalcogenides coupled to Sb2O3 microresonators.This work provides a new route for development of the high-performance monolayer TMDCs-based optoelectronic devices.
基金National Natural Science Foundation of China(61205042,61675096)Natural Science Foundation of Jiangsu Province(BK20141393)+1 种基金Six Talent Peaks Project in Jiangsu Province(XYDXX-027)Fundamental Research Funds for the Central Universities(30919011106)。
文摘Understanding the mode’s origin in planar metamaterials is fundamental for related applications in nanophotonics and plasmonics.For complex planar metamaterials,conventional analysis that directly obtains the final charge/current distribution of a mode is usually difficult in helping to understand the mode’s origin.In this paper,we propose a mode evolution method(MEM)with a core analysis tool,i.e.,plasmonic evolution maps(PEMs),to describe the mode evolution in several complementary planar metamaterials with designed plasmonic atoms/molecules.The PEMs could not only clearly explain a mode’s origin,but also reveal the role of a structure’s symmetry in the mode formation process.The MEM with PEMs can work as a simple,efficient,and universal approach for the mode analysis in different kinds of planar metamaterials.
