In vitro regeneration systems of Atrichum mosses, Atrichurn undulatum (Hedw.) P. Beauv. and A. undulatum var. minus (Hedw.) Par. were established. After one month, soft, friable and green calli were induced successful...In vitro regeneration systems of Atrichum mosses, Atrichurn undulatum (Hedw.) P. Beauv. and A. undulatum var. minus (Hedw.) Par. were established. After one month, soft, friable and green calli were induced successfully from inoculated protonema of Atrichum mosses on MS medium containing glucose (4%) and 6-BA (0.2-2.0 mg/L). The suitable culture medium for the callus induction and regular subculture was MS medium with 1.0-2.0 mg/L 6-BA and 4% glucose. The calli of Atrichum mosses developed into protonema, when it was transferred to phytohormone-free MS medium with 4% glucose. Meanwhile, the calli developed into erect gametophytes through protonema phase on carbohydrate-free Benecke medium.展开更多
Nitrogen fixation is one of the most important and challenging process in production of ammonia at ambient temperature. We have first performed density function theory to propose the edge of Janus MoSSe(EJM) monolayer...Nitrogen fixation is one of the most important and challenging process in production of ammonia at ambient temperature. We have first performed density function theory to propose the edge of Janus MoSSe(EJM) monolayer as a potential catalyst for nitrogen reduction reaction. Our results show that the superficial D-band centers play an important role in nitrogen fixation. The strain effects greatly alter the D-band center, and further change the interaction between the adsorbates and the surface of catalysts.Our findings provide a new thought into designing transition-metal chalcogenide catalysts for nitrogen fixation.展开更多
Twenty-seven moss specimens collected from the Guangfayong section （Early Miocene,22.1 Ma） of the Weichang District,North China were investigated in the present study.Based on the morphological and anatomical featur...Twenty-seven moss specimens collected from the Guangfayong section （Early Miocene,22.1 Ma） of the Weichang District,North China were investigated in the present study.Based on the morphological and anatomical features of gametophytes,all specimens were found to belong to three species：Leptodictyum riparium,Drepanocladus subtrichophyllus sp.nov.,and Amblystegium varium,all of which belong to the family Amblystegiaceae.The microhabitats and living environments of fossil mosses were also investigated based on comparison with living mosses.The results suggest that these mosses grew primarily at the edges of rivers,streams,and lakes and favored being submerged in streams or lakes in the Weichang District in the Early Miocene.展开更多
The transition metal dichalcogenides(TMD)monolayers have shown strong second-harmonic generation(SHG)ow-ing to their lack of inversion symmetry.These ultrathin layers then serve as the frequency converters that can be...The transition metal dichalcogenides(TMD)monolayers have shown strong second-harmonic generation(SHG)ow-ing to their lack of inversion symmetry.These ultrathin layers then serve as the frequency converters that can be intergraded on a chip.Here,taking MoSSe as an example,we report the first detailed experimental study of the SHG of Janus TMD monolayer,in which the transition metal layer is sandwiched by the two distinct chalcogen layers.It is shown that the SHG effectively arises from an in-plane second-harmonic polarization under paraxial focusing and detection.Based on this,the orientation-resolved SHG spectroscopy is realized to readily determine the zigzag and armchair axes of the Janus crystal with an accuracy better than±0.6°.Moreover,the SHG intensity is wavelength-dependent and can be greatly enhanced(~60 times)when the two-photon transition is resonant with the C-exciton state.Our findings uncover the SHG properties of Janus MoSSe monolayer,therefore lay the basis for its integrated frequency-doubling applications.展开更多
Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditio...Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO<sub>2</sub> exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO<sub>2</sub> exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.展开更多
The Janus MoSSe and alloy MoS_(x)Se_((1-x)),belonging to the family of two-dimensional(2D)transition metal dichalcogenides(TMDs),have gained significant attention for their potential applications in nanotechnology.The...The Janus MoSSe and alloy MoS_(x)Se_((1-x)),belonging to the family of two-dimensional(2D)transition metal dichalcogenides(TMDs),have gained significant attention for their potential applications in nanotechnology.The unique asymmetric structure of Janus MoSSe provides intriguing possibilities for tailored applications.The alloy MoS_(x)Se_((1-x))offers a tunable composition,allowing for the fine-tuning of the properties to meet specific requirements.These materials exhibit remarkable mechanical,electrical,and optical properties,including a tunable band gap,high absorption coefficient,and photoconductivity.The vibrational and magnetic properties also make it a promising candidate for nanoscale sensing and magnetic storage applications.Properties of these materials can be precisely controlled through different approaches such as size-dependent properties,phase engineering,doping,alloying,defect and vacancy engineering,intercalation,morphology,and heterojunction or hybridisation.Various synthesis methods for 2D Janus MoSSe and alloy MoS_(x)Se_((1-x))are discussed,including hydro/solvothermal,chemical vapour transport,chemical vapour deposition,physical vapour depositio,and other approaches.The review also presents the latest advancements in Janus and alloy MoSSe-based applications,such as chemical and gas sensors,surface-enhanced Raman spectroscopy,field emission,and energy storage.Moreover,the review highlights the challenges and future directions in the research of these materials,including the need for improved synthesis methods,understanding of their stability,and exploration of new applications.Despite the early stages of research,both the MoSSe-based materials have shown significant potential in various fields,and this review provides valuable insights for researchers and engineers interested in exploring its potential.展开更多
Janus transition metal dichalcogenides(TMDs)structures,as a new type of two-dimensional layered materials,have drawn increasing research efforts mostly by the Raman characterization technique since their successful sy...Janus transition metal dichalcogenides(TMDs)structures,as a new type of two-dimensional layered materials,have drawn increasing research efforts mostly by the Raman characterization technique since their successful synthesis.First-and second-order resonant Raman spectra(RRS)have been reported by experiments.But,unlike much interest paid to the first-order RRS,there has been so far no much discussion dedicated to the second-order double resonant Raman(DRR)bands and band assignments of Janus TMDs,which nevertheless is indispensable but hampered by the difficulty of calculations.In this work,we calculate the DRR spectra of Janus Mo SSe monolayer within the first-principles framework and succeed in achieving accurate assignments of the DRR bands.The assignments are in agreement with our group theoretical analysis.Moreover,taking advantage of its strain-sensitive feature,we calculate the DRR spectra under biaxial strain,and further verify the rationality of our assignments by analyzing strain-induced shift of the DRR bands.Our present study supplies an efficient strategy for quantitative understanding on the electron-phonon coupling in the Janus structures.展开更多
Bryophytes dominate northern peatlands. Obtaining reliable measurements of moss-growth and how it may be affected by global changes are therefore important. Several methods have been used to measure moss-growth but it...Bryophytes dominate northern peatlands. Obtaining reliable measurements of moss-growth and how it may be affected by global changes are therefore important. Several methods have been used to measure moss-growth but it is unclear how comparable they are in different conditions and this uncertainty undermines comparisons among studies. In a field experiment we measured the growth and production of Sphagnum fallax (Sphagnum) and Polytrichum strictum (Polytrichum) using two handling methods, using cut and uncut plants, and three growth-variables, height-growth, length-growth, and mass-growth. We aimed “benchmarking” a combination of six methodological options against exactly the same set of factorial experiments: atmospheric CO2 enrichment and N addition. The two handling methods produced partly different results: in half of the cases, one method revealed a significant treatment effect but the other one did not: significant negative effects on growth were only observed on uncut plants for elevated CO2 and on cut plants for N addition. Furthermore, the correspondence between measurements made with various growth-variables depended on the species and, to a lesser extent, treatments. Sphagnum and Polytrichum growth was inhibited under elevated CO2, and correlated to higher ammonium values. Sphagnum was however less affected than Polytrichum and the height difference between the two species decreased. N addition reduced the P/N ratio and probably induced P-limiting conditions. Sphagnum growth was more inhibited than Polytrichum and the height difference between the two species increased. Our data show that such a problem indeed exists between the cut and uncut handling methods. Not only do the results differ in absolute terms by as much as 82% but also do their comparisons and interpretations depend on the handling method—and thus the interpretation would be biased—in half of the cases. These results call for caution when comparing factorial studies based on different handling methods.展开更多
提出了用于现金自助设备的钞票类型快速识别技术。该技术通过综合利用图像感知哈希和MOSSE(Minimum Output Sum of Squared Error)算法实现,利用图像感知哈希快速计算机制,初步筛选出可能的钞票类型,再利用MOSSE相关滤波器最终确定钞票...提出了用于现金自助设备的钞票类型快速识别技术。该技术通过综合利用图像感知哈希和MOSSE(Minimum Output Sum of Squared Error)算法实现,利用图像感知哈希快速计算机制,初步筛选出可能的钞票类型,再利用MOSSE相关滤波器最终确定钞票类型。展开更多
Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major...Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20°in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World)are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.展开更多
文摘In vitro regeneration systems of Atrichum mosses, Atrichurn undulatum (Hedw.) P. Beauv. and A. undulatum var. minus (Hedw.) Par. were established. After one month, soft, friable and green calli were induced successfully from inoculated protonema of Atrichum mosses on MS medium containing glucose (4%) and 6-BA (0.2-2.0 mg/L). The suitable culture medium for the callus induction and regular subculture was MS medium with 1.0-2.0 mg/L 6-BA and 4% glucose. The calli of Atrichum mosses developed into protonema, when it was transferred to phytohormone-free MS medium with 4% glucose. Meanwhile, the calli developed into erect gametophytes through protonema phase on carbohydrate-free Benecke medium.
文摘CT血管造影(computed tomography angiography,CTA)作为一种无创、检测精确较高的辅助诊断方法,尚急需能有效消除冠脉目标附近干扰噪声并寻求可全自动快速准确追踪目标的新算法以大幅减轻医生阅片压力、辅助其进行可靠诊断与治疗。提出了一种特征融合的误差最小平方和(minimum output sum of squared error,MOSSE)冠脉目标追踪新算法,通过提取冠脉血管多个特征,将其融合加入现有的MOSSE追踪方法,实现全自动准确快速追踪冠脉目标。使用河北大学附属医院9位患者(5男4女,均龄65岁,其中6位有冠心病史)的CTA数据进行了算法验证,并与文献已报道基于中心线提取和基于区域生长的现有冠脉目标提取算法进行了处理结果对比分析。结果表明,新算法处理追踪一例患者切片数据仅需耗时0.02 s,多个病例的平均准确度达94.30%,性能优于上述现有冠脉目标提取算法,能实现全自动准确高效追踪到形态变化剧烈的冠脉目标,可为冠心病的临床诊治起到更为高效的辅助作用。
基金supported by the National Natural Science Foundation of China (Grant no. 51302079 and 11675051)the Natural Science Foundation of Hunan Province (Grant no. 2017JJ1008)
文摘Nitrogen fixation is one of the most important and challenging process in production of ammonia at ambient temperature. We have first performed density function theory to propose the edge of Janus MoSSe(EJM) monolayer as a potential catalyst for nitrogen reduction reaction. Our results show that the superficial D-band centers play an important role in nitrogen fixation. The strain effects greatly alter the D-band center, and further change the interaction between the adsorbates and the surface of catalysts.Our findings provide a new thought into designing transition-metal chalcogenide catalysts for nitrogen fixation.
基金supported by grants from China Geological Survey (No. 1212011120116)the Natural Science Foundation of China (Nos. 41072022 and 41210001)+2 种基金the International S & T Cooperation Project of China (No. 2009DFA32210)the Outlay Research Fund of the Institute of Geology, Chinese Academy of Geological Sciences (No. J1213)a contribution to a bilateral research project supported by the Chinese Ministry of Science and Technology and the Belgian Federal Science Policy Office (BL/36/C54)
文摘Twenty-seven moss specimens collected from the Guangfayong section （Early Miocene,22.1 Ma） of the Weichang District,North China were investigated in the present study.Based on the morphological and anatomical features of gametophytes,all specimens were found to belong to three species：Leptodictyum riparium,Drepanocladus subtrichophyllus sp.nov.,and Amblystegium varium,all of which belong to the family Amblystegiaceae.The microhabitats and living environments of fossil mosses were also investigated based on comparison with living mosses.The results suggest that these mosses grew primarily at the edges of rivers,streams,and lakes and favored being submerged in streams or lakes in the Weichang District in the Early Miocene.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.61888102,51771224,and 62175253)the National Key R&D Program of China(Grant Nos.2018YFA0305803 and 2019YFA0308501)+4 种基金the Chinese Academy of Sciences(Grant Nos.XDB33030100 and XDB30010000)J.S.and X.L.thank the supports from the National Natural Science Foundation of China(Grant Nos.20173025,22073022,and 11874130)the National Key R&D Program of China(Grant No.2017YFA0205004)the Chinese Academy of Sciences(Grant Nos.XDB3600000 and Y950291)the DNL Cooperation Fund(Grant No.DNL202016).
文摘The transition metal dichalcogenides(TMD)monolayers have shown strong second-harmonic generation(SHG)ow-ing to their lack of inversion symmetry.These ultrathin layers then serve as the frequency converters that can be intergraded on a chip.Here,taking MoSSe as an example,we report the first detailed experimental study of the SHG of Janus TMD monolayer,in which the transition metal layer is sandwiched by the two distinct chalcogen layers.It is shown that the SHG effectively arises from an in-plane second-harmonic polarization under paraxial focusing and detection.Based on this,the orientation-resolved SHG spectroscopy is realized to readily determine the zigzag and armchair axes of the Janus crystal with an accuracy better than±0.6°.Moreover,the SHG intensity is wavelength-dependent and can be greatly enhanced(~60 times)when the two-photon transition is resonant with the C-exciton state.Our findings uncover the SHG properties of Janus MoSSe monolayer,therefore lay the basis for its integrated frequency-doubling applications.
文摘Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO<sub>2</sub> exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO<sub>2</sub> exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.
基金financial assistance from the SERB Core Research Grant(Grant No.CRG/2022/000897)Department of Science and Technology(DST/NM/NT/2019/205(G))+1 种基金Minor Research Project Grant,Jain University(JU/MRP/CNMS/29/2023)CSR acknowledges National Research Foundation of Korea for the Brain Pool program funded by the Ministry of Science and ICT,South Korea(Grant No.RS-2023-00222186).
文摘The Janus MoSSe and alloy MoS_(x)Se_((1-x)),belonging to the family of two-dimensional(2D)transition metal dichalcogenides(TMDs),have gained significant attention for their potential applications in nanotechnology.The unique asymmetric structure of Janus MoSSe provides intriguing possibilities for tailored applications.The alloy MoS_(x)Se_((1-x))offers a tunable composition,allowing for the fine-tuning of the properties to meet specific requirements.These materials exhibit remarkable mechanical,electrical,and optical properties,including a tunable band gap,high absorption coefficient,and photoconductivity.The vibrational and magnetic properties also make it a promising candidate for nanoscale sensing and magnetic storage applications.Properties of these materials can be precisely controlled through different approaches such as size-dependent properties,phase engineering,doping,alloying,defect and vacancy engineering,intercalation,morphology,and heterojunction or hybridisation.Various synthesis methods for 2D Janus MoSSe and alloy MoS_(x)Se_((1-x))are discussed,including hydro/solvothermal,chemical vapour transport,chemical vapour deposition,physical vapour depositio,and other approaches.The review also presents the latest advancements in Janus and alloy MoSSe-based applications,such as chemical and gas sensors,surface-enhanced Raman spectroscopy,field emission,and energy storage.Moreover,the review highlights the challenges and future directions in the research of these materials,including the need for improved synthesis methods,understanding of their stability,and exploration of new applications.Despite the early stages of research,both the MoSSe-based materials have shown significant potential in various fields,and this review provides valuable insights for researchers and engineers interested in exploring its potential.
基金financially supported by the National Natural Science Foundation of China(No.52031014)the National Key R&D Program of China(No.2017YFA0206301)。
文摘Janus transition metal dichalcogenides(TMDs)structures,as a new type of two-dimensional layered materials,have drawn increasing research efforts mostly by the Raman characterization technique since their successful synthesis.First-and second-order resonant Raman spectra(RRS)have been reported by experiments.But,unlike much interest paid to the first-order RRS,there has been so far no much discussion dedicated to the second-order double resonant Raman(DRR)bands and band assignments of Janus TMDs,which nevertheless is indispensable but hampered by the difficulty of calculations.In this work,we calculate the DRR spectra of Janus Mo SSe monolayer within the first-principles framework and succeed in achieving accurate assignments of the DRR bands.The assignments are in agreement with our group theoretical analysis.Moreover,taking advantage of its strain-sensitive feature,we calculate the DRR spectra under biaxial strain,and further verify the rationality of our assignments by analyzing strain-induced shift of the DRR bands.Our present study supplies an efficient strategy for quantitative understanding on the electron-phonon coupling in the Janus structures.
文摘Bryophytes dominate northern peatlands. Obtaining reliable measurements of moss-growth and how it may be affected by global changes are therefore important. Several methods have been used to measure moss-growth but it is unclear how comparable they are in different conditions and this uncertainty undermines comparisons among studies. In a field experiment we measured the growth and production of Sphagnum fallax (Sphagnum) and Polytrichum strictum (Polytrichum) using two handling methods, using cut and uncut plants, and three growth-variables, height-growth, length-growth, and mass-growth. We aimed “benchmarking” a combination of six methodological options against exactly the same set of factorial experiments: atmospheric CO2 enrichment and N addition. The two handling methods produced partly different results: in half of the cases, one method revealed a significant treatment effect but the other one did not: significant negative effects on growth were only observed on uncut plants for elevated CO2 and on cut plants for N addition. Furthermore, the correspondence between measurements made with various growth-variables depended on the species and, to a lesser extent, treatments. Sphagnum and Polytrichum growth was inhibited under elevated CO2, and correlated to higher ammonium values. Sphagnum was however less affected than Polytrichum and the height difference between the two species decreased. N addition reduced the P/N ratio and probably induced P-limiting conditions. Sphagnum growth was more inhibited than Polytrichum and the height difference between the two species increased. Our data show that such a problem indeed exists between the cut and uncut handling methods. Not only do the results differ in absolute terms by as much as 82% but also do their comparisons and interpretations depend on the handling method—and thus the interpretation would be biased—in half of the cases. These results call for caution when comparing factorial studies based on different handling methods.
文摘Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in ecology.This latitudinal diversity gradient has been observed in many major groups of organisms.In plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and liverworts.However,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now.Here,we analyze a comprehensive data set including moss species in each band of 20°in latitude worldwide.Our results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World)are considered separately.This result holds when variation in area size among latitudinal bands is taken into account.Pearson's correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern Hemispheres.Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.
