As part of the Dragon 4 project,the water extents of Wuchang and Shengjin lakes have been extracted from Sentinel-2 time series,using all exploitable images since the beginning of the acquisitions in 2015.The aim of t...As part of the Dragon 4 project,the water extents of Wuchang and Shengjin lakes have been extracted from Sentinel-2 time series,using all exploitable images since the beginning of the acquisitions in 2015.The aim of the study is to assess the capability of the Sentinel-2 constellation and Landsat 8 over the Anhui region,especially the high temporal resolution.A total of 32 dates have been used and 10 Landsat 8 images(Libra)have been added to try to reduce the temporal gaps in the Sentinel-2 acquisitions caused by cloudy conditions.Extractions were done using a SERTIT-ICube automatized routine based on a supervised Maximum Likelihood Classification.These extractions allow to recreate the dynamic of the two lakes and show the drought and wet periods.During the 3 years interval,the surface peaks in July 2016 for both lakes.The lowest level appears at two different dates for each lake;in January 2018 for Wuchang,in February 2017 for Shengjin.Wuchang Lake surface area appears to be more variable than Shengjin Lake,with many local maximum and minimum between the end of 2017 and April 2018.In the case of Wuchang Lake,floating vegetation is a problem for automatic water surface area extraction.The lake is covered by vegetation during long periods of time and the water below can’t be detected by automatic radiometric means.Nevertheless,Sentinel-2 stays a pertinent and powerful tool for hydrological monitoring of lakes confirming the expectation from the remote sensing wetland community before launch.The presence of NIR and SWIR bands induces a strong discrimination between water and other classes,and the systematic acquisitions create dense time series,making analysis more consistent.It makes possible to sensor events occurring over short periods of time.Thanks to this a link can be done between endangered bird species,such as the Siberian Crane and the Lesser White-Fronted Goose and periodically flooded areas.These midterm results illustrated the pertinence and powerful of multi-source optical satellite data for enviro展开更多
In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving...In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving processor in accordance to the expected target down-range profile was highlighted and performance predictions were provided. In this paper, we present and evaluate an adaptive scheme devised to on-line estimate the target profile, in order to overcome a limited a-priori knowledge. In addition, we introduce a more general model of target impulse response, based on a statistical description, and we discuss the corresponding processing scheme and detection performance.展开更多
Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and...Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and related crops. The most promising solution is to cultivate resistant varieties, which contribute to sustainable crop production. Two epistatically interacting major SCMV resistance loci （Scmvl and Scmv2） are required to confer complete resistance against SCMV in the resistant nearisogenic line F7RPJRR （the letters left of the slash refer to the genotype at Scmv2 on chromosome 3 and those on the right refer to the genotype at Scmvl on chromosome 6, with R indicating a resistance allele and S a susceptibility allele） （Xing et al., 2006）.展开更多
Breeding of apple is a long-term and costly process due to the time and space requirements for screening selection candidates.Genomics-assisted breeding utilizes genomic and phenotypic information to increase the sele...Breeding of apple is a long-term and costly process due to the time and space requirements for screening selection candidates.Genomics-assisted breeding utilizes genomic and phenotypic information to increase the selection efficiency in breeding programs,and measurements of phenotypes in different environments can facilitate the application of the approach under various climatic conditions.Here we present an apple reference population:the apple REFPOP,a large collection formed of 534 genotypes planted in six European countries,as a unique tool to accelerate apple breeding.The population consisted of 269 accessions and 265 progeny from 27 parental combinations,representing the diversity in cultivated apple and current European breeding material,respectively.A high-density genome-wide dataset of 303,239 SNPs was produced as a combined output of two SNP arrays of different densities using marker imputation with an imputation accuracy of 0.95.Based on the genotypic data,linkage disequilibrium was low and population structure was weak.Two well-studied phenological traits of horticultural importance were measured.We found marker–trait associations in several previously identified genomic regions and maximum predictive abilities of 0.57 and 0.75 for floral emergence and harvest date,respectively.With decreasing SNP density,the detection of significant marker–trait associations varied depending on trait architecture.Regardless of the trait,10,000 SNPs sufficed to maximize genomic prediction ability.We confirm the suitability of the apple REFPOP design for genomics-assisted breeding,especially for breeding programs using related germplasm,and emphasize the advantages of a coordinated and multinational effort for customizing apple breeding methods in the genomics era.展开更多
Accurate,high-throughput phenotyping for quantitative traits is a limiting factor for progress in plant breeding.We developed an automated image analysis to measure quantitative resistance to septoria tritici blotch(S...Accurate,high-throughput phenotyping for quantitative traits is a limiting factor for progress in plant breeding.We developed an automated image analysis to measure quantitative resistance to septoria tritici blotch(STB),a globally important wheat disease,enabling identification of small chromosome intervals containing plausible candidate genes for STB resistance.335 winter wheat cultivars were included in a replicated field experiment that experienced natural epidemic development by a highly diverse but fungicide-resistant pathogen population.More than 5.4 million automatically generated phenotypes were associated with 13,648 SNP markers to perform the GWAS.We identified 26 chromosome intervals explaining 1.9-10.6%of the variance associated with four independent resistance traits.Sixteen of the intervals overlapped with known STB resistance intervals,suggesting that our phenotyping approach can identify simultaneously(i.e.,in a single experiment)many previously defined STB resistance intervals.Seventeen of the intervals were less than 5 Mbp in size and encoded only 173 genes,including many genes associated with disease resistance.Five intervals contained four or fewer genes,providing high priority targets for functional validation.Ten chromosome intervals were not previously associated with STB resistance,perhaps representing resistance to pathogen strains that had not been tested in earlier experiments.The SNP markers associated with these chromosome intervals can be used to recombine different forms of quantitative STB resistance that are likely to be more durable than pyramids of major resistance genes.Our experiment illustrates how high-throughput automated phenotyping can accelerate breeding for quantitative disease resistance.展开更多
Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants con...Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants continue to store NSCs.This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth.The former pathway implies that NSCs may be a by-product of sink limitation,while the latter suggests a functional role of NSCs for use during poor conditions.Methods Using 13C pulse labelling,we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought.We monitored growth,stomatal conductance,stem water potential and NSC storage to assess a broad carbon response to drought.Important Findings We found that the drought-sensitive species had reduced growth,conserved NSC concentrations in leaf,stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions.In contrast,the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings.These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition,while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs.These strategies seem correlated with baseline maximum growth rates,which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.展开更多
Common buckwheat(Fagopyrum esculentum)is an ancient crop with a world-wide distribution.Due to its excellent nutritional quality and high economic and ecological value,common buckwheat is becoming increasingly importa...Common buckwheat(Fagopyrum esculentum)is an ancient crop with a world-wide distribution.Due to its excellent nutritional quality and high economic and ecological value,common buckwheat is becoming increasingly important throughout the world.The availability of a high-quality reference genome sequence and population genomic data will accelerate the breeding of common buckwheat,but the high heterozygosity due to the outcrossing nature has greatly hindered the genome assembly.Here we report the assembly of a chromosome-scale high-quality reference genome of F.esculentum var.homotropicum,a homozygous self-pollinating variant of common buckwheat.Comparative genomics revealed that two cultivated buckwheat species,common buckwheat(F.esculentum)and Tartary buckwheat(F.tataricum),underwent metabolomic divergence and ecotype differentiation.The expansion of several gene families in common buckwheat,including FhFAR genes,is associated with its wider distribution than Tartary buckwheat.Copy number variation of genes involved in the metabolism of flavonoids is associated with the difference of rutin content between common and Tartary buckwheat.Furthermore,we present a comprehensive atlas of genomic variation based on whole-genome resequencing of 572 accessions of common buckwheat.Population and evolutionary genomics reveal genetic variation associated with environmental adaptability and floral development between Chinese and non-Chinese cultivated groups.Genome-wide association analyses of multi-year agronomic traits with the content of flavonoids revealed that Fh05G014970 is a potential major regulator of flowering period,a key agronomic trait controlling the yield of outcrossing crops,and that Fh06G015130 is a crucial gene underlying flavor-associated flavonoids.Intriguingly,we found that the gene translocation and sequence variation of FhS-ELF3 contribute to the homomorphic self-compatibility of common buckwheat.Collectively,our results elucidate the genetic basis of speciation,ecological adaptation,fertility,and unique fl展开更多
High-latitude terrestrial ecosystems face the triple threats of climate warming,increased exposure to UV arising from polar ozone depletion,and deforestation.Lichen communities of southernmost Chile are recognized for...High-latitude terrestrial ecosystems face the triple threats of climate warming,increased exposure to UV arising from polar ozone depletion,and deforestation.Lichen communities of southernmost Chile are recognized for their high diversity,which includes nitrogen-fixing cyanolichens.Such lichens are common on forest trees,contribute nitrogen to forests,and are sensitive to exposure following deforestation(widespread in this region).In a pilot study of exposure effects on tree lichens,using nondestructive imaging methods,we compared lichen communities on trunks of isolated vs.forest tree trunks of southern Chilean beech(Nothofagus dombeyi,Nothofagaceae).We chose trees of similar diameter and trunk lean angle in conserved forest and nearby logged meadow on Navarino Island,XII Region Magallanes and Chilean Antarctica,Chile,within the annual southern ozone hole.Ninety-five percent of cyanolichen records,including Nephroma antarcticum,and 66%of records for other foliose lichens were from the forest,whereas pendulous usneoid lichens dominated N.dombeyi bark at the meadow site.Limitation of cyanolichen growth on isolated trees could affect ecosystem function in this poorly studied habitat.Possible factors contributing to strong community differences were increased light intensity,UV radiation,and wind stress,plus limited ability of lichens to colonize isolated trees in the logged meadow.UV radiation was likely an important stressor for some lichen species but not others.We recommend more extensive monitoring to pinpoint causes of differing lichen communities,and we encourage better protection of bark-dwelling lichens in southern hemisphere regions facing multiple threats.展开更多
This review covers the recent literature on oxidative generation of N-centered radicals using photoredox catalysis.The concept of proton-coupled electron transfer is briefly discussed.Applications of such reactive N-c...This review covers the recent literature on oxidative generation of N-centered radicals using photoredox catalysis.The concept of proton-coupled electron transfer is briefly discussed.Applications of such reactive N-centered radicals in cascade processes comprising arene amidation,alkene amidation,C—C bond cleavage reactions,and remote C—H functionalization are addressed.In addition,novel reagents allowing for clean oxidative N-radical generation are discussed.展开更多
Morphotropic phase boundary(MPB)containing piezoelectric systems generally exhibit enhanced piezoelectric performance at compositions within,or close to,the MPB region.The mechanism/s underlying such enhancement,howev...Morphotropic phase boundary(MPB)containing piezoelectric systems generally exhibit enhanced piezoelectric performance at compositions within,or close to,the MPB region.The mechanism/s underlying such enhancement,however,are still contentious due to complex micro/nanostructure and apparently inherent local structural variability associated with octahedral tilt disorder/platelet precipitates in such piezoelectric materials.This paper reviews some recent structural analysis results from Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and other binary,lead-free,piezoelectric materials systems derived from it via electron diffraction and in situ neutron diffraction.The results suggest that intrinsically existing local microstructure(LMS)in BNT essentially continues across the MPB region.The LMS,originating from inherent octahedral tilt disorder,is strongly temperature-,electric field-,pressure-and chemical composition-dependent,and may help to explain a series of phenomena observed in BNT-based binary materials systems,including the enhanced piezoelectric effect in the region of the MPB.展开更多
文摘As part of the Dragon 4 project,the water extents of Wuchang and Shengjin lakes have been extracted from Sentinel-2 time series,using all exploitable images since the beginning of the acquisitions in 2015.The aim of the study is to assess the capability of the Sentinel-2 constellation and Landsat 8 over the Anhui region,especially the high temporal resolution.A total of 32 dates have been used and 10 Landsat 8 images(Libra)have been added to try to reduce the temporal gaps in the Sentinel-2 acquisitions caused by cloudy conditions.Extractions were done using a SERTIT-ICube automatized routine based on a supervised Maximum Likelihood Classification.These extractions allow to recreate the dynamic of the two lakes and show the drought and wet periods.During the 3 years interval,the surface peaks in July 2016 for both lakes.The lowest level appears at two different dates for each lake;in January 2018 for Wuchang,in February 2017 for Shengjin.Wuchang Lake surface area appears to be more variable than Shengjin Lake,with many local maximum and minimum between the end of 2017 and April 2018.In the case of Wuchang Lake,floating vegetation is a problem for automatic water surface area extraction.The lake is covered by vegetation during long periods of time and the water below can’t be detected by automatic radiometric means.Nevertheless,Sentinel-2 stays a pertinent and powerful tool for hydrological monitoring of lakes confirming the expectation from the remote sensing wetland community before launch.The presence of NIR and SWIR bands induces a strong discrimination between water and other classes,and the systematic acquisitions create dense time series,making analysis more consistent.It makes possible to sensor events occurring over short periods of time.Thanks to this a link can be done between endangered bird species,such as the Siberian Crane and the Lesser White-Fronted Goose and periodically flooded areas.These midterm results illustrated the pertinence and powerful of multi-source optical satellite data for enviro
文摘In a previous companion paper [1], the potential advantages of high resolution radar for improved target detection were introduced. In particular, the concept of shaping both the transmitted waveform and the receiving processor in accordance to the expected target down-range profile was highlighted and performance predictions were provided. In this paper, we present and evaluate an adaptive scheme devised to on-line estimate the target profile, in order to overcome a limited a-priori knowledge. In addition, we introduce a more general model of target impulse response, based on a statistical description, and we discuss the corresponding processing scheme and detection performance.
文摘Dear Editor,Sugarcane mosaic virus （SCMV） causes severe viral diseases in maize worldwide （Fuchs and Gruntzig, 1995）, resulting in significant losses in grain and forage yield in susceptible cultivars of maize and related crops. The most promising solution is to cultivate resistant varieties, which contribute to sustainable crop production. Two epistatically interacting major SCMV resistance loci （Scmvl and Scmv2） are required to confer complete resistance against SCMV in the resistant nearisogenic line F7RPJRR （the letters left of the slash refer to the genotype at Scmv2 on chromosome 3 and those on the right refer to the genotype at Scmvl on chromosome 6, with R indicating a resistance allele and S a susceptibility allele） （Xing et al., 2006）.
基金supported by the project RIS3CAT(COTPAFRUIT3CAT)financed by the European Regional Development Fund through the FEDER frame of Catalonia 2014–2020 and by the CERCA Program from Generalitat de Catalunya.
文摘Breeding of apple is a long-term and costly process due to the time and space requirements for screening selection candidates.Genomics-assisted breeding utilizes genomic and phenotypic information to increase the selection efficiency in breeding programs,and measurements of phenotypes in different environments can facilitate the application of the approach under various climatic conditions.Here we present an apple reference population:the apple REFPOP,a large collection formed of 534 genotypes planted in six European countries,as a unique tool to accelerate apple breeding.The population consisted of 269 accessions and 265 progeny from 27 parental combinations,representing the diversity in cultivated apple and current European breeding material,respectively.A high-density genome-wide dataset of 303,239 SNPs was produced as a combined output of two SNP arrays of different densities using marker imputation with an imputation accuracy of 0.95.Based on the genotypic data,linkage disequilibrium was low and population structure was weak.Two well-studied phenological traits of horticultural importance were measured.We found marker–trait associations in several previously identified genomic regions and maximum predictive abilities of 0.57 and 0.75 for floral emergence and harvest date,respectively.With decreasing SNP density,the detection of significant marker–trait associations varied depending on trait architecture.Regardless of the trait,10,000 SNPs sufficed to maximize genomic prediction ability.We confirm the suitability of the apple REFPOP design for genomics-assisted breeding,especially for breeding programs using related germplasm,and emphasize the advantages of a coordinated and multinational effort for customizing apple breeding methods in the genomics era.
基金STB research in BAM's lab wassupported by the Swiss National Science Foundation(grants155955,134755,104145,and 56874)the ETH ZurichResearch Commission(grants 12-03 and 15-02)AM and PK were supported by the Swiss National Science Foundationthrough Ambizione grant PZ00P3_161453.
文摘Accurate,high-throughput phenotyping for quantitative traits is a limiting factor for progress in plant breeding.We developed an automated image analysis to measure quantitative resistance to septoria tritici blotch(STB),a globally important wheat disease,enabling identification of small chromosome intervals containing plausible candidate genes for STB resistance.335 winter wheat cultivars were included in a replicated field experiment that experienced natural epidemic development by a highly diverse but fungicide-resistant pathogen population.More than 5.4 million automatically generated phenotypes were associated with 13,648 SNP markers to perform the GWAS.We identified 26 chromosome intervals explaining 1.9-10.6%of the variance associated with four independent resistance traits.Sixteen of the intervals overlapped with known STB resistance intervals,suggesting that our phenotyping approach can identify simultaneously(i.e.,in a single experiment)many previously defined STB resistance intervals.Seventeen of the intervals were less than 5 Mbp in size and encoded only 173 genes,including many genes associated with disease resistance.Five intervals contained four or fewer genes,providing high priority targets for functional validation.Ten chromosome intervals were not previously associated with STB resistance,perhaps representing resistance to pathogen strains that had not been tested in earlier experiments.The SNP markers associated with these chromosome intervals can be used to recombine different forms of quantitative STB resistance that are likely to be more durable than pyramids of major resistance genes.Our experiment illustrates how high-throughput automated phenotyping can accelerate breeding for quantitative disease resistance.
基金supported by the Universität Zürich MSc Ecology Program with additional support by the Universität Zürich Research Priority Program on Global Change and Biodiversity(URPP-GCB).M.O.B.was supported by the Atracción de Talento Investigador Modalidad I Fellowship from the Comunidad de Madrid(grant number 2018-T1/AMB-11095)during the preparation of the manuscript.
文摘Aims Non-structural carbohydrates(NSCs)are plant storage compounds used for metabolism,transport,osmoregulation and regrowth following the loss of plant tissue.Even in conditions suitable for optimal growth,plants continue to store NSCs.This storage may be due to passive accumulation from sink-inhibited growth or active reserves that come at the expense of growth.The former pathway implies that NSCs may be a by-product of sink limitation,while the latter suggests a functional role of NSCs for use during poor conditions.Methods Using 13C pulse labelling,we traced the source of soluble sugars in stem and root organs during drought and everwet conditions for seedlings of two tropical tree species that differ in drought tolerance to estimate the relative allocation of NSCs stored prior to drought versus NSCs assimilated during drought.We monitored growth,stomatal conductance,stem water potential and NSC storage to assess a broad carbon response to drought.Important Findings We found that the drought-sensitive species had reduced growth,conserved NSC concentrations in leaf,stem and root organs and had a larger proportion of soluble sugars in stem and root organs that originated from pre-drought storage relative to seedlings in control conditions.In contrast,the drought-tolerant species maintained growth and stem and root NSC concentrations but had reduced leaf NSCs concentrations with a larger proportion of stem and root soluble sugars originated from freshly assimilated photosynthates relative to control seedlings.These results suggest the drought-sensitive species passively accumulated NSCs during water deficit due to growth inhibition,while the drought-tolerant species actively responded to water deficit by allocating NSCs to stem and root organs.These strategies seem correlated with baseline maximum growth rates,which supports previous research suggesting a trade-off between growth and drought tolerance while providing new evidence for the importance of plasticity in NSC allocation during drought.
基金the National Key R&D Program of China(2022YFE0140800)the European Union Horizon 2020 project ECOBREED(771367)+4 种基金the Youth Innovation Program of Chinese Academy of Agricultural Sciences(No.Y2022QC02)Project of Sanya Yazhou Bay Science and Technology City(SCKJ-JYRC-2022-22)National Natural Science Foundation of China(32161143005,31911530772,32111540258)PlantaSYST(SGA No 739582 under FPA No.664620)the BG05M2OP001-1.003-001-C01 project,financed by the European Regional Development Fund through the“Science and Education for Smart Growth”Operational Programme and Slovenian Research Agency,program P4-0077“Genetics and Modern Technologies of Crops”.
文摘Common buckwheat(Fagopyrum esculentum)is an ancient crop with a world-wide distribution.Due to its excellent nutritional quality and high economic and ecological value,common buckwheat is becoming increasingly important throughout the world.The availability of a high-quality reference genome sequence and population genomic data will accelerate the breeding of common buckwheat,but the high heterozygosity due to the outcrossing nature has greatly hindered the genome assembly.Here we report the assembly of a chromosome-scale high-quality reference genome of F.esculentum var.homotropicum,a homozygous self-pollinating variant of common buckwheat.Comparative genomics revealed that two cultivated buckwheat species,common buckwheat(F.esculentum)and Tartary buckwheat(F.tataricum),underwent metabolomic divergence and ecotype differentiation.The expansion of several gene families in common buckwheat,including FhFAR genes,is associated with its wider distribution than Tartary buckwheat.Copy number variation of genes involved in the metabolism of flavonoids is associated with the difference of rutin content between common and Tartary buckwheat.Furthermore,we present a comprehensive atlas of genomic variation based on whole-genome resequencing of 572 accessions of common buckwheat.Population and evolutionary genomics reveal genetic variation associated with environmental adaptability and floral development between Chinese and non-Chinese cultivated groups.Genome-wide association analyses of multi-year agronomic traits with the content of flavonoids revealed that Fh05G014970 is a potential major regulator of flowering period,a key agronomic trait controlling the yield of outcrossing crops,and that Fh06G015130 is a crucial gene underlying flavor-associated flavonoids.Intriguingly,we found that the gene translocation and sequence variation of FhS-ELF3 contribute to the homomorphic self-compatibility of common buckwheat.Collectively,our results elucidate the genetic basis of speciation,ecological adaptation,fertility,and unique fl
文摘High-latitude terrestrial ecosystems face the triple threats of climate warming,increased exposure to UV arising from polar ozone depletion,and deforestation.Lichen communities of southernmost Chile are recognized for their high diversity,which includes nitrogen-fixing cyanolichens.Such lichens are common on forest trees,contribute nitrogen to forests,and are sensitive to exposure following deforestation(widespread in this region).In a pilot study of exposure effects on tree lichens,using nondestructive imaging methods,we compared lichen communities on trunks of isolated vs.forest tree trunks of southern Chilean beech(Nothofagus dombeyi,Nothofagaceae).We chose trees of similar diameter and trunk lean angle in conserved forest and nearby logged meadow on Navarino Island,XII Region Magallanes and Chilean Antarctica,Chile,within the annual southern ozone hole.Ninety-five percent of cyanolichen records,including Nephroma antarcticum,and 66%of records for other foliose lichens were from the forest,whereas pendulous usneoid lichens dominated N.dombeyi bark at the meadow site.Limitation of cyanolichen growth on isolated trees could affect ecosystem function in this poorly studied habitat.Possible factors contributing to strong community differences were increased light intensity,UV radiation,and wind stress,plus limited ability of lichens to colonize isolated trees in the logged meadow.UV radiation was likely an important stressor for some lichen species but not others.We recommend more extensive monitoring to pinpoint causes of differing lichen communities,and we encourage better protection of bark-dwelling lichens in southern hemisphere regions facing multiple threats.
文摘This review covers the recent literature on oxidative generation of N-centered radicals using photoredox catalysis.The concept of proton-coupled electron transfer is briefly discussed.Applications of such reactive N-centered radicals in cascade processes comprising arene amidation,alkene amidation,C—C bond cleavage reactions,and remote C—H functionalization are addressed.In addition,novel reagents allowing for clean oxidative N-radical generation are discussed.
基金the financial support from the Australian Research Council(ARC)in the form of ARC Discovery Grantssupport via the CAS/SAFEA International Partnership Program for Creative Research Teams.
文摘Morphotropic phase boundary(MPB)containing piezoelectric systems generally exhibit enhanced piezoelectric performance at compositions within,or close to,the MPB region.The mechanism/s underlying such enhancement,however,are still contentious due to complex micro/nanostructure and apparently inherent local structural variability associated with octahedral tilt disorder/platelet precipitates in such piezoelectric materials.This paper reviews some recent structural analysis results from Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and other binary,lead-free,piezoelectric materials systems derived from it via electron diffraction and in situ neutron diffraction.The results suggest that intrinsically existing local microstructure(LMS)in BNT essentially continues across the MPB region.The LMS,originating from inherent octahedral tilt disorder,is strongly temperature-,electric field-,pressure-and chemical composition-dependent,and may help to explain a series of phenomena observed in BNT-based binary materials systems,including the enhanced piezoelectric effect in the region of the MPB.
