Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline d...Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.展开更多
The effects of composite supports of CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 on the methanation activity of supported Co-Mo-based sulphur-resistant catalysts were investigated.The catalysts were further characte...The effects of composite supports of CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 on the methanation activity of supported Co-Mo-based sulphur-resistant catalysts were investigated.The catalysts were further characterized by nitrogen adsorption measurement,X-ray diffraction and X-ray photoelectron spectroscopy.The catalyst of 5%CoO-15%MoO3 supported on CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 composite oxides,respectively,showed different catalytic performances of syngas methanation in the presence of hydrogen sulphide as compared with that of the 5%CoO-15%MoO3/Al2O3 catalyst.The Co-Mo/CeO2-Al2O3 catalyst shows the highest methanation activity among the tested catalysts.The enhanced methanation activity may be attributed to the improvement of the dispersion of active metal species and the inhibition of the formation of S6+.展开更多
Hydroxycinnamoyl-CoA quinate transferase(HQT)is one of the key enzymes in the biosynthesis of chlorogenic acid(CGA)in the flowers of Lonicera japonica.However,the spatiotemporal expression patterns of HQT and its rela...Hydroxycinnamoyl-CoA quinate transferase(HQT)is one of the key enzymes in the biosynthesis of chlorogenic acid(CGA)in the flowers of Lonicera japonica.However,the spatiotemporal expression patterns of HQT and its relationship to the dynamics of CGA biosynthesis,transport,and storage remain largely unknown.In this study,we collected L.japonica flower samples at different growth stages(S1–S6)and examined the spatiotemporal expression pattern of HQT and the dynamic accumulation patterns of CGA using a combination of molecular and cytological techniques.Our results suggest that the spatiotemporal expression pattern of HQT is directly correlated with dynamic changes in CGA accumulation and distribution in L.japonica flowers.We further show that CGA is synthesized primarily in the cytoplasm and chloroplasts.CGA synthesized in the cytoplasm first accumulates in specialized vesicles and is then transferred to large central vacuoles for storage by fusion of CGA-containing vesicles with vacuoles.Furthermore,CGA synthesized in the chloroplasts appears to be transferred into the vacuoles for storage by direct membrane fusion between the tonoplast and the disrupted chloroplast membranes.Collectively,our results suggest that CGA is synthesized in chloroplasts and cytoplasm and finally transferred to the vacuole for long-term storage.展开更多
Located at the northeastern margin of the Tibetan plateau,the Ordos block is a stable tectonic unit in North China.With its active boundary fault zones,the Ordos block played an important role in the eastward extrusio...Located at the northeastern margin of the Tibetan plateau,the Ordos block is a stable tectonic unit in North China.With its active boundary fault zones,the Ordos block played an important role in the eastward extrusion mechanism of the Tibetan plateau.Peking University deployed a linear array of 15 portable broadband seismometers across the western Weihe graben during September 2005 to August 2006 and later a 2-D seismic array(Southwest Ordos Array) of 14 portable broadband seismometers during 2007-2008 at its southwestern boundary.Analyses of shear wave splitting of SKS and SKKS phases at these stations show that the fast directions trend ～110° with an average delay time of 0.9 s in the southwestern margin of the Ordos block.The agreement between the lithosphere deformation indicated by GPS data and Quaternary fault slip-rate observations and the mantle flow represented by shear wave splitting implies that accordant deformation patterns from lithosphere to asthenosphere in relation to the eastward extrusion of the Tibetan plateau could extend at least to 200 km depth.Spatial distribution of splitting polarization directions indicates that the mantle flow driven by the Tibetan plateau is blocked by the Ordos block and locally restricted in a narrow channel along the Qinling-Dabie fault zones between the Ordos block and Sichuan basin.展开更多
In this paper, a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch. The effects of injection time ...In this paper, a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch. The effects of injection time of pre-ionization, pulse rise time, and the pre-ionization jitter are discussed and verified through experiments. It indicates that the pre-ionization should be injected when the electric field is high enough in the gap, injection after 80% peak-time can ensure its effectiveness.Then the statistical time delay jitter will be determined by the pre-ionization jitter, which is an intrinsic restriction of the self-triggered switch. However, when the changing rate of the pulsed electric field exceeds a certain value, the breakdown time delay jitter can be partly offset in the formative stage because the formative time delay has an exponential relationship with the electric field. Therefore, lower time jitter can be obtained under pulses with a shorter pulse rise time. In general, the results of the calculation model agree with the experimental results, and the experimental parameters which lead to a low jitter can also be used as a reference.展开更多
MV pulsed switch plays a key role as the transfer switch in large electromagnetic pulse simulators. To broaden the range of self-triggering time, a novel spark-discharge pre-ionization switch, in which the main gap el...MV pulsed switch plays a key role as the transfer switch in large electromagnetic pulse simulators. To broaden the range of self-triggering time, a novel spark-discharge pre-ionization switch, in which the main gap electric field is superposed at the trigger gap to let the electrons in its spark channel also become initial electrons, is proposed and tested. The design idea is: as electrons in the spark channel of the trigger gap always exist after its breakdown, the injection time of pre-ionization should have a more negligible effect on reducing the switch jitter. The experiment results under pulses with a rise time of ~100 ns support the above assumptions.When the operating voltage is from ~300 to ~800 kV and the self-triggering time is ~45% to~75% of the peak time, the breakdown time delay jitter is less than 2 ns, and the breakdown voltage jitter is smaller than 1.25%. Under specific self-triggering time, the breakdown time delay jitter is less than 1.5 ns, and the breakdown voltage jitter is smaller than 0.8%.展开更多
Carbonate reservoirs in Western China show tremendous exploration and development potential.These have become the key area for oil and gas reserves addition and sustainable resource development for China.Compared to c...Carbonate reservoirs in Western China show tremendous exploration and development potential.These have become the key area for oil and gas reserves addition and sustainable resource development for China.Compared to conventional carbonate reservoirs,prediction of this kind of reservoir predominated by secondary storage is much more difficultand presents significant challenges.展开更多
This work investigates the pulsed breakdown processes and mechanisms of self-triggered preionized switches with a four-electrode structure in nitrogen through intensified charge coupled device photographs.The diameter...This work investigates the pulsed breakdown processes and mechanisms of self-triggered preionized switches with a four-electrode structure in nitrogen through intensified charge coupled device photographs.The diameter of the trigger plane hole mainly determines the switch’s electric field distribution.Two configurations with minimum and maximum trigger plane holes are adopted for comparison.In the switch with a minimum trigger plane hole,the maximum electric field distributes at the surfaces of the main electrodes.Although charged particles in the triggering spark channel cannot drift out,homogeneous discharges can be stimulated from both the cathode and anode surfaces through ultraviolet illumination.Two sub-gaps are likely to break down simultaneously.In the switch with a maximum trigger plane hole,the maximum electric field locates near the trigger electrodes.Discharges in both sub-gaps initiate from the trigger electrodes in the form of a positive or negative streamer.Due to the lower breakdown voltage and electric field threshold for discharge initiation,the cathode side sub-gap breaks down first.The analysis of two extreme examples can be referenced in the future design and improvement of self-triggered four-electrode switches with different trigger electrode structures.展开更多
The carbon cycle plays a pivotal role in regulating Earth’s surface environment through atmospheric-oceanic acid-base and redox processes, functioning as the engine driving the evolution of our planet’s surface. A d...The carbon cycle plays a pivotal role in regulating Earth’s surface environment through atmospheric-oceanic acid-base and redox processes, functioning as the engine driving the evolution of our planet’s surface. A deep understanding of the carbon cycle’s evolution is thus essential for our understanding of the evolution of our planet’s habitability.展开更多
In the last decade,it has become increasingly recognized that a balanced gut microbiota plays an important role in maintaining the health of the host.Numerous clinical and preclinical studies have shown that changes i...In the last decade,it has become increasingly recognized that a balanced gut microbiota plays an important role in maintaining the health of the host.Numerous clinical and preclinical studies have shown that changes in gut microbiota composition are associated with a variety of neurological diseases,e.g.,Parkinson’s disease,Alzheimer’s disease,and myasthenia gravis.However,the underlying molecular mechanisms are complex and remain unclear.Behavioral phenotypes can be transmitted from humans to animals through gut microbiota transplantation,indicating that the gut microbiota may be an important regulator of neurological diseases.However,further research is required to determine whether animal-based findings can be extended to humans and to elucidate the relevant potential mechanisms by which the gut microbiota regulates neurological diseases.Such investigations may aid in the development of new microbiota-based strategies for diagnosis and treatment and improve the clinical management of neurological disorders.In this review,we describe the dysbiosis of gut microbiota and the corresponding mechanisms in common neurological diseases,and discuss the potential roles that the intestinal microbiome may play in the diagnosis and treatment of neurological disorders.展开更多
Despite intensive study of the early Cambrian Nanhua Basin(ECNB)in South China,its degree of connectedness to the open ocean remains uncertain,impeding analysis of contemporaneous oceanic redox evolution and its role ...Despite intensive study of the early Cambrian Nanhua Basin(ECNB)in South China,its degree of connectedness to the open ocean remains uncertain,impeding analysis of contemporaneous oceanic redox evolution and its role in the Cambrian Explosion.We analyzed bulk-shale B/Ga,a newly proposed proxy for watermass salinity in ancient depositional systems,for three sections(Daotuo,Yuanjia,and Zhalagou)representing a range of water depths in the ECNB and spanning early Cambrian Stages 2 and 3.The B/Ga proxy records a salinity gradient in the basin,with increasing salinity from shallow-to deep-water areas,particularly during the deposition of black shales of the lower Jiumenchong/Niutitang/Zhalagou Formation.The gradient was probably due to the mixing of freshwater from adjacent landmasses with marine waters within a moderately restricted basin.All three study sections exhibit a monotonic rise in salinity over the~9-Myr study interval,reflecting increased watermass exchange with the open ocean due to regional tectonic and/or global sea-level changes.The improved watermass exchange may have weakened water-column stratification and reduced deep-water anoxia in the ECNB,contributing the enhanced oceanic oxygenation along with global environmental controls and further modulating the expression of the Cambrian Explosion recorded in Lower Cambrian sections of South China.Our study thus highlights the need for comprehensive analyses of hydrographic dynamics in marginal-marine settings that are used to explore co-evolutionary relationships between early animals and environmental oxygen levels.展开更多
The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the...The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the SE has been widely attributed to an increase in atmospheric-oceanic oxygen levels and the subsequent oxidation of organic matters in Earth’s surface system.However,the oxygen levels in the Ediacaran ocean during the SE remain poorly constrained,limiting our ability to better understand the cause and mechanisms behind the SE.Recently,the ratio of I/(Ca+Mg)in carbonate has emerged as an effective proxy for quantifying dissolved oxygen([O_(2)])in the local surface seawaters.In this study,we analyzed I/(Ca+Mg)ratios in the Shuiquan Formation at the Mochia-Khutuk(MK)section,which records the SE event in the Tarim continent.The I/(Ca+Mg)ratio shows synchronous variation withδ^(13)Ccarbin the MK section,with the average value decreasing from 2.2μmol/mol at the bottom of the section to 0.8μmol/mol in the middle and then increasing to 3.4μmol/mol at the very top along with the decline and recovery ofδ^(13)Ccarb.According to the relationship between I/(Ca+Mg)and oxygen content in minimum oxygen zones of the modern ocean,we infer that[O_(2)]of surface water in the MK section decreased from>20–70μmol/L to<20–70μmol/L during the SE,which may reflect the upwelling of the deep seawater enriched dissolved organic carbon(DOC)and reduced substance(such as Fe^(2+))together with its subsequent consumption of[O2]in the surface ocean.The I/(Ca+Mg)pattern in the MK section is significantly different from those of other contemporaneous SE records on other continents,indicating the surface[O_(2)]in the Ediacaran ocean could have been temporally and spatially heterogeneous.Local factors,such as latitude,temperature,productivity,and input of anoxic water masses could play important roles in regulating the surface ocean redox conditions.This observation further suggests that the atmospheric oxygen level during the Ediacaran was relatively low and insufficient to dominate the regulation of[O_(2)]in the surface ocean.The results of our study imply that the oxidation of the ocean and in turn the DOC reservoir therein during the SE could be spatially restricted to the continental shelf,rather than the whole ocean.展开更多
Solution blow spinning(SBS)applies high-speed airflow to prepare fibers by generating a strong stretching force.It has the advantages of scalable production,tailorable morphologies,and wide applicability.Yet,the SBS s...Solution blow spinning(SBS)applies high-speed airflow to prepare fibers by generating a strong stretching force.It has the advantages of scalable production,tailorable morphologies,and wide applicability.Yet,the SBS strategy can hardly prepare fibers down to the sub-100 nanometers,which limits its performance in demanding applications.Herein,we overcome the limitation of SBS by introducing a second airflow.This novel strategy is termed double-stretching SBS(DS-SBS)because an extra stretching force is exerted on the fiber when it converges with the second airflow.Polyamide6 nanofibers with an average diameter of 80 nm are successfully prepared with the DS-SBS strategy,while the SBS strategy could only prepare submicron fibers with an average diameter of 120 nm.Further,the generality of the DS-SBS strategy to reduce fiber diameter is verified on numerous solute-solvent pairs.展开更多
Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrin-sically high chemical stability,superior mechanical performance,and excellent high-temperature...Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrin-sically high chemical stability,superior mechanical performance,and excellent high-temperature resistance.However,the mass production of hard-to-dissolve nanofibers still remains a critical challenge.A simple,scalable,and low-cost ionic solu-tion blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm.After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide(LiCl/DMAc)solution system,the conductive solution can be stably and conductivity-independently processed into nanofibers.The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity.Owing to nanofibrous structure and high dipole moment,Nomex nanofibrous filters show a stable high filtration efficiency of 99.92%for PM_(0.3) with a low areal density of 4.6 g m^(-2),as well as a low-pressure drop of 189.47 Pa.Moreover,the flame-retardant filter can work at 250°C and 280°C for a long and short time without shrinking or burning,respectively,exhibiting a high filtration efficiency of 99.50%for PM_(0.3-10.0).The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts,making Nomex nanofi-brous membrane an even more ideal industrial-grade air filter than polypropylene,polytetrafluoroethylene,polyimide,and ceramic nanofibrous filters.展开更多
Plastid-to-nucleus retrograde signaling coordinates nuclear gene expression with chloroplast developmental status and is essential for the photoautotrophic lifestyle of plants.Previous studies have established that te...Plastid-to-nucleus retrograde signaling coordinates nuclear gene expression with chloroplast developmental status and is essential for the photoautotrophic lifestyle of plants.Previous studies have established that tetrapyrrole biosynthesis(TPB)and plastid gene expression(PGE)play essential roles in plastid retrograde signaling during early chloroplast biogenesis;however,their functional relationship remains unknown.In this study,we generated a series of rice TPB-related gun(genome uncoupled)mutants and systematically analyzed their effects on nuclear and plastid gene expression under normal conditions or when subjected to treatments with norflurazon(NF;a noncompetitive inhibitor of carotenoid biosynthesis)and/or lincomycin(Lin;a specific inhibitor of plastid translation).We show that under NF treatment,expression of plastid-encoded polymerase(PEP)-transcribed genes is significantly reduced in the wild type but is derepressed in the TPB-related gun mutants.We further demonstrate that the derepressed expression of PEPtranscribed genes may be caused by increased expression of the PEP core subunit and nuclear-encoded sigma factors and by elevated copy numbers of plastid genome per haploid genome.In addition,we show that expression of photosynthesis-associated nuclear genes(PhANGs)and PEP-transcribed genes is correlated in the rice TPB-related gun mutants,with or without NF or Lin treatment.A similar correlation between PhANGs and PGE is also observed in the Arabidopsis gun4 and gun5 mutants.Moreover,we show that increased expression of PEP-transcribed plastid genes is necessary for the gun phenotype in NF-treated TPB-related gun mutants.Further,we provide evidence that these TPB-related GUN genes act upstream of GUN1 in the regulation of retrograde signaling.Taken together,our results suggest that the TPB-related GUN genes control retrograde plastid signaling by regulating the PGE-dependent retrograde signaling pathway.展开更多
A field measurement campaign for ozone and ozone precursors(VOCs and NOx) was conducted in summer 2011 around a petroleum refinery in the Beijing rural region. Three observation sites were arranged, one at southwest o...A field measurement campaign for ozone and ozone precursors(VOCs and NOx) was conducted in summer 2011 around a petroleum refinery in the Beijing rural region. Three observation sites were arranged, one at southwest of the refinery as the background, and two at northeast of the refinery as the downwind receptors. Monitoring data revealed the presence of serious surface O3 pollution with the characteristics of high average daily mean and maximum concentrations(64.0 and 145.4 ppbV in no-rain days, respectively) and multi-peak diurnal variation. For NOx, the average hourly concentrations of NO2 and NO were in the range of 20.5–46.1 and 1.8–6.4 ppbV, respectively. For VOC measurement, a total of 51 compounds were detected. Normally, TVOCs at the background site was only dozens of ppbC, while TVOCs at the downwind sites reached several hundreds of ppbC. By subtracting the VOC concentrations at background, chemical profiles of VOC emission from the refinery were obtained, mainly including alkanes(60.0% ± 4.3%), alkenes(21.1% ± 5.5%) and aromatics(18.9% ± 3.9%). Moreover, some differences in chemical profiles for the same measurement hours were observed between the downwind sites; the volume ratios of alkanes with low reactivity and those of alkenes with high reactivity respectively showed an increasing trend and a decreasing trend. Finally, based on temporal and spatial variations of VOC mixing ratios, their photochemical degradations and dispersion degradations were estimated to be 0.15–0.27 and 0.42–0.62, respectively, by the photochemical age calculation method, indicating stronger photochemical reactions around the refinery.展开更多
Crop breeding aims to generate pure in bred lines with multiple desired traits. Doubled haploid (DH) and genome editing using CRISPR/Cas9 are two powerful game-changing technologies in crop breeding. However, both of ...Crop breeding aims to generate pure in bred lines with multiple desired traits. Doubled haploid (DH) and genome editing using CRISPR/Cas9 are two powerful game-changing technologies in crop breeding. However, both of them still fall short for rapid generation of pure elite lines with integrated favorable traits. Here, we report the development of a Haploid-Inducer Mediated Genome Editing (IMGE) approach, which utilizes a maize haploid inducer line carrying a CRISPR/Cas9 cassette targeting for a desired agronomic trait to pollinate an elite maize in bred line and to generate genome-edited haploids in the elite maize background. Homozygous pure DH lines with the desired trait improvement could be generated within two generations, thus bypassing the lengthy procedure of repeated crossing and backcrossing used in conventional breeding for integrating a desirable trait into elite commercial backgrounds.展开更多
The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^(13)C...The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^(13)C_(carb)). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon(DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence(TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO_2, N_2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction(ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon(TIC) content(R^2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence(CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice(termed as "X-OM"). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation(R^2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter(i.e., Δ^(13)C_(carb-org), a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the evolution of the possible DOC reservoir in the Ediacaran Doushantuo Ocean. If this is correct, the stratigraphic variations of the CL intensity in the Doushantuo Formation at Jiulongwan support the pulsed oxidation of the DOC reservoir in the Ediacaran Ocean. Our findings indicate that the CL derived from the oxidation of non-volatile organic matter which is strongly associated with carbonate mineral lattices in rocks may provide a feasible approach for probing the evolution of DOC reservoir in the ancient oceans, thus likely provide direct geological evidence for the development of oceanic DOC reservoir in geological times.展开更多
文摘Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.
文摘The effects of composite supports of CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 on the methanation activity of supported Co-Mo-based sulphur-resistant catalysts were investigated.The catalysts were further characterized by nitrogen adsorption measurement,X-ray diffraction and X-ray photoelectron spectroscopy.The catalyst of 5%CoO-15%MoO3 supported on CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 composite oxides,respectively,showed different catalytic performances of syngas methanation in the presence of hydrogen sulphide as compared with that of the 5%CoO-15%MoO3/Al2O3 catalyst.The Co-Mo/CeO2-Al2O3 catalyst shows the highest methanation activity among the tested catalysts.The enhanced methanation activity may be attributed to the improvement of the dispersion of active metal species and the inhibition of the formation of S6+.
基金supported by the National Natural Science Foundation of China(31500261)the Guangdong Province Science and Technology Plan Project(2014B090904074)+1 种基金the Youth Foundation of the College of Forestry and Landscape Architecture of South China Agricultural University(201603)open funds from the State Key Laboratory for the Conservation and Utilization of Subtropical Agro-Bioresources(SKLCUSA-b201701).
文摘Hydroxycinnamoyl-CoA quinate transferase(HQT)is one of the key enzymes in the biosynthesis of chlorogenic acid(CGA)in the flowers of Lonicera japonica.However,the spatiotemporal expression patterns of HQT and its relationship to the dynamics of CGA biosynthesis,transport,and storage remain largely unknown.In this study,we collected L.japonica flower samples at different growth stages(S1–S6)and examined the spatiotemporal expression pattern of HQT and the dynamic accumulation patterns of CGA using a combination of molecular and cytological techniques.Our results suggest that the spatiotemporal expression pattern of HQT is directly correlated with dynamic changes in CGA accumulation and distribution in L.japonica flowers.We further show that CGA is synthesized primarily in the cytoplasm and chloroplasts.CGA synthesized in the cytoplasm first accumulates in specialized vesicles and is then transferred to large central vacuoles for storage by fusion of CGA-containing vesicles with vacuoles.Furthermore,CGA synthesized in the chloroplasts appears to be transferred into the vacuoles for storage by direct membrane fusion between the tonoplast and the disrupted chloroplast membranes.Collectively,our results suggest that CGA is synthesized in chloroplasts and cytoplasm and finally transferred to the vacuole for long-term storage.
文摘Located at the northeastern margin of the Tibetan plateau,the Ordos block is a stable tectonic unit in North China.With its active boundary fault zones,the Ordos block played an important role in the eastward extrusion mechanism of the Tibetan plateau.Peking University deployed a linear array of 15 portable broadband seismometers across the western Weihe graben during September 2005 to August 2006 and later a 2-D seismic array(Southwest Ordos Array) of 14 portable broadband seismometers during 2007-2008 at its southwestern boundary.Analyses of shear wave splitting of SKS and SKKS phases at these stations show that the fast directions trend ～110° with an average delay time of 0.9 s in the southwestern margin of the Ordos block.The agreement between the lithosphere deformation indicated by GPS data and Quaternary fault slip-rate observations and the mantle flow represented by shear wave splitting implies that accordant deformation patterns from lithosphere to asthenosphere in relation to the eastward extrusion of the Tibetan plateau could extend at least to 200 km depth.Spatial distribution of splitting polarization directions indicates that the mantle flow driven by the Tibetan plateau is blocked by the Ordos block and locally restricted in a narrow channel along the Qinling-Dabie fault zones between the Ordos block and Sichuan basin.
文摘In this paper, a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch. The effects of injection time of pre-ionization, pulse rise time, and the pre-ionization jitter are discussed and verified through experiments. It indicates that the pre-ionization should be injected when the electric field is high enough in the gap, injection after 80% peak-time can ensure its effectiveness.Then the statistical time delay jitter will be determined by the pre-ionization jitter, which is an intrinsic restriction of the self-triggered switch. However, when the changing rate of the pulsed electric field exceeds a certain value, the breakdown time delay jitter can be partly offset in the formative stage because the formative time delay has an exponential relationship with the electric field. Therefore, lower time jitter can be obtained under pulses with a shorter pulse rise time. In general, the results of the calculation model agree with the experimental results, and the experimental parameters which lead to a low jitter can also be used as a reference.
文摘MV pulsed switch plays a key role as the transfer switch in large electromagnetic pulse simulators. To broaden the range of self-triggering time, a novel spark-discharge pre-ionization switch, in which the main gap electric field is superposed at the trigger gap to let the electrons in its spark channel also become initial electrons, is proposed and tested. The design idea is: as electrons in the spark channel of the trigger gap always exist after its breakdown, the injection time of pre-ionization should have a more negligible effect on reducing the switch jitter. The experiment results under pulses with a rise time of ~100 ns support the above assumptions.When the operating voltage is from ~300 to ~800 kV and the self-triggering time is ~45% to~75% of the peak time, the breakdown time delay jitter is less than 2 ns, and the breakdown voltage jitter is smaller than 1.25%. Under specific self-triggering time, the breakdown time delay jitter is less than 1.5 ns, and the breakdown voltage jitter is smaller than 0.8%.
文摘Carbonate reservoirs in Western China show tremendous exploration and development potential.These have become the key area for oil and gas reserves addition and sustainable resource development for China.Compared to conventional carbonate reservoirs,prediction of this kind of reservoir predominated by secondary storage is much more difficultand presents significant challenges.
文摘This work investigates the pulsed breakdown processes and mechanisms of self-triggered preionized switches with a four-electrode structure in nitrogen through intensified charge coupled device photographs.The diameter of the trigger plane hole mainly determines the switch’s electric field distribution.Two configurations with minimum and maximum trigger plane holes are adopted for comparison.In the switch with a minimum trigger plane hole,the maximum electric field distributes at the surfaces of the main electrodes.Although charged particles in the triggering spark channel cannot drift out,homogeneous discharges can be stimulated from both the cathode and anode surfaces through ultraviolet illumination.Two sub-gaps are likely to break down simultaneously.In the switch with a maximum trigger plane hole,the maximum electric field locates near the trigger electrodes.Discharges in both sub-gaps initiate from the trigger electrodes in the form of a positive or negative streamer.Due to the lower breakdown voltage and electric field threshold for discharge initiation,the cathode side sub-gap breaks down first.The analysis of two extreme examples can be referenced in the future design and improvement of self-triggered four-electrode switches with different trigger electrode structures.
基金supported by the National Natural Science Foundation of China(Grants Nos.41821001,42130208,41825019,41888101,42103072)the National Key Research and Development Program of China(Grant No.2022YFF0800100)。
文摘The carbon cycle plays a pivotal role in regulating Earth’s surface environment through atmospheric-oceanic acid-base and redox processes, functioning as the engine driving the evolution of our planet’s surface. A deep understanding of the carbon cycle’s evolution is thus essential for our understanding of the evolution of our planet’s habitability.
基金National Key R&D Program of China(No.2017YFA0505700)Non-Profit Central Research Institute Fund of the Chinese Academy of Medical Sciences(No.2019PT320002)+2 种基金Natural Science Foundation Project of China(No.81820108015)China Postdoctoral Science Foundation(Nos.2020TQ0393,2020M683634XB,and 2021M693926)Chongqing Science and Technology Commission(Nos.cstc2021jcyj-bsh0026 and cstc2021jcyj-bsh0034)
文摘In the last decade,it has become increasingly recognized that a balanced gut microbiota plays an important role in maintaining the health of the host.Numerous clinical and preclinical studies have shown that changes in gut microbiota composition are associated with a variety of neurological diseases,e.g.,Parkinson’s disease,Alzheimer’s disease,and myasthenia gravis.However,the underlying molecular mechanisms are complex and remain unclear.Behavioral phenotypes can be transmitted from humans to animals through gut microbiota transplantation,indicating that the gut microbiota may be an important regulator of neurological diseases.However,further research is required to determine whether animal-based findings can be extended to humans and to elucidate the relevant potential mechanisms by which the gut microbiota regulates neurological diseases.Such investigations may aid in the development of new microbiota-based strategies for diagnosis and treatment and improve the clinical management of neurological disorders.In this review,we describe the dysbiosis of gut microbiota and the corresponding mechanisms in common neurological diseases,and discuss the potential roles that the intestinal microbiome may play in the diagnosis and treatment of neurological disorders.
基金supported by the Key R&D Project of Ministry of Science and Technology(Grant No.2022YFF0800100)the National Natural Science Foundation of China(Grant Nos.42072335,42002027,41825019,41821001,42130208)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB26000000).
文摘Despite intensive study of the early Cambrian Nanhua Basin(ECNB)in South China,its degree of connectedness to the open ocean remains uncertain,impeding analysis of contemporaneous oceanic redox evolution and its role in the Cambrian Explosion.We analyzed bulk-shale B/Ga,a newly proposed proxy for watermass salinity in ancient depositional systems,for three sections(Daotuo,Yuanjia,and Zhalagou)representing a range of water depths in the ECNB and spanning early Cambrian Stages 2 and 3.The B/Ga proxy records a salinity gradient in the basin,with increasing salinity from shallow-to deep-water areas,particularly during the deposition of black shales of the lower Jiumenchong/Niutitang/Zhalagou Formation.The gradient was probably due to the mixing of freshwater from adjacent landmasses with marine waters within a moderately restricted basin.All three study sections exhibit a monotonic rise in salinity over the~9-Myr study interval,reflecting increased watermass exchange with the open ocean due to regional tectonic and/or global sea-level changes.The improved watermass exchange may have weakened water-column stratification and reduced deep-water anoxia in the ECNB,contributing the enhanced oceanic oxygenation along with global environmental controls and further modulating the expression of the Cambrian Explosion recorded in Lower Cambrian sections of South China.Our study thus highlights the need for comprehensive analyses of hydrographic dynamics in marginal-marine settings that are used to explore co-evolutionary relationships between early animals and environmental oxygen levels.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0800100)the National Natural Science Foundation of China(Grant Nos.42130208,41825019,42072335,42002027)。
文摘The Ediacaran Period(635–539 Ma)witnessed the largest negative excursion in inorganic carbon isotope(δ^(13)Ccarb)over the Earth’s geological history,also known as the Shuram Excursion(SE)event.The occurrence of the SE has been widely attributed to an increase in atmospheric-oceanic oxygen levels and the subsequent oxidation of organic matters in Earth’s surface system.However,the oxygen levels in the Ediacaran ocean during the SE remain poorly constrained,limiting our ability to better understand the cause and mechanisms behind the SE.Recently,the ratio of I/(Ca+Mg)in carbonate has emerged as an effective proxy for quantifying dissolved oxygen([O_(2)])in the local surface seawaters.In this study,we analyzed I/(Ca+Mg)ratios in the Shuiquan Formation at the Mochia-Khutuk(MK)section,which records the SE event in the Tarim continent.The I/(Ca+Mg)ratio shows synchronous variation withδ^(13)Ccarbin the MK section,with the average value decreasing from 2.2μmol/mol at the bottom of the section to 0.8μmol/mol in the middle and then increasing to 3.4μmol/mol at the very top along with the decline and recovery ofδ^(13)Ccarb.According to the relationship between I/(Ca+Mg)and oxygen content in minimum oxygen zones of the modern ocean,we infer that[O_(2)]of surface water in the MK section decreased from>20–70μmol/L to<20–70μmol/L during the SE,which may reflect the upwelling of the deep seawater enriched dissolved organic carbon(DOC)and reduced substance(such as Fe^(2+))together with its subsequent consumption of[O2]in the surface ocean.The I/(Ca+Mg)pattern in the MK section is significantly different from those of other contemporaneous SE records on other continents,indicating the surface[O_(2)]in the Ediacaran ocean could have been temporally and spatially heterogeneous.Local factors,such as latitude,temperature,productivity,and input of anoxic water masses could play important roles in regulating the surface ocean redox conditions.This observation further suggests that the atmospheric oxygen level during the Ediacaran was relatively low and insufficient to dominate the regulation of[O_(2)]in the surface ocean.The results of our study imply that the oxidation of the ocean and in turn the DOC reservoir therein during the SE could be spatially restricted to the continental shelf,rather than the whole ocean.
基金supported by the Basic Science Center Program of the National Natural Science Foundation of China(NSFC)(No.51788104)Beijing Natural Science Foundation(No.JQ19005).
文摘Solution blow spinning(SBS)applies high-speed airflow to prepare fibers by generating a strong stretching force.It has the advantages of scalable production,tailorable morphologies,and wide applicability.Yet,the SBS strategy can hardly prepare fibers down to the sub-100 nanometers,which limits its performance in demanding applications.Herein,we overcome the limitation of SBS by introducing a second airflow.This novel strategy is termed double-stretching SBS(DS-SBS)because an extra stretching force is exerted on the fiber when it converges with the second airflow.Polyamide6 nanofibers with an average diameter of 80 nm are successfully prepared with the DS-SBS strategy,while the SBS strategy could only prepare submicron fibers with an average diameter of 120 nm.Further,the generality of the DS-SBS strategy to reduce fiber diameter is verified on numerous solute-solvent pairs.
基金support of the Basic Science Center Program of the National Natural Science Foundation of China(NSFC)under Grant no.51788104 and Beijing Natural Science Foundation under Grant no.JQ19005China Postdoctoral Science Foundation Grant no.2021M691713.
文摘Hard-to-dissolve polymers provide next-generation alternatives for high-performance filter materials owing to their intrin-sically high chemical stability,superior mechanical performance,and excellent high-temperature resistance.However,the mass production of hard-to-dissolve nanofibers still remains a critical challenge.A simple,scalable,and low-cost ionic solu-tion blow-spinning method has herein been provided for the large-scale preparation of hard-to-dissolve Nomex polymeric nanofibers with an average diameter of nearly 100 nm.After rapidly dissolving Nomex microfibers in the lithium chloride/dimethylacetamide(LiCl/DMAc)solution system,the conductive solution can be stably and conductivity-independently processed into nanofibers.The method optimizes electrospinning and avoids spinnability degradation and potential safety hazards caused by high electrical conductivity.Owing to nanofibrous structure and high dipole moment,Nomex nanofibrous filters show a stable high filtration efficiency of 99.92%for PM_(0.3) with a low areal density of 4.6 g m^(-2),as well as a low-pressure drop of 189.47 Pa.Moreover,the flame-retardant filter can work at 250°C and 280°C for a long and short time without shrinking or burning,respectively,exhibiting a high filtration efficiency of 99.50%for PM_(0.3-10.0).The outstanding properties and low cost enable the efficient capture of PM from various high-temperature exhausts,making Nomex nanofi-brous membrane an even more ideal industrial-grade air filter than polypropylene,polytetrafluoroethylene,polyimide,and ceramic nanofibrous filters.
基金supported by grants from the National Natural Science Foundation of China(91935301)National Natural Science Foundation of China Joint Program(U1701232)+4 种基金Jiangsu Science and Technology Development Program(BE2021360)Jiangsu Agricultural Science and Technology Innovation Fund Project(SCX(19)1079)Jiangsu Province Agriculture Independent Innovation Fund Project(CX(19)1002)National Key Research and Development Program of China(2016YFD0100903)the Fundamental Research Funds for the Central Universities(JCQY201902).
文摘Plastid-to-nucleus retrograde signaling coordinates nuclear gene expression with chloroplast developmental status and is essential for the photoautotrophic lifestyle of plants.Previous studies have established that tetrapyrrole biosynthesis(TPB)and plastid gene expression(PGE)play essential roles in plastid retrograde signaling during early chloroplast biogenesis;however,their functional relationship remains unknown.In this study,we generated a series of rice TPB-related gun(genome uncoupled)mutants and systematically analyzed their effects on nuclear and plastid gene expression under normal conditions or when subjected to treatments with norflurazon(NF;a noncompetitive inhibitor of carotenoid biosynthesis)and/or lincomycin(Lin;a specific inhibitor of plastid translation).We show that under NF treatment,expression of plastid-encoded polymerase(PEP)-transcribed genes is significantly reduced in the wild type but is derepressed in the TPB-related gun mutants.We further demonstrate that the derepressed expression of PEPtranscribed genes may be caused by increased expression of the PEP core subunit and nuclear-encoded sigma factors and by elevated copy numbers of plastid genome per haploid genome.In addition,we show that expression of photosynthesis-associated nuclear genes(PhANGs)and PEP-transcribed genes is correlated in the rice TPB-related gun mutants,with or without NF or Lin treatment.A similar correlation between PhANGs and PGE is also observed in the Arabidopsis gun4 and gun5 mutants.Moreover,we show that increased expression of PEP-transcribed plastid genes is necessary for the gun phenotype in NF-treated TPB-related gun mutants.Further,we provide evidence that these TPB-related GUN genes act upstream of GUN1 in the regulation of retrograde signaling.Taken together,our results suggest that the TPB-related GUN genes control retrograde plastid signaling by regulating the PGE-dependent retrograde signaling pathway.
基金supported by the National Natural Science Foundation of China (No. 51108006)Ph.D. Programs Foundation of the Ministry of Education of China (No. 20111103120008)the State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex
文摘A field measurement campaign for ozone and ozone precursors(VOCs and NOx) was conducted in summer 2011 around a petroleum refinery in the Beijing rural region. Three observation sites were arranged, one at southwest of the refinery as the background, and two at northeast of the refinery as the downwind receptors. Monitoring data revealed the presence of serious surface O3 pollution with the characteristics of high average daily mean and maximum concentrations(64.0 and 145.4 ppbV in no-rain days, respectively) and multi-peak diurnal variation. For NOx, the average hourly concentrations of NO2 and NO were in the range of 20.5–46.1 and 1.8–6.4 ppbV, respectively. For VOC measurement, a total of 51 compounds were detected. Normally, TVOCs at the background site was only dozens of ppbC, while TVOCs at the downwind sites reached several hundreds of ppbC. By subtracting the VOC concentrations at background, chemical profiles of VOC emission from the refinery were obtained, mainly including alkanes(60.0% ± 4.3%), alkenes(21.1% ± 5.5%) and aromatics(18.9% ± 3.9%). Moreover, some differences in chemical profiles for the same measurement hours were observed between the downwind sites; the volume ratios of alkanes with low reactivity and those of alkenes with high reactivity respectively showed an increasing trend and a decreasing trend. Finally, based on temporal and spatial variations of VOC mixing ratios, their photochemical degradations and dispersion degradations were estimated to be 0.15–0.27 and 0.42–0.62, respectively, by the photochemical age calculation method, indicating stronger photochemical reactions around the refinery.
基金National Key R&D Program of China (2016YFD0100303 and 2016YFD0101001)Beijing Natural Science Foundation (6172032).
文摘Crop breeding aims to generate pure in bred lines with multiple desired traits. Doubled haploid (DH) and genome editing using CRISPR/Cas9 are two powerful game-changing technologies in crop breeding. However, both of them still fall short for rapid generation of pure elite lines with integrated favorable traits. Here, we report the development of a Haploid-Inducer Mediated Genome Editing (IMGE) approach, which utilizes a maize haploid inducer line carrying a CRISPR/Cas9 cassette targeting for a desired agronomic trait to pollinate an elite maize in bred line and to generate genome-edited haploids in the elite maize background. Homozygous pure DH lines with the desired trait improvement could be generated within two generations, thus bypassing the lengthy procedure of repeated crossing and backcrossing used in conventional breeding for integrating a desirable trait into elite commercial backgrounds.
基金supported by the Chinese 973 Program (No. 2013CB955704)the National Natural Science Foundation of China (No. 41172030)
文摘The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^(13)C_(carb)). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon(DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence(TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO_2, N_2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction(ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon(TIC) content(R^2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence(CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice(termed as "X-OM"). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation(R^2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter(i.e., Δ^(13)C_(carb-org), a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the evolution of the possible DOC reservoir in the Ediacaran Doushantuo Ocean. If this is correct, the stratigraphic variations of the CL intensity in the Doushantuo Formation at Jiulongwan support the pulsed oxidation of the DOC reservoir in the Ediacaran Ocean. Our findings indicate that the CL derived from the oxidation of non-volatile organic matter which is strongly associated with carbonate mineral lattices in rocks may provide a feasible approach for probing the evolution of DOC reservoir in the ancient oceans, thus likely provide direct geological evidence for the development of oceanic DOC reservoir in geological times.
