Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacus...Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacustrine shell limestones to determine the surface erosion thickness and δ^(18)O of Early Jurassic lake water in the northern Sichuan Basin.We analyzed nine shell limestone and seventeen shale samples from the Early Jurassic Da'anzhai Member(J_(1)z^(4))in the Yuanba area.Whether the shell's shapes are well or partially preserved,the J_(1)z^(4)shell limestones in the Yuanba area show no significant recrystallization and dull cathodoluminescence.These characteristics suggest that the shell limestones did not undergo significant diagenetic alteration during late burial.The Δ_(47)values of the J_(1)z^(4)shell limestones range from 0.448±0.005‰to 0.463±0.006‰,yielding clumped isotope temperature(T_(Δ47))of 64.4±0.8 to 69.7±1.4℃,which is significantly higher than the Early Jurassic paleotemperature.It suggests that the Δ_(47)of shell limestones was altered by solid-state reordering,meaning the T_(Δ47)does not reflect the initial formation temperatures.By integrating organic matter's maturation model(Easy%R_(o))of coexisting shales with Δ_(47)solid-state reordering model of calcite,we constrained the maximum burial temperature(~170℃)and the initial formation temperature(~28℃)of these shell limestones.Based on reported paleotemperature gradient,we estimated that the surface erosion thickness was about 1500 m.Furthermore,using the determined initial formation temperatures and conventional oxygen isotope thermometer,we determined that the δ^(18)O values of the Early Jurassic lake water in the Sichuan Basin,which ranged from-10.8‰to-8.0‰(SMOW).The reconstructed paleo temperature and δ^(18)O of lake water suggest that the Early Jurassic in the Sichuan Basin was warm and humid,which was favorable for the deposition of organic-rich lacustrine shale.The methods developed in this study,which employ Δ_(47)of shell limestones to reconstruct the maximum burial temperature and paleolake environmental conditions,demonstrate broad applicability to the Sichuan Basin and similar lacustrine basins.展开更多
为了模拟堆石料三轴压缩实验中颗粒间的咬合作用,提出了一种不改变模型孔隙率、不添加删除颗粒的随机CLUMP颗粒生成方法,并利用该方法进行堆石料细观本构模型参数反演。以蒲石河抽水蓄能电站输水洞开挖出的堆石料三轴压缩实验为例进行计...为了模拟堆石料三轴压缩实验中颗粒间的咬合作用,提出了一种不改变模型孔隙率、不添加删除颗粒的随机CLUMP颗粒生成方法,并利用该方法进行堆石料细观本构模型参数反演。以蒲石河抽水蓄能电站输水洞开挖出的堆石料三轴压缩实验为例进行计算,结果表明:每个CLUMP颗粒由两个球型颗粒构成时计算结果与实验结果吻合最好,各载荷步偏应力相对误差均值为6.31%。随着构成CLUMP颗粒的球型颗粒数量的增加,细观参数中的接触弹性模量随之线性减小,法向刚度与切向刚度之比随之略有增加,而摩擦系数趋于一个常数。使用反演参数对400和600 k Pa围压下的实验结果进行预测,平均相对误差分别为8.29%和10.60%,模拟曲线与实验曲线基本一致,验证了该方法的有效性。展开更多
To properly simulate hard rock with a high ratio of the uniaxial compressive strength to tensile strength(UCS/TS) and realistic strength-failure envelope,the rock deformation and mechanical characteristics were discus...To properly simulate hard rock with a high ratio of the uniaxial compressive strength to tensile strength(UCS/TS) and realistic strength-failure envelope,the rock deformation and mechanical characteristics were discussed in detail when the particle simulation method with the clump parallel-bond model(CPBM) was used to conduct a series of numerical experiments at the specimen scale.Meanwhile,the effects of the loading procedure and crack density on the mechanical behavior of a specimen,which was modeled by the particle simulation method with the CPBM,were investigated.The related numerical results have demonstrated that:1) The uniaxial compressive strength(UCS),tensile strength(TS) and elastic modulus are overestimated when the conventional loading procedure is used in the particle simulation method with the CPBM; 2) The elastic modulus,strength and UCS/TS decrease,while Poisson ratio increases with the increase of the crack density in the particle simulation method with the CPBM; 3) The particle simulation method with the CPBM can be used to reproduce a high value of UCS/TS(>10),as well as a high friction angle and reasonable cohesion strength; 4) As the confining pressure increases,both the peak strength of the simulated specimen and the number of microscopic cracks increase,but the ratio of tensile cracks number to shear cracks number decreases in the particle simulation method with the CPBM; 5) Compared with the conventional parallel-bond model,the CPBM can be used to reproduce more accurate results for simulating the rock deformation and mechanical characteristics.展开更多
The humid agroclimatic conditions of Kerala,India permit the cultivation of an array of bamboo species of which Dendrocalamus strictus Roxb.(Nees.) is an important one on account of its high growth rate and multiple u...The humid agroclimatic conditions of Kerala,India permit the cultivation of an array of bamboo species of which Dendrocalamus strictus Roxb.(Nees.) is an important one on account of its high growth rate and multiple uses. Stand density, a potential tool in controlling the productivity of woody ecosystems, its effect on growth and root distribution patterns may provide a better understanding of productivity optimization especially when bamboo-based intercropping options are considered.Growth attributes of 7-year-old bamboo(D. strictus) stands managed at variable spacing(4×4 m, 6×6 m, 8×8 m,10×10 m, 12×12 m) were studied. Functional root activity among bamboo clumps were also studied using a radio tracer soil injection method in which the radio isotopeP was applied to soil at varying depths and lateral distances from the clump. Results indicate that spacing exerts a profound influence on growth of bamboo. Widely spaced bamboo exhibited higher clump diameters and crown widths while clump heights were better under closer spacing. Clump height was 30% lower and DBH 52%higher at the widest spacing(12×12 m) compared to the closest spacing(4×4 m). With increasing soil depth and lateral distance, root activity decreased significantly. Root activity near the clump base was highest(809 counts per minute, cpm; 50 cm depth and 50 cm lateral distance) at 4×4 m. Tracer study further showed wider distribution of root activity with increase in clump spacing. It may be concluded that the intensive foraging zone of bamboo is within a 50-cm radius around the clump irrespective of spacing. N, P and K content in the upper 20 cm was 2197,21, and 203 kg/ha respectively for the closely spaced bamboo(4×4 m) which were significantly higher than corresponding nutrient content at wider spacings. About 50% of N, P and K were present within the 0–20 cm soil layer, which decreased drastically beyond the 20 cm depth.The results suggest that stand management practices through planting density regulation can modify the resource acquisition patterns of D. strictus which in turn can change growth and productivity considerably. Such information on root activities, spatial and temporal strategies of resource sharing will be helpful in deciding the effective nutrition zone for D. strictus. Further, the study throws light on the spatial distribution of non-competitive zones for productivity optimization yields, especially when intercropping practices are considered.展开更多
Isolating rare circulating tumor cells(CTCs)from blood is critical for the downstream analysis that is important in cancer-related research,diagnosis,and medicine,and efforts are ongoing to increase the efficiency and...Isolating rare circulating tumor cells(CTCs)from blood is critical for the downstream analysis that is important in cancer-related research,diagnosis,and medicine,and efforts are ongoing to increase the efficiency and purity of CTC isolation in microfluidics.Reported in this paper is a two-stage integrated microfluidic chip for coarse-to-fine CTC isolation from whole blood.First,blood cells are removed by filtration using a micropore-array membrane,then CTCs and other cells that are trapped in the micropores are peeled off the membrane by a novel release method based on air–liquid interfacial tension,which significantly increases the recovery rate of CTCs.The second stage is CTC capture based on an on-chip dense immuno-magnetic-bead clump,which offers high capture efficiency and purity.Both the micropore filtration and immuno-magnetic-bead capture are validated and optimized experimentally.Overall,the integrated microfluidic chip can realize a recovery rate of 85.5%and a purity of 37.8%for rare cancer cells spiked in whole blood.展开更多
Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor int...Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.展开更多
Here we present the study on chemical properties of massive star forming clumps using N2H^+(1-0),H^13CO+(1-0),HCN(1-0)and HN^13C(1-0)data from the literature[Astron.Astrophys.563,A97(2014)].We found that abundances of...Here we present the study on chemical properties of massive star forming clumps using N2H^+(1-0),H^13CO+(1-0),HCN(1-0)and HN^13C(1-0)data from the literature[Astron.Astrophys.563,A97(2014)].We found that abundances of H^13CO+ and HN^13C are a ected by H2 column densities.As the median values of these two abundances increase by nearly 10 times from stages A to B,H^13CO+and HN^13C are suitable for tracing the evolution of massive star forming clumps.The order of rapidity in growth of abundances of all the four studied molecules from stages A to B,is H^13CO^+,HCN,HN^13C,and N2H^+,from the highest to the lowest.Our results suggest that the observing optically thin molecular lines with high angular resolution are necessary to study the chemical evolution of massive star forming clumps.展开更多
Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clu...Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clumped isotope(D47)and fluid inclusion analyses of carbonate minerals filled in pores and fractures,this study ascertained the fracturing timing of the Jurassic reservoirs in the Dibei-Tuziluoke Gas Field,Kuqa Foreland Basin.Data from outcrops and borehole images show two dominant fracture sets in the study area:W-E and NE-SW striking fractures.Some W-E striking fractures are carbonate-filled,while NE-SW striking fractures lack mineral fillings.Bitumen veins,not easy to be identified in borehole images,are prevalent in cores.The petrographic analysis reveals that these bitumen veins formed before the calcite cementation in pores and display high viscosity and low maturity.Homogenization temperatures(T_(h))from primary fluid inclusion assemblages in two representative calcite vein samples were notably lower than T_(△47) values from corresponding samples.This suggests the △_(47) signature underwent alteration due to partial reordering during burial.Thus,△_(47)-derived temperatures(apparent temperatures)may not faithfully represent the mineral precipitation temperatures.When plotting these apparent temperatures vs.the burial history,only the possible latest ages of fracturing emerged.These ages were further refined by considering petroleum charging,tectonic evolution,and stress orientation.Bitumen-filled fractures likely resulted from the Late Cretaceous uplift,marking the migration of low-maturity hydrocarbons in the study area.Carbonate-filled E-W striking fractures emerged during the late Miocene(~13-6.5 Ma)alongside fold development.NE-striking fractures that crosscut W-E ones possibly formed recently due to stress reorientation.展开更多
Enteroaggregative Escherichia coli (EAggEC) strains cause the persistent diarrhea in infants and compromised hosts in developing countries. These strains are currently defined as E. coli that adheres to HEp-2 cells in...Enteroaggregative Escherichia coli (EAggEC) strains cause the persistent diarrhea in infants and compromised hosts in developing countries. These strains are currently defined as E. coli that adheres to HEp-2 cells in an aggregative adherence (AA) pattern. In this study, we compared 4 different rapid methods for the detection of EAggEC using a PCR assay, clump formation test, glass slide adherence assay, and the HEp-2 cell adherence assay. Out of 683 E. coli strains isolated from diarrheal stool samples, we detected 17 aggR and/or clump-positive strains, and identified 2 aggR-positive, clump-negative strains and 2 aggR-negative, clump-positive strains. All the aggR positive and clump positive strains also showed positive results in glass slide adherence and HEp-2 cell adherence assays. From all these results, we suggest the following procedure for the rapid identification of EAggEC strains: first, screen E. coli strains with the clump formation test and subsequently perform the glass slide adherence assay to observe AA for confirmation.展开更多
The vegetation canopy clumping index(CI)is an important indicator for understanding radiative transport processes,radiation interception,and the photosynthesis of vegetation canopies.However,most studies consider CI o...The vegetation canopy clumping index(CI)is an important indicator for understanding radiative transport processes,radiation interception,and the photosynthesis of vegetation canopies.However,most studies consider CI only in the nadir or specific direction.In this study,we analyze the directional characteristics of the CI based on RAMI-V(radiation transfer model intercomparison)activity,which represents most typical canopies.The directional gap fraction and CI of these scenes are accurately calculated based on the LESS(large-scale remote sensing data and image simulation framework)model.According to our results,the directional characteristics of the CI are affected by many factors,such as vegetation type,season,and canopy structure.Generally,the CI of a coniferous forest varies little with zenith angle,while the CI of a broad-leaf forest demonstrates the different trend.In winter,the CI is smaller than that in summer,and the variation in the CI at the zenith angle is less.The row structure scenes exhibit different directional characteristics along and perpendicular to the row direction,and their CIs tend to increase with zenith angle.To accurately model the directional CI,we propose a modified Gompertz function model.Compared with other directional CI models,this model has the advantages of high precision and strong applicability(R^(2)=0.975).By studying the directional characteristics of CI,we can enhance the usability of radiative transfer modeling and the accuracy of canopy biophysical parameter retrieval for vegetation with different structures.展开更多
Background Platelet （PLT） clumping occurring in pseudothrombocytopenia （PTCP） can result in inaccurate PLT. Automated platelet clump count （APCC） is a quantitative parameter of platelet aggregation. In this stud...Background Platelet （PLT） clumping occurring in pseudothrombocytopenia （PTCP） can result in inaccurate PLT. Automated platelet clump count （APCC） is a quantitative parameter of platelet aggregation. In this study, we evaluated the clinical utility of APCC in the screening for platelet aggregation related ethylene diamine tetraacetic acid （EDTA）-dependent PTCP （EDTA-PTCP）. Methods A total of 105 patients and 200 healthy individuals were enrolled in this study. Blood samples were collected with dipotassium EDTA and sodium citrate respectively. ADVIA 2120 hematology analyzer was used to perform complete blood count （CBC） and APCC. Blood smears of both EDTA- and citrate-anticoagulated samples were made for microscope observation and manual PLT counting. Results In 25 patients with EDTA-PTCP patients, for EDTA-2K anticoagulated-blood, PLT was （55±6）×10^9/L, significantly lower than citrate anticoagulated blood （（186±13）×10^9/L））. APCC was （905±694）×10^9/L, significantly higher than citrate anticoagulated blood （98±37）×10^9/L. In true thrombocytopenia and healthy control groups, APCC was （63±60）×10^9/L and （69±59）×10^9/L respectively and there was no significant difference between EDTA and citrate anticoagulants. Receiver operator characteristic （ROC） curve showed both sensitivity and specificity of APCC were 96% when the cutoff value of APCC was set as 182×10^9/L. Other platelet parameters had poor performance. Conclusion The APCC has a good sensitivity and specificity in differentiating EDTA-PTCP from true thrombocytopenia compared with other platelet parameters.展开更多
A kind of quick, efficient and season-free inducing embryoid and multiple shoot clumps system from shoot tip meristems that derived from elite inbreds of maize was established. The herbicide-resistant gene a/s (coding...A kind of quick, efficient and season-free inducing embryoid and multiple shoot clumps system from shoot tip meristems that derived from elite inbreds of maize was established. The herbicide-resistant gene a/s (coding Acetolactate synthase) isolated from a mutant of Arabidopsis thaliana was transferred to tissue pieces of maize multiple shoot clumps by microprojectile bombardment. Herbicide-resistant tissue and regenerants were obtained through selections with herbicide chlorsulfuron. PCR analysis and Southern blot hybridization indicated that gene a/s has been transferred to some regenerants. The test of spraying chlorsulfuron displayed that the transgenic plantlets and R1 plants had favorable herbicide-resistant trait. We have established a new genotype-free system of maize which could rapidly and efficiently produce large quantities of transgenic plantlets.展开更多
Carbonate clumped isotope(Δ47)is a new and reliable geothermometer.Endogenic carbonates in lake sediments are good archives to reconstruct lake water temperature using clumped isotope thermometry.However,applications...Carbonate clumped isotope(Δ47)is a new and reliable geothermometer.Endogenic carbonates in lake sediments are good archives to reconstruct lake water temperature using clumped isotope thermometry.However,applications of carbonate clumped isotope thermometry to lacustrine carbonates are still scarce because the existed organic and/or sulfur contaminants in such samples interfere with clumped isotope analysis and cause notable temperature biases.Therefore,exploring an effective way to remove contamination is a prerequisite to widely applying carbonate clumped isotope thermometry to lake sediments.By pretreating fine-grained endogenic carbonates from Dali lake sediments with hydrogen peroxide of different concentrations for different lengths of time,we conducted a series of conditional experiments to seek the optimal pretreatment condition for clumped isotope analysis.Δ47,Δ48 offset and 49 parameter were obtained from clumped isotope measurements to assess the effect of contamination removal.Results showed that untreated samples("0%-0")had a very high 49 parameter.After the treatment with hydrogen peroxide,the 49 parameter was significantly reduced while theΔ48 offset evidently increased.TheΔ47,Δ48 offset and 49 parameter of samples pretreated under different conditions showed significant variability,even though the measuredΔ47 temperatures changed within a relatively narrow range(i.e.,from 17.0±1.3 to 22.8±1.6°C).Among various treated samples,the sample"3%-8"yielded a smallerΔ48 offset and 49 parameter,and lowerΔ47 temperature of 17.0±1.3°C.Therefore,"reacting with 3%hydrogen peroxide for 8 h"was suggested to be the optimal condition for removing contaminants from lacustrine endogenic carbonates prior to clumped isotope analysis.At the time when the pretreatment condition was too intense(i.e.,H2O2 concentration>3%and/or reaction time>8 h),secondary contaminants might have been generated in the closed reaction system,whose ultimately transformed state may interfere with masses 47,48.Using the optimal pretreatment procedure,we obtained reasonableΔ47 temperature changes during the last deglaciation and found a temperature decrease of about 6°C in Northern China during the Younger Dryas period.Our study demonstrates a great potential of applying carbonate clumped isotope thermometry to lacustrine carbonates for paleo-temperature and paleo-elevation reconstructions in the future.展开更多
With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for t...With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for the origin of the broad-line region in Active Galactic Nuclei,which was published展开更多
叶面积指数(leaf area index,LAI)是反映植物冠层结构和光能利用的重要指标.随着遥感技术的不断发展,利用遥感数据获取大面积LAI已经成为监测作物生长和估产的重要手段.基于物理模型的LAI遥感反演方法经常假设作物冠层结构是均匀分布,然...叶面积指数(leaf area index,LAI)是反映植物冠层结构和光能利用的重要指标.随着遥感技术的不断发展,利用遥感数据获取大面积LAI已经成为监测作物生长和估产的重要手段.基于物理模型的LAI遥感反演方法经常假设作物冠层结构是均匀分布,然而,作为典型的垄行结构,作物冠层被公认为是介于连续植被与离散植被之间的一种过渡形式,而简单的均匀假设必然会给反演带来偏差.本文以农作物玉米为研究对象,首先重建了玉米三维冠层结构,并定量对比分析了一维辐射传输模型PROSAIL和三维辐射传输模型LESS在玉米冠层不同生长期的反射率差异,确定了玉米冠层的非均匀分布特征是引起PROSAIL模型模拟和反演误差的主要因素;然后,考虑到玉米冠层生长过程中聚集指数的变化特征,利用LESS模型定量计算了不同生育期玉米冠层结构对应的聚集指数,建立了聚集指数和有效叶面积指数(LAI_(e))之间的关系;进而,利用该关系对基于PROSAIL模型反演得到的LAI进行修正.结果表明,修正后的LAI精度有明显提高,R^(2)从0.27提高到了0.55.该方法有望提高中高分辨率遥感数据在农作物LAI反演精度.展开更多
基金supported by National Natural Science Foundation of China(42372148)。
文摘Oxygen isotope(δ^(18)O)of paleolake water is a key indicator for reconstructing the formation temperature and diagenetic history of lacustrine carbonate minerals.In this study,we use clumped isotopes(Δ_(47))of lacustrine shell limestones to determine the surface erosion thickness and δ^(18)O of Early Jurassic lake water in the northern Sichuan Basin.We analyzed nine shell limestone and seventeen shale samples from the Early Jurassic Da'anzhai Member(J_(1)z^(4))in the Yuanba area.Whether the shell's shapes are well or partially preserved,the J_(1)z^(4)shell limestones in the Yuanba area show no significant recrystallization and dull cathodoluminescence.These characteristics suggest that the shell limestones did not undergo significant diagenetic alteration during late burial.The Δ_(47)values of the J_(1)z^(4)shell limestones range from 0.448±0.005‰to 0.463±0.006‰,yielding clumped isotope temperature(T_(Δ47))of 64.4±0.8 to 69.7±1.4℃,which is significantly higher than the Early Jurassic paleotemperature.It suggests that the Δ_(47)of shell limestones was altered by solid-state reordering,meaning the T_(Δ47)does not reflect the initial formation temperatures.By integrating organic matter's maturation model(Easy%R_(o))of coexisting shales with Δ_(47)solid-state reordering model of calcite,we constrained the maximum burial temperature(~170℃)and the initial formation temperature(~28℃)of these shell limestones.Based on reported paleotemperature gradient,we estimated that the surface erosion thickness was about 1500 m.Furthermore,using the determined initial formation temperatures and conventional oxygen isotope thermometer,we determined that the δ^(18)O values of the Early Jurassic lake water in the Sichuan Basin,which ranged from-10.8‰to-8.0‰(SMOW).The reconstructed paleo temperature and δ^(18)O of lake water suggest that the Early Jurassic in the Sichuan Basin was warm and humid,which was favorable for the deposition of organic-rich lacustrine shale.The methods developed in this study,which employ Δ_(47)of shell limestones to reconstruct the maximum burial temperature and paleolake environmental conditions,demonstrate broad applicability to the Sichuan Basin and similar lacustrine basins.
文摘为了模拟堆石料三轴压缩实验中颗粒间的咬合作用,提出了一种不改变模型孔隙率、不添加删除颗粒的随机CLUMP颗粒生成方法,并利用该方法进行堆石料细观本构模型参数反演。以蒲石河抽水蓄能电站输水洞开挖出的堆石料三轴压缩实验为例进行计算,结果表明:每个CLUMP颗粒由两个球型颗粒构成时计算结果与实验结果吻合最好,各载荷步偏应力相对误差均值为6.31%。随着构成CLUMP颗粒的球型颗粒数量的增加,细观参数中的接触弹性模量随之线性减小,法向刚度与切向刚度之比随之略有增加,而摩擦系数趋于一个常数。使用反演参数对400和600 k Pa围压下的实验结果进行预测,平均相对误差分别为8.29%和10.60%,模拟曲线与实验曲线基本一致,验证了该方法的有效性。
基金Project(11272359) supported by the National Natural Science Foundation of China
文摘To properly simulate hard rock with a high ratio of the uniaxial compressive strength to tensile strength(UCS/TS) and realistic strength-failure envelope,the rock deformation and mechanical characteristics were discussed in detail when the particle simulation method with the clump parallel-bond model(CPBM) was used to conduct a series of numerical experiments at the specimen scale.Meanwhile,the effects of the loading procedure and crack density on the mechanical behavior of a specimen,which was modeled by the particle simulation method with the CPBM,were investigated.The related numerical results have demonstrated that:1) The uniaxial compressive strength(UCS),tensile strength(TS) and elastic modulus are overestimated when the conventional loading procedure is used in the particle simulation method with the CPBM; 2) The elastic modulus,strength and UCS/TS decrease,while Poisson ratio increases with the increase of the crack density in the particle simulation method with the CPBM; 3) The particle simulation method with the CPBM can be used to reproduce a high value of UCS/TS(>10),as well as a high friction angle and reasonable cohesion strength; 4) As the confining pressure increases,both the peak strength of the simulated specimen and the number of microscopic cracks increase,but the ratio of tensile cracks number to shear cracks number decreases in the particle simulation method with the CPBM; 5) Compared with the conventional parallel-bond model,the CPBM can be used to reproduce more accurate results for simulating the rock deformation and mechanical characteristics.
基金financially supported by the Kerala Agricultural University
文摘The humid agroclimatic conditions of Kerala,India permit the cultivation of an array of bamboo species of which Dendrocalamus strictus Roxb.(Nees.) is an important one on account of its high growth rate and multiple uses. Stand density, a potential tool in controlling the productivity of woody ecosystems, its effect on growth and root distribution patterns may provide a better understanding of productivity optimization especially when bamboo-based intercropping options are considered.Growth attributes of 7-year-old bamboo(D. strictus) stands managed at variable spacing(4×4 m, 6×6 m, 8×8 m,10×10 m, 12×12 m) were studied. Functional root activity among bamboo clumps were also studied using a radio tracer soil injection method in which the radio isotopeP was applied to soil at varying depths and lateral distances from the clump. Results indicate that spacing exerts a profound influence on growth of bamboo. Widely spaced bamboo exhibited higher clump diameters and crown widths while clump heights were better under closer spacing. Clump height was 30% lower and DBH 52%higher at the widest spacing(12×12 m) compared to the closest spacing(4×4 m). With increasing soil depth and lateral distance, root activity decreased significantly. Root activity near the clump base was highest(809 counts per minute, cpm; 50 cm depth and 50 cm lateral distance) at 4×4 m. Tracer study further showed wider distribution of root activity with increase in clump spacing. It may be concluded that the intensive foraging zone of bamboo is within a 50-cm radius around the clump irrespective of spacing. N, P and K content in the upper 20 cm was 2197,21, and 203 kg/ha respectively for the closely spaced bamboo(4×4 m) which were significantly higher than corresponding nutrient content at wider spacings. About 50% of N, P and K were present within the 0–20 cm soil layer, which decreased drastically beyond the 20 cm depth.The results suggest that stand management practices through planting density regulation can modify the resource acquisition patterns of D. strictus which in turn can change growth and productivity considerably. Such information on root activities, spatial and temporal strategies of resource sharing will be helpful in deciding the effective nutrition zone for D. strictus. Further, the study throws light on the spatial distribution of non-competitive zones for productivity optimization yields, especially when intercropping practices are considered.
基金This work was funded by the National Natural Science Foundation of China(Grant Nos.61774095 and 21727813)the Beijing Research Institute of Mechanical Equipment.
文摘Isolating rare circulating tumor cells(CTCs)from blood is critical for the downstream analysis that is important in cancer-related research,diagnosis,and medicine,and efforts are ongoing to increase the efficiency and purity of CTC isolation in microfluidics.Reported in this paper is a two-stage integrated microfluidic chip for coarse-to-fine CTC isolation from whole blood.First,blood cells are removed by filtration using a micropore-array membrane,then CTCs and other cells that are trapped in the micropores are peeled off the membrane by a novel release method based on air–liquid interfacial tension,which significantly increases the recovery rate of CTCs.The second stage is CTC capture based on an on-chip dense immuno-magnetic-bead clump,which offers high capture efficiency and purity.Both the micropore filtration and immuno-magnetic-bead capture are validated and optimized experimentally.Overall,the integrated microfluidic chip can realize a recovery rate of 85.5%and a purity of 37.8%for rare cancer cells spiked in whole blood.
基金funded by the fellowship of the China Postdoctoral Science Foundation(No.2020M682134)the National Natural Science Foundation of China(Nos.41872149,42076220)the Shandong Postdoctoral Innovation Research Project。
文摘Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.
基金the Open Program of the Key Laboratory of Xinjiang Uygur Autonomous Region(No.2019D04023)the National Natural Science foundation of China(No.11973076)+1 种基金the National Natural Science foundation of China(No.11433008,No.11603063,No.11703074 and No.11703073)the CAS"Light of West China"Program(No.2018-XBQNXZ-B-024,No.2016-QNXZB-23,and No.2016-QNXZ-B-22).
文摘Here we present the study on chemical properties of massive star forming clumps using N2H^+(1-0),H^13CO+(1-0),HCN(1-0)and HN^13C(1-0)data from the literature[Astron.Astrophys.563,A97(2014)].We found that abundances of H^13CO+ and HN^13C are a ected by H2 column densities.As the median values of these two abundances increase by nearly 10 times from stages A to B,H^13CO+and HN^13C are suitable for tracing the evolution of massive star forming clumps.The order of rapidity in growth of abundances of all the four studied molecules from stages A to B,is H^13CO^+,HCN,HN^13C,and N2H^+,from the highest to the lowest.Our results suggest that the observing optically thin molecular lines with high angular resolution are necessary to study the chemical evolution of massive star forming clumps.
基金funded by the PetroChina Major Research Program on Deep Petroleum System in the Tarim Basin(No.ZD 2019-183-01-003)the Major Research Project on the Tethys Geodynamic System from the National Natural Science Foundation of China(No.92055204)the National Natural Science Foundation of China(No.42072134).
文摘Determining the timing of fracturing is crucial for understanding reservoir evolution and hydrocarbon accumulation in foreland basins.Using fracturing data from cores,borehole images,and outcrops,combined with the clumped isotope(D47)and fluid inclusion analyses of carbonate minerals filled in pores and fractures,this study ascertained the fracturing timing of the Jurassic reservoirs in the Dibei-Tuziluoke Gas Field,Kuqa Foreland Basin.Data from outcrops and borehole images show two dominant fracture sets in the study area:W-E and NE-SW striking fractures.Some W-E striking fractures are carbonate-filled,while NE-SW striking fractures lack mineral fillings.Bitumen veins,not easy to be identified in borehole images,are prevalent in cores.The petrographic analysis reveals that these bitumen veins formed before the calcite cementation in pores and display high viscosity and low maturity.Homogenization temperatures(T_(h))from primary fluid inclusion assemblages in two representative calcite vein samples were notably lower than T_(△47) values from corresponding samples.This suggests the △_(47) signature underwent alteration due to partial reordering during burial.Thus,△_(47)-derived temperatures(apparent temperatures)may not faithfully represent the mineral precipitation temperatures.When plotting these apparent temperatures vs.the burial history,only the possible latest ages of fracturing emerged.These ages were further refined by considering petroleum charging,tectonic evolution,and stress orientation.Bitumen-filled fractures likely resulted from the Late Cretaceous uplift,marking the migration of low-maturity hydrocarbons in the study area.Carbonate-filled E-W striking fractures emerged during the late Miocene(~13-6.5 Ma)alongside fold development.NE-striking fractures that crosscut W-E ones possibly formed recently due to stress reorientation.
文摘Enteroaggregative Escherichia coli (EAggEC) strains cause the persistent diarrhea in infants and compromised hosts in developing countries. These strains are currently defined as E. coli that adheres to HEp-2 cells in an aggregative adherence (AA) pattern. In this study, we compared 4 different rapid methods for the detection of EAggEC using a PCR assay, clump formation test, glass slide adherence assay, and the HEp-2 cell adherence assay. Out of 683 E. coli strains isolated from diarrheal stool samples, we detected 17 aggR and/or clump-positive strains, and identified 2 aggR-positive, clump-negative strains and 2 aggR-negative, clump-positive strains. All the aggR positive and clump positive strains also showed positive results in glass slide adherence and HEp-2 cell adherence assays. From all these results, we suggest the following procedure for the rapid identification of EAggEC strains: first, screen E. coli strains with the clump formation test and subsequently perform the glass slide adherence assay to observe AA for confirmation.
基金National Natural Science Foundation of China(grant nos.42071304 and 42090013)the National Key Research and Development Program of China(grant nos.2020YFA0608701 and 2022YFB3903304).
文摘The vegetation canopy clumping index(CI)is an important indicator for understanding radiative transport processes,radiation interception,and the photosynthesis of vegetation canopies.However,most studies consider CI only in the nadir or specific direction.In this study,we analyze the directional characteristics of the CI based on RAMI-V(radiation transfer model intercomparison)activity,which represents most typical canopies.The directional gap fraction and CI of these scenes are accurately calculated based on the LESS(large-scale remote sensing data and image simulation framework)model.According to our results,the directional characteristics of the CI are affected by many factors,such as vegetation type,season,and canopy structure.Generally,the CI of a coniferous forest varies little with zenith angle,while the CI of a broad-leaf forest demonstrates the different trend.In winter,the CI is smaller than that in summer,and the variation in the CI at the zenith angle is less.The row structure scenes exhibit different directional characteristics along and perpendicular to the row direction,and their CIs tend to increase with zenith angle.To accurately model the directional CI,we propose a modified Gompertz function model.Compared with other directional CI models,this model has the advantages of high precision and strong applicability(R^(2)=0.975).By studying the directional characteristics of CI,we can enhance the usability of radiative transfer modeling and the accuracy of canopy biophysical parameter retrieval for vegetation with different structures.
文摘Background Platelet （PLT） clumping occurring in pseudothrombocytopenia （PTCP） can result in inaccurate PLT. Automated platelet clump count （APCC） is a quantitative parameter of platelet aggregation. In this study, we evaluated the clinical utility of APCC in the screening for platelet aggregation related ethylene diamine tetraacetic acid （EDTA）-dependent PTCP （EDTA-PTCP）. Methods A total of 105 patients and 200 healthy individuals were enrolled in this study. Blood samples were collected with dipotassium EDTA and sodium citrate respectively. ADVIA 2120 hematology analyzer was used to perform complete blood count （CBC） and APCC. Blood smears of both EDTA- and citrate-anticoagulated samples were made for microscope observation and manual PLT counting. Results In 25 patients with EDTA-PTCP patients, for EDTA-2K anticoagulated-blood, PLT was （55±6）×10^9/L, significantly lower than citrate anticoagulated blood （（186±13）×10^9/L））. APCC was （905±694）×10^9/L, significantly higher than citrate anticoagulated blood （98±37）×10^9/L. In true thrombocytopenia and healthy control groups, APCC was （63±60）×10^9/L and （69±59）×10^9/L respectively and there was no significant difference between EDTA and citrate anticoagulants. Receiver operator characteristic （ROC） curve showed both sensitivity and specificity of APCC were 96% when the cutoff value of APCC was set as 182×10^9/L. Other platelet parameters had poor performance. Conclusion The APCC has a good sensitivity and specificity in differentiating EDTA-PTCP from true thrombocytopenia compared with other platelet parameters.
基金This work was supported by the National "863" Project and Key Items of Scientific Technique Research from the Ministry of Education of China.
文摘A kind of quick, efficient and season-free inducing embryoid and multiple shoot clumps system from shoot tip meristems that derived from elite inbreds of maize was established. The herbicide-resistant gene a/s (coding Acetolactate synthase) isolated from a mutant of Arabidopsis thaliana was transferred to tissue pieces of maize multiple shoot clumps by microprojectile bombardment. Herbicide-resistant tissue and regenerants were obtained through selections with herbicide chlorsulfuron. PCR analysis and Southern blot hybridization indicated that gene a/s has been transferred to some regenerants. The test of spraying chlorsulfuron displayed that the transgenic plantlets and R1 plants had favorable herbicide-resistant trait. We have established a new genotype-free system of maize which could rapidly and efficiently produce large quantities of transgenic plantlets.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grants Nos.XDA19050104 and XDB26000000)the National Key R&D Program of China(Grant No.2017YFA0603400)+1 种基金the National Natural Science Foundation of China(Grants Nos.41931181&41672166)the Key Research Program of the Institute of Geology&Geophysics,CAS(Grant No.IGGCAS-201905)。
文摘Carbonate clumped isotope(Δ47)is a new and reliable geothermometer.Endogenic carbonates in lake sediments are good archives to reconstruct lake water temperature using clumped isotope thermometry.However,applications of carbonate clumped isotope thermometry to lacustrine carbonates are still scarce because the existed organic and/or sulfur contaminants in such samples interfere with clumped isotope analysis and cause notable temperature biases.Therefore,exploring an effective way to remove contamination is a prerequisite to widely applying carbonate clumped isotope thermometry to lake sediments.By pretreating fine-grained endogenic carbonates from Dali lake sediments with hydrogen peroxide of different concentrations for different lengths of time,we conducted a series of conditional experiments to seek the optimal pretreatment condition for clumped isotope analysis.Δ47,Δ48 offset and 49 parameter were obtained from clumped isotope measurements to assess the effect of contamination removal.Results showed that untreated samples("0%-0")had a very high 49 parameter.After the treatment with hydrogen peroxide,the 49 parameter was significantly reduced while theΔ48 offset evidently increased.TheΔ47,Δ48 offset and 49 parameter of samples pretreated under different conditions showed significant variability,even though the measuredΔ47 temperatures changed within a relatively narrow range(i.e.,from 17.0±1.3 to 22.8±1.6°C).Among various treated samples,the sample"3%-8"yielded a smallerΔ48 offset and 49 parameter,and lowerΔ47 temperature of 17.0±1.3°C.Therefore,"reacting with 3%hydrogen peroxide for 8 h"was suggested to be the optimal condition for removing contaminants from lacustrine endogenic carbonates prior to clumped isotope analysis.At the time when the pretreatment condition was too intense(i.e.,H2O2 concentration>3%and/or reaction time>8 h),secondary contaminants might have been generated in the closed reaction system,whose ultimately transformed state may interfere with masses 47,48.Using the optimal pretreatment procedure,we obtained reasonableΔ47 temperature changes during the last deglaciation and found a temperature decrease of about 6°C in Northern China during the Younger Dryas period.Our study demonstrates a great potential of applying carbonate clumped isotope thermometry to lacustrine carbonates for paleo-temperature and paleo-elevation reconstructions in the future.
文摘With the support by the National Natural Science Foundation of China,a collaboration led by Prof.Wang Jianmin(王建民)from the Institute of High Energy Physics,Chinese Academy of Sciences proposes a new mechanism for the origin of the broad-line region in Active Galactic Nuclei,which was published
文摘叶面积指数(leaf area index,LAI)是反映植物冠层结构和光能利用的重要指标.随着遥感技术的不断发展,利用遥感数据获取大面积LAI已经成为监测作物生长和估产的重要手段.基于物理模型的LAI遥感反演方法经常假设作物冠层结构是均匀分布,然而,作为典型的垄行结构,作物冠层被公认为是介于连续植被与离散植被之间的一种过渡形式,而简单的均匀假设必然会给反演带来偏差.本文以农作物玉米为研究对象,首先重建了玉米三维冠层结构,并定量对比分析了一维辐射传输模型PROSAIL和三维辐射传输模型LESS在玉米冠层不同生长期的反射率差异,确定了玉米冠层的非均匀分布特征是引起PROSAIL模型模拟和反演误差的主要因素;然后,考虑到玉米冠层生长过程中聚集指数的变化特征,利用LESS模型定量计算了不同生育期玉米冠层结构对应的聚集指数,建立了聚集指数和有效叶面积指数(LAI_(e))之间的关系;进而,利用该关系对基于PROSAIL模型反演得到的LAI进行修正.结果表明,修正后的LAI精度有明显提高,R^(2)从0.27提高到了0.55.该方法有望提高中高分辨率遥感数据在农作物LAI反演精度.
