砂土堆积试验的组合Clump颗粒离散元模拟

为研究颗粒形状对砂土力学性质的影响,以室内试验结果为基础,采用离散元软件PFC3D模拟了颗粒堆积试验。选取球形度为颗粒形状特征系数,生成一系列球形度为0.33~1.0的Clump颗粒,用PFC软件对颗粒之间分别赋予不同的摩擦系数共模拟了81种试样。通过将模拟结果与室内试验结果对比以验证采用球形度模拟砂土的可行性,探讨了颗粒球形度及摩擦系数对颗粒堆积体宏观响应和细观组构变化的影响。结果表明：组合Clump颗粒试样的最大孔隙比与最小孔隙比与室内实测结果基本一致,验证了该方法的可行性;试样的自然休止角及孔隙率均与颗粒摩擦系数存在正相关关系,平均接触数则随摩擦系数增大而减小;根据颗粒球形度统计结果在离散元中模拟砂土颗粒可直接采用实际颗粒的摩擦系数;该方法对传统散体颗粒的细观模拟研究方法进行了改进,能够弥补离散元中用圆球颗粒模拟不规则颗粒的不足。

堆石料细观本构参数反演的CLUMP颗粒模型

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。

有机化合物“Clumped”同位素平衡分馏信号的理论预测

"Clumped"同位素指同位素体中含有两个或两个以上稀有同位素的情况(Eiler,2007)。就目前而言,其主要的研究形式是针对碳酸盐矿物中13C与18O相成键的同位素个体,使用高分辨率气相质谱技术来测定其浓度进而反推古温度,从而在地质温度领域打开了单一矿物相测温的新篇章。"Clumped"同位素地质温度计区别于传统同位素地质测温的特性在于其只需测定单一物质便可重建地质温度,而不需要了解该碳酸盐形成过程中与其平衡的水的同位素信息。自碳酸盐"Clumped"

Effects of clump spacing on nutrient distribution and root activity of Dendrocalamus strictus in the humid region of Kerala,peninsular India

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.

On-chip circulating tumor cells isolation based on membrane filtration and immuno-magnetic bead clump capture

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.

E ect of Optical Depth on Study of Chemical Properties of Massive Star Forming Clumps

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.

Rapid Detection Method for Enteroaggregative <i>Escherichia coli</i>Using Simple Clump Formation and Aggregative Assay

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.

Simulation of rock deformation and mechanical characteristics using clump parallel-bond models

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.

Fracturing timing of Jurassic reservoirs in the Dibei-Tuziluoke gas field,Kuqa foreland basin:Evidence from petrography,fluid inclusions,and clumped isotopes

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.

Clumped Isotope Analysis of Calcite and Dolomite Mixtures Using Selective Acid Extraction

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.

Cell replacement with stem cell-derived retinal ganglion cells from different protocols

Glaucoma,characterized by a degenerative loss of retinal ganglion cells,is the second leading cause of blindness worldwide.There is currently no cure for vision loss in glaucoma because retinal ganglion cells do not regenerate and are not replaced after injury.Human stem cell-derived retinal ganglion cell transplant is a potential therapeutic strategy for retinal ganglion cell degenerative diseases.In this review,we first discuss a 2D protocol for retinal ganglion cell differentiation from human stem cell culture,including a rapid protocol that can generate retinal ganglion cells in less than two weeks and focus on their transplantation outcomes.Next,we discuss using 3D retinal organoids for retinal ganglion cell transplantation,comparing cell suspensions and clusters.This review provides insight into current knowledge on human stem cell-derived retinal ganglion cell differentiation and transplantation,with an impact on the field of regenerative medicine and especially retinal ganglion cell degenerative diseases such as glaucoma and other optic neuropathies.

“Eternal Motion” as a “Form of Movement of a Special Nature” and the Main Condition for the Creation of the Universe

The article hypothesizes that DE and DM (UCM) are a “Form of Motion of a Special Nature”, where “Form of Motion” means “Eternal Motion” as the power of dynamics of different levels and varying degrees of self-sufficiency, and by “Special Nature”, gravitational and two other properties of matter, “tied” to the “Eternal Movement” and completely dependent on it. Carriers of key properties of a “Special Nature” have been established: “0”-DE particles and “3”-DM particles (UDM). The unity of their inherent “motionally-gravitational” properties and the peculiarity of the relationship between “motion” and “gravity” are revealed: the higher the intensity of “Eternal Motion”, the stronger the gravitational properties of matter are manifested (and vice versa). The relationship of “time” with the “vibration frequency” and the “mass” of photons with the “degree of bonding and deformation properties of the field” is shown. The maximum level of gravity has been determined, which allows Nature to successfully create the Universe: such a landmark is the proximity to the property of the Primary Source—the “pure graviton” of the OSP space, the most powerful “motionally-gravitational” particle of the Universe. The reasons for the emergence of such an identity of the gravitational properties of particles with the indicators of a “pure graviton” are established: for “0”-DE particles, this is the acquisition of the function of “freedom of movement”;for “3”-DM particles (UDM), the creation of a special structure—a “double field” (“Main” and “Small”). The presence in the “double field” of specific “tools” for the creation of the worlds of the Universe—gravitational “waves” gives rise to impulses (shocks) of varying intensity and shape. A list of functions performed by “waves” in the “Main” and “Small” fields has been compiled. The specific conditions for the formation of “UDM Streams”, their transformation into a “Vortex” and, under the influence of a powerful Initial Impulse (push), sending them to the “place” of the creation of galaxies, are shown. It is suggested that there is a “Cycle of Matter in Nature” in the closed structure of our Universe due to the “work” of “waves” and the functioning of special “factories” in the form of exotic space objects—Black holes.

293T细胞生产慢病毒工艺优化

随着细胞治疗的快速发展,大规模慢病毒的生产成为工艺环节中的瓶颈,因此,优化293T高滴度和高纯度的CAR慢病毒载体生产工艺显得至关重要。本研究旨在优化包装慢病毒的293T贴壁细胞,节省时间,节约成本,提高慢病毒包装的能力。同时对优化慢病毒载体中出现悬浮细胞结团生长的现象进行探索,检测其影响结团的因素。分别采用快速、慢速驯化方式将293T贴壁细胞驯化为悬浮培养,并比较其细胞形态、细胞密度、细胞活率、慢病毒包装能力和冻存复苏后稳定一致性,筛选出最优的悬浮驯化条件。通过调节Ca^(2+)浓度和EDTA添加量来研究比较细胞结团生长状况。结果证明,使用无血清培养基OPM-293 CD05溶剂(medium)可以将293T贴壁细胞快速驯化为293T悬浮细胞,并能制备出慢病毒滴度且优于贴壁细胞的包装滴度(^(*)P<0.05)。Ca^(2+)浓度会影响细胞结团大小,添加EDTA能有效分离分散非必要的细胞抱团生长。研究结果显示,传统293T贴壁细胞可以使用无血清培养基OPM-293 CD05溶剂快速驯化成悬浮细胞;在一定范围内,Ca^(2+)浓度越高细胞所结团块及粒径越大,EDTA添加量越高细胞所结团块及粒径变小。这为优化慢病毒载体包装工艺和悬浮培养条件,同时为体外规模化细胞培养放大和生产奠定了理论基础,具有一定的实用价值。

Gm-柠檬酸联合植物对矿山污染土壤的修复

以典型铀矿山周边放射性核素污染土壤为研究对象,采用盆栽试验,分析螯合剂与丛枝菌根真菌联合植物对强化修复放射性污染土壤的影响,揭示螯合剂和丛枝菌根真菌联合植物修复污染土壤的特征。结果表明:施加柠檬酸(CA)与摩西球囊霉菌(Glomus mosseae,Gm)对黑麦草-空心菜间作模式下的生长、铀富集存在不同程度的促进作用,以二者联合处理效果最明显;联合修复不仅增强了植物地下部分对放射性核素的固定,同时也降低了土壤中有机质的浓度,增强了放射性核素的附着能力;根际土样、植物灰样的扫描电镜分析和能谱图显示,接种Gm或施加CA对植物修复起到积极作用,以联合修复效果最好。

Clinical utility of automated platelet clump count in the screening for ethylene diamine tetraacetic acid-dependent pseudothrombocytopenia

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.

Establishment of multiple shoot clumps from maize(Zea mays L.)and regeneration of herbicide-resistant transgenic plantlets

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 als(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 als 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.

Clumped isotope analysis of lacustrine endogenic carbonates and implications for paleo-temperature reconstruction:A case study from Dali Lake

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.

北半球中高纬植被聚集指数遥感产品长时间序列变化特征的案例研究

植被聚集指数(clumping index,CI(Ω))是表征植被冠层聚集程度的重要结构参数,由于其定量化研究起步较晚,导致对CI季相变化特征的研究不充分,结论争议较大.为此,本文基于长时间序列的MODIS CI产品,从北半球中高纬度植被物候特征敏感区,在13个国际地圈-生物圈计划(IGBP)类型中,优选了84个高质量的代表性像元,开展典型像元CI季相变化特征的案例研究.以归一化植被指数(normalized difference vegetation index,NDVI)作为对比,提出改进的动态阈值法,结合离散Fourier变换方法,分别提取不同地类的生长季开始时间(start of season,SOS)及生长季结束时间(end of season,EOS),最终建立北半球中高纬度各地类生长季与休眠期的经验Ω.结果表明:CI具有较为明显的物候变化规律及季节变化特征,甚至能够识别出耕地的一年两熟迹象,但相对于NDVI相对稳定的季相变化特征,大部分地类的CI表现出较大的变化和不确定性,其中,SOS和EOS多分别在第100和第300天左右变化,生长季则多维持在200d左右;提取物候特征参数的最佳阈值随提取时期、地物类别的变化而变化,其中提取SOS和EOS的最佳阈值多集中在40%~80%和80%~90%;经验Ω呈现出针叶林的聚集效应最强,耕地的聚集效应最弱的特征.本研究对于揭示不同地类CI季相特征及相关应用研究提供了有用的证据和参考.

聚集指数和最大羧化速率对基于遥感产品的植被生产力估算的影响

【目的】明确聚集指数和最大羧化速率遥感产品对BEPS模型估算植被生产力的影响。【方法】利用中国陆地通量站点观测数据,分析BEPS模型中聚集指数(CI)和最大羧化速率(V_(cmax))的敏感性程度,并比较聚集指数和最大羧化速率遥感产品对植被生产力估算的精度提升作用。在此基础上估算2012年中国陆地生态系统植被生产力,通过与参数缺省值估算结果对比,研究CI和V_(cmax)的时空变化对模型估算结果的影响。【结果】1) CI和V_(cmax)均为BEPS模型中较为敏感的参数,两者均与植被生产力呈正相关关系,且不同植被类型下V_(cmax)敏感性均高于CI。2)聚集指数和最大羧化速率遥感产品同时使用情况下,模拟结果的误差最小,精度最高,总初级生产力(GPP)均方根误差从665.60 g·m^(-2)a^(-1)降至584.71 g·m^(-2)a^(-1),平均误差和相对平均误差均为4种模拟情况最低值。3)2012年中国陆地生态系统GPP和净初级生产力(NPP)总量分别为5.21和2.49 Pg·a^(-1),受CI遥感产品(NDHD-CI)和V_(cmax)遥感产品(SIF-V_(cmax))的时空变化影响,GPP和NPP估算分别较模型缺省值偏低3.06%和4.72%。【结论】NDHD-CI和SIF-V_(cmax)能够提升BEPS模型估算植被生产力的精度,未来可对其他高敏感度参数和模型机理进行优化改进。受CI和V_(cmax)时空变化影响,植被生产力估算结果略低于缺省情况。V_(cmax)对植被生产力估算影响高于CI。

川西北地区中二叠统栖霞组白云岩形成机理——以车家坝剖面为例

以岩石学观察为基础,结合稳定同位素与团簇同位素分析,探讨了川西北地区中二叠统栖霞组白云岩形成机理。川西北车家坝剖面白云岩集中发育于栖霞组上段,可识别出基质白云石与白云石胶结物2种不同类型的白云石。基质白云岩呈灰白色,与灰岩接触界线截然,呈指状交错接触;白云石胶结物呈乳白色,局限分布于溶蚀孔洞的边缘。镜下可进一步划分为3种类型基质白云石,即漂浮状细晶直面自形—半自形基质白云石(Md1)、细—中晶直面自形—半自形基质白云石(Md2)、中—粗晶它形曲面基质白云石(Md3),以及一种鞍形白云石胶结物(Sd)。Md1沿缝合线呈漂浮状分布于灰泥基质中,可能为浅埋藏环境下压溶作用的产物。Md2与Md3具有与宿主灰岩相似的δ^(13)C、δ^(18)O和^(87)Sr/^(86)Sr同位素特征,指示白云石化流体主要来源于二叠纪同期海水,而相对较高的成岩温度说明受二叠纪末大规模火山活动的影响显著。鞍形白云石及其后的方解石胶结物具有明显偏负的δ^(18)O值和放射性^(87)Sr/^(86)Sr值,说明它们形成于高温外源富放射性锶的白云石化流体中,可能为来自或穿过碎屑岩地层的深部热流体。川西北地区栖霞组白云岩的形成受原始沉积相与断裂活动的双重控制,热流体的注入使原始滩相地层发生白云石化作用,形成大量溶洞与晶间溶孔,对储层的改造起到了积极的建设性作用。