褐藻寡糖抗三氧化二砷(As2O3)诱导蚕豆根尖的细胞遗传毒性

采用蚕豆根尖细胞的微核试验和染色体畸变试验方法,测定不同浓度的褐藻寡糖对As2O3诱导的蚕豆根尖细胞的微核率、有丝分裂指数和染色体畸变率的影响.结果表明:褐藻寡糖能有效抑制As2O3诱导的蚕豆根尖细胞微核的产生,即在一定浓度范围内,微核率随褐藻寡糖处理浓度的降低而减少,但低于一定浓度后反而呈上升趋势;不同浓度的褐藻寡糖均可使蚕豆根尖细胞有丝分裂指数增大;褐藻寡糖还能有效降低蚕豆根尖细胞染色体畸变率.因此,褐藻寡糖对蚕豆根尖细胞具有明显的诱抗活性和调节细胞分裂生长的效应.     

明矾对蚕豆和大蒜根尖毒性效应的细胞遗传学比较研究

以蚕豆和大蒜根尖为实验材料，研究不同浓度明矾对蚕豆和大蒜胚根根尖的细胞遗传学效应。结果表明，不同浓度明矾在不同处理时间内均能诱发较高微核率和染色体畸变率，且在同样的条件下，蚕豆根尖细胞的微核率和染色体畸变率明显高于大蒜的(p＜0．01或p＜0．001)。结论是明矾对蚕豆和大蒜根尖均具有明显的细胞遗传学务性效应，且对蚕豆根尖的务性效应明显高于对大蒜根尖的毒性效应。     

氯霉素对蚕豆根尖细胞有丝分裂的影响

氯霉素在动物性食品中的残留对人类健康造成威胁。用不同浓度氯霉素处理蚕豆根尖，结果表明，氯霉素会造成蚕豆根尖细胞有丝分裂指数下降，微核率上升和染色体畸变，畸变类型主要有染色体落后、染色体断片、染色体桥和染色体多极分裂等。染色体异常行为与氯霉素处理浓度呈正相关，说明氯霉素是一种环境诱变剂。     

宜宾油樟的化感作用对蚕豆根尖细胞有丝分裂的影响

利用油樟水浸提液作用蚕豆根尖研究了油樟化感作用对蚕豆根尖细胞有丝分裂的影响.结果表明：油樟对蚕豆根尖细胞有丝分裂的化感作用和浸提液浓度、作用时间有密切关系.在实验设计的范围内,随油樟水浸提液浓度的加大,蚕豆根尖细胞有丝分裂指数显著减小,而细胞微核率显著提高;油樟浸提液作用48 h时,对蚕豆根尖细胞有丝分裂的化感作用最强;油樟水浸提液诱导蚕豆根尖细胞产生染色体断片和滞后染色体等多种畸变染色体,并使有丝分裂各时期的分裂相减少.说明油樟化感物质抑制了细胞的有丝分裂,促进微核的产生,从而影响蚕豆根尖的生长和细胞的     

盐酸吗啉胍对蚕豆根尖细胞的遗传毒性效应

以不同浓度的盐酸吗啉胍为诱变剂，运用蚕豆根尖微核检测技术和染色体畸变实验方法，测定蚕豆根尖细胞的有丝分裂指数、微核率和染色体畸变率．结果表明：盐酸吗啉胍能够降低蚕豆根尖细胞有丝分裂指数，能诱发较高频率的微核和染色体畸变，产生染色体断片、滞后染色体和染色体桥．随着盐酸吗啉胍处理浓度的增加，有丝分裂指数降低，而微核率和染色体畸变率均升高；随着盐酸吗啉胍浓度的进一步增加，染色体畸变率却下降，但仍明显高于对照组．     

镉对蚕豆根尖细胞染色体畸变的影响

通过光学显微镜观察发现,蚕豆根尖经镉染毒后,染色体会发生畸变,在一定浓度和时间范围内,畸变率随浓度和时间的增加而增加,但当大于或小于这一浓度或时间范围后,畸变率反而减少.在蚕豆根尖细胞染色体的几种畸变中,以染色体断片出现的几率最高,染色体环出现的几率最低. 本文讨论了蚕豆根尖细胞染色体畸变与染毒的浓度和时间的关系.     

8-羟基喹啉和对苯二酚诱导蚕豆根尖细胞异常性的比较研究

采用8-羟基喹啉与对苯二酚处理蚕豆根尖,根尖经恢复培养后,以孚尔根染色法制片观察.同时以低温处理的相同材料为对照.经2种药物不同浓度处理后观察其根尖细胞的微核率,以及它们对有丝分裂指数的影响,同时还观察了它们对染色体畸变的效应.得出以下结果:(1)2种诱变剂均能诱发高频率的微核细胞;8-HQ还可以产生较高频率的双核细胞.(2)HQ在2个不同处理浓度均可明显提高有丝分裂指数,且可有效地积累中期分裂相;而8-HQ对有丝分裂指数的提高影响不明显,且在0.004 mol.L-1浓度时对有丝分裂指数具有显著的抑制效应.(3)2种诱变剂均能导致染色体畸变及其他核异常.本研究结果表明8-HQ和HQ均是细胞板有效的抑制剂和诱发染色体数目和结构变异较强的诱变剂.     

酸性铝诱发蚕豆根尖细胞的遗传损伤效应

采用蚕豆根尖细胞染色体畸变实验,研究酸性铝对蚕豆体细胞染色体稳定性的影响.以不同酸度(pH 5.8和pH 4.5)和不同浓度铝溶液处理蚕豆,结果表明:在pH 5.8时,用浓度30μm o l/L~50 000μm o l/L的铝处理,能诱发蚕豆根尖细胞染色体畸变,畸变率随铝浓度的升高而增加;pH 4.5时,用浓度30μm o l/L~300μm o l/L的铝处理组诱发的染色体畸变同样随铝浓度的升高而增加,但铝浓度为1 000μm o/L~50 000μm o l/L时抑制根尖细胞分裂,几乎没有中期相.比较不同pH的铝处理结果可知,相同铝浓度(30μm o l/L~300μm o l/L)时pH 4.5组比pH 5.8组的染色体畸变率高,其中30μm o l/L的两组差异较小,300μm o l/L两组差异较大.研究结果表明,环境铝对植物的遗传损伤与植物生存环境中可溶性铝的浓度有关,铝离子浓度增高会导致其毒性作用增强,酸度降低在一定程度上加剧了铝的毒性作用.     

平阳霉素和丝裂霉素C对蚕豆根尖细胞的诱变效应

蚕豆根尖细胞对于平阳霉素、丝裂霉素C极为敏感。在其细胞分裂的各个时期均出现微核和染色体畸变,而染色体畸变率和微核细胞率与平阳霉素、丝裂霉素C的浓度密切相关。在一定范围内二者的浓度增高,染色体畸变率和微核细胞率同时表现线性增长。故可确认蚕豆根尖细胞在水质监测和诱变剂筛选中的重要作用。     

蚕豆根尖微核实验监测几种重金属污染研究

采用蚕豆根尖微核实验方法,研究重铬酸钾、乙酸铜和氯化汞这几种重金属对蚕豆根尖细胞核的致畸效应.分别以不同浓度的重铬酸钾、乙酸铜和氯化汞作为诱变剂,处理并测定蚕豆根尖细胞的微核率,实验结果表明,在一定浓度范围内,其微核率随重金属溶液浓度的升高而增加,但高于一定浓度后,反而呈下降趋势; 同样浓度下,经重铬酸钾处理的蚕豆根尖细胞的微核率最高,乙酸铜次之,氯化汞最低.结论是：重金属化合物对蚕豆根尖细胞具有明显的致畸效应,并且以重铬酸钾的致畸效应最为明显.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the