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1.
研究了谷氨酸阴离子(G-)和晶种对其晶体二次成核与生长的影响.结果表明成核速率随晶种粒度和晶种量减少而减少;在高过饱和度时G-对成核有促进作用,而在低过饱和度时则有抑制作用;晶体生长速率随粒度减小而增大;G-对晶体生长有抑制作用;结晶时使用粒度小的晶种可得到粒度分布较均匀的晶体.  相似文献   

2.
采用静态体视显微法测定了在3.03.15K下,二水甲酸锶晶体的(110)和(011)面的生长速率,通过用生长速率(R)与过饱和度(σ)的关系,计算了生长参数,发现其生长机制符合水溶液中晶体生长的BCF面扩散模型。研究了体扩散对生长速率的影响,结果表明:在低过饱和度下,体扩散影响很小,当过饱和度σ≥0.200时,体扩散影响显著。  相似文献   

3.
在水/乙二醇混合溶剂中,通过微波辅助加热的方法,研究溶液过饱和度对碳酸钙成核生长的影响。分别采用扫描电子显微镜(SEM)、X-射线粉末衍射(XRD)对所得的样品进行了表征。结果表明,过饱和度的改变对碳酸钙形貌和晶型具有非常明显的影响,分别获得了菱面体状方解石、纤维捆扎状文石、松树枝状球霰石为主体的碳酸钙晶体。  相似文献   

4.
为了得到不同晶型的碳酸钙晶体,采用凝胶法生长出了碳酸钙的三种同质异象体:方解石、文石、球霰石.讨论了反应物浓度和杂质离子(Na^+)对碳酸钙晶体生长的影响.结果表明:通过改变反应物浓度和利用不同的反应物可以生长出不同晶型的碳酸钙晶体.同时,利用原子力显微镜对生长的方解石晶体表面的形貌观察发现:晶体生长是以台阶簇(大台阶)的方式推进,不同高度的堆垛层错呈现在表面上.  相似文献   

5.
本文测定了2,4-二硝基苯丙氨酸钠·2.4-二硝基苯丙氨酸(NaAP·HAP)晶体在乙醇溶液中的溶解度、过饱和度曲线和(201)、(110)晶面的生长速率,由溶液热力学计算了界面熵因子(α).根据α值讨论了该晶体在溶液中的界面状况,并用BCF模型和B+S模型联合影响的生长机理来解释晶体生长速率与过饱和度之间的关系。  相似文献   

6.
反溶剂重结晶法制备多晶型比卡鲁胺   总被引:1,自引:0,他引:1  
采用反溶剂重结晶法制备多晶型比卡鲁胺,通过改变重结晶过程中所使用的溶剂,对比单一溶剂和共溶剂对所制得晶体的晶型和颗粒形貌差别,探索最优化的共溶剂类型和体积比参数,以达到将比卡鲁胺原料药进行晶型纯化的目的。在反溶剂重结晶过程中采用共溶剂制备比卡鲁胺晶体发现:共溶剂(二甲基亚砜+乙醇)以及(丙酮+乙醇)可制备比卡鲁胺晶型I,并通过调节共溶剂中乙醇的用量可得到粒度均一,分散性好的I型比卡鲁胺。  相似文献   

7.
考察了青霉素G,丙酮和苯乙酸(PAA)杂质在6 氨基青霉烷酸(6 APA)结晶过程中对晶习的影响及其在乙醇溶液中的生长过程。发现6 氨基青霉烷酸在乙醇溶液的生长过程中存在由菱形晶体向六面体晶体的晶习转变;6 APA晶体在青霉素G存在时趋向于破碎;在丙酮存在时变厚;在苯乙酸存在时易于形成六面形晶体。  相似文献   

8.
研究了琥珀酸十八酯(OSO)晶体过饱和溶液的成核过程,测量了以诱导期表示的成核速率,讨论了温度、过饱和度和溶剂对成核速率的影响。OSO过饱和溶液的成核速率随着温度的升高和过饱和度的增大而增大,溶剂不同其数值也不同,实验结果根据经典成核理论进行了分析。  相似文献   

9.
研究马来酸氢十八酯(OHM)过饱和溶液的成核过程,测量以诱导时间表示的成核速率,讨论温度、过饱和比和溶剂对成核速率的影响,根据经典均匀成核理论计算了晶体的固-液表面张力、成核自由能和临界成核半径.结果表明,OHM晶体过饱和溶液的成核速率随着温度和过饱和度的提高而增大,不同的溶剂有不同的数值.  相似文献   

10.
氢化可的松晶体形貌预测   总被引:3,自引:0,他引:3  
氢化可的松(HC)是一种重要的肾上腺皮质激素,它不仅是最重要的即效抗炎药和免疫抑制剂之一,而且具有低剂量、持续时间长和疗效确切等特点.从甲醇溶剂中培养出长方拄形的单晶,采用Cerius~2分子模拟软件对其晶体形貌进行了理论预测.将Cerius~2软件的几个模型对氢化可的松在“真空中”晶习进行预测,其中BFDH和AE模型较符合实际晶习,AE模型预测效果更佳,故选其作进一步的计算.采用DREIDING 2.21力场,通过电荷及能量的最小化计算井修正各晶面的附着能,得到的理论预测晶习与实验晶体形貌能很好吻合.  相似文献   

11.
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.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
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.  相似文献   

14.
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。  相似文献   

15.
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.  相似文献   

16.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

17.
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.  相似文献   

18.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

19.
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-  相似文献   

20.
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-  相似文献   

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