光合细菌Rhodobacter sphaeroides的醋酸代谢

利用PSB处理高浓度有机废水是一项十分诱人的废水处理新技术和废水资源化途径。本文就R.sphaeroides对醋酸的利用性,共存有机酸对醋酸代谢的影响进行了试验研究,并对它醋酸代谢的可能途径作了探讨。 R.sphaeroides生长的最适醋酸浓度为25 mmnol.dm~(-3),醋酸浓度增至200mmol.dm~(-3)时,虽然R.sphaeroides迟缓期长达24小时以上,但仍能缓慢地生长。共存的琥珀酸对R.sphaeroides的醋酸代谢有明显影响。当TCA循环中的α-酮戊二酸脱氢酶被抑制时,R.sphae-roides的生长几乎完全受阻,当乌头酸酶被抑制时,醋酸仍能被利用。R.sphaeroides中有苹果酸合成酶活性,没检测到异柠檬酸裂介酶和高柠檬酸合成酶的活性。因而R.sphaeroides可能既不通过TCA循环右半部分和乙醛酸循环生成乙醛酸,也不通过高柠檬酸循环生成乙醛酸,进而由苹果酸的合成而生成草酰乙酸。     

肉鸭肝脏脂肪酸合成酶活性及脂肪酸合成途径的研究

利用放射线检测器和分光光度计,对肉鸭肝脏中参与脂肪酸合成的酶类:乙酰辅酶-A羧化酶,脂肪酸合成酶,NADP-苹果酸脱氢酶,葡萄糖-6-磷酸脱氢酶等酶的活性进行了测试分析.结果表明,肉鸭肝脏的各种脂肪酸代谢酶类的活性表现为:42日龄比21日龄的显著增加,显示随着日龄的增加,鸭肝脏合成脂肪的能力也显著增强.鸡的肝脏进行脂肪酸合成所必需的NADPH主要是由NADP-苹果酸脱氢酶参与的丙酮酸-苹果酸途径提供.与此相比,鸭的葡萄糖-6-磷酸脱氢酶的活性非常高,显示鸭的脂肪酸合成途径与鸡不同,脂肪酸的合成不仅仅有丙酮酸-苹果酸途径参与,戊糖磷酸循环也起到关键性的作用.     

NADP-异柠檬酸脱氢酶的结构与功能

异柠檬酸脱氢酶(isocitrate dehydrogenase,IDH)在三羧酸(TCA)循环中催化异柠檬酸生成α-酮戊二酸,将NAD 或NADP 还原成NADH或NADPH.根据空间结构特点,NADP-依赖性IDH可分为同源二聚体IDH和单体IDH,它们对生物体的能量代谢、生物合成以及抗氧化胁迫起重要作用.当碳源贫乏时,NADP-依赖性IDH的可逆磷酸化对TCA循环和乙醛酸旁路碳通量(carbon flux)的分配起关键性调控作用.因此目前IDH是研究蛋白质的结构与功能关系、酶的催化与调节机制、蛋白质功能进化的最好模型之一.     

有机酸在西索米星发酵过程中的影响

考察了有机酸对西索米星产生菌的菌体生长和产物合成的影响 .不同的有机酸对西索米星产生菌的菌体生长有不同程度的抑制作用 ,在产物合成阶段添加苹果酸、柠檬酸或延胡索酸有助于菌体的比产物合成能力 (Qp)的提高 ,这可能与发酵过程中胞内ALP的活力和TCA循环受到调节有关 .     

植物乙醇酸氧化酶的研究进展

乙醇酸氧化酶存在于细胞过氧化物酶体中,是光呼吸代谢的关键酶之一,能催化乙醇酸氧化生成乙醛酸,催化乙醛酸生成草酸;光呼吸与农业生产关系紧密.乙醇酸氧化酶是一种黄素蛋白,不同来源的乙醇酸氧化酶全酶分子质量和亚基相差很大.     

细菌纤维素生物合成网络的构建及代谢通量分析

构建了木醋杆菌合成细菌纤维素(Bacterial Cellulose,简称 BC)的代谢网络.基于流量平衡模型,通过物料衡算和Lingo线性规划,得到发酵前期和后期BC合成的代谢通量分布.代谢通量分析结果表明,葡萄糖进入磷酸戊糖途径(PPP)和三羧酸(TCA)循环,前期菌体大量合成,BC产量较高;后期形成大量无效循环,BC产量降低.由于部分代谢流流向副产物和无效循环,减少了合成BC的代谢流,造成了碳源的浪费,所以需通过遗传改造、诱变或改变发酵条件等方法,减少副产物生成,提高BC的产率.     

乙二醛电氧化制备乙醛酸的研究

以间接氧化技术电化学法合成乙醛酸.Br-在阳极上氧化生成Br2,继而以Br2作媒介,间接氧化乙二醛生成乙醛酸,同时Br2被还原为Br-,从而实现了溴的循环使用.研究了氧化媒介、电流密度、温度、乙二醛初始浓度等因素对氧化过程的影响.实验表明,在电流密度为25 mA·cm-2,反应温度为(30±5)℃,乙二醛初始质量分数为10%～25%,氢溴酸质量分数为10%的条件下,电流效率75%～83%.     

PAAS-CMC/Mel-CS双极膜的制备及其应用

以聚丙烯酸钠改性羧甲基纤维素钠和三聚氰胺改性壳聚糖选用流延法制备了PAAS-CMC/Mel-CS双极膜,并测定其性能。将PAAS-CMC/Mel-CS双极膜作为电解槽的隔膜,应用于成对电合成乙醛酸.实验结果表明,以质量分数10%乙二醛和质量分数10%氢溴酸的混合液为阳极液,以饱和草酸和质量分数20%硫酸的混合液为阴极液,在20 m A·cm~(-2)的电流密度下电解5 h,阴阳极室乙醛酸的浓度达48.37 mmol·L~(-1)和59.43 mmol·L~(-1),电压稳定在2.9 V左右.     

抑制大肠杆菌粘多糖荚膜合成的相关基因的筛选

大肠杆菌(Escherichia coli)通过二信号传导体系RcsC-RcsB能够激活cps(capsule polysaccharide synthesis)基因群,在细胞表面形成一层粘性的保护性荚膜,使大肠杆菌具有较强的致病性。本文通过将基因组文库导入大肠杆菌,筛选到了名为acnA的基因,它编码合成乌头酸酶,在细胞内三羧酸循环和乙醛酸循环代谢中起关键作用,多拷贝的acnA能有效地抑制cps基因群的表达。     

Fe_3O_4纳米颗粒的制备及其催化性能

采用水热法制备Fe3O4纳米颗粒,并进行脱水催化性能研究.考察催化剂Fe3O4纳米颗粒的用量及循环利用次数对苹果酸二乙酯的酯化率和转换数的影响.通过不同催化过程后的Fe3O4纳米颗粒的形貌的变化,研究Fe3O4纳米颗粒在催化中的脱水性与酸性敏感性,进而利用Fe3O4纳米颗粒的成环反应合成1,4-二噻烷.实验结果表明:水热法制备的Fe3O4纳米颗粒可以作为催化剂合成苹果酸二乙酯,最佳的催化剂条件为第1次催化循环0.1mmol Fe3O4纳米颗粒,Fe3O4纳米颗粒的催化活性随循环利用次数的增加而降低.     

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