核黄素的光电化学性质及其应用

基于核黄素的光化学和电化学性质,通过探讨核黄素的光致还原反应机理,将核黄素的光致还原与其产物的电极反应纳入一个光电化学过程,发展了一种新的核黄素光致电化学分析法．在pH4．5的醋酸盐缓冲溶液中,以EDTA 为光还原剂,在峰值波长为450 nm、能量为15 mW／cm2的光照下,在偏压0 V 处测得的光电流与5．00×10－10～5．00×10－5 mol／L核黄素浓度的对数值成正比,灵敏度为3．00×10－10 mol／L （S／N＝3）．将该方法分别应用于多合维生素、小米中核黄素的测定,显示相对标准偏差小于7．86％,加标回收率为96％～105％．与其他测定核黄素的方法相比,本方法具有测量范围宽、灵敏度高、仪器设备简单、实验操作简便的优点．     

离子对反相高效液相色谱法考察糖浆口服液中核黄素—5—磷酸钠稳定性

建立了离子对反相高效液相色谱分析方法考察复方制剂诺平糖浆口服液的稳定性。以核黄素-5-磷酸钠为指标组分,采用Hypersil C18色谱柱,流动相为：0．01：mol／L K2HPO4(含50mmol／L PIC-B7)：乙腈(90：10),检测波长为254nm,流速：1．0mL／min。结果表明,核黄素-5-磷酸钠在8．0～320μg／mL范围内呈良好的线性,降解产物不干扰测定;方法准确、灵敏、操作简单、重现性好,可对复方制剂中核黄素-5-磷酸钠的降解产物进行有效监控。     

性别对核黄素片剂消除速率常数及生物利用度的影响

目的探讨性别对核黄素片剂药物动力学的影响。方法采用尿药法测定核黄素片剂在28位志愿者体内的消除速率常数及生物利用度。结果男性体内核黄素片剂的消除速率常数为0.518 4,女性体内核黄素片剂的消除速率常数为0.287 2。核黄素片剂在男性体内的生物利用度为55.86%,在女性体内的生物利用度为38.46%。结论不同性别影响核黄素片剂在体内的药物动力学过程。     

荧光法测定面粉中的核黄素

采用分子荧光法测定面粉中痕量核黄素的含量.核黄素浓度在1×10-6～5×10-4g/L范围内与荧光强度呈良好的线性关系,方法的检出限为4×10-8g/L;对浓度为1×10-5g/L的核黄素标准溶液进行11次平行测定,得相对标准偏差为3.4%.方法简便快速、灵敏度高、选择性好,已用于面粉中核黄素含量的测定,回收率为98%～105%,结果令人满意.     

不同流加发酵方式对重组枯草芽孢杆菌生产维生素B2的影响

在5 L发酵罐中培养重组枯草芽孢杆菌RH33生产核黄素,该重组菌的染色体上含有多个解除了转录调节的核黄素操纵子．由于过高的初糖浓度导致严重的代谢溢流,因此间歇发酵过程只能得到较低的菌体量和产物产量．分别采用了3种不同的流加培养方式：分批流加、恒速流加和葡萄糖限制流加来减弱代谢溢流并提高核黄素的产量．同间歇培养相比,分批流加培养能微弱提高重组菌的核黄素产量,而恒速流加和葡萄糖限制流加均能显著提高菌体量和核黄素产量．对于恒速流加培养,当流加速率为0．48 mL／min时核黄素产量和菌体量可以分别达到9．8g/L和27．3g/L对于葡萄糖限制流加培养,通过人工控制葡萄糖流加速率使培养基中的葡萄糖浓度为10～2 g/L时,重组菌RH33可以达到最高的核黄素产量和菌体量(分别为12．5g/L和34．7g/L)．在葡萄糖限制流加培养中核黄素产率约为0．06 g(核黄素)／g(葡萄糖),高于其他几种培养方式．     

干燥方式对沉淀白炭黑性能的影响

以水玻璃和硫酸为原料,文章采用化学沉淀法制备了白炭黑料浆,然后通过烘箱干燥、微波干燥和喷雾干燥3种不同的干燥方式获得白炭黑颗粒.采用X射线衍射、扫描电子显微镜、比表面积(BET)分析、吸油值(DBP)分析等对3种不同颗粒的结构、形貌及性能进行了表征.结果表明:喷雾干燥得到的颗粒较适中,为30～50 μm;微波干燥的颗粒...     

电子穿梭体核黄素对菌株Clostridium sp.LQ25异化铁还原性质的影响

菌株Clostridium sp.LQ25分离自海洋沉积物,是一株发酵型异化铁还原细菌,通过外加核黄素和测定内源核黄素分泌量,分析外源型和内源型电子穿梭体对异化铁还原性质的影响.在外源核黄素质量浓度为40～120 mg/L的范围内,菌株LQ25的异化铁还原能力均得到显著提高(P<0.05),其中当核黄素质量浓度为100...     

甲基纤维素/壳聚糖/海藻酸钠茶树油微胶囊的制备及稳定性

以甲基纤维素、壳聚糖及海藻酸钠作为复合壁材,采用喷雾干燥法制备了茶树精油微胶囊,确定最佳的喷雾干燥条件为:进风温度220℃,通针为2 s/次,蠕动泵55r/h.以精油含量为指标,采用正交实验法获得微胶囊的最佳制备条件为:甲基纤维素0.6 g/100 m L H2O,茶树精油0.4 m L,壳聚糖0.6 g/50 m L H2O,海藻酸钠3 g/50 m LH2O,含油率为13.4%,该工艺条件所得的精油微胶囊重现性好.其茶树油微胶囊呈球形,表面光滑,颗粒较均匀,对精油具有较好的缓释效果,它在空气中存放2周后,其粒径有所增加,且其表面出现细小裂纹.     

可见光深度催化氧化脱硫研究

以溶胶-凝胶法制备了纳米TiO2和稀土离子Eu3+、Nd3+掺杂的TiO2,并以TiO2和核黄素溶液为催化剂氙灯照射光催化深度去除油品中苯并噻吩,考察了氧化剂、双氧水浓度、核黄素浓度等工艺条件的影响。结果表明:体积浓度为25;的双氧水脱硫效果较好,当核黄素浓度达到25μg · mL-1时,脱硫率达到最高,稀土掺杂TiO2后可提高油品硫的脱除率,TiO2光响应范围向可见光拓展。     

聚核黄素膜修饰电极的制备及催化作用

用循环伏安法聚合制备核黄素膜修饰电极 ,研究该修饰电极的电化学性质及电催化性能。聚核黄素膜在PBS底液中有一对氧化还原峰 ,氧化峰电流与υ1/ 2 在 10 0～70 0mV·s-1范围内成正比。该修饰电极在酸性和碱性溶液中对半胱氨酸均有显著的催化作用 ,且碱性溶液的电催化反应步骤中无H+ 参加     

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.     

Features of Women's language

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

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