EXAFS研究不同酸度下Zn2+在水锰矿表面的吸附和沉淀

用EXAFS(extended X-ray absorption fine structure)研究了pH 7.00、7.50、8.00时Zn(II)在水锰矿表面的吸附和沉淀. Zn第一层配位Zn—O距离约为0.202 nm, 不随pH变化, 表明Zn的构型为四面体和八面体的混合物. 在pH 7.00 条件下, Zn—Mn距离约为0.300 nm, Zn主要以双边形式吸附在水锰矿(010)或(110)面. pH 7.50和pH 8.00时, 大部分的Zn在表面形成了结构类似于沉淀样品的多核羟基络合物, 其中0.311 nm Zn—Zn距离对应两个Zn八面体连接, 而0.353 nm Zn—Zn距离对应Zn八面体和Zn四面体连接.     

应用平衡稳定条件分析化学平衡的移动

化学平衡的移动规律是物理化学中重要的知识点之一。平衡稳定条件在经典热力学中占有重要的地位,但很少用于处理化学平衡问题。根据热力学原理,推导了简单的均匀隔离系统的平衡稳定条件,并将其用于分析温度和总压力对化学平衡移动的影响,结论为改变温度和总压力,使化学平衡朝着稳定平衡的方向移动。这种分析方法非常简单,也加深了我们对稳定平衡的理解。同时,也指出了该方法的局限性。     

壳聚糖-盐酸溶液中温度敏感的相分离行为

研究了壳聚糖 盐酸溶液温度敏感的相分离行为.通过对壳聚糖-盐酸溶液浊度变化的考察以确定相分离温度.测定不同盐酸浓度、壳聚糖浓度以及不同脱乙酰度的条件下的相分离温度，并用DLVO理论(Deijaguin-Landau and Verwey-Overbeck Theory)进行了解释. FTIR、X-ray以及SEM分别描绘了壳聚糖经相分离过程后官能团、结晶状态、颗粒形态的特点.     

Effects of High-voltage Pulse Electric Field Treatment on the Structure Stability of Konjac Glucomannan

Structures of KGM treated in two high-voltage pulse electric fields were characterized by infrared spectroscopy,Raman spectroscopy,X-ray diffraction and so on.The results showed that intermolecular hydrogen bonding interactions of KGM were reduced after being treated with high-voltage pulse electric field,but there was no significant effect on its fiber chain form and thermal characteristics.Results of the study can provide a useful reference for further study on the structure and property of KGM,and especially can provide theoretical basis for the effect of physical field on the foodstuff deep processing related to KGM.     

苯热条件下GaP纳米晶的稳定性

用高温高压苯热合成方法制备了GaP纳米晶,用X射线衍射、光吸收谱及透射电子显微镜对所得样品进行了分析测试．结果表明,GaP纳米晶在苯热条件下是亚稳定态的,反应时间过长及反应温度过高均不利于它的生成和生长．文中还讨论了晶粒度分布与合成条件间的关系,并进行了理论上的定性分析．     

Thermal Stability of Haemoglobin Solutions Under DC and AC Magnetic Field and UV and IR Radiation

The influence of electromagnetic field in wide range of frequency (extra low frequency magnetic field, monochromatic laser light 840 nm, ultraviolet light) and static magnetic field on the stability of aqueous and NaCl 0.9% haemoglobin solutions was studied using differential scanning calorimetry (DSC) method. Three steps of denaturation process can be derived from experimental data. The shifts of transition temperatures are more marked for NaCl 0.9% than for aqueous solutions. The results suggest that static magnetic field is effective in protecting protein, while ultraviolet radiation destabilises haemoglobin. The laser light and alternating magnetic field have a little effect on the thermal stability of haemoglobin. This revised version was published online in July 2006 with corrections to the Cover Date.     

Flow Injection Analysis of Hydrogen Peroxide,Sulfite, Formaldehyde and Hydroxymethanesulfonic Acid in Precipitation Samples

Abstract

Hydroxymethanesulfonic acid (HMSA), the reaction product of sulfite and formaldehyde plays an important part in the aqueous phase conversion of sulfite to sulfate. HMSA is fairly stable under acidic conditions and in presence of hydrogen peroxide. Sulfite is unstable under these conditions.

A flow injection set-up was developed, which allows the determination of H₂O₂, sulfite, formaldehyde and hydroxymethanesulfonic acid.

H₂O₂ analysis by amperometric detection offers the possibility of a simple, robust field instrument. The detection limit is 5μg/l and the method is linear up to 5mg/l.

Based on the 4,4-dithiodipyridine/sulfite reaction selective and sensitive spectrophotometric detections were developed for sulfite, formaldehyde and hydroxymethanesulfonic acid. The detection limit of these compounds is 50μg/l and the method is linear up to 5mg/l.

A large fraction of S(IV) is present as HMSA in fog, dew and precipitation samples in The Netherlands.     

离子色谱法分析油气田地层取样样品中的阴、阳离子

探讨使用离子色谱仪分析油气田地层取样样品的可行性。该方法使用ICS900型离子色谱仪(配阴离子色谱柱AS19和阳离子色谱柱CS12A),同时由自动淋洗液发生器RFC30产生20 mmol/L氢氧化钾溶液和20mmol/L甲烷磺酸溶液,流量为1 m L/min。7种离子测定结果的相对标准偏差为0.87%~3.40%,样品加标回收率为98.00%~104.0%。该方法精密度和准确度满足油气田地层取样样品中阴阳离子的分析要求。     

仿生超疏油材料在苛刻工况条件下的应用

超双疏兼备超疏水和超疏油两种极端不润湿现象,其中超疏油的实现难度更大,应用前景广阔。为了获得超疏油材料,通常采用仿生思路,在材料表面构建粗糙结构和以含氟低表面能物质修饰表面。表面粗糙结构在机械力学作用下易遭到破坏,例如摩擦和冲击。低表面能物质修饰层在光照条件下易分解,而诸多的太阳能装置如太阳能电池板,必须在室外工作。耐紫外的超疏油性可以帮助这些设施实现高效工作并延长使用期限,节约资源。更进一步,科研人员研究了超疏油材料在各种苛刻条件下的可靠性。本文应用新进展聚焦在超疏油材料在紫外线照射下的可靠性或可逆响应性;超疏油材料经过撞击之后的油滴接触角变化;在高温条件下超疏油材料的极端润湿性能保持能力;在冲击条件下的稳定性,甚至包括了多种复合苛刻条件下的超疏油材料的耐受性。由于大多的工业环境无法避开摩擦和腐蚀,因此本文着重从超疏油材料的耐摩擦性和抗腐蚀性两个方面讨论了其研究现状,同时也讨论了超疏油在其他工程应用方面的可靠性。最后,总结了各实验方案的优缺点、实验与工业化过程中存在的问题、有望突破的方向,以及作者对于在苛刻工况条件下提升超疏油材料可靠性的观点。     

Stability of Alum-Containing Paper under Alkaline Conditions

The present contribution evaluates the methods of degradation and stabilization of alum-containing paper with a focus on the alkaline environment achieved by deacidification procedures. In terms of reviewed subjects, the contribution focuses on alum-rosin sized paper, which is still used as a carrier of knowledge and information; however, it also mentions cellulose itself and other brands of paper. The contribution summarizes the results on the homogeneity of the distribution of alum and rosin in the paper mass and on the paper surface. It provides the knowledge gained in the field of alkaline hydrolysis and oxidation with special regard to transition metal species. It shows the values of alkaline reserves achieved in the main mass-deacidification processes. On the basis of the acquired knowledge, the contribution emphasizes the procedures of paper stabilization. Criteria of “increased mechanical permanence and lifetime prolongation” adopted to evaluate and compare the efficacy of individual mass-deacidification processes were applied and corresponding data are introduced. The contribution also draws attention to the existence of open issues in the area of paper degradation and stabilization.     

LC Method for the Determination of the Stability of Levetiracetam Drug Substance under Stressing Conditions

Levetiracetam is used in combination with other medications to treat certain types of seizures in people with epilepsy. Levetiracetam is in a class of medications called anticonvulsants and it works by decreasing abnormal excitement in the brain. A chromatographic separation was achieved on a YMC pack ODS AQ, 250 mm × 4.6 mm, 5 μm column using diluted phosphoric acid and acetonitrile in the ratio 85:15 v/v. Forced degradation studies were performed on the levetiracetam drug substance. The drug substance was degraded to Imp-B during acid and base hydrolysis. When the stress samples were assayed, the mass balance was matching. The sample solution and mobile phase was found to be stable up to 48 h at 25 °C. The developed method was validated with respect to linearity, accuracy, precision and robustness.     

电场作用下苏氨酸的电流特性研究

制备了以液态苏氨酸为沟道材料的四端有机场效应晶体管,观测了其随着栅极电压的不同呈现出源漏两极之间不同的电学特异现象;还观测了苏氨酸在外电场作用下,阻抗随着源漏之间电压频率变化的关系,提出一个极性液体模型解释了其导电机理。     

在酸性条件下合成氧化亚铜纳米立方体(英)

在微酸性(pH：4～6)的水热体系中130 ℃反应18 h合成了氧化亚铜纳米粒子，粒径约为100 nm，呈立方体外形。乙二胺和十六烷基胺在反应体系中充当缓冲试剂，调节反应液的pH值并控制体系中游离Cu²⁺的浓度，使得Cu²⁺不会被迅速还原成单质铜。所合成的纳米立方体的能带宽度约为2.51 eV，比氧化亚铜体材料和氧化亚铜纳米线蓝移了0.51 eV和0.17 eV，它有利于把太阳光谱中能量高的可见光转化成其他形式的能量。     

The Role and Efficiency of Ammonium Sulphate Precipitation in Purification Process of Papain Crude Extract

It has been common to do fractionation (for example using ammonium sulphate as a precipitating agent) before doing a more sophisticated method for purification of a protein. The logic behind this is easy to understand, but in fact, the precipitation step often causes severe loss in yield and activity of the protein, making the whole purification effort too costly. In this work we evaluated the specific activity (thus, purification factor) and total activity (yield) during the purification process of papain from a crude extract using ion exchange chromatography (IEC), with and without prior fractionation using ammonium sulphate. Detail assays in each step were recorded and SDS-PAGE was also done to reveal the protein profile of the purification products.     

Optimal Conditions for Existence of Vesicles Under Electric Field

Giant vesicles have been of intense interest as the model system for cell membranes. To bring numerous applications of the vesicles into full play, the existence time of the vesicles becomes particularly important. In this work, we explored the existence time of the vesicles in distilled water under four kinds of representative alternative current (AC) electric fields with different energizing time. When the application time of AC electric field reached 1 hour, the existence time of the vesicles reached the maximum value. As the applied electric field time increased, the existence time of the vesicles decreased. Thus, after obtaining the best vesicles on the carbon fiber electrode, disconnecting the external electric field is very necessary. Based on the in situ observation using inverted microscope, the disappearing phenomena of the vesicles were presented. In addition, it is found that vesicles in phosphate buffer solutions (PBSs) can last about 2–3 days when the electric field was applied for 1 hour, which was much longer than that in distilled water.     

Evaluation of Water-in-Crude-Oil Emulsion Stability Using Critical Electric Field: Effect of Emulsion Preparation Procedure and Crude Oil Properties

The critical electrical field has been used as a tool to probe water in crude emulsion stability to electrical fields in many previous studies. Given the increasing importance of this metric, this study investigates factors that are important to the reproducibility of the measurement and the effect of emulsion preparation variables on the critical electric field. It was observed that the emulsion preparation procedure has a strong effect on the measured critical electric field due to droplet size effects. Furthermore, the effect of crude oil properties on the critical electric field was investigated using emulsions from different oils but with the same average droplet diameter, where it was found that the measurement was dominated by crude oil viscosity.     

Stability studies of high-stable water-in-oil model emulsions

Different compositions and emulsification protocols were used to prepare stable water-in-oil (w/o) emulsions. Water, mineral oil, and a mixture of Span 80 and Tween 80 surfactants were combined to form emulsions that can be used as reference for electrolyte-free systems. Here, we have proposed emulsions wherein different properties were evaluated. Electrical conductivity measurements indicated that conductivity increases linearly with increasing surfactant content. The emulsions’ flow curves and viscoelastic behaviors were delineated by rheological measurements. Stability studies by centrifugal testing have shown that smaller the surfactant content, lower the stability, for any used stirring speeds. Furthermore, higher the applied mixing rate to make the emulsion, higher the stability, regardless of the amount of surfactant. Electrical field stability analysis showed, for all systems, that critical electric field (CEF) values were dependent on either surfactant amount and emulsion elastic modulus.     

高场不对称波形离子迁移谱快速检测水样中苯含量

建立了高场不对称波形离子迁移谱(FAIMS)检测水中苯含量的分析方法。研究了不同分离电压(Dispersion voltage,DV)下的苯标准谱图,获得用于苯识别的非线性函数二阶α2及四阶α4系数值分别为-3.8×10-5Td-2和5.1×10-8Td-4;通过平衡灵敏度与分离度,得到用于苯识别的最佳分离电压为800 V;通过不同质量浓度(0.08~0.64 mg/L)的苯样品与苯离子信号强度的关系,确定高场不对称波形离子迁移谱(FAIMS)对水中苯的检出限为0.89μg/L,远优于国家饮用水中苯浓度的限值10μg/L。本研究为水中苯检测提供了一种快速、高灵敏的方法。     

直链烷烃的超临界热稳定性研究

本文考察了正辛烷、正壬烷、正癸烷、正十一烷和正十二烷等5种直链烷烃在超临界条件下的恒容热裂解,采用一级反应动力学简化描述其热裂解过程。跟踪裂解气液产物分布,探讨了液体产物中芳烃含量与热稳定性的关系。在相同反应条件下,奇数碳和偶数碳烷烃热裂解速率、转化率和液体组分中芳烃含量分别随碳数的增加而增加。芳烃产物含量随裂解转化率增加呈指数形式增加,表达了烷烃类化合物热稳定性和裂解变化的规律。