测定啤酒和白葡萄酒中有机酸的离子排斥色谱法

研究了离子排斥色谱法分离测定啤酒和白葡萄酒中有机酸；选用常见的盐酸溶液作淋洗液，以四丁基氢氧化铵为再生液，考察了淋洗液浓度、流量等因素对分离和测定的影响，对啤酒和白葡萄酒中常见有机酸在阴离子排斥色谱柱上的保留行为进行了系统的研究；通过试验确定最佳的色谱条件为盐酸浓度1．10mmol/L，流量0．80mL/min；四丁基氢氧化铵浓度5.0mmol/L，流量1.10mL/min；并在该条件下，测定了啤酒和白葡萄酒中的有机酸。     

Physicochemical aspects of microbial adhesion — Influence of antibody adsorption on the deposition ofStreptococcus sobrinus in a parallel-plate flow chamber

Deposition of the oral bacteriumStreptococcus sobrinus HG977 onto glass (water contact angle 0°) and onto FEP-Teflon (fluoroethylenepropylene; water contact angle 110°) was studied in a parallel-plate flow chamber in the presence and absence of polyclonal antibodies (pAb) and monoclonal antibodies (mAbs) adsorbed onto the cells. The zeta potentials of the bacteria ranged from −7.1 to −8.5 mV at pH 6.8 and were not affected by the presence of pAb or mAbs. Hydrophobicity (by water contact angles) increased from 30° (no antibodies) to 88° in the presence of pAb adsorbed onto the bacterial cell surface. The untreatedS. sobrinus had a greater tendency to adhere to glass (44.5 × 10⁶ cm⁻²) than to FEP-Teflon (18.3 × 10⁶ cm⁻²), in accordance with thermodynamic modelling. After preincubation ofS. sobrinus with pAb, its clear preference for adhesion to glass disappeared as expected from its increased hydrophobicity. Although forS. sobrinus preincubated with OMVU10 no difference was found in hydrophobicity in comparison to the untreated bacteria, the number of bacteria adhering to glass decreased to 10.2 ¢ 10⁶ cm⁻². Formation of bacterial aggregates was found whenS. sobrinus, preincubated with pAb or OMVU10, adhered to glass and FEP. This was also observed when untreated bacteria adhered to glass coated with OMVU10, or to FEP coaled with OMVU10 or pAb. Adhesion in these experiments is therefore thought to occur via near-neighbour collection induced by the presence of pAb or mAbs. Low numbers of bacteria were removed from glass after draining the flow cell, whereas high numbers of untreated bacteria and bacteria preincubated with OMVU10 were removed from FEP.S. sobrinus cells preincubated with pAb were not removed but piled up. It was concluded that the adhesion of untreatedS. sobrinus andS. sobrinus preincubated with pAb is in accordance with thermodynamic modelling, based on the overall wettability of the cell surfaces, whereas the adhesion ofS. sobrinus preincubated with OMVU10 may be through localized interactions, not expressed in overall surface properties.     

Thermodynamic studies of monuron

Monuron (C₉H₁₁ClN₂O; N,N-dimethyl-N′-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6±0.1 K, 29.3±0.2 kJ mol⁻¹, and 65.4 J K⁻¹ mol⁻¹, respectively.     

Temperature-induced gelation of concentrated silicon carbide suspensions

Due to the steric barrier provided by the adsorption of the dispersant hypermer KD1 (a polyester/polyamine condensation polymer), stable and low-viscosity suspensions of SiC, Y(2)O(3), and Al(2)O(3) powder mixtures could be prepared in methyl ethyl ketone (MEK)/ethanol (E) solvent with solids loading as high as 60 vol%. The solvency of the dispersant in MEK/E decreased dramatically on cooling. Steady shear viscosity and oscillatory measurements were performed as a function of temperature for suspensions with different solids loading. The viscosity and elastic modulus of suspension increased with decreasing temperature and became more sensitive with the increase of solids loading. The suspensions with solids loading higher than 40 vol% could be solidified with decreasing temperature, but gelation temperature and gelation stiffness decreased with decreasing solids loading. The 60 vol% solid-loaded suspension was a stable and free-flowing fluid at 20 degrees C and gradually transformed to a very highly viscous and elastic system upon cooling to about 13 degrees C. Complete solidification occurred when the temperature was decreased to 5 degrees C. The gelation mechanism was mainly based on the collapse of the adsorbed layer as the temperature decreases, which induced incipient flocculation and formed a stiff network. The gelled body was further strengthened by separation of the dispersant from the suspension.     

羟基羧酸钛(Ⅲ)配合物的合成和热性质研究

三氯化钛分别与苹果酸铵、酒石酸铵和柠檬酸铵反应，制得三种新的固态配合物：苹果酸羟基钛(Ⅲ)、酒石酸羟基钛(Ⅲ)和柠檬酸钛(Ⅲ)(化学式分别为Ti(OH)(C₄H₄O₅)·1.5H₂O、Ti(OH)(C₄H₄O₆)·1.5H₂O和Ti(C₆H₅O₇)·1.5H     

肝素化壳聚糖季铵盐／壳聚糖复合膜抗凝血性能的研究

以壳聚糖季铵盐，壳聚糖为基本原材料，选用戊二醛为交剂剂及固定剂，制备一种物理机械性能较优的抗凝血材料。探讨了戊二醛及肝素钠两者用量对肝素化程度及血液生的影响。     

New Approach to Detecting Phenoxyl Free Radicals Generated in Enzyme Reaction by Stopped-flow Spectrophotometry

Quantification of free radical formation is critical for evaluation and interpretation of many radical-mediated biological processes1-4. Numerous studies have been devoted to the determination of free radicals, but the most of the reports have been focuse…     

用数值遗传算法改进非线性PLS法进行构效关系研究

将数值遗传算法同非线性ＰＬＳ结合，改进和完善了非线性ＰＬＳ，推导了指数，对数，倒数和Ｓｉｇｍｏｉｄ函数的公式，构造了可以处理多种非线性函数关系的算法，可用于解决复杂的结构与性能相互关系。     

超高效合相色谱法快速检测塑料食品接触材料中13种紫外吸收剂

建立了一种同时检测塑料食品接触材料中13种紫外吸收剂的超高效合相色谱法。以甲醇为溶剂对塑料食品接触材料样品进行超声提取，经C18固相萃取柱净化，过0.22 μm有机滤膜，采用超高效合相色谱仪分析。选择ACQUTY UPC² HSS C18 SB色谱柱（150 mm×3.0 mm，1.8 μm），以超临界二氧化碳为流动相，异丙醇为改性剂进行梯度洗脱，在最优色谱条件下，13种紫外吸收剂能够在4 min内实现有效分离。结果表明，在各自线性范围内，13种紫外吸收剂的线性关系良好，标准曲线相关系数不低于0.9985，检出限（S/N=3）为0.05~0.15 mg/kg，加标回收率为86.8%~115.7%，相对标准偏差为0.73%~5.61%。该方法快速简便，准确可靠，同时大大减少了有机溶剂的消耗，可用于塑料食品接触材料中13种紫外吸收剂的快速检测。     

模式识别—人工神经网络在化学中的若干新应用

本文通过我们应用模式识别－人工神经网络方法预报新化合物、熔盐相图以及复杂化学反应体系的研究，展示应用模式识别－人工神经网络方法与物理化学理论相结合，研究化学现象的可能性和应用价值。