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121.
《Journal of Molecular Structure》1995,343(1-3):125-132
A computer method has been developed which is an alternative to molecular dynamics in the sense that it pictures conformational motion. It simulates propagation in conformational movement based on conformational interconversion phenomena. The method starts with the knowledge of the topology of the conformational potential energy hyper-surface, which is described by the minima and the transition states. The topology is obtained by the recently described software
. The simulation of conformational motion is based on the Boltzmann statistics of movement between the minima and the transition states at a given temperature. The method is illustrated for methyl--glucopyranoside and -
-galNAc(1-3)[-
-Fuc(1-2)]Gal-O-Me molecules. Conformational transitions of hydroxyl groups as well as glycosidic linkages are discussed. 相似文献
122.
F. A. L. van der Horst M. H. Post J. J. M. Holthuis U. A. Th. Brinkman 《Chromatographia》1989,28(5-6):267-273
Summary Micellar phase-transfer catalysis (MPTC) offers the opportunity to derivatize carboxylic acids directly in an aqueous matrix without prior extraction of the acids into a suitable aprotic solvent. The currently developed MPTC system consists of a non-ionic surfactant, Arkopal N-130, an ion-pair agent, tetrakis-(decyl)-ammonium bromide, and a novel fluorescence reagent, 9-bromomethylacridine. The MPTC system can be applied to the derivatization of many types of carboxylic acids. The reaction rate is affected by the lipophilicity of the acid and by the presence of other functional groups. For lipophilic carboxylic acids the reaction is complete within 5 min at 60°C and pH 7.0. 相似文献
123.
124.
125.
《Electroanalysis》2005,17(2):178-181
Voltammetric behavior of water‐soluble endohedral metallofullerene derivatives Gd@C82(OH)5(NHCH2COOH)9 (GN) and Gd@C82(OH)6(NHCH2CH2SO3H)8 (GS) was characterized in 0.1 M KCl solution by CV and DPV. They showed similar redox behavior, that is, a reversible electroreduction process on HMDE was found; in the mean time, an irreversible oxidation process and an irreversible reduction process on GC electrodes were also observed. The results reveal that these two water‐soluble endohedral metallofullerene derivatives have good electron donating ability and poor electron accepting ability due to hydroxy groups, aminoacetic acid and aminoethyl sulfonic acid connected to the C82 cage in comparison with Gd@C82. 相似文献
126.
About the Structure and Reactivity of Diammonium Hexafluoromanganate(IV) Electrolytic oxidation of an aqueous suspension of MnF2 containing NH4F, and subsequent crystallization in 40% HF yields yellow crystals of (NH4)2MnF6. It crystallizes in the hexagonal K2MnF6 type structure with the space group P63mc and a = 5.903; c = 9.565 Å; Z = 2. With in situ powder diffraction studies it is shown, that (NH4)2MnF6 is gradually reduced in a NH3 atmosphere between 30 and 230 °C to afford (NH4)3MnF6, (NH4)2MnF5, and finally NH4MnF3. (NH4)3MnF6, thereby, forms a hitherto unknown cubic (a = 9.082 Å) high temperature modification with the cryolite type structure. Under N2 the thermal decomposition of (NH4)2MnF6 proceeds via NH4MnF4 to yield MnF2. 相似文献
127.
研究了D160大孔吸附树脂对染料木黄酮的吸附性能.结果表明,在pH4.00时,该树脂对染料木黄酮有较好的吸附性能;静态饱和吸附容量为64.5mg/g树脂;用95%乙醇溶液作解吸剂,二次累计解吸率接近100%;表现速率常数k298=1.01×10-4s-1;测得吸附热力学参数分别为:△H=32.2kJ/mol,△S=119J/(mol·K),△G288=-2.03kJ/mol,△G298=-3.22kJ/mol,△G308=4.41kJ/mol.等温吸附服从Freundlich和Langmuir等温吸附规律;研究还表明,提高振荡频率对吸附有利. 相似文献
128.
比较两种超高交联聚苯乙烯吸附树脂NJ-8、AM-1与Amberlite XAD-4(以下简称XAD-4)对对硝基苯乙酮的静态吸附行为,根据吸附等温线研究了吸附热力学性质.在298~318K和研究的浓度范围内,NJ-8,AM-1、XAD-4对对硝基苯乙酮的吸附平衡数据符合Freundlich吸附等温方程.结果表明:吸附为放热过程,适当降低温度有利于吸附.计算了对硝基苯乙酮在NJ-8,AM-1、XAD-4树脂上的吸附焓变、自由能变,吸附熵变.对吸附行为作了合理的解释。 相似文献
129.
The LC phase behavior of ternary mixtures of the two corresponding branched non-ionic surfactants 1,3-bis-(methoxy-tetraoxyethylene)-2-propoxy-tetradecane (Y-surfactant) and 1,3-bis-(heptyloxy)-2-propoxyoctaoxyethylene mono-methyl ether (V-surfactant) and water were studied by polarizing microscopy. The two branched surfactants, which have different molecular geometries but nearly the same hydrophilic-lipophilic volume ratio, exhibit extremely different phase behavior in binary surfactant/water systems. For the ternary mixtures of Y- and V-surfactant and water we found-according to established packing models-a continuous stabilization of the cubic and hexagonal phases and a destabilization of the lamellar phase with increasing amount of Y-surfactant. On the other hand, we observed a thermal stabilization of the lamellar phase. The maximal transition temperatures of the lamellar phase pass a maximum with increasing amount of Y-surfactant. 相似文献
130.
采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了微球状Fe/Cu/K/Al2O3催化剂, 结合TG、N2物理吸附、XRD、H2-TPR、CO-TPR、Mossbauer谱等表征手段, 研究焙烧温度对Fischer-Tropshc (F-T)合成铁基催化剂的结构性质、还原行为和碳化行为的影响. 结果表明, 较高的焙烧温度有利于碳酸盐的分解和结晶水的脱除, 促进了催化剂的还原. 随着焙烧温度的进一步升高, 催化剂的比表面积减小, 平均孔径增大, α-Fe2O3晶粒的粒径增大, 催化剂中金属与载体的相互作用增强, 从而削弱了CuO、K2O助剂的作用, 严重抑制了催化剂的还原和碳化. 相似文献