共查询到20条相似文献,搜索用时 109 毫秒
1.
通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化.该方法限制了某些低沸点溶剂的凝胶化.利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了3种反应型凝胶剂.这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂形成热可逆的有机分子凝胶.场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构.随着烷基胺中的烷基链长度不同,形成的纤维状聚集体的形态也不同.FT-IR和1H NMR研究表明分子间氢键作用是反应型凝胶剂自组装的驱动力.通过XRD和分子模拟推测了其聚集体的结构形态. 相似文献
2.
3.
4.
用溶液聚合法制备出轻度交联的含铅微凝胶,用光子相关光谱技术测定其在良溶剂中与H2S反应前、后的扩散行为,由外推法得到在浓度无限稀时的分子扩散系数,给出微凝胶的流体力学半径。结果表明:相同量的含铅微凝胶在不同的初始浓度下与H2S反应,生成含PbS纳米微粒的凝胶;但其体积增大不同,这说明H2S与含铅微凝胶的反应既可以在分子内也可以在分子间进行,分子间的反应使含硫化铅微凝胶扩散系数随浓度的变化曲线的线性范围变小。 相似文献
5.
6.
7.
水凝胶是一种交联高分子材料, 在药物传输、传感器技术、组织工程中发挥重要作用。通过高效率和高精确度的点击反应合成水凝胶, 具有快速、模块化以及副反应少等优点, 并且能够得到近乎理想的网络结构。Cu(Ⅰ) 催化的叠氮-炔之间的环加成 (CuAAC) 反应作为点击反应的典型代表, 已广泛应用于水凝胶的制备。但由于该反应在制备水凝胶的过程中使用了Cu(Ⅰ) 催化剂, 导致产品易被金属铜盐污染, 从而使该反应在其制备领域受到限制。基于此, 无铜点击反应,如巯基-烯/炔反应、呋喃/蒽-马来酰亚胺 (MI) 修饰的 Diels-Alder 环加成 (D-A) 反应以及环张力促进的叠氮-炔环加成反应 (SPAAC) 已经被应用到水凝胶的制备以及功能化方面。本文就近年来上述无铜点击反应在水凝胶合成及功能化方面的应用进行综述, 并对其发展趋势进行展望。 相似文献
8.
用溶液聚合法制备出轻度交联的含铅微凝胶,用光子相关光谱技术测定其在良溶剂中与H2S反应前、后的扩散行为,由外推法得到在浓度无限稀时的分子扩散系数,给出微凝胶的流体力学半径。结果表明:相同量的含铅微凝胶在不同的初始浓度下与H2S反应,生成含PbS纳米微粒的凝胶;但其体积增大不同,这说明H2S与含铅微凝胶的反应既可以在分子内也可以在分子间进行,分子间的反应使含硫化铅微凝胶扩散系数随浓度的变化曲线的线性范围变小。 相似文献
9.
10.
通常制备有机分子凝胶是在高温下溶解凝胶剂,凝胶剂分子在冷却过程中进行自组装并使有机溶剂凝胶化。该方法限制了某些低沸点溶剂的凝胶化。利用甲苯二异氰酸酯与烷基胺的高反应活性,制备了三种不同烷基链长的反应型凝胶剂甲苯–2, 4–二(N, N’ –烷基)脲。这种反应型凝胶剂能以较低的浓度在室温下使某些芳香族和卤代烃溶剂中形成热可逆的有机分子凝胶。不同烷基链长的亲溶剂作用以及溶剂性质对有机分子凝胶的形成有较大影响。场发射扫描电镜表明这种反应型凝胶剂在有机溶剂中自组装形成纤维状三维网络结构。烷基链长度不同,形成的纤维状聚集体的形态也不同。红外光谱(FT-IR)和核磁共振波谱(1H-NMR)研究表明分子间氢键作用是这种凝胶剂自组装的驱动力。通过X射线衍射(XRD)和分子模拟推测了其聚集体的结构形态。 相似文献
11.
核磁共振代谢组学数据预处理中的自适应分段积分方法 总被引:2,自引:1,他引:1
提出一种用于核磁共振代谢组学数据预处理的自适应分段积分方法. 通过计算各数据点统计特性, 并根据相邻数据点的统计差特性进行自适应积分, 克服了目前普遍采用的等间隔分段积分法可能存在的缺陷(如统计差异性相反的信号相互抵消、微弱特征信号被掩盖及谱图信噪比下降等), 从而避免了对后续统计分析所产生的负面影响. 为比较自适应分段积分和等间隔积分对数据预处理的效果, 分别采用计算机模拟数据和饮食差异人群两种模型进行分析. 研究结果表明, 新方法能够有效地削弱噪声和非特异信号的影响, 提高后续的主成分分析结果的可靠性, 使代谢组学数据分析更具生物学意义. 相似文献
12.
. Nagy 《International journal of quantum chemistry》1987,31(2):269-278
The method of statistical exchange-correlation parameter is presented. It has been shown that there is only a small difference between the self-consistent, the statistical, and the αHF parameters. We suggest using statistical exchange-correlation parameters in molecular calculations. 相似文献
13.
Assessment of the quality of goodness-of-fit and the confidence in predictivity (prediction power) are the main terms used to define the statistical quality of QSAR models. Three parts of this assessment can be defined as: (1)?Measure of goodness-of-fit. (2)?Validation of model stability. (3)?Predictivity analysis. Currently there are no mandatory requirements for the validation methods to be used and rules for the quantitative confidence estimates. To compare the statistical quality of QSAR models it is necessary to have an overall statistical quality index which will depend on the goodness-of-fit, validation and predictivity results together. To do so it is necessary to define the set of mandatory parameters for all three parts of assessment listed above and develop the approach for overall quality estimates based on these parameters. It is also necessary to include into the overall index the penalty mechanism for parameter absence. The goal of the present study is to analyse parameters for all three parts of the QSAR model statistical quality assessment and investigate the flexible weighting approach for the overall statistical quality index development. Due the different statistical parameters traditionally used for assessment of goodness-of-fit it is necessary to create the mechanism, which allows flexible set of parameters to be used for the overall statistical quality index. Only after approval by scientific community and regulatory boards the final set of mandatory parameters can be selected. 相似文献
14.
A statistical mechanical (one-dimensional Ising model) treatment, based on the dominance of short-range interactions, is developed in this series of papers; it is intended as an improvement over empirical prediction schemes for obtaining approximate initial conformations of proteins (to be used to try to deduce the native conformation by subsequent energy minimization). In the present paper, the statistical weights for a two-state model (alpha-helical and other conformations) and for a three-state model (alpha-helical, extended, and other conformations) are evaluated from x-ray data on 16 native proteins. The method for evaluating the statistical weights is presented. Asymmetric alpha-helical nucleation parameters are also evaluated for the 20 naturally occurring amino acids. On the basis of these statistical weights, the conformational properties of the twenty naturally occurring amino acids are discussed. The statistical weights evaluated from x-ray data are also discussed in comparison with experimental results on the helix--coil transition in polyamino acids in solution. The predominant role of short-range interactions, and some possible long-range effects in determining the statistical weights, are discussed in conjunction with the mechanism of protein folding. 相似文献
15.
The quality of QSAR models: problems and solutions 总被引:1,自引:0,他引:1
Assessment of the quality of goodness-of-fit and the confidence in predictivity (prediction power) are the main terms used to define the statistical quality of QSAR models. Three parts of this assessment can be defined as: (1) Measure of goodness-of-fit. (2) Validation of model stability. (3) Predictivity analysis. Currently there are no mandatory requirements for the validation methods to be used and rules for the quantitative confidence estimates. To compare the statistical quality of QSAR models it is necessary to have an overall statistical quality index which will depend on the goodness-of-fit, validation and predictivity results together. To do so it is necessary to define the set of mandatory parameters for all three parts of assessment listed above and develop the approach for overall quality estimates based on these parameters. It is also necessary to include into the overall index the penalty mechanism for parameter absence. The goal of the present study is to analyse parameters for all three parts of the QSAR model statistical quality assessment and investigate the flexible weighting approach for the overall statistical quality index development. Due the different statistical parameters traditionally used for assessment of goodness-of-fit it is necessary to create the mechanism, which allows flexible set of parameters to be used for the overall statistical quality index. Only after approval by scientific community and regulatory boards the final set of mandatory parameters can be selected. 相似文献
16.
Filtered backprojection method has been commonly used to reconstruct images in the field of the computed tomography (CT). However, in the emission CT such as positron and single photon CT, poor counting static which are caused by limited dosage to patients, limited counting rate capacity and limited efficiency of the imaging device, produce a statistical noise in the reconstructed image. The magnitude of the statistical noise and the spatial resolution were evaluated for various shapes of the filter used in the convolution integrals of the filtered back-projection procedure. The statistical noise was proportional to the inverse of the root of the total number of counts for any filters. The high-frequency-cut characteristic of the filter reduced the statistical noise, but increased the spatial resolution in the images. It was possible to optimize the shape of the filter for given total number of counts and required statistical noise and spatial resolution. 相似文献
17.
18.
~(13)C_(60)气相统计熵及热容的计算 总被引:1,自引:0,他引:1
采用统计热力学方法及理想气体模型计算了气相~(13)C_(60)分子在101325Pa压力及不同温度下的统计熵与热容。给出了统计熵与热力学温度K之间的关系,以及等容热容和等压热容与热力学温度K之间的关系表达式。 相似文献
19.
20.
The statistical properties of vibrational energy levels in C6H6 are analyzed. The results show that they belong to a completely different type, of which the spectral rigidity is larger but the fractal dimensional function is smaller than both the Wigner law and Poisson law, and this new statistical property is called the low Poisson law. In fact, this special statistical property reflects the speciality in the structure of C6H6 in a way. 相似文献