A note on the weighted norm inequality for the one-sided maximal operator

Let be the one-sided maximal function. In this note we obtain some necessary and sufficient conditions in order that the weighted weak type inequality holds for . Meanwhile, some necessary or sufficient conditions for the weighted inequality for are given.

     

Orientation-reversing involutions on handlebodies

The observation that the quotient orbifold of an orientation- reversing involution on a 3-dimensional handlebody has the structure of a compression body leads to a strong classification theorem, and general structure theorems. The structure theorems decompose the action along invariant discs into actions on handlebodies which preserve the -fibers of some -bundle structure. As applications, various results of R. Nelson are proved without restrictive hypotheses.

     

SYNTHESIS AND THERMAL PROPERTIES OF POLYBENZOXAZOLE FROM SOLUBLE PRECURSOR WITH HYDROXY-SUBSTITUTED POLYENAMINONITRILE

Aromatic polybenzoxazole (PBO) precursor, hydroxy-substituted polyenaminonitrile, was prepared by direct polycondensation of 1,4-bis(l-chloro-2,2-dicyanovinyl)benzene (CCB) and 4,6-diaminoresorcinol dihydrochloride (DAR) using pyridine and N,N-dimethylacetamide as condensing agent and solvent. The precursor has good solubility in polar aprotic solvent which is due to the strong dipolar nature of the main chain. The soluble precursor was subjected to thermal cyclization in an inert atmosphere to convert it into the corresponding PBO, which has its 5% weight loss temperature at 540℃ The fully cyclized PBO were characterized by FT-IR and TGA. The introduction of 10% mol 1,3,5-benzenetricarboxylic chloride (BTC) into the main chain not only has little effect on the solubility of PBO precursor but also raises its 5% weight loss temperature to 552℃ and char yield at 700℃ for the cyclized PBO with BTC.     

Quantitative weight of evidence method for combining predictions of quantitative structure-activity relationship models

ABSTRACT

A method for combining statistical-based QSAR predictions of two or more binary classification models is presented. It was assumed that all models were independent. This facilitated the combination of positive and negative predictions using a quantitative weight of evidence (qWoE) procedure based on Bayesian statistics and the additivity of the logarithms of the likelihood ratios. Previous studies combined more than one prediction but used arbitrary strengths for positive and negative predictions. In our approach, the combined models were validated by determining the sensitivity and specificity values, which are performance metrics that are a point of departure for obtaining values that measure the weight of evidence of positive and negative predictions. The developed method was experimentally applied in the prediction of Ames mutagenicity. The method achieved a similar accuracy to that of the experimental Ames test for this endpoint when the overall prediction was determined using a combination of the individual predictions of more than one model. Calculating the qWoE value would reduce the requirement for expert knowledge and decrease the subjectivity of the prediction. This method could be applied to other endpoints such as developmental toxicity and skin sensitisation with binary classification models.     

自增强高性能聚合物的成型工艺同力学性能间相关性研究——1.超高分子量聚乙烯的应力诱导结晶理论和其自增强作用

本文发展了一种高分子量聚合物熔融体的应力诱导结晶结构形态模型,它是由微晶聚集体(以下简称微区)-高分子链组网和缠结网的网络结构组成。基于上述模型,把二种网中的单个链组作为独立的统计单元和形变单元,计算了二种网中单个链组的末端距分布函数,进一步计算了二种网和总网的形变自由能。在此基础上,讨论了诱导结晶结晶机理和自增强聚合物网络自由能的依赖性,并着重地研究了超拉伸高聚物的起始熔点拉伸比间的关系。用超高分子量聚乙烯膜和超取向高密度聚乙烯纤维的起始熔点和拉伸比的实验数据进行处理,得到理论予期的近似直线关系,初步验证了聚合物网应力诱导结晶理论。     

聚N-异丙基丙烯酰胺溶液的粘度的温度依赖关系

用自由基聚合法合成了聚Ｎ 异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，用乌氏粘度计考查了该聚合物的四氢呋喃（ＴＨＦ）溶液和水溶液的粘度与温度的依赖关系．发现ＰＮＩＰＡＡＭ ＴＨＦ体系的特性粘数随温度升高而增大，ＰＮＩＰＡＡＭ Ｈ２Ｏ体系的特性粘数 温度曲线表现出较为复杂的变化规律．并用实验确定的特性粘数对合成样品的分子量进行了表征Ｍｎ＝８４４×１０５ｇ·ｍｏｌ－１．     

Influence of operational parameters on retention of ultra-high molecular weight polystyrenes in thermal field-flow fractionation

Summary The influence of various parameters (concentration of the injected polymer solution, flow rate, temperature gradient, relaxation conditions) on the retention and shape of the fractogram of ultra-high molecular weight polystyrenes in thermal field-flow fractionation was investigated. Under the operating conditions adopted, reproducible oscillations in the peak shape are observed for molecular weights larger than a few millions, especially at relatively high polymer concentration. They are attributed to some hydrodynamic instabilities. The retention of ultra-high molecular weight polystyrenes at high flow rate is strongly dependent on the initial relaxation period. All of the investigated operational variables have a complex effect on the resulting shape of the fractogram. Consequently, the confirmation of the shear-induced focusing of macromolecules across the channel thickness requires further study. Experiments on reinjection of fractions collected after an initial high speed pass through the separation system leads to the conclusion that shear degradation of the ultra-high molecular weight polymers did not occur under the investigated experimental conditions even at the highest flow rates.     

磁场对含稀土铝锂合金断裂特征的影响

以含铈铝锂合金为研究对象，研究了磁场对含稀土铝锂合金时效过程的影响，从断裂特征及微观组织两方面分析了磁场作用规律。实验结果表明：未加磁场时，合金的断裂特征以理断裂为主；扁平晶粒厚度不匀，在磁场作用下，此合金的断裂特征与微观组织发生明显改观，随磁感应强度增强，合金主断裂面上准解理断裂特征减弱，同时二次裂纹增多，分层比较升高；扁平晶粒厚度变薄，尺寸趋于均匀。用少体物理理论，探讨了磁场对含稀土合金原子扩散过程的影响，为进一步研究稀土元素在磁场中的行为及其局域效应提供了一定的实验依据。     

聚苯胺在一些有机溶剂中溶解性

本文通过改变反应条件用化学方法制得了不同分子量的聚苯胺，考察了它们在有机溶剂中的溶解性．实验结果表明：分子量的大小是影响它们在有机溶剂中溶解度的主要因素，能在有机溶剂中溶解的只是聚苯胺中分子量较小的级分．我们还用聚苯胺（［η］＝０．４９ｄｌ／ｇ）与－ＣＯＣＩ封端的果对苯二甲酰对苯二胺（ＰＰＴＡ）进行嵌段共聚，经过产物的元素分析与计算结果比较，确定出特性黏数为０．４９ｄｌ／ｇ的聚苯胺平均分子量．     

A new Co(II) complex with N,O-donor Schiff base: Synthesis, structure and characterization

A new Co(II) complex with tridentate Schiff base ligand with a N,N,O donor set has been synthesized and characterized by single X-ray technique and spectroscopic techniques. The thermochemical properties have been studied. X-ray structure analysis of the title compound Co(II)L₂ [HL = 2-methyl-6-(2′-hydroxybenzylideneamino) pyridine] shows that the polyhedron around Co(II) is a distorted tetrahedron, and the self-assembly via intermolecular π-π interactions leads to a three-dimensional network. Crystal data for the title complex C₂₆H₂₂CoN₄O₂: Monoclinic, space group Ia, a = 11.741(7) Å, b = 8.149(5) Å, c = 22.764(16) Å, β = 98.530(12)°, V = 2154(2) ų, Z = 4.