The effect of methyl group on the mechanical properties of hydrophobic association hydrogel

Hydrophobic association hydrogels were fabricated via micellar copolymerization of acrylamide and hydrophobic monomers lauryl (meth)acrylate (LA or LMA) in an aqueous solution of sodium dodecyl sulfate. The effect of methyl groups of hydrophobic monomers on the crosslinking network structure and mechanical behavior of the gels was investigated on the basis of rubber elastic theory. It was found that the LMA-gel exhibited higher effective crosslink density and elastic modulus. The methyl groups of hydrophobic monomers limited the flexibility of the methacrylate backbone in the association domain, which resulted in the increment of chains constraints. With the increase of stretch rate, the dissipated energy of LMA-gel increased more highly than that of LA-gel. In addition, the methyl group hindered the movement of polymer chains, leading to the lower recovery efficiency of dissipated energy for LMA-gel. In contract, the LA-gel exhibited a rapid response to external force, and possessed better elasticity and self-recovery property. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1505–1512     

Synthesis and hydrophobic association of poly(N,N‐dimethylacrylamide) end‐functionalized with perfluorocarbon and hydrocarbon groups

Polydimethylacrylamides (PDMAs) end‐functionalized with hydrophobic groups were synthesized by the reaction of cesium salts of one‐ or two‐ended living PDMA anion with octadecanoyl and perfluorooctanoyl chlorides and with α‐phenylacrylate monomers containing an octadecyl group attached via oligooxyethylene spacers to the acrylate functionality. Size exclusion chromatography or NMR studies indicated that the end functionalizations were nearly quantitative. Reduced viscosity measurements were consistent with predominantly dimeric association of the perfluorooctanoyl‐end‐functionalized PDMAs. The association of the two‐ended, perfluorooctanoyl‐ and octadecanoyl‐functionalized polymers was more extensive and consistent with pairwise association. Furthermore, the presence of oligoethylene oxide spacers between the octadecyl and α‐phenylacrylate groups greatly enhanced the hydrophobic association of bis(octadecyl)‐end‐functionalized PDMA. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1403–1418, 2001     

Ion association in lithium metaborate solution: a Raman and ab initio insight

Ion association and hydration clusters in aqueous lithium borate solution are extremely important to understand some extraordinary properties of lithium borates. In the present work, polyborate distribution in aqueous LiBO₂ solution was investigated through Raman and thermodynamics equilibrium analysis. Geometry and stability of hydrated clusters LiB(OH)₄(H₂O)_n up to n = 8 were calculated at the B3LYP/aug-cc-pVDZ level. Three different types of ion association, namely, contact ion pairs (CIP), solvent-shared ion pairs (SIP) and solvent separated ion pairs (SSIP) were obtained; characteristics of all of these stable configurations were determined, and the most stable hydrated clusters were chosen. Then the mechanisms of ion aggregation and crystal nuclei formation in the LiB(OH)₄ solution were proposed. The tight four-hydrated sphere of Li⁺ makes it difficult for the dehydrated form of its first hydration sphere to from a CIP, which is the passible reason that lithium borate always has a large super-saturation degree.     

pH,Definition and measurement at high temperatures

In this review paper, the NBS scale and its limitations are briefly discussed. The magnitude of liquid junction potentials and some calculated values are presented. The use of a molality scale for hydrogen electrode concentration cells at high temperatures is described, and results from measurements on ionization equilibria are summarized. Use of this scale is also recommended for certain circumstances with cells without liquid junction. As an alternative activity scale, use of the Pitzer ion-interaction treatment for ions is recommended for special cases. Finally, reference data are presented for _±HCl in HCl(aq) to 350°C and (HCl+NaCl)(aq) to 200°C that were derived by use of the Pitzer ion-interaction treatment.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

Dissociation of photochromic spiroanthrooxazine dimers in the excited state

The influence of temperature and concentration on the spectral polarization properties of the luminescence and absorption of molecules of the original form of photochromic spiroanthrooxazine (SAO) in petroleum ether and polyethylene was investigated. It was shown that the long-wave part of the absorption spectra of the molecules is formed by at least two -*-type electronic transitions, the oscillators of which are mutually orthogonal. It is suggested that the SAO molecules form dimers in nonpolar media through dipole-dipole interaction, and at high concentrations they also form higher associates. Dimers stable in the ground state dissociate when excited to the second electronic transition with a rate constant of 10¹²–10¹³ s^–1.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Department of the Institute of Solid-State Physics and Semiconductors, Academy of Sciences of Belarus, 211177 Vitebsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 99–106, January, 1992.     

Investigations on association schemes with elementary abelian thin residue

In this paper, we give a new class of association schemes whose thin residues are isomorphic to an elementary abelian $p$-group of order $p^2$. We then study the automorphism groups of these schemes and determine whether these schemes are schurian.     

Distance regularity of Kerdock codes

A code is called distance regular, if for every two codewords x, y and integers i, j the number of codewords z such that d(x, z) = i and d(y, z) = j, with d the Hamming distance, does not depend on the choice of x, y and depends only on d(x, y) and i, j. Using some properties of the discrete Fourier transform we give a new combinatorial proof of the distance regularity of an arbitrary Kerdock code. We also calculate the parameters of the distance regularity of a Kerdock code.     

基于主成分分析下候选基因关联检验的数学模型

对候选基因的关联检验,都是针对性状在候选基因内使用多个SNP标记,并通过检验SNP单倍型来完成的,众所周知,多标记单倍型方法往往要比单标记方法表达出更多的信息,但是,单倍型的数量往往会随着所标记的SNP的数目增多而急剧的增加,这又会大大增加检验统计量的自由度,使用统计学中的主成分分析法来降低单倍型空间的维数,并构造关联检验来检验一个数量性状与多个单倍型的关联情况,模拟结果显示,此检验方法是较合理的.     

基于粗糙集理论的超稠油油藏水平井吞吐效果评价及其影响因素分析

影响超稠油油藏水平井蒸汽吞吐开发效果的因素包括地质参数、流体参数、开发参数、水平井设计参数等众多因素,寻找主要因素对于超稠油油藏水平井吞吐效果评价及开发调整设计具有重要意义.基于粗糙集理论对影响超稠油油藏水平井吞吐效果的10个因素进行数据属性约简,同时利用灰色关联分析,对这些因素进行敏感性分析;应用Elman神经网络比较上述两种结果,证明了粗糙集理论进行数据属性约简的方法更准确.最终得到注汽干度、注汽强度、注汽速度、水平段长度和注汽压力对水平井的开发效果影响最大.实例计算表明,方法实用有效,精度较高,可用于超稠油油藏水平井吞吐效果评价及开发、调整设计.     

Association Schemes and Fusion Algebras (An Introduction)

We introduce the concept of fusion algebras at algebraic level, as a purely algebraic concept for the fusion algebras which appear in conformal field theory in mathematical physics. We first discuss the connection between fusion algebras at algebraic level and character algebras, a purely algebraic concept for Bose-Mesner algebras of association schemes. Through this correspondence, we establish the condition when the matrix S of a fusion algebra at algebraic level is unitary or symmetric. We construct integral fusion algebras at algebraic level, from association schemes, in particular from group association schemes, whose matrix S is unitary and symmetric. Finally, we consider whether the modular invariance property is satisfied or not, namely whether there exists a diagonal matrix T satisfying the condition (ST)³ = S ². We prove that this property does not hold for some integral fusion algebras at algebraic level coming from the group association scheme of certain groups of order 64, and we also prove that the (nonintegral) fusion algebra at algebraic level obtained from the Hamming association scheme H(d, q) has the modular invariance property.