Viscosity index. I. Evaluation of selected copolymers incorporating n-octadecyl acrylate as viscosity index improvers

Compositionally and structurally varied copolymers all containing n-octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n-octadecyl acrylate with, respectively, methyl methacrylate, 2-ethylhexyl acrylate, and n-dodecyl acrylate; and homopolymers of poly(n-octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n-octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these composition was somewhat greater than that of the acryloids. A parameter that related concentration and weight-average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agree within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement.     

H型气体水合物导热系数的分子动力学模拟

气体水合物^[1]是由水和小分子气体形成的非水学计量型笼型晶体。到目前为止,已经发现的气体水合物结构有3种,即Ⅰ型、Ⅱ型和H型,水合物的导热系数是一个很重要的物性参数,人们已对Ⅰ型和Ⅱ型水合物的导热系数进行了较多的实验和理论研究,包括分子模拟研究^[2],由于H型水合物发现较晚,其导热系数无论是实验值还是理论值均未见文献报道,因此本文对H型水合物的导热系数进行了分子动力学模拟。为了给H型气体水合物导热系数的模拟计算提供可靠的热能模型和模拟算法,本文首先对冰体系和空水合物的导热系数进行了分子动力学模拟。     

Representing rules as random sets,II: Iterated rules

I. R. Goodman, H. T. Nguyen, and others have proposed the theory of random sets as a unifying paradigm for knowledge-based systems. The more types of ambiguous evidence that can be brought under the random-set umbrella, the more potentially useful the theory becomes as a systematic methodology for comparing and fusing seemingly incongruent kinds of information. Conditional event algebra provides a general framework for dealing with rule-based evidence in a manner consistent with probability theory. This and a previous companion article bring conditional event logic—and through it, rules and iterated rules—under the random set umbrella. In this article, we derive a new conditional event algebra, denoted GNW₂, for rules which are contingent on other rules. We show that this logic is the only one which extends the GNW first-degree logic, admits a simple embedding into random sets, and has GNW-like behavior. We show that GNW events are contained in a Boolean subalgebra GNW* of GNW₂. Finally, we show how GNW₂ can be used to recursively define a GNW-like Boolean logic for iterated rules of any degree. © 1996 John Wiley & Sons, Inc.     

Zur Existenzfähigkeit von 2-Imino-2H-1,3-thiazinen

On the Existence of 2-Imino-2H-1,3-thiazines The title compounds 2 are readily liberated from the 2-amino-1,3-thiazinium salts 1 by treatment with bases. Their stability depends sensitively on the substituents at the imino-N. The imino-N substituted 2a – i are isolable as well-defined coloured substances. Reaction of the 2 as well 1 with nucleophilic agents affords pyrimidine-2-thiones ( 4 , 9 – 11 , 16 – 18 ). In these ring transformations a nucleophilic addition at ring position 6 as primary reaction step is preferred. The imino-N unsubstituted representatives display a more complicated behaviour; the highly enhanced reactivity prevents or handicaps, respectively, any isolation. As exemplified in the base-induced ring-transformation of 1 m to the pyrimidine derivative 19 , these 2 are able to react as nucleophiles too, and versatile intermolecular self-reactions are increasingly favoured.     

Synthese von 4-Alkoxy-2-hydroxyphenylketoximen als Metallextraktions-Reagenzien

Synthesis of 4-Alkoxy-2-hydroxyphenyl Ketoximes as Reagents for Metal Extraction The C-Acylation (Friedel-Crafts reaction) of resorcinol with aluminium chloride, the monoetherification in 4-position of the resulting 2,4-dihydroxyphenylketones, and the preparation of oximes ( 8, 9, 10, 11 ) from this ketones were investigated. The compounds obtained are characterized by elemental analysis, and the i.r., u.v. and ¹H-n.m.r. spectra are discussed. Solubility data of some oximes are determined in water, octane and toluene. The extraction properties for copper-(II)-and iron-(III)-ions are measured by isotope methods in relation to the extragent structure, the extraction time and the pH-range.