Comparison of the instantaneous and conversion chemical heterogeneity of random copolymers

The calculation of a general distribution function of chemical composition of random copolymers involving the instantaneous and conversion chemical heterogeneity is demonstrated. Typical examples offer a semiquantitative view about the effect of the two types of chemical heterogeneity on the shape and width of the distribution of chemical composition.     

Superoxide produced in the heme pocket of the beta-chain of hemoglobin reacts with the beta-93 cysteine to produce a thiyl radical

The role of the beta-93 cysteine residue in the hemoglobin autoxidation process has been delineated by electron paramagnetic resonance. At low temperatures (8 K) after incubation at 235 K, free radical signals were detected. An analysis of the free radical spectrum produced implies that, besides the superoxide radical expected to be formed during autoxidation, an isotropic free radical is produced with a giso of 2.0133. This g value is consistent with that expected for a sulfur radical. Blocking the beta-93 sulfhydryl group with N-ethylmaleimide was found to eliminate the formation of the isotropic radical, but not the superoxide. This finding confirms the assignment of the isotropic radical as a thiyl radical originating from the oxidation of the cysteine SH group. A kinetic analysis of the time course for the formation of both the superoxide and thiyl radicals is consistent with a reversible electron transfer process between superoxide in the heme pocket of the beta-chains and the cysteine residue. This reaction is expected to produce both a thiyl radical and a peroxide. Direct evidence for peroxide production comes from the detection of a transient Fe(III) heme peroxide complex. The significance of the electron transfer process producing a thiyl radical is discussed. It is shown that the formation of the thiyl radical decreases the rate of autoxidation for the beta-chain and reduces heme degradation attributed to the reaction of superoxide with the heme. The insights gained from these low-temperature studies are believed to be relevant to room-temperature autoxidation.     

Solution of counter-current separation processes—IV. Application of the GPM method to solution of distillation problems

A new non-iterative method for a parametric study of a particular distillation column is devised. The technique takes use of the similarity between difference and differential equations. For solution of nonlinear boundary value problems for difference equations the GPM technique is used. The method is illustrated by calculated examples.     

Photochromic polymers

Summary Two soluble photochromic polymers containing 1-(ß-hydroxyethyl)-3,3-dimethyl-6-nitrospiro[2H-1-benzopyran-2,2-indoline] bound on a variously long side chain were prepared. It was found that the discolouration process depends on the length of the side chain to which the photochromic centre is bound.     

Rationalized Load and Lifetime of Brittle Materials

The design and testing of structural parts from materials which exhibit subcritical crack growth can be improved by introducing auxiliary quantities into the classical concepts of fracture mechanics. The equivalent static stress, equivalent loading time, standardized loading time, and standardized lifetime, as well as the decrease in lifetime and residual lifetime, are defined, with examples of their application.     

Fast determination of fatty acids in oil-utilizing resins by NMR spectroscopy

This work describes the determination of oil either as such or in oil-utilizing resins such as alkyds and urethanes, by means of NMR techniques. Both the qualitative and quantitative analyses are demonstrated and the accuracy is assessed. Typically, the complete analysis of an alkyd resin takes less than 1 hr.     

Refractive index increments of polyethylene

The refractive index increments of linear and branched polyethylene were determined for several solvents and various wavelengths (403, 436, 546, and 633 nm), mainly at 135°C. Differences were observed between values for linear and branched samples. Data obtained in this investigation are compared with the reported ones.     

Reactive polymers,XXXVII. An investigation of the internal structure of polymeric sorbents based on poly(2,3-epoxypropyl methacrylate-co-ethylene dimethacrylate)

The internal structure of polymeric sorbents based on 2,3-epoxypropyl methacrylateethylene dimethacrylate was investigated by means of mercury porosimetry and by employing the sorption method. The results were confronted with characteristic chromatographic data and helped to elucidate the relationships existing between the internal structure of copolymers and their chromatographic properties.     

Reaktive Polymere. II. Die Herstellung von Metallchelaten vernetzter Polymerer

The reaction of bivalent ions (Cu, Co, Zn, Ni) with ethylene diamine bounded to homogeneous crosslinked terpolymer glycidyl methacrylate-styrene-divinylbenzene or macroporous copolymer glycidyl methacrylate-ethyleneglycole dimethacrylate has been studied. The capacity of polymer sorbent, exchange ability and the kinetic of the reaction has been studied.     

Antioxidantien und Stabilisatoren XXVIII. Gelchromatographie nichtflüchtiger phenolischer antioxidantien zur stabilisierung von polymeren

High resolution gel chromatography was applied to the analysis of phenolic antioxidants mixtures formed by an alkylation of 4,4'-isopropylidenebisphenol and used for the stabilisation of polyolefins and rubbers. The calibration by pure model substances provided values of relative zone rates on S-GEL-832 for a series of tert-butyl and tert-octyl derivatives of phenol and 4,4'-isopropylidenebisphenol. The chromatograms show in some cases a separation of isomers differing in size of their molecules in solution.