Effect of temperature and molecular weight on the rate of spreading of polystyrene melts on plane soda lime glass surfaces

The effect of temperature T and weight-average molecular weight M?_w on the rate of spreading of polystyrene melts on plane solid surfaces has been examined. The activation energy E of spreading was estimated to be 25.2 ± 3 kcal/mole, which is of the same magnitude as the activation energy for flow of polystyrene melts. The rate of spreading was found to be inversely proportional to M?_w raised to the 1.5 power. This rate of spreading, measured as the time rate of increase in the liquid–solid contact area, dA/dt, could be expressed as where γ_1v is the melt surface tension and θ_d and θ_s are the dynamic and static contact angles, respectively. The numerical value of K has been calculated to be (6.025 ± 3.693) × 10^?14 in the temperature range of 110–260°C and for the values of M?_w from 2000 to 37000.     

Diethyl-2,2′-bipyridyl-palladium(II), a case for the study of combination vs. disproportionation products.

Diethyl-2,2′-bipyridyl-palladium(II) is synthesized and its decomposition reactions in absence and presence of methyl acrylate are compared with those of the corresponding nickel and platinum complexes. Depending on the reaction conditions either CC-coupling or disproportionation can be induced.     

Constrained stochastic controllability of infinite-dimensional linear systems

The main purpose of this article is to investigate the problem of (ε, δ)-stochastic controllability for linear systems of evolution type in infinite-dimensional spaces, wherein the controls are subjected to norm-bounded constrained sets. Some basic prerequisites of infinite-dimensional measures, in particular, Gaussian distributed type, are discussed. Corresponding to this measure, various properties of (ε, δ)-stochastic attainable sets in Hilbert spaces are studied. Necessary and sufficient conditions for (ε, δ)-stochastic controllability with respect to Hilbert space valued linear systems are obtained. Relationships with the deterministic counterpoint are noted. Pursuit game problems are also considered. Examples on systems governed by stochastic linear partial differential equations and stochastic differential delay equations are given for illustration.     

Differential scanning calorimetry—thin layer chromatography study of ribonucleosides

Thermal mutagenesis has been associated with cleavage of the glycosidic bond and modification of the base structure. Using deoxynucleosides as models, thermal analysis has been utilized to determine the influence of structure on relative ease of these thermolysis reactions. Differential enthalpic analyses of series of crystalline ribonucleosides indicate that they are more resistent to glycosidic cleavage than are the corresponding 2′—deoxyribonucleosides. This difference in thermal stability is attributed to the retarding influence of the 2′-hydroxyl group on the initiation of ion pair formation in the proposed cyclic transition state. Cytosine exhibits a unique behavior insofar as partial deamination of the base occurs, subsequent to cleavage from the sugar, to yield uracil as indicated by a combined DSC-TLC analysis.     

Oxidation of aromatic bis-amides by thallium (III) trifluoroacetate

Aromatic 1,2-bisamides undergo thallium (III) promoted oxidative intramolecular cyclization to generate new 5-membered heterocyclic rings. Formation of $\text{para}$-quinone was shown to be a minor pathway in one case.     

Trivalent cobalt in nickel-zinc ferrites—I. chemical problems

By using special preparation techniques the amounts of trivalent cobalt present in irondeficient Ni-Zn-Co ferrites have been varied.Co³⁺ concentrations have been measured very accurately by careful chemical analyses. It has been shown that under normal sintering conditions, e.g. 1200°C in oxygen, the amount of Co³⁺ just compensates the iron deficiency. The cation vacancy concentration is low. Cation vacancies are formed at lower temperatures near pores and grain boundaries.     

The stereospecific synthesis of leukotriene A4 (LTA4), 5-epi-LTA4, 6-epi-LTA4 and 5-epi,6-epi-LTA4

The stereospecific syntheses of the four isomers of 6-formyl-5,6-epoxy hexanoic acid methyl ester $\text{8}$, $\text{15}$, $\text{23}$ and $\text{30}$ from Z-deoxy-D-ribose have allowed the preparation of methyl esters of LTA₄, $\text{1}$, and its three unnatural isomers.