Small-angle neutron scattering studies of polyethylene crystallized at high pressure

The technique of small-angle neutron scattering (SANS) has been used to study the chain configuration in pressure crystallized polyethylene. Two narrow molecular weight fractions of deuterated molecules (PED) of M_w 23 000 and 54 000 were solution blended with a protonated matrix polymer of M_w 81 500. Although pressure crystallization was shown to have produced a clustering of the PED molecules, the radii of gyration $\text{〈}\text{S}{}^2\text{〉}{}_{\mathrm{z}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ were, nevertheless, shown to be consistent with a model in which the PED molecules possessed rod-like configurations. The predicted rod lengths were in close agreement with the molecular stem lengths of the PEH matrix polymer, which were independently determined by nitric acid etching. Furthermore, a doubling of the PED molecular weight produced no change in the value of $\text{〈S}{}^2\text{〉}{}_{\mathrm{z}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. This was interpreted in terms of a chain folding mechanism in which a molecule is bounded by the surfaces of a lamellar block and is therefore unable to increase its' rod length.     

Bücherschau

Ohne Zusammenfassung VDI     

Behavior of biliary phospholipids in intestinal lumen during fat digestion in rat

The phospholipids present in the intestinal lumen of rats following ingestion of triglycerides are of biliary origin. They consist of lecithins accompanied by a small proportion of lysolecithins. Their behavior in comparison with the other lipid constituents of the intestinal content was studied by subjecting the latter to gel filtration on an agarose column in the presence of a solution of 6 mM sodium taurocholate in 0.1 M NaCl. Part of the phospholipids is present with the triglycerides and diglycerides in the emulsified phase excluded from the gel where pancreatic lipase and colipase also are found. The remainder is found in optically clear fractions containing fatty acids, monoglycerides, and bile salts. These fractions are eluted at 2.0 column volumes, while mixed fatty acids, monoglycerides, bile salts micelles emerge from the column at 2.4 column volumes in the same chromatographic conditions. This difference in behavior may be explained by the presence of biliary lecithins. This presence could have an important bearing upon the mucosal uptake of the lipolysis products of triglycerides.     

Aplysia sea hare assimilation of secondary metabolites from brown seaweed,Stypopodium zonale

JuvenileAplysia dactylomela were found feeding in abundance on the tropical brown algaStypopodium zonale, a seaweed previously shown to contain numerous unique terpene-quinone natural products. Lipid extracts of these herbivorous mollusks were shown by TLC and HPLC-NMR analyses to contain appreciable quantities of twoS. zonale metabolites as well as one new but closely related compound. Spectroscopic analyses of the new compound in concert with functional group modifications identified this new compound as 3-keto epitaondiol. A careful analysis of the seaweed extract failed to locate this ketone, and thus, it most likely represents anAplysia-biotransformed compound. This is the first clear reported observation of metabolite transfer between an alga of the phylum Phaeophyta and a sea hare.     

Heat and mass transfer during air drying of solids

Heat and mass transfer are studied for drying of a semi-infinite solid in warm air. The mathematical model, a system of partial differential equations, gives an exact analytical solution if transfer coefficients are constant and free water present at the surface. An analogy has been found for heat transfer with and without drying. A finite-difference solution of broader application than the analytical method has been developed, and the two methods agree closely. Experiments are described which show fair agreement with calculations of heat transfer during the first step of drying. Water content profiles remain flat during that period and no precise comparison can be made     

Mixing effects and hydrodynamics of vortex rings

Vortex rings have been formed in water by impulsive flow through an orifice, and mixing effects due to the lings have been measured. Laboratory tests on the mixing of stratified layers of salt solution by vortex rings formed at a 6.35 cm diameter orifice have indicated that Froude number is an important factor in determining the energy efficiency of mixing. Field tests using a 25.4 cm orifice in Hamilton Harbour (18 m depth of water) have shown a small mixing effect. Further experiments with a 25.4 cm orifice in a test tank have shown that the vortex rings have a range of at least 30 m.     

Reactions of conjugated fatty acids. V. Preparation and properties of diels-alder adducts and their esters fromtrans,trans-conjugated fatty acids derived from soybean oil

Summary Soybean fatty acids were conjugated with alkali, and the contained, conjugated dienoic acids were isomerized with iodine to thetrans,trans configuration. Adducts were prepared from thesetrans,trans-conjugated acids by condensation with maleic anhydride and acrylic acid. The adducts were isolated, purified, and converted to esters by using a variety of alcohols, including methyl, ethyl,n-propyl,n-butyl, and allyl alcohols. Esters made from saturated alcohols were converted into the corresponding epoxy derivatives. All of the esters (except allyl) and all of the epoxy esters were compatible with an equal weight of polyvinyl chloride and appeared to be primary plasticizers for this plastic. The epoxy esters were effective in inhibiting heat deterioration of polyvinyl chloride. Presented at fall meeting. American Oil Chemists' Society, September 23–26, 1956, Chicago, Ill.