Separation of the oxidation products of fatty acids by means of gas-liquid partition chromatography

Conclusions The oxidation of oleic, and particularly of linoleic and linolenic acids, indicated the presence of a considerable number of unexpected products in addition to those foreseen from a simple severance of the double bonds. The chromatograms of the oxidized pure C₁₈ acids, of Neo-Fat No. 140, and of a mixture of fatty acids from hydrolyzed soybean oil showed a striking similarity in many respects. It was not possible to identify all the peaks, especially those of trace amounts, in the chromatograms and to obtain a quantitative estimate of the oxidation products. Further work on this is in progress. The results indicate that gas-liquid partition chromatography is a sensitive method for the study of the oxidation of vegetable oils. Presented at the fall meeting, American Oil Chemists' Society, Chicago, Ill., September 24–26, 1956. One of the divisions of the Agricultural Research Service, U. S. Department of Agriculture.     

Hydrogel membranes based on genipin-cross-linked chitosan blends for corneal epithelium tissue engineering

Novel polymeric hydrogel scaffolds for corneal epithelium cell culturing based on blends of chitosan with some other biopolymers such as hydroxypropylcellulose, collagen and elastin crosslinked with genipin, a natural substance, were prepared. Physicochemical and biomechanical properties of these materials were determined. The in vitro cell culture experiments with corneal epithelium cells have indicated that a membrane prepared from chitosan-collagen blend (Ch-Col) provided the regular stratified growth of the epithelium cells, good surface covering and increased number of the cell layers. Ch-Col membranes are therefore the most promising material among those studied. The performance of Ch-Col membranes is comparable with that of the amniotic membrane which is currently recommended for clinical applications.     

Hydrogenation of linolenate. II. Hydrazine reduction

Observations by Aylward and Rao that hydrazine is a reducing agent for a number of unsaturated fatty acids were extended. The hydrazine reaction on linolenic acid was followed by periodic sampling until methyl esters prepared from the reduced acids had an iodine value of 162. These esters were shown by countercurrent distribution to consist of 26% triene, 43% diene, 26% monoene, and 5% stearate and by infrared analysis to contain notrans bonds. Oxidation of the separated monoene and diene fractions by permanganate-periodate mixtures and gas chromatography of the dibasic acids showed that the double bonds were in the original 9, 12, and 15 positions and that the double bonds farthest from the carboxyl were reduced at a slightly faster rate. Gas chromatography of the monoene fraction indicated three components that were identified in the order of elution from the column as 9, 12, and 15 monoenes; in the diene fraction three components were identified in the order of elution as 9,12; 9,15; and 12,15 dienes. After alkali isomerization of this diene fraction, the conjugated material was reacted with maleic anhydride; the unreacted 9,15 diene isomer was separated by distillation. Presented at fall meeting, American Oil Chemists’ Society, New York, October 17–19, 1960. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

New bilayer-coated microbead system for controlled release of 5-aminosalicylic acid

A new bilayer-coated microbeads for oral delivery of 5-aminosalicylic acid (5-ASA) were prepared from naturally occurring polysaccharides via emulsification method. 5-ASA was successfully encapsulated in chitosan–λ-carrageenan-coated alginate microbeads. The morphology and sizes of microparticles were studied using optical microscopy and dynamic light scattering. Drug release profiles were followed using high-performance liquid chromatography (HPLC) with spectrophotometric detection. The effect of chitosan thin layer and chitosan–λ-carrageenan bilayer on the drug release was studied at pH values simulating these characteristic for stomach (pH = 1.2) and intestine (pH = 7.4). Chitosan layer slightly increased 5-ASA release at pH = 1.2, whereas double-layer external coating decreased the release rates. Due to the bilayer properties, the micro-carriers were additionally protected against acidic conditions of the stomach and drug release in the intestine could be better controlled.     

Influence of heat flux on the minimum liquid flow rate required for complete wetting of a horizontal tube surface

An experimental study is described, concerning the influence of the heat flux through a wetted surface of a horizontal tube and of the temperature of a wetting liquid on the minimum liquid flow rate required for complete wetting of the tube. The results are presented in the form of correlating equations. Good agreement was found with the theoretical predictions of Zuber and Staub.     

Cluster analysis,graphs, and branching processes as new methodologies for intelligent systems on example of bibliometric and social network data

This article presents (1) a general formalism for cluster analysis, allowing a systemic study of simulation research, in particular its dynamic aspects, (2) a model of small bibliographical clusters, allowing inference (among others) on the connectivity of domains, and (3) an outline of new theories of networks with randomly changing nodes and edges, applicable for analysis of different types of relations, e.g., communication between scientists, etc. These models may be useful for analysis of large databases in artificial intelligence. They may also have significance as new approaches to neural network analysis.     

The roles for a Lewis base and MgCl2 in third-generation Ziegler-Natta catalysts

Activity of a titanium catalyst supported on a bimetallic magnesium–aluminium system, involving a Lewis base [MgCl₂(THF)₂/Al(C₂H₅)₂Cl], was studied in ethylene polymerization, and the effect of the catalyst composition on the properties of the final polymer produced was investigated. Analysis and discussion of the findings covering also some part of the kinetic study, resulted in defining the roles for MgCl₂ and a Lewis base in the third-generation Ziegler-Natta catalysts. MgCl₂ forms a bimetallic complex with an organoaluminium compound, which involves also a Lewis base. Its reaction with TiCl₄ yields a very active catalyst wherein the Mg : Ti molar ratio is close to 1. This means that MgCl₂ is involved in creating catalytic active sites. The structure of these catalytic sites were suggested. Hence, the role for MgCl₂ can be twofold: it is a component of a catalytic active site, and it is a support if Mg : Ti > 5. It was found in the study that the catalytic function of MgCl₂ can be maintained while its supporting function can be omitted. Thus, MgCl₂ can be substituted for Al₂O₃ and the catalytic system obtained will have the same activity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1005–1011, 1998     

Smart anionic polyelectrolytes based on natural polymer for complexation of cationic surfactant

The thermosensitive polyelectrolytes were obtained by grafting 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) onto hydroxypropylcellulose (HPC), a biodegradable polysaccharide. The interactions of the polymers with dodecyltrimethylammonium chloride (DTAC), a model cationic surfactant, were studied. It was found by the measurements of the surface tension and the analysis of fluorescence emission of pyrene used as a fluorescent probe, that the HPC–AMPS graft polymers strongly interact with DTAC with the formation of polymer–surfactant complexes. The critical aggregation concentrations of these polymer–surfactant systems were found to be of the order of 10^?5 mol/dm³. The polymers were found to be potentially useful in the purification of water from cationic surfactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2401–2407, 2006