The structure of polyenoic odd- and even-numbered fatty acids of mullet (Mugil cephalus)

Mullet oil contains more than 25% straight-chain odd-numbered fatty acids. Odd- and even-numbered components of chain lengths C₁₅ to C₂₀ were isolated and their structures determined. The vinylmethane rhythm prevails in all polyun-saturated acids. Numerous homologs have their double bonds in identical positions, relative to the carboxyl group, as for example, 舥^9,12- and 舥^6,9,12-C₁₅, -C₁₆, -C₁₇ and -C₁₈ acids. The terminal structures which are characteristic for oleic, linoleic, etc., families are not found in the unsaturated odd-numbered acids. The results show: that the proximal structure has greater influence than the terminal structure on the biosynthesis of unsaturated odd-numbered acids; that chain lengths of 17 and 18 carbon atoms with double bonds in position 9 are crucial for synthesis of the polyenoic C₁₉ and C₂₀ acids; that chain lengths C₁₅ and C₁₆ with double bonds in position 9 are suitable for desaturation but that they are not suitable for desaturation after elongation. These specifications bring all acids of mullet into a rational order and reflect their possible interconversions. Presently, such classification has only limited predictive value in regard to the physiological properties of polyunsaturated acids. However, the new definitions for grouping the polyunsaturated fatty acids lead to interesting working hypotheses.     

Weighted residual methods in optimal control

Weighted residual methods (WRM) afford a viable approach to the numerical solution of differential equations. Application of WRM results in the transformation of differential equations into systems of algebraic equations in the modal coefficients. This suggests that WRM can be used as a tool for reducing optimal control problems to mathematical programming problems. Thereby, the optimal control problem is replaced by the minimization of a cost function of static coefficients subject to algebraic constraints. The motivation for this approach lies in the profusion of sophisticated computational algorithms and digital computer codes for the solution of mathematical programming problems. In this note the solution of optimal control problems as mathematical programming problems via WRM is illustrated. The example presented indicates that reasonable accuracy is obtained for modest computational effort. While the simplest types of modes-polynomials and piecewise constants-are employed in this note, the ideas delineated can be applied in conjunction with cubic splines for the generation of computational algorithms of enhanced efficiency.     

Homogeneous hydroformylation of cyclohexene with bis(acetylacetonato)diaquo cobalt (II)

Hydroformylation of cyclohexane by bis(acetylacetonato)diaquo cobalt(II) [Co(acac)₂ (H₂O)₂] in benzene solution produced the corresponding aldehyde, alcohol and saturated hydrocarbon. The influence of various experimental conditions on the product distribution has been investigated and the optimum conditions for the maximum yield of aldehyde (45%) and alcohol (55%) have been established. A tentative mechanism for hydroformylation has been suggested on the basis of the isolated green complex [Co(acac)₂]₂(C₆H₁₀) having catalytic activity comparable with Co (acac)₂(H₂O)₂ which has been isolated from the product mixture and also synthesised separately.     

Logical data base design: A management-oriented approach

A logical data base consists of data definitions and data relationships. It is typically very large and complex even for a small organization, but it is generally designed in an ad hoc manner. However, several approaches have recently been proposed that allow for a systematic logical data base design.To make a data base more useful to the managers, it is imperative to encourage and obtain their involvement in the initial phase of the logical data base design. “Surface semantic models” are used in the logical data base design process to increase this involvement. A special type of this, called a “hierarchical external view model”, is proposed. It has been successfully used to develop a logical data base for the Department of Aging in Pennsylvania.     

Schnellmethode zur Bestimmung des ?lanteils in Lecithin

Zusammenfassung Eine Schnellmethode zur routinemäßigen Bestimmung des Ölanteils in Handelsleeithin und ähnlichen Phospholipidproben wurde ausgearbeitet. Sie beruht auf der Beobachtung, dam 1 g Phospholipid an 45 g mit Wasser desaktiviertem Kieselgel unter den Versuchsbedingungen vollständig adsorbiert werden.Die Lecithinprobe wird in ätherischer Lösung durch eine mit desaktiviertem Kieselgel gefüllte Säule filtriert und mit etwas Äther nacheluiert. Das gesamte Äther-Eluat wird i. Vak. eingedampft und der Rückstand gewogen. Dieser Rückstand entspricht dem Ölanteil, der aus Mono-, Di- und Triglyceriden, freien Fettsäuren, Sterinen und deren Derivaten besteht. Eine Bestimmung dauert etwa 20 min.

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A rapid method for determination of oil in lecithins

Summary A rapid method for routine determination of oil in commercial lecithins and similar phospholipid samples has been worked out. This based on the observation that under the described experimental conditions 1 g of phospholipids is completely adsorbed on 45 g silica gel which has previously been disactivated by the addition of 15% water.The lecithin sample is filtered in ethereal solution through a column filled with disactivated silica gel which is subsequently washed with a little ether. The combined ether eluates are evaporated to drynessin vacuo and the residue weighed. This residue is the oil part of the sample and is constituted of mono-, di-, and triglycerides, free fatty acids, sterols and their derivatives. The duration for one such determination is about 20 min.

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Vorgetragen anläßlich des 11. ISF-Kongresses in Göteborg, Juni 1972.     

Synthesis of multi-walled and single-walled nanotubes, aligned-nanotube bundles and nanorods by employing organometallic precursors

 Pyrolysis of organometallic precursors such as metallocenes and iron pentacarbonyl as well as of their mixtures with hydrocarbons such as acetylene or benzene has been carried out under a variety of conditions to synthesize nanotubes. While the use of benzene as a hydrocarbon source generally yields multi-walled nanotubes, it has been possible to obtain single-walled nanotubes (∼1 nm diameter) by pyrolyzing a metallocene or a mixture of metallocenes along with acetylene under a high flow rate of Ar. These experiments show that the organometallic precursor produces small nanoparticles of ∼1 nm diameter which then catalyze the formation of the single-walled nanotubes. Copious quantities of aligned-nanotube bundles have been obtained by the pyrolysis of acetylene in the presence of high concentrations of ferrocene. Nanorods have been produced by the pyrolysis of ferrocene under vacuum. Single walled nanotubes can be filled or decorated by metals. Received: 31 July 1998 / Accepted: 28 August 1998     

溶胶凝胶法制备的ZnO气敏薄膜

Zn(CH_3COO)_2通过溶胶凝胶法(Sol-Gel)被制备成粒度分布均匀的ZnO气敏薄膜,固有构参数已被确定。通过XRD(X射线衍射仪)和TEM(透射电镜)的分析结果,确认膜为ZnO多晶材料,并且利用高阻计测试了在不同气氛中试件的气体灵敏度。     

Kinetic studies on dehydrogenation of butanol to butyraldehyde using zinc oxide as catalyst

Butyraldehyde is an important chemical for many industrial applications, especially in the production of polyvinylbutyral. A systematic study of its synthesis by catalytic dehydrogenation of butanol, using zinc oxide as catalyst has been carried out. The effect of the method of preparation of zinc oxide on its catalytic activity for the title reaction has also been studied. The optimum conditions for maximum yield have been worked out and on the basis of secondary electron micrograms the reasons for higher activity/selectivity in the case of zinc oxide calcined from zinc hydroxide is attributed to the presence of hexagonal morphology. A kinetic study for the best zinc oxide catalyst has been carried out and the rate equation has been determined.