Micromechanical model of nacre tested in tension

A modified shear lag theory is used to model the tensile behavior of Pinctada nacre. A two-dimensional model is used to analyze the stress transfer between the aragonite platelets of nacre assuming that the ends of the platelet are not bonded with the organic matrix. Elastic-perfectly plastic behavior of the organic matrix is assumed. A model for stress transfer between the platelets when the matrix between the platelets starts behaving plastically is developed. It is assumed that nacre fails when the matrix breaks after the ultimate shear strain in the matrix is exceeded. This theory can be used to model the stress transfer in platelet reinforced composites at high volume fractions.     

Iron‐Catalyzed Direct Synthesis of Amides from Methylarenes

An efficient, green and first catalytic process has been developed for the direct synthesis of amides from readily available petroleum by‐products (methylarenes) and amines using an iron catalyst. In this new catalytic reaction, the methyl group of the methylarene is oxidized to the corresponding aldehyde through non‐directed C H oxidation followed by its oxidative amidation with N‐chloroamine, yielding the carboxylic amide. Oxidation with an iron catalyst, tert‐butyl hydroperoxide (TBHP) as sole oxidant, the synthesis of amides under mild reaction conditions and the utilization of methylarenes as starting material make this methodology novel and environmentally benign.

     

Formation of Arenes via Diallylarenes: Strategic Utilization of Suzuki–Miyaura Cross‐Coupling,Claisen Rearrangement and Ring‐Closing Metathesis

Two new synthetic strategies for benzoannulation are reported. The first strategy is based on the Suzuki–Miyaura cross‐coupling reaction. To this end, various ortho‐diallylbenzene derivatives were prepared from the corrresponding diiodo derivatives by an allylation strategy using an allylboronate as coupling partner. These diallyl derivatives were subjected to a ring‐closing metathesis (RCM) and one‐pot dichlorodicyanoquinone (DDQ) oxidation sequence to deliver 2‐substituted naphthalenes. In the second strategy, a double Claisen rearrangement and RCM protocol have been used as key steps to give highly functionalized benzoannulated quinone derivatives.     

Advanced manufacturing technology use: Exploring the effect of the nationality variable

A few studies (Jaikumar 1986) have left an impression among researchers that Japanese manufacturers use more advanced manufacturing technologies (AMTs) then their US counterparts. Presuming this were to be true, we hypothesized that nationality of the firm is an important factor in AMT use. To test the effect of the nationality variable on AMT use we compared the use of 18 AMTs in the US and Japan in an exploratory study using data from 160 US firms and 125 Japanese firms.There is clear evidence that the nationality of the firm is a factor in AMT use; that is AMT use is significantly different in the two countries. One explanation for the differences in AMT use may lie in the respective strategic orientations of the manufacturers in the two countries. A major finding in this study is that, while US manufacturers use more scheduling and control technologies, their Japanese counterparts use more factory floor technologies. Several hypothesis are offered as propositions for future research.     

Tetraoxaspiroalkanes for polymerization stress reduction of Silorane resins

This study involved the synthesis and characterization of tetraoxaspiroalkane monomers and evaluated their potential to reduce polymerization stress when formulated in a Silorane resin system. The tetraoxaspiroalkane monomers had two main structural features (a) two different types of core ring structures (a 1,5,7,11-tetraoxaspirocyclic ring or a 2,4,8,10-tetraoxaspirocyclic ring) and (b) four different types of ring substituents (normal alkyl, allyloxyalkyl, trimethylsilylalkyl, or oxabicycloalkyl). The resin formulations contained (a) 20 mol % of a 1,5,7,11- or 2,4,8,10-tetraoxaspiroalkyl monomer; (b) a phenylmethylsilane containing two oxabicycloheptyl groups; (c) a cyclotetrasiloxane containing four oxabicycloheptyl groups; and (d) a photocationic initiator system. Three main aspects were studied (a) the photoreactivity of the formulations using PDSC, (b) photopolymerization stress, and (c) mechanical properties (flexural elastic modulus, ultimate strength, and work of fracture) which were measured using an electromagnetic mechanical testing machine. The main findings were (a) formulations containing 2,4,8,10-tetraoxaspiroalkane monomers had measured net enthalpies greater than those containing 1,5,7,11-tetraoxaspiroalkane monomers, and above those calculated for addition of an inert diluent; (b) all formulations containing tetraoxaspiroalkane monomers exhibited photopolymerization stress values that were 40–99% less than the nonaddition control; (c) the formulation containing a 1,5,7,11-tetraoxaspiroalkane monomer with an oxirane functionality had mechanical properties that were not significantly different from the nonaddition control. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Hydrogenation of linolenate. XII. Effect of solvents on selectivity

Selectivity of heterogeneous catalysts for hydrogenation of linolenate over linoleate is increased by the presence of certain polar solvents. A ratio of specific reaction rate constants for linolenate to linoleate of 4 was obtained with a 5% palladium-on-alumina catalyst when dimethyl formamide (DMF) was used as the solvent. This high selectivity of DMF was independent of temperature and catalyst concentration. Other solvents that improved selectivity include furfural, acetonitrile, tetramethyl urea and trimethyl phosphate. Presented at AOCS meeting in Chicago, 1964. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, USDA.     

Selective hydrogenation of soybean oil: V. A Novel copper catalyst with excellent re-use properties

A procedure for the preparation of highly active copper catalyst by chemisorption of copper-ammonia complex on silica gel is described. This catalyst was highly selective towards the reduction of linolenate in soybean oil. The catalyst was re-used four times with no loss in activity.     

Alkali isomerization of linoleate isomers: Characterization of products

Geometrical isomers of methyl linoleate were reacted with alakli, and the resulting conjugated isomers were separated intotrans,trans;cis,trans; andcis,cis fractions. The position of double bonds in the various fractions was determined by reductive ozonolysis.trans-9,trans-12-Isomer of linoleate formedtrans,trans- andcis,trans-conjugated dienes, whereascis-9,trans-12- andtrans-9,cis-12-isomers in addition formedcis,cis-conjugated dienes. The formation of the products is in accordance with the theoretical predictions. During conjugationtrans double bonds shifted to form atrans bond preferentially. During conjugation ofcis-9,trans-12- andtrans-9,cis-12-linoleate isomers, thecis double bond shifted preferentially over thetrans double bond. A small amount of diene not conjugated was probably a geometrical and positional isomer of the starting material.