Dynamic surface rearrangement and thermal stability of nitrogen functional groups on carbon nanotubes

Dynamic surface rearrangement and thermal stability of N-functional groups on carbon nanotubes (CNTs), obtained by functionalization of pristine CNTs with NH(3), were studied by temperature-programmed XPS and MS: a link between the stability of the functional group and decomposition temperature have been established and a conversion into graphitic nitrogen was observed.     

On the General Structure of Small on Large Problems for Elastic Deformations of Varga Materials II: Axially Symmetric Deformations

In Part I of this article, we have formulated the general structure of the equations governing small plane strain deformations which are superimposed upon a known large plane strain deformation for the perfectly elastic incompressible 'modified' Varga material, and assuming only that the initial large plane deformation is a known solution of one of three first integrals previously derived by the authors. For axially summetric deformations there are only two such first integrals, one of which applies only to the single term Varga strain-energy function, and we give here the corresponding general equations for small superimposed deformations. As an illustration, a partial analysis for the case of small deformations superimposed upon the eversion of a thick spherical shell is examined. The Varga strain-energy functions are known to apply to both natural and synthetic rubber, provided the magnitude of the deformation is restricted. Their behaviour in both simple tension and equibiaxial tension, and in comparison to experimental data, is shown graphically in Part I of this paper [1]. This revised version was published online in August 2006 with corrections to the Cover Date.     

1-Naphthyl-TADDOL/Emim BF<Subscript>4</Subscript>: A new catalytic system for the asymmetric addition of Chan’s diene to aromatic aldehydes

A new organocatalytic system was tested as a promoter for the asymmetric addition of Chan’s diene to aldehydes under solvent-free conditions. This new organocatalyst generated in situ by mixing 1-naphthyl-TADDOL derivative and Emim BF₄ was able to give enantioenriched vinylogous aldols and hetero-Diels-Alder cycloadducts. A mechanistic investigation through the detection of nonlinear effects confirmed the involvement of the ionic liquid in the formation of a new catalytic supramolecular species.     

Naphthyl-l-α-amino acids via chemo-enzymatic dynamic kinetic resolution

A double catalyst system (protease + base) was applied to the dynamic kinetic resolution (DKR) of isomeric 1- and 2-α-naphthyl-glycines and -alanines exploiting the in situ racemization of their thioesters. Due to the different C-acidity of the two sets of compounds, different experimental conditions have been devised to perform the simultaneous resolution/racemization process.In all cases, the racemic N-Boc-thioesters were converted into the aminoacids with an l-configuration almost quantitatively and with complete enantioselectivity.     

One‐factorizations of complete graphs with vertex‐regular automorphism groups

We consider one‐factorizations of K_2n possessing an automorphism group acting regularly (sharply transitively) on vertices. We present some upper bounds on the number of one‐factors which are fixed by the group; further information is obtained when equality holds in these bounds. The case where the group is dihedral is studied in some detail, with some non‐existence statements in case the number of fixed one‐factors is as large as possible. Constructions both for dihedral groups and for some classes of abelian groups are given. © 2002 John Wiley & Sons, Inc. J Combin Designs 10: 1–16, 2002     

Computer aided design of chains of four-bar linkages with an interactive method

Summary For some time in the Section of Applied Mechanics at Milan's Politecnico, various routines for the kinematic analysis of linkages have been prepared. These and similar routines are satisfying for that which concerns analysis, but cannot be adapted or are often insufficient when dealing with synthesis using trial and error methods. Given that the major difficulty of using these methods is the scarce possibility of communication between the designer and the machine, we thought that the best solution would be to equip these analysis routines with a new part thus facilitating communication between the designer and the machine. This paper represents a further step in this direction and contains a number of examples of the design of linkage systems for application in mechanical presses.

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Sommario Ormai da tempo si ricorre all'uso dell'elaboratore per lo studio dei meccanismi. Presso la Sezione di Meccanica delle Macchine del Politecnico di Milano sono stati messi a punto numerosi programmi per l'analisi cinematica dei meccanismi articolati. Questi programmi ed altri similari, si rivelano del tutto soddisfacenti per quanto riguarda l'analisi ma sono poco adatti e spesso insufficienti per procedere alla sintesi con metodi del tipo ?trial and error?. Constatato che la maggiore difficoltà che si incontra nel procedere con questi metodi sta nelle scarse possibilità di dialogo tra operatore e macchina, ci si è resi conto che la strada da seguire è quella di corredare questi programmi di analisi di una larga parte nuova con lo scopo appunto di rendere il più agevole possibile il colloquio tra operatore e macchina. Il presente lavoro rappresenta un ulteriore passo in questa direzione rispetto al precedente degli stessi autori.

     

Asymmetric allylation of aldehydes with allyltrichlorosilane promoted by chiral sulfoxides

Allylation of aldehydes with allyltrichlorosilane in the presence of sulfoxides is reported. The use of excess of (R)-methyl-p-tolylsulfoxide resulted in the formation of the corresponding homoallylic alcohols in good yields and moderate enantiomeric excesses.     

(S)-(+)-N-acetylphenylglycineboronic acid: a chiral derivatizing agent for Ee determination of 1,2-diols

A new chiral derivatizing agent for ee determination of 1,2-diols via (1)H NMR is described. (S)-(+)-N-acetylphenylglycineboronic acid (1) is synthesized in enantiomerically pure form; its reaction with chiral diols quantitatively yields cyclic boronic esters 5a-g. The latter show a remarkably high diastereodifferentiation of proton NMR signals useful for de determination. [reaction: see text]