Structure-properties relationships in some random copolymers of propylene

Correlations have been investigated between the content of short isotactic segments and thermal properties in some propylene/olefin random copolymers. Polypropylene copolymers modified by ethylene show variations different from those for copolymers modified by ethylene and butene. However, in both cases, the weldability temperature decreases on increasing the comonomer concentration.     

Reactions de transcetalisation—I: Mise en evidence du caractere thermodynamique des reactions de transcetalisation et applications a la chimie de synthese

Evidence for the thermodynamic character of the transketalisation reaction allows the calculation of relative energies based upon ethyl methyl ketone. A scale of stability of the different types of ketones has thus been established and one can predict the selectivity of transketalisation reactions in polyketone molecules and hence choose the most suitable reagent. In the case of cyclic ketones, the variation of the transketalisation energies according to ring size has been related to changes in hybridation states.     

Operatori ellittici estremanti

Sunto Si provano alcune proprietà generali degli operatori ellittici estremanti. Mediante particolari soluzioni delle equazioni estremanti si esaminano le singolarità isolate delle soluzioni di equazioni ellittiche delII ordine e si stabiliscono alcune limitazioni.

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Summary Some general properties of the maximizing elliptic operators are established. Particular solutions of the maximizing equation are used to get information about bounds and isolated singularities of solutions of second order elliptic equations.

     

Sulla risoluzione di un problema isoperimetrico

Sunto Si riassume un precedente studio relativo ad un problema isoperimetrico e si dà una formulazione generale al procedimento impiegato. A Mauro Picone nel suo 70^mo compleanno. Lavoro eseguito nell'Istituto Nazionale per le applicazioni del calcolo.     

Limitazioni per soluzioni di equazioni ellittiche

Sunto Si stabilisce una limitazione puntuale per soluzioni di una equazione ellittica, a coefficienti misurabili, in m variabili, in dipendenza della normal L_m del secondo membro della equazione. Le ipotesi sono discusse mediante la costruzione di alcuni esempi.

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Summary We consider an elliptic equation of the second order, with measurable coefficients, in m variables, not homogeneous; a solution, equal zero on the boundary, is bounded with the norm L_m of the second member of the equation. Some examples are constructed to discuss the hypothesis.