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An explicit categorical equivalence is defined between a proper subvariety of the class of $PMV$-algebras, as defined by Di Nola and Dvure$\check{c}$enskij, to be called $PMV_f$-algebras, and the category of semi-low $f_u$-rings. This categorical representation is done using the prime spectrum of the $MV$-algebras, through the equivalence between $MV$-algebras and $l_u$-groups established by Mundici, from the perspective of the Dubuc-Poveda approach, that extends the construction defined by Chang on chains. As a particular case, semi-low $f_u$-rings associated to Boolean algebras are characterized. Besides we show that class of $PMV_f$-algebras is coextensive.

In this article we develop a new version of the intuitionist existential graphs presented by Arnol Oostra [4]. The deductive rules presented in this article have the same meaning as those described in the work of Yuri Poveda [5], because the deductions according to the parity of the cuts are eliminated and are replaced by a finite set of recursive rules. This way, $ Alfa_I $ the existential graphs system for intuitional propositional logic follows the course of the deductive rules of the system $ Alfa_0 $ described by Poveda [5], and is equivalent to the intuitionistic propositional calculus. In this representation the $ Alfa_0 $ system is improved, there are a series of deductive rules of second degree incorporated that previously had not been considered and that allow a better management of deductions and finally from the ideas proposed by Van Dalen [6], a mixture is incorporated in the deduction techniques, the natural deductions of the Gentzen system are combined with new system rules $ Alfa_0 $ and $ Alfa_I $. The symbols proposed for the $Alfa_I$ representation relate open, closed and quasi-open sets of the usual topology of the plot with the intuitional propositional logic, usefull for approaching new problems in the representation of this logic from a more geometrical perspective.

In this note we exhibit a very simple proof of McNaughton Theorem, almost right out of the definitions, and at the same time we observe that this theorem does not depend of Chang's completeness theorem., 1 and 1/2 pages