NON-POINTED EXACTNESS, RADICALS, CLOSURE OPERATORS

In this paper it is shown how nonpointed exactness provides a framework which allows a simple categorical treatment of the basics of Kurosh-Amitsur radical theory in the nonpointed case. This is made possible by a new approach to semi-exactness, in the sense of the first author, using adjoint functors. This framework also reveals how categorical closure operators arise as radical theories

Fair semigroups and Morita equivalence

In analogy to the xst-rings studied by García and Marín, we define fair semigroups and investigate Morita equivalence for a subclass of them. In particular, we present examples for semigroups which are Morita equivalent but not strongly Morita equivalent. © 2015 Springer Science+Business Media New Yor

Commutative orders revisited

This article studies commutative orders, that is, commutative semigroups having a semigroup of quotients. In a commutative order S, the square-cancellable elements S(S) constitute a well-behaved separable subsemigroup. Indeed, S(S) is also an order and has a maximum semigroup of quotients R, which is Clifford.We present a new characterisation of commutative orders in terms of semilattice decompositions of S(S) and families of ideals of S. We investigate the role of tensor products in constructing quotients, and show that all semigroups of quotients of S are homomorphic images of the tensor product R ⊗S(S) S. By introducing the notions of generalised order and semigroup of generalised quotients, we show that if S has a semigroup of generalised quotients, then it has a greatest one. For thiswe determine those semilattice congruences on S(S) that are restrictions of congruences on S

Recovery of aroma compounds from model solution by pervaporation membrane

The aim of our study was to examine applicability of pervaporation in reference to the apple aroma recovery and the effects of the operating parameters on the process. Based on performed experiments the pervaporation, as membrane process, may be capable to reduce the loss of aroma compounds in the beverages production, due to its low operating temperature and high aroma recovery efficiency so organoleptic characteristics of the products would satisfy the growing consumer expectations as well. The studied main aroma compounds were i-amyl-alcohol, ethanol, butanol, i-butanol, ethyl-acetate, which could be separated with high selectivity. The values of activation energy of investigated compounds follow their order of polarity that requires further investigation. The data were analysed statistically, which showed negligible effects of flow-rate and initial concentration on the process