in this paper we introduce condition (e?p) a generalization of conditions (e?), (e) and (p) of acts over monoids and will give a classification of monoids by comparing this condition of their (rees factor) acts with other properties. we give also a criterion of cyclic acts to satisfy condition (e?p).

In living cells, new membranes are produced basically through two processes: mitosis and autopoiesis. These two processes have inspired two variants of cell-like membrane systems, namely P systems with active membranes and P systems with membrane creation. In this paper, we provide the first uniform, efficient solution to the SAT problem in the framework of recogniser P systems with membrane cr...

In 1979, Valiant proved that computing the permanent of a 01-matrix is #PComplete. In this paper we present another proof for the same result. Our proof uses \black box" methodology, which facilitates its presentation. We also prove that deciding whether the permanent is divisible by a small prime is #P-Hard. We conclude by proving that a polynomially bounded function can not be #P-Complete und...

Study of which the social work survey forms a part is anticipated and in that we shall deal again with some of the points raised earlier and those raised by critics such as your correspondent. However, lest your readers should misapprehend our tentative arguments, may I outline them here? The context is one of shortage of professionally qualified mental health social workers, particularly in th...

In the paper, we consider the problem of computing visibility information on digital terrain models. Visibility problems on polyhedral terrains are classi ed according to the kind of visibility information computed into point visibility, line visibility and region visibility. A survey of the state-of-the-art of the algorithms for computing visibility is presented, according to the classi cation...

We regret to record the death of Dr. P. P. Johnson, of Yatton, .after a long and painful illness, borne with much fortitude. Dr. Johnson was 57 years of age, and was educated at Sedbergh, afterwards proceeding to Edinburgh University, where he took his degree in 1877. He practised for over nine years at Littleborough, in Lancashire, and for a short time in Starbotton, Yorkshire, and came to Yat...